Surface acoustic wave filter

Abstract

The utility model provides a surface acoustic wave filter, which is characterized in that a through electrode comprises a first through electrode positioned in a wall body and a second through electrode positioned in a cover body, the second through electrode is connected with the first through electrode, the first through electrode is connected with a substrate electrode, and the second through electrode is connected with the substrate electrode. And the bottom surface of the second through electrode protrudes out of the top surface of the first through electrode, so that a locking structure is formed between the second through electrode and the first through electrode, the connection reliability of the through electrodes, the wall body and the cover body is improved, the occurrence of stripping is reduced / avoided, and the service life of the through electrodes is prolonged. And the yield and the reliability of the formed surface acoustic wave filter are improved. Furthermore, the bottom surface of the second through electrode protrudes out of the top surface of the first through electrode, so that the stress of the through electrodes is also dispersed, and the yield and reliability of the surface acoustic wave filter can be further improved.

Description

Technical Field

[0001] The utility model relates to the technical field of semiconductors, in particular to a surface acoustic wave filter. Background Art

[0002] At present, many electronic devices with communication functions are usually equipped with multiple surface acoustic wave (SAW) filters. Compared with chip size package (CSP) surface acoustic wave filters, the process complexity of wafer level package (WLP) surface acoustic wave filters is higher, but due to the relatively small package size, it is conducive to the current high-integration packaging process.

[0003] The existing wafer-level packaged surface acoustic wave filter mainly includes a piezoelectric substrate; an interdigital transducer and a substrate electrode located on the piezoelectric substrate; a wall and a cover located on the piezoelectric substrate, the wall and the cover form a cavity structure, and the interdigital transducer is located in the cavity structure. The substrate electrode is led out via a through electrode that passes through the wall and the cover. In the prior art, the through electrode is prone to peeling, which leads to a reduction in the yield and / or reliability of the surface acoustic wave filter. Utility Model Content

[0004] The utility model aims to provide a surface acoustic wave filter to solve the problem in the prior art that the through-electrodes of the surface acoustic wave filter are easily peeled off, thereby reducing the yield and / or reliability of the surface acoustic wave filter.

[0005] In order to solve the above technical problems, the utility model provides a surface acoustic wave filter, the surface acoustic wave filter comprising:

[0006] Piezoelectric substrate;

[0007] An interdigital transducer and a substrate electrode located on the piezoelectric substrate;

[0008] A wall and a cover located on the piezoelectric substrate, wherein the wall and the cover form a cavity structure, and the interdigital transducer is located in the cavity structure;

[0009] A through electrode passes through the wall and the cover, the through electrode includes a first through electrode located in the wall and a second through electrode located in the cover, the second through electrode is connected to the first through electrode, the first through electrode is connected to the base electrode, and the bottom surface of the second through electrode protrudes outside the top surface of the first through electrode to form a locking structure.

[0010] Optionally, in the surface acoustic wave filter, the through electrode also includes a third through electrode located on the cover body, and the surface acoustic wave filter also includes a bump located on the third through electrode, the bump is connected to the third through electrode, and the third through electrode is connected to the second through electrode.

[0011] Optionally, in the surface acoustic wave filter, the through-electrode further includes a fourth through-electrode located between the third through-electrode and the bump, the bump and the fourth through-electrode are connected, and the fourth through-electrode and the third through-electrode are connected.

[0012] Optionally, in the surface acoustic wave filter, a first projection of a top surface of the second through-electrode on the piezoelectric substrate is located within a second projection of a bottom surface of the second through-electrode on the piezoelectric substrate.

[0013] Optionally, in the surface acoustic wave filter, the minimum cross-section of the second through-electrode in the horizontal direction of the piezoelectric substrate is the top surface of the second through-electrode.

[0014] Optionally, in the surface acoustic wave filter, a cross-section of the second through-electrode in a vertical direction of the piezoelectric substrate is trapezoidal.

[0015] Optionally, in the surface acoustic wave filter, a minimum cross-section of the second through-electrode in the horizontal direction of the piezoelectric substrate is located in a middle portion of the second through-electrode.

