Bulk acoustic wave resonator and filter

Abstract

The invention discloses a bulk acoustic wave resonator and a filter, which are applied to the field of communication, and a first bulge structure and a second bulge structure are arranged between a top electrode and a piezoelectric layer; the first convex structures surround to form a first convex polygonal area on the inner side, the second convex structures surround to form a second convex polygonal area on the inner side, the inner side boundaries of the second convex structures are all located on the first convex structures, and the inner side of each edge of the second convex polygonal area comprises the first convex structures with the preset width; the top surfaces of the top electrodes corresponding to the inner side boundaries of the first convex structures are all higher than the top surfaces of the top electrodes corresponding to the first convex polygonal areas; and the top surfaces of the top electrodes corresponding to the inner side boundaries of the second convex structures are all higher than the top surfaces of the top electrodes corresponding to the outer side boundaries of the second convex polygonal regions. According to the invention, the second projection structure is used, so that the influence of the first projection structure on the Q value below the resonant frequency of the bulk acoustic wave resonator is reduced.

Description

Technical Field

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

[0002] Bulk acoustic wave filter (BAW) technology is one of the main technologies currently used in the field of mobile communications. With the popularization of 5G communications, higher frequency and wider bandwidth frequency bands are used in mobile communications, so filters are required to support larger bandwidths and higher frequencies. In order to improve the performance of bulk acoustic wave filters in the prior art, a protruding structure is usually added to the boundary of the bulk acoustic wave resonator to suppress and reflect the lateral mode. However, as the bandwidth of mobile communications continues to expand, the above-mentioned protruding structure used to improve the performance of bulk acoustic wave filters will introduce new resonant modes in the low-frequency region while improving the performance of the bulk acoustic wave filters, thereby seriously affecting the performance of large-bandwidth filters, resulting in the inability of the prior art to achieve high-performance large-bandwidth filters.

[0003] Therefore, how to provide a resonant mode that can suppress the resonant frequency of the BAW resonator while ensuring a high Q value (Q value is the quality factor, used to describe the energy loss and storage capacity of the BAW resonator) of the BAW resonator above the resonant frequency is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a bulk acoustic wave resonator and filter, which solves the problem of the protruding structure used in the prior art to improve the performance of the bulk acoustic wave filter. While improving the performance of the bulk acoustic wave filter, a new resonance mode will be introduced in the low-frequency region, which will seriously affect the performance of the large-bandwidth filter, resulting in the problem that the prior art cannot achieve a high-performance large-bandwidth filter.

[0005] In order to solve the above technical problems, the present invention provides a bulk acoustic wave resonator, comprising:

[0006] A substrate, an acoustic reflection unit, a bottom electrode, a top electrode and a piezoelectric layer;

[0007] The top electrode is provided with a first convex structure and a second convex structure between the top electrode lead-out end and the non-top electrode lead-out end and the piezoelectric layer;

[0008] The first convex structure surrounds and forms a first convex polygonal area on the inner side, and the second convex structure surrounds and forms a second convex polygonal area on the inner side, and the inner side boundaries of the second convex structure are all located on the first convex structure, and the inner side of each side of the second convex polygonal area includes the first convex structure of a preset width;

[0009] The top surface of the top electrode at the inner boundary corresponding to the first protruding structure is higher than the top surface of the top electrode corresponding to the first convex polygonal area;

[0010] The top surface of the top electrode at the inner boundary corresponding to the second protruding structure is higher than the top surface of the top electrode at the outer boundary corresponding to the second convex polygonal area.

[0011] Optionally, at at least one side of the BAW resonator, an outer boundary of the first protruding structure does not exceed an outer boundary of the top electrode in a lateral direction.

[0012] Optionally, a third protruding structure is provided between the top electrode and the piezoelectric layer within the first convex polygonal region;

[0013] There is no overlapping area between the third protruding structure and the first protruding structure in the thickness direction.

[0014] Optionally, a distance between the third protruding structure and the first protruding structure in a lateral direction is greater than 0 and less than 2λ;

[0015] The λ is the operating wavelength of the BAW resonator.

[0016] Optionally, on a side corresponding to the bottom electrode lead-out end, the second protruding structure and the first protruding structure have a first overlapping region in a thickness direction, and a width of the first overlapping region is less than or equal to λ; λ is an operating wavelength of the BAW resonator;

[0017] On a side corresponding to the bottom electrode lead-out terminal, the preset width is less than or equal to λ.

[0018] Optionally, on a side corresponding to the bottom electrode lead-out end, the preset width is less than 3 / 4λ and greater than 1 / 8λ;

[0019] Or, on a side corresponding to the bottom electrode lead-out end, the preset width is equal to 3 / 4λ;

[0020] Alternatively, on a side corresponding to the bottom electrode lead-out end, the preset width is equal to 1 / 8λ, where λ is an operating wavelength of the BAW resonator.

[0021] Optionally, on a side corresponding to the top electrode lead-out end, the second protruding structure and the first protruding structure have a second overlapping region in a thickness direction, and a width of the second overlapping region is equal to a width of the first overlapping region;

[0022] The preset width on the side corresponding to the top electrode lead-out terminal is the same as the preset width on the side corresponding to the bottom electrode lead-out terminal.

[0023] Optionally, the outer boundary of the first protruding structure and the spacing between the outer adjacent first protruding structure are greater than 10 microns.

[0024] Optionally, an etch stop layer is also included;

[0025] The etch stop layer is at least located on the upper surface of the first protruding structure.

[0026] Optionally, a passivation layer is disposed on a portion of the top surface of the top electrode.

[0027] Optionally, the bottom electrode does not completely cover the sound reflection unit at least at one edge corresponding to the lead-out end of the top electrode;

[0028] The top electrode is provided with a hollow structure at the top electrode lead-out end, and the bottom electrode covers the sound reflection unit in at least a part of the side length area at a position corresponding to the hollow structure;

[0029] At a location corresponding to the top electrode lead-out terminal, the bottom electrode, the top electrode and the substrate do not have a common overlapping area.

