Evaluation of x-ray irradiation on 65nm Multi-Level Cell NOR flash technologies

Abstract

In this work, 65nm NOR flash memory is used for an evaluation of data retention and impact on cell charge based on varying levels of exposure to x-ray waves. A sample of 100 fully tested and configured units were programmed with a physical checkerboard pattern (half programmed, half erased) and exposed to conditions found in industrial x-ray stations. Readouts of the data pattern were done at various stages throughout the experiment and a comparison of cell Vt was performed on a population of worst case cells (lowest Vt on programmed cells, highest Vt on erased cells). Data was collected on a bit by bit basis and plotted as a cumulative probability function. Bakes were also performed to introduce any potential defects not seen initially as part of the exposure - and the readout data was collected for this stage as well. Results indicated there is a correlation on the amount of charge gain and loss seen based on the amount of total radiation incident upon the cells in extreme conditions.