CN119210382A

CN119210382A - Bulk acoustic wave resonator, electronic device and manufacturing method

Info

Publication number: CN119210382A
Application number: CN202411487135.5A
Authority: CN
Inventors: 杨清华
Original assignee: Suzhou Huntersun Electronics Co Ltd
Current assignee: Suzhou Huntersun Electronics Co Ltd
Priority date: 2024-10-24
Filing date: 2024-10-24
Publication date: 2024-12-27
Anticipated expiration: 2044-10-24
Also published as: CN119210382B

Abstract

The disclosure provides a bulk acoustic wave resonator, an electronic device and a manufacturing method thereof, wherein the bulk acoustic wave resonator comprises a substrate and an acoustic wave reflection area, wherein the acoustic wave reflection area is formed in or on the substrate, a lower electrode layer, a first piezoelectric layer, a second piezoelectric layer and an upper electrode layer are formed on the substrate with the acoustic wave reflection area formed thereon, a protrusion structure is arranged on the upper electrode layer, a gap is formed below the protrusion structure and is arranged on the same layer as the second piezoelectric layer, the height of the gap is equal to that of the second piezoelectric layer, the orthographic projection of the protrusion structure on the upper surface of the substrate covers the orthographic projection of the gap on the upper surface of the substrate, and the width of the gap does not exceed the width of the protrusion structure.

Description

Bulk acoustic wave resonator, electronic equipment and manufacturing method

Technical Field

The present disclosure relates to the field of electronics, and more particularly, to a bulk acoustic wave resonator, an electronic device, and a method of manufacturing.

Background

The filter is used as a core device of the radio frequency front end, has excellent performances such as low insertion loss, steep filtering curve, high isolation and smaller size, and has important significance for promoting the development of new generation communication standards and miniaturization and multifunction of personal mobile terminals. The new generation of thin film bulk acoustic technology is effectively solving the two problems. Thin film bulk acoustic wave filters prepared using thin film bulk acoustic wave (Bulk Acoustic Wave, BAW) technology have steeper filter curves, lower insertion loss and excellent out-of-band rejection capability.

The film bulk acoustic resonator (Flim Bulk Acoustic Resonator, abbreviated as FBAR) plays an important role in the fields of communication, sensors and the like because of the advantages of small volume, high frequency, large power capacity, high sensitivity and the like, has larger and larger share in the field of radio frequency front ends, particularly in the market of radio frequency filters, and has larger development advantages in the fields of biological sensing, medical measurement and the like.

Fig. 1 shows a schematic structure of a thin film bulk acoustic resonator in the prior art. As shown in fig. 1, the thin film bulk acoustic resonator generally includes an acoustic wave reflecting region 101, and a lower electrode layer 200 formed on a substrate 100 to entirely cover the acoustic wave reflecting region 101, a first piezoelectric layer 300 formed on the lower electrode layer 200, and an upper electrode layer 400 disposed on the first piezoelectric layer 300. Due to the presence of the transverse mode, a portion of the transverse wave leaks away from the edges of the electrodes, so that the acoustic wave energy in the thin film bulk acoustic resonator is reduced, resulting in a reduced Q-value of the thin film bulk acoustic resonator.

It is necessary to provide a new product and manufacturing method of the thin film bulk acoustic resonator to improve the Q value of the thin film bulk acoustic resonator and further improve the performance of the thin film bulk acoustic filter.

Disclosure of Invention

The present disclosure is directed to the above-mentioned technical problems, and designs a thin film bulk acoustic resonator, a filter and a manufacturing method thereof, which can overcome the above-mentioned technical problems existing in the prior art, thereby providing a thin film bulk acoustic resonator, a filter and a manufacturing method thereof with a high Q value.

