bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal process effects on NiFe and NiFeRh films
Authors: Valletta R. M. , Hwang C. , Lefakis H.
Published: July 2002

The effect of thermal processing on thin films ≲1000 Å of permalloy and a permalloy alloyed with Rh has been examined. Coercivity, anisotropy field, and magnetostriction were measured both before and after annealing for 30 min. The films were exposed to temperatures representative of those employed in thin-film head fabrication, 92 and 185 °C anneals representing photo processes and 240 °C approximating the highest temperatures used during thin-film head processing. Significant changes occurred in the thinner films after the 185 and 240 °C anneals. Changes were observed in both types of films. The largest occurred in the permalloy films. The magnetostriction of both film compositions became significantly more negative after annealing at the higher temperatures, with the change in the Rh alloy films smaller. The changes in properties decreased with increasing thickness for both permalloy and the Rh alloy. Auger electron spectroscopy analysis has shown that the differences before and after annealing at the higher temperatures result from oxidation of the upper (exposed) surface of the films. These studies show that the magnetic properties, especially magnetostriction, are strong functions of the process history of permalloy thin films.
The effects of precoating and bias voltage on the adhesion of reactive arc evaporated TiN and ZrN coatings
Authors: Oh Soo G. , Han Jeon G.
Published: July 2002

The effects of precoating and bias voltage on adhesion have been studied for reactive arc evaporated TiN and ZrN coatings on high speed steel. Pure Ni, Ti, and Zr interlayers were precoated as single or double layers with different thicknesses prior to the deposition of the compound coatings. The adhesion was evaluated by comparing acoustic signals through the scratch test method with incremental applied load. Precoating with a double layer significantly enhanced the adhesion of both TiN and ZrN coatings. A single interlayer precoating also produced an effective improvement of adhesion. The improvement was more pronounced for thicker single interlayers of Ti and Ni in TiN coating. Adhesion was also improved with increasing negative bias voltage for TiN coating without interlayer precoating. The mechanism for the improvement of adhesion by precoating is proposed to be stress accommodation in the interlayer.
Conversion of a vacuum generators model V80H molecular-beam epitaxy system from HgCdTe to fluoride deposition and from 3- to 4-in. wafer handling capabilities
Authors: Bogdon J. M. , Sinharoy S. , Noreika A. J.
Published: July 2002

We have converted a Vacuum Generators V80H molecular-beam epitaxy (MBE) system, originally designed to handle 3-in. diam wafers, to accommodate and process 4-in. diam wafers. The MBE system, which was previously used in the same laboratory for the deposition of HgCdTe films, has been subjected to a thorough cleaning procedure, and is now being used successfully to grow high quality BaMgF4 films on 4-in. silicon wafers. The modification procedure is described in this note.
Direct synthesis of GaAs quantum-wire structures by molecular-beam epitaxy on (311) surfaces
Authors: Nötzel R. , Ploog K.
Published: July 2002

We have developed a new method to directly synthesize GaAs quantum-wire structures by molecular-beam epitaxy. The method is based on the in situ formation of a periodic array of nanometer scale macrosteps or facets by breaking up a surface with high surface energy into facets comprising planes with lower energy. Reflection high-energy electron diffraction (RHEED) directly reveals the formation of such macrosteps on the GaAs (311)A surface which are composed of two sets of (331̄) and (3̄13̄) facets oriented along the [2̄33] direction. The lateral periodicity of 32 Å is determined by the splitting of the (00) streak observed along [2̄33] into sharp satellites and the height of the steps of 10.2 Å by the splitting along its length. RHEED intensity dynamics recorded during growth of GaAs/AlAs multilayer structures show a distinct oscillation at the onset of GaAs and AlAs growth, respectively, due to a phase change of the surface corruption during the first monolayer deposition induced by strain. The whole structure then contains well ordered thicker and thinner channels of GaAs and AlAs forming the quantum wires oriented along [2̄33]. The existence of GaAs quantum-wire structures is confirmed by the pronounced anisotropy of the electronic properties including the conductivity and the excitonic resonances. For application of these new GaAs quantum-wire structures in optoelectronic devices it is important to note that their high luminescence intensity does not degrade up to temperatures as high as 400 K.
Microstructure and stoichiometry dependence of ion beam nitrides as a function of energy and temperature: A comparative study between Si and SiGe
Authors: Hellman Olof C. , Herbots Nicole , Vancauwenberghe Olivier , Culbertson R. J. , Croft W. J.
Published: July 2002

The microstructure and stoichiometry of nitrides formed by direct low-energy ion beam nitridation has been investigated as a function of ion energy and substrate temperature for Si(100) and SiGe/Si(100) films. Cross-sectional transmission electron microscopy, Rutherford backscattering spectroscopy combined with ion channeling and in situ x-ray photoelectron spectroscopy were used. It was established that a substrate temperature of 700 K produces a homogeneous amorphous nitride layer, whereas lower substrate temperatures decrease the incorporation of nitrogen in the film, while causing the formation of a nitrogen-poor amorphous layer beneath the nitride film. The N-to-Si or N-to-(Si+Ge) atomic ratio is found be close to 1.33 at 1 keV and decreases with ion energy. Effects of chemically enhanced physical sputtering of germanium are observed.
Kinetics of morphological change during annealing of amorphous yttria
Authors: Mukherjee S. N. , Aita C. R.
Published: July 2002

