The METAL 1 TRENCH - Photo step is a critical back-end-of-line (BEOL) lithography process that defines the first major lateral routing layer in the 40nm CMOS Image Sensor flow A1.Positioned after the Pre Litho Cleaning and before the PMD Oxide Etch, this step patterns the inter-metal dielectric stack to prepare for copper metallization T1.Unlike previous contact opening steps (such as M0 Gate and S/D Contact) that define deep, narrow vertical connections to the substrate, the M1 trench step defi