Reduced electron mobility due to nitrogen implant prior to the gate oxide growth

We have found that nitrogen incorporation in the gate-oxide, by implantation into the Si, degrades the low field inversion mobility. Although submicron transistors fabricated using nitrogen implantation have been reported to show higher drive currents compared with "pure" oxides, we have measured about 20% degradation in large area transistors for a 2e14 cm/sup -2/ nitrogen implant. These measurements were done using nMOS transistors with thin gate-oxides (<4 nm). Thickness determination was done by simulation fit to capacitance-voltage (C-V) measurements by including quantization and tunneling effects. Furthermore, we observed that the decrease in the mobility has an increased sensitivity to the channel doping concentration.