The Al Metal Etch step in the PACKAGING module defines the bulk geometry of the top-level bond pads for a 40nm BSI CMOS Image Sensor A2.This step sits strategically between two distinct Ta-barrier etch operations, targeting the thick, highly conductive aluminum layer while leaving the thin refractory metal liners for separate, highly selective removal P3.Forming this bulk Al structure correctly is essential to achieve a low specific contact resistance during final packaging and external system i