Film bulk acoustic resonator and preparation method therefor
By fabricating temperature compensation layers and electrode layers on both sides of the first piezoelectric layer of the thin-film bulk acoustic resonator, the temperature stability problem of FBAR is solved, high-quality piezoelectric and resonant performance are maintained, and the temperature stability and performance of the device are improved.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- WUHAN MEMSONICS TECH CO LTD
- Filing Date
- 2025-05-21
- Publication Date
- 2026-06-04
AI Technical Summary
Existing thin-film bulk acoustic resonators (FBARs) have poor temperature stability, which leads to frequency drift and affects the performance and reliability of high-precision applications. In particular, they may cause signal distortion and filter performance degradation in communication equipment.
A temperature compensation layer and an electrode layer are fabricated on both sides of the first piezoelectric layer of the thin-film bulk acoustic resonator by bonding, avoiding direct coverage of the piezoelectric layer by the temperature compensation layer, ensuring that the quality of the piezoelectric layer is not affected, and improving temperature stability.
This improves the temperature stability of the thin-film bulk acoustic resonator while maintaining excellent piezoelectric and resonant performance, avoiding the negative impact of the temperature compensation layer on the quality of the piezoelectric layer.
Smart Images
Figure CN2025096358_04062026_PF_FP_ABST
Abstract
Description
A thin-film bulk acoustic resonator and its fabrication method
[0001] Cross-reference to related applications
[0002] This disclosure claims priority to Chinese Patent Application No. 202411722391.8, filed on November 27, 2024, entitled "A Thin Film Bulk Acoustic Resonator and a Method for Preparing the Same", the entire contents of which are incorporated herein by reference. Technical Field
[0003] This disclosure relates to the field of semiconductor technology, and more specifically, to a thin-film bulk acoustic resonator and its fabrication method. Background Technology
[0004] Thin-film bulk acoustic resonators (FBARs) are high-performance devices widely used in radio frequency filters and wireless communication. Their core advantages lie in their high quality factor, low insertion loss, and miniaturization. However, the resonant frequency of FBARs is extremely sensitive to temperature changes. Temperature fluctuations cause thermal expansion of the material, changes in sound velocity, and alterations in mechanical stress, resulting in frequency drift. This temperature-induced frequency instability severely impacts the performance and reliability of FBARs in high-precision applications, especially in communication equipment, where frequency shifts can lead to signal distortion, filter performance degradation, and system failure.
[0005] In order to improve the temperature stability of FBAR, a temperature compensation layer is deposited on the electrode layer before the first piezoelectric layer is deposited. However, the introduction of the temperature compensation layer will have a negative impact on the subsequent film, especially on the quality of the first piezoelectric layer, which will lead to the damage of FBAR performance. Summary of the Invention
[0006] The purpose of this disclosure is to address the shortcomings of the prior art by providing a thin-film bulk acoustic resonator and its fabrication method, which can improve the temperature stability of FBAR while maintaining its superior performance.
[0007] To achieve the above objectives, the technical solutions adopted in the embodiments of this disclosure are as follows:
[0008] One aspect of this disclosure provides a method for fabricating a thin-film bulk acoustic resonator, comprising: providing a first substrate structure and forming a first piezoelectric layer on the first substrate structure; forming a first temperature compensation layer on the first piezoelectric layer, wherein the first temperature compensation layer covers a portion of the first piezoelectric layer; sequentially forming a first electrode layer and a first bonding layer on the first temperature compensation layer, wherein the first electrode layer covers the first temperature compensation layer and a portion of the first piezoelectric layer; providing a second substrate structure and forming a second bonding layer on the second substrate structure; bonding the first bonding layer and the second bonding layer; removing the first substrate structure and sequentially forming a second temperature compensation layer and a second electrode layer on the exposed first piezoelectric layer, wherein the second temperature compensation layer covers a portion of the first piezoelectric layer, the second temperature compensation layer corresponds to the position of the first temperature compensation layer, and the second electrode layer covers the temperature compensation layer and a portion of the first piezoelectric layer.
[0009] Optionally, after forming a first temperature compensation layer on the first piezoelectric layer, the method further includes: forming a second piezoelectric layer on the first piezoelectric layer and the first temperature compensation layer; forming a first electrode layer and a first bonding layer sequentially on the first temperature compensation layer includes: forming a first electrode layer and a first bonding layer sequentially on the second piezoelectric layer.
[0010] Optionally, forming a second temperature compensation layer and a second electrode layer sequentially on the exposed first piezoelectric layer includes: forming a second temperature compensation layer on the exposed first piezoelectric layer, wherein the second temperature compensation layer covers a portion of the first piezoelectric layer; forming a third piezoelectric layer on the first piezoelectric layer and the second temperature compensation layer; and forming a second electrode layer on the third piezoelectric layer, wherein the second electrode layer covers a portion of the third piezoelectric layer.
[0011] Optionally, forming a first temperature compensation layer on the first piezoelectric layer includes: forming a third electrode layer on the first piezoelectric layer and forming a first temperature compensation layer on the third electrode layer, wherein the third electrode layer covers a portion of the first piezoelectric layer and the first temperature compensation layer covers a portion of the third electrode layer; sequentially forming a first electrode layer and a first bonding layer on the first temperature compensation layer includes: forming a first electrode layer on the third electrode layer and the first temperature compensation layer, and forming a first bonding layer on the first electrode layer.
[0012] Optionally, forming a second temperature compensation layer and a second electrode layer sequentially on the exposed first piezoelectric layer includes: forming a fourth electrode layer on the exposed first piezoelectric layer and forming a second temperature compensation layer on the fourth electrode layer, wherein the fourth electrode layer covers a portion of the first piezoelectric layer and the second temperature compensation layer covers a portion of the fourth electrode layer; and forming a second electrode layer on the fourth electrode layer and the second temperature compensation layer.
[0013] Optionally, after removing the first substrate structure and sequentially forming a second temperature compensation layer and a second electrode layer on the exposed first piezoelectric layer, the method further includes:
[0014] A passivation layer is formed on the second electrode layer, and an annular groove is formed on the passivation layer. The annular groove is configured to suppress parasitic series resonant frequencies of the thin-film bulk acoustic resonator.
[0015] Optionally, the first temperature compensation layer includes a first sub-temperature compensation layer and a second sub-temperature compensation layer that surrounds the first sub-temperature compensation layer and is spaced apart from the first sub-temperature compensation layer, and the orthographic projection of the outer edge of the annular groove on the first sub-temperature compensation layer coincides with the outer edge of the first sub-temperature compensation layer.
[0016] Optionally, the second temperature compensation layer includes a third sub-temperature compensation layer and a fourth sub-temperature compensation layer that surrounds the third sub-temperature compensation layer and is spaced apart from the third sub-temperature compensation layer. The third sub-temperature compensation layer corresponds to the position of the first sub-temperature compensation layer, and the fourth sub-temperature compensation layer corresponds to the position of the second sub-temperature compensation layer.
