阅读说明：本技术 体声波谐振结构及其制造方法 (Bulk acoustic wave resonant structure and method of manufacturing the same ) 是由 张大鹏 高智伟 林瑞钦 段志 于 2021-02-22 设计创作，主要内容包括：本发明实施例公开了一种体声波谐振结构及其制造方法,其中,所述体声波谐振结构包括：衬底；依次层叠于衬底上的第一电极层、反射结构、压电层和第二电极层；其中,所述压电层中设置有环状的凹槽；所述凹槽处于有源区内,且靠近所述有源区的边缘。(The embodiment of the invention discloses a bulk acoustic wave resonance structure and a manufacturing method thereof, wherein the bulk acoustic wave resonance structure comprises: a substrate; a first electrode layer, a reflective structure, a piezoelectric layer and a second electrode layer sequentially stacked on a substrate; wherein an annular groove is arranged in the piezoelectric layer; the groove is located in the active region and close to the edge of the active region.)

1. A bulk acoustic wave resonant structure, comprising:

a substrate;

a first electrode layer, a reflective structure, a piezoelectric layer and a second electrode layer sequentially stacked on a substrate; wherein, an annular groove is arranged in the piezoelectric layer, and the groove is positioned in the active region and close to the edge of the active region.

2. The resonant structure of claim 1, wherein the outer profile of the groove comprises a closed shape comprising an arc and two or more straight lines.

3. The resonator structure of claim 1, wherein the number of grooves comprises a plurality of grooves, and the plurality of grooves are arranged in sequence along a first direction, wherein the first direction comprises a direction from an edge of the active region to a middle of the active region.

4. The resonant structure of claim 3, wherein the number of grooves comprises three.

5. The resonating structure of claim 3, wherein the opening depths of the plurality of recesses are all less than the thickness of the piezoelectric layer, and the opening depth of each recess in the plurality of recesses decreases sequentially along the first direction, increases sequentially along the first direction, is partially the same, or is all the same.

6. The resonant structure of claim 5, wherein the opening depth of each of the plurality of grooves decreases sequentially along the first direction.

7. The resonant structure of claim 6, wherein the number of grooves comprises N; the opening depth of the ith groove in the N grooves along the first direction is as follows: (N-i +1) × H/(N + 1); and N is a positive integer larger than 1, i is a positive integer, i is not less than 1 and not more than N, and H is the thickness of the piezoelectric layer.

8. The resonant structure of claim 5, wherein the opening depth of each of the plurality of grooves increases sequentially along the first direction; the number of the grooves comprises N; the opening depth of the ith groove in the N grooves along the first direction is as follows: i H/(N +1), wherein N is a positive integer greater than 1, i is a positive integer, i is not less than 1 and not more than N, and H is the thickness of the piezoelectric layer.

9. The resonant structure of claim 5, wherein the opening depth of each of the plurality of grooves is the same; the opening depth range of each groove in the plurality of grooves is: 1/2H-H; wherein H is the thickness of the piezoelectric layer.

10. The resonant structure of claim 3, wherein one groove comprises a plurality of sub-grooves; the plurality of sub-grooves together form a ring shape; the opening depth of each of the plurality of sub-grooves is the same.

11. The resonant structure of claim 10, wherein the cross-sectional shape of each of the plurality of sub-grooves comprises a stripe, a circle, or an oval.

12. The resonant structure according to claim 10, wherein the opening width of the sub-grooves and the spacing between adjacent sub-grooves are not equal to an integral multiple of a half wavelength of a higher harmonic of a lateral wave generated in the piezoelectric layer.

13. The resonant structure of claim 12, wherein the sub-grooves have an opening width ranging from: 0.05um to 10 um; the distance range between the adjacent sub-grooves is as follows: 0.05um to 10 um.

14. The resonant structure according to claim 1, wherein the opening of the recess is towards the top surface of the piezoelectric layer, or the opening of the recess is towards the bottom surface of the piezoelectric layer, or the recess is located in the middle of the piezoelectric layer.

15. The resonant structure of claim 1, wherein the recess has a filler material disposed therein, wherein the filler material has an acoustic impedance that differs from an acoustic impedance of the material of the piezoelectric layer by more than a predetermined amount.

16. The resonant structure of claim 15, wherein the filler material in the recess comprises air or an amorphous material.

17. The resonator structure according to any one of claims 1 to 16, wherein a frame is disposed on the second electrode layer, the frame has a ring-shaped three-dimensional structure, and the frame is located in the active region and near an edge of the active region.

18. A method of fabricating a bulk acoustic wave resonant structure, comprising:

forming a first electrode layer on a substrate;

forming a reflective structure between the substrate and the first electrode layer;

forming a piezoelectric layer on the first electrode;

forming an annular groove in the piezoelectric layer, wherein the groove is within the active region and near an edge of the active region;

a second electrode layer is formed on the piezoelectric layer.

19. The method of claim 18, further comprising:

filling an amorphous material in the groove;

the second electrode layer is formed on the piezoelectric layer filled with the amorphous material in the groove.

20. The method of claim 18, wherein forming an annular groove in the piezoelectric layer comprises:

forming an annular groove opened toward a top surface of the piezoelectric layer in the piezoelectric layer and filling a sacrificial layer in the groove;

the method further comprises the following steps:

and after the second electrode layer is formed on the piezoelectric layer, removing the sacrificial layer to fill the groove with air.

21. The method of claim 18, wherein the piezoelectric layer comprises M sub-piezoelectric layers, wherein M is a positive integer greater than or equal to 2, and wherein M is related to a variation rule of an opening depth of the recess;

the forming a piezoelectric layer on the first electrode, forming an annular recess in the piezoelectric layer, comprising:

sequentially forming a jth sub-piezoelectric layer in the M sub-piezoelectric layers on the first electrode layer, forming k annular jth sub-through holes penetrating through the jth sub-piezoelectric layer after each sub-piezoelectric layer is formed, filling an amorphous material in the jth sub-through hole, wherein j is a positive integer, j is greater than or equal to 1 and less than or equal to M < -1 >, k is a positive integer, the k is related to the number of grooves and the change rule of the opening depth of the grooves, and the jth sub-through hole +1 is communicated with the corresponding jth sub-through hole;

forming an Mth sub-piezoelectric layer on the Mth sub-piezoelectric layer after forming an Mth-1 sub-piezoelectric layer in the M sub-piezoelectric layers and filling an Mth sub-through hole to form the piezoelectric layer; all sub-vias together form the recess.

22. The method of claim 18, wherein prior to forming the second electrode layer on the piezoelectric layer, the method further comprises:

forming an annular through hole through the piezoelectric layer;

filling an amorphous material into the annular through hole to a preset height, wherein the preset height is related to the change rule of the depth of the groove opening;

and continuously filling the annular through hole with the same material as the piezoelectric layer material until the material is flush with the top surface of the piezoelectric layer.

