Bulk acoustic wave resonator, filter and electronic equipment

Abstract

The invention provides a bulk acoustic wave resonator, a filter and electronic equipment. The bulk acoustic wave resonator comprises a substrate layer, a Bragg reflection layer arranged on the substrate layer and a piezoelectric transduction structure layer arranged on the Bragg reflection layer. The Bragg reflection layer comprises a plurality of film layers which are arranged in a stacked mode, and the refractive indexes of every two adjacent film layers are different; the piezoelectric transduction structure layer comprises a piezoelectric layer and an electrode layer which are stacked; at least one film layer, close to the piezoelectric transduction structure layer, in the Bragg reflection layer is a preset film layer, the preset film layer comprises cavity parts and supporting parts, the cavity parts and the supporting parts are alternately arranged in the first direction, and the first direction is parallel to the substrate layer. According to the bulk acoustic wave resonator, acoustic wave energy is concentrated on the piezoelectric layer through the cavity parts, the electromechanical coupling coefficient of the bulk acoustic wave resonator is increased, under the alternate arrangement of the cavity parts and the supporting parts, the slowness curve of the main vibration mode of the bulk acoustic wave resonator is flattened, the transverse mode and stray response are restrained, and therefore the quality factor of the bulk acoustic wave resonator is improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and particularly to a bulk acoustic wave resonator, a filter, and an electronic device. Background Art

[0002] With the popularization of 5G communication, the requirements for communication speed are constantly increasing. In order to meet the needs of massive data and real-time high-speed transmission in the communication network, it is necessary to increase the channel bandwidth and improve the signal-to-noise ratio in the communication network. The key device affecting the channel bandwidth and signal-to-noise ratio is the filter. Therefore, higher requirements are put forward for the filter in the communication network.

[0003] As a resonator, which is a filter design unit, in addition to the two performance parameters of quality factor Q and effective electromechanical coupling coefficient, there is also an important parameter, namely spurious response. The spurious response of the resonator will cause ripples in the filter passband, increase the insertion loss of the filter, and deteriorate the performance. Therefore, the suppression of the spurious response of the resonator is particularly important.

[0004] Therefore, designing a resonator that can suppress spurious response and improve the quality factor is a problem that those skilled in the art need to overcome currently. Summary of the Invention

[0005] The present application provides a bulk acoustic wave resonator, a filter, and an electronic device, which are used to suppress spurious response, improve the quality factor of the resonator, and thus improve the performance of the filter.

[0006] In a first aspect, a bulk acoustic wave resonator is provided, including a substrate layer, a Bragg reflector layer, and a piezoelectric transducer structure layer; the Bragg reflector layer is disposed on the substrate layer, the Bragg reflector layer includes a plurality of stacked film layers, and the refractive indices of two adjacent film layers are different; and, the piezoelectric transducer structure layer is disposed on the Bragg reflector layer, the piezoelectric transducer structure layer includes a stacked piezoelectric layer and electrode layer; wherein, at least one film layer of the Bragg reflector layer close to the piezoelectric transducer structure layer is a preset film layer, the preset film layer includes a cavity portion and a support portion, and the cavity portion and the support portion are alternately arranged in a first direction, and the first direction is parallel to the substrate layer.

[0007] For the bulk acoustic wave resonator provided by the present application, since the Bragg reflector can reflect the acoustic wave energy towards the piezoelectric transducer structure layer, and at least one film layer of the Bragg reflector close to the piezoelectric transducer structure layer is a preset film layer, and the preset film layer includes a cavity portion and a support portion, it can be understood that during the propagation of the acoustic wave energy, the Bragg reflector supports the piezoelectric layer and the electrode layer through the support portion, and concentrates the acoustic wave energy on the piezoelectric layer through the cavity portion, which helps to improve the electromechanical coupling coefficient of the bulk acoustic wave resonator; moreover, due to the alternating arrangement of the cavity portion and the support portion, while helping to improve the electromechanical coupling coefficient of the bulk acoustic wave resonator, it can also regulate the slowness curve of the main vibration mode of the bulk acoustic wave resonator, so that the slowness curve of the main vibration mode of the bulk acoustic wave resonator becomes flat, suppress the transverse mode of the bulk acoustic wave resonator, and further suppress the spurious response of the bulk acoustic wave resonator, thereby improving the quality factor of the bulk acoustic wave resonator.

[0008] In the first aspect, "the Bragg reflector includes a plurality of film layers arranged in a stack, and the refractive indices of two adjacent film layers are different", it can be understood that, for example, the Bragg reflector includes four film layers arranged in a stack, and the refractive indices of two adjacent film layers among the four film layers are different, which can be formed by alternating two film layers with different refractive indices, or formed by four film layers with different refractive indices. And "at least one film layer of the Bragg reflector close to the piezoelectric transducer structure layer is a preset film layer, and the preset film layer includes a cavity portion and a support portion", it can be understood that, for example, the Bragg reflector includes four film layers arranged in a stack, and the number of preset film layers of the Bragg reflector close to the piezoelectric transducer structure layer can be one layer, two layers or three layers. That is to say, the preset film layer of the Bragg reflector close to the piezoelectric transducer structure layer can be a film layer composed entirely of a cavity portion and a support portion for one layer, or a film layer composed entirely of a cavity portion and a support portion for two layers, or a film layer composed entirely of a cavity portion and a support portion for three layers.

[0009] In some embodiments, the cavity portion and the support portion are alternately arranged in a second direction, the second direction is parallel to the substrate layer, and the second direction intersects the first direction. With such an arrangement, the cavity portion and the support portion can be arranged in a determinant pattern on one side of the piezoelectric layer, making the arrangement of the cavity portion and the support portion more uniform to support the piezoelectric layer, which helps to improve the stability of the piezoelectric layer.

[0010] In some embodiments, the preset film layer includes a first surface close to the piezoelectric transducer structure layer; the cavity portion at least penetrates the first surface. With such an arrangement, it is convenient for the cavity portion to concentrate the acoustic wave energy on the piezoelectric transducer structure layer through the first surface, which helps to improve the acoustic wave energy confinement effect of the cavity portion.

[0011] In some embodiments, the preset film layer includes a second surface facing away from the piezoelectric transducer structure layer, and the cavity portion also penetrates through the second surface. With such an arrangement, it is convenient to concentrate the acoustic wave energy on the cavity portion through the second surface, which helps to improve the concentration effect of the acoustic wave energy in the cavity portion.

[0012] In some embodiments, the preset film layer includes a plurality of the support portions and a plurality of the cavity portions. The plurality of support portions are arranged at intervals, and the cavity portions adjacent to each support portion communicate with each other. With such an arrangement, the etched portion around the support portion is the cavity portion, so as to adjust the range of the etched cavity portion, and further facilitate changing the shape and size of the support portion, thereby adjusting the support of the support body to the piezoelectric layer.

[0013] In some embodiments, the support portion is arranged in at least one of the following manners: the shape of the cross-section of the support portion in a direction parallel to the substrate layer includes any one of a polygon, a star shape, a circle, and an ellipse; among the plurality of cross-sections of the support portion in a direction parallel to the substrate layer, the area of the cross-section far from the piezoelectric layer is greater than or equal to the area of the cross-section close to the piezoelectric layer; in the support portion: the area of the end far from the piezoelectric layer is greater than or equal to the area of the end close to the piezoelectric layer; or, the included angle range between the support portion and a reference line perpendicular to the substrate layer is 0° - 60°. With such an arrangement, it is convenient to process the support portion into different shapes. While reducing the processing difficulty of the support portion, it helps to improve the support stability of the support portion to the piezoelectric layer.

[0014] In some embodiments, the preset film layer includes a plurality of the support portions and a plurality of the cavity portions. The plurality of cavity portions are arranged at intervals, and the plurality of support portions are connected into a whole. With such an arrangement, the unetched portion around the cavity portion is the support portion, so as to change the shape of the cavity portion through the preset film layer formed by etching the support portion, and adjust the effect of the cavity portion on confining the concentration of acoustic wave energy.

[0015] In some embodiments, the cavity portion is arranged in at least one of the following manners: the shape of the cross-section of the cavity portion in a direction parallel to the substrate layer includes any one of a polygon, a star shape, a circle, and an ellipse; among the plurality of cross-sections of the cavity portion in a direction parallel to the substrate layer, the area of the cross-section far from the piezoelectric layer is less than or equal to the area of the cross-section close to the piezoelectric layer; in the cavity portion: the area of the end far from the piezoelectric layer is less than or equal to the area of the end close to the piezoelectric layer; or, the included angle range between the cavity portion and a reference line perpendicular to the substrate layer is 0° - 60°. With such an arrangement, it is convenient to etch the cavity portion into different shapes. While reducing the etching difficulty of the cavity portion, it helps to improve the effect of the cavity portion on confining the acoustic wave energy.

