Effect of lightly doped drain on the electrical characteristics of CMOS compatible vertical MOSFETs

Abstract

Effects of lightly doped drain (LDD) on the 100 nm CMOS compatible vertical MOSFETs are investigated for different body doping. It is found that with the increase of LDD doping drive current of vertical MOSFET increases whereas sub-threshold performance is degraded. The degradation of sub-threshold performance is found to be more prominent at low body doping values. In addition, the threshold voltage of vertical MOSFET is found to decrease with the increase of LDD doping. These effects are explained by the reduction of the effective channel lengths and decrease in the source/ drain series resistances with the increase of LDD doping. This analysis reveals that the body doping of 100 nm vertical MOSFETs should be around 6 × 1017 / cm3 to 1 × 1018 / cm3 with an appropriate anneal to deliver a LDD doping around 5 × 1019 / cm3 for a good sub-threshold characteristics which is very significant for choosing appropriate body doping and LDD doping values for fabricating 100nm CMOS compatible vertical MOSFETs.