A Feasibility Study on Piezoelectric MEMS Lateral Bulk Acoustic Wave Resonators including Thermal Effect

This paper presents a feasibility study on the design of piezoelectric MEMS lateral bulk acoustic wave resonators with particular reference to the thermal effect on the resonant frequency. This study compares the results obtained from both analytical models as well as finite element simulations with the temperature effects included. This comparative study has been carried out on resonators having a resonant frequency of around 19.5 MHz using two different Thin-Film Piezoelectric-on-Substrate (TPoS) MEMS processes: the first process consists of a 1 μm PZT layer over an SOI structure having a thickness of 5.5 μm, while the second process is the PiezoMUMPs MPW process consisting of a 0.5 μm AlN layer over an SOI structure having a thickness of 10 μm. Both the analytical and the finite element models indicate a frequency variation of 300 kHz over a temperature range of 273-573 K. Based on these results, a number of PiezoMUMPs resonator prototypes, including a thermal heating element, have been designed in order to explore the feasibility of fine tuning the resonant frequency using the thermal effect. The possibility of fine tuning can be applied to high precision timing circuits such as frequency counters.