Single crystal piezoelectric bulk acoustic resonator, filter, and electronic device

Abstract

The present application relates to a bulk acoustic wave resonator, comprising: a substrate; an acoustic mirror cavity; a bottom electrode; a top electrode; and a single-crystal piezoelectric layer disposed between the bottom electrode and the top electrode, wherein: a support structure is disposed between a lower surface of the piezoelectric layer and an upper surface of the substrate, the piezoelectric layer and the substrate are arranged substantially in parallel; a lower passivation layer is disposed on a lower side of the bottom electrode, the lower passivation layer covers at least a portion of a surface of the bottom electrode within the cavity; and a boundary of the lower passivation layer is inside a boundary of the piezoelectric layer in a horizontal direction. The piezoelectric layer is a single-crystal lithium niobate piezoelectric layer or a single-crystal lithium tantalate piezoelectric layer. The present application 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 single-crystal piezoelectric acoustic resonator, a filter having the resonator, and an electronic device. Background Technology

[0002] In recent years, silicon-based semiconductor devices, especially integrated circuit chips, have developed rapidly and firmly occupied a mainstream position in the industry. MEMS semiconductor devices, including bulk acoustic wave (BAW) filters, are among the most commonly used semiconductor devices. MEMS devices typically have movable units, requiring a cavity-type packaging structure to ensure their normal operation. Taking BAW filters as an example, they are composed of many series and parallel resonators. The core unit of the BAW resonator is a suspended piezoelectric thin film, whose lateral dimensions are mostly on the order of micrometers, and whose film thickness is mostly on the order of nanometers. Therefore, BAW filters are fragile and highly sensitive to the environment; even water molecules in the air can interact with the semiconductor device surface, leading to performance degradation. Therefore, protecting thin-film BAW filters is extremely important.

[0003] In existing technologies, protection is achieved by depositing a passivation layer on the surface of the top electrode and the lower surface of the bottom electrode of the resonator, such as... Figure 1 As shown, 01 is the substrate, 02 is the acoustic mirror cavity, 03 is the passivation layer below the bottom electrode, 04 is the bottom electrode, 05 is the piezoelectric layer, 06 is the top electrode, and 07 is the passivation layer on the top electrode. The material of the passivation layer below the bottom electrode is chosen to match the crystal orientation of the piezoelectric layer to promote a better crystal orientation in the grown piezoelectric layer. While the passivation layer below the bottom electrode protects it and prevents the resonator from being affected by the external environment, the fact that the passivation layers in the effective and ineffective regions of the resonator are connected causes energy leakage from the effective region to the ineffective region, thus reducing the resonator's performance. Furthermore, as... Figure 1 The fully extended passivation layer shown can impair the sealing between the resonator diaphragm layers, thus reducing the reliability of the resonator. This is because moisture in the environment or corrosive gases / liquids during the manufacturing process can gradually corrode the resonator. Figure 1 The passivation layer 03 causes the piezoelectric layer 05 to separate from the substrate 01.

[0004] Furthermore, in traditional thin-film bulk acoustic resonators fabricated from the bottom up using thin-film sputtering of piezoelectric thin films, the passivation layer (e.g., on the lower surface of the lower electrode) Figure 1 The passivation layer 03 in the film also plays a role in assisting the optimized growth of the piezoelectric thin film crystal phase. Therefore, the material and thickness of the passivation layer 03 are subject to great restrictions (such as needing to match the crystal lattice of the piezoelectric thin film and having a thickness of less than 50 nanometers). Summary of the Invention

[0005] The present invention is proposed to alleviate or solve at least one of the above-mentioned problems in the prior art.

[0006] According to one aspect of an embodiment of the present invention, a bulk acoustic resonator is provided, comprising:

[0007] Base;

[0008] Acoustic mirror;

[0009] Bottom electrode;

[0010] Top electrode; and

[0011] A single-crystal piezoelectric layer is disposed between the bottom electrode and the top electrode.

