bluuebunny/crossref_metadata_2025 huggingface dataset:
Errors in Pressure Measurement and Impurity Generation in Hydrogen using Bayard-Alpert Ionization Gauges
Authors: Singleton J. H.
Published: July 2002

A Bayard–Alpert ion gauge, with thoria-coated electron emitters, was used to measure hydrogen pressures using emission currents as high as 10 mA without production of serious amounts of impurities. The use of high emission currents does not result in a high pumping speed and has the advantage of reducing measurement errors. Such errors result from the adsorption of carbon monoxide on the grid of the ion gauge and occur at carbon monoxide pressures as low as 0.3% of the hydrogen pressure. The total desorption probability of carbon monoxide is approximately 2 × 10−5 particles/electron and approximately half of the gas is desorbed as ions. At high emission currents the adsorption of carbon monoxide on the grid is kept at a minimum thus reducing the spurious current to the ion collector. For example, in hydrogen at 3.5 × 10−9 Torr, in the presence of 1 to 2% carbon monoxide, the ion-gauge indication of pressure is ∼10% high for operation at 10-mA electron emission, while at 100 μA the indicated pressure increases to ten times the true pressure.
Diffusion of Nitrogen through Zr–Al Alloys in Vacuum
Authors: della Porta P. , Kindl B. , Ruetsch Ch. , Schönhuber M. J.
Published: July 2002

Sorption of nitrogen by a Zr–Al alloy has been measured at constant temperatures at 300 °C and 500 °C and for nitrogen pressures in the range 10−6 to 1 Torr. The pumping speed of the Zr–Al alloy for nitrogen decreases as the nitrogen pressure is increased and increases with temperature. For a constant nitrogen pressure the pumping speed tends to decrease with time owing to increase in surface concentration. After sorption has been completed the pumping speed can be partially or entirely restored to its initial value by maintaining the active surface at the operating temperature under a low nitrogen partial pressure, e.g., 10−6 Torr. During this recovery process nitrogen compounds at the surface migrate towards the interior of the Zr–Al alloy. The data obtained facilitate, at least qualitatively, the measurement of the diffusion of nitrogen from the surface to the bulk metal as a function of time at constant temperature. The data can also be used to predict the behavior of Zr–Al based getter pumps during and after high throughput applications.
Effects of Added O2 upon Argon Emission from an rf Glow Discharge
Authors: Lounsbury J. B.
Published: July 2002

Emission and absorption measurements have been made in rf glow discharges through pure argon and through argon with 1% O2 added. The results indicate that added O2 reduces the amount of excitation of neutral argon, particularly the concentration of metastable atoms. At the same time, increased emission is observed from argon ions when O2 is added. This is attributed to an increase in the argon ion concentration. The results of these experiments have important implications regarding the mechanisms operative in rf sputtering processes. Namely, under the conditions studied (rf power density of 10 W/cm2 and argon pressure 4×10−2 Torr) direct electron impact ionization appears to be the predominant maintenance mechanism of the glow rather than ionization resulting from metastable atom collisions. In addition, it is proposed that addition of oxygen to the argon discharge atmosphere serves to increase the secondary electron emission coefficient of the fused silica target.
Some aspects of high-current relativistic electron-beam generation
Authors: Forster D. W. , Goodman M. J. , Herbert H. G.
Published: July 2002

Diode characteristics in two electron-beam generators, IT and ACE, are examined, with particular reference to the role of prepulse conditions. The advantages and limitations of field-enhanced edge emitters are discussed. In both low- and high-current-density applications, a stable impedance–time history is shown to be associated with a band of prepulse voltage which is a function of both its time variation and driving impedance. Above this band rapid impedance collapse occurs, and below it long current switch-on times are experienced. This behavior is postulated to be dependent upon cathode plasma formation and growth during prepulse and early main pulse phases. The results of a preliminary investigation into the controlled use of prepulse for high-current-density beam production from field-enhanced edges are examined. The characteristics of hollow cylindrical cathodes operating in pinched mode are shown to depend on prepulse conditions. In particular, the transfer of finite energy (of order tens of millijoules) to the diode during the prepulse phase is shown to be desirable for rapid establishment of the required diode impedance in the main pulse phase.
Abstract: Temperature profiles of targets bombarded by electron beams
Authors: El-Kareh A. B. , Moravan K. Y. Y.
Published: July 2002

A detailed theoretical calculation is presented of the relationship between the spot size and temperature as a function of the physical properties of a target material when it is bombarded by an electron beam. As a result of this analysis, it is possible to determine the desired characteristics of materials which are suitable for application in mass-storage devices.

The thermal problem can be analyzed by solving the appropriate radial heat-flow equation. The electron beam heating of the target can be determined within certain limitations by assuming that the heat is generated uniformly in a spot of hemispherical shape whose radius is given by the effective range of electron penetration. This range is determined by making use of the universal curve of the normalized Bohr–Bethe range obtained by Everhart and Hoff.

