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

3

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

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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

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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

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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

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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

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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

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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

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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