Boron diffusion into silicon crystal with SiNx layer as a reaction barrier

A boron depletion layer is formed on a silicon substrate, due to the presence of a silicon oxide layer, in which the solubility of boron is higher than that in the silicon substrate. This silicon oxide layer is formed during the boron diffusion process employing the BBr3 solution. To avoid the formation of this silicon oxide layer, a silicon nitride layer was used as a reaction barrier on the surface of the silicon substrate. A 500 Å thick SiNx layer deposited by PECVD on the silicon substrate was found to prevent the formation of the silicon oxide and resulting boron depletion layer on the silicon substrate. The PC1D simulation suggests that preventing the formation of this boron depletion layer by using SiNx as a reaction barrier can enhance the solar cell conversion efficiency by 0.9% in an absolute value.