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Sep 2004

Volume 22, Issue 5, pp. L7-2215

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Radio frequency line-plasma source using permanent magnets

Youichi Sakawa, Kentaro Yano, and Tatsuo Shoji

J. Vac. Sci. Technol. A 22, L7 (2004); http://dx.doi.org/10.1116/1.1786594 (4 pages) | Cited 3 times

Online Publication Date: 24 September 2004

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A high-density and uniform line-plasma source is developed by an inductive rf discharge using a rectangular discharge chamber (200×100×20 mm) with a pair of permanent magnets placed on top and bottom of the chamber. Ion-saturation current-density Jis profile is controlled by varying the width of the magnets and the distance between the antenna and the magnets. A 140-mm-wide plasma [plasma density ≃ (1.8-2.5)×1012 cm−3 for electron temperature = 4–8 eV] of a uniformity variation within 90% is produced using a 140-mm-long antenna for an Ar pressure of 20 mTorr and a rf power of 3 kW. The measured Jis profiles are explained by solving the equation of motion for electrons under a magnetic field structure of longitudinal line cusps.
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52.50.Dg Plasma sources
52.25.-b Plasma properties
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High resolution, high speed ultrahigh vacuum microscopy

Helmut Poppa

J. Vac. Sci. Technol. A 22, 1931 (2004); http://dx.doi.org/10.1116/1.1786304 (17 pages) | Cited 1 time

Online Publication Date: 20 September 2004

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The history and future of transmission electron microscopy (TEM) is discussed as it refers to the eventual development of instruments and techniques applicable to the real time in situ investigation of surface processes with high resolution. To reach this objective, it was necessary to transform conventional high resolution instruments so that an ultrahigh vacuum (UHV) environment at the sample site was created, that access to the sample by various in situ sample modification procedures was provided, and that in situ sample exchanges with other integrated surface analytical systems became possible. Furthermore, high resolution image acquisition systems had to be developed to take advantage of the high speed imaging capabilities of projection imaging microscopes. These changes to conventional electron microscopy and its uses were slowly realized in a few international laboratories over a period of almost 40 years by a relatively small number of researchers crucially interested in advancing the state of the art of electron microscopy and its applications to diverse areas of interest; often concentrating on the nucleation, growth, and properties of thin films on well defined material surfaces. A part of this review is dedicated to the recognition of the major contributions to surface and thin film science by these pioneers. Finally, some of the important current developments in aberration corrected electron optics and eventual adaptations to in situ UHV microscopy are discussed. As a result of all the path breaking developments that have led to today’s highly sophisticated UHV–TEM systems, integrated fundamental studies are now possible that combine many traditional surface science approaches. Combined investigations to date have involved in situ and ex situ surface microscopies such as scanning tunneling microscopy/atomic force microscopy, scanning Auger microscopy, and photoemission electron microscopy, and area-integrating techniques such as x-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, Auger electron spectroscopy, low-energy electron diffraction, temperature programmed desorption, high-resolution electron energy-loss and Fourier-transform infrared spectroscopies, and others. Material systems ranging from atomic layers of metals and semiconductors to biology related depositions are being investigated. In the case of biological materials, however, strict limitations to high-resolution applications are imposed by electron radiation damage considerations.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.81.+a Electron and ion spectrometers
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
07.60.Rd Visible and ultraviolet spectrometers
07.79.Lh Atomic force microscopes
07.79.Cz Scanning tunneling microscopes
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Generation of low-energy neutral beam for Si etching

S. J. Kim, S. J. Wang, J. K. Lee, D. H. Lee, and G. Y. Yeom

J. Vac. Sci. Technol. A 22, 1948 (2004); http://dx.doi.org/10.1116/1.1774198 (8 pages) | Cited 8 times

Online Publication Date: 20 September 2004

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As the feature size shrinks toward the nanoscale, charge-up damage from ion-induced etching becomes a very serious problem. Neutral beam etching is one of the most popular techniques used to reduce charge-up damage. We have performed a neutral beam simulation to optimize the neutral beam, which is generated by collisions between ions produced by a plasma source with an ion gun and low angle reflectors. An ion gun is simulated using the two-dimensional Xgrafic object oriented particle-in-cell (XOOPIC) code to obtain a higher ion flux and to improve the directionality of ions. For neutral beam simulation, we use the modified XOOPIC code to which reflection data obtained by the transport of ions in matter (TRIM) code are appended. Neutral flux, energy and angle distributions, which have an influence upon the etch rate, are calculated in the neutral beam simulation. A low-energy neutral beam from an ion gun with two grids has a low neutral flux and a broad angle distribution. Therefore, we propose a three-grid ion gun that has one additional grid with positive voltage, allowing independent control of the ion flux and ion energy. By increasing the ion flux, the neutral flux by three grids is three times larger than that by two grids. The neutral beam source using a three-grid ion gun has several advantages for trench etching: increased etch rate, decreased sidewall etching, and reduced variation in the etch rate as the trench size changes. A low-energy neutral beam source using the three-grid ion g 0un and low-angle reflectors is experimentally tested.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Cy Elemental semiconductors
52.77.Bn Etching and cleaning

Infrared reflectance of GaN1−xPx ternary alloys grown by metalorganic chemical vapor deposition

J. B. Wang, Z. F. Li, W. Lu, D. J. Chen, B. Shen, and Y. D. Zheng

J. Vac. Sci. Technol. A 22, 1956 (2004); http://dx.doi.org/10.1116/1.1776178 (6 pages) | Cited 1 time

Online Publication Date: 20 September 2004

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Infrared (IR) reflection spectra of GaN1−xPx alloys, grown by light-radiation heating, low-pressure metalorganic chemical vapor deposition, have been investigated with phosphorus composition x=0–0.15. A multi-oscillator model has been used to fit the IR reflection spectra. In addition to the demonstration of a GaN-like transverse-optical (TO) mode, a GaP-like TO mode, located at about 355 cm−1, has been identified for x>0, showing a typical two-mode behavior. With the increment of x the frequency of the GaN-like TO phonon decreases and the GaP-like TO phonon keeps its frequency almost unchanged within the measured composition range. A simple random-element-isodisplacement model has been employed to interpret the frequency change of both GaN-like and GaP-like phonons with the phosphorous composition x. The damping of the GaN-like TO mode increases significantly with x and is explained by the disorder effect resulting from the introduction of foreign P atoms.
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78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
78.20.-e Optical properties of bulk materials and thin films
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Interpretation of stress variation in silicon nitride films deposited by electron cyclotron resonance plasma

M. P. Besland, M. Lapeyrade, F. Delmotte, and G. Hollinger

J. Vac. Sci. Technol. A 22, 1962 (2004); http://dx.doi.org/10.1116/1.1776179 (9 pages) | Cited 2 times

Online Publication Date: 20 September 2004

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We report here on internal stress variations in SiNx films deposited on silicon by plasma enhanced chemical vapor deposition-electron cyclotron resonance (PECVD-ECR) plasma. The effects of deposition parameters, film thickness and surface morphology have been considered. SiNx films can exhibit a compressive or a tensile internal stress, ranging from −1970 to +465 MPa, depending on deposition parameters. Among published results, usual reported residual stress for PECVD films is compressive. Versatility of our experimental ECR equipment allows one to deposit films exhibiting a weak stress in the range of a few tens MPa. On the basis of atomic force microscopy observations, a correlation between the intensity of the stress and the granular morphology of the films has been observed. The rms value for SiNx film surfaces is never higher than 1.5 nm, with a grain height ranging from 1.2 to 5 nm and a grain width varying from 20 to 60 nm. Both the grain size and the residual stress vary with the thickness of the films. This work highlights the influence of the initial surface properties on the deposition mechanism. An exhaustive review of the stress generation model is given and a tentative interpretation for the origin of stress, either compressive or tensile, is proposed.
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68.60.Bs Mechanical and acoustical properties
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth
52.77.Dq Plasma-based ion implantation and deposition
68.37.Ps Atomic force microscopy (AFM)

Microstructure and Mg concentration of Mg–Si thin film deposited by ion beam sputtering on glass substrate

