Investigation of NiSi and TiSi as CMOS gate materials

Abstract

NiSi is a promising new candidate for CMOS gate metal material because its workfunction can be adjusted by the implantation of dopants into the silicon before silicidation. In this report, NiSi and TiSi are studied, and the work functions of each are found to be adjustable over a wider range than previously published. This range covers the work function values required to achieve correct threshold voltages (V/sub t/) for both deep-scaled bulk CMOS and fully depleted, silicon-on-insulator MOSFETs. The influence of these silicides on the gate oxide and interface quality is also examined thoroughly via measurements of capacitance, minority carrier mobility, and gate-leakage current. While no degradation of the interface is observed with NiSi gates, TiSi gates generate interface traps and significantly degrade transistor device performance. With all the merits of a metal gate and no apparent degradation of interface quality, NiSi can be integrated with minor modification into a standard CMOS process and is a promising gate metal material for future CMOS technology generations.