A device includes a semiconductor substrate having a front side and a backside. A photo-sensitive device is disposed at a surface of the semiconductor substrate, wherein the photo-sensitive device is configured to receive a light signal from the backside of the semiconductor substrate, and convert the light signal to an electrical signal. An amorphous-like adhesion layer is disposed on the backside of the semiconductor substrate. The amorphous-like adhesion layer includes a compound of nitrogen and a metal. A metal shielding layer is disposed on the backside of the semiconductor substrate and contacting the amorphous-like adhesion layer.