A surface acoustic wave resonator, filter and electronic device

Abstract

This invention relates to the field of semiconductor structure technology and discloses a surface acoustic wave (SAW) resonator, filter, and electronic device. The SAW resonator includes a piezoelectric layer and an interdigital transducer. The interdigital transducer includes multiple electrode strips and a first busbar and a second busbar arranged opposite each other along a first direction. The first and second strips are alternately arranged along a second direction, and the first and second directions intersect. The interdigital transducer includes a central region and edge regions located on both sides of the central region along the second direction. A first metal duty cycle is smaller than a second metal duty cycle, and the difference between the second and first metal duty cycles ranges from 0.05 to 0.3. The first metal duty cycle is the metal duty cycle of the electrode strips in the edge regions, and the second metal duty cycle is the metal duty cycle of the electrode strips in the central region. This invention weakens the strong coupling between the incident wave and the reflected wave, thereby reducing the ripple on the low-frequency side of the resonant frequency.

Description

Technical Field

[0001] This utility model relates to the field of semiconductor structure technology, specifically to a surface acoustic wave resonator, filter, and electronic device. Background Technology

[0002] Surface acoustic wave (SAW) resonators are passive electronic components that utilize the piezoelectric effect and the physical characteristics of surface acoustic wave propagation to achieve functions such as acoustic filtering and frequency control. SAW resonators have excellent stability, reliability, high frequency characteristics, and low loss characteristics, and are widely used in wireless communication, radar, satellite communication, and navigation and positioning.

[0003] Currently, when the frequency of the input electrical signal is less than the resonant frequency (i.e., to the left of the resonant frequency in the frequency response curve), the surface acoustic wave resonator usually has strong ripple due to the reflection between the electrode fingers. This causes the frequency response of the broadband acoustic filter based on it to generate corresponding spurious signals, which seriously affects the integrity of the link signal in the communication system. Utility Model Content

[0004] In view of this, the present invention provides a surface acoustic wave resonator, filter and electronic device to improve the defect of strong ripple in surface acoustic wave resonators due to reflection between electrode fingers.

[0005] In a first aspect, this utility model provides a surface acoustic wave (SAW) resonator, which includes a piezoelectric layer and an interdigital transducer disposed on one side of the piezoelectric layer. The interdigital transducer includes multiple electrode fingers and a first bus bar and a second bus bar arranged opposite to each other along a first direction. The first finger of the multiple electrode fingers is disposed on the side of the first bus bar closer to the second bus bar, and the second finger of the multiple electrode fingers is disposed on the side of the second bus bar closer to the first bus bar. The first finger and the second finger are alternately arranged along a second direction, which is parallel to the plane of the piezoelectric layer and intersects with it. The interdigital transducer includes a central region and edge regions located on both sides of the central region along the second direction. The first metal duty cycle is less than the second metal duty cycle, and the difference between the second metal duty cycle and the first metal duty cycle ranges from 0.05 to 0.3. The first metal duty cycle is the metal duty cycle of the electrode fingers in the edge region, and the second metal duty cycle is the metal duty cycle of the electrode fingers in the central region.

[0006] In one alternative implementation, the interdigitation spacing in the central region is the same as that in the edge region, and the interdigitation width in the edge region is smaller than that in the central region.

[0007] In one alternative implementation, the interdigitation width of the central region is the same as that of the edge region, and the interdigitation gap of the edge region is greater than that of the central region.

[0008] In one alternative embodiment, the surface acoustic wave resonator further includes a reflective grating; the reflective grating is located on the side of the piezoelectric layer where the interdigital transducer is located, and is located on at least one side of the interdigital transducer along the second direction, and the third metal duty cycle is greater than the second metal duty cycle, the third metal duty cycle being the metal duty cycle of the reflective grating.

[0009] In one alternative implementation, the difference between the third metal duty cycle and the second metal duty cycle ranges from 0.05 to 0.3.

[0010] In one alternative implementation, the number of electrode fingers in the edge region ranges from 5 to 15.

[0011] In one optional embodiment, the surface acoustic wave resonator further includes a piston structure; at least one piston structure is provided in the extension direction of the electrode fingers, the width of the piston structure in the second direction is greater than the width of the interdigitated fingers, and when the width of the interdigitated fingers in the central region and the width of the interdigitated fingers in the edge region are not the same, a first ratio is equal to a second ratio, the first ratio is the ratio of the width of the piston structure in the second direction to the width of the interdigitated fingers in the edge region, and the second ratio is the ratio of the width of the piston structure in the second direction to the width of the interdigitated fingers in the central region.

[0012] In one optional embodiment, the interdigital transducer further includes a plurality of first pseudo-fingers and a plurality of second pseudo-fingers; the first pseudo-fingers are disposed on the side of the first busbar near the second busbar, and the second pseudo-fingers are disposed on the side of the second busbar near the first busbar, the first finger bar and the second pseudo-fingers are disposed opposite to each other along a first direction, and the second finger bar and the first pseudo-fingers are disposed opposite to each other along the first direction.

