Breakdown characteristics of ultra thin gate oxides following field and temperature stresses

Abstract

Here, we investigate the reliability of silicon dioxide layers for two different thickness values (8 and 4.5 nm). The time to breakdown ( t bd) was determined using constant voltage stress (CVS) under different experimental conditions. The first set of data, which was used to determine the activation energy, corresponds to t bd at fixed electric field and different temperatures. The second set of data was obtained at fixed temperature and increasing electric field and was used to determine the field acceleration factor. It is shown that both activation energy and field acceleration factor can be used to determine the lifetime and the reliability of the gate oxide. For the thinner oxide, we observed a different behavior. In fact, during the CVS of the 4.5 nm thick oxide a quasi-breakdown phenomenon was found. The light emission which occurred during this phenomenon was investigated.