We report a time-at-temperature study of air annealing at 700 °C of amorphous yttria films sputter deposited on fused silica. The results show that crystallization was limited (7%). A striking morphological change involved the formation of 2.5 μm-maximum diameter globules. By comparing changes in globule number with maximum diameter, the time-at-temperature ranges for which nucleation+growth and growth+coarsening processes occurred was determined. The globule formation rate initially followed an Arrhenius curve: dNV/dt = (4 × 105/cc s)exp[ − 0.28 × 10−3/s)t]. The activation energy estimated for globule formation was close to that for Y diffusion in yttria.
Molecular-beam experiment for adsorption kinetics and catalytic reactions studies
Authors: Calpini B. , Croci M. , David R. , Monot R.
Published: July 2002

An ultrahigh-vacuum apparatus has been designed to study the chemisorption of molecules on surfaces, as well as chemical reactions catalyzed on small metal particles, by molecular-beam techniques. Two beams of reactant molecules threefold differentially pumped can be aimed onto the sample surface under variable angle of incidence. A mass spectrometer, located at a variable distance from the sample in a separate chamber, detects molecules which have left the surface after interaction. Auger electron and x-ray photoelectron spectroscopies can be used to characterize the sample. The drift time from the source to the detector has been calibrated using supersonic pulsed beams of rare gases; the time resolution of the experiment is about 2 μs. Measurements of the adsorption of CO on Pt(111) and Pt(997) surfaces have been performed. First results using the pulsed beam technique on both surfaces are presented along with results obtained from the Pt(111) surface by thermal helium beam scattering.
Behavior of rigid macromolecules in self-assembly at an interface
Authors: Enriquez Erwin P. , Gray Kimberley H. , Guarisco Victoria F. , Linton Richard W. , Mar Kevin D. , Samulski Edward T.
Published: July 2002

Self-assembly (SA) on gold substrates of α-helical poly(γ-benzyl-L-glutamate) [(PBLG); molecular weight ∼20 000 kd] with a disulfide moiety attached at its N-terminus (PBLGSS) was investigated. The SA films were compared with control experiments using unlabeled physisorbed (PS) PBLG and Langmuir–Blodgett (LB) deposited PBLG monolayers. Characterization of the films included angle-dependent x-ray photoelectron spectroscopy, reflection–absorption Fourier transform infrared spectroscopy, ellipsometry, and contact angle measurements. For PBLGSS, a SA monolayer was formed wherein the α-helical conformation was retained and the polypeptides were preferentially bound to gold through the disulfide moiety. This terminal bond to the substrate results in a nonplanar distribution of helix axes (i.e., on average tilted up from the gold surface). This is different from the unlabeled PBLG controls, PS film and LB monolayers, wherein, respectively, less polymer was adsorbed and the helices lie in the plane of the gold substrate. Furthermore, polypeptide aggregation in the solution (e.g., in dichloromethane or 1,4-dioxane) appears to have an influence on the self-assembling behavior of these macromolecules relative to known nonaggregating solvents (N,N-dimethylformamide).
Secondary ion mass spectrometry time of flight and in situ x-ray photoelectron spectroscopy studies of polymer surface modifications by a remote oxygen plasma treatment
Authors: Lianos L. , Parrat D. , Hoc Tran Quoc , Duc Tran Minh
Published: July 2002

Surface modifications induced by a remote oxygen microwave plasma on three different polymers (LDPE, PS, PMMA) have been extensively investigated in situ by x-ray photoelectron spectroscopy (XPS) and, after transfer in atmosphere, by time of flight secondary ion mass spectrometry (TOF SIMS). By a direct transfer from the plasma chamber to the XPS spectrometer the chemical functionalities introduced on the surface of the polymeric substrate are identified and quantitatively determined. Furthermore, high resolution molecular analysis by TOF SIMS allows a better understanding of the chemical changes induced by the oxygen plasma. The information gathered from the two techniques permits us to propose oxidation mechanisms of the polymer surfaces. The relative density of ground state atomic oxygen O (3P) in the remote discharge is shown to be of fundamental importance for the initiation of the oxidation. This species is responsible for the formation of radicals from which are further produced highly oxidized functionalities (O—C=O, O2C=O). Specific sites of oxidation for the three polymers and a depolymerization mechanism for PMMA are evidenced by TOF SIMS analysis.
Long-term stability of Bayard–Alpert gauge performance: Results obtained from repeated calibrations against the National Institute of Standards and Technology primary vacuum standard
Authors: Filippelli A. R. , Abbott P. J.
Published: July 2002

This article presents and briefly discusses information on the long-term stability of the sensitivity of Bayard–Alpert ionization gauges with time and use, derived from an analysis of data for Bayard–Alpert gauge calibrations performed at the National Institute of Standards and Technology over a ten year period.
Discharge characteristics of a facing target sputtering device using unbalanced magnetrons
Authors: Muralidhar G. K. , Musil J. , Kadlec S.
Published: July 2002

This article presents the details of our investigations on the characteristics of a facing target sputter discharge using two highly efficient unbalanced magnetrons with electromagnetic coils. The variation of ignition and extinction pressures has been studied as a function of the current in the coils (I1 and I2) in both the magnetrons at two intertarget distances 290 and 125 mm, respectively. These studies have been carried out in closed as well as cusp field configurations and the results are compared. A negative resistance region has been observed in the discharge characteristic in the cusp field at longer intertarget distances (290 mm), which has been explained on the basis of electron trapping efficiency. Although the closed field has been found to be advantageous in achieving the lower pressure operation possible (0.01 Pa), deposition rates are relatively higher (about 20%) in the cusp field.
Surface wave operation mode of the slot antenna microwave plasma source SLAN
Authors: Werner F. , Korzec D. , Engemann J.
Published: July 2002

