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Nov 2000

Volume 18, Issue 6, pp. 2611-3611

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Growth of low-defect density In0.25Ga0.75As on GaAs by molecular beam epitaxy

G. W. Pickrell, K. L. Chang, J. H. Epple, K. Y. Cheng, and K. C. Hsieh

J. Vac. Sci. Technol. B 18, 2611 (2000); http://dx.doi.org/10.1116/1.1322040 (4 pages) | Cited 6 times

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The growth parameters of In0.25Ga0.75As grown on GaAs by molecular beam epitaxy were investigated. Low substrate temperatures coupled with lower growth rates and low arsenic overpressures were explored and the corresponding threading dislocation densities were determined using transmission electron microscopy. Threading dislocation densities in layers much thicker than the critical thickness were found to be as low as 1×107 cm−2 using optimal growth conditions. In addition, the critical thickness of the ternary alloy was estimated. The evolution of the misfit dislocations and threading dislocations was also examined as a function of epilayer thickness. © 2000 American Vacuum Society.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Investigation of mesa-sidewall effects on direct current and radio frequency characteristics of Ga0.51In0.49P/In0.15Ga0.85As/Ga0.51In0.49P pseudomorphic high electron mobility transistors

Chih-Hung Yen, Kuan-Po Lin, Kuo-Hui Yu, Wen-Lung Chang, Kun-Wei Lin, and Wen-Chau Liu

J. Vac. Sci. Technol. B 18, 2615 (2000); http://dx.doi.org/10.1116/1.1322047 (5 pages) | Cited 1 time

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The influences and improved methods for mesa-sidewall effects of GaInP/InGaAs/GaInP pseudomorphic high electron mobility transistors are investigated and demonstrated. The mesa-sidewall effects of gate leakage current path and parasitic capacitance seriously degrade the device characteristics. For instance, the excessive gate leakage current, reduced breakdown voltage and transconductance, variation of threshold voltage, increased sidegating effect, and degraded radio frequency response are found when the number of the mesa sidewall is increased. In the work, a simple and low-cost technique of the selective removal of mesa-sidewall materials is introduced. This selective etching method can substantially eliminate the mesa-sidewall contact problems of heterostructure field-effect transistor devices. © 2000 American Vacuum Society.
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85.30.Tv Field effect devices

Diode structures based on p-GaN for optoelectronic applications in the near-ultraviolet range of the spectrum

D. Starikov, I. Berishev, J.-W. Um, N. Badi, N. Medelci, A. Tempez, and A. Bensaoula

J. Vac. Sci. Technol. B 18, 2620 (2000); http://dx.doi.org/10.1116/1.1326943 (4 pages)

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It was previously reported that spectrally matched n-SiC and n-GaN-based MIS Schottky barrier diode structures exhibited optical emission and photosensitivity in the near-ultraviolet (UV) range of the spectrum and rectification at elevated temperatures. However, such structures were not practical due to the low mechanical and thermal stability of the semitransparent Au contacts. In addition, we experienced difficulties in achieving stable optical emission from the n-GaN-based structures. In this work various Schottky barrier diode structures based on p-type GaN layers grown on sapphire with silicon (Si), boron nitride (BN), and silicon dioxide (SiO2) interfacial layers were investigated. Blue and wide-spectrum optical emissions at forward and reverse bias, respectively, and photosensitivity were observed from these structures. A spectral match in the range of 365–400 nm between the light emitting diode (LED) and photodetector structures fabricated on the same substrate was achieved. A total Lambertian radiant UV power of ∼466 μW was measured from a blue/UV LED at 22 V. UV-transparent and electrically conductive SnOx layers were fabricated, characterized, and employed for fabrication of p-GaN-based photodiode structures. © 2000 American Vacuum Society.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.30.Kk Junction diodes
85.60.Jb Light-emitting devices
85.60.Gz Photodetectors (including infrared and CCD detectors)

Study of current leakage in InAs p–i–n photodetectors

Ray-Ming Lin, Shiang-Feng Tang, and C. H. Kuan

J. Vac. Sci. Technol. B 18, 2624 (2000); http://dx.doi.org/10.1116/1.1319693 (3 pages) | Cited 1 time

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The current leakages of InAs photodiodes have been systematically studied by adding undoped layers having thicknesses of 0, 0.30, and 0.72 μm between the p–n junction. At reverse bias V=−0.5 V, the dark currents of the InAs p–i–n diodes with undoped layer thicknesses of 0, 0.30, and 0.72 μm are about 5×10−6, 7×10−8, and 1×10−10 A, respectively, at 77 K. The leakage current of the InAs p–n diode was successfully reduced by adding 0.72-μm-thick undoped layer between the p–n junction. © 2000 American Vacuum Society.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Dw Photodiodes; phototransistors; photoresistors

Low temperature deposition for high performance photodetector

Lili He

J. Vac. Sci. Technol. B 18, 2627 (2000); http://dx.doi.org/10.1116/1.1320802 (4 pages)

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Thin metal films are of considerable interest for optoelectronic device fabrication. The high resistivity of thin metal films results in drawbacks of their application in the devices. The low Schottky barrier height for certain important material such as InGaAs blocks its application in optoelectronic device at long wavelength. Recent studies have been conducted in low temperature (LT) deposition of thin metal films. The LT thin films showed 4–5 orders lower resistivity compared to those formed at room temperature. The LT process also results in increased Schottky barrier height for most III–V semiconductor materials. Therefore, the LT processed thin films show superior properties for optoelectronic devices applications. In this work, computer simulation was conducted by partially implementing the LT results in device parameters. The optimum design for the high performance metal–semiconductor–metal photodetector was obtained by simulation. The results show that the LT processing is of convenient, cost-effective, and could be implemented in more optoelectronic device fabrications. © 2000 American Vacuum Society.
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73.61.At Metal and metallic alloys
73.40.Sx Metal-semiconductor-metal structures
85.60.Gz Photodetectors (including infrared and CCD detectors)
81.05.Bx Metals, semimetals, and alloys
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
73.30.+y Surface double layers, Schottky barriers, and work functions

Effect of growth interruption and the introduction of H2 on the growth of InGaN/GaN multiple quantum wells

Yong-Tae Moon, Dong-Joon Kim, Keun-Man Song, Dong-Wan Kim, Min-Su Yi, Do-Young Noh, and Seong-Ju Park

J. Vac. Sci. Technol. B 18, 2631 (2000); http://dx.doi.org/10.1116/1.1327298 (4 pages)

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The effects of the growth interruption and the introduction of H2 during interruption time on the optical and structural properties of InGaN/GaN multiquantum wells (MQWs), grown by metalorganic chemical vapor deposition, were investigated. When the growth was interrupted during the formation of interfaces in the MQWs, the intensity of photoluminescence (PL) was greatly increased and the formation of InN-rich regions near the surface of the InGaN well layer was suppressed. As the interruption time increased, however, the PL intensity decreased and the average In composition of InGaN/GaN MQWs decreased. When H2 was introduced during the growth interruption, the intensity of the PL was significantly enhanced by eliminating the impurities at the interface and the PL peaks were blueshifted due to the reduction in the thickness of the InGaN well layers, as a result of H2 etching of well and barrier layers. © 2000 American Vacuum Society.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors

Site control of InAs quantum dots on GaAs surfaces patterned by in situ electron-beam lithography

T. Ishikawa, S. Kohmoto, S. Nishikawa, T. Nishimura, and K. Asakawa

J. Vac. Sci. Technol. B 18, 2635 (2000); http://dx.doi.org/10.1116/1.1322039 (5 pages) | Cited 8 times

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We studied a site-control technique for InAs quantum dots (QDs) on GaAs substrates using a combination of in situ electron-beam (EB) lithography and self-organized molecular-beam epitaxy. On prepatterned square-mesa structures with a dimension of several tens of microns, we were able to control the average density of Stranski–Krastanow QDs. On these mesa structures, submicron holes in an array were formed as preferential growth sites of QDs by EB writing and Cl2 gas etching. By supplying 1.8 monolayer (ML) of InAs, QDs were formed in the patterned holes without any formation on the flat region between them. The QD concentration in each hole was dependent on the hole depth, that is, on the density of atomic steps inside holes. In the holes deeper than 50 Å, QDs were so densely formed that carrier tunneling occurred between them. In the shallow holes with 5–6 ML steps, on the other hand, single QDs were formed.© 2000 American Vacuum Society.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
85.40.Hp Lithography, masks and pattern transfer
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Fabrication technology of a Si nanowire memory transistor using an inorganic electron beam resist process

Toshiyuki Tsutsumi, Kenichi Ishii, Hiroshi Hiroshima, Sukti Hazra, Mitsuyuki Yamanaka, Isao Sakata, Hirohisa Taguchi, Eiichi Suzuki, and Kazutaka Tomizawa

J. Vac. Sci. Technol. B 18, 2640 (2000); http://dx.doi.org/10.1116/1.1314373 (6 pages) | Cited 7 times

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We report on a novel fabrication technology of a Si nanowire memory transistor using an inorganic SiO2 electron beam (EB) resist process. The inorganic EB resist process technique was put to practical use in Si nanodevice fabrication for the first time. We have successfully demonstrated the 15-nm-wide and 20-nm-thick Si nanowire memory transistor with a Si nanodot less than 10 nm in diameter. In the fabricated Si nanowire nanodot memory transistor, we have observed a large electron memory effect, i.e., a threshold voltage shift ΔVth of 2.2 V at room temperature. It is experimentally shown that the inorganic EB resist process is promising for fabricating various Si nanodevices. © 2000 American Vacuum Society.
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85.30.Tv Field effect devices
85.40.Hp Lithography, masks and pattern transfer
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

Deposition of Fe clusters on Si surfaces

M. D. Upward, B. N. Cotier, P. Moriarty, P. H. Beton, S. H. Baker, C. Binns, and K. Edmonds

J. Vac. Sci. Technol. B 18, 2646 (2000); http://dx.doi.org/10.1116/1.1320808 (4 pages) | Cited 12 times

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We have used an ultrahigh vacuum scanning tunneling microscope to investigate the deposition of mesoscopic iron clusters from a gas aggregation source. The size of the clusters was found to be in the range 1–7 nm. The effect of exposure of the iron clusters to the atmosphere results in a significant increase in cluster size, which we believe is consistent with total oxidation of the clusters. A specially designed quadrupole mass filter is incorporated inside the cluster source. We have investigated the sizes of the clusters deposited using different quadrupole settings and find that it is possible to size select the clusters prior to deposition. Finally we have studied the effect of sample surface reactivity and annealing on cluster distribution. © 2000 American Vacuum Society.
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61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.05.Bx Metals, semimetals, and alloys
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.65.Mq Oxidation
07.75.+h Mass spectrometers
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Initial growth analysis of Si overlayers on cerium oxide layers

Chong Geol Kim

J. Vac. Sci. Technol. B 18, 2650 (2000); http://dx.doi.org/10.1116/1.1319697 (3 pages) | Cited 14 times

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CeO(OH)2 and Ce(OH)4 capped on cerium oxide were observed in x-ray photoemission spectroscopy. Since the cerium oxide surface is partially covered with hydroxide before Si deposition, the Si layer is expected to have a poor crystal quality at the initial Si growing stage. Cross-sectional transmission electron microscopy analysis verified that there was not SiO2, but amorphous Si and Ce2O3 between the Si overlayer and CeO2. The reason why SiO2 is not formed is explained. The transition of the growth mode for the Si overlayer was observed in atomic force microscopy images. It is confirmed that the growth mode of Si on CeO2/Si is step flow at the low deposition rate and island growth at the high deposition rate. © 2000 American Vacuum Society.
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68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.35.B- Structure of clean surfaces (and surface reconstruction)

Electrical properties of self-organized nanostructures of alkanethiol-encapsulated gold particles

Shujuan Huang, Gen Tsutsui, Hiroyuki Sakaue, Shoso Shingubara, and Takayuki Takahagi

J. Vac. Sci. Technol. B 18, 2653 (2000); http://dx.doi.org/10.1116/1.1318190 (5 pages) | Cited 8 times

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In this article, we present the fabrication and electrical characterization of nanostructures made of alkanethiol-encapsulated gold particles. We fabricated ordered close-packed monolayer and multilayer structures of encapsulated gold particles using a self-organization process. Room-temperature electrical properties of these nanostructures were studied by using a conductive atomic force microscope. In both cases of monolayer and multilayer structures, the current suppression around zero bias was observed for 9-nm-diameter gold particles. However, it was not observed for 20-nm-diameter particles. This suggests that the Coulomb blockade has occurred in the case of 9-nm-diameter particles. Moreover, the current–voltage properties of multilayer structures demonstrate a nearly linear relation between the Coulomb gap Vg and the number of layers NL, which is in good agreement with the theory of single-electron tunneling in a tunnel-junction array. These electrical properties suggest that an alkanethiol shell on gold particles can serve as a stable tunnel barrier. As a consequence, the proposed method for fabricating quantum dot structures is very useful for developing nanoelectronic devices. © 2000 American Vacuum Society.
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73.63.-b Electronic transport in nanoscale materials and structures
61.46.-w Structure of nanoscale materials
73.23.Hk Coulomb blockade; single-electron tunneling

Atomic force microscopy of reaction of ammonia gas with crystalline substituted benzoic acid

Qingdao Zeng, Chen Wang, Chunli Bai, Yan Li, and Xinjian Yan

J. Vac. Sci. Technol. B 18, 2658 (2000); http://dx.doi.org/10.1116/1.1314372 (6 pages)

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Regular nanostructures are formed by chemical reaction of ammonia gas with crystalline substituted benzoic acid such as p-bromobenzoic (1a), p-toluic (1b), p-aminobenzoic (1c), and p-nitrobenzoic acid (1d). Their size and shape are determined and depicted by atomic force microscopy (AFM). AFM reveals that the crystal main face (100) of 1a, (100) of 1b, (100) of 1c, and (001) of 1d exhibits craters and volcanoes, craters and volcanoes, volcanoes, and volcanoes, respectively, whereas the long side face (100) of 1d gives rise to craters and volcanoes. All the experimental results are correlated with the crystal structures. Molecular interpretations of the AFM features of 1a, 1b, 1c, and 1d are given. © 2000 American Vacuum Society.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Effect of photoenhanced minority carriers in metal-oxide-semiconductor capacitor studied by scanning capacitance microscopy

S. Shin, J.-I. Kye, U. H. Pi, Z. G. Khim, J. W. Hong, Sang-il Park, and S. Yoon

J. Vac. Sci. Technol. B 18, 2664 (2000); http://dx.doi.org/10.1116/1.1326947 (5 pages) | Cited 8 times

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A scanning capacitance microscope was used to study the photoenhanced minority-carrier contribution to the capacitance of the metal-oxide-semiconductor (MOS) capacitor at high frequencies. When a light is induced over the semiconductor surface, electron-hole pairs are generated and recombined. This steady-state generation-recombination process yields the temporary source of minority carriers, and the inversion layer underneath the oxide layer can respond to very fast-varying ac bias. We measured the differential capacitance (dC/dV) of the MOS capacitor under various light intensities, and observed a peak at the inversion region where the amplitude increased as the irradiation intensity increased. By integrating dC/dV with respect to V, we obtained C–V curves in which the capacitance of the depletion region recovered its value up to that of the accumulation region as the light intensity increased. We also observed that the C–V curves shifted in one direction under irradiation which we believe is due to the surface photovoltaic effect. © 2000 American Vacuum Society.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
84.32.Tt Capacitors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.40.+w Photoconduction and photovoltaic effects

Integrated atomic force microscopy array probe with metal–oxide–semiconductor field effect transistor stress sensor, thermal bimorph actuator, and on-chip complementary metal–oxide–semiconductor electronics

T. Akiyama, U. Staufer, N. F. de Rooij, D. Lange, C. Hagleitner, O. Brand, H. Baltes, A. Tonin, and H. R. Hidber

J. Vac. Sci. Technol. B 18, 2669 (2000); http://dx.doi.org/10.1116/1.1327299 (7 pages) | Cited 15 times

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A microfabricated 2×1 array of active and self-detecting cantilevers is presented for applications in atomic force microscopy (AFM). The integrated deflection sensor is based on a stress sensing metal–oxide–semiconductor transistor. Full custom complementary metal–oxide–semiconductor amplifiers for signal readout are combined on the same chip. A sensor sensitivity of 2.25 mV/nm, or a change in current ΔId/Id=2.8×10−6/nm, was obtained at the final output stage. Three Al–Si thermal bimorph actuators are integrated on each cantilever for self-excitation and feedback actuation. The efficiencies of the heaters are 2.4–4.7 K/mW. In the experimental setup, a maximum displacement of 8 μm was achieved at 45 mW input. A pair of parallel AFM images in the constant height mode, a typical tapping mode image, and a constant force image with 1.3 μm high features have been successfully taken with the array probe. © 2000 American Vacuum Society.
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07.79.Lh Atomic force microscopes
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.30.Tv Field effect devices

X-ray source combined ultrahigh-vacuum scanning tunneling microscopy for elemental analysis

Y. Hasegawa, K. Tsuji, K. Nakayama, K. Wagatsuma, and T. Sakurai

J. Vac. Sci. Technol. B 18, 2676 (2000); http://dx.doi.org/10.1116/1.1318189 (5 pages) | Cited 6 times

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An ultrahigh-vacuum scanning tunneling microscope (UHV-STM) combined with an x-ray source has been developed. STM samples were irradiated with an x-ray beam and an x-ray induced photoemission current was detected with the tip. By using the system, apparent height increases due to the x-ray induced current were successfully observed in STM images of Cr/Cu(111), Au/Cu(111), Si(111)7×7, and Si(111)-5×1 Au surfaces. A bias voltage applied to the tip enhances collection of the x-ray induced current and increases the apparent height. The relative height increase of the Au overlayer to the Cu substrate in the STM images of the Au/Cu(111) surface was found to depend on the x-ray irradiation, suggesting that it may be a promising tool for elemental analysis in a STM. © 2000 American Vacuum Society.
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82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
07.79.Cz Scanning tunneling microscopes

New method for imaging atoms

Juying Dou, Ergang Chen, Changchun Zhu, and Deqing Yang

J. Vac. Sci. Technol. B 18, 2681 (2000); http://dx.doi.org/10.1116/1.1318191 (3 pages) | Cited 1 time

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We introduce the principle on a new high resolution thermal field emission microscope (HRTFEM). The crystalline structures of W(111), W(100), and W(110) tips have been observed. Both theoretical analyses and experiments show that HRTFEM has high resolving power with which atoms can be distinguished clearly. By using this HRTFEM, the states of atoms on tip surface can be studied easily. © 2000 American Vacuum Society.
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68.37.Vj Field emission and field-ion microscopy
68.35.B- Structure of clean surfaces (and surface reconstruction)

Dual tunneling-unit scanning tunneling microscope for practical length measurement based on reference scales

Haijun Zhang, Lan Wu, Feng Huang, and Shuwen Cheng

J. Vac. Sci. Technol. B 18, 2684 (2000); http://dx.doi.org/10.1116/1.1319696 (4 pages) | Cited 2 times

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A new setup of dual tunneling-unit scanning tunneling microscope (DTU STM) has been developed that can realize simultaneous calibration between test sample images and standard reference scales. The crystalline lattices and periodic grating features are employed as such scales for practical length measurements, respectively, in the nanometer and the micron orders. The DTU STM consists of a reference unit and a test unit horizontally set in parallel to eliminate Abbe’s errors. Their probe tips are attached to one single XY scanner on the same surface, while the reference and test sample holders are open. As the tips scan over the sample surfaces, two images with the same lateral size are simultaneously acquired. Line lengths in the test image could be measured by counting the number of crystalline lattices or grating patterns in the reference side. Two vertical impact drive mechanisms were applied to coarsely positioned samples in the Z direction. Another two impact drive mechanisms were employed to the horizontal drive sample holders as to automatically position the samples in the lateral plane. We present a brief discussion about the concept and setup of the DTU STM. Some comparison results using crystalline lattices and grating patterns, respectively, as reference scales for length calibration are provided. Experiments show a satisfactory matching between the two tunneling units when covering a wide scan range from 5 nm to 10 μm. With its new setup, the DTU STM is confirmed to be a more accurate device for practical length measurement even when measuring comparatively large and heavy samples. © 2000 American Vacuum Society.
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07.79.Cz Scanning tunneling microscopes
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
06.20.F- Units and standards

Effect of metal–insulator–semiconductor structure derived space charge field on the tip vibration signal in electrostatic force microscopy

Seungbum Hong, Jungwon Woo, Hyunjung Shin, Eunah Kim, Keun-Ho Kim, Jong Up Jeon, Y. Eugene Pak, and Kwangsoo No

J. Vac. Sci. Technol. B 18, 2688 (2000); http://dx.doi.org/10.1116/1.1323968 (4 pages) | Cited 2 times

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The role of metal–insulator–semiconductor structure derived space charge field in the tip vibration signal of electrostatic force microscopy was studied using boron doped Si tip and Pt film sputtered on Si substrate. The ohmic contact between the tip and the film was confirmed by current–voltage characterization. Then the tip was held at a position so that an air gap of 100 nm existed between the tip and the film. The tip deflection and the tip vibration signals were examined by applying dc voltage to the film and ac voltage to the tip. The asymmetry in both signals supports the existence of the space charge field, and the direction of the field at zero dc bias field is from the tip to the sample as expected from the band bending theory. © 2000 American Vacuum Society.
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07.79.-v Scanning probe microscopes and components
07.68.+m Photography, photographic instruments; xerography
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Wide dynamic range silicon diaphragm vacuum sensor by electrostatic servo system

Haruzo Miyashita and Masayoshi Esashi

J. Vac. Sci. Technol. B 18, 2692 (2000); http://dx.doi.org/10.1116/1.1320807 (6 pages) | Cited 4 times

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A wide dynamic range silicon diaphragm vacuum sensor by an electrostatic servo system and an electrical circuit for servo control have been made. In nonservo mode, i.e., when the sensor was used as a capacitive vacuum sensor, a linear characteristic between pressure and output voltage was obtained in the pressure range from 0.1 to 100 Pa. On the other hand, the square root of the servo voltage was proportional to the pressure in a wide pressure range from 0.1 to 530 Pa in servo mode. The servo mechanism is effective for widening the dynamic range of vacuum sensors. © 2000 American Vacuum Society.
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07.30.Dz Vacuum gauges
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.07.Tw Servo and control equipment; robots
07.68.+m Photography, photographic instruments; xerography
07.10.Cm Micromechanical devices and systems

Field emission properties of nanocomposite carbon nitride films

I. Alexandrou, M. Baxendale, N. L. Rupesinghe, G. A. J. Amaratunga, and C. J. Kiely

J. Vac. Sci. Technol. B 18, 2698 (2000); http://dx.doi.org/10.1116/1.1322043 (6 pages) | Cited 11 times

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A modified cathodic arc technique has been used to deposit carbon nitride thin films directly on n+ Si substrates. Transmission electron microscopy showed that clusters of fullerene-like nanoparticles are embedded in the deposited material. Field emission in vacuum from as-grown films starts at an electric field strength of 3.8 V/μm. When the films were etched in an HF:NH4F solution for 10 min, the threshold field decreased to 2.6 V/μm. The role of the carbon nanoparticles in the field emission process and the influence of the chemical etching treatment are discussed. © 2000 American Vacuum Society.
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79.70.+q Field emission, ionization, evaporation, and desorption
61.46.-w Structure of nanoscale materials
68.55.-a Thin film structure and morphology

Study of the emission performance of carbon nanotubes

Lei Wei, Wang Baoping, Tong Linsu, Yin Hanchun, Tu Yan, and Zhu Changchun

J. Vac. Sci. Technol. B 18, 2704 (2000); http://dx.doi.org/10.1116/1.1319692 (6 pages) | Cited 5 times

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The carbon nanotube has good field emission properties, so it has been used as the electron source on the field emission display panel. To obtain a high emission current, the electric field at the tip of the nanotube must be large enough. This article studies the variation of electric field with different types of nanotubes. The emission current of the nanotube is also calculated for various geometrical parameters of nanotubes. From the simulation results, the influence of the geometrical parameters on the emission performance of nanotubes is studied. © 2000 American Vacuum Society.
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79.70.+q Field emission, ionization, evaporation, and desorption
85.45.Db Field emitters and arrays, cold electron emitters
85.45.Fd Field emission displays (FEDs)
85.65.+h Molecular electronic devices

Influence of diamond film thickness on field emission characteristics

H. Ji, Z. S. Jin, C. Z. Gu, J. Y. Wang, X. Y. Lu, B. B. Liu, C. X. Gao, G. Yuan, and W. B. Wang

J. Vac. Sci. Technol. B 18, 2710 (2000); http://dx.doi.org/10.1116/1.1326945 (4 pages) | Cited 4 times

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Diamond films with various thicknesses (0.15–9 μm) were grown by microwave plasma chemical vapor deposition. The lowest threshold field strength for electron emission was 4 V/μm for the ∼1.5-μm-thick diamond film. The results were analyzed by effective emission areas and effective work function according to Fowler–Nordheim theory. It was found that the threshold voltage was strongly affected by the ratio of (111) and (110) oriented grains in the films. The larger the fraction of (111) oriented grains, the lower the effective work function in agreement with the reported negative electron affinity of (111) surfaces. © 2000 American Vacuum Society.
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79.70.+q Field emission, ionization, evaporation, and desorption
73.30.+y Surface double layers, Schottky barriers, and work functions

Characterization of the surface morphology and electronic properties of microwave enhanced chemical vapor deposited diamond films

A. G. Fitzgerald, Y. Fan, P. John, C. E. Troupe, and J. I. R. Wilson

J. Vac. Sci. Technol. B 18, 2714 (2000); http://dx.doi.org/10.1116/1.1326946 (8 pages) | Cited 3 times

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The surface morphology, electronic structure and atomic bonding configurations of chemical vapor deposition (CVD) diamond films prepared at different stages of the deposition process and subjected to different postdeposition surface treatments have been studied by scanning probe microscopy (SPM), scanning tunneling spectroscopy (STS), and x-ray photoelectron spectroscopy (XPS) surface analysis techniques. SPM image observations show that (a) in the biasing nucleation process, diamond crystallites grow in a three-dimensional manner and the nucleation density reaches 109–1010/cm2; (b) both as-deposited and boron ion implanted films exhibit a hillock morphology on (100) crystal faces; (c) atomic flatness can be achieved on crystal faces by hydrogen plasma etching. STS analysis indicates that (i) the films obtained after an initial biasing nucleation process show a metallic tunneling behavior; (ii) both as-deposited and hydrogen plasma etched CVD diamond films possess typical p-type semiconductor surface electronic properties; (iii) when the as-deposited diamond films are subjected to boron implantation or argon ion etching, the surface electronic properties change from p-type semiconducting behavior to metallic behavior. XPS analysis confirmed that the surfaces for both as-deposited and hydrogen plasma etched diamond films have a tetrahedral atomic bonding configuration. However, the surfaces of boron ion implanted and argon ion etched diamond films exhibited an amorphous carbon-like feature which can be attributed to the surface damage caused by ion bombardment. © 2000 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.ub Fullerenes and related materials
68.55.-a Thin film structure and morphology
73.20.At Surface states, band structure, electron density of states

Enhancement in field emission of silicon microtips by bias-assisted carburization

P. D. Kichambare, F. G. Tarntair, L. C. Chen, K. H. Chen, and H. C. Cheng

J. Vac. Sci. Technol. B 18, 2722 (2000); http://dx.doi.org/10.1116/1.1320809 (8 pages) | Cited 6 times

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Ultrathin carbon layers with thicknesses below 50 Å have been deposited on silicon microtip arrays by bias-assisted carburization (BAC) using microwave plasma chemical vapor deposition. The tip radius of these silicon tips is reduced below 55 nm under low deposition temperature. The field emission characterization has been performed in a high-vacuum environment. An enhancement in the field emission is observed of about 3 orders of magnitude in BAC silicon microtips over untreated silicon microtips. With an applied voltage of 1100 V, emission currents of 80 and 120 μA have been achieved for the films grown (at dc bias of −200 V for 40 min) with 15% and 25% CH4/H2 gas ratio, respectively. An emission current of 40 μA has been achieved for the film grown (at dc bias of −300 V for 40 min) with 3.5% CH4/H2 ratio. The BAC silicon emitter has good emission stability at a constant voltage of 1100 V. These investigations indicate that further improvement of this technology will lead to simple and inexpensive field emission display devices. © 2000 American Vacuum Society.
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85.45.Db Field emitters and arrays, cold electron emitters
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
79.70.+q Field emission, ionization, evaporation, and desorption

