Elastic wave device and module

Abstract

The utility model relates to an elastic wave device and a module. The tail end of an electrode finger of the elastic wave device is provided with an extension part; the joint of the extension part and the tail end of the electrode finger is observed from the direction perpendicular to the main surface of the piezoelectric substrate, and the length is larger than the width of the electrode finger. According to the elastic wave device, the forming material of the extension part is different from the forming material of the electrode fingers, the problem that the filtering performance of the elastic wave device is poor due to the fact that a high-frequency and high-power SAW device has large clutters is solved, and the clutters are effectively restrained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, and in particular to an elastic wave device and module. BACKGROUND

[0002] With the development of science and technology and society, the fifth generation mobile communication technology (5G communication) has become the current mainstream, especially in the field of radio frequency front-end, the demand for high-performance, high-frequency and high-power communication devices has increased.

[0003] A surface acoustic wave (SAW) resonator is an elastic wave device that utilizes the characteristics of piezoelectric materials to achieve the conversion between electrical signals and acoustic signals. Its core lies in its ability to convert electrical energy into mechanical energy using the piezoelectric effect of the material, and then convert the mechanical energy back into electrical energy. Its basic structure includes a piezoelectric substrate and an interdigital transducer (IDT) deposited on its surface. When an electrical signal is applied to the IDT, an elastic wave propagating in a specific direction is generated on the surface of the piezoelectric material, i.e. a surface acoustic wave. In this process, the IDT not only acts as a transducer, but also functions as a reflection grating, concentrating acoustic wave energy within a certain frequency range through multiple reflections, thereby achieving resonance.

[0004] In the prior art, SAW devices with high frequency and high power have large spurs, resulting in poor filtering performance of the elastic wave device. Therefore, a high-performance SAW device combining new structures and materials is proposed, which has the advantage of suppressing spurious modes. CONTENT OF THE INVENTION

[0005] The present application provides an elastic wave device and module to solve the problem of poor filtering performance of the elastic wave device caused by large spurs in SAW devices with high frequency and high power.

[0006] In a first aspect, the present application provides an elastic wave device, comprising a piezoelectric substrate;

[0007] An IDT electrode located on the main surface of the piezoelectric substrate for exciting elastic waves with a wavelength of λ; wherein the IDT electrode comprises a first bus bar, an electrode finger and a virtual electrode finger; the two first bus bars are oppositely arranged; the top end of the electrode finger is connected with the first bus bar and is arranged between the two first bus bars and staggered; the top end of the virtual electrode finger is connected with the first bus bar and is located between the two first bus bars; the length direction of the electrode finger is the first direction, the length direction of the first bus bar is the second direction, and the first direction is perpendicular to the second direction;

[0008] The tail end of the electrode finger has an extension; the joint of the extension and the tail end of the electrode finger has a length greater than the width of the electrode finger in a third direction perpendicular to the main surface of the piezoelectric substrate;

[0009] The extension is made of a material different from that of the electrode finger.

[0010] In some embodiments, the joint of the extension and the tail end of the electrode finger is arc-shaped in the third direction; the arc-shaped joint has waveform consistency with the waveform of the elastic wave.

[0011] In some embodiments, the joint of the extension and the tail end of the electrode finger is a trigonometric function curve in the third direction; the trigonometric function curve has waveform consistency with the waveform of the elastic wave.

[0012] In some embodiments, the IDT electrode is made of at least one of aluminum, copper, platinum, and gold.

[0013] In some embodiments, the first bus bar is made of a material different from that of the electrode finger.

[0014] In some embodiments, the IDT electrode further comprises a second bus bar, and the electrode finger and the dummy electrode finger are connected to the second bus bar; the first bus bar is parallel to the second bus bar in the second direction.

[0015] In some embodiments, the second bus bar is made of a material different from that of the first bus bar.

[0016] In some embodiments, the area between the first bus bar and the second bus bar is an edge area, and the area between the two second bus bars is a center area; the electrode finger in the edge area is made of a material different from that of the electrode finger in the center area; the dummy electrode finger in the edge area is made of a material different from that of the dummy electrode finger in the center area.

[0017] In some embodiments, the IDT electrode has a thickness of 0.03λ-0.2λ.