[0030] The present invention also provides a filter, comprising:

[0031] A series branch and a plurality of parallel branches, wherein the series branch includes a plurality of series resonators, and each of the parallel branches includes a parallel resonator;

[0032] The series resonator and the parallel resonator are both bulk acoustic wave resonators as described above.

[0033] Optionally, the series branch and the parallel branch each include a plurality of BAW resonators with different resonator frequencies;

[0034] In at least some of the series resonators in the series branch, the preset widths at the top electrode lead-out terminal and at the bottom electrode lead-out terminal are different from the preset widths at the top electrode lead-out terminal and at the bottom electrode lead-out terminal in the parallel resonator.

[0035] It can be seen that the bulk acoustic wave resonator provided by the present invention includes a substrate, a sound reflection unit, a bottom electrode, a top electrode and a piezoelectric layer; the top electrode is provided with a first protruding structure and a second protruding structure between the top electrode lead-out end and the non-top electrode lead-out end and the piezoelectric layer; the first protruding structure surrounds the first convex polygonal area to form an inner side, the second protruding structure surrounds the second convex polygonal area to form an inner side, and the inner boundary of the second protruding structure is located on the first protruding structure, and the inner side of each side of the second convex polygonal area includes a first protruding structure of a preset width; the top surface of the top electrode at the inner boundary corresponding to the first protruding structure is higher than the top surface of the top electrode at the corresponding first convex polygonal area; the top surface of the top electrode at the inner boundary corresponding to the second protruding structure is higher than the top surface of the top electrode at the outer boundary corresponding to the second convex polygonal area. The present invention utilizes the second protruding structure to limit a partial area of ​​the first protruding structure outside the effective working area of ​​the BAW resonator. On the one hand, the influence of the first protruding structure on the Q value below the resonant frequency is reduced. On the other hand, an acoustic impedance discontinuity is formed at the boundary of the effective working area of ​​the BAW resonator, which further suppresses the resonant mode introduced by the first protruding structure and effectively improves the Q value below the resonant frequency.

[0036] In addition, the present invention also provides a filter, which also has the above beneficial effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0038] Figure 1 A schematic structural diagram of a bulk acoustic wave resonator provided by an embodiment of the present invention;

[0039] Figure 2 It is a structural schematic diagram of an existing bulk acoustic wave resonator;

[0040] Figure 3 is an example diagram showing a quality factor below the parallel resonance frequency in a conventional bulk acoustic wave resonator, which varies with an overlap width d between the first protruding structure and the top electrode;

[0041] Figure 4 This is an example diagram of a test curve of an existing bulk acoustic wave resonator;

[0042] Figure 5 is an exemplary diagram showing a quality factor below the series resonance frequency in a conventional bulk acoustic wave resonator, which varies with an overlap width d between the first protruding structure and the top electrode;

[0043] Figure 6 This is an example diagram comparing the BAW resonator test curves of the embodiment of the present invention and the prior art;

[0044] Figure 7 A schematic structural diagram of another bulk acoustic wave resonator provided by an embodiment of the present invention;

[0045] Figure 8 A schematic structural diagram of another bulk acoustic wave resonator provided in an embodiment of the present invention;

[0046] Fig. 9 A schematic structural diagram of a bulk acoustic wave resonator including an etch stop layer provided in an embodiment of the present invention;

[0047] Fig.10 A schematic structural diagram of a bulk acoustic wave resonator including a passivation layer provided in an embodiment of the present invention;

[0048] Fig.11 A schematic diagram of a top view of a bulk acoustic wave resonator including a hollow structure provided in an embodiment of the present invention;

[0049] Fig.12 A cross-sectional view of the A-A' section in a schematic top view of a bulk acoustic wave resonator including a hollow structure provided by an embodiment of the present invention;

[0050] Fig.13 A cross-sectional view of a BB' section in a top view structural diagram of a bulk acoustic wave resonator including a hollow structure provided by an embodiment of the present invention;

[0051] Fig.14 A schematic diagram of the structure of a filter provided by an embodiment of the present invention;

[0052] Figure 1 , Figure 2 , Figures 9 to 14 In the figure, the reference numerals are described as follows:

[0053] 1-series branch, 2-parallel branch, 3-series resonator, 4-parallel resonator;

[0054] 10 - substrate, 20 - acoustic reflection unit, 30 - bottom electrode, 40 - top electrode, 50 - piezoelectric layer, 61 - first protruding structure, 62 - second protruding structure, 63 - third protruding structure, 70 - etching stop layer, 80 - passivation layer, 90 - hollow structure. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution 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 described embodiments 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 creative work are within the scope of protection of the present invention.

[0056] Please refer to Figure 1 , Figure 1 A schematic diagram of the structure of a bulk acoustic wave resonator provided in an embodiment of the present invention. The bulk acoustic wave resonator may include:

[0057] A substrate 10, a sound reflecting unit 20, a bottom electrode 30, a top electrode 40 and a piezoelectric layer 50;

[0058] The top electrode 40 is provided with a first protruding structure 61 and a second protruding structure 62 between the top electrode 40 lead end and the non-top electrode 40 lead end and the piezoelectric layer 50;

[0059] The first convex structure 61 surrounds and forms a first convex polygonal area on the inside, and the second convex structure 62 surrounds and forms a second convex polygonal area on the inside, and the inner boundary of the second convex structure 62 is located on the first convex structure 61, and the inner side of each side of the second convex polygonal area includes a first convex structure 61 with a preset width;

[0060] The top surface of the top electrode 40 at the inner boundary corresponding to the first protruding structure 61 is higher than the top surface of the top electrode 40 corresponding to the first convex polygonal area;

[0061] The top surface of the top electrode 40 at the inner boundary corresponding to the second protruding structure 62 is higher than the top surface of the top electrode 40 at the outer boundary corresponding to the second convex polygonal region.

