arXiv subjects

Yasuo Arai

Publications and source records attributed to Yasuo Arai.

At least 37 records · Page 2Linked to original sources

arXiv2018

Performance of SOI Pixel Sensors Developed for X-ray Astronomy

We have been developing monolithic active pixel sensors for X-rays based on the silicon-on-insulator technology. Our device consists of a low-resistivity Si layer for readout CMOS electronics, a high-resistivity Si sensor layer, and a SiO$_2$ layer between them. This configuration allows us both high-speed readout circuits and a thick (on the order of $100~μ{\rm m}$) depletion layer in a monolithic device. Each pixel circuit contains a trigger output function, with which we can achieve a time resolution of $\lesssim 10~μ{\rm s}$. One of our key development items is improvement of the energy resolution. We recently fabricated a device named XRPIX6E, to which we introduced a pinned depleted diode (PDD) structure. The structure reduces the capacitance coupling between the sensing area in the sensor layer and the pixel circuit, which degrades the spectral performance. With XRPIX6E, we achieve an energy resolution of $\sim 150$~eV in full width at half maximum for 6.4-keV X-rays. In addition to the good energy resolution, a large imaging area is required for practical use. We developed and tested XRPIX5b, which has an imaging area size of $21.9~{\rm mm} \times 13.8~{\rm mm}$ and is the largest device that we ever fabricated. We successfully obtain X-ray data from almost all the $608 \times 384$ pixels with high uniformity.

astro-ph.IM↗

arXiv2018

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

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 $μ\rm s$ 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 $\rm μ$m 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 back-illuminated device XRPIX3b with lower readout noise. In this work, we irradiated 2--5 keV X-ray beam collimated to 4 $\rm μm ϕ$ to the sensor layer side of the XRPIX3b at 6 $\rm μm$ 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. has improved.

astro-ph.IM↗

arXiv2018

Proton Radiation Damage Experiment for X-Ray SOI Pixel Detectors

In low earth orbit, there are many cosmic rays composed primarily of high energy protons. These cosmic rays cause surface and bulk radiation effects, resulting in degradation of detector performance. Quantitative evaluation of radiation hardness is essential in development of X-ray detectors for astronomical satellites. We performed proton irradiation experiments on newly developed X-ray detectors called XRPIX based on silicon-on-insulator technology at HIMAC in National Institute of Radiological Sciences. We irradiated 6 MeV protons with a total dose of 0.5 krad, equivalent to 6 years irradiation in orbit. As a result, the gain increases by 0.2% and the energy resolution degrades by 0.5%. Finally we irradiated protons up to 20 krad and found that detector performance degraded significantly at 5 krad. With 5 krad irradiation corresponding to 60 years in orbit, the gain increases by 0.7% and the energy resolution worsens by 10%. By decomposing into noise components, we found that the increase of the circuit noise is dominant in the degradation of the energy resolution.

astro-ph.IM↗

arXiv2018

Performance of the Silicon-On-Insulator Pixel Sensor for X-ray Astronomy, XRPIX6E, Equipped with Pinned Depleted Diode Structure

We have been developing event driven X-ray Silicon-On-Insulator (SOI) pixel sensors, called "XRPIX", for the next generation of X-ray astronomy satellites. XRPIX is a monolithic active pixel sensor, fabricated using the SOI CMOS technology, and is equipped with the so-called "Event-Driven readout", which allows reading out only hit pixels by using the trigger circuit implemented in each pixel. The current version of XRPIX has lower spectral performance in the Event-Driven readout mode than in the Frame readout mode, which is due to the interference between the sensor layer and the circuit layer. The interference also lowers the gain. In order to suppress the interference, we developed a new device, "XRPIX6E" equipped with the Pinned Depleted Diode structure. A sufficiently highly-doped buried p-well is formed at the interface between the buried oxide layer and the sensor layer, and acts as a shield layer. XRPIX6E exhibits improved spectral performances both in the Event-Driven readout mode and in the Frame readout mode in comparison to previous devices. The energy resolutions in full width at half maximum at 6.4 keV are 236 $\pm$ 1 eV and 335 $\pm$ 4 eV in the Frame and Event-Driven readout modes, respectively. There are differences between the readout noise and the spectral performance in the two modes, which suggests that some mechanism still degrades the performance in the Event-Driven readout mode.

