Projected life-times of circuits in Krypton85contaminated packages

This article presents a Monte Carlo model which calculates the radiation dose absorbed by the oxide layers on the chip from the radioactivity level in a package. The simulation allows one to obtain the time of failure of a given circuit, based on the initial activity in the package and the radiation hardness of the circuit. The model includes the effects of β-particle energy spectrum, package geometry, electron backscattering, and beta absorption through layers of various materials on the chip. Our simulation shows that the levels of Kr⁸⁵contamination assumed to be harmless in the literature may in fact cause long term failures in some memories in typical hermetically-sealed ceramic packages.