Nanoelectromechanical Binary Comparator for Edge-Computing Applications

Bitwise comparison is a fundamental operation in many digital arithmetic functions and is ubiquitous in both datapath and control elements; for example, many machine learning algorithms depend on binary comparison. This work proposes a new class of binary comparator circuit using 4-terminal nanoelectromechanical (NEM) relays that use just 6 devices compared to 9 transistors in CMOS implementations. Moreover, NEM implementations are capable of withstanding much higher temperatures, up to 300°C, and radiation levels, well over 1 Mrad absorbed dose, conditions which are common across many industrial edge applications, with near zero standby power. A 1-bit magnitude and equality comparators comprising two in-plane silicon 4-terminal relays each were fabricated on a silicon-on-insulator substrate and electrically characterized for proof of concept, the first such demonstration. Using the 1-bit comparators as building blocks, a scalable tree-based topology is proposed to implement higher-order comparators, resulting in ≈47% reduction in device count over a CMOS implementation for a 64-bit comparator. Circuit level simulations of the comparators using accurate device models show that a single operation consumes at most 21 fJ a 9-fold reduction over the best CMOS offering in an equivalent process node.