Bulk acoustic wave resonator, preparation method and bulk acoustic wave filter

Abstract

The present invention provides a bulk acoustic wave resonator, a preparation method, and a bulk acoustic wave filter. The preparation method of the bulk acoustic wave resonator includes: providing a substrate; forming a bottom electrode and a piezoelectric layer on the substrate; forming a sacrificial layer at the edge of the surface of the piezoelectric layer away from the bottom electrode, wherein the sacrificial layer includes at least one of an air bridge structure sacrificial layer and a cantilever structure sacrificial layer; forming an uneven surface on at least part of the surface of the sacrificial layer away from the piezoelectric layer through a surface treatment process to form a first rough surface; forming a top electrode on the surface of the sacrificial layer away from the piezoelectric layer; and releasing the sacrificial layer. The technical solution provided by the embodiment of the present invention effectively consumes the shear waves and clutter entering the air bridge structure or the cantilever structure by providing a rough scattering surface on the air bridge structure or the cantilever structure, thereby improving the Q value of the bulk acoustic wave resonator.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a bulk acoustic wave resonator, a preparation method and a bulk acoustic wave filter. Background Art

[0002] A bulk acoustic wave resonator (BAW) comprises a stacked structure consisting of a bottom electrode, a piezoelectric layer, and a top electrode. The edge of the top electrode is provided with a microstructure, which is an air bridge structure or a cantilever structure that is separated from the piezoelectric layer and gradually suspended in the air. During the resonance process, some of the sound waves in the effective area of ​​the BAW resonator are conducted into the air bridge structure or cantilever structure in the form of transverse waves or noise waves, and are reflected back and forth in the air bridge structure or cantilever structure electrodes and even return to the effective area. The noise waves that return to the effective area will superimpose and interfere with other normal resonating waves, causing energy loss and reducing the Q value of the BAW resonator.

[0003] Existing techniques for creating air bridge or cantilever structures typically involve forming a sacrificial layer of a specific shape on the surface of the piezoelectric layer, depositing a top electrode, and then releasing the sacrificial layer. The smooth surface of the air bridge or cantilever structure produced by this method facilitates the reflection of shear waves or clutter from the air bridge structure, even returning to the active area.

[0004] Therefore, it is necessary to prepare a bulk acoustic wave resonator so that the shear waves or clutter waves can be scattered and consumed effectively in the air bridge structure or cantilever structure area as quickly as possible, thereby improving the Q value of the bulk acoustic wave resonator. Summary of the Invention

[0005] The present invention provides a bulk acoustic wave resonator, a preparation method, and a bulk acoustic wave filter, by providing a rough scattering surface on an air bridge structure or a cantilever structure to effectively consume shear waves and clutter entering the air bridge structure or the cantilever structure, thereby improving the Q value of the bulk acoustic wave resonator.

[0006] According to one aspect of the present invention, there is provided a method for preparing a bulk acoustic wave resonator, comprising:

[0007] providing a substrate;

[0008] forming a bottom electrode on the substrate;

[0009] forming a piezoelectric layer on a side of the bottom electrode facing away from the substrate;

[0010] forming a sacrificial layer at an edge of a surface of the piezoelectric layer facing away from the bottom electrode, wherein the sacrificial layer comprises at least one of an air bridge structure sacrificial layer and a cantilever structure sacrificial layer;

[0011] forming an uneven surface on at least a portion of the surface of the sacrificial layer facing away from the piezoelectric layer through a surface treatment process to form a first rough surface;

[0012] forming a top electrode on a surface of the sacrificial layer facing away from the piezoelectric layer;

[0013] The sacrificial layer is released to form at least one of an air bridge structure and a cantilever structure at the edge of the top electrode, wherein the air gap of the air bridge structure is the location of the sacrificial layer of the air bridge structure, and the air gap of the cantilever structure is the location of the sacrificial layer of the cantilever structure.

[0014] Optionally, after forming a top electrode on at least a portion of the surface of the sacrificial layer facing away from the piezoelectric layer, the method further comprises:

[0015] A second rough surface is formed by forming an uneven surface on at least a portion of the surface of the top electrode away from the sacrificial layer through a surface treatment process, wherein the orthographic projection of the second rough surface on the substrate is within the orthographic projection of the sacrificial layer on the substrate.

[0016] Optionally, after forming a top electrode on at least a portion of the surface of the sacrificial layer facing away from the piezoelectric layer, the method further comprises:

[0017] forming at least one of a concave structure and a convex structure at an edge of a surface of the top electrode facing away from the piezoelectric layer;

[0018] A surface treatment process is performed to form an uneven surface on at least a portion of the surface of at least one of the concave structure and the convex structure to form a third rough surface.

[0019] Optionally, before forming the sacrificial layer on the edge of the surface of the piezoelectric layer away from the bottom electrode, the method further includes:

[0020] A surface treatment process is performed to form an uneven surface on the edge of the surface of the piezoelectric layer facing away from the bottom electrode, so as to form a fourth rough surface.

[0021] Optionally, the surface treatment process includes at least one of an ion bombardment process, a Bosch process, and a photolithography and etching process.

