Mechanisms of D-C Electrical Breakdown in Thin Siliconoxide Films

BREAKDOWN was investigated on capacitors produced by vacuum deposition on glass slides. Dielectric thickness varied from 1000 to 10,000 Ã… and the aluminum electrodes were a few hundred angstroms thick. Breakdown events were not shorting, punching an opening through dielectric and electrodes. Single holes are produced below a voltage limit, while above the limit breakdowns destroy large areas. The voltage versus time oscillograms of these two events are different. Rate of breakdown events increases rapidly with voltage. On application of a certain voltage, breakdown events continue for some time at a decreasing rate. Increase of humidity and decrease of the external resistance in series with the capacitor increase considerably the frequency of breakdown events. The initial capacitance Co decreases to C due to breakdowns on the application of voltage, V. C/Co versus V curves, with series resistor as a parameter, present the breakdown properties of the capacitor. Based on these curves suggestions are made for quantitative data on the dielectric strength of capacitors with non-shorting breakdown events. Single hole breakdown is promoted by the appearance of hot, conducting channels occurring in the dielectric at flaws, due to thermal instability. The charge of the capacitor discharges through such a channel and the energy of the capacitor evaporates material and produces the hole, often explosively.