We have been developing monolithic active pixel sensors , X-ray Astronomy SOI pixel sensors , XRPIXs , based on a Silicon-On-Insulator ( SOI ) CMOS technology as soft X-ray sensors for a future Japanese mission , FORCE ( Focusing On Relativistic universe and Cosmic Evolution ) .
The mission is characterized by broadband ( 1-80 keV ) X-ray imaging spectroscopy with high angular resolution ( < 15 arcsec ) , with which we can achieve about ten times higher sensitivity in comparison to the previous missions above 10 keV .
Immediate readout of only those pixels hit by an X-ray is available by an event trigger output function implemented in each pixel with the time resolution higher than 10 ~ { } { \mu sec } ( Event-Driven readout mode ) .
It allows us to do fast timing observation and also reduces non-X-ray background dominating at a high X-ray energy band above 5–10 keV by adopting an anti-coincidence technique .
In this paper , we introduce our latest results from the developments of the XRPIXs .
( 1 ) We successfully developed a 3-side buttable back-side illumination device with an imaging area size of 21.9 mm \times 13.8 mm and an pixel size of 36 ~ { } { \mu m } \times 36 ~ { } { \mu m } .
The X-ray throughput with the device reaches higher than 0.57 kHz in the Event-Driven readout mode .
( 2 ) We developed a device using the double SOI structure and found that the structure improves the spectral performance in the Event-Driven readout mode by suppressing the capacitive coupling interference between the sensor and circuit layers .
( 3 ) We also developed a new device equipped with the Pinned Depleted Diode structure and confirmed that the structure reduces the dark current generated at the interface region between the sensor and the SiO _ { 2 } insulator layers .
The device shows an energy resolution of 216 eV in FWHM at 6.4 keV in the Event-Driven readout mode .