Bulk acoustic wave resonator, method of manufacturing bulk acoustic wave resonator, filter, and electronic device

Abstract

This invention relates to a bulk acoustic wave resonator and its manufacturing method. The bulk acoustic wave resonator includes: a resonant structure comprising a piezoelectric layer and electrodes disposed on the piezoelectric layer; a substrate; an acoustic mirror cavity disposed between the resonant structure and the substrate; a dielectric layer and a metal bonding layer, wherein the dielectric layer and the metal bonding layer are co-layered and of the same thickness and disposed between the resonant structure and the substrate, wherein the metal bonding layer includes a defining portion that defines the horizontal boundary of the acoustic mirror cavity, and the dielectric layer is located outside the defining portion in the horizontal direction. This invention also relates to a filter and an electronic device.

Description

Technical Field

[0001] Embodiments of the present invention relate to the semiconductor field, and more particularly to a bulk acoustic wave resonator and a method for manufacturing the same, a filter having the resonator, and an electronic device. Background Technology

[0002] With the rapid development of 5G communication technology, the requirements for communication frequency bands are becoming increasingly stringent. Traditional radio frequency filters, limited by their structure and performance, cannot meet the requirements of high-frequency communication. Thin-film bulk acoustic resonators (FBARs), as a novel MEMS device, have advantages such as small size, light weight, low insertion loss, wide bandwidth, and high quality factor, making them well-suited for the upgrading of wireless communication systems and making FBAR technology one of the research hotspots in the field of communication.

[0003] The main structure of a thin-film bulk acoustic resonator (FBAR) is a "sandwich" structure consisting of an electrode-piezoelectric thin film-electrode, that is, a piezoelectric material sandwiched between two layers of metal electrodes. By inputting a sinusoidal signal between the two electrodes, the FBAR uses the inverse piezoelectric effect to convert the input electrical signal into mechanical resonance, and then uses the piezoelectric effect to convert the mechanical resonance into an electrical signal output.

[0004] FBAR and transverse resonant cavity devices place high demands on the quality of piezoelectric materials. Traditional processes require consideration of the surface characteristics of the piezoelectric material before growth, such as flatness and crystal orientation, which necessitates very stringent process control and makes the fabrication process extremely difficult.

[0005] Some piezoelectric materials cannot be grown on devices by deposition, or the process is too difficult, such as LiNbO3 and LiTaO3. Currently, the common approach is to grow an entire crystal pillar, then cut it according to a specific crystal orientation, and then use smart-cut technology to attach a material of a specific usable thickness (0.01-50um) onto an auxiliary substrate.

[0006] Based on the above two issues, it is necessary to transfer high-quality piezoelectric materials that meet the requirements from the auxiliary substrate to the device. The most crucial step in this transfer process is bonding, specifically bonding the auxiliary substrate with the piezoelectric layer to the device substrate. Bonding requires specific bond strength to ensure good adhesion between the device substrate and the device during subsequent processes. Metal bonding is a commonly used method, but bonding metals are generally highly reactive substances that can easily contaminate the equipment. Most equipment, such as deposition and etching machines, does not allow exposed bonding metals, which imposes significant limitations on subsequent processes.

[0007] In addition, FBAR and transverse resonant cavity devices require the formation of an acoustic reflection cavity (i.e., an acoustic mirror cavity) between the device substrate and the acoustic device, which requires multiple steps in the device fabrication process.

[0008] For piezoelectric layer growth technology, to form the cavity beneath the resonator, it is necessary to form a groove on the substrate, fill the groove with a sacrificial material layer, or utilize the difference in materials between the substrate and the sacrificial layer to remove only the sacrificial material layer to form the cavity. However, forming the acoustic reflection cavity in an early step can easily lead to low device mechanical strength, impose more restrictions on subsequent processes, and make the device prone to damage.

[0009] For transfer piezoelectric layer technology, since it needs to be bonded to the substrate, a simpler solution is to directly use metal bonding, which directly utilizes the space between the metal bonding layers. This method will first form a cavity, resulting in poor mechanical strength. Summary of the Invention

[0010] The present invention is proposed to alleviate or solve at least one of the above-mentioned problems in the prior art.

[0011] Embodiments of the present invention relate to a bulk acoustic resonator, comprising:

[0012] A resonant structure, the resonant structure comprising a piezoelectric layer and electrodes disposed on the piezoelectric layer;

[0013] Base;

[0014] Acoustic mirror cavity, positioned between the resonant structure and the substrate; and

[0015] A dielectric layer and a metal bonding layer, both of the same thickness, are disposed between the resonant structure and the substrate.

[0016] in:

[0017] The metal bonding layer includes a defining portion that defines the horizontal boundary of the acoustic mirror cavity, and the dielectric layer is located outside the defining portion in the horizontal direction.

[0018] Embodiments of the present invention also relate to a method for manufacturing a bulk acoustic resonator, comprising the steps of:

[0019] An auxiliary substrate assembly is provided, the auxiliary substrate assembly including an auxiliary substrate and a piezoelectric layer disposed on the auxiliary substrate, the piezoelectric layer having a first surface facing the auxiliary substrate and a second surface opposite to the first surface in the thickness direction of the piezoelectric layer, and a first release medium layer, a first metal bonding layer and a first dielectric layer arranged in the same layer are formed on one side of the second surface of the piezoelectric layer of the auxiliary substrate assembly, the first metal bonding layer being located between the first release medium layer and the first dielectric layer in the horizontal direction;

[0020] A device substrate assembly is provided, the device substrate assembly including a device substrate and a second release dielectric layer, a second metal bonding layer and a second dielectric layer disposed on the same layer on one side of the device substrate, wherein the second metal bonding layer is located horizontally between the second release dielectric layer and the second dielectric layer.

[0021] The auxiliary substrate assembly and the device substrate assembly are bonded to each other, that is, the first release dielectric layer, the first metal bonding layer and the first dielectric layer of the auxiliary substrate assembly are respectively bonded to the second release dielectric layer, the second metal bonding layer and the second dielectric layer of the device substrate assembly, wherein the first metal bonding layer and the second metal bonding layer are bonded to each other.

[0022] Remove the entire auxiliary substrate to expose at least a portion of the first surface of the piezoelectric layer;

[0023] The electrode structure of the bulk acoustic resonator is formed;

[0024] At least a portion of the first release dielectric layer and at least a portion of the second release dielectric layer are released to form the acoustic mirror cavity of the bulk acoustic resonator, wherein the first metal bonding layer and the second metal bonding layer together define the horizontal boundary of the acoustic mirror cavity.

[0025] Embodiments of the present invention also relate to a filter, including the aforementioned bulk acoustic resonator.

[0026] Embodiments of the present invention also relate to an electronic device, including the filter described above or the bulk acoustic resonator described above. Attached Figure Description

[0027] The following description and accompanying drawings will better aid in understanding these and other features and advantages of the various embodiments disclosed herein, wherein the same reference numerals in the drawings always denote the same parts, wherein:

[0028] Figure 1 This is a top view schematic diagram of a bulk acoustic resonator according to an exemplary embodiment of the present invention;

[0029] Figure 2A For a bulk acoustic resonator according to an exemplary embodiment of the present invention, the edge Figure 1 A schematic diagram of the cross-section intercepted by line AA' in the diagram;

[0030] Figure 2B For a bulk acoustic resonator according to an exemplary embodiment of the present invention, the edge Figure 1 A schematic diagram of the cross-section obtained by the BB' line in the diagram, showing the release hole;

[0031] Figure 2C and Figure 2D They were displayed respectively Figure 2A and Figure 2B Enlarged schematic diagram of the first and second metal bonding layers in the process;

[0032] Figure 3A-3O Manufacturing is shown as an example Figure 1 A cross-sectional schematic diagram of the process of the bulk acoustic resonator is shown.