[0016] In some embodiments, the material of the preset film layer includes at least one of SiO2, SiOC, Si3N4, AlN, Pt, Mo, W, and HfO2. With such a setting, the support part of the preset film layer has a relatively high reflection coefficient, thereby improving the acoustic energy confinement effect of the cavity part around the support part on the target acoustic wave.

[0017] In some embodiments, the electrode layer includes a first electrode layer and a second electrode layer. The piezoelectric layer is disposed between the first electrode layer and the second electrode layer, and the first electrode layer is closer to the Bragg reflection layer than the piezoelectric layer. With such a setting, the piezoelectric layer is surrounded, and by using the piezoelectric effect of the piezoelectric layer, electrical energy is converted into acoustic energy, and a standing wave oscillation is formed between the interfaces of the first electrode layer and the second electrode layer to reduce the acoustic wave loss of the bulk acoustic wave resonator.

[0018] In a second aspect, a method for manufacturing a bulk acoustic wave resonator is provided, including: forming a Bragg reflection layer on one side of a substrate layer; the Bragg reflection layer includes a plurality of film layers stacked, and the refractive indices of two adjacent film layers are different; forming a piezoelectric transducer structure layer on the side of the Bragg reflection layer facing away from the substrate layer, the piezoelectric transducer structure layer includes a piezoelectric layer and an electrode layer stacked; processing at least one film layer in the Bragg reflection layer close to the piezoelectric transducer structure layer into a preset film layer, the preset film layer includes a cavity part and a support part, and the cavity part and the support part are alternately arranged in a first direction, and the first direction is parallel to the substrate layer.

[0019] The bulk acoustic wave resonator formed based on the method for manufacturing a bulk acoustic wave resonator provided in the embodiments of the present application includes the above-mentioned bulk acoustic wave resonator, and thus has all the beneficial effects of the above-mentioned bulk acoustic wave resonator, which will not be elaborated here.

[0020] In some embodiments, the processing of at least one film layer in the Bragg reflection layer close to the piezoelectric transducer structure layer into a preset film layer includes: before forming the piezoelectric transducer structure layer on the side of the Bragg reflection layer facing away from the substrate layer, forming a cavity part in at least one film layer in the Bragg reflection layer close to the piezoelectric transducer structure layer; filling a sacrificial material in the cavity part; after forming the piezoelectric transducer structure layer on the side of the Bragg reflection layer facing away from the substrate layer, removing the sacrificial material.

[0021] With such a setting, after the preset film layer is etched to form the cavity part and the support part, the cavity part is first filled with the sacrificial material, then the piezoelectric transducer structure layer is formed on the side of the preset film layer facing away from the substrate layer, and then the sacrificial material is removed from the cavity part by wet etching, so as to avoid the piezoelectric transducer structure layer collapsing into the cavity part when the piezoelectric transducer structure layer is formed, thereby facilitating the formation of the cavity part and the support part on one side of the piezoelectric transducer structure layer.

[0022] In some embodiments, the preset film layer includes a plurality of cavity portions and support portions. When the plurality of support portions are arranged at intervals and the cavity portions adjacent to each support portion are interconnected: the removal of the sacrificial material includes: removing the sacrificial material through an opening in the side surface of the preset film layer that communicates with the cavity portion. With such an arrangement, when the plurality of support portions are arranged at intervals and the cavity portions adjacent to each support portion are interconnected, the sacrificial material filled in the cavity portion can be removed through the opening on the side surface of the preset film layer, thereby facilitating the formation of a plurality of cavity portions and support portions on one side of the piezoelectric transducer structure layer.

[0023] In some embodiments, the preset film layer includes a plurality of cavity portions and support portions. When the plurality of cavity portions are arranged at intervals and the plurality of support portions are connected as a whole, the piezoelectric layer includes an opening that communicates the cavity portion with the side surface of the piezoelectric layer. The removal of the sacrificial material includes: removing the sacrificial material through the opening in the piezoelectric layer. With such an arrangement, when the plurality of cavity portions are arranged at intervals and the plurality of support portions are connected as a whole, the sacrificial material filled in the cavity portion can be removed through the opening in the piezoelectric layer, thereby facilitating the formation of a plurality of cavity portions and support portions on one side of the piezoelectric transducer structure layer.

[0024] In a third aspect, a filter is provided, which includes a plurality of cascaded resonators, and at least one resonator among the plurality of cascaded resonators is the bulk acoustic wave resonator in any of the above embodiments.

[0025] In this embodiment, by utilizing the characteristics of the resonator to suppress spurious responses and reduce the ripples appearing in the filter, the effect of reducing the insertion loss of the filter is achieved, thereby improving the performance of the filter.

[0026] In a fourth aspect, an electronic device is provided, which includes a filter and a circuit board. The filter is disposed on the circuit board, and the filter is the filter described in the third aspect. Since the electronic device has the same technical effects as the bulk acoustic wave resonator provided in the first aspect above, the relevant descriptions in the first aspect can be referred to and will not be elaborated here. Description of the Drawings

[0027] Figure 1 It is a structural block diagram of an electronic device provided in this embodiment;

[0028] Figure 2 It is a three-dimensional structure diagram of the bulk acoustic wave resonator provided in this embodiment;

[0029] Figure 3 It is a schematic diagram of a block structure of the support portion on the film layer close to the piezoelectric layer in the Bragg reflector layer provided in this embodiment;

[0030] Figure 4Schematic diagram of the columnar structure of the support part provided in this embodiment on the film layer close to the piezoelectric layer in the Bragg reflection layer;

[0031] Figure 5 Schematic cross-sectional view of the support part provided in this embodiment with a triangular cross-section in the direction parallel to the substrate layer;

[0032] Figure 6 Schematic cross-sectional view of the support part provided in this embodiment with a parallelogram cross-section in the direction parallel to the substrate layer;

[0033] Figure 7 Schematic cross-sectional view of the support part provided in this embodiment with a hexagonal cross-section in the direction parallel to the substrate layer;

[0034] Figure 8 Schematic cross-sectional view of the support part provided in this embodiment with an elliptical cross-section in the direction parallel to the substrate layer;

[0035] Figure 9 Schematic cross-sectional view of the support part provided in this embodiment with a rhombus cross-section in the direction parallel to the substrate layer;

[0036] Figure 10 Schematic cross-sectional view of the support part and the cavity part provided in this embodiment with an included angle between the extending direction and the substrate layer;

[0037] Figure 11 Schematic cross-sectional view of the support part and the cavity part provided in this embodiment in the direction perpendicular to the base layer;

[0038] Figure 12 Schematic cross-sectional view of the support part and the cavity part provided in this embodiment with a rectangular cross-section in the direction perpendicular to the substrate layer;

[0039] Figure 13 Schematic cross-sectional view of the support part and the cavity part provided in this embodiment with a trapezoidal cross-section in the direction perpendicular to the substrate layer;

[0040] Figure 14 Schematic cross-sectional view of the cavity part provided in this embodiment as a circular columnar cavity;

[0041] Figure 15 Schematic cross-sectional view of the cavity part provided in this embodiment as a triangular columnar cavity;

[0042] Figure 16 Schematic cross-sectional view of the cavity part provided in this embodiment as a rectangular columnar cavity;

[0043] Figure 17 Schematic cross-sectional view of the cavity part provided in this embodiment as a pentagonal columnar cavity;

[0044] Figure 18 A graph showing the relationship between the film thickness and the electromechanical coupling coefficient of the Bragg reflector layer provided in this embodiment, which has a cavity portion and a support portion;

[0045] Figure 19 A graph showing the relationship between the number of layers of the Bragg reflector layer provided in this embodiment and the quality factor;

[0046] Figure 20 A slowness graph of the bulk acoustic wave resonator provided in this embodiment in the X-Z direction;

[0047] Figure 21 A admittance graph of the bulk acoustic wave resonator provided in this embodiment without a cavity portion and a support portion;

[0048] Figure 22 A admittance graph of the bulk acoustic wave resonator provided in this embodiment with a cavity portion and a support portion;

[0049] Figure 23 A flowchart of the manufacturing method of the bulk acoustic wave resonator provided in this embodiment;

[0050] Figure 24 A flowchart of the manufacturing method of the preset film layer in the bulk acoustic wave resonator provided in this embodiment;

[0051] Figure 25 A flowchart of the method for removing sacrificial materials in the bulk acoustic wave resonator provided in this embodiment. Detailed implementation manners

[0052] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0053] The terms "first", "second", etc. (if any) in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments described herein can be implemented in an order different from that shown or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0054] First, some concepts that may be involved in the embodiments of the present invention will be briefly introduced below.