[0017] Optionally, the orthographic projection of the outer edge of the third sub-temperature compensation layer onto the first sub-temperature compensation layer is located within the outer edge of the first sub-temperature compensation layer; a passivation layer is formed on the second electrode layer, and an annular groove is formed on the passivation layer, the annular groove being configured to suppress parasitic series resonant frequencies of the thin-film bulk acoustic resonator, including: forming a thickening layer on the second electrode layer, wherein the thickening layer and the region of the second electrode layer directly above the third sub-temperature compensation layer are spaced apart; a passivation layer is deposited on the second electrode layer and the thickening layer, wherein an annular groove is formed between the region of the passivation layer directly above the third sub-temperature compensation layer and the thickening layer.
[0018] Optionally, the orthographic projection of the outer edge of the second sub-temperature compensation layer onto the first electrode layer is located within the outer edge of the first electrode layer, and a plurality of first through holes are provided at intervals on the second sub-temperature compensation layer; and / or, the orthographic projection of the outer edge of the fourth sub-temperature compensation layer onto the second electrode layer is located within the outer edge of the second electrode layer, and a plurality of second through holes are provided at intervals on the fourth sub-temperature compensation layer.
[0019] Optionally, forming a first electrode layer and a first bonding layer sequentially on the first temperature compensation layer includes:
[0020] A first electrode layer is formed on the first temperature compensation layer, and a cavity layer is formed on the first electrode layer, wherein the cavity layer covers a portion of the first electrode layer;
[0021] A first bonding layer is formed on the cavity layer;
[0022] After removing the first substrate structure and sequentially forming a second temperature compensation layer and a second electrode layer on the exposed first piezoelectric layer, the method further includes:
[0023] Etch the release holes to remove the cavity layer.
[0024] In another aspect of the present disclosure, a thin-film bulk acoustic resonator is provided, which is prepared by the method for preparing a thin-film bulk acoustic resonator as described in any of the above embodiments.
[0025] The beneficial effects of the embodiments disclosed herein include:
[0026] This disclosure provides a method for fabricating a thin-film bulk acoustic wave resonator, comprising: providing a first substrate structure and forming a first piezoelectric layer on the first substrate structure; forming a first temperature compensation layer on the first piezoelectric layer, wherein the first temperature compensation layer covers a portion of the first piezoelectric layer; sequentially forming a first electrode layer and a first bonding layer on the first temperature compensation layer, wherein the first electrode layer covers the first temperature compensation layer and a portion of the first piezoelectric layer; providing a second substrate structure and forming a second bonding layer on the second substrate structure; bonding the first bonding layer and the second bonding layer; removing the first substrate structure, and sequentially forming a second temperature compensation layer and a second electrode layer on the exposed first piezoelectric layer, wherein the second temperature compensation layer covers a portion of the first piezoelectric layer, the second temperature compensation layer corresponds to the first temperature compensation layer in position, and the second electrode layer covers the temperature compensation layer and a portion of the first piezoelectric layer. This method for fabricating the thin-film bulk acoustic wave resonator employs a bonding method, first fabricating the first temperature compensation layer and the first electrode layer on one side of the first piezoelectric layer, and then fabricating the second temperature compensation layer and the second electrode layer on the other side of the first piezoelectric layer. Since both sides of the first piezoelectric layer have temperature compensation layers, the temperature stability of the thin-film bulk acoustic wave resonator can be improved. Furthermore, since the first piezoelectric layer is formed on the first substrate structure rather than on the temperature-compensated layer, a high-quality first piezoelectric layer can still be obtained even when temperature-compensated layers are fabricated on both sides of the first piezoelectric layer. This avoids the negative impact of introducing the temperature-compensated layer on the quality of the first piezoelectric layer, thereby maintaining the superior performance of the thin-film bulk acoustic wave resonator (such as piezoelectric properties, resonant properties, and mechanical properties). Therefore, the thin-film bulk acoustic wave resonator fabricated using the above-described method possesses both good temperature stability and superior performance. Attached Figure Description
[0027] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0028] Figure 1 is a flowchart of one of the methods for fabricating a thin-film bulk acoustic resonator provided in this embodiment of the present disclosure;
[0029] Figure 2 is one of the schematic diagrams illustrating the fabrication process of the thin-film bulk acoustic resonator provided in the embodiments of this disclosure;
[0030] Figure 3 is a second schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiments of this disclosure;
[0031] Figure 4 is a third schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiments of this disclosure;
[0032] Figure 5 is a fourth schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiments of this disclosure;
[0033] Figure 6 is a fifth schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiments of this disclosure;
[0034] Figure 7 is a schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiments of this disclosure;
[0035] Figure 8 is a schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiments of this disclosure (the seventh one).
[0036] Figure 9 is a schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiment of this disclosure;
[0037] Figure 10 is a schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiments of this disclosure;
[0038] Figure 11 is a second flowchart of the fabrication method of the thin-film bulk acoustic resonator provided in the embodiment of this disclosure;
[0039] Figure 12 is a schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiment of this disclosure;
[0040] Figure 13 is an eleventh schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiments of this disclosure;
[0041] Figure 14 is a schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiments of this disclosure, number 12.
[0042] Figure 15 is a schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiments of this disclosure, number thirteen.
[0043] Figure 16 is a flowchart of the third method for fabricating a thin-film bulk acoustic resonator according to an embodiment of this disclosure;
[0044] Figure 17 is a schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiments of this disclosure, number fourteen.
[0045] Figure 18 is a schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiments of this disclosure, number fifteen.
[0046] Figure 19 is a schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiment of this disclosure;
[0047] Figure 20 is a schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiments of this disclosure, number seventeen.
[0048] Figure 21 is an eighteenth schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiments of this disclosure;
[0049] Figure 22 is a schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiment of this disclosure, number nineteen.
[0050] Figure 23 is a schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiment of this disclosure;
[0051] Figure 24 is a flowchart of the fourth method for fabricating a thin-film bulk acoustic resonator according to an embodiment of this disclosure;
[0052] Figure 25 is a schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiment of this disclosure, number twenty-one.
[0053] Figure 26 is a flowchart of the fifth method for fabricating a thin-film bulk acoustic resonator according to an embodiment of this disclosure;
[0054] Figure 27 is a schematic diagram of the fabrication process of the thin-film bulk acoustic resonator provided in the embodiments of this disclosure, number twenty-two.
