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Nov 2003

Volume 21, Issue 6, pp. L9-3185

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Synthesis of oxide nanoparticles embedded in polyimide

Yoon Chung, Hwan Pil Park, Hyung Jun Jeon, C. S. Yoon, Sung K. Lim, and Young-Ho Kim

J. Vac. Sci. Technol. B 21, L9 (2003); http://dx.doi.org/10.1116/1.1624269 (3 pages) | Cited 18 times

Online Publication Date: 7 November 2003

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© 2003 American Vacuum Society.
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81.07.Bc Nanocrystalline materials
82.35.Np Nanoparticles in polymers
81.16.Be Chemical synthesis methods
61.46.-w Structure of nanoscale materials

Nanometer-period gratings in hydrogen silsesquioxane fabricated by electron beam lithography

Michael J. Word, Ilesanmi Adesida, and Paul R. Berger

J. Vac. Sci. Technol. B 21, L12 (2003); http://dx.doi.org/10.1116/1.1629711 (4 pages) | Cited 27 times

Online Publication Date: 18 November 2003

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Hydrogen silsesquioxane (HSQ) is a high-resolution negative-tone inorganic resist for electron beam lithography. Investigations on the smoothness of the surfaces of thin films (less than 100 nm thick) have been conducted for nanolithography applications. It is demonstrated that films at thicknesses down to 25 nm have very low rms roughness and are defect free. Using 50 kV electron beam lithography, we demonstrate the achievement of isolated 6-nm-wide lines and 27 nm period gratings in 30 nm HSQ films on silicon substrates. These results are superior to those achieved with poly(methylmethacrylate) resist and demonstrates the versatility of HSQ for nanolithography. © 2003 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
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Atomic layer deposition of metal and nitride thin films: Current research efforts and applications for semiconductor device processing

H. Kim

J. Vac. Sci. Technol. B 21, 2231 (2003); http://dx.doi.org/10.1116/1.1622676 (31 pages) | Cited 132 times

Online Publication Date: 3 November 2003

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Atomic layer deposition (ALD) has been studied for several decades now, but the interest in ALD of metal and nitride thin films has increased only recently, driven by the need for highly conformal nanoscale thin films in modern semiconductor device manufacturing technology. ALD is a very promising deposition technique with the ability to produce thin films with excellent conformality and compositional control with atomic scale dimensions. However, the applications of metals and nitrides ALD in semiconductor device processes require a deeper understanding about the underlying deposition process as well as the physical and electrical properties of the deposited films. This article reviews the current research efforts in ALD for metal and nitride films as well as their applications in modern semiconductor device fabrication. © 2003 American Vacuum Society.
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01.30.Rr Surveys and tutorial papers; resource letters
68.55.-a Thin film structure and morphology
73.61.At Metal and metallic alloys
73.61.Ey III-V semiconductors
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Adhesion and stiction: Mechanisms, measurement techniques, and methods for reduction

Bharat Bhushan

J. Vac. Sci. Technol. B 21, 2262 (2003); http://dx.doi.org/10.1116/1.1627336 (35 pages) | Cited 115 times

Online Publication Date: 24 November 2003

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Solid–solid adhesion occurs at contacting asperities in two contacting solids. A thin liquid film with a small contact angle, present at the interface, can result in the so-called liquid-mediated adhesion. This may result in high adhesion during normal pull and high static friction during sliding, both commonly referred to as “stiction.” The problem of high stiction is especially important in an interface involving two very smooth surfaces under lightly loaded conditions. This article provides a critical and comprehensive review of mechanisms of adhesion and stiction, various measurement techniques, and methods used to reduce stiction in magnetic storage devices and micro/nanoelectromechanical systems. © 2003 American Vacuum Society.
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62.20.Qp Friction, tribology, and hardness
81.40.Pq Friction, lubrication, and wear
68.35.Np Adhesion
68.35.Gy Mechanical properties; surface strains
46.55.+d Tribology and mechanical contacts
68.03.Cd Surface tension and related phenomena
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
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Demonstrations of electronic pattern switching and 10× pattern demagnification in a maskless microion-beam reduction lithography system

V. V. Ngo, B. Akker, K. N. Leung, Isaac Noh, K. L. Scott, and S. Wilde

J. Vac. Sci. Technol. B 21, 2297 (2003); http://dx.doi.org/10.1116/1.1615978 (7 pages) | Cited 1 time

Online Publication Date: 24 November 2003

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A proof-of-principle ion projection lithography (IPL) system called maskless microion-beam reduction lithography (MMRL) has been developed and tested at the Lawrence Berkeley National Laboratory for future integrated circuits manufacturing and thin-film media patterning [V. V. Ngo et al., J. Vac. Sci. Technol. B 17, 6 (1999)]. This MMRL system is aimed at completely eliminating the first stage of the conventional IPL system [G. Stengl et al., J. Vac. Sci. Technol. B 10, 2824 (1992)] that contains the complicated beam optics design in front of the stencil mask and the mask itself. It consists of a multicusp rf plasma generator, a multibeamlet pattern generator, and an all-electrostatic ion optical column. Results from ion beam exposures on poly(methymethacrylate) and Shipley UVII-HS resists using 75 keV H+ are presented in this article. Proof-of-principle electronic pattern switching together with 10× reduction ion optics (using a pattern generator made of nine 50 μm switchable apertures) has been performed and is reported in this article. In addition, the fabrication of a microfabricated pattern generator [K. L. Scott et al., J. Vac. Sci. Technol. B 18, 6 (2000)] on a silicon on insulator membrane is also presented. © 2003 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Critical dimension control of a plasma etch process by integrating feedforward and feedback run-to-run control

Chadi El Chemali, Jim Freudenberg, Matt Hankinson, Wenli Collison, and Tom Ni

J. Vac. Sci. Technol. B 21, 2304 (2003); http://dx.doi.org/10.1116/1.1615983 (9 pages) | Cited 2 times

Online Publication Date: 24 November 2003

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In this article, we have derived a run-to-run (R2R) control design technique that integrates feedforward and feedback control on the etch process. The purpose is to minimize the effect of an oxygen flow disturbance during the resist trim on the polysilicon critical dimension (CD) after the main etch. The R2R controller manipulates the resist trim time based on feedforward measurements of the resist CD at the end of the lithography and feedback measurements from polysilicon CD at the end of the etch process. The purpose of the feedforward measurement is to adjust the resist trim time using a model of the relation between trim time, resist CD before the resist trim and polysilicon CD after the main etch. The purpose of the feedback measurement is to adjust this model to compensate for the oxygen flow disturbance during the resist trim. The resulting controller is called feedforward/feedback (FF/FB) controller. The FF/FB controller is tested using simulations and experiments conducted on an etch tool manufactured by Lam Research. The simulations and experimental results show that the FF/FB controller attenuates linear drift and shift in the polysilicon CD caused by the oxygen flow disturbance. Moreover, the results quantify the significant benefit of integrating feedforward and feedback control in addition to only using a feedforward control in minimizing the polysilicon CD deviations from the etch target. © 2003 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning

Nanoparticle beam formation and investigation of gold nanostructured films

A. Khabari, F. K. Urban, P. Griffiths, I. Petrov, Y.-W. Kim, and C. Bungay

J. Vac. Sci. Technol. B 21, 2313 (2003); http://dx.doi.org/10.1116/1.1615985 (6 pages) | Cited 2 times

Online Publication Date: 24 November 2003

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The object of the present work is the formation of a nearly collimated beam of gold nanoparticles with a high deposition rate and investigation of the resulting nanostructured gold film deposited onto (111) silicon substrates. The shape, size, and orientation of nanostructured gold crystals were analyzed by transmission electron microscopy and x-ray diffraction, and optical properties were investigated by ellipsometry. It was found that the optical properties of gold nanostructured films are completely different from the optical properties of conventionally deposited films reported in the literature. It was also found most crystals were grown on (111) plane with an indication of an expitaxial contact between the film and the substrate. The crystallite size was approximately 8 nm in diameter. High-resolution transmission electron microscopy also revealed that the gold nanophase crystals are cubo-octahedral with larger surface areas (octahedral part) at (111) orientation. © 2003 American Vacuum Society.
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68.55.-a Thin film structure and morphology
78.66.Bz Metals and metallic alloys
68.37.Lp Transmission electron microscopy (TEM)

Thermal stability of Pd supported on single crystalline SiO2 thin films

B. K. Min, A. K. Santra, and D. W. Goodman

J. Vac. Sci. Technol. B 21, 2319 (2003); http://dx.doi.org/10.1116/1.1617282 (5 pages) | Cited 11 times

Online Publication Date: 24 November 2003

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The effect of annealing temperature on a model Pd/SiO2 catalyst has been investigated using Auger electron spectroscopy (AES) and scanning tunneling microscopy. Pd clusters on a single crystalline SiO2 thin film are not altered with respect to size or shape upon heating to 700 K; however, interdiffusion and sintering of the Pd clusters take place between 750 and 1050 K. At 1000 K, AES data imply the formation of Pd–silicide. Above 1050 K, desorption of Pd occurs concomitant with the decomposition of SiO2. © 2003 American Vacuum Society.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.40.Gh Other heat and thermomechanical treatments
68.55.-a Thin film structure and morphology
68.35.Fx Diffusion; interface formation
61.72.Cc Kinetics of defect formation and annealing
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.43.Mn Adsorption kinetics

Photoluminescence quenching mechanisms in GaInNAs/GaAs quantum well grown by solid source molecular beam epitaxy

T. K. Ng, S. F. Yoon, W. J. Fan, W. K. Loke, S. Z. Wang, and S. T. Ng

J. Vac. Sci. Technol. B 21, 2324 (2003); http://dx.doi.org/10.1116/1.1617284 (5 pages) | Cited 8 times

Online Publication Date: 24 November 2003

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The photoluminescence (PL) quenching characteristics of a thermal-annealed ∼7 nm GaInNAs/GaAs quantum well (QW) with In=30% and N=1.5% were studied from 4 to 150 K. It is found that the integrated PL intensity versus temperature characteristic can be well fitted by a double activation energy model. One of the centers with low activation energy EB=9 meV is thought to originate from a localized state that traps carriers at temperatures below ∼100 K. Therefore, EB is the thermal energy required to activate the localized state carriers to the e1 state of the GaInNAs QW. Another center with larger activation energy EA=38 meV has a more significant PL quenching effect at temperatures above ∼120 K. This center is possibly contributed by the EL6 defect level in the GaAs barrier layer, as a result of low V/III ratio of 15, and low growth temperature of 450 °C. © 2003 American Vacuum Society.
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78.67.De Quantum wells
78.55.Cr III-V semiconductors
73.21.Fg Quantum wells
61.72.Cc Kinetics of defect formation and annealing
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Wavelet monitoring of plasma etching

