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

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
¹³⁷
Cs 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.