Backside illumination (BSI) CMOS image sensors require extreme thinning of the silicon substrate to allow direct light incidence onto the photodiode region without interference from the frontside metal routing layers T1.Following bulk mechanical grinding and ultrasonic cleaning, the wafer surface exhibits significant sub-surface damage, work-hardened zones, and topographical variations, known as total thickness variation (TTV) A2.The CIS Backside Si, CMP1 step is a high-removal-rate planarizatio