A new slot antenna concept allows the generation of large volume 2.45 GHz discharges. The microwave power is coupled from an annular waveguide (ring cavity) through ten equidistantly positioned resonant coupling slots into the quartz plasma chamber. Langmuir double probe axial distribution measurements of the electron density and temperature are performed for argon, helium and nitrogen discharges in a power range from 120 to 1200 W and a pressure range from 10 to 150 Pa. Characteristic differences in the discharge behavior for the various gases are presented. With argon a surface wave at the plasma-quartz interface can be excited, already at 200 W. The resulting plasma column can extend up to 450 mm in length along the tube with 160 mm diameter. The surface wave mode is identified as a m=5 mode by visual inspection of the plasma formation and by recording the azimuthal electric field distribution. In contrast to argon, for helium and nitrogen no surface wave generation for power levels up to 1200 W are observed. Within the investigated power range both gases show a diffusion controlled variation of the electron density. This is verified by fitting the axial density data to the time-independent diffusion equation for helium and nitrogen and to a simplified surface wave model for argon.
Infrared redistribution of D2 and HD layers for inertial confinement fusion
Authors: Collins G. W. , Bittner D. N. , Monsler E. , Letts S. , Mapoles E. R. , Bernat T. P.
Published: July 2002

We describe a technique to form uniform solid D2 or HD layers for inertial confinement fusion targets. Pumping the infrared (IR) collision induced vibration–rotation band in solid D2 or HD redistributes the solid into a relatively uniform layer depending on the IR intensity profile. Measured redistribution time constants are near the calculated values. We have observed redistribution time constants in HD up to ten times smaller than the DT value.
Anodic fluoride on HgMnTe
Authors: Weiguo Sun , Kosyachenko L. A. , Rarenko I. M.
Published: July 2002

The formation of anodic fluoride on HgMnTe has been studied and the composition of the interface and the chemical depth profiles have been characterized by x-ray photoelectron spectroscopy technique. Comparison results between HgMnTe and HgCdTe were given. Metal–insulator–semiconductor devices containing an anodic fluoride layer and a ZnS coating were fabricated and characterized. The mixture of anodic fluoride and thin native oxide layer may create a good interface for HgMnTe passivation.
Growth of very low temperature polysilicon film by remote plasma-enhanced chemical-vapor deposition
Authors: Oh Jin-Ho , Park Chong-Yun , Cho Nam-Ihn , Nam Hyoung Gin
Published: July 2002

Silicon thin films have been prepared on SiO2 substrates by remote plasma-enhanced chemical-vapor deposition using H2/SiH4/Ar gases. The film properties were found to critically depend on the variations of deposition parameters, which include the SiH4 flow rate with a fixed H2 flow rate, Ar flow rate, and radio frequency (rf) power. The substrate temperature was fixed at 280±5 °C. The best quality polysilicon film was obtained when the rfpower/Ar ratio was set near 0.5±0.05. In addition, the electrical mobility was observed to increase with the increasing SiH4 flow rate. The effects of the deposition parameters variation were discussed to properly account for the observed properties of the thin films studied.
Effect of plasma and thermal annealing on chemical vapor deposition dielectrics grown using SIH4–H2O2 gas mixtures
Authors: Gaillard F. , Brault P. , Brouquet P.
Published: July 2002

Silicon dioxide has been deposited at low pressure (1 Torr) and low substrate temperature (0 °C) by chemical vapor deposition (CVD) using SiH4 and hydrogen peroxide (H2O2) concentrated at 30% or 60%. The effect of solution concentration on film properties has been investigated: characterization of the deposited films has been carried out by ex situ Fourier transform infrared spectroscopy, ellipsometry, and mechanical stress measurements. For shallow trench isolation applications, the physical and electrical properties of the CVD oxide must be close to those of a thermal oxide. Such properties can be obtained by in situ annealing.
Characterization of arclike Ti vapor plasma on the high-voltage electron-beam evaporator
Authors: Kajioka H.
Published: July 2002

The generation mechanisms of vaporization and electron emission from the melted evaporator in an arclike Ti vapor plasma are different from those in typical cold cathode arc plasma, but the ionization and excitation processes of Ti vapor by electron impact are similar. The plasma expansion is strongly affected by the anode. However, this high-density plasma can be controlled by the anode voltage and/or emission current of an electron-beam gun. The relationship between the plasma parameters and the optical emission spectrum consisting of only Ti I (neutral) and Ti II (Ti+) is investigated. When anode voltage Va increases from 20 to 60 V at the anode current Ia 30 A, Ji increases from 6 to 12 A/m2 while Rd decreases from 1.4 to 1.0 nm/s at the distance 0.45 m from the evaporator, and flux ionization increases from 40% to 100%. The content of the high excited species of Ti increases. On the other hand, when Ia increases from 10 to 60 A at Va 30 V, Ji and Rd increases from 4 to 38 A/m2 and from 0.8 to 2.2 nm/s, respectively, and flux ionization increases from 20% to 80%. The content of the high excited species of Ti increases, which suggests the formation of a “potential hump” due to positive space charge. The calculated ion and excited species production rates (where the minimum ion production rate required to sustain this plasma,2.7×1024 ions/m3 s, is much higher than that to sustain a typical glow discharge,7.6×1020 ions/m3 s) are related to Ji and the optical emission intensity, respectively. Furthermore, the behavior of Ji agrees with that of the optical emission intensity of Ti II (376.0 nm).
Model for hydrogen desorption in SiGe(100) films
Authors: Vizoso J. , Martı́n F. , Suñé J. , Nafrı́a M.
Published: July 2002