Polysubstituted derivatives of triphenylene as high resolution electron beam resists for nanolithography

A. P. G. Robinson, R. E. Palmer, T. Tada, T. Kanayama, M. T. Allen, J. A. Preece, and K. D. M. Harris

J. Vac. Sci. Technol. B 18, 2730 (2000); http://dx.doi.org/10.1116/1.1322045 (7 pages) | Cited 8 times

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We have explored the application of polysubstituted derivatives of triphenylene as high resolution, high etch durability electron beam resists. Room temperature spin coating was used to produce films of the derivatives on silicon substrates. Exposure to a 20 keV electron beam was found to alter the dissolution rate of these derivatives in various organic solvents. Doses of between ∼3×10−4 and ∼2.5×10−3 C/cm2 substantially increased the solubility of the derivative hexapentyloxytriphenylene in polar solvents (positive tone behavior). Doses greater than ∼2.5×10−3 C/cm2 led to a decrease in solubility in both polar and nonpolar solvents (negative tone behavior). Other derivatives also demonstrated a reduction in their dissolution rate for doses between ∼1.5×10−3 and ∼6.5×10−3 C/cm2. The etch durabilities of the positive and negative tone patterns were found to be, respectively, ∼25% less and ∼70% greater than that of a conventional novolac based negative tone resist. Line and space patterns were defined in one of the resists with a resolution of ∼14 nm and structures with an aspect ratio of ∼50–1 were etched into silicon. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

Comparative study of sputtered and spin-coatable aluminum oxide electron beam resists

M. S. M. Saifullah, K. Kurihara, and C. J. Humphreys

J. Vac. Sci. Technol. B 18, 2737 (2000); http://dx.doi.org/10.1116/1.1323970 (8 pages) | Cited 8 times

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The electron beam exposure characteristics of sputtered AlOx and spin-coatable Al2O3 resists are compared and contrasted. When exposed to an electron beam, sputtered AlOx resists on a silicon substrate undergo an intense mass loss. However, electron energy loss spectroscopy shows that even after a prolonged exposure some aluminum and oxygen remains on the silicon surface. Spin-coatable Al2O3 resist was prepared by reacting aluminum tri-sec-butoxide, Al(OBus)3, with acetylacetone (AcAc) in isopropyl alcohol. These are negative tone resists and they are >106 times more sensitive to an electron beam than the sputtered AlOx, bringing its sensitivity very close to high resolution organic resists such as calixarene. The exposure properties of spin-coatable and sputtered aluminum oxide resists are discussed together with their sensitivity, damage mechanisms, line edge roughness, and etching characteristics. A brief note on the change of methodology of resist design is added when inorganic resists are to be used in high resolution electron beam nanolithography. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.15.Cd Deposition by sputtering
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

How to make polyvinylphenol inhibitable by diazonaphthoquinone sulfonates

Zhenglin Yan, Tung-Feng Yeh, Xiaohua He, Arnost Reiser, Frank L. Schadt, and Curtis R. Fincher

J. Vac. Sci. Technol. B 18, 2745 (2000); http://dx.doi.org/10.1116/1.1322041 (5 pages)

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There is interest in phenolic resins that are transparent at 248 nm and the dissolution of which in alkaline aqueous developers can be inhibited by diazonaphthoquinone sulfonic acid derivatives, the standard photoactive compounds (PACs) of novolak resists. Poly(4-hydroxystyrene), i.e., poly(vinylphenol), has the requisite optical properties, but its dissolution is not very effectively inhibited by standard PACs. We have now found that poly(4-hydroxystyrene) can be made more inhibitable by increasing the acidity of its OH groups and, at the same time, lowering the concentration of the acidic OH groups in the resin. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

High performance micropane electron beam window

Roger A. Dougal and Shengyi Liu

J. Vac. Sci. Technol. B 18, 2750 (2000); http://dx.doi.org/10.1116/1.1319694 (7 pages) | Cited 2 times

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A silicon disk etched so that it contains a multitude of microscopic and thin window panes (micropanes) can potentially transmit a larger average electron beam current density and absorb a smaller fraction of the beam energy than a common metal foil window. The enhanced performance is achieved by a combination of decreased power loss due to the extremely small window thickness (∼1 μm), and increased conductive cooling due to the small diameter (∼50 μm) of the micropanes and the large cross section of the honeycomb structure that supports the micropanes. Beam current densities up to 34 A/cm2 are permitted within each micropane. When integrated over many micropanes across the face of a window, average current densities up to 1 A/cm2 are permitted—at least three orders of magnitude larger than the <mA/cm2 typical of foil windows. The small mass thickness yields high transparency, even for low energy beams. The transmission efficiency for a 100 keV beam is 99.5. © 2000 American Vacuum Society.
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41.75.Fr Electron and positron beams
07.77.Ka Charged-particle beam sources and detectors
41.85.Ar Particle beam extraction, beam injection

Design and development of plasma enhanced chemical vapor deposition universal antireflective layer films for deep subquarter micron deep ultraviolet applications

Ying Wang, Ken MacWilliams, Zia Karim, Wendy Fan, Michael Reilly, and James M. Holden

J. Vac. Sci. Technol. B 18, 2757 (2000); http://dx.doi.org/10.1116/1.1319695 (6 pages)

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A dual-layer, oxynitride film stack functions as a universal antireflective layer (UARL) for patterning deep subquarter micron features on transparent dielectric films. The UARL optical constants at 248 nm are n=1.96 and k=0.3 for top layer and n=2.24 and k=1.04 for bottom layer with film thickness 360 and 650 Å, respectively. The bottom UARL layer absorbs most of the incoming light, minimizing the light reflected from the underlying substrate. Therefore, the reflectance back into the photoresist is a few tenths of one percent and is independent of the substrate material’s optical properties and structures. Results of patterning 0.18 μm photoresist lines with the UARL on various Damascene film stacks show very tight critical dimension control. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.40.Sz Deposition technology
42.79.Wc Optical coatings
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Effects of fluorocarbon polymer deposition on the selective etching of SiO2/photoresist in high density plasma

Changwoong Chu, Taehyuk Ahn, Jisoo Kim, Sangsup Jeong, and Jootae Moon

J. Vac. Sci. Technol. B 18, 2763 (2000); http://dx.doi.org/10.1116/1.1322046 (6 pages) | Cited 2 times

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A new periodic two-step process composing SiO2 etching with high bias radio frequency (rf) power and fluorocarbon deposition with low bias rf power was studied for the highly selective etching of SiO2 to photoresist (PR). In this experiment, the time scale of each step is longer than the conventional time-modulation technique in order to maximize the protection layer on PR and prevent the etch stop. Many works have focused on the gaseous chemical species especially CF2 radicals for selective surface reaction. However, normally utilizing only the difference of stoichiometric surface reaction, they inherently limit the etching conditions such as dependence on the chemical composition of PR, densities, and impurities of SiO2 layers. And these conventional processes severely suffer reactive ion etching lag or etch stop in high selective etching. The new process utilizes fluorocarbon deposition with low bias rf power to increase the mask selectivity by enhancing the difference between the polymer thickness on the mask and that on the bottom surface of hole. After the etching step, the polymer film remains only on the mask, and then the higher selectivity of SiO2 to PR can be achieved. In this article it has been investigated whether the polymer deposition in the suggested process is governed by aspect ratio of holes, surface temperature, bias rf, and microwave powers. The ratio of the amount of etching to deposition is a very important factor in determining the selectivity. With the process a small and deep contact etching with thin PR is possible without shortage of mask thickness with the mask selectivity improved from 6 to 20. We can also find that the etch rate of this new process does not depend significantly on the aspect ratio. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning

Direct pattern etching for micromachining applications without the use of a resist mask

Byeong-Ok Cho, Jung-Hyun Ryu, Sung-Wook Hwang, Gyeo-Re Lee, and Sang Heup Moon

J. Vac. Sci. Technol. B 18, 2769 (2000); http://dx.doi.org/10.1116/1.1322044 (5 pages) | Cited 8 times

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The method of direct pattern etching without the use of a conventional resist mask has been developed. This method takes advantage of the field-shielding effect of a Faraday cage, inside which the substrate is located. A stainless-steel stencil mask, constituting the upper plane of the cage fixed on a cathode in a plasma etcher, was used as a pattern mask in reactive ion etching. A CF4 plasma at 5 mTorr was used to etch the initially bare substrate of a Si wafer covered with a 1-μm-thick blanket SiO2 film. The mask patterns with the minimal dimension of 40 μm were accurately transferred to the substrate with the etch profiles vertical to the substrate surface. When the gap distance between the stencil mask and the substrate surface was as small as 0.5 mm, the ratio of the etch rate below an opening to that below a blocking portion of the mask was over 5600. On the other hand, the etch rate ratio fell virtually to unity when the substrate was apart from the mask by 10.5 mm. The simulation study of ion trajectories showed that the ion beams were increasingly diverged as ions traveled away from the mask inside the cage. That is, the beams were well separated from each other in close proximity to the stencil mask, resulting in fine pattern etching. At positions sufficiently far from the mask, however, the deviated ion beams extensively overlapped with each other to yield the uniform ion flux. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning

Electron population above 13.5 eV in ultrahigh frequency and inductively coupled plasmas through C2F4/CF3I and C4F8/Ar gas mixtures

Toshiki Nakano and Seiji Samukawa

J. Vac. Sci. Technol. B 18, 2774 (2000); http://dx.doi.org/10.1116/1.1316104 (6 pages) | Cited 3 times

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Electron population above 13.5 eV in the plasma through the C2F4/CF3I mixture, which is novel chemistry proposed for low-damaged, fine structure etching of SiO2, is studied by Ar emission analysis and Langmuir probe measurement. The integrated electron energy distribution function (eedf) above threshold energy for Ar 750.4 nm emission (13.5 eV) exhibits the weaker dependence on the gas composition for the C2F4/CF3I mixture than for the C4F8/Ar mixture which is conventional chemistry for SiO2 etching. In the practical etching conditions, the integrated eedf above 13.5 eV for the C2F4/CF3I mixture becomes smaller than one third of that for the C4F8/Ar mixture, regardless of the plasma sources used in this study (ultrahigh-frequency plasma and inductively coupled plasma sources). These results indicate that even lower charging damage of devices would be expected in SiO2 etching using the C2F4/CF3I chemistry than the C4F8/Ar chemistry. © 2000 American Vacuum Society.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning

Study of grass formation in GaAs backside via etching using inductively coupled plasma system

P. S. Nam, L. M. Ferreira, T. Y. Lee, and K. N. Tu

J. Vac. Sci. Technol. B 18, 2780 (2000); http://dx.doi.org/10.1116/1.1320803 (5 pages) | Cited 7 times

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Grass formation in GaAs backside via etching with Cl2 based chemistry was studied using the inductively coupled plasma (ICP) system. A parametric approach adjusting rf bias power, ICP source power, pressure, and gas ratio was performed to observe the effect of etching condition on grass formation. Scanning electron microscopy was used to investigate the surface morphology as well as the cross section of the via hole. Vertical grass was observed at the bottom of the via hole at certain unique processing and etching conditions. The grass growth is attributed to the surface defects on GaAs induced during a backside thinning combined with weak physical ion bombardment in the etch condition. We found that the grass formation can be prevented by pre-etching with Ar bombardment on the surface © 2000 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
68.35.Dv Composition, segregation; defects and impurities

Two-channel spectroscopic reflectometry for in situ monitoring of blanket and patterned structures during reactive ion etching

Brooke S. Stutzman, Hsu-Ting Huang, and Fred L. Terry

J. Vac. Sci. Technol. B 18, 2785 (2000); http://dx.doi.org/10.1116/1.1327301 (9 pages) | Cited 5 times

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In this article we present a low-cost, high-speed, high-accuracy in situ thin film measurement system for real-time process monitoring and industrial process control. This sensor, the two-channel spectroscopic reflectometer (2CSR), is a hybrid of spectroscopic ellipsometry and spectroscopic reflectometry. In 2CSR a polarized beam of white light is directed at the sample. The reflected light is resolved into its two orthogonal components, s and p, using a Wollaston prism. These data, ∣Rs∣2 and ∣Rp∣2, are recorded simultaneously as a function of wavelength using a two-channel spectrometer with linear array detectors. The fact that 2CSR has no moving parts, coupled with the use of the two-channel linear array detectors, enables high-accuracy data acquisition across the sensor’s spectral range in 6 ms. This makes the 2CSR ideal for real-time high-speed process monitoring and control in an industrial setting. We have used the 2CSR to make accurate in situ, high speed film thickness measurements during the plasma etching of both silicon dioxide and polycrystalline silicon samples. We show that, in addition to our ability to measure blanket film thicknesses and etch rates, the accuracy of the 2CSR makes this a viable technique for patterned wafer analysis. © 2000 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
07.60.Fs Polarimeters and ellipsometers
07.60.Hv Refractometers and reflectometers
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
68.55.-a Thin film structure and morphology

Development and qualification of a vacuum pumping system for metalorganic vapor phase epitaxy copper precursors

R. P. Davis and R. A. Abreu

J. Vac. Sci. Technol. B 18, 2794 (2000); http://dx.doi.org/10.1116/1.1320805 (5 pages) | Cited 1 time

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Semiconductor devices incorporating copper interconnects are set to revolutionize the performance and functionality of integrated circuits. Copper interconnects enable faster and more reliable circuitry at sub-0.25 μm dimensions with lower resistivity and excellent resistance to electromigration. Numerous methodologies exist whereby copper can be deposited, with chemical vapor deposition (CVD) being one such technique. A vacuum pumping system that effectively and efficiently handles the process byproducts from the CVD precursor Cu(hfac)(TMVS) has been developed and qualified. It is shown that a standard dry pump used in conjunction with additional apparatus in the vacuum system results in the safe handling of process byproducts. The performance of each component of the vacuum system has been individually qualified and the abatement performance of the overall system shows >99% destruction efficiency of process effluent. © 2000 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.40.Ls Metallization, contacts, interconnects; device isolation
81.05.Bx Metals, semimetals, and alloys
07.30.Cy Vacuum pumps
06.60.Wa Laboratory safety procedures

Oxygen plasma induced degradation in InGaAs/InP heterostructures

R. Driad, W. R. McKinnon, and S. P. McAlister

J. Vac. Sci. Technol. B 18, 2799 (2000); http://dx.doi.org/10.1116/1.1320801 (4 pages)

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The effects of oxygen plasma conditions on the performance of InGaAs/InP heterostructure bipolar transistors (HBTs) have been studied by comparing the HBT’s characteristics, such as current gain and breakdown voltage, before and after treatment. The base–emitter junction characteristics of InGaAs/InP HBTs were unaffected by oxygen plasma treatments, for exposure periods of up to 10 min and rf powers <200 W. Higher rf powers degrade the current gain. In contrast, the base–collector junction was degraded even for short periods and low rf powers; the base–collector leakage current increased and the breakdown voltage decreased. Further reduction of the current gain was observed when dielectric films were deposited by plasma-enhanced chemical vapor deposition on oxygen treated devices. The dielectric film does not reduce the gain of devices that were not treated by oxygen plasma. © 2000 American Vacuum Society.
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85.30.Pq Bipolar transistors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning

CH4/H2 reactive ion etching induced damage of InP

H. C. Neitzert, R. Fang, M. Kunst, and N. Layadi

J. Vac. Sci. Technol. B 18, 2803 (2000); http://dx.doi.org/10.1116/1.1326944 (5 pages) | Cited 4 times

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Electrical modifications of InP samples induced by reactive ion etching (RIE) with CH4/H2 have been studied using (a) electrochemical capacitance–voltage measurements, (b) current–voltage characteristics of Schottky diode structures, and (c) transient reflected microwave conductivity measurements. From the capacitance–voltage measurements we confirm a depletion of holes near the surface of the dry-etched p-InP sample and an accumulation of electrons near the surface of the dry-etched n-InP sample. The hole concentration in p-InP sample can be recovered after a 400 °C, 1 min heat treatment in an Ar ambient. From the transient reflected microwave conductivity measurements we reveal new information on the modification of charge carrier mobilities and kinetics caused by dry etching and subsequent annealing procedures on p-InP, n-InP, and semi-insulating (Fe-doped) InP samples. The n-InP sample shows a loss in electron mobility after RIE and annealing; the p-InP sample shows a weakly n-type behavior after RIE and recovers the p-type behavior after annealing. © 2000 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Ea III-V semiconductors

Characterization of showerhead performance at low pressure

D. B. Hash, T. Mihopoulos, T. R. Govindan, and M. Meyyappan

J. Vac. Sci. Technol. B 18, 2808 (2000); http://dx.doi.org/10.1116/1.1322048 (6 pages) | Cited 1 time

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The performance of showerheads used in semiconductor processing applications has been examined over a wide range of Knudsen number and Reynolds number. Both computational fluid dynamics and direct simulation Monte Carlo techniques have been used to characterize the showerhead flow with the intent of developing correlations between the upstream velocity and the pressure drop across the showerhead. Empirical correlations developed to account for entrance effects and rarefaction are also examined. Recommendations are made concerning boundary conditions and, when appropriate, correlations for given pressures and flow rates. © 2000 American Vacuum Society.
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47.60.-i Flow phenomena in quasi-one-dimensional systems
47.45.-n Rarefied gas dynamics
47.11.-j Computational methods in fluid dynamics
02.70.Rr General statistical methods

Thermal stability and adhesion improvement of Ag deposited on Pa-n by oxygen plasma treatment

Kaustubh S. Gadre and T. L. Alford

J. Vac. Sci. Technol. B 18, 2814 (2000); http://dx.doi.org/10.1116/1.1327300 (6 pages) | Cited 12 times

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Parylene-n (Pa-n) and silver are being studied for ultralarge scale integrated circuits because of their favorable properties. These include low dielectric constant (2.65), negligible water take-up, chemical inertness, low temperature deposition, as well as compatibility with current integrated circuits manufacturing for Pa-n and the low resistivity (1.6 μΩ cm), high electromigration resistance for silver. To meet integration requirements, Pa-n and Ag are studied to understand specific reliability issues, e.g., diffusion, delamination, or loss of adhesion, compatibility, etc. Initial measurements of silver and dielectric Pa-n were done using four-point probe. Thermal stability and texturing of Ag films on Pa-n were confirmed using x-ray diffraction analysis. The change associated with resistivity of Ag films on Pa-n sample supports the changes observed in x-ray spectra. Rutherford backscattering spectrometry and secondary ion mass spectroscopy analysis show insignificant diffusion of Ag in Pa-n. Adhesion analysis of Ag/Pa-n and Pa-n/Si was done using scratch and tape tests. Oxygen plasma surface treatment of Pa-n shows drastic improvement of adhesion between Ag and Pa-n without loss of thermal stability of the system. The improvement in adhesion is associated with increased roughness of Pa-n surface after plasma treatment. © 2000 American Vacuum Society.
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68.60.Dv Thermal stability; thermal effects
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Thermal modeling of a polysilicon-metal test structure used for thermally induced voltage alteration characterization

Paiboon Tangyunyong, David Benson, and Edward I. Cole

J. Vac. Sci. Technol. B 18, 2820 (2000); http://dx.doi.org/10.1116/1.1327297 (6 pages)

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Thermal modeling and simulations were used to analyze the thermal profiles of a polysilicon-metal test structure generated by localized heating with an infrared laser. Localized laser heating is the basis of a new failure analysis technique, thermally induced voltage alteration (TIVA), that can identify shorted interconnects in integrated circuits. The modeling results show that variations in thermal profiles of the test structure measured by the TIVA technique are due mainly to preferential laser absorption in various locations in the test structure. Differences in oxide thickness also affect the local heat conduction and temperature distribution. Modeling results also show that local variation in heat conduction is less important than the absorbed laser power in determining the local temperatures since our test structure has feature sizes that are small compared to the length over which the heat spreads. © 2000 American Vacuum Society.
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85.40.Qx Microcircuit quality, noise, performance, and failure analysis

Influence of underlying interlevel dielectric films on extrusion formation in aluminum interconnects

Fen Chen, Baozhen Li, Timothy D. Sullivan, Clara L. Gonzalez, Christopher D. Muzzy, H. K. Lee, Mark D. Levy, Michael W. Dashiell, and James Kolodzey

J. Vac. Sci. Technol. B 18, 2826 (2000); http://dx.doi.org/10.1116/1.1319691 (9 pages) | Cited 12 times

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Knowledge of the mechanical properties of interlevel dielectric films and their impact on submicron interconnect reliability is becoming more and more important as critical dimensions in ultralarge scale integrated circuits are scaled down. For example, lateral aluminum (Al) extrusions into spaces between metal lines, which become more of a concern as the pitches shrink, appear to depend partially on properties of SiO2 underlayers. In this article nanoindentation, wafer curvature, and infrared absorbance techniques have been used to study the mechanical properties of several common interlevel dielectric SiO2 films such as undoped silica glass using a silane (SiH4) precursor, undoped silica glass using a tetraethylorthosilicate precursor, phosphosilicate glass deposited by plasma-enhanced chemical vapor deposition and borophosphosilicate glass (BPSG) deposited by subatmosphere chemical vapor deposition. The elastic modulus E and hardness H of the as-deposited and densified SiO2 layers are measured by nanoindentation. The coefficients of thermal expansion (CTE) of the densified layers are estimated by temperature-dependent wafer curvature measurements. Fourier transform infrared spectroscopy is used to obtain the chemical structures of all SiO2 layers. Among the four common interlevel layers, BPSG exhibits the smallest modulus/hardness and a relatively small amount of moisture loss during anneal. The BPSG shows the highest CTE, which generates the smallest thermal stress due to a closer match in the CTE between Al and SiO2. BPSG again has the lowest as-deposited compressive stress and the lowest local Si–O–Si strain before annealing. The center frequency of the Si–O bond stretching vibration exhibits a linear dependence on total film stress. The shifts of Si–O peaks for all the SiO2 layers also correlate well with the stress hysteresis obtained from wafer curvature measurements. Stress interactions between the various SiO2 underlayers and the Al metal film are also investigated. The impact of dielectric elastic properties on interconnect reliability during thermal cycles is proposed. © 2000 American Vacuum Society.
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85.40.Ls Metallization, contacts, interconnects; device isolation
68.60.Bs Mechanical and acoustical properties
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
68.60.Dv Thermal stability; thermal effects
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
62.20.Qp Friction, tribology, and hardness
62.20.D- Elasticity
65.40.De Thermal expansion; thermomechanical effects
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.66.Nk Insulators
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Characterization of additive systems for damascene Cu electroplating by the superfilling profile monitor

Shao-Yu Chiu, Jia-Min Shieh, Shih-Chieh Chang, Kun-Cheng Lin, Bau-Tong Dai, Chia-Fu Chen, and Ming-Shiann Feng

J. Vac. Sci. Technol. B 18, 2835 (2000); http://dx.doi.org/10.1116/1.1322042 (7 pages) | Cited 24 times

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Gap-filling dynamics of several different species of additives for copper electrodeposition was investigated by monitoring the cross section of a partially filled copper profile on the scanning electron microscopy photo. The filling ration Δy/Δx between “bottom-up” with “sidewall shift” was found to be proportional to the filling power of additives. The adsorption-diffusion model combined with cathode polarization and cyclic voltammetric stripping measurements was employed to explain the attribution of additives in superfilling phenomena. The superfilling dynamics was achieved under behavior of additives providing selective inhibition gradient within the damascene feature. By means of those analyses, we have optimized the appropriate amount of additives and achieved the superfilling performance for 0.15 μm vias with aspect ratio 6 by an acid-copper electrolyte with polyethylene glycol, C1−, and 2-mercaptopyridine (2-MP). Due to the additive of 2-MP, chelate formed which enhanced adsorption ability on Cu0 surface, and the concentration gradient between side-wall shift and bottom-up in the damascene became high enough to attend superfilling electroplating. © 2000 American Vacuum Society.
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85.40.Ls Metallization, contacts, interconnects; device isolation
81.15.Pq Electrodeposition, electroplating
85.40.Sz Deposition technology

Effect of various sputtering parameters on Ta phase formation using an I-Optimal experimental design

Charles S. Whitman

J. Vac. Sci. Technol. B 18, 2842 (2000); http://dx.doi.org/10.1116/1.1319701 (6 pages) | Cited 5 times

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Five process factors are varied to find conditions necessary for α and β phase formation in tantalum thin films deposited on SiC. These are: sputtering time, input power, presputter etch time, preheat time at 250 °C, and sputtering temperature. An empirical model is developed that predicts the maximum or minimum amount of β phase possible over a large range of film thickness (∼25–∼2000 nm). The maximum predicted (average) percent β phase at the maximum sputtering temperature is only 8%, with 95% confidence bounds of [3%, 17%]. The other factors place a much lower restriction on β phase formation. Pure α phase is easily produced over a wide range of operating conditions. Only a weak relationship is found between film thickness and phase composition. The Ta film resistivity increases with the amount of β phase, in agreement with the literature. © 2000 American Vacuum Society.
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68.55.Nq Composition and phase identification
81.15.Cd Deposition by sputtering
81.05.Bx Metals, semimetals, and alloys
07.05.Fb Design of experiments
73.61.At Metal and metallic alloys
81.65.Cf Surface cleaning, etching, patterning

Electrical characteristics of metal–ferroelectric (PbZrxTi1−xO3)–insulator(Ta2O5)–silicon structure for nonvolatile memory applications

Chi-yuan Sze and Joseph Ya-min Lee

J. Vac. Sci. Technol. B 18, 2848 (2000); http://dx.doi.org/10.1116/1.1319698 (3 pages) | Cited 2 times

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A metal–ferroelectric–insulator–silicon (MFIS) structure using lead–zirconate–titanate (PZT) as the ferroelectric layer and Ta2O5 as the insulator layer is fabricated. This structure is studied for the potential application of nonvolatile memory devices. The Ta2O5 layer is used as a buffer layer to minimize the out diffusion of silicon atoms during heat treatment processes. High frequency capacitance–voltage measurements show a flat band voltage shift of 13 V under a ±15 V writing pulse. The interface-trap density Dit is measured by the conductance method. The MFIS capacitors are shown to have a fatigue lifetime of 1×1011 cycles and 5×107 cycles for 11.4 and 15 V writing pulses, respectively. © 2000 American Vacuum Society.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
84.32.Tt Capacitors
84.30.Sk Pulse and digital circuits
77.55.-g Dielectric thin films
73.20.-r Electron states at surfaces and interfaces

Electronic structure and mechanical properties of hard coatings from the chromium–tungsten nitride system

P. Hones, M. Diserens, R. Sanjinés, and F. Lévy

J. Vac. Sci. Technol. B 18, 2851 (2000); http://dx.doi.org/10.1116/1.1320806 (6 pages) | Cited 11 times

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Cr1−xWxNy films were deposited on silicon by rf reactive magnetron sputtering. The phase and texture were determined by x-ray diffraction analysis. All the films crystallize in the fcc phase. Scanning tunneling microscopy revealed a finely grained surface morphology. The grain size decreases with increasing tungsten content in the films. Quantitative values can be assigned to morphology differences through the measurement of the optical reflectivity. Hardness values obtained by nanoindentation, and the packing density significantly increase upon addition of a small percentage of W to CrN. The electronic structure was analyzed using x-ray photoelectron spectroscopy. As deduced from core level binding energy values (chemical shifts), the W2N and Cr1−xWxN films are more covalent than binary CrN. The higher hardness values in W2N and Cr1−xWxN compounds compared to that of CrN are related to their prominent covalent bonding character between the metal and nitrogen ions. © 2000 American Vacuum Society.
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68.60.Bs Mechanical and acoustical properties
68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
73.61.Ng Insulators
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Electron-beam direct writing using RD2000N for fabrication of nanodevices

A. Dutta, S. P. Lee, Y. Hayafune, and S. Oda

J. Vac. Sci. Technol. B 18, 2857 (2000); http://dx.doi.org/10.1116/1.1323969 (5 pages) | Cited 6 times

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A simple but potent method for electron-beam (EB) direct writing is introduced. This method is based on the use of negative electron-beam resist RD2000N. The resist offers high sensitivity to EB exposure and high resistance to halide plasma etching conditions, which is ideal for application in Si/SiO2 based nanodevice fabrication. Dot exposure shows that dots of a minimum diameter of 16 nm could be patterned using this resist. Linear arrays of dots, connected to each other by very narrow constrictions, are patterned using this resist. When transferred to a thin silicon-on-insulator layer, by reactive ion etching, this structure forms a multiple tunnel junction. Memory devices based on this multiple tunnel junction are fabricated. Memory operation is observed at 20 K. © 2000 American Vacuum Society.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
85.40.Hp Lithography, masks and pattern transfer
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Thin SiO2 layers on Si(111) with ultralow atomic step density

Antonio C. Oliver and Jack M. Blakely

J. Vac. Sci. Technol. B 18, 2862 (2000); http://dx.doi.org/10.1116/1.1320804 (3 pages) | Cited 2 times

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The morphologies of the oxide surface and of the Si–SiO2 interface that form on special Si(111) substrates have been studied by atomic force microscopy (AFM). The substrates are totally free of atomic steps or have very low step density. Step-free regions are formed on patterned Si(111) by thermal processing. AFM scans of the same areas prior to oxidation, after oxidation, and after chemical removal of the oxide allow the relative roughnesses to be compared. The step structure of the Si(111) substrate is translated to the oxide surface even for SiO2 layers in the 10 nm range. The lack of significant displacement of the atomic steps at the Si–SiO2 interface indicates that the oxide grows by a layer-by-layer mechanism. © 2000 American Vacuum Society.
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81.65.Mq Oxidation
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Ct Interface structure and roughness
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back to top OPTICAL LITHOGRAPHY

Implementing advanced lithography technology: A 100 MHz, 1 V digital signal processor fabricated with phase shifted gates

G. P. Watson, I. C. Kizilyalli, O. Nalamasu, R. A. Cirelli, M. Miller, Y. Wang, B. Pati, J. Radosevich, R. Kohler, R. Freyman, F. Klemens, W. Mansfield, H. Vaidya, A. Timko, L. Trimble, et al.