A brief summary of the disclosure will be presented below in order to provide a basic understanding of some aspects of the disclosure. It should be understood that this summary is not an exhaustive overview of the disclosure. It is not intended to identify key or critical elements of the disclosure or to delineate the scope of the disclosure. Its purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

According to an aspect of the present disclosure, there is provided a bulk acoustic wave resonator including a substrate and an acoustic wave reflection region formed in or on the substrate, a lower electrode layer, a first piezoelectric layer, a second piezoelectric layer, and an upper electrode layer formed on the substrate on which the acoustic wave reflection region is formed, a bump structure disposed on the upper electrode layer, a void formed below the bump structure and disposed in the same layer as the second piezoelectric layer, the height of the void being equal to the height of the second piezoelectric layer, an orthographic projection of the bump structure on an upper surface of the substrate covering an orthographic projection of the void on the upper surface of the substrate, and a width of the void not exceeding a width of the bump structure.

Further, the width of the protruding structures is 0.5-3.5 micrometers.

Further, the width of the gap is the width of the protruding structure。

Further, the protruding structures are first-order protruding structures, multi-order continuous protruding structures or multiple groups of protruding structures.

Further, when the protrusion structure is a first-stage protrusion structure or a multi-stage continuous protrusion structure, a first-stage recess structure or a multi-stage recess structure is formed on the inner side of the protrusion structure.

Further, when the protrusion structures are a plurality of groups of protrusion structures, a void is formed at least below one protrusion structure.

Further, no void is provided below the recessed structure.

Further, the materials of the first piezoelectric layer and the second piezoelectric layer are different.

Further, the protrusion structure is further provided on the lower electrode layer, or the protrusion structure formed on the upper electrode layer is replaced with the protrusion structure formed on the lower electrode layer.

Further, the structure of the upper electrode and/or the lower electrode is selected from the group consisting of having only a two-dimensional structure, having a first portion of a two-dimensional structure and a second portion of a three-dimensional structure, when the structure of the upper electrode and/or the lower electrode has only a two-dimensional structure and has a protruding structure, or when the structure of the upper electrode and/or the lower electrode has a first portion of a two-dimensional structure and a second portion of a three-dimensional structure and has a protruding structure, the width of the void is a difference between an outermost edge of the protruding structure and an edge of the second piezoelectric layer, and when the structure of the upper electrode and/or the lower electrode has a first portion of a two-dimensional structure and a second portion of a three-dimensional structure, the second portion is regarded as the protruding structure, and the width of the void is a difference between a boundary of the first portion and the second portion to an edge of the second piezoelectric layer.

According to another aspect of the present disclosure, there is provided a method of manufacturing a bulk acoustic wave resonator including providing a substrate, forming an acoustic wave reflection region in or on the substrate, forming a lower electrode layer, a first piezoelectric layer, a second piezoelectric layer, and an upper electrode layer on or on the substrate, forming a protrusion structure on an edge of the upper electrode layer, forming a void below the protrusion structure, the void having a height of the second piezoelectric layer and being provided in the same layer as the second piezoelectric layer, an orthographic projection of the protrusion structure on an upper surface of the substrate covering an orthographic projection of the void on the upper surface of the substrate, and a width of the void not exceeding a width of the protrusion structure.

According to yet another aspect of the present disclosure there is provided an electronic device comprising any of the foregoing bulk acoustic wave resonators provided by the present disclosure.

Drawings

The above and other objects, features and advantages of the present disclosure will be more readily appreciated by reference to the following description of the specific details of the disclosure taken in conjunction with the accompanying drawings. The drawings are only for the purpose of illustrating the principles of the present disclosure. The dimensions and relative positioning of the elements in the figures are not necessarily drawn to scale.

FIG. 1 shows a schematic structure of a thin film bulk acoustic resonator of the prior art;

FIG. 2 illustrates a first embodiment of a structure and method of a thin film bulk acoustic resonator of the present disclosure;

FIGS. 3 a-3 b illustrate variations of a first embodiment of the structure and method of the thin film bulk acoustic resonator of the present disclosure;

fig. 4 is a schematic structural view of a thin film bulk acoustic resonator of a comparative example;

FIG. 5 is a graph of the Q-factor of a thin film bulk acoustic resonator provided by the present disclosure and a graph of the Q-factor of a thin film bulk acoustic resonator of a comparative example;

FIG. 6 is a graph of amplitude versus frequency for a film bulk acoustic resonator with an oversized bump structure;

FIGS. 7a-7b are graphs of void thickness versus impedance curves for a thin film bulk acoustic resonator having a protruding structure and voids;

FIG. 8 is a thin film bulk acoustic resonator provided by a second embodiment of the present disclosure;

Fig. 9 is a thin film bulk acoustic resonator provided in a third embodiment of the present disclosure.