A model to describe hydrogen desorption from SiGe(100) that takes into account the nature of the surface bonding is presented. It is based on the presence of three dimer types in the SiGe(100) surface (Si–Si, Ge–Ge, and Si–Ge), in which there is a thermodynamic preference of hydrogen atoms to pair up before the desorption reaction. The desorption kinetics are, therefore, assumed to be controlled by the population of paired hydrogens in the three dimer types, according to a first-order law. It is also assumed that diffusion, which tends to drive the occupancy of hydrogen atoms in the dimers towards the thermodynamic equilibrium distribution, is not instantaneous. The comparison with experimental results shows that desorption is a diffusion limited process.
Evaluation of plasma and thermal sources for atomic hydrogen-assisted epitaxy of InP
Authors: LaPierre R. R. , Thompson D. A. , Robinson B. J.
Published: July 2002

Homoepitaxial layers of InP have been grown on (100) InP substrates by gas source molecular beam epitaxy while simultaneously exposed to an atomic hydrogen flux produced either by plasma or by thermal cracking. The thermal H-assisted growths were performed with various H fluxes, H2 cracker cell temperatures, PH3 cracker cell temperatures, annealing conditions, and Be doping levels. Photoluminescence and Hall effect studies indicate improved optical and electrical properties of the InP layers grown in the presence of H as compared to layers grown by conventional epitaxy without H. This improvement is attributed to a reduction in point defects due to the removal of unwanted phosphine cracker products, such as P4, from the sample surface during growth by reaction with H. The reconstructed 2×1 H-terminated surface may also reduce P vacancy defects due to the absence of the missing phosphorus dimer row present on the conventional 2×4 surface. Problems associated with donor impurity contamination, which increased with thermal source temperature, were avoided by use of the plasma source.
Structural and compositional studies of a-Si,C:H thin films obtained by excimer lamp chemical vapor deposition from acetylene and silane
Authors: Redondas X. , González P. , León B. , Pérez-Amor M. , Soares J. C. , da Silva M. F.
Published: July 2002

Amorphous silicon–carbon thin films were obtained on silicon and steel substrates, by irradiating a gas mixture of Ar-diluted silane and acetylene by Xe2* excimer lamp in a reaction chamber. The influence of the deposition parameters on film properties was analyzed by different techniques. Film composition was determined by Rutherford backscattering spectroscopy and elastic recoil detection analysis and the structure of the material was studied by infrared and Raman spectroscopies, x-ray photoelectron and Auger electron spectroscopies. Thickness and refractive index were evaluated by ellipsometry. Structural studies reveal that carbon and silicon are present in the films mainly forming homonuclear and hydrogenated bonds. Compositional analyses indicate high carbon concentrations and only slight variations for dramatical changes of precursor gas mixture composition. Lamp power tuning affects the growth rate and film density. Moreover, oxygen is incorporated when the layers are exposed to the atmosphere forming silicon oxides.
Modeling of GaN hydride vapor phase epitaxy
Authors: Meyyappan M.
Published: July 2002

A reactor model for the hydride vapor phase epitaxy of GaN is presented. The governing flow, energy, and species conservation equations are solved in two dimensions to examine the growth characteristics as a function of process variables and reactor geometry. The growth rate varies with GaCl composition but is independent of NH3 and H2 flow rates. A change in carrier gas for Ga source from H2 to N2 affects the growth rate and uniformity for a fixed reactor configuration. The model predictions are in general agreement with observed experimental behavior.
Antireflective coating on TeO2 crystal for the high power acousto-optic modulator
Authors: Park J. H. , Park Y. J. , Hwang Y. M. , Kim Y. H. , Lee J. H. , Hwangbo C. K. , Cho H. J.
Published: July 2002

The purpose of this research is to develop broadband antireflection (A/R) coating for a high power acousto-optic modulator with the following specifications: the substrate material is TeO2 and the requirement of T (transmittance) for both sides greater than 98% in the spectral region 410–700 nm with laser power damage threshold is greater than 40 W/mm2. The technology of A/R coating is based on the conventional method of nonreactive evaporation from electron beam gun sources oxides of Zr (ZrO2 films as a layer with high refractive index) and Si (SiO2 films as a layer with low refractive index), and YF3 (yttrium fluoride) films on TeO2 crystals substrate with pre-cleaning by using an ion beam gun (Refs. Reference 1 and Reference 5). The refractive indices of the mentioned films are: n(ZrO2)=1.96–1.98, n(SiO2)=1.45–1.46, and n(YF3)=1.48–1.50 (Ref. Reference 2). In all cases properties of A/R coating are strongly dependent on the method of surface cleaning, type of polishing, and even the bulk properties of the substrate.
SiO
2
etching in magnetic neutral loop discharge plasma
Authors: Chen W. , Itoh M. , Hayashi T. , Uchida T.
Published: July 2002