[0016] Optionally, in the surface acoustic wave filter, a cross section of the first through-electrode in a direction perpendicular to the piezoelectric substrate is rectangular.

[0017] Optionally, in the surface acoustic wave filter, a first projection of the top surface of the second through-electrode on the piezoelectric substrate is located within a third projection of the bottom surface of the third through-electrode on the piezoelectric substrate, or the first projection and the third projection completely overlap.

[0018] Optionally, in the surface acoustic wave filter, the bump is a tin ball, the fourth through-electrode is a nickel metal electrode, and the third through-electrode, the second through-electrode and the first through-electrode are all copper metal electrodes.

[0019] In the prior art, the through-electrode is usually an inverted trapezoidal structure with a large upper portion and a small lower portion, which is very easy to peel off under the action of subsequent processes; and due to the small bottom area, it is also easy to cause stress concentration, which makes the through-electrode prone to fatigue cracks, thereby reducing the yield and / or reliability of the formed surface acoustic wave filter.

[0020] In the surface acoustic wave filter provided by the utility model, the through-electrode includes a first through-electrode located in the wall and a second through-electrode located in the cover, the second through-electrode is connected to the first through-electrode, the first through-electrode is connected to the base electrode, and the bottom surface of the second through-electrode protrudes from the top surface of the first through-electrode, thereby forming a locking structure between the second through-electrode and the first through-electrode, improving the connection reliability between the through-electrode and the wall and the cover, reducing / avoiding the occurrence of peeling, and improving the yield and reliability of the formed surface acoustic wave filter. Furthermore, the bottom surface of the second through-electrode protrudes from the top surface of the first through-electrode, thereby also dispersing the stress of the through-electrode, thereby further improving the yield and reliability of the surface acoustic wave filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of the surface acoustic wave filter of the first embodiment of the utility model.

[0022] Figure 2 It is a schematic structural diagram of a surface acoustic wave filter according to the second embodiment of the utility model.

[0023] Figures 3 to 11 The present invention is a schematic diagram of a device structure formed by a method for manufacturing a surface acoustic wave filter according to an embodiment of the present invention.

[0024] The reference numerals are described as follows:

[0025] 10-surface acoustic wave filter; 100-piezoelectric substrate; 102-interdigital transducer; 104-substrate electrode; 106-wall; 108-cover; 110-cavity structure; 112-through electrode; 1120-first through electrode; 1122-second through electrode; 1124-third through electrode; 1126-fourth through electrode; 114-bump; 200-wall material layer; 210-first opening; 212-second opening; 214-third opening; 216-fourth opening; 220-cover material layer; 230-sacrificial layer. DETAILED DESCRIPTION

[0026] The following is a further detailed description of the surface acoustic wave filter proposed by the utility model in combination with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the utility model will be more clear. It should be noted that the accompanying drawings are all in a very simplified form and are not in precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the utility model.

[0027] The terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. Unless otherwise defined in the present application document, the technical terms or scientific terms used in the present invention should be the common meanings understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention specification and claims do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one" or "one" do not indicate a quantity limit, but indicate the existence of at least one. "Multiple" or "several" means two or more. Unless otherwise specified, words such as "upper / upper layer" and / or "lower / lower layer" are only for the convenience of explanation and are not limited to one position or one spatial orientation. Words such as "include" or "comprise" mean that the elements or structures appearing in front of "include" or "comprise" include the elements or structures listed after "include" or "comprise" and their equivalents, and do not exclude other elements or structures. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The singular forms "a", "said" and "the" used in the present utility model specification and the appended claims are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0028] The core idea of ​​the utility model is to provide a surface acoustic wave filter, wherein the through-electrode includes a first through-electrode located in the wall and a second through-electrode located in the cover, the second through-electrode is connected to the first through-electrode, the first through-electrode is connected to the base electrode, and the bottom surface of the second through-electrode protrudes outside the top surface of the first through-electrode, thereby forming a locking structure between the second through-electrode and the first through-electrode, improving the connection reliability between the through-electrode and the wall and the cover, reducing / avoiding the occurrence of peeling, and improving the yield and reliability of the formed surface acoustic wave filter. Furthermore, the bottom surface of the second through-electrode protrudes outside the top surface of the first through-electrode, thereby also dispersing the stress of the through-electrode, thereby further improving the yield and reliability of the surface acoustic wave filter.

