The Metal 4 (M4) Trench Photo step is a critical lithographic process in the back-end-of-line (BEOL) module, specifically executed within a via-first, trench-last dual-damascene integration scheme P2.Following the ILD 3-2 Oxide and ILD 3-1 SiCN via etches and subsequent cleans, the wafer surface contains deep, open Via 3 (V3) cavities (Engineering Practice).The primary function of this photo step is to define the lateral interconnect routing patterns for the M4 layer in the photoresist, preparin