Acoustic resonator and method of making the same
By combining an unpatterned first piezoelectric layer and a patterned second piezoelectric layer with an interdigitated electrode design, multiple acoustic waves are excited, solving the problem of acoustic resonators in terms of large bandwidth and high electromechanical coupling coefficient. This achieves a simplified process and high-performance acoustic resonator that meets the requirements of 5G/6G frequency bands.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- UNIV OF SCI & TECH OF CHINA
- Filing Date
- 2024-12-20
- Publication Date
- 2026-06-23
AI Technical Summary
Existing acoustic resonators exhibit fatigue in the context of large bandwidths. Traditional fabrication methods are complex and difficult to achieve high electromechanical coupling coefficients, thus failing to meet the requirements of 5G/6G frequency bands.
By employing an unpatterned first piezoelectric layer and a patterned second piezoelectric layer, combined with the design of interdigitated electrodes, multiple acoustic waves are excited under the action of a longitudinal electric field, achieving a high electromechanical coupling coefficient, avoiding the bottom electrode, and simplifying the process.
The quality factor and energy conversion efficiency of the acoustic resonator were improved, a high electromechanical coupling coefficient was achieved, the performance requirements of the 5G/6G frequency band were met, and the fabrication process was simplified.
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Figure CN119813984B_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of resonator technology, and more specifically, to an acoustic resonator and its fabrication method. Background Technology
[0002] With the advent of the 5G / 6G era, the rapid development of the Internet of Things and artificial intelligence has placed higher demands on data transmission capacity. In the field of mobile communications, traditional operating frequency bands are mainly concentrated below 3GHz, resulting in very congested spectrum resources. To alleviate this problem, high-frequency bands such as millimeter wave and centimeter wave bands provide abundant available spectrum resources, effectively supporting the capacity and transmission rate requirements of 5G.
[0003] Electromechanical coupling coefficient (k) 2 As a crucial indicator of filter and resonator performance, a high electromechanical coupling coefficient ensures that filters and resonators have a sufficiently large passband bandwidth, enabling the transmission of larger amounts of data. Therefore, achieving resonators with high electromechanical coupling coefficients in 5G / 6G is key to realizing wideband filters and resonators.
[0004] Currently, acoustic resonators have become one of the most popular components in radio frequency resonators due to their advantages such as small size, high frequency, low insertion loss, and large bandwidth. However, acoustic resonators based on traditional surface acoustic waves (SAW) or film bulk acoustic resonators (FBAR) cannot achieve significant breakthroughs in relative bandwidth, resulting in a noticeable decline in their performance regarding large bandwidth. Related technologies typically achieve high electromechanical coupling coefficients through methods such as modal coupling, doping, and polarization-reversed piezoelectric thin film stacking. However, these methods suffer from complex fabrication processes and strict requirements on the size / linewidth of the metal electrodes, hindering large-scale application. Therefore, improving the performance of acoustic resonators is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention
[0005] In view of this, the present disclosure provides an acoustic resonator and a method for its fabrication.
[0006] According to one aspect of this disclosure, an acoustic resonator is provided, comprising: a substrate; a first piezoelectric layer disposed on the substrate for coupling multiple acoustic waves, wherein the first piezoelectric layer is not patterned; a second piezoelectric layer comprising: at least two piezoelectric structures disposed on the first piezoelectric layer, the at least two piezoelectric structures being used to excite the multiple acoustic waves under the action of a longitudinal electric field, wherein the second piezoelectric layer is patterned; and at least two interdigitated electrodes disposed on the second piezoelectric layer, the at least two interdigitated electrodes being used to form the longitudinal electric field, wherein the positions of the at least two interdigitated electrodes correspond one-to-one with the positions of the at least two piezoelectric structures.
[0007] For example, the chamfer formed between the side edge of the second piezoelectric layer and the first piezoelectric layer is greater than 0° and less than or equal to 90°.
[0008] For example, the thickness of the first piezoelectric layer is 1 nm - 2000 nm; the thickness of the second piezoelectric layer is 1 nm - 4000 nm.
[0009] For example, the linewidth of the interdigitated electrodes is 10 nm - 100 μm; the spacing between two adjacent interdigitated electrodes is 10 nm - 100 μm; and the number of interdigitated electrodes is 2 - 1000.
[0010] The thickness of the interdigitated electrodes is 1 nm - 10 μm.
[0011] For example, the first piezoelectric layer is bonded to the substrate.
[0012] For example, there is a cavity between the first piezoelectric layer and the substrate.
[0013] For example, the substrate may include a groove or the first piezoelectric layer may include a groove, the groove being used to realize the cavity.
[0014] For example, the materials of the interdigitated electrodes are gold, silver, copper, aluminum, molybdenum, chromium, nickel, platinum, titanium gold, titanium aluminum, chromium gold, chromium aluminum, or an alloy composed of titanium gold, titanium aluminum, titanium copper, chromium gold, chromium aluminum, and chromium copper; the materials of each of the first and second piezoelectric layers are lithium niobate, lithium tantalate, aluminum nitride, scandium aluminum nitride, or a composite layer formed by at least two of the following: lithium niobate, aluminum nitride, scandium-doped aluminum nitride, lithium tantalate, and zinc oxide.
[0015] For example, the acoustic resonator includes a first temperature compensation layer disposed on the top layer of the acoustic resonator; and / or the acoustic resonator includes a second temperature compensation layer disposed between the substrate and the first piezoelectric layer.
