Lamb waves pressure sensor using an AlN/Si structure

Electrical and optical characterisation of aluminium nitride piezoelectric films on silicon nitride membranes

“…2 and compared with analytical simulations. In this large membrane the multiple nodes and antinodes of the [1,1], [2,2] and [3,3] resonant modes can be clearly identified within the available frequency range and correspond well to the simulations. A frequency sweep 10-250 kHz was carried out and the displacement measured at a single point, approximately in the centre of the membrane.…”

“…3) shows peaks which can be identified as the [1,1], [1,3] and [3,3] modes. Analytical simulations gave the following frequencies for the resonant modes: [1,1] 83, [1,2] 131, [2,2] 166, [1,3] 185, and Fig. 1 Schematic representation of membrane structure incorporating AlN layer.…”

“…Size of the Si pressure sensor die was 5×5 mm 2 with 300 nm thick Si 3 N 4 membrane [3,3] 248 kHz. The [1,2] and [2,2] modes are expected to have antinodes at the centre of the membrane, therefore it is not possible to identify them on the frequency sweep.…”

“…Acoustic excitation was by a 1 MHz piezoelectric transducer transmitting through air. The 1 MHz transducer was excited off-resonance in the 10-300 kHz frequency range so that its resonant frequency was much higher than the natural flexural modes [1,1] to [3,3] of the devices under test in order to minimize its influence on the results. Displacement results were normalised by the measured response of the transducer.…”

“…Thin membranes of Si 3 N 4 fabricated as "windows" in a silicon substrate have been extensively used to provide a support to complex structures such as micro-electromechanical systems (MEMS) in applications such as sensors, actuators or transducers [1][2][3][4]. Thus understanding the behaviour of the base support of the composite structure becomes a requirement when it is necessary to control the physical deformation of the system, for example for energy harvesting [5].…”