Thermally robust dual-work function ALD-MN _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 x)/ SiON (or high-k)/Si stack with atomic layer deposition (ALD)-TaN x for the NFET and ALD-WN x for the PFET. Much enhanced drive current (I d) and transconductance (G m) values, and reduced off current (I off) characteristics were attained with ALD-MN x gated devices over control poly-Si and PVD-MN x devices within controllable V t shifts. Excellent scalability of dual work function MN x/high-k gate stack was demonstrated: the EOT was down to 6.6A° with low leakage in a low thermal budget device scheme.