Performance study of SOI monolithic pixel detectors for X-ray application

We are now developing Silicon-on-insulator (SOI) monolithic pixel detectors for X-ray and charged particle applications in collaboration with OKI Semiconductor Co., Ltd. The detector development project started in 2005 and the SOI process for pixel detectors was developed. We developed some prototypes of SOI pixel detectors. Specifically, integration type and counting type pixel detectors were irradiated with a continuous red laser, infrared laser and X-rays and their performances were studied. One of the issues in the SOI detectors is the back-gate effect, that is, higher back bias voltages affect the characteristics of SOI-CMOS transistors. As a result of the new process step to protect the device against the back-gate effect, images with higher back bias voltages were obtained in the integration-type pixel detector. We also confirmed the dependence on 8 keV X-ray intensity for the counting type pixel detector. In 2009, new versions of the detectors were designed to improve their performances with X-rays and charged particles.