Bulk acoustic wave resonator, bulk acoustic wave filter, and communication device

Abstract

The application discloses a bulk acoustic wave resonator, a bulk acoustic wave filter and a communication device, the bulk acoustic wave resonator comprising a vertical stack structure of an inner electrode, a piezoelectric layer and an outer electrode; the vertical stack structure of the inner electrode, the piezoelectric layer and the outer electrode is in a closed ring distribution or a semi-closed ring distribution; the inner electrode, the piezoelectric layer and the outer electrode are arranged on the surface of a substrate, and the stacking direction of the inner electrode, the piezoelectric layer and the outer electrode is perpendicular to the thickness direction of the substrate. The technical scheme provided by the embodiment of the application reduces the horizontal packaging size of the bulk acoustic wave resonator, the bulk acoustic wave filter and the communication device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to a bulk acoustic wave resonator, a bulk acoustic wave filter and a communication device. BACKGROUND

[0002] The bulk acoustic wave resonator has the characteristics of small size, high operating frequency, low power consumption, high quality factor and compatibility with CMOS process, and has become an important device in the field of communication devices and is widely used. A plurality of bulk acoustic wave resonators in series and parallel connection can constitute a bulk acoustic wave filter.

[0003] Figure 1 It is a top view of a bulk acoustic wave filter in the prior art. Figure 2 It is Figure 1 It is a cross-sectional view in A1-A2 direction. Referring to Figure 1 , the existing bulk acoustic wave filter includes a substrate 100, and a first surface 100a of the substrate 100 is provided with a bulk acoustic wave resonator 200a, a bulk acoustic wave resonator 200b, a bulk acoustic wave resonator 200c, a bulk acoustic wave resonator 200d, a bulk acoustic wave resonator 200e, a bulk acoustic wave resonator 200f, a bulk acoustic wave resonator 200g and a bulk acoustic wave resonator 200h. Referring to Figure 2 , the bulk acoustic wave resonator, for example, the bulk acoustic wave resonator 200a, includes a bottom electrode 201, a piezoelectric layer 202 and a top electrode 203. The bottom electrode 201, the piezoelectric layer 202 and the top electrode 203 are tiled on the first surface 100a of the substrate 100. For example, the horizontal cross section of the bulk acoustic wave resonator is a polygon, and the sum of the areas of the horizontal cross sections of the bulk acoustic wave resonators needs to be less than the area of the first surface 100a of the substrate 100, so if a large number of bulk acoustic wave resonators need to be placed on the first surface 100a of the substrate 100, the area of the substrate 100 needs to be increased, which in turn leads to a large increase in the horizontal packaging size of the bulk acoustic wave resonator, the bulk acoustic wave filter and the communication device. And the cavity structure 001 built-in in the substrate 100 leads to poor structural stability of the bulk acoustic wave filter. It should be noted that the plane direction of the first surface 100a of the substrate 100 is the horizontal direction. SUMMARY

[0004] Therefore, the embodiments of the present application provide a bulk acoustic wave resonator, a bulk acoustic wave filter and a communication device to reduce the horizontal packaging size of the bulk acoustic wave resonator, the bulk acoustic wave filter and the communication device.

[0005] The embodiments of the present application provide a bulk acoustic wave resonator, which comprises a vertical stack structure of an inner electrode, a piezoelectric layer and an outer electrode.

[0006] The vertical stack structure of the inner electrode, the piezoelectric layer and the outer electrode is in a closed ring distribution or a semi-closed ring distribution.

[0007] The inner electrode, piezoelectric layer and outer electrode are arranged on a surface of a substrate, and a stacking direction of the inner electrode, piezoelectric layer and outer electrode is perpendicular to a thickness direction of the substrate.

[0008] Optionally, further comprising an air-bridge microstructure.

[0009] The air-bridge microstructure is located between the inner electrode, the piezoelectric layer and the substrate, and / or the air-bridge microstructure is located between the outer electrode, the piezoelectric layer and the substrate.

[0010] Optionally, the inner electrode comprises a stack of a first sub-electrode and a second sub-electrode.

[0011] The stacking direction of the first sub-electrode and the second sub-electrode is perpendicular to the thickness direction of the substrate.

[0012] A first air-penetrating microstructure is arranged between the first sub-electrode and the second sub-electrode, the first air-penetrating microstructure penetrates through two oppositely arranged surfaces of the inner electrode, and a penetrating direction of the first air-penetrating microstructure is a surrounding direction of the vertical stack structure of the inner electrode, piezoelectric layer and outer electrode.

[0013] Optionally, the outer electrode comprises a stack of a third sub-electrode and a fourth sub-electrode.

[0014] The stacking direction of the third sub-electrode and the fourth sub-electrode is perpendicular to the thickness direction of the substrate.

[0015] A second air-penetrating microstructure is arranged between the first sub-electrode and the second sub-electrode, the second air-penetrating microstructure penetrates through two oppositely arranged surfaces of the outer electrode, and a penetrating direction of the second air-penetrating microstructure is a surrounding direction of the vertical stack structure of the inner electrode, piezoelectric layer and outer electrode.

[0016] Optionally, further comprising a temperature compensation layer, the temperature compensation layer comprising a positive frequency drift coefficient material.

