Following the ILD 3-2 Oxide Etch, this Ashing & Strip/Clean step is explicitly required to completely remove the bulk photoresist hardmask and fluorocarbon polymer residues from the newly defined dual-damascene MET4 trenches A2.Unlike earlier front-end or lower-metal cleans, this specific MET4 step is uniquely challenging because the surrounding inter-layer dielectric (ILD) consists of highly porous low-k materials that are exceptionally sensitive to plasma and chemical damage P2.Establishing a