CN114900145A

CN114900145A - Bulk acoustic wave resonator and manufacturing method thereof

Info

Publication number: CN114900145A
Application number: CN202210388389.6A
Authority: CN
Inventors: 唐滨; 赖志国; 杨清华
Original assignee: Suzhou Huntersun Electronics Co Ltd
Current assignee: Suzhou Huntersun Electronics Co Ltd
Priority date: 2022-04-14
Filing date: 2022-04-14
Publication date: 2022-08-12

Abstract

The invention provides a method for manufacturing a bulk acoustic wave resonator, which comprises the following steps: providing a substrate, wherein the substrate comprises a first surface and a second surface opposite to the first surface; etching the substrate to form a groove on the first surface, and filling the groove with a sacrificial material; forming a laminated structure covering the groove on the substrate, wherein the laminated structure sequentially comprises a lower electrode, a piezoelectric layer and an upper electrode from bottom to top; etching the second surface of the substrate to form at least one release hole in communication with the recess; and releasing the sacrificial material in the groove through at least one release hole to form a cavity between the laminated structure and the substrate, wherein the cavity has an overlapping region with the lower electrode, the piezoelectric layer and the upper electrode in the thickness direction of the device. Correspondingly, the invention also provides the bulk acoustic wave resonator. The implementation of the invention is beneficial to improving the reliability, stability and productivity of the device.

Description

Bulk acoustic wave resonator and manufacturing method thereof

Technical Field

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

Background

The air-gap bulk acoustic wave resonator is one of the most widely used bulk acoustic wave resonators at present. Referring to fig. 1(a) to 1(d), fig. 1(a) to 1(d) are schematic cross-sectional views of stages of manufacturing an air-gap bulk acoustic wave resonator according to the prior art. First, as shown in fig. 1(a), a substrate 10 is provided and the substrate 10 is etched to form a groove, and a sacrificial material 11 is filled in the groove. Next, as shown in fig. 1(b), a stacked structure is formed on the substrate 10, and the stacked structure is located above the groove and includes a lower electrode 12, a piezoelectric layer 13, and an upper electrode 14 in this order from bottom to top. Wherein the formation process of the laminated structure is as follows: a lower electrode 12 covering a sacrificial material 11 is first formed on a substrate 10, a piezoelectric layer 13 covering the lower electrode 12 is then formed on the substrate 10, and finally an upper electrode 14 is formed on the piezoelectric layer 13. The stack is then etched to form release holes 15 exposing the sacrificial material, as shown in figure 1 (c). Finally, as shown in fig. 1(d), the sacrificial material 11 in the groove is removed through the release hole 15 using an etching solution to form a cavity 16 for acoustic wave reflection between the lower electrode 12 and the substrate 10. The upper electrode 14, the piezoelectric layer 13, the lower electrode 12, and the cavity 16 have an overlapping region (i.e., a region between two dotted lines in fig. 1 (d)) in the device thickness direction, which is a resonance region of the bulk acoustic wave resonator. Accordingly, the region of the bulk acoustic wave resonator outside the resonance region is the non-resonance region.

In order to avoid the formation of the release holes 15 affecting the resonant region of the bulk acoustic wave resonator and thus affecting the device performance, and at the same time to ensure that the sacrificial material 11 in the recess is exposed, the release holes 15 are usually formed in the stacked structure at positions outside the resonant region and above the sacrificial material 11 in the prior art. The disadvantages of this approach are: (1) after the cavity 16 is formed by removing the sacrificial material 11 through the release holes 15, the portion of the stacked structure above the cavity 16 is suspended, and since the release holes 15 are formed in the suspended portion of the stacked structure, the stability and reliability of the device are reduced, and the device is prone to break; (2) since the release holes 15 are formed outside the resonant region, when the sacrificial material 11 in the groove is released through the release holes 15, the etching solution can only gradually corrode from the edge of the sacrificial material 11 inwards, which leads to low release efficiency of the sacrificial material and further affects the manufacturing yield of the device; (3) since it is necessary to provide a region for forming the release hole 15 in the stacked structure, a waste of the device area is caused to some extent.

Disclosure of Invention

In order to overcome the above-mentioned drawbacks of the prior art, the present invention provides a method for manufacturing a bulk acoustic wave resonator, the method comprising:

providing a substrate, wherein the substrate comprises a first surface and a second surface opposite to the first surface;

etching the substrate to form a groove on the first surface, and filling the groove with a sacrificial material;

forming a laminated structure covering the groove on the substrate, wherein the laminated structure sequentially comprises a lower electrode, a piezoelectric layer and an upper electrode from bottom to top;

etching the second surface of the substrate to form at least one release hole in communication with the recess;

and releasing the sacrificial material in the groove through the at least one release hole to form a cavity between the laminated structure and the substrate, wherein the cavity has an overlapping area with the lower electrode, the piezoelectric layer and the upper electrode in the thickness direction of the device.

According to an aspect of the present invention, in the manufacturing method, the horizontal sectional shape of the release hole is a circle, a polygon, or an irregular shape.

According to another aspect of the invention, in the manufacturing method, the bottom surface of the groove is in a regular N-sided polygon shape, wherein N is greater than or equal to 3; the number of the release holes is equal to N +1, one of the release holes penetrates through the central area of the bottom surface of the groove, and the other N release holes respectively penetrate through the N vertex areas of the bottom surface of the groove.

According to still another aspect of the present invention, the manufacturing method further includes, after forming the stacked-layer structure on the substrate: forming a protective layer covering the laminated structure; and the manufacturing method further comprises the following steps after the second surface of the substrate is etched to form at least one release hole communicated with the groove: and removing the protective layer.

According to still another aspect of the present invention, before etching the second surface of the substrate to form at least one release hole communicating with the groove, the manufacturing method further includes: thinning the substrate from the second surface.

According to still another aspect of the present invention, after the sacrificial material within the groove is released through the at least one release hole to form a cavity between the stacked structure and the substrate, the manufacturing method further includes: forming a sealing layer on the second surface of the substrate to seal the release hole.

According to still another aspect of the present invention, in the manufacturing method, a temperature coefficient of a material of the sealing layer is opposite to a temperature coefficient of a material of the piezoelectric layer, and/or a thermal conductivity of a material of the sealing layer is higher than a thermal conductivity of the substrate.

The present invention also provides a method of manufacturing a bulk acoustic wave resonator, the method comprising:

etching the substrate to form a groove on the first surface and at least one release hole extending towards the second surface but not penetrating through the second surface on the bottom surface of the groove;

filling the release holes and the grooves with a sacrificial material;

forming a laminated structure on the substrate, wherein the laminated structure sequentially comprises a lower electrode, a piezoelectric layer and an upper electrode from bottom to top;

thinning the substrate from the second surface until the sacrificial material is exposed;

and releasing the sacrificial material to form a cavity between the laminated structure and the substrate, wherein the cavity and the lower electrode, the piezoelectric layer and the upper electrode have an overlapping area in the thickness direction of the device.

According to another aspect of the invention, in the manufacturing method, the bottom surface of the groove is in a regular N-sided polygon shape, wherein N is greater than or equal to 3; the number of the release holes is equal to N +1, one of the release holes is formed in the central region of the groove bottom surface, and the other N release holes are respectively formed in the N vertex regions of the groove bottom surface.

According to still another aspect of the present invention, after releasing the sacrificial material to form a cavity between the stacked structure and the substrate, the manufacturing method further includes: forming a sealing layer on the second surface of the substrate to seal the release hole.

The present invention also provides a bulk acoustic wave resonator, comprising:

a substrate comprising a first surface and a second surface opposite thereto;

the laminated structure is formed on the substrate and sequentially comprises a lower electrode, a piezoelectric layer and an upper electrode from bottom to top;

a cavity formed between the laminated structure and the substrate, wherein an overlapping area exists between the lower electrode, the piezoelectric layer, the upper electrode and the cavity in the thickness direction of the device;

at least one release hole formed at the second surface of the substrate and communicating with the cavity.

According to an aspect of the present invention, in the bulk acoustic wave resonator, a horizontal sectional shape of the release hole is a circle, a polygon, or an irregular shape.

According to another aspect of the present invention, in the bulk acoustic wave resonator, a bottom surface of the cavity is in a regular N-sided polygon shape, where N is greater than or equal to 3; the number of the release holes is equal to N +1, one of the release holes penetrates through the central area of the bottom surface of the cavity, and the other N release holes respectively penetrate through the N vertex areas of the bottom surface of the cavity.

According to still another aspect of the present invention, the bulk acoustic wave resonator further includes: a sealing layer formed on the second surface of the substrate, forming a seal against the release hole.

According to still another aspect of the present invention, in the bulk acoustic wave resonator, a temperature coefficient of a material of the sealing layer is opposite to a temperature coefficient of a material of the piezoelectric layer, and/or a thermal conductivity of the material of the sealing layer is higher than a thermal conductivity of the substrate.

etching the substrate to form a first groove on the first surface, and at least one first release hole extending towards the second surface but not penetrating through the second surface on the bottom surface of the first groove, and filling the first release hole and the first groove with a first sacrificial material;

forming a first laminated structure covering the first groove on the first surface of the substrate, wherein the first laminated structure sequentially comprises a first lower electrode, a first piezoelectric layer and a first upper electrode from bottom to top;

etching the second surface of the substrate to form a second groove communicated with the first release hole, and filling the second groove with a second sacrificial material;

forming a second laminated structure covering the second groove on the second surface of the substrate, wherein the second laminated structure sequentially comprises a second lower electrode, a second piezoelectric layer and a second upper electrode from bottom to top;

and releasing the first sacrificial material and the second sacrificial material through the second release hole to form a first cavity between the first stacked structure and the substrate and a second cavity between the second stacked structure and the substrate, wherein the first cavity and the first lower electrode, the first piezoelectric layer and the first upper electrode have a first overlapping area in a device thickness direction, and the second cavity and the second lower electrode, the second piezoelectric layer and the second upper electrode have a second overlapping area in the device thickness direction.

According to an aspect of the present invention, in the manufacturing method, the horizontal sectional shape of the release hole is a circle, a polygon or an irregular shape.

