200 mm Surface and Bulk Acoustic Wave Devices Based on Piezoelectric-On-Insulator Substrate

The availability of Piezoelectric-On-Insulator (POI) substrates, made of a thin single crystal LiTaO3 film atop a silicon substrate, has promoted the development of innovative Surface and Bulk Acoustic Wave (SAW and BAW) devices. However, these substrates are so far only commercially available in 100 and 150 mm diameter. In this work, we successfully demonstrate acoustic devices based on 200 mm POI substrates. First, we fabricate SAW resonators displaying an electromechanical coupling coefficient of 8.8\% at a resonance frequency of 1.6 GHz. Then, we implement Film Bulk Acoustic Resonators (FBAR), integrating buried electrodes and an acoustic isolation structure, which exhibits a single resonance at 2.8 GHz, with an electromechanical coupling coefficient of 8.8\% and a quality factor close to 190. Eventually, we show a Solidly Mounted Resonator (SMR) based on a dielectric (AlN/SiO2) Bragg mirror, which exhibits performances close to AlN-based resonators, i.e. a coupling coefficient of 6.1\% and a quality factor of 405 at 4 GHz. For the later, a Temperature Coefficient of Frequency (TCF) of -14 and -22 ppm/°C at resonance and antiresonance are obtained respectively. Such TCF values are among the lowest ever reported for LiNbO3 and LiTaO3 BAW resonators. These results offer promising perspectives towards the development of 200 mm SAW and BAW filters based on POI substrates.

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Toyama, Japan
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