阅读说明：本技术 体声波谐振器及制造方法、体声波谐振器组件、滤波器及电子设备 (Bulk acoustic wave resonator, method of manufacturing bulk acoustic wave resonator, bulk acoustic wave resonator assembly, filter, and electronic apparatus ) 是由 庞慰 闫德海 杨清瑞 于 2020-05-07 设计创作，主要内容包括：本发明涉及一种体声波谐振器及其制造方法。该谐振器包括：基底；声学镜；底电极；顶电极；和压电层,其中：声学镜、顶电极、底电极和压电层在谐振器的厚度方向上的重叠部分构成谐振器的有效区域；压电层的上下两侧中的至少一侧设置有凹陷部,凹陷部的底部为平坦面；凹陷部的区域内设置有顶电极和底电极中对应的电极。本发明还涉及一种体声波谐振器组件、一种滤波器以及一种电子设备。(The present invention relates to a bulk acoustic wave resonator and a method of manufacturing the same. The resonator includes: a substrate; an acoustic mirror; a bottom electrode; a top electrode; and a piezoelectric layer, wherein: the overlapping parts of the acoustic mirror, the top electrode, the bottom electrode and the piezoelectric layer in the thickness direction of the resonator form an effective area of the resonator; at least one of the upper side and the lower side of the piezoelectric layer is provided with a concave part, and the bottom of the concave part is a flat surface; and the corresponding electrodes in the top electrode and the bottom electrode are arranged in the area of the sunken part. The invention also relates to a bulk acoustic wave resonator assembly, a filter and an electronic device.)

1. A bulk acoustic wave resonator comprising:

a substrate;

an acoustic mirror;

a bottom electrode;

a top electrode; and

a piezoelectric layer is formed on the substrate,

wherein:

the overlapping parts of the acoustic mirror, the top electrode, the bottom electrode and the piezoelectric layer in the thickness direction of the resonator form an effective area of the resonator;

at least one of the upper side and the lower side of the piezoelectric layer is provided with a concave part, and the bottom of the concave part is a flat surface;

and the corresponding electrodes in the top electrode and the bottom electrode are arranged in the area of the sunken part.

2. The resonator of claim 1, wherein:

the depression has a depression depth of no more than half of the original thickness of the piezoelectric layer.

3. The resonator of claim 1, wherein:

the upper side and the lower side of the piezoelectric layer are provided with concave parts, and the top electrode and the bottom electrode are respectively arranged in the corresponding concave parts.

4. The resonator of claim 3, wherein:

the thickness of the piezoelectric layer between the recesses is not less than one fifth of the original thickness of the piezoelectric layer in the thickness direction of the resonator.

5. The resonator of claim 1, wherein:

the side wall of at least one recess is at an angle in the range of 90-160 deg. to the bottom of the recess.

6. The resonator of any of claims 1-5, wherein:

an acoustic impedance structure is arranged between the piezoelectric layer and the substrate;

the acoustic impedance structure includes a first acoustic impedance layer and a second acoustic impedance layer disposed adjacent to each other in a lateral direction, the first acoustic impedance layer being different in acoustic impedance from the second acoustic impedance layer, the acoustic mirror being located between the first acoustic impedance layers in the lateral direction of the resonator.

7. The resonator of claim 6, wherein:

the widths of the parts of the first acoustic impedance layer and the second acoustic impedance layer in contact with the piezoelectric layer are m lambda₁A/4 and n lambda₂A/4, where m and n are both odd numbers, λ₁And λ₂Respectively, the acoustic wave wavelengths propagated in the lateral direction at the resonance frequency by the first acoustic impedance layer and the second acoustic impedance layer.

8. The resonator of claim 7, wherein:

m is the same as n.

9. The resonator of claim 6, wherein:

the material forming one of the first and second acoustic impedance layers is selected from the group consisting of aluminum nitride, silicon dioxide, silicon nitride, polysilicon, amorphous silicon, the material forming the other of the first and second acoustic impedance layers is selected from the group consisting of silicon dioxide, doped silicon dioxide, polysilicon, amorphous silicon, and the material forming the first acoustic impedance layer is different from the material forming the second acoustic impedance layer.

10. The resonator of claim 6, wherein:

the acoustic mirror is an acoustic mirror cavity;

the boundary of the acoustic mirror cavity in the lateral direction of the resonator is defined by the first acoustic impedance layer.

11. The resonator of any of claims 1-10, wherein:

the piezoelectric layer is a single crystal piezoelectric layer.

12. A bulk acoustic wave resonator assembly comprising:

first and second resonators, both being bulk acoustic wave resonators, and at least the second resonator being a resonator according to any of claims 1-11, the first and second resonators sharing the same piezoelectric layer, and the original thickness of the piezoelectric layer of the first resonator being the original thickness of the piezoelectric layer of the second resonator.

13. The resonator assembly of claim 12 wherein:

the first resonator and the second resonator are adjacent in the transverse direction and respectively have a first acoustic impedance structure and a second acoustic impedance structure, and the two acoustic impedance structures share at least one first acoustic impedance layer or at least one second acoustic impedance layer.

14. The resonator assembly of claim 12 or 13, wherein:

the thickness of the piezoelectric layer of the first resonator in its active area is the original thickness of the piezoelectric layer of the second resonator.

15. The assembly of any of claims 12-14, further comprising:

a third resonator being a bulk acoustic wave resonator and being a resonator according to any of claims 1-11, the third resonator sharing the same piezoelectric layer as the first and second resonators.

16. The assembly of claim 15, wherein:

the thickness of the piezoelectric layer of the third resonator within the active area of the third resonator is different from the thickness of the piezoelectric layer of the second resonator within the active area of the second resonator.

17. The assembly of any of claims 12-16, wherein:

the sum of the thicknesses of the top electrode and the bottom electrode of at least one resonator is different from the sum of the thicknesses of the top electrode and the bottom electrode of the other resonator, or the thickness of one electrode of at least one resonator is different from the thickness of the corresponding electrode of the other resonator; and/or

At least one resonator is provided with a mass loading layer.

18. A method of manufacturing a bulk acoustic wave resonator, the bulk acoustic wave resonator comprising a substrate; an acoustic mirror; a bottom electrode; a top electrode; and a piezoelectric layer disposed between the bottom electrode and the top electrode, the method comprising the steps of:

at least one side of the upper side and the lower side of the piezoelectric layer is provided with a concave part, and the bottom of the concave part is a flat surface; and

corresponding ones of the top and bottom electrodes are disposed within the area of the recess.

19. The method of claim 18, wherein: the method comprises the following steps:

step 1: forming a piezoelectric layer on a substrate, the substrate being disposed on a first side of the piezoelectric layer;

step 2: forming a second recess on a second side of the piezoelectric layer, wherein the bottom of the second recess is a flat surface;

and step 3: depositing and patterning a layer of bottom electrode material on the second side of the piezoelectric layer to form a bottom electrode in the second recess;

and 4, step 4: after step 3, forming a first acoustic impedance layer and a second acoustic impedance layer arranged adjacent to each other in the lateral direction on the piezoelectric layer, one of the first acoustic impedance layer and the second acoustic impedance layer bridging a sidewall of the second recess, an acoustic mirror space being formed between the first acoustic impedance layers adjacent in the lateral direction, at least a portion of the bottom electrode being located in the space in the lateral direction, the first acoustic impedance layer being different in acoustic impedance from the second acoustic impedance layer;

and 5: interfacing the base with the first and second acoustic impedance layers, and removing the substrate to expose the first side of the piezoelectric layer; and

step 6: a top electrode and a corresponding electrode electrical connection structure are formed on a first side of the piezoelectric layer.

