A quantitative physical model for time-dependent breakdown in SiO2

A quantitative physical breakdown model for thin SiO2 is developed. The physical mechanism responsible fcor oxide breakdown has been reexamined and found to be hole trapping at localized areas. A quantitative model is built on this physical understanding of the wearout mechanism. Using this model, which considers electron injection, hole generation and charge trapping during electrical stresses and their effects on oxide I-V characteristics, all commonly used reliability tests can be simulated. Results are presented for constant-voltage, constant-current and ramp-voltage stress tests. One important result of the model is that log(tBD) of constant-voltage accelerated test is a linear function of 1/Eox, not Eox. The elctcric field dependence of log(QBD) is the same as that of the hole generation rate ¿. The correlation between ramp-voltage stress and constant-voltage stress is treated in detail, and an analytical expression relating the two is presented. This correlation provides a method and a theoretical basis for substituting the time-consuming tBD test with the simple ramp-voltage breakdown test.