[0022] Optionally, the sacrificial layer includes single crystal silicon, and forming an uneven surface on at least a portion of a surface of the sacrificial layer facing away from the piezoelectric layer through a surface treatment process to form the first rough surface includes:

[0023] At least a portion of the surface of the sacrificial layer away from the piezoelectric layer is corroded by a texturing liquid, so as to form an uneven surface on the surface of the sacrificial layer away from the piezoelectric layer, thereby forming a first rough surface.

[0024] Optionally, before performing the surface treatment process on the BAW resonator, the method further includes:

[0025] Forming uniformly distributed foreign particles on the surface to be subjected to the surface treatment process, wherein the hardness of the foreign particles is greater than the hardness of the film layer where the foreign particles are located;

[0026] After performing the surface treatment process on the surface to be subjected to the surface treatment process, the method further includes:

[0027] The foreign particles are removed.

[0028] Optionally, before forming the bottom electrode on the substrate, the method further includes:

[0029] An acoustic reflection structure is formed on the surface or inside of the substrate.

[0030] According to another aspect of the present invention, a bulk acoustic wave resonator is provided, which is manufactured using the method for manufacturing a bulk acoustic wave resonator as described in any one of the embodiments of the present invention.

[0031] According to another aspect of the present invention, a bulk acoustic wave filter is provided, comprising the bulk acoustic wave resonator according to any one of the embodiments of the present invention.

[0032] The technical solution provided in this embodiment is to form a sacrificial layer including at least one of an air bridge structure sacrificial layer and a cantilever structure sacrificial layer, and then form an uneven surface on at least a portion of the surface of the sacrificial layer away from the piezoelectric layer through a surface treatment process to form a first rough surface. Accordingly, an uneven surface, i.e., a rough reflective surface, is formed correspondingly at the position where at least one of the air bridge structure and the cantilever structure in the top electrode contacts the first rough surface of the sacrificial layer. The rough reflective surface can scatter the shear waves or clutter entering the air bridge structure or the cantilever structure, thereby effectively consuming the energy of the shear waves or clutter, and can prevent the shear waves or clutter from reflecting back and forth in the air bridge structure or the cantilever structure electrode or even returning to the effective area, thereby preventing the shear waves or clutter from interfering with the normal resonant waves of the bulk acoustic wave resonator after returning to the effective area, thereby reducing the energy loss of the normal resonant sound waves of the bulk acoustic wave resonator and improving the Q value of the bulk acoustic wave resonator.

[0033] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0035] Figure 1 is a schematic flow chart of a method for preparing a bulk acoustic wave resonator according to an embodiment of the present invention;

[0036] Figure 2-Figure 9 1 is a schematic structural diagram corresponding to each step of a method for preparing a bulk acoustic wave resonator provided by an embodiment of the present invention;

[0037] Figure 10 is a schematic flow chart of another method for preparing a bulk acoustic wave resonator according to an embodiment of the present invention;

[0038] Figure 11-12 2 is a schematic structural diagram corresponding to each step of another method for preparing a bulk acoustic wave resonator provided by an embodiment of the present invention;

[0039] Figure 13 is a schematic flow chart of another method for preparing a bulk acoustic wave resonator provided according to an embodiment of the present invention;

[0040] Figure 14-16 2 is a schematic structural diagram corresponding to each step of a method for preparing a bulk acoustic wave resonator provided by an embodiment of the present invention;

[0041] Figure 17 is a schematic flow chart of another method for preparing a bulk acoustic wave resonator provided according to an embodiment of the present invention;

[0042] Figures 18-25 1 is a structural schematic diagram corresponding to each step of another method for preparing a bulk acoustic wave resonator provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0043] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0044] It should be noted that the terms "first," "second," and the like 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 precedence. It should be understood that the numbers used in this manner are interchangeable where appropriate so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or devices is not necessarily limited to those steps or devices explicitly listed, but may include other steps or devices that are not explicitly listed or that are inherent to these processes, methods, products, or apparatuses.

[0045] In order to enable the air bridge structure or cantilever structure to effectively consume the transverse waves and clutter entering therein, thereby improving the Q value of the bulk acoustic wave resonator, the embodiment of the present invention provides the following technical solutions:

[0046] Figure 1 FIG is a flow chart of a method for preparing a bulk acoustic wave resonator according to an embodiment of the present invention. Figure 1 The preparation method of the bulk acoustic wave resonator comprises the following steps:

[0047] S110 , providing a substrate.

[0048] See also Figure 2 , providing a substrate 10. Exemplarily, the substrate 10 can be made of materials such as single crystal silicon, gallium arsenide, sapphire and quartz. In order to reduce the loss of the substrate 10 for acoustic waves, an acoustic reflection structure can also be formed on the surface or inside the substrate 10 before forming the bottom electrode. Exemplarily, in this embodiment, the acoustic reflection structure is a cavity structure 10a. In S110, the cavity structure 10a is filled with a material containing silicon oxide, such as phosphosilicate glass (PSG) as a sacrificial layer. In subsequent steps, the sacrificial layer is corroded by an etching solution to remove the filling material in the cavity structure 10a. It should be noted that, in other embodiments, the acoustic reflection structure can also include a Bragg reflection layer formed by alternating stacking of high and low acoustic impedance layers, a groove on the back of the substrate 10, or a cavity structure surrounded by the substrate 10, the bottom electrode, and a support structure located between the substrate 10 and the bottom electrode.

