Soft Error Rates (SER) of hardened and unhardened SRAM cells need to be experimentally characterized to determine their appropriate applications in radiation environments. This characterization is especially important when low supply voltage is preferred. In this paper, we developed an SRAM test chip with four cell arrays including two types of unhardened cells (standard 6T and subthreshold 10T) and two types of hardened cells (Quatro and DICE). This test chip was fabricated in a 65 nm bulk technology and irradiated by heavy ions at different supply voltages. Experimental results show that the SERs of 6T and 10T cells present significant sensitivities to supply voltages when the particle linear energy transfers (LETs) are relatively low. For Quatro and DICE cells, one does not consistently show superior hardening performance over the other. It is also noted that Quatro cells show significant advantage in single event resilience over 10T cells although they consume similar areas. TCAD simulations were carried out to validate the experimental data. In addition, the error amount distributions follow a Poisson distribution very well for each type of cell array.
This paper presents a new SEU-tolerant latch design based on Quatro and NMOS feedback transistors. By using these feedback transistors, the SEU susceptibility is decreased because of the cutoff feedback loop. Simulation results demonstrate that the proposed design is immune to static single node upsets. The proposed latch and the reference Quatro were designed and fabricated on a 130 nm process. The test chip was exposed to heavy ions at the TAMU Cyclotron facility. The testing results show that the proposed design has a higher upset LET threshold and lower cross-section when compared to the reference latch. Its lower SEU vulnerability comes with small area penalty.Index Terms-Charge sharing, quatro, radiation hardening, single event upset (SEU), soft error.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.