Accurate doping profile extraction for predictive SPAD design

Physical models play a fundamental role in the evolution of SPAD technology. However, as the majority of the detector properties strongly depends on the electric field, a thorough knowledge of the doping profile is mandatory. Conventional doping extraction methods proved to be not accurate enough, hence the need to develop a new profiling technique which allows us to reach the desired level of accuracy. To this aim, we adopted an inverse modeling approach based on the combined use of capacitance-voltage measurements and electrical simulations. We applied the method to several SPADs, which differ both in terms of doping profile and internal structure, and we used the extracted profile to simulate their breakdown voltages. Calculated results very close to the experimental data were obtained, providing us a convincing validation of the proposed extraction technique.