Structural dependence of dielectric breakdown in ultra-thin gate oxides and its relationship to soft breakdown modes and device failure

For the first time, we report strong channel-length dependence and weak channel-width dependence of soft breakdown modes and device failure for ultra-thin gate oxides. For channel lengths around 0.2 mu m, oxide-breakdown events in FETs cause a sharp increase in FETs off-current which permanently degrades the switching performance of short-channel devices; this is not observed for longer channel length FETs. The results also indicate that both hard- and soft-breakdown events have a common origin but manifest themselves differently depending on the test structure and geometry being measured.