[0018] In a second aspect, the utility model provides a module which comprises a plurality of elastic wave devices as described in the first aspect.

[0019] Compared with the related art, the elastic wave device of the embodiment includes a piezoelectric substrate; an IDT electrode on a main surface of the piezoelectric substrate, used for exciting an elastic wave with a wavelength of λ; wherein the IDT electrode includes first bus bars, electrode fingers and virtual electrode fingers; the two first bus bars are oppositely arranged; the top ends of the electrode fingers are connected with the first bus bars and are arranged between the first bus bars in an interleaved manner; the top ends of the virtual electrode fingers are connected with the first bus bars and are arranged between the two first bus bars; the length direction of the electrode finger is a first direction, the length direction of the first bus bar is a second direction, and the first direction is perpendicular to the second direction; the tail end of the electrode finger has an extension; the joint of the extension and the tail end of the electrode finger has a length greater than the width of the electrode finger, as viewed in a direction perpendicular to the main surface of the piezoelectric substrate; the direction perpendicular to the main surface of the piezoelectric substrate is a third direction, and the material constituting the extension is different from the material constituting the electrode finger. Through the above elastic wave device, the problem that the high-frequency and high-power SAW device has a large spurious wave, resulting in poor filtering performance of the elastic wave device, is solved, and the spurious mode is effectively suppressed.

[0020] The details of one or more embodiments of the present application are presented in the following drawings and description to make other features, objects and advantages of the present application more apparent. BRIEF DESCRIPTION OF DRAWINGS

[0021] The drawings described herein are intended to provide further understanding of the present application, form a part of the present application, and the illustrative embodiments of the present application and the description thereof are used to explain the present application, and do not constitute improper limitation on the present application.

[0022] Figure 1 is a structural schematic diagram of an elastic wave device of a first embodiment of the present application;

[0023] Figure 2 is a conductance characteristic diagram of the elastic wave device of the embodiment and comparative example 1;

[0024] Figure 3 is a real part conductance characteristic diagram of the elastic wave device of the embodiment and comparative example 1;

[0025] Figure 4 is a structural schematic diagram of an elastic wave device of a second embodiment of the present application;

[0026] Figure 5 is a structural schematic diagram of an elastic wave device of a third embodiment of the present application;

[0027] Figure 6 is a structural schematic diagram of an elastic wave device of a fourth embodiment of the present application;

[0028] Figure 7 is a structural schematic diagram of an elastic wave device of a fifth embodiment of the present application;

[0029] Figure 8 Structure diagram of an elastic wave device of the preferred embodiment;

[0030] Figure 9 Admittance characteristic diagram of an elastic wave device of the preferred embodiment and Comparative Example 2;

[0031] Figure 10 Admittance real part characteristic diagram of an elastic wave device of the preferred embodiment and Comparative Example 2;

[0032] Figure 11 Cross-sectional view of a module of an elastic wave device of an embodiment of the present application.

[0033] In the figure: 100, piezoelectric substrate; 210, first bus bar; 220, electrode finger; 230, dummy electrode finger; 240, extension; 250, second bus bar; 600, elastic wave device; 700, inductor; 800, wiring substrate; 900, sealing portion; 801, IC integrated circuit component; 802, connection terminal. DETAILED DESCRIPTION

[0034] In order to more clearly understand the objects, technical solutions and advantages of the present application, the present application will be described and explained in detail below in connection with the drawings and embodiments.

[0035] Unless otherwise defined, technical terms or scientific terms used in the present application shall have the general meaning understood by a person with ordinary skill in the art to which the present application belongs. In the present application, "one", "a", "an", "the", "these" and similar words do not represent a quantitative limitation, and they can be singular or plural. In the present application, the terms "include", "contain", "have" and any variants thereof have the purpose of covering non-exclusive inclusion; for example, a process, method and system, product or device containing a series of steps or modules (units) are not limited to the listed steps or modules (units), but can include steps or modules (units) not listed, or can include other steps or modules (units) inherent to the process, method, product or device. In the present application, the terms "connected", "connected", "coupled" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. In the present application, "multiple" means two or more. The association between the associated objects is described by the term "and / or", which means that there can be three relationships, for example, "A and / or B" can mean that A exists alone, A and B exist together, and B exists alone. In general, the character " / " represents an "or" relationship between the objects before and after it. In the present application, the terms "first", "second", "third" and the like are only used to distinguish similar objects, and do not represent a specific order of the objects.