[0049] S120 , forming a bottom electrode on the substrate.

[0050] See also Figure 3, a thin film electrode can be first deposited on the substrate 10, and then a bottom electrode 20 of a preset pattern can be formed by etching the pattern. Alternatively, a thin film electrode can be first deposited on the substrate 10, and then a bottom electrode 20 of a preset pattern can be formed by a lift-off method. Specifically, the lift-off method for forming the bottom electrode 20 of a preset pattern includes: first photolithography a specific area corresponding to the pattern of the bottom electrode 20, then depositing the thin film electrode on the entire surface, and then stripping off the photoresist and the thin film electrode thereon, leaving the thin film electrode in the specific area as the bottom electrode 20. Exemplarily, the bottom electrode 20 can be selected from at least one of molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper and titanium with good conductivity.

[0051] S130 , forming a piezoelectric layer on a side of the bottom electrode facing away from the substrate.

[0052] See also Figure 4 A thin film of a piezoelectric layer 30 is grown on the side of the bottom electrode 20 facing away from the substrate 10, and then a patterning process is performed to form the piezoelectric layer 30, wherein the piezoelectric layer 30 partially covers the bottom electrode 20. For example, the piezoelectric layer 30 can be made of at least one of a single crystal piezoelectric thin film material such as aluminum nitride, zinc oxide, lead zirconate titanate piezoelectric ceramic, lithium niobate, lithium tantalate, potassium niobate, or a polycrystalline piezoelectric thin film material. A certain proportion of rare earth elements can also be doped into the piezoelectric layer 30 to improve the performance of the piezoelectric material layer.

[0053] S140 , forming a sacrificial layer at an edge of a surface of the piezoelectric layer facing away from the bottom electrode, wherein the sacrificial layer includes at least one of an air bridge structure sacrificial layer and a cantilever structure sacrificial layer.

[0054] See also Figure 5 A sacrificial layer 40 is formed on the side of the piezoelectric layer 30 facing away from the bottom electrode 20. A sacrificial layer 40 including an air bridge structure sacrificial layer 41 and a cantilever structure sacrificial layer 42 is then formed on the edge of the surface of the piezoelectric layer 30 facing away from the bottom electrode 20 through a patterning process. For example, the sacrificial layer 40 includes any one of undoped silicon dioxide, phosphosilicate glass (PSG), borophosphosilicate glass (BPSG), and photoresist.

[0055] S150 , forming an uneven surface on at least a portion of the surface of the sacrificial layer facing away from the piezoelectric layer through a surface treatment process to form a first rough surface.

[0056] See also Figure 6, a surface treatment process is used to form an uneven surface on the portion of the surface of the sacrificial layer 40 facing away from the piezoelectric layer 30, thereby forming a first rough surface A1. It should be noted that in other embodiments, an uneven surface can also be formed on the entire surface of the sacrificial layer 40 facing away from the piezoelectric layer 30 through a surface treatment process. The specific position of the first rough surface A1 on the surface of the sacrificial layer 40 facing away from the piezoelectric layer 30 is not specifically limited in the embodiment of the present invention. In this embodiment, the uneven surface obtained through the surface treatment process is composed of repeated arc-shaped undulations.

[0057] S160 , forming a top electrode on a side of the sacrificial layer facing away from the piezoelectric layer.

[0058] See also Figure 7 , a thin film electrode can be first deposited on the surface of the sacrificial layer 40 away from the piezoelectric layer 30, and then a top electrode 50 of a preset pattern can be formed by etching a pattern. Alternatively, a thin film electrode can be first deposited on the surface of the sacrificial layer 40 away from the piezoelectric layer 30, and then a top electrode 50 of a preset pattern can be formed by a lift-off method. Specifically, the lift-off method for forming the top electrode 50 of a preset pattern includes: first photolithography a specific area corresponding to the top electrode 50, then depositing a thin film electrode on the entire surface, and then stripping off the photoresist and the thin film electrode thereon, leaving the thin film electrode in the specific area as the top electrode 50. Exemplarily, the thin film electrode forming the top electrode 50 includes a stack of at least two metal films. The bulk acoustic wave resonator includes a stacked structure of a bottom electrode 20, a piezoelectric layer 30 and a top electrode 50. Exemplarily, the top electrode 50 can be selected from at least one of molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper and titanium with good conductivity.

[0059] S170. Release the sacrificial layer to form at least one of an air bridge structure and a cantilever structure at the edge of the top electrode, wherein the air gap of the air bridge structure is the location of the sacrificial layer of the air bridge structure, and the air gap of the cantilever structure is the location of the sacrificial layer of the cantilever structure.

[0060] See also Figure 8The sacrificial layer 40 is released by wet etching to form an air bridge structure 51 and a cantilever structure 52 at the edge of the top electrode 50, wherein the air gap between the air bridge structure 51 and the piezoelectric layer 30 is the location of the sacrificial layer 41 of the air bridge structure, and the air gap between the cantilever structure 52 and the piezoelectric layer 30 is the location of the sacrificial layer 42 of the cantilever structure. Since the portion of the surface of the sacrificial layer 40 facing away from the piezoelectric layer 30 includes an uneven surface, namely the first rough surface A1, the positions where the air bridge structure 51 and the cantilever structure 52 contact the first rough surface A1 of the sacrificial layer 40 form an uneven surface, namely a rough reflective surface. The raised portion of the rough reflective surface corresponds to the recessed portion of the first rough surface A1 of the sacrificial layer 40. The recessed portion of the rough reflective surface corresponds to the raised portion of the first rough surface A1 of the sacrificial layer 40.

