Gamma-Ray Effects on an N-Channel MOS Microprocessor (Z8002) in the Zero-Bias Condition

A Cobalt-60 gamma-ray test of Z8002 n-channel MOS microprocessors in a zero-bias condition is described and discussed. The devices were irradiated at room temperature before being functionally tested at high, room and low temperatures. For all devices the total dose failure levels were found to reduce with increasing temperature. The results of these tests have shown a wide spread in failure level with temperature for one of the two manufacturer's products examined (AMD) with high temperature failure first recorded as low as 13.1 Krads (Si), after testing devices from three batches. The other manufacturer's product to be examined (Zilog) had a considerably better worst case failure level of 35.1 Krads (Si) at high temperature, but this result is based on devices taken from a single batch. Some limited parametric testing has provided trend information on supply current, input leakage and threshold voltage change versus total dose. Room temperature annealing effects on post irradiation performance were also studied for an approximate 40 day period and significant changes were found to occur.