Improvement and Evaluation of Event-driven Performance

Improvement and Evaluation of Event-driven Performance with Double-SOI Pixel Detectors for X-ray Astronomy

The 9th International Workshop on Semiconductor Pixel Detectors for Particles and Imaging@ Academia Sinica, Taipei, Taiwan

10 – 14 December 2018

Ayaki Takeda (Univ. of Miyazaki)takeda @astro.miyazaki-u.ac.jp

K. Mori, Y. Nishioka, K. Fukuda, T. Hida, M. Yukumoto (Univ. of Miyazaki), T. G. Tsuru, T. Tanaka, H. Uchida, S. Harada, T. Okuno, K. Kayama (Kyoto Univ.), H. Matsumura (Kavli/IPMU),

Y. Arai, I. Kurachi (KEK), T. Kohmura, K. Hagino, K. Neghishi, K. Oono, K. Yarita (Tokyo Univ. of Sci.), S. Kawahito, K. Kagawa, K. Yasutomi, S. Shrestha, S. Nakanishi (Shizuoka Univ.) H. Kamehama (Okinawa College)

http://astro.miyazaki-u.ac.jp

2PIXEL 2018 @ Taipei, Taiwan - A. Takeda - December 11, 2018

Outline

- Introduction for X-ray Astronomy

- XRPIX Series- Improvement of energy resolution -> Our new device : XRPIX6D- Summary

Detector for X-ray Astronomy

3

X-rayhigh energy particle

X-ray CCD raw image

Standard imaging spectrometer of modern X-ray astronomical satellites ...-> X-ray CCD : Wide and fine imaging with the sensor size of ~20 – 30 mm, pixel size of ~30 µm sq. Fano limited spectroscopy with the readout noise ~3 e- (rms).

Non X-ray background of Suzaku XIS (BI)

Due to high energy particles on orbit.

However ...-> Non X-ray background (NXB) above 10 keV is too high to study faint sources.-> The timing resolution is too poor (~sec) to make fast timing observation of time variable source.

PIXEL 2018 @ Taipei, Taiwan - A. Takeda - December 11, 2018

In order to achieve specification, we have been developing X-ray SOI Pixel Detector (XRPIX).XRPIX has self-trigger function ! -> Realization of event-driven

4

XRPIX for Future X-ray Astronomy

X-rayHard Soft Cosmic Ray

(Non-Xray-BG)Field of View

XRPIX

X-ray SOIPIX with Active Shield

Onboard Processor・Anti-coincidence (NXB rejection)・Hit-pattern Selection (NXB rejection)・Direct Pixel Access (X-ray Readout)

Target Specification(1) FWHM ≤140 eV at 6 keV Readout Noise : req. ≤ 10 e-/ goal ≤ 3 e- (2) <100 μm pitch pixel(3) ∼10 μs per event readout (Trigger, Direct Pixel Access) (4) Wide energy range : 0.3– 40 keV (Thick Depletion Stacks)

The performance required of a future X-ray astronomical satellite is the following ...


5

SOI Pixel Detector- A monolithic pixel detector with silicon-on-insulator (SOI) CMOS Technology -> 0.2 μm fully-depleted (FD) - SOI pixel process

- SOI Pixel Detector (SOIPIX) : Processed by LAPIS Semi. Co., Ltd.

~8 µm

200 nm BOX (Buried Oxide)

BPW (Buried p-Well)

n+

Si Sensor Layer(High Resistivity Substrate)

p+

n-

50 ~ 725 µm

Peripheral CircuitBias Ring Pixel Array

CMOS Circuit Layer

+++

+

---

-

X-rays

PMOS NMOS

sense-node

Both high X-ray sensitivity and advanced signal processing are compatible!PIXEL 2018 @ Taipei, Taiwan - A. Takeda - December 11, 2018

