bluuebunny/crossref_metadata_2025 huggingface dataset:
Photoemission extended x-ray absorption fine structure of oxidized Al films
Authors: Kim S. T. , Choudhary K. M. , Shah S. N. , Lee J. H. , Rothberg G. M. , denBoer M. L. , Williams G. P.
Published: July 2002

A significant advantage of photoelectron extended x-ray absorption fine structure (PEXAFS) is that it has chemical sensitivity afforded by measuring chemically shifted photopeaks as functions of photon energy. The structures responsible for the different peaks may be studied. In addition other features of the photoelectron spectrum may be used. We have studied evaporated, polycrystalline aluminum films exposed to oxygen and obtained PEXAFS data using the unshifted Al 2p photopeak, the chemically shifted (2.4-eV) photopeak, and the bulk and surface plasmon loss peaks. At low oxygen exposures and also using the unshifted peak at 1000-L exposure the Al–O and Al–Al separations are, respectively, 1.76(4) and 3.00(5) Å. The shifted peak yields distances larger by 0.04(1) and 0.06(3) Å. Nearest-neighbor oxygen is found about the unshifted aluminum atoms, which suggests a reinterpretation of earlier surface EXAFS using O 1s photoabsorption. We propose this dissolved oxygen is in or near threefold sites in (111) planes.
Formations of TiN and TiC in titanium coated stainless steel by heat treatment
Authors: Machida O. , Hashiba M. , Hino T. , Yamashina T.
Published: July 2002

Titanium coated stainless steel prepared by magnetron sputtering was heated from 600 to 1000 °C in a vacuum with pressure less than 10−6 Pa in order to modify the surface structure. The change of the surface state was analyzed by Auger electron spectroscopy and x-ray photoelectron spectroscopy (XPS). From the depth profile, it was observed that carbon and nitrogen atoms from the stainless steel considerably diffused into the film. The XPS analysis showed the formations of TiC and TiN in the film region at the heating temperature of 800 and 1000 °C, respectively. In particular, TiN was formed in the thick surface region. For stainless steels with various contents of carbon and nitrogen, the dependence of the contents on the formation of TiC and TiN was examined. The microhardnesses of the samples were measured by a Knoop hardness tester. The dominant formation of TiN was observed in the sample with high nitrogen content. The hardness of the sample with lower nitrogen (0.029%) and higher carbon (0.078%) contents was highest (2900±500 kG/mm2), approximately five times greater than that of the uncoated stainless-steel sample. Thermal desorption processes of gases in the titanium coated stainless steels with the modified surface was also investigated, and the result showed that desorptions of H2, CH4, and N2 were very suppressed by the surface modification.
Ultrahigh speed high electron mobility transistor large scale integration technology
Authors: Abe Masayuki , Mimura Takashi , Notomi Seishi , Odani Koichiro , Kondo Kazuo , Kobayashi Masaaki
Published: July 2002

Current status and recent advances in high electron mobility transistor (HEMT) technology for high performance very large scale integration (VLSI) are presented with the focus on material, self-alignment device fabrication, and HEMT large-scale integration (LSI) implementations. HEMT is a very promising device for ultrahigh speed LSI/VLSI due to the supermobility GaAs/AlGaAs heterojunction structure. The technological challenges for large scale integrations are discussed with refined HEMT with self-aligned gate structure, controllability of device parameters, and molecular beam epitaxy material problems. Master–slave flip–flop, divide-by-two circuits achieved the internal logic delay of 22 ps per gate at 77 K at a fan-out of about 2, roughly three times faster than that of GaAs metal-semiconductor field-effect transistor technology. HEMT has already made it possible to develop 16 kb static random access memory (RAM) and a 1.5-kgate gate array, demonstrating high speed LSI operations. With submicron gates, as well as advanced material technologies, a HEMT 64 kb static RAM with subnanosecond access operation and 10 kgate logic LSI with sub-100-ps logic delays, will be achieved.
Surface analysis and electrochemical studies of sulfur enhanced corrosion of nickel
Authors: Baer D. R. , Danielson M. J.
Published: July 2002

A combined surface analysis and electrochemical study of sulfur implanted nickel has examined the lifetime and mobility of sulfur on the surface and in an acid solution. X-ray photoelectron spectroscopy and Auger electron spectroscopy have been used to examine the chemistry, location, and amount of sulfur on the surface and in films formed on the implanted nickel in a 0.5N nitric acid solution at various electrochemical potentials. Specimens were prepared in a low-oxygen partial pressure glove box and transferred to the spectrometer in an anaerobic transfer vessel. Although most sulfur is removed from the implanted nickel during rapid dissolution, a submonolayer of sulfur remains on the surface in ‘‘sulfide’’ form in the active region of potential. Upon exposure to higher oxidizing potentials, some of the sulfur is oxidized and both sulfate and sulfide are found in the film. Recycling the film back to the active region removed some of the oxidized sulfur, but much of the sulfur remains on the surface. Sulfur transfers through the solution to nearby materials, where it appears on the surface in both sulfide and sulfate states. Current studies suggest only a very slow oxidation of sulfur on the surface or in solution.
Crack initiation and crack growth in polymers induced by electron bombardment
Authors: Dickinson J. T. , Tonyali K. , Klakken M. L. , Jensen L. C.
Published: July 2002

