Correlation between Si–SiO2 heterojunction and Fowler–Nordheim conduction mechanism after soft breakdown in ultrathin oxides

A stress-induced defect band model is proposed to investigate the Fowler–Nordheim tunneling characteristics of ultrathin gate oxides after soft breakdown. Soft breakdown occurs when the average distance between stress-induced defects locally reaches a critical value to overlap the bound electron wavefunction on adjacent defects and to form a defect band. This model shows that an n+-poly-Si/N-SiO2/p-Si heterojunction structure is formed between electrodes at a local area after a soft breakdown in the ultrathin SiO2 and the soft breakdown current can be described in terms of the Fowler–Nordheim tunneling process with a barrier height of ∼1 eV.