Preparation method of surface acoustic wave device, surface acoustic wave device and radio frequency front-end module

Abstract

The invention discloses a preparation method of a surface acoustic wave device, the surface acoustic wave device and a radio frequency front-end module, and relates to the technical field of radio frequency filtering. The method comprises the following steps: forming a first photoresist layer with an interdigital transducer region and a gap region on a piezoelectric substrate; forming a metal thin film, wherein the metal thin film comprises a first thin film part located in the first hollow area and a second thin film part located in the first photoresist layer; a second photoresist layer is formed on the metal thin film, the second photoresist layer is provided with a plurality of second hollow-out areas arranged at intervals, and the second hollow-out areas at least enable the first thin film part located in the gap area to be exposed to the second photoresist layer; removing the part, located in the second hollow area, of the first film to form an interdigital transducer; and removing the first photoresist layer, the second photoresist layer and the second thin film part. According to the invention, the shape and the width of the prepared IDT metal electrode are not changed abnormally, so that the performance and the production and manufacturing yield of the surface acoustic wave device are improved.

Description

Technical Field

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

[0002] Surface acoustic wave (SAW) devices, such as surface acoustic wave resonators, are passive electronic components that use the transmission and reflection of surface acoustic waves on the surface of a chip to achieve functions such as acoustic filtering and frequency control. Surface acoustic wave devices usually include a piezoelectric substrate and an interdigital transducer (IDT). The IDT is formed on the piezoelectric substrate and can be used to convert electrical signals into acoustic signals or convert acoustic signals into electrical signals.

[0003] At present, the preparation of IDT metal electrodes with high electrode width (CD) uniformity on piezoelectric substrates is extremely important for the performance and manufacturing yield of surface acoustic wave devices. However, due to the influence of the optical proximity effect, the shape and width of the IDT metal electrodes will change abnormally, resulting in poor performance of surface acoustic wave devices and low manufacturing yield. Summary of the invention

[0004] The present application provides a method for preparing a surface acoustic wave device, a surface acoustic wave device and a radio frequency front-end module, which can ensure that the shape and width of the prepared IDT metal electrode will not undergo abnormal changes, thereby improving the performance and production yield of the surface acoustic wave device.

[0005] In a first aspect, the present application provides a method for preparing a surface acoustic wave device, the method comprising:

[0006] Forming a first photoresist layer on a piezoelectric substrate, wherein the first photoresist layer has a first hollow region, wherein the first hollow region exposes the piezoelectric substrate to the first photoresist layer, wherein the first hollow region includes an IDT region and a gap region connected to the IDT region;

[0007] forming a metal film, wherein the metal film includes a first film portion located in the first hollowed-out area and a second film portion located in the first photoresist layer;

[0008] Forming a second photoresist layer on the metal film, wherein the second photoresist layer has a plurality of second hollow regions arranged at intervals, and the second hollow regions at least expose the first film portion located in the gap region to the second photoresist layer;

[0009] removing the first film portion located in the second hollow area to form an interdigital transducer;

[0010] The first photoresist layer, the second photoresist layer, and the second thin film portion are removed.

[0011] In a second aspect, the present application provides a surface acoustic wave device, wherein the surface acoustic wave device is prepared by using the above-mentioned preparation method, wherein the surface acoustic wave device comprises an interdigital transducer, and the interdigital transducer comprises:

[0012] Two comb-shaped electrodes are arranged opposite to each other, each of the comb-shaped electrodes includes a bus bar and a plurality of electrode fingers connected to the bus bar and arranged at intervals, and the electrode fingers of the two comb-shaped electrodes are arranged alternately with each other; in the extension direction of the electrode fingers, there is an overlapping area between the two bus bars, and the overlapping area is an area where the projections of the electrode fingers overlap with each other, and a gap area is included between the overlapping area and the bus bar, and the gap area is adjacent to the overlapping area.

[0013] In a third aspect, the present application provides a surface acoustic wave device, the surface acoustic wave device comprising an interdigital transducer, the interdigital transducer comprising two comb electrodes and a dummy finger arranged opposite to each other;

[0014] Each of the comb-shaped electrodes comprises a bus bar and a plurality of electrode fingers connected to the bus bar and arranged at intervals, and the electrode fingers of two comb-shaped electrodes are arranged alternately with each other; in the extension direction of the electrode fingers, there is an overlapping area between the two bus bars, and the overlapping area is the area where the electrode fingers overlap with each other, and there is a gap area between the overlapping area and the bus bar, and the overlapping area comprises a middle area and edge areas located on both sides of the middle area in the extension direction of the electrode fingers;

[0015] The first end of the dummy finger is connected to the bus bar, the second end of the dummy finger is spaced apart from the opposite electrode finger, and the gap region is formed between the second end of the dummy finger and the overlapping region;

[0016] The electrode fingers located in the edge region are in a rectangular shape, and the dummy fingers are in a rectangular shape.

[0017] The present application provides a method for preparing a surface acoustic wave device, a surface acoustic wave device and a radio frequency front-end module. The method comprises forming a first photoresist layer having a first hollow region on a piezoelectric substrate, wherein the first hollow region includes an interdigital transducer region and a gap region connected to the interdigital transducer region; forming a metal film, the metal film including a first film portion located in the first hollow region and a second film portion located in the first photoresist layer; forming a second photoresist layer having a plurality of second hollow regions arranged at intervals on the metal film; removing the first film portion located in the second hollow region to form an interdigital transducer; and removing the first photoresist layer, the second photoresist layer and the second film portion. Therefore, a second photoresist layer having a plurality of second hollow regions spaced apart can be directly formed on the metal film, so that when the first film portion of the second hollow region is removed, the first photoresist layer can be used to protect the piezoelectric substrate, thereby effectively avoiding damage to the piezoelectric substrate during the process of removing the first film portion of the second hollow region. At the same time, it can also ensure that the shape and width of the prepared IDT metal electrode will not undergo abnormal changes due to the optical proximity effect, thereby improving the performance and production yield of the surface acoustic wave device, and can be applicable to piezoelectric substrates of any material, with a wide range of application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 It is a structural schematic diagram of an acoustic surface device provided by the related technology;

[0020] Figure 2 It is a structural schematic diagram of another acoustic surface device provided by the related technology;

[0021] Figure 3 It is a schematic flow chart of the steps of a method for preparing a surface acoustic wave device provided in an embodiment of the present application;

[0022] Figure 4 is a schematic diagram of a top view structure of a first photoresist layer provided in an embodiment of the present application;

[0023] Figure 5 is a schematic diagram of a top view structure of another first photoresist layer provided in an embodiment of the present application;

[0024] Figure 6 yes Figure 4 Schematic diagram of the cross-sectional structure along the aa direction;

[0025] Figure 7 is a schematic diagram of a top view structure of another first photoresist layer provided in an embodiment of the present application;

[0026] Figure 8 is a schematic diagram of a top view structure of a metal film provided in an embodiment of the present application;

