bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface stresses in ion−implanted steel
Authors: Hartley N. E. W.
Published: July 2002

Recent work on ion−implanted metals has demonstrated the existence of substantial changes in friction and wear properties brought about by ion implantation. The effects have been attributed to corrosion inhibition, metallurgical transformation, or mechanical surface hardening. In the work to be presented, a capacitance probe apparatus is described which has been used to detect the deflection occurring during ion implantation of thin specimens of annealed steel. The deflection is related to the introduction of a surface compressive stress. 100−keV argon ion implantation is found to produce surface stresses of several thousand lbs/in.2 which reach a maximum at a dose approximately 5.0×1016 ions−cm−2. Light ions, such as nitrogen, which form chemically stable compounds within the steel, generate similar stresses within the surface such that a macroscopic deflection of the specimen can be observed. In this case very high doses are required to maximize the stress (∠1017 ions−cm−2). The results are interpreted with reference to damage mechanisms and nitride formation, and are discussed in relation to the mechanical property changes previously reported.
Relative sputtering yields and quantitative surface analysis by Auger spectroscopy
Authors: West L. A.
Published: July 2002

During the past few years, the qualitative analysis of surfaces by Auger electron spectroscopy has become an accepted analytical technique. With all analytical techniques, however, the ultimate goal is to obtain quantitative information. This paper presents data on the relative sputtering yield of several elements obtained by studying the surface composition of alloy systems (Cr–Pd, Ag–Pd, Cu–Pd, Mn–Ag–Pd, and Nb–U) varying in composition from a few to roughly fifty atomic percent. The reported measurements were taken while sputtering after the alloy surface had reached a steady state composition. Peak heights were referenced to in situ standards of the pure alloy components. Multiple determinations were carried out over a period of several weeks in order to check the reproducibility and to estimate the standard deviation in the data. This information was used to obtain uncertainty limits for the calculated sputtering yields.
Electron-stimulated processes at solid surfaces
Authors: Madden H. H.
Published: July 2002

Surface analytic techniques that use incident electrons as the initial stimuli have, in many cases, been shown to be destructive. Examples of such destructive processes include the decomposition of chemisorbed species, stimulated surface reactions with gas-phase components, and the desorption of chemisorbed atoms. Since such processes reflect chemical changes in the surface under investigation, studies of these processes can yield useful surface information. In a review of some electron-stimulated surface reactions, the types of surface-chemistry information to be expected is discussed. Recent results of an electron-stimulated-desorption (ESD) investigation of the interaction of oxygen with Ni, W, and Mo surfaces are presented. Measurements of threshold values and of the energy distribution of ions desorbed for excitation energies near and well above threshold were made using potential-modulation techniques. A comparison is presented between these ESD results and soft-x-ray appearance potential measurements made on the same chemisorptive systems.
XPS studies of surfaces and thin films of small-band-gap inorganic azides
Authors: DiBona P. , Wiegand D. A. , Sharma J.
Published: July 2002

Since XPS samples only a few surface layers of the solid for most materials, the signal from these first few layers makes a dominant contribution to the total signal. For the inorganic azides available, cross sections indicate that in most cases the surface layers contain less than the stoichiometric amount of azide (nitrogen). Since most of the metals are reactive, the excess metal is predominantly in the form of compounds, e.g. oxides. Carbon and oxygen are always observed as surface contaminants and in many cases the amounts of C and O detected are of the same order of magnitude as the metals and azide. The lack of stoichiometry and C and O contamination may be important for electrical properties involving the surface, e.g., electric-field initiation to detonation of explosive azides. The surface films may tend to provide protective coatings, so that twenty-year-old lead azide does not show significant bulk decomposition. The decomposed surfaces can be reactivated for most azides by exposure to hydrazoic acid. Short exposure of copper metal to HN3 vapor produces a thin film of copper azide.
ESCA surface studies of Pb1−xSnxTe devices
Authors: Grant R. W. , Pasko J. G. , Longo J. T. , Andrews A. M.
Published: July 2002

ESCA studies have been carried out on a number of Pb1−xSnxTe surfaces with the goal of correlating surface chemistry with surface leakage currents observed in Pb1−xSnxTe infrared detectors. A diode array structure has been developed which permits I–V and ESCA measurements to be carried out on the same surface. It is possible to reprocess this array to change the surface chemistry without altering the bulk semiconductor characteristics. ESCA results have established the existence of thick (hundreds of angstrom) elemental Te0 layers on several chemically processed device surfaces. These surfaces are shown to produce exceptionally low surface leakage currents at 77 K which suggests that Te0 may be a surface passivant for Pb1−xSnxTe. A dimensional analysis model has been developed which seems capable of estimating surface and bulk contributions to leakage currents.
Ion etching for pattern delineation
Authors: Melliar-Smith C. M.
Published: July 2002

This paper is a review of the application of ion etching (both ion beam milling and rf sputter etching) to pattern delineation in integrated circuit fabrication. Typical equipment and use conditions are described along with the advantages and disadvantages of each process. Two case histories are described where ion etching has been successfully used to pattern delineate the metallization levels of silicon integrated circuits by sputter etching and magnetic bubble devices by ion milling.
Anomalous effect of UHV-component-generated atomic hydrogen on the surface properties of ZnO
Authors: Shapira Y. , Lichtman David
Published: July 2002