20. The method of claim 19, wherein:

the step 6 comprises the following steps:

step 61: forming a first concave part on the first side of the piezoelectric layer, wherein the bottom of the first concave part is a flat surface;

step 62: a layer of top electrode material is deposited and patterned on the first side of the piezoelectric layer to form a top electrode within the first recess.

21. The method of claim 18, wherein: the method comprises the following steps:

step 1: forming a piezoelectric layer on a substrate, the substrate being disposed on a first side of the piezoelectric layer;

step 2: depositing and patterning a layer of bottom electrode material on the second side of the piezoelectric layer to form a bottom electrode;

and step 3: after step 2, forming a first acoustic impedance layer and a second acoustic impedance layer arranged adjacent to each other in the lateral direction on the piezoelectric layer, an acoustic mirror space being formed between the first acoustic impedance layers adjacent in the lateral direction, at least a part of the bottom electrode being located in the space in the lateral direction, the first acoustic impedance layer being different in acoustic impedance from the second acoustic impedance layer;

and 4, step 4: interfacing the base with the first and second acoustic impedance layers, and removing the substrate to expose the first side of the piezoelectric layer;

and 5: forming a first concave part on the first side of the piezoelectric layer, wherein the bottom of the first concave part is a flat surface;

step 6: a layer of top electrode material is deposited and patterned on the first side of the piezoelectric layer to form a top electrode and corresponding electrode electrical connection structure within the first recess.

22. The method of any one of claims 19-21, wherein:

the step of forming a recess on one side of the piezoelectric layer includes:

forming and patterning a barrier layer on the one side of the piezoelectric layer;

thinning the barrier layer and the exposed piezoelectric layer simultaneously by using a trimming process, wherein the thinning speed of the barrier layer is less than that of the piezoelectric layer, and forming a concave part with a flat bottom on one side of the piezoelectric layer based on thinning of the exposed piezoelectric layer;

removing the barrier layer remaining on the one side of the piezoelectric layer.

23. The method of any one of claims 19-22, wherein:

the widths of the parts of the first acoustic impedance layer and the second acoustic impedance layer in contact with the piezoelectric layer are m lambda₁A/4 and n lambda₂A/4, where m and n are both odd numbers, λ₁And λ₂Respectively, the acoustic wave wavelengths propagated in the lateral direction at the resonance frequency by the first acoustic impedance layer and the second acoustic impedance layer.

24. A method of adjusting the electromechanical coupling coefficients of resonators within a filter, the filter comprising at least one first resonator and at least one second resonator, at least the second resonator being a bulk acoustic wave resonator according to any of claims 1-11, the method comprising the steps of:

the depth of the recess is selected to adjust an electromechanical coupling coefficient of the second resonator based on a thickness of a piezoelectric layer of the second resonator within the active area.

25. The method of claim 24, wherein:

the filter comprising at least two second resonators, the method comprising the steps of: adjusting a thickness of the piezoelectric layer of one of the at least two second resonators within the active area to be different from a thickness of the piezoelectric layer of the other of the at least two second resonators within the active area based on the depth of the recess such that there is a difference in electromechanical coupling coefficient for the at least two second resonators.

26. The method according to claim 24 or 25, further comprising the step of:

the sum of the thicknesses of the top and bottom electrodes of at least one second resonator, and/or the thickness of the individual electrodes of at least one second resonator, is selected, and/or a mass loading layer is provided at least one second resonator to adjust the electromechanical coupling coefficient of the second resonator.

27. A filter comprising a bulk acoustic wave resonator according to any of claims 1-11, or a bulk acoustic wave resonator assembly according to any of claims 12-17.

28. An electronic device comprising a filter according to claim 27, or a bulk acoustic wave resonator according to any of claims 1-11, or a bulk acoustic wave resonator assembly according to any of claims 12-17.

Technical Field

Embodiments of the present invention relate to the field of semiconductors, and in particular, to a bulk acoustic wave resonator, a method of manufacturing the same, a filter having the same, a bulk acoustic wave resonator assembly, and an electronic device.

Background

With the increasing development of 5G communication technology, the requirement on the data transmission rate is higher and higher. Corresponding to the data transmission rate is a high utilization of spectrum resources and spectrum complications. The complexity of the communication protocol imposes stringent requirements on the various performances of the rf system, and the rf filter plays a crucial role in the rf front-end module, which can filter out-of-band interference and noise to meet the signal-to-noise ratio requirements of the rf system and the communication protocol.

The traditional radio frequency filter is limited by structure and performance and cannot meet the requirement of high-frequency communication. As a novel MEMS device, a Film Bulk Acoustic Resonator (FBAR) has the advantages of small volume, light weight, low insertion loss, wide frequency band, high quality factor and the like, and is well suitable for the update of a wireless communication system, so that the FBAR technology becomes one of the research hotspots in the communication field. However, since the frequency of FBAR is determined by thickness, the prior art can only obtain a small range of frequency adjustment by adding a proper mass loading layer, and therefore, how to integrate rf filters with different frequencies having a large frequency interval on a single substrate remains a big challenge in FBAR technology.

On the other hand, the series resonators and the parallel resonators of the prior art filter cooperate to form a filter pass band characteristic. By setting the series resonance frequencies of the series resonators to be different from each other and the electromechanical coupling coefficient Kt of the series resonators²The roll-off characteristic on the right side of the filter passband can be effectively improved. Filter application Small Kt²While good roll-off characteristics are easily achieved for a resonator, once design criteria (bandwidth, insertion loss, out-of-band rejection, etc.) are determined, the Kt of the resonator²It is basically determined that such filter bandwidth and good roll-off characteristics of the filter are contradictory, that it is difficult to achieve good roll-off characteristics with a wide bandwidth filter design under a conventional architecture, and that Kt of a 50Ohm resonator is determined by a change in resonator structure under a condition that a resonator stack in a general filter has been determined²The change is only about +/-0.5%, and the improvement on the roll-off characteristic of the filter is limited. So as to release Kt between resonators²The limitation of the degree of freedom is beneficial to improving the roll-off performance of the whole filter.

Disclosure of Invention

For increasing Kt of bulk acoustic wave resonator²The invention provides a method for selectingThe technical scheme of adjusting the thickness of the piezoelectric layer of the bulk acoustic wave resonator.

Based on the technical scheme, the method is also suitable for manufacturing piezoelectric layers with different thicknesses on the same wafer, and on the one hand, the electromechanical coupling coefficient of the bulk acoustic wave resonator can be adjusted in a large range, so that the Kt of the resonator in a single filter can be favorably adjusted²The choice of values provides a greater degree of freedom and on the other hand monolithic integration of a plurality of different frequency filters with a greater frequency separation is also possible.

