bluuebunny/crossref_metadata_2025 huggingface dataset:
Mn(C2H3O2)2 by XPS
Authors: Stranick Michael A.
Published: July 2002

Manganese compounds have many applications in areas such as catalysis, electrochemistry, and metallurgy, among others. Distinguishing between the various chemical states of manganese is an important aspect of research in many of these areas. It has been shown that the different chemical states of manganese can be identified with XPS through the Mn 2p3/2 peak positions, Mn 2p1/2 satellite–Mn 2p1/2 peak separations, Mn 3s multiplet splittings, or Mn Auger parameters. To date, however, all of these values have not been available in a single reference. In this study, XPS has been used to obtain core level, Auger, and valence band spectra for a commercial, high purity Mn(C2H3O2)2 powder. This submission provides a reference that contains all of the Mn XPS data necessary for the identification of Mn(C2H3O2)2 and also provides information that may be useful for the analysis of other Mn compounds.
Titanium Zirconium Nitride by XPS
Authors: Milošev Ingrid , Strehblow Hans-Henning , Navinšek Boris , Panjan Peter
Published: July 2002

Titanium zirconium nitride (Ti0.53Zr0.47N) coatings have been deposited on polished steel substrates by dc reactive sputtering in a Sputron (Balzers AG) plasma-beam sputtering apparatus at 200 °C. A thin intermediate layer of TiZr (0.08 μm) was deposited between the substrate and the 2.8 μm thick TiZrN coating. The deposition rate was 12 nm min−1. The partial pressure of nitrogen was 3 × 10−2 Pa, while the total working pressure was 2 × 10−1 Pa. Using a planetary substrate holder with double rotation, thickness and composition uniformity better than 2% were obtained. The average roughness, Ra, of the substrate was <0.04 μm, whereas after the deposition Ra values between 0.06 and 0.08 μm were measured for TiZrN coatings. The XPS measurements were performed in an Escalab 200-X spectrometer (VG Instruments) using nonmonochromatized Al Kα radiation from a twin Mg/Al anode operating at 300 W. The hemispherical energy analyzer was operated in the CAE mode with a constant pass energy of 20 eV. In the present paper the following spectra are presented: survey spectrum, spectra of major elements titanium, zirconium, and nitrogen (Ti 2p, Zr 3d, and N 1s), spectra of minor elements oxygen and carbon (O 1s and C 1s), and valence band spectrum. Spectra were background subtracted using a Shirley method. Peak positions and widths were determined by least squares fitting.
Proposal and dynamics simulation of scanning tunneling microscope with a giant magnetostrictive alloy
Authors: Sakuta Shigeru
Published: July 2002

This article presents a novel approach to building a scanning tunneling microscope (STM): the magnetostrictive scanning tunneling microscope (MSTM). The MSTM makes it possible to visualize a sample with atomic-scale resolution. A giant magnetostrictive alloy in a coil with a STM tip changes in dimensions in response to a magnetic field generated by a tunnel current, which allows the scanned surface to be observed. Potentially the MSTM provides intrinsic negative feedback to function as an automatic constant current mode STM without any current amplifier circuits for feedback control. The dynamics and feasibility of the MSTM in constant current mode are described.
Dry via hole etching of GaAs using high-density Cl2/Ar plasma
Authors: Chen Y. W. , Ooi B. S. , Ng G. I. , Radhakrishnan K. , Tan C. L.
Published: July 2002

In this article, we report on a high etch rate GaAs via hole processes in an electron cyclotron resonance system using a Cl2/Ar plasma. The effects of process parameters on the GaAs etch rate were investigated. The influences of process parameters on the resultant profiles were also studied. The GaAs etch rate was found to increase as the Cl2 percentage in the Cl2/Ar plasma, process pressure, and rf power or the microwave power increased. A maximum etch rate of 6.7 μm/min has been obtained from a sample etched using a microwave power, rf power, and process pressure of 800 W, 150 W, and 50 mTorr, respectively. The degree of anisotropy of the etched profile was controlled by varying the process pressure and rf power.
Electron field emission from a patterned diamond-like carbon flat thin film using a Ti interfacial layer
Authors: Mao D. S. , Wang X. , Li W. , Liu X. H. , Li Q. , Xu J. F. , Okano K.
Published: July 2002

A 200-nm-thick diamond-like carbon film was prepared on Ti-deposited Si (ρ<0.01 Ω cm) using a filtered arc deposition technique. Field-emission properties of it are enhanced as compared to films deposited on Si, showing an increased current and emission site density (∼1.2×103/cm2). A patterned diamond-like carbon flat thin film on Ti-deposited Si fabricated by the oxygen reactive ion-beam etching technique shows further enhanced field-emission properties. An emission site density of 3×103/cm2 was obtained. Field emission could be observed at a field value as low as 2.1 V/μm. It is shown that the low potential barrier at the interface and high local geometric electric field enhancement around the edges produced by reactive ion-beam etching are possible causes for the enhanced effects. It can also be explained by the Geis’ metal–diamond–vacuum triple junction emission mechanism.
Nanoscale surface modification and nanostructural fabrication of YBa2Cu3O7−x thin films by scanning tunneling microscopy
Authors: Fan Y. C. , Fitzgerald A. G. , Cairns J. A.
Published: July 2002

