This step transfers the Via 1 lithographic pattern into the upper bulk dielectric (ILD 1-2 Oxide) to create vertical pathways for interconnecting Metal 1 and Metal 2 A2.Following the Via 1 Photo step, this reactive ion etch (RIE) strictly removes the ILD 1-2 layer while preserving the underlying ILD 1-1 SiCN layer, which acts as a protective etch-stop layer A2.Unlike front-end pad oxide etches that prepare the silicon surface or thin hard mask etches for pattern transfer, this step requires high