Observation of oxide breakdown and its effects on the characteristics of ultra-thin-oxide nMOSFET's

Ultra-thin gate oxide breakdown in nMOSFET's has been studied for an oxide thickness of 1.5 nm using constant voltage stressing. The pre- and post-oxi de breakdown characteristics of the device have been compared, and the resu lts have shown a strong dependence on the breakdown locations, The oxide br eakdown near the source/drain-to-gate overlap regions was found to be more severe on the post-breakdown characteristics of the device than breakdown i n the channel. This observation may be related to the dependence of breakdo wn on the distribution of electric field and areas of different regions wit hin the nMOSFET under stress.