According to another aspect of the invention, in the manufacturing method, a horizontal projection of the first groove bottom surface falls within a horizontal projection of the second groove bottom surface; the horizontal projection of the first overlapping area falls within the horizontal projection of the second overlapping area.

According to still another aspect of the present invention, in the manufacturing method, a bottom surface of the first groove is in a regular N-sided polygon shape, where N is 3 or more; the number of the first release holes is equal to N +1, one of the first release holes is formed in the central area of the bottom surface of the first groove, and the other N first release holes are respectively formed in the N vertex areas of the bottom surface of the first groove.

According to still another aspect of the present invention, in the manufacturing method, the second release hole is formed in the first lamination structure at a position outside the first overlapping area.

According to still another aspect of the present invention, in the manufacturing method, there are at least one of the second release holes and one of the first release holes aligned in a thickness direction of the device.

According to still another aspect of the present invention, before etching the second surface of the substrate to form the second groove communicating with the first relief hole, the manufacturing method further includes: thinning the substrate from the second surface.

According to still another aspect of the present invention, after forming the first stacked structure on the first surface of the substrate, the manufacturing method further includes: forming a protective layer covering the first stacked structure; and after forming a second stacked structure on the second surface of the substrate, the manufacturing method further includes: and removing the protective layer.

etching the substrate to form a second groove on the second surface, and filling the second groove with a second sacrificial material;

etching the substrate to form a first groove on the first surface, and at least one first release hole communicated with the second groove on the bottom surface of the first groove, and filling the first release hole and the first groove with a first sacrificial material;

forming a first laminated structure on the first surface of the substrate, wherein the first laminated structure sequentially comprises a first lower electrode, a first piezoelectric layer and a first upper electrode from bottom to top;

According to an aspect of the invention, in the manufacturing method, a horizontal projection of the first groove bottom surface falls in a horizontal projection of the second groove bottom surface; the horizontal projection of the first overlapping area falls within the horizontal projection of the second overlapping area.

According to another aspect of the present invention, in the manufacturing method, a bottom surface of the first groove is in a regular N-sided polygon shape, where N is greater than or equal to 3; the number of the first release holes is equal to N +1, one of the first release holes is formed in a central region of the bottom surface of the first groove, and the other N first release holes are formed in N vertex regions of the bottom surface of the first groove, respectively.

According to still another aspect of the present invention, in the manufacturing method, there is at least one of the second release holes and one of the first release holes aligned in a device thickness direction.

According to still another aspect of the present invention, before etching the substrate to form the first groove on the first surface, the manufacturing method further includes: the substrate is thinned from the first surface.

According to still another aspect of the present invention, after forming the second stacked structure on the second surface of the substrate, the manufacturing method further includes: forming a protective layer covering the second stacked structure; and after forming a first stacked structure on the first surface of the substrate, the manufacturing method further includes: and removing the protective layer.

The present invention also provides a bulk acoustic wave resonator, comprising:

a substrate comprising a first surface and a second surface opposite thereto;

the first laminated structure is formed on the first surface of the substrate and sequentially comprises a first lower electrode, a first piezoelectric layer and a first upper electrode from bottom to top;

a second laminated structure formed on the second surface of the substrate and sequentially including a second lower electrode, a second piezoelectric layer and a second upper electrode from bottom to top

A first cavity formed between the first stacked structure and the substrate, and having a first overlap region in a device thickness direction with the first lower electrode, the first piezoelectric layer, the first upper electrode, and the first cavity;

a second cavity formed between the second stacked structure and the substrate, and a second overlapped region exists between the second lower electrode, the second piezoelectric layer, the second upper electrode and the second cavity in a device thickness direction;

at least one first release hole penetrating through a bottom surface of the first cavity and a bottom surface of the second cavity;

at least one second release aperture in communication with the first cavity or the second cavity.

According to another aspect of the present invention, in the bulk acoustic wave resonator, a horizontal projection of the bottom surface of the first cavity falls within a horizontal projection of the bottom surface of the second cavity; the horizontal projection of the first overlapping region falls within the horizontal projection of the second overlapping region.

According to still another aspect of the present invention, in the bulk acoustic wave resonator, a bottom surface of the first cavity has a regular N-sided polygonal shape, where N is 3 or more; the number of the first release holes is equal to N +1, one of the first release holes penetrates through the central area of the bottom surface of the first cavity, and the other N first release holes respectively penetrate through the N vertex areas of the bottom surface of the first cavity.

According to still another aspect of the present invention, in the bulk acoustic wave resonator, the second release hole is formed in the first stacked structure at a position outside the first overlap region.

According to still another aspect of the present invention, in the bulk acoustic wave resonator, there is at least one of the second release holes and one of the first release holes aligned in a device thickness direction.

Compared with the prior art, the method for manufacturing the bulk acoustic wave resonator has the following advantages: (1) the release hole is formed in the substrate below the groove, and the release hole is prevented from being formed in the suspended part of the laminated structure like the prior art, so that the reliability and the stability of the bulk acoustic wave resonator can be effectively ensured, and the risk of breaking the device is further effectively reduced; (2) in order to avoid etching the resonance region of the bulk acoustic wave resonator and further influencing the performance of the device, the release holes in the prior art can only be formed at the position close to the resonance region in the laminated structure, and the release holes are formed in the substrate positioned below the groove and are not limited by the resonance region, so the release holes can be formed at any position of the bottom surface of the groove, the release efficiency of the release holes can be greatly improved by reasonably designing the positions of the release holes (for example, the release efficiency can be improved by more than one time by arranging the release holes at the center and the top of the bottom surface of the groove), and further the manufacturing capacity of the bulk acoustic wave resonator is improved; (3) since the release hole is formed in the substrate under the recess and not in the stacked structure, the stacked structure does not need to provide a region for forming the release hole, and thus, no waste of device area is caused. Accordingly, the bulk acoustic wave resonator formed by the manufacturing method provided by the invention has the characteristics of high reliability, excellent stability and high productivity, and the problem of device area waste does not exist.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments made with reference to the following drawings:

fig. 1(a) to 1(d) are schematic cross-sectional views of stages in the manufacture of an air-gap bulk acoustic resonator according to the prior art;

figure 2 is a flow chart of a method of fabricating a bulk acoustic wave resonator according to an embodiment of the present invention;

FIGS. 3(a) through 3(h) are schematic cross-sectional views of stages in the fabrication of a bulk acoustic wave resonator according to the process flow of FIG. 2;

FIG. 3(i) is a schematic cross-sectional view after forming a sealing layer on the structure shown in FIG. 3 (h);

FIG. 4 is a schematic top view of a second surface side of a substrate after release holes are formed in accordance with one embodiment of the present invention;

FIG. 5 is a flow chart of a method of fabricating a bulk acoustic wave resonator according to another embodiment of the present invention;

FIGS. 6(a) through 6(g) are schematic cross-sectional views of various stages in the fabrication of a bulk acoustic wave resonator according to the process flow of FIG. 5;

figure 7 is a flow chart of a method of fabricating a bulk acoustic wave resonator according to yet another embodiment of the present invention;

fig. 8(a) to 8(k) are schematic cross-sectional views of stages in manufacturing a bulk acoustic wave resonator according to the method flow shown in fig. 7.

The same or similar reference numbers in the drawings identify the same or similar elements.

Detailed Description

For a better understanding and explanation of the present invention, reference will now be made in detail to the present invention as illustrated in the accompanying drawings.

The invention provides a method for manufacturing a bulk acoustic wave resonator. Referring to fig. 2, fig. 2 is a flow chart of a method for manufacturing a bulk acoustic wave resonator according to an embodiment of the invention. As shown, the manufacturing method includes:

in step S101, providing a substrate, the substrate including a first surface and a second surface opposite thereto;

in step S102, etching the substrate to form a groove on the first surface, and filling the groove with a sacrificial material;

in step S103, forming a stacked structure covering the groove on the substrate, where the stacked structure includes a lower electrode, a piezoelectric layer, and an upper electrode in sequence from bottom to top;

in step S104, etching the second surface of the substrate to form at least one release hole communicated with the groove;

in step S105, the sacrificial material in the groove is released through the at least one release hole to form a cavity between the stacked structure and the substrate, wherein the cavity has an overlapping region with the lower electrode, the piezoelectric layer, and the upper electrode in a device thickness direction.

Next, the above steps S101 to S106 will be described in detail with reference to fig. 3(a) to 3 (h).

Specifically, in step S101, as shown in fig. 3(a), a substrate 100 is provided, the substrate 100 including two opposing surfaces, which will be hereinafter denoted as a first surface 100a and a second surface 100 b. The material of the substrate 100 includes, but is not limited to, semiconductor materials such as silicon, germanium, silicon germanium, etc. Where materials suitable for bulk acoustic wave resonator substrates are known to be suitable for use in the present invention, all possible materials for substrate 100 will not be enumerated here for the sake of brevity. In addition, the thickness of the substrate 100 is not limited in the present invention, and can be set according to the actual design requirement.

In step S102, first, as shown in fig. 3(b), the first surface 100a of the substrate 100 is etched to form a groove 101, wherein the bottom surface of the groove 101 is denoted by reference numeral 101a in the drawing. In the present embodiment, the formation process of the groove 101 is as follows: a photoresist layer (not shown) is first deposited on the first surface 100a of the substrate 100, then the photoresist layer is patterned to expose the region of the first surface 100a of the substrate 100 where the groove is to be formed, then the first surface 100a of the substrate 100 is etched using a method such as dry etching to form the groove 101, and finally the photoresist layer is removed.

Next, as shown in fig. 3(c), the groove 101 is filled with a sacrificial material 103. In the present embodiment, the filling step for the groove 101 is as follows: firstly, depositing a sacrificial material 103 on the first surface 100a of the substrate 100 until the groove 101 is completely filled with the sacrificial material 103 and the upper surface of the sacrificial material 103 is higher than the first surface 100a of the substrate 100; the sacrificial material 103 is then planarized until its upper surface is flush with the first surface 100a of the substrate 100. The term "flush" herein means that the difference in height between the two is within the allowable range of process tolerances. The sacrificial material 103 is not limited in any way, and conventional sacrificial materials such as phosphosilicate glass (PSG), borophosphosilicate glass (BPSG), intrinsic silicon dioxide (USG), etc. are suitable for use in the present invention.