[0012] in:

[0013] A support structure is provided between the lower surface of the piezoelectric layer and the upper surface of the substrate, and the piezoelectric layer and the substrate are arranged in a generally parallel manner.

[0014] A lower passivation layer is provided on the lower side of the bottom electrode, and the lower passivation layer covers at least a portion of the surface of the bottom electrode within the cavity; and

[0015] The boundary of the lower passivation layer is located inside the boundary of the piezoelectric layer in the horizontal direction.

[0016] Embodiments of the present invention also relate to a filter, including the resonator described above.

[0017] Embodiments of the present invention also relate to an electronic device, including the filter or the resonator described above. Attached Figure Description

[0018] 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:

[0019] Figure 1 This is a schematic cross-sectional view of a bulk acoustic resonator in the prior art.

[0020] Figure 2-9 These are schematic cross-sectional views of bulk acoustic resonators according to different exemplary embodiments of the present invention;

[0021] Figure 10 This is a schematic cross-sectional view of a bulk acoustic resonator according to an exemplary embodiment of the present invention, showing the insulating layer. Detailed Implementation

[0022] 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.

[0023] This invention proposes a single-crystal thin-film acoustic resonator structure that, while protecting the bottom electrode of the resonator, minimizes or reduces any adverse effects on the resonator's performance.

[0024] First, the reference numerals in the accompanying drawings of this invention are explained as follows:

[0025] 100: Substrate, the specific material can be silicon, silicon carbide, sapphire, silicon dioxide, or other silicon-based materials.

[0026] 101: Support layer or support material layer, the material can be aluminum nitride, silicon nitride, polycrystalline silicon, silicon dioxide, amorphous silicon, boron-doped silicon dioxide and other silicon-based materials, etc.

[0027] 102: Acoustic mirror cavity.

[0028] 103: Passivation layer, the material of which can be crystalline or amorphous, including silicon dioxide (SiO2), silicon nitride (Si3N4), aluminum nitride (AlN), aluminum oxide (Al2O3), magnesium oxide (MgO), zirconium oxide (ZrO2), piezoelectric ceramic PZT, gallium arsenide (GaAs), halogen oxide (HfO2), titanium dioxide (TiO2), zinc oxide (ZnO), etc.

[0029] 104: Bottom electrode, materials can be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or composites of the above metals or their alloys, etc.

[0030] 105: Single-crystal piezoelectric layer, which is a single-crystal lithium niobate piezoelectric layer or a single-crystal lithium tantalate piezoelectric layer.

[0031] 106: Top electrode. Materials can include molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or composites or alloys of these metals. The material of the top electrode can be the same as or different from that of the bottom electrode.

[0032] 107: Passivation layer, which is generally a dielectric material, such as silicon dioxide, aluminum nitride, silicon nitride, etc.

[0033] 108: Top electrode electrical connection part, the material can be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or composites of the above metals or their alloys, etc. The material of the top electrode electrical connection part can be the same as or different from the top electrode.

[0034] 109: Bottom electrode lead-out section, the material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite of the above metals or their alloys, etc. The material of the bottom electrode electrical connection section can be the same as or different from that of the top electrode.

[0035] 110: Bottom electrode electrical connection part, the material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite of the above metals or their alloys, etc. The material of the bottom electrode electrical connection part can be the same as or different from that of the top electrode.

[0036] 111, 113: Bridge structures that define gap layers 112 and 114, respectively.

[0037] 112, 114: Gap layers, defined by bridge structures 111 and 113 respectively, can be air gaps, vacuum gaps, or non-conductive dielectric layers.

[0038] 115, 117: Cantilever structures, which define void layers 116 and 118, respectively.

[0039] 116, 118: Void layers, defined by cantilever structures 115 and 117, respectively.

[0040] 119, 121: Protruding structure.

[0041] 120, 122: Concave structure.

[0042] 123: Insulating layer, which serves as an electrical insulation layer, such as silicon dioxide.

