JP2003037473A - Surface acoustic wave device, and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface acoustic wave device, which enables high-density mounting by scaling down the package size, and to obtain high reliability of bump junctions. SOLUTION: This surface acoustic wave device has at least a piezoelectric substrate, a comb-toothed electrode which is made on one main surface of the piezoelectric substrate, a coating material layer which is arranged in a region where the comb-toothed electrode is not made out of one main surface of the piezoelectric substrate; a laminate film which is arranged on the coating material layer and is arranged at a specified interval above the comb-toothed electrode; a rear electrode which is arranged on the laminate film; and a bump, which connects the rear electrode with one main surface of the piezoelectric substrate, piercing the laminate film and the coating material layer. Specified space is formed above the comb-toothed electrode by the coating material layer and the laminate film, and also the comb-toothed electrode is sealed airtightly. The bump and the rear electrode are directly connected with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave device and a method for manufacturing the same, and more particularly to a surface acoustic wave device that is face-down bonded via bumps and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, many surface acoustic wave devices have been used as elements such as filters, delay lines, and oscillators of electronic devices that use radio waves. In addition, electronic devices used in the field of mobile communication and the like are required to be reduced in size and have high reliability, and due to this reduction, miniaturization of surface acoustic wave devices is also required.

The surface acoustic wave element applies an electric signal to an input interdigital transducer of a comb-shaped electrode formed on a piezoelectric substrate, converts it into a surface acoustic wave, and transmits it on the piezoelectric substrate. Then, the surface acoustic wave reaching the output interdigital transducer of the other comb-teeth electrode is converted into an electric signal again and taken out to the outside.

The conventional surface acoustic wave device has an FDB (face down bonding) structure. Bumps are formed on the surface acoustic wave element using a bump bonding apparatus. Then, the surface acoustic wave element is bonded to a conventional ceramic base substrate using a flip chip bonder device. After that, the cap is bonded to the ceramic base substrate to seal the surface acoustic wave element. The surface elastic breaking device configured as described above is inexpensive and rich in mass production, but there is a limit to size reduction in the direction horizontal to the element surface in order to secure a region for bonding the cap.

This problem is solved by using a thermosetting resin instead of the cap to seal the element. As shown in FIGS. 3A and 3B, the surface acoustic wave element 51 is bonded to the surface of the flat ceramic base substrate 54 by the above method using the bump 55. Then, the surface of the base substrate 54 including the surface acoustic wave element 51 is covered with a fluid resin material 52, and the resin material 52 is thermally cured. The horizontal size is reduced by not using the cap. At the same time, since there is no cap, size reduction in the direction perpendicular to the surface of the element 51 is also realized.

[0006]

However, the conventional package structure using the cap or the thermosetting resin is based on the use of the ceramic base substrate 54. The ceramic base substrate 54 has a technical problem in terms of strength, and there is a limit to its thickness reduction.

Further, since the ceramic base 54 has almost no flexibility, the bump 5 can be used in the bump forming process and the FDB process of the element 51 through the bump.
There was a problem that 5 was easy to come off due to stress or the like.

Further, in recent years, the miniaturization of portable information equipment requires a reduction in the direction perpendicular to the surface of the element 51 (height direction), that is, so-called "reduction of the surface acoustic wave device", and the thickness can be reduced. In addition, there is a demand for a new material that replaces conventional ceramics and that has less problems in terms of material strength.

The present invention has been made in order to solve the problems of the prior art, and its purpose is to reduce the package size, obtain high bonding reliability of bumps, and realize high-density mounting. It is an object of the present invention to provide a surface acoustic wave device and a method for manufacturing the same.

[0010]

In order to achieve the above object, the first feature of the present invention is to provide a piezoelectric substrate, comb-teeth electrodes formed on one main surface of the piezoelectric substrate, and one main surface of the piezoelectric substrate. Among them, a coating material layer arranged in a region where the comb-teeth electrode is not formed, and a laminate film arranged on the coating material layer and arranged at a predetermined interval above the comb-teeth electrode, A back electrode arranged on the laminate film,
The surface acoustic wave device has at least a bump that penetrates the laminate film and the coating material layer and connects the back electrode and the one main surface of the piezoelectric substrate.

According to the first aspect of the present invention, the coating material layer and the laminate film form a predetermined space above the comb-teeth electrode and hermetically seal the comb-teeth electrode. In addition, since the bump and the back surface electrode are directly connected to each other, the conventional ceramic base substrate is not required, and “the height of the surface acoustic wave device can be reduced”.