[0017] Optionally, the temperature compensation layer is located at least one of within the piezoelectric layer, a surface of the piezoelectric layer adjacent to the inner electrode, a surface of the piezoelectric layer adjacent to the outer electrode, within the inner electrode, a surface of the inner electrode facing away from the piezoelectric layer, within the outer electrode, and a surface of the outer electrode facing away from the piezoelectric layer.

[0018] Optionally, a horizontal cross-sectional shape of the bulk acoustic wave resonator comprises at least one of a polygonal ring shape, a circular ring shape, and an elliptical ring shape.

[0019] The embodiment of the present application also provides a bulk acoustic wave filter, at least one substrate, the substrate comprising a first surface and a second surface arranged opposite to the first surface, characterized in that the first surface of the substrate is provided with at least one bulk acoustic wave resonator as described in any of the above technical solutions.

[0020] Optionally, the substrate comprises adjacent first and second substrates.

[0021] The first surface of the first substrate is provided with at least one bulk acoustic wave resonator, and the second surface of the second substrate is provided with at least one bulk acoustic wave resonator.

[0022] The bulk acoustic wave resonators between the first and second substrates are distributed in an interdigital manner.

[0023] Optionally, the bulk acoustic wave resonators of the outer layer are arranged around the bulk acoustic wave resonators of the inner layer.

[0024] Optionally, the sound reflection structure is arranged between the two adjacent bulk acoustic wave resonators.

[0025] And / or, the sound reflection structure is arranged in the space around the innermost bulk acoustic wave resonator.

[0026] Optionally, the sound reflection structure comprises a cavity or a Bragg reflection layer.

[0027] Optionally, the conductive connection structure is further provided.

[0028] The conductive connection structure is used to lead the electrical signal of the bulk acoustic wave resonator to the first surface side of the uppermost substrate, and / or the conductive connection structure is used to lead the electrical signal of the bulk acoustic wave resonator out to the second surface side of the lowermost substrate.

[0029] Optionally, a cap wafer is further provided, and the cap wafer is located on the first surface side of the uppermost substrate.

[0030] The conductive connection structure is used to lead the electrical signal of the bulk acoustic wave resonator to the surface of the cap wafer away from the uppermost substrate.

[0031] Optionally, the first surface of the first substrate is provided with a first bulk acoustic wave resonator, a second bulk acoustic wave resonator and a third bulk acoustic wave resonator.

[0032] The second bulk acoustic wave resonator is arranged around the first bulk acoustic wave resonator, and the third bulk acoustic wave resonator is arranged around the second bulk acoustic wave resonator.

[0033] Optionally, the second surface of the second substrate is provided with a fourth bulk acoustic wave resonator, a fifth bulk acoustic wave resonator and a sixth bulk acoustic wave resonator.

[0034] The fifth bulk acoustic resonator is arranged around the fourth bulk acoustic resonator, and the sixth bulk acoustic resonator is arranged around the fifth bulk acoustic resonator.

[0035] The fourth bulk acoustic resonator is located in the first bulk acoustic resonator.

[0036] The fifth bulk acoustic resonator is located in the annular interval space of the first bulk acoustic resonator and the second bulk acoustic resonator.

[0037] The sixth bulk acoustic resonator is located in the annular interval space of the second bulk acoustic resonator and the third bulk acoustic resonator.

[0038] Optionally, in the thickness direction parallel to the substrate, the spacing between adjacent substrates is less than the sum of the heights of the bulk acoustic resonators distributed in an interdigital manner between the adjacent substrates.

[0039] Optionally, in the horizontal direction, the two bulk acoustic resonators distributed in an interdigital manner are spaced apart by a preset spacing.

[0040] The embodiment of the present application also provides a communication device, characterized in that the communication device comprises the bulk acoustic wave filter according to any of the above technical solutions.

[0041] The communication device comprises at least one of a filter, a duplexer and a multiplexer.

[0042] In the technical solution provided by the embodiment of the present application, in a first aspect, the bulk acoustic resonator comprises a vertical laminated structure of an inner electrode, a piezoelectric layer and an outer electrode, which reduces the size of the bulk acoustic resonator in the horizontal direction compared with the planar layout mode of the bulk acoustic resonator. In a second aspect, the gap inside the bulk acoustic resonator can reflect the longitudinal wave in the acoustic wave back to the bulk acoustic resonator, thereby reducing the loss of the acoustic wave and improving the quality factor of the bulk acoustic resonator. In a third aspect, the embodiment of the present application can not need to set the acoustic reflection structure by the groove mode on the substrate, which simplifies the preparation process, reduces the preparation cost and improves the structural stability of the bulk acoustic resonator. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 It is a top view of a bulk acoustic wave filter in the prior art;

[0044] Figure 2 It is a sectional view in A1-A2 direction in the prior art; Figure 1

[0045] Figure 3 It is a top view of a bulk acoustic resonator provided by the embodiment of the present application;

[0046] Figure 4 It is a top view of a bulk acoustic resonator provided by the embodiment of the present application;​Figure 3 A cross-sectional view in the direction of A1-A2;

[0047] Figure 5 A cross-sectional view in the direction of A1-A2; Figure 3 A cross-sectional view in the direction of A1-A2;

