JP2007150824A - Surface acoustic wave element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface acoustic wave element in which an interdigital electrode and the propagation region of surface acoustic waves are surely protected, and its manufacturing method. <P>SOLUTION: The surface acoustic wave element is provided, on a piezoelectric substrate 10, with the lid body of a double structure composed of a first lid body part 14 in a bridge shape forming a space wherein the interdigital electrode and the propagation region 12 of the surface acoustic waves are housed and striding so as to cover the comb-line electrode and the propagation region 12 of the surface acoustic waves and a second lid body part 16 for covering the first lid body part 14 and sealing the space wherein the interdigital electrode and the propagation region 12 of the surface acoustic waves are housed. By the lid body, the interdigital electrode and the propagation region 12 of the surface acoustic waves are sealed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface acoustic wave element used for a surface acoustic wave device such as a filter mounted on a mobile communication device, for example, and a manufacturing method thereof.

  In general, a surface acoustic wave device represented by a surface acoustic wave filter mounted on a mobile communication device such as a mobile phone uses a surface acoustic wave that propagates on the surface of a piezoelectric substrate. The comb electrode and the surface acoustic wave propagation region are protected so that moisture and dust do not adhere to the region and the comb electrode that excites the surface acoustic wave.

  In the following Patent Document 1, a surface acoustic wave element is mounted face-down on a mounting board with metal bumps, and the entire surface acoustic wave element mounted in this manner is covered with a resin film. A surface acoustic wave device in which a film is brought into close contact is described. In this surface acoustic wave device, the space between the mounting substrate and the surface acoustic wave element (that is, the space where the comb-shaped electrode and the surface acoustic wave propagation region exist) is sealed with a resin film, so that the comb shape The electrode and the surface acoustic wave propagation region are protected.

  In the following Patent Document 2, a surface acoustic wave element having a functional portion (a surface portion on which a surface acoustic wave propagates such as a comb electrode portion) including at least one comb electrode portion on a piezoelectric substrate is provided around the functional portion. A protective member (such as a side wall surrounding the functional part) is formed, a protective film is adhered to the piezoelectric substrate so as to cover the functional part and the protective member, and then the surface acoustic wave element is combed. A surface acoustic wave device is described in which a surface having a mold electrode portion is opposed to and bonded to a mounting substrate via a bump. In this surface acoustic wave device, a functional film (corresponding to a comb electrode and a surface acoustic wave propagation region) is sealed by adhering a protective film to the piezoelectric substrate so as to cover the functional portion and the protective member. The comb electrode and the surface acoustic wave propagation region are protected.

JP 2005-184309 A Japanese Patent Laid-Open No. 2004-153212

  In each of the above conventional techniques, the mounting substrate and the surface acoustic wave element are combined (mounted), and the comb-shaped electrode and the surface acoustic wave propagation region are reliably protected (packaging). Yes. In the surface acoustic wave device described in Patent Document 1, the entire surface acoustic wave element mounted face-down on the mounting substrate is covered with a resin film, and the mounting surface of the mounting substrate and the resin film are brought into close contact with each other. The space between the surface acoustic wave element (that is, the space where the comb-shaped electrode and the surface acoustic wave propagation region exist) is sealed with a resin film to protect the comb electrode and the surface acoustic wave propagation region. .

  Further, in the surface acoustic wave device described in Patent Document 2, a protective film is adhered to the piezoelectric substrate so as to cover the functional part (comb-shaped electrode and surface acoustic wave propagation region) and the protective member, thereby sealing the functional part. By stopping, the functional portion (comb electrode and surface acoustic wave propagation region) is protected. At this time, simply covering the protective member (such as the side wall surrounding the functional part) with a protective film will cause the protective film to bend, and depending on the orientation of the surface acoustic wave element, the bent protective film will function. There is a risk of touching the part. Therefore, in the surface acoustic wave device described in Patent Document 2, the surface acoustic wave element is bumped with the mounting substrate positioned below the surface acoustic wave element facing the surface having the comb-shaped electrode portion. Thus, the problem due to the bending of the protective film is eliminated, and the functional portions (comb-shaped electrodes and surface acoustic wave propagation regions) are protected by the protective film.

  As described above, in the past, as a surface acoustic wave device in a state where the mounting substrate and the surface acoustic wave element are combined (mounted), reliable protection of the propagation area of the comb-shaped electrode and the surface acoustic wave (packaging) ) Is realized. Here, if reliable protection (packaging) of the comb-shaped electrode and the propagation region of the surface acoustic wave can be realized only on the surface acoustic wave element side, it becomes possible to supply the bare chip of the surface acoustic wave element to the mounting substrate. Since the advantageous effects such as simplification of the mounting process can be obtained, the comb-shaped electrode and the surface acoustic wave propagation region can be reliably protected (packaging) only on the surface acoustic wave element side. It is very preferable.

  Accordingly, an object of the present invention is to provide a surface acoustic wave element in which a comb electrode and a surface acoustic wave propagation region are reliably protected (packaged) and a method for manufacturing the same, in view of the above-described problems of the prior art.

  In order to achieve the above object, a surface acoustic wave device according to the present invention includes a piezoelectric substrate, a comb electrode formed on the piezoelectric substrate, and a surface acoustic wave propagation region propagating from the comb electrode to the surface of the piezoelectric substrate and the vicinity of the surface. And a bridge-shaped first lid that covers the comb-shaped electrode and the surface acoustic wave propagation region so as to cover the comb-shaped electrode and the surface acoustic wave propagation region. A double-structure lid body comprising a body portion and a second lid body covering the first lid body and sealing a space in which the comb-shaped electrode and the surface acoustic wave propagation region are accommodated is The comb-shaped electrode and the surface acoustic wave propagation region are sealed with the lid provided on the substrate.

  Here, in the surface acoustic wave device having the above configuration, an electrode pad disposed outside the lid body and an electrode pattern connecting the electrode pad and the comb-shaped electrode are formed on the piezoelectric substrate, and the electrode pad is further formed. Bumps may be formed on the top.

  The surface acoustic wave element manufacturing method of the present invention includes a plurality of surface acoustic wave elements each having a comb-shaped electrode and a surface acoustic wave propagation region propagating from the comb-shaped electrode to the surface of the piezoelectric substrate and the vicinity of the surface. The piezoelectric substrate is formed with a space in which the comb-shaped electrode and the surface acoustic wave propagation region are accommodated, and the bridge-shaped first lid that covers the comb-shaped electrode and the surface acoustic wave propagation region is provided with each elastic. First lid body forming step for forming each surface acoustic wave element individually, and covering the bridge-shaped first lid part formed on each surface acoustic wave element, and comb electrodes and elastic surfaces in each surface acoustic wave element And a second lid portion forming step for individually forming a second lid portion for individually sealing the space in which the wave propagation region is accommodated for each surface acoustic wave element.

  Here, in the method of manufacturing the surface acoustic wave device having the above-described configuration, the first lid body forming step includes a sacrificial layer so as to cover the comb-shaped electrode and the surface acoustic wave propagation region in each surface acoustic wave device. A step of individually forming each surface acoustic wave element, a step of applying and curing a resin so as to straddle over each sacrificial layer, and a step of removing each sacrificial layer by sacrificial layer etching, By removing each sacrificial layer, a comb-shaped electrode and a surface acoustic wave propagation region are formed, and a bridge-shaped first lid portion straddling the comb-shaped electrode and the surface acoustic wave propagation region is formed. It is preferable to form each surface acoustic wave element individually.

  In the method of manufacturing the surface acoustic wave element having the above-described structure, a photosensitive resin is used as a resin for forming the first lid portion, and a sacrificial layer withstands the curing temperature of the photosensitive resin. It is preferable that the sacrificial layer be removed by performing a sacrificial layer etching using an organic solvent using a resist having heat resistance to be obtained and removable by an organic solvent.

  According to the surface acoustic wave element of the present invention, reliable protection (packaging) of the comb electrode and the surface acoustic wave propagation region can be realized only on the surface acoustic wave element side. Therefore, it becomes possible to supply the bare chip of the surface acoustic wave element, and it is possible to obtain an advantageous effect that the mounting process on the mounting substrate is simplified or the surface acoustic wave element is easily handled. Become.

  The surface acoustic wave element according to the embodiment of the present invention has a configuration in which the comb-shaped electrode on the piezoelectric substrate 10 and the surface acoustic wave propagation region 12 are sealed with a lid. Regardless of the relationship, the comb-shaped electrode and the surface acoustic wave propagation region 12 are reliably protected (packaged) on the surface acoustic wave element side. For example, as shown in FIG. 5, in a state where a space for accommodating the comb-shaped electrode and the surface acoustic wave propagation region 12 is formed, a bridge-shaped lid portion (first step) straddling the comb-shaped electrode and the surface acoustic wave propagation region 12 One lid portion 14 is further covered with a second lid portion 16 from the outside, thereby sealing the space in which the comb-shaped electrode and the surface acoustic wave propagation region 12 are accommodated, and the bridge-like lid portion 14. And a lid having a double structure of the second lid 16, and the double-structured lid securely protects the comb-shaped electrode and the surface acoustic wave propagation region 12 in the surface acoustic wave element. ing.

  The surface acoustic wave element according to this embodiment is manufactured as follows. First, as shown in FIG. 1, a plurality of surface acoustic wave elements are formed on the piezoelectric substrate 10. Each surface acoustic wave element is formed with a comb-shaped electrode and a surface acoustic wave propagation region 12, and an electrode pattern 20 and an electrode pad 30 drawn from the comb-shaped electrode. In FIG. 1, for convenience of explanation, two sets of surface acoustic wave elements formed on the piezoelectric substrate 10 are shown as an example. In this embodiment, for each of the surface acoustic wave elements formed on the piezoelectric substrate 10, a lid for sealing each comb-shaped electrode and the surface acoustic wave propagation region 12 is produced.

  In the lid manufacturing process, first, the sacrificial layer 40 is formed on the comb-shaped electrode on the piezoelectric substrate 10 and the surface acoustic wave propagation region 12 (see FIG. 2). The sacrificial layer 40 is formed by applying a sacrificial layer to the entire piezoelectric substrate 10 and then applying a known photolithography technique to remove the extra sacrificial layer, and comb electrodes in each surface acoustic wave element. The sacrificial layer 40 may be formed as shown in FIG. 2 so as to cover the surface acoustic wave propagation region 12. Here, the height H1 of the formed sacrificial layer 40 is about 1 to 10 μm.

  Next, for example, using a resin, the resin is applied with a dispenser or the like so as to straddle the sacrificial layer 40, and the resin is cured (see FIG. 3). This cured resin becomes the later bridge-shaped lid (first lid) 14. Also in this resin application and curing process, after applying the resin to the entire piezoelectric substrate 10, by applying a known photolithography technique such as exposure, baking, development, resist removal, etc., the excess resin is removed, As shown in FIG. 3, the resin bodies may be cured after the resin bodies are individually straddled over the sacrificial layers 40. Here, the height H2 of the formed resin body (that is, the height H2 of the bridge-shaped lid body portion 14) is about 5 to 100 μm.

  And after the resin body which straddles each sacrificial layer 40 is formed in this way, sacrificial layer etching is performed. As a result, only the sacrificial layer 40 is removed, so that a space for accommodating the comb-shaped electrode and the surface acoustic wave propagation region 12 is formed and straddled so as to cover the comb-shaped electrode and the surface acoustic wave propagation region 12. A resin body, that is, a bridge-shaped first lid portion 14 is formed on the piezoelectric substrate 10 (see FIG. 4). Since the first lid 14 has a bridge-like structure, the etching solution used for removing the sacrificial layer 40 can easily escape from the inside of the first lid 14 to the outside, and the etching process is good. It can be done efficiently and efficiently.

  In the present embodiment, a photosensitive resin (for example, a chemically amplified resist or a permanent resist) is used as the resin for forming the bridge-shaped first lid 14, and the sacrificial layer 40 is chemically amplified. A resist having heat resistance that can withstand the curing temperature of the mold resist or permanent resist and removable by an organic solvent is used. In particular, the reason why the resist that can be removed by the organic solvent is used as the sacrificial layer 40 is as follows. In an acoustic wave device, it is common to use an electrode made of aluminum. However, if the etching solution is made acidic or alkaline, it reacts with the aluminum electrode during the sacrificial layer etching. The frequency characteristics of this will change. Therefore, in order to avoid a reaction between the etchant and the electrode, it is preferable to use a resist that can be removed by an organic solvent for the sacrificial layer 40 and perform the etching using the organic solvent.

  In addition, a chemically amplified resist or permanent resist having a high curing temperature (for example, 150 ° C.) is used as a material for the bridge-shaped first lid portion 14 and has heat resistance that can withstand this high curing temperature. The use of a resist that can be removed by an organic solvent as the sacrificial layer 40 has the following advantages. Since a normal resist needs to be used at 95 ° C. or lower, when such a resist is used as the sacrificial layer 40, a temperature of 95 ° C. or higher is applied when the bridge-shaped lid portion 14 is formed. The resin cannot be cured, and if a higher temperature is applied, the resist will adhere to the electrode fingers of the comb electrode, and the resist removal residue will remain after the sacrificial layer removal treatment. There is a concern that However, a chemically amplified resist or permanent resist having a high curing temperature (for example, 150 ° C.) is used as a material for the bridge-shaped lid body portion 14 and has heat resistance that can withstand this high curing temperature, and depending on the organic solvent. If a removable resist is used as the sacrificial layer 40, exposure, baking, and development are performed after the formation of the sacrificial layer 40, followed by curing by hard baking at 150 ° C. Even when the body part 14 is formed, the sacrificial layer 40 has heat resistance that can withstand a high curing temperature, and thus the problem that occurs in the case of a normal resist is solved. Therefore, according to the material used in the present embodiment, the sacrificial layer 40 can be reliably removed, and the bridge-shaped first lid portion 14 can be reliably cured. A space for accommodating the comb-shaped electrode and the surface acoustic wave propagation region 12 (that is, a space having a height H1 of about 1 to 10 μm) is formed and straddles the comb-shaped electrode and the surface acoustic wave propagation region 12. The bridge-shaped first lid portion 14 can be favorably formed on the piezoelectric substrate 10.

  And after forming the bridge-shaped first lid portion 14 as shown in FIG. 4, a resin is applied with a dispenser or the like so as to cover the entire lid portion 14, and the resin is cured, A second lid portion 16 that further covers the entire first lid portion 14 is formed (see FIG. 5). Thus, the second lid portion 16 closes the opening of the bridge-shaped first lid portion 14, and the comb-shaped electrode formed between the bridge-shaped first lid portion 14 and the piezoelectric substrate 10 and The accommodation space of the surface acoustic wave propagation region 12 is sealed. In this process, too, the resin is applied to the entire piezoelectric substrate 10, and then a known photolithography technique such as exposure, baking, development, and resist removal is applied to remove excess resin, and the first lid What is necessary is just to form the 2nd cover body part 16 which further covers the whole body part 14 with respect to each of the 1st cover body part 14. FIG.

  As described above, in the present embodiment, in the plurality of surface acoustic wave elements formed on the piezoelectric substrate 10, the double structure of the bridge-shaped first lid portion 14 and the second lid portion 16. A lid made of is produced for each surface acoustic wave element. Such a lid reliably protects the comb-shaped electrode and the surface acoustic wave propagation region 12 in each surface acoustic wave element.

  Then, in the piezoelectric substrate 10 on which a plurality of surface acoustic wave elements are formed, after the above-described lid is formed on each surface acoustic wave element, by cutting out individual surface acoustic wave elements from the piezoelectric substrate 10, A surface acoustic wave element in which the comb electrode and the surface acoustic wave propagation region 12 are reliably protected by the lid is manufactured.

  Here, the lid formed in each surface acoustic wave element is composed of a comb-shaped electrode and a surface acoustic wave propagation region 12 by a resin-made bridge-shaped first lid portion 14 and second lid portion 16. It has not only good sealing performance but also sufficient durability against external forces. Therefore, there is an advantage that the surface acoustic wave element after the lid is manufactured can be easily handled.

  In addition, before cutting out each surface acoustic wave element from the piezoelectric substrate 10 on which a plurality of surface acoustic wave elements are formed, a bump base metal (UBM) 50 and a bump 60 are formed on the electrode pad 30 in each surface acoustic wave element. A plurality of surface acoustic wave elements having a configuration as shown in FIG. 6 can be manufactured by forming and then cutting out individual surface acoustic wave elements from the piezoelectric substrate 10, whereby the comb-shaped electrode and the surface acoustic wave propagation region 12 are formed. It is possible to supply a bare chip of a surface acoustic wave element that is reliably protected by a lid. In this case, the step of forming the bump base metal (UBM) 50 and the bump 60 may be performed for each cut out surface acoustic wave element after the surface acoustic wave element is cut out.

It is a figure which shows an example of a structure of the several surface acoustic wave element formed on a piezoelectric substrate. FIGS. 2A and 2B are diagrams illustrating a process of manufacturing a cover for a surface acoustic wave element according to an embodiment of the present invention. FIG. 2A is a cross-sectional view illustrating a state where a sacrificial layer is formed on a substrate, and FIG. It is a top view. FIGS. 3A and 3B are views showing a process of manufacturing a surface acoustic wave element lid according to an embodiment of the present invention, FIG. 3A is a cross-sectional view showing a state where a resin is applied on a sacrificial layer, and FIG. It is a top view. It is a figure which shows the process of producing the cover body of the surface acoustic wave element in embodiment of this invention, and is sectional drawing which shows the state which removed the sacrificial layer. It is a figure which shows the structure of the surface acoustic wave element in this embodiment. It is a figure which shows the state which attached the bump to the surface acoustic wave element of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Piezoelectric substrate, 12 Comb-shaped electrode and surface acoustic wave propagation region, 14 Bridge-shaped lid (first lid), 16 Second lid, 20 Electrode pattern, 30 Electrode pad, 40 Sacrificial Layer, 50 bump base metal, 60 bump.

Claims (6)

In a surface acoustic wave device having a piezoelectric substrate, a comb electrode formed on the piezoelectric substrate, and a surface acoustic wave propagation region propagating from the comb electrode to the surface of the piezoelectric substrate and the vicinity of the surface,
A bridge-shaped first lid portion that forms a space in which the comb-shaped electrode and the surface acoustic wave propagation region are accommodated and covers the comb-shaped electrode and the surface acoustic wave propagation region, and the first lid body Having a double-structured lid body on the piezoelectric substrate, the second lid body section covering the portion and sealing the space in which the comb-shaped electrode and the surface acoustic wave propagation region are accommodated,
A surface acoustic wave element in which a comb electrode and a surface acoustic wave propagation region are sealed by the lid. The surface acoustic wave device according to claim 1,
An electrode pad arranged outside the lid, an electrode pattern connecting the electrode pad and the comb-shaped electrode are formed on the piezoelectric substrate, and a bump is formed on the electrode pad. A surface acoustic wave device.   A surface acoustic wave device formed by mounting the surface acoustic wave element according to claim 2 on a mounting surface of a mounting substrate via a bump. For a piezoelectric substrate on which a plurality of surface acoustic wave elements having a comb-shaped electrode and a surface acoustic wave propagation region propagating from the comb-shaped electrode to the surface of the piezoelectric substrate and the vicinity of the surface are formed,
For each surface acoustic wave element, a bridge-shaped first lid that forms a space in which the comb electrode and the surface acoustic wave propagation region are accommodated and covers the comb electrode and the surface acoustic wave propagation region. A first lid part forming step to be formed individually;
A second lid that covers the bridge-shaped first lid portion formed in each surface acoustic wave element and individually seals the space in which the comb-shaped electrode and the surface acoustic wave propagation region are accommodated in each surface acoustic wave element. A second lid part forming step for individually forming the body part for each surface acoustic wave element;
A method for producing a surface acoustic wave device, comprising: In the manufacturing method of the surface acoustic wave device according to claim 4,
The first lid part forming step
Forming a sacrificial layer individually for each surface acoustic wave element so as to cover the comb-shaped electrode and the surface acoustic wave propagation region in each surface acoustic wave element;
Applying and curing a resin so as to straddle over each sacrificial layer;
Removing each sacrificial layer by sacrificial layer etching;
Have
By removing each sacrificial layer, a comb-shaped electrode and a surface acoustic wave propagation region are formed, and a bridge-shaped first lid portion straddling the comb-shaped electrode and the surface acoustic wave propagation region is formed. Formed individually for each surface acoustic wave element,
A method of manufacturing a surface acoustic wave device. In the manufacturing method of the surface acoustic wave device according to claim 5,
For the resin for forming the first lid body, a photosensitive resin is used,
For the sacrificial layer, a resist having heat resistance that can withstand the curing temperature of the photosensitive resin and removable by an organic solvent is used.
Removing the sacrificial layer by performing sacrificial layer etching using an organic solvent;
A method of manufacturing a surface acoustic wave device.

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