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Nov 2002

Volume 20, Issue 6, pp. 2183-3117

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Comparison of atomic force microscopy imaging methods and roughness determinations for a highly polished quartz surface

Eleni Dokou, Lanping Zhang, and Mark A. Barteau

J. Vac. Sci. Technol. B 20, 2183 (2002); http://dx.doi.org/10.1116/1.1513633 (4 pages) | Cited 3 times

Online Publication Date: 9 December 2002

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The morphology and microstructure of a polished quartz surface have been studied using atomic force microscopy (AFM) under ambient conditions, high vacuum and ultrahigh vacuum. The general features observed in air and vacuum environments are consistent, showing the existence of long corrugations, scratches, and holes. The root-mean-square surface roughness ranged from 0.2 to 0.4 nm. Imaging of hydrophilic surfaces, such as quartz, with contact-mode AFM can be problematic because of the presence of adsorbed water and contamination layers on the surface. Using tapping-mode AFM in air and noncontact mode AFM under vacuum, we are able to study the true structure of the surface; detection of more local features with higher resolution was achieved under ultrahigh-vacuum conditions. © 2002 American Vacuum Society.
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07.79.Lh Atomic force microscopes
68.37.Ps Atomic force microscopy (AFM)
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Ct Interface structure and roughness
42.70.Ce Glasses, quartz

Initial oxidation phenomena of heavily phosphorus-doped silicon in dry oxygen

Y. Kamiura, K. Hasegawa, Y. Sano, Y. Mizokawa, and K. Kawamoto

J. Vac. Sci. Technol. B 20, 2187 (2002); http://dx.doi.org/10.1116/1.1513792 (5 pages) | Cited 4 times

Online Publication Date: 9 December 2002

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The oxidation of heavily phosphorus-doped Si(100) and polycrystalline Si in the room temperature (RT) to 800 °C range in dry oxygen was studied by Auger electron spectroscopy (AÉS) and quadrupole mass spectrometry. The oxidation rate of the phosphorus-doped (P-doped) Si(100) was larger than the P-doped poly-Si at RT. In thermal oxidation at 650 °C in the P-doped Si(100), the delay of the dioxide formation was found above 5×105 L. The AES measurements in the range of 97–137 eV showed that phosphorus oxidized in the initial stages of the oxidation of both samples. In the thermal oxidation of both samples at 800 °C, oxygen uptake on the silicon surfaces did not take place under 104 L. And dioxide formation took place rapidly above 104 L for both samples. Then, a large amount of phosphorus piled up at the interfaces due to the formation of SiO2. We gave explanations for these initial stages of oxidation of P-doped Si by the competition process between the oxidation of silicon and the desorption of SiO and P2O5. © 2002 American Vacuum Society.
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81.65.Mq Oxidation
81.05.Cy Elemental semiconductors
79.20.Fv Electron impact: Auger emission
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Silicon oxide contact hole etching employing an environmentally benign process

Kazushi Fujita, Masaru Hori, Toshio Goto, and Masafumi Ito

J. Vac. Sci. Technol. B 20, 2192 (2002); http://dx.doi.org/10.1116/1.1513632 (7 pages) | Cited 1 time

Online Publication Date: 9 December 2002

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An environmentally benign etching process using a solid material evaporation technique has been investigated for preventing global warming. In this process, a polytetrafluoroethylene is evaporated by a CO2 laser, resulting in production of fluorocarbon species working as the etching species. Therefore, this system employs no perfluorocompound feed gases, which cause global warming, and enables us to design a new plasma chemistry using the solid material. The system was successfully applied to a SiO2 contact hole etching process employing a planar electron cyclotron resonance plasma. The etched profile was successfully controlled by varying the Ar dilution ratio and the process pressure. In a 0.6 μm contact hole and a 0.08 μm trench fabrication process, this novel process enables us to realize high etching performances, where the etching rate of SiO2, selectivities of SiO2/resist, and SiO2/Si were 340 nm/min, 6.8 and 31, respectively, in optimal condition. To clarify the plasma chemistry using solid material evaporation, CFx (x=1–3) radical densities and F atom density were measured by infrared diode laser absorption spectroscopy and actinometric optical emission spectroscopy, and fluorocarbon films deposited on SiO2 were analyzed by x-ray photoelectron spectroscopy. On the basis of these results, the etching mechanism was discussed. © 2002 American Vacuum Society.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Simulations and experiments of etching of silicon in HBr plasmas for high aspect ratio features

Helen H. Hwang, M. Meyyappan, G. S. Mathad, and R. Ranade

J. Vac. Sci. Technol. B 20, 2199 (2002); http://dx.doi.org/10.1116/1.1513621 (7 pages) | Cited 10 times

Online Publication Date: 9 December 2002

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Etching in semiconductor processing typically involves using halides because of the relatively fast rates. Bromine-containing plasmas can generate high aspect ratio trenches, desirable for dynamic random access memory and microelectromechanical system applications, with relatively straight sidewalls. We present scanning electron microscope images for silicon-etched trenches in a HBr plasma. Using a feature profile simulation, we show that the removal yield parameter, or number of neutrals removed per incident ion due to all processes (sputtering, spontaneous desorption, etc.), dictates the profile shape. We find that the profile becomes pinched off when the removal yield is a constant, with a maximum aspect ratio (AR) of about 5 to 1 (depth to height). When the removal yield decreases with increasing ion angle, the etch rate increases at the corners and the trench bottom broadens. The profiles have ARs of over 9:1 for yields that vary with ion angle. To match the experimentally observed etched time of 250 s for an AR of 9:1 with a trench width of 0.135 μm, we find that the neutral flux must be 3.336×1017 cm2 s−1. © 2002 American Vacuum Society.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
81.05.Cy Elemental semiconductors
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.16.Rf Micro- and nanoscale pattern formation
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Resist distribution effect of spin coating

Sang-Kon Kim, Ji-Yong Yoo, and Hye-Keun Oh

J. Vac. Sci. Technol. B 20, 2206 (2002); http://dx.doi.org/10.1116/1.1513582 (4 pages) | Cited 6 times

Online Publication Date: 9 December 2002

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The thin-film formation of the spin coating is one of the important factors in the fabrication of microelectronic devices. In this study, the theoretical models for thickness variation during spin coating and nanotopography impact are analyzed. The finite-difference–time-domain method and the finite-element method are used to solve the convective diffusion equation for solvent distribution and the Navier–Stokes equation including solvent evaporation for the film thickness change. These numerical calculations are in good agreement with experimental results for 193 nm chemically amplified resist (CAR) and i-line non-CAR resists. Solvent distributions of nonspin coating are described through mesoscale modeling by using the Monte Carlo method. Nanotopography impact on the variation of resist distribution after spin coating is investigated quantitatively. The reason for the similarity in the transfer functions for different types of wafers is due to solvent diffusion and evaporation. © 2002 American Vacuum Society.
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81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
02.70.Dh Finite-element and Galerkin methods
02.70.Bf Finite-difference methods

Reflection high-energy electron diffraction observation of the dynamics of semiconductor quantum dot formation and decay

P. Finnie, B. J. Riel, and Z. R. Wasilewski

J. Vac. Sci. Technol. B 20, 2210 (2002); http://dx.doi.org/10.1116/1.1515912 (4 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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The fabrication of nanostructures can be greatly assisted by the use of in situ tools. Reflection high-energy electron diffraction (RHEED) is a classic tool for in situ monitoring of growth by molecular-beam epitaxy, and it has gained renewed relevance for the production of quantum dots. The evolution of RHEED spot intensities provides information about quantum dot ensembles during nucleation, growth, growth interruptions, decay, and dissolution. The integrated RHEED spot intensity evolves in a characteristic way whether InAs or InxGa1−xAs is grown on GaAs(100), and whether quantum dots are growing or decaying. The application of RHEED to practical issues in the growth of quantum dots is described. © 2002 American Vacuum Society.
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81.07.Ta Quantum dots
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.Hb Quantum dots (patterned in quantum wells)
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

Improved surface treatments for recycled (100) GaAs substrates in view of molecular-beam epitaxy growth: Auger electron spectroscopy, Raman, and secondary ion mass spectrometry analyses

Fabienne Négri and Eléna Bedel-Pereira

J. Vac. Sci. Technol. B 20, 2214 (2002); http://dx.doi.org/10.1116/1.1515908 (5 pages) | Cited 1 time

Online Publication Date: 9 December 2002

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The effects of chemical treatments on recycled (100) GaAs surfaces processed in microelectronic industry have been studied. The recycling process consists in establishing reproductive techniques of polishing and chemical cleaning of rejected processed wafers (with diameter of 100 mm) in order to obtain surfaces reusable to molecular-beam epitaxy (MBE). The recycling process is applied to any processed surface whatever the former technological applications and the doping type. Surfaces were first chemically treated in acid and basic solutions (HCl, diluted HF, and NH4OH solutions). Then, thin layers of GaAs by MBE on them have been elaborated to study the chemical quality at the interface. Surfaces and epilayers have been analyzed using Raman and Auger electron spectroscopies (AES) to qualify the crystalline disorder as well as the chemical composition. Also, secondary ion mass spectrometry (SIMS) have been used to determine the level of contamination at the interface epilayer/substrate. A systematic comparison between the various treatments applied on the GaAs substrates has enabled us to obtain a high surface quality suitable for MBE. Specific results of AES and SIMS analyses clearly indicate that the diluted NH4OH solutions remove the carbon contamination and, reduce the polishing residues content and the oxide thickness. © 2002 American Vacuum Society.
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81.05.Ea III-V semiconductors
81.65.Ps Polishing, grinding, surface finishing
81.65.Cf Surface cleaning, etching, patterning
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
85.40.Sz Deposition technology
79.20.Fv Electron impact: Auger emission
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
78.30.Fs III-V and II-VI semiconductors
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
82.80.Gk Analytical methods involving vibrational spectroscopy
68.35.Dv Composition, segregation; defects and impurities

Comparison of in situ and ex situ plasma-treated metalorganic chemical vapor deposition titanium nitride thin films

Boon Kiat Lim, Hun Sub Park, Alex K. H. See, Er Zhuang Liu, and Shao Hui Wu

J. Vac. Sci. Technol. B 20, 2219 (2002); http://dx.doi.org/10.1116/1.1515911 (6 pages) | Cited 9 times

Online Publication Date: 9 December 2002

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Titanium nitride (TiN) thin films deposited by metalorganic chemical vapor deposition, using tetrakis-dimethyl-amino-titanium as a precursor, are known to have high sheet resistivity. A plasma treatment in forming gas ambient is one way of reducing the high sheet resistivity down to that of the films deposited by physical vapor deposition. This plasma treatment is normally done in situ (without breaking the vacuum) immediately after deposition. However, an ex situ (breaking vacuum after deposition) plasma treatment will provide a more economical way of manufacturing in which less time is required in the chemical vapor deposition chamber, hence allowing high deposition throughput. Furthermore, the plasma treatment can be done in a high-pressure chamber, which translates into low cost. In this study, we compared film properties of TiN with in situ and ex situ plasma treatments. Analyses were performed on chemical composition, sheet resistance, amount of Ti atoms, via resistance and reliability using x-ray photoelectron spectroscopy, four-point probe, x-ray fluorescence, and a current–voltage multiprobe. The ex situ plasma treatment was capable of removing carbon from the TiN film, but not without a sacrifice of the reliability and electrical performance of the TiN film. Further development on the ex situ plasma treatment must be made to improve the reliability and electrical performance of the TiN film. © 2002 American Vacuum Society.
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85.40.Ls Metallization, contacts, interconnects; device isolation
68.55.Nq Composition and phase identification
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.61.At Metal and metallic alloys
85.40.Sz Deposition technology
52.77.Bn Etching and cleaning
73.40.Cg Contact resistance, contact potential
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
85.40.Qx Microcircuit quality, noise, performance, and failure analysis

Effect of implant oxide on ultrashallow junction formation

R. Lindsay, A. Lauwers, J. Frühauf, M. de Potter, and K. Maex

J. Vac. Sci. Technol. B 20, 2225 (2002); http://dx.doi.org/10.1116/1.1515909 (4 pages)

Online Publication Date: 9 December 2002

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For optimal device performance in sub-100 nm complementary metal–oxide–semiconductor, the junction is required to have high wafer uniformity, a high peak dopant concentration, a shallow junction depth, and an abrupt profile. In this article, we will show how all these criteria are strongly influenced by the implant oxide for B, BF2, and As. Due mainly to dopant retention, a thicker implant oxide is shown to significantly reduce the peak concentration of spike annealed B junctions causing a degradation in the sheet resistance for a given junction depth. This Rs to Xj tradeoff is further worsened by a soak anneal or annealing in 5% O2 where more dopants outdiffuse from the silicon. This outdiffusion not only lowers the peak concentration, but also degrades the junction abruptness. Both the oxide and the O2 in the ambient also degrade wafer uniformity. Arsenic implanted into the oxide is driven into the junction during annealing and thus the oxide has a lesser effect on peak concentration, abruptness, and uniformity. © 2002 American Vacuum Society.
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85.40.Ry Impurity doping, diffusion and ion implantation technology
85.30.Tv Field effect devices
68.35.Fx Diffusion; interface formation
68.43.Mn Adsorption kinetics
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.30.-z Semiconductor devices
61.72.S- Impurities in crystals

Polymer thickness effects on Bosch etch profiles

C. J. D. Craigie, T. Sheehan, V. N. Johnson, S. L. Burkett, A. J. Moll, and W. B. Knowlton

J. Vac. Sci. Technol. B 20, 2229 (2002); http://dx.doi.org/10.1116/1.1515910 (4 pages) | Cited 17 times

Online Publication Date: 9 December 2002

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Time-multiplexed etching, the Bosch process, is a technique consisting of alternating etch and deposition cycles to produce high aspect-ratio etched features. The Bosch process uses SF6 and C4F8 as etch and polymer deposition gases, respectively. In these experiments, polymer thickness is controlled by both C4F8 gas flow rates and by deposition cycle time. The authors show that polymer thickness can be used to control wall angle and curvature at the base of feature walls. Wall angle is found to be independent of trench width under thin-polymer deposition conditions. Experimental results are compared to results obtained by other researchers using the more conventional simultaneous etch/deposition technique. © 2002 American Vacuum Society.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
85.40.Sz Deposition technology
61.41.+e Polymers, elastomers, and plastics
52.77.Dq Plasma-based ion implantation and deposition
85.40.Ls Metallization, contacts, interconnects; device isolation

Leveling effects of copper electrolytes with hybrid-mode additives

Kun-Cheng Lin, Jia-Min Shieh, Shih-Chieh Chang, Bau-Tong Dai, Chia-Fu Chen, Ming-Shiann Feng, and Ying-Hao Li

J. Vac. Sci. Technol. B 20, 2233 (2002); http://dx.doi.org/10.1116/1.1517262 (5 pages) | Cited 5 times

Online Publication Date: 9 December 2002

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100 nm vias were completely filled with copper for interconnect applications using an electrolyte in the presence of polyethylene glycols (PEG) and a hybrid-mode additive, benzotriazole (BTA). Electrochemical analyses indicated that BTA with a higher concentration inhibited the copper deposition rate, whereas BTA with a lower concentration accelerated the copper deposition rate. This electrolyte thus generated an enhanced deposition gradient within a gap because the PEG molecules and the high concentration of BTA, adsorbed at the opening of the gap, inhibited the deposition. Meanwhile, a little BTA diffused into the inner part of the gap and thus accelerated the deposition of copper. Therefore, this two-component (PEG and BTA) additive electrolyte had the capacity of a three-additive bath (accelerators, suppressors, and levelers). © 2002 American Vacuum Society.
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85.40.Ls Metallization, contacts, interconnects; device isolation
81.15.Pq Electrodeposition, electroplating
81.05.Bx Metals, semimetals, and alloys
82.45.Qr Electrodeposition and electrodissolution
82.80.Fk Electrochemical methods
85.40.Sz Deposition technology

Study of focused ion beam response of GaAs in the nanoscale regime

A. Lugstein, B. Basnar, and E. Bertagnolli

J. Vac. Sci. Technol. B 20, 2238 (2002); http://dx.doi.org/10.1116/1.1517261 (5 pages) | Cited 10 times

Online Publication Date: 9 December 2002

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Focused ion beam (FIB) technology has been demonstrated to be a powerful tool in microfabrication, primarily for semiconductor related processing. The migration of the critical dimensions of devices toward the nanometer regime necessitates the knowledge of fundamental milling process mechanisms to gain full use of the opportunities offered by the focused ion beam technique. We have investigated the influence of declining feature sizes on the focused ion beam response of GaAs. Based on our experimental results, a sputter yield promoting the self-focusing effect combined with a sputter rate increase at oblique angles, an opposing dose deficiency effect, and material redeposition for milling aspect ratios >1 are identified to be responsible for the complex sputter response of GaAs. In addition, the observed preferential etching of arsenic results in local precipitates of mobile Ga-rich residues influencing the fundamental characteristics of FIB patterning, like sputter yield, crater bottom flatness, and ripple formation. © 2002 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
81.05.Ea III-V semiconductors

Influence of the surface Si/buried oxide interface on extended defect evolution in silicon-on-insulator scaled to 300 Å

A. F. Saavedra, J. Frazer, K. S. Jones, I. Avci, S. K. Earles, M. E. Law, and E. C. Jones

J. Vac. Sci. Technol. B 20, 2243 (2002); http://dx.doi.org/10.1116/1.1517410 (5 pages) | Cited 7 times

Online Publication Date: 9 December 2002

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As device dimensions continue to be scaled, incorporation of silicon-on-insulator (SOI) as mainstream complementary metal–oxide–semiconductor technology also increases. This experiment set out to further investigate the effect of the surface Si/buried oxide (BOX) interface on the formation and dissolution of extended defects in SOI. UNIBOND® wafers were thinned to 300, 700, and 1600 Å. Si+ ion implantation was performed from 5 to 40 keV with a constant, nonamorphizing dose of 2×1014 cm−2. Inert ambient furnace anneals were performed at 750 °C for times of 5 min up to 8 h. Transmission electron microscopy was used to study the evolution of extended defects, as well as to quantify the number of trapped interstitials. It is observed that the surface Si/BOX interface does not enhance the dissolution rate of extended defects unless ⩾15% of the dose is truncated by the BOX. Further, no reduction in the trapped interstitial concentration is seen unless ⩾6% of the dose is truncated. It is concluded that the surface Si/BOX interface does not serve as a significant sink for interstitial recombination, as long as the interstitial profile is mostly confined to the surface Si layer.© 2002 American Vacuum Society.
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61.72.uf Ge and Si
61.72.Nn Stacking faults and other planar or extended defects
61.72.J- Point defects and defect clusters
68.35.Ct Interface structure and roughness
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Submicron pattern transfer to binary semiconductors via micromolding in capillaries

Dario Pisignano, Giuseppe Gigli, Paolo Visconti, Anna Zocco, Alessio Perrone, and Roberto Cingolani

J. Vac. Sci. Technol. B 20, 2248 (2002); http://dx.doi.org/10.1116/1.1517263 (4 pages) | Cited 3 times

Online Publication Date: 9 December 2002

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We report on the high-resolution patterning of III–V semiconductors through polymeric masks by a soft lithographic technique based on micromolding in capillaries. The basic study of the capillarity process and the optimization of the technological steps allowed us to transfer patterns on both GaAs and InP with resolution of 800 nm over areas up to 1 cm2 and of a few microns over areas up to 4 cm2. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.10.Fq Growth from melts; zone melting and refining
81.65.Cf Surface cleaning, etching, patterning

Dry etching of GaP with emphasis on selective etching over AlGaP

J. H. Epple, C. Sanchez, T. Chung, K. Y. Cheng, and K. C. Hsieh

J. Vac. Sci. Technol. B 20, 2252 (2002); http://dx.doi.org/10.1116/1.1517260 (4 pages) | Cited 1 time

Online Publication Date: 9 December 2002

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A technique to etch GaP by reactive ion etching was developed and the effects of different etching parameters were studied. Also, selective etching of GaP over AlGaP was examined and demonstrated. Etching is achieved by using SiCl4, which will react with GaP to form volatile compounds. Selective etching is accomplished when SiF4 is used in addition to SiCl4. The addition of the fluorine-based gas will result in a nonvolatile etch-inhibiting layer, AlF3, when aluminum is present on the sample surface. By adjusting etching parameters, a selectivity as high as 126 is demonstrated. The presence of the AlF3 etch-inhibiting layer is verified by Auger electron spectroscopy, and the removal of this layer by buffered oxide etch is demonstrated. In addition, a direct comparison of etch rates for GaP and GaAs was made, and etch rates were found to be similar. © 2002 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
81.05.Ea III-V semiconductors
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Comparative study of Ga- and N-polar GaN films grown on sapphire substrates by molecular beam epitaxy

D. Huang, M. A. Reshchikov, P. Visconti, F. Yun, A. A. Baski, T. King, H. Morkoç, J. Jasinski, Z. Liliental-Weber, and C. W. Litton

J. Vac. Sci. Technol. B 20, 2256 (2002); http://dx.doi.org/10.1116/1.1518969 (9 pages) | Cited 11 times

Online Publication Date: 9 December 2002

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We report the surface, structural, and optical properties of typical Ga- and N-polar GaN films grown on sapphire substrates by molecular beam epitaxy. The Ga-polar films were grown on AlN buffer while the N-polar films were grown on GaN buffer layers. Atomic force microscopy imaging shows that the as-grown and chemically etched Ga-polar films have a flat and pitted surface while the N-polar surface is rougher with isolated columns or islands. Transmission electron microscopy demonstrates a low density of inversion domains in the Ga-polar films, while a much higher density of inversion domains was observed in the N-polar films. X-ray diffraction curves show a narrower (002) peak for Ga-polar films than that for N-polar films. On the other hand, both Ga- and N-polar films show a similar width of (104) peak. Despite their rough surfaces, high density of inversion domains, and broader (002) x-ray diffraction peaks, N-polar films with low dislocation density were demonstrated. In addition, higher PL efficiency for the N-polar films than that for the Ga-polar films was observed. © 2002 American Vacuum Society.
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81.05.Ea III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.A- Nucleation and growth
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
68.37.Ps Atomic force microscopy (AFM)
81.65.Cf Surface cleaning, etching, patterning

Cryogenic cleavage used in gold substrate production

Jakub Mazurkiewicz, Freya J. Mearns, Dusan Losic, Laura Weeks, Eric R. Waclawik, Craig T. Rogers, Joseph G. Shapter, and J. Justin Gooding

J. Vac. Sci. Technol. B 20, 2265 (2002); http://dx.doi.org/10.1116/1.1518968 (6 pages) | Cited 12 times

Online Publication Date: 9 December 2002

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An improved method for the production of ultralarge flat and patterned gold surfaces for use in scanning probe studies using a procedure based on epitaxial gold growth on mica is described. The approach is superior in terms of simplicity and reliability without any loss of substrate quality. The gold surface is glued onto an aluminum stub with two part ceramic or polyester glue. The mica is removed by immersing the sample in liquid nitrogen. The liquid nitrogen causes differential contraction of the mica and gold resulting in clean separation to leave large atomically flat planes or patterned features. © 2002 American Vacuum Society.
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68.47.De Metallic surfaces
81.05.Bx Metals, semimetals, and alloys
81.65.Ps Polishing, grinding, surface finishing
81.16.-c Methods of micro- and nanofabrication and processing
68.37.Ps Atomic force microscopy (AFM)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.35.B- Structure of clean surfaces (and surface reconstruction)

Beam-focusing characteristics of the diamond-film field emission arrays with parallel emitter, gates, and in-plane lens

Baoqing Zeng, Yang Liu, Zhonghai Yang, Shangjie Qian, and Chongfeng Yang

J. Vac. Sci. Technol. B 20, 2271 (2002); http://dx.doi.org/10.1116/1.1518970 (4 pages) | Cited 1 time

Online Publication Date: 9 December 2002

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A focusing structure of field-emission arrays (FEAs) made of a parallel planar emitter, gate, and in-plane lens is suggested. Using the particle-in-cell simulation code MAGIC, the diamond-film FEAs made of a strip planar emitter, a parallel gate, and an anode with and without an in-plane lens have been simulated. The electron-beam streamlines and the x-py phase show that the in-plane lens focuses the electron beam. For a typical model, the beam width decreases about 1/10 for every cell, and the transverse velocity decreases from ±5.5×106 to ±0.4×106 m/s when including the in-plane lens. This structure can be used as a moderated field-emission cathode to emit a collimated electron beam, such as in field-emission displays. © 2002 American Vacuum Society.
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85.45.Db Field emitters and arrays, cold electron emitters
41.85.Lc Particle beam focusing and bending magnets, wiggler magnets, and quadrupoles
85.45.Fd Field emission displays (FEDs)

Plasma assisted deposition of nanocrystalline BCN thin films and property characterization

Z. X. Cao, L. M. Liu, and H. Oechsner

J. Vac. Sci. Technol. B 20, 2275 (2002); http://dx.doi.org/10.1116/1.1518973 (6 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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Electron-cyclotron-wave-resonance plasma assisted deposition is an effective technique for preparing superhard materials. In this work, nanocrystalline BCN thin films were grown on Si(001) wafers and Corning glass substrates, where the growing surface was bombarded with nitrogen plasma at energies between 60 and 180 eV. Energy-dispersive x-ray analysis revealed the formation of very clean, homogeneous films with a bulk composition around B42C33N25, which changes only slightly with ion energy. Under an atomic force microscope the films displayed a morphology composed of crystallites of about 200 nm in lateral size in cubic habits. Both the x-ray photoelectron spectroscopy and infrared absorption indicated that the deposits are ternary BCN compounds. The films are highly transparent and hard; the Vicker’s hardness scatters in the range of 26–28 GPa. Strong photoluminescence peaked at 430 nm was detected on the as-deposited specimens at room temperature. The band gap for the deposits was estimated to be circa 3.0 eV. © 2002 American Vacuum Society.
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81.07.Bc Nanocrystalline materials
52.77.Dq Plasma-based ion implantation and deposition
61.46.-w Structure of nanoscale materials
68.55.-a Thin film structure and morphology
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
68.37.Ps Atomic force microscopy (AFM)
79.60.Bm Clean metal, semiconductor, and insulator surfaces
78.55.Hx Other solid inorganic materials

Evaluation of the ion bombardment energy on silicon dioxide films deposited from O2/TEOS plasmas on Si and unstrained Si0.83Ge0.17/Si substrates

D. Goghero, A. Goullet, L. Lebrizoual, F. Meyer, and G. Turban

J. Vac. Sci. Technol. B 20, 2281 (2002); http://dx.doi.org/10.1116/1.1518967 (7 pages)

Online Publication Date: 9 December 2002

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Silicon dioxide films are deposited on Si and unstrained Si0.83Ge0.17 from O2/tetraethylorthosilicate plasmas in a helicon reactor operated at low pressure (2 mTorr). The effect of the negative dc self-bias voltage (0 to −200 V) on the film properties is investigated. X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry measurements have been performed on ultrathin (∼5 nm) films to gain better insight into the quality of the dielectric/semiconductor interface. We observed that the ion bombardment energy is responsible for the amorphization of the substrate, which is in agreement with the TRIM (transport and range of ions in matter) simulation results. In the case of SiGe samples, a GeO2 phase is detected in the XPS spectra which increases with the applied bias. Changes on the vibrational properties are observed on thick films (500 nm) while refractive index and p-etch measurements are only slightly sensitive to the voltage applied to the substrate. Complementary electrical measurements have been carried out on metal–oxide–semiconductor capacitors. For films deposited on Si substrates, C–V measurements indicated a degradation of the electrical properties with increasing energy of the impinging ions. The results obtained on SiGe samples exhibit typical negative fixed charges in the oxide with a rather low density of interface states (Dit∼5×1011 cm−2 eV−1). © 2002 American Vacuum Society.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
79.60.Jv Interfaces; heterostructures; nanostructures
73.20.At Surface states, band structure, electron density of states
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.30.Hv Other nonmetallic inorganics
78.66.Nk Insulators
73.61.Ng Insulators

