Saw filter package and method for manufacturing same

Abstract

A SAW filter package and a method for manufacturing same are provided. A surface acoustic wave (SAW) filter package comprises: a first substrate on which a SAW filter is formed; an electrode pad layer formed on the first substrate; an under bump metallurgy (UBM) layer formed on the electrode pad; a second substrate; and a metal bump electrically connecting the first substrate and the second substrate to each other, wherein the UBM layer includes an aluminum-copper alloy, and the metal bump includes a gold-palladium alloy.

Description

SAW filter package and method of manufacturing the same

[0001] The present invention relates to a SAW filter package and a method for manufacturing the same, and more specifically, to a SAW filter package and a method for manufacturing the same in which the possibility of void defects occurring is reduced by including a metal bump and an Under Bump Metallurgy (UBM) layer with improved reliability.

[0002] Since forming solder or gold bumps on aluminum pads formed on semiconductor chips results in poor adhesion, UBM (Under Bump Metallurgy) is additionally formed to act as an intermediary between the bumps and the pads, thereby reinforcing the bonding strength.

[0003] These UBM devices form a connection structure by, for example, forming a gold UBM layer on an aluminum electrode formed with a titanium (Ti) layer, and forming gold UBM and gold bumps. However, since gold, a precious metal, increases manufacturing costs during the mass production of SAW filter packages, research is ongoing on connection structures that can guarantee the same performance, such as bonding performance and reliability, while reducing the amount of gold included.

[0004] The technical problem that the present invention aims to solve is to provide a SAW filter package and a method for manufacturing the same, in which the possibility of void defects occurring is reduced by including a metal bump with improved reliability and an Under Bump Metallurgy (UBM) layer.

[0005] The technical problems of the present invention are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art from the description below.

[0006] A SAW filter package for solving the aforementioned technical problem comprises: a first substrate on which a SAW (Surface Acoustic Wave) filter is formed; an electrode pad layer formed on the first substrate; an Under Bump Metallurgy (UBM) layer formed on the electrode pad; a second substrate; and a metal bump electrically connecting the first substrate and the second substrate, wherein the UBM layer comprises an aluminum and copper alloy, and the metal bump comprises a gold and palladium alloy.

[0007] In some embodiments of the present invention, the copper content relative to the total mass of the UBM layer may be 0.5% to 2%.

[0008] In some embodiments of the present invention, the bonding strength by the UBM layer may be 600g or more.

[0009] In some embodiments of the present invention, the palladium content relative to the total mass of the metal bump may be 1% or more.

[0010] In some embodiments of the present invention, an Intermetallic Compound (IMC) is formed between the metal bump and the UBM layer, and a palladium-rich layer may be formed between the IMC and the metal bump.

[0011] In some embodiments of the present invention, Kirkendall voids formed in the IMC may not diffuse into the metal bump by the palladium-rich layer.

[0012] A method for manufacturing a SAW filter package to solve the aforementioned technical problem comprises the steps of: forming an electrode pad layer and a UBM layer in sequence on a first substrate on which a SAW filter is formed; forming a metal bump on the UBM layer; and bonding a second substrate and the first substrate through the metal bump, wherein the UBM layer comprises an aluminum and copper alloy and the metal bump comprises a gold and palladium alloy.

[0013] In some embodiments of the present invention, the step of bonding the second substrate and the first substrate via the metal bump may include the step of performing annealing on the metal bump.

[0014] In some embodiments of the present invention, the step of forming a metal bump on the UBM layer includes the step of forming an IMC layer between the UBM layer and the metal bump, and the step of performing annealing on the metal bump may include the step of growing the IMC layer.

[0015] In some embodiments of the present invention, Kirkendall voids formed in the IMC may not diffuse into the metal bump due to a palladium-rich layer formed between the IMC and the metal bump.

[0016] Specific details of other embodiments are included in the detailed description and drawings.

[0017] According to the SAW filter package and the method for manufacturing the same according to an embodiment of the present invention, the bonding strength with a metal bump containing gold can be improved by configuring the UBM layer containing aluminum with an alloy containing copper.

[0018] In addition, by including a gold alloy containing palladium as a metal bump, a palladium-rich layer is formed at the interface between the IMC and the metal bump, and by preventing Kirkendall voids from diffusing into the metal bump even after the reflow process, the mechanical reliability of the electrical connection by the metal bump can be maintained.

[0019] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims.

[0020] FIG. 1 is a drawing for illustrating a SAW filter package according to an embodiment of the present invention.

[0021] FIG. 2 is a diagram illustrating the connection structure of a first substrate and a second substrate included in a SAW filter package according to an embodiment of the present invention.

[0022] Figure 3 is a diagram illustrating the IMC formed in the connection structure of Figure 2.

[0023] Figures 4a and 4b are SEM images of the IMC of Figure 3.