[0043] In this invention, a bulk acoustic wave resonator is fabricated based on a POI (Piezoelectrics on Insulator) substrate. The POI substrate includes an auxiliary substrate, a single-crystal piezoelectric layer, and an insulating layer disposed between the single-crystal piezoelectric layer and the auxiliary substrate.

[0044] During the resonator transfer process, the insulating layer can better protect the single-crystal piezoelectric film (i.e., the single-crystal piezoelectric layer), thereby reducing or even avoiding damage to the single-crystal piezoelectric film during the subsequent removal of the auxiliary substrate, reducing or even avoiding surface damage to the piezoelectric film, so as to obtain a high-performance bulk acoustic resonator.

[0045] Furthermore, the presence of insulating layer 123 facilitates the diversification of substrate removal methods and simplifies device fabrication processes. Insulating layer 123 can also be partially retained, for example, see [reference needed]. Figure 10 In this invention, outside the effective region, at least a portion of the upper surface of the piezoelectric layer 105 is provided with an insulating layer 123. More specifically, in Figure 10 In the middle, outside the effective area, an insulating layer 123 is provided between the top electrode and the piezoelectric layer.

[0046] In this invention, since the fabrication process of the single-crystal thin-film acoustic resonator involves bonding the single-crystal piezoelectric layer 105 to the support layer 101, the passivation layer 103 on the lower surface of the bottom electrode 104 does not need to function as... Figure 1 The auxiliary role of the structure shown allows for greater freedom in the choice of the material and thickness of the passivation layer.

[0047] In an exemplary embodiment of the present invention, the material of the passivation layer 103 can be selected such that the lattice of the passivation layer 103 is mismatched with that of the piezoelectric layer 105. Here, lattice mismatch means that the lattice constants of the two thin film layers are different. For resonators in conventional technology, if the seed layer under the bottom electrode and the piezoelectric layer material are lattice mismatched, that is, the lattice constants of the two thin films are different, stress will be generated near the growth interface, which will lead to crystal defects and thus affect the performance of the device. Therefore, the choice of seed layer material is limited for resonators fabricated by conventional technology, while there are no restrictions on the choice of passivation layer material in the present invention.

[0048] In one exemplary embodiment of the present invention, the thickness of the passivation layer 103 can be selected to be in the range of 10 nanometers to 1000 nanometers, and more specifically, in the range of 50 nanometers to 500 nanometers. This thickness range helps to protect the resonator without affecting its performance.

[0049] Based on the above selection of a passivation layer 103 that does not match the lattice of the piezoelectric layer 105, and / or the selection of the thickness of the passivation layer 103 to be in the range of 10 nanometers to 1000 nanometers, and further, in the range of 50 nanometers to 500 nanometers, this reduces the limitations on the material and thickness of the passivation layer 103.

[0050] Figure 2 The diagram shown is a cross-sectional schematic of a single-crystal thin-film acoustic resonator according to an exemplary embodiment of the present invention. Figure 2 In the embodiment shown, the passivation layer 103 is located below the bottom electrode 104 and has the same area as the lower surface of the bottom electrode, thus protecting the bottom electrode and preventing or reducing its contamination or damage from the external environment. Furthermore, since the passivation layer is only located on the lower surface of the bottom electrode and does not extend to one side (…),… Figure 2 (middle is left) extends (in) Figure 2The passivation layer extends to the left into the non-effective region, thus reducing the loss of acoustic energy through the passivation layer into the non-effective region, which is beneficial to improving the performance of the single-crystal thin-film acoustic resonator. Moreover, since there is no passivation layer between the piezoelectric layer and the support layer in the film structure of the non-effective regions on both sides of the single-crystal thin-film acoustic resonator, the sealing and stability of the device are more reliable, allowing the single-crystal thin-film acoustic resonator to be used in more complex environments.