Investigation of active Si pitting and its impact on 0.15 and 0.30 μm n-type metal–oxide–semiconductor and p-type metal–oxide–semiconductor transistors

C. S. Chua, E. F. Chor, F. Goh, A. See, and L. Chan

J. Vac. Sci. Technol. B 20, 2288 (2002); http://dx.doi.org/10.1116/1.1518972 (7 pages)

Online Publication Date: 9 December 2002

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The causes of pitting on an active silicon surface and its impact on 0.15 and 0.30 μm n-type metal–oxide semiconductor (NMOS) and p-type metal–oxide–semiconductor (PMOS) transistors have been assessed. During polysilicon gate patterning, the gate oxide at the source/drain regions of the NMOS transistors may be etched away due to insufficient selectivity of the etch chemistry, improper etch chamber configuration, pattern density, and the adoption of dual-doped gate technology. The exposed silicon substrate has poor selectivity against the polysilicon gate, this causes Si pitting to occur on the source/drain active regions of the NMOS transistors. However, there is no significant pitting observed for the PMOS transistors due to the slower etch rate of the undoped polysilicon of the PMOS transistors. Pitting on the active areas severely degrades the device parameters, such as drive current, series resistance, and transconductance. This is worse for the 0.15 μm NMOS transistors compared to the 0.30 μm NMOS transistors. The channel resistance of the 0.30 μm transistors is much larger than any increase in the external resistance caused by the pitting. As a result, Si pitting has negligible effects on the device performance of long channel devices. © 2002 American Vacuum Society.
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85.30.Tv Field effect devices
81.65.Cf Surface cleaning, etching, patterning

Investigations of pulse current electrodeposition for damascene copper metals

Shih-Chieh Chang, Jia-Min Shieh, Bau-Tong Dai, and Ming-Shiann Feng

J. Vac. Sci. Technol. B 20, 2295 (2002); http://dx.doi.org/10.1116/1.1518974 (4 pages) | Cited 7 times

Online Publication Date: 9 December 2002

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The influence of current density, duty cycle, and frequency of the applied pulse current on film qualities of electroplated copper was discussed. With various filled damascene structures, the corresponding filling power was optimized in a range of pulse current frequency. The optimized pulse current plating in conjunction with a leveler-free electrolyte resulted in a defect-free filling in approximate 100 nm damascenes and reduced the resistivity of Cu deposits. © 2002 American Vacuum Society.
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85.40.Ls Metallization, contacts, interconnects; device isolation
81.15.Pq Electrodeposition, electroplating
81.05.Bx Metals, semimetals, and alloys

Effects of Ar inductively coupled plasma exposure on 4H-SiC Schottky rectifiers

K. Ip, S. Nigam, K. P. Lee, K. H. Baik, G. Y. Chung, M. F. MacMillan, F. Ren, and S. J. Pearton

J. Vac. Sci. Technol. B 20, 2299 (2002); http://dx.doi.org/10.1116/1.1518971 (4 pages) | Cited 1 time

Online Publication Date: 9 December 2002

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4H-SiC Schottky rectifiers were exposed to inductively coupled Ar plasmas as a function of source power (150–750 W), rf chuck power (75–350 W), and process pressure (5–30 mTorr). The reverse breakdown voltage (VB) was increased by increases in both incident ion energy and ion flux, with the former having the strongest influence. As an example, Ar plasma exposure at ion energies of ∼335 eV led to an increase in VB from approximately −500 to −950 V. These results suggest strategies for minimizing plasma-induced damage during both deposition and etching steps used in the fabrication of SiC rectifiers. © 2002 American Vacuum Society.
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85.30.Kk Junction diodes
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Structure and size distribution of TiO2 nanoparticles deposited on stainless steel mesh

W. Li, S. Ismat Shah, M. Sung, and C.-P. Huang

J. Vac. Sci. Technol. B 20, 2303 (2002); http://dx.doi.org/10.1116/1.1520557 (6 pages) | Cited 7 times

Online Publication Date: 9 December 2002

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Doped and undoped TiO2 nanoparticles with narrow size distribution were deposited on stainless steel mesh substrates by metalorganic chemical vapor deposition. The chemical composition of TiO2 nanoparticles was measured by energy dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy. X-ray diffraction and transmission electron microscopy were performed to investigate the size and the size distribution of particles as well as the structural phase transitions. For pure TiO2, the results showed that anatase polycrystalline nanoparticles with average size from 23 to 31 nm were obtained for substrate temperatures between 350 and 600 °C. Particles deposited below 350 °C were x-ray amorphous and rutile began to precipitate at temperatures above 700 °C. The particles synthesized at 600 °C had the smallest size and narrowest size distribution. In order to study the dopant effects on the photocatalytic properties, growth temperature of 600 °C was selected to prepare 1 at. % Nd3+ doped TiO2 nanoparticles. The results of photodegradation of the pollutant 2-chlorophenol solution irradiated under ultraviolet light showed that 1 at. % of Nd3+ doped TiO2 had an enhanced degradation of the pollutant. The enhancement of photocatalytic efficiency by doped nanoparticles was ascribed to the large surface area and trapping induced prolonged lifetime of holes. © 2002 American Vacuum Society.
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61.46.-w Structure of nanoscale materials
64.70.Nd Structural transitions in nanoscale materials
81.07.Bc Nanocrystalline materials
82.50.-m Photochemistry
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
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.)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Fabrication of Si field emitter arrays integrated with metal–oxide–semiconductor field-effect transistor driving circuits

M. Nagao, Y. Tamura, T. Matsukawa, S. Kanemaru, J. Itoh, and K. Tokunaga

J. Vac. Sci. Technol. B 20, 2309 (2002); http://dx.doi.org/10.1116/1.1520553 (5 pages) | Cited 8 times

Online Publication Date: 9 December 2002

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Si field emitter arrays (FEAs) were monolithically integrated with metal–oxide–semiconductor field-effect-transistor (MOSFET) based driving circuits on a Si chip for the first step toward developing the field-emission-display-on-a-chip (FED-on-a-chip), which is a candidate for the next-generation FED. We developed a fabrication process of Si FEAs integrated with MOSFET driving circuits. A 4×4 matrix Si FEA, emission-control MOSFET, and simple driving circuits consisting of a shift register were integrated on the same chip. The operation of each element, such as MOSFET-controlled Si FEAs and logic circuits for the driver, was confirmed. The emission current from the Si FEA can be controlled by the built-in MOSFET at a voltage of less than 5 V, which can be driven by the built-in driving circuits. The operation of the 4×4 matrix FEA with driving circuits was demonstrated. This is the first operation of the FEA integrated with MOSFET logic circuits. The detailed design and fabrication processes are described. © 2002 American Vacuum Society.
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85.45.Fd Field emission displays (FEDs)
85.40.Sz Deposition technology

Texture and resistivity of dilute binary Cu(Al), Cu(In), Cu(Ti), Cu(Nb), Cu(Ir), and Cu(W) alloy thin films

A. Gungor, K. Barmak, A. D. Rollett, C. Cabral, and J. M. E. Harper

J. Vac. Sci. Technol. B 20, 2314 (2002); http://dx.doi.org/10.1116/1.1520549 (6 pages) | Cited 6 times

Online Publication Date: 9 December 2002

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Annealing of dilute Cu(Al), Cu(In), Cu(Ti), Cu(Nb), Cu(Ir), and Cu(W) alloy films resulted in the lowest resistivity for Cu(Ti) and Cu(In) and the strongest 〈111〉 fiber texture also for Cu(Ti). Electron-beam evaporated films with compositions in the range of 2.0–4.2 at. % and thicknesses in the range of 420–560 nm were annealed at 400 °C for 5 h. Four-point probe resistance measurements, x-ray diffraction, Rutherford backscattering, and particle-induced x-ray emission were used to characterize the films and to follow the changes in film texture, phase constitution, and resistivity upon annealing. The behavior of the alloy films was compared and contrasted with that for a pure evaporated Cu film. © 2002 American Vacuum Society.
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73.61.At Metal and metallic alloys
61.72.Cc Kinetics of defect formation and annealing
68.55.-a Thin film structure and morphology
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
68.55.Nq Composition and phase identification

Direct printing of polymer microstructures on flat and spherical surfaces using a letterpress technique

Scott M. Miller, Sandra M. Troian, and Sigurd Wagner

J. Vac. Sci. Technol. B 20, 2320 (2002); http://dx.doi.org/10.1116/1.1520554 (8 pages) | Cited 11 times

Online Publication Date: 9 December 2002

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We have developed a letterpress technique capable of printing polymer films with micrometer scale feature sizes onto flat or spherically shaped nonporous substrates. This printing technique deposits polymer only in desired regions thereby eliminating subsequent developing and subtraction steps. Flat or curved printing plates, which are fabricated from either rigid or deformable materials, are used to transfer thin molten polymer films onto flat target substrates. By deforming the printing plates into a spherical shape, it is also possible to print patterned films onto the concave side of a spherically deformed target substrate. These printed films serve as good resists for both wet chemical etching and reactive ion etching. Interferometric measurements of the polymer film thickness are used to probe physical mechanisms affecting printing instabilities, pattern fidelity, and edge resolution. Our experimental study indicates that this letterpress technique may prove suitable for high-throughput device fabrication involving large-area microelectronics. © 2002 American Vacuum Society.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
68.55.A- Nucleation and growth
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
85.40.Hp Lithography, masks and pattern transfer

Characteristics of ultrathin Ta and TaN films

S. M. Rossnagel

J. Vac. Sci. Technol. B 20, 2328 (2002); http://dx.doi.org/10.1116/1.1520556 (9 pages) | Cited 26 times

Online Publication Date: 9 December 2002

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The electrical resistivity of thin films of Ta and TaN has been examined as a function of film thickness and other processing parameters. The films were deposited by magnetron sputtering of Ta cathodes with Ar, or mixtures of Ar and N2 for the case of TaN. Ta films deposited on silicon dioxide or Cu surfaces were always beta phase, and showed little resistance increase as the thickness was reduced. The TaN films were deposited in a broad range of compositions, depending on reactive gas flow and system configuration, and showed strong increases in resistivity as thickness was decreased. Ta films deposited on TaNx with x equal to or greater than 1, an electrical resistivity greater than 300 mΩ cm, and with thickness greater than 2 nm were alpha phase, and showed significant increases in resistivity as thickness was reduced. The application and electrical properties of these films as diffusion barriers in interconnect structures depends strongly on the thicknesses at the contact points at the bottoms of vias and only weakly on the phase of the Ta. The resistivity of the barrier films on via and trench sidewalls is high enough to be irrelevant to circuit performance. © 2002 American Vacuum Society.
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73.61.At Metal and metallic alloys
68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
68.35.Fx Diffusion; interface formation
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
68.55.Nq Composition and phase identification
85.40.Ls Metallization, contacts, interconnects; device isolation

Direct patterning of nanostructures by field-induced deposition from a scanning tunneling microscope tip

A. Houel, D. Tonneau, N. Bonnail, H. Dallaporta, and V. I. Safarov

J. Vac. Sci. Technol. B 20, 2337 (2002); http://dx.doi.org/10.1116/1.1520548 (9 pages) | Cited 9 times

Online Publication Date: 9 December 2002

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The process of local-field-induced deposition on a surface facing a scanning tunneling microscope (STM) tip has been investigated for several tip-sample systems. Applying negative voltage pulses, atoms can be transferred from the STM tip to the surface and, for example, platinum dots and lines have been drawn on gold or silicon samples by this technique. In this latter case, a discussion is proposed on growth mechanisms involved in field-induced deposition processes on the basis of growth kinetics studies. When positive voltage pulses are applied to a silicon sample placed in tunneling conditions with a STM tip, silicon nanofeatures are elaborated on the substrate surface by field-enhanced surface diffusion of silicon atoms. © 2002 American Vacuum Society.
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68.43.Jk Diffusion of adsorbates, kinetics of coarsening and aggregation
81.16.Ta Atom manipulation
79.70.+q Field emission, ionization, evaporation, and desorption
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.43.Mn Adsorption kinetics
68.35.Fx Diffusion; interface formation
07.79.Cz Scanning tunneling microscopes

Electrical conductivity of sidewall-deposited fluorocarbon polymer in SiO2 etching processes

T. Shimmura, S. Soda, S. Samukawa, M. Koyanagi, and K. Hane

J. Vac. Sci. Technol. B 20, 2346 (2002); http://dx.doi.org/10.1116/1.1520551 (5 pages) | Cited 5 times

Online Publication Date: 9 December 2002

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High-aspect-ratio SiO2 contact hole etching is one of the key processes in the fabrication of ultralarge scale integration devices. However, there are many serious problems, such as charge-build-up damage, etching-stop, and microloading effects. Charge accumulation in high-aspect-ratio contact holes during etching is one of the main causes of these problems. In SiO2 etching using fluorocarbon gases, it is well known that a fluorocarbon film is deposited on the underlayer surface and sidewall of contact holes. It is also predicted that an increase in the conductivity of the fluorocarbon film deposited on the SiO2 sidewall markedly reduces the charging potential in the high-aspect-ratio contact holes because of the high conductivity of the deposited polymer. To clarify these phenomena, it is necessary to obtain quantitative measurements of the conductivity of the sidewall surfaces in contact holes. Therefore, we fabricated the sensing device using semiconductor production technology, and monitored sidewall current of SiO2 contact holes on the silicon wafer. The relationship between the chemical structure and sidewall current of the fluorocarbon films deposited in contact holes is investigated. We have found that highly cross-linked and unsaturated fluorocarbon polymer causes high sidewall conductivity in SiO2 contact holes. It is suggested that the deposited fluorocarbon film reduces the charging potential during the SiO2 etching process. © 2002 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
73.25.+i Surface conductivity and carrier phenomena
73.61.Ph Polymers; organic compounds
78.66.Qn Polymers; organic compounds
78.30.Jw Organic compounds, polymers

Thickness metrology and end point control in W chemical vapor deposition process from SiH4/WF6 using in situ mass spectrometry

Y. Xu, T. Gougousi, L. Henn-Lecordier, Y. Liu, S. Cho, and G. W. Rubloff

J. Vac. Sci. Technol. B 20, 2351 (2002); http://dx.doi.org/10.1116/1.1520555 (10 pages) | Cited 11 times

Online Publication Date: 9 December 2002

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Real-time, in situ chemical sensing has been applied to achieve reaction metrology and advanced process control in a low pressure tungsten chemical vapor deposition process based on WF6 and SiH4 reactants (silane reduction process). Using mass spectrometry as the sensor to detect both product generation (H2) and reactant depletion (SiH4) at wafer temperature of 200–250 °C, these signals provided a direct real-time measurement of deposited film thickness with an uncertainty less than 2%, and this thickness metrology signal was employed to achieve real-time process end point control. When reactant conversion rates are sufficient (∼20% in this case) as often occurs in manufacturing processes, the thickness metrology (1.0%–1.5%) and control (∼1.5%–2.0%) accuracies are in the regime needed for meaningful application of advanced process control. Since the in situ sensor delivers a metrology signal in real time, real-time process control is achieved, enabling compensation for random process disturbances during an individual process cycle as well as for systematic wafer-to-wafer process drifts. These results are promising for manufacturing from the standpoints of metrology accuracy and application in real-time control. © 2002 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Bx Metals, semimetals, and alloys
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

Effects of Ti addition on the morphology, interfacial reaction, and diffusion of Cu on SiO2

C. J. Liu, J. S. Jeng, J. S. Chen, and Y. K. Lin

J. Vac. Sci. Technol. B 20, 2361 (2002); http://dx.doi.org/10.1116/1.1520552 (6 pages) | Cited 19 times

Online Publication Date: 9 December 2002

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In this work, thin films of pure Cu, and Cu with 0.02 or 2.98 wt % Ti were deposited on SiO2 covered Si substrates. The samples were annealed at 500–800 °C in vacuum to investigate their morphological evolution, interfacial reaction, and diffusion. X-ray diffraction reveals Cu(111) and Cu(200) peaks for pure Cu and Cu(0.02 wt % Ti) films. However, the Cu(2.98 wt % Ti) film exhibits a very weak Cu(200) peak, indicating that this film is textured in 〈111〉 orientation. Concurrently, scanning electron microscopy shows that the grain size of the Cu(2.98 wt % Ti) film is significantly smaller than those of pure Cu and Cu(0.02 wt % Ti) films. In addition, Cu(2.98 wt % Ti) film remains smooth after annealing up to 800 °C, while the other two films become discontinuous. X-ray photoelectron spectroscopy indicates that a TiOx layer has formed at the Cu(0.02 wt % Ti)/SiO2 and Cu(2.98 wt % Ti)/SiO2 interfaces after 700 °C annealing. Nevertheless, the TiOx layer is thicker in the Cu(2.98 wt % Ti) system than in the Cu(0.02 wt % Ti) system. Consequently, the Cu(2.98 wt % Ti) film shows no diffusion of Cu into SiO2 at temperatures up to 700 °C. Connections between the segregation of Ti addition and the morphological/interfacial characteristics are discussed. © 2002 American Vacuum Society.
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68.35.Ct Interface structure and roughness
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
68.55.-a Thin film structure and morphology
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.35.Dv Composition, segregation; defects and impurities
79.60.Jv Interfaces; heterostructures; nanostructures

Assessment of extreme ultraviolet-induced charging of subtractive metal lithography masks

L. E. Klebanoff, W. M. Clift, N. Franco, C. Bostedt, and L. J. Terminello

J. Vac. Sci. Technol. B 20, 2367 (2002); http://dx.doi.org/10.1116/1.1520550 (8 pages)

Online Publication Date: 9 December 2002

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An assessment was made of the extent of charging induced in a patterned multilayer-based extreme ultraviolet (EUV) mask and a model mask structure by exposure to EUV radiation. An aluminum subtractive metal lithography mask, consisting of ∼1700 Å of Al spaced from underlying Mo/Si multilayer by ∼500–700 Å of SiO2, was taken as representative of subtractive metal masks in general. Photoelectron spectra measured from patterned and model mask Al samples during EUV exposures were compared with spectra from samples known not to be charging. These studies indicate that EUV-induced charging of the Al absorber layer in the subtractive metal masks is zero to within ∼0.4 V accuracy. We speculate that the mask does not charge up due to an increase in the electrical conduction of the SiO2 spacer layer upon EUV irradiation. Irradiation of the spacer will create large numbers of low-energy secondary electrons in the SiO2 conduction band, providing a conducting path from the Al absorber layer to the electrically grounded Mo/Si multilayer. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
79.60.Jv Interfaces; heterostructures; nanostructures

Morphology and luminescence of porous GaN generated via Pt-assisted electroless etching

Diego J. Díaz, Todd L. Williamson, Ilesanmi Adesida, Paul W. Bohn, and Richard J. Molnar

J. Vac. Sci. Technol. B 20, 2375 (2002); http://dx.doi.org/10.1116/1.1521428 (9 pages) | Cited 19 times

Online Publication Date: 9 December 2002

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Porous gallium nitride (PGaN) is produced by Pt-assisted electroless etching of GaN. Ultrathin Pt films are sputtered onto the surface of GaN, and etching is carried out in a 1:2:1 or 1:2:2 solution of CH3OH:HF:H2O2. Etching proceeds by first forming a network of small pores, after which ridge structures form, with the porous network in trenches between the ridges. As the etch progresses further the sidewalls of the ridges become steeper, and then the ridges start to disappear. Cathodoluminescence (CL) spectroscopy and imaging show the ridges to be optically inactive, suggesting that the ridges might arise from grain boundaries or dislocations present ins the starting GaN material. CL emission is confined to the porous areas between the ridges. CL properties of the PGaN vary depending on the source of the original, nonporous GaN material. Undoped and unintentionally doped hydride vapor phase epitaxy materials produce PGaN which shows only band gap emission at 368 nm before and after etching, whereas PGaN produced from the Si-doped metalorganic chemical vapor deposited material exhibits two blueshifted luminescence bands at 358 and 326 nm. The origin of the 358 nm blueshifted emission can plausibly be explained by quantum confinement effects, but the 326 nm band can only be explained by other mechanisms, such as the creation of specific surface states by etching. The etched morphology is very similar among the different types of GaN substrates used, however the difference in light emission properties must be ascribed to growth conditions, or to the nature and concentration of the dopants. © 2002 American Vacuum Society.
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78.60.Hk Cathodoluminescence, ionoluminescence
68.55.-a Thin film structure and morphology
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
81.65.Cf Surface cleaning, etching, patterning
61.43.Gt Powders, porous materials

Photoresponse characteristics of n-ZnO/p-Si heterojunction photodiodes

Y. S. Choi, J. Y. Lee, S. Im, and S. J. Lee

J. Vac. Sci. Technol. B 20, 2384 (2002); http://dx.doi.org/10.1116/1.1524152 (4 pages) | Cited 11 times

Online Publication Date: 9 December 2002

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We report on the photoresponse behavior of n-ZnO/p-Si photodiodes. Semiconducting n-ZnO films have been deposited on p-Si substrates at 480 °C using various Ar/O2 ratios, 2:1, 4:1, and 6:1, to fabricate n-ZnO/p-Si photodiodes. As a laser of 670 nm wavelength illuminated the photodiodes, a maximum responsivity of 0.286 A/W and a maximum quantum efficiency of 53% were obtained at a reverse bias of 5 V from a diode prepared with an Ar/O2 ratio of 6:1. The response time of the photodiode was as short as 35 ns as measured using pulse modulation of the illuminating laser. © 2002 American Vacuum Society.
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85.60.Dw Photodiodes; phototransistors; photoresistors
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Pz Photoconduction and photovoltaic effects

Scanning tunneling microscopy of endohedral metallofullerene Lu–C82 on C60 film

Bo-Rong Shi, Xue-Sen Wang, Houjin Huang, Shi-He Yang, A. Bachmann, and Nelson Cue

J. Vac. Sci. Technol. B 20, 2388 (2002); http://dx.doi.org/10.1116/1.1524151 (5 pages) | Cited 4 times

Online Publication Date: 9 December 2002

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Endohedral metallofullerene Lu–C82 molecules adsorbed on C60 film have been investigated by an ultra-high-vacuum scanning tunneling microscopy. The C60 film was obtained by depositing 2–3 ML of C60 molecules on a highly oriented pyrolytic graphite surface. The as-deposited Lu–C82 molecules were observed to form various structures on the C60 film. The nucleation behavior of Lu–C82 was compared with that of Nd–C82 and Tb–C82 on the C60 film. These structures were explained based on the interactions of Lu–C82–C60, Lu–C82–Lu–C82, and Lu–C82 scanning tunneling microscopy tip. © 2002 American Vacuum Society.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.43.Fg Adsorbate structure (binding sites, geometry)

Radio-frequency discharge cleaning of silicon-capped Mo/Si multilayer extreme ultraviolet optics

Samuel Graham, Charles Steinhaus, Miles Clift, and Leonard Klebanoff

J. Vac. Sci. Technol. B 20, 2393 (2002); http://dx.doi.org/10.1116/1.1524153 (8 pages) | Cited 12 times

Online Publication Date: 9 December 2002

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Remote oxygen and hydrogen radio-frequency (rf) discharge cleaning experiments have been performed to explore their potential for cleaning carbon-contaminated extreme ultraviolet optics. The samples consisted of silicon wafers coated with 100 Å sputtered carbon, as well as bare Mo/Si multilayer mirrors (Si terminated). The samples were exposed for 3 h to rf plasma discharges at 100, 200, and 300 W. The carbon removal and surface oxidation rates were evaluated using sputter through depth profiling Auger spectroscopy. Reflectivity changes and surface roughness measurements were performed using at-wavelength reflectometry (13.4 nm) and atomic force microscopy, respectively. Data show that excited rf O2 consistently removes carbon at a rate approximately six times faster than excited rf H2 for a given discharge power and pressure. rf O2 also induces loss of reflectivity that is related to the growth of SiO2 on the optic surface. rf H2 shows a much lower oxidation rate of the optic surface. In spite of the lowered oxidation risk, reflectivity loss in Mo/Si multilayers was still observed, although this loss is not related to surface oxidation. © 2002 American Vacuum Society.
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42.79.Bh Lenses, prisms and mirrors
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
68.35.B- Structure of clean surfaces (and surface reconstruction)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Two-dimensional transverse cross-section nanopotentiometry of actively driven buried-heterostructure multiple-quantum-well lasers

D. Ban, E. H. Sargent, St. J. Dixon-Warren, I. Calder, T. Grevatt, G. Knight, and J. K. White

J. Vac. Sci. Technol. B 20, 2401 (2002); http://dx.doi.org/10.1116/1.1524150 (7 pages) | Cited 10 times

Online Publication Date: 9 December 2002

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We report results of two-dimensional local potential measurement of the transverse cross-section of operating buried-heterostructure (BH) multiple-quantum-well lasers. The measured two-dimensional image of potential distribution resolved clearly the multiquantum-well active region and the p-n-p-n current-blocking structure of the BH laser, showing close correlation to the scanning spreading resistance microscopy image. Nanopotentiometry measurements were also performed on the p-n-p-n current-blocking structure of a BH laser under different forward bias voltages. The nanopotentiometry results provide direct insight into the behavior of p-n-p-n current-blocking layers intended to minimize current leakage. Our results demonstrate the application of nanopotentiometry to the delineation of complex buried structures in quantum optoelectronic devices. © 2002 American Vacuum Society.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Near-surface deep-trap and bulk deep-trap states in InxGa1−xAs/GaAs

N. C. Halder and Kimberly Genareau

J. Vac. Sci. Technol. B 20, 2408 (2002); http://dx.doi.org/10.1116/1.1525813 (5 pages) | Cited 1 time

Online Publication Date: 9 December 2002

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Field-effect studies have been performed to investigate the near-surface deep-trap and bulk deep-trap states in molecular-beam epitaxy-grown InxGa1−xAs (where x=0.1) on n+ GaAs. We have measured the isothermal capacitance transients for the major trap levels in the range of 77–380 K in the reverse-bias field of −1 to −3.8 V/cm. The results of our investigation indicate a distinct effect on the deep level spectra due to the applied field, suggesting a definitive way to identify the near-surface deep traps from the bulk deep traps, and vice versa. The two major deep traps identified in the present investigation further display a transition from one state to another, from near-surface to bulk state in the high-field region, when the applied reverse-bias field is increased from −3.0 to −3.8 V/cm. “Field” means “normalized” field, F(norm)=F(appl)×10−5. © 2002 American Vacuum Society.
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71.55.Eq III-V semiconductors
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Effect of photoacid generator concentration on sensitivity, photoacid generation, and deprotection of chemically amplified resists

