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Material developments for the HL-LHC upgrade of the CMS tracker . 19 January 2012 Joachim Erfle University of Hamburg. Overview. The tracker and its challenges at HL-LHC Some layout possibilities for a new tracker and sensor modules The basic working principle of silicon sensors

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Material developments for the HL-LHC upgrade of the CMS tracker

Material developments for the HL-LHC upgrade of the CMS tracker

19 January 2012

Joachim Erfle

University of Hamburg

overview
Material developments for the HL-LHC upgrade of the CMS tracker Overview
  • The trackeranditschallengesat HL-LHC
  • Somelayoutpossibilitiesfor a newtrackerandsensormodules
  • The basicworkingprincipleofsiliconsensors
  • A campaignto find thenexttracker‘ssensor material
  • First resultsofthiscampaign
the current tracker
Material developments for the HL-LHC upgrade of the CMS tracker The currenttracker
  • Over 200m2activesilicon
  • About 26000 sensors
  • 9.6 millionstripchannels + 66 millionpixelchannels
challenges for the tracker at hl lhc
Material developments for the HL-LHC upgrade of the CMS tracker Challengesforthetrackerat HL-LHC
  • Requiredfeaturesfor HL-LHC:
  • Higher radiationtolerance
  • More (smaller) channelsfor a loweroccupancyat high pile-up
  • Trigger informationforlevel 1

New trackerneeded

strip sensors
Material developments for the HL-LHC upgrade of the CMS tracker Strip sensors

Basic layoutof a stripsensor

Depletionof a n-bulksensor

  • Basicallytwo different types:
  • N dopedbulk:
    • Holes readout
    •  slower
    • Easiertoproduce
    • Tendstoundergotype inversion
  • P dopedbulk:
    • Electronreadout
    •  faster, lesstrapping
    • Harder toproduce

Depletionof a p-bulksensor

radiation damage in silicon
Material developments for the HL-LHC upgrade of the CMS tracker Radiation damage in silicon
  • Twotypesofradiationdamage:
    • Surfacedamage
    • Bulkdamage mainproblemforhadronicirradiation
      • Subdivided in threedamagetypes:

courtesyofM. Moll, UHH CERN

Reduceschargecollection

Increasesleakagecurrent

Changeseffectivedopingconcentration

 fulldepletionvoltage

goals of the hkp c ampaign
Material developments for the HL-LHC upgrade of the CMS tracker Goals ofthe HKP-campaign
  • The mainchallengesforthetrackeratthe HL-LHC will be:
      • Higher radiation dose (upto a fluenceofΦeq= 1016 cm-2)
      • Higher occupancy
  • The currenttrackerwould not withstandtheradiationand also developoccupancyproblems
  • → Find bestbestsuitablesilicon material andlayoutfor a futuretrackingdetector
  • Toachievethatweinvestigate a large varietyofmaterials:
      • Different oxygen, carbon,… content
      • Different bulkdoping (n and p)
  • Test sensor geometries andlayouts
  • Irradiationswithneutronsor/andprotonstosimulate HL-LHC radiation dose
silicon material
Material developments for the HL-LHC upgrade of the CMS tracker Silicon material
  • Ofeach material thereare 3 different types:
    • n-type (N)
    • Two different stripisolationtechnologiesfor p-bulk:
    • p-type with p-stop (P)
    • p-type with p-spray (Y)
wafer processing deep diffusion
Material developments for the HL-LHC upgrade of the CMS tracker Wafer-Processing (deep diffusion)
  • At high irradiation thick sensors not fully depletable
  • Mean free path of charge carriers severely reduced due to trapping for highly irradiated sensors
  • → In thin sensors less charge is trapped and
  • voltage needed for full depletion is lower.
  • Standard method for thinning: wafer bonding of Si to Si-substrate (low ohmic)
    • Well known process
    • Relatively expensive
  • New method: deep diffusion
    • Active volume of a 320μm wafer reduced by diffusing high doping from the back.

activevolume

inactivevolume

activethickness

pn-junction

physicalthickness

sequence of measurements and irradiations
Material developments for the HL-LHC upgrade of the CMS tracker SequenceofMeasurementsandirradiations

courtesyof A. Dierlamm, KIT

HL-LHC: Lint=3000 fb-1

Prequalification

First irradiation

Single irradiationqualification

Second irradiation

Measurementsand time development

ofdefect (annealing) studies

courtesyofS. Müller, KIT

i rradations
Material developments for the HL-LHC upgrade of the CMS tracker Irradations

HL-LHC: Lint=3000 fb-1

  • Neutrons: 1 MeV (TRIGA Reactor Ljubljana)
  • Protons: 23 MeV (Karlsruhe cyclotron)

courtesyofS. Müller, KIT

v olume current versus fluence
Material developments for the HL-LHC upgrade of the CMS tracker Volume current versus fluence

protons

neutrons

neutrons

protons

currentsaremeasured after annealingof 10 min@ 60°C at 0°C andscaledto 20°C

J. Erfle, UHH

Currentsmatchexpectedvaluefromliterature (M. Moll‘sthesis) withintheuncertainties. -> dose measurementsare ok.

type inversion and the effective doping
Material developments for the HL-LHC upgrade of the CMS tracker Type-inversion andtheeffectivedoping

Partlydepletedsensor, not type inverted

  • Defectsclosetothebandgapperformlikedopants, so theychangetheeffectivedopingbyproviding a freeelectronor hole
  • Influence on:
  • Fulldepletionvoltage
  • Type ofbulkdoping
  • Possibleproblems:
  • fulldepletionvoltagecanriseabovethevaluethatcanbeapplied
  • Ifthathappens in the type invertedcase, thechargemeasurementisdisturbed

Effectivethicknessreduced,

but fullyfunctional

Partlydepletedsensor, type inverted

Readoutchannelsaresomewhat „isolated“ fromcollectedcharge

n eff for different materials irradiations
Material developments for the HL-LHC upgrade of the CMS tracker Nefffor different materials / irradiations

n-type

protons

J. Erfle, UHH

neutrons

J. Erfle, UHH

capacitancesaremeasuredat 0°C, 1kHz after annealingof 10min@60°C

All measured n-type materials (FZ andMCz) are type-inverted after neutronorprotonirradiation.

n eff for different materials irradiations1
Material developments for the HL-LHC upgrade of the CMS tracker Nefffor different materials / irradiations

n-type

p-type

protons

J. Erfle, UHH

J. Erfle, UHH

neutrons

J. Erfle, UHH

capacitancesaremeasuredat 0°C, 1kHz after annealingof 10min@60°C

J. Erfle, UHH

All n-type materialsundergo type inversion

No p-type material undergoes type inversion

All p-type materialsshow a steepincrease in Neffandthereforedepletionvoltage

time resolved charge collection measurement with tct shows type inversion
Material developments for the HL-LHC upgrade of the CMS tracker Time resolvedchargecollectionmeasurementwith TCT shows type inversion

Front

Rear

E

red

depth

FZ320N

- holes

- electrons

FZ320P

courtesyof J. Lange

unirradiated

p@3E14

Laser: 672 nm, red

3µm penetrationdepth

courtesyof T. Pöhlsen, UHH

courtesyof T. Pöhlsen, UHH

not type inverted

U=600V

type inverted

U=300V

type inversionof FZ andMCz n-type materialsisconfirmedby TCT.

