Münster 2017 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 92: Strahlenschäden (gemeinsam mit HK)

T 92.2: Vortrag

Mittwoch, 29. März 2017, 17:00–17:15, F 234

X-ray dose and electric field dependence of oxide charges at the Si-SiO₂ interface of high-ohmic Si — •Ioannis Kopsalis, Eckhart Fretwurst, Erika Garutti, Robert Klanner, and Joern Schwandt — Institute for Experimental Physics, Hamburg University, Luruper Chaussee 149, D-22761 Hamburg, Germany

The surface radiation damage of the Si-SiO₂ system on high-ohmic Si has been investigated. Circular p- and n-MOSFETs biased to an electric field of about 500 kV/cm at the Si-SiO₂ interface, have been irradiated up to an X-ray dose of about 17 kGy(SiO₂). From the measured drain-source current the change of oxide charge density during irradiation has been determined. Cycling the gate voltage before and after irradiation the oxide charge density N_ox, the interface traps N_it and the charging and discharging of border traps as function of X-ray dose and field direction has been determined. The study has been performed for two field directions at an electric field of 500 kV/cm, which according to TCAD simulations is the maximum field at the Si-SiO₂ interface in segmented sensors under normal operation.
The N_ox increases and decreases as function of dose depending on the field direction in the SiO₂. An increase of N_it has been observed for all the conditions. The observations predict that the position dependence of the electric field at the Si-SiO₂ interface in segmented silicon sensors will result in a non-uniform oxide charge density due to surface damage. The results presented can be used to improve simulations of the surface radiation damage of silicon sensors.