bluuebunny/crossref_metadata_2025 huggingface dataset:
Interaction between water and fluorine-doped silicon oxide films deposited by plasma-enhanced chemical vapor deposition
Authors: Yoshimaru M. , Koizumi S. , Shimokawa K.
Published: July 2002

The interaction between water and fluorine-doped silicon oxide (SiOF) films has been studied using Fourier transform infrared spectroscopy and thermal desorption spectroscopy. The effects of the interaction on the relative dielectric constant of films were also studied using capacitance–voltage measurements. It was found that SiOF films with high fluorine concentration have three absorption bands attributable to Si–Fn stretching vibration, however, the SiOF films have only one absorption band after humidification. The residual band is assumed to be attributable to silicon monofluoride [Si(O–)3F] sites and the disappearing bands are attributable to silicon difluoride [Si(O–)2F2] sites. Si(O–)2F2 sites are hydrided during humidification and generate Si–OH bonds and HF in the film. In addition, Si(O–)2F2 sites increase the water absorbed in film. The relative dielectric constant of SiOF films capped by silicon nitride decreased steadily with increased fluorine concentration, from 4.5 (SiO2) to less than 2.8 [11.5 at. % (F)], however, that of uncapped SiOF films saturated the decrease at about 3.6 in films having 7.6 at. % (F) or more. This saturation is caused by the increase of Si(O–)2F2 sites in film because the ratio of Si(O–)2F2 sites to total fluorine bonding sites increases markedly at a fluorine concentration above 7.6 at. % (F). Si(O–)2F2 sites increase Si–OH bonds and water absorbed in film, and both, in turn, increase the film dielectric constant.
Measurements of current transport in metal/Si1−xGex Schottky diodes
Authors: He L. , Shi Z. Q.
Published: July 2002

Schottky contacts formed by Al/Si1−xGex and Pd/Si1−xGex, with x=0.17 and 0.20, have been investigated by using current–voltage–temperature analysis. The Schottky barrier height varied with Al and Pd as the Schottky metal. The current transport mechanism was strongly affected by 550 °C annealing. In as-deposited samples, thermionic emission and field emission combined as the conduction mechanism. After 550 °C annealing, thermionic emission is the dominant mechanism. The barrier height, φB, was also found to decrease with the increase of germanium composition for the two used samples. X-ray diffraction was utilized to study the substrate crystal quality versus processing. The variation of surface crystal structure and stress with processing temperature was observed.
Metastable chlorine ion kinetics in inductively coupled plasmas
Authors: Hebner G. A. , Fleddermann C. B. , Miller P. A.
Published: July 2002

Laser induced fluorescence has been used to measure the temperature, radial drift velocity, and relative number density of metastable chlorine ions, Cl+*, in inductively coupled discharges containing mixtures of BCl3, Cl2, N2, and Ar. In the center of the plasma, the Cl+* temperature varied between 2000 and 3000 K for most conditions investigated. The addition of BCl3 to a Cl2 plasma significantly decreased the density of metastable chlorine ions without changing their temperature. Addition of nitrogen to a BCl3 plasma resulted in a factor of 3 increase in the Cl+* density. Spatially resolved measurements of the Cl+* density are compared with Langmuir probe measurements of the spatially resolved electron density and ion saturation current. In general, the normalized Cl+* density was a factor of 2–3 lower than the electron density at the edge of the plasma. Spatially resolved measurements of the ion temperature indicated that the ion temperature increased to between 4500 and 5500 K at the edge of the discharge and increased approximately 600–1400 K moving from the rf source towards the lower electrode. Ion drift velocity in the radial direction was between 5×104 and 8×104 cm/s at the edge of the plasma. Measurements within one millimeter of the biased lower electrode surface showed the ion energy parallel to the biased electrode was independent of rf bias voltage while the density decreased with increased bias voltage. Implications of these measurements on the plasma chemistry and the energy transport in the plasma are discussed.
Molecular dynamics simulations of Ar+ and Cl+ impacts onto silicon surfaces: Distributions of reflected energies and angles
Authors: Helmer B. A. , Graves D. B.
Published: July 2002

Previous profile evolution studies of plasma-assisted etch processes have shown that ions scattered from sidewalls can lead to microtrench formation on the bottom of an etched feature [see, for example, Dalton et al., J. Electrochem. Soc. 140, 2395 (1993)]. In these studies, the ions impacting feature surfaces with incident angles above a critical value were assumed to reflect specularly from the surfaces. In the present article, we describe the energy and angle distributions of reflected atoms obtained from molecular dynamics (MD) simulations. We simulated Ar+ and Cl+ ions impacting model silicon surfaces. The ion incident energies Ei were 20, 50, and 100 eV. We varied the ion incident angles θi from 0° to 85° from the surface normal. The model silicon surfaces had chlorine coverages of 0 monolayers (ML) of Cl, 1 ML Cl, and 2.3 ML Cl. We determined the Ar and Cl reflection probabilities, i.e., the fraction of Ar and Cl atoms scattered from the surfaces during the 1–2 ps MD trajectories. For θi⩾75°, we found that the reflection probabilities were greater than 90% in most cases. For these large incident angles, we describe the distributions of energies Er and angles (polar θr and azimuthal φr) for the Ar and Cl atoms reflected from the surfaces. The results of the MD simulations are compared with the assumption of specular scattering. In addition, we compare the average energies of the reflected atoms with the predictions of two simple models based on the binary collision approximation. We discuss the effects of incident ion species, Ei, θi, chlorine surface coverage, and surface roughness on these results.
X-ray photoelectron spectroscopy valence band data for ZnS, SrS, and Sr0.45Ca0.55Ga2S4 luminescent thin films
Authors: Sosa Victor , Rack Philip D. , Holloway Paul H.
Published: July 2002

