High-field breakdown in thin oxides grown in N/sub 2/O ambient

A detailed study of time-dependent dielectric breakdown (TDDB) in N/sub 2/O-grown thin (47-120 AA) silicon oxides is reported. A significant degradation in breakdown properties was observed with increasing oxide growth temperatures. A physical model based on undulations at the Si/SiO/sub 2/ interface is proposed to account for the degradation. Accelerated breakdown for higher operating temperatures and higher oxide fields as well as thickness dependence of TDDB are studied under both polarities of injection. Breakdown under unipolar and bipolar stress in N/sub 2/O oxides is compared with DC breakdown. An asymmetric improvement in time-to-breakdown under positive versus negative gate unipolar stress is observed and attributed to charge detrapping behavior in N/sub 2/O oxides. A large reduction in time-to-breakdown is observed under bipolar stress when the thickness is scaled below 60 AA. A physical model is suggested to explain this behavior. Overall, N/sub 2/O oxides show improved breakdown properties compared with pure SiO/sub 2/.<
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