Method of forming a metal gate for CMOS devices using a replacement gate process

摘要

A method of forming a metal gate for a CMOS device using a replacement gate process wherein sidewall spacers are formed on a dummy electrode prior to forming the metal gate allowing source and drain formation prior to metal gate formation and a tungsten layer is selectively deposited to act as an each or CMP stop and to reduce source and drain resistance. The process begins by forming a dummy gate oxide layer and a polysilicon dummy gate electrode layer on a substrate structure and patterning them to form a dummy gate. Lightly doped source and drain regions are formed by ion implantation using the dummy gate as an implant mask. Spacers are formed on the sidewalls of the dummy gate. Source and drain regions are formed by implanting ions using,the dummy gate and spacers as an implant mask and performing a rapid thermal anneal. A tungsten layer is selectively deposited on the dummy gate electrode and the source and drain regions. A blanket dielectric layer is formed over the dummy gate and the substrate structure. The blanket dielectric layer is planarized using a chemical mechanical polishing process stopping on the tungsten layer. The tungsten layer overlying the dummy gate and the dummy gate are removed, thereby forming a gate opening. A gate oxide layer and a metal gate electrode layer are formed in the gate opening. The gate electrode layer is planarized to form a metal gate, stopping on the blanket dielectric layer. Alternatively, the dummy gate electrode can be composed of silicon nitride and the selectively deposited tungsten layer can be omitted.