[0036] Hereinafter, based on Figures 1 to 11 , an elastic wave device of the present application is described.

[0037] Embodiments are described below with reference to the accompanying drawings. In the drawings, like or corresponding parts are denoted by like reference numerals. For parts described repeatedly, appropriate simplification or omission will be made or omitted.

[0038] Figure 1 is a structural schematic diagram of an elastic wave device of a first embodiment of the present application, as Figure 1 shown, from the direction perpendicular to the main surface of the piezoelectric substrate 100, the elastic wave device of the present embodiment includes a piezoelectric substrate 100, the constituting material of which includes, but is not limited to, lithium tantalate or lithium niobate, etc. piezoelectric material, the thickness range is 0.1λ~0.4λ, where λ is the wavelength, the thickness and the Euler angle range can excite larger electromechanical coupling coefficient and higher Q value, at the same time, the in-band spurs of the elastic wave device are smaller; IDT electrode located on the main surface of the piezoelectric substrate 100, used to excite elastic wave with wavelength λ, the thickness of the IDT electrode is 0.03λ~0.2λ, wherein the IDT electrode includes first bus bar 210, electrode finger 220, and virtual electrode finger 230; two first bus bars 210 are oppositely arranged; the top end of the electrode finger 220 is connected with the first bus bar 210, and is located between the two first bus bars 210 and is staggered distributed, and the constituting material thereof includes at least one metal of copper, aluminum, platinum, gold, tungsten and titanium. The top end of the virtual electrode finger 230 is connected with the first bus bar 210, and is located between the two first bus bars 210, and the constituting material thereof is the same as that of the electrode finger 220. The length direction of the electrode finger 230 is the first direction, i.e. Figure 1 Y direction in the middle, the length direction of the first bus bar 210 is the second direction, i.e. Figure 1 X direction in the middle, the first direction is perpendicular to the second direction. The tail end of the electrode finger has an extension 240, from the direction perpendicular to the main surface of the piezoelectric substrate 100, the length of the joint between the extension 240 and the tail end of the electrode finger 220 is greater than the width W of the electrode finger; the direction perpendicular to the main surface of the piezoelectric substrate 100 is the third direction; the constituting material of the extension 240 is different from that of the electrode finger.

[0039] The duty cycle of the electrode finger 220 of the IDT electrode of the present embodiment is 0.3~0.75, which is defined as the ratio of the width W (i.e. line width) of the electrode finger 220 to 0.5 times the wavelength λ of the acoustic wave. By adjusting the duty cycle of the electrode finger 220 to adjust the acoustic wave speed, the leakage of the transverse energy of the elastic wave device can be effectively suppressed, and the frequency response of the elastic wave device can be better controlled.

[0040] The elastic wave device sets the extension 240 with a material different from the electrode finger 220 to provide the acoustic impedance difference between the electrode finger 220 and the extension 240, and further to make the acoustic velocity of the elastic wave at the electrode finger 220 and the extension 240 different, thereby suppressing the elastic wave energy leakage excited by the IDT electrode. The length of the joint between the extension 240 and the electrode finger 220 is set to be greater than the width W of the electrode finger 220 to enhance the acoustic wave reflection at the joint, thereby suppressing the spurious scattering in the passband.

[0041] In some embodiments, the joint between the extension 240 and the tail end of the electrode finger 220 is arc-shaped as viewed from the third direction; the arc-shaped has waveform consistency with the waveform of the elastic wave.

