SiPM technology at FBKSiPM technology at FBK

C. Piemonte

piemonte@fbk.eu

Fondazione Bruno Kessler, Trento, Italy

IPRD10, Siena, 8 June 2010C. Piemonte 2

OutlineOutline

FBK SiPM technology overview FBK SiPM for TOF-PET

Conclusion

IPRD10, Siena, 8 June 2010C. Piemonte 3

Simulation & designSimulation & design Device testingDevice testingFabricationFabrication

FBK expertiseFBK expertiseSilicon Radiation Sensors group (http://srs.fbk.eu)

Process and device physical simulations

CAD design ofthe sensor

750m2 clean roomequipped for manufacturing of silicon devices

Wafer-level testingwith manual andfully automatic probestations

Lab for functional testing

IPRD10, Siena, 8 June 2010C. Piemonte 4

13

14

15

16

17

18

19

20

0 0.2 0.4 0.6 0.8 1 1.2 1.4

depth (um)

Do

pin

g c

on

c. (1

0^) [

1/cm

^3]

0E+00

1E+05

2E+05

3E+05

4E+05

5E+05

6E+05

7E+05

E f

ield

(V/c

m)

Doping

Field

n+ p

Technology characteristics: 1) Integrated polysilicon resistor 2) Very shallow junction to enhance QE at short wavelengths 2) possible ARC to optimize QE at certain wavelengths

p+ subst.

epi

n+

SJ-SiPM TechnologySJ-SiPM Technology

Cross sectionCross section

Development started in 2005 in collaboration with INFN

IPRD10, Siena, 8 June 2010C. Piemonte 5

Device Layout: Device Layout: example of internal structureexample of internal structure

Metal line connectingall cells in parallel(one common anode)

Polysilicon resistor

Field-plateto reduce electricfield around the junction

Resistor is locatedaround the active area => no fill factorloss

The cathode is contacted on the rear side.

FF ~ 45% 40x40um2 cell ~ 55% 50x50um2 “ ~ 72% 100x100um2 “

IPRD10, Siena, 8 June 2010C. Piemonte 6

200920098x8 array of SiPMs1.5x1.5mm pitch50x50m2 cell

Device Layout:Device Layout: examples of SiPM geometriesexamples of SiPM geometries

20062006

1x1mm2

40x40m2 cell

20072007

4x4mm2

50x50m2 cell

Scale of the pictures is the same

Produced for DaSiPM (INFN project)

IPRD10, Siena, 8 June 2010C. Piemonte 7

Process & Device characterization at FBKProcess & Device characterization at FBK

Wafer level testing:-Automatic IVs: forward and reverse on all devices-Failure analysis in case of problems

Wafer dicing

Packaging of some samples

Functional tests:- Dark analysis in climatic chamber- Laser response- Photo-detection efficiency- Energy & timing resolution with scintillators

8

On-wafer automatic characterizationOn-wafer automatic characterization

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

0 5 10 15 20 25 30 35

I [A

]

Vrev [V]

Reverse charact.Reverse charact.

- Functionality of the device- Breakdown voltage- Dark count estimate

4 elements of the array

0.0E+00

1.0E-03

2.0E-03

3.0E-03

4.0E-03

5.0E-03

6.0E-03

7.0E-03

8.0E-03

0 0.5 1 1.5

I [A

]

Vfor [V]

Forward charact.Forward charact.

- Functionality of the device- Resistor value estimate

4 elements of the array

9

Example of faulty deviceExample of faulty device

1.0E-09

1.0E-08

1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

0 5 10 15 20 25 30 35 40

no defect

1 defective pixel (13V)

I22

I11

Most common defect is premature breakdown

Working SiPM.The current canbe roughly modeled as I=q*DC*G

SiPM with 1 defective cell. I=(V-Vbd)/Rq

Vbdlight emission picture @16V

Reverse IV plot

10

… … after packaging…after packaging…

1.E-13

1.E-12

1.E-11

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0

Curr

ent (

A)

Bias Voltage (V)

