Download SchedaFinale_SOIPD_referee

1)
Titolo del progetto:
Responsabile nazionale:
Data inizio - data fine:
area in CSN5:
Sezioni coinvolte:
Responsabile locale:
SOIPD
Dario Bisello
2009-2012
Elettronica
Padova
D. Bisello
2) Numero di partecipanti (media): 7.75; FTE (media): 4.1
3) Tutti i partner non INFN coinvolti: LBNL (USA), SCIPP UCSC (USA)
4) Fondi esterni acquisiti (totale): Università di Padova 67 k€
5) Fondi INFN ricevuti:
1)missioni:
2)inventariabile/costruzione apparati:
3)consumo:
105.4 k€
16.9 k€
0
88.5 k€
6) Descrizione obiettivi del progetto
Goal of the SOIPD experiment is the fabrication of Monolithic Pixel Sensors in Silicon On Insulator
Technology (SOI). In the SOI technology, electronic circuits lie on a thin Silicon layer, electrically
insulated from the rest of the Silicon wafer by a thick oxide layer (Buried OXide, BOX). Being the
electronics insulated, it becomes possible to use high resistivity substrates. The possibility to deplete
the sensor layer, greatly improves the charge collection efficiency. The sensitive volume can be hence
used both for charged particle detection and for imaging applications.
7) Risultati Ottenuti
In the framework of the SOIPD experiment we have developed several working prototypes of monolithic
pixel sensors in SOI technology.

We successfully faced and solved the problem of the back-gating effect: the reverse bias of the silicon
substrate increases the potential at the silicon surface, so that the BOX acts as a second gate for the
CMOS electronics on top, typically causing a shift in the transistor thresholds as a function of the
increasing depletion voltage. This undesired and parasitic effect was present in the first prototype
produced (SOImager-1), where some floating guard-ring structures have been introduced in the pixel to
screen the reverse bias. However, guard- rings take considerable space in the pixel, reduce charge
collection efficiency and are only partially effective. Instead, the implant of a buried p-well (BPW)
beneath the BOX and the transistors has been found to successfully screen the potential applied to the
high-resistivity layer in single transistor test structures. This motivated the adoption of a BPW in the
design of pixel cells immune from back-gating (implemented in all the chip designs since SOImager-2
on).

We studied the radiation tolerance of this technology to ionizing radiation (both total dose and Single
Event Upset); we have shown that monolithic pixel sensors in SOI technology are very sensitive to
charge trapped in the thick Buried Oxide (BOX) and that this effect is even more worrying when a
voltage is applied to the substrate to deplete it. Ionizing dose levels of few tens (hopefully hundreds) of
krad are tolerated.
With respect to Single Event Upset (SEU), we measured the global cross section curve for different
reverse voltages; we also used advanced microscopy techniques (Ion Electron Emission Microscopy) to
pinpoint SEU-sensitive regions of digital circuitry with micrometric resolution.

The SOImager-2 tracking performances have been studied with 200 GeV pion using data collected at
the CERN SPS complex; the detector was characterized in terms of the detection efficiency (>95% for
Vrev >50V) and single point resolution (1.1µm for Vrev>40V). These results are very encouraging for the
further development of pixel sensors in SOI technology for applications demanding particle
reconstruction with high spatial resolution and efficiency.

In order to reduce the material budget for vertex tracking applications in HEP and to allow backside
illumination for imaging applications, a set of SOImager-2 chips was then back-thinned to 70um. The
thinned sensors were post-processed to create a thin entrance window (400nm) on the back-plane and
anneal the crystal damage from the thinning. The thin SOImager-2 response was evaluated in backillumination using fluorescence radiation in the energy range of 2.12–8.6 keV at the LBNL Advanced
Light Source. After thinning and back-plane implant the pixel noise and conversion gain are measured
and found to be consistent to those of sensors before post-processing. Over the X-ray energy range
considered, the sensor showed an efficiency in excess of 60%, consistent with the expectations from
photo-absorption in Si and transmission through the entrance window.