[0033] Figure 4 A schematic cross-sectional view of a bulk acoustic resonator according to another exemplary embodiment of the present invention;

[0034] Figure 5 A schematic cross-sectional view of a bulk acoustic resonator according to another exemplary embodiment of the present invention;

[0035] Figure 6 A cross-sectional schematic diagram of a bulk acoustic resonator according to another exemplary embodiment of the present invention. Detailed Implementation

[0036] The technical solution of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings. In this specification, the same or similar reference numerals indicate the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall inventive concept of the present invention and should not be construed as a limitation thereof. These are only some embodiments of the invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0037] First, the reference numerals in the accompanying drawings of this invention are explained as follows:

[0038] 100: Substrate, which is the device substrate. Selectable materials include single-crystal silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, diamond, etc.

[0039] 101: Piezoelectric layer, which may be made of aluminum nitride, zinc oxide, PZT, etc., and contain rare earth element doping materials in a certain atomic ratio of the above materials, as well as single crystal aluminum nitride, single crystal gallium nitride, single crystal lithium niobate, single crystal lead zirconate titanate, single crystal potassium niobate, single crystal quartz film, or single crystal lithium tantalate, etc. It may also contain rare earth element doping materials in a certain atomic ratio of the above materials, such as doped aluminum nitride, which contains at least one rare earth element, such as scandium (Sc), yttrium (Y), magnesium (Mg), titanium (Ti), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), etc.

[0040] 102: Bottom electrode (including electrode lead-out end), the material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite or alloy of the above metals, etc.

[0041] 104: Top electrode (including electrode lead-out end), the material of which may be the same as or different from that of the bottom electrode. The material of the top electrode may be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite or alloy of the above metals.

[0042] 1010, 1020, 1010A, 1010B, 1020A, 1020B: Metal bonding layer, materials can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a combination of the above metals or their alloys.

[0043] 103A, 103B: Dielectric layer or dielectric layer, the material of which can be silicon oxide, silicon nitride, aluminum nitride, etc.

[0044] 1030: Acoustic mirror cavity.

[0045] 105: Passivation layer, which is generally a dielectric material, such as silicon dioxide, aluminum nitride, silicon nitride, etc.

[0046] 106: Electrical isolation layer, the material of which can be non-conductive materials such as silicon dioxide and silicon nitride.

[0047] 107: External leads, with optional materials including high conductivity materials such as gold, copper, and aluminum.

[0048] 108: Release hole, communicating with the acoustic mirror cavity, used for the passage of etchant or release agent for releasing or etching the sacrificial material inside the acoustic mirror cavity.

[0049] 200: Substrate, which is an auxiliary substrate. Optional materials include single-crystal silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, diamond, etc.

[0050] 201: Insulating layer, which can be silicon dioxide and its dopants, silicon nitride, silicon carbide, sapphire, etc.

[0051] Figure 1 This is a top view schematic diagram of a bulk acoustic resonator according to an exemplary embodiment of the present invention; Figure 2A For a bulk acoustic resonator according to an exemplary embodiment of the present invention, the edge Figure 1 A schematic diagram of the cross-section intercepted by line AA' in the diagram; Figure 2B For a bulk acoustic resonator according to an exemplary embodiment of the present invention, the edge Figure 1 A schematic diagram of the cross-section obtained by the BB' line in the figure, which shows the release hole 108.

[0052] like Figure 1 , 2AAs shown in Figure 2B, in the illustrated embodiment, the bulk acoustic resonator includes: a substrate 100, an acoustic mirror cavity 1030, a bottom electrode 102, a top electrode 104, and a piezoelectric layer 101. The piezoelectric layer 101 is disposed between the bottom electrode 102 and the top electrode 104.

[0053] like Figure 1 , 2A As shown in Figure 2B, in the illustrated embodiment, a first dielectric layer 103A and a first metal bonding layer 1020 are disposed in the same layer on the bottom electrode 102 side. A second dielectric layer 103B and a second metal bonding layer 1010 are disposed in the same layer on the substrate 100 side. The first dielectric layer 103A and the second dielectric layer 103B correspond to and are bonded together. The first metal bonding layer 1020 and the second metal bonding layer 1010 correspond to and are bonded together.

[0054] As those skilled in the art will understand, although in the embodiments of the present invention the first dielectric layer 103A and the second dielectric layer 103B are connected to each other by bonding, they can also be connected by other means besides bonding, such as adhesive bonding.

[0055] like Figure 1 , 2A As shown in Figure 2B, in the illustrated embodiment, the dielectric layer 103B on the substrate 100 side is bonded to the dielectric layer 103A on the piezoelectric layer 101 side, and the metal bonding layer 1010 on the substrate 100 side is bonded to the metal bonding layer 1020 on the piezoelectric layer 101 side. This enables metal bonding and dielectric layer bonding, thereby improving the bonding strength between the bulk acoustic wave resonator device and the substrate 100.

[0056] like Figure 1 , 2A As shown in Figure 2B, in the illustrated embodiment, the first metal bonding layer 1020 and the second metal bonding layer 1010, bonded together, isolate the acoustic mirror cavity 1030 from the first dielectric layer 103A and the second dielectric layer 103B. Figure 2A and 2B In the illustrated embodiment, the first metal bonding layer 1020 and the second metal bonding layer 1010 together constitute a defining portion that defines the horizontal boundary of the acoustic mirror cavity. The advantage of this structure is that it protects the dielectric layers 103A and 103B located outside the first and second metal bonding layers 1020 and 1010 from removal when the sacrificial material layer inside the first and second metal bonding layers 1020 and 1010 is removed. How to remove the sacrificial material layer will be explained in more detail later in the manufacturing process.

[0057] Figure 2C Showing Figure 2A and Figure 2B An enlarged schematic diagram of the first metal bonding layer in the process; Figure 2D Showing Figure 2A and Figure 2B An enlarged schematic diagram of the second metal bonding layer in the image.

[0058] like Figure 2A , 2B As shown in Figures 2C and 2D, in the illustrated embodiment, the first metal bonding layer 1020 includes a first body portion 10201 and a first deformable structure 10202. The first body portion 10201 has a flat top surface. The first deformable structure 10202 is formed on the flat top surface of the first body portion 10201.

[0059] like Figure 2A , 2B As shown in Figures 2C and 2D, in an exemplary embodiment of the present invention, the material of the first main body portion 10201 and the material of the first deformable structure 10202 can be the same or different. If the material of the first main body portion 10201 and the first deformable structure 10202 are the same, the first main body portion 10201 of the overall height can be fabricated first by electroplating, and then the deformable structure 10202 can be fabricated by metal etching. If the material of the first main body portion 10201 and the first deformable structure 10202 are different, the first main body portion 10201 of the overall height can be fabricated first by electroplating, and then the first deformable structure 10202 can be fabricated on the first main body portion 10201 by a lift-off method. It should be noted that the method of fabricating the first metal bonding layer 1020 is not limited to the foregoing embodiments, and can be fabricated by any other suitable method.

[0060] like Figure 2A , 2B As shown in Figures 2C and 2D, in the illustrated embodiment, the second metal bonding layer 1010 includes a second body portion 10101 and a second deformable structure 10102. The second body portion 10101 has a flat top surface. The second deformable structure 10102 is formed on the flat top surface of the second body portion 10101.

[0061] like Figure 2A , 2BAs shown in Figures 2C and 2D, in an exemplary embodiment of the present invention, the material of the second main body portion 10101 can be the same as or different from the material of the second deformable structure 10102. If the material of the second main body portion 10101 is the same as the material of the second deformable structure 10102, the second main body portion 10101 of the overall height can be fabricated first by electroplating, and then the deformable structure 10102 can be fabricated by metal etching. If the material of the second main body portion 10101 is different from the material of the second deformable structure 10102, the second main body portion 10101 of the overall height can be fabricated first by electroplating, and then the second deformable structure 10102 can be fabricated on the second main body portion 10101 by a lift-off method. It should be noted that the method of fabricating the second metal bonding layer 1010 is not limited to the foregoing embodiments, and can be fabricated by any other suitable method.

