A Current Pulse Screening Test for Metal Step Coverage

The response of aluminum thin films to single shot, constant current pulses was investigated to seek a ZAP test method for screening out inadequate metal coverage. At current density J, constant cross section stripes melt and open in time durations, tm and to respectively, which obey adiabatic heating laws J2tm - Km and J2to = Ko if heating time is sufficiently brief to minimize heat loss to the substrate. During ZAP testing of metal stripes, which have reduced cross sections as they cover oxide steps, the heat input needed to open the thin spots was significantly greater than predicted values because of lateral heat flow to the thicker portions of the metal stripes. However, the test method is capable of readily differentiating, in 7KÃ… to 10KÃ… A1 films, stripes with 30% step coverage from those with 45% coverage (and both from flat, 100% coverage, metal) solely by the measured burnout time. In summary, the potential utility of ZAP testing as a metal coverage screen was demonstrated.