T. Serikawa, M. Henmi, and K. Kondoh

J. Vac. Sci. Technol. A 22, 1971 (2004); http://dx.doi.org/10.1116/1.1778406 (4 pages) | Cited 11 times

Online Publication Date: 20 September 2004

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Mg–Si thin films are deposited by ion beam sputtering from the target composed of Mg and Si with 50%:50% area ratios. Intermetallic compound magnesium silicide (Mg2Si) films are obtained at room temperature on glass substrates. Observation of the thin film by cross sectional transmission electron microscopes indicates that films of 1 μm thickness show a microstructure composed of a crystalline upper layer of Mg2Si with columnar structure 300 nm thick and an amorphous bottom layer with uniform structure 700 nm in thickness. Energy dispersive x-ray measurements show that magnesium concentration in the crystalline Mg2Si upper layer are larger than in the amorphous bottom layer. Moreover, the magnesium concentration at grain boundaries is larger than that in grains in the crystalline Mg2Si upper layer. It is also observed that magnesium segregates on the film surface. The film formation is explained in terms of magnesium migration-to-surface and magnesium evaporation from film surface.
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68.55.-a Thin film structure and morphology
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
61.43.Dq Amorphous semiconductors, metals, and alloys
61.72.Mm Grain and twin boundaries
81.15.Cd Deposition by sputtering
68.35.Dv Composition, segregation; defects and impurities
81.05.Gc Amorphous semiconductors

Optical properties of tantalum nitride films fabricated using reactive unbalanced magnetron sputtering

S. M. Aouadi and M. Debessai

J. Vac. Sci. Technol. A 22, 1975 (2004); http://dx.doi.org/10.1116/1.1778410 (5 pages) | Cited 12 times

Online Publication Date: 20 September 2004

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Coatings of tantalum nitride with various compositions were deposited on silicon substrates using unbalanced reactive magnetron sputtering. An optical emission spectrometer was used to monitor the ratio of tantalum to nitrogen particles in the plasma in real time. The coatings were characterized using x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SE). The primary nitride phases (Ta, Ta2N, TaN) in the films were determined using XRD and XPS. The elemental composition was revealed from XPS measurements. The refractive indices were deduced from analysis of the SE data, which were subsequently simulated using the Drude–Lorentz model. The resistivity and electron mean free paths were deduced from this simulation and were correlated to the film composition and microstructure. The resistivity increased whereas the electron mean free path decreased with an increase in nitrogen content or a decrease in grain size.
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79.60.Bm Clean metal, semiconductor, and insulator surfaces
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.15.Cd Deposition by sputtering
78.47.-p Spectroscopy of solid state dynamics
68.47.-b Solid-gas/vacuum interfaces: types of surfaces
68.55.Nq Composition and phase identification
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Evaluation of Schottky barrier height of TiN∕p-type Si(100)

Joshua Pelleg and A. Douhin

J. Vac. Sci. Technol. A 22, 1980 (2004); http://dx.doi.org/10.1116/1.1774199 (4 pages) | Cited 1 time

Online Publication Date: 23 September 2004

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Zero-bias Schottky barrier height (ϕBp) of reactive-sputtered TiN (∼40 nm) on p-type Si(100) was determined at room temperature and the effect of heat treatment was investigated by forward current–voltage (I–V) measurements. The TiN remained amorphous following annealing. The zero-bias barrier heights for the as-deposited and annealed specimens were in the range of 0.53–0.64 V. The lower ϕBp values of 0.53–0.54 V are related to as-deposited and 673 K annealed specimens, whereas the 0.62–0.64 V values refer to samples annealed at 773–783 K. Forward I–V measurements of as-deposited (300 K) TiN∕Si diodes were performed in the temperature range of 220–285 K. The barrier height was determined by the activation energy method, resulting in ϕBp=0.58 V.
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85.30.Hi Surface barrier, boundary, and point contact devices
85.30.Kk Junction diodes
81.40.Gh Other heat and thermomechanical treatments

Real-time acoustic sensing and control of metalorganic chemical vapor deposition precursor concentrations delivered from solid phase sources

L. Henn-Lecordier, J. N. Kidder, and G. W. Rubloff

J. Vac. Sci. Technol. A 22, 1984 (2004); http://dx.doi.org/10.1116/1.1776180 (8 pages) | Cited 5 times

Online Publication Date: 23 September 2004

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We have investigated the performance and potential benefit of acoustic sensing for real-time monitoring and closed loop control of binary gas mixture compositions delivered from low vapor pressure metalorganic sources. Two solid phase sources were investigated in the presence of H2 as a carrier gas: (1) trimethylindium (TMI) and (2) bis(cyclopentadienyl) magnesium (Cp2Mg), which have room temperature (25°C) vapor pressures of 2.5 and 0.04 Torr, respectively. An acoustic sensor was implemented on the gas feed line to measure the concentration-dependent speed of sound in the gas mixture. This enabled sensitivity and control at precursor levels as low as 0.6 ppm in H2. Closed loop process control was implemented to maintain TMI and Cp2Mg concentration target in the presence of intentionally introduced long term temperature drifts. Despite induced variations of the precursor vapor pressure up to 50%, the delivered composition was controlled to within ±0.15% for TMI (at 0.5 mol% set point) and ±0.3% for Cp2Mg (at 0.01 mol% set point). Short term variability could also be substantially reduced by the control scheme. This work demonstrates the feasibility of sensor-driven control systems for stable delivery of low vapor pressure, normally problematic precursor materials. In turn, this opens the door to utilization of a broader range of species which can be synthesized as chemical precursors.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
43.20.Ye Measurement methods and instrumentation

Wide range flow sensor—Vacuum through viscous flow conditions

Hemi Sagi, Yabin Zhao, and S. T. Wereley

J. Vac. Sci. Technol. A 22, 1992 (2004); http://dx.doi.org/10.1116/1.1776181 (8 pages) | Cited 2 times

Online Publication Date: 23 September 2004

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An intelligent molecular flow sensor [see Note (1) on next page] enables direct gas flow measurements in the transitional and molecular flow regimes, as well as in the slip and continuum flow regimes, thereby enabling flow measurements at pressures ranging from vacuum through atmospheric. The properties of this sensor are investigated, along with the sensor’s transitional operating ranges. The IMFS operates as a mass flow sensor (directly measures the mass flow) in the transitional and molecular flow regimes, and it operates as a volumetric flow sensor in the continuum and slip flow regimes. Understanding of these properties and ranges of operation are critical for demanding leak testing, sealed closure integrity testing and vacuum test applications.
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47.80.-v Instrumentation and measurement methods in fluid dynamics
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.30.Hd Vacuum testing methods; leak detectors

Effect of nano-crystallization of high velocity oxy-fuel-sprayed amorphous NiCrBSi alloy on properties of the coatings

Chang-Jiu Li, Yu-Yue Wang, and Hua Li

J. Vac. Sci. Technol. A 22, 2000 (2004); http://dx.doi.org/10.1116/1.1776183 (5 pages) | Cited 1 time

Online Publication Date: 23 September 2004

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NiCrBSi self-fluxing alloy coatings were deposited by high velocity oxy-fuel (HVOF) spraying. Annealing treatment was applied to the as-sprayed coatings to develop the microstructure of the Ni-based coating. The microstructure of the coating was characterized using optical microscopy, x-ray diffraction and transmission electron microscopy. The crystallization behavior of the amorphous coating was also characterized by differential scanning calorimetry. The properties of the coating were characterized by microhardness and abrasive wear tests. The results showed that the as-sprayed HVOF coating deposited by well melted spray particles exhibited a dense microstructure of amorphous phase. It was revealed that the crystallization of the amorphous phase in HVOF NiCrBSi coating occurs at a temperature of about 502°C. Annealing at temperature a little higher than recrystallization temperature leads to the formation of the nano-crystalline microstructure. The subsequent nanostructured Ni-based coating presents higher microhardness and excellent wear performance. With the further increase in annealing temperature, the growth of the nano-crystalline grains occurs and, accordingly, the microhardness of the coating and the wear performance decrease. Thereafter, the microstructure and properties of the Ni-based self-fluxing alloy coating can be controlled through postannealing treatment.
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68.60.Bs Mechanical and acoustical properties
61.46.-w Structure of nanoscale materials
75.50.Tt Fine-particle systems; nanocrystalline materials
81.07.Bc Nanocrystalline materials
75.50.Kj Amorphous and quasicrystalline magnetic materials
64.70.D- Solid-liquid transitions
68.37.Lp Transmission electron microscopy (TEM)
62.20.Qp Friction, tribology, and hardness
68.35.Gy Mechanical properties; surface strains
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.40.Pq Friction, lubrication, and wear

