Ultrathin silicon oxide films 5ndash;6 nm thick have been grown in a doublehyphen;walled furnace and annealed in N2and Ar at temperatures varying between 850 and 1100thinsp;deg;C. The breakdown field distribution obtained is very tight and centered above 11 MV/cm for ashyphen;grown oxides at 850thinsp;deg;C. The oxides that received a posthyphen;oxidation anneal (POA) at 1000thinsp;deg;C show a consistent improvement in breakdown field distribution and breakdown charge density as compared to the oxides annealed at lower temperatures. Furthermore, under high field current stress, oxides with a POA at 1000thinsp;deg;C show a positive voltage flatbandVfbshift, while oxides with POA at a temperatureT1000thinsp;deg;C show a negativeVfbshift. These results point out the efficacy of a highhyphen;temperature POA of 5ndash;6 nm oxides on breakdown strength and on the reduction of some defects responsible for the positive charge trapping.
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