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Semiconductors as particle detectors
Ingrid-Maria Gregor, DESY
Thanksto:MarcWinter,LaciAndricek,CinziadaVia,PaulaCollins,UliKoetz,JimVirdee,CarstenNiebuhr,FrankSimon,FabianHügging,MarkusChrisDanzani,LutzFeld,RobertKlanner,ChristophedelaTaille,NorbertWermes
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Outline
MoDvaDonBasicsofSemiconductorDetectorsStripDetectorsPixelDetectorsPixelsforFutureExperimentsSummary
FieldofsemiconductordetectorsforparDcledetecDonisextremelylarge
Cangiveonlyaroughoverview
Myviewisbiased
alotofsilicon
morepixelsthanstrips
almostonlyHEP
Thefirsttransistor,inventedatBellLaboratories1947
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Motivation
Semiconductorshavebeenusedinpar?cleiden?fica?onformanyyears:
~1950:Discoverythatpn‐JuncDonscanbeusedtodetectparDcles.
Semiconductordetectorsusedforenergymeasurements(Germanium)
Since~30years:SemiconductordetectorsforpreciseposiDonmeasurements.
preciseposiDonmeasurementspossiblethroughfinesegmentaDon(10‐100μm)
mulDpliciDescanbekeptsmall(goal:<1%)
TechnologicaladvancementsinproducDontechnology:
developmentsformicroelectronics
ZEUSMVD2000
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DELPHIVFT1996
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CDFSVXIIa(2001‐)
~11m2siliconarea
~750000readoutchannels
DELPHI(1996)
~1.8m2siliconarea
~175000readoutchannels
Large Silicon Systems
CMSSiliconTracker(~2007)
~12,000modules
~223m2siliconarea
~25,000siliconwafers
~10Mreadoutchannels
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Basics of semiconductor Detectors
Ingr
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Gre
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Sem
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Largegap:thesolidisaninsulator.
Nogap:itisaconductor.
Smallbandgap:semiconductor
Forsilicon,thebandgapis1.1eV,butittakes3.6eVtoionizeanatom.TherestoftheenergygoestophononexitaDons(heat).
Inagas,electronenergylevelsarediscrete.Inasolid,energylevelssplitandformanearly‐conDnuousband.
Semiconductor Basics I
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n‐type:Inann‐typesemiconductor,negaDvechargecarriers(electrons)areobtainedbyaddingimpuriDesofdonorions(eg.Phosphorus(typeV))
DonorsintroduceenergylevelsclosetoconducDonbandthusalmostfullyionized=>FermiLevelnearCB
Electronsarethemajoritycarriers.
p‐type:Inap‐typesemiconductor,posiDvechargecarriers(holes)areobtainedbyaddingimpuriDesofacceptorions(eg.Boron(typeIII))
Acceptorsintroduceenergylevelsclosetovalencebandthus‘absorb’electronsfromVB,creaDngholes=>FermiLevelnearVB.
Holesarethemajoritycarriers.
Doping Silicon
7
p‐andn‐dotedsemiconductorcombined
GradientofelectronandholedensiDesresultsinadiffusemigraDonofmajoritycarriersacrossthejuncDon.
MigraDonleavesaregionofnetchargeofoppositesignoneachside,calledthedepleDonregion(depletedofchargecarriers).