Organosilane self-assembled monolayers directly linked to the diamond surfaces

Riichiro Ohta, Nagahiro Saito, Yasushi Inoue, Hiroyuki Sugimura, and Osamu Takai

J. Vac. Sci. Technol. A 22, 2005 (2004); http://dx.doi.org/10.1116/1.1776184 (5 pages) | Cited 9 times

Online Publication Date: 23 September 2004

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An amino-terminated self-assembled monolayer (SAM) was prepared from p-aminophenyltrimethoxysilane (H2N(CH)6Si(OCH3)3, APhS) on diamond substrates irradiated by vacuum ultraviolet (VUV) light (wavelength: 172 nm) through chemical vapor deposition. Furthermore, the APhS-SAM was irradiated by VUV light in air. After the VUV irradiation, only one layer of siloxane (SiOx) was left as a result of the selective decomposition of organic compounds. APhS-SAM was reprepared on the SiOx surface. The evidence as to the respective processes was clearly obtained by x-ray photoelectron spectroscopy (XPS) and water contact angle measurements. Based on the chemical bonding states analysis, APhS-SAMs were confirmed to be directly linked to the diamond substrates and SiOx layers with bonding types of Si–O–C and Si–O–Si, respectively. The compositions obtained by XPS measurement indicate that the thickness of the SiOx layer was increased gradually by repeating the APhS-SAM formations and VUV irradiations in this order. Finally, we are successful in controlling the nano-scale thickness of the SiOx layer, which is the interface between APhS-SAMs and diamond substrates.
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68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces
68.55.A- Nucleation and growth
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
79.60.Fr Polymers; organic compounds
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Pv Polymers, organic compounds
79.60.Dp Adsorbed layers and thin films

Dielectric response of asymmetric KNbO3∕KTaO3 superlattices

J. Sigman, H. J. Bae, D. P. Norton, J. Budai, and L. A. Boatner

J. Vac. Sci. Technol. A 22, 2010 (2004); http://dx.doi.org/10.1116/1.1778403 (4 pages) | Cited 5 times

Online Publication Date: 23 September 2004

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The synthesis and properties of asymmetric KNbO3∕KTaO3 superlattices is examined. Interdigitated electrodes are fabricated for temperature-dependent capacitance measurements. The nonlinear dielectric response of 1∕N superlattice exhibits the anomalous positive tunability behavior indicative of antiferroelectricity. In contrast, the N∕1 KNbO3∕KTaO3 structures (N>1) appear to be either ferroelectric or paraelectric, depending on the temperature. Discussion of possible mechanisms for this behavior is given.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
68.65.Cd Superlattices
77.80.-e Ferroelectricity and antiferroelectricity

Neutral gas temperature measurements within transformer coupled toroidal argon plasmas

Bo Bai and Herbert Sawin

J. Vac. Sci. Technol. A 22, 2014 (2004); http://dx.doi.org/10.1116/1.1778404 (8 pages) | Cited 10 times

Online Publication Date: 23 September 2004

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Spatially resolved neutral gas temperature of Ar plasmas within a new type of transformer-coupled toroidal plasma source was measured by fitting unresolved rovibrational bands of trace gas N2 (C 3Πu→B 3Πg). With power density as high as 4.8 W∕cm3, the maximum neutral gas temperature inside Ar plasmas was found to be 2000 K. The position with maximum neutral gas temperature was off the center of the cross section and close to the ferrite core, where higher electric field contributes to higher heating power. The dependence of neutral gas temperature on pressure was measured and can be empirically fitted by proportionality between gas temperature and logarithm of the pressure, as found by other researchers. A simple physical model gives the dependence of pressure as the sixth order of neutral gas temperature, which fits the experimental data as well. It was also found that added N2 gas perturbed Ar plasmas obviously, and therefore we recommend adding less than 1% N2 as trace gas. There is no dependence of fitted neutral gas temperature on the optical resolution of monochromator, as would be expected.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.50.Dg Plasma sources
52.25.-b Plasma properties
33.20.Vq Vibration-rotation analysis

Pressure field in a tube with a general and arbitrary time- and position-dependent gas source

F. T. Degasperi, M. N. Martins, J. Takahashi, and S. L. L. Verardi

J. Vac. Sci. Technol. A 22, 2022 (2004); http://dx.doi.org/10.1116/1.1778408 (5 pages) | Cited 1 time

Online Publication Date: 23 September 2004

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In this article we present analytical and numerical results for a pressure profile along the axis of a tube with a general and arbitrary time- and position-dependent gas source. The model is able to determine the pressure values along the tube, once the pumping speed at each extremity and the gas sources are specified. The time evolution of the pressure along a tube is presented for situations commonly found in high-vacuum applications, such as particle accelerators, colliders, storage rings, and synchrotron light sources.
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07.30.-t Vacuum apparatus

Design and performance of a molecular beam epitaxy system for metallic heterostructure deposition illustrated by a study of the controlled epitaxy of Cu(111)∕Al2O3(0001)

M. S. Lund and C. Leighton

J. Vac. Sci. Technol. A 22, 2027 (2004); http://dx.doi.org/10.1116/1.1781181 (8 pages) | Cited 4 times

Online Publication Date: 23 September 2004

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We describe the design and construction of an ultrahigh-vacuum molecular beam epitaxy (MBE) system for the growth of metallic heterostructures, particularly magnetic metals, and alloys. The system, which was specifically designed to be both cost-effective and compact, incorporates an “axial” design with a large source to substrate distance (>69 cm) to meet demands for high uniformity, low deposition rate, and compatibility with nanolithographic masks and templates. The growth and in situ characterization capabilities are specifically tailored to metallic film growth allowing for greatly reduced costs in comparison to commercial MBE systems. We demonstrate the performance of the system via a study of the controlled epitaxy of Cu(111) on Al2O3(0001), a useful substrate/buffer layer combination for the growth of many magnetic transition metals and their alloys. Exploiting the three-dimensional nature of the growth at room temperature we are able to control the in-plane crystallite size, independent of the surface roughness, by varying the deposition rate.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.A- Nucleation and growth

Atomic layer deposition and characterization of hafnium oxide grown on silicon from tetrakis(diethylamino)hafnium and water vapor

Anand Deshpande, Ronald Inman, Gregory Jursich, and Christos Takoudis

J. Vac. Sci. Technol. A 22, 2035 (2004); http://dx.doi.org/10.1116/1.1781183 (6 pages) | Cited 13 times

Online Publication Date: 23 September 2004

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In this work thin films of hafnium oxide are deposited on Si(100) substrates by means of atomic layer deposition (ALD) using tetrakis(diethylamino)hafnium and water vapor at substrate temperatures of 250–350ºC. Our system capabilities include fast transient delivery of reactive fluids, real-time vapor phase detection (in situ tunable diode laser hygrometer), precursor thermochemical capabilities, and ppt level elemental analysis by inductive coupling plasma mass spectrometry. The composition, purity, and other properties of the films and resulting interfaces are determined using x-ray and Fourier transform infrared spectroscopies, Z-contrast imaging and electron energy loss spectroscopy in a scanning transmission electron microscope with math scale resolution, and spectroscopic ellipsometry. The observed ALD rate is ∼1.4 math per cycle. The nonuniformity across the film is less than 4%. Negligible carbon contamination is found in the resulting stoichiometric films under all conditions studied. The pulse sequence was optimized to prevent disastrous particulate problems while still minimizing purge times. The film deposition is investigated as a function of substrate temperature and reagent pulsing characteristics. A mild inverse temperature dependence of the ALD rate is observed. The initial stage of the HfO2 growth is investigated in detail.
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68.55.A- Nucleation and growth
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
79.20.Uv Electron energy loss spectroscopy
78.30.Hv Other nonmetallic inorganics
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
68.35.Ct Interface structure and roughness
68.37.Lp Transmission electron microscopy (TEM)
81.05.-t Specific materials: fabrication, treatment, testing, and analysis

Influence of substrate bias on practical adhesion, toughness, and roughness of reactive dc-sputtered zirconium nitride films

Cheng-Shi Chen, Chuan-Pu Liu, Heng-Ghieh Yang, and C.-Y. A. Tsao

J. Vac. Sci. Technol. A 22, 2041 (2004); http://dx.doi.org/10.1116/1.1782635 (7 pages) | Cited 7 times

Online Publication Date: 23 September 2004

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The ZrN films were grown on Si (100) substrates using dc magnetron sputtering where the substrate bias was varied from −45 to 50 V. In this article, the film/substrate practical adhesion of the ZrN films were measured by scratch testing while the hardness, elastic modulus, and fracture toughness were measured by nanoindentation. The structures and morphologies of the ZrN films were analyzed using scanning electron microscopy, atomic force microscopy, and x-ray diffraction. The results indicate that the introduction of either negative or positive bias results in the degradation of the practical adhesion properties, while the films under zero bias exhibit the best adhesion. In addition, positive bias results in the increase in both the hardness and elastic modulus, while negative bias enhances the hardness and toughness of the ZrN thin films. The mechanical properties are greatly influenced by substrate bias and can be correlated to microstructure variations. The detailed mechanisms accounted for these phenomena are discussed.
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68.60.Bs Mechanical and acoustical properties
68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
68.35.Np Adhesion
68.35.Gy Mechanical properties; surface strains
68.37.Ps Atomic force microscopy (AFM)
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials
62.20.Qp Friction, tribology, and hardness
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
81.05.-t Specific materials: fabrication, treatment, testing, and analysis

