In some embodiments, the present disclosure relates to an image sensor structure. The image sensor structure includes a substrate. The substrate includes a first side and a second side opposite the first side. A photodetector extends into the first side of the substrate. An isolation structure comprises a first isolation segment and a second isolation segment that extend through the substrate. The first isolation segment and the second isolation segment are respectively on opposite sides of the photodetector and comprise a dielectric. A first metal line is on the first side of the substrate. A dummy contact structure comprises a first dummy segment and a second dummy segment. Both the first dummy segment and the second dummy segment comprise metal and extend from the first metal line to the first isolation segment and the second isolation segment, respectively.