It is well known that atomic hydrogen can cause significant changes in surface conductivity of many semiconductors such as ZnO. We have found that some of the atomic hydrogen produced during the operation of ionization gauges, ion pumps, and titanium sublimators can reach ZnO samples even when the samples have no line of sight to these devices. Conductivity changes of many orders of magnitude are produced when the residual-gas background contains sufficient amounts of hydrogen. This effect must be considered when surface conductivity measurements are being made on materials such as ZnO.
Some properties of the oxides of the tetrahedral semiconductors and the oxide–semiconductor interfacesa)
Authors: Pantelides Sokrates T.
Published: July 2002

Continuous-random-network models have been constructed for the Si–SiO2 interface. It is found that an abrupt interface with no SiOx layer is posible. A simple tight-binding model is described that is applicable for the calculation of the electronic properties of the bulk oxides and the oxide–semiconductor interfaces. Results are given only for selected bulk properties, namely the photoemission and x-ray emission spectra, and the dielectric constants of SiO2, GeO2, and various ABO4-type oxides.
Electron spectroscopic study of oxygen-plasma-treated polymer surfaces
Authors: Burkstrand James M.
Published: July 2002

Oxygen plasma treatment of ABS polymer surfaces has the effect of increasing the adhesion of evaporated metal films on those surfaces. To help understand this, surfaces of commercial ABS and polypropylene were examined with ESCA both before and after oxygen plasma treatment. The plasma treatment was found to change the basic chemical nature of the polymer surface by increasing the number of single and double bonds between carbon and oxygen atoms. It is suspected that these additional carbon–oxygen chemical bonds affect the adhesion between polymers and metals. In addition to the carbon–oxygen bond formation, the plasma treatment removed residual impurities of silicon and increased the residual amounts of other metallic impurities originating in the bulk. The binding energies of these metallic impurities are all indicative of oxides.
Solid-state reaction of Ti and sapphire
Authors: Chamberlain M. B.
Published: July 2002

The growth-rate of the products of the solid-state reaction between a polycrystalline Ti thin films and polished. (111) -oriented sapphire (A1203) wafers was determined from 757 to 839 K by combing Auger electron spectroscopy and Ar-ion-beam sputtering. A parabolic growth rate was fit to the data: The activation energy of the rate constant was 170 kJ mol−1 K−1. The rate constant was smaller for a Ti thin film epitaxially grown on a wafer.
Trapping of deuterium implanted into stainless steel at low temperatures
Authors: Altstetter C. J. , Behrisch R. , Scherzer B. M. U.
Published: July 2002

Stainless steel 316 specimens have been implanted with deuterium ions at 7 keV up to doses of 2×1018 D/cm2 at −120°C. Trapped quantities and depth profiles of the implanted atoms have been determined using the 3He (d,p) 4He nuclear reaction, using both the product particles for making the analyses. Up to doses of 5×1017 D/cm2 the implanted deuterons were retained within the analyzing zone, but at higher fluences the amounts retained no longer increased linearly with the bombardment dose. Deuterium to metal atom ratios of nearly 1:1 were observed. The density of retained deuterium was not a function of holding time at −120°C, but upon warming, the loss of deterium could be measured. At roughly −50°C the rate of loss was a maximum, and by +40°C only a few percent of the original amount of deuterium remained.
Photolithographic fabrication of thin-film metal–oxide–metal diodes with submicrometer-square junction areas
Authors: Havemann R. H.
Published: July 2002

A technique is described which uses conventional photolithography in fabricating metal–oxide–metal diodes with submicrometer-square junction areas. The junction is formed at the edge of the first thin-film electrode, thereby reducing one dimension of the junction by an order of magnitude or more over linewidths obtainable by standard photolithographic methods. Although the technique is applied specifically to the fabrication of a metal–oxide–metal diode array, it is generally applicable to other thin-film devices requiring submicrometer-square junction areas.
Radiation effects of electron-beam metal depositions on IGFET’s
Authors: El-Kareh B. , Puttlitz A. F.
Published: July 2002

Electron-beam radiation effects on n-channel IGFET parameters were studied. This paper summarizes the resulting surface- and dielectric-radiation effects obtained with a series of experiments incorporating e-gun metal deposition on MOS, MNOS, and SNOS structures. The results are compared with those using resistance-heated metal deposition for various thin-film compositions between the metal and silicon surfaces. A comparison is also made with the effects of controlled direct e-beam irradiation of the structures. The efficiency of quartz and aluminum thin films over MNOS structures, in reducing e-gun radiation effects, is evaluated for double-level metallurgy structures. The effect of different thermal-annealing conditions for offsetting the radiation effects is determined. It is concluded that e-gun metallization causes large negative voltage shifts in MOS, MNOS, and SNOS devices. While MOS threshold shifts are fully ’’annealable’’, residual MNOS and SNOS VT shifts are observed after an anneal of 350°/450°C. Thin films of quartz and aluminum over MOS and MNOS structures effectively reduce radiation effects. Other IGFET parameters are not substantially affected by e-gun radiation.
Alloy compositional profiles by AES, ESCA, and ion sputtering: Air-exposed Fe1−xPdx films
Authors: Lee Wen-Yaung , Lee M. H. , Eldridge Jerome M.
Published: July 2002