The valence band of ZnS, SrS, and Sr0.45Ca0.55Ga2S4 thin film phosphors were measured by x-ray photoelectron spectroscopy. The valence band spectrum from polycrystalline ZnS film compared favorably with that previously reported for ZnS single crystals, and with calculated theoretical densities of states (after convolution with a Gaussian curve). The SrS valence band spectrum exhibited three peaks, which generally agree with the expected densities of states. The Sr0.45Ca0.55Ga2S4 spectrum features were much less intense, consistent with the film being amorphous.
Etch characteristics of GaN using inductively coupled Cl2/Ar and Cl2/BCl3 plasmas
Authors: Lee Y. H. , Kim H. S. , Yeom G. Y. , Lee J. W. , Yoo M. C. , Kim T. I.
Published: July 2002

In this study, Cl2/Ar and Cl2/BCl3 inductively coupled plasmas were used to etch GaN and the effects of etch parameters such as gas combination and operation pressure on the characteristics of the plasmas and etch properties of GaN were investigated. The characteristics of the plasmas were estimated using a Langmuir probe and optical emission spectroscopy. Surface residue remaining after the etch was investigated using x-ray photoelectron spectroscopy (XPS). The increase of Ar and BCl3 in Cl2 generally reduced GaN etch rates except for the small addition of Ar or BCl3. With the addition of 10% Ar or 10% BCl3  to Cl2, the GaN etch rates showed the maximum etch rates. Also, the increase of operational pressure up to 30 mTorr increased the GaN etch rates. By optimizing etch process parameters, etch conditions having smooth and nearly vertical etch profiles with the etch rates close to 8500 A/min and the selectivity over SiO2 higher than 3.5 could be obtained with Cl2-rich Cl2/BCl3 gas combinations. The change of Cl radical density measured by optical emission spectroscopy as a function of gas combination showed the same trend as the change of GaN etch rates, therefore, chemical reactions between Ga in GaN and Cl from Cl2 appear to be one of the most important factors controlling the GaN etch rates. Ga/N ratios of the etched GaN surfaces measured by angle resolved XPS were less than 1 for all of the etch conditions used in the experiment. However, when Ar was added to Cl2, Ga/N ratio increased and, when BCl3 was added, the Ga/N ratio decreased from that of the GaN surface etched using pure Cl2.
Ciliary microactuator array for scanning electron microscope positioning stage
Authors: Darling Robert B. , Suh John W. , Kovacs Gregory T. A.
Published: July 2002

The performance of a ciliary microactuator array as a positioning stage inside a scanning electron microscope is described. Such arrays are attractive because they can provide micron scale positioning resolution with direct electronic control within the sample chamber. The present array uses thermal actuation of a polyimide bimorph to produce long-travel deflection of each cilium and electrostatic actuation to provide a low-power hold-down mode. Each cell in the array consists of four orthogonally oriented cilia which, with proper drive signals, can produce object motion along any direction within the plane of the array. Adapting this array for use inside a scanning electron microscope (SEM) requires only a small mounting block and a modest multiconductor feedthrough. Improved thermal isolation within the vacuum chamber of the SEM drastically reduces the electrical input power requirements over those in air, while still allowing full positioning resolution. The addition of a gold ground plane coating to the array eliminates charging problems by the electron beam and reduces electrical interference from the drive signals.
Optimization of nitrided gate dielectrics by plasma-assisted and rapid thermal processing
Authors: Lucovsky G. , Niimi H. , Wu Y. , Parker C. R. , Hauser J. R.
Published: July 2002

This article addresses several aspects of nitrogen atom (N atom) incorporation into ultrathin gate oxides including: (i) monolayer incorporation of N atoms at the Si–SiO2 interfaces to reduce tunneling currents and improve device reliability; and (ii) the incorporation of silicon nitride films into stacked oxide–nitride (ON) gate dielectrics to (a) increase the capacitance in ultrathin dielectrics without decreasing film thickness, and (b) suppress boron atom (B atom) diffusion from p+ polycrystalline Si gate electrodes through the dielectric layer to the Si substrate channel region. The results of this article demonstrate that these N-atom spatial distributions can be accomplished by low thermal budget, single wafer processing which includes (i) low-temperature (300 °C) plasma assisted oxidation, nitridation, and/or deposition to achieve the desired N-atom incorporation, followed by (ii) low thermal budget (30 s at 900 °C) rapid thermal annealing to promote chemical and structural bulk and interface relaxation.
Application of a toroidal plasma source to TiN thin film deposition
Authors: Zhang B. C. , Cross R. C.
Published: July 2002

A toroidal plasma source for plasma deposition at the University of Sydney (PLADEPUS) has been developed for studies of deposition of thin films, such as titanium nitride (TiN). This article describes measurements of the plasma parameters at a low rf power input, the experimental setup of the preliminary thin film deposition and the method of titanium (Ti) atom injection into the plasma by using a small current Ti arc. The microstructure of the TiN thin films is analyzed and the results are presented.
Optical properties of zirconia–yttria single crystal compounds by reflection electron energy loss spectroscopy
Authors: Yubero F. , Espinós J. P. , González-Elipe A. R.
Published: July 2002

