Development of Kyoto’s X-ray
Astronomical SOI pixel sensor
T.G.Tsuru (tsuru@cr.scphys.kyoto-u.ac.jp)
S.G. Ryu, S.Nakashima, Matsumura, T.Tanaka (Kyoto), A.Takeda, Y.Arai (KEK), + SOIPIX group
T. Imamura, A. Iwata, T. Ohmoto, T. Maeda (A-R-Tec) for Chip Design
M. Bautz, G.Y.Prigozhin, S.E.Kissel, B.LaMarr, R.F.Foster (MIT)for experiment of XRPIX1b-CZ-FI/BI
H. Nakajima, H. Tsunemi (Osaka) J.P.Doty (Noqsi) for design of ADC

Publication
Ryu et al.
Ryu et al.
Tsuru et al.
Ryu et al.
Nakashima et al.
Nakashima et al.
Ryu et al.
Takeda et al.
Tsuru et al.
Nakashima et al.

IEEE NSS 2010, Conf. Record
XRPIX1-CZ -FI
IEEE TNS 58, 2528 (2011)
XRPIX1-CZ-FIIEEE NSS 2011
Review
IEEE NSS 2011, Conf. Record
Event-Driven Readout system
IEEE NSS 2011, Conf. Record
XRPIX-ADC1
Physics Procedia 37, 1373 (2012) XRPIX1-FZ-FIIEEE TNS 60, 465 (2013)
XRPIX1b-CZ-FI, Inter-pixel cross-talkIEEE TNS 60, 586 (2013)
Event-Driven Readout with XRPIX1b-CZ-FISPIE Astro2012
Review
NIM A, Accepted (2013)
XRPIX2
20130506_Krakow_XRPIX_v5.key

1

Talk Plan

• X-ray Astronomy• “XRPIX”

Kyoto’s X-ray Astronomical SOI pixel sensor• Depletion Layer and Dark current• FZ of 2010 and 2012
• Spectral Performance• Back Illumination• Coming Soon2

事で初めて観測が可能に。。
Why X-ray Astronomy ?

The Andromeda Galaxy

光画像Optical
X-ray Image
Image

3

Cluster of Galaxies
X線画像
OpticalImage
X-rayImage

X-ray astronomy makes the hotand violent universe visible.
~106 lyStars likes the sun in the optical.
Hot plasma = several x sum of galaxies.
••
一千万度から一億度もの高温もの銀河が集団をなし、Blackholes and neutron stars in X-ray. • Most of normal (baryonic) matter in the•
ガスが重力の井戸に閉じ込め最大規模の構造を形成るのが見える

universe is visible ONLY in X-ray.

られているのが見えるX-ray CCD
Chandra (1999)“The” standard Imaging
Spectrometer
ASTRO-H (2015)

XMM-Newton (2000)

Suzaku (2005)

4

5

The standard Imaging Spectrometer ofX-rayCCD
satellites
et al. modern X-ray astronomical[Vol. 59,
Suzaku「すざく」 XIS • Fano limited spectroscopy withthe readout noise ~3e- (rms).

• Wide and fine imagingwith the sensor size of ~20-30mm
pixel size of ~30μm□• Non X-ray background above

Fig. 5. The CCD and heat sink assembly installed in the base. The
cover shield is removed in this picture.

10keV is too high to study
sources.
n alsofaintsupply reverse
current to the TEC, to warm up theCD chip in orbit. The CCD temperature may be raised a few
ns of ◦C above that of the base. In practice, the requirement tovoid excessive mechanical stresses due to differential thermal
xpansion of the copper heat sink relative to the alumina CCDbstrate imposes an upper limit on CCD temperature in thisode. For example, with the heat sink at a typical operating
mperature of −35 ◦C, we have adopted a maximum allowble CCD temperature of about + 15 ◦C. The CCD temperature
pper limit is higher at higher heat sink temperatures.

• The time resolution is toopoor (~sec) to make fast
timing obervation of time
variable sources.

