Surface acoustic wave device with piston mode

Abstract

The utility model relates to a surface acoustic wave device with a piston mode, and relates to the field of radio frequency. Compared with a common piston mode, the surface acoustic wave device with the piston mode, provided by the invention, has the advantages that the weight increasing electrode of the electrode finger completely covers all the surfaces of the edge of the excitation part of the electrode finger, so that the sound velocity of the area can be reduced to the greatest extent, the best effect on inhibition of a transverse mode is achieved, and the requirement on the process is simpler.

Description

Technical Field

[0001] The present application relates to the field of radio frequency technology, and in particular to a surface acoustic wave device with a piston mode. Background Art

[0002] Surface acoustic wave devices are widely used in filters, duplexers and other RF communication equipment due to their advantages such as miniaturization, low loss and high out-of-band suppression. However, surface acoustic wave devices will produce some clutter responses due to factors such as materials and device structure, which will seriously deteriorate device performance.

[0003] At present, methods have been developed to increase the mass load at the end of the IDT electrode to reduce the speed of sound to suppress noise, which generally includes increasing the metallization rate of the interdigital electrodes at the end of the IDT electrode or adding a layer of material above the electrode fingers at the end of the IDT electrode. In order to achieve a greater mass load effect, a combination of the above two methods is often used. However, this method places stringent requirements on the photolithography accuracy. Once an alignment deviation occurs, not only will the effect of suppressing noise fail to be achieved, but it will also affect the device performance and lead to a decrease in product consistency. Summary of the invention

[0004] The purpose of the present application is to provide a surface acoustic wave device with a piston mode to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above purpose, the technical solution adopted in this application is:

[0006] The present application provides a surface acoustic wave device with a piston mode, comprising:

[0007] a piezoelectric substrate having a surface for propagating acoustic waves;

[0008] an interdigital transducer electrode disposed on the piezoelectric substrate; and

[0009] Electrode refers to weighted electrode;

[0010] The IDT electrode comprises a plurality of first electrode fingers and a plurality of second electrode fingers interlaced with each other, and a first bus bar and a second bus bar facing each other in the extending direction of the first electrode fingers and the second electrode fingers;

[0011] In the extending direction of the electrode finger, the first electrode finger and the second electrode finger each include an electrode finger excitation portion, an electrode finger weighted portion located on both sides of the electrode finger excitation portion, and an electrode finger connecting portion located outside the electrode finger weighted portion;

[0012] The electrode finger excitation portion, the electrode finger weighted portion, and the electrode finger connecting portion of each of the first electrode finger and the second electrode finger form a central region, a first low-speed portion, and a first high-speed portion in sequence along the projection area parallel to the propagation direction of the surface acoustic wave, and the first bus bar and the second bus bar form a second low-speed portion along the projection area parallel to the propagation direction of the surface acoustic wave;

[0013] The sound speed of the surface acoustic wave propagating in the first low speed portion and the second low speed portion is lower than the sound speed of the surface acoustic wave propagating in the central region, and the sound speed of the surface acoustic wave propagating in the first high speed portion is higher than the sound speed of the surface acoustic wave propagating in the central region, thereby forming a piston mode;

[0014] The electrode finger weighted electrodes are coated on all surfaces of the electrode finger weighted portions of the first electrode fingers and the second electrode fingers.

[0015] In a possible implementation, the IDT electrode is at least one of titanium, aluminum, copper, silver, nickel, chromium, platinum, gold, molybdenum, tungsten, or an alloy mainly composed of the above materials;

[0016] The metallization ratio of the IDT electrode is 0.3 to 0.7, and the thickness of the IDT electrode is 3% to 15% of the period length of the IDT electrode.

[0017] In one possible implementation, the electrode finger weighted electrodes are a periodic array, extending outward along the propagation direction of the surface acoustic wave from the center of the electrode finger weighted portions of the first electrode finger and the second electrode finger, and the metallization ratio of the electrode finger weighted electrodes is greater than the metallization ratio of the interdigital transducer electrode.