In step S103, as shown in fig. 3(d), a stacked structure including a lower electrode 104, a piezoelectric layer 105, and an upper electrode 106 in this order from bottom to top is formed on the first surface 100a of the substrate 100. In this embodiment, the formation process of the stacked structure is as follows: first, a lower electrode metal layer is deposited on the first surface 100a of the substrate 100 and patterned to form a lower electrode 104 covering the sacrificial material 103; then depositing a piezoelectric material to form a piezoelectric layer 105 covering the first surface 100a of the substrate 100 and the lower electrode 104; finally, an upper electrode metal layer is deposited on the piezoelectric layer 105 and patterned to form an upper electrode 106. Wherein the upper electrode 106, the piezoelectric layer 105, the lower electrode 104, and the groove have an overlapping area in the device thickness direction.

It should be noted that (1) the present invention does not limit the materials of the lower electrode 104, the piezoelectric layer 105, and the upper electrode 106, the materials of the lower electrode 104 and the upper electrode 106 may be implemented by using a conventional electrode metal such as molybdenum (Mo), and the material of the piezoelectric layer 105 may be implemented by using a conventional piezoelectric material such as aluminum nitride (AlN). In addition, the thicknesses of the lower electrode 104, the piezoelectric layer 105 and the upper electrode 106 can be determined according to the actual design requirements, and are not limited herein. (2) In the present embodiment, the bottom electrode 104 is formed to completely cover the sacrificial material 103 (i.e., to completely cover the recess 102). In other embodiments, the lower electrode 104 may only cover a portion of the sacrificial material 103. (3) In other embodiments, a seed layer (not shown) may be formed between the substrate 100 and the lower electrode 104, a passivation layer (not shown) may be formed on the upper electrode 106, and the like according to actual design requirements, which is not limited herein.

Preferably, after the stacked-layer structure is formed, as shown in fig. 3(e), the method for manufacturing a bulk acoustic wave resonator provided by the present invention further includes: a protective layer 107 is formed covering the stacked structure. The protective layer 107 mainly serves to protect the stacked structure during the subsequent etching of the second surface 100b of the substrate 100 to form the release holes. The protective layer 107 is preferably implemented using a sacrificial material, considering that the protective layer 107 eventually needs to be removed. More preferably, the material of the protection layer 107 is the same as the sacrificial material 103, facilitating subsequent removal of the protection layer 107 while releasing the sacrificial material 103. The following steps will be explained based on the structure shown in fig. 3 (e).

Preferably, after the protective layer is formed, as shown in fig. 3(f), the method for manufacturing a bulk acoustic wave resonator provided by the present invention further includes: the substrate 100 is thinned from the second surface 100b of the substrate 100. The thinning of the substrate 100 is performed to make the thickness of the substrate 100 meet the design requirement of the bulk acoustic wave resonator, and to make the release holes formed on the second surface 100b of the substrate 100 have a suitable aspect ratio to facilitate the formation of the release holes. It will be appreciated by those skilled in the art that in other embodiments, the second surface of the substrate may be thinned before forming the protective layer covering the stacked structure.

In step S104, as shown in fig. 3(g), the second surface 100b of the substrate 100 is etched to form at least one release hole 102 extending into the substrate 100 and penetrating through the bottom surface 101a of the groove 101, i.e., the at least one release hole 102 is in communication with the groove. In the present embodiment, the release hole 102 is formed as follows: a photoresist layer (not shown) is first deposited on the substrate 100 to cover the second surface 100b of the substrate 100, then the photoresist layer is patterned to expose the region where the release holes are to be formed, then the second surface 100b of the substrate 100 is etched using a method such as dry etching to form the release holes, and finally the photoresist layer is removed.

It should be noted that, the specific number and forming position of the release holes 102 are not limited in the present invention, and can be set according to the actual design requirement. It will be understood by those skilled in the art that the number and positions of the release holes 102 in the cross-sectional schematic diagram of the bulk acoustic wave resonator shown in fig. 3(f) are merely illustrative examples, and should not be construed as limiting the present invention. Preferably, the release holes penetrate through the middle area and the edge area of the bottom surface of the groove to be communicated with the groove, in this case, when the sacrificial material in the groove is released through the release holes subsequently, the corrosive solution enters the release holes and corrodes outwards from the middle of the sacrificial material and corrodes inwards from the edge of the sacrificial material, and therefore, the release efficiency can be effectively improved, and the manufacturing capacity of the device is further improved. In the case of the bottom surface 101a of the groove 101 having a regular N-sided polygonal shape (N ≧ 3), in a preferred embodiment, the number of the release holes is equal to N +1, one of the release holes has a horizontal projection located at the central region of the horizontal projection of the bottom surface 101a of the groove 101, and the other N release holes have horizontal projections located at the N vertex regions of the horizontal projection of the bottom surface 101a of the groove 101, respectively, i.e., one of the release holes communicates with the groove 101 by penetrating the central region of the bottom surface 101a of the groove 101, and the other N release holes communicate with the groove 101 by penetrating the N vertex regions of the bottom surface 101a of the groove 101, respectively. A specific embodiment is described. Referring to fig. 4, fig. 4 is a schematic top view of the second surface side of the substrate after the release holes are formed, according to an embodiment of the invention. As shown in the figure, the groove bottom surface 101a (since the groove bottom surface 101a cannot be seen in a plan view from the second surface 100b side of the substrate 100, the edge of the groove bottom surface 101a is drawn in a dotted line in the figure) has a regular pentagon shape (i.e., N ═ 5), and the number of the discharge holes 102 is equal to six, one of the regular pentagon communicating with the central region thereof, and the other five communicating with five vertex regions of the regular pentagon, respectively. It will be appreciated by those skilled in the art that the communication between the discharge holes and the central region and the apex region of the floor of the recess is a preferred embodiment only, and that in other embodiments the specific communication between the discharge holes and the floor of the recess may be tailored to the actual design requirements, and for the sake of brevity, all possible communication locations between the discharge holes and the floor of the recess when the floor of the recess is a regular N-sided polygon will not be enumerated herein. In the case that the bottom surface 101a of the groove 101 is in a regular pattern (e.g., circular shape, etc.) other than a regular polygon, or in an irregular shape, the communication position of the release holes with the bottom surface of the groove can be properly designed according to the specific shape of the bottom surface 101a of the groove, and for the sake of brevity, all possible communication positions of the release holes with the bottom surface of the groove will not be listed.

It should be noted that the shape of the release hole 102 is not limited in the present invention, and the horizontal cross-section of the release hole 102 may be circular as shown in fig. 4, or may be rectangular, triangular, elliptical, regular polygonal, or even irregular, and for the sake of brevity, all possible horizontal cross-sectional shapes of the release hole 102 are not listed. In addition, the present invention is not limited in any way as to the specific size of the release hole 102 (including the aperture, depth, etc. of the release hole). Preferably, the pore size of the release pores 102 ranges from 1 μm to 30 μm, more preferably between 10 μm and 20 μm.

In step S105, as shown in fig. 3(h), the sacrificial material 103 in the groove 101 is released through the release hole 102 using an etching solution to form a cavity 103a between the stacked-layer structure and the substrate 100. Here, since the cavity 103a is surrounded by the surface of the recess 101 and the lower surface of the laminated structure, the overlapping region of the recess 101, the lower electrode 104, the piezoelectric layer 105, and the upper electrode 106 in the device thickness direction, that is, the overlapping region of the cavity 103a, the lower electrode 104, the piezoelectric layer 105, and the upper electrode 106 in the device thickness direction, constitutes the resonance region of the bulk acoustic wave resonator. The etching solution of the present invention is not limited, and a conventional etching solution may be selected according to the specific type of the sacrificial material 103. Further, in the present embodiment, since the material of the protective layer 107 is the same as the sacrificial material 103, the protective layer 107 is also removed while releasing the sacrificial material 103. This completes the manufacture of the bulk acoustic wave resonator. It should be noted that, when the material of the protection layer 107 is different from the material of the sacrificial material 103, the sacrificial material 103 may be released first and then the protection layer 107 is removed, or the protection layer 107 may be removed first and then the sacrificial material 103 is released, which is not limited herein.

Compared with the prior art, the method for manufacturing the bulk acoustic wave resonator has the following advantages: (1) the release hole is formed in the substrate below the groove, and the release hole is prevented from being formed in the suspended part of the laminated structure like the prior art, so that the reliability and the stability of the bulk acoustic wave resonator can be effectively ensured, and the risk of breaking the device is further effectively reduced; (2) in order to avoid etching the resonance region of the bulk acoustic wave resonator and further influencing the performance of the device, the release holes in the prior art can only be formed at the position close to the resonance region in the laminated structure, and the release holes are formed in the substrate positioned below the groove and are not limited by the resonance region, so the release holes can be formed at any position of the bottom surface of the groove, the release efficiency of the release holes can be greatly improved by reasonably designing the positions of the release holes (for example, the release efficiency can be improved by more than one time by arranging the release holes at the center and the top of the bottom surface of the groove), and further the manufacturing capacity of the bulk acoustic wave resonator is improved; (3) since the release hole is formed in the substrate under the recess and not in the stacked structure, the stacked structure does not need to provide a region for forming the release hole, thereby not causing a waste of device area.