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PN-Junction
ArDficiallyincreasingthisdepletedregionbyapplyingareversedbiasvoltageallowchargecollecDonfromalargervolume
with
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Principle of semiconductor Detectors
1. CreaDonofelectricfieldvoltagetodepletethicknessd
:dopingconcentraDon
2. Keepdarkcurrentlow
:chargecarrierlifeDme
3. IonisingparDclescreatefreechargecarrier
4. Chargecarrierdriltoelectrodesandinducesignal
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Material Properties
Si Ge GaAs CdTe Diamant SiC
bandgap 1.12 0.67 1.42 1.56 5.48 2.99
energyfore‐ppair[eV] 3.6 2.9 4.2 4.7 13.1 6.9
e‐forMIP(300µm) 24000 50000 35000 35000 9300 19000
Z 14 32 31+33 48+52 6 14+6
Siliconistheonlymaterialwhichcanbeproducedinlargerwafersinhighquality
comparetokT=0.026eVatroomtemperature‐>darkcurrentundercontrol
highdensitycomparedtogases:ρ=2.33g/cm3
goodmechanicalstability‐>possibletoproducemechanicallystablelayers
largechargecarriermobility
fastchargecollecDonδt~10ns
Whyissiliconusedmoreolen?
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Protons in Silicon
0.4keV/µm‐>3.6eVcreateselectronholepair =>~110electron‐holepairsperµm(meanvalue)most probably number: 80 electrons
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Radiation Damage
ImpactofRadiaDononSilicon:
SiliconAtomscanbedisplacedfromtheirlatceposiDon
Pointdefects(EMRadiaDon)
Damageclusters(NuclearReacDons)
Importantinthiscontext:BulkEffects:Latcedamage:GeneraDonofvacanciesandintersDDalatoms(NIEL:NonIonizingEnergyLoss)
Surfaceeffects:GeneraDonofchargetraps(Oxides)(byionizingenergyloss)
Fillingofenergylevelsinthebandgap➭directexcitaDonnowpossible➭higherleakagecurrent➭morenoise➭“Chargetrapping”,causinglowerchargecollecDonefficiency
Canalsocontributetospacecharge:Higherbiasvoltagenecessary. 12
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Consequences of Radiation Damage
n
n+
p+
n
n+
p+
++ +
+ ++
--
--
--
++ +
+ ++
--
--
--
) )
))
Chargetrappingindefects
Macroscopicconstant:leakagecurrentanddepleDonvoltage
CountermeasuresGeometrical:developsensorsthatcanwithstandhigherdepleDonvoltages
Thinnersensors(butFEelectronicswithhighersensiDvityneeded)
Environment:sensorcooling(~‐10C)
Slowingdownof“reverseannealing”
Lowerleakagecurrents13
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Some Words onFront-End Electronics
Ingr
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Gre
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Sem
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Overview of readout electronics
Most front-ends follow a similar architecture
Verysmallsignals(fC)‐>needamplificaDon
Measurementofamplitudeand/orDme(ADCs,discriminators,TDCs)
Severalthousandstomillionsofchannels
example:ALICEPixeldetector
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Very Large Scale Integration
VLSIenables
highchanneldensity
pre‐amplificaDon,datastorageetc.veryclosetothedetector
reducednoise
lowpowerdissipaDon
industrialproducDon
integraDondensityisgrowingrapidly
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Industry Scaling Roadmap
New generation every ~2 years with α = √2from 1970 (8 µm) to 2009 (35 nm) (industrial application)End of the road ? Power dissipation sets limits HEP nowadays at 90nm and 130nmProblem: by the time a technology is ready for HEP -> “old” in industry standards
HEP
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Radiation effects on CMOS: ionizing
Decreaseoffeaturesize:higherradiaDontolerance:
PosiDvechargetrappedingateandfieldoxidesTrappedchargedissipatesbytunnellinginthin‐oxidetransistors
RadiaDontolerantlayouttechniquesdesignedbyCERNRD49in0.25µmtoavoidparasiDctransistorleakage
Source
Drain Gate
Guard
Bird’s beak
Field oxide
Parasitic MOS
Parasitic channel
Standarddevicelayout
EnclosedlayoutTID on IBM 130nm NMOS [F. Faccio CERN]
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gateenclosesalln+regionsavoidinganythicktransistorrelevantoxidestructures
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Strip Detectors
Ingr
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Strip Detectors
FirstdetectordevicesusingthelithographiccapabiliDesofmicroelectronics
FirstSilicondetectors‐>stripdetectors
Canbefoundinallhighenergyphysicsexperimentsofthelast20years
Principal:Siliconstripdetector
p+-strips
metallization (Al)
depletion voltage
n-siliconionizingparticle
n+-siliconmetallization (Al)
80 e-h/µm
ArrangementofstripimplantsacDngaschargecollecDngelectrodes.
