Acoustic wave filter device and method of manufacturing the same

An acoustic wave filter device includes a substrate, a filter disposed on the substrate, a wall member disposed on the substrate and surrounding the filter, and a cap member disposed above the wall member and, with the wall member, forming an internal space. The cap member has a curved shape and comprises a first cap member comprising a first material and a second cap member comprising a second material.

CROSS-REFERENCE TO RELATED APPLICATION(S)

BACKGROUND

The following description relates to an acoustic wave filter device and a method of manufacturing the same.

2. Description of Related Art

Currently, most wafer-level packages (WLP) having a cavity include a micro-electro-mechanical-system (MEMS) and a filter package.

As filter packages included in wafer-level packages have become smaller and thinner, manufacturing techniques such as chip-scale packaging (CSP), wafer-to-wafer level packaging, and film packaging, among others, have been developed. Acoustic wave filter devices have been manufactured using these manufacturing techniques.

During a manufacturing process of an acoustic wave filter device, and specifically during the molding process, when internal pressure increases in order to realize a proper internal pressure for molding, and/or when a polymer having a low strain rate is used as a cap member, it is necessary to have a thicker cap member to avoid deformation or other problems. Inclusion of a thicker cap member is problematic in the production of thin acoustic wave filter packages as it increases thickness of the overall package.

Thus, it is necessary to develop a structure capable of reducing a thickness of a cap member while ensuring proper internal pressure. In other words, it is necessary to develop a structure capable of suppressing deformation of a cap member during a molding process.

SUMMARY

This Summary is provided to introduce a selection of concepts that are further described below in the Detailed Description in simplified form. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

According to an exemplary embodiment, an acoustic wave filter device includes a substrate, a filter disposed on the substrate, a wall member disposed on the substrate and surrounding the filter, and a cap member disposed above the wall member and, with the wall member, forming an internal space. The cap member has a curved shape and comprises a first cap member comprising a first material and a second cap member comprising a second material.

The first cap member may be disposed on the wall member, the second cap member may be disposed on the first cap member, and at least one of the first cap member and the second cap member may have a residual stress curvature.

The cap member may include an upwardly convex central portion.

The first cap member may have a same thickness as or thinner thickness than a thickness of the second cap member.

The acoustic wave filter may also include a metal layer disposed on the substrate outside of the wall member in a top-down view.

The acoustic wave filter device may also include an under-bump metal member disposed on the metal layer.

The acoustic wave filter device may also include a bump disposed on the under-bump metal member and a molding layer disposed such that the under-bump metal member, the wall member, and the cap member are embedded, and such that the bump is partially externally exposed.

A metal film may be disposed under the bump and on the under-bump metal member.

The molding layer may be disposed on the cap member.

The second material comprising the second cap member may have a greater elastic modulus than an elastic modulus of the first material comprising the first cap member.

The first material comprising the first cap member and the second material comprising the second cap member may be different metals.

According to an exemplary embodiment, a method of manufacturing an acoustic wave filter device includes forming a filter on a substrate, forming a wall member to surround the filter, forming a cap member having an upwardly convex central portion. The cap member includes a first cap member formed on the wall member and a second cap member formed on the first cap member.

The first cap member may have a same thickness as or thinner thickness than a thickness of the second cap member.

The material comprising the first cap member and the material forming the second cap member may be different metals.

The second material forming the second cap member may have a greater elastic modulus than an elastic modulus of the first material forming the first cap member.

The second cap member may be formed by an electroless or electrolytic plating process.

Forming the second cap member may include applying tensile stress to the second cap member when the second cap member is formed such that residual stress remains in the second cap member after the second cap member is formed.

Forming the first cap member may include bonding a metal sheet to the wall member and removing an edge of the metal sheet.

Manufacturing an acoustic wave filter device may further include forming a metal layer on the substrate during the same process as forming the filter on the substrate.

Examples provide an acoustic wave filter device capable of reducing narrowing of an internal space in which a filter is disposed when a molding layer is formed, and a method of manufacturing the same.

