Dual workfunction fully silicided metal gates

Abstract

Fully silicided (FUSI), dual workfunction (WF), Ni monosilicide metal gates are demonstrated using Sb predoped polySi for setting the nFET WF and for the first time a combination of Al predoped polySi and a Ni(Pt) alloy silicide for the pFET WF. The combination of the Sb and Al predoped polySi along with the Ni(Pt)Si, allow for WFs spanning the Si band gap to within 0.2 eV of the band edges. With this large WF range the FUSI, dual WF, NiSi process is applicable for both high performance and low power CMOS applications. It is shown that the Al and Sb predoped polySi and the Ni(Pt)Si alloy have leakage currents equivalent to NiSi formed from intrinsic polySi. A fundamental voiding problem in the formation of CoSi2 metal gates is also demonstrated, indicating the superiority of the NiSi gates.