CN116938190A

CN116938190A - Surface acoustic wave filter, surface acoustic wave filter device, and electronic apparatus

Info

Publication number: CN116938190A
Application number: CN202210327182.8A
Authority: CN
Inventors: 耿永红; 金美佳; 陶翔; 蒋欣; 古健; 周俭军; 钱云贵; 刘伟
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2022-03-30
Filing date: 2022-03-30
Publication date: 2023-10-24
Also published as: WO2023185554A1

Abstract

The embodiment of the application provides a surface acoustic wave filter, a device and electronic equipment, which relate to the technical field of semiconductors and are used for improving the performance of the surface acoustic wave filter. A surface acoustic wave filter comprising: a piezoelectric layer (21) and an interdigital transducer (22) which are stacked; the interdigital transducer (22) comprises electrode fingers, wherein the electrode fingers comprise an electrode layer (30) and a wrapping layer (40), and the wrapping layer (40) wraps the periphery of the electrode layer (30) and covers the side surface of the electrode layer (30); the wrapping layer (40) is positioned on the surface of the piezoelectric layer (30); wherein the surface roughness of the wrapping layer (40) is smaller than the surface roughness of the bottom surface of the electrode layer (30), and the bottom surface is in contact with the piezoelectric layer (21). The surface acoustic wave filter can be applied to the radio frequency field.

Description

Surface acoustic wave filter, surface acoustic wave filter device, and electronic apparatus

Technical Field

The present application relates to the field of semiconductor technologies, and in particular, to a surface acoustic wave filter, a device, and an electronic apparatus.

Background

With the development of mobile communication level and the continuous increase of communication speed, more and more frequency bands are applied to mobile communication systems. Among them, the surface acoustic wave filter is an important component in a mobile communication system.

The existing surface acoustic wave filter is a bottleneck for improving communication quality, and with the landing of more communication modes and communication scenes, the performance of the surface acoustic wave filter faces greater challenges, and the improvement of the performance of the surface acoustic wave filter is a research focus and difficulty of the existing surface acoustic wave filter.

Disclosure of Invention

The embodiment of the application provides a surface acoustic wave filter, a device and electronic equipment, which can improve the performance of the surface acoustic wave filter.

In order to achieve the above purpose, the application adopts the following technical scheme:

in a first aspect of an embodiment of the present application, there is provided a surface acoustic wave filter including: a piezoelectric layer and an interdigital transducer disposed on the piezoelectric layer; the interdigital transducer comprises electrode fingers, wherein the electrode fingers comprise electrode layers and wrapping layers, and the wrapping layers wrap the periphery of the electrode layers and cover the side surfaces of the electrode layers; the wrapping layer is in contact with the piezoelectric layer; the surface roughness of the wrapping layer is smaller than that of the bottom surface of the electrode layer, and the bottom surface of the electrode layer is the surface of the electrode layer, which is in contact with the piezoelectric layer.

According to the surface acoustic wave filter provided by the embodiment of the application, the electrode fingers of the interdigital transducer in the surface acoustic wave resonator further comprise a wrapping layer on the basis of comprising the electrode layer. The wrapping layer covers the side face of the electrode layer and is in contact with the piezoelectric layer. In this way, the corners of the electrode fingers in contact with the piezoelectric layer are changed from the electrode layer to the wrapping layer. When the surface roughness of the wrapping layer is smaller than that of the bottom surface of the electrode layer, the atomic radius of the material in the wrapping layer is smaller than that of the material in the electrode layer, the dislocation gap between atoms in the wrapping layer is small, and the defect density of the wrapping layer is small. Therefore, under the action of mechanical stress and thermal stress, the probability of defects such as holes or gaps formed by diffusion and migration of atoms in the wrapping layer is reduced, the interface binding force of the interdigital transducer and the piezoelectric layer can be improved, the reliability and the power tolerance of the surface acoustic wave resonator are improved, and the performance of the surface acoustic wave resonator is ensured. Moreover, the influence on the power resistance of the surface acoustic wave resonator is not large regardless of the change in the material of the electrode layer.

In one possible implementation, the wrapping layer also covers the top surface of the electrode layer, and the material of the wrapping layer is a conductive material. Since the surface roughness of the encapsulation layer 40 is smaller than that of the top surface of the electrode layer 30, the diffusion migration capacity of the metal atoms in the encapsulation layer 40 is smaller than that of the metal atoms in the electrode layer 30, and the encapsulation layer 40 can block the diffusion of the metal atoms in the electrode layer 30 to the temperature compensation layer 24. In this way, the power tolerance of the surface acoustic wave resonator 20 can be further improved, the insertion loss of the surface acoustic wave resonator 20 can be reduced, and the quality factor of the surface acoustic wave resonator 20 can be improved.

In one possible implementation, the electrode layer comprises an electrode body layer. This is a structurally simple implementation.

In one possible implementation, the density of the material of the wrapping layer is less than the density of the material of the electrode body layer. The density of the material of the wrapping layer is limited to be smaller than that of the material of the electrode body layer, so that the formed wrapping layer is lighter in weight, the influence of the wrapping layer on the weight of the first electrode finger can be reduced, the sensitivity of the frequency of the surface acoustic wave resonator to the change of the film thickness of the wrapping layer is reduced, the requirement on the preparation process of the first electrode finger is reduced, and the frequency consistency of the surface acoustic wave resonator is improved.

In one possible implementation, the thickness of the encapsulation layer is 5nm-50nm. The film thickness of the wrapping layer is mainly influenced by a film plating process, and the sensitivity of the frequency of the surface acoustic wave resonator to the film thickness change of the wrapping layer can be reduced by limiting the film thickness of the wrapping layer to 5-50 nm, so that the requirement on the preparation process of the first electrode finger is reduced.

In one possible implementation, the material of the wrapping layer includes at least one of Al, alCu, alTi, alMg, alNi or AlW.

In one possible implementation, the electrode layer further comprises a first conductive adhesion layer disposed on a side of the electrode body layer adjacent to the piezoelectric layer. By arranging the first conductive adhesive layer on one side of the electrode body layer close to the piezoelectric layer, on one hand, the strength of the electrode layer can be enhanced, and the mechanical stress of the interdigital transducer can be improved. On the other hand, a first conductive adhesive layer is arranged between the electrode body layer and the piezoelectric layer, and can change the binding force between the interdigital transducer and the piezoelectric layer, prevent metal atoms in the electrode body layer from diffusing into the piezoelectric layer and improve the power tolerance of the surface acoustic wave resonator.

In one possible implementation, the electrode layer further comprises a second conductive adhesion layer disposed on a side of the electrode body layer remote from the piezoelectric layer. Through setting up the second conductive adhesion layer in electrode body layer one side of keeping away from the piezoelectricity layer, be provided with one deck second conductive adhesion layer between electrode body layer and the parcel layer, the cohesion between electrode body layer and the parcel layer can be changed to the second conductive adhesion layer, hinders the diffusion of metal atom in the electrode body layer to the temperature compensation layer, improves the power tolerance of surface acoustic wave resonator.

In one possible implementation, the resistivity of the material of the encapsulation layer is less than the resistivity of the material of the second conductive adhesion layer. By selecting the material of the wrapping layer as a material with low resistivity, the influence of the wrapping layer on the guiding electrical property of the first electrode can be reduced as much as possible, and the piezoelectric conversion rate is improved.

In one possible implementation, the resistivity of the material of the encapsulation layer is less than 0.42 x 10 ^-6 Ωm。

In one possible implementation, the electrode finger further comprises a third conductive adhesive layer, the third conductive adhesive layer being located on a surface layer of the electrode finger remote from the piezoelectric layer. By setting the surface layer of the first electrode finger as the third conductive adhesion layer, the binding force between the first electrode finger and the subsequent laminated film layer can be improved, the diffusion of metal atoms in the electrode body layer into the subsequent laminated film layer is prevented, and the power tolerance of the surface acoustic wave resonator is improved.

In one possible implementation, the saw filter further includes a water-oxygen barrier layer covering the surface of the interdigital transducer. The water-oxygen barrier layer covers the top surface and the side surface of the interdigital transducer so as to prevent water vapor and oxygen from entering the interdigital transducer and avoid the damage of the water vapor and the oxygen to the interdigital transducer.

