Characterization of single-photon avalanche diodes in a 0.5 μm standard CMOS process - Part 1: Perimeter breakdown suppression

We report on the breakdown characteristics of a single-photon avalanche diode structure fabricated in a 0.5 μm single-well CMOS process. This paper features two mechanisms for reducing perimeter breakdown. The first mechanism consists of using the lateral diffusion of adjacent n-wells to reduce the electric field at the diode's periphery, and the second makes use of a poly-silicon gate over the high field regions to modulate the electric field. We studied each technique independently as well as their combined effect on the devices' avalanche profiles. In addition to marked alterations in the current-voltage curves near and above breakdown, the diodes' breakdown voltages were increased by more than 4 V, indicating that perimeter breakdown was curtailed.