Surface acoustic wave device and surface acoustic wave device preparation method
By adding a sound velocity adjustment medium layer in the gap region of the surface acoustic wave device and setting a sound velocity difference, the problem of limited quality factor improvement in traditional surface acoustic wave devices is solved, and a higher quality factor and better sound wave confinement effect are achieved.
Patent Information
- Application Number
- CN202411127158.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-16
- Publication Date
- 2026-03-03
AI Technical Summary
Traditional surface acoustic wave (SAW) devices have many parasitic modes, resulting in limited improvement in quality factor.
By adding a sound velocity modulation medium layer with a sound wave velocity greater than that of the electrode in the gap region of the surface acoustic wave device, the transverse mode clutter can be suppressed and the sound wave can be confined to the effective region by setting a sound velocity difference in different regions.
This improves the quality factor of surface acoustic wave devices, reduces the influence of stray waves, and enhances the confinement effect of sound waves.
Smart Images
Figure CN121602949A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor device technology, and in particular to a surface acoustic wave (SAW) device and a method for fabricating a SAW device. Background Technology
[0002] Surface acoustic wave (SAW) devices have been widely used in wireless communication due to their excellent performance, low cost, and simple manufacturing process. However, traditional SAW devices, due to their inherent characteristics, exhibit numerous parasitic modes, which reduce their quality factor. Existing technologies typically employ... Figure 1 The conventional surface acoustic wave (SAW) device shown has openings between two opposing electrodes in an interdigital transducer that are distributed sequentially from the center toward the busbar from left to right, and then from a position close to the busbar toward the center. The quality factor of the SAW device is improved by apodization, but this method has limited effect on improving the quality factor. Summary of the Invention
[0003] The purpose of this application is to provide a surface acoustic wave (SAW) device and a method for fabricating a SAW device, thereby improving the quality factor of the SAW device.
[0004] To achieve the above objectives, this application provides a surface acoustic wave device, comprising: a piezoelectric substrate, an interdigital transducer located on one side surface of the piezoelectric substrate, and a sound velocity modulation dielectric layer; the sound velocity modulation dielectric layer is located between the piezoelectric substrate and the interdigital transducer;
[0005] The interdigitated transducer includes two first busbars arranged opposite each other; at least two first electrodes are disposed between the two first busbars; each first electrode includes a first end, a second end opposite to the first end, and an intermediate portion located between the first end and the second end; the first end contacts the first busbar, and the first ends of two adjacent first electrodes contact different first busbars; a gap exists between the second end and another first busbar, the gap forming a gap region extending in a direction parallel to the first busbar;
[0006] The second end forms an edge region extending in a direction parallel to the first busbar, and the middle part forms a middle region extending in a direction parallel to the first busbar; the sound wave velocity in the middle region is greater than the sound wave velocity in the edge region.
[0007] The sound wave velocity of the sound velocity regulating medium layer is greater than that of the first electrode. The sound velocity regulating medium layer is located in the gap region and is covered by the first end, so that the sound wave velocity in the gap region is greater than that in the middle region.
[0008] Optionally, the sound velocity adjustment medium layer is located in the gap region and the portion of the first busbar that contacts the gap region, and the sound velocity adjustment medium layer is covered by the first end and a portion of the first busbar.
[0009] Optionally, a metal mass load block is provided on the surface of the second end away from the piezoelectric substrate, and on the surface of the adjacent first electrode at the position corresponding to the second end away from the piezoelectric substrate, so that the sound wave velocity in the middle region is greater than the sound wave velocity in the edge region.
[0010] Optionally, the sound velocity modulation medium layer is a high sound velocity medium layer.
[0011] Optionally, the surface acoustic wave device further includes at least two reflective gratings located on one side of the piezoelectric substrate, the reflective gratings being located on both sides of the interdigital transducer.
[0012] Optionally, the reflective grid includes two second busbars arranged opposite each other; a second electrode is disposed between the two second busbars; and the two ends of the second electrode are respectively in contact with the two second busbars.
[0013] Optionally, the surface acoustic wave device further includes a temperature compensation layer located on one side of the piezoelectric substrate, the temperature compensation layer covering the interdigital transducer.
[0014] Optionally, the surface acoustic wave device further includes a metal electrical connection layer located on the surface of the temperature compensation layer opposite to the piezoelectric substrate.
[0015] Optionally, the surface acoustic wave device further includes a protective layer located on the surface of the metal electrical connection layer facing away from the piezoelectric substrate.