[0062] like Figure 2A , 2B As shown in Figures 2C and 2D, in the illustrated embodiments, the first deformable structure 10202 and the second deformable structure 10102 are adapted to engage and bond together. The first deformable structure 10202 includes a plurality of spaced-apart first protrusions formed on the flat top surface of the first body portion 10201. The second deformable structure 10102 includes a plurality of spaced-apart second protrusions formed on the flat top surface of the second body portion 10101. The plurality of first protrusions of the first deformable structure 10202 and the plurality of second protrusions of the second deformable structure 10102 engage with each other and are bonded together in an engaged state.

[0063] like Figure 2A , 2B As shown in Figures 2C and 2D, in the illustrated embodiments, in order to ensure that the first dielectric layer 103A and the second dielectric layer 103B can contact and bond or join together when the first metal bonding layer 1020 and the second metal bonding layer 1010 are bonded together, the dimensions of the first metal bonding layer 1020 and the second metal bonding layer 1010 in the height direction (i.e., the thickness direction of the substrate 100) must meet certain conditions. These dimensional relationships will be explained below with reference to the accompanying drawings.

[0064] like Figure 2A , 2BAs shown in Figures 2C and 2D, in the illustrated embodiments, the height of the first main body portion 10201 of the first metal bonding layer 1020 is less than the height of the first dielectric layer 103A, resulting in a first height difference between the first dielectric layer 103A and the first main body portion 10201. Similarly, the height of the second main body portion 10101 of the second metal bonding layer 1010 is less than the height of the second dielectric layer 103B, resulting in a second height difference between the second dielectric layer 103B and the second main body portion 10101.

[0065] like Figure 2A , 2B As shown in Figures 2C and 2D, in the illustrated embodiments, after the first metal bonding layer 1020 and the second metal bonding layer 1010 are bonded together, that is, after the first metal bonding layer 1020 and the second metal bonding layer 1010 are bonded together, the height of the first metal bonding layer 1020 and the second metal bonding layer 1010 after being bonded together should be equal to the sum of the aforementioned first height difference and second height difference. This ensures that after the first metal bonding layer 1020 and the second metal bonding layer 1010 are bonded together, the first dielectric layer 103A and the second dielectric layer 103B can contact each other and be bonded together.

[0066] like Figure 2A , 2B As shown in 2C and 2D, in the illustrated embodiment, the acoustic mirror cavity 1030 is connected to the outside via a release hole 108 passing through the bottom electrode 102 and the piezoelectric layer 101.

[0067] like Figure 2A , 2B As shown in Figures 2C and 2D, in the illustrated embodiment, the bulk acoustic resonator further includes an electrical isolation layer 106 disposed between the bottom electrode 102 and the top electrode 104. This electrical isolation layer 106 is used to electrically isolate the bottom electrode 102 and the top electrode 104, preventing electrical connection between them. Figure 2A As shown, the electrical isolation layer 106 at least covers the end face of the non-electrode connection end of the bottom electrode to electrically isolate the bottom electrode from the top electrode.

[0068] like Figure 2A , 2B As shown in 2C and 2D, in the illustrated embodiment, the bulk acoustic resonator further includes a passivation layer 105 disposed on the outer surface of the top electrode 104.

[0069] like Figure 2A , 2B As shown in Figures 2C and 2D, in the illustrated embodiments, the bulk acoustic wave resonator further includes two external leads 107 electrically connected to the bottom electrode 102 and the top electrode 104, respectively. The top and bottom electrodes of the bulk acoustic wave resonator can be connected to an external circuit through these two external leads.

[0070] Figure 3A-3O Manufacturing is illustrated as an example. Figure 1 , 2A A series of schematic cross-sectional views of the bulk acoustic resonator process in 2B are shown below. Figure 3A-3O Detailed description Figure 1 , 2A The manufacturing process of the bulk acoustic resonator in 2B.

[0071] First, provide such as Figure 3E The auxiliary base component shown.

[0072] like Figure 3E As shown in the illustrated embodiment, the auxiliary substrate assembly includes: an auxiliary substrate 200, an insulating layer 201 formed on the auxiliary substrate 200 (the insulating layer 201 may also be absent), a piezoelectric layer 101 formed on the insulating layer 201, a bottom electrode 102 formed on the piezoelectric layer 101, a first dielectric layer 103A and a first metal bonding layer 1020 disposed on the bottom electrode 102 in the same layer.

[0073] The following will refer to the appendix. Figures 3A-3E Provide a detailed description of the process for preparing the auxiliary substrate component.

[0074] First, such as Figure 3A As shown, an auxiliary substrate 200 is provided, an insulating layer 201 is formed on the auxiliary substrate 200, and a piezoelectric layer 101 is formed on the insulating layer 201.

[0075] like Figure 3A As shown in the illustrated embodiment, a piezoelectric layer 101 is fabricated on an auxiliary substrate 200, wherein the insulating layer 201 is an intermediate layer, the function of which is to facilitate the separation of the piezoelectric layer 101 from the auxiliary substrate 200. The insulating layer 201 can be a dielectric layer such as SiO2. The insulating layer 201 is not necessary and can be omitted.

[0076] Then, as Figure 3B As shown, a first electrode material layer (denoted as 102) for a bottom electrode 102 is formed on the surface (i.e., the bottom surface) of the first side of the piezoelectric layer 101. The first electrode material layer may be formed on the piezoelectric layer 101 by deposition or any other suitable method.

[0077] Next, as Figure 3C As shown, a first dielectric layer 103A is formed on the bottom electrode 102. The first dielectric layer 103A can be formed on the bottom electrode 102 by deposition or any other suitable method.

[0078] Then, as Figure 3DAs shown, a first dielectric layer 103A is etched to form a first trench G1 in the first dielectric layer 103A. The etching of the first dielectric layer 103A can be performed using any suitable etching method, such as photolithography or chemical etching. As will be understood, the first trench G1 is an annular trench defining the horizontal boundary of the acoustic mirror cavity, and the depth of the first trench G1 is consistent with the thickness of the first dielectric layer.

[0079] Finally, as Figure 3E As shown, a first metal bonding layer 1020 is formed in the first trench G1 to form an auxiliary substrate assembly.

[0080] like Figure 2C As shown in the illustrated embodiment, the first metal bonding layer 1020 includes a first main body portion 10201 and a first deformable structure 10202 formed on top of the first main body portion 10201. In one embodiment of the invention, if the material of the first main body portion 10201 of the first metal bonding layer 1020 is the same as the material of the first deformable structure 10202, the first main body portion 10201 of the overall height can be fabricated first by electroplating, and then the deformable structure 10202 can be fabricated by metal etching. If the material of the first main body portion 10201 of the first metal bonding layer 1020 is different from the material of the first deformable structure 10202, the first main body portion 10201 of the overall height can be fabricated first by electroplating, and then the first deformable structure 10202 can be fabricated on the first main body portion 10201 by a lift-off method.

[0081] Second, provide such as Figure 3F The device substrate assembly shown.

[0082] like Figure 3F As shown in the illustrated embodiment, the device substrate assembly includes: a device substrate 100 and a second dielectric layer 103B and a second metal bonding layer 1010 disposed on the device substrate 100 in the same layer.

[0083] The following will refer to the appendix. Figure 3F Provide a detailed description of the process for preparing the substrate component.

[0084] First, provide such Figure 3F The device substrate 100 is shown.

[0085] Then, as Figure 3F As shown, a second dielectric layer 103B is formed on the substrate 100. The second dielectric layer 103B can be formed on the substrate 100 by deposition or any other suitable method.

[0086] Next, as Figure 3FAs shown, the second dielectric layer 103B is etched to form a second trench G2 in the second dielectric layer 103B. The etching of the second dielectric layer 103B can be performed using any suitable etching method, such as photolithography or chemical etching. As will be understood, the second trench G2 is an annular trench used to define the horizontal boundary of the acoustic mirror cavity, and the depth of the second trench G2 is consistent with the thickness of the second dielectric layer.

