A bulk acoustic wave filter, a communication device, and a method for manufacturing a bulk acoustic wave filter

Abstract

The present invention provides a bulk acoustic wave filter, a communication device, and a method for manufacturing a bulk acoustic wave filter. The bulk acoustic wave filter includes: a first substrate; at least two bulk acoustic wave resonators arranged vertically on the first substrate, the bulk acoustic wave resonator including a stacked structure of a bottom electrode, a piezoelectric layer, and a top electrode; the vertically adjacent bulk acoustic wave resonators include a first bulk acoustic wave resonator and a second bulk acoustic wave resonator; a first cavity structure is provided in the first substrate, the first cavity structure is located between the first bulk acoustic wave resonator and the first substrate, and the first cavity structure serves as an acoustic reflection structure of the first bulk acoustic wave resonator; the second bulk acoustic wave resonator is located in the first cavity structure and is spaced a preset distance from the first bulk acoustic wave resonator in the vertical direction. The technical solution provided by the embodiments of the present invention reduces the package size of the bulk acoustic wave filter and avoids the coupling parasitic effect between the bulk acoustic wave resonators to improve the out-of-band rejection of the bulk acoustic wave filter.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular, to a bulk acoustic wave filter, a communication device, and a method for manufacturing a bulk acoustic wave filter. Background Art

[0002] The bulk acoustic wave filter has the characteristics of high operating frequency, low power consumption, high quality factor, etc., and has now become an important device in the field of communication devices and is widely used.

[0003] The existing bulk acoustic wave filter has the following two defects: First, the lateral layout method of the bulk acoustic wave resonator in the current bulk acoustic wave filter makes the package size of the bulk acoustic wave filter too large. Second, the coupling parasitic effect between the two bulk acoustic wave resonators in the current layout will have a negative effect on the out-of-band suppression of the bulk acoustic wave filter, such as the degradation of out-of-band zeros, etc.

[0004] Therefore, on the one hand, it is necessary to change the lateral layout method of the bulk acoustic wave resonator in the bulk acoustic wave filter to reduce the package size of the bulk acoustic wave filter; on the other hand, it is also necessary to avoid the coupling parasitic effect between the bulk acoustic wave resonators to improve the out-of-band suppression of the bulk acoustic wave filter. Summary of the Invention

[0005] The present invention provides a bulk acoustic wave filter, a communication device, and a method for manufacturing a bulk acoustic wave filter to reduce the package size of the bulk acoustic wave filter and avoid the coupling parasitic effect between the bulk acoustic wave resonators to improve the out-of-band suppression of the bulk acoustic wave filter.

[0006] According to one aspect of the present invention, a bulk acoustic wave filter is provided, including:

[0007] A first substrate;

[0008] At least two bulk acoustic wave resonators arranged vertically on the first substrate, the bulk acoustic wave resonator including a stacked structure of a bottom electrode, a piezoelectric layer, and a top electrode;

[0009] The bulk acoustic wave resonators adjacent to each other vertically include a first bulk acoustic wave resonator and a second bulk acoustic wave resonator;

[0010] A first cavity structure is provided in the first substrate, the first cavity structure is located between the first bulk acoustic wave resonator and the first substrate, and the first cavity structure serves as an acoustic reflection structure of the first bulk acoustic wave resonator;

[0011] The second bulk acoustic wave resonator is located in the first cavity structure and is spaced a preset distance from the first bulk acoustic wave resonator in the vertical direction.

[0012] Optionally, the first bulk acoustic wave resonator is located on the surface of the first substrate;

[0013] The first substrate is provided with a first receiving groove, and the second bulk acoustic wave resonator is located in the first receiving groove, and the first receiving groove serves as the first cavity structure.

[0014] Optionally, the first substrate is provided with a second receiving groove, and part or all of the first bulk acoustic wave resonator is located in the second receiving groove;

[0015] The first substrate is further provided with a third receiving groove, and the second bulk acoustic wave resonator is located in the third receiving groove. The third receiving groove is located at the bottom surface of the second receiving groove, and the horizontal dimension of the third receiving groove is smaller than the horizontal dimension of the second receiving groove;

[0016] The third receiving groove serves as the first cavity structure.

[0017] Optionally, the first substrate is further provided with a second cavity structure, and the second cavity structure is located between the first substrate and the second bulk acoustic wave resonator, and the second cavity structure serves as an acoustic reflection structure of the second bulk acoustic wave resonator.

[0018] Optionally, three vertically adjacent bulk acoustic wave resonators include the first bulk acoustic wave resonator, the second bulk acoustic wave resonator, and a third bulk acoustic wave resonator. The third bulk acoustic wave resonator and the second bulk acoustic wave resonator are vertically adjacent to each other. The third bulk acoustic wave resonator is located in the second cavity structure, and there is a preset distance between the third bulk acoustic wave resonator and the second bulk acoustic wave resonator in the vertical direction.

[0019] Optionally, the first substrate is provided with a fourth receiving groove, and the third bulk acoustic wave resonator is located in the fourth receiving groove. The fourth receiving groove is located at the bottom surface of the receiving groove for placing the second bulk acoustic wave resonator, and the horizontal dimension of the fourth receiving groove is smaller than the horizontal dimension of the receiving groove for placing the second bulk acoustic wave resonator. The fourth receiving groove serves as the second cavity structure.

[0020] Optionally, the first substrate is further provided with a third cavity structure, and the third cavity structure is located between the first substrate and the third bulk acoustic wave resonator.

[0021] Optionally, the horizontal dimension of the second bulk acoustic wave resonator is smaller than the horizontal dimension of the first bulk acoustic wave resonator.

[0022] Optionally, it further includes a second substrate stacked with the first substrate in the vertical direction, and at least one bulk acoustic wave resonator is provided on a side of the second substrate close to the first substrate.

[0023] Optionally, at least two bulk acoustic wave resonators arranged in the vertical direction are provided on one side of the second substrate close to the first substrate;

[0024] The bulk acoustic wave resonators arranged adjacent to each other in the vertical direction include a fourth bulk acoustic wave resonator and a fifth bulk acoustic wave resonator;

[0025] A fourth cavity structure is provided in the second substrate, the fourth cavity structure is located between the fourth bulk acoustic wave resonator and the second substrate, and the fourth cavity structure serves as an acoustic reflection structure for the fourth bulk acoustic wave resonator;

[0026] The fifth bulk acoustic wave resonator is located in the fourth cavity structure and is spaced a preset distance from the fourth bulk acoustic wave resonator in the vertical direction.

[0027] Optionally, the orthographic projections of the bulk acoustic wave resonators on the first substrate and on the second substrate in the horizontal plane do not overlap.

[0028] Optionally, the orthographic projections of the electrodes of the bulk acoustic wave resonators on the surface of the first substrate and the electrodes of the bulk acoustic wave resonators on the surface of the second substrate in the vertical plane do not overlap, and the electrodes include at least one of a bottom electrode and a top electrode.

[0029] Optionally, the orthographic projections of the piezoelectric layer of the bulk acoustic wave resonator on the surface of the first substrate and the top electrode of the bulk acoustic wave resonator on the surface of the second substrate in the vertical plane overlap;

[0030] The orthographic projections of the top electrode of the bulk acoustic wave resonator on the surface of the first substrate and the piezoelectric layer of the bulk acoustic wave resonator on the surface of the second substrate in the vertical plane overlap;

[0031] The orthographic projections of the top electrode of the bulk acoustic wave resonator on the surface of the first substrate and the top electrode of the bulk acoustic wave resonator on the surface of the second substrate in the vertical plane do not overlap;

[0032] The orthographic projections of the bottom electrode of the bulk acoustic wave resonator on the surface of the first substrate and the bottom electrode and the top electrode of the bulk acoustic wave resonator on the surface of the second substrate in the vertical plane do not overlap.