6

History of XRPIX Series

XRPIX1b

2.4 mm

1.0 mm

XRPIX1

2.4 mm

1.0 mm

XRPIX2

6.0 mm

4.0 mm

6.0 mm

4.6 mm

XRPIX2b

First Model Trigger Output

(Event-driven readout)Middle Size Buttable

Charge Sensitive Amplifier

XRPIX3

1.0 mm

2.9 mm

XRPIX3b

1.0 mm

2.9 mm

2011 2012 20132010 2014

20152014

4.6 mm

6.0 mmNew Readout Circuit

2016

Large Size 24.6 mm

15.3 mm

XRPIX5

21.9 mm

13.8 mm

608 x 384 pixels36 µm sq. pixel

Pixel Structure4.45 mm

XRPIX6H

XRPIX6D

XRPIX6EXRPIX4

This talk

PIXEL2016

PIXEL 2012PIXEL 2014

PIXEL 2014

7

Signal Deterioration by Event-driven modeWe had a critical issue in event-driven mode… The signal is degraded…

PIXEL 2018 @ Taipei, Taiwan - A. Takeda - December 11, 2018*ADU : Analog Digital Unit (= 244 µV/ADU)

100 200 300 400 5000

20

40

60

80

100

120

140

160

18013.9 keV

17.8 keV

20.8 keV

11.4 keV

9.7 keV

20

40

60

80

100

120

140

160

180

Cou

nts

FWHM ~ 400 eV (2.9%)

241Am

Frame readout mode(not use trigger)

XRPIX3b / CSA

0 100 200 300 400 500

Pulse Height (ADU)PH

1000 1100 1200 1300 1400

Counts

0

200

400

600

800

1000

1200

1400 13.9 keV

17.8 keV

20.8 keV

11.4 keV9.7 keV

200

400

600

800

1000

1200

1400

Cou

nts

FWHM ~ 1.3 keV (9.3%)

241Am

Event-driven readout mode(use trigger)

XRPIX3b / CSA

1000 1100 1200 1300 14000

Pulse Height (ADU)0 5 10 15 20 25 300

200

400

600

800

1000

1200

1400

200

400

600

800

1000

1200

1400

Puls

e H

eigh

t (A

DU

)

5 10 15 20 250

Energy (keV)30

offset ~900 ADU

Frame readout mode

Event-driven readout mode

Gain: 17.8 µV/e-

Gain: 16.8 µV/e-

Calibration Plot(Frame & Event-driven readout mode)

BOX2middle SiBOX1

sense-node

VSi

middle Si layer

Fixed potential layer

BOX

sense-node

F

VBPWVBPW

Double SOI structure Pinned Depleted Diode structure-> XRPIX6D* This talk

-> XRPIX6E* Mr. Kayama’s talk -> 12/13 THU 9:50 —

- We understood that the signal degradation was caused by interference of digital signal in the pixel.

- The digital signal transmits a signal change of the comparator inversion to the analog signal via the parasitic capacitance. -> It is important to suppress capacitive coupling (Takeda+2014, Ohmura+2016)

new approach to suppress capacitive coupling

8

Improvement for interference issue

sense-nodeSensor layer

Circuit layerSiO2

parasiticcapacitance

crosstalk200 nm

500 nm 200 nm


9

XRPIX6 Design Specification

Components- Chip size : 4.45 mm x 4.45 mm (Effective area : 1.7 mm x 1.7 mm)- Pixel size : 36 µm sq.- # of pixel : 48 x 48 (= ~2.3k) - Thickness of sensor layer -> 300 µm (CZ wafer) -> 500 µm (FZ wafer)

We aim to improve spectroscopic performance by developing new sensor structure.

XRPIX6

48 x 48 pixel array1 Pixel : 36 µm sq.

4.45 mm

4.45 mm

S/H Cap.

PGACol. Amp.

OUT BUFDECODER & TRIGGER

PROCESSOR

DEC

OD

ER &

TRI

GG

ER

PRO

CESS

OR

1.7 mm

1.7 mm

XRPIX6H -> Conventional Single-SOIXRPIX6D -> Double-SOIXRPIX6E -> Pinned Depleted Diode (Single-SOI)

Other- Programmable Gain Amplifier (PGA) circuit for column line.- Differential output of signal and pedestal level.- We considered more suitable architect constitution for event-driven readout. -> 8 x 8 pixel readout per unit.


