SPAD Pixel Detectors with HighSPAD Pixel Detectors with HighTime ResolutionTime Resolution

Edoardo CharbonEdoardo CharbonTU DelftTU Delft

2

Photons

3

Not Only IntensityNot Only Intensity……

•• CountingCounting•• Time-of-arrivalTime-of-arrival•• CorrelationCorrelation

4

Correlating PhotonsCorrelating PhotonsPolaritons in GaAs

microcavity (λ=770nm)

Balili, Science 316, 1007 (2007)

Photon states

=gg(2)(2)(0)(0)

gg(1)(1)(0)(0)

ThermalThermal CoherentCoherentIncoherentIncoherent

221111

111100

≠

Green Hg line from Hg-Ardischarge lamp (λ=546nm)

Young’ interference fringes

5

Stellar Stellar Hanbury-Brown Hanbury-Brown and and TwissTwissInterferometerInterferometer

6

4x4 SPAD arrayCMOS chip

10Hz dark count rate 120dB dynamic range70ps resolution25% detection prob.

Modern g(2) ImagerModern g(2) Imager

•• On-chip electronics for digital outputs On-chip electronics for digital outputs•• Off-chip processing (e.g. with digital oscilloscope) Off-chip processing (e.g. with digital oscilloscope)•• 4x4 array: 120 HBT coincidence experiments running simultaneously 4x4 array: 120 HBT coincidence experiments running simultaneously

7

Time-resolved BioimagingTime-resolved Bioimaging

• Super-resolution Microscopy– Stimulated Emission Depletion (STED)– Single Plane Illumination Microscopy (SPIM)– Scanning Photoionization Microscopy (SPIM)

• Molecular Imaging– Fluorescence Lifetime Imaging Microscopy (FLIM)– Förster Resonant Energy Transfer (FRET)– Fluorescence Correlation Spectroscopy (FCS)

• Nuclear Medicine– Positron Emission Tomography (PET)– PET & Magnetic Resonance Imaging (MRI)– Single-photon Emission Computer Tomography (SPECT)

8

OutlineOutline

•• Single-Photon DetectionSingle-Photon Detection•• From Pixel to ImagerFrom Pixel to Imager•• Scaling Up ApplicationsScaling Up Applications•• The Next Big ChallengesThe Next Big Challenges

9

Single-Photon DetectionSingle-Photon Detection

10

Single/few-photon DetectorsSingle/few-photon Detectors

•• Charge coupled devices (Charge coupled devices (CCDsCCDs))•• Electron Multiplying Electron Multiplying CCDs CCDs ((EMCCDsEMCCDs))•• Streak CamerasStreak Cameras•• Photomultiplier Tubes (Photomultiplier Tubes (PMTsPMTs))•• Multi/micro-channel plates (Multi/micro-channel plates (MCPsMCPs))

Silicon Avalanche Photodiodes Silicon Avalanche Photodiodes ((SiAPDsSiAPDs))Single-Photon Avalanche DiodesSingle-Photon Avalanche Diodes ( (SPADsSPADs))

11

Multiplication in SiliconMultiplication in Silicon

•• ReviewReview::Photon to electron - Secondary electron - MultiplicationPhoton to electron - Secondary electron - MultiplicationMultiplication in depletion region by Multiplication in depletion region by impact ionizationimpact ionization

p+

n-

n+

V

+

-depletion region

Reverse bias

12

Linear (or Proportional) ModeLinear (or Proportional) Mode

High variability of gain From bias

n

p+V

IA

V

V

-IA

ConventionalAvalanche

opticalgain<G>

Vbd

1

Ve + Vbd

13

Geiger Mode (SPAD)Geiger Mode (SPAD)

V

V

-IA

Conventional AvalancheGeiger

opticalgain<G>

Vbd

1Ve + Vbd

n

p+V

IA

Virtually infinite gain

14

•• Reach-through APD (RAPD)Reach-through APD (RAPD)–– VerticalVertical structure, thick device, high voltages structure, thick device, high voltages

Early SPAD Early SPAD Si Si IntegrationIntegration

n+p

π

p+

Multiplication

AbsorptionMcIntyre et al.

n-substrate

p-epi

p+

n+

Cova et al.Multiplication

•• Patterned double epitaxial APD (DJ-SPAD)Patterned double epitaxial APD (DJ-SPAD)–– PlanarPlanar structure, thin device, rel. low voltages structure, thin device, rel. low voltages

