An analytical formulation of the peripheral base resistance with application to statistical process variations

Abstract The npn emitter in this particular BiCMOS technology is not self-aligned to the heavily doped base contact region. As a consequence, there is a substantial resistance in series with the base contact that varies with photolithographic alignment and image size. In this paper we apply the solution of the Dirichlet and Neumann problems to obtain a general analytical formulation of the effective base resistance as a function of the device dimensions and the photolithographic alignment parameters. The analytical expressions are used to determine the variation of base resistance as a function of the alignment and also to evaluate the statistics of the resistance as a function of the randomly varying alignment.