-40 -30-20 -100 1020 3040

0.0E+00

2.0E-04

4.0E-04

6.0E-04

8.0E-04

1.0E-03

1.2E-03

1.4E-03

0.25 0.40 0.55 0.70 0.85 1.00 1.15

Curr

ent (

A)

Bias Voltage (V)

-40-30-20-10010203040

Reverse IV plot

Forward IV plot(quenching resistor valueis temperature dependent)

Temperature (C)

Temperature (C)

11

Dark analysis in climatic chamberDark analysis in climatic chamber

original data,pulse identification

Dark count ratevsthreshold (blue)

single-cell signal(blue),mean signal(red)

pulse area histogram (blue),baseline (red)

pulse distancehistogram

pulse amplitudedistributionvsdistance

For each bias voltage, Labview program performs following:

underconstruction

IPRD10, Siena, 8 June 2010C. Piemonte

Breakdown&Gain

Dark analysis in climatic chamberDark analysis in climatic chamber

0.0E+00

5.0E+05

1.0E+06

1.5E+06

2.0E+06

2.5E+06

3.0E+06

3.5E+06

4.0E+06

4.5E+06

5.0E+06

28 30 32 34 36 38 40

Gai

n

Bias (V)

-30C

+30CGai

n

Bias Voltage (V)

0%1%2%3%4%5%6%7%8%9%

10%

0 1 2 3 4 5 6

Gai

n sh

ift (1

/K)

Bias Voltage (V)

Gai

n s

hift

(1/

K)

Bias Voltage (V)

y = 0.076x + 30.934

28

29

30

31

32

33

34

35

-40 -20 0 20 40

BV (V

)

Temperature (°C)

Bre

akd

own

vol

tage

(V

)

Temperature (C)

76mV/C

IPRD10, Siena, 8 June 2010C. Piemonte 13

0.0E+00

5.0E+05

1.0E+06

1.5E+06

2.0E+06

2.5E+06

3.0E+06

3.5E+06

4.0E+06

0 1 2 3 4 5 6 7

Dar

k co

uts (

Hz)

Overvoltage (V)

.-30° C

.-20° C

.-10° C

0° C

10° C

20° C

30° C

0.0E+00

1.0E+05

2.0E+05

3.0E+05

4.0E+05

5.0E+05

-45 -35 -25 -15 -5 5 15 25 35 45

Que

nchi

ng re

sist

ance

(Ohm

)

Temperature (°C)

Dark count

Quenching resistor

Dark analysis in climatic chamberDark analysis in climatic chamber

doubles every 10Ctemperature increase

increasing withdecreasing temperature

Dar

k co

unt

rate

(H

Z/m

m2)

Over-Voltage (V)

Que

nchi

ng r

esis

tanc

e (

ohm

)

Temperature (C)

IPRD10, Siena, 8 June 2010C. Piemonte 14

Photo-detection efficiencyPhoto-detection efficiency

50x50um2 cellno after-pulses included

0%

5%

10%

15%

20%

25%

30%

350 400 450 500 550 600

PDE

Wavelength (nm)

Vex=1.91

Vex=4

PDE =PoissonLight - PoissonDark

Number of incident photons

Measured with low level constant light

IPRD10, Siena, 8 June 2010C. Piemonte 15

Application-oriented developmentApplication-oriented development

Many parameters to be considered for:system performance optimization:- Photo-detection efficiency- Dark noise rate- Correlated noise (after-pulse, optical cross-talk)

- Intrinsic timing capability- Signal shape- Geometry- Gain

and for real system implementation:- Temperature dependence- Operability range- packaging

16

w/o-ToF

With ToF

Example: TOF-PETExample: TOF-PETTime-Of-Flight Positron Emission Tomography

Info form the SiPM: Energy and timing

IPRD10, Siena, 8 June 2010C. Piemonte 17

Critical SiPM parameters for TOF-PETCritical SiPM parameters for TOF-PET

Photo-detection efficiency Dark noise rate

Correlated noise Intrinsic timing capability

Signal shape Geometry

Gain

Temperature dependence Operability range

packaging

SiPM parameters

Energy resolution

Timing resolution

Large complicated system

System requirements

IPRD10, Siena, 8 June 2010C. Piemonte 18

Framework of the developmentFramework of the development

Development of a hybrid TOF-PET/MR test system with improved effective sensitivity

