Elastic wave device and electronic module

Abstract

The invention relates to the technical field of semiconductor manufacturing, in particular to an elastic wave device and an electronic module. The structure comprises a piezoelectric substrate, a supporting layer, an IDT electrode, a bonding pad electrode, a cover layer and a metal connecting structure, the supporting layer and the IDT electrode are arranged on the piezoelectric substrate, the supporting layer is provided with a first opening, the IDT electrode is located in a cavity of the supporting layer, the bonding pad electrode is arranged on the piezoelectric substrate, the cover layer is arranged on the supporting layer, and the metal connecting structure is arranged on the cover layer. The first opening has a first size and a second size on the upper surface and the lower surface of the supporting layer respectively, the second opening has a third size and a fourth size on the upper surface and the lower surface of the cover layer respectively, the first size is larger than the second size, the fourth size is larger than the first size, and the third size is larger than the fourth size. By means of the arrangement, stacking of metal can be facilitated, generation of holes is reduced, and device performance is improved.

Description

Elastic wave devices and electronic modules Technical Field

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

[0002] Wafer-level packaging (WLP) is a mainstream packaging method for filters. It is an advanced packaging technology that directly completes the fabrication of protective layers, interconnect structures, and solder balls on the wafer, and finally dices them into individual chips. Its core logic is the opposite of traditional packaging: traditional packaging dices the wafer first and then packages it, while WLP packages it first and then dices it.

[0003] Currently, wafer-level packaging technology is widely used; however, as manufacturers' performance requirements increase, current wafer-level packaging technology still needs improvement. Specifically, the packaging structure contains a wall structure and a roof structure located on the wall. Both structures have openings, which are crucial as their shape affects packaging manufacturing. For example, the chamfers on the sidewalls of the roof and wall structures affect metal stacking. If the chamfers are too large, it can lead to insufficient filling or the generation of numerous voids, affecting device performance.

[0004] It should be noted that the information disclosed in this background section is intended only to enhance the understanding of the overall background of the present invention, and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] The present invention provides an elastic wave device, which includes a piezoelectric substrate, a support layer, an IDT electrode, a pad electrode, a capping layer, and a metal connection structure.

[0006] A support layer is disposed on a piezoelectric substrate and has a cavity formed therein, the support layer having a first opening. An IDT electrode is disposed on the piezoelectric substrate and located within the cavity. A pad electrode is disposed on the piezoelectric substrate, and the support layer partially covers the pad electrode. A capping layer is disposed on the support layer and has a second opening. A metal connection structure is disposed on the capping layer and electrically connects to the pad electrode through the first and second openings. The dimension of the first opening at the upper surface of the support layer is defined as a first dimension, the dimension of the first opening at the lower surface of the support layer as a second dimension, the dimension of the second opening at the upper surface of the capping layer as a third dimension, and the dimension of the second opening at the lower surface of the capping layer as a fourth dimension, wherein the first dimension is larger than the second dimension, the fourth dimension is larger than the first dimension, and the third dimension is larger than the fourth dimension.

[0007] Furthermore, both the first opening and the second opening are inverted trapezoidal openings.

[0008] Furthermore, the first size range is 33 to 63 micrometers, and the second size range is 30 to 60 micrometers.

[0009] Furthermore, the third size range is 50-80 micrometers, and the fourth size range is 40-70 micrometers.

[0010] Furthermore, the first dimension is 3 to 10 micrometers larger than the second dimension.

[0011] Furthermore, the third dimension is 5 to 15 micrometers larger than the fourth dimension.

[0012] Furthermore, the upper surface of the support layer has a first platform, which refers to the upper surface of the support layer that is not covered by the cover layer, and the size of the first platform ranges from 2 to 8 μm.

[0013] Furthermore, the thickness of the capping layer is 15-50 micrometers.

[0014] Furthermore, the thickness of the support layer is 5 to 25 micrometers.

[0015] Furthermore, the upper and lower surfaces of the support layer are connected by a first sidewall, and the first sidewall and the lower surface of the support layer have a first angle, the angle of which ranges from 70° to 89°.

[0016] Furthermore, the upper and lower surfaces of the cover layer are connected by a second sidewall, and the second sidewall and the lower surface of the cover layer have a second included angle, the angle of which ranges from 70° to 89°.

[0017] Furthermore, the elastic wave device also has a seed layer, the upper and lower surfaces of the support layer are connected by a first sidewall, the upper and lower surfaces of the cover layer are connected by a second sidewall, and the seed layer is disposed on the pad electrode, as well as on the first and second sidewalls.

