Adaptive word line stress for leak detection in non-volatile memory

Abstract

In a word line leakage detection process in a NAND or other non-volatile memory device, a stress selected set of word lines have a high stress voltage applied while other parts of an array are biased to a low level. While stressing the memory array, the current drawn by the array is compared to a leakage detection current that increases in amplitude. For example, this can be done by mirroring the array current and comparing this with the current from a current source that increases in response to a digital input value and determining when it exceeds the mirror current, at which point the stress is discontinued. In addition to determining the amount of leakage, this approach results in low leakage word lines receiving less stress, while greater leakage result in greater amounts of stress being applied.