Radiation Hardness of CMOS LSI Circuits

Microprocessors and their associated support chips selected from commercially available types are being investigated for use in applications having radiation survival requirements. The radiation responses of advanced technology CMOS LSI devices were assessed in this study. The microprocessors tested were the RCA COSMAC CDP 1802 CD and preproduction samples of the RCA TCS 074 General Processor Unit. The memory devices tested were the Intersil 6508 and 6508A, Harris 6508-8 and RCA MWS 5001D 1K RAMs, and Intersil 6312 12K ROM. The I/O device tested was the Intersil 6402 UART. The radiation tests, in general, were performed under zero bias and also dynamic operating bias conditions provided by various "exercisers", which were designed and built to stimulate selected functional operations of the complex LSI circuits. The results of the total dose tests indicate that devices required for a microprocessor module can be selected from commercial CMOS LSI devices to provide a basic survival level of approximately 104 rad(Si). A careful selection of the CMOS ICs is mandatory since functional failure levels as low as 1,500 rad(Si) have been observed for some of the 1K RAMs. Additional experimental data presented in this paper indicate that the total-dose survival levels of systems using CMOS LSI circuits can be increased significantly if system operation is designed so that the effects of room temperature annealing, zero bias operation during irradiation, or zero bias during irradiation after a biased irradiation ("radiation annealing") can be employed.