Surface Acoustic Wave Component Structure and Manufacturing Method

Abstract

This invention discloses a surface acoustic wave (SAW) component structure and its manufacturing method, wherein the SAW component structure includes a substrate. A plurality of SAW units are disposed on the substrate. A conductive surrounding structure includes: a wall portion disposed on the substrate and surrounding the plurality of SAW units; and a lateral layer portion disposed on the wall portion. The lateral layer portion has an opening above the plurality of SAW units. A capping layer covers the lateral layer portion and closes the opening.

Description

Technical Field

[0001] This invention relates to semiconductor manufacturing, and more particularly to the structure of a surface acoustic wave (SAW) assembly and its manufacturing method. Background Technology

[0002] Surface acoustic waves (SAWs) are sound waves that propagate along the surface of an elastic material, and their amplitude typically decreases exponentially with the depth of penetration into the material.

[0003] Surface acoustic wave (SAW) components are used in circuits to provide a variety of functions, including delay lines, filters, correlators, and DC-DC converters. Due to their lightweight and compact structure, SAW components are also used in mobile phones.

[0004] Taking surface acoustic wave (SAW) components as examples of SAW filters, they, along with piezoelectric thin-film resonators, are used in communication devices such as cellular phones. The structure of a SAW component includes a group of interdigital transducers (IDTs), which can be used to convert acoustic signals into electronic signals. From a broader functional perspective, an IDT unit can also be considered a surface acoustic wave unit.

[0005] Interdigital transducers are prone to oxidation in high-temperature or high-humidity environments. Therefore, surface acoustic wave (SAW) components have a protective cap on the outer layer. In traditional manufacturing methods, the cap is made of materials such as polyimide (PI). However, PI material's moisture resistance is significantly reduced in high-temperature or high-humidity environments, resulting in decreased protection and making the interdigital transducer more susceptible to oxidation.

[0006] To maintain proper operation of interdigital transducers, effective moisture protection is essential. Further research and development are needed to design and manufacture surface acoustic wave (SAW) components with sufficient moisture resistance. Summary of the Invention

[0007] This invention provides a surface acoustic wave assembly that protects the structure of the interdigital transducer. With changes in the manufacturing process, the use of polyimide materials can be eliminated, effectively improving moisture resistance.

[0008] In one embodiment, the present invention provides a surface acoustic wave (SAW) assembly including a substrate. A plurality of SAW units are disposed on the substrate. A conductive surrounding structure includes: a wall portion disposed on the substrate and surrounding the plurality of SAW units; and a lateral layer portion disposed on the wall portion. The lateral layer portion has an opening above the plurality of SAW units. A capping layer covers the lateral layer portion and closes the opening.

[0009] In one embodiment, for the surface acoustic wave assembly structure, the cap layer is a solder layer.

[0010] In one embodiment, for the surface acoustic wave assembly structure, the cap layer is only on top of the transverse layer.

[0011] In one embodiment, for the surface acoustic wave assembly structure, the cap layer is a reflow solder layer to close the opening in the lateral layer.

[0012] In one embodiment, for the surface acoustic wave assembly structure, the conductive surrounding structure is metal, and the capping layer is solder.

[0013] In one embodiment, for the surface acoustic wave assembly structure, the conductive surrounding structure comprises copper or an electroplated material.

[0014] In one embodiment, for the surface acoustic wave assembly structure, the cap layer is a molding compound structure.

[0015] In one embodiment, for the surface acoustic wave assembly structure, the molding compound structure also covers the outer wall of the conductive surrounding structure and is on the substrate.

[0016] In one embodiment, for the surface acoustic wave assembly structure, the capping layer is an epoxy resin cap that closes the opening in the transverse layer.

[0017] In one embodiment, for the surface acoustic wave assembly structure, the conductive surrounding structure is metal, and the capping layer is an epoxy resin material.

[0018] In one embodiment, for the surface acoustic wave assembly structure, the conductive surrounding structure comprises copper or an electroplated material.

[0019] In one embodiment, the present invention provides a method for manufacturing a surface acoustic wave (SAW) assembly, comprising: providing a substrate; forming a plurality of SAW cells on the substrate; forming a sacrificial layer over the plurality of SAW cells, wherein the sacrificial layer includes a surrounding trench to expose the substrate and surrounds the plurality of SAW cells; performing an electroplating process to form a conductive surrounding structure from the exposed surface of the substrate in the surrounding trench, wherein the conductive surrounding structure includes a lateral layer portion on the sacrificial layer, and the lateral layer portion has an opening over the plurality of SAW cells; forming a capping layer over the lateral layer portion and closing the opening.

