Electron mobility in ULSI MOSFETs: effect of interface traps and oxide nitridation

We provide a comprehensive set of electron mobility measurements at 300 K and 77 K on standard and N/sub 2/O-nitrided MOSFETs, with channel doping in the range 3.8/spl times/10/sup 17/-1.25/spl times/10/sup 18/ cm/sup -3/. In such heavily-doped devices, the Fermi level always lies very close to the conduction band edge, where interface traps reach the highest density and the shortest lifetimes. We show that these traps contribute to the gate-channel capacitance, leading to a systematic overestimate of the channel charge. This effect has the largest impact precisely in the roll-off region of the mobility curves, which has been the subject of recent theoretical investigations.