Development of Particle Detectors made of Czochralski Grown Silicon

Transcription

1 Development of Particle Detectors made of Czochralski Grown Silicon Helsinki Institute of Physics, CERN/EP, Switzerland Microelectronics Centre, Helsinki University of Technology, Finland Okmetic Ltd., Finland Ioffe PTI, Russia Brookhaven National Laboratory, USA CERN RD39 & RD50 Accelerator Laboratory, University of Jyväskylä, Finland

2 OUTLINE Czochralski grown silicon as a detector substrate Processing Electrical performance Test beam results Conclusions

3 WHY CZ-Si AS A DETECTOR SUBSTRATE 1. Radiation hardness * Oxygen increases the radiation hardness of silicon detectors * Cz-Si intrinsically contains oxygen, cm Cost-effectiveness * Cz-Si wafers are cheaper than traditional Fz-Si wafers * Large area wafers available -> possibility for large detectors -> cost-effectiveness for frontend electronics, interconnection and module assembly

4 WHY CZ-Si AS A DETECTOR SUBSTRATE 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 intrest on high resistivity Cz-Si (=lower substrate losses of RF-signal) * Cz-Si of resistivity 5kΩcm reported: T.Abe and W.Qu, High resistivity CZ silicon for RF applications substituting GaAs, Electrochemical Society Proc. Vol (2000)

5 DEVICE PROCESSING Processed at the Clean Room of Helsinki University of Technology Microelectronics Center Cz-Si substrate: 4 single side polished, nominal resistivity 900 Ωcm, thickness 380 um, orientation <100>, oxygen concentration <10 ppma grown by magnetic Czochralski method -> oxygen concentration is low and well controlled

6 Very simple fabrication process: 4 Lithographies 2 Ion implantations 2 Thermal dry oxidation 3 Sputter metal depositions DEVICE PROCESSING II

7 ELECTRICAL CHARACTERIZATION 3,5 0, Current(m A) 2,5 2 1,5 1 Cz-Si detector Fz-Si detector 1/C2 0,0020 0,0015 0,0010 Fz-Si Cz-Si 0,5 0, Voltage(V) Cz Si: I L (900 V) = 3 ua Fz Si: I L (900 V) = 1.1 ua A=32.5 cm 2 0, Voltage (V) Cz Si: V fd = 420 V (380 um) Fz Si: V fd = 340 V (525 um)

8 LIFETIME CHARACTERIZATION Cz-Si Fz-Si Measured by Photoconductive Decay method

9 DEFECT CHARACTERIZATION by Elena Verbitskaya N T =5.4*10 10 cm -3 Cz-Si N T =3.5*10 9 cm -3 Fz-Si Shallow level E c -0.27eV, N T =1*10 11 cm -3 Cz-Si N T =3*10 11 cm -3 Fz-Si Midgap level E c -0.56eV, DLTS peaks: C. T. Sah and C. T. Wang, J. Appl. Phys. 46 (1975) 1767.

10 HELSINKI SILICON BEAM TELESCOPE AT CERN H2 TEST STATION * eight silicon detectors * front-end electronics with VA1 chips * commercial ADC * PC based DAQ

11 BEAM TEST RESULTS Resolution 10 um Efficiency 95 % Signal/Noise 10

12 CONCLUSIONS Full size (32.5 cm 2 ) Cz-Si strip detectors were processed Electrical performance: Depletion voltage 420V Leakage current 3µA@900V No breakdown under 900V Detection performance: Resolution 10 um Efficiency 95 % S/N 10 Radiation hardness: being tested by gamma, proton and neutron beams