Patent ID: 8501626

Claim:
A method of etching a film stack for forming a gate structure, comprising: providing a substrate having a film stack formed thereon in an etch chamber, wherein the film stack includes a high-k material sandwiched between a first and a second polysilicon layers; etching the first polysilicon layer on the substrate to form a trench exposing the high-k material in the etch chamber; forming a protection layer on the sidewalls of the trench; etching the high-k material through the protected trench by at least a BCl 3 gas without applying a bias power in the etch chamber at a temperature between about 100 degrees Celsius and about 250 degrees Celsius while etching the high-k material layer in the presence of the plasma; and etching the second polysilicon layer disposed on the substrate while maintaining the substrate temperature between about 100 degree Celsius and about 250 degrees Celsius and the interior surface of the etch chamber at a temperature in excess of about 100 degrees Celsius in the same etch chamber.