bluuebunny/crossref_metadata_2025 huggingface dataset:
Automatic measurement and correction of deflection astigmatism and defocusing in the Hewlett–Packard 605 electron beam lithography system.
Authors: Owen G.
Published: July 2002

The specifications for the Hewlett–Packard 605 electron beam lithography system call for an angular aperture of 2.5 mrad, a main deflector field size of 5×5 mm2, and a spot diameter of 0.5 μm over the entire field. Without dynamic corrections for deflection astigmatism and defocusing, the spot diameter would increase to about 1.6 μm at the perimeter of the main deflector field, and so an aberration measurement and correction scheme is required. A scheme is described in which both measurement and correction are performed under machine control, with no operator assistance. Astigmatism and defocus corrections are first measured automatically at a number of sample points within the main deflector field of view. The measured data are then processed to express the corrections as polynomial functions of deflection, and values for the polynomial coefficients are evaluated. During exposure, the coefficients are used to evaluate the aberration corrections, which are applied as the beam is deflected. The main deflector has an octupole configuration and stigmation is achieved by adjustment of the voltages on the eight electrodes. The automatic measurement of the defocus and astigmatism aberrations at each sample point is done by taking a through local series of edge scan measurements over a specially fabricated test target. The target, the through focal series measurement technique, and the manipulation of the resulting data are described. Experimental evidence of the success of the scheme in maintaining a 0.5 μm diam spot over a 5×5 mm2 field of view is presented.
Accuracy of image positioning in an electron beam proximity printer
Authors: Nehmiz P. , Bohlen H. , Greschner J.
Published: July 2002

Electron Beam Proximity Printing is a novel method for high throughput submicron lithography. The employed method of shadow projection of a mask pattern to the wafer requires physical holes in the mask. The so-called mask stencil problem associated with self-supporting masks is eliminated by using complementary masks. The required accuracy of complementary mask stitching is independent of the printed linewidth. Exposures in 1 μm thick PMMA demonstrate that with a stitching accuracy of ±0.2 μm the edge roughness at the stitching positions is ?0.1 μm. Experiments show that a prototype machine equipped with a laser interferometer of λ/8 = 79 nm resolution fulfills this requirement.
A new type pattern generator applied to the electron-beam exposure system
Authors: De-xiang An , Jian-kun Wang , Pei-yong Qiu
Published: July 2002

This paper describes a new type pattern generator, used in the scanning e-beam system suitable to generate smooth skewed vector with given slope. The initial coordinate of the vector is defined by two 16 BIT DACs, each equipped with a fixed reference source, and the components of the vector are given by other two 12 BIT DACs, each equipped with a variable reference source digitally controlled by a common triangular wave generator. Digital controlled period of the triangular wave ranges from 1 μs to 10 s. A high speed dynamic zero-correction deflection amplifier is applied to the pattern generator. The deflection amplifier and coil system are optimized to give a flat frequency response to 5 or 10 Mc, and the output current ±0.5 to ±5 A. Experimental exposure has been practiced in the 20×20 mm2 scanning field with smooth skewed vectors, location accuracy 0.03%. Scanning speed is equivalent to 100 kc to 10 Mc of the digital point–to–point scanning e-beam system.
Control configuration for the electron beam lithographic system EL–3
Authors: Craft J. , Williams M. , DeFiglio G. , Pavick J.
Published: July 2002

Automated electron beam lithographic tools have throughput requirements which dictate some essential control features. Data of various types flows continuously to and from the tool for deflections, field corrections, patterns, pattern registration, synchronization, and control. Data must be transferred at high speeds and in synchronization with tool writing cycles. In addition, preparation of pattern data and wafer or mask control parameters must be accommodated simultaneously. The IBM electron beam lithographic tool, EL–3, includes a control system driven by two Series 1 (S/1) minicomputers. One is the system controller; the second controls only mechanical operations, such as wafer or mask loading and X–Y stage moving. The primary S/1 controls all system activities through high-speed memory buffers, a distributed digital control bus which interfaces to functional logic modules, and a direct connection to the S/1 mechanical controller. The buffers allow the primary S/1 to collect or transfer data at its specified rates, while tool functions are executed at high speed by the digital hardware for optimized throughput. The control system can operate stand alone or integrated into a computer-aided manufacturing environment called Quick Turn Around Time (QTAT). In this QTAT environment, large data volume transfers are made directly into the high-speed memory buffers at 500–600 kbyte/sec, which improves system throughput for applications requiring frequent pattern buffer reloading. This paper describes the control system configuration, data preparation, data transfer and performance features of EL–3 for both the stand-alone and manufacturing environments.
Distributed control/support architecture for direct wafer write e-beam lithography systems: Throughput considerations
Authors: Merritt P. E. , Ozdemir F. S.
Published: July 2002

