Evaluation of 10MeV proton irradiation on 5.5 Mpixel scientific CMOS image sensor

Abstract

We evaluate the effects of 10 MeV proton irradiation on the performance of a 5.5 Mpixel scientific grade CMOS image sensor based on a 5T pixel architecture with pinned photodiode and transfer gate. The sensor has on-chip dual column level amplifiers and 11-bit single slope analog to digital converters (ADC) for high speed readout and wide dynamic range. The operation of the sensor is programmable and controlled by on-chip digital control modules. Since the image sensor features two identical halves capable of operating independently, we used a mask to expose only one half of the sensor to the proton beam, leaving the other half intact to serve as a reference. In addition, the pixel array and the digital logic control section were irradiated separately, at dose rates varying from 4 rad/s to 367 rad/s, for a total accumulated dose of 146 krad(Si) to assess the radiation effects on these key components of the image sensor. We report the resulting damage effects on the performance of the sensor including increase in dark current, temporal noise, dark spikes, transient effects and latch-up. The dark signal increased by about 55 e-/pixel after exposure to 14 krad (Si) and the dark noise increased from about 2.75e- to 6.5e-. While the number of hot pixels increased by 6 percent and the dark signal non uniformity degraded, no catastrophic failure mechanisms were observed during the tests, and the sensor did not suffer from functional failures.