The response of the thinned SOImager-2 sensor to high momentum particles has been tested at a test
beam at the CERN SPS with 300 GeV pions and has been compared to that of thick sensors of same
design in terms of signal and noise, detection efficiency and single point resolution. We observed that
the charge collected and the signal-to-noise ratio scale according to the estimated thickness of the
sensitive volume and the efficiency and single point resolution of the thinned chip are comparable to
those measured for the thick sensors.

At the end of 2011 a new design has been submitted, selecting the most performing pixel layout among
the 8 sectors of SOImager-2. This is a larger chip (512x320 pixels with 13.75um pitch) and has been
realized in three different substrates (both n-type and p-type, with different resistivities). However, due
to the poor quality of the substrates (high leakage current), no significant results have been obtained.
We are waiting for the foundry to improve the quality of processed wafers.
8) Pubblicazioni:
1. Studies of vertex tracking with SOI pixel sensors for future lepton colliders
M. Battaglia, D. Contarato, P. Denes, D. Liko, S. Mattiazzo, D. Pantano
Nucl. Instr. Meth. A, Volume 681 (2012) 61-67
2. Characterisation of a thin fully depleted SOI pixel sensor with high momentum charged particles
M. Battaglia, D. Bisello, D. Contarato, P. Denes, P. Giubilato, S. Mattiazzo, D. Pantano
Nucl. Instr. Meth. A, Volume 676 (2012) 50-53
3. Characterisation of a Thin Fully Depleted SOI Pixel Sensor with Soft X-ray Radiation
M. Battaglia, D. Bisello, R. Celestre, D. Contarato, P. Denes, S. Mattiazzo, C. Tindall
Nucl. Instr. Meth. A, Volume 674 (2012) 51-54
4.
First results in micromapping the sensitivity to SEE of an electronic device in a SOI technology at the
LNL IEEM
S. Mattiazzo, D. Bisello, P. Giubilato, A. Kaminsky, D. Pantano, L. Silvestrin, M. Tessaro, J. Wyss
Nucl. Instr. Meth. A, Volume 658 (2011) 125-128
5. Characterisation of a pixel sensor in 0.20m SOI technology for charged particle tracking
M. Battaglia, D. Bisello, D. Contarato, P. Denes, P. Giubilato, S. Mattiazzo, D. Pantano, S. Zalusky
Nucl. Instr. Meth. A, Volume 654 (2011) 258-265
6. Tests of monolithic pixel detectors in SOI technology with depleted substrate
P. Giubilato, M. Battaglia, D. Bisello, D. Contarato, P. Denes, T. S. Kim, S. Mattiazzo, D. Pantano, N.
Pozzobon, C.S. Tindall, S. Zalusky
Nucl. Instr. Meth. A, Volume 650, (2010) 184-188.
7. Total Dose Effects on a FD-SOI Technology for Monolithic Pixel Sensors
Mattiazzo, S.; Battaglia, M.; Bisello, D.; Contarato, D.; Denes, P.; Giubilato, P.; Pantano, D.;
Pozzobon, N.; Tessaro, M.; Wyss, J.
IEEM Trans. Nucl. Sci, 57 (2010) 2135.
8. Monolithic pixel sensors in deep-submicron SOI Technology
M.Battaglia, D. Bisello, D. Contarato, P. Denes, P. Giubilato, L. Glesener, S. Mattiazzo, C. Vu
JINST 4 P04007; doi: 10.1088/1748-0221/4/04/P04007
9. A DAQ system for pixel detectors R&D
M. Battaglia, D. Bisello, D. Contarato, P. Giubilato, D. Pantano, M. Tessaro
Nucl. Instr. Meth. A, Volume 611, (2009) 105-110.
10. Monolithic Pixel Sensors in Deep-Submicron SOI Technology with Analog and Digital Pixels
M. Battaglia, D. Bisello, D. Contarato, P. Denes, P. Giubilato, L. Glesener, S. Mattiazzo, C. Vu
Nucl. Instr. Meth. A, Volume 604 (2009) 380-384.