The response to electron bombardment of highly stressed Kapton-HTM, TeflonTM (polytetrafluoroethylene), and linear high-density polyethylene is investigated. Evidence is presented for electron induced crack initiation and crack growth. Calculations show that the electron exposures used in these experiments are sufficiently small that thermal heating of the zone near the crack tip does not dominate. Video recording of the shape of the crack before and during bombardment is presented as well as scanning electron microscopy analysis of the bombarded regions of the specimens. Instabilities in the form of microcracks appear to be the dominant consequence of electron bombardment of stressed materials. The role of highly localized electronic excitations of stressed molecular bonds is also discussed.
Characterization of copper heterocyclic compounds: X-ray photoelectron spectroscopy study
Authors: Katnani A. D. , Drolet D. P. , Lees A. J.
Published: July 2002

Several Cu–azole complexes were synthesized by mixing solutions of cupric chloride and an azole ligand at the appropriate metal-to-ligand ratio. The products were isolated as powders and analyzed by elemental analysis, diffuse reflectance Fourier transform infrared spectroscopy, and x-ray photoelectron spectroscopy. Both the bulk and the surface elemental atomic ratios were identical suggesting no surface reconstruction. This paper primarily addresses the radiation effect on the surface composition of the exposed powder. All powders exhibited Cu(2p) line shape typical of paramagnetic copper; no elemental or diamagnetic copper atoms were observed over a very short period of exposure to x radiation. The position and intensity of the Cu(2p) shakeup satellite revealed differences among the complexes that can be attributed to the nature of the azole ligand and to the coordination geometry. Upon exposure to x radiation or electron beam no change was observed in the relative atomic ratios; however, a new peak evolved on the low-binding-energy side of the Cu(2p) suggesting the formation of diamagnetic copper. The evolution of the Cu+1/Cu+2 ratio and the relative intensity of the shakeup satellite suggested that radiation affects the coordination geometry and electronic structure of the surface layers of these complexes.
Extension of thermocouple gauge sensitivity to atmospheric pressure
Authors: Zettler J. , Sud R.
Published: July 2002

The amount of heat lost from a heated thermocouple (TC) junction through gaseous conduction varies widely with pressure over the range from 1 mTorr to atmosphere and this has largely confined accurate measurement by this technique to the range of about 1 mTorr to 2 Torr. A new design, which matches the junction temperature to a reference temperature, creates a basic constant temperature gauge controller and is largely responsible for fast response to pressure changes. A second control function which adjusts the reference temperature in a nonlinear manner depending on the pressure, modifies the controller response to the TC gauge’s intrinsic pressure sensitivity in such a way as to enhance response in the 1–15 mTorr and 2–200 T ranges, while attenuating its high sensitivity in the 15 mTorr to 2 Torr and 200 Torr to atmosphere regime. This technique gives rise to an output signal which better approximates the log of pressure over six decades. By time multiplexing the junction heating with measurements of its thermal emf, contamination of the thermal signal by the heating current is eliminated, while requiring only two connections to the remote gauge tube. The inclusion of a baffle in the gauge tube reduces inaccuracies in the response during fast pressure changes.
Helium cryopumping for fusion applications
Authors: Sedgley D. W. , Batzer T. H. , Call W. R.
Published: July 2002

Large quantities of helium and hydrogen isotopes will be exhausted continuously from fusion power reactors. This paper summarizes two development programs undertaken to address vacuum pumping for this application: (i) A continuous duty cryopump for pumping helium and/or hydrogen species using charcoal sorbent and (ii) a cryopump configuration with an alternative shielding arrangement using charcoal sorbent or argon spray. A test program evaluated automatic pumping of helium, helium pumping by charcoal cryosorption and with argon spray, and cryosorption of helium/hydrogen mixtures. The continuous duty cryopump pumped helium continuously and conveniently. Helium pumping speed was 7.7 l/s/cm2 of charcoal, compared to 5.8 l/s/cm2 for the alternative pump. Helium speed using argon spray was 18% of that obtained by charcoal cryosorption in the same (W-panel) pump. During continuous duty cryopump mixture tests with helium and hydrogen copumped on charcoal, gas was released sporadically. Testing was insufficient to explain this unacceptable event.
Design aspects of a differential vacuum pumping system
Authors: Bridgman C. , Meyer E. A.
Published: July 2002

A differential vacuum pumping system was designed as part of an experiment to study the neutralizing characteristics of different gases in the presence of a high-energy H− ion beam. The pumping system consisted of three vacuum chambers (stages) attached to each end of a 2-l neutralizer with each stage separated by a thin orifice plate. The test gases (nitrogen, argon, and xenon) were pressure fed into the neutralizer at a variety of flow rates to allow the experimenters to investigate neutralization at different gas densities. Working with fixed orifice sizes, dictated by the beam dimensions, the neutralizer exit orifices were extended in length to meet the density requirements in the neutralizer without exceeding the refrigeration capacity of the first-stage cryopumps. Because more than 90% of the gas expanding out of each end of the neutralizer into the first stages was pumped by the cryopumps, the gas loads into the second and third stages could be managed by lower pumping speed turbomolecular pumps. The double-ended differential pumping system met the requirements of neutralizer pressures as high as 1.1 Torr while, at the same time, maintaining <1×10−6 Torr in the third stage. This paper will describe the vacuum system and compare calculated data with measured data.
Experimental Fermi surface for W(011)
Authors: Gaylord R. H. , Jeong K. , Dhar S. , Kevan S. D.
Published: July 2002

