Modeling of charge effects in dielectric films of radiation MOS sensors

Abstract

We have modeled the charge effects in radiation metal-oxide-semiconductor (MOS) sensors functioning in a wide range of electric fields including high-field injection of electrons into the dielectric film. In order to study the charge effects taking place in MOS sensors, we use the extended model suggested by us previously. The extended model, besides the accumulation of positive charge in the dielectric and the generation of the surface states at the interface, takes into consideration the accumulation of negative charge in the bulk of dielectric film caused by the electron capturing on traps. We demonstrate that the accumulation of the negative and positive charges in the bulk of the gate dielectric under high fields can significantly influence on the redistribution of electric fields inside the dielectric and, as a sequence, on change of the charge state of MOS structure which describes the sensor characteristics. We have ascertained that in order to properly utilize MOS sensors under high-field injection of electrons it has been necessary to take into consideration the possible capturing of electrons in the bulk of gate dielectric and adjust results of measurements with the model suggested.