Abstract :
We have implemented linear and nonlinear optical spectroscopies to monitor and control the growth of Si Ge films. x 1yx
Using spectroscopic ellipsometry and the virtual substrate approximation VSA., controlled growth of compositionally
graded SiGe films deposited by chemical vapor deposition CVD.is achieved by adjustment of disilane flow based on
feedback from ellipsometric inputs. Stepped and linear growth profiles are investigated. Using spectroscopic, surface second
harmonic generation SHG.by a tunable, unamplified Ti:sapphire 100 femtosecond fs.laser, shifts of the SH spectral
feature near the Si E1 critical point with varying Ge composition are observed. A comparison is made to linear spectroscopy
and related qualitatively to surface composition. Data acquisition time is then reduced to a few seconds by substituting a 10
fs laser and spectrally dispersing generated SH radiation onto an array detector, thus enabling real-time spectroscopic SHG.
The reflected SH spectrum near the E1 region is also highly sensitive to bulk boron doping of SiGe. Definite trends in the
peak positions and amplitudes as a function of boron incorporation are observed and interpreted qualitatively in terms of
dc-electric-field-induced SHG in the depletion region. The results demonstrate the feasibility of SE and spectroscopic SHG
operating as complementary, in situ sensors of SiGe CVD. q2000 Elsevier Science B.V. All rights reserved.