DETAILED DESCRIPTION

Subsequently, examples are described in further detail with reference to the accompanying drawings.

Unless indicated otherwise, a statement that a first layer is “on” or “connected to” a second layer or a substrate is to be interpreted as covering both a case where the first layer directly contacts the second layer or the substrate, and a case where one or more other layers are disposed between the first layer and the second layer or the substrate.

Words describing relative spatial relationships, such as “below”, “beneath”, “under”, “lower”, “bottom”, “above”, “over”, “upper”, “top”, “left”, and “right”, may be used to conveniently describe spatial relationships of one device or elements with other devices or elements. Such words are to be interpreted as encompassing a device oriented as illustrated in the drawings, and in other orientations in use or operation. For example, an example in which a device includes a second layer disposed above a first layer based on the orientation of the device illustrated in the drawings also encompasses the device when the device is flipped upside down in use or operation.

FIG. 1is a schematic cross-sectional view illustrating an acoustic wave filter device according to an exemplary embodiment.

Referring toFIG. 1, an acoustic wave filter device100according to an exemplary embodiment includes a substrate110, a filter unit120, a wall member130, a cap member140, an under-bump metal member150, a molding layer160, and a bump170.

The substrate110may be a piezoelectric substrate. For example, the substrate110may be a substrate in which a piezoelectric single crystal, such as LiTaO3, LiNbO3, etc., a piezoelectric ceramic, and/or a piezoelectric thin film, is formed on a main surface. However, these are merely exemplary, and piezoelectric single crystals may be formed of other materials or combinations of materials.

A metal layer112formed to surround the filter unit120in a top-down view may be formed on the substrate110. The metal layer112may be formed of the same material as the filter unit120. For example, the metal layer112may be formed to contain one or more of titanium (Ti), nickel (Ni), aluminum (Al), copper (Cu), or AlCu.

As described above, the metal layer112and the filter unit120may be formed of the same material, so formation of the metal layer112may be more easily performed. Thus, the process of forming the metal layer112and the filter layer120may have increased efficiency.

The metal layer112and the filter unit120may be formed by a chemical vapor deposition (CVD) or a physical vapor deposition (PVD) process, but the formation process is not limited thereto. For example, the metal layer112and the filter unit120may be formed by a plating method, a metalorganic chemical vapor deposition (MOCVD), or the like.

As shown inFIG. 1, The filter unit120may be formed in a central portion of the substrate110. For example, the filter unit120may be formed in a single interdigital (IDT) pattern, however, embodiments are not limited thereto. For example, various IDT patterns may be formed together on the portion of the substrate110to form the filter unit120. The metal layer112and the wall member130may be formed to surround the filter unit120in a top-down view.

The filter unit120may be formed of the same material as the metal layer112, as described above.

The wall member130may be formed to surround the filter unit120in a top-down view, and may form an internal space S bounded by the cap member140. The wall member130may be formed of, for example, a photoimageable film, but is not limited thereto. As only an example, the wall member130may be formed of one of a liquid resin or a film resin.

The cap member140may be formed above the wall member130and may form the internal space S with the wall member130. The cap member140may be formed of at least two materials having different physical characteristics, and may have a shape having a curvature, as shown inFIG. 1.

For example, the cap member140may include a first cap member142formed at least partially on the wall member130, and a second cap member144formed on the first cap member142. When at least one of the first cap member142and the second cap member144is manufactured, tensile stress is applied, so the cap member140may have a curvature due to residual stress.

As an example, the cap member140may have a dome shape whose central portion is upwardly convex, as shown inFIG. 1.

The first cap member142and the second cap member144may be formed of different materials, for example, different metal materials. However, this is merely an example, as the cap members may be formed of different materials that may include or may not include metal elements. The first cap member142and the second cap member144may be formed of materials at different strain rates.

The first cap member142may have a thickness the same as or thinner than a thickness of the second cap member144. Thus, the cap member140may have a central portion that is upwardly convex, rather than a shape of a central portion which is downwardly concave.

