Title: Development of the first prototypes of Silicon Photomultiplier at ITCirst
1Development of the first prototypes ofSilicon
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
2Outline
- Motivations for new photon detectors
- What is a Silicon PhotoMultiplier (SiPM)?
- Characteristics of the first SiPM prototypes
developed at ITC-irst - Summary and outlook
3- 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
4A look on photon detectors characteristics
5APDs 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
Reach-through diode J.R. McIntire, IEEE Trans.
El. Dev. ED-13 (1966) 164
Planar diode R. H. Haitz, J. App.Phys. Vol. 36,
No. 10 (1965) 3123
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
6What 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
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
7Our 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
8Simulations
- 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)
9Layout 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
10Wafer and SiPM design
- SiPM geometric characteristics
- area 1 x 1 mm2
- number of micro-cells 625
- micro-cell size 40 x 40 ?m2
11IV 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
12Quenching resistance
- Uniform micro-cell quenching
- resistance over the wafer
SiPM (625 micro-cells)
- Uniform SiPM quenching resistance over the wafer
- Very good correlation between Rmicro-cell and
RSiPM
13SiPM internal gain
- Gain
- linear variable with Vbias
- in the range 5 x 105 ? 2 x 106
- micro-cell capacitance
- Cmicro-cell 48 fF
- micro-cell recovery time
- ? Rquenching Cmicro-cell 20 ns
- Rise time
- ? 1 ns (limited by the read-out
- system)
14SiPM dark count
- Room temperature ( 23C)
- 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 the
- first run
34.5 V
32.0 V
33.5 V
34.0 V
32.5 V
33.0 V
- Dark count rate
- linear variable with Vbias
- increases with the temperature
15Single photon counting capability
- A LED was pulsed at low-light-level to record
the single - photoelectron spectrum
16Summary 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 _at_ 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