[0013] Secondly, this utility model provides a filter, which includes the surface acoustic wave resonator of the first aspect or any corresponding embodiment described above.

[0014] Thirdly, this utility model provides an electronic device, which includes the filter described in the second aspect above or any corresponding embodiment thereof.

[0015] The surface acoustic wave resonator, filter, and electronic device provided in this embodiment have at least the following advantages:

[0016] In this embodiment, by making the first metal duty cycle in the edge region of the interdigital transducer smaller than the second metal duty cycle in the central region, the phase consistency of the reflected sound wave can be disrupted, thereby weakening the strong coupling between the incident and reflected waves. This suppresses ripple on the low-frequency side of the resonant frequency and improves the passband performance of the broadband filter. Simultaneously, limiting the difference between the second and first metal duty cycles to within 0.05 to 0.3 enhances the suppression of ripple on the low-frequency side of the resonant frequency while reducing the impact on the admittance value at the resonant frequency. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the specific embodiments or related technologies of this utility model, the drawings used in the description of the specific embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a top view schematic diagram of a conventional surface acoustic wave resonator;

[0019] Figure 2 This is a top view schematic diagram of a first type of surface acoustic wave resonator according to an embodiment of the present utility model;

[0020] Figure 3 This is a schematic cross-sectional view of the first type of surface acoustic wave resonator according to an embodiment of the present invention;

[0021] Figure 4 yes Figure 1 The surface acoustic wave resonator shown (Comparative Example 1) and Figure 2 A comparison of the frequency response simulation results of the surface acoustic wave resonator (Example 1) shown in the figure;

[0022] Figure 5 This is a comparison diagram of the frequency response simulation results of surface acoustic wave resonators with different first metal duty cycles according to an embodiment of the present invention;

[0023] Figure 6 This is a comparison of the frequency response simulation results of surface acoustic wave resonators with different first metal duty cycles according to another embodiment of this utility model;

[0024] Figure 7 This is a top view schematic diagram of a second type of surface acoustic wave resonator according to an embodiment of the present utility model;

[0025] Figure 8 This is a top view schematic diagram of a third type of surface acoustic wave resonator according to an embodiment of the present utility model;

[0026] Figure 9 This is a top view schematic diagram of the fourth type of surface acoustic wave resonator according to an embodiment of the present utility model;

[0027] Figure 10 yes Figure 1 The surface acoustic wave resonator shown (Comparative Example 1) and Figure 9 A comparison of the frequency response simulation results of the surface acoustic wave resonator (Example 2) shown in the figure;

[0028] Figure 11 This is a comparison of the simulation results of the frequency response of surface acoustic wave resonators with different third metal duty cycles according to an embodiment of the present invention;

[0029] Figure 12 This is a comparison diagram of the simulation results of the frequency response of the surface acoustic wave resonator when the number of electrode fingers in the edge region changes according to an embodiment of the present invention.

[0030] Figure 13 This is a top view schematic diagram of the fifth type of surface acoustic wave resonator according to an embodiment of the present utility model;

[0031] Figure 14 This is a top view schematic diagram of the sixth type of surface acoustic wave resonator according to an embodiment of the present utility model;

[0032] Figure 15 This is a cross-sectional structural schematic diagram of a second type of surface acoustic wave resonator according to an embodiment of the present utility model;

[0033] Figure 16 This is a cross-sectional structural schematic diagram of a third type of surface acoustic wave resonator according to an embodiment of the present utility model;

[0034] Figure 17 This is a cross-sectional structural schematic diagram of the fourth type of surface acoustic wave resonator according to an embodiment of the present utility model;

[0035] Figure 18 This is a cross-sectional structural schematic diagram of the fifth type of surface acoustic wave resonator according to an embodiment of the present utility model;

[0036] Figure 19 This is a cross-sectional structural schematic diagram of the sixth type of surface acoustic wave resonator according to an embodiment of the present utility model.

[0037] Reference numerals: 10, piezoelectric layer; 20, interdigital transducer; 21, electrode finger; 211, first finger; 212, second finger; 22, first busbar; 23, second busbar; 24, first pseudo-finger; 25, second pseudo-finger; 201, central region; 202, edge region; 30, reflective grating; 31, third finger; 32, first short-circuit bar; 33, second short-circuit bar; 40, piston structure; 50, multilayer structure; 51, high-velocity substrate; 52, low-velocity layer; 53, high-velocity layer; 60, temperature compensation layer. Detailed Implementation

[0038] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, not the entire structure.

[0039] In the following description, descriptions of well-known structures and techniques are omitted to avoid unnecessarily obscuring the concept of this utility model. Various structural schematic diagrams according to embodiments of this utility model are shown in the accompanying drawings. These drawings are not to scale, and some details are enlarged for clarity, and some details may be omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed. In the context of this utility model, when a layer / element is referred to as being "on" another layer / element, the layer / element may be directly on the other layer / element, or there may be an intermediate layer / element between them. Additionally, if a layer / element is "on" another layer / element in one orientation, then when the orientation is reversed, the layer / element may be "below" the other layer / element.