Technical Field

The embodiment of the invention relates to the field of semiconductors, in particular to a bulk acoustic wave resonance structure and a manufacturing method thereof.

Background

Bulk Acoustic Wave (BAW) resonators (or "Bulk Acoustic Wave resonator structures") have the advantages of small size, high quality factor (Q value), and the like, and thus are widely used in mobile communication technologies, such as filters or duplexers in mobile terminals. In a mobile terminal, there is a case where a plurality of frequency bands are used simultaneously, which requires a steeper skirt and a smaller insertion loss of a filter or a duplexer. The performance of the filter is determined by the wave resonators constituting it, and increasing the Q value of the resonators enables a steep skirt and a small insertion loss. At the same time, too large a parasitic resonance may also adversely affect the performance of the filter or duplexer. How to reduce the parasitic resonance and improve the Q value of the bulk acoustic wave resonator becomes an urgent problem to be solved.

Disclosure of Invention

In view of the above, embodiments of the present invention provide a bulk acoustic wave resonator structure and a method for manufacturing the same.

An embodiment of the present invention provides a bulk acoustic wave resonant structure, including: a substrate; a first electrode layer, a reflective structure, a piezoelectric layer and a second electrode layer sequentially stacked on a substrate; wherein, an annular groove is arranged in the piezoelectric layer; the groove is located in the active region and close to the edge of the active region.

Another aspect of the embodiments of the present invention provides a method for manufacturing a bulk acoustic wave resonant structure, including: forming a first electrode layer on a substrate; forming a reflective structure between the substrate and the first electrode layer; forming a piezoelectric layer on the first electrode; forming an annular recess in the piezoelectric layer; the groove is positioned in the active region and close to the edge of the active region; a second electrode layer is formed on the piezoelectric layer.

In the embodiment of the invention, the annular groove is arranged at the edge of the active region in the piezoelectric layer, and the groove can inhibit the transverse shear wave generated when the bulk acoustic wave resonator is excited by an electric field from being transmitted to an external region, limit energy on longitudinal waves in the active region, reduce energy leakage and parasitic resonance and improve the Q value.

Drawings

Fig. 1 is a schematic diagram of a piezoelectric layer in a bulk acoustic wave resonator structure according to an embodiment of the present invention generating an acoustic wave due to a piezoelectric effect;

2 a-2 b are schematic diagrams illustrating simulation results of mode patterns of a bulk acoustic wave resonator at a series resonance frequency under the condition that no groove or a groove exists in a piezoelectric layer in a bulk acoustic wave resonance structure provided by the embodiment of the invention;

fig. 3 a-3 b are schematic diagrams illustrating test results of frequency quality factor and impedance of a bulk acoustic wave resonator under the condition that no groove or a groove exists in a piezoelectric layer in a bulk acoustic wave resonant structure according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a Smith chart showing whether there is a groove in the bulk acoustic wave resonator structure according to an embodiment of the present invention;

fig. 5a is a schematic top view of a bulk acoustic wave resonator structure 100 according to an embodiment of the present invention;

FIG. 5b is a schematic cross-sectional view of the bulk acoustic wave resonator structure 100 of FIG. 5a along the A-direction;

fig. 6 is a schematic diagram illustrating the effect of different positions on eliminating the lateral parasitic mode and increasing the Q value when the positions of the grooves are respectively set at different positions of the piezoelectric layer according to an embodiment of the present invention;

fig. 7 is a schematic diagram illustrating the effect of different numbers of grooves on eliminating the lateral parasitic mode and increasing the Q value according to an embodiment of the present invention;

FIGS. 8 a-8 c are schematic cross-sectional views of a film bulk acoustic wave resonator structure according to an embodiment of the present invention;

fig. 9 is a schematic view illustrating a groove filled with an amorphous material according to an embodiment of the present invention;

fig. 10 is a schematic view of a recess opening to a bottom surface of a piezoelectric layer according to an embodiment of the present invention;

fig. 11 is a schematic diagram illustrating the influence of different setting rules on eliminating the lateral parasitic mode and increasing the Q value when setting different rules satisfied by the opening depths respectively according to the embodiment of the present invention;

12 a-12 h are graphs showing experimental results of impedance versus frequency of a bulk acoustic wave resonator for different aperture depth values according to an embodiment of the present invention;

FIGS. 13 a-13 h are schematic diagrams illustrating experimental results of Smith charts of bulk acoustic wave resonators for different opening depth values according to embodiments of the present invention;

FIG. 14 is a schematic top view of another bulk acoustic wave resonator structure according to an embodiment of the present invention;

fig. 15 is a schematic smith chart of the bulk acoustic wave resonator structure according to the present invention, showing whether there is a frame or not;

FIG. 16 is a schematic cross-sectional view of another bulk acoustic wave resonator structure provided in accordance with an embodiment of the present invention;

fig. 17 is a schematic diagram of the effect of different positions on eliminating the lateral parasitic mode and increasing the Q value when the positions of the grooves are respectively set at different positions on the piezoelectric layer according to another embodiment of the present invention;

fig. 18 is a schematic diagram of the effect of different numbers of grooves on the elimination of the lateral parasitic mode and the increase of the Q value according to another embodiment of the present invention;

FIG. 19 is a schematic diagram illustrating the effect of different setting rules on eliminating lateral parasitic modes and increasing Q value when setting different rules satisfied by opening depths according to another embodiment of the present invention;

fig. 20 is a schematic flow chart illustrating an implementation of a method for manufacturing a bulk acoustic wave resonant structure according to an embodiment of the present invention;

FIGS. 21 a-21 f are schematic cross-sectional views illustrating a process of manufacturing a bulk acoustic wave resonator structure according to an embodiment of the present invention;

fig. 22a to 22d are schematic process cross-sectional views illustrating another method for manufacturing a bulk acoustic wave resonator structure according to an embodiment of the present invention.

Detailed Description

The technical solution of the present invention will be further elaborated with reference to the drawings and the embodiments. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

The present invention is more particularly described in the following paragraphs with reference to the accompanying drawings by way of example. Advantages and features of the present invention will become apparent from the following description and from the claims. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.

In the embodiments of the present invention, the terms "first", "second", and the like are used for distinguishing similar objects, and are not necessarily used for describing a particular order or sequence.

The technical means described in the embodiments of the present invention may be arbitrarily combined without conflict.

As shown in fig. 1, when electric energy is applied to upper and lower electrodes of a bulk acoustic wave resonator, piezoelectric layers located in the upper and lower electrodes generate an acoustic wave due to a piezoelectric effect. In addition to longitudinal waves, transverse shear waves (transverse shear waves may also be referred to as lateral waves or shear waves) are generated within the piezoelectric layer. The presence of transverse shear waves affects the energy of the primary longitudinal wave, which results in loss of energy and degrades the Q-value of the bulk acoustic wave resonator.

