Bulk acoustic wave resonator

Abstract

Disclosed in the present disclosure is a bulk acoustic wave resonator. The bulk acoustic wave resonator comprises an active area and a passive area at least partially surrounding the active area. The bulk acoustic wave resonator further comprises a substrate, a first electrode layer, a piezoelectric layer, a second electrode layer, and at least one acoustic rebound structure; the first electrode layer is located on one side of the substrate; the first electrode layer comprises a first electrode located at least in the active area; part of the first electrode is not in contact with the substrate to form a dielectric cavity; the piezoelectric layer is located on the side of the first electrode layer facing away from the substrate; the second electrode layer is located on the side of the piezoelectric layer facing away from the substrate; the second electrode layer comprises a second electrode located in the active area and the passive area; part of the second electrode is not in contact with the piezoelectric layer to form a cavity structure, and the cavity structure at least partially surrounds the active area; and at least one acoustic rebound structure is located in the cavity structure, the second electrode forming the cavity structure at least comprises a first portion and a second portion connected to each other, and the acoustic rebound structure is fixed onto the surface of the side of the second electrode close to the piezoelectric layer.

Description

Bulk acoustic wave resonator

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] The present disclosure claims priority to the Chinese patent application No. 202410782322X, filed on June 17, 2024, and entitled “Bulk acoustic wave resonator”, the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates to the field of filtering technology, and in particular, to a bulk acoustic wave resonator. BACKGROUND

[0004] With the rapid development of mobile communication technology, a large number of radio frequency resonators are needed on terminal devices, mainly to filter out unwanted radio frequency signals, improve communication quality, and improve user experience. The bulk acoustic wave resonator (BAWR) is a resonator widely used in the field of radio frequency at present. The bulk acoustic wave resonator utilizes the piezoelectric effect and the inverse piezoelectric effect, and combines the signal gating characteristics to achieve the effect of signal filtering.

[0005] In the layer structure of the thin film bulk acoustic wave resonator, an air bridge structure is arranged, especially at the boundary of the overlapping area of the bottom acoustic reflection cavity and the upper and lower electrode layers. The air bridge structure is beneficial to reduce the leakage of acoustic energy to the substrate, thereby improving the quality factor of the resonator. However, a part of the acoustic energy in the technical solution still leaks to the external area through the air bridge structure, which still greatly damages the quality factor of the resonator. Therefore, how to improve the quality factor of the resonator has become a technical problem to be solved at present.

[0006] SUMMARY

[0007] The present disclosure provides a bulk acoustic wave resonator to improve the quality factor and resonance quality of the bulk acoustic wave resonator.

[0008] The present disclosure provides a bulk acoustic wave resonator, comprising an active region and a passive region at least partially surrounding the active region.

[0009] The bulk acoustic wave resonator further comprises:

[0010] a substrate;

[0011] a first electrode layer located on one side of the substrate; the first electrode layer comprises a first electrode located at least on the active region; part of the first electrode is not in contact with the substrate to form a dielectric cavity;

[0012] a piezoelectric layer located on the side of the first electrode layer away from the substrate;

[0013] a second electrode layer on a side of the piezoelectric layer away from the substrate; the second electrode layer comprises second electrodes on the active region and the passive region; part of the second electrodes are not in contact with the piezoelectric layer to form a cavity structure, and the cavity structure at least partially surrounds the active region; in a direction perpendicular to a plane in which the substrate lies, the active region is an area where the dielectric cavity, the first electrode, the piezoelectric layer and the second electrode overlap and the adjacent layers are in contact with each other;

[0014] at least one acoustic reflector structure in the cavity structure, fixed to a side surface of the second electrode close to the piezoelectric layer;

[0015] The second electrode forming the cavity structure comprises at least a first part and a second part connected to each other, an angle between the first part and the second part is θ1, θ1≠n1×π / 2, n1∈N; a width of the first part is d1, a width of the second part is d2; a width of the acoustic reflector structure is d0; wherein, d0

[0016] Optionally, in a direction perpendicular to a plane in which the substrate lies, the second electrode forming the cavity structure further comprises a third part; the second part is located between the first part and the third part, and the second part is connected to the third part;

[0017] An angle between the third part and the second part is θ2, θ2≠n2×π / 2, n2∈N; a width of the third part is d3; wherein, d0

[0018] Optionally, when the cavity structure comprises a plurality of acoustic reflector structures, there is a gap between any two adjacent acoustic reflector structures.

[0019] Optionally, the volumes of at least two acoustic reflector structures are different.

[0020] Optionally, in a direction perpendicular to a side surface of the second electrode close to the piezoelectric layer, the heights of at least two acoustic reflector structures are different.

[0021] Optionally, in a direction parallel to a side surface of the second electrode close to the piezoelectric layer, the widths of at least two acoustic reflector structures are different.

[0022] Optionally, the volumes of each acoustic reflector structure are the same, and the materials of at least two acoustic reflector structures are different.

[0023] Optionally, the acoustic reflector structure and the second electrode are an integral structure.