Signals aremeasuredat 0°C, after annealingof 10min@60°C

cce of diodes after p@3e14
Material developments for the HL-LHC upgrade of the CMS tracker CCE ofdiodes, after p@3E14

infrared

redlaser, front injection

infraredlaser

courtesyof J. Lange

unirradiated

p-type:

hole

collection

n-type

p-type

n-type:

electron

collection

courtesyof T. Pöhlsen, UHH

courtesyof T. Pöhlsen, UHH

measurementsareperformedat 0°C and 600V, with 20ns integration time

infraredlaser: CCE isabout 90%

Electronsonly: CCE ~ 85%, holescollectiononly: CCE ~ 67%

Electronreadoutperformsbetter

s ignal of fz320p baby sensor after p@3e14
Material developments for the HL-LHC upgrade of the CMS tracker Signal of FZ320P babysensor, after p@3E14

Signal inducedby a 90Sr source, readoutbyALiBaVa

Vdepl

CCE of FZ320 p-type isabout 87% at p@3E14, comparedto non-irradiated

measurementsareperformedat -20°C

courtesyof K. Hoffman, KIT

some experimental structures
Material developments for the HL-LHC upgrade of the CMS tracker

Idea to reduce occupancy and increase resolution

To be able to read out from the sides, inner strips are routed out in the first metal layer

Some experimental structures

Strip-sensor with integrated Pitchadapter in the first metal layer

Strixel-sensor

  • Pitchadapter needed for readout-chip connection
  • Is it possible to integrate it on the sensor without loosing active area?

courtesyofA. Kornmayer, KIT

first results for integrated pitch adapter
Material developments for the HL-LHC upgrade of the CMS tracker First results for integrated pitch adapter

courtesyofA. Kornmayer, KIT

courtesyofA. Kornmayer, KIT

Electron from a Sr90-source

at different positions

Reduced S/N in PA-region, noise stays constant

Flat S/N in standard region of about 17

first results for strixel sensors
Material developments for the HL-LHC upgrade of the CMS tracker First results for strixelsensors

Electron from a Sr90-source at near area

Electron from a Sr90-source at far area

1. far neighbour

1. near neighbour

1. near neighbour

1. far neighbour

Seed strip (near)

Seed strip (far)

1. near neighbour

Signal in the far area only measured on strips in the far area.

Signals in near area appear also on far strips

1. far neighbour

courtesyofA. Kornmayer, KIT

Seed strip (far)

conclusions
Material developments for the HL-LHC upgrade of the CMS tracker Conclusions
  • HL-LHC: CMS needscompletelynewtrackingdetectors:
    • Higher granularity
    • More radiationtolerance
    • HPK-campaign to identify Si-material, polarity, sensor-layout
  • First results:
  • Diode currents increase as a function of fluence as expected
  • Neff shows:
    • - type inversion for all n-type materials
    • - no type inversion for p-type, with steep increase
    • Not expected:
  • CCE with baby sensors and diodes reduced to ~90% after 3E14 proton irradiation
outlook
Material developments for the HL-LHC upgrade of the CMS tracker Outlook
  • More irradiations to come: Higher fluences!
  • Trying to understand material properties in detail
  • Full annealing studies to be done
  •  Definethe material andlayouttobeused in the Phase II upgrade ofthetracker

ThankYou !

cce of fz320 after proton irradiation
Material developments for the HL-LHC upgrade of the CMS tracker CCE of FZ320 after protonirradiation

courtesyof T. Pöhlsen

measurementsareperformedat 0°C

tct pulses p type
Material developments for the HL-LHC upgrade of the CMS tracker TCT pulses – p-type

FZ200P

FZ320P

MCZ200P

courtesyof T. Pöhlsen

courtesyof T. Pöhlsen

courtesyof T. Pöhlsen

300V

600V

250V

measurementsareperformedat 0°C, using a redlaser

not type inverted

tct pulses n type
Material developments for the HL-LHC upgrade of the CMS tracker TCT pulses – n-type

FZ200N

FZ320N

MCZ200N

courtesyof T. Pöhlsen

courtesyof T. Pöhlsen

courtesyof T. Pöhlsen

300V

300V

200V

type inverted

measurementsareperformedat 0°C, using a redlaser