In a preferred embodiment, after performing step S105 to release the sacrificial material 103 to form the cavity 103a, as shown in fig. 3(i), the manufacturing method provided by the present invention further includes: the sealing layer 107 is formed on the second surface 100b of the substrate 100 to seal the release hole 102. Among them, the formation of the sealing layer 107 can effectively improve the airtightness of the bulk acoustic wave resonator. The material of the sealing layer is not limited in any way, and any material with certain viscosity which cannot flow to the surface of the lower electrode through the release hole during the forming process and has an influence on the device performance is suitable for the sealing layer of the invention. In addition to having a certain viscosity, the sealing layer 107 material may also have other properties. In a preferred embodiment, the thermal conductivity of the material of the sealing layer 107 is higher than that of the material of the substrate 100 (i.e. the thermal conductivity of the material of the sealing layer 107 is better than that of the material of the substrate 100), such as epoxy resin, etc., so as to improve the heat dissipation efficiency of the substrate side of the bulk acoustic wave resonator. In another preferred embodiment, the temperature coefficient of the material of the sealing layer 107 is opposite to the temperature coefficient of the material of the piezoelectric layer (for example, the material of the sealing layer 107 is silicon dioxide, and the material of the piezoelectric layer is aluminum nitride), so that the temperature compensation function can be effectively performed. In yet another embodiment, the thermal conductivity of the material of the sealing layer 107 is higher than that of the material of the substrate 100, and at the same time, the temperature coefficient of the material of the sealing layer 107 is opposite to that of the material of the piezoelectric layer, so that the substrate side of the bulk acoustic wave resonator is favorably improved, and the temperature compensation function can be effectively performed.

The invention also provides a manufacturing method of the bulk acoustic wave resonator. Referring to fig. 5, fig. 5 is a flow chart of a method for manufacturing a bulk acoustic wave resonator according to another embodiment of the invention. As shown, the manufacturing method includes:

in step S201, providing a substrate, the substrate including a first surface and a second surface opposite thereto;

in step S202, etching the substrate to form a groove on the first surface and at least one release hole extending to the second surface but not penetrating the second surface on a bottom surface of the groove;

in step S203, filling the release hole and the groove with a sacrificial material;

in step S204, forming a stacked structure on the substrate, wherein the stacked structure sequentially includes a lower electrode, a piezoelectric layer, and an upper electrode from bottom to top;

in step S205, thinning the substrate from the second surface until the sacrificial material is exposed;

in step S206, the sacrificial material is released to form a cavity between the stacked structure and the substrate, and the cavity has an overlapping region with the lower electrode, the piezoelectric layer, and the upper electrode in a device thickness direction.

Next, the above-described steps S201 to S206 will be described in detail with reference to fig. 6(a) to 6 (g).

Specifically, in step S201, as shown in fig. 6(a), a substrate 100 is provided, the substrate 100 comprising opposing first and

second surfaces

100a and 100 b.

In step S202, first, as shown in fig. 6(b), the first surface 100a of the substrate 100 is etched to form a groove 101, wherein the bottom surface of the groove 101 is denoted by reference numeral 101a in the drawing.

Next, as shown in fig. 6(c), the bottom surface 101a of the groove 101 (i.e., the surface of the substrate 100 that constitutes the bottom surface 101a of the groove 101) is etched continuously to form at least one release hole 102 extending toward the second surface 100b of the substrate 100. In the present embodiment, the release hole 102 is a blind hole that does not penetrate the second surface 100b of the substrate 100, i.e. the depth of the release hole 102 (shown by H) ₁ Indicated) is smaller than the vertical distance (indicated by H in the figure) between the bottom surface 101a of the recess 101 and the second surface 100b of the substrate 100 ₂ Representation). In the present embodiment, the release hole 102 is formed as follows: a photoresist layer (not shown) is first deposited on the substrate 100 to cover the first surface 100a of the substrate 100 and the surface of the groove 101 (including the side wall and the bottom 101a of the groove 101), then the photoresist layer is patterned to expose the bottom 101a of the groove 101 in the region where the release holes are to be formed, then the bottom 101a of the groove 101 is etched using a method such as dry etching to form the release holes, and finally the photoresist layer is removed.

Preferably, the release holes are distributed in the middle area and the edge area of the bottom surface of the groove, in this case, when the sacrificial material in the groove is released through the release holes, the etching solution enters the release holes and then etches outwards from the middle of the sacrificial material and also etches inwards from the edge of the sacrificial material, so that the release efficiency can be effectively improved, and the manufacturing capacity of the device can be further improved. In the case where the bottom surface 101a of the recess 101 has a regular N-sided polygonal shape (N.gtoreq.3), the number of the discharge holes is equal to N +1 in a preferred embodiment, one of the discharge holes is formed at a central region of the bottom surface 101a of the recess 101, and the other N discharge holes are formed at N apex regions of the bottom surface 101a of the recess 101, respectively. In addition, the shape of the release hole 102 is not limited in the present invention, and the horizontal cross-section may be circular, rectangular, triangular, elliptical, regular polygonal, or even irregular, and for the sake of brevity, all possible horizontal cross-sectional shapes of the release hole 102 are not listed. The present invention is also not limited in any way as to the particular dimensions of the release aperture 102, including the aperture, depth, etc. of the release aperture. In view of the convenience of subsequent filling of the release holes 102, the pore diameter of the release holes 102 is preferably in the range of 1 μm to 30 μm, more preferably between 10 μm and 20 μm.

In step S203, as shown in fig. 6(d), the release hole 102 and the groove 101 are filled with the sacrificial material 103. In this embodiment, the filling steps for the release hole 102 and the groove 101 are as follows: firstly, sacrificial material 103 is deposited on the first surface 100a of the substrate 100 until the release holes 102 and the grooves 101 are completely filled with the sacrificial material 103 and the upper surface of the sacrificial material 103 is higher than the first surface 100a of the substrate 100; the sacrificial material 103 is then planarized until its upper surface is flush with the first surface 100a of the substrate 100.

In step S204, as shown in fig. 6(e), a stacked structure including the lower electrode 104, the piezoelectric layer 105, and the upper electrode 106 in this order from bottom to top is formed on the first surface 100a of the substrate 100.

In step S205, as shown in fig. 6(f), the substrate 100 is thinned from the second surface 100b of the substrate 100 until the thickness of the substrate 100 meets the design requirements and the sacrificial material 103 in the release hole is exposed. At this time, the release hole penetrates from the bottom surface 101a of the groove 101 to the second surface 100b of the substrate 100.

In step S206, the release hole 102 and the sacrificial material 103 in the groove 101 are removed by using an etching solution. Since the sacrificial material 103 in the release hole 102 is exposed after thinning of the substrate 100, the etching solution first etches the sacrificial material 103 in the release hole 102 and then further etches the sacrificial material 103 within the groove 101 through the release hole 102. After the sacrificial material 103 in the recess 101 is completely released, as shown in fig. 6(g), a cavity 103a is formed between the stacked structure and the substrate 100. In the present embodiment, the cavity 103a, the lower electrode 104, the piezoelectric layer 105, and the upper electrode 106 have an overlapping area in the device thickness direction, which constitutes a resonance region of the bulk acoustic wave resonator. The bulk acoustic wave resonator is thus manufactured.

The method flow shown in fig. 2 is different from the method flow shown in fig. 5 mainly in the step of forming the release hole. The former release holes are formed directly by etching the second surface of the substrate, and the latter release holes are formed by etching the bottom surface of the groove and then thinning the second surface of the substrate. Although both methods can form the release holes through the second surface of the substrate, the former method is relatively simpler than the latter method in terms of process since it is not necessary to thin the second surface of the substrate.

Preferably, after the sacrificial material is released to form the cavity in step S206, a sealing layer may be further formed on the second surface of the substrate to seal the release hole, so as to improve the airtightness of the bulk acoustic wave resonator. In addition to having a viscosity to ensure that flow through the release holes to the lower electrode surface during formation does not affect device performance, it is preferred that the thermal conductivity of the encapsulant material be higher than the thermal conductivity of the substrate material and/or that the temperature coefficient of the encapsulant material be opposite to the temperature coefficient of the piezoelectric layer material.

Accordingly, the present invention also provides a bulk acoustic wave resonator, comprising:

a substrate comprising a first surface and a second surface opposite thereto;

a cavity formed between the laminated structure and the substrate, and an overlapping region of the lower electrode, the piezoelectric layer, the upper electrode and the cavity exists in a device thickness direction;

The respective components of the above-described structure will be described in detail with reference to fig. 3 (h).

Specifically, as shown in fig. 3(h), the bulk acoustic wave resonator provided by the present invention includes a substrate 100, a stacked-layer structure, and a cavity 103 a. In the present embodiment, the substrate 100 includes a first surface 100a and a second surface 100b opposite to each other, wherein the first surface 100a of the substrate 100 is formed with a groove. A stacked structure is formed on the first surface 100a of the substrate 100 and covers the groove, and the stacked structure includes, from bottom to top, a lower electrode 104, a piezoelectric layer 105, and an upper electrode 106. A cavity 103a is formed between the stacked structure and the substrate 100, which is enclosed by the lower surface of the stacked structure and the surface of the recess (including the recess frontal wall and the bottom surface). Wherein the upper electrode 106, the piezoelectric layer 105, the lower electrode 104, and the cavity 103a have an overlapping area in the direction of the device thickness. It should be noted that, for the materials and dimensions of the substrate 100, the lower electrode 104, the piezoelectric layer 105, and the upper electrode 106 (1), reference may be made to the contents of the corresponding parts in the foregoing manufacturing method, and for the sake of brevity, no further description is provided here. (2) In the present embodiment, the lower electrode 104 is formed to completely cover the cavity 103a, that is, the edge of the lower electrode 104 is formed on the substrate 100, which can improve the reliability of the device while ensuring the Q value of the device. It will be appreciated by those skilled in the art that in other embodiments, the lower electrode 104 may only cover a portion of the cavity 103 a. (3) In other embodiments, a seed layer (not shown) may be further formed between the substrate 100 and the lower electrode 104, and a passivation layer (not shown) may be further formed on the upper electrode 106, etc., according to actual design requirements, which is not limited herein.

As shown in fig. 3(h), the bulk acoustic wave resonator provided by the present invention further includes at least one release hole 102, and the at least one release hole 102 is formed on the second surface 100b of the substrate 100 and communicates with the cavity 103 a. The release hole 102 is mainly used to release the sacrificial material filled in the groove to form the cavity 103a during the manufacturing process of the bulk acoustic wave resonator.