Therefore, one method to raise the Q value of a bulk acoustic wave resonator is to suppress the transverse shear wave to prevent the transverse shear wave from propagating from the active region to the outer region, thereby reducing the leakage of energy.

Researches show that the grooves are arranged at the edge of the active area of the piezoelectric layer of the bulk acoustic wave resonator, so that transverse shear waves can be restrained from being transmitted to the external area, energy is limited in the active area, parasitic resonance is reduced, and the Q value is improved.

Further, a simulation test was conducted on a mode shape diagram of the bulk acoustic wave resonator at the series resonance frequency, respectively, for different cases of whether or not there is a groove in the piezoelectric layer. FIG. 2a is a graph showing the simulation results of a mode shape plot of a bulk acoustic wave resonator at a series resonance frequency without a recess in the piezoelectric layer; figure 2b is a schematic diagram of the simulation result of the mode shape diagram of a bulk acoustic wave resonator at the series resonance frequency in the presence of a recess in the piezoelectric layer. As can be seen from fig. 2a and 2 b: the side waves of the bulk acoustic wave resonator with the grooves have less interference on the longitudinal waves, and the vibration is more concentrated in the middle of the active area. At the edge of the active region, the lateral wave is suppressed by the annular groove, and the vibration amplitude is smaller.

The frequency quality factor and the impedance of the bulk acoustic wave resonator are tested separately for different situations in which a recess is present in the piezoelectric layer. FIG. 3a is a graph showing the frequency quality factor and impedance of a bulk acoustic wave resonator without a recess in the piezoelectric layer; fig. 3b is a graph showing the results of the frequency quality factor and impedance test of the bulk acoustic wave resonator in the presence of a recess in the piezoelectric layer. As can be seen from fig. 3a and 3 b: the grooves can reduce parasitic resonance below the series resonance frequency, and the Q value of the bulk acoustic wave resonator with the grooves at the series resonance frequency is 2460, and the Q value of the bulk acoustic wave resonator without the grooves at the series resonance frequency is 2397, i.e., the Q value of the bulk acoustic wave resonator with the grooves is higher.

A Smith (english may be expressed as Smith) chart when observing whether or not there is a groove in the bulk acoustic wave resonator. Figure 4 is a schematic diagram of a smith chart of a bulk acoustic wave resonator with or without the presence of a recess in the piezoelectric layer. As shown in fig. 4, the notch can effectively reduce the parasitic resonance in the series-parallel resonance region, so that the parasitic resonance shifts below the series resonance point. That is, the design of adding the groove at the edge of the active region of the bulk acoustic wave resonator in the piezoelectric layer can attenuate the lateral wave, so that the energy is concentrated on the longitudinal wave in the active region, and the effects of suppressing the transverse parasitic mode (i.e. suppressing the parasitic resonance) and increasing the Q value are achieved.

Based on the above, in the embodiments of the present invention, the annular groove is provided at the edge of the active region in the piezoelectric layer, and the annular groove can suppress the propagation of the transverse shear wave generated when the bulk acoustic wave resonator is excited by the electric field to the external region, confine energy to the longitudinal wave in the active region, reduce the leakage of energy, reduce parasitic resonance, and improve the Q value.

Fig. 5a is a schematic top view of a bulk acoustic wave resonator structure 100 according to an embodiment of the present invention; fig. 5b is a schematic cross-sectional view of the bulk acoustic wave resonator structure 100 in fig. 5a along the direction a. Referring to fig. 5b, the bulk acoustic wave resonant structure 100 includes: a substrate 101; a first electrode layer 102, a reflective structure 103, a piezoelectric layer 104, and a second electrode layer 105 sequentially stacked on a substrate; wherein an annular groove 106 is provided in the piezoelectric layer 104, the groove 106 being located within the active region and near an edge of the active region.

In practical applications, the constituent material of the substrate 101 may include silicon (Si), germanium (Ge), and the like.

The first electrode layer 102 may be referred to as an upper electrode, and correspondingly, the second electrode layer 105 may be referred to as a lower electrode, through which electric energy may be applied to the bulk acoustic wave resonator. The first electrode layer 102 and the second electrode layer 105 may be made of the same material, and specifically may include: aluminum (Al), molybdenum (Mo), ruthenium (Ru), iridium (Ir), platinum (Pt), or the like.

The piezoelectric layer 104 can be used to generate vibration according to inverse piezoelectric characteristics, convert the electrical signals loaded on the first electrode layer 102 and the second electrode layer 105 into acoustic signals, and convert electrical energy into mechanical energy. In practical applications, the composition of the piezoelectric layer 104 may include: materials having piezoelectric characteristics such as aluminum nitride, zinc oxide, lithium tantalate, or the like; it may also be a doped piezoelectric material such as scandium doped.

The reflective structure 103 is used to reflect acoustic signals. When the acoustic wave signal generated by the piezoelectric layer 104 propagates towards the reflective structure 103, the acoustic wave signal may be totally reflected at the interface where the first electrode layer 102 and the reflective structure 103 contact, such that the acoustic wave signal is reflected back into the piezoelectric layer 104. Here, the active region includes a region where the first electrode layer 102, the reflective structure 103, the piezoelectric layer 104, and the second electrode layer 105 overlap in the second direction (the active region as shown in fig. 5 b); the second direction is a direction perpendicular to the surface of the substrate 101. It is to be understood that the second direction may also be understood as a direction in which the first electrode layer 102, the reflective structure 103, the piezoelectric layer 104 and the second electrode layer 105 are stacked on the substrate 101.

A recess 106 is provided in the piezoelectric layer 104 and along the edge of the active area, i.e. the outer contour of the recess 106 is similar to the shape of the upper or lower electrode. It should be noted that in practice the top view shown in fig. 5a does not allow direct viewing of the recess 106 in the piezoelectric layer, where the recess 106 is shown through the second electrode 105 in order to show the recess 106 more clearly.

In this embodiment, the location of the recess 106 cannot extend beyond the edge of the active area. Specifically, in order to determine the optimal arrangement position of the groove 106, the positions of the groove 106 are respectively arranged at different positions such as the inner edge of the active region, the first position outside the active region, the second position outside the active region, and the like for specific analysis. Here, the second location is further from the active region than the first location.

