Finite Element Simulation Of Laser-Induced Diffusion In Silicon

Laser-assisted diffusion of dopants is a promising way to realize selective emitter solar cells with a reduced number of technological steps. This paper discusses the simulation by finite element method of laser doping in order to optimise the fabrication process. A finite element method is used to solve the heat-transfer equation which describes the thermal effects and Fick's second law which describes the diffusion of dopants. The phosphosilicate glass (PSG) layer that is produced during the emitter formation on p-type silicon solar cells is used as the doping source during the laser-assisted diffusion process. The influence of laser parameters and material properties are studied. Modelling results are compared to SIMS measurements of the phosphorous doping profile. A structure is discussed in the perspective of a self-aligned process for selective emitter fabrication, where the PSG layer is present underneath the silicon nitride (SiNx) passivation layer.