Notch elimination in polycide gate stack etching for advanced DRAM technology

The notch phenomenon in etching of complex TEOS/oxynitride/WSi/sub x//poly DRAM gate stacks is eliminated by adding N/sub 2/ gas in the poly over-etch (OE) step. The N/sub 2/ addition in poly OE can passivate poly surface against Cl-atom attack; however, it also results in increasing poly residues. Therefore, by increasing the over-etch time of WSi/sub x/ etching, these residues can be removed. The optimized recipe can achieve both residue-free and notch-free processing with no impact on the critical dimensions (CD) of the gate stack and remaining oxide after etching.