Defect Size Effect and Defect Band Conduction of Ultrathin Oxides After Degradation and Breakdown

In this letter, the relationship between gate oxide degradation and defect band formation is investigated quantitatively based on the 1-D linear chain model of defects. Results show that degradation as a defect band occurs when the local defect distance reaches a critical value to make the bound-electron wave function overlap within adjacent defects; that the degradation oxide energy band is composition; that there is a defect band in the oxide band gap, besides the ordinary conduction band, which contributes to the electron tunneling current; and that both Weibull slope and defect current increase with decreasing defect spacing. Therefore, the variation of defect size and leakage current after degradation and breakdown of ultrathin SiO₂ can be explained by the change of defect distance ratio.