Non X-ray backgroundof XIS (BI)Due to high energy
particles on orbit.

Sensor(high ρ,depleted Si)“XRPIX” = Monolithic SOI pixel sensorfor future X-ray astronomical satellites
X-ray

V_backElectronInsulator(SiO2)
Fast CMOS(low ρ Si)

X-ray

HoleP+CMOS
Readout

CMOS
Readout

CMOSReadout

V_sig

BPW
CMOS
Readout

6

non X-ray
BGD(high energyparticle)

scintillatorTimeon-board processor
Our SOIPIX (XRPIX)
Each pixel has its own trigger and Very low BGD by anti-coincidence
analogue readout CMOS circuit.
(1/100 of CCD at 20keV)

Imaging
Energy Band
Target Spectroscopy
Spec. Timing
Dark Current
Function
Non X-ray BGD

area > 25x25mm2, pixel ~ 30-60μm□ (1” @ F=9m)
0.3-40keV with BI (<0.1μm), and thick depletion (>250μm)
ΔE < 140eV @ 6keV, Fano limit (Req.<10e-, Goal < 3e-)
<1μsec<2pA/cm2 (assuming working T = -40℃)
Trigger signal & pixel address output, built-in ADC
5e-5 c/s/keV/10x10mm2 at 20keV (1/100 of CCD)XRPIX Series - Road Map -20102011

1.0 mm

1.0 mmXRPIX1XRPIX1b2012

2013

4.0 mm

4.5 mmXRPIX2XRPIX2b6.0 mm

6.0 mm

2.4 mm

2.4 mmX-ray imaging area

2.4 mm2.4mm

XRPIX
ΔΣ-typeADC

A-R-Tec PROPRIETARY/CONFIDENTIAL

2.4mm

57

Depletion Depth [um]

XRPIX1-CZ (0.7kΩcm), -FZ(2010) (7kΩcm): Depletion Depth
350

8FZ : 250μm @ VBB=30V

300

FZ : Physical Thickness

250
200

CZ : 150μm @ VBB=100V

150
100

+ : Experimental results– : Expected value

50
001020304050Back Bias [V]

6070

80

90100110• Measure the depletion thickness by observing the ratio between thecounting rates of two energies X-rays having different attenuation
lengths.
Nakashima et al.,• CZ: Depletion thickness of 150μm at VBB=100V.
2012, Physics
Procedia 37, 1373
• FZ: Full depletion of 250μm is achieved at VBB=30V.

XRPIX1b-FZ(2012)-FI (7kΩcm) : Depletion Depth

9Counting Rate of 22keV X-ray
Physical Thickness 500μm (not 260μm)

Preliminary
Depletion

VBB^1/2
back_bias

200V

• Counting Rate of 22keV X-ray (Cd-109) as a function of VBB.

(Attenuation Length = 1200μm > Physical Thickness = 500μm.)• The data follow the expected slope of depletion VBB^1/2.

• Full Depletion is reached at VBB=200V.

