Method of increasing gate nitridation and its impact on CMOS devices

A process that combines shallow nitrogen implant with rapid thermal nitridation is shown to double the nitrogen content in ultra-thin oxynitrides for the same EOT. Implanted nitrogen acts as a second source of nitrogen during gate dielectric formation and amount of incorporated nitrogen is directly proportional to the implant dose. Nitridation is shown to have opposite effects on N and PMOS mobilities. PMOS mobilities show a continuous decrease with increasing gate nitrogen content. In addition, increasing nitridation leads to severe NBTI effect on PMOS devices. Therefore, a trade-off between boron penetration resistance and performance for PMOS transistors is indicated.