1. Design study and spectroscopic performance of SOI pixel detector with a pinned depleted diode structure for X-ray astronomy
- Author
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Yukumoto, Masataka, Mori, Koji, Takeda, Ayaki, Nishioka, Yusuke, Yonemura, Syuto, Izumi, Daisuke, Iwakiri, Uzuki, Tsuru, Takeshi G., Kurachi, Ikuo, Hagino, Kouichi, Arai, Yasuo, Kohmura, Takayoshi, Tanaka, Takaaki, Kimura, Miraku, Fuchita, Yuta, Yoshida, Taiga, and Ikeda, Tomonori
- Subjects
Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
We have been developing silicon-on-insulator (SOI) pixel detectors with a pinned depleted diode (PDD) structure, named "XRPIX", for X-ray astronomy. The PDD structure is formed in a thick p-type substrate, to which high negative voltage is applied to make it fully depleted. A pinned p-well is introduced at the backside of the insulator layer to reduce a dark current generation at the Si-SiO$_{2}$ interface and to fix the back-gate voltage of the SOI transistors. An n-well is further introduced between the p-well and the substrate to make a potential barrier between them and suppress a leakage current. An optimization study on the n-well dopant concentration is necessary because a higher dopant concentration could result in a higher potential barrier but also in a larger sense-node capacitance leading to a lower spectroscopic performance, and vice versa. Based on a device simulation, we fabricated five candidate chips having different n-well dopant concentrations. We successfully found out the best n-well design, which suppressed a large leakage current and showed satisfactory X-ray spectroscopic performance. Too low and too high n-well dopant concentration chips showed a large leakage current and degraded X-ray spectroscopic performance, respectively. We also found that the dependency of X-ray spectroscopic performance on the n-well dopant concentration can be largely explained by the difference in sense-node capacitance., Comment: 9 pages, 9 figures, accepted for publication in NIM A
- Published
- 2024
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