According to an aspect of an embodiment of the present invention, there is provided a bulk acoustic wave resonator including:

a substrate;

an acoustic mirror;

a bottom electrode;

a top electrode; and

a piezoelectric layer is formed on the substrate,

wherein:

the overlapping parts of the acoustic mirror, the top electrode, the bottom electrode and the piezoelectric layer in the thickness direction of the resonator form an effective area of the resonator;

at least one of the upper side and the lower side of the piezoelectric layer is provided with a concave part, and the bottom of the concave part is a flat surface;

and the corresponding electrodes in the top electrode and the bottom electrode are arranged in the area of the sunken part.

The embodiment of the invention also relates to a bulk acoustic wave resonator assembly which comprises a first resonator and a second resonator, wherein the first resonator and the second resonator are both bulk acoustic wave resonators, at least the second resonator is the resonator, the first resonator and the second resonator share the same piezoelectric layer, and the original thickness of the piezoelectric layer of the first resonator is the original thickness of the piezoelectric layer of the second resonator.

The invention also relates to a method of manufacturing a bulk acoustic wave resonator comprising a substrate; an acoustic mirror; a bottom electrode connected to the electrode lead-out portion; a top electrode connected to the top electrode lead-out portion; and a piezoelectric layer disposed between the bottom electrode and the top electrode, the method comprising the steps of:

at least one side of the upper side and the lower side of the piezoelectric layer is provided with a concave part, and the bottom of the concave part is a flat surface; and

corresponding ones of the top and bottom electrodes are disposed within the area of the recess.

Embodiments of the present invention also relate to a method of adjusting electromechanical coupling coefficients of resonators in a filter, the filter comprising at least one first resonator and at least one second resonator, at least the second resonator being a bulk acoustic wave resonator as described above, the method comprising the steps of:

the depth of the recess is selected to adjust an electromechanical coupling coefficient of the second resonator based on a thickness of a piezoelectric layer of the second resonator within the active area.

Embodiments of the invention also relate to a filter comprising a bulk acoustic wave resonator or resonator assembly as described above.

Embodiments of the invention also relate to an electronic device comprising a filter as described above or a resonator or an assembly as described above.

Drawings

These and other features and advantages of the various embodiments of the disclosed invention will be better understood from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate like parts throughout, and in which:

fig. 1 is a schematic cross-sectional view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention, showing two bulk acoustic wave resonators, with recesses on the top and bottom sides of the piezoelectric layer of the right-hand resonator and no recesses on the piezoelectric layer of the left-hand resonator;

FIGS. 2a-2s illustrate a process for fabricating the bulk acoustic wave resonator assembly shown in FIG. 1;

figure 3 is a schematic cross-sectional view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention showing two bulk acoustic wave resonators, differing from figure 1 in that only the lower side of the piezoelectric layer of the right-hand resonator has a recess;

figure 4 is a schematic cross-sectional view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention showing two bulk acoustic wave resonators differing from figure 1 in that only the upper side of the piezoelectric layer of the right-hand resonator has a recess;

FIG. 5 is a schematic cross-sectional view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention showing two bulk acoustic wave resonators, differing from FIG. 1 in that the resonator mass loading layer on the right side is disposed on the bottom electrode side;

figure 6 is a cross-sectional schematic view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention showing two bulk acoustic wave resonators differing from figure 1 in that the resonator mass loading layers on the right side are disposed on the top and bottom electrodes, respectively;

figure 7 is a cross-sectional schematic view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention showing two bulk acoustic wave resonators differing from figure 1 in that the electrode thickness of the left side resonator differs from the electrode thickness of the right side resonator;

fig. 8 is a schematic cross-sectional view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention, which differs from the structure shown in fig. 1 in that in fig. 8, the outside of the sidewall of the second acoustic impedance layer makes an angle of more than 90 ° with the piezoelectric layer, and in fig. 1, the outside of the sidewall of the first acoustic impedance layer makes an angle of more than 90 ° with the piezoelectric layer.

Detailed Description

The technical scheme of the invention is further specifically described by the following embodiments and the accompanying drawings. In the specification, the same or similar reference numerals denote the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the general inventive concept of the present invention and should not be construed as limiting the invention. Some, but not all embodiments of the invention are described. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.

First, the reference numerals in the drawings of the present invention are explained as follows:

1: the first substrate or the auxiliary substrate can be made of monocrystalline silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, diamond and the like, or can be a monocrystalline piezoelectric substrate of lithium niobate, lithium tantalate, potassium niobate and the like.

2: the piezoelectric layer can be a single crystal piezoelectric material, and can be selected from the following: the material may be polycrystalline piezoelectric material (corresponding to single crystal, non-single crystal material), optionally, polycrystalline aluminum nitride, zinc oxide, PZT, or a rare earth element doped material containing at least one rare earth element, such as scandium (Sc), yttrium (Y), magnesium (Mg), titanium (Ti), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), erbium (Ho), erbium (holmium), thulium (Tm), ytterbium (Yb), lutetium (Lu), or the like.

3: first hard mask layer (hard mask): it may be a first barrier layer, the material may be selected from silicon nitride, molybdenum, silicon oxide, etc.

4: the bottom electrode is made of molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or their composite or their alloy.

5: the acoustic reflection layer or the first acoustic impedance layer can be made of silicon nitride, silicon dioxide, polysilicon, amorphous silicon, aluminum nitride and the like.

6: the sacrificial layer is also a second acoustic impedance layer, and can be made of materials such as silicon dioxide, doped silicon dioxide, polysilicon and amorphous silicon, but the materials are different from the materials of the first acoustic impedance layer 5, and an etchant of the sacrificial layer is not easy to etch or does not etch the first acoustic impedance layer 5.

7: and the second substrate is made of monocrystalline silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, diamond and the like.

8: a second hard mask layer: it may be a second barrier layer, the material of which may be selected from silicon nitride, molybdenum, silicon oxide, etc.

9: the electrode is connected with the hole, conductive metal is arranged in the hole, and the selected material is metal material, such as molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, platinum, iridium, osmium, chromium or the composition of the above metals or alloy thereof.

10: the top electrode can be made of the same material as the bottom electrode, and the material can be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or the composite of the above metals or the alloy thereof, and the like. The top and bottom electrode materials are typically the same, but may be different.

11: the electrode connecting Part (PAD) is made of molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or their composite or their alloy.

12: the acoustic mirror can be a cavity, and a Bragg reflection layer and other equivalent forms can also be adopted. The embodiment of the present invention takes the form of a cavity.

13 and 14: the frequency adjusting layer or the mass loading layer can be made of molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or the composite of the metals or the alloy thereof. The piezoelectric material can also be selected from dielectric materials such as silicon dioxide, aluminum nitride, zinc oxide, PZT and the like, and also comprises rare earth element doping materials with certain atomic ratios of the piezoelectric material.

Fig. 1 is a schematic cross-sectional view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention, in fig. 1, the bulk acoustic wave resonator assembly includes two bulk acoustic wave resonators with piezoelectric layers arranged in the same layer, the piezoelectric layer of the resonator on the right side has recesses on the upper and lower sides of the piezoelectric layer, and the piezoelectric layer of the resonator on the left side does not have a recess. In the present invention, the same layer arrangement means that the bottom sides or the upper sides of the two piezoelectric layers are in the same plane or formed in the same piezoelectric layer forming step.

