Elastic wave device

Abstract

The invention relates to an elastic wave device, and relates to the field of radio frequency. The scandium-doped aluminum nitride layer is arranged on the high-sound-velocity component, the piezoelectric layer is arranged on the scandium-doped aluminum nitride layer, the interdigital transducer electrode and the reflector electrodes are arranged on the piezoelectric layer, the reflector electrodes are located on the two sides of the interdigital transducer electrode, and the scandium doping proportion of the scandium-doped aluminum nitride layer is 15%-40%. Under the condition, the problem of mode crosstalk between a duplexer or a radio frequency module caused by clutter response near a dominant mode of an elastic wave device of a composite multilayer structure based on a lithium tantalate / lithium niobate piezoelectric film in the prior art, deterioration of in-band fluctuation of a filter can be solved, and the overall performance of a communication device can be improved.

Description

Technical Field

[0001] The present application relates to the field of radio frequency technology, and in particular to an elastic wave device. Background Art

[0002] Elastic wave devices have the characteristics of low cost, small size and multiple functions, and have been widely used in radar, communication, navigation and other fields. The most commonly used elastic wave devices in mobile phone and base station communications are elastic wave resonators, elastic wave filters composed of multiple elastic wave resonators, and elastic wave duplexers and elastic wave multiplexers composed of multiple elastic wave filters. In any type of elastic wave device, a conductive material film pattern is set on a piezoelectric multilayer substrate to determine a number of interdigital transducer electrodes and reflector electrodes, and the frequency characteristics of the conversion function of converting the electrical signal of the interdigital transducer electrode into elastic waves are used to obtain the bandpass characteristics.

[0003] Mobile communication systems are developing from 3G and 4G to 5G, and the frequency bands used are moving to bands above 3GHz. Traditional surface acoustic wave devices are subject to the limitations of the materials themselves, with low Q values ​​and coupling coefficients, and cannot fully meet the high performance requirements of mobile communications devices. The surface acoustic wave device based on the composite multilayer structure of lithium tantalate / lithium niobate piezoelectric film has attracted much attention due to its advantages of low insertion loss, low temperature drift, large bandwidth, and high power.

[0004] However, the composite multilayer structure based on piezoelectric film will also cause many parasitic noise problems, such as the noise response near the main mode, which will deteriorate the in-band fluctuation of the filter and cause mode crosstalk between duplexers or RF modules, greatly affecting the performance of the communication device. Summary of the invention

[0005] The purpose of this application is to provide an elastic wave device to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above purpose, the technical solution adopted in this application is:

[0007] In a first aspect, the present application provides an elastic wave device, comprising:

[0008] High sound velocity components;

[0009] A scandium-doped aluminum nitride layer disposed on the high-acoustic-velocity component;

[0010] A piezoelectric layer disposed on the scandium-doped aluminum nitride layer;

[0011] an interdigital transducer electrode disposed on the piezoelectric layer; and

[0012] A reflector electrode, which is disposed on the piezoelectric layer and is located on both sides of the IDT electrode;

[0013] Wherein, the scandium-doped aluminum nitride layer has a doping ratio of 15%-40%.

[0014] In a possible implementation manner, the material of the IDT electrode and the reflector electrode is composed of one or more of aluminum, copper, platinum, tungsten, gold, silver, molybdenum, and tantalum.

[0015] In a possible implementation, the high acoustic velocity component includes:

[0016] A supporting substrate, used for supporting the scandium-doped aluminum nitride layer; or

[0017] A support substrate and a capture material layer disposed between the support substrate and the scandium-doped aluminum nitride layer, wherein the capture material layer is used to support the scandium-doped aluminum nitride layer.

[0018] In a possible implementation manner, the capture material layer is formed of one or more combinations of amorphous silicon, polycrystalline silicon, amorphous germanium, and polycrystalline germanium.

[0019] In a possible implementation manner, a low sound velocity layer is further provided between the high sound velocity component and the scandium-doped aluminum nitride layer.

