In back-side illumination (BSI) CMOS image sensors, an array of microlenses is required to concentrate incident light onto the active photodiode area, thereby compensating for any fill factor losses P1.Before forming these upper microlenses, the underlying Color Filter Array (CFA) inevitably presents topographical variations and gaps due to the sequential deposition and patterning of different color resists A2.The Upper OCL planarization base layer is coated directly over the final hard-baked CF