From the above calculation, the properties of suitable targets can be obtained. It is found that to have a small spot, a high mass density of the target is desirable. The requirement that the equilibrium temperature to be greater than the boiling temperature of the target sets an upper limit for the conductivity of the target. In order for the rise time (the time needed for temperature at the center of the spot to reach a significant portion of the equilibrium temperature value) to be of the same order as the machining time, a lower limit for conductivity and the inter-relationship between heat capacity, conductivity, and mass density can be obtained. A set of curves are given to show the space and time dependence of the temperature of the spot being machined for different beam powers. It can be seen that both higher temperature and better resolution can be obtained for electron-beam powers between 2.5 and 10 keV than for above 10 keV.
Abstract: Scanning microspot Auger spectroscopy and microscopy as a device diagnostic technique
Authors: Christou A. , Day H. M.
Published: July 2002

Auger spectroscopy with a focused electron beam in the scanning electron microscope (SEM) has been applied as a diagnostic technique for solid state devices. The focused electron beam in a SEM allows one to determine the surface topography (SEM mode) of the specimen and then determine the Auger spectra of selected areas. In addition, a scanning Auger image may be obtained by using the amplitudes of the Auger peaks for intensity or amplitude modulation of the cathode ray tube. In the present system, a SEM designed with a dry-pump UHV system and equipped with an Auger electron detector and sputter etching capability has been applied to device failure diagnostics. Vacuum levels of 3×10−9 Torr (4×10−7 Pa) at the specimen stage have been obtained with an electro-ion-titanium sublimation pumping system. A secondary electron image resolution of less than 2000 Å with Auger spectra of features less than 1 μm have been attained. Gray-scale images from Auger electrons have been obtained at beam currents of 10−6 to 10−8 A. The Auger electron detector used has an energy resolution of 0.5% and transmission of 10%. A sputter-etching capability for sputter cleaning of specimen surfaces prior to analysis is provided.

The energy source of the SEM is a triode electron gun with a high-emission filament (3.5×105 A cm−2 sr−1 at 20 kV). The relationship between probe current and diameter for a fixed working distance was measured in order to determine the optimum spatial resolution for AES. For optimum conditions and high beam currents (10−6 A) spatial resolution is essentially determined by the probe diameter. For low beam currents, it is shown that parameters such as escape depth, atomic number, surface area, and beam energy affect spatial resolution. AES recording time and its variation with signal-to-noise ratio has also been determined.

The normal modes for microspot AES investigations in the SEM include spot analysis, line scan, and Auger electron imaging. For Auger imaging the vacuum levels and probe currents are shown to be the critical parameters since the time to record such an image is usually greater than five minutes.
Quantitative surface profilimetry applied to sputter ion bombarded sapphire
Authors: Pellerin Charles J. , Christensen James , Jerner R. C. , Peavey Jerris H.
Published: July 2002

A Dektak surface profilimeter has been interfaced with a PDP8/e minicomputer, surface profiles digitally recorded, and the data subsequently numerically manipulated. Programs were written to calculate hav, hrms, and rf. Comparison of these values to roughness standards traceable to NBS verified the validity of the interfacing and subsequent data processing. Average roughness had a limit of sensitivity of 5 Å (signal/noise = 1). Preliminary studies using the technique to study the effects of 500 eV argon ion sputter bombardment have begun. Three orientations (112̄0), (1̄012), and (0001) of sapphire were studied. Slight differences were observed between the two slip planes (112̄0), (0001), and the cleavage plane (1̄012).
Atomic implantation of Nb in amorphous Nb2O5 by rf sputtering
Authors: Fuschillo N. , Lalevic B. , Annamalai N. K.
Published: July 2002

It is shown that amorphous Nb2O5 films 2400 Å thick produced by anodization can be doped with Nb by rf sputtering of Nb atoms at substrate temperatures of 150°C. Large increases in electrical conductivity, reductions in thermal activation energy, and increases in capacitance as function of sputtering voltage in the range 2−5 kV support this interpretation. The high−field conduction process also changes from the Poole−Frankel mechanism often found in insulating films, where the conductance G = G0 exp(KV1/2) to the Poole mechanism where G = G0 exp(KV) found in Nb doped films. The doping concentration for 2400−Å films was calculated using the experimental values of the exponent K and found to be 1019 atoms/cm3 for films sputtered with Nb at an rf voltage of 3 kV. Capacitance variation as a function of voltage and temperature also support these conclusions. These effects are interpreted on the basis of possible implantation and temperature−aided diffusion process.
System for deposition and hydriding of thin metallic films without air exposure
Authors: Eichman C. C. , Comeau J. L. , Rinehuls K. R.
Published: July 2002

This completely self−contained system provides capability to deposit erbium thin films on a substrate and to hydride the films without exposure to air. Precise controls are provided for cold crucible electron beam deposition of the erbium, for monitoring the film thickness during deposition, and for controlling the film bakeout temperature. A mechanical device transfers the deposited substrates to the hydriding chamber without exposure to air. The system is capable of analyzing gases within the system during various phases of processing to determine if outgassing is complete, to monitor for vacuum leaks and for health physics control. A major advantage is that the hydriding chamber can be vacuum baked and gas processed with hydriding gas before the erbium−deposited substrates are transferred into the chamber.
Abstract: An evaporator facility for deposition of multielement thin film patterns
Authors: Meray Lorand H.
Published: July 2002

