Surface acoustic wave resonator and filter

Abstract

The utility model relates to the technical field of semiconductor devices, in particular to a surface acoustic wave resonator and a filter, comprising a substrate, a piezoelectric layer and an electrode layer which are stacked in sequence, a substrate bulge is arranged on the substrate; the piezoelectric layer covers the substrate bulge and forms a piezoelectric layer bulge; the electrode layer comprises a plurality of interdigital electrodes arranged on the surface of the piezoelectric layer at intervals, and the ends of the interdigital electrodes cover the piezoelectric layer protrusions and form electrode protrusions. The acoustic impedance of the substrate protrusions is inconsistent with the acoustic impedance of the piezoelectric layer. The pseudo mode can be effectively inhibited, and the quality factor of the device is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor devices, in particular to a surface acoustic wave resonator and filter. BACKGROUND

[0002] Surface acoustic wave resonators have been widely used in the fields of wireless communication, sensors, signal processing, etc. At present, the surface acoustic wave resonator technology still faces some deficiencies. There are certain difficulties in the suppression of pseudo modes of the surface acoustic wave resonator, especially for high-frequency or narrow-band applications, the influence of pseudo modes is particularly significant. These pseudo modes usually cause signal distortion and reduce the performance of the device. In addition, as the operating frequency increases, the improvement of the quality factor of the device is limited, resulting in high energy loss and poor frequency selectivity of the device. CONTENT OF THE UTILITY MODEL

[0003] The purpose of the present application is to provide a surface acoustic wave resonator and filter which can effectively suppress pseudo modes and improve the quality factor of the device.

[0004] Embodiments of the present application are implemented as follows:

[0005] In one aspect, the present application provides a surface acoustic wave resonator, comprising a substrate, a piezoelectric layer and an electrode layer which are sequentially stacked; the substrate is provided with a substrate protrusion; the piezoelectric layer covers the substrate protrusion and forms a piezoelectric layer protrusion; the electrode layer comprises a plurality of interdigital electrodes arranged at intervals on the surface of the piezoelectric layer, the end of the interdigital electrode covers the piezoelectric layer protrusion and forms an electrode protrusion; the acoustic impedance of the substrate protrusion is inconsistent with the acoustic impedance of the piezoelectric layer.

[0006] As an optional implementation, one end of each interdigital electrode projected on the substrate is provided with the substrate protrusion; two adjacent interdigital electrodes correspond to two substrate protrusions, one of which is located at the first end of one interdigital electrode; the other substrate protrusion is located at the second end of the other interdigital electrode.

[0007] As an optional implementation, both ends of each interdigital electrode projected on the substrate are respectively provided with the substrate protrusion.

[0008] As an optional implementation, the end of the interdigital electrode is provided with a reflective grid structure; the projection of at least part of the reflective grid structure falls on the surface of the piezoelectric layer protrusion.

[0009] As an optional implementation, the height of the substrate protrusion is less than the thickness of the piezoelectric layer; the height of the piezoelectric layer protrusion is less than the thickness of the interdigital electrode.

[0010] As an optional implementation, the width of the piezoelectric layer protrusion is equal to the width of the interdigital electrode; or, the width of the piezoelectric layer protrusion is less than the width of the interdigital electrode; or, the width of the piezoelectric layer protrusion is greater than the width of the interdigital electrode.

[0011] As an optional implementation, the piezoelectric layer protrusion is consistent with the width of the substrate protrusion.

[0012] As an optional implementation, the substrate protrusion includes any one of a quartz protrusion, a silicon carbide protrusion, and an aluminum nitride protrusion.

[0013] As an optional implementation, there is a spacing between adjacent substrate protrusions.

[0014] In a second aspect, an embodiment of the present application provides a filter, including the above-mentioned surface acoustic wave resonator.

[0015] The beneficial effects of the embodiments of the present application include:

[0016] The surface acoustic wave resonator provided by the embodiments of the present application includes a substrate, a piezoelectric layer, and an electrode layer which are sequentially stacked; the substrate is provided with a substrate protrusion; the piezoelectric layer covers the substrate protrusion and forms a piezoelectric layer protrusion; the electrode layer includes a plurality of interdigital electrodes arranged at intervals on the surface of the piezoelectric layer, the end of the interdigital electrode covers the piezoelectric layer protrusion and forms an electrode protrusion; the acoustic impedance of the substrate protrusion is inconsistent with the acoustic impedance of the piezoelectric layer, which can form a Bragg reflection structure with high and low acoustic impedance superposition, and the effect of suppressing pseudo modes is achieved by improving the leakage of longitudinal waves. The embodiments of the present application not only can effectively suppress pseudo modes, but also can improve the quality factor of the device. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0018] Figure 1 FIG. 1 is a structural schematic diagram of a surface acoustic wave resonator according to an embodiment of the present application;

