Single-crystal piezoelectric thin film-based sound wave resonator and fabrication method thereof

Abstract

The invention provides a single-crystal piezoelectric thin film-based sound wave resonator and a fabrication method thereof. The fabrication method comprises the steps of 1) providing a single-crystalpiezoelectric substrate; 2) forming a patterned lower electrode on an injection surface after ion injection onto the single-crystal piezoelectric substrate from the injection surface, or forming a uniform lower electrode on the injection surface, and patterning the uniform lower electrode to form a patterned lower electrode after ion injection onto the single-crystal piezoelectric substrate froma uniform lower electrode surface; 3) forming a first low sound-resistant material layer with a preset thickness on a patterned lower electrode surface; 4) providing a support substrate having a second low sound-resistant material layer with a preset thickness on a surface, bonding the structure obtained in the step 3) and the support substrate; 5) stripping a part of single-crystal piezoelectricsubstrate along a defect layer to obtain a single-crystal piezoelectric thin film; and 6) forming a patterned upper electrode on a surface, far away from the support substrate, of the single-crystal piezoelectric thin film. By the fabrication method, an air-cavity resonant structure is prevented, the mechanical property is stable, a great electromechanical coupling efficient is maintained, and theworking bandwidth of a filter can be improved.

Description

technical field [0001] The invention belongs to the technical field of microelectronic devices, in particular to an acoustic wave resonator based on a single crystal piezoelectric film and a preparation method thereof. Background technique [0002] With the rapid development of communication technology and the increasingly crowded existing communication frequency bands, the demand for high-performance acoustic wave filters in RF front-ends (especially mobile devices) is increasing. Currently commonly used acoustic wave filters include surface acoustic wave filters (SAW Filters) and bulk acoustic wave filters (BAW Filters). Among them, SAW filters are generally only suitable for applications below 2GHz, and are easily affected by temperature changes and have low power density. ; BAW filters have excellent performance in high-frequency applications and high power density, and are suitable for very demanding high-frequency signal filtering of 4G and 5G communications. In curre...

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Problems solved by technology

[0003] Aiming at the above-mentioned deficiencies in the prior art, the present invention proposes an acoustic wave resonator based on a single crystal piezoelectric film and a preparation method thereof, which is used to solve the problem that the acoustic wave filter in the prior art is due to the use of ZnO, AlN or Sc-doped The low electromechanical coupling coefficient of piezoelectric materials such as AlN greatly limits the problem of the bandwidth of the acoustic wave filter, and the existing acoustic wave filter adopts metal upper electrode-piezoelectric film-metal lower electrode-air cavity (or Bragg The structure of the reflective layer) has the problems of complex structure, complex processing technology, high precision and difficulty, poor mechanical stability and easy cracking of the film above the air cavity.

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