6H-SiC microdisk torsional resonators in a “smart-cut” technology

Abstract

We report on experimental demonstration of high frequency torsional resonators based on microdisk structures enabled by a “smart-cut” 6H-silicon carbide (6H-SiC) technology. Circular microdisks axially supported by pairs of thin tethers, with diameters of ∼5–15 μm, exhibit torsional-mode micromechanical resonances with frequency of ∼1–60 MHz, and quality (Q) factors up to 1280 at room temperature in moderate vacuum (∼10 mTorr). Measured intrinsic thermomechanical vibrations of a microdisk with diameter d ≈ 15.9 μm (and triangular cross-section tethers with width wT ≈ 1.5 μm, length LT ≈ 2 μm, and thickness tT ≈ 0.4 μm) demonstrate a torque resolution of ST1/2 ≈ 3.7 × 10−20 (N m)/√Hz, a force sensitivity of SF1/2 ≈ 5.7fN/√Hz, and an angular displacement sensitivity of Sθ1/2 ≈ 4.0 × 10−8 rad/√Hz. By examining devices with varying disk size, different tether shape, width, and length, and by combining experimental data and theoretical calculations, we depict the scaling pathways for ultrasensitive torsional resonant sensors based on this smart-cut 6H-SiC platform.