This Pre Litho Cleaning step prepares the freshly grown well oxide for the Periphery N-Well photoresist coating (Engineering Practice).The preceding oxide growth acts as an implant screen layer to minimize channeling effects and surface damage during the subsequent high-energy N-Well ion implantation P3.This specific step is distinct from other cleaning operations in the process flow because its primary objective is to provide a pristine, particle-free surface strictly for photolithography adhes