Development and Performance of Kyoto's X-ray Astronomical SOI pixel sensor

T.G.Tsuru (tsuru@cr.scphys.kyoto-u.ac.jp)

20121217_国立天文台_可視赤外観測技術ワークショップ_v2.key

S.G. Ryu, S.Nakashima (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

Ryu et al. IEEE NSS 2010, Conf. Record XRPIX1-CZ -FIRyu et al. IEEE TNS 58, 2528 (2011) XRPIX1-CZ-FITsuru et al. IEEE NSS 2011 ReviewRyu et al. IEEE NSS 2011, Conf. Record Trigger Readout systemNakashima et al. IEEE NSS 2011, Conf. Record XRPIX-ADC1Nakashima et al. NIM A Accepted (2012) XRPIX1-FZ-FIRyu et al. IEEE TNS Accepted (2012) XRPIX1b-CZ-FI, Inter-pixel cross-talkTakeda et al. IEEE TNS Accepted (2012) Trigger Readout with XRPIX1b-CZ-FITsuru et al. SPIE Astro2012 ReviewNakashima et al. NIM A, Submitted (Pixel 2012) XRPIX2

10μsec

•SOI / SOIPIX とは？•Ｘ線SOIPIX検出器•現在の開発状況，到達点

•ゲイン，ノイズ，エネルギー分解能•トリガ読み出し•空乏層厚み，裏面不感層，暗電流

•今後

内容

3

はじめに... 2008年11月20日 - 京都新聞(夕刊) -

これはもちろん宮崎さんらによる2k4kBICCDのことです．

HSCの2k4kBICCDとASTRO-HのPchNeXT4は兄弟光赤外とＸ線 ⇒ 実は欲しい物は似ている．

(裏面照射，厚い空乏層，低ノイズ)

�87852<12,��.<.,<8:�1*>270�/27.�:.;85=<287�8/�;252,87�*7-�-*<*�9:8,.;;270�98?.:�8/���!$��$��+A�=;270�$252,87�!7��7;=5*<8:��$!���%.,178580A��

SOI Pixel Detector (SOIPIX)

B�

What is SOI pixel sensor ?

• Monolithic Detector using Bonded wafer (SOI: Silicon On Insulator)• Thick Depletion Layer in the high resistivity Si substrate.• Standard CMOS circuits can be build in the low resistivity Si.

• Seamless connection between the two layers → No bump bonding.

• Based on Industrial Standard Technology → Stable• No latch Up & High Radiation Tolerance.

Tohoku U.�

Kyoto U.�Tsukuba U.�

JAXA� AIST�

SOIPIX Collaboration: Regular Multi-Project Wafer (MPW) run. (~twice/year)�

Osaka U.�

SOIPIX MPW run Wafer��

RIKEN�

Fermi Nat'l Accl. Lab.�

Lawrence Berkeley Nat'l Lab.�

U. Heidelberg�

U. of Hawaii�

Louvain-la-Neuve Univ.�

IHEP/IMECAS China�

INP Krakow�

KEK�

C�

• PI=Prof. Y.Arai @ KEK, 2005.10~

• With OKI semiconductor → Lapis semiconductor• Kyoto joins the collaboration in 2008.

=>�

SOIPIX Applications��

E�INTPIX : �!#�b7%'X(23���c E�CNTPIX : �!,�b7S/N,�c E�SOPHIAS : XFEL!b7[W]_\X`aYc E�PIXOR : &$��6b�����c E�XRPIX : X(*��1!(�^WZc E�MALPIX : ��.4��+)!(�5,�c E�TDIPIX : X(" ��+)! E�STJPIX :0������b/ (d����c8 E�. . .�

The standard Imaging Spectrometer of modern X-ray astronomical satellites X-ray CCD

• Fano limited spectroscopy with the readout noise ~3e- (rms).

• Wide and fine imaging with the sensor size of ~20-30mm pixel size of ~30μm□

Non X-ray background of XIS (BI)

Due to high energy particles on orbit.

