Dopant interactions during the diffusion of arsenic and boron in opposite directions in polycrystalline/monocrystalline silicon structures

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Experimental results of the effects of the arsenic doping concentration on the boron outdiffusion in n-polycrystalline/p-monocrystalline silicon structures are presented. The boron diffusivity is only 30 times larger in polycrystalline silicon than in monocrystalline silicon if the arsenic doping is high enough to cause enhanced grain growth. The diffusivity increase is about 130 if the polycrystalline silicon has small grains due to low arsenic doping. The boron loss from the base region of an advanced bipolar transistor doping profile by outdiffusion into the emitter polycrystalline silicon is of the order of 20% and needs to be considered for accurate device modeling.