[0033] Optionally, the distance between the first substrate and the second substrate is greater than the height of any one bulk acoustic wave resonator on the substrate surface, and the distance between the first substrate and the second substrate is less than the sum of the height of any one bulk acoustic wave resonator on the surface of the first substrate and the height of any one bulk acoustic wave resonator on the surface of the second substrate.

[0034] It further includes a passivation protection layer, which is located on the surface side of the second bulk acoustic wave resonator close to the first bulk acoustic wave resonator, is located within the first cavity structure, and has a preset distance from the first bulk acoustic wave resonator in the vertical direction.

[0035] According to another aspect of the present invention, there is provided a communication device, characterized in that it includes the bulk acoustic wave filter according to any one of the embodiments of the present invention;

[0036] The communication device includes at least one of a filter, a duplexer, and a multiplexer.

[0037] According to another aspect of the present invention, there is provided a method for manufacturing a bulk acoustic wave filter, including:

[0038] Providing a first substrate;

[0039] Forming at least two bulk acoustic wave resonators arranged in the vertical direction on the first substrate;

[0040] Wherein, the bulk acoustic wave resonator includes a stacked structure of a bottom electrode, a piezoelectric layer, and a top electrode;

[0041] The bulk acoustic wave resonators arranged adjacent to each other in the vertical direction include a first bulk acoustic wave resonator and a second bulk acoustic wave resonator;

[0042] A first cavity structure is provided within the first substrate, and the first cavity structure is located between the first bulk acoustic wave resonator and the first substrate, and the first cavity structure serves as an acoustic reflection structure for the first bulk acoustic wave resonator;

[0043] The second bulk acoustic wave resonator is located within the first cavity structure and has a preset distance from the first bulk acoustic wave resonator in the vertical direction.

[0044] Optionally, forming at least two bulk acoustic wave resonators arranged in the vertical direction on the first substrate includes:

[0045] Forming a first receiving groove in the first substrate;

[0046] Forming a second bulk acoustic wave resonator within the first receiving groove;

[0047] Forming a first sacrificial layer on the side of the second bulk acoustic wave resonator facing away from the first substrate, and the surface of the first sacrificial layer is flush with the surface of the first substrate;

[0048] Forming the first bulk acoustic wave resonator on the side of the first sacrificial layer facing away from the second bulk acoustic wave resonator;

[0049] Releasing the first sacrificial layer to form the first cavity structure.

[0050] Optionally, before forming the second BAW resonator in the first accommodating groove, the method further includes:

[0051] A fifth accommodating groove is formed on the bottom surface of the first accommodating groove, wherein the horizontal dimension of the fifth accommodating groove is smaller than the horizontal dimension of the first accommodating groove;

[0052] forming a second sacrificial layer on the bottom surface of the fifth accommodating groove, wherein the second sacrificial layer is flush with the bottom surface of the first accommodating groove;

[0053] The method further includes releasing the first sacrificial layer to form the first cavity structure:

[0054] The second sacrificial layer is released to form a second cavity structure, where the second cavity structure serves as an acoustic reflection structure of the second BAW resonator.

[0055] Optionally, forming a first sacrificial layer on a side of the second BAW resonator facing away from the first substrate, wherein the first sacrificial layer is flush with a surface of the first substrate comprises:

[0056] forming a passivation protection layer on a side of the second BAW resonator facing away from the first substrate;

[0057] A first sacrificial layer is formed on a side of the passivation protection layer away from the second BAW resonator, and the first sacrificial layer is flush with a surface of the first substrate.

[0058] The technical solution provided in this embodiment is that, in a first aspect, the bulk acoustic wave resonator included in the bulk acoustic wave filter is arranged on the first substrate in the vertical direction, which reduces the size of the bulk acoustic wave filter in the horizontal direction, thereby reducing the package size of the bulk acoustic wave filter. In a second aspect, the bulk acoustic wave resonators arranged adjacent to each other in the vertical direction include a first bulk acoustic wave resonator and a second bulk acoustic wave resonator; the second bulk acoustic wave resonator is located in a first cavity structure that serves as an acoustic reflection structure of the first bulk acoustic wave resonator, that is, the bulk acoustic wave resonators arranged adjacent to each other in the vertical direction extend toward the space in the first substrate, which reduces the size of the bulk acoustic wave filter in the vertical direction, thereby further reducing the package size of the bulk acoustic wave filter. On the third aspect, the first BAW resonator and the second BAW resonator represent any two BAW resonators arranged adjacent to each other in the vertical direction. Since the second BAW resonator is located in the first cavity structure which serves as the sound reflection structure of the first BAW resonator and is spaced at a preset distance in the vertical direction from the first BAW resonator, the coupling parasitic effect between the two BAW resonators arranged adjacent to each other in the vertical direction can be avoided, thereby improving the out-of-band suppression of the BAW filter.

[0059] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become readily understood from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts.

[0061] Figure 1 is a schematic structural diagram of a bulk acoustic wave filter provided according to an embodiment of the present invention;

[0062] Figure 2 is a schematic structural diagram of another bulk acoustic wave filter provided according to an embodiment of the present invention;

[0063] Figure 3 is a schematic structural diagram of yet another bulk acoustic wave filter provided according to an embodiment of the present invention;

[0064] Figure 4 is a schematic structural diagram of yet another bulk acoustic wave filter provided according to an embodiment of the present invention;

[0065] Figure 5 is a schematic structural diagram of yet another bulk acoustic wave filter provided according to an embodiment of the present invention;

[0066] Figure 6 is a schematic structural diagram of yet another bulk acoustic wave filter provided according to an embodiment of the present invention;

[0067] Figure 7 is a schematic structural diagram of yet another bulk acoustic wave filter provided according to an embodiment of the present invention;

[0068] Figure 8 is a flowchart of a method for manufacturing a bulk acoustic wave filter provided according to an embodiment of the present invention;

[0069] Figure 9 is a flowchart of another method for manufacturing a bulk acoustic wave filter provided according to an embodiment of the present invention;

[0070] Figure 10 is Figure 9 a flowchart of the manufacturing method included in S230 in

[0071] Figures 11 - 17 is a schematic structural diagram corresponding to each step of a method for manufacturing a bulk acoustic wave filter provided according to an embodiment of the present invention;

[0072] Figure 18 Yes Figure 9 It is a flowchart of the preparation method included in S240;

[0073] Figures 19 - 21 Yes Figure 18 It is a schematic structural diagram corresponding to each step of the preparation method included in S240. Detailed implementation manners

[0074] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0075] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order different from those illustrated or described here. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or components does not have to be limited to those steps or components clearly listed, but may include other steps or components not clearly listed or inherent to these processes, methods, products or devices.

[0076] In order to reduce the package size of the bulk acoustic wave filter and avoid the coupling parasitic effect between the bulk acoustic wave resonators, the embodiments of the present invention provide the following technical solutions:

[0077] The bulk acoustic wave filter includes: a first substrate; at least two bulk acoustic wave resonators arranged vertically on the first substrate, the bulk acoustic wave resonator including a stacked structure of a bottom electrode, a piezoelectric layer and a top electrode; the bulk acoustic wave resonators arranged adjacent to each other vertically include a first bulk acoustic wave resonator and a second bulk acoustic wave resonator; a first cavity structure is arranged in the first substrate, the first cavity structure is located between the first bulk acoustic wave resonator and the first substrate, and the first cavity structure serves as an acoustic reflection structure of the first bulk acoustic wave resonator; the second bulk acoustic wave resonator is located in the first cavity structure and is spaced a preset distance from the first bulk acoustic wave resonator in the vertical direction.