[0027] Fig. 9 yes Figure 8 A schematic diagram of the cross-sectional structure along the bb direction;

[0028] FIG. 10( a ) is a schematic diagram of a top view of a second photoresist layer provided in an embodiment of the present application;

[0029] FIG10( b ) is a partial enlarged view of the E region in FIG10( a );

[0030] Fig.11 is a schematic cross-sectional view of the structure along the cc direction in FIG. 10( a );

[0031] Fig.12 is a schematic cross-sectional structural diagram along the dd direction in FIG10( a );

[0032] Fig.13 is a schematic diagram of a top view structure of another second photoresist layer provided in an embodiment of the present application;

[0033] Fig.14 yes Fig.13 Schematic diagram of the cross-sectional structure along the ee direction;

[0034] Fig.15 is a schematic structural diagram of a surface acoustic wave device provided in an embodiment of the present application;

[0035] Fig.16 is a schematic structural diagram of another acoustic wave surface device provided in an embodiment of the present application;

[0036] Fig.17 It is a schematic structural diagram of another acoustic wave surface device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0037] 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 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.

[0038] The flowcharts shown in the accompanying drawings are only examples and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps may also be decomposed, combined or partially merged, so the actual execution order may change according to actual conditions.

[0039] It should be understood that the terms used in this application specification are only for the purpose of describing specific embodiments and are not intended to limit the application. As used in this application specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0040] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0041] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0042] In the related art, the metal electrode of the interdigital transducer (IDT) of the surface acoustic wave device is usually formed by a stripping process or an etching process. The preparation of IDT by the stripping process generally first forms an IDT photoresist pattern by a photolithography process on the piezoelectric substrate, then plates a metal film, and then strips the photoresist and the metal film on the photoresist by an organic solvent, and finally obtains the IDT metal electrode. The process of preparing IDT by the etching process generally involves first plating a metal film on the piezoelectric substrate, then forming an IDT photoresist pattern on the metal film, then etching away the metal film exposed by the photoresist, and finally removing the photoresist to obtain the IDT metal electrode.

[0043] The preparation of highly uniform IDT metal electrodes on piezoelectric substrates is extremely important for the performance and manufacturing yield of surface acoustic wave devices, especially medium and high frequency surface acoustic wave devices. Figure 1 As shown in FIG. 1 , the IDT metal electrode is rectangular, its width should be uniform, and the ends of the IDT metal electrode and the ends of the dummy fingers should be right angles. However, whether it is through a lift-off process or an etching process, in the process of preparing the IDT metal electrode, due to the influence of the optical proximity effect, the metal electrode near the gap area between the IDT metal electrode and the dummy finger (such as Figure 1 The shape and electrode width of the electrode fingers at positions A and B will change abnormally. At the same time, due to the optical proximity effect generated in the gap area, the electrode shape of the electrode finger may not be rectangular, but circular or elliptical (for example, Figure 2The problem is most serious at electrode finger tip position A near the gap area (as shown by the dotted line). As for electrode finger position B nearby, due to the optical proximity effect, the electrode width of the electrode finger may also abnormally increase or decrease, resulting in poor performance of the SAW device and low production yield.

[0044] In order to reduce the influence of the gap area on the shape of the IDT metal electrode in the nearby area, the relevant technology generally performs optical proximity effect correction on the mask corresponding to the IDT metal electrode lithography pattern. However, different types of piezoelectric substrates such as lithium tantalate (LT), lithium niobate (LN), POI (LT-POI, LN-POI), etc., different crystal cuts of various substrates, and the color depth of various substrates will affect the correction effect of the optical proximity effect. Especially for the POI substrate, since it is bonded by a combination of SiO2 layers of different thicknesses and piezoelectric wafer layers such as LT or LN of different thicknesses, it will make the optical proximity effect correction in the gap area more difficult.

[0045] In order to solve the above problems, the present application proposes a method for preparing a surface acoustic wave device. The preparation method can directly form a second photoresist layer having a plurality of second hollow regions spaced apart on a metal film, so that when the first film portion of the second hollow region is removed, the first photoresist layer can be used to protect the piezoelectric substrate, thereby effectively avoiding damage to the piezoelectric substrate during the process of removing the first film portion of the second hollow region, and at the same time, it can also ensure that the shape and width of the prepared IDT metal electrode will not undergo abnormal changes due to the optical proximity effect, thereby improving the performance and production yield of the surface acoustic wave device, and can be applied to piezoelectric substrates of any material, with a wide range of application scenarios. The preparation method of the surface acoustic wave device will be described in detail below.

[0046] See also Figure 3 , Figure 3 is a schematic flow chart of the steps of a method for preparing a surface acoustic wave device provided in an embodiment of the present application, such as Figure 3 As shown, the method for preparing a surface acoustic wave device includes steps S101 to S105.

[0047] S101, forming a first photoresist layer on a piezoelectric substrate, wherein the first photoresist layer has a first hollow region, and the first hollow region exposes the piezoelectric substrate to the first photoresist layer, wherein the first hollow region includes an IDT region and a gap region connected to the IDT region.

[0048] like Figure 4-Figure 7As shown, a first photoresist layer 20 having a first hollow region 21 can be formed on the piezoelectric substrate 10, and the first hollow region 21 can expose the piezoelectric substrate 10 to the first photoresist layer 20, wherein the first hollow region 21 includes an IDT region 22 and a gap region 23 connected to the IDT region 22.

[0049] The IDT region 22 is a region corresponding to the electrode fingers and bus bars formed subsequently, and may include two oppositely disposed bus bar regions 221 and a plurality of finger regions disposed between the two bus bar regions 221. The gap region 23 is located between the finger region and the bus bar region 221.

[0050] It should be noted that Figure 4 , Figure 5 and Figure 7 The filling area in is the IDT area 22 .

[0051] Exemplarily, if the interdigital transducer to be prepared subsequently has dummy fingers, the gap area 23 is connected to the finger area and is spaced apart from the bus area 221; if the interdigital transducer to be prepared subsequently has dummy fingers, the gap area 23 is connected to the finger area and is connected to the bus area 221.

[0052] It should be noted that the piezoelectric substrate 10 may include at least one of lithium niobate (LiNbO 3 ) and lithium tantalate (LiTaO 3 ), which is not specifically limited herein.

[0053] Exemplarily, a layer of photoresist may be coated on the piezoelectric substrate 10 , and the layer of photoresist may be exposed and developed using a mask to form a first photoresist layer 20 having a first hollow region 21 .

[0054] It should be noted that the photoresist used to form the first photoresist layer 20 may include a positive photoresist and a negative photoresist, etc., which are not specifically limited here. The morphology of the photoresist may include an undercut and a top cut. Exemplarily, in the thickness direction, the cross-sectional shape of the photoresist may be an inverted trapezoid, so that the stripping liquid can be fully in contact with the photoresist later, thereby facilitating the stripping of the photoresist on the piezoelectric substrate 10 and there will be no residual photoresist on the piezoelectric substrate 10 after stripping.