[0042] Specifically, Figure 2 The admittance characteristic diagram of the elastic wave device of the present embodiment and comparative example 1 is shown, in which the red solid line is the admittance characteristic of the elastic wave device of the present embodiment, and the blue solid line is the admittance characteristic of the elastic wave device of comparative example 1; Figure 3 The real part of the admittance characteristic diagram of the elastic wave device of the present embodiment and comparative example 1 is shown, in which the red solid line is the real part of the admittance characteristic of the elastic wave device of the present embodiment, and the blue solid line is the real part of the admittance characteristic of the elastic wave device of comparative example 1. The difference between the present embodiment and comparative example 1 is that the joint between the extension 240 and the electrode finger 220 of comparative example 1 is a straight line parallel to the second bus bar 210 as viewed from the third direction, i.e., the length of the joint of comparative example 1 is equal to the width W of the electrode finger 220, and the other structures are the same as those of the present embodiment. Figure 2 and Figure 3 As shown, the transverse spurious of the present embodiment is suppressed in the passband (1750MHz-1850MHz) compared with comparative example 1. Therefore, the joint is set to be arc-shaped, which is approximately fitted with the waveform of the elastic wave propagation, thereby suppressing the transverse spurious mode of the elastic wave device and improving the filtering effect of the elastic wave device.

[0043] In some embodiments, the joint between the extension 240 and the tail end of the electrode finger 220 is a trigonometric function curve as viewed from the third direction, and the trigonometric function curve has waveform consistency with the waveform of the elastic wave.

[0044] Specifically, as shown, Figure 1 a coordinate system is established with the midpoint of the tail end of the extension as the origin, and a trigonometric function curve is established in the coordinate system, and the trigonometric function curve in the horizontal coordinate [-0.5W, 0.5W] interval is the joint between the extension 240 and the tail end of the electrode finger 220, in which the trigonometric function is specifically:

[0045] y=a*cos(b*x+c) (Formula 1)

[0046] The above formula 1 is a trigonometric function of the present embodiment, wherein a, b and c are electrode finger constants, a ranges from 1 to 5, b ranges from 0.1 to 10, and c ranges from 0 to 10; x and y are horizontal and vertical coordinate values of a coordinate system, respectively, the shape of the joint is constructed by setting the trigonometric function, the transverse noise mode of the elastic wave device is suppressed, and the filtering effect of the elastic wave device is improved.

[0047] In some embodiments, the first bus bar 210 is made of a material different from that of the electrode fingers.

[0048] Specifically, Figure 4 The structure of the elastic wave device of the second embodiment of the present application is shown in FIG. 2B. Figure 4 As shown in FIG. 2B, the first bus bar 210 is made of gold, and the electrode fingers 220 are made of aluminum. Since the acoustic impedance of gold is higher than that of aluminum, the use of gold as the material of the first bus bar 210 further increases the difference in acoustic velocity between the first bus bar region and the electrode finger region, thereby further suppressing the leakage of elastic wave energy. It should be noted that in other embodiments, the material of the first bus bar 210 can also be other metal materials having a higher acoustic impedance than that of the electrode fingers.

[0049] Figure 5 The structure of the elastic wave device of the third embodiment of the present application is shown in FIG. 3B. Figure 5 As shown in FIG. 3B, the IDT electrode further includes a second bus bar, and the electrode fingers 220 and the dummy electrode fingers 230 are connected to the second bus bar 250; the first bus bar 210 and the second bus bar 250 are parallel in the second direction. By providing the second bus bar 250, the acoustic velocity of the second bus bar region is reduced, so that the elastic wave device has an increased region with a difference in acoustic velocity, thereby further suppressing the leakage of elastic wave energy in the first direction (Y direction).

[0050] In some embodiments, the second bus bar 250 is made of a material different from that of the first bus bar 210.

[0051] Figure 6 The structure of the elastic wave device of the fourth embodiment of the present application is shown in FIG. 4B. Figure 6 As shown in FIG. 4B, the second bus bar 250 is made of platinum, and the first bus bar is made of aluminum. Since the acoustic impedance of platinum is higher than that of aluminum, the use of platinum as the material of the second bus bar 250 further increases the difference in acoustic velocity between the second bus bar region and the electrode finger region, thereby further suppressing the leakage of elastic wave energy.

[0052] In some embodiments, the area between the first busbar 210 and the second busbar 250 is designated as an edge region; the area between the two second busbars 250 is designated as a center region; the electrode fingers 220 in the edge region are made of a different material than the electrode fingers 220 in the center region; and the virtual electrode fingers 230 in the edge region are made of a different material than the virtual electrode fingers 230 in the center region.

