Experimental evidence and statistical modeling of cooperating defects in stressed oxides [FLASH memory example]

Abstract

This work reports experimental data of stress induced leakage current (SILC) extracted from large FLASH cell arrays that indicate the possible presence of two types of defects in the stressed tunnel oxides. In order to support this interpretation, both an analytical and a numerical analysis of the generation and of the current conduction of cooperating defects in large arrays of cells have been developed. Our results demonstrate that the average number of two cooperating defects increases quadratically with the average number of single defects. This is in agreement with the experimental observation that the average number of defects per cell exhibits a super-linear dependence on the duration of the stress, for heavy stress conditions. The numerical simulations qualitatively reproduce all the main features of the experiments in the memory array, thus confirming the interpretation based on cooperating defects.