[0061] It should be pointed out that when S150 corresponds to Figure 6 When the first rough surface A1 continues to increase, it can be obtained after S170 Figure 9 The bulk acoustic wave resonator shown in FIG. Figure 9 The area of ​​the rough reflective surface of the air bridge structure 51 and the cantilever structure 52 is greater than Figure 8 The air bridge structure 51 and the cantilever structure 52 have rough reflective surface areas.

[0062] It should be noted that the most basic structure of a bulk acoustic wave resonator is a sandwich structure consisting of two electrodes sandwiching a piezoelectric layer 30. Under the action of the alternating electric field of the bottom electrode 22 and the top electrode 50, the piezoelectric layer 30 will deform, which manifests itself as the vibration of phonons on a microscopic level and forms sound waves vibrating in the piezoelectric layer 30 on a macroscopic level. The sound waves vibrate in the piezoelectric layer 30 to form standing waves, which are mainly longitudinal waves, but a small amount of transverse waves still exist. In longitudinal waves, the direction of particle movement is parallel to the direction of sound wave propagation, but each particle does not move in the direction of the sound wave, but only vibrates back and forth in its own equilibrium state. In transverse waves, the direction of particle movement and the direction of sound wave propagation are perpendicular to each other. The particles also do not move in the direction of sound wave propagation, but only vibrate up and down in their own equilibrium state. In existing bulk acoustic wave resonator structures, the surface of the air bridge structure or cantilever structure in the top electrode is relatively smooth, which is very conducive to the transverse waves or noise waves to be mirror-reflected back and forth in the area of ​​the air bridge structure or the cantilever structure, or even return to the effective area.

[0063] The technical solution provided in this embodiment, after forming a sacrificial layer including at least one of an air bridge structure sacrificial layer and a cantilever structure sacrificial layer, forms an uneven surface on at least a portion of the surface of the sacrificial layer facing away from the piezoelectric layer through a surface treatment process to form a first roughened surface. Accordingly, an uneven surface, i.e., a roughened reflective surface, is formed correspondingly at the location in the top electrode where at least one of the air bridge structure and the cantilever structure contacts the first roughened surface of the sacrificial layer. This roughened reflective surface can scatter shear waves or clutter entering the air bridge structure or cantilever structure, thereby effectively consuming the energy of the shear waves or clutter, preventing the shear waves or clutter from reflecting back and forth in the air bridge structure or cantilever structure electrode or even returning to the effective area, thereby preventing the shear waves or clutter from interfering with the normal resonant waves of the BAW resonator after returning to the effective area, thereby reducing the energy loss of the normal resonant sound waves of the BAW resonator and improving the Q value of the BAW resonator. It should be noted that in this embodiment, the effective area of ​​the BAW resonator can be understood as the area where the bottom electrode, piezoelectric layer, top electrode, and acoustic reflective structure overlap in the vertical direction.

[0064] Optionally, based on the above technical solution, in S150, the surface treatment process includes at least one of an ion bombardment process, a Bosch process, and a photolithography and etching process.

[0065] For details, see Figure 6 , an uneven surface is formed on the surface of the sacrificial layer 40 away from the piezoelectric layer 30 by at least one of an ion bombardment process, a Bosch process, and a photolithography and etching process to form a first rough surface A1. Among them, the ion bombardment process uses high-energy ions to bombard the surface of the membrane layer. A nanometer-scale uneven surface is formed on the surface of the sacrificial layer 40 away from the piezoelectric layer 30 by a photolithography and etching process to form a first rough surface A1. The Bosch process can effectively prevent or weaken lateral etching. Optionally, the same membrane layer can be simultaneously subjected to surface treatment using at least two of the ion bombardment process, the Bosch process, and the photolithography and etching process. For example, for Figure 6 The sacrificial layer 40 in the embodiment can be processed by ion bombardment process for the plane portion of the sacrificial layer 40 away from the surface of the piezoelectric layer 30, and then the side portion of the sacrificial layer 40 away from the surface of the piezoelectric layer 30 is processed by Bosch process, and finally the sacrificial layer 40 can be obtained. Figure 9 It should be noted that, in other embodiments, the top electrode 50 and the piezoelectric layer 30 may also be surface-treated by at least one of an ion bombardment process, a Bosch process, and a photolithography and etching process to form an uneven surface.

[0066] Optionally, based on the above technical solution, before performing the surface treatment process on the BAW resonator by at least one of an ion bombardment process, a Bosch process, and a photolithography and etching process, the process further includes:

[0067] Evenly distributed foreign particles are formed on the surface to be subjected to the surface treatment process, wherein the hardness of the foreign particles is greater than the hardness of the film layer where the foreign particles are located.

[0068] After performing the surface treatment process on the surface to be subjected to the surface treatment process, the method further includes removing foreign particles.

