This step follows the V4 SiCN breakthrough etch and precedes the M5 Trench photolithography (Engineering Practice).It distinguishes itself from other routine resist strip operations in the flow because the underlying Metal 4 copper has just been physically exposed by the removal of the SiCN barrier (Engineering Practice).The primary objective is to entirely remove the remaining photoresist, anti-reflective coatings, and complex post-etch residues (PER) generated during the deep via etch without