Radiation Damage Effects on Double-SOI Pixel Sensors for X ......In order to solve the interference problem, we adopt a Double-SOI wafer (DSOI) in which we introduce an additional

Radiation Damage Effects onDouble-SOI Pixel Sensors

for X-ray Astronomy

○Kouichi Hagino (Tokyo University of Science)K. Yarita, K. Negishi, K. Oono, M. Hayashida (Tokyo Univ. of Science)

M. Kitajima, T. Kohmura (Tokyo Univ. of Science) T. G. Tsuru, T. Tanaka, H. Uchida, K. Kayama, Y. Amano, R. Kodama (Kyoto Univ.)

A. Takeda, K. Mori, Y. Nishioka, M. Yukumoto, T. Hida (Univ. of Miyazaki) Y. Arai, I. Kurachi (KEK), T. Hamano, H. Kitamura (QST)

12th International "Hiroshima" Symposium on the Development and Application of Semiconductor Tracking Detectors (HSTD12)

@Hiroshima

2019.12.15 HSTD12 @Hiroshima / 15

Future X-ray Astronomical Satellite: FORCE• FORCE : Focusing On the Relativistic universe and Cosmic Evolution

• 3 pairs of super-mirrors and detectors with a focal length of 10 m

2

X-ray super-mirror✓Light-weight Si mirror by NASA/GSFC✓Multi-layer coating directly on the Si

mirror surface ➡Unprecedented angular resolution

of <15” in hard X-ray

Wideband Hybrid X-ray Imager (WHXI) ✓Stacked Si / CdTe hybrid detector✓Low instrumental background with

active shield➡Wideband sensitivity of 1-80 keV

Imaging Area: >20 × 20 mm2

Depletion layer thickness : >200 μm Dead layer thickness : <1 μm

Energy resolution : <300 eV (FWHM) at 6 keVReadout noise : <10 e−Time resolution : <10 μsThroughput : 2 kHz

Requirement for the Si sensor

2019.12.15 HSTD12 @Hiroshima / 15

X-ray SOI Pixel Sensor：XRPIX

3

✓ High ρ Si for sensor layer→ Thick depletion layer of ~ a few ×100 μm

✓ Self-trigger function in each pixel circuit→ Time resolution better than ~10 μs

✓ Energy resolution comparable to X-ray CCDs ~150−300 eV @ 6 keV

XRPIX: Monolithic active pixel sensor composed of

‣ High-resistivity Si sensor

‣ Thin SiO2 insulator

‣ CMOS pixel circuits (low ρ Si)by Silicon-On-Insulator (SOI) technology

#13 by Ayaki Takeda: Event pattern processing#12 by Ryota Kodama: Trigger performance

CMOScircuit

sense node

X-ray

---

++ +

Back bias voltage

CMOScircuit

CMOScircuit

~300−500 μm

~0.2 μm

~10 μm

Sensor(high ρ Si)

Burred Oxide (BOX)

Pixel size ~36 μm

Si sensor

2019.12.15 HSTD12 @Hiroshima / 15

CMOScircuit

sense node

CMOScircuit

CMOScircuit

BOX

Si sensor

Radiation Effects on SOI Sensors

4

• SOI pixel sensors are known to be sensitive to total ionization dose (TID) effects

High energy particles

-

-

-

+

+

+

-+

-+

-+

2019.12.15 HSTD12 @Hiroshima / 15

CMOScircuit

sense node

CMOScircuit

CMOScircuit

BOX

Si sensor

Radiation Effects on SOI Sensors

4

• SOI pixel sensors are known to be sensitive to total ionization dose (TID) effects

➡Radiation hardness has been one of the major issues in development of the SOI pixel sensors

++ + + + +Positive potential by accumulated charges affects the transistor characteristics (e.g., Vth, gm)

➡TID (Total Ionizing Dose) effect

2019.12.15 HSTD12 @Hiroshima / 15

5.9keV

FWHM:200eV

2017 Nov.

No Tail

Mn-Kα (5.9 keV)FWHM

200eV

Mn-Kβ (6.5 keV)

ENC ~10e (rms)

2010Cu-K (8keV)

FWHM 1.4keV

ENC ~130e (rms)

2011-2013

Mn-K (6keV)

FWHM 730eV

Energy [keV]

ENC ~68e (rms)

2017 Mar.

Tail

FWHM 200eV

Mn-Kα (5.9keV)

Mn-Kβ (6.5keV)

ENC ~16e (rms)

2013Mn-Kα

(5.9keV)FWHM 320eV

Mn-Kβ (6.5 keV)

Separation of Kα and Kβ

Energy [keV]

ENC ~35e (rms)

2009

FWHM 4keV

Cu-K (8keV)Zero level

ENC ~600e (rms)

