SIMULATION TO STUDY THE EFFECT OF TEMPERATURE, PHOSPHORUS SOURCES AND TIME ON DIFFUSION PROFILE USING SSUPREM 4

Abstract

1 INTRODUCTION A profile of phosphorus concentration diffused into Silicon is an important parameter in the design of semiconductor devices. The understanding of the diffusion mechanism of dopant impurities into silicon is of great interest. In this work, we studied phosphorus diffusion by phosphorus Penta oxide disc source with constant concentration. Profiles of phosphorus concentration are measured by SSUPREM 4 models. In SSUPREM4, diffusion of dopants and point defects is described by a number of user-specifiable models. We used fully coupled diffusion model. The Fully Coupled Diffusion Model is identical to the Two-Dimensional Model. The Fully Coupled Diffusion Model rely on the concept of Pair Diffusion which says that a dopant atom cannot diffuse on its own, it needs the carrier of a point defect in the near vicinity as a diffusion vehicle. If there is some binding energy between the two, they can move as one pair through a number of jumps and inversion cycles before eventually breaking up. When we talk about dopant diffusivity within the scope of these models, it actually means the diffusivity of the pair as a whole. This model depends onthe concept of Chemical and Active Concentration Values. The chemical concentration is the actual implanted value of the dopant but when dopants are present at high concentrations, clustering or electrical deactivation can occur so that the electrically active concentration may be less than the corresponding chemical concentration. The diffusivity of a free point defect can actually be different from the diffusivity of a point defect pair. The one important difference is that the diffusion of the defects is now influenced by the diffusion of the dopants by the addition of the joint pair fluxes to the flux terms in the governing equation of the defects. Therefore, there is a true two-way interaction between the diffusion of dopants and the diffusion of point defects, which gives this model its name.