In practical applications, fig. 6 shows that, in the embodiment of the present invention, when the positions of the grooves are respectively set at different positions, the influences on eliminating the lateral parasitic mode and increasing the Q value are eliminated. In fig. 6, the first column is the corresponding test result of the bulk acoustic wave resonant structure when no groove is provided; the second column is a corresponding test result of the bulk acoustic wave resonance structure when the groove is arranged in the active region; the third column is a corresponding test result of the bulk acoustic wave resonant structure at the first position (corresponding to the position outside the active region 1 in fig. 6, specifically, outside the active region, but inside the reflective structure) outside the active region when the groove is disposed; the fourth column is a corresponding test result of the bulk acoustic wave resonant structure at a second position (corresponding to the position outside the active region 2 in fig. 6, specifically, outside the active region and outside the reflective structure) outside the active region when the groove is disposed. Figure 6 is a schematic diagram of a recess in a piezoelectric layer of a first behavioral bulk acoustic wave resonator arranged in a different position; the simulation test result of the mode shape diagram of the second action bulk acoustic wave resonator at the series resonance frequency is shown schematically; the third row is a schematic diagram of the slice simulation test result of the bulk acoustic wave resonator; the fourth line is a schematic diagram of the test results of the frequency quality factor and the impedance of the bulk acoustic wave resonator; the fifth element is a schematic diagram of the smith chart test results of the bulk acoustic wave resonator. As can be seen from fig. 6, compared with the bulk acoustic wave resonator without the groove, the bulk acoustic wave resonator with the groove disposed in the active region can effectively reduce the parasitic resonance in the series-parallel resonance region, and improve the Q value; when the groove is arranged on the bulk acoustic wave resonator at the first position outside the active area, the effect of inhibiting parasitic resonance is not obvious, but the Q value is improved; when the groove is arranged on the bulk acoustic wave resonator at the second position outside the active area, the effect of inhibiting parasitic resonance is not obvious, and the parasitic resonance in the series-parallel resonance area can be enhanced. That is, in order to achieve the effects of reducing the parasitic resonance in the series-parallel resonance region and increasing the Q value, the position of the groove 106 needs to be located in the active region. In practical applications, the distance from the outer edge of the groove 106 to the edge of the active region may be: 0-10 μm. Preferably 0 μm.

It will be appreciated that when the recess 106 is located near the middle of the active region, lateral waves formed in the piezoelectric layer 104 near the edges of the active region may not encounter the centrally located recess as they propagate in the transverse direction, thereby rendering the recess 106 inoperable.

In some embodiments, the outer profile of the groove 106 comprises a closed shape, the closed shape comprising an arc and two or more straight lines.

In practice, as shown in fig. 5a, the outer profile of the recess 106 may be slightly smaller than the upper electrode to ensure that the energy is confined within the active region. Here, the outer contour, which is the outer edge shape of the groove 106 as seen from a top view, can be understood with reference to fig. 5 a. It can be understood that when the outer contour of the groove 106 is a closed line segment with a uniform width, the shape of the groove is better, and the energy can be better confined in the active region.

In some embodiments, the number of the grooves 106 includes a plurality of grooves, and the plurality of grooves are sequentially arranged along a first direction, wherein the first direction includes a direction from the edge of the active region to the middle of the active region. Preferably, the number of grooves 106 includes three. When the lateral wave propagates along the film transversely to the edge of the active region, the lateral wave is mostly reflected and a small part is refracted and transmitted through the groove after meeting the air groove. After the side wave successively encounters the plurality of grooves, a substantial portion of the side wave is reflected.

Here, the plurality of grooves 106 are all annular and are sequentially arranged along the first direction. In practice, as shown in fig. 5a, the circumference of the ring in which the three grooves 106 are located is sequentially reduced along the first direction.

In practical application, fig. 7 shows that, in the embodiment of the present invention, when different numbers of grooves are respectively provided, the influences on eliminating the lateral parasitic mode and increasing the Q value are eliminated. In fig. 7, the first column is the corresponding test result of the bulk acoustic wave resonant structure when no groove is provided; the second column is a corresponding test result of the bulk acoustic wave resonance structure when the number of the grooves is 3; the third column is a corresponding test result of the bulk acoustic wave resonance structure when the number of the grooves is 1; the fourth column is a corresponding test result of the bulk acoustic wave resonance structure when the number of the grooves is 2; and the fifth column is a corresponding test result of the bulk acoustic wave resonance structure when the number of the grooves is 4. The test subjects represented by each row in fig. 7 are the same as the test subjects represented by each row in fig. 6. As can be seen from fig. 7, compared with the bulk acoustic wave resonator without the grooves, the bulk acoustic wave resonator with 3 grooves can effectively reduce the parasitic resonance in the series-parallel resonance region and improve the Q value; when 1 groove bulk acoustic resonator or 4 groove bulk acoustic resonators are arranged, parasitic resonance can be inhibited, meanwhile, the Q value is improved, but partial energy leaks to a second position outside the active region; when 2 groove bulk acoustic resonators are provided, the effect of parasitic resonance can be suppressed, but the effect is slightly worse than when 3 grooves are provided. That is, when the number of the grooves is set to 3, the best effect of reducing the parasitic resonance in the series-parallel resonance region and improving the Q value can be achieved.

It should be noted that the bulk acoustic wave resonant structure shown in fig. 5a and 5b is only an example provided by the present invention, and in practical application, the bulk acoustic wave resonant structure may be specifically divided into: a first type cavity Film Bulk Acoustic Wave Resonator (FBAR), a second type cavity FBAR, a Solid-state assembled Resonator (SMR), and the like. The scheme provided by the implementation of the invention can be suitable for the different types of bulk acoustic wave resonant structures.

In some embodiments, when the bulk acoustic wave resonator structure 100 includes the first cavity type FBAR, the reflective structure 103 includes a first electrode layer 102 protruding upward and forming a first cavity between the surface of the substrate 101, as shown in fig. 8 a.

In some embodiments, when the bulk acoustic wave resonator structure 100 includes the second cavity-type FBAR, the reflective structure 103 includes a second cavity formed between the surface of the substrate recessed downward and the first electrode layer 102, as shown in fig. 8 b.

In some embodiments, when the bulk acoustic wave resonant structure 100 includes an SMR resonant structure, the reflective structure 103 includes first dielectric layers and second dielectric layers having different acoustic impedances and alternately disposed in a stack, as shown in fig. 8 c.

In some embodiments, a filler material is disposed in the recess 106, and the difference between the acoustic impedance of the filler material and the acoustic impedance of the material of the piezoelectric layer 104 is greater than a predetermined value. Here, the preset value can be adjusted according to actual conditions. In practical applications, the larger the difference between the acoustic impedance of the filling material in the groove 106 and the acoustic impedance of the piezoelectric material is, the higher the reflection efficiency is. The recess 106 may be filled with air having an acoustic impedance much smaller than that of the piezoelectric material, or the recess 106 may be filled with an amorphous material. Illustratively, the amorphous material comprises silicon oxide (SiO)₂). When the recess 106 is filled with an amorphous material, as shown in fig. 9.