An optimized implementation of the necessary control and support functions for direct wafer write e-beam lithography systems is prerequisite to realizing the full potential of this lithography technology. This optimization must take into account both functional perfomance and cost. A real-time process control network for the support and control of multiple direct write e-beam lithography systems is currently operational at the Hughes Research Laboratories. This paper describes this e-beam lithography system support and control network from the perspective of the minicomputer network.
Reactive ion etching for submicron structures
Authors: Chinn J. D. , Adesida I. , Wolf E. D. , Tiberio R. C.
Published: July 2002

The etch resistance of PMMA was measured under various reactive ion etching conditions and compared with that of silicon dioxide, silicon and Shipley AZ 1350 resist. The resulting profiles transferred into the substrates masked with PMMA were also studied under various reactive ion etching conditions. This study showed that PMMA can be used as a masking resist for etching silicon dioxide using fluorine-deficient etch gases. Linewidths with dimensions of 0.1 μm have been obtained in silicon dioxide with usable selectivity between PMMA and silicon dioxide.
Ion source performance in a focusing column with large deflection fields
Authors: Berry I. L.
Published: July 2002

The theoretical performance of liquid metal and field ionization ion sources in systems with large deflection fields is discussed. It is shown that simple postlens electrostatic deflection with dynamic focusing has the capability of achieving large deflection fields at reasonable beam currents. A deflection field of 3×103 spot diameters on a side is theoretically achievable for liquid gallium ion sources at beam currents of 1 nA at 100 kV and a spot size of 50 nm. Recent data from Hanson and Siegel for liquid helium cooled hydrogen field ionization indicate that even better performance may be achieved with this source.
High power 13.3 Å x-ray source for submicron lithography
Authors: Fay B.
Published: July 2002

This paper discusses the design, fabrication, and performance of a high-power x-ray source for submicron x-ray lithography. The source is a conventional x-ray source featuring a high perveance (1.0×10−6 A V−3/2) electron gun and a water cooled high-speed rotating anode (8000 rpm). The anode material is copper and the main characteristic line radiated is the CuL line of 13.3 Å wavelength. Details are given on the geometrical design of the source, the realization of the pure Tantalum cathode indirectly heated by electron bombardment, and the high-speed rotating anode. Results will be given on the operating conditions of the source as well as on the x-ray exposure of high resolution x-ray masks.
Application of zone plates to alignment in microlithography
Authors: Feldman M. , White A. D. , White D. L.
Published: July 2002

Zone plates are patterned areas with imaging properties. When printed on masks and wafers and suitably illuminated, they form high contrast images which are useful for alignment in microlithography. As with holograms, defects in the pattern arising from variations in processing and linewidth control and poor edge definition degrade the image only marginally. This paper describes the use of zone plate alignment systems for die alignment in step and repeat cameras and for x-ray proximity printing. We find extended targets incoherently illuminated are suitable for manual alignment but better signal-to-noise ratios (important in automatic alignment) are obtained by using the zone plates to focus laser beams to nearly diffraction limited point sources. With zone plates approximately 100 μ in diameter and 300 μ focal length, we have obtained signal-to-noise ratios greater than 100 to 1 and alignment accuracy better than ±0.1 μ.
The effect of extra doses at the pattern edges on negative electron resist profiles
Authors: Nakata H. , Kato T. , Murata K. , Hirai Y. , Nagami K.
Published: July 2002

Theoretical and experimental studies have been performed to improve a quality of negative electron resist patterning of an infinite array of 1, 2, and 3 μm lines and spaces. We examined the effect of extra doses at the line pattern edges on their cross sectional profiles. Experiments were carried out using a PGMA resist with an electron beam exposure system of EBMG-40 at 10 keV. The cross sections were observed with a scanning electron microscope. It was found that a horned shape at the edges produced by extra doses had a favorable effect on the profiles during O2 plasma treatment to remove scum. It kept the edges from rounding due to a faster etching rate. The results showed some improvement in both the linewidth and the edge slope. An analysis of experimental cross sections has also been performed based on the so-called contrast curve. From a comparison between theory and experiment we found that the patterns seemed to shrink by 30% to 50% in the lateral direction, depending on the linewidth. A theoretical approach is useful for investigations into the characteristics of negative electron resists.
The use of molecular beams to support microspheres during plasma coating
Authors: Crane J. K. , Smith R. D. , Johnson W. L. , Jordan C. W. , Letts S. A. , Korbel G. R. , Krenik R. M.
Published: July 2002

Spherical targets can be levitated on beams of Ar or other gas atoms. This is an especially useful technique for supporting microspheres during plasma coating and processing. Measurements of gas flow and pressure indicate that the levitation device operates in the regime of Knudsen’s flow. This device is currently being used in the development of future generation laser targets.
First-principles determination of the structure of the Al/GaAs(110) surface
Authors: Ihm J. , Joannopoulos J. D.
Published: July 2002

