Analysis of time dependent dielectric failures

The Time Dependent Dielectric Breakdown (TDDB) has been studied for silicon dioxide by using a staircase voltage ramping technique. The result of the ramp tests on MOS capacitors indicates a definitive substrate effect on the TDDB, which manifests itself as an enhancement of the intermediate field breakdown in the breakdown histogram. The substrate effect observed may be caused by the oxygen impurities of the starting material. This conclusion is based on the observed fact that the gate oxide grown on the high oxygen content Czochralski wafers (35 ppm) shows the breakdown enhancement, while the gate oxide grown on the low oxygen content (<1ppm) float-zone wafers does not.