In the fabrication of a 40nm Backside Illuminated (BSI) CMOS Image Sensor, the P-Well Ion Implantation (IIP) step establishes the fundamental p-type body regions for peripheral NMOS devices T1.Following the Periphery P-Well IIP - Photo step, a patterned photoresist layer exposes only the designated NMOS active and isolation areas while masking the remainder of the wafer T1.This implantation introduces acceptor impurities into the silicon substrate to precisely modulate the local conductivity and