•Non X-ray background above 10keV is too high to study faint sources.

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

S26 K. Koyama et al. [Vol. 59,

2.4. Heat Sink and Thermo-Electric Cooler (TEC)

A three-stage thermo-electric cooler (TEC) is used to coolthe CCD to the nominal operating temperature of !90!C. Thecold-end of the TEC is directly connected to the substrateof the CCD, which is mechanically supported by 3 Torlon(polyamide-imide plastic) posts attached to the heat sink. Theheat is transferred through a heat pipe to a radiator panel on thesatellite surface, and is radiated away to space. The radiatorand the heat pipe are designed to cool the base below !40!Cunder the nominal TEC operating conditions. Figure 5 is aphotograph of the inside of base with the frame-store covershield removed. Since the TEC is placed under the CCD, andthe heat pipe is running under the base plate, these are not seenin figure 5.

2.5. Radiation Shield

The performance of any CCD gradually degrades due toradiation damage in orbit. For satellites in low-Earth orbit likeSuzaku, most of the damage is due to large fluxes of chargedparticles in the South Atlantic Anomaly (SAA). The radia-tion damage increases the dark current and the charge transferinefficiency (CTI). The XIS sensor body provides radiationshielding around the CCD. We found from the ASCA SISexperiment that radiation shielding of > 10 g cm"2 equivalentAl thickness is required. The proton flux density at 2 MeV onthe CCD chip through 10gcm"2 of shielding is estimated to be" 2# 103 protonscm"2 MeV"1 d"1 in the Suzaku orbit (sameas the ASCA orbit) at solar minimum.

3. On-Board Data Processing

3.1. XIS Electronics

The XIS control and processing electronics consist ofAE/TCE (analog electronics/TEC control electronics) and DE(digital electronics). The DE is further divided into PPU (pixelprocessing unit) and MPU (main processing unit). Two sets ofAE/TCE are installed in each of two boxes, respectively, calledAE/TCE01 and AE/TCE23. Similarly, 4 PPUs are housedin pairs, and are designated PPU01 and PPU23, respectively.AE/TCE01 and PPU01 jointly take care of XIS 0 and XIS 1,while AE/TCE23 and PPU23 are for XIS 2 and XIS 3. Oneunit of MPU is connected to all the AE/TCEs and PPUs.

The AE/TCE provides the CCD clock signals, controls theCCD temperature, and processes the video signals from theCCD to create the digital data. The clock signals are generatedin the AE with a step of 1/48 pixel cycle (" 0.5µs) accordinga micro-code program, which is uploaded from the ground.The pixel rate is fixed at 24.4µs pixel"1. Therefore one line,consisting of 4 under-clocked pixels, 256 active pixels, and16 over-clocked pixels, is read out in about 6.7 ms. The CCDoutput is sampled with 16-bit precision, but only 12 bits aresent to the PPU. The 12 bits are selected to cover the full energyscale of $ 15 keV in the normal setting of the gain. The fullenergy scale of $ 60 keV can also be selected in the low gainmode.

The AE/TCE controls the TEC (thermo-electric cooler) togenerate a temperature difference of " 50!C relative to thebase, while keeping the CCD chip at !90!C. The AE/TCE

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

can also supply reverse current to the TEC, to warm up theCCD chip in orbit. The CCD temperature may be raised a fewtens of !C above that of the base. In practice, the requirement toavoid excessive mechanical stresses due to differential thermalexpansion of the copper heat sink relative to the alumina CCDsubstrate imposes an upper limit on CCD temperature in thismode. For example, with the heat sink at a typical operatingtemperature of !35!C, we have adopted a maximum allow-able CCD temperature of about + 15!C. The CCD temperatureupper limit is higher at higher heat sink temperatures.

