In Backside Illuminated (BSI) CMOS Image Sensor architectures, forming robust backside contacts is essential for device grounding and pixel isolation A2.Following photolithography and the Backside Pre-Metal Dielectric (BPMD) etch, the HKD (High-k Dielectric) and AR2 (Anti-Reflective layer 2) stack must be sequentially removed to continue the pattern transfer A1.This step breaches the optical and passivation dielectric layers to expose the underlying AR1 and silicon substrate for the subsequent d