Test structures for the evaluation of Si substrates

The quality of Si substrates affecting the oxide reliability was investigated using various kinds of test structures like flat capacitor, field edge array and gate edge array. The field edge array test structure which resembles the conditions found for a real device is shown to be quite effective to determine the quality of oxides. Oxide grown on a P type epitaxial layer on P/sup +/ silicon substrate shows highest reliability in all test structures. Gettering of heavy metals and/or crystal defects by the P/sup +/ silicon substrate is the dominant mechanism for the improvement of the oxide reliability.