[0055] Electromechanical coupling coefficient K 2 : It is a key parameter of the resonator. The electromechanical coupling coefficient K 2 can reflect the conversion efficiency between mechanical energy and electrical energy. The electromechanical coupling coefficient K of the resonator 2 determines the difference between the series and parallel resonance frequencies of the resonator. When the resonator is applied in filter design, this difference directly determines the bandwidth of the filter. It can be considered that the electromechanical coupling coefficient K 2 is larger, the conversion efficiency of the resonator is higher, the filter bandwidth is larger, and the performance is better.

[0056] Quality factor Q: It represents the energy utilization rate of the device, that is, the ratio of the total energy received by the device to the dissipated energy within one vibration cycle. In the design of the filter, the electromechanical coupling coefficient K of the resonator that constitutes the filter 2 and the quality factor Q value are both important parameters.

[0057] Euler angle (eulerangle) of the piezoelectric material: In a bulk acoustic wave (BAW) resonator, the Euler angle (eulerangle) representation method is a method for representing the crystal direction of the normal of the wafer surface and the direction of the reference plane that coincides with the propagation direction of the BAW resonator. This Euler angle can also be called the cut angle.

[0058] Slowness characteristic, slowness curve: The slowness characteristic is usually characterized by a slowness curve. The slowness characteristic is a physical parameter that measures the propagation of waves in a medium. Slowness is the reciprocal of velocity. Therefore, the propagation time of a wave is the distance traveled by the wave multiplied by the slowness of the medium.

[0059] This embodiment provides an electronic device, which includes, but is not limited to, products such as a radio frequency front end and a filter amplification module, and may also include a mobile phone, a tablet computer (pad), smart wearable products (such as smart watches and smart bracelets), virtual reality (VR) devices, augmented reality (AR), drones, etc. Home electronic products such as smart door locks, televisions, remote controls, refrigerators, and small household appliances for charging (such as soybean milk machines and floor cleaning robots), etc. In-vehicle electronic products such as in-vehicle navigators and in-vehicle high-density digital video discs (DVDs), etc. Financial terminal products such as automated teller machines (ATMs) and terminals for self-service business handling, etc. The specific form of the above communication devices is not particularly limited in the embodiments of the present application.

[0060] Refer to Figure 1 , Figure 1 FIG. is a structural block diagram of an electronic device 1000 provided in this embodiment. The electronic device 1000 may include a filter 100 and a circuit board 200. The filter 100 is disposed on the circuit board 200. Under the control of the circuit board 200, the filter 100 can perform the conversion of an electrical signal - acoustic signal (acoustic wave) - electrical signal. And during the conversion process, the filter 100 can effectively filter the frequency of a specific frequency point or the frequency outside this frequency point in the signal, to obtain a signal with a specific frequency, or a signal after eliminating a specific frequency, so as to improve the working performance of the electronic device 1000.

[0061] The filter 100 provided in the embodiments of the present application may be, for example, a low-pass acoustic filter, a high-pass acoustic filter, a band-pass acoustic filter, a band-stop acoustic filter, or an active acoustic filter, etc.

[0062] In this embodiment, the filter 100 may include a plurality of serially connected acoustic resonators 110, or include a plurality of parallel-connected acoustic resonators 110, or include acoustic resonators 110 combined in series and parallel.

[0063] The acoustic resonator 110 may be classified into a bulk acoustic wave (BAW) resonator and a surface acoustic wave (SAW) resonator, etc.

[0064] Among them, at least one acoustic resonator 110 in the filter 100 can be a bulk acoustic wave resonator (BAW). The main working principle of the bulk acoustic wave resonator is to use the piezoelectric characteristics of piezoelectricity and use input and output transducers to convert the input signal of the radio wave into mechanical energy to generate reliable oscillation, thereby achieving high-frequency clock output.

[0065] Bulk acoustic wave resonator BAW is one of the design units of filter 100. Compared with surface acoustic wave resonator SAW, it has the characteristics of high frequency, high power capacity, high Q value, etc. It is believed that it will replace SAW and dominate the mobile communication filtering technology of 5G and future 6G. Bulk acoustic wave resonator can be divided into free-edge beam resonator (FBAR) and solid mounted resonator (SMR) according to different structures.

[0066] The characteristics of free boundary resonators are high quality factor Q value and large effective electromechanical coupling coefficient. However, since there is air under the electrode, which is a poor thermal conductor, the heat dissipation condition of this resonator is very poor, resulting in high temperature of the resonator under high-power working conditions, and the resonator is easily damaged, thus affecting the power tolerance of the device; the resonator with solid assembly structure sets a Bragg radiation layer under the electrode to simulate the reflection of sound waves by air. This structure allows the heat generated by the resonator to be well dissipated from the substrate, thus having good power tolerance. However, due to the addition of the Bragg reflection structure, the effective electromechanical coupling coefficient of the traditional solid assembly structure resonator will be reduced.

[0067] It can be known that the above two types of resonators have the problem that power tolerance and electromechanical coupling coefficient cannot be taken into account at the same time. However, in addition to the two properties of power tolerance and electromechanical coupling coefficient, the performance of the resonator also has an important parameter, which is the quality factor Q. The factor Q that affects the quality factor Q includes the spurious response of the resonator. The more obvious the spurious response is suppressed, the higher the quality factor Q. The spurious response of the resonator will cause ripples in the filter 100, increase the insertion loss of the filter 100, and deteriorate the performance. Therefore, it is particularly important to suppress the spurious response of the resonator.

[0068] Based on at least the above three problems existing in the resonator, an embodiment of the present application provides a bulk acoustic wave resonator 300, which is applied to the above-mentioned filter 100, can solve the problem that power tolerance and electromechanical coupling coefficient cannot be taken into account at the same time, and suppress the spurious response of the bulk acoustic wave resonator 300 to improve the quality factor of the bulk acoustic wave resonator 300.

[0069] See also Figure 2 , Figure 2This is a three-dimensional structure diagram of the bulk acoustic wave resonator 300 provided by an embodiment of the present application. The bulk acoustic wave resonator 300 includes: a substrate layer 310, a piezoelectric transducer structure layer 340, and a Bragg reflector layer 320. The piezoelectric transducer structure layer 340 is disposed on one side of the substrate layer 310. The Bragg reflector layer 320 is disposed between the substrate layer 310 and the piezoelectric transducer structure layer 340. The Bragg reflector layer 320 includes a plurality of stacked film layers, and the refractive indices of two adjacent film layers are different. At least one film layer of the Bragg reflector layer 320 close to the piezoelectric transducer structure layer 340 includes a preset film layer 323. The preset film layer 323 includes a cavity portion 325 and a support portion 324, and the cavity portion 325 and the support portion 324 are alternately arranged in a direction parallel to the substrate layer 310.

[0070] Among them, for the substrate layer 310, substrate materials such as Si, sapphire, and SiC are used.

[0071] It should be noted that the Bragg reflector layer 320 is composed of high acoustic impedance materials and low acoustic impedance materials alternately. In this embodiment, at least one film layer of the Bragg reflector layer 320 close to the piezoelectric transducer structure layer 340 is replaced with a cavity portion 325 and a support portion 324. It can be understood that one side of the piezoelectric transducer structure layer 340 has a plurality of alternately distributed cavity portions 325 and support portions 324. The meaning of "at least one film layer" refers to the number of preset film layers 323 of the Bragg reflector layer 320 close to the piezoelectric transducer structure layer 340, which can be one layer, two layers, or more layers. In this embodiment, the number of preset film layers 323 of the Bragg reflector layer 320 close to the piezoelectric transducer structure layer 340 is one layer. As Figure 2 shown, in this embodiment, the Bragg reflector layer can be four film layers, and one film layer close to the piezoelectric transducer structure layer 340 is replaced with a plurality of cavity portions 325 and support portions 324.

