Bulk acoustic wave resonator, electronic device and manufacturing method

Abstract

The present disclosure provides a bulk acoustic wave resonator, an electronic device and a manufacturing method. The bulk acoustic wave resonator includes: a substrate and an acoustic wave reflection region, wherein the acoustic wave reflection region is formed in or on the substrate; a lower electrode layer, a first piezoelectric layer, a second piezoelectric layer and an upper electrode layer are formed on the substrate with the acoustic wave reflection region formed thereon; a protrusion structure is arranged on the upper electrode layer; and a gap, wherein the gap is formed below the protrusion structure and is arranged in the same layer as the second piezoelectric layer, the height of the gap is equal to the height of the second piezoelectric layer, the orthographic projection of the protrusion structure on the upper surface of the substrate covers the orthographic projection of the gap on the upper surface of the substrate, and the width of the gap does not exceed the width of the protrusion structure.

Description

Technical Field

[0001] The present disclosure relates to the field of electronics, and more specifically, to a bulk acoustic wave resonator, an electronic device, and a manufacturing method thereof. Background Art

[0002] As the core component of the RF front end, the filter has excellent performance, such as low insertion loss, steep filtering curve, high isolation, and smaller size. It is of vital importance to promote the development of the next generation of communication standards and the miniaturization and multifunctionality of personal mobile terminals. The new generation of thin film bulk acoustic wave technology is effectively solving the above two problems. The thin film bulk acoustic wave filter prepared by the thin film bulk acoustic wave (BAW) technology has a steeper filtering curve, lower insertion loss and excellent out-of-band suppression capability.

[0003] Film Bulk Acoustic Resonator (FBAR) plays an important role in communications, sensors and other fields due to its advantages such as small size, high frequency, large power capacity and high sensitivity. It occupies an increasingly large share in the RF front-end field, especially in the RF filter market. It also has great development advantages in the fields of biosensing and medical measurement.

[0004] Figure 1 FIG. 2 shows a schematic diagram of the structure of a thin film bulk acoustic wave resonator in the prior art. Figure 1 As shown, the FBAW resonator generally includes an acoustic wave reflection region 101, a lower electrode layer 200 formed on a substrate 100 and completely covering the acoustic wave reflection region 101, a first piezoelectric layer 300 formed on the lower electrode layer 200, and an upper electrode layer 400 disposed on the first piezoelectric layer 300. Due to the existence of the transverse mode, a portion of the transverse wave will leak out from the edge of the electrode, so that the acoustic wave energy in the FBAW resonator is reduced, thereby reducing the Q value of the FBAW resonator.

[0005] It is necessary to provide a new thin film bulk acoustic wave resonator product and a manufacturing method to improve the Q value of the thin film bulk acoustic wave resonator and thereby improve the performance of the thin film bulk acoustic wave filter. Summary of the invention

[0006] In view of the above technical problems, the present disclosure designs a thin film bulk acoustic wave resonator, a filter and a manufacturing method, which can overcome the above technical problems existing in the prior art, thereby providing a thin film bulk acoustic wave resonator, a filter and a manufacturing method with a high Q value.

[0007] A brief overview of the disclosure will be given below in order to provide a basic understanding of certain aspects of the disclosure. It should be understood that this overview is not an exhaustive overview of the disclosure. It is not intended to identify key or important parts of the disclosure, nor is it intended to limit the scope of the disclosure. Its purpose is simply to give certain concepts in a simplified form as a prelude to a more detailed description discussed later.

[0008] According to one aspect of the present disclosure, a bulk acoustic wave resonator is provided, comprising: a substrate and an acoustic wave reflection region, wherein the acoustic wave reflection region is formed in or on the substrate; a lower electrode layer, a first piezoelectric layer, a second piezoelectric layer and an upper electrode layer are formed on the substrate having the acoustic wave reflection region; a protrusion structure is arranged on the upper electrode layer; and a gap, wherein the gap is formed below the protrusion structure and is arranged in the same layer as the second piezoelectric layer, the height of the gap is equal to the height of the second piezoelectric layer, the orthographic projection of the protrusion structure on the upper surface of the substrate covers the orthographic projection of the gap on the upper surface of the substrate, and the width of the gap does not exceed the width of the protrusion structure.

[0009] Furthermore, the width of the protrusion structure is 0.5-3.5 microns.

[0010] Furthermore, the width of the gap is equal to the width of the protrusion structure. .

[0011] Furthermore, the protrusion structure is a single-stage protrusion structure, a multi-stage continuous protrusion structure or a multi-group protrusion structure.