[0069] by Figure 6 For example, before an uneven surface is formed on a portion of the surface of the sacrificial layer 40 away from the piezoelectric layer 30 by at least one of an ion bombardment process, a Bosch process, and a photolithography and etching process to form a first rough surface A1, uniformly distributed foreign particles can be formed on a portion of the surface of the sacrificial layer 40 away from the piezoelectric layer 30, and the foreign particles can be removed after the surface treatment process.

[0070] Specifically, if the hardness of the foreign particles is greater than the hardness of the film layer in which the foreign particles are located, when the surface of the sacrificial layer 40 facing away from the piezoelectric layer 30 is processed by at least one of an ion bombardment process, a Bosch process, and a photolithography and etching process, the foreign particles can be etched to a depth less than the etched depth of the sacrificial layer 40 relative to the sacrificial layer 40, thereby further increasing the degree of unevenness of the first rough surface A1. Accordingly, the degree of unevenness of the rough reflective surface of the air bridge structure 51 and the cantilever structure 52 is also increased, which can enhance the scattering effect of shear waves or noise entering the air bridge structure or cantilever structure, thereby quickly and effectively consuming the energy of the shear waves or noise, further preventing the shear waves or noise from reflecting back and forth in the air bridge structure or cantilever structure electrode or even returning to the effective area, thereby further preventing the shear waves or noise from interfering with the normal resonant waves of the BAW resonator after returning to the effective area, thereby further reducing the energy loss of the normal resonant sound waves of the BAW resonator and improving the Q value of the BAW resonator.

[0071] In other embodiments, foreign particles may be formed before the sacrificial layer 40, the top electrode 50, and the piezoelectric layer 30 are subjected to a surface treatment process by at least one of an ion bombardment process, a Bosch process, and a photolithography and etching process, and the foreign particles may be removed after the surface treatment process. Specifically, if the hardness of the foreign particles is greater than the hardness of the film layer where the foreign particles are located, when the surface of the film layer where the foreign particles are located is treated by at least one of an ion bombardment process, a Bosch process, and a photolithography and etching process, the depth to which the foreign particles are etched relative to the film layer where the foreign particles are located is less than the depth to which the foreign particles are etched relative to the film layer where the foreign particles are located, thereby further increasing the degree of unevenness of the foreign particles relative to the surface of the film layer where the foreign particles are located. Correspondingly, the degree of unevenness of the rough reflective surface of the BAW resonator also increases, which can enhance the scattering effect on the shear waves or clutter entering the air bridge structure or cantilever structure, and thus can quickly and effectively consume the energy of the shear waves or clutter, and can further prevent the shear waves or clutter from reflecting back and forth in the air bridge structure or cantilever structure electrode or even returning to the effective area, thereby further preventing the shear waves or clutter from interfering with the normal resonant waves of the BAW resonator after returning to the effective area, thereby further reducing the energy loss of the normal resonant sound waves of the BAW resonator and further improving the Q value of the BAW resonator.

[0072] Optionally, based on the above technical solution, the sacrificial layer 40 includes single crystal silicon, and S150 forms an uneven surface on at least a portion of the surface of the sacrificial layer facing away from the piezoelectric layer through a surface treatment process to form the first rough surface, including:

[0073] See also Figure 6 The surface of the sacrificial layer 40 facing away from the piezoelectric layer 30 is corroded by a texturing liquid, so as to form an uneven surface on the surface of the sacrificial layer 40 facing away from the piezoelectric layer 30, thereby forming a first rough surface A1.

[0074] Specifically, in industrial production, a mixed solution of alkali and alcohol is used as a texturing solution to anisotropically etch single-crystal silicon with a (100) crystal orientation, forming a pyramid-like textured surface on the surface. This effectively creates an uneven surface on the portion of the sacrificial layer 40 facing away from the piezoelectric layer 30, thereby forming the first rough surface A1. The alkali solution in the texturing solution is, for example, a KOH solution or a NaOH solution.

[0075] Figure 10 FIG is a flow chart of another method for preparing a bulk acoustic wave resonator according to an embodiment of the present invention. Figure 10 The preparation method of the bulk acoustic wave resonator comprises the following steps:

[0076] S210 , providing a substrate.

[0077] S220 , forming a bottom electrode on the substrate.

[0078] S230 , forming a piezoelectric layer on a side of the bottom electrode facing away from the substrate.

[0079] S240 , forming a sacrificial layer at an edge of a surface of the piezoelectric layer facing away from the bottom electrode, wherein the sacrificial layer includes at least one of an air bridge structure sacrificial layer and a cantilever structure sacrificial layer.

[0080] S250 , forming an uneven surface on at least a portion of the surface of the sacrificial layer facing away from the piezoelectric layer through a surface treatment process to form a first rough surface.

[0081] S260 , forming a top electrode on a surface of the sacrificial layer facing away from the piezoelectric layer.

[0082] The preparation method and beneficial effects of S210-S260 can be performed with reference to the preparation method and beneficial effects of S110-S160.

[0083] S270, forming an uneven surface on at least a portion of the surface of the top electrode away from the sacrificial layer through a surface treatment process to form a second rough surface, wherein the orthographic projection of the second rough surface on the substrate is within the orthographic projection of the sacrificial layer on the substrate.