[0062] It should be noted that, in this embodiment, the substrate 10, the sound reflection unit 20, the bottom electrode 30, the top electrode 40 and the piezoelectric layer 50 are the basic structures for forming a bulk acoustic wave resonator, and a first protrusion structure 61 and a second protrusion structure 62 are arranged between the top electrode 40 and the piezoelectric layer 50. In this embodiment, the substrate 10 can be set as a silicon substrate, a sapphire substrate, a silicon carbide substrate or a glass substrate, the sound reflection unit 20 can be set as an air gap, or a Bragg reflection layer formed by alternating high and low acoustic impedance materials, and the top electrode 40 and the bottom electrode 30 can be set as a molybdenum metal electrode, a ruthenium metal electrode, a tungsten metal electrode, an aluminum metal electrode, an iridium metal electrode, or electrodes formed by a combination of the above metals. The piezoelectric layer 50 can be set to an aluminum nitride piezoelectric film, a doped aluminum nitride piezoelectric film (doped aluminum nitride is Doped AlN), a lithium niobate piezoelectric film (lithium niobate is LiNbO3), a lithium tantalate piezoelectric film (lithium tantalate is LiTaO3), a zinc oxide piezoelectric film (zinc oxide is ZnO), and a lead zirconate titanate piezoelectric film (lead zirconate titanate is PZT). Specifically, in this embodiment, the first protruding structure 61 is a ring-shaped protruding structure formed by an inner polygonal boundary and an outer polygonal boundary. At the same time, the first protruding structure 61 can be set to an inner polygonal boundary and an outer polygonal boundary, and each side corresponds to a parallel structure, and the second protruding structure 62 can be set to the shape of the first protruding structure 61 described above. Furthermore, in the present embodiment, the inner contour edge of the first protruding structure 61 is set to a polygonal shape, and then on the inner side of the first protruding structure 61, a first convex polygonal area is formed by the first protruding structure 61. It should be pointed out that in the present embodiment, unless otherwise specified, the inner side and the outer side both correspond to the inner side and the outer side along the transverse direction, that is, the first annular first protruding structure 61 mentioned above, the first convex polygonal area formed by the inner polygon is located on the inner side of the first protruding structure 61, and the top surface of the next layer structure of the first protruding structure 61 in the thickness direction, the direction formed by extending at various places is used as the above-mentioned transverse direction, that is, the transverse direction changes with the top surface structure of the next layer structure, and is not fixed to a horizontal plane. In the present embodiment, specifically in the present embodiment, when the surface of the piezoelectric layer 50 is a flat horizontal plane, the above-mentioned transverse direction can be set to a horizontal plane.

[0063] You can refer to Figure 2 , Figure 2It is a schematic diagram of the structure of an existing BAW resonator. Among them, the overlapping area between the bottom electrode 30, the piezoelectric layer 50, the top electrode 40 and the sound reflection unit 20 in the existing BAW resonator constitutes the effective working area of ​​the existing BAW resonator. The first protruding structure 61 forms an acoustic impedance discontinuity area at the boundary of the effective working area of ​​the BAW resonator, which can effectively reflect and suppress the lateral resonance mode of the BAW resonator, thereby improving the Q value above the resonance frequency of the BAW resonator (typically, it can be represented by the Q value at the parallel resonance frequency, i.e., Qp), and the overlapping width d between the first protruding structure 61 and the top electrode 40 has a strong correlation with the Qp of the BAW resonator, such as Figure 3 As shown, Figure 3 The figure is an example of the quality factor below the parallel resonance frequency in an existing BAW resonator, which varies with the overlap width d of the first protruding structure and the top electrode. It can be seen that as d increases, Qp shows a fluctuating upward trend. Furthermore, when d increases, since the first protruding structure 61 forms a resonance at the boundary of the effective area of ​​the BAW resonator with a frequency lower than the frequency of the central area of ​​the BAW resonator, that is, at a position below the resonant frequency of the BAW resonator, an additional resonant mode will appear, such as Figure 4 As shown, Figure 4 This is an example of a test curve of an existing BAW resonator. Figure 4 The existence of the resonant mode shown in the figure causes the Q value of the BAW resonator below the resonant frequency to deteriorate, such as Figure 5 As shown, Figure 5 This is an example diagram of the quality factor below the series resonance frequency in an existing BAW resonator, which varies with the overlap width d of the first protrusion structure and the top electrode. The Q value below the resonance frequency of the BAW resonator (typically, it can be represented by the Q value at the series resonance frequency, i.e., Qb) shows a fluctuating downward trend as d increases. After applying the BAW resonator provided by the present invention, you can refer to Figure 6 , Figure 6This is an example diagram comparing the test curves of the BAW resonator of the embodiment of the present invention and the prior art. The solid line represents the present embodiment, and the dotted line represents the prior art. It can be seen that the embodiment of the present invention has a good suppression of the resonant mode below the resonant frequency of the BAW resonator, while maintaining a high Q value above the resonant frequency of the BAW resonator. Specifically, in the prior art, the effective working area of ​​the BAW resonator is composed of the overlapping area of ​​the sound reflection unit 20, the bottom electrode 30, the piezoelectric layer 50 and the top electrode 40. Therefore, the first protruding structure 61 falls within the effective working area of ​​the BAW resonator, which has a greater impact on the Q value below the resonant frequency; while in the present invention, the second protruding structure 62 is used to limit a part of the area of ​​the first protruding structure 61 outside the effective working area of ​​the BAW resonator. On the one hand, the influence of the first protruding structure 61 on the Q value below the resonant frequency is minimized, and on the other hand, an acoustic impedance discontinuity is formed at the boundary of the effective working area of ​​the BAW resonator, which further suppresses the resonant mode introduced by the first protruding structure 61, and effectively improves the Q value below the resonant frequency.