[0012] Furthermore, when the protrusion structure is a single-step convex structure or a multi-step continuous protrusion structure, a single-step concave structure or a multi-step concave structure is formed inside the protrusion structure.

[0013] Furthermore, when the protrusion structure is a plurality of groups of protrusion structures, a gap is formed under at least one protrusion structure.

[0014] Furthermore, there is no gap below the recessed structure.

[0015] Furthermore, the first piezoelectric layer and the second piezoelectric layer are made of different materials.

[0016] Furthermore, the protrusion structure is further disposed on the lower electrode layer; or the protrusion structure formed on the upper electrode layer is replaced by the protrusion structure formed on the lower electrode layer.

[0017] Further, the structure of the upper electrode and / or the lower electrode is selected from: having only a two-dimensional structure; having a first part with a two-dimensional structure and a second part with a three-dimensional structure; when the structure of the upper electrode and / or the lower electrode has only a two-dimensional structure and has a protrusion structure, or when the structure of the upper electrode and / or the lower electrode has a first part with a two-dimensional structure and a second part with a three-dimensional structure and has a protrusion structure, the width of the gap is the difference between the outermost edge of the protrusion structure and the edge of the second piezoelectric layer; when the structure of the upper electrode and / or the lower electrode has a first part with a two-dimensional structure and a second part with a three-dimensional structure, the second part is regarded as a protrusion structure, and the width of the gap is the difference from the boundary between the first part and the second part to the edge of the second piezoelectric layer.

[0018] According to another aspect of the present disclosure, a method for preparing a bulk acoustic wave resonator is provided, comprising: providing a substrate, forming an acoustic wave reflection region in or on the substrate; forming a lower electrode layer, a first piezoelectric layer, a second piezoelectric layer and an upper electrode layer on the substrate, or forming a lower electrode layer, a second piezoelectric layer, a first piezoelectric layer and an upper electrode layer on the substrate; forming a protrusion structure on the edge of the upper electrode layer; forming a gap below the protrusion structure, the height of the gap being the height of the second piezoelectric layer, and the gap being arranged in the same layer as the second piezoelectric layer, the orthographic projection of the protrusion structure on the upper surface of the substrate covering the orthographic projection of the gap on the upper surface of the substrate, and the width of the gap not exceeding the width of the protrusion structure.

[0019] According to yet another aspect of the present disclosure, an electronic device is provided, the electronic device comprising any of the aforementioned BAW resonators provided by the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The specific contents of the present disclosure are described below with reference to the accompanying drawings, which will help to more easily understand the above and other purposes, features and advantages of the present disclosure. The accompanying drawings are only for illustrating the principles of the present disclosure. The sizes and relative positions of the units in the accompanying drawings need not be drawn to scale.

[0021] Figure 1 A schematic diagram of the structure of a thin film bulk acoustic resonator in the prior art is shown;

[0022] Figure 2 The first embodiment of the structure and method of the thin film bulk acoustic resonator of the present disclosure is shown;

[0023] Figure 3a-Figure 3b A variation of the first embodiment of the structure and method of the thin film bulk acoustic resonator of the present disclosure is shown;

[0024] Figure 4 is a schematic structural diagram of a thin film bulk acoustic resonator of a comparative example;

[0025] Figure 5A Q value curve of the thin film bulk acoustic wave resonator provided by the present disclosure and a Q value curve of the thin film bulk acoustic wave resonator in a comparative example;

[0026] Figure 6 The amplitude-frequency curve of the film bulk acoustic wave resonator with a protruding structure with too large width;

[0027] Figure 7a-7b is a graph showing the relationship between the gap thickness and the impedance curve of a thin film bulk acoustic resonator having a protrusion structure and a gap;

[0028] Figure 8 A thin film bulk acoustic resonator provided for a second embodiment of the present disclosure;

[0029] Fig. 9 A thin film bulk acoustic resonator is provided as a third embodiment of the present disclosure. DETAILED DESCRIPTION

[0030] Below, exemplary disclosures of the present disclosure will be described in conjunction with the accompanying drawings. For the sake of clarity and conciseness, not all features of implementing the present disclosure are described in the specification. However, it should be understood that many decisions specific to the present disclosure may be made in the process of developing any such implementation of the present disclosure in order to achieve the developer's specific goals, and these decisions may vary from one disclosure to another.

[0031] It should also be noted that, in order to avoid obscuring the present disclosure due to unnecessary details, only device structures closely related to the solutions according to the present disclosure are shown in the drawings, while other details that are not closely related to the present disclosure are omitted.