(a) (b) (c)

(d) (e) (f)

Figure 4. Evolution of the spectral performance of X-ray astronomy SOIPIX in the Frame readout.9,11–13

Event-Driven readout mode

PH1000 1100 1200 1300 1400

Counts

0

200

400

600

800

1000

1200

1400

時，ののスペクトル．　先程のキャリブレーションプロットの元データ．

10

CSA PixelFWHM : 9.6 % (1.34 keV)

13.95 keV

17.74 keV

20.77 keV

11.44 keV

9.71 keV

-30 ℃CSACo

unts

Pulse Height (ADU)

Preliminary

時，ののスペクトル．　先程のキャリブレーションプロットの元データ． 13.95 keV

XRPIX3b-CZ w/CSA

Frame readout mode

Readout noise reduction 　

History of Spectroscopic Performance

8

[A.Takeda + JINST (2015)]

100 200 300 400 5000

20

40

60

80

100

120

140

160

180

CSA PixelFWHM : 2.9 % (400 eV)

17.74 keV

20.77 keV

11.44 keV

9.71 keV

CSA-PIX

readout noise : 32 e- (rms)

Counts

Pulse Height (ADU)

241Am

~600 e- (rms) -> 35 e- (rms) ! … But our goal is 3 e- (rms).

35 e- (rms)

Radiation sensors and emerging applications @ OIST - A. Takeda - 18th Jan. 2017



8


13.95 keV


XRPIX3b-CZ w/CSA

Figure 5. The spectra of the Am-241 X-rays obtained with an XRPIX3b (left) in the Frame readout mode and (right)in the Event-Driven readout mode.9

In order to solve the interference problem, we adopt a Double-SOI wafer (DSOI) in which we introduce anadditional Si layer (middle Si layer) between the circuit and sensor layers.14 The BOX layer is interleaved withthe middle Si layer,15–17 as shown in Figure 6 (b). Note that the sensor layer of this Double-SOI device is p-typewhereas that of the XRPIX5b is n-type. The middle Si layer is expected to act as an electrostatic shield and toreduce the capacitive coupling between the BNW and the digital circuit.

Figure 7 shows the spectra of Co-57 X-ray we obtained with an XRPIX6D having the Double-SOI structurein the Frame and Event-Driven readout modes. The performance in the Event-Driven mode is significantlyimproved by adopting the Double-SOI structure and is now close to that in the Frame readout mode. The

Proc. of SPIE Vol. 10709 107090H-5Downloaded From: https://www.spiedigitallibrary.org/conference-proceedings-of-spie on 1/15/2019Terms of Use: https://www.spiedigitallibrary.org/terms-of-use

Single SOIwithout trigger

function

with trigger

function

Please cite this article in press as: K. Hara, et al., Radiation hardness of silicon-on-insulator pixel devices, Nuclear Inst. and Methods in Physics Research, A (2018),https://doi.org/10.1016/j.nima.2018.05.077.

K. Hara et al. Nuclear Inst. and Methods in Physics Research, A ( ) –

Fig. 4. Id-Vg curves of (left) NMOS and (right) PMOS irradiated to 2 MGy for various settings of the SOI2 voltages. The curve for pre-irradiation is shown in brokenlines.

Fig. 5. Relative evolution of gm as a function of dose for (left) NMOS and (right) PMOS FET. The curves are for different settings of SOI2 voltages.

Fig. 6. (a) Most probable ADC values to 120-GeV protons compared between non-irradiated and 100 kGy irradiated FPIX2 of 300 �m thickness [13]. The horizontalscale is linear in

˘VDET. (b) Charge distributions at 200 V bias are compared between non-irradiated (darker histogram) and 100 kGy irradiated (lightly shaded

histogram) samples. The VSOI2 settings are as shown in the plot.

3. Double SOI with original LDD profile

Double SOI (DSOI) is the ultimate innovation to address these prob-lems. The DSOI wafer is fabricated by repeating the Soitex SmartCut™process twice. The two BOX layers are each 145 nm thick and the middleSi layer (SOI2) is 80 nm thick, first fabricated by Soitec with n-type Czof 0.6 k⌦ cm handle wafer resistivity, and then by Shin-etsu Chemicalwith low-oxygen n-type Cz (1 k⌦ cm). The latest fabrication techniqueuses DSOI of p-type FZ of 5 k⌦ cm resistivity. The middle SOI silicon was

changed to n-type to reduce the sheet resistance for negative voltagesapplied, which is required for TID compensation.