Surface studies of air-exposed, 1000 Å-thick Fe1−xPdx alloy films with x=0.06–0.74 were carried out using AES, ESCA, and in situ ion sputtering techniques. It was found that Fe is preferentially oxidized on the surface with a Pd-enriched region formed underneath the oxide layer. The iron oxide thickness decreases linearly as the Pd concentration is increased, becoming quite small for x≳0.6. Fe2O3 is the dominant oxidation product for the lower Pd concentration alloys while Fe3O4 appears to be the major oxide for x≳0.36. The steady state composition of the surfaces measured both by AES and ESCA techniques afer prolonged sputtering also indicated that the relative Pd-to-Fe sputtering yield remains constant for films with x between 0.06 and ∠0.38 and decreases to another constant value for films with larger x values. No preferential sputtering is observed in the AES case for alloys with x≳0.38, if the atomic density is taken into account; for x<0.38, Pd sputters about twice as fast as Fe. In the ESCA case, very strong preferential sputtering of Pd to Fe is observed. Possible origins for this sputtering yield change, including the phase transition and the residual oxygen content of the alloy, are discussed.
Two-step process for thin films of tin dioxide
Authors: Sabnis Anant G.
Published: July 2002

A two-step process for deposition of thin films of tin dioxide is described. The first step consists of depositing opaque films of oxygen deficient tin dioxide by dc sputtering of porous targets in an argon atmosphere; the second step is to oxidize the films at 400 °C in air. The target, which is used in this research, contains 80% SnO2 and 20% Sb by weight. Its density is about 60%–70% of the solid density of SnO2. The films have been heated in air at different temperatures. The variations in conductivity, transparency, and thickness with heating temperature and duration are presented. The stability and annealing behavior of the films are discussed. It seems possible to control the film conductivity by controlling heating time. The films, at the end of 6 h of heating at 400 °C in air, have conductivity of about 2Ω−1 cm−1 and transparency of about 80%.
Annealing behavior and selected applications of ion-implanted alloys
Authors: Myers S. M.
Published: July 2002

Thermally activated processes cause ion-implanted metals to evolve from the initial state toward thermodynamic equilibrium. The degree of this equilibration is strongly dependent upon temperature, and is considered here for three temperature regimes which are distinguished by the varying mobilities of interstitial and substitutional atoms. In addition, perturbations resulting from the irradiation environment are discussed. Examples are given of the use of implanted and annealed alloys in studies of diffusion, phase diagrams, and solute trapping.
Effects of substrate orientation and rotation on internal stresses in sputtered metal films
Authors: Hoffman D. W. , Thornton John A.
Published: July 2002

This paper reports the influence of substrate orientation and rotation on internal stresses in sputtered films of Cr, Mo, Ta, and 304 stainless steel (SS). The sample films were prepared by magnetron sputtering from cylindrical cathodes under conditions (0.13 Pa argon; deposition rate ∠0.4 nm s−1) known to yield compressive stresses at normal incidence with minimal heating of the deposits. The effects of fixed, oblique incidence are found to fall into three regions. At near-normal incidence little effect is observed. The width of this region is much greater for Ta and SS (±45°) than for Cr and Mo (±5°, ±20°). Beyond the first region the stresses change rapidly with increasing angle, becoming sharply tensile in Cr and SS, while in Mo and Ta they remain compressive but become small. In the third, high-angle region the stresses diminish gradually toward zero. The stress dependence on angle of incidence is similar to a dependence on working gas pressure that was observed in previous studies. Stresses in samples rotated continuously through all angles of incidence were always more tensile than the appropriate average of the static results would indicate. Data are also given for the effects of oblique deposition and rotation on electrical resistivity, optical reflectance, and gas incorporation in the deposited metals.
Ion bombardment effects on elemental incorporation probabilities during sputter deposition of GaSb and InSb
Authors: Eltoukhy A. H. , Barnett S. A. , Greene J. E.
Published: July 2002

The relative elemental incorporation probability of Sb in GaSb and InSb films deposited by multitarget sputtering has been measured as a function of growth temperature Ts, the ratio r of elemental Sb to Ga (or In) impingement fluxes, and substrate bias during deposition. The average film composition was determined by electron microprobe measurements. The application of a negative substrate bias, Vs, during film growth was found to result in preferential resputtering of second phase precipitates formed in the film whenever JSbφSb≠JIIIφIII where J and φ are the elemental impingement rates and thermal sticking probabilities, respectively. At any value of r investigated, a value of Vs could be found such that for negative substrate biases greater than this value, the films were single phase. No preferential resputtering was observed for Vs up to 250 V in films in which JSbφSb=JIIIφIII. Thus, the range of r and Ts values over which single-phase stoichiometric films could be deposited from the vapor phase was extended by low energy ion bombardment of the growing film.
Effects of thermal spikes on the characteristics of cryosorption pumps with condensed carbon dioxide layers
Authors: Arakawa I. , Kobayashi M. , Tuzi Y.
Published: July 2002