[0048] Figure 6 A cross-sectional view in the direction of A1-A2; Figure 3 A cross-sectional view in the direction of A1-A2;

[0049] Figure 7 A top view of another bulk acoustic wave resonator provided by an embodiment of the present application;

[0050] Figure 8 A cross-sectional view in the direction of A1-A2; Figure 7 A cross-sectional view in the direction of A1-A2;

[0051] Figure 9 A top view of a substrate of a bulk acoustic wave filter provided by an embodiment of the present application;

[0052] Figure 10 A top view of another substrate of a bulk acoustic wave filter provided by an embodiment of the present application;

[0053] Figure 11 A cross-sectional view in the direction of A1-A2; Figure 9 A cross-sectional view in the direction of A1-A2; Figure 10 A cross-sectional view in the direction of A1-A2;

[0054] Figure 12 A cross-sectional view in the direction of A1-A2; Figure 9 A cross-sectional view in the direction of A1-A2; Figure 10 A cross-sectional view in the direction of A1-A2;

[0055] Figure 13 A cross-sectional view in the direction of A1-A2; Figure 9 A cross-sectional view in the direction of A1-A2; Figure 10 A cross-sectional view in the direction of A1-A2;

[0056] Figure 14 A top view of another bulk acoustic wave filter provided by an embodiment of the present application;

[0057] Figure 15 A cross-sectional view in the direction of A1-A2; Figure 14 A cross-sectional view in the direction of A1-A2;

[0058] Figure 16 A top view of a substrate of another bulk acoustic wave filter provided by an embodiment of the present application;

[0059] Figure 17 A top view of another substrate of another bulk acoustic wave filter provided by an embodiment of the present application;

[0060] Figure 18 for Figure 16 and Figure 17 A top view of the constructed bulk acoustic wave filter excluding the topmost substrate;

[0061] Figure 19 for Figure 18 Cross-sectional view along the B1-B2 direction;

[0062] Figure 20 for Figure 18 Cross-sectional view along the C1-C2 direction;

[0063] Figure 21 for Figure 9 The equivalent circuit connection diagram of a bulk acoustic resonator;

[0064] Figure 22 for Figure 18 The equivalent circuit connection diagram of the bulk acoustic wave filter. Detailed Implementation

[0065] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0066] As described in the background section, existing bulk acoustic wave (BAW) resonators employ a planar layout, with the BAW resonator, consisting of a bottom electrode 201, a piezoelectric layer 202, and a top electrode 203, laid flat on the first surface 100a of the substrate 100. This planar layout requires a large number of BAW resonators to be placed on the first surface 100a of the substrate 100, necessitating an increase in the area of ​​the substrate 100. This significantly increases the horizontal package size of the BAW resonators, BAW filters, and communication devices. Furthermore, the cavity structure 001 embedded in the substrate 100 results in relatively poor structural stability of the BAW filter. It should be noted that the plane of the first surface 100a of the substrate 100 is horizontal. To address the above technical problems, this invention provides the following technical solution:

[0067] This invention provides a bulk acoustic wave resonator. The bulk acoustic wave resonator includes a vertical stacked structure of an inner electrode, a piezoelectric layer, and an outer electrode; the vertical stacked structure of the inner electrode, piezoelectric layer, and outer electrode is arranged in a closed ring or a semi-closed ring; the inner electrode, piezoelectric layer, and outer electrode are disposed on the surface of a substrate, and the stacking direction of the inner electrode, piezoelectric layer, and outer electrode is perpendicular to the thickness direction of the substrate.

[0068] For example, Figure 3 and Figure 4A bulk acoustic resonator 300 is shown disposed on the first surface 100a of the substrate 100. The bulk acoustic resonator 300 includes a vertical stack structure of an inner electrode 301, a piezoelectric layer 302 and an outer electrode 303. The vertical stack structure of the inner electrode 301, the piezoelectric layer 302 and the outer electrode 303 is in a closed loop distribution. It should be noted that the bulk acoustic resonator can be in a closed loop distribution or a semi-closed loop distribution according to the preset size of the bulk acoustic resonator 300. The stacking direction of the inner electrode 301, the piezoelectric layer 302 and the outer electrode 303 is perpendicular to the thickness direction of the substrate 100. In the embodiment of the application, the thickness direction of the substrate 100 is parallel to the Y direction. The gap 400 inside the bulk acoustic resonator 300 can reflect the longitudinal wave in the acoustic wave back to the bulk acoustic resonator 300.

[0069] In the technical scheme provided by the embodiment of the application, in a first aspect, the bulk acoustic resonator includes a vertical stack structure of an inner electrode, a piezoelectric layer and an outer electrode, which reduces the size of the bulk acoustic resonator in the horizontal direction compared with the planar layout of the bulk acoustic resonator. In a second aspect, the gap inside the bulk acoustic resonator can reflect the longitudinal wave in the acoustic wave back to the bulk acoustic resonator, thereby reducing the loss of the acoustic wave and improving the quality factor of the bulk acoustic resonator. In a third aspect, the embodiment of the application can not use the groove method to dispose the acoustic reflection structure on the substrate, which simplifies the preparation process, reduces the preparation cost and improves the structural stability of the bulk acoustic resonator.

