Elastic wave device and module

Abstract

The utility model relates to an elastic wave device and module, comprising a piezoelectric substrate, a piezoelectric layer and an IDT electrode, the IDT electrode is formed on the main surface of the piezoelectric layer and is used for exciting an elastic wave with a wavelength of lambda; the piezoelectric layer is laminated on the piezoelectric substrate; wherein the piezoelectric layer is made of lithium niobate or lithium tantalate; the cutting angle of the piezoelectric layer is different from that of the piezoelectric substrate; the cutting angle of the piezoelectric layer is a Y-direction cutting X-direction propagation angle of-30 degrees to 30 degrees or 140 degrees to 220 degrees; the thickness ratio of the piezoelectric layer to the piezoelectric substrate is less than 0.1; the piezoelectric layer is provided with a plane layer and a pattern layer, the pattern layer is provided with a plurality of patterns which are arranged at intervals, and the pattern layer is arranged below the plane layer and extends towards the direction far away from the plane layer. The excitation efficiency of in-band clutters can be effectively reduced, and the passband flatness of the filter is improved.

Description

Technical Field

[0001] This utility model relates to the field of semiconductor technology, and in particular to an elastic wave device and module. Background Technology

[0002] With the continuous development of radio frequency communication technology, the requirements for the bandwidth and quality factor of filters are also constantly increasing. Surface acoustic wave (SAW) resonators, based on surface acoustic wave (SAW) technology, are widely used in filter design due to their advantages such as high quality factor, low cost, and small size.

[0003] like Figure 1 As shown, a traditional SAW resonator consists of a piezoelectric layer 200 and an IDT electrode 300 (Interdigital Transducer) disposed on the main surface of the piezoelectric layer. The piezoelectric layer 200 is usually made of piezoelectric materials such as lithium tantalate, lithium niobate, and quartz. Lithium niobate is widely used in wide-bandwidth surface acoustic wave filters due to its high electromechanical coupling coefficient. However, surface acoustic wave resonators using lithium niobate as the piezoelectric material often exhibit in-band clutter such as Rayleigh waves in the passband, affecting the insertion loss and flatness of the filter passband. At the same time, bulk leakage occurs on the high-end side of the resonator, leading to a decrease in the quality factor and affecting the insertion loss at the high end of the filter passband.

[0004] There is currently no suitable solution to the problem of large noise in existing high-bandwidth SAW filters. Utility Model Content

[0005] This invention provides an elastic wave device and module to solve the problem of large noise in existing high-bandwidth SAW filters.

[0006] Firstly, this embodiment provides an elastic wave device, including a piezoelectric substrate, a piezoelectric layer, and an IDT electrode.

[0007] The IDT electrode is formed on the main surface of the piezoelectric layer and is used to excite elastic waves with a wavelength of λ.

[0008] The piezoelectric layer is stacked on the piezoelectric substrate;

[0009] The piezoelectric layer is made of lithium niobate or lithium tantalate; the cutting angle of the piezoelectric layer is different from the cutting angle of the piezoelectric substrate; the cutting angle of the piezoelectric layer is -30° to 30° along the Y direction and the X direction propagation angle is 140° to 220°; the thickness ratio of the piezoelectric layer to the piezoelectric substrate is less than 0.1.

[0010] The piezoelectric layer has a planar layer and a patterned layer. The patterned layer has multiple patterns arranged at intervals. The patterned layer is disposed below the planar layer and extends in a direction away from the planar layer.

[0011] In some embodiments, the pattern in the patterned layer has a height h along the direction from the IDT electrode toward the piezoelectric substrate. gap The h gap The range of / λ is 0.02–0.1.

[0012] In some embodiments, the pattern in the patterned layer has a width w in a direction perpendicular to the direction of the IDT electrode toward the piezoelectric substrate. gap The w gap The range of / λ is 0.2–0.7.

[0013] In some embodiments, the piezoelectric substrate is made of lithium tantalate or lithium niobate.

