The ILD 3-2 Oxide Etch is a critical back-end-of-line (BEOL) step in the Via 3 module for the 40nm BSI CMOS Image Sensor flow P4.Positioned immediately after Via 3 photolithography, this step transfers the defined via patterns into the main bulk inter-layer dielectric (ILD 3-2) P4.Unlike shallower pad oxide etches used in front-end processing or non-critical oxide hard mask etches, this step must create high-aspect-ratio contact (HARC) profiles while strictly stopping on the underlying ILD 3-1 S