[0055] Specifically, the IDT area 22 includes two bus bar areas 221 and multiple finger areas. The two bus bar areas 221 are arranged opposite to each other, and the multiple finger areas are arranged in parallel between the two bus bar areas 221. The gap area 23 is located in the gap between the finger area and the bus bar area 221 and is connected to the finger area.

[0056] The bus bar region 221 is a region for subsequently forming a bus bar, and the finger region may be a region for subsequently forming an electrode finger, or may include a region for forming an electrode finger and a region for forming a dummy finger. Since one end of an electrode finger in an interdigital transducer is not connected to a bus bar, the bus bar region 221 is not connected to one end of a region for forming an electrode finger, so there is a gap region 23 between the bus bar region 221 and the finger region.

[0057] Exemplarily, if the interdigital transducer to be prepared subsequently does not have dummy fingers, the finger strip area is the area used to form electrode fingers; if the interdigital transducer to be prepared subsequently includes electrode fingers and dummy fingers, the finger strip area includes an area for forming electrode fingers (hereinafter referred to as "electrode finger area") and an area for forming dummy fingers (hereinafter referred to as "dummy finger area").

[0058] It should be noted that each finger area is connected to at least one bus bar area 221, and the finger area intersects with the bus bar area 221. Figure 4 As shown, the extending direction of the finger bar region and the extending direction of the bus bar region may be perpendicular to each other.

[0059] As an embodiment, the IDT of the surface acoustic wave device prepared by the method for preparing the surface acoustic wave device of the present application has a pseudo-finger structure. Figure 4 As shown, exemplarily, each finger bar area includes a first finger bar area 222 and a second finger bar area 223, and the first finger bar area 222 is connected to the second finger bar area 223 through a corresponding gap area 23, wherein in the same finger bar area, the first finger bar area 222 and the second finger bar area 223 are respectively connected to different bus bar areas 221.

[0060] In this embodiment, in the same finger area, the first finger area 222 and the second finger area 223 are arranged at intervals and connected by the gap area 23. The first finger area 222 is connected to one of the bus bar areas 221 and the gap area 23, and the second finger area 223 is connected to the other bus bar area 221 and the gap area 23. The first finger area 222 and the second finger area 223 in the same finger area are used to prepare the electrode fingers and the dummy fingers of the interdigital transducer, respectively. Exemplarily, the first finger area 222 is used to form the electrode fingers of the interdigital transducer, and the second finger area 223 is used to form the dummy fingers of the interdigital transducer.

[0061] Exemplarily, each finger area includes a first finger area 222 and a second finger area 223, and multiple first finger areas 222 are alternately connected to different bus bar areas 221, for example, one first finger area 222 is connected to the bus bar area 221, and the next first finger area 222 is connected to the opposite bus bar area 221, and so on; multiple second finger areas 223 are also alternately connected to different bus bar areas 221, for example, one second finger area 223 is connected to the bus bar area 221, and the next second finger area 223 is connected to the opposite bus bar area 221, and so on.

[0062] As an embodiment, the IDT of the surface acoustic wave device prepared by the method for preparing the surface acoustic wave device of the present application does not have a pseudo-finger structure. Figure 5 As shown, illustratively, each finger region includes a first finger region 222 , the first finger region 222 is connected to a bus bar region 221 , and is connected to another bus bar region 221 through a gap region 23 .

[0063] In this embodiment, in the same finger region, the first finger region 222 and the bus bar region 221 are arranged at intervals and connected through the gap region 23. The first finger region 222 is connected to one of the bus bar regions 221 and the gap region 23, and is arranged at intervals with another bus bar region 221. The first finger region 222 in the same finger region is used to prepare electrode fingers of the interdigital transducer.

[0064] Exemplarily, each finger area includes a first finger area 222, and multiple first finger areas 222 are alternately connected to different bus bar areas 221. For example, one first finger area 222 is connected to the bus bar area 221, and the next first finger area 222 is connected to the opposite bus bar area 221, and so on.

[0065] As an embodiment, the IDT of the surface acoustic wave device prepared by the method for preparing the surface acoustic wave device of the present application has a gap electrode structure. Figure 7As shown, exemplarily, in the same finger-bar area, the number of gap areas 23 connected to the finger-bar area may be multiple, and the example in which the number of gap areas 23 is 2 is used for explanation, the gap area 23 may include a first gap area 231 and a second gap area 232, each finger-bar area includes a first finger-bar area 222 and a second finger-bar area 223, the first finger-bar area 222 is connected to the second finger-bar area 223 through the first gap area 231, and the first gap area 231 is connected to the second gap area 232 through the second finger-bar area 223, wherein, in the same finger-bar area, the first finger-bar area 222 and the second gap area 232 are respectively connected to different bus bar areas 221.

[0066] In this embodiment, in the same finger area, the first finger area 222 is connected to one of the bus bar areas 221, and is connected to the second finger area 223 through the first gap area 231, and the second finger area 223 is connected to another bus bar area 221 through the second gap area 232, that is, the first finger area 222 and the second finger area 223 are arranged at intervals and connected through the first gap area 231, and the first gap area 231 and the second gap area 232 are arranged at intervals and connected through the second finger area 223. The first finger area 222 and the second finger area 223 in the same finger area are respectively used to prepare the electrode fingers and gap electrodes of the interdigital transducer. Exemplarily, the first finger area 222 is used to form the electrode fingers of the interdigital transducer, and the second finger area 223 is used to form the gap electrodes of the interdigital transducer.

[0067] exist Figure 7 In a corresponding embodiment, the second finger region 223 is used to form a gap electrode of the IDT, the gap electrode is arranged between the bus bar and the electrode finger, and the gap electrode is spaced apart from the bus bar and the electrode finger.

[0068] In the related art, in the step of "forming a first photoresist layer having a first hollowed-out area on a piezoelectric substrate", in order to facilitate the subsequent preparation of the interdigital transducer, the corresponding first hollowed-out area generally does not include the gap area, that is, the gap area is also covered with photoresist. However, since this preparation method reserves the photoresist for the gap area in advance, an optical proximity effect will occur in the subsequent preparation of the interdigital transducer, resulting in abnormal changes in the shape and width of the IDT metal electrode. In order to avoid the influence of the optical proximity effect, the present application also includes a gap area in the first hollowed-out area formed in step S101, that is, the gap area is not covered with photoresist, and the gap area of ​​the interdigital transducer is prepared through subsequent steps, thereby effectively avoiding the optical proximity effect from affecting the shape and width of the IDT metal electrode, thereby improving the performance and production yield of the surface acoustic wave device.

[0069] S102 , forming a metal film, wherein the metal film includes a first film portion located in the first hollow area and a second film portion located in the first photoresist layer.

[0070] like Figure 8 and Fig. 9 As shown, a metal film 30 can be formed on a first photoresist layer 20 having a first hollow region 21 by using an evaporation process to form a first film portion 31 in the first hollow region 21, and a second film portion 32 is formed on the first photoresist layer 20. In the first hollow region 21, the first film portion 31 located in the IDT region 22 is used to form an IDT.

