Ultrahigh-frequency acoustic resonator and preparation method thereof

Abstract

The invention provides an ultrahigh frequency acoustic resonator and a preparation method thereof, which can be applied to the field of microelectronic devices. The resonator comprises a metal electrode layer and a piezoelectric layer, a first etching hole is etched in the piezoelectric layer, and the first etching hole is only located in the middle of the piezoelectric layer; the metal electrode layer is composed of a first metal electrode array and a second metal electrode array, and the projection position of the first metal electrode array and the projection position of the second metal electrode array are located on the two sides of the projection position of the first etching hole respectively; wherein the first metal electrode array and the second metal electrode array respectively comprise at least one pair of positive and negative metal electrodes which are alternately arranged. In this way, the quality factor, the heat dissipation capability, the power processing capability and the stability of the resonator can be improved.

Description

Technical Field

[0001] This application relates to the field of microelectronic devices, specifically to the field of resonator design, and more specifically to an ultra-high frequency acoustic resonator and its fabrication method. Background Technology

[0002] With the continuous development of the 5G / 6G era, the demand for data volume in wireless communication is constantly increasing, and the Sub-6GHz frequency band is being fully allocated. Higher frequency bands and wider bandwidths to achieve faster data transmission rates have become the development requirements for future wireless communication. As one of the core components of the radio frequency front end, the performance of radio frequency filters directly determines the anti-interference capability and signal-to-noise ratio of the communication system. High-performance ultra-high frequency acoustic wave filtering devices will gradually become a potential filter solution in future 5G wireless communication.

[0003] As a core component of radio frequency filters, resonators are essential for designing high-performance ultra-high frequency acoustic (UHF) filters. Currently, research on UHF resonators mainly focuses on bulk acoustic resonators based on scandium-doped aluminum nitride (AlScN / AlN) thin films and Lamb wave resonators based on lithium niobate (LiNbO3) thin films. The resonant frequency of these two types of acoustic resonators is mainly determined by the thickness of the piezoelectric thin film. To meet the demands of wireless communication for higher frequencies, the thickness of the piezoelectric thin film needs to be continuously reduced. As wireless communication frequencies enter the millimeter-wave band, the thickness of the piezoelectric thin film has reached below 100 nm. However, ultra-thin piezoelectric thin films are prone to breakage when the etched buffer layer is suspended, which seriously affects the yield and robustness of device fabrication. Summary of the Invention

[0004] In view of the above problems, this application provides an ultra-high frequency acoustic resonator with improved quality factor, heat dissipation capacity, power handling capacity and stability, and a method for its fabrication.

[0005] According to a first aspect of this application, an ultra-high frequency acoustic resonator is provided, comprising: a metal electrode layer and a piezoelectric layer; the piezoelectric layer is etched with a first etched hole, wherein the first etched hole is located only in the middle of the piezoelectric layer; the metal electrode layer is composed of a first metal electrode array and a second metal electrode array, wherein the projection positions of the first metal electrode array and the second metal electrode array are located on both sides of the projection position of the first etched hole; wherein the first metal electrode array and the second metal electrode array each include at least one pair of alternately arranged positive and negative metal electrodes.

[0006] According to an embodiment of this application, the ultra-high frequency acoustic resonator further includes: a support anchor structure disposed in the first etched hole, the support anchor structure being used to connect the piezoelectric layers on both sides of the first etched hole; a metal electrode layer disposed on the first surface of the piezoelectric layer, or the metal electrode layer disposed on the second surface of the piezoelectric layer, or the metal electrode layer being disposed on both the first surface and the second surface of the piezoelectric layer.

[0007] According to an embodiment of this application, an ultra-high frequency acoustic resonator further includes: a substrate, with a piezoelectric layer located on the substrate; wherein the substrate includes a sacrificial layer, a well-rich layer, and a supporting substrate connected sequentially from top to bottom; a second etched hole is etched in the middle portion of the sacrificial layer to form a first cavity; or, a third etched hole is etched in the middle portion of the well-rich layer to form a second cavity; or, a second etched hole is etched in the middle portion of the sacrificial layer and a third etched hole is etched in the middle portion of the well-rich layer to form a third cavity.

[0008] According to an embodiment of this application, when the third cavity is formed, the ultra-high frequency acoustic resonator further includes: a temperature compensation layer grown on the metal electrode layer; wherein the temperature compensation layer is used to ensure frequency stability.

[0009] According to embodiments of this application, the sacrificial layer comprises one or more layers, each layer being made of one of silicon oxide, silicon nitride, and silicon, and the thickness of the sacrificial layer is 0.1 mm. ~10 The well-rich layer is made of amorphous silicon or polycrystalline silicon; the supporting substrate is made of one of silicon, silicon carbide, sapphire, and quartz.

[0010] According to embodiments of this application, the thickness of the piezoelectric layer is 10 nm to 1 nm. The thickness of the metal electrode layer is 1nm~500nm.

[0011] According to embodiments of this application, the piezoelectric layer is made of at least one of lithium niobate, lithium tantalate, aluminum nitride, and scandium-doped aluminum nitride; the metal electrode layer is made of one of gold, aluminum, molybdenum, platinum, copper, titanium-gold alloy, titanium-aluminum alloy, titanium-copper alloy, titanium-molybdenum alloy, titanium-platinum alloy, chromium-gold alloy, chromium-aluminum alloy, chromium-copper alloy, chromium-molybdenum alloy, and chromium-platinum alloy.

[0012] The second aspect of this application provides a method for fabricating an ultra-high frequency acoustic resonator, comprising:

[0013] A piezoelectric thin film is grown on a substrate and then thinned. A metal electrode layer is grown and patterned on the thinned piezoelectric thin film. A mask layer is grown and patterned on the patterned metal electrode layer. The thinned piezoelectric thin film is etched using the patterned mask layer to obtain a piezoelectric layer with a first etch hole and a support anchor structure connecting the piezoelectric layers on both sides of the first etch hole. A sacrificial layer or a well-rich layer or a sacrificial layer and a well-rich layer are etched in the substrate to form a cavity in the substrate. The patterned mask layer is then removed.