[0018] The present invention also provides an electronic module, which includes an elastic wave device and a circuit board, wherein the elastic wave device is disposed on the circuit board and the elastic wave device is an elastic wave device as described in any of the foregoing.

[0019] The present invention provides an elastic wave device and electronic module. By defining the size of the first opening and the size of the second opening, the first size is larger than the second size, the fourth size is larger than the first size, and the third size is larger than the fourth size. This setting is beneficial to the stacking of metal connection structures, thereby avoiding the generation of holes at the openings and improving device performance.

[0020] Other features and advantages of the present invention will be set forth in the following description, and some of the technical features and advantages may be apparent from the description or learned by practicing the invention. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, some of the drawings in the following description are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 is a structural schematic diagram of an elastic wave device provided in an embodiment of the present invention; Figure 2 is a partially enlarged schematic diagram of region A in Figure 1; Figures 3 to 6 are structural schematic diagrams of the elastic wave device provided in an embodiment of the present invention at each stage of the fabrication process.

[0023] Reference numerals: 10-Piezoelectric substrate; 12-Support layer; 121-First opening; 122-Cavity; 14-IDT electrode; 16-Pad electrode; 18-Cap layer; 181-Second opening; 20-Metal connection structure; 22-Solder layer; 40-First mesa; 41-First sidewall; 42-Second sidewall; S1-First dimension; S2-Second dimension; S3-Third dimension; S4-Fourth dimension; S5-Dimension of the first mesa; B-First included angle; C-Second included angle. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The technical features designed in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] In the description of this invention, it should be understood that the terms "center," "lateral," "upper," "lower," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. Additionally, the term "comprising" and any variations thereof mean "at least comprising."

[0026] Please refer to Figures 1 and 2. Figure 1 is a structural schematic diagram of an elastic wave device provided in an embodiment of the present invention, and Figure 2 is a partially enlarged schematic diagram of region A in Figure 1. To achieve at least one or more of the aforementioned advantages, an embodiment of the present invention provides an elastic wave device, which includes a piezoelectric substrate 10, a support layer 12, an IDT electrode 14, a pad electrode 16, a capping layer 18, and a metal connection structure 20.

[0027] The piezoelectric substrate 10 is a functional material capable of converting mechanical energy into electrical energy, with its core being the piezoelectric effect. It generates mechanical strain (inverse piezoelectric effect) by applying an alternating electric field or generates charge through mechanical stress (direct piezoelectric effect), and is widely used in devices such as surface acoustic wave filters and sensors. The piezoelectric substrate 10 can be made of materials such as quartz, lithium niobate, lithium tantalate, or aluminum nitride; in this embodiment, the piezoelectric substrate 10 can be made of lithium tantalate.

[0028] A support layer 12 is disposed on the piezoelectric substrate 10 and forms a cavity 122. The support layer 12 has a first opening 121. The support layer 12 surrounds the IDT electrode 14 and, together with the upper capping layer 18, forms a sealed cavity 122. The support layer 12 can provide support and fixation, maintain the stability of the cavity 122 structure, and ensure that the internal environment is isolated from the external environment. The material of the support layer 12 can be resin, metal (e.g., one or more stacked combinations of aluminum (Al), copper (Cu), tungsten (W), molybdenum (Mo), titanium (Ti), chromium (Cr), gold (Au), nickel (Ni), etc.), or ceramic, silicon, etc., to provide sufficient structural strength and sealing.

[0029] IDT electrode 14 is disposed on piezoelectric substrate 10 and located within cavity 122. The IDT (interdigital transducer) metal layer is the core component of the surface acoustic wave device, and it is fabricated on the piezoelectric substrate using photolithography to create an interdigitated electrode structure. When an alternating voltage is applied, it can efficiently excite surface acoustic waves through the inverse piezoelectric effect, achieving acoustic-to-electric conversion. IDT electrode 14 can be made of metal materials such as Al or Cu, or alloy materials.

[0030] The pad electrode 16 is disposed on the piezoelectric substrate 10, and the support layer 12 covers a portion of the pad electrode 16. The pad electrode 16 serves to conduct electricity and can be formed using metallic materials, such as Al, Cu, or alloy materials.

