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.