Byungwhan Kim, Won Sun Choi, and Myo Teak Lim

J. Vac. Sci. Technol. B 21, 2329 (2003); http://dx.doi.org/10.1116/1.1617285 (5 pages) | Cited 2 times

Online Publication Date: 24 November 2003

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In device manufacturing sites, plasma states are conventionally monitored by measuring the etch rate. A means for plasma monitoring is presented. This was accomplished by characterizing profile variations by means of a discrete wavelet transformation (DWT). The sensitivity of wavelet coefficients was evaluated as a function of plasma faults, which were simulated with the variations in the process parameters, including radio frequency source power, bias power, and SF6 flow rate. For each plasma fault, wavelet sensitivity was conducted separately for vertical, lateral, and overall profiles. Wavelet coefficients demonstrated high sensitivity to detecting plasma faults. Improved sensitivity was obtained as they were monitored individually. Compared to conventional etch rate- or profile anisotropy-based sensitivity, the wavelet-based one was considerably enhanced. By the demonstrated high sensitivity, the proposed DWT-based profile monitoring can be effectively used to monitor and diagnose plasma processes. © 2003 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning

Focused ion beam milling of diamond: Effects of H2O on yield, surface morphology and microstructure

D. P. Adams, M. J. Vasile, T. M. Mayer, and V. C. Hodges

J. Vac. Sci. Technol. B 21, 2334 (2003); http://dx.doi.org/10.1116/1.1619421 (10 pages) | Cited 27 times

Online Publication Date: 24 November 2003

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The effects of H2O vapor introduced during focused ion beam (FIB) milling of diamond(100) are examined. In particular, we determine the yield, surface morphology, and microstructural damage that results from FIB sputtering and H2O-assisted FIB milling processes. Experiments involving 20 keV Ga+ bombardment to doses ∼1018 ions/cm2 are conducted at a number of fixed ion incidence angles, θ. For each θ selected, H2O-assisted ion milling shows an increased material removal rate compared with FIB sputtering (no gas assist). The amount by which the yield is enhanced depends on the angle of incidence with the largest difference occurring at θ=75°. Experiments that vary pixel dwell time from 3 μs to 20 ms while maintaining a fixed H2O gas pressure demonstrate the additional effect of beam scan rate on yield for gas-assisted processes. Different surface morphologies develop during ion bombardment depending on the angle of ion incidence and the presence/absence of H2O. In general, a single mode of ripples having a wave vector aligned with the projection of the ion beam vector forms for θ as high as 70°. H2O affects this morphology by lowering the ripple onset angle and decreasing the ripple wavelength. At high angles of incidence (θ>70°) a step/terrace morphology is observed. H2O-assisted milling at θ>70° results in a smoother stepped surface compared with FIB sputtering. Transmission electron microscopy shows that the amorphized thickness is reduced by 20% when using H2O-assisted FIB milling. © 2003 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
68.35.B- Structure of clean surfaces (and surface reconstruction)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.37.Lp Transmission electron microscopy (TEM)

Electric field effects in single semiconductor quantum dots observed by scanning tunneling luminescence

U. Håkanson, H. Håkanson, M. K.-J. Johansson, L. Samuelson, and M.-E. Pistol

J. Vac. Sci. Technol. B 21, 2344 (2003); http://dx.doi.org/10.1116/1.1620511 (4 pages) | Cited 3 times

Online Publication Date: 24 November 2003

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Scanning tunneling microscopy (STM) and scanning tunneling luminescence were used to correlate the topography with the emission spectra from individual self-assembled InP quantum dots (QDs). We have investigated in detail how the electric field induced by the STM tip affects the emission from the QDs. This was done when exciting a QD, by altering the bias for constant current, by altering the current for constant bias, or by changing the tip position. An increased bias (increased electric field) leads to Stark shift of the QD emission, whereas a larger tunneling current results in state filling of the emission. Furthermore, when exciting the QD, the position of the STM tip is shown to have large effects on the QD luminescence. © 2003 American Vacuum Society.
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78.67.Hc Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
73.21.La Quantum dots
78.55.Cr III-V semiconductors
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
78.60.Fi Electroluminescence
78.20.Jq Electro-optical effects

High aspect ratio nano-oxidation of silicon with noncontact atomic force microscopy

N. Clement, D. Tonneau, B. Gely, H. Dallaporta, V. Safarov, and J. Gautier

J. Vac. Sci. Technol. B 21, 2348 (2003); http://dx.doi.org/10.1116/1.1620513 (4 pages) | Cited 7 times

Online Publication Date: 24 November 2003

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We report the formation of high aspect ratio ∼0.3 (height/width) oxide features with noncontact mode atomic force microscopy assisted lithography. The process requires high humidity levels, series of short pulses <100 ns, high voltage level >25 V, a tip oscillation amplitude ∼20 nm, and feedback “on.” We also show that the application of a voltage at magnitude higher than a certain limit damages the surface. © 2003 American Vacuum Society.
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81.16.Pr Micro- and nano-oxidation
81.65.Mq Oxidation
81.16.Ta Atom manipulation
81.16.Nd Micro- and nanolithography
68.37.Ps Atomic force microscopy (AFM)
85.40.Hp Lithography, masks and pattern transfer

20 nm polysilicon gate patterning and application in 36 nm complementary metal–oxide–semiconductor devices

Qiuxia Xu, Qian He, Ming Liu, Yuying Zhao, Baoqing Chen, Zhengsheng Han, Tianchun Ye, and Dexin Wu

J. Vac. Sci. Technol. B 21, 2352 (2003); http://dx.doi.org/10.1116/1.1620514 (8 pages) | Cited 4 times

Online Publication Date: 24 November 2003

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Plasma etching with high selectivity and anisotropy for 20 nm poly-Si gate patterning on EOT of 1.4 nm gate oxynitride is developed in a Cl2/HBr/O2 gas mixture successfully. Direct write e-beam lithography is used for an SAL601 chemically amplified negative resist pattern. Using a combination of resist ashing and TEOS hard mask trimming process, sub-25 nm TEOS SiO2 mask patterns are obtained in the control. Various gas mixtures based on Cl2, HBr, and O2 have been used to study the etching characteristics of poly-Si on EOT of 1.4 nm gate oxynitride. The O2 content as well as HBr are very sensitive to etch rate, selectivity, and the protection of the sidewalls of polysilicon, owing to SiO2-like film, SiOxBry, formed on the etched surface confirmed by x-ray photoelectron spectroscopy. And the ratio of Cl2/HBr/O2 in gas mixture is also tightly related to the etching profile. Using a four-step etching process under optimum conditions the selectivity of poly-Si to oxide is much higher than 500:1, in fact, after polysilicon etching the net deposition of oxide is observed, and no damage on the active area beside the gates for EOT of 1.4 nm gate oxide is observed, too. The etching profile of the 20 nm poly-Si gate pattern is perfectly vertical and an overall narrowing by an estimated 5 nm is observed for oxide masked poly-Si gate etching. The possible mechanism is discussed. This etching process combined with resist ashing and the TEOS hard mask trimming process are implemented successfully to the fabrication of high performance 36 nm gate length complementary metal–oxide–semiconductor (CMOS) devices and 42 nm gate length 32 frequency dividers with 57 stage/201 stage CMOS ring oscillators embedded, the EOT of gate oxynitrid is 1.4 nm, and very good results are obtained. © 2003 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
81.16.Rf Micro- and nanoscale pattern formation
81.05.Cy Elemental semiconductors
81.65.Cf Surface cleaning, etching, patterning
79.60.Jv Interfaces; heterostructures; nanostructures

Switching characteristics of electrostatically actuated miniaturized micromechanical metallic cantilevers

W. H. Teh, J. K. Luo, M. R. Graham, A. Pavlov, and C. G. Smith

J. Vac. Sci. Technol. B 21, 2360 (2003); http://dx.doi.org/10.1116/1.1620515 (8 pages) | Cited 1 time

Online Publication Date: 24 November 2003

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We report the fabrication and characterization of the smallest near-curvature-free electrostatically actuated Ni micromechanical switches reported to date. Our smallest one, which measures 10.0 μm×4.0 μm×0.15 μm suspended over a 430 nm gap is realized by using electron beam cross-linked polymethylmethacrylate as the sacrificial layer and electroplated nickel as the main structural material. Tunnel barriers are defined via in situ formation of Al2O3 during the oxygen plasma dry release step with a metal–insulator–metal junction formed when the switch closes. The reliable curvature-free properties of these devices demonstrate low pull-in voltage drifts (<1.5 V), even after 1 billion switching cycles. Also, they did not reveal an appreciable physical change even after being subjected to sintering treatments of 450 °C for 30 min, making them promising candidates for encapsulations. These devices have low hysteretic switching behavior (∼0.5–4.5 V), as compared with similarly fabricated switches without the barrier, which remain stuck once turned on. © 2003 American Vacuum Society.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
73.40.Rw Metal-insulator-metal structures

Magnesium oxide gate dielectrics grown on GaN using an electron cyclotron resonance plasma

B. P. Gila, A. H. Onstine, J. Kim, K. K. Allums, F. Ren, C. R. Abernathy, and S. J. Pearton

J. Vac. Sci. Technol. B 21, 2368 (2003); http://dx.doi.org/10.1116/1.1620516 (3 pages) | Cited 8 times

Online Publication Date: 24 November 2003

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Magnesium oxide was grown by gas source molecular beam epitaxy on (0001) oriented metalorganic chemical vapor deposition n-GaN using elemental Mg and atomic oxygen supplied from an electron cyclotron resonance plasma source. X-ray diffraction (XRD) indicated that the oxide was single crystal for TSUB=350 °C and mostly polycrystalline for TSUB=100 °C. Reflection high energy electron diffraction suggests that the films deposited at the lower temperature begin with a single crystal nucleation layer then quickly become polycrystalline. For both growth temperatures, the magnesium oxide was highly textured toward the (111) direction, with the polycrystalline samples showing a broader XRD peak but smoother surfaces. Single crystal MgO grown at 350 °C had high current leakage, prohibiting electrical measurements. A breakdown field of 2.3 MV/cm and an interface state density of 4×1011 cm−2 eV−1 were measured for the polycrystalline (TSUB=100 °C) magnesium oxide/GaN heterostructure. © 2003 American Vacuum Society.
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68.55.-a Thin film structure and morphology
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
52.77.Dq Plasma-based ion implantation and deposition
68.55.A- Nucleation and growth
77.22.Jp Dielectric breakdown and space-charge effects
73.20.-r Electron states at surfaces and interfaces
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Generation mechanism of residual clamping force in a bipolar electrostatic chuck

