EVALUATION OF SOFT-ERROR HARDNESS OF DRAMS UNDER QUASI-HEAVY ION IRRADIATION USING HE SINGLE-ION MICROPROBE TECHNIQUE

Soft-error immunity of a 256kbit DRAM against quasi-heavy ion irradiat ion has been evaluated using He single ion microprobe at Waseda Univer sity. The technique for hitting micron size area with arbitrary number of He ions enables us to simulate the space environment under irradia tion of heavy ions with higher LET than that of alpha-particles. From the maps of error-sensitive sites obtained by irradiating various numb er of He ions, the threshold LET of soft-errors, effect of diffused ch arges on the soft-error cross section, and susceptibility to multi-bit errors have been estimated. The results of measuring single-ion induc ed noise charges at the PN junction which is considered as equivalent to the storage node of the DRAM have been presented and the origins wh ich determine the soft-error immunity under irradiation with various L ET have been discussed.