It should be noted that, the specific number and position of the release holes 102 are not limited in the present invention, and can be set according to the actual design requirement. It will be understood by those skilled in the art that the number and positions of the release holes 102 in the cross-sectional schematic diagram of the bulk acoustic wave resonator shown in fig. 3(h) are merely illustrative examples, and should not be construed as limiting the present invention. Preferably, the release hole penetrates through the middle area and the edge area of the bottom surface of the cavity to realize communication with the cavity, in this case, when the sacrificial material in the groove is released through the release hole in the manufacturing process of the bulk acoustic wave resonator, the etching solution enters the release hole and then corrodes from the middle of the sacrificial material outwards and also corrodes from the edge of the sacrificial material inwards, and therefore, the release efficiency can be effectively improved, and further, the manufacturing capacity of the device is improved. For the case that the bottom surface of the cavity 103a is in a regular N-sided polygon shape (N ≧ 3), in a preferred embodiment, the number of the release holes is equal to N +1, one of the release holes has a horizontal projection located at the central region of the horizontal projection of the bottom surface of the cavity 103a, and the other N release holes have horizontal projections located at the N vertex regions of the horizontal projection of the bottom surface of the cavity 103a, respectively, i.e., one of the release holes communicates with the cavity 103a by penetrating through the central region of the bottom surface of the cavity 103a, and the other N release holes communicate with the cavity 103a by penetrating through the N vertex regions of the bottom surface of the cavity 103a, respectively. It will be understood by those skilled in the art that the above-mentioned communication between the release hole and the central region and the vertex region of the bottom surface of the cavity is only a preferred embodiment, and in other embodiments, the specific communication position between the release hole and the bottom surface of the cavity can be determined according to the actual design requirement, and for the sake of brevity, all the possible communication positions between the release hole and the bottom surface of the cavity when the bottom surface of the cavity is a regular N-shape are not listed. In the case of other regular patterns (e.g., circles, etc.) or irregular shapes, which are not regular polygons, the communication positions of the release holes and the bottom surface of the cavity can be reasonably designed according to the specific shape of the bottom surface of the cavity 103a, and for the sake of brevity, all the communication positions of the release holes and the bottom surface of the cavity are not listed.

It should also be noted that the shape of the release hole 102 is not limited in the present invention, and the horizontal cross-section may be circular, rectangular, triangular, oval, regular polygon, or even irregular, and for the sake of brevity, all possible horizontal cross-sectional shapes of the release hole 102 are not listed. In addition, the present invention is not limited in any way as to the specific size of the release hole 102 (including the aperture, depth, etc. of the release hole). Preferably, the pore size of the release pores 102 ranges from 1 μm to 30 μm, more preferably between 10 μm and 20 μm.

The bulk acoustic wave resonator provided by the invention has the characteristics of high reliability, excellent stability and high productivity, and the problem of device area waste does not exist.

In a preferred embodiment, as shown in fig. 3(i), the bulk acoustic wave resonator provided by the present invention further includes a sealing layer 107, and the sealing layer 107 is formed on the second surface 100b of the substrate 100 to seal the release hole 102. Among them, the provision of the sealing layer 107 can effectively improve the airtightness of the bulk acoustic wave resonator. The material of the sealing layer is not limited in any way, and any material with certain viscosity which cannot flow to the surface of the lower electrode through the release hole during the forming process and has an influence on the device performance is suitable for the sealing layer of the invention. In addition to having a certain viscosity, the sealing layer 107 material may also have other properties. In a preferred embodiment, the thermal conductivity of the material of the sealing layer 107 is higher than that of the material of the substrate 100 (i.e. the thermal conductivity of the material of the sealing layer 107 is better than that of the material of the substrate 100), such as epoxy resin, etc., which is beneficial for improving the heat dissipation efficiency of the substrate side of the bulk acoustic wave resonator. In another preferred embodiment, the temperature coefficient of the material of the sealing layer 107 is opposite to the temperature coefficient of the material of the piezoelectric layer (for example, the material of the sealing layer 107 is silicon dioxide, and the material of the piezoelectric layer is aluminum nitride), so that the temperature compensation function can be effectively performed. In yet another embodiment, the thermal conductivity of the material of the sealing layer 107 is higher than that of the material of the substrate 100, and at the same time, the temperature coefficient of the material of the sealing layer 107 is opposite to that of the material of the piezoelectric layer, so that the substrate side of the bulk acoustic wave resonator is favorably improved, and the temperature compensation function can be effectively performed.

The invention also provides a manufacturing method of the bulk acoustic wave resonator. Referring to fig. 7, fig. 7 is a flow chart of a method for manufacturing a bulk acoustic wave resonator according to another embodiment of the invention. As shown, the manufacturing method includes:

in step S301, providing a substrate, the substrate including a first surface and a second surface opposite thereto;

in step S302, etching the substrate to form a first groove on the first surface, and forming at least one first release hole on a bottom surface of the first groove, the first release hole extending toward the second surface but not penetrating through the second surface, and filling the first release hole and the first groove with a first sacrificial material;

in step S303, forming a first stacked structure covering the first groove on the first surface of the substrate, where the first stacked structure sequentially includes a first lower electrode, a first piezoelectric layer, and a first upper electrode from bottom to top;

in step S304, etching a second surface of the substrate to form a second groove communicating with the first release hole, and filling the second groove with a second sacrificial material;

in step S305, forming a second stacked structure covering the second groove on the second surface of the substrate, the second stacked structure sequentially including a second lower electrode, a second piezoelectric layer, and a second upper electrode from bottom to top;

in step S306, at least one second release hole exposing the first sacrificial material or the second sacrificial material is formed, and the first sacrificial material and the second sacrificial material are released through the second release hole to form a first cavity between the first stacked structure and the substrate and a second cavity between the second stacked structure and the substrate, wherein the first cavity and the first lower electrode, the first piezoelectric layer and the first upper electrode have a first overlapping area in a device thickness direction, and the second cavity and the second lower electrode, the second piezoelectric layer and the second upper electrode have a second overlapping area in the device thickness direction.

Next, the above-described steps S201 to S206 will be described in detail with reference to fig. 8(a) to 8 (k).

Specifically, in step S201, as shown in fig. 8(a), a substrate 200 is provided, the substrate 200 including a first surface 200a and a second surface 200b opposite to the first surface 200 a.

In step S202, first, as shown in fig. 8(b), the first surface 200a of the substrate 200 is etched to form a groove 201 (hereinafter, denoted as a first groove 201).

Next, as shown in fig. 8(c), the bottom surface of the first groove 201 (i.e., the surface of the substrate 200 that is used to form the bottom surface of the first groove 201) is etched to form at least one release hole 202 (hereinafter, the first release hole 202) extending toward the second surface 200b of the substrate 200. In the present embodiment, the first release hole 202 is a blind hole that does not penetrate through the second surface 200b of the substrate 200, i.e., the depth of the first release hole 202 is smaller than the vertical distance between the bottom surface of the first groove 201 and the second surface 200b of the substrate 200. It should be noted that the shape of the first release hole 202 is not limited in the present invention, and the horizontal cross-section may be circular, rectangular, triangular, oval, regular polygonal, or even irregular, and for the sake of brevity, all possible horizontal cross-sectional shapes of the first release hole 202 are not listed. In addition, the present invention does not have any limitation on the specific size of the first release hole 202 (including the aperture, depth, etc. of the release hole). In consideration of convenience in subsequent filling of the first release holes 202, it is preferable that the pore diameter of the first release holes 202 is in a range of 1 μm to 30 μm, and more preferably, between 10 μm and 20 μm.

Finally, as shown in fig. 8(d), the first release hole 202 and the first groove 201 are filled with a sacrificial material 203 (hereinafter, denoted as a first sacrificial material 203).

In step S203, as shown in fig. 8(e), a stacked structure (hereinafter, referred to as a first stacked structure) covering a first groove is formed on the first surface 200a of the substrate 200, and the first stacked structure includes, from bottom to top, a lower electrode 204 (hereinafter, referred to as a first lower electrode 204), a piezoelectric layer 205 (hereinafter, referred to as a first piezoelectric layer 205), and an upper electrode 206 (hereinafter, referred to as a first upper electrode 206). Wherein the first upper electrode 206, the first piezoelectric layer 205, the first lower electrode 204 and the first recess 201 have an overlapping area in the device thickness direction.

It should be noted that, the material and thickness of the substrate 200 can be referred to the related contents of the substrate 100 in the foregoing; the formation process of the first groove 201 and the first release hole 202 can refer to the related contents of the groove 101 and the release hole 102 in the foregoing; the filling and specific implementation of the first sacrificial material 203 can refer to the related contents of the sacrificial material 103 in the foregoing; the formation process and materials of the first lower electrode 204, the first piezoelectric layer 205 and the first upper electrode 206 can refer to the related contents of the lower electrode 104, the piezoelectric layer 105 and the upper electrode 106. For the sake of brevity, the above description will not be repeated here.

Preferably, after the first stacked-layer structure is formed, as shown in fig. 8(f), the method for manufacturing a bulk acoustic wave resonator provided by the present invention further includes: a protective layer 207 is formed covering the first stacked structure. The protection layer 207 mainly serves to protect the first stacked structure during subsequent device formation on the second surface 200b of the substrate 200. The protective layer 207 is preferably implemented using a sacrificial material, considering that the protective layer 207 needs to be removed after the formation of the second stacked structure. More preferably, the material of the protection layer 207 is the same as the first sacrificial material 203, which facilitates subsequent removal of the protection layer 207 while releasing the first sacrificial material 203. The following steps will be explained based on the structure shown in fig. 8 (f).

Preferably, after the protective layer is formed, the method for manufacturing a bulk acoustic wave resonator further includes: the substrate is thinned from the second surface of the substrate. The substrate is thinned in order to make the thickness of the substrate meet the design requirements of the bulk acoustic wave resonator. It will be understood by those skilled in the art that (1) when the thickness of the substrate itself is just in accordance with the device design requirements, no thinning step may be performed; (2) in other embodiments, the second surface of the substrate may be thinned first, and then a protective layer covering the first stacked structure may be formed.

In step S204, first, as shown in fig. 8(g), the second surface 200b of the substrate 200 is etched to form a groove 208 (hereinafter, referred to as a second groove 208), wherein the formation of the second groove 208 exposes the first sacrificial material 203 in the first release hole 202, i.e., the second groove 208 communicates with the first release hole 202. Next, as shown in fig. 8(h), the second groove 208 is filled with a sacrificial material 209 (hereinafter, referred to as a second sacrificial material 209). The second sacrificial material 209 is preferably the same as the first sacrificial material 203 to facilitate subsequent removal at one time. It will be understood by those skilled in the art that the second sacrificial material 209 may also be different from the first sacrificial material 203, and the invention is not limited thereto. For the formation and filling of the second groove 208, reference may be made to the formation and filling of the first groove 201, and for brevity, the description is omitted here.