S. Kanno and T. Usui

J. Vac. Sci. Technol. B 21, 2371 (2003); http://dx.doi.org/10.1116/1.1620517 (7 pages) | Cited 3 times

Online Publication Date: 24 November 2003

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Clamping and residual clamping forces of a Johnsen–Rahbek-type (JR-type) bipolar electrostatic chuck (ESC), which has electrically independent dual electrodes, were measured. Area ratios of the ESC’s two electrodes ranged from 1 to 4.6. It was found that the clamping force per unit area decreases with increasing area ratio and that the residual clamping force per unit area increases with increasing area ratio. To reveal the mechanism of residual clamping force, an equivalent circuit model of a JR-type bipolar ESC was devised. The model showed that the residual clamping force is caused by the residual charge that results from the charge difference in two monopolar ESCs. The charge difference is due to the resistance dependency on voltage of the dielectric layer of the ESC. The wafer voltage calculated from the model agreed well with the voltage measured by an electrostatic voltmeter. It can be concluded that the model is suitable for simulating the performance of a bipolar ESC. © 2003 American Vacuum Society.
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41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
85.30.-z Semiconductor devices
77.55.-g Dielectric thin films
84.30.Bv Circuit theory
07.05.Tp Computer modeling and simulation

Annealing temperature dependence of contact resistance and stablity for Ti/Al/Pt/Au ohmic contacts to bulk n-ZnO

K. Ip, K. H. Baik, Y. W. Heo, D. P. Norton, S. J. Pearton, J. R. LaRoche, B. Luo, F. Ren, and J. M. Zavada

J. Vac. Sci. Technol. B 21, 2378 (2003); http://dx.doi.org/10.1116/1.1621651 (4 pages) | Cited 11 times

Online Publication Date: 24 November 2003

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E-beam deposited Ti/Al/Pt/Au contacts on undoped (n∼1017 cm−3) bulk ZnO showed minimum specific contact resistance, ρc, of ∼6×10−4 Ω cm2 after annealing at 250 °C. This value was essentially independent of the surface cleaning procedure employed, including sequential solvent cleaning or H2 plasma exposure. Higher annealing temperatures degraded the ρc, and Auger electron spectroscopy depth profiling revealed increasing intermixing of the metal layers. The Al outdiffuses to the surface at temperatures as low as 350 °C, and the contact metallization is almost completely intermixed by 600 °C. © 2003 American Vacuum Society.
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73.40.Cg Contact resistance, contact potential
73.40.Ns Metal-nonmetal contacts
61.72.Cc Kinetics of defect formation and annealing
68.35.Fx Diffusion; interface formation
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
61.72.S- Impurities in crystals
66.30.J- Diffusion of impurities

Electron field emission of radio frequency magnetron sputtered CNx films annealed at different temperatures

J. J. Li, W. T. Zheng, Z. S. Jin, X. Wang, H. J. Bian, G. R. Gu, Y. N. Zhao, S. H. Meng, X. D. He, and J. C. Han

J. Vac. Sci. Technol. B 21, 2382 (2003); http://dx.doi.org/10.1116/1.1621653 (6 pages) | Cited 8 times

Online Publication Date: 24 November 2003

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The carbon nitride films deposited by rf magnetron sputtering in a pure N2 discharge were annealed in vacuum up to 900 °C. The chemical composition and bonding structure of the films were studied using x-ray photoelectron spectroscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy. It was found that the nitrogen atoms were bound to sp, sp2, and sp3 hybridized carbon atoms in as-deposited films. The effects of the thermal annealing on bonding structure and the electron field emission characteristics of CNx films were investigated. The results showed that thermal annealing treatment caused a great loss of N content and favor formation of sp2 bonds in CNx films, which would significantly influence the field emission properties for the CNx films. The CNx films annealed at temperature of 750 °C showed the optimal electron emission properties. Besides, the correlation between the chemical bonding structures and electron emission properties for the CNx films was discussed. © 2003 American Vacuum Society.
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79.70.+q Field emission, ionization, evaporation, and desorption
81.15.Cd Deposition by sputtering
68.55.Nq Composition and phase identification
85.45.Db Field emitters and arrays, cold electron emitters
61.72.Cc Kinetics of defect formation and annealing
68.55.-a Thin film structure and morphology
79.60.Dp Adsorbed layers and thin films
78.30.Hv Other nonmetallic inorganics
78.66.Nk Insulators
82.80.Gk Analytical methods involving vibrational spectroscopy

Si adatom diffusion on Si (100) surface in selective epitaxial growth of Si

Seung-Hyun Lim, Sukchan Song, Tai-su Park, Euijoon Yoon, and Jong-Ho Lee

J. Vac. Sci. Technol. B 21, 2388 (2003); http://dx.doi.org/10.1116/1.1621656 (5 pages) | Cited 1 time

Online Publication Date: 24 November 2003

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The growth temperature dependence of Si adatom diffusion on Si (100) surface was systematically investigated in a cold wall ultrahigh vacuum chemical vapor deposition system. Si epitaxial layers were selectively grown on local oxidation of silicon patterned Si substrates. By cross-sectional transmission electron microscopy analysis, the increase in Si growth rate on the Si (100) surface near the edge of (311) facet was observed at various growth temperatures. This can be understood as a consequence of the mass transport from the sidewall (311) facet to the top (100) surface. Based on a simple diffusion model, the surface diffusion lengths of Si adatoms along the [110] direction were estimated to be about 70, 140, and 200 nm at 550, 600, and 650 °C, respectively. The calculated activation energy of 1.4 eV for diffusion of Si adatoms from the temperature dependence of the diffusion length was relatively higher than those in previous reports obtained under ultrahigh vacuum environment. This difference was discussed in terms of the discrepancy in the surface states by hydrogen adsorption on the Si surface. © 2003 American Vacuum Society.
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68.43.Jk Diffusion of adsorbates, kinetics of coarsening and aggregation
68.35.Fx Diffusion; interface formation
68.55.A- Nucleation and growth
81.05.Cy Elemental semiconductors
73.20.Hb Impurity and defect levels; energy states of adsorbed species
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.47.Fg Semiconductor surfaces

Deep dry etching of GaAs and GaSb using Cl2/Ar plasma discharges

Alexander R. Giehl, Michael Gumbel, Matthias Kessler, Norbert Herhammer, Goetz Hoffmann, and Henning Fouckhardt

J. Vac. Sci. Technol. B 21, 2393 (2003); http://dx.doi.org/10.1116/1.1623507 (5 pages) | Cited 5 times

Online Publication Date: 24 November 2003

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Deep dry etch processes for GaAs and GaSb are investigated. Reactive ion etching in Cl2/Ar plasma discharges is used to pattern GaAs and GaSb with a single-layer soft mask resist. Soft masks have many advantages over (metal) hard masks such as easy and inexpensive processing, low pinhole density, and high etching reproducibility. Using TI35ES, an image reversal resist developed by MicroChemicals, GaAs etch profiles of up to 25 μm depth and GaSb structures of more that 50 μm depth are obtained revealing considerable dimensional stability. Even for etch durations of more than 50 min the resist can be easily removed from the sample surface after the etch process. Roughnesses of etched surfaces of less than 1 nm (rms, measured by atomic force microscopy) are obtained after reactive ion etching for both materials. Photoluminescence measurements reveal that the surface stoichiometry is conserved during the etching step. Deep dry etching of GaAs and GaSb can be exploited for example to fabricate fiber or capillary connections to and between optoelectronic devices or to create substrate windows for backside-illuminated photodetectors in the infrared wavelength range. © 2003 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Ea III-V semiconductors
52.77.Bn Etching and cleaning

Positive charge effect in atomic force microscope anodization lithography using self-assembled monolayers of metal phosphate as resists

Sang Min Kim and Haiwon Lee

J. Vac. Sci. Technol. B 21, 2398 (2003); http://dx.doi.org/10.1116/1.1623510 (6 pages) | Cited 9 times

Online Publication Date: 24 November 2003

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Various metal phosphate monolayers prepared as resists on silicon substrates were prepared for atomic force microscope (AFM) anodization lithography. The metal phosphate monolayers were prepared by binding tetravalent (Zr4+, Hf4+) or divalent (Ca2+, Mg2+) metal ions on a phosphorylated Si substrate. The presence of the metal ions on a phosphorylated Si substrate was confirmed using Auger electron spectroscopy. Since the divalent and tetravalent metal ions are changed to be neutral and divalent, respectively, after binding on phosphorylated substrates, the role of a positive ion in the monolayer structure in AFM anodization lithography was systematically investigated. The presence of positively charged metal ions in case of Zr4+ and Hf4+ enhances the electron transfer from a tip to a substrate under a tip negative bias. In addition to the effect of lowering a bias for anodization process, the lithographic scan speed was also enhanced by the order of magnitude in the presence of the positive ions. After patterning of protruding lines on Zr2+ phosphate monolayer, the etching process was also accomplished. © 2003 American Vacuum Society.
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81.16.Nd Micro- and nanolithography
81.16.Ta Atom manipulation
07.79.Lh Atomic force microscopes
81.16.Dn Self-assembly

Study of beveled angle effect on morphology of dual damascene via filling using ionized physical vapor deposition

