New experimental data for the minority-carrier surface recombination velocity of n-type silicon, Sp, are reported. The data, obtained from photoconductance decay measurements of the recombination currents corresponding to different phosphorus diffusions, include oxide-passivated, unpassivated and metal-coated surfaces. For the passivated case, Sp increases linearly with surface dopant density, ND, for dopant densities higher than 1×1018 cm−3, while for unpassivated (bare) and for metal-coated silicon Sp remains essentially constant, at about 2×105 cm/s and 3×106 cm/s, respectively. The experiments also allow for a determination of the apparent energy bandgap narrowing as a function of dopant density, ΔEgapp=14 meV [ln(ND/1.4×1017 cm−3)]. These surface recombination velocity and ΔEgapp data form, together with the dependences of minority-carrier lifetime, τp, and mobility, μp, used in the analysis, a consistent set of parameters that fully characterize highly doped n-type silicon.
Silicon dioxide films have been deposited at low pressure (a few millitorr) and low substrate temperature (<200 °C) by oxygen/silane helicon diffusion radio frequency plasmas. High deposition rates (20–80 nm/min) are achieved at 800 W rf source power. The effect of the oxygen/silane flow rate ratio (R) on the film properties has been investigated: characterization of the deposited films has been carried out by in situ ellipsometry, ex situ Fourier transform infrared spectroscopy, Rutherford backscattering, x-ray photoelectron spectroscopy (XPS), and chemical etch rate measurements (P etch) and the results have been compared to thermally grown oxide. The deposition kinetics has a great effect on the internal film structure: for films presenting a good stoichiometry ([O]/[Si]≥1.95 for R≥3), a decrease in the deposition rate is accompanied by a decrease of the refractive index, P-etch rate and XPS line width and by an increase of the Si–O stretching peak frequency toward the thermal oxide respective values. A sufficient oxygen/silane flow rate ratio (R=10) leads to stoichiometric films which exhibit good optical properties. Small differences in the P-etch rate, XPS linewidth, and infrared stretching peak frequency are still observed between our stoichiometric plasma deposited film and a thermally grown oxide film.
France (3) Sandis Nation4 Laboratories, P.O. Ror 6800, AlbuqUerQUe, NM 6718547552, U.3.A: (4) Siarirens Solar Industries, P.0. Box 6032, Camarillo, CA 93011, tJ.S.A. ABS rRACT An malylical procedure to extraa the surface rawnibitlalioii volocity of the SO& typo silicon interfoco, S$? from PC6 rnnasiiremenfs of emitter recombination currents is deswibd. The analyois shows that tho extracted values af + are significantly affected by the assumed marerial parameters for highly JopuJ silicon. tp,+,, andd baE4 Updatod v duoe for these parameters arn rised IO obtain the dependence 01 S, on rhe phosphorus wr1centi.atiun, &J, using both previous and new experimental data The new e d dence suppatts rhe finding rhar 5$ tncreases s~ruiiyly will) Nu0
Silicon dioxide thick films (1–18 μm) have been deposited at very reasonable deposition rates (20–80 nm/min) with no intentional heating of the substrate (T∼200 °C) using SiH4/O2 plasmas coupled in a new type of plasma reactor: The radio frequency plasma excitation used in the helicon diffusion reactor induces the formation of high-density plasmas (∼1012 cm−3) with low plasma potentials. Three main parameters have been investigated; the total gas flow, the oxygen/silane gas flow ratio, and the magnetic confinement in the diffusion chamber. An in situ control of the refractive index and deposition rate has been obtained and correlated to an ex situ analysis of the deposited films (infrared transmission spectroscopy and chemical etch rate measurements) and the effects of the deposition kinetics on the film properties such as the hydrogen content and the voids fraction have been analyzed.
In this paper we present an investigation of the static performance over the 300K-80K temperature range of pseudo-heterojunction bipolar transistors using an advanced single-polysilicon CMOS compatible self-aligned structure and epitaxial growth for the base and the low doped emitter spacer. These devices exhibit ideal collector currents and non-ideal base currents. By analysing the base leakage current, we have been able to identify the main critical fabrication steps. The bandgap narrowing in the base has been deduced from the temperature dependence of the collector current and the effect of a parasitic boron spike in the base doping profile on the low temperature performance of the transistor has been studied.
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