Measurement of the relative response of small-electrode CMOS sensors at Diamond Light Source

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Accelerators, spectrometers, detectors and associated equipment, 2020-03, Vol.956, p.163381, Article 163381
• Main Authors: Mironova, M., Metodiev, K., Allport, P., Berdalovic, I., Bortoletto, D., Buttar, C., Cardella, R., Dao, V., Dyndal, M., Freeman, P., Flores Sanz de Acedo, L., Gonella, L., Kugathasan, T., Pernegger, H., Piro, F., Plackett, R., Riedler, P., Sharma, A., Schioppa, E.J., Shipsey, I., Solans Sanchez, C., Snoeys, W., Wennlöf, H., Weatherill, D., Wood, D., Worm, S.
• Format: Article
• Language: English
• Subjects: CMOS sensors; MALTA; Monolithic active pixel sensors; Radiation-hard detectors; Synchrotron light source; TowerJazz
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/j.nima.2019.163381

This paper outlines the results of investigations into the effects of radiation damage in the mini-MALTA depleted monolithic pixel sensor prototype. Measurements were carried out at Diamond Light Source using a micro-focus X-ray beam, which scanned across the surface of the device in 2 μm steps. This allowed the in-pixel photon response to be measured directly with high statistics. Three pixel design variations were considered: one with the standard continuous n− layer layout and front-end, and extra deep p-well and n− gap designs with a modified front-end. Five chips were measured: one unirradiated, one neutron irradiated, and three proton irradiated. The standard design showed a decrease of 12% in pixel response after irradiation to 1e15 neq∕cm2. For the two new designs the pixel response did not decrease significantly after irradiation. A decrease of pixel response at high biasing voltages was observed. The charge sharing in the chip was quantified and found to be in agreement with expectations.