[0032] In general, it should be understood that the drawings and the various elements depicted therein are not drawn to scale. Furthermore, the use of relative terms such as "above," "below," "top," "bottom," "upper," and "lower" to describe the relationship of various elements to one another should be understood to encompass different orientations of the device and / or elements in addition to the orientation depicted in the drawings.

[0033] It should be understood that the present disclosure is not limited to the described implementation forms due to the following description with reference to the accompanying drawings. Herein, where feasible, features between different embodiments may be replaced or borrowed, and one or more features may be omitted in one embodiment, wherein the same reference numerals represent the same components. It should be understood that the manufacturing steps of the present disclosure are exemplary in the embodiments, and the order of the steps is adjustable.

[0034] First embodiment

[0035] See also Figure 2-Figure 3b , Figure 2The first embodiment of the structure and method of the thin film bulk acoustic wave resonator of the present disclosure is shown. Figure 3a-Figure 3b Modifications of the first embodiment of the thin film bulk acoustic resonator structure and method of the present disclosure are shown, wherein the same reference numerals denote the same components.

[0036] A substrate 100 is provided, in which an acoustic wave reflection region 101 consisting of a structure such as an air cavity or a Bragg reflection layer is formed. The substrate 100 may be formed of a material compatible with semiconductor processes, such as silicon (Si), gallium arsenide (GaAs), indium phosphide (InP), glass, sapphire, aluminum oxide, SiC, etc. The air cavity may be formed by etching a portion of the substrate 100; the Bragg reflection layer is formed by stacking films of different acoustic impedances. More preferably, the Bragg reflection layer is formed by stacking films of different acoustic impedances and the films are controlled to have a thickness of 1 / 4 wavelength. It should be understood that the air cavity may be, for example, Figure 2 The cavity shown in FIG. 1 does not penetrate the upper and lower surfaces of the substrate 100 , or the air cavity shown in FIG. 3 is a cavity that completely penetrates the upper and lower surfaces of the substrate 100 .

[0037] A seed layer (not shown in the figure) is formed on the substrate 100 to completely cover the acoustic wave reflection area 101, and a lower electrode layer 200 is formed on the seed layer. The lower electrode layer 200 can be a single layer or multiple layers. A first piezoelectric layer 300 and a second piezoelectric layer 301 are formed on the lower electrode layer 200, and an upper electrode layer 400 is arranged on the second piezoelectric layer 301. The upper electrode layer 400 can be a single layer or multiple layers. The upper / lower electrodes can be formed of one or more conductive materials, such as various metals compatible with semiconductor processes including tungsten (W), molybdenum (Mo), iridium (Ir), aluminum (Al), platinum (Pt), ruthenium (Ru), niobium (Nb) or hafnium (Hf). The materials of the upper electrode and the lower electrode can be the same or different.

[0038] The first piezoelectric layer 300 and the second piezoelectric layer 301 may be formed of any piezoelectric material compatible with semiconductor processes, such as aluminum nitride (AlN), doped aluminum nitride or zirconate titanate (PZT). The materials of the first piezoelectric layer 300 and the second piezoelectric layer 301 may be the same or different. Further, when the first piezoelectric layer 300 and the second piezoelectric layer 301 have doped impurities, the doping concentrations of the first piezoelectric layer 300 and the second piezoelectric layer 301 may be the same or different. The projection profile of the first piezoelectric layer 300 on the upper surface of the substrate 100 may be greater than the projection profile of the second piezoelectric layer 301 on the upper surface of the substrate 100, and the projection profile of the second piezoelectric layer 301 on the upper surface of the substrate 100 is smaller than the projection profile of the upper electrode layer 400 on the upper surface of the substrate 100.

[0039] A first-order protrusion structure 401 is further formed at the edge of the upper electrode layer 400. The first-order protrusion structure 401 can be formed at the edge of the upper electrode layer 400, so that the energy transmitted laterally can be greatly reflected back to the thin film bulk acoustic wave resonator, reducing energy leakage, thereby improving the Q value. Since the projection profile of the second piezoelectric layer 301 on the upper surface of the substrate 100 is smaller than the projection profile of the upper electrode on the upper surface of the substrate 100, that is, the second piezoelectric layer 301 is retracted relative to the edge of the upper electrode layer 400 in the width direction, a gap 3011 is formed below the first-order protrusion structure 401, and the height of the gap 3011 is the height of the second piezoelectric layer 301.