[0018] In a possible implementation, the electrode finger weighted electrodes are a periodic array extending outward along the length direction of the electrode fingers from the center of the electrode finger weighted portions of the first electrode fingers and the second electrode fingers, and the length of the electrode finger weighted electrodes is 0.35 to 2 times the wavelength of the surface acoustic wave.

[0019] In one possible implementation, the electrode finger weighting electrodes are a periodic array, extending outward along the electrode finger height direction with the center of the electrode finger weighting portion of the first electrode finger and the second electrode finger, and the extension distance of the electrode finger weighting electrodes is 0.05 to 1.5 times the thickness of the interdigital transducer electrode.

[0020] In a possible implementation, the electrode finger weighted electrode is formed by electroplating or chemical plating.

[0021] In a possible implementation, the electrode finger weighted electrode is at least one of titanium, aluminum, chromium, copper, nickel, gold, lead, zinc, and tin, or a combination of two or more thereof.

[0022] The beneficial effects of the technical solution provided by this application include at least:

[0023] Compared with the common piston mode, the electrode finger weighted electrode of the surface acoustic wave device with piston mode provided in the present application completely covers all surfaces at the edge of the electrode finger excitation part, which can minimize the speed of sound in this area, has the best effect on suppressing the lateral mode, and has simpler process requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation of the present application. In the accompanying drawings:

[0025] Figure 1 1 shows a top view of a surface acoustic wave device 100 provided in Comparative Example 1;

[0026] Figure 2 shows a conductance-frequency curve 30 of the surface acoustic wave device 100 provided in Comparative Example 1;

[0027] Figure 3 A top view of a surface acoustic wave device 200 provided in Comparative Example 2 is shown;

[0028] Figure 4 A comparison diagram of the conductance-frequency curve 40 of the surface acoustic wave device 200 and the conductance-frequency curve 30 of the surface acoustic wave device 100 provided in Comparative Example 2 is shown;

[0029] Figure 5 FIG. 4 shows a top view of a surface acoustic wave device 300 provided in the first embodiment;

[0030] Figure 6 A detailed diagram of the electrode finger weighted electrode in the surface acoustic wave device 300 provided in the first embodiment is shown;

[0031] Figure 7 A comparison diagram of the conductance-frequency curve 50 of the surface acoustic wave device 300 provided in the first embodiment, the conductance-frequency curve 40 of the surface acoustic wave device 200, and the conductance-frequency curve 30 of the surface acoustic wave device 100 is shown;

[0032] Figure 8 FIG. 4 shows a top view of a surface acoustic wave device 400 provided in a first modification example;

[0033] Fig. 9 FIG. 4 shows a top view of a surface acoustic wave device 500 provided in a second modification example;

[0034] Fig.10A flow chart of a method for preparing a surface acoustic wave device with a piston mode provided in the second embodiment of the present application is shown. DETAILED DESCRIPTION

[0035] 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.

[0036] Among them, the same parts are represented by the same figure marks. It should be noted that the words "front", "rear", "left", "right", "up" and "down" used in the following description refer to the directions in the drawings of the present application specification, and the words "bottom surface" and "top surface", "inside" and "outside" refer to the direction towards or away from a specific component, respectively. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present application specification, the meaning of "multiple" is two or more.

[0037] The present application is further described below in conjunction with the accompanying drawings and embodiments.

[0038] Comparative Example 1:

[0039] Figure 1 1 shows a top view of the surface acoustic wave device 100 provided in Comparative Example 1. The height direction of the surface acoustic wave device 100 is not shown.

[0040] In detail, the surface acoustic wave device 100 includes a piezoelectric substrate 6, and an IDT electrode and a reflector electrode disposed above the piezoelectric substrate 6; the reflector electrode includes a reflector bus bar 4 and a plurality of reflector electrode fingers 5. The IDT electrode includes a plurality of first electrode fingers 1a and a plurality of second electrode fingers 1b interlaced with each other, and a first bus bar 2 and a second bus bar 3 facing each other in the extending direction of the first electrode fingers 1a and the second electrode fingers 1b. In the extending direction of the electrode fingers, the first electrode fingers 1a and the second electrode fingers 1b each include an electrode finger excitation portion 12 and an electrode finger connection portion 11 outside the electrode finger excitation portion 12; the electrode finger excitation portion 12 and the electrode finger connection portion 11 of each first electrode finger 1a and the second electrode finger 1b form a central area and a first high-speed portion in sequence along the projection area parallel to the propagation direction of the surface acoustic wave; the first bus bar 2 and the second bus bar 3 each include a bus bar portion 10, and form a second low-speed portion along the projection area parallel to the propagation direction of the surface acoustic wave.

