Hard mask process to control etch profiles in a gate stack

Abstract

A process increases the etch control on the thin gate oxidation near the edges of a poly-silicon or amorphous silicon gate stack, minimizing the formation of micro-trenches while achieving nearly vertical profiles. In an example embodiment, a method for manufacturing a semiconductor gate stack a gate stack having an anti-reflective coating, has a pattern defined with a photoresist mask The unmasked areas of the gate stack are etched with a first etch. The first etch removes the anti-reflective layer and a majority of the poly or amorphous silicon from the unmasked areas. After the first etch, the photoresist mask is removed. Using the anti-reflective coating as a hard mask the poly or amorphous silicon is removed with a second etch from unmasked areas until the gate oxide exposed. An over etch removes any poly or amorphous silicon residues.