In Backside Illuminated (BSI) CMOS Image Sensors, photons enter through the thinned backside silicon surface, making interface reflection a primary source of optical loss P1.To maximize optical quantum efficiency, a multi-layer Anti-Reflective Coating (ARC) is required to bridge the refractive index gap between the silicon substrate and the external environment P1.The HKD/AR2 Tantalum Oxide (TaO) deposition immediately follows the AlO (AR1) layer and precedes the SiO (BPMD) deposition P2.This sp