9) Presentazioni a congressi:
1. 19-25 Ottobre 2008 (Dresda, Germania): Piero Giubilato, Poster a IEEE NSS (“Nuclear Science
Symposium, Medical Imaging Conference”);
2. 14-18 Settembre 2009 (Bruges, Belgio): Jeffery Wyss, Poster a RADECS 2009 (10th European
Conference on Radiation Effects on Component and Systems”);
3. 29 Agosto – 1 Settembre 2009 (Hiroshima, Giappone): Piero Giubilato, Talk a HSTD7 (“7th
International Hiroshima Symposium on the Development and Application of Semiconductor
Tracking Detectors”);
4. 21-25 Settembre 2009 (Parigi, Francia): Serena Mattiazzo, Poster a TWEPP2009 (“Topical
Workshop on Electronics for Particle Physics”);
5. 22-24 Aprile 2010 (Pavia, Italia): Serena Mattiazzo, Talk a VIPS2010 (“Workshop on Vertically
Integrated Pixel Sensors”);
6. 6-10 Settembre 2010 (Grindelwald, Svizzera): Piero Giubilato, Talk a PIXEL2010 (“5th
International Workshop on Semiconductor Pixel Detectors for Particles and Imaging”);
7. Ottobre 2010 (Firenze, Italia): Serena Mattiazzo, Invited talk a RESMDD10 (“8th International
Conference on Radiation Effects on Semiconductor Materials Detectors and Devices”);
8. 3-7 Settembre 2012 (Inawashiro, Giappone): Serena Mattiazzo, Talk a PIXEL2012 (“6th
International Workshop on Semiconductor Pixel Detectors for Particles and Imaging”);
9. 9-12 Ottobre 2012 (Firenze, Italia): Serena Mattiazzo, Talk a RESMDD12 (“9th International
Conference on Radiation Effect on Semiconductor Materials Detectors and Devices”);
10. 18-20 Febbraio 2013 (Trento, Italia): Serena Mattiazzo, Talk a TREDI2013 (“8th Trento
Workshop on Advanced Silicon Radiation Detectors (3D and P-Type Technologies)”).
10) Tesi
1) Giulio Lovat “Caratterizzazione di un rivelatore monolitico a pixel realizzato con tecnologia SOI”,
2) Marco Marcante “Calibrazione in energia di un rivelatore monolitico a pixel in tecnologia SOI”,
Settembre 2010.
11) Sviluppo tecnologico, se c’e’ stato nel caso precisare:
Stato dell’arte, risultati ottenuti,eventuali brevetti o spin-off
The technology development of SOI process for pixel detector has been very encouraging in the
past years.
The introduction of the Buried P-Well process was a real breakthrough in the technological
development of Monolithic pixel sensors in SOI technology, since it allowed for the first time to apply
several tens of Volt of reverse bias to the substrates (which means tens of micron of depletion
width).
We have verified and characterized a processing technique (developed at LBNL) to recover the
damage induced by the thinning process on the detector backplane which allows to open a thin
entrance window on the backside for Soft X-ray detection.
(auto)classificare i risultati ottenuti dal punto di vista tecnologico: caso interessante work in
progress
12) Applicazioni Mediche: possibili ma non esistono al momento prototipi funzionanti in validazione
clinica
13) Applicazioni interdisciplinari: no
Indicare se esistono prototipi funzionanti utilizzati da altri enti o istituzioni nazionali o
internazionali:
Sì, a LBNL
14) Parere dei referees
L’esperimento SOIPD ha prodotto risultati innovativi e originali in un settore di particolare
interesse per l’integrazione di rivelatori su silicio, in loro interfacciamento con elettronica
on-chip e per aspetti legati alla resistenza alla radiazione. Il giudizio complessivo
dell’attivita’ svolta e’ ottimo.