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(-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. We furthermore, observed that the decrease in the mobility has an increased sensitivity to the channel doping concentration.