Elastic wave device, radio frequency front end module and preparation method of elastic wave device

Abstract

The invention is suitable for the technical field of radio frequency filtering, and discloses an elastic wave device, a radio frequency front-end module and a preparation method of the elastic wave device, the elastic wave device comprises a piezoelectric substrate and at least one interdigital transducer arranged on the piezoelectric substrate, the interdigital transducer comprises a first conductive layer, a second conductive layer and a protective layer, the first conducting layer is located between the second conducting layer and the piezoelectric substrate, the protective layer is arranged on the upper surface of the target conducting layer and extends in the direction close to the piezoelectric substrate so as to cover the side face of the target conducting layer, the target conducting layer is the first conducting layer or the second conducting layer, the length of the side face of the protective layer is L1, the length of the side face of the target conducting layer is L2, and L1 is larger than L2. According to the embodiment, the interdigital transducer can be prevented from being damaged, and the performance of the elastic wave device is improved.

Description

Technical Field

[0001] The present application relates to the field of radio frequency filtering technology, and in particular to an elastic wave device, a radio frequency front-end module, and a method for preparing the elastic wave device. Background Art

[0002] A SAW device includes a piezoelectric substrate and an IDT disposed on the piezoelectric substrate. With the development of SAW devices, there is a requirement for miniaturization of the IDT size and a higher requirement for the power tolerance of the SAW device.

[0003] At present, the electrodes of the IDT generally adopt a multi-layer structure to improve the power handling capacity of the elastic wave device. However, it is found in practice that when making electrodes with a multi-layer film structure, if a stripping process is used to remove the photoresist, in some cases the electrodes will be corroded, damaging the IDT and affecting the performance of the elastic wave device. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the purpose of the present application is to provide an elastic wave device, a radio frequency front-end module and a method for preparing the elastic wave device, which aims to avoid damage to the interdigital transducer and improve the performance of the elastic wave device.

[0005] In order to solve the above technical problems, an embodiment of the present application provides an elastic wave device, which includes: a piezoelectric substrate and at least one interdigital transducer arranged on the piezoelectric substrate, wherein the interdigital transducer includes:

[0006] A first conductive layer including a first metal element;

[0007] A second conductive layer, comprising a second metal element, a potential difference exists between a standard electrode potential of the first metal element and a standard electrode potential of the second metal element, and the first conductive layer is located between the second conductive layer and the piezoelectric substrate;

[0008] a protective layer, which is disposed on the upper surface of the target conductive layer and extends toward the direction close to the piezoelectric substrate to cover the side surface of the target conductive layer, wherein the protective layer extends from the edge of the upper surface of the target conductive layer along the side surface of the target conductive layer toward the direction close to the piezoelectric substrate by a length L1, and the length of the side surface of the target conductive layer is L2, and L1 is greater than L2;

[0009] The target conductive layer is the first conductive layer or the second conductive layer, and the length of the side surface of the target conductive layer is the length from the upper surface edge of the target conductive layer to the lower surface edge of the target conductive layer.

[0010] An embodiment of the present application also provides a radio frequency front-end module, which includes the above-mentioned elastic wave device.

[0011] The embodiment of the present application further provides a method for preparing an elastic wave device, which is used to prepare the elastic wave device mentioned above, and the preparation method comprises:

[0012] forming a photolithography pattern layer having a hollow region on the piezoelectric substrate, wherein the hollow region exposes the piezoelectric substrate to the photolithography pattern layer;

[0013] forming a first conductive layer, wherein the first conductive layer is located in the hollow region and on the photolithography pattern layer, and the first conductive layer includes a first metal element;

[0014] forming a second conductive layer on the first conductive layer, wherein the second conductive layer includes a second metal element, and there is a potential difference between a standard electrode potential of the first metal element and a standard electrode potential of the second metal element;

[0015] removing the photolithography pattern layer by a lift-off process;

[0016] After forming the first conductive layer, or after forming the second conductive layer on the first conductive layer and before removing the photolithography pattern layer by a stripping process, the method further includes:

[0017] forming a protective layer on a target conductive layer to cover an upper surface and a side surface of the target conductive layer, wherein the target conductive layer is the first conductive layer or the second conductive layer, and a length of a side surface of the protective layer is greater than a length of a side surface of the target conductive layer;

[0018] Among them, the length of the side surface of the protective layer is the length of the protective layer extending from the upper surface edge of the target conductive layer along the side surface of the target conductive layer toward the direction close to the piezoelectric substrate; the length of the side surface of the target conductive layer is the length from the upper surface edge of the target conductive layer to the lower surface edge of the target conductive layer.

[0019] The elastic wave device provided by the present application has the following beneficial effects:

[0020] In the elastic wave device of this embodiment, a protective layer is arranged on the first conductive layer, or a protective layer is arranged on the second conductive layer, so that the protective layer covers the upper surface and the side surface of one of the target conductive layers in the first conductive layer and the second conductive layer, and the length L1 of the side surface of the protective layer is greater than the length L2 of the side surface of the target conductive layer. In this way, when the photoresist on the piezoelectric substrate is stripped off by a stripping process to obtain the interdigital transducer, the protective layer can separate the target conductive layer and the stripping liquid to avoid contact between the target conductive layer and the stripping liquid, so as to avoid the first conductive layer and the second conductive layer from forming a galvanic cell structure in the stripping liquid, thereby avoiding the first conductive layer or the second conductive layer from being corroded based on the galvanic cell effect, thereby avoiding damage to the interdigital transducer and improving the performance of the elastic wave device.

[0021] At the same time, the present embodiment sets a protective layer to cover the upper surface and side surfaces of the target conductive layer, which can prevent atoms in the target conductive layer from diffusing around under high power, thereby suppressing the target conductive layer from breaking under high power and improving the power tolerance of the elastic wave device. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0023] Figure 1 is a schematic diagram of the first structure of the elastic wave device provided in the embodiment of the present application;

[0024] Figure 2 is a schematic diagram of a second structure of the elastic wave device provided in an embodiment of the present application;

[0025] Figure 3 is a schematic diagram of a third structure of the elastic wave device provided in an embodiment of the present application;

[0026] Figure 4 is a schematic diagram of a fourth structure of the elastic wave device provided in an embodiment of the present application;

[0027] Figure 5 is a schematic diagram of a structure in which a protective layer covers a target conductive layer in an elastic wave device provided in an embodiment of the present application;

[0028] Figure 6 is a partial structural schematic diagram of an elastic wave device provided in an embodiment of the present application;

[0029] Figure 7 It is a schematic diagram of the method for preparing an elastic wave device provided in an embodiment of the present application, in which the photolithography pattern layer is not stripped off when preparing the elastic wave device;

[0030] Figure 8 It is a structural schematic diagram of forming a photolithography pattern layer on a piezoelectric substrate when preparing an elastic wave device in a method for preparing an elastic wave device provided in an embodiment of the present application;

[0031] Fig. 9 is a schematic diagram of not forming an adhesion layer 24 on a piezoelectric substrate when preparing an elastic wave device provided in an embodiment of the present application;

[0032] Fig.10 It is a schematic flow chart of the steps of a method for preparing an elastic wave device provided in an embodiment of the present application;

[0033] Fig.11 It is a schematic flow chart of the steps of another method for preparing an elastic wave device provided in an embodiment of the present application.

[0034] Description of Figure Numbers:

[0035] 1. Elastic wave device; 2. Photolithography pattern layer; 2A. Hollow area;

[0036] 10. Piezoelectric substrate;

[0037] 20. IDT; 201. Target conductive layer; 21. First conductive layer; 22. Second conductive layer; 23. Protective layer; 24. Adhesion layer; 25. Third conductive layer. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0039] It should be noted that all directional indications in the embodiments of the present application (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0040] It should also be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element at the same time. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or may be indirectly connected to the other element through an intermediate element.

[0041] In addition, the descriptions of "first", "second", etc. in this application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0042] In some related technologies, elastic wave devices such as surface acoustic wave filters are mainly composed of a piezoelectric substrate and an interdigital transducer arranged on the piezoelectric substrate. The electrodes of the interdigital transducer can adopt a multi-layer structure to improve the power handling capacity of the elastic wave device.

[0043] However, in the process of preparing the elastic wave device, when the photoresist on the piezoelectric substrate is removed by a stripping process, if there are two conductive layers in direct or indirect contact in the electrode of the IDT, such as conductive layers made of two metals with different activities, and there is a potential difference between the two conductive layers, a galvanic cell structure is easily formed in the stripping solution. In this case, the electrode will be corroded in the stripping solution due to the galvanic cell effect, causing damage to the IDT.

[0044] In addition, after removing the photoresist using a stripping process, the IDT can be exposed to a plasma atmosphere to remove the stripping solution remaining on the IDT, but this will cause the outer wall of the IDT electrode to be damaged, resulting in damage to the IDT. Currently, the electrode of the IDT is completely covered with a protective layer to alleviate the damage of the electrode side wall by the plasma atmosphere, but this method will cause the performance of the electrode to deteriorate.