[0040] Furthermore, when the upper electrode layer 400 is Figure 2-Figure 3a When a two-dimensional structure is shown and there is a first-order protrusion structure 401 thereon, the orthographic projection of the protrusion structure on the upper surface of the substrate covers the orthographic projection of the gap 3011 on the upper surface of the substrate, and the width of the gap 3011 is the difference between the outermost edge of the protrusion structure 401 and the edge of the second piezoelectric layer 301.

[0041] When the upper electrode layer 400 has a first portion consisting of a two-dimensional structure and a second portion consisting of a three-dimensional structure, and the upper electrode layer 400 has a first-order protrusion structure 401, illustratively, as Figure 3b When the second part B shown in the figure has an air bridge or air wing, and the first part A formed on a two-dimensional plane except the second part, the width of the gap 3011 is the difference between the outermost edge of the protrusion structure 401 and the edge of the second piezoelectric layer 301.

[0042] It can be understood that when the upper electrode layer 400 has a first part consisting of a two-dimensional structure and a second part consisting of a three-dimensional structure, the thin film bulk acoustic wave resonator provided by the present invention may not have the first-order protrusion structure 401, and the second part B of the upper electrode layer 400 can be regarded as a first-order protrusion structure. In this case, the width of the gap 3011 is the difference between the boundary between the first part and the second part of the upper electrode layer 400 and the edge of the second piezoelectric layer 301.

[0043] The width of the protrusion structure in the present disclosure is exemplarily greater than 0 microns and less than 4 microns, and the preferred width of the protrusion structure is 0.5-3.5um. The width of the gap 3011 does not exceed the width of the protrusion structure. The preferred width of the gap 3011 is 1 / 2 of the width of the protrusion structure. The gap thickness range is generally between 0.005-0.02um.

[0044] While forming a first-order protrusion structure 401 at the edge of the upper electrode layer 400, a first-order or multi-order recessed structure 402 may be further formed inside the first-order protrusion structure 401. The provision of the first-order or multi-order recessed structure 402 is conducive to reflecting transverse waves, weakening or reducing adverse effects such as energy attenuation caused by the transverse mode between the active area and the peripheral area. However, it should be noted that when there is a recessed structure, there is no gap directly below the first-order or multi-order recessed structure 402.

[0045] Although in Figure 2-Figure 3b In the embodiment of the present invention, the second piezoelectric layer 301 is formed above the first piezoelectric layer 300 and below the upper electrode layer 400. However, it should be noted that the second piezoelectric layer 301 can also be formed above the lower electrode layer 200 and below the first piezoelectric layer 300.

[0046] Furthermore, although Figure 2-Figure 3b In the embodiment, the protrusion structure 401 is formed above the upper electrode layer 400, but it is understood that the protrusion structure 401 may also be formed on the lower electrode layer 200, or the protrusion structure 401 may be formed on both the upper electrode layer 400 and the lower electrode layer 200.

[0047] A passivation layer (not shown) is further formed on the upper electrode layer 400 . The material of the passivation layer may be silicon nitride, hafnium dioxide, polyimide (PI) or polyethylene terephthalate (PET).

[0048] The following is a further comparative test description of the thin film bulk acoustic wave resonator provided by the present disclosure by way of comparative examples.

[0049] See also Figure 4 , Figure 4 Schematic diagram of the structure of a thin film bulk acoustic wave resonator of a comparative example. Figure 4 The structure and structure of the thin film bulk acoustic wave resonator Figure 2 The structure of the provided thin film bulk acoustic wave resonator is different only in that the second piezoelectric layer 301 is not present, and the rest of the structure is the same.

[0050] See also Figure 5 , Figure 5 The Q value curve of the thin film bulk acoustic wave resonator provided by the present disclosure and the Q value curve of the thin film bulk acoustic wave resonator in the comparative example. Figure 5 As shown, curve 1 is the Q value curve of the conventional film bulk acoustic wave resonator in the comparative example, curve 2 is the Q value curve of the film bulk acoustic wave resonator with a gap width of 0.5 microns, curve 3 is the Q value curve of the film bulk acoustic wave resonator with a gap width of 1 micron, and curve 4 is the Q value curve of the film bulk acoustic wave resonator with a gap width of 1.5 microns.