More specifically, for the resonator on the right in fig. 1, it comprises: a substrate 7; an acoustic mirror 12; a bottom electrode 4; a top electrode 10; and a piezoelectric layer 12, wherein: the upper and lower both sides of piezoelectric layer 2 all are provided with the depressed part, and the bottom of depressed part is the plain surface, and bottom electrode setting is in the depressed part down, and top electrode setting is in last depressed part.

For bulk acoustic wave resonators, the frequency is determined by the thickness of the layers and is inversely related, i.e., decreasing the thickness of any layer results in an increase in frequency. Meanwhile, the electromechanical coupling coefficient is determined by the thickness ratio of each layer, and the overall trend shows that the electromechanical coupling coefficient is smaller when the ratio of the total thickness of the upper and lower electrodes to the thickness of the piezoelectric layer is larger, and meanwhile, the electromechanical coupling coefficient is maximum when the thickness ratio of the upper and lower electrodes is 1 and is reduced when the ratio of the upper and lower electrodes is more than 1 or less than 1 when the thickness of the piezoelectric layer is constant.

In fig. 1, for the right-hand side resonator, whose piezoelectric layer thickness is smaller than that of the left-hand side resonator, the resonance frequency is higher when the electrode thickness is the same as that of the left-hand side resonator, and at the same time, the electromechanical coupling coefficient is lower. Optionally, a mass loading layer may be further disposed on the top electrode of the right resonator, so as to reduce the frequency and further reduce the electromechanical coupling coefficient. Therefore, the frequencies of the left resonator and the right resonator can be equivalent but the electromechanical coupling coefficients are different greatly by reasonably selecting the depth of the concave part (namely the thickness of the piezoelectric layer) and the thickness of the mass loading layer.

As shown in fig. 1, the recess depth of the upper recess is h1, the recess depth of the lower recess is h2, the original thickness of the piezoelectric layer is h4, and the thickness of the piezoelectric layer between two recesses is h 3.

In one embodiment of the present invention, h1 and h2 may be the same or different. Optionally, h1 or h2 is no more than one-half of h 4. Optionally, h3 is no less than one fifth of h 4.

Also shown in fig. 1 is an angle a between the groove wall of the recess and the recess bottom (flat face), which in an alternative embodiment is in the range of 90 ° -160 °. The angle may be chosen to be close to 90 ° when the depth of the recess is smaller; and when the depth of the recess is larger, the angle should be selected larger, e.g. 120 °. When the depth of the recess is large, if the angle is close to 90 °, coverage of an electrode (which may be a top electrode or a bottom electrode) at the interface is poor, and a fault is easily generated, so that electrical connection of resonators with different adjacent piezoelectric layer thicknesses is broken.

As shown in fig. 1, an acoustic impedance structure is provided between the piezoelectric layer 4 and the substrate 7, said acoustic impedance structure comprising a first acoustic impedance layer 5 and a second acoustic impedance layer or sacrificial layer 6 arranged adjacent to each other in the transverse direction, the acoustic impedance of the first acoustic impedance layer 5 being different from that of the second acoustic impedance layer 6, said acoustic mirror being located between the first acoustic impedance layers 5 in the transverse direction of the resonator, in other words, in the embodiment shown in fig. 1, in the case of the acoustic mirror 12 being in the form of a cavity, the boundary of the acoustic mirror cavity in the transverse direction of the resonator being defined by said first acoustic impedance layers 5.

In the invention, the acoustic impedance of the first acoustic impedance layer 5 is different from that of the second acoustic impedance layer 6, so that impedance mismatching is formed, continuous reflection is formed on sound waves, and a reflection structure for transverse sound waves is formed, so that transverse sound waves are prevented from leaking, energy is favorably locked in a resonator, and the Q value is improved.

In the invention, when the piezoelectric layer is made of single crystal piezoelectric material, the piezoelectric loss can be lower, so that a higher Q value of the resonator can be obtained, and the electromechanical coupling coefficient and the power capacity can be improved.

In a further embodiment, the widths of the portions of the first acoustic impedance layer 5 and the second acoustic impedance layer 6 in contact with the piezoelectric layer 2 are m λ₁A/4 and n lambda₂A/4, where m and n are both odd, e.g. 1,3, 5,7, etc.. lambda.₁And λ₂Respectively, the acoustic wave wavelengths propagated in the lateral direction at the resonance frequency by the first acoustic impedance layer 5 and the second acoustic impedance layer 6. The resonance frequency is a certain frequency in a resonance interval of the resonator, and may be a series resonance frequency or a parallel resonance frequency of the resonator, or a certain frequency between the series resonance frequency and the parallel resonance frequency, or a certain frequency slightly lower than the series resonance frequency or slightly higher than the parallel resonance frequency. In fig. 1, the width of the first acoustic impedance layer 5 is denoted by a, and the width of the second acoustic impedance layer 6 is denoted by B. The width is selected, so that effective acoustic impedance mismatching is favorably formed, transverse sound wave leakage is prevented, and the Q value of the resonator is further improved. m and n may be the same or different and are within the scope of the present invention.

The material forming the first acoustic impedance layer 5 comprises aluminum nitride, silicon dioxide, silicon nitride, polysilicon, amorphous silicon, and the material forming the second acoustic impedance layer 6 comprises silicon dioxide, doped silicon dioxide, polysilicon, amorphous silicon. The material of the first acoustic impedance layer 5 and the material of the second acoustic impedance layer 6 are different from each other. Alternatively, the material forming the first acoustic impedance layer 5 comprises silicon dioxide and the material forming the second acoustic impedance layer 6 comprises polysilicon. Alternatively, the material forming the first acoustic impedance layer 5 comprises silicon nitride or aluminum nitride, and the material forming the second acoustic impedance layer 6 comprises silicon dioxide or doped silicon dioxide. In the present invention, in order to increase the degree of acoustic mismatch at the junction of the first acoustic impedance layer 5 and the second acoustic impedance layer 6, the difference between the acoustic impedances of the two layers may be selected to be as large as possible.

As will be described later with reference to fig. 2a-2s, the second acoustic impedance layer 6 simultaneously acts as a sacrificial layer during the manufacture of the resonator, and therefore when releasing the sacrificial layer, a suitable release etchant needs to be chosen such that the etchant etches only the first acoustic impedance material and not or only a very small amount of the second acoustic impedance material.

As shown in fig. 1, the end face of the non-electrode connection terminal of the bottom electrode 4 (the left end of the left-hand resonator in fig. 1, and the right end of the right-hand resonator) below the top electrode connection side is spaced apart from the first acoustic impedance layer 5 in the acoustic impedance structure in the lateral direction, so that the acoustic wave is also totally reflected at the lateral interface between the non-electrode connection terminal of the bottom electrode and the air gap, thereby reducing the acoustic wave leakage. Based on the gap structure at the non-electrode connecting end, transverse sound wave leakage can be further prevented, and the Q value of the resonator is improved. On the other hand, if the end surfaces of the non-electrode connection terminals (the left end of the left resonator and the right end of the right resonator in fig. 1) of the bottom electrode 4 below the top electrode connection side are covered with the first acoustic impedance layer 5, parasitic capacitance is formed with the portion of the top electrode outside the cavity, and the electromechanical coupling coefficient of the resonator is affected.

