1. Eija Tuominen 26.09.2003 DEVELOPMENT OF RADIATION HARD DETECTORS Helsinki Institute of Physics (HIP) In close cooperation with: Microelectronics Centre, Helsinki University of Technology, Finland Accelerator Laboratory, University of Jyväskylä, Finland Okmetic Ltd., Finland Ioffe PTI, Russia Brookhaven National Laboratory, USA University of Hamburg, Germany CERN RD39 & RD50

2. Eija Tuominen 26.09.2003 OUTLINE 1.Why Radiation Hard Detectors 2.Why Czochralski Silicon Detectors 3.Detector Processing 4.Detector Characterization 5.Detectors in Particle Beam 6.Radiation Hardness of the Detectors

3. Eija Tuominen 26.09.2003 WHY RADIATION HARD RADIATION DETECTORS Silicon particle detectors are cost effective and have excellent position resolution. Exposure of the silicon material to particle radiation causes irreversible defects that deteriorate the performance of the silicon detectors Our approach: oxygen in silicon

4. Eija Tuominen 26.09.2003 WHY CZOCHRALSKI SILICON DETECTORS I 1.Radiation hardness * Oxygen increases the radiation hardness of silicon detectors * Cz-Si intrinsically contains oxygen, 10 17 -10 18 cm -3 2.Cost-effectiveness * Cz-Si wafers are cheaper than traditional Fz-Si wafers * Large area wafers available -> possibility for large detectors -> cost-effectiveness for front-end electronics, interconnection and module assembly

5. Eija Tuominen 26.09.2003 WHY CZOCHRALSKI SILICON DETECTORS II 3.High oxygen concentration allows some additional benefits * Depletion voltage of detectors can be tailored by adjusting a) oxygen concentration in the bulk b) thermal history of wafers (Thermal Donor killing) WHY NOT BEFORE? * 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) * Cz-Si of resistivity  5k  cm reported: T.Abe and W.Qu, High resistivity CZ silicon for RF applications substituting GaAs”, Electrochemical Society Proc. Vol. 2000-17 (2000) 491-500.

6. Eija Tuominen 26.09.2003 DETECTOR PROCESSING Simple Fabrication Process: 4 Lithographies 2 Ion implantations 2 Thermal dry oxidations 3 Sputter metal depositions Processed at the Clean Room of Helsinki University of Technology Microelectronics Center (MEC) Silicon Material: * 4” single side polished * nominal resistivity 900  cm * thickness 380 um * grown by magnetic Czochralski method (MCZ) -> oxygen concentration is ”low” <10 ppma and well controlled

7. Eija Tuominen 26.09.2003 DETECTOR CHARACTERIZATION I: ELECTRICAL PROPERTIES Large Area Detectors: A = 32.5 cm 2 I L (900 V) = 3 uA V fd = 420 V (380 um) No Breakdown <1000V = Good Detectors for Silicon Trackers Measured at HIP/Kumpula, Oulu University, and CERN

8. Eija Tuominen 26.09.2003 DETECTOR CHARACTERIZATION II: CHARGE CARRIER LIFETIMES Cz-SiFz-Si Measured by Photoconductive Decay (PCD) method at Helsinki University of Technology, Electron Physics Laboratory

9. Eija Tuominen 26.09.2003 DETECTION PERFORMANCE Measured by HIP Silicon Beam Telescope at CERN * eight silicon detectors * front-end electronics with VA1 chips * commercial ADC * PC based DAQ Resolution  10 um Efficiency  95 % Signal/Noise  10 = Good Detectors

10. Eija Tuominen 26.09.2003 RADIATION HARDNESS Proton irradiations: Similar results with gamma and neutron irradiations (results to be published)

11. Eija Tuominen 26.09.2003 CONCLUSIONS Czochralski silicon detectors were processed and studied: Electrical performance: depletion voltage, leakage current, breakdown voltage - GOOD Detection performance: resolution, efficiency, signal-to-noise - GOOD Radiation hardness: EXCELLENT ! More info: Eija Tuominen, Doctoral Thesis (and its publications), ”Development of Radiation Hard Radiation Detectors”, to be publicly examined at 10.10.2003 at Helsinki University of Technology http://www.hut.fi/~emtuomin/Thesis.pdf