[0014] In some of these embodiments, the thickness h of the piezoelectric layer LN It ranges from 0.1λ to 0.4λ.

[0015] In some embodiments, a temperature compensation layer is further included between the piezoelectric layer and the piezoelectric substrate.

[0016] In some embodiments, the temperature compensation layer comprises a positive temperature coefficient material with temperature compensation properties.

[0017] In some embodiments, a high-velocity layer and a low-velocity layer are further included between the piezoelectric layer and the piezoelectric substrate.

[0018] In some embodiments, the high-velocity layer is made of silicon carbide or silicon nitride; the low-velocity layer is made of silicon oxide, gallium arsenide, or tantalum oxide.

[0019] Compared with the prior art, the present invention provides an elastic wave device. By using the structure of a piezoelectric layer and a piezoelectric substrate, and simultaneously patterning the interface where the two contact, the excitation efficiency of in-band clutter can be effectively reduced and the passband flatness of the filter can be improved.

[0020] Secondly, this utility model provides a module comprising the elastic wave device as described in any of the preceding claims. Due to the use of the aforementioned elastic wave device, this module also possesses corresponding advantages.

[0021] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0022] The accompanying drawings, which are provided to further illustrate this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application.

[0023] Figure 1 This is a cross-sectional view of an existing elastic wave device;

[0024] Figure 2 This is a cross-sectional view of the elastic wave device according to the first embodiment of this application;

[0025] Figure 3 The elastic wave device of the first embodiment of this application varies with the piezoelectric layer thickness h LN Frequency-admittance characteristic diagram;

[0026] Figure 4 This is a graph showing the variation characteristics of the electromechanical coupling coefficient and the piezoelectric layer cutting angle of the elastic wave device of this application;

[0027] Figure 5 In the elastic wave device of the first embodiment of this application, the height h of the pattern layer increases with the height of the pattern layer. gap Frequency-admittance characteristic diagram;

[0028] Figure 6 In the elastic wave device of the first embodiment of this application, the pattern width w varies with the pattern layer. gap Frequency-admittance characteristic diagram;

[0029] Figure 7 The frequency-admittance characteristics of the elastic wave device of the first embodiment and the comparative example are shown in the diagram.

[0030] Figure 8 This is a cross-sectional view of the elastic wave device according to the second embodiment of this application;

[0031] Figure 9 This is a cross-sectional view of the elastic wave device according to the third embodiment of this application;

[0032] Figure 10 This is a cross-sectional view of a module of an elastic wave device using any of the first to third embodiments of this application.

[0033] In the diagram: 100, piezoelectric substrate; 200, piezoelectric layer; 210, planar layer; 220, patterned layer; 300, IDT electrode; 400, temperature compensation layer; 510, low-velocity layer; 520, high-velocity layer; 600, elastic wave device; 700, inductor; 800, wiring substrate; 900, sealing part; 801, IC integrated circuit assembly; 802, connection terminal; w gap : Graphic width, h gap : Graphic height, h LN : Thickness of the piezoelectric layer. Detailed Implementation

[0034] To better understand the purpose, technical solution, and advantages of this application, the application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0035] Unless otherwise defined, the technical or scientific terms used in this application shall have the general meaning as understood by one of ordinary skill in the art to which this application pertains. Words such as “a,” “an,” “an,” “the,” “the,” and “these,” used in this application, do not indicate quantitative limitation and may be singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a series of steps or modules (units) is not limited to the listed steps or modules (units) but may include steps or modules (units) not listed, or may include other steps or modules (units) inherent to such processes, methods, products, or devices. The terms “connected,” “linked,” and “coupled,” used in this application, are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. The term “multiple” used in this application refers to two or more. The "and / or" operator describes the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: A alone, A and B simultaneously, and B alone. Typically, the character " / " indicates that the objects before and after it are in an "or" relationship. The terms "first," "second," and "third," etc., used in this application are merely for distinguishing similar objects and do not represent a specific ordering of the objects.

