Lowering of effective work function induced by metal carbide/HfO2 interface dipole for advanced CMOS

We investigated the origin of the voltage shift induced by metal carbide (MeC)/HfO₂ interface as metal gates in a Si or Ge channel for advanced CMOS. In the MeC/HfO₂ gate stacks, the oxidation reaction occurs at the MeC/HfO₂ interface, inducing electron transfer from HfO₂ to MeC, resulting in the generation of dipole at the MeC/HfO₂ interface. It was found that the MeC/HfO₂ interface dipole causes a negative voltage shift of about -0.4 V regardless of metal atoms. Thus, the effective work function of MeC in a metal/high-k gate stack structure can be lowered by the negative voltage shift induced by the MeC/HfO₂ interface dipole.