Transcript dinu_152.ppt

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
10th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
Outline
• Motivations for new photon detectors
• What is a Silicon PhotoMultiplier (SiPM)?
• Characteristics of the first SiPM prototypes
developed at ITC-irst
• Summary and outlook
Nicoleta Dinu
10th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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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
10th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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A look on photon detectors characteristics
VACUUM
TECHNOLOGY
SOLID-STATE
TECHNOLOGY
PMT
MCP-PMT
HPD
PN, PIN
APD
GM-APD
Blue
20 %
20 %
20 %
60
70 %
50 %
30%
Green-yellow
40 %
40 %
40 %
80-90 %
60-70 %
50%
Red
6%
6%
6%
90-100
80 % %
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
200V
105 - 106
1 kV
3 kV
20 kV
10-100V
100-500V
 100 V
 10-3 T
Axial
magnetic
field  2 T
Axial
magnetic
field  4 T
Threshold sensitivity
(S/N1)
1 ph.e
1 ph.e
1 ph.e
Shape characteristics
sensible
bulky
compact
sensible,
bulky
Photon
detection
efficiency
Operation voltage
Operation in the
magnetic field
Nicoleta Dinu
No
No
sensitivity sensitivity
100 ph.e
10 ph.e
No
sensitivity
1 ph.e
robust, compact, mechanically
rugged
10th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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APDs in Geiger mode (GM-APD)
Current (a.u.)
Rquenching
Standardized output signal
-Vbias
Planar diode
R. H. Haitz, J. App.Phys.
Vol. 36, No. 10 (1965) 3123
Reach-through diode
J.R. McIntire, IEEE Trans.
El. Dev. ED-13 (1966) 164
Time (a.u.)
Quenching circuits development:
• F. Zappa & all, Opt. Eng. J., 35 (1996) 938
• S. Cova & all, App. Opt. 35 (1996) 1956
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
10th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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What is a SiPM ?
• matrix of n microcells in parallel
• each microcell: GM-APD + Rquenching
Main inventors: V. M. Golovin and A. Sadygov
Russian patents 1996-2002
Front contact
Out
Al
Current (a.u.)
h
Rquenching
Two pixels fired
One pixel
fired
ARC

n+
p
n+
Three pixels
fired
p
n pixels
p+ silicon wafer
Back contact
-Vbias
Time (a.u.)
- Vbias
The advantage of the SiPM in comparison with GM-APD
ANALOG DEVICE – the output signal is the sum of the signals from all fired pixels
SiPM – photon detector candidate for many future applications
Nicoleta Dinu
10th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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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
10th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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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
SiPM   geom  QE   avalanche
• 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)
Nicoleta Dinu
10th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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Layout & Fabrication Process
• Layout includes:
• several SiPM designs with different implant geometries
• test structures for process monitoring
• test structures for analysis of the SiPM behavior
• 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
Nicoleta Dinu
10th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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Wafer and SiPM design
Wafer
Main block
1 mm
SiPM geometric characteristics:
• area: 1 x 1 mm2
• number of micro-cells: 625
• micro-cell size: 40 x 40 m2
1 mm
Nicoleta Dinu
10th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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IV & breakdown
Single micro-cell test structures
1.E-04
pixel/ block1
pixel/ block2
1.E-05
pixel/ block3
Leakage current [A]
1.E-06
pixel/ block4
VBD = 31 V
1.E-07
pixel/ block5
pixel/ block6
1.E-08
pixel/ block7
1.E-09
pixel/ block8
1.E-10
pixel/ block9
pixel/ block10
1.E-11
1.E-12
1.E-13
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
Vback [V]
SiPM (625 micro-cells)
1.E-04
 Uniform working point Vbias for
different SiPM devices
VBD = 31 V
1.E-05
• Vbias= VBD + V, V  3 V
• very important when matrix of
many SiPMs devices of 1 mm2 are
built
Leakage current [A]
1.E-06
1.E-07
1.E-08
SiPM/ block1
SiPM/ block2
SiPM/ block3
SiPM/ block4
SiPM/ block5
SiPM/ block6
SiPM/ block7
SiPM/ block8
SiPM/ block9
SiPM/ block10
1.E-09
1.E-10
1.E-11
1.E-12
1.E-13
-45
-40
-35
 Uniform breakdown voltage VBD
for different micro-cell and SiPM
devices over the wafer
-30
-25
-20
-15
-10
-5
0
Vback [V]
Nicoleta Dinu
10th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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Quenching resistance
Single micro-cell test structures
0.E+00
Rmicrocell  312 k
y = -0.0000032x + 0.0000018
R = 312 kohm
Forward current [A]
-2.E-06
-4.E-06
 Uniform micro-cell quenching
resistance over the wafer
-6.E-06
Pixel block 1
Pixel block 2
Pixel block 3
-8.E-06
Pixel block 4
Pixel block 5
-1.E-05
0
1
2
3
4
Vback [V]
SiPM (625 micro-cells)
0.0E+00
R
R
 microcell  499 Ω
SiPM N
microcell
y = -0.002x + 0.0011
R = 500 ohm
Forward current [A]
-5.0E-04
-1.0E-03
-1.5E-03
-2.0E-03
SiPM-block4
SiPM-block5
-2.5E-03
0.0
0.5
1.0
1.5
2.0
 Uniform SiPM quenching
resistance over the wafer
 Very good correlation between
Rmicro-cell and RSiPM
Vback [V]
Nicoleta Dinu
10th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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SiPM internal gain
2.0E+06
1.8E+06
 Gain:
1.6E+06
• linear variable with Vbias
• in the range 5 x 105  2 x 106
1.4E+06
Gain
1.2E+06
1.0E+06
8.0E+05
 micro-cell capacitance
6.0E+05
• Cmicro-cell = 48 fF
4.0E+05
2.0E+05
0.0E+00
30
31
32
33
34
35
36
Bias Voltage (V)
rise time
recovery time
 micro-cell recovery time
•  = Rquenching · Cmicro-cell ~ 20 ns
 Rise time
•  1 ns (limited by the read-out
system)
Nicoleta Dinu
10th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
13
SiPM dark count
1.E+07
 Room temperature (~ 23°C)
dark count rate (Hz)
1.E+06
• 1 p.e. dark count rate: ~ 3 MHz
• 3 p.e. dark count rate: ~ 1 kHz
1.E+05
1.E+04
34.5 V
1.E+03
32.0 V
33.5 V
32.5 V
34.0 V
33.0 V
1.E+02
0
50
100
150
200
250
threshold (mV)
 Mention:
• trenches for the optical
isolation between micro-cells
were not implemented in the
first run
4,0E+06
3,5E+06
Dark Count rate (Hz
3,0E+06
 Dark count rate
2,5E+06
• linear variable with Vbias
• increases with the temperature
2,0E+06
1,5E+06
1,0E+06
5,0E+05
0,0E+00
30
31
32
33
34
35
36
Voltage (V)
Nicoleta Dinu
10th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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Single photon counting capability
 A LED was pulsed at low-light-level to record the single
photoelectron spectrum
4 p.e.
5 p.e.
3 p.e.
6 p.e.
2 p.e.
7 p.e.
1 p.e.
Excellent single
photoelectron resolution
0
Nicoleta Dinu
10th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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Summary and outlook
• 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
Nicoleta Dinu
10th Pisa Meeting on Advanced Detectors, Isola d’Elba, May 2006
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