The PPU extracts a charge pattern characteristic of X-rays,called an event, after applying various corrections to the digitaldata supplied by the AE/TCE. Extracted event data are sent tothe MPU. Details of the event extraction process are describedin subsection 3.3. The PPU first stores the data from itsAE/TCE in a memory called the pixel RAM. In this process,copied and dummy pixels1 are inserted in order to avoid agap in the event data at segment boundaries, to ensure properevent extraction at segment boundaries and to enable identicalprocessing of all segments of the data. The raw data fromAE/TCE may include a pulse height (PH) offset from the truezero level due to dark current, small light leakage through theOBF, and/or an electric offset. Since the offsets depend onthe CCD position and time, offset corrections are also positionand time dependent. To reduce the computing power and timerequired for such corrections, the offsets are divided into twoparts, dark-level and light-leak. The dark-level is the averageoutput from a pixel with no irradiation of X-rays or chargedparticles. The dark-level is determined for individual pixels,and is up-dated by command only after each SAA passage in1 The data of each CCD segment are transferred through independent lines

from the AE/TCE to the PPU, and are processed in parallel by the sameprocessing scheme in the PPU. For a proper event extraction at thesegment boundary, the data in the two columns of the adjacent CCDsegments must be used. Therefore hard-wired logic is installed to “copy”the two column data in the adjacent CCD segments to the proper locationsin the PPU pixel RAM. These are called as “copied pixels”. In the caseof outer boundaries of segments A and D, such “copied pixels” can not beprepared. Instead, two columns of zero data are prepared in the PPU pixelRAM. These are called “dummy pixels” in the PPU pixel RAM.

Suzaku「すざく」 XIS

“XRPIX” = Monolithic SOI pixel sensor for future X-ray astronomical satellites

10μsec

Target Specification

Imaging area > 25x25mm2, pixel ~ 30-60μm□ (1” @ F=9m)Energy Band 0.3-40keV with BI, and thick depletion (>300μm) Spectroscopy ΔE < 140eV @ 6keV, Fano limit (<10e-)Timing <1μsecDark Current <1pA/cm2Function Trigger signal & pixel address output, built-in ADCNon X-ray BGD 5e-5 c/s/keV/10x10mm2 at 20keV (1/100 of CCD)

Realize Very Low BGD by Anti-coincidence

non X-ray BGD

(high energy particle)

on-board processor

X-ray

scintillator

Each pixel has its own trigger and analogue readout CMOS circuit.

Fast CMOS (low ρ Si)

Insulator(SiO2)

V_back

Hole

Electron

TimeV_sig

X-ray

BPW

CMOSReadout

CMOSReadout

CMOSReadout

P+

CMOSReadout

Sensor (high ρ,

depleted Si)

Our SOIPIX (XRPIX)

Applications for X-ray Astronomy

10μsec

Ｘ線CCDと明確に違う点（同じ完全空乏・裏面照射，解像度，素子大きさ，ノイズ性能を持った上で）

•デジタル(FPGA)だけの簡単な駆動・読み出し回路•高度なアナログ・デジタル処理機能•トリガ出力可能，高速読み出し，高時間分解能(~μsec)

•反同時計数法による低い非X線バックグラウンド(1/100 @ 20keV)

•高い耐放射線性能

考えられるアプリケーション•ASTRO-Hに続く次期中型・大型Ｘ線衛星の焦点面検出器•全天X線監視モニター，γ線バーストモニター（MAXI, Swift）•偏光Ｘ線撮像分光器•惑星探査用X線検出器（高い耐放射線性能）

　　　　　　　　　　　　　　　　　　　　　　　　　　など...

XRPIX1-CZ (X-Ray PIXel detector - CZochralski)

・2.