Neutral loop discharge (NLD) plasma, which has attractive characteristics in both plasma production and spatial controllability, was successfully applied to large-wafer etching process, yielding satisfactory uniformity. Comparison of the etching characteristics in the NLD plasma with those in the inductively coupled plasma (ICP) plasma which was generated without magnetic field in the same device was made. SiO2 etch rate and selectivity to photoresist and Si in the NLD plasma were remarkably improved, comparing with those in the ICP plasma in a pressure range of 0.1–1 Pa. In the application of SiO2 etching process using the NLD plasma, a hole pattern of a high aspect ratio, 0.35 μm diameter and 2 μm depth, was successfully fabricated with a resist mask in an Ar (90%) +C4F8 (10%) plasma at 0.4 Pa. The selectivity to Si at the hole bottom was higher than 30. The etched profile was almost vertical (89°–90°) and the deviation of the SiO2 etch rate was within 3% on 200 mm wafer.
Reactive ion etching for AlGalnP/GaInP laser structures
Authors: Juang Y. Z. , Su Y. K. , Chang S. J. , Huang D. F. , Chang S. C.
Published: July 2002

To fabricate the AlGaInP/GaInP strained-multiple-quantum well laser, the reactive ion etching of GaAs, GaInP, AlGaInP, and AlInP in BCl3/Ar discharges was investigated as a function of plasma parameters such as power, pressure, gas flow rate, and reactive composition, as well as etching time. Photoluminescence and Auger electron spectroscopy measurements were used to characterize the damage and surface residues caused by reactive ion etching. We have achieved a highly selective etching of GaAs with underlying GaInP. Selective etching of GaInP with AlInP and a smooth etching surface were also achieved.
Deposition and characterization of gold thin films on Si by CF4+O2 gas microwave plasma
Authors: Taniguchi Yasuyuki , Shin-mura Tadashi
Published: July 2002

Thin films of Au deposited on Si[(100), n type] wafers using a solid Au source and CF4+O2 microwave plasma were studied. Solid Au heated at 200 °C in a vacuum crystal reactor was vaporized in a CF4+O2 microwave (2.45 GHz power 200 W) plasma flow, and the Au film was deposited on a Si wafer heated to 270 °C in a low-pressure (10 mTorr) O2 atmosphere. The density of Au in this film was about 91.7% as analyzed by x-ray photoelectron spectroscopy, and the film resistivity was 2.8 μΩ cm, which is almost the same as that of the initial bulk Au (2.4 μΩ cm). The deposition mechanism was deduced. The heated solid Au reacts with O2 and (CF2)n from the CF4+O2 microwave plasma, and then the Au is converted into AuO(CF2)n. This Au compound carries Au atoms to the vacuum chamber. In the O2 atmosphere, vaporized AuO(CF2)n is oxidized and changed into oxides such as AuO and COFx. AuO is deposited on the Si wafer heated to 270 °C, and then reduced into Au and O2 by heating. This process results in a high purity deposited gold film.
Influence of surface impurities on plasma-driven permeation of deuterium through nickel
Authors: Hatano Yuji , Nakamura Hirofumi , Furuya Hirotaka , Sugisaki Masayasu
Published: July 2002

The plasma-driven permeation behavior of deuterium through nickel membrane was examined in the temperature range from room temperature to 723 K. The modification of its surface impurities by exposing it to the hydrogen plasma was examined with Auger electron spectroscopy. The influence of surface impurities on the penetration and recombination behavior of deuterium atoms at the nickel surface is discussed.
Synchrotron radiation induced SiC formation on Si substrate employing methanol and H radical
Authors: Ikeda M. , Inayoshi M. , Hori M. , Goto T. , Hiramatsu M. , Hiraya A.
Published: July 2002

A novel system for a material processing was developed using synchrotron radiation (SR) induced reaction. This system consisted of a SR, a radical source with a microwave plasma for an injection of radicals, and a CO2 laser for heating a substrate. Film formation was performed using this system. CH4 and CH3OH were used as a source gas and H radicals were injected by the radical source during film formation. The synthesized films were characterized by an atomic force microscope, a micro Auger electron spectroscopy, and a Fourier transform infrared absorption spectroscopy. CH3OH gas was found to be dissociated by an irradiation of SR. When CH3OH gas was employed without H radical injection, a carbon film was formed only in the area of SR irradiation on Si substrate. Using SR irradiation employing CH3OH gas with H radical injection, nuclei of silicon carbide (SiC) were successfully formed in the area of SR irradiation on Si substrate at a temperature of 800 °C. The mechanism of SiC nucleation induced by SR irradiation is discussed.
High-performance x-ray detector for appearance potential spectroscopy
Authors: Rangelov G. , Ertl K. , Passek F. , Vonbank M. , Bassen S. , Reinmuth J. , Donath M. , Dose V.
Published: July 2002

A high-performance detector for soft x-ray appearance potential spectroscopy is described. It basically consists of an alkali halide photon-to-electron converting layer evaporated onto a self-supporting amorphous carbon foil. This combination absorbs the low energy photons thereby increasing the signal-to-noise ratio. Further improvement of the signal-to-noise ratio is achieved by an additional x-ray filter. The choice of filter and converter material depends on the characteristic radiation of interest. The electrons emitted from the converter are detected by means of a microchannel plate. With this detector a signal-to-noise ratio of 150 was obtained at the diamond appearance potential spectroscopic peak for 5 mC charge per point.
Surface-mediated reaction pathways of 2,4-pentanedione on clean and oxygen covered Cu (210)
Authors: Nigg H. L. , Ford Laura P. , Masel R. I.
Published: July 2002

