| dc.description |
Fourier transform infrared spectroscopy (FTIR) has been used to characterize inductively coupled CF<sub>4</sub> 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 CF<sub>4</sub>, accounting for 40-60% of the gas products. The amount of CF<sub>4</sub> 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 C<sub>2</sub>F<sub>6</sub> are observed at low power. Also observed are etching products from the quartz window - SiF<sub>4</sub>, COF<sub>2</sub> and CO - which occur in approximately equal ratios and together account for 17-19% of the gas at 300 W and 6-9% of the gas at 100 W. The concentrations of these species are nearly independent of pressure. CF<sub>x</sub> radicals are below the detection limit of this apparatus (~10<sup>13</sup> cm<sup>-3</sup>). |
