Gas-phase studies in inductively coupled fluorocarbon plasmas

Abstract

Quantitative results from infrared laser absorption spectroscopy (IRLAS) of CF and CF2 radicals and COF2 products in inductively coupled plasmas fed with C2F6, CHF3 and C4F8 are presented and compared with results simultaneously obtained by mass spectrometry and optical emission spectroscopy. These plasma gas-phase analysis results are discussed and compared to fluorocarbon deposition and etching rates resulting from plasma–surface interactions at the substrate. It is found that COF2 species are being formed (1) during O2 plasma cleaning of a fluorocarbon contaminated reactor and (2) during SiO2 etching in fluorocarbon plasmas, which in this work occurred at the quartz coupling window as a result of capacitive coupling between the induction coil and the plasma. IRLAS results on CF and CF2 densities are compared to fluorocarbon deposition and etching rates and it is found that low CF and/ or CF2 density does not necessarily translate into a low fluorocarbon deposition rate. A relatively high deposition rate can be achieved at conditions with a high ion current density and low CF and CF2 densities.