Lamb wave microresonators with wavelengths of 5–8 μm, vibrating in the S0 mode, and having 75 electrode pairs were fabricated and characterized. The results were compared to theoretical predictions obtained by finite element simulation. The active material was a 1 μm-thick Al0.85Sc0.15N thin film. Two types of acoustic isolation solutions were implemented: the first one with freestanding plates fixed by two bridges to a device frame [freestanding Lamb wave resonator (FS-LWR)] and the second one containing an acoustic W/SiO2 5-layer reflector [solidly mounted Lamb wave resonator (SM-LWR)]. All devices showed excellent agreement with FEM predictions, regarding resonance frequency and piezoelectric coupling. The quality factors of the SM-LWR devices were 5–6 times larger than the ones of the freestanding structures fabricated by the same Al0.85Sc0.15N deposition process: we achieved a figure of merit of 12–18 (Qp = 771, Qs = 507, k2 = 2.29%) at an operation frequency of 1430 MHz, which is so far the best performance realized with a MEMS Lamb wave resonator having a large number of electrode fingers. This performance opens up perspectives for filter applications.
Free standing and solidly mounted Lamb wave resonators based on Al0.85Sc0.15N thin film
Fazel Parsapour, Vladimir Pashchenko, Hugo Chambon, Pascal Nicolay, Ingo Bleyl, Ulrike Roesler, Paul Muralt; Free standing and solidly mounted Lamb wave resonators based on Al0.85Sc0.15N thin film. Appl. Phys. Lett. 3 June 2019; 114 (22): 223103. https://doi.org/10.1063/1.5088892
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