A surface acoustic wave filter, a radio frequency front end module and an electronic device

Abstract

The application relates to a surface acoustic wave filter, a radio frequency front-end module and electronic equipment, comprising a piezoelectric substrate, an interdigital transducer, a temperature compensation layer and a frequency modulation layer, the interdigital transducer is arranged on a first surface of the piezoelectric substrate, the temperature compensation layer is located on the first surface and covers the interdigital transducer, and the frequency modulation layer is arranged on a side of the temperature compensation layer away from the piezoelectric substrate; the interdigital transducer comprises bus bars and electrode fingers, the electrode fingers are connected with one bus bar and are spaced from another bus bar, and the electrode fingers connected with different bus bars are alternately arranged; the center distance between two adjacent electrode fingers connected with the same bus bar is lambda, and along the thickness direction of the piezoelectric substrate, the thickness of the frequency modulation layer is greater than or equal to 0.005 lambda and less than or equal to 0.15 lambda. The thickness range of the frequency modulation layer is controlled to be between 0.005 lambda and 0.15 lambda, so that the sensitivity of the frequency modulation layer is reduced, and the performance of the surface acoustic wave filter is ensured.

Description

Technical Field

[0001] This application relates to the field of radio frequency, and more particularly to a surface acoustic wave filter, a radio frequency front-end module including the surface acoustic wave filter, and an electronic device including the radio frequency front-end module. Background Technology

[0002] In the radio frequency (RF) field, surface acoustic wave (SAW) filters typically consist of a piezoelectric substrate and interdigital transducers. The filtering function of the SAW filter is achieved through the interaction between the interdigital transducers and the piezoelectric substrate. Temperature compensation layers and frequency modulation layers are often also included to optimize the filtering effect.

[0003] The operating frequency of a surface acoustic wave (SAW) filter is a crucial performance indicator. To ensure the filter's operating frequency matches actual requirements, a frequency modulation (FM) layer is typically required, such as when setting up a temperature-compensated SAW (TCSAW) filter. This FM layer allows for frequency adjustment and control. However, excessive sensitivity of the FM layer can negatively impact the FM effect, thereby affecting the overall performance of the SAW filter. Utility Model Content

[0004] In view of the shortcomings of the prior art, the purpose of this application is to provide a solution for adjusting sensitivity, specifically including the following technical solution:

[0005] In a first aspect, embodiments of this application provide a surface acoustic wave filter, including a piezoelectric substrate, an interdigital transducer, a temperature compensation layer, and at least one frequency modulation layer. Along the thickness direction of the piezoelectric substrate, the interdigital transducer is disposed on a first surface of the piezoelectric substrate, the temperature compensation layer is located on the first surface and covers the interdigital transducer, and the frequency modulation layer is disposed on the side of the temperature compensation layer away from the piezoelectric substrate.

[0006] The interdigital transducer includes at least two busbars and a plurality of electrode fingers located between the at least two busbars. The busbars are spaced apart along a first direction and extend along a second direction. One end of each electrode finger is connected to a busbar, and the other end is spaced apart from another busbar. The electrode fingers connected to different busbars are alternately arranged along the second direction, which intersects with the first direction.

[0007] Along the second direction, the center-to-center distance between two adjacent electrode fingers connected to the same busbar is λ, and along the thickness direction of the piezoelectric substrate, the thickness of at least one frequency modulation layer is greater than or equal to 0.005λ and less than or equal to 0.15λ.

[0008] The surface acoustic wave (SAW) filter provided in this application achieves its filtering function by placing an interdigital transducer on the first surface of a piezoelectric substrate and utilizing the interaction between the interdigital transducer and the piezoelectric substrate. Furthermore, the SAW filter provided in this application also improves its performance by placing a temperature compensation layer on the first surface, which covers the interdigital transducer, thereby reducing the drift of the filter's center frequency with temperature changes.

[0009] The surface acoustic wave (SAW) filter provided in this application also achieves frequency adjustment by setting frequency modulation layers. The thickness of all frequency modulation layers is greater than or equal to 0.005λ and less than or equal to 0.15λ, thus limiting the sensitivity of the sound velocity within the frequency modulation layer to thickness changes within the corresponding thickness range. This reduces the difficulty of the ion beam frequency modulation process during SAW filter manufacturing, thereby precisely controlling the frequency of the prepared SAW filter and ensuring its performance.

[0010] In one embodiment, along the second direction, the center-to-center distance λ between two adjacent electrode fingers connected to the same busbar is greater than or equal to 0.4 μm and less than or equal to 10 μm.

[0011] In one embodiment, the thickness of the frequency modulation layer is greater than or equal to 0.01λ and less than or equal to 0.04λ.

[0012] In one embodiment, the frequency modulation layer includes one of a silicon nitride film, a silicon oxynitride film, an aluminum oxide film, and a diamond film.

[0013] In one embodiment, at least one frequency modulation layer is configured as a silicon nitride film layer, and the thickness of the at least one frequency modulation layer is greater than or equal to 0.01λ and less than or equal to 0.1λ.

[0014] In one embodiment, at least one frequency modulation layer is configured as a silicon oxynitride film layer, and the thickness of the at least one frequency modulation layer is greater than or equal to 0.01λ and less than or equal to 0.15λ.

[0015] In one embodiment, at least one frequency modulation layer is configured as an alumina film layer or a diamond film layer, and the thickness of at least one frequency modulation layer is greater than or equal to 0.005λ and less than or equal to 0.1λ.

[0016] In one embodiment, a temperature compensation layer covers the electrode fingers, and the thickness of the temperature compensation layer in different regions is greater than the thickness of the electrode fingers.

[0017] In one embodiment, the number of frequency modulation layers is one, and the sensitivity of the frequency modulation layer is less than or equal to 0.5; wherein: the sensitivity is used to characterize the slope of the fitted straight line corresponding to the linear relationship between the sound velocity and the thickness of the corresponding frequency modulation layer at the corresponding thickness.

[0018] In one embodiment, there are multiple frequency modulation layers, including an adjacent first frequency modulation layer and a second frequency modulation layer. The first frequency modulation layer and the second frequency modulation layer are sequentially stacked on the surface of the temperature compensation layer away from the piezoelectric substrate. The first frequency modulation layer and the second frequency modulation layer are made of different material films.

[0019] In one embodiment, the first frequency modulation layer is in contact with the temperature compensation layer, and the expansion coefficient of the first frequency modulation layer is lower than that of the second frequency modulation layer.

[0020] In one embodiment, the first frequency modulation layer is configured as a diamond film or an alumina film, and the second frequency modulation layer is configured as a silicon nitride film or a silicon oxynitride film.

[0021] In one embodiment, along the thickness direction of the piezoelectric substrate, the second frequency modulation layer is located on top of at least one frequency modulation layer, and the sensitivity of the second frequency modulation layer is less than or equal to 0.5; wherein: the sensitivity is used to characterize the slope of the fitted straight line corresponding to the linear relationship between the sound velocity and the thickness of the corresponding frequency modulation layer at the corresponding thickness.

[0022] In one embodiment, the sensitivity of the second frequency modulation layer is less than that of the first frequency modulation layer.

[0023] In one embodiment, the thickness of the second frequency modulation layer is greater than the thickness of the first frequency modulation layer.

[0024] In one embodiment, the surface acoustic wave filter further includes a substrate, and the substrate, the piezoelectric substrate, and the interdigital transducer are stacked sequentially along the thickness direction of the piezoelectric substrate.

[0025] Secondly, embodiments of this application provide a radio frequency front-end module, including a filter.

[0026] Thirdly, embodiments of this application provide a radio frequency front-end module, including a piezoelectric substrate, an interdigital transducer, a temperature compensation layer and at least one frequency modulation layer. Along the thickness direction of the piezoelectric substrate, the interdigital transducer is disposed on a first surface of the piezoelectric substrate, the temperature compensation layer is located on the first surface and covers the interdigital transducer, and the frequency modulation layer is disposed on the side of the temperature compensation layer away from the piezoelectric substrate.