[0084] See also Figure 11 A second roughened surface A2 is formed by forming an uneven surface on a portion of the top electrode 50 facing away from the sacrificial layer 40 through at least one surface treatment process selected from the group consisting of an ion bombardment process, a Bosch process, a photolithography process, and an etching process. The second roughened surface A2 has an orthographic projection on the substrate 10 that is within the orthographic projection of the sacrificial layer 40 on the substrate 10. The specific area and position of the second roughened surface A2 are not specifically limited in this embodiment.

[0085] S280. Release the sacrificial layer to form at least one of an air bridge structure and a cantilever structure at the edge of the top electrode, wherein the air gap of the air bridge structure is the location of the sacrificial layer of the air bridge structure, and the air gap of the cantilever structure is the location of the sacrificial layer of the cantilever structure.

[0086] See also Figure 12 The sacrificial layer 40 is released by wet etching to form an air bridge structure 51 and a cantilever structure 52 at the edge of the top electrode 50, wherein the air gap between the air bridge structure 51 and the piezoelectric layer 30 is the location of the sacrificial layer 41 of the air bridge structure, and the air gap between the cantilever structure 52 and the piezoelectric layer 30 is the location of the sacrificial layer 42 of the cantilever structure.

[0087] On the basis of the above technical solution, this embodiment forms an uneven surface on at least a portion of the surface of the top electrode away from the sacrificial layer to form a second rough surface, thereby increasing the area of ​​the rough reflective surface of at least one of the air bridge structure and the cantilever structure in the top electrode, enhancing the scattering effect on the shear waves or clutter entering from the effective area of ​​the bulk acoustic wave resonator and the effective energy consumption efficiency of the shear waves or clutter, and can further prevent the shear waves or clutter from reflecting back and forth in the air bridge structure or cantilever structure electrode or even returning to the effective area, thereby further preventing the shear waves or clutter from interfering with the normal resonant waves of the bulk acoustic wave resonator after returning to the effective area, thereby further reducing the energy loss of the normal resonant sound waves of the bulk acoustic wave resonator and further improving the Q value of the bulk acoustic wave resonator.

[0088] Figure 13 FIG is a flow chart of another method for preparing a bulk acoustic wave resonator according to an embodiment of the present invention. Figure 13 The preparation method of the bulk acoustic wave resonator comprises the following steps:

[0089] S310 , providing a substrate.

[0090] S320 , forming a bottom electrode on the substrate.

[0091] S330 , forming a piezoelectric layer on a side of the bottom electrode facing away from the substrate.

[0092] S340 , forming a sacrificial layer at an edge of a surface of the piezoelectric layer facing away from the bottom electrode, wherein the sacrificial layer includes at least one of an air bridge structure sacrificial layer and a cantilever structure sacrificial layer.

[0093] S350 , forming an uneven surface on at least a portion of the surface of the sacrificial layer facing away from the piezoelectric layer through a surface treatment process to form a first rough surface.

[0094] S360 , forming a top electrode on a surface of the sacrificial layer facing away from the piezoelectric layer.

[0095] S370. Form an uneven surface on at least a portion of the surface of the top electrode away from the sacrificial layer through a surface treatment process to form a second rough surface, wherein the orthographic projection of the second rough surface on the substrate is within the orthographic projection of the sacrificial layer on the substrate.

[0096] The preparation method and beneficial effects of S310-S370 can be performed with reference to the preparation method and beneficial effects of S210-S270.

[0097] S3801. Form at least one of a concave structure and a convex structure on an edge of a surface of the top electrode facing away from the piezoelectric layer.

[0098] See also Figure 14A concave structure 53 and a convex structure 54 are formed on the edge of the surface of the top electrode 50 away from the piezoelectric layer through a patterning process.

[0099] S3802: Form an uneven surface on at least a portion of the surface of at least one of the concave structure and the convex structure through a surface treatment process to form a third rough surface.

[0100] See also Figure 15 At least one surface treatment process selected from the group consisting of an ion bombardment process, a Bosch process, a photolithography process, and an etching process is used to form an uneven surface on a portion of the surface of the concave structure 53 and the convex structure 54, thereby forming a third rough surface A3. The specific area and position of the third rough surface A3 are not specifically limited in this embodiment.

[0101] S390. Release the sacrificial layer to form at least one of an air bridge structure and a cantilever structure at the edge of the top electrode, wherein the air gap of the air bridge structure is the location of the sacrificial layer of the air bridge structure, and the air gap of the cantilever structure is the location of the sacrificial layer of the cantilever structure.

[0102] See also Figure 16 The sacrificial layer 40 is released by wet etching to form an air bridge structure 51 and a cantilever structure 52 at the edge of the top electrode 50, wherein the air gap between the air bridge structure 51 and the piezoelectric layer 30 is the location of the sacrificial layer 41 of the air bridge structure, and the air gap between the cantilever structure 52 and the piezoelectric layer 30 is the location of the sacrificial layer 42 of the cantilever structure.

[0103] On the basis of the above technical solution, at least one of a concave structure and a convex structure is formed on the edge of the surface of the top electrode away from the piezoelectric layer, and an uneven surface is formed on at least part of the surface of at least one of the concave structure and the convex structure through a surface treatment process to form a third rough surface, which further increases the area of ​​the rough reflective surface of at least one of the air bridge structure and the cantilever structure in the top electrode, enhances the scattering effect on the shear waves or clutter entering from the effective area of ​​the bulk acoustic wave resonator and the effective energy consumption efficiency of the shear waves or clutter, and can further prevent the shear waves or clutter from reflecting back and forth in the air bridge structure or cantilever structure electrode or even returning to the effective area, thereby further preventing the shear waves or clutter from interfering with the normal resonant waves of the bulk acoustic wave resonator after returning to the effective area, thereby further reducing the energy loss of the normal resonant sound waves of the bulk acoustic wave resonator and further improving the Q value of the bulk acoustic wave resonator.