[0029] For details, please refer to Figure 1 and Figure 2 , which is a schematic diagram of the structure of the surface acoustic wave filter of the embodiment of the utility model. Figure 1As shown, the surface acoustic wave filter 10 includes: a piezoelectric substrate 100; an IDT 102 and a substrate electrode 104 located on the piezoelectric substrate 100; a wall 106 and a cover 108 located on the piezoelectric substrate 100, the wall 106 and the cover 108 forming a cavity structure 110, and the IDT 102 is located in the cavity structure 110; a through electrode 112 penetrating the wall 106 and the cover 108, the through electrode 112 includes a first through electrode 1120 located in the wall 106 and a second through electrode 1122 located in the cover 108, the second through electrode 1122 is connected to the first through electrode 1120, the first through electrode 1120 is connected to the substrate electrode 104, and the bottom surface of the second through electrode 1122 protrudes outside the top surface of the first through electrode 1120 to form a locking structure.

[0030] In the embodiment of the present application, since the bottom surface of the second through electrode 1122 protrudes outside the top surface of the first through electrode 1120, a locking structure is formed between the second through electrode 1122 and the first through electrode 1120, thereby improving the connection reliability between the through electrode 112 and the wall 106 and the cover 108, reducing / avoiding the occurrence of peeling, and improving the yield and reliability of the formed surface acoustic wave filter 10. Further, the bottom surface of the second through electrode 1122 protrudes outside the top surface of the first through electrode 1120, thereby also dispersing the stress of the through electrode 112, thereby further improving the yield and reliability of the surface acoustic wave filter 10.

[0031] Wherein, the piezoelectric substrate 100 may be a single-layer structure or a multi-layer stacked structure. In one embodiment of the present application, the piezoelectric substrate 100 may include only one piezoelectric layer, and the material of the piezoelectric layer may be, for example, LT (lithium tantalate), LN (lithium niobate), AlN (aluminum nitride), PZT (lead zirconate titanate piezoelectric ceramic) or ZnO (zinc oxide). In another embodiment of the present application, the piezoelectric substrate 100 may include a piezoelectric layer, and may further include a substrate layer, a trap layer and / or a dielectric layer. For example, the piezoelectric substrate 100 may include a piezoelectric layer, a substrate layer and a dielectric layer, wherein the dielectric layer is located on the substrate layer, and the piezoelectric layer is located on the dielectric layer; for another example, the piezoelectric substrate 100 may include a piezoelectric layer, a substrate layer, a trap layer and a dielectric layer, wherein the trap layer is located on the substrate layer, the dielectric layer is located on the trap layer, and the piezoelectric layer is located on the dielectric layer. Furthermore, the material of the substrate layer may be, for example, silicon; the material of the trap layer may be, for example, polysilicon; and the material of the dielectric layer may be, for example, silicon dioxide, silicon nitride, etc.

[0032] The IDT 102 and the substrate electrode 104 are made of conductive materials. In the embodiment of the present application, the IDT 102 and the substrate electrode 104 are made of the same material, which is metal, for example, gold, silver, aluminum, copper, tungsten, titanium, nickel, metal alloys, etc. In other embodiments of the present application, the materials of the IDT 102 and the substrate electrode 104 may also be different, and both may be selected from gold, silver, aluminum, copper, tungsten, titanium, nickel, metal alloys, etc.

[0033] Furthermore, the IDT 102 and the substrate electrode 104 may be formed simultaneously in the same process step, or may be formed separately in different process steps. For example, the IDT 102 and the substrate electrode 104 may be formed simultaneously by sputtering, electroplating, or the like. The IDT 102 and the substrate electrode 104 have the same thickness.