The scanning tunneling microscope has been used to modify the surface of YBa2Cu3O7−x (YBCO) high Tc superconducting thin films by operating the instrument in the so-called mechanical milling or field-induced evaporation mode. Nanostructures such as holes, lines, and trenches were fabricated on the YBCO thin film surface in a controlled manner. In the surface modification and nanostructure fabrication processes, the effect of bias voltage, tunneling current, and scanning feedback control parameters on the modification efficiency have been investigated.
Ion-bombardment effects on PtSi/n-Si Schottky contacts studied by ballistic electron emission microscopy
Authors: Ru Guo-Ping , Qu Xin-Ping , Zhu Shi-Yang , Li Bing-Zong , Detavernier C. , Van Meirhaeghe R. L. , Cardon F. , Donaton R. A. , Maex K.
Published: July 2002

Ballistic electron emission microscopy has been used to study physical damage effects on PtSi/n-Si Schottky contacts. The physical damages are introduced into Si substrates by ion bombardment with well-defined energies in an ion-milling process. Schottky barrier height (SBH) distribution is measured on the subsequently formed PtSi/n-Si Schottky diodes. The results show that mean SBH decreases with ion energy in a square-root relation. A simple SBH model is developed to consider image-force lowering effect for a semiconductor with a step-function distribution of donor concentration. The model is successfully used to explain quantitatively the experimental relation between SBH and ion energy.
Effect of ramp rate on the C49 to C54 titanium disilicide phase transformation from Ti and Ti(Ta)
Authors: Smith Paul Martin , Bailey Glenn , Hu Yao Zhi , Tay Sing Pin
Published: July 2002

The C49 to C54 TiSi2 transformation temperature is shown to be reduced by increasing the ramp rate during rapid thermal processing and this effect is more pronounced for thinner initial Ti and Ti(Ta) films. Experiments were performed on blanket wafers and on wafers that had patterned polycrystalline Si lines with Si3N4 sidewall spacers. Changing the ramp rate caused no change in the transformation temperature for 60 nm blanket Ti films. For blanket Ti films of 25 or 40 nm, however, increasing the ramp rate from 7 to 180 °C/s decreased the transformation temperature by 15 °C. Studies of patterned lines indicate that sheet resistance of narrow lines is reduced by increased ramp rates for both Ti and Ti(Ta) films, especially as the linewidths decrease below 0.4 μm. This improvement is particularly pronounced for the thinnest Ti(Ta) films, which exhibited almost no linewidth effect after being annealed with a ramp rate of 75 °C/s.
Chlorination of Si surfaces under strain conditions
Authors: Halicioglu Timur
Published: July 2002

Energetics for the chlorination process of Si(100)-(2×1) surfaces with an A-type single step edge were investigated under strain conditions. Strains applied uniaxially in the direction parallel to the exposed surfaces produced little or no effect on the energetics of the first chlorination step leading to fully Cl-covered terraces (one Cl attached to every exposed Si atom). The energy of the second chlorination step (leading to the formation of attached –SiCl2 units) taking place near a step-edge site, however, is affected considerably by the applied strain. The effect was found to be largest for strains applied in the direction perpendicular to the step edge.
Through-wafer electrical interconnect for multilevel microelectromechanical system devices
Authors: Mehra Amit , Zhang Xin , Ayón Arturo A. , Waitz Ian A. , Schmidt Martin A.
Published: July 2002

This article reports the design, fabrication, and experimental demonstration of through-wafer interconnects capable of allowing direct electrical access to the interior of a multilevel microelectromechanical system device. The interconnects exploit the ability to conformally coat a high aspect ratio trench with a thick layer of tetraethylorthosilicate to isolate a through-wafer silicon plug that can provide electrical contact across two sides of a low resistivity wafer. They hold the potential of a tenfold reduction in the parasitic capacitance of previously reported through-wafer vias, and are shown to make reliable contacts to the back side of a polysilicon resistive element. The high temperature capability of the interconnects is also examined, however, their application is found to be limited to temperatures below 1000 °C due to localized degradation near the isolating trenches.
Optimized Nonevaporable Getter Cartridges
Authors: della Porta P. , Ferrario B. , Borghi M.
Published: July 2002

A matrix method is described for calculating the pumping speed of a cyclindrical gettering surface with pleated strips. The effect of cartridge geometry and sticking probability of the incident gases were calculated using a theoretical model for the gases carbon monoxide, nitrogen, and hydrogen. The results of the computations show that the pumping speed can be increased by decreasing the angle between the strips to an optimum value that depends on the ratio of the thickness of the strip to its width and on the incident gas. A comparison of calculated and experimental values for H2 on Zr–Al agreed to within approximately 20%.
Metallurgical Characteristics of Titanium-Alloy Foil Prepared by Electron-Beam Evaporation
Authors: Smith H. R. , Kennedy K. , Boericke F. S.
Published: July 2002

