Vertical acoustic confinement for high-Q fully-differential CMOS-RBTs

Abstract

This work demonstrates the use of phononic crystals (PnCs) to create solid-state phononic waveguides in standard CMOS technology. Such waveguides confine vibrational energy in CMOS front-end-of-line (FEOL) layers. Fully-differential driving ensures wave guiding and lowers scattering. Unreleased CMOS resonant body transistors (RBTs) based on these waveguides were implemented in IBM 32nm SOI technology. Quality factors exceeding 13,000 are achieved at 3.185GHz for an foQ of 4.2×1013, marking the highest foQ RBT and highest foQ unreleased MEMS resonator to date.