The Fermi surfaces for the surface-localized states on W(011) are experimentally determined using high-resolution angle-resolved photoemission. The significance of our results in terms of phonon anomalies, hydrogen-induced reconstruction, and work function changes is examined.
Thin-film topography control with transient liquid underlayer
Authors: Khandros Igor Y. , Baseman Robert J. , Farrell Curtis E. , Ting Chung-Y.
Published: July 2002

A novel and effective technique for fabricating metal surfaces with controlled topography is described. The metal of interest is deposited onto a thin (25–200 Å) underlayer of a liquid metal. Transient liquid reactions during film growth and coalescence lead to characteristic roughening of the deposits. Studies of 1-μm Al films deposited on thin Ga underlayers revealed a consistent increase of the size of Al features with the average thickness of the Ga underlayer. No apparent change in the films’ resistivity was detected. Limited studies of 1-μm Cu films with a Ga underlayer suggest the general applicability of this technique.
Properties of low-pressure chemical vapor deposited dielectric films from hexamethyldisilazane
Authors: Freeman Dean , Kern Werner
Published: July 2002

Hexamethyldisilazene (HMDS) is shown to be an effective single-source reactant of Si, C, and N for electronic thin films deposited using low-pressure chemical vapor deposition (LPCVD). Pyrolytic deposition, at 800 °C, in the absence of oxidants yielded silicon carbide–nitride films which are insoluble in buffered HF. These films have a refractive index of 2.3 to 2.5 and an infrared absorption maximum at 804 cm−1. Controlled addition of oxygen to HMDS yielded silicon carbide–oxynitride films which are etchable with buffered HF. These films have a refractive index of 1.45 to 2.0 and are an effective diffusion barrier for phosphorus. Complete oxidation forms films of SiO2 with a refractive index of 1.41 and an infrared absorption maximum at 1060 cm−1. Auger electron spectrometry, secondary ion mass spectrometry profile analysis, ellipsometry, and Fourier transform infrared spectrometry were used to study the chemical composition of the films as a function of LPCVD parameters.
Externally strained Si(100) observed with scanning tunneling microscopy
Authors: Packard William E. , Dai Ning , Dow John D. , Jaklevic Robert C. , Kaiser William J. , Tang S. L.
Published: July 2002

Applying a uniaxial strain to Si(100) lifts the orientational degeneracy of the surface energy for 2×1 and 1×2 domains, with a corresponding population increase for the favored domains. An external uniaxial strain was applied to Si(100) by pushing or pulling the free end of a long thin cantilevered sample and the resulting domain structure was observed with a scanning tunneling microscope (STM). On externally unstrained Si(100) there were equal populations of 2×1 and 1×2 domains. The STM images show that under strain individual domains of  2×1 grew in size at the expense of individual domains of 1×2, and the pattern on the strained surface was a large majority terrace, a single-atom-high step to a thin minority terrace, followed by a single-atom-high step back to a large majority terrace. The minority domains formed thin terraces which could have meandering directions. Regions of 2×2 reconstruction were frequently observed on the strained surface.
Thomson space charge in D–T gas
Authors: Souers P. C. , Tsugawa R. T. , Bisson C. L. , Wolfer W. G.
Published: July 2002

Space-charge electrical conductivity data for 0.1% tritium in deuterium gas is compared to the predictions made by the J. J. Thomson theory of 1899. While this theory is in no way competitive with a full computer model, it is simple and physically illustrates the problem. Thomson’s theory fails at high potentials where the electric charges are swept out. At the lowest potential of 0.1 V, the recombination coefficient from Thomson’s theory agrees with the correct value given by the computer model’s fit of the data.
Computer-assisted microballoon selection for inertial confinement fusion targets
Authors: Immesoete C. K. , Scarantino S. , Kim H. , Forsley L.
Published: July 2002

Current inertial confinement fusion experiments require large numbers of well-characterized microballoon targets. Microballoons are batch-produced, and balloons of target quality are selected based on several parameters: outside diameter, wall thickness, and wall concentricity. Selection and characterization of these targets is a labor intensive process. We have developed a computer-controlled microballoon selection system that allows us to select microballoons five times faster than our previous methods with less operator fatigue and with less emphasis on operator skill.
Amorphous NbO films prepared by reactive evaporation
Authors: Ding J. R. , Zhou X. , Bai J. N. , Liu B. X.
Published: July 2002

Reactive evaporation technique was employed to produce amorphous NbO thin films directly. It was revealed that the sheet electrical resistance of the amorphous NbO films was much greater than that of the crystalline counterpart. The thermal stability of the amorphous NbO films was studied by in situ annealing, and the crystallization temperature of the amorphous NbO was observed to be 1120±50 K. The amorphous NbO thin films also crystallized upon 250 keV Xe+ irradiation to a dose of 5×1015 Xe+/cm2.
Slow positron annihilation spectroscopy and electron microscopy of electron beam evaporated cobalt and nickel silicides
Authors: Frost R. L. , DeWald A. B. , Zaluzec M. , Rigsbee J. M. , Nielsen B. , Lynn K. G.
Published: July 2002

