Device simulation study of the SEU sensitivity of SRAMs to internal ion tracks generated by nuclear reactions

Single-even upsets (SEUs) in static random access memories (SRAMs) are inve stigated using three-dimensional (3-D) full cell device simulations for tra cks that do not cross the OFF n-channel MOSFET drain. These tracks are repr esentative of the most probable geometrical cases when the ions are generat ed inside the device by nuclear reactions, and then address one important p art of neutron- or protons-induced soft errors. It is found that the durati on and magnitude of the ion-induced current pulse strongly depends on the t rack location, As a result, the flipping of the memory cell is delayed, and the critical charge involved during the upset is no longer constant, A lin ear relationship between the critical charge and the delay is found and is explained by the contribution of the ON p-channel MOSFET. The increase of t he ion current pulse delay and broadening when the track is moved away from the drain is explained on the basis of the diffusion-collection mechanism. Indications on the size of the sensitive regions are derived.