Characterization of Bulk Damage in CMOS MAPS With Deep N-Well Collecting Electrode

Monolithic active pixel sensors in CMOS technology, featuring a deep N-well as the collecting electrode (so called DNW MAPS), have been exposed to neutrons from a nuclear reactor, up to a total 1 MeV neutron equivalent fluence of about $3.7\times 10^{13}~{\hbox {cm}}^{-2}$ . The irradiation campaign was aimed at studying the effects of radiation induced displacement damage on the charge collection properties of the device, which was conceived for applications to charged particle tracking in high energy physics experiments. A number of different techniques, including electrical characterization of the front-end electronics and of DNW diodes, laser stimulation of the sensors and tests with $^{55}{\hbox {Fe}}$ and $^{90}{\hbox {Sr}}$ radioactive sources, has been employed for evaluating the device operation before and after irradiation. This paper discusses the measurement results and their relation with the bulk damage mechanisms underlying performance degradation in DNW MAPS.