[0041] Among them, the sound speed of the surface acoustic wave propagating in the second low-speed portion is lower than the sound speed of the surface acoustic wave propagating in the central area, and the sound speed of the surface acoustic wave propagating in the first high-speed portion is higher than the sound speed of the surface acoustic wave propagating in the central area.

[0042] Optionally, the material of the piezoelectric substrate 6 is quartz, lithium niobate, lithium tantalate, aluminum nitride, zinc oxide, lead zirconate titanate, and a multilayer composite material including a film of the above materials. Optionally, the electrode material of the interdigital transducer includes at least one of titanium, aluminum, copper, silver, nickel, chromium, platinum, gold, molybdenum, and tungsten, or an alloy mainly composed of the above materials. Optionally, the electrode finger weighted electrode material includes at least one of copper, nickel, gold, lead, zinc, and tin, or a combination of two or more thereof.

[0043] It is worth noting that the SAW device 100 does not have a piston mode and cannot change the physical properties of the sound wave at the edge of the electrode finger excitation portion 12, resulting in a large amount of diffraction of the sound wave propagating in a certain direction, thereby failing to generate a flat propagation waveform.

[0044] Figure 2 The conductance-frequency curve 30 of the surface acoustic wave device 100 provided in the first comparative example is shown. It can be found that the regular fluctuation between the resonant frequency and the anti-resonant frequency of the surface acoustic wave device 100 is specifically caused by the transverse mode.

[0045] Desirably, the physical properties of the IDT electrodes at the edge of the electrode finger excitation portion 12 are modified so that the acoustic wave velocity in the edge region is less than that of the electrode finger excitation portion 12, and the acoustic wave velocity of the electrode finger connection portion 11 is greater than that of the electrode finger excitation portion 12, thereby generating a flat propagation waveform in the electrode finger excitation portion 12. Therefore, the following method is often used in the industry to suppress waveforms with regular fluctuations.

[0046] Comparative Example 2:

[0047] Figure 3 FIG. 2 shows a top view of a surface acoustic wave device 200 provided in Comparative Example 2. The height direction of the surface acoustic wave device 200 is not shown.

[0048] In detail, the surface acoustic wave device 200 includes a piezoelectric substrate 6, an IDT electrode and a reflector electrode disposed above the piezoelectric substrate 6; the surface acoustic wave device 200 also includes an electrode finger weighting electrode 7. The reflector electrode includes a reflector bus bar 4 and a plurality of reflector electrode fingers 5; the IDT electrode includes a plurality of first electrode fingers 1a and a plurality of second electrode fingers 1b interlaced with each other, and a first bus bar 2 and a second bus bar 3 facing each other in the extending direction of the first electrode fingers 1a and the second electrode fingers 1b. In the extension direction of the electrode fingers, the first electrode finger 1a and the second electrode finger 1b each include an electrode finger excitation portion 12, an electrode finger weight portion 13 on both sides of the electrode finger excitation portion 12, and an electrode finger connection portion 11 outside the electrode finger weight portion 13; the electrode finger excitation portion 12, the electrode finger connection portion 11, and the electrode finger weight portion 13 of each first electrode finger 1a and the second electrode finger 1b form a central area, a first high-speed portion, and a first low-speed portion in sequence along a projection area parallel to the propagation direction of the surface acoustic wave; the first bus bar 2 and the second bus bar 3 include a bus bar portion 10, and form a second low-speed portion along a projection area parallel to the propagation direction of the surface acoustic wave.

[0049] Among them, the sound speed of the surface acoustic wave propagating in the first low-speed section and the second low-speed section is lower than the sound speed of the surface acoustic wave propagating in the central area, and the sound speed of the surface acoustic wave propagating in the first high-speed section is higher than the sound speed of the surface acoustic wave propagating in the central area.

