Single-photon avalanche diodes with deep trench isolation

A structure for a single-photon avalanche detector, the structure comprising:

• a plurality of semiconductor layers including a first well, a second well defining a p-n junction with the first well, a first surface, and a second surface opposite from the first surface;
• a micro-lens adjacent to the second surface of the semiconductor layers;
• an interlayer dielectric layer on the first surface of the semiconductor layers;
• a deep trench isolation region including a conductor layer and a dielectric liner, the conductor layer including a first portion in the semiconductor layers and a second portion in the interlayer dielectric layer, the conductor layer having a first end, a second end opposite from the first end, and a sidewall that connects the first end to the second end, the second end of the conductor layer coplanar with the second surface of the semiconductor layers, and the dielectric liner arranged to surround the sidewall of the conductor layer;
• and
• a metal feature directly connected to the first end of the conductor layer,
• wherein the second surface of the semiconductor layers is free of metal.