[0051] Depend on Figure 5 It can be found that when the width of the first-order protrusion structure 401 is 0.5-3.5 microns, when the gap 3011 as shown in the present disclosure is provided, the Q value of the film bulk acoustic wave resonator is better than the Q value of the film bulk acoustic wave resonator without a gap under the first-order protrusion structure in the comparative example. Figure 5 It can be further found that when the width of the first-order protrusion structure 401 is too large, such as when the width of the protrusion structure is greater than 4 microns, the Q value of the FBAR with the gap 3011 arranged under the protrusion structure is not significantly different from the Q value of the FBAR in the comparative example. Figure 6 , Figure 6 This is the amplitude-frequency curve of the thin film bulk acoustic wave resonator with a protruding structure with too large a width. Figure 6 As shown, an overly large protruding structure will introduce a larger parasitic vibration to the left of the series resonance frequency fs of the resonator, thereby seriously affecting the out-of-band suppression of the filter or multiplexer.

[0052] For further information, see Figure 7a-Figure 7b , Figure 7a is a graph showing the relationship between the gap thickness and the impedance curve of a thin film bulk acoustic resonator having a protrusion structure and a gap; Figure 7b for Figure 7a A partial enlarged view of the box. Figure 7a-Figure 7b It can be seen that when the gap thickness is 0.004 microns, 0.006 microns, 0.008 microns and 0.01 microns, the different gap thicknesses have little effect on the performance of the thin film bulk acoustic wave resonator. However, it should be pointed out that when the second piezoelectric layer 301 uses a piezoelectric material with a doping concentration, the value of the effective electromechanical coupling coefficient Kt2 of the thin film bulk acoustic wave resonator can be controlled by changing the thickness of the second piezoelectric layer 301.

[0053] It can be seen from this that when the thin film bulk acoustic wave resonator has a smaller protrusion structure, by setting the gap structure disclosed in the present invention, the Q value of the thin film bulk acoustic wave resonator can be maximized as much as possible and the impact on the effective kt2 can be reduced, avoiding the use of a larger protrusion structure to obtain a larger Q value, thereby reducing the effective electromechanical coupling coefficient kt2 of the thin film bulk acoustic wave resonator and introducing serious parasitic vibrations.

[0054] Please continue reading Figure 2 , based on the device structure of the first embodiment of the present disclosure, its manufacturing method is further described in detail.

[0055] Step 1: Provide a substrate 100. The material of the substrate 100 is as described above and will not be repeated here. The substrate 100 mainly serves as a support carrier. Taking the Si substrate 100 as an example, it has good mechanical robustness and can ensure that it is relatively firm and reliable during processing and packaging.

[0056] Step 2: Etching the substrate 100 can form a cavity that does not penetrate the upper and lower surfaces of the substrate 100 or a cavity that passes through the upper and lower surfaces of the substrate 100, and filling the air cavity with a stack of films with different acoustic impedances, for example, with a thickness of 1 / 4 wavelength, or filling the air cavity with a sacrificial layer, the sacrificial layer is used to support the deposition of the film above.

[0057] It should also be understood that a support layer may be formed on the substrate 100, a groove may be formed by etching the support layer, and the sacrificial layer may be filled in the groove. The sacrificial layer may be selected from a thin film material such as phosphosilicate glass, silicon dioxide, amorphous silicon, etc., which is compatible with the deposition temperature of subsequent thin films, does not pollute the process system, and has good etching selectivity and chemical polishing properties.

[0058] Step three: A seed layer may then be formed on the substrate 100 . The seed layer is used to promote good deposition and adhesion of subsequent electrode layers, ensure that the electrode is not easy to fall off during use, and improve the conductivity of the electrode.

[0059] Step 4: Then, the lower electrode layer 200 is formed on the seed layer. It should be understood that the material of the lower electrode layer is not limited to the electrode material as described above, and an electrode material with high acoustic impedance and high acoustic velocity can be used. A first-order protrusion structure can also be formed on the lower electrode layer, and the protrusion structure of the lower electrode layer can be used to replace the protrusion structure subsequently formed on the upper electrode layer.

[0060] Step 5: Deposit the first piezoelectric layer 300 on the lower electrode layer 200. The material of the first piezoelectric layer 300 can be selected to meet the bandwidth requirements of wireless mobile communication signal reception and transmission. As mentioned above, it is preferred to consider materials compatible with the semiconductor process, such as aluminum nitride (AlN) or zirconate titanate (PZT). The first piezoelectric layer 300 is blanket-covered on the substrate 100 formed with the lower electrode.

[0061] Step 6: forming a second piezoelectric layer 301 on the first piezoelectric layer 300. The materials of the second piezoelectric layer 301 and the first piezoelectric layer 300 may be the same or different. When the material of the second piezoelectric layer 301 is the same as that of the first piezoelectric layer 300, the first piezoelectric layer 300 and the second piezoelectric layer 301 may have different doping concentrations.