[0034] The first through electrode 1120 and the second through electrode 1122 are made of metal, such as gold, silver, aluminum, copper, tungsten, titanium, nickel, metal alloy, etc. In the embodiment of the present application, the first through electrode 1120 and the second through electrode 1122 are both made of copper.

[0035] In the embodiment of the present application, the cross section of the first through electrode 1120 in the vertical direction of the piezoelectric substrate 100 is rectangular. In other embodiments of the present application, the cross section of the first through electrode 1120 in the vertical direction of the piezoelectric substrate 100 may also be other shapes, such as a trapezoid.

[0036] A first projection of the top surface of the second through electrode 1122 on the piezoelectric substrate 100 is located within a second projection of the bottom surface of the second through electrode 1122 on the piezoelectric substrate 100. That is, the top surface of the second through electrode 1122 is smaller than the bottom surface of the second through electrode 1122.

[0037] Please refer to Figure 1 In one embodiment of the present application, the minimum cross-section of the second through-electrode 1122 in the horizontal direction of the piezoelectric substrate 100 is the top surface of the second through-electrode 1122. Figure 1 As shown, here, the cross section of the second through electrode 1122 in the vertical direction of the piezoelectric substrate 100 is a trapezoid, which is a regular trapezoid with a larger end close to the piezoelectric substrate 100 and a smaller end away from the piezoelectric substrate 100.

[0038] Please refer to Figure 2In another embodiment of the present application, the minimum cross section of the second through electrode 1122 in the horizontal direction of the piezoelectric substrate 100 is located in the middle of the second through electrode 1122. That is, in another embodiment of the present application, the minimum cross section of the second through electrode 1122 in the horizontal direction of the piezoelectric substrate 100 is the cross section other than the top and bottom surfaces of the second through electrode 1122. For example, Figure 2 As shown, the second through electrode 1122 may be in the shape of an inverted trapezoid superimposed on a regular trapezoid. In other embodiments of the present application, the second through electrode 1122 may also be in the shape of a stack of multiple shapes such as an inverted trapezoid, a rectangle, and a regular trapezoid.

[0039] Please continue to refer to Figure 1 and Figure 2 In the embodiment of the present application, the through electrode 112 further includes a third through electrode 1124 located on the cover 108, and the surface acoustic wave filter 10 further includes a bump 114 located on the third through electrode 1124, the bump 114 is connected to the third through electrode 1124, and the third through electrode 1124 is connected to the second through electrode 1122. Here, the third through electrode 1124 is located on the cover 108, that is, protruding from the surface of the cover 108, so as to facilitate the formation of the bump 114 and the connection with the through electrode 112.

[0040] In the embodiment of the present application, the cross section of the third through electrode 1124 in the vertical direction of the piezoelectric substrate 100 is rectangular. The first projection of the top surface of the second through electrode 1122 on the piezoelectric substrate 100 is also located within the third projection of the bottom surface of the third through electrode 1124 on the piezoelectric substrate 100; or, the first projection and the third projection completely overlap, that is, the shape and size of the first projection are the same as the shape and size of the third projection. In other embodiments of the present application, the cross section of the third through electrode 1124 in the vertical direction of the piezoelectric substrate 100 may also be other shapes, such as a trapezoid.

[0041] The third through electrode 1124 is made of metal, such as gold, silver, aluminum, copper, tungsten, titanium, nickel, or a metal alloy.

[0042] In one embodiment of the present application, the third through electrode 1124 is a nickel metal electrode, the bump 114 is a solder ball, and the third through electrode 1124 is directly connected to the bump 114. The nickel metal electrode can not only be firmly connected to the solder ball, but also prevent the bump 114 from reacting with the through electrode 112 to reduce the electrical performance between the two.

[0043] Please continue to refer to Figure 1and Figure 2 In another embodiment of the present application, the through electrode 112 further includes a fourth through electrode 1126 located between the third through electrode 1124 and the bump 114, the bump 114 is connected to the fourth through electrode 1126, and the fourth through electrode 1126 is connected to the third through electrode 1124. That is, in the embodiment of the present application, the bump 114 is directly connected to the fourth through electrode 1126, and the fourth through electrode 1126 is directly connected to the third through electrode 1124.

