Elastic wave resonator and filter

Abstract

The invention discloses an elastic wave resonator and a filter, and belongs to the technical field of radio frequency filtering. The invention provides an elastic wave resonator which comprises a supporting layer, a piezoelectric layer and an interdigital transducer which are sequentially stacked, and the interdigital transducer comprises first true fingers and first false fingers which are alternately arranged in the second direction and second true fingers and second false fingers which are alternately arranged in the second direction; in the second direction, the lengths of the first true fingers and the first false fingers are gradually reduced, the lengths of the second true fingers and the second false fingers are gradually increased, and a first included angle is formed between the connecting line of the centers of the gaps between the first true fingers and the corresponding second false fingers and the second direction; and a second included angle is formed between the center connecting line of the gap between each second true finger and the corresponding first false finger and the second direction. According to the elastic wave resonator, the oblique angle is provided for the gap area between the true finger and the false finger to suppress transverse mode stray, the length of the false finger is prolonged to match the oblique angle, transverse energy leakage is reduced, and the characteristics of the resonator are improved.

Description

Technical Field

[0001] This application belongs to the field of radio frequency filtering technology, and in particular relates to an elastic wave resonator and filter. Background Technology

[0002] Surface acoustic wave (SAW) technology plays a crucial role in signal separation and filtering in mobile communications. Existing multilayer SAW resonators are prone to SAW energy leakage in lateral modes, which degrades the resonator's performance between the resonant and anti-resonant frequencies. Furthermore, existing SAW resonators generate severe spurious modes below the resonant frequency or in the frequency range between the resonant and anti-resonant frequencies, worsening the characteristics of the resonator and filter both inside and outside the passband. Summary of the Invention

[0003] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes an elastic wave resonator and filter that significantly improves the characteristics of the resonator by providing a bevel angle to the gap region between the real and fake fingers to suppress lateral mode spurious signals, and by extending the length of the fake finger to match the bevel angle and reduce lateral energy leakage.

[0004] In a first aspect, this application provides an elastic wave resonator, comprising: a support layer, a piezoelectric layer, and an interdigital transducer stacked sequentially. The interdigital transducer includes a first interdigital electrode structure and a second interdigital electrode structure arranged opposite to each other along a first direction. The first interdigital electrode structure includes a first true finger and a first false finger alternately arranged along a second direction. The second interdigital electrode structure includes a second true finger and a second false finger alternately arranged along the second direction. The first true finger and the second false finger are arranged opposite to each other, and the first direction and the second direction intersect.

[0005] In the second direction, the lengths of the first true finger and the first false finger gradually change, and the trend of the lengths of the second true finger and the second false finger gradually changing is opposite to the trend of the lengths of the first true finger and the first false finger gradually changing. The line connecting the center of the gap between each first true finger and the corresponding second false finger forms a first angle with the second direction, and the line connecting the center of the gap between each second true finger and the corresponding first false finger forms a second angle with the second direction.

[0006] According to the elastic wave resonator of this application, the extension direction of the center line connecting the gaps between each first true finger and the corresponding second false finger forms a first angle with the second direction, and the extension direction of the center line connecting the gaps between each second true finger and the corresponding first false finger forms a second angle with the second direction. By providing an angle to the gap region between the true and false fingers to suppress transverse mode spurious signals, and by extending the length of the false fingers to match the angle and reduce transverse energy leakage, the characteristics of the resonator are significantly improved.

[0007] According to one embodiment of this application, the height of the first pseudo-finger is h, and the height H of the Nth pseudo-finger satisfies the following relationship:

[0008]

[0009] Where pitch is half the wavelength of the elastic wave, θ is the angle formed by the line connecting the center of the gap between the pseudo-finger and the corresponding real finger and the second direction, and N_IDT is the sum of the real and pseudo-finger values ​​from the first pseudo-finger to the nth pseudo-finger.

[0010] According to one embodiment of this application, the material of the support layer includes an AT-cut 0°X quartz crystal, and the first included angle and the second included angle are greater than or equal to 2° or less than or equal to -2°.

[0011] According to one embodiment of this application, the first included angle and the second included angle are greater than or equal to 2° and less than or equal to 16°, or the first included angle and the second included angle are greater than or equal to -16° and less than or equal to -2°.

[0012] According to one embodiment of this application, the material of the support layer includes an AT-cut 90°X quartz crystal, with a first included angle and a second included angle greater than or equal to 4° or less than or equal to -4°.

[0013] According to one embodiment of this application, the first included angle and the second included angle are greater than or equal to 4° and less than or equal to 18°, or the first included angle and the second included angle are greater than or equal to -18° and less than or equal to -4°. According to one embodiment of this application, the first included angle and the second included angle are equal.

[0014] According to one embodiment of this application, the lengths of the first and second pseudofingers are 0.025λ to 50λ, where λ is the wavelength of the elastic wave.

[0015] According to one embodiment of this application, the length of the gap between each first true finger and the corresponding second false finger along the first direction is 0.025λ to 2.0λ, and the length of the gap between each second true finger and the corresponding first false finger along the first direction is 0.025λ to 2.0λ.