Chi-Chuan Hwang, Jee-Gong Chang, Ming-Hang Weng, and Hong-Chang Lin

J. Vac. Sci. Technol. B 21, 2404 (2003); http://dx.doi.org/10.1116/1.1623511 (7 pages) | Cited 1 time

Online Publication Date: 24 November 2003

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This article employs a molecular dynamics (MD) simulation approach to investigate the influence of beveled angles on the filling mechanisms of a dual damascene process. The objective of the present study is to propose a method that overcomes the problem of incomplete via filling associated with the traditional dual damascene process. The simulation incorporates three separate MD models, namely the dual via model, the deposition model, and the potential model. Furthermore, the simulation adopts the thermal control layer marching algorithm to increase the accuracy of the solution and to reduce the computational time. The present results indicate that the introduction of beveled angles at the upper via corners has a detrimental impact upon the filling of the lower via at moderately low via-radius ratios (1.75, 2.0). At a via-radius ratio of 1.75, the filling morphology changes from one of complete filling to one with trapped voids within the via when beveled angles are introduced, while at the slightly larger via-radius ratios of 2.0 and 2.5, the voids in the lower via are observed to grow in size. It is noted that the influence of beveled angles at the upper via corners on the lower via filling becomes less significant as the via-radius ratio increases (2.5, 3.0). In general, it is found that the introduction of beveled angles at the lower via corners is beneficial to the filling coverage of the lower via, but has no impact upon the filling of the upper via. © 2003 American Vacuum Society.
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85.40.Ls Metallization, contacts, interconnects; device isolation
02.70.Ns Molecular dynamics and particle methods
85.40.Sz Deposition technology
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Formation of metastable c-AlN and its effect on the mechanical properties of AlN/(Ti,Al)N nanoscale multilayers

Xiaoping Hu, Xiaojiang Yu, Jijun Lao, Geyang Li, and Mingyuan Gu

J. Vac. Sci. Technol. B 21, 2411 (2003); http://dx.doi.org/10.1116/1.1624270 (4 pages) | Cited 3 times

Online Publication Date: 24 November 2003

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The formation of metastable phases has a great influence on the mechanical properties of multilayers. A series of AlN/(Ti,Al)N nanoscale multilayers with various modulation periods were synthesized by reactive magnetron sputtering. X-ray diffraction analysis, high resolution transmission microscopy and the microindentation technique were employed to characterize the microstructure and mechanical properties of the multilayers. The results show that metastable c-AlN forms due to the “template” effect of (Ti,Al)N in AlN/(Ti,Al)N multilayers with small modulation periods, and forms columnar crystals with (Ti,Al)N through epitaxial growth and results in lattice distortion due to the lattice mismatch between c-AlN and (Ti,Al)N. Correspondingly, the hardness and the elastic modulus of the multilayers increase with a decrease of modulation period monotonically and reach the maximal hardness (29 GPa) and elastic modulus (377.8 GPa) at a modulation period of 1.3 nm. © 2003 American Vacuum Society.
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68.65.Ac Multilayers
68.35.Gy Mechanical properties; surface strains
62.20.Qp Friction, tribology, and hardness
62.20.D- Elasticity
81.15.Cd Deposition by sputtering

Growth of semiconductor gallium nitride nanowires with different catalysts

Jun Zhang and Lide Zhang

J. Vac. Sci. Technol. B 21, 2415 (2003); http://dx.doi.org/10.1116/1.1625968 (5 pages) | Cited 10 times

Online Publication Date: 24 November 2003

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Semiconductor gallium nitride nanowires had been prepared by different catalysts using chemical vapor deposition. In, Fe, Ni, and Au nanoparticles were used in the growth of semiconductor GaN nanowires. Preliminary results indicate that the In, Fe, and Ni are efficient catalysts in the large-scale synthesis of GaN nanowires and the size of the nanowires depends on the size of catalyst particle. The nanowires have a diameter of 20–100 nm and a length of up to several hundreds of micrometers. The growth of GaN nanowires obeys the vapor–liquid–solid mechanism. However, no GaN nanowires were observed on the substrate when Au was used. It may be because of the poor solubility between Au and nitrogen. Au does not have any catalytic activity in this system. © 2003 American Vacuum Society.
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81.16.Hc Catalytic methods
81.07.Bc Nanocrystalline materials
82.33.Ya Chemistry of MOCVD and other vapor deposition methods
61.46.-w Structure of nanoscale materials
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Ion-enhanced chemical etching of HfO2 for integration in metal–oxide–semiconductor field effect transistors

Lin Sha, Ragesh Puthenkovilakam, You-Sheng Lin, and Jane P. Chang

J. Vac. Sci. Technol. B 21, 2420 (2003); http://dx.doi.org/10.1116/1.1627333 (8 pages) | Cited 40 times

Online Publication Date: 24 November 2003

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High-density chlorine plasmas were used to chemically etch HfO2, a promising high dielectric constant material, where the etch rate scaled up linearly with the square root of ion energy at energies above 50 eV. Higher etch rates were obtained at lower pressures and high microwave powers, where the electron temperature and ion densities were high. Optical emission spectroscopy and quadrupole mass spectrometry were used to identify the etching products, which are mainly highly chlorinated hafnium (HfCl3 and HfCl4) and ClO. Surface chlorination was confirmed after etching was confirmed by x-ray photoelectron spectroscopy. The addition of BCl3 in the Cl2 plasmas was found to significantly enhance the HfO2 etch rate and improve the etching selectivity to Si from ∼0.01 in a pure Cl2 plasma to ∼0.9 in a pure BCl3 plasma at an ion energy of 75 eV. The etching selectivity was improved to 4 as the ion energies reduced towards the etching threshold energy in a pure BCl3 plasma. BCl3 plasmas were found effective in patterning HfO2 for fabricating the metal–oxide–semiconductor field effect transistors, enabling a complete removal of HfO2 from the source and drain regions yielding high electron mobility. © 2003 American Vacuum Society.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
85.30.Tv Field effect devices
77.55.-g Dielectric thin films

Thickness effects on properties of GaInNAs quantum dots grown by molecular-beam epitaxy with nitrogen plasma source

K. C. Yew, S. F. Yoon, and Z. Z. Sun

J. Vac. Sci. Technol. B 21, 2428 (2003); http://dx.doi.org/10.1116/1.1627335 (4 pages) | Cited 2 times

Online Publication Date: 24 November 2003

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Self-assembled GaInNAs quantum dots (QDs) were grown on a GaAs (001) substrate by solid-source molecular-beam epitaxy equipped with a radio-frequency nitrogen plasma source. The GaInNAs QD growth characteristics were investigated using atomic-force microscopy (AFM) and photoluminescence (PL) measurements. The growth experiment was conducted using indium and nitrogen compositions of 50% and ∼1%, respectively, at different nominal thicknesses of 3 monolayers (MLs) to 6 MLs. AFM images suggest the onset of QD formation at ∼3 MLs and QD coalescence at ∼6 MLs. The highest PL intensity at low temperature (5 K) was obtained from the sample with nominal thickness of 5 ML, consistent with the highest QD density observed from AFM measurement. Under the present experimental conditions, GaIn0.5N0.01As QDs of 5–6 MLs gave the best optical property in terms of the lowest full width at half maximum and highest PL intensity. The reduced barrier potential of a strain-compensated layer (SCL) of GaNAs inserted between the substrate and GaInNAs QD layer was able to extend the PL emission wavelength by more than 140 nm compared to the sample without the GaNAs SCL. © 2003 American Vacuum Society.
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81.07.Ta Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.37.Ps Atomic force microscopy (AFM)
81.05.Ea III-V semiconductors
78.55.Cr III-V semiconductors
78.67.Hc Quantum dots

Etching mechanisms of low-k SiOCH and selectivity to SiCH and SiO2 in fluorocarbon based plasmas

N. Posseme, T. Chevolleau, O. Joubert, L. Vallier, and P. Mangiagalli

J. Vac. Sci. Technol. B 21, 2432 (2003); http://dx.doi.org/10.1116/1.1627337 (9 pages) | Cited 28 times

Online Publication Date: 24 November 2003

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This study is dedicated to an analysis of the etch mechanisms of SiOCH, SiO2 and SiCH in fluorocarbon plasmas. The etching of these materials is performed on blanket wafers in a magnetically enhanced reactive ion etcher reactor using fluorocarbon based chemistry (CF4/N2/Ar). After partial etching, the Fourier transform infrared spectroscopy and mercury probe measurement indicate that the remaining substrate of SiOCH is not altered by the reactive plasma. A decrease in the etch rate of SiOCH, SiO2 and SiCH is observed either with increasing Ar dilution or polymerizing gas addition as CH2F2 and C4F6. X-ray photoelectron spectroscopy analysis of the surface after partial etching shows that the thickness of the fluorocarbon layer formed at the film surface and its composition play a key role in controlling etch rate and selectivity of SiOCH, SiO2 and SiCH. The etch rate of these materials is getting lower when the fluorocarbon layer thickness increases and also when its fluorine concentration decreases. The fluorocarbon layer thickness and composition depend on the plasma chemistry but also on the concentration and nature of impurities (C and H) in the etched materials. Etch rates are presented and discussed with respect to plasma parameters and material composition in terms of etching mechanisms. © 2003 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
78.30.Hv Other nonmetallic inorganics
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Electrical properties of SiO2 films with embedded nanoparticles formed by SiH4/O2 chemical vapor deposition

R. M. Rassel, T. Kim, Z. Shen, S. A. Campbell, and P. H. McMurry

J. Vac. Sci. Technol. B 21, 2441 (2003); http://dx.doi.org/10.1116/1.1627795 (7 pages) | Cited 1 time

Online Publication Date: 24 November 2003

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This article uses real-time particle measurements as well as physical, chemical, and electrical film measurements to report on the properties of films with embedded particles formed during low-pressure chemical vapor deposition of SiO2 from silane and oxygen. The depositions were carried out at pressures and temperatures ranging from 0.3 to 2.0 Torr and 200–800 °C, using an O2/SiH4 ratio of 20. Aerosol size distributions were measured using a particle beam mass spectrometer. The effects of these particles on film properties, such as stoichiometry, particle concentration, dielectric constant, and current–voltage characteristics are presented along with transmission electron microscopy images to support findings. In addition the charge retention properties of these particle-incorporated films are discussed. © 2003 American Vacuum Society.
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73.61.Ng Insulators
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.Nq Composition and phase identification
77.22.Ch Permittivity (dielectric function)
68.55.-a Thin film structure and morphology
78.47.-p Spectroscopy of solid state dynamics
61.66.Bi Elemental solids
61.66.Dk Alloys
77.55.-g Dielectric thin films

