Design and Fabrication Method of Cavity Thin Film Bulk Acoustic Resonator Filter

Abstract

The invention discloses a design and preparation method of a cavity type film bulk acoustic wave resonator filter. The method includes applying ADS software to simulate the FBAR ladder filter based on the Mason model to obtain the physical parameters of each film layer whose transmission performance meets the requirements of in-band insertion loss and out-of-band suppression index; growing a piezoelectric layer with a corresponding thickness on the prepared substrate , the composite film layer of the electrode layer, another supporting substrate is taken to form a cavity, the composite film layer is bonded to the supporting substrate, the original prepared substrate is peeled off, and upper electrode layers of different thicknesses are grown to form an electrode / piezoelectric layer / Electrode / cavity composite structure. The parameter control of the upper electrode film layer of the FBAR filter designed and prepared by the present invention is precise, and the obtained filter has excellent performance; it avoids the possible damage to the resonant structure caused by the introduction of the sacrificial layer and the chemical mechanical grinding method in the traditional process, and reduces the device loss.

Description

technical field [0001] The invention relates to a design and preparation method of a film bulk acoustic resonator (FBAR) filter, in particular to a design method of an FBAR ladder filter using ADS software and a preparation method of a corresponding cavity filter. Background technique [0002] With the development of wireless communication technology, the radio frequency front end in the communication terminal is constantly developing in the direction of miniaturization and integration. In the RF front-end structure, duplexers and filters urgently need to be integrated into the chip. As a substitute for the previous generation of ceramic filters, dielectric filters and surface acoustic wave filters, the film bulk acoustic resonator filter (FBAR) has the advantages of small size, good performance, large power capacity, and can be integrated with CMOS technology, attracting It has attracted a lot of attention from research institutions at home and abroad. [0003] The workin...

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Problems solved by technology

However, the current application of various EDA tools to simulate the FBAR filter in the specified frequency band can only manually change the physical parameters or geometric parameters of the piezoelectric layer and the electrode layer to achieve the given index of the filter design.

This method of manually modifying parameters is very inefficient, and the effect of modifying the parameters of each film layer is limited, and it often cannot guarantee that the in-band insertion loss is lower than -3 dB and the out-of-band rejection is higher than -30 dB at the same time.

The filter film parameters obtained by this design method are not accurate enough, and it is difficult to prepare FBAR filters with small loss and fast roll-off through complex MEMS technology.

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