[0050] Optionally, the material of the piezoelectric substrate 6 is quartz, lithium niobate, lithium tantalate, aluminum nitride, zinc oxide, lead zirconate titanate, and a multilayer composite material including a film of the above materials. Optionally, the interdigital transducer electrode material includes at least one of titanium, aluminum, copper, silver, nickel, chromium, platinum, gold, molybdenum, and tungsten, or an alloy mainly composed of the above materials.

[0051] It is worth noting that the surface acoustic wave device 200 has a piston mode, which changes the physical properties of the acoustic wave at the edge of the electrode finger excitation portion 12 and suppresses the diffraction of the acoustic wave propagating in a certain direction, thereby generating a flat propagation waveform.

[0052] Figure 4 A comparison diagram of the conductance-frequency curve 40 of the surface acoustic wave device 200 provided in the second comparative example and the conductance-frequency curve 30 of the surface acoustic wave device 100 is shown. It can be found that the regular fluctuation between the resonant frequency and the anti-resonant frequency of the surface acoustic wave device 100 is suppressed, and the surface acoustic wave device 200 can generate a relatively flat propagation waveform.

[0053] However, the piston mode commonly used in the industry, such as the surface acoustic wave device 200, often leads to two fatal defects. First, the first low-frequency part formed by the piston mode is not low enough, and the suppression of the lateral mode is not complete; second, the electrode finger excitation part and the electrode finger weight part are formed by secondary lithography, and the electrode finger weight part often shifts in position due to lithography accuracy problems, thereby affecting the performance of the surface acoustic wave device.

[0054] Embodiment 1:

[0055] Figure 5 FIG. 1 shows a top view of the surface acoustic wave device 300 provided in Embodiment 1. The height direction of the surface acoustic wave device 300 is not shown.

[0056] In detail, the surface acoustic wave device 300 includes a piezoelectric substrate 6, an IDT electrode and a reflector electrode disposed above the piezoelectric substrate 6; the surface acoustic wave device 300 also includes an electrode finger weighting electrode 7. The reflector electrode includes a reflector bus bar 4 and a plurality of reflector electrode fingers 5; the IDT electrode includes a plurality of first electrode fingers 1a and a plurality of second electrode fingers 1b interlaced with each other, and a first bus bar 2 and a second bus bar 3 facing each other in the extending direction of the first electrode fingers 1a and the second electrode fingers 1b. In the extension direction of the electrode fingers, the first electrode finger 1a and the second electrode finger 1b each include an electrode finger excitation portion 12, an electrode finger weight portion 13 on both sides of the electrode finger excitation portion 12, and an electrode finger connection portion 11 outside the electrode finger weight portion 13; the electrode finger excitation portion 12, the electrode finger connection portion 11, and the electrode finger weight portion 13 of each of the first electrode finger 1a and the second electrode finger 1b form a central area, a first high-speed portion, and a first low-speed portion in sequence along a projection area parallel to the propagation direction of the surface acoustic wave; the first bus bar 2 and the second bus bar 3 include a bus bar portion 10, and form a second low-speed portion along a projection area parallel to the propagation direction of the surface acoustic wave.

[0057] Among them, the sound speed of the surface acoustic wave propagating in the first low-speed section and the second low-speed section is lower than the sound speed of the surface acoustic wave propagating in the central area, and the sound speed of the surface acoustic wave propagating in the first high-speed section is higher than the sound speed of the surface acoustic wave propagating in the central area.

[0058] Optionally, the material of the piezoelectric substrate 6 is quartz, lithium niobate, lithium tantalate, aluminum nitride, zinc oxide, lead zirconate titanate, and a multilayer composite material including a film of the above materials. Optionally, the electrode material of the interdigital transducer includes at least one of titanium, aluminum, copper, silver, nickel, chromium, platinum, gold, molybdenum, and tungsten, or an alloy mainly composed of the above materials. Optionally, the electrode finger weighted electrode material includes at least one of copper, nickel, gold, lead, zinc, and tin, or a combination of two or more thereof.

