In the fabrication of 40nm Backside Illuminated (BSI) CMOS Image Sensors, the Pre Litho Cleaning step immediately follows the Lower OCL (Optical Clear Layer) Planar Layer Deposition and prepares the surface for the Sacrificial Lower OCL photolithography sequence A2.The modern photolithography workflow necessitates rigorous wafer preparation and cleaning to ensure defect-free pattern transfer P1.What makes this specific cleaning step distinct from previous pre-lithography cleans in the flow is th