[0078] It should be noted that in this embodiment, the first bulk acoustic wave resonator and the second bulk acoustic wave resonator refer to any two vertically adjacent bulk acoustic wave resonators among the bulk acoustic wave resonators located on the first substrate. Since the second bulk acoustic wave resonator is located within the first cavity structure that serves as the acoustic reflection structure of the first bulk acoustic wave resonator, and the first cavity structure is located within the first substrate, the vertically adjacent bulk acoustic wave resonators extend towards the space within the first substrate.

[0079] Figure 1 is a schematic structural diagram of a bulk acoustic wave filter provided according to an embodiment of the present invention. Exemplarily, referring to Figure 1 , the bulk acoustic wave filter includes: a first substrate 10a; two bulk acoustic wave resonators 20 arranged vertically on the first substrate 10a are respectively a first bulk acoustic wave resonator 20a and a second bulk acoustic wave resonator 20b. The bulk acoustic wave resonator 20 includes a stacked structure of a bottom electrode 21, a piezoelectric layer 22, and a top electrode 23; the bulk acoustic wave resonators 20 include a first bulk acoustic wave resonator 20a and a second bulk acoustic wave resonator 20b arranged vertically adjacent to each other; a first cavity structure 30 is provided within the first substrate 10a, and the first cavity structure 30 is located between the first bulk acoustic wave resonator 20a and the first substrate 10a. The first cavity structure 30 serves as the acoustic reflection structure of the first bulk acoustic wave resonator 20a, which is used to reflect acoustic waves back to the bulk acoustic wave resonator, reduce the loss of acoustic waves, and thereby improve the quality factor of the filter; the second bulk acoustic wave resonator 20b is located within the first cavity structure 30 and is spaced a preset distance from the first bulk acoustic wave resonator 20a in the vertical direction. In the embodiment of the present invention, the vertical direction is the Z direction determined by the three-dimensional rectangular coordinate system.

[0080] In the technical solution provided in this embodiment, on the one hand, the bulk acoustic wave resonators included in the bulk acoustic wave filter are arranged vertically on the first substrate, reducing the size of the bulk acoustic wave filter in the horizontal direction, thereby reducing the package size of the bulk acoustic wave filter. On the other hand, the vertically adjacent bulk acoustic wave resonators include a first bulk acoustic wave resonator and a second bulk acoustic wave resonator; the second bulk acoustic wave resonator is located within the first cavity structure that serves as the acoustic reflection structure of the first bulk acoustic wave resonator, that is, the vertically adjacent bulk acoustic wave resonators extend towards the space within the first substrate, reducing the size of the bulk acoustic wave filter in the vertical direction, thereby further reducing the package size of the bulk acoustic wave filter. On the third hand, the first bulk acoustic wave resonator and the second bulk acoustic wave resonator represent any two vertically adjacent bulk acoustic wave resonators. Since the second bulk acoustic wave resonator is located within the first cavity structure that serves as the acoustic reflection structure of the first bulk acoustic wave resonator and is spaced a preset distance from the first bulk acoustic wave resonator in the vertical direction, the coupling parasitic effect between the two vertically adjacent bulk acoustic wave resonators can be avoided, thereby improving the out-of-band rejection of the bulk acoustic wave filter.

[0081] In the above technical solution, the first bulk acoustic wave resonator and the second bulk acoustic wave resonator represent any two vertically adjacent bulk acoustic wave resonators. Since the second bulk acoustic wave resonator is located in the first cavity structure that is the acoustic reflection structure of the first bulk acoustic wave resonator, and the first cavity structure is located in the first substrate, the positional relationship between the bulk acoustic wave resonator closest to the surface of the first substrate can include two cases. In the first case, among the two vertically adjacent bulk acoustic wave resonators, one is located on the surface of the first substrate and the other is located inside the first substrate.

[0082] Optionally, the first bulk acoustic wave resonator is located on the surface of the first substrate; the first substrate is provided with a first receiving groove, and the second bulk acoustic wave resonator is located in the first receiving groove, and the first receiving groove serves as the first cavity structure.

[0083] Exemplarily, referring to Figure 1 , the first bulk acoustic wave resonator 20a is located on the surface of the first substrate 10a; the first substrate 10a is provided with a first receiving groove 40, and the second bulk acoustic wave resonator 20b is located in the first receiving groove 40, and the first receiving groove 40 serves as the first cavity structure 30.

[0084] Specifically, among the two vertically adjacent bulk acoustic wave resonators, one is located on the surface of the first substrate and the other is located inside the first substrate. When the bulk acoustic wave filter includes a larger number of bulk acoustic wave resonators, the other bulk acoustic wave resonators extend into the space inside the first substrate instead of being vertically arranged only in the space above the surface of the first substrate, reducing the vertical size of the bulk acoustic wave filter, thereby further reducing the package size of the bulk acoustic wave filter. Exemplarily, in the embodiment of the present invention, the first substrate may be a wafer, the thickness of the wafer may be about 100 microns, and the thickness of the bulk acoustic wave resonator may be about 1.5 microns.

[0085] In the second case, among the two vertically adjacent bulk acoustic wave resonators, a part or all of one is located inside the first substrate and the other is located inside the first substrate.

[0086] Optionally, the first substrate is provided with a second receiving groove, and a part or all of the first bulk acoustic wave resonator is located in the second receiving groove; the first substrate is further provided with a third receiving groove, the second bulk acoustic wave resonator is located in the third receiving groove, the third receiving groove is located on the bottom surface of the second receiving groove, and the horizontal dimension of the third receiving groove is smaller than the horizontal dimension of the second receiving groove; the third receiving groove serves as the first cavity structure.

[0087] Exemplarily, referring to Figure 2, a first substrate 10a is provided with a second receiving groove 41, and the entire first bulk acoustic wave resonator 20a is located within the second receiving groove 41; the first substrate 10a is further provided with a third receiving groove 42, and the second bulk acoustic wave resonator 20b is located within the third receiving groove 42. The third receiving groove 42 is located at the bottom surface of the second receiving groove 41, and the horizontal dimension of the third receiving groove 42 is smaller than the horizontal dimension of the second receiving groove 41; the third receiving groove 42 serves as the first cavity structure 30.

[0088] In an embodiment of the present invention, the horizontal dimension is the direction parallel to the XOY plane in a three-dimensional rectangular coordinate system.

[0089] Specifically, among two vertically adjacent bulk acoustic wave resonators, part or all of one of them is located within the first substrate, and the other is located within the first substrate, further reducing the vertical dimension of the bulk acoustic wave filter, thereby further reducing the package size of the bulk acoustic wave filter.

[0090] Optionally, the first substrate is further provided with a second cavity structure, and the second cavity structure is located between the first substrate and the second bulk acoustic wave resonator. The second cavity structure serves as an acoustic reflection structure for the second bulk acoustic wave resonator.

[0091] Exemplarily, referring to Figure 1 and Figure 2 , the first substrate 10a is further provided with a second cavity structure 31, and the second cavity structure 31 is located between the first substrate 10a and the second bulk acoustic wave resonator 20b. The second cavity structure 31 serves as an acoustic reflection structure for the second bulk acoustic wave resonator 20b, and is used to reflect acoustic waves back to the bulk acoustic wave resonator, reducing the loss of acoustic waves, and thereby improving the quality factor of the filter.

