Alpha Particle-Induced Persistent Effects in a COTS 3-D-Integrated CMOS Imager

A three-layer heterogeneously integrated commercial off-the-shelf (COTS) complementary metal-oxide-semiconductor (CMOS) imaging sensor’s (CIS) post-irradiation response to 1.7- and 4.0-MeV alpha particles is analyzed. The energies of the alpha particles are selected such that they stop in two separate functional layers of the device under test (DUT). Similarities in the captured datasets reveal the photodiodes in the topmost pixel layer are most vulnerable to alpha particle-induced persistent effects. Despite black-level clamping, alpha particles of both energies are found to increase the mean dark RGB values, a surrogate for dark current. Observation of multilevel random telegraph signal (RTS) pixels suggests that displacement damage dose (DDD) effects dominate the persistent effect response, rather than total ionizing dose (TID) effects. The energy of incoming alpha particles was found to affect the frequency of RTS pixels. Similarly, particle energy affects the number of RTS levels. Additionally and possibly most importantly for certain operational scenarios, the chip was found to perform at least two types of on-board processing that impacted the observed radiation effects: pixel demosaicing and discrete cosine transform (DCT).