Metal silicide thin films on single-crystal silicon substrates are the subject of much research, due to their applications as electrical contacts and interconnects, diffusion barriers, low resistance gates, and field-assisted positron moderators, among others. Defects within the silicide layer and/or at the silicide/silicon interface are detrimental to device performance, since they can act as traps for charge carriers, as well as positrons. Pinholes penetrating the film are another detriment particularly for cobalt silicide films, since they allow electrons to permeate the film, rather than travel ballistically, in addition to greatly increasing surface area for recombination events. A series of epitaxial cobalt and nickel silicide thin films, deposited via electron-beam evaporation and annealed at various temperatures, have been grown on single-crystal silicon (111) substrates, in an effort to establish a relationship between deposition and processing parameters and film quality. The films have been analyzed by transmission and scanning electron microscopy, sputter depth profile Auger, and slow positron annihilation spectroscopy. The latter has been shown to both correlate and complement the traditional electron microscopy results.
Sputtering of excited-state potassium atoms from electron-bombarded KBr crystals
Authors: Kamada M. , Arakawa E. T.
Published: July 2002

Sputtering of excited-state potassium atoms from electron-bombarded KBr crystals has been investigated at 300 and 443 K by measuring simultaneously the optical emission, Auger, and mass spectra. The beam current dependences of the intensities of the ground-state and excited-state potassium atoms at 443 K are nearly linear and quadratic, respectively, indicating that excited-state potassium atoms are produced by gas-phase collisions of potassium atoms desorbed from the surface. On the other hand, the room-temperature data show complicated dependences, which can be divided into three current regions. In the low-current region (<13 μA), electronic excitation followed by Auger-induced Coulomb repulsion produces the excited-state potassium atoms. In the high-current region (>25 μA), effects due to sample decomposition, nonstoichiometry, and gas-phase collisions play important roles in the production of excited-state potassium atoms. The nonlinear sputtering yield of excited-state potassium atoms in the intermediate-current region may be due to secondary effects including the formation of defects and cluster ions.
The coadsorption of ethylene and hydrogen on Pt(210), (1×1)Pt(110), and (2×1)Pt(110)
Authors: Yagasaki E. , Backman A. L. , Chen B. , Masel R. I.
Published: July 2002

Previous work has shown that the rate of ethylene hydrogenation on a hydrogen covered platinum surface is significantly different than the rate of ethylene hydrogenation on clean platinum. However, it is unclear why the difference in rate occurs. In this paper, the coadsorption of ethylene and hydrogen on (2×1)Pt(110), (1×1)Pt(110), and Pt(210) was examined using temperature programmed desorption (TPD) and electron energy-loss spectroscopy (EELS). It is found that adsorbed hydrogen substantially modifies the adsorption of ethylene. While ethylene adsorption on a clean 93 K (2×1)Pt(110) sample results in the production of a mixture of di-σ and π-bound ethylene, little di-σ ethylene is observed if the sample is exposed to 100 L of H2 before the surface is exposed to ethylene. Instead, a new form of adsorbed ethylene is seen. The new form of adsorbed ethylene has a vibrational spectrum very similar to that of gas phase ethylene suggesting it is weakly bound. We also observe the weakly bound form of ethylene on (1×1)Pt(110) and Pt(210). These results show that the adsorbed hydrogen significantly modifies the adsorption of ethylene on various platinum surfaces.
Continuous-wave laser doping of micrometer-sized features in gallium arsenide using a dimethylzinc ambient
Authors: Licata T. J. , Podlesnik D. V. , Tang H. , Herman I. P. , Osgood R. M. , Schwarz S. A.
Published: July 2002

We present a single-step process for the direct writing of micron-scale Zn-doped regions on GaAs substrates. A focused continuous-wave Ar+ laser drives both pyrolysis of the dimethylzinc source gas and solid-state diffusion of the Zn atoms into the GaAs. Secondary ion mass spectroscopy (SIMS) has been used to measure the dopant depth profiles as a function of laser-induced temperature. Raman microprobe spectroscopy has been used to corroborate the SIMS measurements and measure the lateral extent of micron-sized doped lines. In a preliminary measurement of electrical activation, Al contacts to n-GaAs have been modified using the process.
Electromigration lifetime and crystal structure of thin aluminum film connectors for microelectronic devices deposited by the ionized cluster beam technique
Authors: Hummel R. E. , Morrone A. , Lambers E.
Published: July 2002

A comparison of electromigration failure in aluminum films deposited by conventional means and by the ‘‘ionized cluster beam’’ technique on silicon and on SiO2 is presented. The crystal structures of the respective films have been investigated utilizing transmission electron microscopy (TEM), electron diffraction, and x-ray diffraction. An elemental analysis was performed by Auger spectroscopy. The electromigration resistance in some of the films has been found to increase considerably. Possible reasons for this larger lifetime under dc stressing are discussed on the basis of the crystal structures of the films.
Rapid contactless electrical characterization of process-induced damage in HgCdTe
Authors: Elkind Jerry , Chen Men-Chee
Published: July 2002

Microwave reflectance measurements of minority carrier lifetime and eddy-current measurements of conductivity are proposed as rapid, contactless electrical characterization methods for the detection and tracking of process-induced damage in HgCdTe. Changes induced in HgCdTe by ion milling are used to illustrate the utility of the proposed methods.
Analysis of native and anodic oxides of n-doped Al films by Auger and photoemission spectroscopy
Authors: Avila J. , Sacedón J. L.
Published: July 2002

N-doped Al films have been grown by reactive sputtering at increasing N2 partial pressures up to a N concentration of 6%. Whereas depth profiles of the native oxide layer show a constant oxide thickness of about 20 Å, the contact resistance of the coatings decreases exponentially with increasing N2 pressure. From the analysis of N(1s), Al(KLL), and Al(2p) spectra obtained at different depths in the oxide and in the Al bulk of the N 6% doped films the N chemical environment in the bulk of Al films, and in the Al native oxide are studied. The core level and Auger spectra are compared with those corresponding to anodized N doped films, and AlN films prepared by ion beam. They are interpreted in terms of an AlN clustering process, and on the interaction of O with the cluster structures. The relation between the contact resistance and the structure of the native oxide is discussed.
Spectroscopic studies of a solenoid filtered vacuum arc
Authors: Wang Z. H. , McKenzie D. R. , Martin P. J. , Netterfield R. P.
Published: July 2002

The light emissions from a magnetically filtered vacuum cathodic arc are investigated using an optical multichannel analyzer. In principle, a curved magnetic solenoid prevents the neutral species produced in the vicinity of the cathode from arriving at the film deposition area. This is demonstrated in this work from the spectra obtained near the substrate in which no neutral emissions could be found. The emission spectra of copper, aluminum, and titanium vacuum arcs in H2, He, N2, and Ar ambient gases are studied. It is found that the ambient gases enhance the ion emissions with the exception of hydrogen, and the relative enhancement effect is greater for gases with larger cross sections for ionization by electron impact. When a substrate is introduced, neutral emission is observed resulting from sputtering of the deposited film by the energetic ions. Ambient gas reduces this neutral emission, while applying a negative substrate bias increases it.
Spin-dependent s-level and valence photoemission from ferromagnetic nickel
Authors: See A. K. , Klebanoff L. E.
Published: July 2002

Recent spin-resolved x-ray photoelectron spectroscopy studies of Ni core-level and valence-band features are reviewed. Exchange splitting was observed in the main lines of 3s and 2s spectra. These results suggest that the final state Ni 3d electron configuration upon core-hole creation is not purely c3d10 (c=core hole) but rather a mixture of ∼50% c3d9 and ∼50% c3d10. We propose a revised view of core hole screening in Ni in which both unoccupied 3d and unoccupied, unpolarized, and hybridized 3d–4sp states are involved.
Assessment of overlayer thickness determination model by controlled monolayers
Authors: Beard Bruce C. , Brizzolara Robert A.
Published: July 2002

The thickness of carbon overlayers that spontaneously form on the surface of real-world samples needs to be accurately determined to enhance the accuracy of quantitative surface compositional analysis. One method for this determination proposed by Ebel et al. [J. Electron. Spectrosc. 34, 313 (1984)] for use in x-ray photoelectron spectroscopy determines the film thickness based on the area ratio of the C(1s) photoelectron and carbon (KVV) Auger peaks. The Ebel model has been evaluated in this work through the use of self-assembled monolayers (SAMs). The SAM approach permits the comparison of film thicknesses determined by the model with the known thickness of the controlled monolayers. Data from the SAMs consistently fell below the curve predicted by the model. Discussions of potential sources for error are presented with respect to photoelectron attenuation models. Examination of these potential sources, however, could not identify a source of sufficient magnitude to account for the difference between predicted and actual results. It is suggested that the error is due to an incorrect assumption with respect to the normalization factor used in the model. Additional excitation of the C(KVV) due to the large number of energetic photoelectrons originating from the substrate is suggested as the cause for the discrepancy between prediction and experiment. Experimental evidence supporting this assertion, and possible methods of correction are offered.
Characteristics of Cu thin films on a glass substrate by partially ionized beam deposition at room temperature
Authors: Yoon Y. S. , Kim K. H. , Jang H. G. , Jung H. J. , Koh S. K.
Published: July 2002

Partially ionized beam deposition of Cu thin films onto glass at room temperature was carried out to fabricate laser mirrors with good structural and reflective properties. At a constant film thickness of 600 Å, the grain size of as-grown Cu films increased with acceleration voltage. There was no indication of defects such as cracks and/or large pores in the film surface as shown in scanning electron microscopy images. Rms surface roughnesses of 600 Å thick films were measured by atomic force microscopy images. Rms surface roughness increased when acceleration voltage increased from 0 to 2 kV, but decreased at 3 kV. Rms surface roughness of the film grown at 4 kV, however, increased. At the acceleration voltage of 3 kV, reflectance of the films increased with the film thickness until 600 Å and decreased at 800 Å. The reflectance results showed that the Cu films deposited at 3 kV had higher reflectance than that of others. Our results suggested that it is possible to grow Cu films with good structural and optical properties on glass substrates at room temperature by partially ionized beam deposition. Copper films showed greater reflectivity than aluminum films used for laser mirrors by 2%–7%.
Time-resolved mass spectrometry in rough vacuum environment
Authors: Laimer J. , Schnabl O. , Schwärzler C. G. , Störi H.
Published: July 2002

A specially constructed helium flushed probe system was developed in order to ensure a quick transport of species extracted from a process gas at a few tens of mbar to a quadrupole mass spectrometer. The amount of extracted process gas can be adjusted by the setting of the helium gas flow. The time response of the probe system was simulated and compared with measurements performed on a pulsed hydrogen-deuterium discharge. The probe system is characterized by a delay time of a few tens of ms depending on the process pressure and a time resolution of about 20 ms. A decrease of the time resolution to values well below 10 ms is possible.
Adhesion improvement between Au films and glass by 1 keV Ar+ ion irradiation
Authors: Jang H. G. , Kim K. H. , Han S. , Choi W. K. , Jung H.-J. , Koh S. K. , Kim H. B.
Published: July 2002

Au films with a thickness of around 1600 Å were deposited onto glass substrates at room temperature by an ion beam sputtering method, using a 5 cm cold hollow cathode ion gun at a pressure of 4–8×10−6 Torr. Irradiation of the Au/glass samples was carried out at pressure of 7×10−6 Torr. For the sputter deposition, the Ar+ ion energy was 1 keV and the current density at the surface of the substrate was 15 μA cm−2. Effects of 1 keV Ar+ ion doses (Id) ranging from 1×1016 to 2×1017 Ar+cm−2 on the properties such as crystallinity, surface roughness, and adhesion of the films have been investigated. Rutherford backscattering spectrometry showed that the thickness of Au films and sputtering yield were reduced by increase of Id and rms surface roughness of the films increased from 16 to 118 Å, as the ion dose was changed from 0 to 2×1017 Ar+ cm−2. Adhesion of Au films on the glass irradiated at Id=2×1017 Ar+ cm−2 was nine times greater than that of untreated Au films, as determined by a scratch test.
Characterization of the ion-plated TiN on AISI 304 stainless steel by energy filtering transmission electron microscopy
Authors: Shieu F. S. , Cheng L. H. , Sung Y. C. , Huang J. H. , Yu G. P.
Published: July 2002

The microstructure and chemistry of TiN coatings on AISI 304 stainless steel was characterized by a Zeiss EM 902A energy filtering transmission electron microscope (TEM) equipped with an electron energy loss spectroscopy (EELS) detector. Deposition of the TiN thin films was carried out by a hollow cathode discharge ion plating coater. The microstructure across the coating thickness direction and near the TiN/steel interfaces was investigated by plan-view TEM. It was found that the microstructure of the TiN coatings is thickness dependent. The grain size of TiN ranges from 88 nm at the coating surface down to 9 nm near the TiN/steel interface. In addition, the TiN surface layer shows slightly textured microstructure, but the subsurface and internal TiN layers have mainly equiaxial and randomly oriented microstructure. Chemical analysis of the coating and the interfacial region was done by EELS. It was obtained that the relative oxygen content increases linearly from the TiN surface to the TiN/steel interface, whereas the relative nitrogen content first decreases slowly and then drops rapidly near the interface. The presence of a Ti2N phase and the deficiency of nitrogen near the TiN/steel interface suggest that the early deposited TiN may be nonstoichiometry.
Mirror-finished, surface-seal-type gate valve with a long life of about 104 cycles
Authors: Satou M. , Momose T. , Tamura K. , Ishimaru H.
Published: July 2002

We have fabricated a mirror-finished, surface-seal-type gate valve with diaphragms made of silver and with independent compressed air systems for the seal diaphragms and seal bellows. The previous design had diaphragms made from an aluminum alloy and a common air system for the seal diaphragms and seal bellows. For the new design, after 9523 open/close sequences, a stainless steel bellows for the isolation plate vertical motion broke. However, this is a lifetime improvement of more than one order of magnitude over the old design. Further improvement of the bellows can lead to an even longer lifetime for the valve.
Orientation of vacuum–evaporated BaF2 films in the presence of nitrogen
Authors: Sircar Parthasarathi , LeBret Norman G.
Published: July 2002

BaF 2 films were vacuum deposited on borosilicate glass substrates at room and higher temperatures. The films were polycrystalline with different orientations. Introduction of N2 at 3×10−4 mbar pressure during evaporation resulted in a dramatic improvement in orientation along a given direction, which itself was a function of the substrate temperature. Thus, at room temperature, the orientation was along the (111) direction, while at 100 °C it was along the (220) direction.
High resolution Auger electron spectroscopy studies on (100) and (111) facets of chemical vapor deposited diamond
Authors: Sharda T. , Misra D. S. , Seibt E. W. , Selvam P.
Published: July 2002

Diamond thin films were grown by microwave plasma and hot filament chemical vapor deposition (MPCVD and HFCVD, respectively) techniques. Films were systematically characterized by x-ray diffraction, micro-Raman spectroscopy, scanning electron microscopy (SEM), and Auger electron spectroscopy (AES). Although the results obtained using various characterization techniques are broadly similar, there are however subtle differences. For instance, Raman spectra show a sharp peak at ≃ 1332 cm−1 corresponding to natural diamond in both types of films. The intensity and the position of the non-diamond band in the two sets of films differ. While the maxima of the non-diamond band in HFCVD film lies at 1450 cm−1, in MPCVD film it occurs at 1525 cm−1. Also the values of FWHM in HFCVD film (≃ 7.5 cm−1) are smaller than the MPCVD films (≃ 9.5 cm−1). This may indicate that the concentration of non-diamond carbon impurities on the grain boundaries of HFCVD films are really small. SEM results on the other hand indicate that the grain size of the MPCVD films is larger than HFCVD films. AES was performed in a survey scan (beam size ∼10 μm × 8 μm) and high resolution (beam size ≃ 0.2 μm) mode with an initial aim to investigate the surface characteristics and environment of carbon atoms of the diamond films. In the survey scan, the spectra show a line shape typical of CVD diamond films. Anomalous results were obtained when the AES was performed on (100) and (111) facets in high resolution mode. This may be explained in terms of the surface reconstruction taking place due to hydrogen desorption via core-hole Auger decay process. Auger depth profiles were also obtained on the facets which reveal that Si, O, and N are the dominant impurities. The impurity content of HFCVD films is observed to be lower by a factor of 2 as compared to MPCVD films.
Reduction in x-ray lithography shot noise exposure limit by dissolution phenomena
Authors: Neureuther Andrew R. , Willson C. Grant
Published: July 2002

Statistical variations in the local energy deposition in resist can result in defect generation and unacceptable linewidth variation. The lower limit of exposure dose at which these variations limit pattern integrity is termed the shot noise limit. Several analyses of the shot noise limit have been published. We find that refinements in the underlying assumptions on which these analyses are based have led to a substantial reduction in the shot noise limit. The refined assumptions include optimization of the resist absorption, use of a binary exposure-dissolution model with a sharp, percolation threshold, consideration of multipath dissolution effects, and separation of bias and linewidth variation in algebraic models. The infrequent occurrence of large defects is shown to dominate over the 3σ linewidth variation. While typically 30 exposure events per defect volume is still required, a factor of 30 reduction in the shot noise exposure limit is established primarily by showing that defect sizes up to (1)/(3) of the linewidth are tolerable. For lithography at 0.37-μm-feature size, consistent with 64 Mbit dynamic random access memories, the refined shot noise limit is below 1 mJ/cm2 for 1.0 μm-resist coating thickness. Thus the shot noise limit does not appear to be a fundamental road block to the use of high sensitivity resists with nonsynchrotron x-ray sources.
Surface structure studies of quasi-one-dimensional charge-density wave compounds by scanning tunneling microscopy
Authors: Gammie G. , Hubacek J. S. , Skala S. L. , Tucker J. R. , Lyding J. W.
Published: July 2002

Scanning tunneling microscopy (STM) has been used to study the atomic and charge-density wave (CDW) structure of the surface of the trichalcogenides NbSe3 and o-TaS3. Atomic images of NbSe3 suggest the presence of an adatom on untreated surfaces imaged in air, making chain identification difficult. Although the detailed structure of o-TaS3 is not known, STM images provide evidence that it is more closely related to the ZrSe3 structure than to that of NbSe3, as previously assumed. Images of o-TaS3 below Tp=215 K reveal the detailed structure of the CDW, yielding some insight as to why its CDW properties differ from those of NbSe3 and m-TaS3.
Ultrahigh vacuum and air observations of Pd clusters grown on clean graphite
Authors: Humbert A. , Dayez M. , Granjeaud S. , Ricci P. , Chapon C. , Henry C. R.
Published: July 2002

Comparison between UHV and air observations on Pd clusters deposited under UHV on a clean graphite surface is made. For the largest clusters (>10 nm), no dramatic influence of air exposure is observed. Quite surprisingly, we have been able to image in air the surface atomic arrangement of 1.5 nm Pd clusters. They have a tetrahedron shape with (111) facets and are epitaxially oriented: Pd (111)//graphite (00.1), Pd[112̄]//graphite [01.0].
Fabrication of flip-bonded mesa masks for x-ray lithography
Authors: Schattenburg M. L. , Polce N. A. , Smith Henry I. , Stein R.
Published: July 2002

A novel ‘‘mesa’’ type of x-ray mask is introduced which utilizes the flip-bonding method of anodic bonding to join the mask membrane to a rigid, mechanically stable Pyrex ring. The new design eliminates several debilitating problems of conventional mesa masks, including the membrane overhang and resist edge bead problems. Flip-bond masks are much flatter than conventional mesa masks, typically <500 nm mask total flatness and <150 nm membrane flatness. A novel method of strengthening mesa masks is introduced, involving a polysilicon shock collar in the inner diameter of the mask ring designed to distribute the strain of mechanical disturbances. Flip-bond fabrication procedures have been designed to be amenable to volume manufacturing.
Pattern width evaluation method for electron-beam pattern data
Authors: Watanabe Toshifumi , Moriya Shigeru , Komatsu Kazuhiko
Published: July 2002

A new pattern width evaluation method for electron-beam (e-beam) writing has been developed. The method can predict the overall pattern width accuracy objectively and quantitatively by taking into account the exposure intensity distribution function and specific e-beam writing data in which the dose is often modulated for proximity effect correction. The evaluation is carried out by calculating the effective exposure energies and distances for sampling points on layout patterns from the ideal location of the pattern edge, the probability of pattern edge resolution as a function of the distance, and the mean and standard deviation of the edge positioning accuracy. Experiments verify the validity of this approach. The method enables the evaluation of linewidth accuracy using e-beam writing data after proximity effect correction. Furthermore, it can be applied under various writing conditions and has the potential for use in the development of e-beam writing systems.
Radiation damage-induced changes in silicon nitride membrane mechanical properties
Authors: Wells G. M. , Chen H. T. H. , Wallace J. P. , Engelstad R. L. , Cerrina F.
Published: July 2002

Traditional x-ray lithography mask radiation damage studies have concentrated on the pattern placement errors produced by stress changes within the mask membrane. The usual approach is to measure the location of fiducial marks on the mask membrane to measure the distortions for pre- and postirradiation. The measured distortions are not directly related to changes in individual mechanical properties of the membrane material. To isolate the individual mechanical parameters this study has utilized a silicon nitride membrane structure in the form of a bridge with lithographically patterned strain gauges to allow independent measurement of changes in the elastic modulus and Poisson’s ratio as a function of incident dose. It was found that the modulus of elasticity decreased by 37% for an incident dose of 114 kJ/cm2 while the Poisson ratio for the material remained unchanged within the accuracy of the experiment. The results of these measurements have been incorporated into a finite element model to numerically determine the resulting distortions and compare them with published experimental results.
Simultaneous measurement of gap and superposition in a precision aligner for x-ray nanolithography
Authors: Moon E. E. , Everett P. N. , Rhee K. , Smith Henry I.
Published: July 2002

