Interface Properties and Channel Mobility of Plasma Nitrided Devices

Electrical properties of gate oxides nitrided in plasma at 950 °C and 70 ¿bar NH3 pressure are studied for thicknesses ranging from 10 nm to 60 nm, and various RF powers and nitridation times. No interface states are generated during plasma nitridation, but fixed charges density rises with increasing nitridation times and/or RF power. Plasma nitridation (950 °C, 3 hours, 70 ¿bar pNH3, 0.6 kW RF power) of 15 nm gate oxide MOSFET achieves an improvement of channel mobility and current drivability under high normal field (Vg-Vt ≫ 2.5 Volt), whereas the peak transconductance remains comparable to that of a thermal oxide · Finally, hot channel stressing experiments on N-mosfet (lox=15 nm, Leff¿1 ·5 ¿m) show that plasma nitridation reduces the transconduclance degradation rate by a factor 2.