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  • 1
    Electronic Resource
    Electronic Resource
    Absolute concentration and loss kinetics of hydrogen atom in methane and hydrogen plasmas (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 5497-5503 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A measurement technique of the absolute concentration of hydrogen (H) atoms in methane (CH4) and/or hydrogen molecule (H2) plasmas has been established. The H-atom concentration was evaluated by vacuum ultraviolet absorption spectroscopy (VUVAS) using a high-pressure H2 microdischarge hollow cathode lamp (H2-MHCL) as the Lyman α (Lα 121.6 nm) light emission source. A measurement technique of the background absorption caused by species other than H atoms at the Lα line was developed by using the VUVAS technique with the MHCL employing nitrogen molecules (N2-MHCL). The lines around Lα used for the background absorption measurements are 2p23s 4P5/2–2p3 4S3/20 at 119.955 nm, 2p23s 4P3/2–2p3 4S3/20 at 120.022 nm, and 2p23s 4P1/2–2p3 4S3/20 at 120.071 nm of the N atom. By using the VUVAS technique with the MHCLs and subtracting the background absorption from the absorption of H atoms at Lα, we have achieved the measurement of the H-atom concentration in an inductively coupled plasma operated in CH4 and/or H2. The H-atom concentration increased from 2×1011 to 3×1012 cm−3 when increasing the CH4 flow rate ratios from 0% to 50% in the CH4–H2 mixture and was almost constant in its range between 50% and 100% at a pressure of 1.33 Pa, a radio frequency power of 200 W, and a total flow rate of 100 sccm. The behavior of the H-atom concentration was compared with that of the Balmer α emission intensity. The decay of the H-atom concentration in the H2 plasma afterglow was investigated to clarify the loss kinetics of H atoms. The dependence of the decay time constant on the pressure showed that H atoms were dominantly lost through diffusion to the wall surface. The diffusion constant of H atoms in H2 plasmas was determined to be 3.0×105 cm2 Pa s−1 at 400 K. The surface loss probability of H atoms on the stainless-steel and the hydrocarbon walls were estimated to be 0.15 and 0.07, respectively. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1410327
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  • 2
    Electronic Resource
    Electronic Resource
    Behavior of hydrogen atoms in ultrahigh-frequency silane plasma (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4727-4731 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the behavior of the absolute density of hydrogen (H) atoms in ultrahigh-frequency (UHF), (500 MHz) silane (SiH4) plasma by using a vacuum ultraviolet absorption spectroscopy technique with a microdischarge hollow cathode lamp. In the UHF plasma using SiH4 highly diluted with hydrogen molecule (H2) at a pressure of 20 Pa, an UHF power of 1000 W, and a total flow rate of 200 sccm, the absolute density of H atoms slightly increased from 7.4×1011 to 7.9×1011 cm−3 with increasing the SiH4 flow rate ratios from 0% to 2.5% and then the H atom density decreased at the ratio of 5%. The decrease of the density is due to the increase of the reaction between the H atom and the SiH4 molecule. The behavior of the absolute density of H atoms was compared with that of the Balmer α(Hα) emission intensity. It was found that the behaviors of the absolute H atom density and the Hα emission intensity were quite different. Moreover, the kinetics of H atom density in SiH4 plasmas have been clarified on the basis of measured results. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1362414
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  • 3
    Electronic Resource
    Electronic Resource
    Dual-electrode biasing for controlling ion-to-adatom flux ratio during ion-assisted deposition of diamond (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4714-4718 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A dual-bias method using a grid mesh inserted into the front of a substrate has been employed to control the ion-to-adatom flux ratio in an inductively coupled plasma for depositing crystalline materials preferring low-energy ion bombardment. The Langmuir probe measurements revealed that the ion flux toward the substrate decreased with increasing a positive substrate bias with the grid grounded, while it increased with increasing a positive grid bias with the substrate grounded. Ion energy analyses along the diffusing plasma stream by using a probe and a mass spectrometer revealed the contribution of a high-energy tail in the ion-energy distribution into the bombarding ion flux. The ion-assisted deposition of diamond at a pressure of 10 mTorr was performed at a bombarding ion energy as low as the drifting energy (∼several eV). The results indicate the need for optimizing the ion-to-adatom flux ratio for efficient migration and clustering of precursor adatoms yielding a high nucleation density over 109 cm−2. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1359159
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  • 4
    Electronic Resource
    Electronic Resource