The second cap member144may be formed of a material having a higher elastic modulus than that of the first cap member142.

The first cap member142is formed to be at least partially supported by an upper surface of the wall member130. For example, a metal sheet may be bonded to the wall member130using a hot press forming apparatus, a wafer bonder, a vacuum laminator, etc. The first cap member142may be formed using a photolithography process and a wet etching process thereafter.

Thereafter, the second cap member144may be formed using electroless or electrolytic plating.

However, an example is not limited thereto, and a metal sheet may be bonded to the wall member130using a hot press forming apparatus, a wafer bonder, or a vacuum laminator, and the second cap member144is formed on a metal sheet using electroless plating or electrolytic plating. Thereafter, the first cap member142may be formed using a photolithography process and a wet etching process.

As described above, the second cap member144may be formed of a material having a higher elastic modulus than the first cap member142. The second cap member144may be formed using electroless or electrolytic plating. Thus, as residual stress remains in the second cap member144, a central portion of the cap member140may have a shape which is upwardly convex, as shown inFIG. 1.

The under-bump metal member150is formed on the metal layer112of the substrate110. Further, a metal film152may be formed to allow the bump170to be bonded to the under-bump metal member150. The metal film152may include a suitable metal depending on a metal forming the under-bump metal member150. However, the metal film152is not necessarily required.

The under-bump metal member150may be exposed externally through an opening162(seeFIG. 8) of the molding layer160, during manufacturing, which will be described later.

The molding layer160may be formed to expose the bump170externally, and may be formed to embed the under-bump metal member150, the wall member130, and the cap member140therein. In other words, the bump170may be inserted into and disposed in an opening162(seeFIG. 8) of the molding layer160, such that remaining elements, such as the under-bump metal member150, the wall member130, and the cap member140disposed in the molding layer160are isolated from the outside.

The molding layer160may be formed of a polymer material, such as a synthetic resin material, but is not limited thereto.

As described above, the molding layer160may be formed to cover the internal space S formed by the wall member130and the cap member140. When the molding layer160is formed, uniform pressure is applied to the cap member140.

In accordance with the above, the cap member140may have a shape having an upwardly convex curvature. That is, due to pressure applied when the molding layer160is formed, a central portion of the cap member140may be prevented from being deformed to be downwardly concave.

The bump170is formed on the under-bump metal member150, and may be formed to pass through an opening162(seeFIG. 8) of the molding layer160to be externally exposed, as shown inFIG. 1.

As described above, a central portion of the cap member140may have a dome shape, which is upwardly convex. Thus, due to pressure applied when the molding layer160is formed, a central portion of the cap member140may be prevented from being deformed to be downwardly concave.

Further, due to the first cap member142and the second cap member144being formed of metal materials, an increase in a thickness, caused by the cap member140, may be prevented.

Since the cap member140is formed in a simple process, the cap member140may be prevented from being deformed during the manufacturing process, and the manufacturing process may be less complicated.

Hereinafter, a method of manufacturing an acoustic wave filter device according to an exemplary embodiment will be described with reference to the accompanying drawings.

FIGS. 2, 3, 4, 5, 6, 7, 8, and 9are process diagrams illustrating a method of manufacturing an acoustic wave filter device according to an exemplary embodiment.

As shown inFIG. 2, the filter unit120may be formed on an upper surface of a central portion of the substrate110. For example, the filter unit120may be formed of an IDT pattern. The filter unit120may be formed to be disposed inside of the metal layer112formed on the substrate110.

As illustrated inFIG. 3, the under-bump metal member150may be formed on an upper surface of the metal layer112disposed on the substrate110. The metal film152may be formed on an upper surface of the under-bump metal member150to allow the under-bump metal member150to be easily connected to the bump170, which will be described later. A configuration in which the metal film152is formed on an upper surface of the under-bump metal member150is illustrated by way of example, but is not limited thereto. That is, the metal film152may be omitted and bump170may be disposed directly on under-bump metal member150.

The under-bump metal member150may be formed, for example, by an electrolytic plating method, but other methods may be used.

