Bulk acoustic resonator and its manufacturing method, packaging structure and its manufacturing method

Abstract

This invention provides a method for manufacturing a bulk acoustic wave resonator, comprising: providing a substrate; forming a first groove on the upper surface of the substrate, the first groove having a bottom shape that is narrower at the top and wider at the bottom in a longitudinal section; forming a first thermally conductive layer with a thickness less than the depth of the first groove on a first predetermined surface of the first groove, wherein the first predetermined surface is the bottom surface of the first groove, or the bottom surface of the first groove and at least part of the sidewalls; filling the first groove with a sacrificial material; forming a stacked structure on the substrate, the stacked structure including a lower electrode, a piezoelectric layer, and an upper electrode from bottom to top; removing the sacrificial material to form a cavity below the stacked structure, the cavity overlapping the lower electrode, the piezoelectric layer, and the upper electrode in the thickness direction of the device. This invention also provides a bulk acoustic wave resonator, a packaging structure, and a method for manufacturing the same. Implementing this invention is beneficial for improving the heat dissipation efficiency of the device.

Description

Technical Field

[0001] This invention relates to the field of electronic communication device technology, and in particular to a bulk acoustic wave resonator and its manufacturing method, packaging structure and manufacturing method. Background Technology

[0002] Please refer to Figure 1 , Figure 1 This is a cross-sectional schematic diagram of a common bulk acoustic resonator in existing technology. For example... Figure 1 As shown, the bulk acoustic wave resonator includes a substrate 10, a stacked structure, and a cavity 14. The stacked structure is formed on the substrate 10, and from bottom to top, it includes a lower electrode 11, a piezoelectric layer 12, and an upper electrode 13. The cavity 14 is formed between the substrate 100 and the stacked structure, and overlaps with the lower electrode 11, the piezoelectric layer 12, and the upper electrode 13 in terms of device thickness (this overlapping area is the resonant region of the bulk acoustic wave resonator). The formation process of the above-mentioned conventional bulk acoustic wave resonator is as follows: first, a substrate is provided and etched to form a groove; then, the groove is filled with a sacrificial material; then, a stacked structure is formed on the substrate; finally, the sacrificial material is released to form a cavity. Considering the convenience of filling and releasing the sacrificial material, in the prior art, the cavity is usually designed with an inverted trapezoidal shape in longitudinal section (e.g., Figure 1 The structure shown is a trapezoid with an upper base larger than the lower base.

[0003] The advantage of a cavity is its ability to effectively reflect sound waves, thus reducing sound leakage. However, it also has a drawback: its heat conduction capability is not strong. This means that the existing bulk acoustic wave resonators cannot be used to realize high-power capacity devices (such as high-power capacity filters). Otherwise, when a high-power capacity device is operating, the heat generated by the bulk acoustic wave resonator, as a heat-generating component, cannot be transferred to the substrate in a timely manner through the cavity, and consequently, it cannot be transferred to the outside of the device in a timely manner through the substrate. As a result, the device will experience overheating, which may affect the device's performance or even cause damage.

[0004] Currently, to improve the heat dissipation efficiency of bulk acoustic wave (BAS) resonators, heat dissipation structures are typically formed on the surface of the BAS resonator, especially the surface of the substrate (e.g., the upper or lower surface of the substrate). While the formation of heat dissipation structures can accelerate the transfer of heat to the outside of the device to some extent, the problem of delayed heat transfer from the cavity to the substrate cannot be solved because the heat dissipation structures are formed on the surface of the BAS resonator. Furthermore, due to the different coefficients of thermal expansion / contraction between the heat dissipation structures and the substrate, their expansion / contraction during heat transfer differs, which can affect the bonding between the heat dissipation structures and the substrate, potentially leading to the heat dissipation structures detaching from the substrate surface. Summary of the Invention

[0005] To overcome the above-mentioned defects in the prior art, the present invention provides a bulk acoustic resonator, which includes:

[0006] Provide substrate;

[0007] A first groove is formed on the upper surface of the substrate, and the bottom of the longitudinal section of the first groove is narrow at the top and wide at the bottom;

[0008] A first thermally conductive layer with a thickness less than the depth of the first groove is formed on a first preset surface of the first groove, wherein the first preset surface is the bottom surface of the first groove, or the bottom surface of the first groove and at least part of the sidewall;

[0009] The first groove is filled with sacrificial material;

[0010] A stacked structure is formed on the substrate, the stacked structure comprising, from bottom to top, a lower electrode, a piezoelectric layer and an upper electrode;

[0011] The sacrificial material is removed to form a cavity beneath the stacked structure, the cavity having an overlapping region with the lower electrode, the piezoelectric layer, and the upper electrode in the device thickness direction.

[0012] According to one aspect of the invention, in this manufacturing method, the longitudinal section of the first groove is a trapezoidal shape, an inverted T-shape, or a Σ-shape with the upper base smaller than the lower base.

[0013] According to another aspect of the invention, in this manufacturing method, the upper surface of the substrate is etched using a Bosch process to form a first groove with a rough surface on the sidewalls.

[0014] According to another aspect of the present invention, in the manufacturing method, the step of forming a first thermally conductive layer with a thickness less than the depth of the first groove on a first predetermined surface of the first groove includes: forming a thermally conductive material on the upper surface of the substrate and on the sidewalls and bottom surface of the first groove, the thermally conductive material having a thickness less than the depth of the first groove; removing the portion of the thermally conductive material located outside the first predetermined surface of the first groove to form a first thermally conductive layer on the first predetermined surface of the first groove.

[0015] According to another aspect of the invention, in this manufacturing method, the thermal conductivity of the thermally conductive material is higher than that of the substrate material.

[0016] According to another aspect of the invention, in this manufacturing method, the thermally conductive material is graphene, silicon carbide, or a metal.

[0017] According to another aspect of the present invention, in this manufacturing method, the thermally conductive material is graphene; the step of forming a layer of thermally conductive material on the upper surface of the substrate and the sidewalls and bottom surface of the first groove includes: forming a graphene oxide layer on the upper surface of the substrate and the sidewalls and bottom surface of the first groove by spraying or immersing a graphene oxide solution; and reducing the graphene oxide layer to form a graphene layer; the step of removing the portion of the thermally conductive material located outside the first predetermined surface of the first groove includes: irradiating the portion of the graphene layer located outside the first predetermined surface of the first groove with ultraviolet light until that portion of the graphene layer is removed.

[0018] According to another aspect of the invention, the manufacturing method further includes forming a second thermally conductive layer on the lower surface of the substrate, the second thermally conductive layer having a material thermal conductivity higher than that of the substrate.

[0019] The present invention also provides a bulk acoustic resonator, the bulk acoustic resonator comprising:

[0020] Substrate;

[0021] A stacked structure is formed on the upper surface of the substrate, and from bottom to top includes a lower electrode, a piezoelectric layer and an upper electrode.

[0022] A cavity is formed between the substrate and the stacked structure. The cavity overlaps with the lower electrode, the piezoelectric layer and the upper electrode in the thickness direction of the device, and the bottom of the longitudinal section of the cavity is narrow at the top and wide at the bottom.

[0023] A first thermally conductive layer is formed on a second predetermined surface of the cavity and has a thickness less than the depth of the cavity, wherein the second predetermined surface is the bottom surface of the cavity, or the bottom surface of the cavity and at least part of the sidewall.

[0024] According to one aspect of the invention, in the bulk acoustic resonator, the longitudinal section of the cavity is a trapezoidal shape, an inverted T-shape, or a Σ-shape with the upper base smaller than the lower base.

[0025] According to another aspect of the invention, in this bulk acoustic resonator, the sidewalls of the cavity have rough surfaces.

[0026] According to another aspect of the invention, in the bulk acoustic resonator, the thermal conductivity of the material of the first thermally conductive layer is higher than that of the material of the substrate.

[0027] According to another aspect of the invention, in the bulk acoustic resonator, the material of the first thermally conductive layer is graphene, silicon carbide, or metal.

[0028] According to another aspect of the invention, the bulk acoustic resonator further includes: a second thermally conductive layer formed on the lower surface of the substrate, wherein the thermal conductivity of the material of the second thermally conductive layer is higher than that of the material of the substrate.

[0029] The present invention also provides a method for manufacturing a packaging structure, the method comprising:

[0030] A device wafer is provided, the device wafer including a plurality of bulk acoustic wave resonators, wherein at least one of the bulk acoustic wave resonators is formed using the aforementioned manufacturing method or implemented using the aforementioned bulk acoustic wave resonator;

[0031] A cap wafer is provided, the cap wafer including a body, on which a second groove is formed that corresponds one-to-one with the plurality of bulk acoustic resonators in position, wherein at least one of the second grooves has a bottom of its longitudinal section that is narrow at the top and wide at the bottom, and a third thermal conductive layer is formed on its third predetermined surface, the third predetermined surface being the bottom surface of the second groove, or the bottom surface of the second groove and at least part of the sidewall.

[0032] A connection structure for connecting the device wafer and the cap wafer is formed between the two, wherein the surface of the device wafer in which the bulk acoustic resonator is formed and the surface of the cap wafer in which the second groove is formed are disposed opposite to each other;

[0033] A conductive structure is formed for extracting electrical signals from the device wafer.

[0034] According to one aspect of the invention, in the encapsulation structure, the longitudinal section of the second groove is a trapezoidal shape, an inverted T-shape, or a Σ-shape with the upper base smaller than the lower base.

[0035] According to another aspect of the invention, in this encapsulation structure, the sidewall of the second groove has a rough surface.

[0036] According to another aspect of the invention, in this packaging structure, the thermal conductivity of the material of the third thermally conductive layer is higher than that of the material of the body.

[0037] According to another aspect of the invention, in this packaging structure, the material of the third thermally conductive layer is graphene, silicon carbide, or metal.