In step S205, as shown in fig. 8(i), a stacked structure (hereinafter, referred to as a second stacked structure) covering the second groove is formed on the second surface 200b of the substrate 200, and the second stacked structure includes, from bottom to top, a lower electrode 210 (hereinafter, referred to as a second lower electrode 210), a piezoelectric layer 211 (hereinafter, referred to as a second piezoelectric layer 211), and an upper electrode 212 (hereinafter, referred to as a second upper electrode 212). Specifically, the second lower electrode 210 is formed on the second surface 200b of the substrate 200, the second piezoelectric layer 211 is formed on the second surface 200b of the substrate 200 and covers the second lower electrode 210, and the second upper electrode 212 is formed on the second piezoelectric layer 211, wherein there is an overlapping area of the second upper electrode 212, the second piezoelectric layer 211, the second lower electrode 210, and the second groove 208 in the device thickness direction.

It should be noted that (1) the present invention does not limit the materials of the second upper electrode 212, the second piezoelectric layer 211, and the second lower electrode 210, the materials of the second upper electrode 212 and the second lower electrode 210 may be implemented by using a conventional electrode metal such as molybdenum (Mo), and the material of the second piezoelectric layer 211 may be implemented by using a conventional piezoelectric material such as aluminum nitride (AlN). In addition, the thicknesses of the second upper electrode 212, the second piezoelectric layer 211, and the second lower electrode 210 may be determined according to actual design requirements, and are not limited herein. (2) In the present embodiment, the second bottom electrode 210 is formed to completely cover the second sacrificial material 209 (i.e., to completely cover the second recess 208). In other embodiments, the second lower electrode 210 may only cover a portion of the second sacrificial material 209. (3) In other embodiments, a seed layer (not shown) may be formed between the substrate 200 and the second lower electrode 210, and a passivation layer (not shown) may be formed on the second upper electrode 212, etc., according to actual design requirements, which is not limited herein.

In step S206, in the present embodiment, as shown in fig. 8(j), the first stacked structure is etched to form at least one release hole 213 (hereinafter, referred to as a second release hole 213), and the second release hole 213 penetrates through the first stacked structure to expose the first sacrificial material 203 in the first groove 201. Next, as shown in fig. 8(k), the first sacrificial material 203 in the first groove 201 and the first release hole 202 and the second sacrificial material 209 in the second groove 208 are released through the second release hole 213 by using an etching solution. Since the first groove 201 and the second groove 208 are communicated through the first release hole 202, and the first sacrificial material 203 and the second sacrificial material 209 are the same in this embodiment, the first sacrificial material 203 and the second sacrificial material 209 can be released at one time. Wherein the first sacrificial material 203 in the first recess 201 is released to form a cavity 203a (hereinafter referred to as the first cavity 203 a) between the first stacked structure and the substrate 200, and the second sacrificial material 209 in the second recess 208 is released to form a cavity 209a (hereinafter referred to as the second cavity 203 a) between the second stacked structure and the substrate 200. In this embodiment, the material of the protection layer 207 is the same as the first sacrificial material 203 and the second sacrificial material 209, so the protection layer 207 is also removed while the first sacrificial material 203 and the second sacrificial material 209 are released. The bulk acoustic wave resonator is thus manufactured.

It should be noted that, (1) in other embodiments, the second release hole 213 may also be formed in the second stacked structure, and the second release hole 213 penetrates through the second stacked structure to expose the second sacrificial material 209 in the second groove 208. The second sacrificial material 209 in the second groove 208 and the first sacrificial material 203 in the first release hole 202 and the first groove 201 can be released through the second release hole 213 by using an etching solution. (2) For the case that the material of the protection layer 207 is different from the first sacrificial material 203 and the second sacrificial material 209, the protection layer 207 may be removed at any stage after the second stacked structure is formed, for example, the protection layer 207 is directly removed after the second stacked structure is formed, the protection layer 207 is removed after the second release hole 213 is formed, the protection layer 207 is removed after the first cavity 203a and the second cavity 209a are formed, and even when the first sacrificial material 203 and the second sacrificial material 209 are different, the protection layer 207 may be removed after one of the sacrificial materials is released, which is not limited in this disclosure. (3) Since the first cavity 203a is surrounded by the surface of the first groove 201 and the lower surface of the first laminated structure, the overlapping area of the first upper electrode 206, the first piezoelectric layer 205, the first lower electrode 204, and the first groove 201 in the device thickness direction, that is, the overlapping area of the first upper electrode 206, the first piezoelectric layer 205, the first lower electrode 204, and the first cavity 203a in the device thickness direction (hereinafter, referred to as a first overlapping area), constitutes a resonance region of the bulk acoustic wave resonator (hereinafter, referred to as a first resonance region) located on the first surface 200a of the substrate 200. Accordingly, the overlapping area of the second upper electrode 212, the second piezoelectric layer 211, the second lower electrode 210, and the second groove 208 in the device thickness direction, that is, the overlapping area of the second upper electrode 212, the second piezoelectric layer 211, the second lower electrode 210, and the second cavity 209a in the device thickness direction (hereinafter, referred to as a second overlapping area), constitutes a resonance area (hereinafter, referred to as a second resonance area) of the bulk acoustic wave resonator on the second surface 200b of the substrate 200. (4) In order to avoid that the formation of the second release hole 213 affects the resonance region of the device, the second release hole 213 is formed in the first stacked structure at a position outside the first resonance region and above the first sacrificial material 203, which may be realized by etching the protective layer 207, and the first piezoelectric layer 205 and the first lower electrode 204 in the first stacked structure; or in a position in the second stack outside the second resonance region and above the second sacrificial material 209, which can be achieved by etching the second piezoelectric layer 211 and the second lower electrode 210 in the second stack.

According to the manufacturing method of the bulk acoustic wave resonator, the first release holes are formed in the substrate to be communicated with the grooves on the two surfaces of the substrate, so that after the laminated structures are formed on the two surfaces of the substrate respectively, only the second release holes which expose the sacrificial materials in the grooves below the laminated structures are formed on one of the laminated structures, the sacrificial materials in the two grooves can be removed through the second release holes and the first release holes, and the bulk acoustic wave resonator is formed on the two surfaces of the substrate respectively. On one hand, the arrangement of the first release holes enables the two grooves to be communicated, so that the second release holes do not need to be formed in the two laminated structures, and therefore, the reliability and the stability of the device can be improved to a certain extent, and the risk of breaking the device is reduced to a certain extent. On the other hand, the first release holes are arranged so that the second release holes only need to be formed on one of the laminated structures, and therefore, for the laminated structure without the second release holes, no area for forming the second release holes is required to be provided, and therefore no waste of device area is caused.

Preferably, the second groove is larger in size than the first groove. Specifically, when the second groove is etched, the area of the bottom surface of the second groove is larger than that of the bottom surface of the first groove, and the horizontal projection of the bottom surface of the first groove falls into the horizontal projection of the bottom surface of the second groove, so that the first release holes can be effectively ensured to be completely communicated with the second groove, and the subsequent rapid release of the second sacrificial material in the second groove is facilitated. On the basis that the horizontal projection of the bottom surface of the first groove falls into the horizontal projection of the bottom surface of the second groove, the horizontal projection of the first overlapping region can correspondingly fall into the horizontal projection of the second overlapping region, namely the area of the second resonance region of the bulk acoustic wave resonator on the second surface of the substrate is larger than the area of the first resonance region of the bulk acoustic wave resonator on the first surface of the substrate. It will be appreciated by those skilled in the art that the horizontal projection of the bottom surface of the second groove may also completely or partially coincide with the horizontal projection of the bottom surface of the first groove, as long as communication between the first release hole and the second groove is ensured.

The specific number and the forming positions of the first release holes are not limited, and the first release holes can be made according to actual design requirements. For the case that the horizontal projection of the bottom surface of the first groove falls into the horizontal projection of the bottom surface of the second groove, it is preferable that the first release holes are distributed in the middle area and the edge area of the bottom surface of the first groove, and in this case, when the sacrificial material in the groove (the first groove or the second groove) is subsequently released through the first release holes, the etching solution enters the first release holes, and then corrodes from the middle of the sacrificial material to the outside and from the edge of the sacrificial material to the inside, so that the release efficiency can be effectively improved, and the manufacturing yield of the device can be further improved. In a preferred embodiment, the number of the first discharge holes is equal to N +1 in case that the first groove bottom surface has a regular N-sided polygonal shape (N.gtoreq.3), wherein one first discharge hole is formed at a central region of the first groove bottom surface and N first discharge holes are formed at N vertex regions of the first groove bottom surface, respectively. It will be understood by those skilled in the art that the above-mentioned distribution of the first release holes at the central region and the vertex region of the bottom surface of the first groove is only a preferred embodiment, and in other embodiments, the specific forming positions of the first release holes can be further determined according to actual design requirements, and for the sake of brevity, all possible forming positions of the release holes when the bottom surface of the first groove is a regular N-sided shape are not listed. When the first groove bottom surface is in a regular pattern (e.g., a circle, etc.) or an irregular shape, the forming position of the first release hole may be properly designed according to the specific shape of the first groove bottom surface, and for the sake of brevity, all the possible forming positions of the first release hole are not listed.