Pixel Circuit

Comparator

RST_COMP1 RST_COMP2

VCDS

TRIGGERL/H OUT

ROW_READ

SF

RST_

CDS

CDS Cap.Sa

mpl

e Ca

p.STORE

RST_PDB

Prot

ectio

n D

iode

VDD18VB_SF

PDSense-node

GND

TRIG_COL (OR)

TRIG_ROW (OR)Trigger Output

GND

Feedback Cap.

VB_CSA

CSA

COM

P Ca

p. 1

COM

P Ca

p. 2

RST_D SR LatchRS Q

Pixel Circuit

VTH

RST_

TH

COL_LIN

E [n]

RS

BAD PIXEL MASK(SR Latch)

ver. XR6D2018.08.25

SET_MASKRST_MASKQ

Pixel Circuit consists of …- Charge-sensitive amplifier (CSA)- Correlated Double Sampling- Inverter-chopper type comparator- SR Latch for bad pixel mask

10

analog part

digital part


COL AMP.with CDS

OUT BUF

S/H Cap.

PED

SIG

PED

SW m

atrixVCO

M

VcVc

SIG

PGA : x1, x4, x19

Differential Output

Readout Circuit

OUT BUF

SIG

PED

Vc

Differential Output

S/H[i]

CSIG[i]

VcϕH[i]

ϕRR

ϕRR

ϕSS ϕSR

COL AMP.with CDS

SW M

atrix

VCOM

PGA : x1, x4, x19ϕR

COL_LIN

E [n]

COL_AMP_OUT [i]

SW [n]

CPED[i]

…COL_AMP_OUT[0]

Column CDS & PGA

Sam

ple

/ Ho

ldO

utpu

t Buff

er

S/H[0]

S/H[7]

SIG PED

SIG PED

SIG

PED

COL_AMP_OUT[7]

Column Selector

Event Center

PIXEL ARRAY

RA (center)

CA (center)

~

~~…CA[0]

RA[0]

Shield Wire

SIG

PED

(A)

(B)

(C)

(D)

(A)

(B)(C)

(D)

(I) (II)

n : 0 - 47i : 0 - 7

ver. 2018.08.25

each column line

8 sets

Readout Pixel Unit : 8 x 8 pixels S/H Cap. : 8 sets8 pixels scan/line x 8 lines This configuration is more suitable for event-driven mode.

(A) Column amplifier with programable gain.(B) Switch matrix(C) Sample / Hold Capacitance(D) Output buffer

Analog Readout Circuit


12

Event-driven Readout

Row

AD

DR.

DEC

OD

ER

Trig

ger

Det

ectio

n (O

R)

FPGA

Column ADDR. DECODER

ADC

DAQ-PC

(ii)

(iii)

(v)

(vi)

(viii)

XRPIX

(vii)

PATT

ERN

PRO

CES

SOR

PATTERN PROCESSOR

(ii)

TRIG_OUT

Column Amp. / SH / OUTBUF

HIT_COL_ADDR

HIT_ROW_ADDR(v)

(vi)

X-ray(i)

ROW_ADDRCOL_ADDR

ANALOG_OUT

Dig

ital D

ata

Ethernet

≈

Analog Signal

Trigger Detection (OR)

Row

AD

DR.

EN

CO

DER

Column ADDR. ENCODER

(iv) HIT_INFO

Hit Information- multi hit ?- multi pattern ?

Hit Patternoutput the address value by encoder with pattern scanner

XRPIX


13

Spectral Performance- XRPIX6D has improved the spectroscopic performance.- Comparison spectra of the frame and the event-driven mode -> We succeeded in greatly improving spectral performance for event-driven mode by Double-SOI structure.