Adam R. Pawloski and Paul F. Nealey

J. Vac. Sci. Technol. B 20, 2413 (2002); http://dx.doi.org/10.1116/1.1525811 (8 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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The dependence of resist processes (sensitivity, efficiency of photoacid generation, polymer deprotection) on the concentration of the photoacid generator (PAG) in formulations of chemically amplified photoresist was investigated as a function of the concentration of photoacid that was generated upon exposure. Although the sensitivity of a photoresist formulation improved by increasing the concentration of PAG in the resist formulation, the concentration of photoacid required to achieve an appropriate extent of deprotection to render development also increased. Using a standard addition technique, the efficiency of photoacid generation was quantified for resist systems consisting of triphenylsulfonium triflate as the PAG in an environmentally stable chemically amplified photoresist-type polymer primarily composed of 4-hydroxystyrene and tert-butyl acrylate monomers. Determination of the apparent efficiency of photoacid generation (the resist C parameter) allowed the concentration of photoacid within the resist film to be calculated for any exposure dose. Deprotection of the polymer was measured using infrared spectroscopy and analyzed as a function of the photoacid concentration within the resist. We determined from these results that the increase in the concentration of photoacid required for development of the resist was caused by a change in the deprotection process during the postexposure bake and was not due to dissolution inhibition by the unexposed PAG. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Comparing ionized physical vapor deposition and high power magnetron copper seed deposition

P. J. Stout, D. Zhang, S. Rauf, and P. L. G. Ventzek

J. Vac. Sci. Technol. B 20, 2421 (2002); http://dx.doi.org/10.1116/1.1525812 (12 pages) | Cited 6 times

Online Publication Date: 9 December 2002

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A computational modeling comparison is made between ionized physical vapor deposition (IPVD) and high power magnetron (HPM) deposition of copper. For the comparison the point of view of the feature scale is stressed where the two reactors are distinguishable by the magnitude and ratio of specie (Cu,Cua,Cu+,Ar+) flux, the angular distribution of the specie, and the energy of the ions incident on the feature surface. The HPM is characterized for the conditions studied by a metal flux content made up almost entirely of copper athermals, an Ar+ ion flux about four times the Cu metal flux, decreasing Cu+ fraction and increasing Cu athermal flux to surface with increasing target power, and both no sputter and sputter regimes at the wafer possible. The IPVD reactor is characterized for the conditions studied by a Cu metal flux with a large neutral fraction but significant ions and athermals, an Ar+ ion flux on the order of the Cu metal flux, and only a sputter regime at the wafer possible. An increase in target power increases the deposition rate and decreases the Cu+ fraction in both systems. In IPVD the bottom coverage increases and the side wall coverage decreases due to a decrease in the sputter rate and an increase in the Cu neutral and athermal fraction. In HPM bottom coverage is reduced with increasing target power due to the lower Cu+ fraction. An increase in wafer power decreases the deposition rate in both systems by increasing the sputter rate. A lower ion current to the wafer for IPVD versus HPM gives the ions a higher energy at the wafer for the same power. In HPM lower energy ions are sufficient for the same sputtering rate versus IPVD due to the higher ion/neutral fraction. With no wafer bias HPM has thicker bottom versus IPVD since no sputtering of the feature bottom is occurring and the more focused athermals (versus neutrals) are less shadowed to the feature bottom. The IPVD side wall deposits have more thickness variation than HPM due to the large Cu neutral component in IPVD. An increase in wafer power increases side wall coverage and decreases feature bottom coverage in both systems as metal deposited at feature bottom is redeposited to the sidewalls. For increased coil power in IPVD the Cu+ fraction increases and the Cu neutral fraction decreases. Both bottom and side wall coverage increase as more Cu enters the feature as focused ions. © 2002 American Vacuum Society.
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85.40.Ls Metallization, contacts, interconnects; device isolation
81.15.Cd Deposition by sputtering
81.15.Jj Ion and electron beam-assisted deposition; ion plating
85.40.Sz Deposition technology
68.55.-a Thin film structure and morphology

Molybdenum-based nanostructured mixed oxides for sensing applications: Effect of the Mo oxide composition on the structure of sol–gel thin films

A. Taurino, M. Catalano, P. Siciliano, K. Galatsis, Y. X. Li, and W. Wlodarski

J. Vac. Sci. Technol. B 20, 2433 (2002); http://dx.doi.org/10.1116/1.1526360 (8 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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In this work, we report on the structural investigation by transmission electron microscopy of molybdenum-based mixed oxides for use as gas sensitive films. In particular, sol–gel thin films of molybdenum–titanium and molybdenum–tungsten oxides, deposited by spin coating on silicon substrates, have been analyzed by selected area electron diffraction, conventional, and high-resolution transmission electron microscopy. Our results show that the relative percentage of the molybdenum precursors used during the sol–gel deposition controls the morphology of the films, by modifying the size and the arrangements of the polycrystalline grains on the substrate. © 2002 American Vacuum Society.
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68.55.-a Thin film structure and morphology
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)
68.37.Lp Transmission electron microscopy (TEM)

Near-surface electronic defects and morphology of CuIn1−xGaxSe2

Y. M. Strzhemechny, P. E. Smith, S. T. Bradley, D. X. Liao, A. A. Rockett, K. Ramanathan, and L. J. Brillson

J. Vac. Sci. Technol. B 20, 2441 (2002); http://dx.doi.org/10.1116/1.1526357 (8 pages) | Cited 4 times

Online Publication Date: 9 December 2002

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CuIn1−xGaxSe2 (CIGS) is a leading candidate for high-efficiency solar cells, yet the defects and electronic structure that define performance are relatively unexplored. We employed low-energy depth-resolved cathodoluminescence to measure the local band and defect properties of epitaxial CIGS films having (002), (220)/(204), or (112) orientations on GaAs substrates. Along with a near-band-edge emission, room-temperature luminescence spectra for all epitaxial samples reveal a well-defined deep-level transition confined within ∼100 nm of the surface. The intensity of this defect-related feature reaches a maximum at the surface relative to the near-band-edge peak. Polycrystalline CdS/CIGS/Mo/glass and CIGS/Mo/glass solar-cell layers were also studied. These exhibit a weaker deep-level emission modulated by CIGS-thickness-related optical cavity effects. The integrated intensity of this emission relative to the near-band-edge peak intensity is also a maximum at the surface and decreases into the sample. A strong deep-level emission due to CdS was also observed decaying with depth relative to the near-band-edge emission of the CIGS. The CdS emission was the only significant change in the polycrystalline emission spectrum with and without the CdS layer. The observed behavior is consistent with the existence of a nanoscale near-surface defective region whose properties can impact charge generation and recombination in solar energy-generating structures. © 2002 American Vacuum Society.
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73.20.Hb Impurity and defect levels; energy states of adsorbed species
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.-a Thin film structure and morphology
78.66.Li Other semiconductors
71.55.Ht Other nonmetals
78.60.Hk Cathodoluminescence, ionoluminescence

Development of the point diffraction interferometer for extreme ultraviolet lithography: Design, fabrication, and evaluation

K. Otaki, K. Ota, I. Nishiyama, T. Yamamoto, Y. Fukuda, and S. Okazaki

J. Vac. Sci. Technol. B 20, 2449 (2002); http://dx.doi.org/10.1116/1.1526605 (10 pages) | Cited 12 times

Online Publication Date: 9 December 2002

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A point diffraction interferometer (PDI) for extreme ultraviolet lithography (EUVL) aspheric mirror measurement has been developed. In order to realize an accuracy of 0.1 nm rms, various optical error factors have been numerically analyzed and the maximum tolerable error has been determined. From the error estimation results, the optimal pinhole diameter has been determined as 0.5 μm. In a PDI, air turbulence reduces the precision and accuracy because of the long optical path. In order to avoid this problem, the apparatus is filled with helium gas, which has a smaller refractive index than that of air. By using this apparatus, precision of 0.03–0.04 nm rms and a system error of 0.10 (0.16) nm rms have been obtained for a spheric mirror with numerical aperture (NA) 0.08 (0.15). In aspheric mirror measurement, an accuracy of 0.74 (1.18) nm rms for NA 0.08 (0.15) has been obtained. The accuracy becomes 0.34 (0.97) nm rms for NA 0.08 (0.15) with 36-term Zernike polynomial fitting. © 2002 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

Fabrication of flexible polymer tubes for micro and nanofluidic applications

B. Ilic, D. Czaplewski, M. Zalalutdinov, B. Schmidt, and H. G. Craighead

J. Vac. Sci. Technol. B 20, 2459 (2002); http://dx.doi.org/10.1116/1.1526356 (7 pages) | Cited 13 times

Online Publication Date: 9 December 2002

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We describe a method for fabricating narrow, flexible, polymeric fluid conduction tubes with dimensions down to the 100 nm regime. Vapor deposited Parylene tubes of various dimensions were integrated into silicon substrates forming a microfluidic network. In one approach we replicated fluidic systems in polymer by detaching free-standing flexible Parylene tubes from the silicon mold. We demonstrated capillary flow and electrophoretic drive of ions through polymer tubes of up to 5 cm in length. © 2002 American Vacuum Society.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
61.41.+e Polymers, elastomers, and plastics
81.07.Bc Nanocrystalline materials

Photoinduced organic nanowires from self-assembled monolayers

Ying-Hong Qiao, Qing-Dao Zeng, Zhong-Yin Tan, Shan-Dong Xu, Dong Wang, Chen Wang, Li-Jun Wan, and Chun-Li Bai

J. Vac. Sci. Technol. B 20, 2466 (2002); http://dx.doi.org/10.1116/1.1526601 (4 pages) | Cited 9 times

Online Publication Date: 9 December 2002

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The self-assembled diacetylene molecular monolayer was prepared on highly oriented pyrolitic graphite and observed by scanning tunneling microscopy. Upon applying ultraviolet irradiation, the self-assembled conjugated polydiacetylene nanowires resulting from photoinduced topochemical reaction of diacetylene molecules were obtained. Control of the spacings between nanowires was achieved by a simple coadsorption method. The result presented here may supply a general method to obtain spacing-controllable organic nanowires. © 2002 American Vacuum Society.
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81.07.Nb Molecular nanostructures
81.16.Dn Self-assembly
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
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back to top SURFACE DYNAMICS, SURFACE PHASE TRANSITIONS, NUCLEATION, AND GROWTH

Low energy electron microscopy studies of steps on single crystal thin films of refractory metals

M. Ondrejcek, W. Swiech, G. Yang, and C. P. Flynn

J. Vac. Sci. Technol. B 20, 2473 (2002); http://dx.doi.org/10.1116/1.1521958 (5 pages) | Cited 5 times

Online Publication Date: 9 December 2002

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We describe low energy electron microscopy (LEEM) studies of the behavior at high temperatures of step edges on the close-packed surfaces of refractory metal thin films grown by molecular beam epitaxy. The research includes bcc Mo (011), V (011), Nb (011), and Ta (011), and comparison with bulk single crystals of Nb (011) and fcc Pt (111). Properties observed include faceting of individual steps, step–step interactions, and the interactions of steps with defects such as threading dislocations and with surface reconstructions. Step fluctuations on these surfaces are quantified. For Mo (011) observed by LEEM, the Fourier amplitudes are fit with an attachment model to obtain the step stiffness and its entropy, the step free energy, and its orientation dependence. © 2002 American Vacuum Society.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Md Surface thermodynamics, surface energies
68.37.Nq Low energy electron microscopy (LEEM)
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.55.-a Thin film structure and morphology
65.40.G- Other thermodynamical quantities
61.72.Lk Linear defects: dislocations, disclinations

Low energy electron microscopy study of In on Si(111)

A. Pavlovska, E. Bauer, and M. Giessen

J. Vac. Sci. Technol. B 20, 2478 (2002); http://dx.doi.org/10.1116/1.1523370 (14 pages) | Cited 7 times

Online Publication Date: 9 December 2002

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The structural phase transitions in the multiphase system indium (In) on Si(111) are studied as a function of coverage at different temperatures between −100 and 550 °C by low energy electron microscopy (LEEM) and low energy electron diffraction (LEED). All phase transitions observed with increasing In coverage are first order. Nucleation of a new phase starts only after the previous phase is completed. At high temperatures only a disordered monolayer with high atomic density forms. When In is deposited at room temperature on a (√3×√3)-R30°–In surface four new phases are observed: a (2×1), a near coincidence (1.5√3×1.5√3), a “(1×1)-R30°” and a (6×6) phase. At room temperature and up at least to 400 °C a double layer forms. Below 120 °C this layer is compressed and ordered in two coexisting structures, (√7×√3) and “(1×1)-R30°”. Above 120 °C it shows a (1×1) LEED pattern, which is attributed to a disordered layer on the Si(111)-(1×1) surface. A third monolayer with the packing density of a slightly compressed In(111) plane is unstable at room temperature against formation of three-dimensional crystals but becomes stable during growth at temperatures below about −80 °C. Three-dimensional crystals grow at room temperature on the double layer in the Stranski–Krastanov mode. These crystals are primarily (100)-oriented and are bounded by the equilibrium planes known from bulk crystals, including the reconstructed (100) surface, which is no longer reconstructed above 120 °C. © 2002 American Vacuum Society.
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68.35.Rh Phase transitions and critical phenomena
68.43.Fg Adsorbate structure (binding sites, geometry)
68.37.Nq Low energy electron microscopy (LEEM)
68.55.A- Nucleation and growth
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

Growth shapes of Ag crystallites on the Si(111) surface

W. X. Tang, K. L. Man, Hanchen Huang, C. H. Woo, and M. S. Altman

J. Vac. Sci. Technol. B 20, 2492 (2002); http://dx.doi.org/10.1116/1.1523372 (4 pages) | Cited 6 times

Online Publication Date: 9 December 2002

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Kinetically limited growth shapes of Ag crystallites on the Si(111) surface have been studied by low energy electron microscopy and diffraction. Triangular hexagons are predominant with the (111) plane parallel to the substrate. The major side facets are determined by facet diffraction spot analysis to be {100}. Absence of facet diffraction spots from the minor side facets suggests that they may be the more steeply inclined {1math1} or {1math1} orientations. Preliminary evidence is also obtained that codeposition of In causes the steeper side facets to dominate the growth shape. © 2002 American Vacuum Society.
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68.55.A- Nucleation and growth
68.35.Dv Composition, segregation; defects and impurities
68.37.Nq Low energy electron microscopy (LEEM)

Low energy electron microscopy/diffraction study on growth of Ge on Si(113) surface

T. Yasue, T. Koshikawa, and E. Bauer

J. Vac. Sci. Technol. B 20, 2496 (2002); http://dx.doi.org/10.1116/1.1523374 (4 pages) | Cited 1 time

Online Publication Date: 9 December 2002

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We studied the growth process of Ge on a Si(113) surface by low energy electron microscopy (LEEM) combined with low energy electron diffraction (LEED). It is demonstrated that the transition from layer growth to island growth can be detected by the variation of the (00) spot intensity. The (00) spot intensity showed a minimum at around a coverage of 4.4 monolayer at about 560 °C. Three-dimensional (3D) clusters form preferentially at the step bunches at the same coverage followed by the formation of 3D islands. This means that the reduction of the (00) spot intensity is caused by the formation of 3D clusters while the growth of 3D islands whose center part shows bright contrast corresponds to the recovery of (00) intensity. The LEED patterns of the 3D islands show many spots originating from facets. The energy dependence of the spot positions reveals that the 3D islands have {15x} side facets. © 2002 American Vacuum Society.
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68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.37.Nq Low energy electron microscopy (LEEM)
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
68.43.Fg Adsorbate structure (binding sites, geometry)

Growth dynamics of titanium silicide nanowires observed with low-energy electron microscopy

P. A. Bennett, B. Ashcroft, Zhian He, and R. M. Tromp

J. Vac. Sci. Technol. B 20, 2500 (2002); http://dx.doi.org/10.1116/1.1525006 (5 pages) | Cited 15 times

Online Publication Date: 9 December 2002

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We report in situ low-energy electron microscopy observations of spontaneous nanowire (NW) formation during deposition of Ti on Si(111) at T∼850 °C. The NWs are oriented primarily along {110} directions, with typical dimensions 50 nm wide, 20 nm high, and several microns long. The NW shape persists even at temperatures high enough to shrink the wires, suggesting that these are equilibrium shapes. During growth, the NW advances at both ends at a constant rate, independent of NW length or collisions with steps, which pile up at the ends. We argue that the rate-limiting kinetic step during growth is the reaction of silicide at the island ends. NWs that intersect during growth do not fuse, and will separate upon annealing. Occasionally, they form a temporary junction that connects and disconnects in an oscillating cycle. © 2002 American Vacuum Society.
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68.65.La Quantum wires (patterned in quantum wells)
81.07.Vb Quantum wires
68.37.Nq Low energy electron microscopy (LEEM)
81.15.Np Solid phase epitaxy; growth from solid phases
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In situ emission microscopy of field emitter cathode arrays

G. A. Mulhollan, K. D. Jamison, and M. E. Kordesch

J. Vac. Sci. Technol. B 20, 2505 (2002); http://dx.doi.org/10.1116/1.1525008 (4 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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Emission microscopes have been used to image devices used for cold cathodes, in situ. The use of emission microscopy in the evaluation of these materials and devices is described. © 2002 American Vacuum Society.
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85.45.Db Field emitters and arrays, cold electron emitters
79.70.+q Field emission, ionization, evaporation, and desorption
68.37.Vj Field emission and field-ion microscopy

Scanning photoelectron microscopy study of as-grown and heat-treated chemical vapor deposition boron-doped diamond films

A. A. Zakharov, V. Ralchenko, R. Khmelnitskii, and I. Lindau

J. Vac. Sci. Technol. B 20, 2509 (2002); http://dx.doi.org/10.1116/1.1525009 (5 pages)

Online Publication Date: 9 December 2002

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The electronic structure of as-grown and high temperature (1625 °C) annealed chemical vapour deposition boron-doped (1–4 ppm) diamond films has been studied using a scanning photoelectron microscope with lateral resolution in the 1 μm range. The fresh surfaces have been obtained by cleaving free-standing films in situ at a pressure of 7×10−11 Torr. The major part of the contrast in photoelectron images is due to topography effect but grain structure (grain size 10–50 μm) can be also detected. The detailed study of separate grains shows that as-grown films demonstrate significant intensity in the vicinity of the Fermi level with a characteristic band tail which is believed to result from static and dynamic site disorder. In annealed films a sharp drop in Fermi level intensity is observed and samples show charging effects in scanning electron microscope measurements. As-grown films contain different types of defects which appear as electrically active trapping centers and give rise to the increased density of states at the Fermi level. The evolution of the defect structure and possible boron redistribution upon annealing explains the much lower photoemission signal around the Fermi level in heat-treated films. © 2002 American Vacuum Society.
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68.37.Xy Scanning Auger microscopy, photoelectron microscopy
71.20.Mq Elemental semiconductors
71.55.Cn Elemental semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.05.U- Carbon/carbon-based materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.Cc Kinetics of defect formation and annealing
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Photoelectron emission microscopy of ultrathin oxide covered devices

V. W. Ballarotto, M. Breban, K. Siegrist, R. J. Phaneuf, and E. D. Williams

J. Vac. Sci. Technol. B 20, 2514 (2002); http://dx.doi.org/10.1116/1.1525007 (5 pages) | Cited 7 times

Online Publication Date: 9 December 2002

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Photoelectron emission microscopy (PEEM) has been used to investigate simple device structures buried under ultrathin oxides. In particular, we have imaged Au–SiO2 and p-type Si–SiO2 structures and have demonstrated that PEEM is sensitive to these buried structures. Oxide overlayers ranging up to 15.3 nm were grown by systematically varying the exposure time of the structures to a plasma-enhanced chemical-vapor deposition process. The change in image contrast as the oxide thickness increases was used to quantify the inelastic mean-free path of low-energy photoelectrons (∼1 eV) in amorphous silicon dioxide. For Au structures we find that the dominant mean-free path for photoelectrons in the overlying oxide is about 1.18±0.2 nm. Yet, we find a residual observable signal from the buried Au structure through roughly 13 oxide attenuation lengths. The signal attenuation from the Au can be explained by the spread of the photoelectron energies and the energy dependence of the electron–phonon interaction. Similar intensity attenuation behavior is also seen from heavily p-doped silicon (1020 cm−3) regions, but the signal is only observable through roughly 3.0 nm of oxide, and the signal from the 1018 cm−3 regions is not detectable through the thinnest oxide layer of approximately 2.5 nm. Here, the energy spread (∼2.0 eV) is more narrowly distributed about the phonon loss energies, leading to the observed attenuation behavior from heavily p-doped silicon. © 2002 American Vacuum Society.
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79.60.Jv Interfaces; heterostructures; nanostructures
73.40.Ns Metal-nonmetal contacts
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
71.38.-k Polarons and electron-phonon interactions
72.15.Lh Relaxation times and mean free paths
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Comparison of stigmatically focusing magnetic prisms of square versus round symmetries

H.-C. Kan, T. Dürkop, and R. J. Phaneuf

J. Vac. Sci. Technol. B 20, 2519 (2002); http://dx.doi.org/10.1116/1.1523375 (7 pages) | Cited 1 time

Online Publication Date: 9 December 2002

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Based on the results of electron optical simulations, we report on a comparison of the performance of stigmatically focusing magnetic prisms designed with two different symmetries. One type consists of a set of square inner pole pieces surrounded with rectangular outer pole pieces, which is similar to the magnetic prism in Tromp’s design [R. M. Tromp et al., Surf. Rev. Lett. 5, 1189 (1995)]. The other type consists of a set of nested round inner and outer pole pieces, which is similar to the magnetic prism we constructed for our low energy electron microscope [H. C. Kan, D. Auerbach, and R. J. Phaneuf, Rev. Sci. Instrum. (submitted)]. One interesting difference is that the square pole piece prism produces a strong linear dependence of the focal point position on the impact parameter in the deflection dimension, compared to what is seen in the performance of round pole pieces. This linear dependence produces asymmetric distortion in the imaging in the deflection dimension. © 2002 American Institute of Physics.
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41.85.Lc Particle beam focusing and bending magnets, wiggler magnets, and quadrupoles
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Correction of chromatic and spherical aberration in electron microscopy utilizing the time structure of pulsed excitation sources

G. Schönhense and H. Spiecker

J. Vac. Sci. Technol. B 20, 2526 (2002); http://dx.doi.org/10.1116/1.1523373 (9 pages) | Cited 14 times

Online Publication Date: 9 December 2002

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A theoretical ansatz for correction of the chromatic and spherical aberration of round-lens systems in photoemission and low-energy electron microscopy (PEEM/LEEM) is presented. The method is based on fast switching of electrical acceleration or lens fields. It exploits the highly precise time structure of pulsed photon sources like electron storage rings for synchrotron radiation or pulsed lasers as well as pulsed photocathodes of a LEEM. The initial results indicate that the approach is a promising alternative to the implementation of multipole or mirror correctors in the electron optical column of a microscope. © 2002 American Vacuum Society.
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41.85.Gy Chromatic and geometrical aberrations
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
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Scanning electron microscope with polarization analysis: Micromagnetic structures in ultrathin films

Hans Peter Oepen, Gerold Steierl, and Jürgen Kirschner

J. Vac. Sci. Technol. B 20, 2535 (2002); http://dx.doi.org/10.1116/1.1519863 (4 pages) | Cited 3 times

Online Publication Date: 9 December 2002

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The basics of the scanning electron microscope with polarization analysis are presented and special features of the microscope are discussed. The spin polarization of the secondary electrons allows for a high contrast as the topography of the sample is strongly suppressed. The feature of the method is that the orientation of the magnetization is measured and used for domain imaging. For complex domain patterns that makes the interpretation easy and direct. Examples are shown how the high surface sensitivity is used for the investigation of all kind of samples. The decoration by a thin ferromagnetic film makes even contaminated and samples with strongly spoiled surfaces accessible for scanning electron microscope with polarization analysis (SEMPA) investigation. Recently, the magnetic resolution of SEMPA has been pushed into the range of a few nm. © 2002 American Vacuum Society.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.50.Bb Fe and its alloys
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Low-energy electron microscopy/x-ray magnetic circular dichroism photoemission electron microscopy study of epitaxial MnAs on GaAs

E. Bauer, S. Cherifi, L. Daeweritz, M. Kaestner, S. Heun, and A. Locatelli

J. Vac. Sci. Technol. B 20, 2539 (2002); http://dx.doi.org/10.1116/1.1525005 (4 pages) | Cited 21 times

Online Publication Date: 9 December 2002

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Epitaxial MnAs films on GaAs(001) substrates are studied at room temperature and in the completely ferromagnetic state below room temperature with low-energy electron microscopy, x-ray magnetic circular dichroism photoemission electron microscopy, and low-energy electron diffraction. The combination of these techniques shows a clear relation between the two-phase structure of the layers and their magnetic domain structure. © 2002 American Vacuum Society.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.50.Pp Magnetic semiconductors
68.55.-a Thin film structure and morphology
68.37.Nq Low energy electron microscopy (LEEM)
79.60.Bm Clean metal, semiconductor, and insulator surfaces
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ch Domain walls and domain structure
78.20.Ls Magneto-optical effects

Magnetic dichroisms in absorption and photoemission for magnetic characterization in x-ray photoelectron emission microscopy

W. Kuch, L. I. Chelaru, F. Offi, M. Kotsugi, and J. Kirschner

J. Vac. Sci. Technol. B 20, 2543 (2002); http://dx.doi.org/10.1116/1.1523371 (7 pages) | Cited 10 times

Online Publication Date: 9 December 2002

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Magnetic contrast for the operation of a photoelectron emission microscope (PEEM) with synchrotron radiation is provided by magnetic dichroisms. Besides the most frequently employed magnetic dichroism, magnetic circular dichroism in x-ray absorption spectroscopy, energy filtering of photoemitted electrons allows one to also use magnetic dichroisms in photoelectron emission as complementary contrast mechanisms. We demonstrate that it is possible to obtain magnetic contrast in photoemission using PEEM equipped with a simple retarding field electron energy analyzer. Magnetic domain images of an ultrathin film of 10 atomic monolayers of Fe on W(001), obtained by three different contrast mechanisms (circular magnetic dichroism in x-ray absorption, circular magnetic dichroism in Fe valence band photoemission, and linear magnetic dichroism in Fe 3p photoemission) are presented and compared. © 2002 American Vacuum Society.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.50.Bb Fe and its alloys
75.70.Ak Magnetic properties of monolayers and thin films
78.20.Ls Magneto-optical effects
79.60.Bm Clean metal, semiconductor, and insulator surfaces
78.70.Dm X-ray absorption spectra
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back to top OPTICAL LITHOGRAPHY

Effect of high numerical aperture lens on lithographic performance in 157 nm lithography

Toshiro Itani, Toshifumi Suganaga, Noriyoshi Kanda, Jae-Hwan Kim, Kunio Watanabe, Julian Cashmore, and Malcolm Gower