20130502_matsumura.pdf

Confidential10ၮ᧼Ყᛶ᛫䈱䉡䉢䊊ౝಽᏓXRPIX1b-FZ(2012)-FI (7kΩcm) : Depletion Deptha) MX1542-001JA(HR1)b) MX1542-002JA (NဳဳFZ)@ VBB=200V• 500μm→ 㩺㪇㪈ρ=4kΩcm < average (7kΩcm) 㩺㪇㪈㪊㪉㪅㪋㪉㪅㪇㪏㪋㪅㪏㪋㪅㪍to• ρ is 㪐different㪉㪅㪈
㪈㪅㪍from㪈㪅㪍 position㪈㪅㪍㪐 㪋㪅㪏㪊㪅㪌
㪊㪅㪏
㪋㪅㪈
FWP-300377
㪈㪅㪋 on 㪈㪅㪋㪈㪅㪌㪈㪅㪋㪈㪅㪍㪋㪅㪍㪋㪅㪈㪊㪅㪎㪊㪅㪍㪌㪅㪊
positiona wafer.
Confidential㪈㪅㪋㪈㪅㪊㪈㪅㪊㪈㪅㪉㪈㪅㪌㪋㪅㪉㪌㪅㪈㪋㪅㪉㪊㪅㪐㪌㪅㪏
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usedinthis•㪈㪅㪉㪈㪅㪈㪈㪅㪈㪈㪅㪊㪈㪅㪐㪋㪅㪍㪋㪅㪎㪋㪅㪉㪋㪅㪊㪍㪅㪉ဳ㪝㪱䉡䉢䊊䋨㪉㫂㱅䊶㪺㫄䋩䈮䈍䈔䉎ၮ᧼Ყᛶ᛫device.㪉㪅㪉 㪈㪅㪎 㪈㪅㪍 㪉㪅㪇㪌㪅㪍㪌㪅㪉㪌㪅㪇㪌㪅㪍b) Ყᛶ᛫䈱Ყᛶ᛫䈱䉡䉢䊊䊋䊤䉿䉨㪉㪅㪊㪉㪅㪇㪘㫍㪼㩷㩿㪟㪩㪈㪀㪤㫀㫅㩷㩿㪟㪩㪈㪀㪈㪅㪏㪈㪅㪍㪈㪅㪏㪠㫉㪼㫍㩷㪲㪭㫔㪈㪅㪐㪈㪅㪍㪈㪅㪊㪈㪅㪊㪈㪅㪐㪈㪅㪇㪜㪄㪇㪏㪈㪅㪇㪜㪄㪇㪐㪏㪅㪉㪎㪅㪏㪏㪅㪇㪏㪅㪏㪈㪇㪅㪌㪈㪅㪇㪜㪄㪈㪇㩺㪈㪉㩺㪇㪋㩺㪇㪊㩺㪇㪉㩺㪇㪈㪌㪅㪇㪇㩺㪈㪉㪏㪊㪇㪍㪈㪅㪇㪜㪄㪇㪎㩺㪈㪈㪡㪘㪀㪈㪅㪇㪜㪄㪇㪍㩺㪈㪇㪉㪅㪉㪉㪅㪉㪈㪅㪏㪈㪅㪌㪈㪅㪎㪉㪅㪈㪈㪅㪎㪈㪅㪐㪈㪅㪎㪈㪅㪉㪈㪅㪍㪈㪅㪐㩺㪇㪐㪉㪅㪇㪈㪅㪏㪈㪅㪐㪈㪅㪏㪈㪅㪉㪈㪅㪍㪉㪅㪉㩺㪇㪏㪡㪘㪀㪘㫍㪼㩷㩿㪥㪝㪱㪀㪤㫀㫅㩷㩿㪥㪝㪱㪀㩺㪇㪎㪌㪤㪸㫏㩷㩿㪟㪩㪈㪀㩺㪇㪍㩺㪇㪌㪊㪈㪇㪈㪈㪎㪤㪸㫏㩷㩿㪥㪝㪱㪀㩺㪇㪌㪩㪼㫊㫀㫊㫋㫀㫍㫀㫋㫐㩷㪲㫂㫆㪿㫄㪄㪺㫄㪴㪈㪌c) ⓨਲጀ᏷䈮ㅒᣇะ㔚ᵹⓨਲጀ᏷䈮ኻ䈜䉎ㅒᣇะ㔚ᵹ䈜䉎㪌㪅㪎㪍㪅㪇© 2011 LAPIS Semiconductor Miyagi
Co., Ltd. All Rights Reserved㪮㪸㪽㪼㫉㩷㪥㫆㪅㪇㪉㪇㪇㪏㪅㪌㪏㪅㪏㪍㪅㪐㪍㪅㪏㪏㪅㪉㪍㪅㪊㪍㪅㪐㪐㪅㪉㪎㪅㪊㪎㪅㪈㪏㪅㪉㪟㪩㪈㩷㩿㪈㪅㪍㫂㱅䊶㪺㫄㪀㪎㪅㪏 㪥ဳ㪝㪱㩷㩿㪍㪅㪊㫂㱅䊶㪺㫄㪀㪎㪅㪏㪏㪅㪎㪐㪅㪐 㪥ဳ㪝㪱㩷㩿㪐㪅㪐㫂㱅䊶㪺㫄㪀㪐㪅㪎㪈㪇㪅㪏㪈㪈㪅㪉 㪥ဳ㪝㪱㩷㩿㪈㪉㪅㪉㫂㱅䊶㪺㫄㪀㪈㪇㪅㪌㪋㪇㪇㪍㪇㪇㪈㪈㪅㪈㪈㪇㪅㪐㪈㪉㪅㪉㪏㪇㪇㪛㪼㫇㫃㪼㫋㫀㫆㫅㩷㪮㫀㪻㫋㪿㩷㪲㫌㫄㪴
121001_MX1542_Lapis.pdf