[0031] A cover layer 18 is disposed on the support layer 12, and the cover layer 18 has a second opening 181. A first opening 121 communicates with the second opening 181. The second opening 181 is positioned above the first opening 121, meaning that when viewed from above, the first opening 121 is completely contained within the second opening 181. The cover layer 18 is located at the top of the encapsulation structure and primarily serves a sealing and protective function, preventing the intrusion of external environments (such as moisture and contaminants) while also providing mechanical protection for the internal structure. The material of the cover layer 18 is typically a metal (such as copper or aluminum) or ceramic, silicon, resin, or glass, all of which possess good sealing properties and mechanical strength.

[0032] In some embodiments, a seed layer (not shown in the figure) may be provided on the pad electrode 16. The seed layer facilitates subsequent electroplating of metal (metal connection structure 20) and improves its adhesion to the pad electrode 16. The upper and lower surfaces of the support layer 12 are connected by the first sidewall 41, and the upper and lower surfaces of the capping layer 18 are connected by the second sidewall 42. Furthermore, the seed layer may cover the first sidewall 41 and the second sidewall 42. The seed layer may be attached along the sidewall morphology, which is beneficial to the electroplating growth of the subsequent metal connection structure 20. The material of the seed layer may be one or more stacks of metals such as Ti / Cu / Cr / Ni / Au, and its thickness may be 30-500nm.

[0033] A metal connection structure 20 is disposed on the cover layer 18 and electrically connected to the pad electrode 16 through a first opening 121 and a second opening 181. The metal connection structure 20 is mainly used to conduct electricity, and its material can be a metal material, such as Al, Cu, or an alloy material.

[0034] The dimension of the first opening 121 on the upper surface of the support layer 12 is defined as the first dimension S1, the dimension of the first opening 121 on the lower surface of the support layer 12 is defined as the second dimension S2, the dimension of the second opening 181 on the upper surface of the cover layer 18 is defined as the third dimension S3, and the dimension of the second opening 181 on the lower surface of the cover layer 18 is defined as the fourth dimension S4. The first dimension S1 is greater than the second dimension S2, the fourth dimension S4 is greater than the first dimension S1, and the third dimension S3 is greater than the fourth dimension S4. In other words, S3 > S4 > S1 > S2, and the size gradually decreases from top to bottom in the diagram. This design has two advantages: firstly, the top-wide and bottom-narrow structure makes it easier to clean the photoresist; secondly, the top-wide and bottom-narrow design reduces the process difficulty of the seed layer and subsequent electroplating of metal (metal connection structure 20), which is conducive to the coverage and stacking of metal, and facilitates the complete filling of the first opening 121 and the second opening 181, avoiding the generation of dead corners and holes at the first opening 121 and the second opening 181. This improves electroplating defects, bump uniformity, and abnormal filling structure, thereby enhancing device performance.

[0035] In some embodiments, both the first opening 121 and the second opening 181 are inverted trapezoidal openings. However, this invention is not limited to this. Due to limitations in actual manufacturing processes, it is sufficient to ensure the relationship S3 > S4 > S1 > S2 to avoid the formation of holes. As for the sidewalls at the openings, they can be non-linear sidewalls, but rather sidewalls with curvature or bending.

[0036] In some embodiments, the first dimension S1 ranges from 33 to 63 micrometers, preferably from 38 to 48 micrometers; the second dimension S2 ranges from 30 to 60 micrometers, preferably from 35 to 45 micrometers. The difference between the first dimension S1 and the second dimension S2 should not be too large. Within this suitable range, it is more conducive to the deposition of the seed layer and the metal connection layer 20, effectively improving problems such as electroplating omissions, bump uniformity, and abnormal filling structure, thereby ensuring device performance.

[0037] In some embodiments, the third dimension S3 ranges from 50 to 80 micrometers, preferably from 55 to 65 micrometers; the fourth dimension S4 ranges from 40 to 70 micrometers, preferably from 45 to 55 micrometers. The difference between the third dimension S3 and the fourth dimension S4 should not be too large. Within this suitable range, it is more conducive to the deposition of the seed layer and the metal connection layer 20, effectively improving problems such as electroplating omissions, bump uniformity, and abnormal filling structure, thereby ensuring device performance.

[0038] In some embodiments, the first dimension S1 is 3-10 micrometers larger than the second dimension S2, and the third dimension S3 is 5-15 micrometers larger than the fourth dimension S4. Optionally, the second dimension S2 differs from the first dimension S1 by 5-10 micrometers, the fourth dimension S4 differs from the first dimension S1 by 5-15 micrometers, and the third dimension S3 differs from the fourth dimension S4 by 5-15 micrometers. This difference setting is more conducive to forming a more suitable top-wide and bottom-narrow structure. If the difference is too small, the sidewalls will be close to vertical, which is not conducive to metal stacking and photoresist cleaning. If the difference is too large, it may cause instability of the metal interconnect layer 20. By optimizing this difference, problems such as electroplating defects, bump uniformity, and abnormal filling structure can be improved, thereby ensuring device performance.

