Simulation of the Phosphorus Profiles in a c-Si Solar Cell Fabricated Using POCl3 Diffusion or Ion Implantation and Annealing

In this paper, we present the development of accurate process simulations for the processes leading to the formation of the n-type (phosphorus doped) regions in high efficiency crystalline silicon solar cells. We consider the Phosphorus profile formation either using POCl3 diffusion or by ion implantation; the results are applicable for the formation of the Front Surface Field, emitter, as well as the Back Surface Field regions. The main focus in this paper was on the modeling of the oxidation process, both in terms of the oxide growth rate dependence on the substrate doping concentration and on the doping diffusion enhancement due to oxidation. The detailed description of these two phenomena allows for the accurate prediction of the doping distribution and the oxide thickness, enabling the engineering of the junction formation based on process simulations. For the model calibrations we have used both POCl3 and Phosphorus ion implanted samples, annealed at various temperatures, durations and ambient conditions (oxidizing or inert), so as to quantify the effect of transient and oxidation enhanced diffusion and dopant enhanced oxidation.