[0044] The bump 114 is a solder ball, the fourth through electrode 1126 is a nickel metal electrode, and the third through electrode 1124, the second through electrode 1122, and the first through electrode 1120 are all copper metal electrodes. In the embodiment of the present application, the third through electrode 1124 and the fourth through electrode 1126 are both protruding from the surface of the cover 108, wherein the third through electrode 1124 and the second through electrode 1122 are both copper metal electrodes, thereby ensuring the connection reliability between the two and improving the quality and reliability of the weak position of the through electrode 112; and the fourth through electrode 1126 is a nickel metal electrode, which can improve the connection reliability between the through electrode 112 and the bump 114, and can also prevent the bump 114 and the through electrode 112 from reacting to reduce the electrical performance between the two.

[0045] Furthermore, the present application also provides a method for manufacturing the surface acoustic wave filter. For details, please refer to Figure 1 , Figure 2 as well as Figures 3 to 11 ,in, Figures 3 to 11 The present invention is a schematic diagram of a device structure formed by a method for manufacturing a surface acoustic wave filter according to an embodiment of the present invention.

[0046] like Figure 3 As shown, a piezoelectric substrate 100 is provided. Then, an IDT 102 and a substrate electrode 104 are formed on the piezoelectric substrate 100. Specifically, a metal layer can be formed on the piezoelectric substrate 100, and then, the metal layer is etched to form the IDT 102 and the substrate electrode 104. Further, while forming the IDT 102, structures such as bus bars and surface circuits can also be formed, which is not limited in the present application.

[0047] Then, if Figure 4As shown, a wall material layer 200 is formed, and the wall material layer 200 covers the IDT 102, the substrate electrode 104 and the exposed piezoelectric substrate 100. In the embodiment of the present application, the material of the wall material layer 200 is an insulating material, and in other embodiments of the present application, the material of the wall material layer 200 may also be a resin material, etc.

[0048] Then, if Figure 5 As shown, the wall material layer 200 is etched to form the wall 106, and to form a first opening 210 exposing the IDT 102 and a second opening 212 exposing the substrate electrode 104. In the embodiment of the present application, the cross section of the second opening 212 in the vertical direction of the piezoelectric substrate 100 is rectangular.

[0049] Please refer to Figure 6 In the embodiment of the present application, a cover material layer 220 is then formed on the wall 106. The material of the cover material layer 220 can be, for example, an insulating material, a resin material, and the like.

[0050] like Figure 7 As shown, the cover material layer 220 is etched to form a cover 108, and a third opening 214 connected to the second opening 212 is formed, and the third opening 214 also exposes a portion of the wall 106. The cover 108 and the wall 106 form a cavity structure 110, and the interdigital transducer 102 is located in the cavity structure 110. In the embodiment of the present application, the cross-section of the third opening 214 in the vertical direction of the piezoelectric substrate 100 is trapezoidal, wherein the diameter of the end close to the piezoelectric substrate 100 is larger than the diameter of the end away from the piezoelectric substrate 100. In other embodiments of the present application, the third opening 214 may also be in other shapes, which is not limited in the present application.

[0051] Next, please refer to Figure 8 In the embodiment of the present application, further, a sacrificial layer 230 is formed on the cover 108. The sacrificial layer 230 may be made of, for example, insulating material, resin material, etc., and may be the same as or different from the material of the cover 108.

[0052] like Fig. 9 As shown, further, the sacrificial layer 230 is etched to form a fourth opening 216, and the fourth opening 216 is connected to the third opening 214. In the embodiment of the present application, the fourth opening 216 also exposes a portion of the cover 108. Here, the cross-section of the fourth opening 216 in the vertical direction of the piezoelectric substrate 100 is rectangular.