[0062] It is understandable that the second piezoelectric layer 301 may be formed first in step 5, and then the first piezoelectric layer 300 may be formed in step 6. This is not specifically limited in the present disclosure.

[0063] Step seven: Deposit an upper electrode layer on the second piezoelectric layer 301, and form a first-order protrusion structure 401 on the upper electrode layer. The size of the first-order protrusion structure 401 is as described above and will not be repeated here. And further, a recessed structure can also be formed on the inner side of the first-order protrusion structure 401. It can be further understood that the first-order protrusion structure 401 can be integrally formed with the upper electrode, or it can be an additional first-order protrusion structure 401. When the first-order protrusion structure 401 is an additional first-order protrusion structure 401, it can be selected from a metal material that is the same as or different from the upper electrode material, or the protrusion structure can be a dielectric material, such as silicon dioxide or aluminum oxide.

[0064] The second piezoelectric layer 301 is retracted in the width direction relative to the edge of the upper electrode layer 400, so a gap 3011 is formed below the protruding structure. The height of the gap 3011 is the height of the second piezoelectric layer 301. The width range of the gap 3011 is set as described above and will not be repeated here.

[0065] Step 8: A passivation layer is further formed on the upper electrode or the frame structure. The material of the passivation layer can be silicon nitride, hafnium dioxide, polyimide (PI) or polyethylene terephthalate (PET). The passivation layer can protect the internal structure of the resonator from the influence of the external environment on the one hand, and can also reduce surface losses, inhibit the generation of parasitic modes, and improve the quality factor of the resonator on the other hand.

[0066] Second embodiment

[0067] Please see attached Figure 8 , attached Figure 8 The thin film bulk acoustic wave resonator provided in the second embodiment of the present disclosure. The thin film bulk acoustic wave resonator provided in the second embodiment of the present disclosure has the same features as those in the first embodiment and is not described in detail. Only the differences are described in detail below:

[0068] As attached Figure 8 As shown, a multi-stage continuous protrusion structure 403 is further formed on the upper electrode layer 400 in the thin film bulk acoustic wave resonator provided in the second embodiment, wherein multi-stage means greater than or equal to the second stage, and the width of the multi-stage continuous protrusion structure 403 is 0.5-3.5 microns. It is understandable that a single-stage or multi-stage depression 402 can also be formed adjacent to the inner side of the multi-stage continuous protrusion structure 403.

[0069] Furthermore, the second piezoelectric layer 301 is retracted relative to the edge of the upper electrode layer 400 in the width direction. When a gap 3011 is formed below the multi-stage continuous protrusion structure 403, the outer edge of the second piezoelectric layer 301 can be located below the outermost protrusion in the multi-stage protrusion, or the outer edge of the second piezoelectric layer 301 can be located below the innermost protrusion in the multi-stage protrusion. In this embodiment, the width of the gap 3011 is 1 / 2 of the width of the protrusion structure. , the thickness range is generally between 0.005-0.02um. More preferably, the width range of the gap 3011 is generally between 0.5-3um, and the thickness range is generally between 0.005-0.02um.

[0070] In the preparation process of the thin film bulk acoustic wave resonator provided by the second embodiment, the width of the second piezoelectric layer 301 is adjusted only when the second piezoelectric layer 301 is prepared in step six, so that its outer edge is located between directly below the outermost protrusion among the multi-order protrusions and directly below the innermost protrusion among the multi-order protrusions.

[0071] And in step seven, a multi-step continuous protrusion structure 403 and the recess 402 are formed on the upper electrode.

[0072] Third embodiment

[0073] See also Fig. 9 , Fig. 9 The thin film bulk acoustic wave resonator provided in the third embodiment of the present disclosure. The same features of the thin film bulk acoustic wave resonator provided in the third embodiment of the present disclosure as those in the first embodiment are not described here in detail, and only the differences are described in detail below:

[0074] like Fig. 9 As shown, the edge of the upper electrode layer 400 in the thin film bulk acoustic wave resonator provided in the third embodiment is further formed to include multiple groups of protrusion structures 404, wherein the multiple groups of protrusion structures 404 mean that the protrusions are discrete structures. The width of each protrusion in the multiple groups of protrusion structures 404 is 0.5-3.5 microns. It is understandable that one or more steps of depressions 402 can also be formed at adjacent locations inside each protrusion structure in the multiple groups of protrusion structures 404.

