In situ PL imaging toward real-time plating process control

Light induced plating (LIP) of front grid contacts is an industry-scalable potential alternative to silver paste, but LIP requires an additional patterning step to create openings in the silicon nitride (SiN_x) antireflection coating (ARC) layer for metallization. One approach for patterning SiN_x is masking and wet chemical etching. However, nitride etch rates can vary from cell to cell depending on the SiN_x PECVD deposition parameters, previous processing steps, and etching solution usage and maintenance. Under-etching results in poor contact adhesion and over-etching results in undercutting and possible emitter damage. We demonstrate in situ real-time photoluminescence imaging (PLI) as a method to determine the point when SiN_x has been fully removed. This method has the potential to be integrated into a commercial processing line to improve process control, uniformity, and repeatability.