Systematic and detailed compensation studies were carried out[10,11]. Fig. 4 shows a comparison of the FET Id-Vg curve before (bro-ken lines) and after 2 MGy (black solid) irradiation for NMOS and PMOSFETs. Also shown are evolution of the Id-Vg curves by changing thevoltage to SOI2, VSOI2. As the curve returns beyond the pre-irradiationthreshold point, we can find the VSOI2 to be compensated, althoughthe Id-Vg characteristics is not identical to the pre-irradiation case,especially for PMOS. Furthermore, substantial degradation is recognized

3

Improvement with Double SOI Structure

5

• Double SOI structure was introduced to reduce the TID effect‣ Thin middle Si layer in BOX‣ Apply negative voltage

CMOS circuitCMOS circuitCMOS circuit

BOX

Si sensor

+ + + + + + + + + + + + +middle Si−VMS

1M layer

Sensor

Circuit Middle Si Layer

BNW

Insulator (SiO2)

p-

Double SOI1M layer

Sensor

Circuit

BNW

Insulator (SiO2)

p-

Single SOI

capacitive coupling

(a) (b)

Figure 6. Cross-sectional views of (a) the single SOI and (b) Double-SOI structures.15–17 A p-type Si sensor layer isassumed in this figure.

energy resolutions are 312 eV and 346 eV at 6 keV in the Frame and Event-Driven readout modes, respectively.No significant offset in the output channel is observed in the Event-Driven readout mode. The results show thatthe crosstalk between the circuit and sensor layers is suppressed as expected. We found that the sense-nodegain is increased by about a factor of two in comparison to the single SOI device having the same design of thein-pixel CSA. This should be due to the reduction in the sense-node parasitic capacitance by making the area ofthe BNW smaller, and also to the increase in the closed-loop gain by reducing the feedback parasitic capacitancebetween the CSA and the BNW.13,18,19

0 100 200 300 400 500 600 700 8000

500

1000

1500

2000

2500

Counts/bin

PH [ADU]

Temp. ＝ ‒60 ℃ Vb = ‒400 V

FWHM 312 ± 5 eV (4.9 ± 0.1 %)

6.4 keV

7.1 keV14.4 keV

57Co

0 100 200 300 400 500 600 700 8000

200

400

600

800

1000

Counts/bin

PH [ADU]

FWHM 346 ± 11 eV (5.4 ± 0.2 %)

6.4 keV

14.4 keV7.1 keV

57Co

XRPIX6D-PCZ-FI-300um_Frame_EventDriven_v0

Temp. ＝ ‒60 ℃ Vb = ‒400 V

(a) (b)Frame readout mode


Figure 7. Co-57 spectra obtained with the Double-SOI device (XRPIX6D) (a) in the Frame readout mode and (b) in theEvent-Driven readout mode.13

3.3 Pinned Depleted Diode structure

In the single SOI structure, the charge generated in the interface region between the sensor and BOX layers iscollected, which results in a significantly large dark current degrading the spectral performance. The device alsosuffers from the possibility of signal charge loss by the traps at the interface, which results in the degradation ofthe charge collection efficiency.20 This situation is unchanged even with the Double-SOI structure.

In order to solve these problems, Kamehama et al. (2018) recently developed a Pinned Depleted Diode (PDD)structure.12 The PDD structure has a BPW region beneath the BOX layer, and a BNW region below that inthe single SOI wafer as shown in Figure 8. The signal charge generated by an X-ray collects through the steppedburied n-well (BNW1, BNW2 and BNW3) into the readout node (n+) without touching the interface betweenthe sensor (p–) and the BOX layers. Thus, the signal charge loss by the traps at the interface does not occur.


Double SOIwithout trigger

functionwith

trigger function

✓ Compensate positive potential due to TID effect

Hara et al., NIM-A, 2019

2019.12.15 HSTD12 @Hiroshima / 15

5.9keV

FWHM:200eV

2017 Nov.

No Tail

Mn-Kα (5.9 keV)FWHM

200eV

Mn-Kβ (6.5 keV)

ENC ~10e (rms)

2010Cu-K (8keV)

FWHM 1.4keV

ENC ~130e (rms)

2011-2013

Mn-K (6keV)

FWHM 730eV

Energy [keV]

ENC ~68e (rms)

2017 Mar.

Tail

FWHM 200eV

Mn-Kα (5.9keV)

Mn-Kβ (6.5keV)

ENC ~16e (rms)

2013Mn-Kα

(5.9keV)FWHM 320eV

Mn-Kβ (6.5 keV)

Separation of Kα and Kβ

Energy [keV]

ENC ~35e (rms)

2009

FWHM 4keV

Cu-K (8keV)Zero level

ENC ~600e (rms)

(a) (b) (c)

(d) (e) (f)

Figure 4. Evolution of the spectral performance of X-ray astronomy SOIPIX in the Frame readout.9,11–13