2,4-Pentanedione, also called acetylacetone (Hacac) is a precursor that has been considered for copper etching, or as a carrier for copper in copper deposition. Generally, 2,4-pentanedione is less effective than other similar molecules. In this article, temperature-programmed desorption was used to examine the decomposition of acetylacetone adsorbed on clean and oxygen precovered Cu (210) to see if we could understand how the chemistry of 2,4-pentanedione is different than that of another species, hexafluoroacetylacetone. On the clean surface, several reaction pathways were found including decomposition and desorption of 2,4-pentanedione. Most notable was that 2,4-pentanedione lost a methyl group below 300 K. By comparison hexafluoropentanedione is stable on an oxidized copper surface to 600 K. These results show that 2,4-pentanedione decomposes at temperatures below that for formation of volatile copper species. In contrast, hexafluoropentanedione is stable to temperatures above where the volatile copper species desorbs. We suggest that the difference in stability of the two molecules leads to the difference in etching characteristics that has been observed previously.
Ferroelectric SrBi2Ta2O9 thin film deposition at 550 °C by plasma-enhanced metalorganic chemical vapor deposition onto a metalorganic chemical vapor deposition platinum bottom electrode
Authors: Seong Nak-Jin , Choi Eun-Suck , Yoon Soon-Gil
Published: July 2002

Ferroelectric bismuth-layer SrBi2Ta2O9 (SBT) thin films were prepared on Pt/SiO2/Si substrates by plasma-enhanced metalorganic chemical vapor deposition. The platinum bottom electrode deposited by metalorganic chemical vapor deposition shows a dense smooth state after deposition of SBT films and prevents bismuth diffusion into the platinum layer. The c-axis oriented SBT films were crystallized at a deposition temperature of 550 °C. The dielectric constant and dissipation factor of SBT films are 310 and 0.08, respectively, at 100 kHz. The remanent polarization and the coercive field obtained for 180 nm thick Sr0.9Bi2Ta2O9 films deposited at 550 °C were 15 μ/cm2 and 50 kV/cm, respectively, at an applied voltage of 5 V. The leakage current density was about 5.0×10−7 A/cm2 at 250 kV/cm. The films showed fatigue-free characteristics up to 7.0×109 switching bipolar pulses under 5 V.
Deposition of amorphous nitrogenated carbon films using an alternate plasma deposition method in a dual electron cyclotron resonance-radio frequency plasma
Authors: Hong Junegie , Turban Guy
Published: July 2002

In this article, we present a new method for the synthesis of amorphous nitrogenated carbon films using an alternate CH4 plasma deposition/subsequent N2 plasma treatment, so-called alternate plasma deposition (APD), in a dual electron cyclotron resonance (ECR)-rf plasma. The nitrogen to carbon ratio in the film surface deposited by this method, estimated by x-ray photoelectron spectroscopy (XPS), is considerably higher, by about a factor of 2, than that obtained in the film deposited from a conventional CH4/N2 plasma. From infrared spectroscopy it is shown that the APD film has the more enhanced disordered phase, which is accompanied by an increase of the amount of sp2 hybridized carbon-nitrogen bonds, as shown by XPS spectra.
Thickness determination of metal thin films with spectroscopic ellipsometry for x-ray mirror and multilayer applications
Authors: Liu Chian , Erdmann J. , Maj J. , Macrander A.
Published: July 2002

Sputtered thin film and multilayer x-ray mirrors are made at the Advanced Photon Source (APS) deposition lab for the APS users. Film thickness calibrations are carried out using in situ and ex situ spectroscopic ellipsometry, interferometry, and x-ray reflectometry. Here, we present a systematic study of thickness and optical constant determination of sputtered thin films of Au, Pt, Pd, Rh, Cr, Cu, as well as W and C, using in situ ellipsometry. Multiple data sets were obtained for each film material with incremental thicknesses and were analyzed with their correlation in mind. Results are compared with those obtained from interferometry and x-ray reflectivity measurements. The applications and limitations of spectroscopic ellipsometry for metal thin films are discussed. Observations of a relaxation effect of a Rh/Si film and a difference in growth mode in the Cr/Si system compared with other metal/Si systems are presented.
Visible and infrared photochromic properties of amorphous WO3−x films
Authors: Mo Yeon-Gon , Dillon R. O. , Snyder P. G.
Published: July 2002

The photochromic properties of sputtered amorphous tungsten oxide (a-WO3−x) films have been studied. The a-WO3−x films, prepared under different oxygen partial pressures, were irradiated with ultraviolet (UV) light at room temperature, and the transmission decrease of the films was measured. We used ellipsometry for the first time with and without UV irradiation to extract the optical indices n and k of magnetron direct-current sputtered films in the VIS/IR wavelength region. We have applied for the first time the Cauchy–Lorentz model for simulating the photochromic properties of the irradiated a-WO3−x films. The results are consistent with previous reports showing that oxygen deficiency is very important in determining the photochromic properties of the a-WO3−x films.
Wide band gap amorphous hydrogenated carbon films grown by plasma enhanced chemical vapor deposition
Authors: Convertino A. , Visconti P. , Cingolani R.
Published: July 2002

We have fabricated amorphous hydrogenated carbon films by rf plasma enhanced chemical vapor deposition with very low ion bombardment energy. We demonstrate that the optical gap of the films can be tuned in a wide range, from 3.46 up to 4.95 eV, i.e., close to the diamond gap (5.5 eV), by proper control of the negative dc self-bias voltage. This behavior suggests that a dramatic reduction in the content and clustering of the sp2 sites occurs by lowering the ion bombardment energy.
Optimization of the reflectivity of magnetron sputter deposited silver films
Authors: Vergöhl M. , Malkomes N. , Szyszka B. , Neumann F. , Matthée T. , Bräuer G.
Published: July 2002

