10 th pisa meeting on advanced detectors, isola d’elba, may 2006 development of the first...

10th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006

Development of

the first prototypes of

Silicon Photomultiplier at ITC-irst

N. Dinu, R. Battiston, M. Boscardin, F. Corsi, GF. Dalla Betta,

A. Del Guerra, G. Llosa-Llacer, M. Ionica, G. Levi, S. Marcatili, C. Marzocca,

C. Piemonte, G. Pignatel, A. Pozza, L. Quadrani, C. Sbarra, N. Zorzi

representing the INFN – ITC-irst collaboration for

Development and Applications of SiPM to Medical Physics and Space Physics

Nicoleta Dinu 210th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006

• Motivations for new photon detectors

• What is a Silicon PhotoMultiplier (SiPM)?

• Characteristics of the first SiPM prototypes developed at ITC-irst

• Summary and outlook

Outline


Many fields of applications require photon detectors:• Astroparticle physics (detection of the radiation in space)

• Nuclear medicine (medical imaging)

• High energy physics (calorimetry)

• Many others ..………

Characteristics to be fulfilled by the photon detector candidate:

• Highest possible photon detection efficiency

(blue –green sensitive)

• High speed

• High internal gain

• Single photon counting resolution

• Low power consumption

• Robust, stable, compact

• Insensitive to magnetic fields

• Low cost


A look on photon detectors characteristicsVACUUM

TECHNOLOGY

SOLID-STATE

TECHNOLOGY

PMT MCP-PMT HPD PN, PIN APD GM-APD

Photon detection efficiency

Blue 20 % 20 % 20 % 70 % 50 %

Green-yellow 40 % 40 % 40 % 80-90 % 60-70 %

Red 6 % 6 % 6 % 80 % 80 %

Timing / 10 ph.e 100 ps 10 ps 100 ps few ns tens of ps

Gain 106 - 107 106 - 107 3 - 8x103 1 200 V 105 - 106

Operation voltage 1 kV 3 kV 20 kV 100-500V 100 V

Operation in the magnetic field

10-3 T Axial magnetic

field 2 T

Axial magnetic field 4

T

No sensitivity

No sensitivity

No sensitivity

Threshold sensitivity (S/N1)

1 ph.e 1 ph.e 1 ph.e 100 ph.e

10 ph.e 1 ph.e

Shape characteristics sensible

bulky

compact sensible, bulky

robust, compact, mechanically rugged

VACUUM

TECHNOLOGY

SOLID-STATE

TECHNOLOGY

PMT MCP-PMT HPD PN, PIN APD GM-APD

Photon detection efficiency

Blue 20 % 20 % 20 % 60 % 50 % 30%

Green-yellow 40 % 40 % 40 % 80-90 % 60-70 % 50%

Red 6 % 6 % 6 % 90-100 % 80 % 40%

Timing / 10 ph.e 100 ps 10 ps 100 ps tens ns few ns tens of ps

Gain 106 - 107 106 - 107 3 - 8x103 1 200 105 - 106

Operation voltage 1 kV 3 kV 20 kV 10-100V 100-500V 100 V

Operation in the magnetic field

10-3 T Axial magnetic

field 2 T

Axial magnetic field 4

T

No sensitivity

No sensitivity

No sensitivity

Threshold sensitivity (S/N1)

1 ph.e 1 ph.e 1 ph.e 100 ph.e

10 ph.e 1 ph.e

Shape characteristics sensible

bulky

compact sensible, bulky

robust, compact, mechanically rugged


Rquenching

-Vbias

APDs in Geiger mode (GM-APD)

Quenching circuits development:• F. Zappa & all, Opt. Eng. J., 35 (1996) 938• S. Cova & all, App. Opt. 35 (1996) 1956

Current (a.u.)

Time (a.u.)

Standardized output signal

Planar diodeR. H. Haitz, J. App.Phys. Vol. 36, No. 10 (1965) 3123

Reach-through diodeJ.R. McIntire, IEEE Trans. El. Dev. ED-13 (1966) 164

The main disadvantage for many applications

It is a binary device:

One knows there was at least one electron/hole initiating the breakdown

but not how many of them


What is a SiPM ?

- Vbias

n pixels

One pixel fired

Two pixels fired

Three pixels fired

Current (a.u.)

Time (a.u.)

Al

ARC

-Vbias

Back contact

ppnn++

ppnn++

Rquenching

hh

p+ silicon wafer

Front contact

• matrix of n microcells in parallel

• each microcell: GM-APD + Rquenching

Main inventors: V. M. Golovin and A. Sadygov

Russian patents 1996-2002

Out

The advantage of the SiPM in comparison with GM-APDANALOG DEVICE – the output signal is the sum of the signals from all fired pixels

SiPM – photon detector candidate for many future applications


Our activity for SiPM development• SiPM: INFN – ITC-irst research project

• technological development of SiPM devices of 1 mm2

• matrix of few cm2 using SiPMs of 1 mm2 for Medical and Space Physics applications

• Groups involved• ITC-irst – Institute for Scientific and Technological Research, Trento

- simulations, design and layout- fabrication- electrical and functional characterization of the SiPM devices

• INFN – Pisa, Perugia, Bologna, Bari, Trento branches - electrical and functional characterization of the SiPM devices- development of the read-out electronics- functional characterization of the system composed of SiPM and read-out

electronics for medical (PET) and space (TOF) applications• 1.5 year activity

• simulations, design and layout• first run fabrication• characterization of the first SiPM prototypes• the second run fabrication with optimised parameters finishes next week


Simulations• Aim: to identify the most promising configuration for:

• Doping layers• the optimum dopant concentration of the implants which gives a breakdown voltage in the range 20 - 50 V

• Layout design • to avoid breakdown developing at junctions borders

• Optimum photon detection efficiency in the blue region

• QE (wavelength dependent) optimisation• minimize the amount of light reflected by the Si surface• maximize the generation of e-h pair in the depletion region

avalanche optimisation• maximization of the breakdown initiation probability

geom optimisation• minimize the dead area around each micro-cell (uniform breakdown and optical isolation through trenches)

avalanchegeomSiPM QE


Layout & Fabrication Process

• First fabrication run completed in September 2005

• Main characteristics:• p-type epitaxial substrate• n+ on p junctions• poly-silicon quenching resistance• anti-reflective coating optimized for short wavelength light

• Layout includes:• several SiPM designs with different implant geometries• test structures for process monitoring• test structures for analysis of the SiPM behavior


Wafer and SiPM designMain blockWafer

SiPM geometric characteristics:• area: 1 x 1 mm2

• number of micro-cells: 625• micro-cell size: 40 x 40 m2

SiPM

1 mm

1 m

m


IV & breakdown

Uniform breakdown voltage VBD

for different micro-cell and SiPM devices over the wafer

Uniform working point Vbias for different SiPM devices

• Vbias= VBD + V, V 3 V

• very important when matrix of many SiPMs devices of 1 mm2 are built

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

1.E-04

-45 -40 -35 -30 -25 -20 -15 -10 -5 0

Vback [V]

Lea

kag

e cu

rren

t [A

]

pixel/ block1

pixel/ block2

pixel/ block3

pixel/ block4

pixel/ block5

pixel/ block6

pixel/ block7

pixel/ block8

pixel/ block9

pixel/ block10

VBD = 31 V

Single micro-cell test structures

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

1.E-04

-45 -40 -35 -30 -25 -20 -15 -10 -5 0

Vback [V]

Le

ak

ag

e c

urr

en

t [A

]

SiPM/ block1SiPM/ block2SiPM/ block3SiPM/ block4SiPM/ block5SiPM/ block6SiPM/ block7SiPM/ block8SiPM/ block9SiPM/ block10

VBD = 31 V

SiPM (625 micro-cells)


Quenching resistance

Ωmicrocell

Nmicrocell

R

SiPMR 499

-2.5E-03

-2.0E-03

-1.5E-03

-1.0E-03

-5.0E-04

0.0E+00

0.0 0.5 1.0 1.5 2.0

Vback [V]

For

war

d cu

rren

t [A

]

SiPM-block4

SiPM-block5

y = -0.002x + 0.0011

R = 500 ohm

SiPM (625 micro-cells)

Uniform micro-cell quenching

resistance over the wafer

Uniform SiPM quenching resistance over the wafer

Very good correlation between Rmicro-cell and RSiPM

kR cellmicro 312

-1.E-05

-8.E-06

-6.E-06

-4.E-06

-2.E-06

0.E+00

0 1 2 3 4

Vback [V]

Fo

rwa

rd c

urr

en

t [A

]

Pixel block 1

Pixel block 2

Pixel block 3

Pixel block 4

Pixel block 5

y = -0.0000032x + 0.0000018

R = 312 kohm

Single micro-cell test structures


SiPM internal gain

Gain:• linear variable with Vbias

• in the range 5 x 105 2 x 106

micro-cell capacitance• Cmicro-cell = 48 fF

rise time recovery time micro-cell recovery time• = Rquenching · Cmicro-cell ~ 20 ns

Rise time• 1 ns (limited by the read-out system)

0.0E+00

2.0E+05

4.0E+05

6.0E+05

8.0E+05

1.0E+06

1.2E+06

1.4E+06

1.6E+06

1.8E+06

2.0E+06

30 31 32 33 34 35 36

Bias Voltage (V)

Gai

n


1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

0 50 100 150 200 250

threshold (mV)

dar

k co

un

t ra

te (

Hz)

Room temperature (~ 23°C)•1 p.e. dark count rate: ~ 3 MHz•3 p.e. dark count rate: ~ 1 kHz

Mention:•trenches for the optical isolation between micro-cells were not implemented in thefirst run

SiPM dark count

32.0 V32.5 V 33.0 V

33.5 V 34.0 V34.5 V

Dark count rate•linear variable with Vbias

•increases with the temperature

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

30 31 32 33 34 35 36

Voltage (V)

Dar

k C

ount

rat

e (H

z


Single photon counting capability

0

1 p.e.

2 p.e.

3 p.e.

4 p.e.5 p.e.

6 p.e.

7 p.e.

A LED was pulsed at low-light-level to record the single photoelectron spectrum

Excellent single photoelectron resolution


• SiPM - a research project of our INFN – ITC-irst collaboration team

• Characteristics of the first SiPM prototypes developed by ITC-irst• SiPM area: 1 mm2, 625 micro-cells, size: 40 x 40 m2

• Uniform breakdown voltage (VBD ~ 31 V) uniform working point • Uniform micro-cell quenching resistance: Rquenching ~ 320 k• Fast signals (rise time ~ 1 ns, small recovery time ~ 20 ns)• High internal gain, linear variable with the overvoltage: 5 x 105 2 x 106

• Dark count rate: ~ MHz @ 3 V overvoltage and room temperature• Excellent photon counting resolution

• Outlook• The characterization of the prototypes is in progress…….• The second run fabrication with optimised parameters (dark count rate and

optical cross-talk) finishes next week

Summary and outlook

10 th pisa meeting on advanced detectors, isola d’elba, may 2006 development of the first...

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