Optical characterization of zirconia–yttria (YSZ) based single crystal compounds (9–32 mol% of yttria) has been carried out in the 5–60 eV energy range from reflection electron energy loss spectroscopy measurements. The stoichiometry and the chemical state of the elements at the surface of the samples were studied by x-ray photoemission spectroscopy. The procedure of analysis to obtain optical properties relies in a quantitative description of the electron energy losses. Inelastic mean free paths of 23, 13 and 5.8 Å for electrons traveling in a reflected geometry in YSZ are obtained for electrons of 1500, 800 and 300 eV, respectively, independently from its yttria content. It has been found that there is a dependence of optical magnitudes on the Zr/Y ratio. Thus, the energy of the bulk plasmon excitations varies from 14.3 to 14.6 eV when the doping dose increases from 9 to 32 mol% of yttria. Surface plasmon excitations appear at 12.6 and 13.2 eV for the 9 and 32 mol% YSZ samples, respectively. Individual electronic transitions have been identified in the absorption coefficient. Besides, the analysis of the absorption coefficient suggests that for the increasing amount of yttria, the conduction band loses gradually the two peak structure observed in pure ZrO2 due to the crystal field splitting of the 4d orbitals of zirconium.
Atomic force microscopy and ellipsometry study of the nucleation and growth mechanism of polycrystalline silicon films on silicon dioxide
Authors: Basa C. , Tinani M. , Irene E. A.
Published: July 2002

The primary purpose of this research was to elucidate the mechanism of Si nucleation on SiO2 in a rapid thermal chemical vapor deposition (RTCVD) environment. To this end a combination of in situ real time ellipsometry and atomic force microscopy (AFM) to follow the RTCVD process in real time and measure key nucleation parameters was used. Real time ellipsometry data, in terms of Δ versus time, show significant changes as the deposition evolves from critical nuclei through coalescence to continuous film growth. From these data nuclei parameters such as the incubation time (tinc), coalescence point, nuclei density, and nuclei size are obtained from nucleation models. From the AFM images, nuclei parameters such as nuclei height, radius, and density were collected and compared across processing temperatures. It was found that kinetics rather than thermodynamics controls nuclei growth, and the mechanism depended upon the temperature regime (pressure not varied) due to the higher activation energy (212 kJ/mol) for vertical growth relative to lateral growth (167 kJ/mol). A transition temperature (∼600 °C) was identified where the size, shape, and density of the nuclei abruptly change from small numerous nuclei at temperatures less than 660 °C to large, sparse, disklike nuclei for temperatures greater than 660 °C. The temperature regime also affected the shape of the nuclei during growth with low temperature nuclei becoming flatter with time as the adatoms attached to the nuclei circumference, whereas high temperature nuclei grew taller with time. It is demonstrated that the RTCVD temperature regime dictates both the initial nuclei size and the nuclei growth mechanism with high temperature processes (i.e., highest adatom mobility), yielding the lowest nuclei density, largest nuclei, and roughest final Si film.
Electrical properties of (Pb,La)TiO3 thin films deposited by low pressure metal-organic chemical vapor deposition using solid delivery system
Authors: Shin Ju Cheol , Lee Jong Myeong , Hong Suk-Kyoung , Cho Ho Jin , Kim Kwon Seok , Hwang Cheol Seong , Kim Hyeong Joon
Published: July 2002

(Pb,La)TiO 3 (PLT) thin films were deposited on various substrates by metal-organic chemical vapor deposition technique using a solid delivery system. A mixture of metal-organic precursors with wide range of La dopant concentration was prepared to investigate the effects of La doping concentration on the structural and dielectric properties of PLT thin films. As La concentration increases, the crystal structure of PLT thin films changed from tetragonal to pseudocubic and their dielectric constant increased. An annealing process after fabrication of PLT thin film capacitor improved ferroelectric properties. Pt top electrode was more effective in the improvement than RuO2 top electrode in rapid thermal annealing process using halogen lamp heater.
Hydrogen passivation at the Al/H:Si(111)-(1×1) interface
Authors: Grupp C. , Taleb-Ibrahimi A.
Published: July 2002

A direct comparative study of the interfaces Al/H:Si(111)-(1×1) and Al/Si(111)-(7×7) by means of high-resolution photoelectron spectroscopy and Auger spectroscopy reveals large differences for aluminum coverages below Θ∼5 ML. Hydrogen termination suppresses the formation of interfacial AlSi and promotes island growth. The Schottky barrier formation is delayed compared to the Al/Si(111)-(7×7) interface. For high coverages the Schottky barrier is the same for both interfaces.
Temperature dependence of SiO2/Si interfacial structure formed by radio-frequency magnetron sputter deposited SiO2 thin films on Si(111)
Authors: Li Boquan , Fujimoto Toshiyuki , Kojima Isao
Published: July 2002

X-ray reflectivity has been used to characterize the interfacial structure of as-grown SiO2 layers deposited on Si(111) substrates by rf magnetron sputtering under different substrate temperatures. Results indicate that there exists a higher-density interfacial layer between crystalline Si and the amorphous SiO2 overlayer. As the substrate temperature was increased from 200 to 620 °C, the density of the interfacial layer increased from 2.37 to 2.67 g/cm3, and the thickness of the interfacial layer also increased slightly.
Rectangular magnetron with full target erosion
Authors: Musil J.
Published: July 2002

