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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*cm2/mg under normal irradiation, and a layout-based hardened DFF started to see errors at a LET of 50 MeV*cm2/mg with the tilt angle of 600. 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. [ABSTRACT FROM PUBLISHER]

In this paper, we present D flip-flop, Quatro, and stacked Quarto flip-flop designs fabricated in a commercial 28-nm CMOS FDSOI technology. Stacked-transistor structures are introduced in the stacked Quatro design to protect the sensitive devices of the original structure. Striking either of the stacked devices will not upset the latch because the conduction path to the supply rail is still cut off by the other off-state device. The irradiation experimental results substantiate that the stacked Quatro design has significantly better SEU tolerance (e.g., higher heavy ion upset Linear Energy Transfer threshold and smaller cross-section data) than the reference designs. It introduces power and area penalties because the proposed design duplicates and stacks two sensitive PMOS devices. Additionally, the impact of technology scaling on Quatro in various technology nodes (130-nm, 65-nm, and 40-nm) has been studied suggesting decreasing upset threshold and decreasing cross-section data. [ABSTRACT FROM AUTHOR]