In one possible implementation, the saw filter further includes a temperature compensation layer disposed on a side of the interdigital transducer remote from the piezoelectric layer. By coating the interdigital transducer with a temperature compensation layer, the frequency Temperature Coefficient (TCF) of the surface acoustic wave resonator is reduced to 0 to-25 ppm/DEG C, which is significantly improved compared with the frequency temperature coefficient (usually about-45 to-60 ppm/DEG C) of a surface acoustic wave resonator without the temperature compensation layer.

In one possible implementation, the saw filter further includes a frequency trimming layer disposed on a side of the interdigital transducer remote from the piezoelectric layer, the frequency trimming layer being configured to trim a frequency of the saw filter. The frequency of the surface acoustic wave resonator can be adjusted to a required value by adjusting the thickness of the trimming frequency layer, so that the power accuracy of the surface acoustic wave filter is improved.

In a second aspect of embodiments of the present application, there is provided an apparatus comprising a power amplifier and a surface acoustic wave filter, the power amplifier being coupled to the surface acoustic wave filter, the surface acoustic wave filter being as in any one of the first aspects.

The device provided in the second aspect of the embodiment of the present application includes the surface acoustic wave filter in the first aspect, and the beneficial effects thereof are the same as those of the surface acoustic wave filter, and are not repeated here.

In a third aspect of the embodiment of the present application, there is provided an electronic apparatus including a surface acoustic wave filter and a circuit board, the surface acoustic wave filter being disposed on the circuit board; wherein the surface acoustic wave filter is the surface acoustic wave filter according to any one of the first aspects.

The electronic device provided in the third aspect of the embodiment of the present application includes the surface acoustic wave filter in the first aspect, and the beneficial effects thereof are the same as those of the surface acoustic wave filter, and are not repeated here.

Drawings

Fig. 1 is a schematic diagram of a frame of an electronic device according to an embodiment of the present application;

fig. 2 is a schematic structural diagram of a surface acoustic wave filter according to an embodiment of the present application;

fig. 3A is a schematic structural diagram of a surface acoustic wave resonator according to an embodiment of the present application;

FIG. 3B is a focused ion beam interface topography of a SAW resonator provided by an embodiment of the present application;

fig. 4A is a schematic top view of a surface acoustic wave resonator according to an embodiment of the present application;

fig. 4B is a cross-sectional view of a surface acoustic wave resonator according to an embodiment of the present application;

fig. 4C is a cross-sectional view of a surface acoustic wave resonator according to an embodiment of the present application;

FIG. 4D is a cross-sectional view taken along the line A1-A2 in FIG. 4A, in accordance with an embodiment of the present application;

FIG. 4E is a cross-sectional view taken along line A1-A2 of FIG. 4A in accordance with an embodiment of the present application;

fig. 5 is a cross-sectional view of another surface acoustic wave resonator according to an embodiment of the present application;

FIGS. 6A-6B are cross-sectional views of yet another SAW resonator provided in an embodiment of the present application;

fig. 7A to fig. 7K are schematic views illustrating a manufacturing process of an interdigital transducer according to an embodiment of the present application;

FIGS. 8A-8C are cross-sectional views of yet another SAW resonator provided in an embodiment of the present application;

fig. 9A-9B are cross-sectional views of yet another surface acoustic wave resonator according to an embodiment of the present application;

fig. 10 is a cross-sectional view of still another surface acoustic wave resonator according to an embodiment of the present application;

FIGS. 11A-11D are cross-sectional views of yet another SAW resonator provided in an embodiment of the present application;

FIGS. 12A-12D are cross-sectional views of yet another SAW resonator provided in an embodiment of the present application;

fig. 13A to 13E are sectional views of yet another surface acoustic wave resonator according to an embodiment of the present application.

Detailed Description

The following description of the technical solutions according to the embodiments of the present application will be given with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, but not all embodiments.

In the following, in the embodiments of the present application, the terms "first", "second", etc. are used for descriptive convenience only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first", "a second", etc. may explicitly or implicitly include one or more such feature. In the description of the present application, unless otherwise indicated, the meaning of "a plurality" is two or more.

In the embodiments of the present application, "upper", "lower", "left" and "right" are not limited to the orientation in which the components in the drawings are schematically disposed, but it should be understood that these directional terms may be relative concepts, which are used for descriptive and clarity with respect thereto, which may be varied accordingly with respect to the orientation in which the components in the drawings are disposed.

In embodiments of the present application, the term "comprising" is to be construed as an open, inclusive meaning, i.e. "including, but not limited to", throughout the specification and claims, unless the context requires otherwise. In the description of the present specification, the terms "one embodiment," "some embodiments," "example embodiments," "exemplary," or "some examples," etc., are intended to indicate that a particular feature, structure, material, or characteristic associated with the embodiment or example is included in at least one embodiment or example of the present disclosure. The schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.

In describing some embodiments, the expression "coupled" and its derivatives may be used. For example, the term "coupled" may be used in describing some embodiments to indicate that two or more elements are in direct physical or electrical contact. However, the term "coupled" may also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other. The embodiments disclosed herein are not necessarily limited to the disclosure herein.

In the embodiment of the present application, "and/or" is merely an association relationship describing an association object, and indicates that three relationships may exist, for example, a and/or B may indicate: a exists alone, A and B exist together, and B exists alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship.

Exemplary embodiments are described in the examples of the application with reference to cross-sectional and/or plan views and/or equivalent circuit diagrams as idealized exemplary figures. In the drawings, the thickness of layers and regions are exaggerated for clarity. Thus, variations from the shape of the drawings due to, for example, manufacturing techniques and/or tolerances, are to be expected. Thus, the exemplary embodiments should not be construed as limited to the shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an etched region shown as a rectangle will typically have curved features. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of example embodiments.

The embodiment of the application provides electronic equipment. The electronic device is, for example, a consumer electronic product, a household electronic product, a vehicle-mounted electronic product, a financial terminal product, or a communication electronic product. Among the consumer electronics products are, for example, mobile phones, tablet computers (pad), notebook computers, electronic readers, personal computers (personal computer, PC), personal digital assistants (personal digital assistant, PDA), desktop displays, smart wearable products (e.g., smart watches, smart bracelets), virtual Reality (VR) terminals, augmented reality (augmented reality, AR) terminals, drones, etc. Household electronic products such as intelligent door locks, televisions, remote controllers, refrigerators, small household appliances (e.g., soymilk makers, sweeping robots) and the like. The vehicle-mounted electronic products are, for example, vehicle-mounted navigator, vehicle-mounted high-density digital video disc (digital video disc, DVD) and the like. Financial end products such as automated teller machine (automated teller machine, ATM) machines, self-service terminals, and the like.

For convenience of explanation, an electronic device is taken as an example of a mobile phone. As shown in fig. 1, the electronic device 1 mainly includes a cover plate 11, a display screen 12, a middle frame 13, and a rear case 14. The rear shell 14 and the display screen 12 are respectively positioned at two sides of the middle frame 13, the middle frame 13 and the display screen 12 are arranged in the rear shell 14, the cover plate 11 is arranged at one side of the display screen 12 far away from the middle frame 13, and the display surface of the display screen 12 faces the cover plate 11.

The display 12 may be a liquid crystal display (liquid crystal display, LCD), in which case the liquid crystal display includes a liquid crystal display panel and a backlight module, the liquid crystal display panel is disposed between the cover plate 11 and the backlight module, and the backlight module is used to provide a light source for the liquid crystal display panel. The display 12 may also be an organic light emitting diode (organic light emitting diode, OLED) display. The OLED display screen is a self-luminous display screen, so that a backlight module is not required to be arranged.

The middle frame 13 includes a supporting plate 131 and a frame 132 surrounding the supporting plate 131. The electronic device 1 may further include electronic components such as a printed circuit board (printed circuit boards, PCB), a battery, and a camera, and the electronic components such as the printed circuit board, the battery, and the camera may be disposed on the carrier 131.

The electronic device 1 may further include a System On Chip (SOC), a radio frequency chip, etc. disposed on a PCB, and the PCB is configured to carry and be electrically connected to the system on chip, the radio frequency chip, etc. The radio frequency chip may include, among other things, a surface acoustic wave (surface acoustic wave, SAW) filter, a processor, etc. The processor is used for processing various signals, and the SAW filter is an important part of radio frequency signal processing and is used for blocking signals with other frequencies by signals with specific frequencies.