The supersonic titanium aircraft has requirements for high-strength titanium-alloy foil for honeycomb structures. In conventional rolling of such alloys as titanium-6% aluminum-4% vanadium, multiple high-vacuum anneals are required to reach the thin-foil gages, from 0.001–0.004 in., used for honeycomb cores. The advantages of electron-beam evaporation and deposition in the desired thicknesses, and without rolling and multiple vacuum annealing, are studied. The present research program is designed to prove that foils of such alloys, produced by EB evaporation on a moving substrate, are equivalent to the rolled products. EB foils easily meet the chemical and mechanical property requirements of aerospace specifications. Bend tests are superior to the rolled foil. The metallurgical characteristics have been evaluated using optical micrography and electron micrography with replica, transmission, and scanning techniques. The deposits are fully dense and of grain sizes from 0.2–0.8 μ. Microprobe analyses indicate that the chemical composition is uniform and contains alpha and beta phases. All metallurgical characteristics of EB evaporated foils appear to be suitable for the intended end uses. Evaluations in the form of actual honeycomb structures are underway.
Investigation of Tantalum Film Properties by Layers
Authors: Livermore F. C. , Wilcox P. S. , Westwood W. D.
Published: July 2002

A technique has been developed which has made it possible to determine the resistivity (ρ) and the temperature coefficient of resistance (TCR) of layers at different depths in thin tantalum films. The method involves a measurement of the sheet resistance and TCR before and after anodization steps, and simultaneous measurements of the oxide growth kinetics. It is shown that there can be a significant variation in the film properties with depth. A 1000-Å thick film, reactively sputtered in an argon-oxygen atmosphere, appeared to have a resistivity of 1000 μΩ cm and a TCR of −120 ppm/°C. but investigation by this technique showed that ρ actually varied from approximately 3000 μΩ cm at the air-film interface to 400 μΩ cm at the film-substrate interface, while the TCR varied from −1200 ppm/°C to approximately 0 ppm/°C. Oxide growth kinetics showed that the oxygen content of the film was approximately 50 at.% near the surface but only 30 at.% in the bulk of the film.
Long-Term Operation of Crystal Oscillators in Thin-Film Deposition
Authors: Behrndt Klaus H.
Published: July 2002

Quartz-crystal oscillators were operated in conjunction with film thickness monitors which convert the shift of the period of oscillation into indicated film thickness t. Films exceeding 125 kÅ of Cu (>415 kÅ of Al equivalent) were deposited on individual crystals. The deposit on glass slides simultaneously exposed to the deposition process was weighed. Up to the largest masses investigated, the indicated thickness of the deposit was linearly proportional to the deposit thickness on the slides. This result is unexpected since differences in the elastic constants of film material and quartz and/or changes of the oscillatory behavior could lead to deviations. Furthermore, the effective oscillating area of various crystals was only slightly larger than that of the deposit. The relationship between frequency shift and incremental deposit thickness was found to agree with theoretical predictions.
Vacuum Duplexing—A Fresh Look at Existing Melting Techniques
Authors: Cremisio R. S. , Hornbaker R. W.
Published: July 2002

Changing technology patterns, coupled with growing demands for high product reliability at low cost, will result in a pronounced growth in the preparation of alloy grades subject to some form of vacuum melting of iron, nickel, and cobalt base alloys in the next 10 years. It is predicted that all grades slated for high reliability and/or performance products will see some form of vacuum processing, whether degassing or primary melting. A trend towards duplexing of various melting methods into “melting systems” consisting of two or more melting methods is also developing for the same reason. The paper describes various iron, nickel, and cobalt base alloy systems and several product applications along with the characteristic problems thereof. A complete description of all known melting schemes is presented along with their specific characteristics relating to charge material, tendency for contamination, and applications to a full range of prevalent forms. The paper further describes unique combinations (duplexing) of these various methods in such a way as to result in optimized quality and melting cost. Application to specific problems known in the melting industry will be discussed. Recommendations for maximizing productivity at lowest cost through duplexing will be made.
Vacuum Heat Treating
Authors: Pine W. C.
Published: July 2002

The use of vacuum equipment to heat treat materials to improve their physical characteristics is covered in this paper. Types of vacuum furnaces and their part in the heat treating of these materials is covered in depth. The newer methods of quenching brought about by the widening of the varieties of materials to be heat treated are also thoroughly discussed and reasons are given for the changes which have taken place. The use of a vacuum furnace in heat treating is not new, but during the past few years there has been more interest shown in this method than ever before with the inevitable increase in the number of facilities available. The first vacuum furnaces cooled materials from the austenitizing temperature by merely backfilling with an inert gas. Later a fan was added to increase the cooling rate and finally this was succeeded by a recirculator utilizing a heat exchanger and the movement of greater velocities of gas which resulted in the broadening of the number of materials that could be successfully vacuum heat treated. Later liquid quenching became available and the list of materials that could be vacuum heat treated was broadened even more. At about this time it became more and more apparent that hard vacuums were not required to successfully heat treat without changes in the surface chemistry of the materials. As a result, most heat treating is now carried out at pressures ranging from 20 to 150 μ rather than in the submicron range. It is concluded that the use of vacuum provides an excellent environment for the heat treatment of various materials even in some cases resulting in unusual wear resistance and greatly improved life.
Doping Characteristics of Flash-Evaporated Thin Film Gallium Arsenide
Authors: Hu Ding Hua , Charlson E. J.
Published: July 2002

Thin films of gallium arsenide were deposited on glass substrates by flash-evaporating the powder with an excess of pure arsenic. An independently controlled tin boat supplied the n-type dopant. Doping characteristics were evaluated by a metal-insulator-semiconductor (MIS) capacitance measurements and field effect conductivity modulation using a thin-film-transistor structure. Results showed that drift mobility for carriers in the space charge depletion region greater than 1 cm2/V sec can be observed only for a narrow range of carrier concentrations. Surface state densities and surface carrier trapping was reduced by an indium alloy process.
Adhesion of chromium films to soda lime glass
Authors: Poley Neil M. , Whitaker Howard L.
Published: July 2002