[0045] In view of this, if Figure 1 , Figure 3 and Figure 5 As shown, the present application provides an elastic wave device 1, which is provided with a protective layer 23 in the interdigital transducer 20 to cover the upper surface and the side of the target conductive layer 201, wherein the target conductive layer 201 is one of the first conductive layer 21 and the second conductive layer 22 which are stacked, and the length L1 of the side of the protective layer 23 is also provided to be greater than the length L2 of the side of the target conductive layer 201, so that when the photoresist on the piezoelectric substrate 10 is stripped by a stripping process to obtain the interdigital transducer 20, the protective layer 23 can separate the target conductive layer 201 and the stripping solution, thereby preventing the first conductive layer 21 and the second conductive layer 22 from forming a galvanic cell structure in the stripping solution, and preventing the first conductive layer 21 or the second conductive layer 22 from being corroded based on the galvanic cell effect, thereby avoiding damage to the interdigital transducer 20, and thereby improving the performance of the elastic wave device 1.

[0046] The following is combined with Figures 1 to 11 , some embodiments of the present application are described in detail. In the absence of conflict, the following embodiments and features of the embodiments can be combined with each other.

[0047] It should be noted that in the accompanying drawings, Figures 1 to 11 It is only exemplary, and for the sake of convenience, as shown in Figure 2 In FIG. 1 , not all reference numerals of all structures in the elastic wave device 1 are indicated. Figure 2 Structures not marked with reference numerals may be in other drawings, such as Figure 7 As shown in the figure, the various drawings can be used together if there is no conflict. Figures 1 to 4 The following are schematic diagrams of one structure of the elastic wave device 1, respectively. Figure 5 The figure shows an exemplary comparison between the length L1 of the side of the protective layer 23 and the length L2 of the side of the target conductive layer 201 when the protective layer 23 covers the target conductive layer 201. Figure 6 The schematic diagram of the structure of the elastic wave device 1 in which the protective layer 23 is not formed on the second conductive layer 22 is exemplarily shown. Figure 7 The lamination state between the elastic wave device 1 and the photolithography pattern layer 2 when preparing the elastic wave device 1 is exemplarily shown. Figure 8 The structural diagram of the piezoelectric substrate 10 having the photolithography pattern layer 2 is exemplarily shown. Fig. 9 The schematic diagram of manufacturing the IDT 20 directly on the piezoelectric substrate 10 is exemplarily shown. Fig.10 and Fig.11 Each exemplarily shows one method of preparing the elastic wave device 1 , and the drawings can be used together if there is no conflict. These are not limitations on the elastic wave device 1 , nor on the method for preparing the elastic wave device 1 .

[0048] like Figure 1 , Figure 3 and Figure 5 As shown, the elastic wave device 1 of the embodiment of the present application includes a piezoelectric substrate 10 and at least one interdigital transducer 20 disposed on the piezoelectric substrate 10, the interdigital transducer 20 includes a first conductive layer 21, a second conductive layer 22 and a protective layer 23, the first conductive layer 21 includes a first metal element, the second conductive layer 22 includes a second metal element, there is a potential difference between the standard electrode potential of the first metal element and the standard electrode potential of the second metal element, the first conductive layer 21 is located between the second conductive layer 22 and the piezoelectric substrate 10; the protective layer 23 is disposed on the target conductive layer 21. The protective layer 23 extends from the upper surface edge of the target conductive layer 201 along the side of the target conductive layer 201 toward the piezoelectric substrate 10 to cover the side of the target conductive layer 201. The length of the protective layer 23 extending from the upper surface edge of the target conductive layer 201 along the side of the target conductive layer 201 toward the piezoelectric substrate 10 is L1, and the length of the side of the target conductive layer 201 is L2, and L1 is greater than L2; wherein, the target conductive layer 201 is the first conductive layer 21 or the second conductive layer 22, and the length of the side of the target conductive layer 201 is the length from the upper surface edge of the target conductive layer 201 to the lower surface edge of the target conductive layer 201.

[0049] In this embodiment, the elastic wave device 1 includes a piezoelectric substrate 10 and an interdigital transducer 20 formed on the piezoelectric substrate 10, wherein the interdigital transducer 20 is used to realize acoustic-electric transduction, wherein the interdigital transducer 20 includes a first conductive layer 21 and a second conductive layer 22 which are stacked, wherein the first conductive layer 21 includes a first metal element, and the second conductive layer 22 includes a second metal element, wherein the first metal element and the second metal element have different metallic activities, and there is a potential difference between the standard electrode potential of the first metal element and the standard electrode potential of the second metal element, so if the first conductive layer 21 and the second conductive layer 22 are directly placed in an electrolyte, a galvanic cell structure will be formed, thereby causing the first conductive layer 21 or the second conductive layer 22 to be corroded under the catalysis of the electric current based on the galvanic cell effect. Therefore, in the elastic wave device 1 of the present embodiment, a protective layer 23 is provided on the first conductive layer 21, or a protective layer 23 is provided on the second conductive layer 22, so that the protective layer 23 covers the upper surface and the side surface of one of the target conductive layers 201 in the first conductive layer 21 and the second conductive layer 22, and the length L1 of the side surface of the protective layer 23 is greater than the length L2 of the side surface of the target conductive layer 201. In this way, when the photoresist on the piezoelectric substrate 10 is stripped off by a stripping process to obtain the interdigital transducer 20, the protective layer 23 can separate the target conductive layer 201 and the stripping solution (such as an electrolyte such as N-methylpyrrolidone solution) to avoid contact between the target conductive layer 201 and the stripping solution, so as to avoid direct or indirect contact between the first conductive layer 21 and the second conductive layer 22 in the stripping solution and form a galvanic cell structure, thereby avoiding corrosion of the first conductive layer 21 or the second conductive layer 22 due to the galvanic cell effect, effectively avoiding damage to the interdigital transducer 20, and improving the performance of the elastic wave device 1.

[0050] Furthermore, on the basis that the protective layer 23 covers the upper surface and side surfaces of the target conductive layer 201, the length L1 of the side surfaces of the protective layer 23 is greater than the length L2 of the side surfaces of the target conductive layer 201. Compared with setting the protective layer 23 to extend to cover the edge of the bottom surface of the target conductive layer 201 and not cross the edge of the bottom surface of the target conductive layer 201 (that is, the length L1 of the side surfaces of the protective layer 23 is equal to the length L2 of the side surfaces of the target conductive layer 201), the stripping liquid can be prevented from penetrating into and contacting the target conductive layer 201 from the gap at the adjacent position of the protective layer 23 and the target conductive layer 201, and the stripping liquid can be prevented from penetrating into the edge of the bottom surface of the target conductive layer 201, and even penetrating into between the first conductive layer 21 and the second conductive layer 22, so as to effectively ensure that the target conductive layer 201 is not in contact with the stripping liquid, thereby preventing the first conductive layer 21 and the second conductive layer 22 from forming a primary battery structure in the stripping liquid.

[0051] At the same time, the protective layer 23 is provided in this embodiment to cover the upper surface and the side of the target conductive layer 201, which can prevent the atoms in the target conductive layer 201 from diffusing to the surroundings under high power, thereby suppressing the phenomenon of the target conductive layer 201 breaking under high power, and improving the power tolerance of the elastic wave device 1. In addition, the IDT 20 with the above structure is placed in a plasma atmosphere. Since the protective layer 23 covers the upper surface and the side of the first conductive layer 21 or the second conductive layer 22, the damage degree of the side wall with the first conductive layer 21 and the second conductive layer 22 as the main electrode can be reduced. Moreover, in the IDT 20 with the first conductive layer 21 and the second conductive layer 22 as the main electrode, the protective layer 23 only wraps the first conductive layer 21 or the second conductive layer 22, which can effectively prevent the performance of the IDT 20 from deteriorating compared to the method of providing the protective layer 23 to completely cover the main electrode.

[0052] In this embodiment, the elastic wave device 1 can be a surface acoustic wave resonator having an interdigital transducer 20, or a filter or other equipment having one or more interdigital transducers 20, which is not specifically limited here. In combination with the relevant technology, the interdigital transducer 20 in this embodiment can include two parallel bus bars (not shown in the figure), and at least two interdigital electrodes (not shown in the figure) are arranged between the two bus bars, and specifically can be two or more, a part of the interdigital electrodes is connected to one bus bar, and another part of the interdigital electrodes is connected to another bus bar, and the interdigital electrodes connected to different bus bars are arranged alternately and at intervals.

[0053] Combination Figure 1 and Figure 5 In some embodiments, the length L1 of the side surface of the protective layer 23 and the length L2 of the side surface of the target conductive layer 201 satisfy: L1 / L2 is 1.05 to 1.30, for example, L1 / L2 is 1.05 to 1.20.

[0054] It can be understood that if the length L1 of the side of the protective layer 23 is too long, for example, L1 is greater than 1.3 times L2, the protective layer 23 will affect the dominant effect of the first conductive layer 21 and the second conductive layer 22 as the main electrode, and will also enhance the sensitivity of the device and affect the excitation effect of the IDT 20 on the sound wave. In particular, when the target conductive layer 201 is the second conductive layer 22, when the length L1 of the side of the protective layer 23 is too long to cover the entire side of the first conductive layer 21, it will cause an increase in harmonics, thereby causing the acoustic performance of the IDT 20 to deteriorate. If the length L1 of the side of the protective layer 23 is too short, for example, L1 is less than 1.05 times L2, the stripping liquid is easy to penetrate and contact the target conductive layer 201 through the gap at the adjacent position of the protective layer 23 and the target conductive layer 201 and / or from the bottom surface edge of the target conductive layer 201 through capillary action, so that the protective layer 23 cannot play the role of protecting the target conductive layer 201, and the target conductive layer 23 cannot separate the target conductive layer 201 and the stripping liquid.