Counts/bin

0

250

500

750

1000

1250

1500

PulseHeight[ADU]

0 200 400 600 800

Counts/bin

0

500

1000

1500

2000

2500

PulseHeight[ADU]

0 200 400 600 800

57Co

FWHM ~ 310 eV (4.8%)

7.1 keV14.4 keV

Temp. –60 ℃Readout noise:36 e- (rms)

Frame readout mode(not use trigger)

Event-driven readout mode(use trigger)

Temp. –60 ℃Readout noise:16 e- (rms)

6.4 keV


200 400 600 800Pulse Height (ADU)

200 400 600 800Pulse Height (ADU)

Cou

nts

500

1000

1500

2000

2500

Cou

nts

250

500

750

1000

1500

1250

0 00 5 10 15 20 250

200

400

600

800

1000

1200

X-ray Energy (keV)

Puls

e H

eigh

t (A

DU

)

Event-driven Mode (solid) : 40.5 µV/e-

Frame Mode (dashed) : 40.3 µV/e-

CDS_RSTV : 300 mVVTH : 320 mV (Event-Driven) 900 mV (Frame)

Gain57Co

FWHM ~ 350 eV (5.5%)

7.1 keV14.4 keV

6.4 keV

Calibration Plot(Frame & Event-driven readout mode)

5 10 15 20 250

Energy (keV)

200

400

600

800

1000

1200

Puls

e H

eigh

t (A

DU

)

VTH - VCDS [mV]100− 0 100 200 300 400

Puls

e H

eigh

t [AD

U]

0

200

400

600

800

1000

1200

1400

1600

1800C°Am Frame Mode,VTH SCAN @-60241

14

Evaluation of VTH Scan | XRPIX3b

100200

300400

500020406080100120140160180

PH

1000

1100

1200

1300

1400

Counts

0

200

400

600

800

1000

1200

1400

100 200 300-100 4000∆VTH (mV)PIXEL 2018 @ Taipei, Taiwan - A. Takeda - December 11, 2018

∆VTH v.s. Pulse Height @XRPIX3b

0

200

400

600

800

1000

1200

1400

1600

1800

Puls

e H

eigh

t (A

DU

)

Counts

Counts

13.9 keV17.8 keV20.8 keV

13.9 keV17.8 keV20.8 keV

offset ~900 ADU

Fram

e(n

ot u

se tr

igge

r)Ev

ent-d

riven

(use

trig

ger)

241 A

m24

1 Am

- Energy peak “jump” of XRPIX3b (conventional SOIPIX) by threshold voltage scan.- The signal level jumps due to the inversion operation of the comparator circuit.

comparator : non-inverting

comparator : inverting

Channel[ADU]

0200

400

600

800

1000

1200

Counts/bin

050100

150

200

250

300

350

400

450

VCDS - VTH [mV]100− 0 100 200 300 400

Puls

e H

eigh

t [AD

U]

0

200

400

600

800

1000

1200

1400

1600

1800C°Am Frame Mode,VTH SCAN @-60241

15

Evaluation of VTH Scan | XRPIX6D

100 200 300-100 4000∆VTH (mV)

0

200

400

600

800

1000

1200

1400

1600

1800

Puls

e H

eigh

t (A

DU

) ∆VTH v.s. Pulse Height @XRPIX6D

13.9 keV

17.8 keV20.8 keV

Counts

Fram

e(n

ot u

se tr

igge

r)

241 A

m

Energy peak shift

Energy peak shift


- We succeeded in suppressing electrical crosstalk by Double-SOI structure.- However… it has an energy peak shift. -> Electrical crosstalk in the circuit

16

Summary

- We have been developing an event-driven SOIPIX sensor, “XRPIX”, for future X-ray astronomical satellite mission.- We realize the event-driven readout mode and very low non-X-ray background by the function of the trigger signal output.- We designed the new prototype, “XRPIX6D” with Double-SOI structure to improve spectroscopic performance. -> chip size: 4.45 mm x 4.45 mm, pixel size: 36 µm sq., number of pixel: 48 x 48 (= ~2.3k) - We succeeded in improving the spectroscopic performance and suppressing the electrical crosstalk between sense-node and CMOS circuit by XRPIX6D. -> frame mode: readout noise: 16 e- (rms), 310 eV (4.8%) @ 6.4 keV (FWHM) -> event-driven mode: readout noise: 36 e- (rms), 350 eV (5.5%) @ 6.4 keV (FWHM)- We will optimize the condition to further improve spectroscopic performance.


Documents

Improvement and Evaluation of Event-driven Performance