[0019] Figure 2 FIG. 2 is a structural schematic diagram of a surface acoustic wave resonator according to another embodiment of the present application;

[0020] Figure 3 FIG. 3 is a structural schematic diagram of a surface acoustic wave resonator according to another embodiment of the present application;

[0021] Figure 4Fig. 4 is a structural schematic diagram of a surface acoustic wave resonator according to an embodiment of the present application;

[0022] Figure 5 Fig. 5 is a structural schematic diagram of a surface acoustic wave resonator according to an embodiment of the present application;

[0023] Figure 6 Fig. 6 is a structural schematic diagram of a surface acoustic wave resonator according to an embodiment of the present application;

[0024] Figure 7 Fig. 7 is a structural schematic diagram of a surface acoustic wave resonator according to an embodiment of the present application;

[0025] Figure 8 Fig. 8 is a structural schematic diagram of a surface acoustic wave resonator according to an embodiment of the present application.

[0026] Fig. 1: 100 - substrate; 101 - piezoelectric layer; 102 - electrode layer; 103 - substrate protrusion; 104 - piezoelectric layer protrusion; 105 - interdigital electrode; 106 - electrode protrusion. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings for the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present application.

[0029] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. In addition, the terms "first", "second", "third" and the like are only used to distinguish description, and cannot be understood as indicating or implying relative importance.

[0030] In the description of the application, it should be explained that, unless otherwise explicitly specified and limited, the terms "set", "install", "connect", "connect" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0031] As an important technical route, surface acoustic wave resonators are widely used in radio frequency resonators and have been widely applied in the fields of wireless communication, sensors, signal processing, etc. Currently, the surface acoustic wave resonator technology still faces some deficiencies, especially in the aspects of spurious mode suppression and quality factor improvement. Spurious modes refer to non-rational modes caused by device structure or material defects near the operating frequency of the surface acoustic wave resonator. These spurious modes often lead to signal distortion and reduce the performance of the device. Current surface acoustic wave resonators have certain difficulties in suppressing spurious modes, especially for high-frequency or narrow-band applications, the influence of spurious modes is particularly significant, but in practical applications, completely suppressing spurious modes is still a challenge, therefore, more efficient spurious mode suppression strategies are needed to ensure the stability and frequency selectivity of the resonator. The quality factor is an important parameter to measure the performance of the resonator, which represents the degree of energy loss of the resonator. High Q value means low energy loss and higher frequency selectivity, which is a key requirement in many high-frequency applications. However, the current technology faces some bottlenecks in improving the quality of surface acoustic wave resonators. Although the Q value can be improved to some extent by optimizing materials, reducing electrode loss and improving structural design, the improvement of Q value is still limited due to surface effects, mechanical mismatch and interface loss between electrodes and materials. In addition, as the operating frequency increases, the improvement of Q value will face more difficulties, because the device size and structural complexity at high frequency will also affect the loss performance.

[0032] To solve the above technical problems, the embodiments of the present application provide a surface acoustic wave resonator and a filter.

[0033] Reference Figure 1 , Figure 2As shown, the surface acoustic wave resonator provided by the embodiment of the present application comprises a substrate 100, a piezoelectric layer 101 and an electrode layer 102 which are sequentially stacked; the substrate 100 is provided with a substrate protrusion 103; the piezoelectric layer 101 covers the substrate protrusion 103 and forms a piezoelectric layer protrusion 104; the electrode layer 102 comprises a plurality of interdigital electrodes 105 arranged at intervals on the surface of the piezoelectric layer 101, the end of the interdigital electrode 105 covers the piezoelectric layer protrusion 104 and forms an electrode protrusion 106; the acoustic impedance of the substrate protrusion 103 is inconsistent with the acoustic impedance of the piezoelectric layer 101, which can form a Bragg reflection structure with high and low acoustic impedance superposition, and the effect of suppressing pseudo modes is achieved by improving the leakage of longitudinal waves.

[0034] Specifically, the embodiment of the present application suppresses pseudo modes by establishing an acoustic impedance boundary, and the stacking structures in different regions of the interdigital electrode 105 are different, and the acoustic impedance is different during the transmission of acoustic waves, which further suppresses pseudo modes and improves the quality factor of the device.

