Bulk acoustic wave resonator

Abstract

According to the bulk acoustic wave resonator provided by the utility model, the boundary ring and the dielectric layer are formed between the piezoelectric layer and the top electrode, the introduction of the dielectric layer is equivalent to the series connection of a stray capacitor to the resonator, and the capacitance value of the stray capacitor can be adjusted by adjusting the thickness and the material of the dielectric layer. Therefore, the electromechanical coupling coefficient of the resonator is regulated and controlled. And the Q value of the bulk acoustic wave resonator can be improved through the boundary ring.

Description

Technical Field

[0001] This utility model relates to the field of resonator technology, and in particular to a bulk acoustic resonator. Background Technology

[0002] With the rapid development of 5G technology, the proportion of filters in RF front-end modules has further increased. Compared with traditional inductor-capacitor (LC) filters and surface acoustic wave (SAW) filters, bulk acoustic wave (BAW) filters have characteristics such as higher operating frequency, higher power capacity, better temperature sensitivity and low insertion loss, making them more popular in 5G applications.

[0003] For traditional bulk acoustic wave resonators, the electromechanical coupling coefficient can usually be adjusted by changing the resonator area and the thickness of the electrodes and piezoelectric layer. However, the adjustment range is extremely limited, which restricts filter design. Connecting inductors and capacitors in series or parallel across the resonator can effectively adjust the electromechanical coupling coefficient, but this also makes the filter design complex, bulky, and costly, hindering the miniaturization of module devices.

[0004] Therefore, those skilled in the art are working to conveniently and efficiently adjust the electromechanical coupling coefficient of a resonator. Utility Model Content

[0005] The purpose of this invention is to provide a bulk acoustic resonator that allows for convenient and efficient adjustment of the electromechanical coupling coefficient of the resonator.

[0006] Therefore, this utility model provides a bulk acoustic wave resonator, the bulk acoustic wave resonator comprising: a substrate; a bottom electrode located on the substrate; a piezoelectric layer located on the bottom electrode; a boundary ring located on the piezoelectric layer; a dielectric layer covering the boundary ring; and a top electrode located on the dielectric layer.

[0007] Optionally, in the bulk acoustic resonator, the bulk acoustic resonator further includes a passivation layer located on the top electrode.

[0008] Optionally, in the bulk acoustic resonator, the boundary ring is a ring-shaped structure.

[0009] Optionally, in the bulk acoustic resonator, the projection profile of the boundary ring on the substrate is similar to the projection profile of the overlapping portion of the top electrode and the bottom electrode on the substrate; wherein the projection profile of the boundary ring on the substrate coincides with the projection profile of the overlapping portion of the top electrode and the bottom electrode on the substrate, or is located within the projection profile of the overlapping portion of the top electrode and the bottom electrode on the substrate.

[0010] Optionally, in the bulk acoustic resonator, the dielectric layer is a single-layer structure or a multi-layer stacked structure, and the dielectric layer includes at least one of a silicon oxide layer, a silicon nitride layer, a silicon carbide layer, and a silicon carbide layer.

[0011] Optionally, in the bulk acoustic resonator, the dielectric layer covers the boundary ring and the piezoelectric layer within the inner boundary of the boundary ring; or, the dielectric layer covers the boundary ring and a portion of the piezoelectric layer within the inner boundary of the boundary ring.

[0012] Optionally, in the bulk acoustic resonator, the dielectric layer includes a first portion covering the boundary ring and a second portion covering the piezoelectric layer, wherein the surface of the first portion is higher than the surface of the second portion.

[0013] Optionally, in the bulk acoustic resonator, the boundary ring and the dielectric layer are made of the same material.

[0014] Optionally, in the bulk acoustic resonator, the boundary ring and the bottom electrode are made of the same material layer.

[0015] Optionally, in the bulk acoustic resonator, the substrate includes a substrate and a cavity located in the substrate and facing the bottom electrode; or, the substrate includes a substrate and a back cavity located in the substrate and facing away from the bottom electrode; or, the substrate includes a substrate and a reflective grating located on the substrate, with the bottom electrode located on the reflective grating.

[0016] In the bulk acoustic resonator provided by this utility model, a boundary ring and a dielectric layer are formed between the piezoelectric layer and the top electrode. The introduction of the dielectric layer is equivalent to connecting a parasitic capacitor in series with the resonator. The capacitance value of the parasitic capacitor can be adjusted by controlling the thickness and material of the dielectric layer, thereby realizing the control of the electromechanical coupling coefficient of the resonator.