[0055] Icons: 10-First substrate structure; 11-First substrate layer; 12-Seed layer; 20-First piezoelectric layer; 30-First temperature compensation layer; 31-First sub-temperature compensation layer; 32-First airfoil region; 33-First air bridge region; 40-First electrode layer; 50-First bonding layer; 60-Second substrate structure; 61-Second substrate layer; 62-First oxide layer; 63-First via; 70-Second bonding layer; 80-Second temperature compensation layer; 81-Third sub-layer Temperature compensation layer; 82-Second air wing region; 83-Second air bridge region; 84-Second through hole; 90-Second electrode layer; 100-Second piezoelectric layer; 110-Third piezoelectric layer; 120-Third electrode layer; 130-Fourth electrode layer; 140-Passivation layer; 141-Annular groove; 150-Outlet hole; 160-Protective layer; 170-Cavity layer; 180-Release hole; 190-Buffer layer; 200-Second oxide layer; 210-Thickening layer. Detailed Implementation
[0056] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. The components of the embodiments of this disclosure described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.
[0057] Therefore, the following detailed description of the embodiments of this disclosure provided in the accompanying drawings is not intended to limit the scope of the claimed disclosure, but merely to illustrate selected embodiments of the disclosure. It should be noted that, unless otherwise specified, various features in the embodiments of this disclosure can be combined with each other, and the combined embodiments remain within the protection scope of this disclosure.
[0058] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.
[0059] In the description of this disclosure, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, the terms "first," "second," and "third," etc., are only configured to distinguish descriptions and should not be construed as indicating or implying relative importance.
[0060] In the description of this disclosure, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure based on the specific circumstances.
[0061] In one aspect of this disclosure, referring to FIG1, a method for fabricating a thin-film bulk acoustic resonator is provided, comprising:
[0062] S100: Provide a first substrate structure and form a first piezoelectric layer on the first substrate structure.
[0063] Referring to Figure 2, the first piezoelectric layer 20 is formed on the surface of the first substrate structure 10. Optionally, the first piezoelectric layer 20 completely covers the surface of the first substrate structure 10.
[0064] Optionally, forming the first piezoelectric layer 20 on the first substrate structure 10 includes depositing a piezoelectric material on the first substrate structure 10 to form the first piezoelectric layer 20. For example, the first piezoelectric layer 20 is formed using an MOCVD (Metal-Organic Chemical Vapor Deposition) process.
[0065] Piezoelectric materials may include at least one of aluminum nitride (AlN), lithium niobate (LiNbO3), lithium tantalate (LiTaO3), lead zirconate titanate (PZT), zinc oxide (ZnO), scandium-doped aluminum nitride (ScAlN), quartz crystal, lead magnesium niobate (PMN), and lead fluoride (PbTiO3).
[0066] Optionally, the first substrate structure 10 includes a first substrate layer 11, and a first piezoelectric layer 20 is formed on the surface of the first substrate layer 11 and adhered to the first substrate layer 11. Alternatively, the first substrate structure 10 includes a first substrate layer 11 and a seed layer 12 disposed on the first substrate layer 11, the seed layer 12 completely covering the surface of the first substrate layer 11 and adhering to the first substrate layer 11, and the first piezoelectric layer 20 is formed on the surface of the seed layer 12 and adhering to the seed layer 12.
[0067] The seed layer 12 provides a good growth basis for the preparation of the first piezoelectric layer 20 and can control the direction of crystal growth in the first piezoelectric layer 20, thereby improving the film quality of the first piezoelectric layer 20.
[0068] The material of the first substrate layer 11 may include at least one of sapphire (Al2O3), silicon carbide (SiC), and silicon (Si). The material of the seed layer 12 may include at least one of copper and nickel.
[0069] S200: A first temperature compensation layer is formed on the first piezoelectric layer, wherein the first temperature compensation layer covers a portion of the first piezoelectric layer.
[0070] Referring to Figure 3, the first temperature compensation layer 30 is formed on the side of the first piezoelectric layer 20 facing away from the first substrate structure 10 and covers a portion of the first piezoelectric layer 20. The material of the first temperature compensation layer 30 may include at least one of silicon dioxide (SiO2), titanium dioxide (TiO2), tantalum oxide (Ta2O5), silicon nitride (Si3N4), and aluminum oxide (Al2O3). The first temperature compensation layer 30 may also be a multilayer composite thin film.
[0071] It should be noted that, in the foregoing and subsequent descriptions, "one membrane layer completely covers another membrane layer" means that the orthographic projection of one membrane layer onto the other membrane layer completely covers the surface of the other membrane layer, without requiring that one membrane layer must be in direct contact with the other membrane layer. "One membrane layer partially covers another membrane layer" means that the orthographic projection of one membrane layer onto the other membrane layer partially covers the surface of the other membrane layer, without requiring that one membrane layer must be in direct contact with the other membrane layer. "One membrane layer covering another membrane layer" can mean either that one membrane layer completely covers the other membrane layer, or that one membrane layer partially covers the other membrane layer.
[0072] The first temperature compensation layer 30 may only have a first sub-temperature compensation layer 31 (as shown in Figure 3), or it may also have a second sub-temperature compensation layer surrounding the outside of the first sub-temperature compensation layer 31 and spaced apart from the first sub-temperature compensation layer 31. The second sub-temperature compensation layer is divided into a first air wing region 32 and a first air bridge region 33 (as shown in Figure 4). The first sub-temperature compensation layer 31 is configured to perform temperature compensation for the thin-film bulk acoustic resonator, and the first air wing region 32 and the first air bridge region 33 are respectively configured to form an air wing structure and an air bridge structure.
[0073] Optionally, forming the first temperature compensation layer 30 on the first piezoelectric layer 20 includes: depositing at least one layer of temperature compensation material on the first piezoelectric layer 20 to form a complete first temperature compensation film layer; etching the complete first temperature compensation film layer to remove part of the temperature compensation material and expose the first piezoelectric layer 20 below the temperature compensation material to form the first temperature compensation layer 30.
[0074] S300: A first electrode layer and a first bonding layer are sequentially formed on the first temperature compensation layer, wherein the first electrode layer covers the first temperature compensation layer and part of the first piezoelectric layer.
[0075] Referring to Figures 5 and 6, a first electrode layer 40 is first formed on the side of the first temperature compensation layer 30 opposite to the first piezoelectric layer 20, and then a first bonding layer 50 is formed on the side of the first electrode layer 40 opposite to the first piezoelectric layer 20. The first electrode layer 40 covers the first temperature compensation layer 30 and also partially covers the first piezoelectric layer 20. Optionally, the first bonding layer 50 completely covers the first piezoelectric layer 20. The first electrode layer 40 can be obtained by deposition followed by etching, and the first bonding layer 50 can be obtained by deposition.
[0076] The material of the first electrode layer 40 may include at least one of molybdenum (Mo), aluminum (Al), copper (Cu), tungsten (W), tantalum (Ta), platinum (Pt), ruthenium (Ru), rhodium (Rh), iridium (Ir), chromium (Cr), titanium (Ti), gold (Au), osmium (Os), rhenium (Re), and palladium (Pd). The material of the first bonding layer 50 may be gold (Au).