[0016] According to one embodiment of this application, the intersection of the first true finger and the second true finger forms an aperture region, and the length of the aperture region along the first direction is 10λ to 50λ.

[0017] According to one embodiment of this application, the metallization rate of the interdigital transducer is 0.3 to 0.7.

[0018] According to one embodiment of this application, a temperature compensation layer is provided on the side of the interdigital transducer away from the piezoelectric layer.

[0019] According to one embodiment of this application, an oxide buried layer is further disposed between the piezoelectric layer and the support layer.

[0020] Secondly, this application provides a filter that includes at least one of the aforementioned elastic wave resonators.

[0021] According to the filter of this application, the extension direction of the center line connecting the gaps between each first true finger and the corresponding second false finger in the elastic wave resonator forms a first angle with the second direction, and the extension direction of the center line connecting the gaps between each second true finger and the corresponding first false finger forms a second angle with the second direction. By providing a bevel angle to the gap region between the true and false fingers to suppress transverse mode spurious signals, and by extending the length of the false fingers to match the bevel angle to reduce transverse energy leakage, the characteristics of the resonator are significantly improved.

[0022] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0023] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0024] Figure 1 This is a schematic diagram of the structure of an elastic wave resonator in related technologies;

[0025] Figure 2 This is a schematic diagram showing the variation of admittance and conductance characteristics of surface wave resonators with frequency in related technologies;

[0026] Figure 3 This is a schematic diagram illustrating the variation of the Bodeaux characteristic of a surface wave resonator with frequency in related technologies;

[0027] Figure 4 This is a schematic diagram of the acoustic wave velocity distribution in different regions of the cross section of an elastic wave resonator in related technologies;

[0028] Figure 5 This is one of the structural schematic diagrams of the elastic wave resonator provided in the embodiments of this application;

[0029] Figure 6 This is one of the cross-sectional views of the elastic wave resonator provided in the embodiments of this application;

[0030] Figure 7 This is one of the schematic diagrams showing the change of admittance and conductance characteristics of an elastic wave resonator with frequency according to an embodiment of this application;

[0031] Figure 8 This is one of the schematic diagrams illustrating the variation of the Bode effect of the elastic wave resonator with frequency provided in the embodiments of this application;

[0032] Figure 9 This is the second schematic diagram showing the change of admittance and conductance characteristics of the elastic wave resonator with frequency provided in the embodiments of this application;

[0033] Figure 10 This is a second schematic diagram showing the variation of the Bode characteristics of the elastic wave resonator with frequency provided in the embodiments of this application;

[0034] Figure 11 This is a schematic diagram illustrating the calculation of the height of the nth pseudo-finger provided in an embodiment of this application;

[0035] Figure 12 This is one of the schematic diagrams showing the variation of the Bodeaux characteristic of the elastic wave resonator provided in the embodiments of this application with the first included angle / second included angle;

[0036] Figure 13 This is a second schematic diagram showing the variation of the Bodeaux characteristic of the elastic wave resonator provided in the embodiments of this application with the first included angle / second included angle;

[0037] Figure 14 This is a schematic diagram showing the variation of the admittance and conductance characteristics of the elastic wave resonator provided in the embodiments of this application with the first included angle / second included angle;

[0038] Figure 15 This is a second schematic diagram of the structure of the elastic wave resonator provided in the embodiments of this application;

[0039] Figure 16 This is a second cross-sectional view of the elastic wave resonator provided in the embodiments of this application;

[0040] Figure 17 This is the third cross-sectional view of the elastic wave resonator provided in the embodiments of this application.

[0041] Figure label:

[0042] Support layer 10, piezoelectric layer 20, interdigital transducer 30, first busbar 31, first true finger 32, first false finger 33, second busbar 34, second true finger 35, second false finger 36, temperature compensation layer 40, buried oxide layer 50, first included angle θ1, second included angle θ2. Detailed Implementation

[0043] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0044] In the following description, a "circuit" refers to a conductive loop consisting of at least one element or sub-circuit connected by an electrical or electromagnetic link. When an element or circuit is said to be "coupled to" or "connected to" another element, or when an element / circuit is said to be "coupled at" or "connected at" two nodes, it can be directly coupled to or connected to the other element, or there may be intermediate elements. The connection between elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there are no intermediate elements between them.

[0045] In the description, the terms "first," "second," etc., are used to distinguish similar objects, not to describe a specific order or sequence. It should be understood that such numerical descriptors can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class, not limited in number; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0046] Furthermore, the use of terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicates 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 this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0047] In the field of mobile communications, surface acoustic wave (SAW) technology plays a crucial role in the effective separation and filtering of signals, and it is widely used in filter manufacturing.

[0048] Reference Figure 1 , Figure 1 The structure of an elastic wave resonator in the related art is shown. The interdigital transducer in the elastic wave resonator includes a first interdigital electrode structure and a second interdigital electrode structure arranged opposite each other along a first direction. The first interdigital electrode structure includes a first true finger electrode and a first false finger electrode arranged alternately along a second direction. The second interdigital electrode structure includes a second true finger electrode and a second false finger electrode arranged alternately along the second direction. The first true finger electrode and the second false finger electrode are arranged opposite each other, and the first false finger electrode and the second true finger electrode are arranged opposite each other, with a gap between each true finger and false finger.