[0024] Optionally, the acoustic reflection structure is not in contact with the piezoelectric layer.

[0025] Optionally, the bulk acoustic wave resonator further comprises a protective layer.

[0026] The protective layer is located on a side of the second electrode layer away from the piezoelectric layer. BRIEF DESCRIPTION OF DRAWINGS

[0027] Fig. 1 is a structural schematic diagram of a bulk acoustic wave resonator according to an embodiment of the present disclosure;

[0028] Fig. 2 is a structural schematic diagram of another bulk acoustic wave resonator according to an embodiment of the present disclosure;

[0029] Fig. 3 is a structural schematic diagram of yet another bulk acoustic wave resonator according to an embodiment of the present disclosure;

[0030] Fig. 4 is a structural schematic diagram of still another bulk acoustic wave resonator according to an embodiment of the present disclosure;

[0031] Fig. 5 is a structural schematic diagram of a bulk acoustic wave resonator according to an embodiment of the present disclosure;

[0032] Fig. 6 is a structural schematic diagram of another bulk acoustic wave resonator according to an embodiment of the present disclosure;

[0033] Fig. 7 is a structural schematic diagram of yet another bulk acoustic wave resonator according to an embodiment of the present disclosure;

[0034] Fig. 8 is a structural schematic diagram of still another bulk acoustic wave resonator according to an embodiment of the present disclosure;

[0035] Fig. 9 is a structural schematic diagram of a bulk acoustic wave resonator according to an embodiment of the present disclosure;

[0036] Fig. 10 is a structural schematic diagram of another bulk acoustic wave resonator according to an embodiment of the present disclosure;

[0037] Fig. 11 is a structural schematic diagram of yet another bulk acoustic wave resonator according to an embodiment of the present disclosure;

[0038] Fig. 12 is a structural schematic diagram of still another bulk acoustic wave resonator according to an embodiment of the present disclosure;

[0039] Fig. 13 is a structural schematic diagram of a bulk acoustic wave resonator according to the prior art;

[0040] Fig. 14 is a diagram of a relationship between a quality factor and a frequency of a bulk acoustic wave resonator according to the prior art and the present disclosure according to an embodiment of the present disclosure;

[0041] Fig. 15 is another diagram of a relationship between a quality factor and a frequency of a bulk acoustic wave resonator according to the prior art and the present disclosure according to an embodiment of the present disclosure;

[0042] FIG. 16 is another graph of the relationship between the quality factor and the frequency of a bulk acoustic resonator according to the prior art and the bulk acoustic resonator according to the present disclosure;

[0043] FIG. 17 is a schematic diagram of a process for manufacturing a bulk acoustic resonator according to an embodiment of the present disclosure;

[0044] FIG. 18 is a schematic diagram of a bulk acoustic resonator according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0045] The present disclosure will be further described below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are intended to be illustrative only and are not to be limiting of the present disclosure. Furthermore, the drawings are not necessarily to scale and certain features can be exaggerated in order to illustrate and emphasize principles of the present disclosure. The examples set forth herein are intended to be illustrative and not intended to limit the scope of the disclosure.

[0046] FIG. 1 is a schematic diagram of a bulk acoustic resonator according to an embodiment of the present disclosure. As shown in FIG. 1, the bulk acoustic resonator 100 includes an active region A1 and a passive region B1 at least partially surrounding the active region A1. The bulk acoustic resonator further includes a substrate 01, a first electrode layer 10, a piezoelectric layer 30, and a second electrode layer 20. The first electrode layer 10 is located on one side of the substrate 01. The first electrode layer 10 includes a first electrode located at least in the active region A1. Part of the first electrode is not in contact with the substrate 01 to form a dielectric cavity 40. The piezoelectric layer 30 is located on a side of the first electrode layer 10 facing away from the substrate 01. The second electrode layer 20 is located on a side of the piezoelectric layer 30 facing away from the substrate 01. The second electrode layer 20 includes a second electrode located in the active region A1 and the passive region B1. Part of the second electrode is not in contact with the piezoelectric layer 30 to form a cavity structure 50, and the cavity structure 50 at least partially surrounds the active region A1. At least one acoustic reflector 60 is located in the cavity structure 50 and is fixed to a side surface of the second electrode close to the piezoelectric layer 30. The second electrode forming the cavity structure 50 includes at least a first portion 21 and a second portion 22 connected together. The included angle between the first portion 21 and the second portion 22 is θ1, θ1≠n1π, n1∈N. The width of the first portion 21 is d1, and the width of the second portion 22 is d2. The width of the acoustic reflector 60 is d0. Wherein, d0

[0047] The dielectric cavity 50 includes air or a high acoustic impedance dielectric material, and can be located on the surface of the substrate 01, or formed by etching grooves into the substrate 01 and creating the dielectric cavity 50 within those grooves. The configuration can be tailored to specific needs. The substrate 01 includes materials such as silicon or silicon nitride. The first electrode layer 10 and the second electrode layer 20 include alloys of molybdenum, ruthenium, gold, aluminum, magnesium, copper, tungsten, titanium, iridium, argon, chromium, platinum, or other metals. The piezoelectric layer 30 includes materials such as aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), lithium silane (LiNbO3), quartz, potassium silane (KNbO3), or lithium tantalate (LiTaO3), and may also contain rare earth element doping materials in a certain atomic ratio. The acoustic rebound structure 60 includes dielectric materials such as aluminum nitride or metallic materials such as copper, and the configuration can be tailored to specific needs; no specific limitations are specified here.

