DEVELOPMENT OF RADIATION HARD DETECTORS

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


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


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


WHY CZOCHRALSKI SILICON DETECTORS I

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


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 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.


DETECTOR PROCESSING

Simple Fabrication Process:4 Lithographies 2 Ion implantations2 Thermal dry oxidations3 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


DETECTOR CHARACTERIZATION I:ELECTRICAL PROPERTIES

Large Area Detectors: A = 32.5 cm2 IL(900 V) = 3 uAVfd = 420 V (380 um)No Breakdown <1000V

= Good Detectors for Silicon Trackers

Measured at HIP/Kumpula, Oulu University, and CERN


DETECTOR CHARACTERIZATION II:CHARGE CARRIER LIFETIMES

Cz-Si Fz-Si

Measured by Photoconductive Decay (PCD) method at Helsinki University of Technology, Electron Physics Laboratory


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 umEfficiency 95 %Signal/Noise 10= Good Detectors


RADIATION HARDNESS

Proton irradiations:

Similar results with gamma and neutron irradiations(results to be published)


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

DEVELOPMENT OF RADIATION HARD DETECTORS

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