First clinical whole body PET/MR investigations of breast cancer

HYPERimageHYPERimagehttp://www.hybrid-pet-mr.eu

Challenges in Simultaneous ToF-PET/MRChallenges in Simultaneous ToF-PET/MR

• Ultra compact, stable and reliable ToF Solid State PET Detector

• Modification of MRI to enable PET integration

• Interference reduction of PET with MR

• Stable and high accurate MR attenuation and motion correction techniques

• Identification of key applications

IPRD10, Siena, 8 June 2010C. Piemonte 20

HYPERimageToF-PETHYPERimageToF-PET

PMT APD SiPM

MR compliant no yes yes

ToF compliant yes no yes

The Stack

The module

Pre-clinicalsystem

WB system

Why SiPMs?

IPRD10, Siena, 8 June 2010C. Piemonte 21

2008 FBK SiPM technology2008 FBK SiPM technology

3x3mm2 SiPM 50x50m2 cell

Energy spectrum Na22Energy spectrum Na22

Measurements by Philips Aachen

dE/E~14% FWHM@511keV

Energy (a.u.)

3x3x15mm3 LYSO crystal

Coincidence time resolutionCoincidence time resolution

unfolded timingresol. ~305ps FWHM

IPRD10, Siena, 8 June 2010C. Piemonte 22

HYPERimage SiPM geometryHYPERimage SiPM geometry

IPRD10, Siena, 8 June 2010C. Piemonte 23

HYPERimage SiPM - productionHYPERimage SiPM - production

Lot production time: ~3-4 months

2x2 array of ~4x4mm2 SiPMs3600 cells per element

Wafer view

Data analysis (1) - yieldData analysis (1) - yield

white = OKred = premature breakdowngreen/blue = problems after breakdown

29.0 6.0 28.8 28.9 28.8 28.7 28.6 28.8 26.0 29.4

28.8 28.5 28.4 28.6 28.9 28.9 28.7 28.7 28.8 29.0

28.7 28.7 28.9 28.7 28.4 28.4 28.5 28.7 28.9 29.1 29.1 28.9 28.9 15.0

28.6 28.4 28.4 28.6 28.7 28.9 28.6 28.6 28.6 28.8 29.2 29.3 12.0 28.9

28.8 28.6 27.0 28.4 28.8 29.1 29.2 29.1 28.9 28.8 28.7 29.0 29.2 29.1

28.3 28.7 28.7 28.7 28.8 28.9 29.3 29.4 29.3 29.1 28.8 28.7 28.6 28.7

28.3 28.2 15.0 29.1 29.4 29.4 29.4 29.3 29.3 29.4 29.1 28.8 28.7 28.5

28.4 28.4 28.5 28.8 16.0 29.9 29.9 29.6 29.3 29.1 28.9 28.9 28.8 28.6

28.6 28.6 28.8 29.1 29.4 29.8 30.1 30.1 29.8 29.2 28.8 28.6 28.5 28.9

28.4 28.5 29.1 15.0 29.6 29.8 29.9 29.9 29.5 29.4 29.0 28.6 28.6 28.5

28.5 15.0 28.9 16.0 29.7 30.1 30.0 29.6 29.2 29.0 29.0 28.7 28.7 28.5

28.9 29.0 29.1 29.3 29.4 29.7 29.9 29.7 29.1 28.6 28.5 28.7 28.5 28.7

28.7 29.1 29.3 29.6 29.6 29.5 29.4 29.3 29.1 28.8 28.6 28.3 28.3 28.6

28.9 28.9 29.1 29.5 29.7 29.6 29.4 29.0 28.6 28.7 28.6 28.4 28.4 28.4

29.1 29.1 29.0 29.3 29.4 29.6 29.3 28.9 28.6 28.4 28.2 28.4 28.6 28.7

29.1 29.2 18.0 12.0 29.2 29.2 29.0 28.9 28.8 28.4 28.2 28.3 28.4 28.7

26.9 29.1 29.3 29.3 29.3 17.0 28.7 28.6 28.6 28.6 28.5 28.5 28.5 28.5

12.0 29.2 12.0 29.2 29.1 13.0 28.7 28.5 28.4 28.4 28.6 28.7 28.7 28.9

25

27

28

29

30

31

Brea

kdow

n vo

ltage

(V)

