Radiation effects in five volt and advanced lower voltage DRAMs

This work examines the effects of ionizing radiation on highly scaled DRAMs. Several 4 Mb and 16 Mb DRAMs with 5.0, 3.6, and 3.3 volt memory arrays are compared. A novel approach using memory cell retention time is introduced and applied that allows insight into the effects of radiation on individual devices within a DRAM array. Data from this new application of retention time exhibits significant changes due to ionizing radiation, even at low levels where other device parameters do not change significantly. The parameter, /spl tau/ (50%), is introduced that helps classify DRAM radiation response. Data are presented showing that there are two different damage mechanisms that affect DRAM radiation response. Finally, a relationship between threshold voltage and retention time is shown for several DRAMs.>