astro-ph.IM↗

arXiv2018

Kyoto's Event-Driven X-ray Astronomy SOI pixel sensor for the FORCE mission

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 $10~{\rm μsec}$ (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 $36~{\rm μm} \times 36~{\rm μm}$. 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.

astro-ph.IM↗

arXiv2018

Development of high-speed X-ray imaging system for SOI pixel detector

We are now developing new X-ray imaging system by using Silicon-On-Insulator (SOI) Pixel Detectors. The SOI detector is a monolithic radiation imaging detector based on a 0.2um FD-SOI CMOS process. Special additional process steps are also developed to create fully depleted sensing region of 50~500um thick. SOI detector has up to mega pixels, so development of high speed Data Acquisition (DAQ) system is very important in conducting experiments. We have developed readout board named SEABAS2 (Soi EvAluation BoArd with Sitcp 2) for SOI detector. The SEABAS2 board has 16 channels of 65 MSPS ADCs, 4ch DAC, FPGAs and Gigabit Ethernet I/F. To achieve high throughput of the DAQ, we aggressively adopt parallel processing (data taking and storing) and implement FIFO buffers in software. DAQ throughput in previous DAQ system was 6 Hz (41 Mbps) for INTPIX4 detector which has 423 kpixels of 17 um square. With newly developed system, we could improve this rate to 90 Hz (613 Mbps). To take X-ray images for practical purpose such as 3D CT, user have to control the peripheral devices (moving stage, beam shutter, monitoring devices etc.) while taking images. To ease such data taking, we also implemented automatic control function of peripheral devices. Introduction of SOI detectors, the detail of the DAQ system and experimental results are presented.

physics.ins-det↗

arXiv2016

X-ray Performance of Back-Side Illuminated Type of Kyoto's X-ray Astronomical SOI Pixel Sensor, XRPIX

We have been developing X-ray SOI pixel Sensors, called "XRPIX", for future X-ray astronomy satellites that enable us to observe in the wide energy band of 0.5-40 keV. Since XRPIXs have the circuitry layer with a thickness of about 8 μm in the front side of the sensor, it is impossible to detect low energy X-rays with a front-illuminated type. So, we have been developing back-illuminated type of XRPIX with a less 1 μm dead layer in the back-side, which enables the sensitivity to reach 0.5 keV. We produced two types of back-side illuminated (BI) XRPIXs, one of which is produced in "Pizza process" which LBNL developed and the other is processed in the ion implantation and laser annealing. We irradiated both of the BI-XRPIXs with soft X-ray and investigate soft X-ray performance of them. We report results from soft X-ray evaluation test of the device.

astro-ph.IM↗

arXiv2016

Improvement of Spectroscopic Performance using a Charge-sensitive Amplifier Circuit for an X-Ray Astronomical SOI Pixel Detector

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 ({\rm \sim}1 {\rm μ}s), superior readout time ({\rm \sim}10 {\rm μ}s), 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{\rm ^{-}} (rms) and the energy resolution of 320 eV (FWHM) at 6 keV without significant loss of the charge collection efficiency.