[0024] Figures 5a and 5b are SEM images illustrating the degree of void formation according to the palladium ratio of the metal bumps.

[0025] FIG. 6 is a diagram illustrating the bonding strength according to the aluminum alloy ratio of the UBM layer included in a SAW filter package according to an embodiment of the present invention.

[0026] FIGS. 7 and 8 are intermediate step drawings for explaining a method for manufacturing a SAW filter package according to an embodiment of the present invention.

[0027] Figures 9a and 9b are SEM images illustrating the IMC formed during the manufacturing process of a SAW filter package according to an embodiment of the present invention.

[0028] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Throughout the specification, the same reference numerals refer to the same components.

[0029] When one component is referred to as being "connected to" or "coupled to" another component, it includes cases where it is directly connected or coupled to the other component, or cases where another component is interposed. Conversely, when one component is referred to as being "directly connected to" or "directly coupled to" another component, it indicates that no other component is interposed. "And / or" includes each of the mentioned items and all combinations of one or more of them.

[0030] The terms used herein are for describing the embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components, steps, actions, and / or elements to the mentioned components, steps, actions, and / or elements.

[0031] Although terms such as "first," "second," etc., are used to describe various components, it goes without saying that these components are not limited by these terms. These terms are used merely to distinguish one component from another. Therefore, it goes without saying that the "first component" mentioned below may be the "second component" within the technical scope of the present invention.

[0032] Unless otherwise defined, all terms used in this specification (including technical and scientific terms) may be used in a meaning commonly understood by those skilled in the art to which the present invention pertains. Additionally, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0033] FIG. 1 is a drawing for illustrating a SAW filter package according to an embodiment of the present invention.

[0034] Referring to FIG. 1, a SAW filter package according to an embodiment of the present invention may include a first substrate (100) and a second substrate (200), etc.

[0035] The first substrate (100) may be a substrate on which a Surface Acoustic Wave (SAW) filter is formed. The first substrate (100) may include, for example, a silicon substrate or a piezoelectric substrate such as LiTaO3 (LT) or LiNbO3 (LN).

[0036] The first substrate (100) can be bonded to the second substrate (200) by a flip chip bonding method. A bump (130) may be formed to connect the first substrate (100) and the second substrate (200), and a description regarding the connection structure including the bump (130) will be provided later.

[0037] The second substrate (200) may include a package substrate connected to the first substrate (100), and may include, for example, a lead frame, a PCB (Printed Circuit Board), but is not limited thereto. A pad (210) may also be formed on one side of the second substrate (200).

[0038] A metal bump (130) may be formed to electrically connect the first substrate (100) and the second substrate (200). In a SAW filter package according to an embodiment of the present invention, the metal bump (130) can form a reliable connection by combining the Under Bump Metallurgy (UBM) formed on the first substrate (100) side. The connection structure of the first substrate (100) and the second substrate (200) will be explained in more detail using FIG. 2, etc.

[0039] FIG. 2 is a diagram illustrating the connection structure of a first substrate and a second substrate included in a SAW filter package according to an embodiment of the present invention.

[0040] Referring to FIG. 2, a SAW filter package according to an embodiment of the present invention may include an electrode pad layer (110) formed on a first substrate (100), a UBM layer (120) formed on the electrode pad layer (110), a metal bump (130) formed on the UBM layer (120), and a conductive layer (205) formed between the metal bump (130) and a second substrate (200).

[0041] The electrode pad layer (110) may include a conductive material, for example, titanium (Ti). The electrode pad layer (110) may be formed in any region on the first substrate (100), and another conductive layer may be formed between the electrode pad layer (110) and the first substrate (100).

[0042] A UBM layer (120) may be formed on the electrode pad layer (110). A SAW filter package according to an embodiment of the present invention may include an aluminum (Al) alloy containing copper (Cu) as the UBM layer (120).

[0043] Typically, bonding a metal bump containing gold to an aluminum layer does not guarantee sufficient reliability. Accordingly, the inventors of the present invention have configured the aluminum-containing UBM layer (120) with an alloy containing copper to prevent excessive diffusion with the gold-containing metal bump (130) and to improve reliability.

[0044] In some embodiments of the present invention, the ratio of copper content to the total mass of the UBM layer (120) may be 0.5% to 2%. If the copper content is 0.5% or less, it approaches pure aluminum, and if it is 2% or more, the overall hardness of the UBM layer (120) increases, which hinders the sufficient formation of the IMC (Intermetallic compound) and prevents securing sufficient bonding strength with the metal bump (130). This is explained using FIG. 6, which shows a graph of the amount of copper contained in the UBM layer (120) and bonding strength.

[0045] FIG. 6 is a diagram illustrating the bonding strength according to the aluminum alloy ratio of the UBM layer included in a SAW filter package according to an embodiment of the present invention.

