Investigation of the Defect Distribution of Laser Contact Opening Applied to poly-Si/SiNx Stacks

Herein, an analysis on the impact of laser contact opening of TOPCon/SiNx stacks is presented. By etching in tetramethylammonium hydroxide (TMAH), the defect distribution in the interfacial tunnel oxide is accessed and analyzed. The defect density is significantly increased in areas where adjacent laser contact openings (LCO) overlap. Using microscopic photoluminescence (m-PL) spectroscopy, it is verified that correlates with an increase in the local recombination rate and thus an increase in the J0,Met. Therefore, overlapping LCO of SiNx in TOPCon/SiNx stacks should be avoided as much as possible. Furthermore, the investigations indicate that defects in the interfacial oxide are dominantly created along exposed structures like tips and edges of (etched-back) pyramids. A comparison of TOPCon/SiNx stacks with a variation of TOPCon thicknesses indicate that etch pits, and thus the defect density, related to LCO become more significant at lower thicknesses.