[0055] Therefore, setting L1 / L2 to 1.05-1.30 so that the length of the side of the protective layer 23 is appropriate can avoid the protective layer 23 from affecting the dominant effect of the main electrode (the first conductive layer 21 and the second conductive layer 22), avoid affecting the device sensitivity and reduce harmonics to improve the acoustic performance of the IDT 20, and effectively separate the target conductive layer 201 and the stripping liquid to avoid the first conductive layer 21 or the second conductive layer 22 from being corroded in the stripping liquid. At the same time, setting L1 / L2 to 1.05-1.30 can also reduce the weight of the protective layer 23 compared to the method of using the protective layer 23 to completely cover the main electrode (the first conductive layer 21 and the second conductive layer 22), so as to reduce the mass load on the target conductive layer 201, thereby reducing the weight of the IDT 20, which is conducive to the lightweight design of the IDT 20.

[0056] Preferably, L1 / L2 is 1.05-1.10, which can prevent the protective layer 23 from affecting the dominant effect of the first conductive layer 21 and the second conductive layer 22 as the main electrodes, improve the acoustic performance of the interdigital transducer 20, and prevent the first conductive layer 21 or the second conductive layer 22 from being corroded in the stripping solution.

[0057] like Figure 2 and Figure 5 As shown, in some embodiments, the protective layer 23 covers the upper surface of the second conductive layer 22 and extends toward the direction close to the piezoelectric substrate 10 to cover the side surfaces of the second conductive layer 22 and part of the side surfaces of the first conductive layer 21; the length of the side surfaces of the first conductive layer 21 is L3, and the length of the protective layer 23 extending from the edge of the upper surface of the first conductive layer 21 along the side surfaces of the first conductive layer 21 toward the direction close to the piezoelectric substrate 10 is L4, wherein L4 / L3≤15%.

[0058] In this embodiment, the target conductive layer 201 is the second conductive layer 22, and the length L1 of the side of the protective layer 23 is greater than the length of the side of the second conductive layer 22 (i.e., the length L2 of the side of the target conductive layer 201), so that the protective layer 23 covers the upper surface and side of the second conductive layer 22, and extends to cover part of the side of the first conductive layer 21, thereby preventing the stripping liquid from penetrating into the edge of the bottom surface of the second conductive layer 22, so as to prevent the first conductive layer 21 and the second conductive layer 22 from forming a galvanic cell structure in the stripping liquid, and further preventing the first conductive layer 21 or the second conductive layer 22 from being corroded by the stripping liquid under the catalysis of the electric current, thereby preventing damage to the interdigital transducer 20.

[0059] It can be understood that when the target conductive layer 201 is the second conductive layer 22, if the protective layer 23 covers most of the sides of the first conductive layer 21, or even covers all the sides of the first conductive layer 21, it will affect the dominant effect of the first conductive layer 21 and the second conductive layer 22 as the main electrodes, and will also enhance the sensitivity of the device and affect the excitation effect of the IDT 20 on sound waves. In particular, when the protective layer 23 covers all the sides of the first conductive layer 21, it will lead to an increase in harmonics, thereby causing the acoustic performance of the IDT 20 to deteriorate. Therefore, in order to solve the above problems, the present embodiment sets the length L3 of the side of the first conductive layer 21 and the length L4 of the side of the protective layer 23 covering the second conductive layer 22 to satisfy L4 / L3≤15%, for example, L4 / L3≤10%. This can not only effectively prevent the first conductive layer 21 and the second conductive layer 22 from forming a primary battery in the stripping solution, but also reduce to a certain extent the adverse effect on the IDT 20 caused by the excessive length of the side of the protective layer 23 covering the second conductive layer 22, thereby improving the acoustic performance of the IDT 20, but also reduce the weight of the protective layer 23, reduce the mass load on the target conductive layer 201, and reduce the weight of the IDT 20.

[0060] Preferably, L4 / L3≤7%, which can effectively prevent the first conductive layer 21 and the second conductive layer 22 from forming a primary cell in the stripping solution. Compared with setting the protective layer 23 to completely cover the first conductive layer 21 and the second conductive layer 22, it can effectively prevent the performance deterioration of the interdigital transducer 20, thereby improving the acoustic performance of the interdigital transducer 20.

[0061] like Figure 1 , Figure 3 and Figure 5As shown, in some embodiments, the potential difference between the standard electrode potential of the first metal element and the standard electrode potential of the second metal element is greater than 1.5 V. For example, the first metal element is copper and the second metal element is aluminum. In combination with the standard electrode potential table, it can be seen that under standard conditions (25.0°C, 101.325 kPa), relative to the standard hydrogen electrode, the standard electrode potential of copper is 0.52 V, and the standard electrode potential of aluminum is -1.65 V. At this time, the potential difference between copper and aluminum is 2.17 V. In this case, if the first conductive layer 21 having the first metal element and the second conductive layer 22 having the second metal element are in direct or indirect contact in the electrolyte, the first conductive layer 21 and the second conductive layer 22 will form a galvanic cell structure, causing the first conductive layer 21 or the second conductive layer 22 to be corroded under the catalysis of the current. Therefore, in this embodiment, a protective layer 23 is arranged on the first conductive layer 21, or a protective layer 23 is arranged on the second conductive layer 22, so that the protective layer 23 covers the upper surface and the side surface of one of the target conductive layers 201 of the first conductive layer 21 and the second conductive layer 22, and the length L1 of the side surface of the protective layer 23 is greater than the length L2 of the side surface of the target conductive layer 201, so that when the photoresist on the piezoelectric substrate 10 is stripped by a stripping process to obtain the IDT 20, the first conductive layer 21 and the second conductive layer 22 of the IDT 20 can be prevented from forming a galvanic cell structure in the stripping solution, thereby preventing the first conductive layer 21 or the second conductive layer 22 from being corroded in the stripping solution based on the galvanic cell effect, thereby avoiding damage to the IDT 20.

[0062] Combination Figure 4 In some embodiments, the sum of the thickness of the first conductive layer 21 and the thickness of the second conductive layer 22 is less than or equal to 700 nm. In this embodiment, the thickness of the first conductive layer 21 and the sum of the thickness of the second conductive layer 22 are designed as above, so that the first conductive layer 21 and the second conductive layer 22 can play a leading role as the main electrode.

[0063] Combination Figure 4 and Figure 5 In some embodiments, the thickness of the protective layer 23 is less than 9 nm, which can protect the target conductive layer 201 from being contacted by the stripping liquid and does not affect the dominant role of the main electrode (the first conductive layer 21 and the second conductive layer 22).

[0064] Combination Figure 4 and Figure 5In some embodiments, the thickness of the protective layer 23 is 2nm to 6nm. In the process of designing the thickness of the protective layer 23, on the basis of satisfying that the protective layer 23 isolates the target conductive layer 201 from the stripping liquid, the thinner the thickness of the protective layer 23 is, the more conducive it is for the first conductive layer 21 and the second conductive layer 22 to play a leading role. Therefore, in this embodiment, the thickness of the protective layer 23 is set to 2nm to 6nm, which can protect the target conductive layer 201 from being contacted by the stripping liquid, and does not affect the leading role of the main electrode (the first conductive layer 21 and the second conductive layer 22). It can also reduce the mass load on the target conductive layer 201, which is conducive to the lightweight design of the interdigital transducer 20.

[0065] Combination Figure 4 In some embodiments, the material of the first conductive layer 21 is aluminum, copper, magnesium, or a composite of the above metals or an alloy thereof.

[0066] In this embodiment, the first conductive layer 21 uses the above metal materials, and the first conductive layer 21 can be prepared on the piezoelectric substrate 10 by electron beam evaporation process.

[0067] Combination Figure 4 In some embodiments, the second conductive layer 22 is made of aluminum, copper, magnesium, or a composite of the above metals or an alloy thereof.

[0068] In this embodiment, the second conductive layer 22 is made of the above metal materials, and the second conductive layer 22 can be prepared on the piezoelectric substrate 10 by electron beam evaporation process.

[0069] It should be noted that, although the first conductive layer 21 and the second conductive layer 22 can be prepared by aluminum, copper, magnesium or a composite of the above metals or one of their alloys, at least one metal element is different in the first conductive layer 21 and the second conductive layer 22. For example, the first conductive layer 21 is made of copper and aluminum, and the second conductive layer 22 is made of copper and magnesium, or the first conductive layer 21 is made of copper, and the second conductive layer 22 is made of aluminum.

[0070] Combination Figure 3 and Figure 4 In some embodiments, the material of the protective layer 23 is titanium, molybdenum, platinum, gold, chromium or a composite of the above metals or one of their nitrides or oxides.

