METHOD AND APPARATUS FOR DETECTING ENDPOINT DURING PLASMA ETCHING OF THIN FILMS

摘要

A method for controlling a plasma etch process while etching a layer stack having a first layer disposed above an end-point generating layer is disclosed. Method includes etching through first layer and at least partially through end-point generating layer while monitoring an absorption rate of a light beam traversing an interior portion of the plasma processing chamber, wherein the end-point generating layer is selected from material that produces a detectable change in absorption rate when etched. The end-point generating layer is characterized by at least one of a first characteristic and a second characteristic. The first characteristic is an insufficient thickness to function as an etch stop layer, and the second characteristic is an insufficient selectivity to etchants employed to etch through the first layer to function as the etch stop layer. The method additionally includes generating an end-point signal upon detecting the detectable change.