[0027] The interdigital transducer includes at least two busbars and a plurality of electrode fingers located between the at least two busbars. The busbars are spaced apart along a first direction and extend along a second direction. One end of each electrode finger is connected to a busbar, and the other end is spaced apart from another busbar. The electrode fingers connected to different busbars are alternately arranged along the second direction, which intersects with the first direction.

[0028] Wherein, along the second direction, the center distance between two adjacent electrode fingers connected to the same busbar is λ, and along the thickness direction of the piezoelectric substrate, at least one frequency modulation layer is set as a silicon nitride film layer, and the thickness of the silicon nitride film layer is greater than or equal to 0.005λ and less than or equal to 0.15λ.

[0029] The RF front-end module provided in this application achieves its filtering function by setting an interdigital transducer on the first surface of a piezoelectric substrate and utilizing the interaction between the interdigital transducer and the piezoelectric substrate. Simultaneously, the RF front-end module also improves its performance by setting a temperature compensation layer on the first surface, which covers the interdigital transducer, thereby reducing the center frequency drift of the RF front-end module with temperature variations.

[0030] The RF front-end module provided in this application also achieves frequency adjustment by setting a frequency modulation layer. Specifically, the thickness of the silicon nitride film in all frequency modulation layers is greater than or equal to 0.005λ and less than or equal to 0.15λ, thus limiting the sensitivity of the sound velocity within the silicon nitride film to thickness changes within the corresponding thickness range. This reduces the difficulty of the ion beam frequency modulation process during the manufacturing of the RF front-end module, thereby precisely controlling the frequency of the prepared RF front-end module and ensuring its performance.

[0031] In one embodiment, along the thickness direction of the piezoelectric substrate, the silicon nitride film layer is located on top of at least one frequency modulation layer.

[0032] In one embodiment, the thickness of the silicon nitride film is greater than or equal to 100 nm and less than or equal to 200 nm.

[0033] Fourthly, embodiments of this application provide an electronic device, including a radio frequency front-end module.

[0034] It is understandable that the electronic device provided in the fourth aspect of this application uses the radio frequency front-end modules provided in the second and third aspects of this application, and the radio frequency front-end module provided in the second aspect of this application uses the surface acoustic wave filter provided in the first aspect of this application. Accordingly, the frequency and performance of the electronic device and the surface acoustic wave filter of this application are guaranteed. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of an electronic device provided in one embodiment of this application;

[0036] Figure 2 This is a schematic diagram of the structure of the radio frequency front-end module provided in one embodiment of this application;

[0037] Figure 3 This is a schematic diagram of the structure of a multiplexer provided in one embodiment of this application;

[0038] Figure 4 This is a schematic diagram of the structure of a surface acoustic wave filter provided in one embodiment of this application;

[0039] Figure 5 This is a schematic diagram of a partial structure of the surface acoustic wave filter provided in one embodiment of this application at the interdigital transducer.

[0040] Figure 6 The graph shows the linear relationship between the sound velocity and thickness of the frequency modulation layer in Comparative Example 1 for a surface acoustic wave filter in the prior art.

[0041] Figure 7 This is a linear relationship fitting graph of the sound velocity and thickness of the frequency modulation layer in Embodiment 1 of the surface acoustic wave filter provided in one embodiment of this application.

[0042] Figure 8 This is a linear relationship fitting graph of the sound velocity and thickness of the frequency modulation layer in Embodiment 2 of the surface acoustic wave filter provided in one embodiment of this application.

[0043] Figure 9 This is a fitting graph showing the linear relationship between the sound velocity and thickness of the frequency modulation layer in Embodiment 3 of the surface acoustic wave filter provided in one embodiment of this application.

[0044] Figure 10 The graph shows the linear relationship between the sound velocity and thickness of the frequency modulation layer in Comparative Example 2 for surface acoustic wave filters in the prior art.

[0045] Figure 11 This is a linear relationship fitting graph of the sound velocity and thickness of the frequency modulation layer in embodiment 4 of the surface acoustic wave filter provided in one embodiment of this application.

[0046] Figure 12 This is a schematic diagram of another structure of the surface acoustic wave filter provided in one embodiment of this application;

[0047] Figure 13 This is another structural schematic diagram of the surface acoustic wave filter provided in one embodiment of this application;

[0048] Figure 14 This is a cross-sectional structural diagram of the radio frequency front-end module provided in one embodiment of this application;

[0049] Figure 15 This is a partial structural diagram of the radio frequency front-end module provided in one embodiment of this application at the interdigital transducer. Detailed Implementation

[0050] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0051] The following descriptions of the embodiments are based on the accompanying illustrations and are used to illustrate specific embodiments in which this application can be implemented. The component designations used herein, such as "first," "second," etc., are merely for distinguishing the described objects and do not have any sequential or technical meaning. Unless otherwise specified, the terms "connection" and "linkage" used in this application include both direct and indirect connections (linkages). Directional terms used in this application, such as "up," "down," "front," "rear," "left," "right," "inner," "outer," "side," etc., are merely for reference to the accompanying drawings. Therefore, the use of directional terms is for better and clearer explanation and understanding of this application, and does not indicate or imply that the referred device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this application.

[0052] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joint" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances. It should be noted that the terms "first," "second," etc., in the specification, claims, and drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising," "may include," "include," or "may include" used in this application indicate the presence of the corresponding disclosed function, operation, element, etc., and do not limit one or more other functions, operations, elements, etc. Moreover, the terms "comprising" or "include" indicate the presence of the corresponding features, numbers, steps, operations, elements, components, or combinations thereof disclosed in the specification, but do not exclude the presence or addition of one or more other features, numbers, steps, operations, elements, components, or combinations thereof, and are intended to cover non-exclusive inclusion.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0054] Please see Figure 1 The diagram shown is a structural schematic of an electronic device 400 provided in one embodiment of this application.

[0055] like Figure 1 As shown, the electronic device 400 of this application includes a substrate 401 and a radio frequency front-end module 300, with the radio frequency front-end module 300 mounted on the substrate 401. The substrate 401 and the radio frequency front-end module 300 are electrically connected.

[0056] In one embodiment, the substrate 401 includes a printed circuit board to drive and control the radio frequency front-end module 300. The electronic device 400 of this application receives and / or transmits signals through the radio frequency front-end module 300. Exemplarily, the electronic device 400 includes at least one of a computer, mobile phone, tablet computer, smartwatch, and navigator, etc., and this application does not specifically limit it.

[0057] Please see Figure 2 The diagram shown is a structural schematic of the radio frequency front-end module 300 provided in one embodiment of this application.

[0058] like Figure 2 As shown, the RF front-end module 300 includes at least a signal terminal 301, a switch 302, an amplifier 303, and a surface acoustic wave (SAW) filter 100. The signal terminal 301 receives and transmits external signals; for example, if the signal terminal 301 is connected to an antenna, the antenna can be used to receive or transmit signals. The switch 302 is connected between the signal terminal 301 and the SAW filter 100 to control signal transmission between them. The SAW filter 100 outputs a signal with a preset frequency from the signal transmitted to it. The amplifier 303 is electrically connected to the SAW filter 100 to amplify the signal processed by the SAW filter 100 and transmit it to subsequent modules.

[0059] It is understood that, in another embodiment, the surface acoustic wave filter 100 may be one or more, and multiple surface acoustic wave filters 100 may constitute a multiplexer 200. This application does not impose any particular limitation on this.

[0060] Please see Figure 3 The diagram shown is a structural schematic of the multiplexer 200 provided in one embodiment of this application.