Placedonalowdopedfullydepletedsiliconwafertheseimplantsformaone‐dimensionalarrayofdiodes
ByconnecDngeachofthemetalizedstripstoachargesensiDveamplifieraposiDonsensiDvedetectorisbuilt.
TwodimensionalposiDonmeasurementscanbeachievedbyapplyinganaddiDonalstriplikedopingonthewaferbackside(doublesidedtechnology)
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First HEP Application: NA11
Alerdiscoveryofcharm(1974),τ‐lepton(1975)andbeauty(1977)withlifeDmescτ~100μm:needfast(ns),andprecise(μm)electronictrackingdetectors
stripdetectorforNA11in1981
1200strip‐diodes
20μmpitch
60μmreadoutpitch
24x36mm2acDvearea~0.01m2
posiDonresoluDon~5.4μm
8layeratthestart
precisetrackreconstrucDon
readoutelectronic:~1m2!
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Si Microstrip Detectors for LHC
Early1990’s:Atthe?meoftheConceptual
DesignoftheppExperiments
RadiaDondamagepoorlyunderstood
Cost/unitareawasprohibiDvelylarge
Largeno.ofchannelsrequired
Whatwasknown:
leakagecurrentincreasedlinearlywithfluence
typeinversion–higherandhigherbiasvoltage
lrequired
reverseannealing
What was doneHVbehaviourimprovedbycarefulprocessinganduseofmulDpleguardringsSidetectorshadtobekeptpermanentlycoldFastpre‐amplifiersdevelopedtocopewith25nscollidingbunchesLeakagecurrentdealtwithfastamplifiersCost/unitareasignificantlyreducedbygrowinglargerdiameteringots(6”insteadof4”),single‐sidedprocessing(p‐on‐n)ImplementaDonoffront‐endread‐outchipinindustrystandarddeepsub‐microntechnology
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CMS Si-Tracker
Si‐Strip‐Detector:
~210m2Silicon
25000Sensors,9.6Mchannels
10barrellayers,2x9discs
Thelargesteverbuiltsilicontracker
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CMS Si Barrel
Single and double sided layers
CMSInnerbarrelSiTracker:Single‐SidedSi‐Strip
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ATLAS SCT
ATLAS Si-Detector SCT: Si- strips: 4 Barrel-layer, 2 x 9 discs
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ATLAS SCT
SCT strips: 61 m2 silicon, ~6.2 M channels4088 modules, 2112 barrel (1 type), 1976 in the discs (4 different types)
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ATLAS SCT Module
barrel-module
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ATLAS SCT Module
barrel-module
disc-module27
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Pixel Detectors
Ingr
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Limits of Strip Detectors
In case of high particle fluences ambiguities give difficulties for the track reconstruction
DerivingthepointresoluDonfromjustonecoordinateisnotenoughinformaDontoreconstructasecondaryvertex
PixeldetectorsallowtrackreconstrucDonathighparDcleratewithoutambiguiDes
GoodresoluDonwithtwocoordinates(dependingonpixelsizeandchargesharingbetweenpixels)
‣ Veryhighchannelnumber:complexread‐out
‣ ReadoutinacDveareaadetectorFirstpixels(CCDs)inNA11/NA32:~1983
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Hybrid Pixels – “classical” Choice HEP
chip
sensor
Theread‐outchipismounteddirectlyontopofthepixels(bump‐bonding)
Eachpixelhasitsownread‐outamplifier
Canchooseproperprocessforsensorandread‐outseparately
Fastread‐outandradiaDon‐tolerant
…but:
Pixelareadefinedbythesizeoftheread‐outchip
HighmaterialbudgetandhighpowerdissipaDon
HybridPixel(CMS)
CMSPixels:~65Mchannels150µmx150µm
ATLASPixels:~80Mchannels50µmx400µm(longinzorr)
Alice:50µmx425µmLHCb
Phenixupgrade
Fair
CBM
PANDA 30
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Apixelmodulecontains:1sensor(2x6cm)~40000pixels(50x500mm)16frontend(FE)chips2x8arraybumpbondedtosensorFlex‐hybrid1modulecontrolchip(MCC)Thereare~1700modules
ATLAS-Pixels
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ATLAS-Pixels
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Services!!