[0014] According to embodiments of this application, the piezoelectric thin film is grown by one of ion implantation, sputtering growth, molecular beam epitaxy, and vapor phase epitaxy; the metal electrode layer is grown by one of electron beam evaporation, vacuum evaporation, and magnetron sputtering; and the method for thinning the piezoelectric thin film includes ion beam etching.

[0015] According to an embodiment of this application, the patterned mask layer is removed by means of a buffered oxide etching solution or a tetramethylammonium hydroxide solution; wherein the material of the mask layer includes one of photoresist, silicon oxide, silicon nitride, and aluminum oxide.

[0016] The above one or more embodiments have the following beneficial effects: by etching the first etching hole in the middle of the piezoelectric layer, the deformation generated when the piezoelectric layer is released and suspended during the fabrication process of the resonator can be greatly reduced, effectively preventing the ultra-thin piezoelectric film from breaking, thereby greatly improving the stability of the resonator. Attached Figure Description

[0017] The above-mentioned contents, other objects, features and advantages of this application will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0018] Figure 1 A schematic diagram of the three-dimensional structure of a conventional acoustic resonator is shown.

[0019] Figure 2 A schematic diagram illustrating a three-dimensional structure of a first ultra-high frequency acoustic resonator according to an embodiment of this application is shown.

[0020] Figure 3 A schematic diagram illustrating a three-dimensional structure of a second type of ultra-high frequency acoustic resonator according to an embodiment of this application is shown.

[0021] Figure 4 A schematic diagram illustrating a three-dimensional structure of a third type of ultra-high frequency acoustic resonator according to an embodiment of this application is shown.

[0022] Figure 5 A schematic diagram illustrating a third-dimensional structure of a fourth ultra-high frequency acoustic resonator according to an embodiment of this application is shown.

[0023] Figure 6 A schematic diagram illustrating a third-dimensional structure of a fifth ultra-high frequency acoustic resonator according to an embodiment of this application is shown.

[0024] Figure 7 The schematic diagram shows a top view of the fifth type of ultra-high frequency acoustic resonator according to an embodiment of this application;

[0025] Figure 8(a) schematically shows the structure of an ultra-high frequency acoustic resonator with a first cavity and a support anchor structure according to an embodiment of the present application in section AA';

[0026] Figure 8(b) schematically shows the structure of an ultra-high frequency acoustic resonator with a first cavity and a support anchor structure according to an embodiment of the present application in section BB';

[0027] Figure 8(c) schematically shows the structure of a sixth ultra-high frequency acoustic resonator with a first cavity and a support anchor structure according to an embodiment of this application in section BB';

[0028] Figure 8(d) schematically shows a structural diagram of a seventh type of ultra-high frequency acoustic resonator with a first cavity and a support anchor structure according to an embodiment of this application in section BB'.

[0029] Figure 9(a) schematically shows the structure of an ultra-high frequency acoustic resonator with a second cavity and a support anchor structure according to an embodiment of the present application in section AA';

[0030] Figure 9(b) schematically shows the structure of an ultra-high frequency acoustic resonator with a second cavity and a support anchor structure according to an embodiment of the present application in section BB';

[0031] Figure 9(c) schematically shows the structure of the eighth ultra-high frequency acoustic resonator with a second cavity and a support anchor structure according to an embodiment of this application in the BB' section;

[0032] Figure 9(d) schematically shows the structural diagram of the ninth ultra-high frequency acoustic resonator with a second cavity and a support anchor structure according to an embodiment of this application in the BB' section;

[0033] Figure 10(a) schematically shows the structure of an ultra-high frequency acoustic resonator with a third cavity and a support anchor structure according to an embodiment of the present application in section AA';

[0034] Figure 10(b) schematically shows a structural diagram of an ultra-high frequency acoustic resonator with a third cavity and a support anchor structure according to an embodiment of the present application in section BB';

[0035] Figure 10(c) schematically shows the structural diagram of the tenth ultra-high frequency acoustic resonator with a third cavity and a support anchor structure according to an embodiment of this application in the BB' section;

[0036] Figure 10(d) schematically shows the structural diagram of the eleventh ultra-high frequency acoustic resonator with a third cavity and a support anchor structure according to an embodiment of the present application in the BB' section;

[0037] Figure 11 A flowchart illustrating a method for fabricating an ultra-high frequency acoustic resonator according to an embodiment of this application is shown.

[0038] Figure 12 This illustration schematically shows a fabrication process diagram of an ultra-high frequency acoustic resonator according to an embodiment of this application;

[0039] Figure 13(a) schematically shows the deformation test results of a conventional acoustic resonator;

[0040] Figure 13(b) schematically illustrates the deformation test results of a fifth type of ultra-high frequency acoustic resonator according to an embodiment of this application;

[0041] Figure 14(a) schematically shows the admittance test results of a conventional acoustic resonator;

[0042] Figure 14(b) schematically illustrates the admittance test results of a fifth type of ultra-high frequency acoustic resonator according to an embodiment of this application;

[0043] Figure 15(a) schematically shows the power capacity test results of a conventional acoustic resonator;

[0044] Figure 15(b) schematically shows the power capacity test results of a fifth type of ultra-high frequency acoustic resonator according to an embodiment of this application.

[0045] Reference numerals: 1. Substrate; 11. Supporting substrate; 12. Well-rich layer; 13. Sacrificial layer; 2. Piezoelectric thin film; 3. Metal electrode layer; 4. Patterned mask layer; 5. Piezoelectric layer; 6. Support anchor structure; 7. Etched hole; 71. Fifth etched hole; 8. Cavity; 9. Temperature compensation layer; d1. Width of support anchor structure; d2. Width of first etched hole. Detailed Implementation

[0046] The embodiments of this application will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this application. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of this application for ease of explanation. However, it will be apparent that one or more embodiments may be implemented without these specific details. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0047] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0048] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0049] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0050] The embodiments of this application provide an ultra-high frequency acoustic resonator and its fabrication method. By etching a hole in the middle of the piezoelectric layer and connecting the piezoelectric layers on both sides of the etched hole with a support anchor structure, large deformation and breakage of the ultra-thin piezoelectric film during release can be avoided during the fabrication of the resonator. It can also provide a larger heat dissipation path for the heat generated in the resonant region, thereby improving the high power processing capability of the resonator. Setting a cavity in the substrate can improve the quality factor of the resonator.

