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Study of X-ray radiation damage in silicon sensors

Zhang, J. LU ; Fretwurst, E. ; Klanner, R. ; Perrey, H. LU ; Pintilie, I. ; Poehlsen, T. and Schwandt, J. (2011) In Journal of Instrumentation 6(11).
Abstract

The European X-ray Free Electron Laser (XFEL) will deliver 30,000 fully coherent, high brilliance X-ray pulses per second each with a duration below 100 fs. This will allow the recording of diffraction patterns of single complex molecules and the study of ultra-fast processes. Silicon pixel sensors will be used to record the diffraction images. In 3 years of operation the sensors will be exposed to doses of up to 1 GGy of 12 keV X-rays. At this X-ray energy no bulk damage in silicon is expected. However fixed oxide charges in the insulating layer covering the silicon and interface traps at the Si-SiO 2 interface will be introduced by the irradiation and build up over time. We have investigated the microscopic defects in test... (More)

The European X-ray Free Electron Laser (XFEL) will deliver 30,000 fully coherent, high brilliance X-ray pulses per second each with a duration below 100 fs. This will allow the recording of diffraction patterns of single complex molecules and the study of ultra-fast processes. Silicon pixel sensors will be used to record the diffraction images. In 3 years of operation the sensors will be exposed to doses of up to 1 GGy of 12 keV X-rays. At this X-ray energy no bulk damage in silicon is expected. However fixed oxide charges in the insulating layer covering the silicon and interface traps at the Si-SiO 2 interface will be introduced by the irradiation and build up over time. We have investigated the microscopic defects in test structures and the macroscopic electrical properties of segmented detectors as a function of the X-ray dose. From the test structures we determine the oxide charge density and the densities of interface traps as a function of dose. We find that both saturate (and even decrease) for doses between 10 and 100 MGy. For segmented sensors the defects introduced by the X-rays increase the full depletion voltage, the surface leakage current and the inter-pixel capacitance. We observe that an electron accumulation layer forms at the Si-SiO2 interface. Its width increases with dose and decreases with applied bias voltage. Using TCAD simulations with the dose dependent parameters obtained from the test structures, we are able to reproduce the observed results. This allows us to optimize the sensor design for the XFEL requirements. In addition the Si-SiO2 interface region has been studied with time resolved signals induced by sub-nanosecond 660 nm laser light, which has a penetration of about 3 μm in silicon. Depending on the biasing history, humidity and irradiation dose, losses of either electrons or holes or no charge losses are observed. The relevance of these results for the sensor stability and performance is under investigation.

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author
; ; ; ; ; and
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Instrumentation for FEL, Radiation damage to detector materials (solid state), Solid state detectors, X-ray detectors
in
Journal of Instrumentation
volume
6
issue
11
article number
C11013
publisher
IOP Publishing
external identifiers
  • scopus:82955225047
ISSN
1748-0221
DOI
10.1088/1748-0221/6/11/C11013
language
English
LU publication?
no
id
f4e71aae-fb24-49af-8f24-be0e24adb1e6
date added to LUP
2019-01-07 15:56:20
date last changed
2022-03-14 09:26:00
@article{f4e71aae-fb24-49af-8f24-be0e24adb1e6,
  abstract     = {{<p>The European X-ray Free Electron Laser (XFEL) will deliver 30,000 fully coherent, high brilliance X-ray pulses per second each with a duration below 100 fs. This will allow the recording of diffraction patterns of single complex molecules and the study of ultra-fast processes. Silicon pixel sensors will be used to record the diffraction images. In 3 years of operation the sensors will be exposed to doses of up to 1 GGy of 12 keV X-rays. At this X-ray energy no bulk damage in silicon is expected. However fixed oxide charges in the insulating layer covering the silicon and interface traps at the Si-SiO <sub>2</sub> interface will be introduced by the irradiation and build up over time. We have investigated the microscopic defects in test structures and the macroscopic electrical properties of segmented detectors as a function of the X-ray dose. From the test structures we determine the oxide charge density and the densities of interface traps as a function of dose. We find that both saturate (and even decrease) for doses between 10 and 100 MGy. For segmented sensors the defects introduced by the X-rays increase the full depletion voltage, the surface leakage current and the inter-pixel capacitance. We observe that an electron accumulation layer forms at the Si-SiO<sub>2</sub> interface. Its width increases with dose and decreases with applied bias voltage. Using TCAD simulations with the dose dependent parameters obtained from the test structures, we are able to reproduce the observed results. This allows us to optimize the sensor design for the XFEL requirements. In addition the Si-SiO<sub>2</sub> interface region has been studied with time resolved signals induced by sub-nanosecond 660 nm laser light, which has a penetration of about 3 μm in silicon. Depending on the biasing history, humidity and irradiation dose, losses of either electrons or holes or no charge losses are observed. The relevance of these results for the sensor stability and performance is under investigation.</p>}},
  author       = {{Zhang, J. and Fretwurst, E. and Klanner, R. and Perrey, H. and Pintilie, I. and Poehlsen, T. and Schwandt, J.}},
  issn         = {{1748-0221}},
  keywords     = {{Instrumentation for FEL; Radiation damage to detector materials (solid state); Solid state detectors; X-ray detectors}},
  language     = {{eng}},
  month        = {{11}},
  number       = {{11}},
  publisher    = {{IOP Publishing}},
  series       = {{Journal of Instrumentation}},
  title        = {{Study of X-ray radiation damage in silicon sensors}},
  url          = {{http://dx.doi.org/10.1088/1748-0221/6/11/C11013}},
  doi          = {{10.1088/1748-0221/6/11/C11013}},
  volume       = {{6}},
  year         = {{2011}},
}