X-ray performance of a small pixel size sCMOS sensor and the effect of depletion depth

• Published in: Journal of instrumentation Vol. 17; no. 12; p. P12006
• Main Authors: Hsiao, Y., Ling, Z., Zhang, C., Wang, W., Zhou, Q., Wang, X., Zhang, S.-N., Yuan, W.
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.12.2022
• Subjects: CMOS; Dark current; Depletion; Energy resolution; Noise tolerance; Photoelectrons; Pixels; Radiation tolerance; Sensors; Soft x rays
• ISSN: 1748-0221; 1748-0221
• DOI: 10.1088/1748-0221/17/12/P12006

Abstract In recent years, scientific Complementary Metal Oxide Semiconductor (sCMOS) devices have been increasingly applied in X-ray detection, thanks to their attributes such as high frame rate, low dark current, high radiation tolerance and low readout noise. We tested the basic performance of a backside-illuminated (BSI) sCMOS sensor, which has a small pixel size of 6.5 μm × 6.5 μm. At a temperature of -20°C, The readout noise is 1.6 e - , the dark current is 0.5 e - /pixel/s, and the energy resolution reaches 204.6 eV for single-pixel events. The effect of depletion depth on the sensor's performance was also examined, using three versions of the sensors with different deletion depths. We found that the sensor with a deeper depletion region can achieve a better energy resolution for events of all types of pixel splitting patterns, and has a higher efficiency in collecting photoelectrons produced by X-ray photons. We further study the effect of depletion depth on charge diffusion with a center-of-gravity (CG) model. Based on this work, a highly depleted sCMOS is recommended for applications of soft X-ray spectroscopy.