[0020] In a possible implementation, the acoustic velocity of the body wave propagating in the low acoustic velocity layer is lower than that of the body wave propagating in the piezoelectric layer; the acoustic velocity of the body wave propagating in the high acoustic velocity component is higher than that of the body wave propagating in the piezoelectric layer.

[0021] In a possible implementation, the low acoustic velocity layer is composed of one or more combinations of relatively low acoustic velocity materials such as silicon dioxide, glass, silicon oxynitride, tantalum oxide, or silicon dioxide with compounds containing fluorine, carbon, or boron as main components added thereto.

[0022] In a second aspect, the present application provides a filter device having:

[0023] a series arm resonator; and

[0024] Parallel arm resonator;

[0025] Here, at least one of the series arm resonator and the parallel arm resonator is the elastic wave device as described above.

[0026] In a third aspect, the present application provides a multiplexer having:

[0027] an antenna terminal connected to the antenna; and

[0028] a plurality of filter devices commonly connected to the antenna terminal;

[0029] Therein, at least one of the filter devices is a filter device as described above.

[0030] The beneficial effects of the technical solution provided by this application include at least:

[0031] The present application provides a scandium-doped aluminum nitride layer on a high-acoustic-velocity component, a piezoelectric layer on the scandium-doped aluminum nitride layer, an interdigital transducer electrode and a reflector electrode on the piezoelectric layer, and the reflector electrode is located on both sides of the interdigital transducer electrode, wherein the scandium-doped aluminum nitride layer has a doping ratio of 15% to 40%. In this case, the problems of clutter response near the main mode of an elastic wave device based on a composite multilayer structure of lithium tantalate / lithium niobate piezoelectric film in the prior art, deterioration of the in-band fluctuation of the filter, and mode crosstalk between duplexers or radio frequency modules can be solved, and the overall performance of the communication device can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] 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:

[0033] Figure 1 Schematic top view and cross-sectional view of a typical elastic wave device 100 based on a piezoelectric composite substrate are shown;

[0034] Figure 2 A schematic cross-sectional view of an elastic wave device 200 provided in Embodiment 1 of the present application is shown;

[0035] Figure 3 shows a broadband admittance / conductance-frequency curve of the elastic wave device 200 when ψ is 0;

[0036] Figure 4 shows the admittance-frequency comparison curve of the elastic wave device 200 when ψ is 0 and 5% respectively;

[0037] Figure 5 The admittance-frequency comparison curve of the elastic wave device 200 when ψ is 0 and 40% respectively is shown.

[0038] Figure 6 A schematic cross-sectional view of an elastic wave device 300 provided in the second embodiment of the present application is shown. DETAILED DESCRIPTION

[0039] 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.

[0040] 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.

[0041] The present application is further described below in conjunction with the accompanying drawings and embodiments.

[0042] Device Description:

[0043] Figure 1 A schematic top view and a cross-sectional view of a typical piezoelectric composite substrate-based elastic wave device 100 are shown. In recent years, elastic wave devices based on piezoelectric composite substrates of a piezoelectric layer 1 and a non-piezoelectric substrate 3 have attracted wide attention due to their high Q value performance and have been applied to many fields such as radar, communication, and navigation.

[0044] The elastic wave device 100 based on the piezoelectric composite substrate is composed of a piezoelectric layer 1 and a conductive material thin film pattern formed on a piezoelectric composite substrate of a non-piezoelectric substrate 3. The piezoelectric layer 1 is a thin single crystal layer made of a piezoelectric material with a thickness of h. The piezoelectric material is lithium niobate, lithium tantalate, gallium nitride, aluminum nitride or zinc oxide. As is common knowledge, the piezoelectric layer 1 is cut so as to be consistent with the front and back crystal axes of the piezoelectric layer 1, so that the piezoelectric layer 1 has different tangent options. We often use Euler angles to define its tangent, for example, the Euler angle of the piezoelectric layer cut at 15°Y is (0°, 105°, 0°), the Euler angle of the piezoelectric layer cut at Z is (0°, 0°, 0°), the Euler angle of the piezoelectric layer cut at 128°Y is (0°, 38°, 0°), and the Euler angle of the piezoelectric layer cut at 32°Y45°X is (0°, 122°, 45°).