4 m

m

30.6 µm x 32 Pixel

COL Hit Pattern

1.0 mm

COL Hit Pattern

Row H

it Pattern

COL ADDRCOL Amp

ROW

AD

DR

TRIG_OOR

TRIG_COLTRIG_ROW

A_OUT

◆ CZ (0.7kΩcm), 260μm thick◆ Front Illumination

XRPIX1: Pixel Circuit

STORE

CDS C100fF

Sample C100fF

Sensor

Triggeroutput

Trigger

CDS

Comparator

CDS _VRST VTH

VDD18

PD_VRST

COL_AMP OUT_BUFSF2

SF1

VDD18

GND18

GND18

Sample/Store

Sensor C

Analogoutput

Analog Readout

G=1 G=1

TEST_ECA EOXX

XRPIX Series - Road Map -2010 2011 2012 2013

XRPIX2

XRPIX1 XRPIX1b

5A-R-Tec PROPRIETARY/CONFIDENTIAL

� �� ������������

2.4mm

2.4mm

XRPIXΔΣ-type

ADC

2.4 mm 2.4 mm

2.4 mm6.0 mm

1.0 mm1.0 mm 4.0 mm

X-ray imaging area

XRPIX2b

4.5 mm

6.0 mm

12

Channel40 60 80 100 120 140

Counts

50

100

150

200

250 Red: 109CdBlue: 241Am22.2 keV

FWHM = 1.1 keV

24.9 keV

13.9 keV17.7 keV

Sensitivity = 4.0 μV/e- (including SF, amps)Sensor C = 34 fF

Good Linearity

Energy Resolution

ΔE = 1.1-1.2keV (FWHM) ≫ Fano limitReadout Noise = 100e- (rms)

X-ray Energy [keV]

0 5 10 15 20 25

Ou

tpu

t [A

DU

]

0

20

40

60

80

100

120

140

160

XRPIX1-CZ (T=-50C, VBB=100V)

XRPIX1-CZ : X-ray Spectra in the frame mode

Ryu et al., IEEE TNS 58, 2528 (2011)

• See whether the readout noise of 100e- (rms) is explained by the sum of circuit noises or not.

• Measure the noise of individual circuit element through several DC voltage input points.

XRPIX1-CZ : Readout Noise

Sum = 94e

SF113e

CDS kTC70e

SF213e

COL_AMP31e

OUT_BUFExternal on PCB

53e(100fF ⇒ 51e)

STORE

CDS C100fF

Sample C100fF

CDS _VRST VTH

VDD18

PD_VRST

COL_AMP OUT_BUFSF2

GND18

Sensor C

G=1 G=1

TEST_ECA EOXX

Sensor

CDSSF1

Sample/Store

A

B C DVB

Vout

VC VD

The sum of these noises is almost consistent with the observed readout noise of 100e.

Ryu et al., IEEE TNS 58, 2528 (2011)

XRPIX2-CZ-FI (Small Pixel) : Spectrum

Nakashima et al., 2012, NIM A submitted

0 2 4 6 8 10 12 14 16 18 200

20

40

60

80

100

120

140

0 20100

150

50

100

X-ray Energy (keV)

Pulse

Hig

ht (c

h)

XRPIX2 Gain 6.5 µV/e-

XRPIX1 Gain 3.6 µV/e-

Observed Readout Noise

FanoNoise

Pixel-Pixel GainDispersion 1%

Sum

Cu Kα 656 eV 548 eV (FWHM)64 e-(rms)

139 eV 255 eV 620 eV

Mo Kα 800 eV

548 eV (FWHM)64 e-(rms) 205 eV 553 eV 805 eV

PH [ADU]

40 60 80 100 120 140 160

PH [ADU]

40 60 80 100 120 140 1600

200

400

600

800

1000

1200

1400

1600

1800

40 80 120 160Pulse Hight (ch = 244 µV)

1000

500

1500

Cu C

ount

100

200

00

Mo

Coun

t

Cu Kα (8.0 keV) Mo Kα (17.4 keV)

Mo Kβ(19.6 keV)

656 eVFWHM

800 eVFWHM

XRPIX1b-CZ : Single Pixel Readout• In order to study the limit of the spectroscopic performance.• Observe the waveform of analogue output from a single pixel by fixing the

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=100μs

sample number in one frame0 200 400 600 800 1000

PH [A

DU

]

625

630

635

640

645

650

655

660

sample number in one frame0 200 400 600 800 1000

PH [A

DU

]