J. Vac. Sci. Technol. B 20, 2562 (2002); http://dx.doi.org/10.1116/1.1520577 (5 pages) | Cited 1 time

Online Publication Date: 9 December 2002

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157 nm lithography is the most promising candidate for the post-193 nm lithography at the sub-70 nm technology node of semiconductor devices. In order to realize sub-70 nm resolution using 157 nm lithography, the critical components such as F2 laser, optics, photomasks, and resists have been studied extensively [Bloomstein et al., J. Vac. Sci. Techol. B 15, 2112 (1997); Rothschild et al., J. Photopolymer Sci. Technol. 13, 369 (2000); Rothschild et al. (unpublished); Itani and Wakamiya, Microelectron. Eng. 61–62, 49 (2002)]. Moreover, for improving the numerical aperture (NA) of the projection lens and thus the resolution capability at 157 nm, liquid immersion interference lithography at 157 nm has been studied and has obtained a minimum resolution of less than 70 nm lines and spaces [Switkes, Bloomstein, and Rothschild, Appl. Phys. Lett. 77, 3149 (2000); Switkes and Rothschild, J. Vac. Sci. Technol. B 19, 2353 (2001)]. In this article we will report on the feasibility study of a high NA (0.85 NA) projection lens on a 157 nm microstepper, focusing on the resolution capability, the residual aberrations of the lens, and the effect of intrinsic birefringence of CaF2 upon imaging performance. These issues have been evaluated experimentally and combined with simulation analysis of the lithographic performance. Simulation results of focus margin versus exposure latitude have demonstrated suitable values for mass production of actual semiconductor devices. We estimate that such high NA optics are effective for improving the resolution and process margin, particularly when combined with resolution enhancement techniques. We confirmed that 157 nm lithography with high NA optics could realize sub-70 nm patterns, and it has sufficient potential for mass production of the sub-70 nm technology node for semiconductor devices. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Prospects for photolithography at 121 nm

V. Liberman, M. Rothschild, P. G. Murphy, and S. T. Palmacci

J. Vac. Sci. Technol. B 20, 2567 (2002); http://dx.doi.org/10.1116/1.1524974 (7 pages) | Cited 7 times

Online Publication Date: 9 December 2002

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We have evaluated several subsystems that would be required for lithography at 121 nm: radiation sources, optics, ambient control, and resists. Dense plasma sources can generate significant power, >0.5 J of 121 nm radiation per pulse. An extensive survey of commercially available LiF, as well as specially grown LiF, shows that transmission losses are ∼20% per cm, a value which is at least 5× too high if LiF is to be used as lens material. At present it is not clear whether there is a fundamental limitation to LiF transparency at 121 nm, but the main source of absorption arises from lithium oxide or hydroxide in the crystal. Polymers, fluorinated or not, exhibit very high absorption at 121 nm, indicating that ultrathin resists or bilayer resists will have to be used at 121 nm. However, the photochemistry at 121 nm is probably not much different from that at longer wavelengths. The resists are sensitive, ∼1 mJ/cm2 required dose, and they have high contrast at 121 nm. Finally, we have also performed preliminary patterning experiments. Using contact printing with a phase shifting mask we have printed 45 nm features in an ultrathin photoresist. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

121.6 nm radiation source for advanced lithography

Jianxun Yan, Ashraf El-Dakrouri, Mounir Laroussi, and Mool C. Gupta

J. Vac. Sci. Technol. B 20, 2574 (2002); http://dx.doi.org/10.1116/1.1515302 (4 pages) | Cited 5 times

Online Publication Date: 9 December 2002

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A vacuum ultraviolet (VUV) light source based on a high-pressure cylindrical dielectric barrier discharge (DBD) has been developed. Intense and spectrally clean Lyman-α line at 121.6 nm was obtained by operating a DBD discharge in neon with a small admixture of hydrogen. The spectrum, optical power, stability, and efficiency of the source were measured. The influence of the gas mixture and total gas pressure on the VUV intensity has been investigated. Maximum optical power of 3.2 W and spectral width <0.03 nm was achieved. Power stability of ±2% for 100 h of operation has also been obtained. The newly developed Lyman-α line source at 121.6 nm appears very promising for advanced lithography and other applications. © 2002 American Vacuum Society.
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52.80.Yr Discharges for spectral sources (including inductively coupled plasma)
42.72.Bj Visible and ultraviolet sources
85.40.Hp Lithography, masks and pattern transfer

Optimizing vacuum ultraviolet attenuated phase shift masking materials

B. W. Smith, A. Y. Bourov, and Y. Liu

J. Vac. Sci. Technol. B 20, 2578 (2002); http://dx.doi.org/10.1116/1.1526099 (5 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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Extensive vacuum ultraviolet (VUV) optical data have been collected for sputter-deposited thin films of masking material compounds for use at 157 nm. The use of VUV optical data and effective media modeling has lead to 27 possible material candidates for further study. These composite material films consist of a silicon dioxide host combined with various oxides and nitrides, generally of refractory metals. By adjusting material stoichiometry through control of deposition parameters (target composition ratios, pressure, power, flow rates, etc.), films have been tailored for specific optical properties. By using extinction coefficient/refractive index relationships for 180° phase shift, 4%–25% transmission, and <15% reflectivity, evaluation of the materials is possible. Additional detailed analysis of three specific composite materials is shown for use as attenuated phase shift masking at 157 nm. In each case, silicon dioxide is the host material within the film and the various metal oxides provide the appropriate absorption. The use of fluoride film etch stop materials is also described as a method to improve etch selectivity. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Polarization contact: Concept and initial assessment

Michael Lam and Andy Neureuther

J. Vac. Sci. Technol. B 20, 2583 (2002); http://dx.doi.org/10.1116/1.1526098 (6 pages)

Online Publication Date: 9 December 2002

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Simulations using the aerial image simulator SPLAT are performed to analyze various structures for printing contacts, motivated by trying to condense the double exposure of two lines into a single exposure. The polarization contact uses polarization bars in the arms of two crossed orthogonal lines as a means to generate a contact in a single exposure. Characterizations of the contact structures are possible by investigating their normalized unit contours. From cut lines of these contours, each structure can be understood based solely on its geometries. The scaling property of optical systems allows these unit spread functions to ultimately characterize its behavior. The structures are similar in their response to 1 Rayleigh unit of defocus, with each structure having an intensity ratio of peak defocus to perfect focus of about 0.79. Dense contacts are generated using a polarization-phase carpet that condenses a double exposure with phase shifting into a single exposure, at a cost of 75% less throughput. © 2002 American Vacuum Society.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
85.40.Hp Lithography, masks and pattern transfer

Optical imaging properties of dense phase shift feature patterns

M. Fritze, B. Tyrrell, R. Mallen, B. Wheeler, P. Rhyins, and P. Martin

J. Vac. Sci. Technol. B 20, 2589 (2002); http://dx.doi.org/10.1116/1.1520567 (8 pages) | Cited 4 times

Online Publication Date: 9 December 2002

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Optical lithography resolution enhancement methods are continuing to develop, driven by the semiconductor industry’s requirements for imaging subwavelength feature sizes. In the phase shift area, pattern decomposition into multiple exposures has been found to be useful and is finding its way into production. Recently, layout construction based on dense fine-pattern imaging has received increasing interest. This type of approach can minimize the proximity and other spatial frequency effects that otherwise limit strong phase shift technologies. Simple fine-feature template masks are easier and cheaper to fabricate and inspect as well as offering the potential to be reused for multiple designs. In this article, imaging and process issues specific to dense phase shift patterns are explored both experimentally and through simulation. Progress is reported in applying our gratings of regular arrays and trim exposures for ultralarge scale integrated circuit lithography (GRATEFUL) imaging method to fine features in both x and y orientations. The use of a graytone trim mask to vary fine-feature dimensions in a dual-exposure, strong phase shift process has been explored. We have also studied multiple-exposure lithography using one mask and varying illumination between exposures. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Parallel maskless optical lithography for prototyping, low-volume production, and research

Dario Gil, Rajesh Menon, Xudong Tang, Henry I. Smith, and D. J. D. Carter

J. Vac. Sci. Technol. B 20, 2597 (2002); http://dx.doi.org/10.1116/1.1526353 (5 pages) | Cited 15 times

Online Publication Date: 9 December 2002

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Earlier we reported on a proof-of-concept maskless-lithography system that used an array of Fresnel zone plates to focus multiple beams of 442 nm light onto a substrate, and micromechanics for multiplexing light to the several zone plates, enabling patterns of arbitrary geometry, at 350 nm linewidth, to be written. We referred to the technique as zone-plate-array lithography (ZPAL). We also demonstrated zone-plate-array microscopy. Here, we report on a “preprototype” ZPAL system operating at an exposure wavelength of 400 nm, capable of quick-turn-around, maskless lithography. We describe the lithography results with this system as well the development of high-speed data delivery systems, high-numerical-aperture zone plates (up to 0.95), and a multiplexing scheme that will enable us to move to a “full-prototype” system capable of 210 nm feature sizes at a moderate but useful throughput of ∼0.25 cm2 in 20 min. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
42.79.Ci Filters, zone plates, and polarizers

Interference pattern formation from an array of coherent laser beams

Y. Liu, J. Barhen, Y. Braiman, and J. X. Zhong

J. Vac. Sci. Technol. B 20, 2602 (2002); http://dx.doi.org/10.1116/1.1523396 (4 pages)

Online Publication Date: 9 December 2002

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We present numerical analysis of interferometric patterns formed by multiple sources. Multiple beams can be achieved either from a synchronized laser array or by splitting a coherent light source. We assume Gaussian form for each beam, and all the beams are combined at the near field. The condition for achieving periodic structures with the feature size significantly smaller than λ/4 is obtained. Multiple beam interference has the potential of achieving smaller feature size, less power requirement, and more flexibility than the conventional two-beam interferometric lithography method. © 2002 American Vacuum Society.
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42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.25.Hz Interference
81.16.Nd Micro- and nanolithography
81.16.Rf Micro- and nanoscale pattern formation

Simulation of critical dimension error using Monte Carlo method and its experimental verification

Sonny Y. Zinn, Sung-Woo Lee, Sung-Woon Choi, and Jung-Min Sohn

J. Vac. Sci. Technol. B 20, 2606 (2002); http://dx.doi.org/10.1116/1.1524978 (4 pages) | Cited 6 times

Online Publication Date: 9 December 2002

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In order to assess the effects of process parameter variations, we developed an optical lithography simulation program that handles the parameter variations statistically by the Monte Carlo (MC) method and predicts the mean and standard deviation of critical dimensions (CDs). As an application of the simulation program, we analyzed the error sources that contribute to the in-shot wafer CD uniformity. For experiments, we employed an attenuated phase-shift mask that is actually used for manufacturing a memory device. The CD uniformity of the mask was 4 nm on wafer scale. We performed a MC simulation using mask uniformity of 4 nm, illumination uniformity of 3%±1% (where the error stands for three times the standard deviation), defocus of 0.0±0.2 μm, mask transmittance error of ±0.3%, and mask phase error of ±5°. Simulation gave wafer CD uniformities of 19.2 and 13.3 nm for 0.7 and 0.8 NA, respectively. These predictions agree reasonably well with experimental values 21.7 and 11.4 nm. The error sources were analyzed for both values of NA. In either case, the contribution of mask uniformity is very significant, being about 85%. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
02.50.Ng Distribution theory and Monte Carlo studies
85.40.Bh Computer-aided design of microcircuits; layout and modeling
02.70.Uu Applications of Monte Carlo methods

Operational model for pattern and probe based aberration monitors

Garth Robins and Andrew Neureuther

J. Vac. Sci. Technol. B 20, 2610 (2002); http://dx.doi.org/10.1116/1.1526603 (7 pages) | Cited 1 time

Online Publication Date: 9 December 2002

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A one-dimensional treatment of pattern and probe based aberration monitors is discussed, yielding significant insight into the characteristics of optimum targets for measuring Zernike aberrations. One key new result is that each target possesses a “double-width” thick ring, resulting from the stationary phase condition between the aberration and the wave front incident upon the pupil. The characteristic radius of the ring is given by R≈(0.186×n+y0)λ/NA. The use of simple on/off mask openings to synthesize targets proves to be beneficial, increasing sensitivity by a factor of 4/π, but it is also shown to increase cross contamination between aberrations on the order of 10%. A full algebraic formulation of the principle of operation including amplitude and phase effects is presented, demonstrating that effects of target phase variation outweigh the effect of amplitude variation by a factor of 2π/λ. © 2002 American Vacuum Society.
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42.15.Fr Aberrations
85.40.Hp Lithography, masks and pattern transfer
42.79.Bh Lenses, prisms and mirrors

Generalized scanning beam interference lithography system for patterning gratings with variable period progressions

G. S. Pati, R. K. Heilmann, P. T. Konkola, C. Joo, C. G. Chen, E. Murphy, and M. L. Schattenburg

J. Vac. Sci. Technol. B 20, 2617 (2002); http://dx.doi.org/10.1116/1.1520563 (5 pages) | Cited 6 times

Online Publication Date: 9 December 2002

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We demonstrate a versatile interference lithography system that can continuously vary the pattern period and orientation during fabrication of general periodic structures in one or two dimensions. Initial experimental results, using closed-loop beam steering control and double exposures on a stationary substrate, are obtained in order to illustrate its principle of operation. A fringe-locking scheme for phase control is also demonstrated including discussion of issues related to future system developments. © 2002 American Vacuum Society.
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42.79.Dj Gratings
42.82.Cr Fabrication techniques; lithography, pattern transfer
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Electron projection lithography tool development status

Takaharu Miura

J. Vac. Sci. Technol. B 20, 2622 (2002); http://dx.doi.org/10.1116/1.1520576 (5 pages) | Cited 3 times

Online Publication Date: 9 December 2002

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In the development of an electron beam projection lithography (EPL) tool, the most important tasks are to develop the high-speed vacuum stage system, reliable vacuum body system, and total control system. Nikon has a long history of over 22 years in precision stage development for its optical lithography tools as well as over 10 years in electron beam (EB) instrument development such as the EB 60 with NTT. Recently, optical lithography stages have been developed based on air bearing and linear motor technologies. It is desirable and of minimum risk to utilize those technologies for the EPL system in order to shorten the total time period of development, but the requirements for the EB stage, body, and system control are much different from their optical counterparts and much more difficult. In this article development and implementation of the EPL vacuum stage system, vacuum body system, vacuum loader system, and control system are discussed and overviewed. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
07.30.-t Vacuum apparatus
07.07.Tw Servo and control equipment; robots

Evolution of electron projection optics from variable axis immersion lenses to projection reduction exposure with variable axis immersion lenses

W. Stickel, H. C. Pfeiffer, S. D. Golladay, and M. S. Gordon

J. Vac. Sci. Technol. B 20, 2627 (2002); http://dx.doi.org/10.1116/1.1515303 (7 pages) | Cited 1 time

Online Publication Date: 9 December 2002

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The optics of the electron projection lithography (EPL) system PREVAIL (projection reduction exposure with variable axis immersion lenses) is retraced from its conceptual and practical foundation in IBM’s shaped beam probe-forming tools via the EPL proof-of-concept system to the implementation of the complex three-dimensional curvilinear variable axis lens optics in the Alpha column, part of the first-of-a-kind electron-beam stepper presently under construction by the IBM alliance partner Nikon Corporation. The significant elements of the optics are described, as well as the innovations, which were required to establish an advanced lithography tool viable in an integrated circuit production environment. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.-p Beam optics

Direct measurement of chromatic aberrations induced by SiNx continuous membrane mask

Takehisa Yahiro, Shohei Suzuki, Takeshi Irita, Shintaro Kawata, and Kazuaki Suzuki

J. Vac. Sci. Technol. B 20, 2634 (2002); http://dx.doi.org/10.1116/1.1523016 (6 pages) | Cited 1 time

Online Publication Date: 9 December 2002

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In this article, we present experimental results that quantify the magnitude of chromatic aberrations induced by a SiNx continuous membrane mask. We used a continuous membrane mask, which consists of a TaSi scatterer layer on a SiNx membrane layer of 100 nm thickness, for the experiments. The beam edge profiles were measured directly by the knife-edge method, which can measure the image blur with the repeatability of 3 nm (3 sigma). The effect of electron energy loss induced by inelastic scattering is clearly shown in the measured beam edge profiles. The magnitude of chromatic aberrations is quantified from the measured beam edge profiles considering lens aberrations and measurement errors. The results show that lower atomic number Z and lower density materials and thinner membrane are required on the mask membrane for a high resolution lithography. © 2002 American Vacuum Society.  
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41.85.Gy Chromatic and geometrical aberrations
79.20.Uv Electron energy loss spectroscopy
85.40.Hp Lithography, masks and pattern transfer
68.49.Jk Electron scattering from surfaces

Development of a mask-scan electron beam mask writer

Shinsuke Nishimura, Mitsuko Shimizu, Soichiro Mitsui, Kiminobu Akeno, Hideo Kusakabe, Munehiro Ogasawara, Ryuji Hayashi, Shinji Yanaga, Noboru Kobayashi, and Toru Tojo

J. Vac. Sci. Technol. B 20, 2640 (2002); http://dx.doi.org/10.1116/1.1521738 (6 pages)

Online Publication Date: 9 December 2002

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Mask-scan strategy for writing large complex patterns such as oblique lines and contact holes with assist bar and serif is more effective for decreasing the number of shots than is variable shaped beam (VSB) strategy and character projection strategy. In a simple case, the number of shots for writing the oblique lines can be as small as 1/600 of that of VSB strategy. Oblique parallel lines of 250 nm width and assist bar of 120 nm width were projected using the mask-scan strategy. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.Ct Particle beam shaping, beam splitting

Digital electrostatic electron-beam array lithography

L. R. Baylor, D. H. Lowndes, M. L. Simpson, C. E. Thomas, M. A. Guillorn, V. I. Merkulov, J. H. Whealton, E. D. Ellis, D. K. Hensley, and A. V. Melechko

J. Vac. Sci. Technol. B 20, 2646 (2002); http://dx.doi.org/10.1116/1.1520559 (5 pages) | Cited 29 times

Online Publication Date: 9 December 2002

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A concept for maskless digital electrostatically focused e-beam array direct-write lithography (DEAL) has been developed at Oak Ridge National Laboratory. This concept incorporates a digitally addressable field-emission array (DAFEA) integrated into a logic and control circuit implemented as an integrated circuit. The design goal is for 3 000 000 individually addressable field-emission cathodes with a 4 μm by 8 μm pitch on a single ∼1 cm2 integrated circuit. The DAFEA design includes built-in electrostatic focusing for each emitter with feedback dose-control circuits to drive each emitter for tightly controlled electron delivery. With the electrostatic focusing, an array of ∼460 of these integrated circuits (up to 30 across by ∼23 rows deep) are suspended on a back plane ∼100 μm above a 300 mm semiconductor wafer. This arrangement could lithographically expose an entire 300 mm wafer, with 30 nm pixels, in less than 45 s, with every wafer pixel redundantly illuminated eight times allowing gray-scale edge placement. Only ∼1.5 cm of wafer motion is required for complete wafer exposure. High-speed data paths are proposed to program the patterns into the DAFEA to be written to the wafer. The DEAL concept thus requires no mask and can be extended to the 10 nm linewidth regime. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
85.45.Db Field emitters and arrays, cold electron emitters

Maskless lithography using low-energy electron beam: Recent results for proof-of-concept system

T. Nakasugi, A. Ando, R. Inanami, N. Sasaki, T. Ota, O. Nagano, Y. Yamazaki, K. Sugihara, I. Mori, M. Miyoshi, K. Okumura, and H. Fujioka

J. Vac. Sci. Technol. B 20, 2651 (2002); http://dx.doi.org/10.1116/1.1520562 (6 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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In order to realize a system on a chip fabrication at low cost with quick turn-around-time, we have proposed a maskless lithography strategy, a low-energy electron-beam direct writing (LEEBDW) system with a common character projection (CP) aperture. This article presents a status report on our proof-of-concept (POC) system. We have developed a compact EB column consisting of small electrostatic lenses and deflectors. The experimental results for our POC system indicated that the patterns corresponding to 50-nm-node logic devices can be obtained with CP exposure at the incident energy of 5 keV. The technique to reduce the raw process time using a scanning electron microscope function of LEEBDW system is also reported. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.Ne Electrostatic lenses, septa
84.30.Sk Pulse and digital circuits
85.30.Tv Field effect devices

Prototype raster multibeam lithography tool

S. T. Coyle, D. Holmgren, X. Chen, T. Thomas, A. Sagle, J. Maldonado, B. Shamoun, P. Allen, and M. Gesley

J. Vac. Sci. Technol. B 20, 2657 (2002); http://dx.doi.org/10.1116/1.1520574 (5 pages) | Cited 3 times

Online Publication Date: 9 December 2002

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A prototype raster multibeam lithography tool was constructed and is being evaluated for use as a mask writer at the 50 nm node. The photocathode illumination module (PIM) focuses a linear brush of 32 individually modulated laser beams into 300 nm full width at half maximum spots on the surface of a photocathode. The PIM has been module tested with satisfactory results and integrated into the prototype tool. A new electron-beam photocathode gun and column have also been integrated into the tool. The tool has generated a linear array of 32 electron beams which have been magnified and focused onto a YAG screen as well as demagnified and scanned across a knife edge. Preliminary results have produced 86 nm spots at the writing plane. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
85.60.Ha Photomultipliers; phototubes and photocathodes

Distributed axis electron-beam system for lithography and inspection—preliminary experimental results

D. S. Pickard, C. Campbell, T. Crane, L. J. Cruz-Rivera, A. Davenport, W. D. Meisburger, R. F. W. Pease, and T. R. Groves

J. Vac. Sci. Technol. B 20, 2662 (2002); http://dx.doi.org/10.1116/1.1520566 (4 pages) | Cited 5 times

Online Publication Date: 9 December 2002

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A distributed-axis system can be used to avoid the space-charge limits of conventional electron-beam lithography systems. Our approach is to use a uniform magnetic field to simultaneously focus an array of beams. We have built a test bed and report the first experimental results. Sub-100 nm resolution has been obtained and is presently limited by aperture size and interference. Sub-10 nm resolution should be possible given a suitably small source. © 2002 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

Comprehensive model of electron energy deposition

Geng Han, Mumit Khan, Yanghua Fang, and Franco Cerrina

J. Vac. Sci. Technol. B 20, 2666 (2002); http://dx.doi.org/10.1116/1.1526633 (6 pages) | Cited 9 times

Online Publication Date: 9 December 2002

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We present our effort in developing a complete model of electron energy transfer from fast electrons (0.1–100 keV) to the photoresist. Our model is based on the direct Monte Carlo method, instead of using continuous slowing down approximation, model and a stopping power curve. We separate the interaction events into four types: Elastic, ionization, excitation, and plasmon. Our results show that: First, secondary electrons are major mechanism of energy distribution; and second, plasmons are very efficient “friction” mechanism but do not create molecular changes; and finally, excitations lead to molecular changes. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
68.49.Jk Electron scattering from surfaces
79.20.Hx Electron impact: secondary emission
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons

Development of data conversion system for electron beam projection lithography

Kokoro Kato, Kuninori Nishizawa, Tamae Haruki, Tadao Inoue, Koichi Kamijo, Shinichi Kojima, Hideyuki Minami, and Kazuya Okamoto

J. Vac. Sci. Technol. B 20, 2672 (2002); http://dx.doi.org/10.1116/1.1520571 (6 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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Electron beam projection lithography (EPL) has been developed as one of the most promising candidates for the next generation lithography below 70 nm node devices. Stencil masks, which are used in the EPL technology as masks, have brought new necessities of data conversion such as dividing the data into two complementary masks. The patterns have to be divided and dispatched optimally onto each of the complementary masks in order to make the stencil masks manufacturable. We have developed a data conversion system for EPL, called “EPLON.” EPLON provides a solution to the problems mentioned and converts the data available on EPL. In this article, our method of converting the complementary mask data is presented. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Testing an electrostatic deflection innovation: Initial experimental results

Michael Retsky and Richard Stein

J. Vac. Sci. Technol. B 20, 2678 (2002); http://dx.doi.org/10.1116/1.1523020 (4 pages)

Online Publication Date: 9 December 2002

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When deflecting a charged particle beam into small angles, electrostatic deflection is commonly used. For larger angles, magnetic is the usual choice mainly because the deflection aberrations are two- or threefold less. Methods to reduce electrostatic deflection aberrations have been proposed over the years but a major solution has not been identified. This subject has recently been revisited and, based on computations, it has been proposed that electrostatic deflection aberrations can be reduced 10-fold if the beam is injected asymmetrically into the gap between two conventional shaped oppositely charged conducting plates. According to this theory, with the proper injection offset, the only surviving aberration is astigmatism that is totally correctable with a quadrupole prior to deflection. The predicted optimal offset was either 33% or 42% (depending on the method of calculation) from the center toward the attracting plate. We have built a demountable test bed to experimentally determine if the innovation is correct. The beam is deflected by shaped plates according to a previously reported design. This plate design was predicted to provide ±38.1° of deflection for a beam 0.050 in. in diameter with undetectable deflection aberrations at optimal offsets. Compared to the calculated design, the voltages used in the demountable test bed are smaller (6 compared to 20 kV), the throw distance from the plate entrance to the screen is smaller (4.5 compared to 12 in.), and the deflection angle is ±28.2° but otherwise the setups are very similar. Initial data from the test bed are deflection of a 0.010 in. diam probe after injection into the deflection plate gap at various offset positions. It is found that 1/3 of the way from center toward the attracting plate, there is a 0.2 in. wide section of the deflection versus offset curve that is flat indicating a segment in which the aberrations are not detectable. Based on these initial results, the concept is valid and the injection offset was where it was predicted to be. © 2002 American Vacuum Society.
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41.75.Fr Electron and positron beams
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Copper device editing: Strategy for focused ion beam milling of copper

J. David Casey, Michael Phaneuf, Clive Chandler, Michael Megorden, Kathryn E. Noll, Richard Schuman, Thomas J. Gannon, Alex Krechmer, David Monforte, Nicholas Antoniou, Neil Bassom, Jian Li, Peter Carleson, and Chuong Huynh

J. Vac. Sci. Technol. B 20, 2682 (2002); http://dx.doi.org/10.1116/1.1521736 (4 pages) | Cited 9 times

Online Publication Date: 9 December 2002

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Focused ion beam (FIB) methodologies for successfully milling copper (U.S. Patent No. 6,322,672 B1) have been demonstrated. Approaches to milling copper (Cu) are required because standard FIB mill procedures produce rough, uneven cuts that are unsuitable for circuit edits, a principal FIB function. Efforts to develop gas assisted etching (GAE) processes which would smoothly mill Cu failed because Cu halides are not volatile and remain on the substrate as corrosive electrically conductive debris. Single crystal studies show that Cu grains with different crystal orientations vary in mill rate by as much as 4×. Moreover, the (110) crystal orientation, which mills most slowly, forms a Cu3Ga phase when milled with a focused Ga ion beam. This phase is particularly resistant to milling and, in polycrystalline Cu, propagates during the milling operation, contributing to the uneven trench profiles. CoppeRx, a novel scan strategy, cleanly and uniformly removes polycrystalline Cu with minimal damage to the underlying dielectric. CoppeRx minimizes the formation and propagation of the Cu3Ga phase and equalizes the etch rates of the Cu crystal orientations. The CoppeRx strategy includes the milling of an “egg crate” topography to minimize the propagation of the Cu3Ga phase and the creation of a heavy atom sacrificial layer of the Cu surface (U.S. Patent Application No. 20010053605) which scatters the incident Ga ion beam, thereby reducing the channeling influence on Cu milling rates. This heavy atom layer is created by flowing W(CO)6 vapor during the FIB milling process. The CoppeRx scan strategy is especially beneficial for milling thick (>0.8 μm) Cu structures with large, prominent grains. Because Cu interconnect lines are relatively thin (<0.4–0.5 μm), grain-related milling roughness is less of a problem. The CoppeRx egg crate topography and W scattering layer are not required. Instead, the successful cutting of 40 ohm Cu interconnect lines to produce >20 M ohm open circuits is achieved by flowing O2 or H2O during the milling process (U.S. Patent No. 6,322,672B1). The O2/H2O flow smoothes the Cu milling by producing an amorphous surface oxide, thereby reducing channeling, and by enhancing the etch selectivity for Cu relative to the surrounding and underlying SiO2 based dielectric. These interconnect cuts have been routinely done at the bottom of high aspect ratio holes (e.g., 1×1×9 μm). © 2002 American Vacuum Society.
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85.40.Ls Metallization, contacts, interconnects; device isolation
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
81.05.Bx Metals, semimetals, and alloys

Graphitization of Fe-doped amorphous carbon pillars grown by focused-ion-beam-induced chemical-vapor deposition

J. Fujita, M. Ishida, T. Ichihashi, Y. Ochiai, T. Kaito, and S. Matsui

J. Vac. Sci. Technol. B 20, 2686 (2002); http://dx.doi.org/10.1116/1.1518022 (4 pages) | Cited 21 times

Online Publication Date: 9 December 2002

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Graphitization of amorphous carbon pillar grown by focused-ion-beam-induced chemical-vapor deposition was demonstrated using an iron catalyst. The graphitization was induced by iron particles at the top of the pillar that were locally doped. Such graphitization of amorphous carbon seems to be based on solid phase crystallization, where homo-epitaxial growth on a graphite template appeared to have occurred. The original three-dimensional shape of an as-grown structure survived solid phase graphitization at 820 °C. © 2002 American Vacuum Society.
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81.05.U- Carbon/carbon-based materials
61.43.Er Other amorphous solids
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.40.Gh Other heat and thermomechanical treatments

Conductance-atomic force microscope characterization of focused ion beam chip repair processes

H. Marchman, J. McMurray, and H. Wildman

J. Vac. Sci. Technol. B 20, 2690 (2002); http://dx.doi.org/10.1116/1.1524982 (5 pages)

Online Publication Date: 9 December 2002

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Measurements of electrical test structure resistances have traditionally served as the primary metrics for judging the merit of new and existing focused ion beam (FIB) chip repair processes. However, more understanding of physical changes occurring on the sample surface after various FIB processes can be gained through the use of a relatively new version of atomic force microscopy (AFM) that employs electrically conductive tips. This technique is referred to as “conducting-AFM,” or C-AFM, and provides spatial mapping of both surface height and electronic conduction simultaneously at each image pixel. A key advantage is that electrical leads and large probing pads are not necessary for determining the electrical behavior of a desired region. Results from C-AFM have also been compared with spectroscopic analysis in order to spatially correlate the elemental composition and electrical conductivity of FIB-induced reaction products. © 2002 American Vacuum Society.
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68.37.Ps Atomic force microscopy (AFM)
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.-b Surface treatments

End point of silicon milling using an optical beam induced current signal for controlled access to integrated circuits for backside circuit editing

N. Antoniou, N. J. Bassom, C. Huynh, D. Monforte, J. D. Casey, A. Krechmer, and P. Carleson

J. Vac. Sci. Technol. B 20, 2695 (2002); http://dx.doi.org/10.1116/1.1526665 (5 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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Integrated devices increasingly use flip chip packaging, which complicates modification of the circuitry using focused ion beam (FIB) systems, as the thickness of the silicon must be reduced to a few micrometers before work can begin. A technique for end pointing the milling of bulk silicon from the backside of flip chip devices, using laser illumination to produce an optical beam induced current (OBIC), is described. System design and operation are described and results shown. The OBIC signal varies strongly with the thickness of the silicon above the bulk to well junction—by monitoring the OBIC signal in real time and end pointing on a characteristic feature the technique can reliably end point the bulk-well interface. It is shown that this system represents a significant advance over previous techniques and provides a robust and reliable way of end pointing. Theory of operation and reasons for the improved performance are discussed. © 2002 American Vacuum Society.
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
81.20.Wk Machining, milling
81.05.Cy Elemental semiconductors

Improvements in focused ion beam micromachining of interconnect materials

J. C. Gonzalez, M. I. N. da Silva, D. P. Griffis, and P. E. Russell

J. Vac. Sci. Technol. B 20, 2700 (2002); http://dx.doi.org/10.1116/1.1515310 (5 pages) | Cited 3 times

Online Publication Date: 9 December 2002

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Focused ion beam micromachining (FIBM) of integrated circuits continues to be an important tool for design debug, editing, and verification; for metrology; and for process control. FIBM of copper interconnects has presented challenges not faced when micromachining aluminum interconnects and the introduction of low-k dielectrics present additional challenges. A new approach to chemically assisted FIBM of thin film Cu, SiO2, and SiLK low-k material using polar precursor molecules has been investigated. Polar alcohols were used to reduce the sputter rate of SiO2 and SiLK while having a minimal effect on the Cu sputter rate. A new FIBM process based on the reduction of the FIB Ga+ energy from the typical 25 to 15 keV is also introduced. The new low energy FIBM process was shown to increase the sputter rate of polycrystalline Cu with strong (111) crystallographic texture by a factor of 2.5. This increase in the sputter rate of Cu combined with a slight reduction of the sputter rate of SiO2 and SiLK results in a Cu/SiO2 selectivity of greater than 7 and a Cu/SiLK selectivity of approximately 3. These are the largest selectivity values reported until now for both systems. The Onderdelinden theory of single-crystal sputtering was used to explain this seemingly anomalous increase of the Cu sputter rate with the reduction of the FIB Ga+ energy. © 2002 American Vacuum Society.
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85.40.Ls Metallization, contacts, interconnects; device isolation
87.85.Va Micromachining
81.15.Cd Deposition by sputtering

Scattering mask concept for ion-beam nanolithography

P. Ruchhoeft, J. C. Wolfe, J. L. Torres, and R. Bass

J. Vac. Sci. Technol. B 20, 2705 (2002); http://dx.doi.org/10.1116/1.1520568 (4 pages) | Cited 7 times

Online Publication Date: 9 December 2002

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In this article, we demonstrate the concept of scattering masks for ion-beam proximity lithography. In this process, stencil mask openings are fabricated with larger-than-nominal sizes and are coated with a conformal scatter layer that reduces the size of the features at the mask surface. The process reduces the complexity of etching high aspect-ratio mask openings. Printed images of masks with 100 and 40 nm circular openings, fabricated from masks with 225 nm openings, are shown. The printing process has excellent exposure latitude: less than a 20% change in critical dimension is observed for a 33% change in dose for 40 nm structures. We show that the diffuse background exposure that results from ions traversing through the scatter layer is around 0.1% of the primary exposure for a 2 μm pitch pattern. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
81.65.Cf Surface cleaning, etching, patterning

Correcting for global space charge by positive ion generation

Trevor Crane, Colin Campbell, Dan Pickard, Liqun Han, Kimitoshi Takahashi, W. Dan Meisburger, and R. Fabian Pease

J. Vac. Sci. Technol. B 20, 2709 (2002); http://dx.doi.org/10.1116/1.1523398 (4 pages)

Online Publication Date: 9 December 2002

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In proposed high throughput electron beam projection systems there are surprisingly serious problems due to the first and third order lens action of the global space charge of the beam. Computer simulations [e.g., Takahashi et al., J. Vac. Sci. Technol. B 19, 2572 (2001)] show it may be possible to eliminate the deleterious effects of global space charge in these systems by introducing positive ions into the optical column. We have checked these claims experimentally on a scaled system designed to enhance global space charge effects. In our system, global space charge produces a first order focus shift of 5.4 mm and a field curvature of 2.2 mm. Introducing 4 mTorr of argon corrects the focus shift to 1 mm and reduces the field curvature to 1.3 mm, and we observed similar results with 7 mTorr of hydrogen. Introducing helium had no effect. Our experiment provides no significant information on stochastic Coulomb effects, although simulations indicate that these have little effect (e.g., Takahashi, ibid.). © 2002 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
41.75.Fr Electron and positron beams

Ion projection sensitized selective Cu electroplating on uncoated p-Si

A. Spiegel, W. H. Bruenger, C. Dzionk, and P. Schmuki

J. Vac. Sci. Technol. B 20, 2713 (2002); http://dx.doi.org/10.1116/1.1524977 (4 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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We present a resistless technique with the potential to produce metallic nanostructures. By combining ion projection direct structuring (IPDS) and selective electroplating, structures as small as 200 nm have been obtained on p-Si (100). IPDS is based on ion projection lithography (IPL) which uses an open stencil mask and 4–10 times ion optical demagnification of the mask structures onto the wafer; IPL can expose resist at doses of some 1012 ions/cm2 with smallest feature sizes of 50 nm. IPDS does not need any resist; rather it uses the fact that impinging ions create defects at the wafer surface, which can be used to selectively trigger electrochemical reactions. So far Cu, Au, and Ni nanostructures have been produced by this process. Ion doses of 1012–3×1013 ions/cm2 (Xe+, Ar+) have been processed. Applications lie in the field of microelectrochemical systems and biosensor technology. © 2002 American Vacuum Society.
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81.05.Bx Metals, semimetals, and alloys
81.15.Pq Electrodeposition, electroplating
81.16.Nd Micro- and nanolithography
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Improvement in brightness of multicusp-plasma ion source

Q. Ji, X. Jiang, T.-J. King, K.-N. Leung, K. Standiford, and S. B. Wilde

J. Vac. Sci. Technol. B 20, 2717 (2002); http://dx.doi.org/10.1116/1.1526694 (4 pages) | Cited 11 times

Online Publication Date: 9 December 2002

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The beam brightness of a multicusp-plasma ion source has been substantially improved by optimizing the source configuration and extractor geometry. The current density of a 2 keV He+ beam extracted from a 7.5-cm-diameter source operating at 2.5 kW rf power is ∼100 mA/cm2, which is ∼10 times larger than that of a beam extracted from a 5-cm-diameter source operating at 1 kW rf power. A smaller focused beam spot size is achieved with a counter-bored extractor instead of a conventional (“through-hole”) extractor, resulting another order of magnitude improvement in beam current density. Measured beam brightness can be as high as 440 A/cm2Sr, which represents a 30 times improvement over prior work. © 2002 American Vacuum Society.
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52.50.Dg Plasma sources
85.40.Hp Lithography, masks and pattern transfer
52.80.-s Electric discharges

Role of oxygen in semiconductor negative electron affinity photocathodes

Francisco Machuca, Zhi Liu, Yun Sun, P. Pianetta, W. E. Spicer, and R. F. W. Pease

J. Vac. Sci. Technol. B 20, 2721 (2002); http://dx.doi.org/10.1116/1.1521742 (5 pages) | Cited 12 times

Online Publication Date: 9 December 2002

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Source contamination, photovoltage effects, and stimulated electron desorption of cesium are factors that determine the initial high performance and longevity of negative electron affinity electron sources. As part of the study of these factors, we investigate the effect of oxygen contamination during the activation process and operation of a traditional GaAs (100) and a novel GaN (0001) emitter. We use synchrotron radiation photoemission spectroscopy, a focused mercury arc discharge lamp, and a helium neon (HeNe) laser to obtain simultaneously elemental analyses of the emitting surface and the corresponding total quantum yield at various stages, respectively, for GaN and GaAs. Our results indicate: (1) carbon uptake does not occur in our carbon free system over time, (2) oxygen uptake is observed for both GaN (0001) and GaAs (100) activated surfaces, a property common to the chemistry of the Cs/O adlayer, (3) the oxygen species appears to change over time and the initial species is assigned to an ion of nondissociated oxygen in the Cs/O activation layer, (4) the chemical changes of the Cs/O adlayer are not accompanied by a significant loss of cesium from the surface, and (5) the onset of decay of the quantum yield begins at a later time for the GaN (0001) emitter in comparison to the GaAs (100) electron source. A chemical model for the activation layer and its transformation over time is developed, consistent with points (1) through (4) in a separate report [F. Machuca et al. (unpublished)]. The complete account of the decay of the quantum yield of both Cs/O activated III–V emitters is compared and discussed in this article. © 2002 American Vacuum Society.
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85.60.Ha Photomultipliers; phototubes and photocathodes
79.60.Dp Adsorbed layers and thin films
68.43.Rs Electron stimulated desorption
72.40.+w Photoconduction and photovoltaic effects
79.20.La Photon- and electron-stimulated desorption
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Development of electromagnetic lenses for multielectron beam lithography system

T. Haraguchi, T. Sakazaki, S. Hamaguchi, and H. Yasuda

J. Vac. Sci. Technol. B 20, 2726 (2002); http://dx.doi.org/10.1116/1.1524981 (4 pages) | Cited 5 times

Online Publication Date: 9 December 2002

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High-throughput electron-beam (EB) lithography systems require high current. However, beam blur increases because of the individual Coulomb interaction among the electron beams. Isolating the electron beam into 4–16 perfectly independent beamlets is effective. As for the electromagnetic lens, many openings in the parallel flat plates can form the compound eye lens. This lens is called the lotus root lens (LRL). Simulations and experiments with the LRL were carried out. In the case of LRL of 4×4 openings with a 22 mm pitch, the uniformity of magnetic field along the axis was within 0.2%. The basic lens function between two openings separated by 44 mm in the LRL with 21 openings in the conventional column qualitatively evaluated. The LRL should be a potential platform for a multicolumn cell system that provides a multibeam direct-writing system that utilizes variable-shaped beam or character projection as unit-column optics. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.Ne Electrostatic lenses, septa
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Nanopipe fabrication using vertically aligned carbon nanofiber templates

A. V. Melechko, T. E. McKnight, M. A. Guillorn, D. W. Austin, B. Ilic, V. I. Merkulov, M. J. Doktycz, D. H. Lowndes, and M. L. Simpson

J. Vac. Sci. Technol. B 20, 2730 (2002); http://dx.doi.org/10.1116/1.1515306 (4 pages) | Cited 3 times

Online Publication Date: 9 December 2002

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We report a method to fabricate tubular nanostructures using vertically aligned carbon nanofibers grown by plasma-enhanced chemical vapor deposition as templates. The resulting nanopipes are oriented perpendicular to the substrate and have internal diameters ranging from 30 to 200 nm and can be up to several micrometers in length. These nanopipes can be deterministically positioned on a substrate and arranged into singular devices or arrays. © 2002 American Vacuum Society.
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81.07.De Nanotubes
61.46.-w Structure of nanoscale materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Electrode modification by electron-induced patterning of self-assembled monolayers

G. Kaltenpoth, B. Völkel, C. T. Nottbohm, A. Gölzhäuser, and M. Buck

J. Vac. Sci. Technol. B 20, 2734 (2002); http://dx.doi.org/10.1116/1.1523026 (5 pages) | Cited 10 times

Online Publication Date: 9 December 2002

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Gold electrodes were coated with self-assembled monolayers of 1-1′-biphenyl-4-thiol(C6H5–C6H4–SH, BPT) and 1-octadecanethiol (CH3–(CH2)17–SH, ODT) and patterned by proximity printing with stencil masks using electron energies of 300 eV and area doses of 40 000 μC/cm2 (BPT) as well as 10 000 μC/cm2 (ODT). The subsequent copper deposition in an electrochemical cell revealed that e-beam patterned alkanethiol behaves opposite to that of e-beam patterned biphenyl. ODT acts as a “positive template” leading to copper deposition only on the irradiated parts. BPT on the other hand acts as a “negative template,” where the irradiated and therefore cross-linked biphenyl layer exhibits a blocking behavior, and hence copper is only deposited on the nonirradiated parts. The influence of the deposition potential and the copper ion concentration of the electrolyte on the process has been investigated to find the optimal parameters for producing nanostructures with high selectivity. © 2002 American Vacuum Society.
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81.16.Dn Self-assembly
81.15.Pq Electrodeposition, electroplating
81.65.Cf Surface cleaning, etching, patterning
82.45.Fk Electrodes
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.Nd Micro- and nanolithography
82.45.Mp Thin layers, films, monolayers, membranes
82.45.Qr Electrodeposition and electrodissolution

Exploiting intermolecular interactions and self-assembly for ultrahigh resolution nanolithography

M. E. Anderson, R. K. Smith, Z. J. Donhauser, A. Hatzor, P. A. Lewis, L. P. Tan, H. Tanaka, M. W. Horn, and P. S. Weiss

J. Vac. Sci. Technol. B 20, 2739 (2002); http://dx.doi.org/10.1116/1.1515301 (6 pages) | Cited 20 times

Online Publication Date: 9 December 2002

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The combination of self-, directed, and positional assembly techniques, i.e., “bottom up” fabrication, will be essential for patterning and connecting future nanodevices. Systematic exploration of local intermolecular interactions on surfaces will permit their exploitation for the rational design of molecular-scale surface structures. We use the scanning tunneling microscope to probe the local behavior of self-assembled films at the nanometer scale. The ability to control the molecular placement within and by self-assembled monolayers is a means of patterning surfaces. A monolayer with customized features can be produced by manipulating the dynamics of film formation, which are heavily affected by the selectable intermolecular interactions of adsorbates and the structural components naturally occurring within the films. Additionally, the controlled placement and thickness of self-assembled multilayers created from alternating strata of α,ω-mercaptoalkanoic acids and coordinated metal ions can be developed to form precise “molecular ruler” resists and to assist in the formation of tailored, lithographically defined metal contacts. © 2002 American Vacuum Society.
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81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
81.16.Ta Atom manipulation
81.07.Nb Molecular nanostructures
85.65.+h Molecular electronic devices

Localized and directed lateral growth of carbon nanotubes from a porous template

S. J. Wind, R. Martel, and Ph. Avouris

J. Vac. Sci. Technol. B 20, 2745 (2002); http://dx.doi.org/10.1116/1.1523019 (4 pages) | Cited 5 times

Online Publication Date: 9 December 2002

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We report on the growth of laterally oriented carbon nanotubes with both positional and directional control. The growth was done by chemical vapor deposition from Fe/Mo catalyst embedded inside a porous silicon medium which was formed electrochemically on the vertical faces of etched posts on a silicon substrate. A solution containing the catalyst was allowed to diffuse into the porous medium only in lithographically defined areas. Nanotubes grew only in the patterned areas with a preferred orientation normal to the edges of the etched posts. © 2002 American Vacuum Society.
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81.07.De Nanotubes
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.16.Be Chemical synthesis methods
81.16.Hc Catalytic methods
61.46.-w Structure of nanoscale materials
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Tunable distributed-feedback laser gratings for telecom applications, manufactured by electron-beam lithography

S. A. Rishton, B. Pezeshki, S. Zou, G. Yoffe, and W. Henschel

J. Vac. Sci. Technol. B 20, 2749 (2002); http://dx.doi.org/10.1116/1.1524979 (4 pages)

Online Publication Date: 9 December 2002

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A wide-range tunable laser component has been developed, based on a closely spaced array of 12 distributed feedback (DFB) grating lasers, 3 nm apart in wavelength, fabricated by electron-beam lithography. Coarse wavelength selection is achieved by selecting the appropriate laser stripe with a microelectromechanical system tilt mirror. We describe the application of direct-wire e-beam lithography to array DFB grating manufacture, with accurate multiple wavelengths and phase shifts required to optimize the spectral characteristics of the laser. The grating pitch is approximately 0.24 μm, but must be controlled to better than 0.01 nm. We have used an averaging technique with relatively coarse address unit and pixel size to fabricate multiple-pitch gratings without rescaling. This allows the use of a conventional thermal-field-emission Gaussian-beam system, at high throughput appropriate for manufacturing. © 2002 American Vacuum Society.
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42.79.Dj Gratings
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.60.Fc Modulation, tuning, and mode locking
42.86.+b Optical workshop techniques

Optical waveguides with apodized sidewall gratings via spatial-phase-locked electron-beam lithography

J. T. Hastings, Michael H. Lim, J. G. Goodberlet, and Henry I. Smith

J. Vac. Sci. Technol. B 20, 2753 (2002); http://dx.doi.org/10.1116/1.1521744 (5 pages) | Cited 25 times

Online Publication Date: 9 December 2002

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We describe a technique to fabricate Bragg gratings in the sides of optical waveguides using a single lithographic step. This technique is particularly suited to the apodized gratings required for add/drop filters in dense-wavelength-division multiplexing. Apodization minimizes cross talk between channels and improves the filter response. Silicon-on-insulator rib waveguides with both uniform and apodized gratings were fabricated using direct-write spatial-phase-locked electron-beam lithography (SPLEBL). This approach combines SPLEBL’s pattern-placement accuracy with the flexibility of direct-write device prototyping. The resulting grating-based devices exhibited substantially reduced side-lobe levels. © 2002 American Vacuum Society.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
42.79.Dj Gratings
42.79.Gn Optical waveguides and couplers

Surface diffusion and size evolution of nanostructures in laser-focused atomic deposition

Jianxin Zhong, Jack C. Wells, and Yehuda Braiman

J. Vac. Sci. Technol. B 20, 2758 (2002); http://dx.doi.org/10.1116/1.1520558 (5 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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We examine the effect of adatom diffusion on the size broadening of nanostructures in laser-focused deposition by considering two major diffusion processes, namely, terrace diffusion and step-edge descending. We find that adatom diffusion sets a limit of the structure size no matter how well focused the atomic beam. A criterion is derived from rate-equation analysis to predict the limiting size of the structure, which is further confirmed by kinetic Monte Carlo simulations. The criterion suggests that, for a given growth system, the structure feature size can be minimized by increasing deposition flux rate or by decreasing growth temperature. Applications of the criterion to existing experiments are also discussed. © 2002 American Vacuum Society.
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68.43.Jk Diffusion of adsorbates, kinetics of coarsening and aggregation
81.16.Mk Laser-assisted deposition
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.Fx Diffusion; interface formation
81.15.Fg Pulsed laser ablation deposition

Method for manufacturing nanoscale structures in transition metal layers

Falco C. M. J. M. van Delft, W. S. M. M. Ketelaars, M. Kroon, and J. Lambregts

J. Vac. Sci. Technol. B 20, 2763 (2002); http://dx.doi.org/10.1116/1.1526635 (5 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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In most transition metals, steeply profiled nanoscale structures can not easily be obtained by dry etching, due to the redeposition of the etch products. An alternative method is presented here, which comprises the deposition of a plating base, electron-beam writing of nanoscale structures in negative tone hydrogen silsesquioxane resist, and electroplating of the desired metal layer between the resist lines. This method is used for making transmittive and reflective masks, alignment marks, and other optical gratings, consisting of features down to 40 nm wide that are embedded in transition metal layers. These gratings can, e.g., be applied in extreme-UV lithographic sensors. More generally, other devices, e.g., magnetic recording heads, can also be manufactured using this technology. © 2002 American Vacuum Society.
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81.16.Nd Micro- and nanolithography
81.07.Bc Nanocrystalline materials
81.15.Pq Electrodeposition, electroplating
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
42.79.Dj Gratings

Nanostructure fabrication by direct electron-beam writing of nanoparticles

Saul Griffith, Mark Mondol, David S. Kong, and Joseph M. Jacobson

J. Vac. Sci. Technol. B 20, 2768 (2002); http://dx.doi.org/10.1116/1.1526697 (5 pages) | Cited 6 times

Online Publication Date: 9 December 2002

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Direct additive-layer fabrication of nanostructures is a widely sought goal, which is not possible using traditional layered resist optical and electron-beam lithographic techniques. However, recently, it has been shown that certain metallic and semiconducting nanoparticles capped with protective organic groups are promising “inklike” resist materials for patterning a variety of electronic and mechanical structures [C. A. Bulthaup et al., Appl. Phys. Lett. 79, 1525 (2001)]. Several groups have successfully patterned single-layer gold nanoparticle films by means of direct electron-beam writing [X. M. Lin, R. Parthasarathy, and H. M. Jaeger, Appl. Phys. Lett. 78, 1915 (2001); T. R. Bedson, R. E. Palmer, T. E. Jenkins, D. J. Hayton, and J. P. Wilcoxon, Appl. Phys. Lett. 78, 1921 (2001); L. Clarke et al., Appl. Phys. Lett. 71, 617 (1997)]. In this work, we apply these materials in a new lithographic mode, using an electron beam to cause direct sintering of these 2–10 nm nanoparticles, building structures of multiple layers and multiple materials with linewidth resolutions of 80–100 nm. © 2002 American Vacuum Society.  
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81.16.Nd Micro- and nanolithography
81.07.Bc Nanocrystalline materials
68.65.Ac Multilayers
81.16.Rf Micro- and nanoscale pattern formation
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Characteristics of multiwalled carbon nanotube nanobridges fabricated by poly(methylmethacrylate) suspended dispersion

S.-B. Lee, K. B. K. Teo, L. A. W. Robinson, A. S. Teh, M. Chhowalla, D. G. Hasko, G. A. J. Amaratunga, W. I. Milne, and H. Ahmed

J. Vac. Sci. Technol. B 20, 2773 (2002); http://dx.doi.org/10.1116/1.1520569 (4 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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We report on the transport characteristics of individual multiwalled carbon nanotube/nanofibers (MWCNTs) grown by plasma-enhanced chemical vapor deposition (PECVD). The measurements were performed on individual MWCNT nanobridges suspended by sputtered Nb contacts. Temperature dependent measurements of conductance revealed that the conductance is dominated by a contribution from thermally activated carriers. High-field measurements show that the PECVD grown MWCNTs are able to carry high current densities (∼108 A/cm2) and after reaching a critical limit, break down in segments of nanotube shells while still being electrically stable. The high-density current transport and reliability make PECVD grown MWCNTs good candidates for applications as field emission cathodes and nanoelectronic interconnects. © 2002 American Vacuum Society.
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73.63.Fg Nanotubes
81.07.De Nanotubes

Nanoscale electron beam lithography and etching for fully depleted silicon-on-insulator devices

L. Dreeskornfeld, J. Hartwich, J. Kretz, L. Risch, W. Roesner, and D. Schmitt-Landsiedel

J. Vac. Sci. Technol. B 20, 2777 (2002); http://dx.doi.org/10.1116/1.1518023 (3 pages)

Online Publication Date: 9 December 2002

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This article describes the process integration and optimization of nanoscale electron beam lithography and etching for the fabrication of fully depleted silicon-on-insulator devices with ultrathin bodies. For the fabrication, standard complementary metal–oxide–semiconductor (CMOS) production line processes with an optimized process flow were supplemented by advanced nanoscale patterning. The nanoscale processes have to fulfill several requirements, such as sub 20 nm exposure with small line edge roughness as well as sub 20 nm highly selective etching with vertical sidewalls. The development and optimization of these fully integrated CMOS processes, which require no additional shrinking step, is shown in this work. 18 nm wide features in calixarene negative tone resist and highly anisotropic etching of sub 30 nm structures with a selectivity to tetraethylorthosilicate of in excess of 300:1 are demonstrated. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning
81.16.Nd Micro- and nanolithography

Multilevel silicon diffractive optics for terahertz waves

E. D. Walsby, S. Wang, J. Xu, T. Yuan, R. Blaikie, S. M. Durbin, X.-C. Zhang, and D. R. S. Cumming

J. Vac. Sci. Technol. B 20, 2780 (2002); http://dx.doi.org/10.1116/1.1518021 (4 pages) | Cited 3 times

Online Publication Date: 9 December 2002

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A multilevel microfabrication process has been developed to produce silicon Fresnel lenses for terahertz waves. A repeated binary fabrication process was used to create lenses with up to eight levels in complexity and these lenses have been compared to both less complex structures and refractive optic lenses. The microfabrication required deep reactive ion etching and multilevel resist processing using SU8 photoresist. At the design frequency of 1 THz an eight-level lens showed significant improvement in intensity at the focus and had much reduced energy lost into sidelobes compared with refractive lenses. © 2002 American Vacuum Society.
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42.79.Bh Lenses, prisms and mirrors
42.82.Cr Fabrication techniques; lithography, pattern transfer

Density estimation for amorphous carbon nanopillars grown by focused ion beam assisted chemical vapor deposition

Masahiko Ishida, Jun-ichi Fujita, and Yukinori Ochiai

J. Vac. Sci. Technol. B 20, 2784 (2002); http://dx.doi.org/10.1116/1.1526699 (4 pages) | Cited 19 times

Online Publication Date: 9 December 2002

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The mechanical resonant frequency and spring constant of amorphous carbon nanopillars grown by focused ion beam assisted chemical vapor deposition (FIB CVD) were measured to evaluate the pillar density. The measured density ranged from 2.5 to 4.2×3 kg/m3, depending on the growth conditions. Annealing the pillars at 600 °C completely removed the Ga incorporated in the pillar during FIB CVD. The pillar density after annealing decreased to about 1.9×103 kg/m3, which indicated the density excess was mainly due to the implantation of Ga. At lower growth rates, a sharp decrease in the Ga content suggested higher sputtering rate of Ga through ion beam irradiation. © 2002 American Vacuum Society.
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81.05.U- Carbon/carbon-based materials
68.60.Bs Mechanical and acoustical properties
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
07.10.Cm Micromechanical devices and systems
62.20.D- Elasticity
61.72.Cc Kinetics of defect formation and annealing
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.16.-c Methods of micro- and nanofabrication and processing

Process integration of self-assembled polymer templates into silicon nanofabrication

K. W. Guarini, C. T. Black, Y. Zhang, H. Kim, E. M. Sikorski, and I. V. Babich

J. Vac. Sci. Technol. B 20, 2788 (2002); http://dx.doi.org/10.1116/1.1521730 (5 pages) | Cited 66 times

Online Publication Date: 9 December 2002

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Self-assembled diblock copolymer thin films are used as sacrificial layers for the transfer of dense nanoscale patterns into more robust materials. We detail the processes used to achieve highly uniform nanoporous dielectric films, high-aspect-ratio nanotextured silicon, silicon nitride dot arrays, silicon pillar arrays, and silicon tip arrays. All techniques are compatible with standard semiconductor fabrication processes. We also discuss the possible applications of each resulting nanometer-scale structure, including high surface area substrates for capacitors and biochips, quantum dot arrays for nonvolatile memories, and silicon pillar arrays for vertical transistors or field-emission displays. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Dn Self-assembly
81.16.Nd Micro- and nanolithography
81.65.Cf Surface cleaning, etching, patterning

Design and prototyping of a micropropulsion system for microsatellites attitude control and orbit correction

L. Vaccari, M. Altissimo, E. Di Fabrizio, F. De Grandis, G. Manzoni, F. Santoni, F. Graziani, A. Gerardino, F. Perennes, and P. Miotti

J. Vac. Sci. Technol. B 20, 2793 (2002); http://dx.doi.org/10.1116/1.1523015 (5 pages)

Online Publication Date: 9 December 2002

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Silicon micromachining is an attractive technique for batch production of a wide class of miniaturized components and systems. In particular, micromachined components can be combined with semiconductor lasers, microlenses, and micromechanics to develop a new class of instruments. A worldwide impulse in micromachining is originated by the space industry. Space exploration in the new millennium will mostly rely on drastically miniaturized spacecraft by today’s standards. It is worth to note that the space community is used to speak about nanosatellites when satellite mass ranges between 1 and 10 kg, while microsatellites range between 10 and 100 kg (ESA/IPC 81 Information Note, Paris, October 2000). A key point for precise micronanosatellites orbit and attitude control is the development of a suitable propulsion system, weighting a few grams and capable of few μN of thrust. A microthruster complying these requirements is under development jointly by our laboratory and Mechatronic, using MEMS technology. The article will show the microthruster design, fabrication processes, and the experimental setup to test in space the micropropulsion system prototype. The experiment will be performed on-board the microsatellite UNISAT-2 of the University of Roma. © 2002 American Vacuum Society.
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89.40.-a Transportation
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
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Fabrication and electrical characterization of top gate single-wall carbon nanotube field-effect transistors

S. J. Wind, J. Appenzeller, R. Martel, V. Derycke, and P. Avouris

J. Vac. Sci. Technol. B 20, 2798 (2002); http://dx.doi.org/10.1116/1.1521731 (4 pages) | Cited 12 times

Online Publication Date: 9 December 2002

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We describe the fabrication of single-wall carbon nanotube field-effect transistors in a conventional metal–oxide–semiconductor field-effect transistor structure, with gate electrodes above the conduction channel separated from the channel by a thin dielectric. We use these devices to study the performance improvements achieved by reducing the gate-to-channel separation. The top gate structure offers certain structural advantages over earlier, back gated carbon nanotube devices. In addition, these devices exhibit excellent electrical characteristics, including steep subthreshold slope and high transconductance, at gate voltages close to 1 V. The measured device characteristics are significantly better than previously reported carbon nanotube devices, providing further motivation to explore the use of carbon nanotubes for future nanoelectronic applications. © 2002 American Vacuum Society.
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85.35.Kt Nanotube devices
85.30.Tv Field effect devices

Hybrid assembly technique using alternating current field for molecular electronic measurements

Islamshah Amlani, Adam M. Rawlett, Larry A. Nagahara, and Raymond K. Tsui

J. Vac. Sci. Technol. B 20, 2802 (2002); http://dx.doi.org/10.1116/1.1523025 (4 pages) | Cited 5 times

Online Publication Date: 9 December 2002

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We present an approach to facilitate transport measurements of electronic molecules. The technique consists of forming a self-assembled monolayer of the investigated molecule on prepatterned electrodes and then bridging the electrodes with nanoparticles using an alternating electric field. This technique can potentially allow screening of a large number of electronic molecules in a facile manner. Application of an alternating current field is equally useful for trapping other nanometer-scale structures such as carbon nanotubes. As an example of our hybrid technique, we report preliminary transport measurements of a test molecule that has been reported using a different test bed. Our results show qualitative agreement with previously published data. © 2002 American Vacuum Society.
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81.07.Nb Molecular nanostructures
85.65.+h Molecular electronic devices
81.16.Dn Self-assembly
81.07.De Nanotubes
81.07.Lk Nanocontacts
73.63.Rt Nanoscale contacts
73.63.Fg Nanotubes

Single-electron parametron memory cell

E. G. Emiroglu, Z. A. K. Durrani, D. G. Hasko, and D. A. Williams

J. Vac. Sci. Technol. B 20, 2806 (2002); http://dx.doi.org/10.1116/1.1524975 (4 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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A single-electron parametron memory cell, based on two conducting islands separated by a multiple tunnel junction, has been realized in highly doped silicon-on-insulator. A memory cell with integrated read-out electrometers was fabricated using a combination of high-resolution electron beam lithography and reactive ion etching. The layout and operation of the memory cell is based on a proposal by Korotkov and Likharev, but modified in order to simplify fabrication. The operation of the electrometer, and the cell polarization characteristics are investigated by low temperature electrical measurements. Memory operation is indicated by current hysteresis in the electrometer characteristics with appropriate gate bias voltages. © 2002 American Vacuum Society.
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84.30.Sk Pulse and digital circuits
85.35.Gv Single electron devices
84.30.Ng Oscillators, pulse generators, and function generators
85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning

Quantum dot with independently tunable tunneling barriers fabricated using an atomic force microscope

R. Nemutudi, C. G. Smith, C. J. B. Ford, N. J. Appleyard, M. Pepper, D. A. Ritchie, and G. A. C. Jones

J. Vac. Sci. Technol. B 20, 2810 (2002); http://dx.doi.org/10.1116/1.1524973 (4 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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We fabricate independently tunable tunneling barriers on a GaAs/AlGaAs heterostructure using a conducting tip of an atomic force microscope (AFM). In a humid ambient, a negatively biased AFM tip induces an oxide beneath it, which oxide depletes a shallow two-dimensional electron gas (2DEG). We exploit the depletion property of the oxide and use it to electrically isolate different regions of the 2DEG. In particular, we manipulate the tip movement to generate two oxide patterns whose combined geometry defines two quantum point contacts, in series, with a quantum dot between them. Our device not only permits independent tuning of the transmission probability of each quantum point contact, but it also allows us to observe Coulomb-blockade oscillations when both contacts are tuned into the tunneling regime. © 2002 American Vacuum Society.
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68.65.Hb Quantum dots (patterned in quantum wells)
73.63.Kv Quantum dots
73.23.Hk Coulomb blockade; single-electron tunneling
81.16.Ta Atom manipulation
73.21.La Quantum dots
73.63.Rt Nanoscale contacts
81.07.Lk Nanocontacts

Fabrication of spin-current-induced domain-wall-nucleation device in planar configuration

Takashi Kimura, Fujio Wakaya, and Kenji Gamo

J. Vac. Sci. Technol. B 20, 2814 (2002); http://dx.doi.org/10.1116/1.1518014 (5 pages)

Online Publication Date: 9 December 2002

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We proposed the control of the domain-wall-nucleation process by injection of the spin-polarized current into the wire end of the ferromagnetic wire via the nonmagnetic material, and attempted to observe the change of the switching field due to the spin injection in two-type planar-configuration devices. In one device using focused ion beam (FIB) in situ etching, the changes of the switching field, which were consistent with the spin-injection model, were very small. This may be because the irradiation effects induced by the FIB etching modify the properties of the ferromagnetic wire near the etched region. In the other device using multi-angle deposition, the clear changes of the switching field were observed and were quantitatively consistent with the model based on the spin-transfer effect. The interface fabricated by the multi-angle deposition may be useful for forming the ideal ferromagnet/nonmagnet interface. © 2002 American Vacuum Society.
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75.75.-c Magnetic properties of nanostructures
72.25.Mk Spin transport through interfaces
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.60.Jk Magnetization reversal mechanisms
75.47.De Giant magnetoresistance
75.60.Ch Domain walls and domain structure
81.65.Cf Surface cleaning, etching, patterning
75.50.Cc Other ferromagnetic metals and alloys

Single ion implantation for solid state quantum computer development

T. Schenkel, A. Persaud, S. J. Park, J. Meijer, J. R. Kingsley, J. W. McDonald, J. P. Holder, J. Bokor, and D. H. Schneider

J. Vac. Sci. Technol. B 20, 2819 (2002); http://dx.doi.org/10.1116/1.1518016 (5 pages) | Cited 10 times

Online Publication Date: 9 December 2002

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Several solid state quantum computer schemes are based on the manipulation of electron and/or nuclear spins of single 31P atoms in a solid matrix. The fabrication of qubit arrays requires the placement of individual atoms with nanometer precision and high efficiency. We describe the status of our development of a low energy, single ion implantation scheme for 31Pq+ ions. High ion charge states enable registration of single ion impacts with unity efficiency through the detection of secondary electrons. Imaging contrast in secondary electron emission allows alignment of the implantation and integration with consecutive lithography steps. Critical issues of process integration and resolution limiting factors are discussed. © 2002 American Vacuum Society.
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61.72.uf Ge and Si
61.80.Jh Ion radiation effects
07.77.Ka Charged-particle beam sources and detectors
03.67.Lx Quantum computation architectures and implementations

Single-electron transistor structures based on silicon-on-insulator silicon nanowire fabrication by scanning probe lithography and wet etching

J. T. Sheu, K. S. You, C. H. Wu, and K. M. Chang

J. Vac. Sci. Technol. B 20, 2824 (2002); http://dx.doi.org/10.1116/1.1523017 (5 pages) | Cited 3 times

Online Publication Date: 9 December 2002

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We propose a promising fabrication technology for single-electron transistors based on a silicon-on-insulator (SOI) nanowire fabricated by scanning probe lithography and KOH wet etching. The 10-nm-wide and 10-nm-high silicon nanowire is defined by scanning probe lithography and KOH wet etching process technology. Along the [100] direction on a (100) SOI silicon wafer, local oxidation was performed in ambient using highly doped Si cantilevers with a resistivity of 0.01–0.0025 Ω cm and a commercial atomic force microscope/scanning tunneling microscope instrument. Using the oxide pattern as a Si etching mask, the Si substrate was dipped in aqueous KOH solution, in which unoxidized regions are selectively etched by aqueous KOH orientation-dependent etching. The silicon nanowire was obtained by well-controlled overetching of 34 wt % at 40 °C for 50 s. The top gate, back gates and contact pads were defined by photolithography and dry etching. Statistics showing the reproducibility of this technique are also demonstrated. © 2002 American Vacuum Society.
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81.16.Nd Micro- and nanolithography
81.16.Pr Micro- and nano-oxidation
85.35.Gv Single electron devices
81.07.Vb Quantum wires
81.05.Cy Elemental semiconductors
85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning
07.79.Lh Atomic force microscopes
07.79.Cz Scanning tunneling microscopes
81.65.Mq Oxidation
68.65.La Quantum wires (patterned in quantum wells)
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Sub-70 nm extreme ultraviolet lithography at the Advanced Light Source static microfield exposure station using the engineering test stand set-2 optic

Patrick Naulleau, Kenneth A. Goldberg, Erik H. Anderson, David Attwood, Phillip Batson, Jeffrey Bokor, Paul Denham, Eric Gullikson, Bruce Harteneck, Brian Hoef, Keith Jackson, Deirdre Olynick, Seno Rekawa, Farhad Salmassi, Ken Blaedel, et al.

J. Vac. Sci. Technol. B 20, 2829 (2002); http://dx.doi.org/10.1116/1.1524976 (5 pages) | Cited 13 times

Online Publication Date: 9 December 2002

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Static microfield printing capabilities have recently been integrated into the extreme ultraviolet interferometer operating at the Advanced Light Source synchrotron radiation facility at Lawrence Berkeley National Laboratory. The static printing capabilities include a fully programmable scanning illumination system enabling the synthesis of arbitrary illumination coherence (pupil fill). This new exposure station has been used to lithographically characterize the static imaging performance of the Engineering Test Stand Set-2 optic. Excellent performance has been demonstrated down to the 70 nm equal line/space level with focus latitude exceeding 1 μm and dose latitude of approximately 10%. Moreover, equal line/space printing down to a resolution of 50 nm has been demonstrated using resolution-enhancing pupil fills. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Testing extreme ultraviolet optics with visible-light and extreme ultraviolet interferometry

Kenneth A. Goldberg, Patrick Naulleau, Jeffrey Bokor, Henry N. Chapman, and Anton Barty

J. Vac. Sci. Technol. B 20, 2834 (2002); http://dx.doi.org/10.1116/1.1523401 (6 pages) | Cited 6 times

Online Publication Date: 9 December 2002

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Optics for extreme ultraviolet (EUV) lithography arguably have the most strict fabrication tolerances of any optical systems fabricated to date, and the development of EUV lithography pushes advanced optical fabrication techniques toward never before realized levels of figure accuracy and finish quality. As EUV lithography advances toward viability, the need for ultrahigh-accuracy wave front metrology tools has never been greater. To enable the development of diffraction-limited EUV optical systems, visible-light and EUV interferometries must work in close collaboration. We present a detailed comparison of EUV and visible-light wave front measurements performed across the field of view of a lithographic-quality projection optical system designed for use in the Engineering Test Stand developed by the Virtual National Laboratory and the EUV Limited Liability Company. The comparisons reveal that the present level of root mean square agreement lies in the 0.3–0.4 nm range, with an agreement of 0.15±0.03 nm, excluding astigmatism. Astigmatism is the most significant aberration component for the alignment of this optical system; it is also the dominant term in the discrepancy, and the aberration with the highest measurement uncertainty. With EUV optical systems requiring total wave front quality in the λEUV/50 (0.25 nm) range, and even higher surface-figure quality for the individual mirror elements (∼0.1 nm), improved accuracy through future comparisons, and additional studies, are required. © 2002 American Vacuum Society.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
42.87.-d Optical testing techniques
07.60.Ly Interferometers

Particle-induced distortion in extreme ultraviolet lithography reticles during exposure chucking

R. Tejeda, R. Engelstad, E. Lovell, and K. Blaedel

J. Vac. Sci. Technol. B 20, 2840 (2002); http://dx.doi.org/10.1116/1.1518017 (4 pages) | Cited 9 times

Online Publication Date: 9 December 2002

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Since the goal of extreme ultraviolet lithography is to produce circuit patterns with critical dimensions less than 65 nm, a key to its success will be to identify and minimize the major sources of image placement (IP) error at the wafer. Two sources of IP error are in-plane distortion (IPD) and out-of-plane deformation (OPD) of the patterned reticle during chucking in the exposure tool. Among the many possible causes of IPD and OPD is particle contamination. Small pieces of debris lodged between the reticle and chuck have the potential to distort the pattern that is transferred to the device wafer. Such distortions may consume an unduly large portion of the error budget allotted to image placement. In order to limit these IP errors, it is first necessary to gain a thorough understanding of the behavior of a particle trapped during the chucking process. This article describes the techniques that were used to study these trapped particles and their potential effects on pattern placement accuracy. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Multiple-beam interference lithography with electron beam written gratings

H. H. Solak, C. David, J. Gobrecht, L. Wang, and F. Cerrina

J. Vac. Sci. Technol. B 20, 2844 (2002); http://dx.doi.org/10.1116/1.1518015 (5 pages) | Cited 24 times

Online Publication Date: 9 December 2002

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Interference lithography with multiple beams provides two-dimensional periodic patterns in a single exposure step. It is possible to obtain various symmetries and shapes such as sparse hole arrays or dots on a hexagonal grid. However, when the number of interfering beams exceeds three, the intensity pattern depends strongly on the relative phases of the beams. In this article we show that this problem can be overcome with a scheme where transmission diffraction gratings written on a single substrate create the interfering beams possessing the required phase relations. The relative phases of the diffracted beams are controlled by the relative positions of the gratings in the substrate plane. We used electron beam lithography with an interferometrically controlled stage to obtain the required precise placement of the gratings. This method enabled us to produce hexagonal and square arrays of holes where we used three and four beam configurations, respectively. Moreover, we created sparse hole arrays that have hexagonal and square symmetries with six and eight beam interference. The experiments were carried out in the extreme ultraviolet region with synchrotron radiation and with laser light in the visible spectrum. The technique requires spatially coherent light but it is achromatic and it is not sensitive to small errors in the alignment of the incoming beam. © 2002 American Vacuum Society.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
42.79.Dj Gratings

Lithographic aerial-image contrast measurement in the extreme ultraviolet engineering test stand

Sang H. Lee, Daniel A. Tichenor, and Patrick Naulleau

J. Vac. Sci. Technol. B 20, 2849 (2002); http://dx.doi.org/10.1116/1.1526354 (4 pages) | Cited 3 times

Online Publication Date: 9 December 2002

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An important metric in determining both system and optic performance is aerial-image contrast. Here, we describe aerial-image contrast characterization for the extreme ultraviolet (EUV) Engineering Test Stand prototype EUV stepper. The system has been characterized operating with a developmental projection optic (the set-1 optic). Characterization was performed using the resist-clearing (Kirk) method and the results were compared to simulations based on the known system parameters. In this method, the image contrast is determined from the dose required to clear the bright features and the dose required to clear the dark features in a pattern of dense lines and spaces. Comparisons to simulations have shown discrepancies that increase as the contrast dose is reduced. Although various potential sources exist for these discrepancies (as described herein), analysis points to finite resist resolution as being the primary cause. An empirical model that accounts for finite resist resolution in aerial-image contrast measurements is presented. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
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High-resolution transfer printing on GaAs surfaces using alkane dithiol monolayers

Yueh-Lin Loo, Julia W. P. Hsu, Robert L. Willett, Kirk W. Baldwin, Ken W. West, and John A. Rogers

J. Vac. Sci. Technol. B 20, 2853 (2002); http://dx.doi.org/10.1116/1.1523405 (4 pages) | Cited 28 times

Online Publication Date: 9 December 2002

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We describe a transfer printing technique for directly patterning thin gold films onto GaAs surfaces. This additive transfer process is mediated by the presence of an alkane dithiol monolayer on the wafer surface. The transferred patterns are chemically bound to the wafer surface and they exhibit strong adhesion (i.e., they easily pass Scotch tape adhesion tests.) A variety of gold patterns with a wide range of feature sizes can be printed onto GaAs (100), (110), (211)A, and (211)B using this approach. © 2002 American Vacuum Society.
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81.16.Rf Micro- and nanoscale pattern formation

Characterization of and imprint results using indium tin oxide-based step and flash imprint lithography templates

W. J. Dauksher, K. J. Nordquist, D. P. Mancini, D. J. Resnick, J. H. Baker, A. E. Hooper, A. A. Talin, T. C. Bailey, A. M. Lemonds, S. V. Sreenivasan, J. G. Ekerdt, and C. G. Willson

J. Vac. Sci. Technol. B 20, 2857 (2002); http://dx.doi.org/10.1116/1.1520575 (5 pages) | Cited 13 times

Online Publication Date: 9 December 2002

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As compared to quartz relief structures currently employed, indium tin oxide-based (ITO-based) step and flash imprint lithography templates offer advantages in terms of electron-beam writing, scanning electron microscope inspection, and pattern transfer. The material properties of the ITO have been completely characterized, and data is presented for resistivity, crystal structure, transmission, stress, surface roughness, adhesion, composition, and etch characteristics. For a 600 Å annealed ITO film, the resistivity is approximately 3.5×102 Ω/sq and the optical transmission 77% at 365 nm. The atomic film composition was found to be 31.5% In, 4.3% Sn, and 64.2% O by x-ray photoelectron spectroscopy. When contrasted with SiO2 films, temperature programmed desorption data suggests that hydroxyl groups on the ITO surface bind H2O less strongly but are more abundant. Ultimate verification of compatibility was obtained by imprinting features into an etch barrier layer using an ITO-based template. The fidelity of 20 nm isolated and semi-isolated features, the smallest features present on the template, was successfully reproduced via the imprinting process. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
78.66.Li Other semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology
73.25.+i Surface conductivity and carrier phenomena
61.72.Cc Kinetics of defect formation and annealing
68.60.Bs Mechanical and acoustical properties
78.40.Fy Semiconductors
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
68.43.Vx Thermal desorption

Polymer microring resonators fabricated by nanoimprint technique

Chung-yen Chao and L. Jay Guo

J. Vac. Sci. Technol. B 20, 2862 (2002); http://dx.doi.org/10.1116/1.1521729 (5 pages) | Cited 59 times

Online Publication Date: 9 December 2002

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Microring optical resonators have important applications in integrated photonic circuits for optical communications. We have developed two methods to fabricate polymer microring devices based on the nanoimprint technique. The first method uses a hard mold to directly imprint a polymer film to form optical waveguides in microring devices. We have demonstrated polymethylmethacrylate, polystyrene, and polycarbonate microring resonators fabricated using this technique. The second method employs a template filling approach, which allows a thicker waveguide to be fabricated, as well as polymers that are difficult to directly imprint. Optical filtering behavior of a microring resonator is demonstrated with a Q factor as high as 5800. The technique developed in this work could offer a cost-effective method to fabricate integrated photonic circuits based on polymer microring resonators. © 2002 American Vacuum Society.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
42.70.Jk Polymers and organics
42.79.Ci Filters, zone plates, and polarizers
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
42.86.+b Optical workshop techniques
42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
81.10.Fq Growth from melts; zone melting and refining
81.16.Rf Micro- and nanoscale pattern formation

Imprint lithography for curved cross-sectional structure using replicated Ni mold

Yoshihiko Hirai, Satoshi Harada, Hisao Kikuta, Yoshio Tanaka, Masato Okano, Satoshi Isaka, and Michio Kobayasi

J. Vac. Sci. Technol. B 20, 2867 (2002); http://dx.doi.org/10.1116/1.1515305 (5 pages) | Cited 17 times

Online Publication Date: 9 December 2002

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Fabrication of patterns with curved cross-sectional profiles for diffractive optical elements are demonstrated by imprint lithography using replicated Ni mold. The master mold pattern is fabricated by an electron beam lithography, where dosage distribution is automatically optimized by a computer aided design (CAD) system taking the proximity effects and resist development process into account. Utilizing the CAD system, a modulated pitched resist pattern with polynomial shaped cross-sectional profiles are successfully obtained by poly (methylmethacrylate) (PMMA) on Si substrate. Using the PMMA resist as a master pattern, replicated mold is fabricated by Ni electroforming followed by Ni electroless plating. Fine and curved cross-sectional patterns are successfully transferred to a resist on Si substrate by imprint lithography using the Ni replicated mold. In the same way, fabrication of sine waved and circular curved structures are demonstrated. This method is exceedingly useful for fabrication of integrated diffractive optical elements with a cross-sectional profile. © 2002 American Vacuum Society.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
85.40.Hp Lithography, masks and pattern transfer

Reversal imprinting by transferring polymer from mold to substrate

X. D. Huang, L.-R. Bao, X. Cheng, L. J. Guo, S. W. Pang, and A. F. Yee

J. Vac. Sci. Technol. B 20, 2872 (2002); http://dx.doi.org/10.1116/1.1523404 (5 pages) | Cited 50 times

Online Publication Date: 9 December 2002

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A reversal imprinting technique was developed in this study. A polymer layer was first spin coated on a patterned hard mold, and then transferred to a substrate under an elevated temperature and pressure. The reversal imprinting method offers an advantage over conventional nanoimprinting by allowing imprinting onto substrates that cannot be easily spin coated, such as flexible polymer substrates. Another unique feature of reversal imprinting is that three different pattern-transfer modes can be achieved by controlling the degree of surface planarization of the mold after spin coating the polymer resist as well as the imprinting temperature. “Embossing” occurs at temperatures well above the glass transition temperature (Tg) of a polymer; “inking” occurs at temperatures around Tg with nonplanarized polymer coating surface on the mold; and “whole-layer transfer” occurs at temperatures around Tg but with a somewhat planarized surface. These three imprinting modes have been quantitatively correlated with the surface planarization of the mold after polymer coating and the imprinting temperature. © 2002 American Vacuum Society.
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81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
81.16.Rf Micro- and nanoscale pattern formation
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
82.35.Gh Polymers on surfaces; adhesion
81.10.Fq Growth from melts; zone melting and refining
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition

High-resolution organic polymer light-emitting pixels fabricated by imprinting technique

Xing Cheng, Yongtaek Hong, Jerzy Kanicki, and L. Jay Guo

J. Vac. Sci. Technol. B 20, 2877 (2002); http://dx.doi.org/10.1116/1.1515307 (4 pages) | Cited 24 times

Online Publication Date: 9 December 2002

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We have developed an approach to fabricate pixelated organic polymer light-emitting devices (OPLED) using an imprinting technique. The pixel array pattern was first defined in an insulating polymer layer on indium tin oxide glass by direct imprinting, followed by the spin-coating of OPLED polymers and cathode metal deposition. We demonstrated successful fabrication and operation of OPLED pixels of sizes from 50 μm down to 2 μm. Optoelectronic characterization is performed on these devices, and measured results show comparable device performance with OPLED pixels patterned by other methods. This fabrication scheme holds many merits such as easy to process, low-cost, high yield, expandable to flexible substrate, capable of repeated imprinting for large area arrays, and the potential to pattern submicron and nanoscale organic polymer light emitters. © 2002 American Vacuum Society.
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85.60.Jb Light-emitting devices
81.16.Nd Micro- and nanolithography
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
78.60.Fi Electroluminescence
81.16.Rf Micro- and nanoscale pattern formation