[0087] Finally, as Figure 3F As shown, a second metal bonding layer 1010 is formed in the second trench G2, thereby forming a device substrate assembly.

[0088] like Figure 2D As shown in the illustrated embodiment, the second metal bonding layer 1010 includes a second main body portion 10101 and a second deformable structure 10102 formed on top of the second main body portion 10101. In an exemplary embodiment of the invention, if the material of the second main body portion 10101 of the second metal bonding layer 1010 is the same as the material of the second deformable structure 10102, the second main body portion 10101 of the overall height can be fabricated first by electroplating, and then the deformable structure 10102 can be fabricated by metal etching. If the material of the second main body portion 10101 of the second metal bonding layer 1010 is different from the material of the second deformable structure 10102, the second main body portion 10101 of the overall height can be fabricated first by electroplating, and then the second deformable structure 10102 can be fabricated on the second main body portion 10101 by a lift-off method.

[0089] Third, such as Figure 3G As shown, Figure 3E The auxiliary base component shown and Figure 3F The base components shown are bonded together.

[0090] like Figure 3G As shown in the illustrated embodiment, the bonding process involves bonding the first dielectric layer 103A on the auxiliary substrate assembly to the second dielectric layer 103B on the substrate assembly, and bonding the first metal bonding layer 1020 on the auxiliary substrate assembly to the second metal bonding layer 1010 on the substrate assembly.

[0091] like Figure 3G As shown in the illustrated embodiment, the first and second dielectric layers 103A and 103B located inside the first and second metal bonding layers 1020 and 1010 (i.e., the dielectric layers located below the effective region of the piezoelectric layer 101) are referred to as sacrificial material layers or dielectric layers to be released. These sacrificial material layers will be removed in subsequent steps to form an acoustic mirror cavity.

[0092] Fourth, remove the auxiliary substrate 200 and the insulating layer 201.

[0093] like Figure 3H As shown, the auxiliary substrate 200 is removed. This can be done by grinding and dry etching, in which case the insulating layer 201 protects the piezoelectric layer 101 from damage during this step. Alternatively, a wet process can be used to remove the auxiliary substrate 200. If the process used in this step does not damage the piezoelectric layer 101, the insulating layer 201 is not required (i.e., the insulating layer 201 can be omitted from the initial fabrication).

[0094] like Figure 3I As shown, in Figure 3H Based on the structure, remove the insulating layer 201 (this step can be omitted if there is no insulating layer 201) to expose the piezoelectric layer 101.

[0095] However, regardless of whether the piezoelectric layer 101 is damaged during the removal of the auxiliary substrate 200, the insulating layer 201 can still be provided. A portion of the insulating layer 201 can be retained in the non-effective region of the resonator.

[0096] Fifth, such as Figure 3J As shown, the patterned piezoelectric layer 101.

[0097] Sixth, such as Figure 3K As shown, the first electrode material layer is patterned to form the bottom electrode 102.

[0098] Seventh, such as Figure 3L As shown, an electrical isolation layer 106 is fabricated, which at least covers the end face of the non-electrode connection terminal of the bottom electrode, for electrically isolating the bottom electrode 102 from the top electrode 104 that will be formed subsequently.

[0099] Eighth, such as Figure 3M As shown, a top electrode 104 and a passivation layer 105 covering the top electrode 104 are fabricated.

[0100] Ninth, such as Figure 3N As shown, external leads 107 are fabricated to be electrically connected to the bottom electrode 102 and the top electrode 104, respectively.

[0101] Tenth, such as Figure 3O As shown, the first and second dielectric layers 103A and 103B (i.e., sacrificial material layers or dielectric layers to be released) located inside the first and second metal bonding layers 1020 and 1010 are removed to form the acoustic mirror cavity 1030. Figure 3OAs shown in the illustrated embodiment, the liquid or reactive gas (etchant) used to remove the sacrificial material layer can enter through the release hole 108 and react with the sacrificial material layer. Reaction byproducts flow out from the release hole 108, ultimately forming the acoustic mirror cavity 1030. As will be understood, at least a portion of the first and second dielectric layers 103A and 103B (i.e., the dielectric layers to be released) inside the first and second metal bonding layers 1020 and 1010 can be removed to form the acoustic mirror cavity. Similarly, as will be understood, even if a portion of the dielectric layer to be released is not removed, its thickness is less than the thickness of the dielectric layer (as a support layer) outside the first and second metal bonding layers 1020 and 1010.

[0102] like Figure 3O As shown in the illustrated embodiment, the first and second dielectric layers 103A and 103B located outside the first and second metal bonding layers 1020 and 1010 can also be referred to as support layers. The support layer is horizontally separated from the first and second metal bonding layers 1020 and 1010, which are bonded together with the sacrificial material layer or the dielectric layer to be released. This helps to ensure that the support layer is not damaged when the sacrificial material layer is removed.

[0103] Figure 4 This is a cross-sectional schematic diagram of a bulk acoustic resonator according to another exemplary embodiment of the present invention.

[0104] Figure 4 The bulk acoustic resonator of the embodiment shown is Figure 2B The only difference between the bulk acoustic resonators in the illustrated embodiments is the structure of the metal bonding layer.

[0105] like Figure 4 As shown in the illustrated embodiment, both the first metal bonding layer 1020 and the second metal bonding layer 1010 are divided into two parts. The first metal bonding layer 1020 includes a first metal bonding portion 1020A (i.e., the first inner metal bonding portion) and a second metal bonding portion 1020B (i.e., the first outer metal bonding portion) spaced apart from each other. The second metal bonding layer 1010 includes a third metal bonding portion 1010A (i.e., the second inner metal bonding portion) and a fourth metal bonding portion 1010B (i.e., the second outer metal bonding portion) spaced apart from each other. The first metal bonding portion 1020A corresponds to and is bonded to the third metal bonding portion 1010A. The second metal bonding portion 1020B corresponds to and is bonded to the fourth metal bonding portion 1010B.

[0106] like Figure 4As shown in the illustrated embodiment, the first and third metal bonding portions 1020A and 1010A, bonded together, surround or define the boundary of the acoustic mirror cavity 1030 and isolate the acoustic mirror cavity 1030 from the first and second dielectric layers 103A and 103B. This helps protect the dielectric layer located outside the first and third metal bonding portions 1020A and 1010A from damage when the sacrificial material layer located inside the first and third metal bonding portions 1020A and 1010A is removed.

[0107] like Figure 4 As shown in the illustrated embodiment, the width of the first metal bonding portion 1020A and the third metal bonding portion 1010A in the horizontal direction perpendicular to the thickness direction of the substrate 100 is smaller than the width of the second metal bonding portion 1020B and the fourth metal bonding portion 1010B in the horizontal direction; the width of the second metal bonding portion 1020B and the fourth metal bonding portion 1010B in the horizontal direction is greater than the width of the first metal bonding portion 1020A and the third metal bonding portion 1010A in the horizontal direction.

[0108] The primary purpose of the second and fourth metal bonding portions 1020B and 1010A is bonding; to ensure sufficient bonding strength, their widths are relatively large. The primary purpose of the first and third metal bonding portions 1020A and 1010A is to isolate the sacrificial material layer from the outer dielectric layer when forming the acoustic mirror cavity. Therefore, the widths of the first and third metal bonding portions 1020A and 1010A can be smaller to reduce their interference with the edge of the effective region (potentially creating energy leakage paths).

[0109] In one embodiment of the present invention, the width of the inner metal bonding portion is not less than 5 μm, and the width of the outer metal bonding portion is not less than 8 μm. More specifically, the width of the inner metal bonding portion is in the range of 5-100 μm, while the width of the outer metal bonding portion is in the range of 6-100 μm.

[0110] Figure 4 The bulk acoustic resonator of the embodiment shown is Figure 2B The other technical features of the bulk acoustic resonator in the illustrated embodiment are basically the same, and will not be repeated here for the sake of brevity.

[0111] also, Figure 4 The manufacturing process of the bulk acoustic resonator in the illustrated embodiment can also be referred to Figure 2B The embodiments shown are not described in detail here.