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Services!!
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Material Budget of LHC Experiments
Atlas
CMS&AtlasbothslippedconsiderableinkeepingX/X0originallyaimedfor!
OldargumentthatSiliconwouldbetoothickisnotreallytrue==>power&cooling
CMS
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Next Generation Pixel Detectors
Ingr
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Current Challenges (ILC, sLHC)
Mainchallenge:idenDfycquarkandleptonjets
lifeDme~10‐12sec=>~100um
=>parDclesdecaywithinthevacuumbeampipe
reconstructdecayproducts
Alsohere:Trendintrackingdetectors:pixelliseddetectorsinstalledveryclosetothebeaminteracDonregion
MinimaldistancelimitaDons:
• beampiperadius
• beamassociatedbackgrounds
• densityofparDclesproducedattheIP
Consequencesonoccupancyandradia?onlevel
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Optimising = Compromising
ConflictbetweenphysicsperformancedrivenparametersandrunningcondiDonconstraints:
Physicsperformance:spaDalresoluDonandmaterialbudget(+distancetoIR)
RunningcondiDons:read‐outspeedandradiaDontolerance
Moreover:
➡ limitaDonsfrommaximumpowerdissipaDoncompaDblewithrunningcondiDonsandmaterialbudget
➡ limitaDonsfromhighestdataflowacceptablebyDAQ
UlDmateperformanceonallspecificaDonscannotbereachedsimultaneously
eachfacility&experimentrequiresdedicatedopDmizaDon(hierarchybetweenphysicsrequirementsandrunningconstraints
thereisnosingletechnologybestsuitedtoallapplicaDons
explorevarioustechnologicalopDons
moDvaDonforconDnuousR&D(opDmumisstronglyDmedependent)
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physics or Running Conditions
Physicsperformancedriven:
thin(potenDallyundepleted)sensiDvevolume
ILC,RHIC,CLIC,SuperB,FAIR
CMOSsensors,CCDs,DEPFETs,VerDcallyintegrated(“3D”)
Runningcondi?onsdriven:
”thick”depletedsensiDvevolume
LHC&SLHC
Hybridpixelsensors,3Dsensors,VerDcallyintegrated(“3D”)
Future : 3D integrated pixel devices reduce the gap between the two main
optimization optionsTwotypesof3D:3Dsensors‐>CinziaDaVia3Dintergrateddevices‐>ChrisDanKiesling
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Harsh Running Conditions - SLHC
Improvement/evoluDonofhybridpixelsensors:SmallerCMOSfeaturesizemorecompactFEμcircuits
smallerpixelsoccupancy
ImprovedsensiDvevolumeradiaDonhardness
LargernumberofpixelspowerdissipaDonisanissue!
AlternaDvestohybridpixels:ParDcularlyinfashion:3Dsensors
Others:3Dintegrateddevices
300–400pile‐upeventsatstartoffill
wanttosurviveatleast3000�‐1datataking
B‐layerat37mm:
~30trackspercm‐2perbunchcrossing
>10161MEVn‐equivalentnon‐ionising
Few10sofMGray(10xLHC)
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ThinplanarpixelsfortheinnerlayersofthenewATLASpixelsystematSLHC:Atthesamevoltagethin(=overdepleted)detectorsareexpectedtohaveahigherelectricfieldthanthick(=parDallydepleted)detectors.Theycontributetokeepthematerialbudgetlow,whichisextremelyimportantintheinnerlayerstomaintaingoodtrackingperformances.
