The Lower OCL Etch is a critical process step in the LS_GRID module of 40nm Backside Illuminated (BSI) CMOS Image Sensor manufacturing A2.Positioned immediately after the Lower OCL Coating Etch, this step directly transfers the pre-defined mid-vertical grid or pad structures into the bulk lower on-chip lens (OCL) material A2.Unlike the preceding coating etch, which primarily opens superficial anti-reflective or protective hardmask layers, this primary etch step removes the bulk volume of the opt