Mechanism of Reactive Ion Etching Lag in WSi2 Etching Using Electron Cyclotron Resonance Plasma

Abstract

The electron cyclotron resonance (ECR) plasma is one of the suitable methods to generate plasma at a low pressure; however, unprecedented low pressure (<0.1 Pa) and smaller feature size have created unexpected problems. We study the relationship between ion energy and WSi2 etching products in order to discuss the mechanism of the reactive ion etching (RIE) lag observed in the WSi2 etching results. We investigate the dependence of WSi2 etch rate and RIE lag on etching parameters at low pressures (4×10-2 Pa). The RIE lag of WSi2 etching is stronger than that of poly-Si etching. Also, the RIE lag increases as rf power increases. Two possible reasons for the RIE lag can be suggested. One is the decrease of the flux ratio of a high-aspect-ratio pattern. Another is that partial pressure of the etch products at the bottom of a narrow space pattern is higher than that at the wide space pattern.