High temperature anneal for aluminum surface protection

摘要

The present disclosure also provides another embodiment of a method for making metal gate stacks. The method includes forming a first dummy gate and a second dummy gate on a substrate; removing a polysilicon layer from the first dummy gate, resulting in a first gate trench; forming a first metal layer and a first aluminum layer in the first gate trench; applying a chemical mechanical polishing (CMP) process to the substrate; performing an annealing process to the first aluminum layer using a nitrogen and oxygen containing gas, forming an interfacial layer of aluminum, nitrogen and oxygen on the first aluminum layer; thereafter removing the polysilicon layer from the second dummy gate, resulting in a second gate trench; and forming a second metal layer and a second aluminum layer on the second metal layer in the second gate trench.