The METAL 6 TRENCH - Photo step is a critical lithographic process in the back-end-of-line (BEOL) via-first dual-damascene integration scheme P2.Having completed the Via 5 (V5) etching through the inter-layer dielectric (ILD) and etch stop layers, the wafer surface possesses significant topography that must be patterned with Trench 6 routing lines A1.Unlike Metal 0 or Metal 1 photo steps that define ultra-dense local routing near the device level, Metal 6 typically serves as a semi-global or glo