In an alternative embodiment, in a longitudinal section of the resonator through the electrode connection end of the bottom electrode 4 (e.g. in the sectional view shown in fig. 1), the end face of the non-electrode connection end of the bottom electrode 4 is spaced apart from the acoustic impedance structure in the lateral direction by a distance in the range of 0.5 μm-10 μm. The distance may be, for example, 5 μm, 7 μm, or the like, in addition to the end value.

In the embodiment shown in fig. 1, the bottom electrode 4 is surrounded by a continuous reflective layer or acoustic impedance structure formed by the first acoustic impedance layer 5 and the second acoustic impedance layer 6 on the side of the electrode connection end, and more specifically, covered by the first acoustic impedance layer 5, which is advantageous for improving the mechanical stability of the resonator and for easier conduction of the heat generated by the resonator during operation to the substrate or base through the electrodes and the first acoustic impedance layer 5, thereby improving the power capacity of the resonator, and is advantageous for locking the energy inside the resonator as much as possible due to the reflective interface formed by the second acoustic impedance layer and the first acoustic impedance layer, although the energy may leak from the bottom electrode end face into the first acoustic impedance layer 5, thereby maintaining the resonator at a higher Q value.

In the embodiment shown in fig. 1, the electrode connection end of the bottom electrode 4 is covered with the first acoustic impedance layer 5, but the present invention is not limited thereto. For example, the electrode connecting end of the bottom electrode 4 may be spaced apart from the first acoustic impedance layer 5 by a distance in the transverse direction, and at this time, since the end surface of the non-electrode connecting end of the bottom electrode 4 and the end surface of the electrode connecting end are both spaced apart from the first acoustic impedance layer 5 in the transverse direction, the acoustic wave is also totally reflected at the transverse interface between the bottom electrode and the gap, so that the acoustic wave leakage is reduced, and the Q value of the resonator can be improved. Compared with the structure shown in fig. 1, the gap is also provided at the electrode connecting end, which is advantageous for further preventing the lateral sound wave from leaking, but since the electrode is not in direct contact with the first acoustic impedance layer, heat must be indirectly conducted to the first acoustic impedance layer and the substrate through the piezoelectric material, which results in poor power capacity.

In an alternative embodiment, in another longitudinal section of the resonator through the non-electrode connection end of the bottom electrode 4 and the non-electrode connection end of the top electrode 10, the end face of the non-electrode connection end of the bottom electrode 4 may be spaced apart from the acoustic impedance structure in the lateral direction by a distance in the range of 0.5 μm-10 μm; alternatively, the non-electrode connection terminal of the bottom electrode 4 is surrounded by a continuous reflective layer or acoustic impedance structure formed of the first acoustic impedance layer 5 and the second acoustic impedance layer 6, and more specifically, covered by the first acoustic impedance layer 5.

In the present invention, the first acoustic impedance layer 5 and the second acoustic impedance layer 6 may together constitute an acoustic impedance structure. However, the present invention is not limited thereto, in other words, the arrangement of the acoustic impedance layer is not limited thereto. It may be a multilayer structure including a first acoustic resistive layer and a second acoustic resistive layer, or a first acoustic resistive layer, a second acoustic resistive layer, and a first acoustic resistive layer, or a combination thereof, which are adjacently arranged in order in the lateral direction.

In the bulk acoustic wave resonator assembly shown in fig. 1, three acoustic impedance layers, a first acoustic impedance layer, a second acoustic impedance layer, and a first acoustic impedance layer, are included between the acoustic mirrors of the two resonators. The two resonators share at least the second acoustic impedance layer 4 located at the center. Thus, for a single resonator, the acoustic impedance structure surrounding the acoustic mirror 12 comprises a first acoustic impedance layer and a second acoustic impedance layer arranged in this order from the inside to the outside.

In the embodiment shown in fig. 1, the first acoustic impedance layer 5, the second acoustic impedance layer 6, and the first acoustic impedance layer 5 are disposed between the two resonators, but the present invention is not limited thereto. For example, five acoustic impedance layers, a first acoustic impedance layer, a second acoustic impedance layer, and a first acoustic impedance layer are included between the acoustic mirrors of the two resonators. The two resonators share at least the first acoustic impedance layer 5 located in the middle. Thus, for a single resonator, the acoustic impedance structure surrounding the acoustic mirror 12 comprises a first acoustic impedance layer, a second acoustic impedance layer, a first acoustic impedance layer arranged in this order from the inside to the outside. Thus, the acoustic impedance structure between the two resonators shares at least one first acoustic impedance layer 5 or at least one second acoustic impedance layer 6.

Figure 3 is a schematic cross-sectional view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention showing two bulk acoustic wave resonators, differing from figure 1 in that only the lower side of the piezoelectric layer of the right-hand resonator has a recess.

Figure 4 is a schematic cross-sectional view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention showing two bulk acoustic wave resonators, differing from figure 1 in that only the upper side of the piezoelectric layer of the right-hand resonator has a recess.

Fig. 5 is a schematic cross-sectional view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention, in which two bulk acoustic wave resonators are shown, and differs from fig. 1 in that the resonator mass loading layer on the right side is disposed on the side of the bottom electrode, and although the mass loading layer is disposed below the bottom electrode in the figure, it is to be understood that the mass loading layer may be disposed between the bottom electrode and the piezoelectric layer.

Figure 6 is a cross-sectional schematic view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention showing two bulk acoustic wave resonators, differing from figure 1 in that the resonator mass loading layers on the right side are disposed on the top and bottom electrodes, respectively. The thickness ratio of the bottom electrode, the piezoelectric layer and the top electrode can be flexibly changed by adding the mass loading layer on the top electrode and the bottom electrode, so that the piezoelectric ceramic capacitor has better electrical performance, such as higher Q value, on the basis of adjusting the electromechanical coupling coefficient.

Fig. 7 is a schematic cross-sectional view of a bulk acoustic wave resonator assembly according to an exemplary embodiment of the present invention, in which two bulk acoustic wave resonators are shown, which differs from fig. 1 in that the electrode thickness of the left-side resonator is different from that of the right-side resonator, and in an alternative embodiment, the electrode thickness of the left-side resonator is thicker than that of the right-side resonator, and the piezoelectric layer of the left-side resonator is also thicker than that of the right-side resonator, so that the left-side resonator has a lower frequency, and the integration of two filters with a larger frequency span (e.g., two filters in a duplexer) can be realized. The thicknesses of the top electrode, the piezoelectric layer and the bottom electrode of the two resonators are respectively adjusted, so that the resonators with any frequency and electromechanical coupling coefficient can be combined on a single wafer, and the resonator can be used in different application scenes.

The fabrication of the bulk acoustic wave resonator assembly shown in figure 1 is illustrated with reference to figures 2a-2 s.