In some embodiments, the opening of the recess 106 is toward the top surface of the piezoelectric layer 104, or the opening of the recess 106 is toward the bottom surface of the piezoelectric layer 104, or the recess 106 is located in the middle of the piezoelectric layer. In practice, reference is made to fig. 5a for the case where the opening of the recess 106 is directed toward the top surface of the piezoelectric layer 104, and to fig. 10 for the case where the opening of the recess 106 is directed toward the bottom surface of the piezoelectric layer 104. The recess 106 being located in the middle of the piezoelectric layer 104 is to be understood that the recess 106 is actually a cavity located in the middle of the piezoelectric layer 104 with no opening facing. Note that when the opening of the groove 106 is directed to the bottom surface of the piezoelectric layer 104, or the groove 106 is located in the middle of the piezoelectric layer 104, a filling material is provided in the groove 106, and the filling material includes an amorphous material.

In practical applications, when the number of the grooves 106 includes a plurality of grooves, the opening depths of the plurality of grooves 106 satisfying different rules will have different effects on eliminating the lateral parasitic mode and increasing the Q value.

In some embodiments, the opening depths of the plurality of recesses 106 are each less than the thickness of the piezoelectric layer 104, and the opening depths of each of the plurality of recesses 106 decrease sequentially along the first direction, or increase sequentially along the first direction, or are partially the same, or are all the same.

It can be understood that when the lateral wave generated in the piezoelectric layer propagates to the edge of the active region along the transverse direction of the membrane (the propagation direction is opposite to the first direction), the lateral wave encounters the plurality of grooves successively, and when the opening depths of the plurality of encountered grooves gradually increase (the opening depths of the plurality of grooves decrease successively along the first direction), the lateral wave undergoes a plurality of transitions from weak to strong from the propagation direction of the lateral wave to the longitudinal propagation direction, and based on this, most of the lateral wave is reflected. The conversion into longitudinal waves is shown as reducing parasitic resonance in the series-parallel resonance area, and the effect of improving the Q value is optimal.

In practical applications, in order to determine the optimal rule that the opening depths of the plurality of grooves 106 satisfy and the optimal rule that the opening depths of the plurality of grooves vary, different rules are respectively set for specific analysis, as shown in fig. 11. The first column in fig. 11 is the corresponding test result of the bulk acoustic wave resonant structure without the provision of the recess; the second column is a corresponding test result of the bulk acoustic wave resonance structure when the opening depths of the plurality of grooves are sequentially decreased in the first direction; the third row is a corresponding test result of the bulk acoustic wave resonance structure when the depths of the openings of the plurality of grooves are sequentially increased along the first direction; the fourth column is a corresponding test result of the bulk acoustic wave resonance structure when the depths of the openings of the plurality of grooves are the same and are all the first depths; the fifth column is a schematic diagram of a rule that when the depths of the plurality of groove openings are the same and are all the second depths, the corresponding test results of the bulk acoustic wave resonant structure are sufficient (wherein the first depth is greater than the second depth). The test subjects represented by each row in fig. 11 are the same as the test subjects represented by each row in fig. 6. As can be seen from fig. 11, compared with the bulk acoustic wave resonator without the grooves, the depth of the openings of the grooves is decreased along the first direction, so that the parasitic resonance in the series-parallel resonance region can be effectively reduced, the parasitic resonance is shifted to a position below the series resonance point, and the Q value is increased; the depths of the openings of the plurality of grooves are increased in sequence along the first direction, so that parasitic resonance in a series-parallel resonance area can be reduced, and the Q value is slightly improved; the depth of the openings of the plurality of grooves meets the same requirement, and the bulk acoustic wave resonators with the same depth (such as 0.6 mu m) can effectively reduce parasitic resonance, the parasitic resonance is transferred to a position below a series resonance point, but the transferred parasitic resonance is larger than the parasitic resonance of the resonators with the grooves with different depths, and meanwhile, the Q value is improved; the bulk acoustic wave resonators with the same depth of the recess openings and all having a second depth (e.g., 0.4 μm) can reduce parasitic resonance, but have less than the first depth. That is to say, when the depths of the openings of the plurality of grooves are decreased gradually along the first direction, the best effect of reducing the parasitic resonance in the series-parallel resonance region and improving the Q value can be achieved.

Based thereon, in some embodiments, the opening depth of each of the plurality of grooves 106 decreases sequentially along the first direction. Wherein, in some embodiments, the number of grooves 106 comprises N; the opening depth of the ith groove in the N grooves along the first direction is as follows: (N-i +1) × H/(N + 1); wherein N is a positive integer greater than 1, i is a positive integer, i is greater than or equal to 1 and less than or equal to N, and H is the thickness of the piezoelectric layer.

In other implementations, the opening depths of some of the plurality of grooves 106 are the same, such as the opening depths of any two or more grooves are the same, and are different from the opening depths of the remaining grooves, that is, the opening depth of each of the plurality of grooves may not be set to decrease or increase sequentially along the first direction. For example, when there are 3 grooves, there may be 2 grooves having the same opening depth and different from the opening depth of the 3 rd groove.

In practical applications, N may range from: 1 to 4. When the number of the grooves is 3, the depth of the 3 grooves may be a multiple of the thickness of the 1/4 piezoelectric layer, and specifically, the opening depth of the 3 grooves in the first direction may be, in order: 3/4H, 2/4H, and 1/4H. When the depth of the groove is a multiple of a quarter of the thickness of the piezoelectric layer, the propagation direction of the lateral wave which is refracted is changed into longitudinal propagation, and the lateral wave is converted into a longitudinal wave, which is required.

In some embodiments, the opening depth of each of the plurality of grooves 106 increases sequentially along the first direction; the number of the grooves comprises N; the opening depth of the ith groove in the N grooves along the first direction is as follows: i H/(N +1), wherein N is a positive integer greater than 1, i is a positive integer, i is greater than or equal to 1 and less than or equal to N, and H is the thickness of the piezoelectric layer.

In practical applications, when the number of the grooves is 3, the depth of the 3 grooves may be a multiple of the thickness of the 1/4 piezoelectric layer, and specifically, the opening depth of the 3 grooves along the first direction may be sequentially: 1/4H, 2/4H, and 3/4H.

In some embodiments, the opening depth of each of the plurality of grooves 106 is the same; the opening depth range of each groove in the plurality of grooves is: 1/2H-H; where H is the thickness of the piezoelectric layer.

In practical application, when the opening depth of each groove in the plurality of grooves is the same, different opening depth values can be set, and the corresponding test results are analyzed specifically to determine a range value of a better opening depth.