[0051] Figure 3 The diagram shown is a cross-sectional schematic of a single-crystal thin-film acoustic resonator according to another exemplary embodiment of the present invention. Figure 3 The structure shown is the same as Figure 2 They are basically the same, the difference being: Figure 2 In the illustrated embodiment, the passivation layer 103 not only covers the lower surface of the bottom electrode 104 but also completely encloses both sides of the bottom electrode, thus better protecting the bottom electrode from the influence of the external environment. Similarly, since the passivation layer does not extend to one side ( Figure 3 (middle is left) extends (in) Figure 3 The passivation layer extends to the left into the non-effective region, thus reducing the loss of acoustic energy through the passivation layer into the non-effective region, which is beneficial to improving the performance of the single-crystal thin-film acoustic resonator. Moreover, since there is no passivation layer between the piezoelectric layer and the support layer in the film structure of the non-effective regions on both sides of the single-crystal thin-film acoustic resonator, the sealing and stability of the device are more reliable, allowing the single-crystal thin-film acoustic resonator to be used in more complex environments.

[0052] Figure 4 The diagram shown is a cross-sectional schematic of a single-crystal thin-film acoustic resonator according to another exemplary embodiment of the present invention. Figure 4 The structure shown is the same as Figure 3 They are basically the same, the difference being: Figure 4 In the illustrated embodiment, the passivation layer 103 not only covers the lower surface of the bottom electrode 104, completely enveloping both sides of the bottom electrode, but also extends to both sides by a certain distance. This ensures good coverage at the steps on both sides of the bottom electrode, thereby ensuring complete protection of the bottom electrode by the passivation layer, thus protecting the bottom electrode from the influence of the external environment. Similarly, since the passivation layer does not extend to one side ( Figure 4 (middle is left) extends (in) Figure 4 (Extending to the left in the middle) into the non-effective region, thus reducing the loss of acoustic wave energy through the passivation layer into the non-effective region, which is beneficial to improving the performance of the single crystal thin film acoustic resonator.

[0053] Figure 5 The diagram shown is a cross-sectional schematic of a single-crystal thin-film acoustic resonator according to another exemplary embodiment of the present invention. Figure 5The structure shown is the same as Figure 4 They are basically the same, the difference being: Figure 5 In the illustrated embodiment, the passivation layer 103 is located below the bottom electrode and completely covers both sides of the bottom electrode, extending a certain distance to both sides. Simultaneously, the left side of the passivation layer extends a certain distance beyond the left side of the cavity structure. In this way, the passivation layer 103 not only completely covers the electrode but also completely covers the corresponding piezoelectric layer within the cavity, thereby protecting the bottom electrode and the piezoelectric layer from external environmental influences and damage.

[0054] like Figure 4-5 As shown, even though the passivation layer 103 extends between the support layer 101 and the piezoelectric layer 105, the end of the passivation layer 103 remains inside the boundary of the piezoelectric layer in the horizontal direction. This avoids the following... Figure 1 The fully extended passivation layer shown can lead to poor sealing between the resonator film layers, thus reducing the reliability of the resonator. Of course, as mentioned above... Figure 2-3 The structure can also solve Figure 1 The above-mentioned technical problem of poor sealing is illustrated.

[0055] Figure 6 The diagram shown is a cross-sectional schematic of a single-crystal thin-film acoustic resonator according to another exemplary embodiment of the present invention. Figure 6 The structure shown is the same as Figure 2 They are basically the same, the difference being: Figure 6 In the illustrated embodiment, bridge structures 113 and 111 and gap layers 114 and 112 are located above the top electrode 106 and the bottom electrode 104. At the bridge structures, the presence of air gaps or gap layers causes a mismatch between the acoustic impedance and the acoustic impedance within the effective region of the resonator, resulting in discontinuous sound wave propagation at the boundaries. Therefore, at the boundaries of the effective region, some acoustic energy is coupled and reflected back into the effective region and converted into a piston sound wave mode perpendicular to the surface of the piezoelectric layer, thereby increasing the Q value of the resonator.

[0056] exist Figure 6 In the middle, the passivation layer 103 corresponding to the bottom electrode is set in the same way as... Figure 2 Corresponding, but if it is understandable, it can also be used. Figure 3-5 The arrangement method.