J. Vac. Sci. Technol. B 18, 2877 (2000); http://dx.doi.org/10.1116/1.1328056 (4 pages) | Cited 1 time

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To demonstrate the effectiveness of alternating aperture phase shift lithography for integrated circuit manufacturing, a demonstration device was designed and processed. A 2 million transistor integrated circuit was processed with a phase shifted gate level using 248 nm wavelength lithography. The lithographic results were confirmed by careful feature size measurements throughout the process sequence and finally by the performance of the devices themselves. Gate lengths were reduced from 240 to 120 nm, resulting in fully functional chips with 100 MHz circuit speed at 1.0 V operation, more than a two-fold speed improvement and a record for communication circuits of this type at a low supply voltage. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
84.30.Sk Pulse and digital circuits

Lithographic patterning and confocal imaging with zone plates

Darío Gil, Rajesh Menon, D. J. D. Carter, and Henry I. Smith

J. Vac. Sci. Technol. B 18, 2881 (2000); http://dx.doi.org/10.1116/1.1321293 (5 pages) | Cited 13 times

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Zone-plate-array lithography (ZPAL) uses an array of zone plates, combined with an array of micromechanical mirrors or shutters, to pattern features on a substrate without a mask. In this article, we investigate the patterning characteristics of individual zone plates. We show patterns printed with pixel-dose modulation (gray scaling) and subpixel beam stepping. Using a combination of these techniques for linewidth control, edge placement, and proximity-effect correction, ZPAL can produce arbitrary patterns with features as small as the focal spot of a zone plate. We also demonstrate the use of zone plates in a confocal-microscopy mode for placing the substrate at the focus of the zone plates, and for imaging. Zone-plate-array scanning-confocal microscopy (ZPAM) could be useful for gapping and alignment in ZPAL, and possibly for wafer or mask inspection at deep ultraviolet wavelengths. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
07.60.Pb Conventional optical microscopes
42.79.Ci Filters, zone plates, and polarizers

Sub-100 nm silicon on insulator complimentary metal–oxide semiconductor transistors by deep ultraviolet optical lithography

M. Fritze, J. Burns, P. W. Wyatt, C. K. Chen, P. Gouker, C. L. Chen, C. Keast, D. Astolfi, D. Yost, D. Preble, A. Curtis, P. Davis, S. Cann, S. Deneault, and H. Y. Liu

J. Vac. Sci. Technol. B 18, 2886 (2000); http://dx.doi.org/10.1116/1.1314387 (5 pages) | Cited 7 times

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We report results on the fabrication of deep sub-100 nm silicon-on-insulator (SOI) complimentary metal–oxide semiconductor transistors using phase-shift double-exposure deep ultraviolet optical lithography. Resist gate features down to 40 nm were resolved corresponding to λ/6 resolution or k1=0.1. Using an etch bias, we have fabricated polysilicon gate features down to 25 nm corresponding to λ/10 resolution or k1=0.06. Good process latitudes were obtained, and SOI transistor results down to 50 nm gate length are reported. © 2000 American Vacuum Society.
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85.30.Tv Field effect devices
85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning

Defect formation and structural alternation in modified SiO2 glasses by irradiation with F2 laser or ArF excimer laser

Yoshiaki Ikuta, Shinya Kikugawa, Masahiro Hirano, and Hideo Hosono

J. Vac. Sci. Technol. B 18, 2891 (2000); http://dx.doi.org/10.1116/1.1328055 (5 pages) | Cited 18 times

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The formation and restoration of defects by F2 laser irradiation with high laser fluence were investigated for modified silica glasses, and the results were compared with those by ArF excimer laser irradiation. F2 laser irradiation induced oxygen deficient centers (ODCs) and E′ centers via one-photon-absorption processes, while ODC and E′ defects are generated by two-photon-absorption processes by an ArF excimer laser. As-doped SiOHs and photoinduced SiOHs enhanced the formation of defects markedly in the case of F2 laser irradiation. F2 laser light transformed isolated SiOH bonds into hydrogen-bonded SiOHs, while such a process did not occur under ArF excimer laser light. These results suggest that silica glass networks were dissociated by two types of processes. The dominant process is the formation of pairs of E′ centers and NBOHCs, followed by conversion to the SiHs and SiOHs as a result of chemical reactions with hydrogen molecules in silica glass at room temperature. The other is the generation of ODC defects accompanied by interstitial oxygen molecules, which are also decomposed partly into E′ centers with the aid of F2 laser light. © 2000 American Vacuum Society.
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61.43.Fs Glasses
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Ms Insulators
78.40.Ha Other nonmetallic inorganics

Shape engineering: A novel optical proximity correction technique for attenuated phase-shift mask

S. Pau, K. Bolan, M. Blakey, and O. Nalamasu

J. Vac. Sci. Technol. B 18, 2896 (2000); http://dx.doi.org/10.1116/1.1313570 (4 pages)

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Modifications of the shapes and relative orientations of contact windows in attenuated phase shifting mask are studied theoretically and experimentally to maximize process latitude and resolution and to minimize sidelobe printability. By utilizing a non-square contact window shape and maintaining the overall pattern transmission, we achieve considerable sidelobe suppression with no loss in process latitude and resolution. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Analytic study of gratings patterned by evanescent near field optical lithography

S. J. McNab, R. J. Blaikie, and M. M. Alkaisi

J. Vac. Sci. Technol. B 18, 2900 (2000); http://dx.doi.org/10.1116/1.1319837 (5 pages) | Cited 3 times

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Simulation results which investigate the near field of conducting gratings are presented to show some of the major issues affecting evanescent near field optical lithography (ENFOL), namely ultimate resolution, depth of field, exposure variations due to edge enhancements, and resonant diffraction. Ultimate resolution down to 10 nm for grating structures is predicted, independent of illumination wavelength. The depth of field reduces approximately linearly as the feature size reduces in the evanescent regime. Variations in mask profile were investigated by modeling the radii of curvature of mask conductors from 1–10 nm. Strict mask profile control is shown to be important to avoid exposure variations due to the increasing zeroth transmitted order with increasing radii. A diffraction resonance occurs when the grating pitch matches the wavelength for a transverse magnetic excited grating. The cut off of the ±1 diffracted orders coincides with a plasmon resonance and a strong, frequency doubled interference pattern is produced. To avoid such resonant conditions, standard ENFOL requires a low coherence source and/or strongly absorbing resists. However, this near field interference offers the possibility of frequency-doubled interferometric replication of quasiperiodic structures, with strong intensity enhancement at the expense of reduced depth of field. Overall, the key to successful evanescent lithography is restricting the lithography to a depth in which high contrast is available with good process latitude due to the presence of sufficient numbers of diffracted orders of sufficient strength. © 2000 American Vacuum Society.
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42.79.Dj Gratings
42.82.Cr Fabrication techniques; lithography, pattern transfer
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
07.60.Ly Interferometers
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Development of the large field extreme ultraviolet lithography camera

T. Watanabe, H. Kinoshita, H. Nii, Y. Li, K. Hamamoto, T. Oshino, K. Sugisaki, K. Murakami, S. Irie, S. Shirayone, Y. Gomei, and S. Okazaki

J. Vac. Sci. Technol. B 18, 2905 (2000); http://dx.doi.org/10.1116/1.1319712 (6 pages) | Cited 4 times

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We have developed a three-aspherical mirror system which is capable of replicating in a large exposure area (30 mm×28 mm). This system consists of the synchronized scanning mechanism of a mask and a wafer, the alignment optics between a mask and a wafer, the focus detector of a wafer position, and the load-lock chamber for exchanging wafers. The aspherical mirrors have a figure error of 0.58 nm and a surface roughness of 0.3 nm. To obtain a high efficiency mirror, a couple of mirrors were coated with a graded d spacing Mo/Si multilayer. The peak reflectivity is 65% at the wavelength of 13.5 nm. The wavelength matching of each mirror spans 0.45 nm. The mirrors were aligned with a Fizeau-type phase shift interferometer, and a final wave front error of less than 3 nm was achieved. Exposure experiments carried out at NewSUBARU synchrotron facility and a diffraction limited resolution of 56 nm was obtained in an exposure-field size of 10 mm×2 mm in static exposure. Furthermore, fine patterns in an area of 10 mm×5.2 mm were obtained using the mask and wafer synchronized scanning stages. These results revealed that this system can be applied to fabricate large scale integrated devices. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
42.79.Bh Lenses, prisms and mirrors
42.15.Eq Optical system design
07.60.Ly Interferometers
42.79.Wc Optical coatings
42.60.By Design of specific laser systems

Extreme ultraviolet alignment and testing of a four-mirror ring field extreme ultraviolet optical system

Kenneth A. Goldberg, Patrick Naulleau, Phillip Batson, Paul Denham, Erik H. Anderson, Henry Chapman, and Jeffrey Bokor

J. Vac. Sci. Technol. B 18, 2911 (2000); http://dx.doi.org/10.1116/1.1319703 (5 pages) | Cited 12 times

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Extreme ultraviolet (EUV) interferometry has been used to characterize and align a recently fabricated, 4× reduction, four-mirror, aspheric optical system designed for EUV lithography. This system is called the Engineering Test Stand Set-1 Optic. An EUV phase-shifting point diffraction interferometer constructed on an undulator beamline at the Advanced Light Source was used to perform high-accuracy wavefront measurements during several alignment iterations. For each iteration, the alignment algorithm used 35 wavefront measurements recorded across the 26-mm-wide image-side ring field. Adjustments were made to systematically reduce the root mean square wavefront error magnitude to approximately 1 nm, bringing the system to nearly diffraction-limited performance. © 2000 American Vacuum Society.
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42.87.Bg Phase shifting interferometry
07.60.Ly Interferometers
85.40.Hp Lithography, masks and pattern transfer
06.60.Sx Positioning and alignment; manipulating, remote handling
42.79.Bh Lenses, prisms and mirrors
42.79.Wc Optical coatings

At-wavelength extreme ultraviolet lithography mask inspection using a Mirau interferometric microscope

Tsuneyuki Haga, Hisataka Takenaka, and Makoto Fukuda

J. Vac. Sci. Technol. B 18, 2916 (2000); http://dx.doi.org/10.1116/1.1319702 (5 pages) | Cited 13 times

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We have developed a novel at-wavelength inspection system for extreme ultraviolet lithography (EUVL) masks that employs an EUV interferometric microscope. The main advantage of this system is the ability to observe a mask directly and detect defects as they are, thus allowing phase defects to be detected even in a finished mask with the absorber. Moreover, this system provides the high spatial resolution of an EUV microscope, the high phase resolution of interferometric measurements, and a high throughput. We investigated the defect detection capability using several types of EUVL masks with programmed defects, and found that programmed phase defects with steps as low as 5 nm can be detected. These results demonstrate the capabilities of a Mirau interferometric microscope for at-wavelength EUVL mask inspection. Considering the diffraction-limited resolution of Schwarzschild optics (∼50 nm), this system should be applicable to the subhundred nanometer technology node. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.70.Fy Nondestructive testing: optical methods
07.60.Ly Interferometers
07.60.Pb Conventional optical microscopes
42.79.Wc Optical coatings

Reticle’s contribution to critical dimension control and overlay in extreme-ultraviolet lithography

H. Meiling, J. P. H. Benschop, E. Loopstra, J. E. van der Werf, and M. H. A. Leenders

J. Vac. Sci. Technol. B 18, 2921 (2000); http://dx.doi.org/10.1116/1.1321276 (5 pages) | Cited 3 times

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In order to design an exposure tool for extreme-ultraviolet (EUV) lithography that adheres to technology roadmap requirements, we translated overall system performance requirements to system design specifications by setting up detailed error budgets for critical dimension (CD) control and overlay. In this article we concentrate on the EUV reticle contributions, including surface flatness, hydrocarbon contamination, multilayer d-spacing variations, and mounting in the writer and exposure tool. It is determined that in order to meet the CD-control budget, the reticle multilayer d-spacing variation must be limited to 0.25%, whereas the thickness variation of the hydrocarbon growth should be less than 1.5 nm. The overlay budget requires that the reticle flatness within the site area must be better than ±25 nm, both on the patterned side and on the back side. Also, the chuck of the exposure tool must be flat within ±25 nm. To avoid in-plane pattern distortion, the flatness of the chuck in the e-beam writer must be identical to that of the chuck in the exposure tool, and hence also must be flat within ±25 nm. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Extreme ultraviolet mask defect simulation: Low-profile defects

Tom Pistor, Yunfei Deng, and Andrew Neureuther

J. Vac. Sci. Technol. B 18, 2926 (2000); http://dx.doi.org/10.1116/1.1324616 (4 pages) | Cited 15 times

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An assessment is made of the tendency of low-profile EUV multilayer mirror defects to print as a function of their height, width, and proximity to features. The study is based on rigorous electromagnetic simulation with TEMPEST and aerial image calculation with SPLAT. A special numerical technique involving the averaging of material properties at multilayer mirror surfaces is used to reduce error introduced by the FDTD gridding. Aerial images are calculated for Gaussian shaped mirror profiles of heights ranging from 1 to 5 nm and for several widths. The dip in clear field intensity for an isolated defect was found to be a strong linear function of defect height from 1 to 5 nm. For a given defect height a worse-case width was observed. As width increased beyond the worst-case width, defects become less printable because they become very flat and begin to approximate perfect mirror surfaces. Aerial images were calculated for mirrors with defects in proximity to mask features. A 1 nm high, 56 nm wide defect caused a significant change in a line's width depending on where the defect was in relation to the line. In the worst case, when the defect was centered 22 nm from the line edge a 12% line width change was observed. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
02.70.Bf Finite-difference methods
42.79.Bh Lenses, prisms and mirrors

Characterization of extreme ultraviolet lithography mask defects from extreme ultraviolet far-field scattering patterns

Moonsuk Yi, Seongtae Jeong, Seno Rekawa, and Jeffrey Bokor

J. Vac. Sci. Technol. B 18, 2930 (2000); http://dx.doi.org/10.1116/1.1319843 (5 pages) | Cited 2 times

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We present far-field scattering patterns from programmed phase and opaque defects on extreme ultraviolet lithography mask blanks. Distinct diffraction fringes were observed for both defect types, with fringe spacing dependent on the defect size. Phase defects and opaque defects were found to show clear differences in scattering properties that can be utilized to classify defects. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Extreme ultraviolet holographic microscopy and its application to extreme ultraviolet mask-blank defect characterization

Sang Hun Lee, Jeffrey Bokor, Patrick Naulleau, Seong Tae Jeong, and Kenneth A. Goldberg

J. Vac. Sci. Technol. B 18, 2935 (2000); http://dx.doi.org/10.1116/1.1314382 (4 pages) | Cited 2 times

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100-nm-resolution at-wavelength holographic microscopy of aerial images produced by extreme ultraviolet (EUV) lithographic optics has recently been demonstrated. It provides a simple and compact method allowing image monitoring without printing in photoresist. Here, the concept of holographic microscopy is extended to the characterizations of defects on EUV multilayer mask blanks. As a proof of principle, defect characterization using the holographic microscope is demonstrated with programmed defects in transmission masks. Amplitude defects as small as 100 nm have been successfully characterized. Extension of this technique to the more relevant reflection mask configuration is also discussed. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
42.40.Kw Holographic interferometry; other holographic techniques
42.40.My Applications

Extreme ultraviolet carrier-frequency shearing interferometry of a lithographic four-mirror optical system

Patrick P. Naulleau, Kenneth A. Goldberg, and Jeffrey Bokor

J. Vac. Sci. Technol. B 18, 2939 (2000); http://dx.doi.org/10.1116/1.1321290 (5 pages) | Cited 10 times

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The phase-shifting point diffraction interferometer (PS/PDI) has recently been developed to address the problem of at-wavelength metrology of extreme ultraviolet (EUV) optical systems. Although extremely accurate, the fact that the PS/PDI is limited to use with coherent EUV sources, such as undulator radiation, is a drawback for its widespread use. An alternative to the PS/PDI, with relaxed coherence requirements, is lateral shearing interferometry (LSI). Here we describe various LSI implementations and demonstrate the use of a cross-grating, carrier-frequency configuration to characterize a large-field 4×-reduction EUV lithography optic. The results obtained are directly compared with PS/PDI measurements. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
07.60.Ly Interferometers
42.79.Bh Lenses, prisms and mirrors

Effects of smoothing on defect printability at extreme ultraviolet wavelengths

G. F. Cardinale, A. K. Ray-Chaudhuri, A. Fisher, P. S. J. Mangat, J. Wasson, P. B. Mirkarimi, and E. Gullikson

J. Vac. Sci. Technol. B 18, 2944 (2000); http://dx.doi.org/10.1116/1.1324637 (6 pages) | Cited 1 time

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Improvements in mask blank yield by the reduction in defects dramatically reduces the reticle cost of any lithography. Extreme ultraviolet lithography (EUVL) masks typically consist of a substrate coated with reflective multilayer (ML) materials (e.g., Mo and Si), followed by a sacrificial or “repair” layer (e.g., SiO2) and top absorber layer material (e.g., Cr or TaSiNx). Defects of the following two types exist: substrate and absorber defects. Substrate defects are generally below the absorber and buffer layers, i.e., at the substrate–ML interface or within the ML stack, whereas the absorber defects are located at the absorber layer. In addition, the printability of substrate-type defects may be reduced by coating the defects with a planarizing or smoothing layer. In this work, we discuss simulation and experimental results that compare the printability of programmed defect reticles with and without smoothing layers covering the programmed defect. We propose several criteria for smoothing layer specifications that are necessary to mitigate a size range of defects for an EUV imaging system. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
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Proposal for a 50 nm proximity x-ray lithography system and extension to 35 nm by resist material selection

Toyoki Kitayama, Kenji Itoga, Yutaka Watanabe, and Shunichi Uzawa

J. Vac. Sci. Technol. B 18, 2950 (2000); http://dx.doi.org/10.1116/1.1324644 (5 pages) | Cited 8 times

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In this article, a 50 nm generation proximity x-ray lithography (PXRL) system is proposed using shorter wavelengths of exposure light down to around 3 Å. The illumination system uses a mirror at 1° incidence angle such as in the Canon stepper XRA-1000, which can be realized by coating with a fourth or fifth period metal such as Co or Rh. The resist containing chemical elements such as Cl, S, P, Si, and Br whose x-ray absorption edge lies in the wavelength band of the exposure light can yield a strong absorption using this system. Therefore, a resist material containing such elements is highly sensitive when applied to the 50 nm system. The average wavelength of power absorbed by the resist depends on the elements contained in the resist. This suggests that the resolution limits also depend on the resist material even for the same exposure system. Therefore, this system should be extendible down to the 35 nm generation by using such a resist and a thick diamond mask membrane. The system described assumes that the mask–wafer gap is the currently available 10 μm. In the future, an additional gain in resolution can be expected from a narrower gap. With these improvements, it is foreseeable that PXRL technology can be applied to the 20 nm regime, down to the operational limits of silicon devices at room temperature. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Technology and performance of the Canon XRA-1000 production x-ray stepper

Nobutoshi Mizusawa, Kouji Uda, Yutaka Tanaka, Hirohisa Ohta, and Yutaka Watanabe

J. Vac. Sci. Technol. B 18, 2955 (2000); http://dx.doi.org/10.1116/1.1324619 (6 pages) | Cited 2 times

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In order to introduce next generation lithography (NGL) into practical use, developing a production-worthy exposure tool is as important as developing a proof-of-concept system and mask technology. The progress of the exposure tool can be used as a measure of the status of each NGL choice. Canon has been focusing on the development of a proximity x-ray lithography (PXL) system for volume production use since the start of development. This has included development of magnification correction, development of a high-seed wafer stage, improvement of illumination intensity, extension of process latitude in the alignment system design, and development of an accurate environment control system. For example, we introduced a new method, using mechanical deformation of the mask, for magnification correction. We also developed a new wafer stage based on a field proven-high-speed wafer stage from our current optical lithography systems. A stepping time (including settling time) of less than 400 ms for a 50 mm step in a low-pressure helium environment was achieved. These achievements have been integrated into our volume production tool: the XRA-1000 x-ray stepper. The XRA-1000 has been installed in ASET and it will be used as the means for other process module development. Its results will demonstrate that PXL technology is the most practical NGL technology for volume production. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Overlay evaluation of proximity x-ray lithography in 100 nm device fabrication

H. Aoyama, T. Taguchi, Y. Matsui, M. Fukuda, K. Deguchi, H. Morita, M. Oda, T. Matsuda, F. Kumasaka, Y. Iba, and K. Horiuchi

J. Vac. Sci. Technol. B 18, 2961 (2000); http://dx.doi.org/10.1116/1.1319686 (5 pages) | Cited 2 times

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In the semiconductor manufacturing of below 100 nm devices, overlay accuracy is a critical issue for high resolution on proximity x-ray lithography (PXL). We applied PXL for five layers (mark, isolation, gate, contact, and wiring) to fabricate a 100 nm n-type metal–oxide–semiconductor field effect transistor and evaluated the accuracy. Alignment exposure was done with optical heterodyne alignment and magnification correction. The overall overlay accuracy (mean±3σ) was 25–45 nm, and the best was about 25 nm for the contact layer. The overlay error was classified into several components to estimate the error budget. The analysis revealed that the alignment error of the x-ray stepper is less than 20 nm under various conditions in device fabrication. Individual x and y scaling errors caused by mask image placement and the difference of wafer-to-mask gap was from 18–35 nm: the error of common in-plane deformation was about 20 nm. The present accuracy may make it possible to fabricate devices with a 100 nm ground rule. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
85.30.Tv Field effect devices
06.60.Sx Positioning and alignment; manipulating, remote handling

Membrane-mask distortion correction: Analytical and experimental results

Ken-ichi Murooka, Michael H. Lim, and Henry I. Smith

J. Vac. Sci. Technol. B 18, 2966 (2000); http://dx.doi.org/10.1116/1.1314368 (4 pages) | Cited 5 times

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We describe a strategy for eliminating distortion in x-ray masks. Prior to patterning the x-ray absorber, the mask membrane is patterned with a shallow, fine-period fiducial grid, made by interference lithography. After patterning the absorber, the grid is measured using a holographic-phase-shifting interferometer (HPSI) to determine the distortion, i.e., the distribution of displacements from the original grid caused by stress in the absorber. Using an analytical technique we developed, the stress distribution that caused the distortion is calculated from the HPSI measurements using a rapid algorithm. To correct the distortion we follow the proposal of Feldman [J. Vac. Sci. Technol. B 17, 3407 (1999)] and apply a heat distribution such that taking into account thermal diffusion and heat loss the resulting thermal expansion produces a compensating stress distribution. This adaptive x-ray mask should enable real-time distortion correction. We show first-stage experimental results which support its feasibility. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
42.40.Kw Holographic interferometry; other holographic techniques

Nanofabrication and diffractive optics for high-resolution x-ray applications

Erik H. Anderson, Deirdre L. Olynick, Bruce Harteneck, Eugene Veklerov, Gregory Denbeaux, Weilun Chao, Angelic Lucero, Lewis Johnson, and David Attwood

J. Vac. Sci. Technol. B 18, 2970 (2000); http://dx.doi.org/10.1116/1.1321282 (6 pages) | Cited 41 times

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Short wavelength x-ray radiation microscopy is well suited for a number of material and life science studies. The x-ray microscope (XM1) at the Advanced Light Source Synchrotron in Berkeley, California uses two diffractive Fresnel zone plate lenses. The first is a large condenser lens, which collects soft x-ray radiation from a bending magnet, focuses it, and serves as a linear monochromator. The second is the objective zone plate lens, which magnifies the image of the specimen onto a high-efficiency charge coupled device detector. The objective lens determines the numerical aperture and ultimate resolution. New objective lens zone plates with a minimum linewidth of 25 nm and excellent linewidth control have been fabricated using Berkeley Lab’s 100 keV Nanowriter electron beam lithography tool, a calixarene high-resolution negative resist, and gold electroplating. Although the condenser zone plate is less critical to the resolution of the instrument, its efficiency determines the flux on the sample and ultimately the exposure time. A new condenser zone plate was fabricated and has a 9 mm diameter, 44 000 zones, and a minimum zone width of 54 nm (optimally the condenser and objective should have the same zone width). It is also fabricated with the Nanowriter at 100 keV using poly(methylmethacrylate) resist and nickel electroplating. The phase shift through the nickel absorber material enhances the diffraction efficiency over an amplitude only zone plate. To evaluate the microscope’s performance transmission test patterns have been made and imaged. Lineout data show modulation for 30 nm lines and 60 (1:2) spaces to be almost 100%. These new diffractive optical elements represent a significant advancement in the field of high-resolution soft x-ray microscopy. Diffractive optical elements have been used to measure the wave front error of an extreme ultraviolet projection optical system. The reference wave is generated by the spherical wave generated by diffraction from a small freestanding pinhole. © 2000 American Vacuum Society.
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07.85.Tt X-ray microscopes
42.79.Bh Lenses, prisms and mirrors
42.79.Ci Filters, zone plates, and polarizers
42.82.Cr Fabrication techniques; lithography, pattern transfer

Generation of arbitrary three dimensional surfaces by x-ray lithography

M. Feldman, G. S. Lee, D. Noel, C. Khan Malek, and R. Bass

J. Vac. Sci. Technol. B 18, 2976 (2000); http://dx.doi.org/10.1116/1.1321272 (5 pages)

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High aspect ratio microstructure systems with nearly vertical walls are routinely produced by conventional deep x-ray lithography. More complex structures, in which the height is an arbitrary function of position, have many practical applications, for example, as molds for arrays of microscopic optical elements. We have demonstrated a very accurate technique by which such structures may be fabricated by an entirely dry process, using the x-ray ablation of heated Teflon [poly(tetrafluoroethylene)] in an x-ray lithography beamline at the Center for Advanced Microstructures and Devices at Louisiana State University. We observed that the total amount of material ablated is directly proportional to the incident dose. By using a half tone mask, the dose, and hence the amount of material removed, may be accurately controlled at every point on the sample. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Zone-plate-array lithography using synchrotron radiation

A. Pépin, D. Decanini, and Y. Chen

J. Vac. Sci. Technol. B 18, 2981 (2000); http://dx.doi.org/10.1116/1.1321275 (5 pages) | Cited 2 times

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We present our results in the design and development of a multiple-beam x-ray pattern generator based on an array of Fresnel zone plates (FZPs). Exposures have been carried out using a synchrotron source at SuperACO (France), a PC-controlled piezoelectric scanning stage, and an array of FZPs fabricated by high resolution electron-beam lithography and reactive-ion etching of a tungsten absorber. In particular, we have implemented an array of apertures using a self-aligned process in order to minimize background intensity coming from diffraction orders other than the positive first order. We show that even with polychromatic synchrotron radiation and relatively low resolution FZPs, patterns of various geometries could be successfully written in poly(methylmethacrylate) resist and submicrometer resolution was obtained after metal liftoff. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
07.85.Qe Synchrotron radiation instrumentation
42.79.Ci Filters, zone plates, and polarizers

