Dual metal fill and dual threshold voltage for replacement gate metal devices

Abstract

A structure and method for forming a dual metal fill and dual threshold voltage for replacement gate metal devices is disclosed. A selective deposition process involving titanium and aluminum is used to allow formation of two adjacent transistors with different fill metals and different workfunction metals, enabling different threshold voltages in the adjacent transistors.

What is claimed is: 
     
         1 - 13 . (canceled) 
     
     
         14 . A semiconductor structure comprising:
 a first field effect transistor comprising a first gate cavity;   a second field effect transistor comprising a second gate cavity;   a first fill metal disposed in the first gate cavity; and   a second fill metal disposed in the second gate cavity.   
     
     
         15 . The semiconductor structure of  claim 14 , wherein the first fill metal comprises aluminum. 
     
     
         16 . The semiconductor structure of  claim 15 , wherein the second fill metal comprises tungsten. 
     
     
         17 . The semiconductor structure of  claim 15 , wherein a titanium layer is disposed under the first fill metal and is not disposed under the second fill metal. 
     
     
         18 . The semiconductor structure of  claim 17 , further comprising a first workfunction metal disposed under the titanium layer, and a second workfunction metal disposed under the second fill metal. 
     
     
         19 . The semiconductor structure of  claim 18 , wherein the first workfunction metal comprises titanium nitride. 
     
     
         20 . The semiconductor structure of  claim 18 , wherein the second workfunction metal is comprised of a material selected from the group consisting of titanium aluminum nitride and tantalum carbide.