[0020] In one embodiment, for the method of manufacturing a surface acoustic wave assembly, the conductive surrounding structure is an electroplated metal.

[0021] In one embodiment, for the method of manufacturing a surface acoustic wave assembly, the conductive surrounding structure comprises copper or an electroplated material.

[0022] In one embodiment, the step of forming the cap layer in the method of manufacturing a surface acoustic wave assembly includes forming a solder layer on the lateral layer portion of the conductive surrounding structure, removing the sacrificial layer, and performing a reflow process on the solder layer, wherein the openings in the lateral layer portion are also closed.

[0023] In one embodiment, for the method of manufacturing a surface acoustic wave assembly, the solder layer is electroplated on the transverse layer of the conductive surrounding structure before the reflow process.

[0024] In one embodiment, the step of forming the cap layer in the method of manufacturing a surface acoustic wave assembly includes: removing the sacrificial layer; and forming a molding compound structure that covers the transverse layer as the cap layer, wherein the opening is closed.

[0025] In one embodiment, for the method of manufacturing a surface acoustic wave assembly, the molding compound structure also covers the outer wall of the conductive surrounding structure and is on the substrate.

[0026] In one embodiment, the molding compound structure is made of epoxy resin in the method for manufacturing the surface acoustic wave assembly.

[0027] In one embodiment, for the method of manufacturing a surface acoustic wave assembly, the conductive surrounding structure comprises copper or an electroplated material. Attached Figure Description

[0028] The accompanying drawings are included to further illustrate the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0029] Figure 1 This is a schematic diagram of the surface acoustic wave assembly explored in one embodiment of the present invention;

[0030] Figures 2A to 2F This is a cross-sectional schematic diagram of the manufacturing process of a surface acoustic wave (SAW) component according to an embodiment of the present invention; and

[0031] Figures 3A-3C This is a cross-sectional schematic diagram of the manufacturing process of a surface acoustic wave assembly according to an embodiment of the present invention.

[0032] Explanation of icon numbers

[0033] 50:Substrate

[0034] 52: Metal layer

[0035] 54: Metal layer

[0036] 56: Interlayer dielectric layer

[0037] 58: Surrounding the wall

[0038] 58a: Sensing area

[0039] 60: Top Floor

[0040] 100:Substrate

[0041] 102: Surface Acoustic Wave Unit

[0042] 104: Sacrifice Layer

[0043] 106: Around the trench

[0044] 108: Conductive surrounding structure

[0045] 108a: Wall

[0046] 108b: Lateral layer

[0047] 110: Opening

[0048] 112: Solder layer

[0049] 112a: Opening

[0050] 120: Molding compound structure Detailed Implementation

[0051] This invention relates to the structure and manufacturing method of a surface acoustic wave (SAW) module, which, in the later-stage packaging process, eliminates the need to use materials with weak moisture resistance, such as polyimide, to protect the IDT (Integrated Device Transformer) cells from oxidation. The proposed manufacturing method for the SAW module allows the use of metallic materials to protect the IDT cells, effectively achieving the requirement of preventing oxidation.

[0052] The present invention is illustrated by the following embodiments. Appropriate combinations are also permitted among these embodiments.

[0053] Before proposing the structure and manufacturing method of the surface acoustic wave (SAW) assembly, this invention has explored the general structure of SAW assemblies in order to at least effectively prevent the oxidation of the IDT units of the SAW assembly.

[0054] Figure 1 This is a schematic diagram of the structure of a surface acoustic wave assembly investigated according to an embodiment of the present invention. (See also...) Figure 1The surface acoustic wave (SAW) assembly structure comprises a metal layer 52, such as copper or aluminum, formed on a substrate 50. The sensing region 52a of the metal layer 52 is formed with multiple individual dielectric units (IDTs) through a defined process. Furthermore, to complete the overall SAW assembly structure, another metal layer 54 is formed on the metal layer 52. Some component regions of the metal layer 52 corresponding to the sensing region 52a are isolated using an inter-metal dielectric (IMD) 56. The IMD 56 covers this region of the metal layer 52. Subsequently, a cap structure is formed using a perimeter wall 58 made of PI material and a top layer 60 to protect the multiple IDTs in the sensing region 52a.

