10 th 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
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10 th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006 Development of the first prototypes of Silicon Photomultiplier at ITC-irst N. Dinu, R.
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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
Nicoleta Dinu 310th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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
Nicoleta Dinu 410th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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
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
Nicoleta Dinu 510th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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
Nicoleta Dinu 610th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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
Nicoleta Dinu 710th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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
Nicoleta Dinu 810th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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
Nicoleta Dinu 910th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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
Nicoleta Dinu 1010th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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
Nicoleta Dinu 1110th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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
Nicoleta Dinu 1210th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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
Nicoleta Dinu 1310th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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
Nicoleta Dinu 1410th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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
Nicoleta Dinu 1510th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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
Nicoleta Dinu 1610th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
• 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