The Effect of Nitrogen in a p + Polysilicon Gate on Boron Penetration Through the Gate Oxide

Abstract

Effects of nitrogen in polysilicon gates on boron penetration into a silicon substrate through the gate oxide are studied. Four factors that might be involved in how nitrogen in the polysilicon gate suppresses boron penetration were investigated: first, boron diffusivity in the interior of the nitrogen‐doped polysilicon film; second, segregation of boron at the polysilicon/ interface; third, pileup of nitrogen at the polysilicon/ interface; and fourth, boron diffusivity in decreased by incorporation of nitrogen into from polysilicon. From several experimental results, it was confirmed that the decrease in the boron diffusivity in the interior of the polysilicon gate is responsible for the suppression of boron penetration.