development and performance of kyoto's x-ray astronomical soi …€¦ · kek c • pi=prof....
TRANSCRIPT
Development and Performance of Kyoto's X-ray Astronomical SOI pixel sensor
T.G.Tsuru ([email protected])
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
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