[0040] SAW resonators are devices that utilize the propagation characteristics of surface acoustic waves on the surface of piezoelectric materials to achieve resonance. They are the core basic components of SAW filters. Filters are key components in communication systems, used to filter out unwanted signal frequency bands, ensuring that the communication system can operate within specific frequency bands. Surface acoustic waves, also known as surface acoustic waves, refer to various modes of mechanical waves generated on the free surface of an elastic body and propagating along the surface or interface. In solids, sound waves have two propagation paths: one propagates within the solid as longitudinal or transverse waves, called bulk acoustic waves; the other concentrates energy on the solid surface and propagates along the surface, called surface acoustic waves.

[0041] like Figure 1As shown, a conventional surface acoustic wave (SAW) resonator may include a piezoelectric layer 10, an interdigital transducer 20, and a reflector grating 30. The interdigital transducer 20 is disposed on the piezoelectric layer 10 and includes multiple electrode fingers that excite and detect SAW waves on the surface of the piezoelectric layer 10, thereby achieving the interconversion between electrical and acoustic signals. The reflector grating 30 consists of periodically arranged metal strips or grooves used to reflect the SAW waves, allowing the SAW waves to oscillate back and forth between the interdigital transducer 20 and the reflector grating 30 to form standing waves, enhancing the resonance effect and improving the quality factor (Q value).

[0042] As mentioned in the background section, at the low-frequency side of the resonant frequency, since the phase difference of the acoustic waves reflected by the electrode fingers does not reach constructive interference, surface acoustic wave resonators usually have strong ripple. The frequency response of the broadband acoustic filter based on this will generate corresponding spurious signals, which will seriously affect the integrity of the link signal in the communication system.

[0043] Among them, broadband acoustic filters refer to acoustic filters with a relative bandwidth greater than 5%. Broadband acoustic filters are usually composed of multiple resonators combined through circuit topologies (such as trapezoidal or lateral coupling structures). Their overall frequency response is the result of the linear superposition or nonlinear interaction of the characteristics of each resonator.

[0044] In view of this, this embodiment provides a surface acoustic wave resonator, filter, and electronic device. By changing the metal duty cycle of the electrode fingers at the edge of the interdigital transducer, the phase consistency of the acoustic wave reflection is disrupted, the strong coupling between the incident wave and the reflected wave is weakened, thereby reducing the ripple on the low-frequency side of the resonant frequency, improving the spurious problem in the frequency response of the filter prepared by the acoustic wave resonator, and ensuring the integrity of the link signal in the communication system.

[0045] The structure of the surface acoustic wave resonator provided by this utility model will be described in detail below with reference to the accompanying drawings.

[0046] like Figure 2 and Figure 3 As shown, the surface acoustic wave resonator includes a piezoelectric layer 10 and an interdigital transducer 20 disposed on one side of the piezoelectric layer 10.

[0047] The piezoelectric layer 10 can be a single-crystal piezoelectric layer. Under the excitation of an electric field, the piezoelectric layer 10 excites sound waves through the inverse piezoelectric effect. The materials of the piezoelectric layer 10 include, but are not limited to, lithium tantalate (LiTaO3) and lithium niobate (LiNbO3).

[0048] The interdigital transducer 20 includes multiple electrode fingers 21 and a first busbar 22 and a second busbar 23 arranged opposite to each other along a first direction X. The first finger 211 of the multiple electrode fingers 21 is located on the side of the first busbar 22 near the second busbar 23, and the second finger 212 of the multiple electrode fingers 21 is located on the side of the second busbar 23 near the first busbar 22. The first finger 211 and the second finger 212 are arranged alternately along a second direction Y.

[0049] Specifically, the electrode fingers disposed on the first busbar 22 are the first finger bars 211, and the electrode fingers disposed on the second busbar 23 are the second finger bars 212. That is to say, in this embodiment, multiple first finger bars 211 are arranged at intervals in the second direction Y, and multiple second finger bars 212 are also arranged at intervals in the second direction Y, and the multiple first finger bars 211 and multiple second finger bars 212 are arranged alternately in the second direction Y, with the first finger bars 211 and the second finger bars 212 having intervals in the second direction Y. At the same time, the first busbar 22 and the second finger bars 212 have intervals in the first direction X, and the second busbar 23 and the first finger bars 211 have intervals in the first direction X.

[0050] The length extension directions of the first busbar 22 and the second busbar 23 are parallel to the second direction Y, and the length extension directions of the plurality of electrode fingers are parallel to the first direction X. The first direction X and the second direction Y are parallel to the plane where the piezoelectric layer 10 is located, and the first direction X and the second direction Y intersect. This utility model takes the first direction X and the second direction Y being perpendicular to each other as an example, but is not limited thereto.

[0051] Furthermore, the interdigital transducer 20 also includes a central region 201 and edge regions 202 located on both sides of the central region 201 along the second direction Y. The first metal duty cycle is less than the second metal duty cycle, and the difference between the second metal duty cycle and the first metal duty cycle ranges from 0.05 to 0.3.