A comprehensive empirical study of chromium-glass adhesion is described. The experimental matrix includes variations in cleaning procedures, substrates, and vacuum treatments. Particular attention is given to glow discharge ambients, including active and noble gases. The effect of substrate heating was also investigated. The dynamic peel adhesion test was used for comparison of adhesion strengths, and this technique is described. The study was directed toward finding a process compatible with high-throughput production techniques. Quantitative data are given that compare various deposition regimes, and results show a significantly improved chromium deposition process for this particular class of substrates. Some general comments are made regarding the adhesion mechanism and other related phenomena.
Design and development of plasma enhanced chemical vapor deposition universal antireflective layer films for deep subquarter micron deep ultraviolet applications
Authors: Wang Ying , MacWilliams Ken , Karim Zia , Fan Wendy , Reilly Michael , Holden James M.
Published: July 2002

A dual-layer, oxynitride film stack functions as a universal antireflective layer (UARL) for patterning deep subquarter micron features on transparent dielectric films. The UARL optical constants at 248 nm are n=1.96 and k=0.3 for top layer and n=2.24 and k=1.04 for bottom layer with film thickness 360 and 650 Å, respectively. The bottom UARL layer absorbs most of the incoming light, minimizing the light reflected from the underlying substrate. Therefore, the reflectance back into the photoresist is a few tenths of one percent and is independent of the substrate material’s optical properties and structures. Results of patterning 0.18 μm photoresist lines with the UARL on various Damascene film stacks show very tight critical dimension control.
Diode structures based on p-GaN for optoelectronic applications in the near-ultraviolet range of the spectrum
Authors: Starikov D. , Berishev I. , Um J.-W. , Badi N. , Medelci N. , Tempez A. , Bensaoula A.
Published: July 2002

It was previously reported that spectrally matched n-SiC and n-GaN-based MIS Schottky barrier diode structures exhibited optical emission and photosensitivity in the near-ultraviolet (UV) range of the spectrum and rectification at elevated temperatures. However, such structures were not practical due to the low mechanical and thermal stability of the semitransparent Au contacts. In addition, we experienced difficulties in achieving stable optical emission from the n-GaN-based structures. In this work various Schottky barrier diode structures based on p-type GaN layers grown on sapphire with silicon (Si), boron nitride (BN), and silicon dioxide (SiO2) interfacial layers were investigated. Blue and wide-spectrum optical emissions at forward and reverse bias, respectively, and photosensitivity were observed from these structures. A spectral match in the range of 365–400 nm between the light emitting diode (LED) and photodetector structures fabricated on the same substrate was achieved. A total Lambertian radiant UV power of ∼466 μW was measured from a blue/UV LED at 22 V. UV-transparent and electrically conductive SnOx layers were fabricated, characterized, and employed for fabrication of p-GaN-based photodiode structures.
In situ physical vapor deposition of ionized Ti and TiN thin films using hollow cathode magnetron plasma source
Authors: D’Couto G. C. , Tkach G. , Ashtiani K. A. , Hartsough L. , Kim E. , Mulpuri R. , Lee D. B. , Levy K. , Fissel M. , Choi S. , Choi S.-M. , Lee H.-D. , Kang H.-K.
Published: July 2002

The in situ deposition of titanium (Ti) and titanium nitride (TiN) films for aggressive contacts [diameter <0.25 μm diameter, with aspect ratio (AR)∼5] using the hollow cathode magnetron (HCM)™ plasma source has been demonstrated. The TiN films were deposited in an in situ non-nitrided (metallic) mode and the deposition rates are high (>700 Å/min) for both Ti and TiN. Rutherford backscattering data demonstrated that the process is truly non-nitrided, and that the Ti deposited after a TiN deposition does not contain any significant amounts of atomic nitrogen in it. In addition, TiN with low resistivity (∼30 μΩ cm for a 1000 Å film) is obtained. Due to the high fractional ionization of the sputtered titanium, a bottom coverage of >30% (5:1 aspect ratio, 0.25 μm) is obtained for both Ti and TiN without application of rf bias to the wafer pedestal. Contact resistances of the liner barrier film were compared to the control films that were deposited using collimation. The HCM Ti and TiN films show lower contact resistance for both n+ and p+ contacts. The spread in the contact resistances is also minimal, indicating within-wafer bottom coverage uniformity that is better than the control films. The as-deposited TiN acted as a good enough barrier to allow subsequent chemical vapor deposition W fill on these 5:1 AR structures. This is the first demonstrated case of in situ deposition of ionized Ti and TiN in the same chamber without the use of a collimator or a shutter present between the target and the wafer.
Surface superstructure of carbon clusters deposited on graphite during recrystallization
Authors: An B. , Fukuyama S. , Yokogawa K. , Yoshimura M.
Published: July 2002

The recrystallization process of carbon clusters deposited on highly oriented pyrolytic graphite (HOPG) was investigated by scanning tunneling microscopy and high-resolution transmission electron microscopy. The carbon clusters deposited on HOPG at low coverage recrystallized epitaxially by annealing above 1623 K. The carbon clusters deposited at high coverage coalesced to form larger graphitic particles stacked with several layers of hexagonal planes in the annealing temperature range from 1873 to 2773 K. Four types of ringlike superstructures of (∛×∛)R30° of graphite, the circular type, the U-type, and the semicircular types I and II, were identified on the curved surface of these graphitic particles, and were well simulated by a modified interference model.
Robust high current field emitter tips and arrays for vacuum microelectronics devices
Authors: Charbonnier F. M. , Mackie W. A. , Hartman R. L. , Xie Tianbao
Published: July 2002