Results of a first characterization of the pixel structures on p-type wafers:
Lowleakagecurrents(<7nA/cm2for75μmstructures,<15nA/cm2for150μmstructures).DepleDonvoltagesaround20and80Vforthe75μmand150μmthickstructuresrespecDvelyHighVbreakforallthepixelstructuresproduced
Thin Planar Pixel Sensors
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3D Sensors
3‐darrayofpandnelectrodesthatpenetrateintothedetectorbulkLateraldepleDon:
Max.drilanddepleDondistancesetbyelectrodespacingReducedcollecDonDmeanddepleDonvoltageThickerdetectorspossibleLowchargesharing
BUT:non‐standard(planar)technology
Bothelectrodetypesareprocessedinsidethedetectorbulkinsteadofbeingimplantedonthewafer'ssurface.
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The Vertex Detector at the ILC
Need: Goodangularcoveragewithmanylayersclosetovertex:
|cosθ|<0.97.
Firstmeasurementatr~15‐16mm.5‐6layersouttor~60mm.
EfficientdetectorforverygoodimpactparameterresoluDon
Material~0.1%X0perlayer.
CapabletocopewiththeILCbeamstrahlungsbackground
ModestaveragepowerconsumpDon<100WSinglepointresoluDonbe�erthan3μm.
smallpixels,thinsensors,thinr/oelectronics,lowpower(gascooling)
Measureimpactparameter,chargeforeverychargedtrackinjets,andvertexmass.
FigureofmeritfortheVXD:
ImpactParameterResoluDon
(MarcWinter)
Accelerator a(µm) b(µm)
LEP 25 70
SLD 8 33
LHC 12 70
RHIC‐II 13 19
ILC <5 <10
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The Vertex Detector at the ILC
Innerlayer1.6MPixelsensorsOnceperbunch=300nsperframe:toofast
Oncepertrain~100hits/mm2:tooslow
5hits/mm2=>50μsperframe:maybetolerable (Note:fastestcommercialimaging~1ms/MPixel)
FourdifferenttechnologiesunderstudyforILCvertexdetectorCCD,DEPFET,CMOS,and3DdifferentvariantsofeachtechnologyapproachunderinvesDgaDon
Themainsplitisbetweenthese2categories:conDnuousread‐outinsidetrainsdelayedread‐outinbetweenconsecuDvetrains
369 ns
x2625
0.2 s
~1 ms
BunchTrain
BunchSpacing
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ILC: What's on the Pixel Market?
Accumula?onof~70‐150BX
1.cont.r/oduringtrain
CPCCD(LCFI)DEPFETMimosa(Strasbourgatal.)
2.storeandr/oinpause
CAPs(Hawaii)ISIS(LCFI)
Accumula?onofabout3000BX
FP‐CCD(KEK,JAXA/ISAS,TohokuUni)
single‐bunch?mestamping"hybridpixelsw/obumps"
3Dintegratedpixels(Fermilab)
SOI(Fermilab,LBNL)
ChronoPixels(Yale/Oregon)
DeepN‐WellMAPSSDR(INFNMilan,Pavia,RomaIIIUni.Bergamo,Insubria,Pavia)
Currentlythereareabout~10“candidates”fortheILCVTXDetector.