[0053] Figure 7 This is a schematic diagram of the structure of the elastic wave device according to the fifth embodiment of this application, as shown below. Figure 7 As shown, the materials used to construct the electrode fingers 220 and virtual electrode fingers 230 in the edge region are selected to have a lower acoustic impedance than those used to construct the electrode fingers 220 and virtual electrode fingers 230 in the center region. For example, in this embodiment, the electrode fingers 220 and virtual electrode fingers 230 in the center region are made of copper, while the electrode fingers 220 and virtual electrode fingers 230 in the edge region are made of aluminum. Since the acoustic impedance of aluminum is lower than that of copper, the sound velocity difference between the edge region and the busbar region (first busbar and second busbar) is greater than the sound velocity difference between the center region and the busbar region, thereby suppressing the leakage of elastic waves from the center region to the first direction.

[0054] The elastic wave device of this application will now be described through preferred embodiments and Comparative Example 2.

[0055] Preferred embodiment

[0056] Figure 8 This is a schematic diagram of the structure of the elastic wave device according to a preferred embodiment. Figure 8 This is a schematic diagram of the structure of an elastic wave device for comparison.

[0057] The elastic wave device of the preferred embodiment includes a piezoelectric substrate; an IDT electrode on a main surface of the piezoelectric substrate, for exciting an elastic wave with a wavelength of λ, the IDT electrode having a thickness of 0.03λ-0.2λ; wherein the IDT electrode includes first bus bars, electrode fingers, and dummy electrode fingers; the two first bus bars are oppositely arranged; the top ends of the electrode fingers are connected to the first bus bars and are arranged between the two first bus bars in an interleaved manner; the top ends of the dummy electrode fingers are connected to the first bus bars and are arranged between the two first bus bars; the length direction of the electrode fingers is a first direction, the length direction of the first bus bars is a second direction, the first direction is perpendicular to the second direction; the tail end of the electrode finger has an extension; the joint between the extension and the tail end of the electrode finger has a length greater than the width of the electrode finger, as viewed in a third direction perpendicular to the main surface of the piezoelectric substrate; the extension is made of a material different from that of the electrode finger. The joint between the extension and the tail end of the electrode finger is a trigonometric function curve as viewed in the third direction, the trigonometric function being y=a*cos(b*x+c), where a=0.11, b=5.71, and c=0, the trigonometric function curve has the same waveform as that of the elastic wave. The IDT electrode further includes second bus bars 250, the electrode fingers 220 and the dummy electrode fingers 230 are connected to the second bus bars 250; the first bus bars 210 and the second bus bars 250 are parallel in the second direction. The area between the first bus bars 210 and the second bus bars 250 is an edge area; the area between the two second bus bars 250 is a central area. The first bus bars 210 are made of gold, the second bus bars 250 are made of platinum, the electrode fingers and the dummy electrode fingers in the edge area are made of aluminum, and the electrode fingers and the dummy electrode fingers in the central area are made of copper.

[0058] Figure 9 The admittance characteristic diagram of the elastic wave device of the preferred embodiment and comparative example 2 is shown, wherein the red solid line is the admittance characteristic of the elastic wave device of the preferred embodiment, and the blue solid line is the admittance characteristic of the elastic wave device of comparative example 2; Figure 10 The real part of the admittance characteristic diagram of the elastic wave device of the preferred embodiment and comparative example 2 is shown, wherein the red solid line is the real part of the admittance characteristic of the elastic wave device of the preferred embodiment, and the blue solid line is the real part of the admittance characteristic of the elastic wave device of comparative example 2, the difference between comparative example 2 and the preferred embodiment is that the joint between the extension 240 and the electrode finger 220 of comparative example 2 is a straight line parallel to the first bus bar 210 in the third direction, i.e., the length of the joint of comparative example 2 is equal to the width W of the electrode finger 220, and the other structures are the same as those of the preferred embodiment, as shown in Figs. Figure 9 and Figure 11 The transverse noise in the passband (1750MHz-1850MHz) of the preferred embodiment is suppressed compared with comparative example 2.

[0059] In summary, the elastic wave device of the preferred embodiment suppresses the transverse noise mode of the elastic wave device by setting the junction as a trigonometric function, and fitting the trigonometric function curve to the waveform of the elastic wave propagation, thereby improving the filtering effect of the elastic wave device.