[0057] Figure 7 The diagram shown is a cross-sectional schematic of a single-crystal thin-film acoustic resonator according to another exemplary embodiment of the present invention. Figure 7 The structure shown is the same as Figure 2 They are basically the same, the difference being: Figure 7In the illustrated embodiment, cantilever structures 117 and 115 and air gaps or void layers 118 and 116 are located above the top electrode 106 and the bottom electrode 104. At the cantilever structures, the presence of air gaps causes a mismatch between the acoustic impedance and the acoustic impedance within the effective region of the single-crystal thin-film acoustic resonator, resulting in discontinuous sound wave propagation at the boundaries. Therefore, at the boundaries of the effective region, some acoustic energy is coupled and reflected back into the effective region and converted into a piston acoustic wave mode perpendicular to the surface of the piezoelectric layer, thereby improving the Q value of the single-crystal thin-film acoustic resonator.

[0058] Figure 8 The diagram shown is a cross-sectional schematic of a single-crystal thin-film acoustic resonator according to another exemplary embodiment of the present invention. Figure 8 The structure shown is the same as Figure 2 They are basically the same, the difference being: Figure 8 In the illustrated embodiment, there are protruding structures 121 and 119 and recessed structures 122 and 120 located above the top electrode 106 and the bottom electrode 104. Since the acoustic impedance in the protruding and recessed structures does not match the acoustic impedance in the effective region of the single-crystal thin-film acoustic resonator, the sound wave transmission is discontinuous at the boundary. Therefore, at the boundary of the effective region, some acoustic energy will couple and reflect into the effective region and be converted into a piston acoustic wave mode perpendicular to the surface of the piezoelectric layer, thereby improving the Q value of the single-crystal thin-film acoustic resonator.

[0059] exist Figure 8 In the middle, the passivation layer 103 corresponding to the bottom electrode is set in the same way as... Figure 2 Corresponding, but if it is understandable, it can also be used. Figure 3-5 The arrangement method.

[0060] Figure 9 The diagram shown is a cross-sectional schematic of a single-crystal thin-film acoustic resonator according to another exemplary embodiment of the present invention. Figure 9 The structure shown is the same as Figure 2 They are basically the same, the difference being: Figure 9 In the illustrated embodiment, a bridge structure 113 and an air gap 114 are located above the top electrode 106, along with a cantilever structure 117 and an air gap 118 located below the bridge structure, and a protruding structure 119 and a recessed structure 120 are located above the bottom electrode. Because the acoustic impedance of the air under the bridge and cantilever structures, as well as the acoustic impedance in the protruding and recessed structures, is mismatched with the acoustic impedance within the effective region of the single-crystal thin-film acoustic resonator, sound wave transmission becomes discontinuous at the boundaries. Therefore, at the boundaries of the effective region, some acoustic energy couples and reflects back into the effective region and is converted into a piston-like acoustic wave mode perpendicular to the piezoelectric layer surface, thereby increasing the Q value of the single-crystal thin-film acoustic resonator.

[0061] exist Figure 9 In the middle, the passivation layer 103 corresponding to the bottom electrode is set in the same way as... Figure 2 Corresponding, but if it is understandable, it can also be used. Figure 3-5 The arrangement method.

[0062] In addition, such as Figure 2-9 As shown, a passivation layer 107 is provided on the upper surface of the top electrode 106. In an optional embodiment, the passivation layer 107 may not be provided.

[0063] It should be noted that, in this invention, each numerical range, except where explicitly stated not to include endpoint values, can be either an endpoint value or the median of each numerical range, and all of these are within the protection scope of this invention.

[0064] 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.

[0065] In this invention, "inner" and "outer" are relative to the center (i.e., the center of the effective region) of the resonator (the overlapping area of ​​the piezoelectric layer, top electrode, bottom electrode, and acoustic mirror in the thickness direction of the resonator constitutes the effective region) in the lateral or radial direction. A component's side or end closer to the center of the effective region is called the inner side or inner end, while the side or end of the component farther from the center of the effective region is called the outer side or outer end. For a reference position, being inside the position means being between that position and the center of the effective region in the lateral or radial direction, while being outside the position means being farther from the center of the effective region in the lateral or radial direction than that position.