[0046] Referring to FIG. 6, a graph of the bonding strength (g) with respect to the copper content relative to the total mass of the UBM layer (120) is shown. Specifically, when the copper content is 0.5%, 1%, and 2%, the bonding strength is secured to be approximately 1200, 1100, and 800 (g), respectively, thereby forming sufficient bonding strength between the first substrate (100) and the second substrate (200). However, at 4% or more, due to the increase in hardness, the IMC is not formed to the extent that sufficient bonding reliability can be secured, so a reliable connection structure is not formed between the first substrate (100) and the second substrate (200).

[0047] Referring again to FIG. 2, the metal bump (130) formed between the conductive layer (205) and the UBM layer (120) may be an alloy containing palladium (Pd) in gold. In particular, the role and effect of the metal bump (130) forming a bond with the UBM layer (120) will be explained using FIG. 3.

[0048] Figure 3 is a diagram illustrating the IMC formed in the connection structure of Figure 2.

[0049] Referring to FIG. 3, when a UBM layer (120) and a metal bump (130), i.e., heterogeneous metals are bonded, an IMC (Intermetallic compound, 135) is formed between the UBM layer (120) and the metal bump (130). The IMC (135) is a metal compound formed by combining aluminum and copper contained in the UBM layer (120) and gold and palladium contained in the metal bump (130) in a certain ratio, which can provide mechanical bonding strength, and in particular, when bonding the metal bump (130), the IMC (135) grows further during heat treatment such as annealing. FIG. 4a and 4b are Scanning Electron Microscope (SEM) images of the IMC of FIG. 3, and it can be confirmed that an IMC (Intermetallic compound, 135) is formed between the UBM layer (120) and the metal bump (130).

[0050] Meanwhile, a Kirkendall void is formed at the interface between the IMC (135) and the metal bump (130). The Kirkendall void can have an adverse effect on reliability, such as mechanical impact characteristics of the connection.

[0051] However, in the SAW filter package according to the embodiment of the present invention, when the IMC (135) is formed by heating for bonding the metal bump (130), a palladium-rich layer (136) is additionally formed at the interface between the IMC (135) and the metal bump (130). When the metal bump (130) is heated during the formation of the IMC (135) or in a subsequent process, an aging phenomenon occurs in which Kirkendall voids expand. In the SAW filter package according to the embodiment of the present invention, the palladium-rich layer (136) formed due to the palladium contained in the metal bump (130) prevents the diffusion of Kirkendall voids and can reduce the degradation of reliability, such as the mechanical properties of the entire metal bump (130).

[0052] Figures 5a and 5b are SEM images illustrating the degree of void formation according to the palladium ratio of the metal bumps.

[0053] Referring to FIG. 5a, SEM images of the metal bump (130) and IMC (135) are shown when a metal bump of 99.99% gold (Au 99.99%), a metal bump of gold containing 0.5% palladium (Au 99.5% + Pd 0.5%), and a metal bump of gold containing 1% palladium (Au 99% + Pd 1%) are formed. Regardless of the palladium content, an IMC (135) is formed between the UBM layer (120) and the metal bump (130).

[0054] Meanwhile, referring to FIG. 5b, an SEM image is shown of a situation in which Kirkendall voids are formed by heat treatment in the case where metal bumps of 99.99% gold (Au 99.99%), metal bumps of gold containing 0.5% palladium (Au 99.5% + Pd 0.5%), and metal bumps of gold containing 1% palladium (Au 99% + Pd 1%) are formed.

[0055] In the case of gold metal bumps that do not contain palladium and gold metal bumps containing 0.5% palladium, Kirkendall voids are formed by heat treatment and can be observed to diffuse toward the metal bumps. On the other hand, in the case of metal bumps containing 1% palladium, some Kirkendall voids are formed between the interface of the IMC and the metal bumps, but it is observed that even when heat treatment is performed, the Kirkendall voids do not diffuse into the metal bumps and remain only at the interface.

[0056] In this way, the SAW filter package according to the embodiment of the present invention includes a gold alloy containing 1% or more of palladium as a metal bump (130), thereby forming a palladium-rich layer (136) at the interface between the IMC (135) and the metal bump (130), and by preventing Kirkendall voids from spreading into the metal bump (130) even after the reflow process, the mechanical reliability of the electrical connection by the metal bump (130) can be maintained.

[0057] FIGS. 7 and 8 are intermediate step drawings for explaining a method for manufacturing a SAW filter package according to an embodiment of the present invention.

[0058] First, referring to FIG. 7, an electrode pad layer (110) and a UBM layer (120) are formed on a first substrate (100). As previously described, the electrode pad layer (110) may include titanium, and the UBM layer (120) may include an alloy of aluminum and copper. More specifically, the UBM layer (120) may include an aluminum-copper alloy containing 0.5 to 2.0% copper.

