Influence of Capping Layer on Threshold Voltage for HKMG FinFET With Short Channel.

The influence of SiO2 and SiNx capping layer on threshold voltage (${V}_{t}$) for FinFET with TiAl-based metal gate (MG) is studied. After metal gate-stack formation, SiNx capping is revealed to be able to serve as a new N source, resulting in the diffusion of N into the effective work function (EWF) TiNx layer. Correspondingly, the accumulation of N in the TiNx layer is demonstrated to be able to lower the EWF for both n- and p-FinFETs. Compared to SiO2 capping, SiNx capping can induce $\sim 100$ –150 mV ${V}_{t}$ lowering for short n- and p-FinFETs. No obvious ${V}_{t}$ shift is found for long-channel devices. [ABSTRACT FROM AUTHOR]