Evaluation of SEU Performance of 28-nm FDSOI Flip-Flop Designs

In this paper, a variety of flip-flop (FF) designs fabricated in a commercial 28-nm Fully-Depleted Silicon on Insulator (FDSOI) technology are evaluated for their single-event upset performance with ions and pulsed laser experiments. These FF designs consist of unhardened DFF, hardened DFF with stacked transistors in the inverters, and the layout-optimized DFFs. These DFFs were exposed to alpha particles and heavy ions (HIs). None of the hardened DFFs exhibit any errors up to a Linear Energy Transfer (LET) of 50 MeV*cm
²
/mg under normal irradiation, and a layout-based hardened DFF started to see errors at a LET of 50 MeV*cm
²
/mg with the tilt angle of 60
⁰
. The testing data substantiates effective SEU reduction of these hardened designs. Two-photon absorption (TPA) laser experiments were carried to test these DFF designs, and the results showed that pulsed laser may not be a valid tool to evaluate the FFs designed with nano-scale SOI stacked structures. This brings new challenges in laser hardness assurance for RHBD designs.