Relationship between optical properties and microstructure of CeO2–SiO2 composite thin films

Won Hoe Koo, Soon Moon Jeong, Sang Hun Choi, Hong Koo Baik, Se Jong Lee, and Sung Man Lee

J. Vac. Sci. Technol. A 22, 2048 (2004); http://dx.doi.org/10.1116/1.1782638 (4 pages) | Cited 3 times

Online Publication Date: 23 September 2004

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CeO2–SiO2 composite thin films were prepared by e-beam evaporation and ion beam assisted deposition using an End-Hall ion source. The refractive index of composite thin films exhibited a maximum value at 20%–35%SiO2 fraction, indicating the high packing density. Optical analysis revealed that the transmittance and reflectance spectra of composite films were consistent with the results of the refractive index. The results from x-ray diffractometry, atomic force microscopy and scanning electron microscopy measurements showed that composite thin films containing 20%–35%SiO2 concentration had a dense and smooth amorphous surface, compared to the roughened granular structure of the pure SiO2 and CeO2 thin films. The composite thin films with 20%–35%SiO2 concentration exhibited a higher resistance to water absorption than the CeO2 thin films in spite of the highest refractive index.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
78.30.Hv Other nonmetallic inorganics
42.70.-a Optical materials
78.66.Sq Composite materials
81.40.Tv Optical and dielectric properties related to treatment conditions
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.47.Gh Oxide surfaces
68.55.-a Thin film structure and morphology

Sub-100 °C a‐Si:H thin-film transistors on plastic substrates with silicon nitride gate dielectrics

A. Sazonov and C. McArthur

J. Vac. Sci. Technol. A 22, 2052 (2004); http://dx.doi.org/10.1116/1.1784826 (4 pages) | Cited 16 times

Online Publication Date: 23 September 2004

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Fabrication on thin-film transistors (TFTs) on flexible plastic substrates for large-area imagers and displays has been made possible by lowering the deposition temperatures, which reduces the thermal deformation of plastic substrates, greatly facilitating substrate preparation and device patterning. Furthermore, at extremely low deposition temperatures, much wider variety of low-cost substrates, plastics or otherwise, are available for use. In this article, we report on a‐Si:H TFTs fabricated at 75 °C on glass and plastic substrates. The TFTs were fabricated using inverted–staggered topology, in a full wet etch process. The TFT structures consisted of 140 nm of sputtered Mo for gate, 380 nm of plasma-enhanced chemical vapor deposition (PECVD) a‐SiNx:H gate dielectric optimized for 75 °C, 50 nm of PECVD a‐Si:H channel material, 50 nm of PECVD n+ a‐Si:H for source∕drain contacts, and sputtered Al for contact metallization. Current–voltage characteristics were measured, and relevant transistor parameters were calculated. TFTs exhibited the leakage current below 10−12 A, and on∕off current ratio exceeding 105. The results were compared to those for high temperature a‐Si:H TFTs, and the differences are discussed.
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85.30.Tv Field effect devices
81.05.Cy Elemental semiconductors
81.05.Gc Amorphous semiconductors
68.55.A- Nucleation and growth
61.43.Dq Amorphous semiconductors, metals, and alloys
73.61.Cw Elemental semiconductors
81.65.Cf Surface cleaning, etching, patterning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Contribution and origin of H3O+ in the mass spectral peak at 19 amu

C. R. Cole, R. A. Outlaw, R. L. Champion, D. H. Baker, and B. C. Holloway

J. Vac. Sci. Technol. A 22, 2056 (2004); http://dx.doi.org/10.1116/1.1784827 (5 pages) | Cited 6 times

Online Publication Date: 23 September 2004

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Typically, the mass spectral peak observed at 19 amu in residual gas analyzers at very high vacuum (VHV) and ultrahigh vacuum (UHV) has been attributed to fluorine. Using Fourier transform mass spectrometry (FTMS), the presence of the hydronium ion H3O+ has been fully resolved from F+. Correlation of the mass 19 signals for a conventional quadrupole mass spectrometer (QMS) and the FTMS, positioned adjacent, unambiguously indicates hydronium as the source of mass 19. At partial pressures of H2O in the VHV range and higher there is sufficient density for the formation of the hydronium ion through ion–molecule interactions. Formation of the hydronium was found to directly correlate with the partial pressure of H2O. However, in a QMS, formation of H3O+ in UHV appears to occur principally by electron stimulated desorption (ESD). Dosing the system with hydrogen from 1 L exposure to saturation (1×10−6 Torr for 8 h) was found to increase the H3O+ ESD yield detected by the QMS by as much as a factor of 10. The initial hydronium ESD cross section from a hydrogen saturated grid was estimated to be σ∼1×10−19 cm2. In a separate experiment, time of flight–secondary ion mass spectrometry sputter yields from the stainless steel grid of a quadrupole mass spectrometer also showed small signals of H3O+, as well as its constituents, H+, O+ and OH+, but no F+.
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82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
68.43.Rs Electron stimulated desorption
82.80.Nj Fourier transform mass spectrometry
82.80.Rt Time of flight mass spectrometry
07.75.+h Mass spectrometers

Laser-triggered hollow-cathode plasma process for film growth

S. Witanachchi, P. Mahawela, and P. Mukherjee

J. Vac. Sci. Technol. A 22, 2061 (2004); http://dx.doi.org/10.1116/1.1784828 (6 pages) | Cited 2 times

Online Publication Date: 23 September 2004

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A method of generating a pulsed plasma plume of metallic species using a hollow-cathode arc discharge arrangement is presented. Electrical energy from a pulse-forming network (PFN) generates the transient plasma that evaporates material from the anode that is placed inside a hollow cathode. The discharge is triggered by thermionic electrons produced by a CO2 laser pulse that impinges on one of the electrodes. This plasma process has been used to deposit carbon films in a low-pressure argon or nitrogen ambient. Current pulses of 4–10 ms in duration with peak currents of 350 A have been produced by the PFN. Characteristics of the produced plasma have been studied by optical emission spectroscopy. The amount of energy imparted to the argon plasma is more than that for a nitrogen plasma. Comparison of on-axis intensity for the 426.9 nm line of C+ for the two plasmas shows that the density of carbon ions generated in the nitrogen plasma is higher than that in the argon plasma. Films deposited by this method have fairly uniform thickness profiles that are of the form cos0.4 θ for the argon plasma and cos2.2 θ for the nitrogen plasma. This indicates that the nitrogen plasma is more forward directed than the argon plasma. Deposition rates of about 10–16 math∕pulse have been obtained for carbon films.
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52.77.Dq Plasma-based ion implantation and deposition
52.80.Hc Glow; corona
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.50.Dg Plasma sources

Chemical state of nitrogen in a high nitrogen face-centered-cubic phase formed on plasma source ion nitrided austenitic stainless steel

M. K. Lei and X. M. Zhu

J. Vac. Sci. Technol. A 22, 2067 (2004); http://dx.doi.org/10.1116/1.1786305 (4 pages) | Cited 6 times

Online Publication Date: 23 September 2004

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A single high nitrogen face-centered-cubic phase (γN) was formed on the plasma source ion nitrided 1Cr18Ni9Ti (18-8 type) austenitic stainless steel. Auger electron spectroscopy and x-ray photoelectron spectroscopy, in conjuction with ion beam sputtering, were used to determine the chemical composition and bonding of nitrogen in the γN phase. The chemical composition of the γN phase was shown as a formula with atomic fraction (Fe0.60,Cr0.22,Ni0.18)2N. The γN phase possessed weaker Cr–N ionic-type bonds and stronger Fe–N ionic-type bonds, compared with the stoichiometric nitrides. The Cr 2p3∕2 binding energy was 1.1 eV lower than that of CrN and Cr2N phases (at 575.5 eV). The chemical shift of the Fe–N bonding compared with the Fe–Fe bonding was nearly 2.1 eV. The N 1s binding energies showed that the nitrogen was in the chemical state with iron (at 396.6 eV) and chromium (at 397.7 eV). All the chromium appeared to be in the Cr–N bond. A part of iron was also observed in the nitride state, and all the nickel was contained in the metallic state.
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82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
79.20.Fv Electron impact: Auger emission
52.77.-j Plasma applications
81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Degradation of ZrN films at high temperature under controlled atmosphere