[0064] In this embodiment, the inner contour edge of the second protruding structure 62 is also set to a polygonal shape, and then on the inner side of the second protruding structure 62, a second convex polygonal area is formed by surrounding the inner contour edge of the second protruding structure 62. In this embodiment, the second protruding structure 62 can be set to be parallel to each side of the first protruding structure 61. In the second convex polygonal area formed by the inner contour edge of the second protruding structure 62 in this embodiment, the bottom electrode 30, the top electrode 40, the piezoelectric layer 50 and the sound reflection unit 20 form an overlapping area in the thickness direction, which serves as the effective working area of ​​the bulk acoustic wave resonator in this embodiment, and the contour edge of the non-top electrode 40 lead-out end of the top electrode 40, the contour edge of the non-bottom electrode 30 lead-out end of the bottom electrode 30, and the contour edge of the sound reflection unit 20 can all be set to a shape corresponding to the inner contour edge of the second protruding structure 62, so that the effective working area of ​​the bulk acoustic wave resonator is a convex polygonal area. In this embodiment, the inner side of the second protruding structure 62 is partially overlapped on the upper side of the first protruding structure 61. As Figure 1 In the figure, the left side of the effective working area of ​​the BAW resonator is the bottom electrode lead-out terminal, and the right side of the effective working area of ​​the BAW resonator is the top electrode lead-out terminal.

[0065] It should be further explained that, in the present embodiment, within the above-mentioned convex polygonal effective working area, at the inner polygonal boundary of the first convex structure 61, a step structure is formed between the first convex structure 61 and the first convex polygonal area, and the top electrode 40 is at a position corresponding to the step structure, that is, at the top electrode 40 directly above the step structure in the thickness direction, so that the top electrode 40 forms a corresponding step structure, that is, the top surface of the top electrode 40 at the inner boundary corresponding to the first convex structure 61 is higher than the top surface of the top electrode 40 corresponding to the first convex polygonal area, that is, at the step structure formed corresponding to the top electrode 40, an acoustic impedance discontinuity region is further formed, which can reflect and suppress the lateral resonance mode of the bulk acoustic wave resonator, thereby improving the Q value above the resonance frequency of the bulk acoustic wave resonator. In this embodiment, on the basis of the above structure, a step structure is formed between the first protruding structure 61 and the second protruding structure 62 at the boundary of the above-mentioned convex polygonal effective working area, and the step structure formed between the first protruding structure 61 and the second protruding structure 62 forms another step structure corresponding to the top electrode 40 directly above the top electrode 40 in the thickness direction, that is, the top surface of the top electrode 40 at the inner boundary corresponding to the second protruding structure 62 is higher than the top surface of the top electrode 40 at the outer boundary corresponding to the second convex polygonal area, that is, another acoustic impedance discontinuity area is further formed at the other step structure formed corresponding to the top electrode 40, and another acoustic impedance discontinuity is formed at the boundary of the effective working area of ​​the BAW resonator, which can further suppress the resonant mode introduced by the second protruding structure 62, and effectively improve the Q value below the resonant frequency of the BAW resonator. On the other hand, limiting a partial area of ​​the first protruding structure 61 outside the effective working area of ​​the BAW resonator can minimize the influence of the first protruding structure 61 on the Q value below the resonant frequency of the BAW resonator.

[0066] In addition, it should be noted that, in the present embodiment, the inner boundary of the first protruding structure 61 includes at least part of the protruding structure connected to the inner boundary of the first protruding structure 61 in the area close to the inner boundary of the first protruding structure 61, that is, the inner boundary of the first protruding structure 61 is formed by extending a part of the width outward from the inner boundary of the first protruding structure 61 along the transverse direction. The inner boundary of the first protruding structure 61 belongs to the first protruding structure 61. Similarly, the inner boundary of the second protruding structure 62 includes an area formed by extending a part of the width outward from the inner boundary of the second protruding structure 62 along the transverse direction, which belongs to the second protruding structure 62. Correspondingly, the outer boundary of the second convex polygonal area includes an area formed by extending a part of the width inward from the outer boundary of the second convex polygonal area along the transverse direction, which belongs to the second convex polygonal area. In this embodiment, the top electrode 40 lead-out end is the end corresponding to the top electrode 40 lead-out end in the above-mentioned convex polygonal effective working area, and the other end is the non-top electrode 40 lead-out end, and correspondingly, in the above-mentioned convex polygonal effective working area, the end corresponding to the bottom electrode 30 lead-out end is the bottom electrode 30 lead-out end, and the top electrode 40 lead-out end and the bottom electrode 30 lead-out end can be the corresponding edges in the convex polygonal effective working area, and the area formed by extending part of the width outward or inward in the lateral direction. In this embodiment, both inward and outward are relative to the center of the convex polygonal effective working area. The direction close to the center of the convex polygonal effective working area is inward, and the direction away from the center of the convex polygonal effective working area is outward, and it is only applicable to partial structures constituting the same bulk acoustic wave resonator. In this embodiment, the first protruding structure 61 can be set to a molybdenum metal medium, a ruthenium metal medium, a tungsten metal medium, a silicon oxide medium, a silicon nitride medium, or an aluminum nitride medium; the second protruding structure 62 can be set to a silicon oxide medium, a silicon nitride medium, or can also be set to an air gap; the third protruding structure 63 can be set to a molybdenum metal medium, a ruthenium metal medium, a tungsten metal medium, a silicon oxide medium, a silicon nitride medium, or an aluminum nitride medium.