[0045] Admittance is a physical quantity that describes the response of a circuit element to alternating current and voltage, and is usually represented by the symbol Y. For a circuit element, its admittance Y is equal to the ratio of its conductance G to its susceptance B, that is, Y=G+jB, where j is an imaginary unit. In this embodiment, the admittance (dB) can be expressed by the formula Y=20×log 10 |Y| is obtained.

[0046] The admittance ratio is calculated by the formula "admittance ratio = (20 × log 10 |Y1|)-(20×log 10 |Y2|)”, Y1 is the admittance at the resonant frequency of the circuit element, and Y2 is the admittance at the anti-resonant frequency of the circuit element. To a certain extent, the admittance ratio can measure the strength of the resonance of the circuit element.

[0047] The non-piezoelectric substrate 3 is a single-layer or multi-layer substrate made of a high-acoustic-velocity material, and is therefore also referred to as a high-acoustic-velocity component. The acoustic velocity of the body wave propagating in the high-acoustic-velocity component is higher than the acoustic velocity of the elastic wave propagating in the piezoelectric layer, thereby increasing the acoustic velocity of the elastic wave in the piezoelectric layer and the frequency of the device. In addition, the high-acoustic-velocity component can effectively seal the elastic wave propagating in the piezoelectric layer in the piezoelectric layer without leakage, thereby increasing the Q value of the device.

[0048] The high acoustic velocity component is made of a material with a relatively high acoustic velocity, such as silicon, sapphire, silicon carbide, aluminum nitride, etc. Table 1 shows the acoustic velocities of three different modes of elastic waves in various materials.

[0049] [Table 1]:

[0050]

[0051] The conductive material film pattern includes an interdigital transducer (IDT) electrode 2a, a reflector electrode 2b, an interdigital transducer bus bar 4a and a reflector bus bar 4b, and its thickness is hm. The IDT electrode 2a 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 opposite to each other in the direction in which the first electrode fingers and the second electrode fingers extend. The distance λ between adjacent first (or second) electrode fingers is usually referred to as the "wavelength" of the IDT. The distance AP where the first and second electrode fingers overlap is usually referred to as the "aperture" of the IDT. The reflector electrode 2b includes a plurality of third electrode fingers and a plurality of fourth electrode fingers interlaced with each other, and a third bus bar and a fourth bus bar opposite to each other in the direction in which the third electrode fingers and the fourth electrode fingers extend.

[0052] Embodiment 1:

[0053] Figure 2FIG. 2 is a schematic cross-sectional view of an elastic wave device 200 provided in the first embodiment of the present application. The elastic wave device 200 provided in the present embodiment is improved based on the structure of the elastic wave device 100, wherein the piezoelectric layer 1 is lithium niobate, the Euler angle is (0°, 105°, 0°), and the thickness h is LN ;

[0054] The wavelength of the elastic wave is set to λ, and the conductive film material pattern is composed of copper electrodes with a thickness of h m 8%λ;

[0055] The wavelength of the elastic wave is λ, and the thickness of the piezoelectric layer 1 is h LN is 0.3λ;

[0056] The high-acoustic-speed component is a c-plane sapphire substrate 5, and the Euler angle is (0°, 0°, 0°);

[0057] There is also a scandium-doped aluminum nitride layer 6 between the sapphire substrate 5 and the piezoelectric layer 1 , the scandium doping ratio is ψ, and the Euler angle is (0°, 0°, 0°).

[0058] Figure 3 The broadband admittance / conductance-frequency curve of the elastic wave device 200 is shown when ψ is 0. The wavelength λ is 2 μm. When the scandium doping ratio ψ is 0, two obvious clutters appear between the resonant frequency and the anti-resonant frequency of the elastic wave device 200, which seriously affects the communication performance of the elastic wave device 200.

[0059] Figure 4 The admittance-frequency comparison curve of the elastic wave device 200 when ψ is 0 and 5% respectively is shown. The wavelength λ is 2μm. It can be seen from the curve that when 5% of scandium is doped into the scandium-doped aluminum nitride layer 6, the resonant frequency of the elastic wave device 200 decreases, but the clutter between the resonant frequency and the anti-resonant frequency still exists.