[0072] In this embodiment, refer to Figure 2 , Figure 2 This is a three-dimensional structure diagram of the bulk acoustic wave resonator 300 provided by an embodiment of the present application. The piezoelectric transducer structure layer 340 includes a stacked electrode layer and a piezoelectric layer 342. The electrode layer includes: a first electrode layer 341 and a second electrode layer 343. The piezoelectric layer 342 is disposed between the first electrode layer 341 and the second electrode layer 343; the first electrode layer 341 is closer to the Bragg reflector layer 320 than the piezoelectric layer 342. In this embodiment, the piezoelectric effect of the piezoelectric layer 342 is utilized to convert electrical energy into acoustic energy, and a standing wave oscillation is formed at the interface between the first electrode layer 341 and the second electrode layer 343 to reduce the acoustic wave loss of the bulk acoustic wave resonator 300.

[0073] In order to meet different required electromechanical coupling coefficients, different piezoelectric layer 342 materials and the tangential direction of the Euler angles of the piezoelectric layer 342 material can be selected. For example, the materials of the piezoelectric layer 342 are shown in Table 1:

[0074] Table 1

[0075] Piezoelectric material Chemical abbreviation Remarks Quartz <![CDATA[Main component SiO2]]> Small piezoelectric coefficient Lithium niobate LN Select the tangential direction as needed Lithium tantalate LT Select the tangential direction as needed Aluminum nitride AlN Scandium-doped aluminum nitride <![CDATA[Sc x AlN 1-x > X: Scandium doping ratio

[0076] It should be noted that different piezoelectric layer 342 materials have different anisotropic characteristics, and the anisotropic characteristics of the same piezoelectric layer 342 material in different Euler angle tangential directions are also different. Therefore, in order to suppress the transverse mode of the bulk acoustic wave resonator 300, the piezoelectric layer 342 is designed according to the anisotropic characteristics of the material in the horizontal direction.

[0077] In other embodiments, a single-layer electrode can also be used, that is, a single-layer metal, or an electrode layer formed by the superposition combination of different metals.

[0078] In order to obtain a larger electromechanical coupling coefficient in this embodiment, the materials of the first electrode layer 341 and the second electrode layer 343 are shown in Table 2:

[0079] Table 2

[0080] Electrode material Chemical formula Ruthenium Ru Molybdenum Mo Platinum Pt Tungsten W Aluminum Al Gold Au Silver Ag Copper Cu

[0081] In this embodiment, the Bragg reflector layer 320 can reflect the acoustic wave back into the piezoelectric transducer structure layer 340, so as to concentrate the acoustic wave energy in the piezoelectric layer 342. The Bragg reflector layer 320 includes a high sound velocity layer 321, a low sound velocity layer 322 and a preset film layer 323. As Figure 2 shown, the high sound velocity layer 321 and the low sound velocity layer 322 are alternately stacked in three layers, and the preset film layer 323 is closer to the piezoelectric transducer structure layer 340. That is to say, the preset film layer 323 is closer to the second electrode layer 343. In addition, the high sound velocity layer 321 far from the preset film layer 323 is close to the substrate layer 310. It should be noted that the film layer where the plurality of support portions 324 are located is the preset film layer 323.

[0082] In this embodiment, the preset film layer 323 includes a first surface close to the piezoelectric transducer structure layer 340, and the cavity portion 325 at least penetrates the first surface, so that the cavity portion 325 can concentrate the acoustic wave energy on the piezoelectric transducer structure layer 340 through the first surface, which helps to improve the acoustic wave energy confinement effect of the cavity portion 325.

[0083] The preset film layer 323 further includes a second surface facing away from the piezoelectric transducer structure layer 340, and the cavity portion 325 also penetrates the second surface, which is convenient for concentrating the acoustic wave energy on the cavity portion 325 through the second surface, and helps to improve the acoustic wave energy concentration effect of the cavity portion 325.

[0084] In this embodiment, the material of the support portion 324 in the preset film layer 323 may include at least one of SiO2, SiOC, Si3N4, AlN, Pt, Mo, W, and HfO2, or other materials. By using the above materials for the support portion 324, on the one hand, the acoustic wave energy is concentrated on the piezoelectric layer 342 through the cavity portion 325 between the multiple support portions 324, which helps to improve the electromechanical coupling coefficient of the bulk acoustic wave resonator 300. By adjusting the arrangement quantity and arrangement gap of the support portion 324 and the cavity portion 325, the main vibration mode of the bulk acoustic wave resonator 300 can be regulated, making the slowness curve of the main vibration mode flatten, suppressing the transverse mode of the bulk acoustic wave resonator 300, and thus the spurious response of the bulk acoustic wave resonator 300 is suppressed, thereby improving the quality factor Q of the bulk acoustic wave resonator 300. On the other hand, the piezoelectric layer 342 is supported by the support portion 324, enhancing the stability of the piezoelectric layer 342.

[0085] It should be noted that the high acoustic velocity layer 321 is the high acoustic impedance layer, usually made of a material with a high dielectric constant, and the low acoustic velocity layer 322 is the low acoustic impedance layer, usually made of a material with a low dielectric constant. The high acoustic velocity layer 321 and the low acoustic velocity layer 322 are overlapped to improve the performance of the device.

[0086] This embodiment provides a material matching table for the high acoustic impedance layer and the low acoustic impedance layer, as shown in Table 3:

[0087] Table 3

[0088] High acoustic impedance layer / Low acoustic impedance layer <![CDATA[SiO2 / W]]> SiOC / Pt <![CDATA[SiO2 / Mo]]> <![CDATA[SiO2 / Pt]]> <![CDATA[SiO2 / TiN]]> <![CDATA[SiO2 / AlN]]> <![CDATA[SiO2 / Ta2O5]]> <![CDATA[SiO2 / HfO2]]> <![CDATA[Si3N4 / W]]> <![CDATA[Si3N4 / Mo]]>

[0089] In addition, both the high acoustic impedance layer and the low acoustic impedance layer can be used to control the resonance frequency and amplitude of the device to meet different application requirements.

[0090] For ease of description, it is defined that Figure 2 the length direction of the partial bulk acoustic wave resonator 300 intercepted is the X-axis, the width direction of the bulk acoustic wave resonator 300 is the Y-axis, and the thickness direction of the bulk acoustic wave resonator 300 is the Z-axis. It can be understood that the coordinate system setting of the bulk acoustic wave resonator 300 can be flexibly set according to specific actual needs.

[0091] Referring to Figure 2 , Figure 2 is the three-dimensional structure diagram of the bulk acoustic wave resonator 300 provided by the embodiment of the present application. In the cross-section of the Bragg reflection layer 320 in the Z direction, the cross-section of the preset film layer 323 close to the piezoelectric transducer structure layer 340 includes multiple alternately arranged cavity portions 325 and support portions 324, which are composed of Figure 2It can be known that the XY plane is parallel to the plane where the substrate layer 310 is located. The multiple support portions 324 and the multiple cavity portions 325 are alternately arranged at intervals along the first direction and also alternately arranged at intervals along the second direction. The first direction and the second direction intersect, but both the first direction and the second direction are parallel to the substrate layer 310. In this embodiment, the first direction and the second direction can be perpendicular to each other, so that the multiple support portions 324 and the cavity portions 325 are arranged in a determinant pattern in the first direction and the second direction. It should be noted that the first direction can be Figure 2 the X direction in Figure 2 and the second direction can be

[0092] It should be noted that since the electrode part of the resonator not only includes the electrode structure in which the first electrode layer 341 and the second electrode layer 343 surround the piezoelectric layer 342, but also includes the interdigital electrode structure, therefore:

[0093] For the bulk acoustic wave resonator 300 with the structure that the first electrode layer 341 and the second electrode layer 343 surround the piezoelectric layer 342, on the one hand, using the electrode materials in Table 2 as the materials of the first electrode layer 341 and the second electrode layer 343 has the characteristic of large acoustic impedance, which is convenient for obtaining a large electromechanical coupling coefficient. On the other hand, due to the wrapping of the piezoelectric layer 342 by the first electrode layer 341 and the second electrode layer 343, the first electrode layer 341, the piezoelectric layer 342 and the second electrode layer 343 are stacked in the Z direction. Furthermore, the bulk acoustic wave resonator 300 in this embodiment propagates acoustic waves in the Z direction, and both the first direction and the second direction are parallel to the substrate layer 310. Therefore, when etching the Bragg reflector layer 320 along the first direction and the second direction, there is no need to consider the relationship between the first direction, the second direction and the acoustic wave propagation direction, that is, there is no need to consider the direction corresponding to the first direction and the first electrode layer 341 and the second electrode layer 343, and the direction corresponding to the second direction and the first electrode and the second electrode layer 343. Therefore, for the bulk acoustic wave resonator 300 with the structure that the first electrode layer 341 and the second electrode layer 343 surround the piezoelectric layer 342, an etching process for etching the Bragg reflector layer 320 along the first direction and the second direction can be used, and the first direction and the second direction can be any direction. Therefore, the Bragg reflector layer 320 can be etched along any two different directions, making the etching process of the bulk acoustic wave resonator 300 in this embodiment simple. It can be seen from this that the bulk acoustic wave resonator 300 in this embodiment has no requirement for the etching direction of the Bragg reflector layer 320, so that at least one film layer of the Bragg reflector layer 320 of the bulk acoustic wave resonator 300 close to the piezoelectric layer 342 can be etched in any two different directions to form the cavity portion 325 and the support portion 324.

