Polymer layers formed on silicon wafer during silicon oxide overetching usi
ng C4F8 helicon wave plasmas and their properties were investigated using s
pectroscopic ellipsometry, X-ray photoelectron spectroscopy, and secondary
ion mass spectrometry. Thr degree of overetching and d.c. self-bias voltage
were varied to investigate the effects on the characteristics of the polym
ers remaining on the overetched silicon surface. The increase of bias volta
ge from - 80 V to - 120 V increased the CIF ratio and carbon bonds such as
C-C, C-CFx, and C-Si in the polymer while reducing the thickness of the pol
ymer layer. However, prolongation of the overetch time from 50% to 100% did
not change the chemical composition of the polymer layer and the carbon bi
nding states in the polymer layer remained the same even though the polymer
thickness was increased. The polymer layer formed at the higher d.c. self-
bias voltage was more difficult to remove by the subsequent post-etch treat
ments compared to that formed at longer overetch time. (C) 1999 Elsevier Sc
ience S.A. All rights reserved.