[0060] Figure 5 The admittance-frequency comparison curve of the elastic wave device 200 when ψ is 0 and 40% respectively is shown. The wavelength λ is 2μm. It can be seen from the curve that when 40% of scandium is doped into the scandium-doped aluminum nitride layer 6, the resonant frequency of the elastic wave device 200 is reduced, and the clutter between the resonant frequency and the anti-resonant frequency disappears, and the performance is improved.

[0061] Therefore, by analyzing Figure 4 and Figure 5 It can be found that setting a suitable scandium doping ratio in the scandium-doped aluminum nitride layer 6 can suppress the clutter of the elastic wave device. Further verification shows that when the scandium doping ratio in the scandium-doped aluminum nitride layer 6 is 15%-40%, the elastic wave device 200 has no clutter.

[0062] Embodiment 2:

[0063] Figure 6 A schematic cross-sectional view of an elastic wave device 300 provided in the second embodiment of the present application is shown. The difference between the elastic wave device 300 provided in this embodiment and the elastic wave device 200 is that a capture material layer 7 is further provided between the scandium-doped aluminum nitride layer 6 and the c-plane sapphire substrate 5 .

[0064] The capture material layer 7 is formed of one or a combination of amorphous silicon, polycrystalline silicon, amorphous germanium, and polycrystalline germanium.

[0065] For the same reason as in the first embodiment, when the scandium-doped aluminum nitride layer 6 has a doping ratio of 15% to 40%, the elastic wave device 300 of the second embodiment has no spurious waves.

[0066] 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.

[0067] 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. An elastic wave device, characterized in that: include: High sound velocity components; A scandium-doped aluminum nitride layer disposed on the high-acoustic-velocity component; A piezoelectric layer disposed on the scandium-doped aluminum nitride layer; an interdigital transducer electrode disposed on the piezoelectric layer; as well as A reflector electrode, which is disposed on the piezoelectric layer and is located on both sides of the IDT electrode; Wherein, the scandium-doped aluminum nitride layer has a doping ratio of 15%-40%.

2. The elastic wave device according to claim 1, wherein: The materials of the IDT electrodes and the reflector electrodes are composed of one or more of aluminum, copper, platinum, tungsten, gold, silver, molybdenum, and tantalum.

3. The elastic wave device according to claim 1, wherein: The high sonic velocity component comprises: A supporting substrate, used for supporting the scandium-doped aluminum nitride layer; or A support substrate and a capture material layer disposed between the support substrate and the scandium-doped aluminum nitride layer, wherein the capture material layer is used to support the scandium-doped aluminum nitride layer.

4. The elastic wave device according to claim 3, characterized in that: The capture material layer is formed of one or more combinations of amorphous silicon, polycrystalline silicon, amorphous germanium, and polycrystalline germanium.

5. The elastic wave device according to claim 1, wherein: A low acoustic velocity layer is further provided between the high acoustic velocity member and the scandium-doped aluminum nitride layer.

6. The elastic wave device according to claim 5, characterized in that: The acoustic velocity of the body wave propagating in the low acoustic velocity layer is lower than the acoustic velocity of the body wave propagating in the piezoelectric layer; The acoustic velocity of the bulk wave propagating in the high-acoustic-velocity member is higher than the acoustic velocity of the bulk wave propagating in the piezoelectric layer.

7. The elastic wave device according to claim 5, wherein: The low acoustic velocity layer is composed of one or more combinations of relatively low acoustic velocity materials such as silicon dioxide, glass, silicon oxynitride, tantalum oxide, or silicon dioxide added with a compound mainly composed of fluorine, carbon, or boron.

8. A filter device comprising: a series arm resonator; and Parallel arm resonator; in, At least one of the series arm resonator and the parallel arm resonator is the elastic wave device according to any one of claims 1 to 7.

9. A multiplexer comprising: an antenna terminal connected to the antenna; and a plurality of filter devices commonly connected to the antenna terminal; in, At least one of the filter devices is a filter device as claimed in claim 8.

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