The article reports on the operation of a rectangular magnetron with three and four closed discharges simultaneously formed on the surface of sputtered target. The closed discharges, elliptically shaped with the longer axis perpendicular to the long side of the rectangular magnetron, are formed using magnetic circuits placed behind the sputtered target. By moving these magnetic circuits along the long axis of a rectangular target, it is possible to achieve almost full target erosion and therefore significantly increase the usage lifetime of the target. This principle can be used for rectangular magnetrons with arbitrary length of the target. The longer the target, the greater the number of closed discharges that are required. Experimentally, it was found that neighboring closed discharges can interact which may significantly modify the sputtering characteristics of the magnetron cathode. This interaction is described and the physical requirements to avoid its occurrence are given. The I–V characteristics of a rectangular magnetron with one, two, and three closed discharges are given.
Silicon etch rate enhancement by traces of metal
Authors: Sebel P. G. M. , Hermans L. J. F. , Beijerinck H. C. W.
Published: July 2002

We report the effect of nickel and tungsten contamination on the etch behavior of silicon. This is studied in a molecular beam setup, where silicon is etched by XeF2 and Ar+ ions. The etch process is directly monitored by the SiF4 reaction products which leave the surface. The effect of contamination appears very pronounced after the ion beam is switched off: it leads to a temporary enhancement of the spontaneous etch rate on a time scale of 500 s. With traces of contamination on the order of 0.01 ML, the etch rate may be enhanced by a factor of 2 for W and somewhat less for Ni. It is concluded that the contamination moves into the silicon by diffusion to vacancies created by the Ar+ ions. For 1 keV Ar+ ions the contamination moves to a depth of 25 Å, comparable to the penetration depth of the ions. After etching a 170 Å thick layer, the catalytic effect of contamination is reduced to less than 5%. A simple model, which describes the measured effect of contamination very well, indicates that only 3% of the contamination is removed when a monolayer of silicon is etched away. Besides this catalytic effect there are indications that contamination can also lower the etch rate under certain conditions, because of the formation of silicides. From the measurements no conclusions could be drawn about the underlying mechanism of etch rate enhancement.
In situ x-ray photoelectron spectroscopy studies of interactions of evaporated metals with Poly(p-phenylene vinylene) and its ring-substituted derivatives
Authors: Atreya M. , Li S. , Kang E. T. , Neoh K. G. , Ma Z. H. , Tan K. L.
Published: July 2002

The results obtained from the in situ analysis by angle resolved x-ray photoelectron spectroscopy (XPS) of the interactions between thermally evaporated metals (aluminum and indium) and conjugated electroluminescent polymer films, such as poly(p-phenylene vinylene) and its soluble derivative, poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV), are reported. The changes in the carbon and metal core-level spectra and the chemical stoichiometries of polymer–metal interfaces with progressive deposition of the metal atoms were monitored. The interactions of the Al and In atoms with the polymer surfaces were compared. For both metals, a simple electrical contact was not formed. From the XPS studies, it was deduced that chemical reactions had occurred between the polymer and the metal, leading to the formation of an interfacial layer of metal oxides and complexes. The interfacial reactions were promoted by the surface oxidation states of the polymer, the migration of bulk adsorbed oxygen to the polymer surface upon metal deposition, and also in the case of MEH-PPV, by the oxygen from the alkoxy side chains.
Two-dimensional carrier profiling of InP-based structures using scanning spreading resistance microscopy
Authors: De Wolf P. , Geva M. , Reynolds C. L. , Hantschel T. , Vandervorst W. , Bylsma R. B.
Published: July 2002

Scanning spreading resistance microscopy (SSRM) is a powerful tool originally developed for measuring two-dimensional (2D) carrier distributions in Si device structures with nm spatial resolution. Whereas its application has been explored in detail on Si structures, very little work was made on III–V materials. In this article, we report on the application of SSRM for the analysis of III–V semiconductor structures, and in particular metalorganic chemical vapor deposition-grown InP-based structures. We found that the application of SSRM to InP-based structures is much simpler than to Si. Minimal surface preparation is required, much lower tip forces are needed, and metal tips instead of diamond tips can be used. When imaging complex multilayer epitaxial structures (containing p, n, and semi-insulating layers), close agreement between the SSRM profile and secondary ion mass spectroscopy profiles can be obtained. More importantly is the capability of SSRM to image and determine 2D structures in actual devices, such as mesas and trenches, common in semiconductor laser devices. SSRM also proved very valuable in characterizing with high spatial resolution 2D dopant and implant distributions. In this article, we present SSRM analysis of dedicated InP test structures with multiple p-n layers, varying in concentration level and in thickness.
Interdiffusion studies of single crystal TiN/NbN superlattice thin films
Authors: Engström C. , Birch J. , Hultman L. , Lavoie C. , Cabral C. , Jordan-Sweet J. L. , Carlsson J. R. A.
Published: July 2002

