X-ray Performance of a Small Pixel Size sCMOS Sensor and the Effect of Depletion Depth

TL;DR

This study evaluates a small pixel size sCMOS sensor's X-ray detection performance, highlighting how increased depletion depth improves energy resolution and charge collection efficiency, with implications for soft X-ray spectroscopy.

Contribution

It provides the first detailed analysis of how depletion depth affects the performance of small pixel sCMOS sensors in X-ray detection.

Findings

Deeper depletion regions improve energy resolution.

Higher depletion depth enhances photoelectron collection efficiency.

Depletion depth influences charge diffusion behavior.

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 um * 6.5 um. At a temperature of -20C, 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 spectroscop.