Nanoimprinting over topography and multilayer three-dimensional printing

L.-R. Bao, X. Cheng, X. D. Huang, L. J. Guo, S. W. Pang, and A. F. Yee

J. Vac. Sci. Technol. B 20, 2881 (2002); http://dx.doi.org/10.1116/1.1526355 (6 pages) | Cited 48 times

Online Publication Date: 9 December 2002

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We have developed a simple imprinting technique that allows patterning over a nonflat substrate without the need for planarization. In this process, a polymer film is spin coated onto the mold and then transferred to a patterned substrate by imprinting. By selecting polymers with different mechanical properties, either suspended structures over wide gaps or supported patterns on raised features of the substrate can be obtained with high uniformity. It is found that imprinting at a temperature well above the glass transition temperature (Tg) of the polymer causes the thin residue film between features to dewet from the mold, which can greatly simplify the subsequent pattern transfer process. Multilayer three-dimensional polymer structures have also been successfully fabricated using this new imprinting method. The yield and dimensional stability in the multilayer structure can both be improved when polymers with progressively lower Tg are used for different layers. Compared to existing techniques for patterning on nonflat substrates, the current method has a number of advantages, including simplicity, versatility, high resolution, and low pattern distortion. © 2002 American Vacuum Society.
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81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

Fabrication of high electron mobility transistors with T-gates by nanoimprint lithography

Y. Chen, D. Macintyre, E. Boyd, D. Moran, I. Thayne, and S. Thoms

J. Vac. Sci. Technol. B 20, 2887 (2002); http://dx.doi.org/10.1116/1.1520564 (4 pages) | Cited 10 times

Online Publication Date: 9 December 2002

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T-gates are commonly used in high frequency low noise transistors on III–V materials since they provide a combination of short gate length and low gate resistance. Nanoimprint lithography can produce minimum pattern feature sizes equivalent to those attainable by high resolution electron beam lithography and it has potential advantages in terms of speed and cost. The imprint lithography step must be reliable and compatible with existing device process flows. In this article we describe a bilayer resist imprinting procedure for the fabrication of 120 nm T-gates for high electron mobility transistors. The results of transistor dc characterization are also presented and are similar to those obtained for transistors fabricated on the same material with gates realized by electron beam lithography. © 2002 American Vacuum Society.
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85.30.Tv Field effect devices
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

Prediction of fabrication distortions in step and flash imprint lithography templates

C. J. Martin, R. L. Engelstad, E. G. Lovell, D. J. Resnick, and E. J. Weisbrod

J. Vac. Sci. Technol. B 20, 2891 (2002); http://dx.doi.org/10.1116/1.1521743 (5 pages) | Cited 5 times

Online Publication Date: 9 December 2002

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Step and flash imprint lithography (SFIL) is an alternative approach for printing sub-100 nm features that relies on chemical and mechanical techniques to transfer patterns. The imprint process requires no projection optics and is performed at room temperature with low imprint pressures to reduce thermal and mechanical template distortions. Because imprint lithographies are 1× pattern transfer processes that preclude magnification corrections, the minimization of template distortions during fabrication and imprinting is critical. The processes and materials used in the fabrication of SFIL templates are similar to those used in the manufacturing of optical masks. The various process steps have been simulated using finite element techniques in order to predict the resulting pattern distortions. Two proposed template fabrication schemes were modeled, the resulting pattern distortions compared, and the error sources were quantified. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Hydrogen silsesquioxane for direct electron-beam patterning of step and flash imprint lithography templates

D. P. Mancini, K. A. Gehoski, E. Ainley, K. J. Nordquist, D. J. Resnick, T. C. Bailey, S. V. Sreenivasan, J. G. Ekerdt, and C. G. Willson

J. Vac. Sci. Technol. B 20, 2896 (2002); http://dx.doi.org/10.1116/1.1515311 (6 pages) | Cited 21 times

Online Publication Date: 9 December 2002

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The feasibility of using hydrogen silsesquioxane (HSQ) to directly pattern the relief layer of step and flash imprint lithography (SFIL) templates has been successfully demonstrated. HSQ is a spin-coatable oxide, which is capable of high resolution electron-beam lithography. Negative acting and nonchemically amplified, HSQ has moderate electron-beam sensitivity and excellent processing latitude. In this novel approach, 6 ×6 × 0.25 in.3 quartz photomask substrates are coated with a 60 nm indium tin oxide (ITO) charge dissipation layer and directly electron-beam written using a 100 nm film of HSQ. Direct patterning of an oxide relief layer eliminates the problems of critical dimension control associated with both chromium and oxide etches, both required processes of previous template fabrication schemes. Resolution of isolated and semidense lines of 30 nm has been demonstrated on imprinted wafers using this type of template. During this evaluation, a failure of the release layer to provide a durable nonstick surface on ITO was discovered and investigated. This problem was successfully remedied by depositing a 5 nm oxide layer over the patterned ITO/HSQ template. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.15.Rs Spray coating techniques
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Evaluation of siloxane and polyhedral silsesquioxane copolymers for 157 nm lithography

V. Bellas, E. Tegou, I. Raptis, E. Gogolides, P. Argitis, H. Iatrou, N. Hadjichristidis, E. Sarantopoulou, and A. C. Cefalas

J. Vac. Sci. Technol. B 20, 2902 (2002); http://dx.doi.org/10.1116/1.1526358 (7 pages) | Cited 10 times

Online Publication Date: 9 December 2002

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Siloxane and silsesquioxane copolymers have been synthesized and first evaluated as potential components of 157 nm resist materials. In block copolymers of dimethylsiloxane and tert-butyl methacrylate negative imaging chemistry dominates at 157 nm, due to the presence of the siloxane component, although positive imaging in aqueous base developers via chemical amplification was obtained at longer wavelengths (248 nm). The same behavior is observed in graft copolymers of dimethylsiloxane and tert-butyl methacrylate. On the other hand, random copolymers of polymerizable polyhedral oligomeric silsesquioxane monomers with various acrylates, including partially fluorinated, can be used as components of resist formulations that provide positive imaging at 157 nm, aqueous base development, and physicochemical properties which resemble those of conventional poly(meth)acrylates. Pattern transfer properties depend on the selection of the silsesquioxane component. Polymers containing 30% or higher w/w ethyl-substituted silsesquioxane cages provide the necessary etch resistance as well as low surface roughness to oxygen plasma at 100 nm film thickness, allowing bilayer 157 nm lithography, even without further absorbance optimization. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
61.41.+e Polymers, elastomers, and plastics
68.55.Nq Composition and phase identification
78.66.Qn Polymers; organic compounds
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.47.Mn Polymer surfaces
81.65.Cf Surface cleaning, etching, patterning

Fluoropolymer-based resists for a single-resist process of 157 nm lithography

M. Toriumi, T. Yamazaki, T. Furukawa, S. Irie, S. Ishikawa, and T. Itani

J. Vac. Sci. Technol. B 20, 2909 (2002); http://dx.doi.org/10.1116/1.1526359 (4 pages) | Cited 4 times

Online Publication Date: 9 December 2002

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We investigated two types of main-chain fluorinated polymers and found that incorporating fluorine into their backbones reduced their absorption coefficients to less than 1 μm−1 at 157 nm and showed good dry-etching resistance. Fluoropolymer dissolution during development was studied using a quartz-crystal microbalance and evaluated from the standpoint of molecular structures and polymer acidity. The fluorine and hydrophobic effects, rather than the polymer acidity effect, were found to play the dominant role in forming the swelling layer during development. The use of main-chain fluorinated polymers for the base resin of positive-tone resists results in fine imaging with a film thickness of 300 nm. The incorporation of fluorine into the backbones will thus enable these polymers to be used as single-layer resists for 157 nm lithography. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
81.65.Cf Surface cleaning, etching, patterning

Electrostatic effects during dissolution of positive tone photoresists

Gerard M. Schmid, Sean D. Burns, Pavlos C. Tsiartas, and C. Grant Willson

J. Vac. Sci. Technol. B 20, 2913 (2002); http://dx.doi.org/10.1116/1.1521735 (7 pages) | Cited 5 times

Online Publication Date: 9 December 2002

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Positive tone photoresist function is based upon modulation of the dissolution rate of an acidic polymer in aqueous base developer. During dissolution, a negative surface charge accumulates at the surface of the photoresist film as acidic sites on the polymer are ionized by the basic developer. This negative surface charge causes a depletion of hydroxide ions in the developer solution immediately adjacent to the film. One effect of this phenomenon is to reduce the dissolution rate relative to rates predicted from the bulk base concentration. The depletion of base at the resist/developer interface has been studied through the application of the Poisson–Boltzmann equation and through Monte Carlo simulations. It is shown that the extent of depletion of hydroxide at the surface of the film is related to the bulk developer concentration and the local geometry of the interface. Interfacial geometry is found to be most influential on the length scale of 1–10 nm. When electrostatic effects are considered in conjunction with the equilibrium of the acid–base reaction, the fractional ionization of the surface of the film is significantly lower than previously calculated. Understanding the relationship between the acid–base equilibrium and electrostatic equilibrium represents an important step in our efforts to understand the fundamental dissolution mechanism of positive tone photoresists. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
82.50.Hp Processes caused by visible and UV light
02.50.Ng Distribution theory and Monte Carlo studies

Probing surface and bulk chemistry in resist films using near edge x-ray absorption fine structure

Joseph L. Lenhart, Ronald L. Jones, Eric K. Lin, Christopher L. Soles, Wen-li Wu, Daniel A. Fischer, Sharadha Sambasivan, Dario L. Goldfarb, and Marie Angelopoulos

J. Vac. Sci. Technol. B 20, 2920 (2002); http://dx.doi.org/10.1116/1.1524970 (7 pages) | Cited 10 times

Online Publication Date: 9 December 2002

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The performance of chemically amplified photoresists is extremely sensitive to interfacial and surface phenomena, which cause deviations in the pattern profile near an interface. Striking examples include T-topping or closure near the air/resist interface and footing or undercutting near the resist/substrate interface. One focus of our research is to identify mechanisms that cause lithographic patterns to deviate near interfaces. Near edge x-ray absorption fine structure (NEXAFS) is a powerful tool that can be developed and adapted to probe for detailed chemical information near lithographically relevant interfaces. NEXAFS showed that our model resist films exhibited significant surface segregation of the photo acid generator (PAG) at the air interface. The PAG surface mole fraction was 20–70 times greater than the bulk mole fraction and the amount of surface segregation was dependent on the polarity of the polymer. NEXAFS also revealed that the PAG surface fraction was reduced after a postexposure bake. In the absence of delay times between processing steps, the PAG surface enhancement led to a faster deprotection reaction rate near the air interface relative to the bulk. However, when significant postexposure delay times were incorporated into the processing, NEXAFS showed that the surface deprotection reaction was incomplete after postexposure baking. Comparison of carbon K-edge, and oxygen K-edge NEXAFS spectra showed that the incomplete surface reaction was localized at the air interface. While delay effects have previously been linked to deterioration of resist performance, NEXAFS proved to be a valuable tool for providing detailed chemical specificity about the resist surface composition and deprotection kinetics. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
78.70.Dm X-ray absorption spectra
68.35.Dv Composition, segregation; defects and impurities

Depth dependence of resist line-edge roughness: Relation to photoacid diffusion length

J. Shin, Y. Ma, and F. Cerrina

J. Vac. Sci. Technol. B 20, 2927 (2002); http://dx.doi.org/10.1116/1.1526638 (5 pages) | Cited 7 times

Online Publication Date: 9 December 2002

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We report the results of an experimental and simulation study of the correlation between line-edge roughness (LER) and height along the sidewall for resists patterned with electron-beam lithography. The characterization has been performed using atomic force microscopy with carbon nanotube tips and scanning electron microscopy. Experimental results generally support that LER depends on resist height and aerial image modulation. Finally, percolation simulation results based on stochastic modeling are compared with experimental results, and allow us to set an upper limit of 3–5 nm on acid diffusion length. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
68.37.Ps Atomic force microscopy (AFM)
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Delay-time and aging effects on contrast and sensitivity of hydrogen silsesquioxane

Falco C. M. J. M. van Delft

J. Vac. Sci. Technol. B 20, 2932 (2002); http://dx.doi.org/10.1116/1.1524980 (5 pages) | Cited 13 times

Online Publication Date: 9 December 2002

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Hydrogen silsesquioxane (HSQ) has been shown to behave as a negative tone inorganic e-beam resist with a resolution better than 20 nm established. In this article, delay-time and aging effects on contrast and sensitivity have been investigated. The effect of a 1 week delay in air between softbake and exposure is much larger than either the aging effect or the effect of the softbake temperature. A pre-exposure delay in air seems to decrease the sensitivity and to enhance the contrast of HSQ. A general correlation between sensitivity and contrast has been established for various pre-exposure and postexposure treatments for 20, 50, and 100 kV exposures. The possible causes for the various delay-time effects are discussed. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Low stress development of poly(methylmethacrylate) for high aspect ratio structures

M. J. Rooks, E. Kratschmer, R. Viswanathan, J. Katine, R. E. Fontana, and S. A. MacDonald

J. Vac. Sci. Technol. B 20, 2937 (2002); http://dx.doi.org/10.1116/1.1524971 (5 pages) | Cited 21 times

Online Publication Date: 9 December 2002

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Magnetic head fabrication for >100 Gbit/in.2 areal density requires minimum lithographic feature size <0.15 μm, with aspect ratios of 8:1–10:1. Electron-beam lithography can provide adequate resolution for research and development of magnetic heads, and at 100 kV can provide greater than 10:1 aspect ratios in 1–3 μm thick single-layer resist poly(methylmethacrylate). Poly (methylmethacrylate) (PMMA) is well known for withstanding the rigors of plating baths, but at these thicknesses requires a nonswelling, low-stress developer such as the LIGA mixture (also known as “GG Developer (U.S. Patent No. 4,393,129)”). In this work we present the results of isopropyl alcohol:water development for thick PMMA, and describe the dependence of resist contrast on the temperature of the developer. We also demonstrate the advantage of ultrasonic agitation during development. These development techniques have brought resist profiles in PMMA to the theoretical limit predicted by Monte Carlo simulations. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
02.70.Uu Applications of Monte Carlo methods

Photopatternable sol-gel for compound semiconductor processing

Mahmoud Fallahi, Robert Bedford, and Dong Lu

J. Vac. Sci. Technol. B 20, 2942 (2002); http://dx.doi.org/10.1116/1.1521740 (4 pages)

Online Publication Date: 9 December 2002

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A simple technique using hybrid organic–inorganic sol-gel films for compound semiconductor processing is proposed and demonstrated. The dual organic and inorganic nature of the hybrid sol-gel films allows high quality photopatternability and robust masking for the dry-etching process. The sol-gel channels on GaAs and InP are fabricated and high-aspect-ratio dry etching of semiconductors is shown. In addition, the potential of the hybrid sol-gel as a planarizing layer on deep-etched InP with overcut and undercut profiles is demonstrated. © 2002 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Acid catalyst mobility in resist resins

Michael D. Stewart, Hoang Vi Tran, Gerard M. Schmid, Timothy B. Stachowiak, Darren J. Becker, and C. Grant Willson

J. Vac. Sci. Technol. B 20, 2946 (2002); http://dx.doi.org/10.1116/1.1523027 (7 pages) | Cited 28 times

Online Publication Date: 9 December 2002

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In a chemically amplified resist absorbed photons generate stable catalyst molecules instead of directly switching resist solubility via photochemical reaction. This allows for much lower exposure doses to be used in imaging. Some catalyst mobility is necessary to achieve amplification since the catalyst must move from reaction site to reaction site, but a mobile catalyst can blur the deposited aerial image. Catalyst molecules that are free to move in exposed regions are also free to move into adjacent unexposed regions. Understanding acid catalyst diffusion in photoresist resins is complicated by the constantly changing chemical environment the diffusing catalyst experiences as the resist undergoes chemical reactions. The diffusing catalyst promotes chemical reactions which change the properties of its surrounding resin. In addition, it is possible a transient material state is generated by volatile reaction byproducts and their desorption from the film. In most photoresist systems it is impossible to separate reaction and diffusion effects. This work describes studies of acid diffusion in polymers that are close structural analogs to reactive photoresist resins but do not react with the diffusing acidic catalyst. The purpose of this study into nonreactive polymer is to gain insight into the more complex, reactive systems. In addition, experiments with polymeric photoacid generators are reported. These materials provide added insight into acid transport in photoresist materials. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
82.30.Vy Homogeneous catalysis in solution, polymers and zeolites
82.35.-x Polymers: properties; reactions; polymerization
82.50.Hp Processes caused by visible and UV light

Suppression of secondary electron blur by using Br-containing resists in x-ray lithography

K. Kise, K. Marumoto, H. Watanabe, K. Itoga, T. Kumada, H. Sumitani, T. Kitayama, M. Amemiya, Y. Watanabe, and K. Uda

J. Vac. Sci. Technol. B 20, 2953 (2002); http://dx.doi.org/10.1116/1.1520565 (5 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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Second generation proximity x-ray lithography (PXL-II), which uses shorter incident x-ray wavelengths and resist materials, is expected to be a candidate for next generation lithography. In the PXL-II technique, the x-ray wavelength absorbed in the resist becomes shorter, but degradation of the pattern quality due to secondary electron blur has not been sufficiently evaluated. In this article, we present our investigation of the secondary electron blur’s suppression in Br-containing resist using a lithographic simulator and a Monte Carlo simulator for electron scattering. By introducing the Br element into resist materials, the electron stopping power improves. In addition, secondary electron blur is suppressed in regions with wavelengths shorter than that of the Br absorption edge. In order to evaluate pattern resolution, the image contrast of the lateral absorbed image in the resist is defined. We found that image contrast is improved in Br-containing resist for the wavelength range down to about 4.5 Å, which is suitable for PXL-II. We also show that it should be possible to extend PXL-II for resolutions of less than 40 nm at a narrower gap. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Evaluation of calixarene—derivatives as high-resolution negative tone electron-beam resists

H. Sailer, A. Ruderisch, D. P. Kern, and V. Schurig

J. Vac. Sci. Technol. B 20, 2958 (2002); http://dx.doi.org/10.1116/1.1521737 (4 pages) | Cited 9 times

Online Publication Date: 9 December 2002

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We present a systematic evaluation of calixarene derivatives as high-resolution negative tone resists for electron-beam lithography with a focus on their sensitivities. We studied the effect of a modification of the calixarene molecules to trimethysilyl ethers as well as the effect of an introduction of an allyl group and showed that the introduction of double bonds into the molecules can improve the sensitivity of the resists while their position does not seem to be important. The high-resolution capability of tetraallylcalix[4]arene was confirmed by fabricating an 18 nm dot array. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Photospeed considerations for extreme ultraviolet lithography resists

Paul M. Dentinger, Luke L. Hunter, Donna J. O’Connell, Scott Gunn, Daniel Goods, Theodore H. Fedynyshyn, Russell B. Goodman, and David K. Astolfi

J. Vac. Sci. Technol. B 20, 2962 (2002); http://dx.doi.org/10.1116/1.1520561 (6 pages) | Cited 10 times

Online Publication Date: 9 December 2002

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Photospeed is a prime consideration for wafer throughput of extreme ultraviolet (EUV) lithography. Faster photoresists additionally provide system advantages such as less thermal management of the mirrors and mask, and potentially increased component lifetimes. However, there are some predicted detrimental considerations when using fast photoresists such as shot noise. In this article, we report details of the formulation of photoresists exposed at 248 nm and identical formulations exposed at 13.4 nm. Compositions typically contained co- or terpolymers of poly-4-hydroxystyrene, t-butyl acrylate and as an option, styrene, a photoacid generator of bis-t-butylphenyl iodonium camphorsulfonate or perfluoroxbenzensulfonate and tetrabutyalummonium or triphenylsulphonium hydroxide base. With these formulations, the EUV photospeed was varied from 34 to 2.7 mJ/cm2. Scanning electron microscope analysis was done for all wafers at Sandia using GORA software to determine the line-edge roughness (LER). Identical formulations were exposed at photon dense deep UV (DUV) wavelengths and comparatively photon-sparse EUV wavelengths. Therefore, ratioing the LER of identical formulations exposed at DUV minimizes the confounding effects of formulation changes that affect dissolution, resolution, etc. A plot of the line-edge roughness ratio of LEREUV/LERDUV as a function of the photospeed was used to gain insight into the effect of shot noise on the LER of dense lines. If shot noise effects were dominating the LER for EUV, then the ratio would increase above the nominal value as the dose to size was decreased. It is clear that the current generation of DUV resists, with the invention of no new material required, can be reformulated to satisfy the photospeed specification of 5 mJ/cm2 for EUV lithography and no shot noise effects have been observed. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Partially hydrogenated poly(vinyl phenol) based photoresist for near UV, high aspect ratio micromachining

M. Chatzichristidi, I. Raptis, P. Argitis, and J. Everett

J. Vac. Sci. Technol. B 20, 2968 (2002); http://dx.doi.org/10.1116/1.1521741 (5 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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A negative resist platform based on a low Mw epoxy novolac polymer, partially hydrogenated poly(vinyl phenol)s and suitable onium salt photoacid generators is presented and evaluated for high aspect ratio micromachining. The high content of hydroxyl groups in this resist system allows development in standard aqueous base solutions (TMAH 0.26 N). The effects of material parameters such as the degree of poly(vinyl phenol) hydrogenation and the onium salt hydrophobicity on the development process are examined. The cross-linked areas of this resist can be easily removed by commercial wet photoresist strippers after processing. Experimental data demonstrate a promising lithographic performance with an aspect ratio of 7:1 for 5 μm closely spaced lines under exposure at 365 nm. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
82.50.Hp Processes caused by visible and UV light
82.35.-x Polymers: properties; reactions; polymerization

Thermal-flow techniques for sub-35 nm contact-hole fabrication in electron-beam lithography

H. L. Chen, C. H. Chen, F. H. Ko, T. C. Chu, C. T. Pan, and H. C. Lin

J. Vac. Sci. Technol. B 20, 2973 (2002); http://dx.doi.org/10.1116/1.1526352 (6 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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In this article, we demonstrate that 200 nm contact-hole resist patterns can easily be shrunk to less than 35 nm after a simple thermal-flow procedure. The optimal thermal-flow temperature was determined by differential-scanning calorimetry and wafer-curvature measurement. The effects of postapplied baked temperature, thermal-flow temperature, baking time period, and pattern density were evaluated. The resist after thermal flow is more intact than during dry-etching processes. The resist can overcome the resist-thickness loss during the thermal-flow procedure. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.40.Gh Other heat and thermomechanical treatments
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Extendibility of proximity x-ray lithography to 25 nm and below

Eijiro Toyota and Masakazu Washio

J. Vac. Sci. Technol. B 20, 2979 (2002); http://dx.doi.org/10.1116/1.1524972 (5 pages) | Cited 6 times

Online Publication Date: 9 December 2002

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Extendibility of proximity x-ray lithography (PXL) relates to three technical issues. They are the minimum proximity gap usable for steppers, the maximum allowable gap by exposure methods, and overall blur effect. The minimum usable gap gs (μm) for steppers is presumed to be gs=W1/2, where W (nm) is the design rule (half pitch). The maximum allowable gap g is expressed as g=αW2/λ, where λ is the average wavelength and α is a coefficient, which depends on the exposure methods using 1× masks or 2× masks. In the article, we have verified the equation (g=αW2/λ) by simulation for one- and two-dimensional patterns, and determined the α values for each exposure method. For the blur effect, we evaluated the sigma values using a simple model. As a result, we concluded that PXL can be used by 25 nm and most probably by 18 nm design rule by changing the exposure methods corresponding to the progress of the design rule generations. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Collimated point-source x-ray nanolithography

R. A. Forber, Z. W. Chen, R. Menon, R. Grygier, S. Mrowka, I. C. E. Turcu, C. J. Gaeta, K. Cassidy, and Henry I. Smith

J. Vac. Sci. Technol. B 20, 2984 (2002); http://dx.doi.org/10.1116/1.1521733 (7 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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The most efficient use of radiation point sources for x-ray lithography requires a collimator to capture a large fraction of spherically emitted radiation and deliver the rays with acceptable divergence properties. We describe an x-ray point source utilizing a polycapillary collimator. The optical performance of the collimator was measured and is described. Dense line-space patterns (∼100 nm lines) were printed in poly(methylmethacrylate) using a mask-wafer gap of 16 μm. Lithography results are consistent with modeling analysis. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
81.16.Nd Micro- and nanolithography
52.38.Ph X-ray, γ-ray, and particle generation

Achieving nanometer-scale, controllable pattern shifts in x-ray lithography using an assembly-tilting technique

Minghao Qi and Henry I. Smith

J. Vac. Sci. Technol. B 20, 2991 (2002); http://dx.doi.org/10.1116/1.1523021 (4 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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In x-ray lithography the finite gap between the mask and substrate, and the highly directional nature of the short wavelength radiation, enable one to shift the entire mask image by tilting the mask–substrate assembly relative to the axis of illumination. The amount of image shift depends on the mask–substrate gap and the tilt angle, and it can be calculated by simple geometry. The shift can be into any azimuthal direction. The experimental results are consistent with the calculated shift. In our experiments we typically used gaps of 3 μm and tilts of 5.7° (0.1 rad) to achieve a shift of the order of 300 nm. There are a number of advantages and new lithography features that can be accessed using the assembly-tilting technique. For example, various double-exposure schemes, some of which are designed to achieve extremely fine lines or unique patterns, are easily accomplished by the assembly-tilting technique. Moreover, if a mask and substrate contain appropriate alignment marks, viewed optically at normal incidence, and a small misalignment is measured, this can be corrected by tilting the entire assembly rather than by moving the mask relative to the substrate. © 2002 American Vacuum Society.
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81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
07.85.-m X- and γ-ray instruments
41.50.+h X-ray beams and x-ray optics
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Dynamic studies of hard pellicle response during exposure scanning

Eric P. Cotte, Amr Y. Abdo, Roxann L. Engelstad, and Edward G. Lovell

J. Vac. Sci. Technol. B 20, 2995 (2002); http://dx.doi.org/10.1116/1.1520573 (5 pages) | Cited 1 time

Online Publication Date: 9 December 2002

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Meeting the stringent image placement error budgets for 157 nm lithography in the sub-90 nm regime requires that mask-related distortions be minimized, corrected, or possibly eliminated. One of the sources of image placement error is the pellicle system. Static pellicle-induced distortions have previously been characterized, both experimentally and numerically. This article focuses on the dynamic response of modified fused silica (hard) pellicles during exposure scanning and takes into account inertia effects as well as fluid/structure interactions. Parametric studies were performed to identify conditions causing the pellicle behavior to become dynamic. Distortions of the 800-μm-thick hard pellicle for different acceleration pulse widths were assessed, both numerically and analytically, and the agreement was excellent. The results presented here will facilitate the establishment of pellicle standards for 157 nm lithography. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Characterization of extreme ultraviolet lithography mask defects by actinic inspection with broadband extreme ultraviolet illumination

Mincheol Park, Moonsuk Yi, Paul Mirkarimi, Cindy Larson, and Jeffrey Bokor

J. Vac. Sci. Technol. B 20, 3000 (2002); http://dx.doi.org/10.1116/1.1523397 (6 pages) | Cited 1 time

Online Publication Date: 9 December 2002

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We present our study on actinic detection of defects on extreme ultraviolet (EUV) lithography mask blanks with broadband EUV illumination from a synchrotron light source. A mirror blank was substituted for the monochromator grating in the synchrotron beamline. This increases the spectral bandwidth that is taken from the broadband synchrotron beam by 1 order of magnitude, leading to a commensurate increase in the total available flux. The detection sensitivity of this actinic inspection system is able to reach approximately 20 nm in equivalent defect size. This has been determined through cross correlation experiments done with commercial visible-light inspection tools. Experimental results also show that this broadband EUV inspection system has a capability of detecting phase defects with 5 nm surface height. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Ultraviolet and direct ultraviolet inspection of next generation lithography reticles