A versatile mask changer and evaporator has been developed for use in fabricating experimental thin film circuits. Composite masks consisting of a combination of movable wire grills and electroformed metal sheets serve to define the required patterns of metal, insulator, semiconductor, and photoconductor. Precision motion of a 3.81−cm sq glass substrate relative to the masks permits the deposition in one pumpdown of large area arrays and circuits having electrode spacings accurate to within 1 μ. The substrate is located within 2.54 cm of a viewing window to permit convenient microscopic examination of the evaporated pattern during deposition. The mechanical problems are to provide sufficient mask storage, which can be aligned accurately to each other within microns. This will be demonstrated in the case of two examples: the preparation of the integrated sensor (512×512 units, each containing active and passive elements) and the optical three−color stripe filter having each color 30−40 layers spaced within 8 μ side by side, up to 5.08−cm sq area.
Abstract: Dynamic control of the vacuum deposition of optically effective thin films
Authors: Wilmanns Ingo
Published: July 2002

The control of the deposition of optically effective thin films by optical measurements was in the past often restricted to the evaluation of static measurements of the optical parameters (reflection and transmission) of thin films for the generation of a cutoff signal for the deposition. This cutoff condition was at a later date obtained by differentiation of the optical signal with respect to time. We have expanded this method to obtain rate control during the entire deposition and achieve cutoff at different than quarter wave thickness. Furthermore, we have made the system ’’self−learning’’ so that the optimized evaporation power level of each deposition cycle is used to start the next cycle under near optimum conditions. The results which can be achieved in large scale production with this method will be dicussed.
Vacuum applications of quartz resonators
Authors: EerNisse E. P.
Published: July 2002

The principles of quartz resonator operation are reviewed. Particular emphasis is placed on resonant frequency shifts induced by changes in ambient temperature and in the areal mass density, and the lateral stress of thin films on the resonator surfaces. The fact that these three effects depend upon the crystallographic cut of the quartz resonator plate is exploited in developing one−, two−, and three−resonator configurations to measure thin film lateral stress, thin film mass areal density, and/or temperature simultaneously in vacuum. Examples are presented for simultaneous stress and mass measurements for a variety of experimental situations. Additional areas for application of the multiple resonator principle are proposed.
Deposition of semiconductor films with high solar absorptivity
Authors: Mattox D. M. , Kominiak G. J.
Published: July 2002

Thin films of narrow−gap (∠0.6 eV) semiconductors should be good selective solar absorbers since they absorb in the solar spectrum (<2 μ) but transmit in the infrared (≳2 μ). Unfortunately, semiconductors have high indices of refraction which give high reflectivity from smooth surfaces and thus have poor solar−absorbing efficiency. In this investigation, the effect of deposition conditions on surface morphology and solar absorptivity of silicon, germanium, and lead sulfide thin films is examined. It is found that the solar absorptivity of germanium films can be greatly increased by ’’gas evaporating’’ them in a low−pressure (20 mTorr) argon atmosphere apparently due to changes in the film−surface morphology. Solar absorptances of greater than 95% are obtained from 1−μ thick films of gas−evaporated germanium and vacuum−evaporated PbS films. Gas−evaporated silicon films showed a shift in the absorption edge which makes them unacceptable for solar absorbers.
Abstract: Photovoltaic effect in obliquely deposited germanium films
Authors: Ma William , Anderson R. M. , Hruska S. J.
Published: July 2002

If germanium is obliquely deposited at relatively high pressures, an inplane photovoltaic effect can produce voltages as high as 3000 V. Reproducibility of the effect within a single laboratory and among various laboratories has been poor. No satisfactory explanation of the phenomenon has been offered. We find that the partial pressure of oxygen during deposition and the angle of deposition are both of first−order importance in determining both the magnitude and the polarity of the photovoltage. Increasing the partial pressure of oxygen PO2 increases the magnitude of the photovoltage. Decreasing the angle of incident Ge flux from normal (90°) to 15° increases the magnitude of the photovoltage. There is a polarity reversal as PO2 goes from 10−5 Torr to 10−4 Torr. Photovoltage magnitudes increase slowly as average thickness of the film increases. ESCA studies indicate that for highest photovoltages, the film must be made up of two distinct constituents that are (or are associated with) Ge and GeO2. These new results, along with previous findings, are consistent with a structural model for the film which appears to provide the basis for an understanding of the phenomena.
Abstract: LEED, Auger spectroscopy, and contact potential studies of copper−gold alloy single−crystal surfaces
Authors: Potter H. C. , Blakely J. M.
Published: July 2002

The (100), (111), and (110) surfaces of copper−gold alloy single crystals (Cu, Cu3Au, CuAu, Au3Cu, Au) have been studied. Results are presented for (i) the variation of relative Auger peak strengths with bulk composition, (ii) the variation of work function with orientation and bulk composition, and (iii) the occurrence of surface ordering. The average work function φ increases as the bulk Au concentration increases from Cu to Au3Cu with the orientation dependence in accord with the expected variation of surface dipole with ’atomic roughness’, i.e., φ (111) ≳ φ (100) ≳ φ (110); the surfaces of Au do not follow this simple rule. LEED indicates that Au(100), Au(110), Au3Cu(110), and CuAu(110) surfaces have complex structures. Observed differences in the kinetics of ordering of the Cu3Au(100) and (111) surfaces are discussed.
Abstract: Ion etching of electronic devices with 1−μ periodicity
Authors: Bazzarre D. Frank , Barr Robert W.
Published: July 2002

