Effect of Surface Field on Breakdown for CMOS Single Photon Avalanche Diodes

This paper investigates the effect of the surface field on the breakdown of single-photon avalanche diodes (SPADs) implemented in a standard CMOS process. Surface fields have been applied around the junction as well as in other diffusion regions. Sentaurus device simulation software was used to simulate the effect of surface fields on the breakdown considering all the aspects of a real SPAD device implemented in a standard single-well CMOS process. Our investigation revealed that the surface field helps make the electric field uniform around the junction thereby preventing the perimeter edge breakdown (PEB) problem, a major drawback of SPAD implemented in a standard CMOS process, without an unnecessary increase in device size. Simulation results also verified the modulation of breakdown voltage through the applied surface field. Since the performance of the SPAD device relies on the breakdown voltage, the applied surface field can improve and tune the performance of the SPAD device.