15

Planar ProcessesPlanar Processes

p substratep substraten-welln-well

p+p+ p-p-

Electric Field Electric Field ξξ

Multiplication regionMultiplication region

•• p- guard ring for electric field reduction in edgesp- guard ring for electric field reduction in edges•• Prevention of premature edge breakdownPrevention of premature edge breakdown•• Creation of zone with constant electric fieldCreation of zone with constant electric field

16

Quenching the AvalancheQuenching the Avalanche

Passive quenching: Operation cycle:

t

VVbdbd

VVopop’’

V

V photonarrival

avalanchequenching

SPADrecharge

VVopop’’

RRqq

VIIAA

Dead time

DEAD TIME

17

Controlling Dead TimeControlling Dead Time

t

VVbdbd

VVopop’’

V

V photonarrival

avalanchequenching

SPADrecharge

Dead time

DEAD TIME

18Niclass, Thesis 2008

Double Threshold Active QuenchingDouble Threshold Active Quenching

19

Salient Specs in Salient Specs in SPADsSPADs

•• Dead timeDead time•• AfterpulsingAfterpulsing•• Dark countsDark counts•• Photon detection probabilityPhoton detection probability (PDP) (PDP)•• Timing resolutionTiming resolution

…… and in SPAD imagers and in SPAD imagers•• Cross-talkCross-talk•• PDP UniformityPDP Uniformity

20

Dark Counts: Dark Count RateDark Counts: Dark Count Rate

•• State-of-the-art State-of-the-art SPADs SPADs in dedicated technology:in dedicated technology:0.1~1Hz/0.1~1Hz/µµmm22

•• State-of-the-art CMOS State-of-the-art CMOS SPADsSPADs::1~10Hz/1~10Hz/µµmm22

1 15x15 50x50

1Hz250Hz

3kHz

Mechanisms:

–Band-to-band tunneling generation–Trap-assisted thermal generation–Trap/tunneling assisted generation

21

Band-to-band TunnelingBand-to-band Tunneling

Ineffective guard ring:Tunneling due to high doping

Effective guard ring:Low-probability tunneling

22

Guard Ring EfficacyGuard Ring Efficacy

•• Ineffective guard ringIneffective guard ring•• Thus, high DCRThus, high DCR

•• Uniform multiplication zoneUniform multiplication zone•• Good prevention of prematureGood prevention of premature

edge breakdownedge breakdown

Niclass, Charbon, et al., JSTQE’07Gersbach, Charbon, et al., ESSDERC’08

23

Dark Count RateDark Count RateN

iclass et al. 2006

24

Photon Detection ProbabilityPhoton Detection Probability

Gersbach, C

harbon, et al. SS

Sensors 2009

25

Timing ResolutionTiming Resolution

PMT: 28psCMOS SPAD: 47ps

[Becker & Hickl]

26

From Pixel To ImagerFrom Pixel To Imager

27

DIGITAL DOMAINDIGITAL DOMAIN

SPAD in CMOSSPAD in CMOS

RRQQ

VVOPOP

VIIAA

Passive quenching technique

OUTOUT

digitalpulse

VDDVDDVVOPOP’’

TTQQ

28

ChallengeChallenge

•• Photocharges Photocharges cannot be accumulated like incannot be accumulated like inCCDsCCDs

•• Photon pulses arrive when photons impingePhoton pulses arrive when photons impinge

How to capture photon counting?How to capture photon counting?

How to capture photon arrivals?How to capture photon arrivals?

…… in parallel, on thousands of in parallel, on thousands ofpixels!pixels!

29

Imaging: Three ArchitecturesImaging: Three Architectures

1.1. Random Access ReadoutRandom Access Readout2.2. Event-driven ReadoutEvent-driven Readout3.3. Fully-parallel ProcessingFully-parallel Processing

30

1. Random Access Readout1. Random Access Readout

•• ProsPros–– SimpleSimple

•• ConsCons–– Highly inefficientHighly inefficient–– Low frame rateLow frame rate–– Enormous number of photons lost!Enormous number of photons lost!