[0036] The following is based on Figures 2 to 10 The elastic wave device of this application will be described.

[0037] The embodiments are described below with reference to the accompanying drawings. In each drawing, the same or corresponding parts are labeled with the same reference numerals. For parts that are described repeatedly, they will be appropriately simplified or omitted.

[0038] Figure 2 This is a cross-sectional view of the elastic wave device according to the first embodiment of this application, as shown below. Figure 2As shown, the elastic wave device includes a piezoelectric substrate 100, a piezoelectric layer 200, and IDT electrodes 300. A set of opposing and staggered IDT electrodes 300 are formed on the main surface of the piezoelectric layer 200 to excite elastic waves with a wavelength of λ. These elastic waves include Rayleigh waves, transverse shear waves, or Lamb waves. The constituent material includes at least one of aluminum, copper, platinum, gold, silver, titanium, nickel, chromium, molybdenum, or tungsten, and can also be a stacked structure of the above-mentioned metal materials. In this embodiment, λ can be 1 μm. The piezoelectric layer 200 is stacked on the piezoelectric substrate 100, and its constituent material is lithium niobate with a thickness of 0.1λ to 0.4λ. Figure 3 The elastic wave device of the first embodiment of this application varies with the thickness h of the piezoelectric layer (200 mm). LN The frequency-admittance characteristic diagram of the change, such as Figure 2 As shown, in the admittance-frequency coordinate system, the piezoelectric layer thickness h is from top to bottom. LN The frequency-admittance characteristic curves of the elastic wave device at 0.1λ, 0.2λ, 0.3λ, 0.4λ, 0.5λ, 0.6λ, 0.7λ, 0.8λ, 0.9λ, and 1λ are given, with the piezoelectric layer thickness h. LN Within the range of 0.1λ to 0.4λ, clutter suppression within the red dashed box is effectively achieved. The clutter suppression effect is even better when the piezoelectric thickness is between 0.2λ and 0.4λ; in this embodiment, 0.3λ is selected. Furthermore, the cutting angle of the piezoelectric layer 200 differs from that of the piezoelectric substrate 100. The piezoelectric layer 200 is cut along the Y-axis with an X-axis propagation angle of -30° to 30°, or 140° to 220°. Specifically, the three crystal axes of the lithium niobate single crystal material are set as the X-axis, Y-axis, and Z-axis. The layer is cut at the surface where the Z-axis is the normal after rotating -30° to 30°, or 140° to 220° from the Y-axis with the X-axis as the central axis, and the elastic wave propagates in the X-axis direction. The piezoelectric substrate 100, on the other hand, has a cutting angle along the X-axis of 0° to 180°. Figure 4 The graph shows the variation characteristics of the electromechanical coupling coefficient and the piezoelectric layer cutting angle of the elastic wave device of this application, as shown in the figure. Figure 4 As shown, when the cutting angle of the piezoelectric layer 200 is within the aforementioned angle range, the electromechanical coupling coefficient of the passband region of the elastic wave device is greater than or equal to 15%, thereby enabling the elastic wave device to receive and transmit signals in more frequency bands. The piezoelectric substrate 100 is made of lithium tantalate, lithium niobate, or quartz, and the thickness ratio of the piezoelectric layer 200 to the piezoelectric substrate 100 is less than 0.1, more preferably less than 0.05.

[0039] In this embodiment, it is preferred that both the piezoelectric substrate 100 and the piezoelectric layer 200 are made of lithium niobate.