[0051] Figure 1 A schematic diagram of the three-dimensional structure of a conventional acoustic resonator is shown.

[0052] like Figure 1As shown, a conventional acoustic resonator includes a substrate 1, a piezoelectric layer 5, a metal electrode layer 3, and a fifth etched hole 71. The substrate 1 includes a sacrificial layer 13, a well-rich layer 12, and a supporting substrate 11 connected sequentially from top to bottom. The fifth etched hole 71 is located on both sides of the metal electrode layer 3, forming the fifth etched hole on both sides of the piezoelectric layer 5. The metal electrode layer 3 includes a metal electrode array, which includes at least one pair of metal electrodes with alternating positive and negative electrodes. The metal electrode array is distributed in the middle part of the metal electrode layer.

[0053] Figure 2 A schematic diagram of the three-dimensional structure of a first ultra-high frequency acoustic resonator according to an embodiment of this application is shown.

[0054] like Figure 2 As shown, the ultra-high frequency acoustic resonator includes a metal electrode layer 3 and a piezoelectric layer 5. The metal electrode layer 3 is located on the piezoelectric layer 5. The piezoelectric layer 5 has a first etched hole, also known as an etched hole 7, etched only in the center of the piezoelectric layer 5. There are no etched holes around the perimeter of the piezoelectric layer 5, and the perimeter of the piezoelectric layer 5 is connected to the substrate. The metal electrode layer 3 consists of a first metal electrode array and a second metal electrode array. The projection positions of the first and second metal electrode arrays are located on either side of the projection position of the first etched hole. Each of the first and second metal electrode arrays includes at least one pair of alternately arranged positive and negative metal electrodes. The alternating arrangement of metal electrodes includes a first metal electrode array comprising at least one pair of metal electrodes with alternating positive and negative electrodes, and a second metal electrode array comprising at least one pair of metal electrodes with alternating positive and negative electrodes. Further, the ultra-high frequency acoustic resonator also includes a substrate 1, with a piezoelectric layer 5 located on the substrate 1. The substrate 1 includes a sacrificial layer 13, a well-rich layer 12, and a supporting substrate 11 connected sequentially from top to bottom. A second etched hole is etched in the middle portion of the sacrificial layer, thereby forming a first cavity in the sacrificial layer portion; or, a third etched hole is etched in the middle portion of the well-rich layer, thereby forming a second cavity in the well-rich layer portion; or, a second etched hole is etched in the middle portion of the sacrificial layer and a third etched hole is etched in the middle portion of the well-rich layer, thereby forming a third cavity in the substrate. Further... Figure 2 The metal electrodes shown are interdigitated electrodes, with the positive and negative polarities of the electrodes between adjacent interdigitated electrodes being opposite. By using metal electrodes with alternating positive and negative electrodes, an alternating transverse electric field can be formed. Under the action of the alternating transverse electric field, the piezoelectric layer can generate sound waves, thereby achieving resonance.

[0055] According to embodiments of this application, compared to Figure 1The method of etching holes on both sides of the resonator shown in this application involves etching the first etching hole in the middle of the piezoelectric layer, which can provide a wider heat dissipation path for the heat generated when the resonator is working; setting a cavity in the substrate is beneficial to improving the quality factor.

[0056] In some embodiments, a metal electrode layer may be disposed on a first surface of the piezoelectric layer, or a metal electrode layer may be disposed on a second surface of the piezoelectric layer, or a metal electrode layer may be disposed on both the first and second surfaces of the piezoelectric layer. Specifically, the first surface may be above the piezoelectric layer and the second surface may be below the piezoelectric layer, or the first surface may be below the piezoelectric layer and the second surface may be above the piezoelectric layer.

[0057] In some embodiments, the ultra-high frequency acoustic resonator proposed in this application may or may not have a support anchor structure in the first etched hole. Figure 2 The first etched hole of the ultra-high frequency acoustic resonator shown does not have a support anchor structure.

[0058] In some embodiments, the ultra-high frequency acoustic resonator proposed in this application includes not only Figure 2 The structure of the ultra-high frequency acoustic resonator shown also includes a supporting anchor structure 6, such as... Figure 3 As shown, Figure 3 The second type of ultra-high frequency acoustic resonator shown is in Figure 2 Based on the first type of ultra-high frequency acoustic resonator shown, a support anchor structure 6 is added. Specifically, the support anchor structure is set in the first etched hole, and the support anchor structure is used to connect the piezoelectric layers on both sides of the first etched hole. Figure 3 The support anchor structure shown is a single structure located in the middle of the first etched hole.

[0059] According to embodiments of this application, by etching a first etched hole in the middle of the piezoelectric layer and connecting the piezoelectric layers on both sides of the first etched hole with a support anchor, the deformation generated when the piezoelectric layer is released and suspended during the fabrication process of the resonator can be greatly reduced, effectively preventing the ultra-thin piezoelectric film from breaking, thereby greatly improving the stability of the resonator. By connecting the piezoelectric layers on both sides of the first etched hole with the support anchor, the piezoelectric layers on both sides of the first etched hole are completely fixed on the substrate, thereby providing a wider heat dissipation path for the heat generated when the resonator is working, quickly reducing the temperature of the effective resonance region, reducing the probability of a large shift in the resonance frequency, maintaining the stability of the resonator under high power input, and thus improving the high power processing capability of the resonator.

[0060] In some embodiments, when forming the second cavity, the ultra-high frequency acoustic resonator further includes a fourth etched hole, wherein the fourth etched hole is disposed in the middle portion of the sacrificial layer, and the size of the fourth etched hole can be greater than or equal to the size of the first etched hole, or smaller than the size of the first etched hole. Generally, the size of the fourth etched hole is equal to the size of the first etched hole.

[0061] In some embodiments, when the third cavity is formed, the ultra-high frequency acoustic resonator may further include a temperature compensation layer 9, which is grown on the metal electrode layer; wherein the temperature compensation layer is used to ensure frequency stability.