Reduction of ultraviolet-radiation damage in SiO2 using pulse-time-modulated plasma and its application to charge coupled 44 device image sensor processes

Mitsuru Okigawa, Yasushi Ishikawa, and Seiji Samukawa

J. Vac. Sci. Technol. B 21, 2448 (2003); http://dx.doi.org/10.1116/1.1629712 (7 pages) | Cited 16 times

Online Publication Date: 24 November 2003

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We found that vacuum-ultra/violet (VUV) light emitted by plasmas causes dark current in charge coupled device (CCD) image sensors. When a CCD was irradiated with inductively coupled plasmas using helium (He), argon (Ar) or oxygen (O2) gas, the He plasma caused higher plasma-induced dark current in the CCD than the Ar or O2 plasmas. To investigate the influence of VUV radiation in He plasma, the plasma-induced electric current in SiO2 was measured using two types of on-wafer monitoring devices to separate the effects of He ions and He VUV radiation. One monitoring device has an aluminum filter that only allows He VUV 58.4 nm to pass through, and the other has no filter. We performed time-resolved-measurement experiments using the two types of devices in pulse-time-modulated He plasma (He-TM plasma). With the filter device, the decay of the VUV intensity after plasma off corresponded completely to the decay of the plasma-induced current curve. On the other hand, in the no-filter device, decay curve of the plasma-induced current coincided with that of the electron density in the plasma. In other words, the TM plasma does not reduce the ion-induced current, but can completely reduce the photoinduced current in SiO2. In the CCD image sensor we found that the TM plasma dramatically suppresses plasma-induced dark current. Consequently, the effect of TM plasma on the CCD dark current is due to the influence of reducing the photons in the plasma. © 2003 American Vacuum Society.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Ms Insulators
72.40.+w Photoconduction and photovoltaic effects
81.65.Cf Surface cleaning, etching, patterning
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
42.79.Pw Imaging detectors and sensors
85.60.Gz Photodetectors (including infrared and CCD detectors)
52.77.Bn Etching and cleaning
78.47.-p Spectroscopy of solid state dynamics

Etching of 4H–SiC in a NF3/CH4 inductively coupled plasma

Byungwhan Kim, Suk Yong Lee, and Byung Teak Lee

J. Vac. Sci. Technol. B 21, 2455 (2003); http://dx.doi.org/10.1116/1.1629715 (6 pages) | Cited 5 times

Online Publication Date: 24 November 2003

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In this study, SiC was etched in a NF3/CH4 inductively coupled plasma. Process parameters and experimental ranges are radio frequency (rf) source power 700–900 W, bias power 50–150 W, pressure 6–12 mTorr, and NF3 percentage 20%–100%. The etch rate and profile angle were examined as a function of process parameters. For optimization, effects of various parameter combinations were investigated by means of a 24 full factorial experiment. Main effect analysis revealed that the etch rate is the most significantly affected by NF3 percentage. In contrast, the source power effect was the most insignificant for both etch rate and profile. For the dc bias less than about 385 V, the etch rate was strongly correlated to the dc bias induced by the source power. This correlation was observed for variations in other parameters. This reveals that the dc bias played an important role in determining the etch rate. For variations in NF3 percentage, both etch rate and profile angle behaved in a conflicting way. The highest etch rate optimized by the experimental design is 450 nm/min, obtained at 700 W source power, 150 W bias power, 12 mTorr, and 100% NF3 percentage. © 2003 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning

Ab initio calculations of field emission from ultrathin Si(100) films

Y. Gohda and S. Watanabe

J. Vac. Sci. Technol. B 21, 2461 (2003); http://dx.doi.org/10.1116/1.1624266 (5 pages) | Cited 4 times

Online Publication Date: 24 November 2003

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We have analyzed field emission from ultrathin Si(100) films on a metal substrate by using ab initio density functional calculations incorporating scattering states. We have shown that the clean Si(100) film can screen an external electric field sufficiently due to metallic states of surface dangling bonds, and thus field emission from the clean silicon film is attributed to that from surface states. We have also analyzed effects of metal adsorption on field emission from Si(100) films. We have obtained a much larger emission current from the Si(100)2×2-Al surface at 0.5 monolayer coverage than that from clean silicon and aluminum surfaces. The minimum local barrier height clearly explains the difference between the Si(100)2×2-Al surface and the clean Al(100) surface, which cannot be explained from the small difference in the work function between the two surfaces. We have also found that the emission current further increases with a change in the atomic position of adsorbed aluminum addimers which causes both a decrease in the minimum local barrier height and an increase in the local density of states at a surface around the Fermi level. © 2003 American Vacuum Society.
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79.70.+q Field emission, ionization, evaporation, and desorption
73.20.Hb Impurity and defect levels; energy states of adsorbed species
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
73.30.+y Surface double layers, Schottky barriers, and work functions

Evaluation of the cleanliness of the ion-assisted Mo–Si deposition process for extreme ultraviolet lithography

Stefan P. Hau-Riege, Paul B. Mirkarimi, Christopher C. Walton, Victor Sperry, and Cindy Larson

J. Vac. Sci. Technol. B 21, 2466 (2003); http://dx.doi.org/10.1116/1.1615979 (5 pages) | Cited 2 times

Online Publication Date: 25 November 2003

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Particles are a serious concern in the fabrication of reticles for extreme ultraviolet lithography because they nucleate perturbations in the reflective multilayer film that can print in the lithographic image. We call these perturbations defects. It has been suggested that reticle substrates can be planarized and the high-spatial-frequency roughness of the multilayer film can be reduced by using an ion-assisted Mo–Si deposition process. In this article we discuss the cleanliness of this ion-assisted deposition process. Within one cleaning cycle, we improved the cleanliness of the deposition process without ion assist from 3–4 to 0.26 particles/cm2. Of these, 0.09 particles/cm2 are due to manual handling of the wafers. We found that in our experimental setup, the added particle density using a process with ion assist is more then six times larger than the added density without ion-assist, suggesting that further work is necessary to develop a clean ion-assisted deposition process. We characterized the chemical composition of some of the added particles and found that they contain Al, C, Fe, Mo, and Si. © 2003 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Comparative hydrogen sensing performances of Pd– and Pt–InGaP metal–oxide–semiconductor Schottky diodes

Yan-Ying Tsai, Kun-Wei Lin, Huey-Ing Chen, Chun-Tsen Lu, Hung-Ming Chuang, Chun-Yuan Chen, and Wen-Chau Liu

J. Vac. Sci. Technol. B 21, 2471 (2003); http://dx.doi.org/10.1116/1.1615980 (7 pages) | Cited 5 times

Online Publication Date: 25 November 2003

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The hydrogen sensing performances of Pd– and Pt–InGaP metal–oxide–semiconductor (MOS) Schottky diodes are systematically studied and compared under different operating temperature. It is known that, from experimental results, the Pd–InGaP MOS Schottky diode exhibits higher hydrogen detecting capability at lower hydrogen concentration regimes. On the contrary, the MOS Schottky diode with Pt catalytic material shows better hydrogen detecting capability and higher operating temperature. It is believed that the refractory Pt metal is responsible for detecting high hydrogen concentration in air, especially at high operating temperature. Furthermore, the temperature dependence of equilibrium constants is investigated and reported. In order to study the steady-state reaction kinetics, the van’t Hoff equation is used to estimate the values of initial heat of adsorption for both devices. Based on the Temkin isotherm model, the experimental results and theoretical simulation of hydrogen coverage are also studied and compared. © 2003 American Vacuum Society.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.30.Kk Junction diodes

Patterning of gold film on muscovite mica by using a helium-metastable atom beam and an octanethiol self-assembled monolayer

X. Ju, M. Kurahashi, T. Suzuki, and Y. Yamauchi

J. Vac. Sci. Technol. B 21, 2478 (2003); http://dx.doi.org/10.1116/1.1615981 (4 pages)

Online Publication Date: 25 November 2003

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Using a helium-metastable atom beam and an octanethiol (OT) self-assembled monolayer (SAM), we carried out atom lithography to the gold film on muscovite mica having a flat surface. A large intact area and a clear pattern with a nanoscale width ∼80–100 nm of the etched step was obtained. The gold surface, as well as the surface of the mica substrate, was flat. From the analysis of the roughness, appreciable gold islands were not detected in the area exposed to the He∗ atom beam. This finding demonstrates that the OT SAMs on atomically flat surfaces can be used as a resist for exposure to metastable-atom beams. © 2003 American Vacuum Society.
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81.16.Nd Micro- and nanolithography
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology

Mitigation of residual film stress deformation in multilayer microelectromechanical systems cantilever devices

Jeffrey S. Pulskamp, Alma Wickenden, Ronald Polcawich, Brett Piekarski, Madan Dubey, and Gabe Smith

J. Vac. Sci. Technol. B 21, 2482 (2003); http://dx.doi.org/10.1116/1.1615982 (5 pages) | Cited 19 times

Online Publication Date: 25 November 2003

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An approach to compensate for the residual thin film stress deformation of multilayer microelectromechanical systems (MEMS) devices is presented based upon analytical and numerical modeling and in-process thin film characterization. Thermal and intrinsic deposition stresses can lead to the warping of released MEMS structures. This detrimental phenomenon in many cases can prevent proper device operation. Ellispsometric and laser wafer bow measurements yield thickness and film stress values that are used to update the deflection model during device fabrication, allowing for the compensation of the fabrication process variability. The derivations of linear and nonlinear residual film stress induced deflection models are presented. These models are based upon Bernoulli–Euler beam theory and are thus restricted to the associated geometric constraints. The models are initially validated by comparison with surface micro-machined sol–gel lead–zirconate–titanate cantilever structures; with initial experimental results agreeing well with both. © 2003 American Vacuum Society.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Comparison of dry etching of AlGaAs and InGaP in a planar inductively coupled BCl3 plasma

