A physical model for boron penetration through thin gate oxides from p/sup +/ polysilicon gates

Abstract

Based on numerical device and process simulation, it is shown that enhancement of the boron diffusivity by as much as 300 times in the thin gate oxide results in a very shallow exponential p-type profile in the underlying silicon substrate. The effect of fluorine and phosphorus coimplantation into the p-type polysilicon gate is modeled by changes in the boron diffusivity in the gate oxide and segregation at the polysilicon-oxide interface. An inverse PMOS short-channel behavior in which the threshold voltage becomes more negative with decreasing channel length is modeled by two-dimensional boron segregation effects caused by the poly gate oxidation.