In the 40nm BSI CMOS Image Sensor fabrication flow, bond pads require deep cavities etched through a complex Back-End-Of-Line (BEOL) dielectric stack to expose the underlying metal pad P3.The etching is performed sequentially through alternating bulk oxide (ILD x-2) and thin SiCN etch-stop (ILD x-1) layers P1.Following the removal of the ILD 6 layers, the ILD 5-2 Oxide Etch specifically targets the bulk silicon dioxide of the 5th metal level, preparing the cavity to stop precisely on the underly