A novel approach for integration of dual metal gate process using ultra thin aluminum nitride buffer layer

We report and demonstrate a novel approach for dual metal gate CMOS process integration using an ultra thin aluminum nitride (AlN/sub x/) buffer layer between metal gate and gate dielectric. The buffer layer prevents the gate oxide from being exposed to a metal etching process and plays a key role in determining the work functions at the metal/dielectric interface. During annealing, this buffer layer is completely consumed through the reaction with metal gate and converted into a new metal alloy, resulting in no increase of EOT. The work functions of the original gate metals are modified as a result of this reaction, making this approach extremely attractive for dual metal gate CMOS applications.