[0038] The present invention also provides a packaging structure, the packaging structure comprising:

[0039] A device wafer comprising a plurality of bulk acoustic wave resonators, at least one of which is formed using the aforementioned manufacturing method or implemented using the aforementioned bulk acoustic wave resonator;

[0040] A cap wafer includes a body on which second grooves are formed, each corresponding to one of the plurality of bulk acoustic wave resonators in position. The surface of the cap wafer with the second grooves is disposed opposite to the surface of the device wafer with the bulk acoustic wave resonators. At least one of the second grooves has a bottom section that is narrow at the top and wide at the bottom, and a third thermally conductive layer is formed on its third predetermined surface. The third predetermined surface is either the bottom surface of the second groove or the bottom surface of the second groove and at least part of the sidewall.

[0041] A connection structure is disposed between the device wafer and the cap wafer for connecting the device wafer and the cap wafer;

[0042] A conductive structure for bringing out electrical signals on the device wafer.

[0043] According to one aspect of the invention, in the encapsulation structure, the longitudinal section of the second groove is a trapezoidal shape, an inverted T-shape, or a Σ-shape with the upper base smaller than the lower base.

[0044] According to another aspect of the invention, in this encapsulation structure, the sidewall of the second groove has a rough surface.

[0045] According to another aspect of the invention, in this packaging structure, the thermal conductivity of the material of the third thermally conductive layer is higher than that of the material of the body.

[0046] According to another aspect of the invention, in this packaging structure, the material of the third thermally conductive layer is graphene, silicon carbide, or metal.

[0047] The method for manufacturing a bulk acoustic wave (SAW) resonator provided by this invention involves, on one hand, forming a groove on a substrate and forming a first thermally conductive layer on the bottom surface of the groove, or on the bottom surface and at least part of the sidewalls of the groove. The presence of the first thermally conductive layer improves the heat dissipation efficiency of the SAW resonator. Specifically, when the heat generated by the SAW resonator during operation is transferred to the substrate, the first thermally conductive layer effectively accelerates the heat transfer from the cavity to the substrate, ensuring that heat can be transferred from the substrate to the outside of the device in a timely manner. This improved heat dissipation efficiency effectively ensures that the temperature of the SAW resonator does not become excessively high during operation, thus ensuring that the performance of the SAW resonator is not affected, and making the SAW resonator suitable for the implementation of high-power capacity devices (such as high-power capacity filters). On the other hand, the groove on the substrate has a longitudinal section with a shape that is narrower at the top and wider at the bottom. This shape not only effectively prevents the first thermally conductive layer from shifting but also effectively increases the space for lateral heat transfer from the first thermally conductive layer, further ensuring the timely transfer of heat from the cavity to the substrate. The SAW resonator provided by this invention has high heat dissipation efficiency and is suitable for the implementation of high-power capacity devices. Accordingly, the packaging structure and manufacturing method of the bulk acoustic resonator provided by the present invention can effectively improve the heat dissipation efficiency of the packaging structure and are suitable for high power capacity scenarios. Attached Figure Description

[0048] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0049] Figure 1 This is a cross-sectional schematic diagram of a common bulk acoustic resonator in the prior art;

[0050] Figure 2 This is a flowchart of a method for manufacturing a bulk acoustic resonator according to a specific embodiment of the present invention;

[0051] Figures 3(a) to 3(g) According to Figure 2 The diagram shows cross-sectional schematics of each stage in the process of manufacturing a bulk acoustic resonator.

[0052] Figure 4(a) is a cross-sectional schematic diagram of the structure obtained after performing step S102 according to a specific embodiment of the present invention, wherein the first preset surface includes the bottom surface of the first groove and part of the sidewall;

[0053] Figure 4(b) is a cross-sectional schematic diagram of the structure obtained after performing step S102 according to another specific embodiment of the present invention, wherein the first preset surface includes the bottom surface of the first groove and the entire sidewall;

[0054] Figures 5(a) and 5(b) are flowcharts of a method for forming a first groove according to another specific embodiment of the present invention, wherein the longitudinal section of the first groove presents an inverted T-shape;

[0055] Figures 5(c) and 5(d) are cross-sectional schematic diagrams of the structure obtained after performing steps S102 and S105 based on the structure shown in Figure 5(b).

[0056] Figures 6(a) and 6(b) are flowcharts of a method for forming a first groove according to another specific embodiment of the present invention, wherein the longitudinal section of the first groove presents a Σ shape;

[0057] Figures 6(c) and 6(d) are cross-sectional schematic diagrams of the structure obtained after performing steps S102 and S105 based on the structure shown in Figure 6(b).

[0058] Figures 7(a) and 7(b) are flowcharts of a method for forming a first groove according to another specific embodiment of the present invention, wherein the longitudinal section of the first groove presents an inverted T-shape;

[0059] Figures 7(c) and 7(d) are schematic cross-sectional views of the structure obtained after performing steps S102 and S105 based on the structure shown in Figure 7(b).

[0060] Figures 8(a) to 8(d) This is a flowchart of a method for forming a first groove using a Bosch process according to a preferred embodiment of the present invention;

[0061] Figure 9 This is a cross-sectional schematic diagram of a bulk acoustic resonator according to a preferred embodiment of the present invention;

[0062] Figure 10 This is a flowchart of a manufacturing method for a packaging structure according to a specific embodiment of the present invention;

[0063] Figures 11(a) to 11(d) According to Figure 10 The diagram shows cross-sectional views of each stage of the process for manufacturing the packaging structure.

[0064] The same or similar reference numerals in the accompanying drawings represent the same or similar parts. Detailed Implementation

[0065] To better understand and explain the present invention, a further detailed description of the invention will be provided below in conjunction with the accompanying drawings.

[0066] This invention provides a method for manufacturing a bulk acoustic resonator. For example... Figure 2 As shown, the manufacturing method includes:

[0067] In step S100, a substrate is provided;

[0068] In step S101, a first groove is formed on the upper surface of the substrate, and the bottom of the longitudinal section of the first groove is narrow at the top and wide at the bottom.

[0069] In step S102, a first heat-conducting layer with a thickness less than the depth of the first groove is formed on a first preset surface of the first groove, wherein the first preset surface is the bottom surface of the first groove, or the bottom surface of the first groove and at least part of the sidewall.

[0070] In step S103, the first groove is filled with sacrificial material;

[0071] In step S104, a stacked structure is formed on the substrate, which includes a lower electrode, a piezoelectric layer and an upper electrode from bottom to top.

[0072] In step S105, the sacrificial material is removed to form a cavity below the stacked structure, the cavity having an overlapping area with the lower electrode, the piezoelectric layer and the upper electrode in the device thickness direction.

[0073] The following will combine Figures 3(a) to 3(g) , Figures 4(a) to 4(b) , Figures 5(a) to 5(d) , Figures 6(a) to 6(d) ,as well as Figures 7(a) to 7(d) The above steps will be explained in detail.

[0074] Specifically, in step S100, as shown in FIG3(a), a substrate 100 is provided. The present invention does not limit the material of the substrate 100; it can be implemented using existing or future materials used for manufacturing bulk acoustic wave resonator substrates, such as silicon, germanium, silicon-germanium, etc. For the sake of simplicity, not all possible materials for the substrate 100 will be listed here. Furthermore, the dimensions (including thickness, etc.) of the substrate 100 can be determined according to actual design requirements.

[0075] In step S101, the upper surface of the substrate is etched to form a first groove, wherein the bottom of the longitudinal section of the first groove is narrower at the top and wider at the bottom. In this embodiment, as shown in FIG3(b), the longitudinal section of the first groove 100a is a trapezoidal shape with the upper base smaller than the lower base (e.g., an isosceles trapezoid), and correspondingly, the bottom of the longitudinal section of the first groove 100a (the part circled in the figure) is narrower at the top and wider at the bottom. The steps for forming the first groove with the trapezoidal shape of the upper base smaller than the lower base are as follows: First, a photoresist layer (not shown) is formed on the upper surface of the substrate, and the photoresist layer is patterned to expose the area on the upper surface of the substrate where the first groove is to be formed; then, using the photoresist layer as a mask, an anisotropic etching process is used to etch the exposed area on the upper surface of the substrate to form a trapezoidal shape with the upper base smaller than the lower base; finally, the photoresist is removed. In this embodiment, the anisotropic etching process is implemented using a dry etching process, such as reactive ion etching (RIE), which can produce directional etching. By adjusting process parameters (e.g., bias voltage, and / or gas pressure in the reaction chamber), the angle between the sidewall and bottom surface of the first groove is adjusted, so that the longitudinal section of the first groove presents a trapezoidal shape with the upper base smaller than the lower base. Those skilled in the art will understand that the RIE process is only a preferred embodiment. Any etching process that can form a groove with a trapezoidal shape in longitudinal section with the upper base smaller than the lower base is applicable to this invention. For the sake of simplicity, not all possible etching processes will be listed here.

[0076] It should be noted that, considering the limitations and errors of existing processes, the trapezoidal shape mentioned in this invention includes not only a trapezoidal shape in the strict sense, but also shapes whose actual shape approximates a trapezoid. For example, if the surface of a groove has a rough appearance, but its longitudinal section generally resembles a trapezoid with the upper base smaller than the lower base, then the actual shape of the groove's longitudinal section is considered to be approximately trapezoidal, and therefore falls within the scope of protection of this invention. Those skilled in the art will understand that any subsequent references to the shape of the groove's longitudinal section refer to the explanation of the trapezoidal shape described herein.

[0077] In another specific embodiment, as shown in FIG5(b), the longitudinal section of the first groove 100a is an inverted T-shape, and correspondingly, the bottom of the longitudinal section of the first groove 100a (the part circled in the figure) is narrower at the top and wider at the bottom. The steps for forming the first groove with an inverted T-shaped longitudinal section are as follows: First, a photoresist layer (not shown) is formed on the upper surface of the substrate, and the photoresist layer is patterned to expose the area on the upper surface of the substrate where the first groove will be formed; then, as shown in FIG5(a), using the photoresist layer as a mask, an anisotropic etching process is used to etch the exposed area on the upper surface of the substrate to form a first rectangular groove 100b with a rectangular longitudinal section, the width of which is W1; then the photoresist layer is removed. An adhesive layer is applied, and a protective layer (not shown) is formed on the upper surface of the substrate 100 and the sidewalls of the first rectangular groove 100b. The material of this protective layer needs to have a large etching selectivity ratio with the material of the substrate 100. Then, as shown in FIG. 5(b), using the protective layer as a mask, an anisotropic etching process is employed to continue etching the bottom of the first rectangular groove 100b to form a second rectangular groove with a rectangular longitudinal section below the first rectangular groove 100b. The width of the longitudinal section of the second rectangular groove is W2, where W2 is greater than W1. The second rectangular groove and the first rectangular groove together constitute the first groove 100a with an inverted T-shaped longitudinal section. Finally, the protective layer is removed.

[0078] In another specific embodiment, as shown in FIG6(b), the longitudinal section of the first groove 100a is Σ-shaped, and correspondingly the bottom of the longitudinal section of the first groove 100a (the part circled in the figure) is narrow at the top and wide at the bottom. The steps for forming the first groove with a Σ-shaped longitudinal section are as follows: First, a photoresist layer (not shown) is formed on the upper surface of the substrate, and the photoresist layer is patterned to expose the area on the upper surface of the substrate where the first groove is to be formed; then, as shown in FIG6(a), the exposed area on the upper surface of the substrate is etched using the photoresist layer as a mask and an anisotropic etching process to form a first trapezoidal groove 100c with a longitudinal section where the upper base is larger than the lower base; then, as shown in FIG6(b), the first trapezoidal groove 100c is further etched using an anisotropic etching process to form a second trapezoidal groove with a longitudinal section where the upper base is smaller than the lower base below the first trapezoidal groove 100c, and the second trapezoidal groove and the first trapezoidal groove together constitute the first groove 100a with a Σ-shaped longitudinal section; finally, the photoresist layer is removed.

[0079] In another specific embodiment, as shown in FIG7(b), the longitudinal section of the first groove 100a is an inverted T-shape, and correspondingly, the bottom of the longitudinal section of the first groove 100a (the part circled in the figure) is narrower at the top and wider at the bottom. The steps for forming the first groove with an inverted T-shaped longitudinal section are as follows: First, a photoresist layer (not shown) is formed on the upper surface of the substrate, and the photoresist layer is patterned to expose the area on the upper surface of the substrate where the first groove is to be formed; then, as shown in FIG7(a), using the photoresist layer as a mask, an anisotropic etching process is used to etch the exposed area on the upper surface of the substrate to form a third trapezoidal groove 100d with a longitudinal section where the upper base is larger than the lower base; then, the photoresist layer is removed, and etching is performed on the upper surface of the substrate 100 and the sides of the third trapezoidal groove 100d. A protective layer (not shown) is formed on the wall. The material of this protective layer needs to have a large etching selectivity ratio with the material of the substrate 100. Then, as shown in FIG7(b), the bottom of the third trapezoidal groove 100c is etched using an anisotropic etching process with the protective layer as a mask to form a third rectangular groove with a rectangular longitudinal section below the third trapezoidal groove 100c. The width of the longitudinal section of the third rectangular groove is greater than the width of the bottom of the third trapezoidal groove. The third rectangular groove and the third rectangular groove together constitute a first groove 100a with an inverted T-shaped longitudinal section. Finally, the protective layer is removed. It should be noted here that the sidewall of the third trapezoidal groove is obtuse to the bottom surface, and the sidewall of the third rectangular groove is perpendicular (or approximately perpendicular) to the bottom surface. The different angles between the sidewall of the groove and the bottom surface can be achieved by adjusting the process parameters (e.g., bias voltage, gas ratio in the reaction chamber, gas pressure in the reaction chamber, etc.).

[0080] Those skilled in the art will understand that the above examples of the longitudinal section of the first groove are merely preferred embodiments and should not be construed as limiting the shape of the longitudinal section of the first groove. Any groove that is feasible and whose bottom of the longitudinal section is narrow at the top and wide at the bottom falls within the protection scope of this invention. For the sake of brevity, all possible shapes of the longitudinal section of the first groove will not be listed here.

[0081] The following explanation will continue based on the structure shown in Figure 3(b) (i.e., the longitudinal section of the first groove presents a trapezoidal shape with the upper base smaller than the lower base).

[0082] In step S102, in this embodiment, firstly, as shown in FIG3(c), a layer of thermally conductive material 101 is formed on the upper surface of the substrate 100 and the surface (including the sidewalls and bottom surface) of the first groove 100a (i.e., a layer of thermally conductive material 101 covering the upper surface of the structure formed by opening the first groove 100a is formed), wherein the thickness of the thermally conductive material 101 is less than the depth of the first groove 100a. Next, as shown in FIG3(d), the portion of the thermally conductive material 101 located outside the first predetermined surface of the first groove 100a is removed to form a first thermally conductive layer 101a on the first predetermined surface of the first groove 100a. The first predetermined surface refers to a region in the surface of the first groove 100a pre-defined for forming the first thermally conductive layer 101a. In this embodiment, the first predetermined surface is the bottom surface of the first groove 100a. It should be noted that (1) the first preset surface in this invention includes at least the bottom surface of the first groove 100a. That is, in addition to the case in this embodiment, in other embodiments, as shown in FIG4(a), the first heat-conducting layer 101a can also be formed on the bottom surface and part of the sidewall of the first groove 100a (i.e., the first preset surface is the bottom surface and part of the sidewall of the first groove 100), or as shown in FIG4(b), the first heat-conducting layer 101a can be formed on the bottom surface and all the sidewalls of the first groove 100a (i.e., the first preset surface is the bottom surface and the entire sidewall of the first groove 100a). (2) The above-mentioned method of forming a heat-conducting material on the upper surface of the substrate and the surface of the first groove first, and then removing the part of the heat-conducting material located outside the first preset surface of the first groove to form the first heat-conducting layer is only a preferred embodiment. It should not be construed as a limitation on the formation method of the first heat-conducting layer. Any method that can form the first heat-conducting layer on the first preset surface of the first groove is applicable to this invention. For the sake of brevity, all possible formation methods of the first heat-conducting layer will not be listed here. (3) For the structures shown in Figures 5(b) and 7(b) (i.e., the longitudinal section of the first groove is inverted T-shaped), the structure obtained after forming the first heat-conducting layer 101a on the bottom surface of the first groove 100a can be referred to Figures 5(c) and 7(c) respectively; for the structure shown in Figure 6(b) (i.e., the longitudinal section of the first groove is Σ-shaped), the structure obtained after forming the first heat-conducting layer 101a on the bottom surface of the first groove 100a can be referred to Figure 6(c) respectively.

[0083] In this embodiment, the thermal conductivity of the thermally conductive material 101 (i.e., the thermal conductivity of the material of the first thermally conductive layer 101a) is higher than that of the substrate 100. Preferably, the thermally conductive material 101 is implemented using graphene, which has excellent thermal conductivity. Those skilled in the art will understand that the thermally conductive material 101 should not be limited to graphene; in other embodiments, the thermally conductive material 101 can also be implemented using materials with good thermal conductivity such as silicon carbide and metals. For the sake of simplicity, not all possible thermally conductive materials will be listed here.

[0084] When the thermally conductive material is graphene, a graphene oxide layer is first formed on the upper surface of the substrate and the surface (including the sidewalls and bottom surface) of the first groove by, for example, spraying a graphene oxide solution or immersing the substrate with the first groove in a graphene oxide solution. It should be noted that (1) after spraying or immersing the upper surface of the substrate and the surface of the first groove in a graphene oxide solution, the substrate can be left for a period of time to allow the solvent in the graphene oxide solution to evaporate, thereby forming a graphene oxide layer on the upper surface of the substrate and the surface of the first groove. Of course, the solvent evaporation can also be accelerated by baking, thereby accelerating the formation of the graphene oxide layer. (2) Regarding the method of immersing the substrate in a graphene oxide solution, after the substrate is removed from the graphene oxide solution, the graphene oxide solution formed on the sidewalls and bottom surface of the substrate can be rinsed off, leaving only the portion formed on the upper surface of the substrate and the surface of the first groove. Then, the solvent in the graphene oxide solution can be evaporated by placing or baking, thereby forming a graphene oxide layer on the upper surface of the substrate and the surface of the first groove. After the graphene oxide layer is formed, a reducing agent, such as hydrazine and its derivatives, sodium borocyanide, reducing sugars (glucose, chitosan, etc.), vitamin C, etc., is used to reduce the graphene oxide layer to form a graphene layer. Finally, ultraviolet light is used to irradiate the portion of the graphene layer outside the first predetermined surface of the first groove until that portion of the graphene layer is removed, thereby forming a first thermally conductive layer of graphene material on the first predetermined surface of the first groove. The specific process of removing the graphene layer by ultraviolet light irradiation is as follows: First, a patterned mask layer is formed on the surface of the graphene layer. This mask layer only covers the portion of the graphene layer located on the first predetermined surface of the first groove, while the other portions of the graphene layer are exposed. Next, in a specific environment (containing a protective gas such as nitrogen and a reactive gas such as oxygen), the substrate is irradiated with ultraviolet light of a specific wavelength until the exposed portion of the graphene layer is completely removed. Finally, the mask layer is removed to form a first thermally conductive layer of graphene material on the first predetermined surface of the first groove.

[0085] When the thermally conductive material is silicon carbide (or metal), a silicon carbide layer (or metal material layer) can be formed on the upper surface of the substrate and the surface of the first groove by deposition. Then, a patterned photoresist layer is formed on the silicon carbide layer (or metal material layer). The photoresist layer only covers the portion of the silicon carbide layer (or metal material layer) located on the first predetermined surface of the first groove. Then, the silicon carbide layer (or metal material layer) is etched using the photoresist layer as a mask to remove the portion of the silicon carbide layer (or metal material layer) located outside the first predetermined surface. Finally, the photoresist layer is removed to form a first thermally conductive layer of silicon carbide (or metal) on the first predetermined surface of the first groove.

[0086] Those skilled in the art will understand that the first thermally conductive layer is not limited to being formed using the methods described above. In other embodiments, it can also be achieved using the following steps: First, a thermally conductive material (e.g., graphene, silicon carbide, metal, etc.) is formed on the upper surface of the substrate and the surface of the first groove; then, a sacrificial material (e.g., PSG) is deposited on the substrate to fill the first groove; next, the sacrificial material is planarized until the portion of the sacrificial material located on the upper surface of the substrate is ground flat and removed; then, a certain depth of the sacrificial material in the first groove is removed using a wet etching process (e.g., BOE etching process, etc.) so that the remaining sacrificial material only covers the thermally conductive material located on the first preset surface of the first groove (this step can be omitted if the first preset surface includes the bottom surface and the entire sidewall of the first groove); then, the exposed thermally conductive material is etched using a wet etching solution until it is completely removed; finally, the remaining sacrificial material is removed by wet etching, thereby forming the first thermally conductive layer on the first preset surface of the first groove.

[0087] In step S103, as shown in FIG3(e), the space above the first thermally conductive layer 101a in the first groove 100a is filled using sacrificial material 102. In this embodiment, the filling step includes: firstly, depositing sacrificial material (not shown) on the upper surface of the structure shown in FIG3(d), wherein the thickness of the sacrificial material is greater than the depth of the space above the first thermally conductive layer 101a in the first groove 100a, so that the upper surface of the portion of the sacrificial material filled in the first groove 100a is higher than the upper surface of the substrate 100; then, performing a planarization operation on the sacrificial material until the upper surface of the substrate 100 is exposed, that is, removing the sacrificial material located on the upper surface of the substrate 100 and retaining only the sacrificial material located in the first groove 100a (represented by reference numeral 102 in the figure), and the upper surface of this portion of the sacrificial material 102 is flush with the upper surface of the substrate 100. The term "flush" here means that the height difference between the two is within the range allowed by process error. This invention does not limit the sacrificial material in any way. Existing conventional sacrificial materials such as phosphosilicate glass (PSG), borosilicate glass (BPSG), and intrinsic silicon dioxide (USG) are all applicable to this invention.

[0088] In step S104, as shown in FIG3(f), a stacked structure covering the first groove is formed on the substrate 100. The stacked structure includes a lower electrode 103, a piezoelectric layer 104, and an upper electrode 105 from bottom to top. In this embodiment, the formation process of the stacked structure is as follows: First, a layer of lower electrode metal material (not shown) is deposited on the upper surface of the substrate 100, and the lower electrode metal material is patterned to form the lower electrode 103. The lower electrode 103 may cover the entire first groove or cover part of the first groove. It should be noted that, for cases where the material of the first thermally conductive layer 101a is conductive, the first thermally conductive layer 101a and the lower electrode 103 need to be reasonably designed so that there is no electrical contact between them. For example, the lower electrode 103 covers the entire first groove. In this case, the first thermally conductive layer 101a is formed on the area of ​​the sidewall of the first groove that is not at the upper edge to avoid electrical contact with the lower electrode 103. For example, if the horizontal projection of the lower electrode 103 falls within the horizontal projection of the opening of the first groove, the first thermally conductive layer 101a will not make electrical contact with the lower electrode 103 even if it is formed on the entire sidewall of the first groove. The material of the lower electrode 103 can be a conventional electrode metal such as molybdenum (Mo). Next, a piezoelectric material is deposited on the upper surface of the structure obtained by forming the lower electrode 103, and it is planarized to form a piezoelectric layer 104. Those skilled in the art will understand that in other embodiments, the piezoelectric layer 104 can also be formed directly by depositing a piezoelectric material without performing a planarization operation. The material of the piezoelectric layer 104 can be a conventional piezoelectric material such as aluminum nitride, zinc oxide, lithium niobate, lead zirconate titanate, etc. Finally, an upper electrode metal material (not shown) is deposited on the piezoelectric layer 104, and the upper electrode metal material is patterned to form an upper electrode 105. The material of the upper electrode 105 can be a conventional electrode metal such as molybdenum (Mo), which can be the same as or different from the material of the lower electrode 103.

[0089] It should be noted that (1) the present invention does not impose any limitation on the specific thickness of the upper electrode 105, the piezoelectric layer 104 and the lower electrode 103, and can be set accordingly according to actual design requirements. (2) In other embodiments, other components of the bulk acoustic resonator can also be formed according to actual design requirements. For example, a seed layer can be formed on the substrate before forming the lower electrode, or a passivation layer can be formed on the upper electrode after forming the stacked structure, or a lower electrode connection portion connected to the lower electrode can be formed at the same time as forming the lower electrode, and an upper electrode connection portion connected to the upper electrode can be formed at the same time as forming the upper electrode, or a frame structure, air bridge structure, air wing structure, etc. can be formed in the stacked structure (e.g., the edge of the upper electrode). This article does not impose any limitations on these.

[0090] In step S105, as shown in FIG3(g), the sacrificial material 102 is removed to form a cavity 106 below the stacked structure. The cavity 106 is surrounded by a first groove formed on the substrate 100 and the lower surface of the stacked structure. The upper electrode 105, piezoelectric layer 104, lower electrode 103, and cavity 106 overlap in the device thickness direction. This overlapping region is the resonant region of the bulk acoustic wave resonator. The present invention does not limit the specific method of removing the sacrificial material 102. For example, it can be achieved by forming a release hole on the stacked structure to expose the sacrificial material 102 and removing the sacrificial material 102 through the release hole using an etching solution.

[0091] For the structures shown in Figures 5(c) and 7(c) (i.e., the longitudinal section of the first groove is inverted T-shaped), the final structure formed after performing steps S103 to S105 can be referred to Figures 5(d) and 7(d) respectively; for the structure shown in Figure 6(c) (i.e., the longitudinal section of the first groove is Σ-shaped), the final structure formed after performing steps S103 to S105 can be referred to Figure 6(d) respectively.

[0092] The method for manufacturing a bulk acoustic wave (BAW) resonator provided by this invention effectively improves the heat dissipation efficiency of the BAW resonator by forming a first thermally conductive layer on the bottom surface of a substrate groove (i.e., the first groove), or on the bottom surface of the substrate groove and at least part of its sidewalls. Specifically, when the heat generated by the BAW resonator during operation is transferred to the substrate side, the first thermally conductive layer can effectively accelerate the speed of heat transfer from the cavity to the substrate, thereby ensuring that heat can be transferred from the substrate to the outside of the device in a timely manner. The improved heat dissipation efficiency can effectively ensure that the temperature of the BAW resonator does not become too high during operation, thereby effectively ensuring that the performance of the BAW resonator is not affected, and thus making the BAW resonator suitable for the implementation of high-power capacity devices (such as high-power capacity filters). In addition, the bottom of the groove formed on the substrate has a shape that is narrow at the top and wide at the bottom in its longitudinal section, that is, the bottom space of the groove has a structure that is small at the top and large at the bottom. When the first thermally conductive layer is formed on the bottom surface of the groove (and at least part of its sidewalls), since the bottom space of the groove is small at the top and large at the bottom, the first thermally conductive layer can be well confined within the bottom space of the groove. In this scenario, even if the first thermally conductive layer detaches from the bottom of the groove due to the difference in thermal expansion / contraction between the first thermally conductive layer and the substrate during heat transfer, the bottom space of the groove is designed with a structure that is narrower at the top and wider at the bottom (correspondingly, the bottom of the groove's longitudinal section is narrower at the top and wider at the bottom). This design still firmly confines the first thermally conductive layer to the bottom surface of the groove, effectively preventing displacement and thus avoiding any impact on heat dissipation. For graphene, a material prone to detachment (besides the potential for detachment due to differences in thermal expansion / contraction, its specific formation process can also lead to delamination from the groove), the groove with a narrower-at-the-top and wider-at-the-bottom longitudinal section provided by this invention offers particularly good confinement. Furthermore, the narrower-at-the-top and wider-at-the-bottom shape of the bottom of the groove's longitudinal section effectively increases the space for lateral heat transfer by the first thermally conductive layer, further ensuring timely heat transfer from the cavity to the substrate.

[0093] It should be noted that, for the structures shown in Figure 3(d) and Figure 6(c), the longitudinal section of the first groove 100a is a trapezoidal shape with the upper base smaller than the lower base and a Σ shape, respectively (correspondingly, in the structures shown in Figure 3(d) and Figure 6(c), the bottom of the longitudinal section of the first groove 100a is a trapezoidal shape with the upper base smaller than the lower base). In this case, the bottom space of the first groove 100a can play a good limiting role for the first heat-conducting layer 101a of any thickness. Therefore, the thickness of the first heat-conducting layer 101a can be determined according to the actual design requirements. For the structures shown in Figures 5(c) and 7(c), the longitudinal section of the first groove 100a is an inverted T-shape (correspondingly, the bottom of the longitudinal section of the first groove 100a in the structures shown in Figures 5(c) and 7(c) is an inverted T-shape, and the lower end of the inverted T-shape is rectangular). In this case, as shown in Figures 5(c) and 7(c), it is preferable that the thickness of the first heat-conducting layer 101a is at least matched with the height of the rectangular shape at the lower end of the inverted T-shape (preferably greater than the height of the rectangular shape at the lower end of the inverted T-shape), so that the first heat-conducting layer 101a can be well confined. That is to say, for this case, the structure of the bottom space of the first groove and the thickness of the first heat-conducting layer need to be considered together when designing the structure of the bottom space of the first groove. Since there are many possibilities for the shape of the bottom of the longitudinal section of the first groove to be narrow at the top and wide at the bottom, the thickness of the first heat-conducting layer in all possible structures will not be described here. As long as the structure of the bottom space of the first groove and the thickness of the first heat-conducting layer are matched to achieve good confining of the first heat-conducting layer, it is acceptable. Furthermore, when the material of the first thermally conductive layer is graphene, graphene layers of different thicknesses can be obtained by adjusting, for example, the concentration of the graphene oxide solution and the spraying / soaking time; when the material of the first thermally conductive layer is silicon carbide or metal, silicon carbide layers or metal material layers of different thicknesses can be obtained by adjusting, for example, process parameters such as deposition time.

[0094] In a preferred embodiment, the etching process used to form the first groove on the upper surface of the substrate is the Bosch process. The first groove formed by the Bosch process has a corrugated structure on its sidewalls. This corrugated structure can create a surface roughness with undulations of up to 5 nm or more, which helps to increase the bonding force between the first thermally conductive layer and the sidewalls of the first groove, thereby further preventing the displacement of the first thermally conductive layer. The following describes how to form the first groove using the Bosch process, taking an example where the longitudinal section of the first groove has a trapezoidal shape with the upper base smaller than the lower base. First, as shown in FIG8(a), an isotropic etching process is used to form the first isotropic groove 100-1; next, as shown in FIG8(b), the sidewalls of the first isotropic groove 100-1 are passivated to form a first etching protective film 107a on the sidewalls; next, as shown in FIG8(c), isotropic etching is continued on the bottom surface of the first isotropic groove 100-1 to form a second isotropic groove below the first isotropic groove 100-1, and the bottom surface is passivated. The sidewalls of the second isotropic groove are etched to form a second etch protection film 107b, wherein the second isotropic groove and the first isotropic groove 100-1 constitute groove 100-2; the isotropic etching and passivation operations are repeated until a first groove 100a with the required depth is formed as shown in FIG8(d), wherein the etch protection film 107 on the sidewall of the first groove 100a is composed of etch protection films on the sidewalls of multiple isotropic grooves. It should be noted that by adjusting the process parameters of each isotropic etching, a trapezoidal shape with an upper base smaller than the lower base can be obtained in the longitudinal section.

[0095] In a preferred embodiment, such as Figure 9As shown, a second thermally conductive layer 108 is formed on the lower surface of the substrate 100. The thermal conductivity of the material of the second thermally conductive layer 108 is higher than that of the material of the substrate 100. The formation of the second thermally conductive layer 108 is beneficial to accelerating the transfer of heat generated by the device from the substrate 100 to the outside of the device, thereby further improving the heat dissipation performance of the device. It should be noted that (1) the material of the second thermally conductive layer 108 can be the same as or different from the material of the first thermally conductive layer 101a; (2) the second thermally conductive layer 108 is preferably formed simultaneously with the first thermally conductive layer 101a (in this case, the materials of the first thermally conductive layer 101a and the second thermally conductive layer 108 are the same). The specific process is as follows: First, a thermally conductive material is formed on the entire surface of the substrate with the first groove. Then, part of the thermally conductive material is removed, leaving only the thermally conductive material on the first preset surface of the first groove and the bottom surface of the substrate, thereby simultaneously forming the first thermally conductive layer 101a and the second thermally conductive layer 108. Those skilled in the art will understand that the second thermally conductive layer 108 may not be formed simultaneously with the first thermally conductive layer 101a; for example, the second thermally conductive layer 108 may be formed after the formation of the stacked structure. In this case, it is preferable to form a protective layer covering the front side of the device before forming the second thermally conductive layer 108, then form the second thermally conductive layer 108 on the lower surface of the substrate 100, and finally remove the protective layer. The formation of the protective layer helps to protect the device during the formation of the second thermally conductive layer 108, thereby preventing damage to the device.

[0096] The present invention also provides a bulk acoustic resonator, the bulk acoustic resonator comprising:

[0097] Substrate;

[0098] A stacked structure is formed on the upper surface of the substrate, and from bottom to top includes a lower electrode, a piezoelectric layer and an upper electrode.

[0099] A cavity is formed between the substrate and the stacked structure. The cavity overlaps with the lower electrode, the piezoelectric layer and the upper electrode in the thickness direction of the device, and the bottom of the longitudinal section of the cavity is narrow at the top and wide at the bottom.

[0100] A first thermally conductive layer is formed on a second predetermined surface of the cavity and has a thickness less than the depth of the cavity, wherein the second predetermined surface is the bottom surface of the cavity, or the bottom surface of the cavity and at least part of the sidewall.

[0101] The components of the above-mentioned bulk acoustic resonator will be described in detail below with reference to Figures 3(g), 5(d), 6(d) and 7(d).

[0102] Specifically, as shown in Figure 3(g), the bulk acoustic wave resonator provided by the present invention includes a substrate 100 and a stacked structure formed on the substrate 100. A first groove is formed on the upper surface of the substrate 100. The stacked structure is formed on the upper surface of the substrate 100 and covers the first groove, wherein the stacked structure includes a lower electrode 103, a piezoelectric layer 104, and an upper electrode 105 from bottom to top. The materials and dimensions of the substrate 100, the lower electrode 103, the piezoelectric layer 104, and the upper electrode 105 can be referred to the corresponding sections above, and will not be repeated here for the sake of brevity.

[0103] As shown in Figure 3(g), the bulk acoustic wave resonator provided by the present invention further includes a cavity 106, which is formed between the substrate 100 and the stacked structure, and is surrounded by a first groove formed on the upper surface of the substrate 100 and the lower surface of the stacked structure. The upper electrode 105, the piezoelectric layer 104, the lower electrode 103, and the cavity 106 overlap in the thickness direction of the device, and this overlapping region constitutes the resonant region of the bulk acoustic wave resonator. The bottom of the longitudinal section of the cavity 106 has a shape that is narrower at the top and wider at the bottom. In this embodiment, as shown in Figure 3(g), the longitudinal section of the cavity 106 has a trapezoidal shape with the upper base smaller than the lower base. In other embodiments, as shown in Figures 5(d) and 7(d), the longitudinal section of the cavity 106 has an inverted T-shape, or as shown in Figure 6(d), the longitudinal section of the cavity 106 has a Σ-shape. Those skilled in the art will understand that the above examples of the longitudinal section of the first groove are merely preferred embodiments and should not be construed as limiting the shape of the longitudinal section of the first groove. Any groove that is feasible and whose bottom of the longitudinal section is narrow at the top and wide at the bottom falls within the protection scope of this invention. For the sake of brevity, all possible shapes of the longitudinal section of the first groove will not be listed here.

[0104] As shown in Figure 3(g), the bulk acoustic wave resonator provided by the present invention further includes a first thermally conductive layer 101a, which is formed on a second predetermined surface of the cavity 106 and has a thickness less than the depth of the cavity 106. The second predetermined surface refers to the area in the surface of the cavity 106 used to form the first thermally conductive layer 101a. In this embodiment, as shown in Figure 3(g), the second predetermined surface is the bottom surface of the cavity 106. In other embodiments, the second predetermined surface includes the bottom surface of the cavity 106 and part of the sidewalls, or the second predetermined surface includes the bottom surface of the cavity 106 and all the sidewalls. The present invention does not limit the material of the first thermally conductive layer 101a; any material that can accelerate the transfer of heat from the cavity 106 to the substrate 100 is applicable to the present invention. Preferably, the thermal conductivity of the material of the first thermally conductive layer 101a is higher than that of the material of the substrate 100, for example, it can be graphene, silicon carbide, or metal. It should be noted that (1) when the material of the first thermal conductive layer 101a is conductive, there is no electrical contact between the first thermal conductive layer 101a and the lower electrode 103; (2) the design of the thickness of the first thermal conductive layer 101a and the bottom space structure of the cavity 106 can be referred to the corresponding part above. For the sake of brevity, it will not be repeated here.

[0105] The bulk acoustic wave (BAW) resonator provided by this invention has a first thermally conductive layer formed on the bottom surface of its cavity, or on the bottom surface of the cavity and at least part of its sidewalls. The presence of this first thermally conductive layer improves the heat dissipation efficiency of the BAW resonator. Specifically, when the heat generated by the BAW resonator during operation is transferred to the substrate, the first thermally conductive layer effectively accelerates the heat transfer from the cavity to the substrate, ensuring that heat can be transferred from the substrate to the outside of the device in a timely manner. This improved heat dissipation efficiency effectively ensures that the temperature of the BAW resonator does not become excessively high during operation, thus ensuring that the performance of the BAW resonator is not affected. This allows the BAW resonator to be used in the implementation of high-power capacity devices (such as high-power capacity filters). Furthermore, the bottom of the cavity's longitudinal section is narrower at the top and wider at the bottom. This shape not only effectively prevents the first thermally conductive layer from shifting but also effectively increases the space for lateral heat transfer from the first thermally conductive layer, further ensuring the timely transfer of heat from the cavity to the substrate.

[0106] In a preferred embodiment, the sidewalls of the cavity have rough surfaces. This roughness increases the bonding force between the first thermally conductive layer and the cavity sidewalls, thereby further preventing displacement of the first thermally conductive layer. Preferably, the first groove on the substrate can be formed using a Bosch process to give its sidewalls a corrugated structure. Correspondingly, the cavity sidewalls formed by the first groove also have a corrugated structure, which can create a surface roughness of up to 100 nm or more.

[0107] In a preferred embodiment, such as Figure 9 As shown, the bulk acoustic wave resonator provided by the present invention further includes a second thermally conductive layer 108, which is formed on the lower surface of the substrate 100, and the thermal conductivity of the material of the second thermally conductive layer 108 is higher than that of the substrate 100. The formation of the second thermally conductive layer 108 facilitates the accelerated transfer of heat generated by the device from the substrate 100 to the outside of the device, further improving the heat dissipation performance of the device. It should be noted that the material of the second thermally conductive layer 108 can be the same as or different from the material of the first thermally conductive layer 101a.

[0108] This invention also provides a method for manufacturing a packaging structure. For example... Figure 10 As shown, the manufacturing method includes:

[0109] In step S200, a device wafer is provided, the device wafer including a plurality of bulk acoustic wave resonators, wherein at least one of the bulk acoustic wave resonators is formed using the aforementioned manufacturing method or implemented using the aforementioned bulk acoustic wave resonator;

[0110] In step S201, a cap wafer is provided, on which a second groove is formed that corresponds one-to-one with the plurality of bulk acoustic resonators in position. At least one of the second grooves has a bottom of its longitudinal section that is narrow at the top and wide at the bottom, and a third heat-conducting layer is formed on its third preset surface. The third preset surface is the bottom surface of the second groove, or the bottom surface of the second groove and at least part of the sidewall.

[0111] In step S202, a connection structure for connecting the device wafer and the cap wafer is formed between the two, wherein the surface of the device wafer in which the bulk acoustic resonator is formed and the surface of the cap wafer in which the second groove is formed are disposed opposite to each other.

[0112] In step S203, a conductive structure is formed for drawing out electrical signals from the device wafer.

[0113] The following will combine Figures 11(a) to 11(d) The above steps will be explained in detail.

[0114] Specifically, in step S200, as shown in FIG11(a), a device wafer is provided, which includes a plurality of bulk acoustic wave resonators, wherein at least one bulk acoustic wave resonator is formed using the aforementioned manufacturing method or implemented using the aforementioned bulk acoustic wave resonator. For the sake of simplicity, the aforementioned bulk acoustic wave resonators and their manufacturing methods will not be described again here. For other bulk acoustic wave resonators in the device wafer that are not formed using the aforementioned manufacturing method or implemented using the aforementioned bulk acoustic wave resonators, the present invention does not limit them in any way, and they can be implemented using existing conventional bulk acoustic wave resonators. In addition, for the sake of simplicity, FIG11(a) only schematically shows a bulk acoustic wave resonator, and schematically shows the longitudinal section of the cavity in the bulk acoustic wave resonator as a trapezoidal shape with the upper base smaller than the lower base.

[0115] In this embodiment, as shown in FIG11(a), a first bonding structure is formed on the surface of the device wafer on which the bulk acoustic wave resonator is formed. Typically, the first bonding structure includes a first bonding portion 300a and a second bonding portion 300b. The first bonding portion 300a is typically formed in the edge region of the device wafer for subsequent wall formation (typically a sealing wall); the second bonding portion 300b is typically formed in the inner region of the device wafer for electrical connection with the stacked structure (for simplicity, only the second bonding portion is schematically shown in the figure, and the electrical connection between the second bonding portion 300b and the stacked structure is omitted). The first bonding portion 300a and the second bonding portion 300b are made of conventional bonding materials (e.g., Au, Cu, etc.).

[0116] In step S201, a cap wafer is provided for use with the device wafer. In this embodiment, as shown in FIG11(b), the cap wafer includes a body 200, and the front side of the body 200 (the surface facing the bulk acoustic wave resonators in the device wafer during subsequent packaging) has a second groove 200a that corresponds one-to-one with the position of a plurality of bulk acoustic wave resonators on the device wafer. At least one of the second grooves 200a has a bottom section that is narrower at the top and wider at the bottom, and a third thermally conductive layer 201 is formed on its third predetermined surface. The bottom section of the second groove 200a having a narrower top and wider bottom shape not only helps prevent displacement of the third thermally conductive layer 201 but also increases the space for lateral heat transfer by the third thermally conductive layer 201. For other second grooves in the cap wafer whose longitudinal section does not have a narrower top and wider bottom shape, the present invention does not limit the shape of their longitudinal section; it can be a conventional trapezoidal shape with a larger upper base than lower base, or a rectangular shape, etc.

[0117] Regarding the second groove whose longitudinal section bottom is narrower at the top and wider at the bottom, in this embodiment, as shown in FIG11(b), the longitudinal section of the second groove 200a presents a trapezoidal shape with the upper base smaller than the lower base. In other embodiments, the longitudinal section of the second groove 200a may also present an inverted T-shape, or a Σ-shape, etc. It will be understood by those skilled in the art that the above examples of the longitudinal section of the second groove 200a are merely preferred embodiments and should not be construed as limiting the shape of the longitudinal section of the second groove 200a. Any groove that is feasible and whose longitudinal section bottom presents a shape that is narrower at the top and wider at the bottom falls within the protection scope of this invention. For the sake of brevity, not all possible shapes of the longitudinal section of the second groove 200a will be listed here.

[0118] The third preset surface refers to the area in the surface of the second groove 200a used to form the third heat-conducting layer 201. In this embodiment, as shown in FIG11(b), the third preset surface is the bottom surface of the second groove 200a. In other embodiments, the third preset surface includes the bottom surface of the second groove 200a and part of the sidewalls, or the third preset surface includes the bottom surface of the second groove 200a and all of the sidewalls.

[0119] This invention does not limit the material of the third thermally conductive layer 201; any material that can accelerate the transfer of heat from the second groove 200a to the body 200 is applicable. Preferably, the thermal conductivity of the material of the third thermally conductive layer 201 is higher than that of the material of the body 200, and it can be, for example, graphene, silicon carbide, or metal.

[0120] It should be noted that (1) for the sake of simplicity, only a second groove 200a is schematically drawn in Figure 11(b). (2) The present invention does not limit the thickness of the third thermal conductive layer. In the subsequent packaging process, the surface of the cap wafer with the second groove is opposite to the surface of the device wafer with the bulk acoustic wave resonator, and the second groove on the cap wafer corresponds one-to-one with the bulk acoustic wave resonator on the device wafer. In this case, as long as the thickness of the third thermal conductive layer does not affect the performance of the corresponding bulk acoustic wave resonator, it is acceptable. Preferably, the thickness of the third thermal conductive layer 201 is less than the depth of the second groove. (3) For the corresponding second groove and the bulk acoustic wave resonator, the bottom of the longitudinal section of the second groove may be narrow at the top and wide at the bottom, and / or the bottom of the longitudinal section of the cavity of the bulk acoustic wave resonator may be narrow at the top and wide at the bottom. (4) For the case where the bottom of the longitudinal section of the second groove and the cavity in the corresponding bulk acoustic resonator both have a shape that is narrow at the top and wide at the bottom, their longitudinal sections can be the same or different, and the materials of the third heat-conducting layer and the first heat-conducting layer can be the same or different. (5) The formation process of the second groove and the third heat-conducting layer can refer to the formation process of the first groove and the first heat-conducting layer in the bulk acoustic resonator mentioned above. For the sake of simplicity, it will not be repeated here. (6) Preferably, the sidewall of the second groove has a rough surface. The rough surface of the sidewall is beneficial to increasing the bonding force between the sidewall of the second groove and the third heat-conducting layer, thereby further preventing the displacement of the third heat-conducting layer. In a specific embodiment, the second groove can be formed by etching with a Bosch process to make its sidewall have a rough surface. (7) For the design of the thickness of the third heat-conducting layer and the bottom space structure of the second groove, refer to the content of the design of the corresponding part of the bottom space of the first heat-conducting layer and the first groove mentioned above. For the sake of simplicity, it will not be repeated here.

[0121] In this embodiment, as shown in FIG11(b), a second bonding structure is formed on the front side of the cap wafer body 200. The second bonding structure includes a third bonding portion 301a corresponding in position to the first bonding portion 300a in the first bonding structure, and a fourth bonding portion 301b corresponding in position to the second bonding portion 300b in the first bonding structure. The third bonding portion 301a and the fourth bonding portion 301b are made of conventional bonding materials (e.g., Au, Cu, etc.).

[0122] In step S202, as shown in FIG11(c) in this embodiment, the surface of the cap wafer with the second groove 200a is positioned opposite to the surface of the device wafer with the bulk acoustic resonator, and the second bonding structure of the cap wafer is aligned with the first bonding structure of the device wafer. Then, the cap wafer and the device wafer are bonded and fixed. The second bonding structure of the cap wafer and the first bonding structure of the device wafer form a connection structure after bonding. Thus, the cap wafer and the device wafer are connected. It should be noted that the connection structure includes a first connection portion 302 and a second connection portion 303. The first connection portion 302 is located in the edge region of the device wafer and the cap wafer and is formed by bonding the first bonding portion 300a and the third bonding portion 301a. The second connection portion 303 is located in the inner region of the device wafer and the cap wafer and is formed by bonding the second bonding portion 300b and the fourth bonding portion 301b. In this embodiment, both the first connecting portion 302 and the second connecting portion 303 are bonded together with metal or alloy. However, in other embodiments, the first connecting portion 302 and the second connecting portion 303 may also be formed by other materials or processes. For example, the first connecting portion 301 may also be formed using photoresist. Considering that there are various materials and forming methods for the first connecting portion 302 and the second connecting portion 303, for the sake of simplicity, not all possible materials and forming methods will be listed here.

[0123] In step S203, a conductive structure for extracting electrical signals from the device wafer is formed. In this embodiment, as shown in FIG11(d), the conductive structure includes a through-silicon via (TSV) 400, a redistribution layer 401, and solder balls 402. The formation process of the conductive structure is as follows: First, the back side of the cap wafer (i.e., the back side of the cap wafer body 200) is thinned to meet the thickness requirements; then, a TSV 400 electrically connected to the second connection portion 303 is formed on the back side of the cap wafer; finally, a redistribution layer 401 electrically connected to the TSV 400 and solder balls 402 electrically in contact with the redistribution layer 401 are formed on the back side of the cap wafer. The conductive structure is thus completed. It will be understood by those skilled in the art that the above-described conductive structure is only a preferred embodiment; in other embodiments, any structure that can extract electrical signals from the device wafer from the second connection portion is applicable to the conductive structure of this invention.

[0124] It should be noted that (1) under normal circumstances, after performing step S203, the packaging method provided by the present invention further includes soldering the structure shown in FIG11(d) to the packaging substrate (not shown) by solder balls 402, and molding the structure shown in FIG11(d) after soldering. (2) The present invention does not limit the specific device type of the packaging structure, which can be a filter, a duplexer, etc.

[0125] In the manufacturing method of the packaging structure provided by the present invention, at least one bulk acoustic wave resonator is formed on a device wafer. The bottom of the longitudinal section of the cavity of the bulk acoustic wave resonator is narrower at the top and wider at the bottom, and a first thermally conductive layer is formed on the bottom surface (and at least part of the sidewalls) of the cavity. Similarly, at least one second groove is formed on a cap wafer. The bottom of the longitudinal section of the second groove is narrower at the top and wider at the bottom, and a third thermally conductive layer is formed on the bottom surface (and at least part of the sidewalls) of the second groove. When the packaged device is in operation, the bulk acoustic wave resonator on the device wafer acts as a heat-generating component, and the heat generated by it is transferred outward from the device wafer side and the cap wafer side, respectively. Since the first thermally conductive layer is formed on the bottom surface (and at least the sidewalls) of the cavity of the bulk acoustic wave resonator on the device wafer side, it is beneficial for heat to be transferred from the cavity of the bulk acoustic wave resonator to the substrate, and further beneficial for heat to be transferred from the substrate to the outside of the packaging structure. Similarly, the presence of a third thermally conductive layer on the cap wafer side facilitates heat transfer from the second groove to the cap wafer body, and further facilitates heat transfer from the cap wafer body to the outside of the package structure. This effectively improves the heat dissipation performance of the package structure, making it suitable for high-power capacity applications. Furthermore, the bottom of the longitudinal section of both the cavity in the bulk acoustic wave resonator and the second groove in the cap wafer is narrower at the top and wider at the bottom. This not only helps prevent the thermally conductive layer formed inside from shifting and affecting heat dissipation, but also increases the space for lateral heat transfer from the thermally conductive layer, further ensuring heat transfer.

[0126] The present invention also provides a packaging structure, the packaging structure comprising:

[0127] A device wafer comprising a plurality of bulk acoustic wave resonators, at least one of which is formed using the aforementioned manufacturing method or implemented using the aforementioned bulk acoustic wave resonator;

[0128] A cap wafer has a second groove formed on it that corresponds one-to-one with the plurality of bulk acoustic wave resonators in position, and the surface of the cap wafer with the second groove is disposed opposite to the surface of the device wafer with the bulk acoustic wave resonator. At least one of the second grooves has a bottom section that is narrow at the top and wide at the bottom, and a third thermal conductive layer is formed on its third predetermined surface. The third predetermined surface is the bottom surface of the second groove, or the bottom surface of the second groove and at least part of the sidewall.

[0129] A connection structure is disposed between the device wafer and the cap wafer for connecting the device wafer and the cap wafer;

[0130] A conductive structure for bringing out electrical signals on the device wafer.

[0131] The components of the above-mentioned packaging structure will be described in detail below with reference to Figure 11(d).

[0132] Specifically, as shown in Figure 11(d), the packaging structure provided by this invention includes a device wafer comprising multiple bulk acoustic wave (SAW) resonators, wherein at least one SAW resonator is formed using the aforementioned manufacturing method or implemented using the aforementioned SAW resonator. For the sake of simplicity, the aforementioned SAW resonators and their manufacturing methods will not be described again here. This invention does not limit other SAW resonators in the device wafer that are not formed using the aforementioned manufacturing method or implemented using the aforementioned SAW resonators; they can be implemented using existing conventional SAW resonators. Furthermore, for the sake of simplicity, Figure 11(d) only schematically illustrates one SAW resonator, and schematically shows the longitudinal section of the cavity in the SAW resonator as a trapezoidal shape with the upper base smaller than the lower base.

[0133] The packaging structure provided by this invention also includes a cap wafer used in conjunction with a device wafer. In this embodiment, as shown in FIG11(d), the cap wafer includes a body 200, on the front side of which a second groove 200a is formed, corresponding one-to-one with a plurality of bulk acoustic wave resonators on the device wafer, and the front side of the body 200 is opposite to the surface of the device wafer on which the bulk acoustic wave resonators are formed. At least one of the second grooves 200a has a bottom section with a shape that is narrower at the top and wider at the bottom (in this invention, the longitudinal section of the second groove refers to the longitudinal section of the second groove when the front side of the cap wafer body 200 is facing upwards), and a third thermally conductive layer 201 is formed on its third predetermined surface. The bottom section of the second groove 200a having a shape that is narrower at the top and wider at the bottom not only helps prevent the third thermally conductive layer 201 from shifting, but also helps increase the space for the third thermally conductive layer 201 to transfer heat laterally. For other second grooves in the cap wafer whose longitudinal section does not present a shape that is narrow at the top and wide at the bottom, the present invention does not limit the shape of its longitudinal section. It can be a conventional trapezoidal shape with the upper base larger than the lower base, or a rectangular shape, etc.

[0134] Regarding the second groove whose longitudinal section bottom is narrower at the top and wider at the bottom, in this embodiment, as shown in FIG11(d), the longitudinal section of the second groove 200a presents a trapezoidal shape with the upper base smaller than the lower base. In other embodiments, the longitudinal section of the second groove 200a may also present an inverted T-shape, or a Σ-shape, etc. It will be understood by those skilled in the art that the above examples of the longitudinal section of the second groove 200a are merely preferred embodiments and should not be construed as limiting the shape of the longitudinal section of the second groove 200a. Any groove that is feasible and whose longitudinal section bottom presents a shape that is narrower at the top and wider at the bottom falls within the protection scope of this invention. For the sake of brevity, not all possible shapes of the longitudinal section of the second groove 200a will be listed here.

[0135] The third preset surface refers to the area in the surface of the second groove 200a used to form the third heat-conducting layer 201. In this embodiment, as shown in FIG11(d), the third preset surface is the bottom surface of the second groove 200a. In other embodiments, the third preset surface includes the bottom surface of the second groove 200a and part of the sidewalls, or the third preset surface includes the bottom surface of the second groove 200a and all of the sidewalls.

[0136] This invention does not limit the material of the third thermally conductive layer 201; any material that can accelerate the transfer of heat from the second groove 200a to the body 200 is applicable. Preferably, the thermal conductivity of the material of the third thermally conductive layer 201 is higher than that of the material of the body 200, and it can be, for example, graphene, silicon carbide, or metal.

[0137] It should be noted that (1) for the sake of simplicity, only a second groove 200a is schematically drawn in Figure 11(d). (2) The present invention does not impose any limitation on the thickness of the third heat-conducting layer, as long as the thickness of the third heat-conducting layer does not affect the performance of the corresponding bulk acoustic wave resonator. Preferably, the thickness of the third heat-conducting layer 201 is less than the depth of the second groove. (3) For the corresponding second groove and the bulk acoustic wave resonator, the bottom of the longitudinal section of the second groove may be narrow at the top and wide at the bottom, and / or the bottom of the longitudinal section of the cavity in the bulk acoustic wave resonator may be narrow at the top and wide at the bottom. (4) When both the bottom of the longitudinal section of the second groove and the cavity in the corresponding bulk acoustic wave resonator are narrow at the top and wide at the bottom, their longitudinal sections may be the same or different, and the materials of the third heat-conducting layer and the first heat-conducting layer may be the same or different. (5) Preferably, the sidewall of the second groove has a rough surface, wherein the rough surface of the sidewall is beneficial to increasing the bonding force between the sidewall of the second groove and the third heat-conducting layer, thereby further preventing the displacement of the third heat-conducting layer. In a specific embodiment, the second groove can be formed by etching using a Bosch process to give its sidewall a rough surface. (6) For the design of the thickness of the third heat-conducting layer and the bottom space structure of the second groove, refer to the corresponding parts of the design of the first heat-conducting layer and the bottom space of the first groove mentioned above. For the sake of brevity, it will not be repeated here.

[0138] The packaging structure provided by this invention also includes a connection structure disposed between the device wafer and the cap wafer for connecting the device wafer and the cap wafer. In this embodiment, as shown in FIG11(d), the connection structure includes a first connection portion 302 and a second connection portion 303. The first connection portion 302 is located at the edge region of the device wafer and the cap wafer for protecting the bulk acoustic wave resonator on the device wafer. The second connection portion 303 is located in the inner region of the device wafer and the cap wafer for electrically connecting with the stacked structure in the bulk acoustic wave resonator (for simplicity, only the second connection portion 303 is schematically shown in the figure, and the electrical connection between the second connection portion 303 and the stacked structure is omitted). In this embodiment, both the first connection portion 302 and the second connection portion 303 are bonded by metal (e.g., Au, Cu, etc.). However, in other embodiments, the first connection portion 302 and / or the second connection portion 303 can also be made of other materials. For example, the first connection portion 301 can also be formed by photoresist.

[0139] The packaging structure provided by this invention also includes a conductive structure for extracting electrical signals from the device wafer. In this embodiment, as shown in FIG11(d), the conductive structure includes a through-silicon via (TSV) 400, a redistribution layer 401, and solder balls 402. The TSV 400 penetrates the cap wafer body 200 and is electrically connected to the second connection portion 303. The redistribution layer 401 is formed on the back side of the cap wafer (i.e., the back side of the cap wafer body 200) and is electrically connected to the TSV 400. The solder balls 402 are formed on the back side of the cap wafer and are in electrical contact with the redistribution layer 401. It will be understood by those skilled in the art that the above-described conductive structure is only a preferred embodiment. In other embodiments, any structure that can extract electrical signals from the device wafer from the second connection portion is applicable to the conductive structure of this invention.

[0140] It should be noted that (1) under normal circumstances, the packaging structure provided by the present invention also includes a packaging substrate (not shown) and a molding compound (not shown), wherein the structure shown in FIG11(d) is soldered to the packaging substrate by solder balls 402, and the molding compound forms a wrap around the outer surface of the structure shown in FIG11(d). (2) The present invention does not limit the specific device type of the packaging structure, which can be a filter, a duplexer, etc.

[0141] In the packaging structure provided by this invention, at least one bulk acoustic wave (BAW) resonator is formed on the device wafer. The bottom of the longitudinal section of the cavity of the BAW resonator is narrower at the top and wider at the bottom, and a first thermally conductive layer is formed on the bottom surface (and at least part of the sidewalls) of the cavity. Similarly, at least one second groove is formed on the cap wafer. The bottom of the longitudinal section of the second groove is narrower at the top and wider at the bottom, and a third thermally conductive layer is formed on the bottom surface (and at least part of the sidewalls) of the second groove. When the packaged device is in operation, the BAW resonator on the device wafer acts as a heat-generating component, and the heat generated by it is transferred outward from the device wafer side and the cap wafer side, respectively. Since the first thermally conductive layer is formed on the bottom surface (and at least the sidewalls) of the cavity of the BAW resonator on the device wafer side, it is beneficial for heat to be transferred from the cavity of the BAW resonator to the substrate, and further beneficial for heat to be transferred from the substrate to the outside of the packaging structure. Similarly, the presence of a third thermally conductive layer on the cap wafer side facilitates heat transfer from the second groove to the cap wafer body, and further facilitates heat transfer from the cap wafer body to the outside of the package structure. This effectively improves the heat dissipation performance of the package structure, making it suitable for high-power capacity applications. Furthermore, the bottom of the longitudinal section of both the cavity in the bulk acoustic wave resonator and the second groove in the cap wafer is narrower at the top and wider at the bottom. This not only helps prevent the thermally conductive layer formed inside from shifting and affecting heat dissipation, but also increases the space for lateral heat transfer from the thermally conductive layer, further ensuring heat transfer.

[0142] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be embraced within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims. Furthermore, it is clear that the word "comprising" does not exclude other components, units, or steps, and the singular does not exclude the plural. Multiple components, units, or devices recited in the system claims may also be implemented by a single component, unit, or device in software or hardware.

[0143] The above-disclosed embodiments are merely some preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for manufacturing a bulk acoustic resonator, characterized in that, The manufacturing method includes: Provide substrate; A first groove is formed on the upper surface of the substrate. The bottom of the longitudinal section of the first groove is narrow at the top and wide at the bottom, so as to limit the thermal conductive layer formed therein during device operation. A first thermally conductive layer with a thickness less than the depth of the first groove is formed on a first predetermined surface of the first groove. The first thermally conductive layer is made of graphene material and is formed by the following process: spraying or immersing a graphene oxide layer solution on the upper surface of the substrate and in the first groove and drying it to form a graphene oxide layer; reducing the graphene oxide layer to form a graphene layer; and then selectively irradiating with ultraviolet light to remove the graphene layer located outside the first groove, so as to form a first thermally conductive layer of graphene material on the first predetermined surface of the first groove. The first predetermined surface is the bottom surface of the first groove, or the bottom surface of the first groove and at least part of the sidewall. The first groove is filled with sacrificial material; A stacked structure is formed on the substrate, the stacked structure comprising, from bottom to top, a lower electrode, a piezoelectric layer and an upper electrode; The sacrificial material is removed to form a cavity below the stacked structure. This cavity overlaps with the lower electrode, the piezoelectric layer, and the upper electrode in the device thickness direction. The first thermally conductive layer is fixed to the bottom of the cavity due to the narrow top and wide bottom shape of the groove. This improves the heat transfer efficiency from the cavity to the substrate and prevents the first thermally conductive layer from shifting when the high-power capacity device is operating.

2. The manufacturing method according to claim 1, characterized in that, in, The longitudinal section of the first groove is a trapezoidal shape with the upper base smaller than the lower base, or an inverted T-shape, or a Σ-shape.

3. The manufacturing method according to claim 1, characterized in that, in, The upper surface of the substrate is etched using a Bosch process to form the first groove with a rough surface on the sidewalls.

4. The manufacturing method according to any one of claims 1 to 3, characterized in that, in, The step of forming a first thermally conductive layer with a thickness less than the depth of the first groove on a first predetermined surface of the first groove includes: A layer of thermally conductive material is formed on the upper surface of the substrate and on the sidewalls and bottom surface of the first groove, the thickness of which is less than the depth of the first groove; Remove the portion of the thermally conductive material located outside the first preset surface of the first groove to form a first thermally conductive layer on the first preset surface of the first groove.

5. The manufacturing method according to claim 4, characterized in that, in, The thermal conductivity of the thermally conductive material is higher than that of the substrate material.

6. The manufacturing method according to claim 5, characterized in that, in, The thermally conductive material is graphene, silicon carbide, or a metal.

7. The manufacturing method according to claim 1, characterized in that, The manufacturing method also includes: A second thermally conductive layer is formed on the lower surface of the substrate, the thermal conductivity of the material of the second thermally conductive layer being higher than that of the material of the substrate.

8. A bulk acoustic resonator, characterized in that, The bulk acoustic resonator includes: Substrate; A stacked structure is formed on the upper surface of the substrate, and from bottom to top includes a lower electrode, a piezoelectric layer and an upper electrode. A cavity is formed between the substrate and the stacked structure. The cavity overlaps with the lower electrode, the piezoelectric layer, and the upper electrode in the thickness direction of the device. The bottom of the longitudinal section of the cavity is narrow at the top and wide at the bottom to limit the thermal conductive layer formed therein during device operation. The cavity corresponds to a first groove formed on the upper surface of the substrate. A first thermally conductive layer is formed on a second predetermined surface of the cavity and its thickness is less than the depth of the cavity. The first thermally conductive layer is made of graphene material and is formed by the following process: spraying or immersing a graphene oxide layer solution on the upper surface of the substrate and in the first groove and drying it to form a graphene oxide layer; reducing the graphene oxide layer to form a graphene layer; and then selectively irradiating it with ultraviolet light to remove the graphene layer located outside the first groove, so as to form a first thermally conductive layer of graphene material on the first predetermined surface of the first groove; wherein, the second predetermined surface is the bottom surface of the cavity, or the bottom surface of the cavity and at least part of the sidewalls. The first thermal conductive layer is fixed to the bottom of the cavity due to the narrow top and wide bottom shape of the first groove, thereby improving the heat transfer efficiency from the cavity to the substrate and preventing the first thermal conductive layer from shifting when the high power capacity device is working.

9. The bulk acoustic resonator according to claim 8, characterized in that, in, The longitudinal section of the cavity is a trapezoidal shape with the upper base smaller than the lower base, or an inverted T-shape, or a Σ-shape.

10. The bulk acoustic resonator according to claim 8, characterized in that, in, The sidewalls of the cavity have a rough surface.

11. The bulk acoustic resonator according to any one of claims 9 to 10, characterized in that, in, The thermal conductivity of the material of the first thermally conductive layer is higher than that of the material of the substrate.

12. The bulk acoustic resonator according to claim 11, characterized in that, in, The material of the first thermally conductive layer is graphene, silicon carbide, or metal.

13. The bulk acoustic resonator according to claim 9, characterized in that, The bulk acoustic resonator also includes: A second thermally conductive layer is formed on the lower surface of the substrate, and the thermal conductivity of the material of the second thermally conductive layer is higher than that of the material of the substrate.

14. A method for manufacturing a packaging structure, characterized in that, The manufacturing method includes: A device wafer is provided, the device wafer comprising a plurality of bulk acoustic wave resonators, wherein at least one of the bulk acoustic wave resonators is formed using the manufacturing method of any one of claims 1 to 7, or implemented using the bulk acoustic wave resonator of any one of claims 8 to 13; A cap wafer is provided, the cap wafer including a body, on which a second groove is formed that corresponds one-to-one with the plurality of bulk acoustic resonators in position, wherein at least one of the second grooves has a bottom of its longitudinal section that is narrow at the top and wide at the bottom, and a third thermal conductive layer is formed on its third predetermined surface, the third predetermined surface being the bottom surface of the second groove, or the bottom surface of the second groove and at least part of the sidewall. A connection structure for connecting the device wafer and the cap wafer is formed between the two, wherein the surface of the device wafer in which the bulk acoustic resonator is formed and the surface of the cap wafer in which the second groove is formed are disposed opposite to each other; A conductive structure is formed for extracting electrical signals from the device wafer.

15. The method for manufacturing the packaging structure according to claim 14, characterized in that, in, The longitudinal section of the second groove is a trapezoidal shape with the upper base smaller than the lower base, or an inverted T-shape, or a Σ-shape.

16. The method for manufacturing the packaging structure according to claim 14, characterized in that, in, The sidewalls of the second groove have a rough surface.

17. The method for manufacturing the packaging structure according to any one of claims 14 to 16, characterized in that, in, The thermal conductivity of the material in the third thermally conductive layer is higher than that of the material in the main body.

18. The method for manufacturing the packaging structure according to claim 17, characterized in that, in, The material of the third thermally conductive layer is graphene, silicon carbide, or metal.

19. A packaging structure, characterized in that, The packaging structure includes: A device wafer comprising a plurality of bulk acoustic wave resonators, at least one of the plurality of bulk acoustic wave resonators being formed using the manufacturing method of any one of claims 1 to 7, or implemented using the bulk acoustic wave resonator of any one of claims 8 to 13; A cap wafer includes a body on which second grooves are formed, each corresponding to one of the plurality of bulk acoustic wave resonators in position. The surface of the cap wafer with the second grooves is disposed opposite to the surface of the device wafer with the bulk acoustic wave resonators. At least one of the second grooves has a bottom section that is narrow at the top and wide at the bottom, and a third thermally conductive layer is formed on its third predetermined surface. The third predetermined surface is either the bottom surface of the second groove or the bottom surface of the second groove and at least part of the sidewall. A connection structure is disposed between the device wafer and the cap wafer for connecting the device wafer and the cap wafer; A conductive structure for bringing out electrical signals on the device wafer.

20. The packaging structure according to claim 19, characterized in that, in, The longitudinal section of the second groove is a trapezoidal shape with the upper base smaller than the lower base, or an inverted T-shape, or a Σ-shape.

21. The packaging structure according to claim 20, characterized in that, in, The sidewalls of the second groove have a rough surface.

22. The packaging structure according to any one of claims 19 to 21, characterized in that, in, The thermal conductivity of the material in the third thermally conductive layer is higher than that of the material in the main body.

23. The packaging structure according to claim 22, characterized in that, in, The material of the third thermally conductive layer is graphene, silicon carbide, or metal.

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