[0077] It should be noted that in this embodiment, the first bonding layer 50 can be bonded to the first electrode layer 40, and other films can also be disposed between the first bonding layer 50 and the first electrode layer 40.
[0078] S400: Provides a second substrate structure and forms a second bonding layer on the second substrate structure.
[0079] Referring to Figure 7, the second bonding layer 70 is formed on the surface of the second substrate structure 60. Optionally, the second bonding layer 70 completely covers the surface of the second substrate structure 60.
[0080] Optionally, forming a second bonding layer 70 on the second substrate structure 60 includes depositing a bonding material on the second substrate structure 60 to form the second bonding layer 70.
[0081] The material of the second bonding layer 70 can be gold (Au). Optionally, the material of the second bonding layer 70 is the same as that of the first bonding layer 50 to facilitate bonding between the two.
[0082] Optionally, the second substrate structure 60 includes a second substrate layer 61, and a second bonding layer 70 is formed on the surface of the second substrate layer 61 and adhered to the second substrate layer 61. Alternatively, the second substrate structure 60 includes a second substrate layer 61 and first oxide layers 62 respectively disposed on two opposite surfaces of the second substrate layer 61, the first oxide layers 62 completely covering the surface of the second substrate layer 61 and adhering to the second substrate layer 61, and the second bonding layer 70 is formed on the surface of one of the first oxide layers 62 and adhered to the first oxide layer 62.
[0083] The material of the second substrate layer 61 may include at least one of sapphire (Al2O3), silicon carbide (SiC), and silicon (Si). The material of the first oxide layer 62 may include SiO2.
[0084] S500: Bond the first bonding layer and the second bonding layer together.
[0085] The first bonding layer 50 and the second bonding layer 70 are aligned and bonded to obtain the semi-finished product shown in Figure 8.
[0086] S600: Remove the first substrate structure and sequentially form a second temperature compensation layer and a second electrode layer on the exposed first piezoelectric layer, wherein the second temperature compensation layer covers part of the first piezoelectric layer, the second temperature compensation layer corresponds to the position of the first temperature compensation layer, and the second electrode layer covers the temperature compensation layer and part of the first piezoelectric layer.
[0087] Referring to Figure 9, the first substrate structure 10 in the finished product is removed, thereby exposing the surface of the first piezoelectric layer 20 facing away from the first temperature compensation layer 30. Referring to Figure 10, a second temperature compensation layer 80 is first formed on the side of the first piezoelectric layer 20 facing away from the first temperature compensation layer 30, and then a second electrode layer 90 is formed on the side of the second temperature compensation layer 80 facing away from the first piezoelectric layer 20. This yields the sandwich structure of the thin-film bulk acoustic resonator (first electrode layer 40 - first piezoelectric layer 20 - second electrode layer 90), with temperature compensation layers on both sides of the first piezoelectric layer 20. Other process steps for fabricating the thin-film bulk acoustic resonator can be interspersed within or after the above steps.
[0088] Both the second temperature compensation layer 80 and the second electrode layer 90 can be obtained by deposition followed by etching. The material of the second temperature compensation layer 80 may include at least one of silicon dioxide (SiO2), titanium dioxide (TiO2), tantalum oxide (Ta2O5), silicon nitride (Si3N4), and aluminum oxide (Al2O3). The second temperature compensation layer 80 may also be a multilayer composite thin film. The material of the second electrode layer 90 may include at least one of molybdenum (Mo), aluminum (Al), copper (Cu), tungsten (W), tantalum (Ta), platinum (Pt), ruthenium (Ru), rhodium (Rh), iridium (Ir), chromium (Cr), titanium (Ti), gold (Au), osmium (Os), rhenium (Re), and palladium (Pd). Optionally, the structure and material of the second temperature compensation layer 80 are the same as those of the first temperature compensation layer 30; the material of the second electrode layer 90 is the same as that of the first electrode layer 40.
[0089] Optionally, forming a second temperature compensation layer 80 and a second electrode layer 90 sequentially on the exposed first piezoelectric layer 20 includes: depositing a temperature compensation material on the surface of the exposed first piezoelectric layer 20 to form a complete second temperature compensation film; etching the complete second temperature compensation film to remove part of the temperature compensation material and expose the first piezoelectric layer 20 below the temperature compensation material to form a second temperature compensation layer 80; depositing an electrode material on the second temperature compensation layer 80 and the first piezoelectric layer 20 exposed by the second temperature compensation layer 80 to form a complete second electrode film; etching the complete second electrode film to remove part of the electrode material and expose the first piezoelectric layer 20 below the electrode material to form a second electrode layer 90; and planarizing the surface of the second electrode layer 90 away from the first piezoelectric layer 20.
[0090] The second temperature compensation layer 80 may only have the third sub-temperature compensation layer 81, or it may also have a fourth sub-temperature compensation layer that surrounds the outside of the third sub-temperature compensation layer 81 and is spaced apart from the third sub-temperature compensation layer 81. The fourth sub-temperature compensation layer is divided into a second air wing region 82 and a second air bridge region 83 (as shown in Figure 4). The third sub-temperature compensation layer 81 is configured to perform temperature compensation for the thin-film bulk acoustic resonator, and the second air wing region 82 and the second air bridge region 83 are respectively configured to form an air wing structure and an air bridge structure.
[0091] The fabrication method of the aforementioned thin-film bulk acoustic wave resonator employs a bonding method. First, a first temperature compensation layer 30 and a first electrode layer 40 are fabricated on one side of the first piezoelectric layer 20. Then, a second temperature compensation layer 80 and a second electrode layer 90 are fabricated on the other side of the first piezoelectric layer 20. Since temperature compensation layers are present on both sides of the first piezoelectric layer 20, the temperature stability of the thin-film bulk acoustic wave resonator can be improved. Furthermore, because the first piezoelectric layer 20 is formed on the first substrate structure 10, rather than on the temperature compensation layer, a high-quality first piezoelectric layer 20 can still be obtained even with temperature compensation layers on both sides. This avoids the negative impact of introducing the temperature compensation layer on the quality of the first piezoelectric layer 20, thereby maintaining the superior performance of the thin-film bulk acoustic wave resonator (such as piezoelectric properties, resonant properties, and mechanical properties). Therefore, the thin-film bulk acoustic wave resonator fabricated using the above-described method possesses both good temperature stability and superior performance.
[0092] Optionally, referring to Figure 11, after forming the first temperature compensation layer on the first piezoelectric layer, the method further includes:
[0093] S700: A second piezoelectric layer is formed on the first piezoelectric layer and the first temperature compensation layer.
[0094] Referring to Figure 12, a first temperature compensation layer 30 is formed on the side of the first piezoelectric layer 20 facing away from the first substrate structure 10, and partially covers the first piezoelectric layer 20. After obtaining the first temperature compensation layer 30, a second piezoelectric layer 100 is formed on the side of the first temperature compensation layer 30 facing away from the first piezoelectric layer 20. The second piezoelectric layer 100 completely covers the first temperature compensation layer 30 and also covers the first piezoelectric layer 20 exposed by the first temperature compensation layer 30. The second piezoelectric layer 100 can be obtained by deposition, and the material of the second piezoelectric layer 100 is preferably the same as the material of the first piezoelectric layer 20.
[0095] Optionally, the thickness of the second piezoelectric layer 100 is greater than the thickness of the first temperature compensation layer 30, and the ratio of the thickness of the second piezoelectric layer 100 to the thickness of the first piezoelectric layer 20 is 0.08 to 0.12.
[0096] The formation of a first electrode layer and a first bonding layer sequentially on the first temperature compensation layer includes:
[0097] S310: A first electrode layer and a first bonding layer are sequentially formed on the second piezoelectric layer.
[0098] Referring to Figure 13, a first electrode layer 40 is first formed on the side of the second piezoelectric layer 100 away from the first piezoelectric layer 20, and then a first bonding layer 50 is formed on the side of the first electrode layer 40 away from the first piezoelectric layer 20.
[0099] The first temperature compensation layer 30 may only have a first sub-temperature compensation layer 31 (as shown in Figure 12), or it may also have a second sub-temperature compensation layer located on the side of the first sub-temperature compensation layer 31 and spaced apart from the first sub-temperature compensation layer 31. The second sub-temperature compensation layer is divided into a first air wing region 32 and a first air bridge region 33 (as shown in Figure 14). If the first temperature compensation layer 30 also has a first air wing region 32 and a first air bridge region 33, then after the second piezoelectric layer 100 is formed, the first air wing region 32 and the first air bridge region 33 of the first temperature compensation layer 30 must first be formed on the second piezoelectric layer 100, and then the first electrode layer 40 and the first bonding layer 50 are formed.
[0100] The first piezoelectric layer 20 and the second piezoelectric layer 100 constitute the first composite piezoelectric layer. The first temperature compensation layer 30 is located within the first composite piezoelectric layer, which can improve the temperature compensation effect and further improve the temperature stability of the thin-film bulk acoustic resonator. During fabrication, the thickness of the second piezoelectric layer 100 can be significantly smaller than the thickness of the first piezoelectric layer 20. In this way, the negative impact of the first temperature compensation layer 30 on the quality of the second piezoelectric layer 100 will not have a significant impact on the performance of the thin-film bulk acoustic resonator.
[0101] Optionally, referring again to Figure 11, the formation of a second temperature compensation layer and a second electrode layer sequentially on the exposed first piezoelectric layer includes:
[0102] S610: A second temperature compensation layer is formed on the exposed first piezoelectric layer, wherein the second temperature compensation layer covers a portion of the first piezoelectric layer.
[0103] Referring to Figure 15, the second thermal compensation layer 80 is formed on the side of the first piezoelectric layer 20 away from the second substrate structure 60, and covers part of the second piezoelectric layer 100.
[0104] S620: A third piezoelectric layer is formed on the first piezoelectric layer and the second thermal compensation layer.
[0105] After obtaining the second temperature compensation layer 80, a third piezoelectric layer 110 is formed on the side of the second temperature compensation layer 80 opposite to the first piezoelectric layer 20. The third piezoelectric layer 110 completely covers the second temperature compensation layer 80 and also covers the first piezoelectric layer 20 exposed by the second temperature compensation layer 80. The third piezoelectric layer 110 can be obtained by deposition, and the material of the third piezoelectric layer 110 is preferably the same as the material of the first piezoelectric layer 20.
[0106] Optionally, the thickness of the third piezoelectric layer 110 is greater than the thickness of the second temperature compensation layer 80, and the ratio of the thickness of the third piezoelectric layer 110 to the thickness of the first piezoelectric layer 20 is 0.08 to 0.12.
[0107] S630: A second electrode layer is formed on the third piezoelectric layer, and the second electrode layer partially covers the third piezoelectric layer.
[0108] The second temperature compensation layer 80 may only have the third sub-temperature compensation layer 81, or it may also have a fourth sub-temperature compensation layer that surrounds the outside of the third sub-temperature compensation layer 81 and is spaced apart from the third sub-temperature compensation layer 81. The fourth sub-temperature compensation layer is divided into a second air wing region 82 and a second air bridge region 83. If the second temperature compensation layer 80 also has the second air wing region 82 and the second air bridge region 83, then after the third piezoelectric layer 110 is formed, the second air wing region 82 and the second air bridge region 83 of the fourth temperature compensation layer must first be formed on the third piezoelectric layer 110, and then the second electrode layer 90 is formed.
[0109] The first piezoelectric layer 20 and the third piezoelectric layer 110 constitute the second composite piezoelectric layer. The second temperature compensation layer 80 is located within the second composite piezoelectric layer, which can improve the temperature compensation effect and further enhance the temperature stability of the thin-film bulk acoustic resonator. During fabrication, the thickness of the third piezoelectric layer 110 can be significantly smaller than the thickness of the first piezoelectric layer 20. In this way, the negative impact of the second temperature compensation layer 80 on the quality of the third piezoelectric layer 110 will not have a significant impact on the performance of the thin-film bulk acoustic resonator.
[0110] Optionally, referring to Figure 16, forming a first temperature compensation layer on the first piezoelectric layer includes:
[0111] S210: A third electrode layer is formed on the first piezoelectric layer, and a first temperature compensation layer is formed on the third electrode layer, wherein the third electrode layer covers a portion of the first piezoelectric layer, and the first temperature compensation layer covers a portion of the third electrode layer.
[0112] Referring to Figure 17, a third electrode layer 120 is first formed on the side of the first piezoelectric layer 20 that is away from the first substrate structure 10, and then a first temperature compensation layer 30 is formed on the side of the third electrode layer 120 that is away from the first substrate structure 10. Both the third electrode layer 120 and the first temperature compensation layer 30 can be obtained by deposition followed by etching.
[0113] The formation of a first electrode layer and a first bonding layer sequentially on the first temperature compensation layer includes:
[0114] S320: A first electrode layer is formed on the third electrode layer and the first temperature compensation layer, and a first bonding layer is formed on the first electrode layer.
[0115] Referring to Figure 18, after obtaining the first temperature compensation layer 30, a first electrode layer 40 is first formed on the side of the first temperature compensation layer 30 away from the first piezoelectric layer 20. The first electrode layer 40 simultaneously covers the first temperature compensation layer 30 and the third electrode layer 120 exposed by the first temperature compensation layer 30. Then, a first bonding layer 50 is formed on the side of the first electrode layer 40 away from the first piezoelectric layer 20.
[0116] The first temperature compensation layer 30 may only have a first sub-temperature compensation layer 31 (as shown in Figure 18), or it may also have a second sub-temperature compensation layer located on the side of the first sub-temperature compensation layer 31 and spaced apart from the first sub-temperature compensation layer 31. The second sub-temperature compensation layer is divided into a first air wing region 32 and a first air bridge region 33 (as shown in Figure 19). If the first temperature compensation layer 30 also has a first air wing region 32 and a first air bridge region 33, then after the third electrode layer 120 is formed, first etching holes configured to form the first air wing region 32 and the first air bridge region 33 can be etched on the third electrode layer 120 firstly, and then temperature compensation material can be deposited and a portion of the temperature compensation material can be etched away to simultaneously form the first sub-temperature compensation layer 31 and the second sub-temperature compensation layer.
[0117] The third electrode layer 120 and the first electrode layer 40 constitute the first composite electrode layer, and the first temperature compensation layer 30 is located within the first composite electrode layer.
[0118] Optionally, referring again to Figure 16, the formation of a second temperature compensation layer and a second electrode layer on the exposed first piezoelectric layer includes:
[0119] S640: A fourth electrode layer is formed on the exposed first piezoelectric layer, and a second temperature compensation layer is formed on the fourth electrode layer, wherein the fourth electrode layer covers a portion of the first piezoelectric layer, and the second temperature compensation layer covers a portion of the fourth electrode layer.
[0120] Referring to Figure 20, the fourth electrode layer 130 is formed on the side of the first piezoelectric layer 20 facing away from the second substrate structure 60, and partially covers the first piezoelectric layer 20. The second thermal compensation layer 80 is formed on the side of the fourth electrode layer 130 facing away from the second substrate structure 60, and partially covers the fourth electrode layer 130. The fourth electrode layer 130 can be formed by deposition followed by etching.
[0121] S650: A second electrode layer is formed on the fourth electrode layer and the second temperature compensation layer.
[0122] After obtaining the second temperature compensation layer 80, a second electrode layer 90 is formed on the side of the second temperature compensation layer 80 away from the first piezoelectric layer 20. The second electrode layer 90 covers the second temperature compensation layer 80 and the fourth electrode layer 130 exposed by the second temperature compensation layer 80.
[0123] The second temperature compensation layer 80 may only have a third sub-temperature compensation layer 81 (as shown in Figure 20), or it may also have a fourth sub-temperature compensation layer surrounding the outside of the third sub-temperature compensation layer 81 and spaced apart from the third sub-temperature compensation layer 81. The fourth sub-temperature compensation layer is divided into a second air wing region 82 and a second air bridge region 83 (as shown in Figure 21). If the second temperature compensation layer 80 also has a second air wing region 82 and a second air bridge region 83, a second etching hole configured to form the second air wing region 82 and the second air bridge region 83 can be etched on the fourth electrode layer 130 first, and then temperature compensation material can be deposited and a portion of the temperature compensation material can be etched away to simultaneously form the third sub-temperature compensation layer 81 and the fourth sub-temperature compensation layer.
[0124] The fourth electrode layer 130 and the second electrode layer 90 constitute the second composite electrode layer, and the second temperature compensation layer 80 is located within the second composite electrode layer.
[0125] In summary, the first temperature compensation layer 30 can be disposed between the first piezoelectric layer 20 and the first electrode layer 40, or within the first composite piezoelectric layer, or within the first composite electrode layer. The second temperature compensation layer 80 can be disposed between the first piezoelectric layer 20 and the second electrode layer 90, or within the second composite piezoelectric layer, or within the second composite electrode layer.
[0126] Optionally, after removing the first substrate structure and sequentially forming a second temperature compensation layer and a second electrode layer on the exposed first piezoelectric layer, the method further includes:
[0127] S800: A passivation layer is formed on the second electrode layer, and an annular groove is formed on the passivation layer. The annular groove is configured to suppress parasitic series resonant frequencies of the thin-film bulk acoustic resonator.
[0128] Referring to Figure 22, a passivation layer 140 is formed on the side of the second electrode layer 90 facing away from the second substrate structure 60. The passivation layer 140 is configured to protect the second electrode layer 90 and prevent oxidation. The passivation layer 140 can be formed by deposition followed by etching. The material of the passivation layer 140 may include at least one of SiO2, Si3N4, AlN, and Al2O3. An annular groove 141 is formed on the surface of the passivation layer 140 facing away from the second electrode layer 90. The annular groove 141 can be formed by etching the passivation layer 140, or it can be formed naturally on the passivation layer 140 during deposition.
[0129] Optionally, the first temperature compensation layer 30 includes a first sub-temperature compensation layer 31 and a second sub-temperature compensation layer that surrounds the first sub-temperature compensation layer 31 and is spaced apart from the first sub-temperature compensation layer 31. The orthographic projection of the outer edge of the annular groove 141 on the first sub-temperature compensation layer 31 coincides with the outer edge of the first sub-temperature compensation layer 31.
[0130] Optionally, the second temperature compensation layer 80 includes a third sub-temperature compensation layer 81 and a fourth sub-temperature compensation layer that surrounds the third sub-temperature compensation layer 81 and is spaced apart from the third sub-temperature compensation layer 81. The third sub-temperature compensation layer 81 corresponds to the position of the first sub-temperature compensation layer 31, and the fourth sub-temperature compensation layer corresponds to the position of the second sub-temperature compensation layer.
[0131] Both the second and fourth sub-temperature compensation layers are annular. Optionally, the fourth sub-temperature compensation layer and the second sub-temperature compensation layer have a rotationally symmetric structure, that is, the fourth sub-temperature compensation layer can be obtained by rotating the second sub-temperature compensation layer by 180°.
[0132] Optionally, referring to Figures 23 and 24, a passivation layer is formed on the second electrode layer on the outer edge of the third sub-temperature compensation layer 81, and an annular groove is formed on the passivation layer. The annular groove is configured to suppress parasitic frequencies of the series resonant frequency of the thin-film bulk acoustic resonator, including:
[0133] S810: A thickening layer is formed on the second electrode layer, wherein the thickening layer and the region of the second electrode layer located directly above the third sub-temperature compensation layer are spaced apart.
[0134] S820: A passivation layer is deposited on the second electrode layer and the thickening layer, wherein the passivation layer forms an annular groove between the region directly above the third sub-temperature compensation layer and the thickening layer.
[0135] The surface of the second electrode layer 90 is uneven, and the region of the second electrode layer 90 directly above the third sub-temperature compensation layer 81 is higher than other regions of the second electrode layer 90. A thickened layer 210 is formed on the other regions of the second electrode layer 90, forming a gap between the thickened layer 210 and the region of the second electrode layer 90 directly above the third sub-temperature compensation layer 81. A passivation layer 140 covers the thickened layer 210 and the region of the second electrode layer 90 directly above the third sub-temperature compensation layer 81, and fills the gap. Since the passivation layer 140 is obtained by deposition, its thickness is uniform. Therefore, an annular groove 141 is naturally formed between the region of the passivation layer 140 directly above the third sub-temperature compensation layer 81 and the thickened layer 210 during the preparation of the passivation layer 140. In this way, one etching operation on the passivation layer 140 can be reduced, thereby effectively reducing the process cost.
[0136] Optionally, the orthographic projection of the outer edge of the second sub-temperature compensation layer onto the first electrode layer 40 is located within the outer edge of the first electrode layer 40, and a plurality of first through holes 63 are provided at intervals on the second sub-temperature compensation layer; and / or, the orthographic projection of the outer edge of the fourth sub-temperature compensation layer onto the second electrode layer 90 is located within the outer edge of the second electrode layer 90, and a plurality of second through holes 84 are provided at intervals on the fourth sub-temperature compensation layer.
[0137] Referring to Figure 25, the orthographic projection of the outer edge of the second sub-temperature compensation layer onto the first electrode layer 40 lies within the outer edge of the first electrode layer 40. That is, the first electrode layer 40 is located outside the second sub-temperature compensation layer. After the second sub-temperature compensation layer is released, the region of the first electrode layer 40 located outside the second sub-temperature compensation layer can provide support, thereby improving the stability of the thin-film bulk acoustic resonator. Similarly, the orthographic projection of the outer edge of the fourth sub-temperature compensation layer onto the second electrode layer 90, which lies within the outer edge of the second electrode layer 90, can also improve the stability of the thin-film bulk acoustic resonator.
[0138] Multiple first through-holes 63 are spaced apart on the second sub-temperature compensation layer. When the first electrode layer 40 is formed on the second sub-temperature compensation layer, the first electrode layer 40 fills the first through-holes 63. After the second sub-temperature compensation layer is released, the area of the first electrode layer 40 located within the first through-holes 63 can provide support, thereby improving the stability of the thin-film bulk acoustic resonator. Similarly, multiple second through-holes 84 spaced apart on the fourth sub-temperature compensation layer can also improve the stability of the thin-film bulk acoustic resonator.
[0139] Optionally, after removing the first substrate structure 10 and sequentially forming the second temperature compensation layer 80 and the second electrode layer 90 on the exposed first piezoelectric layer 20, the method further includes: forming an outlet hole 150 in the area of the first piezoelectric layer 20 exposed by the second electrode layer 90, the outlet hole 150 exposing the surface of the first electrode layer 40; and forming a protective layer 160 within the second electrode layer 90 and the outlet hole 150, wherein the protective layer 160 is conductive.
[0140] Optionally, referring to Figures 26 and 6, the formation of a first electrode layer and a first bonding layer sequentially on the first temperature compensation layer includes:
[0141] S330: A first electrode layer is formed on the first temperature compensation layer, and a cavity layer is formed on the first electrode layer, wherein the cavity layer covers a portion of the first electrode layer.
[0142] S340: The first bonding layer is formed on the cavity layer.
[0143] After removing the first substrate structure and sequentially forming a second temperature compensation layer and a second electrode layer on the exposed first piezoelectric layer, the method further includes:
[0144] S900: Etch release holes to remove the cavity layer.
[0145] Referring to Figure 25, the cavity layer 170 can be released and removed in subsequent processes, thereby forming a cavity in the region where the cavity layer 170 is located. The material of the cavity layer 170 may include at least one of Si and Si3N4.
[0146] Optionally, the release hole 180 also passes through a second sub-temperature compensation layer and / or a fourth sub-temperature compensation layer, releasing the second and / or fourth sub-temperature compensation layers simultaneously with the release of the cavity layer 170, to form an air wing structure or an air bridge structure. Of course, the second and fourth sub-temperature compensation layers may not be released.
[0147] Before forming the cavity layer 170, a buffer layer 190 may be formed on the surface of the first electrode layer 40 away from the first piezoelectric layer 20. The buffer layer 190 completely covers the first electrode layer 40 and the first piezoelectric layer 20 exposed by the first electrode layer 40. The cavity layer 170 is formed on the surface of the buffer layer 190 away from the first electrode layer 40. The cavity layer 170 is located above the first temperature compensation layer 30 and covers part of the buffer layer 190.
[0148] Introducing a buffer layer 190 between the first electrode layer 40 and the cavity layer 170 can improve the interface matching between the two layers and reduce the difference in their coefficients of thermal expansion. The material of the buffer layer 190 may include at least one of SiO2 and Si3N4.
[0149] Before forming the first bonding layer 50, a second oxide layer 200 may be formed on the surface of the cavity layer 170 away from the first electrode layer 40. The second oxide layer 200 completely covers the cavity layer 170 and the buffer layer 190 exposed by the cavity layer 170. The first bonding layer 50 is formed on the surface of the second oxide layer 200 away from the first piezoelectric layer 20.
[0150] The second oxide layer 200 serves as an insulator, provides support and protection for the first bonding layer 50, limits the diffusion area of the first bonding layer 50, and reduces warping or breakage of the first bonding layer 50 due to differences in thermal expansion coefficients. Alignment marks can also be etched on the oxide layer to improve the bonding accuracy of the first bonding layer 50 and the second bonding layer 70 during subsequent bonding. The material of the second oxide layer 200 may include SiO2.
[0151] It should be understood that although the steps in the flowchart of the fabrication method of the thin-film bulk acoustic resonator are shown sequentially according to the arrows, these steps are not necessarily performed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be performed in other orders. Moreover, at least some steps in the flowchart of the fabrication method of the thin-film bulk acoustic resonator may include multiple steps or stages, which are not necessarily completed at the same time, but can be performed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.
[0152] Referring to Figures 25 and 27, this embodiment also provides a thin-film bulk acoustic wave resonator, which is fabricated using any of the above-described methods for fabricating thin-film bulk acoustic wave resonators. This thin-film bulk acoustic wave resonator exhibits both good temperature stability and superior performance.
[0153] The above description is merely a preferred embodiment of this disclosure and is not intended to limit the scope of this disclosure. Various modifications and variations can be made to this disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure. Industrial applicability
[0154] The method for fabricating a thin-film bulk acoustic wave resonator disclosed herein includes: providing a first substrate structure and forming a first piezoelectric layer on the first substrate structure; forming a first temperature compensation layer on the first piezoelectric layer; sequentially forming a first electrode layer and a first bonding layer on the first temperature compensation layer; providing a second substrate structure and forming a second bonding layer on the second substrate structure; bonding the first bonding layer and the second bonding layer; removing the first substrate structure and sequentially forming the second temperature compensation layer and the second electrode layer on the exposed first piezoelectric layer. This method for fabricating a thin-film bulk acoustic wave resonator employs a bonding method, first fabricating the first temperature compensation layer and the first electrode layer on one side of the first piezoelectric layer, and then fabricating the second temperature compensation layer and the second electrode layer on the other side of the first piezoelectric layer. Therefore, it can both improve the temperature stability of the thin-film bulk acoustic wave resonator and maintain its superior performance.
Claims
1. A method for fabricating a thin-film bulk acoustic resonator, characterized in that, include: A first substrate structure is provided, and a first piezoelectric layer is formed on the first substrate structure; A first temperature compensation layer is formed on the first piezoelectric layer, wherein the first temperature compensation layer covers a portion of the first piezoelectric layer; A first electrode layer and a first bonding layer are sequentially formed on the first temperature compensation layer, wherein the first electrode layer covers the first temperature compensation layer and a portion of the first piezoelectric layer; A second substrate structure is provided, and a second bonding layer is formed on the second substrate structure; Bond the first bonding layer and the second bonding layer together; The first substrate structure is removed, and a second temperature compensation layer and a second electrode layer are sequentially formed on the exposed first piezoelectric layer, wherein the second temperature compensation layer covers part of the first piezoelectric layer, the second temperature compensation layer corresponds to the position of the first temperature compensation layer, and the second electrode layer covers the temperature compensation layer and part of the first piezoelectric layer.
2. The method for fabricating a thin-film bulk acoustic resonator as described in claim 1, characterized in that, After forming the first temperature compensation layer on the first piezoelectric layer, the method further includes: A second piezoelectric layer is formed on the first piezoelectric layer and the first temperature compensation layer; The step of sequentially forming a first electrode layer and a first bonding layer on the first temperature compensation layer includes: A first electrode layer and a first bonding layer are sequentially formed on the second piezoelectric layer.
3. The method for fabricating a thin-film bulk acoustic resonator as described in claim 1, characterized in that, The step of sequentially forming a second temperature compensation layer and a second electrode layer on the exposed first piezoelectric layer includes: A second temperature compensation layer is formed on the exposed first piezoelectric layer, wherein the second temperature compensation layer covers a portion of the first piezoelectric layer; A third piezoelectric layer is formed on the first piezoelectric layer and the second temperature compensation layer; A second electrode layer is formed on the third piezoelectric layer, and the second electrode layer covers a portion of the third piezoelectric layer.
4. The method for fabricating a thin-film bulk acoustic resonator as described in claim 1, characterized in that, The formation of the first temperature compensation layer on the first piezoelectric layer includes: A third electrode layer is formed on the first piezoelectric layer, and a first temperature compensation layer is formed on the third electrode layer, wherein the third electrode layer covers a portion of the first piezoelectric layer, and the first temperature compensation layer covers a portion of the third electrode layer; The step of sequentially forming a first electrode layer and a first bonding layer on the first temperature compensation layer includes: A first electrode layer is formed on the third electrode layer and the first temperature compensation layer, and a first bonding layer is formed on the first electrode layer.
5. The method for fabricating a thin-film bulk acoustic resonator as described in claim 1, characterized in that, The step of sequentially forming a second temperature compensation layer and a second electrode layer on the exposed first piezoelectric layer includes: A fourth electrode layer is formed on the exposed first piezoelectric layer, and a second temperature compensation layer is formed on the fourth electrode layer, wherein the fourth electrode layer covers a portion of the first piezoelectric layer, and the second temperature compensation layer covers a portion of the fourth electrode layer; A second electrode layer is formed on the fourth electrode layer and the second temperature compensation layer.
6. The method for fabricating a thin-film bulk acoustic resonator as described in claim 1, characterized in that, After removing the first substrate structure and sequentially forming a second temperature compensation layer and a second electrode layer on the exposed first piezoelectric layer, the method further includes: A passivation layer is formed on the second electrode layer, and an annular groove is formed on the passivation layer, the annular groove being configured to suppress parasitic series resonant frequencies of the thin-film bulk acoustic resonator.
7. The method for fabricating a thin-film bulk acoustic resonator as described in claim 6, characterized in that, The first temperature compensation layer includes a first sub-temperature compensation layer and a second sub-temperature compensation layer that surrounds the first sub-temperature compensation layer and is spaced apart from the first sub-temperature compensation layer. The orthographic projection of the outer edge of the annular groove on the first sub-temperature compensation layer coincides with the outer edge of the first sub-temperature compensation layer.
8. The method for fabricating a thin-film bulk acoustic resonator as described in claim 7, characterized in that, The second temperature compensation layer includes a third sub-temperature compensation layer and a fourth sub-temperature compensation layer that surrounds the third sub-temperature compensation layer and is spaced apart from the third sub-temperature compensation layer. The third sub-temperature compensation layer corresponds to the position of the first sub-temperature compensation layer, and the fourth sub-temperature compensation layer corresponds to the position of the second sub-temperature compensation layer.
9. The method for fabricating a thin-film bulk acoustic resonator as described in claim 8, characterized in that, The orthographic projection of the outer edge of the third sub-temperature compensation layer onto the first sub-temperature compensation layer is located within the outer edge of the first sub-temperature compensation layer; The step of forming a passivation layer on the second electrode layer and forming an annular groove on the passivation layer, wherein the annular groove is configured to suppress parasitic series resonant frequencies of the thin-film bulk acoustic resonator, includes: A thickening layer is formed on the second electrode layer, wherein the thickening layer and the second electrode layer are spaced apart in the region directly above the third sub-temperature compensation layer; A passivation layer is deposited on the second electrode layer and the thickened layer, wherein the passivation layer forms an annular groove between the region directly above the third sub-temperature compensation layer and the thickened layer.
10. The method for fabricating a thin-film bulk acoustic resonator as described in claim 8, characterized in that, The orthographic projection of the outer edge of the second sub-temperature compensation layer onto the first electrode layer is located within the outer edge of the first electrode layer, and a plurality of first through holes are provided at intervals on the second sub-temperature compensation layer; And / or, The orthographic projection of the outer edge of the fourth sub-temperature compensation layer onto the second electrode layer is located within the outer edge of the second electrode layer, and a plurality of second through holes are provided at intervals on the fourth sub-temperature compensation layer.
11. The method for fabricating a thin-film bulk acoustic resonator as described in claim 1, characterized in that, The step of sequentially forming a first electrode layer and a first bonding layer on the first temperature compensation layer includes: A first electrode layer is formed on the first temperature compensation layer, and a cavity layer is formed on the first electrode layer, wherein the cavity layer covers a portion of the first electrode layer; A first bonding layer is formed on the cavity layer; After removing the first substrate structure and sequentially forming a second temperature compensation layer and a second electrode layer on the exposed first piezoelectric layer, the method further includes: The release hole is etched, and the cavity layer is removed through the release hole.
12. A thin-film bulk acoustic resonator, characterized in that, It is prepared by the method for preparing a thin-film bulk acoustic resonator as described in any one of claims 1 to 11.