1. 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/

2. 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. Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007 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 Helsinki Esa Tuovinen loading MCz-Si wafers into oxidation furnace at the Microelectronics Center of Helsinki University of Technoly, Finland.

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

5. Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007 5 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 (I leak ) increases 10 X - Increased heat dissipation - Increased shot noise 2. Full depletion voltage (V fd ) will be >1000V 3. Trapping will limit the Charge Collection efficiency (CCE). - CCE at 1×10 15 cm -2 ≈ 50%(strip layers of S-LHC Tracker) - CCE at 1×10 16 cm -2 ≈ 10-20% (pixel layers of S-LHC Tracker)

6. Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007 6 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 detector operational conditions CERN-RD39 “Cryogenic Tracking Detectors”

7. Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007 7 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 V fd. * 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 ?

8. Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007 8 Requirements for detector applications High resistivity Oxygen concentration 5-10×10 17 cm -3 Homogeneity High minority carrier lifetime Oxygen donor compensation Boron/Aluminum contamination Okmetic Oyj is world’s 8 th largest Si wafer manufacturer with about 340 employers and 50M€ turnover

9. Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007 9 Radiation hardness of MCz-Si Proton radiation: Less prone for V fd increase than std Fz-Si or Diffusion oxygenated Fz-Si Neutron 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. Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007 10 Charge Collection Efficiency Measurement with IR laser and 500V bias Pad detectors >> no weighting field effect >> test beam for strip detectors needed >1×10 15 cm -2 fluence MCz (300μm) and epi (150μm) are under depleted both Unpublished preliminary data. 10% error bars should be assumed

11. Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007 11 Does MCz-Si type invert ? TCT raw data indicates SCSI and Double Junction With Trapping Correction signal is manipulated by multiplying measured signal × e 4.2ns/time i.e. by monotonosly increasing function >> no SCSI G.Kramberger 4 th RD50 Workshop, CERN, May 2004

12. Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007 12 Type inversion and Double Junction A. Messineo, Tracker Upgrade Workshop 8 th February 2007. MCz-Si 7×10 14 n eq /cm 2 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

13. Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007 13 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. V fd can be tailored by Thermal Donors (TD) in MCz-Si >> CCE geometrical factor is improved. Single sided process. Type inversion p > n

14. Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007 14 Why to go low temperatures ? The detrapping time-constant depends exponentially on T If a trap is filled (electrically non- active) the detrapping time-constant is crucial Example: A-center (O-V at E c -0.18 eV with  10 -15 cm 2 ) ECEC EVEV Hole trap Electron trap T> 77K Hole trap T< 77K filled Electron trap ECEC EVEV Fill Freeze

15. Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007 15 RD39 Cryogenic Transient Current Technique (C-TCT) With C-TCT it is possible to measure and extract -Full depletion voltage V fd -Charge Collection Efficiency (CCE) -Type of the space charge (n or p) -Trapping time constant τ e,h - Electric field distibution E(x) IR laser signal equivalent to 1 MIP Characterization of heavily irradiated detectors

16. Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007 16 Charge Injected Detector CID log J log V Ohmic, J ~ V SCLC, J ~ V 3/2 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 detectors material properties. *CID is insensitive on type of irradiation. *CID is insensitive on reverse annealing of radiation defects >> importnant in HEP applications. *Treshold for sharp current increase V T increases with respect of fluence *V T can be affected by temperature VTVT Together with Ioffe PTI and BNL (V.Eremin, E.Verbitskaya, Z. Li)

17. Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007 17 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 I leak At 2.5x10 15 cm -2 J leak ≈16μA/cm 2 @ 500V Same device measured in Current Injected Detector (CID) mode J leak ≈4μA/cm 2 at 500V and 200K Is 200K feasible for future Tracker upgrades ?

18. Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007 18 Summary CCE at 3×10 15 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 V fd. Material/defect engineering of Si does not provide any improvement for I leak Current injection (CID) provides 2X higher 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 V fd by TDs.

19. Jaakko Härkönen,Workshop on Silicon Detector Systems for the CBM Experiment at FAIR, Darmstadt 20.04.2007 19 References General reference: RD50 homepage and Status Reports Processing of MCz-Si J. 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-Si E. 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.