Silver films were deposited using direct current (dc) and midfrequency (MF) magnetron sputter deposition processes on floatglass in order to achieve maximum reflectivity over the entire visual and infrared spectral range. The films were investigated by means of ex situ and in situ spectroscopic ellipsometry, spectral photomety, electrical conductivity measurements, and atomic force microscopy. The following deposition parameters were varied: midfrequency and dc technique, power density, sputtering pressure, substrate temperature, sputtering gas (Ar, Kr, Ne), oxygen residual gas, and film thickness. With the aid of in situ spectroscopic ellipsometry, it can be shown that for certain process parameters an optimum layer thickness exists for achieving a maximum reflectivity in the visual spectral range. With increasing thickness, optical losses which are due to the formation of larger grains come into play. This optimum layer thickness is smaller for the films deposited by MF sputtering, indicating a smoother surface and smaller grain sizes compared to that of the dc mode. As a maximum value, a reflectivity of R=99.3% is achieved, which is close to the theoretical value, which was determined from the Drude fit parameters with respect to the resistivity. The resistivity of this film was found to be ρ=2.4 μΩ cm. The measured reflectivity of the sputter deposited films is comparable to e-beam evaporated silver films.
Experiments with a thin-walled stainless-steel vacuum chamber
Authors: Nemanič Vincenc , Šetina Janez
Published: July 2002

The application of a reasonably thin stainless-steel wall has been recently suggested as an alternative approach in ultra-high-vacuum (UHV) chamber construction, since the hydrogen outgassing rate qout can be decreased much easily to the level required to reach UHV and EXV. Two identical stainless-steel chambers (AISI type 304, volume 12 l) with uniform wall thickness (0.6 mm) were constructed. Each was equipped with a miniature ion-getter pump and spinning rotor gauge (SRG) thimble. They were pumped down and initially degassed by a moderate bakeout (2.5 h, 150 °C) using a turbomolecular pump system. The gas accumulation method was applied for the determination of qout and the total amount of released gases. A capacitance manometer was used during bakeout but a SRG was applied after the chamber was sealed off. The qout at room temperature after initial bakeout was in the order of ≅3×10−12 mbar l/(cm2 s). SRG measurements of qout at 50 °C over several days showed a tendency of slight decrease. The bakeout of the chambers was being repeated in a duration of 72 h at 200 °C. The amount of released hydrogen was much smaller than expected, whereas the decrease of qout was noticeable. In fact, it was one tenth of the value before the bakeout. The results show the benefit of using a moderately thin wall and agree with the model of recombination-limited hydrogen outgassing from stainless steel.
Adsorption probabilities of CO on O–ZnO: A molecular beam study
Authors: Becker Th. , Boas Ch. , Burghaus U. , Wöll Ch.
Published: July 2002

We present measurements of initial adsorption probabilities, S0, as well as its coverage dependence, S(ΘCO), of CO on oxygen terminated ZnO(0001). The impact energies of the CO (48 meV<Ei<750 meV) and surfaces temperature (75 K<TS< 220 K) have been varied. The shape of the coverage dependent adsorption probability curves indicates the presence of precursor mediated adsorption. The heat of adsorption has been determined to (7–2 ΘCO) kcal/mol by assuming a pre-exponential factor of 1×1013 l/s.
Rutherford backscattering/channeling and transmission electron microscopy analysis of epitaxial BaF2 films on Ge and InP
Authors: Phillips J. M. , Feldman L. C. , Gibson J. M. , McDonald M. L.
Published: July 2002

We have used Rutherford backscattering/channeling and transmission electron microscopy to study the epitaxial growth of BaF2 vacuum deposited onto (100) and (111) surfaces of InP and Ge. We have observed no epitaxy in BaF2 on Ge(100), and only poor quality growth on InP(111). Both the BaF2/InP(100) and BaF2/Ge(111) systems show excellent epitaxy. For these latter two cases the epitaxial quality depends strongly on substrate temperature. Even though a large lattice mismatch exists TEM analysis indicates that for BaF2/Ge(111) neither are there misfit dislocations at the interface nor is the structure coherent.
The magnitude and significance of proximity effects in electron image projector defined layers
Authors: Nicholas K. H. , Ford R. A. , Brockman H. E. , Stemp I. J.
Published: July 2002

Electron image projection is an attractive technique for making submicron integrated circuits (IC) but long and short range proximity effects cause some pattern distortion. Long range proximity effects have now been measured and the significance of long and short range effects to IC fabrication assessed. Long range proximity exposure effects due to re-entrant electrons are sufficiently uniform for local corrections to be unnecessary. With automatic proximity correction IC patterns could be scaled down to below 0.5 μm (1 μm pitch) even with single level resist and 20 keV electrons.
Electron beam fabrication of high resolution masks
Authors: Kenty J. L. , Puzio L. C. , Schauerte F. J.
Published: July 2002

