Speaker
Joern Schwandt
(Institute for Experimental Physics, Hamburg University, Germany)
Description
The European X-ray Free Electron Laser (XFEL) will deliver 30,000 fully coherent, high brilliance X-ray pulses per second with a duration below 100 fs. This will allow to record diffraction patterns of single molecules and study ultra-fast processes.
One of the detectors under development for the XFEL is the Adaptive Gain Integrating Pixel Detector (AGIPD), which consists of a classical hybrid pixel array with readout ASICs bump-bonded to a silicon sensor with pixels of $200 \times 200$ $\mu$m$^2$.
The particular requirements for the detector are a high dynamic range (0, 1 up to $10^5$ 12 keV photons/XFEL-pulse), a distance between XFEL-pulses of 200 ns, and doses up to 1 GGy of 12 keV X-rays for 3 years of operation. At these X-ray energies no bulk damage in silicon is expected. However fixed oxide charges in the SiO$_{\text{2}}$ layer and interface traps at the Si-SiO$_{\text{2}}$ interface will build-up.
We have investigated as function of the 12 keV X-ray dose the microscopic defects in test structures and the macroscopic electric properties of segmented sensors. From the test structures we have determined as function of dose the oxide charge density, the density of interface traps and their properties. We find that both saturate (and even decrease) for doses above a few 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. In addition an electron accumulation layer forms at the Si-SiO$_{\text{2}}$ interface which increases with dose and decreases with applied voltage.
Using TCAD simulations with the dose dependent parameters obtained from the test structures, we are able to reproduce the results of the measurements. This allows us to optimize the sensor design for the XFEL requirements.
Preferred medium (Oral/poster)
Oral
Author
Joern Schwandt
(Institute for Experimental Physics, Hamburg University, Germany)
Co-authors
Eckhart Fretwurst
(Institute for Experimental Physics, Hamburg University, Germany)
Ioana Pintilie
(National Institute of Materials Physics, Romania)
Jiaguo Zhang
(Institute for Experimental Physics, Hamburg University, Germany)
Robert Klanner
(Institute for Experimental Physics, Hamburg University, Germany)