[0067] Furthermore, in order for the first protrusion structure, the second protrusion structure and the third protrusion to effectively improve the Q value below the resonant frequency of the BAW resonator without affecting the Q value above the resonant frequency, reference may be made to Figure 7 , Figure 7 A schematic diagram of another BAW resonator structure provided by an embodiment of the present invention. In this embodiment, it can be arranged that at least one side of the BAW resonator has an outer boundary of the first protruding structure 61 that does not exceed the outer boundary of the top electrode 40 in the lateral direction.

[0068] It should be noted that, in this embodiment, the outer contour edge of the first protruding structure 61 can be set as an outer polygonal boundary. At this time, at least one edge of the outer contour edge of the first protruding structure 61 can be selected not to exceed the outer boundary of the top electrode 40 on this side, that is, at least one edge of the outer contour edge of the first protruding structure 61 is located on the inner side of the outer boundary of the top electrode 40 in the lateral direction, so as to form an acoustic impedance discontinuous boundary at the edge of the BAW resonator, thereby further improving the Q value above the resonant frequency of the BAW resonator. Specifically, corresponding to Figure 7 In this embodiment, D1 is greater than 0.

[0069] Furthermore, in order to suppress the clutter below the resonance frequency of the BAW resonator and improve the Q value below the resonance frequency, in this embodiment, a third protrusion structure 63 may be provided between the top electrode 40 and the piezoelectric layer 50 in the first convex polygonal region;

[0070] There is no overlapping area between the third protrusion structure 63 and the first protrusion structure 61 in the thickness direction.

[0071] It should be noted that in this embodiment, a third protruding structure 63 is additionally provided between the top electrode 40 and the piezoelectric layer 50, corresponding to the first convex polygonal region, so as to form another acoustic impedance discontinuity region at the boundary of the BAW resonator, thereby reducing the acoustic loss below the resonant frequency of the BAW resonator and improving the Q value below the resonant frequency. Figure 7 That is, D2 is greater than or equal to 0.

[0072] Furthermore, in order to effectively suppress and reflect the stray modes at the boundary, in this embodiment, the spacing between the third protrusion structure 63 and the first protrusion structure 61 in the lateral direction may be set to be greater than 0 and less than 2λ;

[0073] λ is the operating wavelength of the BAW resonator.

[0074] It should be noted that, in this embodiment, by setting the spacing between the third protruding structure 63 and the first protruding structure 61 in the lateral direction to be between 0 and 2λ, another acoustic impedance discontinuity region can be formed at the boundary of the BAW resonator, thereby reducing the acoustic loss below the resonant frequency of the BAW resonator and improving the Q value below the resonant frequency. Figure 7 That is, D2 is greater than 0 and less than 2λ.

[0075] Furthermore, in order to improve the quality factor of the BAW resonator at the parallel resonant frequency and improve the quality factor of the BAW resonator at the series resonant frequency, and at the same time suppress the resonant mode excited by the first protruding structure 61, the second protruding structure 62 can be arranged on the side corresponding to the lead end of the bottom electrode 30, and there is a first overlapping area with the first protruding structure 61 in the thickness direction, and the width of the first overlapping area is less than or equal to λ; λ is the operating wavelength of the BAW resonator;

[0076] On a side corresponding to the lead-out end of the bottom electrode 30 , the preset width is less than or equal to λ.

[0077] It should be noted that in this embodiment, on the side corresponding to the lead-out end of the bottom electrode 30, the first protruding structure 61 inside the second convex polygonal region is set to a preset width less than or equal to λ and greater than 0 along the direction pointing to the center of the effective working area of ​​the BAW resonator, which can ensure that the third protruding structure 63 improves the quality factor of the resonator at the series resonant frequency, and the preset width directly affects the quality factor of the BAW resonator at the parallel resonant frequency. Setting the preset width greater than 0 can improve the quality factor of the BAW resonator at the parallel resonant frequency. Further, in this embodiment, any contour edge located at the bottom electrode satisfies the preset width less than or equal to the working wavelength of the BAW resonator. In addition, in this embodiment, by setting the width of the first overlapping area to be less than or equal to λ, it is ensured that an acoustic impedance discontinuity boundary is formed, so that the resonant mode excited by the first protruding structure 61 can be suppressed. Corresponding to Figure 7 That is, D3 is greater than 0 and less than λ, or D3 is equal to λ, and D4 is greater than 0 and less than λ, or D4 is equal to λ.

[0078] Further, in order to improve the quality factor of the BAW resonator at the parallel resonant frequency and the quality factor at the series resonant frequency, the preset width on the side corresponding to the lead end of the bottom electrode 30 may be set to be less than 3 / 4λ and greater than 1 / 8λ;

[0079] Or, on the side corresponding to the lead-out end of the bottom electrode 30, the preset width is equal to 3 / 4λ;

[0080] Alternatively, on a side corresponding to the lead-out end of the bottom electrode 30 , the preset width is equal to 1 / 8λ, where λ is the operating wavelength of the BAW resonator.

[0081] In this embodiment, by setting the preset width of one side of the lead end of the corresponding bottom electrode 30 to be between one eighth of λ and three quarters of λ, the quality factor of the BAW resonator at the parallel resonant frequency and the quality factor of the BAW resonator at the series resonant frequency can be further improved to the maximum extent. Figure 7That is, D4 is greater than one-eighth times λ and less than three-quarters times λ, or D4 is equal to three-quarters times λ, or D4 is equal to one-eighth times λ.

[0082] Furthermore, in order to minimize the energy leakage at each boundary of the BAW resonator, we can refer to Figure 8 , Figure 8 A schematic diagram of the structure of another BAW resonator provided by an embodiment of the present invention. It can be arranged on one side of the lead end of the corresponding top electrode 40, and the second protruding structure 62 and the first protruding structure 61 have a second overlapping region in the thickness direction, and the width of the second overlapping region is equal to the width of the first overlapping region;

[0083] The preset width on the side corresponding to the lead-out end of the top electrode 40 is the same as the preset width on the side corresponding to the lead-out end of the bottom electrode 30 .

