PMD 5 Etch is the final stage of a multi-step Pre-Metal Dielectric (PMD) etching sequence in the bondpad module A2.In 40nm Backside Illuminated (BSI) CMOS Image Sensors, reaching the contact pads requires etching through a thick, composite PMD stack to form high-aspect-ratio contacts (HARC) P1.This step completes the deep contact profile before transitioning to the subsequent Inter-Layer Dielectric (ILD) processing steps, such as ILD 1-1 Etch A2.The ultimate goal is to provide a low-resistance p