[0059] In one example, the metallization ratio of the IDT electrode is 0.3 to 0.7, and the thickness of the IDT electrode is 3% to 15% of the period length of the IDT electrode. In another example, the electrode finger weighted electrode is a periodic array, extending outward along the propagation direction of the surface acoustic wave from the center of the electrode finger weighted portion of the first electrode finger and the second electrode finger, and the metallization ratio of the electrode finger weighted electrode is greater than the metallization ratio of the IDT electrode. In another example, the electrode finger weighted electrode is a periodic array, extending outward along the length direction of the electrode finger from the center of the electrode finger weighted portion of the first electrode finger and the second electrode finger, and the length of the electrode finger weighted electrode is 0.35 to 2 times the wavelength of the surface acoustic wave. In another example, the electrode finger weighted electrode is a periodic array, extending outward along the height direction of the electrode finger from the center of the electrode finger weighted portion of the first electrode finger and the second electrode finger, and the extension distance of the electrode finger weighted electrode is 0.05 to 1.5 times the thickness of the IDT electrode.

[0060] It should be noted that, unlike the surface acoustic wave device 200 of the second comparative example, the electrode finger weighted electrode 7 of the surface acoustic wave device 300 is formed by an electroplating or chemical plating process, and covers all surfaces of the edge of the electrode finger excitation portion 12 of the first electrode finger 1a and the second electrode finger 1b. This is determined by the characteristics of electroplating or chemical plating; while the electrode finger weighted electrode 7 of the surface acoustic wave device 200 is formed by an electron beam evaporation process, and cannot completely cover all surfaces of the edge of the electrode finger excitation portion 12 of the first electrode finger 1a and the second electrode finger 1b, and cannot reduce the sound speed in this area to the greatest extent, so as to maximize the suppression of the lateral mode.

[0061] In addition, since the electron beam evaporation process requires prior photolithography, it has very high requirements for photolithography accuracy. In the actual preparation process, the electrode finger weighted electrodes of the surface acoustic wave device 200 often have a certain position offset due to insufficient photolithography accuracy, thereby destroying the performance of the surface acoustic wave device.

[0062] Figure 6 The detailed diagram of the electrode finger weighted electrode in the surface acoustic wave device 300 provided in the first embodiment is shown. It can be seen that the surface acoustic wave device 300 has a piston mode, and the electrode finger weighted electrode 7 completely covers all surfaces at the edge of the electrode finger excitation part 12, which can reduce the sound speed in this area to the greatest extent and has the best effect on suppressing the lateral mode.

[0063] Figure 7 The diagram shows a comparison of the conductance-frequency curve 50 of the surface acoustic wave device 300 provided in the first embodiment with the conductance-frequency curve 40 of the surface acoustic wave device 200 and the conductance-frequency curve 30 of the surface acoustic wave device 100. It can be found that, compared with the surface acoustic wave device 200 and the surface acoustic wave device 100, the waveform of the surface acoustic wave device 300 propagating between the resonant frequency and the anti-resonant frequency is flatter.

[0064] Modification 1:

[0065] Figure 8 FIG. 1 shows a top view of a surface acoustic wave device 400 provided in Modification 1. The height direction of the surface acoustic wave device 400 is not shown.

[0066] In detail, the surface acoustic wave device 400 includes a piezoelectric substrate, an interdigital transducer electrode and a reflector electrode arranged above the piezoelectric substrate; the surface acoustic wave device 400 also includes an electrode finger weighting electrode. The reflector electrode includes a reflector bus bar and a plurality of reflector electrode fingers; the interdigital transducer electrode includes a plurality of first electrode fingers and a plurality of second electrode fingers interlaced with each other, and a first bus bar and a second bus bar facing each other in the extending direction of the first electrode finger and the second electrode finger. In the extending direction of the electrode finger, the first electrode finger and the second electrode finger each include an electrode finger excitation portion, an electrode finger weighting portion on both sides of the electrode finger excitation portion, and an electrode finger connecting portion outside the electrode finger weighting portion; the electrode finger excitation portion, the electrode finger connecting portion, and the electrode finger weighting portion of each first electrode finger and the second electrode finger sequentially form a central area, a first high-speed portion, and a first low-speed portion along the projection area parallel to the propagation direction of the surface acoustic wave; the first bus bar and the second bus bar include a bus bar portion, and form a second low-speed portion along the projection area parallel to the propagation direction of the surface acoustic wave.

