Soft Upsets in 16K Dynamic RAMs Induced by Single High Energy Photons

Soft upsets have been observed in dynamic random access memories (RAMs) that can be attributed to single high energy photon interactions. In the experiments, bremsstrahlung produced by the interaction of 40 MeV electrons with a thin tungsten converter has been found to produce soft upsets at flux levels well below those where photocurrent generation of upsets dominates. The number of upsets observed at low photon fluxes depends on the total number of photons which have been incident on the device but is independent of the dose rate. This behavior is consistent with preliminary calculations which assume that the upsets are caused by alpha particles Produced in the silicon chip by the nuclear reaction 28Si(γ,α)24Mg. In these calculations the bremsstrahlung spectrum and the reaction cross section were integrated over the range from 15 to 22 MeV.