A surface acoustic wave resonator, a method for manufacturing the same, and a filter

Abstract

The application provides a surface acoustic wave resonator, a preparation method thereof and a filter. An insertion layer is formed on a side of a reflection grating away from a piezoelectric substrate, the sound velocity of a covered area of the insertion layer is changed, the band gap width of the reflection grating is increased, the reflection grating can reflect a wide-band signal back to an interdigital electrode, the quality factor of the surface acoustic wave resonator is improved, the transverse stray mode is reduced, energy dissipation is reduced, and the performance of the surface acoustic wave resonator is comprehensively improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor structure technology, and more specifically, to a surface acoustic wave resonator, its fabrication method, and a filter. Background Technology

[0002] SAW (Surface Acoustic Wave) resonators are a type of filtering device that utilizes the piezoelectric effect and the physical characteristics of surface acoustic wave propagation. They are widely used in various fields, such as radio frequency (RF) applications. Surface acoustic waves are elastic waves whose energy is concentrated near a surface.

[0003] In current surface acoustic wave (SAW) product designs, the transverse propagation of acoustic waves in the SAW resonator can cause transverse modes to appear in the SAW resonator, or the electrode fingers can excite other resonant modes besides the main acoustic mode. These are manifested as clutter in and around the passband of the SAW resonator, which can degrade the performance of the SAW resonator.

[0004] Therefore, improving the performance of surface acoustic wave resonators is the top priority in resonator design today. Summary of the Invention

[0005] In view of this, to solve the above problems, the present invention provides a surface acoustic wave resonator, its fabrication method, and a filter, the technical solution of which is as follows:

[0006] A surface acoustic wave (SAW) resonator, the SAW resonator comprising:

[0007] piezoelectric substrate;

[0008] An interdigitated electrode is located on one side of the piezoelectric substrate; the interdigitated electrode includes a busbar, the busbar includes a first busbar and a second busbar disposed opposite each other in a first direction, and electrode fingers located on the first busbar and the second busbar; the busbar extends along a second direction, the length extension direction of the electrode fingers is parallel to the first direction, the first direction and the second direction are parallel to the plane where the piezoelectric substrate is located, and the first direction and the second direction are perpendicular to each other;

[0009] A reflective grid located at at least one end of the interdigitated electrode along the second direction;

[0010] A dielectric layer located on the side of the interdigitated electrodes opposite to the piezoelectric substrate;

[0011] An insertion layer is located on the side of the dielectric layer opposite to the piezoelectric substrate. The orthogonal projection of the reflective grating on the piezoelectric substrate completely covers the orthogonal projection of the insertion layer on the piezoelectric substrate. The insertion layer includes a first portion and a second portion in the direction away from the interdigitated electrode. The length of the first portion in the first direction is the same as the length of the reflective grating in the first direction. The length of the second portion in the first direction gradually decreases in the direction away from the interdigitated electrode.

[0012] Preferably, in the above-described surface acoustic wave resonator, the surface acoustic wave resonator further includes:

[0013] The dummy electrode fingers are located on the first busbar and the second busbar, and the length extension direction of the dummy electrode fingers is parallel to the first direction.

[0014] Preferably, in the above-mentioned surface acoustic wave resonator, the thickness of the insertion layer is 50nm-200nm.

[0015] Preferably, in the above-mentioned surface acoustic wave resonator, the material of the insertion layer is a metallic material or Si3N4 material.

[0016] Preferably, in the above-described surface acoustic wave resonator, the orthographic projection of the second portion of the insertion layer onto the piezoelectric substrate is a triangle, and the height of the triangle is perpendicular to the first direction.

[0017] Preferably, in the above-mentioned surface acoustic wave resonator, the apex angle of the triangle is 90°-120°.

[0018] Preferably, in the above-described surface acoustic wave resonator, the orthographic projection pattern of the second portion of the insertion layer on the piezoelectric substrate is a stepped gradient pattern.

[0019] Preferably, in the above-mentioned surface acoustic wave resonator, the stepped gradient pattern has multiple strip portions, the length extension direction of the strip portions is parallel to the first direction, the multiple strip portions are arranged sequentially in the direction away from the interdigitated electrode, and the orthogonal projection area of ​​the multiple strip portions in the direction away from the interdigitated electrode gradually decreases.

[0020] Preferably, in the above-described surface acoustic wave resonator, the second portion of the insertion layer has an arc-shaped orthographic projection on the piezoelectric substrate, and the arc protrudes toward the side away from the interdigitated electrode.

[0021] Preferably, in the above-described surface acoustic wave resonator, the reflective grating includes a first reflective grating and a second reflective grating located at both ends of the interdigital electrodes in the second direction;

[0022] The insertion layer includes a first insertion layer corresponding to the first reflective grating and a second insertion layer corresponding to the second reflective grating.

[0023] Preferably, in the above-described surface acoustic wave resonator, the orthographic projection pattern of the second portion of the first insertion layer on the piezoelectric substrate is different from the orthographic projection pattern of the second portion of the second insertion layer on the piezoelectric substrate.

[0024] Preferably, in the above-described surface acoustic wave resonator, the orthographic projection pattern of the second portion of the first insertion layer on the piezoelectric substrate is the same as the orthographic projection pattern of the second portion of the second insertion layer on the piezoelectric substrate.

[0025] Preferably, in the above-described surface acoustic wave resonator, the material of the first insertion layer is different from the material of the second insertion layer.

[0026] Preferably, in the above-described surface acoustic wave resonator, the material of the first insertion layer is the same as the material of the second insertion layer.