Previously we described an x-ray mask alignment system, capable of nanometer-level superposition precision, whose alignment signal did not appear to be adversely affected by overlayers of resist, polysilicon, or metal [E. E. Moon, P. N. Everett, and H. I. Smith, J. Vac. Sci. Technol. B 13, 2648 (1995)]. The system, called interferometric broad-band imaging (IBBI), employs grating and grid type alignment marks on mask and substrate, respectively. These are viewed at an inclined angle, through the mask, using f/10 optics with a working distance of 110 mm. The inclined angle and long working distance avoid interruption of the x-ray beam. Using a charge-coupled-device camera, misalignment is measured from two identical sets of interference fringes (∼50 μm period) that move in opposite directions as the mask is moved relative to the substrate. Alignment corresponds to matching the spatial phases of the two sets of fringes. Here we demonstrate that the same alignment optics and grating type alignment mark on the mask can be used to measure the mask–sample gap, with a sensitivity ∼50 nm, via a diffractive-Michelson interferometer. No mark is required on the substrate. X-ray exposures were carried out with the IBBI system. The disparity between (a) the misalignment as measured by the IBBI system and (b) the postprocessing misalignment, as measured on the substrate by a related moiré technique, was evaluated. Mean disparities of 0.1, −0.4, and −0.3 nm were measured for alignment marks of 1, 2, and 4 μm period, respectively. The 3-σ values of the distributions were 2.4, 7.3, and 5.9 nm. The larger values for the 2 μm period case are attributed to multiple defects in the grating alignment marks.
Merit functions for lithographic lens design
Authors: Progler Christopher J. , Byrne Dale M.
Published: July 2002

We describe a new approach to the optimization of lithography lenses where lithographic quality factors are enclosed inside the optimization loop. These quality factors are derived from an image simulation program which calculates the relevant lithography metrics each time an optimization cycle is attempted. We find lithographic merit functions strongly impact the final lens performance, and superior lithographic imaging is possible when they are employed. We also show that lens users benefit by understanding the aberration balance inherent in each lithography lens.
General aspheric refractive micro-optics fabricated by optical lithography using a high energy beam sensitive glass gray-level mask
Authors: Däschner Walter , Long Pin , Stein Robert , Wu Chuck , Lee S. H.
Published: July 2002

General aspheric refractive microlens arrays with an almost 100% fill factor are useful in a wide range of applications ranging from display, optoelectronic interconnections, or improving the efficiency of detector arrays to lithography techniques utilizing microlens arrays. In this article a technique will be discussed which allows the microlithographic fabrication of general aspheric non rotationally symmetric refractive lenses with a 100% fill factor. A gray-level mask based on high energy beam sensitive (HEBS) glass is used to pattern a thick (4–5 micron) photoresist layer. After development, the refractive structure is transferred into the substrate material using a chemically assisted ion beam etching (CAIBE) process. The HEBS-glass gray-level mask is generated by a electron-beam writer, allowing for complete freedom in terms of the shape and location of the lenses.
Triangular-variable-shaped beams using the cell projection method
Authors: Someda Yasuhiro , Shoda Yasunari , Saitou Norio
Published: July 2002

A triangular variable shaped electron beam lithography method using the cell projection method is proposed. The shaped beams are formed by a conventional rectangular beam method and variable triangular apertures. This method has three significant characteristics: The plural kind of triangles can be made. This increases the pattern flexibility and decreases the number of shots. The position of one corner of the triangles is automatically determined. Therefore, there is no fluctuation of the triangular beam position and the size of the triangle can be varied with high precision. The triangular apertures are located such as to minimize the deflection distance. This realizes high speed and high precision beam formation. With these characteristics, this method is expected to be used for high speed and high precision mask fabrication.
Quantum dots fabricated in InP/InGaAs by free Cl2 gas etching and metalorganic chemical vapor deposition regrowth
Authors: Panepucci R. , Reuter E. , Fay P. , Youtsey C. , Kluender J. , Caneau C. , Coleman J. J. , Bishop S. G. , Adesida I.
Published: July 2002

The free Cl2 thermal etching of InGaAs/InP was characterized for the fabrication of quantum well dots (QDs). The effects of mask shape on the three-dimensional structure of the dot was investigated. Quantum dots with dimensions as small as 56 nm were fabricated using electron beam lithography and free Cl2 etching. The dots were characterized using scanning electron microscopy and low temperature photoluminescence (PL). Metalorganic chemical vapor deposition (MOCVD) regrowth of InP on quantum dots of different mask shapes was investigated. The effect of non-radiative recombination at the etched sidewall was evaluated through the normalized intensity of the PL. A red shift of the PL peak with decreasing dot sizes was observed for the as-etched structures and attributed to the effect of residual compressive biaxial strain on the InGaAs layer. Free Cl2 etching is an important etch technique for in situ etch and regrowth processes due to the high quality of the etched interface and the ability to perform selective area regrowth with a SiO2 mask still present.