[0092] Optionally, three vertically adjacent bulk acoustic wave resonators include a first bulk acoustic wave resonator, a second bulk acoustic wave resonator, and a third bulk acoustic wave resonator. The third bulk acoustic wave resonator and the second bulk acoustic wave resonator are vertically adjacent, and the third bulk acoustic wave resonator is located within the second cavity structure, and the third bulk acoustic wave resonator and the second bulk acoustic wave resonator have a preset distance in the vertical direction.

[0093] It should be noted that the first bulk acoustic wave resonator, the second bulk acoustic wave resonator, and the third bulk acoustic wave resonator represent any three vertically adjacent bulk acoustic wave resonators provided on the first substrate. The first bulk acoustic wave resonator, the second bulk acoustic wave resonator, and the third bulk acoustic wave resonator extend into the space inside the first substrate in sequence in the vertical direction.

[0094] Exemplarily, referring to Figure 3, the vertically adjacent bulk acoustic wave resonators include a first bulk acoustic wave resonator 20a, a second bulk acoustic wave resonator 20b, and a third bulk acoustic wave resonator 20c. The third bulk acoustic wave resonator 20c and the second bulk acoustic wave resonator 20b are adjacent to each other in the vertical direction. The third bulk acoustic wave resonator 20c is located within the second cavity structure 31, and there is a preset distance between the third bulk acoustic wave resonator 20c and the second bulk acoustic wave resonator 20b in the vertical direction.

[0095] Specifically, the second bulk acoustic wave resonator is located within the first cavity structure, and the third bulk acoustic wave resonator is located within the second cavity structure. That is, when the bulk acoustic wave filter includes a larger number of bulk acoustic wave resonators, the bulk acoustic wave resonators extend into the space inside the first substrate instead of being vertically arranged only in the space above the surface of the first substrate, reducing the size of the bulk acoustic wave filter in the vertical direction and thus further reducing the package size of the bulk acoustic wave filter.

[0096] Optionally, the first substrate is provided with a fourth receiving groove. The third bulk acoustic wave resonator is located within the fourth receiving groove. The fourth receiving groove is located at the bottom surface of the receiving groove for placing the second bulk acoustic wave resonator, and the horizontal dimension of the fourth receiving groove is smaller than the horizontal dimension of the receiving groove for placing the second bulk acoustic wave resonator. The fourth receiving groove serves as the second cavity structure.

[0097] Exemplarily, referring to Figure 3 , the first substrate 10a is provided with a fourth receiving groove 43. The third bulk acoustic wave resonator 20c is located within the fourth receiving groove 43. The fourth receiving groove 43 is located at the bottom surface of the receiving groove for placing the second bulk acoustic wave resonator 20b, and the horizontal dimension of the fourth receiving groove 43 is smaller than the horizontal dimension of the receiving groove for placing the second bulk acoustic wave resonator 20b. The fourth receiving groove 43 serves as the second cavity structure 31.

[0098] Specifically, the fourth receiving groove is located at the bottom surface of the receiving groove for placing the second bulk acoustic wave resonator, that is, the bulk acoustic wave resonator extends into the space inside the first substrate, reducing the size of the bulk acoustic wave filter in the vertical direction and thus further reducing the package size of the bulk acoustic wave filter.

[0099] Optionally, referring to Figure 3 , the first substrate 10a is further provided with a third cavity structure 32. The third cavity structure 32 is located between the first substrate 10a and the third bulk acoustic wave resonator 20c. The third cavity structure 32 serves as an acoustic reflection structure for the third bulk acoustic wave resonator 20c, which is used to reflect the acoustic wave back to the bulk acoustic wave resonator, reducing the loss of the acoustic wave and thereby improving the quality factor of the filter.

[0100] Optionally, the horizontal dimension of the second bulk acoustic wave resonator is smaller than the horizontal dimension of the first bulk acoustic wave resonator.

[0101] Exemplarily, refer to Figure 1 and Figure 2 , the horizontal dimension of the second bulk acoustic wave resonator 20b is smaller than that of the first bulk acoustic wave resonator 20a.

[0102] Specifically, among two vertically adjacent bulk acoustic wave resonators, the first bulk acoustic wave resonator closer to the first substrate surface has a larger horizontal dimension. When the bulk acoustic wave filter further includes a larger number of bulk acoustic wave resonators, the other bulk acoustic wave resonators extend towards the space inside the first substrate in a manner that the horizontal dimension gradually decreases. The horizontal package dimension of the entire bulk acoustic wave filter can be controlled by controlling the horizontal dimension of the bulk acoustic wave resonator closest to the first substrate surface.

[0103] Optionally, it further includes a second substrate stacked with the first substrate in the vertical direction, and at least one bulk acoustic wave resonator is disposed on the side of the second substrate close to the first substrate.

[0104] Exemplarily, refer to Figure 4 , it further includes a second substrate 10b stacked with the first substrate 10a in the vertical direction, and a bulk acoustic wave resonator 20 is disposed on the side of the second substrate 10b close to the first substrate 10a. In other embodiments, the second substrate 10b may further be provided with a larger number of bulk acoustic wave resonators. It should be noted that when the number of substrates is at least two, a bonding structure 60 may be disposed between adjacent substrates for hermetically connecting different substrates.

[0105] Specifically, the bulk acoustic wave filter includes at least two substrates stacked in the vertical direction. As the number of substrates increases, the horizontal dimension of the bulk acoustic wave filter can be reduced, thereby contributing to the formation of a miniaturized bulk acoustic wave filter.

[0106] Optionally, at least two bulk acoustic wave resonators arranged in the vertical direction are disposed on the side of the second substrate close to the first substrate; the vertically adjacent bulk acoustic wave resonators include a fourth bulk acoustic wave resonator and a fifth bulk acoustic wave resonator; a fourth cavity structure is disposed in the second substrate, and the fourth cavity structure is located between the fourth bulk acoustic wave resonator and the second substrate, and the fourth cavity structure serves as an acoustic reflection structure for the fourth bulk acoustic wave resonator; the fifth bulk acoustic wave resonator is located in the fourth cavity structure and is preset with a distance from the fourth bulk acoustic wave resonator in the vertical direction.

[0107] It should be noted that in this embodiment, the fourth bulk acoustic wave resonator and the fifth bulk acoustic wave resonator refer to any two vertically adjacent bulk acoustic wave resonators among the bulk acoustic wave resonators located on the second substrate. Since the fifth bulk acoustic wave resonator is located within the fourth cavity structure that serves as the acoustic reflection structure of the fourth bulk acoustic wave resonator, and the fourth cavity structure is located within the second substrate, the vertically adjacent bulk acoustic wave resonators extend towards the space within the second substrate. The bulk acoustic wave resonator closer to the surface of the second substrate is referred to as the fourth bulk acoustic wave resonator, and the other bulk acoustic wave resonator is referred to as the fifth bulk acoustic wave resonator.

[0108] Exemplarily, referring to Figure 5 , on the side of the second substrate 10b close to the first substrate 10a, there are two vertically arranged bulk acoustic wave resonators, namely the fourth bulk acoustic wave resonator 20d and the fifth bulk acoustic wave resonator 20e; the fourth bulk acoustic wave resonator 20d and the fifth bulk acoustic wave resonator 20e are vertically adjacent; a fourth cavity structure 33 is provided within the second substrate 10b, and the fourth cavity structure 33 is located between the fourth bulk acoustic wave resonator 20d and the second substrate 10b, and the fourth cavity structure 33 serves as the acoustic reflection structure of the fourth bulk acoustic wave resonator 20d; the fifth bulk acoustic wave resonator 20e is located within the fourth cavity structure 33 and is spaced a preset distance from the fourth bulk acoustic wave resonator 20d in the vertical direction.

[0109] Exemplarily, referring to Figure 6 , the second substrate 10b is provided with a fourth bulk acoustic wave resonator 20d, a fifth bulk acoustic wave resonator 20e, and a sixth bulk acoustic wave resonator 20f that are vertically adjacent. The sixth bulk acoustic wave resonator 20f and the fifth bulk acoustic wave resonator 20e are vertically adjacent, and the sixth bulk acoustic wave resonator 20f is located within the fifth cavity structure 34 of the fifth bulk acoustic wave resonator 20e and the second substrate 10b. It should be noted that the fourth bulk acoustic wave resonator, the fifth bulk acoustic wave resonator, and the sixth bulk acoustic wave resonator represent any three vertically adjacent bulk acoustic wave resonators provided on the second substrate. The fourth bulk acoustic wave resonator, the fifth bulk acoustic wave resonator, and the sixth bulk acoustic wave resonator extend towards the space inside the second substrate in sequence in the vertical direction.

[0110] Specifically, in the first aspect, the bulk acoustic wave resonators included in the bulk acoustic wave filter are arranged vertically on the first substrate and the second substrate, reducing the size of the bulk acoustic wave filter in the horizontal direction, thereby reducing the package size of the bulk acoustic wave filter. In the second aspect, the bulk acoustic wave resonators adjacent to each other vertically on the second substrate include a fourth bulk acoustic wave resonator and a fifth bulk acoustic wave resonator; the fifth bulk acoustic wave resonator is located within a fourth cavity structure that serves as an acoustic reflection structure for the fourth bulk acoustic wave resonator, that is, the bulk acoustic wave resonators adjacent to each other vertically extend towards the space within the second substrate, reducing the size of the bulk acoustic wave filter in the vertical direction, thereby further reducing the package size of the bulk acoustic wave filter. In the third aspect, the fourth bulk acoustic wave resonator and the fifth bulk acoustic wave resonator represent any two bulk acoustic wave resonators adjacent to each other vertically on the second substrate. Since the fifth bulk acoustic wave resonator is located within the fourth cavity structure that serves as an acoustic reflection structure for the fourth bulk acoustic wave resonator and has a preset distance from the fourth bulk acoustic wave resonator in the vertical direction, the coupling parasitic effect between the two bulk acoustic wave resonators adjacent to each other vertically on the second substrate is avoided in the vertical direction, thereby improving the out-of-band rejection of the bulk acoustic wave filter.

[0111] Optionally, referring to Figures 4 - 6 , the orthographic projections of the bulk acoustic wave resonators 20 located on the first substrate 10a and the second substrate 10b in the horizontal plane do not overlap, which can avoid the parasitic capacitance existing in the vertical direction of the electrodes of the bulk acoustic wave resonators 20 between the first substrate 10a and the second substrate 10b, so as to avoid the coupling parasitic effect between the bulk acoustic wave resonators, and thereby improve the out-of-band rejection of the bulk acoustic wave filter. It should be noted that in the embodiments of the present invention, the horizontal plane refers to the XOY plane determined by the three-dimensional rectangular coordinate system.

[0112] Optionally, referring to Figure 4 , the orthographic projections of the electrodes of the bulk acoustic wave resonators 20 located on the surface of the first substrate 10a and the electrodes of the bulk acoustic wave resonators 20 located on the surface of the second substrate 10b in the vertical plane do not overlap, and the electrodes include at least one of a bottom electrode 21 and a top electrode 23. In the embodiments of the present invention, the vertical plane refers to the XOZ plane determined by the three-dimensional rectangular coordinate system.

[0113] Specifically, the orthographic projections of the electrodes of the bulk acoustic wave resonators located on the surface of the first substrate and the electrodes of the bulk acoustic wave resonators located on the surface of the second substrate in the vertical plane do not overlap, which can avoid the parasitic capacitance existing in the horizontal direction of the electrodes of the bulk acoustic wave resonators between the first substrate and the second substrate, so as to avoid the coupling parasitic effect between the bulk acoustic wave resonators, and thereby improve the out-of-band rejection of the bulk acoustic wave filter.

[0114] Optionally, the positive projection in the vertical plane of the piezoelectric layer of the bulk acoustic wave resonator located on the first substrate surface and the top electrode of the bulk acoustic wave resonator located on the second substrate surface overlap; the positive projection in the vertical plane of the top electrode of the bulk acoustic wave resonator located on the first substrate surface and the piezoelectric layer of the bulk acoustic wave resonator located on the second substrate surface overlap; the positive projection in the vertical plane of the top electrode of the bulk acoustic wave resonator located on the first substrate surface and the top electrode of the bulk acoustic wave resonator located on the second substrate surface do not overlap; the positive projection in the vertical plane of the bottom electrode of the bulk acoustic wave resonator located on the first substrate surface and the bottom electrode and the top electrode of the bulk acoustic wave resonator located on the second substrate surface do not overlap.

[0115] Exemplarily, referring to Figure 5 and Figure 6 , the positive projection in the vertical plane of the piezoelectric layer 22 of the first bulk acoustic wave resonator 20a located on the surface of the first substrate 10a and the top electrode 23 of the fourth bulk acoustic wave resonator 20d located on the surface of the second substrate 10b overlap; the positive projection in the vertical plane of the top electrode 23 of the first bulk acoustic wave resonator 20a located on the surface of the first substrate 10a and the piezoelectric layer 22 of the fourth bulk acoustic wave resonator 20d located on the surface of the second substrate 10b overlap; the positive projection in the vertical plane of the top electrode 23 of the first bulk acoustic wave resonator 20a located on the surface of the first substrate 10a and the top electrode 23 of the fourth bulk acoustic wave resonator 20d located on the surface of the second substrate 10b do not overlap; the positive projection in the vertical plane of the bottom electrode 21 of the first bulk acoustic wave resonator 20a located on the surface of the first substrate 10a and the bottom electrode 21 and the top electrode 23 of the fourth bulk acoustic wave resonator 20d located on the surface of the second substrate 10b do not overlap.

[0116] On the one hand, the above technical solution can further reduce the size of the bulk acoustic wave filter in the vertical direction, and further reduce the package size of the bulk acoustic wave filter. On the other hand, the above technical solution can avoid the parasitic capacitance of the electrodes of the bulk acoustic wave resonators on the first substrate and the second substrate in the horizontal direction, and thus avoid the coupling parasitic effect between the bulk acoustic wave resonators between the first substrate and the second substrate, thereby improving the out-of-band rejection of the bulk acoustic wave filter.

[0117] Optionally, the distance between the first substrate and the second substrate is greater than the height of any one bulk acoustic wave resonator located on the substrate surface, and the distance between the first substrate and the second substrate is less than the sum of the height of any one bulk acoustic wave resonator located on the first substrate surface and the height of any one bulk acoustic wave resonator located on the second substrate surface.

[0118] Exemplarily, referring to Figures 4 - 6, the distance between the first substrate 10a and the second substrate 10b is greater than the height of any bulk acoustic wave resonator on the first substrate 10a or the second substrate 10b, which can prevent the bulk acoustic wave resonators on the first substrate 10a from contacting the bulk acoustic wave resonators on the second substrate 10b. The distance between the first substrate 10a and the second substrate 10b is less than the sum of the height of any bulk acoustic wave resonator 20 on the surface of the first substrate 10a and the height of any bulk acoustic wave resonator 20 on the surface of the second substrate 10b, which can further reduce the size of the bulk acoustic wave filter in the vertical direction, thereby further reducing the package size of the bulk acoustic wave filter.