[0061] like Figure 3As shown, the multiplexer 200 of this application can be a duplexer or a tripplexer, etc. The multiplexer 200 includes an antenna 201, a transmit filter 202a, and a receive filter 202b. Both the transmit filter 202a and the receive filter 202b include a first port 203 and a second port 204, and the first port 203 of both the transmit filter 202a and the receive filter 202b are communicatively connected to the antenna 201.

[0062] For the transmitting filter 202a, the first port 203 is used to transmit signals, and the second port 204 is used to receive signals. For the receiving filter 202b, the first port 203 is used to receive signals, and the second port 204 is used to transmit signals.

[0063] Signals of different frequencies are input from the first port 203 to the transmitting filter 202a. The transmitting filter 202a processes the signals of the corresponding frequencies and transmits them outward from the antenna 201. Signals are input from the antenna 201 to the receiving filter 202b. The receiving filter 202b processes the received signals and transmits them outward from the second port 204. In this embodiment, the transmitting filter 202a and the receiving filter 202b are spaced apart from each other. It is understood that the multiplexer 200 of this application allows the transmitting filter 202a and the receiving filter 202b to operate simultaneously. That is, the multiplexer 200 of this application can simultaneously receive and transmit signals.

[0064] In the embodiments of this application, at least one of the transmitting filter 202a and the receiving filter 202b is the surface acoustic wave filter 100 of this application.

[0065] Please refer to the above. Figure 4 The diagram shown is a structural schematic of a surface acoustic wave filter 100 provided in one embodiment of this application.

[0066] like Figure 4 As shown, the surface acoustic wave filter 100 of this application includes a piezoelectric substrate 10 and an interdigital transducer 20. Along the thickness direction of the piezoelectric substrate 10, the interdigital transducer 20 is disposed on the first surface 11 of the piezoelectric substrate 10. The interdigital transducer 20 is used to cooperate with the piezoelectric substrate 10 to realize the filtering function of the surface acoustic wave filter 100 of this application.

[0067] Specifically, the interdigital transducer 20 includes at least two busbars 21 and a plurality of electrode fingers 22 located between the at least two busbars 21. For example, Figure 5As shown, the interdigital transducer 20 has two busbars 21, which are arranged alternately. In one example, the two busbars 21 are arranged in parallel, or other corresponding arrangements can be made as needed. One of the two busbars 21 is used to receive external signals, and the other busbar 21 is used to output signals. Multiple electrode fingers 22 are located between the two busbars 21. Some of the electrode fingers 22 are connected to one busbar 21, and other electrode fingers 22 are connected to the other busbar 21.

[0068] For ease of description, the busbar 21 used for receiving external signals is defined as the first busbar 211, and the busbar 21 used for outputting signals is defined as the second busbar 212. The electrode finger 22 connected to the first busbar 211 is defined as the first electrode finger 221, and the electrode finger 22 connected to the second busbar 212 is defined as the second electrode finger 222.

[0069] Specifically, the first busbar 211 and the second busbar 212 are arranged alternately along the first direction 001 and extend along the second direction 002. The first electrode finger 221 and the second electrode finger 222 are arranged alternately along the second direction 002. Both the first electrode finger 221 and the second electrode finger 222 extend along the first direction 001. Specifically, as... Figure 5 As shown, along the second direction 002, there is a second electrode finger 222 between any two adjacent first electrode fingers 221, and there is a first electrode finger 221 between any two adjacent second electrode fingers 222.

[0070] Wherein, the second direction 002 intersects the first direction 001. For example, the second direction 002 and the first direction 001 can be perpendicular to each other, so that each electrode finger 22 has a 90° angle with its connected busbar. For example, the second direction 002 and the first direction 001 can also not be perpendicular, so that each electrode finger 22 has an angle greater than 90° or less than 90° with its connected busbar 21.

[0071] In this embodiment, when an external excitation signal is applied to the interdigital transducer 20, the interdigital transducer 20 converts the electrical signal into a surface acoustic wave. The surface acoustic wave propagates along the surface of the piezoelectric substrate 10 and is reflected by a reflective grating (not shown in the figure), and is then converted back into an electrical signal by the interdigital transducer 20 for output.

[0072] Surface acoustic waves (SAWs) are used to implement the frequency selection and signal processing functions of the SAW filter 100. During SAW propagation, the primary propagation direction is the second direction 002. However, in practice, due to edge effects and acoustic diffraction, the propagation direction of SAWs formed on the piezoelectric substrate surface may also be other directions. In one embodiment, SAWs propagating in other directions are absorbed by a sound-absorbing material (not shown in the figure).

[0073] exist Figure 4 In the illustrated figure, the surface acoustic wave filter 100 of this application further includes a temperature compensation layer 30. Along the thickness direction of the piezoelectric substrate 10, the temperature compensation layer 30 is located on the first surface 11 and covers the interdigital transducer 20. The temperature compensation layer 30 is used to reduce the drift of the center frequency of the surface acoustic wave filter 100 with temperature changes. In one embodiment, the material of the temperature compensation layer 30 is any one of silicon dioxide, barium strontium titanate, and bismuth strontium titanate. For example, the material of the temperature compensation layer 30 is silicon dioxide.

[0074] Specifically, during the operation of the surface acoustic wave filter 100 of this application, when the temperature of the piezoelectric substrate 10 surface increases, the piezoelectric substrate 10, based on its own material properties, will reduce the sound velocity at the first surface 11, thereby causing the center frequency of the surface acoustic wave filter 100 to decrease. The temperature compensation layer 30 can offset the effect of temperature change on the sound velocity at the first surface 11 based on its own material properties, thereby reducing or offsetting the drift of the center frequency of the surface acoustic wave filter 100 with temperature change, thereby improving the operating performance of the surface acoustic wave filter 100 of this application.

[0075] The surface acoustic wave (SAW) filter 100 of this application further includes at least one frequency modulation layer 40. Along the thickness direction of the piezoelectric substrate 10, at least one frequency modulation layer 40 is disposed on the side of the temperature compensation layer 30 away from the piezoelectric substrate 10. Due to manufacturing tolerances in the manufacturing process of the SAW filter 100 of this application, the operating frequency of the SAW filter 100 may not match the actual required operating frequency. During the manufacturing process of the SAW filter 100 of this application, the structure of the frequency modulation layer 40 is usually adjusted, such as optimizing the thickness of the frequency modulation layer 40, to obtain the required frequency of the SAW filter 100. Specifically, an ion beam frequency modulation process is used to adjust the thickness of the frequency modulation layer 40 to adjust the mass load of the interdigital transducer 20, thereby adjusting the sound velocity of the SAW wave so that the operating frequency of the SAW filter 100 matches the actual required operating frequency.

[0076] That is, the setting of the frequency modulation layer 40 can ensure the frequency adjustment and control of the surface acoustic wave filter 100, thereby facilitating the manufacturing of the surface acoustic wave filter 100 of this application and ensuring the performance of the surface acoustic wave filter 100.

[0077] In this embodiment of the application, along the second direction 002, the center-to-center distance between two adjacent electrode fingers 22 connected to the same busbar 21 is λ. Specifically, in Figure 4 In the illustration, the center-to-center spacing λ refers to the distance between the central axes of two adjacent electrode fingers 22 connected to the same busbar 21. Along the thickness direction of the piezoelectric substrate 10, the thickness of at least one frequency modulation layer 40 is greater than or equal to 0.005λ and less than or equal to 0.15λ. In this application, when one frequency modulation layer 40 is provided, the thickness of the frequency modulation layer 40 is within the above range; or multiple frequency modulation layers are provided, and the total thickness of the multiple frequency modulation layers 40 is greater than or equal to 0.005λ and less than or equal to 0.15λ. This ensures the effective adjustment of the surface acoustic wave filter frequency.

