FinFET multi-Vt tuning with metal gate work function modulation by plasma doping

Multiple Vt tuning is required for SOC FinFET devices at and beyond the 22nm technology node. Traditional Vt tuning method used for planar devices is limited in terms of tuning range and sensitivity. Alternative approaches are needed to enable muti-Vt tuning needs. Previously we reported work function modulation for Vt tuning on both n-metal gate (TiAl) and p-metal gate (TiN) with beamline ion implantation in replacement metal gate and high-k last process flow. The report showed 200mV effective work function (eWF) modulation by ion implantation with fine control and no Effective Oxide Thickness (EOT) or Gate Leakage (Jg) degradation. Ion implant approach offers simplified integration flow where resist mask can be used. In this paper we are focusing on using plasma doping (PLAD) for modulating p-metal gate (TiN) work function to achieve multiple Vt with high productivity. The effect of plasma doping on eWF, EOT and Jg was studied on planar MOS Capacitor (MOSCAP) wafers. Sheet resistance (Rs) was also measured on blanket metal film stack to study the effect of doping on metal film properties such as resistance. Top-down SIMS analysis was employed for characterizing the sidewall doping on high aspect ratio silicon trench structures.