[0040] like Figure 2As shown, in addition to the features mentioned above, the piezoelectric layer 200 is further divided into a double-layer structure. Specifically, the upper layer is a planar layer 210, which is in direct contact with the IDT electrode and is a relatively flat piezoelectric thin film. A patterned layer 220 is disposed between the planar layer 210 and the piezoelectric substrate 100. The patterned layer 220 consists of multiple spaced patterns. The planar layer 210 and the patterned layer 220 are made of the same material and together constitute the piezoelectric layer 200. This design can effectively reduce the excitation efficiency of in-band clutter and improve the passband flatness of the filter. Figure 7 As shown, Figure 7 The graphs show the frequency-admittance characteristics of the elastic wave device. The vertical axis of the upper graph represents the admittance, and the vertical axis of the lower graph represents the real part of the admittance. The comparative example, compared to the elastic wave device of the first embodiment, has the same IDT electrode structure. Specifically, the IDT electrode is made of platinum, its excitation wavelength λ is 1 μm, its metallization ratio is 0.5, and its IDT electrode thickness is 0.03λ. The piezoelectric layer 200 also has the same material, cutting angle, and thickness as the piezoelectric layer 200 in the first embodiment of this application. Specifically, the piezoelectric layer is made of lithium niobate, has a thickness of 0.3λ, and a cutting angle of 160° along the Y direction. The difference is that the comparative example does not have a piezoelectric substrate 100, and the piezoelectric layer 200 does not have a patterned design. Figure 7 As shown, the red curve is the admittance characteristic curve of the elastic wave device of the first embodiment of this application, and the blue curve is the admittance characteristic curve of the elastic wave device of the comparative example. The passband regions of the elastic wave devices of the first embodiment and the comparative example are both 3200MHz to 3700MHz. The elastic wave device of the comparative example has obvious clutter at 3400MHz. The clutter of the elastic wave device of the first embodiment in the passband region is significantly less than that of the comparative example.

[0041] Therefore, by setting up a patterned piezoelectric layer 200, while providing a large bandwidth, the clutter of the elastic wave device in the passband region is effectively suppressed, thus solving the problem of large clutter in the existing large bandwidth SAW filter.

[0042] Furthermore, the shape of the graphics layer 220 can be defined.

[0043] Figure 5 In this embodiment, the elastic wave device has a pattern height h that varies with the pattern layer 220. gap The frequency-admittance characteristic graph shows the frequency change. The left graph's vertical axis represents admittance, and the right graph's vertical axis represents the real part of the admittance. From the graphs, it can be concluded that when h... gap When / λ is in the range of 0.02-0.1, less clutter is generated. Furthermore, when h gap When / λ is in the range of 0.02-0.06, clutter generation can be further suppressed. In this embodiment, h is preferred. gap / λ is 0.06.

[0044] akin, Figure 6 In the elastic wave device of this embodiment, the pattern width w of the pattern layer 220 increases with the wave pattern. gap The frequency-admittance characteristic graph shows the frequency change. The left graph's vertical axis represents admittance, and the right graph's vertical axis represents the real part of the admittance. Based on the graphs, it can be concluded that when 2w... gap When / λ is in the range of 0.2-0.7, less clutter is generated; furthermore, when 2w gap When / λ is in the range of 0.4-0.6, clutter is further suppressed. In this embodiment, 2w is preferred. gap / λ is 0.6.

[0045] Figure 8 This is a cross-sectional view of the elastic wave device according to the second embodiment of this application, as shown below. Figure 8 As shown, based on the first embodiment, this embodiment provides a temperature compensation layer 400 between the piezoelectric substrate 100 and the piezoelectric layer 200. Specifically, the temperature compensation layer 400 is made of a positive temperature coefficient material such as silicon oxide, which has temperature compensation characteristics, so that the elastic wave device has good temperature characteristics, reduces the stress influence between the piezoelectric layer 200 and the piezoelectric substrate 100 caused by temperature changes, and improves the reliability and service life of the elastic wave device.

[0046] Figure 9 This is a cross-sectional view of the elastic wave device according to the third embodiment of this application, as shown below. Figure 9 As shown, the piezoelectric layer 200 and the piezoelectric substrate 100 also include a high-velocity layer 520 and a low-velocity layer 510.