[0071] In this embodiment, the protective layer 23 can be made of a material that is not easily corroded, difficult to oxidize, has good chemical stability, and has a high reflectivity. For example, the material of the protective layer 23 is at least one of titanium, molybdenum, platinum, gold, chromium and other metals, or a nitride or oxide of any metal such as titanium, molybdenum, platinum, gold, chromium and other metals, or silicon nitride or silicon oxide, so that the prepared protective layer 23 is chemically stable, will not be corroded by the stripping solution, and is difficult to be oxidized by the stripping solution, so that the protective layer 23 can effectively isolate the target conductive layer 201 from contacting with the stripping solution, so as to avoid the first conductive layer 21 and the second conductive layer 22 from contacting in the stripping solution to form a galvanic cell structure, thereby avoiding the first conductive layer 21 or the second conductive layer 22 from being corroded by the stripping solution under the catalysis of the current, and avoiding the damage of the interdigital transducer 20. At the same time, compared with using the oxide or nitride of any metal among titanium, molybdenum, platinum, gold, chromium to prepare the protective layer 23, it is easier to prepare the protective layer 23 using any metal among titanium, molybdenum, platinum, gold, chromium or a composite material of any metal.

[0072] Combination Figure 4 In some embodiments, the material of the piezoelectric substrate 10 is lithium niobate or lithium tantalate. In this embodiment, the piezoelectric substrate 10 is a piezoelectric material having a piezoelectric effect. The piezoelectric substrate 10 can be mainly made of lithium niobate (LiNbO3) or lithium tantalate (LiTaO3), and the embodiment does not specifically limit this.

[0073] Combination Figure 4 In some embodiments, the piezoelectric substrate 10 may include a substrate (not shown) and a piezoelectric layer (not shown). Specifically, the material of the piezoelectric layer is mainly lithium niobate or lithium tantalate. The material of the piezoelectric layer uses a piezoelectric material with a piezoelectric effect. For example, the piezoelectric layer may be mainly made of lithium niobate (LiNbO3) or lithium tantalate (LiTaO3). The substrate may be made of silicon, quartz, sapphire, silicon carbide, etc. This embodiment does not impose specific restrictions on this.

[0074] Combination Figure 4 In some embodiments, the IDT 20 further includes an adhesion layer 24 , which is located between the first conductive layer 21 and the piezoelectric substrate 10 , and a thickness of the adhesion layer 24 is less than a thickness of at least one of the first conductive layer 21 and the second conductive layer 22 .

[0075] Combination Fig. 9 In the experiment, it was found that if the adhesion layer 24 is not provided between the piezoelectric substrate 10 and the first conductive layer 21, but the first conductive layer 21 is directly formed on the piezoelectric substrate 10, the first conductive layer 21 is easily deformed, thereby causing the performance of the interdigital transducer 20 to be unstable, thereby deteriorating the performance of the elastic wave device 1. Fig. 9As shown in the figure, no adhesion layer 24 is provided between the first conductive layer 21 and the piezoelectric substrate 10. It can be seen from the figure that the first conductive layer 21 is deformed. Therefore, in this embodiment, an adhesion layer 24 is provided between the first conductive layer 21 and the piezoelectric substrate 10, and the first conductive layer 21 is formed on the upper surface of the adhesion layer 24, which can improve the adhesion between the first conductive layer 21 and the piezoelectric substrate 10, improve the structural stability of the first conductive layer 21, thereby avoiding the deformation or even collapse of the first conductive layer 21, and further stabilize the structure with the first conductive layer 21 and the second conductive layer 22 as the main electrodes, improve the performance stability of the interdigital transducer 20, and improve the performance of the elastic wave device 1.

[0076] In this embodiment, the thickness of the first conductive layer 21 and the second conductive layer 22 can also be set to be greater than the thickness of the adhesion layer 24, or the thickness of the first conductive layer 21 or the second conductive layer 22 can be greater than the thickness of the adhesion layer 24, so that the overall thickness of the first conductive layer 21 and the second conductive layer 22 is greater than the thickness of the adhesion layer 24, thereby avoiding the adhesion layer 24 from affecting the dominant role of the first conductive layer 21 and the second conductive layer 22 as the main electrode.

[0077] Combination Figure 4 In some embodiments, the thickness of the first conductive layer 21 and the thickness of the second conductive layer 22 are both greater than the thickness of the adhesion layer 24, so that the first conductive layer 21 and the second conductive layer 22 can play a dominant role, and the total thickness of the first conductive layer 21 and the second conductive layer 22 is less than or equal to 700nm, which can prevent the adhesion layer 24 from affecting the dominant role of the first conductive layer 21 and the second conductive layer 22 as the main electrode.

[0078] Combination Figure 4 and Figure 5 In some embodiments, the thickness of the protective layer 23 is less than the thickness of the adhesion layer 24. For example, on the basis of satisfying that the protective layer 23 isolates the target conductive layer 201 and the stripping liquid, the thickness of the protective layer 23 is set within the range of 2nm to 4nm, so as to avoid the protective layer 23 affecting the dominant role of the main electrode (the first conductive layer 21 and the second conductive layer 22).

[0079] like Figure 4 As shown, in some embodiments, the angle formed between the side surface of the adhesion layer 24 and the bottom surface of the adhesion layer 24 is an acute angle, the angle formed between the side surface of the first conductive layer 21 and the bottom surface of the first conductive layer 21 is an acute angle, and the angle formed between the side surface of the second conductive layer 22 and the bottom surface of the second conductive layer 22 is an acute angle.

[0080] In this embodiment, the angle formed between the side surface of the adhesive layer 24 and the bottom surface of the adhesive layer 24 is set to be less than 90 degrees. Compared with setting the side surface of the adhesive layer 24 to be perpendicular to the bottom surface of the adhesive layer 24, the slope of the adhesive layer 24 can be reduced, the flatness of the adhesive layer 24 can be improved, and the adhesion between the first conductive layer 21 and the piezoelectric substrate 10 can be improved. In this embodiment, the angle formed between the side surface of the first conductive layer 21 and the bottom surface of the first conductive layer 21 is set to be an acute angle, and the angle formed between the side surface of the second conductive layer 22 and the bottom surface of the second conductive layer 22 is set to be an acute angle. Compared with setting the side surface of the target conductive layer 201 to be perpendicular to the bottom surface of the target conductive layer 201, the difficulty of the protective layer 23 covering the side surface of the target conductive layer 201 can be reduced, thereby facilitating the formation of the protective layer 23 on the target conductive layer 201.

[0081] like Figure 4 , Figure 5 and Figure 6 As shown, in some embodiments, the angle formed between the side surface of the adhesion layer 24 and the bottom surface of the adhesion layer 24 is β1, the angle formed between the side surface of the first conductive layer 21 and the bottom surface of the first conductive layer 21 is equal to the angle formed between the side surface of the second conductive layer 22 and the bottom surface of the second conductive layer 22, and both are β2, wherein β1<β2.

[0082] In this embodiment, the angle β2 formed between the side surface of the target conductive layer 201 and the bottom surface of the target conductive layer 201, and the angle β1 formed between the side surface of the adhesion layer 24 and the bottom surface of the adhesion layer 24, and β1 and β2 satisfy β1<β2, can further reduce the slope of the adhesion layer 24, improve the smoothness of the adhesion layer 24, improve the adhesion of the first conductive layer 21 and the piezoelectric substrate 10, improve the structural stability of the interdigital transducer 20, and can also better form the first conductive layer 21 and the second conductive layer 22, and prevent the first conductive layer 21 from forming a structure similar to the adhesion layer 24, avoid deteriorating the performance of the first conductive layer 21 and the second conductive layer 22 as the main electrodes, thereby improving the ability of the interdigital transducer 20 to withstand acoustic migration and improving the power tolerance of the elastic wave device 1. At the same time, an adhesion layer 24 is provided, and the angle β1 of the adhesion layer 24 is made smaller than the angle β2 of the first conductive layer 21 and the second conductive layer 22, so that in the process of preparing the elastic wave device 1, the angle β2 of the first conductive layer 21 can be kept consistent with the angle β2 of the second conductive layer 22, so that the electrode structure is more stable and the electrical performance is consistent.

[0083] Combination Figure 4 In some embodiments, the thickness of the adhesion layer 24 is 5 nm to 20 nm, which can not only improve the adhesion between the first conductive layer 21 and the piezoelectric substrate 10, but also avoid affecting the guiding function of the main electrode composed of the first conductive layer 21 and the second conductive layer 22.

[0084] Combination Figure 4 In some embodiments, the material of the adhesion layer 24 is titanium, nickel, chromium, zirconium, tantalum, tungsten or a composite of the above metals or an alloy thereof. In this embodiment, the adhesion layer 24 is made of a metal with a high melting point and a high Young's modulus, such as at least one of titanium, nickel, chromium, zirconium, tantalum, tungsten and the like, so that the adhesion layer 24 can remain stable and not easily melted in a high temperature environment, and has extremely high hardness and is difficult to deform, thereby helping the adhesion layer 24 to maintain a stable shape, so as to play an adhesion role and improve the adhesion between the first conductive layer 21 and the piezoelectric substrate 10.

[0085] like Figure 3 and Figure 5 As shown, in some embodiments, the protection layer 23 covers the upper surface of the first conductive layer 21 and extends along the side of the first conductive layer 21 toward the piezoelectric substrate 10 to cover at least part of the side of the first conductive layer 21 and the side of the adhesion layer 24 .

