P-type BSI Image Sensor with Active Deep Trench Interface Passivation for Radiation-hardened Imaging Systems

We propose a P-type back-side-illuminated (BSI) image sensor for applications involving harsh ionizing environment. Its pixel structure implements a hole-collection vertical photodiode and 2T PMOS shared-readout circuitry. It also integrates capacitive deep trench isolation (CDTI) which allows active surface passivation. The proposed pixel structure exhibits intrinsically lower level of dark current than its N-type counterpart and improved radiation hardness. After receiving a total ionizing dose up to 1 kGy from 6 MeV gamma radiation, the average dark current of the P-type CDTI sensor increases only by a factor 3.6 compared with a 30-fold increase for the N-type counterpart. The proposed P-type exhibits much more effective surface passivation, which prevents dark current degradation due to surface thermal generation mechanism.