Fourier-transform infrared measurements of CHF3/O-2 discharges in an electron cyclotron resonance reactor

Knowledge of the neutral gas composition in a discharge is important for un derstanding the chemical processes involved in both etching and deposition environments. We have performed Fourier-transform infrared absorption spect rometry measurements of CHF3/O-2 plasmas in an electron cyclotron etching t ool. Spectral bands were observed from both gas-phase and surface-phase spe cies (deposited on the vacuum windows). The primary gas-phase species were CF4, H2O2, and HF. Strong absorption bands due to CFx, where x=1, 2, or 3, deposition on the vacuum windows were also observed. The densities of the g as-phase species were calculated from the strength of the measured absorpti on. It was found for typical discharge powers that the HF density was appro ximately 80% of the total gas density and depended on the plasma density an d neutral pressure. In addition, because HF, H2O2, and CF4 are not the feed gas, these data clearly show that recycling of the daughter species (C,CFx , F-x, etc.) on the chamber walls play an important role in determining the plasma chemistry in this high-electron density, > 10(11) cm(-3), low neutr al pressure, <10 mTorr, discharge, (C) 1999 American Vacuum Society. [S0734 -2101(99)06005-4].