Parametric Influences on System Soft Error Rates

An extremely alpha-radiation sensitive test population of 16K RAMs was subjected to a test matrix designed to determine the actual influence of major system operating parameters on dynamic RAM alpha particle induced soft error rates. Two megabytes of memory (1024 each 16K RAMs) were exercised in a specially developed system capable of distinguishing between and logging all types of error/failure events. In excess of 4 million device hours were accumulated in the course of this experiment. The alpha particle induced soft error rate dependence on VDD, VBB, refresh interval, and system ambient temperature was investigated. A second population was subjected to tests designed to yield insight to the soft error rate behavior over the life of the system. A general description of the test system and a discussion of the philosophical aspects of error/failure event segregation is included. Parametric guidelines are developed and a microcomputer system example is presented to illustrate how these guidelines can be followed to minimize system level alpha induced soft error rates.