We studied the effects of nitrogen implantation into highly doped polysilicon gates in detail. It was found that highly arsenic-doped polysilicon gates caused degradation of gate oxide films and highly boron-doped polysilicon gates resulted in a shift of threshold voltage by boron penetration. Nitrogen implantation into polysilicon gates can effectively overcome these problems. The nitrogen implanted into the polysilicon gate is segregated into the gate oxide film during heat treatment after implantation. The nitrogen in the gate oxide film can act as a barrier layer for boron penetration and reduce the random failures of gate oxide films under highly doped polysilicon gates. Moreover, the hot carrier resistance can also be improved by nitrogen implantation. Highly reliable and high-performance dual-gate Complementary metal oxide semiconductor (CMOS) can be realized by the highly doped gate and the nitrogen implantation technique.
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