[0048] Optionally, when an electrical signal is applied to the first electrode or the second electrode, the piezoelectric layer 30 will undergo longitudinal deformation due to the inverse piezoelectric effect, generating a longitudinally propagating and vibrating bulk acoustic wave. The surface of the second electrode facing away from the substrate 01 is in contact with the air, causing the bulk acoustic wave to be reflected on the surface of the second electrode facing away from the substrate 01. At the same time, a dielectric cavity 50 is provided on the surface of the first electrode facing the substrate 01, and the dielectric cavity 50 also reflects the bulk acoustic wave, so that energy will not leak into the substrate 01. Thus, the bulk acoustic wave is reflected back and forth between the first electrode and the second electrode, forming a standing wave in the piezoelectric layer 30 to resonate. After the bulk acoustic wave is converted into an electrical signal by the piezoelectric effect of the piezoelectric layer 30, it is output by the other electrode that has not been given an electrical signal. Therefore, in the direction Z perpendicular to the plane where the substrate 01 is located, the region where the dielectric cavity 50, the first electrode, the piezoelectric layer 30, and the second electrode overlap and adjacent layers are in contact with each other is the active region A1, also known as the effective resonant region. The dielectric cavity 50 can reflect bulk acoustic waves to the active region A1 and the passive region B1. The bulk acoustic waves reflected to the active region A1 can resonate in the piezoelectric layer 30, while the bulk acoustic waves reflected to the passive region B1 cannot resonate, resulting in bulk acoustic wave leakage. In this embodiment, a cavity structure 50 is provided in the passive region B1, at least partially surrounding the active region A1, and at least one acoustic rebound structure 60 is provided in the cavity structure 50, so that the bulk acoustic waves reflected to the passive region B1 are reflected back to the active region A1 through the cavity structure 50 and the acoustic rebound structure 60, thereby improving the resonance performance of the bulk acoustic resonator 100. The specific principle is as follows:

[0049] It should be noted that when the bulk acoustic wave propagates from the first impedance region to the second impedance region, due to the difference in impedance between the second and second impedance regions, an impedance mismatch interface is formed at the interface between the first and second impedance regions. The bulk acoustic wave will rebound horizontally at the impedance mismatch interface, and some of the energy that would originally enter the cavity structure 50 will be rebounded to the active region A1, reducing the propagation of energy to the external region and thus improving the quality factor of the bulk acoustic resonator.

[0050] In this embodiment, the second electrode constituting the cavity structure 50 is configured to include at least a first portion 21 and a second portion 22 connected together, with an angle θ1 between the first portion 21 and the second portion 22, where θ1 ≠ n1 × π / 2 and n1 ∈ N. This ensures that the first portion 21 and the second portion 22 are neither perpendicular nor parallel, i.e., they form a certain angle. This angle causes the airflow in the region where the first portion 21 is located and the region where the second portion 22 is located to be different in the direction Z perpendicular to the plane of the substrate 01 before the acoustic rebound structure 60 is provided. Consequently, the impedance values ​​in the regions where the first portion 21 is located and the second portion 22 are located are different. The cavity structure 50 includes two regions with different impedances. At least one acoustic rebound structure 60 is provided within the cavity structure 50, and the width d0 of the acoustic rebound structure 60 is smaller than the width d1 of the first part 21 or the width d2 of the second part 22. Regardless of whether the acoustic rebound structure 60 is located on the surface of the first part 21 near the piezoelectric layer 30, or on the surface of the second part 22 near the piezoelectric layer 30, or on a portion of the surface of the first part 21 and the second part 22 near the piezoelectric layer 30, the cavity structure 50 can include at least three regions with different impedances. This increases the bulk acoustic wave energy reflected from the cavity structure 50 to the active region A1, reduces energy loss, and thus improves the quality factor and resonance quality of the bulk acoustic resonator 100.

[0051] For example, continuing to refer to Figure 1, an acoustic rebound structure 50 is provided inside the cavity structure 50. The acoustic rebound structure 50 is fixed to the surface of the second part 22 near the piezoelectric layer 30. The width d0 of the acoustic rebound structure 50 is smaller than the width d2 of the second part 22. At this time, in the direction Z perpendicular to the plane where the substrate 01 is located, the impedance of the region where the first part 21 is located is Z1, the impedance of the region in the second part 22 located near the first part 21 of the acoustic rebound structure 60 is Z2, the impedance of the region in the second part 22 located where the acoustic rebound structure 60 is located is Z3, and the impedance of the region in the second part 22 located away from the first part 21 of the acoustic rebound structure 60 is Z4. In this way, four regions with different impedances are formed inside the cavity structure 50, so that the bulk acoustic wave reflected from the active region A1 to the cavity structure 50 can be reflected at the five impedance mismatch interfaces, thereby increasing the amount of bulk acoustic wave reflected by the cavity structure 50, and thus improving the quality factor and resonance quality of the bulk acoustic resonator 100.

