A thin-film bulk acoustic resonator with a multi-frame structure
By setting multi-layer frame units at the edges of the top and bottom electrodes of the thin-film bulk acoustic resonator to form a multi-layer acoustic impedance interface, and using the acoustic Bragg reflection principle to suppress Lamb wave leakage, the problems of energy loss and low frequency quality factor of traditional thin-film bulk acoustic resonators are solved, and the stability and performance of high-frequency filters are improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI UNIV
- Filing Date
- 2026-05-12
- Publication Date
- 2026-07-31
AI Technical Summary
Traditional thin-film bulk acoustic resonators are prone to Lamb wave transverse acoustic leakage during operation, which leads to increased energy loss and reduced anti-resonance frequency quality factor, failing to meet the technical requirements of 5G communication high-frequency filters.
A thin-film bulk acoustic resonator with a multi-frame structure forms a multi-layer acoustic impedance mismatch interface by setting multiple frame units at the edges of the top and bottom electrodes. It uses the acoustic Bragg reflection principle to directionally reflect Lamb waves and suppress transverse acoustic leakage and stray modes.
It significantly improves the quality factor of the anti-resonance frequency, reduces energy loss, and enhances the stability of device operation, making it suitable for high-frequency filters in 5G communication.
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Figure CN122496002A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of radio frequency resonator technology, and specifically relates to a thin-film bulk acoustic resonator with a multi-frame structure. Background Technology
[0002] Radio frequency (RF) filters are core components for signal filtering in mobile communication terminals. Miniaturized mobile terminals commonly use acoustic filters to meet the requirements of low power consumption and small size. Acoustic filters are mainly divided into surface acoustic wave (SAW) filters and bulk acoustic wave (BAW) filters. SAW filters have mature technology and low cost, but are only suitable for low-frequency filtering scenarios below 2GHz. BAW filters have low insertion loss and excellent high-frequency response, making them suitable for the high-frequency filtering requirements of 5G communication and the core choice for current RF front-ends.
[0003] Thin-film bulk acoustic wave (BAS) resonators are the core components of BAS filters. Traditional BAS resonators consist of a piezoelectric layer and upper and lower electrodes. An alternating electric field excites the piezoelectric layer to complete electromechanical energy conversion. Standing wave oscillations are formed when the thickness of the piezoelectric layer is an odd multiple of the half-wavelength of the bulk acoustic wave. However, during operation, traditional BAS resonators are prone to Lamb wave transverse acoustic wave leakage at the resonator edges. This leads to increased energy loss, a decreased quality factor at the anti-resonance frequency, and the induction of stray modes, significantly reducing the filter's operational stability and filtering performance.
[0004] However, existing technologies have the following shortcomings: some thin-film bulk acoustic resonators use a single-sided single-frame structure to try to suppress acoustic leakage. Such structures can only form a local acoustic impedance interface, do not optimize the frame size based on the Lamb wave mode wavelength, and do not adopt a coordinated layout of upper and lower electrodes with double-sided frames. The acoustic leakage suppression effect is limited and cannot meet the technical requirements of 5G high-frequency filtering for high Q value and low loss.
[0005] Therefore, a new device is urgently needed. Summary of the Invention
[0006] The purpose of this invention is to provide a thin-film bulk acoustic resonator with a multi-frame structure. This device forms a multi-layer acoustic impedance mismatch interface through the acoustic Bragg reflection principle, directionally reflects Lamb waves, suppresses transverse acoustic leakage and stray modes, effectively improves the anti-resonance frequency quality factor, reduces energy loss, and has excellent high-frequency performance, making it suitable for use in 5G communication high-frequency filters.
[0007] To achieve the above objectives, the present invention provides a thin-film bulk acoustic resonator with a multi-frame structure, comprising: A piezoelectric layer composed of a single-layer piezoelectric thin film; A top electrode is attached to the upper surface of the piezoelectric layer; A top-side multi-frame structure is attached to the edge of the upper surface of the top electrode. The top-side multi-frame structure includes at least one frame unit, and the frame units are arranged at intervals. The bottom electrode is attached to the lower surface of the piezoelectric layer.
[0008] Preferably, it also includes a bottom-side multi-frame structure; the bottom-side multi-frame structure is fitted onto the lower surface edge of the bottom electrode, and the bottom-side multi-frame structure includes at least one frame unit, with each frame unit arranged at intervals.
[0009] Preferably, both the top-side multi-frame structure and the bottom-side multi-frame structure are composed of frame units of the same size; the top-side multi-frame structure is evenly spaced from the edge of the top electrode to the center, and the bottom-side multi-frame structure is evenly spaced from the edge of the bottom electrode to the center, and the bottom-side multi-frame structure and the top-side multi-frame structure are symmetrically aligned vertically.