[0060] Figure 11 As shown in the sectional view of the module of the elastic wave device of an embodiment of the present application, Figure 11 The module of the elastic wave device includes the elastic wave device 600, the inductor 700, the sealing part 900, the wiring substrate 800, the IC integrated circuit component 801, and the connection terminal 802. The connection terminal 802 is formed on the lower surface of the wiring substrate 800 and is connected to an external circuit board; the IC integrated circuit component 801 is mounted inside the wiring substrate 800, and the IC integrated circuit component 801 includes a switching circuit and a low-noise amplifier. The inductor 700 is mounted on the main surface of the wiring substrate 800 and is used to realize impedance matching of a signal transmission circuit. It should be noted that the inductor 700 can also be other passive devices in other embodiments. The sealing part 900 is used to seal the elastic wave device 600 and the inductor 700 and the like.

[0061] The expressions and terms used in the present application are for illustration only and should not be considered limiting. The use of "including," "possessing," "having," "containing," and variations thereof in this document means including the listed items and their equivalents and additional items.

[0062] The term "embodiment" in the present application means that the specific features, structures or characteristics described in conjunction with the embodiment can be included in at least one embodiment of the present application. The presence of this phrase in various places in the specification does not necessarily mean the same embodiment, nor does it mean independence or alternatives to other embodiments. It is clear or implicitly understood by those skilled in the art that the embodiments described in the present application can be combined without conflict with other embodiments.

[0063] The above-described embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of patent protection. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications, corrections and improvements can be made, which are within the scope of protection of the present application. Therefore, the scope of protection of the present application should be subject to the appended claims.

Claims

1. An elastic wave device characterized by, The application relates to an elastic wave device, comprising: a piezoelectric substrate; an IDT electrode on a main surface of the piezoelectric substrate, used for exciting an elastic wave with a wavelength of lambda; wherein the IDT electrode comprises first bus bars, electrode fingers and virtual electrode fingers; the two first bus bars are oppositely arranged; the top ends of the electrode fingers are connected with the first bus bars and are arranged between the two first bus bars and staggered; the top ends of the virtual electrode fingers are connected with the first bus bars and are arranged between the two first bus bars; the length direction of the electrode fingers is a first direction, the length direction of the first bus bars is a second direction, and the first direction is perpendicular to the second direction; the tail end of the electrode finger has an extension; the joint between the extension and the tail end of the electrode finger has a length greater than the width of the electrode finger when viewed in a third direction perpendicular to the main surface of the piezoelectric substrate; the material of the extension is different from that of the electrode finger.

2. The elastic wave device according to claim 1, characterized by, the joint between the extension and the tail end of the electrode finger is arc-shaped when viewed in the third direction; the arc-shaped joint has similarity with the wave field distribution of the elastic wave.

3. The elastic wave device according to claim 1, characterized by, the joint between the extension and the tail end of the electrode finger is a trigonometric function curve when viewed in the third direction; the trigonometric function curve has waveform consistency with the waveform of the elastic wave.

4. The elastic wave device according to claim 1, characterized by, the material of the IDT electrode comprises at least one of aluminum, copper, platinum, tungsten and gold.

5. The elastic wave device according to claim 1, characterized in that, the material of the first bus bar is different from that of the electrode finger.

6. The elastic wave device according to claim 1, characterized in that, the IDT electrode further comprises second bus bars, and the electrode fingers and the virtual electrode fingers are connected with the second bus bars; the first bus bars are parallel to the second bus bars in the second direction.

7. The elastic wave device according to claim 6, characterized in that, the material of the second bus bar is different from that of the first bus bar.

8. The elastic wave device according to claim 6, characterized in that, the region between the first bus bar and the second bus bar is an edge region; the region between the two second bus bars is a center region; the material of the electrode finger in the edge region is different from that of the electrode finger in the center region; the material of the virtual electrode finger in the edge region is different from that of the virtual electrode finger in the center region.

9. The elastic wave device of claim 1, wherein, the thickness of the IDT electrode is 0.03 lambda to 0.2 lambda.

10. A module characterized by the elastic wave device comprises the IDT electrode according to any one of claims 1 to 9.

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