[0062] In some embodiments, the sacrificial layer comprises one or more layers, each layer being made of a material selected from silicon oxide, silicon nitride, and silicon, and the thickness of the sacrificial layer is 0.1 mm. ~10 The well-rich layer is made of amorphous silicon or polycrystalline silicon; the supporting substrate is made of one of silicon, silicon carbide, sapphire, and quartz.

[0063] According to the embodiments of this application, setting multiple sacrificial layers is beneficial to improving etching accuracy and enhancing energy confinement capability; setting well-rich layers is beneficial to optimizing frequency characteristics and improving device stability.

[0064] In some embodiments, the thickness of the piezoelectric layer is 10 nm to 1 nm. The thickness of the metal electrode layer is 1nm~500nm.

[0065] According to the embodiments of this application, since the resonant frequency is mainly related to the thickness of the piezoelectric layer or the thickness of the piezoelectric film, the piezoelectric layer of this application is very thin, so ultra-high frequency resonance can be achieved, with a resonant frequency greater than 10 GHz, which is suitable for 5G / 6G wireless communication scenarios.

[0066] In some embodiments, the number of metal electrodes in the ultra-high frequency acoustic resonator can be up to 50 pairs.

[0067] In some embodiments, the piezoelectric layer is made of at least one of lithium niobate, lithium tantalate, aluminum nitride, and scandium-doped aluminum nitride; the metal electrode layer is made of one of gold, aluminum, molybdenum, platinum, copper, titanium-gold alloy, titanium-aluminum alloy, titanium-copper alloy, titanium-molybdenum alloy, titanium-platinum alloy, chromium-gold alloy, chromium-aluminum alloy, chromium-copper alloy, chromium-molybdenum alloy, and chromium-platinum alloy.

[0068] According to the embodiments of this application, piezoelectric layers prepared from materials such as lithium niobate, lithium tantalate, aluminum nitride, and scandium-doped aluminum nitride have high piezoelectric performance and can balance high-frequency and broadband characteristics, have strong process compatibility, and can be applied to various scenarios; the metal electrode layer materials used in this application are beneficial to reducing current conduction loss and improving interface reliability.

[0069] In some embodiments, the substrate 1 is made of a high resistivity material, and a well-rich layer is provided in the substrate to reduce the radio frequency loss of the resonator.

[0070] In some embodiments, the type of ultra-high frequency acoustic resonator can be a bulk acoustic resonator, a Lamb wave resonator, or other types of acoustic resonators.

[0071] Figure 4 A schematic diagram of the three-dimensional structure of a third type of ultra-high frequency acoustic resonator according to an embodiment of this application is shown.

[0072] like Figure 4 As shown, this ultra-high frequency acoustic resonator... Figure 2 Based on the first type of ultra-high frequency acoustic resonator shown, a support anchor structure 6 is added. Specifically, the support anchor structure is set in the first etched hole, and the support anchor structure is used to connect the piezoelectric layers on both sides of the first etched hole. Figure 4 There are two support anchor structures shown. One support anchor structure is located in the middle of the first etched hole, and the other support anchor structure is located on one side of the middle of the first etched hole.

[0073] Figure 5 A schematic diagram of the three-dimensional structure of a fourth type of ultra-high frequency acoustic resonator according to an embodiment of this application is shown.

[0074] like Figure 5 As shown, this ultra-high frequency acoustic resonator... Figure 2 Based on the first type of ultra-high frequency acoustic resonator shown, a support anchor structure 6 is added. Specifically, the support anchor structure is set in the first etched hole, and the support anchor structure is used to connect the piezoelectric layers on both sides of the first etched hole. Figure 5 There are two support anchor structures shown, which are located on both sides of the middle position of the first etched hole.

[0075] Figure 6 A schematic diagram of the three-dimensional structure of a fifth type of ultra-high frequency acoustic resonator according to an embodiment of this application is shown.

[0076] like Figure 6 As shown, this ultra-high frequency acoustic resonator... Figure 2 Based on the first type of ultra-high frequency acoustic resonator shown, a support anchor structure 6 is added. Specifically, the support anchor structure is set in the first etched hole, and the support anchor structure is used to connect the piezoelectric layers on both sides of the first etched hole. Figure 6 The support anchor structure shown has three parts, which are arranged in the middle of the first etched hole and on both sides of the middle of the first etched hole.

[0077] Figure 7The schematic diagram shows a top view of a fifth type of ultra-high frequency acoustic resonator according to an embodiment of this application.

[0078] like Figure 7 As shown, AA' represents the cross section taken along the vertical line of a certain support anchor structure in the top view of the UHF acoustic resonator, BB' represents the cross section taken along the vertical line of the part where there is no support anchor structure at the first etched hole in the top view of the UHF acoustic resonator, d1 represents the width of the support anchor structure, and d2 represents the width of the first etched hole. In the metal electrode layer 3, the polarity of the interdigitated metal electrode on the left and the interdigitated metal electrode on the right are opposite, which can form an alternating positive and negative transverse electric field, thereby exciting sound waves and generating resonance.

[0079] Figure 8(a) schematically shows the structure of an ultra-high frequency acoustic resonator with a first cavity and a support anchor structure according to an embodiment of the present application in section AA'.

[0080] As shown in Figure 8(a), the structure consists of a metal electrode layer 3, a piezoelectric layer 5, a sacrificial layer 13, a well-rich layer 12, and a support substrate 11 from top to bottom. A second etched hole is etched in the sacrificial layer 13 to form a cavity 8. The cavity 8 can represent a first cavity, a second cavity, or a third cavity. A first etched hole is etched in the piezoelectric layer 5. The size of the second etched hole can be greater than or equal to the size of the first etched hole, or it can be smaller than the size of the first etched hole. A support anchor structure 6 is provided in the first etched hole.

[0081] Figure 8(b) schematically shows the structure of an ultra-high frequency acoustic resonator with a first cavity and a support anchor structure according to an embodiment of the present application in section BB'.

[0082] As shown in Figure 8(b), the piezoelectric layer 5 is divided into two parts by the first etched hole, and these two parts are connected by a support anchor structure.