[0078] Since the thickness of the frequency modulation layer 40 is related to the speed of sound. Specifically, when ion beam frequency modulation process is used to etch frequency modulation layers 40 of the same material but different thicknesses, under the condition of etching the same thickness, the surface acoustic wave filter 100 corresponding to the relatively thicker frequency modulation layer 40 has a relatively smaller change in speed of sound. Correspondingly, the speed of sound of the frequency modulation layer 40 of this thickness is less sensitive to the change in thickness.

[0079] In one embodiment of this application, the thickness of any frequency modulation layer 40 is greater than or equal to 0.005λ and less than or equal to 0.15λ, so as to limit the sensitivity of the sound velocity in the frequency modulation layer 40 to the thickness change within the corresponding thickness range. This reduces the difficulty of the ion beam frequency modulation process in the manufacturing process of the surface acoustic wave filter 100, and can better control the frequency change to obtain a surface acoustic wave filter 100 that meets the frequency requirements.

[0080] In one embodiment, the thickness of the frequency modulation layer 40 is greater than or equal to 0.01λ and less than or equal to 0.04λ to limit the sensitivity of the sound velocity within the frequency modulation layer 40 to thickness changes within the corresponding thickness range. This reduces the difficulty of the ion beam frequency modulation process during the manufacturing of the surface acoustic wave filter 100, allows for better control of frequency changes, and results in a surface acoustic wave filter 100 that meets the frequency requirements.

[0081] In one embodiment, along the second direction 002, the center-to-center distance λ between two adjacent electrode fingers 22 connected to the same busbar 21 is greater than or equal to 0.4 μm and less than or equal to 10 μm. For example, the center-to-center distance λ between two adjacent electrode fingers 22 connected to the same busbar 21 is any one of 1 μm, 3 μm, 5 μm, 8 μm, and 10 μm.

[0082] In one embodiment, the frequency modulation layer 40 includes one of a silicon nitride film, a silicon oxynitride film, an aluminum oxide film, and a diamond film. That is, the material of the frequency modulation layer 40 can be any one of silicon nitride, silicon oxynitride, aluminum oxide, and diamond.

[0083] In one embodiment, at least one frequency modulation layer 40 is configured as a silicon nitride film layer, and the thickness of the at least one frequency modulation layer 40 is greater than or equal to 0.01λ and less than or equal to 0.1λ. Specifically, when the number of frequency modulation layers 40 is one, and the material of the frequency modulation layer 40 is silicon nitride, the thickness of the frequency modulation layer 40 is between 0.01λ and 0.1λ.

[0084] Specifically, in this embodiment, the frequency modulation layer 40 is a silicon nitride film layer, and the silicon nitride film layer is a single layer. The thickness of the silicon nitride film layer is set to 0.01λ-0.03λ. Optionally, the thickness of the silicon nitride film layer is set to 80nm-200nm, such as 100nm, 120nm, 130nm, 140nm, 150nm, and 160nm. The above thickness can be determined according to the product requirements or the frequency of the surface acoustic wave filter 100, which will not be elaborated here.

[0085] In one embodiment, at least one frequency modulation layer 40 is configured as a silicon oxynitride film layer, and the thickness of the at least one frequency modulation layer 40 is greater than or equal to 0.01λ and less than or equal to 0.15λ. Specifically, when the number of frequency modulation layers 40 is one, and the material of the frequency modulation layer 40 is silicon oxynitride, the thickness of the frequency modulation layer 40 is between 0.01λ and 0.15λ.

[0086] Specifically, in this embodiment, the frequency modulation layer 40 is a silicon oxynitride film layer, and the silicon oxynitride film layer is a single layer. The thickness of the silicon oxynitride film layer is set to 0.01λ-0.1λ. Optionally, the thickness of the silicon oxynitride film layer is set to 70nm-210nm, such as 80nm, 100nm, 120nm, 140nm, 160nm, and 180nm. The above thickness can be determined according to the requirements of the product or the frequency of the surface acoustic wave filter 100, which will not be elaborated here.

[0087] In one embodiment, at least one tuning layer 40 is configured as an alumina film or a diamond film, and the thickness of the at least one tuning layer 40 is greater than or equal to 0.005λ and less than or equal to 0.1λ. That is, when there is only one tuning layer 40, and the material of the tuning layer 40 is alumina or diamond, the thickness of the tuning layer 40 is between 0.005λ and 0.1λ.

[0088] Specifically, in this embodiment, the frequency modulation layer 40 is configured as an alumina film layer or a diamond film layer, and the alumina film layer or the diamond film layer is configured as a single layer. The thickness of the alumina film layer or the diamond film layer is set to 0.005λ-0.008λ. Optionally, the thickness of the alumina film layer or the diamond film layer is set to 60nm-150nm, such as 60nm, 80nm, 100nm, 120nm, and 140nm. The above thickness can be determined according to the product requirements or the frequency of the surface acoustic wave filter 100, and will not be elaborated further here.

[0089] Based on the above three embodiments, it can be seen that when the surface acoustic wave filter 100 of this application has only one frequency modulation layer 40, the thickness range of the frequency modulation layer 40 can be selected according to the different materials of the frequency modulation layer 40. On the one hand, this ensures that the sound velocity of the frequency modulation layer 40 within the corresponding thickness range is less sensitive to thickness changes. On the other hand, it also ensures that the thickness range of the frequency modulation layer 40 can match the time required for the ion beam frequency modulation process, avoiding the phenomenon that the frequency modulation layer 40 is too thick, resulting in an excessively long process time when adjusting the thickness of the frequency modulation layer 40 using the ion beam frequency modulation process. This allows for precise control of the frequency of the fabricated surface acoustic wave filter 100 and ensures its performance.

[0090] Specifically, for low-frequency surface acoustic wave filters, if the operating frequency is in the range of 800MHz to 950MHz, when using the structure provided in the embodiments of this application, if the frequency modulation layer is set as a silicon nitride film layer and the thickness of the silicon nitride film layer is set to 150mm, then the frequency sensitivity is lower for every 1nm change in the thickness of the silicon nitride film layer.

[0091] In one embodiment, the temperature compensation layer 30 covers the electrode finger 22, and the thickness of the temperature compensation layer 30 in different regions is greater than the thickness of the electrode finger 22. That is, in Figure 4 In the illustrated figure, along the thickness direction of the piezoelectric substrate 10, the surface of the temperature compensation layer 30 away from the piezoelectric substrate 10 is parallel to the first surface 11. In this embodiment, the thickness of the temperature compensation layer 30 is greater than the thickness of the electrode finger 22, and at different locations, the thickness between the top surface of the temperature compensation layer 30 and the surface of the piezoelectric substrate 10 is the same along the thickness direction. This facilitates the fabrication of both the temperature compensation layer 30 and the frequency modulation layer 40.

[0092] In one embodiment, the number of frequency modulation layers 40 is one, and the sensitivity of the frequency modulation layer 40 is less than or equal to 0.5; wherein: the sensitivity is used to characterize the slope of the fitted straight line corresponding to the linear relationship between the sound velocity and the thickness of the corresponding frequency modulation layer 40 at a given thickness. Specifically, the sensitivity shows the relationship between the sound velocity and the film thickness, the change in sound velocity when the film thickness changes by a unit. That is, the ratio of the change in sound velocity to the change in thickness (dV / dT, where V represents the sound velocity and T is the film thickness). In the embodiments of this application, if the film thickness T is in nm and the sound velocity V is in m / s, then the unit of the sensitivity is 10. 9 / s.

[0093] In this embodiment of the application, a frequency modulation layer 40 with a sensitivity of less than or equal to 0.5 is provided to avoid the situation where the sensitivity of the frequency modulation layer 40 is too high, which would lead to a greater difficulty in the ion beam frequency modulation process. This allows for precise control of the frequency of the prepared surface acoustic wave filter 100 and ensures the performance of the surface acoustic wave filter 100.