The structure of Al atoms deposited on the GaAs (110) surface has been studied using a first- principles pseudopotential energy minimization calculation. The lowest energy configurations are determined by minimizing the total energy of the system with respect to its structural degrees of freedom. The most stable configuration is such that Al atoms replace the second (or deeper) layer Ga atoms. At temperatures where this reaction cannot be activated, two important processes are found to exist. In the low coverage limit, atoms favor twofold sites connecting an As atom and a Ga atom (in the next zigzag chain) on the surface, forming strong chemical bonds with the substrate. At higher coverages, on the other hand, Al atoms tend to cluster and make new bonds among themselves. The chemisorption energy map over the surface has been obtained and the possible path of the migration of Al atoms for clustering is investigated.
Laser-enhanced gas–surface chemistry: Basic processes and applications
Authors: Chuang T. J.
Published: July 2002

Chemical reactions in homogeneous systems activated by laser radiation have been extensively investigated for many years. The applications of lasers to promote gas–surface interactions have just begun to be realized. The purpose of the paper is to examine the fundamental processes involved in laser-enhanced gas–surface chemistry with particular emphases on aspects directly related to chemical etching of solids. Specifically, three basic surface processes, i.e., adsorption, product formation, and desorption affected by the presence of the laser radiation field, are discussed. Current studies on laser-induced chemical etching including etch rates, spatial resolution, directionality, and selectivity are reviewed. Examples to illustrate the basic laser-stimulated processes and possible applications of the laser technique to material processing are also given.
A review of compositional changes of multicomponent materials (especially biomaterials) induced by ion sputtering
Authors: Kowalski Zbigniew W.
Published: July 2002

It is well known that the ion sputtering process may modify the surface chemical composition of multicomponent materials as a result of preferential sputtering. Ion bombardment leads generally to surface enrichment of the component having a lower sputtering yield. Although the sputtering yield studies are very important, they do not contribute to understanding the mechanism of the preferential sputtering. The main reason is that the sputtering yield is the phenomenological coefficient and it depends on many factors, particularly on ion energy, its angle of incidence, target atomic mass to ion mass ratio, and target surface binding energy. For multicomponent materials, the effects of component mass difference and binding energy seem to be of fundamental importance for understanding the nature of the preferential sputtering mechanism. Another interesting problem is the influence of ion mixing and diffusion on the compositional changes of multicomponent materials. The main purpose of the article is to discuss the mechanism of preferential sputtering of multicomponent materials and to present the role of such phenomena as recoil and cascade sputtering, recoil implantation, mixing, diffusion, and segregation. Another issue worthy of discussion is the practical aspect of preferential sputtering, i.e., the influence of ion sputtering on compositional changes of biological implant materials.
Net molecular flow conductance of series elements
Authors: Stubblefield V. E.
Published: July 2002

The problem of calculating the total molecular flow conductance of ductwork made up of series connections of elements of known conductance is discussed from the transmission probability point of view. Cases in which there is a discontinuity in cross section between adjacent elements are included. Two criteria for evaluating methods for this calculation are discussed and applied to two such methods. One method, which includes a short procedure for treating discontinuities in duct cross section, is shown to satisfy both evaluation criteria.
Growth and electrical properties of high mobility epitaxial films of Pb0.8Sn0.2Te deposited by vacuum evaporation
Authors: Dawar A. L. , Sadana T. D. , Kumar Pratap , Paradkar S. K. , Mathur P. C.
Published: July 2002

It is reported that as-grown vacuum evaporated thin films of Pb0.8Sn0.2Te were p-type with low mobility. Annealing of these films in vacuum and under tin pressure resulted in a significant increase in mobility. The mobility of the films annealed in tin for 60 min was about 3.6 ×103 cm2/V s.
Microspot elementary and chemical analyses using combined high energy resolution Auger electron spectroscopy and x-ray photoelectron spectroscopy
Authors: Staib P. , Contour J. P. , Massies J.
Published: July 2002

Chemical information contained in Auger lines, measured on a spot area of less than 10 μm, is compared to x-ray photoelectron spectroscopy (XPS) data obtained on a larger scale. Measurements for Auger electron spectroscopy (AES) and XPS are performed under exactly the same experimental conditions using a new high sensitivity and high resolution energy analyzer, so that the Auger lines excited by electrons and photons are directly comparable. An application is the analysis of the chemical composition of the molecular beam epitaxy (MBE) grown GaAs layer on a microscopic scale. Chemical heterogeneities associated with the presence of growth defects are revealed.
Measurement and calibration techniques used in computer partial pressure analysis
Authors: Mitchell Dean J.
Published: July 2002

The uses of residual gas analyzers (RGA’s) in computer controlled analytical studies and process monitoring applications are discussed in this paper. The relative merits are compared for the two most commonly used RGA’s, which are the magnetic sector and the quadrupole mass analyzer. Methods of installing RGA’s in vacuum systems and computer interfacing techniques are described. Measurement and calibration methods are outlined for applications where it is desirable to characterize either partial pressures or gas evolution rates. Interpretation of RGA spectra and limitations imposed by analytical errors are also discussed.
The development of large cryopumps from space chambers to the fusion program
Authors: Hood Charles B.
Published: July 2002

