Single crystal FBAR with LiNbO3 and LiTaO3 piezoelectric substance layers

Abstract

The film bulk acoustic resonator (hereinafter referred to as FBAR) has been proposed for use as a high performance filter. FBAR consists of an acoustic resonator through use of a thin film deposition process. On the other hand, single crystals have been widely utilized as material for resonators due to their material uniformity, low material defect rates, and high material stability. The use of a single crystal to achieve a high frequency resonator will further expand FBAR's application ranges. In this paper, we present single crystal FBAR that is characterized by low loss and high bandwidth. Additionally, this device has the following features: the capability to fabricate a single crystal acoustic resonator through the use of single crystal micro processing technology, such as a single crystal wafer junction, polishing, and etching; and the capability of a wide range of desired filter bandwidths, each able to secure an ample amount of high performance characteristics by varying the single crystal's type and direction. LiNbO₃ (LN) and LiTaO₃ (LT), each with the large electromechanical coupling factor kt², are used for the single crystal. 3-inch full-wafer processing is performed, thereby yielding superior uniformity resonators.