[0055] After investigating the structure of surface acoustic wave (SAW) components, this invention observed that the moisture resistance of PI materials may be insufficient; for example, they may not effectively prevent the oxidation of IDT units under high humidity or high temperature conditions. This invention proposes a structure for protecting IDT units and a method for manufacturing it.

[0056] Figures 2A to 2F This is a cross-sectional schematic diagram illustrating the manufacturing process of a surface acoustic wave (SAW) component according to an embodiment of the present invention. (See also...) Figure 2A Multiple surface acoustic wave units 102 are formed on the substrate 100 to form a sensing group to sense sound waves. Figure 2A The following explanation uses only two surface acoustic wave (SAW) units 102 as an example. In one embodiment, the SAW unit 102 functions as an IDT (Integrated Device Transformer) unit, for example.

[0057] See Figure 2B A sacrificial layer 104 is formed on the substrate 100 and covers the surface acoustic wave units 102. The sacrificial layer 104 is, for example, a photoresist material, or other materials that can be removed in subsequent processes. The sacrificial layer 104 has surrounding trenches 106 surrounding the surface acoustic wave units 102 to be protected. When the sacrificial layer 104 is made of a photoresist material, it can be completed, for example, using a photolithography process, after which the photoresist material can be easily and completely removed.

[0058] See Figure 2C A portion of the surface of the substrate 100 is exposed around the trench 106. Using the exposed surface of the substrate 100, in one embodiment, the present invention, for example, performs an electroplating process to form the conductive surrounding structure 108 starting from the exposed surface. The conductive surrounding structure 108 may be made of copper, or other metals or electroplating materials that can be used. The material of the conductive surrounding structure 108 is not limited to the illustrated embodiment.

[0059] The conductive surrounding structure 108 has a wall portion 108a formed in the surrounding trench 106 of the sacrificial layer 104, followed by a transverse layer portion 108b formed on the top surface of the sacrificial layer 104. Although the conductive surrounding structure 108 is a single electroplated structure, in detail, the transverse layer portion 108b is disposed on the wall portion 108a. The wall portion 108a and the transverse layer portion 108b constitute the conductive surrounding structure 108.

[0060] Here, the lateral layer 108b has an opening 110 above the plurality of surface acoustic wave units 102. That is, the lateral layer 108b does not completely cover the area. This opening 110 can be used for subsequent processes to remove the sacrificial layer 104 in the allowable area.

[0061] See Figure 2D A solder layer 112 is formed on the lateral layer 108b, and solder may be electroplated onto the lateral layer 108b, but is not limited thereto. Here, the solder layer 112 also has an opening 112a connected to the opening 110, thereby maintaining the exposure of the sacrificial layer 104.

[0062] See Figure 2E Depending on the material used in the sacrificial layer 104, the sacrificial layer 104 is removed using a corresponding process. For example, if the sacrificial layer 104 is a photoresist material, it can be removed using an ashing process. Since the opening 112a is connected to the opening 110, the sacrificial layer 104 covering the surface acoustic wave unit 102 is also removed. In this way, the surface acoustic wave unit 102 can be completely released into space for sensing surface acoustic waves.

[0063] See Figure 2F The surface acoustic wave unit 102 needs to be protected, requiring dust and moisture resistance. In one embodiment, the solder layer 112 can be melted and then solidified using a reflow process to form a monolithic solder layer 112, which naturally covers the opening 110 of the transverse layer portion 108b, achieving a sealing effect. The solder layer 112 acts as a cap structure, sealing the opening 110. However, the formation of the cap structure is not limited to this embodiment; for example, it will be described later. Figures 3A-3C The cap structure of the present invention is used to enclose the conductive surrounding structure 108, and it is not necessarily limited to the embodiments described herein.

[0064] Furthermore, in order for the solder layer 112 to close the opening 110 of the transverse layer 108b after the reflow process, the size of the opening 110 and the opening 112a can be appropriately controlled in advance.

[0065] Here, the conductive metal surrounding structure 108 is combined with solder layer 112 to construct a space above surface acoustic wave unit 102, which can effectively protect surface acoustic wave unit 102.