31

Random Access ReadoutRandom Access Readout

Logic GatesLogic Gates

Guard RingGuard Ring

AnodeAnode

Niclass, Charbon, et al. JSSC 05

32

First First MassiveMassive SPAD Pixel Array SPAD Pixel Array

Niclass, Charbon, Niclass, Charbon, ISSCCISSCC 05 05

33

Photon Counting UniformityPhoton Counting Uniformity

•• Uniform counting at low, medium and high illuminationUniform counting at low, medium and high illumination

34

Spatio-Temporal Spatio-Temporal UniformityUniformity

Ti:Sapphire femtosecond laserλ= 470nmTAC resolution = 4.88ps

0 5 10 15 20 25 30

50

55

60

65

70

75

80

FW

HM

/ps

column number

35

Cross-talkCross-talk•• Electrical cross-talk reduced by potential barrierElectrical cross-talk reduced by potential barrier•• Optical cross-talk alleviated by reduced number of carriers in avalancheOptical cross-talk alleviated by reduced number of carriers in avalanche

Niclass, C

harbon, et al. JSS

C 2005

36

4µs 10µs 25µs 100µs 1ms

Ultra-high Dynamic RangeUltra-high Dynamic Range

37

2. Event-Driven Readout2. Event-Driven Readout

•• ProsPros–– Ideal with low photon countsIdeal with low photon counts

•• ConsCons–– First photon of column detectedFirst photon of column detected–– Large dead timeLarge dead time

SPAD SPAD SPAD SPAD

ID IDTDC

COLUMN

38

LASP ArchitectureLASP Architecture

Niclass, Favi, Kluter, Gersbach, Charbon, Niclass, Favi, Kluter, Gersbach, Charbon, ISSCC2008, JSSCISSCC2008, JSSC 2008 2008

39

LASP:LASP:First Fully Integrated SensorFirst Fully Integrated Sensor

128x128 SPAD array32 parallel TDCs

R = 70-500nsTP = 97ps

6.4Gb/s I/Os

32 Event-driven MU

Xes

Niclass, Favi, Kluter, Gersbach, Charbon, Niclass, Favi, Kluter, Gersbach, Charbon, ISSCCISSCC 2008, 2008, JSSCJSSC 2008 2008

40

TCSPC TestTCSPC Test

41

3D Imaging: Time-of-flight Cam3D Imaging: Time-of-flight Cam

pulsedlight source

TOF measurement

3D image reconstruction d

d = (c/2) TOFd = (c/2) TOF

Single-photonsensor

target

Time-of-flight

42

Three Dimensional ImagingThree Dimensional Imaging

Accuracy:• 1mm

Frame rate:• 1Hz

Digital output

43

3. Fully Parallel Processing3. Fully Parallel Processing

Control/DataControl/DataLinesLines

Supply/Bias LinesSupply/Bias Lines

Pixel-levelprocessing

44

Pros and ConsPros and Cons

•• ProsPros–– Full parallelismFull parallelism–– No photons are lost within detection cycleNo photons are lost within detection cycle

•• ConsCons–– Readout bandwidthReadout bandwidth–– Substrate/supply noiseSubstrate/supply noise

45

MEGAFRAME:MEGAFRAME:Massive Integration in DSMMassive Integration in DSM

Y-D

ecod

er

32x16 Array

32x16 Array

Serializer

Serializer

I/O pads

I/O pads SPAD TDC

RegisterControls

Fine interpolator Coarse

interpolator

PLL clock

START

STOP

Principle of TDC

Implemented on 130nm CMOS

46

Pixel SchematicPixel SchematicThermometer

coder

16 element delay line

6b ripple counter

Quenching

SPAD

Cal

10b memory

Global clock280MHzFrequency doubler

Global STOPFF

START

Vdd

Delay element

Column data bus

Gersbach, Charbon, et al., ESSCIRC 2009

Pitch: 50umMax. Resolution: 119psBandwidth: 1MS/sAccuracy: 1.2LSB (INL)Timing jitter: 128ps (FWHM)Timing uniformity: < 2LSB

47

Pixel LayoutPixel Layout

Over 500 transistorsIn 50 x 50 µm2

48

TDC PerformanceTDC Performance

INL

DNL

49

TDC UniformityTDC Uniformity

50

Dark Count RateDark Count Rate

Median DCR: 100Hz

51

Timing JitterTiming Jitter

52

Gersbach, Maruyama, Labonne, Richarson, Walker,Grant, Henderson, Borghetti, Stoppa, and Charbon,ESSCIRC 2009

