The ILD 5-2 Oxide Etch step is a critical back-end-of-line (BEOL) process designed to transfer the Via 5 (V5) pattern from the photoresist into the bulk interlayer dielectric P4.Unlike shallow "Pad Oxide Etch" used in front-end-of-line isolation or thin "Oxide Hard Mask Etch" steps, this process requires deep, high-aspect-ratio etching through thick dielectric layers to connect adjacent metal interconnects A1.The etch must selectively remove the bulk SiO2 or low-k oxide and land precisely on the