After STI CMP and the final densification anneal, the wafer surface consists of planarized STI oxide and the underlying silicon nitride (SiN) pad layer P2.During the chemical mechanical polishing process, residual oxide often remains on top of the SiN pad, or the STI oxide requires a slight recess to prepare for the subsequent SiN strip A2.The Wet Deglaze Etch removes this residual oxide layer, ensuring that the subsequent hot-phosphoric acid bath can uniformly access and remove the SiN layer wi