  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.