[0112] Although Figure 4In the illustrated embodiment, an inner metal bonding portion and an outer metal bonding portion are provided. However, as will be understood, the outer metal bonding portion may not be limited to one layer, but may be two or more layers.

[0113] exist Figure 4 In the illustrated embodiment, the inner metal bonding portion corresponds to the defining portion that defines the horizontal boundary of the acoustic mirror cavity. Clearly, the dielectric layer is located entirely outside this defining portion in the horizontal direction.

[0114] Figure 5 This is a cross-sectional schematic diagram of a bulk acoustic resonator according to another exemplary embodiment of the present invention.

[0115] Figure 5 The bulk acoustic resonator of the embodiment shown is Figure 2B The only difference between the bulk acoustic resonators in the illustrated embodiments is the structure of the metal bonding layer.

[0116] like Figure 5 As shown in the illustrated embodiment, an inclined first bonding bevel is formed on the top of the first metal bonding layer 1020. An inclined second bonding bevel is formed on the top of the second metal bonding layer 1010. The first bonding bevel and the second bonding bevel engage and can slide relative to each other, and the first bonding bevel and the second bonding bevel are bonded together under pressure.

[0117] like Figure 5 As shown in the illustrated embodiment, since the first bonding bevel on the first metal bonding layer 1020 and the second bonding bevel on the second metal bonding layer 1010 can slide relative to each other, it can be ensured that when the first bonding bevel and the second bonding bevel are bonded together, the first dielectric layer 103A and the second dielectric layer 103B can contact each other and bond together.

[0118] like Figure 5 As shown, in an exemplary embodiment of the present invention, the width of the first metal bonding layer 1020 in the horizontal direction perpendicular to the thickness direction of the substrate 100 may be the same as or different from the width of the second metal bonding layer 1010 in the horizontal direction. For example, in the illustrated embodiment, the width of the first metal bonding layer 1020 in the horizontal direction is greater than the width of the second metal bonding layer 1010 in the horizontal direction. However, the present invention is not limited thereto, and the width of the first metal bonding layer 1020 in the horizontal direction may also be equal to or less than the width of the second metal bonding layer 1010 in the horizontal direction.

[0119] Figure 5 The bulk acoustic resonator of the embodiment shown is Figure 2BThe other technical features of the bulk acoustic resonator in the first embodiment shown are basically the same, and will not be repeated here for the sake of brevity.

[0120] also, Figure 5 The manufacturing process of the bulk acoustic resonator in the illustrated embodiment can also be referred to Figure 2B The first embodiment shown will not be described in detail here.

[0121] Figure 6 A cross-sectional schematic diagram of a bulk acoustic resonator according to another exemplary embodiment of the present invention.

[0122] Figure 6 The bulk acoustic resonator shown in the embodiment is an electric field modulated frequency bulk acoustic resonator (lateral vibration resonant cavity), and its electrode structure differs from that of the traditional bulk acoustic resonator. Figures 1 to 5 The bulk acoustic resonator shown.

[0123] like Figure 6 As shown in the illustrated embodiment, the electric field modulated frequency bulk acoustic resonator includes: a substrate 100, an acoustic mirror cavity 1030, a piezoelectric layer 101, a plurality of first electrodes 301, and a plurality of second electrodes 302. The plurality of first electrodes 301 and the plurality of second electrodes 302 are disposed alternately on the upper surface of the piezoelectric layer 101.

[0124] like Figure 6 As shown in the illustrated embodiment, a first dielectric layer 103A and a first metal bonding layer 1020 are disposed on the bottom surface of the piezoelectric layer 101, arranged in the same layer. A second dielectric layer 103B and a second metal bonding layer 1010 are disposed on the substrate 100, arranged in the same layer. The first dielectric layer 103A and the second dielectric layer 103B correspond to and are bonded together. The first metal bonding layer 1020 and the second metal bonding layer 1010 correspond to and are bonded together.

[0125] like Figure 6 As shown in the illustrated embodiment, the first and second metal bonding layers 1020 and 1010 bonded together isolate the acoustic mirror cavity 1030 from the first and second dielectric layers 103A and 103B.

[0126] It should be noted that the aforementioned Figures 1 to 5 The structures of the metal bonding layers in the illustrated embodiments can all be applied to Figure 6 The electric field modulated frequency bulk acoustic resonator shown is obvious to those skilled in the art. For the sake of brevity, it will not be repeated here, but can be found in [reference needed]. Figures 1 to 5 The example shown.

[0127] In this invention, "upper" and "lower" are relative to the bottom surface of the resonator's base. For a component, the side closer to the bottom surface is the lower side, and the side farther from the bottom surface is the upper side.

[0128] In this invention, for example... Figure 1-5 In the illustrated bulk acoustic resonator, "inner" and "outer" refer to the center (i.e., the effective region center) of the resonator's effective region (the overlapping area of ​​the piezoelectric layer, top electrode, bottom electrode, and acoustic mirror along the thickness direction of the resonator) in the lateral or radial direction. The side or end of a component closer to the center of the effective region is called the inner side or inner end, while the side or end farther from the center of the effective region is called the outer side or outer end. For a reference position, being inside the position indicates being between that position and the center of the effective region in the lateral or radial direction, while being outside the position indicates being farther from the center of the effective region in the lateral or radial direction.

[0129] In this invention, for example... Figure 6 In the illustrated bulk acoustic resonator, "inner" and "outer" refer to the centroid of the acoustic mirror cavity in the top view, in the lateral or radial direction. The side or end of a component closer to the centroid is called the inner side or inner end, while the side or end of the component farther from the centroid is called the outer side or outer end. For a reference position, being inside the position indicates being between that position and the centroid in the lateral or radial direction, while being outside the position indicates being farther from the centroid in the lateral or radial direction.

[0130] As will be understood by those skilled in the art, the bulk acoustic resonator according to the present invention can be used to form filters or other semiconductor devices.

[0131] In the technical solution of the present invention, the method of arranging the metal bonding layer and the dielectric layer in the same layer so that the dielectric layer and the metal bonding layer are flush, and then removing a part of the dielectric layer used to form the cavity of the acoustic mirror, not only proposes a technical solution to fill the horizontal space between the metal bonding layers, but also solves the following technical problem in the transfer piezoelectric layer technology: directly utilizing the space between the metal bonding layers will first form a cavity, resulting in poor mechanical strength.

[0132] Furthermore, by employing the technical solution of this invention, no metal is exposed after the bonding step is performed, thus solving the technical problem in the prior art that "most equipment, such as deposition and etching equipment, does not allow exposed bonding metal to enter, which imposes many restrictions on subsequent processes."

[0133] Based on the above, the present invention proposes the following technical solution:

[0134] 1. A bulk acoustic resonator, comprising:

[0135] A resonant structure, the resonant structure comprising a piezoelectric layer and electrodes disposed on the piezoelectric layer;

[0136] Base;

[0137] Acoustic mirror cavity, positioned between the resonant structure and the substrate; and

[0138] A dielectric layer and a metal bonding layer, both of the same thickness, are disposed between the resonant structure and the substrate.

[0139] in:

[0140] The metal bonding layer includes a defining portion that defines the horizontal boundary of the acoustic mirror cavity, and the dielectric layer is located outside the defining portion in the horizontal direction.

[0141] 2. The bulk acoustic resonator according to 1, wherein:

[0142] The metal bonding layer includes a single metal bonding layer, which is the defined portion. The inner side of the single metal bonding layer in the horizontal direction is the acoustic mirror cavity, and the outer side of the single metal bonding layer in the horizontal direction is the dielectric layer.

[0143] 3. The bulk acoustic resonator according to 1, wherein:

[0144] The metal bonding layer includes an inner metal bonding layer and an outer metal bonding layer, wherein the inner metal bonding layer is the defined portion;

[0145] The dielectric layer includes an inner dielectric layer located between the inner and outer metal layers in the horizontal direction, and an outer dielectric layer located outside the outer metal layer in the horizontal direction.