The method comprises the following steps: as shown in fig. 2a, a single crystal piezoelectric thin film layer (i.e. single crystal piezoelectric layer) 2, such as single crystal aluminum nitride (AlN), gallium nitride (GaN) is deposited on the surface of a substrate or auxiliary base 1 (e.g. silicon, silicon carbide) by using deposition processes including, but not limited to, MOCVD (metal organic chemical vapor deposition), MBE (molecular beam epitaxy), CBE (chemical molecular beam epitaxy), LPE (liquid phase epitaxy), etc.; or forming a boundary layer on the surface of an auxiliary substrate 1 (such as a lithium niobate or lithium tantalate substrate) by ion implantation, and forming a piezoelectric thin film layer 2 above the boundary layer, wherein the material of the piezoelectric thin film layer 2 is the same as that of the substrate or the auxiliary substrate 1.

Step two: as shown in fig. 2b, a hard mask layer 3, which may be silicon nitride, is deposited and etched as a barrier layer on the surface of the piezoelectric layer 2. In the present invention, other materials may be used as the barrier layer of the piezoelectric layer, as long as the barrier layer can block the thickness of the piezoelectric layer of other parts of the resonator, for example, when the trimming process in the following step three is used to form the recess, and the barrier layer may remain at the end of trimming. The barrier layer may be further selected such that the barrier layer is removed without excessive piezoelectric layer loss.

Step three: as shown in fig. 2c, the single crystal piezoelectric layer 2 and the hard mask layer 3 are trimmed by a trimming process (trim) using particle beam bombardment, for example argon bombardment of the target surface, the hard mask layer thinning at a slower rate than the single crystal piezoelectric layer until a recess of a predetermined depth appears on the piezoelectric layer 2, the bottom of which recess is a flat surface as shown in fig. 2 c.

In the present invention, the conditioning is physical bombardment of the target surface with a particle beam. The bombardment has no chemical reaction, and has high control precision, and the thickness precision can be controlled within 3%, such as trimming off the target(Is a suitable range for the trimming method, and exceeding the range can lead to overlong process time, and the method can be realized by combining partial etching and trimming), and the actual situation is probably in practiceThis control accuracy is incomparable with etching. The thickness of the bombarded material layer can be controlled very accurately by using a trimming mode, the process is simple, and the precision is high.

Step four: as shown in fig. 2d, the hard mask layer remaining on the piezoelectric layer 2 is removed by a dry or wet etching process to expose the entire surface of the piezoelectric layer. Both dry and wet methods require significant consideration of the effect on the piezoelectric layer when removing the hard mask layer.

Step five: as shown in fig. 2e, a layer of bottom electrode material is deposited and etched to form the bottom electrode 4.

Step six: as shown in fig. 2f, a layer of first acoustic impedance material, which may be aluminum nitride, silicon dioxide, silicon nitride, polysilicon, amorphous silicon, etc., is deposited on the surface of the piezoelectric layer 2 and the bottom electrode 4 of the structure obtained in step five and patterned to form the first acoustic impedance layer 5.

Step seven: as shown in fig. 2g, a second acoustic impedance material or a sacrificial layer material is deposited on the surfaces of the piezoelectric layer 2, the first acoustic impedance layer 5 and the bottom electrode 4 of the structure obtained in step six, wherein the second acoustic impedance layer material may be silicon dioxide, doped silicon dioxide, polysilicon, amorphous silicon, etc., but is different from the first acoustic impedance layer material.

The above-mentioned steps six and seven may also be exchanged in the processing order, for example, in step six, the second acoustic impedance material is deposited and patterned first, and in step seven, the first acoustic impedance material is deposited again. The resulting structure is shown in fig. 8. In fig. 8, the outside of the side wall of the second acoustic impedance layer makes an angle with the piezoelectric layer of more than 90 °, whereas in fig. 1 the outside of the side wall of the first acoustic impedance layer makes an angle with the piezoelectric layer of more than 90 °.

Step eight: as shown in fig. 2h, the second acoustic impedance material is polished by CMP (chemical mechanical polishing) until the first acoustic impedance layer 5 is exposed, the second acoustic impedance material located outside the first acoustic impedance layer 5 constitutes the second acoustic impedance layer 6, and the second acoustic impedance material located between the first acoustic impedance layers 5 constitutes the sacrificial layer. In other words, in the present embodiment, the second acoustic impedance material is also a sacrificial material.

Step nine: as shown in fig. 2i, a substrate 7 is bonded (bonding) on the lower side of the first acoustic impedance layer 5 and the second acoustic impedance layer 6. Optionally, the surface of the substrate 7 may further have an auxiliary bonding layer (not shown), such as silicon dioxide, silicon nitride, or the like.

Step ten: as shown in fig. 2j, the substrate or the auxiliary substrate 1 is removed by grinding, etching process or ion implantation layer separation method to expose the upper surface of the piezoelectric layer 2, and optionally, the separation interface is subjected to CMP processing to make the surface smooth and have low roughness.

Step eleven: as shown in fig. 2k, a hard mask layer 8, which may also be silicon nitride or a different mask layer than hard mask layer 3, is deposited and etched on the structure in step ten. The process of step eleven is similar to that of step two.

Step twelve: as shown in fig. 2l, the single crystal piezoelectric layer 2 and the hard mask layer 8 are bombarded with particle beams using a trimming process (trim), in which the thinning speed of the hard mask layer is slower than that of the single crystal piezoelectric layer until a recess of a predetermined depth appears on the piezoelectric layer 2, the bottom of which is a flat surface as shown in fig. 2 l. The process of step twelve is similar to that of step three.

Step thirteen: as shown in fig. 2m, the hard mask layer 8 remaining on the piezoelectric layer 2 is removed by a dry or wet etching process to expose the entire upper surface of the piezoelectric layer 2. The process of step thirteen is similar to step four.

Fourteen steps: as shown in fig. 2n, a through hole 9 is etched in the piezoelectric layer 2 by a photolithography and etching process, and at the same time, a sacrificial layer release hole (not shown) is etched in the piezoelectric layer 2, the through hole directly communicating with the electrode connection terminal of the bottom electrode 4, or the release hole directly communicating with the acoustic mirror cavity or directly communicating with the second acoustic impedance material, i.e., the sacrificial layer, located in the acoustic mirror cavity.

Step fifteen: as shown in fig. 2o, a layer of electrode material for the top electrode 10 is deposited, covering the top surface of the piezoelectric layer 2 and into the through hole 9 and the release hole.

Sixthly, the steps are as follows: as shown in fig. 2p, a layer of mass loading material is deposited on the top electrode 9.

Seventeen steps: as shown in fig. 2q, the top electrode material layer and the mass loading material layer are etched to remove the electrode material in the release holes and patterned to form the top electrode 10 and the mass loading layer 13. In the invention, the frequency can be compensated by thickening the top electrode. The sixteen and seventeen steps may also be omitted.

Eighteen steps: as shown in fig. 2r, a conductive material is deposited through a process of thin film deposition and then patterned to form electrode connection portions 11 including a top electrode connection portion and a bottom electrode connection portion. As shown in fig. 2r, electrode connection portions 11 are deposited and patterned to electrically connect electrode lead-out portions (conductive vias) of the bottom electrodes of the two resonators.

Nineteen steps: as shown in fig. 2s, an etchant is introduced through the release holes to release the second acoustic impedance layer material or the sacrificial layer inside the acoustic mirror cavity 12, so as to obtain a structure corresponding to fig. 1.