[0094] Specifically, in one embodiment, the frequency modulation layer 40 is a silicon nitride film layer. Figure 6 The graph shows the linear relationship between the sound velocity and thickness of the frequency-modulated layer in Comparative Example 1 for the surface acoustic wave filter. Figure 7 This is a graph showing the linear relationship between the sound velocity and thickness of the frequency modulation layer 40 in Embodiment 1 of the surface acoustic wave filter 100 of this application. Figure 8 This is a graph showing the linear relationship between the sound velocity and thickness of the frequency modulation layer 40 in Embodiment 2 of the surface acoustic wave filter 100 of this application. Figure 9 This is a fitting graph showing the linear relationship between the sound velocity and thickness of the frequency modulation layer 40 in Embodiment 3 of the surface acoustic wave filter 100 of this application.

[0095] For each embodiment and comparative example, the surface acoustic wave filter includes a piezoelectric substrate, an interdigital transducer, a temperature compensation layer, and at least one frequency modulation layer. Along the thickness direction of the piezoelectric substrate, the interdigital transducer is disposed on a first surface of the piezoelectric substrate, the temperature compensation layer is located on the first surface and covers the interdigital transducer, and the frequency modulation layer is disposed on the side of the temperature compensation layer away from the piezoelectric substrate.

[0096] In this application, there are three embodiments, namely Embodiment 1, Embodiment 2, and Embodiment 3, and one comparative example, namely Comparative Example 1. The structural schematic diagram corresponding to Comparative Example 1 is identical to the structural schematic diagram corresponding to any of the embodiments, and all are... Figure 4 As shown. The structural schematic diagram corresponding to Comparative Example 1 is the same as the center-to-center spacing λ corresponding to any embodiment, and the center-to-center spacing λ is equal to 10 μm.

[0097] In Comparative Example 1, the thickness of the frequency modulation layer is 54 nm. In Example 1, the thickness of the frequency modulation layer 40 is 110 nm. In Example 2, the thickness of the frequency modulation layer 40 is 160 nm. In Example 3, the thickness of the frequency modulation layer 40 is 220 nm. Apart from the above differences, all other parameters of Comparative Example 1, Example 1, Example 2, and Example 3 are exactly the same.

[0098] exist Figures 6-9 In this process, the frequency modulation layer 40 is processed using an etching process to obtain the desired surface acoustic wave (SAW) filter frequency 100. Specifically, an ion beam frequency modulation process is used to etch the frequency modulation layer of corresponding thickness, and different thicknesses are etched. Then, the sound velocity corresponding to the SAW filter with different etched thicknesses is simulated to obtain the relationship between film thickness and sound velocity. Finally, a straight line is fitted to form a relationship between film thickness and sound velocity. The simulation results are detailed in [link to simulation]. Figure 6 In the process, when the thickness of the frequency modulation layer 40 is set to 54 nm, by adjusting it and recording the corresponding sound velocity at each thickness, multiple sets of data are fitted to form a fitted linear equation: V = 0.8T + 3546.4. Similarly, in Figure 7 In the process, when the thickness of the frequency modulation layer 40 is set to 110 nm, by adjusting it and recording the corresponding sound velocity at each thickness, multiple sets of data are fitted to form a fitted linear equation: V = 0.3536T + 3542. Figure 8 In the process, when the thickness of the frequency modulation layer 40 is set to 160nm, by adjusting it and recording the corresponding sound velocity at each thickness, multiple sets of data are fitted to form a fitted linear equation: V=0.16T+3601. Figure 9 In this study, when the thickness of the frequency modulation layer 40 is set to 220 nm, by adjusting it and recording the corresponding sound velocity at each thickness, multiple sets of data are fitted to form a fitted linear equation: V = 0.0832T + 3614. Here, the vertical axis V represents the sound velocity in m / s, and the horizontal axis represents the corresponding thickness of the frequency modulation layer in nm.

[0099] The above-mentioned fitted linear equations are linear equations relating sound velocity and thickness. For any fitted linear equation, during the manufacturing process of the surface acoustic wave (SAW) filter, when its thickness is reduced to a certain value, the center frequency of the corresponding SAW filter decreases to the corresponding frequency. The larger the slope K of the linear relationship between sound velocity and thickness, the higher the frequency adjusted for the same thickness. Correspondingly, in the actual frequency modulation process, if the frequency needs to be adjusted to the target frequency, the larger the slope K, the smaller the thickness of the frequency modulation layer 40 needs to be etched, and the higher the etching difficulty. In this case, the slope K of each fitted linear equation can be characterized as the sensitivity of the frequency modulation layer 40 at the corresponding thickness. The value of the slope K is equal to the value of the sensitivity.

[0100] That is, based on the slope K of the fitted linear equations above, the sensitivity of the frequency modulation layer in Comparative Example 1 is 0.8. In Example 1, the sensitivity of the frequency modulation layer 40 is 0.3536, which is 55.8% lower than that of Comparative Example 1. In Example 2, the sensitivity of the frequency modulation layer 40 is 0.16, which is 80% lower than that of Comparative Example 1. In Example 3, the sensitivity of the frequency modulation layer 40 is 0.0832, which is 89.6% lower than that of Comparative Example 1. This is because the thickness of the frequency modulation layer 40 corresponding to Examples 1-3 is between 0.005λ and 0.15λ, thus having a relatively low sensitivity, which facilitates precise control of the frequency of the fabricated surface acoustic wave filter 100 and ensures the performance of the surface acoustic wave filter 100.

[0101] On the other hand, based on the sensitivity values ​​corresponding to Examples 1-3, it can be seen that when the thickness of the silicon nitride film increases to more than 160 nm, the increase in the sensitivity of the frequency modulation layer 40 decreases. That is, in one embodiment, the thickness of the frequency modulation layer 40 is equal to 160 nm.

[0102] In another embodiment, the frequency modulation layer 40 is an aluminum oxide film layer. Figure 10 The graph shows the linear relationship between the sound velocity and thickness of the frequency-modulated layer in Comparative Example 2 for the surface acoustic wave filter. Figure 11 This is a fitting graph showing the linear relationship between the sound velocity and thickness of the frequency modulation layer 40 in Embodiment 4 of the surface acoustic wave filter 100 of this application.

[0103] For both Example 4 and Comparative Example 2, the surface acoustic wave filter includes a piezoelectric substrate, an interdigital transducer, a temperature compensation layer, and at least one frequency modulation layer. Along the thickness direction of the piezoelectric substrate, the interdigital transducer is disposed on the first surface of the piezoelectric substrate, the temperature compensation layer is located on the first surface and covers the interdigital transducer, and the frequency modulation layer is disposed on the side of the temperature compensation layer away from the piezoelectric substrate.

[0104] In this application, there is one embodiment, namely Embodiment 4, and one comparative example, namely Comparative Example 2. The structural schematic diagram corresponding to Comparative Example 2 is identical to that corresponding to Embodiment 4, and both are... Figure 4 As shown. The structural schematic diagram corresponding to Comparative Example 2 is the same as that corresponding to Example 4 in terms of center spacing λ, and the center spacing λ is equal to 10 μm.

[0105] In Comparative Example 2, the thickness of the frequency modulation layer is 54 nm. In Example 4, the thickness of the frequency modulation layer 40 is 110 nm. Apart from the above differences, all other parameters of Comparative Example 2 and Example 4 are exactly the same.

[0106] exist Figure 10 and Figure 11 In this process, the frequency modulation layer 40 is processed using an etching process to obtain the desired surface acoustic wave (SAW) filter frequency 100. Specifically, an ion beam frequency modulation process is used to etch the frequency modulation layer of corresponding thickness, and different thicknesses are etched. Then, the sound velocity corresponding to the SAW filter with different etched thicknesses is simulated to obtain the relationship between film thickness and sound velocity. Finally, a straight line is fitted to form a relationship between film thickness and sound velocity. The structure obtained through simulation is detailed in [link to simulation]. Figure 10 In the process, when the thickness of the frequency modulation layer 40 is set to 54 nm, by adjusting it and recording the corresponding sound velocity at each thickness, multiple sets of data are fitted to form a fitted linear equation: V = 0.792T + 3574. Similarly, in Figure 11 In the experiment, when the thickness of the frequency modulation layer 40 is set to 110 nm, by adjusting it and recording the corresponding sound velocity at each thickness, multiple sets of data are fitted to form a fitted linear equation: V = 0.1192T + 3621. Here, the vertical axis V represents the sound velocity in m / s, and the horizontal axis represents the corresponding thickness of the frequency modulation layer in nm.

[0107] The above-mentioned fitted linear equations are linear equations relating sound velocity and thickness. For any fitted linear equation, during the manufacturing process of the surface acoustic wave (SAW) filter, when its thickness is reduced to a certain value, the center frequency of the corresponding SAW filter decreases to the corresponding frequency. The larger the slope K of the linear relationship between sound velocity and thickness, the higher the frequency adjusted for the same thickness. Correspondingly, in the actual frequency modulation process, if the frequency needs to be adjusted to the target frequency, the larger the slope K, the smaller the thickness of the frequency modulation layer 40 needs to be etched, and the higher the etching difficulty. In this case, the slope K of each fitted linear equation can be characterized as the sensitivity of the frequency modulation layer 40 at the corresponding thickness. The value of the slope K is equal to the value of the sensitivity.

[0108] That is, based on the slope K of the fitted linear equations mentioned above, the sensitivity of the frequency modulation layer in Comparative Example 2 is 0.792. In Example 4, the sensitivity of the frequency modulation layer 40 is 0.1192. This is because the thickness of the frequency modulation layer 40 corresponding to Example 4 is between 0.005λ and 0.15λ, thus having a relatively low sensitivity, which facilitates precise control of the frequency of the fabricated surface acoustic wave filter 100 and ensures the performance of the surface acoustic wave filter 100.

[0109] Please refer to the above. Figure 12 The diagram shown is another structural schematic of the surface acoustic wave filter 100 provided in one embodiment of this application.

[0110] like Figure 12 As shown, the frequency modulation layer 40 is configured as a multilayer layer, and the multiple frequency modulation layers 40 include an adjacent first frequency modulation layer 41 and a second frequency modulation layer 42. The first frequency modulation layer 41 and the second frequency modulation layer 42 are sequentially stacked on the surface of the temperature compensation layer 30 away from the piezoelectric substrate 10. The first frequency modulation layer 41 and the second frequency modulation layer 42 are configured as different material films.

[0111] In this embodiment, the first frequency modulation layer 41 and the second frequency modulation layer 42 are made of different film materials. During the manufacturing process of the surface acoustic wave filter 100, the material properties of the first frequency modulation layer 41 and the second frequency modulation layer 42, such as the different sensitivities and different expansion coefficients of the two different frequency modulation layers, can be utilized to ensure the working performance of the surface acoustic wave filter 100.

[0112] In one embodiment, the first frequency modulation layer 41 is in contact with the temperature compensation layer 30, and the expansion coefficient of the first frequency modulation layer 41 is lower than that of the second frequency modulation layer 42. During the operation of the surface acoustic wave filter 100 of this application, when the temperature of the first surface 11 rises, the first surface 11 of the piezoelectric substrate 10 expands under the influence of temperature, and this expansion causes a drift in the center frequency of the piezoelectric substrate 10. The temperature of the first surface 11 is transferred to the temperature compensation layer 30, and the temperature compensation layer 30 also expands. The temperature compensation layer 30 can offset the expansion of the piezoelectric substrate 10 based on its own high expansion coefficient, thereby offsetting the drift in the center frequency of the piezoelectric substrate 10.

[0113] Since the first frequency modulation layer 41 is in contact with the temperature compensation layer 30, when the temperature of the first surface 11 is transferred to the first frequency modulation layer 41, the first frequency modulation layer 41 can produce a small deformation based on its low coefficient of thermal expansion, thereby avoiding the deformation of the first frequency modulation layer 41 from affecting the connection stability between the first frequency modulation layer 41 and the second frequency modulation layer 42. This facilitates the adjustment of the frequency of the surface acoustic wave filter 100 of this application through each frequency modulation layer 40, thereby precisely controlling the frequency of the fabricated surface acoustic wave filter 100 of this application and ensuring its performance.

[0114] In one embodiment, the first frequency modulation layer 41 is configured as a diamond film or an alumina film, and the second frequency modulation layer 42 is configured as a silicon nitride film or a silicon oxynitride film. Specifically, since the etching rate of the ion beam frequency modulation process on diamond and alumina materials is lower than that on silicon nitride and silicon oxynitride materials, during the manufacturing process of the surface acoustic wave filter 100 of this application, when etching the frequency modulation layer 40 using the ion beam frequency modulation process, the lower etching rate of the first frequency modulation layer 41 can prevent the ion beam frequency modulation process from etching down to the temperature compensation layer 30. Simultaneously, the higher etching rate of the second frequency modulation layer 42 can reduce the duration of the ion beam frequency modulation process. This allows for precise control of the frequency of the fabricated surface acoustic wave filter 100 and ensures its performance.

[0115] In one embodiment, along the thickness direction of the piezoelectric substrate 10, the second frequency modulation layer 42 is disposed on the outermost layer, that is, the second frequency modulation layer 42 is the top film layer, and no other film layers are disposed on the second frequency modulation layer 42. The sensitivity of the second frequency modulation layer 42 is less than or equal to 0.5; wherein: the sensitivity is used to characterize the slope of the fitted straight line corresponding to the linear relationship between the sound velocity and the thickness of the corresponding frequency modulation layer 40 at the corresponding thickness.

[0116] In the manufacturing process of the surface acoustic wave filter 100 of this application, the ion beam frequency modulation process first etches the top frequency modulation layer 40. A second frequency modulation layer 42 with a sensitivity of less than or equal to 0.5 is disposed on the top layer to control the etching thickness of the second frequency modulation layer 42 by the ion beam frequency modulation process, thereby reducing the problem of large frequency fluctuations in the top frequency modulation layer during etching, and thus controlling the frequency and performance of the final surface acoustic wave filter 100.

[0117] In one embodiment, the sensitivity of the second frequency modulation layer 42 is less than that of the first frequency modulation layer 41. Since the second frequency modulation layer 42 is farther away from the temperature compensation layer 30 than the first frequency modulation layer 41, reducing the sensitivity of the second frequency modulation layer 42 facilitates control of the etching thickness of the second frequency modulation layer 42 by the ion beam frequency modulation process, thereby precisely controlling the frequency of the fabricated surface acoustic wave filter 100 and ensuring its performance.

[0118] In one embodiment, the thickness of the second frequency modulation layer 42 is greater than the thickness of the first frequency modulation layer 41. Since the second frequency modulation layer 42 is farther away from the temperature compensation layer 30 than the first frequency modulation layer 41, increasing the thickness of the second frequency modulation layer 42 facilitates precise control of the frequency of the fabricated surface acoustic wave filter 100 and ensures the performance of the surface acoustic wave filter 100.

[0119] Please refer to the above. Figure 13 The diagram shown is another structural schematic of the surface acoustic wave filter 100 provided in one embodiment of this application.

[0120] like Figure 13 As shown, the surface acoustic wave filter 100 of this application also includes a substrate 50. Along the thickness direction of the piezoelectric substrate 10, the substrate 50, the piezoelectric substrate 10, and the interdigital transducer 20 are stacked sequentially. The substrate 50 is used to support the piezoelectric substrate 10, the interdigital transducer 20, the temperature compensation layer 30, and the frequency modulation layer 40, so as to improve the structural strength of the surface acoustic wave filter 100 of this application.

[0121] In one embodiment, the substrate 50 is made of any one of aluminum oxide, aluminum nitride, silicon, silicon carbide, and sapphire.

[0122] Please see Figure 14 The diagram shown is a cross-sectional view of a radio frequency front-end module 300 provided in one embodiment of this application.

[0123] like Figure 14 As shown, the RF front-end module 300 of this application includes a piezoelectric substrate 10 and an interdigital transducer 20. Along the thickness direction of the piezoelectric substrate 10, the interdigital transducer 20 is disposed on the first surface 11 of the piezoelectric substrate 10. The interdigital transducer 20 is used to cooperate with the piezoelectric substrate 10 to realize the filtering function of the RF front-end module 300 of this application.

[0124] Specifically, the interdigital transducer 20 includes at least two busbars 21 and a plurality of electrode fingers 22 located between the at least two busbars 21. For example, Figure 14 As shown, the interdigital transducer 20 has two busbars 21, which are arranged alternately. In one example, the two busbars 21 are arranged in parallel, or other corresponding arrangements can be made as needed. One of the two busbars 21 is used to receive external signals, and the other busbar 21 is used to output signals. Multiple electrode fingers 22 are located between the two busbars 21. Some of the electrode fingers 22 are connected to one busbar 21, and other electrode fingers 22 are connected to the other busbar 21.

[0125] For ease of description, the busbar 21 used for receiving external signals is defined as the first busbar 211, and the busbar 21 used for outputting signals is defined as the second busbar 212. The electrode finger 22 connected to the first busbar 211 is defined as the first electrode finger 221, and the electrode finger 22 connected to the second busbar 212 is defined as the second electrode finger 222.

[0126] Specifically, the first busbar 211 and the second busbar 212 are arranged alternately along the first direction 001 and extend along the second direction 002. The first electrode finger 221 and the second electrode finger 222 are arranged alternately along the second direction 002. Both the first electrode finger 221 and the second electrode finger 222 extend along the first direction 001. Specifically, as... Figure 15 As shown, along the second direction 002, there is a second electrode finger 222 between any two adjacent first electrode fingers 221, and there is a first electrode finger 221 between any two adjacent second electrode fingers 222.

[0127] Wherein, the second direction 002 intersects the first direction 001. For example, the second direction 002 and the first direction 001 can be perpendicular to each other, so that each electrode finger 22 has a 90° angle with its connected busbar. For example, the second direction 002 and the first direction 001 can also not be perpendicular, so that each electrode finger 22 has an angle greater than 90° or less than 90° with its connected busbar 21.

[0128] In this embodiment, when an external excitation signal is applied to the interdigital transducer 20, the interdigital transducer 20 converts the electrical signal into a surface acoustic wave. The surface acoustic wave propagates along the surface of the piezoelectric substrate 10 and is reflected by a reflective grating (not shown in the figure), and is then converted back into an electrical signal by the interdigital transducer 20 for output.

[0129] Surface acoustic waves (SAWs) are used to implement the frequency selection and signal processing functions of the RF front-end module 300. During SAW propagation, the primary propagation direction is the second direction 002. However, in practice, due to edge effects and acoustic diffraction, the propagation direction of SAWs formed on the piezoelectric substrate surface may also be other directions. In one embodiment, SAWs propagating in other directions are absorbed by a sound-absorbing material (not shown in the figure).

[0130] exist Figure 14 In the illustration shown, the radio frequency front-end module 300 of this application also includes a temperature compensation layer 30. Along the thickness direction of the piezoelectric substrate 10, the temperature compensation layer 30 is located on the first surface 11 and covers the interdigital transducer 20. The temperature compensation layer 30 is used to reduce the drift of the center frequency of the radio frequency front-end module 300 with temperature changes.

[0131] Specifically, during the operation of the RF front-end module 300 of this application, when the temperature of the piezoelectric substrate 10 surface increases, the piezoelectric substrate 10, based on its own material properties, will reduce the sound velocity at the first surface 11, thereby causing the center frequency of the RF front-end module 300 to decrease. The temperature compensation layer 30 can offset the effect of temperature change on the sound velocity at the first surface 11 based on its own material properties, thereby reducing or offsetting the drift of the center frequency of the RF front-end module 300 with temperature changes, thereby improving the operating performance of the RF front-end module 300 of this application.

[0132] The RF front-end module 300 of this application also includes at least one frequency modulation layer 40. Along the thickness direction of the piezoelectric substrate 10, at least one frequency modulation layer 40 is disposed on the side of the temperature compensation layer 30 away from the piezoelectric substrate 10. Due to manufacturing tolerances in the manufacturing process of the RF front-end module 300, the operating frequency of the RF front-end module 300 may not match the actual required operating frequency. During the manufacturing process of the RF front-end module 300, an ion beam frequency modulation process is typically used to adjust the thickness of the frequency modulation layer 40 to adjust the mass load of the interdigital transducer 20, thereby reducing the sound velocity of the surface acoustic wave and ensuring that the operating frequency of the RF front-end module 300 matches the actual required operating frequency.

[0133] That is, the setting of the frequency modulation layer 40 can facilitate the adjustment of the operating frequency of the RF front-end module 300, thereby accurately controlling the frequency of the prepared RF front-end module 300 and ensuring its performance.

[0134] In this embodiment of the application, at least one frequency modulation layer 40 is configured as a silicon nitride film layer 40a. Along the second direction 002, the center distance between two adjacent electrode fingers 22 connected to the same busbar 21 is λ. Along the thickness direction of the piezoelectric substrate 10, the thickness of the silicon nitride film layer 40a is greater than or equal to 0.005λ and less than or equal to 0.15λ.

[0135] Because the thickness of the silicon nitride film 40a is related to the velocity of sound. Specifically, when silicon nitride films 40a of different thicknesses are etched to the same thickness using an ion beam frequency modulation process, the RF front-end module 300 corresponding to the relatively thicker silicon nitride film 40a has a relatively smaller change in velocity of sound. Correspondingly, the velocity of sound of the silicon nitride film 40a of this thickness is less sensitive to changes in thickness.

[0136] In this embodiment, the thickness of the silicon nitride film 40a is greater than or equal to 0.005λ and less than or equal to 0.15λ, so as to limit the sensitivity of the sound velocity within the silicon nitride film 40a to thickness changes within the corresponding thickness range. This reduces the difficulty of the ion beam frequency modulation process during the manufacturing of the RF front-end module 300, facilitates precise control of the frequency of the prepared RF front-end module 300, and ensures the performance of the RF front-end module 300.

[0137] In one embodiment, along the thickness direction of the piezoelectric substrate 10, the silicon nitride film layer 40a is located on top of at least one frequency modulation layer 40. During the manufacturing process of the RF front-end module 300 of this application, an ion beam frequency modulation process is required to adjust the thickness of the frequency modulation layer 40. By placing the silicon nitride film layer 40a on top of all frequency modulation layers 40, the thickness of the silicon nitride film layer 40a can be adjusted using the ion beam frequency modulation process. This allows for precise control of the frequency of the fabricated surface acoustic wave filter 100 and ensures the performance of the surface acoustic wave filter 100.

[0138] In one embodiment, the thickness of the silicon nitride film 40a is greater than or equal to 100 nm and less than or equal to 200 nm. On the one hand, this limits the sensitivity range of the silicon nitride film 40a, avoiding the situation where the silicon nitride film 40a is too thin and thus the sensitivity is too high, which facilitates the manufacturing of the RF front-end module 300 of this application. On the other hand, it also avoids the phenomenon that the ion beam frequency modulation process takes too long due to the silicon nitride film 40a being too thick, thereby accurately controlling the frequency of the fabricated surface acoustic wave filter 100 and ensuring its performance.

[0139] In one embodiment, the piezoelectric substrate 10 includes at least one of a lithium tantalate substrate and a lithium niobate substrate.

[0140] In one embodiment, the temperature compensation layer 30 is a silicon oxide film layer.

[0141] In one embodiment, the thickness of the temperature compensation layer 30 is greater than or equal to 600 nm and less than or equal to 2000 nm. On the one hand, this ensures that the temperature compensation layer 30 compensates for the offset caused by temperature changes in the center frequency of the interdigital transducer 20, thus guaranteeing the compensation effect of the temperature compensation layer 30. On the other hand, it avoids the temperature compensation layer 30 being too thick, which would affect the electromechanical coupling coefficient, thereby ensuring the operating performance of the RF front-end module 300 of this application.

[0142] It should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0143] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an 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. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0144] It should be understood that the application of this application is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Those skilled in the art will understand that implementing all or part of the processes of the above embodiments, and making equivalent changes according to the claims of this utility model, still falls within the scope of this utility model.

Claims

1. A surface acoustic wave filter, characterized by, The device includes a piezoelectric substrate, an interdigital transducer, a temperature compensation layer, and at least one frequency modulation layer. Along the thickness direction of the piezoelectric substrate, the interdigital transducer is disposed on a first surface of the piezoelectric substrate, the temperature compensation layer is located on the first surface and covers the interdigital transducer, and the frequency modulation layer is disposed on the side of the temperature compensation layer away from the piezoelectric substrate. The interdigital transducer includes at least two busbars and a plurality of electrode fingers located between the at least two busbars. The busbars are spaced apart along a first direction and extend along a second direction. One end of each electrode finger is connected to one of the busbars, and the other end is spaced apart from another of the busbars. Each electrode finger connected to a different busbar is alternately arranged along the second direction, which intersects the first direction. Along the second direction, the center-to-center distance between two adjacent electrode fingers connected to the same busbar is λ, and along the thickness direction of the piezoelectric substrate, the thickness of the at least one frequency modulation layer is greater than or equal to 0.005λ and less than or equal to 0.15λ.

2. The surface acoustic wave filter according to claim 1, characterized by, Along the second direction, the center-to-center distance λ between two adjacent electrode fingers connected to the same busbar is greater than or equal to 0.4 μm and less than or equal to 10 μm.

3. The surface acoustic wave filter according to claim 1, characterized by, The thickness of the frequency modulation layer is greater than or equal to 0.01λ and less than or equal to 0.04λ.

4. The surface acoustic wave filter according to claim 1, characterized by, The frequency modulation layer includes one of a silicon nitride film, a silicon oxynitride film, an aluminum oxide film, and a diamond film.

5. The surface acoustic wave filter according to any one of claims 1 to 4, characterized by, The at least one frequency modulation layer is configured as a silicon nitride film layer, and the thickness of the at least one frequency modulation layer is greater than or equal to 0.01λ and less than or equal to 0.1λ.

6. The surface acoustic wave filter according to any one of claims 1 to 4, characterized by, The at least one frequency modulation layer is configured as a silicon oxynitride film layer, and the thickness of the at least one frequency modulation layer is greater than or equal to 0.01λ and less than or equal to 0.15λ.

7. The surface acoustic wave filter according to any one of claims 1 to 4, characterized by, The at least one frequency modulation layer is configured as an alumina film layer or a diamond film layer, and the thickness of the at least one frequency modulation layer is greater than or equal to 0.005λ and less than or equal to 0.1λ.

8. The surface acoustic wave filter according to any one of claims 1 to 4, characterized by, The temperature compensation layer covers the electrode finger, and the thickness of the temperature compensation layer in different regions is greater than the thickness of the electrode finger, and the thickness of the frequency modulation layer is greater than or equal to 100 nm and less than or equal to 200 nm.

9. The surface acoustic wave filter according to any one of claims 1 to 4, characterized by, The number of frequency modulation layers is one, and the sensitivity of the frequency modulation layer is less than or equal to 0.5; wherein: Sensitivity is used to characterize the slope of the fitted straight line corresponding to the linear relationship between the sound velocity and thickness of the corresponding frequency-modulated layer at a given thickness.

10. The surface acoustic wave filter according to any one of claims 1 to 4, characterized by, The number of frequency modulation layers is multiple, and the multiple frequency modulation layers include an adjacent first frequency modulation layer and a second frequency modulation layer. The first frequency modulation layer and the second frequency modulation layer are stacked sequentially on the surface of the temperature compensation layer away from the piezoelectric substrate. The first frequency modulation layer and the second frequency modulation layer are made of different material films.

11. The surface acoustic wave filter according to claim 10, wherein The first frequency modulation layer is in contact with the temperature compensation layer, and the expansion coefficient of the first frequency modulation layer is lower than that of the second frequency modulation layer.

12. The surface acoustic wave filter according to claim 10, wherein, The first frequency modulation layer is configured as a diamond film or an alumina film, and the second frequency modulation layer is configured as a silicon nitride film or a silicon oxynitride film.

13. The surface acoustic wave filter according to claim 10, wherein, Along the thickness direction of the piezoelectric substrate, the second frequency-modulated layer is located on top of the at least one frequency-modulated layer, and the sensitivity of the second frequency-modulated layer is less than or equal to 0.5; wherein: Sensitivity is used to characterize the slope of the fitted straight line corresponding to the linear relationship between the sound velocity and thickness of the corresponding frequency-modulated layer at a given thickness.

14. The surface acoustic wave filter according to claim 13, characterized in that, The sensitivity of the second frequency modulation layer is less than that of the first frequency modulation layer.

15. The surface acoustic wave filter of claim 10, wherein, The thickness of the second frequency modulation layer is greater than the thickness of the first frequency modulation layer.

16. The surface acoustic wave filter according to any one of claims 1-4, characterized in that, The surface acoustic wave filter further includes a substrate, and the substrate, the piezoelectric substrate, and the interdigital transducer are stacked sequentially along the thickness direction of the piezoelectric substrate.

17. A radio frequency front end module, comprising: Includes the surface acoustic wave filter as described in any one of claims 1-16.

18. A radio frequency front end module, comprising: The device includes a piezoelectric substrate, an interdigital transducer, a temperature compensation layer, and at least one frequency modulation layer. Along the thickness direction of the piezoelectric substrate, the interdigital transducer is disposed on a first surface of the piezoelectric substrate, the temperature compensation layer is located on the first surface and covers the interdigital transducer, and the frequency modulation layer is disposed on the side of the temperature compensation layer away from the piezoelectric substrate. The interdigital transducer includes at least two busbars and a plurality of electrode fingers located between the at least two busbars. The busbars are spaced apart along a first direction and extend along a second direction. One end of each electrode finger is connected to one of the busbars, and the other end is spaced apart from another of the busbars. Each electrode finger connected to a different busbar is alternately arranged along the second direction, which intersects the first direction. The thickness of the temperature compensation layer is greater than that of the electrode finger in different regions, and the frequency modulation layer includes at least a first frequency modulation layer and a second frequency modulation layer arranged adjacent to each other, wherein the first frequency modulation layer and the second frequency modulation layer are made of different material films.

19. The radio frequency front end module of claim 18, wherein, Along the second direction, the center distance between two adjacent electrode fingers connected to the same busbar is λ. Along the thickness direction of the piezoelectric substrate, the at least one frequency modulation layer is a silicon nitride film layer with a thickness greater than or equal to 0.005λ and less than or equal to 0.15λ.

20. The radio frequency front-end module according to claim 19, characterized in that, Along the thickness direction of the piezoelectric substrate, the silicon nitride film is located on top of the at least one frequency modulation layer.

21. The radio frequency front end module of claim 19, wherein, The thickness of the silicon nitride film is greater than or equal to 100 nm and less than or equal to 200 nm.

22. An electronic device, comprising: Includes the radio frequency front-end module as described in any one of claims 17-21.

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