Finite element modelling of particle sensors based on Solidly Mounted Resonators

A highly sensitive acoustic wave device based on Solidly Mounted Resonators (SMR) has been designed and modelled as part of the development of a smart monolithic sensor system for the detection of fine particles (PM2.5 and PM10). A 3D finite element model has been developed based on COMSOL software for the two-port resonators, operating at a frequency of 870 MHz. The model explores the frequency response of the SMRs to the deposition of different sizes particles. A comparative study between SMR devices using two different types of acoustic mirrors (W/SiO₂ and Mo/SiO₂) has been performed. From the Finite Element Analysis (FEA), it was demonstrated that the W/SiO₂ based SMR is capable of detecting PM2.5 with a mass sensitivity of 4.8 kHz/pg with Mo/SiO₂ exhibiting sensitivity of 5.3 kHz/pg. The study has demonstrated suitability of SMR devices for CMOS integration in a low-cost, miniature smart sensor system for the monitoring of airborne particulate matter.