Hardness Assurance through Lot Sampling - Homogeneity Studies

This paper describes a study of the homogeneity of neutron response as a function of the level at which parts are sampled, i.e., over several diffusion runs, several wafers within a single diffusion run, a single wafer or parts within a wafer. The results indicate that variations in neutron response across a wafer may be comparable to those of a diffusion run or production lot. However, homogeneity within an area comparable to that of a "standard" SSI integrated circuit is shown to be quite good and it appears that circuit neutron response can be predicted to within ~10% by the use of 100% electrical screening of radiation correlation parameters on a specially bonded transistor within the IC chip (breakout transistor). Variations within an area on a wafer somewhat larger than that of an SSI chip are large enough to indicate that the breakout transistor approach may not be useful for prediction of the neutron response of MSI or LSI circuits.