6th ROSE Workshop - CERN 23/24 October 2000
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6th ROSE Workshop - CERN 23/24 October 2000. Performances after irradiation of Micron oxygenated and ST standard silicon microstrip detectors and diodes. Riccardo Rando , Dario Bisello, Nicola Bacchetta University of Padova & INFN Padova. Samples.

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6th ROSE Workshop - CERN 23/24 October 2000

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6th ROSE Workshop - CERN 23/24 October 2000

Performances after irradiation ofMicron oxygenated and ST standard silicon microstrip detectors and diodes

Riccardo Rando,

Dario Bisello, Nicola Bacchetta

University of Padova & INFN Padova


  • Multiguard diodes and full size detectors (CDF-L00)

  • Silicon: Wacker, float zone

  • Crystal orientation: <100>

  • Manufacturers:

    • ST Microelectronics (ST) - Catania, Italy

    • Micron Semiconductors (Micron) – UK

  • Resistivity: 2 KWcm (ST), 7 KWcm (Micron)

  • Oxygen concentration:

    • ST: standard (not oxygenated)

    • Micron: oxygenated


      from deposition and drive-in (110 hrs @ 1100°C)

      from implant and drive-in (110 hrs @ 1000°C)


  • Neutrons: TRIGA reactor at the Jozef Stefan Institute, Ljubljana, Slovenia (kLju=0.9)

    • single fluence of 2·1014 neutrons/cm2

      • Micron oxygenated samples

  • Protons: 63MeV at the University of California - Davis, USA (k63MeV=1.62)

    • 2.8·1013 protons/cm2

    • 1.1·1014 protons/cm2

      • Micron oxygenated and ST standard samples

  • Thermal Annealing

    • Neutron irradiated samples:

      • Annealing for 4 min at 80 °C

    • Proton irradiated samples:

      • Annealing for 80 min at 60 °C

    Effective Doping Concentration

    • For neutron irradiated Micron oxygenated samples there are no benefits from using oxygenated substrates: DVDEP=345 V

      after 2·1014 neutrons/cm2

    • For protons irradiated Micron oxygenated samples: DVDEP=205 V

      after 1.11·1014 protons/cm2

       ST standard samples show performances similar to Micron oxygenated devices after 1.11·1014 protons/cm2

       Neff values agree with previous results

    Neff for ST devices

    Data from M.Moll

    5th Rose Workshop

    • ST devices, even if on standard silicon, have DNeffvalues similar to the oxygenated Micron devices after substrate type inversion

      Data are renormalized to 24 GeV protons using standard K factors

    Leakage Current

    • Neutrons:

      • Micron oxygenated

        DJ=7.4 mA/cm3


        at the highest fluence

    • Protons:

      • Micron oxygenated

      • ST standard

        Current is smaller than expected if the proton fluence is normalized to 1 MeV equivalent neutrons by the standard k value

    Detectors Leakage Current (Protons)

    Hardness Factor k (Protons)

    Assuming that after the standard thermal cycle of 80 min at 60°C the a value for 1 MeV equivalent neutrons is 4*10-17 A/cm, we find that the hardness factor for 63 MeV protons is smaller than expected and it shows a dependence on substrate type

    a Annealing

    • Micron oxygenated diode after 1.11·1014 63 MeV protons/cm2

    • Once taken into account the difference in the k factor, our normalized a values are close to data from other authors

    Measurements on detectors confirm very well data taken on diodes(1)

    Micron oxygenated detectors behave very well even after heavy irradiation (~2·1014 1 MeV eq.n/cm2)

    ST standard detectors have performances similar to Micron oxygenated ones

    Microstrip Detectors

    • No change was measured on coupling capacitance and bias resistance

    • Interstrip resistance >10 GW

    • Interstrip capacitance decreases by increasing the bias voltage as expected, down to values equal to those measured before irradiation

    (1) when appropriate we have scaled the results in order to take into account the difference in volume between detectors and diodes and no significant difference has been found

    Micron oxygenated detectors with an oxygen concentration of 1017 cm-3 are found to be radiation hard

    Micron oxygenated devices will be used in the L00 vertex detector for the CDF experiment at FNAL. L00 will be ready to take data on March 1st 2001. Total fluence expected: 1014 1 MeV equivalent neutrons/cm2

    Micron Oxygenated Detectors

    A high oxygen concentration in the substrate ensures radiation hardness

    Even standard (not oxygenated) detectors can be radiation hard

    The crystal orientation and the resistivity of the substrate, as well as the processing play an important role


    • Neff changes following previous results for fluences up to 2·1014 1 MeV equivalent neutrons/cm2

      a values are smaller than expected for 63 MeV protons. This behaviour will be further investigated, even though it agrees with 7-10 MeV (M. Moll et al.) and 21 MeV (J. Wyss et al.) proton irradiations

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