The interdiffusion of TiN and NbN in superlattice structures has been investigated by studying the evolution of superlattice satellite peaks in x-ray diffraction, as well as by cross-sectional transmission electron microscopy. Single crystal TiN/NbN superlattices with composition modulation periods of 4.4 and 12.3 nm were deposited, by reactive dual-cathode unbalanced magnetron sputtering in an Ar/N2 discharge, onto MgO(001) substrates held at a temperature of 700 °C. Isothermal annealings (in the range of 750–875 °C for 20 min) as well as a ramped annealing (3 °C s−1 up to 1200 °C) were performed, and in situ x-ray diffraction spectra were continuously recorded using synchrotron light and a linear detector. The results pointed to a nonlinear diffusion in TiN–NbN couples. The structure maintained abrupt interfaces throughout annealing, while the position of the interfaces was continuously shifted into the TiN layers. A model is proposed where Ti diffuses into the NbN layer to form a NbTiN alloy, while the diffusion of Nb in the opposite direction is restricted. Within the temperature range from 750 to 875 °C, activation energies for metal interdiffusion were limited to 1.2 eV for the lower temperature end, and 2.5 eV for the higher temperature end. The expected lifetime against alloying has been determined using the random walk theory, and a TiN/NbN superlattice with a period of 4.4 nm is expected to sustain a layered structure for ∼10 h at 750 °C and ∼2 h at 850 °C.
Ni–Cr passivation of very thin Ag films for low-emissivity multilayer coatings
Authors: Martín-Palma R. J. , Martínez-Duart J. M.
Published: July 2002

In the present work, the optical properties in the visible and infrared ranges of glass/SnO2(380 Å)/Ni–Cr(15 Å)/Ag(90 Å)/Ni–Cr(25 Å)/SnO2(380 Å) and glass/SnO2(380 Å)/Ni–Cr(15 Å)/Ag(90 Å)/SnO2(380 Å) systems are compared in order to determine the influence of the external Ni–Cr film on the optical behavior of low-emissivity multilayer coatings for energy saving applications. It has been observed that the lack of either one Ni–Cr film results in the hampering of the low-emissivity behavior (from 2.5% to 49.5% at λ=10 μm), as a result of the diminution of the reflectance values in the infrared range (from 97.5% to 50.5% at λ=10 μm). The lack of the Ni–Cr film also affects the optical performance in the visible range, by decreasing the transmittance from approximately 80% to 60% at λ=550 nm, and increasing the reflectance from about 5% to 30%. This behavior is attributed to the partial oxidation of the silver layer which might result both in a variation of the chemical and structural properties of this film.
Pulsed and continuous wave plasma deposition of amorphous, hydrogenated silicon carbide from SiH4/CH4 plasmas
Authors: McCurdy Patrick R. , Truitt Jason M. , Fisher Ellen R.
Published: July 2002

Continuous wave (cw) and equivalently powered, pulsed radio frequency plasmas are used to deposit a-Si1−xCx:H films. Films produced from SiH4/CH4 and SiH4/CH4/H2 gas mixtures were analyzed with Fourier-transform infrared, x-ray photoelectron spectroscopy, scanning electron microscopy, and profilometery. Gas-phase plasma species were identified using optical emission spectroscopy. The effects of biasing (±1000 V) and grounding the substrates, pulse peak power, pulse on time and off time, and duty cycle on film composition were examined. Films deposited with cw plasmas show an increase in hydrogen incorporation compared to films deposited in the pulsed systems. In the pulsed plasmas, deposition rates depend on both the on time and off time of the plasma pulse cycle, while grounding the substrate causes a significant reduction in oxidation rates for films deposited under all conditions.
Cathodic plasma polymerization and treatment by anode magnetron torch. I. The influence of operating parameters on anode magnetron torch glow discharge
Authors: Zhao J. G. , Yasuda H. K.
Published: July 2002

The anode magnetron torch (AMT), which is a physically confined magnetron plasma system, was developed for large-scale applications. It was found that a uniform funnel-shaped negative glow is crucial to achieve uniform plasma treatment in the focused area; this can be attained by adjusting the distance between two electrodes. The relationship between the gap distance (the distance from the edge of the glass tube to the cathode surface) and CDST e2 (the cathodic dark space thickness at the edge of the glass tube) is another important factor which affects whether materials removed by sputtering will redeposit on the substrate surface. The CDST shrinks not only with the increase of input power, applied voltage or current, but also with the increase of the magnetic field strength or system pressure. The CDST e1 (the CDST at the center of the focused area) will contract and the CDST e2 will expand with a decrease in the gap distance. The influence of the electrode distance on the CDST is complicated, because it causes not only a change in magnetic field strength, but also a change in the distribution of the magnetic field strength near the cathode surface.
Simulation of the influence of the filament arrangement on the gas phase during hot filament chemical vapor deposition of diamond films
Authors: Song G. H. , Sun C. , Huang R. F. , Wen L. S.
Published: July 2002

The uniform temperature and mass current density of gas in deposition regions of films were very important to obtain uniform diamond films over a large area during hot filament chemical vapor deposition. The simulation showed that the two physical parameters of gas in the chamber varied as a function of space and were influenced by the arrangement of the filaments and the initial rate of the introduced gas. Regions of uniform temperature and mass current density existed in the chamber. The distributions of temperature and mass current density did not vary with the filament diameter. However, the value of the two physical parameters increased and declined with the increment of the diameter, respectively. An optimum distance between filaments was necessary to obtain uniform films over a large area. The mass current density increased with the initial rate of the introduced gas. These results might provide a basis for optimizing the technological parameters to obtain uniform diamond films over a large area.
Plasma enhanced chemical vapor deposition Si-rich silicon oxynitride films for advanced self-aligned contact oxide etching in sub-0.25 μm ultralarge scale integration technology and beyond
Authors: Kim Jeong-Ho , Yu Jae-Seon , Ku Ja-Chun , Ryu Choon-Kun , Oh Su-Jin , Kim Si-Bum , Kim Jin-Woong , Hwang Jeong-Mo , Lee Su-Youb , Kouichiro Inazawa
Published: July 2002