[0084] In this embodiment, by setting the same preset width on one side of the lead-out end of the top electrode 40 and the same preset width on one side of the lead-out end of the bottom electrode 30, and the same corresponding first overlapping area and second overlapping area, the energy leakage at each boundary of the BAW resonator can be effectively suppressed, thereby improving the Q value of the BAW resonator. Figure 7 and the above Figure 8 That is, D3 equals D5, and D4 equals D6.

[0085] Furthermore, in order to facilitate production and manufacturing, the top electrode can be thickened by using the first protruding structure outside the effective working area of ​​the BAW resonator to reduce the connection resistance of the BAW resonator. The outer boundary of the first protruding structure 61 can be set, and the spacing between the first protruding structures 61 adjacent to the outer side can be greater than 10 microns.

[0086] In this embodiment, the outer boundary of the first protruding structure 61 is set, and the spacing between the first protruding structures 61 adjacent to the outer side is greater than 10 microns, thereby reducing the connection resistance of the BAW resonator. Figure 8 Medium, that is, D7 is greater than 10 microns.

[0087] Further, in order to improve the convenience of preparation, reference can be made to Fig. 9 , Fig. 9 A schematic diagram of the structure of a bulk acoustic wave resonator including an etch stop layer provided in an embodiment of the present invention. The etch stop layer 70 may also be included;

[0088] The etch stop layer 70 is at least located on the upper surface of the first protrusion structure 61 .

[0089] It should be noted that, in this embodiment, by providing an etch stop layer 70 on the upper side of the first protruding structure 61, the first protruding structure 61 can be protected from damage when the second protruding structure 62 is formed, which is convenient for process processing. It should also be noted that, in this embodiment, when the third protruding structure 63 is present, the etch stop layer 70 can be provided on the lower side of the third protruding structure 63. Specifically, the etch stop layer is a dielectric material, which can be provided as an aluminum nitride dielectric layer or a silicon nitride dielectric layer.

[0090] Furthermore, in order to protect the top electrode 40 while ensuring the conductive lead-out, reference may be made to Fig.10 , Fig.10 A schematic diagram of the structure of a bulk acoustic wave resonator including a passivation layer provided in an embodiment of the present invention: A passivation layer 80 may be disposed on a portion of the top surface of the top electrode 40 .

[0091] It should be noted that in this embodiment, a passivation layer 80 is provided on a portion of the top surface of the top electrode 40, that is, the passivation layer 80 is provided in the non-conducting area to protect the outside without affecting the conduction. Specifically, the passivation layer 80 can be provided as a silicon oxide layer, a silicon nitride layer, or an aluminum nitride layer.

[0092] Furthermore, at the top electrode lead-out end of the BAW resonator, there is an overlapping area between the top electrode and the bottom electrode that is not within the acoustic reflection unit. The top electrode in this area and the overlapping area of ​​the top electrode and the piezoelectric film form a capacitor. Since there is no acoustic reflection unit, the acoustic waves generated in this area will propagate along the substrate, which not only introduces additional capacitance loss, but also reduces the coupling coefficient and quality factor Q of the BAW resonator. In order to reduce the acoustic wave leakage and capacitance loss at the boundary of the acoustic reflection unit of the top electrode lead-out end of the BAW resonator, reference can be made to Fig.11 , Fig.11 A schematic diagram of a top view of a BAW resonator including a hollow structure provided by an embodiment of the present invention. The bottom electrode 30 may be arranged at least at one edge corresponding to the lead end of the top electrode 40, not completely covering the sound reflection unit 20;

[0093] The top electrode 40 is provided with a hollow structure 90 at the leading end of the top electrode 40, and the bottom electrode 30 covers the sound reflection unit 20 in at least a part of the side length area at a position corresponding to the hollow structure 90;

[0094] At the corresponding top electrode 40 lead-out end, the bottom electrode 30 , the top electrode 40 and the substrate 10 do not have a common overlapping area.

[0095] For ease of understanding, this embodiment can also refer to Fig.12 and Fig.13 , Fig.12A cross-sectional view of the A-A' section in a schematic top view of a bulk acoustic wave resonator including a hollow structure provided by an embodiment of the present invention; Fig.13 A cross-sectional view of the BB' section in a schematic diagram of a top view of a BAW resonator including a hollow structure provided by an embodiment of the present invention. Fig.12 As shown, at the A-A' section, one end of the bottom electrode 30 is located inside the sound reflection unit 20. At the B-B' section, the top electrode 40 is located at the position where the bottom electrode 30 covers the sound reflection unit 20, and the discontinuous hollow structure 90 formed can be as shown in FIG. Fig.13 In this embodiment, by reducing the connection width of the top electrode lead-out end and removing the bottom electrode portion at the corresponding position, the overlapping area of ​​the top electrode, the bottom electrode and the piezoelectric film all falls inside the sound reflection unit.

[0096] The BAW resonator provided by the embodiment of the present invention includes a substrate 10, an acoustic reflection unit 20, a bottom electrode 30, a top electrode 40 and a piezoelectric layer 50; the top electrode 40 is provided with a first protruding structure 61 and a second protruding structure 62 between the piezoelectric layer 50 and the top electrode 40 lead-out end and the non-top electrode 40 lead-out end; the first protruding structure 61 surrounds a first convex polygonal area to form an inner side, the second protruding structure 62 surrounds a second convex polygonal area to form an inner side, and the inner side boundary of the second protruding structure 62 is located on the first protruding structure 61, and the inner side of each side of the second convex polygonal area includes a first protruding structure 61 of a preset width; the top surface of the top electrode 40 at the inner side boundary corresponding to the first protruding structure 61 is higher than the top surface of the top electrode 40 corresponding to the first convex polygonal area; the top surface of the top electrode 40 at the inner side boundary corresponding to the second protruding structure 62 is higher than the top surface of the top electrode 40 at the outer side boundary corresponding to the second convex polygonal area. The present invention utilizes the second protruding structure 62 to limit a partial area of ​​the first protruding structure 61 outside the effective working area of ​​the BAW resonator. On the one hand, the influence of the first protruding structure 61 on the Q value below the resonant frequency is reduced. On the other hand, an acoustic impedance discontinuity is formed at the boundary of the effective working area of ​​the BAW resonator, which further suppresses the resonant mode introduced by the first protruding structure 61 and effectively improves the Q value below the resonant frequency.