[0039] In some embodiments, the thickness of the capping layer 18 is 15 to 50 micrometers, and the thickness of the support layer 12 is 5 to 25 micrometers, thereby ensuring device performance.

[0040] In some embodiments, the support layer 12 directly contacts the cover layer 18, and no other layer structures are provided between them, which helps to avoid the generation of holes and thus ensure device performance.

[0041] In some embodiments, the upper surface and the lower surface of the support layer 12 are connected by a first sidewall 41, and the first sidewall 41 and the lower surface of the support layer 12 have a first included angle B, the angle of which is in the range of 70° to 89°.

[0042] In some embodiments, the upper surface and lower surface of the cover layer 18 are connected by a second sidewall 42, and a second included angle C is formed between the second sidewall 42 and the lower surface of the cover layer 18, the angle range of the second included angle C being 70° to 89°.

[0043] By setting the first included angle B and the second included angle C within the range of 70° to 89°, the manufacturing process can be facilitated, the effective adhesion of the vapor-deposited metal can be improved, the stacking of the metal connection results 20 can be enhanced, the risk of breakage in the vapor-deposited metal can be reduced, abnormalities in the bump structure, as well as anomalies such as uneven height and voids can be avoided, thereby improving device performance. Optionally, the first included angle B and the second included angle C can be set within the same range. This setting can reduce the difficulty of the process and also ensure the continuity of the subsequent overlay layer structure and better coverage effect.

[0044] In some embodiments, the upper surface of the support layer 12 has a first platform 40, which refers to the upper surface of the support layer 12 not covered by the capping layer 18. That is, the portion of the upper surface of the support layer 12 extending beyond the lower surface of the capping layer 18 constitutes the first platform 40. The size S5 of the first platform 40 ranges from 2 to 8 μm. It should be noted that the size S5 of the first platform 40 refers to the size on one side of the first opening 121. Controlling the size S5 of the first platform 40 within the range of 2 to 8 μm has the following advantages: First, it ensures a process tolerance window; the lower surface of the capping layer 18 cannot exceed the upper surface of the support layer 12. Designing this platform and ensuring a certain width range facilitates process implementation. Secondly, when depositing metal later, after the deposited part reaches the height of the support layer 12, the first platform 40 can be used as the bottom base of the cover layer 18, and the metal can be deposited more stably at the cover layer 18. The first platform 40 can form a certain support, reduce the difficulty of the seed layer and subsequent electroplating process, and facilitate the coverage of the metal connection structure 20.

[0045] In some embodiments, the elastic wave device further includes a solder layer 22, which is located on the metal connection structure 20. The solder layer 22 may be made of a metallic solder such as Sn metal.

[0046] Please refer to Figures 3 to 6, which are schematic diagrams of the elastic wave device provided in an embodiment of the present invention at each stage of the fabrication process.

[0047] First, as shown in Figure 3, a piezoelectric substrate 10 is provided. An IDT electrode 14 and a pad electrode 16 are disposed on the piezoelectric substrate 10, with the pad electrode 16 located outside the IDT electrode 14.

[0048] Secondly, based on Figure 3, a film of support wall 12 is applied, and through exposure and development steps, a support wall 12 with a first opening 121 as shown in Figure 4 is obtained. After exposure, by controlling the temperature, an inverted trapezoidal first opening 121 can be obtained. As shown in Figure 4, the support wall 12 covers part of the piezoelectric substrate 10 and part of the pad electrode 16. The support arm 12 has a first opening 121 and a cavity 122. The first opening 121 exposes the pad electrode 16, and the cavity 122 is used to accommodate the IDT electrode 14.

[0049] Then, based on Figure 4, a layer of material 18 is applied, and through exposure and development steps, the structure shown in Figure 5 is obtained. After exposure, by controlling the temperature, an inverted trapezoidal second opening 181 can be obtained.

[0050] As shown in Figure 5, the cover layer 18 has a second opening 181, which is located above the first opening 121 and is larger than the first opening 121. The dimensional relationship between the first opening 121 and the second opening 181 can be referred to the relationship between S1, S2, S3 and S4 mentioned above.

