Method of etching a trench in a silicon-on-insulator (SOI) structure

摘要

Disclosed herein is a method of etching a trench in silicon overlying a dielectric material which reduces or substantially eliminates notching at the base of the trench, while reducing scalloping on the sidewalls of the trench. The method comprises etching a first portion of a trench by exposing a silicon substrate, through a patterned masking layer, to a plasma generated from a fluorine-containing gas. This etching is followed by a polymer deposition step comprising exposing the substrate to a plasma generated from a gas which is capable of forming a polymer on etched silicon surfaces. The etching and polymer deposition steps are repeated for a number of cycles, depending on the desired depth of the first portion of the trench. The final portion of the trench is etched by exposing the silicon to a plasma generated from a combination of a fluorine-containing gas and a polymer-forming gas.