Imaging systems with backside isolation trenches

Abstract

An image sensor such as a backside illumination image sensor may be provided with analog circuitry, digital circuitry, and an image pixel array on a semiconductor substrate. Trench isolation structures may separate the analog circuitry from the digital circuitry on the substrate. The trench isolation structures may be formed from dielectric-filled trenches in the substrate that isolate the portion of the substrate having the analog circuitry from the portion of the substrate having the digital circuitry. The trench isolation structures may prevent digital circuit operations such as switching operations from negatively affecting the performance of the analog circuitry. Additional trench isolation structures may be interposed between portions of the substrate on which bond pads are formed and other portions of the substrate to prevent capacitive coupling between the bond pad structures and the substrate, thereby enhancing the high frequency operations of the image sensor.