We intentionally introduced excessive Si during the SiOxNy film deposition in order to increase the etch selectivity-to-SiOxNy for advanced self-aligned contact (SAC) etching in sub-0.25 μm ultralarge scale integration devices. The SiOxNy layer was deposited at a conventional plasma enhanced chemical vapor deposition chamber by using a mixture of SiH4, NH3, N2O, and He. The gas mixing ratio was optimized to get the best etch selectivity and low leakage current. The best result was obtained at 10% Si–SiOxNy. In order to employ SiOxNy film as an insulator as well as a SAC barrier, the leakage current of SiOxNy film was evaluated so that SiOxNy may have the low leakage current characteristics. The leakage current of 10% Si–SiOxNy film was 7×10−9 A/cm2. Besides, the Si-rich SiOxNy layer excellently played the roles of antireflection coating for word line and bit line photoresist patterning and sidewall spacer to build a metal–oxide–semiconductor transistor as well as a SAC oxide etch barrier. The contact oxide etching with the Si-rich SiOxNy film was done using C4F8/CH2F2/Ar in a dipole ring magnet plasma. As the C4F8 flow rate increases, the oxide etching selectivity-to-SiOxNy increases but etch stop tends to happen. Our optimized contact oxide etch process showed the high selectivity to SiOxNy larger than 25 and a wide process window (⩾5 sccm) for the C4F8 flow rate. When the Si-rich SiOxNy SAC process was applied to a gigabit dynamic random access memory of cell array, there was no electrical short failure between conductive layers.
Effects of copper seedlayer deposition method for electroplating
Authors: Cooney E. C. , Strippe D. C. , Korejwa J. W.
Published: July 2002

We have investigated copper seedlayer deposition using both ionized physical vapor deposition (IPVD) and collimation methods by depositing similar films into single and dual damascene structures. Step coverage measurements using transmission electron microscopy indicated that IPVD seedlayers exhibited better bottom and sidewall coverage as compared to collimated seedlayers. Subsequent electroplating of contact structures did not indicate differences in the quality of the filling when observed using scanning electron microscopy (SEM). However electrical testing of 68 000 link dual damascene via chains did show improved chain yield for the IPVD deposited films. Cross sections of the chains revealed small voids at the bottom of some of the vias deposited using collimated seedlayers, while no voiding was observed for the IPVD copper films. Finally SEM examinations of unfilled dual damascene cross sections indicated the IPVD copper seedlayer morphology to be rougher as compared to copper films sputtered using collimation.
In situ study of the formation of SiC thin films on Si(111) surfaces with 1,3-disilabutane: Adsorption properties and initial deposition characteristics
Authors: Yoon H. G. , Boo J.-H. , Liu W. L. , Lee S.-B. , Park S.-C. , Kang H. , Kim Y.
Published: July 2002

The initial formation of silicon carbide by the interaction of 1,3-disilabutane (DSB) with a Si(111) surface has been studied in the temperature range of 100–1200 K using the low-energy Cs+ reactive scattering and x-ray photoelectron spectroscopy (XPS). By combining the results of these two techniques, adspecies in the intermediate states during the decomposition of DSB were qualitatively identified and the binding energies and full widths at half maximum of their C(1s) peaks were characterized. At 100 K, 1,3-DSB was found to adsorb on the surface as the C2H8Si2 species as well as CH4Si and to condense molecularly on the monolayer of C2H8Si2 adspecies. XPS indicates that the molecular species desorbs mostly at 200 K and completely at 300 K. Up to 600 K, the C2H8Si2 adspecies are converted to CH4Si with increasing temperature and then above this temperature the CH4Si species decomposes to form the SiC film. The intensity variations of Si(2p) and total C(1s) peaks and the analysis by curve fitting of the C(1s) peaks suggest that one C2H8Si2 adspecies makes only one CH4Si adspecies by breakage of the central C–Si bond rather than two CH4Si adspecies.
Applications of surface textures produced with natural lithography
Authors: Deckman H. W. , Dunsmuir J. H.
Published: July 2002

Surface textures with carefully controlled size, order, and morphology can be prepared by using monolayers of colloidal particles to form a lithographic mask. Microstructures produced from the mask are identical and of predetermined size because monodisperse colloidal particles can be obtained in sizes ranging from ∼200 Å–30 μm. Ordering of particles, and hence, surface texture can be either random or periodic depending upon the method used to deposit the particles. Several applications of reproducible fine structure fabricated on the surface of large area substrates are discussed.
Theory of Schottky barrier formation for transition metals on Si, Ge, diamond, and Six Ge1−x alloys
Authors: Sankey Otto F. , Allen Roland E. , Dow John D.
Published: July 2002

The heights of the Schottky barriers for various transition metals on Si, Ge, diamond, and Six Ge1−x alloys are calculated using a defect model, in which the Fermi energy is pinned by deep levels associated with interfacial dangling bonds.
Radio-frequency biased microwave plasma etching technique: A method to increase SiO2 etch rate
Authors: Suzuki Keizo , Ninomiya Ken , Nishimatsu Shigeru , Okudaira Sadayuki
Published: July 2002