[0016] According to another aspect of this disclosure, a method for fabricating the aforementioned acoustic resonator is provided, comprising: forming a first piezoelectric layer on a substrate, wherein the first piezoelectric layer is not patterned; forming a second piezoelectric layer on the first piezoelectric layer, wherein the second piezoelectric layer is patterned and includes at least two piezoelectric structures; forming at least two interdigitated electrodes on the second piezoelectric layer to obtain an acoustic resonator, wherein the positions of the at least two interdigitated electrodes correspond one-to-one with the positions of the at least two piezoelectric structures.
[0017] According to embodiments of this disclosure, the second piezoelectric layer in the acoustic resonator includes at least two piezoelectric structures disposed on the first piezoelectric layer. These at least two piezoelectric structures are used to excite multiple sound waves under a longitudinal electric field. At least two interdigitated electrodes are disposed on the second piezoelectric layer and are used to form a longitudinal electric field. The technique of one-to-one correspondence between the at least two interdigitated electrodes and the at least two piezoelectric structures, compared to traditional acoustic resonators capable of exciting a longitudinal electric field, can achieve an effect similar to generating a longitudinal electric field by adding a bottom electrode to the bottom surface of the piezoelectric material without adding a bottom electrode, thereby achieving a high electromechanical coupling coefficient. Furthermore, since there is no bottom electrode and no transfer bonding process is required, the process is simple. Moreover, growing the second piezoelectric layer on the unpatterned first piezoelectric layer results in a higher quality second piezoelectric layer compared to growing it on a bottom electrode, improving the quality factor of the acoustic resonator and enhancing its performance. Coupling multiple sound waves using an unpatterned first piezoelectric layer can enhance the sound waves, improve energy conversion efficiency, and help to further improve the electromechanical coupling coefficient. Attached Figure Description
[0018] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:
[0019] Figure 1 A schematic cross-sectional view of an acoustic resonator according to an embodiment of the present disclosure is shown.
[0020] Figure 2A An admittance response diagram of an acoustic resonator according to an embodiment of the present disclosure is schematically shown;
[0021] Figure 2B A schematic diagram illustrating a three-dimensional simulated vibration displacement of an acoustic resonator according to an embodiment of the present disclosure is shown.
[0022] Figure 3 An admittance response diagram of an acoustic resonator according to another embodiment of the present disclosure is schematically shown;
[0023] Figure 4AAn admittance response diagram of an acoustic resonator according to another embodiment of the present disclosure is schematically shown;
[0024] Figure 4B A schematic diagram illustrating a three-dimensional simulated vibration displacement of an acoustic resonator according to another embodiment of the present disclosure is shown.
[0025] Figure 5 An admittance response diagram of an acoustic resonator according to another embodiment of the present disclosure is schematically shown;
[0026] Figure 6A A schematic cross-sectional view of an acoustic resonator according to another embodiment of the present disclosure is shown.
[0027] Figure 6B A schematic diagram illustrating the chamfer formed between the side edge of the second piezoelectric layer and the first piezoelectric layer according to an embodiment of the present disclosure;
[0028] Figure 7 An admittance response diagram of an acoustic resonator according to another embodiment of the present disclosure is schematically shown;
[0029] Figure 8 A schematic cross-sectional view of an acoustic resonator according to another embodiment of the present disclosure is shown.
[0030] Figure 9 A schematic cross-sectional view of an acoustic resonator according to another embodiment of the present disclosure is shown.
[0031] Figure 10 A schematic cross-sectional view of an acoustic resonator according to another embodiment of the present disclosure is shown.
[0032] Figure 11 A schematic cross-sectional view of an acoustic resonator according to another embodiment of the present disclosure is shown.
[0033] Figure 12 A schematic diagram illustrating a method for fabricating an acoustic resonator according to an embodiment of the present disclosure is shown. Detailed Implementation
[0034] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.
[0035] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.
[0036] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.
[0037] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).
[0038] Currently, acoustic resonators have gained widespread attention in the radio frequency industry due to their advantages such as small size, high frequency, low insertion loss, and large bandwidth. However, as the frequency of acoustic resonators continues to increase, the system's requirements for large bandwidth are also increasing. For example, the relative bandwidth (FBW, fractional band-width) required by the 5G NR (5th Generation New Radio) band exceeds 24% (n77 band, 3.3 GHz - 4.2 GHz). This necessitates a higher electromechanical coupling coefficient (k) in the acoustic resonator. 2 (Reaching 50%)
[0039] Traditional acoustic resonators capable of achieving high electromechanical coupling coefficients require a bottom electrode to excite the longitudinal electric field. For example, a traditional thin-film bulk acoustic resonator (FBAR) consists of a substrate, a bottom electrode, a piezoelectric layer, and a top electrode, from bottom to top. Adding a bottom electrode to an FBAR presents several problems: directly growing piezoelectric material on the bottom electrode can affect the growth quality of the piezoelectric material, thus reducing the resonator's quality factor; growing the bottom electrode on the substrate using transfer bonding increases process complexity, makes patterning difficult, and increases bonding difficulty. FBARs primarily change their resonant frequency by adjusting the size / linewidth of the metal electrode, placing strict requirements on the size / linewidth of the metal electrode.
[0040] Therefore, how to improve the performance of acoustic resonators is a problem that urgently needs to be solved by those skilled in the art.
[0041] In view of this, the embodiments of this disclosure provide an acoustic resonator and a method for fabricating the same, which can be applied to the field of resonator technology.
[0042] Figure 1 A schematic cross-sectional view of an acoustic resonator according to an embodiment of the present disclosure is shown.
