Wafer bonding of polycrystalline spinel with LiNbO3/LiTaO3 for temperature compensation of RF surface acoustic wave devices

This paper proposes use of polycrystalline spinel for the temperature compensation of RF surface acoustic wave (SAW) devices. Spinel can be bonded with LiTaO₃ (LT) and LiNbO₃ (LN) wafers by using adhesive and direct bonding techniques. A series of RF SAW resonators were fabricated on the LT(LN)/spinel structure, and their performance including the temperature coefficient of frequency (TCF) was measured. For comparison, SAW resonators employing Si, sapphire and alumina in place of spinel were also fabricated. The result indicated that the polycrystalline spinel offers TCF improvement better than the other materials.