[0104] Figure 17 FIG is a flow chart of another method for preparing a bulk acoustic wave resonator according to an embodiment of the present invention. Figure 17 The preparation method of the bulk acoustic wave resonator comprises the following steps:

[0105] S410: Provide a substrate.

[0106] S420 , forming a bottom electrode on the substrate.

[0107] S430 , forming a piezoelectric layer on a side of the bottom electrode facing away from the substrate.

[0108] The preparation method and beneficial effects of S410-S430 can be performed with reference to the preparation method and beneficial effects of S310-S330.

[0109] S4301. Form an uneven surface on the edge of the surface of the piezoelectric layer facing away from the bottom electrode through a surface treatment process to form a fourth rough surface.

[0110] See also Figure 18 At least one surface treatment process selected from the group consisting of an ion bombardment process, a Bosch process, a photolithography process, and an etching process is used to form an uneven surface at the edge of the piezoelectric layer 30 facing away from the bottom electrode 20, thereby forming a fourth rough surface A4. The specific area and location of the fourth rough surface A4 are not specifically limited in this embodiment.

[0111] S440 , forming a sacrificial layer at an edge of a surface of the piezoelectric layer facing away from the bottom electrode, wherein the sacrificial layer includes at least one of an air bridge structure sacrificial layer and a cantilever structure sacrificial layer.

[0112] See also Figure 19 A thin film of a sacrificial layer 40 is formed on the side of the piezoelectric layer 30 away from the bottom electrode 20, and then a sacrificial layer 40 including an air bridge structure sacrificial layer 41 and a cantilever structure sacrificial layer 42 is formed on the edge of the surface of the piezoelectric layer 30 away from the bottom electrode 20 through a patterning process.

[0113] S450 , forming an uneven surface on at least a portion of the surface of the sacrificial layer facing away from the piezoelectric layer through a surface treatment process to form a first rough surface.

[0114] See also Figure 20 The sacrificial layer 40 is formed with an uneven surface on a portion of the surface facing away from the piezoelectric layer 30 by at least one surface treatment process selected from the group consisting of an ion bombardment process, a Bosch process, a photolithography process, and an etching process, thereby forming a first rough surface A1. The sacrificial layer 40 comprises single crystal silicon, and at least a portion of the surface of the sacrificial layer 40 facing away from the piezoelectric layer 30 can be corroded with a texturing solution to form an uneven surface on the surface of the sacrificial layer 40 facing away from the piezoelectric layer 30, thereby forming the first rough surface A1.

[0115] S460 , forming a top electrode on a surface of the sacrificial layer facing away from the piezoelectric layer.

[0116] See also Figure 21, a top electrode 50 may be formed on a side of the sacrificial layer 40 facing away from the piezoelectric layer 30 by a metal lift-off method.

[0117] S470, forming an uneven surface on at least a portion of the surface of the top electrode away from the sacrificial layer through a surface treatment process to form a second rough surface, wherein the orthographic projection of the second rough surface on the substrate is within the orthographic projection of the sacrificial layer on the substrate.

[0118] See also Figure 22 , an uneven surface is formed on the surface of the top electrode 50 facing away from the sacrificial layer 40 through at least one surface treatment process selected from the group consisting of an ion bombardment process, a Bosch process, a photolithography process, and an etching process, so as to form a second rough surface A2, wherein the orthographic projection of the second rough surface A2 on the substrate 10 is within the orthographic projection of the sacrificial layer 40 on the substrate 10.

[0119] S4801. Form at least one of a concave structure and a convex structure on an edge of a surface of the top electrode facing away from the piezoelectric layer.

[0120] See also Figure 23 A concave structure 53 and a convex structure 54 are formed on the edge of the surface of the top electrode 50 away from the piezoelectric layer through a patterning process.

[0121] S4802: forming an uneven surface on at least a portion of the surface of at least one of the concave structure and the convex structure through a surface treatment process to form a third rough surface.

[0122] See also Figure 24 A surface treatment process is used to form an uneven surface on a portion of the surface of the concave structure 53 and the convex structure 54 to form a third rough surface A3.

[0123] S490. Release the sacrificial layer to form at least one of an air bridge structure and a cantilever structure at the edge of the top electrode, wherein the air gap of the air bridge structure is the location of the sacrificial layer of the air bridge structure, and the air gap of the cantilever structure is the location of the sacrificial layer of the cantilever structure.

[0124] See also Figure 25 The sacrificial layer 40 is released by wet etching to form an air bridge structure 51 and a cantilever structure 52 at the edge of the top electrode 50, wherein the air gap between the air bridge structure 51 and the piezoelectric layer 30 is the location of the sacrificial layer 41 of the air bridge structure, and the air gap between the cantilever structure 52 and the piezoelectric layer 30 is the location of the sacrificial layer 42 of the cantilever structure.