[0017] The boundary ring can improve the Q value of the bulk acoustic wave resonator. In bulk acoustic wave devices, the acoustic waves excited by the electrical signal propagate vertically within the effective region. Due to diffraction, not only vertically propagating acoustic waves exist in the resonant cavity, but also acoustic waves parallel to the electrode direction, called transverse modes. These transverse modes oscillate and reflect at the resonator's boundaries, leading to energy loss and ultimately a decrease in the resonator's Q value. The boundary ring effectively suppresses the propagation of transverse modes. The principle is that the active region of the resonator has a first acoustic impedance, while the vertical region of the boundary ring has a second acoustic impedance. The greater the difference in acoustic impedance between the two, the stronger the reflection capability of the acoustic waves. Therefore, a portion of the transverse modes can be reflected back to the effective region, thereby reducing energy leakage and improving the Q value.

[0018] The dielectric layer also serves as a physical isolation layer. When the resonator is operating, the load thickness of the piezoelectric layer in the boundary ring region differs from that of the main body of the resonator, leading to the introduction of new resonances. However, the dielectric layer allows the electrodes in the boundary ring region to be separated from the piezoelectric layer by a certain distance, and is not limited by the boundary ring material. This weakens the electric field strength of the piezoelectric layer in the vertical region of the boundary ring, thus significantly reducing the impact of the new resonances on the main resonance. This ensures the achievement of the optimal Q value while reducing the adverse effects of the new resonances on the filter passband. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a bulk acoustic resonator according to an embodiment of the present invention.

[0020] Figure 2 This is another structural schematic diagram of the bulk acoustic resonator according to an embodiment of the present invention.

[0021] Figure 3 This is another structural schematic diagram of the bulk acoustic resonator according to an embodiment of the present invention.

[0022] Figure 4 This is another structural schematic diagram of the bulk acoustic resonator according to an embodiment of the present invention.

[0023] Figure 5 This is another structural schematic diagram of the bulk acoustic resonator according to an embodiment of the present invention.

[0024] Figure 6 This is another structural schematic diagram of the bulk acoustic resonator according to an embodiment of the present invention.

[0025] Figure 7 This is a schematic diagram showing the relationship between the dielectric layer thickness and the electromechanical coupling coefficient of the bulk acoustic resonator in an embodiment of this utility model.

[0026] Figure 8 This is a schematic diagram showing the relationship between the dielectric layer thickness and the resonant frequency Qr of the bulk acoustic resonator according to an embodiment of this utility model.

[0027] Figure 9 This is a schematic diagram showing the relationship between the dielectric layer thickness and the parallel resonant frequency Qa of the bulk acoustic resonator according to an embodiment of this utility model.

[0028] The reference numerals in the attached figures are explained as follows:

[0029] 100 - Bulk acoustic resonator; 110 - Substrate; 111 - Substrate; 112 - Cavity; 120 - Bottom electrode; 130 - Piezoelectric layer; 140 - Boundary ring; 150 - Dielectric layer; 151 - First part; 152 - Second part; 160 - Top electrode; 170 - Passivation layer.

[0030] 200 - Bulk acoustic resonator; 210 - Substrate; 211 - Substrate; 212 - Back cavity; 220 - Bottom electrode; 230 - Piezoelectric layer; 240 - Boundary ring; 250 - Dielectric layer; 260 - Top electrode; 270 - Passivation layer.

[0031] 300 - Bulk acoustic resonator; 310 - Substrate; 311 - Substrate; 312 - Reflection grating; 320 - Bottom electrode; 330 - Piezoelectric layer; 340 - Boundary ring; 350 - Dielectric layer; 360 - Top electrode; 370 - Passivation layer.

[0032] 400 - Bulk acoustic resonator; 410 - Substrate; 420 - Bottom electrode; 430 - Piezoelectric layer; 440 - Boundary ring; 450 - Dielectric layer; 451 - First part; 452 - Second part; 460 - Top electrode; 470 - Passivation layer.

[0033] 500 - Bulk acoustic resonator; 510 - Substrate; 520 - Bottom electrode; 530 - Piezoelectric layer; 540 - Boundary ring; 550 - Dielectric layer; 551 - First part; 552 - Second part; 553 - Opening; 560 - Top electrode; 570 - Passivation layer.