[0010] Preferably, the top-side multi-frame structure is composed of alternating arrangement of first frame units and second frame units; the bottom-side multi-frame structure is composed of alternating arrangement of third frame units and fourth frame units; the size of the third frame unit is the same as that of the first frame unit, and the size of the fourth frame unit is the same as that of the second frame unit.
[0011] Preferably, the width of the frame unit is 0.01μm to 10μm.
[0012] Preferably, the height of the frame unit is 10nm~2000nm.
[0013] Preferably, the piezoelectric layer is a piezoelectric thin film material, such as zinc oxide (ZnO), aluminum nitride (AlN) with or without rare earth elements, lead zirconate titanate (PZT), barium strontium titanate (BST), etc. In this embodiment of the invention, aluminum nitride is used as a specific implementation.
[0014] Preferably, the materials of the top electrode, bottom electrode, top-side multi-frame structure, and bottom-side multi-frame structure can be one or more alloys of molybdenum (Mo), aluminum (Al), tungsten (W), platinum (Pt), magnesium (Mg), gold (Au), silver (Ag), chromium (Cr), titanium (Ti), or copper (Cu). In this embodiment of the invention, platinum is used as a specific implementation.
[0015] Therefore, the present invention employs a thin-film bulk acoustic resonator with a multi-frame structure as described above. Compared with the prior art, the technical solution of the present invention has the following beneficial effects: (1) The double-sided multi-frame collaborative reflection of the upper and lower electrodes greatly improves the anti-resonance frequency quality factor, and continues to optimize as the number of frames increases. (2) Optimize the frame size based on Lamb wave wavelength to block lateral leakage from the source of sound wave propagation path and reduce device energy loss; (3) The multi-layered frame forms a multi-level acoustic impedance barrier, which suppresses stray oscillations and improves the working stability of the device; (4) It is compatible with existing micro-nano fabrication processes and can be directly applied to 5G communication high-frequency filters.
[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0017] Figure 1 This is a schematic cross-sectional view of a thin-film bulk acoustic resonator with a multi-frame structure according to an embodiment of the present invention. Figure 2 This is an example of an embodiment of a thin-film bulk acoustic resonator with a multi-frame structure according to the present invention, showing impedance curves and anti-resonance quality factor Qa for different numbers of frames; wherein, Figure 2 (a) in the figure shows the impedance curves as the number of frames n changes. Figure 2 (b) in the figure shows the relationship between the anti-resonance quality factor Qa and the number of frames n; Figure 3 This is a schematic cross-sectional view of a thin-film bulk acoustic resonator with a multi-frame structure according to a second embodiment of the present invention. Figure 4 This is an example of an embodiment of a thin-film bulk acoustic resonator with a multi-frame structure according to the present invention, showing impedance curves and anti-resonance quality factor Qa for different numbers of frames; wherein, Figure 4 (a) in the figure shows the impedance curves as the number of frames n changes. Figure 4 (b) in the figure shows the relationship between the anti-resonance quality factor Qa and the number of frames n.
[0018] Figure 5 This is a schematic cross-sectional view of a thin-film bulk acoustic resonator with a multi-frame structure according to Embodiment 3 of the present invention. Figure 6 This is an example of an embodiment of a thin-film bulk acoustic resonator with a multi-frame structure according to the present invention, showing impedance curves and anti-resonance quality factor Qa for different numbers of frames; wherein, Figure 6 (a) in the figure shows the impedance curves as the number of frames n changes. Figure 6 (b) in the figure shows the relationship between the anti-resonance quality factor Qa and the number of frames n.
[0019] Figure 7 This is a schematic cross-sectional view of a thin-film bulk acoustic resonator with a multi-frame structure according to Embodiment 4 of the present invention. Figure 8This is an example of an embodiment four of a thin-film bulk acoustic resonator with a multi-frame structure, showing impedance curves and anti-resonance quality factor Qa for different numbers of frames; wherein, Figure 8 (a) in the figure shows the impedance curves as the number of frames n changes. Figure 8 (b) in the figure shows the relationship between the anti-resonance quality factor Qa and the number of frames n.
[0020] Figure Labels 101. First frame unit; 102. Second frame unit; 103. Third frame unit; 104. Fourth frame unit; 200. Top electrode; 300. Piezoelectric layer; 400. Bottom electrode. Detailed Implementation
[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used in the present invention should have the ordinary meaning understood by those skilled in the art.
[0022] In this invention, the top electrode, bottom electrode, and frame unit can be made of one or more alloys of molybdenum (Mo), aluminum (Al), tungsten (W), platinum (Pt), magnesium (Mg), gold (Au), silver (Ag), chromium (Cr), titanium (Ti), or copper (Cu). The following embodiments use platinum as the material for specific implementation.
[0023] The piezoelectric layer is a piezoelectric thin film material, which can be selected from conventional piezoelectric materials such as zinc oxide (ZnO), undoped or doped aluminum nitride (AlN), lead zirconate titanate (PZT), barium strontium titanate (BST), etc. The following embodiments use aluminum nitride as the specific implementation material.
[0024] Example 1 like Figure 1 As shown, this embodiment provides a multi-frame structure thin-film bulk acoustic resonator, which includes a piezoelectric layer 300, a top electrode 200, a first frame unit 101, and a bottom electrode 400.
[0025] The top electrode 200 is attached to the upper surface of the piezoelectric layer 300, and the bottom electrode 400 is attached to the lower surface of the piezoelectric layer 300. The top electrode 200 and the bottom electrode 400 are aligned vertically, which makes a uniform vertical electric field form inside the piezoelectric layer 300, ensuring stable and distortion-free electromechanical energy conversion.
[0026] The first frame unit 101 is attached to the edge region of the upper surface of the top electrode 200, without covering the effective oscillation region of the resonator center, thus avoiding interference with the main standing wave oscillation. The first frame unit 101 is composed of frame units of the same size, evenly spaced from the edge of the top electrode 200 to the center, with adjacent frame units maintaining a fixed spacing. This multi-layered spacing structure forms a continuous acoustic Bragg reflection interface, realizing the stepwise reflection of the Lamb wave. The number of frame units is n, and n≥1.
[0027] In this embodiment, the piezoelectric layer 300 is made of aluminum nitride and has a thickness of 1.0 μm; the top electrode 200 and the bottom electrode 400 are both made of platinum and have a thickness of 0.1 μm; the first frame unit 101 is made of platinum and has a width of 2.8 μm and a height of 0.1 μm, with the dimensions optimized according to the Lamb wave mode wavelength.
[0028] During operation, an alternating electric field signal is applied to the top electrode 200 and the bottom electrode 400. The piezoelectric layer 300 completes the conversion of electrical energy and mechanical energy and excites bulk acoustic waves. When the bulk acoustic waves propagate to the edge of the resonator, the first frame unit 101 in the edge region is tightly attached to the top electrode 200 to form a stable acoustic impedance interface, and the Lamb wave is reflected in a directional manner through the acoustic Bragg reflection principle. The position setting of the edge layout and the spacing arrangement blocks the transverse acoustic wave leakage from the source of the propagation path, reduces the energy loss of the device, and effectively improves the anti-resonance frequency quality factor Qa.
[0029] like Figure 2 As shown, in this embodiment, the width of the first frame unit 101 is 2.8 μm and the height is 0.1 μm. The impedance curve and Qa relationship curve of the frame number n changing in the range of 1 to 6 were measured. The test results show that the resonator using the frame structure of the present invention has a higher Qa value than the traditional frameless resonator, and the Qa value increases with the increase of the frame number n.
[0030] Example 2 like Figure 3 As shown, in this embodiment, based on embodiment one, a third frame unit 103 is attached to the lower surface edge of the bottom electrode 400. The third frame unit 103 is located in the transition area from the edge to the center of the bottom electrode 400, and is symmetrically aligned with the first frame unit 101 on one side of the top electrode 200. The third frame unit 103 is composed of frame units of the same size that are evenly spaced from the edge of the bottom electrode 400 to the center. The number, size and spacing of the frame units are the same as those of the first frame unit 101. The parameters of the upper and lower frame units are matched and their positions correspond to form a cooperative reflection structure, eliminating the blind zone of sound wave leakage.
[0031] During operation, the first frame unit 101 and the third frame unit 103 are symmetrically attached to each other, forming an acoustic impedance barrier simultaneously. The double-sided edge alignment interception position realizes bidirectional reflection of Lamb waves. Compared with the single-sided frame structure, it further suppresses transverse acoustic wave leakage, reduces device energy loss, and improves the device Qa value.
[0032] like Figure 4 As shown, in this embodiment, the width of the first frame unit 101 and the height of the third frame unit 103 are both 2.8 μm and 0.1 μm respectively. The impedance curves and Qa relationship curves were measured when the number of frames n varied from 1 to 6. The test results show that the double-sided frame structure has a better effect on improving the Qa value than the single-sided frame structure and the frameless traditional resonator.
[0033] Example 3 like Figure 5 As shown, in this embodiment, a first frame unit 101 and a second frame unit 102 are attached to the edge of the upper surface of the top electrode 200. The two types of frame units are arranged alternately and evenly, with one first frame unit 101 and one second frame unit 102 forming a group, and the number of frame groups is n, n≥1. The two types of frame units are arranged in adjacent positions to form a multi-level acoustic impedance interface of different widths, covering the Lamb wave multimode wavelength and avoiding the reflection blind zone of a single-size frame.
[0034] In this embodiment, the first frame unit 101 has a width of 2.8 μm and a height of 0.1 μm, and the second frame unit 102 has a width of 5.1 μm and a height of 0.1 μm. Both frame sizes are optimized according to the different mode wavelengths of the Lamb wave.
[0035] During operation, frames of different widths are alternately attached to the edge area of the top electrode 200 to form a multi-level acoustic impedance interface. The alternating arrangement of positions enables the step-by-step reflection of Lamb waves of different wavelengths, effectively suppressing stray modes and transverse acoustic wave leakage, and improving the Qa value of the device.
[0036] like Figure 6 As shown, the Qa value of the dual-size alternating frame structure is higher than that of the frameless conventional resonator.
[0037] Example 4 like Figure 7As shown, in this embodiment, based on embodiment three, a third frame unit 103 and a fourth frame unit 104 are attached to the lower surface edge of the bottom electrode 400. The size of the third frame unit 103 is the same as that of the first frame unit 101, and the size of the fourth frame unit 104 is the same as that of the second frame unit 102. The two types of frame units on one side of the bottom electrode 400 are arranged alternately and evenly, and the number of frame groups is consistent with that on the top electrode 200 side. The top double frame and the bottom double frame are arranged in a one-to-one correspondence and alternating alignment, forming a multi-layer acoustic Bragg reflection system with alternating frames of two sizes on both sides, which fully surrounds and covers the entire edge sound wave propagation path of the resonator.
[0038] During operation, the first frame unit 101, the second frame unit 102, the third frame unit 103, and the fourth frame unit 104 are aligned and alternately attached. The coordinated setting of the alternating frames on both sides completely blocks the transverse acoustic wave leakage of Lamb wave, minimizes the energy loss of the device, and maximizes the Qa value.
[0039] like Figure 8 As shown, the Qa value of the structure in this embodiment reaches the optimal level, which is significantly higher than that of traditional resonators and other frame structures.
[0040] Therefore, the present invention adopts a thin-film bulk acoustic resonator with a multi-frame structure as described above. This device forms a multi-layer acoustic impedance mismatch interface through the acoustic Bragg reflection principle, directionally reflects Lamb waves, suppresses transverse acoustic leakage and stray modes, effectively improves the anti-resonance frequency quality factor, reduces energy loss, has excellent high-frequency performance, and is suitable for use in 5G communication high-frequency filters.
[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. A film bulk acoustic resonator having a multi- frame structure, characterized by, include: A piezoelectric layer composed of a single-layer piezoelectric thin film; A top electrode is attached to the upper surface of the piezoelectric layer; A top-side multi-frame structure is attached to the edge of the upper surface of the top electrode. The top-side multi-frame structure includes at least one frame unit, and the frame units are arranged at intervals. The bottom electrode is attached to the lower surface of the piezoelectric layer.
2. The film bulk acoustic resonator with multi-frame structure according to claim 1, wherein, It also includes a bottom-side multi-frame structure; the bottom-side multi-frame structure is attached to the lower surface edge of the bottom electrode, and the bottom-side multi-frame structure includes at least one frame unit, with each frame unit arranged at intervals.
3. The film bulk acoustic resonator with multi-frame structure according to claim 2, wherein, Both the top and bottom multi-frame structures are composed of frame units of the same size. The top multi-frame structure is evenly spaced from the edge of the top electrode to the center, and the bottom multi-frame structure is evenly spaced from the edge of the bottom electrode to the center. The bottom multi-frame structure and the top multi-frame structure are symmetrically aligned vertically.
4. The film bulk acoustic resonator with multi-frame structure of claim 2, wherein, The top-side multi-frame structure is composed of alternating arrangement of first and second frame units; the bottom-side multi-frame structure is composed of alternating arrangement of third and fourth frame units; the size of the third frame unit is the same as that of the first frame unit, and the size of the fourth frame unit is the same as that of the second frame unit.
5. The film bulk acoustic resonator with multi-frame structure of claim 1, wherein, The width of the frame unit is 0.01μm to 10μm.
6. The film bulk acoustic resonator with multi-frame structure of claim 1, wherein, The height of the frame unit is 10nm~2000nm.
7. A thin-film bulk acoustic resonator with a multi-frame structure according to claim 1, characterized in that, The piezoelectric layer is made of aluminum nitride.
8. A thin-film bulk acoustic resonator with a multi-frame structure according to claim 1, characterized in that, The top electrode, bottom electrode, top-side multi-frame structure, and bottom-side multi-frame structure are all made of platinum.