The pumping characteristics of the condensed CO2 layers for He at low temperature depend on the structure of the layers which is determined by the formation conditions and the thermal history after deposition. During the continuous condensation process of CO2 on the cryosurface kept at the temperatures lower than about 8 K, abrupt temperture changes, ’’thermal spikes,’’ are repeatedly observed. The amount of heat generated at each thermal spike is directly proportional to the amount of condensed CO2 in the period subsequent to the last spike. The thermal spikes reduce the adsorption capacities of the condensed CO2 layers for He, assumed to depend on the inner surface area of the layers. Thus the spikes seem to be caused by some structure changes of the condensed CO2 layers.
Model of ion knock-on mixing with application to Si–SiO2 interface studies
Authors: Schwarz S. A. , Helms C. R.
Published: July 2002

We have developed an ion knock-on mixing model which yields quantitative predictions of the broadening observed in sputter profiling experiments. The model is based on an analogy to thermal diffusion theory. Interface widths and peak widths are seen to broaden in an rms fashion with a broadening factor W which is inversely proportional to the square root of the sputtering yield. We have also performed Auger sputter profiling experiments to examine the broadening of the Si–SiO2 interface as a function of ion energy for Ne+, Ar+, and Xe+ bombardment. The experimental results are consistent with the mixing model.
Ion beam sputtering of fluoropolymers
Authors: Sovey J. S.
Published: July 2002

Etching and deposition of fluoropolymers are of considerable industrial interest for applications dealing with adhesion, chemical inertness, hydrophobicity, and dielectric properties. This paper describes ion beam sputter processing rates as well as pertinent characteristics of etched targets and films. An argon ion beam source was used to sputter etch and deposit the fluoropolymers PTFE, FEP, and CTFE. Ion beam energy, current density, and target temperature were varied to examine effects on etch and deposition rates. The ion etched fluoropolymers yield cone- or spirelike surface structures which vary depending upon the type of polymer, ion beam power density, etch time, and target temperature. Also presented are sputter target and film characteristics which were documented by spectral transmittance measurements, x-ray diffraction, ESCA, and SEM photomicrographs.
Physical properties of plasma-grown GaAs oxides
Authors: Chang R. P. H. , Polaka) A. J. , Allara D. L. , Chang C. C. , Lanford W. A.
Published: July 2002

The growth kinetics and the compositions of plasma grown oxides on GaAs have been studied in detail using Auger spectroscopy combined with nuclear resonance profiling and infrared spectroscopy. We have carefully mapped out the growth rate as a function of the substrate temperature (0°–100° C) and bias voltage (20–100 V). We find with low substrate temperatures during oxidation stoichiometric oxides are formed, and high temperatures and voltages give the fastest growth rates. In particular, under optimum growth condition (i.e., the fastest growth rate 50 Å/s stoichiometric oxides with extremely sharp interface width (∠20 Å) can be achieved. The ambients in which postoxidation anneals take place do influence the interfacial and oxide properties. Anneals in nitrogen for less than thirty minutes at temperatures below 450° C do not affect the oxide properties, while annealing in hydrogen under the same conditions show that oxides are being chemically reduced (most likely through forming OH groups with the As and/or Ga in the oxide). Annealing in hydrogen can also reduce the oxide density by as much as 30%.
Reactive sputtering of platinum in Ar–O2 mixtures
Authors: Hecq M. , Hecq A. , Robert T.
Published: July 2002

Platinum sputtering in argon–oxygen mixtures is studied utilizing the technique of glow discharge mass spectrometry which involves penning ionization in the plasma and analysis in a quadrupole filter. (AIP)
Electronic structure of semi-infinite III–V compound semiconductor surfaces and interfaces: Application to InAs/GaSb(110)
Authors: Dandekar N. V. , Madhukar A. , Lowy D. N.
Published: July 2002

The Green’s function technique has been generalized, within the tight binding approximation, to describe realistically the electronic structure of semi-infinite III–V compound semiconductor surfaces and their interfaces. Results for the InAs(110) and GaSb(110) surfaces and the InAs/GaSb(110) interface are reported. For each of the individual semi-infinite solids the dispersion of surface states and their density, ρSS(E), follows the general trend found in the (110) surfaces of III–V compounds. No intrinsic interface states are found in the common energy gap regions of the two materials. The electronic density of states on the interface layers is accurately calculated in the energy region in which the chemical potential resides. A finite density of states at the interface, ρI(E) is found, indicating the absence of a barrier at the interface. This is in contrast to the semiconductor like energy gap found in the calculations on InAs/GaSb thin superlattices. A novel feature implied by the finite density of states at the interface is the ’’metal’’ like transport characteristics of the electrons and holes in the interfacial plane. However, on the basis of the expected self-consistent charge transfer and the attendant interface dipole, it is argued that in spite of the absence of an interface barrier, the transport characteristics in the normal direction will not be ’’metallic.’’
Comparative studies of oxygen adsorption on GaAs(110) surfaces with ultrathin aluminum and cesium overlayers
Authors: Skeath Perry , Su C. Y. , Chye P. W. , Pianetta P. , Lindau I. , Spicer W. E.
Published: July 2002

