Net positive-charge buildup in various MOS insulators due to high-field stressing

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Abstract
The buildup of net positive charge with field stressing has been observed in all thermally grown oxides, viz. dry, pyrogenic, reoxidized nitrided oxides (RNO), and reoxidized nitrided pyrogenic oxides (RNPO). The authors observed a faster rate of growth of net positive charge for dry oxides given a postmetalization anneal (PMA) in hydrogen than for those given a PMA in nitrogen; the fastest growth of net positive charge, however, was observed in pyrogenic oxides. It has been observed that in dry and pyrogenic oxides the positive-charge growth as a function of time obeys a power law with time under the stress of constant current or voltage. On the other hand, growth of positive charge in RNO and RNPO shows a two-piece linear growth of positive charge. These results suggest that positive-charge growth at high fields is related to both the hydrogen concentration and its drift in the oxide.