In order to avoid the formation of the second release hole from affecting the resonance region of the device, the second release hole is generally formed at a position outside the first resonance region in the first stacked structure (or at a position outside the second resonance region in the second stacked structure). For this case, it is preferable that there be at least one second release hole and one first release hole, which are aligned in the device thickness direction. The second release holes are aligned with the first release holes, so that the distance between the first release holes and the second release holes can be effectively shortened, corrosive solution can rapidly enter the second release holes to remove the second sacrificial material, the release efficiency can be further improved, and the manufacturing productivity can be further improved. Aiming at the condition that the horizontal projection of the bottom surface of the first groove falls into the horizontal projection of the bottom surface of the second groove, the horizontal projection of the first overlapped area falls into the horizontal projection of the second overlapped area, and the vertex area of the bottom surface of the first groove is provided with the first release hole, the area above the vertex of the bottom surface of the first groove in the first laminated structure is etched to form the second release hole aligned with the first release hole.

in step S401, providing a substrate, the substrate including a first surface and a second surface opposite thereto;

in step S402, etching the substrate to form a second groove on the second surface, and filling the second groove with a second sacrificial material;

in step S403, forming a second stacked structure covering the second groove on the second surface of the substrate, where the second stacked structure sequentially includes a second lower electrode, a second piezoelectric layer, and a second upper electrode from bottom to top;

in step S404, etching the substrate to form a first groove on the first surface and at least one first release hole communicating with the second groove on a bottom surface of the first groove, and filling the first release hole and the first groove with a first sacrificial material;

in step S405, forming a first stacked structure on the first surface of the substrate, where the first stacked structure includes, from bottom to top, a first lower electrode, a first piezoelectric layer, and a first upper electrode in this order;

in step S406, at least one second release hole exposing the first sacrificial material or the second sacrificial material is formed, and the first sacrificial material and the second sacrificial material are released through the second release hole to form a first cavity between the first stacked structure and the substrate and a second cavity between the second stacked structure and the substrate, wherein the first cavity and the first lower electrode, the first piezoelectric layer and the first upper electrode have a first overlapping area in a device thickness direction, and the second cavity and the second lower electrode, the second piezoelectric layer and the second upper electrode have a second overlapping area in the device thickness direction.

The manufacturing method shown in fig. 7 differs from the present embodiment in that: in the manufacturing method shown in fig. 7, the first surface of the substrate is etched to form a first groove and a first release hole, the first groove and the first release hole are filled, then the first stacked structure is formed, the second surface of the substrate is etched to form a second groove, and finally the second stacked structure is formed. In this embodiment, the second surface is etched to form a second groove, the second stacked structure is formed, the first surface of the substrate is etched to form a first groove and a first release hole communicating the first groove and the second groove, the first sacrificial material is filled in the first release hole, and the first stacked structure is formed.

The following describes steps S401 to S406.

Specifically, step S401 is first performed, and reference may be made to step S301, which is not described herein again for brevity. Next, step S402 is performed, in which the substrate is etched to form a second groove on the second surface, and the second groove is filled with a second sacrificial material. Step S403 is executed, which can refer to step S305, and for brevity, will not be described herein again. Next, step S404 is performed, the substrate is etched to form a first groove on the first surface, and at least one first release hole communicating with the second groove is formed on the bottom surface of the first groove, and the first release hole and the first groove are filled with a first sacrificial material. Finally, step S405 and step S406 are executed, which may refer to steps S303 and S306, respectively, and are not described herein again for brevity.

The shape of the first release hole is not limited in any way, and the horizontal section of the first release hole can be circular, rectangular, triangular, oval, regular polygon or even irregular. In addition, the present invention does not have any limitation on the specific size of the first release hole (including the aperture, depth, etc. of the release hole). In view of the convenience of subsequent filling of the first release holes, the pore size of the first release holes is preferably in the range of 1 μm to 30 μm, more preferably between 10 μm to 20 μm.

In a preferred embodiment, the horizontal projection of the bottom surface of the first groove falls into the horizontal projection of the bottom surface of the second groove to ensure communication of the first release hole with the second groove. Furthermore, the horizontal projection of the first overlapping area falls into the horizontal projection of the second overlapping area, so that bulk acoustic wave resonators with different areas of the resonance areas can be formed on the two surfaces of the substrate, and the improvement of the design flexibility of the device and the satisfaction of different design requirements are facilitated.

For the case that the horizontal projection of the first groove bottom surface falls within the horizontal projection of the second groove bottom surface, it is preferable that the first relief holes are distributed in the middle region and the edge region of the first groove bottom surface. In a preferred embodiment, the number of the first discharge holes is equal to N +1 in case that the first groove bottom surface has a regular N-sided polygonal shape (N.gtoreq.3), wherein one first discharge hole is formed at a central region of the first groove bottom surface and N first discharge holes are formed at N vertex regions of the first groove bottom surface, respectively.

In order to avoid the formation of the second release hole from affecting the resonance region of the device, the second release hole is generally formed at a position outside the first resonance region in the first stacked structure (or at a position outside the second resonance region in the second stacked structure). The second release hole is formed in the first stacked structure at a position outside the first overlapped region, for a case where the horizontal projection of the bottom surface of the first groove falls in the horizontal projection of the bottom surface of the second groove and the horizontal projection of the first overlapped region falls in the horizontal projection of the second overlapped region. Furthermore, at least one second release hole and one first release hole are aligned in the thickness direction of the device, so that the corrosive solution can rapidly enter the second release hole from the first release hole to remove the second sacrificial material, the release efficiency can be further improved, and the manufacturing productivity can be further improved.

In yet another preferred embodiment, after forming the second stacked structure on the second surface of the substrate, the manufacturing method provided by the present invention further includes: and forming a protective layer covering the second laminated structure. After forming the first stacked structure on the first surface of the substrate, the manufacturing method provided by the present invention further includes: and removing the protective layer.

In addition, according to the actual design requirement, before etching the substrate to form the first groove on the first surface, the manufacturing method provided by the invention may further include: and thinning the substrate from the first surface.

a substrate comprising a first surface and a second surface opposite thereto;

The respective components of the above-described structure will be described in detail with reference to fig. 8 (k).

Specifically, as shown in fig. 8(k), the bulk acoustic wave resonator provided by the present invention includes a substrate 200, and the substrate 200 includes a first surface 200a and a second surface 200b which are opposite to each other, wherein the first surface 200a of the substrate 200 is formed with a first groove, and the second surface 200b of the substrate 200 is formed with a second groove.

As shown in fig. 8(k), the bulk acoustic wave resonator provided by the present invention further includes a first stacked structure and a first cavity 203 a. In the present embodiment, a stacked structure is formed on the first surface 200a of the substrate 200 and covers the first groove, and the stacked structure sequentially includes, from bottom to top, a first lower electrode 204, a first piezoelectric layer 205, and a first upper electrode 206. A cavity 203a is formed between the first stacked structure and the substrate 200, which is surrounded by the lower surface of the first stacked structure and the surface of the first groove. Wherein the first upper electrode 206, the first piezoelectric layer 205, the first lower electrode 204 and the first cavity 203a present a first overlapping area in the direction of the device thickness, which constitutes a first resonance region of the bulk acoustic wave resonator located on the first surface 200a of the substrate 200.

As shown in fig. 8(k), the bulk acoustic wave resonator provided by the present invention further includes a second stacked structure and a second cavity 209 a. In the present embodiment, a second stacked structure is formed on the second surface 200b of the substrate 200 and covers the second groove, and the second stacked structure sequentially includes, from bottom to top, a second lower electrode 210, a second piezoelectric layer 211, and a second upper electrode 212. A cavity 209a is formed between the second laminate structure and the substrate 200, which is surrounded by the lower surface of the second laminate structure and the surface of the second recess. Wherein the second upper electrode 212, the second piezoelectric layer 211, the second lower electrode 210 and the second cavity 209a present a second overlapping area in the direction of the device thickness, which constitutes a second resonance region of the bulk acoustic wave resonator located on the second surface 200b of the substrate 200.

It should be noted that, for materials, dimensions, and the like of the substrate (1), the first stacked structure, and each layer in the second stacked structure, reference may be made to the contents of the corresponding parts in the foregoing manufacturing method, and for the sake of brevity, detailed description is omitted here. (2) In other embodiments, a seed layer (not shown) may be further formed between the substrate and the first lower electrode and between the substrate and the second lower electrode, and a passivation layer (not shown) may be further formed on the first upper electrode and the second upper electrode, etc., according to actual design requirements, which is not limited herein.

As shown in fig. 8(k), the bulk acoustic wave resonator provided by the present invention further includes at least one first release hole 202, and the at least one first release hole 202 penetrates from the bottom surface of the first cavity 203a to the bottom surface of the second cavity 209a, that is, the first release hole 202 penetrates through a portion of the substrate located between the bottom surface of the first cavity 203a and the bottom surface of the second cavity 209 a. The horizontal section of the first release hole 202 may be circular, rectangular, triangular, oval, regular polygonal, or even irregular. In addition, the present invention does not have any limitation on the specific size of the first release hole (including the aperture, depth, etc. of the release hole). In view of convenience of filling the first release holes, it is preferable that the pore diameter of the first release holes 202 is in the range of 1 μm to 30 μm, and more preferably between 10 μm to 20 μm.

The bulk acoustic wave resonator provided by the invention further comprises at least one second release hole, and the at least one second release hole is communicated with the first cavity or the second cavity. In the present embodiment, the second release hole 213 is formed in the first lamination structure and communicates with the first cavity 203 a. In other embodiments, a second relief hole may also be formed in the second laminate structure in connection with the second cavity. In the manufacturing process of the bulk acoustic wave resonator, the second release holes and the first release holes are matched for use, and the second release holes and the first release holes are used for releasing the sacrificial materials in the first grooves and the second grooves so as to form the first cavities and the second cavities. Note that (1) in order to avoid the influence of the formation of the second release holes on the resonance region of the bulk acoustic wave resonator, the second release holes are generally formed at positions outside the resonance region in the stacked-layer structure. (2) In the present embodiment, the second release hole is formed in the first stacked structure, in this case, it is preferable that the second lower electrode in the second stacked structure is formed to completely cover the second cavity, that is, the edge of the second lower electrode is entirely formed on the substrate, in this way, the Q value of the device can be ensured, and the reliability of the device can be improved. And vice versa.

The bulk acoustic wave resonator provided by the invention has the characteristics of high reliability and excellent stability, and the problem of device area waste does not exist.

