Total dose effect on the soft-error susceptibility of 64kbit CMOS SRAM has been investigated by using the single ion microprobe technique which enables us to get a map of soft-error sensitivity in a memory cell by hitting a micron-size area with single ions. The effects of the ion dose on the susceptibility of each error-sensitive site have been evaluated. The errors due to the upset of p MOSFETs have become more susceptible at higher dose while that of the N MOSFETs less susceptible. One of the origins of the errors are the negative threshold voltage(Vth) shifts of the MOSFETs which are caused by oxide trapped charges. Displacement damage induced by ion irradiation also affects the susceptibility to the soft-error.
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