A quantitative investigation of electron detrapping in SiO2 under Fowler–Nordheim stress

Abstract

Detrapping of the trapped electrons from the acceptorlike trapping sites in SiO2 under Fowler–Nordheim (FN) stress has been quantitatively investigated using Al/SiO2/Si capacitor structures. Before FN stress, the traps were charged using the avalanche electron injection technique to enhance subsequent detrapping, and facilitate its distinction from trapping in subsequent studies. The quantity of electrons detrapped was assessed from the shift in the electrical field strength near the cathode. Under FN stress with an electrical field of 8 MV/cm or over, the probability of captured electrons remaining trapped was found to be less than 20%. This probability was insensitive to the number of electrons initially trapped in the oxide, decreasing as the stressing field strength increases. Within the experimental range of this study, the transient behavior of electron detrapping cannot be satisfactorily described by the dynamic balance model and a new model is developed based on the reactions occurring in the oxide under FN stress. It is found that there is more than one mechanism contributing to the electron detrapping and that the detrapping efficiency is unrelated to the initial capture cross sections of traps.