Performance of a compact beamline with high brightness for x-ray lithography

Sayumi Hirose, Tsutomu Miyatake, Xuan Li, Eijiro Toyota, Masaoki Hirose, Kiyoshi Fujii, and Katsumi Suzuki

J. Vac. Sci. Technol. B 18, 2986 (2000); http://dx.doi.org/10.1116/1.1319832 (4 pages) | Cited 2 times

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We have developed a short beamline with high brightness for x-ray lithography. The beamline contains a single, a scanning toroidal mirror and a vacuum-protection system with an acoustic delay line. The practical exposure intensity on a wafer was approximately 50 mW/cm2 at stored electron current of 500 mA. Dose uniformity of ±2.8% was achieved in a 26 mm×26 mm exposure area by optimizing the scan speed. Minimum resolution of 80 nm was obtained with a 15 μm gap. The optimum dose for TDUR-N908 (Tokyo Ohka) was 1300 mA s, which corresponds to exposure time of 2.6 s when the stored electron current is 500 mA. Since the sensitivity of TDUR-N908 is 110 mJ/cm2, the beam intensity in our beamline is estimated to be 43 mW/cm2. By reducing the exposure field, a beam intensity of more than 50 mW/cm2 can be achieved. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
07.85.Qe Synchrotron radiation instrumentation

Highly accurate x-ray masks with 100-nm-class high-density device patterns

Shingo Uchiyama, Masaru Shimada, Tai Tsuchizawa, Takashi Ohkubo, Masatoshi Oda, and Hideo Yoshihara

J. Vac. Sci. Technol. B 18, 2990 (2000); http://dx.doi.org/10.1116/1.1321763 (5 pages)

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We investigated the relationship between pattern size and the distortion due to absorber etching using two types of Ta absorber—one deposited by electron cyclotron resonance (ECR) and another deposited by radio frequency sputtering—with and without a Ru layer underneath. From the comparison of the results, it was confirmed that the combination of ECR Ta and a Ru intermediate layer can dramatically reduce the distortion due to absorber etching even when 80 nm wide patterns are delineated. This structure has been successfully applied to the fabrication of x-ray masks for five layers of a 100-nm-test element group (TEG) and two layers of a 1-Gbit-class dynamic random access memory. The image placement accuracy of a set of masks for five layers of a 100 nm TEG was better than 22 nm. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Overlay compatibility between two synchroton radiation steppers

Makoto Fukuda, Masanori Suzuki, Tsuneyuki Haga, Hirofumi Morita, Hajime Aoyama, Souichirou Mitsui, Takao Taguchi, and Yasuji Matsui

J. Vac. Sci. Technol. B 18, 2995 (2000); http://dx.doi.org/10.1116/1.1319831 (4 pages) | Cited 1 time

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A total overlay accuracy of less than 35 nm was obtained with two synchrotron radiation (SR) x-ray steppers developed by NTT and ASET. This value includes the pattern placement errors of two masks, errors due to the wafer etching process, and errors of two steppers that arise in exposure. The error factors affecting the overlay compatibility among SR x-ray steppers were analyzed using double-exposure experiments. The results show that the overlay error induced by the difference in runout between the two steppers was negligibly small and that the magnification change from shot to shot was caused by gap setting variations between the two steppers. These results demonstrate that a SR x-ray stepper can provide sufficient overlay compatibility for the 100 nm technical node and beyond. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
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Scaled measurements of global space-charge induced image blur in electron beam projection system

Liqun Han, R. Fabian Pease, W. Dan Meisburger, Gil I. Winograd, and Kimitoshi Takahashi

J. Vac. Sci. Technol. B 18, 2999 (2000); http://dx.doi.org/10.1116/1.1314367 (5 pages) | Cited 4 times

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Previous results on simulations of space-charge induced blur in electron projection systems indicated serious limitations on throughput particularly as minimum feature sizes (MFSs) are reduced below 100 nm. For example, a 40-cm-long 50 kV column might have a maximum throughput of only 0.2 cm2/s at MFS=50 nm [R. F. W. Pease et al., MNE, Italy, 1999]. Direct experimental verification is difficult, so we have developed a set of theory-based scaling laws for electron optics and have carried out a series of experiments for verifying these laws. Our experimental results support the earlier predictions and also confirmed that shortening the column length to the minimum allowed by the maximum practical focusing field strengths (e.g., 1 T and 107 V/m) should bring about dramatic (20- to 50-fold) improvements. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.-p Beam optics

Structure of stochastic Coulomb interactions in electron beam columns

Bo Wu and Andrew R. Neureuther

J. Vac. Sci. Technol. B 18, 3004 (2000); http://dx.doi.org/10.1116/1.1324645 (6 pages)

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The stochastic Coulomb interactions in a probe forming beam with a crossover show a strong symmetric structure with respect to the crossover region that can be utilized to reduce beam blur, especially in configurations in which all the beam angles are the same. The blur contribution is nearly constant with distance along the column even though the magnitude of the transverse forces increase nearly inversely with the distance from the crossover. A consequence is that to first order the blur only depends on the beam semiangle and column length. Simulations utilizing fast multipole accelerated techniques show that the blur is about 42 nm for 1 μA current in a 40 cm column with a 1.5 mR Gaussian semiangle. For beam projection systems such as SCAPEL simulation shows that an aperture near the crossover can increase the stochastic blur. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.75.Fr Electron and positron beams

Multisource optimization of a column for electron lithography

M. Mankos, S. Coyle, A. Fernandez, A. Sagle, P. Allen, W. Owens, J. Sullivan, and T. H. P. Chang

J. Vac. Sci. Technol. B 18, 3010 (2000); http://dx.doi.org/10.1116/1.1321752 (7 pages) | Cited 16 times

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The optimization of key parameters determining the performance of a multisource electron column is discussed. A 50 keV multisource test bed incorporating a photocathode and multiple modulated light beams has been developed and tested. The multisource test bed allows for a detailed evaluation of both the photocathode sources and the electron optics for sub-100 nm lithography applications and is designed to reduce electron–electron interactions. Results have been obtained using cesiated GaAs negative electron affinity and gold photocathodes at beam energies varying from 10 to 50 kV, allowing the experimental evaluation of key design parameters. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
85.60.Ha Photomultipliers; phototubes and photocathodes
41.85.Gy Chromatic and geometrical aberrations

Electron optical image correction subsystem in electron beam projection lithography

S. Kojima, W. Stickel, J. D. Rockrohr, and M. Gordon

J. Vac. Sci. Technol. B 18, 3017 (2000); http://dx.doi.org/10.1116/1.1324641 (6 pages) | Cited 9 times

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To obtain ultimate image fidelity in the PREVAIL electron beam projection lithography system (EB stepper) [Pfeiffer et al., J. Vac. Sci. Technol. B 17, 2840 (1999)], precise dynamic corrections [Zhu et al., Proc. SPIE 2522, 66 (1995)] of an exposed reticle subfield image on the wafer are required. The electron beam column for the EB stepper covers a large deflection area by a curvilinear variable axis lens (CVAL) [Stickel and Langner, J. Vac. Sci. Technol. B 17, 2847 (1999)] type deflection with high current, and very large 0.25 mm square beam. Because of these features together with tighter specifications for electron optics in below 70 nm node, aberrations which can be negligible in prior art electron beam lithography systems, can no longer be ignored. Therefore the electron optical image correction subsystem in the EB stepper is required to precisely correct the increased numbers of possible measurable aberrations caused by deflection as well as by space charge effects. In this article, a systematic overview of beam corrections is described. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.Gy Chromatic and geometrical aberrations
41.85.Ne Electrostatic lenses, septa
41.75.Fr Electron and positron beams

Analytic evaluation of the intensity point spread function

Gregg M. Gallatin

J. Vac. Sci. Technol. B 18, 3023 (2000); http://dx.doi.org/10.1116/1.1324617 (6 pages) | Cited 1 time

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The intensity point spread function (PSF) for geometric imaging such as occurs in a projection electron system like SCALPEL is derived analytically from the ray aberration coefficients. The results show that, as expected, the PSF for ordinary aberrations has a finite radius and is not Gaussian. Hence blur estimates, which are often based on assuming a Gaussian PSF and computing the root-sum-square or “rss” of the separate blur radii will generally overestimate the true aberration blur. Global space charge acts like an electrostatic lens and hence its effects can be included in the PSF calculation as well. The net PSF can be convolved with an object to produce an accurate representation of the image. The convolution integral can also be performed first which yields the image intensity distribution directly in terms of the aberrations. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.Gy Chromatic and geometrical aberrations
41.75.Fr Electron and positron beams

Application of the generalized curvilinear variable axis lens to electron projection

W. Stickel and G. O. Langner

J. Vac. Sci. Technol. B 18, 3029 (2000); http://dx.doi.org/10.1116/1.1313579 (5 pages) | Cited 3 times

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The concept of the curvilinear variable axis lens (CVAL) has been introduced for the optics of projection reduction exposure with variable axis immersion lenses, an approach to electron projection lithography reported elsewhere. In the proof-of-concept system the special case of a planar CVAL following the fundamental imaging ray of the lens system was implemented and next generation lithography-commensurate performance was demonstrated. The present work addresses the question of whether general types of CVAL with different configurations of the optical elements are practical and acceptable in performance. Specifically, an analysis is presented of the performance trends of such optics in terms of blur and distortion depending on configuration, number and position of the optical elements in the system, as well as their relative drive requirements. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.Ne Electrostatic lenses, septa
41.85.Gy Chromatic and geometrical aberrations

Computer aided design and analysis of imaging energy filters with inhomogeneous bending magnets

Eric Munro and John Rouse

J. Vac. Sci. Technol. B 18, 3034 (2000); http://dx.doi.org/10.1116/1.1319841 (8 pages) | Cited 1 time

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Software has been written to analyze and design magnetic imaging energy filters. The filters can be composed of any number of bending magnets of homogeneous or inhomogeneous type. The sharp cut-off fringing field approximation is used initially to evaluate quickly many possible designs. Promising designs are then analyzed taking the real fringing fields at the edges of the bending magnets into account, including the full three-dimensional field distributions in conical bending magnets. Graphical postprocessing software displays the optical properties in the energy selection plane and the image plane in the form of spot diagrams and current density contours. © 2000 American Vacuum Society.
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41.85.Lc Particle beam focusing and bending magnets, wiggler magnets, and quadrupoles
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems
41.85.Gy Chromatic and geometrical aberrations
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Prospect for high brightness III–nitride electron emitter

Francisco Machuca, Y. Sun, Z. Liu, K. Ioakeimidi, P. Pianetta, and R. F. W. Pease

J. Vac. Sci. Technol. B 18, 3042 (2000); http://dx.doi.org/10.1116/1.1321270 (5 pages) | Cited 21 times

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We describe p-type gallium nitride (GaN) as a candidate for high brightness photocathodes. Experiments utilizing photoemission spectroscopy and quantum yield measurements were performed on GaN films to characterize various cesium and oxygen activations. Quantum efficiencies of 0.1%–4% were obtained in reflection for the cesiated p-type 0.5 μm thick GaN films and 25%–50% on the 0.1 μm thick GaN films. The corresponding emission currents are 142–300 nA for 0.5 μm thick films and 0.7–1.3 μA for the 0.1 μm thick films. This results in an increase of several orders of magnitude in the emission current from the starting GaN films. Furthermore, an initial desorption measurement was performed in order to evaluate the Cs binding strength to GaN relative to GaAs. We observe Cs was bound to the GaN surface (000math) at 700 °C and completely desorbed at 450 °C for a (100) GaAs surface. Finally, an alternate barium activation on GaN is included for preliminary comparison with the various cesium activations. © 2000 American Vacuum Society.
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85.60.Ha Photomultipliers; phototubes and photocathodes

Depth of field at high magnifications of scanning electron microscopes

Mitsugu Sato and Fumio Mizuno

J. Vac. Sci. Technol. B 18, 3047 (2000); http://dx.doi.org/10.1116/1.1319840 (5 pages) | Cited 2 times

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Depth of field (DoF) in scanning electron microscopes is evaluated at high magnifications where the image resolution is limited by the probe size. The calculation of DoF is made in terms of the information passing capacity of an optical system or entropy of the image estimated along the optical axis near focus. Electron diffraction, source brightness (or source size), and signal-to-noise ratio are taken into account in the calculations of the DoF. The DoF at high magnifications is proportional to Rmin2 where Rmin is resolution of the system, and degrades due to the lack of brightness and aberrations. The DoF in semiconductor applications is also estimated. © 2000 American Vacuum Society.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Demonstration of multiblanker electron-beam technology

G. Winograd, V. Krishnamurthi, R. Garcia, L. H. Veneklasen, M. Mankos, and F. Pease

J. Vac. Sci. Technol. B 18, 3052 (2000); http://dx.doi.org/10.1116/1.1321757 (5 pages) | Cited 9 times

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A set of multiple electron-beam (e-beam) aperture/blanker chips have been fabricated using silicon microelectro-mechanical systems (MEMS) techniques. The aperture sizes range from 8 to 4 μm (nominal) squares, and the chip configurations feature either eight individually controlled monopolar blanker electrodes or four bipolar electrode pairs. The chips replace the shapers of a 20 kV AEBLE™ shaped e-beam lithography column. The apertures in the chips convert an incident 150 μm diameter e-beam into multiple beamlets. Each beamlet can be independently blanked off of a 100 μm aperture placed at the following beam crossover. Data are presented that demonstrates the ability to independently blank each beamlet by applying 10 V. Magnified images of the beamlets show square or rectangular shapes with sharp corners, indicating that the apertures were properly fabricated. The degree of electrostatic blanker crosstalk was measured and found to be up to 15% at the crossover plane for different pairs of beamlets, but no observable beam displacement occurred at the image plane. We compared the experimental results to a rough model that estimates the effect of the electrostatic field distribution of one excited blanker electrode on the unblanked beams. The results matched to within 20%. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Optimization of microcolumn electron optics for high-current applications

M. Mankos, K. Y. Lee, L. Muray, J. Spallas, Y. Hsu, C. Stebler, W. DeVore, E. Bullock, and T. H. P. Chang

J. Vac. Sci. Technol. B 18, 3057 (2000); http://dx.doi.org/10.1116/1.1321756 (4 pages) | Cited 4 times

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The optimization of electron-optical properties of a microcolumn for high-current, high-resolution applications in microcolumn arrays is discussed. The goal of the optimization is to increase the current available in the microcolumn to approximately 10–50 nA while maintaining a spot size sufficiently small for sub-100 nm technology (not larger than approximately 20–50 nm). To achieve this goal, it is necessary to operate the microcolumn as a two-lens electron-optical system. The electron-optical performance of the single-lens and two-lens microcolumn operational modes is compared at 1 keV beam energy, angular intensity of 100 μA/sr, and a working distance of 1 mm. The two-lens mode can achieve spot sizes from 25 to 50 nm for a wide range of beam currents, up to 50 nA. A two-lens microcolumn has been built and evaluated, and the experimental data is presented. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.Gy Chromatic and geometrical aberrations
41.85.Ne Electrostatic lenses, septa
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

New concept for high-throughput multielectron beam direct write system

Masato Muraki and Susumu Gotoh

J. Vac. Sci. Technol. B 18, 3061 (2000); http://dx.doi.org/10.1116/1.1320798 (6 pages) | Cited 17 times

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A new multielectron-beam optical system with correction lens array (CLA) is proposed. The CLA is arranged between an electron source and reduction optics. The CLA can generate plural intermediate images of the electron source as a multisource, and moreover can compensate field curvature and distortion of the reduction optics. The proposed system was designed and optimized through simulations. The specifications are field size of 250 μm square, convergence beam angle of 10 mrad, 64×64 beams, individual beam size of ϕ25 nm, accelerating voltage of 50 kV, and demagnification ratio of 50. The practical resolution for various resist processes is estimated considering the Coulomb interaction effect, and the throughput is simulated. The proposed system offers the possibility of “maskless” electron beam lithography with throughput in excess of 50 wafers/h (8 in.) for the International Technology Roadmap for Semiconductors (ITRS) 100 nm and 70 nm nodes at 3 μC/cm2 resist sensitivity. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.Ne Electrostatic lenses, septa
41.75.Fr Electron and positron beams

Correction of the field curvature in SCALPEL projection systems

K. Xiu and J. M. Gibson

J. Vac. Sci. Technol. B 18, 3067 (2000); http://dx.doi.org/10.1116/1.1321287 (5 pages)

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The field curvature and axial chromatic aberration, 2 of 13 aberrations in an electron optical system, make the major contributions to the image blur of a SCALPEL projector. We first give a simple yet quantitative evaluation of the point spread function from the field curvature and chromatic aberration and show the merit of keeping a comparatively low field curvature. Then we describe two ways to reduce the field curvature in an electron projection system. One is to use an immersion magnetic doublet with a constant field along most of the optical column with opposite signs at two ends which are connected by a sharp field transition region. The other way is to use space charge foils. By putting a space charge foil with homogeneously distributed space charge density on either the object or image plane, we show the field curvature can be eliminated in principle without affecting any other aberrations. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.Gy Chromatic and geometrical aberrations
41.85.Lc Particle beam focusing and bending magnets, wiggler magnets, and quadrupoles
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PREVAIL Alpha system: Status and design considerations

S. D. Golladay, H. C. Pfeiffer, J. D. Rockrohr, and W. Stickel

J. Vac. Sci. Technol. B 18, 3072 (2000); http://dx.doi.org/10.1116/1.1314381 (7 pages) | Cited 6 times

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An overview is given of the PREVAIL Alpha system program, a joint project of IBM and Nikon to develop a production-level electron project lithography system. The Alpha system program is based on the successful completion of an initial feasibility phase conducted by the IBM/Nikon alliance team and on the PREVAIL proof of concept results reported at EIPBN 1999. The electron beam column and associated electronics and software are under development at IBM’s Semiconductor R&D Center in East Fishkill, New York, while the high speed, high precision stages for both reticle and wafer as well as the overall systems architecture are being developed at Nikon’s facilities. A key architectural objective is the combination of leading edge stepper technology with state-of-the-art PREVAIL electron optics. The design of the electron optics is based on carefully balancing geometric aberrations and Coulomb interactions for optimum resolution at the required high beam current. Cornerstones of the design are the high emittance gun and the curvilinear variable axis lens concept developed for PREVAIL. Design considerations of the Alpha column are emphasized including a detailed treatment of space-charge lens aberrations. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.Gy Chromatic and geometrical aberrations

PREVAIL: Dynamic correction of aberrations

M. S. Gordon, W. A. Enichen, S. D. Golladay, H. C. Pfeiffer, C. F. Robinson, and W. Stickel

J. Vac. Sci. Technol. B 18, 3079 (2000); http://dx.doi.org/10.1116/1.1319710 (5 pages) | Cited 1 time

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The curvilinear variable axis lens concept for the PREVAIL proof-of-concept (POC) system, and its practical implementation have been described in a previous publication [H. C. Pfeiffer et al., J. Vac. Sci. Technol. B 6, 2844 (1999)]. The objective of this article is to show experimental results regarding the dynamic compensation of the deflection-dependent focus and astigmatism aberration control in the projected subfield. The POC system contains a plurality of dynamic correction elements in the imaging section between reticle and wafer. Using a pair of properly positioned stigmators, we have demonstrated nearly independent control of feature astigmatism (image quality) and subfield distortion (shape astigmatism). In this article, we will describe a technique that was used to control the subfield distortion. In addition, using three dynamic focus coils, and an inverted sensitivity matrix approach, we have also demonstrated independent control of the subfield magnification, rotation, and axial focus. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.Gy Chromatic and geometrical aberrations
41.85.Lc Particle beam focusing and bending magnets, wiggler magnets, and quadrupoles

Patterning performance of EB-X3 x-ray mask writer

Shigehisa Ohki, Toshifumi Watanabe, Yuji Takeda, Tetsuo Morosawa, Kenichi Saito, Tatsuya Kunioka, Junichi Kato, Akira Shimizu, Tadahito Matsuda, Shinji Tsuboi, Hajime Aoyama, Hiroshi Watanabe, and Yoshinori Nakayama

J. Vac. Sci. Technol. B 18, 3084 (2000); http://dx.doi.org/10.1116/1.1319708 (5 pages) | Cited 2 times

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An intensive study of the patterning performance of the EB-X3 revealed that the placement accuracy of a written image was degraded by the thermal effect originating from the temperature difference between the stage and the palette. An optimal writing procedure consisting of two temperature stabilization steps was developed. This procedure enables the EB-X3 to attain an image placement accuracy of better than 10 nm (3σ). A critical dimension control of 7.4 nm (3σ) has been confirmed over a 25-mm-square field. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
07.05.Dz Control systems

Evaluation of a 100 kV thermal field emission electron-beam nanolithography system

D. M. Tennant, R. Fullowan, H. Takemura, M. Isobe, and Y. Nakagawa

J. Vac. Sci. Technol. B 18, 3089 (2000); http://dx.doi.org/10.1116/1.1319707 (6 pages) | Cited 4 times

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We report on the results of performance evaluation tests of a JEOL model JBX-9300FS electron- beam nanolithography system operating at 100 kV. The system was tested in the areas of lithographic resolution, stability, exposure uniformity, and pattern placement accuracy. A minimum spot size of 4 nm was measured at a current of 100 pA. The spot remained below 6.5 nm for beam currents up to 8 nA. Maximum digital to analog converter linearity and deflection amplifier errors were below 0.5 nm. Pattern placement accuracy in a 50 mm square area was found to be within ±16 nm and inside the 500 μm writing field within ±7 nm. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
41.85.-p Beam optics

Calculation of surface potential and beam deflection due to charging effects in electron beam lithography

Yongjae Lee, Woojin Lee, and Kukjin Chun

J. Vac. Sci. Technol. B 18, 3095 (2000); http://dx.doi.org/10.1116/1.1319822 (4 pages) | Cited 5 times

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In this article, we describe the analysis procedures of charging effects and calculation results of surface potential and beam deflection in electron beam lithography. Monte Carlo simulation is performed to obtain the charge distribution in e beam resist. A focused (Gaussian) and a flood beam are considered for beam shapes of the exposure system. The effects of discharging due to electron beam induced conductivity are included in the analysis. The Poisson equation is solved for the potential distribution by using the simultaneous overrelaxation method. The iteration technique is used for the convergence of the potential. With the given potential distribution, beam deflection is calculated using the fourth order Runge–Kutta integration algorithm. Comparison of the values of the surface potential obtained by simulations with experimental results by Pease' group at Stanford University show similar shapes between them. We also have applied this work to a SCALPEL mask with a thin silicon nitride membrane. This work will be helpful for the exact understanding and avoidance of charging effects, when an electron beam is irradiating an insulator. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
02.70.Rr General statistical methods

Advances in arrayed microcolumn lithography

L. P. Muray, J. P. Spallas, C. Stebler, K. Lee, M. Mankos, Y. Hsu, M. Gmur, and T. H. P. Chang

J. Vac. Sci. Technol. B 18, 3099 (2000); http://dx.doi.org/10.1116/1.1321760 (6 pages) | Cited 14 times

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A microcolumn array has been designed, fabricated, and tested. The 2×2 array has a 2 cm pitch and operates at 1 keV. Key components include vertical interconnects, silicon low-distortion octupole deflectors, miniature long-range flexure-based tip positioners, and low-power thermal field emitters. Initial results show no observable crosstalk between columns during simultaneous operation at a 50 MHz beam blanking rate. Preliminary lithography results are presented. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Quantitative factor analysis of resolution limit in electron beam lithography using the edge roughness evaluation method

Masaki Yoshizawa and Shigeru Moriya

J. Vac. Sci. Technol. B 18, 3105 (2000); http://dx.doi.org/10.1116/1.1319844 (6 pages) | Cited 8 times

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Various factors influencing the resolution limit (RL) in electron beam (EB) lithography have been analyzed quantitatively using the edge roughness evaluation (ERE) method. The ERE method is based on the experimental finding that line edge roughness of a resist pattern is inversely proportional to the slope of the Gaussian-distributed quasi-beam-profile (QBP). The analysis reveals that beam blur and development process are primary factors of RL, that electron forward scattering is negligible with the resist thickness under 200 nm, and that the effect of aperture degradation on RL is as large as that of resist performance. A necessary and sufficient condition for realizing 50 nm patterns is following. Use of EB lithography instruments of which beam blur is under 31 nm, resist thickness of 200 nm, and 20% improvement of the resist performance accompanying optimum development condition. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Grid lens approach for high effective emittance in SCALPEL®

D. Moonen, S. van Kranen, P. Kruit, V. Katsap, and W. K. Waskiewicz

J. Vac. Sci. Technol. B 18, 3111 (2000); http://dx.doi.org/10.1116/1.1324643 (4 pages) | Cited 1 time

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The emittance required for the SCALPEL system is very large; on the order of 2 mm mrad. This can be achieved with an electron source using advanced, large area cathodes and complicated extraction optics, but in this article an alternative approach is presented: devices which increase the effective emittance of an electron beam by creating an array of subbeams. After we have explained the theory, we discuss three different configurations which form electrostatic microlens array-like fields, and we show results from computer modeling. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.Ne Electrostatic lenses, septa
41.75.Fr Electron and positron beams

Analytical-based solutions for SCALPEL wafer heating

N. Fares, S. Stanton, J. Liddle, and G. Gallatin

J. Vac. Sci. Technol. B 18, 3115 (2000); http://dx.doi.org/10.1116/1.1319839 (7 pages)

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When operating in high-throughput conditions, SCALPELs 100 keV electron beam causes significant dynamic wafer deformation. To complement extensive finite element analysis, we have undertaken an analytical solution to the governing heat transfer and elastic strain equations and boundary conditions. This efficient, Green’s function-based computational approach is able to support a robust and versatile image-placement correction strategy. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Charge induced pattern distortion in low energy electron beam lithography

K. M. Satyalakshmi, A. Olkhovets, M. G. Metzler, C. K. Harnett, D. M. Tanenbaum, and H. G. Craighead

J. Vac. Sci. Technol. B 18, 3122 (2000); http://dx.doi.org/10.1116/1.1321755 (4 pages) | Cited 8 times

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Charge induced pattern distortions in low voltage electron beam lithography in the energy range of 1 to 5 kV were investigated. Pattern distortion on conducting substrates such as silicon was found to be small, while significant pattern placement errors and pattern distortions were observed in the case of electrically insulating substrates caused by charge trapping and deflection of the incident electron beam. The nature and magnitude of pattern distortions were found to be influenced by the incident electron energy, pattern size, electrical conductivity, and secondary electron emission coefficient of the substrate. Theoretical modeling predicts the electron beam deflection to be directly proportional to the trapped surface charge density and inversely proportional to the accelerating voltage. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Electron optical column for a multicolumn, multibeam direct-write electron beam lithography system

E. Yin, A. D. Brodie, F. C. Tsai, G. X. Guo, and N. W. Parker

J. Vac. Sci. Technol. B 18, 3126 (2000); http://dx.doi.org/10.1116/1.1318187 (6 pages) | Cited 17 times

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Electron beam direct-write lithography systems are capable of meeting the resolution requirements of all future ITRS nodes and have a significant cost of ownership advantage over masked technologies, but these systems typically have very poor throughput due to space charge limitations. Ion Diagnostics has developed a multicolumn, multibeam (M×M™) direct-write system that circumvents the space charge limitations by spreading the electron current over the wafer. The resulting lithography system can achieve critical dimensions of less than 100 nm with production throughputs greater than 60 wafers per hour, independent of wafer size. In this article we describe the electron optical column used in this system. We have developed a novel, microfabricated electron gun that produces 32 parallel electron beams that are individually controlled and blanked and contain deflectors that allow the gun optics to act as a perfect lens. Each column is 2 cm×2 cm and can align and scan the 32 beams in parallel on the wafer. The wafer voltage is typically held at 50–100 kV, and backscattered electrons are collected for imaging and alignment information. Theoretical results and some performance results for a prototype column are presented. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
84.47.+w Vacuum tubes
41.85.Ne Electrostatic lenses, septa

Demagnifying immersion magnetic lenses used for projection electron beam lithography without crossovers

