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

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 V_fb 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 V_fb 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 V_fb modulation of Ni_XSi gates with a PVD Si gate to near the conduction band edge of Si (~4.0 eV). We believe that the V_fb shift of Ni_XSi/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.