Fu-Hsing Lu and Wen-Zheng Lo

J. Vac. Sci. Technol. A 22, 2071 (2004); http://dx.doi.org/10.1116/1.1786308 (6 pages) | Cited 7 times

Online Publication Date: 23 September 2004

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The degradation of ZrN films deposited onto Si substrates by unbalanced magnetron sputtering was investigated over temperatures of 300–1200 °C in different atmospheres by analyzing changes in color and appearance, as well as microstructures. The atmospheres contained air, nitrogen, and forming gas (N2∕H2=9), which exhibited drastically different oxygen/nitrogen partial pressure ratios. The resultant degradation included mainly color changes and formation of blisters on the film surface. Color change was associated with the oxidation of the nitride film, which was analyzed by looking into the Gibbs free-energy changes at various temperatures and oxygen partial pressures. Two types of blisters occurred at different temperature ranges. Several large round blisters, denoted as A-type blisters, occurring at low temperatures originated from the large residual stress in the films. Many small irregular blisters, denoted as B-type blisters, appearing at relatively high temperatures resulted from the oxidation of the film.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.60.-p Physical properties of thin films, nonelectronic
81.15.Cd Deposition by sputtering
81.65.Mq Oxidation
65.40.G- Other thermodynamical quantities
68.60.Bs Mechanical and acoustical properties

In situ cleaning of GaN(0001) surfaces in a metalorganic vapor phase epitaxy environment

Z. J. Reitmeier, J.-S. Park, W. J. Mecouch, and R. F. Davis

J. Vac. Sci. Technol. A 22, 2077 (2004); http://dx.doi.org/10.1116/1.1786309 (6 pages) | Cited 1 time

Online Publication Date: 23 September 2004

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The presence of ammonia in a metalorganic vapor phase epitaxy (MOVPE) system configured for the growth of GaN films is necessary and sufficient to remove adsorbed O- and C-containing species from the (0001) surface of this compound without measurable decomposition of this surface. Chemical and microstructural evidence in support of this statement has been obtained from investigations concerned with the extension of a previously developed in situ process route for cleaning heated GaN(0001) surfaces in a molecular beam epitaxy environment using flowing ammonia to the higher pressure regime of MOVPE. Thin films of GaN were deposited under 20 Torr total pressure on GaN templates, previously exposed to the laboratory ambient, and heated in either a nitrogen∕hydrogen or an ammonia∕hydrogen mixture to the deposition temperature of 1020 °C. Secondary ion mass spectroscopy of these samples revealed significant concentrations of carbon and oxygen at the GaN∕GaN interface in the former and the absence of these contaminants above the detection limits of the instrument in the latter. The surfaces of the templates heated in the nitrogen∕hydrogen atmosphere also decomposed sufficiently to form a very thin liquid Ga layer that reacted with ammonia to form a GaN-containing film either at the outset of film growth or on cooling in an ammonia∕nitrogen atmosphere. Atomic force microscopy (AFM) showed a smoother surface for the GaN films deposited on templates heated and cleaned in the ammonia∕hydrogen mixture relative to films deposited on templates heated in the nitrogen∕hydrogen mixture. The latter surface contained both a higher density of step terminations, indicative of a higher density of threading dislocations having screw and mixed character, and pits.
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81.65.Cf Surface cleaning, etching, patterning
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.37.Ps Atomic force microscopy (AFM)

Ion-bombardment induced light emission from Si(100) surfaces under continuous silane exposures

P. Rajasekar, Evgueni B. Kadossov, and Nicholas F. Materer

J. Vac. Sci. Technol. A 22, 2083 (2004); http://dx.doi.org/10.1116/1.1786310 (8 pages)

Online Publication Date: 23 September 2004

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The intensities of the optical spectral lines emitted from a Si(100) surface under Ar+ ion bombardment are studied as a function of the ion kinetic energy (1–5 keV) and the partial pressure of silane. In these experiments, the ion flux is held constant while either the bombardment energy or the partial pressure of silane is varied. The intensities of the spectral lines are normalized with respect to the intensity of the excited neutral silicon (Si I, 288 nm) optical line emitted from the clean Si surface. The intensities of excited neutral Si (Si I, 288 nm), molecular SiH (A2Δ–X2Π, 414 nm), H Balmer beta (486 nm) and H Balmer gamma (434 nm) optical lines emitted from silane exposed Si surfaces follow a similar increasing trend with respect to increasing partial pressures of silane. During continuous silane exposures, the intensity of these four lines also increases with increasing ion kinetic energy. A qualitative explanation based on the adsorption and decomposition of silane on the Si surfaces can account for this behavior. In contrast to the monotonic increase of the above emission lines with greater incident kinetic energies and higher silane partial pressures, the normalized H Balmer alpha (656 nm) optical line exhibits unique behavior. The intensity of the Balmer alpha transition decreases with increasing incident ion kinetic energy at all measured partial pressures of silane.
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68.43.Mn Adsorption kinetics
78.60.Hk Cathodoluminescence, ionoluminescence

Process issues with Mo∕a-Si:H Schottky diode and thin film transistors integration for direct x-ray detection

Czang-Ho Lee, Yuriy Vygranenko, and Arokia Nathan

J. Vac. Sci. Technol. A 22, 2091 (2004); http://dx.doi.org/10.1116/1.1771661 (5 pages)

Online Publication Date: 24 September 2004

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This article presents an alternate strategy to reduce mechanical stress issues pertinent to the process integration of molybdenum/hydrogenated amorphous silicon (Mo∕a-Si:H) Schottky diodes and thin film transistors (TFTs), used as x-ray sensor pixels for medical imaging. The previous approach was to minimize the intrinsic stress in the Mo layer through appropriate process conditions and film thickness. However, that approach resulted in narrow process latitude and compromised x-ray sensitivity. Alternatively, the mechanical stress in the Mo can be reduced by reducing and/or avoiding the extrinsic stress exerted on the Mo by the underlying films through a different masking sequence in the fabrication. This modified process allows for a more flexible design of the Mo layer for enhanced x-ray sensitivity, while maintaining the mechanical integrity of the various layers. Also, the performance of the Schottky diode is improved in terms of its forward current. The x-ray sensitivity has been measured at different x-ray spectra in the range of 40–100 kVp. The pixel shows good linearity with x-ray dosage and high detection efficiency at low x-ray tube voltages.
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85.30.Kk Junction diodes
85.30.Hi Surface barrier, boundary, and point contact devices
85.30.Tv Field effect devices
81.05.Cy Elemental semiconductors
81.05.Gc Amorphous semiconductors

Target system for fabrication and control of magnetic metal content in diluted magnetic semiconductors by pulsed-laser deposition

T. Orii, T. Seto, and M. Hirasawa

J. Vac. Sci. Technol. A 22, 2096 (2004); http://dx.doi.org/10.1116/1.1772369 (5 pages) | Cited 1 time

Online Publication Date: 24 September 2004

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A synthesis method for control of magnetic metal content in diluted magnetic semiconductors prepared by pulsed laser deposition is presented. We developed a double target system composed of a disc-like semiconductor target and a wire metal target. This system has the advantage that the magnetic metal content is effectively controlled by changing the position of the lens focusing the laser beam. We synthesized Ni-doped ZnTe films using the target system and evaluated the Ni content and crystallinity of the films by electron probe micro analysis and x-ray diffraction.
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81.15.Fg Pulsed laser ablation deposition
81.16.Mk Laser-assisted deposition
75.50.Pp Magnetic semiconductors
81.05.Dz II-VI semiconductors

Etching mechanism of MgO thin films in inductively coupled Cl2∕Ar plasma

A. M. Efremov, Seong-Mo Koo, Dong-Pyo Kim, Kyoung-Tae Kim, and Chang-Il Kim

J. Vac. Sci. Technol. A 22, 2101 (2004); http://dx.doi.org/10.1116/1.1772370 (6 pages) | Cited 11 times

Online Publication Date: 24 September 2004

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The etching mechanism of MgO thin films in Cl2∕Ar plasma was investigated. It was found that the increasing Ar in the mixing ratio of Cl2∕Ar plasma causes nonmonotonic MgO etch rate, which reaches a maximum value at 70%Ar+30%Cl2. Langmuir probe measurement showed the noticeable influence of Cl2∕Ar mixing ratio on electron temperature and electron density. The zero-dimensional plasma model indicated monotonic changes of both densities and fluxes of active species. At the same time, analyses of surface kinetics showed the possibility of nonmonotonic etch rate behavior due to the concurrence of physical and chemical pathways in ion-assisted chemical reaction.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.70.Ds Electric and magnetic measurements
52.25.-b Plasma properties
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

An investigation of amorphous hydrogenated carbon (a-C:H) coatings using x-ray reflectivity and scratch testing