PH1000 1100 1200 1300 1400

Counts

0

200

400

600

800

1000

1200

1400

時，ののスペクトル．　先程のキャリブレーションプロットの元データ．

10

CSA PixelFWHM : 9.6 % (1.34 keV)

13.95 keV

17.74 keV

20.77 keV

11.44 keV

9.71 keV

-30 ℃CSACo

unts

Pulse Height (ADU)

Preliminary

時，ののスペクトル．　先程のキャリブレーションプロットの元データ． 13.95 keV

XRPIX3b-CZ w/CSA

Frame readout mode



8


100 200 300 400 5000

20

40

60

80

100

120

140

160

180

CSA PixelFWHM : 2.9 % (400 eV)

17.74 keV

20.77 keV

11.44 keV

9.71 keV

CSA-PIX

readout noise : 32 e- (rms)

Counts

Pulse Height (ADU)

241Am

~600 e- (rms) -> 35 e- (rms) ! … But our goal is 3 e- (rms).

35 e- (rms)




8


13.95 keV


XRPIX3b-CZ w/CSA

Figure 5. The spectra of the Am-241 X-rays obtained with an XRPIX3b (left) in the Frame readout mode and (right)in the Event-Driven readout mode.9

In order to solve the interference problem, we adopt a Double-SOI wafer (DSOI) in which we introduce anadditional Si layer (middle Si layer) between the circuit and sensor layers.14 The BOX layer is interleaved withthe middle Si layer,15–17 as shown in Figure 6 (b). Note that the sensor layer of this Double-SOI device is p-typewhereas that of the XRPIX5b is n-type. The middle Si layer is expected to act as an electrostatic shield and toreduce the capacitive coupling between the BNW and the digital circuit.

Figure 7 shows the spectra of Co-57 X-ray we obtained with an XRPIX6D having the Double-SOI structurein the Frame and Event-Driven readout modes. The performance in the Event-Driven mode is significantlyimproved by adopting the Double-SOI structure and is now close to that in the Frame readout mode. The


Single SOIwithout trigger

function

with trigger

function

Please cite this article in press as: K. Hara, et al., Radiation hardness of silicon-on-insulator pixel devices, Nuclear Inst. and Methods in Physics Research, A (2018),https://doi.org/10.1016/j.nima.2018.05.077.

K. Hara et al. Nuclear Inst. and Methods in Physics Research, A ( ) –

Fig. 4. Id-Vg curves of (left) NMOS and (right) PMOS irradiated to 2 MGy for various settings of the SOI2 voltages. The curve for pre-irradiation is shown in brokenlines.

Fig. 5. Relative evolution of gm as a function of dose for (left) NMOS and (right) PMOS FET. The curves are for different settings of SOI2 voltages.

Fig. 6. (a) Most probable ADC values to 120-GeV protons compared between non-irradiated and 100 kGy irradiated FPIX2 of 300 �m thickness [13]. The horizontalscale is linear in

˘VDET. (b) Charge distributions at 200 V bias are compared between non-irradiated (darker histogram) and 100 kGy irradiated (lightly shaded

histogram) samples. The VSOI2 settings are as shown in the plot.

3. Double SOI with original LDD profile

Double SOI (DSOI) is the ultimate innovation to address these prob-lems. The DSOI wafer is fabricated by repeating the Soitex SmartCut™process twice. The two BOX layers are each 145 nm thick and the middleSi layer (SOI2) is 80 nm thick, first fabricated by Soitec with n-type Czof 0.6 k⌦ cm handle wafer resistivity, and then by Shin-etsu Chemicalwith low-oxygen n-type Cz (1 k⌦ cm). The latest fabrication techniqueuses DSOI of p-type FZ of 5 k⌦ cm resistivity. The middle SOI silicon was

changed to n-type to reduce the sheet resistance for negative voltagesapplied, which is required for TID compensation.

Systematic and detailed compensation studies were carried out[10,11]. Fig. 4 shows a comparison of the FET Id-Vg curve before (bro-ken lines) and after 2 MGy (black solid) irradiation for NMOS and PMOSFETs. Also shown are evolution of the Id-Vg curves by changing thevoltage to SOI2, VSOI2. As the curve returns beyond the pre-irradiationthreshold point, we can find the VSOI2 to be compensated, althoughthe Id-Vg characteristics is not identical to the pre-irradiation case,especially for PMOS. Furthermore, substantial degradation is recognized

3

Improvement with Double SOI Structure

5

• Double SOI structure was introduced to reduce the TID effect‣ Thin middle Si layer in BOX‣ Apply negative voltage

CMOS circuitCMOS circuitCMOS circuit

BOX

Si sensor

+ + + + + + + + + + + + +middle Si−VMS

1M layer

Sensor

Circuit Middle Si Layer

BNW

Insulator (SiO2)

p-

Double SOI1M layer

Sensor

Circuit

BNW

Insulator (SiO2)

p-

Single SOI

capacitive coupling

(a) (b)