[0071] like Fig. 9 As shown in the cross-sectional view, the cross-sectional shape of the first film portion 31 generally corresponds to the cross-sectional shape of the photoresist. If the cross-sectional shape of the photoresist is an inverted trapezoid, the cross-sectional shape of the first film portion 31 may be a right trapezoid. If the cross-sectional shape of the photoresist is a right trapezoid, the cross-sectional shape of the first film portion 31 may be an inverted trapezoid. No specific limitation is made here.

[0072] Specifically, although the metal film 30 is deposited as a whole layer during the manufacturing process, the first hollow area 21 exposes the piezoelectric substrate 10 to the first photoresist layer 20, that is, the piezoelectric substrate 10 is exposed, that is, there is a step difference at the junction between the surface of the first photoresist layer 20 and the first hollow area 21. Therefore, the formed metal film 30 will be directly deposited on the surface of the photoresist of the first photoresist layer 20 to form the second film part 32 in the area where the photoresist is not removed (that is, the area outside the first hollow area 21), and in the first hollow area 21, the metal film 30 will be directly deposited on the surface of the piezoelectric substrate 10 to form the first film part 31. Due to the existence of the step difference, the first film part 31 and the second film part 32 are independent of each other, so that the first film part 31 constitutes an interdigital transducer.

[0073] S103, forming a second photoresist layer on the metal film, wherein the second photoresist layer has a plurality of second hollow regions arranged at intervals, and the second hollow regions at least expose the first film portion located in the gap region to the second photoresist layer.

[0074] As shown in Figure 10(a), Fig.11 and Fig.12 As shown, a second photoresist layer 40 having a second hollow region 41 may be formed on the metal film 30 , and the second hollow region 41 at least exposes the first film portion 31 located in the gap region 23 to the second photoresist layer 40 .

[0075] Exemplarily, a photoresist layer may be formed on the metal film 30 first, and then the photoresist at the second hollow area 41 may be removed. Therefore, only the first film portion 31 is exposed at the second hollow area 41, and the area outside the second hollow area 41 is coated with photoresist.

[0076] In some embodiments, a layer of photoresist may be coated on the metal film 30 , and the layer of photoresist may be exposed and developed through a mask to form a second photoresist layer 40 having a second hollow region 41 .

[0077] It should be noted that the photoresist used to form the second photoresist layer 40 may include a positive photoresist and a negative photoresist, etc., which are not specifically limited here. The morphology of the photoresist may include an undercut and a top cut. Exemplarily, in the thickness direction, the cross-sectional shape of the photoresist may be an inverted trapezoid, so that the stripping liquid can be fully in contact with the photoresist in the subsequent process, so that the photoresist can be stripped on the piezoelectric substrate 10 and there will be no residue after stripping.

[0078] In some embodiments, according to the size of the finger region, or according to the size of the finger region and the size of the bus bar region 221 , a second photoresist layer 40 having a second hollow region 41 is formed on the metal film 30 .

[0079] Among them, the size of the finger area may include parameters such as the width of the finger area in the first direction, the length in the second direction, and the area, and the size of the bus bar area 221 may include parameters such as the width of the bus bar area 221 in the first direction, the length in the second direction, and the area.

[0080] It should be noted that the first direction refers to the width direction of the stripe area, and the second direction refers to the length direction of the stripe area, that is, the extension direction of the stripe area. The first direction intersects with the second direction, and illustratively, the first direction and the second direction can be set perpendicularly.

[0081] Exemplarily, the position and size of the second hollow region 41 may be determined only according to the size of the finger region, so that the second photoresist layer 40 having the second hollow region 41 is formed on the metal film 30 .

[0082] Exemplarily, the position and size of the second hollow region 41 may be determined according to the size of the finger region and the size of the bus bar region 221 , so as to form a second photoresist layer 40 having the second hollow region 41 on the metal film 30 .

[0083] Exemplarily, a plurality of second hollow regions 41 are disposed on the second photoresist layer 40 . The second hollow regions 41 are generally disposed close to the bus bar region 221 , and may be connected to the bus bar region 221 , or may be spaced apart from the bus bar region 221 .

[0084] Exemplarily, a plurality of second hollowed-out regions 41 may be alternately connected to different bus bar regions 221. For example, one second hollowed-out region 41 is connected to a bus bar region 221, and the next second hollowed-out region 41 will be connected to the opposite bus bar region 221, and so on.

[0085] Exemplarily, each second hollowed-out region 41 may be alternately arranged at intervals close to different bus bar regions 221. For example, one second hollowed-out region 41 is close to one of the bus bar regions 221 and is arranged at an interval from the bus bar region 221, and the next second hollowed-out region 41 is close to another bus bar region 221 and is arranged at an interval from the bus bar region 221, and so on.

[0086] As Fig.12 shown, in some embodiments, the width of the second hollowed-out region 41 in the first direction is d1, the width of the finger region in the first direction is d2, and the gap width between two adjacent finger regions is d3. The first direction is the arrangement direction of the finger regions, which can also be understood as the length direction / extension direction of the bus bar regions; wherein, d2 ≤ d1 < d2 + 2d3. Thus, by controlling the width of the second hollowed-out region 41 in the first direction, it is convenient to subsequently peel off the first thin film portion 31 located in the second hollowed-out region 41 quickly and conveniently.

[0087] Exemplarily, the width d1 of the second hollowed-out region 41 in the first direction is at least greater than the width d2 of the finger region in the first direction, that is, d2 ≤ d1; the gap width d3 between two adjacent finger regions is the width of the adjacent first photoresist layer 20 in the first direction. It is also necessary to control that the second hollowed-out region 41 does not cover the adjacent finger regions, that is, d1 < d2 + 2d3.

[0088] If d2 > d1, it may cause the subsequent inability to completely peel off the first thin film portion 31 located in the second hollowed-out region 41, thereby affecting the performance of the subsequent fabricated interdigital transducer; if d1 ≥ d2 + 2d3, it may cause the first thin film portion 31 (not located in the second hollowed-out region 41) of the adjacent finger regions to be peeled off together during the process of peeling off the first thin film portion 31 located in the second hollowed-out region 41, thereby affecting the performance of the subsequent fabricated interdigital transducer. Therefore, by setting d2 ≤ d1 < d2 + 2d3, the first thin film portion 31 located in the intersecting region of the first hollowed-out region 21 and the second hollowed-out region 41 can be accurately removed, ensuring the preparation accuracy of the gap region, and leaving a certain preparation error, which is convenient for process implementation, thereby effectively improving the performance and production yield of the subsequent fabricated surface acoustic wave device.

[0089] As shown in Figure 10(b), in some embodiments, the distance between the center line F of the second hollow area 41 and the center line G of the corresponding finger area in the first direction is less than or equal to 100 nm, wherein the center line is parallel to the extension direction of the finger area and intersects with the first direction, and the first direction is the arrangement direction of multiple finger areas.