[0052] It is understood that the passive region B1 can partially surround the active region A1. Figure 1 only shows the structure where the passive region B1 partially surrounds the active region A1. Figure 2 is a schematic diagram of another bulk acoustic resonator provided in this embodiment. As shown in Figure 2, the passive region B1 can completely surround the active region A1. In this case, a cavity structure 50 surrounding the active region A1 can be set in the passive region B1 to improve the reflection effect of bulk acoustic waves, further reduce energy loss, and improve the quality factor and resonance performance of the bulk acoustic resonator 100. The specific arrangement of the passive region B1 can be set according to actual needs, and is not specifically limited here.

[0053] Figure 13 is a schematic diagram of the structure of a bulk acoustic wave resonator in the prior art. Figure 14 is a graph showing the relationship between the quality factor and frequency of the bulk acoustic wave resonator of the prior art and the present disclosure provided in the embodiments of the present disclosure. Referring to Figures 13, 14 and 2, in the bulk acoustic wave resonator of the prior art, the cavity structure 50 only includes air and no acoustic rebound structure is provided. In the bulk acoustic wave resonator of Figure 2, the cavity structure 50 is provided with an acoustic rebound structure 60. The black solid line in Figure 14 represents the curve of the quality factor and frequency of the bulk acoustic wave resonator in Figure 13, and the black dashed line in Figure 14 represents the curve of the quality factor and frequency of the bulk acoustic wave resonator in Figure 2. As can be seen from Figure 14, compared with the prior art, the quality factor of the bulk acoustic wave resonator 100 of the present disclosure is significantly improved by providing an acoustic rebound structure 60 in the cavity structure 50.

[0054] The technical solution disclosed herein, by setting the second electrode constituting the cavity structure to include at least a first part and a second part connected together, and such that the first part is not parallel or perpendicular to the second part, that is, the first part and the second part form a certain angle, such that before the acoustic rebound structure is set, the cavity structure includes two regions with different impedances; by setting at least one acoustic rebound structure in the cavity structure, and such that the width of the acoustic rebound structure is smaller than the width of the first part or the width of the second part, the acoustic rebound structure can be set on the surface of the first part near the piezoelectric layer, or on the surface of the second part near the piezoelectric layer, or on the surface of the first part and the second part near the piezoelectric layer, so that the cavity structure includes at least three regions with different impedances, thereby increasing the bulk acoustic wave energy reflected from the cavity structure to the active region, reducing energy loss, and thus improving the quality factor and resonance quality of the bulk acoustic resonator.

[0055] In an optional embodiment, FIG18 is a schematic diagram of a bulk acoustic resonator provided in an embodiment of the present disclosure. As shown in FIG18, a cavity structure 50 is located between a first electrode layer 10 and a piezoelectric layer 30. Part of the first electrode and the piezoelectric layer 30 are not in contact with each other to form a cavity structure 50, and the cavity structure 50 at least partially surrounds the active region A1. At least one acoustic rebound structure 60 is located inside the cavity structure 50 and is fixed to the surface of the piezoelectric layer 30 near the first electrode layer 10. The piezoelectric layer 30 constituting the cavity structure 50 includes at least a fourth part 31 and a fifth part 32 connected to each other. The included angle between the fourth part 31 and the fifth part 32 is θ3, θ3 ≠ n3π, and n3 ∈ N. The width of the fourth part 31 is d4, and the width of the fifth part 32 is d5. The width of the acoustic rebound structure 60 is d0. Wherein, d0 < d4 or d0 < d5.

[0056] Thus, the fourth part 31 and the fifth part 32 are not perpendicular or parallel, that is, the fourth part 31 and the fifth part 32 form a certain angle. This angle causes the airflow in the region where the fourth part 31 and the region where the fifth part 32 are located to be different in the direction Z perpendicular to the plane of the substrate 01 before the acoustic rebound structure 60 is set. This results in different impedance values ​​in the regions where the fourth part 31 and the fifth part 32 are located. At this time, the cavity structure 50 includes two regions with different impedances. At least one acoustic rebound structure 60 is set in the cavity structure 50, and the acoustic rebound... When the width d0 of the acoustic rebound structure 60 is less than the width d1 of the fourth part 31 or the width d2 of the fifth part 32, regardless of whether the acoustic rebound structure 60 is disposed on the surface of the fourth part 31 near the piezoelectric layer 30, or on the surface of the fifth part 32 near the piezoelectric layer 30, or on the partial surfaces of the fourth part 31 and the fifth part 32 near the piezoelectric layer 30, the cavity structure 50 can include at least three regions with different impedances, thereby increasing the bulk acoustic wave energy reflected by the cavity structure 50 to the active region A1, reducing energy loss, and thus improving the quality factor and resonance quality of the bulk acoustic resonator 100.