The need to simulate the conditions of outer space, beginning in 1960, created a requirement for large cryopumps to maintain near-space conditions in large chambers. A variety of cryogenic support systems including both pressurized and boiling liquid nitrogen systems, and helium refrigerators, normally operating near 20 K were required. The fusion program provided a similar, but more stringent, requirement. Here, hydrogen isotopes had to be removed from fusion chambers and neutral beam systems. This resulted in a new group of cryopump arrays having very high speeds. In this case liquid helium systems are required, either boiling with natural convection, or force fed from a refrigerator. More sophisticated Monte Carlo calculation methods were developed, which enabled the prediction of gross pumping speed, and localized pressures, taking into account the temperatures of surrounding surfaces and gas feed location.
Surface composition of SiC after ion bombardment, annealing, and exposure to oxygen
Authors: Jo/rgensen B. , Morgen P.
Published: July 2002

The surface composition and structure of SiC (hexagonal crystallites) are studied under Ar-ion bombardment, high-temperature cycling and adsorption of oxygen. Such treatments are necessary for surface cleaning and they also simulate environments in potential applications of SiC elements. Oxygen adsorption on surfaces which result after various cycles of Ar-ion bombardment and heating, i.e., with varying surface compositions, is studied to reveal details of the initial steps of oxidation. The experimental techniques were AES, XPS, and BAES (bremsstrahlung-induced AES). Bombardment with 3-keV Ar ions results in a nearly stoichiometric (1:1) surface. The implanted Ar accumulates strongly in the subsurface region during annealing at 900 °C. Annealing at higher temperatures (1200 °C) releases the Ar but also leads to decomposition of the surface, with the loss of Si. Oxygen adsorbs on the surface, in a reaction which mainly involves silicon atoms, and with an oxygen coverage related to the initial silicon surface concentration. At room temperature, the adsorption reaction contains two stages as for oxygen on clean silicon surfaces.
A comparison of three-dimensional and two-dimensional simulations of contact step coverage
Authors: Harper Kim W. , Jones Robert E.
Published: July 2002

A model is presented for calculating the film profiles of sputtered metal into axially symmetric contacts. The model assumes an isotropic source of metal vapor and considers the dynamic shadowing of deposition flux into the contact. Simulations from this model predict substantially worse step coverage than simulations from a two-dimensional model but experimentally produced profiles have step coverages in between the two models.
Adsorption of CO on Fe, Cu, and Cu–Fe surface alloys
Authors: Gijzeman O. L. J. , Vink T. J. , van Pruissen O. P. , Geus J. W.
Published: July 2002

The adsorption and decomposition of CO on Fe (100), Fe (110), Cu(111)–Fe, and Cu(110)–Fe surface alloys with different amounts of iron in the surface layers has been studied with ellipsometry. Only on Fe (100) at room temperature is CO found to dissociate rapidly. On all surfaces dissociation takes place, at higher temperatures, leaving equal amounts of C and O on the surface. On this adlayer reversible adsorption of CO takes place. The heats of adsorption have been determined from the observed isotherms. Heats of adsorption have also been determined for adlayers of only oxygen or carbon on the iron crystal faces.
Physical understanding of gas desorption mechanisms
Authors: Horikoshi G.
Published: July 2002

A new set of equations is introduced for the analysis of the evacuation process. The equations are based on the surface processes of adsorption and desorption of gas molecules taking place on the inhomogeneous metal surface but not on the diffusion process. Because the equations are nonlinear, it is difficult to get the analytic solution, and numerical calculations, as well as analytic considerations were made. The results tell us that (i) the outgassing phenomena can only be understood under nonequilibrium conditions, (ii) the evacuation time dependence of the outgassing rate depends on the distribution function of the adsorbing site, i.e., the adsorption site density as a function of the activation energy of desorption E, and (iii) a pressure buildup phenomenon, which is accompanied by a sudden stop of evacuation, can be easily understood. Finally, a new measurement method is proposed for the investigation of surface properties. In this method, a chamber made of a test material is evacuated for a long time and then a measurement follows. In the measurement, one adjusts the pumping speed so as to keep the vacuum pressure in the chamber constant. The amount of outgas is determined as a function of time by knowing the pumping speed. By this method, one can get quite new information concerning the surface properties.
Influence of ion beam parameters on the electrical and optical properties of ion-assisted reactively evaporated vanadium dioxide thin films
Authors: Case F. C.
Published: July 2002

Large reductions in the phase transition temperature of vanadium dioxide thin films have been achieved in the past by doping with elements such as tungsten or niobium; however, considerable degradation of electrical and optical properties are routinely observed. In this investigation, a technique is described which significantly reduces the transition temperature to doped values, without sacrificing film quality. Vanadium oxide films were deposited at room temperature by ion-assisted reactive evaporation and subsequently annealed in flowing oxygen. Deposition parameters include a range of argon-to-oxygen ion ratios, ion energies and fluxes, and background oxygen pressures. The impact of these parameters on microstructural, electrical, and optical properties, as well as on transition temperature, will be discussed.
Characterization and thermal desorption spectroscopy study on a new, low outgassing material surface for improved ultrahigh vacuum uses
Authors: Fujita D. , Homma T.
Published: July 2002