[0090] Exemplarily, due to factors such as errors generated during the preparation process, under the premise of not affecting the performance of the interdigital transducer, the second hollow area 41 may have a certain overlay deviation with the corresponding finger area. Specifically, the distance between the center line F of the second hollow area 41 and the center line G of the corresponding finger area in the first direction may be controlled to be less than or equal to 100nm, that is, the center line F of the second hollow area 41 may not overlap with the center line G of the corresponding finger area, and the distance between the two may be kept within a certain overlay deviation.

[0091] Preferably, the distance between the center line F of the second hollow area 41 and the center line G of the corresponding finger area in the first direction is controlled to be 0, that is, the center line F of the second hollow area 41 coincides with the center line G of the corresponding finger area, which can further improve the performance of the subsequently manufactured interdigital transducer.

[0092] In some embodiments, the second hollow area 41 is connected to the adjacent bus bar area 221 , or the second hollow area 41 is spaced apart from the adjacent bus bar area 221 .

[0093] Exemplarily, if the subsequently manufactured IDT does not include dummy fingers, the second hollow region 41 is connected to the adjacent bus bar region 221 .

[0094] Exemplarily, if the interdigital transducer manufactured subsequently includes dummy fingers, the second hollow region 41 is spaced apart from the adjacent bus bar region 221 .

[0095] Specifically, if the width of the finger area in the first direction is d2, and the gap width between two adjacent finger areas is d3, when the second hollow area 41 is spaced from the adjacent bus bar area 221, the distance between the second hollow area 41 and the adjacent bus bar area 221 in the second direction is greater than 0nm and less than 6*(d2+d3). Exemplarily, the length of the pseudo fingers of the interdigital transducer manufactured later can be effectively controlled by controlling the distance between the second hollow area 41 and the adjacent bus bar area 221 in the second direction, so that pseudo fingers of different lengths can be prepared according to actual conditions, thereby further improving the performance of the interdigital transducer manufactured later.

[0096] Specifically, when the second hollow region 41 is spaced apart from the adjacent bus bar region 221 , the length of the second hollow region 41 in the second direction is less than or equal to 100 nm.

[0097] For example, the length of the gap region 23 in the second direction can be effectively controlled by controlling the length of the second hollow region 41 in the second direction, so that gap regions 23 of different sizes can be prepared according to actual conditions, thereby further improving the performance of the subsequently prepared interdigital transducer.

[0098] It should be noted that the length of the second hollow area 41 in the second direction is the same as the length of the gap area 23 in the second direction, but the width of the second hollow area 41 in the first direction is at least greater than or equal to the width of the gap area 23 in the first direction.

[0099] In the related art, after the step of "forming a metal film", the first photoresist layer formed by the first photolithography is generally stripped off, and then the second photolithography is performed to form the second photoresist layer. However, since the first photoresist layer has been stripped off, that is, the second photolithography is also performed on the piezoelectric substrate, the piezoelectric substrate may be damaged during the second photolithography process. In order to reduce damage to the piezoelectric substrate, the present application does not remove the first photoresist layer after the step of "forming a metal film", but directly performs the second photolithography on the metal film. At this time, due to the presence of the first photoresist layer, the piezoelectric substrate will not be contacted during the second photolithography process, that is, the piezoelectric substrate will not be damaged. Therefore, this preparation method can not only ensure that the shape and width of the prepared electrode fingers and false fingers will not undergo abnormal changes due to the influence of the optical proximity effect, thereby improving the performance and production yield of the surface acoustic wave device, but also can effectively protect the piezoelectric substrate during the preparation process, and is suitable for piezoelectric substrates of any material, and has a wide range of application scenarios.

[0100] S104, removing the first film portion located in the second hollow area to form an interdigital transducer.

[0101] like Fig.13 and Fig.14 As shown, since the second photoresist layer 40 is arranged around the second hollow area 41, a step is formed between the second photoresist layer 40 and the second hollow area 41. Due to the existence of the step, the first film portion 31 located in the second hollow area 41 is independent from the first film portions 31 in other positions. Therefore, the first film portion 31 located in the second hollow area 41 can be removed, and the first film portion 31 outside the second film portion 32 can be retained. Therefore, on the premise of retaining the first film portion 31 for forming the interdigital transducer (i.e., the first film portion 31 outside the second film portion 32), the first film portion 31 located in the second hollow area 41 can be removed in a targeted manner, thereby forming a gap area 23 of the interdigital transducer.

[0102] In some embodiments, the first film portion 31 of the second hollow region 41 is etched away by an etching process, so that the first film portion 31 of the second hollow region 41 can be accurately peeled off, and the first film portion 31 outside the second hollow region 41 is retained.

[0103] Exemplarily, an etching process can be used to specifically corrode the first film portion 31 of the second hollow area 41. Since the specially prepared corrosive liquid generally only corrodes metals but has no effect on photoresists, it is possible to achieve the effect of specifically corroding the first film portion 31 of the second hollow area 41 and retaining the photoresist in the area outside the second hollow area 41.

[0104] In some embodiments, a peeling film is formed on the surface of the first film portion 31 of the second hollow area 41, and the first film portion 31 of the second hollow area 41 is peeled off through the peeling film. Thus, the first film portion 31 of the second hollow area 41 can be accurately peeled off through the peeling film.

[0105] The peeling film may include a gold peeling film, etc., which is not specifically limited here.

[0106] For example, appropriate pressure can be set on the gold tear film so that the gold tear film is in close contact with the first film portion 31 of the second hollow area 41, and then the gold tear film is slowly torn off, so that the first film portion 31 of the second hollow area 41 can be removed. In this way, the first film portion 31 of the second hollow area 41 can be removed simply and quickly, and the first film portion 31 of the second hollow area 41 can be removed quickly without damaging the photoresist.

[0107] For example, a gold tearing film can be directly formed on the surface of the second photoresist layer 40. Due to the presence of a step difference between the first film portion 31 of the second hollow region 41 and the second photoresist layer 40, and the gold tearing film has a certain tension, the roller can be used to make it in close contact with the first film portion 31 of the second hollow region 41. Therefore, when the gold tearing film is torn off, the first film portion 31 of the second hollow region 41 is also removed, thereby achieving the effect of peeling off the first film portion 31 of the second hollow region 41.

[0108] S105 , removing the first photoresist layer, the second photoresist layer and the second film portion.

[0109] like Fig.15 , Fig.16 and Fig.17 As shown, the first photoresist layer 20 , the second photoresist layer 40 and the second film portion 32 may be removed by a lift-off process, thereby manufacturing an interdigital transducer on the piezoelectric substrate 10 .

[0110] In some embodiments, the first photoresist layer 20 and the second photoresist layer 40 are stripped from the piezoelectric substrate 10 by a wet stripping process to strip the second thin film portion 32 .

