ALN/SILICON LAMB-WAVE MICROSENSORS FOR PRESSURE AND GRAVIMETRIC MEASUREMENTS

We have studied a pressure and a gravimetric sensor using an AIN film over a silicon membrane. The membrane is micromachined using both anisotropic and isotropic chemical etching. The AIN thin film is deposited by the sputtering method. Elastic waves are generated and detected through interdigital transducers (IDTs) calculated at the frequency of 90 MHz for the S-o Lamb-wave mode. The behaviour of such a sensor is presented. We have analysed and experimentally tested the pressure and have calculated the gravimetric sensitivity. By using the opposite temperature behaviours of silicon and AlN, a satisfactory temperature compensation is achieved. Results obtained from such experiments show sensitivities that agree with theoretical sensitivities provided by a theoretical model which includes the effect of the mass loading of the deposited thin-layer material.