[0067] Among them, the sound speed of the surface acoustic wave propagating in the first low-speed section and the second low-speed section is lower than the sound speed of the surface acoustic wave propagating in the central area, and the sound speed of the surface acoustic wave propagating in the first high-speed section is higher than the sound speed of the surface acoustic wave propagating in the central area.

[0068] Optionally, the material of the piezoelectric substrate is quartz, lithium niobate, lithium tantalate, aluminum nitride, zinc oxide, lead zirconate titanate, and a multilayer composite material including a film of the above materials. Optionally, the electrode material of the interdigital transducer includes at least one of titanium, aluminum, copper, silver, nickel, chromium, platinum, gold, molybdenum, and tungsten, or an alloy mainly composed of the above materials. Optionally, the electrode finger weight gain electrode material includes at least one of copper, nickel, gold, lead, zinc, and tin, or a combination of two or more thereof.

[0069] It should be noted that the difference between the first variant and the first embodiment is that the shapes of the electrode finger weighting electrodes covering all surfaces of the edge of the electrode finger excitation portion are different.

[0070] Based on the same reasons as those of the first embodiment, the structure of this variation can also exhibit good lateral mode suppression function.

[0071] Modification 2:

[0072] Fig. 9FIG. 1 is a top view of a surface acoustic wave device 500 provided in Modification 2. The height direction of the surface acoustic wave device 500 is not shown.

[0073] In detail, the surface acoustic wave device 500 includes a piezoelectric substrate, an IDT electrode and a reflector electrode disposed on the piezoelectric substrate; the surface acoustic wave device 500 also includes an electrode finger weighting electrode. The reflector electrode includes a reflector bus bar and a plurality of reflector electrode fingers; the IDT electrode includes a plurality of first electrode fingers and a plurality of second electrode fingers interlaced with each other, and a first bus bar and a second bus bar facing each other in the extending direction of the first electrode fingers and the second electrode fingers.

[0074] In the extension direction of the electrode fingers, the first electrode fingers and the second electrode fingers each include an electrode finger excitation portion, an electrode finger weighted portion on both sides of the electrode finger excitation portion, and an electrode finger connecting portion outside the electrode finger weighted portion; the electrode finger excitation portion, the electrode finger connecting portion, and the electrode finger weighted portion of each first electrode finger and the second electrode finger form a central area, a first high-speed portion, and a first low-speed portion in sequence along a projection area parallel to the propagation direction of the surface acoustic wave; the first bus bar and the second bus bar include a bus bar portion, and form a second low-speed portion along a projection area parallel to the propagation direction of the surface acoustic wave.

[0075] Among them, the sound speed of the surface acoustic wave propagating in the first low-speed section and the second low-speed section is lower than the sound speed of the surface acoustic wave propagating in the central area, and the sound speed of the surface acoustic wave propagating in the first high-speed section is higher than the sound speed of the surface acoustic wave propagating in the central area.

[0076] Optionally, the material of the piezoelectric substrate is quartz, lithium niobate, lithium tantalate, aluminum nitride, zinc oxide, lead zirconate titanate, and a multilayer composite material including a film of the above materials. Optionally, the electrode material of the interdigital transducer includes at least one of titanium, aluminum, copper, silver, nickel, chromium, platinum, gold, molybdenum, and tungsten, or an alloy mainly composed of the above materials. Optionally, the electrode finger weight gain electrode material includes at least one of copper, nickel, gold, lead, zinc, and tin, or a combination of two or more thereof.

[0077] It should be noted that the difference between the second variant and the first embodiment is that any electrode finger has two electrode finger weight-added parts.

