In the manufacturing of 40nm BSI CMOS Image Sensors, the formation of the light shield grid requires extremely precise photolithography (Engineering Practice). Prior processing steps, such as the Optical Pad 3 Deposition, introduce surface topography comprising distinct peaks and valleys over the underlying optical elements A1. The Optical Pad 3 CMP (Chemical Mechanical Planarization) step is integrated into the flow to eliminate this topography and achieve rigorous wafer-level global planarizat