In the dual-gate oxide (DGOX) module for 40nm BSI CMOS image sensors, multiple gate oxide thicknesses are required to handle different operating voltages P1.Following the photolithographic patterning and subsequent dry etching of the nitride hard mask, a thick layer of polymerized photoresist and fluorocarbon etch residues remains on the wafer surface A3.This specific Ashing & Strip/Clean step is positioned precisely to eradicate these organics and polymers before the high-temperature thick gate