The embodiment of the application provides a surface acoustic wave filter, which can be applied to the electronic device 1, for example, applied to a radio frequency chip in the electronic device 1, and the surface acoustic wave filter provided in the embodiment of the application can be, for example, a low-pass surface acoustic wave filter, a high-pass surface acoustic wave filter, a band-stop surface acoustic wave filter, an active surface acoustic wave filter, or the like.

Of course, the surface acoustic wave filter provided by the embodiment of the present application is not limited to being integrated in the electronic apparatus 1. The saw filter may be a single component, or the saw filter may be integrated with a power amplifier or the like into a single device (e.g., a radio frequency device, a radio frequency module, a saw filter module, etc.).

The embodiment of the application also provides a device, which comprises a surface acoustic wave filter and a power amplifier, wherein the surface acoustic wave filter is coupled with the power amplifier for signal processing and transmission.

Next, a surface acoustic wave filter provided by an embodiment of the present application will be schematically described.

As shown in fig. 2, the surface acoustic wave filter 2 provided by the embodiment of the present application includes a plurality of cascaded surface acoustic wave resonators 20, where the plurality of surface acoustic wave resonators 20 may have different resonant frequencies and may be cascaded together in a serial-parallel manner, and the performance of the surface acoustic wave filter 2 is closely related to the performance of the surface acoustic wave resonator 20. Referring to fig. 2, fig. 2 also illustrates the signal input Vi, the signal output Vo, and the ground GND of the surface acoustic wave filter 2 when a plurality of surface acoustic wave resonators 20 are cascaded together in series-parallel.

The surface acoustic wave resonator 20 has small volume and good performance, and is used for various radio frequency terminal devices. The surface acoustic wave filter 2 formed by serial-parallel connection of the surface acoustic wave resonators 20 with different resonant frequencies has the advantages of small passband insertion loss, high out-of-band abruptness, strong power tolerance and the like.

As shown in fig. 3A, the surface acoustic wave resonator 20 mainly includes a piezoelectric layer (or referred to as a piezoelectric material layer) 21 and an interdigital transducer (interdigital transducer, IDT) 22. An interdigital transducer 22 is disposed on the piezoelectric layer 21.

With the large-scale commercialization of the fifth generation mobile communication technology (5th generation mobile communication technology,5G) network, there is a large amount of data transmission at high speed for the 5G terminal, which requires the saw resonator 20 to have higher reliability and power tolerance performance.

However, the interdigital transducer 22 produces mechanical vibrations on the surface of the piezoelectric layer 21 as the surface acoustic wave propagates during operation of the surface acoustic wave resonator 20. As shown in fig. 3B, a Focused Ion Beam (FIB) interface topography of the saw resonator 20 is provided, where mechanical vibration is greatest at the interface of the interdigital transducer 22 and the piezoelectric layer 21, most likely resulting in failure of the saw resonator 20. As the input power increases, the vibration amplitude of the interdigital transducer 22 increases, and the mechanical stress at the interface of the interdigital transducer 22 and the piezoelectric layer 21 increases. Meanwhile, as the temperature of the surface acoustic wave resonator 20 increases along with the increase of power in the piezoelectric and inverse piezoelectric conversion processes, the interface between the interdigital transducer 22 and the piezoelectric material has the mechanical stress and the thermal stress, so that the diffusion and migration of metal atoms in the interdigital transducer 22 are accelerated, the interface between the interdigital transducer 22 and the piezoelectric layer 21 is easier to generate a cavity, the reliability of the surface acoustic wave resonator 20 is reduced, and the performance of the surface acoustic wave resonator 20 is accelerated and deteriorated.

As shown in fig. 3B, from the analysis of the failure sample, the atomic diffusion migration of the interdigital transducer 22 occurs mostly at the side elevation positions of the interdigital transducer 22 and the piezoelectric layer 21. Therefore, it is necessary to increase the bonding force between the interdigital transducer 22 and the piezoelectric layer 21 and to increase the interface strength to improve the power withstand characteristics of the surface acoustic wave filter 2.

Based on this, the embodiment of the present application provides a surface acoustic wave resonator 20 for enhancing the bonding force at the interface between the interdigital transducer 22 and the piezoelectric layer 21, so as to improve the performance of the surface acoustic wave resonator 20. The surface acoustic wave resonator 20 can be applied to the surface acoustic wave filter 2 described above.

Next, the structure of the surface acoustic wave resonator 20 provided in the embodiment of the present application will be schematically described by way of several examples.

Example one

The present example provides a surface acoustic wave resonator 20, as shown in fig. 4A, the surface acoustic wave resonator 20 including a piezoelectric layer 21 and an interdigital transducer 22, the interdigital transducer 22 being disposed on one side of the piezoelectric layer 21.

The piezoelectric layer 21 is used for exciting surface acoustic waves under the action of the interdigital transducer 22, and the material of the piezoelectric layer 21 can comprise LiNbO ₃ (lithium niobate), liTaO ₃ (lithium tantalate), quartz (quaterz), etc.

The material of the piezoelectric layer 21 is exemplified by 128 YX-LiNbO ₃ . Alternatively, the piezoelectric layer 21 is made of 42 YX-LiTaO ₃ . In which the resonance characteristics of the surface acoustic wave resonator 20 can be improved by setting the euler angle of the material of the piezoelectric layer 21.

An interdigital transducer 22 is disposed on the piezoelectric layer 21, for example, the interdigital transducer 22 is disposed on a surface of the piezoelectric layer 21.

As shown in fig. 4A, the interdigital transducer 22 includes first and second bus bars (bus bars) 221a and 222a disposed opposite to each other, a plurality of first electrode fingers (IDT electrodes) 221b, and a plurality of second electrode fingers 222b. The extending directions of the first bus bar 221a and the second bus bar 222a are parallel to the first direction X, the extending directions of the first electrode fingers 221b are parallel to the second direction Y, the first electrode fingers 221b protrude from the first bus bar 221a to the second bus bar 222a, the plurality of first electrode fingers 221b are sequentially arranged along the extending direction (first direction X) of the first bus bar 221a, and the plurality of first electrode fingers 221b are coupled with the first bus bar 221 a. The extending direction of the second electrode finger 222b is parallel to the second direction Y, the second electrode finger 222b protrudes from the second bus bar 222a toward the first bus bar 221a, the plurality of second electrode fingers 222b are sequentially arranged along the extending direction (first direction X) of the second bus bar 222a, and the plurality of second electrode fingers 222b are coupled with the second bus bar 222 a.

Wherein the plurality of first electrode fingers 221b and the plurality of second electrode fingers 222b are alternately arranged in order along the extending direction of the first bus bar 221a and the second bus bar 222a between the first bus bar 221a and the second bus bar 222a, and the first electrode fingers 221b and the second electrode fingers 222b are not in contact.

The above-described "a plurality of first electrode fingers 221b and a plurality of second electrode fingers 222b are alternately arranged in order along the extending direction of the first bus bar 221a and the second bus bar 222a between the first bus bar 221a and the second bus bar 222 a" means that: between the first bus bar 221a and the second bus bar 222a, one first electrode finger 221b, one second electrode finger 222b, and the like are disposed in this order.

The number of the first electrode fingers 221b and the number of the second electrode fingers 222b in the interdigital transducer 22 are not limited, and may be set as needed. The plurality of first electrode fingers 221b may be equally spaced apart or non-equally spaced apart. Similarly, the plurality of second electrode fingers 222b may be arranged at equal intervals or non-equal intervals. Taking the first electrode fingers 221b as an example, the plurality of first electrode fingers 221b are arranged in a non-equidistant manner, which means that the spacing between at least one pair of adjacent first electrode fingers 221b is different from the spacing between another pair of adjacent first electrode fingers 221 b.

In addition, the plurality of first electrode fingers 221b and the plurality of second electrode fingers 222b are alternately arranged in sequence, and the pitches between the adjacent first electrode fingers 221b and second electrode fingers 222b may be the same; the pitches between the pairs of adjacent first electrode fingers 221b and second electrode fingers 222b may not be exactly the same, that is, the pitch between at least one pair of adjacent first electrode fingers 221b and second electrode fingers 222b is different from the pitch between the other pair of adjacent first electrode fingers 221b and second electrode fingers 222b.

The widths of the first electrode finger 221b and the second electrode finger 222b are not limited, and may be appropriately set as needed.

It will be appreciated that the pitch (pitch) between the first electrode finger 221b and the second electrode finger 222b, and the finger widths of the first electrode finger 221b and the second electrode finger 222b are mainly affected by the photolithography and development processes, and that the passband frequency of the saw resonator 20 can be changed by adjusting the pitch (pitch) between the first electrode finger 221b and the second electrode finger 222b, and the finger widths of the first electrode finger 221b and the second electrode finger 222b.

The first bus bar 221a, the first electrode finger 221b, the second bus bar 222a, and the second electrode finger 222b may be fabricated at the same time. First bus bar 221a and first electrode finger 221b may be formed, and second bus bar 222a and second electrode finger 222b may be formed. Alternatively, the second bus bar 222a and the second electrode finger 222b are fabricated, and then the first bus bar 221a and the first electrode finger 221b are fabricated.

The film layer structures of the first bus bar 221a, the first electrode finger 221b, the second bus bar 222a, and the second electrode finger 222b may be the same regardless of whether the first bus bar 221a, the first electrode finger 221b, the second bus bar 222a, and the second electrode finger 222b are simultaneously fabricated.

Next, the structure of the first electrode finger 221b will be schematically described.

As shown in fig. 4B (a cross-sectional view of fig. 4A taken along A1-A2), the first electrode finger 221B includes an electrode layer 30 and a wrapping layer 40. The electrode layer 30 and the wrapping layer 40 are disposed over the piezoelectric layer 21, for example, the electrode layer 30 and the wrapping layer 40 are disposed on the surface of the piezoelectric layer 21.

Regarding the structure of the electrode layer 30, in some embodiments, as shown in fig. 4B, the electrode layer 30 includes only one electrode body layer 31.

The material of the electrode body layer 31 may include, for example, but not limited to, at least one of Al (aluminum), cu (copper), pt (platinum), mo (molybdenum), ta (tantalum), au (gold), or Ag (silver) or the like.

In some embodiments, the material of the electrode body layer 31 includes Al and the surface acoustic wave resonator 20 is a conventional surface acoustic wave (surface acoustic wave, SAW) resonator.

In other embodiments, the material of the electrode body layer 31 includes Cu, pt, mo, ta, au, or a simple metal such as Ag. The saw resonator 20 further includes a temperature compensation layer on this basis. Then, the surface acoustic wave resonator 20 may be a temperature compensated surface acoustic wave (temperature compensated surface acoustic wave, TC-SAW) resonator. The temperature compensation layer is described in detail below, and the electrode layer 30 is described here.

In still other embodiments, the material of the electrode body layer 31 includes a metal alloy such as AlCu (aluminum copper) alloy, alTi (aluminum titanium) alloy, alW (aluminum tungsten) alloy, or the like.

The electrode body layer 31 may be formed by a physical vapor deposition process, for example, and the growth modes of different materials during deposition are different, and the surface of the electrode body layer is observed by an atomic force microscope (atomic force microscope, AFM), so that the film layers formed by the different materials can exhibit different surface morphologies and roughness. For the electrode body layer 31 composed of pure Al and pure Cu, the abnormal growth of crystal grains on the surface of the electrode body layer 31 occurs, and metal atoms are easy to diffuse and migrate, so that the power tolerance of the surface acoustic wave resonator 20 is limited.

By forming the electrode body layer 31 by using a metal alloy, the radius of crystal grains on the surface of the electrode body layer 31 is smaller, so that the easy diffusion and migration of metal atoms can be weakened, the mechanical stress of the material of the interdigital transducer 22 can be enhanced, the bonding force of the interface between the interdigital transducer 22 and the piezoelectric layer 21 can be improved, and the power tolerance of the surface acoustic wave resonator 20 can be enhanced.

With continued reference to fig. 4B, the encapsulation layer 40 is located on the surface of the piezoelectric layer 21 and contacts the piezoelectric layer 21. On this basis, the wrapping layer 40 wraps around the periphery of the electrode body layer 31, and the wrapping layer 40 covers the side surface of the electrode body layer 31.

The side of the electrode body layer 31 can be understood as: the surface of the electrode body layer 31 intersecting the piezoelectric layer 21, or the side of the electrode body layer 31 can also be understood as: the surface of the electrode body layer 31 parallel to the third direction Z, or the side of the electrode body layer 31 can also be understood as: the surfaces of the electrode body layer 31 in the XZ plane and YZ plane of the three-dimensional coordinate system illustrated in fig. 4B. Wherein the third direction Z intersects both the first direction X and the second direction Y. Correspondingly, the surface of the electrode body layer 31 contacting the piezoelectric layer 21 is the bottom surface of the electrode body layer 31, and the surface of the electrode body layer 31 away from the piezoelectric layer 21 (the surface opposite to the bottom surface) is the top surface of the electrode body layer 31.

As can be seen in conjunction with fig. 4A and 4B, each electrode body layer 31 has a plurality of sides. Then, the wrapping layer 40 covers the side of the electrode body layer 31, the following can be understood:

alternatively, as shown in fig. 4B, the wrapping layer 40 covers one side of the electrode body layer 31.

As illustrated in fig. 4B, for example, the wrapping layer 40 covers one side surface of the electrode body layer 31, and the wrapping layer 40 covers a portion of the side surface of the electrode body layer 31 near the piezoelectric layer 21.

Alternatively, as illustrated in fig. 4C, the wrapping layer covers one side of the electrode body layer 31, and the wrapping layer 40 covers all of the side of the electrode body layer 31.

Alternatively, as shown in fig. 4D, the wrapping layer covers each side of the electrode body layer 31.

Illustratively, as shown in fig. 4D, the wrapping layer 40 covers each side of the electrode body layer 31, and the wrapping layer 40 covers a portion of each side of the electrode body layer 31 that is close to the piezoelectric layer 21.

Alternatively, as illustrated in fig. 4E, the wrapping layer 40 covers each side of the electrode body layer 31, and the wrapping layer 40 covers all of each side of the electrode body layer 31.

Alternatively, the wrapping layer 40 covers multiple sides of the electrode body layer 31, but does not cover each side of the electrode body layer 31.

The covering condition of the wrapping layer 40 on the side surface of the electrode body layer 31 in the embodiment of the present application is not limited, and may be reasonably set according to needs, and the above is only a few examples.

The material of the wrapping layer 40 is not limited in the embodiment of the present application, and the surface roughness (or understood as grain size) of the formed wrapping layer 40 is smaller than the surface roughness of the surface of the electrode body layer 31 near the piezoelectric layer 21.

For example, the material of the electrode body layer 31 is Cu, and the surface roughness of the wrapping layer 40 may be smaller than that of Cu.

The electrode body layer 31 and the wrapping layer 40 of the interdigital transducer 22 can be formed by physical vapor deposition, for example, in which different materials can be grown in different manners during deposition, and the surface can be observed by an atomic force microscope, so that the film layers formed by the different materials can exhibit different surface morphologies and roughness. Therefore, by reasonably selecting the material of the wrapping layer 40, it is possible to achieve that the surface roughness of the wrapping layer 40 is smaller than that of the electrode body layer 31.

In some embodiments, as shown in fig. 5, the wrapping layer 40 covers the top surface of the electrode body layer 31 away from the piezoelectric layer 21, in addition to covering the side surfaces of the electrode body layer 31.

In this case, the material of the wrapping layer 40 is also required to be a conductive material in order to ensure that the interdigital transducer 20 can perform piezoelectric conversion, on the basis that the surface roughness of the wrapping layer 40 is smaller than that of the electrode body layer 31.

Optionally, the material of the wrapping layer 40 has a density less than the material of the electrode body layer 31.

Illustratively, the material of the electrode body layer 31 is Cu and the material of the wrapping layer 40 has a density of less than 8.96g/cm ³ 。

By limiting the density of the material of the wrapping layer 40 to be smaller than that of the material of the electrode body layer 31, the formed wrapping layer 40 can be lighter in weight, the influence of the wrapping layer 40 on the weight of the first electrode finger 221b can be reduced, the sensitivity of the frequency of the surface acoustic wave resonator 20 to the change of the film thickness of the wrapping layer 40 can be reduced, the requirement on the manufacturing process of the first electrode finger 221b can be reduced, and the uniformity of the frequency of the surface acoustic wave resonator 20 can be improved.

In some embodiments, the thickness of the encapsulation layer 40 is 5nm to 50nm.

Illustratively, the thickness of the encapsulation layer 40 is 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, etc.

The thickness of the wrapping layer 40 is understood to be the film thickness of the wrapping layer 40. I.e., the surface of the wrapping layer 40 in contact with the electrode layer 30 to the surface of the wrapping layer 40 remote from the electrode layer 30.