Figure 6. Cross-sectional views of (a) the single SOI and (b) Double-SOI structures.15–17 A p-type Si sensor layer isassumed in this figure.

energy resolutions are 312 eV and 346 eV at 6 keV in the Frame and Event-Driven readout modes, respectively.No significant offset in the output channel is observed in the Event-Driven readout mode. The results show thatthe crosstalk between the circuit and sensor layers is suppressed as expected. We found that the sense-nodegain is increased by about a factor of two in comparison to the single SOI device having the same design of thein-pixel CSA. This should be due to the reduction in the sense-node parasitic capacitance by making the area ofthe BNW smaller, and also to the increase in the closed-loop gain by reducing the feedback parasitic capacitancebetween the CSA and the BNW.13,18,19

0 100 200 300 400 500 600 700 8000

500

1000

1500

2000

2500

Counts/bin

PH [ADU]

Temp. ＝ ‒60 ℃ Vb = ‒400 V

FWHM 312 ± 5 eV (4.9 ± 0.1 %)

6.4 keV

7.1 keV14.4 keV

57Co

0 100 200 300 400 500 600 700 8000

200

400

600

800

1000

Counts/bin

PH [ADU]

FWHM 346 ± 11 eV (5.4 ± 0.2 %)

6.4 keV

14.4 keV7.1 keV

57Co

XRPIX6D-PCZ-FI-300um_Frame_EventDriven_v0

Temp. ＝ ‒60 ℃ Vb = ‒400 V

(a) (b)Frame readout mode


Figure 7. Co-57 spectra obtained with the Double-SOI device (XRPIX6D) (a) in the Frame readout mode and (b) in theEvent-Driven readout mode.13

3.3 Pinned Depleted Diode structure

In the single SOI structure, the charge generated in the interface region between the sensor and BOX layers iscollected, which results in a significantly large dark current degrading the spectral performance. The device alsosuffers from the possibility of signal charge loss by the traps at the interface, which results in the degradation ofthe charge collection efficiency.20 This situation is unchanged even with the Double-SOI structure.

In order to solve these problems, Kamehama et al. (2018) recently developed a Pinned Depleted Diode (PDD)structure.12 The PDD structure has a BPW region beneath the BOX layer, and a BNW region below that inthe single SOI wafer as shown in Figure 8. The signal charge generated by an X-ray collects through the steppedburied n-well (BNW1, BNW2 and BNW3) into the readout node (n+) without touching the interface betweenthe sensor (p–) and the BOX layers. Thus, the signal charge loss by the traps at the interface does not occur.


Double SOIwithout trigger

functionwith

trigger function

✓ Compensate positive potential due to TID effect

Hara et al., NIM-A, 2019

✓ Work as an electrostatic shield, and reduce the electric interference between sensor and circuit

➡ Improve spectral performance in trigger mode

2019.12.15 HSTD12 @Hiroshima / 15

Radiation Hardness Required for FORCE

6

• In the orbit of the FORCE satellite (altitude~550 km, inclination~30°), the sensors suffers radiation damage mainly by cosmic-ray protons trapped at South Atlantic Anomaly (SAA)

Cosmic-ray proton flux(>10 MeV) @ 500 km altitude Required radiation hardness in XRPIX is

different from high energy accelerators

• Typical dose rate for XRPIX:~0.1 krad / year (~Gy / year)

• Total dose in mission life time: < a few krad (~0.01 kGy)

• Required performance:

‣ Energy resolution = 300 eV

‣ Readout noise = 10e-

SAA

2019.12.15 HSTD12 @Hiroshima / 15

Radiation Hardness Required for FORCE

6

• In the orbit of the FORCE satellite (altitude~550 km, inclination~30°), the sensors suffers radiation damage mainly by cosmic-ray protons trapped at South Atlantic Anomaly (SAA)

Cosmic-ray proton flux(>10 MeV) @ 500 km altitude

We evaluate the radiation hardness of Double-SOI XRPIX by irradiating protons with a dose level of a few krad

Required radiation hardness in XRPIX is different from high energy accelerators

• Typical dose rate for XRPIX:~0.1 krad / year (~Gy / year)

• Total dose in mission life time: < a few krad (~0.01 kGy)

• Required performance:

‣ Energy resolution = 300 eV

‣ Readout noise = 10e-Not evaluated in double SOI

SAA

2019.12.15 HSTD12 @Hiroshima / 15

Proton Irradiation Experiment @ HIMAC

7

• We performed a proton irradiation experiment of double-SOI XRPIX at HIMAC in National Institute of Radiological Sciences

6 MeV Proton

XRPIX

Readout Board

45°

Au Scatterer

Faraday cup

Vacuum chamber

• Sensor Device✓ Double-SOI device “XRPIX6c”✓ Operated with VBB = -250 V✓ Vacuum✓ Temperature ~ -70℃

• Proton beam- 6 MeV proton✓ Penetrate BOX layer

- Scattered by 2.5 μm Au film✓ Uniform irradiation on XRPIX✓ Beam intensity monitor by Faraday cup✓ Scattered flux ~105 protons/s/cm2

ProtonBeam

2019.12.15 HSTD12 @Hiroshima / 15

Leakage Current & Readout Noise• We evaluated leakage current and readout noise at each dose level.