I. K. Baek, W. T. Lim, J. W. Lee, M. H. Jeon, G. S. Cho, and S. J. Pearton

J. Vac. Sci. Technol. B 21, 2487 (2003); http://dx.doi.org/10.1116/1.1615984 (5 pages) | Cited 7 times

Online Publication Date: 25 November 2003

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We studied dry etching of AlGaAs and InGaP in a planar inductively coupled BCl3 plasma. The process parameters were planar ICP source power (0–500 W), reactive ion etching (RIE) chuck power (0–150 W), and chamber pressure (5–15 mTorr). The process results were characterized in terms of etch rate, surface morphology, and surface roughness. The planar inductively coupled BCl3 plasmas were also monitored with in situ optical emission spectroscopy (OES). BCl3 planar inductively coupled process (ICP) etching of AlGaAs showed very vertical sidewall, clean and smooth surface, while that of InGaP showed somewhat rough surface after etching. Etch rates of AlGaAs were generally higher than those of InGaP in the planar BCl3 ICP etching. It indicated that InClX byproducts had relatively low volatility during InGaP etching in the planar inductively BCl3 plasmas. Increase of ICP source power and RIE chuck power strongly raised etch rates of both AlGaAs and InGaP. That of pressure decreased etch rate of both materials. OES data showed that emission intensity of the planar BCl3 ICP was a strong function of ICP source power and chamber pressure, while it was almost independent of RIE chuck power. © 2003 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

SiC/Si-dots multilayer structures formed by supersonic free jets of CH3SiH3 and Si3H8

Yoshifumi Ikoma, Ryota Ohtani, Nobuaki Matsui, and Teruaki Motooka

J. Vac. Sci. Technol. B 21, 2492 (2003); http://dx.doi.org/10.1116/1.1617280 (4 pages) | Cited 1 time

Online Publication Date: 25 November 2003

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We have investigated the formation of multilayer structures of SiC/Si-dots on Si(100) by supersonic free jet chemical vapor deposition. CH3SiH3 and Si3H8 jets were used for SiC and Si-dots, respectively. The first epitaxial SiC layer with a thickness of ∼15 nm and polycrystalline Si-dots with a size of ∼100 nm were grown by the first CH3SiH3 and following Si3H8 jet exposures. When the CH3SiH3 and Si3H8 jets were directed onto the Si-dot surface, thin (∼5 nm) SiC layers and ∼50 nm Si-dots were grown and formed Si-dots/SiC/Si-dots/SiC/Si(100). By repeating these SiC and Si-dots growths, polycrystalline SiC/Si-dots multilayer was formed on Si(100). © 2003 American Vacuum Society.
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68.65.Ac Multilayers

Fabrication of subwavelength surface structures combining self-assembled masking layer with plasma etching techniques

E. Oesterschulze, G. Georgiev, M. Müller-Wiegand, A. Georgieva, and K. Ludolph

J. Vac. Sci. Technol. B 21, 2496 (2003); http://dx.doi.org/10.1116/1.1617281 (4 pages) | Cited 1 time

Online Publication Date: 25 November 2003

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A lithography-free method for producing periodic and nonperiodic surface structures is presented. It combines self-assembly of masking particles with well established plasma etching techniques known from microelectromechanical system technology. The method is generally applicable to bulk as well as layered materials. In our experiments, layers of glass spheres of different diameter were assembled on the sample surface forming a mask against plasma etching. Silicon surface structures with periodicity of 500 nm and feature dimensions of 20 nm were produced in this way. Thermal oxidation of the so structured silicon substrate offers the capability to vary the fill factor of the periodic structure owing to volume expansion during oxidation but also to define silicon dioxide surface structures by selective plasma etching. Similar structures can be simply obtained structuring silicon dioxide layers on silicon. The method offers a simple route, e.g., for photonic crystal fabrication. © 2003 American Vacuum Society.
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42.70.Qs Photonic bandgap materials
81.65.Mq Oxidation

Proton implantation effects on electrical and optical properties of undoped AlGaN with high Al mole fraction

A. Y. Polyakov, N. B. Smirnov, A. V. Govorkov, N. V. Pashkova, S. J. Pearton, J. M. Zavada, and R. G. Wilson

J. Vac. Sci. Technol. B 21, 2500 (2003); http://dx.doi.org/10.1116/1.1617283 (6 pages) | Cited 9 times

Online Publication Date: 25 November 2003

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Electrical and optical properties of undoped n-AlGaN films with Al composition close to 40% were studied before and after implantation of various doses of 100 keV protons. In the virgin samples, the electrical properties were determined by deep donor defects with an energy level near 0.25 eV from the conduction band edge and a concentration of ∼1018 cm−3. Other deep centers present had energy levels of 0.12, 0.3, and 0.45 eV. The luminescence spectra were dominated by two defect bands near 2.3 and 3.6 eV. Proton implantation significantly decreased the concentration of major donors even at the lowest doses of 1012 cm−2. For higher doses the Fermi level became progressively deeper and the data indicated complexing of defects present in the sample with either primary radiation defects or/and hydrogen introduced by implantation. The effect of the proton implantation on the intensity of luminescence bands was complicated but overall the intensity of defect bands was increased with implantation. © 2003 American Vacuum Society.
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61.80.Jh Ion radiation effects
78.66.Fd III-V semiconductors
73.61.Ey III-V semiconductors
61.82.Fk Semiconductors
71.55.Eq III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence

Effect of bismuth oxide as a buffer layer on metal–lanthanum-substituted bismuth titanate–insulator–semiconductor structures

Sang-Woo Kang and Shi-Woo Rhee

J. Vac. Sci. Technol. B 21, 2506 (2003); http://dx.doi.org/10.1116/1.1620512 (6 pages)

Online Publication Date: 25 November 2003

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We have investigated metal/ferroelectric/insulator/semiconductor (MFIS) structures with lanthanum-substituted bismuth titanate (BLT) as a ferroelectric layer and bismuth oxide as an insulating buffer layer between BLT and Si substrate. BLT films and Bi oxide films were prepared by the direct liquid injection metal organic chemical vapor deposition process. The morphology of the Bi oxide film was changed with the increase of its thickness and the annealing temperature. Bi oxide on silicon was converted into Bi silicate during annealing at 750 °C. The morphology of the BLT films deposited on Bi oxide depended on the morphology of the Bi oxide film and on the reaction with Bi oxide during the annealing process, which was confirmed by transmission electron microscopy and energy dispersive x-ray spectroscopy. The maximum memory window was 0.83 V at the sweep voltage of 5 V with the Bi oxide film annealed at 650 °C and with a thickness of 5 nm. With BLT/Bi oxide annealed at 750 °C, the window was decreased due to the reaction between the BLT film, Bi oxide film, and Si substrate, and the leakage current density was increased. By inserting the buffer layer, the MFIS structure had a lower leakage current density than metal/ferroelectric/semiconductor structure. © 2003 American Vacuum Society.
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77.55.-g Dielectric thin films
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
85.50.Gk Non-volatile ferroelectric memories
77.80.-e Ferroelectricity and antiferroelectricity
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.72.Cc Kinetics of defect formation and annealing

Effects of substrate heating and biasing on nanostructural evolution of nonepitaxially grown TiN nanofilms

T. Q. Li, S. Noda, F. Okada, and H. Komiyama

J. Vac. Sci. Technol. B 21, 2512 (2003); http://dx.doi.org/10.1116/1.1621654 (5 pages) | Cited 4 times

Online Publication Date: 25 November 2003

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The effects of substrate heating and substrate biasing on the initial stage of nonepitaxial heterogeneous growth of TiN on Si(111) was studied by using high-resolution transmission electron microscopy. Although TiN films deposited at room temperature (RT) undergo a transition from continuous amorphous films to polycrystalline films with three-dimensional grains when the film thickness is increased from ∼1 to 2 nm, crystallization occurred at a substrate temperature, Ts=570 K, even for film thicknesses less than 1 nm. Compared with growth at Ts=RT, at Ts=570 K, the initial lateral grain size was only slightly larger, and the grains tended to be spherical and discontinuous at higher film thickness. At a substrate bias voltage, Vb=−70 V, the grains were laterally larger and planar. At a film thickness of 50 nm, the films deposited at Vb=−70 V showed the thermodynamically favored (200) preferred orientation, whereas the films deposited at Ts=570 K showed (111) preferred orientation with a weak (200) peak. © 2003 American Vacuum Society.
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68.55.A- Nucleation and growth
61.46.-w Structure of nanoscale materials
81.15.Cd Deposition by sputtering
85.40.Ls Metallization, contacts, interconnects; device isolation
68.37.Lp Transmission electron microscopy (TEM)

Measurement of semi-isolated polysilicon gate structure with the optical critical dimension technique

Deepak Shivaprasad, Jiangtao Hu, Milad Tabet, Ray Hoobler, David Mui, and Wei Liu

J. Vac. Sci. Technol. B 21, 2517 (2003); http://dx.doi.org/10.1116/1.1622946 (7 pages)

Online Publication Date: 25 November 2003

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The semiconductor road map predicts the production of sub-100 nm transistor gates that push further the limits of the size and speed posed by 180 nm gates that are currently in use. With this decrease in gate size, it has become extremely critical to measure these lines accurately using nondestructive techniques. The optical critical dimension (OCD) technique is emerging as one of the most promising CD measurement techniques for sub-0.1 μm device fabrication. Compared to CD scanning electron microscopy and X-SEM, OCD has several distinct advantages. It is nondestructive, has a fast turnaround time, is sensitive to sidewall profiles, and has sensitivity to sub-100 nm linewidths. It has been successfully used in important structures such as photoresist, shallow trench isolation, and polysilicon and tungsten silicide gates. In the OCD technique, a broadband polarized light beam is focused onto a grating at angle normal to the grating surface, and the spectrum of zeroth order reflection is measured. The spectrum contains the signature of the grating profile that is analyzed in real time using rigorous coupled wave analysis. Real time curve fitting algorithms, which do not require library generation, make the analysis simple and easy to extend to a variety of grating structures. Since the OCD technique is based on specular diffraction, a primary requirement for the OCD measurement target is to have periodical grating structures with a line to space ratio typically larger than 1:1. In this article, we report use of the OCD technique to measure polysilicon gate gratings with line to space ratios as large as 1:20. Polysilicon gate grating structures with critical dimensions of 30–40 nm were measured for line to space ratios of 1:10 and 1:20. In both cases, the measurement showed extreme sensitivity to the linewidth and detailed profile, without deterioration of the repeatability. This study has significantly extended the measurement range of the OCD technique and its application to isolated line measurements. © 2003 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
85.30.De Semiconductor-device characterization, design, and modeling

Effects of temperature and HCl flow on the SiGe growth kinetics in reduced pressure–chemical vapor deposition

