SiO2 Etching in C4F8/O2 Electron Cyclotron Resonance Plasma

Abstract
We report the application of C4F8/O2 electron cyclotron resonance (ECR) plasma to SiO2 etching. The effect on SiO2 etching characteristics of O2 addition to C4F8 ECR plasma is investigated. In C4F8 ECR plasma (no O2 addition), strong reactive ion etching (RIE) lag effect of SiO2 and poly-Si etching is observed. However, with O2 addition, the RIE lag effect of SiO2 etching decreases markedly whereas the RIE lag effect of poly-Si etching decreases gradually. Consequently, SiO2 etching selectivity to poly-Si increases. The results of mass spectrometric measurement using two orifices indicate that surface reaction probability of fluorocarbon molecules is affected by O2 addition.