Progressive breakdown in ultrathin SiON dielectrics and its effect on transistor performance

The post-breakdown conduction properties of ultrathin SiON layers were investigated, to determine the impact of various parameters on the growth of a breakdown path after its formation. Post-breakdown conduction is seen to be dependent on stress voltage used to break the oxide, the stress temperature, and the time-to-breakdown. With this knowledge, the performance of transistors of various channel lengths and widths was studied both before and after breakdown occurred to determine whether the devices still function as a digital switches after breakdown. That is, the drain to source current (Ids) in the on-state (Vg ≫ Vth) is much larger than Ids in the off-state (Vg < Vth), allowing the device to continue to function as a switch, after breakdown occurs.