BEOL NEM Relay-Based Inductorless DC-DC Converters

Abstract

In the past few years, Back-End-of-Line (BEOL) Nano-electromechanical (NEM) relays have emerged as promising switching devices for the beyond-CMOS era, due to their zero-leakage current property, and the compatibility to CMOS fabrication processes. Though the mechanical movement causes the relays to be inherently slower than transistors, the metallic contact interface untethers the limitation on gate-to-drain voltage, which makes the relays capable of handling higher voltages. In this work, we propose novel designs for BEOL NEM relay-based inductorless DC-DC converters for on-chip voltage conversions. The design, implementation, and analysis of buck (step-down) and boost (step-up) converters are shown. Both converters consist of only four NEM relays, respectively. By utilizing the charge pump topology in a switched-capacitor configuration, the relay converters exhibit lower output ripple and higher efficiency compared to their CMOS counterparts. This is particularly valuable for DC-DC voltage conversions in the Internet of Things chips, where the converter switching frequency is moderate, while the demands for efficiency, area saving, and on-chip integration are high.