    Ultrathin fluorinated silicon nitride gate dielectric films formed by remote plasma enhanced chemical vapor deposition employing NH3 and SiF4 (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 1955-1961 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrathin fluorinated silicon nitride (SiNx) films of 4 nm in thickness were formed on a Si substrate at 350 °C in the downflow of electron cyclotron resonance plasma-enhanced chemical vapor deposition employing ammonia and tetrafluorosilane (NH3/SiF4) gases. Ultrathin fluorinated SiNx film was evaluated for use as a gate dielectric film. The observed properties indicated an extremely low leakage current, one order of magnitude lower than thermal SiO2 of identical equivalent oxide thickness, as well as an excellent hysteresis loop (20 mV) and interface trap density (Dit=4×1011 cm−2) in the capacitance–voltage characteristics. The film structures and the surface reactions for the fluorinated SiNx film formation were examined via in situ x-ray photoelectron spectroscopy. in situ Fourier-transform infrared reflection absorption spectroscopy, in situ atomic force microscopy, and thermal desorption mass spectroscopy. The control of the fluorine concentration in the SiNx films was found to be a key factor in the formation of fluorinated SiNx films of high quality at low temperatures. Fluorinated SiNx is the effective material for application in ultrathin gate dielectric film in ultralarge-scale integrated circuits. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1381556
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  • 5
    Electronic Resource
    Electronic Resource
    Spatial distribution of the absolute densities of CFx radicals in fluorocarbon plasmas determined from single-path infrared laser absorption and laser-induced fluorescence (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 580-586 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spatial distribution of the absolute density of CFx (x=1–3) radicals and their translational temperatures in an electron cyclotron resonance (ECR) plasma generated from a tetrafluorocarbon (C4F8) gas were examined using infrared diode-laser absorption spectroscopy (IRLAS) without a multiple reflection cell, namely, single-path IRLAS. Furthermore, we have developed a method of measuring CF and CF2 radical densities using single-path IRLAS combined with laser-induced fluorescence (LIF) spectroscopy. This method enables us to measure the spatial distribution of absolute radical densities with high accuracy, because of the IRLAS infrared laser beam and the LIF ultraviolet laser beam having identical paths. Under all the conditions studied, a spatially hollow distribution of the CF2 radical density is formed; the CF2 radical density in the vicinity of the chamber wall is much higher than that in the plasma. However, the spatial distribution of the CF radical density differs greatly from that of the CF2 radical density. The translational temperatures of CF and CF2 radicals are evaluated to be ∼700 K. On the basis of the measured results, we clarify the mechanisms of the formation of the spatial distribution, and conclude that the hollow distribution of the CF2 radical density is not caused by radical generation from the chamber wall, rather, the dominant mechanism for the formation of this distribution is the electron-impact dissociation of C4F8 gas in the ECR region and diffusion from the upper part of the plasma chamber under the present plasma conditions where the flux of ions incident to the chamber wall is low. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1337090
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  • 6
    Electronic Resource
    Electronic Resource
    Measurement and control of absolute nitrogen atom density in an electron-beam-excited plasma using vacuum ultraviolet absorption spectroscopy (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 1756-1759 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The absolute nitrogen (N) atom density in an electron-beam-excited plasma (EBEP) operating at an ultralow pressure has been investigated by vacuum ultraviolet absorption spectroscopy, employing a microdischarge hollow-cathode lamp. The measured N atom density was estimated to be around 6×1011 cm−3, and the dissociation fraction was 4.9% at a N2 pressure of 0.05 Pa, an electron-beam current of 10 A, and an electron-beam acceleration voltage of 120 V. The EBEP potentially enables us to control the electron density and electron energy independently with the electron-beam current and electron-beam acceleration voltages, respectively. It was found that N atom densities increased with increasing electron-beam current and electron acceleration voltage under low-pressure conditions. The EBEP shows great promise as a N atom source operating at an ultralow pressure. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1305559
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  • 7
    Electronic Resource
    Electronic Resource
