THE STATISTICS OF DIELECTRIC-BREAKDOWN IN MOS CAPACITORS UNDER STATIC AND DYNAMIC VOLTAGE STRESS

The statistics of dielectric breakdown at fields greater than equivalent to 8 MV/cm has been studied under both static (constant voltage) and dynamic (ramped voltage) conditions. MOS capacitors of the same size and from the same wafer were used for all measurements. Data from both types of test conformed to a Weibull distribution. The Weibull parameters a and b, which determine the time and field dependence of breakdown, were calculated from static tests at various applied fields and independently from dynamic tests at various ramp-rates. The values of a and b were: a approximately equals 0. 24; b approximately equals 6. 89 and a approximately equals 0. 34; b approximately equals 6. 55, from static and dynamic tests respectively. The similarity of the values for the two pairs of Weibull parameters suggests that breakdown proceeds by the same mechanism in both types of test.