[0146] 4. The bulk acoustic resonator according to 3, wherein:

[0147] The width of the inner metal bonding layer in the horizontal direction is smaller than the width of the outer metal bonding layer in the horizontal direction.

[0148] 5. The bulk acoustic resonator according to 4, wherein:

[0149] The width of the inner metal bonding layer is not less than 5 μm, and the width of the outer metal bonding layer is not less than 6 μm.

[0150] 6. The bulk acoustic resonator according to 5, wherein:

[0151] The width of the inner metal bonding layer is no greater than 100 μm, and the width of the outer metal bonding layer is no greater than 100 μm.

[0152] 7. The bulk acoustic resonator according to claim 1, wherein:

[0153] The metal bonding layer includes a first bonding metal portion disposed on one side of the resonant structure and a second bonding metal portion disposed on one side of the substrate, and the dielectric layer includes a first dielectric portion disposed on one side of the resonant structure and a second dielectric portion disposed on one side of the substrate.

[0154] The first dielectric portion corresponds to and is bonded together with the second dielectric portion, and the first metal bonding portion corresponds to and is bonded together with the second metal bonding portion.

[0155] 8. The bulk acoustic resonator according to 7, wherein:

[0156] The first metal bonding portion includes a first main body portion and a first deformable structure, the first deformable structure being formed on the flat top surface of the first main body portion;

[0157] The second metal bonding portion includes a second main body portion and a second deformable structure, the second deformable structure being formed on the flat top surface of the second main body portion;

[0158] The first deformable structure and the second deformable structure are adapted to fit together and bond together.

[0159] 9. The bulk acoustic resonator according to 8, wherein:

[0160] The first deformable structure includes a plurality of first protrusions spaced apart from each other formed on the flat top surface of the first body portion;

[0161] The second deformable structure includes a plurality of second protrusions spaced apart from each other formed on the flat top surface of the second body portion;

[0162] The plurality of first protrusions and the plurality of second protrusions engage with each other and are bonded together in an engaged state.

[0163] 10. The bulk acoustic resonator according to claim 8, wherein:

[0164] The height of the first main body portion is less than the height of the first medium portion, resulting in a first height difference between the first medium portion and the first main body portion; and

[0165] The height of the second main body portion is less than the height of the second medium portion, resulting in a second height difference between the second medium portion and the second main body portion.

[0166] 11. The bulk acoustic resonator according to 8, wherein:

[0167] The material of the first main body portion may be the same as or different from the material of the first deformable structure; and / or

[0168] The material of the second main body may be the same as or different from the material of the second deformable structure.

[0169] 12. The bulk acoustic resonator according to 7, wherein:

[0170] A first bonding slope is formed on the top of the first metal bonding portion, and a second bonding slope is formed on the top of the second metal bonding portion. The slopes of the first bonding slope and the second bonding slope are the same.

[0171] The first bonding bevel engages with the second bonding bevel and can slide relative to each other. The first bonding bevel and the second bonding bevel bond together under pressure.

[0172] 13. The bulk acoustic resonator according to 12, wherein:

[0173] The width of the first bonding bevel is different from the width of the second bonding bevel.

[0174] 14. The bulk acoustic resonator according to claim 1, wherein:

[0175] The bulk acoustic resonator further includes a release hole that extends through at least a piezoelectric layer of the resonant structure along the thickness direction of the resonator to communicate with the acoustic mirror cavity.

[0176] 15. The bulk acoustic resonator according to claim 1, wherein:

[0177] The piezoelectric layer is a single-crystal piezoelectric layer.

[0178] 16. The bulk acoustic resonator according to any one of 1-15, wherein:

[0179] The electrodes of the resonant structure include a top electrode and a bottom electrode, and the piezoelectric layer is located between the top electrode and the bottom electrode in the thickness direction of the resonator;

[0180] The dielectric layer and the metal bonding layer are disposed in the same layer between the bottom electrode and the substrate of the resonant structure.

[0181] 17. The bulk acoustic resonator according to 16, wherein:

[0182] The bulk acoustic resonator further includes an electrical isolation layer disposed between the bottom electrode and the top electrode, the electrical isolation layer at least covering the end of the non-electrode connection terminal of the bottom electrode to electrically isolate the bottom electrode and the top electrode.

[0183] 18. The bulk acoustic resonator according to any one of 1-15, wherein:

[0184] The electrodes of the resonant structure include a plurality of first electrodes and a plurality of second electrodes, wherein the first electrodes and the second electrodes are alternately disposed on one side of the piezoelectric layer.

[0185] The dielectric layer and the metal bonding layer are disposed in the same layer between the piezoelectric layer and the substrate of the resonant structure.

[0186] 19. A method for manufacturing a bulk acoustic resonator, comprising the following steps:

[0187] An auxiliary substrate assembly is provided, the auxiliary substrate assembly including an auxiliary substrate and a piezoelectric layer disposed on the auxiliary substrate, the piezoelectric layer having a first surface facing the auxiliary substrate and a second surface opposite to the first surface in the thickness direction of the piezoelectric layer, and a first release medium layer, a first metal bonding layer and a first dielectric layer arranged in the same layer are formed on one side of the second surface of the piezoelectric layer of the auxiliary substrate assembly, the first metal bonding layer being located between the first release medium layer and the first dielectric layer in the horizontal direction;

[0188] A device substrate assembly is provided, the device substrate assembly including a device substrate and a second release dielectric layer, a second metal bonding layer and a second dielectric layer disposed on the same layer on one side of the device substrate, wherein the second metal bonding layer is located horizontally between the second release dielectric layer and the second dielectric layer.

[0189] The auxiliary substrate assembly and the device substrate assembly are bonded to each other, that is, the first release dielectric layer, the first metal bonding layer and the first dielectric layer of the auxiliary substrate assembly are respectively bonded to the second release dielectric layer, the second metal bonding layer and the second dielectric layer of the device substrate assembly, wherein the first metal bonding layer and the second metal bonding layer are bonded to each other.

[0190] Remove the entire auxiliary substrate to expose at least a portion of the first surface of the piezoelectric layer;

[0191] The electrode structure of the bulk acoustic resonator is formed;

[0192] The first and second dielectric layers to be released are released to form the acoustic mirror cavity of the bulk acoustic resonator, wherein the first and second metal bonding layers together define the horizontal boundary of the acoustic mirror cavity.

[0193] 20. According to the method described in 19, wherein:

[0194] The first release dielectric layer, the first metal bonding layer, and the first dielectric layer, arranged in the same layer, are formed by the following steps: forming a first dielectric material layer on one side of the second surface of the piezoelectric layer of the auxiliary substrate assembly; etching the first dielectric material layer to form a first trench, the first trench horizontally dividing the first dielectric material layer into the first release dielectric layer and the first dielectric layer; forming a first metal bonding layer within the first trench, wherein the depth of the first trench is the same as the thickness of the first dielectric material layer; and

[0195] The steps of “providing a device substrate assembly” include: forming a second dielectric material layer on one side of a device substrate; etching the second dielectric material layer to form a second trench, the second trench dividing the second dielectric material layer into a second release dielectric layer and a second dielectric layer in a horizontal direction; and forming a second metal bonding layer in the second trench, wherein the depth of the second trench is the same as the thickness of the second dielectric material layer.