The surface of an austenitic stainless steel doped with N, B, and Ce (SUS304-NBCe), which was covered with thin BN precipitated layers, has been characterized using Auger electron spectroscopy (AES), Fourier transform infrared, transmission electron microscopy, transmission electron diffraction (TED), and reflection high-energy electron diffraction (RHEED) techniques. Thermal desorption spectroscopy method was also applied for evaluating its outgassing nature. AES spectra obtained from the BN precipitated layers coincided well with those of a hexagonal BN even in fine structures of B(KLL) and N(KLL) Auger transitions. RHEED and TED patterns obtained from them showed that the structure of the BN layer was hexagonal and that the c axis preferred to be parallel to the surface normal. That is to say, the basal plane of the hexagonal BN, which is more inert to adsorption than other planes are, preferred to cover the surface. The outgassing nature of the above surface has been measured and compared with two other types of stainless-steel surfaces such as an electropolished surface and a S segregated one. Among the three, the amount of desorbed gases from the BN covered surface was the lowest on heating up to 800 °C. The potential of the BN precipitated surface for UHV vessels with low outgassing is pointed out.
Comparison of chemical cleaning methods of aluminum alloy vacuum chambers for electron storage rings
Authors: Mathewson A. G. , Bacher J.-P. , Booth K. , Calder R. S. , Dominichini G. , Grillot A. , Hilleret N. , Latorre D. , Le Normand F. , Unterlerchner W.
Published: July 2002

Three chemical precleaning methods suitable for aluminum alloy vacuum chambers for electron storage rings have been compared. The methods ranged from vapor degreasing with no chemical attack to light alkaline etching and strong alkaline etching in NaOH. The techniques used to evaluate and compare the three treatments included Auger analysis, thermal outgassing, electron and x-ray induced neutral gas desorption, argon glow discharge cleaning, and scanning electron microscope examination of the surface. In general, the NaOH treatment was best followed closely by the light alkaline etch and then the vapor degreasing. A variant of the light alkaline etch method was used to clean the 2000 Al vacuum chambers of the CERN large electron positron storage ring project. Two chambers cleaned by this method were exposed to synchrotron radiation in a dedicated beam line of a synchrotron radiation source. Compared to a reference chamber cleaned by NaOH these two chambers were initially worse, but after 1 A h of machine operation the difference practically vanished.
Decomposition of trimethylaluminum and N2O on Si surfaces using ultraviolet laser photolysis to produce Al2O3 films
Authors: Ishida Makoto , Eto Akira , Nakamura Tetsuro , Suzaki Tetsuo
Published: July 2002

In order to investigate the initial deposition process of Al2 O3 layers on Si surfaces, trimethylaluminum (TMA), and N2 O were introduced on clean Si(111) wafers, and the surface reaction was analyzed by x-ray photoelectron spectroscopy. The irradiation effects of an ArF excimer laser on the gases and substrates were also studied. TMA was adsorbed on clean Si(111) surfaces at room temperature, and then Si–C bonds were easily formed at an annealing temperature of 600 °C. On the other hand, if a few oxide layers were formed on clean Si surfaces, TMA bound with O atoms and Si–C layers did not appear after annealing. Although carbon impurities still remained in the deposited layers, the carbon concentration was reduced by preoxidation of the Si surface and photolysis of TMA with laser irradiation. Moreover, it was found that Al2 O3 layers without carbon atoms could be prepared using an N2 O photolysis reaction process after decomposition of TMA on preoxidized Si surfaces.
Fermi-level movement at metal/HgCdTe contacts formed at low temperature
Authors: Carey G. P. , Wahi A. K. , Friedman D. J. , McCants C. E. , Spicer W. E.
Published: July 2002

In an effort to reduce the disruption to the HgCdTe surface upon metal overlayer formation over that observed at room temperature, interfaces formed at 100 K between HgCdTe and the three overlayer metals, Ag, Al, and Pd, are investigated. The metals were deposited onto the [110] cleaved HgCdTe surfaces in UHV in increments ranging from submonolayer at low coverages to tens of monolayers at high coverages, and the formation of the interfaces were monitored using photoemission spectroscopy subsequent to each deposition. The primary experimental observation of this study is that deposition of all three of these metals onto HgCdTe substrates held at reduced temperatures causes the surface Fermi level (Ef) to move from its initial cleaved position, typically located at or near the conduction-band minimum, into the conduction band, and this movement is correlated with the absence of the movement of the overlayer metal into the semiconductor. This phenomenon is observed at the lowest coverages (submonolayer) for all three overlayer metals, and for the case of Ag grown at 100 K, is observed for higher coverages as well. The final positions of Ef for the three overlayer growths match very closely to those seen for the corresponding room-temperature growths.
Improved automated lens design for liquid metal ion sources
Authors: Szép J. , Szilagyi M.
Published: July 2002