The oxidation of GaAs(110) surfaces is found to be profoundly influenced by the deposition of very thin metal overlayers. However, the Fermi energy pinning at the interfaces is only slightly influenced by the oxidation of the metal overlayer and semiconductor. Aluminum and cesium covered surfaces are investigated using soft x rays (SXPS). Oxygen uptake by the Al and Cs overlayers is much more rapid than by the bare GaAs surface. Oxidation of the GaAs through the Al overlayer occurs more slowly than for the bare surface. In strong contrast to the aluminized surface, oxygen was found to bond to surface As atoms on the cesiated surface with 106 times faster uptake compared to the bare surface. These results are important in the context of GaAs passivation, Schottky barriers, negative electron affinity (NEA) photocathodes, and metal oxidation processes.
Surface analysis of rf plasma oxidized In and PbInAu films using ESCA
Authors: Baker John M. , Johnson R. W. , Pollak R. A.
Published: July 2002

Variable-angle x-ray photoemission spectroscopy (XPS or ESCA) has been used to quantitatively determine the composition of the upper portion of oxide layers on the surface of In and PbInAu alloy films. The oxide layers were formed using a combination of thermal oxidation and rf oxidation, a process in which the films are mounted on a Pb-coated electrode which is coupled to an rf generator to produce a glow discharge in oxygen. In addition to indium oxide, lead oxide was detected in all films. The concentration of the lead oxide was essentially independent of the composition of the underlying metal film (0?cPb?86 at. %), but was strongly related to the rf-oxidation conditions. This indicates that backscattering of material sputtered from the Pb-coated rf electrode during rf oxidation as the primary factor in determining the concentration of the lead oxide within the 20-Å XPS sampling depth. Furthermore, by varying the detection angle, and consequently the effective sampling depth, we obtained results which indicate that this lead oxide was concentrated within the top 10 Å of the oxide. Films which were oxidized at 2.7 Pa O2 for 30 min were thus found to have the equivalent of 2.5–4.0 Å of lead oxide distributed within the top 6 Å of their oxides, independent of their Pb concentration. Increasing the pressure during rf oxidation to 6.7 Pa and extending the oxidation time to 120 min resulted in the backscattering of the equivalent of 6–8 Å of lead oxide distributed within the top 10 Å of the oxide. Electron microprobe measurements of the Pb content of similarly oxidized indium samples showed good agreement regarding the relative amounts of Pb in the surface oxide region but indicated a Pb level about twice that determined by XPS.
Direct e-beam fabrication of 256 BIT bipolar RAMS
Authors: Reynolds J. , Bartelt J. L. , Williamson R. , Varnell G. L.
Published: July 2002

A vector scan laser-controlled e-beam direct writing system (EBMIII) has been utilized to fabricate the 745201A bipolar RAM in a pilot production area. This device is a standard TTL, 256-bit bipolar RAM using a single level metal, junction-isolated, Schottky-clamped bipolar process with 5-m design rules. Two high speed electron resists, one positive (TI-313) and one negative (TI-309), were used in this pilot production demonstration along with a new selective plasma etching process. The completed units were screened and tested according to military specifications and compared to devices processed with conventional photoresist. The results of these stringent tests verified that e-beam lithographic processing does not degrade the performance of this type of device.
Scanning electron beam annealing with a modified SEM
Authors: Ratnakumar K. N. , Pease R. F. W. , Bartelink D. J. , Johnson N. M.
Published: July 2002

A commercial scanning electron microscope, modified for high current operation, has been successfully used to anneal arsenic implanted silicon. The measured parameters of the electron–beam are shown to fit a model for localized heating, taking into account source-dispersal due to beam penetration, and to explain the experimentally observed window for annealing without melting. Recrystallization of the annealed layers is shown by the sharp electron-channeling patterns obtained. Spreading-resistance and junction depth measurements indicate complete electrical activation of the implanted species without any measurable redistribution. The potential for localized annealing through a finely focused scanning electron–beam is illustrated by the fabrication of conducting region of submicron dimensions surrounded by high resistivity amorphous silicon.
Ion-beam lithography for IC fabrication with submicrometer features
Authors: Rensch D. B. , Seliger R. L. , Csanky G. , Olney R. D. , Stover H. L.
Published: July 2002

We report an entirely new pattern-replication technique for IC fabrication. It has demonstrated submicrometer (<0.5 μm) resolution and it has the capability of large throughput (wafer-levels/h). It utilizes high-energy protons as the exposing radiation through a mask placed in proximity to a wafer covered with resist. We call this new technique ’’ion-beam lithography’’ (IBL). System parameters and measurements relevant to the use of IBL as a production technology are discussed and SEM micrographs of submicrometer patterns in PMMA are presented. The technique is similar to x-ray lithography, in that a pattern is produced in a thin resist film after exposing it to radiation through a mask. High-energy protons have the same advantage as x rays in eliminating wavelength diffraction problems which limit the resolution of photolithography. Also, a gap (∠15–25 μm) is permitted between the mask and wafer. Ions have an advantage over x rays in that penumbral distortion is avoided by using highly collimated ion beams which are available with present state of the art; ions are collimated using conventional ion-optical techniques, whereas use of a distant ’’point’’ source is the only feasible scheme for collimation of x rays.
Interface modification of refractory metal–silicon structures by ion implantation
Authors: Wang K. L. , Bacon F. , Reihl R. F.
Published: July 2002

