Multi-step metallization etch

摘要

A method for etching through a selected portion of a metallization layer of a wafer's layer stack in a high density plasma processing chamber includes performing a main etch by etching at least partially through the metallization layer of the layer stack with a main-etch etchant source gas that includes essentially Cl2 and BCl3 having a first Cl2:BCl3 flow ratio. Thereafter, an over etch is performed by etching to a layer underlying the metallization layer with an over-etch etchant source gas that includes essentially Cl2 and BCl3 having a second Cl2:BCl3 flow ratio that is higher than the first Cl2:BCl3 flow ratio. The method may further include the step of performing a barrier layer etching step for etching a barrier layer of the layer stack prior to performing the over etch.