Detailed Description

Exemplary disclosure of the present disclosure will be described hereinafter with reference to the accompanying drawings. In the interest of clarity and conciseness, not all features of an implementation of the present disclosure are described in the specification. It will be appreciated, however, that in the development of any such actual implementation, numerous implementation-specific decisions may be made to achieve the developers' specific goals, and that these decisions may vary from one implementation to another.

Here, it is also to be noted that, in order to avoid obscuring the present disclosure with unnecessary details, only device structures closely related to the scheme according to the present disclosure are shown in the drawings, while other details not greatly related to the present disclosure are omitted.

In general, it should be understood that the drawings and the various elements depicted therein are not drawn to scale. Moreover, the use of relative terms (e.g., "above," "below," "top," "bottom," "upper," and "lower") to describe various elements' relationships to one another should be understood to encompass different orientations of the device and/or elements in addition to the orientation depicted in the figures.

It is to be understood that the present disclosure is not limited to the described embodiments due to the following description with reference to the drawings. Herein, features between different embodiments may be replaced or borrowed, where possible, and one or more features may be omitted in one embodiment, where like reference numerals refer to like parts. It should be understood that the manufacturing steps of the present disclosure are exemplary in embodiments, and that the order of the steps may be varied.

First embodiment

Referring to fig. 2-3 b, fig. 2 shows a first embodiment of the structure and method of the thin film bulk acoustic resonator of the present disclosure, and fig. 3 a-3 b show a variation of the first embodiment of the structure and method of the thin film bulk acoustic resonator of the present disclosure, wherein like reference numerals refer to like elements.

A substrate 100 is provided, and an acoustic wave reflecting region 101 constituted by an air cavity or a structure such as a bragg reflecting layer is formed in the substrate 100. The substrate 100 may be formed of a material compatible with semiconductor processes, such as silicon (Si), gallium arsenide (GaAs), indium phosphide (InP), glass, sapphire, alumina, siC, and the like. The air cavity may be formed by etching a portion of the substrate 100 and the Bragg reflection layer may be formed by stacking films of different acoustic impedances. More preferably, the Bragg reflection layer is formed by stacking films with different acoustic impedances and films controlled to be 1/4 wavelength thick. It should be understood that the air cavity may be a cavity that does not extend through the upper and lower surfaces of the substrate 100 as shown in fig. 2, or an air cavity that extends completely through the upper and lower surfaces of the substrate 100 as shown in fig. 3.

A seed layer (not shown) entirely covering the acoustic wave reflecting region 101 is formed on the substrate 100, a lower electrode layer 200 is formed on the seed layer, the lower electrode layer 200 may be a single layer or a plurality of layers, a first piezoelectric layer 300 and a second piezoelectric layer 301 are formed on the lower electrode layer 200, and an upper electrode layer 400 is disposed on the second piezoelectric layer 301, and the upper electrode layer 400 may be a single layer or a plurality of layers. The upper/lower electrodes may be formed of one or more conductive materials, such as various metals compatible with semiconductor processes including tungsten (W), molybdenum (Mo), iridium (Ir), aluminum (Al), platinum (Pt), ruthenium (Ru), niobium (Nb), or hafnium (Hf). The materials of the upper electrode and the lower electrode may be the same or different.

The first and second piezoelectric layers 300 and 301 may be formed of any piezoelectric material compatible with semiconductor processes, such as aluminum nitride (AlN), doped aluminum nitride, or titanate zirconate (PZT). The materials of the first piezoelectric layer 300 and the second piezoelectric layer 301 may be the same or different, and further, when the first piezoelectric layer 300 and the second piezoelectric layer 301 have doped impurities therein, the doping concentrations of the first piezoelectric layer 300 and the second piezoelectric layer 301 may be the same or different. The projected contour of the first piezoelectric layer 300 on the upper surface of the substrate 100 may be greater than the projected contour of the second piezoelectric layer 301 on the upper surface of the substrate 100, and the projected contour of the second piezoelectric layer 301 on the upper surface of the substrate 100 is smaller than the projected contour of the upper electrode layer 400 on the upper surface of the substrate 100.

The edge of the upper electrode layer 400 is further formed with a first-stage protrusion structure 401, and the first-stage protrusion structure 401 may be formed at the edge of the upper electrode layer 400, so that energy transmitted laterally may be greatly reflected back to the thin film bulk acoustic resonator, reducing energy leakage, and thus improving the Q value. Since the projection profile of the second piezoelectric layer 301 on the upper surface of the substrate 100 is smaller than the projection profile of the upper electrode on the upper surface of the substrate 100, that is, the second piezoelectric layer 301 is retracted with respect to the edge of the upper electrode layer 400 in the width direction, a gap 3011 is formed under the first-stage projection structure 401, and the height of the gap 3011 is the height of the second piezoelectric layer 301.

Further, when the upper electrode layer 400 is a two-dimensional structure as shown in fig. 2-3 a and has the first-stage protrusion structure 401 thereon, the front projection of the protrusion structure on the upper surface of the substrate covers the front projection of the void 3011 on the upper surface of the substrate, and the width of the void 3011 is the difference between the outermost edge of the protrusion structure 401 and the edge of the second piezoelectric layer 301.

When the upper electrode layer 400 has a first portion constituted by a two-dimensional structure and a second portion constituted by a three-dimensional structure, and the upper electrode layer 400 has the first-stage protrusion structure 401 thereon, the width of the void 3011 is the difference between the outermost edge of the protrusion structure 401 and the edge of the second piezoelectric layer 301, as exemplified by the second portion B constituted by an air bridge or an air wing, and the first portion a formed on a two-dimensional plane except for the second portion, as shown in fig. 3B.

It is understood that when the upper electrode layer 400 has a first portion formed of a two-dimensional structure and a second portion formed of a three-dimensional structure, the thin film bulk acoustic resonator provided by the present disclosure may also have no first-order bump structure 401, and the second portion B of the upper electrode layer 400 is regarded as a first-order bump structure, in which case the width of the void 3011 is the difference between the boundary of the first portion and the second portion of the upper electrode layer 400 and the edge of the second piezoelectric layer 301.

The width of the protruding structures in the present disclosure is illustratively greater than 0 microns and less than 4 microns, with preferred protruding structures having a width of 0.5-3.5um. The width of the void 3011 does not exceed the width of the protruding structure. Preferably, the width of the void 3011 is the width of the raised structureThe void thickness is typically in the range of 0.005-0.02 um.

At the same time as the first-stage protrusion structure 401 is formed at the edge of the upper electrode layer 400, a first-stage or multi-stage recess structure 402 may be further formed inside the first-stage protrusion structure 401. The provision of the first or multi-step recess structure 402 facilitates reflection of transverse waves, reducing or minimizing adverse effects such as energy attenuation between the active region and the peripheral region due to transverse modes. It should be noted that when having a recessed structure, there is no void directly beneath the first or multi-level recessed structure 402.

Although in fig. 2-3 b, the second piezoelectric layer 301 is formed above the first piezoelectric layer 300 and below the upper electrode layer 400. It should be noted, however, that the second piezoelectric layer 301 may also be formed above the lower electrode layer 200 and below the first piezoelectric layer 300.

Further, although the protrusion structure 401 is formed above the upper electrode layer 400 in fig. 2 to 3b, it is understood that the protrusion structure 401 may be formed on the lower electrode layer 200 or the protrusion structure 401 may be formed on both the upper electrode layer 400 and the lower electrode layer 200. -

Further, a passivation layer (not shown) is formed on the upper electrode layer 400, and the passivation layer may be made of silicon nitride, hafnium oxide, polyimide (PI), polyethylene terephthalate (Polyethylene Terephthalate, PET), or the like.

Further comparative test descriptions of the thin film bulk acoustic resonator provided by the present disclosure are made below by way of comparative examples.

Referring to fig. 4, fig. 4 is a schematic structural view of a thin film bulk acoustic resonator of a comparative example. The structure of the thin film bulk acoustic resonator in fig. 4 differs from the structure of the thin film bulk acoustic resonator provided in fig. 2 only in that the second piezoelectric layer 301 is absent and the remaining structures are identical.

