Frequency-Stable AIScN-ON-SiC MEMS Lamb Wave Resonator Operating in Very High Temperature Environment up to 1000°C

We report on the frequency stability (Allan deviation, ADEV) and phase noise performance of an aluminum scandium nitride on silicon carbide (AlScN-on-SiC, or simply AlScN/SiC) Lamb wave resonator (LWR) operating in a high temperature$(T)$vacuum$(\sim 1 \text{mTorr})$environment up to$T=1000^{\circ} \mathrm{C}$. The AlScN/SiC LWR has a resonance frequency of$f_{0}=35.53 \text{MHz}$with a quality factor$Q \approx 1015$at$T=27^{\circ} \mathrm{C}$, still exhibits robust$f_{0}$= 34.08 MHz with$Q \approx 717$when operating at$T=1000^{\circ} \mathrm{C}$. A phase-locked loop (PLL) is used to track the$f_{0}$over time to measure both frequency stability (ADEV) and phase noise. The measured ADEV is$\sigma_{\mathrm{A}}=1.73 \times 10^{-7}$at averaging time$\tau \approx 71 ~\text{ms}$, with phase noise of$-117.54 \text{dBc} / \text{Hz}$at 1kHz offset frequency, measured at$T=1000^{\circ} \mathrm{C}$. These experimental results mark the very first experimental study of frequency stability and phase noise performance of a MEMS resonator operating at very high temperatures up to$T=1000^{\circ} \mathrm{C}$, far exceeding earlier record of$T=300^{\circ} \mathrm{C}$.