Elastic wave device and method of manufacturing the same

Abstract

The present application relates to the technical field of elastic wave devices, and particularly relates to an elastic wave device, which comprises a substrate, an excitation electrode, a cover component and a pad electrode, the substrate is provided with a first recess and a second recess in communication, the second recess is higher than the first recess, the excitation electrode is arranged in the first recess, the cover component is arranged in the second recess and covers above the excitation electrode, the cover component and the first recess of the substrate form a cavity, and the pad electrode is arranged on the substrate and electrically connected with the excitation electrode, and the pad electrode is higher than the excitation electrode. By means of the arrangement, the elastic wave device has the characteristics of miniaturization and low height, and the reliability of the elastic wave device is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of elastic wave devices, in particular to an elastic wave device and a preparation method thereof. BACKGROUND

[0002] In current mobile electronic devices, elastic wave devices utilizing surface acoustic waves and bulk acoustic waves have been widely used. As the market increasingly demands miniaturization and thinness of electronic devices, the elastic wave devices themselves are also expected to be miniaturized and low in height. However, due to the particularity of the cavity structure, the current wafer-level elastic wave device needs to be prepared by multiple materials to form the cavity structure and the cover structure, respectively. Therefore, there are multiple bonding layers between the materials, which makes it difficult to miniaturize and lower the height of the product. Therefore, how to make the elastic wave device miniaturized and low in height has become one of the technical difficulties to be solved by the technical personnel in the field.

[0003] It should be noted that the information disclosed in this BACKGROUND section is only intended to increase the understanding of the general background of the present application and should not be considered as recognition or any form of suggestion that this information constitutes prior art that is publicly known. SUMMARY

[0004] The present application provides an elastic wave device, which comprises a substrate, an excitation electrode, a cover member and a pad electrode. The substrate has a first recess and a second recess, the first recess is communicated with the second recess, and the second recess is higher than the first recess. The excitation electrode is arranged in the first recess of the substrate. The cover member is arranged in the second recess of the substrate and covers the excitation electrode, and the cover member forms a cavity with the first recess of the substrate. The pad electrode is arranged on the substrate, and the pad electrode is electrically connected with the excitation electrode, and the pad electrode is higher than the excitation electrode.

[0005] The present application also provides a preparation method of an elastic wave device, which comprises the following steps: opening a first recess and a second recess on a substrate, the first recess is communicated with the second recess, and the second recess is higher than the first recess; arranging an excitation electrode in the first recess of the substrate, the material of the excitation electrode is selected from at least one of a group consisting of aluminum and copper; arranging a connecting electrode and a pad electrode on the substrate, the two ends of the connecting electrode are respectively connected with the excitation electrode and the pad electrode; covering an electrode protection layer on the surface of the excitation electrode; arranging a cover member in the second recess of the substrate, the cover member covers the excitation electrode, the cover member forms a cavity with the first recess of the substrate, and the upper surface of the cover member is not higher than the upper surface of the substrate.

[0006] The present application provides an elastic wave device and a preparation method thereof. By arranging the excitation electrode in the first recess, the cover member in the second recess, and the pad electrode on the uppermost surface of the substrate, the elastic wave device has the characteristics of miniaturization and low height, and the reliability of the elastic wave device is ensured.

[0007] Other features and advantages of the present application will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the application. BRIEF DESCRIPTION OF DRAWINGS

[0008] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, part of the drawings described below is some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of these drawings.

[0009] Figure 1 is a structural schematic diagram of an elastic wave device provided by an embodiment of the present application;

[0010] Figures 2 to 8 is a structural schematic diagram of an elastic wave device at each stage in the preparation process provided by an embodiment of the present application.

[0011] Reference signs:

[0012] 10 - substrate; 101 - first groove; 102 - second groove; 103 - upper surface of the substrate; 12 - excitation electrode; 14 - cover member;

[0013] 16 - pad electrode; 18 - electrode protection layer; 20 - connecting electrode; 22 - electrode terminal portion; 24 - isolation metal layer; H1 - depth of the first groove; H2 - depth of the second groove; D1, D2, D3 - lateral length. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will combine 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 some embodiments of the present application, but not all the embodiments. The technical features designed in different embodiments of the present application can be combined with each other as long as they do not conflict with each other. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0015] In the description of the present application, it is to be understood that the orientation or positional relationship indicated by the terms "center", "transverse", "upper", "lower", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or component referred to must have a particular orientation or be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise stated, the meaning of "a plurality of" is two or more. In addition, the term "comprising" and any variation thereof means "at least including".