[0083] In some embodiments, the metal electrode layer 3 may also be located on the upper and lower surfaces of the piezoelectric layer 5, as shown in FIG8(c). FIG8(c) schematically shows a structural diagram of a sixth type of ultra-high frequency acoustic resonator with a first cavity and a support anchor structure according to an embodiment of the present application in the BB' section. The structure of the sixth type of ultra-high frequency acoustic resonator, from top to bottom, consists of a metal electrode layer 3, a piezoelectric layer 5, a sacrificial layer 13, a well-rich layer 12, and a support substrate 11. A second etched hole is etched in the sacrificial layer 13 to form a cavity 8. The cavity 8 may represent a first cavity, a second cavity, or a third cavity. A first etched hole is etched in the piezoelectric layer 5. The size of the second etched hole may be greater than or equal to the size of the first etched hole, or it may be smaller than the size of the first etched hole. A support anchor structure 6 may be provided in the first etched hole. The difference between the sixth type of ultra-high frequency acoustic resonator and the ultra-high frequency acoustic resonator shown in FIG8(a) is that... The piezoelectric layer 5 has metal electrode layers 3 grown on both its upper and lower surfaces. The projection of the metal electrode layer 3 on the lower surface of the piezoelectric layer 5 is located within the projection of the cavity 8. The shape of the metal electrode array on the upper surface of the piezoelectric layer 5 shown in Figure 8(c) is the same as the shape of the metal electrode array on the lower surface of the piezoelectric layer 5, but they can also be different. For example, as shown in Figure 8(d), Figure 8(d) schematically shows the structure of the seventh type of ultra-high frequency acoustic resonator with a first cavity and a support anchor structure according to an embodiment of this application in the BB' section. The difference between the seventh type of ultra-high frequency acoustic resonator and the sixth type of ultra-high frequency acoustic resonator is that the shape of the metal electrode array on the upper surface of the piezoelectric layer 5 in the seventh type of ultra-high frequency acoustic resonator is different from the shape of the metal electrode array on the lower surface of the piezoelectric layer 5. Furthermore, the metal electrode array of this application includes a first metal electrode array and a second metal electrode array.

[0084] Figure 9(a) schematically shows the structure of an ultra-high frequency acoustic resonator with a second cavity and a support anchor structure according to an embodiment of the present application in section AA'.

[0085] As shown in Figure 9(a), cavity 8 represents the second cavity, that is, a third etched hole is etched in the well-rich layer 12 to form cavity 8. A first etched hole is etched in the piezoelectric layer 5. The size of the third etched hole can be greater than or equal to the size of the first etched hole, or it can be smaller than the size of the first etched hole. A support anchor structure 6 is provided in the first etched hole. Furthermore, the well-rich layer 12 can be etched using dry or wet etching processes to generate the third etched hole. Dry etching can be performed using HF or XeF2, and wet etching can be performed using potassium hydroxide solution. When etching the third etched hole in the well-rich layer 12, the sacrificial layer can serve as a temperature compensation layer, which is beneficial to improving the stability of the resonator.

[0086] Figure 9(b) schematically shows the structure of an ultra-high frequency acoustic resonator with a second cavity and a support anchor structure according to an embodiment of the present application in section BB'.

[0087] As shown in Figure 9(b), the structure of the ultra-high frequency acoustic resonator with the second cavity also includes a fourth etched hole. The fourth etched hole is etched in the middle part of the well-rich layer. The size of the fourth etched hole can be greater than or equal to the size of the first etched hole, or it can be smaller than the size of the first etched hole. Generally, the size of the fourth etched hole is equal to the size of the first etched hole. The size of the fourth etched hole can be greater than or equal to the size of the third etched hole, or it can be smaller than the size of the third etched hole. Generally, the size of the fourth etched hole is smaller than the size of the third etched hole.

[0088] In some embodiments, FIG9(c) schematically shows a structural diagram of an eighth ultra-high frequency acoustic resonator with a second cavity and a support anchor structure according to an embodiment of the present application in section BB'. As shown in FIG9(c), the difference between the structure of the eighth ultra-high frequency acoustic resonator and the structure of the acoustic resonator shown in FIG9(b) is that a metal electrode layer 3 is also grown on the lower surface of the sacrificial layer 13 of the eighth ultra-high frequency acoustic resonator, and the projection of the metal electrode layer grown on the lower surface of the sacrificial layer 13 is located within the projection of the cavity 8. The metal electrode layer located on the upper surface of the piezoelectric layer 5 shown in FIG9(c) is... The shape of the metal electrode array is the same as that of the metal electrode array located on the lower surface of the sacrificial layer, but the two can be different. For example, Figure 9(d) schematically shows the structural diagram of the ninth type of ultra-high frequency acoustic resonator with a second cavity and a support anchor structure according to an embodiment of this application in the BB' section. As shown in Figure 9(d), the difference between the ninth type of ultra-high frequency acoustic resonator and the eighth type of ultra-high frequency acoustic resonator is that the shape of the metal electrode array located on the upper surface of the piezoelectric layer 5 in the ninth type of ultra-high frequency acoustic resonator is different from the shape of the metal electrode array located on the lower surface of the sacrificial layer.

[0089] Figure 10(a) schematically shows the structure of an ultra-high frequency acoustic resonator with a third cavity and a support anchor structure according to an embodiment of the present application in section AA'.

[0090] As shown in Figure 10(a), cavity 8 represents the third cavity. The third cavity includes a cavity structure composed of the second and third etched holes, or a cavity structure composed of the second, third, and sixth etched holes. The sixth etched hole refers to an etched hole obtained by etching the middle portion of the supporting substrate. The size of the second etched hole can be greater than or equal to the size of the third etched hole, or smaller than the size of the third etched hole. The size of the sixth etched hole can also be greater than or equal to the size of the third etched hole, or smaller than the size of the third etched hole. The third etched hole shown in Figure 10(a) is... The three-cavity structure refers to the cavity structure composed of the second, third, and sixth etched holes. The size of the second etched hole is larger than that of the third etched hole, and the size of the second etched hole is the same as that of the sacrificial layer. That is, the sacrificial layer is completely etched by the second etched hole. The size of the third etched hole is the same as that of the sixth etched hole. A support anchor structure 6 is provided in the first etched hole on the piezoelectric layer 5. A temperature compensation layer 9 is also grown on the metal electrode layer 3. The temperature compensation layer 9 is used to improve the stability of the resonator frequency. Furthermore, the material of the temperature compensation layer 9 can be silicon oxide.

[0091] Figure 10(b) schematically shows a structural diagram of an ultra-high frequency acoustic resonator with a third cavity and a support anchor structure according to an embodiment of the present application in section BB'.

[0092] As shown in Figure 10(b), the size of the first etched hole is smaller than the size of the second and third etched holes, respectively.

[0093] In some embodiments, FIG10(c) schematically shows a structural diagram of a tenth ultra-high frequency acoustic resonator with a third cavity and a support anchor structure according to an embodiment of the present application in section BB'. As shown in FIG10(c), the difference between the structure of the tenth ultra-high frequency acoustic resonator and the structure of the acoustic resonator shown in FIG10(b) is that a metal electrode layer 3 is also grown on the lower surface of the piezoelectric layer 5 of the tenth ultra-high frequency acoustic resonator, and the projection of the metal electrode layer grown on the lower surface of the piezoelectric layer 5 is located within the projection of the cavity 8. The metal electrode layer on the upper surface of the piezoelectric layer 5 shown in FIG10(c) is... The shape of the electrode array is the same as that of the metal electrode array located on the lower surface of the piezoelectric layer, but the two can be different. For example, Figure 10(d) schematically shows the structural diagram of the eleventh ultra-high frequency acoustic resonator with a third cavity and a support anchor structure according to an embodiment of this application in the BB' section. As shown in Figure 10(d), the difference between the eleventh ultra-high frequency acoustic resonator and the tenth ultra-high frequency acoustic resonator is that the shape of the metal electrode array located on the upper surface of the piezoelectric layer 5 in the eleventh ultra-high frequency acoustic resonator is different from the shape of the metal electrode array located on the lower surface of the piezoelectric layer.

[0094] Figure 11A flowchart illustrating a method for fabricating an ultra-high frequency acoustic resonator according to an embodiment of this application is shown.

[0095] like Figure 11 As shown, preparation method 200 includes operations S210 to S260.

[0096] Operation S210 is used to grow a piezoelectric thin film on the substrate and then the piezoelectric thin film is slid thin.

[0097] Operation S220 is used to grow and pattern a metal electrode layer on the thinned piezoelectric film.

[0098] Operation S230 grows and patterns a mask layer on the patterned metal electrode layer.

[0099] In operation S240, the patterned mask layer is used to etch the thinned piezoelectric film to obtain a piezoelectric layer with a first etched hole and a support anchor structure connecting the piezoelectric layers on both sides of the first etched hole.

[0100] Operation S250 etches a sacrificial layer or a well-rich layer or both in the substrate to form a cavity in the substrate.

[0101] Operate S260 to remove the patterned mask layer.

[0102] According to the embodiments of this application, the resonator prepared by the above preparation method has characteristics such as resonant frequency greater than 10GHz, high stability, wide heat dissipation path and high power processing capability.

[0103] In some embodiments, the substrate includes a sacrificial layer, a well-rich layer, and a supporting substrate, wherein the growth method of the well-rich layer includes, but is not limited to, ion implantation, sputtering growth, etc.; the growth method of the piezoelectric thin film includes, one of ion implantation, sputtering growth, molecular beam epitaxy, and vapor phase epitaxy; and the growth method of the metal electrode layer includes, one of electron beam evaporation, vacuum evaporation, and magnetron sputtering.

[0104] According to the embodiments of this application, growing a well-rich layer in the above manner can enhance energy confinement; growing a piezoelectric thin film in the above manner can improve energy conversion efficiency; and growing a metal electrode layer in the above manner can improve conductivity and interface reliability.

[0105] In some embodiments, during operation S210, the grown piezoelectric film typically exceeds 300 nm. Therefore, it is necessary to use methods such as ion beam etching to thin the grown piezoelectric film, making the thickness of the piezoelectric film thinner, thereby preparing an acoustic resonator with a higher resonant frequency.

[0106] According to the embodiments of this application, the grown piezoelectric film is thinned by methods such as ion beam etching, which can reduce performance loss. Ion beam can achieve large-area uniform irradiation, thereby reducing the difference in device thickness between the same batch of fabrication. Moreover, the damage layer of ion beam etching is very thin, and such slight damage can be eliminated by subsequent low-temperature annealing. Therefore, such slight damage has minimal impact on the core performance of the piezoelectric film, greatly reducing the cost of subsequent processing.

[0107] In some embodiments, the patterning method for the metal electrode layer can be either a stripping method or an etching method.

[0108] In some embodiments, the thinned piezoelectric film can be etched using methods such as inductively coupled plasma etching.

[0109] In some embodiments, the sacrificial layer or well-rich layer or both sacrificial and well-rich layers in the substrate can be etched using dry etching or wet etching methods; wherein, wet etching can be performed using potassium hydroxide solution, buffered oxidative etching solution, hydrofluoric acid solution or tetramethylammonium hydroxide solution.

[0110] In some embodiments, the patterned mask layer can be removed using a buffered oxide etching solution or a tetramethylammonium hydroxide solution; wherein the material of the mask layer includes one of photoresist, silicon oxide, silicon nitride, and aluminum oxide.

[0111] According to the embodiments of this application, removing the mask layer not only ensures that electromechanical energy can be converted normally, but also helps to optimize the quality factor, improve frequency stability, avoid chemical corrosion, extend device life, and facilitate packaging and integration.

[0112] Figure 12 A schematic diagram illustrating the fabrication process of an ultra-high frequency acoustic resonator according to an embodiment of this application is shown.

[0113] like Figure 12 As shown, a support substrate 11, a well-rich layer 12, and a sacrificial layer 13 are first grown to form a substrate 1. Then, a piezoelectric thin film 2 is grown on the substrate 1 and thinned. A metal electrode layer is grown and patterned on the thinned piezoelectric thin film to obtain a patterned metal electrode layer 3. A mask layer is grown and patterned on the patterned metal electrode layer to obtain a patterned mask layer 4. The thinned piezoelectric thin film is etched using the patterned mask layer to obtain a piezoelectric layer 5 with a first etch hole and a support anchor structure connecting the piezoelectric layers on both sides of the first etch hole. The sacrificial layer in the substrate is etched to obtain an etched sacrificial layer 13. A cavity 8 is formed in the substrate. Finally, the patterned mask layer is removed.

[0114] Furthermore, a metal electrode layer can be grown and patterned on the upper surface of the thinned piezoelectric film. Then, a mask layer is grown and patterned on the patterned metal electrode layer. The patterned mask layer is used to etch the thinned piezoelectric film, resulting in a piezoelectric layer with etched first etch holes. The upper surface of this piezoelectric layer has a metal electrode layer grown on it. Figure 12 As shown, in addition to this, metal electrode layers can also be grown on both the upper and lower surfaces of the thinned piezoelectric film and patterned respectively. Then, a mask layer can be grown on the patterned metal electrode layers and patterned. The patterned mask layer is then used to etch the thinned piezoelectric film to obtain a piezoelectric layer with the first etched hole. In this way, metal electrode layers are grown on the upper and lower surfaces of the obtained piezoelectric layer respectively. Although this method... Figure 12 Although not shown, this method can be used to fabricate ultra-high frequency acoustic resonators that can avoid large deformation and breakage of piezoelectric films during release, increase heat dissipation paths, and improve high-power processing capabilities and quality factors.

[0115] The above describes the ultra-high frequency acoustic resonator and its fabrication method. The following comparison of the test results of the traditional acoustic resonator and the ultra-high frequency acoustic resonator proposed in this application illustrates the superior performance of the ultra-high frequency acoustic resonator proposed in this application.

[0116] by Figure 1 The conventional acoustic resonator shown serves as a control group, with the resistivity of substrate 1 of this conventional acoustic resonator being greater than 1000 Ω / cm. 3 The sacrificial layer is made of silicon oxide, the well-rich layer is made of polycrystalline silicon, the piezoelectric film is made of lithium niobate with a thickness of 160 nm, and the width of each interdigitated structure in the interdigitated metal electrode is between 1 and 10 nm. The distance between adjacent interdigitated metal electrodes is 1~15. The thickness of the metal electrode layer is between 10 and 500 nm. Using the fifth type of ultra-high frequency acoustic resonator of this application as the experimental group, the resistivity of the substrate 1, the material of the sacrificial layer, the material of the well-rich layer, the material of the piezoelectric thin film, the thickness of the piezoelectric thin film, the width of each interdigitated structure in the interdigitated metal electrode, the distance between adjacent interdigitated metal electrodes, and the thickness of the metal electrode layer in the experimental group are the same as the corresponding parts in the control group. Three support anchor structures are provided in the first etched hole in the experimental group, and the width of each support anchor is between 1 and 100 nm. The acoustic resonators prepared in both the experimental and control groups are antisymmetric Lamb wave acoustic resonators. The following are the deformation test results, admittance test results, and power capacity test results for the control and experimental groups.

[0117] Figure 13(a) schematically shows the deformation test results of a conventional acoustic resonator.

[0118] As shown in Figure 13(a), the horizontal axis Location represents the position of the piezoelectric layer, with units of 12000 m / s. The vertical axis, Height, represents the displacement of the piezoelectric layer in the vertical direction, in units of... The Release Window is the release region, i.e., the area containing the first to fourth etched holes and the sixth etched hole. The Active Area is the active region, i.e., the resonant region. Deformation is the deformation parameter. As can be seen from the figure, in the traditional acoustic resonator fabrication process, after releasing the piezoelectric layer, the deformation of the piezoelectric layer is 1.93. .

[0119] Figure 13(b) schematically illustrates the deformation test results of a fifth type of ultra-high frequency acoustic resonator according to an embodiment of this application.

[0120] As shown in Figure 13(b), during the fabrication of the fifth type of ultra-high frequency acoustic resonator, after the piezoelectric layer is released, the deformation of the piezoelectric layer is 0.54. .

[0121] As can be seen from Figures 13(a) and 13(b), the deformation of the ultra-high frequency acoustic resonator of this application is greatly reduced, which can effectively avoid the breakage of the ultra-thin piezoelectric film, thereby greatly improving the stability of the acoustic resonator at ultra-high frequencies (greater than 10 GHz).

[0122] Figure 14(a) schematically shows the admittance test results of a conventional acoustic resonator.

[0123] As shown in Figure 14(a), the horizontal axis represents frequency in GHz, and the vertical axis represents admittance in dB. The solid black line represents the measurement result, and the dashed black line represents the result obtained by fitting using the modified Butterworth-Van Dyke model (MBVD fitting). The measured result of the admittance of the conventional acoustic resonator is almost the same as the fitting result. The resonant frequency fs of the conventional acoustic resonator is 12.35 GHz, and the electromechanical coupling coefficient (k... 2 The series resonant quality factor (Qs) is 44.5%, the parallel resonant quality factor (Qp) is 84, and the static capacitance (C0) is 44fF. The static capacitance represents the equivalent capacitance when the resonator is not working.

[0124] Figure 14(b) schematically illustrates the admittance test results of a fifth type of ultra-high frequency acoustic resonator according to an embodiment of this application.

[0125] As shown in Figure 14(b), the measured results of the admittance of the ultra-high frequency acoustic resonator of this application are almost the same as the fitting results. The resonant frequency fs of the ultra-high frequency acoustic resonator of this application is 12.28 GHz, and the electromechanical coupling coefficient (k 2 The series resonant quality factor (Qs) is 41%, the parallel resonant quality factor (Qp) is 80, and the static capacitance (C0) is 46fF.

[0126] As shown in Figures 14(a) and 14(b), the resonant frequencies of both the conventional acoustic resonator and the UHF acoustic resonator of this application are around 12 GHz, and both can achieve an electromechanical coupling coefficient of over 40%. The calculated parallel resonance quality factors also exceed 800. This indicates that the UHF acoustic resonator of this application can well meet the current requirements of 5G and 6G communication for high-performance UHF acoustic resonators, and the quality factor of the UHF acoustic resonator of this application is also relatively high.

[0127] Figure 15(a) schematically shows the power capacity test results of a conventional acoustic resonator.

[0128] As shown in Figure 15(a), this figure presents the frequency response test results of a traditional acoustic resonator at different input powers. When the input power is gradually increased from -10dBm to 10dBm in 5dBm increments, the frequency shift of the resonant frequency of the traditional acoustic resonator is ( The frequency is 28MHz.

[0129] Figure 15(b) schematically shows the power capacity test results of a fifth type of ultra-high frequency acoustic resonator according to an embodiment of this application.

[0130] As shown in Figure 15(b), when the input power is gradually increased from -10dBm to 10dBm in 5dBm increments, the frequency shift of the resonant frequency of the ultra-high frequency acoustic resonator of this application ( The frequency is 11MHz.

[0131] As shown in Figures 15(a) and 15(b), the higher the input power, the smaller the resonant frequency shift of the ultra-high frequency acoustic resonator of this application. This indicates that the ultra-high frequency acoustic resonator of this application can withstand higher input power and still maintain high stability under high power input.

[0132] Those skilled in the art will understand that the features described in the various embodiments of this application can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this application. In particular, the features described in the various embodiments of this application can be combined and / or combined in various ways without departing from the spirit and teachings of this application. All such combinations and / or combinations fall within the scope of this application.

Claims

1. An ultra-high frequency acoustic resonator, characterized in that, The ultra-high frequency acoustic resonator includes: Metal electrode layer and piezoelectric layer; The piezoelectric layer is etched with a first etched hole, wherein the first etched hole is located only in the middle of the piezoelectric layer; The metal electrode layer is composed of a first metal electrode array and a second metal electrode array, wherein the projection positions of the first metal electrode array and the second metal electrode array are located on both sides of the projection position of the first etched hole; wherein the first metal electrode array and the second metal electrode array each include at least one pair of alternately arranged positive and negative metal electrodes.

2. The ultra-high frequency acoustic resonator according to claim 1, characterized in that, The ultra-high frequency acoustic resonator also includes: A support anchor structure is provided in the first etched hole, and the support anchor structure is used to connect the piezoelectric layers on both sides of the first etched hole; The metal electrode layer is disposed on the first surface of the piezoelectric layer, or the metal electrode layer is disposed on the second surface of the piezoelectric layer, or the metal electrode layer is disposed on both the first surface and the second surface of the piezoelectric layer.

3. The ultra-high frequency acoustic resonator according to claim 1, characterized in that, The ultra-high frequency acoustic resonator also includes: A substrate, wherein the piezoelectric layer is located on the substrate; wherein the substrate includes a sacrificial layer, a well-rich layer and a supporting substrate connected sequentially from top to bottom; The middle portion of the sacrificial layer is etched with a second etch hole to form a first cavity; or, the middle portion of the well-rich layer is etched with a third etch hole to form a second cavity; or, the middle portion of the sacrificial layer is etched with a second etch hole and the middle portion of the well-rich layer is etched with a third etch hole to form a third cavity.

4. The ultra-high frequency acoustic resonator according to claim 3, characterized in that, When the third cavity is formed, the ultra-high frequency acoustic resonator further includes: a temperature compensation layer grown on the metal electrode layer; wherein, The temperature compensation layer is used to ensure frequency stability.

5. The ultra-high frequency acoustic resonator according to claim 3, characterized in that, The sacrificial layer comprises one or more layers, each layer being made of one of silicon oxide, silicon nitride, and silicon, and the thickness of the sacrificial layer is 0.1 mm. ~10 ; The material of the well-rich layer includes amorphous silicon or polycrystalline silicon; The material of the supporting substrate includes one of silicon, silicon carbide, sapphire, and quartz.

6. The ultra-high frequency acoustic resonator according to claim 1, characterized in that, The thickness of the piezoelectric layer is 10 nm~1. The thickness of the metal electrode layer is 1 nm to 500 nm.

7. The ultra-high frequency acoustic resonator according to claim 1, characterized in that, The material of the piezoelectric layer includes at least one of lithium niobate, lithium tantalate, aluminum nitride, and scandium-doped aluminum nitride; The material of the metal electrode layer includes one of the following: gold, aluminum, molybdenum, platinum, copper, titanium-gold alloy, titanium-aluminum alloy, titanium-copper alloy, titanium-molybdenum alloy, titanium-platinum alloy, chromium-gold alloy, chromium-aluminum alloy, chromium-copper alloy, chromium-molybdenum alloy, and chromium-platinum alloy.

8. A method for fabricating an ultra-high frequency acoustic resonator, characterized in that, The preparation method includes: A piezoelectric thin film is grown on a substrate, and the piezoelectric thin film is then slid thin. A metal electrode layer is grown and patterned on the thinned piezoelectric film; A mask layer is grown and patterned on the patterned metal electrode layer; The patterned mask layer is used to etch the thinned piezoelectric film to obtain a piezoelectric layer with a first etched hole and a support anchor structure connecting the piezoelectric layers on both sides of the first etched hole. Etching the sacrificial layer or well-rich layer or both sacrificial and well-rich layers in the substrate to form a cavity in the substrate; Remove the patterned mask layer.

9. The preparation method according to claim 8, characterized in that, The piezoelectric thin film is grown by one of the following methods: ion implantation, sputtering growth, molecular beam epitaxy, and vapor phase epitaxy. The growth method of the metal electrode layer includes one of electron beam evaporation, vacuum evaporation, and magnetron sputtering. The method for thinning the piezoelectric film includes ion beam etching.

10. The preparation method according to claim 8, characterized in that, The patterned mask layer is removed in the following manner: The patterned mask layer is removed using a buffered oxide etching solution or a tetramethylammonium hydroxide solution; wherein the material of the mask layer includes one of photoresist, silicon oxide, silicon nitride, and aluminum oxide.

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