[0097] In addition, the embodiment of the present invention sets at least one edge of the outer contour edge of the first protruding structure 61 to be located on the inner side of the outer boundary of the top electrode 40 in the lateral direction, so as to form an acoustic impedance discontinuous boundary at the edge of the BAW resonator, thereby further improving the Q value of the BAW resonator above the resonant frequency; by additionally setting a third protruding structure 63 between the top electrode 40 and the piezoelectric layer 50, corresponding to the first convex polygonal area, it is possible to form another acoustic impedance discontinuous area at the boundary of the BAW resonator, thereby reducing the acoustic loss below the resonant frequency of the BAW resonator and improving the Q value below the resonant frequency; by setting the third protruding structure 63 and the first protruding structure 61 at The spacing in the lateral direction is between 0 and 2 times the working wavelength of the BAW resonator, and another acoustic impedance discontinuity region can be formed at the boundary of the BAW resonator, thereby reducing the acoustic loss below the resonant frequency of the BAW resonator and improving the Q value below the resonant frequency; on the side corresponding to the lead-out end of the bottom electrode 30, the first protruding structure 61 on the inner side of the second convex polygonal region is set to a preset width less than or equal to the working wavelength of the BAW resonator and greater than 0 along the direction pointing to the center of the effective working area of ​​the BAW resonator, which can ensure that the third protruding structure 63 improves the quality factor of the resonator at the series resonance frequency, and setting the preset width greater than 0 can improve The quality factor of the parallel resonance frequency of the BAW resonator is improved by setting the width of the first overlapping area to be less than or equal to the operating wavelength of the BAW resonator to ensure the formation of an acoustic impedance discontinuous boundary, so as to suppress the resonance mode excited by the first protruding structure 61; by setting the preset width of one side of the lead end corresponding to the bottom electrode 30 to be between one eighth of the operating wavelength of the BAW resonator and three quarters of the operating wavelength of the BAW resonator, the quality factor of the parallel resonance frequency of the BAW resonator and the quality factor of the series resonance frequency of the BAW resonator can be further improved to the maximum extent; by setting the outer boundary of the first protruding structure 61 to The spacing between adjacent first protruding structures 61 on the outside is greater than 10 microns, which reduces the connection resistance of the bulk acoustic wave resonator; by providing an etching stop layer 70 on the upper side of the first protruding structure 61, the first protruding structure 61 can be protected from damage when the second protruding structure 62 is formed, which facilitates process processing; by providing a passivation layer 80 on part of the top surface of the top electrode 40, that is, without affecting the conduction, the passivation layer 80 is provided in the non-conducting area with the outside for protection; by reducing the connection width of the top electrode lead-out end and removing the bottom electrode portion at the corresponding position at the same time, the overlapping area of ​​the top electrode, the bottom electrode and the piezoelectric film all fall inside the sound reflection unit.

[0098] A filter provided by an embodiment of the present invention is introduced below. The filter described below and the BAW resonator described above can be referred to each other.

[0099] Please refer to Fig.14 , Fig.14 A schematic diagram of a filter structure provided by an embodiment of the present invention may include:

[0100] A series branch 1 and a plurality of parallel branches 2, wherein the series branch 1 includes a plurality of series resonators 3, and each parallel branch 2 includes a parallel resonator 4;

[0101] Both the series resonator 3 and the parallel resonator 4 are bulk acoustic wave resonators as described above.

[0102] In this embodiment, the cascade arrangement of the bulk acoustic wave resonators as described above is used to form the filter of this embodiment, which effectively improves the Q value below the resonance frequency and is suitable for a large bandwidth filter.

[0103] Furthermore, in order to improve the passband insertion loss of the BAW filter and reduce the in-band ripple, the series branch 1 or the parallel branch 2 may include a plurality of BAW resonators with different resonator frequencies;

[0104] In at least some of the series resonators 3 in the series branch 1 , the preset widths at the top electrode 40 lead end and the bottom electrode 30 lead end are different from the preset widths at the top electrode 40 lead end and the bottom electrode 30 lead end in the parallel resonator 4 .

[0105] In this embodiment, the series branch 1 and the parallel branch 2 both include a plurality of BAW resonators with different resonator frequencies, and different preset widths are set, thereby improving the passband insertion loss of the BAW filter and reducing the in-band ripple.

[0106] The filter provided by the embodiment of the present invention includes a series branch 1 and multiple parallel branches 2, the series branch 1 includes multiple series resonators 3, each parallel branch 2 includes a parallel resonator 4, and the series resonator 3 and the parallel resonator 4 are both bulk acoustic wave resonators as described above. The BAW resonator at least includes a substrate 10, a sound reflection unit 20, a bottom electrode 30, a top electrode 40 and a piezoelectric layer 50; the top electrode 40 is provided with a first protruding structure 61 and a second protruding structure 62 between the piezoelectric layer 50 and the top electrode 40 lead-out end and the non-top electrode 40 lead-out end; the first protruding structure 61 surrounds a first convex polygonal area to form an inner side, the second protruding structure 62 surrounds a second convex polygonal area to form an inner side, and the inner side boundary of the second protruding structure 62 is located on the first protruding structure 61, and the inner side of each side of the second convex polygonal area includes a first protruding structure 61 of a preset width; the top surface of the top electrode 40 at the inner side boundary corresponding to the first protruding structure 61 is higher than the top surface of the top electrode 40 corresponding to the first convex polygonal area; the top surface of the top electrode 40 at the inner side boundary corresponding to the second protruding structure 62 is higher than the top surface of the top electrode 40 at the outer side boundary corresponding to the second convex polygonal area. The filter formed by the cascade arrangement of BAW resonators as described above is suitable for large bandwidth filters, wherein a second protruding structure 62 is arranged to limit a partial area of ​​the first protruding structure 61 outside the effective working area of ​​the BAW resonator. On the one hand, the influence of the first protruding structure 61 on the Q value below the resonant frequency is reduced. On the other hand, an acoustic impedance discontinuity is formed at the boundary of the effective working area of ​​the BAW resonator, further suppressing the resonant mode introduced by the first protruding structure 61, thereby effectively improving the Q value below the resonant frequency.

