THE EFFECTS ON METAL-OXIDE-SEMICONDUCTOR FIELD-EFFECT TRANSISTOR PROPERTIES OF NITROGEN IMPLANTATION INTO P(+) POLYSILICON GATE

We have studied in detail the effects of nitrogen implantation into a p(+) polysilicon gate on gate oxide properties for the surface p-chann el metal oxide semiconductor (PMOS) below 0.25 mu m. The nitrided oxid e film can be easily formed by the pile-up of nitrogen into the gate o xide film from the polysilicon gate. It was found that boron penetrati on through the gate oxide film can be effectively suppressed by nitrog en implantation into a p(+) polysilicon gate because nitrogen in the p olysilicon film can suppress boron diffusion, and the nitrided oxide f ilm can also act as a barrier to boron diffusion. Moreover the hot-car rier hardness can be remarkably improved by the nitrided oxide film si nce interface state generation can be suppressed by the nitrided oxide film. Furthermore the number of electron traps in the gate oxide film can also be reduced by nitrogen implantation.