Improving charge-collection efficiency of SOI pixel sensors for X-ray astronomy

Matsumura, Hideaki; Tsuru, Takeshi Go; Tanaka, Takaaki; Takeda, Ayaki; Arai, Y.; Mori, Koji; Nishioka, Yusuke; Takenaka, Ryota; Kohmura, Takayoshi; Nakashima, Shinya; Hatsui, Takaki; Kohmura, Yoshiki; Takei, Dai; Kameshima, Takashi

doi:10.1016/j.nima.2015.05.008

Cited by 22 publications

(24 citation statements)

References 12 publications

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“…XRPIX2b was irradiated with X-ray of 2.6-12 keV, and it was confirmed that the sensor layer of 500 µm thick was fully depleted, and the quantum efficiency and the thickness of the dead layer on the back side was estimated. In Matsumura et al [1], the difference of center channel (hereafter peak shift) between the single and the double pixel event due to electric field distortion was found in the XRPIX1b which was the front-illuminated (FI) type XR-PIX, and it was confirmed that the peak shift was improved in the entire surface irradiation of XRPIX2b in which the pixel circuit was changed.…”

Section: Introductionmentioning

confidence: 92%

“…Since the readout speed of the X-ray CCD is about several seconds, it is not suitable for the observation of the celestial bodies varying in a short time of several milliseconds. Therefore, we have developed XRPIX (X-Ray soiPIXel) which is an event-driven pixel detector using SOI (Silicon On Insulator) technology as a detector for future wide band X-ray astronomical satellites [1][2][3][4][5][6][7][8][9][10]. By implementing the trigger output function in each pixel, XR-PIX can selectively read out only the signal of the X-ray event and can obtain high time resolution of several microseconds.…”

Section: Introductionmentioning

confidence: 99%

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X-ray response evaluation in subpixel level for X-ray SOI pixel detectors

Negishi

Kohmura

Hagino

et al. 2019

Nuclear Instruments and Methods in Physics Research Section A:

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We have been developing event-driven SOI Pixel Detectors, named "XRPIX" (X-Ray soiPIXel) based on the silicon-on-insulator (SOI) pixel technology, for the future X-ray astronomical satellite with wide band coverage from 0.5 keV to 40 keV. XRPIX has event trigger output function at each pixel to acquire a good time resolution of a few µs and has Correlated Double Sampling function to reduce electric noises. The good time resolution enables the XRPIX to reduce Non X-ray Background in the high energy band above 10 keV drastically by using anti-coincidence technique with active shield counters surrounding XRPIX. In order to increase the soft X-ray sensitivity, it is necessary to make the dead layer on the X-ray incident surface as thin as possible. Since XRPIX1b, which is a device at the initial stage of development, is a front-illuminated (FI) type of XRPIX, low energy X-ray photons are absorbed in the 8 µm thick circuit layer, lowering the sensitivity in the soft X-ray band. Therefore, we developed a back-illuminated (BI) device XRPIX2b, and confirmed high detection efficiency down to 2.6 keV, below which the efficiency is affected by the readout noise. In order to further improve the detection efficiency in the soft X-ray band, we developed a backilluminated device XRPIX3b with lower readout noise. In this work, we irradiated 2-5 keV X-ray beam collimated to 4 µmφ to the sensor layer side of the XRPIX3b at 6 µm pitch. In this paper, we reported the uniformity of the relative detection efficiency, gain and energy resolution in the subpixel level for the first time. We also confirmed that the variation in the relative detection efficiency at the subpixel level reported by Matsumura et al.[1] has improved.

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Section: Introductionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

X-ray response evaluation in subpixel level for X-ray SOI pixel detectors

Negishi

Kohmura

Hagino

et al. 2019

Nuclear Instruments and Methods in Physics Research Section A:

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“…The noise due to the dark current is simply suppressed by cooling. The charge collection related issues of XRPIX are studied in [12] [15]. In this paper, we focus on reduction of readout noise mainly limited by in-pixel and on-chip readout circuits.…”

Section: Introductionmentioning

confidence: 99%

Improvement of spectroscopic performance using a charge-sensitive amplifier circuit for an X-ray astronomical SOI pixel detector

et al. 2015

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We have been developing monolithic active pixel sensors series, named "XRPIX," based on the silicon-on-insulator (SOI) pixel technology, for future X-ray astronomical satellites. The XRPIX series offers high coincidence time resolution (∼1 µs), superior readout time (∼10 µs), and a wide energy range (0.5-40 keV). In the previous study, we successfully demonstrated X-ray detection by event-driven readout of XRPIX2b. We here report recent improvements in spectroscopic performance. We successfully increased the gain and reduced the readout noise in XRPIX2b by decreasing the parasitic capacitance of the sense-node originated in the buried p-well (BPW). On the other hand, we found significant tail structures in the spectral response due to the loss of the charge collection efficiency when a small BPW is employed. Thus, we increased the gain in XRPIX3b by introducing in-pixel charge sensitive amplifiers instead of having even smaller BPW. We finally achieved the readout noise of 35 e − (rms) and the energy resolution of 320 eV (FWHM) at 6 keV without significant loss of the charge collection efficiency.

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“…Although measurements of the charge cloud size produced by X-ray photons were performed for X-ray CCDs [10], such measurements have never been performed for XRPIX. On XRPIX, the detector response has been studied in Matsumura et al (2015) [11] and Negishi et al (2018) [12]. These were focused on non-uniformity of the charge collection efficiency at a sub-pixel scale because it was one of the major issues in the development of XRPIX.…”

Section: Introductionmentioning

confidence: 99%

Measurement of Charge Cloud Size in X-Ray SOI Pixel Sensors

Hagino

Oono

Negishi

et al. 2019

IEEE Trans. Nucl. Sci.

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We report on a measurement of the size of charge clouds produced by X-ray photons in X-ray SOI (Silicon-On-Insulator) pixel sensor named XRPIX. We carry out a beam scanning experiment of XRPIX using a monochromatic X-ray beam at 5.0 keV collimated to ∼ 10 µm with a 4-µmφ pinhole, and obtain the spatial distribution of single-pixel events at a subpixel scale. The standard deviation of charge clouds of 5.0 keV X-ray is estimated to be σcloud = 4.30 ± 0.07 µm. Compared to the detector response simulation, the estimated charge cloud size is well explained by a combination of photoelectron range, thermal diffusion, and Coulomb repulsion. Moreover, by analyzing the fraction of multi-pixel events in various energies, we find that the energy dependence of the charge cloud size is also consistent with the simulation.

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Improving charge-collection efficiency of SOI pixel sensors for X-ray astronomy

Cited by 22 publications

References 12 publications

X-ray response evaluation in subpixel level for X-ray SOI pixel detectors

X-ray response evaluation in subpixel level for X-ray SOI pixel detectors

Improvement of spectroscopic performance using a charge-sensitive amplifier circuit for an X-ray astronomical SOI pixel detector

Measurement of Charge Cloud Size in X-Ray SOI Pixel Sensors

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