Three-dimensional base distributed effects of long stripe BJT's: base resistance at DC

An analytical model describing the DC voltage and current distributed effects in the polysilicon and intrinsic base regions of long stripe BJTs with double polysilicon technology is presented. It is shown that the bias dependent debiasing effect in the base polysilicon contacts causes an unequal division of base current between two base polysilicon contacts and results in a redistribution of base current in the base regions at different levels of current injection. The base resistance is also modulated by this current re-distribution effect at different biases. The change of base resistance with bias is calculated and the results show the importance of the distributed effects in the base polysilicon region in determining the base resistance.