12 a-12 h are graphs illustrating experimental results of impedance versus frequency for bulk acoustic wave resonators for different aperture depth values; fig. 13 a-13 h are schematic diagrams of experimental results of smith charts of bulk acoustic wave resonators for different opening depth values. It should be noted that H8 in fig. 12a to 12H and fig. 13a to 13H each indicates the opening depth of the groove, and the opening depth is expressed in μm, while the experiments in fig. 12a to 12H and fig. 13a to 13H are premised on the thickness value of the piezoelectric layer being 0.8 μm. As can be seen from fig. 12a to 12h and fig. 13a to 13h, the 0.1 μm notch resonator has a high Q value, but the smith circle is not round and has a large disturbance in the series-parallel resonance point. With the increase of the groove depth, the parasitic resonance in the series-parallel resonance point gradually disappears, the parasitic resonance below the series resonance point gradually increases, and when the groove depth is greater than 0.6 mu m, the parasitic resonance is gradually concentrated to form larger parasitic resonance below the series resonance point.

In some embodiments, one groove 106 may include a plurality of sub-grooves; the plurality of sub-grooves together form a ring shape as shown in fig. 14. That is, one groove may not be a complete groove, but may be formed by a plurality of sub-grooves. In some embodiments, the opening depth of each of the plurality of sub-grooves is the same; the cross-sectional shape of each of the plurality of sub-grooves includes a long strip shape, a circular shape, or an oval shape.

It has been mentioned above that when the depth of the opening of the recess is a multiple of a quarter of the thickness of the piezoelectric layer, the direction of propagation of the refracted lateral wave changes to longitudinal propagation, converting the lateral wave into a longitudinal wave, which is desirable. Meanwhile, if the spacing between the sub-grooves and the opening width of the sub-grooves are not properly designed, the lateral wave may be reflected back and forth between adjacent grooves to form a standing wave, and a certain higher order resonance of the standing wave may be located near the series resonance point of the longitudinal wave, thereby affecting the performance of the resonator. Based on this, in order to destroy interference of the side waves, the inter-gap of the sub-grooves and the opening width of the sub-grooves cannot be integral multiples of half-wavelengths of higher harmonics of the side waves generated in the piezoelectric layer. Here, the opening width of the sub-groove refers to the opening size of the sub-groove in the first direction, and specifically, reference may be made to W shown in fig. 14; the spacing of the sub-grooves refers to the spacing dimension of the sub-grooves along the first direction, and specifically, reference may be made to L in fig. 14.

Based on this, in some embodiments, the opening width of the sub-groove and the interval between the adjacent sub-grooves are not equal to an integral multiple of a half wavelength of a higher harmonic of the side wave generated in the piezoelectric layer.

In some embodiments, the opening width of the sub-groove ranges from: 0.05um to 10 um; the distance range between adjacent sub-grooves is as follows: 0.05um to 10 um.

Exemplarily, as shown in fig. 14, the cross-sectional shape of the sub-groove includes a long strip, the opening width W of the sub-groove is 1 μm, and the interval L of the sub-groove is 1 μm; the length of the sub-groove, i.e., the size of the opening of the sub-groove in the direction perpendicular to the first direction, was 51 μm.

In some embodiments, a bezel may be formed over the upper electrode layer. Fig. 15 is a schematic diagram of a smith chart of the bulk acoustic wave resonator under a different condition of whether a frame exists above the upper electrode layer. As shown in fig. 15, the frame may suppress the lateral wave in the active region, so that the parasitic resonance in the series-parallel resonance point of the bulk acoustic wave resonator is reduced, but the parasitic resonance below the series resonance point is significantly increased. Comparing fig. 4 and fig. 15, the parasitic resonance of the bulk acoustic wave resonator with the groove below the series resonance point is much smaller and almost negligible compared to the bulk acoustic wave resonator with the rim.

In view of this, in the embodiment of the present invention, the frame 107 may be formed above the second electrode layer 105, and the annular groove 106 may be formed in the piezoelectric layer 104, so that the parasitic resonance in the series-parallel resonance point of the bulk acoustic wave resonator is reduced by the frame 107, the Q value is increased, and the parasitic resonance below the series resonance point is significantly reduced by the groove 106.

In some embodiments, at least one of the first electrode layer, the piezoelectric layer, and the second electrode layer is provided with a frame 107 formed by bumps or bumps, and the number of the bumps or bumps is at least 1. The frame 107 has a ring-shaped three-dimensional structure, and the frame 107 is located in the active region and close to the edge of the active region.

In practice, as shown in fig. 16, the frame 107 is disposed on the surface of the second electrode 105 and along the edge of the active region. That is, the outline of the bezel 107 is similar to the shape of the upper electrode or the lower electrode. In some embodiments, the outer contour of the bezel 107 may be formed by one arc line and two or more straight lines. In practice, the outer profile of the frame 107 may be slightly smaller than the upper electrode to ensure that the energy is confined in the active region. Here, the frame 107 has a ring-shaped three-dimensional structure, and it can be understood that the frame 107 has a certain width and thickness. In other embodiments, the outer contour of the bezel 107 includes a closed, uniform width line segment.

In some embodiments, the composition material of the frame 107 and the composition material of the first electrode layer 102 and the second electrode layer 105 may be the same or different. More specifically, the material of the frame 106 may include: preferably, the material of the frame 107 may include aluminum, molybdenum, ruthenium, iridium, platinum, or the like. When the composition material of the frame 107 is the same as that of the second electrode layer 105, the frame 107 may be formed together with the second electrode layer 105 or may be formed separately after the second electrode layer 105 is formed.

In the bulk acoustic wave resonator in which both the grooves 106 and the frame 107 were provided, the positions where the grooves 106 were provided, the number of the grooves 106 provided, and the rules that the opening depths of the plurality of grooves 106 satisfied when a plurality of grooves were present were also analyzed. Specifically, the method comprises the following steps:

in practical application, when the frame 107 is disposed, in order to determine an optimal disposition position of the groove 106, the positions of the groove 106 are respectively disposed at a first position inside the active region, outside the active region, and a second position outside the active region; wherein the second location is a greater distance from the active region than the first location.

In practical applications, fig. 17 shows that, in the embodiment of the present invention, when the positions of the grooves are respectively set at different positions, the different positions have the influence on eliminating the lateral parasitic mode and increasing the Q value. The description of each row and each column of fig. 17 may refer to fig. 6. As can be seen from fig. 17, compared with the bulk acoustic wave resonator without the groove, the bulk acoustic wave resonator with the groove disposed in the active region can reduce the parasitic resonance below the series resonance frequency, and make the Q value more concentrated at the series resonance frequency, and at the same time, the Q value is also improved; when the groove is arranged on the bulk acoustic wave resonator at the first position outside the active area, the effect of inhibiting parasitic resonance is not obvious, and the Q value is not more concentrated; a recess arranged in the bulk acoustic wave resonator at a second location outside the active area will allow a part of the energy to leak to the second location outside the active area, so that the piezoelectric layer at the second location outside the active area will also be displaced vibrationally. That is, when the frame 107 is disposed, the position of the groove 106 also needs to be located in the active region in order to achieve the effects of reducing the parasitic resonance in the series-parallel resonance region and increasing the Q value.

