The mechanism of self healing electrical breakdown in MOS structures

Capacitor structures with non-shorting breakdowns are considered. Three kinds of breakdown events occur: single -- hole, propagating and total breakdown. Single hole breakdowns are due to thermal instability at weak spots. Destruction occurs by evaporation of a crater in the silicon, of an adjoining hole of about 1 µ diameter through the silicondioxyde and a much larger hole in the metal electrode. Energy for evaporation is provided by discharge of the capacitor. Examination of thermal balance shows that only a smaller part of the energy stored in the capacitor causes destruction and the larger part heats the silicon. Some breakdown events occur within 100 nsec, accompanied by non destructive avalanche breakdown in the silicon. Other breakdown events take a few µsec, connected with discharge of charge stored at the silicon- oxyde interface. Current densities around 10⁸A/cm²occur in the breakdown arc. Form of destruction is very different in the metallic electrode for positive and negative metal. In the former case electron bombardment and in the latter case Joule heating seem to cause evaporation.