COTS CMOS active pixel sensors damage after alpha, thermal neutron, and gamma irradiation

Abstract

This work compares the damage produced by alpha particles, thermal neutrons and gamma photons to Commercial-Off-The-Shelf CMOS image sensors. Image sensors were exposed to alpha particles from the decay of Uranium and Americium sources which caused permanent damage to pixels immediately after a particle hit. Similar failure mode was seen when sensors were exposed to thermal neutrons in the Neutron Imaging Facility of the RA-6 Nuclear research reactor, whereas no damage was seen after exposure to 137Cs gamma rays. Due to the similarity between alpha and thermal neutron effects, and since silicon transmutation by neutron capture is very unlikely, we conclude that the Boron-Phosphorous Silicate Glass (BPSG) on top of the silicon acts as a conversion layer producing charged particles which in turn cause damage to the sensor.