Following the PMD 4 Oxide Etch, the Metal 1 trench is physically defined, but the dielectric surface is heavily contaminated with residual photoresist, bottom anti-reflective coating (BARC), and crosslinked fluorocarbon (CFx) polymers generated during the RIE process A2.This Ashing & Strip/Clean step must completely remove these organic and organometallic residues to expose a pristine dielectric surface before the subsequent Ta-based liner deposition P1.If residues remain, they will severely deg