• XRPIX1-FZ(2010)• Wafer Thickness 260μm
Consists of two components.
(1) Depend on T and VBB.
generation in depletion layer.
(2) Almost Constant.
10e/msec = 1.6fA
Next Slide• XRPIX1b-FZ(2012)• Dark is 1/10 of FZ(2010)(at the same VBB)

Dark Current (e/msec/30.6μm□
pixel)
Dark Current (e/ms/pixel)

XRPIX1/1b-FZ(2010/12)-FI (7kΩcm) : Dark (Leak) Current 11106105
104Black：VBB=30V
Blue ：20V
Red ：10V103

FZ (2012)
VBB=20V

1/10

FZ (2010)

10210expectation
FZ (2012)
VBB=30V

110-1
10-2
10-3

3e-2

PchNeXT44e-3-50-40-30-20-10010 20
Temperature (degree C)

Eliminating the constant component Target Spec. at -40C (depletion 250μm)
reach the target specification.

= 0.1e/1msec/30.6μm□ =2pA/cm2
From 20110516_OKImeeting_SOI_Dark_v5

Leak Current from Protection Diode (Arai-sensei)

Protection
diodeSource
FollowerSensornode• Simulation shows leak current from PMOS used as a protection
diode at the sensor node is 2fA = 12.5e/msec.
• Possibly explains the constant component.
• Gate length of the PMOS = 0.2μm → 1μm.
Reduce leak current 2fA → 0.02fA.

12

XRPIX2-CZ-FI (Small Pixel) : Spectrum
Cu Kα (8.0 keV)

Mo Kα (17.4 keV)

150

1800

800 eVFWHM
100
Mo Kβ(19.6 keV)

656 eV
FWHM

1200
1000
1000
800
600

500
400

Pulse Hight (ch)Cu Count

1400

Mo Count

200

1500

120
100
100806050

XRPIX1 Gain
3.6 µV/e-40
2020000XRPIX2 Gain
6.5 µV/e-140

160008040120160
Pulse Hight (ch = 244 µV)
406080100Observed
Cu Kα656 eVMo Kα800 eV120140160
PH [ADU]Readout
Noise

130000Fano
Noise548 eV (FWHM) 139 eV
64 e-(rms)
205 eV

24101214 16
10X-ray Energy (keV)6818Pixel-Pixel Gain
Dispersion 1%Sum

255 eV620 eV553 eV805 eV

2020

Nakashima et al., 2012, NIM A submitted

Coming Soon 1 / Pre Amp in Each Pixel

14Reset SW
ProtectionDiodeSensorNode

XRPIX3Feedback Charge AmpCapacitance• A charge sensitive amp in every pixel in order to increase the gain.
• This is basically the same amp used in PIXOR.
• Gain ~100 μV/e, higher by a factor of ~15.
• Readout noise = 64e (rms) → ~4e (rms).

