A new algorithm for transforming exponential current ramp breakdown distributions into constant current TDDB space, adn the implcations for gate oxide Q_BD measurement methods

摘要

Charge-to-breakdown (Q_BD) is one of the manufacturing parameters that is used as a measure fo oxide quality. In this work the influence of the measurement conditions on Q_BD is examined, as well as the relationship between Q_BD and oxide thickness. Using oxides ranging from 45 to 80 A, two Q_BD measurement methods are employed: constant current stress (CCS) and an exponential current ramp (ECR). A variety of curret densities (for the constant current stress) adn step durations (for the exponential current ramp) are studied. It is shown that not only does Q_BD depend on oxide thickness, but that Q_BD depends strongly on the measurement conditions, adn that, depending on the test conditions, Q_BD can increase or decrease as he oxide thickness decrease. It is also shown that there is a strong agreement between the Q_BD measured with a constant current stress adn the Q_BD measure with an exponential current ramp. Finally, an algorithm is proposed for transforming ht eQ_BD distribution obtained form a series of exponential current ramps into the Q_BD and/or t_BD domains of constant current stressing.