[0052] In other words, the duty cycle of the first metal is at least 0.05 smaller than the duty cycle of the second metal, and at most 0.3 smaller than the duty cycle of the second metal. For example, when the duty cycle of the second metal is A, the duty cycle of the first metal can be A-0.05, A-0.1, A-0.15, A-0.2, or A-0.3, etc.

[0053] The first metal duty cycle is the metal duty cycle of the electrode fingers in the edge region 202, and the second metal duty cycle is the metal duty cycle of the electrode fingers in the center region 201. The metal duty cycles of the electrode fingers in the same region are the same, that is, the metal duty cycles of all electrode fingers in the edge region are the same value, and the metal duty cycles of all electrode fingers in the center region are the same value.

[0054] Specifically, the metal duty cycle η is the ratio between the interdigital width a and the interdigital pitch p, i.e., η = a / p. The interdigital width a can be the width of the electrode strip 21 in the second direction Y, and the interdigital pitch p can be the distance between two adjacent electrode strips 21 on the same side of the second direction Y. For example, if the second direction Y is horizontal, the interdigital pitch p can be the distance between the left side of one electrode strip and the left side of another adjacent electrode strip. Figure 2 In this context, a1 represents the interdigitation width of the central region, a2 represents the interdigitation width of the edge region, p1 represents the interdigitation spacing of the central region, and p2 represents the interdigitation spacing of the edge region.

[0055] The distance between two adjacent electrode fingers 21 on their sides in the second direction Y is defined as the interdigital gap b. The interdigital distance p can be the sum of the interdigital width a and the interdigital gap b, i.e., p = a + b. For example, if the second direction Y is horizontal, the interdigital gap b can be the distance between the right side of one electrode finger and the left side of an adjacent electrode finger. Figure 2 In the diagram, b1 represents the interdigital gap in the central region, and b2 represents the interdigital gap in the edge region.

[0056] In this embodiment, the inventors discovered through research that after determining the metal duty cycle (i.e., the second metal duty cycle) of the interdigital transducer based on actual working needs, changing the metal duty cycle (i.e., the first metal duty cycle) of the edge region of the interdigital transducer, so that the first metal duty cycle is smaller than the second metal duty cycle, can cause the phase of the incident wave and the reflected wave of the surface acoustic wave in the surface acoustic wave resonator to shift, thereby disrupting the phase consistency of the reflected sound wave and weakening the strong coupling between the incident wave and the reflected wave in the low-frequency side of the resonant frequency, thus achieving ripple suppression on the low-frequency side of the resonant frequency.

[0057] For example, Figure 4 The figure shows a comparison of the simulation results of the frequency response of the surface acoustic wave resonator when the duty cycle of the first metal is reduced and when the duty cycle of the first metal is constant. Figure 4 As can be seen, when the duty cycle of the first metal is reduced, the ripple at frequencies below 2.1 GHz is significantly improved.

[0058] In Example 1, the second metal duty cycle DF2 is 0.5 and the first metal duty cycle DF1 is 0.4 as an example for simulation. In Comparative Example 1, the second metal duty cycle DF2 and the first metal duty cycle DF1 are both 0.5 as an example for simulation. In Example 1 and Comparative Example 1, the number of electrode fingers N1 in the edge region is 10. The interdigital spacing p1 in the central region and the interdigital spacing p2 in the edge region are both 0.93μm. All other unspecified parameters in Example 1 and Comparative Example 1 are the same.

[0059] Furthermore, a larger difference between the first metal duty cycle and the second metal duty cycle may result in a greater phase shift between the incident and reflected waves in the surface acoustic wave resonator, thereby further weakening the strong coupling between the incident and reflected waves at the low-frequency side of the resonant frequency. This enhances the suppression effect on ripple at the low-frequency side of the resonant frequency, meaning the ripple at the low-frequency side of the resonant frequency decreases as the first metal duty cycle decreases. However, setting the first metal duty cycle too small will lead to a decrease in the admittance value at the resonant frequency. The admittance value directly reflects the conversion efficiency between sound waves and electrical energy; a decrease in the admittance value will reduce the conversion efficiency. Therefore, in order to improve the suppression effect on ripple at the low-frequency side of the resonant frequency without affecting the admittance value at the resonant frequency, this embodiment limits the difference between the second metal duty cycle and the first metal duty cycle to within 0.05 to 0.3.

[0060] For example, Figure 5 and Figure 6 The simulation results of the frequency response of surface acoustic wave resonators with different first metal duty cycles DF1 are shown. Figure 5 and Figure 6 It can be seen that as the duty cycle DF1 of the first metal decreases, the ripple on the left side of the resonant frequency (i.e., the low-frequency side of the resonant frequency) gradually weakens, but the admittance value at the resonant frequency also decreases.

[0061] in, Figure 5 The simulation is conducted using a second metal duty cycle DF2 of 0.7 and first metal duty cycles DF1 of 0.6, 0.5, and 0.4 as examples. Figure 6 Simulations were conducted using a second metal duty cycle DF2 of 0.5 and first metal duty cycles DF1 of 0.45, 0.4, and 0.35 as examples. Figure 5 All other unspecified parameters of the surface acoustic wave resonators in the three simulated embodiments are the same. Figure 6 The other unspecified parameters of the surface acoustic wave resonators in the three simulated embodiments are also the same.

[0062] The surface acoustic wave resonator provided in this embodiment disrupts the phase coherence of sound wave reflection by making the first metal duty cycle in the edge region of the interdigital transducer smaller than the second metal duty cycle in the central region. This weakens the strong coupling between the incident and reflected waves, thereby suppressing ripple on the low-frequency side of the resonant frequency and improving the passband performance of the broadband filter. Simultaneously, limiting the difference between the second and first metal duty cycles to within 0.05 to 0.3 enhances the suppression of ripple on the low-frequency side of the resonant frequency while reducing the impact on the admittance value at the resonant frequency.

[0063] Specifically, the first metal duty cycle can be adjusted to a set value by changing the interdigit width 'a' and / or the interdigit gap 'b'. This set value can be determined by the designer based on the second metal duty cycle and the difference between the first and second metal duty cycles. The second metal duty cycle can be determined by the designer according to the actual operating requirements of the surface acoustic wave resonator.

[0064] In some embodiments, such as Figure 2 As shown, the interdigitation spacing in the central region (denoted as the first interdigitation spacing p1) and the interdigitation spacing in the edge region (denoted as the second interdigitation spacing p2) are the same, while the interdigitation width in the edge region (denoted as the second interdigitation width a2) is smaller than the interdigitation width in the central region (denoted as the first interdigitation width a1). In other words, this embodiment reduces the interdigitation width in the edge region to achieve a set value for the first metal duty cycle.

[0065] Wherein, the first interdigital spacing p1 can refer to the distance between two adjacent electrode strips on the same side of the second direction Y in the central region, the second interdigital spacing p2 can refer to the distance between two adjacent electrode strips on the same side of the second direction Y in the edge region, the first interdigital width a1 can refer to the width of the electrode strip in the second direction Y in the central region, and the second interdigital width a2 can refer to the width of the electrode strip in the second direction Y in the edge region.

[0066] Specifically, the first interdigital spacing p1, the first interdigital width a1, the second metal duty cycle DF2, and the difference Δη between the first metal duty cycle DF1 and the second metal duty cycle DF2 can be determined by the designer and are known values. Based on Δη and DF, DF1 can be determined, so when p1 = p2, a2 ​​= p2 × DF1 = p1 × (DF - Δη) can be obtained.

[0067] For example, if p1 = p2 = 0.93 μm, DF = 0.5, and Δη = 0.1, then a2 = 0.93 × (0.5 - 0.1) = 0.372 μm.

[0068] In other embodiments, such as Figure 7 As shown, the interdigitation width of the central region is the same as that of the edge region, and the interdigitation gap of the edge region (denoted as the second interdigitation gap b2) is greater than that of the central region (denoted as the first interdigitation gap b1). In other words, this embodiment increases the interdigitation gap of the edge region to make the first metal duty cycle a set value.

[0069] The interdigitated gap in the edge region can refer to the distance between two adjacent electrode fingers 21 in the edge region on the side that are close to each other in the second direction Y, and the interdigitated gap in the center region can refer to the distance between two adjacent electrode fingers 21 in the center region on the side that are close to each other.

[0070] For example, such as Figure 8 As shown, the surface acoustic wave resonator also includes a reflection grating 30, which is located on the side of the piezoelectric layer 10 where the interdigital transducer 20 is located, and is disposed on at least one side of the interdigital transducer 20 along the second direction Y. The reflection grating 30 is used to reflect the sound wave back to the resonant region of the interdigital transducer 20, so that the sound wave continues to resonate in the resonant region, thereby forming a better resonance effect and mode, and improving the transmission performance of the surface acoustic wave resonator.

[0071] Specifically, the reflective grid 30 includes a plurality of third finger strips 31 and a first short-circuit strip 32 and a second short-circuit strip 33 disposed opposite to each other along the first direction X. One end of the third finger strip 31 in the first direction X is connected to the first short-circuit strip 32, and the other end of the third finger strip 31 in the first direction X is connected to the second short-circuit strip 33. The plurality of third finger strips 31 are arranged at intervals in the second direction Y.

[0072] It should be noted that, Figure 8 Taking the example of an interdigital transducer 20 having reflective gratings 30 on both sides along the second direction Y, but not limited to this.

[0073] In some embodiments, the metal duty cycle of the reflective grating (denoted as the third metal duty cycle) can be the same as the second metal duty cycle. The metal duty cycle of the reflective grating can refer to the metal duty cycle of the third finger strip 31, and the calculation method is similar to that of the metal duty cycle of the electrode fingers in the interdigital transducer 20, which will not be repeated here.

[0074] In other embodiments, such as Figure 9 As shown, in order to further reduce the ripple on the low-frequency side of the resonant frequency, the duty cycle of the third metal is made greater than the duty cycle of the second metal, based on the fact that the duty cycle of the first metal is less than the duty cycle of the second metal.

[0075] For example, Figure 10 The figure shows a comparison of the simulation results of the frequency response of the surface acoustic wave resonator when the duty cycle of the third metal increases and when the duty cycle of the third metal remains constant. Figure 10 As can be seen, the ripple between 2.09 GHz and the resonant frequency is significantly improved after the duty cycle of the third metal increases.

[0076] In Example 2, simulations were performed using a second metal duty cycle DF2 of 0.5, a first metal duty cycle DF1 of 0.4, and a third metal duty cycle DF_r of 0.7. Comparative Example 1 used a second metal duty cycle DF2, a first metal duty cycle DF1, and a third metal duty cycle DF_r all of 0.5 as an example. All other parameters not specified in Example 2 and Comparative Example 1 were the same. In this example, the first interdigital spacing, the second interdigital spacing, and the interdigital spacing of the reflective grating (denoted as the third interdigital spacing p3) were all 0.93 μm. The interdigital spacing of the reflective grating can refer to the distance between two adjacent third finger strips 31 on the same side in the second direction Y.

[0077] Specifically, the duty cycle of the third metal can be made greater than that of the second metal by changing the interdigitation width and / or the interdigitation gap of the third finger strip. For example, while keeping the interdigitation gap constant, the duty cycle of the third metal can be made greater than that of the second metal by increasing the interdigitation width of the third finger strip.

[0078] Furthermore, the difference between the third metal duty cycle and the second metal duty cycle can range from 0.05 to 0.3. That is, the third metal duty cycle is at least 0.05 greater than the second metal duty cycle and at most 0.3 greater. For example, when the second metal duty cycle is A, the third metal duty cycle can be A+0.05, A+0.1, A+0.15, A+0.2, or A+0.3, etc.

[0079] Specifically, increasing the third metal duty cycle, which is lower than the second metal duty cycle, has a suppressive effect on the ripple on the low-frequency side of the resonant frequency. However, if the third metal duty cycle is set too high, it will slightly worsen the bulk wave spurious emissions on the high-frequency side of the resonant frequency (the right side of the frequency response curve), affecting the performance of the surface acoustic wave resonator. Therefore, in order to further reduce the ripple on the low-frequency side of the resonant frequency while avoiding bulk wave spurious emissions on the high-frequency side, this embodiment limits the difference between the third metal duty cycle and the second metal duty cycle to within 0.05 to 0.3.

[0080] For example, Figure 11 The simulation results of the frequency response of surface acoustic wave resonators under different third metal duty cycles DF_r are shown. Figure 11 It can be seen that as the duty cycle DF_r of the third metal increases, the ripple to the left of the resonant frequency is improved.

[0081] in, Figure 11 Simulations were conducted using the following examples: a second metal duty cycle DF2 of 0.5, a first metal duty cycle DF1 of 0.4, and third metal duty cycles of 0.5, 0.6, 0.7, and 0.8, respectively. The values ​​p1 = p2 = p3 = 0.93 μm, and N1 = 10 roots. Figure 11 All other unspecified parameters of the surface acoustic wave resonators in the four simulated embodiments are the same.

[0082] For example, the number of electrode fingers 21 in the edge region 202 ranges from 5 to 15. For instance, the number N1 of electrode fingers 21 in the edge region 202 can be 5, 8, 10, 12, or 15, etc.

[0083] Specifically, the inventors discovered through research that the number of electrode fingers in the edge region 202 also affects the suppression effect on the low-frequency side of the resonant frequency. Within a certain range, the suppression effect increases with the increase of the number of electrode fingers in the edge region 202, but beyond this range, the suppression effect decreases with the increase of the number of electrode fingers in the edge region 202.

[0084] For example, Figure 12 The following graph shows a comparison of the simulation results of the frequency response of surface acoustic wave resonators with different numbers N1. Figure 12 As can be seen, when the number N1 of electrode fingers 21 in the edge region 202 is controlled within 5 to 15, the ripple at frequencies below 2.1 GHz is improved.

[0085] In some alternative embodiments, such as Figure 13 As shown, the surface acoustic wave resonator also includes a piston structure 40. At least one piston structure 40 is provided at intervals along the extension direction of the electrode fingers 21. The width of the piston structure 40 in the second direction Y is greater than the width of the interdigitated fingers.

[0086] It should be noted that, Figure 13 Taking the electrode finger strip 21 with two piston structures 40 in a rectangular shape as an example, but not limited to this. For example, each electrode finger strip 21 may have one piston structure 40, which is located at the end of the electrode finger strip 21 away from the busbar, that is, at the end of the electrode finger strip 21. The shape of the piston structure 40 may be trapezoidal or other shapes.

[0087] Specifically, by setting a piston structure, the sound velocity in the resonant region can be changed, achieving a larger sound velocity difference. This causes transverse modes (i.e., clutter appearing in and near the passband) to be reflected in different directions, thus preventing them from resonating and causing energy loss. In other words, the piston structure 40 can suppress transverse mode spurious signals and improve the Q value.

[0088] In this implementation, such as Figure 13As shown, when the interdigitated widths of the central region and the edge region are not the same, the first ratio is equal to the second ratio. The first ratio is the ratio of the width of the piston structure in the second direction to the interdigitated width of the edge region, and the second ratio is the ratio of the width of the piston structure in the second direction to the interdigitated width of the central region.

[0089] Specifically, after setting the piston structure 40, the distance between two adjacent electrode fingers in the region where the piston structure is located becomes smaller, posing a risk of short circuit between adjacent piston structures 40. By reducing the interdigitation width in the edge region to make the first metal duty cycle smaller than the second metal duty cycle, the piston structure 40 scales proportionally based on the difference in interdigitation width. In this case, the distance between two adjacent piston structures in the edge region will be larger than the distance between two piston structures in the center region, reducing the risk of short circuit in the edge region and allowing for more flexible structural design of the surface acoustic wave resonator.

[0090] Optionally, such as Figure 14 As shown, the interdigital transducer 20 may further include a plurality of first pseudo-fingers 24 and a plurality of second pseudo-fingers 25. The first pseudo-fingers 24 are disposed on the side of the first busbar 22 near the second busbar 23, and the second pseudo-fingers 25 are disposed on the side of the second busbar 23 near the first busbar 22. The first finger bar 211 and the second pseudo-finger 25 are arranged opposite each other along the first direction X, and the second finger bar 212 and the first pseudo-finger 24 are also arranged opposite each other along the first direction X. Moreover, the first finger bar 211 and the second pseudo-finger 25 are spaced apart in the first direction X, and the second finger bar 212 and the first pseudo-finger 24 are also spaced apart in the first direction X.

[0091] In this embodiment, by setting the first pseudo-finger 24 and the second pseudo-finger 25, the transverse mode can be reflected through the abrupt change in sound speed boundary of the pseudo-finger region, avoiding the formation of resonance conditions and achieving better resonator performance.

[0092] For example, the surface acoustic wave resonator also includes a stacked structure 50, on which the piezoelectric layer 10 is disposed on a side surface away from the interdigital transducer 20. The stacked structure 50 includes a high-velocity substrate 51, at least one low-velocity layer 52 and at least one high-velocity layer 53.

[0093] For example, such as Figure 15 As shown, the stacked structure 50 may include a high-velocity substrate 51, a high-velocity layer 53, and a low-velocity layer 52 stacked from bottom to top, and the piezoelectric layer 10 is disposed on the side surface of the low-velocity layer 52 away from the interdigital transducer 20.

[0094] like Figure 16As shown, the stacked structure 50 may also include a high-velocity substrate 51 and a low-velocity layer 52 stacked from bottom to top, with the piezoelectric layer 10 on the side of the interdigital transducer 20 away from the low-velocity layer 52 on the side of the high-velocity substrate 51 away from the low-velocity layer 52.

[0095] like Figure 17 As shown, the stacked structure 50 may further include a high-velocity substrate 51, a low-velocity layer 52, a high-velocity layer 53, and a low-velocity layer 54 stacked from bottom to top, with the piezoelectric layer 10 on the side of the interdigital transducer 20 away from the low-velocity layer 52 on the side of the high-velocity substrate 51 away from the low-velocity layer 52.

[0096] like Figure 18 As shown, the stacked structure 50 may further include a high-velocity substrate 51, a high-velocity layer 53, a low-velocity layer 52, and a high-velocity layer 53 and a low-velocity layer 52 stacked from bottom to top, with the piezoelectric layer 10 on the side surface away from the interdigital transducer 20 disposed on the side surface of the low-velocity layer 52 away from the high-velocity substrate 51.

[0097] The low-velocity layer 52 can refer to a sound velocity layer that is slower than the velocity of the bulk wave propagating in the piezoelectric layer 10. The material of the low-velocity layer 52 can be silicon dioxide (SiO2), and the velocity of the bulk wave propagating in the low-velocity layer 52 can be adjusted by adjusting the density of the silicon dioxide. The high-velocity layer 53 can refer to a sound velocity layer that is faster than the velocity of the bulk wave propagating in the piezoelectric layer 10. The material of the high-velocity layer 53 can include at least one of silicon nitride (Si3N4), aluminum nitride (AlN), and aluminum oxide (Al2O3). The high-velocity substrate 51 can refer to a substrate that is faster than the velocity of the bulk wave propagating in the piezoelectric layer 10, and the substrate can be a silicon substrate.

[0098] In this embodiment, by setting a stacked structure to form a sound velocity gradient, the energy can be better confined in the piezoelectric layer 10, thereby improving the Q value of the surface acoustic wave resonator without affecting the transverse modes. Ultimately, this achieves the goal of effectively suppressing the transverse spurious modes of the surface acoustic wave resonator while improving the Q value of the surface acoustic wave resonator and reducing the insertion loss of the communication system.

[0099] In some implementations, compared to the aforementioned stacked structure, such as Figure 19 As shown, the surface acoustic wave resonator may further include a temperature-compensated layer 60, which is disposed on the side of the interdigital transducer 20 away from the piezoelectric layer 10, i.e., the interdigital transducer 20 is disposed between the temperature-compensated layer 60 and the piezoelectric layer 10. In this case, the surface acoustic wave resonator can be a temperature-compensated surface acoustic wave (TC-SAW) resonator.

[0100] Specifically, the temperature compensation layer 60 is used to counteract the effect of temperature changes on the propagation of surface acoustic waves and improve the frequency stability of the resonator. The material of the temperature compensation layer 60 can be silicon dioxide (SiO2).

[0101] Accordingly, this embodiment also provides a filter, including the surface acoustic wave resonator provided in any of the above embodiments. Since the surface acoustic wave resonator has been described in detail in the foregoing embodiments, it will not be repeated here.

[0102] Furthermore, this embodiment also provides an electronic device including the above-described filter.

[0103] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0104] In the description of this specification, the references to terms such as "this embodiment," "an embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0105] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this utility model, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0106] The above description does not provide detailed explanations of the technical aspects of each layer's patterning and etching. However, those skilled in the art should understand that various technical means can be used to form layers and regions of the desired shape. Furthermore, to form the same structure, those skilled in the art can design methods that are not entirely identical to those described above. Additionally, although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be effectively combined.

[0107] The above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described above, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. More other equivalent embodiments may be included without departing from the concept of the present invention, and the protection scope of the present invention is determined by the appended protection scope.

Claims

1. A surface acoustic wave resonator, characterized by, The surface acoustic wave resonator includes a piezoelectric layer and an interdigital transducer disposed on one side of the piezoelectric layer; The interdigitated transducer includes multiple electrode fingers and a first busbar and a second busbar arranged opposite to each other along a first direction. The first finger is located on the side of the first busbar closer to the second busbar, and the second finger is located on the side of the second busbar closer to the first busbar. The first and second fingers are arranged alternately along a second direction. The first and second directions are parallel to the plane of the piezoelectric layer and intersect each other. The interdigital transducer includes a central region and edge regions located on both sides of the central region along the second direction. The first metal duty cycle is less than the second metal duty cycle, and the difference between the second metal duty cycle and the first metal duty cycle ranges from 0.05 to 0.

3. The first metal duty cycle is the metal duty cycle of the electrode fingers in the edge region, and the second metal duty cycle is the metal duty cycle of the electrode fingers in the central region.

2. The surface acoustic wave resonator according to claim 1, characterized in that, The interdigitation spacing in the central region is the same as that in the edge region, and the interdigitation width in the edge region is smaller than that in the central region.

3. The surface acoustic wave resonator according to claim 1, wherein The interdigitated width of the central region is the same as that of the interdigitated width of the edge region, and the interdigitated gap of the edge region is greater than that of the central region.

4. The surface acoustic wave resonator according to any one of claims 1 to 3, characterized by, The surface acoustic wave resonator also includes a reflective grating; The reflective grating is located on the side of the piezoelectric layer where the interdigital transducer is located, and is located on at least one side of the interdigital transducer along the second direction. The third metal duty cycle is greater than the second metal duty cycle, and the third metal duty cycle is the metal duty cycle of the reflective grating.

5. The SAW resonator of claim 4, wherein, The difference between the third metal duty cycle and the second metal duty cycle ranges from 0.05 to 0.

3.

6. The surface acoustic wave resonator according to any one of claims 1 to 3, characterized by, The number of electrode fingers in the edge region ranges from 5 to 15.

7. The surface acoustic wave resonator according to any one of claims 1 to 3, characterized by, The surface acoustic wave resonator also includes a piston structure; At least one piston structure is provided in the extension direction of the electrode finger strip. The width of the piston structure in the second direction is greater than the width of the interdigitated finger. When the width of the interdigitated finger in the central region and the width of the interdigitated finger in the edge region are not the same, a first ratio is equal to a second ratio. The first ratio is the ratio of the width of the piston structure in the second direction to the width of the interdigitated finger in the edge region, and the second ratio is the ratio of the width of the piston structure in the second direction to the width of the interdigitated finger in the central region.

8. The surface acoustic wave resonator according to any one of claims 1 to 3, characterized in that, The interdigital transducer also includes a plurality of first pseudo-fingers and a plurality of second pseudo-fingers; The first dummy finger is disposed on the side of the first busbar closer to the second busbar, and the second dummy finger is disposed on the side of the second busbar closer to the first busbar. The first finger bar and the second dummy finger are disposed opposite each other along a first direction.

9. A filter, characterized by The filter includes the surface acoustic wave resonator according to any one of claims 1 to 8.

10. An electronic device, comprising: The electronic device includes the filter as described in claim 9.

Images