Thermally robust dual-work function ALD-MN/sub x/ MOSFETs using conventional CMOS process flow

Thermally stable dual work function metal gates are demonstrated using a conventional CMOS process flow. The gate structure consists of poly-Si/metal nitrides (MN/sub x/) SiON (or high-k)/Si stack with atomic layer deposition (ALD)-TaN/sub x/ for the NFET and ALD-WN/sub x/ for the PFET. Much enhanced drive current (I/sub d/) and transconductance (G/sub m/) values, and reduced off current (I/sub off/) characteristics were attained with ALD-MN/sub x/ gated devices over control poly-Si and PVD-MN/sub x/ devices within controllable V/sub t/ shifts. Excellent scalability of dual work function MN/sub x//high-k gate stack was demonstrated: the EOT was down to 6.6/spl Aring/ with low leakage in a low thermal budget device scheme.