[0066] Figures 3A-3C This is a cross-sectional schematic diagram illustrating the manufacturing process of a surface acoustic wave (SAW) component according to an embodiment of the present invention. (See also...) Figure 3A , its like Figure 2A Multiple surface acoustic wave units 102 are first formed on the substrate 100.

[0067] See Figure 3B , use as Figure 2B and Figure 2C The manufacturing process involves first forming a conductive surrounding structure 108 on the substrate 100, and then removing the sacrificial layer 104. In this structural state, the surface acoustic wave unit 102 is exposed.

[0068] See Figure 3C In one embodiment, for example, an encapsulation process is used to cover the conductive surrounding structure 108 with a molding compound structure 120, which includes covering the top of the conductive surrounding structure 108 and the outer sidewalls of the conductive surrounding structure 108, with its bottom on the substrate 100. The molding compound structure 120 also acts as a cap structure, closing the opening 110 of the lateral layer portion 108b of the conductive surrounding structure 108, thereby achieving more comprehensive protection.

[0069] This invention proposes a method for manufacturing surface acoustic wave (SAW) components that allows the use of metallic materials to form a protective structure to protect the SAW unit, at least effectively preventing oxidation.

[0070] 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. A surface acoustic wave (SAW) component structure, characterized in that, include: substrate; Multiple surface acoustic wave units are disposed on the substrate; The conductive surrounding structure includes: A wall portion, disposed on the substrate and surrounding the plurality of surface acoustic wave units in a horizontal direction parallel to the surface of the substrate; and A transverse layer is disposed on the wall portion and has an opening above the plurality of surface acoustic wave (SAW) units, wherein the transverse layer includes an inner sidewall and an outer sidewall opposite to the inner sidewall in the horizontal direction, the inner sidewall defining the opening and overlapping the SAW units in a vertical direction perpendicular to the surface of the substrate, and the outer sidewall and the inner sidewall not overlapping the wall portion in the vertical direction; and A capping layer covers the transverse layer and seals the opening. The cap layer is located only on the top of the transverse layer and has an edge flush with the outer wall, and the material of the cap layer is solder.

2. The surface acoustic wave (SAW) component structure according to claim 1, characterized in that, The cap layer is a reflow solder layer to seal the opening in the lateral layer.

3. The surface acoustic wave (SAW) component structure according to claim 1, characterized in that, The conductive surrounding structure is metal.

4. The surface acoustic wave (SAW) component structure according to claim 3, characterized in that, The conductive surrounding structure comprises an electroplated material.

5. A method for manufacturing a surface acoustic wave (SAW) component, characterized in that, include: Provide substrate; Multiple surface acoustic wave units are formed on the substrate; A sacrificial layer is formed to cover the plurality of surface acoustic wave units, wherein the sacrificial layer includes surrounding the trench to expose the substrate and surrounding the plurality of surface acoustic wave units; An electroplating process is performed to form a conductive surrounding structure from the exposed surface of the substrate in the surrounding trench. The conductive surrounding structure includes a wall portion disposed on the substrate and surrounding the plurality of surface acoustic wave (SAW) cells in a horizontal direction parallel to the surface of the substrate, and a transverse layer portion disposed on the wall portion and the sacrificial layer and having an opening above the plurality of SAW cells. The transverse layer portion includes an inner sidewall and an outer sidewall opposite to the inner sidewall in the horizontal direction. The inner sidewall defines the opening and overlaps with the SAW cells in a vertical direction perpendicular to the surface of the substrate. The outer sidewall and the inner sidewall do not overlap with the wall portion in the vertical direction. A capping layer is formed, covering the transverse layer and sealing the opening. The step of forming the cap layer includes: A solder layer is formed on the lateral layer portion of the conductive surrounding structure; Remove the sacrificial layer; and The solder layer is reflowed so that the resulting cap layer is only on the top of the transverse layer and has an edge flush with the outer wall.

6. The method for manufacturing a surface acoustic wave (SAW) component according to claim 5, characterized in that, The conductive surrounding structure is an electroplated metal.

7. The method for manufacturing a surface acoustic wave (SAW) component according to claim 5, characterized in that, The conductive surrounding structure comprises an electroplated material.

8. The method for manufacturing a surface acoustic wave (SAW) component according to claim 5, characterized in that, The solder layer is electroplated on the transverse layer of the conductive surrounding structure before the reflow process.

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