NAND Flash memories are currently the dominant mass storage technology in the commercial market, and they are finding their way into space systems thanks to the technology's high density and low cost [1]. NASA and other government agencies as well as academia have actively investigated the radiation susceptibility of each generation of NAND flash from various commercial vendors, including the Micron and Samsung [2]−[4]. The growing complexity of the device's control circuits as well as the continued shrinking of the memory cell area have introduced new challenges for radiation testing. Existing single-event effect (SEE) test standards include the JESD57, ASTM F1192, and ESCC No. 25100 [5]−[7]. These test standards provide top level guidance for single-event testing in general. NASA has recently published a more detailed test guideline targeted specifically at current nonvolatile memories [8]. However, the current test methodologies need to be continuously updated with test findings.For example, the traditional test protocols are predicated on the assumption that the SEE cross section remains constant with fluence. So the device upset rate in space is constant over time. Therefore, typical heavy ion tests demand a fluence high enough to cover a representative portion of the device sensitive regions. In this investigation, we observed the cross section varies inversely with the test fluence, which we attribute to the range of upset sensitivities of the memory cells.

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