Simulation of Graft Base Formation and Emitter Outdiffusion in High-Performance Bipolar LSIs

Crucial polysilicon-related process steps in high performance bipolar technology are simulated successfully. The forming of a shallow graft base by boron self-aligned outdiffusion from a base-polysilicon film and arsenic outdiffusion from an emitter-polysilicon layer has been studied. Therefore, a two-dimensional simulation model for dopant diffusion in polysilicon has been developed, which includes dopant clustering in polysilicon grain interiors as well as in the grain boundaries. The grain growth model is coupled with the diffusion coefficient of the dopants and the process temperature.