Fourier transform infrared spectroscopy of CF4 plasmas in the GEC reference cell

Fourier transform infrared spectroscopy (FTIR) has been used to characterize inductively coupled CF4 plasmas in a GEC reference cell in situ. In examining these FTIR spectra., several assumptions and approximations of FTIR analysis are addressed. This includes the density dependence of cross-sections, non-linear effects in the addition of overlapping bands and the effect of spatial variations in density and temperature. This analysis demonstrates that temperatures extracted from FTIR spectra may provide a poor estimate of the true neutral plasma temperature. The FTIR spectra are dominated by unreacted CF4. accounting for 40-60% of the gas products. The amount of CF4 consumption is found to have a marked dependence on power. and is nearly independent of pressure in the range of 10-50 mTorr. Small amounts of C2F6 are observed at low power. Also observed are etching products from the quartz window-SiF4, COF2 and CO-which occur in approximately equal ratios and together account for 17-19% of the cas at 300 W and 6-9% of the gas at 100 W. The concentrations of these species are nearly independent of pressure. CFx radicals are below the detection limit of this apparatus (similar to10(13) cm(-3)).