    Analysis of electric field distribution in GaAs metal–semiconductor field effect transistor with a field-modulating plate (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 3483-3487 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electric field distribution in the channel of a field effect transistor (FET) with a field-modulating plate (FP) has been theoretically investigated using a two-dimensional ensemble Monte Carlo simulation. This analysis revealed that the introduction of FP is effective in canceling the influence of surface traps under forward bias conditions and in reducing the electric field intensity at the drain side of the gate edge under pinch-off bias conditions. This study also found that a partial overlap of the high-field region under the gate and that at the FP electrode is important for reducing the electric field intensity. The optimized metal–semiconductor FET with FP (FPFET) (LGF∼0.2 μm) exhibited a much lower peak electric field intensity than a conventional metal–semiconductor FET. Based on these numerically calculated results, we have proposed a design procedure to optimize the power FPFET structure with extremely high breakdown voltages while maintaining reasonable gain performance. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372370
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  • 8
    Electronic Resource
    Electronic Resource
    Precursors of fluorocarbon film growth studied by mass spectrometry (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 7185-7190 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The precursor species of fluorocarbon film growth at the reactor wall irradiated by an electron cyclotron resonance C4F8 plasma have been studied by using a quadrupole mass spectrometer. The amount of polymeric neutral species [CmFn (m≥2)] and absolute densities of CFx (x=1–3) radicals in the vicinity of the wall were measured by electron attachment and threshold ionization mass spectrometry, respectively. The trends in the film growth rate as a function of gas residence time, diluted hydrogen concentration, and microwave power were well accounted for by the competition between the incorporation of CFx radicals and positive ions and the removal by F and H atoms. The fluxes of CFx radicals and positive ions incident upon the wall were shown to be comparable with the net condensed carbon flux derived from the growth rate. In contrast, the trends in the amount of polymeric neutrals were not well correlated to the growth rate. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372967
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  • 9
    Electronic Resource
    Electronic Resource
    Kinetics and role of C, O, and OH in low-pressure nanocrystalline diamond growth (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4572-4579 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A simple low-pressure condition at 80 mTorr has been employed to study the kinetics and role of C, O, and OH in diamond growth by using inductively coupled CO/CH4/H2 and O2/CH4/H2 plasmas. Vacuum ultraviolet absorption spectroscopy (VUVAS) and actinometric optical emission spectroscopy (OES) were used to examine the densities of ground-state C atoms and emissive species such as OH, C2, and O, respectively. Diamond films consisting of nanocrystallites with sizes as small as 20 nm were obtained on positively biased Si substrates only when CH4 was fed. Both diamond and nondiamond growth were enhanced with increasing CO for a fixed CH4 concentration of 5%, while diamond growth was suppressed with increasing O2. Comprehensive discussion along with the VUVAS and OES results suggested that the C atoms resulting mainly from CO by electron impact dissociation had a close relation with the formation of C2 or still larger species as the precursors to nondiamond phase, while the OH radicals resulting predominantly by loss reactions of the byproduct O atoms with H2 and CH4 were highly responsible for the enhanced diamond growth. A large amount of O atoms from O2 was shown to affect the initial nucleation stage seriously. The results support the growth chemistry of diamond from H-hybridized carbon radicals fragmented from CH4 rather than from H-stripped carbon radicals. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373104
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  • 10
    Electronic Resource
    Electronic Resource
    Plasma diagnostics and low-temperature deposition of microcrystalline silicon films in ultrahigh-frequency silane plasma (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 576-581 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Microcrystalline silicon thin films were formed on quartz substrates by ultrahigh-frequency (UHF) plasma enhanced chemical vapor deposition from a mixture of silane (SiH4) and hydrogen (H2) gases at low substrate temperatures (Ts). The UHF plasma was excited at a frequency of 500 MHz. The deposition rate and the crystallinity of the films were investigated as a function of H2 dilution, total pressure, mixture ratio of SiH4 to H2 and Ts. A crystalline fraction of 63% with a high deposition rate of 7.7 Å/s was obtained even at a Ts of 100 °C. At a temperature of 300 °C, a crystalline fraction of approximately 86% was achieved at a deposition rate of 1.4 Å/s. Diagnostics of the UHF plasma have been carried out using a Langmuir probe, ultraviolet absorption spectroscopy, and optical emission spectroscopy. Good crystallinity was explained by the balance of the sheath voltage and atomic hydrogen densities in the UHF plasma. Namely, the UHF plasma source achieving a high density plasma with a low electron temperature enabled us to reduce the ion bombardment energy incident on the substrates while maintaining a high density of hydrogen atoms, and which improved the crystallinity at low Ts. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373698
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