F. Rabbani, R. Staakman, and A. R.H.F. Ettema

J. Vac. Sci. Technol. A 22, 2107 (2004); http://dx.doi.org/10.1116/1.1772371 (5 pages)

Online Publication Date: 24 September 2004

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X-ray reflectivity was used to differentiate between two hydrogenated amorphous carbon (a-C:H) coatings with distinct Raman signatures proving that they are layered, with the top-layer characterized by a density that is either higher or lower than the averaged film density of the coating. The density of the upper-layer was found to be 1.3 g∕cm3 for the coating with the greater intensity ratio Id∕Ig [the intensity ratio of the raman D-band (1350 cm−1) and the G-band (1530 cm−1)], as compared with 2.2 g∕cm3 for the “typical” a-C:H. The coating with the lower-density 8 nm top-layer was manufactured under conditions that allow for the trapping of physisorbed hydrogen. It is likely that this polymeric top-layer was necessary in trapping unbound hydrogen. This coating was also distinguished by a higher surface roughness of 0.98 nm as compared with 0.68 nm for the denser coating. A very low coefficient of friction, 0.02–0.04, was recorded during scratch testing using progressive loading. The critical load to failure was in the range of 28–40 N; and the failure mode was brittle as determined by the Si substrate.
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78.35.+c Brillouin and Rayleigh scattering; other light scattering
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Surface chemistry of the linear chromium chain complex on GaN(0001)

Chien-Hua Lung, Shie-Ming Peng, and Che-Chen Chang

J. Vac. Sci. Technol. A 22, 2112 (2004); http://dx.doi.org/10.1116/1.1772372 (6 pages)

Online Publication Date: 24 September 2004

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Better understanding about the chemistry of the organometallic chain complexes reacting on the solid surface can foster concepts of nanowire fabrication which are central to the continued advance of the electronic and optoelectronic industries. In this study, the adsorption and thermal reactivity of a trinuclear chromium chain complex, tetrakis (2,2′-dipyridylamino)chromium(VI) chloride, on the GaN(0001) surface were investigated using x-ray photoelectron spectroscopy, temperature-programmed desorption, and static secondary ion mass spectrometry in order to obtain some insight into the bonding changes involved in the reaction of the linear metal chain complex on the compound semiconductor surface. One of the two terminal Cr–Cl bonds of the complex may be cleaved upon adsorption at 110 K, leading to the formation of the Ga–Cl bonds on the surface, although some complexes remained intact upon adsorption and bonded strongly to the surface. No ligand was dissociated from the chromium chain complex during the adsorption. The Cl-cleaved complex residue preserved its original chemical configuration. Both the Cl-cleaved and the intact complexes in the first layer were stable on the surface in the substrate temperature range between 110 and 260 K. A partial decomposition in which some ligands were dissociated from the adsorbed complex took place before the substrate temperature reaching 400 K. Additional Cr–Cl bonds were disrupted, resulting in a larger population of Ga–Cl bonds on the surface. Further thermal reaction at higher temperatures led to the dominance of the Ga–Cl bonding for the Cl presence on the surface. Surface etching of Ga by the dissociated Cl atoms started at a substrate temperature of ∼525 K and the etching rate reached its maximum at ∼590 K.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.45.Jn Surface structure, reactivity and catalysis
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
79.60.Dp Adsorbed layers and thin films
68.43.Mn Adsorption kinetics

ZnO synthesis by high vacuum plasma-assisted chemical vapor deposition using dimethylzinc and atomic oxygen

Teresa M. Barnes, Steve Hand, Jackie Leaf, and Colin A. Wolden

J. Vac. Sci. Technol. A 22, 2118 (2004); http://dx.doi.org/10.1116/1.1772373 (8 pages) | Cited 11 times

Online Publication Date: 24 September 2004

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Zinc oxide thin films were produced by high vacuum plasma-assisted chemical vapor deposition (HVP-CVD) from dimethylzinc (DMZn) and atomic oxygen. HVP-CVD is differentiated from conventional remote plasma-enhanced CVD in that the operating pressures of the inductively coupled plasma (ICP) source and the deposition chamber are decoupled. Both DMZn and atomic oxygen effuse into the deposition chamber under near collisionless conditions. The deposition rate was measured as a function of DMZn and atomic oxygen flux on glass and silicon substrates. Optical emission spectroscopy and quadrupole mass spectrometry (QMS) were used to provide real time analysis of the ICP source and the deposition chamber. The deposition rate was found to be first order in DMZn pressure and zero order in atomic oxygen density. All films demonstrated excellent transparency and were preferentially orientated along the c-axis. The deposition chemistry occurs exclusively through surface-mediated reactions, since the collisionless transport environment eliminates gas-phase chemistry. QMS analysis revealed that DMZn was almost completely consumed, and desorption of unreacted methyl radicals was greatly accelerated in the presence of atomic oxygen. Negligible zinc was detected in the gas phase, suggesting that Zn was efficiently consumed on the substrate and walls of the reactor.
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81.05.Dz II-VI semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.55.Et II-VI semiconductors
78.30.Fs III-V and II-VI semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Analysis of adsorbed contaminants of CaF2 surfaces by infrared laser induced desorption

JinMei Fu, Yamini Surapaneni, and Susan D. Allen

J. Vac. Sci. Technol. A 22, 2126 (2004); http://dx.doi.org/10.1116/1.1772374 (5 pages)

Online Publication Date: 24 September 2004

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157 nm photolithography technologies are currently under development and have been accepted as the leading candidate for fabrication of the next generation semiconductor devices after 193 nm. At this and shorter wavelengths, molecular contamination of surfaces becomes a serious problem as almost all molecules absorb at 157 nm and below. The light transmitted by a photolithographic tool can be significantly decreased by the presence of a few monolayers adsorbed on its many optical surfaces. We have developed a laser induced desorption, electron impact ionization, time-of-flight mass spectrometer (LID TOFMS) to study contaminants on 157 nm and other ultraviolet optics, e.g., polished CaF2. The LID TOFMS of CaF2 (100) samples showed water ions, hydrocarbon ions, oxygen-containing hydrocarbon ions, as well as alkali metal ions (Na+,K+). For multiple irradiations of one site at fixed laser fluence, the ion intensities decreased as the number of pulses increased, suggesting that surface contaminants were being removed. A degenerate threshold model that assumes preferential adsorption at surface defects was employed to quantitatively analyze the LID data. Desorption thresholds for water and hydrocarbons were obtained from this model.
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79.20.La Photon- and electron-stimulated desorption

Control of plasma parameters by using noble gas admixtures

Kurt J. Taylor, Seokmin Yun, and George R. Tynan

J. Vac. Sci. Technol. A 22, 2131 (2004); http://dx.doi.org/10.1116/1.1772375 (8 pages) | Cited 8 times

Online Publication Date: 24 September 2004

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Electron temperature and density in pure He, Ar, and Xe plasmas are estimated by zero-dimensional particle and power balance equations and measured by a Langmuir probe. Both of the modeling and experimental results show that the He (Xe) plasma has the highest (lowest) electron temperature and lowest (highest) electron density for a given fill pressure and source power. We find that the electron temperature is weakly dependent on the rf power, and thus the electron density can be controlled using the rf power. The electron temperature and density are also modeled and measured in mixtures of two noble gas species. We find that the electron temperature can be controlled by altering the composition of the noble gas mixture. Thus modulation of noble gas admixture ratios and rf power allows the electron density and temperature to be controlled independently. This independent control is shown to maintained with the addition of up to 20% partial pressure of oxygen, suggesting binary noble gas admixtures may provide additional control of dissociation kinetics.
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52.25.-b Plasma properties
52.50.Qt Plasma heating by radio-frequency fields; ICR, ICP, helicons

Hollow electrode enhanced radio frequency glow plasma and its application to the chemical vapor deposition of microcrystalline silicon

Toshihiro Tabuchi, Hiroyuki Mizukami, and Masayuki Takashiri

J. Vac. Sci. Technol. A 22, 2139 (2004); http://dx.doi.org/10.1116/1.1774200 (6 pages) | Cited 5 times

Online Publication Date: 24 September 2004

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A hollow electrode enhanced radio frequency (rf) glow plasma excitation technique and its application to the chemical vapor deposition of microcrystalline silicon films have been studied. In this technique, the reactor has two types of hollow structure. One is a hollow counterelectrode, and the other serves as both a hollow counterelectrode and a hollow rf electrode. The application of these discharge types to semiconductor processing is studied in the case of plasma enhanced chemical vapor deposition of hydrogenated microcrystalline silicon thin films. High crystallinity, photosensitivity and a maximum deposition rate of 6.0 nm∕s can all be achieved at plasma excitation frequency of 13.56 MHz and substrate temperature of 300°C. Properties of these plasmas are investigated by observing the plasma emission pattern, optical emission spectrum analysis and electrical parameters of the rf electrode. It is found that the plasma technique using both types of hollow discharge not only results in higher intensity of SiH* and Hα but also in much smaller self-bias voltage of the rf electrode. Faster processing of device grade hydrogenated microcrystalline silicon films can also be achieved under lower rf power compared to use of the hollow counterelectrode technique alone.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Dq Plasma-based ion implantation and deposition
52.80.Hc Glow; corona
81.05.Cy Elemental semiconductors
52.70.Ds Electric and magnetic measurements
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.70.Gw Radio-frequency and microwave measurements

