Anomalous breakdown behavior in ultrathin oxides and oxynitrides under dynamic electrical stress

Time-dependent dielectric breakdown (TDDB) and high-field stress-induced leakage behavior of ultrathin oxide (40-110 AA) under static and dynamic electrical stress conditions were investigated. Both thermally grown oxides and oxynitrides prepared by oxidation in N/sub 2/O were used for comparison. For thicker dielectrics, it was found that the charge-to-breakdown (Q/sub BD/) values are much larger when the dielectrics were stressed under bipolar waveform than those under unipolar. However, for thinner oxides (<60 AA), TBBD behavior is significantly worse under bipolar stressing. The anomalous behavior can be explained by the weak spot region of a fixed thickness at the polycrystalline silicon/oxide interface.<
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