Our method for optimum design of electrostatic lenses with high target current densities has been improved. The constraints are periodically tightened and loosened during the optimization procedure resulting in a more effective optimization. The inputs of the computerized method are the given source parameters, the first-order properties of the lens, and some other constraints like a potential limit on the electrodes and a maximum allowed electric field. The output is the potential distribution on the electrodes of a given multielectrode lens or the spline coefficients of a spline lens model. Some computational results are presented for a Ga liquid metal ion source. Keeping the given source parameters and working distances constant, essential improvements of the optical properties of some well-known designs could be achieved by replacing the lenses with those designed by our procedures. A sensitivity analysis is given in conclusion.
Nanomechanics of a Au–Ir contact using a bidirectional atomic force microscope
Authors: Cohen Sidney R. , Neubauer Gabi , McClelland Gary M.
Published: July 2002

Friction and indentation have been studied for a sharp Ir tip contacting a Au(111) surface at loads of ≂10−7 N. The studies were performed using a new atomic force microscope (AFM), in which lever deflection is sensed in the directions normal and lateral to the surface simultaneously through capacitance measurement. The contact behavior varied from spot to spot on the sample. The friction was higher during unloading than during loading, for identical values of the normal load. For the lower range of loading force used, behavior is elastic. The role of nanometer-scale roughness and low level impurities are considered.
Oxidation and diffusion in the formation of sequential-diffusion brass coatings on steel
Authors: Hammer G. E. , Starinshak T. W. , Shemenski R. M.
Published: July 2002

Sequential-diffusion brass alloy coating of steel has been investigated by using Auger electron spectroscopy (AES). In this process the coating is formed by plating pure copper and zinc films on the substrate followed by thermal diffusion of these deposits into a homogeneous alloy. AES with depth profiling has been used to investigate oxidation of the coating between 475 and 625 °C, and migration at the copper–zinc interface. Oxidation below 570 °C appeared to be controlled by bulk diffusion in zinc oxide; above this temperature a reduced activation energy was attributed to the formation of a mixed copper–zinc oxide and a coating phase transformation. Interdiffusion at the copper–zinc interface immediately after plating has been observed and attributed to electromigration during the zinc deposition. Diffusion was found to proceed via the coalescence of crystalline phases of the alloy.
Oxygen concentration on surfaces of carbon fibers
Authors: Lin Sin-Shong
Published: July 2002

The performance of carbon fiber reinforced composites depends significantly on the interface between the fiber surfaces and the resin matrix. Good adhesion is a precondition for the intended transfer of stresses in the fiber polymer composites. For carbon fibers, the oxidized surface treatment is a widely accepted method to achieve good adhesion. In the present study, five pitch/polyacrylonitrile based carbon fibers were surface treated with various chemical agents, such as nitric acid, peroxide, oxygen, and acid/hydrogen. The oxidized surfaces were characterized by scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and Auger spectroscopy for surface morphology, carbon–oxygen functional groups and oxygen distributions. In particular, scanning Auger microanalysis was extensively employed for the detailed determinations of oxygen distributions on the fiber surfaces. These results indicate that the formation of oxides on the fiber surfaces varies widely from region to region, segment to segment, and strand to strand. The available amounts of surface oxides are dependent on the fiber structure as well as the precursors.
Automated peak identification applied to Auger electron spectroscopy
Authors: Bumgarner S. , Hofmeister S. , Griffis D. , Russell P.
Published: July 2002

The peaks in an Auger spectrum have traditionally been identified by reference to handbooks of standard spectra. This traditional identification process has been simplified by a computerized routine for the automatic identification of Auger spectral peaks. Algorithms have been developed for automatic peak selection from derivative Auger spectra and for automatic peak identification. These algorithms were implemented in Microsoft QuickBasic on an 8 MHz IBM PC AT equipped with a math coprocessor and a 20 megabyte (MB) hard disk. When applied to test spectra, the peak selection algorithm consistently located Auger peaks with minimal inclusion of peaks due to shot noise. The peak identification algorithm identified elements correctly in nearly every case. Rather than a single correct element identification attached to a peak, multiple possible identifications were commonly listed for each peak. The combined peak selection/peak identification procedure was found to require no more than ten seconds to execute.
Angular distribution of ions from a AuSi liquid metal ion source
Authors: Rao S. , Bell A. E. , Schwind G. A. , Swanson L. W.
Published: July 2002

The emission characteristics from a AuSi liquid metal ion source show marked changes as a function of angle from its on-axis behavior. The Au+ and Au++ species tend to fall off monotonically as a function of angle, while the different Si species and the AuSi clusters show a tendency to first increase in intensity and then fall off as emission angle is increased. Si++ has a broad shoulder at the low energy end of the on-axis peak, which then merges into a single, well-defined peak with increasing intensity as the angle is increased. While this behavior is mirrored in the AuSi+, Au3Si++, and other cluster species, Si++ and Si+2 just show a monotonic increase and then decrease with increasing angle. The similarity in behavior of the Si species and the AuSi clusters leads to the conclusion that these ions are being formed by the same mechanism, which is different from that contributing to the formation of the Au+ and Au++ ions.
The interaction of a fluorinated ether with a metal surface: Effects of surface morphology and water coadsorption
Authors: Leavitt P. K. , Thiel P. A.
Published: July 2002