We seek to identify the most promising materials and geometries for field emitter tips and arrays (FEA) in applications requiring stable high current and conductance in a moderate vacuum. Mo FEAs have been used successfully in relatively high current (50–100 mA) TWTs. But molybdenum has some undesirable characteristics. For several years we have studied field emission from refractory carbides, particularly ZrC, and found that ZrC surfaces have very desirable characteristics for stable high current field emission. We calculate thermal effects and instabilities for five emitter materials and conclude that W or Mo emitters coated with a thin coating of ZrC have the highest current capability, particularly for dc emission. We then calculate β factors for various field emission microdiodes and triodes. We conclude that broad cone angle ZrC/Mo emitters have the highest conductance capability. We then discuss several factors which cause FEA performance to fall short of theoretical calculations in practice. We then review experiments with ZrC field emitters. We discuss individual single crystal ZrC field emitters made from zone refined ZrC single crystal wires, by the standard electrolytic etch technique or by a temperature enhanced field desorption technique which produces moderately sharp tips (50–100 nm) with broad cone half-angles (0.5–0.6 radian). Hundreds of tips have been tested. Noisy but fairly stable emission of 200–300 μA has been achieved at up to 3×10−5 Torr in air. At high vacuum (10−9 Torr) dc currents up to 25 mA and pulsed currents up to 100 mA have been achieved with fairly blunt (r≅100 nm), broad cone angle single tips, in fair agreement with calculations. We have fabricated small 10×10 FEAs made of bulk ZrC cones formed by physical vapor deposition, and show typical I(V) characteristics. Finally, we have coated Mo FEAs with thin ZrC coatings and achieved a 30% reduction in turn on voltage due to the reduced work function of ZrC. Much remains to be done, particularly on the noise, stability, and life of high current ZrC or ZrC/Mo FEAs at various pressures.
Characterization of (Ti, Al)N films deposited by off-plane double bend filtered cathodic vacuum arc
Authors: Cheng Y. H. , Tay B. K. , Lau S. P. , Shi X. , Chua H. C.
Published: July 2002

(Ti, Al)N films were deposited by a new off-plane double bend filtered cathodic vacuum arc technique under a nitrogen atmosphere at room temperature. Scanning electron microscopy and atomic force microscopy were used to observe the surface morphology of the deposited films. X-ray photoelectron spectroscopy was used to determine the composition and bonding structure of the deposited films. A scratch test was used to access the film adhesion. The deposited films are atomically smooth and particle free. The Al/Ti atomic ratio in the deposited films is around 1. The films deposited at the pressure of 1×10−4 Torr are composed of metallic Ti and Al phase and a small amount of (Ti, Al)N phase. For the films deposited at the pressure of 1.5×10−3 Torr, (Ti, Al)N phases are dominant. The scratch test indicates that the critical load increases with increasing deposition pressure up to 1.5×10−3 Torr, then decrease drastically with the further increase of deposition pressure. As substrate bias is increased, critical load increases and reachs the maximum at the bias of 200 V, then decreases at higher bias. The hardness of the deposited films is found to be the main factor that affects the critical load of the thin films.
Transient brightness, current, and voltage characterization of organic light emitting devices
Authors: Norris B. J. , Wager J. F.
Published: July 2002

Transient current–transient voltage [i(t)–v(t)], transient brightness–transient current [b(t)–i(t)], and transient brightness–transient voltage [b(t)–v(t)] analysis are introduced as novel organic light emitting device (OLED) characterization methods. These analysis methods involve measurement of the instantaneous voltage [v(t)] across, the instantaneous current [i(t)] through, and the instantaneous brightness [b(t)] from an OLED when it is subjected to a bipolar, piecewise-linear applied voltage waveform. Employing these characterization methods, two important OLED device physics conclusions are obtained: (1) Hole accumulation at the electron transport layer (ETL)/hole transport layer (HTL) interface plays an important role in establishing balanced charge injection of electrons and holes into the OLED. (2) Hole accumulation at the ETL/HTL interface is more important in establishing the ac conduction characteristics than charge trapping in the ETL.
Profile evolution during polysilicon gate etching with low-pressure high-density Cl2/HBr/O2 plasma chemistries
Authors: Tuda Mutumi , Shintani Kenji , Ootera Hiroki
Published: July 2002