8

1000 2000 3000 4000 5000 6000Dose (rad)

10

11

12

13

14

15

16

17

18

19

20

]−

Rea

dout

noi

se o

f XR

PIX6

C [e

40

45

50

55

60

65

70

75 ]−R

eado

ut n

oise

of X

RPI

X2b

[e

1000 2000 3000 4000 5000 6000Dose (rad)

40

60

80

100

120

140

160

180

200

/ms/

pixe

l]−

Leak

age

curre

nt o

f XR

PIX6

C [e

10

15

20

25

30

35

40

45

/ms/

pixe

l]−

Leak

age

curre

nt o

f XR

PIX2

b [e

Leakage currentXRPIX2b (single-SOI)XRPIX6c (double-SOI)

Readout noiseXRPIX2b (single-SOI)XRPIX6c (double-SOI)

1.8 ± 0.5% @ 5 krad9.9 ± 4.0% @ 5 krad

Shaded region: 90% confidence interval Y-axes are scaled to match each other at non-irradiation

• With 5 krad irradiation, leakage current and readout noise increased by 9.9% and 1.8%, respectively.

➡Degradation of leakage current and readout noise was reduced in the double-SOI device XRPIX6c.

2019.12.15 HSTD12 @Hiroshima / 15

200 220 240 260 280 300 320 340Channel [ADU]

0

50

100

150

200

250

300

350

400

Cou

nts

0.5 krad1 krad2 krad5 krad

X-ray Spectral Performance• We also evaluated the spectral performance by irradiating X-rays from 55Fe

radioisotope.

9

• The X-ray spectral performance shows a slight degradation with a few krad irradiation.

Mn-Kα (5.9 keV)from 55Fe

Mn-Kβ (6.5 keV)from 55Fe

2019.12.15 HSTD12 @Hiroshima / 15

Gain & Energy Resolution• We qualitatively evaluated the gain and energy resolution by fitting the

5.9 keV emission line.

10

1000 2000 3000 4000 5000 6000Dose (rad)

48.4

48.5

48.6

48.7

48.8

48.9

49

49.1

]−

V/e

µG

ain

of X

RPI

X6C

[

6.81

6.82

6.83

6.84

6.85

6.86

6.87

6.88

6.89

6.9

]−V/

eµ

Gai

n of

XR

PIX2

b [

1000 2000 3000 4000 5000 6000Dose (rad)

220

240

260

280

300

320

340

Ener

gy re

solu

tion

of X

RPI

X6C

@5.

9 ke

V [e

V]700

750

800

850

900

950

1000

1050

Ener

gy re

solu

tion

of X

RPI

X2b

@22

.1 k

eV [e

V]

-0.35 ± 0.09% @ 5 krad 7.1 ± 2.2% @ 5 krad

GainXRPIX2b (single-SOI)XRPIX6c (double-SOI)

Energy resolutionXRPIX2b (single-SOI)XRPIX6c (double-SOI)

• Even after ~5 krad irradiation, energy resolution is ~260 eV, satisfying requirement of FORCE (<300 eV)

• Unlike the leakage current & readout noise, both of the gain and energy resolution do not show significant improvements in double-SOI device.

Requirement of FORCE

2019.12.15 HSTD12 @Hiroshima / 15

Device Simulation

11

• Simulator : HyENEXSS

• Doping

✓ Bulk：ρ = 4 kΩ cm-> Np = 3×1012 cm-3

✓ Detailed profile for Sense node, P-stop, BNW, BPW (provided by LAPIS Semiconductor Co. Ltd.)