[0075] Furthermore, the second piezoelectric layer 301 is retracted relative to the edge of the upper electrode layer 400 in the width direction. When a gap 3011 is formed below the multiple groups of protrusion structures 404, the outer edge of the second piezoelectric layer 301 is located below the outermost protrusion in the multiple groups of protrusions, thereby forming a first gap 3012 below the outermost protrusion. And a second gap 3013 is formed in the second piezoelectric layer 301 located within the projection range of the inner protrusion in the multiple groups of protrusions. In this embodiment, the width range of the first and second gaps is 1 / 4 of the width of the protrusion structure. Preferably, the width of the first and second gaps is generally between 0.5-3 um, and the thickness is generally between 0.005-0.02 um.

[0076] In the preparation process of the thin film bulk acoustic wave resonator provided in the third embodiment, when preparing the second piezoelectric layer 301 in step six, the width of the second piezoelectric layer 301 is etched, so that its outer edge is retracted relative to the outermost protrusion among the multiple groups of protrusions to form a first gap 3012, and the second piezoelectric layer 301 is etched to form a second gap 3013 in the second piezoelectric layer 301 located within the projection range of the inner protrusion.

[0077] In step seven, a frame structure is formed on the upper electrode, and the frame structure has a plurality of protrusion structures 404 and the recesses formed in the upper electrode.

[0078] Fourth embodiment

[0079] A third embodiment of the present disclosure provides an electronic device, including the thin film bulk acoustic wave resonator provided by the present disclosure. The electronic device provided by the present disclosure may be a mobile phone, a personal digital assistant (PDA), a personal wearable device, an electronic game device, etc.

[0080] The present disclosure is described above in conjunction with specific implementation schemes, but it should be clear to those skilled in the art that these descriptions are exemplary and are not intended to limit the scope of protection of the present disclosure. Those skilled in the art can make various variations and modifications to the present disclosure based on the spirit and principles of the present disclosure, and these variations and modifications are also within the scope of the present disclosure.

Claims

1. A bulk acoustic wave resonator, characterized in that: include: a substrate and an acoustic wave reflecting region, wherein the acoustic wave reflecting region is formed in or on the substrate; A lower electrode layer, a first piezoelectric layer, a second piezoelectric layer and an upper electrode layer are formed on a substrate having an acoustic wave reflection area; the second piezoelectric layer is stacked with the first piezoelectric layer, and a projection profile of the first piezoelectric layer on the upper surface of the substrate is larger than a projection profile of the second piezoelectric layer on the upper surface of the substrate; The protrusion structure is formed at the edge of the upper electrode layer so that the energy transmitted laterally is greatly reflected back to the FBAR; A gap, wherein the gap is formed below the protrusion structure and is disposed in the same layer as the second piezoelectric layer, the height of the gap is equal to the height of the second piezoelectric layer, the orthographic projection of the protrusion structure on the upper surface of the substrate covers the orthographic projection of the gap on the upper surface of the substrate, and the width of the gap does not exceed the width of the protrusion structure; The structure of the upper electrode is selected from: having only a two-dimensional structure; having a first portion having a two-dimensional structure and a second portion having a three-dimensional structure; When the structure of the upper electrode has only a two-dimensional structure and has a protrusion structure, or when the structure of the upper electrode has a first part with a two-dimensional structure and a second part with a three-dimensional structure and has a protrusion structure, the width of the gap is the difference between the outermost edge of the protrusion structure and the edge of the second piezoelectric layer; when the structure of the upper electrode has a first part with a two-dimensional structure and a second part with a three-dimensional structure, the second part is regarded as a protrusion structure, and the width of the gap is the difference from the boundary between the first part and the second part to the edge of the second piezoelectric layer.

2. The BAW resonator according to claim 1, wherein: The width of the protrusion structure is 0.5-3.5 microns.

3. The bulk acoustic wave resonator according to claim 2, characterized in that: The width of the gap is the width of the protrusion structure .

4. The bulk acoustic wave resonator according to any one of claims 1 to 3, characterized in that: The protrusion structure is a single-stage protrusion structure, a multi-stage continuous protrusion structure or a multi-group protrusion structure.

5. The BAW resonator according to claim 4, characterized in that: When the protrusion structure is a single-step convex structure or a multi-step continuous protrusion structure, a single-step concave structure or a multi-step concave structure is formed inside the protrusion structure.

6. The BAW resonator according to claim 5, characterized in that: When the protrusion structure is a plurality of protrusion structures, a gap is formed under at least one protrusion structure.