The above steps are exemplary steps, and as will be appreciated by those skilled in the art, the above processing sequence is not exclusive, and for example, the top electrode 10 may be deposited and patterned, followed by the formation of the via hole 9, followed by the deposition and formation of the bottom electrode connection portion 11. The order of the steps can be modified based on the known techniques by those skilled in the art, and all such modifications are within the scope of the present invention.

The manufacturing process of providing recesses on both the upper and lower sides of the piezoelectric layer of a resonator on one side, which can also be used to manufacture the structure shown in fig. 3 and 4, has been described above with reference to fig. 2a-2 s. For example, for the configuration of FIG. 3, steps 2k-2m described above may be omitted, while for the configuration shown in FIG. 4, steps 2a-2d described above may be omitted.

Based on the above manufacturing process for the bulk acoustic wave resonator assembly, the present invention also provides a method for manufacturing a bulk acoustic wave resonator, the bulk acoustic wave resonator comprising a substrate; an acoustic mirror; a bottom electrode; a top electrode; and a piezoelectric layer disposed between the bottom electrode and the top electrode, the method comprising the steps of: at least one side of the upper side and the lower side of the piezoelectric layer is provided with a concave part, and the bottom of the concave part is a flat surface; and disposing corresponding ones of the top and bottom electrodes in the region of the recess.

The invention thins the piezoelectric layer of the resonator, and adjusts the frequency and/or electromechanical coupling coefficient of the resonator in a large range by matching the thicknesses of the top electrode and the bottom electrode, thereby realizing the single-chip integration of the multi-frequency filter and the Kt of the resonator in the filter²The choice of values provides a greater degree of freedom. If it is desired that the difference between the electromechanical coupling coefficients of the two resonators in the resonator assembly shown in fig. 1 is large, for example, above 10%, trimming processes can be performed from both the top and bottom sides of the piezoelectric layer on the right side in fig. 1, so that the thickness of the piezoelectric layer is reduced more than the original thickness to affect the electromechanical coupling coefficient of the resonator on the right side more greatly. If it is desired that the difference in electromechanical coupling coefficients of the two resonators in the resonator assembly shown in fig. 1 is small, for example below 10%, it is possible to thin only one side of the piezoelectric layer on the right side in fig. 1, such as the lower side (fig. 3) or the upper side (fig. 4) so that the thickness of the piezoelectric layer is not reduced much relative to the original thickness, with a small effect on the electromechanical coupling coefficient of the resonator on the right side.

In the embodiment shown in FIG. 7, the thicknesses h3-h8 shown in FIG. 7 may also be selected to further affect the electromechanical coupling coefficient of each resonator. In FIG. 7, h5-h8 are all the thicknesses of the corresponding electrodes.

In the embodiment shown in fig. 3, the electromechanical coupling coefficient of each resonator is also adjusted with the mass loading layer selected.

In the present invention, although a single crystal piezoelectric layer is exemplified, in the present invention, the material of the piezoelectric layer may be a non-single crystal material.

In the present invention, when there are upper and lower grooves, the edges of the upper and lower grooves are not limited to the vertical alignment as shown in the corresponding embodiment, but may also be the projection of the upper groove in the vertical direction falling into the lower groove, or the projection of the lower groove in the vertical direction falling into the upper groove, or the upper and lower grooves have a certain overlapping area, which are all within the protection scope of the present invention.

It should be noted that, in the present invention, the bulk acoustic wave resonator assembly is described by taking an example in which two resonators are disposed on the same substrate, but the present invention is not limited thereto, and for example, more resonators may be disposed on the same substrate, and the plurality of resonators may have two or more piezoelectric layer thicknesses. For example, there may be three resonators in a resonator assembly, and two of the resonators may have upper and lower recesses, with the upper and lower recesses of the two resonators having different depths.

In the present invention, the inner and outer are in the lateral or radial direction with respect to the center of the effective area of the resonator, the side or end of a component near the center being the inner or inner end, and the side or end of the component away from the center being the outer or outer end.

In the present invention, the upper and lower are with respect to the bottom surface of the base of the resonator, and with respect to one component, the side thereof close to the bottom surface is the lower side, and the side thereof far from the bottom surface is the upper side.

In the present invention, the numerical ranges mentioned may be, besides the end points, the median values between the end points or other values, and are within the protection scope of the present invention.

As can be appreciated by those skilled in the art, the bulk acoustic wave resonator according to the present invention may be used to form a filter or other semiconductor device.

Based on the above, the invention provides the following technical scheme:

1. a bulk acoustic wave resonator comprising:

a substrate;

an acoustic mirror;

a bottom electrode;

a top electrode; and

a piezoelectric layer is formed on the substrate,

wherein:

the overlapping parts of the acoustic mirror, the top electrode, the bottom electrode and the piezoelectric layer in the thickness direction of the resonator form an effective area of the resonator;

at least one of the upper side and the lower side of the piezoelectric layer is provided with a concave part, and the bottom of the concave part is a flat surface;

and the corresponding electrodes in the top electrode and the bottom electrode are arranged in the area of the sunken part.

2. The resonator of claim 1, wherein:

the recess has a recess depth of not more than half the thickness of the piezoelectric layer.

3. The resonator of claim 1, wherein:

the upper side and the lower side of the piezoelectric layer are provided with concave parts, and the top electrode and the bottom electrode are respectively arranged in the corresponding concave parts.

4. The resonator of claim 3, wherein:

the thickness of the piezoelectric layer between the recesses is not less than one fifth of the original thickness of the piezoelectric layer in the thickness direction of the resonator.

5. The resonator of claim 1, wherein:

the side wall of at least one recess is at an angle in the range of 90-160 deg. to the bottom of the recess.

6. The resonator of any of claims 1-5, wherein:

an acoustic impedance structure is arranged between the piezoelectric layer and the substrate;

the acoustic impedance structure includes a first acoustic impedance layer and a second acoustic impedance layer disposed adjacent to each other in a lateral direction, the first acoustic impedance layer being different in acoustic impedance from the second acoustic impedance layer, the acoustic mirror being located between the first acoustic impedance layers in the lateral direction of the resonator.

7. The resonator of claim 6, wherein:

a first acoustic impedance layerThe width of the portion in contact with the piezoelectric layer and the second acoustic impedance layer is m λ₁A/4 and n lambda₂A/4, where m and n are both odd numbers, λ₁And λ₂Respectively, the acoustic wave wavelengths propagated in the lateral direction at the resonance frequency by the first acoustic impedance layer and the second acoustic impedance layer.

8. The resonator of claim 7, wherein:

m is the same as n.

9. The resonator of claim 6, wherein:

the material forming one of the first and second acoustic impedance layers is selected from the group consisting of aluminum nitride, silicon dioxide, silicon nitride, polysilicon, amorphous silicon, the material forming the other of the first and second acoustic impedance layers is selected from the group consisting of silicon dioxide, doped silicon dioxide, polysilicon, amorphous silicon, and the material forming the first acoustic impedance layer is different from the material forming the second acoustic impedance layer.

10. The resonator of claim 6, wherein:

the acoustic mirror is an acoustic mirror cavity;

the boundary of the acoustic mirror cavity in the lateral direction of the resonator is defined by the first acoustic impedance layer.

11. The resonator of any of claims 1-10, wherein:

the piezoelectric layer is a single crystal piezoelectric layer.