A second feature of the present invention is (1) a step of forming comb-teeth electrodes on one main surface of the piezoelectric substrate, and (2) formation of comb-teeth electrodes on one main surface of the piezoelectric substrate. The step of selectively forming a coating material layer in the area excluding the area and the area where the bumps are formed; and (3) adhering the laminate film to the coating material layer with an adhesive at the same time as forming the comb-teeth electrode. A step of arranging a laminate film at a predetermined interval above, (4) a step of forming bumps on one main surface of the piezoelectric substrate exposed in a region where bumps are formed, and (5) a laminate film. And a step of forming a back electrode connected to the bump on the surface of the surface acoustic wave device.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and width of layers, the ratio of the thickness of each layer, and the like are different from actual ones. Further, it is needless to say that the drawings include parts in which dimensional relationships and ratios are different from each other.

(First Embodiment) FIG. 1A is a sectional view showing a surface acoustic wave device according to a first embodiment of the present invention. As shown in FIG. 1A, the surface acoustic wave device includes a piezoelectric substrate 1, comb-teeth electrodes 2 formed on one main surface of the piezoelectric substrate 1, and comb-teeth on one main surface of the piezoelectric substrate 1. A coating material layer (solder) arranged in a region where the electrode 2 is not formed.
Resist layer 4; a laminate film 5 arranged on the coating material layer 4 and above the comb-teeth electrode 2 at a predetermined distance; and a back electrode 7 arranged on the laminate film 5. And the bumps 3 arranged so as to penetrate the laminate film 5 and the coating material layer 4. The bump 3 connects between the back electrode 7 and one main surface of the piezoelectric substrate 1.

As the piezoelectric substrate 1, lithium tantalate (LiTaO ₃ ) and lithium niobate (LiNb) are used.
A single crystal substrate made of O ₃ ), a lithium barium oxide substrate (LiB ₄ O ₇ ), sapphire, quartz (SiO ₂ ), or the like can be used. Alternatively, instead of these single crystal substrates, lead titanate (PbTiO ₃ ), lead zirconate titanate (PbZrTiO ₃ (PZT)),
Alternatively, it is also possible to use a piezoelectric ceramic substrate made of these solid solutions.

Although not shown in the drawings, the comb-teeth electrode 2 is a metal electrode having two or more comb-teeth-like planar shapes that mesh with each other. The surface acoustic wave (SAW) is excited and detected by the comb-teeth electrode 2. An electric signal is applied to the input interdigital transducer of the comb-teeth electrode 2, which is converted into a surface acoustic wave and transmitted on the piezoelectric substrate 1. Further, the surface acoustic wave reaching the output interdigital transducer of the other comb-teeth electrode 2 is converted into an electric signal again and can be taken out to the outside. The metal used as the material of the comb-teeth electrode 2 is Al (aluminum) or an alloy containing Al as a main component. In the latter case, copper (C
u), silicon (Si), etc. can be used.

The solder resist layer 4 is used as the coating material layer. The solder resist layer 4 is not arranged in the region where the comb-teeth electrode 2 is formed. Further, the solder-resist layer 4 has a sufficient thickness to form a predetermined space 9 on the comb-teeth electrode 2. The predetermined space 9 above the comb-teeth electrode 2 is necessary for the surface acoustic waves to be stably excited and detected in the comb-teeth electrode 2.

The laminated film 5 is made of epoxy resin 6
It is adhered to the solder resist layer 4 via an adhesive such as. At the same time, the laminate film 5 is arranged above the comb-teeth electrode 2 via a predetermined space 9. That is, the comb-teeth electrode 2 is hermetically sealed by the solder resist layer 4 and the laminate film 5.

The bump 3 is arranged outside the comb-teeth electrode 2 and connects the comb-teeth electrode 2 and the back surface electrode 7. Although not shown, the bump 3 is connected to an electrode pad or the like formed on one main surface of the piezoelectric substrate 1, and the electrode pad is
The comb-teeth electrode 2 and the comb-teeth electrode 2 are connected to the comb-teeth electrode 2 by metal wiring or the like formed on the piezoelectric substrate 1.

FIG. 1 (b) is a transparent perspective view of the surface acoustic wave device shown in FIG. 1 (a). FIG. 1A shows a state where the solder resist layer 4, the laminate film 5, and the back surface electrode 7 are sequentially arranged on the piezoelectric substrate 1. On the other hand, FIG. 1B shows a state in which the solder resist 4 and the piezoelectric substrate 1 are sequentially arranged on the laminate film 5 by arranging them upside down. Also,
The back electrode 7 is omitted, and in order to show the structure of the interface between the solder resist layer 4 and one main surface of the piezoelectric substrate 1, the piezoelectric substrate 1 and the comb-teeth electrode 2 are shown in a transparent state.

