Ionizing Radiation Effects on Various Commercial NMOS Microprocessors

Recent results of ionizing radiation tests indicate that popular commercial NMOS microprocessors are very vulnerable to total ionizing dose. Samples of five device types from six manufacturers were dynamically exposed to Co 60 irradiation. Failure thresholds as low as 1000 Rads (Si) were observed and the entire sample population was dead after exposure to 3000 Rads (Si). The predominant failure mode is the failure to respond to control commands and is caused by shifts in the threshold voltage. Experimental devices made with 700 A° hardened gate oxide raised the failure threshold to 104 Rads (Si). Dynamic irradiation of microprocessor systems yielded failures consistent with the biased static irradiation results.