In practical applications, when the frame 107 is provided, different numbers of the grooves 106 are respectively provided for specific analysis in order to determine the optimal number of the grooves 106.

In practical applications, fig. 18 shows that, in the embodiment of the present invention, when different numbers of grooves are respectively provided, the different numbers of grooves have influences on eliminating the lateral parasitic mode and increasing the Q value. The description of each row and each column of fig. 18 can refer to fig. 7. As can be seen from fig. 18, compared with the bulk acoustic wave resonator without the grooves, the bulk acoustic wave resonator with 3 grooves can reduce the parasitic resonance below the series resonance frequency, and make the Q value more concentrated at the series resonance frequency, and at the same time, the Q value is also improved; when 1 groove bulk acoustic resonator or 4 groove bulk acoustic resonators are arranged, parasitic resonance can be inhibited, meanwhile, the Q value is improved, but partial energy leaks to a non-cavity area; when 2 groove bulk acoustic resonators are provided, the effect of parasitic resonance can be suppressed, but the effect is slightly worse than when 3 grooves are provided. That is, when the frame 107 is provided, when the number of the grooves 106 is set to 3, the best effect of reducing the parasitic resonance in the series-parallel resonance region and improving the Q value can be achieved.

In practical applications, when the frame 107 is provided, different rules are respectively set for specific analysis in order to determine the rule that the optimal opening depths of the plurality of grooves 106 satisfy.

In practical applications, fig. 19 shows that, in the embodiment of the present invention, when different rules satisfied by the opening depths are set respectively, the different setting rules have influences on eliminating the lateral parasitic mode and increasing the Q value. The description of each row and each column of fig. 19 can refer to fig. 11. Note that, in fig. 19, only one set is provided when the opening depths of the plurality of grooves 106 are the same. As can be seen from fig. 19, compared with the bulk acoustic wave resonator without the grooves, the depth of the openings of the grooves is decreased along the first direction, so that the parasitic resonance in the series-parallel resonance region can be effectively reduced, the parasitic resonance is shifted to a position below the series resonance point, and the Q value is increased; the depths of the openings of the plurality of grooves are such that the bulk acoustic wave resonators sequentially increasing along the first direction can reduce parasitic resonance in the series-parallel resonance region, but the reduced amplitude is less than the reduced amplitude when the depths of the openings of the plurality of grooves are such that the depths of the openings of the plurality of grooves sequentially decrease along the first direction, and the Q value is slightly increased; the depth of the plurality of groove openings meets the requirement of the same bulk acoustic wave resonator, so that parasitic resonance can be reduced, the parasitic resonance is transferred to the position below the series resonance point, but the reduced amplitude is less than the depth of the plurality of groove openings, the reduced amplitude under the condition of sequentially decreasing along the first direction is met, and meanwhile, the Q value is improved. That is to say, when the frame 107 is disposed, when the depths of the openings of the plurality of grooves decrease gradually along the first direction, the best effect of reducing the parasitic resonance in the series-parallel resonance region and improving the Q value can be achieved.

In the embodiment of the invention, the annular groove is arranged at the edge of the active region in the piezoelectric layer, and the groove can inhibit the transverse shear wave generated when the bulk acoustic wave resonator is excited by an electric field from being transmitted to an external region, limit energy on a longitudinal wave in the active region, reduce energy leakage, reduce parasitic resonance and improve Q value.

Based on the bulk acoustic wave resonant structure, an embodiment of the present invention further provides a method for manufacturing a bulk acoustic wave resonant structure, as shown in fig. 20, the method includes:

step 2001: forming a first electrode layer on a substrate;

step 2002: forming a reflective structure between the substrate and the first electrode layer;

step 2003: forming a piezoelectric layer on the first electrode;

step 2004: forming an annular groove in the piezoelectric layer, wherein the groove is in the active region and is close to the edge of the active region;

step 2005: a second electrode layer is formed on the piezoelectric layer.

The manufacturing methods of the first electrode layer, the reflective structure, the piezoelectric layer, and the second electrode layer are well known in the related art, and are not described herein again. The following focuses on the manner in which the recesses in the piezoelectric layer are formed.

In some embodiments, the method further comprises:

filling amorphous material in the groove;

a second electrode layer is formed on the piezoelectric layer filled with the amorphous material in the recess.

Different manufacturing methods can be used for different opening orientations, different recesses filled with material. In some embodiments, forming an annular recess in the piezoelectric layer comprises:

forming an annular groove in the piezoelectric layer, the opening of which faces the top surface of the piezoelectric layer, and filling the groove with a sacrificial layer;

after forming the second electrode layer on the piezoelectric layer, the sacrificial layer is removed so that the recess is filled with air.

That is, when the opening of the recess faces the top of the piezoelectric layer and the recess is filled with a solid material, such as an amorphous material, the recess may be formed in the piezoelectric layer by an etching process, and the second electrode layer may be formed on the piezoelectric layer after the recess is filled with the solid material. When the opening of the groove faces the top of the piezoelectric layer and the groove is filled with air, it is necessary to form a groove in the piezoelectric layer by an etching process, then form a sacrificial layer in the groove, then form a second electrode layer on the piezoelectric layer, and finally remove the sacrificial layer.

In other embodiments, the piezoelectric layer includes M sub-piezoelectric layers, where M is a positive integer greater than or equal to 2, and M is related to a variation rule of the opening depth of the groove;

forming a piezoelectric layer on the first electrode, forming an annular recess in the piezoelectric layer, comprising:

sequentially forming a jth sub-piezoelectric layer in the M sub-piezoelectric layers on the first electrode layer, forming k annular jth sub-through holes penetrating through the jth sub-piezoelectric layer after each sub-piezoelectric layer is formed, filling an amorphous material in the jth sub-through hole, wherein j is a positive integer, j is more than or equal to 1 and less than or equal to M-1, k is a positive integer, k is related to the number of grooves and the change rule of the opening depth of the grooves, and the jth sub-through hole +1 is communicated with the corresponding jth sub-through hole;

forming an M sub-piezoelectric layer on the M-1 sub-piezoelectric layer after forming the M-1 sub-piezoelectric layer and filling the M-1 sub-through hole in the M sub-piezoelectric layers to form a piezoelectric layer; all sub-vias together form a recess.