[0043] like Figure 1 As shown, the acoustic resonator 100 may include a substrate 110, a first piezoelectric layer 120, a second piezoelectric layer, and at least two interdigitated electrodes 140.
[0044] The first piezoelectric layer 120 can be disposed on the substrate 110. The first piezoelectric layer 120 is used to couple multiple acoustic waves. The first piezoelectric layer 120 is not patterned, that is, the first piezoelectric layer 120 is not subjected to photolithography or etching.
[0045] The second piezoelectric layer may include at least two piezoelectric structures 131. The at least two piezoelectric structures 131 may be disposed on the first piezoelectric layer 120. The at least two piezoelectric structures 131 can be used to excite multiple sound waves under the action of a longitudinal electric field. The second piezoelectric layer has been patterned, i.e., it has undergone photolithography or etching processes to form at least two piezoelectric structures 131 on the second piezoelectric layer. Each of the at least two piezoelectric structures 131 corresponds one-to-one with a plurality of sound waves. Ideally, the plurality of sound waves have the same frequency.
[0046] The thickness of at least two piezoelectric structures 131 may be the same or different. The width of at least two piezoelectric structures 131 may be the same or different. The materials of at least two piezoelectric structures 131 may be the same or different.
[0047] At least two interdigitated electrodes 140 may be disposed on the second piezoelectric layer. The at least two interdigitated electrodes 140 may be used to form a longitudinal electric field. The positions of the at least two interdigitated electrodes 140 correspond one-to-one with the positions of the at least two piezoelectric structures 131.
[0048] The width of the interdigitated electrode 140 can be the same as or different from the width of the corresponding piezoelectric structure 131.
[0049] According to embodiments of this disclosure, the second piezoelectric layer in the acoustic resonator includes at least two piezoelectric structures disposed on the first piezoelectric layer. These at least two piezoelectric structures are used to excite multiple sound waves under a longitudinal electric field. At least two interdigitated electrodes are disposed on the second piezoelectric layer and are used to form a longitudinal electric field. The technique of one-to-one correspondence between the at least two interdigitated electrodes and the at least two piezoelectric structures, compared to traditional acoustic resonators capable of exciting a longitudinal electric field, can achieve an effect similar to generating a longitudinal electric field by adding a bottom electrode to the bottom surface of the piezoelectric material without adding a bottom electrode, thereby achieving a high electromechanical coupling coefficient. Furthermore, since there is no bottom electrode and no transfer bonding process is required, the process is simple. Moreover, growing the second piezoelectric layer on the unpatterned first piezoelectric layer results in a higher quality second piezoelectric layer compared to growing it on a bottom electrode, improving the quality factor of the acoustic resonator and enhancing its performance. Coupling multiple sound waves using an unpatterned first piezoelectric layer can enhance the sound waves, improve energy conversion efficiency, and help to further improve the electromechanical coupling coefficient.
[0050] According to embodiments of this disclosure, the acoustic resonator 100 can excite an electron with a piezoelectric coefficient of e 3X Sound waves of (x=,1,2,3…6), including but not limited to bulk sound waves and shear sound waves.
[0051] According to embodiments of this disclosure, the resonant frequency of the acoustic resonator 100 can be adjusted simply by changing the thickness of the second piezoelectric layer, or simply by changing the size / linewidth of the interdigitated electrodes, or by changing both the thickness of the second piezoelectric layer and the size / linewidth of the interdigitated electrodes.
[0052] The chamfer formed between the side edge of the second piezoelectric layer and the first piezoelectric layer is greater than 0° and less than or equal to 90°.
[0053] For example, the chamfer formed between the side edge of each piezoelectric structure 131 of the second piezoelectric layer and the first piezoelectric layer 120 is greater than 0° and less than or equal to 0°. Furthermore, at least two piezoelectric structures 131 have the same chamfer formed between their side edges and the first piezoelectric layer 120.
[0054] For example, the chamfer can be 20°, 25°, 30°, 45°, 50°, 60°, 75°, 80° or 90°.
[0055] According to embodiments of this disclosure, since the chamfer formed between the side edge of the second piezoelectric layer and the first piezoelectric layer is greater than 0° and less than or equal to 90°, compared to the conventional acoustic resonator capable of exciting a longitudinal electric field, which requires maintaining a 90° chamfer between the side edge of the piezoelectric layer and the substrate, the requirements for fabricating the first piezoelectric layer can be reduced when fabricating the second piezoelectric layer.
[0056] At least two piezoelectric structures 131 are uniformly arranged on the first piezoelectric layer 120 along a first direction, wherein the first direction can be the direction from the first side edge of the first piezoelectric layer 120 to the other side edge.
[0057] The thickness of the first piezoelectric layer 120 is 1 nm - 2000 nm. The thickness of the second piezoelectric layer is 1 nm - 4000 nm, that is, the thickness of each piezoelectric structure 131 is 1 nm - 4000 nm. The thickness of the first piezoelectric layer 120 and the thickness of the second piezoelectric layer can be the same or different.
[0058] For example, the thickness of the first piezoelectric layer 120 can be 1 nm, 25 nm, 50 nm, 100 nm, 125 nm, 150 nm, 200 nm, 300 nm, 500 nm, 600 nm, 800 nm, 900 nm, 1000 nm, 1200 nm, 1500 nm, 1800 nm, or 2000 nm. The thickness of the second piezoelectric layer can be 10 nm, 25 nm, 60 nm, 100 nm, 300 nm, 500 nm, 700 nm, 800 nm, 1000 nm, 1500 nm, 1800 nm, 2000 nm, 2500 nm, 3000 nm, 3500 nm, 3800 nm, or 4000 nm.
