Design and preparation method for cavity type FBAR (thin-film bulk acoustic resonator) filter

Abstract

The invention discloses a design and preparation method for a cavity type FBAR (thin-film bulk acoustic resonator) filter. The method comprises the following steps: an FBAR ladder filter based on a Mason model is simulated with ADS (Advanced Design System) software, and physical parameters of each film layer whose transmission performance meets index requirements for insertion loss and out-of-band rejection are obtained; a piezoelectric layer in corresponding thickness and a composite film layer of an electrode layer grow on a preparation substrate, a support substrate is taken additionally for forming cavities, the composite film layer is bonded with the support substrate, the original preparation substrate is stripped off, upper electrode layers with different thicknesses grow, and an electrode/piezoelectric layer/electrode/cavity composite structure is formed. Parameters of the upper electrode film layer on the FBAR filter designed and prepared with the method are controlled precisely, and the performance of the obtained filter is excellent; damage probably caused by introduction of a sacrificial layer and adoption of a chemical mechanical polishing method to a resonance structure in the traditional technology is avoided, and device loss is reduced.

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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