Referring to fig. 5, fig. 5 is a Q-value curve of a thin film bulk acoustic resonator provided in the present disclosure and a Q-value curve of a thin film bulk acoustic resonator in a comparative example. As shown in fig. 5, wherein curve 1 is the Q-value curve of the conventional thin film bulk acoustic resonator in the comparative example, curve 2 is the Q-value curve of the thin film bulk acoustic resonator having a void width of 0.5 μm, curve 3 is the Q-value curve of the thin film bulk acoustic resonator having a void width of 1 μm, and curve 4 is the Q-value curve of the thin film bulk acoustic resonator having a void width of 1.5 μm.

As can be seen from fig. 5, when the width of the first-order bump structure 401 is 0.5-3.5 micrometers, the Q value of the thin film bulk acoustic resonator is better than that of the thin film bulk acoustic resonator without the void under the first-order bump structure in the comparative example when the void 3011 as shown in the present disclosure is provided. It can be further found from fig. 5 that when the width of the first-order bump structure 401 is excessively large, for example, the bump structure width is 4 μm or more, the Q value of the thin film bulk acoustic resonator in which the void 3011 is provided under the bump structure is not significantly different from that in the thin film bulk acoustic resonator in the comparative example. Referring to fig. 6, fig. 6 is an amplitude-frequency curve of a thin film bulk acoustic resonator having an excessively large width bump structure. As shown in fig. 6, an excessively large bump structure may introduce a large parasitic vibration to the left of the series resonance frequency fs of the resonator, and thus may seriously affect the out-of-band rejection of the filter or multiplexer.

Further, referring to fig. 7a to 7b, fig. 7a is a graph showing a relationship between a void thickness and an impedance curve of a thin film bulk acoustic resonator having a protrusion structure and voids, and fig. 7b is a partially enlarged view of a square frame in fig. 7 a. As can be seen from fig. 7 a-7 b, the different void thicknesses have little effect on the performance of the thin film bulk acoustic resonator when the void thicknesses are taken at 0.004 microns, 0.006 microns, 0.008 microns, and 0.01 microns, but it should be noted that the effective electromechanical coupling coefficient Kt2 of the thin film bulk acoustic resonator can be tuned by changing the thickness of the second piezoelectric layer 301 when the second piezoelectric layer 301 is a piezoelectric material having a doping concentration.

It can be seen that, when the thin film bulk acoustic resonator has a smaller protrusion structure, by providing the void structure of the present disclosure, the Q value of the thin film bulk acoustic resonator can be maximized as much as possible and the influence on the effective kt2 can be reduced, and the use of a larger protrusion structure for obtaining a larger Q value can be avoided, thereby reducing the effective electromechanical coupling coefficient kt2 of the thin film bulk acoustic resonator and introducing serious parasitic vibration.

With continued reference to fig. 2, a method for fabricating the device structure according to the first embodiment of the present disclosure will be described in further detail.

In the first step, a substrate 100 is provided, and the material of the substrate 100 is selected as described above and will not be described herein. The substrate 100 mainly plays a role of a supporting carrier, and the Si substrate 100 is taken as an example, so that the mechanical robustness is good, and the firmness and reliability in the processing and packaging processes can be ensured.

Etching the substrate 100 to form a cavity which does not penetrate through the upper and lower surfaces of the substrate 100 or a cavity which is light-passing through the upper and lower surfaces of the substrate 100, filling different acoustic impedance film stacks with the thickness of 1/4 wavelength into the air cavity, or filling a sacrificial layer into the air cavity, wherein the sacrificial layer is used for supporting the deposition of the film on the upper surface.

It should also be appreciated that a support layer may also be formed on the substrate 100, and that a recess may be formed by etching the support layer, the recess being filled with the sacrificial layer. The sacrificial layer can be selected from phosphorosilicate glass, silicon dioxide, amorphous silicon and other film materials which can be compatible with the deposition temperature of the subsequent films, do not pollute a process system and have good etching selectivity and chemical polishing property.