[0057] Referring again to Figure 18, the piezoelectric layer 30 constituting the cavity structure 50 also includes a connected sixth part 33, and a fifth part 32 is located between the fourth part 31 and the sixth part 33, and the fifth part 32 is connected to the sixth part 33; the angle between the sixth part 33 and the fifth part 32 is θ4, θ4≠n4×π / 2, n4∈N; the width of the sixth part 33 is d6; where d0<d6. Thus, the fourth part 31 and the fifth part 32 are not perpendicular or parallel, and the fifth part 32 and the sixth part 33 are not perpendicular or parallel. That is, the fourth part 31 and the fifth part 32 form a certain angle, and the fifth part 32 and the sixth part 33 form a certain angle. Angles θ3 and θ4 make the cavity structure 50, before the acoustic rebound structure 60 is set, have different impedance values ​​in the region where the fourth part 31 is located and the region where the fifth part 32 is located in the direction Z perpendicular to the plane where the substrate 01 is located, and different impedance values ​​in the region where the fifth part 32 is located and the region where the sixth part 33 is located. At this time, the cavity structure 50 includes three regions with varying impedance. Based on this, by setting at least one acoustic rebound structure 60 in the cavity structure 50, and making the width of the acoustic rebound structure 60... When the width d0 is less than the width d4 of the fourth part 31, the width d5 ​​of the fifth part 32, or the width d6 of the sixth part 33, regardless of whether the acoustic rebound structure 60 is located on the surface of the fourth part 31 near the piezoelectric layer 30, or on the surface of the fifth part 32 near the piezoelectric layer 30, or on the surface of the sixth part 33 near the piezoelectric layer 30, or on a portion of the surfaces of the fourth part 31 and the fifth part 32 near the piezoelectric layer 30, or on a portion of the surfaces of the fifth part 32 and the sixth part 33 near the piezoelectric layer 30, the cavity structure 50 can include at least four regions with different impedances, thereby increasing the bulk acoustic wave energy reflected by the cavity structure 50 to the active region A1, reducing energy loss, and thus improving the quality factor and resonance quality of the bulk acoustic resonator 100.

[0058] It should be noted that the cavity structure 50 can be disposed between the piezoelectric layer 30 and the first electrode layer 10, and / or disposed between the piezoelectric layer 30 and the first electrode layer 10. The specific position of the cavity structure 50 can be set according to actual needs to improve the quality factor and resonance quality of the bulk acoustic resonator 100.

[0059] Optionally, Figure 3 is a schematic diagram of another bulk acoustic resonator provided in an embodiment of this disclosure. As shown in Figure 3, in the direction Z perpendicular to the plane where the substrate 01 is located, the second electrode constituting the cavity structure 50 further includes a third part 23; the second part 22 is located between the first part 21 and the third part 23, and the second part 22 is connected to the third part 23; the angle between the third part 23 and the second part 22 is θ2, θ2≠n2×π / 2, n2∈N; the width of the third part 23 is d3; where d0<d3.

[0060] Optionally, by setting the second electrode constituting the cavity structure 50 to include at least a first part 21, a second part 22, and a third part 23 connected together, the angle between the first part 21 and the second part 22 is θ1, θ1 ≠ n1×π / 2, n1∈N, and the angle between the third part 23 and the second part 22 is θ2 ≠ n2×π / 2, n2∈N; this makes the first part 21 and the second part 22 not perpendicular or parallel, and the second part 22 and the third part 23 not perpendicular or parallel, that is, the first part 21 and the second part 22 form a certain angle, and the second part 22 and the third part 23 form a certain angle. The angles θ1 and θ2 make the cavity structure 50, before the acoustic rebound structure 60 is set, have different impedance values ​​in the region where the first part 21 is located and the region where the second part 22 is located in the direction Z perpendicular to the plane where the substrate 01 is located, and different impedance values ​​in the region where the second part 22 is located and the region where the third part 23 is located. At this time, the cavity structure Cavity 50 includes three regions with varying impedances. Based on this, by providing at least one acoustic rebound structure 60 within the cavity structure 50, and ensuring that the width d0 of the acoustic rebound structure 60 is less than the width d1 of the first part 21, the width d2 of the second part 22, or the width d3 of the third part 23, regardless of whether the acoustic rebound structure 60 is located on the surface of the first part 21 near the piezoelectric layer 30, or on the surface of the second part 22 near the piezoelectric layer 30, or on the surface of the third part 23 near the piezoelectric layer 30, or on a portion of the surface of the first part 21 and the second part 22 near the piezoelectric layer 30, or on a portion of the surface of the second part 22 and the third part 23 near the piezoelectric layer 30, the cavity structure 50 can include at least four regions with different impedances. This increases the bulk acoustic wave energy reflected from the cavity structure 50 to the active region A1, reduces energy loss, and thus improves the quality factor and resonance quality of the bulk acoustic resonator 100.

