"In Situ" Radiation Tolerance Tests of MOS RAMs

To design the 4Mbit Scientific Data Store for the Faint Object Camera of the NASA/ESA space telescope, MOS RAM radiation hardness has been tested extensively. The radiation tolerance of 36 MOS RAM types has been evaluated by "in situ" testing. For comparison, one I2L type was added. The principal aim was the evaluation of failure doses. Beyond that, the impact of technology, storage mechanism, integration density and manufacturer on failure dose and failure mechanism has been studied. The tests have been performed with different test patterns, to ensure the recognition of specific failure types. Various irradiation sources have been used : X-ray tube, Co60-4329515-source and 1.5 MeV electron accelerator. The irradiation procedure and the functional test equipment are described in this paper. The results are presented and discussed. The influence of technological parameters is less pronounced than expected. Highly integrated memories are therefore preferable for those applications, where weight and shielding problems are involved.