In the process flow for a 40nm BSI CMOS Image Sensor, this specific Ashing & Strip/Clean step immediately follows the ILD 6-5 Etch, which physically defines the trench for the top-level Metal 8 Direct Bond Interconnect (DBI) pad A1.The primary function of this step is to completely remove the bulk photoresist mask and the stubborn fluorocarbon-based polymeric residues generated during the preceding Reactive Ion Etching (RIE) process P3.Unlike upstream routine clean steps, this operation is uniqu