[0061] It should be noted that the angle θ2 between the third part 23 and the second part 22 can be the same as or different from the angle θ1 between the first part 21 and the second part 22, so that the cavity structure 50 includes multiple regions with different impedances, thereby adjusting the degree of reflection of the cavity structure 50 on the bulk acoustic wave. The angles θ1 and θ2 can be set according to actual needs to meet the quality factor requirements of the bulk acoustic resonator 100.

[0062] Optionally, Figure 4 is a schematic diagram of another bulk acoustic resonator provided in an embodiment of this disclosure, and Figure 5 is a schematic diagram of a bulk acoustic resonator provided in an embodiment of this disclosure. Referring to Figure 4 or Figure 5, when the cavity structure 50 includes multiple acoustic rebound structures 60, there is a gap between any two adjacent acoustic rebound structures 60. Thus, an impedance region is formed at the gap between two adjacent acoustic rebound structures 60. The impedance at this gap is different from the impedance of the region where the two adjacent acoustic rebound structures 60 are located, thereby increasing the region with different impedances within the cavity structure 50, increasing the impedance mismatch interface, improving the reflection of bulk acoustic waves by the cavity structure 50, reducing energy loss, and improving the quality factor and resonance quality of the bulk acoustic resonator 100.

[0063] Figure 15 is a graph showing another relationship between the quality factor and frequency of the bulk acoustic resonator provided in the embodiments of this disclosure and the prior art. Referring to Figures 13, 15 and 5, in the bulk acoustic resonator in Figure 5, multiple acoustic rebound structures 60 of the same volume and material are provided in the cavity structure 50. The black solid line in Figure 15 represents the curve of quality factor versus frequency of the bulk acoustic resonator in Figure 13, and the black dashed line in Figure 15 represents the curve of quality factor versus frequency of the bulk acoustic resonator in Figure 5. As can be seen from Figure 15, compared with the prior art, the quality factor of the bulk acoustic resonator 100 of this disclosure is significantly improved by providing multiple acoustic rebound structures 60 in the cavity structure 50.

[0064] It is understood that, based on the fact that the cavity structure 50 includes multiple acoustic rebound structures 60 and there is a gap between any two adjacent acoustic rebound structures 60, the volume or material of each acoustic rebound structure 60 can be the same or different. In an optional embodiment, there are at least two acoustic rebound structures 60 with different volumes to increase the number of impedance mismatch interfaces with different reflection effects in the cavity structure 50, further improve the amount of bulk acoustic wave reflection by the cavity structure 50, and improve the quality factor of the bulk acoustic resonator 100.

[0065] It should be noted that the volume of the acoustic rebound structure 60 is related to the height and thickness of the acoustic rebound structure 60. In an optional embodiment, Figure 6 is a schematic diagram of another bulk acoustic resonator provided by the present disclosure, and Figure 7 is a schematic diagram of yet another bulk acoustic resonator provided by the present disclosure. Referring to Figures 6 and 7, in the direction Z perpendicular to the surface of the second electrode near the piezoelectric layer 30, there are at least two acoustic rebound structures 60 with different heights.

[0066] Optionally, referring to Figure 6, two acoustic rebound structures 60 are provided inside the cavity structure 50. One acoustic rebound structure 60 has a height of h1, and the other acoustic rebound structure 60 has a height of h2, where h1 is greater than h2. The two acoustic rebound structures 60 have the same height, but their volumes are different. This increases the number of impedance mismatch interfaces with different reflection effects inside the cavity structure 50, further improving the amount of bulk acoustic wave reflection by the cavity structure 50 and improving the quality factor of the bulk acoustic resonator 100. Referring to Figure 7, three acoustic rebound structures 60 are disposed within the cavity structure 50. The heights of the three acoustic rebound structures 60 are different, namely h1, h2, and h3, where h1 is greater than h2 and h2 is greater than h3. The acoustic rebound structures 60 with heights h1 and h2 are located on the surface of the second part 22 near the piezoelectric layer 30, and the acoustic rebound structure 60 with height h3 is located on the surface of the third part 23 near the piezoelectric layer 30. At this time, along the direction from the active region A1 to the passive region B1, the cavity structure 50 includes eight regions with different impedances, namely impedance Z1, impedance Z2, impedance Z3, impedance Z4, impedance Z5, impedance Z6, impedance Z7, and impedance Z8. When the two regions located in the second part 22... When the acoustic rebound structures 60 have the same volume and height h1, the cavity structure 50 includes seven regions with different impedances along the direction from the active region A1 to the passive region B1, namely impedance Z1, impedance Z2, impedance Z3, impedance Z4, impedance Z6, impedance Z7, and impedance Z8. The number of regions with different impedances in the cavity structure 50 is reduced. Thus, by setting at least two acoustic rebound structures 60 with different heights, the number of regions with different impedance values ​​in the cavity structure 50 is increased, thereby increasing the number of impedance mismatch interfaces with different reflection effects in the cavity structure 50, so as to improve the amount of bulk acoustic wave reflection by the cavity structure 50 and improve the quality factor of the bulk acoustic resonator 100.

