The Light Shield/Aperture Grid - Photo step is a critical lithographic operation in 40nm BSI CMOS Image Sensors, designed to define the metallic patterns that prevent optical crosstalk and shield memory nodes from unwanted photo-generation A1.Following the blanket deposition of the grid metals and an oxide seal layer, this step applies and exposes photoresist to map out the aperture openings for each pixel A2.The formation of this light shield is essential for architectures where incident photon