Positive-charge trapping in nitrided oxide and reoxidized nitrided oxide gate dielectrics

The charge-trapping characteristics of nitrided oxide and reoxidized nitrided oxide (ROXNOX) gate dielectrics following constant-current stressing are studied, with an emphasis on the behavior of positive trapped charge. The positive charge is attributed to slow donor states, which are created and ionized during electrical stress. Slow donor states are shown to be responsible for a reversible, bias- and temperature-dependent charge relaxation that is observed following electrical stress. The number of slow donor states created during stress is found to be a function of the nitridation and reoxidation conditions. Using optimized process conditions, ROXNOX dielectrics can be grown with essentially no slow donor states and, hence, with little relaxation.