Pixel Detectors: From Fundamentals to Applications

313 Pages·2006·5.168 MB·English

by  Dr. Leonardo Rossi, Dr. Peter Fischer, Dr. Tilman Rohe, Dr. Norbert Wermes (auth.)

PixelDetectors
Particle Acceleration and Detection
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Leonardo Rossi Peter Fischer
Tilman Rohe Norbert Wermes
Pixel Detectors
From Fundamentals to Applications
With177Figures
ABC
Dr.LeonardoRossi Dr.TilmanRohe
InstitutoNazionalediFisicaNucleare PaulScherrerInstitut
DipartimentodiFisica 5232Villigen
ViaDodecaneso33 Switzerland
16146Genova
Italy
E-mail:[email protected]
Dr.PeterFischer Dr.NorbertWermes
InstitutfürTechnischeInformatik PhysikalischesInstitut
UniversitätMannheim UniversitätBonn
B6,26,68131Mannheim Nussallee12,53115Bonn
Germany Germany
LibraryofCongressControlNumber:2005930884
ISSN1611-1052
ISBN-10 3-540-28332-3SpringerBerlinHeidelbergNewYork
ISBN-13 978-3-540-28332-4SpringerBerlinHeidelbergNewYork
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Preface
Progressinsciencerequiresthecontinuousrefinementofexperimentalmeth-
ods. Particle physics is just a particular example where sophisticated ex-
perimental techniques are of utmost importance. Collisions at high-energy
acceleratorsproducemanyparticleswhosedirection,energy,andidentityare
measured with large and complex detectors. One of the most demanding re-
quirements is the simultaneous detection of hundreds of particle tracks with
micrometer spatial and nanosecond timing precision in the harsh radiation
environment close to the point of their production.
Addressingandmasteringsuchrequirementshasbecomepossiblebywhat
onemightwanttocallthe“siliconage”ofthehumandevelopment.Sincethe
discovery of the transistor effect, for which Shockley, Bardeen, and Brattain
wereawardedtheNobelPrizein1956,thenumberofapplicationsusingselec-
tively doped silicon has not ceased to increase. Miniaturization of electronics
deviceshassteadilyprogressedoverthepastdecades.Alreadyin1965Moore
had predicted the doubling of the number of transistors per integrated cir-
cuitevery≈2years.Surprisinglyenough,thisexponentialincreasestillholds
after 40 years and it is today difficult to find a large-scale industrial product
or research project where microelectronics does not play a significant role.
Thedevelopmentofhighlysegmenteddetectorswithmanymillionpixels,
each operating as an independent intelligent sensing element, also has only
become possible from the advancements in microelectronics. Hand in hand
withthecontinuousreductionofthestructuresizes,themanufacturingcosts
were reduced and access to the design tools was made possible. This allowed
the particle physics community to adapt the microelectronics technology to
the needs of the experiments. Silicon microstrip and pixel detectors and also
the associated integrated readout electronics rapidly became standard build-
ingblocksfordetectorsystemsandbrokethewaytotheprecisemeasurement
ofshort-livedparticledecayvertices.Pixeldetectorsarethemostrecentstep
in this evolution, finding important applications in particle physics experi-
ments, most notably in the detectors which are currently being built for the
LargeHadron Collider. Themastering of thepixeltechnology hasalsoled to
first applications in other fields and more are certain to follow soon.
It is therefore time to share the know-how that has been accumulated
over the last years in this field. This book may help pixel detector designers
VI Preface
for other and future applications of the pixel technology, and it shall also
contribute to informing the scientific community about the present status
and possible further developments of these powerful and versatile detection
devices.
We must point out that the field is in a fast evolution at the time of
writing this book. Some very recent results could not be included and some
statements may already be outdated at the time of printing. The many ref-
erences given should help the reader to find the most recent results in the
various fields.
The text is organized as follows: after Chap. 1, which introduces pixel
detectorsingeneraltermsandgivessomehistoricalperspectivetothisdevel-
opment,thesensorisdiscussedindetailinChap.2,theelectronicsinChap.3,
andthewaytoconnecttheminChap.4.Chapter5presentsapplicationsboth
inparticlephysicsandinotherfields.Chapter6,finally,attemptsalookinto
the future and indicates some promising developments.