A mask set was fabricated with electron beam lithography using conventional and novel pattern replication techniques. Minimum feature size on the high resolution layer was 0.5 μm. The masks were later used for deep ultraviolet (UV) contact lithography to produce working MOSFET’s with submicrometer channel lengths. Two 0.5 μm level masks were fabricated on quartz plates, one each by two techniques: conventional chromium wet etching, and a new technique utilizing ion implanted polymethyl methacrylate (PMMA) as the masking medium. In this unconventional method, a PMMA coated quartz plate was exposed by an electron beam and developed to leave 0.5 μm features on a clear background. The subsequent bombardment of the patterned PMMA with 200 keV Si+ created a film which is opaque to near and deep UV, making it a suitable masking medium for conventional and deep UV photolithography. During the ion bombardment, the PMMA undergoes significant structural change, becoming harder, optically denser, and more adherent to the quartz substrate. A 0.5 μm feature size mask of the same polarity was also made using electron beam patterning of PMMA and wet etching of the underlying chromium. A mask set was also fabricated with a minimum feature size of 1.0 μm. In this level, the 1 μm clear areas were surrounded by opaque chromium areas after wet chemical etching. This mask set was used for conventional contact photolithography in the fabrication of working NMOS devices.
Design parameters for a small storage ring optimized as an x-ray lithography source
Authors: Grobman Warren D.
Published: July 2002

This paper examines the design parameters for a ‘‘compact storage ring’’ which is matched well to x-ray lithographic requirements, but is as small as possible. This calculation uses a model of a lithographic system which obtains its input parameters from a technology of mask, resist and beam line based on the IBM program at the Brookhaven National Laboratory vacuum ultraviolet electron storage ring. Based on this lithographic system, we model exposure throughput as a function of storage ring parameters to understand which storage ring designs provide adequate but not excessive soft x-ray flux in the lithographically important region. Our scan of storage ring sources will cover a wide range of energies and magnetic fields, to permit consideration of superconducting as well as more standard strong- or weak-focusing designs. Furthermore, we will show that the results of the calculations presented here can be scaled in a simple way to cover a wide range of x-ray lithography system assumptions.
Negative resist profiles in x-ray lithography
Authors: Suzuki Yoshiki , Yoshioka Nobuyuki , Yamazaki Teruhiko
Published: July 2002

The processing characteristics of a negative resist (CPMS) exposed with a x-ray exposure system are studied by a comparison between developed profiles and calculated results of absorbed energy in the resist. In fine lines, reduction in volume is caused by vertical and horizontal shrinkage. In patterns which cover large areas, where the resist is fixed to the substrate by the adhesion between the resist and the substrate, the reduction in volume is mainly caused by the vertical shrinkage, while the horizontal shrinkage causes deformation of the profile at the pattern edge. This fact means that the normalized thickness for the large patterns agrees with the volume reduction ratio for the fine lines. These results are applied to a simulation program to estimate the profiles of the negative resist exposed with a x-ray exposure system. The program is based on the sensitivity curve of the resist. The theoretical results calculated with the program agree well with the experimental results in the case where penumbral shadows due to mask to wafer gap exist.
The interface between (100) InP and epitaxially grown Al
Authors: Houzay F. , Henoc P. , Bensoussan M. , Barthe F.
Published: July 2002

The properties of epitaxially grown Al on InP(100) are investigated by in situ classical surface techniques and by ex situ TEM and x-ray diffraction. Particular emphasis is put on TEM which clearly shows the growth of Al monocrystalline islands confirming the RHEED and UPS results. In addition, TEM reveals microtopographical properties as well as more detailed aspects of the overlayer. On the basis of these observations, three stages are identified in the growth mechanism: up to a monolayer, a condensation phase with chemical reaction at the interface, then an island growth by diffusion relieved by coalescence leading to, finally, a uniform monocrystalline Al film. Although at the early stages of island growth two crystallographic orientations of Al are found, the final film is single crystal.
SiH4 doping of MBE GaAs and AlxGa1−xAs
Authors: Briones F. , Golmayo D. , González L. , de Miguel J. L.
Published: July 2002

The possibility of using SiH4 as a cold source of Si dopant during MBE growth of GaAs and AlxGa1−xAs has been explored. Layers of these materials grown under SiH4 doping beam showed good electrical characteristics and LPE quality photoluminescence. Neither accumulation nor memory effects have been observed but the overall doping efficiency is low (<10−3) and strongly dependent on growth parameters such as the As4/Ga or As2/Ga and the SiH4/Ga flux ratios.
Measurements of electron range and scattering in high voltage e-beam lithography
Authors: Mankiewich P. M. , Jackel L. D. , Howard R. E.
Published: July 2002

Proximity effect from electron scattering is a major limitation to using e-beam lithography for high density, submicron patterns. Conventional beam writers operate near 20 keV where the range of the backscattered electron energy distribution is about 2 μ, comparable to the feature size in integrated circuits. Exposure from backscattered electrons creates complex interactions between the exposures of adjacent features and requires extensive computation for correcting the local dose. We report experimental measurements of both the magnitude and range of the backscattered electron energy distribution in resist on a Si substrate for beam energies (E) of 20, 40, 60, and 120 keV. The measurements were made using exposure of a 0.1 μ thick PMMA resist layer to determine constant deposited energy contours. The ratio of the integrated energy deposited in the resist by the backscattered electrons to that deposited by the primary electrons, ηE is found to be about 0.8 and is insensitive to energy. The range of the distribution increases from 2 μ at 20 keV to 43 μ at 120 keV following an E1.7 behavior. The long range at high energies greatly simplifies proximity calculations since the exposure can be averaged over areas much larger than the feature size. The proximity effect becomes a relatively uniform background dose without the local pattern distortions characteristic of conventional e-beam lithography at lower voltages.