AN INVESTIGATION OF CHARGE STATES IN ELECTRON IRRADIATED LOW NITRIDED SILICONDIOXIDE FILMS

MOS-structures with pure SiO2-films, with nitrided Si-SiO2 interface region and with an insulator layer with uniform weak nitridation were irradiated with 2 MeV electron beam in steps between 10 krad (SiO2) and 2 Mrad (SiO2) with and without an electrical field. The electrical characterisation with CV-(Capacitance-Voltage) and DLTS- (Deep Level Transient Spectroscopy) method gives us information about the charge states in this structure. The electron irradiation generates electron-hole pairs and a positive gate field effects a hole drift to the interface, where we can find a positive oxide charge and a rising interface density. The amount of density is a function of nitridation and of the electron beam dose. The best electrical stability under irradiation induced hole injection is to be found in an uniform nitrided SiO2 layer