Dopant enhanced in nickel silicide formation for high-k dielectric applications

Abstract

The thermal stability of fully silicided NiSi with arsenic doping on silicon was investigated. The combination of full nickel silicidation gate electrodes and hafnium based high-k gate dielectrics is one of the most promising gate stacks to replace poly-Si/SiO2/Si gate stacks in the future complementary metal–oxide–semiconductor (CMOS) sub-45 nm technology node. The aims of the work were to investigate the Ni silicide phase-related issues associated with arsenic dopant and thermal annealing on Ni–FUSI/HfO2/Si and Ni–FUSI/HfSiO/Si gate stacks. It was found that arsenic-incorporation demonstrated some improvement in both morphology and phase stability of nickel silicided films at high processing temperatures regardless underlying gate dielectrics. The correlations of Ni–Si phase transformation and arsenic doapnt with their electrical and physical changes were established by sheet resistance measurements, X-ray diffraction (XRD), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) analysis. Furthermore, the modulation of the work function (WF) of Ni fully silicided gates by arsenic impurity is presented, comparing the effects of dopant (As) on the WF and silicide phases (NiSi and NiSi2). It confirmed that the work function of NiSi can be tuned by implanting arsenic dopant, but it ineffective for NiSi2 phase.