[0034] 600 - Bulk acoustic resonator; 610 - Substrate; 620 - Bottom electrode; 630 - Piezoelectric layer; 640 - Boundary ring; 650 - Dielectric layer; 6501 - First sub-dielectric layer; 6502 - Second sub-dielectric layer; 6503 - Third sub-dielectric layer; 660 - Top electrode; 670 - Passivation layer. Detailed Implementation

[0035] The bulk acoustic resonator proposed in this utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this utility model will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of this utility model.

[0036] The terminology used in this utility model is for the purpose of describing particular embodiments only and is not intended to limit the utility model. Unless otherwise defined in this application, the technical or scientific terms used in this utility model should be understood in their ordinary sense by one of ordinary skill in the art to which this utility model pertains. The words "first," "second," and similar terms used in this utility model specification and claims do not indicate any order, quantity, or importance, but are only used to distinguish different components. Similarly, the words "a" or "one" and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. "A plurality" or "several" indicates two or more. Unless otherwise indicated, the words "upper / upper layer" and / or "lower / lower layer" and similar terms are for ease of description only and are not limited to a location or spatial orientation. The words "comprising" or "including" and similar terms mean that the elements or structures preceding "comprising" or "including" cover the elements or structures listed after "comprising" or "including" and their equivalents, and do not exclude other elements or structures. The words "connected" or "linked" and similar terms are not limited to physical or mechanical connections and can include electrical connections, whether direct or indirect. The singular forms “a,” “the,” and “the” used in this specification and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0037] Please refer to Figure 1 This is a schematic diagram of the structure of a bulk acoustic resonator according to an embodiment of this utility model. Figure 1 As shown, the bulk acoustic resonator 100 includes: a substrate 110; a bottom electrode 120 located on the substrate 110; a piezoelectric layer 130 located on the bottom electrode 120; a boundary ring 140 located on the piezoelectric layer 130; a dielectric layer 150 covering the boundary ring 140; and a top electrode 160 located on the dielectric layer 150.

[0038] The boundary ring 140 and the dielectric layer 150 are formed between the piezoelectric layer 130 and the top electrode 160. The introduction of the dielectric layer 150 is equivalent to connecting a parasitic capacitor in series with the bulk acoustic resonator 100. The capacitance value of this parasitic capacitor can be adjusted by controlling the thickness and material of the dielectric layer 150, thereby controlling the electromechanical coupling coefficient of the resonator. The capacitance value of this parasitic capacitor can be expressed by the formula C = ε₀ε₀. r A / d is calculated, where ε rLet d be the relative permittivity of the dielectric layer 150 and d be the thickness of the dielectric layer. It can be seen that by adjusting the thickness and material of the dielectric layer 150, the capacitance value of the parasitic capacitor can be adjusted, thereby realizing the control of the electromechanical coupling coefficient of the resonator.

[0039] The boundary ring 140 can improve the Q value of the bulk acoustic resonator 100. The dielectric layer 150 can separate the electrodes in the boundary ring 140 region from the piezoelectric layer 130 by a certain distance, which greatly reduces the influence of the new resonance on the main resonance, thus ensuring the achievement of the optimal Q value and reducing the adverse effects of the new resonance on the filter passband.

[0040] like Figure 1 As shown in this embodiment, the substrate 110 includes a substrate 111 and a cavity 112 located in the substrate 111 and facing the bottom electrode 120. The cavity 112 extends from the front side of the substrate 111 into the substrate 111, and the front side of the substrate 111 is the surface of the substrate 111 near the bottom electrode 120. The substrate 111 is made of semiconductor material, such as a silicon substrate. The bottom electrode 120 is located on the substrate 111 and covers the cavity 112.

[0041] In this embodiment, the bottom electrode 120 and the top electrode 160 are made of metal, which may be the same metal or different metals. For example, the materials of the bottom electrode 120 and the top electrode 160 may be gold (Au), tungsten (W), molybdenum (Mo), platinum (Pt), ruthenium (Ru), iridium (Ir), titanium-tungsten (TiW), aluminum (Al), and / or titanium (Ti).

[0042] The piezoelectric layer 130 is made of a polycrystalline piezoelectric material, such as aluminum nitride (AlN), zinc oxide (ZnO), and / or lead zirconate titanate (PZT). The piezoelectric layer 130 can also be made of a rare earth element doped material, such as doped aluminum nitride, which contains at least one rare earth element, such as scandium (Sc), yttrium (Y), magnesium (Mg), and / or titanium (Ti).