[0059] The linewidth of the interdigitated electrode 140 is 10 nm - 100 μm. The spacing between two adjacent interdigitated electrodes 140 is 10 nm - 100 μm. The number of interdigitated electrodes 140 is 2 - 1000. The thickness of the interdigitated electrode 140 is 1 nm - 10 μm.
[0060] For example, the linewidth of the interdigital electrode 140 can be 10nm, 100nm, 350nm, 500nm, 800nm, 1um, 5um, 8um, 10um, 30um, 60um, 90um, or 100um. The spacing between two adjacent interdigital electrodes 140 can be 10nm, 200nm, 400nm, 650nm, 700nm, 900nm, 1um, 3um, 5um, 10um, 40um, 50um, 80um, or 100um. The number of interdigital electrodes 140 can be 2, 10, 25, 50, 100, 150, 300, 400, 450, 500, 800, 900, or 1000. The thickness of the interdigitated electrode 140 can be 1 nm, 5 nm, 10 nm, 50 nm, 100 nm, 200 nm, 450 nm, 600 nm, 1 μm, 2 μm, 4 μm, 5 μm, 8 μm or 10 μm.
[0061] The interdigitated electrode 140 can be made of gold, silver, copper, aluminum, molybdenum, chromium, nickel, platinum, titanium gold, titanium aluminum, chromium gold, chromium aluminum, or an alloy composed of titanium gold, titanium aluminum, titanium copper, chromium gold, chromium aluminum, and chromium copper.
[0062] The material of each piezoelectric layer in the first piezoelectric layer 120 and the second piezoelectric layer can be lithium niobate, lithium tantalate, aluminum nitride, scandium aluminum nitride, or a composite layer formed by at least two of the following: lithium niobate, aluminum nitride, scandium-doped aluminum nitride, lithium tantalate, and zinc oxide. The materials of the first piezoelectric layer 120 and the second piezoelectric layer can be the same or different.
[0063] The substrate 110 can be made of silicon, silicon and silicon dioxide, sapphire, gallium nitride, silicon dioxide or silicon carbide.
[0064] According to embodiments of this disclosure, when the thickness of the second piezoelectric layer is 10 nm - 800 nm, the material of the second piezoelectric layer is lithium niobate, the thickness of the first piezoelectric layer 120 is 1 nm - 200 nm, the linewidth of the interdigitated electrode 140 is 10 nm - 1000 nm, the spacing between two adjacent interdigitated electrodes 140 is 10 nm - 1000 nm, the number of interdigitated electrodes 140 is 2 - 500, and the thickness of the interdigitated electrode 140 is 5 nm - 2000 nm, the resonant frequency of the resonator provided by the embodiments of this disclosure is above 1 GHz, and the electromechanical coupling coefficient is above 50%.
[0065] For example, the materials of the second piezoelectric layer and the first piezoelectric layer 120 in the acoustic resonator 100 can both be lithium niobate, with an X-axis orientation; the thickness of the second piezoelectric layer can be 200 nm; the thickness of the first piezoelectric layer 120 can be 100 nm; the material of the interdigitated electrodes 140 can be gold; the linewidth of the interdigitated electrodes 140 can be 1 μm; the spacing between two adjacent interdigitated electrodes 140 can be 1 μm; the thickness of the interdigitated electrodes 140 can be 40 nm; the number of interdigitated electrodes 140 can be two; the material of the substrate 110 can be silicon; and the chamfer can be 90°. The admittance response diagram of the acoustic resonator 100 in this embodiment is shown below. Figure 2A As shown, the three-dimensional simulation vibration displacement diagram of the acoustic resonator 100 is as follows. Figure 2B As shown.
[0066] Figure 2A An admittance response diagram of an acoustic resonator according to an embodiment of the present disclosure is illustrated schematically. Figure 2B A schematic diagram of a three-dimensional simulated vibration displacement of an acoustic resonator according to an embodiment of the present disclosure is shown.
[0067] exist Figure 2A In the graph, the horizontal axis represents frequency in GHz, and the vertical axis represents admittance in dB. s f is the resonant frequency. p The anti-resonant frequency is k. 2 The coefficient represents the electromechanical coupling coefficient. The solid line represents the simulation result, and the dashed line represents the fitting result.
[0068] Depend on Figure 2A It can be seen that the embodiments of this disclosure can achieve a resonant frequency f. s The frequency is 2.58 GHz, and the electromechanical coupling coefficient k is... 2 The acoustic resonator 100 boasts an ultra-wide bandwidth of 84.5%. This acoustic resonator 100 effectively meets the performance requirements of high resonant frequency, high bandwidth, and high electromechanical coupling coefficient for resonators in the current 5G frequency band.
[0069] exist Figure 2B The vibration was decomposed (see the arrows), revealing that the vibration displacement comprises two parts: longitudinal vibration and transverse vibration. Figure 2B It can be seen that the two piezoelectric structures 131 can generate multiple sound waves, which can be multiple longitudinal waves, under the action of the longitudinal electric field. The first piezoelectric layer 120 can generate transverse waves under the action of the transverse electric field formed by at least two interdigitated electrodes 140, and can couple multiple longitudinal waves. Thus, a case of vibration with multiple waves coupled together is realized, which includes both longitudinal and transverse waves (see the arrows).
[0070] For example, the materials of the second piezoelectric layer and the first piezoelectric layer 120 in the acoustic resonator 100 can both be lithium niobate, with an X-axis orientation; the thickness of the second piezoelectric layer can be 100 nm; the thickness of the first piezoelectric layer 120 can be 100 nm; the material of the interdigitated electrodes 140 can be gold; the linewidth of the interdigitated electrodes 140 can be 1 μm; the spacing between two adjacent interdigitated electrodes 140 can be 1 μm; the thickness of the interdigitated electrodes 140 can be 40 nm; the number of interdigitated electrodes 140 can be two; the material of the substrate 110 can be silicon; and the chamfer can be 90°. The admittance response diagram of the acoustic resonator 100 in this embodiment is shown below. Figure 3 As shown.
[0071] Figure 3 An admittance response diagram of an acoustic resonator according to another embodiment of the present disclosure is illustrated schematically.
[0072] exist Figure 3 In the graph, the horizontal axis represents frequency in GHz, and the vertical axis represents admittance in dB. s f is the resonant frequency. p The anti-resonant frequency is k. 2 The coefficient represents the electromechanical coupling coefficient. The solid line represents the simulation result, and the dashed line represents the fitting result.
[0073] Depend on Figure 3 It can be seen that the embodiments of this disclosure can achieve a resonant frequency f. s The frequency is 3.92 GHz, and the electromechanical coupling coefficient k is... 2 The acoustic resonator 100 boasts an ultra-wide bandwidth of 64%. This acoustic resonator 100 effectively meets the performance requirements of high resonant frequency, high bandwidth, and high electromechanical coupling coefficient for resonators in the current 5G frequency band.
[0074] For example, the materials of the second piezoelectric layer and the first piezoelectric layer 120 in the acoustic resonator 100 can both be aluminum scandium nitride (AlScN), with an Al content of 0.6 (Al / (Al+Sc)=0.6) and a Sc content of 0.4 (Sc / (Al+Sc)=0.4). The thickness of the second piezoelectric layer can be 200 nm, the thickness of the first piezoelectric layer 120 can be 100 nm, the material of the interdigitated electrode 140 can be gold, the linewidth of the interdigitated electrode 140 can be 1 μm, the spacing between two adjacent interdigitated electrodes 140 can be 1 μm, the thickness of the interdigitated electrode 140 can be 40 nm, the number of interdigitated electrodes 140 can be 2, the material of the substrate 110 can be silicon, and the chamfer can be 90°. The admittance response diagram of the acoustic resonator 100 in this embodiment is shown below. Figure 4A As shown, the three-dimensional simulation vibration displacement diagram of the acoustic resonator 100 is as follows. Figure 4B As shown.
[0075] Figure 4A An admittance response diagram of an acoustic resonator according to another embodiment of the present disclosure is illustrated schematically. Figure 4B A schematic diagram of a three-dimensional simulated vibration displacement of an acoustic resonator according to another embodiment of the present disclosure is shown.
[0076] exist Figure 4A In the graph, the horizontal axis represents frequency in GHz, and the vertical axis represents admittance in dB. s f is the resonant frequency. p The anti-resonant frequency is k. 2 The coefficient represents the electromechanical coupling coefficient. The solid line represents the simulation result, and the dashed line represents the fitting result.
[0077] Depend on Figure 4A It can be seen that the embodiments of this disclosure can achieve a resonant frequency f. s The frequency is 4.98 GHz, and the electromechanical coupling coefficient k is... 2 The 100 is a wide-bandwidth acoustic resonator with a bandwidth of 24.36%. Compared to traditional FBAR / BAW resonators that include a metal-piezoelectric material-metal (bottom electrode), it achieves the same performance without requiring a bottom electrode. Furthermore, it is made from... Figure 4B It is known that the second piezoelectric layer in the acoustic resonator 100 includes two piezoelectric structures 131 that excite longitudinal waves, while the first piezoelectric layer 120 can excite transverse waves and couple multiple longitudinal waves, so that the acoustic resonator 100 has a higher resonant frequency, which can well meet the future high-frequency application requirements.
[0078] For example, the material of the second piezoelectric layer in the acoustic resonator 100 can be aluminum scandium nitride (AlScN), with an Al content of 0.6 (Al / (Al+Sc)=0.6) and a Sc content of 0.4 (Sc / (Al+Sc)=0.4). The thickness of the second piezoelectric layer can be 100 nm. The material of the first piezoelectric layer 120 can be lithium niobate (LN), with a thickness of 50 nm. The material of the interdigitated electrodes 140 can be gold, with a linewidth of 1 μm, a spacing of 1 μm between adjacent interdigitated electrodes 140, a thickness of 40 nm, and a number of interdigitated electrodes 140 of 2. The material of the substrate 110 can be silicon, and the chamfer can be 90°. The admittance response diagram of the acoustic resonator 100 in this embodiment is shown below. Figure 5 As shown.
[0079] Figure 5 An admittance response diagram of an acoustic resonator according to another embodiment of the present disclosure is illustrated schematically.
[0080] exist Figure 5 In the graph, the horizontal axis represents frequency in GHz, and the vertical axis represents admittance in dB. sf is the resonant frequency. p The anti-resonant frequency is k. 2 The coefficient represents the electromechanical coupling coefficient. The solid line represents the simulation result, and the dashed line represents the fitting result.
[0081] Depend on Figure 5 It can be seen that the embodiments of this disclosure can achieve a resonant frequency f. s The frequency is 7.07 GHz, and the electromechanical coupling coefficient k is... 2 The 100 features a large bandwidth acoustic resonator with 26% bandwidth. Compared to traditional FBAR / BAW resonators that consist of a metal-piezoelectric material-metal (bottom electrode), it achieves the same performance without requiring a bottom electrode.
[0082] The second piezoelectric layer in the acoustic resonator 100 includes two piezoelectric structures 131 that excite longitudinal waves, while the first piezoelectric layer 120 can excite transverse waves and couple multiple longitudinal waves, so that the acoustic resonator 100 has a higher resonant frequency, which can well meet the future high-frequency application requirements.
[0083] For example, the materials of the second piezoelectric layer and the first piezoelectric layer 120 in the acoustic resonator 100 can both be aluminum scandium nitride (AlScN), with an Al content of 0.6 (Al / (Al+Sc)=0.6) and a Sc content of 0.4 (Sc / (Al+Sc)=0.4). The thickness of the second piezoelectric layer can be 200 nm, the thickness of the first piezoelectric layer 120 can be 100 nm, the material of the interdigitated electrodes 140 can be gold, the linewidth of the interdigitated electrodes 140 can be 5 μm, the spacing between two adjacent interdigitated electrodes 140 can be 3 μm, the thickness of the interdigitated electrodes 140 can be 40 nm, the number of interdigitated electrodes 140 can be 2, the material of the substrate 110 can be silicon, and the chamfer can be 90°. The resonant frequency f of the acoustic resonator 100 in this embodiment is... s The frequency is 11.43 GHz. This acoustic resonator 100 excites longitudinal waves and has a higher resonant frequency, which can well meet the needs of future high-frequency applications.
[0084] Figure 6A A schematic cross-sectional view of an acoustic resonator according to another embodiment of the present disclosure is shown. Figure 6B A schematic diagram illustrating the chamfer formed between the side edge of the second piezoelectric layer and the first piezoelectric layer according to an embodiment of the present disclosure is shown.
[0085] like Figure 6A As shown, the acoustic resonator 600 may include a substrate 610, a first piezoelectric layer 620, a second piezoelectric layer, and at least two interdigitated electrodes 640. The second piezoelectric layer may include at least two piezoelectric structures 631. Figure 6AThe substrate 610, the first piezoelectric layer 620, and at least two interdigitated electrodes 640 are respectively connected to Figure 1 The substrate 110, the first piezoelectric layer 120 and at least two interdigitated electrodes 140 have similar structures and functions, and will not be described in detail here for the sake of simplicity.
[0086] Figure 6A Acoustic resonator 600 and Figure 1 The difference in the acoustic resonator 100 is that the chamfer formed between the side edge of the second piezoelectric layer and the first piezoelectric layer is different.
[0087] exist Figure 1 In this process, the chamfer formed between the side edge of the second piezoelectric layer and the first piezoelectric layer 120 can be equal to 90°.
[0088] like Figure 6B As shown, the chamfer θ formed between the side edge of the second piezoelectric layer and the first piezoelectric layer 620 is 45°, that is, the chamfer formed between each piezoelectric structure 631 and the first piezoelectric layer 620 is 45°.
[0089] For example, the materials of the second piezoelectric layer and the first piezoelectric layer 620 in the acoustic resonator 600 can both be lithium niobate, with an X-axis orientation; the thickness of the second piezoelectric layer can be 200 nm; the thickness of the first piezoelectric layer 620 can be 100 nm; the material of the interdigitated electrode 640 can be gold; the linewidth of the interdigitated electrode 640 can be 1 μm; the spacing between two adjacent interdigitated electrodes 640 can be 1 μm; the thickness of the interdigitated electrode 640 can be 40 nm; the number of interdigitated electrodes 640 can be two; the material of the substrate 610 can be silicon; and the chamfer can be 45°. The admittance response diagram of the acoustic resonator 600 in this embodiment is shown below. Figure 7 As shown.
[0090] Figure 7 An admittance response diagram of an acoustic resonator according to another embodiment of the present disclosure is illustrated schematically.
[0091] exist Figure 7 In the graph, the horizontal axis represents frequency in GHz, and the vertical axis represents admittance in dB. s f is the resonant frequency. p The anti-resonant frequency is k. 2 The coefficient represents the electromechanical coupling coefficient. The solid line represents the simulation result, and the dashed line represents the fitting result.
[0092] Depend on Figure 7 It can be seen that the embodiments of this disclosure can achieve a resonant frequency f. s The frequency is 3.11 GHz, and the electromechanical coupling coefficient k is... 2The 500 is an ultra-wide bandwidth acoustic resonator with a bandwidth of 74%. This acoustic resonator 500 can well meet the performance requirements of high resonant frequency, high bandwidth, and high electromechanical coupling coefficient of resonators in the current 5G frequency band.
[0093] Based on and Figure 1 The embodiment corresponding to the acoustic resonator 100 and its counterpart Figure 6A As can be seen from the embodiment corresponding to the acoustic resonator 600, the acoustic resonator provided in this disclosure embodiment can achieve a high electromechanical coupling coefficient under any chamfer from 0° to 90°.
[0094] Figure 8 A schematic cross-sectional view of an acoustic resonator according to another embodiment of the present disclosure is shown.
[0095] like Figure 8 As shown, the acoustic resonator 800 may include a substrate 810, a first piezoelectric layer 820, a second piezoelectric layer, and at least two interdigitated electrodes 840. The second piezoelectric layer may include at least two piezoelectric structures 831. Figure 8 The first piezoelectric layer 820, the second piezoelectric layer, and at least two interdigitated electrodes 840 are respectively connected to... Figure 1 The first piezoelectric layer 120, the second piezoelectric layer, and at least two interdigitated electrodes 140 have similar structures and functions, and will not be described in detail here for the sake of simplicity.
[0096] Figure 8 The acoustic resonator 800 in the middle and Figure 1 The difference in the acoustic resonator 100 is that: Figure 1 The first piezoelectric layer 120 is bonded to the substrate 110. Figure 8 There is a cavity between the first piezoelectric layer 820 and the substrate 810.
[0097] For example, substrate 810 may include a groove 811 for creating a cavity. Alternatively, first piezoelectric layer 820 may include a groove for creating a cavity.
[0098] For example, the substrate 810 can be etched using dry etching, thereby suspending the acoustic resonator 800 from the substrate 810. Dry etching allows for more precise control over the degree of suspension of the acoustic resonator 800, achieving a completely suspended device effect.
[0099] According to embodiments of this disclosure, when there is a cavity between the first piezoelectric layer 820 and the substrate 810, the quality factor of the acoustic resonator 800 can be improved, thereby improving the performance of the acoustic resonator 800.
[0100] Figure 9A schematic cross-sectional view of an acoustic resonator according to another embodiment of the present disclosure is shown.
[0101] like Figure 9 As shown, the acoustic resonator 900 may include a substrate 910, a first piezoelectric layer 920, a second piezoelectric layer, at least two interdigitated electrodes 940, and a first temperature compensation layer 950. The second piezoelectric layer may include at least two piezoelectric structures 931. Figure 9 The substrate 910, the first piezoelectric layer 920, the second piezoelectric layer, and at least two interdigitated electrodes 940 are respectively connected to... Figure 1 The substrate 110, the first piezoelectric layer 120, the second piezoelectric layer and at least two interdigitated electrodes 140 have similar structures and functions, and will not be described in detail here for the sake of simplicity.
[0102] The first temperature compensation layer 950 is disposed on the top layer of the acoustic resonator 900.
[0103] According to embodiments of this disclosure, the first temperature compensation layer 950 can effectively eliminate the influence of temperature changes on the acoustic resonator 900, thereby improving the stability and accuracy of the acoustic resonator 900.
[0104] Figure 10 A schematic cross-sectional view of an acoustic resonator according to another embodiment of the present disclosure is shown.
[0105] like Figure 10 As shown, the acoustic resonator 1000 may include a substrate 1010, a first piezoelectric layer 1020, a second piezoelectric layer, at least two interdigitated electrodes 1040, and a second temperature compensation layer 1060. The second piezoelectric layer may include at least two piezoelectric structures 1031. Figure 10 The substrate 1010, the first piezoelectric layer 1020, the second piezoelectric layer, and at least two interdigitated electrodes 1040 are respectively connected to... Figure 1 The substrate 110, the first piezoelectric layer 120, the second piezoelectric layer and at least two interdigitated electrodes 140 have similar structures and functions, and will not be described in detail here for the sake of simplicity.
[0106] The second temperature compensation layer 1060 is disposed between the substrate 1010 and the first piezoelectric layer 1020.
[0107] According to embodiments of this disclosure, the second temperature compensation layer 1060 can effectively eliminate the influence of temperature changes on the acoustic resonator 1000, thereby improving the stability and accuracy of the acoustic resonator 1000.
[0108] Figure 11 A schematic cross-sectional view of an acoustic resonator according to another embodiment of the present disclosure is shown.
[0109] like Figure 11As shown, the acoustic resonator 1100 may include a substrate 1110, a first piezoelectric layer 1120, a second piezoelectric layer, at least two interdigitated electrodes 1140, a first temperature compensation layer 1150, and a second temperature compensation layer 1160. The second piezoelectric layer may include at least two piezoelectric structures 1131. Figure 11 The substrate 1110, the first piezoelectric layer 1120, the second piezoelectric layer, and at least two interdigitated electrodes 1140 are respectively connected to... Figure 1 The substrate 110, the first piezoelectric layer 120, the second piezoelectric layer and at least two interdigitated electrodes 140 have similar structures and functions, and will not be described in detail here for the sake of simplicity.
[0110] A first temperature compensation layer 1150 is disposed on the top layer of the acoustic resonator 1100. A second temperature compensation layer 1160 is disposed between the substrate 1110 and the first piezoelectric layer 1120. The material of each temperature compensation layer can be silicon dioxide (SiO2).
[0111] According to embodiments of this disclosure, the first temperature compensation layer 1150 and the second temperature compensation layer 1160 can effectively eliminate the influence of temperature changes on the acoustic resonator 1100, thereby improving the stability and accuracy of the acoustic resonator 1100.
[0112] According to the embodiments of this disclosure, the acoustic resonators provided in the embodiments of this disclosure have electromechanical coupling coefficients of over 20%, which far exceed those of traditional FBAR resonators, and fully meet the performance requirements of filters in the current 5G and 6G frequency bands.
[0113] Figure 12 A flowchart illustrating a method for fabricating an acoustic resonator according to an embodiment of the present disclosure is shown. Wherein, it is possible to... Figure 12 The method for preparing acoustic resonators disclosed herein is used to prepare various acoustic resonators provided in the embodiments.
[0114] like Figure 12 As shown, the method for fabricating an acoustic resonator may include operations S1210 to S1230.
[0115] In operation S1210, a first piezoelectric layer is formed on the substrate. The first piezoelectric layer is not patterned.
[0116] In operation S1220, a second piezoelectric layer is formed on the first piezoelectric layer. The second piezoelectric layer has been patterned and includes at least two piezoelectric structures.
[0117] In operation S1230, at least two interdigitated electrodes are formed on the second piezoelectric layer to obtain an acoustic resonator. The positions of the at least two interdigitated electrodes correspond one-to-one with the positions of at least two piezoelectric structures.
[0118] For example, a first piezoelectric thin film can be formed on a substrate first, and then a first piezoelectric layer can be formed. The first piezoelectric thin film can be formed by any one of ion implantation transfer, sputtering deposition, molecular beam epitaxy deposition, or vapor phase epitaxial growth deposition.
[0119] Then, a second piezoelectric thin film is formed on the first piezoelectric layer, and the second piezoelectric thin film is etched using inductively coupled plasma etching to pattern the second piezoelectric thin film, thereby obtaining the second piezoelectric layer, which includes at least two piezoelectric structures. The second piezoelectric thin film can be formed by any one of ion implantation transfer, sputtering deposition, molecular beam epitaxy deposition, or vapor phase epitaxial growth deposition.
[0120] Then, one or more layers of metal are deposited on the second piezoelectric layer using electron beam evaporation or magnetron sputtering, and at least two interdigitated electrodes are formed using a stripping process.
[0121] According to embodiments of this disclosure, forming a first piezoelectric layer on a substrate in operation S1210 may include: forming a second temperature compensation layer on the substrate, and forming the first piezoelectric layer on the second temperature compensation layer. The method for fabricating an acoustic resonator may further include: forming a groove on the substrate before operation S1220, or forming the first piezoelectric layer on the substrate in operation S1220, the first piezoelectric layer including the groove. Forming at least two interdigitated electrodes on the second piezoelectric layer to obtain an acoustic resonator includes: forming at least two interdigitated electrodes on the second piezoelectric layer; forming a first temperature compensation layer on the top layer to obtain the acoustic resonator.
[0122] According to embodiments of this disclosure, when the substrate includes a groove, the substrate can be released using a dry release method or a wet release method before operation S1220 to form a groove between the substrate and the first piezoelectric layer, and the groove is used to realize a cavity.
[0123] Those skilled in the art will understand that the features described in the various embodiments and / or claims of this disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure can be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.
[0124] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.
Claims
1. An acoustic resonator, comprising: Substrate; A first piezoelectric layer is disposed on the substrate for coupling multiple longitudinal waves, wherein the first piezoelectric layer is not patterned; The second piezoelectric layer includes: At least two piezoelectric structures are disposed on the first piezoelectric layer. The at least two piezoelectric structures are used to generate the plurality of sound waves under the action of a longitudinal electric field. The second piezoelectric layer is patterned, the sound waves are longitudinal waves, and the second piezoelectric layer is grown on the unpatterned first piezoelectric layer. At least two interdigitated electrodes are disposed on the second piezoelectric layer, the at least two interdigitated electrodes being used to form the longitudinal electric field, wherein the positions of the at least two interdigitated electrodes correspond one-to-one with the positions of the at least two piezoelectric structures; The chamfer formed between the side edge of the second piezoelectric layer and the first piezoelectric layer is greater than 0° and less than or equal to 90°. The thickness of the second piezoelectric layer is The second piezoelectric layer is made of lithium niobate, and the thickness of the first piezoelectric layer is [missing information]. The linewidth of the interdigitated electrode is The spacing between two adjacent interdigital electrodes is The number of interdigitated electrodes is The thickness of the interdigitated electrodes is [number missing]. The acoustic resonator has a resonant frequency of over 1 GHz and an electromechanical coupling coefficient of over 50%. The acoustic resonator has no bottom electrode and its fabrication does not require transfer bonding.
2. The acoustic resonator according to claim 1, wherein, The first piezoelectric layer is bonded to the substrate.
3. The acoustic resonator according to claim 1, wherein, There is a cavity between the first piezoelectric layer and the substrate.
4. The acoustic resonator according to claim 3, wherein, The substrate includes a groove or the first piezoelectric layer includes a groove, the groove being used to realize the cavity.
5. The acoustic resonator according to claim 1, wherein, The interdigitated electrodes are made of gold, silver, copper, aluminum, molybdenum, chromium, nickel, platinum, titanium gold, titanium aluminum, chromium gold, chromium aluminum, or an alloy composed of titanium gold, titanium aluminum, titanium copper, chromium gold, chromium aluminum, and chromium copper. The material of the first piezoelectric layer is lithium niobate, lithium tantalate, aluminum nitride, scandium aluminum nitride, or a composite layer formed by at least two of the following: lithium niobate, aluminum nitride, scandium-doped aluminum nitride, lithium tantalate, and zinc oxide.
6. The acoustic resonator according to claim 5, wherein, The acoustic resonator includes a first temperature compensation layer disposed on the top layer of the acoustic resonator; and / or The acoustic resonator includes a second temperature compensation layer disposed between the substrate and the first piezoelectric layer.
7. A method for fabricating the acoustic resonator according to any one of claims 1-6, comprising: A first piezoelectric layer is formed on a substrate, wherein the first piezoelectric layer is not patterned; A second piezoelectric layer is formed on the first piezoelectric layer, wherein the second piezoelectric layer has been patterned and includes at least two piezoelectric structures; At least two interdigitated electrodes are formed on the second piezoelectric layer to obtain an acoustic resonator, wherein the positions of the at least two interdigitated electrodes correspond one-to-one with the positions of the at least two piezoelectric structures.