We have studied uniform growth of crystalline Ge films on quartz plate from VHF
(60MHz)-ICP of 10% GeH4 diluted with H2 in the temperature range from 150 to 350°C. By
optimizing total gas flow rate, gas pressure, VHF power and antenna-substrate distance, the growth
rate as high as 7.4nm/s was obtained at 150°C and increased gradually up to ~7.9nm/s at 350°C. The
crystallinity, which was evaluated by Raman scattering measurements as an integrated intensity ratio
of TO phonons in crystalline phase to those in disordered phase, reached a value as high as ~93 % at
350°C, but degraded down to 64% at 150°C as a result of the formation of a 60~70nm-thick
amorphous incubation (A. I.) layer on quartz. By applying a two-step deposition method at 150°C, in
which the GeH4 concentration was selected to be 0.6% for the crystalline nucleation in the first 10s
deposition, being as thin as 10nm in thickness, and then changed to 10% GeH4 for the high rate
growth, the crystallinity was improved to 78% with keeping an effective growth rate as high as
7.5nm/s, because of a significant increase in the growth rate after the crystalline nucleation.
Effect of outer gas flow rate on spectral line intensity and background intensity in inductively coupled plasma atomic emission spectrometry.