627

628

629

630

631

632

633

PH [ADU]0 50 100 150 200

Cts

/ A

DU

1

10

210

310

410

CMS Histgram h1Entries 49668Mean 0.2479RMS 1.017

CMS Histgram

Data Name: Fe_minus30c_sp_Vback_100V_Tscan_480ns_25_25_50000f.root

Cut+Ped+Phy[frm]: 300+500+50000

Hit threhold= 10 ADU, Delay=2 frm, Ave=160 frm

X-ray count: 0.001972 Cts/frame

Readout Noise = 0.330654 ADU

X-ray Hit

PulseHeight

average100 samplesτ=100μsec

h1Entries 398490Mean 0.3396RMS 3.101

/ ndf 2χ 3.97e+05 / 9Constant 1.41± 85.81 Mean 1.41± 54.28 Sigma 11.6984± 0.8022

PH [ADU]0 20 40 60 80 100 120 140

Cts

/ A

DU

0

20

40

60

80

100

120

h1Entries 398490Mean 0.3396RMS 3.101

/ ndf 2χ 3.97e+05 / 9Constant 1.41± 85.81 Mean 1.41± 54.28 Sigma 11.6984± 0.8022

CMS Histgra (R10C10)

FWHM=278eV @8.0 keV

rms=14.6e- 44M-BPW

Cu-Kβ

Cu-Kα

ΔE = 278eV @ 8.0keV (FWHM), readout noise = 14.6e (rms)

average 100 samplesτ=100μsec

Nakashima et al.,

2012, NIM A

accepted

XRPIX1b-CZ : Trigger Driven Readout

・

COL Hit Add. Resister

Row H

it Add.

Resister

COL Readout ADDRCOL Amp

ROW

Rea

dout

AD

DR

TRIG_OOR

TRIG_COL

TRIG_ROW

A_OUT

①① ②

X-ray !

FPGA

ADC

Takeda et al., IEEE Accepted (2012)

③

④

④

⑤

XRPIX1b-CZ : Trigger-driven Readout of X-ray Events

h1Entries 1617Mean 58.61RMS 19.57

X-ray PH (ADU)0 20 40 60 80 100 120 140 160

Cou

nts /

AD

U

10

20

30

40

50

60

70h1

Entries 1617Mean 58.61RMS 19.57

h1Entries 487Mean 39.51RMS 10.58

FWHM1.4 keV

8 keV

17.7 keV

13.9 keV

26.4 keV

Data VTH Exposure

Cu+Mo 10 mV 5sec

Am-241 15 mV 20 sec

17.4 keV

X-ray Trigger-driven Spectra

h1Entries 0Mean 0RMS 0

Energy (keV)0 5 10 15 20 25 30

PH (A

DU

)

0

10

20

30

40

50

60

70

80

90

100h1

Entries 0Mean 0RMS 0

/ ndf 2! 16.61 / 4

p0 2.477± 15.78

p1 0.1278± 2.715

/ ndf 2! 16.61 / 4

p0 2.477± 15.78

p1 0.1278± 2.715

X-ray Energy Calibration

Output Gain : = 2.7 ADU/keV = 2.4 !V/e-Offset :=15.8 ADU =3.8 mV

Measured Output Gain : = 2.7 ADU/keV = 2.4 !V/e-Offset :=15.8 ADU =3.8 mV

Expected

- Trigger-driven mode basically operates as designed.

- The gain is different from that of the frame mode.- We are now investigating.

Takeda et al., IEEE Accepted (2012)

TAKEDA et al.: DESIGN AND EVALUATION OF A SOI PIXEL SENSOR FOR X-RAY TRIGGER-DRIVEN READOUT 5

TRIG_OUT

SCLK

CA [31 - 0]

RA [31 - 0]

ADDR[31] ADDR[0]

CA[26]

RA[7]

Fig. 12. Raw X-ray trigger signals recorded by the oscilloscope (c.f., Fig.9).

