JP2015156626A - Acoustic wave element, demultiplexer, and communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acoustic wave element in which a temperature rise of an excitation electrode can be reduced, a demultiplexer, or a communication device.

SOLUTION: The acoustic wave element of the present invention includes: a piezoelectric substrate 2; an excitation electrode 3 disposed on the piezoelectric substrate 2; an electrode pad 4 disposed on the piezoelectric substrate 2; wiring 5 disposed on the piezoelectric substrate 2 and electrically connecting the excitation electrode 3 and the electrode pad 4; and a cover body 6 disposed on the piezoelectric substrate 2 and having a vibration space Sp, in which the excitation electrode 3 is sealed, between itself and the piezoelectric substrate 2. An inner wall surface 6bB of the cover body 6, which is positioned in the vibration space Sp, is in contact with the wiring 5 or the piezoelectric substrate 2.

COPYRIGHT: (C)2015,JPO&INPIT

Description

  The present invention relates to an acoustic wave element, a duplexer, and a communication device.

  In recent years, in a communication apparatus such as a mobile terminal, an acoustic wave element is used as a duplexer for filtering a signal transmitted / received from an antenna. The acoustic wave element includes a piezoelectric substrate and excitation electrodes formed on the main surface of the piezoelectric substrate. The acoustic wave element utilizes a characteristic capable of mutually converting an electric signal and a surface acoustic wave by the relationship between the excitation electrode and the piezoelectric substrate.

In recent years, with the progress of miniaturization of mobile terminals, it is essential to reduce the height of acoustic wave elements. As a structure for reducing the height of an acoustic wave device, for example, a wafer level package (hereinafter simply referred to as WLP) structure is known (see, for example, Patent Document 1). W
The LP-structured acoustic wave element has a conductor electrically connected to the excitation electrode formed on the piezoelectric substrate in the cover body that seals the excitation electrode so that the acoustic wave element can be formed in a wafer state of the piezoelectric substrate. Arranged structure.

JP 2002-261582 A

  By the way, in recent acoustic wave elements, there is a tendency to reduce the line width of the electrode fingers constituting the excitation electrode. When the line width of the electrode fingers is reduced, one of the problems is to reduce the temperature rise of the excitation electrode in order to improve the power durability of the excitation electrode.

  Therefore, the present invention has been conceived under the above circumstances, and an object thereof is to provide an acoustic wave element, a duplexer, or a communication device that can reduce the temperature rise of an excitation electrode. And

  The acoustic wave device of the present invention includes a piezoelectric substrate, an excitation electrode disposed on the piezoelectric substrate, an electrode pad disposed on the piezoelectric substrate, the excitation electrode disposed on the piezoelectric substrate, and the A wiring body electrically connecting the electrode pad, and a cover body disposed on the piezoelectric substrate and having a vibration space for sealing the excitation electrode between the piezoelectric substrate, An inner wall surface of the cover body positioned at is in contact with the wiring or the piezoelectric substrate.

  The duplexer of the present invention is a duplexer including an antenna terminal, a transmission filter that filters a transmission signal and outputs the filtered signal to the antenna terminal, and a reception filter that filters a reception signal from the antenna terminal. The transmission filter or the reception filter has the elastic wave element described above.

  The communication apparatus of the present invention includes an antenna, the above-described duplexer electrically connected to the antenna, and an RF-IC electrically connected to the duplexer.

  ADVANTAGE OF THE INVENTION According to this invention, the elastic wave element, duplexer, or communication apparatus which can reduce the temperature rise of an excitation electrode can be provided.

In the elastic wave element concerning one embodiment of the present invention, it is a top view when a cover body is removed. FIG. 2 is an enlarged plan view of a part of the acoustic wave element of FIG. 1. This corresponds to a cross section when the acoustic wave element of FIG. 1 is cut along line II. This corresponds to a cross section of an acoustic wave device according to a modification of the embodiment of the present invention, and corresponds to a case where the acoustic wave device of FIG. 1 is cut along the line II. This corresponds to a cross section when the acoustic wave device according to the second modification of the present invention is mounted on a circuit board, and corresponds to the case where the acoustic wave device of FIG. 1 is cut along the line II. This corresponds to a cross section of an acoustic wave device according to a modification of the embodiment of the present invention, and corresponds to a case where the acoustic wave device of FIG. 1 is cut along the line II. This corresponds to a cross section of an acoustic wave device according to a modification of the embodiment of the present invention, and corresponds to a case where the acoustic wave device of FIG. 1 is cut along the line II. This corresponds to a cross section of an acoustic wave device according to a modification of the embodiment of the present invention, and corresponds to a part of the acoustic wave device of FIG. 1 cut along the line II. This corresponds to a cross section of an acoustic wave device according to a modification of the embodiment of the present invention, and corresponds to a part of the acoustic wave device of FIG. 1 cut along the line II. This corresponds to a cross section of an acoustic wave device according to a modification of the embodiment of the present invention, and corresponds to a part of the acoustic wave device of FIG. 1 cut along the line II. This corresponds to a cross section of an acoustic wave device according to a modification of the embodiment of the present invention, and corresponds to a part of the acoustic wave device of FIG. 1 cut along the line II. 1 is a circuit diagram of a duplexer according to an embodiment of the present invention. It is a block diagram which shows the communication apparatus concerning one Embodiment of this invention. The manufacturing method of the 2nd columnar electrode of the elastic wave element of this invention is shown, and it corresponds when it cut | disconnects by the II line | wire of the elastic wave element of FIG. The manufacturing method of the columnar electrode of the elastic wave element of this invention is shown, and it corresponds when it cut | disconnects by the II line of the elastic wave element of FIG.

  Hereinafter, an elastic wave element, a duplexer, and a communication device according to an embodiment of the present invention will be described with reference to the drawings. Note that the drawings used in the following description are schematic, and the dimensional ratios and the like on the drawings do not necessarily match the actual ones.

<Elastic wave device>
An acoustic wave device according to an embodiment of the present invention will be described below. The surface acoustic wave (SAW) element 1 according to the present embodiment includes a piezoelectric substrate 2, an excitation electrode 3, an electrode pad 4, a wiring 5, and a cover body 6, as shown in FIGS. .

  Each of the SAW elements 1 can be formed at the wafer level. The SAW element 1 has a function of filtering an electrical signal exchanged between an antenna and a signal arithmetic circuit (for example, an IC) in a mobile terminal.

  The SAW element 1 has a plurality of electrode pads 4, and signals are input through any one of the electrode pads 4. The input signal is filtered by the excitation electrode 3 or the like. Then, the SAW element 1 outputs the filtered signal through the electrode pads 4 other than the electrode pad 4 in which the input signal is entered among the plurality of electrode pads 4. The electrode pads 4 that are not used for signal input / output are connected to a reference potential, for example.

  The piezoelectric substrate 2 is constituted by a piezoelectric crystal substrate such as a lithium tantalate single crystal, a lithium diobate single crystal, or a lithium tetraborate single crystal. The piezoelectric substrate 2 is formed in a rectangular parallelepiped shape, for example, and has a rectangular shape in plan view. The piezoelectric substrate 2 has, for example, a flat upper surface 2A. The thickness of the piezoelectric substrate 2 is set to, for example, 0.2 mm or more and 0.5 mm or less. The length of one side of the piezoelectric substrate 2 is set to, for example, 0.6 mm or more and 3 mm or less. In the present embodiment, the piezoelectric substrate 2 is composed of a lithium tantalate single crystal.

  An excitation electrode 3 is provided on the upper surface 2A of the piezoelectric substrate 2. As shown in FIG. 2, the excitation electrode 3 is composed of a comb-like electrode. The excitation electrode 3 is disposed so that at least two bus bar electrodes 3a face each other. The electrode fingers 3b extend in the direction of the bus bar electrodes 3a and are arranged so that they intersect each other.

  The plurality of excitation electrodes 3 may constitute a ladder-type SAW filter connected by direct connection or parallel connection. The excitation electrode 3 may be a dual mode SAW resonator filter in which a plurality of excitation electrodes 3 are arranged in one direction. Furthermore, the excitation electrode 3 may have a reflector 3c as shown in FIG. 1 or FIG.

  The electrode pad 4 is disposed on the piezoelectric substrate 2 as shown in FIG. 1 or FIG. What is necessary is just to set the planar view shape of the electrode pad 4 suitably. In the present embodiment, the electrode pad 4 is circular. What is necessary is just to set suitably the number and arrangement position of the electrode pad 4 according to the structure of the filter comprised by the some excitation electrode 3. FIG. The width of the electrode pad 4 can be set to be 60 μm or more and 100 μm or less, for example.

  As shown in FIG. 2, the electrode pad 4 is electrically connected to the excitation electrode 3 through a wiring 5. The wiring 5 is formed in a layered manner on the upper surface 2A, and electrically connects the bus bar electrode 3a of the excitation electrode 3 and the electrode pad 4. Note that the wiring 5 does not need to be formed on the upper surface 2A, and for example, there may be a portion that is three-dimensionally crossed via an insulator.

  Excitation electrode 3, electrode pad 4, and wiring 5 (portion formed on upper surface 2A) can be formed by the same manufacturing process. Therefore, the excitation electrode 3, the electrode pad 4, and the wiring 5 are made of, for example, the same conductive material. As the conductive material, for example, an Al—Cu alloy or the like can be used. Moreover, the excitation electrode 3, the electrode pad 4, and the wiring 5 are set to the same film thickness, for example. These thicknesses can be set to, for example, 100 nm or more and 500 nm or less.

A protective film may be formed on the excitation electrode 3, the electrode pad 4, and the wiring 5. The protective film is made of an insulating material. For example, silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), silicon (Si), or the like can be used. The thickness of the protective film can be set to, for example, 5 nm or more and 50 nm or less. By forming such a protective film, the excitation electrode 3 and the wiring 5 can be protected. Specifically, the excitation electrode 3 and the like can be made difficult to be oxidized, and damage in the subsequent process can be prevented. The protective film is provided so that the upper surface of the electrode pad 4 is exposed.

On the electrode pad 4, a connection electrode 4 ′ in which a metal material is laminated may be disposed in order to improve adhesion with an external connection terminal 13 to be described later or electrical characteristics. The thickness of the connection electrode 4 ′ can be set to be 1 μm or more and 2 μm or less, for example. Such a connection electrode 4 ′ can be formed by a lift-off method. What is necessary is just to select the material of connection electrode 4 'suitably. In addition, connection electrode 4 'may be demonstrated as the electrode pad 4 in the following description.

  When metal bumps made of copper are used as the external connection terminals 13, for example, titanium and copper laminated in sequence can be used. The SAW element 1 of the present embodiment is a case where the external connection terminal 13 is constituted by a columnar electrode 13a provided in the cover body 6 and a second columnar electrode 13b provided on the piezoelectric substrate 2 side. .

  The cover body 6 is disposed on the piezoelectric substrate 2. The cover body 6 can be composed of, for example, a substrate made of silicon, a ceramic substrate made of a ceramic material, an organic substrate made of an organic material, a film-like member made of a photosensitive material, or crystal. For the cover body 6, a material having a thermal conductivity larger than that of the piezoelectric substrate 2 can be used. In this embodiment, the cover body 6 made of silicon (thermal conductivity: 165 W / (m · K)) having a thermal conductivity larger than that of the lithium tantalate single crystal (8 W / (m · K)) is used. Is the case.