Profile evolution during polysilicon gate etching has been investigated with low-pressure high-density Cl2/HBr/O2 plasma chemistries. Etching was performed in electron cyclotron resonance Cl2/HBr/O2 plasmas as a function of HBr percentage in a Cl2/HBr mixture, using oxide-masked poly-Si gate structures. The linewidth was nominally 0.18 μm, and the spacing between the two neighboring poly-Si lines was varied in the range ∼0.2–10 μm. In addition, the macroscopic open space of the oxide-masked sample was also varied over a wide range from ≈28% to ≈76%. As the HBr percentage in Cl2/HBr is increased from 0 to 100%, the linewidth shift ΔL of poly-Si relative to the mask width (or the degree of sidewall tapering of poly-Si lines) first decreased linearly, passed through a minimum, and then increased considerably at above ∼80%. In Cl2/O2 plasmas without HBr addition, ΔL was almost independent of the microscopic and macroscopic poly-Si open spaces although its value was relatively large; on the contrary, in HBr/O2 plasmas, ΔL increased with an increase of microscopic line spacing and/or the macroscopic open space of the sample. Comparisons of the etched profiles obtained in Cl2/HBr/O2 plasmas with numerical profile simulations indicate that the strongly tapered sidewalls observed at high HBr percentages (≳80%) result from the simultaneous etch inhibitor deposition onto sidewalls during etching; moreover, such inhibitors are predicted to come from the plasma with a large sticking probability of ∼O(0.1). On the other hand, the relatively large ΔL obtained in Cl2/O2 plasmas is considered to be due to intrinsic sidewall tapering, rather than inhibitor deposition arriving from the plasma or redeposition of etch products desorbed from the surface in microstructures. Such intrinsic tapering is discussed in terms of the angular dependence of the Si etch yield.
Structural, electrical, and optical properties of transparent conductive oxide ZnO:Al films prepared by dc magnetron reactive sputtering
Authors: Chen M. , Pei Z. L. , Wang X. , Sun C. , Wen L. S.
Published: July 2002

ZnO:Al/(ZaO) films were deposited on quartz substrates by dc magnetron reactive sputtering from a Zn target mixed with Al. The effect of oxygen flow rate, target to substrate distance, substrate temperature, and Al doping content on the structural, electrical and optical properties of ZAO were investigated. It was observed that the (002) peak position of all films shifts to lower angle comparable to that of bulk ZnO due to the residual stress change with deposition parameters. X-ray photoemission spectroscopy was introduced to analyze the chemical state of Al on the film surface and the results show Al enrichment. The dependences of electrical properties such as resistivity, carrier concentration and Hall mobility on substrate temperature, and Al doping content were measured. The visible transmittance of above 80% and infrared reflectance of above 80% were obtained. The minimum resistivity is 4.23×10−4 Ω cm with the carrier concentration of 9.21×1020 cm−3 and Hall mobility of 16.0 cm2 v1 s−1. The optical band gap was observed to increase with increasing carrier concentration. The probable mechanisms are discussed.
Enhancement on field-emission characteristics of diamondlike coated Mo substrates by redox process
Authors: Lin Chin-Maw , Chiang Shoou-Jinn , Yokoyama Meiso , Chuang Feng-Yu , Wong Wen-Chun , Lin I-Nan
Published: July 2002

We have improved the emission characteristic of diamondlike carbon (DLC)-coated Mo substrates by using a reduction-oxidation (redox) process. The maximum emission current density of the DLC/Mo films increased substantially from 10 to 225 μA/cm2 with the turn-on field decreased from 12.4 to 6.4 V/μm due to redox treatment. Secondary-ion mass spectrometry spectra and x-ray diffraction patterns show that the structure of Mo films was insignificantly changed due to oxidation and reduction, whereas atomic force microscopy and transmission electron microscopy indicate that the roughness increased markedly. The electron emission characteristics of DLC films coated on redox Mo substrates are much better than those of the films coated on normal Mo film, which is ascribed to the increase in the field enhancement factor of the DC films.
High-temperature real-time observation of surface defects induced by single ion irradiation using scanning-tunneling-microscope/ion-gun combined system
Authors: Shimada Kazuyoshi , Ishimaru Tetusya , Yamawaki Takuya , Uchigasaki Makoto , Tomiki Kenichi , Matsukawa Takashi , Ohdomari Iwao
Published: July 2002

A high-temperature scanning-tunneling-microscope (STM)/low-energy ion-gun combined system has been developed in order to clarify the microscopic aspects of annealing processes of ion-irradiated Si surfaces. This system enables us to perform atom-resolved high-temperature STM observation and ion beam irradiation simultaneously in ultrahigh vacuum conditions. Taking great advantage of this system, we have successfully obtained sequential STM images of high-temperature Si(111) surfaces irradiated with 3 keV Ar+ single ions. The STM results have shown that the surface defects induced by single ion irradiation show various changes in size and shape, which is considered to result from diffusion of vacancies and interstitial atoms in the substrates, diffusion of atoms on the surface, and from an anisotropic character of the surface atomic arrangement.
Monitoring lithographic focus and tilting performance by off-line overlay measurement tools
Authors: Ku Chin-Yu , Lei Tan Fu , Cheng Dong-Shieh
Published: July 2002

In this work we present a novel bar-in-bar (BIB) pattern to monitor the focus and tilting of exposure tools and production wafers. The inner and outer bars contain various hole sizes. When defocused, the shrinkage of the smaller patterns is more significant than that of the larger ones, thus causing the center of gravity to shift. Through the organization of the bar patterns, the centers of inner and outer bars shift in opposite directions when defocused. An overlay measurement tool can be used to easily measure the shift between the centers of inner and outer bars. Therefore, a second-order polynomial equation can precisely fit the measured BIB shift. In addition, an accurate and reliable focus value can be obtained with a maximum error of less than 0.05 μm by simply differentiating the fitting equation. The novel BIB has many applications, such as measuring field curvatures for exposure tools and determining best focus related information for production wafers.
Self-aligned process for single electron transistors
Authors: Berg E. W. , Pang S. W.
Published: July 2002