Preferably, the second cavity is larger in size than the first cavity. Specifically, the area of the bottom surface of the second cavity is larger than that of the bottom surface of the first cavity, and the horizontal projection of the bottom surface of the first cavity falls into the horizontal projection of the bottom surface of the second cavity, so that the first groove and the first release hole are formed first and then the second groove is formed in the manufacturing process of the bulk acoustic wave resonator, and the communication between the first release hole and the second groove can be effectively ensured. On the basis that the horizontal projection of the bottom surface of the first cavity falls into the horizontal projection of the bottom surface of the second cavity, the horizontal projection of the first overlapping region can correspondingly fall into the horizontal projection of the second overlapping region, namely the area of the second resonance region of the bulk acoustic wave resonator on the second surface of the substrate is larger than the area of the first resonance region of the bulk acoustic wave resonator on the first surface of the substrate. It will be appreciated by those skilled in the art that the horizontal projection of the bottom surface of the second cavity may also coincide completely or partially with the horizontal projection of the bottom surface of the first cavity.

The specific number and the forming positions of the first release holes are not limited, and the first release holes can be made according to actual design requirements. In the case where the horizontal projection of the bottom surface of the first cavity falls into the horizontal projection of the bottom surface of the second cavity, it is preferable that the first release holes are distributed in the middle region and the edge region of the bottom surface of the first cavity, and in this case, when the sacrificial material in the groove (the first groove or the second groove) is released through the first release holes in the manufacturing process of the bulk acoustic wave resonator, the etching solution enters the first release holes and then etches outward from the middle portion of the sacrificial material and also etches inward from the edge of the sacrificial material, so that the release efficiency can be effectively improved, and further the manufacturing yield of the device can be improved. In a preferred embodiment, the number of the first discharge holes is equal to N +1 in case that the bottom surface of the first cavity has a regular N-sided polygonal shape (N.gtoreq.3), wherein one first discharge hole is formed at a central region of the bottom surface of the first cavity and N first discharge holes are formed at N vertex regions of the bottom surface of the first cavity, respectively. It will be understood by those skilled in the art that the above-mentioned distribution of the first releasing holes at the central region and the vertex region of the bottom surface of the first cavity is only a preferred embodiment, and in other embodiments, the specific forming positions of the first releasing holes may be further determined according to actual design requirements, and for the sake of simplicity, all possible forming positions of the releasing holes when the bottom surface of the first cavity is a regular N-sided polygon are not listed here. For the other regular patterns (such as circles, etc.) or irregular shapes with non-regular polygons presented on the bottom surface of the first cavity, the forming positions of the first release holes can be designed reasonably according to the specific shape of the bottom surface of the first cavity, and for the sake of brevity, all the possible forming positions of the first release holes are not listed.

In order to avoid the formation of the second release hole from affecting the resonance region of the device, the second release hole is generally formed at a position outside the first resonance region in the first stacked structure (or at a position outside the second resonance region in the second stacked structure). For this case, it is preferable that there be at least one second release hole and one first release hole, which are aligned in the device thickness direction. The second release holes are aligned with the first release holes, so that the distance between the first release holes and the second release holes can be effectively shortened, and in the manufacturing process of the bulk acoustic wave resonator, corrosive solution can enter the second release holes quickly to remove sacrificial materials in the grooves (the first grooves or the second grooves), so that the release efficiency can be further improved, and the manufacturing capacity can be further improved. For the case where the horizontal projection of the bottom surface of the first cavity falls within the horizontal projection of the bottom surface of the second cavity, the horizontal projection of the first overlapped region falls within the horizontal projection of the second overlapped region, and the apex region of the bottom surface of the first cavity is formed with the first release hole, the second release hole is formed in the first stacked structure at a position aligned with the first release hole at the apex region of the bottom surface of the first cavity.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned. Furthermore, it will be obvious that the term "comprising" does not exclude other elements, components or steps, and the singular does not exclude the plural. A plurality of components, units or means recited in the system claims may also be implemented by one component, unit or means in software or hardware.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

Claims

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

2. The manufacturing method according to claim 1, wherein a horizontal sectional shape of the release hole is a circle, a polygon, or an irregular shape.

3. The manufacturing method according to claim 1, wherein:

the bottom surface of the groove is in a regular N-sided polygon shape, wherein N is more than or equal to 3;

the number of the release holes is equal to N +1, one of the release holes penetrates through the central area of the bottom surface of the groove, and the other N release holes respectively penetrate through the N vertex areas of the bottom surface of the groove.

4. The manufacturing method according to any one of claims 1 to 3, wherein:

after forming the stacked structure on the substrate, the manufacturing method further includes: forming a protective layer covering the laminated structure; and

after etching the second surface of the substrate to form at least one release hole communicating with the groove, the manufacturing method further includes: and removing the protective layer.

5. The manufacturing method according to any one of claims 1 to 3, before etching the second surface of the substrate to form at least one release hole communicating with the groove, the manufacturing method further comprising:

thinning the substrate from the second surface.

6. The manufacturing method according to any one of claims 1 to 3, further comprising, after releasing the sacrificial material within the groove through the at least one release hole to form a cavity between the laminated structure and the substrate:

forming a sealing layer on the second surface of the substrate seals the release hole.

7. The manufacturing method according to claim 6, wherein:

the sealing layer has a material with a temperature coefficient opposite to that of the piezoelectric layer material, and/or the sealing layer has a material with a thermal conductivity higher than that of the substrate.

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

filling the release holes and the grooves with a sacrificial material;

9. The manufacturing method according to claim 8, wherein the horizontal sectional shape of the release hole is a circle, a polygon, or an irregular shape.

10. The manufacturing method according to claim 8, wherein:

the bottom surface of the groove is in a regular N-edge shape, wherein N is more than or equal to 3;

the number of the release holes is equal to N +1, one of the release holes is formed in the central region of the groove bottom surface, and the other N release holes are respectively formed in the N vertex regions of the groove bottom surface.

11. The manufacturing method according to any one of claims 8 to 10, further comprising, after releasing the sacrificial material to form a cavity between the laminated structure and the substrate:

forming a sealing layer on the second surface of the substrate to seal the release hole.

12. The manufacturing method according to claim 11, wherein:

13. A bulk acoustic wave resonator, comprising:

a substrate comprising a first surface and a second surface opposite thereto;

14. The bulk acoustic wave resonator according to claim 13, wherein a horizontal sectional shape of the release hole is a circle, a polygon, or an irregular shape.

15. The bulk acoustic wave resonator according to claim 13, wherein:

the bottom surface of the cavity is in a regular N-edge shape, wherein N is more than or equal to 3;

the number of the release holes is equal to N +1, one release hole penetrates through the central area of the bottom surface of the cavity, and the other N release holes penetrate through the N vertex areas of the bottom surface of the cavity respectively.

16. The bulk acoustic wave resonator according to any one of claims 13 to 15, further comprising:

a sealing layer formed on the second surface of the substrate, forming a seal against the release hole.

17. The bulk acoustic wave resonator of claim 16, wherein:

the sealing layer has a material with a temperature coefficient opposite to that of the piezoelectric layer material, and/or has a thermal conductivity higher than that of the substrate.

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

19. The manufacturing method as set forth in claim 18, wherein the horizontal sectional shape of the release hole is a circle, a polygon or an irregular shape.

20. The manufacturing method according to claim 18 or 19, wherein:

the horizontal projection of the bottom surface of the first groove falls into the horizontal projection of the bottom surface of the second groove;

the horizontal projection of the first overlapping area falls within the horizontal projection of the second overlapping area.

21. The manufacturing method according to claim 20, wherein:

the bottom surface of the first groove is in a regular N-edge shape, wherein N is more than or equal to 3;

the number of the first release holes is equal to N +1, one of the first release holes is formed in the central area of the bottom surface of the first groove, and the other N first release holes are respectively formed in the N vertex areas of the bottom surface of the first groove.

22. The manufacturing method according to claim 20, wherein:

the second release hole is formed in the first laminate structure at a position outside the first overlap region.

23. The manufacturing method according to claim 22, wherein:

there is at least one of the second release holes and one of the first release holes aligned in a thickness direction of the device.

24. The manufacturing method according to claim 18 or 19, before etching the second surface of the substrate to form the second groove communicating with the first relief hole, further comprising:

thinning the substrate from the second surface.

25. The manufacturing method according to claim 18 or 19, wherein:

after forming the first stacked structure on the first surface of the substrate, the manufacturing method further includes: forming a protective layer covering the first stacked structure; and

after forming a second stacked structure on the second surface of the substrate, the manufacturing method further includes: and removing the protective layer.

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

27. The manufacturing method according to claim 26, wherein:

28. The manufacturing method according to claim 27, wherein:

the number of the first release holes is equal to N +1, one of the first release holes is formed in a central region of the bottom surface of the first groove, and the other N first release holes are formed in N vertex regions of the bottom surface of the first groove, respectively.

29. The manufacturing method according to claim 27, wherein:

the second release hole is formed in the first laminate structure at a position outside the first overlapping area.

30. The manufacturing method according to claim 29, wherein:

31. The method of manufacturing of claim 26, before etching the substrate to form the first recess in the first surface, further comprising:

the substrate is thinned from the first surface.

32. The manufacturing method according to claim 26, wherein:

after forming a second stacked structure on the second surface of the substrate, the manufacturing method further includes: forming a protective layer covering the second stacked structure; and

after forming the first stacked structure on the first surface of the substrate, the manufacturing method further includes: and removing the protective layer.

33. A bulk acoustic wave resonator, comprising:

a substrate comprising a first surface and a second surface opposite thereto;

34. The bulk acoustic wave resonator according to claim 33, wherein a horizontal sectional shape of the release hole is a circle, a polygon, or an irregular shape.

35. The bulk acoustic wave resonator according to claim 33 or 34, wherein:

the horizontal projection of the bottom surface of the first cavity falls into the horizontal projection of the bottom surface of the second cavity;

36. The bulk acoustic wave resonator of claim 35, wherein:

the bottom surface of the first cavity is in a regular N-edge shape, wherein N is more than or equal to 3;

the number of the first release holes is equal to N +1, one of the first release holes penetrates through the central area of the bottom surface of the first cavity, and the other N first release holes respectively penetrate through the N vertex areas of the bottom surface of the first cavity.

37. The bulk acoustic wave resonator of claim 35, wherein:

38. The bulk acoustic wave resonator of claim 36, wherein: