A bulk acoustic wave resonator and a method for manufacturing the same

Abstract

The present invention provides a bulk acoustic wave resonator and a manufacturing method thereof. The manufacturing method includes: disposing a single crystal aluminum nitride or doped aluminum nitride as a piezoelectric thin film on a temporary substrate; sequentially disposing a first electrode layer, a Bragg reflection structure, and a bonding layer, and bonding to a bonding substrate; removing the temporary substrate, and disposing a second electrode layer and an electrical lead-out structure. By selecting the piezoelectric thin film material of single crystal aluminum nitride, the present invention improves the device performance; at the same time, by disposing the Bragg reflection structure on the bonding layer, the influence of the bonding layer on the resonator performance is small, and various bonding materials and bonding processes can be selected to improve the feasibility of the manufacturing process; in addition, by thinning the piezoelectric thin film, the piezoelectric thin film with poor quality is removed to improve the device performance; finally, by cooperating with the Bragg reflection structure and the bonding process to manufacture a solid-state assembled bulk acoustic wave resonator, the mechanical strength of the resonator can be improved, the heat conduction performance of the substrate can be improved, the resonance frequency drift caused by temperature of the bulk acoustic wave resonator can be reduced, and a higher power density can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor integrated circuit manufacturing, and particularly relates to a bulk acoustic wave resonator and a preparation method thereof. Background Art

[0002] At present, radio frequency filters are developing towards higher operating frequencies. Bulk acoustic wave filters (BAW) have advantages such as high operating frequency, low insertion loss, high frequency selection characteristics, high power capacity, and strong anti-static ability, and are the best solution for future radio frequency front-ends.

[0003] AlN material has advantages such as high sound velocity, low loss, and low temperature coefficient, and is currently widely used in 4G filters. However, the piezoelectric coefficient and electromechanical coupling coefficient of polycrystalline AlN are small, which limits its application in 5G high-frequency broadband filters.

[0004] At the same time, as the operating frequency further increases, the thickness of the piezoelectric thin film in the filter becomes thinner and thinner. The resonant region in the air-gap bulk acoustic wave filter (FBAR) structure is located above the cavity, and problems such as thin film rupture are very likely to occur; and because air is a poor conductor of heat, the operating temperature of FBAR devices is high, resulting in a large frequency drift in the filter performance. Therefore, there is an urgent need for a bulk acoustic wave filter that can improve mechanical strength and reduce temperature drift.

[0005] It should be noted that the above introduction of the technical background is only for the convenience of clearly and completely explaining the technical solutions of the present application and facilitating the understanding of those skilled in the art, and it cannot be considered that the above technical solutions are well-known to those skilled in the art just because these solutions are described in the background art part of the present application. Summary of the Invention

[0006] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide one, which is used to solve the problems of limited performance parameters and poor mechanical strength of bulk acoustic wave resonators in the prior art.

[0007] To achieve the above purpose, the present invention provides a preparation method of a bulk acoustic wave resonator, and the preparation method includes: providing a temporary substrate, and disposing a piezoelectric thin film on the temporary substrate, where the piezoelectric thin film is undoped single-crystal aluminum nitride or scandium-doped single-crystal aluminum nitride;

[0008] Disposing a patterned first electrode layer on the piezoelectric thin film to expose a part of the piezoelectric thin film;

[0009] Disposing a Bragg reflection structure on the first electrode layer;

[0010] Disposing a bonding layer on the Bragg reflection structure;

[0011] Bond the Bragg reflection structure to a bonding substrate through the bonding layer;

[0012] Remove the temporary substrate to expose the piezoelectric thin film, and thin the exposed piezoelectric thin film;

[0013] Form a patterned second electrode layer on the thinned piezoelectric thin film;

[0014] Provide an electrical lead-out structure to lead out the electrical connections of the first electrode layer and the second electrode layer.

[0015] Optionally, the material of the temporary substrate is one or more arbitrary combinations of Si, sapphire, or SiC.

[0016] Optionally, the step of providing the Bragg reflection structure includes: providing a low acoustic impedance layer to cover the first electrode layer and the exposed surface of the piezoelectric thin film; continue to alternately provide multiple high acoustic impedance layers and multiple low acoustic impedance layers to obtain the Bragg reflection structure.

[0017] Optionally, one low acoustic impedance layer and one high acoustic impedance layer in the Bragg reflection layer form a period, and the number of periods included in the Bragg reflection structure is n, where n is a positive integer greater than or equal to 1 and less than or equal to 9.

[0018] Optionally, after thinning the exposed piezoelectric thin film, regrow the piezoelectric thin film on the piezoelectric thin film to a preset thickness to meet the resonance parameters of the bulk acoustic wave resonator.

[0019] Optionally, the material of the piezoelectric thin film regrown on the piezoelectric thin film is undoped aluminum nitride thin film or scandium-doped aluminum nitride.

[0020] Optionally, the step of providing the electrical lead-out structure includes: providing a through hole at the piezoelectric thin film not covered by the second electrode layer above, and the through hole is in contact with the first electrode layer; provide an electrical lead-out structure in the through hole to lead out the electrical connection of the first electrode layer, and provide an electrical lead-out structure on the second electrode layer to lead out the electrical connection of the second electrode layer.

[0021] The present invention also provides a bulk acoustic wave resonator, which is obtained by using any one of the above preparation methods. The bulk acoustic wave resonator includes: a bonding substrate, a bonding layer, a Bragg reflection structure, a first electrode layer, a piezoelectric thin film, a second electrode layer, and an electrical lead-out structure. The material of the piezoelectric thin film is undoped single crystal aluminum nitride or scandium-doped single crystal aluminum nitride;

[0022] The bonding layer is disposed on the bonding substrate, the Bragg reflection structure is disposed on the bonding layer, the first electrode layer is disposed on the Bragg reflection structure, the piezoelectric thin film is disposed on the first electrode layer, the second electrode layer is disposed on the piezoelectric thin film, and one of the electrical lead-out structures penetrates the piezoelectric thin film to lead out the first electrode layer to the surface of the piezoelectric thin film, and the other electrical lead-out structure is electrically connected to the second electrode layer for leading out.

[0023] Optionally, the material of the low acoustic impedance layer is one or more of SiO2, AlN, Si3N4, or SiOC, or any combination thereof.

[0024] Optionally, the piezoelectric thin film is provided with a through-channel at a position where the first electrode layer is not provided, and the through-channel surrounds the edge of the first electrode layer to form an isolation between two adjacent bulk acoustic wave resonators.

[0025] As described above, the bulk acoustic wave resonator and its manufacturing method of the present invention have the following beneficial effects:

[0026] The present invention improves the device performance by selecting the piezoelectric thin film material of single crystal aluminum nitride;

[0027] The present invention disposes the Bragg reflection structure on the bonding layer, so that the bonding layer has little influence on the resonator performance, and various bonding materials and bonding processes can be selected, improving the feasibility of the manufacturing process;

[0028] The present invention thins the piezoelectric thin film to remove the piezoelectric thin film with poor quality, improving the device performance;

[0029] The present invention cooperates with the setting of the Bragg reflection structure and the bonding process to manufacture a solid-state assembled bulk acoustic wave resonator, which can improve the mechanical strength of the resonator and improve the thermal conductivity of the substrate surface to reduce the temperature drift of the bulk acoustic wave resonator and achieve a higher power density. Description of the Drawings

[0030] Figure 1 It shows a schematic structural diagram of setting a temporary substrate and a piezoelectric thin film in step 1 of the manufacturing method of the bulk acoustic wave resonator of the present invention.

[0031] Figure 2 It shows a schematic structural diagram of setting the first electrode layer in step 2 of the manufacturing method of the bulk acoustic wave resonator of the present invention.

[0032] Figure 3 It shows a schematic structural diagram of setting the Bragg reflection structure in step 3 of an optional example of the manufacturing method of the bulk acoustic wave resonator of the present invention.

[0033] Figure 4Shown is a schematic structural diagram of planarizing a low acoustic impedance layer in step 3 of an alternative example of the preparation method of the bulk acoustic wave resonator of the present invention.

[0034] Figure 5 Shown is a schematic structural diagram of alternately arranging a high acoustic impedance layer and a low acoustic impedance layer in step 3 of an alternative example of the preparation method of the bulk acoustic wave resonator of the present invention.

[0035] Figure 6 Shown is a schematic enlarged structural diagram of a Bragg reflection structure in step 3 of an alternative example of the preparation method of the bulk acoustic wave resonator of the present invention.

[0036] Figure 7 Shown is a schematic structural diagram of providing a bonding layer in step 4 of the preparation method of the bulk acoustic wave resonator of the present invention.

[0037] Figure 8 Shown is a schematic structural diagram of performing bonding in step 5 of the preparation method of the bulk acoustic wave resonator of the present invention.

[0038] Figure 9 Shown is a schematic structural diagram of removing a temporary substrate in step 6 of the preparation method of the bulk acoustic wave resonator of the present invention.

[0039] Figure 10 Shown is a schematic structural diagram of thinning a piezoelectric thin film in step 6 of the preparation method of the bulk acoustic wave resonator of the present invention.

[0040] Figure 11 Shown is a schematic structural diagram of regrowing a piezoelectric thin film in step 6 of an alternative example of the preparation method of the bulk acoustic wave resonator of the present invention.

[0041] Figure 12 Shown is a schematic structural diagram of providing a second electrode layer in step 7 of the preparation method of the bulk acoustic wave resonator of the present invention.

[0042] Figure 13 Shown is a schematic structural diagram of providing a through hole in step 8 of an alternative example of the preparation method of the bulk acoustic wave resonator of the present invention.

[0043] Figure 14 Shown is a schematic structural diagram of providing an electrical lead-out structure in step 8 of an alternative example of the preparation method of the bulk acoustic wave resonator of the present invention.

[0044] Element number description

[0045] 11. Temporary substrate; 12. Piezoelectric thin film; 121. Through-channel; 13. First electrode layer; 14. Bragg reflection structure; 141. Low acoustic impedance layer; 142. High acoustic impedance layer; 15. Bonding layer; 16. Bonding substrate; 17. Second electrode layer; 18. Electrical lead-out structure; 19. Through-hole. Detailed implementation manners

[0046] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0047] When detailing the embodiments of the present invention, for the convenience of description, the schematic diagrams showing the device structure will be enlarged locally in a non-general proportion, and the schematic diagrams are only examples and should not limit the protection scope of the present invention here. In addition, in actual production, three-dimensional spatial dimensions including length, width, and depth should be included.

[0048] For the convenience of description, spatial relationship terms such as "under", "below", "lower than", "beneath", "above", "on", etc. may be used here to describe the relationship between an element or feature shown in the drawings and other elements or features. It will be understood that these spatial relationship terms are intended to include other directions of the device in use or operation besides the directions depicted in the drawings.

[0049] In the context of this application, the structure in which the first feature is "above" the second feature may include embodiments in which the first and second features are in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0050] It should be noted that the drawings provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the drawings, rather than being drawn according to the number, shape, and size of the components in actual implementation. The types, quantities, and proportions of the components in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0051] As Figures 1-13 shown, the present invention provides a preparation method for a bulk acoustic wave resonator. The preparation method includes:

[0052] Step 1: Provide a temporary substrate 11, and dispose a piezoelectric thin film 12 on the temporary substrate 11. The piezoelectric thin film 12 is undoped single-crystal aluminum nitride or scandium-doped single-crystal aluminum nitride;

[0053] Step 2: Provide a patterned first electrode layer 13 on the piezoelectric thin film 12 to expose a part of the piezoelectric thin film 12;

[0054] Step 3: Provide a Bragg reflection structure 14 on the first electrode layer 13;

[0055] Step 4: Provide a bonding layer 15 on the Bragg reflection structure 14;

[0056] Step 5: Bond the Bragg reflection structure 14 to a bonding substrate 16 through the bonding layer 15;

[0057] Step 6: Remove the temporary substrate 11 to expose the piezoelectric thin film 12, and thin the exposed piezoelectric thin film 12;

[0058] Step 7: Provide a patterned second electrode layer 17 on the thinned piezoelectric thin film 12;

[0059] Step 8: Provide an electrical lead-out structure 18 to lead out the electrical connection between the first electrode layer 13 and the second electrode layer 17.

[0060] The preparation method of the bulk acoustic wave resonator of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the above sequence does not strictly represent the sequence of the preparation method of the bulk acoustic wave resonator protected by the present invention, and those skilled in the art can make changes according to the actual preparation steps.

[0061] First, as Figure 1 shown, perform Step 1, provide a temporary substrate 11, and provide a piezoelectric thin film 12 on the temporary substrate 11. The piezoelectric thin film 12 is undoped single-crystal aluminum nitride or scandium-doped single-crystal aluminum nitride.

[0062] By providing the piezoelectric thin film 12 as single-crystal aluminum nitride, the present invention overcomes the disadvantages of the relatively small piezoelectric coefficient and electromechanical coupling coefficient obtained by using polycrystalline aluminum nitride as the piezoelectric thin film 12 in the prior art, and uses single-crystal aluminum nitride as the piezoelectric thin film 12 to improve performance parameters such as the effective coupling coefficient, quality factor, and power capacity of the bulk acoustic wave resonator.

[0063] In one embodiment, the material of the temporary substrate 11 is one or more of Si, sapphire, or SiC in any combination.

[0064] In one embodiment, the material of the temporary substrate 11 is Si(111).

[0065] The present invention sets the material of the temporary substrate 11 as Si(111) to cooperate with the single-crystalline silicon nitride material in the piezoelectric thin film 12, reducing the lattice mismatch between the piezoelectric thin film 12 and the temporary substrate 11, thereby further improving the quality of the piezoelectric thin film 12 to ensure the performance reliability of the formed bulk acoustic wave resonator.

[0066] In one embodiment, the material of the temporary substrate 11 can also be a substrate material such as sapphire or silicon nitride.

[0067] In one embodiment, the piezoelectric thin film 12 can be grown by chemical vapor deposition (CVD), or physical vapor deposition (PVD) growth can be carried out after CVD, or CVD can be carried out after PVD and then CVD again.

[0068] Preferably, the piezoelectric thin film 12 is grown by PVD after CVD to avoid large stress generated in the piezoelectric thin film 12 grown by CVD, which makes the piezoelectric thin film 12 prone to cracking.

[0069] In one embodiment, the thickness of the piezoelectric thin film 12 is 10 nanometers - 10,000 nanometers.

[0070] Then, as Figure 2 shown, step 2 is carried out, and a patterned first electrode layer 13 is provided on the piezoelectric thin film 12 to expose a part of the piezoelectric thin film 12.

[0071] Specifically, by patterning the first electrode layer 13, the exposed part of the piezoelectric thin film 12 can be used to set the isolation structure and the electrical lead-out structure 18 subsequently.

[0072] In one embodiment, the material of the first electrode layer 13 is one or more of Mo, Pt, Au, Al, W, or Ru in any combination. Preferably, the first electrode layer 13 uses Mo.

[0073] In one embodiment, the thickness of the first electrode layer 13 is 10 nanometers - 500 nanometers.

[0074] In one embodiment, as Figure 2 shown, after the first electrode layer 13 is provided, the exposed piezoelectric thin film 12 is patterned to form a through-channel 121 surrounding the edge of the first electrode layer 13, forming an island structure to isolate between adjacent two bulk acoustic wave resonators.

[0075] Next, step 3 is carried out, and a Bragg reflection structure 14 is provided on the first electrode layer 13.

[0076] In one embodiment, the step of providing the Bragg reflection structure 14 includes: as Figure 3As shown, a low acoustic impedance layer 141 is provided to cover the exposed surfaces of the first electrode layer 13 and the piezoelectric thin film 12; as Figure 5 shown, multiple high acoustic impedance layers 142 and multiple low acoustic impedance layers 141 are alternately provided to obtain the Bragg reflection structure 14.

[0077] In one embodiment, the low acoustic impedance layer 141 fills the patterned voids of the piezoelectric thin film 12; as Figure 4 shown, after the low acoustic impedance layer 141 is provided, the low acoustic impedance layer 141 is planarized.

[0078] In one embodiment, the low acoustic impedance layer 141 is planarized so that the thickness of the low acoustic impedance material of this layer is 1 / 4 or 3 / 4 of the acoustic wave wavelength corresponding to the resonant frequency of the bulk acoustic wave resonator, and the thickness of each subsequent low acoustic impedance material layer and each high acoustic impedance material layer is 1 / 4 or 3 / 4 of the acoustic wave wavelength corresponding to the resonant frequency of the bulk acoustic wave resonator.

[0079] In one embodiment, as Figure 6 shown, one low acoustic impedance layer 141 and one high acoustic impedance layer 142 in the Bragg reflection layer form a period, and the number of periods included in the Bragg reflection structure 14 is n, where n is a positive integer greater than or equal to 1 and less than or equal to 9.

[0080] The present invention enables the bulk acoustic wave resonator to achieve sufficient reflectivity while ensuring miniaturization of size by setting the number of periods of the Bragg reflection structure 14.

[0081] In one embodiment, the material of the low acoustic impedance layer 141 is one or more of AlN, Si3N4, or SiO2 in any combination.

[0082] Preferably, SiO2 is used as the material of the low acoustic impedance layer 141 to achieve a lower acoustic impedance.

[0083] In one embodiment, the method for growing the low acoustic impedance layer 141 is one or more of PECVD (plasma enhanced chemical vapor deposition), ICPCVD (inductively coupled plasma chemical vapor deposition), ALD (atomic layer deposition), MBE (molecular beam epitaxy), PLD (pulsed laser beam deposition) in any combination. Preferably, ICPCVD is used.

[0084] In one embodiment, the material of the high acoustic impedance layer 142 is one or more of W, Mo, Pt, Au, Ni, Ir in any combination.

[0085] In one embodiment, the method for growing the high acoustic impedance layer 142 is magnetron sputtering or evaporation. Magnetron sputtering is preferably used to grow the high acoustic impedance layer 142.

[0086] Then, as Figure 7 shown, step 4 is performed to dispose a bonding layer 15 on the Bragg reflection structure 14.

[0087] In one embodiment, the material of the bonding layer 15 is Au,, BCB (benzocyclobutene), PI (polyimide), PBO (poly(p-phenylene benzobisoxazole)), SiO2.

[0088] Next, as Figure 8 shown, step 5 is performed to bond the Bragg reflection structure 14 to a bonding substrate 16 through the bonding layer 15.

[0089] Then, as Figures 9-10 shown, step 6 is performed to remove the temporary substrate 11, expose the piezoelectric thin film 12, and thin the exposed piezoelectric thin film 12.

[0090] In one embodiment, the temporary substrate 11 is removed by a method combining mechanical grinding and selective etching, or the temporary substrate 11 is removed by a method combining mechanical grinding and polishing.

[0091] In one embodiment, as Figure 11 shown, after thinning the exposed piezoelectric thin film 12, the piezoelectric thin film 12 is regrown on the piezoelectric thin film 12 to a preset thickness to meet the resonance parameters of the bulk acoustic wave resonator.

[0092] The present invention thins the piezoelectric thin film 12 to remove the portion with poor contact quality between the piezoelectric thin film 12 and the temporary substrate 11, so as to improve the overall performance such as the effective electromechanical coupling coefficient and quality factor of the resonator, and adjusts parameters such as the resonance frequency and bandwidth of the bulk acoustic wave resonator by regrowing the piezoelectric thin film 12 to meet the requirements.

[0093] In one embodiment, the material of the piezoelectric thin film regrown on the piezoelectric thin film 12 is undoped aluminum nitride thin film or scandium-doped aluminum nitride.

[0094] In one embodiment, when the piezoelectric thin film is scandium-doped aluminum nitride, the doping concentration of scandium is 0%-40%.

[0095] In one embodiment, when regrowing the piezoelectric thin film 12, single crystal aluminum nitride or doped aluminum nitride is grown by CVD or PVD methods.

[0096] Next, as Figure 12As shown, step 7 is performed to provide a patterned second electrode layer 17 on the exposed piezoelectric thin film 12.

[0097] In one embodiment, the material of the second electrode layer 17 is one or more of Mo, Pt, Au, Al, W, or Ru, or any combination thereof. Preferably, the material of the second electrode layer 17 is Mo.

[0098] In one embodiment, the thickness of the second electrode layer 17 is 10 nanometers to 500 nanometers.

[0099] Finally, step 8 is performed to provide an electrical lead-out structure 18 to lead out the electrical connections of the first electrode layer 13 and the second electrode layer 17.

[0100] In one embodiment, the step of providing the electrical lead-out structure 18 includes: as Figure 13 shown, a through hole 19 is provided at the piezoelectric thin film 12 that is not covered by the second electrode layer 17 above, and the through hole 19 is in contact with the first electrode layer 13; as Figure 14 shown, an electrical lead-out structure 18 is provided in the through hole 19 to lead out the electrical connection of the first electrode layer 13, and an electrical lead-out structure 18 is provided at the second electrode layer 17 to lead out the electrical connection of the second electrode layer 17.

[0101] The present invention also provides a bulk acoustic wave resonator obtained by using any one of the above preparation methods. The bulk acoustic wave resonator includes: a bonded substrate 16, a bonding layer 15, a Bragg reflector structure 14, a first electrode layer 13, a piezoelectric thin film 12, a second electrode layer 17, and an electrical lead-out structure 18. The material of the piezoelectric thin film 12 is undoped single-crystal aluminum nitride or scandium-doped single-crystal aluminum nitride;

[0102] The bonding layer 15 is provided on the bonded substrate 16, the Bragg reflector structure 14 is provided on the bonding layer 15, the first electrode layer 13 is provided on the Bragg reflector structure 14, the piezoelectric thin film 12 is provided on the first electrode layer 13, the second electrode layer 17 is provided on the piezoelectric thin film 12, one electrical lead-out structure 18 penetrates the piezoelectric thin film 12 to lead out the first electrode layer 13 to the surface of the piezoelectric thin film 12, and the other electrical lead-out structure 18 is electrically connected to the second electrode layer 17 and led out.

[0103] In the present invention, by disposing the Bragg reflection structure 14 on the bonding layer 15, the influence of the bonding layer 15 on the performance of the resonator is reduced, so that various bonding materials and bonding processes can be selected, broadening the selection range of bonding and improving the feasibility of the preparation process. At the same time, the structure of the solid-state assembled bulk acoustic wave resonator obtained by bonding in cooperation with the Bragg reflection structure 14 can improve the mechanical strength of the resonator and improve the heat conduction performance of the substrate to reduce the temperature drift of the bulk acoustic wave resonator and achieve a higher power density. Meanwhile, by setting the material of the piezoelectric thin film 12 as single-crystal aluminum nitride, the present invention can improve performance parameters such as the effective electromechanical coupling coefficient, quality factor, and power capacity of the bulk acoustic wave resonator, which is beneficial to the application of the bulk acoustic wave resonator in 5G high-frequency band resonators, and in cooperation with the structure of the assembled bulk acoustic wave resonator, a high-performance bulk acoustic wave resonator is realized.

[0104] In one embodiment, the material of the low acoustic impedance layer 141 is one or more arbitrary combinations of SiO2, AlN, Si3N4, or SiOC.

[0105] In the present invention, by setting the material of the low acoustic impedance layer 141 as SiO2, a lower acoustic impedance is obtained.

[0106] In one embodiment, the piezoelectric thin film 12 is provided with a through-channel 121 at a position where the first electrode layer 13 is not provided, and the through-channel 121 surrounds the edge of the first electrode layer 13 to form isolation between two adjacent bulk acoustic wave resonators.

[0107] In summary, for the bulk acoustic wave resonator and its preparation method of the present invention, the device performance can be improved by selecting the piezoelectric thin film material of single-crystal aluminum nitride. At the same time, by disposing the Bragg reflection structure on the bonding layer, the influence of the bonding layer on the resonator performance is small, and various bonding materials and bonding processes can be selected, improving the feasibility of the preparation process. In addition, by thinning the piezoelectric thin film, the piezoelectric thin film with poor quality is removed to improve the device performance. Finally, in cooperation with the setting of the Bragg reflection structure and the bonding process to manufacture a solid-state assembled bulk acoustic wave resonator, the mechanical strength of the resonator can be improved and the heat conduction performance of the substrate can be improved to reduce the temperature drift of the bulk acoustic wave resonator and achieve a higher power density.