[0119] Optionally, it further includes a passivation protection layer. The passivation protection layer is located on the surface side of the second bulk acoustic wave resonator close to the first bulk acoustic wave resonator. The passivation protection layer is located inside the first cavity structure and has a preset distance from the first bulk acoustic wave resonator in the vertical direction.

[0120] Exemplarily, referring to Figure 7 , it further includes a passivation protection layer 70. The passivation protection layer 70 is located on the surface side of the second bulk acoustic wave resonator 20b close to the first bulk acoustic wave resonator 20a. The passivation protection layer 70 is located inside the first cavity structure 30 and has a preset distance from the first bulk acoustic wave resonator 20a in the vertical direction. Exemplarily, the passivation protection layer 70 can be made of materials such as aluminum nitride. During the process of forming the first cavity structure 30 by etching the sacrificial layer in the first receiving groove 40 with an etching solution, it can prevent the etching solution from corroding the second bulk acoustic wave resonator 20b, thereby playing a protective role for the second bulk acoustic wave resonator 20b.

[0121] An embodiment of the present invention further provides a communication device, including the bulk acoustic wave filter described in any of the above technical solutions; the communication device includes at least one of a filter, a duplexer, and a multiplexer.

[0122] Specifically, a duplexer can be simply understood as the operation of two bulk acoustic wave filters. One is a receiving bulk acoustic wave filter to receive signals, and the other is a transmitting bulk acoustic wave filter to transmit signals. A multiplexer can be simply understood as a communication device composed of at least two duplexers.

[0123] The communication device provided by the embodiment of the present invention includes the bulk acoustic wave filter described in any of the above technical solutions, so it has the beneficial effects of the above bulk acoustic wave filter, which will not be elaborated here.

[0124] An embodiment of the present invention further provides a method for manufacturing a bulk acoustic wave filter. Figure 8 is a flowchart of a method for manufacturing a bulk acoustic wave filter provided by an embodiment of the present invention. Referring to Figure 8 , the method for manufacturing the bulk acoustic wave filter includes the following steps:

[0125] S110. Provide a first substrate.

[0126] See Figure 11 , and provide a first substrate 10a. Exemplarily, the first substrate 10a can be made of materials such as single-crystal silicon, gallium arsenide, sapphire, and quartz.

[0127] S120. Form at least two bulk acoustic wave resonators arranged in the vertical direction on the first substrate.

[0128] Exemplarily, see Figure 1 , and form two bulk acoustic wave resonators arranged in the vertical direction on the first substrate 10a. Among them, the bulk acoustic wave resonator 20 includes a first bulk acoustic wave resonator 20a and a second bulk acoustic wave resonator 20b arranged adjacent to each other in the vertical direction; a first cavity structure 30 is provided in the first substrate 10a, and the first cavity structure 30 is located between the first bulk acoustic wave resonator 20a and the first substrate 10a, and the first cavity structure 30 serves as an acoustic reflection structure of the first bulk acoustic wave resonator 20a; the second bulk acoustic wave resonator 20b is located in the first cavity structure 30 and is spaced a preset distance from the first bulk acoustic wave resonator 20a in the vertical direction.

[0129] In this embodiment, the first bulk acoustic wave resonator and the second bulk acoustic wave resonator refer to any two bulk acoustic wave resonators arranged adjacent to each other in the vertical direction among the bulk acoustic wave resonators located on the first substrate. Since the second bulk acoustic wave resonator is located in the first cavity structure serving as the acoustic reflection structure of the first bulk acoustic wave resonator, and the first cavity structure is located in the first substrate, the bulk acoustic wave resonators arranged adjacent to each other in the vertical direction extend towards the space inside the first substrate. And the bulk acoustic wave resonator closer to the surface of the first substrate is called the first bulk acoustic wave resonator, and the other bulk acoustic wave resonator is called the second bulk acoustic wave resonator.

[0130] The bulk acoustic wave filter prepared by the technical solution provided in this embodiment has bulk acoustic wave resonators arranged adjacent to each other in the vertical direction extending into the space within the first substrate. By first forming a sacrificial layer and then releasing the sacrificial layer, a space for placing the bulk acoustic wave resonators within the first substrate is obtained. Specifically, in the first aspect, the bulk acoustic wave resonators included in the bulk acoustic wave filter are arranged in the vertical direction on the first substrate, reducing the size of the bulk acoustic wave filter in the horizontal direction, thereby reducing the package size of the bulk acoustic wave filter. In the second aspect, the bulk acoustic wave resonators arranged adjacent to each other in the vertical direction include a first bulk acoustic wave resonator and a second bulk acoustic wave resonator; the second bulk acoustic wave resonator is located within a first cavity structure that serves as an acoustic reflection structure of the first bulk acoustic wave resonator, that is, the bulk acoustic wave resonators arranged adjacent to each other in the vertical direction extend into the space within the first substrate, reducing the size of the bulk acoustic wave filter in the vertical direction, thereby further reducing the package size of the bulk acoustic wave filter. In the third aspect, the first bulk acoustic wave resonator and the second bulk acoustic wave resonator represent any two bulk acoustic wave resonators arranged adjacent to each other in the vertical direction. Since the second bulk acoustic wave resonator is located within the first cavity structure that serves as an acoustic reflection structure of the first bulk acoustic wave resonator and has a preset distance from the first bulk acoustic wave resonator in the vertical direction, the coupling parasitic effect between the two bulk acoustic wave resonators arranged adjacent to each other in the vertical direction can be avoided, thereby improving the out-of-band rejection of the bulk acoustic wave filter.

[0131] Figure 9 is another method for fabricating a bulk acoustic wave filter according to an embodiment of the present invention. Refer to Figure 9 and the method for fabricating the bulk acoustic wave filter includes the following steps:

[0132] S210. Provide a first substrate.

[0133] Refer to Figure 11 and provide a first substrate 10a. Exemplarily, the first substrate 10a can be made of materials such as single crystal silicon, gallium arsenide, sapphire, and quartz.

[0134] S220. Form a first receiving groove in the first substrate.

[0135] Refer to Figure 12 and form a first receiving groove 40 in the first substrate 10a through a patterning process.

[0136] S230. Form a second bulk acoustic wave resonator in the first receiving groove.

[0137] Refer to Figure 15 and form a second bulk acoustic wave resonator 20b in the first receiving groove 40.

[0138] Refer to Figure 10 and before S230 forms the second bulk acoustic wave resonator in the first receiving groove, it further includes:

[0139] S2301. Form a fifth receiving groove on the bottom surface of the first receiving groove, and the horizontal dimension of the fifth receiving groove is smaller than that of the first receiving groove.

[0140] See Figure 13 , a fifth receiving groove 44 is formed on the bottom surface of the first receiving groove 40 through a patterning process, and the horizontal dimension of the fifth receiving groove 44 is smaller than that of the first receiving groove 40.

[0141] S2302. Form a second sacrificial layer in the fifth receiving groove, and the second sacrificial layer is flush with the bottom surface of the first receiving groove.

[0142] See Figure 14 , a second sacrificial layer 51 is formed on the bottom surface of the fifth receiving groove 44, and the second sacrificial layer 51 is flush with the bottom surface of the first receiving groove 40. The material of the second sacrificial layer 51 containing silicon oxide is, for example, phosphosilicate glass (PSG), and the sacrificial layer can be etched and removed by an etching solution.