As shown in FIG. 1B, a hole for forming a space 9 around the comb-teeth electrode 2 is formed in the center of the solder resist layer 4 facing one main surface of the piezoelectric substrate 1. ing. A laminate film 5 is arranged on the bottom surface of this hole with an epoxy resin 6 interposed therebetween. A total of 6 bumps 3 are arranged around the hole for forming the space 9. Through these bumps 3, an input signal, an output signal,
Alternatively, the ground potential is supplied from the back surface electrode 7 to the surface acoustic wave element. Each of these bumps 3 is connected to the back surface electrode 7, and signals can be input and output from the outside of the device. Further, with respect to the surface acoustic wave element (chip), the solder resist 4, the epoxy resin 6, and the laminate film 5 have the same planar shape.

2A to 2D are schematic diagrams of FIG.
FIG. 6 is a process cross-sectional view showing the method of manufacturing the surface acoustic wave device shown in FIGS.

(A) First, as shown in FIG. 2 (a), the comb-teeth electrode 2, the electrode pad, the wiring connecting the comb-teeth electrode 2 and the electrode pad, etc. are provided on one main surface of the piezoelectric substrate 1. A surface acoustic wave element is manufactured by forming a metal pattern containing the element. Specifically, a metal film (Al film) having a film thickness of about several hundreds nm is formed on the piezoelectric substrate 1 by using a magnetron type sputtering device. A resist film is formed on this metal film, and the resist film is exposed and developed by photolithography. Then, using this resist film as a mask, the metal film is selectively etched by a reactive ion etching (RIE) method to form a metal pattern.

(B) Next, as shown in FIG. 2 (b), in one main surface of the piezoelectric substrate 1, a region except the region where the comb-teeth electrode 2 is formed and the region where the bump 3 is formed is excluded. A coating material layer (solder resist layer) 4 is selectively formed. Specifically, the metal mask 8 is selectively formed in the region where the comb-teeth electrode 2 is formed and the region where the bump 3 is formed. And
The solder resist layer 4 is selectively formed on a region of the main surface of the piezoelectric substrate 1 where the metal mask 8 is not formed. After that, the metal mask 8 is selectively removed.

(C) Next, as shown in FIG. 2 (c), the laminate film 5 is adhered onto the solder resist layer 4 using an adhesive (epoxy resin) 6 and, at the same time, above the comb-teeth electrode 2. Laminate film 5 is arranged at a predetermined interval. Specifically, holes are formed in advance in the portions where the bumps 3 are formed in the laminated film 5 made of an extremely thin sheet. And the laminated film 5
Epoxy resin 6 is applied to the bonding surface of and is bonded to the solder resist layer 4. As a result, the laminated film 5 is adhered to the solder resist layer 4, and the laminated film 5
Does not contact the comb-teeth electrode 2, and a predetermined space 9 is formed therebetween. Further, one main surface (electrode pad) of the piezoelectric substrate 1 is exposed from the hole formed in the portion where the bump 3 is formed.

(D) Next, as shown in FIG. 2D, the bump 3 is formed on one main surface of the piezoelectric substrate 1 exposed in the region where the bump 3 is formed. Specifically, a plating method is used to deposit copper (Cu) on the laminate film 5 and at the same time, to fill the holes for forming the bumps 3. Then, a flattening process such as lapping is performed to selectively remove the copper plating deposited on the laminate film 5 while leaving the copper plating buried in the holes for forming the bumps 3.

(E) Finally, the back surface electrode 7 connected to the bump 3 is formed on the laminate film 5. Specifically, copper is deposited on the laminate film 5 by using a plating method. Gold (Au) is plated on the copper plating. Simultaneously patterning copper plating and gold plating,
The back electrode 7 having a predetermined shape is formed. At this time, by the solder resist layer 4 and the laminate film 5,
Since the space 9 is formed above the comb-teeth electrode 2, the comb-teeth electrode 2 is protected and the characteristics of the surface acoustic wave device are not impaired.

As described above, according to the first embodiment of the present invention, the solder resist layer 4 and the laminate film 5 formed on the piezoelectric substrate 1 form a predetermined pattern on the comb-teeth electrode 2. Since the space 9 is formed, the characteristics of the surface acoustic wave device are not impaired. Moreover, since the comb-teeth electrode 2 is hermetically sealed by the solder resist layer 4 and the laminate film 5, the comb-teeth electrode 2 can be protected from the external environment.

Further, since the bumps 3 and the back surface electrodes 7 can be directly connected without using the conventional ceramic base substrate, stress applied to the bumps 3 in the bump 3 manufacturing process and the flip chip bonding process is reduced. It can be eliminated and the bonding reliability of the bump 3 can be improved. Further, by eliminating the need for a ceramic base substrate, it becomes possible to reduce the vertical direction (height direction) to the surface of the element 51, that is, to reduce the height of the surface acoustic wave device, thus reducing the package size. You can

(Other Embodiments) As described above, the present invention has been described according to the first embodiment, but it is assumed that the discussion and drawings forming a part of this disclosure limit the present invention. Should not be understood. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

The first embodiment shows the case where the solder resist layer 4 is used as the coating material layer. The present invention is not limited to this, and a polymer material, an epoxy resin, or the like can be used as the coating material layer.

Although the case where a copper plating material is used as the electrode material used for the back surface electrode 7 has been shown, the present invention is not limited to this. Instead of the copper plating material, other conductive materials such as gold, gold plating material, and copper can be used.

Further, the case where the bump 3 has a two-layer structure of copper plating and gold plating is shown, but the present invention is not limited to this, and gold, copper, solder balls, solder plating, gold bumps, aluminum, and conductivity are used. Other conductive materials such as paste can be used, and it is also possible to use a combination of a plurality of these conductive materials.

Further, although the surface acoustic wave device has been described as an example of the electronic component device, the present invention can be similarly applied to other electronic component devices using the bump bonding method.

As described above, it should be understood that the present invention includes various embodiments and the like not described here. Therefore, the present invention is limited only by the matters specifying the invention according to the scope of claims appropriate from this disclosure.

[0036]

As described above, according to the present invention,
It is possible to provide a surface acoustic wave device that can reduce the package size, obtain high bonding reliability of bumps, and enable high-density mounting, and a method for manufacturing the same.

[Brief description of drawings]

FIG. 1A is a sectional view showing a surface acoustic wave device according to a first embodiment of the present invention. Figure 1 (b) shows
FIG. 2 is a transparent perspective view of the surface acoustic wave device shown in FIG.

FIG. 2 is a schematic diagram of each of FIGS. 2 (a) to 2 (d).
FIG. 6 is a main step sectional view showing the method of manufacturing the surface acoustic wave device shown in FIGS.

FIG. 3A is a transparent perspective view of a surface acoustic wave device according to a conventional technique. FIG. 3B is a cross-sectional view of the surface acoustic wave device shown in FIG. 3A, taken along the line BB ′.

[Explanation of symbols]

1 Piezoelectric substrate 2 comb electrodes 3 bumps 4 Solder resist layer 5 Laminated film 6 Epoxy resin 7 Back electrode 8 metal mask 9 space

Claims (4)

[Claims] 1. A piezoelectric substrate, a comb-tooth electrode formed on one main surface of the piezoelectric substrate, and a piezoelectric substrate, which is arranged in a region of the one main surface of the piezoelectric substrate where the comb-tooth electrode is not formed. A coating material layer, a laminate film arranged on the coating material layer, and arranged at a predetermined interval above the comb-teeth electrode; a back electrode arranged on the laminate film; A surface acoustic wave device comprising at least a bump penetrating the laminate film and the coating material layer to connect the back surface electrode and the one main surface of the piezoelectric substrate. 2. The surface acoustic wave device according to claim 1, wherein the coating material layer is a solder resist layer. 3. A step of forming comb-teeth electrodes on one main surface of a piezoelectric substrate, and a region of the one main surface of the piezoelectric substrate where the comb-teeth electrodes are formed and a region where bumps are formed are excluded. In the area,
A step of selectively forming a coating material layer, and at the same time adhering a laminating film on the coating material layer with an adhesive, at the same time arranging the laminating film above the comb-teeth electrode at a predetermined interval. A step of forming the bump on the one main surface of the piezoelectric substrate exposed in a region where the bump is formed, and forming a back surface electrode connected to the bump on the laminate film. A method for manufacturing a surface acoustic wave device, comprising: 4. The step of forming the coating material layer includes the act of selectively forming a metal mask in a region where the comb-teeth electrode is formed and a region where the bump is formed; 4. The method of manufacturing a surface acoustic wave device according to claim 3, further comprising the act of selectively forming the coating material layer on a region of the surface where the metal mask is not formed.