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Dec 06, 2022 158 likes •307 views

Kazuho Kayama ( Kyoto Univ., JP ) kayama.kazuho.57r@st.kyoto-u.ac.jp T. G. Tsuru, T. Tanaka, H. Uchida, S. Harada, T. Okuno, Y. Amano (Kyoto Univ.) J. S. Hiraga, M. Yoshida, Y. Kamata, S. Sakuma, D. Yuhi (Kwansei-Gakuin Univ.) H. Tsunemi (Osaka

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SLIDE 1

Pushing the Limits of Kyoto’s SOI Pixel Sensor for X-ray Astronomy with the Pinned Depleted Diode

13th December PIXEL2018 @ Academia Sinica 臺灣

Kazuho Kayama (Kyoto Univ., JP)

kayama.kazuho.57r@st.kyoto-u.ac.jp

  • T. G. Tsuru, T. Tanaka, H. Uchida, S. Harada, T. Okuno, Y. Amano (Kyoto Univ.)
  • J. S. Hiraga, M. Yoshida, Y. Kamata, S. Sakuma, D. Yuhi (Kwansei-Gakuin Univ.)
  • H. Tsunemi (Osaka Univ.), H. Matsumura (Kavli IPMU)
  • S. Kawahito, K. Kagawa, K. Yasutomi, S. Shrestha, S. Nakanishi (Shizuoka Univ.)
  • H. Kamehama (NIT, Okinawa College), Y. Arai, I. Kurachi (KEK)
  • A. Takeda, K. Mori, Y. Nishioka, K. Fukuda, T. Hida, M. Yukumoto (Univ. of Miyazaki)
  • T. Kohmura, K. Hagino, K. Oono, K. Negishi, K. Yarita (Tokyo Univ. of Science)
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SLIDE 2

Focusing On Relativistic universe and Cosmic Evolution

Wideband Hybrid X-ray Imager < 20 keV

> 20 keV

Si sensor

CdTe sensor Scintillator for Active Shield

We have been developing X-ray Si sensor for FORCE mission.

★ Wide energy range : 1 - 80 keV (Requirement) ★ Si + CdTe hybrid detector

๏ Energy resolution of < 300 eV(FWHM) @ 6 keV ๏ Time resolution of < 10 µs for anti-coincidence

Requirement of Si sensor

!2

FORCE Satellite Mission

Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan

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SLIDE 3

1 pixel size p+ (sense-node) Buried p-well Back Bias Voltage n type Si substrate (full depleted)

Signal

Al

X-ray

+ + + – – – Sensor layer CMOS circuit sensor layer ( ~ 200 ̶ 500 µm) insulator ( ~ 0.2 µm) circuit layer ( ~ 8 µm)

“XRPIX” = series of SOI pixel sensors for X-ray detection

Previous devices have two known problems related to charge collection efficiency.

X-ray general XRPIX structure

XRPIX Advantages

✴ No mechanical bump bonding → High Density, Low Parasitic Capacitance, High Sensitivity ✴ Standard CMOS circuit can be built → Trigger output function for good time resolution ✴ Based on industrial standard technology

!3

SOI Pixel Detector “XRPIX”

Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan

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SLIDE 4

pixel boundary pixel center

~ 362 eV @ 5 keV

Negishi+2018

1 pixel

  • Tail structure near pixel boundaries.
  • The energy resolutions at pixel boundaries are ~ 4 times larger than that at

the pixel center.

~ 4 times that at the pixel center

Energy spectrum folded in one pixel at 5 keV.

ssssssssssssss sssssssqqqqqq

Single pixel event Total X-ray event Double pixel event

!4

Spectrum Resolution Difference at Sub-Pixel

Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan

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SLIDE 5

Hayashi+2018

We define TSTORE as exposure time after the trigger comes out

TSTORE ~ 320 ns TSTORE ~ 1.2 µs TSTORE ~ 10 µs TSTORE ~ 100 µs TSTORE ~ 1 ms

✴ Fake peak appears when the TSTORE is short. ✴ We speculate that the charge collection efficiency is different at X-ray

incident position in the same pixel. FORCE mission require TSTORE < ~ µs

!5

Spectrum Shape is Related To TSTORE

Counts PH [ADU]

Fe-Kα 6.4 keV Fe-Kβ 7.1 keV

Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan

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SLIDE 6

We speculate that both of those problems are due to the signal charges are trapped at the interface between the sensor layer and SiO2 layer

1 pixel size p+ (sense-node) Buried p-well Back Bias Voltage n type Si substrate (full depleted)

Signal

Al

X-ray

+ + + – – – Sensor layer CMOS circuit

A part of signal charge is lost at the interface region between the insulator and the sensor layer

signal charge

!6

Signal Charges are Trapped at the Interface

general XRPIX structure

Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan

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SLIDE 7

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0

  • 10.0
  • 8.6
  • 7.2
  • 5.8
  • 4.4
  • 3.0
  • 1.6
  • 0.2

1.2 2.6

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0

Z C

  • r

d i n a t e ( u m ) Potential (V)

X C

  • r

d i n a t e ( u m )

