Patent ID: 8163620

Claim:
A method for etching a Mo-based metal gate stack with an aluminum nitride barrier, comprising: forming a high K dielectric layer, a Mo-based metal gate layer, an AlN barrier layer, a silicon gate layer in sequence on a semiconductor substrate; forming a hard mask on the silicon gate layer; performing an anisotropic etching on the silicon gate layer by a first dry etching using the hard mask; and performing an anisotropic etching on the AlN barrier layer, the Mo-based metal gate layer, and the high K dielectric layer by a second dry etching using the hard mask and a BCl 3 -based etching gas having high selectivity for the ALN barrier layer, the Mo-based metal gate layer, and the high K dielectric layer; wherein the BCl 3 -based etching gas has a ratio of Cl 2 : BCl 3 of 0 to 1:4, a ratio of O 2 : BCl 3 of 0 to 1:8, and a ratio of Ar: BCl 3 of 1:5 to 1:2.