[0066] 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 electronic devices.

[0067] Based on the above, the present invention proposes the following technical solution:

[0068] 1. A bulk acoustic resonator, comprising:

[0069] Base;

[0070] Acoustic mirror cavity;

[0071] Bottom electrode;

[0072] Top electrode; and

[0073] A single-crystal piezoelectric layer is disposed between the bottom electrode and the top electrode.

[0074] in:

[0075] A support structure is provided between the lower surface of the piezoelectric layer and the upper surface of the substrate, and the piezoelectric layer and the substrate are arranged in a generally parallel manner.

[0076] A lower passivation layer is provided on the lower side of the bottom electrode, and the lower passivation layer covers at least a portion of the surface of the bottom electrode within the cavity; and

[0077] The boundary of the lower passivation layer is located inside the boundary of the piezoelectric layer in the horizontal direction.

[0078] 2. The resonator according to 1, wherein:

[0079] The piezoelectric layer is a single-crystal lithium niobate piezoelectric layer or a single-crystal lithium tantalate piezoelectric layer.

[0080] 3. The resonator according to 1, wherein:

[0081] The lower passivation layer at least covers the entire lower side of the bottom electrode.

[0082] 4. The resonator according to 3, wherein:

[0083] The lower passivation layer also covers the end face of the bottom electrode within the cavity.

[0084] 5. The resonator according to 4, wherein:

[0085] At the non-electrode connection end of the bottom electrode, the end of the lower passivation layer within the cavity is located horizontally between the boundary of the cavity and the end of the bottom electrode within the cavity.

[0086] 6. The resonator according to 3, wherein:

[0087] At the non-electrode connection end of the bottom electrode, the end of the lower passivation layer is located outside the boundary of the cavity in the horizontal direction, and between the support structure and the piezoelectric layer in the thickness direction of the resonator.

[0088] 7. The resonator according to 3, wherein:

[0089] The lower passivation layer also covers the end face of the electrode connection terminal of the bottom electrode.

[0090] 8. The resonator according to 7, wherein:

[0091] At the electrode connection end of the bottom electrode, the end of the lower passivation layer is located outside the electrode connection end of the bottom electrode in the horizontal direction, and is located between the piezoelectric layer and the support layer in the thickness direction of the resonator.

[0092] 9. The resonator according to claim 1, wherein:

[0093] The non-electrode connection ends of the top electrode and / or bottom electrode are provided with a cantilever structure.

[0094] 10. The resonator according to 9, wherein:

[0095] The electrode connection ends of the top electrode and / or bottom electrode are provided with a bridge structure, the bridge structure defining a gap layer, the gap layer being a void layer, a vacuum gap layer, or a non-conductive dielectric layer.

[0096] 11. The resonator according to claim 1, wherein:

[0097] The top electrode and / or bottom electrode are provided with a bridge structure, the bridge structure defining a gap layer, the gap layer being a void layer, a vacuum gap layer, or a non-conductive dielectric layer.

[0098] 12. The resonator according to claim 1, wherein:

[0099] The top electrode and / or bottom electrode are provided with a raised structure and / or a recessed structure.

[0100] 13. The resonator according to any one of 1-12, wherein:

[0101] The lattice of the lower passivation layer does not match the lattice of the piezoelectric layer.

[0102] 14. The resonator according to any one of 1-13, wherein:

[0103] The thickness of the lower passivation layer is in the range of 10 nanometers to 1 micrometer.

[0104] 15. The resonator according to 14, wherein:

[0105] The thickness of the lower passivation layer is in the range of 50 nanometers to 500 nanometers.

[0106] 16. The resonator according to any one of 1-12, wherein:

[0107] The overlapping region of the acoustic mirror, bottom electrode, piezoelectric layer, and top electrode in the thickness direction of the resonator constitutes the effective region of the resonator.

