Study of shallow bulk traps in thin nitrided oxide films by thermal re-emission of electrons trapped at high field

Abstract

The temperature and field dependence of high-field electron trapping and thermal re-emission of trapped electrons in thin nitrided oxide films at temperatures ranging from 100 to 423 K are investigated. It is found that, when the temperature decreases, the effective surface density of electron traps in nitrided oxide films increases, while for thin SiO 2 film it decreases. The electron trap capture cross-section of thermal oxide and nitrided oxide films is about 10 −19 and 10 −16 cm 2, respectively. Discrete shallow bulk traps in the nitrided oxide are identified. It is suggested that traps with activation energies between 0.046 and 0.072 eV are related to nitrogen. On the other hand, traps having activation energies larger than 0.1 eV are due to hydrogen and Si dangling bonds. Depending on the nitridation duration, the shallow trap density varies from a few percent to over 30% of the total trap density and the energy levels become shallower as the nitridation continues.