[0143] S240. Form a first sacrificial layer on the side of the second bulk acoustic wave resonator facing away from the first substrate, and the first sacrificial layer is flush with the surface of the first substrate.

[0144] See Figure 16 , a first sacrificial layer 50 is formed on the side of the second bulk acoustic wave resonator 20b facing away from the first substrate 10a, and the first sacrificial layer 50 is flush with the surface of the first substrate 10a. The material of the first sacrificial layer 50 containing silicon oxide is, for example, phosphosilicate glass (PSG), and the sacrificial layer can be etched and removed by an etching solution.

[0145] S250. Form a first bulk acoustic wave resonator on the side of the first sacrificial layer facing away from the second bulk acoustic wave resonator.

[0146] See Figure 17 , a first bulk acoustic wave resonator 20a is formed on the side of the first sacrificial layer 50 facing away from the second bulk acoustic wave resonator 20b.

[0147] S260. Release the first sacrificial layer to form a first cavity structure.

[0148] See Figure 1 , the first sacrificial layer 50 can be released through a wet etching process to form a first cavity structure 30, which is used to reflect acoustic waves back to the bulk acoustic wave resonator, reduce the loss of acoustic waves, and thus improve the quality factor of the filter.

[0149] Optionally, when S260 releases the first sacrificial layer to form a first cavity structure, it further includes:

[0150] See Figure 1 Figure 1 , the second sacrificial layer 51 can be released through a wet etching process to form a second cavity structure 31. The second cavity structure 31 serves as an acoustic reflection structure of the second bulk acoustic wave resonator 20b, which is used to reflect acoustic waves back to the bulk acoustic wave resonator, reduce the loss of acoustic waves, and thus improve the quality factor of the filter.

[0151] It should be noted that the bottom electrode 21, piezoelectric layer 22, and top electrode 23 of the bulk acoustic wave resonator 20. The preparation methods of the bottom electrode 21 and the top electrode 23 include: first depositing a thin film electrode, and then forming the bottom electrode 20 or the top electrode 23 with a preset pattern by etching the pattern. Alternatively, first deposit a thin film electrode, and then form the bottom electrode 20 or the top electrode 23 with a preset pattern by the lift-off method. Specifically, forming the bottom electrode 20 or the top electrode 23 with a preset pattern by the lift-off method includes: first lithographing a specific area corresponding to the pattern of the bottom electrode 20 or the top electrode 23, then depositing the thin film electrode over the entire surface, and then stripping off the photoresist and the thin film electrode on it, leaving the thin film electrode in the specific area as the bottom electrode 20 or the top electrode 23. Exemplarily, the bottom electrode 21 and / or the top electrode 23 can be selected from at least one of molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, and titanium with good conductivity. The piezoelectric layer 22 can be selected from at least one of single-crystal piezoelectric thin film materials such as aluminum nitride, zinc oxide, lead zirconate titanate piezoelectric ceramics, lithium niobate, lithium tantalate, potassium niobate, and polycrystalline piezoelectric thin film materials. A certain proportion of rare earth elements can also be doped in the piezoelectric layer 22 to improve the performance of the piezoelectric material layer.

[0152] Based on the above technical solutions, see Figure 18 Figure 18 , S240. Form a first sacrificial layer on the side of the second bulk acoustic wave resonator facing away from the first substrate. The first sacrificial layer is flush with the surface of the first substrate, including:

[0153] S2401. Form a passivation protection layer on the side of the second bulk acoustic wave resonator facing away from the first substrate.

[0154] See Figure 19 Figure 19 , a passivation protection layer 70 is formed on the side of the second bulk acoustic wave resonator 20b facing away from the first substrate 10a.

[0155] S2402. Form a first sacrificial layer on the side of the passivation protection layer facing away from the second bulk acoustic wave resonator. The first sacrificial layer is flush with the surface of the first substrate.

[0156] See Figure 20 Figure 20 , a first sacrificial layer 50 is formed on the side of the passivation protection layer 70 facing away from the second bulk acoustic wave resonator 20b. The first sacrificial layer 50 is flush with the surface of the first substrate 10a.

[0157] Based on the above technical solution, after forming the second bulk acoustic wave resonator 20b in the first receiving groove 40 through S210 - S230, continue to execute Figure 18 the step of S240 in Figure 21 , and form the first bulk acoustic wave resonator 20a on the side of the first sacrificial layer 50 facing away from the second bulk acoustic wave resonator 20b. Then, the first sacrificial layer 50 can be released through a wet etching process to form the first cavity structure 30, and the second sacrificial layer 51 can be released through a wet etching process to form the second cavity structure 31, and finally obtain Figure 7 the bulk acoustic wave filter shown. The passivation protection layer 70 can be made of materials such as aluminum nitride, and can avoid the etching solution from etching the second bulk acoustic wave resonator 20b during the process of the etching solution etching the first sacrificial layer 50 to form the first cavity structure 30, thereby playing a protective role for the second bulk acoustic wave resonator 20b.

[0158] It should be understood that various forms of the processes shown above can be used, re - ordering, adding or deleting steps. For example, the steps described in the present invention can be executed in parallel, sequentially, or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this is not limited herein.

[0159] The above - mentioned specific implementation manners do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub - combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A bulk acoustic wave filter, characterized in that, Comprising: A first substrate; At least two bulk acoustic wave resonators disposed along the vertical direction on the first substrate, the bulk acoustic wave resonator including a stacked structure of a bottom electrode, a piezoelectric layer, and a top electrode; The vertically adjacent bulk acoustic wave resonators include a first bulk acoustic wave resonator and a second bulk acoustic wave resonator; A first cavity structure is disposed in the first substrate, the first cavity structure is located between the first bulk acoustic wave resonator and the first substrate, and the first cavity structure serves as an acoustic reflection structure for the first bulk acoustic wave resonator; The second bulk acoustic wave resonator is located in the first cavity structure and is spaced a preset distance from the first bulk acoustic wave resonator in the vertical direction; The first substrate is provided with a second receiving groove, and part or all of the first bulk acoustic wave resonator is located in the second receiving groove; The first substrate is further provided with a third receiving groove, the second bulk acoustic wave resonator is located in the third receiving groove, the third receiving groove is located on the bottom surface of the second receiving groove, and the horizontal dimension of the third receiving groove is smaller than the horizontal dimension of the second receiving groove; The third receiving groove serves as the first cavity structure; The bulk acoustic wave filter includes a larger number of bulk acoustic wave resonators, and other bulk acoustic wave resonators extend into the space inside the first substrate instead of being vertically arranged only in the space above the surface of the first substrate.

2. The bulk acoustic wave filter according to claim 1, wherein The first bulk acoustic wave resonator is located on the surface of the first substrate; The first substrate is provided with a first receiving groove, the second bulk acoustic wave resonator is located in the first receiving groove, and the first receiving groove serves as the first cavity structure.

3. The bulk acoustic wave filter according to claim 1 or 2, characterized in that, The first substrate is further provided with a second cavity structure, the second cavity structure is located between the first substrate and the second bulk acoustic wave resonator, and the second cavity structure serves as an acoustic reflection structure for the second bulk acoustic wave resonator.