Min Cheng and Tiantong Tang

J. Vac. Sci. Technol. B 18, 3132 (2000); http://dx.doi.org/10.1116/1.1320796 (6 pages)

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Curvilinear-axis electron optical focusing and aberration theory of wide electron beams in immersion magnetic lenses, which can be used for projection electron beam lithography, are put forward, and second-order aberration formulas have been derived using the symbolic manipulation software MATHEMATICA®. A program was written to calculate numerically the wide beam Gaussian focusing and aberration properties of these lenses by using the curvilinear-axis theory. The magnetic structures that have convergent force lines have been studied. As an example, lenses with an analytical axial magnetic field distribution are calculated. The results show that wide beam projection images without crossovers can be formed with demagnified lateral magnification, and with a submicron and nanometer lateral resolution over a larger field size. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.Lc Particle beam focusing and bending magnets, wiggler magnets, and quadrupoles
41.75.Fr Electron and positron beams
41.85.Gy Chromatic and geometrical aberrations

Implementation of real-time proximity effect correction in a raster shaped beam tool

V. Boegli, L. Johnson, H. Kao, L. Veneklasen, U. Hofmann, I. Finkelstein, S. Stovall, and S. Rishton

J. Vac. Sci. Technol. B 18, 3138 (2000); http://dx.doi.org/10.1116/1.1324614 (5 pages) | Cited 1 time

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A method for real-time backscatter correction has been implemented in a 50 keV raster-scan electron-beam mask exposure system. The real-time nature of the correction makes it an attractive, user transparent feature with flexibility to choose the correction algorithm and scattering parameters. This article describes the correction algorithms and the hardware added to the data path. We compare simulated critical dimension (CD) linearity with results from mask exposures in our new raster shaped beam proof-of-concept tool. Performance meets both throughput and CD linearity requirements for the 130 and 100 nm device generations. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Sub-0.1 μ electron-beam lithography for nanostructure development

Martin Peckerar, Robert Bass, and Kee Woo Rhee

J. Vac. Sci. Technol. B 18, 3143 (2000); http://dx.doi.org/10.1116/1.1321278 (7 pages) | Cited 8 times

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This article discusses those factors that lead to resolvability in e-beam lithography. The primary tool of study is the simplex method of linear optimization theory. Resist exposure characteristics can effectively be accounted for using a “minimum contrast” approach. The simplex exposure technique does not require exposure in the normally unexposed field. Feature linearity comparison experiments and boundary placement studies show measurable improvement with simplex when compared to dose scaling or feature boundary resizing. While computational tractability is a significant issue, the technique will rapidly assess whether small groups of features are resolvable. In addition, simplex points to general rules for applying dose modulation to different classes of features. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
02.60.Pn Numerical optimization
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

Proximity effect correction using pattern shape modification and area density map

Kimitoshi Takahashi, Morimi Osawa, Masami Sato, Hiroshi Arimoto, Kozo Ogino, Hiromi Hoshino, and Yasuhide Machida

J. Vac. Sci. Technol. B 18, 3150 (2000); http://dx.doi.org/10.1116/1.1313576 (8 pages) | Cited 7 times

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A proximity effect correction program in which forward scattering is corrected by shape modification and backscattering is corrected by dose modulation is developed. The amount of the shape modification is determined in such a manner that the full width at half maximum of the forward scattering profile is equal to the designed size. The half maximum of the forward scattering profile is equalized by the dose modulation after the amount of the backscattering is evaluated by the area density map method. This algorithm automates pattern biasing to improve the resolution and assures the resulting pattern size is as designed. The following features are included to improve the conventional methods: The area density map is smoothed iteratively to include higher order effect. Smaller meshes are used for better discretization accuracy. Auxiliary shots are generated to refine correction units where the spatial profile of the deposited energy is steep. The corrected results of 60 nm lines are also presented. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
42.30.Va Image forming and processing
02.70.Dh Finite-element and Galerkin methods
02.60.-x Numerical approximation and analysis
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Carrier distribution profiles in Si-doped layers in GaAs formed by focused ion beam implantation and successive overlayer growth

Takuo Hada, Takayuki Goto, Junichi Yanagisawa, Fujio Wakaya, Yoshihiko Yuba, and Kenji Gamo

J. Vac. Sci. Technol. B 18, 3158 (2000); http://dx.doi.org/10.1116/1.1319683 (4 pages) | Cited 1 time

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Selectively doped layers buried in GaAs were formed by low (50 and 200 eV) and high (30 keV) energy focused Si ion implantation and successive overlayer growth using a focused ion beam/molecular beam epitaxy (MBE) combined system to investigate the possibility to form patterned δ-doped layers. Carrier distribution profiles were measured by means of a capacitance–voltage profiling technique at room temperature. It was found for the low-energy implantation that the width of the depth profiles of the carrier distribution decreased with increasing sheet carrier density and was roughly in agreement with a theoretical estimation obtained by solving the Poisson equation. The width was decreased when the sheet carrier density increased by annealing. This indicates that the width is determined by a sheet carrier density and not by Si dopant profiles, and that narrower carrier profiles can be formed by optimizing annealing parameters, although the widths were 2–5 times wider than those observed for the MBE-grown δ-doped GaAs. The same doping efficiency as for the low-energy implantation was achieved but the distribution width was close to that of the dopant distribution. © 2000 American Vacuum Society.
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61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.61.Ey III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing
85.40.Ry Impurity doping, diffusion and ion implantation technology

Focused ion beam patterning of III–V crystals at low temperature: A method for improving the ion-induced defect localization

M. Schneider, J. Gierak, J. Y. Marzin, B. Gayral, and J. M. Gérard

J. Vac. Sci. Technol. B 18, 3162 (2000); http://dx.doi.org/10.1116/1.1328054 (6 pages)

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In this study we have investigated the damage distribution induced by a focused ion beam irradiation on a GaAlAs/GaAs heterostructure. The samples were kept at various temperatures during ion bombardment: room temperature (RT), 80 and 22 K. The samples were then characterized, after being warmed up at RT, using photoluminescence (PL) experiments without any subsequent annealing. Stable, reproducible, and localized modulation of the PL characteristics of several GaAlAs/GaAs heterostructures are demonstrated. The defect localization is found to be considerably improved for a sample kept at 22 K during irradiation. © 2000 American Vacuum Society.
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61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors

Focused electron beam induced deposition of gold

I. Utke, P. Hoffmann, B. Dwir, K. Leifer, E. Kapon, and P. Doppelt

J. Vac. Sci. Technol. B 18, 3168 (2000); http://dx.doi.org/10.1116/1.1319690 (4 pages) | Cited 64 times

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Codeposition of hydrocarbons is a severe problem during focused electron beam writing of pure metal nanostructures. When using organometallic precursors, a low metal content carbonaceous matrix embedding and separating numerous nanosized metal clusters is formed. In this work, we present a new and easy approach to obtain high purity gold lines: the use of inorganic PF3AuCl as a precursor. Electrical resistivities as low as 22 μΩ cm at 295 K (ten times the bulk Au value) were obtained. This is to our knowledge the best value for focused electron beam deposition obtained from the vapor phase so far. No special care was taken to prevent hydrocarbon contamination. The deposited nanostructure consists of gold grains varying in size and percolation with beam parameters. © 2000 American Vacuum Society.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
73.61.At Metal and metallic alloys
68.55.-a Thin film structure and morphology
81.05.Bx Metals, semimetals, and alloys
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
61.46.-w Structure of nanoscale materials

Pattern generators and microcolumns for ion beam lithography

K. L. Scott, T.-J. King, M. A. Lieberman, and K.-N. Leung

J. Vac. Sci. Technol. B 18, 3172 (2000); http://dx.doi.org/10.1116/1.1314384 (5 pages) | Cited 4 times

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A self-aligned microfabrication process has been developed for micron-sized extraction systems, which can be used for pattern generators or microcolumns in ion beam lithography. The extraction of ions from a plasma source through micron-sized apertures is shown not to follow traditional design rules, and the governing equations of interest for meeting design parameters are presented. First order focal properties of the pattern generator and microcolumn are described using Davisson and Calbick’s derivation [C. J. Davisson and C. J. Calbick, Phys. Rev. 38, 558 (1931); 42, 580 (1932)] for an aperture lens. A second order refinement of the focal properties is characterized and explained with computer simulations using MEBS©. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.Ar Particle beam extraction, beam injection
41.85.Ne Electrostatic lenses, septa

Determination of resist exposure parameters in helium ion beam lithography: Absorbed energy gradient, contrast, and critical dose

P. Ruchhoeft and J. C. Wolfe

J. Vac. Sci. Technol. B 18, 3177 (2000); http://dx.doi.org/10.1116/1.1319830 (4 pages) | Cited 3 times

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We study the relationship between the true resist contrast (γtrue) and the apparent contrast (γHD), as determined by the slope of the Hurter–Driffield (HD) curve, in He+ ion beam lithography. These parameters can differ significantly because the absorbed energy density is a function of depth in the resist. We formulate an analytical model, using a linear approximation to the deposited energy distribution, that permits the extraction of the absorbed energy gradient, the true resist contrast, and the critical dose from experimental HD curves. The model accurately describes both experimental and simulation results. We show that the contrast for poly(methylmethacrylate) resist is 2.9 for various He+ ion energies even though the apparent contrast can be as low as unity at 50 keV. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
02.70.Rr General statistical methods

Three-dimensional nanostructure fabrication by focused-ion-beam chemical vapor deposition

Shinji Matsui, Takashi Kaito, Jun-ichi Fujita, Masanori Komuro, Kazuhiro Kanda, and Yuichi Haruyama

J. Vac. Sci. Technol. B 18, 3181 (2000); http://dx.doi.org/10.1116/1.1319689 (4 pages) | Cited 140 times

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Three-dimensional nanostructure fabrication has been demonstrated by 30 keV Ga+ focused ion beam assisted deposition using a aromatic hydrocarbon precursor. The characterization of deposited film on a silicon substrate was performed by a transmission microscope and Raman spectra. This result indicates that the deposition film is a diamondlike amorphous carbon. Production of three-dimensional nanostructure is discussed. Microcoil, drill, and bellows with 0.1 μm dimension were fabricated as parts of the microsystem. Furthermore, microstructure plastic arts is advocated as a new field using microbeam technology, presenting one example of a microwine glass with 2.75 μm external diameter and 12 μm height. © 2000 American Vacuum Society.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
07.10.Cm Micromechanical devices and systems
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
78.66.Jg Amorphous semiconductors; glasses
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Optimal strategy for controlling linewidth on spherical focal surface arrays

P. Ruchhoeft and J. C. Wolfe

J. Vac. Sci. Technol. B 18, 3185 (2000); http://dx.doi.org/10.1116/1.1319842 (5 pages) | Cited 3 times

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We present a method for patterning concave spherical substrates based on ion beam proximity lithography. The approach overcomes both the distortion and radial dose variation that are inherent to projecting a flat mask pattern onto a sphere. We use a self-complementary mask (SCM) concept where an array of discrete ion beamlets is scanned across the substrate to expose the circuit pattern. This scanning is implemented by varying the inclination of the incident ion beam with respect to the mask. Pincushion distortion is corrected by applying a global transformation to the centers of the SCM openings while a local transformation, applied within each opening, ensures that the beamlets stitch together properly on the substrate and that the ion dose is uniform. We show that the linewidth variation for 1 μm features is less than ±80 nm over a 7.2 mm deep, spherical bowl with a 1.5 cm radius of curvature. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.Gy Chromatic and geometrical aberrations
42.79.Pw Imaging detectors and sensors

Modeling of focused ion beam induced surface chemistry

Klaus Edinger and Thomas Kraus

J. Vac. Sci. Technol. B 18, 3190 (2000); http://dx.doi.org/10.1116/1.1321761 (4 pages) | Cited 12 times

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A new macroscopic model for focused ion beam induced surface chemistry is presented. The model consists of two parts. The first part is based on previous work by several authors and assumes a uniform current distribution for the ion beam. In this case an analytical solution for the reaction yield can be obtained. Compared to previous work, the new model shows an improved agreement with experimental data and delivers physically meaningful parameter values. In an extended model a Gaussian beam shape has been used to account for the spatial and temporal variations in the current distribution, which are present in a real focused ion beam system. In this case the analytical solution for the yield dependence has to be solved using a spatially depended ion flux and integrated over the whole area of the pixel, which was done numerically. This model shows very good agreement with experimental data and delivers a consistent set of parameters values. In addition, experimental changes in parameter values such as beam size (defocusing) and pixel step size are accurately reflected in the simulation. © 2000 American Vacuum Society.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
82.50.-m Photochemistry

Performance of multicusp plasma ion source for focused ion beam applications

L. Scipioni, D. Stewart, D. Ferranti, and A. Saxonis

J. Vac. Sci. Technol. B 18, 3194 (2000); http://dx.doi.org/10.1116/1.1320797 (4 pages) | Cited 19 times

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The multicusp plasma ion source has found many uses such as in ion implanters, ion projection lithography, and injectors for particle accelerators. This source is favorable for such applications because of its low ion temperature, small energy spread, and good stability. These properties also offer the tantalizing possibility of utilizing such a source to create a noncontaminating focused ion beam (FIB) system for semiconductor fabrication line use and advanced photomask repair applications. We have made measurements of the brightness of this ion source and have done some preliminary applications work with a Kr+-enabled FIB system for mask repair and ion milling. A specially designed multicusp plasma ion source has been used to measure focused beam spot size versus current relationships for several inert gas ion species. From these data the axial brightness of the ion source was ascertained. For the extraction of Kr+ from the source we find an angular intensity of 12 μA/sr and a virtual source size of 16.9 μm, giving an approximate value for the image-side brightness (at 30 keV) of 1650 A/cm2 sr. We find good sputtering rates for the Kr+ beam, and the Aerial image measurement system measurements show essentially 100% transmission of 193 nm light through photomask quartz that had been implanted with a significant dose of krypton. © 2000 American Vacuum Society.
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29.25.Ni Ion sources: positive and negative
07.77.Ka Charged-particle beam sources and detectors
41.75.Ak Positive-ion beams

Maskless deposition of gold patterns on silicon

Lynden E. Erickson, Patrik Schmuki, and Garth Champion

J. Vac. Sci. Technol. B 18, 3198 (2000); http://dx.doi.org/10.1116/1.1321753 (4 pages) | Cited 4 times

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We demonstrate that electrochemical metal deposition selectivity may be attained by intentionally introducing defects in a semiconductor surface. The electrolyte–semiconductor surface shows a similar characteristic to a p–n junction, which when reverse biased into (Schottky) breakdown, electrochemical reactions become possible. To achieve electrochemical deposition of metals, a p-type semiconductor must be used. The defects are patterned by focused ion beam silicon ion implantation. Gold was selectively deposited only on the defective surface from a gold containing KCN electrolyte. © 2000 American Vacuum Society.
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85.40.Sz Deposition technology
85.40.Ry Impurity doping, diffusion and ion implantation technology
85.40.Hp Lithography, masks and pattern transfer
81.15.Pq Electrodeposition, electroplating
61.72.uf Ge and Si
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Fabrication of open stencil masks with asymmetric void ratio for the ion projection lithography space charge experiment

B. Volland, F. Shi, H. Heerlein, I. W. Rangelow, P. Hudek, I. Kostic, E. Cekan, H. Vonach, H. Loeschner, C. Horner, G. Stengl, H. Buschbeck, M. Zeininger, A. Bleeker, and J. Benschop

J. Vac. Sci. Technol. B 18, 3202 (2000); http://dx.doi.org/10.1116/1.1319688 (5 pages) | Cited 3 times

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For the ion projection lithography space charge experiment [P.W.H. de Jager et al., J. Vac. Sci. Technol. B 17, 3098 (1999)] a suitable stencil test mask has been realized and used. This article addresses the stress engineering and fabrication process of this specific test mask with openings in the range of some few 100 nm up to some 100 μm. This large difference in stencil pattern dimensions causes reactive ion etching (RIE) lag (dependence of the etch rate on feature size and pattern density) during the fabrication process and considerable stress variations across the membrane field. The solution to these problems was by (i) implementing novel doping technologies to create variable thickness areas on the membrane serving as reinforcement and stress relief structures, and (ii) adjusting the design to feature sizes and pattern densities to the same order of magnitude for the e-beam lithography and RIE processing steps. The etching of the openings through the 3 μm thick Si membrane was done by inductively coupled plasma etching with gas chopping techniques. These methods as devoloped for this specific test mask can be used to improve the stencil mask technology in general. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
85.40.Ry Impurity doping, diffusion and ion implantation technology
61.72.uf Ge and Si

Experimental evaluation of an optimized radiation cooling geometry for ion projection lithography masks

J. L. Torres, H. N. Nounu, J. R. Wasson, J. C. Wolfe, J. Lutz, E. Haugeneder, H. Löschner, G. Stengl, and R. Kaesmaier

J. Vac. Sci. Technol. B 18, 3207 (2000); http://dx.doi.org/10.1116/1.1314380 (3 pages) | Cited 3 times

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In this article, we study an optimized radiative cooling geometry for ion projection lithography masks. In this design, a polished infrared mirror guides radiation from the mask to a high-emissivity cooled-cylinder positioned about 0.5 m away. Previous finite element modeling of this system predicts thermal distortion below 1 nm for practical mask designs. This is the first experimental study of the design. We show, by measuring the mean mask stress as a function of cooled cylinder temperature, that radiative cooling balances beam heating, with a power density of 2.15 mW/cm2, when the cooled cylinder is held at 15 °C and the temperature of the mirror and mask frame are at 25 °C. The results agree with finite element modeling. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Fabrication of masks for electron-beam projection lithography

Michael Lercel, Chris Magg, Monica Barrett, Kevin Collins, Michael Trybendis, Neal Caldwell, Ray Jeffer, and Lucien Bouchard

J. Vac. Sci. Technol. B 18, 3210 (2000); http://dx.doi.org/10.1116/1.1314370 (6 pages) | Cited 3 times

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Masks for electron projection lithography (EPL) require the use of thin membranes for either stencil or all membrane scattering masks. The processes of forming the printable patterns before or after the membrane etch step are compared for EPL stencil masks. Image size uniformity and image placement distortions are characterized and indicate, with appropriate process optimization, either process flow is viable for EPL mask manufacture. Image size uniformity within individual membranes has achieved <10 nm (3σ) with the membrane flow process, and the magnitude of process induced image placement distortions is similar for both process flows. Stencil masks have also been fabricated with support rings. The masks with support rings show more repeatable absolute image placement, but the image placement distortion due to patterning is nearly identical for masks with or without a support ring. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Progress in extreme ultraviolet mask repair using a focused ion beam

Ted Liang, Alan Stivers, Richard Livengood, Pei-Yang Yan, Guojing Zhang, and Fu-Chang Lo

J. Vac. Sci. Technol. B 18, 3216 (2000); http://dx.doi.org/10.1116/1.1319687 (5 pages) | Cited 30 times

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The key challenge in extreme ultraviolet (EUV) mask defect repair is to avoid or limit the damage to the sensitive reflective multilayer (ML) stacks on the mask substrate and repair <55 nm mask defects. Our EUV mask design employs an oxide buffer layer between the ML and the absorber to protect the ML during repair. We have developed both opaque and clear EUV mask defect repair processes using focus ion beam (FIB) based gas-assisted etching (GAE) and ion-induced deposition. The process has been successfully demonstrated on our TiN baseline mask by 10× EUV print tests of 100 nm resist lines/spaces. More importantly we have assessed the current FIB tool performance capability and compared it with the general requirements for repairing the EUV mask for the 70 nm lithography node. The characterization includes minimum “effective” beam size, etch selectivity, and edge placement precision. We discussed the required improvements and future directions in repair tool research and development in order for the mask repair technology to keep pace with lithography scaling in future generations. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning
81.15.Jj Ion and electron beam-assisted deposition; ion plating
85.40.Sz Deposition technology

Mechanical analysis of the PLASMAX particle removal process for optical and next-generation lithography masks

W. H. Semke, E. J. Weisbrod, R. L. Engelstad, E. G. Lovell, J. J. Festa, and J. B. Bailey

J. Vac. Sci. Technol. B 18, 3221 (2000); http://dx.doi.org/10.1116/1.1314369 (6 pages) | Cited 1 time

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The ability to clean advanced lithographic masks in a cost-effective manner is becoming increasingly important as the semiconductor industry continues integrated circuit development with ever-decreasing feature sizes. The plasma mechanical activation and extraction of particle contamination (PLASMAX) particle removal process, under development by Beta Squared, Inc., provides a means to achieve the industry’s needs for both the current optical and next-generation lithography (NGL) masks. This cleaning procedure is imperative since all NGL technologies are unable to use a conventional protective pellicle. The cleaning process implements a charged plasma flow in conjunction with mechanical excitation. This article presents the results of research to identify the optimal procedures to mechanically oscillate 6 in. fused silica reticles and electron-beam projection lithography masks. Using both numerical and experimental methods, the analysis characterizes the dynamic response of lithographic masks to quantify and optimize the mechanical force delivered to a surface contaminant in the PLASMAX process. These modeling and simulation efforts are essential to support the experimental program and facilitate development of the cleaning process for advanced optical reticles and NGL masks. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
02.70.Dh Finite-element and Galerkin methods

Characterization of phase defects in phase shift masks

Konstantinos Adam, Shoji Hotta, and Andrew R. Neureuther

J. Vac. Sci. Technol. B 18, 3227 (2000); http://dx.doi.org/10.1116/1.1321284 (5 pages) | Cited 5 times

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Rigorous simulation of electromagnetic scattering and imaging are used to assess the tendency of nonplanar phase defects to print in optical lithography with alternating phase-shifting masks. The ideal model for phase defects, which assumes that the fields are transmitted with unaltered amplitude and a phase shift of 180°, is proven inaccurate through simulation of isolated defects. The brightness and the phase are found to depend strongly not only on their height but on the lateral size as well. Data are also presented on a variety of defect shapes, sizes, heights, positions, and their impact when located near mask features. Linewidth variations due to lines/posts and scratches/holes are typically 30% larger and 50% smaller, respectively, than these predicted from an ideal geometrical mask model. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

TaSiN thin-film pattern transfer optimization for 200 mm SCALPEL and extreme ultraviolet lithography masks

W. J. Dauksher, D. J. Resnick, S. B. Clemens, D. L. Standfast, Z. S. Masnyj, J. R. Wasson, N. M. Bergmann, S.-I. Han, and P. J. S. Mangat

J. Vac. Sci. Technol. B 18, 3232 (2000); http://dx.doi.org/10.1116/1.1313575 (5 pages) | Cited 4 times

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Optimized etch processes for the pattern transfer of TaSiN-based SCALPEL and extreme ultraviolet lithography masks have been developed. For controllability, the etch rate is very commensurate with the pattern transfer of thin films, about 140 Å/min. Furthermore, selectivity to Cr at the process of record conditions (30 W radio frequency, 375 W inductively coupled plasma, 8 mT) is greater than 50:1, a necessity for pattern transfer on membrane-based masks. Critical dimension bias is on the order of 10 nm. For the fabrication of SCALPEL masks, supporting descum and Cr etch processes were also developed and are described later. Typical intramembrane uniformity of a 12.1 mm by 1.1 mm membrane processed through the entire pattern transfer sequence was found to be 8 nm, three sigma, which is quite favorable when compared with the starting resist uniformity (7 nm, three sigma). Similarly, using a test vehicle spanning 528 membranes, the intermembrane three sigma standard deviation was found to be 9 nm (starting resist uniformity of 8 nm, three sigma). © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
07.05.Fb Design of experiments

High-performance membrane mask for electron projection lithography

Hiroshi Yamashita, Isao Amemiya, Eiichi Nomura, Ken Nakajima, and Hiroshi Nozue

J. Vac. Sci. Technol. B 18, 3237 (2000); http://dx.doi.org/10.1116/1.1319829 (5 pages) | Cited 13 times

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A high-performance membrane mask for electron projection lithography (EPL) systems is proposed. The design and material selection of the mask described here were carefully executed by considering not only the lithographic performance but also various properties. The mask described in this article consists of a 600-nm-thick diamond-like carbon (DLC) scatter on a DLC membrane 30–60 nm thick. The optimum thicknesses are obtained by calculating angular distributions of the transmitted electrons by our in-house Monte Carlo simulator. It is expected to have an electron transmission of up to 80% and a beam contrast of 100% with an appropriate limiting aperture. A 1-mm-sq membrane of thickness of down to 30 nm could be successfully prepared. The high-performance membrane mask can obtain high resolution and high throughput of the EPL systems simultaneously. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
79.20.Kz Other electron-impact emission phenomena
81.15.Cd Deposition by sputtering
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Inter- and intramembrane resist critical dimension uniformity across a SCALPEL mask

K. Nordquist, E. Ainley, D. J. Resnick, E. Weisbrod, C. Martin, R. Engelstad, Z. Masnyj, and P. Mangat

J. Vac. Sci. Technol. B 18, 3242 (2000); http://dx.doi.org/10.1116/1.1324642 (6 pages) | Cited 1 time

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The use of chemically amplified (CA) resists in integrated circuit fabrication is accepted in semiconductor manufacturing as a way to achieve high resolution with excellent critical dimension (CD) control and etch selectivity. The use of CA resists for mask fabrication has not had as much favor due to resist storage stability issues and CD variations due to postexposure bake (PEB) sensitivities. One key component to the CD control on SCALPEL membrane masks is the thermal uniformity of the membranes and baking environment during the PEB process. This article discusses the numerical models created to predict temperature gradients within membranes and across membranes on a 200 mm SCALPEL mask. Verifications of the model by comparison of simulation results and actual CD data are also presented. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
02.70.Dh Finite-element and Galerkin methods

Simulating the mechanical response of electron-beam projection lithography masks

A. F. Jachim, C.-F. Chen, R. L. Engelstad, E. G. Lovell, P. J. S. Mangat, and W. J. Dauksher

J. Vac. Sci. Technol. B 18, 3248 (2000); http://dx.doi.org/10.1116/1.1313574 (6 pages) | Cited 2 times

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This article describes the results of distortion simulations for Motorola’s 200 mm electron-beam projection lithography (EPL) mask due to the fabrication process, pattern transfer, and mounting. Finite element models have been created as predictive tools, which incorporate the orthotropic elastic material properties of single crystal silicon. Both membrane-flow and wafer-flow processes have been simulated, identifying the significant advantage of the former. Modeling results for parametric studies of the fabrication process and the effects of mounting under gravitational loading are presented. The predictive studies illustrate that the metal layer (Cr/TaSiN) stress most strongly influences the image placement error. It is also shown that common mounting techniques for e-beam writing and exposure are essential for minimizing pattern placement errors. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
02.70.Dh Finite-element and Galerkin methods

Stencil reticle repair for electron beam projection lithography

Masashi Okada, Sumito Shimizu, Shintaro Kawata, and Takashi Kaito

J. Vac. Sci. Technol. B 18, 3254 (2000); http://dx.doi.org/10.1116/1.1319828 (5 pages) | Cited 4 times

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Repair of stencil reticles for electron beam projection lithography system is one of the critical issues on reticle manufacturing. Focused ion beam deposition is studied as the method for repairing the clear defects of stencil reticle. The film deposition of diamondlike carbon (DLC) across the stencil pattern, on the sidewall of the stencil, and on the pre-etched slot pattern is demonstrated. The deposited DLC films have good properties as the repair material. Deposited patterns across the stencil pattern are imaged on the resist with the Nikon 100 kV experimental projection column. When the thickness of the deposited DLC film is more than 0.5 μm and the contrast aperture size of the projection column is 1.5 mrad, the thickness of the deposited pattern does not affect the critical dimension of the resist pattern imaged the repaired patterns. The profiles, the pattern size, and the electron scattering properties of DLC films are stable for 100 kV electron beam continuous irradiation (2 C/cm2 dosage; corresponding to half-year dosage on electron beam stepper). Moreover, the repaired pattern is not damaged by the wet megasonic cleaning. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Thickness analysis of silicon membranes for stencil masks

E. Sossna, R. Kassing, I. W. Rangelow, C. M. Herzinger, T. E. Tiwald, J. A. Woollam, and Th. Wagner

J. Vac. Sci. Technol. B 18, 3259 (2000); http://dx.doi.org/10.1116/1.1319827 (5 pages) | Cited 1 time

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Stencil masks are key to charged particle projection lithography, in particular for ion projection lithography. To fulfill pattern printing requirements in the sub-70 nm regime, excellent thickness uniformity and thermal emissivity control are critical parameters for high quality stencil mask fabrication. We propose and demonstrate a technique based on infrared variable angle spectroscopic ellipsometry (IR-VASE) to measure these parameters with adequate accuracy and precision. The refractive index of the Si membrane was evaluated using a Sellmeier dispersion model combined with a Drude model. Because of its spectral range from 2 to 33 μm, the IR-VASE method is sensitive to the thickness of layers as well as to the concentration and profile of Si membrane doping. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
07.20.-n Thermal instruments and apparatus
07.60.Fs Polarimeters and ellipsometers
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Db Elemental semiconductors and insulators
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Scanning probe metrology in the presence of surface charge

J. E. Griffith, E. M. Kneedler, S. Ningen, A. Berghaus, C. E. Bryson, S. Pau, E. Houge, and T. Shofner

J. Vac. Sci. Technol. B 18, 3264 (2000); http://dx.doi.org/10.1116/1.1313586 (4 pages) | Cited 1 time

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Surface charge on insulating samples can be a significant source of error for scanning probe microscopes. We have found that it is possible to operate a scanning force microscope in a manner that makes it relatively immune to charge-induced forces while still allowing the probe tip to nondestructively follow the surface topography. The need to maintain close charge balance on the sample is thus obviated. We have used this strategy to perform critical dimension measurements on optical photomasks with the Surface/Interface Stylus NanoProfilometer. This instrument incorporates a servoed force-balance sensor. Surface topography is determined by touching the surface with contact forces between 0.1 and 1 μN. © 2000 American Vacuum Society.
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07.79.-v Scanning probe microscopes and components
85.40.Hp Lithography, masks and pattern transfer
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

Two-dimensional spatial-phase-locked electron-beam lithography via sparse sampling

J. T. Hastings, Feng Zhang, M. A. Finlayson, J. G. Goodberlet, and Henry I. Smith

J. Vac. Sci. Technol. B 18, 3268 (2000); http://dx.doi.org/10.1116/1.1314371 (4 pages) | Cited 13 times

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We report a new mode of spatial-phase-locked electron-beam lithography based on alignment of each e-beam deflection field to a fiducial grid on the substrate. Before exposing the pattern in a given field, the fiducial grid is sparsely sampled with the electron beam at a subexposure dose. These samples form a two-dimensional moiré pattern that is analyzed to calculate field shift, scale, rotation, nonorthogonality, and trapezoidal distortion. Experimental verification of the approach was carried out with a scintillating fiducial grid quenched by interference lithography. Despite a poor signal-to-noise ratio, we achieved sub-beamstep field-stitching and pattern-placement accuracy. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Microcomb design and fabrication for high accuracy optical assembly

Carl G. Chen, Ralf K. Heilmann, Paul T. Konkola, Olivier Mongrard, Glen P. Monnelly, and Mark L. Schattenburg

J. Vac. Sci. Technol. B 18, 3272 (2000); http://dx.doi.org/10.1116/1.1313585 (5 pages) | Cited 3 times

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There are two popular optic designs for x-ray space telescopes: the traditional monolithic design, which has demonstrated subarcsecond resolution but at enormous weight and cost per collecting area, and the foil design, which has achieved far greater collecting area per weight and cost, but with resolution limited to the arcminute level, in part due to foil assembly inaccuracy. In this article, we present the design and the fabrication of a novel micromechanical device, the so-called microcomb, which is used to assemble high-accuracy foil x-ray optics. To achieve submicron foil alignment accuracy, two types of microcombs have been fabricated via microelectromechanical systems technology. Reference combs provide highly accurate single-point contacts against which foils are registered, and spring combs provide the mechanical actuation needed to properly position and shape the foils. Briefly, we introduce some basic concepts regarding grazing-incidence x-ray optics. We then present a theoretical model that has given rise to the unique shape of the spring microcomb. Finally, the fabrication process used to produce the microcombs is discussed. © 2000 American Vacuum Society.
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95.55.Ka X- and γ-ray telescopes and instrumentation
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
07.10.Cm Micromechanical devices and systems
42.15.Eq Optical system design

Relativistic corrections in displacement measuring interferometry

Ralf K. Heilmann, Paul T. Konkola, Carl G. Chen, and Mark L. Schattenburg

J. Vac. Sci. Technol. B 18, 3277 (2000); http://dx.doi.org/10.1116/1.1313584 (5 pages) | Cited 3 times

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Displacement measuring interferometry is based on measuring the Doppler frequency shift that a beam of radiation undergoes upon reflection off a mirror connected to a moving stage. Usually the velocity of the reflecting stage is very small compared to the speed of light and is therefore deduced using the classical expression for the Doppler shift. We calculate relativistic corrections to the Doppler frequency shift, considering arbitrary stage motion in two dimensions and multiple passes through the moving interferometer arm. Changes in optical path lengths due to the varying stage displacement are explicitly taken into account. For stage velocities on the order of only 1 m/s the resulting corrections to the classically derived stage displacement can amount to nanometers. We discuss model velocity profiles similar to those currently employed in industrial step-and-scan systems for integrated circuit manufacturing, and for recently proposed scanning-beam interference lithography schemes. Expected future increases in stage speed and wafer sizes will necessitate the inclusion of relativistic corrections to the Doppler shift to maintain pattern placement accuracy at the nanometer level. © 2000 American Vacuum Society.
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07.60.Ly Interferometers
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

Beam steering system and spatial filtering applied to interference lithography

Paul T. Konkola, Carl G. Chen, Ralf K. Heilmann, and Mark L. Schattenburg

J. Vac. Sci. Technol. B 18, 3282 (2000); http://dx.doi.org/10.1116/1.1314385 (5 pages) | Cited 6 times

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Production of metrologically accurate interference patterns with subnanometer fidelity requires precise control of beam position and angle. We consider the beam stability requirements for the cases of interference by plane and spherical waves. Interferometers using beamsplitter cubes and diffraction gratings are among the analyzed topologies. The limitations of spatial filtering to remove angular variations are also discussed. We present a beam steering system that uses position sensing detectors, tip-tilt actuators, and digital control to lock the beam position and angle at the interference lithography system. We describe the prototype’s performance and limitations of this approach. This beam steering system allows us to locate the laser far (∼10 m) from the sensor assembly, thereby reducing the thermal and mechanical disturbances at the lithography station and allowing sharing of the laser between different lithography tools. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Characterization of field stitching in electron-beam lithography using moiré metrology

T. E. Murphy, Mark K. Mondol, and Henry I. Smith

J. Vac. Sci. Technol. B 18, 3287 (2000); http://dx.doi.org/10.1116/1.1313573 (5 pages)

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We describe a method for characterizing field stitching in e-beam lithography systems. The method, which is based upon the moiré principle, enables one to measure interfield stitching errors to the nanometer level using only a conventional optical microscope. The technique is more sensitive than the commonly used vernier method, and it does not require the use of a coordinate-measuring tool. Our experiments show that this technique can determine the interfield stitching to within 2 nm. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
07.60.Pb Conventional optical microscopes
42.30.Ms Speckle and moiré patterns
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Surface and line-edge roughness in solution and plasma developed negative tone resists: Experiment and simulation

G. P. Patsis, A. Tserepi, I. Raptis, N. Glezos, E. Gogolides, and E. S. Valamontes

J. Vac. Sci. Technol. B 18, 3292 (2000); http://dx.doi.org/10.1116/1.1321281 (5 pages) | Cited 12 times

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A methodology is described for the experimental and theoretical study of surface roughness (SR) and line-edge roughness (LER) and their relation for solution and plasma developed resist schemes. Experimental results for a negative-tone nonchemically amplified siloxane bilayer resist scheme are shown. In addition, a molecular-type simulation of SR and LER is presented. The simulator can follow the appearance of SR and LER after each process step and predict the roughness dependence on material properties and process conditions. The simulation results are compared with SR experimental data for a negative-tone chemically amplified epoxy resist. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Energy transfer between electrons and photoresist: Its relation to resolution

Geng Han and Franco Cerrina

J. Vac. Sci. Technol. B 18, 3297 (2000); http://dx.doi.org/10.1116/1.1318188 (6 pages) | Cited 4 times

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In the study of high-energy photon and electron lithography the photoresist has been treated as a uniform and isotropic medium. As dimensions become smaller and exposure fluctuation more noticeable, we cannot ignore the processes that happen at the molecular scale. Hence, it becomes important to understand how the energy is coupled from an exciting radiation to the various molecular components of a photoresist material. In this article, we present the first step in the development of such a model. We base the analysis on the method of virtual quanta for the incoming electron, and use the dielectric function response theory to describe the medium. The results correctly describe the decreasing strength of the interaction on the electron energy, and yield an estimate of ≈2–3 nm for an average interaction distance. A simple Monte Carlo simulation is implemented to verify the effect of the fluctuations due to the virtual quanta on a line edge. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
78.66.Qn Polymers; organic compounds
61.82.Pv Polymers, organic compounds
82.35.-x Polymers: properties; reactions; polymerization
02.70.Rr General statistical methods
61.80.Fe Electron and positron radiation effects

Comparison of resist collapse properties for deep ultraviolet and 193 nm resist platforms

Heidi B. Cao, Paul F. Nealey, and Wolf-Dieter Domke

J. Vac. Sci. Technol. B 18, 3303 (2000); http://dx.doi.org/10.1116/1.1321280 (5 pages) | Cited 33 times

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A comparison of collapse behavior was made for photoresist features with linewidths from 80 to 200 nm, spacing from 100 to 350 nm, and aspect ratios from 2 to 6 for four different resist platforms: acrylic based resists, acrylic resists based upon the Fujitsu platform, cyclo-olefin–maleic anhydride based resists, and Apex E, a poly(hydroxystyrene) based resist. The percentage of collapse for different gratings was determined using top-down scanning electron microscope images. A methodology was introduced to compare collapse properties between platforms by determining the critical aspect ratio of collapse (CARC) as a function of spacing between resist structures. We demonstrated the validity of this approach using an extensive set of statistically significant data for Apex E, and we determined that the CARC decreased linearly as the spacing between lines of resist decreased. The physical origin of the approach was discussed in terms of the mechanics of beam bending and the thermodynamics of surface tension. The methodology was applied to limited data sets for other resist platforms. The four resist platforms exhibited different values of CARC at constant spacing and a different dependence of CARC as a function of spacing. Resist performance in terms of collapse properties was ranked in the following order: cyclo-olefin–maleic anhydride resists > poly(hydroxystyrene) resist and acrylic resists based on the Fujitsu platform > acrylic resists. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Supercritical drying for water-rinsed resist systems

Hideo Namatsu

J. Vac. Sci. Technol. B 18, 3308 (2000); http://dx.doi.org/10.1116/1.1313583 (5 pages) | Cited 24 times

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Two methods of supercritical resist drying (SRD) using CO2 have been developed for water-rinsed resist patterns. The key to their effectiveness is the use of a surfactant. In indirect SRD, a solution of n-hexane, a CO2-philic liquid, and a surfactant, sorbitan fatty acid ether, first replaces the water, and is in turn replaced with liquid CO2 before SRD is performed. The addition of a compound with a high hydrophilic-lipophilic balance to the surfactant compensates for the poor miscibility of water in a solution of n-hexane and sorbitan fatty acid ether. In direct SRD, which does not require a CO2-philic liquid, the water is replaced directly with liquid CO2 containing a surfactant, fluoroether carboxylate, which makes water miscible in CO2; and then SRD is performed. The excellent results obtained by both methods demonstrate that there is no inherent barrier to the use of SRD on water-rinsed resist patterns. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
64.75.-g Phase equilibria
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Aqueous-based photoresist drying using supercritical carbon dioxide to prevent pattern collapse

Darío L. Goldfarb, Juan J. de Pablo, Paul F. Nealey, John P. Simons, Wayne M. Moreau, and Marie Angelopoulos

J. Vac. Sci. Technol. B 18, 3313 (2000); http://dx.doi.org/10.1116/1.1313582 (5 pages) | Cited 45 times

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A supercritical drying process was developed to eliminate the capillary forces naturally present during normal drying of photoresist materials. Supercritical carbon dioxide (scCO2), organic solvents and surfactants were used to prevent the collapse of high-aspect-ratio structures fabricated from aqueous-based photoresist. Nondistorted resist lines were patterned with this process with aspect ratios of at least 6.8. Water rinsed resist structures cannot be dried directly with scCO2 due to the low solubility of water in the supercritical phase. In our process we introduced the replacement of the aqueous rinse by n-hexane mediated by a compatible surfactant. The surfactant allowed to incorporate the aqueous phase into micellar microdomains in the organic phase while keeping the interfacial tension at values close to zero. Noncollapsed supercritically dried structures were rewet in n-hexane or water and dried using nitrogen at atmospheric pressure. Under these conditions, the patterns were collapsed as a result of capillary forces acting on the resist walls. The effect of capillary forces on pattern stability were qualitatively compared to the relative surface tension values between n-hexane and water. The advantage of using supercritical CO2 in the drying stage of resists compared to normal drying highlights the importance of eliminating the surface (or interfacial) tension forces created by the rinse fluid, if a reduction of linewidth and spacing between resist lines is pursued, while keeping the aspect ratio constant. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Enhancement of resist resolution and sensitivity via applied electric field

Mosong Cheng, Ebo Croffie, Lei Yuan, and Andrew Neureuther

J. Vac. Sci. Technol. B 18, 3318 (2000); http://dx.doi.org/10.1116/1.1324646 (5 pages) | Cited 3 times

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This article presents a methodology for enhancing the resist sensitivity and resolution based on confining the photoacid drift/diffusion by external electric field. An alternating electric field applied to the resist film during postexposure bake can enhance the photoacid drift in the vertical direction, reduce the bake time, and thereby confine the lateral acid diffusion. A mathematical model is presented and a rigorous solution is obtained in the case of Fickean diffusion and constant electric field. The experiments were conducted on UVIIHS resist with a JEOL electron-beam exposure tool. The scanning electron microscope pictures show that electric-field enhanced postexposure bake (PEB) can reduce the PEB time requirement by 30%, and at the same time, improve the sharpness of two-dimensional corners and increase the verticality of resist sidewalls. Electric-field-enhanced PEB also significantly improves the tolerance of overexposure and provides better critical dimension control. It is estimated that it reduces the lateral acid diffusion length by about 70 nm, or 50%. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Optimized bilayer hexamethyldisiloxane film as bottom antireflective coating for both KrF and ArF lithographies

C. H. Lin, L. A. Wang, and H. L. Chen

J. Vac. Sci. Technol. B 18, 3323 (2000); http://dx.doi.org/10.1116/1.1321273 (5 pages) | Cited 1 time

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A new bilayer bottom antireflective coating (BARC) layer composed of hexamethyldisiloxane film stack is demonstrated for both KrF and ArF lithographies. By simply adjusting the gas flow rate ratio, the materials of the bilayer can be varied to have suitable optical constants as BARC materials working at both 248 and 193 nm wavelengths. The swing effect is experimentally shown to be reduced significantly on both silicon and Al–Si substrates. The bilayer scheme is also demonstrated to be capable of providing large thickness-controlled tolerance. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
85.40.Sz Deposition technology
42.79.Wc Optical coatings
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Vacuum ultraviolet spectra of fluorocompounds for 157 nm lithography

Minoru Toriumi, Isao Satou, and Toshiro Itani

J. Vac. Sci. Technol. B 18, 3328 (2000); http://dx.doi.org/10.1116/1.1319836 (4 pages) | Cited 2 times

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The optical characteristics in the vacuum ultraviolet region were studied using the molecular orbital method. A model molecule, p-ethylphenol, was used to represent poly(p-hydroxystyrene), and its spectrum was calculated by the semiempirical molecular orbital calculations. The theoretical results were compared with the experimental ones. The wavelengths of the absorption peaks showed good agreement in both results, though the intensities of the absorption did not agree. The fluorination of p-ethylphenol was investigated and it was found that the increase in the number of fluorine atoms became more transparent in the compound. The cause was explained by two factors. One was the redshift of the π–π∗ electronic transition of the aromatic molecules, of which the oscillator strength did not depend upon the fluorination number. The other was the decrease in the oscillator strength of the peak at 157 nm, of which the wavelength did not significantly shift. © 2000 American Vacuum Society.
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78.40.Me Organic compounds and polymers
36.20.Kd Electronic structure and spectra
85.40.Hp Lithography, masks and pattern transfer
31.15.bu Semi-empirical and empirical calculations (differential overlap, Hückel, PPP methods, etc.)

Polymer photochemistry at advanced optical wavelengths

Theodore H. Fedynyshyn, Roderick R. Kunz, Roger F. Sinta, Russell B. Goodman, and Scott P. Doran

J. Vac. Sci. Technol. B 18, 3332 (2000); http://dx.doi.org/10.1116/1.1318186 (8 pages) | Cited 17 times

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As lithography is extended to 157 nm, the molecular absorptivity becomes high for most organic polymers. Polymer photochemistry depends on photon absorption, and the higher energy associated with 157 nm light should lead to higher quantum yields of photoproducts. Polymers representative of those commonly employed in 193 or 248 nm resists were selected for this study. A gel permeation chromatography based method was developed to determine quantum yields for chain scission and crosslinking on thin polymers films coated on silicon wafers. This method was applied to determine the ΦS and ΦX of a number of lithographically significant homopolymers and copolymers at both the 157 and 248 nm wavelengths. It was found that polymers containing hydroxystyrene only undergo crosslinking while acrylate and methacrylate polymer only undergo chain scission. The film loss of 157 nm exposed poly-t-butyl acrylate and polymethyl methacrylate was found to be very high and attributed primarily to side chain cleavage of the esters, while no film loss of polyhydroxystyrene was detected. The analysis of outgassing materials showed that ester elimination in poly-t-butyl acrylate was responsible for all outgassed products and that the sum of the quantum yields of all outgassed products exceeded one, implying a reaction mechanism that recycled the initially produced radical. Direct polymer photolysis is significant at 157 nm and must be considered in resist design given the relatively high absorbance of most organic molecules at 157 nm. © 2000 American Vacuum Society.
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82.50.Bc Processes caused by infrared radiation
82.50.Hp Processes caused by visible and UV light
85.40.Hp Lithography, masks and pattern transfer
82.35.-x Polymers: properties; reactions; polymerization
82.80.Bg Chromatography

Modeling influence of structural changes in photoacid generators on 193 nm single layer resist imaging

Ebo Croffie, Lei Yuan, Mosong Cheng, Andrew Neureuther, Frank Houlihan, Ray Cirelli, Pat Watson, Om Nalamasu, and Allen Gabor

J. Vac. Sci. Technol. B 18, 3340 (2000); http://dx.doi.org/10.1116/1.1324636 (5 pages) | Cited 2 times

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We present recent modeling work aimed at understanding the influence of structural changes in photoacid generators (PAGs) on acid generation efficiency, deprotection efficiency, and photoacid diffusion in 193 nm chemically amplified resists. An analytical model for the postexposure bake process is used to study the reaction and diffusion properties of the various acids generated by the PAGs. Fourier transfer infrared spectroscopy is used to monitor the generation of photoacid during exposure. Resist thickness loss after PEB as a function of exposure dose is related to the deprotection extent to extract the reaction rate parameters. The effects of the acid size and boiling point on process latitude, line end shortening, and line edge roughness are presented. Analytical model predictions of process latitude and line end shortening are also presented and compared to experimental data. In this study, the photogenerated acid with the smallest molar volume and highest boiling point temperature gave the best overall lithographic performance. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Lithographic performance of thin dendritic polymer resists

Mike Williamson and Andy Neureuther

J. Vac. Sci. Technol. B 18, 3345 (2000); http://dx.doi.org/10.1116/1.1324638 (4 pages) | Cited 1 time

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A dendritic polymer resin lithographic resist is evaluated for surface and line edge roughness, and feasibility to enter the manufacturing environment. This novel resin demonstrates superb surface smoothness; linewidth variation is 5.1 Å and surface roughness is 12.9 Å. Most of the key concerns in the manufacturing environment are adequate, if not excellent. This resist shows excellent potential for processes where very small and smooth features are required, such as gate level definition. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Resist profile characteristics caused by photoelectron and Auger electron blur at the resist–tungsten substrate interface in 100 nm proximity x-ray lithography

Younghun Seo, Changhwan Lee, Yongduk Seo, Ohyun Kim, Hyunpil Noh, and Heesang Kim

J. Vac. Sci. Technol. B 18, 3349 (2000); http://dx.doi.org/10.1116/1.1321292 (5 pages) | Cited 2 times

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The replicated resist pattern characteristics caused by photoelectrons and Auger electrons generated from the W substrate were investigated for 100 nm proximity x-ray lithography. In addition, simulations for a hard x-ray spectrum having 2.36 keV average energy were performed to investigate the substrate electron effects in hard x-ray lithography. In the experiments, it was found that the secondary electrons from the W substrate caused undercut and footing of resist profiles at the resist–substrate interface. Several buffer layers with varying thicknesses were tested to reduce the photoelectron effects from the W substrate. The best thickness of the buffer layers for a good resist pattern profile was discovered to be >30 nm. Furthermore, the experimental results were quantitatively compared to the results from computer simulations using the Monte Carlo method. For hard x rays, we predict that the exposure latitude is worse on both W and Si substrates. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
02.70.Rr General statistical methods

Evaluation of alternative development process for high-aspect-ratio poly(methylmethacrylate) microstructures in deep x-ray lithography

Chantal Khan Malek and Sasi Yajamanyam

J. Vac. Sci. Technol. B 18, 3354 (2000); http://dx.doi.org/10.1116/1.1321759 (6 pages) | Cited 3 times

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The development of very thick commercial sheets of poly(methyl methacrylate) (PMMA) resist patterned by deep x-ray lithography was investigated. The development characteristics were explored, with the alternative methyl-iso-butyl-ketone (MIBK)-based developer systems, MIBK and MIBK/ iso-propyl-alcohol (IPA) 1:3, being compared with the “GG” developer system (2-butoxyethoxy-ethanol, morpholine, 2-aminoethanol, and water) more generally used. In particular, the influence of various parameters were studied: PMMA characteristics (resist thickness, pre-exposure thermal treatment), exposure conditions (x-ray incident energy, dose at the bottom of the resist, rate of dose deposition, distribution of dose inside the resist), development conditions (temperature, megasonic-assistance, length of cycle into developer and rinse baths), postexposure treatments (storage, thermal treatment), etc. The study also focused on surface finish of the parts corresponding to different exposure and development conditions. Using MIBK/IPA megasonic assisted development and postexposure treatment at 40 °C resulted in the best conditions, faster development rate, as well as smoother developed surfaces. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Lithography using ultrathin resist films

Christopher Pike, Scott Bell, Chris Lyons, Marina Plat, Harry Levinson, and Uzodinma Okoroanyanwu

J. Vac. Sci. Technol. B 18, 3360 (2000); http://dx.doi.org/10.1116/1.1324640 (4 pages) | Cited 4 times

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The industry trend toward higher numerical apertures and lower k1 factors is severely constraining the manufacturing process margin for current and future lithography technologies. Ultrathin resist (UTR) films and other thin layer imaging techniques offer the promise of improved process margin as compared to conventional single layer resist schemes. In this study, an UTR over hard mask process was used to pattern the transistor gates of a high performance microprocessor using 248 nm lithography while focusing on four key areas of concern for UTR films: resist film defectivity, response of thin resist to device topography, quality of pattern transfer on device wafers, and device yield comparable to a baseline process. The intrinsic defectivity of resist films as thin as 65 nm is found to be no greater than that of a >500 nm resist film on flat silicon wafers. No pinhole defects are observed during scanning electronic microscopy review of defects on as-coated UTR films. As expected, the UTR process is sensitive to device topography, but the effects are manageable for the conditions used here. Robust pattern transfer with defect levels comparable to the baseline single layer resist process is demonstrated using UTR films as thin as 150 nm and a hardmask. Finally, device yield data confirms that the UTR process is as manufacturable as a conventional single layer resist process. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Outgassing of photoresist materials at extreme ultraviolet wavelengths

Paul M. Dentinger

J. Vac. Sci. Technol. B 18, 3364 (2000); http://dx.doi.org/10.1116/1.1314383 (7 pages) | Cited 7 times

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Outgassing of photoresist materials is a concern for all advanced lithographies. To address this concern, outgassing of photoresist materials exposed at extreme ultraviolet (EUV) wavelengths was studied with a quartz crystal microbalance (QCM) and mass spectrometry and was quantified using the QCM. Mass spectrometry of poly(methylmethacrylate) at 13.4 nm indicated large quantities of hydrogen formed by exposure at EUV wavelengths. QCM studies showed that pure acrylic materials are particularly susceptible to outgassing while pure styrenic materials outgas approximately two orders of magnitude less mass per unit dose. Random copolymers of acrylics and hydroxystyrene, such as found in common 248 nm lithography materials were disproportionately low outgassers. The phenolic moieties randomly introduced into the backbone of acrylics reduced the outgassing by approximately an order of magnitude below what was expected from the pure polymers. It is thought that radical scavenging by phenolic moieties stabilize the acrylic monomers. In addition, judicious selection of the photoacid generator (PAG) is important. It is shown that some PAGs, even at concentrations of 3.8 wt % produce 4 times more volatile mass than the resin itself. The residual solvent left in the film after the postapply bake (PAB) can contribute and even dominate outgassing if the PAB is too low. For the best imaging materials to date, the main sources of outgassing are direct photo/radiolysis of the backbone polymer and the PAG at approximately similar rates, and to a lesser extent, the residual solvent if the PAB is too low. The fate of the outgassed species and their threat to facing optical elements is discussed.
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85.40.Hp Lithography, masks and pattern transfer
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
82.50.Bc Processes caused by infrared radiation
82.50.Hp Processes caused by visible and UV light

Correlation between the chemical compositions and optical properties of AlSixNy embedded layer for attenuated phase-shifting mask in 193 nm and the modification of the R–T method for measuring n and k

Cheng-ming Lin and Wen-an Loong

J. Vac. Sci. Technol. B 18, 3371 (2000); http://dx.doi.org/10.1116/1.1319835 (5 pages)

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The formation and variation of AlN, Si3N4, and nitride compositions in AlSixNy (x∼0.31, y∼0.51) embedded material have been shown to correlate with its optical properties. The increasing content of AlN, Si3N4, and nitrides will increase n and decrease k of AlSixNy. A simple and effective correction of measured reflectance R% and transmittance T% based on scalar scattering theory has been applied to the R–T method for determining n and k of embedded layers for 193 nm lithography masks. A 0.2 μm etched pattern of an AlSixNy embedded layer on an oxide/Si wafer substrate was successfully fabricated. © 2000 American Vacuum Society.
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78.66.Nk Insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.55.Nq Composition and phase identification
85.40.Hp Lithography, masks and pattern transfer
81.15.Cd Deposition by sputtering
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Scaling of Tg and reaction rate with film thickness in photoresist: A thermal probe study

David S. Fryer, Paul F. Nealey, and Juan J. de Pablo

J. Vac. Sci. Technol. B 18, 3376 (2000); http://dx.doi.org/10.1116/1.1324621 (5 pages) | Cited 16 times

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A thermal probe technique, local thermal analysis, was used to measure the glass transition temperature (Tg) and reaction rate as a function of film thickness in chemically amplified photoresists. Using this technique, heat loss into a resist film was monitored as the temperature of the probe was ramped from ambient to temperatures as high as 200 °C. The thermal events, glass transition temperature or heat evolved during reaction, were recorded as a function of the probe temperature. The Tg of the photoresists UVN 30, UV6, UV3, KRS, and KRS-XE was measured for thick films and for ultrathin films approximately 50 nm thick. The measured Tg in ultrathin resist films was 4–22 °C higher relative to that measured in thick films. We also investigated the behavior of polyhydroxystyrene films, and found that crosslinking to the substrate can increase Tg by a large amount. The photoresist films were then exposed with x-ray radiation at the same dose (950 mJ/cm2) for both thick and ultrathin films to ensure a constant photogenerated acid concentration with thickness. The exposed areas of the films were heated with the thermal probe, and an increase in heat flow into the exposure area, attributed to the heat of reaction, prior to the glass transition temperature was measured. Kinetic rate constants were estimated with data from the power supplied to the probe as a function of temperature using a first order reaction model. The results indicate that the rate of reaction in ultrathin resist films is smaller than in thicker films for resists processed at the same postexposure bake temperature. We find that Tg and reaction rate depend on film thickness in ultrathin photoresist films; the differences in these properties are expected to lead to large changes in the processing conditions used for ultrathin films relative to thick films. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
82.20.Pm Rate constants, reaction cross sections, and activation energies

Thin film instabilities and implications for ultrathin resist processes

Uzodinma Okoroanyanwu

J. Vac. Sci. Technol. B 18, 3381 (2000); http://dx.doi.org/10.1116/1.1321291 (7 pages) | Cited 6 times

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The origin and nature of instabilities in ultrathin resist (UTR) polymer films (⩽100 nm) spin coated onto silicon wafer substrates are presented, along with the influence of the substrate on the morphological, thermophysical, and viscoelastic properties of the polymers. The defects, morphology, and density of UTR films spin coated from well-characterized and commercially available phenolic ESCAP polymer based XP-98248 resist from Shipley which were annealed below the glass transition temperature are presented as a function of film thickness and spin coating parameters. For each film, three distinct layers with different densities and varying degrees of roughness are observed: a surface layer, a bulk layer, and a substrate/film interface layer. The thickness of the surface layer is comparable to length scales of cooperative dynamics in polystyrene chains. Dependence of the density and roughness on total film thickness is observed for each layer, with the film/substrate interface layer showing the most variation for film thickness <53 nm, suggesting the onset of instabilities due to interfacial effects, polymer chain packing constraints, and cooperative dynamics. Within the thickness range of 65–100 nm, no dependence of defectivity on total film thickness and spin speed is observed. F2 (157 nm) laser imaging results obtained on these films are discussed. Significant differences between UTR films (∼60 nm) and thick resist films (>400 nm) imaging performance are observed. An explanation is given in terms of polymer cooperative dynamics and interfacial effects. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
61.41.+e Polymers, elastomers, and plastics
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials

Resolution limit of negative tone chemically amplified resist used for hybrid lithography: Influence of the molecular weight

L. Pain, C. Higgins, B. Scarfoglière, S. Tedesco, B. Dal’Zotto, C. Gourgon, M. Ribeiro, T. Kusumoto, M. Suetsugu, and R. Hanawa

J. Vac. Sci. Technol. B 18, 3388 (2000); http://dx.doi.org/10.1116/1.1321288 (8 pages) | Cited 9 times

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The objective of this article was to study the resolution limits of different negative tone chemically amplified resists from both commercial and experimental formulations. Process optimization has been done on all samples and this work underlines the importance of the choice of bake temperature to push resists to their ultimate resolution. Furthermore, the influence of several compounds, such as the polymer matrix blend, molecular weight, and photoacid compound, is detailed to determine the influence of each parameter on the final formulation performance. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

157 nm resist materials: Progress report

Colin Brodsky, Jeff Byers, Will Conley, Raymond Hung, Shintaro Yamada, Kyle Patterson, Mark Somervell, Brian Trinque, H. V. Tran, Sungseo Cho, Takashi Chiba, Shang-Ho Lin, Andrew Jamieson, Heather Johnson, Tony Vander Heyden, et al.

J. Vac. Sci. Technol. B 18, 3396 (2000); http://dx.doi.org/10.1116/1.1321762 (6 pages) | Cited 11 times

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Many semiconductor device manufacturers plan to make products with 157 nm lithography beginning in 2004. There is, at this time, no functional photoresist suitable for 157 nm exposure. Developing resist materials for 157 nm lithography is particularly challenging since water, oxygen, and even polyethylene are strongly absorbing at this wavelength. A modular approach to the design of a single layer resist for 157 nm has been undertaken. In this approach, the resist has been conceptually segmented into four functional modules: an acidic group, an acid labile protecting group, an etch resistant moiety, and a polymer backbone. Each of these modules has an assigned function and each must be transparent at 157 nm. Progress has been made toward finding candidate structures for each of these modules. We have demonstrated that acidic bistrifluoromethylcarbinols are very transparent at 157 nm and function efficiently in chemically amplified resists with both high and low activation energy protecting groups. Judicious incorporation of fluorine in acrylates and alicyclics has provided etch resistant polymers with greatly improved transparency at 157 nm. In particular, esters of poly(α-trifluromethylacrylic acid) are far more transparent than their protio analogs. The Diels–Alder adducts derived from reaction of these and other fluorinated alkenes with cyclopentadiene offer a route to a wide range of alicyclic monomers that show great promise as transparent, etch resistant platforms for the design of 157 nm resists. Polymers of this sort with absorbance below 2 per micrometer are reported. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Outgassing of photoresists in extreme ultraviolet lithography

Maharshi M. Chauhan and Paul F. Nealey

J. Vac. Sci. Technol. B 18, 3402 (2000); http://dx.doi.org/10.1116/1.1321754 (6 pages) | Cited 6 times

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The outgassing characteristics of 100 nm thick films of several commercial photoresists were investigated during and after exposure to lithographically relevant doses of extreme ultraviolet lithography radiation. Three positive tone and two negative tone chemically amplified deep ultraviolet resists were evaluated that are commercially available. The amount and chemical composition of the outgassed species was determined by quartz crystal microbalance and quadrupole mass spectrometry. Outgassed species identified were products from acid catalyzed or photochemical cleavage reactions involving protecting groups, and products from the decomposition of photoacid generator molecules. t-butyl ester protected positive resist based on tetra polymers of methacrylates (IBM version 2.1) outgassed during exposure, and t-butoxy carbonyl protected positive resist based on polyhydroxystyrene (APEX-E) outgassed during and after exposure. Outgassing from t-butyl ester positive resist based on an ESCAP type polymer (UV6) and from negative resists (SAL 605 and NTS-4A4) was below detection limits in our experiments. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

1 kV resist technology for microcolumn-based electron-beam lithography

K. Y. Lee, Y. Hsu, P. Le, Z. C. H. Tan, T. H. P. Chang, and K. Elian

J. Vac. Sci. Technol. B 18, 3408 (2000); http://dx.doi.org/10.1116/1.1321758 (6 pages) | Cited 2 times

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The objective of this article is to evaluate low-voltage electron-beam (e-beam) resists suitable for direct write on wafer and mask fabrication in the sub-100 nm regime. Low kV exposure provides the advantages of high sensitivity, reduced charging, and a lack of proximity and heating effects. However, a major concern is whether a low-voltage e-beam is capable of patterning sub-100 nm features in resist with a thickness substantially greater than the penetration range of the electrons. At 1–2 kV, the penetration range is between 30 and 100 nm, while typical resist thickness is >200 nm. In an effort to overcome this limitation, thin film layer techniques are evaluated for low kV e-beam exposure. Preliminary 1 kV results on two thin imaging schemes, the bilayer CARL process and top surface imaging with NTS-4 resist, are reported here. Important results achieved are high sensitivity (1–2 μC/cm2), high contrast (γ>10), high resolution (70 nm in ∼300 nm thick resist), good critical dimension (CD) linearity (range=7 nm, mean=8 nm), large exposure latitude (ΔCD/Δdose=0.5 nm/% change in dose), and absence of proximity effects. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Nanoscale patterning of self-assembled monolayers with electrons

A. Gölzhäuser, W. Geyer, V. Stadler, W. Eck, M. Grunze, K. Edinger, Th. Weimann, and P. Hinze

J. Vac. Sci. Technol. B 18, 3414 (2000); http://dx.doi.org/10.1116/1.1319711 (5 pages) | Cited 40 times

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We show the fabrication of gold nanostructures using self-assembled monolayers of aliphatic and aromatic thiols as positive and negative electron beam resists. We applied a simple and versatile proximity printing technique using focused ion beam structured stencil masks and low energy (300 eV) electrons. We also used conventional e-beam lithography with a beam energy of 2.5 keV and doses from 3500 to 80 000 μC/cm2. Gold patterns were generated by wet etching in KCN/KOH and characterized by atomic force microscopy and scanning electron microscopy. The width of the finest lines is ∼20 nm; their edge definition is limited by the isotropic etching process in the polycrystalline gold. © 2000 American Vacuum Society.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
85.40.Hp Lithography, masks and pattern transfer
68.18.-g Langmuir-Blodgett films on liquids
81.65.Cf Surface cleaning, etching, patterning

Hydrogen silsesquioxane/novolak bilayer resist for high aspect ratio nanoscale electron-beam lithography

Falco C. M. J. M. van Delft, Jos P. Weterings, Anja K. van Langen-Suurling, and Hans Romijn

J. Vac. Sci. Technol. B 18, 3419 (2000); http://dx.doi.org/10.1116/1.1319682 (5 pages) | Cited 42 times

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A bilayer resist system, consisting of hydrogen silsesquioxane (HSQ) as negative tone electron (e)-beam resist top coat and hard baked novolak resist as bottom coat, has been investigated for its ability to yield high aspect ratio nanoscale structures. For comparison, single layer HSQ (hard mask) has been investigated for its resolution, contrast, and process latitude. In single layer HSQ, dense lines and spaces (1:1) have been resolved down to 20 nm and single lines have been obtained with widths less than 15 nm. Processing conditions which result in higher contrasts in HSQ also result in higher horizontal contrasts, i.e., in poorer process latitudes; this effect has previously been observed for other negative tone e-beam resists as well. In the bilayer combination, HSQ allows nanoscale structures with an aspect ratio exceeding 15 to be etched in hard baked novolak resist. Single lines with 800 nm height and 40 nm width, semidense lines and spaces (1:2) with 155 nm height and 25 nm width, and dense lines and spaces (1:1) with 130 nm height and 40 nm width have been patterned in this bilayer system. Both the single layer HSQ and the HSQ/novolak bilayer system appear to be suitable as e-beam resists for research on nanoscale gates in complementary metal–oxide–semiconductor (CMOS) and other devices. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
85.30.Tv Field effect devices
81.65.Cf Surface cleaning, etching, patterning

High-purity, ultrahigh-resolution calixarene electron-beam negative resist

Shoko Manako, Yukinori Ochiai, Hiromasa Yamamoto, Takahiro Teshima, Jun-ichi Fujita, and Eiichi Nomura

J. Vac. Sci. Technol. B 18, 3424 (2000); http://dx.doi.org/10.1116/1.1321274 (4 pages) | Cited 4 times

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Calixarene is a promising high-resolution negative electron-beam resist having a resolution of the order of 10 nm because of its low molecular weight. We have made a purified calixarene resist containing metal contaminants whose concentrations are measured in parts per billion and which therefore do not degrade the performance of silicon-based electron devices. The purity of the calixarene itself was also improved and we obtained high-purity calix[6]arene and high-purity calix[7]arene, both of which contain the main component, which is more than 95% of all the calixarene present. The resolution of both purified calixarene resists is almost the same as that of the unpurified calixarene, but the sensitivity of calix[7]arene is higher than that of calix[6]arene because its molecular weight is higher. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

Calixarene G-line double resist process with 15 nm resolution and large area exposure capability

Jakub Kedzierski, Erik Anderson, and Jeffrey Bokor

J. Vac. Sci. Technol. B 18, 3428 (2000); http://dx.doi.org/10.1116/1.1314386 (3 pages) | Cited 3 times

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Methods for combining fast optical lithography and slower high-resolution calixarene electron-beam lithography are presented. These methods rely on dividing the pattern into low-resolution and high-resolution components and exposing each with optical and electron-beam lithography steps, respectively. Patterns produced in this way have a minimum linewidth of 15 nm, and arbitrarily large low-resolution features. Although the procedures take two steps, for many patterns the total exposure time is significantly lower then it would be with a single step calixarene-only process. The optical and electron-beam exposures were aligned using SiGe zero-level alignment marks. A 5 nm misalignment between subsequent electron beam exposures is demonstrated. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Aqueous base development and acid diffusion length optimization in negative epoxy resist for electron beam lithography

N. Glezos, P. Argitis, D. Velessiotis, I. Raptis, M. Hatzakis, P. Hudek, and I. Kostic

J. Vac. Sci. Technol. B 18, 3431 (2000); http://dx.doi.org/10.1116/1.1324615 (4 pages) | Cited 5 times

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A new aqueous base developable, chemically amplified negative resist based on epoxy chemistry is evaluated for high-resolution, high-speed e-beam lithography. This resist is formulated using partially hydrogenated poly(hydroxy styrene) and epoxy novolac polymers. Degree of hydrogenation controls the aqueous base solubility and microphase separation phenomena. Reduction of edge roughness compared to the pure epoxy systems is observed whereas the absence of swelling phenomena allows lithography up to 100 nm regime and a sensitivity of 4–8 μC/cm2 at 50 keV. The diffusion coefficient has been evaluated both from high-resolution line and dot exposures and it is found to be 5×10−14 cm2/s for the optimal thermal processing conditions selected. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Roughness study of a positive tone high performance SCALPEL resist

L. E. Ocola, P. A. Orphanos, W.-Y. Li, W. Waskiewicz, A. E. Novembre, and M. Sato

J. Vac. Sci. Technol. B 18, 3435 (2000); http://dx.doi.org/10.1116/1.1321289 (6 pages) | Cited 14 times

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In this article we discuss the line edge roughness of positive chemically amplified resists exposed on the SCALPEL exposure system in terms of the image formation process. The image formation process for a SCALPEL exposure on a positive chemically amplified resist has been simulated using discrete models from exposure through development. Key parameters have been identified that enable image formation simulations without the need of detailed molecular models. Molecular models are needed though to obtain several of these parameters. Surface and line edge roughness, as measured by scanning electron microscopy and atomic force microscopy, have been simulated and compared to experimental results. Results are consistent with a “percolation network formation for diffusion-reaction development” model for chemically amplified resists. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Influence of developer and development conditions on the behavior of high molecular weight electron beam resists

D. G. Hasko, Shazia Yasin, and A. Mumtaz

J. Vac. Sci. Technol. B 18, 3441 (2000); http://dx.doi.org/10.1116/1.1319834 (4 pages) | Cited 10 times

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The nature of the developer and development conditions of high molecular weight electron beam resists is known to influence sensitivity, contrast, line edge roughness, and ultimate resolution. These resist characteristics are explained using a dissolution model based on reptation theory and predictions are compared with experimental results on high molecular weight poly(methylmethacrylate) developed in a range of solvent mixtures and conditions, including ultrasonically assisted development. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
64.75.-g Phase equilibria
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

Evolutionary optimization of the electron-beam lithography process for gate fabrication of high electron mobility transistors

Franck Robin, Andrea Orzati, Otte J. Homan, and Werner Bächtold

J. Vac. Sci. Technol. B 18, 3445 (2000); http://dx.doi.org/10.1116/1.1321277 (5 pages) | Cited 3 times

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An electron-beam lithography simulation tool was realized. This tool models the development of multilayered poly(methylmethacrylate) resist structures after exposure with an electron beam. A development front propagates inside the resist stack as a function of time and the local solubility. The local solubility was experimentally measured versus the electron dose for different types of resist. The efficiency of incident and backscattered electrons was determined using doughnut-shaped structures. The ratio of the backscattered to incident electron efficiencies η was found to be 1.35 for an acceleration voltage of 30 kV on InP substrates. We used genetic algorithms to optimize the electron dose necessary for the realization of a given resist profile. This tool was applied to fabricate T-gates and asymmetric gate recesses. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
02.60.Pn Numerical optimization
85.30.Tv Field effect devices

Mechanical properties and pattern collapse of chemically amplified photoresists

Long Que and Yogesh B. Gianchandani

J. Vac. Sci. Technol. B 18, 3450 (2000); http://dx.doi.org/10.1116/1.1319833 (3 pages) | Cited 5 times

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The mechanical properties of positive tone chemically amplified resists UV6 and APEX-E are measured and used in finite element analysis (FEA) to determine the mechanical compliance of photoresist lines as an indicator of the propensity for pattern collapse. Specifically, the residual strain is determined by surface micromachined resist structures; the residual stress, expansion coefficient, and glass transition temperatures are determined from wafer curvature measurements; and the Young’s modulus is calculated from the stress and strain. The results indicate that UV-6 has higher strain and a higher coefficient of thermal expansion than APEX-E. However, it has lower residual stress because its Young’s modulus is 50%–70% lower than that of APEX-E. FEA indicates that lines of UV6 have greater compliance than those of APEX-E, and are more easily deformed by fluidic forces during develop and rinse steps. This is fully consistent with separate reports that demonstrate a greater likelihood of pattern collapse in UV6 than APEX-E. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
68.60.Bs Mechanical and acoustical properties
62.20.D- Elasticity
65.40.De Thermal expansion; thermomechanical effects
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
02.70.Dh Finite-element and Galerkin methods
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Kinetics and crystal orientation dependence in high aspect ratio silicon dry etching

M. A. Blauw, T. Zijlstra, R. A. Bakker, and E. van der Drift

J. Vac. Sci. Technol. B 18, 3453 (2000); http://dx.doi.org/10.1116/1.1313578 (9 pages) | Cited 24 times

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A quantitative study of dry etch behavior in deep silicon trenches in high density plasmas (electron cyclotron resonance, inductively coupled plasma) at low temperatures (160–210 K) is presented. The quantitative approach implies etch behavior being studied in relation to the relevant particle fluxes (atomic F and O and ions) as measured by in situ diagnostics. Two etch modes are observed. In one mode faceting shows up as due to crystallographic orientation preference, i.e., Si〈111〉 being etched slower than Si〈100〉. In the other mode the normal anisotropic ion-induced behavior is observed. Controlled switch from one mode to the other is studied under influence of process parameters like pressure, ion energy, and substrate temperature. The second part of this study deals with aspect ratio dependent etching (ARDE). Both vertical and horizontal trenches have been taken into account as to distinguish between radical and ion-induced effects. The flux of radical species into the deep trench is governed by Knudsen transport, with a reaction probability of atomic fluorine of about 0.5. As a consequence depletion of the fluorine content at the bottom is the main reason for ARDE. With the bottleneck identified, the plasma process has been readily tuned to the aspect ratio independent etch regime. This regime coincides with the crystallographic preference mode where surface reaction kinetics form the rate limiting step. Detailed surface analysis studies by x-ray photoelectron spectroscopy, in situ ellipsometry, and transmission electron microscopy have been used to characterize the surface reaction process. © 2000 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.05.Cy Elemental semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
07.10.Cm Micromechanical devices and systems
82.20.Hf Product distribution

High speed anisotropic dry etching of CoNbZr for next generation magnetic recording

M. S. P. Andriesse, T. Zijlstra, and E. van der Drift

J. Vac. Sci. Technol. B 18, 3462 (2000); http://dx.doi.org/10.1116/1.1313577 (5 pages) | Cited 10 times

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Dry etch behavior of CoNbZr in an inductively coupled plasma of Cl2/BCl3 at elevated temperatures has been studied. Etch behavior of the alloy is ion induced with a strong chemical enhancement. The etch rate shows nonstoichiometric behavior when compared with the constituting elements. The increase by about 35% is attributed to interactive effects. A further enhancement up to about 40% is obtained under simultaneous exposure of deep ultraviolet irradiation. A fast anisotropic dry patterning process for CoNbZr has been developed, with etch rates up to 300 nm/min at 220 °C. © 2000 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Effects of reactive ion etching on the electrical characteristics of GaN

B. Rong, R. Cheung, W. Gao, M. M. Alkaisi, and R. J. Reeves

J. Vac. Sci. Technol. B 18, 3467 (2000); http://dx.doi.org/10.1116/1.1320799 (4 pages) | Cited 9 times

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We present an investigation of the electrical characteristics of plasma exposed GaN. The specific contact resistance of ohmic contacts fabricated on GaN after argon plasma bombardment for 2.5 min at 0.03 W/cm2 are measured to decrease by a factor of 4 compared to the unetched surface. Gold has been found to be the best material for GaN Schottky diode. A study of the electrical performance of diodes fabricated on plasma exposed GaN has been undertaken. To compare the effect of the chemical versus physical factors, as well as the role played by the ion mass of the etchant species during the etching process on diode behavior, GaN surfaces have been exposed to Ar, N2, as well as SF6+N2 plasmas before diode fabrication. Our data indicate that a plasma with low ion mass etchant species or a dominant chemical mechanism of etching with a high etch rate creates less surface damage. The use of a SF6+N2 plasma should be possible for GaN transistor gate recessing. © 2000 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Ea III-V semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
73.40.Ns Metal-nonmetal contacts
85.30.Kk Junction diodes
73.40.Cg Contact resistance, contact potential

High resolution inductively coupled plasma etching of 30 nm lines and spaces in tungsten and silicon

Andrew L. Goodyear, Sinclair Mackenzie, Deirdre L. Olynick, and Erik H. Anderson

J. Vac. Sci. Technol. B 18, 3471 (2000); http://dx.doi.org/10.1116/1.1326922 (5 pages) | Cited 6 times

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Dry etching of 30 nm features was investigated for x-ray and integrated electronics applications. These typically require etching of either a tungsten absorber layer or a silicon mold. Through the use of an inductively coupled plasma source and accurate control over substrate temperature it was possible to achieve highly anisotropic patterning of tungsten and silicon. Densely patterned features as small as 30 nm and at pitches of 70 nm were etched in tungsten and silicon, to depths of 100 and 200 nm, respectively. © 2000 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Micromask-induced surface defects inside Si trench isolation

Kyeonglan Rho

J. Vac. Sci. Technol. B 18, 3476 (2000); http://dx.doi.org/10.1116/1.1320800 (5 pages)

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A 20-nm-thick pad oxide layer is thermally grown on a 6-in. p-type 〈100〉 Si wafer, and is followed by the deposition of a 315-nm-thick low pressure chemical vapor deposition nitride layer for the trench isolation formation. Nitride and oxide layers are etched and Si is then etched away for trench formation. Initially, CF4/Ar was used to etch the 20 nm/315-nm-thick oxide/nitride layers, after which the wafers were transferred to a different etcher, AME5000 MXP polysilicon etcher, for the Si etch. The Si etch consists of two steps: first, the breakthrough step was performed to remove either the remaining oxide layer from the previous step or the native oxide layer using 35 sccm of CF4 for 15 s. In a second step, the main etch was performed to etch Si using 90 sccm of HBr, 30 sccm of Cl2, and 7 sccm of He–O2 for 250 s. After the Si etch, surface defects on the order of 1000–1600/wafer were observed on the Si surfaces using the Tencor AIT pattern inspection tool. The surface defects are caused by polymer-related micromasking. Instead of employing CF4/Ar for the removal of the oxide/nitride layers, 30 sccm of NF3 and 5 sccm of O2 were used for the main etch step, and 10 sccm of CHF3 and 40 sccm of N2 were used for the overetch step. The Si etch was continued in the AME5000 MXP polysilicon etcher using the original parameters. The use of NF3/O2, which does not polymerize the Si surface, resulted in an almost defect-free surface. More experiments were conducted for the overetch step after the removal of nitride layer because NF3 etches the Si surface quickly once it is exposed. The combination of the NF3/O2 main etch step by endpoint algorithm and the 25 s CHF3/N2 overetch step, resulted in fewer surface defects than using CF4/Ar for both main and overetch steps. © 2000 American Vacuum Society.
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85.40.Ls Metallization, contacts, interconnects; device isolation
81.65.Cf Surface cleaning, etching, patterning
85.40.Hp Lithography, masks and pattern transfer
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Quantum interference in a vacuum nanotriode

A. A. G. Driskill-Smith, D. G. Hasko, and H. Ahmed

J. Vac. Sci. Technol. B 18, 3481 (2000); http://dx.doi.org/10.1116/1.1314388 (7 pages) | Cited 8 times

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The current–voltage and noise characteristics of vacuum nanoelectronic devices, including nanoscale field-emission diodes and vacuum nanotriodes, are presented. The turn-on voltage for field emission in these devices is about 8 V, independent of ambient temperature, and currents of up to 10 nA are obtained. Time-independent fluctuations are observed in the current–voltage characteristics of the vacuum nanoelectronic devices that persist down to 20 K. In the case of the nanotriode, these fluctuations are repeatable in different sweeps performed both at the same and at different temperatures. These measurements, coupled with a model of the nanotriode, which includes an analysis of the electrostatic field within the nanochamber, the electron trajectories, and the role of field-emission resonances, suggest that the origin of the time-independent fluctuations is a quantum-interference effect between the electron wave function in the tip of the nanopillar field emitter and the anode. © 2000 American Vacuum Society.
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85.45.Bz Vacuum microelectronic device characterization, design, and modeling

Comparative study of self-aligned and nonself-aligned SiGe p-metal–oxide–semiconductor modulation-doped field effect transistors with nanometer gate lengths

Wu Lu, Steven J. Koester, Xie-Wen Wang, Jack O. Chu, Tso-Ping Ma, and Ilesanmi Adesida

J. Vac. Sci. Technol. B 18, 3488 (2000); http://dx.doi.org/10.1116/1.1321286 (5 pages) | Cited 4 times

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A self-aligned process used to fabricate p-type SiGe metal–oxide–semiconductor modulation-doped field effect transistors (MOS-MODFET) is described. Self- and nonself-aligned p-type Si0.2Ge0.8/Si0.7Ge0.3 MOS-MODFETs with gate-lengths from 1 μm down to 100 nm were fabricated. The dc and microwave characteristics of these devices are presented. In comparison with nonself-aligned devices, self-aligned devices exhibited higher extrinsic transconductances, lower threshold voltages, higher unity current gain cutoff frequencies fT, and maximum oscillation frequencies fMAX. Self-aligned MOS-MODFETs with a gate length of 100 nm exhibited an extrinsic transconductance of 320 mS/mm, an fT of 64 GHz, and an fMAX of 77 GHz. To our knowledge, these are the highest data ever reported for any MOS-type p-FETs with a SiGe channel. All these excellent performances were measured at very low drain and gate biases. © 2000 American Vacuum Society.
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85.30.Tv Field effect devices

Fabrication technique for nanometer-scale InAs quantum devices: Observation of quantum interference in Aharonov–Bohm rings and Coulomb blockade in quantum dots

T. H. Chang, K. A. Chen, C. H. Yang, M. J. Yang, and D. Park

J. Vac. Sci. Technol. B 18, 3493 (2000); http://dx.doi.org/10.1116/1.1321285 (4 pages) | Cited 2 times

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We report an approach to the lateral confinement of electrons in InAs/AlSb single quantum wells. Using electron-beam lithography and reactive ion etching, we have fabricated conducting wires, rings, and dots with lateral dimensions ⩾50 nm. Characterization on narrow wires and rings indicates that the electron transport is in the quasiballistic regime at 4.2 K. The current–voltage characteristics of 70-nm-diam dots in single-electron transistor structures show the Coulomb gap and the Coulomb staircase features. These artificially patterned devices have an ultimate lateral dimension of a few nanometers, limited by the resolution of electron-beam lithography. © 2000 American Vacuum Society.
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.35.Ds Quantum interference devices
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
73.23.Hk Coulomb blockade; single-electron tunneling
85.35.Gv Single electron devices

Nanofabrication using structure controlled hydrogenated Si clusters deposited on Si surfaces

Toshihiko Kanayama, Miyoko O. Watanabe, Leonid Bolotov, and Noriyuki Uchida

J. Vac. Sci. Technol. B 18, 3497 (2000); http://dx.doi.org/10.1116/1.1324620 (4 pages)

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We studied structure formation by deposition of hydrogen-saturated Si clusters Si6H13+ and Si8H19+ on Si (111)-(7×7) surfaces using the deposition system of cluster ions equipped with a scanning tunneling microscope (STM) for surface observation. The system uses a quadrupole ion trap as a mass-selective source of cluster ion beams and delivers to the substrate a beam of Si6H13+ focused to 2 mm diameter with a current of ∼100 pA for the cluster kinetic energy on impact with the surface >5 eV. It was observed that when these clusters are deposited with suitable kinetic energy, i.e., ∼2 eV/Si atom, the impact energy makes the clusters mobile on the surface, leading to self-formation of cluster-agglomerated structures at step edges and along domain boundaries of (7×7) phases. Intentional manipulation of the deposited clusters is also possible using the STM tip; the clusters can be accumulated to the tip position by applying bias voltage larger than 3 V. © 2000 American Vacuum Society.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
85.40.Sz Deposition technology
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Nanofabrication techniques for lasers with two-dimensional photonic crystal mirrors