[0196] 21. According to the method described in 20, wherein:

[0197] The first dielectric layer is the first inner dielectric layer, and the second dielectric layer is the second inner dielectric layer;

[0198] The first release dielectric layer, the first metal bonding layer, and the first dielectric layer, arranged in the same layer, are formed by the following steps: forming a first dielectric material layer on one side of the second surface of the piezoelectric layer of the auxiliary substrate assembly; etching the first dielectric material layer to form a first trench and a third trench spaced apart in the horizontal direction, the first trench and the third trench dividing the first dielectric material layer from the inside to the outside in the horizontal direction into the first release dielectric layer, the first inner dielectric layer, and the first outer dielectric layer; forming a first metal bonding layer in the first trench and a third metal bonding layer in the third trench, wherein the depth of the third trench is the same as the thickness of the first dielectric material layer;

[0199] The steps of “providing a device substrate assembly” include: forming a second dielectric material layer on one side of the device substrate; etching the second dielectric material layer to form a second trench and a fourth trench spaced apart in a horizontal direction, the second trench and the fourth trench dividing the second dielectric material layer from the inside to the outside in the horizontal direction into a second release dielectric layer, a second inner dielectric layer and a second outer dielectric layer; forming a second metal bonding layer in the second trench and forming a fourth metal bonding layer in the fourth trench, wherein the depth of the fourth trench is the same as the thickness of the second dielectric material layer;

[0200] "Bonding the auxiliary substrate assembly to the device substrate assembly" includes bonding the first release dielectric layer, the first metal bonding layer, the first inner dielectric layer, the third metal bonding layer, and the first outer dielectric layer of the auxiliary substrate assembly to the second release dielectric layer, the second metal bonding layer, the second inner dielectric layer, the fourth metal bonding layer, and the second outer dielectric layer of the device substrate assembly, respectively, wherein the first metal bonding layer and the second metal bonding layer are bonded to each other, and the third metal bonding layer and the fourth metal bonding layer are bonded to each other.

[0201] 22. According to the method described in 21, wherein:

[0202] This makes the width of the third groove in the horizontal direction greater than the width of the first groove in the horizontal direction; and

[0203] This makes the width of the fourth groove in the horizontal direction greater than the width of the second groove in the horizontal direction.

[0204] 23. According to the method described in 19, wherein:

[0205] The auxiliary substrate assembly further includes an insulating layer formed between the auxiliary substrate and the piezoelectric layer;

[0206] "Removing the entire auxiliary substrate to expose at least a portion of the first surface of the piezoelectric layer" includes the steps of: removing at least a portion of the insulating layer to expose at least a portion of the first surface of the piezoelectric layer after removing the auxiliary substrate, or while removing the auxiliary substrate.

[0207] 24. According to the method described in 19, wherein:

[0208] The piezoelectric layer is a single-crystal piezoelectric layer.

[0209] 25. The method according to any one of 19-24, wherein:

[0210] The bulk acoustic resonator includes a top electrode, a bottom electrode, and a piezoelectric layer disposed between the top electrode and the bottom electrode;

[0211] The second surface of the piezoelectric layer of the auxiliary substrate assembly is provided with a first electrode material layer, and a first release dielectric layer, a first metal bonding layer and a first dielectric layer are arranged on one side of the first electrode material layer.

[0212] The step of “forming the electrode structure of the bulk acoustic resonator” includes: patterning the first electrode material layer to form the bottom electrode, and forming the top electrode on at least a portion of the first surface of the piezoelectric layer.

[0213] 26. According to the method described in 25, wherein:

[0214] Before “forming the top electrode on at least a portion of the first surface of the piezoelectric layer”, the method includes the step of: providing an electrical isolation layer that covers at least the end of the non-electrode connection terminal of the bottom electrode, the electrical isolation layer being used to electrically isolate the bottom electrode and the top electrode.

[0215] 27. The method according to any one of 19-24, wherein:

[0216] The bulk acoustic resonator includes a plurality of first electrodes and a plurality of second electrodes, wherein the first electrodes and the second electrodes are disposed alternately on the second surface of the piezoelectric layer.

[0217] The step of “forming the electrode structure of the bulk acoustic resonator” includes: the plurality of first electrodes and the plurality of second electrodes on the upper side of at least a portion of the first surface of the piezoelectric layer.

[0218] 28. A filter comprising a bulk acoustic resonator according to any one of 1-18.

[0219] 29. An electronic device comprising the filter according to claim 28, or the bulk acoustic resonator according to any one of claims 1-18.

[0220] The electronic devices mentioned here include, but are not limited to, intermediate products such as radio frequency front-ends and filtering and amplification modules, as well as terminal products such as mobile phones, WIFI, and drones.

[0221] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that variations may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A bulk acoustic resonator, comprising: A resonant structure, the resonant structure comprising a piezoelectric layer and electrodes disposed on the piezoelectric layer; Base; An acoustic mirror cavity is positioned between the resonant structure and the substrate; and A dielectric layer and a metal bonding layer, both of the same thickness, are disposed between the resonant structure and the substrate. in: The metal bonding layer includes a defining portion that defines the horizontal boundary of the acoustic mirror cavity, and the dielectric layer is located outside the defining portion in the horizontal direction. The bulk acoustic resonator also includes a release hole that extends through at least the piezoelectric layer of the resonant structure along the thickness direction of the resonator and communicates with the acoustic mirror cavity.

2. The bulk acoustic resonator according to claim 1, wherein: The metal bonding layer includes a single metal bonding layer, which is the defined portion. The inner side of the single metal bonding layer in the horizontal direction is the acoustic mirror cavity, and the outer side of the single metal bonding layer in the horizontal direction is the dielectric layer.

3. The bulk acoustic resonator according to claim 1, wherein: The metal bonding layer includes an inner metal bonding layer and an outer metal bonding layer, wherein the inner metal bonding layer is the defined portion; The dielectric layer includes an inner dielectric layer located between the inner and outer metal layers in the horizontal direction, and an outer dielectric layer located outside the outer metal layer in the horizontal direction.

4. The bulk acoustic resonator according to claim 3, wherein: The width of the inner metal bonding layer in the horizontal direction is smaller than the width of the outer metal bonding layer in the horizontal direction.

5. The bulk acoustic resonator according to claim 4, wherein: The width of the inner metal bonding layer is not less than 5 μm, and the width of the outer metal bonding layer is not less than 6 μm.

6. The bulk acoustic resonator according to claim 5, wherein: The width of the inner metal bonding layer is no greater than 100 μm, and the width of the outer metal bonding layer is no greater than 100 μm.

7. The bulk acoustic resonator according to claim 1, wherein: The metal bonding layer includes a first metal bonding portion disposed on one side of the resonant structure and a second metal bonding portion disposed on one side of the substrate, and the dielectric layer includes a first dielectric portion disposed on one side of the resonant structure and a second dielectric portion disposed on one side of the substrate. The first dielectric portion corresponds to and is bonded together with the second dielectric portion, and the first metal bonding portion corresponds to and is bonded together with the second metal bonding portion.

8. The bulk acoustic resonator according to claim 7, wherein: The first metal bonding portion includes a first main body portion and a first deformable structure, the first deformable structure being formed on the flat top surface of the first main body portion; The second metal bonding portion includes a second main body portion and a second deformable structure, the second deformable structure being formed on the flat top surface of the second main body portion; The first deformable structure and the second deformable structure are adapted to fit together and bond together.

9. The bulk acoustic resonator according to claim 8, wherein: The first deformable structure includes a plurality of first protrusions spaced apart from each other formed on the flat top surface of the first body portion; The second deformable structure includes a plurality of second protrusions spaced apart from each other formed on the flat top surface of the second body portion; The plurality of first protrusions and the plurality of second protrusions engage with each other and are bonded together in an engaged state.

10. The bulk acoustic resonator according to claim 8, wherein: The height of the first main body portion is less than the height of the first medium portion, resulting in a first height difference between the first medium portion and the first main body portion; and The height of the second main body portion is less than the height of the second medium portion, resulting in a second height difference between the second medium portion and the second main body portion.

11. The bulk acoustic resonator according to claim 8, wherein: The material of the first main body portion may be the same as or different from the material of the first deformable structure; and / or The material of the second main body may be the same as or different from the material of the second deformable structure.

12. The bulk acoustic resonator according to claim 7, wherein: A first bonding slope is formed on the top of the first metal bonding portion, and a second bonding slope is formed on the top of the second metal bonding portion. The slopes of the first bonding slope and the second bonding slope are the same. The first bonding bevel engages with the second bonding bevel and can slide relative to each other. The first bonding bevel and the second bonding bevel bond together under pressure.

