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 (SiNx) antireflection coating (ARC) layer for metallization. One approach for patterning SiNx is masking and wet chemical etching. However, nitride etch rates can vary from cell to cell depending on the SiNx 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 SiNx has been fully removed. This method has the potential to be integrated into a commercial processing line to improve process control, uniformity, and repeatability.