J. M. Hartmann, V. Loup, G. Rolland, and M. N. Séméria

J. Vac. Sci. Technol. B 21, 2524 (2003); http://dx.doi.org/10.1116/1.1623508 (6 pages) | Cited 10 times

Online Publication Date: 25 November 2003

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Using a reduced pressure chemical vapor deposition cluster tool, we have studied at 20 Torr the growth kinetics of SiGe using a dichlorosilane+germane+hydrochloric acid chemistry. Adding HCl leads at 700 °C to a significant increase in the germanium content x of SiGe layers. Adopting a x2/(1−x)=n(F(GeH4)/F(SiH2Cl2)) dependence of x on the F(GeH4)/F(SiH2Cl2) mass flow ratio, this translates into an n value linearly increasing with the HCl mass flow from n=0.66 (no HCl) up to n=2.24 (F(HCl)/F(H2)=0.00625). The SiGe growth rate increases strongly with an increasing GeH4 flow. This is attributed to an increased hydrogen desorption caused by the presence of Ge atoms on the growing surface that frees nucleation sites for the incoming Ge and Si atoms. Meanwhile, adding HCl leads to a strong, linear reduction of the SiGe growth rate with the HCl mass flow. As expected, the Ge concentration decreases significantly as the growth temperature increases from 650 to 750 °C. The associated n parameter depends exponentially on the reverse absolute temperature, with an “activation energy” of the order of −15 kcal mol−1. At the same time, the SiGe growth rate increases strongly as the growth temperature increases, with an activation energy dropping from 47 down to 12 kcal mol−1 as the Ge content in the film goes up (from 0% up to 27% at 700 °C). © 2003 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Hd Other semiconductors
68.55.A- Nucleation and growth

Technique for preventing stiction and notching effect on silicon-on-insulator microstructure

J. Li, Q. X. Zhang, A. Q. Liu, W. L. Goh, and J. Ahn

J. Vac. Sci. Technol. B 21, 2530 (2003); http://dx.doi.org/10.1116/1.1623509 (10 pages) | Cited 17 times

Online Publication Date: 25 November 2003

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The notching (undercutting or footing) and stiction problem, which widely exists in silicon-on-insulator microstructure were resolved in this study regardless of the feature sizes, by the introduction of a spacer oxide thin film. In this modified process, the deep reactive ion etching was divided into several steps, where conformal plasma enhanced chemical vapor deposition oxide coating, and anisotropic oxide etch were employed to prevent the notching effect. Dry chemical release was also realized in this approach but the deep etching did not etch through the device layer. The notching or footing effect was exploited for attaining the lateral etching following the deployment of the anisotropic plasma etching of the inductively coupled plasma. This method was proven useful for both the uniform and nonuniform feature designs. To validate the proposed etching method, an optical switch was fabricated. The details and benefits of the proposed process and its extensions to more valuable and flexible design were all discussed in this article. © 2003 American Vacuum Society.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Improved productivity on diamond-like carbon coating optical disk stamper

H. Y. Ueng and C. T. Guo

J. Vac. Sci. Technol. B 21, 2540 (2003); http://dx.doi.org/10.1116/1.1624271 (5 pages)

Online Publication Date: 25 November 2003

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We report on a proposed process for depositing a diamond-like carbon (DLC) film on the back surface of a submaster stamper after a nickel electroforming process. This process could keep friction low and improve the productivity of an optical disk. Hydrogenated amorphous carbon films were deposited from a mixture of argon and acetylene by electron cyclotron resonance-chemical vapor deposition at pressures of about 5–9×10−3 mbar. In order to improve the adhesion strength of DLC films, functionally gradient Ti/TiN/TiCN supporting mutilayers were deposited on the stampers. The structural characteristics of DLC films were investigated by Raman spectroscopy. The properties of a DLC film coating on a stamper are summarized as follows: microhardness (five times improved), roughness less than 4 nm, excellent adhesion of 65 N, and coefficients of friction less than 0.1. The characteristics of the back surface coated by DLC film were improved, and the productivity of an optical disk per stamper is estimated at about 1.7 times more than obtained. Finally, the DLC submaster stamper could be used to overcome the barrier and dramatically improve the economics and yield of increased productivity of polymer compact disks. © 2003 American Vacuum Society.
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42.79.Vb Optical storage systems, optical disks
81.05.U- Carbon/carbon-based materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.35.Np Adhesion
68.55.-a Thin film structure and morphology
68.65.Ac Multilayers
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.35.+c Brillouin and Rayleigh scattering; other light scattering
68.35.Gy Mechanical properties; surface strains
62.20.Qp Friction, tribology, and hardness
81.40.Pq Friction, lubrication, and wear
42.82.Cr Fabrication techniques; lithography, pattern transfer

Smooth surface glass etching by deep reactive ion etching with SF6 and Xe gases

Li Li, Takashi Abe, and Masayoshi Esashi

J. Vac. Sci. Technol. B 21, 2545 (2003); http://dx.doi.org/10.1116/1.1624272 (5 pages) | Cited 21 times

Online Publication Date: 25 November 2003

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This article reports on a smooth surface glass etching using deep reactive ion etching with a mixture of sulfur hexafluoride (SF6) and xenon (Xe) gases. A surface roughness of 23 Å was achieved with SF6/Xe(=1/1) and 18 Å with SF6/Ar(=1/4) under a condition of −390 V self-bias voltage and 0.2 Pa pressure. The surface roughness in the order of several angstroms (5.9 Å) was obtained at a pressure of 0.1 Pa (SF6/Xe=1/1). The average surface roughness (Ra) after the etching by SF6/Xe gas was smaller than those after the etching with SF6 only or SF6/Ar at a same mole fraction of the inert gas to SF6+inert gas. Since heavy inert gas increases the physical sputtering effect, the addition of the heavy inert gas helps to remove contaminant residues remaining on the etched surface. The optimum condition of smooth glass etching with high etch selectivity (21) is a pressure of 0.2 Pa and a mole fraction of Xe to SF6 gas is 8 to 7. We also make an analysis of the relationship between the surface average roughness on the bottom and the etched depth. The average roughness of the etched surface was smooth not only for the bottom but also for the sidewalls. The average surface roughness of the sidewalls was about 16 nm for 50-μm-deep etching under the same optimum condition. This technology was applied to a deep etching of quartz crystal used for a mass sensor. © 2003 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
68.35.B- Structure of clean surfaces (and surface reconstruction)

Diffusion barrier properties of very thin TaN with high nitrogen concentration

S. M. Rossnagel and H. Kim

J. Vac. Sci. Technol. B 21, 2550 (2003); http://dx.doi.org/10.1116/1.1625953 (5 pages) | Cited 17 times

Online Publication Date: 25 November 2003

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TaN deposited by magnetron sputtering has application in semiconductor interconnect structures as a diffusion barrier and adhesion layer. TaN used in these applications has a hexagonal or cubic structure consistent with roughly 1:1 Ta:N levels, with a bulk resistivity of 300–500 μΩ cm and a diffusion barrier failure temperature for 5 nm films of around 650 °C (Ref. 1). The diffusion barrier failure temperature (for Si/TaN-barrier/Cu samples) is a strong function of nitrogen concentration in the TaN; at the highest N levels (equivalent to nearly Ta3N5), the failure temperature exceeded 900 °C. At intermediate compositions, the failure temperature was found to exceed 700 °C even for films as thin as 0.4 nm. This suggests an interfacial contribution to diffusion barrier effectiveness, in addition to conventional grain boundary or bulk interdiffusion resistance, which may dominate conventional grain boundary diffusion. © 2003 American Vacuum Society.
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68.35.Fx Diffusion; interface formation
85.40.Ls Metallization, contacts, interconnects; device isolation
68.55.Nq Composition and phase identification
81.15.Cd Deposition by sputtering
66.30.Ny Chemical interdiffusion; diffusion barriers
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
73.61.At Metal and metallic alloys

Investigation of InGaP/GaAs heterojunction bipolar transistor with doping graded base

Yen-Wei Chen, Wei-Chou Hsu, Rong-Tay Hsu, Yue-Huei Wu, Yeong-Jia Chen, and Yu-Shyan Lin

J. Vac. Sci. Technol. B 21, 2555 (2003); http://dx.doi.org/10.1116/1.1625954 (3 pages) | Cited 5 times

Online Publication Date: 25 November 2003

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An n-p-n InGaP/GaAs heterojunction bipolar transistor (HBT) using a graded base doping profile has been fabricated by low pressure metalorganic chemical vapor deposition. A current gain of 77 and a base sheet resistance of 251 Ω/sq are achieved in the graded-base HBT. Compared to the graded-base structure, the nongraded-base structure has a lower current gain (68) and a higher base sheet resistance (294 Ω/sq). Furthermore, the studied graded-base HBT device also shows better microwave characteristics. The measured unity current-gain cutoff frequency (fT) can be improved from 18 to 22 GHz. The functional dependences of current gain, base sheet resistance, and microwave characteristics on the base doping profile are attributed to the graded-doping enhanced built-in field across the base and higher base doping at the emitter edge. © 2003 American Vacuum Society.
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85.30.Pq Bipolar transistors
85.40.Ry Impurity doping, diffusion and ion implantation technology
84.40.-x Radiowave and microwave (including millimeter wave) technology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Deep level defects and doping in high Al mole fraction AlGaN

S. T. Bradley, S. H. Goss, L. J. Brillson, J. Hwang, and W. J. Schaff

J. Vac. Sci. Technol. B 21, 2558 (2003); http://dx.doi.org/10.1116/1.1627331 (6 pages) | Cited 23 times

Online Publication Date: 25 November 2003

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We have used depth-dependent cathodoluminescence spectroscopy (CLS) and secondary ion mass spectrometry (SIMS) to investigate the nature of deep level defects and their effect on Si doping of high Al mole fraction (25%–100%) AlGaN. SIMS results provide correlations between AlGaN deep level emissions from CLS and elemental impurities distributed through the epitaxial bulk films. The highest Al mole fraction (xAl) samples exhibit deep level optical emissions that correlate with O and C impurities measured by SIMS. These O impurities appear to introduce donors at low and intermediate Al compositions versus deep levels in Al-rich alloys. The CLS energy onset of near band edge peak emissions track the b=1 theoretical band gap for 0⩽xAl⩽0.98 while their peak emissions deviate monotonically. Temperature-dependent CLS reveal an activation energy decrease of the near band edge emission intensity from 54 to 36 meV for xAl>∼0.80. The absence of free carriers for xAl>0.80 is consistent with Si donor compensation due to deep levels associated with oxygen. © 2003 American Vacuum Society.
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71.55.Eq III-V semiconductors
78.66.Fd III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
61.72.S- Impurities in crystals
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Vertically aligned carbon nanotubes grown by plasma enhanced chemical vapor deposition

