Influence of the BCl3 Diffusion Process Homogeneity on the Surface Passivation of n-type PERT Solar Cells

This study aims at understanding the influence of the borosilicate glass (BSG) homogeneity obtained by BCl3 diffusion on the passivation quality of the boron emitter. First, the diffusion process was optimized in order to improve the homogeneity along the tube. Average uniformities below 3% were reached on a full loaded furnace. It was showed that the non-homogeneity of the borosilicate glass layer (BSG) thickness has a limited influence on the emitter Rsheet homogeneity. Nevertheless the diffusion homogeneity is much more detrimental on the surface passivation quality when a thermal oxide SiO2/ PECVD SiN stack is used. We showed that the replacement of the SiO2 layer by an ALD deposited Al2O3 layer leads to an improved passivation with no dependence on the BSG thickness.