Investigation of the Kyoto's X-ray Astronomical SOIPIXs with Double-SOI Wafer for Reduction of Cross-talks

TL;DR

This paper presents the development of an improved X-ray SOIPIX sensor with Double-SOI technology to reduce cross-talk, leading to better noise performance and successful detection of X-rays for future astronomy applications.

Contribution

Introduction of a Double-SOI wafer structure in XRPIX to effectively reduce cross-talk and improve readout noise performance in event-driven X-ray detection.

Findings

Cross-talk was significantly reduced with the Double-SOI structure.

Successful detection of $^{241}$Am X-rays demonstrated sensor effectiveness.

Voltage adjustment on the middle silicon layer optimized noise reduction.

Abstract

We have been developing X-ray SOIPIXs, "XRPIX", for future X-ray astronomy satellites. XRPIX is equipped with a function of "event-driven readout", which allows us to readout signal hit pixels only and realizes a high time resolution ($\sim10\mu{\rm s}$). The current version of XRPIX suffers a problem that the readout noise in the event-driven readout mode is higher than that in the the frame readout mode, in which all the pixels are read out serially. Previous studies have clarified that the problem is caused by the cross-talks between buried P-wells (BPW) in the sensor layer and in-pixel circuits in the circuit layer. Thus, we developed new XRPIX having a Double SOI wafer (DSOI), which has an additional silicon layer (middle silicon) working as an electrical shield between the BPW and the in-pixel circuits. After adjusting the voltage applied to the middle silicon, we confirmed the reduction of the cross-talk by observing the analog waveform of the pixel circuit. We also successfully detected $^{241}$Am X-rays with XRPIX.