MONITORING TRAPPED CHARGE GENERATION FOR GATE OXIDE UNDER STRESS

A measurement method to extract the respective quantities and centroid s of positive and negative trapped charges, i.e., Q(p) and Q(n), gener ated by the negative current stress for gate oxides is proposed and de monstrated, The method is based on neutralization of Q(p) by a low pos itive current stress to differentiate the effects of Q(p) and Q(n). Fr om the extracted quantities and centroids of Q(p) and Q(n) of negative ly stressed oxides, it was found that Q(p) and Q(n) are generated near the oxide/substrate interface and Q(p) is initially much larger than Q(n). After the continuous stressing, Q(p) saturates and moves closer to the interface, but Q(n) keeps increasing and moves away from the in terface, especially for those oxides after the post-poly anneal (PPA) treatment, Q(n) is very unstable and easily neutralized, either by a s mall stress of opposite polarity or the same polarity, For the latter, Q(n) is mainly dependent on the level of the final stressing field.