Effect of Proton Energy and Bias Conditions During Irradiation on CMOS Single-Photon Avalanche Diodes

Different proton energies were used to irradiate 2-D- and 3-D-CMOS single-photon avalanche diodes (SPADs) under different biasing conditions. Discrepancies are highlighted between biased SPADs (active irradiation) and unbiased SPADs (passive irradiation) in terms of mean dark count rate (DCR) degradation. Non-ionizing energy loss (NIEL) scaling of the average DCR is then discussed for the two technologies studied, followed by a discussion on the median DCR increase. Coulomb scattering, nuclear elastic and inelastic interactions, and their contributions to the total NIEL are used to explain similarities and differences observed for the mean and the median DCR increase, depending on the proton energy. Radiation tolerance comparison between 2-D- and 3-D-technology is also tackled. Finally, DCR increase distributions are investigated to understand and confirm the analysis of the mean and median DCR alteration.