A temperature-independent field acceleration parameter &ggr; and a field-independent activation energy&Dgr;H0can be produced when different types of disturbed bonding states are mixed during time-dependent breakdown testing ofSiO2thin films. While &ggr; for each defect type alone has the expected1/Tdependence and&Dgr;H0shows a linear decrease with electric field, a nearly temperature-independent &ggr; and a field-independent&Dgr;H0can result when two or more states are mixed. ©1997 American Institute of Physics.