J. Moosburger, Th. Happ, M. Kamp, and A. Forchel

J. Vac. Sci. Technol. B 18, 3501 (2000); http://dx.doi.org/10.1116/1.1319826 (4 pages) | Cited 8 times

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The fabrication of photonic crystals (PC) involves a periodic modulation of the refractive index on nanometer scales thus requiring state-of-the-art patterning and dry etch technologies. In this article, we compare three different mask techniques for the fabrication of ridge waveguide lasers with two-dimensional triangular PC mirrors. After defining the hole pattern in 500 nm polymethylmetacrylate by 100 kV e-beam lithography the structure is transferred to the mask layer. The first mask layer is a metal mask consisting of Ti/Cr/Ti. The second one is formed by wet chemical oxidation of a buried 60 nm AlAs layer and the third one uses a single SiO2 layer in order to transfer the hole pattern into the semiconductor. The periods of the PC, with an average air filling factor of 45%, were chosen in the range of 160–400 nm in order to probe the region where high reflectivity of the PC is expected. The observed laser performance is used to deduce information about the quality of the fabricated PCs. The advantages of each technique are discussed, leading to conclusions for future techniques for the fabrication process of photonic crystals. © 2000 American Vacuum Society.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
42.70.Qs Photonic bandgap materials
42.82.Cr Fabrication techniques; lithography, pattern transfer
85.40.Hp Lithography, masks and pattern transfer
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
42.79.Bh Lenses, prisms and mirrors
81.65.Mq Oxidation
81.65.Cf Surface cleaning, etching, patterning

Fabrication of three-dimensional photonic structures with submicrometer resolution by x-ray lithography

C. Cuisin, A. Chelnokov, J.-M. Lourtioz, D. Decanini, and Y. Chen

J. Vac. Sci. Technol. B 18, 3505 (2000); http://dx.doi.org/10.1116/1.1319825 (5 pages) | Cited 16 times

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We report on the fabrication of diamond-like photonic structures in PMMA resist and their use as porous templates for transferring three-dimensional patterns to metals or dielectrics. Following the original “three drilling holes” approach first proposed by Yablonovitch, we used three consecutive exposures of PMMA resist to an x-ray beam through a triangular lattice of holes. A submicronic patterning was thus obtained in thick PMMA layers (>6 μm). Optical characterizations of 1.3 μm period templates showed a well-defined photonic gap in the midinfrared. The pattern transfers from the PMMA templates to a metal (copper) and a high refractive index dielectric (titania) were achieved by the electrodeposition and sol–gel filling techniques, respectively. Three-dimensional metallic structures of 1.3 μm lattice constant were obtained with extreme regularity over a thickness of ∼6 μm, thereby providing a way to build submicrometer photonic band gap materials for optical wavelengths. © 2000 American Vacuum Society.
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42.70.Qs Photonic bandgap materials
42.82.Cr Fabrication techniques; lithography, pattern transfer
85.40.Hp Lithography, masks and pattern transfer
81.15.Pq Electrodeposition, electroplating
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Drilled alternating-layer structure for three-dimensional photonic crystals with a full band gap

Eiichi Kuramochi, Masaya Notomi, Toshiaki Tamamura, Takayuki Kawashima, Shojiro Kawakami, Jun-ichi Takahashi, and Chiharu Takahashi

J. Vac. Sci. Technol. B 18, 3510 (2000); http://dx.doi.org/10.1116/1.1319824 (4 pages) | Cited 4 times

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A new three-dimensional photonic crystal structure is designed to simplify fabrication. A calculation of the band structure predicts that this photonic crystal has a complete photonic band gap in all directions. The entire three-dimensional periodic structure, except for the vertically drilled holes, is formed by automatic shaping during bias sputtering deposition. The fabrication technologies used to construct this photonic crystal are electron beam lithography, bias sputtering, and fluoride-gas electron cyclotron resonance etching. Our preliminary fabrication reveals that each technology can be controlled well enough to lead to the creation of a photonic band gap material for an optical communication wavelength. © 2000 American Vacuum Society.
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42.70.Qs Photonic bandgap materials
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.15.Cd Deposition by sputtering
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
85.40.Hp Lithography, masks and pattern transfer

Nanoheteroepitaxy: Nanofabrication route to improved epitaxial growth

D. Zubia, S. H. Zaidi, S. D. Hersee, and S. R. J. Brueck

J. Vac. Sci. Technol. B 18, 3514 (2000); http://dx.doi.org/10.1116/1.1321283 (7 pages) | Cited 21 times

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Nanoheteroepitaxy is a fundamentally new epitaxial approach that utilizes three-dimensional stress relief mechanisms available to nanoscale heterostructures to eliminate defects provided the island diameter is below a critical value 2lc. Analysis shows that 2lc∼(15–30)× the critical thickness hc. In the case of GaAs on Si (∼4% misfit), 2lc∼40 nm. In material systems such as GaN on Si (∼20% misfit), where the misfit is much larger and interfacial defects are unavoidable, the nanoheteroepitaxial structure is shown to reduce the formation and propagation of threading defects. Nanostructured substrate parameters that impact growth are discussed and interferometric lithography is introduced as a method for fabrication of large-area substrates for nanoheteroepitaxy. Si nanoisland diameters as small as 20 nm are demonstrated. Scanning and transmission electron microscopy data of GaN grown on Si (via organometallic vapor phase epitaxy) shows reduced threading defects in nanostructured samples compared to growth on planar substrates. Photoluminescence intensity data of nanostructured samples is enhanced by ∼100× as compared to planar-growth samples. © 2000 American Vacuum Society.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

Fabrication of 30 nm T gates using SiNx as a supporting and definition layer

Y. Chen, D. Edgar, X. Li, D. Macintyre, and S. Thoms

J. Vac. Sci. Technol. B 18, 3521 (2000); http://dx.doi.org/10.1116/1.1321279 (4 pages) | Cited 6 times

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A new process has been developed to fabricate 30 nm T gates for high performance metal–semiconductor field effect transistors and high electron mobility transistors. The fabrication of short gate length T gates becomes increasingly difficult as the footwidth of the gate is made smaller and this is particularly true when the footwidth is less than 50 nm. In this process a thin SiNx layer is deposited on the substrate prior to the application of a bilayer of poly(methylmethacrylate)/Shipley UVIII resist. After resist patterning by electron beam lithography the nitride layer is etched at a low bias voltage that causes negligible substrate damage. This process step helps to define the gate footwidth and improves mechanical stability of the gate. The measured gate resistance was 375 Ω/mm. © 2000 American Vacuum Society.
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85.30.Tv Field effect devices
85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning

Progress on nanostructuring with Nanojet

J. Voigt, F. Shi, P. Hudek, I. W. Rangelow, and K. Edinger

J. Vac. Sci. Technol. B 18, 3525 (2000); http://dx.doi.org/10.1116/1.1319823 (5 pages) | Cited 5 times

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Micro- and nanostructuring of a substrate by direct writing of the structures with a localized radical jet using the scanning probe principle is demonstrated. Electrically neutral radicals created in a downstream plasma discharge are pumped through a small nozzle and directed on to the substrate. Due to the small distance between the nozzle and surface of the workpiece, localized interaction is induced. Etched structures with 270 nm resolution produced by a nozzle with a diameter of 250 nm are presented. The etching rates achieved for micro- and nanostructuring are 200 nm/min in photoresist and 400 nm/min in silicon, respectively. It is shown experimentally that the resolution of the process is determined by the diameter of the nozzle, provided that the working distance is small, i.e., less than the diameter of the nozzle. Fundamentals for the development of a tool for direct structuring in the sub-100 nm range, including nanofabrication of a sub-100 nm nozzle, are presented in this work. © 2000 American Vacuum Society.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
52.80.Pi High-frequency and RF discharges

Combining advanced lithographic techniques and self-assembly of thin films of diblock copolymers to produce templates for nanofabrication

Richard D. Peters, Xiao M. Yang, Qiang Wang, Juan J. de Pablo, and Paul F. Nealey

J. Vac. Sci. Technol. B 18, 3530 (2000); http://dx.doi.org/10.1116/1.1313572 (5 pages) | Cited 23 times

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A technique to create templates for nanofabrication using thin films of diblock copolymers is discussed and demonstrated. Advanced lithographic techniques are used to create chemically patterned surfaces that manipulate the wetting behavior of diblock copolymer films and to guide the spatial microphase separation of the block copolymer domains. Guided microphase separation has great potential for application of block copolymer films in nanofabrication because of perpendicular orientation of the domains to the substrate and macroscopic perfection in the ordering of copolymer domains. Lithography allows for registration of the domains with the substrate for creating addressable arrays. Experimental implementation of the technique is demonstrated using extreme ultraviolet interferometric lithography, self-assembled monolayers of octadecyltrichlorosilane as imaging layers, and the self-assembly of films of symmetric poly(styrene-b-methyl methacrylate). © 2000 American Vacuum Society.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
85.40.Hp Lithography, masks and pattern transfer

Oxide nanodots and ultrathin layers fabricated on silicon using nonfocused multicharged ion beams

G. Borsoni, M. Gros-Jean, M. L. Korwin-Pawlowski, R. Laffitte, V. Le Roux, and L. Vallier

J. Vac. Sci. Technol. B 18, 3535 (2000); http://dx.doi.org/10.1116/1.1324647 (4 pages) | Cited 8 times

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We have used slow multicharged argon ions in ultrahigh vacuum with a partial pressure of oxygen to form ultrathin (subnanometer) oxide dots of a few tens of nanometer diameter on a silicon surface. The main characteristic of this technique is that the incident multicharged ion does not penetrate below the surface, so there is no implantation-induced modifications of the substrate. Thus, we utilized a unique possibility provided by the multicharged ions interaction with surfaces of solids, the noncontact trampoline effect, to open the bonds of hydrogenated silicon, and replace it with oxygen. This article presents the fundamentals of slow multicharged ion interaction with a surface, the experimental multicharged ion beam line build at X-ion laboratory, and obtained results of oxide dot formation on silicon, using them as a mask in a reactive ion etching process to grow three-dimensional crystalline silicon structures. Potential applications are in nanoflash–multidot type nonvolatile memories. © 2000 American Vacuum Society.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
85.40.Hp Lithography, masks and pattern transfer

Optimization of a lithographic and ion beam etching process for nanostructuring magnetoresistive thin film stacks

Michael E. Walsh, Yaowu Hao, C. A. Ross, and Henry I. Smith

J. Vac. Sci. Technol. B 18, 3539 (2000); http://dx.doi.org/10.1116/1.1324639 (5 pages) | Cited 18 times

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The patterning of multilayer thin-film stacks to create spin valves, with dimensions ∼100 nm, for magnetic-random-access memories presents novel fabrication challenges since the materials commonly used (e.g., Co, Cu, and Ni) do not form volatile compounds, and hence cannot be reactive-ion etched. The consequent necessity of using ion-beam etching (“ion milling”) demands a solution to the twin problems of faceting and redepostion of sputtered material. In addition, antireflection layers are not used during lithography because of the necessity of avoiding high-temperature curing, which would harm the spin valve characteristics. By using a thin SiOx phase-shifting layer under the resist, we obtained adequate resist profiles; and by using a 15-nm-thick W hard mask, no measurable redeposition was observed after ion milling of cobalt. Improved etch selectivity of W relative to Co is achieved by using neon as the ion-milling gas rather than argon. A simple model for the enhanced ion-milling selectivity is presented. © 2000 American Vacuum Society.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Field emission cathode array with self-aligned gate electrode fabricated by silicon micromachining

W. Barth, T. Debski, F. Shi, P. Hudek, I. Kostic, I. W. Rangelow, S. Biehl, T. Iwert, P. Grabiec, K. Studzinska, S. Mitura, I. I. Bekh, A. E. Lushkin4, L. G. Il’chenko, V. V. Il’chenko, et al.

J. Vac. Sci. Technol. B 18, 3544 (2000); http://dx.doi.org/10.1116/1.1324648 (5 pages) | Cited 2 times

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An electron emission behavior of field emission arrays based on a new bulk/surface silicon micromachining method of fabrication was studied. The process developed is simple and allows self-aligned gate electrode formation. The field emission of the emitter tips is enhanced by a 50 nm diamond-like carbon (DLC) film formed by chemical vapor deposition. Detailed Raman, Auger, and transmission electron microscopy (TEM) investigations of the deposited DLC films will be presented. Results about the presence of nanocrystalline diamond obtained with Raman spectroscopy could not be confirmed by the TEM investigations (the nanocrystalline diamond is smaller than 10 nm). © 2000 American Vacuum Society.
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85.45.Db Field emitters and arrays, cold electron emitters

Actuation and internal friction of torsional nanomechanical silicon resonators

A. Olkhovets, S. Evoy, D. W. Carr, J. M. Parpia, and H. G. Craighead

J. Vac. Sci. Technol. B 18, 3549 (2000); http://dx.doi.org/10.1116/1.1313571 (3 pages) | Cited 10 times

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We report on the actuation and mechanical properties of silicon resonators with nanometer-scale supporting rods operating in the 3–20 MHz range. The symmetrically designed paddles can be excited both in their flexural and torsional modes of motion. Fabrication imperfections as small as 10–20 nm provide enough asymmetry to allow such torsional excitation. We also report on internal friction studies in these systems. Thin Al overlayers contribute to the room temperature internal losses, as quality factor drops from 3300 to 380 for 160 Å thick film. A temperature dependence of internal friction has a broad peak in the T=160–190 K range, and attributed to the Debye relaxation and thermally activated friction mechanisms. Analysis shows that the peak shifts to higher temperatures with increasing resonator frequency. © 2000 American Vacuum Society.
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07.10.Cm Micromechanical devices and systems
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
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Novel alignment system for imprint lithography

D. L. White and O. R. Wood

J. Vac. Sci. Technol. B 18, 3552 (2000); http://dx.doi.org/10.1116/1.1319706 (5 pages) | Cited 21 times

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A novel alignment system for imprint lithography in the deep sub-hundred nanometer realm is proposed. The new system is inherently more precise than the alignment systems used in conventional projection lithography because alignment marks on an imprint mold (the functional equivalent of a photomask in projection lithography) are directly compared to alignment marks on a wafer with no intermediate optics or reference points. If the measured misalignment is so severe that all marks cannot be brought into registration simultaneously by the usual x–y translations and rotations, the mold is deliberately deformed with a system of piezoelectric actuators in such a way that its induced distortions precisely match those on the wafer and all of the alignment marks at each chip site can be pulled into registration simultaneously. Finite-element analysis indicates that using actuators to distort the mold is superior to distorting the wafer. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Nanoimprint lithography at the 6 in. wafer scale

Babak Heidari, Ivan Maximov, and Lars Montelius

J. Vac. Sci. Technol. B 18, 3557 (2000); http://dx.doi.org/10.1116/1.1326923 (4 pages) | Cited 31 times

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We demonstrate the nanoimprint lithography (NIL) technique with sub 100 nm resolution, on 6 in. Si substrates. The pattern transfer is performed using a specially designed NIL machine optimized to achieve a very high degree of parallelism between stamp and substrate. The stamp is made with the help of electron beam lithography and Ni electroplating achieving features below 100 nm in size. The nanoimprint process is done in a single layer as well as in a multilayer resist scheme with subsequent O2-plasma etching and metal lift-off. © 2000 American Vacuum Society.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
85.40.Hp Lithography, masks and pattern transfer

Fabrication of quantum point contacts by imprint lithography and transport studies

Ingo Martini, Silke Kuhn, Martin Kamp, Lukas Worschech, Alfred Forchel, Dominik Eisert, Johannes Koeth, and Rint Sijbesma

J. Vac. Sci. Technol. B 18, 3561 (2000); http://dx.doi.org/10.1116/1.1319705 (3 pages) | Cited 17 times

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This article demonstrates the integration of imprint lithography into nanoelectronic device fabrication. We present a quantum point contact (QPC) with split gates patterned by imprint lithography. The semiconductor substrate is a modulation-doped GaAs/AlGaAs heterostructure with the two-dimensional electron gas located about 90 nm below the surface. A Si mold with a split-gate pattern is embossed into a poly(methylmethacrylate) film located on top of the semiconductor. The Schottky gates are fabricated by metal evaporation and liftoff. The gate tip separation ranges from 120 to 600 nm. Transport studies performed at T=2 K show conductance quantization with varying gate voltages. Measurements performed on a reference QPC with gates defined by electron beam lithography show similar results. This indicates that the imprint does not affect the electronic performance of the semiconductor. © 2000 American Vacuum Society.
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73.23.-b Electronic transport in mesoscopic systems
85.40.Hp Lithography, masks and pattern transfer
85.35.Ds Quantum interference devices
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
73.61.Ey III-V semiconductors

Quantitative analysis of the molding of nanostructures

H. Schift, C. David, J. Gobrecht, A. D’ Amore, D. Simoneta, W. Kaiser, and M. Gabriel

J. Vac. Sci. Technol. B 18, 3564 (2000); http://dx.doi.org/10.1116/1.1324622 (5 pages) | Cited 16 times

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Mass fabrication processes such as injection molding and hot embossing are highly suitable for the replication of micro- and nanostructures. They require thermoplastic polymers with good molding properties at moderate process temperatures. We show a quantitative approach to the analysis of the molding properties of polymers in the nanorange in which the parameters are most important for achieving good replication fidelity. With this information we were able to fabricate high precision calibration chips for scanning probe microscopes. © 2000 American Vacuum Society.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
81.10.Fq Growth from melts; zone melting and refining
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials

Electron-beam fabrication of nonplanar templates for contact printing

K. W. Rhee, L. M. Shirey, P. I. Isaacson, C. F. Kornegay, W. J. Dressick, M.-S. Chen, and S. L. Brandow

J. Vac. Sci. Technol. B 18, 3569 (2000); http://dx.doi.org/10.1116/1.1319704 (3 pages) | Cited 3 times

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Templates for contact printing applications have been fabricated on convex and concave surfaces using electron-beam lithography. Curved quartz lens blanks, coated with a chrome layer to suppress charging, were spincoated with a layer of polymethylmethacrylate (PMMA). Features were patterned into the PMMA followed by development, pattern transfer into the chrome by wet etch, and reactive-ion etching (RIE) of the chrome masked quartz. Features to 0.3 μm have been patterned and transferred ∼600 nm into the underlying quartz substrate by RIE, with less than a 10% etch depth variation across the sample. The patterned substrate was then used as a template to cast polymer stamps from poly(dimethylsiloxane). This approach provides a convenient method of fabricating curved templates for contact printing. © 2000 American Vacuum Society.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning
81.10.Fq Growth from melts; zone melting and refining

Step and flash imprint lithography: Template surface treatment and defect analysis

T. Bailey, B. J. Choi, M. Colburn, M. Meissl, S. Shaya, J. G. Ekerdt, S. V. Sreenivasan, and C. G. Willson

J. Vac. Sci. Technol. B 18, 3572 (2000); http://dx.doi.org/10.1116/1.1324618 (6 pages) | Cited 134 times

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We have finished the construction of an automated tool for step and flash imprint lithography. The tool was constructed to allow defect studies by making multiple imprints on a 200 mm wafer. The imprint templates for this study were treated with a low surface energy, self-assembled monolayer to ensure selective release at the template-etch barrier interface. This surface treatment is very durable and survives repeated imprints and multiple aggressive physical and chemical cleanings. The imprint and release forces were measured for a number of successive imprints, and did not change significantly. The process appears to be “self-cleaning.” Contamination on the template is entrained in the polymerizing liquid, and the number of defects is reduced with repeated imprints. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning

Comparison of infrared frequency selective surfaces fabricated by direct-write electron-beam and bilayer nanoimprint lithographies

Irina Puscasu, G. Boreman, R. C. Tiberio, D. Spencer, and R. R. Krchnavek

J. Vac. Sci. Technol. B 18, 3578 (2000); http://dx.doi.org/10.1116/1.1319838 (4 pages) | Cited 9 times

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We report on the fabrication of crossed-dipole resonant filters by direct-write electron-beam and nanoimprint lithographies. Such structures have been used as spectrally selective components at visible, microwave, and infrared wavelengths. Imprinting is accomplished in a modified commercial hot press at 155 °C. The replica is then etched in oxygen plasma and developed in chlorobenzene to selectively dissolve the poly(methylmethacrylate and methacrylic acid) and poly(methylmethacrylate) bilayer resist. This step enhances undercut and improves lift-off metalization. Infrared fourier transform spectroscopy was performed to characterize the transmission response of the frequency selective surfaces (FSSs) fabricated. The resonant behavior for the direct-write FSS was found to be 5.3 μm and for the nanoimprinted FSS to be 6 μm. The shift towards longer wavelengths is consistent with the dimensions obtained for the FSSs elements in both cases. © 2000 American Vacuum Society.
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84.40.Az Waveguides, transmission lines, striplines
85.40.Hp Lithography, masks and pattern transfer
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

Master replication into thermosetting polymers for nanoimprinting

H. Schulz, D. Lyebyedyev, H.-C. Scheer, K. Pfeiffer, G. Bleidiessel, G. Grützner, and J. Ahopelto

J. Vac. Sci. Technol. B 18, 3582 (2000); http://dx.doi.org/10.1116/1.1319821 (4 pages) | Cited 21 times

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Replication of the e-beam master into thermosetting polymers was investigated for low cost working stamp fabrication for nanoimprint lithography (NIL). Negative as well as positive replicas from a master were fabricated in a thermal replication step from duroplastic material. Without any further treatment these working stamps were able to imprint thermoplastic polymers. To demonstrate the procedure we used the custom polymers mr-I-8130 and mr-I-9030 as well as PMMA for comparison. All replications were done in a NIL process. The replication quality is excellent when a suitable imprint procedure is used. © 2000 American Vacuum Society.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
85.40.Hp Lithography, masks and pattern transfer
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
81.10.Fq Growth from melts; zone melting and refining
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Directed assembly of carbon nanotube electronic circuits by selective area chemical vapor deposition on prepatterned catalyst electrode structures

Y. Y. Wei, X. Fan, and Gyula Eres

J. Vac. Sci. Technol. B 18, 3586 (2000); http://dx.doi.org/10.1116/1.1319709 (4 pages) | Cited 4 times

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Electron-beam lithography was used to pattern Fe thin film electrode structures on silicon dioxide covered Si wafers. The Fe film also serves as a catalyst in subsequent chemical vapor deposition of carbon nanotubes. Chemical vapor deposition was performed in a stainless steel chamber using acetylene at a partial pressure of 100 mTorr and a substrate temperature of 660 °C. Transmission electron microscopy images reveal that the carbon nanotubes grown by this method are multiwalled. The carbon nanotubes selectively grow only on the catalyst film and eventually bridge the intentionally designed micron size electrode gap forming carbon nanotube electronic circuits. The resulting devices were characterized by electronic transport measurements in a temperature range from room temperature down to 2 K. © 2000 American Vacuum Society.
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85.65.+h Molecular electronic devices
81.05.ub Fullerenes and related materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.40.Sz Deposition technology
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
85.40.Hp Lithography, masks and pattern transfer
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Real time pattern changing in atomic beam holography using phase shift by Stark effect

J. Fujita, S. Mitake, and F. Shimizu

J. Vac. Sci. Technol. B 18, 3590 (2000); http://dx.doi.org/10.1116/1.1319685 (4 pages) | Cited 2 times

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An electrically controlled phase hologram has been used to change the reconstructed atomic image on a solid surface. The second order Stark effect of the laser-cooled metastable Ne atom was used to induce the phase shift during the atoms passage through the hologram. By controlling the applied electric voltage, the reconstructed pattern was switched according to the induced phase shift. © 2000 American Vacuum Society.
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03.75.Be Atom and neutron optics
37.10.De Atom cooling methods
37.10.Gh Atom traps and guides
32.60.+i Zeeman and Stark effects
37.10.Vz Mechanical effects of light on atoms, molecules, and ions

Lithographically defined nano and micro sensors using “float coating” of resist and electron beam lithography

H. Zhou, B. K. Chong, P. Stopford, G. Mills, A. Midha, L. Donaldson, and J. M. R. Weaver

J. Vac. Sci. Technol. B 18, 3594 (2000); http://dx.doi.org/10.1116/1.1321271 (6 pages) | Cited 10 times

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The combination of direct-write electron beam lithography and bulk silicon micromachining is shown to give great flexibility in the definition of nanosensors. The technique is based on a novel method for coating the specimen with electron beam resist allowing high resolution features to be defined on the top of micromachined asperities or in 200 μm deep etched holes. Examples of sensors fabricated using this method include advanced magnetic nanosensors such as Hall probe sensors, electromagnetic coils or combined coils and Hall probes. Near-field optical atomic force microscope probes are demonstrated with reproducible aperture size down to 20×35 nm. Near-field optical probes using a shaped aperture to allow the passage of linearly polarized light are shown to offer optical throughputs up to 2% with modest collection optics. The use of a near-field optical probe having a crossed slit form is demonstrated to give high throughput and resolution in two dimensions for the imaging of fluorescent objects. Near-field optical probes with multiple apertures of closely matched size are demonstrated. © 2000 American Vacuum Society.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.10.Cm Micromechanical devices and systems
85.40.Hp Lithography, masks and pattern transfer
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
07.79.Fc Near-field scanning optical microscopes
07.79.Lh Atomic force microscopes

Microcalorimetry applications of a surface micromachined bolometer-type thermal probe

Mo-Huang Li and Yogesh B. Gianchandani

J. Vac. Sci. Technol. B 18, 3600 (2000); http://dx.doi.org/10.1116/1.1313581 (4 pages) | Cited 8 times

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This article describes a surface micromachined scanning thermal probe that uses polyimide as the structural material and an embedded thin film metal resistor as the sensing element. The typical dimensions of a fabricated probe are 350 μm in length, 50 μm in width, and 3–10 μm in thickness. The resistor and the scanning tip are formed by sputter-deposited films of nickel and tungsten, which provide temperature coefficient of resistance of 2963 ppm/K. The probe is used to map surface and subsurface spatial variations in the thermal conductivity of a test sample. It is also used as a spatially localized microcalorimeter to measure the glass transition temperature of photoresists: the values obtained for Shipley 1813 and UV6 are 118±1 °C and 137±1 °C, respectively. These are in close agreement with results obtained by other methods that utilize larger samples. © 2000 American Vacuum Society.
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07.20.Fw Calorimeters
07.10.Cm Micromechanical devices and systems
07.20.Dt Thermometers
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Novel multibridge-structured piezoelectric microdevice for scanning force microscopy

J. Chu, Z. Wang, R. Maeda, K. Kataoka, T. Itoh, and T. Suga

J. Vac. Sci. Technol. B 18, 3604 (2000); http://dx.doi.org/10.1116/1.1319684 (4 pages) | Cited 8 times

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In this article we report the structure and the microfabrication method of a novel micro-scanning force microscopy (SFM) device. It is a lead zirconate titanite (PZT) bimorph structure in the shape of a cantilever supported by bridges. Electric fields applied to the separated sections of the electrodes on the levers can induce lever deflection and actuate the tip in x, y, and z directions. The cantilever can vibrate and sense its own vibration amplitude to detect the surface topography in the cyclic contact SFM mode. In the fabrication process, the sol–gel method is modified for constructing high quality PZT films 3 μm thick. The single bridge device has shown microscopy sensitivity of 0.32 nA/nm in a vertical direction, with actuation sensitivities of 70–80 nm/V in a lateral direction. The multibridged structure has been proven to be effective in elevating the eigenfrequency, which is very important for improving the SPM data rate. © 2000 American Vacuum Society.
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07.79.Lh Atomic force microscopes
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
07.10.Cm Micromechanical devices and systems
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Fabrication of diffractive optical elements for an integrated compact optical microelectromechanical system laser scanner

J. R. Wendt, T. W. Krygowski, G. A. Vawter, O. Blum, W. C. Sweatt, M. E. Warren, and D. Reyes

J. Vac. Sci. Technol. B 18, 3608 (2000); http://dx.doi.org/10.1116/1.1313580 (4 pages) | Cited 2 times

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We describe the microfabrication of a multilevel diffractive optical element (DOE) onto a microelectromechanical system (MEMS) module as a key element in an integrated compact optical-MEMS laser scanner. The DOE is a four-level off-axis microlens fabricated onto a movable polysilicon shuttle. The microlens is patterned by electron beam lithography and etched by reactive-ion-beam etching. The DOE was fabricated on two generations of MEMS components, each of which is briefly described. The compact design of the laser scanner is based on mounting a MEMS module and a vertical cavity surface-emitting laser onto a fused silica substrate that contains the rest of the optical system. The calculated scan range of the system is ±4° with a spot size of 0.5 mm. © 2000 American Vacuum Society.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
42.79.Bh Lenses, prisms and mirrors
42.79.Ls Scanners, image intensifiers, and image converters
42.60.By Design of specific laser systems
42.82.Fv Hybrid systems
81.65.Cf Surface cleaning, etching, patterning
85.40.Hp Lithography, masks and pattern transfer
42.55.Px Semiconductor lasers; laser diodes
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