ThesetechnologieshavedifferentapproachestocopewithbeaminducedbackgroundattheILC
Allapproachesaimfor~3µmprecisionand<40mm2‐hitresoluDon
Targetmaterialbudgetis~0.1%X0perlayer
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DEPFET
DePletedFeld Effect Transistor fullydepletedsensiDvevolume
fastsignalriseDme(~ns),smallclustersize
nochargetransferneeded
fasterreadout
be�erradiaDontolerance
internalamplificaDon
largesignal,evenforthindevices
r/ocap.independentofsensorthickness
charge‐to‐currentconversion:gq=dId/dq≈1nA/electron,scaleswithgatelength
ChargecollecDonin"off"state,readoutondemand
Rowwiseread‐out("rollingshu�er”):selectrowwithexternalgate,readcurrent,clearDEPFET,readcurrentagainthedifferenceisthesignal
onlyonerowacDvelowpowerconsumpDon
But:for40kHzframerate25nsperrowlDEPFETisbaselinetechnologyforthevertexdetectorofSuperBelle
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Monolithic Active Pixels (MAPS)
e.g.Mimosa(MinimumIonizingParDcleMOSAcDvePixelSensor)
h
AcDveareaunderneaththeelectronics(epi‐layer<20µmthick)providing100%fill‐factorChargegeneratedbyionizaDonintheepitaxiallayerthermallydiffusetowardlowpotenDaln‐wellregionStandard,cost‐effecDveCMOSprocess,nopost‐processing
<20µm
FeaturesoftheMIMOSA–detectors:
SinglepointresoluDon1µm–3µm
Pixel–pitch10‐40µm
Thinningachieved50‐120µm
S/NforMIPs20–40
DetecDonefficiency>99%
RadiaDonhardness:1MRad;2x1013neq/cm²
ProducedinvariouscommercialCMOS‐processes
MimosaisbaselinetechnologyforthevertexdetectorofSTAR
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CCD based
Charge‐CoupledDevices(CCDs)Demonstratedinlargesystem(307Mpx)atSLD,butslow.
ColumnParallelCCDs(CPCCD)columnparallelreadout,withbump‐bondconnecDonson20µmpitchtoreadoutchipincludingamp,analogueCDS,ADCs,sparsificaDonandmemory
FPCCD(FinePixelCCD)–fullydepletedepi‐layertosuppressdiffusion
with5µmpixels,readoutoncepertrain;20Dmesfinerpixelgranularityinsteadof20Dmeslices
Image Sensor with In-Situ Storage (ISIS)Combines CCDs, active pixel transistors and edge electronics in one deviceCharge collected under a photo-gateCharge is transferred to 20-pixel storage CCD in situ, 20 times during the ~ 1 ms long bunch train
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DoubleCMOSPixelMacro(50μmpitch)forDmingMicro(5μmpitch)forpreciseposiDonBufferdataduring~3000bunchesinatrainandreadoutbetweenbunchtrains
SOIdetectorsareafirststeptoward3DintegraDonsinceitusesmanyofthesameprocessesas3DintegraDon(oxidebonding,waferthinning,viaformaDon)
ThintoplayerwithsiliconislandsinwhichPMOSandNMOStransistorsarebuilt.Aburiedoxidelayer(BOX)whichseparatesthetoplayerfromthesubstrate.HighresisDvitysubstratewhichformsthedetectorvolume.DiodeimplantsareformedbeneaththeBOXandconnectedbyvias.
Chronopixel and SOI
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Silicon detector size 1981 - 2006[m
2 ]
Space
HEP
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Summary
Solidstatedetectorsplayacentralroleinmodernhighenergyandphotonphysics
UsedintrackingdetectorsforposiDonandmomentummeasurementsofchargedparDclesandforreconstrucDonofverDces(speciallypixeldetectors)
Byfarthemostimportantsemiconductor:Silicon,indirectbandgap1.1eV,however:3.6eVnecessarytoformehpair
AdvantagesSi:largeyieldingeneratedchargecarriers,finesegmentaDon,radiaDontolerant,mechanicallystable,…
Workingprinciple(general)diodeinreversebias(pnjuncDon)
Important:S/Nhastobegood.Noise~1/Cforsystemsthatmeasuresignalchargesmallerfeaturesizesaregood.Pixel!