As illustrated inFIG. 4, the wall member130may be disposed on the substrate110between the metal layer112and the filter unit120, and may be formed to surround the filter unit120in a top-down view. The wall member130may be formed of a photoimageable film, but is not limited thereto. For example, the wall member130may be formed of a liquid resin or a film resin.

The wall member130may have a shape having the internal space S and may have a strip-like shape having an open upper portion in a top-down view.

As illustrated inFIG. 5, a metal sheet10may be bonded to the wall member130using a hot press forming apparatus, a wafer bonder, a vacuum laminator, or another appropriate method.

As illustrated inFIG. 6, the metal sheet10, bonded to the wall member130, is forms the first cap member142via a photolithography process and a wet etching process.

As illustrated inFIG. 7, the second cap member144is formed on the first cap member142. In this case, the second cap member144may be formed using, for example, electroless or electrolytic plating. The second cap member144may have a thickness the same as or thicker than that of the first cap member142. The second cap member144may be formed of the same metal material as the first cap member142but is not limited thereto. For example, the second cap member144may be formed of a material having a higher elastic modulus than that of the first cap member142.

Thus, as illustrated inFIG. 7, the cap member140may have a dome shape having an upwardly convex central portion.

A case in which the second cap member144is sequentially formed after the first cap member142is illustrated by way of example, but is not limited thereto. For example, the metal sheet10may be bonded to the wall member130using a hot press forming apparatus, a wafer bonder, a vacuum laminator, or other appropriate device, and the second cap member144may be formed on the metal sheet10using electroless plating or electrolytic plating. Thereafter, using, for example a photolithography process and a wet etching process, the metal sheet10may form the first cap member142.

As illustrated inFIG. 8, opening162is formed and the molding layer160is formed to embed the under-bump metal member150, the wall member130, and the cap member140therein. In this case, the under-bump metal member150is exposed externally through the opening162.

The molding layer160is formed to cover the internal space S formed by the wall member130and the cap member140. When the molding layer160is formed, uniform pressure is applied to the cap member140.

As described above, the cap member140may have an upwardly convex curvature shape. That is, due to pressure applied when the molding layer160is formed, a central portion of the cap member140is prevented from being deformed to be downwardly concave.

As illustrated inFIG. 9, the bump170may be connected to the under-bump metal member150and may be disposed as to allow one side of the bump170to protrude above the molding layer160.

The processes described above may be performed on the wafer-level package.

As described above, a central portion of the cap member140may have a dome shape, which is upwardly convex. Thus, due to pressure applied when the molding layer160is formed, the central portion of the cap member140may be prevented from being deformed to be downwardly concave.

Further, due to the first cap member142and the second cap member144being formed of metal materials, an increase in a thickness, caused by the cap member140, may be prevented.

In addition, as the cap member140is formed in a simple process, the cap member140may be prevented from being deformed during the manufacturing process, and the manufacturing process may be less complicated.

Hereinafter, an acoustic wave filter device according to an exemplary embodiment will be described with reference to the accompanying drawings. However, the same reference numerals are used for the same components as those described above, and the detailed description thereof will be omitted.

FIG. 10is a schematic cross-sectional view illustrating an acoustic wave filter device according to an exemplary embodiment.

Referring toFIG. 10, an acoustic wave filter device200may include, for example, a substrate110, a filter unit220, a wall member130, a cap member140, an under-bump metal member150, a molding layer160, and a bump170.

Certain elements shown inFIG. 10, with the exception the filter unit220, may correspond to the elements described above regardingFIG. 1, such that a detailed description thereof will be omitted hereinafter.

The filter unit220may include, for example, a lower electrode222formed on a cavity C, a piezoelectric layer224formed to cover at least a portion of the lower electrode222, and an upper electrode226formed to cover at least a portion of the piezoelectric layer224.

The lower electrode222and the upper electrode226may be electrically connected to the metal layer112formed on the substrate110.

As set forth above, according to exemplary embodiments, narrowing of an internal space in which a filter unit is disposed due to deformation of a cap member may be reduced.