Hideki Sato, Hitoshi Takegawa, and Yahachi Saito

J. Vac. Sci. Technol. B 21, 2564 (2003); http://dx.doi.org/10.1116/1.1627332 (5 pages) | Cited 9 times

Online Publication Date: 25 November 2003

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Plasma enhanced chemical vapor deposition, which enables growth of carbon nanotubes directly onto substrates, is potentially suitable for preparing carbon nanotubes as electron sources in field emission displays. In this article, we report the growth of aligned carbon nanotubes by microwave plasma enhanced chemical vapor deposition and investigate the effect of various parameters on the growth. Comparison among three catalysts (Fe, Co, and Ni) revealed that Fe gives the longest carbon nanotubes, while Co gives the carbon nanotubes with the smallest diameter. The growth of the carbon nanotubes strongly depends on the treatment time in the plasma. Field emission characteristics from the carbon nanotubes grown by the microwave plasma enhanced chemical vapor deposition are also shown. © 2003 American Vacuum Society.
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81.07.De Nanotubes
81.16.Hc Catalytic methods
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Dq Plasma-based ion implantation and deposition
61.46.-w Structure of nanoscale materials
79.70.+q Field emission, ionization, evaporation, and desorption
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Investigation of substrate rotation at glancing incidence on thin-film morphology

B. Dick, M. J. Brett, and T. Smy

J. Vac. Sci. Technol. B 21, 2569 (2003); http://dx.doi.org/10.1116/1.1627334 (7 pages) | Cited 23 times

Online Publication Date: 25 November 2003

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Films deposited by evaporation at glancing angles form structures dependent on the speed of substrate rotation. If the substrate is held stationary, oblique columns are grown. For slow substrate rotation, helices are formed while faster rotation yields pillars. Silicon and silicon dioxide films grown under similar conditions were found to follow the typical morphological trend. In contrast, aluminum films formed by glancing angle deposition (GLAD) were found to be facetted structures which were peaked and isolated at high rotation speeds (dφ/dt>42 rpm), and flat for dφ/dt∼1.5 rpm. The results suggest that the primary limiting factor controlling GLAD microstructure growth may be a combination of both material temperature and crystal structure of the resulting film. © 2003 American Vacuum Society.
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68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.A- Nucleation and growth

Molybdenum/pure aluminum gate bus line defect reduction for high-resolution thin film transistor liquid crystal displays

Takatoshi Tsujimura and Atsuya Makita

J. Vac. Sci. Technol. B 21, 2576 (2003); http://dx.doi.org/10.1116/1.1629713 (8 pages) | Cited 2 times

Online Publication Date: 25 November 2003

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Defect mode analysis for pure aluminum was done to improve fabrication of very large high-resolution thin film transistor liquid crystal displays with very low gate line delay. Mouse hole defects in pure aluminum films are caused by the stress voiding due to the heating/cooling process and by vacancy diffusion. An oxygen treatment between the molybdenum and aluminum depositions is very effective in completely suppressing mouse hole formation. An additive material is also effective in suppressing mouse holes because of the reduction in grain size and the vacancy pinning. Blisters are created during heating processes and can be suppressed by using a MoTa/Mo/aluminum structure or by removal of the undercoat layer. © 2003 American Vacuum Society.
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85.30.Tv Field effect devices
42.79.Kr Display devices, liquid-crystal devices
85.60.Pg Display systems
61.72.J- Point defects and defect clusters
66.30.Lw Diffusion of other defects

Structure, hardness, and elastic modulus of Pd/Ti nanostructured multilayer films

Junhua Xu, Masao Kamiko, Hidetaka Sawada, Yaomin Zhou, Ryoichi Yamamoto, Lihua Yu, and Isao Kojima

J. Vac. Sci. Technol. B 21, 2584 (2003); http://dx.doi.org/10.1116/1.1624267 (6 pages) | Cited 2 times

Online Publication Date: 25 November 2003

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The structure, hardness, and elastic modulus of Pd/Ti multilayers deposited by radio-frequency magnetron sputtering were investigated by x-ray diffraction, high-resolution transmission electron microscopy, and nanoindentation. Both the Ti and Pd layers were face-centered-cubic structures in all modulation periods from 2.8 nm to 90.0 nm in Pd/Ti multilayers. There are stacking faults in Ti layers at large modulation periods, where the crystal structure is hexagonal close packed. An anomalous hardness enhancement was observed. The hardness values of Pd/Ti multilayers are three times and two times the values measured in Pd films and as calculated by the rule of mixture for Pd and Ti films, respectively. The modulus values of Pd/Ti multilayers are between those of constituent single layer films at a larger modulation period, and increase slightly at a smaller modulation period. The elastic modulus difference model cannot explain this hardness enhancement, since the elastic modulus is almost the same for the constituent materials in the Pd/Ti multilayers. The hardening mechanisms in the multilayers have been discussed. © 2003 American Vacuum Society.
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68.65.Ac Multilayers
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.40.Jj Elasticity and anelasticity, stress-strain relations
61.72.Nn Stacking faults and other planar or extended defects
62.20.Qp Friction, tribology, and hardness
62.20.D- Elasticity
68.37.Lp Transmission electron microscopy (TEM)

Water-in-carbon dioxide microemulsions for removing post-etch residues from patterned porous low-k dielectrics

Xiaogang Zhang, Joseph Q. Pham, Hunter J. Martinez, P. Josh Wolf, Peter F. Green, and Keith P. Johnston

J. Vac. Sci. Technol. B 21, 2590 (2003); http://dx.doi.org/10.1116/1.1624268 (9 pages) | Cited 14 times

Online Publication Date: 25 November 2003

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A hierarchy of CO2-based solvents is used to remove post-etch residues from vias and trenches in low-k patterned porous methylsilsesquioxane (pMSQ) interlayer dielectrics. Spectroscopic ellipsometry measurements indicate that, upon pressurization and depressurization with CO2, the thickness and refractive index return to values near the original values indicating that collapse or voiding of the pores did not occur. Post-etch residue could not be removed by pure water, CO2, with or without cosolvent, or dry CO2 with a surfactant. These results suggest that the particles could not be removed by a dissolution mechanism alone. The via and the bottom trench were cleaned with a solvent containing water, CO2, and a hydrocarbon surfactant. In this mild detergent system, particles may be removed both as a suspension and in the dissolved state in microemulsions and macroemulsions. The low interfacial tension prevents collapse of the pMSQ during water removal. This mild detergent system does not produce voids in the pMSQ. Thus, this detergent cleaning technique appears to be selective for post-ash residues on pMSQ dielectrics and is of significant practical interest. © 2003 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
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Fabrication of nickel oxide nanostructures by atomic force microscope nano-oxidation and wet etching

Ju-Hung Hsu, Hsin-Wen Lai, Heh-Nan Lin, Chia-Chih Chuang, and Jin-Hua Huang

J. Vac. Sci. Technol. B 21, 2599 (2003); http://dx.doi.org/10.1116/1.1621655 (3 pages) | Cited 7 times

Online Publication Date: 26 November 2003

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We report the fabrication of nickel oxide nanostructures by atomic force microscope nano-oxidation and subsequent wet etching. By applying a negative bias to a conductive tip, nickel oxide patterns are first created by the process of nano-oxidation. The unoxidized nickel film is then etched away in a diluted nitric acid solution. Auger electron spectroscopy measurements confirm the complete removal of the nickel film and the preservation of the oxide patterns. Nickel oxide nanodots with diameters as small as 100 nm are reliably produced by the present method. © 2003 American Vacuum Society.
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81.16.Pr Micro- and nano-oxidation
81.07.Ta Quantum dots
81.16.Rf Micro- and nanoscale pattern formation
81.65.Cf Surface cleaning, etching, patterning
68.37.Ps Atomic force microscopy (AFM)
68.65.Hb Quantum dots (patterned in quantum wells)
79.20.Fv Electron impact: Auger emission

n-type doping characteristics of O-implanted GaN

Yoshitaka Nakano, Tetsu Kachi, and Takashi Jimbo

J. Vac. Sci. Technol. B 21, 2602 (2003); http://dx.doi.org/10.1116/1.1621652 (3 pages) | Cited 2 times

Online Publication Date: 26 November 2003

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Doping characteristics of O-implanted GaN have been investigated systematically from the viewpoint of annealing temperature. The implanted O atoms became electrically active as an n-type dopant after annealing above 1050 °C, but with a low activation efficiency of only 1.1%. From variable temperature Hall effect measurements, O-implanted GaN displayed a shallow ionization level of ∼18.3 meV after 1100 and 1200 °C anneals. In addition, secondary ion mass spectrometry measurements showed no measurable redistribution of the O atoms by the annealing. These results indicate poor probability of the O atoms occupying an N lattice site in GaN. © 2003 American Vacuum Society.
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61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.61.Ey III-V semiconductors
71.55.Eq III-V semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
81.05.Ea III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing

Comments on “Analysis of the I–V characteristics of Al/4H-SiC Schottky diodes” by J. Zhang and W. R. Harrell [J. Vac. Sci. Technol. B 21, 872 (2003)]

Arthur D. van Rheenen

J. Vac. Sci. Technol. B 21, 2605 (2003); http://dx.doi.org/10.1116/1.1621658 (2 pages)

Online Publication Date: 26 November 2003

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© 2003 American Vacuum Society.
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85.30.Hi Surface barrier, boundary, and point contact devices
73.30.+y Surface double layers, Schottky barriers, and work functions

Reply to: “Comments on ‘Analysis of the I–V characteristics of Al/4H–SiC Schottky diodes’ ”

J. Zhang and W. R. Harrell

J. Vac. Sci. Technol. B 21, 2607 (2003); http://dx.doi.org/10.1116/1.1621657 (1 page)

Online Publication Date: 26 November 2003

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© 2003 Am