[0043] Please continue to refer to this. Figure 1 In this embodiment, the boundary ring 140 is disposed on the piezoelectric layer 130. The boundary ring 140 can be, for example, a ring-shaped structure, meaning that the projection of the boundary ring 140 onto the substrate 110 is annular. The boundary ring 140 covers a portion of the piezoelectric layer 130, exposing both the outer boundary of the piezoelectric layer 130 and the inner boundary of the piezoelectric layer 130. The boundary ring 140 can be formed, for example, by a thin film deposition process and an etching process.

[0044] In some embodiments of this application, the projection profile of the boundary ring 140 on the substrate 110 is similar to the projection profile of the overlapping portion of the top electrode 160 and the bottom electrode 120 on the substrate 110; wherein, the projection profile of the boundary ring 140 on the substrate 110 coincides with the projection profile of the overlapping portion of the top electrode 160 and the bottom electrode 120 on the substrate 110, or is located within the projection profile of the overlapping portion of the top electrode 160 and the bottom electrode 120 on the substrate.

[0045] For example, the projected profile of the boundary ring 140 on the substrate 110 is similar to the projected profile of the overlapping portion of the top electrode 160 and the bottom electrode 120 on the substrate 110, both being similar pentagonal structures, with the boundary ring 140 being a pentagonal ring structure. In some embodiments of this application, the projected profile of the boundary ring 140 on the substrate 110 may completely coincide with the projected profile of the overlapping portion of the top electrode 160 and the bottom electrode 120 on the substrate 110. In other embodiments of this application, the projected profile of the boundary ring 140 on the substrate 110 may partially coincide with the projected profile of the overlapping portion of the top electrode 160 and the bottom electrode 120 on the substrate 110, partially located within the projected profile of the overlapping portion of the top electrode 160 and the bottom electrode 120 on the substrate. In other embodiments of this application, the projected profile of the boundary ring 140 on the substrate 110 may be entirely located within the projected profile of the overlapping portion of the top electrode 160 and the bottom electrode 120 on the substrate.

[0046] The boundary ring 140 can be made of metal or non-metal. For example, in this embodiment, the boundary ring 140 can be made of the same material as the bottom electrode 120, such as gold (Au), tungsten (W), molybdenum (Mo), platinum (Pt), ruthenium (Ru), iridium (Ir), titanium-tungsten (TiW), aluminum (Al), and / or titanium (Ti). Having the boundary ring 140 made of the same material as the bottom electrode 120 and / or the top electrode 160 simplifies the manufacturing process of the bulk acoustic wave resonator 100.

[0047] In this embodiment, the dielectric layer 150 covers the boundary ring 140 and the piezoelectric layer 130 within the inner boundary of the boundary ring 140. The dielectric layer 150 can be a single-layer structure or a multi-layer stacked structure. For example, the dielectric layer 150 may include one sub-dielectric layer or multiple sub-dielectric layers stacked sequentially, and the materials of each sub-dielectric layer may be the same or different. In some embodiments of this application, the dielectric layer 150 may include at least one layer selected from silicon oxide, silicon nitride, silicon carbide, and silicon carbide. For example, in one embodiment of this application, the dielectric layer 150 may be a stacked structure including a silicon oxide layer, a silicon nitride layer, and a silicon oxide layer. The multi-layer stacked structure of the dielectric layer 150 facilitates the adjustment of its thickness and material, thereby enabling better control of the electromechanical coupling coefficient of the resonator.

[0048] like Figure 1 As shown, the dielectric layer 150 conformally covers the boundary ring 140 and the piezoelectric layer 130. The dielectric layer 150 includes a first portion 151 covering the boundary ring 140 and a second portion 152 covering the piezoelectric layer 130, wherein the surface of the first portion 151 is higher than the surface of the second portion 152.

[0049] In this embodiment, the top electrode 160 is located on the dielectric layer 150, and the material of the top electrode 160 can be the same as that of the bottom electrode 120. The bulk acoustic wave resonator 100 may further include a passivation layer 170 located on the top electrode 160. The passivation layer 170 can protect the top electrode 160 to improve the lifespan and reliability of the bulk acoustic wave resonator 100.

[0050] In the bulk acoustic resonator 100 provided in this application embodiment, the electromechanical coupling coefficient of the resonator can be conveniently and efficiently adjusted by controlling the thickness and material of the dielectric layer 150.