A fabrication technique for single electron transistors is presented. The charge island for the single electron transistor is confined in the z direction by two epitaxial layers serving as tunnel barriers and the lateral confinement in the x-y plane results from the dry etching of a source-drain pillar using an inductively coupled plasma source. The gate is deposited using a self-aligned process with the source contact serving as a shadow mask and separated from the conducting channel by a small gap for closed coupling of gate voltage, reduced leakage current, and high breakdown voltage (approximately −60 V). The designed and measured values of the tunnel resistance of the epitaxial layers were in good agreement.
Inner surface coating of TiN by the grid-enhanced plasma source ion implantation technique
Authors: Liu Bin , Zhang Guling , Cheng Dajung , Liu Chizi , He Rui , Yang Si-Ze
Published: July 2002

An inner surface coating of a tubular sample was realized by a new method of grid-enhanced plasma source ion implantation (GEPSII), which is an extension of previous plasma source ion implantation inner surface modification. In GEPSII, a rf plasma core is produced between a center cathode and a grid electrode, which are coaxially arranged inside the tubular sample. Negative high voltage pulses are applied between the grid electrode and the inner surface of the tubular sample, thus an accelerating field for positive ions can be established between the grid electrode and the inner surface of the sample. In addition, particles of solid matter can be introduced into the rf plasma by sputtering the cathode, thus, it is possible to realize metal ion implantation and film deposition. In this article, the concept of GEPSII and some preliminary measurement results of this method are presented, and TiN films are produced on the inner surface of a tubular sample, which is a cylinder of an automobile. The plasma density profiles and plasma electron temperature inside the sample are measured by a Langmuir probe. It is shown that the axial plasma density profile is rather uniform in GEPSII. TiN films were also deposited on single-crystal silicon substrates, which are arranged on the inner surface of the cylinder.
Electron-beam CARL resist development for 70 nm direct write
Authors: Kirch O. , Elian K. , Falk G.
Published: July 2002

Because of the need of 70 nm structures in the near future, electron-beam (e-beam) lithography as a means for high resolution lithography is discussed mostly for mask or ASIC fabrication but also for the application in standard lithography. Besides the improvement of new e-beam writing concepts including software and hardware enhancement, the development of new resists and processes is a main objective for a high throughput production. To understand the principal reactions that occur during the patterning process we decided to carry out basic examinations based on chemical amplification of resist lines (CARL) [W.-D. Domke et al., Microlithogr. World 42, 2 (1999)] resist materials. The first step was to look at the interaction between the polymer and e-beam. Polymers consisting of chemically identical monomers were synthesized in different molecular ratios and processed as resists without other additives. Detailed investigations of the resists included e-beam patterning with a JEOL JSM-840A/nanobeam pattern generator. The next step was to examine the CAR reaction, i.e., the interaction of the polymer/photoacid generator matrix with the e-beam electrons. Perfluorinated alkysulfonates as PAGs were focused. These compounds generate very strong acids through irradiation. They can be compared, e.g., by their different acid strength, different vapor pressure of the resulting acid, and by their different molecular size. These parameters strongly affect the acid diffusion and consequently the resist resolution as far as the line edge roughness. Within this current article the first complete resist mixtures have been evaluated under process conditions.
Characteristic features of new electron-multiplying channels in a field emission display
Authors: Yi Whikun , Jeong Taewon , Jin Sunghwan , Yu SeGi , Lee Jeonghee , Heo Jungna , Yoo Jibeom , Kim J. M.
Published: July 2002

We have developed a microchannel plate (MCP) to increase the efficiency of a field emission display (FED) by introducing new materials and process technologies. A substrate was constructed with alumina, and channel walls of pore arrays of the MCP were deposited with thin films using electroless plating and sol-gel process. The resulting MCP has been evaluated with a high input current source from a continuous electron beam and from Spindt-type field emitters. Some features of the MCP were also characterized in terms of brightness, anode current, input and output pulse, and focused luminescent spot, in a FED. With the MCP between the cathode and the anode of a FED, the brightness and anode current increased four- to fivefold due to electron multiplication through an array of pores in the device. In addition, the fabricated microchannel plate was found to prevent spreading of electrons emitted from the cathode tips, thus improving both display resolution and picture quality.
Low-dielectric constant bisbenzo(cyclobutene) and fluorinated poly(arylene)ether films as bottom anti-reflective coating layers for ArF lithography
Authors: Chen H. L. , Chu T. C. , Li M. Y. , Ko F. H. , Cheng H. C. , Huang T. Y.
Published: July 2002

In this article, we demonstrate a bottom anti-reflective coating (BARC) layer for ArF lithography. The anti-reflective layers are composed of a commercial low-dielectric constant bisbenzo(cyclobutene) (BCB)- and fluorinated poly(arylene)ether (FLARE)-based films. By adding an optimized etching hard-mask layer, reflectance of less than 1% at the resist/silicon substrate interface can be achieved. BCB and FLARE also have great potential to be used as BARC layers on highly reflective substrates for metal interconnect applications. It is easy to reduce reflectance without adding an extra BARC layer for patterning low-dielectric materials. It is convenient to use this BARC structure in ArF lithography. In this article, suitable etching characteristics and thermal stability of BCB- and FLARE-based BARC layers are also described.
X-ray photoemission spectroscopy study of silicidation of Ti on BF2+-implanted polysilicon
Authors: Chua H. N. , Pey K. L. , Lai W. H. , Chai J. W. , Pan J. S. , Chua D. H. C. , Siah S. Y.
Published: July 2002

