In the 40nm BSI CIS flow, the BONDPAD module connects the sensor's internal metallization to external packaging substrates (Engineering Practice).Because the BSI sensor requires backside illumination, the bond pads are often opened from the opposite face through extremely thick dielectric stacks (Engineering Practice).The progression from PMD 1 Etch through PMD 5 Etch indicates a sequential, deeply penetrating pattern transfer through multiple pre-metal or interlayer dielectric layers to reach t