Fast wafer level reliability assessment of ultra thick oxides under impact ionization conditions

The ramp rate dependent effect of impact ionization on the MOS-C IV-characteristic of ultra thick oxides during linear voltage ramp dielectric breakdown measurements is investigated. The results obtained open an extension to a recent proposed fast wafer level reliability (fWLR) technique with special attention to compensating for impact ionization (ii) effects. Once the compensation is achieved mathematically, time-dependent dielectric breakdown (TDDB) data can be generated/calculated and used for further lifetime calculations. The basic idea behind the method extension is that the Fowler-Norheim (FN) theory is valid, but the applied electrical field is not the oxide field. Using E_ox + DeltaE_ox (due to positive charge trapping) instead of V_g/t_ox yields a stress profile that accounts for impact ionization effects.