Evaluation of fluorine-related species during Ti silicidation on BF2+-implanted polycrystalline silicon (polySi) under different temperatures has been studied using x-ray photoemission spectroscopy (XPS). The silicidation was carried out under sequential anneals from 500 to 700 °C with an interval of 50 °C in an ultrahigh vacuum (UHV) within the XPS chamber. The binding energy and peak intensity for Si 2p, Ti 2p, F 1s, O 1s, B 1s, and C 1s XPS peaks have been measured in the same XPS chamber immediately after the silicidation anneal without breaking the vacuum. The results show that fluorine from the BF2+ implantation is dissociated to form a mixture of SiFx (1⩽x⩽4) and TiFx (x=3,4) -like gaseous species at/near the TiSi2/polySi interface upon silicidation anneal. This can be characterized by the approximately 1.2 eV per Si–F bond chemical shift of the Si 2p core level, and the peak position for Ti 2p core levels with the resolved peaks at 465.1 eV corresponding to the Ti–F bond. The F 1s peaks further confirm the presence of SiFx and TiFx species. As the silicidation proceeds to higher temperatures, the intensity of these reaction species decreases due to their out-diffusion from the thin TiSi2 layer. These findings correlate well with the previously reported results on the void formation in sub-quarter-micron BF2+-implanted Ti-salicided polySi lines [H. N. Chua et al., J. Appl. Phys. 87, 8401 (2000)].
Characterization of self-assembled alkanethiol monolayers using a low-current scanning tunneling microscope
Authors: Wang D. W. , Tian F. , Lu J. G.
Published: July 2002

A low-current scanning tunneling microscope (STM) was used to image ordered alkanethiol self-assembled monolayers (SAMs) on Au (111) surface. The effects of the tunneling current on the STM images of both decanethiol and dodecanethiol SAMs were studied. At low current, with the tip above the sample surface, domain boundaries and ordered alkanethiol molecules can be seen clearly. When the tunneling current was increased, destructive STM images of decanethiol and dodecanethiol SAMs were observed. However, when the tunneling current was reduced back to the original low values, the ordered structures of alkanethiol molecules reappeared. This reversible process suggests that there is no rearrangement in the sulfur head groups under different tunneling current conditions. In this article, we present a model which supports the important role of the alkyl chain in the STM imaging of SAMs. In our model, the medium conductance is a key factor.
Alloy layer disorder in strained-layer InAs/GaInSb/AlSb superlattices with infrared laser applications
Authors: Kitchin M. R. , Shaw M. J. , Hagon J. P. , Jaros M.
Published: July 2002

A large scale investigation into the effects of alloy layer disorder on emission in antimonide-based superlattices is reported. The potential utility of these systems in infrared (IR) optoelectronic technologies is reviewed and issues inhibiting their realization identified. The Ga0.7In0.3Sb alloy layer is modeled using both the conventional virtual crystal approximation and models which describe microscopic disorder, clustering, and atomistic relaxation. The structures have recently been fabricated for IR laser applications and we investigate the influence of the alloy description on the emission line shapes. For each superlattice we find that the emission linewidth and peak height is very sensitive to the microscopic details of the alloy potential. Comparing the various superlattice systems, which differ regarding the InAs layer widths, we find that their linewidth values (eV) are each of the same order of magnitude for a given population of excited carriers. While values show a strong dependence on the period, reflecting large differences in the interband transition probabilities, the relationship between linewidth and excited carrier population does not show a clear correlation with superlattice period. This article demonstrates quantitative links between microscopic disorder and the optical properties of strained-layer superlattices.
Effect of ion bombardment and substrate orientation on structure and properties of titanium nitride films deposited by unbalanced magnetron sputtering
Authors: Guruvenket S. , Mohan Rao G.
Published: July 2002

The effect of substrate orientation and ion bombardment during the growth on the structure and properties of TiN films deposited by reactive unbalanced magnetron sputtering has been reported. Films deposited at a nitrogen partial pressure of 5×10−5 mbar and a current density of 2.50 mA cm−2 were golden yellow in color, characteristic of stoichiometric TiN. The effect of Si(100) and Si(111) substrates on the TiN film along with the substrate bias has been investigated. With an increase in the substrate bias on Si(111) substrate, TiN(111) is the most preferred orientation. On a Si(100) substrate with an increase in the substrate bias, TiN(220) orientation has been observed. The influence of the substrate on the growth of TiN films has been explained in terms of surface energy. The variation of grain size, resistivity, and the internal stress of TiN films as the function of substrate bias have also been investigated.
Preferential orientation of short chain vapor deposited polyaniline thin films on gold
Authors: Xu B. , Choi Jaewu , Dowben P. A.
Published: July 2002

Vapor deposited short chain polyaniline thin films were studied using angle-resolved photoemission spectroscopy. Films grown on two different substrates, oxidized Si surfaces and Au, show distinctly different properties. Some indication of preferential molecular orientation was observed for ultrathin films deposited on Au substrates, but not on the Si substrates with the native oxide surface. Clear indication of metallic character was observed for some of the polyaniline ultrathin films, consistent with recent theory suggesting that alignment of chains parallel with a metal substrate enhance metallicity.