[0016] Please refer to Figure 1 , Figure 1 is a structural schematic diagram of an elastic wave device provided by an embodiment of the present application. In order to achieve at least one of the advantages described or other advantages, an embodiment of the present application provides an elastic wave device. As shown in the figure, the elastic wave device includes a substrate 10, an excitation electrode 12, a cover member 14 and a pad electrode 16.

[0017] The substrate 10 has a first recess 101 and a second recess 102, the first recess 101 communicates with the second recess 102, and the second recess 102 is higher than the first recess 101. When viewed from above, the first recess 101 is located in the second recess 102. In some embodiments, the depth H1 of the first recess 101 is less than the depth H2 of the second recess 102, which facilitates the sinking of the excitation electrode 12 and ensures the electrical performance of the elastic wave device. Optionally, the depth H1 of the first recess 101 ranges from 5 to 25 μm. Optionally, the depth H2 of the second recess 102 ranges from 10 to 50 μm. In some embodiments, the lateral length D1 of the first recess 101 is less than the lateral length D2 of the second recess 102, and in some of them, D1:D2 = 1:1.05 to 1:1.5, thereby forming a closed cavity and ensuring the packaging reliability of the elastic wave device.

[0018] In some embodiments, the lateral length D3 of the cover member 14 is less than or equal to the lateral length D2 of the second recess 102 and greater than the lateral length D1 of the first recess 101. When the lateral length D3 of the cover member 14 is less than D2 and greater than D1, there is a gap between the two sides of the cover member 14 and the two sides of the second recess 102, which can improve the sealing of the formed cavity by filling resin in the gap, further improving the packaging reliability of the elastic wave device.

[0019] The excitation electrode 12 is disposed in the first recess 101 of the substrate 10. In some embodiments, the material of the excitation electrode 12 is selected from at least one of a group consisting of aluminum and copper. For example, the excitation electrode 12 can be a pure aluminum material, a pure copper material, or the like.

[0020] The cover member 14 is disposed in the second recess 102 of the substrate 10 and covers the excitation electrode 12, and the cover member 14 forms a cavity with the first recess 101 of the substrate 10. In some embodiments, the material of the cover member 14 can include a photosensitive resin type material. The cover member 14 can be formed by connecting the photosensitive resin with the substrate 10 and hardening after baking. In some embodiments, the upper surface of the cover member 14 is not higher than the upper surface 103 of the substrate 10. It should be noted that the upper surface 103 of the substrate 10 refers to the uppermost surface of the substrate 10.

[0021] The pad electrode 16 is disposed on the substrate 10 and electrically connected to the excitation electrode 12. In some embodiments, the material of the pad electrode 16 can include Al, Au, or AlCu, such as Al doped with a small amount of Cu, or the like. In some embodiments, the pad electrode 16 is disposed on the upper surface 103 of the substrate 10, and the excitation electrode 12 is disposed in the first recess 101, so the pad electrode 16 is higher than the excitation electrode 12, to further ensure the reliability of the elastic wave device. In addition, since the excitation electrode 12 is disposed in the first recess 101 and the pad electrode 16 is disposed on the upper surface 103 of the substrate 10, the excitation electrode 12 is naturally protected by the cavity formed by the pad electrode 16, which isolates the excitation electrode 12 and ensures normal operation of the device.

[0022] Compared with the traditional structure of the surface acoustic device, which is a three-layer structure from top to bottom, i.e., the cover member 14 (or the packaging substrate, which is usually a photosensitive resin), the support layer, and the piezoelectric substrate, the present application forms the first recess 101 and the second recess 102 by etching on the substrate 10, then directly sets the cover member 14 at the second recess 102 and sets the excitation electrode 12 at the first recess 101, thereby omitting the support layer, so that the elastic wave device can reduce the overall height and size, achieving the purposes of miniaturization and low height. Moreover, since the cover member 14 is disposed at the second recess 102 and the excitation electrode 12 is disposed at the first recess 101, the upper surface of the cover member 14 is not higher than the upper surface 103 of the substrate 10, which can further reduce the overall height and size compared with disposing the cover member 14 on the upper surface 103 of the substrate 10.