[0049] Reference Figure 2 and Figure 3 In related technologies, the stability of surface acoustic wave (SAW) energy in transverse mode faces challenges, as energy leakage is prone to occur. This energy leakage directly affects the resonator's performance between the resonant and anti-resonant frequencies. Furthermore, existing SAW resonators exhibit significant stray mode phenomena within specific frequency ranges, particularly below the resonant frequency or in the frequency band between the resonant and anti-resonant frequencies. Figure 2 Curve (1) shows the characteristics of admittance and conductance as a function of frequency under ideal conditions, while curve (2) shows the characteristics of admittance and conductance as a function of frequency in related technologies. Figure 3 This diagram illustrates the variation of the Baud rate characteristic of a surface wave resonator with frequency in related technologies. This phenomenon further deteriorates the performance characteristics of the resonator and filter both inside and outside the passband, negatively impacting their overall signal processing capabilities.

[0050] Reference Figure 4 Sound waves travel faster in the gaps between the real and fake fingers. In related technologies, the transverse energy leakage of surface acoustic wave resonators is reduced by shortening the gap length between the real and fake fingers, but this cannot suppress transverse mode straying caused by transverse mode wave scattering effect.

[0051] Reference Figure 5 and Figure 6 One embodiment of this application proposes an elastic wave resonator, comprising: a support layer 10, a piezoelectric layer 20, and an interdigital transducer 30 stacked sequentially. The interdigital transducer 30 includes a first interdigital electrode structure and a second interdigital electrode structure arranged opposite to each other along a first direction. The first interdigital electrode structure includes a first true finger 32 and a first false finger 33 alternately arranged along a second direction. The second interdigital electrode structure includes a second true finger 35 and a second false finger 36 alternately arranged along the second direction. The first true finger 32 and the second false finger 36 are arranged opposite to each other. The second true finger 35 and the first false finger 36 are arranged opposite to each other. The fingers 33 are arranged opposite each other, with the first direction and the second direction intersecting; wherein, in the second direction, the lengths of the first true finger 32 and the first false finger 33 gradually change, and the trend of the lengths of the second true finger 35 and the second false finger 36 gradually changing is opposite to the trend of the lengths of the first true finger 32 and the first false finger 33 gradually changing. The line connecting the center of the gap between each first true finger 32 and the corresponding second false finger 36 forms a first angle θ1 with the second direction, and the line connecting the center of the gap between each second true finger 35 and the corresponding first false finger 33 forms a second angle θ2 with the second direction.

[0052] The support layer 10 is mainly used to support the main structure of the entire elastic wave resonator, ensuring that the elastic wave resonator is not prone to failure when subjected to external stress, and providing the necessary strength and protection for the elastic wave resonator.

[0053] The support layer 10 is typically formed of a material with high hardness. The specific material of the support layer 10 can be selected according to the actual application scenario, and is not limited here. For example, the support layer 10 can be made of silicon, silicon nitride, silicon carbide, aluminum nitride sapphire, spinel, or quartz.

[0054] The piezoelectric layer 20 is the core component of the resonator to realize its function. When the frequency of the applied electrical signal is the same as the natural frequency of the resonator, the material in the piezoelectric layer 20 will deform, thereby generating mechanical vibration. This mechanical vibration will further interact with the electrical signal to realize the resonant amplification of the elastic wave.

[0055] The piezoelectric layer 20 is typically made of materials with high mechanical strength and stiffness to withstand external forces and maintain structural stability, while also maintaining stable piezoelectric properties within a certain temperature range. The specific material of the piezoelectric layer 20 can be selected based on the actual application scenario and is not limited here. For example, the piezoelectric layer 20 can be made of silicon dioxide, aluminum nitride, zinc oxide, lead zirconate titanate piezoelectric ceramics, polyvinylidene fluoride, or lithium tantalate, etc.

[0056] The electrodes of the interdigital transducer 30 are made of a thin metal film. The interdigital transducer 30 is mainly used to realize the mutual conversion between acoustic signals and electrical signals.

[0057] The first interdigital electrode structure includes a first busbar 31 and a first true finger 32 and a first false finger 33 connected to the first busbar 31. The second interdigital electrode structure includes a second busbar 34 and a second true finger 35 and a second false finger 36 connected to the second busbar 34. The first and second interdigital electrode structures of the interdigital transducer 30 are arranged opposite to each other along a first direction. The first true finger 32 and the first false finger 33 are arranged alternately along a second direction, and the second true finger 35 and the second false finger 36 are arranged alternately along a second direction. The first direction can be the Y direction shown in the figure, and the second direction can be the X direction shown in the figure. The first true finger 32 and the second false finger 36 are arranged opposite to each other, and the second true finger 35 and the first false finger 33 are arranged opposite to each other. The area formed by the intersection of the first true finger 32 and the second true finger 35 is the aperture area.

[0058] It should be noted that the trend of change in the length of the true and false fingers includes gradually increasing or decreasing in the second direction. The opposite trend of gradual change in length means that if the length of the first true finger 32 and the first false finger 33 gradually decreases, then the corresponding length of the second true finger 35 and the second false finger 36 gradually increases; if the length of the first true finger 32 and the first false finger 33 gradually increases, then the corresponding length of the second true finger 35 and the second false finger 36 gradually decreases.

[0059] As an example, along the X direction from left to right, the lengths of the first true finger 32 and the first false finger 33 gradually decrease, while the corresponding lengths of the second true finger 35 and the second false finger 36 gradually increase. The extension direction of the center line connecting the gaps between each first true finger 32 and the corresponding second false finger 36 forms a first angle θ1 with the second direction, and the extension direction of the center line connecting the gaps between each second true finger 35 and the corresponding first false finger 33 forms a second angle θ2 with the second direction, that is, providing an oblique angle for the gap area between the true finger and the opposite false finger.

[0060] It should be noted that the shortest of the first pseudofinger 33 and the second pseudofinger 36 is the same length as the pseudofinger in the related technology, and the remaining pseudofingers are longer than the shortest first pseudofinger 33 and the second pseudofinger 36. The lengthened pseudofinger can reduce lateral energy leakage.

[0061] It should be noted that the magnitude of the gradual decrease in length of the first true finger 32 and the first false finger 33 can be selected according to the actual application scenario, and is not limited here. For example, along the X direction from left to right, the lengths of the first true finger 32 and the first false finger 33 can decrease in an arithmetic sequence, and correspondingly, the lengths of the second true finger 35 and the second false finger 36 can increase in an arithmetic sequence. The greater the magnitude of the gradual decrease in length of the first true finger 32 and the first false finger 33, the larger the first included angle θ1. Similarly, the greater the magnitude of the gradual increase in length of the second true finger 35 and the second false finger 36, the larger the second included angle θ2.

[0062] According to the elastic wave resonator of this application, the extension direction of the center line connecting the gaps between each first true finger 32 and the corresponding second false finger 36 forms a first angle θ1 with the second direction, and the extension direction of the center line connecting the gaps between each second true finger 35 and the corresponding first false finger 33 forms a second angle θ2 with the second direction. By providing a bevel angle to the gap region between the true and false fingers to suppress transverse mode spuriousness, and by extending the length of the false fingers to match the bevel angle to reduce transverse energy leakage, the characteristics of the resonator are significantly improved.

[0063] In some embodiments, the support layer is made of AT-cut 0°X quartz crystal, the thickness of the support layer is 0.225λ, the first included angle θ1 and the second included angle θ2 are greater than or equal to -16° and less than or equal to 16°, the lengths of the first pseudo-finger 33 and the second pseudo-finger 36 are 0.5λ to 30λ, the gap between each first true finger 32 and the corresponding second pseudo-finger 36 has a length of 0.25λ along the first direction, the gap between each second true finger 35 and the corresponding first pseudo-finger 33 has a length of 0.25λ along the first direction, the number of fingers is 200, the intersection of the first true finger 32 and the second true finger 35 forms an aperture region with a length of 20λ along the first direction, the thickness of each electrode finger is 0.094125λ, and the metallization rate of the interdigital transducer is 0.5. Here, λ is the wavelength of the elastic wave, and the specific value of λ can be selected according to the actual application scenario; for example, λ can be 4µm.

[0064] Reference Figure 7 , Figure 7 The solid line (3) in the figure shows a schematic diagram of the admittance and conductance characteristics of the elastic wave resonator provided in this application as a function of frequency when the first included angle θ1 or the second included angle θ2 is 16°. Figure 7 The dashed lines in the text show, for example, Figure 1 The schematic diagram shown illustrates the variation of admittance and conductance characteristics of an elastic wave resonator with frequency. This is achieved through... Figure 7 A comparison of the admittance and conductance characteristics of the elastic wave resonator shown by the solid and dashed lines in the middle shows that the stray frequency of the elastic wave resonator provided in the embodiments of this application is significantly reduced.

[0065] Reference Figure 8 , Figure 8 The solid line (4) in the figure shows a schematic diagram of the Bodeaux characteristic of the elastic wave resonator provided in this application as a function of frequency when the first included angle θ1 or the second included angle θ2 is 16°. Figure 8 The dashed lines in the text show, for example, Figure 1 The diagram shows the Bode effect of the elastic wave resonator as a function of frequency. This is illustrated by... Figure 8 A comparison of the Bode characteristics of the elastic wave resonators shown by the solid and dashed lines reveals that the Bode characteristics of the elastic wave resonator provided in this embodiment are significantly improved. The resonator's characteristics can be significantly improved by providing an angled region between the real and pseudo fingers to suppress lateral mode spurious signals, and by extending the length of the pseudo finger to match the included angle and reduce lateral energy leakage.

[0066] In other embodiments, the support layer is made of AT-cut 90°X quartz crystal, the thickness of the support layer is 0.225λ, the first included angle θ1 and the second included angle θ2 are greater than or equal to -18° and less than or equal to 18°, the length of the first pseudo-finger 33 and the second pseudo-finger 36 is 0.025λ to 32.5λ, the length of the gap between each first true finger 32 and the corresponding second pseudo-finger 36 along the first direction is 0.25λ, the length of the gap between each second true finger 35 and the corresponding first pseudo-finger 33 along the first direction is 0.25λ, the number of fingers is 200, the intersection of the first true finger 32 and the second true finger 35 forms an aperture region, the length of the aperture region along the first direction is 20λ, the thickness of each electrode finger is 0.094125λ, and the metallization rate of the interdigital transducer is 0.5.

[0067] Reference Figure 9 , Figure 9 The solid line (3) in the figure shows a schematic diagram of the admittance and conductance characteristics of the elastic wave resonator provided in this application as a function of frequency when the first included angle θ1 or the second included angle θ2 is 10°. Figure 9 The dashed lines in the text show, for example, Figure 1 The schematic diagram shown illustrates the variation of admittance and conductance characteristics of an elastic wave resonator with frequency. This is achieved through... Figure 9 A comparison of the admittance and conductance characteristics of the elastic wave resonator shown by the solid and dashed lines in the middle shows that the stray frequency of the elastic wave resonator provided in the embodiments of this application is significantly reduced.

[0068] Reference Figure 10 , Figure 10 The solid line (4) in the diagram shows a schematic diagram of the Bodeaux characteristic of the elastic wave resonator provided in this embodiment of the application as a function of frequency when the first included angle θ1 or the second included angle θ2 is 10°. Figure 10 The dashed lines in the text show, for example, Figure 1 The diagram shows the Bode effect of the elastic wave resonator as a function of frequency. This is illustrated by... Figure 10 A comparison of the Bode characteristics of the elastic wave resonators shown by the solid and dashed lines reveals that the Bode characteristics of the elastic wave resonator provided in this embodiment are significantly improved. The resonator's characteristics can be significantly improved by providing an angled region between the real and pseudo fingers to suppress lateral mode spurious signals, and by extending the length of the pseudo finger to match the included angle and reduce lateral energy leakage.

[0069] Reference Figure 11 In some embodiments, the height of the first pseudo-finger is h, and the height H of the nth pseudo-finger satisfies the following relationship:

[0070]

[0071] Where pitch is half the wavelength of the elastic wave, θ is the angle formed by the line connecting the center of the gap between the pseudo-finger and the corresponding real finger and the second direction, and N_IDT is the sum of the real and pseudo-finger values ​​from the first pseudo-finger to the nth pseudo-finger.

[0072] The height of the Nth pseudo-finger can be determined based on the height of the first pseudo-finger and the number of pseudo-fingers, which facilitates control over the size of the elastic wave resonator during manufacturing.

[0073] Reference Figure 12 In some embodiments, the support layer is made of AT-cut 0°X quartz crystal, with the first included angle and the second included angle being greater than or equal to 2° or less than or equal to -2°.

[0074] Figure 12 The diagram illustrates the Bodeaux characteristic of the elastic wave resonator provided in this embodiment as a function of a first included angle θ1 or a second included angle θ2 when the support layer material includes an AT-cut 0°X quartz crystal. A simulation diagram from -16° to 16° is used as an example. Figure 12 It is known that when the material of the support layer includes quartz crystal with AT-cut 0°X, the Bodeaux characteristics of the elastic wave resonator increase significantly as the angle increases within the range of 0° to 2° and 0° to -2°, respectively. Therefore, having the first angle θ1 and the second angle θ2 greater than 2° or less than or equal to -2° can save on the material of the pseudo-finger electrode and also make the Bodeaux characteristics of the elastic wave resonator better.

[0075] In some embodiments, the first included angle and the second included angle are greater than or equal to 2° and less than or equal to 16°, or the first included angle and the second included angle are greater than or equal to -16° and less than or equal to -2°.

[0076] Continue to refer to Figure 12When the material of the support layer includes AT-cut 0°X quartz crystal, the Bodeaux characteristics of the elastic wave resonator are relatively stable as the angle increases within the ranges of -4° to -6° and 4 to 6° for the first included angle θ1 or the second included angle θ2. The Bodeaux characteristics of the elastic wave resonator are relatively stable as the angle increases within the ranges of -6° to -8° and 6 to 8° for the first included angle θ1 or the second included angle θ2. The Bodeaux characteristics of the elastic wave resonator decrease slightly as the angle increases within the ranges of -8° to -10° and 8 to 10° for the first included angle θ1 or the second included angle θ2. Within the ranges of -10° to -12° and 10° to 12° for either the first included angle θ1 or the second included angle θ2, the Bodeaux characteristic of the elastic wave resonator significantly improves with increasing angle. Within the ranges of -12° to -14° and 12° to 14° for either the first included angle θ1 or the second included angle θ2, the Bodeaux characteristic of the elastic wave resonator slightly decreases with increasing angle. Within the ranges of -14° to -16° and 14° to 16° for either the first included angle θ1 or the second included angle θ2, the Bodeaux characteristic of the elastic wave resonator slightly increases with increasing angle. (Summary) Figure 12 Overall, having the first included angle and the second included angle greater than or equal to 2° and less than or equal to 16°, or having the first included angle and the second included angle greater than or equal to -16° and less than or equal to -2°, can improve the Bode characteristics of the elastic wave resonator and maintain the Bode characteristics in a good state.

[0077] In some embodiments, the material of the support layer includes an AT-cut 90°X quartz crystal, with the first included angle and the second included angle being greater than or equal to 4° or less than or equal to -4°.

[0078] Reference Figure 13 , Figure 13 The diagram shows the Bodeaux characteristic of the elastic wave resonator provided in this application embodiment as a function of a first included angle θ1 or a second included angle θ2 when the material of the support layer includes an AT-cut 90°X quartz crystal.

[0079] Depend on Figure 13 It is known that when the material of the support layer includes AT-cut 90°X quartz crystal, taking the simulation diagram from -18° to 18° as an example, in the range of 0° to 2° and 0° to -2° for the first included angle θ1 or the second included angle θ2, as the included angle increases, the Bodeaux characteristic of the elastic wave resonator decreases. In the range of 2° to 4° and -2° to -4° for the first included angle θ1 or the second included angle θ2, as the included angle increases, the Bodeaux characteristic of the elastic wave resonator increases. Therefore, having the first included angle θ1 and the second included angle θ2 greater than 4° or less than or equal to -4° can save the material of the pseudo-finger electrode and also make the Bodeaux characteristic of the elastic wave resonator better.

[0080] In some embodiments, the first included angle and the second included angle are greater than or equal to 4° and less than or equal to 18°, or the first included angle and the second included angle are greater than or equal to -18° and less than or equal to -4°.

[0081] Continue to refer to Figure 13 When the material of the support layer includes an AT-cut 90°X quartz crystal, within the ranges of -4° to -6° and 4 to 6° for the first included angle θ1 or the second included angle θ2, the Bode characteristics of the elastic wave resonator are relatively stable as the included angle increases. Within the ranges of -6° to -10° and 6 to 10° for the first included angle θ1 or the second included angle θ2, the Bode characteristics of the elastic wave resonator are significantly improved as the included angle increases. Within the ranges of -10° to -16° and 10 to 16° for the first included angle θ1 or the second included angle θ2, the Bode characteristics of the elastic wave resonator decrease slightly as the included angle increases. Within the ranges of -16° to -18° and 16 to 18° for the first included angle θ1 or the second included angle θ2, the Bode characteristics of the elastic wave resonator increase slightly as the included angle increases. Setting the first included angle θ1 and the second included angle θ2 to be greater than or equal to 4° and less than or equal to 18°, or the first included angle and the second included angle to be greater than or equal to -18° and less than or equal to -4°, can improve the Bode characteristics of the elastic wave resonator and maintain the Bode characteristics in a good state.

[0082] Reference Figure 14 , Figure 14 The curves showing the admittance and conductance characteristics of the elastic wave resonator as a function of the first / second included angle are presented. Figure 14 It can be seen that the larger the first angle and the second angle are, the fewer the stray frequencies of the elastic wave resonator.

[0083] In some embodiments, the first included angle θ1 and the second included angle θ2 are equal.

[0084] The first included angle θ1 and the second included angle θ2 are equal, meaning that the decrease in length of the first true finger 32 and the first false finger 33 is the same as the gradual increase in length of the second true finger 35 and the second false finger 36. The pattern formed by the interdigital transducer 30 is symmetrical about the center point, meaning that the shortest electrode finger in the first interdigital electrode structure and the longest electrode finger in the second interdigital electrode structure are the same length, the increase in length between adjacent electrode fingers is the same, and the width of each corresponding electrode finger that is symmetrical about the center point about the pattern formed by the interdigital transducer 30 is the same, which facilitates manufacturing.

[0085] In some embodiments, the first included angle and the second included angle are greater than or equal to -30° and less than or equal to 30°, the lengths of the first and second pseudo-fingers are 0.025λ to 50λ, the length of the gap between each first true finger and the corresponding second pseudo-finger along the first direction is 0.025λ to 2.0λ, the length of the gap between each second true finger and the corresponding first pseudo-finger along the first direction is 0.025λ to 2.0λ, the intersection of the first and second true fingers forms an aperture region, the length of the aperture region along the first direction is 10λ to 50λ, the thickness of each electrode finger is 0.025λ to 0.15λ, and the metallization rate of the interdigital transducer is 0.3 to 0.7. Here, λ is the wavelength of the elastic wave, and the specific value of λ can be selected according to the actual application scenario; for example, λ can be 4µm.

[0086] The lengths of the first pseudofinger 33 and the second pseudofinger 36 range from 0.025λ to 50λ, allowing for sufficient room for the pseudofinger to increase in length. Appropriately increasing the pseudofinger length can also reduce lateral energy leakage. The lengths of the first pseudofinger 33 and the second pseudofinger 36 can be selected according to the actual application scenario and are not limited here. For example, the interdigital transducer 30 includes five first pseudofingers 33 and five second pseudofingers 36, with the lengths of the first pseudofinger 33 and the second pseudofinger 36 increasing from smallest to largest as λ, 5λ, 10λ, 15λ, and 20λ, respectively.

[0087] The intersection of the first true finger 32 and the second true finger 35 forms an aperture region, which can confine lateral energy within the aperture region to a certain extent. The length of the aperture region along the first direction is 10λ to 50λ, that is, the length of the intersection of the first true finger 32 and the second true finger 35 along the first direction is 10λ to 50λ. The specific length of the aperture region along the first direction can be selected according to the actual application scenario and is not limited here. For example, the length of the aperture region along the first direction can be 15λ, 25λ, or 30λ, etc.

[0088] The uniform thickness of each electrode finger, ranging from 0.025λ to 0.15λ, helps optimize the generation and propagation of surface acoustic waves, thereby improving the acoustic-to-electric conversion efficiency. The thickness of each electrode finger can be selected according to the actual application scenario and is not limited here. For example, the thickness of each electrode finger can be 0.05λ, 0.07λ, or 0.1λ, etc.

[0089] The gaps between each first true finger 32 and its corresponding second false finger 36, and the gaps between each second true finger 35 and its corresponding first false finger 33, are equal in length along the first direction, and are all between 0.025λ and 2.0λ, to achieve electrical isolation between the true and false fingers. The lengths of the gaps between each first true finger 32 and its corresponding second false finger 36, and the gaps between each second true finger 35 and its corresponding first false finger 33, along the first direction can be selected according to the actual application scenario and are not limited here. For example, the length of the gap between each true finger and its corresponding false finger along the first direction can be 0.5λ, λ, or 2λ, etc.

[0090] The metallization rate of the interdigital transducer 30 refers to the ratio of the width of the electrode fingers to the distance between them, mainly reflecting the distribution density and area occupied by the interdigital electrodes on the piezoelectric layer 20. The metallization rate of the interdigital transducer 30 is 0.3–0.7, which allows for the conversion between acoustic and electrical signals while ensuring that the propagation speed and frequency of the elastic wave meet requirements. The metallization rate of the interdigital transducer 30 can be selected according to the actual application scenario and is not limited here. For example, the metallization rate of the interdigital transducer 30 can be 0.4 or 0.5.

[0091] As an example, the wavelength of the elastic wave is 4 μm, the length of the aperture region along the first direction is 20λ, the metallization of the interdigital transducer 30 is 0.5, the length of the gap between each first true finger 32 and the corresponding second false finger 36 along the first direction is 0.25λ, the length of the gap between each second true finger 35 and the corresponding first false finger 33 along the first direction is 0.25λ, the length of the first false finger 33 and the second false finger 36 is 0.5λ to 30λ, and the thickness of each electrode finger is 0.094125λ.

[0092] The metallization rate of the interdigital transducer 30 is 0.5, which means that the width of each electrode finger is the same as the gap width between adjacent electrode fingers along the second direction, which facilitates the manufacturing process.

[0093] The wavelength of the elastic wave is 4 μm, that is, the length of the aperture region along the first direction is 80 μm, the length of the gap between each first true finger 32 and the corresponding second false finger 36 along the first direction is 1 μm, the length of the gap between each second true finger 35 and the corresponding first false finger 33 along the first direction is 1 μm, the length of the first false finger 33 and the second false finger 36 is 2 μm to 120 μm, and the thickness of each electrode finger is 376.5 μm.

[0094] In some embodiments, the width of each electrode finger in the first interdigital electrode structure and the second interdigital electrode structure is the same.

[0095] The fact that all electrode fingers have the same width means that each electrode finger is a regular rectangle, which satisfies the Bode characteristics of the elastic wave resonator and is also easy to manufacture.

[0096] In some embodiments, the material of the support layer 10 includes an AT-cut 0°X quartz crystal or an AT-cut 90°X quartz crystal, and the material of the piezoelectric layer 20 includes lithium tantalate.

[0097] AT-cut quartz crystals typically exhibit a thickness shear vibration mode, which enables the crystal to have stable vibration characteristics at a specific frequency. Elastic wave resonators with AT-cut 0°X or AT-cut 90°X quartz crystals as the support layer 10 have higher energy storage capacity and lower energy loss, thereby improving the performance of the resonator.

[0098] Lithium tantalate is a multifunctional crystal material with excellent electro-optic and piezoelectric properties. Under high-temperature conditions, lithium tantalate is not prone to depolarization, ensuring the stable operation of elastic wave resonators in high-temperature environments. In addition, lithium tantalate has low dielectric loss, resulting in less energy loss during signal transmission, which is beneficial to improving the efficiency and performance of elastic wave resonators.

[0099] Reference Figure 15 and Figure 16 In some embodiments, a temperature compensation layer 40 is provided on the side of the interdigital transducer 30 away from the piezoelectric layer 20.

[0100] The frequency of the temperature compensation layer 40 material increases with temperature, which cancels out the negative frequency temperature coefficient characteristic of the piezoelectric circuit board, thereby achieving the purpose of suppressing frequency temperature dependence.

[0101] The temperature compensation layer 40 is generally made of a material with a positive frequency temperature coefficient. The specific material can be selected according to the actual application scenario and is not limited here. For example, the temperature compensation layer 40 can be made of silicon dioxide.

[0102] Reference Figure 17 In some embodiments, an oxide buried layer 50 is further disposed between the piezoelectric layer 20 and the support layer 10.

[0103] Piezoelectric materials may expand or contract when the temperature changes, causing the frequency to change. The buried oxide layer 50 is mainly used to achieve temperature compensation, suppress this change of piezoelectric materials, and reduce the impact of temperature on the filter frequency.

[0104] The buried oxide layer 50 is mainly composed of oxide materials. The specific material of the buried oxide layer 50 can be selected according to the actual application scenario, and is not limited here. For example, the buried oxide layer 50 can be made of silicon dioxide.

[0105] One embodiment of this application provides a filter that includes at least one of the aforementioned elastic wave resonators.

[0106] In the elastic wave resonator, the extension direction of the line connecting the center of the gap between each first true finger 32 and the corresponding second false finger 36 forms a first angle θ1 with the second direction, and the extension direction of the line connecting the center of the gap between each second true finger 35 and the corresponding first false finger 33 forms a second angle θ2 with the second direction.

[0107] The structure and working principle of the elastic wave resonator can be referred to the aforementioned embodiments, and will not be repeated here.

[0108] According to the filter of this application, the extension direction of the center line connecting the gaps between each first true finger 32 and the corresponding second false finger 36 in the elastic wave resonator forms a first angle θ1 with the second direction, and the extension direction of the center line connecting the gaps between each second true finger 35 and the corresponding first false finger 33 forms a second angle θ2 with the second direction. By providing an oblique angle to the gap region between the true and false fingers to suppress transverse mode spurious signals, and by extending the length of the false fingers to match the angle and reduce transverse energy leakage, the characteristics of the resonator are significantly improved.

[0109] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. An elastic wave resonator, characterized in that, The device includes a support layer, a piezoelectric layer, and an interdigital transducer stacked sequentially. The interdigital transducer includes a first interdigital electrode structure and a second interdigital electrode structure arranged opposite to each other along a first direction. The first interdigital electrode structure includes a first true finger and a first false finger alternately arranged along a second direction. The second interdigital electrode structure includes a second true finger and a second false finger alternately arranged along the second direction. The first true finger and the second false finger are arranged opposite to each other, and the second true finger and the first false finger are arranged opposite to each other. The first direction and the second direction intersect. In the second direction, the lengths of the first true finger and the first false finger gradually change, and the trend of the gradual change in the lengths of the second true finger and the second false finger is opposite to the trend of the gradual change in the lengths of the first true finger and the first false finger. The line connecting the center of the gap between each first true finger and the corresponding second false finger forms a first angle with the second direction, and the line connecting the center of the gap between each second true finger and the corresponding first false finger forms a second angle with the second direction.

2. The elastic wave resonator according to claim 1, characterized in that, When the height of the first pseudofinger is h, the height H of the nth pseudofinger satisfies the following relationship: Where pitch is half the wavelength of the elastic wave, θ is the angle formed by the line connecting the center of the gap between the pseudo-finger and the corresponding real finger and the second direction, and N_IDT is the sum of the real and pseudo-finger values ​​from the first pseudo-finger to the nth pseudo-finger.

3. The elastic wave resonator according to claim 1, characterized in that, The material of the support layer includes an AT-cut 0°X quartz crystal, and the first included angle and the second included angle are greater than or equal to 2° or less than or equal to -2°.

4. The elastic wave resonator according to claim 3, characterized in that, The first included angle and the second included angle are greater than or equal to 2° and less than or equal to 16°, or the first included angle and the second included angle are greater than or equal to -16° and less than or equal to -2°.

5. The elastic wave resonator according to claim 1, characterized in that, The material of the support layer includes an AT-cut 90°X quartz crystal, and the first included angle and the second included angle are greater than or equal to 4° or less than or equal to -4°.

6. The elastic wave resonator according to claim 5, characterized in that, The first included angle and the second included angle are greater than or equal to 4° and less than or equal to 18°, or the first included angle and the second included angle are greater than or equal to -18° and less than or equal to -4°.

7. The elastic wave resonator according to any one of claims 1-6, characterized in that, The first included angle and the second included angle are equal.

8. The elastic wave resonator according to any one of claims 1-6, characterized in that, The lengths of the first and second pseudo-fingers are 0.025λ to 50λ, where λ is the wavelength of the elastic wave.

9. The elastic wave resonator according to any one of claims 1-6, characterized in that, The length of the gap between each first true finger and the corresponding second false finger along the first direction is 0.025λ to 2.0λ, and the length of the gap between each second true finger and the corresponding first false finger along the first direction is 0.025λ to 2.0λ.

10. The elastic wave resonator according to any one of claims 1-6, characterized in that, The intersection of the first true finger and the second true finger forms an aperture region, the length of which along the first direction is 10λ to 50λ.

11. The elastic wave resonator according to any one of claims 1-6, characterized in that, The metallization rate of the interdigital transducer is 0.3 to 0.

7.

12. The elastic wave resonator according to any one of claims 1-6, characterized in that, A temperature compensation layer is provided on the side of the interdigital transducer away from the piezoelectric layer.

13. The elastic wave resonator according to any one of claims 1-6, characterized in that, An oxide buried layer is also provided between the piezoelectric layer and the support layer.

14. A filter, characterized in that, It includes at least one elastic wave resonator according to any one of claims 1-13.

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