[0067] Figure 16 is another graph showing the relationship between the quality factor and frequency of the bulk acoustic resonator provided in the embodiments of this disclosure and the prior art. Referring to Figures 13, 16 and 7, in the bulk acoustic resonator in Figure 7, multiple acoustic rebound structures 60 of different heights are provided in the cavity structure 50. The black solid line in Figure 16 represents the graph of the quality factor and frequency of the bulk acoustic resonator in Figure 13, and the black dashed line in Figure 16 represents the graph of the quality factor and frequency of the bulk acoustic resonator in Figure 7. As can be seen from Figure 16, compared with the prior art, the quality factor of the bulk acoustic resonator 100 of this disclosure is significantly improved by providing multiple acoustic rebound structures 60 of different heights in the cavity structure 50.

[0068] It is understood that the above description is only exemplified by the example of two or three acoustic rebound structures 60 in the cavity structure 50. When the number of acoustic rebound structures 60 in the cavity structure 50 is greater than three, the working principle can be referred to the above description, and will not be repeated here.

[0069] Optionally, Figure 8 is a structural schematic diagram of another bulk acoustic resonator provided in an embodiment of the present disclosure, and Figure 9 is a structural schematic diagram of a bulk acoustic resonator provided in an embodiment of the present disclosure. Referring to Figures 8 and 9, along the direction parallel to the surface of the second electrode near the piezoelectric layer 30, there are at least two acoustic rebound structures 60 with different widths.

[0070] Optionally, the cavity structure 50 includes an acoustic rebound structure 60 with a width of d1 and an acoustic rebound structure 60 with a width of d2, where d1 is greater than d2, so that the impedance of the region where the acoustic rebound structure 60 with width d1 is located is different from that of the region where the acoustic rebound structure 60 with width d2 is located, thereby increasing the number of regions with different impedances in the cavity structure 50, and further increasing the number of impedance mismatch interfaces with different reflection effects in the cavity structure 50, so as to improve the amount of reflection of bulk acoustic waves by the cavity structure 50 and improve the quality factor of the bulk acoustic resonator 100.

[0071] In an optional embodiment, FIG10 is a schematic diagram of another bulk acoustic resonator provided in the present disclosure. As shown in FIG10, each acoustic rebound structure 60 has the same volume, and at least two acoustic rebound structures 60 are made of different materials.

[0072] Optionally, the impedance of the region where the acoustic rebound structure 60 is located is related to the material of the acoustic rebound structure 60. The material density of the acoustic rebound structure 60 is proportional to the impedance. The greater the material density of the acoustic rebound structure 60, the greater the impedance value of the region where the acoustic rebound structure 60 is located. Acoustic rebound structures 60 made of different materials can be provided to increase the number of regions with different impedances in the cavity structure 50, thereby increasing the number of impedance mismatch interfaces with different reflection effects in the cavity structure 50, so as to improve the reflection of bulk acoustic waves by the cavity structure 50 and improve the quality factor of the bulk acoustic resonator 100. For example, one acoustic rebound structure 60 is made of aluminum nitride, and the other acoustic rebound structure 60 is made of tungsten. Other materials are also possible and are not specifically limited here.

[0073] Optionally, Figure 11 is a schematic diagram of another bulk acoustic wave resonator provided in an embodiment of this disclosure. As shown in Figure 11, the acoustic rebound structure 60 and the second electrode are integrally formed. In this way, the acoustic rebound structure 60 can be fabricated simultaneously with the second electrode, improving the contact reliability between the acoustic rebound structure 60 and the second electrode. This not only improves the quality factor of the bulk acoustic wave resonator 100 but also increases the fabrication efficiency of the bulk acoustic wave resonator 100 and simplifies the process flow.

[0074] Optionally, referring to Figure 1, the acoustic rebound structure 60 and the piezoelectric layer 30 are not in contact. Optionally, when the acoustic rebound structure 60 is in contact with the piezoelectric layer 30, the cavity of the acoustic rebound structure 60 in contact with the piezoelectric layer 30 near the active region A1 can reflect bulk acoustic waves, while the cavity of the acoustic rebound structure 60 in contact with the piezoelectric layer 30 away from the active region A1 has a smaller effect on reflecting bulk acoustic waves. Therefore, by ensuring that the acoustic rebound structure 60 and the piezoelectric layer 30 are not in contact, all regions within the cavity structure 50 can reflect bulk acoustic waves, thereby reducing energy loss and improving the quality factor of the bulk acoustic resonator 100.

[0075] Optionally, Figure 12 is a schematic diagram of another bulk acoustic resonator provided in an embodiment of the present disclosure. As shown in Figure 12, the bulk acoustic resonator 100 further includes a protective layer 70; the protective layer 70 is located on the side of the second electrode layer 20 away from the piezoelectric layer 30.

[0076] The protective layer 70 includes materials such as silicon oxide, which can be set according to actual needs and are not limited here.

[0077] Optionally, by providing a protective layer 70 on the side of the second electrode layer 20 away from the piezoelectric layer 30, external impurities such as air can be prevented from corroding the second electrode layer 20, thereby protecting the second electrode layer 20 and improving the operational reliability of the bulk acoustic resonator 100.

