Intrinsic Temperature and Pressure Compensation of Thin-Film Acoustic Resonators

Stabilization of the resonance frequency in thin-film acoustic devices to variations in environmental conditions is commonly reduced to the passive or active compensation of a single factor (usually temperature) and the isolation or addition of a separate correction circuit for every other factor (e.g., pressure and mass loading). In this work, the possibility of dual-factor compensation is proposed, where the response of a multi-layered thin structure to both temperature and ambient pressure variation vanishes due to the choice of intrinsic parameters (materials and thickness ratios). The response functions are derived for the S0 Lamb mode at long wavelengths in an explicit analytical form in terms of bulk material characteristics. It is demonstrated that the dual-factor intrinsic stabilization requires at least a three-layered structure and can be achieved for materials commonly used in temperature-compensated devices (aluminum nitride, fused silica, and aluminum). Identification of the key material characteristics governing the existence of a stability solution can serve for a targeted search of such composites and implementation of new thin-film dual devices.