✓ Back side P-profile measured based on SIMS measurement

• Sensor layer : 300 μm

• VBB = -250 V, VMS = -2.5 V, VSN = 1.0 V

• BOX charge of ~1011 cm-2 as TID effect

• To investigate the mechanism of the gain degradation, we calculated the electric field and carrier distributions with a TCAD device simulation.

sense node (n−)

buried n-well (BNW)

Back bias voltage

Circuit layer

300 µm

0.44 µm8 µm

Sensor

Insulator

buried p-Well (BPW)

p-stop (p+)

0.15 µmMiddle-Si

p-type Si

K. Hagino et al., JINST, 2019

2019.12.15 HSTD12 @Hiroshima / 15

BNW Enlarged by BOX Charge• Positive BOX charges due to irradiation attract electrons towards Si/SiO2 interface,

enlarging BNW size

12

• With BOX charge of 1011 cm-2, BNW size changes from 2.6 μm to 3.0 μm(with 2×1011 cm-2, BNW size is 3.4 μm)

• Larger BNW increases parasitic capacitance, suppressing the gain

Electron density mapNo BOX Charge

Electron density mapBOX charge = 1011 cm-2

5 μm5 μm

Sense node BNW

Sense node BNW

2.6 μm 3.0 μm

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160 180 200 220 240 260 280 300 320Channel [ADU]

0

10

20

30

40

50

60

70

80

90

Cou

nts

/ bin

Gain Degradation by BNW Enlargement• It is difficult to directly estimate the parasitic capacitance and its contribution to the

gain from the BNW size.

• We use an additional experimental data of Test Element Group (TEG) with different BNW size → We can estimate the relation between gain and the BNW size

13

wBNW=3 μmwBNW=5 μmwBNW=7 μmwBNW=9 μmwBNW=11 μmwBNW=13 μm

2019.12.15 HSTD12 @Hiroshima / 15

160 180 200 220 240 260 280 300 320Channel [ADU]

0

10

20

30

40

50

60

70

80

90

Cou

nts

/ bin

Gain Degradation by BNW Enlargement• It is difficult to directly estimate the parasitic capacitance and its contribution to the

gain from the BNW size.

• We use an additional experimental data of Test Element Group (TEG) with different BNW size → We can estimate the relation between gain and the BNW size

13

wBNW=3 μmwBNW=5 μmwBNW=7 μmwBNW=9 μmwBNW=11 μmwBNW=13 μm • ΔS ~ 4 μm2

➡ BNW size: 2.6 μm → 3.3 μm(corresponds to NBOX=1–2×1011 cm-2)

• Opposite trend in XRPIX2b because it has a N-type sensor layer

➡Gain degradation can be explained by BOX charges of 1−2×1011 cm-2

ΔG/G = -15% with ΔS = 160 μm2

ΔG/G = -0.35% (@5 krad)ΔS ~ 4 μm2Scaling

2019.12.15 HSTD12 @Hiroshima / 15

S. Harada, T.G. Tsuru, T. Tanaka et al. Nuclear Inst. and Methods in Physics Research, A 924 (2019) 468–472

Fig. 5. Relation between the gain and the readout noise. The data points without thelabel of ‘‘Event Driven’’ are obtained in the Frame readout mode [4,6,8]. The two solidlines are eye guides for the correlation.

5. Conclusions

XRPIX6E with the Pinned Depleted Diode (PDD) structure is pre-sented in this paper. The XRPIX6E design has successfully suppressed theinterference between the sense-node and the circuit by introducing thePDD structure. The PDD structure improves the spectral performance inthe Event-Driven readout mode in addition to the Frame readout mode,and the charge collection efficiency. The energy resolution of 335 ± 4eV in FWHM at 6.4 keV in the Event-Driven readout mode is the best inXRPIX series. On the other hand, the spectral performance in the Event-Driven readout mode is still degraded in comparison with the Framereadout mode.

Acknowledgments

We acknowledge the valuable advice and great work by the person-nel of LAPIS Semiconductor Co., Ltd. This study was supported by the

Japan Society for the Promotion of Science (JSPS) KAKENHI, JapanGrant-in-Aid for Scientific Research on Innovative Areas 25109002(Y.A.), 25109003 (S.K.), 25109004 (T.G.T. and T.T.), 20365505 (T.K.),23740199 (T.K.), 18740110 (T.K.), Grant-in-Aid for Young Scientists(B) 15K17648 (A.T.), Grant-in-Aid for Challenging Exploratory Research26610047 (T.G.T.) and Grant-in-Aid for JSPS Fellows 15J01842 (H.M.).This study was also supported by the VLSI Design and Education Center(VDEC), the University of Tokyo in collaboration with Cadence DesignSystems, Inc., and Mentor Graphics, Inc.

References

[1] K. Koyama, H. Tsunemi, T. Dotani, et al., X-ray imaging spectrometer (XIS) on boardSuzaku, Publ. Astron. Soc. Japan 59 (2007) S23.

[2] T.G. Tsuru, H. Matsumura, A. Takeda, et al., Development and performance ofKyoto’s x-ray astronomical SOI pixel (SOIPIX) sensor, in: Proc. SPIE, vol. 9144,2014, 914412.

