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Direct charge collection measurements are presented, which prove that the presence of tungsten near sensitive volumes leads to extreme charge collection events through nuclear reactions. We demonstrate that, for a fixed incident particle linear energy transfer (LET), increasing particle energy beyond a certain point causes a decrease in nuclear reaction-induced charge collection. This suggests that a worst-case energy exists for single-event effect (SEE) susceptibility, which depends on the technology, device layout, and the incident ions' fixed LET value. A Monte Carlo approach for identifying the worst-case energy is applied to certam bulk-Si and silicon-on-insulator (SOI) technologies. Simulation results suggest that the decrease in charge collection beyond the worst-case energy occurs because the secondary particles produced from the high-energy nuclear reactions have less mass and higher energy and are therefore less ionizing than those produced by lower-energy reactions. [ABSTRACT FROM AUTHOR]

Experimental evidence and Monte-Carlo simulations for several technologies show that accurate SEE response predictions depend on a detailed description of the variability of radiation events (e.g., nuclear reactions), as opposed to the classical single-valued LET parameter. Rate predictions conducted with this simulation framework exhibit excellent agreement with the average observed SEU rate on NASA's MESSENGER mission to Mercury, while a prediction from the traditional IRPP method, which does not include the contribution from ion-ion reactions, falls well below the observed rate. While rate predictions depend on availability of technology information, the approach described here is sufficiently flexible that reasonably accurate results describing the response to irradiation can be obtained even in the absence of detailed information about the device geometry and fabrication process. [ABSTRACT FROM AUTHOR]

The effects of heavy ion energy and nuclear inter- actions on the single-event upset (SEU) and single-event latchup (SEL) response of commercial and radiation-hardened CMOS ICs are explored. Above the threshold LET for direct ionization-induced upsets, little difference is observed in single-event upset and latchup cross sections measured using low versus high energy heavy ions. However, significant differences between low- and high-energy heavy ion test results are observed below the threshold LET for single-node direct ionization-induced upsets. The data suggest that secondary particles produced by nuclear interactions play a role in determining the SEU and SEL hardness of integrated circuits, especially at low LET. The role of nuclear interactions and implications for radiation hardness assurance and rate prediction are discussed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The effect of proton angle of incidence on proton-induced single-event latchup (SEL) is investigated in detail at room and elevated temperatures in present-day SRAMs. SRAMs from seven different vendors were irradiated at proton energies from 50 to 200 MeV, at temperatures of 25 °C and 75 °C, and at angles of incidence from 0° (normal) to 85° (grazing). The effects of angle of incidence were also investigated for neutron-induced SEL. The angle of incidence can significantly impact SEL hardness. For one SRAM at a temperature of 75 °C, characterizing SEL cross section at grazing angle resulted in a 16 times increase in SEL cross section. Large increases in SEL cross section with angle were also observed for other SRAMs characterized at room temperature. These increases in SEL cross section with angle of incidence are much larger than those measured previously for older SRAM technologies. The mechanism for the effect of angle of incidence on SEL cross section is not due simply to the deposition of more energy in the sensitive volume caused by an increase in path length as the angle of incidence is increased. To investigate possible mechanisms nuclear scattering calculations were performed and combined with device simulations. Simulation results suggest that the mechanism is a consequence of the linear energy transfer (LET) and range distributions of secondary ions produced by proton-material (or neutron-material) interactions coupled with an increase in SEL sensitivity (decrease in LET threshold) as angle of incidence is increased. These results have significant impact on SEL hardness assurance testing, especially for system applications where latchups cannot be tolerated. To best ensure that SEL hardness requirement are met, SRAMs should be characterized at both grazing and normal angles of incidence, and at maximum temperature, voltage, and proton energy. [ABSTRACT FROM AUTHOR]