Heavy Ion Energy Effects in CMOS SRAMs

The impact of heavy ion energy on SEU and SEL in commercial and radiation-hardened CMOS SRAMs is explored. Provided the ion range is large enough for the ions to reach the sensitive device region, standard low-energy heavy ion testing is conservative with respect to high-energy heavy ions, at least for LETs above the threshold for direct ionization-induced upsets. However, below the threshold LET for direct ionization-induced effects we find some differences between low- and high-energy tests. These differences are attributed to the effects of nuclear reaction-induced secondary particles. Implications for hardness assurance testing and error rate calculations are discussed.