[0111] Exemplarily, the first photoresist layer 20 is stripped from the piezoelectric substrate 10 by a wet stripping process, and the second photoresist layer 40 located in the interdigital transducer area 22 is stripped from the first film portion 31. Since part of the second photoresist layer 40 and the second film portion 32 are arranged on the first photoresist layer 20, the second film portion 32 and the second photoresist layer 40 arranged on the second film portion 32 can be stripped while the first photoresist layer 20 is stripped.

[0112] Exemplarily, the first photoresist layer 20 and the second photoresist layer 40 can be immersed in a stripping solution; the first photoresist layer 20 and the second photoresist layer 40 immersed in the stripping solution are subjected to ultrasonic treatment to dissolve the first photoresist layer 20, the second photoresist layer 40 and the second film portion 32. In this way, the first photoresist layer 20, the second photoresist layer 40 and the second film portion 32 can be removed without damaging the piezoelectric substrate 10.

[0113] The stripping liquid may include acetone, N-methylpyrrolidone and other liquids.

[0114] The preparation method of the surface acoustic wave device provided in the present application, when preparing the interdigital transducer, does not reserve the gap area 23 first, forms a strip metal extending from one bus bar to another bus bar, and then etches away part of the gap area 23, so that the strip metal is divided into an electrode finger part and a dummy finger part, so that the shape and width of the electrode finger formed in this way will not change abnormally due to the influence of the optical proximity effect, and effectively improves the performance and production yield of the surface acoustic wave device, and can be applied to piezoelectric substrates 10 of any material, and has a wide range of application scenarios. By directly forming a second photoresist layer 40 having a plurality of second hollow areas 41 spaced apart on the metal film 30, when removing the first film part 31 of the second hollow area 41, the first photoresist layer 20 can also be used to protect the piezoelectric substrate 10, thereby effectively avoiding damage to the piezoelectric substrate 10 during the process of removing the first film part 31 of the second hollow area 41.

[0115] A surface acoustic wave device provided in an embodiment of the present application will be described in detail below.

[0116] like Fig.15 , Fig.16 and Fig.17As shown, the surface acoustic wave device 100 includes an interdigital transducer 50, which is manufactured by the manufacturing method of the surface acoustic wave device 100 provided by the above embodiment. The interdigital transducer 50 includes: two comb-shaped electrodes arranged opposite to each other, each comb-shaped electrode includes a bus bar 51 and a plurality of electrode fingers 52 connected to the bus bar 51 and arranged at intervals, and the electrode fingers 52 of the two comb-shaped electrodes are arranged alternately with each other; in the extension direction of the electrode fingers 52, there is an overlapping area C1 between the two bus bars 51, and the overlapping area C1 is an area where the projections of each electrode finger 52 overlap with each other, and there is a gap area D between the overlapping area C1 and the bus bar 51, and the gap area D is adjacent to the overlapping area C1.

[0117] There are two gap regions D between the bus bar 51 and the overlapping region C1 . The two gap regions D are respectively located at two ends of the overlapping region C1 . Both gap regions D are adjacent to one end of the bus bar 51 close to the overlapping region C1 .

[0118] Exemplarily, the projection of the electrode finger 52 in the thickness direction is usually rectangular, and the cross-section of the electrode finger 52 along the thickness direction may be trapezoidal after being formed under the influence of process conditions. Under normal circumstances, the extension line direction of the long side of the electrode finger 52 will intersect or even be perpendicular to the extension line direction of the bus bar 51, and multiple electrode fingers 52 will be parallel to each other, and a certain gap will be left between adjacent electrode fingers 52.

[0119] Exemplarily, the busbar 51 and the electrode finger 52 may be made of metal materials such as aluminum, molybdenum, copper, gold, platinum, silver, nickel, chromium, and tungsten, which are not specifically limited here and can be determined according to specific circumstances, but the selected material needs to have good conductivity.

[0120] The surface acoustic wave device 100 provided in the present application is manufactured by the above-mentioned method for manufacturing the surface acoustic wave device 100, so the shape and width of the metal electrode in the manufactured surface acoustic wave device 100 will not change abnormally, and the piezoelectric substrate 10 is of good quality and will not be damaged, so the performance of the surface acoustic wave device 100 is better.

[0121] In some embodiments, a gap region D is formed between the overlapping region C1 and the bus bar 51 .

[0122] In the embodiment of the present application, since there is no dummy finger 53 in the IDT 50 , the gap region D is the region between the overlapping region C1 and the bus bar 51 .

[0123] In some embodiments, the IDT 50 further includes a dummy finger 53 , a first end of which is connected to the bus bar 51 , and a second end of the dummy finger 53 is spaced apart from the opposite electrode finger 52 ; wherein a gap region D is formed between the overlapping region C1 and the second end of the dummy finger 53 .

[0124] In the embodiment of the present application, since there are dummy fingers 53 in the IDT 50 and the dummy fingers 53 are spaced apart from the corresponding electrode fingers 52 , the gap region D is the region between the overlapping region C1 and the dummy fingers 53 .

[0125] In some embodiments, the overlapping region C1 includes a middle region C2 and edge regions C3 located on both sides of the middle region C2 in the extension direction of the electrode finger 52; wherein the electrode finger 52 located in the edge region C3 is rectangular in shape, and the dummy finger 53 is rectangular in shape.

[0126] In the related art, due to the optical proximity effect, the shapes of the electrode fingers 52 and the dummy fingers 53 located in the edge region C3 may change abnormally. At the same time, due to the optical proximity effect of the gap region D, the shape of the electrode fingers 52 located in the edge region C3 may not be rectangular, but circular or elliptical, thereby causing the performance of the surface acoustic wave device 100 to deteriorate and the manufacturing yield to decrease.

[0127] The surface acoustic wave device 100 manufactured by the manufacturing method provided in the embodiment of the present application can ensure that the shapes of the prepared electrode fingers 52 and dummy fingers 53 will not undergo abnormal changes due to the optical proximity effect, thereby improving the performance and production yield of the surface acoustic wave device 100.

[0128] In some embodiments, the difference between the maximum width and the minimum width of the electrode finger 52 in the arrangement direction thereof is less than or equal to 10 nm. The arrangement direction of the electrode finger 52 is the first direction.

[0129] Exemplarily, since the IDT 50 has a plurality of parallel electrode fingers 52 , the difference between the maximum width and the minimum width of each electrode finger 52 in the first direction is less than or equal to 10 nm. Preferably, each electrode finger 52 has the same width in the first direction.

[0130] In the related art, due to the optical proximity effect, the electrode width (CD) of the electrode finger 52 and the dummy finger 53 located in the edge region C3 may change abnormally. At the same time, due to the optical proximity effect in the gap region D, the electrode width of the adjacent electrode finger 52 may become abnormally larger or smaller, thereby causing the performance of the surface acoustic wave device 100 to deteriorate and the manufacturing yield to decrease.

[0131] The surface acoustic wave device 100 manufactured by the manufacturing method provided in the embodiment of the present application can ensure that the CD of the prepared electrode fingers 52 and dummy fingers 53 will not undergo abnormal changes due to the optical proximity effect, thereby improving the performance and production yield of the surface acoustic wave device 100.

