JP2010220033A - Elastic wave device and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress abnormality in the shape of an opening of a resist. <P>SOLUTION: An elastic wave device includes: a piezoelectric substrate 10; an interdigital electrode 12 which is formed on the piezoelectric substrate 10; a metal pattern 20 which is formed on the piezoelectric substrate 10, and which is connected to the interdigital electrode 12; and a resist 40 which is formed on the piezoelectric substrate 10 and the metal pattern 20, and which has an opening 40. In the elastic wave device, the metal pattern 20 under the edge of the opening 40 includes: a first metal layer 16; and a second metal layer 18 being a top layer which is formed on the first metal layer 16, and whose light reflectance is smaller than that of the first metal layer 16. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an acoustic wave device and a manufacturing method thereof, and more particularly to an acoustic wave device including a resist having an opening on a metal pattern and a manufacturing method thereof.

  In an acoustic wave device mounted on a mobile phone terminal or the like, an acoustic wave element is provided on a piezoelectric substrate. The acoustic wave device has a functional region in which the acoustic wave of the acoustic wave element vibrates. The functional region is, for example, a comb electrode (IDT). Since the elastic wave vibrates in the functional area, it is a void above it.

  Recently, an acoustic wave device using a wafer level package technology has been proposed for downsizing the acoustic wave device. The functional region side of the piezoelectric substrate is sealed with a sealing portion in a state where a hollow is secured on the functional region of the piezoelectric substrate (comb-shaped electrode and the piezoelectric substrate in the vicinity thereof). The sealing portion is formed of a resist, for example. A metal pattern connected to the comb electrode is formed on the piezoelectric substrate. The metal pattern is, for example, a wiring pattern that connects a comb electrode and the outside.

  Patent Document 1 describes that a taper shape is formed on a resist on the surface of a piezoelectric substrate by forming a reflection control film on the back surface of the piezoelectric substrate.

JP 2004-120132 A

  When forming a resist having an opening on a metal pattern, a shape abnormality such as a resist residue or a resist defect may occur at the end of the opening. The present invention has been made in view of the above problems, and an object of the present invention is to suppress abnormal shapes of resist openings.

  The present invention includes a piezoelectric substrate, a comb-shaped electrode formed on the piezoelectric substrate, a metal pattern formed on the piezoelectric substrate and connected to the comb-shaped electrode, and formed on the piezoelectric substrate and the metal pattern. And a resist having an opening, and the metal pattern below the end of the opening is formed on the first metal layer and on the first metal layer and has a light reflectance that is smaller than that of the first metal layer. An elastic wave device comprising: an upper second metal layer. According to the present invention, since the light reflectance of the second metal layer, which is the uppermost layer of the metal pattern, is small, it is possible to suppress an abnormal shape of the opening of the resist that occurs when the opening is formed in the resist.

  The said structure WHEREIN: It can be set as the structure by which the said metal pattern is provided under a part of said opening part end. According to this configuration, the shape abnormality of the opening can be further suppressed.

  The said structure WHEREIN: The said 2nd metal layer can be set as the structure provided on all the said 1st metal layers located under the said opening part end. According to this configuration, the shape abnormality of the opening can be further suppressed.

  The said structure WHEREIN: The protective layer formed so that the said opening part might be covered on the said resist was comprised, and the said opening part can be set as the structure which forms the hollow formed on the said comb-shaped electrode.

  The said structure WHEREIN: The penetration electrode which penetrates the said resist is comprised, The said metal pattern can be set as the structure which connects the said comb-shaped electrode and the said penetration electrode.

  The said structure WHEREIN: The said light reflectance can be set as the structure which is a reflectance of the pattern light used when exposing the said resist.

  The said structure WHEREIN: The said 1st metal layer can be set as the structure which is Au. Moreover, the said structure WHEREIN: The said 2nd metal layer can be set as the structure which is Ti.

  The present invention includes a step of forming a comb-shaped electrode on a piezoelectric substrate, a step of forming a metal pattern connected to the comb-shaped electrode, and developing by irradiating pattern light on the piezoelectric substrate and the metal pattern. Forming a resist having an opening by the step of forming a first metal layer as the metal pattern to be under the end of the opening, and the step of forming the metal pattern, Forming an uppermost second metal layer having a light reflectance lower than that of the first metal layer on the metal layer, and a method for manufacturing an acoustic wave device. According to the present invention, since the light reflectance of the second metal layer, which is the uppermost layer of the metal pattern, is small, it is possible to suppress an abnormal shape of the opening of the resist that occurs when the opening is formed in the resist.

  The said structure WHEREIN: The said light reflectance can be set as the structure which is the reflectance of the said pattern light.

  According to the present invention, since the light reflectance of the second metal layer, which is the uppermost layer of the metal pattern, is small, it is possible to suppress an abnormal shape of the opening of the resist that occurs when the opening is formed in the resist.

FIG. 1A and FIG. 1B are cross-sectional views when an opening is provided in a positive resist. 2A and 2B are cross-sectional views in the case where an opening is provided in the negative resist. FIG. 3A to FIG. 3D are cross-sectional views illustrating a method for manufacturing an acoustic wave device according to the first embodiment. FIG. 4 is a top view in FIG. FIG. 5A to FIG. 5D are cross-sectional views illustrating a method for manufacturing an acoustic wave device according to Comparative Example 1. FIG. 6 is a top view in FIG. 7A to 7D are cross-sectional views illustrating a method for manufacturing an acoustic wave device according to Comparative Example 2. FIG. 8 is a top view in FIG.

First, the principle of the present invention will be described. FIG. 1A and FIG. 1B are cross-sectional views when an opening is provided in a positive resist. In FIGS. 1A and 1B, the positive resist 22 shows a shape after development. Referring to FIG. 1A, a first metal layer 16 including, for example, Au is formed on a piezoelectric substrate 10 such as LiNbO ₃ or LiTaO ₃ . A photosensitive positive resist made of, for example, an epoxy resin is formed on the first metal layer 16. For example, ultraviolet light UV (pattern light) mainly having light having a wavelength of 365 nm is applied to the positive resist 22 through a mask 60 having a pattern 62. Then develop. Thereby, the region of the resist 22 irradiated with the ultraviolet rays UV is removed, and the opening 40 is formed. When irradiating the resist 22 with the ultraviolet rays UV, since the reflectance of the ultraviolet rays UV of the first metal layer 16 is high, the ultraviolet rays reflected by the first metal layer 16 below the positive resist 22 at the end of the region that should remain as a pattern. UV is irradiated. For this reason, after the development, a resist defect 50 occurs at the end of the pattern.

  Referring to FIG. 1B, a second metal layer 18 containing, for example, Ti or the like is formed on the first metal layer 16. Other configurations are the same as those in FIG. The light reflectance of the ultraviolet ray UV of the second metal layer 18 is smaller than that of the first metal layer 16. For this reason, the reflection of the ultraviolet rays UV by the second metal layer 18 is small. Therefore, the resist defect 50 as shown in FIG. 1A can be suppressed.

  2A and 2B are cross-sectional views in the case where an opening is provided in the negative resist. In FIGS. 2A and 2B, the negative resist 22 shows a shape after development. Referring to FIG. 2A, in the case of the negative resist 22, a region irradiated with light remains. The ultraviolet ray UV reflected by the first metal layer 16 is irradiated to the lower part of the negative resist 22 at the end of the region to be the opening. For this reason, a resist residue 52 is generated at the end of the opening 40 after development. On the other hand, referring to FIG. 2B, when the second metal layer 18 is formed on the first metal layer 16, the resist residue 52 is suppressed because the reflection of the ultraviolet UV by the second metal layer 18 is small. be able to.

  According to the present invention, the second metal layer 18 having a light reflectance smaller than that of the first metal layer 16 is formed on the first metal layer 16. Thereby, abnormal shapes such as the resist defect 50 or the resist residue 52 in the opening 40 of the resist 22 can be suppressed. Examples of the present invention will be described below.

Example 1 is an example using a positive resist. FIG. 3A to FIG. 3D are cross-sectional views illustrating a method for manufacturing an acoustic wave device according to the first embodiment. As shown in FIG. 3A, an electrode layer 14 mainly containing, for example, Al is formed on a piezoelectric substrate 10 such as LiNbO ₃ or LiTaO ₃ by using, for example, a sputtering method or a vapor deposition method. The electrode layer 14 forms a comb-shaped electrode 12 such as a surface acoustic wave element on the piezoelectric substrate 10. In addition, the lowermost layer of the metal pattern 20 connected to the comb electrode 12 is formed. A first metal layer 16 and a second metal layer 18 are formed on the electrode layer 14 using a sputtering method or a vapor deposition method. The first metal layer 16 mainly includes, for example, Au and has a film thickness of, for example, 200 nm. The second metal layer 18 mainly contains, for example, Ti and has a film thickness of, for example, 50 nm. A metal pattern 20 is formed from the electrode layer 14, the first metal layer 16 and the second metal layer 18. Thus, the metal pattern 20 is formed on the piezoelectric substrate 10 and connected to the comb-shaped electrode 12.

  As shown in FIG. 3B, a positive resist 22 made of, for example, a photosensitive resin such as an epoxy resin is applied on the piezoelectric substrate 10 and the metal pattern 20. Openings 42 and 40 are respectively formed in the positive resist 22 on the region to be penetrated by the through electrode and the comb-shaped electrode 12 (functional region of the surface acoustic wave element). The openings 40 and 42 are formed by exposure and development as described in FIG.

  As shown in FIG. 3C, a positive resist 24 made of, for example, a resin such as an epoxy resin is formed on the positive resist 22 so as to cover the openings 40 and 42 using a tenting method. An opening 42 is formed in the positive resist 24. The opening 40 is covered with a positive resist 24, and a hollow 44 is formed on the comb-shaped electrode 12. The opening 42 is formed by exposure and development as shown in FIG. As a result, a sealing portion 26 that seals the surface acoustic wave element from the positive resists 22 and 24 is formed.

  As illustrated in FIG. 3D, the through electrode 30 made of a metal such as Cu and penetrating the sealing portion 26 is formed on the metal pattern 20 in the opening 42. Solder balls 32 are formed on the through electrodes 30. Thereby, the comb-shaped electrode 12 can be connected to the outside through the metal pattern 20, the through electrode 30 and the solder ball 32.

  FIG. 4 is a top view in FIG. Openings 40 and 42 of the positive resist 22 are indicated by broken lines. The comb electrode 12 and the like of the surface acoustic wave element are not shown. Referring to FIG. 4, metal pattern 20 is connected to ground pad region Gnd, input pad region In, and output pad region Out. In the openings 40 and 42, resist defects and resist residues are not formed. According to Example 1, in FIG. 3B and FIG. 3C, the second metal layer 18 is formed under the ends of the regions to be the openings 40 and 42. For this reason, as shown in FIG. 4, FIG. 3 (b) and FIG. 3 (c), it is possible to suppress resist defects generated around the openings 40 and 42.

  FIG. 5A to FIG. 5D are diagrams showing a manufacturing method of Comparative Example 1 in which the metal pattern 20a does not have the second metal layer. As shown in FIG. 5A, the second metal layer is not formed on the metal pattern 20a. As shown in FIG. 5B, when the positive resist 22 is formed, a resist defect 50 is generated around the openings 40 and 42.

  As shown in FIG. 5C, a resist defect 50 is generated around the opening 42 even when the positive resist 24 is formed. As shown in FIG. 5D, the through electrode 30 and the solder ball 32 are formed. Due to the resist defect 50, a gap is formed between the through electrode 30 penetrating the sealing portion 26. Other configurations are the same as those in FIG. 3A to FIG. 3D of the first embodiment, and a description thereof will be omitted.

  FIG. 6 is a top view in FIG. Openings 40 and 42 of the positive resist 22 are indicated by broken lines. Referring to FIG. 6, a resist defect 50 is generated in the portion of openings 40 and 42 that are formed on metal pattern 20a, and openings 40 and 42 are enlarged. The resist defect 50 is, for example, about 1 to 10 μm. As described above, in the first comparative example, as described with reference to FIG. 1A, the first metal layer 16 has a high reflectance at the wavelength of light used when the positive resist 22 is exposed. A resist defect 50 is generated at the end of each of the two.

  In the first embodiment, the metal pattern 20 functions as a wiring for electrically connecting the comb electrode 12 to the outside. The electrode layer 14 has a material and a film thickness suitable for the comb electrode 12. For this reason, it becomes an Al electrode whose resistance is not relatively low. Therefore, the resistance of the metal pattern 20 can be lowered by using Au, Ag, Cu or the like having a lower resistance than the electrode layer 14 as the first metal layer 16. However, Au or the like has a high light reflectance. For this reason, as in Comparative Example 1, when the surface of the metal pattern 20a below the ends of the opening portions 40 and 42 is the first metal layer 16, a resist defect 50 occurs. Therefore, the metal pattern 20 below the ends of the openings 40 and 42 (that is, the portion corresponding to the contour of the openings 40 and 42 projected onto the metal pattern 20) is light emitted from the first metal layer 16 and the first metal layer 16. A structure including the second metal layer 18 of the uppermost layer made of, for example, Ti having a low reflectance. Thereby, the resist defect 50 generated at the ends of the openings 40 and 42 can be suppressed.

  The second metal layer 18 only needs to be provided on a part of the first metal layer 16 located below the ends of the openings 40 and 42, but the second metal layer 18 has the openings 40 and It is preferable to be provided on all the first metal layers 16 located below the end of 42. Furthermore, it is preferable that the second metal layer 18 is provided on the entire surface of the first metal layer 16 for ease of manufacture.

  As shown in FIG. 6, when the metal pattern 20a is provided under a part of the ends of the openings 40 and 42 and the metal pattern 20a is not formed under the other part of the ends of the openings 40 and 42, the opening The shapes of the portions 40 and 42 are more likely to be abnormal. In such a case, by providing the second metal layer 18, the shapes of the openings 40 and 42 can be made less distorted as shown in FIG. 4.