A systematic study of the modifications of the transition metal–silicon interface by ion implantation was carried out. Interface mixing was observed to be a general result in samples implanted at temperatures of 78, 297, and 423 K. Elemental depth distributions obtained using Auger electron spectroscopy combined with ion sputtering illustrated composition plateaus near the interface of the ion-implanted structures. Additionally, high energy resolution Auger analyses of the silicon LVV transition for the implanted samples showed an energy shift and a change of the spectrum relative to the elemental silicon. The Auger-analysis results suggest that compound (silicide) formation can be induced by ion-implantation into transition metal–Si structures, even in cases where high temperatures are normally required for thermal reaction. The implications for potential applications to very large-scale integration of electronic devices are discussed.
Metal methacrylates as sensitizers for poly methyl methacrylate electron resists
Authors: Webb David J. , Hatzakis M.
Published: July 2002

The preparation of copolymers of methyl methacrylate and various metal methacrylates is described. The metals studied are lead, barium, calcium, and strontium. Lead and barium in particular improve many of the properties of PMMA. For instance, sensitivity to electrons and x rays is increased by a factor of approximately 3. Flow temperature is raised and chemical etch resistance is improved. Lead gives the most improvement followed by barium then strontium then calcium. The lead concentration at which the maximum contrast is obtained is 3 wt %.
Summary Abstract: Effect of ion and electron bombardment on the Auger electron surface spectra of Wustite, Magnitite, and Hematite powders
Authors: Buczek D. , Sastri S.
Published: July 2002

The effects of ion and electron bombardment on the auger electron surface spectra of wustite, magnetite and hematite powders are reported.
Effects of deposition parameters on the properties of superconducting rf reactively sputtered NbN films
Authors: Wolf S. A. , Singer I. L. , Cukauskas E. J. , Francavilla T. L. , Skelton E. F.
Published: July 2002

Thin films of NbN were reactively rf sputtered using a range of substrate temperatures and nitrogen partial pressures. The effects of these deposition parameters was to change the morphology rather than the stoichiometry of the sputtered films. Auger composition analysis, x-ray diffractometry, resistivity, resistivity ratio, superconducting critical temperature (Tc), and critical magnetic field [Hc2(T)] data were all used to determine the microstructure of the films and how it related to the measured properties. The best metallic films had Tc’s?16 K, Hc2(T)’s of 18 T and were prepared at 600°C using 1 Pa argon, 0.03 Pa N2, and a target power density of 9.8 W/cm2. All the films had carbon impurities at concentrations estimated to be between 1 and 15%. X-ray analysis indicated the presence of a face- centered-cubic structure, assumed to be the Bl phase, in addition to a second phase in one of the samples. The best superconducting films had several percent carbon. Those films prepared with an excess nitrogen partial pressure had negative temperature derivatives of resistance indicating a granular column void type microstructure. Films prepared with a deficient nitrogen partial pressure had very low Tc0’s (<4.2 K). A film prepared at ambient temperature had the least carbon, was nearly stoichiometric NbN, but had degraded Tc and enhanced Hc2(0).
Acoustic emission and electron emission during deformation of anodized aluminium
Authors: Dickinson J. T. , Snyder D. B. , Donaldson E. E.
Published: July 2002

Tribostimulated exoelectron emission provides a sensitive way to characterize anodic films on aluminium. This paper describes the detection of acoustic emission (AE) and electron emission (EE) during the tensile deformation of anodized aluminum. It is shown that the observed bursts of AE are associated with cracking of the oxide, that AE and EE count rates vs strain are closely related, and that most EE occurs very soon after AE events. Evidence is also presented for a component of EE unrelated to AE which is attributed to chemi-emission.
Sputter-induced roughness in thermal SiO2 during Auger sputter profiling studies of the Si–SiO2 interface
Authors: Cook C. F. , Helms C. R. , Fox D. C.
Published: July 2002

We have used transmission electron microscopy replica techniques in conjunction with Auger sputter profiling (ASP) to study the effect of sputtering on the morphology of SiO2 surfaces. 1 keV Ar ions incident 49° from the surface normal induce a ridge and valley structure with the ridges running normal to the ion beam direction. The degree of roughness is proportional to the amount of SiO2 removed by sputtering and appears to have no effect on the width of the Si–SiO2 interface as seen by ASP.
Observations of stresses in thin films of palladium and platinum silicides on silicon
Authors: Angilello J. , d’Heurle F. , Petersson S. , Segmüller A.
Published: July 2002

The silicides of Pt (PtSi) and of Pd (Pd2Si and PdSi) were formed by the interaction of metallic thin films with single crystal substrates of Si. The stresses in the silicide films were measured at room temperature from the bending of the Si substrates, obtained via an x-ray diffraction technique. The stresses vary approximately linearly with the heat treatment temperatures, without pronounced relationship with the different phase formations. For both Pd2Si and PtSi, the stress levels are correlated with the measured lattice parameter. Approximate values of elastic constants and expansion coefficients are derived.
The effect of overcoats on the ablative writing characteristics of tellurium films
Authors: Chen M. , Marrello V.
Published: July 2002

The change in the ablative writing sensitivity of Te films due to SiO2 and polymethyl methacrylate overcoats of various thicknesses were measured. These experimental data were compared to results of thermal calculations. We found that thermal losses of the absorbed laser energy to the overcoat layer is usually not negligible even for very thin (≲500 Å thick) overcoat layers. In addition to thermal effects which degrade the writing sensitivity of Te films, we found that rigid overcoats combined with rigid substrates can constrain the ablative writing process of Te and hence cause further degradation in the writing sensitivity and in the read-during-write signal.
Indium doped cadmium sulfide films deposited by cylindrical magnetron reactive sputtering
Authors: Thornton J. A. , Cornog D. G. , Anderson W. W.
Published: July 2002