7. The bulk acoustic wave resonator according to any one of claims 5 to 6, characterized in that: There is no void directly below the recessed structure.

8. The BAW resonator according to claim 7, characterized in that: The first piezoelectric layer and the second piezoelectric layer are made of different materials.

9. The bulk acoustic wave resonator according to any one of claims 1 to 3, 5 to 6, and 8, characterized in that: The protrusion structure is further disposed on the lower electrode layer; or the protrusion structure formed on the upper electrode layer is replaced by the protrusion structure formed on the lower electrode layer.

10. The BAW resonator according to claim 9, wherein: The structure of the lower electrode is selected from: having only a two-dimensional structure; having a first portion having a two-dimensional structure and a second portion having a three-dimensional structure; When the structure of the lower electrode has only a two-dimensional structure and has a protrusion structure, or when the structure of the lower electrode has a first part with a two-dimensional structure and a second part with a three-dimensional structure and has a protrusion structure, the width of the gap is the difference between the outermost edge of the protrusion structure and the edge of the second piezoelectric layer; when the structure of the lower electrode has a first part with a two-dimensional structure and a second part with a three-dimensional structure, the second part is regarded as a protrusion structure, and the width of the gap is the difference from the boundary between the first part and the second part to the edge of the second piezoelectric layer.

11. A method for preparing a bulk acoustic wave resonator, characterized in that: include: providing a substrate, and forming a sound wave reflecting area in or on the substrate; A lower electrode layer, a first piezoelectric layer, a second piezoelectric layer and an upper electrode layer are formed on a substrate, or a lower electrode layer, a second piezoelectric layer, a first piezoelectric layer and an upper electrode layer are formed on a substrate; the second piezoelectric layer is stacked with the first piezoelectric layer, and a projection contour of the first piezoelectric layer on the upper surface of the substrate is larger than a projection contour of the second piezoelectric layer on the upper surface of the substrate; A protrusion structure is formed at the edge of the upper electrode layer so that the energy transmitted laterally is greatly reflected back to the thin film bulk acoustic wave resonator; A gap is formed below the protrusion structure and is disposed in the same layer as the second piezoelectric layer, the height of the gap is equal to the height of the second piezoelectric layer, the orthographic projection of the protrusion structure on the upper surface of the substrate covers the orthographic projection of the gap on the upper surface of the substrate, and the width of the gap does not exceed the width of the protrusion structure; The structure of the upper electrode is selected from: having only a two-dimensional structure; having a first portion having a two-dimensional structure and a second portion having a three-dimensional structure; When the structure of the upper electrode has only a two-dimensional structure and has a protrusion structure, or when the structure of the upper electrode has a first part with a two-dimensional structure and a second part with a three-dimensional structure and has a protrusion structure, the width of the gap is the difference between the outermost edge of the protrusion structure and the edge of the second piezoelectric layer; when the structure of the upper electrode has a first part with a two-dimensional structure and a second part with a three-dimensional structure, the second part is regarded as a protrusion structure, and the width of the gap is the difference from the boundary between the first part and the second part to the edge of the second piezoelectric layer.

12. The method for preparing a bulk acoustic wave resonator according to claim 11, characterized in that: The width of the protrusion structure is 0.5-3.5 microns.

13. The method for preparing a bulk acoustic wave resonator according to claim 11, characterized in that: The width of the gap is the width of the protrusion structure .

14. The method for preparing a bulk acoustic wave resonator according to any one of claims 11 to 13, characterized in that: The protrusion structure is formed as a single-step protrusion structure, a multi-step continuous protrusion structure or a multi-group protrusion structure.

15. The method for preparing a bulk acoustic wave resonator according to claim 14, characterized in that: A single-step recessed structure or a multi-step recessed structure is formed inside the protruding structure.

16. The method for preparing a bulk acoustic wave resonator according to claim 15, characterized in that: When the protrusion structure is a plurality of protrusion structures, a gap is formed under at least one protrusion structure.

17. The method for preparing a bulk acoustic wave resonator according to claim 15 or 16, characterized in that: No void is formed directly below the recessed structure.

18. The method for preparing a bulk acoustic wave resonator according to any one of claims 11 to 13, 15 to 16, characterized in that: The protrusion structure is also formed on the lower electrode layer; or the protrusion structure formed on the lower electrode layer is used to replace the protrusion structure formed on the upper electrode layer.

19. An electronic device, characterized in that: The method comprises the bulk acoustic wave resonator according to any one of claims 1 to 10.

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