[0051] Please refer to Figure 2 This is another structural schematic diagram of the bulk acoustic resonator according to an embodiment of this utility model. Figure 2 As shown, the bulk acoustic wave resonator 200 includes: a substrate 210; a bottom electrode 220 located on the substrate 210; a piezoelectric layer 230 located on the bottom electrode 220; a boundary ring 240 located on the piezoelectric layer 230; a dielectric layer 250 covering the boundary ring 240; and a top electrode 260 located on the dielectric layer 250. The bulk acoustic wave resonator 200 also includes a passivation layer 270 located on the top electrode 260.

[0052] The main difference between the bulk acoustic wave resonator 200 and the bulk acoustic wave resonator 100 is that the structure of the substrate 210 is different from the structure of the substrate 110. For example... Figure 2 As shown in the embodiment of this application, the substrate 210 includes a substrate 211 and a back cavity 212 located in the substrate 211 and facing away from the bottom electrode 220. The back cavity 212 extends from the back side of the substrate 211 into the substrate 211, and the back side of the substrate 211 is the surface of the substrate 211 away from the bottom electrode 220.

[0053] In the bulk acoustic wave resonator 200, a boundary ring 240 and a dielectric layer 250 are formed between the piezoelectric layer 230 and the top electrode 260. The introduction of the dielectric layer 250 is equivalent to adding a parasitic capacitor in series with the bulk acoustic wave resonator 200. The capacitance value of this parasitic capacitor can be adjusted by controlling the thickness and material of the dielectric layer 250, thereby controlling the electromechanical coupling coefficient of the resonator. The boundary ring 240 can improve the Q value of the bulk acoustic wave resonator 200. The dielectric layer 250 can separate the electrode in the boundary ring 240 region from the piezoelectric layer 230 by a certain distance, significantly reducing the influence of new resonances on the main resonance, thus ensuring the achievement of the optimal Q value and reducing the adverse effects of new resonances on the filter passband.

[0054] For any parts of the bulk acoustic resonator 200 not mentioned herein, please refer to the bulk acoustic resonator 100 accordingly. This application will not elaborate further on these aspects.

[0055] Please refer to Figure 3 This is another structural schematic diagram of the bulk acoustic resonator according to an embodiment of this utility model. Figure 3 As shown, the bulk acoustic wave resonator 300 includes: a substrate 310; a bottom electrode 320 located on the substrate 310; a piezoelectric layer 330 located on the bottom electrode 320; a boundary ring 340 located on the piezoelectric layer 330; a dielectric layer 350 covering the boundary ring 340; and a top electrode 360 ​​located on the dielectric layer 350. The bulk acoustic wave resonator 300 also includes a passivation layer 370 located on the top electrode 360.

[0056] The main difference between the bulk acoustic wave resonator 300 and the bulk acoustic wave resonator 100 is that the structure of the substrate 310 is different from that of the substrate 100. For example... Figure 3As shown in this embodiment, the substrate 310 includes a substrate 311 and a reflective gate 312 located on the substrate 311, with the bottom electrode 320 located on the reflective gate 312. The reflective gate 312 may, for example, include periodically alternating high acoustic impedance layers and low acoustic impedance layers. The high acoustic impedance layer may be made of materials such as tungsten (W), molybdenum (Mo), or aluminum nitride (AlN), while the low acoustic impedance layer may include materials such as silicon oxide (SiO2) or aluminum oxide (Al2O3).

[0057] In the bulk acoustic wave resonator 300, a boundary ring 340 and a dielectric layer 350 are formed between the piezoelectric layer 330 and the top electrode 360. The introduction of the dielectric layer 350 is equivalent to adding a parasitic capacitor in series with the bulk acoustic wave resonator 300. The capacitance value of this parasitic capacitor can be adjusted by controlling the thickness and material of the dielectric layer 350, thereby controlling the electromechanical coupling coefficient of the resonator. The boundary ring 340 can improve the Q value of the bulk acoustic wave resonator 300. The dielectric layer 350 can separate the electrode in the boundary ring 340 region from the piezoelectric layer 330 by a certain distance, significantly reducing the influence of new resonances on the main resonance, thus ensuring the achievement of the optimal Q value and reducing the adverse effects of new resonances on the filter passband.

[0058] For any parts of the bulk acoustic resonator 300 not mentioned herein, please refer to the aforementioned bulk acoustic resonator; this application will not elaborate further on these details.

[0059] Please refer to Figure 4 This is another structural schematic diagram of the bulk acoustic resonator according to an embodiment of this utility model. Figure 4 As shown, the bulk acoustic wave resonator 400 includes: a substrate 410; a bottom electrode 420 located on the substrate 410; a piezoelectric layer 430 located on the bottom electrode 420; a boundary ring 440 located on the piezoelectric layer 430; a dielectric layer 450 covering the boundary ring 440; and a top electrode 460 located on the dielectric layer 450. The bulk acoustic wave resonator 400 also includes a passivation layer 470 located on the top electrode 460.

[0060] The main difference between the bulk acoustic wave resonator 400 and the bulk acoustic wave resonator 100 is that, in the bulk acoustic wave resonator 400, the boundary ring 440 is made of a dielectric material, which can be the same as the material of the dielectric layer 450; while in the bulk acoustic wave resonator 100, the boundary ring 140 is made of a metallic material, which can be the same as the material of the bottom electrode 120.

[0061] In the bulk acoustic wave resonator 400, the boundary ring 440 is made of the same material as the dielectric layer 450, which facilitates the formation of the bulk acoustic wave resonator 400. The boundary ring 440 partially covers the piezoelectric layer 430, exposing both the outer boundary of the piezoelectric layer 430 and the inner boundary of the piezoelectric layer 430. The boundary ring 440 can be formed, for example, by thin film deposition and etching processes. The dielectric layer 450 covers the boundary ring 440 and the piezoelectric layer 430 within its inner boundary. The outer boundary of the dielectric layer 450 can be aligned with the outer boundary of the boundary ring 440. The dielectric layer 450 conformally covers the boundary ring 440 and the piezoelectric layer 430. The dielectric layer 450 includes a first portion 451 covering the boundary ring 440 and a second portion 452 covering the piezoelectric layer 430, with the surface of the first portion 451 higher than the surface of the second portion 452.

[0062] In the bulk acoustic wave resonator 400, a boundary ring 440 and a dielectric layer 450 are formed between the piezoelectric layer 430 and the top electrode 460. The introduction of the dielectric layer 450 is equivalent to adding a parasitic capacitor in series with the bulk acoustic wave resonator 400. The capacitance value of this parasitic capacitor can be adjusted by controlling the thickness and material of the dielectric layer 450, thereby controlling the electromechanical coupling coefficient of the resonator. The boundary ring 440 can improve the Q value of the bulk acoustic wave resonator 400. The dielectric layer 450 can separate the electrode in the boundary ring 440 region from the piezoelectric layer 430 by a certain distance, significantly reducing the influence of new resonances on the main resonance, thus ensuring the achievement of the optimal Q value and reducing the adverse effects of new resonances on the filter passband.

[0063] For any parts of the bulk acoustic resonator 400 not mentioned herein, please refer to the aforementioned bulk acoustic resonator; this application will not elaborate further on these details.

[0064] Please refer to Figure 5 This is another structural schematic diagram of the bulk acoustic resonator according to an embodiment of this utility model. Figure 5 As shown, the bulk acoustic wave resonator 500 includes: a substrate 510; a bottom electrode 520 located on the substrate 510; a piezoelectric layer 530 located on the bottom electrode 520; a boundary ring 540 located on the piezoelectric layer 530; a dielectric layer 550 covering the boundary ring 540; and a top electrode 560 located on the dielectric layer 550. The bulk acoustic wave resonator 500 also includes a passivation layer 570 located on the top electrode 560.

[0065] The main difference between the bulk acoustic wave resonator 500 and the bulk acoustic wave resonator 100 is that, in the bulk acoustic wave resonator 500, the dielectric layer 550 covers the boundary ring 540 and a portion of the piezoelectric layer 530 within the inner boundary of the boundary ring 540; while in the bulk acoustic wave resonator 100, the dielectric layer 150 covers the boundary ring 140 and the piezoelectric layer 130 within the inner boundary of the boundary ring 140.

[0066] like Figure 5 As shown, the dielectric layer 550 exposes a portion of the piezoelectric layer 530 within the inner boundary of the boundary ring 540. For example, the dielectric layer 550 can be formed by a thin-film deposition process and an etching process, conformally covering the boundary ring 540 and the piezoelectric layer 530. The dielectric layer 550 includes a first portion 551 covering the boundary ring 540 and a second portion 552 covering the piezoelectric layer 530, with the surface of the first portion 551 higher than the surface of the second portion 552. During the etching process, one or more openings 553 can be formed in the second portion 552, exposing a portion of the piezoelectric layer 530, thereby forming the dielectric layer 550 covering a portion of the piezoelectric layer 530 within the inner boundary of the boundary ring 540. By exposing a portion of the piezoelectric layer 530 within the inner boundary of the boundary ring 540 through the dielectric layer 550, the thickness of the dielectric layer 550 can also be adjusted, thereby enabling the control of the electromechanical coupling coefficient of the resonator.

[0067] Please refer to Figure 6 This is another structural schematic diagram of the bulk acoustic resonator according to an embodiment of this utility model. Figure 6 As shown, the bulk acoustic wave resonator 600 includes: a substrate 610; a bottom electrode 620 located on the substrate 610; a piezoelectric layer 630 located on the bottom electrode 620; a boundary ring 640 located on the piezoelectric layer 630; a dielectric layer 650 covering the boundary ring 640; and a top electrode 660 located on the dielectric layer 650. The bulk acoustic wave resonator 600 also includes a passivation layer 670 located on the top electrode 660.

[0068] The main difference between the bulk acoustic wave resonator 600 and the bulk acoustic wave resonator 100 is that in the bulk acoustic wave resonator 600, the dielectric layer 650 is a multi-layered structure; while in the bulk acoustic wave resonator 100, the dielectric layer 150 is a single-layer structure. Figure 6As shown, the dielectric layer 650 may include, for example, a first sub-dielectric layer 6501, a second sub-dielectric layer 6502, and a third sub-dielectric layer 6503 stacked sequentially. The materials of the first sub-dielectric layer 6501, the second sub-dielectric layer 6502, and the third sub-dielectric layer 6503 may be different or partially the same. The first sub-dielectric layer 6501, the second sub-dielectric layer 6502, and the third sub-dielectric layer 6503 may be silicon oxide, silicon nitride, silicon carbide, and / or silicon carbide, respectively. For example, in one embodiment of this application, the first sub-dielectric layer 6501 may be a silicon oxide layer, the second sub-dielectric layer 6502 may be a silicon nitride layer, and the third sub-dielectric layer 6503 may be a silicon carbide layer; in another embodiment of this application, the first sub-dielectric layer 6501 may be a silicon carbide layer, the second sub-dielectric layer 6502 may be a silicon nitride layer, and the third sub-dielectric layer 6503 may be a silicon carbide layer.

[0069] In the bulk acoustic wave resonator 600, a boundary ring 640 and a dielectric layer 650 are formed between the piezoelectric layer 630 and the top electrode 660. The introduction of the dielectric layer 650 is equivalent to connecting a parasitic capacitor in series with the bulk acoustic wave resonator 600. The capacitance value of this parasitic capacitor can be adjusted by controlling the thickness and material of the dielectric layer 650, thereby controlling the electromechanical coupling coefficient of the resonator. In the bulk acoustic wave resonator 600, the dielectric layer 650 has a multi-layered structure, which allows for better adjustment of the parasitic capacitance value by controlling the thickness and material of the dielectric layer 650, thus achieving efficient and precise adjustment of the electromechanical coupling coefficient of the resonator.

[0070] The boundary ring 640 can improve the Q value of the bulk acoustic resonator 600. The dielectric layer 650 can separate the electrodes in the boundary ring 640 region from the piezoelectric layer 630 by a certain distance, which greatly reduces the influence of the new resonance on the main resonance, thus ensuring the achievement of the optimal Q value and reducing the adverse effects of the new resonance on the filter passband.

[0071] For any parts of the bulk acoustic resonator 600 not mentioned herein, please refer to the aforementioned bulk acoustic resonator; this application will not elaborate further on these details.

[0072] Please refer to Figures 7 to 9 ,in, Figure 7 This is a schematic diagram showing the relationship between the dielectric layer thickness and the electromechanical coupling coefficient of the bulk acoustic resonator in an embodiment of this utility model. Figure 8 This is a schematic diagram showing the relationship between the dielectric layer thickness and the resonant frequency Qr of the bulk acoustic resonator according to an embodiment of this utility model; Figure 9 This is a schematic diagram showing the relationship between the dielectric layer thickness and the parallel resonant frequency Qa of the bulk acoustic resonator according to an embodiment of this utility model. Figures 7 to 9 The solid line in the middle corresponds to a bulk acoustic resonator that can be Figures 1 to 6 Any one of the bulk acoustic wave resonators, for example, it can be bulk acoustic wave resonator 100; Figures 7 to 9 The bulk acoustic wave resonator corresponding to the dashed line can be an existing bulk acoustic wave resonator that does not have a dielectric layer and a boundary ring, such as the bulk acoustic wave resonator 100 with the dielectric layer 150 and the boundary ring 140 removed.

[0073] like Figure 7 As shown, by adjusting the thickness of the dielectric layer 150, the electromechanical coupling coefficient of the bulk acoustic wave resonator 100 in this embodiment can be adjusted between 10.9% and 14.25%, thereby conveniently and efficiently adjusting the electromechanical coupling coefficient of the resonator. In contrast, the electromechanical coupling coefficient of existing bulk acoustic wave resonators is more difficult to adjust and is basically maintained at 12.7%.

[0074] like Figure 8 and Figure 9 As shown, the resonant frequencies Qr and Qa change with the thickness of the dielectric layer 150. However, both are significantly improved compared to the existing resonant frequencies Qr and Qa of bulk acoustic resonators, by at least 80%.

[0075] As can be seen, the bulk acoustic wave resonator provided in this application embodiment conveniently and efficiently realizes the adjustment of the electromechanical coupling coefficient of the resonator, while improving the Q value of the bulk acoustic wave resonator.

[0076] In this application, references to "one embodiment" or "some embodiments" mean that a feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment or at least some embodiments of this application. Therefore, the appearance of the phrases "in one embodiment" or "in some embodiments" throughout this application does not necessarily refer to the same or the same embodiments. Furthermore, in one or more embodiments, features, structures, or characteristics can be combined in any suitable combination and / or sub-combination.

[0077] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and not for limiting the scope of this application. The embodiments of this application can be combined in any way without departing from the spirit and scope of this application. Those skilled in the art should also understand that various modifications can be made to the embodiments without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

Claims

1. A bulk acoustic resonator, characterized in that, The bulk acoustic resonator includes: a substrate; a bottom electrode on the substrate; a piezoelectric layer on the bottom electrode; a boundary ring on the piezoelectric layer; a dielectric layer covering the boundary ring; and a top electrode on the dielectric layer.

2. The bulk acoustic resonator as described in claim 1, characterized in that, The bulk acoustic resonator also includes a passivation layer located on the top electrode.

3. The bulk acoustic resonator as described in claim 2, characterized in that, The boundary ring has a ring-shaped structure.

4. The bulk acoustic resonator as described in claim 3, characterized in that, The projection profile of the boundary ring on the substrate is similar to the projection profile of the overlapping portion of the top electrode and the bottom electrode on the substrate; wherein the projection profile of the boundary ring on the substrate coincides with the projection profile of the overlapping portion of the top electrode and the bottom electrode on the substrate, or is located within the projection profile of the overlapping portion of the top electrode and the bottom electrode on the substrate.

5. The bulk acoustic resonator as described in any one of claims 1 to 4, characterized in that, The dielectric layer is a single-layer structure or a multi-layer stacked structure, and the dielectric layer includes at least one of a silicon oxide layer, a silicon nitride layer, a silicon carbide layer, and a silicon carbide layer.

6. The bulk acoustic resonator as described in any one of claims 1 to 4, characterized in that, The dielectric layer covers the boundary ring and the piezoelectric layer within the inner boundary of the boundary ring; or, the dielectric layer covers the boundary ring and a portion of the piezoelectric layer within the inner boundary of the boundary ring.

7. The bulk acoustic resonator as described in claim 6, characterized in that, The dielectric layer includes a first portion covering the boundary ring and a second portion covering the piezoelectric layer, wherein the surface of the first portion is higher than the surface of the second portion.

8. The bulk acoustic resonator as described in any one of claims 1 to 4, characterized in that, The boundary ring and the dielectric layer are made of the same material.

9. The bulk acoustic resonator as described in any one of claims 1 to 4, characterized in that, The boundary ring and the bottom electrode are made of the same material layer.

10. The bulk acoustic resonator according to any one of claims 1 to 4, characterized in that, The substrate includes a substrate and a cavity located in the substrate and facing the bottom electrode; or, the substrate includes a substrate and a back cavity located in the substrate and facing away from the bottom electrode; or, the substrate includes a substrate and a reflective grating located on the substrate, with the bottom electrode located on the reflective grating.

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