10 angstroms u00e5 in thickness may be stressed at about 3 v to 4 v on the other hand an ild about 0 5 microns u03bc in thickness between interconnect metals with a spacing of about 0 3 u03bc to about 0 4 u03bc for 45 nanometer nm technology may be stressed up to about 30 v to 40 v i e about 20 v or 25 v unipolar 0 to v peak and bipolar u2212 v peak to v peak capacitance stressing can be achieved by varying the v bias and v osc levels fig5 shows capacitance measurement results in three different modes dc unipolar and bipolar all three samples started with the same capacitance about 2 35e 12 farads f and at the same temperature of 100 u00b0 c as illustrated in fig5 the application of a dc voltage of 13 5 v caused a breakdown at about 40 seconds the application of a unipolar ac voltage oscillating between 13 5 v and ground caused a breakdown at about 100 seconds and the application of a bipolar ac voltage oscillating between 13 5 v and u2212 13 5v caused no breakdown even after 600 seconds the systematic improvement in tddb lifetime from dc to unipolar to bipolar can easily be quantified and used in product lifetime projections embodiments of the present disclosure can achieve several technical effects including allowing uninterrupted real ac stress which can be sensed for dielectric breakdown in very high time resolution the applied ac frequency can be very high and is only limited by the frequency limits of the test system which is impossible using conventional methods the increase in lifetimes demonstrated by ac detection can be used to push the limits of both projected lifetimes for products having different operating frequencies and also.