Advances in thin piezoelectric film based resonant MEMS technology

Abstract

This work makes an overview of the progress made during the last decade with regard to a novel class of IC compatible piezoelectric devices employing plate-guided micro-acoustic waves in micromachined thin film membranes. This class of devices, originally proposed by the author in 2005, is referred to as either thin film Lamb wave resonators (LWR) or piezoelectric contour-mode resonators (CMR) both employing thin film AlN membranes. Their principle of operation is complementary to the so called thin film bulk acoustic resonators (FBAR), while employing the same technological platform. FBARs are currently widely employed in commercial filters and duplexers for telecom applications. Thin film Lamb wave resonators have shown unique performance in both frequency control and sensing applications. Here we demonstrate high quality factors Lamb wave resonators for low noise and thermally stable performance and discuss their application in high resolution gravimetric and pressure sensors. Ongoing research activities will be further outlined. These are focused on the development of RF Transformer-filters and duplexers with performance comparable to their FBAR counterparts. A specific emphasis is put on the ability of these devices to operate in contact with liquids in view of advanced Bio-sensor applications.