NEW ETCH PROCESS FOR FORMING HIGH ASPECT RATIO TRENCHES IN SILICON

摘要

A multistep etch process for forming high aspect ratio trenches in silicon having a silicon oxide and/or silicon nitride hardmask. In a first step, an etch composition of HBr and oxygen is used, depositing a passivation layer on the sidewalls and producing slightly tapered openings. In the second step, an etch composition of a fluorine- containing gas such as SF.sub.6, HBr and oxygen is used, producing more vertical openings at a high etch rate. The taper of the openings during the second step can be controlled by adjusting the relative amount of HBr or SF.sub.6 employed. This process is a clean process that does not require cleaning of the etch chamber between etch steps.