32x32 pixel array

I2C

PLL

1.6mm

• 1MS/s-pixel• 100ps resolution• 100ns range• 1.2LSB precision• 2LSB uniformity

The MEGAFRAME32 ChipThe MEGAFRAME32 Chip

53

Scaling Up ApplicationsScaling Up Applications

Less than 32 SPADsLess than 32 SPADs

55

Chemiluminescence ReactorChemiluminescence Reactor

Gersbach, Maruyama, Sawada, Charbon, µTAS’06

56

Chemiluminescence ReactorChemiluminescence Reactor

57

Chemiluminescence ReactorChemiluminescence Reactor

58

Integrated Integrated MicroreactorMicroreactor

SU8 channel reactor

IgG Reservoir

ECL Reservoir

Fluidic channel

In Situ Optical Detection

E. Charbon and Y. Maruyama,Springer, 2010

SPAD Array

32 to 1024 Pixels32 to 1024 Pixels

60

Two-photon FLIM SetupTwo-photon FLIM Setup

DichroicBeam Splitter

Mode-lockedTi:Sapphire

Laser (740~920nm)

TDC

Detector

Filter (λ=488nm)

Attenuator

Fluorescent sampleOn x/y table Histogram processing

61

Triple-exponential DecayTriple-exponential Decay

Fluorophore:Oregon Green Bapta-1

Gersbach, Charbon, et al.,Optics Letters, 2009

62

Wide-field One-photon FLIMWide-field One-photon FLIM

Rahmadi Trimananda

63

The SampleSource: W

est Geo

rgia

Micro

scopic C

enterBisaccate Pine Pollen (Magnification: 3200x)

64

Wide-field One-photon FLIMWide-field One-photon FLIM

254ms

Marek Gersbach

1024 to 20,000 Pixels1024 to 20,000 Pixels

The Megaframe-128 Chip

C. Veerappan, J. Richardson, R. Walker, D.-U. Li, M. W. Fishburn, Y. Maruyama, D. Stoppa, F. Borghetti, M. Gersbach, R.K. Henderson, E. Charbon, ISSCC2011

The Megaframe-128 Chip

The Megaframe-128 Chip

50um pitch12.3mm

11.0mm

Imager Block Diagram

Pixel ArchitectureM

att W. Fishburn

Photon CountingM

att W. Fishburn

Photon Time-of-ArrivalM

att W. Fishburn

TDC Characterization

55ps resolution, 55ns range

INL DNL

System-level Timing UncertaintyBlue laser Red laser

Cumulative Noise

Optical Burst Detection UniformityC

hockalingam V

eerappan

MEGAFRAME Summary

• Format: 160x128 pixels• Timing resolution: 55ps• Impulse resp. fun.: 140ps• DCR (median): 50Hz• R/O speed: 250kfps• Size: 11.0 x 12.3 mm2

78

MultisensorMultisensorChipChip

•• Pitch: 25Pitch: 25µµmm•• Single shot time Single shot time resres.:.:

230ps230ps

•• Readout speed:Readout speed:40~2441fps40~2441fps

•• PRNU:PRNU:3.5%3.5%

Y. Maruyama and E. Charbon, TransducersTransducers, 2011

7979

Multisensor Multisensor PrinciplePrinciple•• AnalysisAnalysis

–– ElectrochemicalElectrochemical–– OpticalOptical–– CombinationCombination

opticalexcitation

electrochemical analysis

optical analysis

Labeled and label-less DNA probes

80

DNA from Blood and UrineDNA from Blood and Urine

Yuki Maruyama

81

Point-of-care CyclePoint-of-care Cycle

Yuki Maruyama

Single-photon detection in

Medical Applications

83

Positron Emission Tomography(PET)

Most commonly used: Fludeoxyglucose (18F)

e+e+e-e-

AnnihilationAnnihilation

γγ

γγ

scintillatorscintillator

PMTPMTCoincidenceCoincidence

1m1m

84

Source: S

un

Source: S

un

Positron Emission Tomography(PET)

Cancerous Ganglion

85

The The SPADnet SPADnet ProjectProjectObjective:Fully digital, scalable photonic component capableof detecting single and multi‐photon bursts, theirtime‐of‐arrival and intensity

COMMUNICATIONDETECTOR

DATA BUS

86

The InnovationThe Innovation

•• SPAD sensors with massively parallel chip-levelSPAD sensors with massively parallel chip-leveltime detectiontime detection

•• Large format with through-silicon-via basedLarge format with through-silicon-via basedpackagingpackaging