[0023] In some embodiments, the elastic wave device can further include an electrode protection layer 18, a connecting electrode 20, an electrode terminal portion 22, and an isolation metal layer 24.

[0024] The electrode protection layer 18 covers the excitation electrode 12, and the cover member 14 covers the electrode protection layer 18. In some embodiments, the material of the electrode protection layer 18 includes silicon oxide or silicon nitride. The electrode protection layer 18 can be plated above the excitation electrode 12 by PVD or CVD, etc., so as to protect the excitation electrode 12.

[0025] The two ends of the connecting electrode 20 are connected to the excitation electrode 12 and the pad electrode 16, respectively. In some embodiments, the material of the connecting electrode 20 can include Al, Au or AlCu. The connecting electrode 20 can be formed by sputtering and in communication with the excitation electrode 12. The connecting electrode 20 can be prepared in the same process as the pad electrode 16.

[0026] The isolation metal layer 24 is arranged on the pad electrode 16 and mainly used for preventing the metal of the electrode terminal part 22 from diffusing into the pad electrode 16 below. In some embodiments, the material of the isolation metal layer 24 can include TiCu or NiCu, etc.

[0027] The electrode terminal part 22 is arranged on the isolation metal layer 24. In some embodiments, the material of the electrode terminal part 22 can include a combination of copper pillars and tin balls, or directly use tin balls, etc. In some embodiments, the electrode terminal part 22 can be in a columnar shape.

[0028] Please refer to Figures 2 to 8 , Figures 2 to 8 is a structure diagram of an elastic wave device in each stage of a preparation process provided by an embodiment of the present application. An embodiment of the present application further provides a preparation method of an elastic wave device, which includes the following steps:

[0029] Firstly, as shown in Figure 2 , a first recess 101 and a second recess 102 are formed on a substrate 10, the first recess 101 is in communication with the second recess 102, and the second recess 102 is higher than the first recess 101. Specifically, the surface of the substrate 10 can be exposed to light and developed after being coated with glue, the position where the recess is not needed is protected by photoresist, then the position where the recess is needed is processed by etching, and then the surface photoresist is removed, thereby obtaining the substrate 10 with the first recess 101 and the second recess 102. It should be noted that the rigidity of the cover member 14 to be arranged later will affect the etching depth of the first recess 101, for example, the worse the rigidity of the cover member 14 is, the deeper the depth H1 of the first recess 101 is, so as to avoid the cover member 14 from touching the excitation electrode 12.

[0030] Secondly, as shown in Figure 3As shown, the excitation electrode 12 is disposed in the first groove 101 of the substrate 10. Specifically, the excitation electrode 12 can be formed by coating the upper surface of the substrate 10 with photoresist, protecting the portions of the substrate 10 where the metal electrode is not to be deposited, coating the upper surface of the substrate 10 with photoresist again, exposing the portions of the substrate 10 where the metal electrode is to be deposited, depositing the metal electrode by CVD or PVD to form the excitation electrode 12, and removing the photoresist from the upper surface of the substrate 10. The material of the excitation electrode 12 can be selected from at least one of the group consisting of aluminum and copper.

[0031] Then, as shown in FIG. 2, the connection electrode 20 and the pad electrode 16 are disposed on the substrate 10, and the two ends of the connection electrode 20 are connected to the excitation electrode 12 and the pad electrode 16, respectively. Specifically, the connection electrode 20 and the pad electrode 16 can be formed by coating the substrate 10 on which the excitation electrode 12 is disposed with photoresist, exposing the substrate 10 to light and developing the photoresist to form the connection electrode 20 and the pad electrode 16, and removing the photoresist from the upper surface of the substrate 10. The excitation electrode 12 is electrically connected to the pad electrode 16 on the upper surface of the substrate 10, so that the excitation electrode 12 and the pad electrode 16 are not in the same plane. Finally, the photoresist on the excitation electrode 12 is removed. Figure 4

[0032] Then, as shown in FIG. 3, the electrode protection layer 18 is disposed on the surface of the excitation electrode 12. The material of the electrode protection layer 18 can include silicon oxide or silicon nitride, and the electrode protection layer 18 can be deposited on the surface of the excitation electrode 12 by sputtering. Figure 5

[0033] Then, as shown in FIG. 4, the cover member 14 is disposed in the second groove 102 of the substrate 10, the cover member 14 covers the excitation electrode 12, and the cover member 14 and the first groove 101 of the substrate 10 form a cavity. The upper surface of the cover member 14 is not higher than the upper surface of the substrate 10. Figure 6 In some embodiments, after the cover member 14 is disposed, the following steps are further included.

