Bulk acoustic wave resonator, filter, and electronic device

Abstract

The present invention relates to a bulk acoustic wave resonator comprising: a substrate; a top electrode; a piezoelectric layer; a supporting layer is arranged between the substrate and the resonant structure, and the piezoelectric layer is a single-crystal piezoelectric layer which is approximately parallel to the substrate; in a first cross section parallel to the thickness direction of the resonator through the non-electrical connection end of the bottom electrode and the non-electrical connection end of the top electrode, a part of the outer end of the non-electrical connection end of the bottom electrode is covered by the supporting layer, and at least a part of the piezoelectric layer at the non-electrical connection end of the bottom electrode is removed. And at least one part of the upper surface of the non-electric connection end of the bottom electrode is flush with the upper surface of the supporting layer. The invention also relates to a filter and an electronic device.

Description

technical field [0001] Embodiments of the present invention relate to the field of semiconductors, and in particular, to a bulk acoustic wave resonator, a filter, and an electronic device. Background technique [0002] As a MEMS device, thin film bulk acoustic resonator (FBAR) has the advantages of small size, light weight, low insertion loss, high frequency bandwidth and high quality factor. One of the research hotspots in the field. The structural main body of the thin film bulk acoustic wave resonator is a "sandwich" structure composed of an electrode-piezoelectric film-electrode, that is, a piezoelectric material is sandwiched between two metal electrode layers. By inputting a sinusoidal signal between two electrodes, the FBAR uses the inverse piezoelectric effect to convert the input electrical signal into mechanical resonance, and then uses the piezoelectric effect to convert the mechanical resonance into an electrical signal output. [0003] The schematic diagram of...

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Problems solved by technology

[0003] The schematic diagram of the cross-sectional structure of the existing thin-film bulk acoustic resonator is as follows: Figure 1A as shown, Figure 1A shows the partial cross-sectional structure of the "sandwich" structure formed on the substrate 204 by the piezoelectric layer 202, the top electrode 201 and the bottom electrode 203, wherein the area shown in A1 is the effective area of ​​the resonator, outside the effective area , when the resonator vibrates, the acoustic energy will be transmitted to the outside of the effective area along the piezoelectric layer 202, thereby causing energy leakage, as shown by Q1 in the figure, which will reduce the Q value of the resonator

The resonator requires a support structure for mechanical fixation and a base for bearing; in general, the acoustic energy loss of the resonator mainly comes from leakage from the effective area through the support structure to the support base; in the traditional structure, the support structure is the extension of the piezoelectric layer 202 and The combination of bottom electric layer extension (piezoelectric layer 202+top electrode 201 or piezoelectric layer 202+bottom electrode 203), such as Figure 1A As shown, this structure causes acoustic energy to leak, and then the Q value (especially the Q value at and near the parallel resonance point) is low

[0004] In order to improve the problem of lower Q value caused by the above-mentioned energy leakage problem, the traditionally known improved structure can etch away part of the piezoelectric layer, such as Figure 1B As shown, the transverse Lamb wave transmitted in the piezoelectric layer 202 is reflected back (see Q2) into the active area A1, but the transverse Lamb wave transmitted in the area of ​​the bottom electrode B1 is reflected back (see Q3) into the active area A1 In the process, it will bring serious parasitic mode, which will affect the performance of the device, and it is urgent to improve

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