Cadmium sulfide coatings about 500 nm thick were deposited by reactive sputtering onto borosilicate glass substrates at temperatures in the range 150°–350° C using pure and In-doped Cd cylindrical magnetron sputtering sources. The working gas was Ar–H2S with various H2S injection rates. Deposition rates were ∠1 nm/s. Adatom desorption was found to limit the cadmium sulfide accumulation rate to the extent to which the Cd could interact with the S to produce CdS. Consequently, the undoped deposits were nearly stoichiometric, with resistivities of ∠104 Ω cm. The resistivities of the doped coatings were found to be critically dependent on the H2S injection rate, apparently because of compensation by Cd vacancies. Resistivities in a range 0.1–5 Ω cm, suitable for Cu2S/CdS solar cells, were obtained for target doping levels of 0.1–1 at.% when the deposition flux was rich in Cd. Higher H2S injection rates yielded resistivities in the range 103 Ω cm. Electron Hall mobilities ranged from 2 to 15 cm2/V s in the doped CdS to 20 cm2/V s in the undoped material.
Mössbauer characterization of reactively sputtered iron nitride films
Authors: Lo C. , Krishnaswamy S. V. , Messier R. , Rao K. R. P. M. , Mulay L. N.
Published: July 2002

We have shown by Mössbuaer spectroscopy and x-ray diffraction that single-phase, small crystallite size films in the Fe–N system (γ′-Fe4N and Fe3N) can be synthesized by varying reactive sputtering conditions in Ar+N2 gas mixtures. The γ′-Fe4N phase can be further produced and controlled by addition of H2 to the sputtering gas with single phase films (i.e., no unreacted α-Fe present) obtained only at a 1:3 N2:H2 mixture. The film microstructures are consistent with the structure zone model classification scheme and show that faceted, high surface area, single phase γ′-Fe4N and Fe3N films can be prepared with crystallite sizes of ∠400–500 Å.
Summary Abstract: Silicon MBE
Authors: Bean J. C.
Published: July 2002

This paper summarizes a review of recent developments in silicon molecular beam epitaxy. These include ionized doping, heteroepitaxial growth on insulators and silicides, and MBE devices.
Exposure and development models used in electron beam lithography
Authors: Hawryluk R. J.
Published: July 2002

This review examines exposure and development models which are used in electron beam lithography to predict resist profiles. The following topics are discussed: development models of positive polymeric electron resists, in particular, poly-methyl-methacrylate; exposure models based on analytic or Monte Carlo calculations of energy dissipation; comparisons of experimental measurements of linewidth and profile shape and predictions based upon exposure and development models; the dependence of proximity effects on resist and substrate thickness, beam voltage, and substrate material; and finally algorithms used to alter the exposure or pattern shape or both to compensate for proximity effects. The understanding which is gained from the exposure and development models is discussed in terms of fabrication techniques used in electron beam lithography.
Proton magnetic resonance spectra of plasma-deposited inorganic thin films
Authors: Reimer J. A. , Vaughan R. W. , Knights J. C. , Lujan R. A.
Published: July 2002

Proton magnetic resonance data are presented for the hydrogen alloys of plasma-deposited amorphous boron, carbon, silicon carbide, and silicon nitride. Linewidth and lineshape analysis leads to the conclusion that hydrogen nuclei are clustered in a-Si/C:H, a-C:H, and a-Si/C:H. Both a-Si/C:H and a-C:H data show that the hydrogen exists in two phases. Modeling of line- widths in a-Si/C:H indicates that the two phases are heavily hydrogenated carbon clusters imbedded in a weakly hydrogenated a-Si lattice. Finally, evidence is presented for the presence of motionally narrowed hydrogen spectra in a-Si/N:H, a-B:H, and a-C:H. It is suggested that the hydrogen nuclei giving rise to these spectra are associated with disorder modes.
Use of molecular beam epitaxy for the achievement of low resistance intercell contacts in multiband gap solar cells
Authors: Bouchaib P. , Contour J. P. , Raymond F. , Vérié C. , D’Avitaya F. Arnaud
Published: July 2002

GaAs and Ga1−xAlxAs n+/p+ tunnel junctions have been grown by MBE. The peak current density and the resistance-area product are 2.35×102 A cm−2 and 6×10−4 Ω cm2, respectively, in GaAs. These tunnel junctions provide suitable connections for a cascade solar cell with a power loss lower than 0.65% at 1000 suns AM 1.5 (83.5 W cm−2). Tunnel diodes have been obtained in Ga1−xAlxAs for x<0.2 only. For alloys with band gaps in the range 1.78 eV(x = 0.26)–1.85 eV(x = 0.31), the diodes show backward and rectifying I–V characteristics, respectively.
Optical investigation of the electrical properties of a polycrystalline–semiconductor–electrolyte interface using electroreflectance
Authors: Silberstein R. P. , Lyden Joseph K. , Tomkiewicz Micha , Pollak Fred H.
Published: July 2002

