Analysis of temperature compensated SAW modes in ZnO/SiO2/Si multilayer structures

Temperature stable SAW filters are needed in many communication and sensor applications. The ZnO/SiO₂/Si structure is particularly attractive, as ZnO and Si have positive TCD whereas SiO₂ has negative TCD, from which temperature compensation may be achieved. Furthermore, it allows integration of surface acoustic wave devices with Si circuits for compact communications and sensor systems. In this work, temperature compensated SAW modes in the ZnO/SiO ₂/Si structure have been investigated through computer simulation using the transfer matrix method. Through proper design of the layer thickness´, second order and higher wave modes with temperature compensation at multiple frequency points in the 1 GHz to 2.5 GHz range are achieved. Based on the simulation results on the thickness´ of SiO₂ and ZnO layers, ZnO thin films were grown on SiO₂/Si substrates using the MOCVD technique. Measurement results from SAW test devices are compared with the temperature compensated wave modes predicted by the simulations