Study of the influence of gas chemistry on notching in metal etching

Abstract

A comparison of notching of metal etching in Cl2/BCl3 and HCl plasma was made by using a transformer coupled plasma etcher. We found that notches can be reduced by eliminating BCl3 from gases for overetching. Furthermore, the HCl/He overetch process provides notch-free profiles with high selectivities. The reduction in sidewall attack by heavy ions (e.g., BCl2+ or BCl3+) and scavenging of excess Cl radicals by the H radical are considered possible reasons for reduced notching in the HCl/He process.