That is, when the opening of the groove faces the bottom surface of the piezoelectric layer, and the filling material is disposed in the groove, and the filling material includes an amorphous material, the first manufacturing method may be: forming a part of the piezoelectric layer, then forming a through hole penetrating the formed part of the piezoelectric layer, and completely filling the through hole with an amorphous material (the steps of forming a part of the piezoelectric layer, perforating, and filling may be repeated a plurality of times according to a variation rule of an opening depth of the recess); depositing a residual piezoelectric layer on the formed part of the piezoelectric layer to obtain a complete piezoelectric layer; finally, a second electrode layer is formed on the completed piezoelectric layer.

In practical application, the piezoelectric layer can be divided into a plurality of sub-piezoelectric layers according to the opening depth change rule of the groove, and then a final groove structure is obtained by adopting a layer-by-layer growth and layer-by-layer selective perforation mode. It should be noted that the number of the sub-piezoelectric layers is related to the variation rule of the opening depths of the grooves, for example, if the opening depths of the grooves are the same, the number of the sub-piezoelectric layers is 2; if the opening depth of the grooves increases or decreases along the first direction, the number of the sub-piezoelectric layers is the number of the grooves with different opening depths plus 1 (plus 1 is the part without the opening on the top of the piezoelectric layer). The sub-channel holes formed in the sub-piezoelectric layer of the upper layer communicate with the sub-channel holes formed in the sub-piezoelectric layer of the upper layer, that is, the sub-channel holes formed in the sub-piezoelectric layers of the respective layers are all aligned. For the selective perforation of each layer, the number of the grooves and the variation rule of the opening depth are all related, for example, when the opening depths of three grooves are sequentially increased along a first direction, 3 first sub-channel holes are formed in the first sub-piezoelectric layer, when a second sub-channel hole is formed in the second sub-piezoelectric layer, a second sub-channel hole needs to be formed on 2 first sub-via holes far from the edge of the active region, when a third sub-channel hole is formed in the third sub-piezoelectric layer, a third sub-channel hole needs to be formed on 1 second sub-via hole far from the edge of the active region, and the first sub-via hole, the second sub-via hole and the third sub-via hole together form the groove.

Illustratively, the first manufacturing method is explained in detail with reference to fig. 21a to 21 f. In this example, the openings of the grooves face the bottom surface of the piezoelectric layer, the grooves are provided with amorphous material therein, the number of the grooves is three, and the opening depths of the three grooves decrease in order along the first direction. M is 4; j is 1, 2, 3; k is 3, 2, 1.

Forming a piezoelectric layer on the first electrode, forming an annular recess in the piezoelectric layer, comprising:

as shown in fig. 21a, a first sub-piezoelectric layer 140-1 is formed on the first electrode layer, and 3 ring-shaped first sub-via holes 160-1 penetrating the first sub-piezoelectric layer are formed; as shown in fig. 21b, the amorphous material is filled in all of the 3 first sub-vias 160-1; as shown in fig. 21c, a second sub-piezoelectric layer 140-2 is formed on the first sub-piezoelectric layer 140-1, and 2 ring-shaped second sub-via holes 160-2 penetrating the second sub-piezoelectric layer 140-2 are formed; the second sub-vias 160-2 extend into the corresponding first sub-vias 160-1 (of the 2 annular second sub-vias 160-2 extending into the 2 first sub-vias 160-1 closer to the edge of the active region).

As shown in fig. 21d, the 2 second sub-vias 160-2 are all filled with an amorphous material; as shown in fig. 21d, a third sub-piezoelectric layer 140-3 is formed on the second sub-piezoelectric layer 140-2, and 1 ring-shaped third sub-via hole 160-3 penetrating the third sub-piezoelectric layer 140-3 is formed; the third sub-vias 160-3 extend into the corresponding second sub-vias 160-2 (extension of 1 ring-shaped third sub-via 160-3 into the nearest 1 second sub-via 160-2 near the edge of the active region).

As shown in fig. 21e, the third sub-via 160-3 is filled with an amorphous material; as shown in fig. 21e, a fourth sub-piezoelectric layer 140-4 is formed on the third sub-piezoelectric layer 140-3; the first sub-piezoelectric layer 140-1, the second sub-piezoelectric layer 140-2, the third sub-piezoelectric layer 140-3 and the fourth sub-piezoelectric layer 140-4 together form the piezoelectric layer 140; the first sub-via 160-1, the second sub-via 160-2, and the third sub-via 160-3 collectively form the groove 160.

After that, as shown in fig. 21f, a second electrode layer 105 is formed on the piezoelectric layer 104.

In other embodiments, prior to forming the second electrode layer on the piezoelectric layer, the method further comprises:

forming a ring-shaped through hole penetrating the piezoelectric layer;

filling an amorphous material into the annular through hole to a preset height, wherein the preset height is related to the change rule of the opening depth of the groove;

and continuously filling the annular through hole with the same material as the piezoelectric layer material until the material is flush with the top surface of the piezoelectric layer.

That is, when the opening of the groove faces the bottom surface of the piezoelectric layer, and the filling material is disposed in the groove, and the filling material includes an amorphous material, the second manufacturing method may be: firstly, forming a complete piezoelectric layer and forming a through hole penetrating through the complete piezoelectric layer; then partially filling an amorphous material in the through hole, namely filling the amorphous material to a preset height (the preset height refers to the opening depth of each groove); filling the other part of the rest through hole with the same material as the piezoelectric layer; finally, a second electrode layer is formed on the completed piezoelectric layer.

For example, the second manufacturing method will be described in detail with reference to fig. 22a to 22 d. In this example, the openings of the grooves face the bottom surface of the piezoelectric layer, the grooves are provided with amorphous material therein, the number of the grooves is three, and the opening depths of the three grooves decrease in order along the first direction.

Before forming the second electrode layer 105 on the piezoelectric layer 104, the method further comprises:

as shown in fig. 22a, three ring-shaped through holes are formed through the piezoelectric layer 104; as shown in fig. 22b, filling the three through holes with an amorphous material to a height (sequentially decreasing along the first direction) at which the opening depths of the three grooves are located; as shown in fig. 22c, the three through holes are filled with the same material as the piezoelectric layer material to be flush with the top surface of the piezoelectric layer 104. After that, as shown in fig. 22d, a second electrode layer 105 is formed on the piezoelectric layer 104.

It should be noted that fig. 22 a-22 d only show the manufacturing process in which the opening depths of the three grooves decrease in sequence along the first direction, and it can be understood that when the opening depths of the three grooves increase in sequence along the first direction, the three through holes are filled with the amorphous material to the heights at which the opening depths of the three grooves are located (increase in sequence along the first direction).

Based on the description of the above method, when the groove is located in the middle of the piezoelectric layer, it can be implemented by adding one sub-piezoelectric layer on the basis of the above three embodiments, and details are not repeated here.

In the embodiments provided in the present invention, it should be understood that the disclosed apparatus, system, and method may be implemented in other ways. The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.