•• Advanced optical couplingAdvanced optical coupling•• Network between sensors with high-speedNetwork between sensors with high-speed

message-passingmessage-passing•• Digital coincidence by hierarchical messageDigital coincidence by hierarchical message

snoopingsnooping•• Novel image reconstruction exploiting spatialNovel image reconstruction exploiting spatial

informationinformation

87

The ImpactThe Impact

•• Cheaper, simpler, scalable, robust Cheaper, simpler, scalable, robust PETsPETs•• Higher levels of reliabilityHigher levels of reliability•• Higher speed and flexibility in dataHigher speed and flexibility in data

processing for imagingprocessing for imaging•• Full compatibility with MRI and otherFull compatibility with MRI and other

imaging techniquesimaging techniques•• Use of existing and new radiotracers withUse of existing and new radiotracers with

low lifetime and high specificity will below lifetime and high specificity will befeasiblefeasible

88

The Next Big ChallengesThe Next Big Challenges

89

MooreMoore’’s Law for Single-photons Law for Single-photon

2003 2006

1 kpixel

32 pixel

10 kpixel

100 kpixel

1 Mpixel0.8 CMOS 0.35 CMOS

2009

90nmCMOS

160x128

112x4

64x48

128x2

128x128

2012

512x256

1M

130nmCMOS

90

Fill FactorFill Factor

Guard rings, design rules, on-pixelGuard rings, design rules, on-pixelprocessingprocessing

FF = 1%

0.8µm CMOS

FF = 9%

0.35µm CMOS

FF = 25%

0.13µm CMOS

59µm 25µm 15µm

10µm?

FF = 35%

90nm CMOS

91

How Far Are We from 1Mpx?How Far Are We from 1Mpx?

•• Current minimum pitch: 15Current minimum pitch: 15µµm (0.13m (0.13µµm)m)•• 1024x1024 pixels: 16x16mm1024x1024 pixels: 16x16mm22

•• Assuming a minimum pitch of 10Assuming a minimum pitch of 10µµm (90m (90nnm)m)•• 1024x1024 pixels: 11x11mm1024x1024 pixels: 11x11mm22

Richardson et al., IIS

W 2009

15µµmm

92

•• 2P FLIM (P. French, Imperial College, London)2P FLIM (P. French, Imperial College, London)

•• Fluorescence imaging in 9.4T MRI (with Prof. Fluorescence imaging in 9.4T MRI (with Prof. RudinRudin,,ETH)ETH)

•• SPIM*-FCS (with Prof. SPIM*-FCS (with Prof. LangowskiLangowski, Heidelberg), Heidelberg)

•• TIRF DNA probing (with COSMIC, Edinburgh)TIRF DNA probing (with COSMIC, Edinburgh)

•• NIRI (with Dr. Wolf, USZ)NIRI (with Dr. Wolf, USZ)

Bioimaging ProjectsBioimaging Projects

*Selective/Single Plane Illumination Microscopy*Selective/Single Plane Illumination Microscopy

93

Intra-operative ß+ probe (Intra-operative ß+ probe (CTI-ForimtechCTI-Forimtech))

Concept:Concept: wireless, disposable probe wireless, disposable probe–– Detect and localize small tumours or Detect and localize small tumours or metastatic metastatic lymph nodes intra-lymph nodes intra-

operativelyoperatively–– Guide biopsy probe to tumourGuide biopsy probe to tumour–– Delineate tumour borders or invasion Delineate tumour borders or invasion duringduring operations operations–– Search and localize tumourSearch and localize tumour

residuals at the end of theresiduals at the end of thesurgical interventionsurgical intervention

Target:Target: melanoma, pelvic melanoma, pelvic tumourstumours,,mediastinoscopymediastinoscopy

Other Medical ProjectsOther Medical Projects

94

Other Medical Projects (Cont.)Other Medical Projects (Cont.)

Intra-operative sensors (Intra-operative sensors (EndoTOFPET-USEndoTOFPET-US, FP7 project), FP7 project)

Concept:Concept: asymmetric PET with TOF asymmetric PET with TOF–– External External SiPM SiPM plateplate–– Endoscopic Endoscopic plateplate–– Ultra-sound guidanceUltra-sound guidance

Target:Target: prostate, pancreas prostate, pancreas

Rectal/intestinal Endoscope with Miniature detector array

External SiPMplate forcoincidence

Tumour

95

ConclusionsConclusions

•• Single-photon imagers are here to staySingle-photon imagers are here to stay•• New and old apps enabledNew and old apps enabled•• Next challengesNext challenges

–– More miniaturizationMore miniaturization–– More parallelizationMore parallelization–– More flexibilityMore flexibility–– Novel imaging paradigmsNovel imaging paradigms

96

Acknowledgements

http://cas.et.tudelft.nlhttp://cas.et.tudelft.nl