[0086] In this embodiment, the target conductive layer 201 is the first conductive layer 21, and the protective layer 23 covers the upper surface and the side of the first conductive layer 21, and the length L1 of the side of the protective layer 23 is greater than the length of the side of the first conductive layer 21 (i.e., the length L2 of the side of the target conductive layer 201), so that the protective layer 23 can also extend to cover the side of the adhesive layer 24 to prevent the stripping liquid from penetrating into the bottom end surface edge of the first conductive layer 21. Moreover, compared with the protective layer 23 only covering the side of the first conductive layer 21, the protective layer 23 covers the upper surface and the side of the first conductive layer 21, which can prevent the stripping liquid from penetrating into the gap at the connection between the first conductive layer 21 and the second conductive layer 22, and prevent the stripping liquid from penetrating into the gap between the side of the first conductive layer 21 and the protective layer 23, so as to prevent the first conductive layer 21 and the second conductive layer 22 from forming a primary battery structure in the stripping liquid, thereby preventing the first conductive layer 21 or the second conductive layer 22 from being corroded under the catalysis of the current, and avoiding damage to the interdigital transducer 20.

[0087] In this embodiment, the thickness of the adhesion layer 24 can be set within the range of 5nm to 20nm. The thickness of the adhesion layer 24 is relatively thin, and the effect on the performance of the first conductive layer 21 and the second conductive layer 22 is negligible. Therefore, even if the protective layer covers all sides of the adhesion layer 24, it does not affect the overall performance of the interdigital transducer 20. Therefore, in this embodiment, the protective layer 23 can be set to extend to cover part or all of the sides of the adhesion layer 24.

[0088] Combination Figure 5Furthermore, the length L1 of the side surface of the protective layer 23 and the length L2 of the side surface of the first conductive layer 21 satisfy L1 / L2 of 1.05 to 1.30, so that the length of the side surface of the protective layer 23 is appropriate, which can avoid the protective layer 23 affecting the dominant effect of the main electrode (the first conductive layer 21 and the second conductive layer 22), and avoid affecting the performance of the interdigital transducer due to improper setting of the length of the protective layer 23.

[0089] like Figure 4 and Figure 5 As shown, in some embodiments, the interdigitated electrode further includes a third conductive layer 25 , which is located between the first conductive layer 21 and the second conductive layer 22 , and the thickness of the third conductive layer 25 is less than the thickness of at least one of the first conductive layer 21 and the second conductive layer 22 .

[0090] In this embodiment, the target conductive layer 201 is the second conductive layer 22, and the third conductive layer 25 is disposed between the bottom surface of the first conductive layer 21 and the upper surface of the second conductive layer 22, which can improve the adhesion between the first conductive layer 21 and the second conductive layer 22, and can also make the grains of the second conductive layer 22 form more Al (111) grain orientation, thereby reducing the gaps between the grains in the second conductive layer 22, increasing the difficulty of grain migration in the second conductive layer 22, and improving the power tolerance of the elastic wave device 1. In this embodiment, the thickness of the first conductive layer 21 and the second conductive layer 22 can be set to be greater than the thickness of the third conductive layer 25, or the thickness of the first conductive layer 21 or the second conductive layer 22 is greater than the thickness of the third conductive layer 25, so as to achieve that the overall thickness of the first conductive layer 21 and the second conductive layer 22 is greater than the thickness of the third conductive layer 25, thereby avoiding the third conductive layer 25 from affecting the dominant role of the first conductive layer 21 and the second conductive layer 22 as the main electrode.

[0091] Combination Figure 4 In some embodiments, the thickness of the third conductive layer 25 is 5 nm to 20 nm, which can not only achieve the adhesion effect of the third conductive layer 25 and improve the adhesion between the first conductive layer 21 and the second conductive layer 22, but also avoid affecting the dominant role of the main electrode composed of the first conductive layer 21 and the second conductive layer 22, thereby reducing the impact on the performance of the elastic wave device 1.

[0092] Combination Figure 4 In some embodiments, the thickness of the first conductive layer 21 and the thickness of the second conductive layer 22 are both greater than the thickness of the third conductive layer 25, so that the first conductive layer 21 and the second conductive layer 22 can play a dominant role, and the total thickness of the first conductive layer 21 and the second conductive layer 22 is less than or equal to 700nm, which can avoid the third conductive layer 25 affecting the dominant role of the first conductive layer 21 and the second conductive layer 22 as the main electrode.

[0093] Combination Figure 4 and Figure 5 In some embodiments, the thickness of the protective layer 23 is less than the thickness of the third conductive layer 25. For example, on the basis of satisfying that the protective layer 23 isolates the target conductive layer 201 and the stripping liquid, the thickness of the protective layer 23 is set within the range of 2nm to 4nm. This can prevent the protective layer 23 from affecting the dominant role of the main electrode (the first conductive layer 21 and the second conductive layer 22).

[0094] Combination Figure 4 In some embodiments, the material of the third conductive layer 25 is titanium, nickel, chromium, zirconium, tantalum, tungsten or a composite of the above metals or one of their alloys. In this embodiment, the third conductive layer 25 can be made of a metal with a high melting point and a high Young's modulus, such as at least one of titanium, nickel, chromium, zirconium, tantalum, tungsten and the like, so that the third conductive layer 25 can remain stable and not easily melted in a high temperature environment, and has extremely high hardness and is difficult to deform, thereby helping the third conductive layer 25 to maintain a stable shape and play an adhesive role, so as to improve the adhesion between the first conductive layer 21 and the second conductive layer 22 when the target conductive layer 201 is the second conductive layer 22.

[0095] Combination Figure 1 , Figure 3 and Figure 5 As shown, an embodiment of the present application further provides a radio frequency front-end module (not shown), which includes the elastic wave device 1 in any of the above-mentioned embodiments.

[0096] The RF front-end module of this embodiment uses the elastic wave device 1 described above. When the photoresist on the piezoelectric substrate 10 is stripped by a stripping process to obtain the IDT 20, the target conductive layer 201 and the stripping solution are separated by the protective layer 23 to avoid contact between the target conductive layer 201 and the stripping solution, thereby preventing the first conductive layer 21 and the second conductive layer 22 of the IDT 20 from forming a galvanic cell structure in the stripping solution, thereby preventing the first conductive layer 21 or the second conductive layer 22 from being corroded due to the galvanic cell effect, and preventing damage to the IDT 20. At the same time, since the protective layer 23 covers the upper surface and side surfaces of the target conductive layer 201, the atoms in the target conductive layer 201 can be prevented from diffusing to the surroundings under high power, thereby suppressing the target conductive layer 201 from breaking under high power, thereby improving the power tolerance of the elastic wave device 1 and further improving the performance of the elastic wave device 1.

[0097] like Figure 1 , Figure 5 and Figure 7 As shown, the present application embodiment also provides a method for preparing an elastic wave device 1, which is used to prepare the elastic wave device 1 in any of the above embodiments, for example, to prepare Figure 1 or Figure 3The structure of the elastic wave device 1 is shown, wherein the method for preparing the elastic wave device 1 may include a first preparation method and a second preparation method.

[0098] like Figure 3 , Figure 8 and Fig.10 As shown, a first method for preparing the elastic wave device 1 includes:

[0099] S101, forming a photolithography pattern layer 2 having a hollow region 2A on a piezoelectric substrate 10, wherein the hollow region 2A exposes the piezoelectric substrate 10 to the photolithography pattern layer 2;

[0100] S102, forming a first conductive layer 21;

[0101] S103, forming a protective layer 23 on the first conductive layer 21 to cover the upper surface and side surfaces of the first conductive layer 21, wherein the length of the side surfaces of the protective layer 23 is greater than the length of the side surfaces of the first conductive layer 21;

[0102] S104, forming a second conductive layer 22 on the upper surface of the protective layer 23;

[0103] S105, removing the photolithography pattern layer 2 through a stripping process.

[0104] like Figure 1 , Figure 7 and Fig.10 As shown, the second method for preparing the elastic wave device 1 includes:

[0105] S201, forming a photolithography pattern layer 2 having a hollow region 2A on the piezoelectric substrate 10, wherein the hollow region 2A exposes the piezoelectric substrate 10 to the photolithography pattern layer 2;

[0106] S202, forming a first conductive layer 21;

[0107] S203, forming a second conductive layer 22 on the first conductive layer 21;

[0108] S204, forming a protective layer 23 on the second conductive layer 22 to cover the upper surface and side surfaces of the second conductive layer 22, wherein the length of the side surfaces of the protective layer 23 is greater than the length of the side surfaces of the second conductive layer 22;

[0109] S205, removing the photolithography pattern layer 2 through a stripping process.

[0110] In this embodiment, two structures of the elastic wave device 1 can be manufactured respectively by the above two manufacturing methods.

[0111] Among them, the first conductive layer 21 is located in the hollow area 2A and on the photolithography pattern layer 2, and the first conductive layer 21 includes a first metal element; the second conductive layer 22 includes a second metal element, and there is a potential difference between the standard electrode potential of the first metal element and the standard electrode potential of the second metal element; the length of the side of the protective layer 23 is the length of the protective layer 23 extending from the upper surface edge of the target conductive layer 201 along the side of the target conductive layer 201 toward the piezoelectric substrate 10; the length of the side of the target conductive layer 201 is the length from the upper surface edge of the target conductive layer 201 to the lower surface edge of the target conductive layer 201, and the target conductive layer 201 is the first conductive layer 21 or the second conductive layer 22.

[0112] In this embodiment, the preparation method first forms a hollow photolithography pattern layer 2 on the piezoelectric substrate 10 before preparing the interdigital transducer 20, which can accurately control the pattern shape of the interdigital transducer 20 prepared subsequently. Moreover, in the first preparation method, after preparing the first conductive layer 21 (step S102) and before forming the second conductive layer 22 (step S104), a protective layer 23 is formed on the first conductive layer 21, so that the protective layer 23 covers the upper surface and the side of the first conductive layer 21, and the length of the side of the protective layer 23 is greater than the length of the side of the first conductive layer 21; and, in the second preparation method, after preparing the second conductive layer 22 on the first conductive layer 21 (step S203), the photolithography pattern layer is removed by a stripping process. 2 (step S205), a protective layer 23 is formed on the second conductive layer 22, so that the protective layer 23 covers the upper surface and the side surface of the second conductive layer 22, and the length of the side surface of the protective layer 23 is greater than the length of the side surface of the second conductive layer 22; the above two preparation methods can separate the stripping liquid from the first conductive layer 21 and the second conductive layer 22 respectively through the protective layer 23 when the photolithography pattern layer 2 on the piezoelectric substrate 10 is subsequently stripped by a stripping process to obtain the interdigital transducer 20 respectively, so as to avoid the first conductive layer 21 and the second conductive layer 22 from forming a galvanic cell structure in the stripping liquid, thereby avoiding the first conductive layer 21 and the second conductive layer 22 from being corroded in the stripping liquid, avoiding damage to the interdigital transducer 20, and thereby improving the performance of the elastic wave device 1.

[0113] At the same time, in the elastic wave device 1 prepared by the above method, the protective layer 23 covers the upper surface and side surfaces of the target conductive layer 201, which can prevent the atoms in the target conductive layer 201 from diffusing around under high power, thereby suppressing the target conductive layer 201 from breaking under high power and improving the power tolerance of the elastic wave device 1.

[0114] Combination Figure 1 In some embodiments, the piezoelectric substrate 10 may be mainly made of lithium niobate (LiNbO 3 ) or lithium tantalate (LiTaO 3 ).

[0115] Combination Figure 5 In some embodiments, forming a protective layer 23 on the target conductive layer 201 includes: forming the protective layer 23 on the target conductive layer 201 at a first coating angle through an electron beam evaporation process to cover the upper surface and side surfaces of the target conductive layer 201, the first coating angle being the angle between the electron beam and the upper surface of the target conductive layer 201, and the first coating angle is not equal to 90°.

[0116] It can be known that the electron beam evaporation process can produce high-purity, high-quality thin films. Therefore, the present embodiment forms the protective layer 23 on the target conductive layer 201 through the electron beam evaporation process, which can improve the purity and quality of the formed protective layer 23. Setting the first coating angle to an acute angle or an obtuse angle is conducive to forming a partial side surface of the protective layer 23 on the side surface of the target conductive layer 201, so that the protective layer 23 can cover the upper surface and side surfaces of the target conductive layer 201.

[0117] Combination Figure 5 and Figure 7 In some embodiments, before forming the first conductive layer 21, the method further includes: placing the piezoelectric substrate 10 having the photolithography pattern layer 2 into a vacuum system; wherein, forming a protective layer 23 on the target conductive layer 201 at a first coating angle by an electron beam evaporation process to cover the upper surface and side surfaces of the target conductive layer 201, including: in the vacuum system, performing a first coating on the upper surface of the target conductive layer 201 by an electron beam evaporation process; thereafter, introducing an inert gas into the vacuum system to adjust the coating angle of the electron beam evaporation process to the first coating angle, and performing a second coating at the first coating angle; forming the protective layer 23 by the first coating and the second coating to cover the upper surface and side surfaces of the target conductive layer 201.

[0118] In this embodiment, under vacuum conditions, metal vapor deposition particles are first deposited on the upper surface of the target conductive layer 201 through an electron beam evaporation process to form a portion of the protective layer 23 on the upper surface of the target conductive layer 201 to complete the first coating. Then, an inert gas is introduced into the vacuum system to reduce the vacuum degree of the vacuum system and change the moving path and moving direction of the electron beam to adjust the coating angle of the electron beam evaporation process to the first coating angle. During the second coating, the metal vapor deposition particles are deposited on the target conductive layer 201 at the first coating angle throughout the entire process. During the second coating process, the metal vapor deposition particles can be completely deposited on the side of the target conductive layer 201, or a part of the metal vapor deposition particles can be deposited on the side of the target conductive layer 201 and the other part can be deposited on the upper surface of the target conductive layer 201. Therefore, the protective layer 23 formed after two coatings can cover the upper surface and the side of the target conductive layer 201. It should be noted that, compared with the thickness of the protective layer 23 after the two coatings, the thickness of the portion of the protective layer 23 located on the upper surface of the target conductive layer 201 is thinner when the first coating is completed, so that the metal vapor-deposited particles can also be deposited on the upper surface of the target conductive layer 201 during the subsequent second coating, without causing the thickness of the portion of the protective layer 23 located on the upper surface of the target conductive layer 201 to be too thick, and the difficulty of forming the protective layer 23 can also be reduced. In the first coating, the coating angle of the electron beam evaporation process is 90 degrees, that is, the electron beam of the electron beam evaporation process is perpendicular to the upper surface of the target conductive layer 201, so that the metal vapor-deposited particles are deposited on the upper surface of the target conductive layer 201 in a direction perpendicular to the upper surface of the target conductive layer 201.

[0119] In this embodiment, the protective layer 23 is formed on the target conductive layer 201 by electron beam evaporation process under vacuum conditions, which can ensure the high purity and high quality of the protective layer 23 to a certain extent and avoid the addition of other impurities into the protective layer 23. In a specific embodiment, when preparing the protective layer 23, an inert gas such as argon (Ar) can be introduced into the vacuum system to reduce the vacuum degree of the vacuum system, so as to adjust the coating angle of the electron beam evaporation process to a first coating angle, so that the evaporated particles of the electron beam evaporation process can adhere to the upper surface and side surfaces of the target conductive layer 201, and the protective layer 23 formed can cover the upper surface and side surfaces of the target conductive layer 201. The first coating angle can be an acute angle or an obtuse angle.

[0120] Combination Figure 5 In some embodiments, the preparation method further includes: when the inert gas is introduced into the vacuum system, adjusting the time of the inert gas and / or the flow rate of the inert gas to adjust the length of the side of the protective layer 23.

[0121] In this embodiment, the length of the side of the protective layer 23 can be adjusted by adjusting the time of the inert gas introduced into the vacuum system, or by adjusting the flow rate of the inert gas introduced into the vacuum system, or by adjusting the time and flow rate of the inert gas introduced into the vacuum system at the same time, so as to adjust the length of the side of the protective layer 23 to be greater than the length of the side of the target conductive layer 201. In specific applications, the length of the side of the protective layer 23 can be increased by extending the time of the inert gas introduced into the vacuum system and / or reducing the flow rate of the inert gas.

[0122] For example, in the process of forming the target conductive layer 201 by electron beam evaporation process under vacuum conditions, the deposition rate is Preferably, the coating rate is After the target conductive layer 201 is formed, the metal vapor deposition particles are continuously deposited on the upper surface of the target conductive layer 201 at the deposition rate for 1-3 seconds, and then an inert gas such as argon (Ar) is slowly introduced into the vacuum system to reduce the vacuum degree of the vacuum system to 0.5×10 -9 pa, thereby adjusting the coating angle to the first coating angle, changing the film-forming route of the metal evaporation particles, and reducing the coating rate to In this case, the metal vapor deposition particles will be deposited on the side of the target conductive layer 201 in a circuitous manner. In this process, more metal vapor deposition particles can be deposited on the side of the target conductive layer 201 by changing the flow rate of inert gas such as argon (i.e., the vacuum drop rate of the vacuum system). For example, when the flow rate of argon is 2 sccm (standard cubic meters per minute), the vacuum degree of the vacuum system is reduced to 0.5×10 -9 The time required for the formation of the protective layer 23 is 10 s, and the length of the side surface of the protective layer 23 is L1a. When the flow rate of argon gas is reduced to 1 sccm, the vacuum degree of the vacuum system is reduced to 0.5×10 -9 The time required for pa is 20S, and the length of the side of the protective layer 23 formed is L1b. The L1a and L1b formed above respectively satisfy that L1b is greater than L1a, for example, L1b / L1a=2, that is, the length of the side of the protective layer 23 is extended by increasing the time of introduction of the inert gas.

[0123] Combination Figure 4 and Figure 7 In some embodiments, before forming the first conductive layer 21, the preparation method further includes: forming an adhesion layer 24, the adhesion layer 24 being located on the piezoelectric substrate 10 in the hollow area 2A and on the photolithography pattern layer 2; wherein the first conductive layer 21 is located on a side of the adhesion layer 24 that is away from the piezoelectric substrate 10.

[0124] In the process of preparing the elastic wave device 1, it was found that if the first conductive layer 21 is directly formed on the piezoelectric substrate 10, the first conductive layer 21 is easily deformed, for example Fig. 9 As shown in the figure, the adhesion layer 24 is not prepared before forming the first conductive layer 21, and it can be seen that the first conductive layer 21 in the figure is deformed. Therefore, in this embodiment, the adhesion layer 24 is first formed on the piezoelectric substrate 10, and then the first conductive layer 21 is formed on the upper surface of the adhesion layer 24. The adhesion layer 24 can improve the adhesion between the first conductive layer 21 and the piezoelectric substrate 10, thereby improving the structural stability of the first conductive layer 21 formed on the upper surface of the adhesion layer 24 to avoid deformation and collapse of the first conductive layer 21, thereby improving the performance stability of the interdigital transducer 20 and improving the performance of the elastic wave device 1.

[0125] It can be known that when metal vapor deposition particles are deposited on the piezoelectric substrate 10 by electron beam evaporation process to form the adhesion layer 24, the metal vapor deposition particles have a large energy and are easy to deform the photolithography pattern layer 2 on the piezoelectric substrate 10. Figure 8 Specifically, the angle α between the upper surface of the photolithography pattern layer 2 and the side surface of the photolithography pattern layer 2 will become larger. However, after the adhesion layer 24 is formed, when the metal vapor deposition particles are continuously deposited on the piezoelectric substrate 10 by the electron beam evaporation process, the angle α between the upper surface of the photolithography pattern layer 2 and the side surface of the photolithography pattern layer 2 will not change. It can be seen that the formation of the adhesion layer 24 before the first conductive layer 21 also helps to prevent the photolithography pattern layer 2 from being deformed when the first conductive layer 21, the second conductive layer 22, etc. are subsequently formed by the electron beam evaporation process, and can also prevent the first conductive layer 21, the second conductive layer 22, etc. from being deformed or even collapsed from the side, thereby improving the structural stability of the interdigital transducer 20.

[0126] Combination Figure 7 In some embodiments, forming the first conductive layer 21 includes: forming the first conductive layer 21 on the upper surface of the adhesion layer 24 at a second coating angle by electron beam evaporation process, so that the first conductive layer 21 is located on the side of the adhesion layer 24 away from the piezoelectric substrate 10, the second coating angle is the angle between the electron beam and the upper surface of the adhesion layer 24, and the second coating angle is equal to 90°. In some embodiments, the adhesion layer 24 can be made of a metal with a high melting point and a high Young's modulus, for example, at least one of titanium, nickel, chromium, zirconium, tantalum, tungsten and the like, so that the adhesion layer 24 can remain stable and not easily melted and deformed in a high temperature environment, thereby helping the adhesion layer 24 to maintain a stable shape and facilitating the formation of a first conductive layer 21 with a stable structure on the adhesion layer 24.

[0127] Combination Figure 3In some embodiments, after the first conductive layer 21 is formed, metal vapor-deposited particles may continue to be vertically deposited on the upper surface of the first conductive layer 21 at a second coating angle, and then an inert gas may be introduced into the vacuum system to adjust the second coating angle to the first coating angle. In addition, during the process of forming the protective layer 23 on the first conductive layer 21, an inert gas may continue to be introduced into the vacuum system to maintain the coating angle of the electron beam evaporation process at the first coating angle, so that the metal vapor-deposited particles may be deposited on the upper surface and side surfaces of the first conductive layer 21 and at least part of the side surfaces of the adhesion layer 24 at the first coating angle by the electron beam evaporation process, thereby forming the protective layer 23. Further, after the protective layer 23 is formed on the first conductive layer 21, the inert gas may be extracted from the vacuum system to adjust the first coating angle to the second coating angle, so that the incident direction of the electron beam is perpendicular to the upper surface of the protective layer 23, so that the metal vapor-deposited particles may be deposited on the upper surface of the protective layer 23 at the second coating angle by the electron beam evaporation process, thereby forming the second conductive layer 22.

[0128] Combination Figure 2 In other embodiments, after forming the first conductive layer 21 and before forming the second conductive layer 22 on the first conductive layer 21, the second conductive layer 22 may be formed on the upper surface of the first conductive layer 21 at a second coating angle by electron beam evaporation, so that the second conductive layer 22 is located on the side of the first conductive layer 21 away from the piezoelectric substrate 10. Further, after forming the second conductive layer 22 on the first conductive layer 21, metal evaporation particles may be vertically deposited on the upper surface of the second conductive layer 22 at the second coating angle, and then an inert gas may be introduced into the vacuum system to adjust the second coating angle to the first coating angle. In addition, during the process of forming the protective layer 23 on the second conductive layer 22, an inert gas may be introduced into the vacuum system to keep the coating angle of the electron beam evaporation process at the first coating angle, so that the metal evaporation particles may be deposited on the upper surface and side surface of the second conductive layer 22 and part of the side surface of the first conductive layer 21 at the first coating angle by electron beam evaporation, thereby forming the protective layer 23.

[0129] Combination Figure 4 In some embodiments, after forming the first conductive layer 21 and before forming the second conductive layer 22 on the first conductive layer 21, the method further includes: forming a third conductive layer 25 on the first conductive layer 21, the thickness of the third conductive layer 25 being less than the thickness of at least one of the first conductive layer 21 and the second conductive layer 22.

[0130] In this embodiment, a third conductive layer 25 is formed between the upper surface of the first conductive layer 21 and the bottom surface of the second conductive layer 22. The third conductive layer 25 can play an adhesion role, can improve the adhesion between the first conductive layer 21 and the second conductive layer 22, and can also make the grains of the second conductive layer 22 form more Al (111) grain orientation, thereby reducing the gaps between the grains in the second conductive layer 22, increasing the difficulty of grain migration in the second conductive layer 22, and improving the power tolerance of the elastic wave device 1. At the same time, the thickness of the first conductive layer 21 and the second conductive layer 22 is greater than the thickness of the third conductive layer 25, or the thickness of the first conductive layer 21 or the second conductive layer 22 is greater than the thickness of the third conductive layer 25, which can make the overall thickness of the first conductive layer 21 and the second conductive layer 22 greater than the thickness of the third conductive layer 25, thereby avoiding the third conductive layer 25 from affecting the dominant role of the first conductive layer 21 and the second conductive layer 22 as the main electrode.

[0131] In some embodiments, the third conductive layer 25 can be prepared from a metal with a high melting point and a high Young's modulus, such as at least one of titanium, nickel, chromium, zirconium, tantalum, tungsten and the like, so that the third conductive layer 25 can remain stable and not easily melted in a high temperature environment, and has extremely high hardness and is difficult to deform, thereby helping the third conductive layer 25 to maintain a stable shape and exert an adhesion effect, so as to improve the adhesion between the first conductive layer 21 and the second conductive layer 22 when the target conductive layer 201 is the second conductive layer 22.

[0132] Combination Figure 7 In some embodiments, the stripping solution used in the stripping process is N-methylpyrrolidone solution (NMP solution) or acetone solution, which can strip the photolithography pattern layer 2 on the piezoelectric substrate 10.

[0133] It can be known that the photolithography pattern layer 2 has a hollow area 2A, so when preparing the interdigital transducer 20, a layered film structure (including a first conductive layer 21, a second conductive layer 22 and a protective layer 23) will be formed on the piezoelectric substrate 10 located in the hollow area 2A and on the photolithography pattern layer 2. In this embodiment, when the photolithography pattern layer 2 is peeled off by a peeling process, the elastic wave device 1 and the photolithography pattern layer 2 are both in contact with a peeling liquid, and the photolithography pattern layer 2 and the layered film structure on the photolithography pattern layer 2 will be peeled off by the peeling liquid and fall off the piezoelectric substrate 10, while the layered film structure (interdigital transducer 20) in the hollow area 2A remains on the piezoelectric substrate 10, and finally the elastic wave device 1 is prepared. During this process, the protective layer 23 isolates the stripping liquid from contacting the first conductive layer 21 or the second conductive layer 22 to prevent the first conductive layer 21 and the second conductive layer 22 from forming a galvanic cell structure in the stripping liquid, thereby preventing the first conductive layer 21 or the second conductive layer 22 from being corroded and causing damage to the interdigital transducer 20, thereby improving the performance of the elastic wave device 1.

[0134] like Figure 1 and Figure 3 As shown, in some embodiments, after the photolithography pattern layer 2 on the piezoelectric substrate 10 is stripped off by a stripping process, the preparation method further includes: placing the piezoelectric substrate 10 formed with the interdigital transducer 20 in a plasma atmosphere to remove the residual photoresist on the interdigital transducer 20. In this case, since the protective layer 23 covers the upper surface and side surfaces of the first conductive layer 21 or the second conductive layer 22, the degree of damage to the side walls of the first conductive layer 21 and the second conductive layer 22 as the main electrodes can be reduced.

[0135] like Figure 8 As shown, in some embodiments, a layer of photoresist (i.e., photoresist) may be coated on the piezoelectric substrate 10, and the photoresist layer may be soft-baked, exposed, and developed to form a photolithography pattern layer 2 having a hollow region 2A. The photolithography pattern layer 2 is in the shape of an inverted trapezoid, which can be fully contacted with a stripping liquid in the subsequent process, so as to facilitate the stripping of the photoresist on the piezoelectric substrate 10. Specifically, the hollow region 2A may include at least two hollow sub-regions, and the at least two hollow sub-regions are arranged along a first direction (e.g., Figure 8 x direction as shown) are arranged at intervals, combined with Figure 8 The angle α between the upper surface of the photolithography pattern layer 2 and the side surface of the photolithography pattern layer 2 is an acute angle, so that along the second direction, the cross-sectional shape of the photolithography pattern layer 2 is an inverted trapezoid, and the first direction is perpendicular to the second direction.

[0136] The above description is only a preferred embodiment of the present application, and does not limit the patent scope of the present application. All equivalent structural changes made by using the contents of the present application specification and drawings under the application concept of the present application, or directly / indirectly used in other related technical fields are included in the patent protection scope of the present application.

Claims

1. An elastic wave device, characterized in that: include: A piezoelectric substrate and at least one interdigital transducer disposed on the piezoelectric substrate, wherein the interdigital transducer comprises: A first conductive layer including a first metal element; A second conductive layer, comprising a second metal element, a potential difference exists between a standard electrode potential of the first metal element and a standard electrode potential of the second metal element, and the first conductive layer is located between the second conductive layer and the piezoelectric substrate; a protective layer, which is disposed on the upper surface of the target conductive layer and extends toward the direction close to the piezoelectric substrate to cover the side surface of the target conductive layer, wherein the protective layer extends from the edge of the upper surface of the target conductive layer along the side surface of the target conductive layer toward the direction close to the piezoelectric substrate by a length L1, and the length of the side surface of the target conductive layer is L2, and L1 is greater than L2; The target conductive layer is the first conductive layer or the second conductive layer, and the length of the side surface of the target conductive layer is the length from the upper surface edge of the target conductive layer to the lower surface edge of the target conductive layer.

2. The elastic wave device according to claim 1, wherein: L1 / L2 is 1.05~1.

30.

3. The elastic wave device according to claim 2, wherein: The L1 / L2 is 1.05 to 1.

10.

4. The elastic wave device according to claim 1, wherein: The protective layer covers the upper surface of the second conductive layer and extends toward the piezoelectric substrate to cover the side surface of the second conductive layer and part of the side surface of the first conductive layer; The length of the side surface of the first conductive layer is L3, and the length of the protective layer extending from the upper surface edge of the first conductive layer along the side surface of the first conductive layer toward the piezoelectric substrate is L4, wherein L4 / L3≤15%.

5. The elastic wave device according to claim 4, wherein: The L4 / L3≤7%.

6. The elastic wave device according to claim 1, wherein: A potential difference between a standard electrode potential of the first metal element and a standard electrode potential of the second metal element is greater than 1.5V.

7. The elastic wave device according to claim 1, wherein: The sum of the thickness of the first conductive layer and the thickness of the second conductive layer is less than or equal to 700 nm.

8. The elastic wave device according to claim 1, wherein: The thickness of the protective layer is less than 9 nm.

9. The elastic wave device according to claim 8, wherein: The thickness of the protective layer is 2nm-6nm.

10. The elastic wave device according to claim 1, wherein: Include at least one of the following characteristics: The material of the first conductive layer is aluminum, copper, magnesium or a composite of the above metals or an alloy thereof; The material of the second conductive layer is one of aluminum, copper, magnesium or a composite of the above metals or an alloy thereof; The material of the protective layer is titanium, molybdenum, platinum, gold, chromium or a composite of the above metals or one of their nitrides or oxides; The material of the piezoelectric substrate is lithium niobate or lithium tantalate.

11. The elastic wave device according to claim 1, wherein: The IDT further includes an adhesion layer, the adhesion layer being located between the first conductive layer and the piezoelectric substrate, and the thickness of the adhesion layer being smaller than the thickness of at least one of the first conductive layer and the second conductive layer.

12. The elastic wave device according to claim 11, wherein: The angle formed between the side surface of the adhesion layer and the bottom surface of the adhesion layer is an acute angle, the angle formed between the side surface of the first conductive layer and the bottom surface of the first conductive layer is an acute angle, and the angle formed between the side surface of the second conductive layer and the bottom surface of the second conductive layer is an acute angle.

13. The elastic wave device according to claim 12, wherein: The angle formed between the side surface of the adhesion layer and the bottom surface of the adhesion layer is β1, the angle formed between the side surface of the first conductive layer and the bottom surface of the first conductive layer is equal to the angle formed between the side surface of the second conductive layer and the bottom surface of the second conductive layer, and both are β2, wherein β1<β2.

14. The elastic wave device according to claim 11, wherein: The thickness of the adhesion layer is 5nm to 20nm; and / or, The material of the adhesion layer is titanium, nickel, chromium, zirconium, tantalum, tungsten or a composite of the above metals or an alloy thereof.

15. The elastic wave device according to claim 11, wherein: The protection layer covers the upper surface of the first conductive layer and extends along the side surface of the first conductive layer toward the piezoelectric substrate to cover at least part of the side surface of the first conductive layer and the side surface of the adhesion layer.

16. The elastic wave device according to claim 1, wherein: The interdigitated electrode further includes a third conductive layer, the third conductive layer is located between the first conductive layer and the second conductive layer, and the thickness of the third conductive layer is smaller than the thickness of at least one of the first conductive layer and the second conductive layer.

17. The elastic wave device according to claim 16, wherein: The thickness of the third conductive layer is 5 nm to 20 nm; and / or, The material of the third conductive layer is titanium, nickel, chromium, zirconium, tantalum, tungsten or a composite of the above metals or an alloy thereof.

18. A radio frequency front-end module, characterized in that: Comprising the elastic wave device according to any one of claims 1-17.

19. A method for preparing an elastic wave device, for preparing the elastic wave device according to any one of claims 1 to 17, characterized in that: The preparation method comprises: forming a photolithography pattern layer having a hollow region on the piezoelectric substrate, wherein the hollow region exposes the piezoelectric substrate to the photolithography pattern layer; forming a first conductive layer, wherein the first conductive layer is located in the hollow region and on the photolithography pattern layer, and the first conductive layer includes a first metal element; forming a second conductive layer on the first conductive layer, wherein the second conductive layer includes a second metal element, and there is a potential difference between a standard electrode potential of the first metal element and a standard electrode potential of the second metal element; removing the photolithography pattern layer by a lift-off process; After forming the first conductive layer, or after forming the second conductive layer on the first conductive layer and before removing the photolithography pattern layer by a stripping process, the method further includes: forming a protective layer on a target conductive layer to cover an upper surface and a side surface of the target conductive layer, wherein the target conductive layer is the first conductive layer or the second conductive layer, and a length of a side surface of the protective layer is greater than a length of a side surface of the target conductive layer; Among them, the length of the side surface of the protective layer is the length of the protective layer extending from the upper surface edge of the target conductive layer along the side surface of the target conductive layer toward the direction close to the piezoelectric substrate; the length of the side surface of the target conductive layer is the length from the upper surface edge of the target conductive layer to the lower surface edge of the target conductive layer.

20. The method for preparing an elastic wave device according to claim 19, characterized in that: The step of forming a protective layer on the target conductive layer comprises: The protective layer is formed on the target conductive layer at a first coating angle through an electron beam evaporation process to cover the upper surface and side surfaces of the target conductive layer. The first coating angle is the angle between the electron beam and the upper surface of the target conductive layer, and the first coating angle is not equal to 90°.

21. The method for preparing an elastic wave device according to claim 20, characterized in that: Before forming the first conductive layer, the method further comprises: placing the piezoelectric substrate having the photolithography pattern layer into a vacuum system; The step of forming the protective layer on the target conductive layer at a first coating angle by an electron beam evaporation process to cover the upper surface and side surfaces of the target conductive layer comprises: In the vacuum system, a first coating is performed on the upper surface of the target conductive layer by an electron beam evaporation process; Introducing an inert gas into the vacuum system to adjust the coating angle of the electron beam evaporation process to a first coating angle, and performing a second coating at the first coating angle; The protective layer is formed by the first plating and the second plating to cover the upper surface and the side surface of the target conductive layer.

22. The method for preparing an elastic wave device according to claim 21, characterized in that: The method further comprises: The time of the inert gas and / or the flow rate of the inert gas is adjusted to adjust the length of the side surface of the protective layer.

23. The method for preparing an elastic wave device according to claim 19, wherein: Before forming the first conductive layer, the method further comprises: forming an adhesion layer, wherein the adhesion layer is located on the piezoelectric substrate in the hollowed-out area and on the photolithography pattern layer; The first conductive layer is located on a side of the adhesion layer facing away from the piezoelectric substrate.

24. The method for preparing an elastic wave device according to claim 19, wherein: After forming the first conductive layer and before forming the second conductive layer on the first conductive layer, the method further includes: A third conductive layer is formed on the first conductive layer, wherein a thickness of the third conductive layer is smaller than a thickness of at least one of the first conductive layer and the second conductive layer.

25. The method for preparing an elastic wave device according to claim 19, wherein: The stripping solution used in the stripping process is N-methylpyrrolidone solution or acetone solution.

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