Threshold voltage control in NiSi-Gated MOSFETs through SIIS

Abstract

Complete gate silicidation has recently been demonstrated as an excellent technique for the integration of metal gates into MOSFETs. From the various silicide gate materials NiSi has been shown to be the most scalable. In this paper, a versatile method for controlling the workfunction of an NiSi gate is presented. This method relies on doping the poly-Si with various impurities prior to silicidation. The effect of various impurities including B, P, As, Sb, In, and Al is described. The segregation of the impurities from the poly-Si to the silicide interface during the silicidation step is found to cause the NiSi workfunction shift. The effect of the segregated impurities on gate capacitance, mobility, local workfunction stability, and adhesion is studied. © 2005 IEEE.