[0070] Optionally, the air bridge microstructure is further included; the air bridge microstructure is located between the inner electrode, the piezoelectric layer and the substrate, and / or the air bridge microstructure is located between the outer electrode, the piezoelectric layer and the substrate.

[0071] For example, referring to Figure 5 The bulk acoustic resonator further includes an air bridge microstructure 002 and an air bridge microstructure 003; the air bridge microstructure 002 is located between the inner electrode 301, the piezoelectric layer 302 and the substrate 100. The air bridge microstructure 003 is located between the outer electrode 303, the piezoelectric layer 302 and the substrate 100.

[0072] Specifically, the air bridge microstructure as the acoustic reflection structure can reflect the acoustic wave back to the bulk acoustic resonator, which can effectively prevent the lateral leakage of the acoustic wave and thereby improve the quality factor of the bulk acoustic resonator.

[0073] Optionally, referring to Figure 6The inner electrode 301 comprises a stack of a first sub-electrode 301a and a second sub-electrode 301b; the stacking direction of the first sub-electrode 301a and the second sub-electrode 301b is perpendicular to the thickness direction of the substrate 100; a first air through microstructure 301c is arranged between the first sub-electrode 301a and the second sub-electrode 301b, the first air through microstructure 301c penetrates through two opposite surfaces of the inner electrode 301, and the penetration direction of the first air through microstructure 301c is the surrounding direction of the vertical stack structure of the inner electrode 301, the piezoelectric layer 302 and the outer electrode 303.

[0074] Optionally, referring to Figure 6 The outer electrode 303 comprises a stack of a third sub-electrode 303a and a fourth sub-electrode 303b; the stacking direction of the third sub-electrode 303a and the fourth sub-electrode 303b is perpendicular to the thickness direction of the substrate 100; a second air through microstructure 303c is arranged between the third sub-electrode 303a and the fourth sub-electrode 303b, the second air through microstructure 303c penetrates through two opposite surfaces of the outer electrode 303, and the penetration direction of the second air through microstructure 303c is the surrounding direction of the vertical stack structure of the inner electrode 301, the piezoelectric layer 302 and the outer electrode 303.

[0075] Optionally, the temperature compensation layer comprises a positive frequency drift coefficient material.

[0076] Optionally, referring to Figure 7 and Figure 8 The bulk acoustic wave resonator further comprises a temperature compensation layer 304, and the temperature compensation layer 304 comprises a positive frequency drift coefficient material.

[0077] Optionally, the temperature compensation layer 304 is located at least one of the following positions: in the piezoelectric layer 302, on a surface of the piezoelectric layer 302 adjacent to the inner electrode 301, on a surface of the piezoelectric layer 302 adjacent to the outer electrode 303, in the inner electrode 301, on a surface of the inner electrode 301 away from the piezoelectric layer 302, in the outer electrode 303, and on a surface of the outer electrode 303 away from the piezoelectric layer 302. Figure 7 and Figure 8 In the temperature compensation layer 304 is located on a surface of the outer electrode 303 away from the piezoelectric layer 302.

[0078] Specifically, the temperature compensation layer 304 comprises a positive frequency drift coefficient material, which can compensate for changes in electrical and mechanical properties of the bulk acoustic wave resonator 300 caused by temperature changes, thereby improving the temperature stability of the bulk acoustic wave resonator. For example, the temperature compensation layer 304 can be made of a positive frequency drift coefficient material such as silicon dioxide. It should be noted that the number of temperature compensation layers 304 and the positions of the temperature compensation layers 304 in the bulk acoustic wave resonator can be determined according to actual conditions.

[0079] Optionally, the horizontal cross-sectional shape of the bulk acoustic wave resonator comprises at least one of a polygonal ring shape, a circular ring shape, and an elliptical ring shape.

[0080] Exemplarily, Figure 3 and Figure 7 The case where the horizontal cross-sectional shape of the bulk acoustic wave resonator 300 comprises a rectangle is shown in FIG. 3. The horizontal cross-sectional shape of the bulk acoustic wave resonator can be selected according to the area and shape of the first surface 100a of the substrate 100.

[0081] The embodiment of the present application further provides a bulk acoustic wave filter, at least one substrate, the substrate comprising a first surface and a second surface arranged opposite to the first surface, and the first surface of the substrate is provided with at least one bulk acoustic wave resonator as described above.

[0082] Exemplarily, referring to Figures 9-11 , the bulk acoustic wave filter comprises a substrate 100 and a substrate 101, the substrate 100 and the substrate 101 comprise a first surface 100a and a second surface 100b arranged opposite to the first surface 100a, and the first surface 100a of the substrate 100 is provided with a bulk acoustic wave resonator 300a, a bulk acoustic wave resonator 300b and a bulk acoustic wave resonator 300c. The first surface 100a of the substrate 101 is provided with a bulk acoustic wave resonator 300d, a bulk acoustic wave resonator 300e and a bulk acoustic wave resonator 300f. Optionally, when the number of substrates is at least two, a bonding structure can be provided for sealingly connecting different substrates.