Micro−electronic devices in use today, are being produced with line and space widths of 2−4 μ. This limitation is brought on by the chemical etching and pattern generation procedures in use. A great deal of work is underway by many researchers to improve both the etching and pattern generation procedures. This paper is deliberately confined to advanced etching procedures, i.e., r.f. backsputtering, r.f. plasma etching (ashing) and ion etching. Materials systems studied include dielectrics and metals in thicknesses from 0.1 to 5 μ. Line space resolutions to 1.5 μ were obtained by all etching methods on dielectrics and metals with film thickness of 1 μ. Below 1.5 μ resolution, only ion etching produced satisfactory line definitions with no undercut; resolution to 0.1 μ was obtained and space width−to−depth aspect ratios of 1 to 10 were obtained.
Properties of superconducting rf sputtered ultrathin films of Nb
Authors: Wolf Stuart A. , Kennedy James J. , Nisenoff Martin
Published: July 2002

Superconducting niobium films, both cylindrical and planar, have been prepared by rf sputtering in an uhv chamber which is routinely pumped to a residual pressure of 3×10−9 Torr (7.6×10−7 Pa). The superconducting transition temperature Tc of films with thicknesses greater than 2000 Å was near 9.2 K, the bulk value, while Tc decreased linearly with inverse thickness for films thinner than 1000 Å. Superconductivity was observed for the first time in Nb films thinner than 50 Å; the Tc of a 40 Å film was 4.4 K while for a 27 Å film the onset of the transition was about 2 K. Electrical continuity was maintained down to a nominal film thickness of less than 10 Å, but this film was not superconducting above 1.5 K. These results will be compared with a model which predicts the dependence of Tc on thickness.
UPS studies of virgin CO on W(100)
Authors: Vorburger T. V. , Sandstrom D. R. , Waclawski B. J.
Published: July 2002

The adsorption of CO on W(100) at 80 K has been studied by photoelectron spectroscopy at hν=21.22 eV, and the results have been correlated with previous data for room temperature adsorption. Initial adsorption produces a peak in the emission spectrum at ∠−7.6 eV (relative to the Fermi energy), which is characteristic of the virgin state of adsorbed CO, as well as additional structures which have been previously shown to be characteristic of α- and β-CO. Upon heating the sample to 260 K the −7.6-eV level is depleted and apparent conversion to the β state occurs as indicated by an enhancement of the emission near −5.5 eV. Additional data taken with hν=16.85, 26.9, and 40.81 eV are in general agreement with the measurements at 21.22 eV; however, the peak at −7.6 eV for hν=21.22 eV is shifted to lower kinetic energies by several tenths of an electron volt at the other photon energies.
Hydrogen chemisorption on the silicon (110) 5×1 surface
Authors: Sakurai Toshio , Hagstrum Homer D.
Published: July 2002

We have established that chemisorption of atomic hydrogen on Si(110)5×1 surface forms two distinct 1×1 phases depending on temperature during H exposure. The high temperature phase is found to be the monohydride phase, Si(110):H. The room temperature phase has additional orbital intensity in its electronic density of states, which we interpret as due to hydrogen atoms chemisorbed weakly at nontetrahedral sites in the selvedge. Numerical estimates of the amounts of H involved have been made. The change of LEED pattern during H exposure suggests that the 5×1 superstructure is due to relaxation of surface Si atoms rather than due to surface vacancies.
Introduction to ion and plasma etching
Authors: Somekh S.
Published: July 2002

This paper is an introduction to dry processing techniques such as ion beam etching, rf sputter etching, and plasma etching. A short description of the systems is followed by a comparison of their properties relevant to the fabrication of electronic and optical devices. The comparison includes etch rates and their dependence on various parameters, masking materials and dimensional accuracy in pattern delineation, obtainable aspect ratios, and edge profiles. The paper concludes with some examples of plasma- and ion-etched patterns.
New instrumentation and techniques to monitor chemical surface reactions on single crystals over a wide pressure range (10−8–105 Torr) in the same apparatus
Authors: Blakely D. W. , Kozak E. I. , Sexton B. A. , Somorjai G. A.
Published: July 2002

The development of an apparatus to monitor catalytic reactions on small surface area samples (∠1 cm2) over a wide pressure range [10−8–105 Torr (∠10−6–107Pa)] is discussed. Previous experience with catalysis in the low pressure range (10−8–10−4 Torr) has resulted in the development of a high pressure isolation cell to monitor reactions in the range 0.1–100 atm. The apparatus incorporates all of the surface analysis features (LEED, AES, and mass spectrometry) and permits UHV analysis of the catalyst surface before and after reaction without removing the sample from the chamber. The importance of obtaining data under reaction conditions appropriate to the equivalent industrial process is emphasized.
Vacuum technologies applied to electronic component fabrication
Authors: Curran J. E.
Published: July 2002

The application of rf diode sputtering, evaporation, and plasma-etching processes is finding an important role in the manufacture of such components as surface-wave devices, masks, electroluminescent displays, and magnetic-bubble elements. Descriptions are given of the critical control required when using rf sputtering and evaporation techniques in order to produce components with required characteristics. The use of in situ resistance monitoring during deposition processes for layers of resistance from 1Ω/⧠ to 5MΩ/⧠ is also included. The change in device and component characteristics with variations in process control parameters will be described.
Frontiers of leak detection
Authors: Briggs Walton E. , Blumle Leo J.
Published: July 2002

This paper will discuss the theoretical and practical aspects of current industrial applications of helium mass-spectrometer leak detection. During the past decade the applications of the helium mass-spectrometer leak detector have expanded beyond the familiar vacuum laboratory system testing. With the development of the semiconductor integrated circuits, the need for rapid testing of millions of sealed parts led to the development of a very rapid cycling, operator-controlled leak detector. Frequently, integrity evaluation of high production of components and products does not use vacuum as a part of their processing or end-use application. Since some products need to be tested under pressure, the usage of helium permeable membranes has been applied to both sampling probes and automated fixtures. In order to fulfill the need for high volume production, considerable automation has been introduced to the helium mass-spectrometer leak detector, including the use of fully automated program controlled assembly and test conveyors leading to the accomplishment of a fully automatic leak-detection system. Typical cycle time for a 1-l tare volume can be less than 12 s.
Thin-film deposition using low-energy ion beams (2) Pb+ ion-beam deposition and analysis of deposits
Authors: Amano J. , Lawson R. P. W.
Published: July 2002

Thin films of Pb were grown on C and NaCl substrates by retarding a 4-keV, mass-analyzed Pb+ ion beam to a low energy before deposition. The films were examined using Rutherford backscattering analysis, scanning electron microscopy, and transmission electron microscopy. Adhesion was found to be independent of deposition energy for all deposits grown between 24 and 200 eV. The thickness, degree of surface coverage, and crystalline orientation are dependent on incident Pb+ ion energy. 50 eV is an optimum energy of deposition when parameters such as space-charge expansion, self-sputtering, film thickness, and surface coverage are considered. As the deposition energy is increased above 50 eV, the crystalline structures of deposits grown on single-crystal NaCl substrates becomes more ordered with a strongly preferred [100] orientation. High purity and homogeneity of the deposits were attributed to the use of a mass-analyzed beam and the maintenance of ultra-high-vacuum conditions in the substrate chamber.
Epilayer-substrate interfaces of Sn-doped GaAs
Authors: Lum W. Y. , Clawson A. R. , Wieder H. H.
Published: July 2002

Photoluminescence and charge-carrier transport measurements were used to investigate the electronic properties of liquid-phase, exitaxy-grown Sn-doped GaAs homoepitaxial layers and the interfaces between them and their semi-insulating substrates. Our results suggest that self-compensation takes place in the epilayer and cross-compensation of the deep-level acceptor complexes by Sn donors occurs at the epilayer–substrate interface.
Electronic surface properties of Ga and In containing III–V compounds
Authors: van Laar J. , Huijser A. , van Rooy T. L.
Published: July 2002

Based upon contact potential-difference measurements, photoemission experiments, and low-energy-loss spectra of GaSb, GaAs, GaP, InAs, and InP, we propose an empirical model for the surface states at the (110) cleavage face of all Ga and In containing III–V compounds with the zincblende structure. Three filled and two empty surface-state bands were identified. The positions of two of the filled states for the GaAs (110) face are consistent with available data from angle-resolved photoemission experiments. However, for any other states no experimental data are available.
Electron-beam decomposition of UF4 optical interference layers
Authors: Ellis Walton P.
Published: July 2002

A striking example of electron-beam damage has been observed in a LEED/Auger system with optical interference films of UF4 on single crystalline UO2(111). A 1-kev beam decomposed the UF4 leaving a well-defined ring of metal which displayed detailed spatial distribution of the incident flux. Flourine was absent from the Auger spectrum and only uranium peaks characteristic of unreacted metal were obtained.
Localized substrate heating during ion implantation
Authors: Parry P. D.
Published: July 2002

The enhanced etching of ion-implanted silicon nitride in buffered hydrofluoric acid has been studied as a function of beam current in an ion implantation system using rotating mechanical scan. Reduction of the enhancement due to annealing has been observed under conditions where an earlier model of target heating during ion implantation would predict no annealing. The implication of this observation for future beam heating calculations is explored briefly.
Reflectance and structure of evaporated chromium and molybdenum films
Authors: Nestell J. E. , Christy R. W.
Published: July 2002

Chromium and molybdenum films deposited in a high vacuum at room temperature are shown to have anomalously low optical reflectance throughout the 0.2–2.5-μm wavelength range. Deposition at about 700°C for chromium and 1000°C for molybdenum, or postdeposition annealing, gives films with bulk reflectance. X-ray diffraction and transmission electron microscopy show the films deposited at room temperature to be very fine grained (80–100-Å grain size). Electrical resistivity of the fine grained films is high (3–5 times bulk). High-temperature deposition or annealing gives larger grains (≳400 Å) and lower resistivity. A simple model accounts for the resistivity behavior.
Hydrogen evolution from plasma-deposited amorphous silicon films
Authors: Matysik K. J. , Mogab C. J. , Bagley B. G.
Published: July 2002

The temperature dependence of hydrogen evolution from amorphous silicon films prepared by plasma deposition using a silane–argon mixture was studied by line-of-sight mass spectrometry. The structure changes accompanying hydrogen evolution were simultaneously studied with reflection high-energy electron diffraction (RHEED). Mass spectrometric analysis during linear temperature sweeps showed that H2 was the evolving species indicating that hydrogen atom recombination occurs prior to desorption. H or SiHx were not detected. The evolution spectrum consisted of two broad peaks. The temperature corresponding to the initiation of evolution, the maximum evolution rate and the termination of evolution were dependent on deposition parameters. Attempts at depopulating specific hydrogen binding states by isothermal heat treatments indicated the existence of a broad range of states. The amorphous to crystalline transition was initiated subsequent to hydrogen depletion and at 760° C+10° independent of deposition parameters.
Influence of photoelectrons on the exposure of resists by x rays
Authors: Hundt E. , Tischer P.
Published: July 2002

Sensitivity and contrast ratio of PMMA resist were measured for Ti-K radiation (λ=0.27 nm). We found a constant rate of solubility during development for exposed as well as for unexposed resists. This means that the process of solution is limited by diffusion and that the resist layer is homogeneously irradiated. Looking at the influence of substrate on exposure we found that the exposure time for gold substrate was only half of that with silicon substrate. This is, to a small part, due to x-ray fluorescence and mainly to photoelectrons. We also looked at the profiles of structures during development process and found that the resist behavior was similar for great areas as for fine structures.
Analysis of the oxide/semiconductor interface using Auger and ESCA as applied to InP and GaAs
Authors: Wilmsen C. W. , Kee R. W.
Published: July 2002

This paper compares the Auger and ESCA techniques used to characterize the interfaces of thermally grown and anodic oxides of InP and GaAs. In the anodic oxide of GaAs, the Ga–O bonding extends deeper into the GaAs than the As–O bonding. In the anodic oxide of InP, both the P–O and In–O bonding penetrate to the same depth. The anodic oxide–GaAs interface changes with electrolyte. There is elemental P at the interface of the thermal oxide on InP, but it was not possible to prove or disprove the existence of elemental As at the anodic oxide/GaAs interface. It was found that the ESCA technique provided much needed bonding information which greatly facilitates characterizing the interface. It appears essential that both composition and bonding be determined.
Covalent–ionic trend at Schottky barrier interfaces in a pairing model
Authors: Ngai K. L. , White C. T.
Published: July 2002

We discuss from a theoretical point of view the expected effects of electron pairing states on metal semiconductor interfaces. Several microscopic models are developed which depend on the presence of electron–electron pairing interactions mediated through nonbonded orbitals thought to be present at the interface. It is found that a picture which associates the nonbonded states with metal–anion bonds has a number of features consistent with experiment.
Investigation of the Ag–In–Ge system used for alloyed contacts to GaAs
Authors: McGuire G. E. , Wisseman W. R. , Ragle R. D. , Tregilgas J. H.
Published: July 2002

One of the useful metallization schemes for alloyed contacts to n-type GaAs consists of Ag–In–Ge. The interaction of Ag, In, and Ge within the alloy and with the GaAs substrate has been studied by Auger and photoelectron spectroscopy. In-depth profiling of the metallization scheme indicates segregation of In to the alloy GaAs interface and segregation of Ge to the surface of the alloy. Upon annealing Ge diffuses to and accumulates at the alloy GaAs interface to produce a heavily doped n+ layer which results in ohmic electrical behavior. This is accompanied by the out diffusion of Ga to the alloy surface. Since Ge acts as a donor in GaAs when excess As exists, it compensates for the loss of Ga.
Microfabrication by ion-beam etching
Authors: Lee Robert E.
Published: July 2002

The trend in the microelectronics industry, and in particular that part of the industry concerned with the fabrication of integrated circuits, is toward circuits with increasingly high density and devices with smaller feature size. This trend has spurred interest in several new process technologies for pattern replication. One such emerging technology is ion-beam etching that offers higher resolution, greater dimensional control, and higher yield than conventional wet chemical etching. Several examples of surface relief formation by ion-beam etching illustrate the advantage of this approach. The particular limitations imposed by ion-beam etching, namely mask erosion and faceting, redeposition, and trenching, are treated. Developments of simple models for predicting etch rates on sloped surfaces and sidewall profiles are described. Such models are critical for the successful application of ion-beam etching to patterning high-density integrated circuits.
Preparation and properties of transparent conducting indium films
Authors: Murti D. K.
Published: July 2002

As a result of the pronounced agglomeration of indium at room temperature, an appreciable film thickness (about 200 nm) must be exceeded before electrical continuity is observed. This results in an optical transmittance of about 1% in the visible region. In the present study the effects of substrate temperature and deposition rate on the electrical, optical, and structural properties of thin indium films of about 15 nm have been determined. The results indicate that lower substrate temperatures and higher deposition rates yield conducting films at a lower thickness in agreement with the theories of nucleation and growth of thin films. It was found that both a low-substrate temperature (150 K) and a high-deposition rate (1 nm/s) are required to form transparent, conducting films of indium. Thin films of indium of about 10 nm deposited on Corning 7059 glass substrates had an optical transmittance of 50% in the visible region.
Operational experience with zirconiated T–F emitters
Authors: Wolfe J. E.
Published: July 2002

Additional experience with this type of cathode has added considerable knowledge relative to its characteristics since a report was given by Swanson in 1975 at this conference. The beam current stability is better than ±0.5% at pressures in the region of 10−8 Torr. The source brightness is 109 A/cm2/sr. The operating point is typically 107 V/cm electric field, 1800 K and 105A/cm2. Life tests have indicated life times of 5000 h or greater may be expected at the above operating point and 10−8 Torr vacuum. The virtual source size for our geometry and operating point has been calculated and measured at about 100 Å for an acceptance half angle of 0.015 rad. The zirconiated cathode is also highly recommended for thermionic and Schottky aided thermionic applications. It is more stable and longer lived than LaB6.
Data compaction method for raster–scan exposure system
Authors: Sumi Masahiko , Chiba Fumitaka , Ninomiya Masaharu
Published: July 2002

A data compaction method and a data processing system developed for raster–scan exposure system are presented. The purpose of the method is to enhance flexibility in pattern size and to increase writing speed of a raster–scan system. The data format for compaction and the data transmission scheme are given. The encoding and decoding procedures are described. Data quantity of advanced LSI patterns is examined and it is shown that data compaction ratio of 1/7 to 1/70 is attained. Writing speed of 40 MHz is also achieved. By this method, reticle pattern as large as 105×105 dots and composite patterns are successfully delineated.
Trends in high performance silicon technology
Authors: Rupprecht H. S.
Published: July 2002

The swift and far reaching technological advances over the last 30 years, which are frequently described by terms such as computer age or space age, are inseparably connected with the evolution of the silicon semiconductor technology. In this paper, we will give an overview of the most recent developments in the silicon semiconductor field as they relate to high performance bipolar devices. Trends in process technology as well as performance limits will be described.
Semi-insulating GaAs substrates for integrated circuit devices: promises and problems
Authors: Eastman Lester F.
Published: July 2002

The state of the development of chromium-doped GaAs bulk material for use as semi-insulating substrates for field-effect transistors and monolithic integrated circuits is reviewed. The shallow level impurities and the deep levels are covered, including some of their effects on ion implantation devices. Silicon and oxygen are the main ambient shallow and deep donor, but a fast-diffusing deep acceptor is also important. Chromium has a solubility limit that depends on the growth temperature for liquid phase epitaxy, and its rejection at the surface during extended bakes at lower temperatures is suggested to be due to this result. The reduction of parasitic substrate current by controlled doping is also presented.
Ion implanted high frequency high speed GaAs integrated circuits technology
Authors: Ch’en D. R. , Eisen F. H.
Published: July 2002

GaAs ion implantation technology for n-type dopants is reviewed with emphasis toward device applications. Semi-insulating GaAs substrate selection and postimplantation annealing techniques are discussed. A highly reproducible, low cost ion implantation process technology for high frequency high speed devices is described. The extension of this process technique to high speed GaAs digital integrated circuits and monolithic microwave integrated circuits is discussed with emphasis toward low power circuit concepts that will ultimately be capable of producing LSI circuitry.
Alternative grading profile for sputtered solar selective surfaces
Authors: Harding G. L.
Published: July 2002

Solar selective surfaces of high absorptance have been achieved by sputtering the absorbing layer with a gradation in optical properties through its thickness.
Method for mounting thermocouple gauge tubes
Authors: Rebarchik F. N.
Published: July 2002

A method for mounting thermocouple gauge tubes which eliminates the need for teflon tape wrapping, ring seals, greases, etc. and essentially eliminates all sources of contamination is described.
Submicron optical pattern generator—Electromagnetic drive with automated exposure system
Authors: Nishizawa Jun-ichi
Published: July 2002

The precise positional control is an important factor in various photolithography techniques. Electromagnetic micro-manipulator1) had been developed to realize submicron positional control of an X–Y table. Improvements in precision and controllability have already been attained by driving a magnet in the saturation region, to avoid the uncertainties introduced by Barkhausen noise. Position is measured with a laser-interferometer, which is limiting the accuracy. 0.2 μm positional alignment is attained by electrical feedback of the output signal to an electromagnet. The X–Y table is used in a pattern generator and is applied to draw directly a pattern on a sillcon wafer or a finely patterned master mask. Position of an X–Y table can be detected by a frequency-sweep type laser-interferometer to an accuracy of about 0.01 μm, which seems very useful for step and repeat camera or an electron-beam system. In factory environment a resolving power of 0.6 μm was obtained utilizing a fixed focus lens and a practical resolving power of 1.2 μm was obtained in combination of a zoom lens with a high resolving power lens. In the latter case an auto-focusing control system has applied.2) In the laboratory equivalent numbers were 0.1 and 0.5 μm, respectively, so, in future an improvement can be expected down to 0.2 and 0.6 μm. Exposure is automatically triggered by autofocusing control system only when the sample stage is located within the error of ±0.5 μm from the exact focusing point.
Surface segregation of a NiCu alloy as studied by a computerized atom-probe FIM
Authors: Ng Yee S. , McLane S. B. , Tsong T. T.
Published: July 2002