And thirdly, forming a seed layer on the substrate 100, wherein the seed layer is used for promoting good deposition and adhesion of a subsequent electrode layer, ensuring that the electrode is not easy to fall off in the use process and improving the conductivity of the electrode.

Step four, the lower electrode layer 200 is then formed on the seed layer, and it should be understood that the material of the lower electrode layer is not limited to the electrode material as described above, but an electrode material having high acoustic impedance and high acoustic velocity may be used. A first-order protrusion structure may be formed on the lower electrode layer, and the protrusion structure of the lower electrode layer may be used instead of the protrusion structure formed on the upper electrode layer later.

And fifthly, depositing and forming a first piezoelectric layer 300 on the lower electrode layer 200, wherein the material of the first piezoelectric layer 300 is selected to meet the bandwidth requirement of wireless mobile communication receiving and transmitting signals. As previously mentioned, materials compatible with the semiconductor process, such as aluminum nitride (AlN) or titanate zirconate (PZT), are preferably considered. The first piezoelectric layer 300 is blanket-coated on the substrate 100 on which the lower electrode is formed.

Step six, forming a second piezoelectric layer 301 on the first piezoelectric layer 300. The materials of the second piezoelectric layer 301 and the first piezoelectric layer 300 may be the same or different. When the material of the second piezoelectric layer 301 is the same as that of the first piezoelectric layer 300, the first piezoelectric layer 300 and the second piezoelectric layer 301 may have different doping concentrations.

It will be appreciated that the second piezoelectric layer 301 may be formed first in step five, and then the first piezoelectric layer 300 may be formed in step six. This is not particularly limited in this disclosure.

In step seven, an upper electrode layer is deposited on the second piezoelectric layer 301, and a first-stage protrusion structure 401 is formed on the upper electrode layer, where the dimensions of the first-stage protrusion structure 401 are as described above and are not described herein. And further, a concave structure may be formed inside the first-stage protrusion structure 401. It is further understood that the first-step protrusion 401 may be integrally formed with the upper electrode, or may be an additional first-step protrusion 401. When the first-stage projection structure 401 is an additional first-stage projection structure 401, it may be selected from the same or different metal materials as the upper electrode material or the projection structure may be a dielectric material such as silicon dioxide or aluminum oxide, etc.

The second piezoelectric layer 301 is retracted in the width direction with respect to the edge of the upper electrode layer 400, so that a space 3011 is formed under the protruding structure, the height of the space 3011 is the height of the second piezoelectric layer 301, and the width range of the space 3011 is as described above, which will not be described herein.

And step eight, a passivation layer is further formed on the upper electrode or the frame structure. The passivation layer may be made of silicon nitride, hafnium oxide, polyimide (PI) or polyethylene terephthalate (Polyethylene Terephthalate, PET), etc. The passivation layer can protect the internal structure of the resonator from the external environment, and can reduce surface loss, inhibit parasitic mode and improve the quality factor of the resonator.

Second embodiment

Referring to fig. 8, fig. 8 is a thin film bulk acoustic resonator according to a second embodiment of the present disclosure. The same features of the thin film bulk acoustic resonator provided in the second embodiment of the present disclosure as those of the first embodiment are not described herein, and only differences will be specifically described below:

As shown in fig. 8, the upper electrode layer 400 in the thin film bulk acoustic resonator according to the second embodiment further includes a multi-step continuous protrusion structure 403 formed thereon, wherein the multi-step means that the multi-step continuous protrusion structure 403 has a width of 0.5-3.5 μm. It will be appreciated that a first or multi-step recess 402 may also be formed adjacent to the inner side of the multi-step continuous projection structure 403.

Further, the second piezoelectric layer 301 is contracted in the width direction with respect to the edge of the upper electrode layer 400, and when the void 3011 is formed under the multi-step continuous protrusion structure 403, the outer edge of the second piezoelectric layer 301 may be located under the outermost protrusion among the multi-step protrusions, or the outer edge of the second piezoelectric layer 301 may be located under the innermost protrusion among the multi-step protrusions. The width of the void 3011 in this embodiment is the width of the protruding structureThe thickness is generally in the range of 0.005-0.02 um. More preferably, the width of the void 3011 is generally in the range of 0.5-3um and the thickness is generally in the range of 0.005-0.02 um.