Effects of substrate bias and nitrogen flow ratio on the resistivity, density, stoichiometry, and crystal structure of reactively sputtered ZrNx thin films

Shin-Hui Wang, Ching-Chun Chang, and J. S. Chen

J. Vac. Sci. Technol. A 22, 2145 (2004); http://dx.doi.org/10.1116/1.1776182 (7 pages) | Cited 11 times

Online Publication Date: 24 September 2004

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Thin films of ZrNx were prepared by reactive rf magnetron sputtering from a Zr target in an Ar+N2 atmosphere, with different substrate biases (zero to −200 V) and nitrogen flow ratios (0.5%–24%). The resistivity, density, stoichiometry, and crystal structure of ZrNx films were investigated. With 2% of nitrogen flow ratio, all ZrNx films exhibit the cubic ZrN crystal phase, regardless of the magnitude of substrate bias. The zero-biased ZrNx film contains substantial oxygen and shows high resistivity. Once a negative bias is applied to the substrate, the incorporated oxygen in ZrNx films can be reduced and the (111)ZrN preferred orientation is enhanced. Resistivity as low as 67 μΩ cm can be attained with −200 V of substrate bias. At −200 V of substrate bias, all films show the ZrN phase when the nitrogen flow ratio varies from 0.5% to 24%. However, the nitrogen content in ZrNx films increases continuously with the increasing nitrogen flow ratio. Resistivity of ZrNx films first decreases (0.5%–2%), and then increases with increasing nitrogen flow ratio (2%–24%). The best resistivity is obtained for the ZrNx film sputtered with 2% of nitrogen flow ratio and this sample exhibits the optimum grain size, (111)ZrN prefer orientation, density, and stoichiometry. The connection among the resistivity, density, stoichiometry, and crystal structure of ZrNx films and how they are influenced by the sputtering conditions (substrate bias, nitrogen flow ratio) are discussed.
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81.15.Cd Deposition by sputtering
73.61.-r Electrical properties of specific thin films
68.55.-a Thin film structure and morphology

Chemical vapor deposition boron carbo–nitride deposited using dimethylamine borane with ammonia and ethylene

E. R. Engbrecht, Y.-M. Sun, K. H. Junker, J. M. White, and J. G. Ekerdt

J. Vac. Sci. Technol. A 22, 2152 (2004); http://dx.doi.org/10.1116/1.1778405 (7 pages) | Cited 6 times

Online Publication Date: 24 September 2004

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Amorphous boron carbo–nitride films, BCxNy, (0.05⩽x⩽1.51,0.05⩽y⩽0.67), were deposited on SiO2 at 360 °C and 1 Torr using dimethylamine borane [NH(CH3)2:BH3] with ammonia and/or ethylene. The film composition could be controlled by varying the flow of ammonia and ethylene. X-ray photoelectron spectroscopy indicated a change in bonding environments, increasing the B–N bonding with the addition of ammonia and increasing B–C and C–C bonding with the addition of ethylene. The film dielectric constant, k, was 4.62 without coreactant, decreased to 4.11 by adding ammonia and 3.66 upon adding ethylene. The index of refraction ranged from 2.069 to 1.826 with correlation to k depending on the coreactant added. The root mean square surface roughness ranged from 0.30 to 0.65 nm, increasing with the use of ethylene. A 1 μm film deposited at 3.60 °C using C2H4 had a hardness of 8.7 GPa and modulus of 71.3 GPa.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.33.Ya Chemistry of MOCVD and other vapor deposition methods
79.60.Bm Clean metal, semiconductor, and insulator surfaces
68.55.A- Nucleation and growth
68.35.Gy Mechanical properties; surface strains
77.22.Ch Permittivity (dielectric function)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.35.B- Structure of clean surfaces (and surface reconstruction)

Twin formation in sputter-grown ZnO∕Al2O3(0001) epitaxial film: A real time x-ray scattering study

I. W. Kim, Y. B. Kwon, J. M. Yi, J. H. Je, G. Nouet, T. Wojtowicz, P. Ruterana, and J. Kioseoglou

J. Vac. Sci. Technol. A 22, 2159 (2004); http://dx.doi.org/10.1116/1.1778407 (4 pages) | Cited 3 times

Online Publication Date: 24 September 2004

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Twin formation and strain evolution in highly mismatched sputter-grown ZnO∕Al2O3(0001) hereroepitaxial films were investigated using real time synchrotron x-ray scattering measurements and high resolution electron microscopy (HREM). We reveal the existence of a critical thickness at which the twin of the 30° rotated domains starts to nucleate within the ZnO films, followed by gradual strain relaxation. Twin growth above the critical thickness stops as the strain almost fully relaxes. A HREM image shows that the twin nucleates 5–10 nm away from the interface as isolated domains, not as types of layers.
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61.72.Mm Grain and twin boundaries
81.05.Dz II-VI semiconductors
78.70.Ck X-ray scattering
68.60.Bs Mechanical and acoustical properties
68.55.A- Nucleation and growth
81.15.Cd Deposition by sputtering

Structural and optical characterization of beta barium borate thin films grown by electron beam evaporation

L. J. Q. Maia, C. A. C. Feitosa, F. S. De Vicente, V. R. Mastelaro, M. Siu Li, and A. C. Hernandes

J. Vac. Sci. Technol. A 22, 2163 (2004); http://dx.doi.org/10.1116/1.1778409 (5 pages) | Cited 1 time

Online Publication Date: 24 September 2004

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Thin films of beta barium borate (β-BBO) were deposited by electron beam physical vapor deposition on MgO(100) substrates. The deposition conditions were optimized so that the thin films would grow preferentially in a c-axis orientation. At a deposition temperature of 650°C, thin films grown on a MgO(100) substrate were found to be highly textured, with (00l) orientation (c-axis) normal to their surface. The addition of 4 mol % of TiO2 to the BaO–B2O3 system stabilized the β-BBO crystalline phase without inducing significant variations in the optical properties of the thin films with respect to those of β-BBO bulk single crystal. The film crystallized in situ at 650°C exhibited a maximum effective second harmonic generation coefficient, deff, of 1.85 pm∕V, which is comparable to the d22 coefficient of bulk β-BBO crystal.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.55.-a Thin film structure and morphology
42.70.Mp Nonlinear optical crystals
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Ion effects on CF2 surface interactions during C3F8 and C4F8 plasma processing of Si

Ina T. Martin and Ellen R. Fisher

J. Vac. Sci. Technol. A 22, 2168 (2004); http://dx.doi.org/10.1116/1.1781180 (9 pages) | Cited 21 times

Online Publication Date: 24 September 2004

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Surface interactions of difluorocarbene (CF2) molecules were investigated using our LIF based imaging of radicals interacting with surfaces (IRIS) apparatus. LIF data of CF2 in C3F8 and C4F8 plasma molecular beams reveal that the relative densities of CF2 increase with increasing rf power and source pressure in both plasma systems. The surface reactivity of CF2 molecules during C3F8 and C4F8 plasma processing of room temperature Si substrates was also measured over a broad rf power range and at different pressures. A scatter coefficient (S) greater than one was measured for all unperturbed systems, indicating that CF2 molecules are produced at the substrate surface during film deposition. The same systems were also studied under ion-limited conditions, yielding S∼1, clear indication that ions are partially responsible for CF2 surface production. Plasma ions were identified using plasma-ion mass spectrometry. These data indicate that higher levels of CxFy+ (x>1) are produced in the C4F8 plasmas. X-ray photoelectron spectroscopy analyses of treated substrates showed that amorphous fluorocarbon films were deposited during plasma processing of the substrates. A positive correlation was found between S(CF2) and film composition of FC materials deposited in both the IRIS apparatus and independent reactors.
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52.77.Dq Plasma-based ion implantation and deposition
81.05.Cy Elemental semiconductors
61.80.Jh Ion radiation effects
52.70.Nc Particle measurements
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
79.60.Bm Clean metal, semiconductor, and insulator surfaces
68.55.-a Thin film structure and morphology
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Optical modeling of iridium thin film erosion under oxygen plasma exposure

Li Yan and John A. Woollam

J. Vac. Sci. Technol. A 22, 2177 (2004); http://dx.doi.org/10.1116/1.1781182 (5 pages) | Cited 1 time

Online Publication Date: 24 September 2004

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This work is motivated by interest in use of iridium metal films in the space environment. Optical metrology is a sensitive tool for study of film roughness, optical constants, and microstructural properties. In the present paper, in situ spectroscopic ellipsometry is applied to monitor oxygen plasma etching of films of iridium∕chromium on fused silica substrates, using an electron cyclotron resonance plasma source. Optical modeling allows for a fundamental understanding of the plasma etching mechanism. Analysis of spectroscopic psi and delta data at selected time slices suggests the iridium film is etched away gradually upon plasma irradiation, while showing no signs of oxidation or other chemical changes. Nanoscale atomic mixing and index of refraction grading are observed.
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78.66.Bz Metals and metallic alloys
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning

Temperature-dependent growth mechanisms of CaF2 on Si(111)

C. R. Wang, B. H. Müller, E. Bugiel, and K. R. Hofmann

J. Vac. Sci. Technol. A 22, 2182 (2004); http://dx.doi.org/10.1116/1.1782636 (6 pages) | Cited 1 time

Online Publication Date: 24 September 2004

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The molecular-beam epitaxy of CaF2 layers on Si(111) substrates was studied in the temperature range between 370 and 700 °C. A strong temperature dependence of the CaF2 surface morphology was found. Layer-by-layer growth modes were found in two temperature ranges: (i) between 430 and 490 °C, where growth of atomically flat CaF2 epilayers occurred, and (ii) at ∼700 °C, where a step flow mode resulted in a relatively smooth CaF2 surface containing some rough regions, possibly due to the thermal decomposition of the interface layer. At ∼540 °C, the triangular island shape observed at lower growth temperatures changed to a more hexagonal shape expected for thermodynamic equilibrium, but the top monolayer islands still exhibited a triangular shape, which can be attributed to a relatively higher lateral adatom impingement rate per unit length of island perimeter. The mechanisms of the complex temperature-dependent growth behavior are discussed in detail.
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68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Ct Interface structure and roughness

Comment on “Etch characteristics of CeO2 thin film in Ar∕CF4∕Cl2 plasma” [J. Vac. Sci. Technol. A 21, 426 (2003)]

E. Paparazzo

J. Vac. Sci. Technol. A 22, 2188 (2004); http://dx.doi.org/10.1116/1.1782637 (3 pages) | Cited 1 time

Online Publication Date: 24 September 2004

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Comments are made on a recent article by Kim, Chang, and Kim [J. Vac. Sci. Technol. A 21, 426 (2003)], which describes the preparation and the x-ray photoemission spectroscopy study of the etching effects produced by Ar-based plasmas of different composition on the surface chemistry of a CeO2 film grown on Si. We discuss some chemical interactions taking place between Ce, Si, and the ambient humidity during the early stages of film deposition, and demonstrate that the many-body effects involved in Ce 3d spectra provide a key for better understanding of the etching mechanisms exerted by the plasma treatments.
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52.77.Bn Etching and cleaning
79.60.-i Photoemission and photoelectron spectra
81.65.Cf Surface cleaning, etching, patterning
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
82.30.-b Specific chemical reactions; reaction mechanisms

Pressure measurement repeatability in high current ion implanters using hot cathode ionization gauge with design and operation optimized for stability

Ronald C. Johnson, Randy Tysinger, and Paul Arnold

J. Vac. Sci. Technol. A 22, 2191 (2004); http://dx.doi.org/10.1116/1.1782639 (4 pages)

Online Publication Date: 24 September 2004

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Long-term pressure measurement repeatability in high current ion implanters is an important factor for ion beam current measurement and repeatable dose delivery. In the Axcelis GSD® end station, the issue is particularly acute owing to the small volume of the process chamber. High pressure conditions arise during ion beam irradiation of photoresist layers which, in turn, leads to significant ion beam current neutralization. The GSD design employs a “pressure compensation” algorithm (PCOMP) to offset potential ion beam current measurement errors; the success of this technique depends entirely on accurate and repeatable ion gauge pressure measurement. Incorrect pressure measurement directly leads to dose errors. For example, the dose equation using PCOMP tells us that for a modest PCOMP value of 30%, a chamber pressure measurement error of 2.0E−5 Torr can result in a dose error of 5% at normal process pressures. Standard hot cathode ion gauges used for pressure measurement are not capable of meeting the requirements for good dose control since gauge to gauge differences are not well controlled and gauge accuracy is only on the order of 30%. Of more consequence is the degradation of gauge response over time. Axcelis introduced the Stabil-Ion® Bayard-Alpert (BA) gauge to improve dose reproducibility through much improved gauge to gauge matching (±6%) and more accurate gauge output. This article discusses the operation of this gauge system in a production environment and its impact on process dose and process trends. The focus of the discussion is directed to a particular ion implanter design (Axcelis GSD®) since it is unique in its dependence on a PCOMP scheme to counter the effects of ion beam neutralization. However, the above gauge or any similarly stabilized BA gauge would be of benefit to the long-term output and process trends of most ion implant systems.
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07.30.Dz Vacuum gauges
61.80.Jh Ion radiation effects
61.72.up Other materials
85.40.Ry Impurity doping, diffusion and ion implantation technology

13.56 MHz radio frequency plasma properties on hemispheric electrodes and diamond-like carbon films deposition on three-dimensional polyurethane diaphragms

Yasuharu Ohgoe and Kenji K. Hirakuri

J. Vac. Sci. Technol. A 22, 2195 (2004); http://dx.doi.org/10.1116/1.1786306 (6 pages) | Cited 4 times

Online Publication Date: 24 September 2004

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The characteristics of the radio frequency (rf) plasma that could hold an entire hemispheric polyurethane diaphragm generated using the hemispheric-type electrode were investigated. The plasma states were measured using Langmuir probe. Although the common rf plasma chemical vapor deposition technique using planar electrodes makes it difficult to apply uniform plasma to three-dimensional structures, the hemispheric-type electrode process could uniformly hold a hemispheric polyurethane diaphragm at self-bias voltage. As a result, this process could uniformly keep the ion sheath on the diaphragm. In case of using this process for diamond-like carbon (DLC) film deposition, the DLC film was deposited uniformly on the diaphragm at approximately 300 nm. Besides electron temperatures and electron number of densities were similar to the behavior of common rf plasma. This means that the characteristics of plasma are kept in the same states even if the plasma form is controlled using such a hemispheric-type electrode. Based on these results, this hemispheric-type electrode process was observed to be quite applicable to three-dimensional insulator structures.
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52.77.Dq Plasma-based ion implantation and deposition
68.55.A- Nucleation and growth
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.70.Ds Electric and magnetic measurements
52.80.Hc Glow; corona

Fabrication of dry etched and subsequently passivated laser facets in GaAs∕AlGaAs

Eckard Deichsel and Gerhard Franz

J. Vac. Sci. Technol. A 22, 2201 (2004); http://dx.doi.org/10.1116/1.1786307 (5 pages) | Cited 2 times

Online Publication Date: 24 September 2004

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The aging behavior of edge emitting laser diodes based on GaAs∕AlGaAs is investigated by comparing devices with facets that are alternatively cleaved or dry etched and consecutively treated with H2S. In this work we demonstrate that an in situ exposure to H2S gas is not sufficient to prevent ageing but an additional plasma treatment is rather required to obtain comparable ageing results to lasers with cleaved facets.
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81.65.Cf Surface cleaning, etching, patterning
81.65.Rv Passivation
52.77.Bn Etching and cleaning

Outgassing measurements of stacked laminations for use as an electromagnet core

Y. Saito, Y. Sato, and T. Kubo

J. Vac. Sci. Technol. A 22, 2206 (2004); http://dx.doi.org/10.1116/1.1786311 (6 pages) | Cited 1 time

Online Publication Date: 24 September 2004

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Outgassing from an electromagnet core installed in an accelerator vacuum system is a problem, since it causes a poor vacuum, thus shortening the beam lifetime while also inducing electrical breakdown. Outgassing measurements by a throughput method were carried out for stacked laminations with a few types of insulating coatings. The vacuum performance does not always depend on a small conductance in a narrow gap spacing of a few micrometers, but on the materials coated for electrical insulation. A high-temperature cured inorganic and plasma-sprayed ceramic coating shows a lower outgassing rate than a quasi-inorganic one by an order or more. An outgassing reduction effect by a prebaking treatment is also examined. Furthermore, a time lag in the pumpdown characteristic of the stacked laminations is discussed.
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68.43.Mn Adsorption kinetics
52.77.-j Plasma applications
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Pressure-measurement errors in a cold-cathode-ionization gauge caused by an external-electron source

Hiroshi Saeki, Tamotsu Magome, Yoshihiko Shoji, and Takashi Momose

J. Vac. Sci. Technol. A 22, 2212 (2004); http://dx.doi.org/10.1116/1.1781184 (4 pages) | Cited 2 times

Online Publication Date: 24 September 2004

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Abstract Unavailable
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07.30.Dz Vacuum gauges
06.20.Dk Measurement and error theory
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