Using the computerized energy compensated time-of-flight atoms-probe (AP-FIM), we have obtained an absolute composition depth profile of a NiCu alloy with single atomic layer spatial resolution. For bulk composition of 3.1%±0.5% Cu at 650°±20°C, the topmost layers of the (111) and (001) planes are enriched to (17%±2.7%) and (36.6%±7.5%) Cu, respectively. Slight depletion of Cu is observed in the near surface layers. Both an irregular solution model and a regular solution model with surface enthalpy relaxation are found to agree semiquantitatively with our results. A comparison with the results from other surface techniques is also made.
Modification of evaporated chromium by concurrent ion bombardment
Authors: Hoffman D. W. , Gaerttner M. R.
Published: July 2002

Bombardment of thermally evaporated chromium films with energetic inert gas ions during deposition (ion peening) causes marked changes in properties when the dose exceeds a minimum critical value. The property changes are characterized by a sharp reversal of intrinsic stress from high-tensile to high-compressive values, increases in the optical reflectance and optical density to levels approaching pure bulk chromium, and enhanced resistance to oxidation on heating. Observations of the shift in critical ion dose with accelerating voltage and ionic mass (argon and xenon) indicate that the ion peening transition may be controlled by the transfer of momentum to the depositing film. This observation is found to be consistent with results obtained in low-pressure, cylindrical post-magnetron sputtering, which ion peening was devised to simulate.
A new transmission target for the x-ray lithography source
Authors: Okada K.
Published: July 2002

A new transmission target that is suitable as an x-ray lithography source is described. This target is a large stationary plane-source with a nearly parallel electron beam impinging on it. Problems due to mechanical vibration and irregular discharge encountered with conventional sources are eliminated. A prototype machine, comprising the electron optics and this 10×10 cm target, has been developed. Some excellent replication results were obtained from mask patterns with such exposure times as 6 min and 1.8 h.
Adapting conventional sputtering equipment for coating long tubes and strips
Authors: Lincoln R. L. , Blickensderfer R.
Published: July 2002

A method for coating long tubes and strips by adapting conventional sputtering equipment is described. The only complex modification was the mechanism for rotation of the workpiece while moving it beaneth the targets. (AIP)
Anodic oxide/GaAs and InP interface formation
Authors: Geib K. M. , Wilmsen C. W.
Published: July 2002

The initial stages of anodization of GaAs and InP were investigated in order to determine the factors which affect the oxide–semiconductor interface formation. This was accomplished by ESCA profiling thin anodic layers grown on chemomechanically polished wafers. Oxides on both InP and GaAs appear to be initiated by a nucleation and island growth process with the film becoming continuous at a thickness of approximately 40 Å. The oxide/GaAs interface was found to be composed of a Ga2O3 layer with indications of elemental As near the substrate. The oxide/InP interface had a uniform distribution of In2O3 and P2O5. The data indicates that dissolution of As2O3 or P2O5 is not a significant factor in the interface formation but the thermodynamic stability of the oxide could be important.
Single crystal LaB6 electron gun for variably shaped electron beam optics
Authors: Nakasuji M. , Wada H.
Published: July 2002

A single crystal LaB6 electron gun for variably shaped beams was developed. For the 50 A/cm2 density, 3 μm length maximum beam size, and 1 μA maximum beam current, the best electron gun characteristics were analysed. Optimum brightnesss is 2.5×105 A/cm2 sr. The product of crossover diameter and beam divergence semiangle is larger than 3.4×10−6 cm rad. Developed LaB6 guns have the following characteristics: crossover diameter is about 15 μm, beam divergence semiangle at 90% of the center intensity is larger than 3×10−3 rad and brightness varies from 7×104 to 6×105 A/cm2 sr with emission current conditions. Special features of this gun are the 480 μm tip radius and <110≳ orientation. An electron optical column for a variably shaped beam was constructed with this electron gun. Beam intensity instability for this column was smaller than ±2%/8 h without alignment or brightness servos.
Preferential sputtering from disordered GaAs
Authors: Singer I. L. , Murday J. S. , Comas J.
Published: July 2002

Auger spectroscopy has been used to measure the composition of ion milled GaAs surfaces in ordered and disordered states. Disorder was introduced into GaAs single crystals by implanting Se+ (5×1014/cm2, 100 keV) or Ar+ (5×1016/cm2, 20–100 KeV) ions. Auger composition profiles with 0.5 keV Ar+ ion milling exhibited As-depleted layers that extended to approximately the depth of the implant region. An enhanced Ar concentration was also seen in the disordered region. These results are compared with similar composition changes in GaAs produced by low energy (<5 keV) Ar bombardment. Arsenic depletion in both energy regimes is associated with preferential sputtering from disordered surface layers.
Co-adsorbed phases of hydrogen and oxygen on W(001)
Authors: Barker R. A. , Estrup P. J.
Published: July 2002

LEED studies of the co-adsorption of hydrogen and oxygen on tungsten (001) have revealed the formation of distinct surface phases. At room temperature and a total coverage of about one-half monolayer the adsorption is competitive: oxygen and hydrogen produce separate domains on the surface. When the crystal is heated, a homogeneous, mixed phase is produced. The mixing is reversible and no hysteresis is observed upon cooling. The transition occurs at a temperature substantially below the disordering temperature for the pure oxygen structure; it is ascribed to an effective repulsion between adsorbed H and O. Studies of the adsorption rate show that in this coverage range, the hydrogen sticking probability is independent of any preadsorbed oxygen.