[0078] Embodiment 2:

[0079] Fig.10 A flow chart showing a method for preparing a surface acoustic wave device with a piston mode provided in the second embodiment of the present application is shown. The method is applicable to the surface acoustic wave device described in any of the above embodiments or variations. The method comprises:

[0080] Step S1, preparing a piezoelectric substrate;

[0081] Step S2, patterning the surface of the piezoelectric substrate by photolithography;

[0082] Step S3, depositing IDT electrodes on the piezoelectric substrate by electron beam evaporation process;

[0083] Step S4, removing the photoresist on the piezoelectric substrate by a stripping process;

[0084] Step S5, secondary patterning the surface of the piezoelectric substrate by photolithography;

[0085] Step S6, forming electrode finger weighted electrodes on the IDT electrodes by electroplating or chemical plating process;

[0086] Step S7: removing the photoresist on the piezoelectric substrate through a stripping process.

[0087] To sum up, compared with the common piston mode, the electrode finger weighted electrode of the surface acoustic wave device with piston mode provided in the present application completely covers all surfaces at the edge of the electrode finger excitation part, which can minimize the speed of sound in this area, has the best effect on suppressing the lateral mode, and has simpler process requirements.

[0088] In the embodiments disclosed in the present application, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments disclosed in the present application can be understood according to specific circumstances.

[0089] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A surface acoustic wave device having a piston mode, characterized in that: include: a piezoelectric substrate having a surface for propagating acoustic waves; an interdigital transducer electrode disposed on the piezoelectric substrate; as well as Electrode refers to weighted electrode; The IDT electrode comprises a plurality of first electrode fingers and a plurality of second electrode fingers interlaced with each other, and a first bus bar and a second bus bar facing each other in the extending direction of the first electrode fingers and the second electrode fingers; In the extending direction of the electrode finger, the first electrode finger and the second electrode finger each include an electrode finger excitation portion, an electrode finger weighted portion located on both sides of the electrode finger excitation portion, and an electrode finger connecting portion located outside the electrode finger weighted portion; The electrode finger excitation portion, the electrode finger weighted portion, and the electrode finger connecting portion of each of the first electrode finger and the second electrode finger form a central region, a first low-speed portion, and a first high-speed portion in sequence along the projection area parallel to the propagation direction of the surface acoustic wave, and the first bus bar and the second bus bar form a second low-speed portion along the projection area parallel to the propagation direction of the surface acoustic wave; The sound speed of the surface acoustic wave propagating in the first low speed portion and the second low speed portion is lower than the sound speed of the surface acoustic wave propagating in the central region, and the sound speed of the surface acoustic wave propagating in the first high speed portion is higher than the sound speed of the surface acoustic wave propagating in the central region, thereby forming a piston mode; The electrode finger weighted electrodes are coated on all surfaces of the electrode finger weighted portions of the first electrode fingers and the second electrode fingers.

2. The surface acoustic wave device with piston mode according to claim 1, characterized in that: The IDT electrode is one of titanium, aluminum, copper, silver, nickel, chromium, platinum, gold, molybdenum and tungsten; The thickness of the IDT electrode is 3% to 15% of the period length of the IDT electrode.

3. The surface acoustic wave device with piston mode according to claim 1, characterized in that: The electrode finger weighted electrodes are a periodic array, extending outward from the center of the electrode finger weighted portions of the first electrode finger and the second electrode finger along the propagation direction of the surface acoustic wave.

4. The surface acoustic wave device with piston mode according to claim 1, characterized in that: The electrode finger weighted electrodes are a periodic array, extending outward along the length direction of the electrode fingers from the center of the electrode finger weighted parts of the first electrode fingers and the second electrode fingers, and the length of the electrode finger weighted electrodes is 0.35 to 2 times the wavelength of the surface acoustic wave.

5. The surface acoustic wave device with piston mode according to claim 1, characterized in that: The electrode finger weighted electrodes are a periodic array, extending outward along the electrode finger height direction from the center of the electrode finger weighted portion of the first electrode finger and the second electrode finger, and the extension distance of the electrode finger weighted electrodes is 0.05 to 1.5 times the thickness of the IDT electrode.

6. The surface acoustic wave device with piston mode according to claim 1, characterized in that: The electrode finger weighted electrode is formed by electroplating or chemical plating.

7. The surface acoustic wave device with piston mode according to claim 1, characterized in that: The electrode finger weighting electrode is one of titanium, aluminum, chromium, copper, nickel, gold, lead, zinc and tin.

Images