Overestimation of oxide defects density in large test capacitors due to plasma processing

Oxide shorts density obtained from large test capacitors is found to be higher than that in a multiple of separated small capacitors having the same total oxide area. The observed difference in failure rate is explained by the different oxide charging currents for the weak spots in the two devices during plasma processing. This experiment can explain the observed lower density of shorts after plasma processing in ICs, which is composed of many small devices, than in test structures which are large capacitors. Suggestions on the test structures are presented.