12. A bulk acoustic wave resonator assembly comprising:

the resonator comprises a first resonator and a second resonator, wherein the first resonator and the second resonator are both bulk acoustic wave resonators, at least the second resonator is the resonator according to any one of 1-11, the first resonator and the second resonator share the same piezoelectric layer, and the original thickness of the piezoelectric layer of the first resonator is the original thickness of the piezoelectric layer of the second resonator.

13. The resonator assembly of claim 12 wherein:

the first resonator and the second resonator are adjacent in the transverse direction and respectively have a first acoustic impedance structure and a second acoustic impedance structure, and the two acoustic impedance structures share at least one first acoustic impedance layer or at least one second acoustic impedance layer.

14. The resonator assembly of claim 12 or 13, wherein:

the thickness of the piezoelectric layer of the first resonator in its active area is the original thickness of the piezoelectric layer of the second resonator.

15. The assembly of any of claims 12-14, further comprising:

a third resonator being a bulk acoustic wave resonator and being a resonator according to any of claims 1-11, the third resonator sharing the same piezoelectric layer as the first and second resonators.

16. The assembly of claim 15, wherein:

the thickness of the piezoelectric layer of the third resonator within the active area of the third resonator is different from the thickness of the piezoelectric layer of the second resonator within the active area of the second resonator.

17. The assembly of any of claims 12-16, wherein:

the sum of the thicknesses of the top electrode and the bottom electrode of at least one resonator is different from the sum of the thicknesses of the top electrode and the bottom electrode of the other resonator, or the thickness of one electrode of at least one resonator is different from the thickness of the corresponding electrode of the other resonator; and/or

At least one resonator is provided with a mass loading layer.

18. A method of manufacturing a bulk acoustic wave resonator, the bulk acoustic wave resonator comprising a substrate; an acoustic mirror; a bottom electrode; a top electrode; and a piezoelectric layer disposed between the bottom electrode and the top electrode, the method comprising the steps of:

at least one side of the upper side and the lower side of the piezoelectric layer is provided with a concave part, and the bottom of the concave part is a flat surface; and

corresponding ones of the top and bottom electrodes are disposed within the area of the recess.

19. The method of 18, wherein: the method comprises the following steps:

step 1: forming a piezoelectric layer on a substrate, the substrate being disposed on a first side of the piezoelectric layer;

step 2: forming a second recess on a second side of the piezoelectric layer, wherein the bottom of the second recess is a flat surface;

and step 3: depositing and patterning a layer of bottom electrode material on the second side of the piezoelectric layer to form a bottom electrode in the second recess;

and 4, step 4: after step 3, forming a first acoustic impedance layer and a second acoustic impedance layer arranged adjacent to each other in the lateral direction on the piezoelectric layer, one of the first acoustic impedance layer and the second acoustic impedance layer bridging a sidewall of the second recess, an acoustic mirror space being formed between the first acoustic impedance layers adjacent in the lateral direction, at least a portion of the bottom electrode being located in the space in the lateral direction, the first acoustic impedance layer being different in acoustic impedance from the second acoustic impedance layer;

and 5: interfacing the base with the first and second acoustic impedance layers, and removing the substrate to expose the first side of the piezoelectric layer; and

step 6: a top electrode and a corresponding electrode electrical connection structure are formed on a first side of the piezoelectric layer.

20. The method of claim 19, wherein:

the step 6 comprises the following steps:

step 61: forming a first concave part on the first side of the piezoelectric layer, wherein the bottom of the first concave part is a flat surface;

step 62: a layer of top electrode material is deposited and patterned on the first side of the piezoelectric layer to form a top electrode within the first recess.

21. The method of 18, wherein: the method comprises the following steps:

step 1: forming a piezoelectric layer on a substrate, the substrate being disposed on a first side of the piezoelectric layer;

step 2: depositing and patterning a layer of bottom electrode material on the second side of the piezoelectric layer to form a bottom electrode;

and step 3: after step 2, forming a first acoustic impedance layer and a second acoustic impedance layer arranged adjacent to each other in the lateral direction on the piezoelectric layer, an acoustic mirror space being formed between the first acoustic impedance layers adjacent in the lateral direction, at least a part of the bottom electrode being located in the space in the lateral direction, the first acoustic impedance layer being different in acoustic impedance from the second acoustic impedance layer;

and 4, step 4: interfacing the base with the first and second acoustic impedance layers, and removing the substrate to expose the first side of the piezoelectric layer;

and 5: forming a first concave part on the first side of the piezoelectric layer, wherein the bottom of the first concave part is a flat surface;

step 6: a layer of top electrode material is deposited and patterned on the first side of the piezoelectric layer to form a top electrode and corresponding electrode electrical connection structure within the first recess.

22. The method of any one of claims 19-21, wherein:

the step of forming a recess on one side of the piezoelectric layer includes:

forming and patterning a barrier layer on the one side of the piezoelectric layer;

thinning the barrier layer and the exposed piezoelectric layer simultaneously by using a trimming process, wherein the thinning speed of the barrier layer is less than that of the piezoelectric layer, and forming a concave part with a flat bottom on one side of the piezoelectric layer based on thinning of the exposed piezoelectric layer;

removing the barrier layer remaining on the one side of the piezoelectric layer.

23. The method of any one of claims 19-22, wherein:

the widths of the parts of the first acoustic impedance layer and the second acoustic impedance layer in contact with the piezoelectric layer are m lambda₁A/4 and n lambda₂A/4, where m and n are both odd numbers, λ₁And λ₂Respectively, the acoustic wave wavelengths propagated in the lateral direction at the resonance frequency by the first acoustic impedance layer and the second acoustic impedance layer.

24. A method of adjusting the electromechanical coupling coefficients of resonators within a filter, the filter comprising at least one first resonator and at least one second resonator, at least the second resonator being a bulk acoustic wave resonator according to any one of claims 1-11, the method comprising the steps of:

the depth of the recess is selected to adjust an electromechanical coupling coefficient of the second resonator based on a thickness of a piezoelectric layer of the second resonator within the active area.

25. The method of claim 24, wherein:

the filter comprising at least two second resonators, the method comprising the steps of: adjusting a thickness of the piezoelectric layer of one of the at least two second resonators within the active area to be different from a thickness of the piezoelectric layer of the other of the at least two second resonators within the active area based on the depth of the recess such that there is a difference in electromechanical coupling coefficient for the at least two second resonators.

26. The method of claim 24 or 25, further comprising the step of:

the sum of the thicknesses of the top and bottom electrodes of at least one second resonator, and/or the thickness of the individual electrodes of at least one second resonator, is selected, and/or a mass loading layer is provided at least one second resonator to adjust the electromechanical coupling coefficient of the second resonator.

27. A filter comprising a bulk acoustic wave resonator according to any one of claims 1-11, or a bulk acoustic wave resonator assembly according to any one of claims 12-17.

28. An electronic device comprising a filter according to 27, or a bulk acoustic wave resonator according to any of claims 1-11, or a bulk acoustic wave resonator assembly according to any of claims 12-17.

The electronic device includes, but is not limited to, intermediate products such as a radio frequency front end and a filtering and amplifying module, and terminal products such as a mobile phone, WIFI and an unmanned aerial vehicle.

Although embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.