In order to increase the SiO2 etch rate in microwave plasma etching, a method of controlling the kinetic energy of ions impinging on a substrate surface covered with an insulator film was developed. In this method, radio-frequency voltage is supplied to the substrate. A theoretical model and analysis for this method was made to define the substrate surface potential and the kinetic energy of impinging ions. Experimental verification of the analysis, and application of the method to SiO2 etching have been carried out. A SiO2 etch rate εSiO2 =40 nm/min, and selectivity to Si η2=εSiO2/εSi =4.0 were obtained with C3F8 etching gas and rf peak to peak voltage VBP=200 V.
The prospects of field emission for e-beam inspection
Authors: Orloff J. , Swanson L. W. , Li Jia-Zheng
Published: July 2002

The rate at which e-beam inspection can be performed depends on the current which can be focused into a small spot, nominally 0.05 μm i.d., at an energy which will not damage the device being tested, nominally 1 keV. Rapid inspection, consistent with the needs of a fabrication line will require ∼1 nA current, which appears to be attainable only with a field emission cathode at any reasonable working distance. The results of the application of a thermal field emission system for low voltage, high current work at the Oregon Graduate Center are presented.
Suspended metal mask techniques in Josephson junction fabrication
Authors: Ono R. H. , Sauvageau J. E. , Jain A. K. , Schwartz D. B. , Springer K. T. , Lukens J. E.
Published: July 2002

We report here two processes for in-situ, self-aligned fabrication of niobium based Josephson tunnel junctions and SNS microbridges in which multiple evaporations at varying angles are made through a suspended metal stencil fabricated by electron beam lithography (EBL). Both techniques have proved superior to earlier all-polymer suspended masks, particularly with e-gun evaporated refractory metals such as niobium. The first process uses a trilevel resist and ion milling to pattern a gold stencil suspended on PMMA. In the second process, an aluminum stencil suspended on polyimide (PI) is patterned by lift-off with an EBL mask written in a PMMA layer on top of the PI. The PI is then undercut using an oxygen plasma etch through the aluminum mask. Reproducible (±20 nm) submicrometer dimensions and good junction characteristics have been achieved using these techniques without the need for difficult-to-control surface cleaning procedures.
Optical characteristics of 0.1 μm circular apertures in a metal film as light sources for scanning ultramicroscopy
Authors: Fischer U. Ch.
Published: July 2002

A 0.12 μm aperture in a metal film supported by a glass slide is used to define a submicroscopic source of light for a demonstration of scanning ultramicroscopy in the reflection mode. The aperture is viewed through a microscope in dark field illumination by a totally reflected beam (λ=633 nm). When an interface is brought in proximity to the aperture, the light emission from the aperture is quenched to an extent which depends on the nature of the interface and the polarization of the incident beam. With a 1 μm wide hole in a thin dielectric or metal film as test object, an edge resolution of 0.1 μm is obtained only with scans perpendicular to the direction of the irradiating beam.
Selective removal of metal atoms in hydrogen reactive ion etching
Authors: Hiraoka H.
Published: July 2002

A short exposure of polymer films containing Si, Al, Bi, and other metals to hydrogen reactive ion etching (RIE) reduces their oxygen RIE resistance dramatically. Preferential removal of Si, Al, or other metal atoms in hydrogen RIE is responsible for this reduction of the etch resistance. Selective removal of these atoms by hydrogen RIE may be important in dry stripping of organometallic resist films. Positive tone polymer images can be fabricated by selective removal of metal atoms. Conversely, patternwise deposition of an organometallic compound in H+ beam-induced polymerization or after H+ beam-induced decarboxylation gave rise to negative or positive tone polymer images, respectively, by dry image development.
An indium-free mount for GaAs substrate heating during molecular beam epitaxial growth
Authors: Mars D. E. , Miller J. N.
Published: July 2002

The substrate mounting system for a Varian GEN/II molecular beam epitaxy (MBE) system was modified to allow the growth of device quality GaAs and AlGaAs epitaxial layers on GaAs substrates without the use of indium bonding. The indium-free holders are compatible and interchangeable with the standard molybdenum blocks that use indium bonding. The wafer is heated by direct radiation from the unmodified spiral filaments with no intermediate absorbers or backside wafer coatings. A commercial pyrometer with a silicon detector was used to measure the absolute temperature. The silicon detector is sensitive to radiation from 0.8 to 1.1 μm, which is primarily above the band gap energy of GaAs at substrate temperatures above 550 °C. For photon energies above the band gap the spectral emittance of GaAs is nearly independent of the substrate doping, thickness, and temperature. With this pyrometer a maximum temperature difference of 3 °C was measured over the central two-thirds of a 2 in. diam semi-insulating GaAs wafer. In contrast, the maximum temperature difference on n+GaAs substrates was significantly larger (30 °C over the central two-thirds of the wafer) and showed the same pattern as the filament configuration. This large difference is explained by a simple model which takes into account the smaller thermal conductivity and larger total emittance of n+GaAs compared to undoped GaAs.
Dry process ultraviolet patterning of paracyclophane to polyparaxylylene
Authors: Mariella R. P. , Steinhauser S. W. , Diebold A. C.
Published: July 2002