4. The bulk acoustic wave filter according to claim 3, wherein The three vertically adjacent bulk acoustic wave resonators include the first bulk acoustic wave resonator, the second bulk acoustic wave resonator, and a third bulk acoustic wave resonator. The third bulk acoustic wave resonator and the second bulk acoustic wave resonator are vertically adjacent, the third bulk acoustic wave resonator is located in the second cavity structure, and the third bulk acoustic wave resonator is spaced a preset distance from the second bulk acoustic wave resonator in the vertical direction.

5. The bulk acoustic wave filter according to claim 4, characterized in that, The first substrate is provided with a fourth receiving groove, the third bulk acoustic wave resonator is located in the fourth receiving groove, the fourth receiving groove is located on the bottom surface of the receiving groove where the second bulk acoustic wave resonator is placed, and the horizontal dimension of the fourth receiving groove is smaller than the horizontal dimension of the receiving groove where the second bulk acoustic wave resonator is placed. The fourth receiving groove serves as the second cavity structure.

6. The bulk acoustic wave filter according to claim 4, wherein The first substrate is further provided with a third cavity structure, the third cavity structure is located between the first substrate and the third bulk acoustic wave resonator.

7. The bulk acoustic wave filter according to claim 1, characterized in that, The horizontal dimension of the second bulk acoustic wave resonator is smaller than the horizontal dimension of the first bulk acoustic wave resonator.

8. The bulk acoustic wave filter according to claim 1, wherein It further includes a second substrate stacked with the first substrate in the vertical direction, and at least one bulk acoustic wave resonator is disposed on a side of the second substrate close to the first substrate.

9. The bulk acoustic wave filter according to claim 8, wherein, At least two bulk acoustic wave resonators are disposed on a side of the second substrate close to the first substrate and are arranged in the vertical direction; The vertically adjacent bulk acoustic wave resonators include a fourth bulk acoustic wave resonator and a fifth bulk acoustic wave resonator; A fourth cavity structure is disposed in the second substrate, the fourth cavity structure is located between the fourth bulk acoustic wave resonator and the second substrate, and the fourth cavity structure serves as an acoustic reflection structure of the fourth bulk acoustic wave resonator; The fifth bulk acoustic wave resonator is located in the fourth cavity structure and is spaced apart from the fourth bulk acoustic wave resonator by a preset distance in the vertical direction.

10. The bulk acoustic wave filter according to claim 8, characterized in that, The orthographic projections of the bulk acoustic wave resonators located on the first substrate and the second substrate in the horizontal plane do not overlap.

11. The bulk acoustic wave filter according to claim 8, wherein, The orthographic projections of the electrodes of the bulk acoustic wave resonator on the surface of the first substrate and the electrodes of the bulk acoustic wave resonator on the surface of the second substrate in the vertical plane do not overlap, and the electrodes include at least one of a bottom electrode and a top electrode.

12. The bulk acoustic wave filter according to claim 8, characterized in that, The orthographic projections of the piezoelectric layer of the bulk acoustic wave resonator on the surface of the first substrate and the top electrode of the bulk acoustic wave resonator on the surface of the second substrate in the vertical plane overlap; The orthographic projections of the top electrode of the bulk acoustic wave resonator on the surface of the first substrate and the piezoelectric layer of the bulk acoustic wave resonator on the surface of the second substrate in the vertical plane overlap; The orthographic projections of the top electrodes of the bulk acoustic wave resonators on the surfaces of the first substrate and the second substrate in the vertical plane do not overlap; The orthographic projections of the bottom electrode of the bulk acoustic wave resonator on the surface of the first substrate and the bottom electrode and the top electrode of the bulk acoustic wave resonator on the surface of the second substrate in the vertical plane do not overlap.

13. The bulk acoustic wave filter according to claim 8, wherein, The distance between the first substrate and the second substrate is greater than the height of any one bulk acoustic wave resonator on the substrate surface, and the distance between the first substrate and the second substrate is less than the sum of the height of any one bulk acoustic wave resonator on the first substrate surface and the height of any one bulk acoustic wave resonator on the second substrate surface.

14. The bulk acoustic wave filter according to claim 1, wherein It further includes a passivation protection layer, the passivation protection layer is located on the surface side of the second bulk acoustic wave resonator close to the first bulk acoustic wave resonator, the passivation protection layer is located in the first cavity structure and is spaced apart from the first bulk acoustic wave resonator by a preset distance in the vertical direction.

15. A communication device, characterized in that, It includes the bulk acoustic wave filter according to any one of claims 1-14; The communication device includes at least one of a filter, a duplexer, and a multiplexer.

16. A method for preparing a bulk acoustic wave filter, characterized in that, It includes: Providing a first substrate; Forming at least two bulk acoustic wave resonators arranged in the vertical direction on the first substrate; Wherein, the bulk acoustic wave resonator includes a stacked structure of a bottom electrode, a piezoelectric layer, and a top electrode; The vertically adjacent bulk acoustic wave resonators include a first bulk acoustic wave resonator and a second bulk acoustic wave resonator; A first cavity structure is provided within the first substrate, and the first cavity structure is located between the first bulk acoustic wave resonator and the first substrate. The first cavity structure serves as an acoustic reflection structure for the first bulk acoustic wave resonator. The second bulk acoustic wave resonator is located within the first cavity structure and is spaced apart from the first bulk acoustic wave resonator by a preset distance in the vertical direction.

17. The method for manufacturing a bulk acoustic wave filter according to claim 16, wherein forming at least two bulk acoustic wave resonators arranged vertically on the first substrate includes: forming a first receiving groove in the first substrate; forming a second bulk acoustic wave resonator in the first receiving groove; forming a first sacrificial layer on a side of the second bulk acoustic wave resonator facing away from the first substrate, the first sacrificial layer being flush with the surface of the first substrate; forming the first bulk acoustic wave resonator on a side of the first sacrificial layer facing away from the second bulk acoustic wave resonator; releasing the first sacrificial layer to form the first cavity structure; the first substrate is provided with a second receiving groove, and part or all of the first bulk acoustic wave resonator is located within the second receiving groove; the first substrate is further provided with a third receiving groove, the second bulk acoustic wave resonator is located within the third receiving groove, the third receiving groove is located at the bottom surface of the second receiving groove, and the horizontal dimension of the third receiving groove is smaller than the horizontal dimension of the second receiving groove; the third receiving groove serves as the first cavity structure; The bulk acoustic wave filter includes a greater number of bulk acoustic wave resonators, and other bulk acoustic wave resonators extend into the space inside the first substrate instead of being vertically arranged only in the space above the surface of the first substrate.

18. The method for manufacturing a bulk acoustic wave filter according to claim 17, wherein before forming the second bulk acoustic wave resonator in the first receiving groove, further includes: forming a fifth receiving groove on the bottom surface of the first receiving groove, the horizontal dimension of the fifth receiving groove being smaller than the horizontal dimension of the first receiving groove; forming a second sacrificial layer on the bottom surface of the fifth receiving groove, the second sacrificial layer being flush with the bottom surface of the first receiving groove; when releasing the first sacrificial layer to form the first cavity structure, further includes: releasing the second sacrificial layer to form a second cavity structure, the second cavity structure serving as an acoustic reflection structure for the second bulk acoustic wave resonator.

19. The method for manufacturing a bulk acoustic wave filter according to claim 17, wherein forming a first sacrificial layer on a side of the second bulk acoustic wave resonator facing away from the first substrate, the first sacrificial layer being flush with the surface of the first substrate includes: forming a passivation protection layer on a side of the second bulk acoustic wave resonator facing away from the first substrate; forming a first sacrificial layer on a side of the passivation protection layer facing away from the second bulk acoustic wave resonator, the first sacrificial layer being flush with the surface of the first substrate.

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