Radiation effects in microelectronics for space instruments

The effects, treatment, and prediction of cosmic ray interactions with space-based electronic circuitry are described. Radiation effects occur from the total accumulated dose (TAD) or because of single events. TAD produces voltage shifts or related phenomena that may eventually lead to device failure, and components for space hardware are usually chosen by comparison with laboratory tested levels of radiation tolerance for the type of component. Single events are categorized as soft upsets and latchup. Soft upsets cause a change in the logic state of a digital bit, and can be remedied by rewriting the bit to another state. CMOS RAM has proven to be resistant to soft upsets. Latchup involves a single bit being fixed in one state, a condition ameliorated by turning the power off, then back on. Current to the latchup bit must be limited to prevent damage. A path length distribution has been developed for estimating the soft upset rates by integrating the distribution over the LET spectrum. Further discussion is devoted to the distributions of ions, protons, and heavy ions in the near-earth region and the interplanetary medium.