In the 40nm BSI CMOS Image Sensor process flow, the V3 Ashing & Strip/Clean step is executed immediately after the ILD 3-1 SiCN breakthrough etch P4.Its primary function is to completely remove the remaining photoresist (PR), bottom anti-reflective coating (BARC), and complex post-etch residues (PER) without compromising the structural integrity of the dielectric P3.This prepares the pristine V3 cavity for the upcoming Metal 4 trench patterning and eventual dual-damascene metallization (Engineer