A Novel Multi-Error-Lock-Trace (MELT) Test Structure for SET/SEU Characterization of Radiation-Hardened-By-Design Cells

The design flow for a radiation-hardened-by-design (RHBD) cell library includes the verification of the logic cells therein in terms of soft error rate (SER) under (heavy-ion) irradiation. The RHBD cell library is different from the standard (non-RHBD) cell library in terms of the need to provide test structures to ascertain its radiation hardness. We propose a novel test structure design strategy. This involves a unique Multi-Error-Lock- Trace (MELT) mechanism, which features the ability to temporarily lock the single-event-transient (SET) or single-event-upset (SEU) error into registers, and thereafter the ability to trace back to the location of the error occurrence. We implement the aforementioned methodology with three test structures in 55nm CMOS node to verify 15 RHBD cells. The proposed strategy is very worthwhile. Specifically, when compared to the reported approach of assigning individual liD pads for each device-under-test (DUT), our method reduces the number of l/O pads by 80%, translating to >95% test die area reduction. Further, when compared to the other reported approach of multiplexing I/O pads for each DUT, our method reduces the number of test runs at each linear-energy-transfer (LET) level by 80%.