We have investigated the interaction of perfluorodiethyl ether with Ru(100) using thermal desorption spectroscopy. The ether desorbs from the clean surface in three states: a multilayer at 120 K, and two additional states at 135 and 150 K. The latter states merge and move upward to 170 K as coverage increases. The corresponding low-coverage desorption energies are 37 and 39 kJ/mol, comparable to a value previously observed in perfluorodiethyl ether desorption from Ru(001). There is no detectable decomposition. We have also investigated the effect of water coadsorption. We find that water shifts both high-temperature states of the ether downward, to 125 and 130 K, respectively. Again, there is no detectable decomposition. The weakening of the ether–surface bond in the presence of water is discussed in terms of Lewis acid–base theory. Overall, we find that surface morphology does not strongly affect the ether–surface bond strength, but water coadsorption does.
Surface studies of Os/Re/W alloy-coated impregnated tungsten cathodes
Authors: Ares Fang C. S. , Maloney C. E.
Published: July 2002

Impregnated tungsten cathodes half-coated with Re/W (or Os/W) alloy and Os/Re/W alloy at right angles were studied to compare the effects of Os/Re/W alloy coatings on the electron emission and emission mechanisms. Constant surface metal compositions of 32% Os–29% Re–39% W and 35% Os–26% Re–39% W were obtained from the activated surfaces initially coated with 40% Os–40% Re–20% W and 35% Os–45% Re–20% W alloys, respectively. Thermionic emission microscopy measurements showed that the Os/Re/W alloy-coated surface gives an average effective work function of 0.29, 0.08, and 0.03 eV lower than the uncoated, Re/W and Os/W alloy-coated surfaces. An effective work function of 1.73 eV was obtained from an activated Os/Re/W alloy surface. Auger studies exhibited a smaller BaO coverage and a higher barium coverage in excess of BaO stoichiometry on the Os/Re/W alloy-coated surface compared to the uncoated, Re/W and Os/W alloy-coated surfaces.
Formation of silicon-based heterostructures in multichamber integrated-processing thin-film deposition systems
Authors: Lucovsky G. , Kim S. S. , Tsu D. V. , Parsons G. N. , Fitch J. T.
Published: July 2002

This paper describes the formation of heterostructure devices using multichamber integrated-processing thin-film deposition systems: clustered processing-tools with UHV-compatible inter-chamber transfer. The application of remote plasma-enhanced chemical-vapor deposition (remote PECVD) for the formation of semiconducting and dielectric thin films in several device structures is discussed. Special attention is directed to (i) the deposition conditions required for control of layer and interface chemistry, and (ii) post-deposition-annealing (PDA) for the modification of physical and electronic properties of the individual layers and their interfaces. Due to limitations on in situ patterning, each of the device structures is completed after removal from the cluster. A criterion is proposed for the evaluation of multichamber processing systems that is based on the ability to form multilayer structures with two or more electronically significant interfaces without the removal of the heterostructure from the cluster processing ambient.
X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy studies of the effects of Ni layer on AuGe/GaAs(100) interface
Authors: Fang C. S. Ares , Chang Y. L. , Tse W. S.
Published: July 2002

AuGe Ohmic contacts to Si-doped(100) oriented n-type GaAs with ultrathin Ni interlayer or overlayer of 1 nm were studied by x-ray photoelectron spectroscopy (XPS) and ultraviolet (UV) (He i) photoelectron spectroscopy (UPS). Alloying behaviors at the interfaces was then revealed by Ar+ etching. The interdiffusion between the deposited Ni and AuGe films and GaAs substrate are evident. This study supports the conclusion that the addition of Ni film promotes the interaction between AuGe and GaAs during the alloying process. Results indicate that the more uniform distribution of Ni concentration throughout the interface for AuGe/Ni/GaAs system than Ni/AuGe/GaAs system. It has been concluded that AuGe/Ni/GaAs system exhibits a more uniform distribution of AuGa cluster size throughout the interface than Ni/AuGe/GaAs system.
A unified integrated model for sputter coating uniformity
Authors: Upadhye R. S. , Hsieh E. J.
Published: July 2002

The net sputter coating flux at the surface being coated can be conceptually divided into two constituent fluxes: the directed flux, and the diffusional flux. The former is due to the high initial velocities of the sputtered target atoms, which tend to move in their original direction even after several collisions with the background gas atoms. The latter exists because of the eventual slowing down of the target atoms to the velocities of equilibrium distribution. At a given sputtering pressure, the directed flux dominates in the vicinity of the target, whereas the diffusional flux dominates away from the target. Coating uniformity on nonplanar substrates depends on the relative contributions from these two fluxes. These two contributions have been extensively modeled in the literature. However, to use the models for any specific situation, one needs to make an a priori assumption about the dominant contribution. In many situations, both these mechanisms are equally significant. It is then difficult to decide which model to apply. We have developed a simplified model that takes into account the gradual transition between the two mechanisms, and thus covers the entire range of relative flux distributions. A decay parameter calculated from experimental data is used to determine the relative contributions from the fluxes. Therefore, with this model, one need not resort to arbitrary assumptions about the controlling contributions, and thus the coating uniformity. We will present the development of the model, computation of the decay parameter, and experimental data that support the model.
Chemical imaging using ion microscopy and digital image processing
Authors: Mantus David S. , Morrison George H.
Published: July 2002