astro-ph.IM↗

arXiv2015

Improving Charge-Collection Efficiency of Kyoto's SOI Pixel Sensors

We have been developing X-ray SOIPIXs for next-generation satellites for X-ray astronomy. Their high time resolution ($\sim10~μ$s) and event-trigger-output function enable us to read out without pile-ups and to use anti-coincidence systems. Their performance in imaging spectroscopy is comparable to that in the CCDs. A problem in our previous model was degradation of charge-collection efficiency (CCE) at pixel borders. We measured the response in the sub-pixel scale, using finely collimated X-ray beams at $10~μ$mΦ$ at SPring-8, and investigated the non-uniformity of the CCE within a pixel. We found that the X-ray detection efficiency and CCE degrade in the sensor region under the pixel circuitry placed outside the buried p-wells (BPW). A 2D simulation of the electric fields shows that the isolated pixel-circuitry outside the BPW creates local minimums in the electric potentials at the interface between the sensor and buried oxide layers. Thus, a part of signal charge is trapped there and is not collected to the BPW. Based on this result, we modified the placement of the in-pixel circuitry so that the electric fields would converge toward the BPW. We confirmed that the CCE at pixel borders is successfully improved with the updated model.

physics.ins-det↗

arXiv2015

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

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 ($\sim10μ{\rm s}$). 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.

physics.ins-det↗

arXiv2015

A study on the shielding mechanisms of SOI pixel detector

In order to tackle the charge injection issue that had perplexed the counting type SOI pixel for years, two successive chips CPIXTEG3 and CPIXTEG3b were developed utilizing two shielding mechanisms, Nested-well and Double-SOI, in the LAPIS process. A TCAD simulation showed the shielding effectiveness influenced by the high sheet resistance of shielding layers. Test structures specially designed to measure the crosstalk associated to charge injection were implemented in CPIXTEG3/3b. Measurement results proved that using shielding layer is indispensable for counting type pixel and Double-SOI is superior to Nested-well in terms of shielding effectiveness and design flexibility.

physics.ins-det↗

arXiv2015

SOI pixel circuits with synchronized TMC for time-of-flight stigmatic imaging mass spectrometry

We propose SOI pixel circuits with a synchronized time memory cell (TMC) for time-of-flight stigmatic imaging mass spectrometry. The circuits simultaneously detect the position and the fine/coarse flight time of an ion for the MALDI-ToF mass spectrometer. We discuss the circuit design and present the simulation results of a prototype detector comprised of a 32 x 32 pixel array in which each pixel pitch is 40 um and the time resolution is a minimum of 1 ns. The results of transient analysis demonstrate the fully correct synchronous operation at a 100-MHz clock frequency and simultaneous 32-word SRAM writing.

physics.ins-det↗

arXiv2015

Development FD-SOI MOSFET amplifiers for integrated read-out circuit of superconducting-tunnel-junction single-photon-detectors

We proposed a new high resolution single photon infrared spectrometer for search for radiative decay of cosmic neutrino background(C$ν$B). The superconducting-tunnel-junctions(STJs) are used as a single photoncounting device. Each STJ consists of Nb/Al/Al${}_{\mathrm{x}}$O${}_{\mathrm{y}}$/Al/Nb layers and their thicknesses are optimized for the operation temperature at 370 mK cooled by a ${}^{3}$He sorption refrigerator. Our STJs achieved the leak current 250 pA and the measured data implies that a smaller area STJ fulfills our requirement. FD-SOI MOSFETs are employed to amplify the STJ signal current in order to increase signal-to-noise ratio(S/N). FD-SOI MOSFETs can be operated at cryogenic temperature of 370 mK, which reduces the noise of the signal amplification system. FD-SOI MOSFET characteristics are measured at cryogenic temperature. The Id-Vgs curve shows a sharper turn on with a higher threshold voltage and the Id-Vds curve shows a non linear shape in linear region at cryogenic temperature. Taking into account these effects, FD-SOI MOSFETs are available for read-out circuit of STJ detectors. The bias voltage for STJ detectors are 0.4 mV and it must be well stabilized to deliver high performance. We proposed an FD-SOI MOSFET based charge integrated amplifier design as a read-out circuit of STJ detectors. The requirements for an operational amplifier used in the amplifier is estimated using SPICE simulation. The op-amp required to have a fast response(GBW$\geq$100 MHz) and it must have low power dissipation as compared to the cooling power of refrigerator.