[0059] Forming the electrode pad layer (110) and the UBM layer (120) on the first substrate (100) may be performed by at least one of the following methods: electrolytic or electroless plating, physical vapor deposition (PVD) including sputtering, chemical vapor deposition (CVD), atomic layer deposition (ALD), thermal evaporation, and electron beam evaporation. In some embodiments of the present invention, additional steps such as forming a mask pattern, such as a photoresist, and removing a metal film through etching may be performed to form the electrode pad layer (110) at a specific location on the first substrate (100).

[0060] Additionally, although not shown, an insulating layer of a certain thickness may be formed around the UBM layer (120) to form a recess-shaped UBM layer (120) for later seating of the metal bump (130).

[0061] Next, referring to FIG. 8, a metal bump (130) may be formed on the UBM layer (120). The metal bump (130) may be formed in the shape of a stud bump, for example, using a wire bonder. Of course, after the formation of the metal bump (130), a process of pressing the metal bump (130) may be performed in the bonding step with the second substrate (200) or in the step prior thereto.

[0062] In a SAW filter package according to an embodiment of the present invention, the metal bump (130) may include a gold alloy containing palladium, and more specifically, may include a gold alloy containing 1% or more of palladium.

[0063] Figures 9a and 9b are SEM images illustrating the IMC formed during the manufacturing process of a SAW filter package according to an embodiment of the present invention.

[0064] Referring to FIGS. 9a and 9b, it can be observed that an IMC (131) is formed during the process of using a wire bonder to form a metal bump (130). That is, when forming the metal bump (130), an IMC (131) is primarily formed between the metal bump (130) and the UBM layer (120) during the process in which the wire bonder heats the gold palladium alloy wire to bond it to the UBM layer (120).

[0065] Next, referring to FIG. 2, a process of bonding a second substrate (200) and a first substrate (100) is performed via a metal bump (130). The first substrate (100) can be bonded to the second substrate (200) by flip-chip bonding, and annealing can be performed at 200 to 250°C to grow the IMC (131) primarily formed during the bonding process and increase the bonding strength. This annealing can be carried out for 60 to 120 minutes, and when the annealing is completed, a more grown IMC (135) is produced as shown in FIG. 4a and 4b to reinforce the bonding strength.

[0066] Although embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will understand that the present invention may be implemented in other specific forms without changing its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. A first substrate having a SAW (Surface Acoustic Wave) filter formed thereon; An electrode pad layer formed on the first substrate; A UBM (Under Bump Metallurgy) layer formed on the electrode pad above; Second substrate; and It includes a metal bump that electrically connects the first substrate and the second substrate, The above UBM layer comprises aluminum and copper alloys, and The above metal bump comprises a gold and palladium alloy, SAW filter package.

2. In Paragraph 1, The copper content relative to the total mass of the above UBM layer is 0.5% to 2%, SAW filter package.

3. In Paragraph 2, The bonding strength by the above UBM layer is 600g or more, SAW filter package.

4. In Paragraph 1, The palladium content relative to the total mass of the above metal bump is 1% or more, SAW filter package.

5. In Paragraph 1, An IMC (Intermetallic Compound) is formed between the metal bump and the UBM layer, and A palladium-rich layer is formed between the above IMC and the above metal bump. SAW filter package.

6. In Paragraph 5, Kirkendall voids formed in the above IMC are not diffused into the metal bump by the palladium-rich layer, SAW filter package.

7. A step of sequentially forming an electrode pad layer and a UBM layer on a first substrate on which a SAW filter is formed; A step of forming a metal bump on the above UBM layer; and The method includes the step of bonding the second substrate and the first substrate via the metal bump, The above UBM layer comprises aluminum and copper alloys, and The above metal bump comprises a gold and palladium alloy, Method for manufacturing a SAW filter package.

8. In Paragraph 7, The copper content relative to the total mass of the above UBM layer is 0.5% to 2%, Method for manufacturing a SAW filter package.

9. In Paragraph 7, The palladium content relative to the total mass of the above metal bump is 1% or more, Method for manufacturing a SAW filter package.

10. In Paragraph 7, The step of bonding the second substrate and the first substrate via the metal bump is A step comprising performing annealing on the metal bump above, Method for manufacturing a SAW filter package.

11. In Paragraph 10, The step of forming metal bumps on the above UBM layer is, The method includes the step of forming an IMC layer between the above UBM layer and the above metal bump, The step of performing annealing on the above metal bump is, A step comprising growing the above IMC layer, Method for manufacturing a SAW filter package.

12. In Paragraph 11, Kirkendall voids formed in the IMC are not diffused into the metal bump by the palladium-rich layer formed between the IMC and the metal bump. Method for manufacturing a SAW filter package.

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