Methods and apparatus for forming a bond pad of a semiconductor device such as a backside illuminated (BSI) image sensor device are disclosed. The substrate of a device may have an opening at the backside, through the substrate reaching the first metal layer at the front side of the device. A buffer layer may be formed above the backside of the substrate and covering sidewalls of the substrate opening. A pad metal layer may be formed above the buffer layer and in contact with the first metal layer at the bottom of the substrate opening. A bond pad may be formed in contact with the pad metal layer. The bond pad is connected to the pad metal layer vertically above the substrate, and further connected to the first metal layer of the device at the opening of the substrate.