  The metal pattern 20 connects the comb electrode 12 and the through electrode 30 penetrating the positive resists 22 and 24. A positive resist 24 (protective layer) is formed on the positive resist 22 so as to cover the opening 40. The opening 40 forms a hollow 44 formed on the comb electrode 12. In such a configuration, there are a plurality of metal patterns 20 derived from the hollow 44 (for example, ground, input, and output as shown in FIG. 4). Therefore, the metal pattern 20 is provided under part of the ends of the openings 40 and 42, and the metal pattern 20 is not formed under other parts. For this reason, as shown in FIG. 5, it is preferable that the openings 40 and 42 have a distorted shape, the second metal layer 18 is provided, and the shape has no distortion.

  Example 2 is an example using a negative resist. In Example 2, negative resists 22 and 24 made of a photosensitive resin such as an epoxy resin are used. For this reason, when the openings 40 and 42 are formed in FIGS. 3B and 3C, the region irradiated with ultraviolet rays is reversed from that in the first embodiment. Other configurations are the same as those in FIGS. 3A to 3D of the first embodiment, and a description thereof will be omitted.

  FIG. 7A to FIG. 7B are cross-sectional views showing manufacturing steps of Comparative Example 2 using a negative resist. FIG. 7A is the same as FIG. 5A of Comparative Example 1. As shown in FIG. 5B, when the openings 40 and 42 are formed in the negative resist 22, a resist residue 52 is generated at the pattern ends of the openings 40 and 42. As shown in FIG. 5C, when the opening 42 is formed in the negative resist 24, a resist residue 52 is generated at the pattern end of the opening 42. As shown in FIG. 5D, the through electrode 30 is distorted by the resist residue 52. Other configurations are the same as those in FIG. 3A to FIG. 3D of the first embodiment, and a description thereof will be omitted.

  FIG. 8 is a top view in FIG. Openings 40 and 42 of the positive resist 22 are indicated by broken lines. Referring to FIG. 8, a resist residue 52 is generated in the portion formed on metal pattern 20 a in the end portions of openings 40 and 42, and openings 40 and 42 are reduced. The resist residue 52 is, for example, about 1 to 10 μm. As described above, in Comparative Example 2, as described with reference to FIG. 2A, the openings 40 and 42 are high because the reflectance of the first metal layer 16 is high at the wavelength of light used when exposing the negative resist 22. Resist residue 52 is generated at the end of the substrate.

  In the second embodiment, as in the first embodiment, the uppermost layer of the metal pattern 20 below the ends of the openings 40 and 42 is the second metal layer 18 having a low light reflectance. Thereby, the resist defect 50 generated at the ends of the openings 40 and 42 can be suppressed.

  As described above, according to the first and second embodiments, abnormal shapes of the openings 40 and 42 such as the resist defect 50 or the resist residue 52 can be suppressed.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

DESCRIPTION OF SYMBOLS 10 Piezoelectric substrate 12 Comb electrode 14 Electrode layer 16 1st metal layer 18 2nd metal layer 20 Opening part 22 Resist 24 Resist 30 Through electrode 32 Solder ball 40, 42 Opening part 44 Hollow

Claims (10)

A piezoelectric substrate;
A comb-shaped electrode formed on the piezoelectric substrate;
A metal pattern formed on the piezoelectric substrate and connected to the comb electrode;
A resist formed on the piezoelectric substrate and the metal pattern and having an opening,
The metal pattern below the edge of the opening includes a first metal layer and an uppermost second metal layer formed on the first metal layer and having a light reflectance lower than that of the first metal layer. Characteristic acoustic wave device.   2. The acoustic wave device according to claim 1, wherein the metal pattern is provided under a part of the end of the opening.   3. The acoustic wave device according to claim 1, wherein the second metal layer is provided on all of the first metal layers located below the end of the opening. Comprising a protective layer formed on the resist so as to cover the opening;
4. The acoustic wave device according to claim 1, wherein the opening forms a hollow formed on the comb-shaped electrode. Comprising a through electrode penetrating the resist;
5. The acoustic wave device according to claim 1, wherein the metal pattern connects the comb electrode and the through electrode. 6.   The acoustic wave device according to claim 1, wherein the light reflectance is a reflectance of pattern light used when exposing the resist.   The acoustic wave device according to any one of claims 1 to 6, wherein the first metal layer is Au.   The acoustic wave device according to claim 1, wherein the second metal layer is Ti. Forming a comb-shaped electrode on the piezoelectric substrate;
Forming a metal pattern connected to the comb electrode;
Forming a resist having an opening by irradiating and developing pattern light on the piezoelectric substrate and the metal pattern, and
The step of forming the metal pattern includes a step of forming a first metal layer as the metal pattern to be under the opening end, and a light reflectance smaller than that of the first metal layer on the first metal layer. Forming an uppermost second metal layer, and a method of manufacturing an acoustic wave device.   The method for manufacturing an acoustic wave device according to claim 9, wherein the light reflectance is a reflectance of the pattern light.

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