[0125] On the basis of the above technical solution, an uneven surface is formed on the edge of the surface of the piezoelectric layer away from the bottom electrode through a surface treatment process to form a fourth rough surface, so that the piezoelectric layer opposite to the air bridge structure and the cantilever structure has a rough reflective surface, which enhances the scattering effect on the shear waves or clutter entering from the effective area of ​​the bulk acoustic wave resonator and the effective energy consumption efficiency of the shear waves or clutter, and can further prevent the shear waves or clutter from reflecting back and forth in the air bridge structure or cantilever structure electrode or even returning to the effective area, thereby further preventing the shear waves or clutter from interfering with the normal resonant waves of the bulk acoustic wave resonator after returning to the effective area, thereby further reducing the energy loss of the normal resonant sound waves of the bulk acoustic wave resonator and further improving the Q value of the bulk acoustic wave resonator.

[0126] Embodiments of the present invention further provide a bulk acoustic wave resonator. This bulk acoustic wave resonator is prepared using the method for preparing a bulk acoustic wave resonator described in any of the above embodiments. Therefore, the beneficial effects of the method for preparing a bulk acoustic wave resonator described in any of the above embodiments are not further described here.

[0127] The present invention also provides a bulk acoustic wave filter. The bulk acoustic wave filter includes the bulk acoustic wave resonator described in any of the above embodiments. Therefore, the beneficial effects of the bulk acoustic wave resonator described in any of the above embodiments are not repeated here.

[0128] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present invention can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved. This is not limited herein.

[0129] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A method for preparing a bulk acoustic wave resonator, characterized in that: include: providing a substrate; forming a bottom electrode on the substrate; forming a piezoelectric layer on a side of the bottom electrode facing away from the substrate; forming a sacrificial layer at an edge of a surface of the piezoelectric layer facing away from the bottom electrode, wherein the sacrificial layer comprises at least one of an air bridge structure sacrificial layer and a cantilever structure sacrificial layer; forming an uneven surface on at least a portion of the surface of the sacrificial layer facing away from the piezoelectric layer through a surface treatment process to form a first rough surface; forming a top electrode on a surface of the sacrificial layer facing away from the piezoelectric layer; releasing the sacrificial layer to form at least one of an air bridge structure and a cantilever structure at the edge of the top electrode, wherein the air gap of the air bridge structure is the location of the sacrificial layer of the air bridge structure, and the air gap of the cantilever structure is the location of the sacrificial layer of the cantilever structure; After forming a top electrode on at least a portion of the surface of the sacrificial layer facing away from the piezoelectric layer, the method further comprises: forming at least one of a concave structure and a convex structure at an edge of a surface of the top electrode facing away from the piezoelectric layer; A surface treatment process is performed to form an uneven surface on at least a portion of the surface of at least one of the concave structure and the convex structure to form a third rough surface.

2. The method for preparing a bulk acoustic wave resonator according to claim 1, wherein: After forming a top electrode on at least a portion of the surface of the sacrificial layer facing away from the piezoelectric layer, the method further comprises: A second rough surface is formed by forming an uneven surface on at least a portion of the surface of the top electrode away from the sacrificial layer through a surface treatment process, wherein the orthographic projection of the second rough surface on the substrate is within the orthographic projection of the sacrificial layer on the substrate.

3. The method for preparing a bulk acoustic wave resonator according to claim 1, wherein: Before forming a sacrificial layer on an edge of a surface of the piezoelectric layer facing away from the bottom electrode, the method further comprises: A surface treatment process is performed to form an uneven surface on the edge of the surface of the piezoelectric layer facing away from the bottom electrode, so as to form a fourth rough surface.

4. The method for preparing a bulk acoustic wave resonator according to any one of claims 1 to 3, characterized in that: The surface treatment process includes at least one of an ion bombardment process, a Bosch process, and a photolithography and etching process.

5. The method for preparing a bulk acoustic wave resonator according to claim 1, wherein: The sacrificial layer includes single crystal silicon, and forming an uneven surface on at least a portion of the surface of the sacrificial layer away from the piezoelectric layer through a surface treatment process to form a first rough surface includes: At least a portion of the surface of the sacrificial layer away from the piezoelectric layer is corroded by a texturing liquid, so as to form an uneven surface on the surface of the sacrificial layer away from the piezoelectric layer, thereby forming a first rough surface.

6. The method for preparing a bulk acoustic wave resonator according to claim 4, wherein: Before performing the surface treatment process on the bulk acoustic wave resonator, the method further includes: Forming uniformly distributed foreign particles on the surface to be subjected to the surface treatment process, wherein the hardness of the foreign particles is greater than the hardness of the film layer where the foreign particles are located; After performing the surface treatment process on the surface to be subjected to the surface treatment process, the method further includes: The foreign particles are removed.

7. The method for preparing a bulk acoustic wave resonator according to claim 1, wherein: Before forming a bottom electrode on the substrate, the method further includes: An acoustic reflection structure is formed on the surface or inside of the substrate.

8. A bulk acoustic wave resonator, characterized in that: The bulk acoustic wave resonator is prepared by the preparation method of any one of claims 1 to 7.

9. A bulk acoustic wave filter, characterized in that: The bulk acoustic wave resonator according to claim 8 is included.

Images