BSI CIS manufacturing requires thinning the substrate to a few microns, exposing a backside silicon surface that is highly prone to defects and elevated dark current P1.Following chemical mechanical polishing (CMP) and ultrasonic cleaning, the oxide hard mask deposition step prepares the surface for the Backside Passivation Ion Implantation (IIP) module P1.Unlike front-end hard masks (e (Engineering Practice).g., step #12) which are designed to withstand deep anisotropic silicon etching, this ba