[0094] For a resonator with an interdigital electrode structure, the Bragg reflector layer 320 cannot be etched in any arbitrary direction or any two different directions. This is because, in terms of the resonance mechanism, compared with the structure where the interdigital electrodes surround the piezoelectric layer 342 with the first electrode layer 341 and the second electrode layer 343, the acoustic wave propagation direction of the interdigital electrodes is transverse, that is, it propagates along the X direction or the Y direction. At this time, it is necessary to consider the relative position relationship between the cavity portion 325 etched on the Bragg reflector layer 320 under the interdigital electrode structure and the electrodes. Therefore, there are the following requirements for etching the Bragg reflector layer 320 under the interdigital electrode structure: It is necessary to etch to form the cavity portion 325 along the direction corresponding to the interdigital electrode direction. The cavity portion 325 needs to be aligned with the edge of the interdigital electrode, and there cannot be a situation where the cavity portion 325 and the support portion 324 exist simultaneously in the area corresponding to the interdigital electrode. From this, it can be seen that etching the Bragg reflector layer 320 under the interdigital electrode structure requires detailed settings based on data such as the electrode direction, electrode position, and physical volume size of the interdigital electrode. This makes the etching process accuracy requirement for the interdigital electrode relatively high. The etching of the Bragg reflector layer 320 of the interdigital electrode is easily restricted, and it is difficult to adopt the scheme of etching the Bragg reflector layer 320 in any two different directions in the bulk acoustic wave resonator 300 of this embodiment. Therefore, the way of alternately arranging the cavity portion 325 and the support portion 324 along the first direction, and the way of alternately arranging the cavity portion 325 and the support portion 324 along the second direction are only applicable to the resonator structure where the first electrode layer 341 and the second electrode layer 343 surround the piezoelectric layer 342.

[0095] However, in the cross-section of the Bragg reflector layer 320 parallel to the XY plane, the cross-section of the preset film layer 323 close to the piezoelectric transducer structure layer 340 may include two cases: a plurality of support portions 324 are arranged at intervals, and the cavity portions 325 adjacent to each support portion 324 communicate with each other; a plurality of cavity portions 325 are arranged at intervals, and a plurality of support portions 324 are connected as a whole.

[0096] In the manufacturing process of the bulk acoustic wave resonator 300, in order to meet the above two situations, it is necessary to avoid the piezoelectric transducer structure layer 340 collapsing into the cavity portion 325. Therefore, after the preset film layer 323 of the Bragg reflector layer 320 is etched to form the cavity portion 325 and the support portion 324, the cavity portion 325 is first filled with a sacrificial material (phosphate glass), and then the first electrode layer 341, the piezoelectric layer 342, and the second electrode layer 343 are fabricated on the support portion 324 and the filled cavity portion 325. Finally, the sacrificial material is released by wet etching. However, for the case where multiple support portions 324 are arranged at intervals and the cavity portions 325 adjacent to each support portion 324 communicate with each other, an opening is provided for the side of the preset film layer 323 to communicate with the cavity portion 325, through which the sacrificial material can be released. For the case where multiple cavity portions 325 are arranged at intervals and multiple support portions 324 are connected as a whole, an opening needs to be reserved in the non-electrode region of the piezoelectric layer 342, a release groove communicating with at least one cavity portion 325 is formed on the preset film layer 323, and a communication channel is provided between adjacent cavity portions 325. The opening penetrates through the piezoelectric layer 342 to communicate with the release groove, so that after the first electrode layer 341, the piezoelectric layer 342, and the second electrode layer 343 are fabricated, the sacrificial material can be guided through the communication channel between the cavity portions 325 to the cavity portion 325 connected to the release groove by wet etching, and the released sacrificial material can be discharged out of the bulk acoustic wave resonator 300 through the opening, thereby forming multiple cavity portions 325 and support portions 324 on the side of the first electrode layer 341 facing away from the piezoelectric layer 342.

[0097] The following further explains with reference to the embodiments of the above two situations.

[0098] Embodiment 1:

[0099] In the cross-section of the Bragg reflector layer 320 parallel to the XY plane, the cross-section of the preset film layer 323 of the Bragg reflector layer 320 close to the piezoelectric layer 342 includes: when multiple support portions 324 are arranged at intervals and the cavity portions 325 adjacent to each support portion 324 communicate with each other, refer to Figure 2 and Figure 3 , Figure 2 is a three-dimensional structure diagram of the bulk acoustic wave resonator 300 provided by the embodiment of the present application, Figure 3 is a schematic diagram of the block structure of the support portion 324 on the film layer of the Bragg reflector layer 320 close to the piezoelectric layer 342 in this embodiment. It can be seen that the number of support portions 324 is multiple, and the shape of each support portion 324 among the multiple support portions 324 includes a columnar body. The number of cavity portions 325 is one, and the cavity portions 325 adjacent to each support portion 324 communicate with each other, so as to adjust the range of the etched cavity portion 325, and further facilitate changing the shape and size of the support portion 324.

[0100] In this embodiment, it can be known that the XY plane is parallel to the plane where the substrate layer 310 is located. While the multiple support portions 324 are alternately arranged in a whole cavity portion 325 along the first direction, they are also alternately arranged along the second direction. Moreover, the support portion 324 is in the shape of a cuboid, so as to increase the distribution range of the support portion 324 on one side of the piezoelectric layer 342 in the arrangement mode of a determinant, and improve the support performance of the support portion 324 for the piezoelectric layer 342.

[0101] Refer to Figure 2 and Figure 4 , Figure 2 FIG. Figure 4 is a three-dimensional structure diagram of the bulk acoustic wave resonator 300 provided by the embodiment of the present application.

[0102] It should be noted that the duty ratio range of the projected area of the support portion 324 on the piezoelectric layer 342 is 1%-99%. The duty ratio includes the cross-sectional area of the support portion 324 along the direction parallel to the substrate layer 310 within one array period / the total area of the support portion 324 and the cavity portion 325 within one array period. Here, for one array period, according to actual needs, for example Figure 4 as shown, 4 rows and 5 columns are selected as one array period. Within the array period of 4 rows and 5 columns, the duty ratio range of the support portion 324 is 1%-99%.

[0103] Refer to Figures 5 - 9 , Figures 5 - 9 is a schematic cross-sectional view of the support portion 324 provided by this embodiment with cross-sections of a triangle, a parallelogram, a hexagon, an ellipse, and a rhombus in the direction parallel to the substrate layer 310. In Figures 5 - 9 it, the dashed box schematically shows the alternate arrangement of the cavity portion 325 and the support portion 324 in the first direction. It can be known that in the direction parallel to the XY plane, the shape of the cross-section of the support portion 324 in the first direction or the second direction includes any one of a polygon, a star, a circle, and an ellipse. The polygon can include, for example, any one of a rectangle, a triangle, a parallelogram, a rhombus, and a hexagon. It can be understood that in the direction parallel to the substrate layer 310, the cross-sectional shape of each support portion 324 can be any one of a polygon, a star, a circle, and an ellipse, or the cross-section of the support portion 324 in the direction parallel to the substrate layer 310 adopts a combination of at least two of a polygon, a star, a circle, and an ellipse, so as to facilitate processing the support portion 324 into different shapes.