PixeldetectorsareusedinmostmajorcurrentparDcledetectorsandareplannedforfutureexperiment
R&Dforsemiconductordetectorsalwayshastobeontheedgeoftechnology
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Noise
detectorcapacity
darkcurrent
serialresistor
SegmentaDonintomanychannels
Noise Sources
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Resolution of Tracking Detectors
DependingondetectorgeometryandchargecollecDon
Strippitch
Chargesharingbetweenstrips
Simple case: all charge is collected by one stripTraversing particle creates signal in hit stripFlat distribution along strip pitch; no area is pronounced
Probability distribution for particle passage:
Simplecase:allchargeiscollectedinonestrip
Thereconstructedpointisalwaysthemiddleofthestrip:
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Resolution of Tracking Detectors II
CalculaDngtheresoluDonorthogonaltothestrip:
ResulDnginageneralterm(alsovalidforwirechambers):
Forasiliconstripdetectorwithastrippitchof80µmthisresultsinaminimalresoluDonof~23µm
Incaseofchargesharingbetweenthestrip(signalsizedecreasingwithdistancetohitposiDon)
ResoluDonimprovedbycenterofgravitycalculaDon
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Interactions of Particles with Matter
MaximumkineDcenergywhichcanbetransferredtotheelectroninasinglecollision
ExcitaDonenergy
DensitytermduetopolarizaDon:leadstosaturaDonathigherenergies
ShellcorrecDonterm,onlyrelevantatlowerenergies
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Interactions of Particles with Matter
MaximumkineDcenergywhichcanbetransferredtotheelectroninasinglecollision
ExcitaDonenergy
DensitytermduetopolarizaDon:leadstosaturaDonathigherenergies
ShellcorrecDonterm,onlyrelevantatlowerenergies
“relaDvisDcrise”“minimumionizingparDcles”βγ ≈ 3-4
“kinemaDcterm”
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Landau Distribution Silicon
mostprobableenergyloss
meanenergyloss
Bethe‐Blochdescribesaverageenergyloss
CollisionsstochasDcnature,henceenergylossisdistribuDoninsteadofnumber.
FirstcalculatedforthinlayerswasLandau.HenceenergylossisLandaudistributed.
SignalproporDonaltoenergyloss
Example:MonolithicacDvepixelsensorsensiDvelayer14um
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Literature
SemiconductorDetectorSystems,
HelmuthSpieler,OxfordUniversityPress2005
PixelDetectors–FromFundamentalstoApplica?onsL.Rossi,P.Fischer,T.Rohde,N.Wermes,SpringerVerlag2006
Evolu?onofSiliconSensorTechnologyinPar?clePhysicsFrankHartmann,SpringerVerlag2009
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N-type siliconSiO2
BB
As
n+
P+
n‐typewafersareoxidizedat1030oCtohavethewholesurfacepassivated.
Usingphotolithographicandetchingtechniques,windowsarecreatedintheoxidetoenableionimplantaDon.Differentgeometriesofpadsandstripscanbeachievedusingappropriatemasks.
ThenextstepisthedopingofsiliconbyionimplantaDon.DopantionsareproducedfromagaseoussourcebyionisaDonusinghighvoltage.Theionsareacceleratedinanalectricfieldtoenergyintherangeof10keV‐100keVandthentheionbeamisdirectedtothewondowsintheoxide.P+stripsareimplantedwithboron,whilephosphorousorarsenicareusedforthen+contacts.
Anannealingprocessat600oCallowsparDalrecoveryofthelatcefromthedamagecausedbyirradiaDon.
ThenextstepisthemetallisaDonwithaluminium,requiredtomakeelectricalcontacttothesilicon.Thedesiredpa�erncanbeachievedusingappropriatemasks.
Al
ThelaststepbeforecutngisthepassivaDon,whichhelpstomaintainlowleakagecurrentsandprotectsthejuncDonregionfrommechanicalandambientdegradaDon.