13. The bulk acoustic resonator according to claim 12, wherein: The width of the first bonding bevel is different from the width of the second bonding bevel.

14. The bulk acoustic resonator according to claim 1, wherein: The piezoelectric layer is a single-crystal piezoelectric layer.

15. The bulk acoustic resonator according to any one of claims 1-14, wherein: The electrodes of the resonant structure include a top electrode and a bottom electrode, and the piezoelectric layer is located between the top electrode and the bottom electrode in the thickness direction of the resonator; The dielectric layer and the metal bonding layer are disposed in the same layer between the bottom electrode and the substrate of the resonant structure.

16. The bulk acoustic resonator according to claim 15, wherein: The bulk acoustic resonator further includes an electrical isolation layer disposed between the bottom electrode and the top electrode, the electrical isolation layer at least covering the end of the non-electrode connection terminal of the bottom electrode to electrically isolate the bottom electrode and the top electrode.

17. The bulk acoustic resonator according to any one of claims 1-14, wherein: The electrodes of the resonant structure include a plurality of first electrodes and a plurality of second electrodes, wherein the first electrodes and the second electrodes are alternately disposed on one side of the piezoelectric layer. The dielectric layer and the metal bonding layer are disposed in the same layer between the piezoelectric layer and the substrate of the resonant structure.

18. A method for manufacturing a bulk acoustic resonator, comprising the steps of: An auxiliary substrate assembly is provided, the auxiliary substrate assembly including an auxiliary substrate and a piezoelectric layer disposed on the auxiliary substrate, the piezoelectric layer having a first surface facing the auxiliary substrate and a second surface opposite to the first surface in the thickness direction of the piezoelectric layer, and a first release medium layer, a first metal bonding layer and a first dielectric layer arranged in the same layer are formed on one side of the second surface of the piezoelectric layer of the auxiliary substrate assembly, the first metal bonding layer being located between the first release medium layer and the first dielectric layer in the horizontal direction; A device substrate assembly is provided, the device substrate assembly including a device substrate and a second release dielectric layer, a second metal bonding layer and a second dielectric layer disposed on the same layer on one side of the device substrate, wherein the second metal bonding layer is located horizontally between the second release dielectric layer and the second dielectric layer. The auxiliary substrate assembly and the device substrate assembly are bonded to each other, that is, the first release dielectric layer, the first metal bonding layer and the first dielectric layer of the auxiliary substrate assembly are respectively bonded to the second release dielectric layer, the second metal bonding layer and the second dielectric layer of the device substrate assembly, wherein the first metal bonding layer and the second metal bonding layer are bonded to each other. Remove the entire auxiliary substrate to expose at least a portion of the first surface of the piezoelectric layer; The electrode structure of the bulk acoustic resonator is formed; The first and second dielectric layers to be released are released to form the acoustic mirror cavity of the bulk acoustic resonator, wherein the first and second metal bonding layers together define the horizontal boundary of the acoustic mirror cavity.

19. The method of claim 18, wherein: The first release dielectric layer, the first metal bonding layer, and the first dielectric layer, arranged in the same layer, are formed by the following steps: forming a first dielectric material layer on one side of the second surface of the piezoelectric layer of the auxiliary substrate assembly; The first dielectric material layer is etched to form a first trench, the first trench dividing the first dielectric material layer into a first release dielectric layer and a first dielectric layer in the horizontal direction; A first metal bonding layer is formed in the first trench, wherein the depth of the first trench is the same as the thickness of the first dielectric material layer; and The steps of "providing a device substrate assembly" include: forming a second dielectric material layer on one side of a device substrate; etching the second dielectric material layer to form a second trench, the second trench dividing the second dielectric material layer into a second release dielectric layer and a second dielectric layer in a horizontal direction; and forming a second metal bonding layer in the second trench, wherein the depth of the second trench is the same as the thickness of the second dielectric material layer.

20. The method of claim 18, wherein: The first dielectric layer is the first inner dielectric layer, and the second dielectric layer is the second inner dielectric layer; The first release dielectric layer, the first metal bonding layer, and the first dielectric layer, arranged in the same layer, are formed by the following steps: forming a first dielectric material layer on one side of the second surface of the piezoelectric layer of the auxiliary substrate assembly; The first dielectric material layer is etched to form a first trench and a third trench spaced apart in the horizontal direction. The first trench and the third trench divide the first dielectric material layer from the inside to the outside in the horizontal direction into a first dielectric layer to be released, a first inner dielectric layer, and a first outer dielectric layer. A first metal bonding layer is formed in the first trench, and a third metal bonding layer is formed in the third trench, wherein the depth of the third trench is the same as the thickness of the first dielectric material layer. The step of "providing a device substrate assembly" includes: forming a second dielectric material layer on one side of the device substrate; The second dielectric material layer is etched to form a second trench and a fourth trench spaced apart in the horizontal direction. The second trench and the fourth trench divide the second dielectric material layer from the inside to the outside in the horizontal direction into a second dielectric layer to be released, a second inner dielectric layer and a second outer dielectric layer. A second metal bonding layer is formed in the second trench and a fourth metal bonding layer is formed in the fourth trench, wherein the depth of the fourth trench is the same as the thickness of the second dielectric material layer. "Bonding the auxiliary substrate assembly to the device substrate assembly" includes bonding the first release dielectric layer, the first metal bonding layer, the first inner dielectric layer, the third metal bonding layer, and the first outer dielectric layer of the auxiliary substrate assembly to the second release dielectric layer, the second metal bonding layer, the second inner dielectric layer, the fourth metal bonding layer, and the second outer dielectric layer of the device substrate assembly, respectively, wherein the first metal bonding layer and the second metal bonding layer are bonded to each other, and the third metal bonding layer and the fourth metal bonding layer are bonded to each other.

21. The method of claim 20, wherein: This makes the width of the third groove in the horizontal direction greater than the width of the first groove in the horizontal direction; and This makes the width of the fourth groove in the horizontal direction greater than the width of the second groove in the horizontal direction.

22. The method according to claim 18, wherein: The auxiliary substrate assembly further includes an insulating layer formed between the auxiliary substrate and the piezoelectric layer; "Removing the entire auxiliary substrate to expose at least a portion of the first surface of the piezoelectric layer" includes the steps of: removing at least a portion of the insulating layer to expose at least a portion of the first surface of the piezoelectric layer after removing the auxiliary substrate, or while removing the auxiliary substrate.

23. The method of claim 18, wherein: The piezoelectric layer is a single-crystal piezoelectric layer.

24. The method according to any one of claims 18-23, wherein: The bulk acoustic resonator includes a top electrode, a bottom electrode, and a piezoelectric layer disposed between the top electrode and the bottom electrode; The second surface of the piezoelectric layer of the auxiliary substrate assembly is provided with a first electrode material layer, and a first release dielectric layer, a first metal bonding layer and a first dielectric layer are arranged on one side of the first electrode material layer. The step of "forming the electrode structure of the bulk acoustic resonator" includes: patterning the first electrode material layer to form the bottom electrode, and forming the top electrode on at least a portion of the first surface of the piezoelectric layer.

25. The method according to claim 24, wherein: Before "forming the top electrode on at least a portion of the first surface of the piezoelectric layer", the method includes the step of: providing an electrical isolation layer that covers at least the end of the non-electrode connection terminal of the bottom electrode, the electrical isolation layer being used to electrically isolate the bottom electrode and the top electrode.

26. The method according to any one of claims 18-23, wherein: The bulk acoustic resonator includes a plurality of first electrodes and a plurality of second electrodes, wherein the first electrodes and the second electrodes are disposed alternately on the second surface of the piezoelectric layer. The step of "forming the electrode structure of the bulk acoustic resonator" includes: the plurality of first electrodes and the plurality of second electrodes on the upper side of at least a portion of the first surface of the piezoelectric layer.

27. A filter comprising a bulk acoustic resonator according to any one of claims 1-17.

28. An electronic device comprising the filter of claim 27, or the bulk acoustic resonator of any one of claims 1-17.

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