Radiation Hardness Evaluations of a Stacked Flip Flop in a 22 nm FD-SOI Process by Heavy-Ion Irradiation

In 22 nm FDSOI, the flip-well structure is used instead of the standard-well structure. We evaluated soft-error tolerance by heavy-ion irradiation tests on standard and stacked flip-flops (STDFF and STACKEDFF) in the flip-well structure. The error probability of STACKEDFF was significantly smaller than STDFF. Therefore, the stacked structure is also effective against soft error in the flip-well structure. However, as the supply voltage is lowered, even STACKEDFF becomes vulnerable to soft errors under certain conditions. The origin of these errors was pMOSFETs. Therefore, soft error countermeasures are needed to account for errors from pMOSFETs.