2750
Appl. Phys. Lett., Vol. 72, No. 21, 25 May 1998
Seck et al.
3͑c͒ corresponds to the the difference spectrum obtained by
subtracting a weighted spectrum for plasma oxidized Si
͑‘‘pure’’ SiO2͒ from the unetched spectrum of Si0.65Ge0.35O2
͓solid line in Fig. 3͑b͔͒. We observe, again, evidence for the
presence of two peaks at 1000 and 850 cmϪ1 in the Ge con-
taining sample. The weighting factor used was 0.43 which
corresponds to the statistical number of Si–O–Si bonds in
Si0.65Ge0.35O2.
We have successfully oxidized Si1ϪxGex thin films using
plasma assisted oxidation at temperatures Ͻ100 °C and
characterized these films using SIMS and FTIR. The high Ge
concentration films show evidence for separated regions of
Ge-rich oxide and Si-rich oxide, the former being close to
the oxide surface, in contrast to thermally oxidized films
where Ge excess and/or precipitation near the oxide–
semiconductor interface is observed. This effect has been
confirmed both by SIMS analysis and FTIR combined with
water etching. Our FTIR data enable us, for the first time, to
identify clearly vibrational modes associated with O in Si–
O–Si, Si–O–Ge and Ge–O–Ge structures in the thin films,
confirming that the plasma oxides of SiGe are mixed on an
atomic scale.
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