XRPIX1b-CZ : Single Pixel Readout

15• In order to study the soft X-ray performance.
• Observe the waveform of analogue output from a single pixel by fixing the120

655

average
100 samples
645
τ=100μsec
X-ray Pulse
640
Hit HeightCMS Histgra (R10C10)
PH [ADU]

660

Cts / ADU

PH [ADU]

readout address without clocking (Single Pixel Readout like a SSD).
• Detect an X-ray as a “step” and measure the pulse height. → X-ray spectrum.
• No reset during the measurement → Free from the reset noise• Reduce noises other than the reset noise by introducing LPF.
high_v(100 samples average) - low_v(100 samples average) → LPF with τ=100μs633

rms=14.6e-

100

632

650

635

average
100 samples
τ=100μsec

630
625
0

200

400
600
800
1000
sample number in one frame

631

80

630

60

629

40
628

20044M-BPW

62700

ΔE = 278eV @ 8.0keVh1(FWHM),
CMS Histgram

20h1
Entries398490Mean
0.3396RMS
3.101
χ2 / ndf
3.97e+05 / 9Constant
85.81 ± 1.41
Mean
54.28 ± 1.41
Sigma
0.8022 ± 11.6984

Cu-Kα

Nakashima
et al.,
FWHM=278eV
2012,@8.0 keV
Physics
Procedia37, 1373
Ryu et all,Cu-Kβ
2013, IEEE
200
400
600
800
1000
TNS 60,one frame
4060sample
80 number
100 in120140465
PH [ADU]

readout noise = 14.6e (rms)16
XRPIX1b-CZ-FI/BI (100μm): Spectra in Single Pixel Readout (2011.11.22)

Cts

Target= Al2O3 , Front-I, Back-I,V_tube=6 kV,
V_bais = 100V, Temp=–50ºC, Hit Threshold= 2 ADU, Exposure=400 sec, PIX=R10C10, 2us_sample, 300 µs_ave
CMS Histgram (offset-corrected)

RED: BI BLUE: FI←15 e-rms

h4

Cts

CMS Histgram (offset-corrected)

1200←18 e-rms

410

Entries
Mean
RMS

h4

1100

310900800
600

502 eV

500

byCalibration• Al-K + Bremss(+O-K from Al2O3?)

200• ΔE (FI) = 188eV,

100

1000123456789 10 11 12 13 14
PH [ADU]

HV(6kV)

1-5Detection
Threshold(2ADU)

Si Edge(1.84 keV)

0105

• X-ray generator (target =300210• Back illumination type.
Al, 6kV).

3.417

RMS

700

400

O-Ka ??

Zoom

Entries 128627
AL-Ka 1.608
Mean

1000

AL-Ka
(1.48 keV)

128627
2.282
3.155

15

2025

30

ΔE (BI) = 351eV (if line)• Absolute and relative X-ray
Fluxes are uncalibrated.
→ QE and dead layer
thickness are unknown.

35 40
PH [ADU]
Results on FI : Ryu et al., IEEE TNS 60, 465 (2013)

17Coming Soon 2 / “Pizza Process”• Pizza Proc. is the backside process developedby LBNL.

QE of LBNL’s BI-SOIPIX / SOImager-2-CZ-BI
Dead Layer
0.6±0.2μm• CZ-BI with Back-thinned to 70μm.

Deplation73±2μm• A thin phosphor layer isimplanted.

• Dead Layer : 0.6±0.2μm

Battaglia+12 NIM-A

Pizza Process to FZ devices of XRPIX• The Pizza proc. is now being made at LBNL.
• Evaluation of low energy X-ray spectral performance.

Summary18• We have been developing monolithic SOI sensor ‘XRPIX’for future X-ray Astronomical Satellites.

• It contains the function of trigger signal output for theanti-coincidence, which realizes very low non-X-ray BGD.

• We successfully developed the test devices with thedepletion thickness of ~250μm.

• Under going• Improvement of the readout noise.
• Reduction of dark current.
• Test with new back side process (Pizza Proc.).

A-R-Tec

Analog and RF Technologies

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