physics.ins-det↗

arXiv2015

Development of the Pixelated Photon Detector Using Silicon on Insulator Technology for TOF-PET

To measure light emission pattern in scintillator, higher sensitivity and faster response are required to photo detector. Such as single photon avalanche diode (SPAD), conventional pixelated photo detector is operated at Geiger avalanche multiplication. However higher gain of SPAD seems very attractive, photon detection efficiency per unit area is low. This weak point is mainly caused by Geiger avalanche mechanism. To overcome these difficulties, we designed Pixelated Linear Avalanche Integration Detector using Silicon on Insulator technology (SOI-Plaid). To avoid dark count noise and dead time comes from quench circuit, we are planning to use APD in linear multiplication mode. SOI technology enables laminating readout circuit and APD layer, and high-speed and low-noise signal reading regardless smaller gain of linear APD. This study shows design of linear APD by using SOI fabrication process. We designed test element group (TEG) of linear APD and inspected optimal structure of linear APD.

physics.ins-det↗

arXiv2015

SOI Pixel Sensor for Gamma-Ray Imaging

SOI (Silicon-On-Insulator) pixel sensor is promising technology for developing the high position resolution detector by integrating the small pixels and circuits in the monolithic way. The event driven (trigger mode) SOI based pixel sensor has also been developed for the application of X-ray astronomy with the purpose of reducing the noise using anti-coincidence event. This trigger mode SOI pixel sensor working with in the rate of kilo Hz is also a promising scatter detector for advanced Compton imaging to track the Compton recoiled electrons.

physics.ins-det↗

arXiv2015

A SOI-Based Low Noise and Wide Dynamic Range Event-Driven Detector for X-Ray Imaging

A low noise and wide dynamic range event driven detector for the detection of X-Ray energy is realized using 0.2 [um] Silicon on insulator (SOI) technology. Pixel circuits are divided into two parts; signal sensing circuit and event detection circuit. Event detection circuit is activated when X-Ray energy falls into the detector. In-pixel gain selection is implemented for the detection of a small signal and wide band of energy particle. Adaptive gain and capability of correlated double sampling (CDS) technique for the kTC noise canceling of charge detector realizes the low noise and high dynamic range event driven detector.

physics.ins-det↗

arXiv2015

TID-Effect Compensation and Sensor-Circuit Cross-Talk Suppression in Double-SOI Devices

We are developing double silicon-on-insulator (DSOI) pixel sensors for various applications such as for high-energy experiments. The performance of DSOI devices has been evaluated including total ionization damage (TID) effect compensation in transistors using a test-element-group (TEG) up to 2 MGy and in integration-type sensors up to 100 kGy. In this article, successful TID compensation in a pixel-ASD-readout-circuit is shown up to 100 kGy for the application of DSOI to counting-type sensors. The cross-talk suppression in DSOI is being evaluated. These results encourage us that DSOI sensors are applicable to future high-energy experiments such as the BELLE-II experiment or the ILC experiment.

physics.ins-det↗

arXiv2015

Compensation for TID Damage in SOI Pixel Devices

We are investigating adaption of SOI pixel devices for future high energy physic(HEP) experiments. The pixel sensors are required to be operational in very severe radiation environment. Most challenging issue in the adoption is the TID (total ionizing dose) damage where holes trapped in oxide layers affect the operation of nearby transistors. We have introduced a second SOI layer - SOI2 beneath the BOX (Buried OXide) layer - in order to compensate for the TID effect by applying a negative voltage to this electrode to cancel the effect caused by accumulated positive holes. In this paper, the TID effects caused by Co gamma-ray irradiation are presented based on the transistor characteristics measurements. The irradiation was carried out in various biasing conditions to investigate hole accumulation dependence on the potential configurations. We also compare the data with samples irradiated with X-ray. Since we observed a fair agreement between the two irradiation datasets, the TID effects have been investigated in a wide dose range from 100~Gy to 2~MGy.

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