18 GHz Solidly Mounted Resonator in Scandium Aluminum Nitride on SiO2/Ta2O5 Bragg Reflector

TL;DR

This paper reports an 18.64 GHz solidly mounted resonator using scandium aluminum nitride on a Bragg reflector, achieving high quality factors and potential for advanced RF signal processing at high frequencies.

Contribution

The work demonstrates a high-frequency (18.64 GHz) SMR in ScAlN on a SiO2/Ta2O5 Bragg reflector, with detailed analysis and promising performance metrics for future RF applications.

Findings

Resonator operates at 18.64 GHz, among highest reported frequencies.

Achieves high Qs of 156 and Qp of 142, indicating low energy loss.

Third harmonic observed at 59.64 GHz with moderate coupling and Q.

Abstract

This work reports an acoustic solidly mounted resonator (SMR) at 18.64 GHz, among the highest operating frequencies reported. The device is built in scandium aluminum nitride (ScAlN) on top of silicon dioxide (SiO2) and tantalum pentoxide (Ta2O5) Bragg reflectors on silicon (Si) wafer. The stack is analyzed with X-ray reflectivity (XRR) and high-resolution X-ray diffraction (HRXRD). The resonator shows a coupling coefficient (k2) of 2.0%, high series quality factor (Qs) of 156, shunt quality factor (Qp) of 142, and maximum Bode quality factor (Qmax) of 210. The third-order harmonics at 59.64 GHz is also observed with k2 around 0.6% and Q around 40. Upon further development, the reported acoustic resonator platform can enable various front-end signal-processing functions, e.g., filters and oscillators, at future frequency range 3 (FR3) bands.