[0104] In this embodiment, refer toFigure 10 , Figure 10 It is a schematic cross-sectional view of the extending direction of the supporting part 324 provided in this embodiment forming an angle with the substrate layer 310. It can be known that in the direction parallel to the XY plane, the included angle range between the extending direction of the supporting part 324 and the reference line of the substrate layer 310 is 0°-60°, and the reference line of the substrate layer 310 is the normal line perpendicular to the substrate layer 310. When the included angle between the extending direction of the supporting part 324 and the reference line of the substrate layer 310 is 0 degree, the cavity parts 325 are evenly distributed in the direction perpendicular to the substrate layer 310, so as to evenly concentrate the acoustic wave energy on the piezoelectric layer 342. When the included angle between the extending direction of the supporting part 324 and the reference line of the substrate layer 310 is 60 degrees, the coverage rate of the supporting part 324 on one side of the piezoelectric layer 342 is increased, thereby shortening the processing time of the supporting part 324.

[0105] Exemplarily, refer to Figures 10 - 11 , Figure 10 It is a schematic cross-sectional view of the extending direction of the supporting part 324 provided in this embodiment forming an angle with the substrate layer 310. Figure 11 It is a schematic cross-sectional view of the cross-section of the supporting part 324 provided in this embodiment in the direction perpendicular to the substrate layer 310. It can be known that in the direction parallel to the XZ plane, the shape of the cross-section of the supporting part 324 in the direction perpendicular to the substrate layer 310 includes any one of a rectangle, a parallelogram and a trapezoid.

[0106] Exemplarily, refer to Figures 12 - 13 , Figure 12 It is a schematic cross-sectional view of the cross-section of the supporting part 324 provided in this embodiment in the direction perpendicular to the substrate layer 310 being rectangular. Figure 13 It is a schematic cross-sectional view of the cross-section of the supporting part 324 provided in this embodiment in the direction perpendicular to the substrate layer 310 being trapezoidal. In Figure 13 , among the multiple cross-sections of the supporting part 324 in the first direction or the second direction: the area of the cross-section far from the piezoelectric layer 342 is greater than or equal to the area of the cross-section close to the piezoelectric layer 342. It can be understood that each supporting part 324 has multiple cross-sections in the first direction or the second direction, that is, the multiple cross-sections of the supporting part 324 are distributed in the direction perpendicular to the substrate layer 310. That is to say, in the direction perpendicular to the substrate layer 310, the cross-sections of any two supporting parts 324 in the direction parallel to the substrate layer 310 all satisfy: the area of the cross-section far from the piezoelectric layer 342 is greater than or equal to the area of the cross-section close to the piezoelectric layer 342. Therefore, the supporting part 324 tapers along the direction away from the substrate layer 310.

[0107] Exemplarily, in each support portion 324: the area at the end far from the piezoelectric layer 342 is greater than or equal to the area at the end close to the piezoelectric layer 342. It can be understood that between the cross-section of the support portion 324 far from the piezoelectric layer 342 and the cross-section close to the piezoelectric layer 342, the cross-sectional area of the support portion 324 is not limited. Thus, it can be seen that the shape of the support portion 324 in the direction perpendicular to the substrate layer 310 is diverse.

[0108] Continue to refer to Figures 12 - 13 , Figure 12 FIG. Figure 13 is a schematic cross-sectional view of the support portion 324 provided in this embodiment having a rectangular cross-section in the direction perpendicular to the substrate layer 310.

[0109] Embodiment 2:

[0110] The difference between this embodiment and Embodiment 1 is that in the cross-section of the Bragg reflector layer 320 parallel to the XY plane, the cross-section of the preset film layer 323 of the Bragg reflector layer 320 close to the piezoelectric layer 342 includes: a plurality of cavity portions 325 arranged at intervals, and a plurality of support portions 324 are connected as a whole. Refer to Figure 14 , Figure 14 FIG.

[0111] is a schematic cross-sectional view of the cavity portion 325 provided in this embodiment being a circular columnar cavity. Thus, it can be seen that the number of cavity portions 325 is multiple, and the shape of each cavity portion 325 among the multiple cavity portions 325 includes a columnar type. The number of support portions 324 is one, and a plurality of support portions 324 are connected as a whole. It can be understood that the multiple cavity portions 325 are located within one support portion 324, so as to facilitate the preset film layer 323 formed by etching the support portion 324 to change the shape of the cavity portion 325.

[0112] In this embodiment, refer to Figures 14 - 17 , Figures 14 - 17Schematic cross-sectional views of the cavity portions 325 provided in this embodiment are respectively circular, triangular, rectangular, and pentagonal. In Figures 14 - 17 the dashed boxes schematically show the alternating arrangement of the cavity portions 325 and the support portions 324 in the first direction. It can be known that in the direction parallel to the XY plane, the shape of the cross-sectional area of the cavity portion 325 in the direction parallel to the substrate layer 310 includes any one of polygons, stars, circles, and ellipses. Among them, the polygons include rectangles, triangles, and pentagons. It can be understood that in the direction parallel to the substrate layer 310, the cross-sectional shape of each cavity portion 325 can be any one of polygons, stars, circles, and ellipses, or the cavity portion 325 can adopt at least two combinations of polygons, stars, circles, and ellipses, so as to facilitate processing the cavity portion 325 into cavities of different shapes.

[0113] In this embodiment, referring to Figure 10 , Figure 10 Schematic cross-sectional views of the support portion 324 and the cavity portion 325 provided in this embodiment with an included angle between the extending direction and the substrate layer 310. It can be known that in the direction parallel to the XY plane, the included angle range between the extending direction of the cavity portion 325 and the reference line of the substrate layer 310 is 0° - 60°, and the reference line of the substrate layer 310 is the normal line perpendicular to the substrate layer 310. When the included angle between the extending direction of the cavity portion 325 and the reference line of the substrate layer 310 is 0 degree, the cavity portions 325 are evenly distributed in the direction perpendicular to the substrate layer 310, so as to evenly concentrate the acoustic wave energy on the piezoelectric layer 342. When the included angle between the extending direction of the cavity portion 325 and the reference line of the substrate layer 310 is 60 degrees, the coverage rate of the cavity portion 325 on one side of the piezoelectric layer 342 is increased, thereby shortening the processing time of the cavity portion 325.

[0114] Exemplarily, referring to Figures 10 - 11 , Figure 10 Schematic cross-sectional views of the support portion 324 and the cavity portion 325 provided in this embodiment with an included angle between the extending direction and the substrate layer 310. Figure 11 Schematic cross-sectional views of the support 324 and the cavity portion 325 in the direction perpendicular to the substrate layer 310 provided in this embodiment. It can be known that in the direction parallel to the XZ plane, the shape of the cross-section of the cavity portion 325 in the direction perpendicular to the substrate layer 310 includes any one of rectangles, parallelograms, and trapezoids.

[0115] Exemplarily, referring to Figure 12 and Figure 13 , Figure 12 Schematic cross-sectional views of the support portion 324 and the cavity portion 325 in the direction perpendicular to the substrate layer 310 provided in this embodiment with a rectangular cross-sectional shape. Figure 13The cross-sectional shape of the support portion 324 and the cavity portion 325 provided in this embodiment in the direction perpendicular to the substrate layer 310 is a schematic cross-sectional view of a trapezoid. In Figure 13 Among them, in multiple cross-sections of the cavity portion 325 in the first direction or the second direction: the area of the cross-section far from the piezoelectric layer 342 is less than or equal to the area of the cross-section close to the piezoelectric layer 342. It can be understood that each cavity portion 325 has multiple cross-sections in the first direction or the second direction, that is, the multiple cross-sections of the cavity portion 325 are distributed in the direction perpendicular to the substrate layer 310. That is to say, in the direction perpendicular to the substrate layer 310, the cross-sections of any two cavity portions 325 in the direction parallel to the substrate layer 310 all satisfy: the area of the cross-section far from the piezoelectric layer 342 is less than or equal to the area of the cross-section close to the piezoelectric layer 342. Therefore, the cavity portion 325 gradually expands along the direction away from the substrate layer 310.

[0116] Exemplarily, in each cavity portion 325: the area of the end far from the piezoelectric layer 342 is less than or equal to the area of the end close to the piezoelectric layer 342. It can be understood that between the cross-section of the cavity portion 325 far from the piezoelectric layer 342 and the cross-section close to the piezoelectric layer 342, the cross-sectional area of the cavity portion 325 can be not limited. From this, it can be known that the shape of the cavity portion 325 in the direction perpendicular to the substrate layer 310 is diverse.

