Acoustic resonator with high power tolerance and preparation method thereof

Abstract

The invention provides a high-power tolerant acoustic resonator and a preparation method thereof, and belongs to the field of acoustic resonators. The acoustic resonator comprises a substrate, a heat dissipation layer, an interdigital transducer and a piezoelectric layer which are stacked in sequence. The heat dissipation layer comprises a first heat dissipation plate and a second heat dissipation plate which are oppositely arranged on the upper surface of the substrate, a first heat dissipation column which is connected with the first heat dissipation plate and extends towards the second heat dissipation plate, and a second heat dissipation column which is connected with the second heat dissipation plate and extends towards the first heat dissipation plate. The first heat dissipation column and the second heat dissipation column are both provided with holes. The interdigital transducer comprises a first bus located on the upper surface of the first heat dissipation plate, a first interdigital electrode located on the upper surface of the first heat dissipation column, a second bus located on the upper surface of the second heat dissipation plate and a second interdigital electrode located on the upper surface of the second heat dissipation column. The first heat dissipation columns and the second heat dissipation columns are alternately arranged in the direction parallel to the length of the first bus. The acoustic resonator is stable in structure, high in heat dissipation efficiency, large in tolerance power and large in Q value.

Description

Technical Field

[0001] This invention belongs to the field of acoustic resonator technology, specifically relating to a high-power-tolerant acoustic resonator and its fabrication method. Background Technology

[0002] Lamb wave resonators benefit from their large electromechanical coupling coefficient k 2t With a high efficiency (>20%) and a good factor of quality (FOM), Lamb wave resonators can achieve a wider bandwidth (e.g., supporting high-frequency bands above 5GHz) than traditional bulk acoustic wave (BAW) and surface acoustic wave (SAW) devices at the same frequency, making them particularly suitable for high-frequency, high-bandwidth scenarios such as 5G millimeter-wave filters. Currently, Lamb wave resonators are mainly divided into two types in terms of structure: piezoelectric thin film suspended resonators (XBAR) and solid-state assembled (SMR) Lamb wave resonators with multi-layer Bragg reflectors.

[0003] XBARs with suspended piezoelectric films can achieve a higher quality factor (Q factor) and reduce acoustic loss because the acoustic impedance difference between the piezoelectric layer and the air gap is greater. However, XBARs with suspended piezoelectric films have two significant drawbacks: (1) At high frequencies, the piezoelectric film suspended on the cavity is very thin (for example, the thickness of lithium niobate is less than 300 nm when the frequency is greater than 6 GHz). Due to the brittleness of the piezoelectric material and the large internal stress between the film layers, the mechanical stability of the XBAR resonator is poor. (2) The thermal conductivity of the piezoelectric material is low. For example, the thermal conductivity of the smart-stripped lithium niobate film is 5.6 W / (m·K). Due to the limited contact area between the piezoelectric film and the outside world, the heat generated by vibration and electrode resistance is difficult to dissipate effectively during operation, causing heat accumulation, which leads to an increase in the resonant cavity temperature and frequency drift, thus restricting the application of XBARs in high-power RF front-ends. Furthermore, XBAR acoustic resonators excited on piezoelectric thin film substrates are prone to generating various unintended stray modes (such as higher-order Lamb wave modes). These stray modes appear near the main resonance peak, severely degrading the frequency response curve of the device and reducing spectral purity and out-of-band suppression performance of the filter.

[0004] To address the aforementioned problems, prior art 1 (CN113904652A) discloses a Lamb wave resonator, comprising a supporting substrate, a supporting structure, a piezoelectric thin film, and a top electrode. The supporting substrate and the piezoelectric thin film are spaced apart. One end of the supporting structure is disposed on the surface of the supporting substrate, and the other end is disposed on a first surface of the piezoelectric thin film. The top electrode is disposed on a second surface of the piezoelectric thin film opposite to the supporting substrate. The top electrode and the supporting structure at least partially overlap in the thickness direction of the piezoelectric thin film. This Lamb wave resonator structure, on the one hand, provides physical support to the piezoelectric thin film through the supporting structure, improving the mechanical stability of the piezoelectric thin film and enhancing the resonator's heat dissipation and power characteristics. On the other hand, since the main mode energy of the Lamb wave resonator is mainly concentrated between the electrodes, and the top electrode and the supporting structure at least partially overlap in the thickness direction of the piezoelectric thin film, multiple reflections of sound waves transmitted to the electrode region will generate stray modes. Providing a supporting structure facilitates the leakage of stray sound wave energy to the supporting substrate, thereby mitigating the problem of numerous stray modes. However, in the XBAR Lamb wave resonator, the heat generated by the metal electrode material of the interdigital electrodes cannot be quickly conducted to the substrate through the support structure; that is, when interdigital electrodes are used as electrodes, the heat dissipation performance of this structure still needs to be improved.

[0005] Prior art 2 (CN119254174A) discloses a Lamb wave resonator, including a piezoelectric thin film, interdigitated electrodes and busbars located above the piezoelectric thin film, a functional heat dissipation thin film located below the piezoelectric thin film, and a supporting substrate located below the functional heat dissipation thin film. The bottom of the functional heat dissipation thin film has periodically or non-periodically arranged high aspect ratio grooves. The piezoelectric thin film region corresponding to the interdigitated electrodes is suspended. This Lamb wave resonator, by setting a finned heat dissipation structure, greatly increases the contact area between the thin film and the air, significantly enhancing the heat dissipation capacity of the resonator, thereby enhancing its power capacity and thermal stability; simultaneously, this structure can also suppress the resonance of stray modes in the resonator by scattering sound waves, thus playing a role in suppressing stray modes. However, in this scheme, air, as a heat dissipation medium, has a thermal conductivity of 0.024 W / (m·K), which is much lower than the thermal conductivity of the substrate material (Si substrate in this case, 149 W / (m·K), so the overall heat dissipation efficiency of the suspended structure is not high.

[0006] Prior art 3 (CN119298864A) discloses a transverse exciter acoustic resonator with improved power tolerance, including a support region, a resonant region, and an anchor. The support regions are located at both ends of the transverse exciter acoustic resonator; the resonant region is located between the two support regions and is connected to the two support regions via the anchor. A cavity is also provided between the two support regions, located below the resonant region and the anchor. The resonant region includes a composite film and at least two interdigitated metal electrodes on the surface of the composite film. The composite film includes a first thermally conductive material layer and a first piezoelectric material layer stacked together. The interdigitated metal electrodes are disposed on the surface of the first piezoelectric material layer. This transverse exciter acoustic resonator has high power tolerance characteristics and still possesses the excellent acoustic performance of a resonator; however, this resonator structure generates more stray modes. Summary of the Invention

[0007] To address the problems of poor structural stability, low heat dissipation efficiency, low power handling capacity, numerous stray modes, and low Q-value in existing Lamb wave resonators with suspended piezoelectric layers, this invention provides a high-power-handling acoustic resonator and its fabrication method. This acoustic resonator integrates efficient thermal management and stray mode acoustic suppression by introducing a multifunctional heat dissipation layer, simultaneously achieving the goals of improving structural stability, increasing power handling capacity and heat dissipation efficiency, reducing stray modes, and improving Q-value.

[0008] Specifically, the present invention adopts the following technical solution to achieve the above objectives: An acoustic resonator includes a substrate, a heat dissipation layer, an interdigital transducer, and a piezoelectric layer stacked sequentially from bottom to top. The heat dissipation layer includes a first heat sink, a first heat sink column, a second heat sink, and a second heat sink column. The first heat sink and the second heat sink are disposed opposite each other on the upper surface of the substrate. The first heat sink column is connected to the first heat sink and extends towards the second heat sink, and the second heat sink column is connected to the second heat sink and extends towards the first heat sink. The first heat sink has periodically distributed first pores along the direction of extension of the first heat sink column, and the second heat sink column has periodically distributed second pores along the direction of extension of the second heat sink column. The interdigital transducer includes a first busbar located on the upper surface of the first heat sink, a first interdigital electrode located on the upper surface of the first heat sink column, a second busbar located on the upper surface of the second heat sink, and a second interdigital electrode located on the upper surface of the second heat sink column. The first busbar and the second busbar are disposed opposite each other. The first interdigital electrode is led out from the first busbar and extends towards the second busbar, and the second interdigital electrode is led out from the second busbar and extends towards the first busbar. The first heat sink and the second heat sink column are alternately arranged in a direction parallel to the length of the first busbar.

[0009] In a preferred embodiment, the thermal conductivity of the heat dissipation layer material is >150 W / (m·K).

[0010] In a further preferred embodiment, the material of the heat dissipation layer is at least one of copper, aluminum, copper-aluminum alloy, gold, 4H-silicon carbide, 6H-silicon carbide, diamond, and aluminum nitride.

[0011] In a preferred embodiment, the orthographic projection of the first aperture on the upper surface of the substrate is the same first rectangle, and the ratio of the size W6 of the first rectangle to the size W1 of the first heat sink column is 0.3 to 0.7 along a direction parallel to the length of the first generatrix.

[0012] In a preferred embodiment, the orthographic projection of the second aperture on the upper surface of the substrate is the same second rectangle, and the ratio of the size W7 of the second rectangle to the size W2 of the second heat sink column is 0.3 to 0.7 along a direction parallel to the length of the second generatrix.

[0013] In a preferred embodiment, a plane perpendicular to the upper surface of the substrate and parallel to the extension direction of the first interdigital electrode is defined as section A. In the direction parallel to the extension direction of the first interdigital electrode, the size of the piezoelectric layer projected onto section A is L1, and the length of the overlap between the projections of the first interdigital electrode and the second interdigital electrode onto section A is L2. L1 equals L2, and the two sides of the piezoelectric layer are respectively flush with the ends of the extension of the first interdigital electrode and the end of the extension of the second interdigital electrode.

[0014] In a preferred embodiment, adjacent first interdigitated electrodes and second interdigitated electrodes form a pair of interdigitated electrodes, with a total of n pairs of interdigitated electrodes, where n is an integer ≥ 1; in a direction parallel to the length of the first busbar, the size of both the first interdigitated electrode and the second interdigitated electrode is W3, the distance between adjacent first interdigitated electrodes and second interdigitated electrodes is W4, the size of the piezoelectric layer is W5, W5 = 2nW3 + (2n-1)W4, and the two ends of the piezoelectric layer are flush with the edges of the interdigitated electrodes respectively.

[0015] In a preferred embodiment, the dimensions of the first heat sink are the same as those of the first interdigital electrode in a direction parallel to the direction in which the first interdigital electrode extends, and the dimensions of the second heat sink are the same as those of the second interdigital electrode.

[0016] In a preferred embodiment, the substrate is made of at least one of silicon, silicon carbide, sapphire, gallium nitride, and SOI.

[0017] In a preferred embodiment, the piezoelectric layer is made of at least one of lithium niobate, lithium tantalate, aluminum nitride, scandium-doped aluminum nitride, zinc oxide, and lead zirconate titanate.

[0018] In a preferred embodiment, the thickness of the piezoelectric layer is 100~800nm.

[0019] The method for fabricating the acoustic resonator includes the following steps: S1. The piezoelectric layer is formed on the first substrate, and the interdigital transducer is formed on the upper surface of the piezoelectric layer; the heat dissipation layer is formed on the second substrate. S2. Bond and align the surface of the interdigital transducer away from the piezoelectric layer with the surface of the heat dissipation layer away from the second substrate. S3. Remove the first substrate and retain the second substrate as the substrate; S4. Pattern the piezoelectric layer to obtain the acoustic resonator.

[0020] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: (1) The piezoelectric layer of the acoustic resonator provided by the present invention is located on the interdigital transducer. In addition to converting electrical signals into acoustic signals in the piezoelectric layer, the interdigital transducer can also support the piezoelectric layer and prevent the resonator from collapsing. Therefore, the structure of the acoustic resonator in the present invention is more stable.

[0021] (2) The acoustic resonator provided by the present invention has a multifunctional heat dissipation layer with high thermal conductivity. The structure of the multifunctional heat dissipation layer corresponds to the structure of the interdigital transducer. The busbar of the interdigital transducer is located on the heat dissipation plate in the multifunctional heat dissipation layer. The interdigital electrodes of the interdigital transducer are respectively located on the heat dissipation pillars of the multifunctional heat dissipation layer. The heat dissipation pillars and the interdigital electrodes are arranged in the same periodic manner to form a three-dimensional heat conduction path, which can quickly transfer the heat of the resonant region to the substrate. Therefore, the temperature of the device can be significantly reduced.

[0022] (3) The first heat dissipation column of the multifunctional heat dissipation layer is provided with periodically distributed first holes, and the second heat dissipation column is provided with periodically distributed second holes to form a Bragg reflector, which can accurately match and suppress specific unintended stray modes, thereby eliminating stray peaks, making the resonance curve cleaner, and improving the out-of-band suppression performance of the filter.

[0023] (4) The present invention further improves the Q value by adjusting the relationship between the size of the piezoelectric layer and the size of the interdigitated electrode to cut off the propagation path of the sound wave outside the resonant region. Attached Figure Description

[0024] Figure 1 A three-dimensional structural diagram of an acoustic resonator provided by the present invention; Figure 2 Top view of another acoustic resonator provided by the present invention; Figure 3 A cross-sectional view of another acoustic resonator provided by the present invention at section B; Figure 4 A cross-sectional view of another acoustic resonator provided by the present invention at section B; Figure 5 A cross-sectional view of another acoustic resonator provided by the present invention at section B; Figure 6 A schematic diagram of the pore distribution on the heat sink of an acoustic resonator provided by the present invention; Figure 7 The figures show the admittance curves of the acoustic resonator and the acoustic resonator without a heat dissipation layer in Embodiment 1 of the present invention.

[0025] In the figure: 1. Substrate; 21. First heat sink; 22. First heat sink pillar; 221. First pore; 23. Second heat sink; 24. Second heat sink pillar; 241. Second pore; 31. First busbar; 32. First interdigital electrode; 33. Second busbar; 34. Second interdigital electrode; 4. Piezoelectric layer. Detailed Implementation

[0026] The following description, in conjunction with embodiments, clearly and completely describes the technical solutions of this application, so that those skilled in the art can fully understand this application. Obviously, the described embodiments are merely some preferred embodiments of this application, and not all embodiments. Any equivalent modifications or substitutions made by those skilled in the art to the following embodiments without creative effort are within the protection scope of this application.

[0027] The directional terms described in this application, such as "upper," "lower," "inner," "outer," "bottom," and "upper surface," indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings or the orientations or positional relationships commonly used when the product is in use. These terms are used solely for the purpose of describing and understanding the product structure and should not be construed as limitations on this application. In this application, unless otherwise explicitly defined, expressions such as "upper," "above," "above," and "upper surface" for the first feature and the second feature indicate that the first and second features may be in direct contact or indirectly in contact through an intermediate medium; the first feature may be directly above or diagonally above the second feature, or simply indicate that the first feature is at a higher horizontal level than the second feature. Expressions such as "lower," "below," "below," and "lower surface" for the first feature and the second feature indicate that the first and second features may be in direct contact or indirectly in contact through an intermediate medium; the first feature may be directly below or diagonally below the second feature, or simply indicate that the first feature is at a lower horizontal level than the second feature. Ordinal numbers used in this application, such as "first" and "second," are for descriptive purposes only to distinguish similar objects and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Methods not described in detail in the following embodiments are conventional methods well-known to those skilled in the art.

[0028] like Figure 1 As shown (for ease of observation, regardless of...) Figure 1(Whether the material of the component structure is transparent or not, a portion of the structure is made transparent). A specific embodiment of the present invention provides an acoustic resonator, including a substrate 1, a heat dissipation layer, an interdigital transducer, and a piezoelectric layer 4 stacked sequentially from bottom to top. The heat dissipation layer includes a first heat dissipation plate 21, a first heat dissipation pillar 22, a second heat dissipation plate 23, and a second heat dissipation pillar 24. The first heat dissipation plate 21 and the second heat dissipation plate 23 are disposed opposite each other on the upper surface of the substrate 1. In a direction perpendicular to the upper surface of the substrate 1, the dimension (i.e., the height of the first heat dissipation pillar 22) H1 of the first heat dissipation pillar 22 is equal to the dimension (i.e., the height of the second heat dissipation pillar 24) H2 of the second heat dissipation pillar 24. The first heat dissipation pillar 22 is connected to the first heat dissipation plate 21 and extends towards the second heat dissipation plate 23. A first pore is periodically distributed on the first heat dissipation pillar 22 along its extension direction. The second heat dissipation pillar 24 is connected to the second heat dissipation plate 23 and extends towards the first heat dissipation plate 21 along its extension direction. A second pore is periodically distributed on the second heat dissipation pillar 24. The interdigital transducer includes a first busbar 31, a first interdigital electrode 32, a second busbar 33, and a second interdigital electrode 34. The first busbar 31 and the second busbar 33 are arranged opposite to each other. The first busbar 31 is located on the upper surface of the first heat sink 21. The second busbar 33 is located on the upper surface of the second heat sink 23. The first interdigital electrode 32 extends from the first busbar 31 toward the second busbar 33. The second interdigital electrode 34 extends from the second busbar 33 toward the first busbar 31. The first interdigital electrode 32 is located on the upper surface of the first heat sink 22. The second interdigital electrode 34 is located on the upper surface of the second heat sink 24. The first heat sink 22 and the second heat sink 24 are alternately arranged in a direction parallel to the length of the first busbar 31 (or the second busbar 33). Therefore, the first interdigital electrode 32 and the second interdigital electrode 34 are also alternately arranged in a direction parallel to the length of the first busbar 31 (or the second busbar 33). The acoustic waves excited in the piezoelectric layer 4 are antisymmetric Lamb waves A1 and their higher harmonics A3, A5 and A7, which are quasi-thickness shear waves.

[0029] In the above scheme, the first interdigital electrode 32 and the second interdigital electrode 34 are collectively referred to as interdigital electrodes. The first busbar 31 and the second busbar 33 are collectively referred to as busbars. The first heat sink 21 and the second heat sink 23 are collectively referred to as heat sinks. The first heat sink pillar 22 and the second heat sink pillar 24 are collectively referred to as heat sink pillars. The first pore and the second pore are collectively referred to as pores. The first busbar 31 of the interdigital transducer is located on the upper surface of the first heat sink 21, the second busbar 33 is located on the upper surface of the second heat sink 23, and the interdigital electrodes are located on the upper surfaces of the first heat sink pillar 22 and the second heat sink pillar 24, respectively. The structure in which the interdigital electrodes are in contact with the lower surface of the piezoelectric layer 4 allows the interdigital transducer to convert electrical signals into acoustic signals in the piezoelectric layer 4 while also supporting the piezoelectric layer 4 to prevent the acoustic resonator from collapsing, thus improving the mechanical stability of the acoustic resonator. Since the number and position of the first heat dissipation pillars 22 correspond one-to-one with the first interdigital electrodes 32, and the number and position of the second heat dissipation pillars 24 correspond one-to-one with the second interdigital electrodes 34, the first and second heat dissipation pillars 22 and 24 are arranged in a periodic alternation with the first and second interdigital electrodes 32 and 34, forming a three-dimensional heat conduction path. This transfers the heat generated in the resonant region to the substrate 1, significantly improving the heat dissipation efficiency of the acoustic resonator. The higher the thermal conductivity of the heat dissipation layer material, the better the heat dissipation effect. Simultaneously, since the heat dissipation pillars are provided with periodically distributed pores, these periodically distributed pores act as phonon crystals. On the one hand, they provide heat dissipation channels; on the other hand, the heat dissipation pillars and pores together form a Bragg reflector, which can accurately match and suppress specific unwanted stray modes, thereby eliminating spurious peaks, making the resonance curve cleaner, and improving the out-of-band rejection performance of the filter. Therefore, in addition to its heat dissipation function, the heat dissipation layer also supports the structure above it for mechanical stability and suppresses stray modes generated by the acoustic resonator.

[0030] Furthermore, substrate 1 is one or more of the following: silicon substrate, silicon carbide substrate, sapphire substrate, gallium nitride substrate, and SOI (silicon-on-insulator) substrate.

[0031] Furthermore, the heat dissipation layer is made of a material with a thermal conductivity greater than 150 W / (m·K). That is, the first heat dissipation plate 21, the first heat dissipation column 22, the second heat dissipation plate 23, and the second heat dissipation column 24 are all made of materials with a thermal conductivity greater than 150 W / (m·K). Even further, the heat dissipation layer is made of one or more of the following: copper, aluminum, aluminum-copper alloy, gold, 4H-silicon carbide, 6H-silicon carbide, diamond, and aluminum nitride; for example, the heat dissipation layer may be made of a copper-aluminum alloy or may consist of a copper foil layer and a diamond layer.

[0032] It is understood that the distance between two adjacent first pores can be equal or unequal. The distance between two adjacent second pores can be equal or unequal. The distance between two adjacent first pores and the distance between two adjacent second pores can be equal or unequal. The orthographic projection shapes of the first and second pores on the upper surface of substrate 1 can be regular shapes such as circles, triangles, ellipses, squares, and rectangles, or irregular shapes, or combinations of various shapes. The orthographic projection shapes of the first and second pores on the upper surface of substrate 1 can be the same or different. Further, in some preferred embodiments, such as... Figure 6 As shown (taking three pores as an example), the orthographic projections of the first pore 221 and the second pore 241 onto the upper surface of the substrate 1 are both regular patterns (e.g., Figure 6 The first aperture 221 is periodically distributed on the first heat sink 22, and the second aperture 241 is periodically distributed on the second heat sink 24 with the same period as the first aperture. The distance between the centers of the orthographic projections of two adjacent apertures onto the upper surface of the substrate 1 (the center of the orthographic projection of the aperture onto the upper surface of the substrate 1 is the geometric center of the regular pattern, such as the intersection of the two diagonals of a rectangle or the center of the circumcircle of a regular polygon) is P. col The wavelength of the unexpected acoustic modes (e.g., Lamb wave A3 mode) in piezoelectric layer 4 is λ. sp P col With λ sp Satisfy the following relationship: P col ≈λ sp / 2 or P col ≈λ sp / 4, to achieve Bragg reflection or periodic scattering, thereby uniformly propagating stray modes. In a further preferred embodiment, the orthographic projection of the first aperture 221 onto the upper surface of the substrate 1 is the same first rectangle, and the orthographic projection of the second aperture 241 onto the upper surface of the substrate 1 is the same second rectangle. Along the direction parallel to the length of the first generatrix 31 (or the second generatrix 33), the ratio of the size W6 of the first rectangle to the size W1 of the first heat sink 22 is 0.3 to 0.7, and the ratio of the size W7 of the second rectangle to the size W2 of the second heat sink 24 is 0.3 to 0.7. As an example, the ratio of W6 to W1 is 0.3, 0.4, 0.5, 0.6, or 0.7, and is not limited thereto. As an example, the ratio of W7 to W2 is 0.3, 0.4, 0.5, 0.6, or 0.7, and is not limited thereto.

[0033] Furthermore, the first heat sink 21 has a length of 40-500 μm in the direction parallel to the length of the first busbar 31 (or the second busbar 33), a thickness of 300-2000 nm in the direction perpendicular to the upper surface of the substrate 1, and a width of 0.5-20 μm in the direction extending along the first interdigital electrode 32 (or the second interdigital electrode 34). In the structure of the same acoustic resonator, the second heat sink 23 has the same dimensions as the first heat sink 21.

[0034] As an example, the length of the first heat sink is 40μm, 41μm, 42μm, 45μm, 48μm, 50μm, 55μm, 60μm, 70μm, 80μm, 90μm, 100μm, 105μm, 108μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, 200μm, 300μm, 400μm or 500μm, and is not limited thereto.

[0035] As an example, the thickness of the first heat sink is 300nm, 305nm, 310nm, 315nm, 320nm, 350nm, 380nm, 400nm, 450nm, 500nm, 600nm, 800nm, 900nm, 1000nm, 1100nm, 1300nm, 1500nm, 1800nm, or 2000nm, and is not limited thereto.

[0036] As an example, the width of the first heat sink is 0.5μm, 0.6μm, 0.7μm, 0.8μm, 1μm, 1.2μm, 1.5μm, 1.8μm, 2μm, 2.5μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 14.5μm, 15μm, 15.5μm, 16μm, 16.5μm, 17μm, 17.5μm, 18μm, 19μm, or 20μm, and is not limited thereto. Furthermore, the length of the first busbar 31 is 10~1500μm, its dimension (thickness of the first busbar) in the direction perpendicular to the upper surface of the substrate 1 is 30~1000nm, and its dimension (width of the first busbar) in the direction in which the first interdigital electrode 32 (or the second interdigital electrode 34) extends is 10~100μm. In the structure of the same acoustic resonator, the dimensions of the second busbar 33 and the first busbar 31 are the same.

[0037] As an example, the length of the first busbar is 10μm, 11μm, 12μm, 15μm, 18μm, 20μm, 25μm, 30μm, 50μm, 80μm, 100μm, 125μm, 150μm, 180μm, 200μm, 250μm, 300μm, 400μm, 500μm, 800μm, 1000μm, 1200μm, 1300μm, 1400μm, 1450μm, or 1500μm, and is not limited thereto.

[0038] As an example, the thickness of the first busbar is 30nm, 35nm, 40nm, 45nm, 50nm, 60nm, 80nm, 100nm, 150nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, or 1000nm, but is not limited to this.

[0039] As an example, the width of the first busbar is 10μm, 11μm, 12μm, 13μm, 15μm, 18μm, 20μm, 25μm, 30μm, 35μm, 40μm, 50μm, 60μm, 70μm, 80μm, 85μm, 90μm, 95μm or 100μm, and is not limited thereto.

[0040] It is understandable that the length of the first busbar 31 may be the same as or different from the length of the first heat sink 21, and the width of the first busbar 31 may be the same as or different from the width of the first heat sink 21. Similarly, the length of the second busbar 33 may be the same as or different from the length of the second heat sink 23, and the width of the second busbar 33 may be the same as or different from the width of the second heat sink 23.

[0041] Furthermore, the interdigital transducer is made of at least one of aluminum, copper, gold, and titanium.

[0042] Furthermore, the piezoelectric layer 4 is made of at least one of lithium niobate (LiNbO3), lithium tantalate (LiTaO3), aluminum nitride (AlN), scandium-doped aluminum nitride (AlScN), zinc oxide (ZnO), and lead zirconate titanate (PZT); wherein the scandium content in scandium-doped aluminum nitride is 20 at% to 43 at%. For example, the piezoelectric layer is a lithium niobate layer, or a lithium tantalate layer, or a composite layer of a lithium niobate layer and a lead zirconate titanate layer.

[0043] Furthermore, the thickness of the piezoelectric layer 4 is 100~800nm. For example, the thickness of the piezoelectric layer 4 is 100nm, 101nm, 102nm, 105nm, 110nm, 112nm, 115nm...800nm.

[0044] Furthermore, referring to Figure 2(For ease of observation, when the material of piezoelectric layer 4 is opaque,) Figure 2 (The piezoelectric layer 4 is shown in the image). A section A (not shown) is defined as the surface perpendicular to the upper surface of the substrate 1 and parallel to the extension direction of the first interdigital electrode 32. The dimension of the projection of the piezoelectric layer 4 onto section A in the direction parallel to the extension direction of the first interdigital electrode 32 is L1, and the length of the overlap between the projections of the first interdigital electrode 32 and the second interdigital electrode 34 onto section A is L2. It is understood that L1 and L2 can be equal or unequal. When L1 and L2 are equal, both sides of the piezoelectric layer 4 can be aligned with the ends of the interdigital electrodes; one side can expose the first interdigital electrode, while the other side is closer to the first generatrix; or one side can expose the second interdigital electrode, while the other side is closer to the second generatrix. In some preferred embodiments, L1 equals L2, and one side of the piezoelectric layer 4 is flush with the end of the first interdigital electrode 32, and the other side of the piezoelectric layer 4 is flush with the end of the second interdigital electrode 34. When L1=L2 and both sides of the piezoelectric layer 4 are flush with the ends of the interdigitated electrodes, cracks caused by stress concentration at the edges of the piezoelectric layer can be avoided.

[0045] Furthermore, referring to Figure 2 Adjacent first interdigital electrodes 32 and 34 are defined as a pair of interdigital electrodes, with a total of n pairs of interdigital electrodes, where n is an integer ≥ 1. In a direction parallel to the length of the first generatrix 31, the dimensions of both the first interdigital electrodes 32 and 34 are W3, the spacing between adjacent first interdigital electrodes 32 and 34 is W4, and the dimension of the piezoelectric layer 4 is W5, where W5 = 2nW3 + (2n-1)W4. One end of the piezoelectric layer 4 is flush with the edge of the first interdigital electrode 32 away from the second interdigital electrode 34, and the other end of the piezoelectric layer 4 is flush with the edge of the second interdigital electrode 34 away from the first interdigital electrode 32. This structural arrangement can cut off the propagation path of sound waves outside the resonant region, thereby optimizing the Q value.

[0046] Furthermore, continue to refer to Figures 1-5 In some embodiments, in a direction parallel to the extending direction of the first interdigital electrode 32 (or the second interdigital electrode 34), the size of the first heat sink 22 is the same as the size of the first interdigital electrode 32, and the size of the second heat sink 24 is the same as the size of the second interdigital electrode 34. In other embodiments, in a direction parallel to the extending direction of the first interdigital electrode 32 (or the second interdigital electrode 34), the size of the first heat sink 22 may be smaller or larger than the size of the first interdigital electrode 32, and the size of the second heat sink 24 may be smaller or larger than the size of the second interdigital electrode 34. It is understood that in a direction parallel to the extending direction of the first interdigital electrode 32 (or the first heat sink 22), the centerline of the first interdigital electrode 32 and the centerline of the first heat sink 22 may coincide (e.g., Figure 1 (As shown) They may also not coincide. In a direction parallel to the direction in which the second interdigital electrode 34 (or the second heat sink 24) extends, the centerline of the second interdigital electrode 34 and the centerline of the second heat sink 24 may coincide (as shown). Figure 1 (As shown) They may also not coincide. In some preferred embodiments, in a direction parallel to the extending direction of the first interdigital electrode 32 (or the first heat sink 22), the length of the first interdigital electrode 32 is equal to the length of the first heat sink 22, and the centerline of the first interdigital electrode 32 coincides with the centerline of the first heat sink 22; in a direction parallel to the extending direction of the second interdigital electrode 34 (or the second heat sink 24), the length of the second interdigital electrode 34 is equal to the length of the second heat sink 24, and the centerline of the second interdigital electrode 34 coincides with the centerline of the second heat sink 24.

[0047] Section B is defined as the section perpendicular to the upper surface of substrate 1 and parallel to the length direction of the first heat sink 21, and which cuts through the piezoelectric layer 4, the first interdigital electrode 32, the first heat sink 22, the second interdigital electrode 34, and the second heat sink 24. Figures 3-5 This is a cross-sectional view of the acoustic resonator at section B in some embodiments. It is understood that, as... Figures 3-5 As shown, in a direction parallel to the length of the first heat sink 21, the size of the first heat sink 22 (the width of the first heat sink) can be smaller than the size of the first interdigital electrode 32 (the width of the first interdigital electrode) (see...). Figure 4 It can also be larger than the size of the first interdigital electrode 32 (see...). Figure 5 The dimensions of the first heat sink 22 can also be equal to those of the first interdigital electrode 32. In some preferred embodiments, the dimensions of the first heat sink 22 are equal to those of the first interdigital electrode 32 in a direction parallel to the length of the first heat sink 21 (see [link to original text]). Figure 3 ).

[0048] Specific embodiments of the present invention also provide a method for fabricating the acoustic resonator, comprising the following steps: S1. The piezoelectric layer is formed on the first substrate, and the interdigital transducer is formed on the upper surface of the piezoelectric layer by deposition and patterning; a heat dissipation material is deposited on the second substrate, and the first heat dissipation plate, the first heat dissipation pillar, the second heat dissipation plate and the second heat dissipation pillar are etched to obtain a heat dissipation layer; S2. Bond and align the surface of the interdigital transducer away from the piezoelectric layer with the surface of the heat dissipation layer away from the second substrate. S3. Remove the first substrate and retain the second substrate as the substrate; S4. Pattern the piezoelectric layer to obtain the acoustic resonator.

[0049] Furthermore, the method for forming the piezoelectric layer in step S1 is any one of magnetron sputtering, sol-gel method, or bonding method.

[0050] Further, in step S1, the first substrate includes a body and a sacrificial layer. The material of the sacrificial layer is silicon dioxide, and the body is one or more of the following: silicon substrate, silicon carbide substrate, sapphire substrate, gallium nitride substrate, and SOI (silicon-on-insulator) substrate.

[0051] Further, in step S1, an interdigital transducer is formed on the upper surface of the piezoelectric layer through photolithography, metal deposition, and lift-off. The metal is at least one of aluminum, copper, copper-aluminum alloy, and gold.

[0052] Further, in step S1, a heat dissipation material layer with a thickness of 300~2000nm is deposited on the upper surface of the second substrate by any one of electroplating, sputtering, electron beam evaporation or chemical vapor deposition (CVD). Then, the heat dissipation material layer is patterned by photolithography and reactive ion etching (RIE) to form a first heat dissipation plate and a second heat dissipation plate arranged opposite to each other, as well as a first heat dissipation column and a second heat dissipation column that are periodically distributed.

[0053] The bonding in step S2 employs wafer-level bonding techniques, such as plasma activated bonding (PAB), metal thermocompression bonding, and surface activated bonding, to ensure periodicity and precise alignment of the interdigitated electrodes and heat sink pillars within 50 nm. Furthermore, the bonding in step S2 uses surface activated bonding (SAB) with a bonding temperature of room temperature to 150°C, a pressure of 10 to 50 MPa, and a cavity vacuum of <5 × 10⁻⁶. -3 Pa, to form an interface with a contact resistance of <1mΩ·cm², strength >50MPa, and good thermal conductivity (interfacial thermal resistance <1×10⁻⁶). -8 m 2 The interface is K / W. As an example, the bonding temperatures are 25℃, 30℃, 35℃, 40℃...150℃; the bonding pressures are 10MPa, 11MPa, 12MPa, 15MPa, 18MPa...50MPa.

[0054] Furthermore, in step S2, before the bonding alignment step, an adhesive layer is added to the surface of the interdigital transducer facing away from the piezoelectric layer and the surface of the heat dissipation layer facing away from the second substrate, respectively, to increase the bonding strength between the interdigital transducer and the heat dissipation layer. The adhesive layer is made of a metallic material (typically using metals such as Ti or Cr with a thickness of a few nanometers to tens of nanometers as the adhesive layer), and is deposited by magnetron sputtering or vacuum evaporation.

[0055] The methods for removing the first substrate in step S3 include etching, grinding, and chemical mechanical polishing (CMP). Further, in step S3, the first substrate is removed by wet solution etching or laser ablation to expose the upper surface of the piezoelectric layer. When the first substrate contains a sacrificial layer, the sacrificial layer reacts with the wet solution to separate the piezoelectric layer from the first substrate; or, during laser ablation of the first substrate, the sacrificial layer preferentially absorbs the laser and is ablated, achieving "low-stress ablation" between the piezoelectric layer and the first substrate.

[0056] Furthermore, in step S4, the piezoelectric layer is patterned using the RIE method.

[0057] Example 1 Reference Figure 1 and Figure 6 A high-frequency acoustic resonator based on a silicon substrate (suitable for 5G communication filters) includes a single-crystal silicon wafer with a thickness of 675 μm (resistivity > 10000 Ω·cm) serving as substrate 1, a heat dissipation layer located on the upper surface of substrate 1, an interdigital transducer located on the upper surface of the heat dissipation layer, and a piezoelectric layer 4. The heat dissipation layer is made of copper film (thermal conductivity 385 W / (m·K)). The heat dissipation layer includes a first heat dissipation plate 21, a first heat dissipation pillar 22, a second heat dissipation plate 23, and a second heat dissipation pillar 24. The first heat dissipation plate 21 and the second heat dissipation plate 23 are disposed opposite to each other on the upper surface of substrate 1. The first heat dissipation pillar 22 is connected to the first heat dissipation plate 21 and extends towards the second heat dissipation plate 23. In the direction of extension of the first heat dissipation pillar 22, first pores 221 are periodically distributed on the first heat dissipation pillar 22 (see...). Figure 6 The second heat dissipation column 24 is connected to the second heat dissipation plate 23 and extends towards the first heat dissipation plate 21. In the direction of extension of the second heat dissipation column 24, second pores 241 are periodically distributed on the second heat dissipation column 24 (see...). Figure 6The first heat sink 22 has a length of 120 μm, a width W1 of 6 μm, and a thickness H1 of 300 nm. The second heat sink 24 has a length of 120 μm, a width W2 of 6 μm, and a thickness H2 of 300 nm. The first heat sink 22 and the second heat sink 24 are arranged alternately in a direction parallel to the first heat sink 21 (or the second heat sink 23). The distance between adjacent first heat sink 22 and second heat sink 24 is 17 μm. The orthographic projection of the first aperture 221 onto the upper surface of the substrate 1 is always the same first rectangle. The orthographic projection of the second aperture 241 onto the upper surface of the substrate 1 is always the same second rectangle. The first rectangle and the second rectangle have the same shape, size, and spacing. In a direction parallel to the length of the first generatrix 31 (or the second generatrix 33), the ratio of the dimension W6 of the first rectangle to the width W1 of the first heat sink 22 is 0.5, and the ratio of the dimension W7 of the second rectangle to the width W2 of the second heat sink 24 is 0.5. The distance between the centers of the orthographic projections of the first aperture 221 of two adjacent periods onto the upper surface of substrate 1 is P. col The distance between the centers of the orthographic projections of the second aperture 241 of two adjacent periods onto the upper surface of substrate 1 is also P. colThe interdigital transducer includes a first busbar 31, a first interdigital electrode 32, a second busbar 33, and a second interdigital electrode 34. The first interdigital electrode 32 and the second interdigital electrode 34 are alternately arranged in a direction parallel to the length of the first busbar 31 (or the second busbar 33). The interdigital transducer is made of aluminum thin film with a thickness of 250 nm and contains 10 pairs of interdigital electrodes. Therefore, the first busbar 31, the first interdigital electrode 32, the second busbar 33, and the second interdigital electrode 34 are all made of aluminum thin film with a thickness of 250 nm. The first busbar 31 and the second busbar 33 have the same dimensions, both with a length of 494 μm and a width of 14 μm. The length L2 of the overlapping projections of the first interdigital electrode 32 and the second interdigital electrode 34 on section A is 100 μm. In the direction of extension of the first interdigital electrode 32, the centerline of the first interdigital electrode 32 coincides with the centerline of the first heat sink 22, and the length of the first interdigital electrode 32 is the same as the length of the first heat sink 22, with their ends aligned. In the direction in which the second interdigital electrode 34 extends, the centerline of the second interdigital electrode 34 coincides with the centerline of the second heat sink 24, and the length of the second interdigital electrode 34 is the same as the length of the second heat sink 24, with their ends aligned. In the direction parallel to the length of the first generatrix 31, the dimensions (widths) of the first interdigital electrode 32 and the second interdigital electrode 34 are both W3 = 3 μm, and the spacing between adjacent first interdigital electrodes 32 and second interdigital electrodes 34 is W4 = 20 μm. Therefore, the dimension (length) of the piezoelectric layer 4 in the direction parallel to the length of the first generatrix 31 is W5 = 440 μm. The material of the piezoelectric layer 4 is a lithium niobate thin film, with a thickness (the dimension of the piezoelectric layer 4 in the direction perpendicular to the upper surface of the substrate 1) of 270 nm and a width (the dimension of the piezoelectric layer 4 along the extension direction of the first interdigital electrode 32, which is also the dimension projected onto section A) L1 = 100 μm.

[0058] The fabrication method of this high-frequency acoustic resonator includes the following steps: S1. A Z-cut lithium niobate piezoelectric single-crystal thin film (refer to the technology mentioned in patent application CN119920687A) is formed as a piezoelectric layer on the first substrate through the steps of "ion slicing-bonding-peeling-polishing". An i-line (365nm) photoresist with a coating thickness of 1.2μm is coated on the upper surface of the piezoelectric layer, and 10 pairs of interdigital electrode patterns and two busbar patterns are formed by exposure and development. A 20nm thick chromium layer (as a bonding layer) and a 250nm thick aluminum layer (for fabricating the interdigital transducer) are formed by electron beam evaporation. The photoresist is removed by NMP (N-methylpyrrolidone) wet solution immersion and oxygen plasma ashing to form the interdigital transducer. The first substrate includes a silicon substrate and a silicon dioxide sacrificial layer.

[0059] A copper film is deposited on the second substrate by DC magnetron sputtering at a DC power of 150-250W (e.g., 200W) and a stage rotation speed of 20-30rpm (e.g., 30rpm) for 3 minutes to obtain a copper film with a thickness of 300nm. The patterns of a first heat sink, a first heat sink pillar, a second heat sink, and a second heat sink pillar are defined using photolithography. Then, reactive wet etching (e.g., H2SO4 / H2O2, FeCl3 system) is used to form the first and second heat sink pillars, each with a width of 6μm, a height of 300nm, and a length of 120μm. Simultaneously, first and second pores are etched onto the first and second heat sink pillars, respectively, as well as the first and second heat sinks, each with a length of 500μm, a width of 20μm, and a thickness of 300nm. The second substrate is a silicon substrate.

[0060] S2. The first substrate with interdigitated transducers and piezoelectric layers, and the second substrate with heat dissipation layers, are both placed in an ultra-high vacuum environment (pressure 5×10⁻⁶). -4 The copper and gold layers are bombarded using an argon (Ar) ion beam. The ion beam energy is typically between 40 and 100 eV (e.g., 80 eV), and the bombardment time is 120 to 180 seconds (e.g., 150 s). This step removes the oxide layer and other chemical contaminants from the metal surface while activating surface atoms. At room temperature and a pressure of 10 MPa, the cleaned and activated copper and gold surfaces are brought into contact and external pressure is applied. After bonding, the surfaces are annealed at 250°C for 45 minutes in a nitrogen atmosphere to increase bonding strength (achieving an interfacial bond strength > 50 MPa and an interfacial contact resistance < 1 mΩ·cm²).

[0061] S3. Using an NH4F-NH4Cl buffer solution (pH=4~5) (formulation: 20wt%~30wt% NH4F, 5wt%~10wt% NH4Cl, balance deionized water), wet-etch the silicon dioxide sacrificial layer of the first substrate at 50℃ for 2 minutes to expose the upper surface of the piezoelectric layer. The remaining second substrate is the substrate for the acoustic resonator.

[0062] S4. RIE etching of the piezoelectric layer is performed using a CF4 / O2 mixed gas (volume ratio of 1:1) at a power of 150W, a pressure of 3mTorr, and a rate of 80nm / min to remove excess lithium niobate and obtain a high-frequency acoustic resonator.

[0063] Simulation experiments were conducted on the high-frequency acoustic resonator and the acoustic resonator without a heat dissipation layer in this embodiment, and the results are as follows: Figure 7 The results are shown. The only difference between the acoustic resonator without a heat dissipation layer and the high-frequency acoustic resonator of Example 1 is that it lacks a heat dissipation layer. Figure 7The solid line represents the admittance curve of the acoustic resonator in this embodiment, while the dashed line represents the admittance curve of the acoustic resonator without a heat sink. For ease of alignment at the same frequency, all admittance curves have been offset vertically; the vertical axis does not represent the actual admittance value. Figure 7 As can be seen above, the Qs of the acoustic resonator without a heat dissipation layer is 431.42, while the Qs of the acoustic resonator in this invention is 468.68, representing an 8.64% increase in Q value. The heat dissipation layer in the high-frequency acoustic resonator of this embodiment is replaced with SiC, while the rest of the structure remains unchanged. The average temperature of the lithium niobate piezoelectric layer in the high-frequency acoustic resonator of this embodiment (with a copper heat dissipation layer), the high-frequency acoustic resonator with a SiC heat dissipation layer, and the aforementioned acoustic resonator without a heat dissipation layer were measured at input power levels of 30dBm, 33dBm, and 36dBm, respectively. The results are shown in Table 1.

[0064] Table 1. Average temperature of the piezoelectric layer in acoustic resonators with different structures.

[0065] As can be seen from Table 1, under high input power, the heat dissipation layer in the structure of the acoustic resonator of the present invention can significantly reduce the temperature of the piezoelectric layer, achieve good heat dissipation performance, and increase the reliability of the device.

[0066] Example 2 Reference Figure 1 and Figure 6 An acoustic resonator (suitable for high-frequency, high-power applications) includes a substrate 1, a heat dissipation layer on the upper surface of the substrate 1, an interdigital transducer on the upper surface of the heat dissipation layer, and a piezoelectric layer 4 on the interdigital transducer. The substrate 1 is made of silicon carbide, has a thickness of 500 μm, a thermal conductivity of 490 W / (m·K), and a resistivity of 1 × 10⁻⁶. 10The heat dissipation layer is made of diamond (thermal conductivity >2000 W / (m·K)) and has a thickness of 800 nm. The heat dissipation layer includes a first heat dissipation plate 21, a first heat dissipation pillar 22, a second heat dissipation plate 23, and a second heat dissipation pillar 24. The first heat dissipation plate 21 and the second heat dissipation plate 23 are disposed opposite each other on the upper surface of the substrate 1. The first heat dissipation pillar 22 is connected to the first heat dissipation plate 21 and extends towards the second heat dissipation plate 23. First pores 221 are periodically distributed on the first heat dissipation pillar 22 in the direction of its extension. The second heat dissipation pillar 24 is connected to the second heat dissipation plate 23 and extends towards the first heat dissipation plate 21. Second pores 241 are periodically distributed on the second heat dissipation pillar 24 in the direction of its extension. The first heat dissipation pillar 22 has a length of 100 μm, a width W1 of 8 μm, and a thickness H1 of 800 nm. The second heat dissipation pillar 24 has a length of 100 μm, a width W2 of 8 μm, and a thickness H2 of 800 nm. The first heat sink 22 and the second heat sink 24 are arranged alternately in a direction parallel to the first heat sink 21 (or the second heat sink 23). The distance between adjacent first heat sink 22 and second heat sink 24 is 4 μm. The orthographic projection of the first aperture 221 onto the upper surface of the substrate 1 is always the same first rectangle. The orthographic projection of the second aperture 241 onto the upper surface of the substrate 1 is always the same second rectangle. The first rectangle and the second rectangle are identical in shape, size, and spacing. In a direction parallel to the length of the first generatrix 31 (or the second generatrix 33), the ratio of the dimension W6 of the first rectangle to the width W1 of the first heat sink 22 is 0.7, and the ratio of the dimension W7 of the second rectangle to the width W2 of the second heat sink 24 is 0.7. The distance between the centers of the orthographic projections of two adjacent cycles of the first aperture 221 onto the upper surface of the substrate 1 is P. col The distance between the centers of the orthographic projections of the second aperture 241 of two adjacent periods onto the upper surface of substrate 1 is also P. colThe interdigital transducer includes a first busbar 31, a first interdigital electrode 32, a second busbar 33, and a second interdigital electrode 34. The first interdigital electrode 32 and the second interdigital electrode 34 are alternately arranged in a direction parallel to the length of the first busbar 31 (or the second busbar 33). The interdigital transducer is made of chromium and gold; the chromium layer serves as a bonding layer with a thickness of 10 nm; the gold layer is used to fabricate the interdigital electrodes and the busbar, and has a thickness of 65 nm. The interdigital transducer contains 50 pairs of interdigital electrodes. Therefore, the first busbar 31, the first interdigital electrode 32, the second busbar 33, and the second interdigital electrode 34 are all made of a gold thin film with a thickness of 65 nm. The first busbar 31 and the second busbar 33 have the same dimensions, both with a length of 200 μm and a width of 15 μm. The length L2 of the overlap of the projections of the first interdigital electrode 32 and the second interdigital electrode 34 on section A is 60 μm. In the direction in which the first interdigital electrode 32 extends, the centerline of the first interdigital electrode 32 coincides with the centerline of the first heat sink 22, and the length of the first interdigital electrode 32 is the same as the length of the first heat sink 22, with their ends aligned. In the direction in which the second interdigital electrode 34 extends, the centerline of the second interdigital electrode 34 coincides with the centerline of the second heat sink 24, and the length of the second interdigital electrode 34 is the same as the length of the second heat sink 24, with their ends aligned. In the direction parallel to the length of the first generatrix 31, the size (width) of both the first interdigital electrode 32 and the second interdigital electrode 34 is W3 = 2 μm, and the spacing between adjacent first interdigital electrodes 32 and second interdigital electrodes 34 is W4 = 10 μm. Therefore, the size (length) of the piezoelectric layer 4 in the direction parallel to the length of the first generatrix 31 is W5 = 1190 μm. The piezoelectric layer 4 is made of scandium-doped aluminum nitride (scandium yield is 30 at%) film, with a thickness (the dimension of the piezoelectric layer 4 in the direction perpendicular to the upper surface of the substrate 1) of 600 nm and a width (the dimension of the piezoelectric layer 4 along the extension direction of the first interdigital electrode 32, which is also the dimension projected onto the cross section A) L1 = 60 μm.

[0067] The fabrication method of this acoustic resonator includes the following steps: S1. The first substrate comprises a silicon carbide substrate and a silicon dioxide sacrificial layer: A 6-inch high-resistivity silicon substrate (resistivity 10000 Ω·cm) was cleaned with RCA (SC-1: NH4OH, H2O2, H2O volume ratio 1:1:5, 60℃, 10 min; SC-2: HCl, H2O2, H2O volume ratio 1:1:5, 60℃, 10 min), rinsed with deionized water, and then dried by N2 blowing. A silicon dioxide sacrificial layer was deposited on the cleaned silicon carbide substrate using magnetron sputtering at a power of 50 W, an Ar flow rate of 20 sccm, a substrate temperature of room temperature, and a time of 20 min.

[0068] Scandium-doped aluminum nitride (AlScN) films (Sc content 30 at%) were deposited on the upper surface of a silica sacrificial layer using magnetron sputtering with an AlSc alloy as the target. The magnetron sputtering power was 150 W, the Ar flow rate was 20 sccm, the N2 flow rate was 60 sccm, the total gas pressure was maintained at 0.4–0.6 Pa, and the substrate temperature was 250 °C. After magnetron sputtering, the resulting AlScN film had a thickness of 600 nm (measured by ellipsometry). XRD analysis showed it to be a wurtzite phase (characteristic peak at 2θ = 36.5°), and the Sc content was verified as 25 ± 2 at by EDS.

[0069] SU-8 photoresist was spin-coated onto the upper surface of the AlScN thin film at a speed of 2000 rpm for 30 s, resulting in a thickness of 3 μm. Exposure was performed (UV light, wavelength 365 nm, exposure dose 150 mJ / cm²), followed by development (SU-8 developer, 60℃ for 5 min) to form the busbar and interdigitated electrode patterns. The distance between adjacent interdigitated electrode patterns was 10 μm, and the width of each interdigitated electrode pattern was 2 μm. Chromium and gold were sequentially deposited using magnetron sputtering. The chromium layer was deposited to a thickness of 10 nm at a power of 30 W, an Ar flow rate of 10 sccm, and a substrate temperature of 50℃. The gold layer was deposited to a thickness of 65 nm at a power of 80 W, an Ar flow rate of 20 sccm, and a substrate temperature of 25℃. The photoresist was removed by sonication at 40 kHz for 10 min in NMP (N-methylpyrrolidone), while the interdigitated electrodes and busbars were retained, resulting in an interdigitated transducer (linewidth deviation < ±2%, metal layer thickness uniformity > 95%).

[0070] Using a 6-inch semi-insulating SiC substrate (resistivity 1×10⁻⁶) 10 A second substrate was used, with a thermal conductivity of 490 W / (m·K) and an Ω·cm (Ω·cm). Diamond was deposited on the second substrate by microwave plasma chemical vapor deposition (MPCVD). The microwave power was 3.0 kW, the volume ratio of methane to hydrogen in the CH4 / H2 mixed gas was 1:40, the substrate temperature was 800 °C, the pressure was 45 Torr, and the growth time was 2 h. After deposition, a heat dissipation material layer with a thickness of 800 nm (surface roughness Ra = 0.5 nm as measured by atomic force microscopy) was obtained, and the thermal conductivity (LFA method) result was 2100 ± 100 W / (m·K). The heat dissipation material layer was patterned by reactive ion etching (RIE, O2:CF4 volume ratio of 3:1, power of 80W, pressure of 0.1 Torr, time of 30min) to form a first heat dissipation plate and a second heat dissipation plate, both with a length of 200μm, and a first heat dissipation column and a second heat dissipation column, both with a length of 100μm, a width of 8μm, and a thickness of 800nm. The distance between two adjacent heat dissipation columns was 4μm, thus obtaining the heat dissipation layer.

[0071] S2. The surfaces of the interdigital transducers (AlScN / Al) and the heat dissipation layer (diamond / SiC) were cleaned with oxygen plasma at a power of 30W for 5 minutes to remove organic matter and oxides (X-ray photoelectron spectroscopy showed a 90% reduction in the area of ​​the O 1s peak).

[0072] At room temperature (25℃), pressure of 30 MPa, and cavity vacuum <5×10 -3 Under pressure of Pa, the surfaces of the cleaned interdigital transducers and the cleaned heat dissipation layer were brought into contact and external pressure was applied for 10 minutes to bond the interdigital transducers to the heat dissipation layer. Bonding effectiveness verification: interfacial contact resistance test (four-probe method) result was 0.6 mΩ·cm² (<1 mΩ·cm²); shear strength test (dicing mill, load 50 N) result was 72 MPa (>50 MPa); Raman spectroscopy showed no stress peak shift at the interface (FWHM = 1.0 cm). - ¹).

[0073] S3. The first substrate is removed using a laser ablation method. The laser parameters are as follows: Nd:YAG laser, wavelength 1064nm, pulse width 10ns, power 5W, focused spot diameter 20μm, scanning along the interface between the silicon carbide substrate and the silicon dioxide sacrificial layer at a scanning speed of 10mm / s. The laser energy is preferentially absorbed by SiO2 (absorption rate > 80%), and SiO2 decomposes into SiO and O2, achieving "low-stress ablation" between the piezoelectric layer and the silicon carbide substrate. The remaining second substrate is the substrate for the acoustic resonator.

[0074] S4. The piezoelectric layer is etched using a Cl2 / BCl3 mixed gas (volume ratio 4:1) with a etching power of 80W, a pressure of 0.2 Torr, an etching rate of 30 nm / min, and an etching time of 15 min to remove excess lithium niobate, thus obtaining a high-frequency acoustic resonator. The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Various modifications and variations can be made to the present invention by any person skilled in the art. Any simple equivalent changes and modifications made based on the scope of protection of this application and the content of the specification should be included within the scope of protection of this invention.

Claims

1. An acoustic resonator, characterized in that, The device comprises, from bottom to top, a substrate, a heat dissipation layer, an interdigital transducer, and a piezoelectric layer. The heat dissipation layer includes a first heat dissipation plate and a second heat dissipation plate disposed opposite each other on the upper surface of the substrate, a first heat dissipation column connected to the first heat dissipation plate and extending towards the second heat dissipation plate, and a second heat dissipation column connected to the second heat dissipation plate and extending towards the first heat dissipation plate. The first heat dissipation column has periodically distributed first pores along its extension direction, and the second heat dissipation column has periodically distributed second pores along its extension direction. The interdigital transducer includes a first busbar located on the upper surface of the first heat dissipation plate, a first interdigital electrode located on the upper surface of the first heat dissipation column, a second busbar located on the upper surface of the second heat dissipation plate, and a second interdigital electrode located on the upper surface of the second heat dissipation column. The first busbar and the second busbar are disposed opposite each other, the first interdigital electrode is led out from the first busbar and extends towards the second busbar, and the second interdigital electrode is led out from the second busbar and extends towards the first busbar. The first heat dissipation column and the second heat dissipation column are alternately arranged in a direction parallel to the length of the first busbar.

2. The acoustic resonator according to claim 1, characterized in that, The thermal conductivity of the material of the heat dissipation layer is >150W / (m·K).

3. The acoustic resonator according to claim 2, characterized in that, The heat dissipation layer is made of at least one of copper, aluminum, copper-aluminum alloy, gold, 4H-silicon carbide, 6H-silicon carbide, diamond, and aluminum nitride.

4. The acoustic resonator according to claim 1, characterized in that, The first aperture's orthographic projection on the upper surface of the substrate is always the same first rectangle, and the ratio of the size W6 of the first rectangle to the size W1 of the first heat sink is 0.3 to 0.7 along a direction parallel to the length of the first generatrix; or / and the second aperture's orthographic projection on the upper surface of the substrate is always the same second rectangle, and the ratio of the size W7 of the second rectangle to the size W2 of the second heat sink is 0.3 to 0.7 along a direction parallel to the length of the second generatrix.

5. The acoustic resonator according to claim 1, characterized in that, A plane perpendicular to the upper surface of the substrate and parallel to the extension direction of the first interdigital electrode is defined as section A. In the extension direction of the first interdigital electrode, the size of the piezoelectric layer projected onto section A is L1, and the length of the overlap between the projections of the first interdigital electrode and the second interdigital electrode onto section A is L2. L1 is equal to L2, and the two sides of the piezoelectric layer are flush with the ends of the first interdigital electrode and the second interdigital electrode, respectively.

6. The acoustic resonator according to claim 1, characterized in that, Adjacent first interdigital electrodes and second interdigital electrodes form a pair of interdigital electrodes, and there are a total of n pairs of interdigital electrodes, where n is an integer ≥ 1; in the direction parallel to the length of the first busbar, the size of the first interdigital electrode and the second interdigital electrode is W3, the distance between adjacent first interdigital electrodes and second interdigital electrodes is W4, the size of the piezoelectric layer is W5, W5 = 2nW3 + (2n-1)W4, and the two ends of the piezoelectric layer are flush with the edges of the interdigital electrodes respectively.

7. The acoustic resonator according to claim 1, characterized in that, In a direction parallel to the direction in which the first interdigital electrode extends, the size of the first heat sink is the same as the size of the first interdigital electrode, and the size of the second heat sink is the same as the size of the second interdigital electrode.

8. The acoustic resonator according to claim 1, characterized in that, The substrate is made of at least one of silicon, silicon carbide, sapphire, gallium nitride, and SOI; and / or the piezoelectric layer is made of at least one of lithium niobate, lithium tantalate, aluminum nitride, scandium-doped aluminum nitride, zinc oxide, and lead zirconate titanate.

9. The acoustic resonator according to claim 1, characterized in that, The thickness of the piezoelectric layer is 100~800nm.

10. The method for preparing the acoustic resonator according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1. The piezoelectric layer is formed on the first substrate, and the interdigital transducer is formed on the upper surface of the piezoelectric layer; the heat dissipation layer is formed on the second substrate. S2. Bond and align the surface of the interdigital transducer away from the piezoelectric layer with the surface of the heat dissipation layer away from the second substrate. S3. Remove the first substrate and retain the second substrate as the substrate; S4. Pattern the piezoelectric layer to obtain the acoustic resonator.

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