C. Charles et al., CHARACTERIZATION OF SILICON DIOXIDE FILMS DEPOSITED AT LOW-PRESSURE AND TEMPERATURE IN A HELICON DIFFUSION REACTOR, Journal of vacuum science & technology. A. Vacuum, surfaces, and films, 11(6), 1993, pp. 2954-2963
Silicon dioxide films have been deposited at low pressure (a few milli
torr) and low substrate temperature ( < 200-degrees-C) by oxygen/silan
e helicon diffusion radio frequency plasmas. High deposition rates (20
-80 nm/min) are achieved at 800 W rf source power. The effect of the o
xygen/silane flow rate ratio (R) on the film properties has been inves
tigated: characterization of the deposited films has been carried out
by in situ ellipsometry, ex situ Fourier transform infrared spectrosco
py, Rutherford backscattering, x-ray photoelectron spectroscopy (XPS),
and chemical etch rate measurements (P etch) and the results have bee
n compared to thermally grown oxide. The deposition kinetics has a gre
at effect on the internal film structure: for films presenting a good
stoichiometry ([O]/[Si] greater-than-or-equal-to 1.95 for R greater-th
an-or-equal-to 3), a decrease in the deposition rate is accompanied by
a decrease of the refractive index, P-etch rate and XPS line width an
d by an increase of the Si-O stretching peak frequency toward the ther
mal oxide respective values. A sufficient oxygen/silane flow rate rati
o (R = 10) leads to stoichiometric films which exhibit good optical pr
operties. Small differences in the P-etch rate, XPS linewidth, and inf
rared stretching peak frequency are still observed between our stoichi
ometric plasma deposited film and a thermally grown oxide film.