This book would not have been possible without the help and encourage-
ment of many people. Chris Fabjan suggested to address the issue of pixel
detectors and has continuously stimulated the authors. Murdock Gilchriese
andPeterWeilhammerdidcontributetotheearlystageofthebook.Ladislav
Andricek, Michael Moll, Rainer Richter, and Renate Wunstorf helped with
manyusefuldiscussionsonpixelsensors,IvanPericdidcommentontheelec-
tronics part, Oswin Ehrmann on the bump-bonding processes, and Michael
Overdickonimagingapplicationsofpixeldetectors.WethankFedericoAnti-
nori, Roland Horisberger, and Simon Kwan for carefully reading the descrip-
tion of, respectively, the ALICE, CMS, and BTeV pixel detector description.
We also thank Rinaldo Cenni and Laura Opisso for their help with Latex
when putting the pieces together and Rosanna Puppo and Bert Wiegers for
making many drawings. Finally, we thank our families for their patience and
understanding during the writing of this book.
Geneva, Leonardo Rossi
May 2005 Peter Fischer
Tilman Rohe
Norbert Wermes
Contents
1 Introduction.............................................. 1
1.1 Generalities on Pixel Detectors........................... 1
1.1.1 Motivations for Pixel Detectors in Particle Physics.... 2
1.1.2 Working Principle and Operating Characteristics
of Segmented Silicon Detectors .................... 5
1.1.3 Hybrid Pixel Detectors............................ 9
1.1.4 Monolithic Pixel Detectors ........................ 12
1.2 Evolution of Pixel Detectors in Particle Physics ............ 13
1.2.1 TheFirstPixelDetectorsandTheirUseinExperiments 16
1.2.2 Other Applications ............................... 23
2 The Sensor ............................................... 25
2.1 Introduction ........................................... 25
2.2 Device Physics and Fundamental Sensor Properties ......... 26
2.2.1 Carrier Concentration............................. 26
2.2.2 Charge Generation and Recombination in Silicon ..... 29
2.2.3 Transport of Charge Carriers ...................... 37
2.2.4 The pn-Junction ................................. 40
2.2.5 Surface Barrier................................... 44
2.2.6 Metal Oxide Semiconductor Structure............... 46
2.2.7 Punch Through ................................. 48
2.3 Pixel Sensors and Their Properties ....................... 50
2.3.1 Different Types of Silicon Sensors .................. 50
2.3.2 Leakage Current and Maximum Operation Voltage ... 51
2.3.3 Full Depletion Voltage and Substrate Doping ........ 53
2.3.4 Pixel Capacitance ................................ 57
2.3.5 Charge Motion and Signal Formation ............... 59
2.3.6 Spatial Resolution................................ 61
2.3.7 Radiation Hardness............................... 67
2.4 Radiation-Induced Effects on Silicon ...................... 68
2.4.1 Bulk Damage .................................... 68
2.4.2 Surface Effects ................................... 80
2.5 Sensor Concepts........................................ 81
2.5.1 Overview of Sensor Types ......................... 82
VIII Contents
2.5.2 p+ in n: Low-Cost Solution for Applications
in a Low- or Medium-Radiation Environment ........ 85
2.5.3 n+ in n: Solution for Applications
in a High-Radiation Environment................... 97
2.6 Processing of Silicon Wafers ............................. 110
2.6.1 Production and Cleaning of Silicon ................. 111
2.6.2 Thermal Oxidation ............................... 113
2.6.3 Layer Deposition ................................. 113
2.6.4 Photolithographic Steps........................... 114
2.6.5 Etching ......................................... 115
2.6.6 Doping.......................................... 116
2.6.7 Metallization .................................... 118
2.6.8 Example of a Process Sequence .................... 118
2.7 Detector Materials Other Than Silicon .................... 121
2.7.1 Gallium Arsenide................................. 122
2.7.2 CdTe and CdZnTe................................ 124
2.7.3 Diamond ........................................ 125
3 The Front-End Electronics................................ 129
3.1 Introduction ........................................... 129
3.1.1 Generic Pixel Chip ............................... 130