Upon warming to about 60 °C, [2,2]paracyclophane (PCP) and monochloro[2,2] paracyclophane (cPCP) can be deposited by sublimation onto target surfaces at −78 °C in an evacuated chamber. Light with wavelengths less than 250 nm can then be used to photopolymerize the deposited PCP or cPCP to polyparaxylylenes while still cold or after warming them back to room temperature. When the photolyzed material is heated to roughly 100 °C, the unexposed paracyclophanes evaporate, leaving polyparaxylylene behind. If the paracyclophane is exposed to the UV light through a patterned mask, submicron features of polyparaxylylene can be produced; however, the maximum film thickness which can be made in a single exposure is about 0.1 μm.
Transitions in the reflection high-energy electron-diffraction pattern as a substrate temperature probe in molecular-beam epitaxy
Authors: Ramberg L. P. , Westin J. , Andersson T. G.
Published: July 2002

In molecular-beam epitaxy systems, a substrate reference temperature can be established from observations of transitions in the reflection high-energy electron-diffraction pattern. For GaAs, we present the temperature for one such transition as a function of arsenic background pressure.
The role of Farben centers in electron- and photon-stimulated desorption from alkali halides
Authors: Loubriel G. M. , Green T. A. , Tok N. H. , Haglund R. F.
Published: July 2002

Measurements of the time history of ground-state neutral lithium desorption from LiF during pulsed electron irradiation have resulted in a new model for the lithium-desorption mechanism. We show that the slow diffusion to the surface of bulk Farben (F) centers created by the electron-beam is the rate-controlling factor responsible for most of the time history of the lithium desorption rather than the thermal evaporation of the metal from the surface. Comparison between theoretical and experimental time dependencies yields values for the F center diffusion constant and its activation energy.
Experimental results with a scanning stepper for synchrotron-based x-ray lithography
Authors: Cullmann E. , Cooper K.
Published: July 2002

A second generation of synchrotron-compatible x-ray steppers is described which uses the scanning exposure method to minimize overhead time between alignment and exposure. Available x-ray intensity is increased, since a thin exposure window, only a few mm high, can be used to separate the beam line vacuum from the exposure tool which operates in ambient air. First results indicate sufficient mechanical stability to allow the mask/wafer unit to be scanned in an aligned position.
Reflection high-energy electron diffraction observations during growth of ZnSxSe1−x(0≤x≤1) by molecular-beam epitaxy
Authors: Cornelissen H. J. , Cammack D. A. , Dalby R. J.
Published: July 2002

Different surface reconstructions were observed during growth of ZnSxSe1−x(0≤x≤1) and the growth conditions under which these occur were determined. Zn-rich ZnSe growth shows a c(2×2) surface reconstruction, while under Se-rich growth a (2×1) surface is observed. On ZnSxSe1−x(x≤0.16) and on ZnSe/ZnSxSe1−x superlattice structures a (5×) reconstruction is observed. Se desorption experiments suggest that Se is bound as a dimer to a Se stabilized ZnSxSe1−x surface. The intensity of the specular beam increases after switching from molecular-beam epitaxy growth of ZnSe to atomic layer epitaxy growth. Implications on the ZnSe growth mechanism are discussed.
Electron optical performance of a scanning tunneling microscope controlled field emission microlens system
Authors: Chang T. H. P. , Kern D. P. , McCord M. A.
Published: July 2002

Use of a scanning tunneling microscope (STM) controlled field emission tip in conjunction with microlenses has been explored to form an exceptionally high brightness electron source and low aberration beam forming system at the low-keV energy range. In its basic configuration, the STM feedback principle is used for precision x, y, and z alignment of tip to microlens to form a self-aligned field emission (SAFE) microsource. The microlenses can be made using microfabrication techniques on silicon or other suitable substrates with dimensions reduced by approximately three orders of magnitude from those of conventional lenses. As the lens aberrations generally scale with lens dimensions, such lenses can be designed to have negligible aberrations thus allowing exceptionally high brightness and resolution to be achieved. This paper discusses the electron optical performance of such a microsource and its applications with other microlenses as beam forming systems.
Three-dimensional computer modeling of electrostatic and magnetic electron optical components
Authors: Rouse John , Munro Eric
Published: July 2002

This paper describes and illustrates a suite of programs which have been written for the computer-aided design of three-dimensional electron optical systems. The programs can analyze electrostatic systems containing conductors and dielectrics with specified surface charge distributions and also magnetic systems with permeable polepieces and coil windings. The finite difference method is used to compute the potentials at points on a three-dimensional (3D) rectangular grid but the difference equations at the material interfaces are modified to handle curved boundaries and permeable materials. The programs were written and run on a personal computer and have also been ported to several larger machines.
Laser pulsed GaAs cathodes for electron microscopy
Authors: Sanford Colin A. , MacDonald Noel C.
Published: July 2002

The electron emission properties from activated negative electron affinity GaAs photocathodes have been investigated with respect to focused electron beam applications. We have obtained shot noise limited emission and a long-term drift of less than 0.1% over a 3-h period when the cathode has been operated in a closed-loop configuration. The measured emitted electron energy distribution FWHM is 0.2 eV. The cathode can be operated in either a continuous emission mode or a pulsed mode. When operated in the pulsed mode, stroboscopic images with 100-ps resolution are obtained without beam blanking or electron bunching optics. Using a YAG pumped dye laser, sufficient current is produced in the pulsed mode to allow stroboscopic images to be displayed at TV scan rates.