Impact of total dose on heavy-ion upsets in floating gate arrays

We studied the impact of previous X-ray irradiation on the sensitivity of floating gate cells to heavy-ion upsets, to emulate the concurrent occurrence of both total ionizing dose and single event effects in the space environment. An increasing heavy-ion upset cross section for increasing total dose was measured, especially with low-LET particles, where the enhancement can be bigger than one order of magnitude. We attributed this behaviour to the combination of the threshold voltage shifts induced by X-rays and heavy ions.