The PMD 5 Oxide Etch step is responsible for transferring the Metal 1 trench pattern from the developed photoresist into the upper portion of the pre-metal dielectric stack A1.In advanced backend-of-line (BEOL) interconnect architectures, the dielectric stack is frequently divided into multiple functional layers to enable precise vertical depth control during dual damascene processing A1.This step etches the PMD 5 layer and prepares the structure for the subsequent PMD 4 Oxide Etch, establishing