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8

10

12

14

16

18

20

22

24

26

28

30

32

Fre

qu

en

cy

Breakdown voltage (V)

280000

290000

300000

310000

320000

330000

340000

350000

Rq [Ω]

0

20

40

60

80

100

120

Fre

qu

en

cy

Quenching resistance (ohm)

Breakdown voltageBreakdown voltage

Polysilicon resistorPolysilicon resistor

Data analysis (2)Data analysis (2)

x105

IPRD10, Siena, 8 June 2010C. Piemonte 26

Solution for Scintillator couplingSolution for Scintillator coupling

epoxy (120m)

Si

bonding pad

epoxy

IPRD10, Siena, 8 June 2010C. Piemonte 27

Epoxy layer propertiesEpoxy layer properties

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

350 400 450 500 550 600

Tran

smitt

ance

Wavelength

25 um

59 um

127um

195um

Light transmittance vs wavel.Light transmittance vs wavel.

layer thickness

LSO/LYSO: OK LaBr: epoxy can be removed from active area leaving only

a support frame around the device

bonding pad

epoxy

IPRD10, Siena, 8 June 2010C. Piemonte 28

The SiPM tileThe SiPM tile

32.7mm32.7mm • Fill factor ~ 84%

(not including SiPM FF)• Flat surface for crystal mounting

1300 working arraysdelivered for thepreclinical system

PCB design and mountingat Uni. Heidelberg and Philips

500m

IPRD10, Siena, 8 June 2010C. Piemonte 29

The stackThe stack

Mounting and measurementsat Uni. Heidelberg and Philips

SiPM tile

ASIC tile

First very preliminary tests: Energy resolution ~16% FWHM Coincidence res. time ~670ps FWHM

=> The stack works! Now, need to optimize the set up.

The moduleThe module

IPRD10, Siena, 8 June 2010C. Piemonte 30

PET performance improvementPET performance improvement

4x4mm2 SiPM 67x67m2 cell

4x4x22mm3 LYSO crystal

Na22511keV/1.2MeV

With 2008 technology: dE/E ~ 14% and CRT ~ 460ps

Optimizing geometry and technology:

200 400 600 800 1000 1200 1400 1600 18000

50

100

150

200

250

300

350

400

450

Energy [nVs]

Ene

rgy

His

togr

am [

Cou

nts]

FBK C5 b 250mV Peak

Ch1: E-peak=1101 dE=9.3%

Ch2: E-peak=1159 dE=9.1%

dE/E ~ 11% FWHM(corrected for non linear.)

0 5 10 15 200

100

200

300

400

500

600

700

800

Trigger Threshold [%]

CR

T [

ps]

FBK Typ C5b

150mV peak

200mV peak250mV peak

300mV peak

CRT ~ 380ps FWHM

(timing res. of 270ps)

Energy spectrum CRT vs threshold

Measurement@ Philips

IPRD10, Siena, 8 June 2010C. Piemonte 31

ConclusionConclusion

SiPM technology is improving quickly, meeting requirements of the most challenging applications

FBK has a competitive technology for TOF-PET systems: - excellent performance; - efficient package solution to cover large areas; - production capability; - effective test methodology;

Work in progress: - new technology for higher PDE; - new package solution.

IPRD10, Siena, 8 June 2010C. Piemonte 32

AcknowledgmentAcknowledgment

FBK SRS group:

Gabriele GiacominiAlberto GolaElisabetta MazzuccaMirko MelchiorriAlessandro PiazzaNicola SerraAlessandro TarolliNicola Zorzi

HyperImage:

in particularPhilips Research AachenUniversity of Heidelberg

DaSiPM & MEMS projects

Many thanks to all who contributed to this work.In particular: