A Modified Scheme to Reduce the Specific Contact Resistivity of NiSi/Si Contacts by Means of Dopant Segregation Technique

Abstract

In this work, a proposed modified scheme to reduce the specific contact resistivity (ρc) of NiSi/Si contacts by means of dopant segregation (DS) technique is presented. In contrast to conventional scheme in which NiSi is formed at 500°C/30s followed by B or As implantation and subsequently drive-in anneals to induce DS at the NiSi/Si interface, this modified scheme consists of the following steps: (1) Deposited Ni films undergo a rapid thermal anneal (RTA1) at a low temperature 300°C/60 s to form Ni-rich silicide i.e. Ni2Si instead of NiSi followed by the removal of un-reacted Ni; (2) implant boron (B) or arsenic (As) into pre-formed Ni-rich silicide and perform RTA2 at 500–700°C/30 s to transform Ni-rich silicide to NiSi as well as to induce DS at the NiSi/Si interface. For NiSi/n- and p-Si contacts, the ρc values at 600°C drive-in anneal temperature is reduced from 6.5 × 10−9 Ω-cm2 and 1.3 × 10−7 Ω-cm2 using conventional scheme to 5.1 × 10−9 Ω-cm2 and 1.0 × 10−7 Ω-cm2 using modified scheme respectively, with the presence of As or B DS. Enhanced DS at the NiSi/Si interface accounts for improved ρc in the modified scheme. This proposed modified scheme can be also applied to reduce the ρc values in the state-of-the-art NiGe/Ge contacts.