eija tuominen siena 22.10.2002 test beam results of a large area strip detector made on high...
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Eija Tuominen Siena 22.10.2002
TEST BEAM RESULTS OF A LARGE AREA STRIP DETECTOR MADE ON HIGH
RESISTIVITY CZOCHRALSKI 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
Univesity of Hamburg, Germany
Accelerator Laboratory, University of Jyväskylä, Finland
CERN RD39 & RD50
Eija Tuominen Siena 22.10.2002
OUTLINE
1. Czochralski grown silicon
2. Wafer characteristics
3. Device processing
4. Test beam results
5. Conclusions
Eija Tuominen Siena 22.10.2002
WHY CZ-Si AS A DETECTOR SUBSTRATE
1. Radiation hardness* Oxygen increases the radiation hardness of silicon detectors* Cz-Si intrinsically contains oxygen, 1017-1018 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
Eija Tuominen Siena 22.10.2002
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 bulkb) 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 5kcm reported: T.Abe and W.Qu, High resistivity CZ silicon for RF applications substituting GaAs”, Electrochemical Society Proc. Vol. 2000-17 (2000) 491-500.
Eija Tuominen Siena 22.10.2002
WAFER CHARACTERISTICS
* 4” single side polished * nominal resistivity 900 cm * thickness 380 um * orientation <100> * oxygen concentration <10 ppma
* grown by magnetic Czochralski method (MCZ) -> oxygen concentration is ”low” and well controlled
Eija Tuominen Siena 22.10.2002
DEVICE PROCESSINGSimple fabrication process:
4 Lithographies 2 Ion implantations2 Thermal dry oxidations3 Sputter metal depositions
Large area detectors: A=32.5 cm2 IL(900 V) = 3 uAVfd = 420 V (380 um)
Eija Tuominen Siena 22.10.2002
HELSINKI SILICON BEAM TELESCOPE (hardware)
* Situated at the CERN H2 beam * eight silicon strip detectors* front-end electronics with VA1 chips
Eija Tuominen Siena 22.10.2002
HELSINKI SILICON BEAM TELESCOPE(software)
* Analog to Digital Converter with programmable DSP* PC based data acquisition with on-line monitoring* Separate off-line analysis
Eija Tuominen Siena 22.10.2002
BEAM TEST RESULTS
Resolution 10 umEfficiency 95 %Signal/Noise 10
Eija Tuominen Siena 22.10.2002
CONCLUSIONS
Full size (32.5 cm2) Cz-Si strip detectors were processed
Electrical performance:Depletion voltage 420VLeakage current 3A@900V No breakdown under 900V
Detector performance:Resolution 10 umEfficiency 95 %S/N 10
Radiation hardness:being tested by gamma, proton and neutron beams