Fluorine diffusion on a polysilicon grain boundary network inrelation to boron penetration from P+ gates

The combined effect of boron penetration and fluorine transport from P⁺ polycrystalline gates on flat-band voltage is studied. The SIMS concentration depth profiles elucidate the effect of annealing temperature on the fluorine transport, which in turn affects the boron penetration induced change in flat-band voltage. The fluorine diffusion in the poly gate is dominated by grain boundary diffusion. The identification of this mechanism is supported by SIMS profiles and a simulation based on a new methodology of network diffusion