[0117] Continue to refer to Figures 12 - 13 , Figure 12 The cross-sectional shape of the support portion 324 and the cavity portion 325 provided in this embodiment in the direction perpendicular to the substrate layer 310 is a schematic cross-sectional view of a rectangle, Figure 13 The cross-sectional shape of the support portion 324 and the cavity portion 325 provided in this embodiment in the direction perpendicular to the substrate layer 310 is a schematic cross-sectional view of a trapezoid. It can be known that in the direction parallel to the XZ plane, when the cross-sectional shape of the cavity portion 325 in the direction perpendicular to the substrate layer 310 is a parallelogram or a trapezoid, the included angle between the hypotenuse of the cavity portion 325 and the median line is less than 60 degrees, reducing the inclination angle of the side wall of the cavity portion 325, thereby reducing the processing difficulty of the cavity portion 325.

[0118] In summary, the embodiment of the present application uses multiple spaced cavity portions 325 and an entire support portion 324 as the preset film layer 323 close to the piezoelectric layer 342 in the Bragg reflector 320, replacing the air layer in the free boundary type resonator and the low acoustic impedance layer of the Bragg reflector 320 in the solid assembly type resonator structure, and solving the disadvantages and deficiencies of the structure of the solid assembly type resonator described above, such as the decrease in the electromechanical coupling coefficient and the suppression of the transverse mode.

[0119] Therefore, this embodiment also provides a curve graph to show the design effect of the bulk acoustic wave resonator 300. Refer to Figure 18, Figure 18 The graph shows the relationship between the film thickness of the cavity portion 325 and the support portion 324 of the Bragg reflector 320 provided in this embodiment and the electromechanical coupling coefficient. The abscissa in the graph is the film thickness of the cavity portion 325 in the Bragg reflector 320, and the ordinate is the electromechanical coupling coefficient. Figure 18 The curves in Figure 18 show different ratios of the film thickness of the cavity portion 325 and the support portion 324 to the thickness of the piezoelectric layer 342. It can be seen from

[0120] that when the ratio of the film thickness of the cavity portion 325 and the support portion 324 to the thickness of the piezoelectric layer 342 is 0.3, the electromechanical coupling coefficient is relatively high. It can be understood that in the embodiments of the present application, the effective electromechanical coupling coefficient of the bulk acoustic wave resonator 300 can be adjusted by adjusting parameters such as the number and size of the cavity portion 325 or the support portion 324.

[0121] Referring to Figure 19 , Figure 19 The graph shows the relationship between the number of layers of the Bragg reflector 320 provided in this embodiment and the quality factor Q. Figure 19 In Figure 19 , the abscissa is the frequency, and the ordinate is the quality factor Q. It can be understood that at different frequencies, corresponding to different numbers of layers of the Bragg reflector 320, there are different quality factors Q. It can be seen from

[0122] that when the Bragg reflector 320 has four layers, the quality factor Q exceeds that of the solidly mounted resonator. It can be understood that compared with the solidly mounted resonator, the addition of the cavity portion 325 and the support portion 324 of this embodiment with the same number of layers of the Bragg reflector 320 has a more obvious effect on improving the quality factor Q of the bulk acoustic wave resonator 300.

[0123] Referring to Figure 20 , Figure 20 The graph shows the slowness of the bulk acoustic wave resonator 300 provided in this embodiment in the X-Z direction. Figure 20The solid line in the figure is the slowness curve of the bulk acoustic wave resonator 300 with the cavity portion 325 and the support portion 324 added, and the dashed line is the slowness curve of the solid assembly type resonator. It can be understood that in the embodiment of the present application, due to the addition of the cavity portion 325 and the support portion 324 to the Bragg reflection layer 320, the slowness curve of the bulk acoustic wave resonator 300 becomes smoother.

[0124] In this way, by adjusting the number and size of the cavity portion 325 or the support portion 324, the slowness curve of the main vibration mode of the resonator can be regulated. When the slowness curve of the main vibration mode becomes flat, the transverse mode can be suppressed. As Figures 21 - 22 shown, Figure 21 The admittance curve diagram of the bulk acoustic wave resonator 300 provided in this embodiment without the cavity portion 325 and the support portion 324 is Figure 22 The admittance curve diagram of the bulk acoustic wave resonator 300 provided in this embodiment with the cavity portion 325 and the support portion 324 is Figure 21 、 Figure 22 In both of them, the abscissa is frequency, and the ordinate is the amplitude value of Y11 and the real part of Y11. The solid line in the figure is the admittance Y11, and the dashed line is the real part of the admittance Y11.

[0125] In Figure 21 , since the cavity portion 325 and the support portion 324 are not used as the film layers in the Bragg reflection layer 320, when the amplitude value is about to reach the peak, the transverse mode oscillates and jitters, and at this time, there is a spurious response, and the quality factor Q is affected.

[0126] In Figure 22 , since the cavity portion 325 and the support portion 324 are used as the film layers in the Bragg reflection layer 320, when the amplitude value is about to reach the peak, the transverse mode is suppressed, and there is no oscillation and jitter in this frequency band. At this time, the spurious response is suppressed, and the influence on the quality factor Q is small.

[0127] The embodiment of the present application also provides a preparation method for the bulk acoustic wave resonator 300. Refer to Figure 23 , Figure 23 is the flowchart of the preparation method for the bulk acoustic wave resonator 300 provided in this embodiment. This preparation method includes S1 to S3.

[0128] S1. Form a Bragg reflection layer 320 on one side of the substrate layer 310. The Bragg reflection layer 320 includes a plurality of film layers stacked, and the refractive indices of two adjacent film layers are different.

[0129] S2. Form a piezoelectric transducer structure layer 340 on the side of the Bragg reflection layer 320 facing away from the substrate layer 310. The piezoelectric transducer structure layer 340 includes a piezoelectric layer 342 and an electrode layer stacked.

[0130] S3. Process at least one film layer in the Bragg reflection layer 320 close to the piezoelectric transducer structure layer 340 into a preset film layer 323. The preset film layer 323 includes a cavity portion 325 and a support portion 324. The cavity portion 325 and the support portion 324 are alternately arranged along a first direction, and the first direction is parallel to the substrate layer 310.

[0131] From the above S1 to S3, it can be known that the piezoelectric layer 342 and the electrode layer can be supported by the support portion 324, and the acoustic wave energy can be reflected and concentrated to the piezoelectric layer 342 by the cavity portion 325, so as to improve the electromechanical coupling coefficient of the BAW resonator 300, and under the alternating arrangement of the cavity portion 325 and the support portion 324, the slowness curve of the main vibration mode of the BAW resonator 300 can also be regulated to make the slowness curve of the main vibration mode of the BAW resonator 300 flat, suppress the lateral mode of the BAW resonator 300, and then suppress the spurious response of the BAW resonator 300, so as to improve the quality factor of the BAW resonator 300.

[0132] Since the piezoelectric transducer structure layer 340 formed on the preset film layer 323 is prone to collapse into the cavity portion 325, see Figure 24 , Figure 24 The flowchart of the method for preparing the preset film layer 323 in the BAW resonator 300 provided in this embodiment, in S3, may include S31 as follows:

[0133] S31, processing at least one film layer in the Bragg reflection layer 320 close to the piezoelectric transducer structure layer 340 into a preset film layer 323, including: before forming the piezoelectric transducer structure layer 340 on the side of the Bragg reflection layer 320 away from the substrate layer 310, forming a cavity portion 325 in at least one film layer in the Bragg reflection layer 320 close to the piezoelectric transducer structure layer 340; filling a sacrificial material in the cavity portion 325; after forming the piezoelectric transducer structure layer 340 on the side of the Bragg reflection layer 320 away from the substrate layer 310, removing the sacrificial material.

[0134] In this embodiment, by filling the cavity portion 325 with a sacrificial material before forming the piezoelectric transducer structure layer 340, it is possible to avoid the piezoelectric transducer structure layer 340 from collapsing into the cavity portion 325 after it is formed. After the piezoelectric transducer structure layer 340 is finalized, the sacrificial material is removed by wet etching, so that a plurality of cavity portions 325 and support portions 324 are formed on one side of the piezoelectric transducer structure layer 340.

