Low-temperature conduction mechanisms of 3-nm-thick post-soft breakdown SiO/sub 2/ films

The experimentally determined conduction mechanisms of gate leakage current are examined for two different soft-breakdown events: analog-soft-breakdown and digital-soft-breakdown. It is strongly suggested that neither variable-range-hopping conduction nor space-charge-limited conduction, by themselves, form the major part of possible conduction mechanisms after analog-soft-breakdown events. On the other hand, it is found that the incremental gate current after digital-soft-breakdown events can be expressed in a simple closed form as functions of temperature and gate voltage; the expression indicates that the post-digital-soft-breakdown current is not ruled by a simple or single conduction mechanism.