High frequency bulk acoustic wave resonator using thinned monocrystalline lithium niobate

During the last years, bulk acoustic waves excited in thin piezoelectric films have revealed their capabilities for addressing the problem of high frequency RF filters (above 1 GHz). Sputtered films such as aluminum nitride (AlN) or zinc oxyde (ZnO) are generally used in that purpose. In this paper, we propose an alternative to thin film deposition in which single crystal wafers bonded on a substrate (for instance silicon or glass) are thinned, allowing for a plate thickness close to 10μm. This can be achieved on 4 inches wafers and significantly allows for an accurate selection of the wave characteristics. Furthermore, the properties of the piezoelectric material are found to agree with tabulated values, enabling one to reliably design filters and more generally any passive signal processing device.