[0132] In some embodiments, when the IDT 50 includes the dummy fingers 53 , the length of the gap region D in the extending direction of the electrode fingers 52 is less than or equal to 100 nm.

[0133] For example, the length of the gap region D in the extension direction (second direction) of the electrode finger 52 can be controlled so that dummy fingers 53 of different sizes can be prepared according to actual conditions, thereby further improving the performance of the IDT 50 .

[0134] like Fig.17 As shown, in some embodiments, when the interdigital transducer 50 includes a gap electrode 54, the gap electrode 54 is arranged between the bus bar 51 and the electrode finger 52, and the gap electrode 54 is spaced apart from the bus bar 51 and the electrode finger 52. The gap electrode 54 is also used to form a first gap region D1 and a second gap region D2, wherein the first gap region D1 is adjacent to the edge region C3, and the second gap region D2 is adjacent to the bus bar 51.

[0135] Another surface acoustic wave device 100 provided in an embodiment of the present application will be described in detail below.

[0136] like Fig.16 As shown, the surface acoustic wave device 100 includes an interdigital transducer 50, which includes: two comb-shaped electrodes and dummy fingers 53 arranged opposite to each other, each comb-shaped electrode includes a bus bar 51 and a plurality of electrode fingers 52 connected to the bus bar 51 and arranged at intervals, and the electrode fingers 52 of the two comb-shaped electrodes are arranged alternately with each other; in the extension direction of the electrode fingers 52, there is an overlapping area C1 between the two bus bars 51, and the overlapping area C1 is an area where the projections of each electrode finger 52 overlap with each other, and a gap area D is included between the overlapping area C1 and the bus bar 51, and the gap area D is adjacent to the overlapping area C1; the first end of the dummy finger 53 is connected to the bus bar 51, the second end of the dummy finger 53 is arranged at intervals from the opposite electrode finger 52, and the gap area D is formed between the second end of the dummy finger 53 and the overlapping area C1; wherein, the electrode finger 52 located in the edge area C3 is rectangular in shape, and the dummy finger 53 is rectangular in shape.

[0137] The area between the bus bar 51 and the overlapping area C1 has two gap areas D, which are respectively located at two ends of the overlapping area C1 , and both gap areas D are adjacent to one end of the bus bar 51 close to the overlapping area C1 .

[0138] Exemplarily, the electrode finger 52 is usually rectangular. After the electrode finger 52 is formed under the influence of process conditions, the cross-section in the thickness direction may be a trapezoid. Normally, the extension line direction of the long side of the electrode finger 52 will intersect with the extension line direction of the bus bar 51, such as vertical or with other angles less than 180°, and multiple electrode fingers 52 will be parallel to each other, and a certain gap will be left between adjacent electrode fingers 52.

[0139] Exemplarily, the busbar 51 and the electrode finger 52 may be made of metal materials such as aluminum, molybdenum, copper, gold, platinum, silver, nickel, chromium, and tungsten, which are not specifically limited here and can be determined according to specific circumstances, but the selected material needs to have good conductivity.

[0140] In the related art, due to the optical proximity effect, the shapes of the electrode fingers 52 and the dummy fingers 53 located in the edge region C3 may change abnormally. At the same time, due to the optical proximity effect of the gap region D, the shape of the electrode fingers 52 located in the edge region C3 may not be rectangular, but circular or elliptical, thereby causing the performance of the surface acoustic wave device 100 to deteriorate and the manufacturing yield to decrease.

[0141] The shapes of the electrode fingers 52 and the dummy fingers 53 in the surface acoustic wave device 100 provided in the embodiment of the present application will not undergo abnormal changes due to the optical proximity effect, and the piezoelectric substrate 10 is of good quality without damage, and the performance of the surface acoustic wave device 100 is better.

[0142] In some embodiments, the length of the gap region D in the extending direction of the electrode fingers 52 is less than or equal to 100 nm.

[0143] For example, the length of the gap region D in the extension direction (second direction) of the electrode finger 52 can be controlled so that the gap region D of different sizes can be prepared according to actual conditions, thereby further improving the performance of the IDT 50 .

[0144] In some embodiments, the difference between the maximum width and the minimum width of the electrode finger 52 in the arrangement direction thereof is less than or equal to 10 nm. The arrangement direction of the electrode finger 52 is the first direction.

[0145] Exemplarily, since the IDT 50 has a plurality of parallel electrode fingers 52 , the difference between the maximum width and the minimum width of each electrode finger 52 in the first direction is less than or equal to 10 nm. Preferably, each electrode finger 52 has the same width in the first direction.

[0146] In the related art, due to the optical proximity effect, the electrode width (CD) of the electrode finger 52 and the dummy finger 53 located in the edge region C3 may change abnormally. At the same time, due to the optical proximity effect in the gap region D, the electrode width of the adjacent electrode finger 52 may become abnormally larger or smaller, thereby causing the performance of the surface acoustic wave device 100 to deteriorate and the manufacturing yield to decrease.

[0147] The CD of the electrode fingers 52 and the dummy fingers 53 in the SAW device 100 provided in the embodiment of the present application will not undergo abnormal changes due to the optical proximity effect, and the piezoelectric substrate 10 is of good quality without damage, and the SAW device 100 has better performance.

[0148] In the case where the surface acoustic wave device 100 is a filter, the filter provided in the embodiment of the present application will be described in detail below.

[0149] The filter includes a plurality of series-arm surface acoustic wave devices 100 connected in series between an input end and an output end, and a plurality of parallel-arm surface acoustic wave devices 100 connected to the series-arm surface acoustic wave device 100 at one end and connected to a ground end at the other end, and at least one of the series-arm surface acoustic wave device 100 and the parallel-arm surface acoustic wave device 100 can be a surface acoustic wave device 100 provided by any of the above-mentioned embodiments. The shape and width of the electrode fingers 52 of the interdigital transducer 50 in the filter will not be abnormally changed due to the optical proximity effect, thereby ensuring the performance of the filter.

[0150] The embodiment of the present application also provides a radio frequency front-end module, which includes the surface acoustic wave device 100 described in any of the above embodiments. The shape and width of the electrode fingers 52 of the interdigital transducer 50 in the radio frequency front-end module will not change abnormally due to the optical proximity effect, thereby ensuring the performance of the radio frequency front-end module, thereby improving the reliability, safety and practicality of the radio frequency front-end module.

[0151] Among them, the RF front-end module may include an antenna end, a power amplifier, a low-noise amplifier, a switch, a filter, etc., which are not specifically limited here.

