Fourier transform infrared spectroscopy of trifluoroiodomethane plasma

Abstract

Fluorocarbon species (CxFy) are commonly used in plasma etch processes. Trifluoroiodomethane (CF3I) might also be used as an etch gas, but there is a limited understanding as to how it will react. In this article, the authors examine the creation of CxFy daughter species from CF3I under different plasma conditions. Here, Fourier transform infrared spectroscopy (FTIR) was used to measure the concentration of various gas species. Readings were taken at different plasma powers and different chamber pressures. Outside the parent gas, both CF3 and CF4 were found under all operating conditions. CF3I density decreases monotonically with increasing plasma power. In comparison, CF3 densities peaked at moderate plasma powers (200 W), while CF4 densities increased with power. Above 300 W, small levels of C2F6 were also observed. At high powers, a large fraction of gas phase chemistry is not observable via FTIR spectrometry, suggesting the presence of significant quantities of I, I2, F, and F2. A greater understanding of CF3I could yield better methods for large scale semiconductor etching and help to add clarity to the creation of CxFy species.