[0135] Considering that the multiple cavity portions 325 and the support portions 324 formed by etching have two situations: the multiple support portions 324 are arranged at intervals, and the cavity portions 325 adjacent to each support portion 324 are connected to each other; and the multiple cavity portions 325 are arranged at intervals, and the multiple support portions 324 are connected to form a whole. Figure 25 ,Figure 25 The flowchart of the method for removing the sacrificial material in the bulk acoustic wave resonator 300 provided in this embodiment. In S31, it may include S311 to S312 as follows:

[0136] S311. The preset film layer 323 includes a plurality of cavity portions 325 and support portions 324. When the plurality of support portions 324 are spaced apart and the cavity portions 325 adjacent to each support portion 324 communicate with each other, removing the sacrificial material includes: removing the sacrificial material through an opening in the side surface of the preset film layer 323 that communicates with the cavity portion 325.

[0137] S312. The preset film layer 323 includes a plurality of cavity portions 325 and support portions 324. When the plurality of cavity portions 325 are spaced apart and the plurality of support portions 324 are connected as a whole, the piezoelectric layer 342 includes an opening that communicates the cavity portion 325 with the side surface of the piezoelectric layer 342. Removing the sacrificial material includes: removing the sacrificial material through the opening in the piezoelectric layer 342.

[0138] It can be understood that when the number of support portions 324 is multiple and the cavity portions 325 adjacent to each support portion 324 communicate with each other, in order to prevent the formed piezoelectric transducer structure layer 340 from collapsing into the cavity portion 325, the cavity portion 325 is filled with sacrificial material in advance. Finally, when removing the sacrificial material, since the cavity portions 325 adjacent to each support portion 324 communicate with each other, the sacrificial material can be removed by wet etching through the opening in the side surface of the preset film layer 323 that communicates with the cavity portion 325.

[0139] When the number of cavity portions 325 is multiple and the plurality of support portions 324 are connected as a whole, in order to prevent the formed piezoelectric transducer structure layer 340 from collapsing into the cavity portion 325, the cavity portion 325 is filled with sacrificial material in advance. Finally, when removing the sacrificial material, since the plurality of support portions 324 are connected as a whole, the sacrificial material can be removed by wet etching through the opening in the piezoelectric layer 342 that communicates the cavity portion 325 with the side surface of the piezoelectric layer 342.

[0140] It can be understood that the film layer of the Bragg reflector layer 320 stacked close to the piezoelectric layer 342 is etched so that an alternating structure of support portions 324 and cavity portions 325 is formed between the remaining film layers of the Bragg reflector layer 320 and the piezoelectric layer 342. While realizing the support for the piezoelectric layer 342, the acoustic wave energy is concentrated on the piezoelectric layer 342 by using the cavity portion 325, thereby improving the electromechanical coupling coefficient of the bulk acoustic wave resonator 300.

[0141] As described above, it is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of changes or substitutions, which should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claimed rights.

Claims

1. A bulk acoustic wave resonator, characterized in that, Comprising: A substrate layer; A Bragg reflection layer disposed on the substrate layer, the Bragg reflection layer comprising a plurality of stacked film layers, and the refractive indices of two adjacent film layers being different; And A piezoelectric transducer structure layer disposed on the Bragg reflection layer, the piezoelectric transducer structure layer comprising a stacked piezoelectric layer and electrode layer; Wherein, at least one film layer of the Bragg reflection layer close to the piezoelectric transducer structure layer is a preset film layer, the preset film layer comprising a cavity portion and a support portion, the cavity portion and the support portion being alternately arranged in a first direction parallel to the substrate layer.

2. The bulk acoustic wave resonator according to claim 1, wherein The cavity portion and the support portion are alternately arranged in a second direction parallel to the substrate layer, the second direction intersecting the first direction.

3. The bulk acoustic wave resonator according to claim 1 or 2, characterized in that, The preset film layer comprises a first surface close to the piezoelectric transducer structure layer, and the cavity portion at least penetrates the first surface.

4. The bulk acoustic wave resonator according to any one of claims 1 to 3, characterized in that, The preset film layer comprises a second surface facing away from the piezoelectric transducer structure layer, and the cavity portion also penetrates the second surface.

5. The bulk acoustic wave resonator according to any one of claims 1-4, characterized in that, The preset film layer comprises a plurality of the support portions and a plurality of the cavity portions, the plurality of support portions being spaced apart, and the cavity portions adjacent to each support portion being interconnected.

6. The bulk acoustic wave resonator according to claim 5, wherein The support portion is arranged in at least one of the following manners: The shape of the cross-section of the support portion in a direction parallel to the substrate layer includes any one of a polygon, a star shape, a circle, and an ellipse; Among the plurality of cross-sections of the support portion in a direction parallel to the substrate layer, the area of the cross-section far from the piezoelectric layer is greater than or equal to the area of the cross-section close to the piezoelectric layer; In the support portion: the area of the end far from the piezoelectric layer is greater than or equal to the area of the end close to the piezoelectric layer; or The included angle range between the support portion and a reference line perpendicular to the substrate layer is 0° - 60°.

7. The bulk acoustic wave resonator according to any one of claims 1-4, characterized in that, The preset film layer comprises a plurality of the support portions and a plurality of the cavity portions, the plurality of cavity portions being spaced apart, and the plurality of support portions being connected as a whole.

8. The bulk acoustic wave resonator according to claim 7, wherein The cavity portion is arranged in at least one of the following manners: The shape of the cross-section of the cavity portion in a direction parallel to the substrate layer includes any one of a polygon, a star shape, a circle, and an ellipse; Among the plurality of cross-sections of the cavity portion in a direction parallel to the substrate layer, the area of the cross-section far from the piezoelectric layer is less than or equal to the area of the cross-section close to the piezoelectric layer; In the cavity portion: the area of the end far from the piezoelectric layer is less than or equal to the area of the end close to the piezoelectric layer; or The included angle range between the cavity portion and a reference line perpendicular to the substrate layer is 0° - 60°.

9. The bulk acoustic wave resonator according to any one of claims 1-8, characterized in that The material of the preset film layer comprises at least one of SiO2, SiOC, Si3N4, AlN, Pt, Mo, W, and HfO2.

10. The bulk acoustic wave resonator according to any one of claims 1-9, characterized in that, The electrode layer comprises: a first electrode layer and a second electrode layer, the piezoelectric layer being disposed between the first electrode layer and the second electrode layer, and the first electrode layer being closer to the Bragg reflection layer than the piezoelectric layer.

11. A method for preparing a bulk acoustic wave resonator, characterized in that, Comprising: A Bragg reflector is formed on one side of a substrate layer. The Bragg reflector includes a plurality of stacked film layers, and the refractive indices of two adjacent film layers are different; A piezoelectric transducer structure layer is formed on the side of the Bragg reflector facing away from the substrate layer. The piezoelectric transducer structure layer includes a stacked piezoelectric layer and electrode layer; At least one film layer of the Bragg reflector close to the piezoelectric transducer structure layer is processed into a preset film layer. The preset film layer includes a cavity part and a support part, and the cavity part and the support part are alternately arranged in a first direction parallel to the substrate layer.

12. The method for manufacturing a bulk acoustic wave resonator according to claim 11, wherein The processing of at least one film layer of the Bragg reflector close to the piezoelectric transducer structure layer into a preset film layer includes: Before forming the piezoelectric transducer structure layer on the side of the Bragg reflector facing away from the substrate layer, a cavity part is formed in at least one film layer of the Bragg reflector close to the piezoelectric transducer structure layer; a sacrificial material is filled in the cavity part; After forming the piezoelectric transducer structure layer on the side of the Bragg reflector facing away from the substrate layer, the sacrificial material is removed.

13. The method for manufacturing a bulk acoustic wave resonator according to claim 12, wherein When the preset film layer includes a plurality of cavity parts and support parts, and the support parts are spaced apart and the cavity parts adjacent to each support part are interconnected, the removing of the sacrificial material includes: removing the sacrificial material through an opening in the side surface of the preset film layer communicating with the cavity part.

14. The method for preparing a bulk acoustic wave resonator according to claim 12, wherein When the preset film layer includes a plurality of cavity parts and support parts, and the cavity parts are spaced apart and the support parts are connected as a whole, the piezoelectric layer includes an opening hole communicating the cavity part with the side surface of the piezoelectric layer, the removing of the sacrificial material includes: removing the sacrificial material through the opening hole of the piezoelectric layer.

15. A filter, characterized in that, Comprising a plurality of cascaded resonators, at least one resonator of the plurality of cascaded resonators is a bulk acoustic wave resonator according to any one of claims 1-10.

16. An electronic device, characterized in that, Comprising a filter and a circuit board, the filter is disposed on the circuit board, and the filter is the filter according to claim 15.

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