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Sincethemicro‐stripdetectorprovidesonlyonecoordinatewithgoodprecision,thesegmentaDonofthebackplaneisanaturalwaytoprovideasecondcoordinateandthusaspacepointwithoutaddingmaterialonthetrajectoryoftheparDcles.
Theuseofdouble‐sidedmicro‐stripdetectorsallowsthecorrelaDonofsignalscollectedonthetwosides,whichapartfromthereadoutelectronicsnoiseandresponseisthesame,thusreducingmulD‐hitambiguiDes.
+ + + + + +- - - - - -
SiO2 Al
n+
Al
n+
Fixed oxide charge
R≈ few kΩ
n-type
R > few kΩSiO2
Subdividingsimplythen+contactsthepresenceofposiDvechargeattheSi‐SiO2interfaceinducesinthen‐typesubstrateanaccumulaDonlayerofelectrons,resulDnginalowresistancebetweenthestrips.Thereforethesignalspreadsovermanyelectrodes,makingthesubdivisionineffecDve.
backplane
backplane
Al Al Al
n+ n+p+n-type
+ + + + + + -
- - -
- -
Amethodusedtosolvethisproblemistoimplantap+blockingstripinbetweenthen+ones.TheblockingstripsarelelfloaDng,sincetheirfuncDonisjusttointerrupttheconducDonchannel.
Double-Sided Strip Detectors
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Tevatron: D0
Barrelanddisc:stripdetectors
840kchannels
OperaDonalsince2002
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successfullylaunched11.June200816towermodules
37×37cm2acDvearea
2mminter‐towerseparaDontominimizetheinacDvearea
70m2ofSi(inspace!!!)
11500SSD8.95X8.95cm2,
384strips‐880,000channels
440μmthick
228μmstrippitch
GLAST Mission
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diamond sensor
Polycrystallineandsinglecrystal
Lowleakagecurrent,lownoise
Lowcapacitance
RadiaDonhardmaterial
OperaDonatroomtemperaturepossible
Drawback:50%signalcomparedtosiliconforsameX0Butbe�erS/NraDo(nodarkcurrent)
growth
substrate
Grain size: ~100-150μm
SuccessfultestofscCVDdiamondpixelmodule
StableoperaDon
FullchargecollecDonat0.25V/µm
Goodefficiency: ε>99.9%
MeasuredResoluDon:σ=8.9µm(200V,normalincidence)
scCVDmoduleretains~80%ofiniDalchargecollectedalerirradiaDonto0.7x1015p/cm2
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Tevatron: CDF
Si‐stripdetector
specialfeature:Layer00directlyonbeampipe
720kchannels
OperaDonalsince2002
Inner Strip Layers (ISL):
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Bonding
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Large scale silicon systems
The most critical parts are the sensors, ASICs and system engineering (mechanics, power, cooling, assembly, etc)
To develop and buy silicon sensors for several hundreds of m2 silicon sensors is not an easy task:
Extend previous Multi-Geometry studies to substrate thickness less than or equal the pitch
Strip/Pixel capacitance (back-plane, inter-strip/pixel & total)Critical fields, depletion and break-down voltageSensor functionality (charge collection efficiency etc)Detailed design parameters for masks
Extend previous studies from LHC to SLHC fluence – large irradiation programs neededExtend previous studies to include n-on-pRe-produce complementary sets of measurements and simulationStudy biasing, guard rings, isolation methods
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The International Linear Collider
Parameters:
√s=500GeV,tunablefrom200to500GeV,upgradeableto1TeV
∫Ldt=500�‐1in4years(peakluminosity2∙1034cm‐2s‐1)
e‐‐e+collider:two11kmSClinacsat31.5MV/m
DualtunnelconfiguraDon(safetyandaccessibility)
SingleIR,crossingangle14mrad,twodetectorsinpush‐pulloperaDon
SC Nb Cavity