[0016] To achieve the above objectives, this application also provides a method for fabricating a surface acoustic wave device, comprising:
[0017] A sound velocity modulation dielectric layer is formed on one side surface of the piezoelectric substrate;
[0018] An interdigitated transducer is formed on the surface of the sound velocity modulation medium layer facing away from the piezoelectric substrate to obtain a surface acoustic wave device. The interdigitated transducer includes two first busbars arranged opposite each other. At least two first electrodes are disposed between the two first busbars. Each first electrode includes a first end, a second end opposite to the first end, and a middle portion located between the first end and the second end. The first end is in contact with the first busbar, and the first ends of two adjacent first electrodes are in contact with different first busbars. A gap exists between the second end and another first busbar, and the gap forms a gap region extending in a direction parallel to the first busbar. The second end forms an edge region extending in a direction parallel to the first busbar, and the middle portion forms a middle region extending in a direction parallel to the first busbar. The sound wave velocity in the middle region is greater than the sound wave velocity in the edge region. The sound wave velocity of the sound velocity modulation medium layer is greater than the sound wave velocity of the first electrode. The sound velocity modulation medium layer is located in the gap region and is covered by the first end, such that the sound wave velocity in the gap region is greater than the sound wave velocity in the middle region.
[0019] Obviously, the surface acoustic wave (SAW) device provided in this application increases the sound velocity in the gap region by adding a sound velocity modulation dielectric layer with a sound wave velocity greater than that of the electrodes below the electrodes in the gap region of the SAW device. This results in a larger sound velocity difference between different regions of the SAW device, which can better suppress transverse mode clutter, reduce the influence of stray waves, and confine the sound waves within the effective region, thereby improving the quality factor. This application also provides a method for fabricating a SAW device, and the SAW device fabricated by this method has a high quality factor. Attached Figure Description
[0020] To more clearly illustrate the technical solutions in the embodiments of this application 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 this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0021] Figure 1 A top view of a traditional surface acoustic wave device;
[0022] Figure 2 A top view of a surface acoustic wave device provided in an embodiment of this application;
[0023] Figure 3 for Figure 2 Cross-sectional view from A to A';
[0024] Figure 4 for Figure 2 Cross-sectional view from B to B';
[0025] Figure 5 This is a flowchart illustrating a method for fabricating a surface acoustic wave device according to an embodiment of this application.
[0026] The annotations in the attached figures are explained as follows:
[0027] 1-Piezoelectric substrate; 2-First busbar; 3-First electrode; 31-First end; 32-Second end; 33-Middle part; 4-Metal mass load block; 5-Sound velocity regulating dielectric layer; 6-Reflective grating; 61-Second busbar; 62-Second electrode; 7-Temperature compensation layer. Detailed Implementation
[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0029] Please refer to Figures 2 to 4 , Figure 2 This is a top view of a surface acoustic wave device provided in an embodiment of this application. Figure 3 for Figure 2 Cross-sectional view from A to A' Figure 4 for Figure 2 A cross-sectional view from B to B' shows that the surface acoustic wave device may include: a piezoelectric substrate 1, an interdigital transducer located on one side surface of the piezoelectric substrate 1, and a sound velocity modulation dielectric layer 5; the sound velocity modulation dielectric layer 5 is located between the piezoelectric substrate 1 and the interdigital transducer.
[0030] The interdigitated transducer includes two first busbars 2 arranged opposite to each other; at least two first electrodes 3 are arranged between the two first busbars 2; each first electrode 3 includes a first end 31, a second end 32 opposite to the first end 31, and an intermediate portion 33 located between the first end 31 and the second end 32; the first end 31 contacts the first busbar 2, and the first ends 31 of two adjacent first electrodes 3 contact different first busbars 2; the second end 32 has a gap with another first busbar 2, and the gap forms a gap region extending in a direction parallel to the first busbar 2;
[0031] The second end 32 forms an edge region extending in a direction parallel to the first generatrix 2, and the middle part 33 forms a middle region extending in a direction parallel to the first generatrix 2; the sound wave velocity in the middle region is greater than the sound wave velocity in the edge region.
[0032] The sound velocity of the sound velocity regulating medium layer 5 is greater than that of the first electrode 3. The sound velocity regulating medium layer 5 is located in the gap region and is covered by the first end 31, so that the sound velocity in the gap region is greater than that in the middle region.
[0033] It should be noted that in this embodiment, at least two first electrodes 3 are provided between the two first busbars 2. Typically, the two first busbars 2 are arranged in parallel. The first electrodes 3 are usually rectangular, and the direction of the parallel line of the long side of the first electrode 3 is perpendicular to the direction of the parallel line of the first busbar 2. Multiple first electrodes 3 are parallel to each other, and a certain gap is left between adjacent first electrodes 3. In this embodiment, the first electrode 3 needs to contact one of the first busbars 2 to achieve electrical connection. When the first end 31 of one first electrode 3 contacts one of the first busbars 2, the first end 31 of the first electrode 3 adjacent to that first electrode 3 needs to contact the other first busbar 2. Since the first ends 31 of adjacent first electrodes 3 alternately contact the two first busbars 2, the interdigital transducer in this embodiment includes two gap regions and two edge regions, with the middle region located between the two edge regions. That is, along the direction of the parallel line of the first electrode 3, the interdigital transducer is sequentially divided into a gap region, an edge region, a middle region, an edge region, and a gap region.
[0034] Furthermore, such as Figure 3 As shown, in this embodiment, the sound velocity adjustment medium layer 5 can be located in the gap region and the part of the first busbar 2 that contacts the gap region, and the sound velocity adjustment medium layer 5 is covered by the first end 31 and part of the first busbar 2. It should be noted that by setting the sound velocity adjustment medium layer 5 in part of the busbar, this embodiment can ensure that the deviation caused by photolithography alignment is reduced without affecting the waveform, thereby reducing the manufacturing difficulty of the surface acoustic wave device.
[0035] This embodiment does not limit the specific way of creating a sound speed difference between the middle region and the edge region. For example, a sound speed difference can be created between the middle region and the edge region by increasing the sound wave speed in the middle region, or by decreasing the sound wave speed in the edge region.
[0036] like Figure 4As shown, this embodiment provides a structure that reduces the sound wave velocity in the edge region, creating a sound velocity difference between the middle and edge regions. In this structure, a metal mass load block 4 is provided on the surface of the second end 32 facing away from the piezoelectric substrate 1, and on the surface of the adjacent first electrode 3 facing away from the piezoelectric substrate 1 at the corresponding position of the second end 32. This makes the sound wave velocity in the middle region greater than that in the edge region. It should be noted that in this embodiment, the position of the first electrode 3 occupied by the metal mass load block 4 is the edge region. By adding the metal mass load block 4 to the surface of the first electrode 3 in the edge region, the effective mass of the first electrode 3 increases, thereby reducing the sound wave velocity in the edge region.
[0037] This embodiment does not limit the specific material of the sound velocity adjustment medium layer 5, as long as the sound wave velocity of the sound velocity adjustment medium layer 5 is greater than the sound wave velocity of the first electrode 3. For example, the sound velocity adjustment medium layer 5 can be a high-velocity medium layer, or other high-velocity materials can be used, which can be selected according to the specific material of the actual first electrode 3.
[0038] Furthermore, the surface acoustic wave device in this embodiment may also include at least two reflective gratings 6 located on one side of the piezoelectric substrate 1, with the reflective gratings 6 respectively located on both sides of the interdigital transducer. It should be noted that in this embodiment, reflective gratings 6 are provided on both sides of the interdigital transducer to reflect sound waves. When the sound waves from the interdigital transducer propagate to the reflective gratings 6, they can be reflected back, thereby reducing sound wave leakage.
[0039] This embodiment does not limit the specific structure of the reflective grating 6, as long as it can reflect sound waves. For example, the reflective grating 6 may include two second busbars 61 arranged opposite to each other; a second electrode 62 is arranged between the two second busbars 61; and the two ends of the second electrode 62 are respectively in contact with the two second busbars 61.
[0040] Furthermore, the surface acoustic wave device in this embodiment may also include a temperature compensation layer 7 located on one side of the piezoelectric substrate 1, the temperature compensation layer 7 covering the interdigital transducer. It should be noted that by covering the surface of the interdigital transducer with the temperature compensation layer 7, this embodiment can reduce the influence of temperature on the surface acoustic wave device, thereby improving the stability of the surface acoustic wave device's performance.
[0041] Furthermore, the surface acoustic wave device in this embodiment may also include a metal electrical connection layer located on the surface of the temperature compensation layer 7 facing away from the piezoelectric substrate 1. It should be noted that this embodiment, by providing the metal electrical connection layer, enables the connection between the interdigital transducer and the external circuitry.
[0042] Furthermore, the surface acoustic wave device in this embodiment may also include a protective layer located on the surface of the metal electrical connection layer facing away from the piezoelectric substrate 1. It should be noted that by providing the protective layer, this embodiment can prevent damage to the surface acoustic wave device caused by external environmental factors, thereby improving the service life of the surface acoustic wave device.
[0043] Based on the above embodiments, this application adds a sound velocity adjustment medium layer with a sound wave velocity greater than the electrode sound wave velocity in the gap region of the surface acoustic wave device to increase the sound velocity in the gap region. This results in a greater sound velocity difference between different regions of the surface acoustic wave device, which can better suppress transverse mode clutter of the surface acoustic wave device, reduce the influence of stray waves, and confine the sound waves within the effective region, thereby achieving the effect of improving the quality factor.
[0044] Please refer to Figure 5 , Figure 5 A flowchart illustrating a method for fabricating a surface acoustic wave (SAW) device provided in this application embodiment is included. This method may include:
[0045] S101: A sound velocity modulation dielectric layer is formed on one side surface of the piezoelectric substrate.
[0046] Before step S101, a piezoelectric substrate needs to be provided in advance.
[0047] This embodiment does not limit the specific material of the sound velocity adjustment medium layer. You can refer to the above embodiment of the surface acoustic wave device, which will not be repeated here.
[0048] S102: An interdigital transducer is formed on the surface of the sound velocity modulation dielectric layer away from the piezoelectric substrate to obtain a surface acoustic wave device; the interdigital transducer includes two first busbars arranged opposite each other; at least two first electrodes are disposed between the two first busbars; the first electrode includes a first end, a second end opposite to the first end, and an intermediate portion located between the first end and the second end; the first end is in contact with the first busbar, and the first ends of two adjacent first electrodes are in contact with different first busbars; there is a gap between the second end and another first busbar, the gap forming a gap region extending in a direction parallel to the first busbar; the second end forms an edge region extending in a direction parallel to the first busbar, and the intermediate portion forms an intermediate region extending in a direction parallel to the first busbar; the sound wave velocity in the intermediate region is greater than the sound wave velocity in the edge region; the sound wave velocity in the sound velocity modulation dielectric layer is greater than the sound wave velocity of the first electrode, the sound velocity modulation dielectric layer is located in the gap region, and the sound velocity modulation dielectric layer is covered by the first end, so that the sound wave velocity in the gap region is greater than the sound wave velocity in the intermediate region.
[0049] Furthermore, to reduce sound wave leakage, in this embodiment, after forming an interdigital transducer on the surface of the sound velocity regulating dielectric layer facing away from the piezoelectric substrate, it may further include: forming at least two reflective gratings on the surface of the piezoelectric substrate where the interdigital transducer is disposed, with the reflective gratings located on both sides of the interdigital transducer. This embodiment does not intend to limit the specific structure of the reflective gratings; please refer to the embodiments of the surface acoustic wave device described above, which will not be repeated here.
[0050] This embodiment does not limit the specific way of making the sound velocity difference between the middle region and the edge region. For example, a metal mass load block can be formed on the surface of the second end away from the piezoelectric substrate and on the surface of the adjacent first electrode at the corresponding position of the second end away from the piezoelectric substrate, so that the sound wave velocity in the middle region is greater than the sound wave velocity in the edge region.
[0051] Furthermore, in order to reduce the influence of temperature on the surface acoustic wave device and thus improve the stability of the surface acoustic wave device performance, in this embodiment, an interdigital transducer is formed on the side surface of the sound velocity regulating medium layer away from the piezoelectric substrate; after forming a metal mass load block on the surface of the second end away from the piezoelectric substrate and the surface of the adjacent first electrode at the corresponding position of the second end away from the piezoelectric substrate, it may further include: forming a temperature compensation layer covering the interdigital transducer on the side surface of the interdigital transducer and the metal mass load block away from the piezoelectric substrate.
[0052] Furthermore, in order to achieve the connection between the interdigital transducer and the external circuit, after forming a temperature compensation layer covering the interdigital transducer on the surface of the interdigital transducer and the metal mass load block away from the piezoelectric substrate in this embodiment, it may also include: forming a metal electrical connection layer on the surface of the temperature compensation layer away from the piezoelectric substrate.
[0053] Furthermore, in order to prevent damage to the surface acoustic wave device caused by external environmental factors and thereby improve the service life of the surface acoustic wave device, this embodiment may further include forming a protective layer on the surface of the metal electrical connection layer away from the piezoelectric substrate after forming a metal electrical connection layer on the surface of the temperature compensation layer away from the piezoelectric substrate.
[0054] Furthermore, in order to ensure the reliability of the surface acoustic wave device, after forming a protective layer on the surface of the metal electrical connection layer away from the piezoelectric substrate in this embodiment, the surface acoustic wave device can be tested and tuned to obtain the final surface acoustic wave device.
[0055] Based on the above embodiments, the surface acoustic wave (SAW) device prepared by the method provided in this application has a higher quality factor because a sound velocity modulation medium layer with a sound wave velocity greater than the electrode sound wave velocity is added below the electrode in the gap region of the SAW device to increase the sound velocity in the gap region. This results in a larger sound velocity difference between different regions of the SAW device, which can better suppress transverse mode clutter of the SAW device, reduce the influence of stray waves, and confine the sound waves within the effective region.
[0056] This document uses specific examples to illustrate the principles and implementation methods of this application. The various embodiments are progressive, with each embodiment focusing on its differences from others. Similar or identical parts between embodiments can be referred to interchangeably. The descriptions of the embodiments above are merely illustrative of the method and core ideas of this application. For those skilled in the art, various improvements and modifications can be made to this application without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of this application.
[0057] It should also be noted that, in this specification, 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 a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. 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 the element.
Claims
1. A surface acoustic wave device, characterized in that, include: A piezoelectric substrate, an interdigital transducer located on one side surface of the piezoelectric substrate, and a sound velocity modulation dielectric layer; The sound velocity modulation medium layer is located between the piezoelectric substrate and the interdigital transducer; The interdigitated transducer includes two first busbars arranged opposite each other; at least two first electrodes are disposed between the two first busbars; each first electrode includes a first end, a second end opposite to the first end, and an intermediate portion located between the first end and the second end; the first end contacts the first busbar, and the first ends of two adjacent first electrodes contact different first busbars; a gap exists between the second end and another first busbar, the gap forming a gap region extending in a direction parallel to the first busbar; The second end forms an edge region extending in a direction parallel to the first busbar, and the middle part forms a middle region extending in a direction parallel to the first busbar; the sound wave velocity in the middle region is greater than the sound wave velocity in the edge region. The sound wave velocity of the sound velocity regulating medium layer is greater than that of the first electrode. The sound velocity regulating medium layer is located in the gap region and is covered by the first end, so that the sound wave velocity in the gap region is greater than that in the middle region.
2. The surface acoustic wave device according to claim 1, characterized in that, The sound velocity adjustment medium layer is located in the gap region and the portion of the first busbar that contacts the gap region, and the sound velocity adjustment medium layer is covered by the first end and a portion of the first busbar.
3. The surface acoustic wave device according to claim 1, characterized in that, The second end facing away from the piezoelectric substrate and the adjacent first electrode at the position corresponding to the second end facing away from the piezoelectric substrate are both provided with metal mass load blocks, so that the sound wave velocity in the middle region is greater than the sound wave velocity in the edge region.
4. The surface acoustic wave device according to claim 1, characterized in that, The sound velocity modulation medium layer is a high sound velocity medium layer.
5. The surface acoustic wave device according to claim 1, characterized in that, Also includes: At least two reflective gratings are located on one side of the piezoelectric substrate, and the reflective gratings are located on both sides of the interdigital transducer.
6. The surface acoustic wave device according to claim 5, characterized in that, The reflective grid includes two second busbars arranged opposite each other; a second electrode is disposed between the two second busbars; and the two ends of the second electrode are respectively in contact with the two second busbars.
7. The surface acoustic wave device according to claim 1, characterized in that, Also includes: A temperature compensation layer is located on one side surface of the piezoelectric substrate, and the temperature compensation layer covers the interdigital transducer.
8. The surface acoustic wave device according to claim 7, characterized in that, Also includes: A metal electrical connection layer located on the surface of the temperature compensation layer opposite to the piezoelectric substrate.
9. The surface acoustic wave device according to claim 8, characterized in that, Also includes: A protective layer located on the surface of the metal electrical connection layer opposite to the piezoelectric substrate.
10. A method for fabricating a surface acoustic wave device, characterized in that, include: A sound velocity modulation dielectric layer is formed on one side surface of the piezoelectric substrate; An interdigitated transducer is formed on the surface of the sound velocity modulation medium layer facing away from the piezoelectric substrate to obtain a surface acoustic wave device. The interdigitated transducer includes two first busbars arranged opposite each other. At least two first electrodes are disposed between the two first busbars. Each first electrode includes a first end, a second end opposite to the first end, and a middle portion located between the first end and the second end. The first end is in contact with the first busbar, and the first ends of two adjacent first electrodes are in contact with different first busbars. A gap exists between the second end and another first busbar, and the gap forms a gap region extending in a direction parallel to the first busbar. The second end forms an edge region extending in a direction parallel to the first busbar, and the middle portion forms a middle region extending in a direction parallel to the first busbar. The sound wave velocity in the middle region is greater than the sound wave velocity in the edge region. The sound wave velocity of the sound velocity modulation medium layer is greater than the sound wave velocity of the first electrode. The sound velocity modulation medium layer is located in the gap region and is covered by the first end, such that the sound wave velocity in the gap region is greater than the sound wave velocity in the middle region.