[0027] Preferably, in the above-described surface acoustic wave resonator, the surface acoustic wave resonator further includes:

[0028] A protective layer is located on the side of the dielectric layer opposite to the piezoelectric substrate, and the insertion layer is located between the dielectric layer and the protective layer.

[0029] Preferably, in the above-mentioned surface acoustic wave resonator, the dielectric layer is a temperature compensation layer;

[0030] The orthographic projection of the temperature compensation layer onto the plane of the piezoelectric substrate at least completely covers the orthographic projection of the interdigitated electrodes onto the plane of the piezoelectric substrate, as well as the orthographic projection of the reflective grating onto the plane of the piezoelectric substrate.

[0031] This application also provides a method for fabricating a surface acoustic wave resonator, the method comprising:

[0032] Provide a piezoelectric substrate;

[0033] An interdigitated electrode is formed on one side of the piezoelectric substrate; the interdigitated electrode includes a bus bar, the bus bar includes a first bus bar and a second bus bar disposed opposite each other in a first direction, and electrode fingers located on the first bus bar and the second bus bar; the bus bar extends along a second direction, the length extension direction of the electrode fingers is parallel to the first direction, the first direction and the second direction are parallel to the plane where the piezoelectric substrate is located, and the first direction and the second direction are perpendicular to each other;

[0034] A reflective grid is formed at at least one end of the interdigitated electrode along the second direction;

[0035] A dielectric layer is formed on the side of the interdigitated electrode opposite to the piezoelectric substrate;

[0036] An insertion layer is formed on the side of the dielectric layer away from the piezoelectric substrate. The orthogonal projection of the reflective grating on the piezoelectric substrate completely covers the orthogonal projection of the insertion layer on the piezoelectric substrate. The insertion layer includes a first portion and a second portion in the direction away from the interdigitated electrode. The length of the first portion in the first direction is the same as the length of the reflective grating in the first direction. The length of the second portion in the first direction gradually decreases in the direction away from the interdigitated electrode.

[0037] This application also provides a filter comprising the surface acoustic wave resonator described in any of the preceding claims.

[0038] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0039] The present invention provides a surface acoustic wave resonator, its fabrication method, and a filter. By forming an insertion layer on the side of the reflector grid away from the piezoelectric substrate, the sound velocity in the area covered by the insertion layer is changed, thereby increasing the bandgap of the reflector grid. This allows the reflector grid to reflect wideband signals back to the interdigitated electrodes, thereby improving the quality factor of the surface acoustic wave resonator. At the same time, it reduces transverse spurious modes and energy dissipation, achieving the goal of comprehensively improving the performance of the surface acoustic wave resonator. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0041] Figure 1 This is a top view schematic diagram of a surface acoustic wave resonator provided in an embodiment of the present invention;

[0042] Figure 2 A top view schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention;

[0043] Figure 3 This is a top view schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention;

[0044] Figure 4 This is a top view schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention;

[0045] Figure 5This is a top view schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention;

[0046] Figure 6 A schematic diagram of the cross-sectional structure of a surface acoustic wave resonator provided in an embodiment of the present invention;

[0047] Figure 7 This is a top view schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention;

[0048] Figure 8 A schematic diagram of the cross-sectional structure of another surface acoustic wave resonator provided in an embodiment of the present invention;

[0049] Figure 9 This is a top view schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention;

[0050] Figure 10 This is a top view schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention;

[0051] Figure 11 This is a top view schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention;

[0052] Figure 12 This is a top view schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention;

[0053] Figure 13 This is a top view schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention;

[0054] Figure 14 A schematic cross-sectional view of another surface acoustic wave resonator provided in an embodiment of the present invention;

[0055] Figure 15 This is a schematic diagram showing a performance comparison between a surface acoustic wave resonator in this application and a surface acoustic wave resonator in a prior art solution, provided by an embodiment of the present invention.

[0056] Figure 16 This is a schematic diagram comparing the performance of a surface acoustic wave resonator in another technical solution provided by this application with that of a surface acoustic wave resonator in the prior art.

[0057] Figure 17 This is a schematic flowchart illustrating a method for fabricating a surface acoustic wave resonator according to an embodiment of the present invention. Detailed Implementation

[0058] 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, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] Surface acoustic wave (SAW) resonators and filters are acoustic devices widely used in the radio frequency (RF) field. They combine low insertion loss and good suppression performance in a relatively small size. They are used to filter out interference from different frequency signals, attenuate some frequency components, and allow only specified frequency components. They form the technological foundation for the application of the wireless spectrum as a non-renewable and scarce resource. The principle can be simply understood as being based on the piezoelectric properties of piezoelectric materials. Input and output transducers, such as interdigital transducers, convert electrical signals into mechanical energy, which is then processed and converted back into electrical signals to amplify the desired signal, filter out noise, and improve signal quality. They are widely used in various wireless communication devices.

[0060] Currently, filters are mainly divided into SAW filters and BAW (Bulk Acoustic Wave) filters. Surface acoustic waves are elastic waves generated and propagating on the surface of a piezoelectric substrate with piezoelectric properties, and their amplitude decreases rapidly with increasing depth into the piezoelectric substrate. SAW filters have significantly lower manufacturing costs compared to BAW filters, are suitable for low-frequency applications, have low insertion loss and good suppression, and are temperature sensitive.

[0061] It's also important to note that SAW filters have limitations. One is their susceptibility to temperature changes. As temperature rises, the stiffness of the substrate material decreases, leading to a reduction in sound velocity. This can be described as a temperature drift defect in SAW filters, where the frequency shifts with operating temperature. Therefore, based on traditional SAW filters, TC-SAW filters (temperature-compensated SAW filters) were developed. These filters primarily utilize the contrasting thermoelastic properties of the SiO2 layer and the piezoelectric layer to compensate for temperature drift. Furthermore, there are also SAW filter designs using TF thin-film technology, among others.

[0062] In filter design, resonators are often used as basic units to form corresponding topologies and amplify signals of specified frequency components.

[0063] For TC-SAW resonators, ordinary SAW resonators, or TF-SAW resonators, the transverse modes of the surface acoustic wave resonator are caused by the transverse propagation of acoustic waves, or the electrode fingers excite other resonant modes besides the main acoustic mode. These are manifested as clutter in and around the passband of the surface acoustic wave resonator, which degrades the performance of the surface acoustic wave resonator.

[0064] Currently, most existing design schemes for suppressing noise and improving the quality factor of surface acoustic wave resonators involve improving the electrode fingers in the interdigitated electrodes, such as adding a sound velocity change section at the end of the electrode fingers. However, due to limitations in manufacturing processes and dimensions, the effects are extremely limited, and may even cause other additional defects.

[0065] Based on this, the present invention provides a surface acoustic wave resonator and its fabrication method and filter. By forming an insertion layer on the side of the reflector grid away from the piezoelectric substrate, the sound velocity in the area covered by the insertion layer is changed, thereby increasing the bandgap of the reflector grid. This allows the reflector grid to reflect wideband signals back to the interdigitated electrodes, thereby improving the quality factor of the surface acoustic wave resonator. At the same time, it reduces transverse spurious modes and energy dissipation, achieving the goal of comprehensively improving the performance of the surface acoustic wave resonator.

[0066] It should be noted that the surface acoustic wave resonator provided in the embodiments of the present invention includes, but is not limited to, ordinary SAW resonators, TC-SAW resonators, or TF-SAW resonators. That is to say, the technical solution provided in the embodiments of the present invention can be applied to ordinary SAW resonators, TC-SAW resonators, or TF-SAW resonators. However, in the embodiments of the present invention, the improvement of TC-SAW resonators is the main solution for description and explanation.

[0067] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0068] refer to Figure 1 , Figure 1 This is a top view schematic diagram of a surface acoustic wave resonator provided in an embodiment of the present invention. The surface acoustic wave resonator provided in this embodiment of the present invention includes:

[0069] A piezoelectric substrate 11 having piezoelectric properties.

[0070] An interdigitated electrode 12 is located on one side of the piezoelectric substrate 11; wherein the interdigitated electrode 12 includes a bus bar, the bus bar including a first bus bar 121 and a second bus bar 122 disposed opposite to each other in the first direction X, and electrode fingers 123 located on the first bus bar 121 and the second bus bar 122; the first bus bar 121 and the second bus bar 122 extend in the same direction, both extending along the second direction Y, the first direction X and the second direction Y are parallel to the plane where the piezoelectric substrate 11 is located, and the example is given with the first direction X and the second direction Y perpendicular.

[0071] The length extension direction of the electrode finger strip 123 is parallel to the first direction X. Multiple electrode fingers 123 on the first busbar 121 are arranged at intervals in the second direction Y. Multiple electrode fingers 123 on the second busbar 122 are arranged at intervals in the second direction Y. The multiple electrode fingers 123 on the first busbar 121 and the multiple electrode fingers 123 on the second busbar 122 are arranged in a staggered manner in the second direction Y. There is a gap between the multiple electrode fingers 123 on the first busbar 121 and the second busbar 122. There is a gap between the multiple electrode fingers 123 on the second busbar 122 and the first busbar 121. At this time, the busbar and the electrode fingers 123 are distributed in a manner similar to interlacing fingers, forming the so-called interdigitated electrode 12. When the first busbar 121 and its electrode strips 123 serve as the transmitting end, the second busbar 122 and its electrode strips 123 serve as the receiving end; conversely, when the first busbar 121 and its electrode strips 123 serve as the receiving end, the second busbar 122 and its electrode strips 123 serve as the transmitting end. The transmitting end is used to convert electrical signals into sound waves, which mainly propagate on the surface of the piezoelectric substrate. The receiving end is used to convert the received sound waves into electrical signals for output, thereby achieving filtering.

[0072] refer to Figure 2 , Figure 2 This is a top view schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention. The interdigitated electrode 12 in the surface acoustic wave resonator provided in this embodiment of the present invention may further include:

[0073] Multiple dummy electrode fingers 124 are provided, wherein the length extension direction of the dummy electrode fingers 124 is parallel to the first direction X. Multiple dummy electrode fingers 124 are provided on the first busbar 121 and the second busbar 122 are also provided. The multiple dummy electrode fingers 124 and multiple electrode fingers 123 on the first busbar 121 are arranged alternately in the second direction Y. The multiple dummy electrode fingers 124 and multiple electrode fingers 123 on the second busbar 123 are arranged alternately in the second direction Y. In the first direction X, the electrode fingers 123 on the first busbar 121 and the dummy electrode fingers 124 on the second busbar 122 are arranged opposite each other and are spaced apart. The dummy electrode fingers 124 on the first busbar 121 and the electrode fingers 123 on the second busbar 122 are arranged opposite each other and are also spaced apart.

[0074] In other words, in the embodiments of the present invention, the interdigital electrode 12 can be adopted as follows: Figure 1 The interdigitated electrode 12 shown without the dummy electrode strip 124 can also be as follows: Figure 2 The interdigitated electrode 12 shown has a dummy electrode bar 124. In this embodiment of the invention, the interdigitated electrode 12 is described as having no dummy electrode bar 124.

[0075] It should be noted that when the interdigital electrode 12 is provided with dummy electrode strips 124, the dummy electrode strips 124 can also suppress noise and improve the quality factor of the surface acoustic wave resonator.

[0076] It should be further noted that, in the embodiments of the present invention, the interdigital electrodes can be as follows: Figure 1 or Figure 2 The single-mode interdigitated electrode 12 shown may also be a dual-mode interdigitated electrode 12 or a multi-mode interdigitated electrode 12, see reference. Figure 3 , Figure 3 This is a top view schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention. Figure 3 The interdigitated electrodes shown do not include dummy electrode fingers 124, and the interdigitated electrodes 12 adopt a dual-mode SAW (Dual Mode SAW) structure, see reference. Figure 4 , Figure 4 This is a top view schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention. Figure 4 The interdigitated electrode 12 shown does not include the dummy electrode finger 124, and the interdigitated electrode 12 is a multimode interdigitated electrode.

[0077] like Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, the surface acoustic wave resonator provided in this embodiment of the invention further includes:

[0078] The reflective grating 13 is located at at least one end of the interdigital electrode 12 along the second direction Y. It should be noted that, in this embodiment of the invention, the reflective grating 13 is provided at both ends of the interdigital electrode 12 along the second direction Y as an example.

[0079] refer to Figure 5 , Figure 5 This is a top view schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention, with reference to... Figure 6 , Figure 6 This is a schematic diagram of the cross-sectional structure of a surface acoustic wave resonator provided in an embodiment of the present invention. Figure 6 For along Figure 5 A schematic diagram of the cross-section of the tangent line AA' is shown below. Figure 5 and Figure 6 As shown, the surface acoustic wave resonator provided in this embodiment of the invention further includes:

[0080] The dielectric layer 14 located on the side of the interdigitated electrode 12 away from the piezoelectric substrate 11 has a projection on the plane of the piezoelectric substrate 11 that at least completely covers the projection of the interdigitated electrode 12 on the plane of the piezoelectric substrate 11, as well as the projection of the reflective grating 13 on the plane of the piezoelectric substrate 11.

[0081] It should be noted that when the surface acoustic wave resonator provided in this embodiment of the invention is a TC-SAW resonator, the dielectric layer 14 is a temperature compensation layer. When the surface acoustic wave resonator provided in this embodiment of the invention is a common SAW resonator or a TF-SAW resonator, the dielectric layer 14 can be the corresponding dielectric layer in the common SAW resonator or the TF-SAW resonator.

[0082] Optionally, the temperature compensation layer can be made of SiO2 material. The thickness of the temperature compensation layer is greater than the thickness of the underlying metal layer. It can also be understood that the thickness of the temperature compensation layer is greater than the thickness of the interdigitated electrode 12 and greater than the thickness of the reflective grid 13. The thickness range of the temperature compensation layer is 0.2λ-0.5λ, where λ represents the wavelength of the surface acoustic wave of the surface acoustic wave resonator.

[0083] In other words, in this embodiment of the invention, for the TC-SAW resonator, a temperature compensation layer is deposited in the aperture region of the surface acoustic wave resonator (i.e., the region where the interdigitated electrode 12 is located and the region where the reflective grating 13 is located), and the surface of the temperature compensation layer facing away from the piezoelectric substrate 11 is ground flat. The temperature compensation layer has a dense structure to compensate for the negative temperature effect of the surface acoustic wave resonator. Especially on some chamfered substrates (such as 128°YXLiNbO3), the temperature compensation layer of SiO2 material can effectively suppress the transverse shear wave mode excited by the electrode fingers 123.

[0084] It should be noted that, in order to better illustrate the hierarchical relationship of the film layers, in Figure 5 The example given is that the coverage area of ​​the dielectric layer 14 is different from that of the piezoelectric substrate 11. In some alternative embodiments, the coverage area of ​​the dielectric layer 14 and the coverage area of ​​the piezoelectric substrate 11 can also be the same.

[0085] refer to Figure 7 , Figure 7 This is a top view schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention, with reference to... Figure 8 , Figure 8 This is a schematic diagram of the cross-sectional structure of another surface acoustic wave resonator provided in an embodiment of the present invention. Figure 8 For along Figure 7 A schematic diagram of the cross-section of the tangent line BB', as shown below. Figure 7 and Figure 8 As shown, the surface acoustic wave resonator provided in this embodiment of the invention further includes:

[0086] An insertion layer 15 is located on the side of the dielectric layer 14 facing away from the piezoelectric substrate 11. The orthogonal projection of the reflective gate 13 on the piezoelectric substrate 11 completely covers the orthogonal projection of the insertion layer 15 on the piezoelectric substrate 11. The insertion layer 15 includes a first portion 151 and a second portion 152 in the direction away from the interdigitated electrode 12. The length of the first portion 151 in the first direction X is the same as the length of the reflective gate 13 in the first direction X. The length of the second portion 152 in the first direction X gradually decreases in the direction away from the interdigitated electrode 12.

[0087] It should be noted that when reflective gates 13 are provided at both ends of the interdigital electrode 12 along the second direction Y, for example, when a first reflective gate and a second reflective gate are provided at both ends of the interdigital electrode 12 along the second direction Y, the insertion layer 15 includes a first insertion layer corresponding to the first reflective gate and a second insertion layer corresponding to the second reflective gate. For the first reflective gate, the length of the second portion 152 of the first insertion layer corresponding to the first reflective gate gradually decreases in the first direction X as it moves away from the interdigital electrode 12; for the second reflective gate, the length of the second portion 152 of the second insertion layer corresponding to the second reflective gate gradually decreases in the first direction X as it moves away from the interdigital electrode 12.

[0088] In other words, an insertion layer 15 is prepared in the region of the reflective grating 13. The portion of the reflective grating 13 near the interdigital electrode 12 is completely covered by the first portion 151 of the insertion layer 15, and the remaining portion of the reflective grating 13 is partially covered by the second portion 152 of the insertion layer 15. The length of the second portion 152 of the insertion layer 15 gradually decreases in the first direction X in the direction away from the interdigital electrode 12, forming a transition region.

[0089] Specifically, since surface acoustic waves (SAWs) are generated and propagate on the surface of a piezoelectric substrate 11 with piezoelectric properties, an insertion layer 15 is provided in this embodiment of the invention. Depending on the acoustic impedance of the insertion layer 15, the sound velocity in the region where the insertion layer 15 is located will decrease or increase. In other words, based on the placement of the insertion layer 15, by appropriately selecting its material and coordinating its pattern design, the sound velocity in the area covered by the insertion layer 15 can be changed to increase the bandgap of the reflector grating 13. This allows the reflector grating 13 to reflect broadband signals back to the interdigitated electrodes 12, thereby improving the quality factor of the SAW resonator, reducing transverse spurious modes, reducing energy dissipation, and achieving the overall goal of improving the performance of the SAW resonator.

[0090] Optionally, in another embodiment of the present invention, the thickness of the insertion layer 15 is from tens of nanometers to hundreds of nanometers. In this embodiment of the present invention, the thickness of the insertion layer 15 can be 50nm-200nm.

[0091] Furthermore, in this embodiment of the invention, the material of the insertion layer 15 can be a metal material or a Si3N4 material, or it can be said that the insertion layer 15 is a metal layer or a Si3N4 layer.

[0092] Specifically, metallic materials are materials with relatively high acoustic impedance, and the higher the density of the metal, the higher the acoustic impedance is generally. For example, platinum and gold have relatively high acoustic impedance. Therefore, if the deposited metal layer is used as the insertion layer 15, the presence of the metal layer will reduce the propagation speed of sound waves in the covered area.

[0093] Si3N4 material is a material with very low acoustic impedance. Compared with the piezoelectric substrate 11 and the temperature compensation layer 14 of SiO2 material, the acoustic impedance of the Si3N4 material insertion layer 15 is even lower. Therefore, if a Si3N4 layer is deposited as the insertion layer 15, the area covered by the Si3N4 layer will have an increased sound wave propagation speed due to the presence of the Si3N4 layer.

[0094] Optionally, in another embodiment of the invention, such as Figure 7 As shown, the orthographic projection of the second portion 152 of the insertion layer 15 onto the piezoelectric substrate 11 is a triangle, and the height of the triangle is perpendicular to the first direction.

[0095] The vertex angle of the triangle is 90°-120°, meaning that the second part 152 of the insertion layer 15 has a first hypotenuse and a second hypotenuse. The first hypotenuse and the second hypotenuse intersect at a first angle. Both the first hypotenuse and the second hypotenuse are straight lines, and the first angle can be between 90° and 120°.

[0096] Specifically, in this embodiment of the invention, in this triangular transition region, the first and second hypotenuses generate sound velocity boundaries, which is beneficial for scattering transverse sound waves propagating to both ends, thereby reducing the generation of transverse stray modes; and in this triangular transition region, the sound velocity is continuously changing, thus having a reflection effect on sound waves of different frequencies, increasing the bandgap of the reflection grating 13, so that the reflection grating 13 can reflect broadband signals back to the interdigitated electrodes 12, thereby improving the quality factor of the surface acoustic wave resonator.

[0097] Optionally, in another embodiment of the invention, reference is made to... Figure 9 , Figure 9 This is a top view of another surface acoustic wave resonator provided in an embodiment of the present invention. The orthographic projection of the second part 152 of the insertion layer 15 on the piezoelectric substrate 11 is a stepped gradient pattern.

[0098] The second part 152 of the insertion layer 15 has a plurality of strip portions 16. The length extension direction of the strip portions 16 is parallel to the first direction X. The plurality of strip portions 16 are arranged sequentially in the direction away from the interdigitated electrode 12, and the positive projection area of ​​the plurality of strip portions 16 in the direction away from the interdigitated electrode 12 gradually decreases.

[0099] Specifically, in this embodiment of the invention, in the transition region of this stepped gradient pattern, the stepped gradient edges on both sides of the stepped gradient pattern in the first direction X generate sound velocity boundaries, which is beneficial for scattering transverse sound waves propagating to both ends, thereby reducing the generation of transverse stray modes; and in this transition region of the stepped gradient pattern, the sound velocity is in a continuously changing state, thus having a reflection effect on sound waves of different frequencies, increasing the bandgap of the reflection grating 13, so that the reflection grating 13 can reflect broadband signals back to the interdigitated electrodes 12, thereby improving the quality factor of the surface acoustic wave resonator.

[0100] Optionally, in another embodiment of the invention, reference is made to... Figure 10 , Figure 10 This is a top view of another surface acoustic wave resonator provided in an embodiment of the present invention. The orthographic projection of the second part 152 of the insertion layer 15 on the piezoelectric substrate 11 is arc-shaped, and the arc protrudes to the side away from the interdigitated electrode 12.

[0101] Specifically, in this embodiment of the invention, the arc edge of the arc-shaped transition region generates a sound velocity boundary, which is beneficial for scattering transverse sound waves propagating to both ends, thereby reducing the generation of transverse stray modes; and in this arc-shaped transition region, the sound velocity is continuously changing, thus having a reflection effect on sound waves of different frequencies, increasing the bandgap of the reflection grating 13, so that the reflection grating 13 can reflect wideband signals back to the interdigitated electrodes 12, thereby improving the quality factor of the surface acoustic wave resonator.

[0102] It should be noted that in the embodiments of the present invention, only the triangular transition region, the stepped gradient graphic transition region, and the arc transition region are described as three preferred embodiments. In some optional embodiments, other graphic transition regions can also achieve similar effects, as long as the length of the second part 152 of the insertion layer 15 located in the transition region in the first direction X gradually decreases in the direction away from the interdigitated electrode 12.

[0103] Optionally, in another embodiment of the present invention, the reflective grid 13 includes a first reflective grid and a second reflective grid located at both ends of the interdigital electrode 12 in the second direction Y.

[0104] Wherein, the insertion layer corresponding to the first reflective grating is the first insertion layer, the insertion layer corresponding to the second reflective grating is the second insertion layer, and the orthographic projection pattern of the second part 152 of the first insertion layer on the piezoelectric substrate 11 is different from the orthographic projection pattern of the second part 152 of the second insertion layer on the piezoelectric substrate 11.

[0105] Specifically, in the embodiments of the present invention, reference is made to Figure 11 , Figure 11 This is a top view schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention. The insertion layers 15 are located on both sides of the interdigitated electrodes 12. The second portion 152 of one insertion layer 15 has a triangular orthographic projection on the piezoelectric substrate 11, while the second portion 152 of the other insertion layer 15 has a stepped gradient orthographic projection on the piezoelectric substrate 11. (Reference) Figure 12 , Figure 12 This is a top view schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention. The insertion layers 15 are located on both sides of the interdigitated electrodes 12. The second portion 152 of one insertion layer 15 has a triangular orthographic projection on the piezoelectric substrate 11, while the second portion 152 of the other insertion layer 15 has an arc-shaped orthographic projection on the piezoelectric substrate 11. (Reference) Figure 13 , Figure 13This is a top view of another surface acoustic wave resonator provided in an embodiment of the present invention. The insertion layers 15 are located on both sides of the interdigitated electrode 12. The orthographic projection pattern of the second part 152 of one insertion layer 15 on the piezoelectric substrate 11 is a stepped gradient pattern, and the orthographic projection pattern of the second part 152 of the other insertion layer 15 on the piezoelectric substrate 11 is an arc shape.

[0106] Optionally, in another embodiment of the present invention, the reflective grid includes a first reflective grid and a second reflective grid located at both ends of the interdigital electrode 12 in the second direction Y.

[0107] Wherein, the insertion layer corresponding to the first reflective grating is the first insertion layer, and the insertion layer corresponding to the second reflective grating is the second insertion layer. The materials of the first insertion layer and the second insertion layer can be the same or different.

[0108] Specifically, in the embodiments of the present invention, the materials of the first insertion layer and the second insertion layer can both be metal materials, or both be Si3N4 materials, or one of them can be a metal material and the other can be a Si3N4 material.

[0109] It should be noted that, in the embodiments of the present invention, when the materials of the first insertion layer and the second insertion layer are the same, the orthographic projection pattern of the second portion 152 of the first insertion layer on the piezoelectric substrate 11 may be the same as or different from the orthographic projection pattern of the second portion 152 of the second insertion layer on the piezoelectric substrate 11; similarly, when the materials of the first insertion layer and the second insertion layer are different, the orthographic projection pattern of the second portion 152 of the first insertion layer on the piezoelectric substrate 11 may be the same as or different from the orthographic projection pattern of the second portion 152 of the second insertion layer on the piezoelectric substrate 11.

[0110] In other words, in the embodiments of the present invention, the insertion layer 15 can be flexibly designed based on actual needs, and is not limited to a certain form. Different solutions can achieve similar effects.

[0111] Optionally, in another embodiment of the invention, reference is made to... Figure 14 , Figure 14 This is a cross-sectional schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention. The surface acoustic wave resonator provided in this embodiment of the present invention further includes:

[0112] A protective layer 17 is located on the side of the dielectric layer 14 away from the piezoelectric substrate 11, and the insertion layer 17 is located between the dielectric layer 14 and the protective layer 17.

[0113] Specifically, in this embodiment of the invention, a protective layer 17 is deposited to protect the internal circuit of the surface acoustic wave resonator, or to be used for trimming (by changing the thickness of the protective layer to affect parameters such as the resonant frequency and bandwidth of the surface acoustic wave resonator).

[0114] The material of the protective layer 17 can be SiO2 or Si3N4. It should be noted that when the protective layer 17 is made of Si3N4, the material of the insertion layer 15 can only be a metal. When the protective layer 17 is made of SiO2, the material of the insertion layer 15 is not limited.

[0115] In summary, the surface acoustic wave resonator provided by this embodiment of the invention mainly involves setting an insertion layer 15 above the dielectric layer 14 in the region where the reflector grating 13 is located. The characteristics of the metal material or Si3N4 material are used to form a region with discontinuous changes in acoustic impedance, thereby increasing the bandgap of the reflector grating 13. This allows the reflector grating 13 to reflect broadband signals back to the interdigitated electrodes 12, thereby improving the quality factor of the surface acoustic wave resonator. At the same time, it reduces transverse spurious modes and energy dissipation, achieving the goal of comprehensively improving the performance of the surface acoustic wave resonator.

[0116] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, reference is made to... Figure 15 , Figure 15 This is a schematic diagram comparing the performance of a surface acoustic wave resonator in this application with that in the prior art, provided by an embodiment of the present invention. (Refer to...) Figure 16 , Figure 16 This is a schematic diagram comparing the performance of a surface acoustic wave resonator in another technical solution provided in this application with that of a surface acoustic wave resonator in a prior art solution, wherein the prior art solution is a technical solution without an insertion layer.

[0117] based on Figure 15 In this context, curve 1 represents the real part of the Y parameter in the prior art, i.e., the conductance-frequency curve, and curve 2 represents the real part of the Y parameter in the present application. It is evident from their fluctuations that they effectively suppress stray modes within the range of the resonant frequency and the anti-resonant frequency.

[0118] based on Figure 16 In this context, curve 3 represents the quality factor Q of a surface acoustic wave resonator without an insertion layer in the prior art, while curve 4 represents the quality factor Q of a surface acoustic wave resonator with an insertion layer in the present application. Obviously, the present application achieves a more stable Q value that varies more uniformly with frequency.

[0119] Based on the above embodiments of the present invention, another embodiment of the present invention also provides a method for fabricating a surface acoustic wave resonator, referencing... Figure 17 , Figure 17 This is a schematic flowchart illustrating a method for fabricating a surface acoustic wave (SAW) resonator according to an embodiment of the present invention. The method for fabricating a SAW resonator according to an embodiment of the present invention includes:

[0120] S101: Provide a piezoelectric substrate 11, which has piezoelectric properties.

[0121] S102: An interdigitated electrode 12 is formed on one side of the piezoelectric substrate 11; wherein the interdigitated electrode 12 includes a bus bar, the bus bar including a first bus bar 121 and a second bus bar 122 disposed opposite to each other in the first direction X, and electrode fingers 123 located on the first bus bar 121 and the second bus bar 122; the first bus bar 121 and the second bus bar 122 extend in the same direction, both extending along the second direction Y, the first direction X and the second direction Y are parallel to the plane where the piezoelectric substrate 11 is located, and the first direction X and the second direction Y are perpendicular.

[0122] S103: A reflective grid 13 is formed at at least one end of the interdigitated electrode 12 along the second direction Y.

[0123] S104: A dielectric layer 14 is formed on the side of the interdigitated electrode 12 away from the piezoelectric substrate 11, wherein the orthographic projection of the dielectric layer 14 on the plane of the piezoelectric substrate 11 at least completely covers the orthographic projection of the interdigitated electrode 12 on the plane of the piezoelectric substrate 11 and the orthographic projection of the reflective grating 13 on the plane of the piezoelectric substrate 11.

[0124] S105: An insertion layer 15 is formed on the side of the dielectric layer 14 away from the piezoelectric substrate 11. The orthogonal projection of the reflective gate 13 on the piezoelectric substrate 11 completely covers the orthogonal projection of the insertion layer 15 on the piezoelectric substrate 11. The insertion layer 15 includes a first portion 151 and a second portion 152 in the direction away from the interdigitated electrode 12. The length of the first portion 151 in the first direction X is the same as the length of the reflective gate 13 in the first direction X. The length of the second portion 152 in the first direction X gradually decreases in the direction away from the interdigitated electrode 12.

[0125] In other words, an insertion layer 15 is prepared in the region of the reflective grating 13. The portion of the reflective grating 13 near the interdigital electrode 12 is completely covered by the first portion 151 of the insertion layer 15, and the remaining portion of the reflective grating 13 is partially covered by the second portion 152 of the insertion layer 15. The length of the second portion 152 of the insertion layer 15 gradually decreases in the first direction X in the direction away from the interdigital electrode 12, forming a transition region.

[0126] Specifically, since surface acoustic waves (SAWs) are generated and propagate on the surface of a piezoelectric substrate 11 with piezoelectric properties, an insertion layer 15 is provided in this embodiment of the invention. Depending on the acoustic impedance of the insertion layer 15, the sound velocity in the region where the insertion layer 15 is located will decrease or increase. In other words, based on the placement of the insertion layer 15, by appropriately selecting its material and coordinating its pattern design, the sound velocity in the area covered by the insertion layer 15 can be changed to increase the bandgap of the reflector grating 13. This allows the reflector grating 13 to reflect broadband signals back to the interdigitated electrodes 12, thereby improving the quality factor of the SAW resonator, reducing transverse spurious modes, reducing energy dissipation, and achieving the overall goal of improving the performance of the SAW resonator.

[0127] Optionally, in another embodiment of the present invention, the preparation method provided by the present invention further includes:

[0128] A protective layer 17 is formed on the side of the dielectric layer 14 away from the piezoelectric substrate 11, and the insertion layer 17 is located between the dielectric layer 14 and the protective layer 17.

[0129] Specifically, in this embodiment of the invention, a protective layer is deposited to protect the internal circuitry of the surface acoustic wave resonator, or for trimming (by changing the thickness of the protective layer to affect parameters such as the resonant frequency and bandwidth of the surface acoustic wave resonator).

[0130] Optionally, based on the above embodiments of the present invention, another embodiment of the present invention also provides a filter, which includes the surface acoustic wave resonator described in the above embodiments.

[0131] This filter has the same effect as the surface acoustic wave resonator in the above embodiment.

[0132] The foregoing has provided a detailed description of the surface acoustic wave resonator, its fabrication method, and the filter provided by this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

[0133] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0134] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that elements inherent to a process, method, article, or apparatus that comprises a list of elements, or elements inherent to such processes, methods, articles, or apparatus, are also included. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0135] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A surface acoustic wave resonator, characterized in that, The surface acoustic wave resonator includes: piezoelectric substrate; An interdigitated electrode is located on one side of the piezoelectric substrate; the interdigitated electrode includes a busbar, the busbar includes a first busbar and a second busbar disposed opposite each other in a first direction, and electrode fingers located on the first busbar and the second busbar; the busbar extends along a second direction, the length extension direction of the electrode fingers is parallel to the first direction, the first direction and the second direction are parallel to the plane where the piezoelectric substrate is located, and the first direction and the second direction are perpendicular to each other; A reflective grid located at at least one end of the interdigitated electrode along the second direction; A dielectric layer located on the side of the interdigitated electrodes facing away from the piezoelectric substrate; An insertion layer is located on the side of the dielectric layer opposite to the piezoelectric substrate. The orthogonal projection of the reflective grating on the piezoelectric substrate completely covers the orthogonal projection of the insertion layer on the piezoelectric substrate. The insertion layer includes a first portion and a second portion in the direction away from the interdigitated electrode. The length of the first portion in the first direction is the same as the length of the reflective grating in the first direction. The length of the second portion in the first direction gradually decreases in the direction away from the interdigitated electrode.

2. The surface acoustic wave resonator according to claim 1, characterized in that, The surface acoustic wave resonator also includes: The dummy electrode fingers are located on the first busbar and the second busbar, and the length extension direction of the dummy electrode fingers is parallel to the first direction.

3. The surface acoustic wave resonator according to claim 1, characterized in that, The thickness of the insertion layer is 50nm-200nm.

4. The surface acoustic wave resonator according to claim 1, characterized in that, The material of the insertion layer is a metallic material or Si3N4 material.

5. The surface acoustic wave resonator according to claim 1, characterized in that, The second portion of the insertion layer has a triangular orthographic projection onto the piezoelectric substrate, and the height of the triangle is perpendicular to the first direction.

6. The surface acoustic wave resonator according to claim 5, characterized in that, The vertex angle of the triangle is 90°-120°.

7. The surface acoustic wave resonator according to claim 1, characterized in that, The second part of the insertion layer has a stepped gradient pattern as its orthographic projection onto the piezoelectric substrate.

8. The surface acoustic wave resonator according to claim 7, characterized in that, The stepped gradient pattern has multiple strip sections, the length of which extends parallel to the first direction. The multiple strip sections are arranged sequentially in the direction away from the interdigitated electrode, and the projected area of ​​the multiple strip sections in the direction away from the interdigitated electrode gradually decreases.

9. The surface acoustic wave resonator according to claim 1, characterized in that, The second portion of the insertion layer has an arc-shaped orthographic projection on the piezoelectric substrate, with the arc protruding away from the interdigitated electrode.

10. The surface acoustic wave resonator according to claim 1, characterized in that, The reflective grid includes a first reflective grid and a second reflective grid located at both ends of the interdigitated electrode in the second direction; The insertion layer includes a first insertion layer corresponding to the first reflective grating and a second insertion layer corresponding to the second reflective grating.

11. The surface acoustic wave resonator according to claim 10, characterized in that, The orthographic projection pattern of the second portion of the first insertion layer on the piezoelectric substrate is different from the orthographic projection pattern of the second portion of the second insertion layer on the piezoelectric substrate.

12. The surface acoustic wave resonator according to claim 10, characterized in that, The orthographic projection pattern of the second portion of the first insertion layer on the piezoelectric substrate is the same as the orthographic projection pattern of the second portion of the second insertion layer on the piezoelectric substrate.

13. The surface acoustic wave resonator according to any one of claims 10-12, characterized in that, The material of the first insertion layer is different from the material of the second insertion layer.

14. The surface acoustic wave resonator according to any one of claims 10-12, characterized in that, The material of the first insertion layer is the same as the material of the second insertion layer.

15. The surface acoustic wave resonator according to claim 1, characterized in that, The surface acoustic wave resonator also includes: A protective layer is located on the side of the dielectric layer opposite to the piezoelectric substrate, and the insertion layer is located between the dielectric layer and the protective layer.

16. The surface acoustic wave resonator according to claim 1, characterized in that, The dielectric layer is a temperature compensation layer; The orthographic projection of the temperature compensation layer onto the plane of the piezoelectric substrate at least completely covers the orthographic projection of the interdigitated electrodes onto the plane of the piezoelectric substrate, as well as the orthographic projection of the reflective grating onto the plane of the piezoelectric substrate.

17. A method for fabricating a surface acoustic wave resonator, characterized in that, The preparation method includes: Provide a piezoelectric substrate; An interdigitated electrode is formed on one side of the piezoelectric substrate; the interdigitated electrode includes a bus bar, the bus bar includes a first bus bar and a second bus bar disposed opposite each other in a first direction, and electrode fingers located on the first bus bar and the second bus bar; the bus bar extends along a second direction, the length extension direction of the electrode fingers is parallel to the first direction, the first direction and the second direction are parallel to the plane where the piezoelectric substrate is located, and the first direction and the second direction are perpendicular to each other; A reflective grid is formed at at least one end of the interdigitated electrode along the second direction; A dielectric layer is formed on the side of the interdigitated electrode opposite to the piezoelectric substrate; An insertion layer is formed on the side of the dielectric layer away from the piezoelectric substrate. The orthogonal projection of the reflective grating on the piezoelectric substrate completely covers the orthogonal projection of the insertion layer on the piezoelectric substrate. The insertion layer includes a first portion and a second portion in the direction away from the interdigitated electrode. The length of the first portion in the first direction is the same as the length of the reflective grating in the first direction. The length of the second portion in the first direction gradually decreases in the direction away from the interdigitated electrode.

18. A filter, characterized in that, The filter includes the surface acoustic wave resonator according to any one of claims 1-16.

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