Lamb wave resonant pressure micro-sensor utilizing a thin-film aluminium nitride membrane

Abstract

In this work, pressure sensitivities of aluminium nitride (AlN) thin film plate acoustic resonators (FPAR) operating at the lowest-order symmetric (S0), the first-order asymmetric (A1) as well as the first-order symmetric (S1) Lamb modes are theoretically and experimentally studied in a comparative manner. The finite element method analysis has also been performed to get a further insight into the FPAR pressure sensitivity. The theoretical predictions are found to be in good agreement with the experiment. The S0 Lamb mode is identified as the most pressure-sensitive FPAR mode, while the A1 and S1 modes are found to be much less sensitive. Further, the S0 and the A1 modes exhibit almost equal temperature sensitivities, which can be exploited to eliminate the temperature drift by comparing the resonance frequencies of the latter two modes.

Thin film Lamb wave resonators in frequency control and sensing applications: a review

“…frequency decrease). This expectation was further confirmed by the measured lower sensitivity of the S 1 mode (as compared to S 0 ) excited in the LWR [46]. It is further noted that S 1 is a mode originating from the fundamental thickness longitudinal resonance (i.e.…”

“…These factors determine specific changes in resonant frequency due to either change in the resonance cavity dimensions or change in the acoustic wave velocity, respectively. The S 0 mode has been proved to be more sensitive than all other plate modes in thin AlN membrane since both factors are uniquely working in synergy [46]. The FBAR, unlike the LWR, is expected to have opposite contributions from the strain and the stress-induced changes in elasticity, respectively, since ambient pressure induces effective AlN thickness compression (i.e.…”

“…Figure 17 shows the pressure sensitivity of a 900 MHz S 0 grating-type LWR as measured experimentally. The device is a synchronous LWR with a 12 μm wavelength employing a 2 μm thick AlN membrane having a 0.55 mm 2 surface area [46]. The measured fractional sensitivity of the S 0 mode is found in excess of −6 ppm kPa −1 .…”

Pressure sensing with zero group velocity lamb modes in self-supported a-SiC/c-ZnO membranes

“…The effect provided by the 𝑃𝑖𝑛𝑡 ̅̅̅̅̅̅ changes is positive and smaller than that provided by 𝑆 𝑧𝑧 ̅̅̅̅ , as opposed to the results shown in ref. 14 where the 𝑃𝑖𝑛𝑡 ̅̅̅̅̅̅ contribution is dominant and the pressure-induced mass density changes are not accounted for. In the present simulation the a-SiC and ZnO pressure-induced mass density changes are accounted for: the mass density contribution has the effect to lower the elastic constants contribution to the mode velocity increase.…”

Dual-Resonator-Based (DRB) and Multiple-Resonator-Based (MRB) MEMS Sensors: A Review

“…In the past two decades, single-resonator-based (SRB) Micro-Electro-Mechanical-Systems (MEMS) sensors have been extensively studied for detecting small physical or chemical perturbations, such as pressure [1][2][3][4][5][6][7][8], rotational rate [9][10][11][12][13][14], acceleration [15][16][17], vibration [18][19][20], force [21][22][23], chemical vapor [24][25][26], and biological material [27][28][29][30][31][32][33][34]. Various structures, such as flexural mode resonators (FMR) [28,31,35], surface acoustic wave resonators (SAW) [36], bulk acoustic resonators (BAR) [6,12,[24][25][26]37], lamb wave resonators (LWR) [8,14,38], etc., have been fabricated to enable these SRB sensors to ha...…”