Harada+2018

XRPIX6E structure

Harada+2018

charge

sense node

Potential [V]

Buried p-well(BPW) Buried n-well(BNW)

XRPIX with PDD structure Electric field simulation

PDD Structure

✴ Highly doped buried p-well acts as shield layer to reduce noise. ✴ Signal charges are transported through stepped buried n-well to the sense node

without touching the interface between the sensor layer and SiO2 layers

Pinned Depleted Diode (PDD) Structure (Kamehama+2018) is employed to mitigate the issues in our previous devices

To solve those problems we have developed XRPIX6E with PDD structure

!7

Pinned Depleted Diode Structure

Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan

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SLIDE 8

Device Mesh

X-ray

Hiraga+2002

Placing a thin metal mesh with evenly spaced holes, the hole pitch is multiple to the detector pixel size, parallel to the detector surface and tilted by a small angle. →The hole shadows on the detector gradually shift positions from pixel to pixel

!8

Mesh Experiment

Tsunemi+1997

0.05

1pixel

Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan

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SLIDE 9

✴ X-ray incident position on the detector is

restricted by the mesh hole.

✴ Large number of pixels represent an

expanded one pixel structure.

✴ We can easily determine the incident

position on the pixel from the hole shadow

  • n the detector.

1 pixel

This technique enables us to evaluate the sub-pixel resonance.

!9

Mesh Experiment

Tsunemi+1997

Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan

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SLIDE 10

Readout boards

XRPIX6E

X-ray tube

Output spectrum from X-ray Tube taken by SDD

Mesh

Thermostatic Chamber (-15℃)

pitch: 108 µm hole diameter: 4 µm

X-ray irradiation time: 45 minutes

Pixel size 36 µm × 36 µm

Energy [keV] Intensity [counts/s/eV]

!10

Experimental Setup

Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan

4

slide-11
SLIDE 11

1 pixel

XRPIX6E

pixel center ~ 362 eV @ 5 keV pixel boundary

250 300 350 400 450 500 20 40 60 80 100 120

~ 190 eV @ 8.4 keV

250 300 350 400 450 500 20 40 60 80 100 120

~ 400 eV @ 8.4 keV

previous device (XRPIX3b)

Energy spectrum folded in

  • ne pixel at 8.4 keV.

ssssssssssss sssssssssqq

Single pixel event Total X-ray event Double pixel event

✴ No tail structure is seen near pixel boundaries of XRPIX6E ✴ Energy resolutions near pixel boundaries are ~ 2 times larger than

that at the pixel center.

250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120

zzzzz zzzzz zzz

Single pixel event Total X-ray event Double pixel event

!11

Spectrum Resolution as Sub-Pixel

Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan

Negishi+2018

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SLIDE 12

Pulse Height 200 250 300 350 400 450 500 550 counts 50 100 150 200 250 300 350 400 Pulse Height 200 250 300 350 400 450 500 550 counts 50 100 150 200 250 300 350 400 200 250 300 350 400 450 500 550 50 100 150 200 250 300 350 400 200 250 300 350 400 450 500 550 50 100 150 200 250 300 350 400 200 250 300 350 400 450 500 550 50 100 150 200 250 300 350 400 200 250 300 350 400 450 500 550 50 100 150 200 250 300 350 400 200 250 300 350 400 450 500 550 50 100 150 200 250 300 350 400 200 250 300 350 400 450 500 550 50 100 150 200 250 300 350 400 200 250 300 350 400 450 500 550 50 100 150 200 250 300 350 400 200 250 300 350 400 450 500 550 50 100 150 200 250 300 350 400

TSTORE ~ 320 ns TSTORE ~ 500 ns TSTORE ~ 750 ns TSTORE ~ 1 µs TSTORE ~ 10 µs

XRPIX6D XRPIX6E

Hayashi+2018

PH [ADU]

W-Lα W-Lβ W-Lα W-Lβ

Fake peak not appears at the pixel center and pixel boundaries when the TSTORE is short.

!12

Spectrum Shape is Related to TSTORE

TSTORE ~ 320 ns TSTORE ~ 1.2 µs TSTORE ~ 10 µs TSTORE ~ 100 µs TSTORE ~ 1 ms

Counts

Fe-Kα 6.4 keV Fe-Kβ 7.1 keV

Counts PH [ADU] Counts PH [ADU]

250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120 250 300 350 400 450 500 20 40 60 80 100 120

1 pixel

Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan

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SLIDE 13

✴ We performed the mesh experiment to evaluate the X-ray response at

the sub-pixel level for XRPIX6E with the PDD structure.

✴ No tail structure is seen near pixel boundaries of XRPIX6E. ✴ Energy resolution at the pixel center is about 190 eV. ✴ Energy resolutions near pixel boundaries are ~ 2 times larger than that at

the pixel center.

✴ Fake peak not appears at the pixel center and pixel boundaries. ✴ These results indicate that charges are efficiently collected even near

pixel boundaries. We thus conclude that the PDD structure of XRPIX6E solved the previously-known problems related to the charge collection efficiency.

!13

Summary

Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan