Microstrip Detector R&D at Helsinki Institute of Physics

Microstrip Detector R&D at Helsinki Institute of Physics

J. Härkönen, E. Tuovinen, P. Luukka, E. Tuominen and J. Tuominiemi

Helsinki Institute of Physics

ANDCERN RD50 Collaboration- Radiation hard

semiconductor devices for very high luminosity colliders

http://rd50.web.cern.ch/rd50/

Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007

2

Outline

• HIP detector activities• Radiation hard detector R&D

at CERN• Radiation hardness by

material and device engineering

• Magnetic Cz-Si detectors• Low temperature operation of

heavily irradiated Si detectors• Summary• References

MCz-Si strip detector with 1024 channels attached to the APV read out module


3

Detector activities at HIP

• HIP has been appointed by Finnish government to coordinate the Finnish participation in CERN experiments.

• The main activity is to participate to the upgrade program of CMS experiment

• We participate in two CERN R&D collaborations: RD39 and RD50.

• We have our own detector fabrication process at Micro and Nanofabrication Centre of Helsinki University of Technology.

• Detector system tests in particle beams and by cosmic rays utilizing e.g. FinnCRack and Silicon Beam Telescope (SiBT) located at CERN H2 area.

• Bonding facility in HelsinkiEsa Tuovinen loading MCz-Si wafers into oxidationfurnace at the Microelectronics Center of HelsinkiUniversity of Technoly, Finland.


4

Radiation hard detector R&D at CERN

CERN RD50 Collaboration- Radiation hard semiconductor devices for very high luminosity colliders

http://rd50.web.cern.ch/rd50/

Spokespersons: Michael Moll (CERN) and Mara Bruzzi (INFN Florence)

CERN RD39 Collaboration- Cryogenic Tracking Detectors

http://www.hip.fi/research/cms/tracker/RD39/php/home.php

Spokespersons: Jaakko Härkönen (HIP) and Zheng Li (Brookhaven National Lab)


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R&D Challenge of LHC Upgrade

• Luminosity increase by factor of 10 is foreseen after the 1st phase of the LHC experiments.

• Extensive R&D is required because

1. Leakage current (Ileak) increases 10 X

- Increased heat dissipation- Increased shot noise

2. Full depletion voltage (Vfd) will be >1000V

3. Trapping will limit the Charge Collection efficiency (CCE). - CCE at 1×1015 cm-2 ≈ 50% (strip layers of S-LHC

Tracker)- CCE at 1×1016 cm-2 ≈ 10-20% (pixel layers of S-

LHC Tracker)


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• Defect Engineering of Silicon– Understanding radiation damage

• Macroscopic effects and Microscopic defects

• Simulation of defect properties & kinetics

• Irradiation with different particles & energies

– Oxygen rich Silicon• DOFZ, Cz, MCz, EPI

– Oxygen dimer & hydrogen enriched Si– Pre-irradiated Si– Influence of processing technology

• New Materials– Silicon Carbide (SiC), Gallium Nitride (GaN)– Diamond: CERN RD42 Collaboration

• Device Engineering (New Detector Designs)– p-type silicon detectors (n-in-p)– thin detectors– 3D and Semi 3D detectors– Stripixels

Approaches to develop radiation harder tracking detectors

Scientific strategies:

I. Material engineering

II. Device engineering

III. Change of detectoroperational conditions

CERN-RD39“Cryogenic Tracking Detectors”


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Why Cz-Si ?

• Cz-Si available in larger diameters

• Lower wafer cost

• Better compatibility with advanced CMOS processes

• Oxygen brings significant improvement in thermal slip resistance

• Oxygen gives significant radiation hardness advantage in

terms of reduced incease of Vfd.

* No demand for high resistivity Cz-Si -> No availability* Price for custom specified ingot 15,000 € - 20,000 €* Now RF-IC industry shows interest on high resistivity Cz-Si

(=lower substrate losses of RF-signal)

Why not before ?


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Requirements for detector applications

High resistivity Oxygen concentration 5-10×1017 cm-3

Homogeneity High minority carrier lifetime

0

1000

2000

3000

4000

0 500 1000 1500 2000

Distance from seed /mm

Res

istiv

ity /

Ohm

cm

p-type

n-type

Oxygen donor compensation

Boron/Aluminum contamination

Okmetic Oyj is world’s 8th largest Si wafer manufacturerwith about 340 employers and 50M€ turnover


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Radiation hardness of MCz-Si

0

100

200

300

400

0 1·1014 2·1014 3·1014 4·1014 5·1014 6·1014

eq (1 MeV equivalent neutrons/cm2)

Vde

p(V

)

FZ, E=10 MeVFZ, E=20 MeVFZ, E=30 MeVDOFZ, E=10 MeVDOFZ, E=20 MeV

MCZ, E=10 MeVMCZ, E=20 MeVMCZ, E=30 MeV

Proton radiation: Less prone for Vfd increase than std Fz-Si or Diffusion oxygenated Fz-SiNeutron radiation: No significant difference

Gamma radiation: Increase of positive space charge.

Z.Li, J. Härkönen, E. Tuovinen, P. Luukka et al., Radiation hardness of high resistivity Cz-Si detectors after gamma, neutron and proton radiations, IEEE Trans. Nucl. Sci., 51 (4) (2004) 1901-1908.

Leakage current and trapping: No significant improvement.


10

Charge Collection Efficiency

Measurement with IR laserand 500V bias

Pad detectors >> no weightingfield effect >> test beam for strip detectors needed

trappingdrttrappinglGeometrica e

d

wCCECCECCE /

>1×1015 cm-2 fluence MCz (300μm) and epi (150μm) are under depleted both

Unpublished preliminary data. 10% error bars should be assumed


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Does MCz-Si type invert ?

TCT raw data indicates SCSI and Double Junction

With Trapping Correction signal is manipulated by multiplying measured signal × e4.2ns/time i.e. by monotonosly increasing function >> no SCSI

G.Kramberger 4th RD50 Workshop, CERN, May 2004


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Type inversion and Double Junction

0 50 100 150 200 250 3000

1x104

2x104

3x104

24 GeV protons 2.1x1015 cm-2

Reactor neutrons 5x1014 cm-2

Ele

ctric

Fie

ld [V

/cm

]

x [m]

A. Messineo, Tracker Upgrade Workshop 8th February 2007. MCz-Si 7×1014 neq/cm2 by 50 MeV protons

•When under depleted, the 1. Peak dominates•The 2. Peak takes over when bias is increased

What really matters ?

-What happenes to cluster resolution after certain dose ? >> Beam test for strip detectors needed


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Why to make p-type detectors ?

• No type inversion.• Collecting junction remains on the

segmented side (higher E-field due to the weighting field).

• Charge collection is dominantly electron current >> less trapping.

• Vfd can be tailored by Thermal Donors (TD) in MCz-Si>> CCE geometrical factor is improved.

• Single sided process.

Type inversion p > n


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Why to go low temperatures ?

The detrapping time-constant depends exponentially on T

kTECth

td eNv /

1

If a trap is filled (electrically non-

active) the detrapping time-constant is crucial

Example: A-center (O-V at Ec-0.18 eV with 10-15 cm2 )

T(K) 300 150 100 77 60 55 50 48 47 46

d 3.7 ns 3.9 s 4 ms 2 s 1.22 hrs

1.2 days

53 days

302 days

2.1 years

5.47

years

EC

EV

Hole trap

Electron trap

T> 77K

Hole trap

T< 77K

filled

filled

Electron trap

EC

EV

Fill Freeze


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RD39 Cryogenic Transient Current Technique (C-TCT)With C-TCT it is possible to measure and extract -Full depletion voltage Vfd

-Charge Collection Efficiency (CCE) -Type of the space charge (n or p)

-Trapping time constant τe,h

- Electric field distibution E(x)

IR laser signal equivalent to 1 MIP

Characterization of heavily irradiated detectors


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Charge Injected Detector CID

log J

log V

Ohmic, J ~ V

SCLC, J ~ V3/2

DL saturation

Diode

Current voltage characteristic

Features of CID*Electric field shape is not affected by fluence >> E-field exists at S-LHC conditions*E field exists regardless of thickness*Low temperature makes possible to keep forward current at μA range*No breakdown problem due to self-adjusted electric field by space charge limited current feedback effect*CID is quite insensitive on detectorsmaterial properties. *CID is insensitive on type of irradiation. *CID is insensitive on reverse annealing ofradiation defects >> importnant in HEP applications.

*Treshold for sharp current increase VT increases with respect of fluence*VT can be affected by temperature

VT

Together with Ioffe PTI and BNL (V.Eremin, E.Verbitskaya, Z. Li)


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CCE of CID detector

CCE 100%

CCE 65%

CCE 27%

•Measurement with C-TCT•In CID mode CCE 65% (200K)vs normal reverse bias operation 27%at (240K)

•No material dependence in Ileak

•At 2.5x1015 cm-2 Jleak≈16μA/cm2 @ 500V•Same device measured in Current InjectedDetector (CID) mode Jleak≈4μA/cm2

at 500V and 200K•Is 200K feasible for future Tracker upgrades ?


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Summary

•CCE at 3×1015 cm-2 is about 25%. Thus, MCz-Si is feasible for strip layers but not for pixel barrel.

•The CCE is limited by trapping and elevated Vfd.

•Material/defect engineering of Sidoes not provide any improvementfor Ileak

•Current injection (CID) provides 2Xhigher CCE at 200K.

•Cooling is a demanding challenge.

•MCz-Si shows better radiation hardness against protons than Fz-Si materials. No improvement against neutron and no difference in leakage current.

•CCE can further be improved by implementing n+/p-/p+ structure and compensate Vfd by TDs .


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References• General reference: RD50 homepage and Status Reports

• Processing of MCz-SiJ. Härkönen et al, Processing microstrip detectors on Czochralski grown high resistivity silicon, NIMA 514 (2003) 173-179. M. Bruzzi et al.,Thermal donor generation in Czochralski silicon particle detectors,NIMA 568 (2006) 56-60. J. Härkönen et al, p+/n- /n+ Cz-Si Detectors Processed on p-Type Boron-Doped Substrates With Thermal Donor Induced Space Charge Sign Inversion, IEEE TNS 52 (2005) 1865 - 1868.

• Radiation hardness of MCz-SiE. Tuominen et al.,Radiation Hardness of Czochralski Silicon studied by 10 MeV and 20 MeV protons.IEEE TNS 50 (1) (2003) 1942-1946. Z. Li et al,Radiation Hardness of High Resistivity Magnetic Czochralski Silicon Detectors After Gamma, Neutron and Proton Radiations, IEEE TNS 51 (4) (2004) 1901-1908. P. Luukka et al,Results of proton irradiations of large area strip detectors made on high-resistivity Czochralski silicon, NIMA 530 (2004) 117-121. E. Tuovinen et al.,Czochralski silicon detectors irradiated with 24 GeV/c and 10 MeV protons,NIMA 568 (2006) 83-88.

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Microstrip Detector R&D at Helsinki Institute of Physics

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