[0083] In the technical scheme provided by the embodiment of the present application, in the first aspect, the bulk acoustic wave resonator comprises a vertical stacked structure of an inner electrode, a piezoelectric layer and an outer electrode, compared with a planar layout mode of the inner electrode, the piezoelectric layer and the outer electrode, the size of the bulk acoustic wave resonator in the horizontal direction is reduced. And the bulk acoustic wave filter comprises at least one bulk acoustic wave resonator as described above, thereby reducing the size of the bulk acoustic wave filter in the horizontal direction. In the second aspect, the space between the bulk acoustic wave resonators and inside the bulk acoustic wave resonators can reflect the longitudinal wave in the acoustic wave back to the bulk acoustic wave resonator, thereby reducing the loss of the acoustic wave and improving the quality factor of the bulk acoustic wave filter. In the third aspect, in the embodiment of the present application, the acoustic reflection structure is not arranged on the substrate by the groove method, the preparation process is simplified, the preparation cost is reduced, and the structural stability of the bulk acoustic wave filter is improved.

[0084] Optionally, the bulk acoustic wave resonator of the outer layer is arranged around the bulk acoustic wave resonator of the inner layer. Exemplarily, referring to Figure 9 , among the bulk acoustic wave resonator 300a, the bulk acoustic wave resonator 300b and the bulk acoustic wave resonator 300c arranged on the first surface 100a of the substrate 100, the bulk acoustic wave resonator 300a is arranged around the bulk acoustic wave resonator 300b, and the bulk acoustic wave resonator 300b is arranged around the bulk acoustic wave resonator 300c.

[0085] Specifically, when the substrate surface comprises at least two bulk acoustic resonators, the bulk acoustic resonators of the outer layer are arranged around the bulk acoustic resonators of the inner layer, further reducing the size of the bulk acoustic wave filter in the horizontal direction.

[0086] Optionally, a sound reflection structure is arranged between the two adjacent bulk acoustic resonators; and / or, a sound reflection structure is arranged in the surrounding space of the innermost bulk acoustic resonator. Optionally, the sound reflection structure comprises a cavity or a Bragg reflection layer.

[0087] Exemplarily, Figures 9-11 The technical solution in which the sound reflection structure comprises a cavity structure is shown in FIG. 3. Specifically, a cavity structure 401 is arranged between the bulk acoustic resonator 300a and the bulk acoustic resonator 300b. A cavity structure 402 is arranged between the bulk acoustic resonator 300b and the innermost bulk acoustic resonator 300c. A cavity structure 403 is arranged in the surrounding space of the innermost bulk acoustic resonator 300c. A cavity structure 404 is arranged between the bulk acoustic resonator 300d and the bulk acoustic resonator 300e. A cavity structure 405 is arranged between the bulk acoustic resonator 300e and the innermost bulk acoustic resonator 300f. A cavity structure 406 is arranged in the surrounding space of the innermost bulk acoustic resonator 300f. It should be noted that when the gap between the two adjacent bulk acoustic resonators and the internal gap are not filled with a filling material, the gap between the two adjacent bulk acoustic resonators and the internal gap are referred to as a cavity structure.

[0088] Exemplarily, referring to Figure 14 and Figure 15 The bulk acoustic resonator 300a and the bulk acoustic resonator 300b are arranged adjacent to each other, and a Bragg reflection layer 404 is arranged between the bulk acoustic resonator 300a and the bulk acoustic resonator 300b. A Bragg reflection layer 405 is arranged between the bulk acoustic resonator 300b and the innermost bulk acoustic resonator 300c. A Bragg reflection layer 406 is arranged in the surrounding space of the innermost bulk acoustic resonator 300c.

[0089] Specifically, the sound reflection structure is located in the gap between the two adjacent bulk acoustic resonators or in the surrounding space of the innermost bulk acoustic resonator, which can reflect the longitudinal wave in the sound wave back to the bulk acoustic resonator, thereby reducing the loss of the sound wave and improving the quality factor of the bulk acoustic wave filter. Moreover, the cavity structure or the Bragg reflection layer as the sound reflection structure does not need to be arranged by the groove method on the substrate, which simplifies the preparation process, reduces the preparation cost, and improves the structural stability of the bulk acoustic wave filter.

[0090] Optionally, the substrate comprises adjacent first and second substrates; the first surface of the first substrate is provided with at least one bulk acoustic resonator, and the second surface of the second substrate is provided with at least one bulk acoustic resonator; the bulk acoustic resonators between the first and second substrates are distributed in an interdigital manner.

[0091] For example, referring to Figures 16-19 , the first substrate is the substrate 100, the second substrate is the substrate 101, the first surface 100a of the substrate 100 is provided with the bulk acoustic resonator 300a, the bulk acoustic resonator 300b and the bulk acoustic resonator 300c, the second surface 100b of the substrate 101 is provided with the bulk acoustic resonator 300d, the bulk acoustic resonator 300e and the bulk acoustic resonator 300f, and the bulk acoustic resonators between the substrate 100 and the substrate 101 are distributed in an interdigital manner.

[0092] Specifically, when the number of substrates is greater than or equal to two, the bulk acoustic resonators between the adjacent two substrates are distributed in an interdigital manner, which reduces the size of the bulk acoustic wave filter in the direction parallel to the thickness of the substrate, thereby helping to form a miniaturized bulk acoustic wave filter. It should be noted that the thickness direction of the substrate is the vertical direction perpendicular to the horizontal direction.

