microstrip detector r&d at helsinki institute of physics
DESCRIPTION
Microstrip Detector R&D at Helsinki Institute of Physics . J. Härkönen, E. Tuovinen, P. Luukka, E. Tuominen and J. Tuominiemi Helsinki Institute of Physics. AND CERN RD50 Collaboration- Radiation hard semiconductor devices for very high luminosity colliders http://rd50.web.cern.ch/rd50/. - PowerPoint PPT PresentationTRANSCRIPT
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
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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
Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007
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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.
Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007
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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)
Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007
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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)
Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007
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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”
Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007
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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 ?
Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007
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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
Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007
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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.
Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007
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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
Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007
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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
Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007
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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
Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007
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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
Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007
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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
Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007
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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
Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007
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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)
Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007
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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 ?
Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007
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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 .
Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007
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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.