HARDNESS VARIABILITY IN COMMERCIAL TECHNOLOGIES

The radiation hardness of commercial Floating Gate 256K E(2)PROMs from a single diffusion lot was observed to vary between 5 to 25 krad(Si) when irradiated at a low dose rate of 64 mrad(Si)/s. Additional variat ions in E(2)PROM hardness were found to depend on bias condition and f ailure mode (i.e., inability to read or write the memory), as well as the foundry at which the part was manufactured. This variability is re lated to system requirements, and it is shown that hardness level and variability affect the allowable mode of operation for E(2)PROMs in sp ace applications. The radiation hardness of commercial 1-Mbit CMOS SRA Ms from Micron, Hitachi, and Sony irradiated at 147 rad(Si)/s was appr oximately 12, 13, and 19 krad(Si), respectively. These failure levels appear to be related to increases in leakage current during irradiatio n. Hardness of SRAMs from each manufacturer varied by less than 20%, b ut differences between manufacturers are significant. The Qualified Ma nufacturer's List approach to radiation hardness assurance is suggeste d as a way to reduce variability and to improve the hardness level of commercial technologies.