Mitsuo Shimozuma

Boltzmann equation analysis of electron swarm behaviour in nitrogen

The electron swarm behaviour in nitrogen is studied for E/ rho 0 from 20 to 200 V cm-1 Torr-1 by a Boltzmann equation method. A set of electron collision cross sections is determined using newly published data. The modification of these cross sections when necessary is kept to within experimental error. Moreover, the validity of the vibrational excitation cross sections obtained theoretically by Hazi and co-workers (1981) is examined. The results show that the calculated swarm parameters are in close agreement with those obtained by a photon flux experiment of Wedding and co-workers (1985). This suggests that the set of electron collision cross sections determined in the present work is an appropriate one as far as the swarm parameter analysis is concerned. The electron energy distribution and electronic excitation coefficients and frequencies to various excited states are also calculated and discussed.

The drift velocity and longitudinal diffusion coefficient of electrons in nitrogen and carbon dioxide from 20 to 1000 Td

The distribution of arrival time spectra (ATS) of electrons in nitrogen and carbon dioxide has been measured over the range of E/N from 20 to 1000 Td (1 ) at room temperature by a double-shutter drift tube. The drift velocity of electrons in and was evaluated from these distributions by the ATS method. Moreover, the ratio of the longitudinal diffusion coefficient to the electron mobility was measured. The values of and in and were in good agreement with experimental and theoretical values obtained by previous investigators except for a few of the earlier studies.

Measurement of the effective ionisation coefficient and the static breakdown voltage in SF6 and nitrogen mixtures

The effective ionisation coefficient alpha /p20 is measured for E/p20 from 70 to 160 V cm-1 Torr-1, and the static breakdown voltage Vs between parallel plates for p20d from 8 to 130 Torr cm, for SF6 and nitrogen mixtures. It is found that the alpha /p20 of the mixtures may be approximated by a linear function of the partial pressure of SF6 at fixed E/p20 and that Paschens law holds for the p20d may be estimated with good accuracy from the Vs of the respective pure gases using an experimental formula of Takuma et al. (1972) which has been used for much larger p20d.

Optical emission diagnostics of H2+CH4 50‐Hz–13.56‐MHz plasmas for chemical vapor deposition

The emission spectra of H2+CH4 plasmas excited at 50 Hz–13.56 MHz were measured. The emission intensity ratios of Hα/H*2 (3Σg →3Σu) from H2+CH4 plasma at 50 Hz and 13.56 MHz were about 0.7 and 0.05, respectively. The electron temperature was obtained from the two‐line radiance ratio method using the Balmer lines (Hα and Hβ), and rapidly decreased with an increase above 200 kHz. The electron temperature for H2+CH4 plasma is 16 000 K at 1 kHz and 8200 K at 13.56 MHz. The plasma‐maintaining voltages for H2 and H2+CH4 mixtures were also measured. The maintaining voltages were constant below 200 kHz, and rapidly decreased between 200 kHz and 13.56 MHz. The position dependence of emission intensity was also measured for Hα, Hβ, and H*2 at 50 Hz and 13.56 MHz. The results are interpreted in terms of the electron distribution in the plasma.

Boltzmann equation analysis of the electron swarm development in SF6 and nitrogen mixtures

The ionisation alpha and electron attachment eta coefficients and other electron swarm parameters are calculated for SF6 and nitrogen gas mixtures for E/p0=75-200 V cm-1 Torr-1 by a Boltzmann equation method, in which the effect of generation and loss of free electrons due to ionisation and attachment are fully considered, for the steady-state Townsend (SST) experiment. The results show that the deduced values of the effective ionisation coefficient alpha (= alpha - eta ) are in good to fair agreement with those measured by Itoh et al. (1979) by a SST method, but agreement is less satisfactory with the experimental values of Aschwanden (1979) by a pulse method. The limiting E/p0 value, at which alpha = eta , is also calculated to give slightly higher values than previous experiments. The variation of the electron energy distribution, electron drift velocity, diffusion coefficient and mean energy, and the excitation frequency to C3 Pi u of nitrogen, as a function of the partial SF6 pressure, are calculated and discussed.

Electron swarm parameters in water vapour

Electron swarm parameters, such as the drift velocity and the ionization coefficient, in water vapour have been measured for relatively wide ranges in reduced electric fields (E/N) at room temperature. The drift velocity (Wm) was obtained based upon the arrival-time spectra of electrons by using a double-shutter drift tube for the E/N from 60 to 1000 Td, while the first and second ionization coefficients (α and γ) were determined by the steady-state Townsend method from 50 to 3000 Td. A comparison between the results and other data in the literature shows that our results for both the drift velocity and the effective ionization coefficient are lower than those of the other data in the above ranges.

Room temperature deposition of silicon nitride films using very low frequency (50Hz) plasma CVD

Silicon nitride films have been deposited by low frequency 50Hz plasma CVD using a nitrogen and silane mixture at room temperature. To deposit high quality silicon nitride, the silane fraction in the nitrogen and silane mixture has to be less than 5 %. The refractive index, breakdown field strength and resistivity of the obtained silicon nitride film were 2.0, 1.2x107 V/cm and 6x1015 Ωcm, respectively. Mechanism of the deposition of high quality silicon nitride is discussed on the basis of the experimentally observed light emission spectrum from the plasma and of the electron energy distribution function in the plasma theoretically calculated by the Boltzmann equation method.

Measurement of the ionisation and attachment coefficients in SF6 and air mixtures

The Townsend first ionisation coefficient alpha /p20, the electron attachment coefficient eta /p20, the effective ionisation coefficient alpha /p20(=( alpha /p20)-( eta /p20)) and the secondary coefficient gamma T for SF6 and air mixtures have been measured by the steady-state Townsend method for 51 or approximately=120 V cm-1 Torr-1 and the alpha /p20 varies approximately linearly with k at E/p20=160 V cm-1 Torr-1, but the linear relationship of alpha /p20 with k tends to break down with decreasing E/p20. The results also show that the gamma T decreases rapidly from about 10-3 to the values of gamma T for SF6 with increasing k at fixed E/p20 and the limiting E/p20, at which alpha /p20= eta /p20, rapidly increase with increasing k as those of the SF6 and nitrogen mixture.

Stable passivation systems for GaAs prepared by room-temperature deposition of SiO2 films

The 50-Hz plasma enhanced chemical vapor deposition technique allowed the deposition of high-quality SiO2 onto GaAs at room temperature without destroying the surface structure of amorphous-As covered GaAs, resulting in the stable SiO2/As/GaAs passivation system. Abrupt carrier profiles were reproducibly obtained for the Si-implanted and rapid thermal annealed GaAs using this passivation system.

Measurement of the ionisation and attachment coefficients in monosilane and disilane

The ionisation alpha /p0, electron attachment eta /p0 and effective ionisation alpha /p0(= alpha /p0- eta /p0) coefficients for monosilane (SiH4) and disilane (Si2H6) were measured by the steady-state Townsend method for 60 150 V cm-1 Torr-1 and found to be less than 10-5.