We have investigated the low-field electrolyte electroreflectance (EER) spectra of polycrystalline electrodeposited N–CdSe in the vicinity of the Eo(A,B) transitions (direct gap at ? = 0). Utilizing the properties of low-field EER, we have studied the distribution of the applied ac voltage in situ in the photoelectrochemical solar cell configuration: (1) By measuring the in-phase and quadrature EER signals as a function of modulation frequency f, we have determined the electrical impedance Z(f) of the interface for 10 Hz<f<10 kHz, at the focus of the incident light. These results are in substantial agreement with direct electrical measurements. (2) By measuring the EER amplitude as a function of applied dc bias voltage, we have found evidence for surface states which contribute to Fermi level pinning; similar evidence was not observed for single-crystal CdSe. These techniques are of general applicability for other semiconductor interfaces with optically transparent junctions, and are well suited to topographical scanning.
Exploiting energy-dependent photoemission in Si d-metal interfaces: The Si(111)–Pd case
Authors: Abbati I. , Rossi G. , Lindau I. , Spicer W. E.
Published: July 2002

We present synchrotron radiation photoemission results from Si(111) with increasing Pd coverages ϑ (in monolayer units from 0.5 to 23 monolayers). We have measured photoemission spectra in the Cooper minimum for the Pd 4d electrons (hν = 130 eV) and outside this region (hν = 80 eV) where the d emission in strong. By comparing the two cases, one obtains information on the Si (sp) and Pd (d) states. Making use of this, we discuss in detail the coverage dependence of the spectra in connection with the nature of the chemical bond between Si and Pd and the structure of the Si–silicide interface.
Influence of bias sputtered glass on avalanche breakdown
Authors: Blose W. L. , Magill P. J. , Walsh J. P.
Published: July 2002

The use of sputtered glass for the passivation of integrated circuits is well known. Generally, it has been assumed that the sputtering process has had negligible impact on bipolar IC behavior. Recent evaluation of device parameters pertaining to high voltage applications indicates that this is not the case. It has been found that the influence of substrate bias for a tuned anode system may have a detrimental effect on avalanche breakdown. In particular, the breakdown voltage decreases with increasing substrate voltage. The cause is attributed to argon ions that are embedded in the deposited glass layer.
Models of column III and V elements on GaAs (110): Application to MBE
Authors: Skeath P. , Lindau I. , Su C. Y. , Spicer W. E.
Published: July 2002

Models of ordered Sb overlayers on GaAs (110) are presented and discussed in terms of simple chemical considerations and the available data. The basic character (directional, covalent) of the Sb–GaAs bond is expected to apply to other column V elements on GaAs. Recent developments from theory in the understanding of column III metal–GaAs (110) bonding are summarized and compared to experimental data. It is proposed that the tendency for column III metals to bond nondirectionally on the (110) surface, while column V elements bond directionally, is highly relevant to molecular beam epitaxy (MBE) on all surfaces of III–V compounds. The basis of this proposal is the requirement that a column III atom must have several neighboring column V atoms before it can hybridize and form directional covalent bonds, while no such requirement of hybridization is necessary for the column V elements to bond to the surface directionally. One important result is that the column V element is initially responsible for establishing registry between the growing layer and (110) surface. For MBE on polar surfaces, column III adatoms are not expected to be stabilized in surface lattice sites without several neighboring column V elements.
Metallization for diode lasers
Authors: Ettenberg M. , Ladany I.
Published: July 2002

This paper reviews some of the problems associated with injection laser heat-sink attachment and ohmic contact metallurgy. The effects these have on initial laser characteristics as well as on laser reliability are discussed for both (AlGa)As (0.8 μm) lasers and the newer InGaAsP (1.3 μm) lasers.
Design and performance of a 4 in. electron image projector
Authors: Ward R. , Franklin A. R. , Gould P. , Plummer M. J.
Published: July 2002

An electron image projector has been designed and built which is currently exposing 4 in. wafers and has the capability of going to 5 in. Linewidth control of ±0.04 μm for 1 μm lines has been measured over the whole surface of 4 in. wafers. Machine alignment accuracy of ±0.03 μm has been achieved and nonrepeatable image distortion is shown to be less than 0.1 μm. Examples of resolution capability and step coverage are also shown.
Summary Abstract: High resolution ion beam lithography
Authors: Economou N. P. , Flanders D. C. , Donnelly J. P.
Published: July 2002

A new type of high resolution mask for ion beam lithography is described. The mask employs a thin membrane with regions of two different thicknesses to provide contrast for proton exposure of resist. A conventional ion implantation system is used to generate a collimated beam of protons for flood exposure of the sample. Beam energy is chosen so the the protons pass through the thin areas of the mask and emerge with sufficient energy to expose the resist, but are stopped in the thick areas. Experiments using polyimide membrane masks have yielded promising results. The ability to reactive ion etch structures with nearly vertical sidewalls in polyimide allows the fabrication of masks having both high contrast and high resolution. The stopping power of polyimide was determined by measuring the transmission of protons through membranes of known thickness, as a function of incident beam energy. In the energy range from 50–200 keV, the stopping power of polyimide for protons was measured to be ∠100 keV/μm. Mask fabrication procedures and exposure experiments to determine the resolution of this technique are reported. Patterns with linewidths of 〈0.1μm have been successfully replicated.