[0053] Please refer to Fig.10Then, the second opening 212, the third opening 214 and the fourth opening 216 are filled to form a through electrode 112, and the through electrode 112 is connected to the substrate electrode 104. Here, a first through electrode 1120 is formed in the second opening 212, a second through electrode 1122 is formed in the third opening 214, and a third through electrode 1124 and a fourth through electrode 1126 are formed in the fourth opening 216. Specifically, the through electrode 112 can be formed by chemical plating, electroplating or sputtering.

[0054] like Fig.11 As shown, then, the sacrificial layer 230 is removed to expose the third through electrode 1124 and the fourth through electrode 1126 .

[0055] Then, if Figure 1 or Figure 2 As shown, a bump 114 is formed on the fourth through electrode 1126 by a process such as tinning or ball planting, and the bump 114 is connected to the fourth through electrode 1126 .

[0056] In the present application, references to "one embodiment" or "some embodiments" mean that features, structures, or characteristics described in conjunction with the embodiment are included in at least one embodiment, at least some embodiments, of the present application. Therefore, the appearance of the phrases "in one embodiment" or "in some embodiments" in various places of the present application does not necessarily refer to the same or the same embodiments. In addition, in one or more embodiments, features, structures, or characteristics may be combined in any suitable combination and / or sub-combination.

[0057] Although some specific embodiments of the present application have been described in detail by way of example, it will be appreciated by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present application. The various embodiments of the present application may be combined in any manner without departing from the spirit and scope of the present application. It will also be appreciated by those skilled in the art that various modifications may be made to the embodiments without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A surface acoustic wave filter, characterized in that: The surface acoustic wave filter comprises: Piezoelectric substrate; An interdigital transducer and a substrate electrode located on the piezoelectric substrate; A wall and a cover located on the piezoelectric substrate, wherein the wall and the cover form a cavity structure, and the interdigital transducer is located in the cavity structure; A through electrode passes through the wall and the cover, the through electrode includes a first through electrode located in the wall and a second through electrode located in the cover, the second through electrode is connected to the first through electrode, the first through electrode is connected to the base electrode, and the bottom surface of the second through electrode protrudes outside the top surface of the first through electrode to form a locking structure.

2. The surface acoustic wave filter according to claim 1, wherein The through-electrode further includes a third through-electrode located on the cover body, and the surface acoustic wave filter further includes a bump located on the third through-electrode, the bump is connected to the third through-electrode, and the third through-electrode is connected to the second through-electrode.

3. The surface acoustic wave filter according to claim 2, wherein: The through-electrode further includes a fourth through-electrode located between the third through-electrode and the bump, the bump and the fourth through-electrode are connected, and the fourth through-electrode and the third through-electrode are connected.

4. The surface acoustic wave filter according to any one of claims 1 to 3, wherein A first projection of a top surface of the second through-electrode on the piezoelectric substrate is located within a second projection of a bottom surface of the second through-electrode on the piezoelectric substrate.

5. The surface acoustic wave filter according to any one of claims 1 to 3, wherein A minimum cross-section of the second through-electrode in the horizontal direction of the piezoelectric substrate is a top surface of the second through-electrode.

6. The surface acoustic wave filter according to claim 5, wherein: A cross section of the second through electrode in a vertical direction of the piezoelectric substrate is trapezoidal.

7. The surface acoustic wave filter according to any one of claims 1 to 3, wherein A minimum cross-section of the second through-electrode in a horizontal direction of the piezoelectric substrate is located in a middle portion of the second through-electrode.

8. The surface acoustic wave filter according to any one of claims 1 to 3, wherein The first through electrode has a rectangular cross section in a vertical direction of the piezoelectric substrate.

9. The surface acoustic wave filter according to claim 2 or 3, characterized in that: A first projection of a top surface of the second through-electrode on the piezoelectric substrate is located within a third projection of a bottom surface of the third through-electrode on the piezoelectric substrate, or the first projection and the third projection completely overlap.

10. The surface acoustic wave filter according to claim 3, wherein: The bump is a tin ball, the fourth through electrode is a nickel metal electrode, and the third through electrode, the second through electrode and the first through electrode are all copper metal electrodes.

Images