Accelerated reliability testing of flash memory: Accuracy and issues on a 45nm NOR technology

This work is focused on the accelerated testing of Flash memory reliability, taking our 45 nm NOR technology as a case study to highlight some major issues that may affect the investigation of modern nanoscale devices. In particular, results will be shown on cycling-induced threshold-voltage instabilities coming from charge trapping/detrapping in the cell tunnel oxide during post-cycling data retention or bake experiments, whose characterization relies on the possibility to reduce the experimental time by an increase of the test temperature according to an Arrhenius law via an activation energy EA. These accelerated characterization schemes come from a detailed physical understanding and modeling of the damage creation/recovery dynamics and rely on the careful evaluation of EA. As shown in the case of the investigated NOR technology, this often does not represent a trivial task, due to the large number of spurious effects affecting the threshold voltage of nanoscale memory cells.