Don Pettibone, Aditya Dayal, Andrei Veldman, and Stan Stokowski

J. Vac. Sci. Technol. B 20, 3006 (2002); http://dx.doi.org/10.1116/1.1523400 (4 pages) | Cited 1 time

Online Publication Date: 9 December 2002

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The optical inspection of next generation lithography (NGL) patterned reticles, multilayer-coated blanks, and uncoated substrates is particularly challenging. The difficulties arise not only because of the higher sensitivity necessary at the smaller design rules, but also due to the specifics of the NGL mask materials and structures. Our research program is investigating the theoretical and practical operational limitations facing optical inspections of patterned and unpatterned NGL masks. We are constrained by the necessity to inspect only in reflected light, limitations in mask contrast, and interference effects caused by partially coherent illumination. We present inspection results and images of several types of NGL masks, blanks and substrates obtained on high resolution ultraviolet (UV) and direct ultraviolet (DUV) optical mask inspection systems. While electron projection lithography (EPL) stencil masks can be inspected in reflection, limited transmission through the mask suggests that subsurface defects will be detected with reduced sensitivity, compared to defects on the surface. For unpatterned inspections, we have demonstrated UV system sensitivity to 88 nm PSL spheres on quartz substrates and 117 nm PSLs on silicon substrates. On extreme ultraviolet masks we have achieved DUV system sensitivity down to defects as small as 80 nm in size, both in die-to-die inspections and in simulated die-to-database inspections. In addition to advancing the development of optical inspection systems for NGL reticles, these inspection results provide feedback to NGL mask developers. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Fabrication of complete 8 in. stencil mask for electron projection lithography

Isao Amemiya, Hiroshi Yamashita, Sakae Nakatsuka, Ikuru Kimura, Mitsuharu Tsukahara, Satoshi Yasumatsu, and Osamu Nagarekawa

J. Vac. Sci. Technol. B 20, 3010 (2002); http://dx.doi.org/10.1116/1.1523024 (5 pages) | Cited 6 times

Online Publication Date: 9 December 2002

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We fabricated an 8 in. stencil mask having the complementary pattern of the 70 nm rule system-on-chip device. The 8 in. stencil mask was realized from the development of a mask substrate fabricated by using the sputtering method to form a scattering silicon membrane and an intermediate stopper layer. The intermediate layer material, which functions as an etching stopper, was CrNx. This material has demonstrated high performance in stencil mask fabrication, which is described in detail. The stress in the CrNx could be controlled within ±20 MPa by adjusting the deposition condition. The deposited silicon membrane stress could be easily adjusted in the range of 0–10 MPa. The etching selectivity, when the substrate backside etching was performed, was over 1000 under the low bias power. When the deep etching process was performed using SF6 and CHF3 etching gases for the mask pattern formation, the Si/CrNx etching selectivity was over 100 under the low bias power condition. The mask substrate, which is made up of a 2-μm-thick deposited silicon membrane and 0.35-μm-thick CrNx stopper layer, enabled an 8 in. stencil mask to be fabricated for use with electron projection lithography. In complementary mask split, we used “M-Split” which was developed by Selete and ISS as a pattern split software. © 2002 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

Complementary mask pattern split for 8 in. stencil masks in electron projection lithography

Hiroshi Yamashita, Kimitoshi Takahashi, Isao Amemiya, Kunio Takeuchi, Hideki Masaoka, Hiroshi Takenaka, and Masaki Yamabe

J. Vac. Sci. Technol. B 20, 3015 (2002); http://dx.doi.org/10.1116/1.1518019 (6 pages) | Cited 9 times

Online Publication Date: 9 December 2002

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We have improved the M-Split complementary mask pattern split program and our electron projection lithography (EPL) data conversion system to achieve a practical data processing time and data volume. The system was designed to rehierarchicalize the data, flattened after the subfield split, by extracting polygons that all have an identical shape as a cell. The M-Split stress check function was improved by using a normalized bending moment as a criterion. A clustered computing system was used to reduce the data processing time. The processing time for a complementary mask pattern split without rehierarchicalizing was reduced to 57 min by using the stress check function and a ten PC cluster system −3–10 times as fast as with commercially available EPL data conversion systems. We successfully fabricated a full-size 8 in. Si stencil mask consisting of 8000 subfields using the data for an actual 70 nm design-rule system on chip device to demonstrate the effectiveness of M-Split. With a higher performance PC cluster system and the rehierarchicalizing, we expect to further reduce the M-Split processing time to 10 min. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
85.40.Bh Computer-aided design of microcircuits; layout and modeling

Sub-50 nm stencil mask for low-energy electron-beam projection lithography

Masaki Yoshizawa

J. Vac. Sci. Technol. B 20, 3021 (2002); http://dx.doi.org/10.1116/1.1521739 (4 pages)

Online Publication Date: 9 December 2002

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Low-energy electron-beam-proximity projection lithography using a stencil mask is proposed for sub-70 nm node lithography. In this study, the anisotropic nature of Si wet etching is utilized for the fabrication of sub-50 nm stencil masks. A 20-nm-width aperture with a right angle and a 90-nm-width crossbeam with a smooth edge are obtained using silicon-on-insulator (SOI) wafers. 20-nm-thick Pt is calculated to be thick enough to block 2 keV electrons and it is shown that the evaporation of 10-nm-thick Pt from both sides of a membrane causes no significant degradation of sub-50 nm holes. It is estimated that a 25-nm-width aperture with a 100 nm pitch is feasible using an SOI wafer with an 18-nm-thick surface Si layer and a mask writer with a 50 nm resolution. © 2002 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
81.07.-b Nanoscale materials and structures: fabrication and characterization

Stencil reticle inspection using a deep ultraviolet microscope

Masashi Okada, Norihiro Katakura, and Shintaro Kawata

J. Vac. Sci. Technol. B 20, 3025 (2002); http://dx.doi.org/10.1116/1.1521734 (4 pages)

Online Publication Date: 9 December 2002

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A reticle inspection is one of the important issues in next-generation lithography systems. In this article, a feasibility of a deep ultraviolet (DUV) microscope is described for an inspection tool of a stencil-type reticle for an electron-beam stepper. The resolution and contrast of the DUV microscope are superior to those of the conventional optical microscope using a visible light illumination. Moreover, the DUV image clearly shows particulate contaminations inside the line pattern of the stencil reticle. Although simulation results show that the transmission image of the contact hole pattern is low contrast compared to that of the line pattern, it is possible to improve the visibility of the contact hole pattern. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
07.60.Pb Conventional optical microscopes
42.30.Va Image forming and processing
81.70.Fy Nondestructive testing: optical methods

Proximity and heating effects during electron-beam patterning of ultraviolet lithography masks

B. Lu, J. R. Wasson, E. J. Weisbrod, Z. Masnyj, P. J. S. Mangat, K. Nordquist, and D. Resnick

J. Vac. Sci. Technol. B 20, 3029 (2002); http://dx.doi.org/10.1116/1.1521745 (6 pages) | Cited 4 times

Online Publication Date: 9 December 2002

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Proximity effects and resist heating during high energy electron-beam (e-beam) patterning of extreme ultraviolet lithography (EUVL) mask were investigated for the 50 nm node and beyond. These effects were observed experimentally on both silicon wafers and standard 6025 photomasks coated with two different EUVL absorber stacks. Monte Carlo and resist simulations were used for proximity effect correction and resist heating effect verification. The estimated temperature change during electron-beam writing was also attempted using the finite element method. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Efficient phase defect modeling using domain decomposition methods

Konstantinos Adam and Andrew R. Neureuther

J. Vac. Sci. Technol. B 20, 3035 (2002); http://dx.doi.org/10.1116/1.1520560 (5 pages) | Cited 1 time

Online Publication Date: 9 December 2002

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The domain decomposition method is adapted for the simulation of alternating phase shifting masks that bear phase defects. The scattered signal from a defective mask layout is approximated by the sum of the defect-free signal and a perturbation signal that results from a rigorous electromagnetic simulation of an isolated defect. The perturbation signals are generated off-line by creating a database of scattered electromagnetic fields from various relevant phase defects. Comparison of images of defective masks resulting from the adapted domain decomposition method and from rigorous mask simulations of the complete defective masks show that the normalized mean square error of the method is less than 0.3%. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
03.50.De Classical electromagnetism, Maxwell equations

Fabrication of x-ray masks using evaporated electron sensitive layers for back patterning of membranes

Yousef Awad, Eric Lavallee, Jacques Beauvais, Dominique Drouin, Pan Yang, David Turcotte, and Lau Kien Mun

J. Vac. Sci. Technol. B 20, 3040 (2002); http://dx.doi.org/10.1116/1.1523399 (4 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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A process aimed at fabricating proximity x-ray lithography masks is presented. In this technique, the Ta absorber layer is deposited and patterned on the back side of the membrane and nonspin-coated electron sensitive layers were used in order to achieve high resolution patterning of this absorber. The advantages gained by this approach include a reduction of the membrane temperature during the plasma etching step of the absorber patterns without using any cooling gas. This temperature reduction results from the direct contact of the membrane with a cooling plate. This approach also allows increased protection of the absorber patterns from contamination during exposure of the mask. A third advantage is that the smooth surface of the mask exposed to the wafer in the x-ray lithography stepper may also make it possible to reduce the gap between wafer and mask, thus achieving increased resolution with the x-ray lithography process. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Submicron thermocouple measurements of electron-beam resist heating

Dachen Chu, D. Taner Bilir, R. Fabian W. Pease, and Kenneth E. Goodson

J. Vac. Sci. Technol. B 20, 3044 (2002); http://dx.doi.org/10.1116/1.1523023 (3 pages) | Cited 6 times

Online Publication Date: 9 December 2002

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Pattern distortion caused by resist heating is believed to contribute significantly to errors in feature size and pattern placement. A number of models have been proposed to predict the temperature rise of resist heating but experimental results are scarce. We fabricated and calibrated thin film gold/nickel thermocouples with (400 nm)2 junction size and used these to measure work-piece heating during electron-beam exposure. Irradiation by a 15 kV electron beam of 600 nA and 2 μm radius caused a temperature rise of 70 K, about 15% lower than the calculated result. The discrepancy may be due to the differences between the energy deposition profiles used in modeling and those prevailing in the experiments. © 2002 American Vacuum Society.
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07.20.Dt Thermometers
61.80.Fe Electron and positron radiation effects
85.40.Hp Lithography, masks and pattern transfer

Thermal modeling of extreme ultraviolet and step and flash imprint lithography substrates during dry etch

E. J. Weisbrod, W. J. Dauksher, D. Zhang, S. Rauf, P. J. S. Mangat, P. L. G. Ventzek, K. H. Smith, S. B. Clemens, C. J. Martin, and R. L. Engelstad

J. Vac. Sci. Technol. B 20, 3047 (2002); http://dx.doi.org/10.1116/1.1523028 (6 pages) | Cited 1 time

Online Publication Date: 9 December 2002

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Lithographic mask development requires that attention be paid to all aspects of mask manufacturing. As feature sizes and tolerable errors decrease, processes must be investigated for their effect on final mask quality. One potential area of concern for both extreme ultraviolet lithography (EUVL) and step and flash imprint lithography (SFIL) is temperature control during pattern transfer via dry etch. In particular, the etch tool fixturing for 6 in.×6 in.×0.25 in. (6025) plates used in EUVL development typically do not have provisions for backside helium (He) cooling, and this may allow the substrate to reach an unacceptably high temperature. This article presents the results of thermal finite element modeling and compares them with temperature data gathered during dry etch. Additionally, fused silica wafers were modeled as they are being used in SFIL template development and can also be used to evaluate the effects of backside He cooling. Substrates were etched in inductively coupled plasma and/or reactive ion etch processes. In situ measurements were made using adhesive temperature strips applied to the substrates that provided both transient and steady state temperature information. Results showed 6025 plate temperatures remained within acceptable limits for typical etch process times. Fused silica wafers did not reach temperatures of concern when backside He cooling was incorporated. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
02.70.Dh Finite-element and Galerkin methods

Electron projection lithography mask format layer stress measurement and simulation of pattern transfer distortion

P. L. Reu, C.-F. Chen, R. L. Engelstad, E. G. Lovell, T. Bayer, J. Greschner, S. Kalt, H. Weiss, O. R. Wood, and R. S. Mackay

J. Vac. Sci. Technol. B 20, 3053 (2002); http://dx.doi.org/10.1116/1.1521732 (5 pages) | Cited 6 times

Online Publication Date: 9 December 2002

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Electron projection lithography (EPL) is one of the leading candidates for the sub-65 nm lithography node. The development of a low-distortion mask is critical to the success of EPL. This article proposes and analyzes two new EPL mask formats described as a “corrugated-continuous membrane mask” and a “carbon-continuous membrane mask.” Novel process flows for the manufacture of these masks have been developed at Team Nanotec GmbH. Resonant frequency stress measurements of the ultrathin membrane bilayers were completed and subsequently used in the finite element simulation of the mask fabrication and pattern transfer. The new mask types have the benefits of the lower distortions of a typical continuous membrane mask, but maintain the advantage of the higher throughput stencil format because of the ultrathin films. In addition, the proposed masks remove the need for pattern splitting typically used with complementary systems. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Advanced die-to-database inspection technique for embedded attenuated phase shift mask

Kyoji Yamashita, Ikunao Isomura, Hideo Tsuchiya, Toshiyuki Watanabe, Hiromu Inoue, Satoshi Endo, and Masakazu Tokita

J. Vac. Sci. Technol. B 20, 3058 (2002); http://dx.doi.org/10.1116/1.1520570 (5 pages)

Online Publication Date: 9 December 2002

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We have developed a deep ultraviolet die-to-database inspection system MC-3500 for the 130 nm node and beyond. The system involves comparison of a mask image scanned at a wavelength of 257 nm and a reference data calculated from complex amplitude of objects with 200 Mpixel/s throughput. An approximation of Hopkins formulation in the region of a large partial coherence factor gives a nonlinear filtering scheme for embedded attenuated phase shift mask (EPSM). The nonlinear filtering was evaluated for intensity fidelity of the reference image using comparison with Hopkins formulation. Evaluation results show that phase optimization is effective in eliminating excessive image ringing and the minimum feature size to maintain fidelity is found to be over 3 pixels. The technique is promising in applications to high-transmission EPSM. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
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Two-dimensional dopant profiling of ultrashallow junctions by electron holography

Alexander E. Thesen, Bernhard G. Frost, and David C. Joy

J. Vac. Sci. Technol. B 20, 3063 (2002); http://dx.doi.org/10.1116/1.1523022 (4 pages) | Cited 6 times

Online Publication Date: 9 December 2002

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Electron holography using a transmission electron microscope equipped with a Moellenstedt biprism has emerged as a viable technique for creating two-dimensional voltage maps of semiconductor devices. We are presenting an introduction to this dopant profiling method. Practical details are given on sample preparation, instrumentational considerations, and data interpretation. © 2002 American Vacuum Society.
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68.35.Ct Interface structure and roughness
61.72.S- Impurities in crystals
61.05.jp Electron holography
68.37.Lp Transmission electron microscopy (TEM)
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.Tv Field effect devices

Liquid immersion lens technology applied to laser voltage probing of 130 nm process technology devices

Nagamani Nataraj, Herve Deslandes, William Lo, Travis Eiles, and Patrick Pardy

J. Vac. Sci. Technol. B 20, 3067 (2002); http://dx.doi.org/10.1116/1.1523406 (4 pages)

Online Publication Date: 9 December 2002

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Liquid immersion lens technology has been applied to internal-node, through-silicon probing of 130 nm integrated circuits. A 100×, 1.3 numerical aperture (NA) objective with 100 μm working distance was specifically designed for this application. An optical resolution of 500 nm is achieved using 1064 nm wavelength light, ≈30% improvement over the standard, air immersion, 0.85 NA lens currently used. Significant improvements in wave form quality were also achieved. A >2× signal to noise ratio improvement is demonstrated on 130 nm technology devices. Probing of 90 nm technology devices indicate that laser voltage probing with liquid immersion lens technology and phase-sensitive detection is extensible to this process node. © 2002 American Vacuum Society.
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85.30.De Semiconductor-device characterization, design, and modeling
85.40.Qx Microcircuit quality, noise, performance, and failure analysis

Beam alignment for scanning beam interference lithography

Carl G. Chen, Ralf K. Heilmann, Chulmin Joo, Paul T. Konkola, G. S. Pati, and Mark L. Schattenburg

J. Vac. Sci. Technol. B 20, 3071 (2002); http://dx.doi.org/10.1116/1.1523402 (4 pages) | Cited 7 times

Online Publication Date: 9 December 2002

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By interfering two small diameter Gaussian laser beams, scanning beam interference lithography (SBIL) is capable of patterning linear gratings and grids in resist while controlling their spatial phase distortions to the nanometer level. Our tool has a patterning area that is up to 300 mm in diameter. The motive for developing SBIL is to provide the semiconductor industry with a set of absolute metrology standards, but the technology is easily adaptable to other important applications such as the making of high precision optical encoders. In this article, we describe a system for carrying out automated beam alignment for SBIL. Our design goals require tight alignment tolerances, where beam position and angle alignment errors must be controlled to ∼10 μm and ∼10 μrad, respectively. We describe our system setup, and discuss the so-called iterative beam alignment principle, focusing specifically on deriving a mathematical formalism that can guide the development of similar systems in the future. Repeatability experiments demonstrate that our system fulfills the alignment requirements for nanometer-level SBIL writing. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Precision fringe metrology using a Fresnel zone plate

Chulmin Joo, G. S. Pati, Carl G. Chen, Paul T. Konkola, Ralf K. Heilmann, Mark L. Schattenburg, Alexander Liddle, and Erik H. Anderson

J. Vac. Sci. Technol. B 20, 3075 (2002); http://dx.doi.org/10.1116/1.1523018 (5 pages)

Online Publication Date: 9 December 2002

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In scanning beam interference lithography, a resist-coated substrate is scanned under phase-locked interfering beams to pattern large gratings or grids with nanometer level distortions. To achieve design goals, it is required to measure the spatial period, phase, and rotation of the interference fringes in real-time with high precision. In this article, we report the use of a Fresnel zone plate to characterize interference fringes. With properly controlled errors, it should enable us to achieve high precision measurement of fringe characteristics for a wide range of fringe periods. The mathematical model, details of the metrological procedure, and experimental results are presented. © 2002 American Vacuum Society.
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07.60.Ly Interferometers
42.79.Ci Filters, zone plates, and polarizers
85.40.Hp Lithography, masks and pattern transfer

Accurate reflectometry for extreme-ultraviolet lithography at the National Institute of Standards and Technology

S. Grantham, C. Tarrio, and T. B. Lucatorto

J. Vac. Sci. Technol. B 20, 3080 (2002); http://dx.doi.org/10.1116/1.1526351 (5 pages)

Online Publication Date: 9 December 2002

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The most demanding application of extreme ultraviolet multilayer optics is in lithography. The optics in current alpha-class tools are large, and the multilayer coatings must have both optimized reflectance and extremely high uniformity. At the National Institute of Standards and Technology we have recently commissioned a very large sample chamber at the Synchrotron Ultraviolet Radiation Facility storage ring. This dedicated reflectometer is capable of carrying out complete surface maps of alpha- and beta-class tools for the extreme-ultraviolet lithography community. We have conducted a rigorous characterization of the system by varying the output spectrum of our storage ring in conjunction with multiple filter and detector combinations. This exercise has resulted in an accurate model of the effects of out-of-band radiation and scattering on the measured reflectivity. The model can be directly applied to raw data measured under any typical operating conditions to reduce the uncertainty of our measurements to 0.3%. We will report the findings of the characterization along with the resulting model and sample measurements, which show that the requisite accuracy and precision in reflectivity required for beta-class tools has been achieved. We will also present measurements of large-sized curved multilayer samples. Finally, we will report on an upgrade to the beamline’s monochromator, which is currently in progress. This will improve the stability that will yield the wavelength precision needed for all planned extreme-ultraviolet lithography tools. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
07.60.Hv Refractometers and reflectometers
42.79.Wc Optical coatings

Technique for preparation of precise wafer cross sections and applications to electron beam lithography of poly(methylmethacrylate) resist

Wenchuang Hu, Tatyana Orlova, and Gary H. Bernstein

J. Vac. Sci. Technol. B 20, 3085 (2002); http://dx.doi.org/10.1116/1.1518020 (4 pages) | Cited 3 times

Online Publication Date: 9 December 2002

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We have developed a method of cross-sectioning silicon wafers with high placement precision. It is implemented by using optical lithography and deep plasma high aspect ratio etching of a thin line, which is used as the breaking axis. This technique is then applied to cross-sectional scanning electron microscopy (SEM) studies of sub-50 nm electron beam lithography in (poly)methylmethacrylate resist. We also report the development of a process for protecting the resist during SEM examination. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
81.65.Cf Surface cleaning, etching, patterning

Electromigration in passivated Cu interconnects studied by transmission x-ray microscopy

G. Schneider, M. A. Meyer, G. Denbeaux, E. Anderson, B. Bates, A. Pearson, C. Knöchel, D. Hambach, E. A. Stach, and E. Zschech

J. Vac. Sci. Technol. B 20, 3089 (2002); http://dx.doi.org/10.1116/1.1523403 (6 pages) | Cited 6 times

Online Publication Date: 9 December 2002

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Time-resolved x-ray microscopy studies of the electromigration in inlaid Cu line/via structures were performed on focused-ion-beam-prepared cross sections of an advanced interconnect layer system. Multiple x-ray images were recorded at 1.8 keV photon energy while stressing the passivated Cu structures with an applied current. The image sequences show that void formation is a dynamic process, with voids being observed to nucleate and grow within the Cu via and migrate towards the via sidewall. Correlation of the real time x-ray microscopy images with postmortem high voltage transmission electron and scanning electron micrographs indicates that the void nucleation occurs at grain boundaries in the copper, and that the voids migrate along these grain boundaries during electromigration. By taking multiple images at different viewing angles, the three-dimensional arrangement of an interconnect stack with Cu line / via structures was reconstructed. In future studies time-resolved tomography will be used to visualize void dynamics within the volume, thereby identifying pathways for Cu diffusion. © 2002 American Vacuum Society.
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85.40.Ls Metallization, contacts, interconnects; device isolation
66.30.Qa Electromigration
68.37.Yz X-ray microscopy
61.72.Qq Microscopic defects (voids, inclusions, etc.)
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
61.72.Mm Grain and twin boundaries

High precision stress measurement of ion projection lithography mask membranes

José L. Torres, J. C. Wolfe, Paul Ruchhoeft, Timothy F. Kennedy, Joseph Podolski, Karl Kragler, Albrecht Ehrmann, R. Kaesmaier, and H. Löschner

J. Vac. Sci. Technol. B 20, 3095 (2002); http://dx.doi.org/10.1116/1.1515304 (4 pages) | Cited 2 times

Online Publication Date: 9 December 2002

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In this article, we describe an instrument for measuring the mean stress of large-area membranes for ion projection lithography (IPL) stencil masks. The apparatus incorporates two improvements over the conventional bulge technique, where the deflection at the center of a membrane is measured as a function of differential pressure across it, that provide a hundred-fold improvement in the precision of the measurement. The first is to simply place the membrane, without an o-ring or mechanical clamp, on an optically flat silicon ring separating the two pressure chambers. This eliminates the in-plane mounting forces that previously resulted in 1–2 MPa errors. The close contact between the integral ring supporting the mask and the silicon ring provides an adequate vacuum seal between the chambers. The second improvement is to provide an isothermal environment to reduce stress errors due to temperature variations in the membrane. As a result, the measured stress is independent of temperature and the standard deviation (1σ̣) of measured stress is 0.02 MPa. © 2002 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
46.80.+j Measurement methods and techniques in continuum mechanics of solids

Adaptive alignment of photomasks for overlay improvement

C.-f. Chen, R. L. Engelstad, E. G. Lovell, D. L. White, O. R. Wood, M. K. Smith, and L. R. Harriott

J. Vac. Sci. Technol. B 20, 3099 (2002); http://dx.doi.org/10.1116/1.1515312 (7 pages) | Cited 3 times

Online Publication Date: 9 December 2002

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The International Technology Roadmap for Semiconductors defines a 23 nm overlay error budget at the 65 nm technology node by the year 2007. To meet the stringent requirement, a proof-of-concept adaptive alignment strategy for overlay improvement has been proposed. By positioning a photomask in an adaptive holder that utilizes piezoelectric actuators and passive fixture supports, overlay registration can be significantly improved by deforming the mask with appropriate forces. The desired forces were calculated by solving an inverse problem in which unit loads are applied at actuator sites to determine the mark displacement sensitivities. Tensile loads almost always appeared in the calculated results, indicating a design issue requiring the bonding of corresponding actuators to the mask. Precompressing the mask and superimposing the calculated forces counteracted the tensile loads, but caused degradation of the exact alignment. Design optimization was exploited subsequently to minimize the preload-induced offset residuals at the alignment marks and across the mask. The proposed adaptive alignment procedure is capable of controlling the overlay errors within specified tolerances and can be readily applied to a variety of reticle formats and sizes. © 2002 American Vacuum Society.
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81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
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Advanced time-multiplexed plasma etching of high aspect ratio silicon structures

M. A. Blauw, G. Craciun, W. G. Sloof, P. J. French, and E. van der Drift

J. Vac. Sci. Technol. B 20, 3106 (2002); http://dx.doi.org/10.1116/1.1518018 (5 pages) | Cited 18 times

Online Publication Date: 9 December 2002

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An advanced, time-multiplexed plasma etch process for high aspect ratio structures is presented. Compared to the two pulse Bosch process, the technique consists of a sequence of three pulses. The third pulse is tailored to improved depassivation of the trench bottom prior to each etch pulse. Several depassivation chemistries are explored: O2, CO2, and SO2. In a further extension the bias voltage is also pulsed, with the aim to balance the radical and ion-enhanced components in the passivation of the sidewalls and trench bottom. The process extensions lead to improved mask selectivity and substantial range for profile control from fully anisotropic to strongly negatively tapered. The maximum aspect ratio obtained in the Bosch process could not be improved, because the ion angular distribution probably remains the limiting factor. The role of the ions in passivation and etching has been quantified in separate experiments. © 2002 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
81.65.Rv Passivation
52.77.Bn Etching and cleaning

Profile simulation of gas chopping based etching processes

B. E. Volland, Tzv. Ivanov, and I. W. Rangelow

J. Vac. Sci. Technol. B 20, 3111 (2002); http://dx.doi.org/10.1116/1.1520572 (7 pages) | Cited 5 times

Online Publication Date: 9 December 2002

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A simulation program based on a phenomenological surface etching reaction model and on a reactant transport model including shadowing and diffuse particle reflection at the sidewalls was developed to investigate the dependence of the etching rate and profile quality of gas chopping deep reactive ion etching processes on process parameters and sample temperature. The simulations are in good agreement with the experimental results. The dependence of the heating characteristics on the geometry (area, thickness) of teeny microelectromechanical systems devices or membrane-like silicon samples during microstructuring by means of plasma etching was investigated using finite element simulations. It was found that membrane-like samples are considerably heated unless the membrane area is sufficiently small (<≈5 mm ϕ) and/or is sufficiently thick (≈500 μm). © 2002 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
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