Enhancement of the Flatband Modulation of Ni-Silicided Gates on Hf-Based Dielectrics

Abstract

For the first time, the effect of the poly-Si gate electrode deposition process on the electrical characteristics of Ni-based fully silicided/HfO2 gate stacks is investigated. The flat- band voltage Vfb of Ni2Si/HfO2 (or Ni3Si/HfO2) with a physical vapor deposited (PVD) Si electrode was found to significantly shift to the positive direction by 0.27 V (or 0.15 V), compared to the case with a chemical vapor deposited (CVD) Si electrode. On the contrary, the Vfb of NiSi/HfO2 with a PVD Si electrode slightly shifts to the negative direction from that with a CVD Si electrode (~0.05 V). Further, La is incorporated into HfO2 to enhance the Vfb modulation of NiXSi gates with a PVD Si gate to near the conduction band edge of Si (~4.0 eV). We believe that the Vfb shift of NiXSi/HfO2 is attributed to the release of Fermi-level pinning at the interface between the Si gate electrode and HfO2, arising from the different Si electrode formation process.