Variability suppression of FinFETs by smoothing sidewall roughness using ion beam etching technology

Ion beam milling is successfully implemented for smoothing roughness of the fin sidewalls for the FinFETs with poly-crystalline TiN metal gate (MG). The V
t
variability is improved significantly by smoothing the fin roughness without degradation of the carrier mobility. The suppressed V
t
variability is interpreted as improved uniformity in the grain orientation of TiN which causes work function variation of the MG.