Acoustic Devices (PAW, SAW, and BAW) using Wafer Bonding Technology

By combining different materials with piezoelectric thin plates, acoustic wave devices with novel characteristics have been realized. The bonding technique with high bonding strength enabled the precise polishing of piezoelectric substrates into ultra-thin plates. By bonding ultra-thin piezoelectric thin plates and different substrates, we have developed the following acoustic wave devices with various merits: (1) A high frequency 5.8 GHz A1 mode Lamb wave resonator and an ultrawide 0-th shear horizontal (SH0) mode plate wave devices using LiNbO3 (LN) thin plates. (2) A solidly mounted (SM) type SH surface acoustic wave (SAW) resonator with an ultrawide and high impedance ratio using LN thin film, multi-layer films, and a glass substrate. (3) Hetero Acoustic Layer (HAL) SAW resonator combining a LiTaO3 (LT) thin plate and a quartz substrate, exhibiting zero temperature coefficient of frequency (TCF), high Q, and spurious-free characteristics. (4) various SM type bulk acoustic wave resonators (SM-BAWRs) with low TCF, wideband, or high-frequency using LT and LN. (5) SM-BAWR exciting an overtone frequency of 9.5 GHz, which is three times of the fundamental frequency, by combining LN, an average acoustic film reduced to 1/5 of its conventional thickness, and a support substrate.