Ultrathin gate-oxide breakdown-reversibility at low voltage

Solid-insulator breakdown always leads to a permanent conduction path that is irreversible. This is a built-in assumption in all gate-oxide breakdown reliability measurement and lifetime projection. This assumption is not valid when the gate-oxide thickness is less than 2 nm and the operation voltage is 1 V or less. The authors examine the impact of reversible breakdown using breakdown data from 12 000 devices stressed by plasma charging damage. The data support the notion that when the surge current is limited at breakdown, the breakdown event may not leave any mark such as a permanent conduction path. The implication is that the commonly used accelerated-stress test, such as time dependent dielectric breakdown (TDDB), may be underestimating the actual gate-oxide lifetime by as much as a million folds.