In the process for manufacturing the thin film bulk acoustic resonator according to the second embodiment, only when the second piezoelectric layer 301 is manufactured in the sixth step, the width of the second piezoelectric layer 301 is adjusted so that the outer edge thereof is located between the right under the outermost protrusion of the multi-step protrusions and the right under the innermost protrusion of the multi-step protrusions.

And step seven, forming a multi-step continuous protruding structure 403 and the recess 402 on the upper electrode.

Third embodiment

Referring to fig. 9, fig. 9 is a thin film bulk acoustic resonator according to a third embodiment of the present disclosure. The same features of the thin film bulk acoustic resonator provided in the third embodiment of the present disclosure as those of the first embodiment are not described herein, and only the differences are specifically described below:

As shown in fig. 9, the edge of the upper electrode layer 400 in the thin film bulk acoustic resonator provided in the third embodiment is further formed to include a plurality of sets of protrusion structures 404, wherein the plurality of sets of protrusion structures 404 means a discrete structure between protrusions. The width of each protrusion in the plurality of sets of protrusion structures 404 is 0.5-3.5 microns. It is understood that one or more steps of depressions 402 may also be formed adjacent the inner side of each of the plurality of sets of protrusion structures 404.

Further, the second piezoelectric layer 301 is contracted in the width direction with respect to the edge of the upper electrode layer 400, and when the void 3011 is formed below the plurality of sets of protrusion structures 404, the outer edge of the second piezoelectric layer 301 is positioned below the outermost protrusion among the plurality of sets of protrusions, thereby forming the first void 3012 below the outermost protrusion. And forming a second void 3013 in the second piezoelectric layer 301 located in the projection range of the inner protrusions among the plurality of sets of protrusions. The width of the first and second voids in this embodiment is in the range of the width of the protruding structuresThe thickness is generally in the range of 0.005-0.02 um. More preferably, the first and second voids have a width generally ranging from 0.5 to 3um and a thickness generally ranging from 0.005 to 0.02 um.

In the process for manufacturing the thin film bulk acoustic resonator according to the third embodiment, when the second piezoelectric layer 301 is manufactured in the sixth step, the width of the second piezoelectric layer 301 is etched, so that the outer edge of the second piezoelectric layer 301 is shrunk inwards with respect to the outermost protrusion of the plurality of groups of protrusions to form the first gap 3012, and the second piezoelectric layer 301 is etched to form the second gap 3013 in the second piezoelectric layer 301 located in the projection range of the inner protrusion.

In step seven, a frame structure is formed on the upper electrode, the frame structure having a plurality of sets of protrusion structures 404 and the recesses formed in the upper electrode.

Fourth embodiment

A third embodiment of the present disclosure provides an electronic device including the thin film bulk acoustic resonator provided by the present disclosure. The electronic device provided by the present disclosure may be a cell phone, a Personal digital assistant (Personal DIGITAL ASSISTANT, PDA), a Personal wearable device, an electronic gaming device, or the like.

The present disclosure has been described in connection with specific embodiments, but it should be apparent to those skilled in the art that the description is intended to be illustrative and not limiting of the scope of the disclosure. Various modifications and alterations of this disclosure may be made by those skilled in the art in light of the spirit and principles of this disclosure, and such modifications and alterations are also within the scope of this disclosure.

Claims

1. A bulk acoustic wave resonator, comprising:

a substrate and an acoustic wave reflecting region, the acoustic wave reflecting region being formed in or on the substrate;

a lower electrode layer, a first piezoelectric layer, a second piezoelectric layer, and an upper electrode layer formed on a substrate in which an acoustic wave reflection region is formed;

the protruding structure is arranged on the upper electrode layer;

The gap is formed below the protruding structure and is arranged on the same layer as the second piezoelectric layer, the height of the gap is equal to that of the second piezoelectric layer, the orthographic projection of the protruding structure on the upper surface of the substrate covers the orthographic projection of the gap on the upper surface of the substrate, and the width of the gap does not exceed the width of the protruding structure.

