Radio-frequency biased microwave plasma etching technique: A method to increase SiO2 etch rate

Abstract

In order to increase the SiO2 etch rate in microwave plasma etching, a method of controlling the kinetic energy of ions impinging on a substrate surface covered with an insulator film was developed. In this method, radio-frequency voltage is supplied to the substrate. A theoretical model and analysis for this method was made to define the substrate surface potential and the kinetic energy of impinging ions. Experimental verification of the analysis, and application of the method to SiO2 etching have been carried out. A SiO2 etch rate εSiO2 =40 nm/min, and selectivity to Si η2=εSiO2/εSi =4.0 were obtained with C3F8 etching gas and rf peak to peak voltage VBP=200 V.