3.1.2 Simple Sensor Model.............................. 133
3.1.3 Generic PUC .................................... 135
3.1.4 Module Controller Chips .......................... 143
3.2 Design Aspects......................................... 144
3.2.1 Typical Specifications............................. 145
3.2.2 Radiation-Tolerant Design......................... 154
3.2.3 Cross Talk....................................... 157
3.2.4 Testability and Ease of Operation .................. 160
3.3 Analog Signal Processing ................................ 161
3.3.1 Charge Amplification ............................. 162
3.3.2 Feedback and Leakage Compensation ............... 163
3.3.3 Hit Discrimination................................ 168
3.3.4 Threshold Trim .................................. 170
3.3.5 Noise in a Simple FET Amplifier ................... 171
3.3.6 Noise in Charge Amplifier/Shaper Combination ...... 178
3.3.7 FET Preamplifier ................................ 183
3.3.8 Bipolar Amplifier................................. 184
3.3.9 Summary........................................ 186
3.4 Readout Architectures .................................. 187
3.4.1 Chips Without Data Buffering ..................... 188
3.4.2 Chips with Zero Suppression and Data Buffering ..... 188
3.4.3 Counting Chips .................................. 197
Contents IX
4 Integration and System Aspects .......................... 201
4.1 Introduction ........................................... 201
4.2 Modules............................................... 202
4.3 Bump Bonding......................................... 203
4.3.1 Solder Bumping and Bonding Process............... 204
4.3.2 Indium Bump-Bonding Process .................... 206
4.3.3 Gold-Stud Bump-Bonding Process.................. 210
4.3.4 Quality Control of Bump-Bonded Assemblies ........ 212
4.3.5 Rework of Bump-Bonded Assemblies................ 213
4.3.6 Thinning of Electronics Wafers..................... 214
4.4 “Dressing” the Modules ................................. 214
4.4.1 Flex Hybrid ..................................... 215
4.4.2 Multichip Module Deposited....................... 216
4.5 Support Mechanics and Cooling .......................... 218
4.5.1 Mechanical Supports.............................. 219
4.5.2 Cooling ......................................... 220
4.6 Power and Signal Interconnect
in High-Luminosity Colliders............................. 222
4.7 Operation in High-Radiation Environment................. 223
5 Pixel Detector Applications .............................. 225
5.1 Pixel Detectors for High-Luminosity
Collider Experiments ................................... 225
5.2 Large Systems in Construction ........................... 231
5.2.1 ATLAS ......................................... 232
5.2.2 CMS............................................ 237
5.2.3 ALICE.......................................... 241
5.2.4 BTeV........................................... 243
5.3 Pixel Detectors for Imaging Applications .................. 246
5.4 Pixel Imaging Systems in Operation ...................... 250
5.4.1 Counting Pixels for Radiography ................... 251
5.4.2 Pixel Detectors for Protein Crystallography
with Synchrotron Radiation ....................... 254
5.4.3 Autoradiography with Pixel Detectors .............. 256
6 Trends and New Developments for Pixel Detectors ....... 261
6.1 Introduction ........................................... 261
6.2 Limitations and Prospects
of the Hybrid Pixel Technology........................... 262
6.2.1 MCM-D Integration .............................. 263
6.2.2 Interleaved Hybrid Pixels.......................... 265
6.2.3 Active Edge Three-Dimensional Silicon Pixel Detectors 267
6.3 Monolithic and Semimonolithic Pixel Detectors............. 269
6.3.1 Monolithic Pixels on Bulk Silicon................... 271
6.3.2 Monolithic CMOS Pixels .......................... 272
X Contents
6.3.3 Monolithic SOI Pixels............................. 276
6.3.4 Amorphous Silicon above CMOS Pixel Electronics.... 277
6.3.5 DEPFET Pixels.................................. 278
Glossary...................................................... 283
References.................................................... 289
Index......................................................... 301