Investigation of NiSi fully-silicided gate on SiO2 and HfO2 for applications in metal-oxide-semiconductor field-effect transistors

Abstract

Effective work function modulation (phi(m,eff)) and the thermal/electrical stability of NiSi fully-silicided (FUSI) gates on SiO2 and HfO2 are investigated. A new method, implant-to-silicide, differing from the,pre-doped method, is used to realize Phi(m,eff) adjustments. The Phi(m,eff) of NiSi FUSI gates on SiO2 can be tuned by incorporating BF2+ or P+ dopants after silicidation. Nevertheless, the Fermi-pinning effect was observed in the NiSi/HfO2 gate which limits the Phi(m,eff) adjustment. A thin SiO2 interfacial layer can reduce the Fermi-pinning effect. A NiSi FUSI gate on SiO2 is thermally stable up to 600 degrees C. The thermal stress and impurity diffusion after a prolonged 600 degrees C annealing degraded the oxide integration. The temperature of the post-silicidation process should be as low as possible to lessen the thermal stress and impurity diffusion.