Endpoint detection in low open area and/or high aspect ratio etch applications

Abstract

Disclosed herein is a method for determining the endpoint of an etch operation used for forming high aspect ratio features and/or over low open area (<1%) on a substrate in a processing chamber. The method begins by obtaining a reference emission curve. An etch operation is performed on a patterned substrate. A plasma optical emission intensity is measured for each of the etch cycles. A differential curve between the reference emission and the plasma optical emissions is calculated. And endpoint is determined for the etch operation on the first substrate based on an inflection point detection or other unique features through pattern recognition in the differential curve for stopping the etch of the first substrate.