[0108] Outside the effective region, at least a portion of the upper surface of the piezoelectric layer is provided with an insulating layer.

[0109] 17. A filter comprising a bulk acoustic resonator according to any one of 1-16.

[0110] 18. An electronic device comprising the filter according to claim 17, or the bulk acoustic resonator according to any one of claims 1-16.

[0111] 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.

[0112] 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: Base; Acoustic mirror cavity; Bottom electrode; Top electrode; and A single-crystal piezoelectric layer is disposed between the bottom electrode and the top electrode. in: A support structure is provided between the lower surface of the piezoelectric layer and the upper surface of the substrate, and the piezoelectric layer and the substrate are arranged in a generally parallel manner. A lower passivation layer is provided on the lower side of the bottom electrode, and the lower passivation layer covers at least a portion of the surface of the bottom electrode within the cavity; and The boundary of the lower passivation layer is located inside the boundary of the piezoelectric layer in the horizontal direction.

2. The resonator according to claim 1, wherein: The piezoelectric layer is a single-crystal lithium niobate piezoelectric layer or a single-crystal lithium tantalate piezoelectric layer.

3. The resonator according to claim 1, wherein: The lower passivation layer at least covers the entire lower side of the bottom electrode.

4. The resonator according to claim 3, wherein: The lower passivation layer also covers the end face of the bottom electrode within the cavity.

5. The resonator according to claim 4, wherein: At the non-electrode connection end of the bottom electrode, the end of the lower passivation layer within the cavity is located horizontally between the boundary of the cavity and the end of the bottom electrode within the cavity.

6. The resonator according to claim 3, wherein: At the non-electrode connection end of the bottom electrode, the end of the lower passivation layer is located outside the boundary of the cavity in the horizontal direction, and between the support structure and the piezoelectric layer in the thickness direction of the resonator.

7. The resonator according to claim 3, wherein: The lower passivation layer also covers the end face of the electrode connection terminal of the bottom electrode.

8. The resonator according to claim 7, wherein: At the electrode connection end of the bottom electrode, the end of the lower passivation layer is located outside the electrode connection end of the bottom electrode in the horizontal direction, and is located between the piezoelectric layer and the support layer in the thickness direction of the resonator.

9. The resonator according to claim 1, wherein: The non-electrode connection ends of the top electrode and / or bottom electrode are provided with a cantilever structure.

10. The resonator according to claim 9, wherein: The electrode connection ends of the top electrode and / or bottom electrode are provided with a bridge structure, the bridge structure defining a gap layer, the gap layer being a void layer, a vacuum gap layer, or a non-conductive dielectric layer.

11. The resonator according to claim 1, wherein: The top electrode and / or bottom electrode are provided with a bridge structure, the bridge structure defining a gap layer, the gap layer being a void layer, a vacuum gap layer, or a non-conductive dielectric layer.

12. The resonator according to claim 1, wherein: The top electrode and / or bottom electrode are provided with a raised structure and / or a recessed structure.

13. The resonator according to any one of claims 1-12, wherein: The lattice of the material in the lower passivation layer does not match the lattice of the piezoelectric layer.

14. The resonator according to any one of claims 1-12, wherein: The thickness of the lower passivation layer is in the range of 10 nanometers to 1 micrometer.

15. The resonator according to claim 14, wherein: The thickness of the lower passivation layer is in the range of 50 nanometers to 500 nanometers.

16. The resonator according to any one of claims 1-12, wherein: The overlapping region of the acoustic mirror, bottom electrode, piezoelectric layer, and top electrode in the thickness direction of the resonator constitutes the effective region of the resonator. Outside the effective region, at least a portion of the upper surface of the piezoelectric layer is provided with an insulating layer.

17. A filter comprising a bulk acoustic resonator according to any one of claims 1-16.

18. An electronic device comprising the filter of claim 17, or the bulk acoustic resonator of any one of claims 1-16.

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