The film thickness of the wrapping layer 40 is mainly affected by the film plating process, and by limiting the film thickness of the wrapping layer 40 to 5nm-50nm, the sensitivity of the frequency of the surface acoustic wave resonator 20 to the film thickness variation of the wrapping layer 40 can be reduced, so that the requirement on the preparation process of the first electrode finger 221b is reduced.

Optionally, the resistivity of the material of the cladding layer 40 is less than the resistivity of Ti. The resistivity of the material of the encapsulation layer 40 is less than 0.42 x 10 ^-6 Ωm。

By selecting the material of the encapsulation layer 40 to have a resistivity of less than 0.42 x 10 ^-6 The material of Ω m can minimize the influence of the wrapping layer 40 on the conductivity of the first electrode finger 221b, and improve the piezoelectric conversion rate.

In some embodiments, the material of the cladding layer 40 includes at least one of Al, alCu (aluminum copper alloy), alTi (aluminum titanium alloy), alMg (aluminum magnesium alloy), alNi (aluminum nickel alloy), or AlW (aluminum tungsten alloy).

The material of the wrapping layer 40 is selected as the above-mentioned common conductive material, and the wrapping layer 40 can be directly prepared by adopting the existing coating process without developing a new process.

It should be noted that, the interdigital transducer 22 includes a plurality of first electrode fingers 221b, and the embodiment of the present application is not limited to that each first electrode finger 221b includes a wrapping layer 40, and may be that a part or all of the plurality of first electrode fingers 221b includes a wrapping layer 40, which is reasonably set according to needs.

In some embodiments, as shown in fig. 6A, the first electrode finger 221b further includes a third conductive adhesion layer 50, the third conductive adhesion layer 50 being located on the top surface of the first electrode finger 221 b.

By way of example, as shown in fig. 6A, in the case where the wrapping layer 40 covers only the side face of the electrode body layer 31, the third conductive adhesive layer 50 is located on the surface of the electrode body layer 31 remote from the piezoelectric layer 21.

Alternatively, as illustrated in fig. 6B, in the case where the wrapping layer 40 also covers the top surface of the electrode body layer 31, the third conductive adhesive layer 50 is located on the surface of the wrapping layer 40 away from the piezoelectric layer 21.

The third conductive adhesive layer 50 is always the topmost film layer of the electrode fingers 221b, no matter what structure the electrode fingers 221b are.

The material of the third conductive adhesive layer 50 may be at least one of Ti, cr, ag, or an alloy thereof, and an AlCu alloy, for example.

By providing the surface layer of the first electrode finger 221b as the third conductive adhesive layer 50, the bonding force of the first electrode finger 221b with the subsequent laminated film layer can be improved, diffusion of metal atoms in the electrode body layer 31 into the subsequent laminated film layer can be hindered, and the power tolerance of the surface acoustic wave resonator 20 can be improved.

The thickness of the third conductive adhesion layer 50 may be, for example, between 2nm and 5nm. The thickness of the third conductive adhesive layer 50 is, for example, 3nm or 4nm.

By setting the thickness of the third conductive adhesive layer 50 to 2nm to 5nm, the third conductive adhesive layer 50 can be made to exert a good adhesive effect while also reducing the sensitivity of the frequency of the surface wave resonator 20 to variations in the thickness of the third conductive adhesive layer 50.

The structures of the first bus bar 221a, the second bus bar 222a, and the second electrode finger 222b of the interdigital transducer 22 may be the same as the structures of the first electrode finger 221b, and reference is made to the above description about the first electrode finger 221b, which is not repeated here.

Regarding the fabrication process of the interdigital transducer 22, in some embodiments, the fabrication process of the interdigital transducer 22 comprises:

s1, as shown in fig. 7A, the surface of the piezoelectric layer 21 is cleaned to remove foreign substances, dust, and other interfering substances.

For example, the surface of the piezoelectric layer 21 may be cleaned by ultrasonic cleaning with acetone, alcohol and deionized water, then rinsing with deionized water, and finally drying with nitrogen.

S2, as shown in fig. 7B, a photoresist layer is coated, exposed and developed, the remaining photoresist corresponds to the gaps of the interdigital transducer 22, and the shape and position of the gaps between the photoresists (the portions of the piezoelectric layer 21 not covered with the photoresist) correspond to the electrode layers 30 to be formed.

The photoresist used in this example may be either a positive photoresist or a negative photoresist.

S3, as shown in fig. 7C, the plating film forms an electrode body film that covers the photoresist and the exposed portion of the piezoelectric layer 21.

For example, the electrode body film may be formed using a physical vapor deposition (physical vapor deposition, PVD) process coating.

S4, as shown in fig. 7D, the photoresist and the electrode body film located above the photoresist are peeled off, and the portion of the electrode body film in contact with the piezoelectric layer 21 remains, forming the electrode body layer 31 (i.e., the electrode layer 30).

For example, the process product obtained after step S3 may be put into acetone.

The electrode body layer 31 is prepared by a stripping process, the damage effect of the stripping process on the interface of the electrode body layer 31 and the piezoelectric layer 21 is smaller than the damage effect of the etching process on the interface of the electrode body layer 31 and the piezoelectric layer 21, and the power tolerance of the surface acoustic wave resonator 20 can be improved.

S5, as shown in fig. 7E, a photoresist layer is coated, exposed and developed, the remaining photoresist corresponds to the gaps of the interdigital transducer 22, and the shape and position of the gaps (the portions of the piezoelectric layer 21 not covered by the photoresist) between the photoresists correspond to the encapsulation layer 40 to be formed.

S6, as shown in FIG. 7F, the coating film forms a wrapping film, and the wrapping film covers the photoresist and the exposed part of the piezoelectric layer 21.

S7, stripping the photoresist and the wrapping film above the photoresist, and reserving the part of the wrapping film, which is contacted with the piezoelectric layer, to form a wrapping layer 40, as shown in FIG. 7G.

Wherein, by adjusting the thickness of the wrapping film, the thickness of the wrapping layer 40 can be adjusted to realize that the wrapping layer 40 covers the side surface of the electrode body layer 31.

S8, as shown in FIG. 7H, coating a photoresist layer, and carrying out photoetching development; forming a third adhesive film by coating; the photoresist layer is stripped to form a third conductive adhesion layer 50 to produce the interdigital transducer 22.

In the case where the interdigital transducer 22 does not include the third conductive adhesive layer 50, step S8 described above is not performed.

In the case where the wrapping layer 40 also covers the top surface of the electrode body layer 31 in the interdigital transducer 22, the above steps S5 to S7 are:

s5', as shown in fig. 7I, a photoresist layer is coated, exposed and developed, the remaining photoresist corresponds to the gaps of the interdigital transducer 22, and the shape and position of the gaps between the photoresists (the portions of the piezoelectric layer 21 and the electrode body layer 31 not covered with the photoresist) correspond to the encapsulation layer 40 to be formed.

S6', as shown in FIG. 7J, the coating film forms a wrapping film, and the wrapping film covers the photoresist and the exposed part of the piezoelectric layer 21.

S7', as shown in FIG. 7K, the photoresist and the wrapping film above the photoresist are peeled off, and the portion of the wrapping film, which is in contact with the piezoelectric layer 21 and the electrode body layer 31, is left to form a wrapping layer 40.

The process of preparing the interdigital transducer 22 provided in this example is merely illustrative and not limiting. Fig. 7A to 7K illustrate an example of simultaneously preparing the first electrode finger 221b and the second electrode finger 222b. Of course, the first electrode finger 221b and the second electrode finger 222b may be prepared separately.

In some embodiments, as shown in fig. 8A, the saw resonator 20 further includes a water-oxygen barrier layer 23, and the water-oxygen barrier layer 23 covers the surface of the interdigital transducer 22.

That is, the water-oxygen barrier 23 covers the top and side surfaces of the interdigital transducer 22 to block moisture and oxygen from entering the interdigital transducer 22, thereby avoiding damage to the interdigital transducer 22 caused by moisture and oxygen.

The material of the water-oxygen barrier layer 23 may be, for example, amorphous silicon or oxide.

It will be appreciated that in the case where the first electrode finger 221b and the second electrode finger 222b include the third conductive adhesive layer 30, as shown in fig. 8A, the water oxygen barrier layer 23 covers the third conductive adhesive layer 50.

As shown in fig. 8B, in the case where the first electrode finger 221B and the second electrode finger 222B do not include the third conductive adhesive layer 30, the water oxygen barrier layer 23 covers the wrapping layer 40.

As shown in fig. 8C, in the case where the wrapping layer 40 does not cover the top surface of the electrode body layer 31 in the first electrode finger 221b and the second electrode finger 222b, the water oxygen barrier layer 23 covers the electrode body layer 31.

In some embodiments, as shown in fig. 9A, the saw resonator 20 further includes a temperature compensation layer 24, the temperature compensation layer 24 being disposed on a side of the interdigital transducer 22 remote from the piezoelectric layer 21.

Alternatively, as shown in fig. 9A, the surface acoustic wave resonator 20 further includes a water-oxygen blocking layer 23, and a temperature compensation layer 24 is provided on a surface of the water-oxygen blocking layer 23.

Alternatively, as shown in fig. 9B, the surface acoustic wave resonator 20 does not include the water-oxygen barrier layer 23, and the temperature compensation layer 24 is provided on the surface of the interdigital transducer 22.

The SAW resonator 20 after the temperature compensation layer 24 is disposed may be referred to as a temperature compensated SAW (temperature compensated surface acoustic Wave, TC-SAW) resonator, and the material of the temperature compensation layer 24 may be, for example, silicon dioxide (SiO) ₂ )。

By coating the interdigital transducer 22 with the temperature compensation layer 24, the Temperature Coefficient of Frequency (TCF) of the SAW resonator 20 is reduced to 0 to-25 ppm/DEG C, which is significantly improved over the temperature coefficient of frequency (typically about-45 to-60 ppm/DEG C) of the SAW resonator 20 without the temperature compensation layer 24.

In some embodiments, as shown in fig. 10, the saw resonator 20 further includes a frequency trimming layer 25, where the frequency trimming layer 25 is disposed on a side of the interdigital transducer 22 away from the piezoelectric layer 21, and the frequency trimming layer 25 is used to trim the frequency of the saw resonator 20.

It is understood that, as shown in fig. 10, in the case where the surface acoustic wave resonator 20 includes the temperature compensation layer 24, the frequency trimming layer 25 is provided on the surface of the temperature compensation layer 24. In the case where the surface acoustic wave resonator 20 does not include the temperature compensation layer 24, the frequency trimming layer 25 is provided on the surface of the water oxygen barrier layer 23. In the case where the surface acoustic wave resonator 20 does not include the temperature compensation layer 24 and the water-oxygen barrier layer 23, the frequency trimming layer 25 is provided on the surface of the interdigital transducer 22.

The material of the trimming layer 25 may be, for example, silicon nitride (SiN). By adjusting the thickness of the trimming frequency layer 25, the frequency of the surface acoustic wave resonator 20 can be adjusted to a desired value.

As is apparent from the above description of the material of the electrode layer 30, the selection of the material of the electrode layer 30 as a metal alloy can improve the mechanical stress of the interdigital transducer 22, thereby improving the bonding force at the contact corner of the interdigital transducer 22 and the piezoelectric layer 21. However, when the electrode finger materials of the interdigital transducer 22 in the surface acoustic wave resonator 20 are different, there is a difference in the surface topography of the interdigital transducer 22, and the problem of power tolerance of the surface acoustic wave resonator 20 cannot be completely solved. Moreover, as the input power increases (e.g., from 30dBm to 33dBm to 35 dBm), the mechanical stress and thermal stress of the interdigital transducer 22 further increase, and the bonding force at the contact corner of the interdigital transducer 22 and the piezoelectric layer 21 needs to be further improved to satisfy the high power application scenario.

The surface acoustic wave resonator 20 according to the embodiment of the present application further includes the wrapping layer 40 on the basis of including the electrode layer 30 by making the electrode fingers (the first electrode finger 221b or the second electrode finger 222 b) of the interdigital transducer 22. The wrapping layer 40 covers the side of the electrode layer 30, contacting the piezoelectric layer 21. Thus, the corners of the electrode fingers contacting the piezoelectric layer 21 are changed from the electrode layer 30 to the wrapping layer 40. When the surface roughness of the clad layer 40 is smaller than that of the electrode layer 30, the atomic radius of the material in the clad layer 40 is smaller than that of the material in the electrode layer 30, the dislocation gap between atoms in the clad layer 40 is small, and the defect density of the clad layer 40 is small. In this way, under the action of mechanical stress and thermal stress, the probability of forming defects such as holes or notches by diffusion and migration of the atoms in the wrapping layer 40 is reduced, so that the interface bonding force between the interdigital transducer 22 and the piezoelectric layer 21 can be improved, the reliability and the power tolerance of the surface acoustic wave resonator 20 can be improved, and the performance of the surface acoustic wave resonator 20 can be ensured. Moreover, the influence on the power resistance of the surface acoustic wave resonator 20 is not large regardless of the change in the material of the electrode layer 30.

On this basis, when the wrapping layer 40 also covers the top surface of the electrode layer 30, since the surface roughness of the wrapping layer 40 is smaller than that of the electrode layer 30, the diffusion migration capacity of metal atoms in the wrapping layer 40 is smaller than that of metal atoms in the electrode layer 30, and the wrapping layer 40 can block the diffusion of metal atoms in the electrode layer 30 to the temperature compensation layer 24. In this way, the power tolerance of the surface acoustic wave resonator 20 can be further improved, the insertion loss of the surface acoustic wave resonator 20 can be reduced, and the quality factor of the surface acoustic wave resonator 20 can be improved.

Example two

The main difference between the second example and the first example is that the electrode layer 30 is not a single-layer structure any more, but includes a first conductive adhesive layer and an electrode body layer which are stacked.

The present example provides a surface acoustic wave resonator 20, as shown in fig. 11A, the surface acoustic wave resonator 20 including a piezoelectric layer 21 and an interdigital transducer 22, the interdigital transducer 22 being disposed on one side of the piezoelectric layer 21.

The interdigital transducer 22 is disposed on the piezoelectric layer 21, and the piezoelectric layer 21 is configured to excite a surface acoustic wave under the action of the interdigital transducer 22.

The interdigital transducer 22 includes first and second bus bars 221a and 222a disposed opposite to each other, a plurality of first electrode fingers 221b, and a plurality of second electrode fingers 222b; the positional relationship of the first and second bus bars 221a and 222a, the plurality of first electrode fingers 221b, and the plurality of second electrode fingers 222b may be the same as in example one, and the related description in example one may be referred to. The structure of the first electrode finger 221b may be the same as that of the second electrode finger 222b, and the first electrode finger 221b will be described as an example.

As to the structure of the first electrode finger 221b, as shown in fig. 11A, the first electrode finger 221b includes an electrode layer 30 and a wrapping layer 40.

Regarding the structure of the electrode layer 30, in one possible implementation, as shown in fig. 11A, the electrode layer 30 includes a first conductive adhesive layer 32 and an electrode body layer 31 that are stacked, the first conductive adhesive layer 32 being disposed on the side of the electrode body layer 31 that is close to the piezoelectric layer 21. The surface roughness of the encapsulation layer 40 is smaller than the surface roughness of the electrode layer 30 near the bottom surface of the piezoelectric layer 21. In this case, the surface roughness of the wrapping layer 40 is smaller than that of the first conductive adhesive layer 32.

The material of the electrode body layer 31 may be the same as in example one, and reference is made to the description related to example one.

The material of the first conductive adhesion layer 32 may be, for example, at least one of Ti, cr, ag, or an alloy thereof.

The thickness of the first conductive adhesion layer 32 may be, for example, between 2nm and 5nm. The first conductive adhesion layer 32 is, for example, 3nm or 4nm thick.

By setting the thickness of the first conductive adhesive layer 32 to 2nm to 5nm, the first conductive adhesive layer 32 can be made to have a good adhesive effect while also reducing the sensitivity of the frequency of the surface wave resonator 20 to variations in the thickness of the first conductive adhesive layer 32.

On the basis of this, a wrapping layer 40 is provided on the surface of the piezoelectric layer 21, and the wrapping layer 40 covers at least the side face of the electrode layer 30.

Illustratively, as shown in fig. 11A, the wrapping layer 40 covers the side of the first conductive adhesive layer 32 in the electrode layer 30.

In this case, the surface roughness of the wrapping layer 40 is smaller than that of the first conductive adhesive layer 32.

Alternatively, as illustrated in fig. 11B, the wrapping layer 40 covers the side surfaces of the first conductive adhesive layer 32 and the electrode body layer 31 in the electrode layer 30.

In this case, the surface roughness of the wrapping layer 40 is at least smaller than the surface roughness of the first conductive adhesive layer 32. That is, the surface roughness of the wrapping layer 40 is at least smaller than that of the film layer closest to the piezoelectric layer 21 in the electrode layer 30.

Of course, the surface roughness of the wrapping layer 40 may be smaller than both the surface roughness of the first conductive adhesive layer 32 and the surface roughness of the electrode body layer 31. That is, the surface roughness of the wrapping layer 40 is smaller than that of each of the electrode layers 30 covered by the wrapping layer 40.

Fig. 11A and 11B illustrate only that the wrapping layer 40 covers each side of the electrode layer 30, and the wrapping layer 40 may cover only one or more (but not all) sides of the electrode layer 30.

In some embodiments, as shown in fig. 11C, the wrapping layer 40 also covers the top surface of the electrode layer 30. That is, the wrapping layer 40 also covers the top surface of the electrode body layer 31.

At this time, as shown in fig. 11C, the wrapping layer 40 also covers the top surface of the electrode body layer 31. The surface roughness of the wrapping layer 40 is smaller than that of the electrode body layer 31.

For the material, thickness, density, and resistivity of the wrapping layer 40, reference may be made to the relevant descriptions in example one, and will not be repeated here.

In some embodiments, the saw resonator 20 further includes at least one of a third conductive adhesion layer 50, a water oxygen barrier layer 23, a temperature compensation layer 24, or a frequency tuning layer 25. Fig. 11D illustrates an example in which the saw resonator 20 further includes a third conductive adhesive layer 50, a water-oxygen barrier layer 23, a temperature compensation layer 24, and a tuning layer 25.

The structure and location of the third conductive adhesive layer 50, the water oxygen barrier layer 23, the temperature compensation layer 24, or the frequency modulation layer 25 may be referred to the related description in example one, and will not be repeated here.

By providing the first conductive adhesive layer 32 on the side of the electrode body layer 31 close to the piezoelectric layer 21, on the one hand, the strength of the electrode layer 30 can be enhanced, and the mechanical stress of the interdigital transducer 22 can be improved. On the other hand, a first conductive adhesion layer 32 is disposed between the electrode body layer 31 and the piezoelectric layer 21, and the first conductive adhesion layer 32 can change the bonding force between the interdigital transducer 22 and the piezoelectric layer 21, so as to prevent the metal atoms in the electrode body layer 31 from diffusing into the piezoelectric layer 21, and improve the power tolerance of the surface acoustic wave resonator 20.

Example three

The main difference between the third example and the first example is that the electrode layer 30 in this example is no longer a single-layer structure but includes an electrode body layer and a second conductive adhesive layer that are stacked.

The present example provides a surface acoustic wave resonator 20, as shown in fig. 12A, the surface acoustic wave resonator 20 including a piezoelectric layer 21 and an interdigital transducer 22, the interdigital transducer 22 being disposed on one side of the piezoelectric layer 21.

Regarding the structure of the electrode layer 30, in one possible implementation, as shown in fig. 11A, the electrode layer 30 includes an electrode body layer 31 and a second conductive adhesive layer 33 that are stacked, the second conductive adhesive layer 33 being disposed on the side of the electrode body layer 31 remote from the piezoelectric layer 21. The surface roughness of the encapsulation layer 40 is smaller than the surface roughness of the electrode layer 30 near the bottom surface of the piezoelectric layer 21. In this case, the surface roughness of the wrapping layer 40 is smaller than that of the electrode body layer 31.

The material of the second conductive adhesion layer 33 may be, for example, at least one of Ti, cr, ag, or an alloy thereof.

The thickness of the second conductive adhesion layer 33 may be, for example, between 2nm and 5nm. The second conductive adhesion layer 33 has a thickness of 3nm or 4nm, for example.

By setting the thickness of the second conductive adhesive layer 33 to 2nm to 5nm, the second conductive adhesive layer 33 can be made to exert a good adhesive effect while also reducing the sensitivity of the frequency of the surface wave resonator 20 to the variation in the thickness of the second conductive adhesive layer 33.

On the basis of this, a wrapping layer 40 is provided on the surface of the piezoelectric layer 21, and the wrapping layer 40 covers at least the side face of the electrode layer 30. The surface roughness of the wrapping layer 40 is smaller than the surface roughness of the surface covered by the wrapping layer 40.

Illustratively, as shown in fig. 12A, the wrapping layer 40 covers the side of the electrode body layer 31 in the electrode layer 30.

In this case, the surface roughness of the wrapping layer 40 is smaller than that of the electrode body layer 31.

Alternatively, as illustrated in fig. 12B, the wrapping layer 40 covers the second conductive adhesive layer 32 and the side face of the electrode body layer 31 in the electrode layer 30.

In this case, the surface roughness of the wrapping layer 40 is at least smaller than that of the electrode body layer 31. That is, the surface roughness of the wrapping layer 40 is at least smaller than that of the film layer closest to the piezoelectric layer 21 in the electrode layer 30.

Of course, the surface roughness of the wrapping layer 40 may be smaller than both the surface roughness of the electrode body layer 31 and the surface roughness of the second conductive adhesive layer 33. That is, the surface roughness of the wrapping layer 40 is smaller than that of each of the electrode layers 30 covered by the wrapping layer 40.

Fig. 12A and 12B illustrate only the case where the wrapping layer 40 covers each side of the electrode layer 30, and the wrapping layer 40 may cover only one or more (but not all) of the sides of the electrode layer 30.

In some embodiments, as shown in fig. 12C, the wrapping layer 40 also covers the top surface of the electrode layer 30. That is, the wrapping layer 40 also covers the top surface of the second conductive adhesive layer 33.

At this time, as shown in fig. 12C, the wrapping layer 40 also covers the top surface of the second conductive adhesive layer 33. The surface roughness of the wrapping layer 40 is smaller than that of the second conductive adhesive layer 33. The surface roughness of the wrapping layer 40 may be smaller than that of the conductive body layer 31.

That is, in the case where the wrapping layer 40 covers the side surface of the electrode layer 30, the surface roughness of the wrapping layer 40 is smaller than the surface roughness of the side surface of the electrode layer 30 covered by the wrapping layer 40. In the case where the wrapping layer 40 also covers the top surface of the electrode layer 30, the surface roughness of the wrapping layer 40 also needs to be smaller than that of the film layer of the top layer of the electrode layer 30 on the premise that the surface roughness of the side surface of the electrode layer 30 covered by the wrapping layer 40 is smaller. Alternatively, in the case where the wrapping layer 40 also covers the top surface of the electrode layer 30, the surface roughness of the wrapping layer 40 may be smaller than the surface roughness of the electrode body layer 31 on the premise that the surface roughness of the side surface of the electrode layer 30 covered by the wrapping layer 40 is smaller than the surface roughness of the topmost film layer of the electrode layer 30.

In some embodiments, the resistivity of the material of the encapsulation layer 40 is less than the resistivity of the material of the second conductive adhesion layer 33.

In this way, the placement of the encapsulation layer 40 does not affect the original conductivity of the interdigital transducer 22.

The material of the second conductive adhesion layer 33 is illustratively Ti, and the resistivity of the material of the encapsulation layer 40 is less than 0.42 x 10 ^-6 Ωm。

For the material, thickness, and density of the wrapping layer 40, reference may be made to the descriptions related to example one, and will not be repeated here.

In some embodiments, the saw resonator 20 further includes at least one of a third conductive adhesion layer 50, a water oxygen barrier layer 23, a temperature compensation layer 24, or a frequency tuning layer 25. Fig. 12D illustrates an example in which the saw resonator 20 further includes a third conductive adhesive layer 50, a water-oxygen barrier layer 23, a temperature compensation layer 24, and a tuning layer 25.

It will be appreciated that the saw resonator 20 may not include the third conductive adhesive layer 50 in the case where the encapsulation layer 40 does not cover the top surface of the second conductive adhesive layer 33.

By disposing the second conductive adhesive layer 33 on the side of the electrode body layer 31 away from the piezoelectric layer 21, a layer of second conductive adhesive layer 33 is disposed between the electrode body layer 31 and the wrapping layer 40, and the second conductive adhesive layer 33 can change the bonding force between the electrode body layer 31 and the wrapping layer 40, so as to hinder the diffusion of metal atoms in the electrode body layer 31 into the temperature compensation layer 24, and improve the power tolerance of the saw resonator 20.

Example four

The main difference between the fourth example and the first example is that the electrode layer 30 is not a single-layer structure any more, but includes a first conductive adhesive layer, an electrode body layer, and a second adhesive layer which are stacked.

The present example provides a surface acoustic wave resonator 20, as shown in fig. 13A, the surface acoustic wave resonator 20 including a piezoelectric layer 21 and an interdigital transducer 22, the interdigital transducer 22 being disposed on one side of the piezoelectric layer 21.

The interdigital transducer 22 includes first and second bus bars 221a and 222a disposed opposite to each other, a plurality of first electrode fingers 221b, and a plurality of second electrode fingers 222b; the positional relationship of the first and second bus bars 221a and 222a, the plurality of first electrode fingers 221b, and the plurality of second electrode fingers 222b may be the same as in example one, and the related description in example one may be referred to.

As to the structure of the first electrode finger 221b, as shown in fig. 13A, the first electrode finger 221b includes an electrode layer 30 and a wrapping layer 40.

Regarding the structure of the electrode layer 30, in one possible implementation, as shown in fig. 13A, the electrode layer 30 includes a first conductive adhesive layer 32, an electrode body layer 31, and a second conductive adhesive layer 33 that are stacked, the first conductive adhesive layer 32 being disposed on the side of the electrode body layer 31 near the piezoelectric layer 21, and the second conductive adhesive layer 33 being disposed on the side of the electrode body layer 31 remote from the piezoelectric layer 21. The surface roughness of the encapsulation layer 40 is smaller than the surface roughness of the electrode layer 30 near the bottom surface of the piezoelectric layer 21. In this case, the surface roughness of the wrapping layer 40 is smaller than that of the first conductive adhesive layer 32.

The material and thickness of the first conductive adhesive layer 32 may be the same as in example two, and reference is made to the description in example two.

The material and thickness of the second conductive adhesive layer 33 may be the same as in example three, and reference is made to the description thereof.

The wrapping layer 40 is disposed on the surface of the piezoelectric layer 21, and the wrapping layer 40 covers at least the side surfaces of the electrode layer 30. The surface roughness of the wrapping layer 40 is smaller than the surface roughness of the surface covered by the wrapping layer 40.

Illustratively, as shown in fig. 13A, the wrapping layer 40 covers the side of the first conductive adhesive layer 32 in the electrode layer 30.

Alternatively, as illustrated in fig. 13B, the wrapping layer 40 covers the side surfaces of the first conductive adhesive layer 32 and the electrode body layer 31 in the electrode layer 30.

Of course, the surface roughness of the wrapping layer 40 may be smaller than both the surface roughness of the first conductive adhesive layer 32 and the surface roughness of the electrode body layer 31.

Alternatively, as illustrated in fig. 13C, the wrapping layer 40 covers the sides of the first conductive adhesive layer 32, the electrode body layer 31, and the second conductive adhesive layer 33 in the electrode layer 30.

Of course, the surface roughness of the wrapping layer 40 may be smaller than the surface roughness of the first conductive adhesive layer 32, the surface roughness of the electrode body layer 31, and the surface roughness of the second conductive adhesive layer 33. That is, the surface roughness of the wrapping layer 40 is smaller than that of each of the electrode layers 30 covered by the wrapping layer 40.

Fig. 13A-13C illustrate only the case where the wrapping layer 40 covers each side of the electrode layer 30, and the wrapping layer 40 may cover only one or more (but not all) of the sides of the electrode layer 30.

In some embodiments, as shown in fig. 13D, the wrapping layer 40 also covers the top surface of the electrode layer 30. That is, the wrapping layer 40 also covers the top surface of the second conductive adhesive layer 33.

At this time, as shown in fig. 13D, the wrapping layer 40 also covers the top surface of the second conductive adhesive layer 33. The surface roughness of the wrapping layer 40 is smaller than that of the second conductive adhesive layer 33. The surface roughness of the wrapping layer 40 may be smaller than that of the conductive body layer 31.

In some embodiments, the saw resonator 20 further includes at least one of a third conductive adhesion layer 50, a water oxygen barrier layer 23, a temperature compensation layer 24, or a frequency tuning layer 25. Fig. 13E illustrates an example in which the saw resonator 20 further includes a third conductive adhesive layer 50, a water-oxygen barrier layer 23, a temperature compensation layer 24, and a tuning layer 25.

By providing the first conductive adhesive layer 32 on the side of the electrode body layer 31 adjacent to the piezoelectric layer 21, on the one hand, the strength of the electrode layer 30 can be enhanced and the mechanical stress of the interdigital transducer 22 can be improved. On the other hand, a first conductive adhesion layer 32 is disposed between the electrode body layer 31 and the piezoelectric layer 21, and the first conductive adhesion layer 32 can change the bonding force between the interdigital transducer 22 and the piezoelectric layer 21, so as to prevent the metal atoms in the electrode body layer 31 from diffusing into the piezoelectric layer 21, and improve the power tolerance of the surface acoustic wave resonator 20.

The foregoing is merely illustrative of the present application, and the present application is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the scope of the present application should be included in the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A surface acoustic wave filter, comprising:

a piezoelectric layer;

the interdigital transducer is arranged on one side of the piezoelectric layer and comprises electrode fingers;

the electrode finger comprises an electrode layer and a wrapping layer, wherein the wrapping layer wraps the periphery of the electrode layer and covers the side face of the electrode layer; the wrapping layer is in contact with the piezoelectric layer;

The surface roughness of the wrapping layer is smaller than that of the bottom surface of the electrode layer, and the bottom surface is in contact with the piezoelectric layer.

2. The surface acoustic wave filter according to claim 1, wherein the wrapping layer further covers a top surface of the electrode layer, and a material of the wrapping layer is a conductive material; the surface roughness of the wrapping layer is smaller than the surface roughness of the top surface of the electrode layer.

3. The surface acoustic wave filter according to claim 1 or 2, wherein the electrode layer comprises an electrode body layer.

4. A surface acoustic wave filter according to claim 3, wherein the material of the wrapping layer has a density smaller than that of the material of the electrode body layer.

5. The surface acoustic wave filter according to any one of claims 1 to 4, wherein the thickness of the wrapping layer is 5nm to 50nm.

6. The surface acoustic wave filter of any of claims 1-5, wherein the material of the cladding layer comprises at least one of Al, alCu, alTi, alMg, alNi or AlW.

7. The surface acoustic wave filter according to claim 3, wherein the electrode layer further comprises a first conductive adhesive layer provided on a side of the electrode body layer close to the piezoelectric layer.

8. The surface acoustic wave filter according to claim 3 or 7, wherein the electrode layer further comprises a second conductive adhesive layer provided on a side of the electrode body layer remote from the piezoelectric layer.

9. The surface acoustic wave filter according to claim 8, wherein a resistivity of a material of the wrapping layer is smaller than a resistivity of a material of the second conductive adhesive layer.

10. The surface acoustic wave filter according to any one of claims 1 to 9, wherein the resistivity of the material of the wrapping layer is less than 0.42 x 10 ^-6 Ωm。

11. The surface acoustic wave filter according to any one of claims 1 to 10, wherein the electrode finger further comprises a third conductive adhesive layer, the third conductive adhesive layer being located on a top surface of the electrode finger.

12. The surface acoustic wave filter according to any one of claims 1 to 11, further comprising a water-oxygen barrier layer covering a surface of the interdigital transducer.

13. The surface acoustic wave filter according to any one of claims 1 to 12, further comprising a temperature compensation layer provided on a side of the interdigital transducer remote from the piezoelectric layer.

14. The surface acoustic wave filter according to any one of claims 1 to 13, further comprising a frequency correction layer provided on a side of the interdigital transducer remote from the piezoelectric layer, the frequency correction layer being for correcting a frequency of the surface acoustic wave filter.

15. An apparatus comprising a power amplifier coupled to a surface acoustic wave filter, the surface acoustic wave filter being a surface acoustic wave filter as claimed in any one of claims 1-14.

16. An electronic device comprising a surface acoustic wave filter and a circuit board, the surface acoustic wave filter being disposed on the circuit board; wherein the surface acoustic wave filter is a surface acoustic wave filter according to any one of claims 1 to 14.