[0152] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for preparing a surface acoustic wave device, characterized in that: The method comprises: Forming a first photoresist layer on a piezoelectric substrate, wherein the first photoresist layer has a first hollow region, wherein the first hollow region exposes the piezoelectric substrate to the first photoresist layer, wherein the first hollow region includes an IDT region and a gap region connected to the IDT region; forming a metal film, wherein the metal film includes a first film portion located in the first hollowed-out area and a second film portion located in the first photoresist layer; Forming a second photoresist layer on the metal film, wherein the second photoresist layer has a plurality of second hollow regions arranged at intervals, and the second hollow regions at least expose the first film portion located in the gap region to the second photoresist layer; removing the first film portion located in the second hollow area to form an interdigital transducer; The first photoresist layer, the second photoresist layer, and the second thin film portion are removed.

2. The method for preparing a surface acoustic wave device according to claim 1, characterized in that: The interdigital transducer area includes two bus bar areas and multiple finger areas, the two bus bar areas are arranged opposite to each other, the multiple finger areas are arranged in parallel between the two bus bar areas, and the gap area is located at the gap between the finger areas and the bus bar areas and is connected to the finger areas.

3. The method for preparing a surface acoustic wave device according to claim 2, characterized in that: Each of the finger stripe areas includes a first finger stripe area and a second finger stripe area, and the first finger stripe area is connected to the second finger stripe area through the corresponding gap area; Wherein, in the same finger bar area, the first finger bar area and the second finger bar area are respectively connected to different bus bar areas.

4. The method for preparing a surface acoustic wave device according to claim 2, characterized in that: Each of the finger areas includes a first finger area, the first finger area is connected to one of the bus bar areas, and is connected to another of the bus bar areas through the gap area.

5. The method for preparing a surface acoustic wave device according to claim 2, characterized in that: The width of the second hollow area in the first direction is d1, the width of the finger area in the first direction is d2, the width of the gap between two adjacent finger areas is d3, and the first direction is the arrangement direction of the finger areas; Where d2≤d1 <d2+2d3。 6. The method for preparing a surface acoustic wave device according to claim 2, characterized in that: The distance between the center line of the second hollow area and the center line of the corresponding finger area in the first direction is less than or equal to 100 nm, the center line is parallel to the extension direction of the finger area and intersects with the first direction, and the first direction is the arrangement direction of multiple finger areas.

7. The method for preparing a surface acoustic wave device according to claim 2, characterized in that: The step of forming a second photoresist layer on the metal film comprises: According to the size of the finger area, or according to the size of the finger area and the size of the bus bar area, a second photoresist layer having the second hollow area is formed on the metal film.

8. The method for preparing a surface acoustic wave device according to claim 2, characterized in that: The second hollow area is connected to the adjacent bus bar area, or the second hollow area is spaced apart from the adjacent bus bar area.

9. The method for preparing a surface acoustic wave device according to claim 8, characterized in that: The width of the finger bar area in the first direction is d2, the gap width between two adjacent finger bar areas is d3, and when the second hollow area is spaced apart from the adjacent bus bar area, the distance between the second hollow area and the adjacent bus bar area in the second direction is less than 6*(d2+d3).

10. The method for preparing a surface acoustic wave device according to claim 8, characterized in that: When the second hollow region is spaced apart from the adjacent bus bar region, a length of the second hollow region in the second direction is less than or equal to 100 nm.

11. The method for preparing a surface acoustic wave device according to claim 1, characterized in that: The removing of the first film portion located in the second hollow area includes: The first film portion of the second hollow area is etched away by an etching process.

12. The method for preparing a surface acoustic wave device according to claim 1, characterized in that: The removing of the first film portion located in the second hollow area includes: forming a peeling film on the surface of the first film portion of the second hollow area; The first film portion of the second hollow area is peeled off by the peeling film.

13. The method for preparing a surface acoustic wave device according to claim 1, characterized in that: The removing of the first photoresist layer, the second photoresist layer and the second film portion comprises: The first photoresist layer and the second photoresist layer are peeled off from the piezoelectric substrate by a wet peeling process to peel off the second film portion.

14. A surface acoustic wave device, characterized in that: The surface acoustic wave device is prepared by using any one of the preparation methods of claims 1 to 13, and the surface acoustic wave device comprises an interdigital transducer, and the interdigital transducer comprises: Two comb-shaped electrodes are arranged opposite to each other, each of the comb-shaped electrodes includes a bus bar and a plurality of electrode fingers connected to the bus bar and arranged at intervals, and the electrode fingers of the two comb-shaped electrodes are arranged alternately with each other; in the extension direction of the electrode fingers, there is an overlapping area between the two bus bars, and the overlapping area is an area where the projections of the electrode fingers overlap with each other, and a gap area is included between the overlapping area and the bus bar, and the gap area is adjacent to the overlapping area.

15. The surface acoustic wave device according to claim 14, characterized in that: The gap region is formed between the overlapping region and the bus bar.

16. The surface acoustic wave device according to claim 14, characterized in that: The IDT further comprises a dummy finger, a first end of the dummy finger is connected to the bus bar, and a second end of the dummy finger is spaced apart from an opposite electrode finger; Wherein, the gap region is formed between the overlapping region and the second end of the dummy finger.

17. The surface acoustic wave device according to claim 16, characterized in that: The overlapping region includes a middle region and edge regions located on both sides of the middle region in the extending direction of the electrode fingers; The electrode fingers located in the edge region are in a rectangular shape, and the dummy fingers are in a rectangular shape.

18. The surface acoustic wave device according to claim 16, characterized in that: The length of the gap region in the extending direction of the electrode fingers is less than or equal to 100 nm.

19. The surface acoustic wave device according to claim 14, characterized in that: The difference between the maximum width and the minimum width of the electrode fingers in the arrangement direction is less than or equal to 10 nm.

20. A surface acoustic wave device, characterized in that: The surface acoustic wave device comprises an interdigital transducer, and the interdigital transducer comprises: Two comb-shaped electrodes are arranged opposite to each other, each of the comb-shaped electrodes comprises a bus bar and a plurality of electrode fingers connected to the bus bar and arranged at intervals, the electrode fingers of the two comb-shaped electrodes are arranged alternately with each other; in the extension direction of the electrode fingers, there is an overlapping area between the two bus bars, the overlapping area is the area where the electrode fingers overlap with each other, a gap area is included between the overlapping area and the bus bar, and the overlapping area comprises a middle area and edge areas located on both sides of the middle area in the extension direction of the electrode fingers; A dummy finger, wherein a first end of the dummy finger is connected to the bus bar, a second end of the dummy finger is spaced apart from an opposite electrode finger, and the gap region is formed between the second end of the dummy finger and the overlapping region; The electrode fingers located in the edge region are in a rectangular shape, and the dummy fingers are in a rectangular shape.

21. The surface acoustic wave device according to claim 20, characterized in that: The length of the gap region in the extending direction of the electrode fingers is less than or equal to 100 nm.

22. The surface acoustic wave device according to claim 20, characterized in that: The difference between the maximum width and the minimum width of the electrode fingers in the arrangement direction is less than or equal to 10 nm.

23. A radio frequency front-end module, characterized in that: Comprising the surface acoustic wave device according to any one of claims 14-22.

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