eija tuominen siena 22.10.2002 test beam results of a large area strip detector made on high...

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