[0035] It should be noted that the substrate 100 is provided with a substrate protrusion 103, and the piezoelectric layer 101 covers the substrate protrusion 103 to form its own protrusion; the interdigital electrode 105 of the electrode layer 102 partially covers these protrusions. The structure design of the embodiment of the present application can affect the propagation path of acoustic waves by changing the acoustic impedance between different levels. The high and low acoustic impedance superposition formed by the different acoustic impedances between the substrate 100 and the piezoelectric layer 101 constructs a Bragg reflection structure.

[0036] It should be noted that the acoustic impedance of the piezoelectric layer protrusion 104 and the interdigital electrode 105 is also not the same, and a Bragg reflection structure with high and low acoustic impedance superposition can also be formed.

[0037] It should be noted that the high and low acoustic impedance superposition region described above includes not only the side surface of the substrate protrusion 103 away from the substrate 100, but also the side surface of the substrate protrusion 103 perpendicular to the substrate 100. Similarly, the side surface of the piezoelectric layer protrusion 104 away from the piezoelectric layer 101 and the side surface of the piezoelectric layer protrusion 104 also constitute a high and low acoustic impedance superposition region.

[0038] The technical effects that can be achieved by the embodiment of the present application are as follows:

[0039] The embodiment of the present application establishes an acoustic impedance boundary, especially forms different stacking structures in different regions of the interdigital electrode 105, so that the acoustic wave encounters different acoustic impedances during transmission, which effectively suppresses the generation of pseudo modes. This is crucial for improving signal clarity and device performance, especially in high-frequency or narrow-band applications.

[0040] Due to the effective suppression of pseudo modes, unnecessary energy loss is reduced, and at the same time, the propagation efficiency of sound waves inside the device is improved through the above design, further improving the quality factor of the resonator. Higher Q value means lower energy loss and better frequency selectivity, so the application embodiment can meet the application scenarios of high-precision frequency control.

[0041] Referring to Figure 3 , Figure 4 and Figure 5 , as an optional implementation, each interdigital electrode 105 is provided with a substrate protrusion 103 at one end of its projection on the substrate 100; the two adjacent interdigital electrodes 105 correspond to two substrate protrusions 103, one of which is located at the first end of one interdigital electrode 105; the other substrate protrusion 103 is located at the second end of the other interdigital electrode 105.

[0042] The projection of each interdigital electrode 105 on the substrate 100 is provided with a substrate protrusion 103 at one end, and on the two adjacent interdigital electrodes 105, one substrate protrusion 103 is located at the first end of one interdigital electrode 105, and the other substrate protrusion 103 is located at the second end of the other interdigital electrode 105.

[0043] The asymmetric layout provided by the application embodiment forms an asymmetric acoustic impedance environment, so that the sound waves encounter different acoustic impedance conditions when passing through different positions. This not only helps to form a more complex Bragg reflection structure, but also more effectively controls the propagation path and mode of the sound waves.

[0044] It should be noted that the application embodiment can form more complex and effective acoustic impedance boundaries around the interdigital electrode 105 by asymmetrically arranging the substrate protrusion 103. These boundaries can better restrict unnecessary sound wave modes, especially those that may cause signal distortion. Therefore, the design of the application embodiment can significantly improve the suppression effect of pseudo modes, thereby improving the overall performance of the resonator.

[0045] It should be noted that the layout of the substrate protrusion 103 of the application embodiment helps to optimize the leakage of longitudinal waves, reduce energy loss, and improve frequency selectivity. This is particularly important for applications that require high-precision frequency control. In addition, due to the effective suppression of pseudo modes, the stability of the resonator within the operating frequency range is also enhanced.

[0046] In addition, the design provided by the application embodiment reduces the energy loss inside the surface acoustic wave resonator, especially by optimizing the sound wave propagation path and reducing interface loss. The quality factor of the resonator is effectively improved, making the device have higher efficiency and better performance.

[0047] Referring to Figure 6、 Figure 7 and Figure 8 As an optional embodiment, as shown in FIG. 1, each interdigital electrode 105 is provided with a substrate protrusion 103 at each end of the projection on the substrate 100.

[0048] Unlike the above embodiment, the present embodiment forms an electrode protrusion 106 at each end of each interdigital electrode 105. That is, each interdigital electrode 105 is provided with a substrate protrusion 103 at each end of the projection on the substrate 100, and each interdigital electrode 105 is supported by the corresponding substrate protrusion 103 at each end. In this way, a more uniform and symmetrical acoustic impedance boundary can be formed in the entire resonator structure. Such a design helps to more accurately control the propagation path and mode of acoustic waves inside the device.

[0049] It should be noted that the symmetrically arranged substrate protrusions 103 can form a more stable and consistent acoustic impedance environment around the interdigital electrodes 105, thereby more effectively suppressing spurious modes. This design of the present embodiment reduces unnecessary acoustic modes, especially in high-frequency or narrow-band applications, which can significantly reduce signal distortion and improve device performance.

[0050] The present embodiment controls the longitudinal wave leakage better through the symmetrical acoustic impedance boundary design, thereby improving the frequency selectivity and stability. This is particularly important for applications that require high-precision frequency control, such as filter design in wireless communication.

[0051] In addition, compared with the above asymmetric layout, the symmetric layout is easier to implement and control, thereby simplifying the manufacturing process, reducing costs, and ensuring or even improving product performance.

[0052] That is, the new embodiment of the present embodiment forms a more uniform and stable acoustic impedance environment by providing a substrate protrusion 103 at each end of each interdigital electrode 105. This method not only can more effectively suppress spurious modes, but also can further improve frequency selectivity and stability, and improve the quality factor, providing another effective solution for the design of high-performance surface acoustic wave resonators. In addition, its relatively simple layout may also bring advantages in manufacturing process.

[0053] As an optional embodiment, the interdigital electrode 105 is provided with a reflective grating structure at the end; at least part of the projection of the reflective grating structure falls on the surface of the piezoelectric layer protrusion 104.

[0054] It should be noted that the reflective grating structure is provided at the end of the interdigital electrode 105. These reflective gratings can be small structures made of similar or different materials from the interdigital electrode 105, and their main function is to reflect acoustic waves to enhance the propagation of acoustic waves in a specific direction.

[0055] In this embodiment, a portion of the reflective grating structure is projected onto the surface of the piezoelectric layer protrusion 104. The piezoelectric layer protrusion 104 can lift the reflective grating structure, forming a complex three-dimensional acoustic impedance boundary. By combining the substrate protrusion 103, the piezoelectric layer protrusion 104, and the reflective grating structure, a multi-level acoustic impedance modulation mechanism is formed. This multi-level design allows for more precise control of the propagation path and mode of sound waves in different media.

[0056] It should be noted that by setting a reflective grating structure at the end of the interdigital electrode 105 and having part of its projection fall on the piezoelectric layer protrusion 104, the propagation path and mode of the sound wave can be controlled more precisely. This design helps to improve longitudinal wave leakage, reduce energy loss, and thus improve frequency selectivity and stability.

[0057] Furthermore, the presence of the reflector grating structure can help extend the operating frequency band of the resonator. By adjusting the size, shape, and position of the reflector grating, more effective control of sound waves in different frequency ranges can be achieved, thereby meeting a wider range of application needs.

[0058] Reference Figure 6 , Figure 7 as well as Figure 8 As shown, in one optional implementation, the height of the substrate protrusion 103 is less than the thickness of the piezoelectric layer 101; the height of the piezoelectric layer protrusion 104 is less than the thickness of the interdigitated electrode 105.

[0059] It should be noted that the height of the substrate protrusion 103 is less than the thickness of the piezoelectric layer 101. This means that the protrusion on the substrate 100 will not exceed the thickness of the piezoelectric layer 101, ensuring that the piezoelectric layer 101 can completely cover the substrate protrusion 103 and form a new protrusion structure thereon. The height of the piezoelectric layer protrusion 104 is less than the thickness of the interdigitated electrode 105, meaning that the protrusion on the piezoelectric layer 101 will not exceed the thickness of the interdigitated electrode 105, ensuring that the interdigitated electrode 105 can effectively cover the piezoelectric layer protrusion 104, forming a stable electrode protrusion 106.

[0060] As an optional implementation, the width of the piezoelectric layer protrusion 104 is equal to the width of the interdigitated electrode 105; or, the width of the piezoelectric layer protrusion 104 is less than the width of the interdigitated electrode 105; or, the width of the piezoelectric layer protrusion 104 is greater than the width of the interdigitated electrode 105.

[0061] The piezoelectric layer protrusion 104 has the same width as the substrate protrusion 103.

[0062] It should be noted that, referring to Figure 3 , Figure 6As shown, the width of the piezoelectric layer protrusion 104 is equal to the width of the interdigital electrode 105. This design can ensure that the propagation path of the acoustic wave between the interdigital electrode 105 and the piezoelectric layer 101 is more uniform and stable, reducing unnecessary energy loss. Due to the consistency and symmetry of the structure, this design helps to improve the frequency selectivity and stability, which is particularly suitable for application scenarios that require high-precision frequency control.

[0063] It should be noted that, as shown in Figure 4 、 Figure 7 , the width of the piezoelectric layer protrusion 104 is less than the width of the interdigital electrode 105. The partially covered design provides more propagation path options for the acoustic wave, which can adjust the propagation direction and mode of the acoustic wave to a certain extent.

[0064] It should be noted that, as shown in Figure 5 、 Figure 8 , the width of the piezoelectric layer protrusion 104 is greater than the width of the interdigital electrode 105, forming an expanded reflection boundary, which helps to more effectively reflect and focus the acoustic wave, further suppressing the pseudo mode.

[0065] The person skilled in the art can select any one of the structural arrangements according to different needs.

[0066] As an optional implementation, the substrate protrusion 103 includes any one of a quartz protrusion, a silicon carbide protrusion, and an aluminum nitride protrusion.

[0067] Among them, the adjacent substrate protrusions 103 have a spacing.

[0068] It should be noted that the material of the substrate protrusion 103 can be the same as the substrate 100, and the person skilled in the art can select it according to the needs without special limitation.

[0069] The filter provided by the embodiment of the present application includes the above-mentioned surface acoustic wave resonator.

[0070] The filter provided by the embodiment of the present application suppresses the pseudo mode by establishing an acoustic impedance boundary through the above-mentioned surface acoustic wave resonator. The layer-by-layer structure is different in different regions of the interdigital electrode 105, and the acoustic impedance is different in the acoustic wave transmission process, further suppressing the pseudo mode and improving the device quality factor.

[0071] It should be noted that the structure provided by the embodiment of the present application is also applicable to other radio frequency MEMS devices.

[0072] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A surface acoustic wave resonator, characterized in that, The device includes a substrate (100), a piezoelectric layer (101), and an electrode layer (102) stacked sequentially. The substrate (100) has a substrate protrusion (103). The piezoelectric layer (101) covers the substrate protrusion (103) and forms a piezoelectric layer protrusion (104). The electrode layer (102) includes a plurality of interdigitated electrodes (105) spaced apart on the surface of the piezoelectric layer (101). The ends of the interdigitated electrodes (105) cover the piezoelectric layer protrusion (104) and form electrode protrusions (106). The acoustic impedance of the substrate protrusion (103) is inconsistent with that of the piezoelectric layer (101).

2. The surface acoustic wave resonator according to claim 1, characterized in that, Each of the interdigitated electrodes (105) has a substrate protrusion (103) at one end projected onto the substrate (100); two adjacent interdigitated electrodes (105) correspond to two substrate protrusions (103), one of which is located at the first end of one interdigitated electrode (105); the other substrate protrusion (103) is located at the second end of another interdigitated electrode (105).

3. The surface acoustic wave resonator according to claim 1, characterized in that, Each of the interdigitated electrodes (105) has a substrate protrusion (103) at both ends of its projection onto the substrate (100).

4. The surface acoustic wave resonator according to any one of claims 1-3, characterized in that, The interdigitated electrode (105) has a reflective grating structure at its end; at least part of the projection of the reflective grating structure falls on the surface of the piezoelectric layer protrusion (104).

5. The surface acoustic wave resonator according to any one of claims 1-3, characterized in that, The height of the substrate protrusion (103) is less than the thickness of the piezoelectric layer (101); the height of the piezoelectric layer protrusion (104) is less than the thickness of the interdigitated electrode (105).

6. The surface acoustic wave resonator according to any one of claims 1-3, characterized in that, The width of the piezoelectric layer protrusion (104) is equal to the width of the interdigitated electrode (105); or, the width of the piezoelectric layer protrusion (104) is less than the width of the interdigitated electrode (105); or, the width of the piezoelectric layer protrusion (104) is greater than the width of the interdigitated electrode (105).

7. The surface acoustic wave resonator according to any one of claims 1-3, characterized in that, The width of the piezoelectric layer protrusion (104) is the same as that of the substrate protrusion (103).

8. The surface acoustic wave resonator according to any one of claims 1-3, characterized in that, The substrate bumps (103) include any one of quartz bumps, silicon carbide bumps, and aluminum nitride bumps.

9. The surface acoustic wave resonator according to any one of claims 1-3, characterized in that, There is a gap between adjacent substrate protrusions (103).

10. A filter, characterized in that, Includes the surface acoustic wave resonator according to any one of claims 1-9.

Images