0 10 20 30 40 50 60

10

20

30

40

50

60

70

0 10 20 30 40 50 60

5

10

15

20

25

30

35

40

45

X-ray Energy (keV)

VTH : 10 mVExposure : 5 sec

8 keV

17.4 keV

1.4 keVFWHM

Cou

nts

X-ray Energy (keV)

Cou

nts

VTH : 15 mVExposure : 20 sec13.9 keV

17.7 keV

20.7 keV

26.4 keV

Fig. 13. X-ray spectra of the Cu+Mo target (top) and the 241Am radioisotope (bottom) obtained in the trigger-driven mode.

h1Entries 0Mean 0RMS 0

400 450 500 550 600 6500

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

h1Entries 0Mean 0RMS 0

Calibration

Input Voltage (mV)

-10 ℃ -30 ℃ -50 ℃

VBack = 100 V

Tri

gger

Ass

ert

Prob

abili

ty

Fig. 14. Dependence of the trigger output on the input signal at a fixedthreshold voltage of 500 mV. The trigger assert probability is calculated fromthe fraction of trigger-on events after 10000 tests at the corresponding inputvoltage.

because in this case Cu�K↵ and K� lines are not separsated.The energy resolution value is used for comparison with thetrigger-driven mode described in section IV-B. The ADC gainis 6.94 (ADU / keV), based on the slope of the linear fitting.In silicon, 274 electron-hole pairs are generated at an averagewith the X-ray energy of 1 keV. As a result, the total gain ofthe sensor is 6.94 (ADU / keV) ⇥ 244 (µV / ADU) / 274 (e-/ keV) = 6.18 (µV / e-).

B. Verification in X-ray Trigger-driven Mode

We performed X-ray irradiation tests so as to verify thetrigger-driven mode. This test was carried out under the sametemperature and back bias voltage (VBack) as used in sectionIV-A.

We successfully observed the X-ray trigger waveform (Fig.12) on an oscilloscope. This figure shows the oscillation in theTRIG OUT signal. This is probably because the TRIG OUTsignal is affected by the SCLK signal true capacitive couplingof the signals.

Fig. 13 shows the first resolved X-ray spectra of the Cu+Motarget and the 241

Am radio isotope obtained in the trigger-driven mode. The energy resolution is 1.4 keV FWHM at8 keV. This result indicates that the X-ray trigger-drivenmode works successfully, although the energy resolution isnoticeably worse than that of the non-trigger driven mode.This might be due to interference between the trigger circuitand the signal readout circuit.

C. Trigger Sensitivity for Low-energy X-rays

The trigger sensitivity for the detection of low-energy X-rays is determined primarily by the circuit noise level. If thethreshold level is lowered close to the noise level, the triggeroutput would be turned high by the noise (a false detection).To measure that limit, we supplied an input voltage from the

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Column Row

Trigger !

Address of Triggered Pixel

Trigger Address Readout Clock

2μsec

XRPIX1-FZ (7kΩcm): Depletion Depth

Back Bias [V]0 10 20 30 40 50

Dep

letio

n D

epth

[um

]

0

50

100

150

200

250

300

350

60 70 80 90 100 110Back Bias [V]

0 10 20 30 40 50

Dep

letio

n D

epth

[um

]

0

50

100

150

200

250

300

350

60 70 80 90 100 110

FZ : 250μm @ VBB=30V

• The X-ray measured thickness of the depletion layer of XRPIX1-FZ reaches ~250μm at 30V and stops its growth there.

• The 250μm is nearly equal to the hi-ρ Si thickness (260μm). • Full depletion is achieved at VBB=30V.

