Static and Dynamic Tests on a 40-nm Commercial SRAM Under Muons and Neutrons

The single-bit and multiple-cell upset cross sections for positive and negative muons and 14-MeV neutrons of a commercial 40-nm CMOS SRAM have been experimentally determined in static and dynamic modes. In the case of the muons, the momentum with the highest cross section was predicted by EVA, a custom simulation tool, in spite of not having the characteristics of the chemicals used to build the device and the printed circuit boards. Positive muons only cause single-bit upsets, while negative muons and neutrons also induce multiple cell upsets of various multiplicities. The number of multiple events was determined by using LELAPE, a tool that explores the statistical properties of the set of data. In all the tests, the static cross-section was on the same order as the dynamic one, or even higher. Besides, in the case of muons, the cross section is not negligible at standard power supply voltages. These phenomena are attributed to a side effect of the internal circuitry added by the manufacturer to adapt the bias voltage and to minimize the power consumption.