Design and Performance Evaluation of Radiation Hardened Latches for Nanoscale CMOS

Deep sub-micrometer/nano CMOS circuits are more sensitive to externally induced radiation phenomena that are likely to cause the occurrence of so-called soft errors. Therefore, the tolerance of the circuit to the soft errors is a strict requirement in nanoscale circuit designs. Since the traditional error tolerant methods result in significant cost penalties in terms of power, area, and performance, the development of low-cost hardened designs for storage cells (such as latches and memories) is of increasing importance. This paper proposes three new hardened designs for CMOS latches at 32 nm feature size; these circuits are Schmitt trigger based, while the third one utilizes a cascode configuration in the feedback loop. The Cascode ST latch has 112% higher critical charge than the conventional reference latch with only 10% area increase. A novel design metric (QPAR) for latches is introduced to assess the overall design effectiveness such as area, performance, power, and soft error tolerance. The novel metric (QPAR) shows the proposed cascode ST latch achieves up to 36% improvement in terms of QPAR compared with the existing hardening designs. Monte Carlo analysis has confirmed the robustness of the proposed hardened latches to process, voltage, and temperature (PVT) variations.