[0093] Optionally, the conductive connection structure is further included; the conductive connection structure is used to lead the electrical signal of the bulk acoustic resonator to the first surface side of the uppermost substrate, and / or the conductive connection structure is used to lead the electrical signal of the bulk acoustic resonator out to the second surface side of the lowermost substrate.

[0094] For example, referring to Figure 13 , the conductive connection structure 500 is further included; the conductive connection structure 500 comprises a wiring layer 501, a conductive hole 502 and a conductive bonding part 503. The conductive connection structure 500 is used to lead the electrical signal of the bulk acoustic resonator to the first surface 100a side of the uppermost substrate 101, and the conductive connection structure 500 is also used to lead the electrical signal of the bulk acoustic resonator out to the second surface 100b side of the lowermost substrate 100.

[0095] Specifically, the conductive connection structure 500 is used to lead the electrical signal of the bulk acoustic resonator out, so as to facilitate the electrical connection of the compensation circuit composed of at least one of the electrical signal of the bulk acoustic wave filter and the capacitance, inductance, resistance and functional chip.

[0096] Optionally, a cap wafer is further included, and the cap wafer is located on the first surface side of the uppermost substrate; the conductive connection structure is used to lead the electrical signal of the bulk acoustic resonator to the surface of the cap wafer away from the uppermost substrate. Optionally, a bonding structure for connection can be arranged between the cap wafer and the substrate. For example, referring to Figure 13The bulk acoustic wave filter further comprises a cap wafer 600, which is located on the side of the first surface 100a of the uppermost substrate 101. The conductive connection structure 500 can lead the electrical signal of the bulk acoustic wave resonator to the surface of the cap wafer 600, which is away from the uppermost substrate 101. The material of the substrate and the cap wafer 600 can be the same or different.

[0097] Optionally, referring to Figure 13 , the cap wafer 600 is provided with a groove 600a on the surface adjacent to the side of the uppermost substrate 101. For example, Figure 13 The substrate in the middle is 2, the uppermost substrate is 101, and the lowermost substrate is 100. The groove 600a can reflect the acoustic wave back to the bulk acoustic wave resonator on the side of the uppermost substrate 101, so as to improve the quality factor of the bulk acoustic wave filter.

[0098] Optionally, when the bulk acoustic wave resonator is only provided on the first surface of the substrate, the second surface 101b of the substrate 101 above the lowermost substrate such as the substrate 100 can also be provided with a groove for reflecting the acoustic wave, so as to reduce the volume of the bulk acoustic wave filter, and further improve the performance of the bulk acoustic wave filter.

[0099] Optionally, the bulk acoustic wave resonators can be connected in series or in parallel through the conductive connection part. Optionally, the inner electrode or the outer electrode of the outermost bulk acoustic wave resonator is connected with the conductive connection structure through the conductive connection part; the inner electrode of the inner bulk acoustic wave resonator is connected with the conductive connection structure through the conductive connection part, and the outer electrode of the inner bulk acoustic wave resonator is connected with the conductive connection structure through the conductive connection part, so as to realize the connection circuit of the inner bulk acoustic wave resonators connected in parallel and the outermost bulk acoustic wave resonator connected in series.

[0100] For example, referring to Figure 9 and Figure 12 and Figure 16 , Figure 18 and Figure 20 , the inner electrode 301 of the outermost bulk acoustic wave resonator 300a provided on the first surface 100a of the substrate 100 is connected with the conductive connection structure 50 through the conductive connection part 700. The outer electrode 303 of the outermost bulk acoustic wave resonator 300a is connected with the conductive connection structure 500 through the conductive connection part 702. The inner electrodes 301 of the inner bulk acoustic wave resonators 300b and 300c are connected with the conductive connection structure through the conductive connection part 701, and the outer electrodes 303 of the inner bulk acoustic wave resonators 300b and 300c are connected with the conductive connection structure 500 through the conductive connection part 702. For example, Figure 21 and Figure 22The above technical solution can realize the connection circuit of the inner layer bulk acoustic wave resonator 300b and the inner layer bulk acoustic wave resonator 300c connected in parallel and then connected in series with the outermost bulk acoustic wave resonator 300a. It should be noted that the conductive connection structure 500 is not shown in the top view of the bulk acoustic wave filter.

[0101] See Figure 10 and Figure 12 as well as Figure 17 , Figure 18 and Figure 20 The inner electrode 301 of the outermost bulk acoustic wave resonator 300d on the substrate 101 is connected to the conductive bonding portion 503 of the conductive connection structure 500 via a conductive connection portion 700. The outer electrode 303 of the outermost bulk acoustic wave resonator 300d is connected to the conductive bonding portion 503 of the conductive connection structure 500 via a conductive connection portion 702. The inner electrodes 301 of the inner bulk acoustic wave resonators 300e and 300f are connected to the conductive connection structure via conductive connection portions 701, and the outer electrodes 303 of the inner bulk acoustic wave resonators 300e and 300f are connected to the conductive bonding portion 503 of the conductive connection structure 500 via conductive connection portions 702, thereby realizing the connection circuit of the inner bulk acoustic wave resonators connected in parallel and the outermost bulk acoustic wave resonators connected in series. It should be noted that the conductive connection structure 500 is not shown in the top view of the bulk acoustic wave filter.