[0108] Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0109] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a bulk acoustic wave resonator, characterized in that, The preparation method includes: providing a temporary substrate, and disposing a piezoelectric thin film on the temporary substrate, where the piezoelectric thin film is undoped single-crystal aluminum nitride or scandium-doped single-crystal aluminum nitride; disposing a patterned first electrode layer on the piezoelectric thin film to expose a part of the piezoelectric thin film, forming a through-channel surrounding the edge of the first electrode layer, forming an island structure, and isolating between adjacent two bulk acoustic wave resonators; disposing a Bragg reflection structure on the first electrode layer; the step of disposing the Bragg reflection structure includes: disposing a low acoustic impedance layer to cover the first electrode layer and the exposed surface of the piezoelectric thin film; continuously and alternately disposing multiple high acoustic impedance layers and multiple low acoustic impedance layers to obtain the Bragg reflection structure; disposing a bonding layer on the Bragg reflection structure; bonding the Bragg reflection structure to a bonding substrate through the bonding layer; removing the temporary substrate to expose the piezoelectric thin film, and thinning the exposed piezoelectric thin film; disposing a patterned second electrode layer on the thinned piezoelectric thin film; disposing an electrical lead-out structure to lead out the electrical connections of the first electrode layer and the second electrode layer.

2. The manufacturing method of the bulk acoustic wave resonator according to claim 1, characterized in that, The material of the temporary substrate is any one or a combination of at least two of Si, sapphire, or SiC.

3. The manufacturing method of the bulk acoustic wave resonator according to claim 1, characterized in that, One layer of the low acoustic impedance layer and one layer of the high acoustic impedance layer in the Bragg reflection structure form a period, and the number of periods included in the Bragg reflection structure is n, where n is a positive integer greater than or equal to 1 and less than or equal to 9.

4. The manufacturing method of the bulk acoustic wave resonator according to claim 1, characterized in that, After thinning the exposed piezoelectric thin film, regrowing the piezoelectric thin film on the piezoelectric thin film to a preset thickness to meet the resonance parameters of the bulk acoustic wave resonator.

5. The manufacturing method of the bulk acoustic wave resonator according to claim 1, characterized in that, The step of disposing the electrical lead-out structure includes: disposing a through-hole at the piezoelectric thin film not covered by the second electrode layer above, where the through-hole is in contact with the first electrode layer; disposing an electrical lead-out structure in the through-hole to lead out the electrical connection of the first electrode layer, and disposing an electrical lead-out structure on the second electrode layer to lead out the electrical connection of the second electrode layer.

6. A bulk acoustic wave resonator, characterized in that, The bulk acoustic wave resonator is obtained by using the preparation method described in any one of claims 1-5. The bulk acoustic wave resonator includes: a bonding substrate, a bonding layer, a Bragg reflection structure, a first electrode layer, a piezoelectric thin film, a second electrode layer, and an electrical lead-out structure. The material of the piezoelectric thin film is undoped single-crystal aluminum nitride or scandium-doped single-crystal aluminum nitride; The bonding layer is disposed on the bonding substrate, the Bragg reflection structure is disposed on the bonding layer, the first electrode layer is disposed on the Bragg reflection structure, the piezoelectric thin film is disposed on the first electrode layer, the second electrode layer is disposed on the piezoelectric thin film, one of the electrical lead-out structures penetrates through the piezoelectric thin film to lead out the first electrode layer to the surface of the piezoelectric thin film, and the other electrical lead-out structure is electrically connected to the second electrode layer for leading out; a through-channel is provided at a position of the piezoelectric thin film where the first electrode layer is not provided, and the through-channel surrounds the edge of the first electrode layer to form isolation between two adjacent bulk acoustic wave resonators.

7. The bulk acoustic wave resonator according to claim 6, wherein, The material of the low acoustic impedance layer is any one or a combination of at least two of SiO2, AlN, Si3N4 or SiOC.

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