Second breakdown behavior in bipolar ESD protection devices during low current long duration stress and its relation to moving current-tubes

Bipolar ESD protection devices subjected to low current long pulse stress can sustain a relatively long time during thermal second breakdown without any damage. The effect is related to a particular current filamentary behavior, which is observed optically by TIM and explained by device simulation. It is also shown that the second breakdown is initiated at the edges of the device when a moving current-tube arrives at the device edge. Thus circular devices, having no edges, exhibit lower risk of second breakdown.