[0102] For example, see Figure 22 The bulk acoustic wave resonator 300a of substrate 100 and the bulk acoustic wave resonator 300d of substrate 101 are connected in parallel.

[0103] Optional, see Figure 19 A first bulk acoustic wave resonator 300c, a second bulk acoustic wave resonator 300b, and a third bulk acoustic wave resonator 300a are disposed on the first surface 101a of the first substrate 100; the second bulk acoustic wave resonator 300b is disposed around the first bulk acoustic wave resonator 300c, and the third bulk acoustic wave resonator 300a is disposed around the second bulk acoustic wave resonator 300b.

[0104] Optional, see Figure 19The second surface 100b of the second substrate 101 is provided with a fourth bulk acoustic resonator 300f, a fifth bulk acoustic resonator 300e and a sixth bulk acoustic resonator 300d; the fifth bulk acoustic resonator 300e is arranged around the fourth bulk acoustic resonator 300f, and the sixth bulk acoustic resonator 300d is arranged around the fifth bulk acoustic resonator 300e; the fourth bulk acoustic resonator 300f is located in the first bulk acoustic resonator 300c; the fifth bulk acoustic resonator 300e is located in the annular interval space between the first bulk acoustic resonator 300c and the second bulk acoustic resonator 300b; and the sixth bulk acoustic resonator 300d is located in the annular interval space between the second bulk acoustic resonator 300b and the third bulk acoustic resonator 300a.

[0105] In the technical scheme provided by the embodiment of the present application, in the first aspect, the bulk acoustic resonator comprises a vertical stacked structure of an inner electrode 301, a piezoelectric layer 302 and an outer electrode 303, compared with a planar layout mode of the bulk acoustic resonator, the size of the bulk acoustic resonator in the horizontal direction is reduced. And the bulk acoustic filter comprises a first bulk acoustic resonator 300c, a second bulk acoustic resonator 300b and a third bulk acoustic resonator 300a, and a fourth bulk acoustic resonator 300f, a fifth bulk acoustic resonator 300e and a sixth bulk acoustic resonator 300d, thereby reducing the size of the bulk acoustic filter in the horizontal direction. In the second aspect, the intervals between the bulk acoustic resonators and the gaps inside the bulk acoustic resonators can reflect the longitudinal waves in the acoustic waves back to the bulk acoustic resonators, thereby reducing the loss of the acoustic waves and improving the quality factor of the bulk acoustic filter. In the third aspect, in the embodiment of the present application, the acoustic reflection structure is not arranged on the substrate by the groove method, the preparation process is simplified, the preparation cost is reduced, and the effect of improving the structural stability of the bulk acoustic filter is achieved.

[0106] Optionally, in the thickness direction parallel to the substrate, the interval between the adjacent substrates is less than the sum of the heights of the bulk acoustic resonators distributed in an interdigital manner between the adjacent substrates.

[0107] For example, referring to FIG. 1, Figure 19 In the thickness direction parallel to the substrate, the interval L3 between the adjacent substrates 100 and 101 is less than the sum of the height L2 of the bulk acoustic resonator arranged on the substrate 100 and the height L1 of the bulk acoustic resonator arranged on the substrate 101, which reduces the size of the bulk acoustic filter in the thickness direction parallel to the substrate, thereby helping to form a miniaturized bulk acoustic filter. It should be noted that the thickness direction parallel to the substrate is a vertical direction perpendicular to the horizontal direction.

[0108] Optionally, in the horizontal direction, the interval between the two bulk acoustic resonators distributed in an interdigital manner is a preset interval.

[0109] For example, referring to FIG. 1, Figure 19In the horizontal direction, the two body acoustic wave resonators distributed in the interdigital form are spaced apart by a preset interval.

[0110] The embodiment of the present application further provides a communication device, comprising the body acoustic wave filter in any of the above technical solutions.

[0111] Specifically, the duplex can be simply understood as the operation of two body acoustic wave filters, one is a receiving body acoustic wave filter to receive signals, and the other is a transmitting body acoustic wave filter to transmit signals.

[0112] The communication device provided by the embodiment of the present application comprises the body acoustic wave filter in any of the above technical solutions, and thus has the beneficial effects of the body acoustic wave filter, which will not be repeated here.

[0113] Note that the above are only the preferred embodiments of the present application and the technical principles applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that various obvious changes, re-adjustments and substitutions can be made by those skilled in the art without departing from the scope of the present application. Therefore, although the present application has been described in more detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the appended claims.

Claims

1. A bulk acoustic wave filter, at least one substrate, the substrate comprising a first surface and a second surface disposed opposite the first surface, characterized in that, The first surface of the substrate is provided with at least one bulk acoustic resonator; The bulk acoustic resonator comprises a vertical stack structure of an inner electrode, a piezoelectric layer and an outer electrode; The vertical stack structure of the inner electrode, the piezoelectric layer and the outer electrode is in a closed ring distribution or a semi-closed ring distribution; The inner electrode, the piezoelectric layer and the outer electrode are arranged on the surface of the substrate, and the stacking direction of the inner electrode, the piezoelectric layer and the outer electrode is perpendicular to the thickness direction of the substrate; The outer layer bulk acoustic resonator is arranged around the inner layer bulk acoustic resonator; The sound reflection structure is arranged between two adjacent bulk acoustic resonators; And / or, the sound reflection structure is arranged in the surrounding space of the innermost layer bulk acoustic resonator.