2. The bulk acoustic wave resonator of claim 1, wherein the width of the protruding structures is 0.5-3.5 microns.

3. The bulk acoustic wave resonator according to claim 2, characterized in that the width of the void is the width of the protruding structure 。

4. The bulk acoustic wave resonator according to any of claims 1-3, characterized in that the bump structure is a first-order bump structure, a multi-order continuous bump structure, or a plurality of sets of bump structures.

5. The bulk acoustic wave resonator according to claim 4, wherein when the bump structure is a first-order bump structure or a multi-order continuous bump structure, a first-order concave structure or a multi-order concave structure is formed on the inner side of the bump structure.

6. The bulk acoustic resonator according to claim 5, wherein when the bump structures are plural sets of bump structures, a void is formed at least under one of the bump structures.

7. The bulk acoustic wave resonator according to any of claims 5-6, characterized in that there is no void directly under the recess structure.

8. The bulk acoustic resonator of claim 7, wherein the first piezoelectric layer and the second piezoelectric layer are of different materials.

9. The bulk acoustic wave resonator according to any of claims 1-3, 5-6, 8, characterized in that the bump structure is further provided on the lower electrode layer, or the bump structure formed on the upper electrode layer is replaced with the bump structure formed on the lower electrode layer.

10. The bulk acoustic resonator according to claim 9, characterized in that the structure of the upper electrode and/or the lower electrode is selected from the group consisting of having only a two-dimensional structure, having a first portion of a two-dimensional structure and a second portion of a three-dimensional structure, when the structure of the upper electrode and/or the lower electrode has only a two-dimensional structure and has a protruding structure, or when the structure of the upper electrode and/or the lower electrode has a first portion of a two-dimensional structure and a second portion of a three-dimensional structure and has a protruding structure, the width of the void is the difference between the outermost edge of the protruding structure and the edge of the second piezoelectric layer, and when the structure of the upper electrode and/or the lower electrode has a first portion of a two-dimensional structure and a second portion of a three-dimensional structure, the second portion is regarded as the protruding structure, and the width of the void is the difference between the boundary of the first portion and the second portion to the edge of the second piezoelectric layer.

11. A method of manufacturing a bulk acoustic wave resonator, comprising:

Providing a substrate, and forming an acoustic wave reflecting area in or on the substrate;

Forming a lower electrode layer, a first piezoelectric layer, a second piezoelectric layer, and an upper electrode layer on a substrate or forming a lower electrode layer, a second piezoelectric layer, a first piezoelectric layer, and an upper electrode layer on a substrate;

Forming a protrusion structure on the upper electrode layer;

and forming a gap below the protruding structure, wherein the gap is arranged in the same layer as the second piezoelectric layer, the height of the gap is equal to that of the second piezoelectric layer, the orthographic projection of the protruding structure on the upper surface of the substrate covers the orthographic projection of the gap on the upper surface of the substrate, and the width of the gap does not exceed the width of the protruding structure.

12. The method of manufacturing a bulk acoustic wave resonator according to claim 11, characterized in that the width of the protruding structures is 0.5-3.5 μm.

13. The method of manufacturing a bulk acoustic wave resonator according to claim 11, wherein the width of the void is the width of the bump structure。

14. The method of manufacturing a bulk acoustic wave resonator according to any of claims 11-13, characterized in that the bump structure is formed as a first-order bump structure, a multi-order continuous bump structure, or a plurality of sets of bump structures.

15. The method of manufacturing a bulk acoustic wave resonator according to claim 14, wherein a first-order concave structure or a multi-order concave structure is formed inside the protruding structure.

16. The method of manufacturing a bulk acoustic wave resonator according to claim 15, wherein when the bump structures are plural sets of bump structures, a void is formed at least under one bump structure.

17. The method of manufacturing a bulk acoustic wave resonator according to claim 15 or 16, wherein no void is formed directly under the recess structure.

18. The method for manufacturing a bulk acoustic wave resonator according to any of claims 11-13, 15-16, characterized in that the bump structure is also formed on the lower electrode layer, or the bump structure formed on the upper electrode layer is replaced with the bump structure formed on the lower electrode layer.

19. An electronic device comprising a bulk acoustic wave resonator as claimed in any one of claims 1-10.