[0051] Then, in some embodiments, after the steps in Figure 5, a seed layer can be deposited by PVD (physical vapor deposition). The material of the seed layer can be one or more of metals such as Ti / Cu / Cr / Ni / Au. The seed layer can be a single layer or multiple layers, and the thickness of the seed layer is 30-500 nm.

[0052] Finally, as shown in Figure 6, a metal connection structure 20 is provided on the capping layer 18. The metal connection structure 20 is electrically connected to the pad electrode 16 through the first opening 121 and the second opening 181. Any excess seed layer (if present) is removed. A solder layer 22 is provided on the metal connection structure 20 for subsequent electrical connections.

[0053] The present invention also provides an electronic module, which includes an elastic wave device and a circuit board, wherein the elastic wave device is disposed on the circuit board, and the elastic wave device adopts the elastic wave device as described in any of the foregoing embodiments.

[0054] In summary, the elastic wave device and electronic module provided by the present invention, by defining the size of the first opening 121 and the size of the second opening 181, such that the first size S1 is larger than the second size S2, the fourth size S4 is larger than the first size S1, and the third size S3 is larger than the fourth size S4, is set in such a way that it is beneficial to stack the metal connection structure 20, thereby avoiding the generation of holes at the openings and improving the device performance.

[0055] Furthermore, those skilled in the art should understand that although many problems exist in the prior art, each embodiment or technical solution of the present invention can be improved in only one or a few aspects, without necessarily solving all the technical problems listed in the prior art or the background art simultaneously. Those skilled in the art should understand that any content not mentioned in a claim should not be construed as a limitation on that claim.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An elastic wave device, characterized in that: The elastic wave device includes: a piezoelectric substrate; a support layer disposed on the piezoelectric substrate and forming a cavity, the support layer having a first opening; an IDT electrode disposed on the piezoelectric substrate and located within the cavity; a pad electrode disposed on the piezoelectric substrate, the pad electrode being partially covered by the support layer; a capping layer disposed on the support layer, the capping layer having a second opening; and a metal connection structure disposed on the capping layer and electrically connected to the pad electrode through the first opening and the second opening; wherein, the size of the first opening at the upper surface of the support layer is defined as a first dimension, the size of the first opening at the lower surface of the support layer is defined as a second dimension, the size of the second opening at the upper surface of the capping layer is defined as a third dimension, and the size of the second opening at the lower surface of the capping layer is defined as a fourth dimension, the first dimension being larger than the second dimension, the fourth dimension being larger than the first dimension, and the third dimension being larger than the fourth dimension.

2. The elastic wave device according to claim 1, characterized in that: Both the first opening and the second opening are inverted trapezoidal openings.

3. The elastic wave device according to claim 1, characterized in that: The first size range is 33 to 63 micrometers, and the second size range is 30 to 60 micrometers.

4. The elastic wave device according to claim 1, characterized in that: The third size range is 50 to 80 micrometers, and the fourth size range is 40 to 70 micrometers.

5. The elastic wave device according to claim 3, characterized in that: The first dimension is 3 to 10 micrometers larger than the second dimension.

6. The elastic wave device according to claim 4, characterized in that: The third dimension is 5 to 15 micrometers larger than the fourth dimension.

7. The elastic wave device according to claim 1, characterized in that: The upper surface of the support layer has a first platform, which refers to the upper surface of the support layer that is not covered by the cover layer, and the size of the first platform ranges from 2 to 8 μm.

8. The elastic wave device according to claim 1, characterized in that: The thickness of the cover layer is 15-50 micrometers, and the thickness of the support layer is 5-25 micrometers.

9. The elastic wave device according to claim 1, characterized in that: The upper and lower surfaces of the support layer are connected by a first sidewall, and the first sidewall and the lower surface of the support layer have a first included angle, the angle of which ranges from 70° to 89°. The upper and lower surfaces of the cover layer are connected by a second sidewall, and the second sidewall and the lower surface of the cover layer have a second included angle, the angle of which ranges from 70° to 89°.

10. The elastic wave device according to claim 1, characterized in that: The elastic wave device further includes a seed layer, the upper and lower surfaces of the support layer are connected by a first sidewall, the upper and lower surfaces of the cover layer are connected by a second sidewall, and the seed layer is disposed on the pad electrode, as well as on the first and second sidewalls.

11. An electronic module, characterized in that, The electronic module includes an elastic wave device and a circuit board. The elastic wave device is disposed on the circuit board and is an elastic wave device as described in any one of claims 1 to 10.

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