[0034] As shown in FIG. 5, the isolation metal layer 24 is disposed on the pad electrode 16. The isolation metal layer 24 can be disposed on the pad electrode 16 by plating to prevent metal migration between the electrode terminal portion 22 and the pad electrode 16 and affect the reliability. The isolation metal layer 24 can be composed of a titanium-nickel metal stack.

[0035] Figure 7 Finally, as shown in FIG. 6, the electrode terminal portion 22 is disposed on the isolation metal layer 24. The material of the electrode terminal portion 22 can include tin.

[0036] The above preparation steps are used to indicate one preparation method of the elastic wave device, and the present application is not limited thereto. Figure 8

[0037] The above preparation steps are used to indicate one preparation method of the elastic wave device, and the present application is not limited thereto. ​​​​

[0038] In summary, the elastic wave device and the manufacturing method thereof provided by the present application have the characteristics of miniaturization and low height, and guarantee the reliability of the elastic wave device, by arranging the excitation electrode 12 at the bottom of the first groove 101, arranging the cover member 14 above the excitation electrode 12 at the bottom of the second groove 102, and arranging the pad electrode 16 on the upper surface 103 of the substrate 10.

[0039] In addition, those skilled in the art should understand that, although there are many problems in the prior art, each embodiment or technical solution of the present application can only improve in one or several aspects, and it is not necessary to solve all the technical problems listed in the prior art or background art at the same time. Those skilled in the art should understand that what is not mentioned in a claim should not be regarded as a limitation on the claim.

[0040] Finally, it should be pointed out that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An elastic wave device, characterized by: The elastic wave device comprises: a substrate having a first recess and a second recess formed thereon, the first recess being communicated with the second recess, the second recess being higher than the first recess; an excitation electrode disposed in the first recess of the substrate; a cover member disposed in the second recess of the substrate and covering the excitation electrode, the cover member forming a cavity with the first recess of the substrate; a pad electrode disposed on the substrate, the pad electrode being electrically connected to the excitation electrode, the pad electrode being higher than the excitation electrode; wherein an upper surface of the cover member is not higher than an upper surface of the substrate.

2. The elastic wave device according to claim 1, characterized by: The depth of the first recess is less than the depth of the second recess.

3. The elastic wave device according to claim 1, characterized by: The depth of the first recess ranges from 5 to 25 μm, and the depth of the second recess ranges from 10 to 50 μm.

4. The elastic wave device according to claim 1, characterized by: The lateral length of the first recess is less than the lateral length of the second recess, and the ratio of the lateral length of the first recess to the lateral length of the second recess ranges from 1:1.05 to 1:1.

5.

5. The elastic wave device of claim 1, wherein: The elastic wave device further comprises an electrode protection layer covering the excitation electrode, and the cover member covers the electrode protection layer.

6. The elastic wave device of claim 1, wherein: The elastic wave device further comprises a connection electrode, two ends of the connection electrode being connected to the excitation electrode and the pad electrode, respectively.

7. The elastic wave device of claim 1, wherein: The elastic wave device further comprises an electrode terminal portion and an isolation metal layer, the isolation metal layer being disposed on the pad electrode, and the electrode terminal portion being disposed on the isolation metal layer.

8. The elastic wave device of claim 1, wherein: The material of the excitation electrode is selected from at least one of a group consisting of aluminum and copper.

9. A method of manufacturing an elastic wave device, characterized by: The preparation method comprises the following steps: forming a first recess and a second recess on a substrate, the first recess being communicated with the second recess, the second recess being higher than the first recess; disposing an excitation electrode in the first recess of the substrate, the material of the excitation electrode being selected from at least one of a group consisting of aluminum and copper; disposing a connection electrode and a pad electrode on the substrate, two ends of the connection electrode being connected to the excitation electrode and the pad electrode, respectively; covering an electrode protection layer on the surface of the excitation electrode; disposing a cover member in the second recess of the substrate, the cover member covering the excitation electrode, the cover member forming a cavity with the first recess of the substrate, and an upper surface of the cover member being not higher than an upper surface of the substrate.

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