The ability to quantitatively map the distribution of elements on the micrometer scale and smaller with high sensitivity and isotopic discrimination is unique to ion microscopy. This capability is a powerful tool for investigation of the solid state, where properties correlate not only with chemical composition but also with the degree of chemical heterogeneity. The use of digital image processing allows for the quantitative study of ion images, as well as the extraction of quantitative information from the image data. The use of image processing techniques to acquire, amend, and analyze ion images is discussed. Methods for the identification and correction of contrast artifacts, and the application of ion microscopy to problems in biology and medicine are presented.
The effects of chlorine content on the properties of titanium carbonitride thin film deposited by plasma assisted chemical vapor deposition
Authors: Kim Si Bum , Choi Si Kyung , Chun Soung Soon , Kim Kwang Ho
Published: July 2002

Wear resistant titanium carbonitride (TiCxNy) films were deposited onto high speed steel (AISI M2) by plasma assisted chemical vapor deposition using the gaseous mixture of TiCl4, CH4, N2, H2, and Ar. The effects of deposition conditions on the deposition rate and residual chlorine content were investigated. The influences of the chlorine on the crystallinity, microstructure, and mechanical properties of coatings were also studied. It was found that the residual chlorine content in the films greatly varied with the deposition conditions. Subsequently the crystallinity of the TiCxNy films deteriorated with the increase in the chlorine content. The microhardness and adhesion strength also decreased with the chlorine content. However, in spite of the low residual chlorine content, TiCxNy film deposited at high radio-frequency power shows inferior mechanical properties due to the micropore network structure.
Statistical approach to parameter study of stress in multilayer films of phosphosilicate glass and silicon nitride
Authors: Dharmadhikari Vineet S.
Published: July 2002

Mechanical stress in chemical vapor deposited phosphosilicate (APCVD-PSG), plasma deposited PSG (P-PSG), plasma deposited SiN (P-SiN) and a combination of APCVD-PSG and P-SiN films has been characterized through the use of screening and modeling experimental designs. Total stress in these films was determined by measuring the changes in the radius of curvature of silicon substrate. As deposited APCVD-PSG exhibits tensile stress at room temperature. This stress decreases with increase in phosphorus content. The total stress in P-PSG films was compressive. Of the seven process factors studied in the screening experiment, only three factors (phosphorus content, silane and argon flow rates) had statistical significant effect on stress. Over the process domain covered, no factor–factor interactions were observed. P-SiN films showed high compressive stress levels. Modeling study resulted in a parametric model relating room temperature stress to deposition temperature and ammonia flow rate. For dual films, APCVD-PSG and P-SiN, the total stress was a function of nitride film thickness and phosphorus content in PSG. Parametric models were developed for stress after deposition, sinter and aging. In all cases studied, the total stress changed from tensile to compressive with additional processing. The general trend tends to support the direction observed in previous single factor studies for single dielectric films. The current experiments extend these studies for single films and their combinations, by quantifying the various process factor interactions.
Characterization of the interfacial failure of metal thin films on oxidized silicon using fracto-emission
Authors: Xiong-Skiba P. , Doering D. L. , Siek K. H.
Published: July 2002

The fracto-emission behavior during the adhesive failure of metal thin films from oxidized silicon surfaces has been compared for gold, silver and copper films. In general, the electron emission during failure can be characterized by a sharp emission peak followed by an extended emission tail. The prompt emission intensity is thought to be related to microdischarges across the gap formed during failure, suggesting a relationship to the relative work functions of the metal and the Si substrate. This metal–oxide–semiconductor system produces a naturally charged capacitor whose charge is partially determined by the relative work functions of the metals and the Si substrate. We present results which compare the electron emission from the failure of Au, Ag, and Cu thin films on the Si surface and find a correlation with the relative work functions opposite to the expected behavior.
Practical advantages of a cascade diffusion pump system of a scanning electron microscope
Authors: Norioka Setsuo , Yoshimura Nagamitsu
Published: July 2002

A cascade diffusion pump (DP) system shows a superior performance in dynamic evacuation when switching from roughing to fine pumping, as well as in clean static evacuation. This is particularly true when the DPs have a relatively low tolerable forepressure. Moreover, a cascade DP system shows stable performance during variations of the DP heater voltage. A scanning electron microscope (SEM) with a large specimen chamber was evacuated by a cascade DP system with a buffer tank. With a cascade DP system, the requirements for the vacuum system of a SEM, such as rapid pumping down and a clean vacuum, were almost completely satisfied. This report presents experimental data on the cascade DP system of a SEM, which shows practical advantages over the single DP system.