Widely Tunable Work Function TaN/Ru Stacking Layer on HfLaO Gate Dielectric

For the first time, we demonstrate experimentally that using HfLaO high- kappa gate dielectric and vertical stacks of TaN/Ru metal layers, dual metal gates with continuously tunable work function over a very wide range from 3.9 to 5.2 eV, can be achieved after 1000 degC annealing required by a conventional CMOS source/drain activation process. The wide tunability of work function for this bilayer metal structure is attributed to metal interdiffusion during annealing and the release of Fermi level pinning between metal gates (Ru and TaN) and HfLaO. Moreover, this change is thermally stable and unaffected by a subsequent high temperature process.