The Bond Pad module in a 40nm BSI CMOS Image Sensor requires exposing the underlying metal or forming a stable aluminum pad for external packaging connections A2.This specific "Ta-Barrier etch" occurs immediately after the bulk Al Metal Etch, indicating it is the bottom barrier removal step in a stacked metal pad structure P2.Removing this bottom barrier is critical to establish a direct, low-resistance ohmic contact to the underlying M7 copper layer T1.Minimizing the specific contact resistance