In the 40nm BSI CIS flow, after the W CMP and Optical Pad 2 Deposition steps, the substrate typically exhibits localized topography variations P1.The Lower OCL (On-Chip Lens) Planar Layer Deposition step is strictly designed to eliminate these nanoscale topographical variations and provide an optically flat baseline for the subsequent sacrificial lens lithography P1.This objective distinctly separates it from prior steps like the Oxide Grid Seal Layer Deposition, which conformally encapsulates s