Münster 2017 – scientific programme
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T: Fachverband Teilchenphysik
T 92: Strahlenschäden (gemeinsam mit HK)
T 92.2: Talk
Wednesday, March 29, 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 Nox, the interface traps Nit 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 Nox increases and decreases as function of dose depending on the
field direction in the SiO2. An increase of Nit 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.