[3] Y. Arai, T. Miyoshi, Y. Unno, et al., Development of SOI pixel process technology,Nucl. Instrum. Methods Phys. Res. A 636 (2011) S31.

[4] A. Takeda, T.G. Tsuru, T. Tanaka, et al., Improvement of spectroscopic performanceusing a charge-sensitive amplifier circuit for an X-ray astronomical SOI pixeldetector, J. Instrum. 10 (2015) C06005.

[5] T. Miyoshi, Y. Arai, Y. Fujita, et al., Front-end electronics of double SOI X-rayimaging sensors, J. Instrum. 12 (2017) C02004.

[6] S. Ohmura, T.G. Tsuru, T. Tanaka, et al., Reduction of cross-talks between circuitand sensor layer in the Kyoto’s X-ray astronomy SOI pixel sensors with Double-SOIwafer, Nucl. Instrum. Methods Phys. Res. A 831 (2016) 61.

[7] T. Miyoshi, Y. Arai, T. Chiba, et al., Monolithic pixel detectors with 0.2 �m FD-SOIpixel process technology, Nucl. Instrum. Methods Phys. Res. A 732 (2013) 530.

[8] H. Kamehama, S. Kawahito, S. Shrestha, et al., A low-noise X-ray astronomicalsilicon-on-insulator pixel detector using a pinned depleted diode structure, Sensors18 (2018) 27.

[9] T. Uchida, Hardware-based TCP processor for gigabit ethernet, IEEE Trans. Nucl.Sci. 55 (2008) 1631.

[10] S.G. Ryu, T.G. Tsuru, S. Nakashima, et al., First performance evaluation of an X-raySOI pixel sensor for imaging spectroscopy and intra-pixel trigger, IEEE Trans. Nucl.Sci. 58 (2011) 2528.

[11] A. Takeda, Y. Arai, S.G. Ryu, et al., Design and evaluation of an SOI pixel sensorfor trigger-driven X-ray readout, IEEE Trans. Nucl. Sci. 60 (2013) 586.

[12] S. Nakashima, S.G. Ryu, T.G. Tsuru, et al., Progress in development of monolithicactive pixel detector for X-ray astronomy with SOI CMOS technology, PhysicsProcedia 37 (2012) 1373.

[13] A. Takeda, T.G. Tsuru, T. Tanaka, et al., Development and evaluation of event-driven SOI pixel detector for X-ray astronomy, in: Proceedings of Science,TIPP2014, vol. 213, 2014, p. id138.

[14] S. Nakashima, S.G. Ryu, T. Tanaka, et al., Development and characterization ofthe latest X-ray SOI pixel sensor for a future astronomical mission, Nucl. Instrum.Methods Phys. Res. A 731 (2013) 74.

[15] H. Hayashi, T.G. Tsuru, T. Tanaka, et al., Evaluation of Kyoto’s event-driven X-rayastronomical SOI pixel sensor with a large imaging area, Nucl. Instrum. MethodsPhys. Res. A 924 (2018) 400–403.

472

Origin of Readout Noise Degradation

• Readout noise degradation of 1.8±0.5%@5 krad would be due to the gain degradation and the increase of leakage current.

14

➡ corresponds to ΔG/G = 0.35 %

Δσ ∼ 0.3 %

1000 2000 3000 4000 5000 6000Dose (rad)

36

37

38

39

40

41

42

43

44

45

/ m

s / p

ixel

)-

Leak

age

curre

nt (e

➡

Δσ2 = ΔIτ ≃ 3.7 ± 1.5e−

Δσ ∼ 1.3 ± 0.5 %

• The gain degradation can also contribute to the readout noise

• In XRPIX, readout noise and gain are known to have a power law relation

σ ∝ G−0.7

Harada et al., NIM-A, 2019

2019.12.15 HSTD12 @Hiroshima / 15

Conclusions• We evaluated the radiation hardness of new XRPIX with Double SOI

structure, by irradiating 6 MeV proton beam at HIMAC

‣ With 5 krad irradiation,

✓ Leakage current increases by 9.9 ± 4.0%

✓ Readout noise increases by 1.8 ± 0.5%

✓ Gain decreases by 0.35 ± 0.09%

✓ Energy resolution increases by 7.1 ± 2.2%

‣ Degradation of leakage current and readout noise was improved in the double-SOI device

‣ Even after ~5 krad irradiation, energy resolution satisfies requirement of FORCE (<300 eV)

‣ Gain degradation can be explained by the BNW size enlarged by the BOX charge (1–2×1011 cm-2)

‣ Readout noise degradation would be due to the gain degradation and the increase of leakage current

15

Documents

Radiation Damage Effects on Double-SOI Pixel Sensors for X ......In order to solve the interference problem, we adopt a Double-SOI wafer (DSOI) in which we introduce an additional