[0107] In addition, the embodiment of the present invention improves the passband insertion loss of the BAW filter and reduces the in-band ripple by setting the series branch 1 and the parallel branch 2 to include multiple BAW resonators with different resonator frequencies and setting different preset widths.

[0108] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0109] In addition, it should be noted that, in this article, relationships such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0110] The bulk acoustic wave resonator and filter provided by the present invention are introduced in detail above. Specific examples are used in this article to illustrate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A bulk acoustic wave resonator, characterized in that: include: A substrate, an acoustic reflection unit, a bottom electrode, a top electrode and a piezoelectric layer; The top electrode is provided with a first convex structure and a second convex structure between the top electrode lead-out end and the non-top electrode lead-out end and the piezoelectric layer; The first convex structure surrounds and forms a first convex polygonal area on the inner side, and the second convex structure surrounds and forms a second convex polygonal area on the inner side, and the inner side boundaries of the second convex structure are all located on the first convex structure, and the inner side of each side of the second convex polygonal area includes the first convex structure of a preset width; The top surface of the top electrode at the inner boundary corresponding to the first protruding structure is higher than the top surface of the top electrode corresponding to the first convex polygonal area; The top surface of the top electrode at the inner boundary corresponding to the second protruding structure is higher than the top surface of the top electrode at the outer boundary corresponding to the second convex polygonal area.

2. The bulk acoustic wave resonator according to claim 1, characterized in that At least one side of the BAW resonator has an outer boundary of the first protruding structure that does not exceed an outer boundary of the top electrode in a lateral direction.

3. The bulk acoustic wave resonator according to claim 1, characterized in that: A third protruding structure is provided between the top electrode and the piezoelectric layer within the first convex polygonal region; There is no overlapping area between the third protruding structure and the first protruding structure in the thickness direction.

4. The bulk acoustic wave resonator according to claim 3, characterized in that: A distance between the third protruding structure and the first protruding structure in a lateral direction is greater than 0 and less than 2λ; λ is an operating wavelength of the BAW resonator.

5. The bulk acoustic wave resonator according to claim 1, characterized in that: On a side corresponding to the bottom electrode lead-out end, the second protruding structure and the first protruding structure have a first overlapping region in the thickness direction, and a width of the first overlapping region is less than or equal to λ; λ is an operating wavelength of the BAW resonator; On a side corresponding to the bottom electrode lead-out terminal, the preset width is less than or equal to λ.

6. The bulk acoustic wave resonator according to claim 5, characterized in that On a side corresponding to the bottom electrode lead-out end, the preset width is less than 3 / 4λ and greater than 1 / 8λ; Or, on a side corresponding to the bottom electrode lead-out end, the preset width is equal to 3 / 4λ; Alternatively, on a side corresponding to the bottom electrode lead-out end, the preset width is equal to 1 / 8λ, where λ is an operating wavelength of the BAW resonator.

7. The bulk acoustic wave resonator according to claim 5, characterized in that On a side corresponding to the top electrode lead-out end, the second protruding structure and the first protruding structure have a second overlapping region in the thickness direction, and a width of the second overlapping region is equal to a width of the first overlapping region; The preset width on the side corresponding to the top electrode lead-out terminal is the same as the preset width on the side corresponding to the bottom electrode lead-out terminal.

8. The bulk acoustic wave resonator according to claim 1, characterized in that The outer boundary of the first protruding structure and the spacing between the first protruding structure and the outer adjacent first protruding structure are greater than 10 micrometers.

9. The BAW resonator according to claim 1, characterized in that: Also included is an etch stop layer; The etch stop layer is at least located on the upper surface of the first protruding structure.

10. The bulk acoustic wave resonator according to claim 1, characterized in that A passivation layer is disposed on a portion of the top surface of the top electrode.

11. The bulk acoustic wave resonator according to any one of claims 1 to 10, characterized in that: The bottom electrode does not completely cover the sound reflection unit at least at one edge corresponding to the lead-out end of the top electrode; The top electrode is provided with a hollow structure at the top electrode lead-out end, and the bottom electrode covers the sound reflection unit in at least a part of the side length area at a position corresponding to the hollow structure; At a location corresponding to the top electrode lead-out terminal, the bottom electrode, the top electrode and the substrate do not have a common overlapping area.

12. A filter, characterized in that: include: A series branch and a plurality of parallel branches, wherein the series branch includes a plurality of series resonators, and each of the parallel branches includes a parallel resonator; The series resonator and the parallel resonator are both the BAW resonator according to any one of claims 1 to 11.

13. The filter according to claim 12, characterized in that The series branch and the parallel branch both include a plurality of bulk acoustic wave resonators with different resonator frequencies; In at least some of the series resonators in the series branch, the preset widths at the top electrode lead-out terminal and at the bottom electrode lead-out terminal are different from the preset widths at the top electrode lead-out terminal and at the bottom electrode lead-out terminal in the parallel resonator.

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