CZ : 150μm @ VBB=100V

+ : Experimental results– : Expected value

Nakashima et al., 2012, NIM A accepted

XRPIX1-FZ，with CMPPchNeXT4 (normalized to 30.6μm□)

Temperature (degree C)-50 -40 -30 -20 -10 0 10 20

Dar

k C

urre

nt (e

/ms/

pixe

l)

-310

-210

-110

1

10

210

310

410

510

610

黒：VBB=30V青：20V赤：10V

3e-2

4e-3PchNeXT4

Dar

k C

urre

nt (

e/m

sec/

30.6μm□

pixe

l)

XRPIX1-FZ-FI (7kΩcm) : Dark (Leak) Current20

From 20110516_OKImeeting_SOI_Dark_v5

Requierment at -40C

= 0.1e/msec/30.6μm□ pix

(depletion = 250μm)

= 2pA/cm2

1/100

Filter Transmission

Filter Transmission http://henke.lbl.gov/tmp/xray9837.html

1 / 1 12/03/14 14:41

Si 1μm

Si 10μm

00.

51.

0Q

E

0.3 1.0 5.0(keV)

Dead Layer = Si 0.1μm

Energy

Back Illumination is Essential

→ BI is essential

• Scientific Target : observe C-Kα X-ray line at 0.3keV.

• The front side of SOIPIX has a circuit-layer of 10μm thickness. (Note: XIS FI-CCD~1μm, BI-CCD~0.07μm)

• Difficult to detect Soft X-rays with FI.

• Difficult to reduce the thickness of the circuit layer.

QE of LBNL’s BI-SOIPIX / SOImager-2-CZ-BI

•CZ-BI with Back-thinned to 70μm.

•A thin phosphor layer is implanted. ※ これは我々の素子ではなく，同じウェハを使用した別の素子です．

Deplation 73±2μm

Dead Layer 0.6±0.2μm

Battaglia+12 NIM-A

XRPIX1b-CZ-FI/BI (100μm): Spectra in Single Pixel Readout (2011.11.22)

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

h4Entries 128627Mean 1.608RMS 3.417

PH [ADU]-5 0 5 10 15 20 25 30 35 40

Cts

1

10

210

310

410 h4Entries 128627Mean 1.608RMS 3.417

CMS Histgram (offset-corrected)

h4Entries 128627Mean 1.608RMS 3.417

AL-Ka(1.48 keV)

Si Edge (1.84 keV)

RED: BI BLUE: FIh4Entries 128627Mean 2.282RMS 3.155

PH [ADU]0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Cts

0

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h4Entries 128627Mean 2.282RMS 3.155CMS Histgram (offset-corrected)

h4Entries 128627Mean 2.282RMS 3.155

Zoom

O-Ka ??

HV(6kV)

←15 e-rms

←18 e-rms

Cts

DetectionThreshold(2ADU)

502 eVby

Calibration

AL-Ka

• Back illumination type.

• X-ray generator (target = Al, 6kV).

• Al-K + Bremss(+O-K from Al2O3?)

• ΔE (FI) = 188eV, ΔE (BI) = 351eV (if line)

Results on FI : Ryu et al., IEEE Accepted (2012)

XRPIX3 and after

Spectral Performance•全てのピクセルにチャージアンプを持つ•ノイズ性能の改善，エネルギー分解能の改善

Backside•裏面プロセスの改良•暗電流の削減とデットレイヤーを薄く　　　　　　　　　→以上の要素技術の合体System•反同時計数システムの試作•非Ｘ線BGDの減少の実証•外部回路のノイズ削減

Conclusion

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SOI Pixel Project : General View�

Feb. 28, 2011

SOI International Review Meeting

Yasuo Arai, KEK

yasuo.arai@kek.jp

http://rd.kek.jp/project/soi/�

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•Ｘ線天文衛星用のＸ線SOIピクセル検出器(XRPIX)を開発．

•反同時計数による低非Ｘ線BGDを目指し，トリガ機能を持つ．

•4.5mm角の素子の開発に成功

•空乏層厚み~250μm，裏面不感層~0.6μm

•読み出しノイズ64e-(rms)，ΔE=656eV @ 8.0keV (FWHM)

•トリガ読み出しに成功

•今後，読み出しノイズ，裏面不感層，反同時計数の実証を行う