What is the harm of PSG etching process in solar cell production?

If dry plasma etching is used, it is easy to carve too wide, which will destroy the pn junction around the outer layer and reduce the final efficiency. At the same time, plasma etching will cause edge collapse around it, resulting in high fragmentation rate. If laser trimming is used, it will not cause any harm because it is operated on the back; When PSG is removed only by traditional HF method, the square resistance is slightly larger and the periphery is black after soaking for too long, and there will be no problem in a short time; Corrosion with HF/HNO3 will cause the surface layer to be corroded by steam containing HF or HNO3, and the surface layer square resistance will become larger.