2. The bulk acoustic wave filter of claim 1, wherein, Further comprising an air bridge microstructure; The air bridge microstructure is located between the inner electrode, the piezoelectric layer and the substrate, and / or the air bridge microstructure is located between the outer electrode, the piezoelectric layer and the substrate.

3. The bulk acoustic wave filter of claim 1, wherein, The inner electrode comprises a stack of a first sub-electrode and a second sub-electrode; The stacking direction of the first sub-electrode and the second sub-electrode is perpendicular to the thickness direction of the substrate; A first air through microstructure is arranged between the first sub-electrode and the second sub-electrode, the first air through microstructure penetrates through two opposite surfaces of the inner electrode, and the penetration direction of the first air through microstructure is the surrounding direction of the vertical stack structure of the inner electrode, the piezoelectric layer and the outer electrode.

4. The bulk acoustic wave filter of claim 1 or 3, wherein, The outer electrode comprises a stack of a third sub-electrode and a fourth sub-electrode; The stacking direction of the third sub-electrode and the fourth sub-electrode is perpendicular to the thickness direction of the substrate; A second air through microstructure is arranged between the first sub-electrode and the second sub-electrode, the second air through microstructure penetrates through two opposite surfaces of the outer electrode, and the penetration direction of the second air through microstructure is the surrounding direction of the vertical stack structure of the inner electrode, the piezoelectric layer and the outer electrode.

5. The bulk acoustic wave filter of claim 1, wherein, Further comprising a temperature compensation layer, the temperature compensation layer comprises a positive frequency drift coefficient material.

6. The bulk acoustic wave filter of claim 5, wherein, The temperature compensation layer is located at least one of the following positions: in the piezoelectric layer, on the surface of the piezoelectric layer adjacent to the inner electrode, on the surface of the piezoelectric layer adjacent to the outer electrode, in the inner electrode, on the surface of the inner electrode away from the piezoelectric layer, in the outer electrode, and on the surface of the outer electrode away from the piezoelectric layer.

7. The bulk acoustic wave filter of claim 1, wherein, The horizontal cross-sectional shape of the bulk acoustic resonator comprises at least one of a polygonal ring, a circular ring and an elliptical ring.

8. The bulk acoustic wave filter of claim 1, wherein, The substrate comprises adjacent first and second substrates; The first surface of the first substrate is provided with at least one bulk acoustic resonator, and the second surface of the second substrate is provided with at least one bulk acoustic resonator; The bulk acoustic resonators between the first substrate and the second substrate are in an interdigital distribution.

9. The bulk acoustic wave filter of claim 1, wherein, The sound reflection structure comprises a cavity or a Bragg reflection layer.

10. The bulk acoustic wave filter of claim 1 or 8, wherein, Further comprising a conductive connection structure; The conductive connection structure is used to introduce the electrical signal of the bulk acoustic resonator to the first surface side of the uppermost substrate, and / or the conductive connection structure is used to introduce the electrical signal of the bulk acoustic resonator to the second surface side of the lowermost substrate.

11. The bulk acoustic wave filter of claim 10, wherein, Further comprising a cap wafer located on the first surface side of the uppermost substrate; The conductive connection structure is used to lead an electrical signal of the bulk acoustic resonator to a surface of the cap wafer away from the uppermost substrate.

12. The bulk acoustic wave filter of claim 8, wherein, The first surface of the first substrate is provided with a first bulk acoustic resonator, a second bulk acoustic resonator and a third bulk acoustic resonator; The second bulk acoustic resonator is arranged around the first bulk acoustic resonator, and the third bulk acoustic resonator is arranged around the second bulk acoustic resonator.

13. The bulk acoustic wave filter of claim 12, wherein, The second surface of the second substrate is provided with a fourth bulk acoustic resonator, a fifth bulk acoustic resonator and a sixth bulk acoustic resonator; The fifth bulk acoustic resonator is arranged around the fourth bulk acoustic resonator, and the sixth bulk acoustic resonator is arranged around the fifth bulk acoustic resonator; The fourth bulk acoustic resonator is located within the first bulk acoustic resonator; The fifth bulk acoustic resonator is located within the annular spacing space between the first bulk acoustic resonator and the second bulk acoustic resonator; The sixth bulk acoustic resonator is located within the annular spacing space between the second bulk acoustic resonator and the third bulk acoustic resonator.

14. The bulk acoustic wave filter of claim 8, wherein, In the thickness direction parallel to the substrate, the spacing between adjacent substrates is less than the sum of the heights of the bulk acoustic resonators distributed in an interdigital manner between the adjacent substrates.

15. The bulk acoustic wave filter of claim 8, wherein, In the horizontal direction, the two bulk acoustic resonators distributed in an interdigital manner are spaced apart by a preset spacing.

16. A communication device, comprising: The bulk acoustic wave filter comprises the bulk acoustic wave filter according to any one of claims 1-15. The communication device comprises at least one of a filter, a diplexer and a multiplexer.

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