[0047] Specifically, the high-velocity layer 520 is made of silicon carbide or silicon nitride, and the low-velocity layer 510 is made of silicon oxide, gallium arsenide, or tantalum oxide. By setting the high-velocity layer 520 and the low-velocity layer 510, the cutoff frequency of the piezoelectric substrate 100 is adjusted, causing higher-order clutter to leak towards the piezoelectric substrate 100, thereby suppressing higher-order clutter.

[0048] Figure 10 This is a cross-sectional view of a module of an elastic wave device employing any of the above embodiments in this application.

[0049] like Figure 10As shown, the module of the elastic wave device includes an elastic wave device 600, an inductor 700, a sealing portion 900, a wiring substrate 800, an IC integrated circuit assembly 801, and a connection terminal 802. The connection terminal 802 is formed on the lower surface of the wiring substrate 800 and connects to an external circuit board. The IC integrated circuit assembly 801 is mounted inside the wiring substrate 800 and 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 achieve impedance matching of the signal transmission circuit. It should be noted that in other embodiments, the inductor 700 can also be other passive devices. The sealing portion 900 is used to seal the elastic wave device 600 and the inductor 700, etc.

[0050] The expressions and terms used in this utility model are for illustrative purposes only and should not be considered limiting. The use of "comprising," "possessing," "having," "including," and variations thereof as used herein means to include the following items, their equivalents, and additional items.

[0051] The term "embodiment" in this application refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily imply the same embodiment, nor does it imply that it is mutually exclusive with or independent of other embodiments. It will be clearly or implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0052] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of patent protection. It should be noted that those skilled in the art can make various modifications, alterations, and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. An elastic wave device characterized by, Includes piezoelectric substrate, piezoelectric layer and IDT electrode; The IDT electrode is formed on the main surface of the piezoelectric layer and is used to excite elastic waves with a wavelength of λ. The piezoelectric layer is stacked on the piezoelectric substrate; The piezoelectric layer is made of lithium niobate or lithium tantalate; the cutting angle of the piezoelectric layer is different from the cutting angle of the piezoelectric substrate; the cutting angle of the piezoelectric layer is -30° to 30° along the Y direction and the X direction propagation angle is 140° to 220°; the thickness ratio of the piezoelectric layer to the piezoelectric substrate is less than 0.

1. The piezoelectric layer has a planar layer and a patterned layer. The patterned layer has multiple patterns arranged at intervals. The patterned layer is disposed below the planar layer and extends in a direction away from the planar layer.

2. The elastic wave device according to claim 1, characterized by, Along the direction of the IDT electrode toward the piezoelectric substrate, the pattern in the patterned layer has a height hgap, and the hgap / λ ranges from 0.02 to 0.

1.

3. The elastic wave device according to claim 1, characterized in that, The pattern in the patterned layer has a width wgap in a direction perpendicular to the direction of the IDT electrode toward the piezoelectric substrate, and the range of 2wgap / λ is 0.2–0.

7.

4. The elastic wave device according to claim 1, characterized in that, The piezoelectric substrate is composed of lithium tantalate and lithium niobate.

5. The elastic wave device according to claim 1, characterized in that, The thickness of the piezoelectric layer is 0.1λ to 0.4λ.

6. The elastic wave device according to claim 1, characterized in that, A temperature compensation layer is also included between the piezoelectric layer and the piezoelectric substrate.

7. The elastic wave device according to claim 6, characterized in that, The temperature compensation layer contains a positive temperature coefficient material with temperature compensation properties.

8. The elastic wave device according to claim 1, characterized in that, The piezoelectric layer and the piezoelectric substrate also include a high-velocity layer and a low-velocity layer.

9. The elastic wave device according to claim 8, characterized in that, The high-velocity layer is composed of silicon carbide or silicon nitride; the low-velocity layer is composed of silicon oxide, gallium arsenide or tantalum oxide.

10. A module, characterized in that, Including the elastic wave device as described in any one of claims 1-9.

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