[0078] Figure 17 is a schematic diagram of the process structure for fabricating a bulk acoustic resonator according to an embodiment of this disclosure. As shown in Figure 17, a substrate 01 is provided, and an etching is performed on one side of the substrate 01 to form a groove on one side of the substrate 01. Then, a first sacrificial layer 41 is filled in the groove. A first electrode layer 10 is formed on a portion of the first sacrificial layer 41 facing away from the substrate 01 and on a portion of the substrate 01. A piezoelectric layer 30 is formed on the surface of the first electrode layer 10 facing away from the substrate 01. An active region A1 is formed on the side of the piezoelectric layer 30 facing away from the substrate. The second sacrificial layer 51 is etched to form a receiving groove 61 for accommodating the acoustic rebound structure 60. A second electrode layer 20 is formed on the surface of the second sacrificial layer 51 facing away from the substrate 01 and on the surface of the piezoelectric layer 30 facing away from the substrate 01. The second electrode layer 20 fills the receiving groove 61. At this time, the acoustic rebound structure 60 and the second electrode layer 20 are an integral structure. Then, the first sacrificial layer 41 and the second sacrificial layer 42 are removed using an etching solution to form the dielectric cavity 40 and the cavity structure 50. The above only shows one method for fabricating the bulk acoustic resonator 100. Other methods for fabricating the bulk acoustic resonator 100 are also possible and are not specifically limited here.

[0079] Note that the above description is merely a preferred embodiment and the technical principles employed in this disclosure. Those skilled in the art will understand that this disclosure is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of this disclosure. Therefore, although this disclosure has been described in detail through the above embodiments, it is not limited to the above embodiments. Many other equivalent embodiments may be included without departing from the concept of this disclosure, and the scope of this disclosure is determined by the scope of the appended claims. Industrial applicability

[0080] This disclosure provides a bulk acoustic resonator that can increase the bulk acoustic wave energy reflected from the cavity structure to the active region, reduce energy loss, and thereby improve the quality factor and resonance quality of the bulk acoustic resonator.

Claims

1. A bulk acoustic resonator, characterized in that, include: An active region and a passive region that at least partially surrounds the active region; The bulk acoustic resonator also includes: Substrate; A first electrode layer is located on one side of the substrate; the first electrode layer includes at least a first electrode located in the active region; a portion of the first electrode is not in contact with the substrate to form a dielectric cavity; A piezoelectric layer is located on the side of the first electrode layer that faces away from the substrate; A second electrode layer is located on the side of the piezoelectric layer facing away from the substrate; the second electrode layer includes a second electrode located in the active region and the passive region; a portion of the second electrode is not in contact with the piezoelectric layer to form a cavity structure, and the cavity structure at least partially surrounds the active region; in a direction perpendicular to the plane of the substrate, the region where the dielectric cavity, the first electrode, the piezoelectric layer and the second electrode overlap and adjacent layers are in contact with each other is the active region; At least one acoustic rebound structure is located within the cavity structure and fixed to the side surface of the second electrode near the piezoelectric layer. The second electrode constituting the cavity structure includes at least a first part and a second part connected together, the angle between the first part and the second part is θ1, θ1≠n1×π / 2, n1∈N; the width of the first part is d1, the width of the second part is d2; the width of the acoustic rebound structure is d0; wherein, d0<d1 or d0<d2.

2. The bulk acoustic resonator according to claim 1, characterized in that, In a direction perpendicular to the plane of the substrate, the second electrode constituting the cavity structure further includes a third portion; the second portion is located between the first portion and the third portion, and the second portion is connected to the third portion; The angle between the third part and the second part is θ2, θ2≠n2×π / 2, n2∈N; the width of the third part is d3; where d0<d3.

3. The bulk acoustic resonator according to claim 1 or 2, characterized in that, When the cavity structure includes multiple acoustic rebound structures, there is a gap between any two adjacent acoustic rebound structures.

4. The bulk acoustic resonator according to claim 3, characterized in that, There are at least two of the aforementioned acoustic rebound structures with different volumes.

5. The bulk acoustic resonator according to claim 4, characterized in that, In a direction perpendicular to the side surface of the second electrode near the piezoelectric layer, there are at least two acoustic rebound structures with different heights.

6. The bulk acoustic resonator according to claim 4, characterized in that, Along a direction parallel to the side surface of the second electrode near the piezoelectric layer, there are at least two acoustic rebound structures with different widths.

7. The bulk acoustic resonator according to claim 3, characterized in that, All of the acoustic rebound structures have the same volume, but at least two of the acoustic rebound structures are made of different materials.

8. The bulk acoustic resonator according to claim 1, characterized in that, The acoustic rebound structure is an integral part of the second electrode.

9. The bulk acoustic resonator according to claim 1, characterized in that, The acoustic rebound structure is not in contact with the piezoelectric layer.

10. The bulk acoustic resonator according to claim 1, characterized in that, Also includes: Protective layer; The protective layer is located on the side of the second electrode layer opposite to the piezoelectric layer.

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