  As silicon used for the cover body 6, for example, high resistance silicon having a sheet resistance of 5 kΩ · cm or more can be used. When high resistance silicon is used for the cover body 6, when forming the external connection terminal 13 arranged in the lid portion 6b, or when forming a pattern such as an inductor formed on the cover body 6 (for example, FIG. The configuration of the cover body 6)) can also reduce leakage of signals from the cover body 6. As a result, characteristic deterioration such as insertion loss of the SAW element 1 can be reduced. When silicon having a sheet resistance of less than 5 kΩ · cm is used for the cover body 6, the cover body 6 in which the surface of the cover body 6 is oxidized and a silicon oxide film is formed on the surface may be used.

  The cover body 6 includes a frame portion 6a and a lid portion 6b. By arranging the lid portion 6b on the frame portion 6a, a vibration space Sp is formed between the excitation electrode 3 and the cover body 6. The frame part 6a is disposed so as to surround the plurality of excitation electrodes 3, and the height of the vibration space Sp is generally determined by the thickness of the frame part 6a. When the cover body 6 is formed integrally with the frame portion 6a and the lid portion 6b, another frame member (adhesion layer) may be interposed between the frame portion 6a and the piezoelectric substrate 2.

  The lid portion 6b may be formed by laminating a plurality of plate members made of different materials, or by laminating a metal layer so as to overlap the vibration space Sp, thereby improving the strength of the lid portion 6b. Thus, by improving the strength of the lid 6b, it is possible to improve the impact resistance when the SAW element 1 is mounted. In the SAW element of the present embodiment, the frame portion 6a and the lid portion 6b are integrally formed, but both may be formed separately. As the frame portion 6a, an epoxy resin material or a metal material such as copper can be used.

  The cover 6b of the cover body 6 can be set so that the thickness of one layer is, for example, 40 μm or more and 60 μm or less. The total thickness of the cover body 6 can be set to be 80 μm or more and 300 μm or less, for example. The width of the cover body 6 in the planar direction can be set to be, for example, 0.6 mm or more and 3 mm or less.

  The cover body 6 has a through hole 6c. The through hole 6c may be arranged such that the opening on the piezoelectric substrate 2 side is smaller than the outer periphery of the electrode pad 4, for example. The inner wall of the through-hole 6c may be perpendicular to the electrode pad 4, or may be inclined so as to increase in diameter toward the upper surface 6bA side of the lid portion 6b. When the through hole 6c is inclined, it is possible to improve the adhesion with the external connection terminal 13 described later.

The cover body 6 is disposed such that the inner wall surface 6bB is in contact with the wiring 5 or the piezoelectric substrate 2. In this embodiment, the cover body 6 has a protrusion 7, and this protrusion 7 is in contact with the wiring 5 or the piezoelectric substrate 2 as the inner wall surface 6 b </ i> B of the cover body 6. In the present embodiment, the protrusion 7 is in contact with the wiring 5. The protrusion 7 is disposed on a part of the inner wall surface 6bB of the lid 6b or the frame 6a. This embodiment demonstrates the case where it arrange | positions to the inner wall face 6bB of the cover part 6b. The protrusion 7 may be formed integrally with the lid 6b, or may be made of a material different from that of the lid 6b.

  When the projection 7 is formed integrally with the lid 6b, the adhesion between the projection 7 and the lid 6b can be increased. On the other hand, when the projection part 7 is comprised with a material different from the cover part 6b, the freedom degree of material selection can be raised. For example, the effect of the present invention can be improved by using a material having a thermal expansion coefficient higher than the thermal expansion coefficient of the material constituting the lid portion 6b as the protruding portion 7. This embodiment is a case where the cover body 6 and the protrusion 7 are integrally formed.

  The protrusion 7 is in direct or indirect contact with the wiring 5 or the piezoelectric substrate 2. The case where the protruding portion 7 is in indirect contact with the wiring 5 is a case where the wiring 5 and the protruding portion 7 are in contact with each other through, for example, a heat conductive member. As shown in FIG. 3, the protruding portion 7 may be in contact with a part of the wiring 5, or may be arranged so as to surround one excitation electrode 3. When the protrusion 7 is disposed so as to surround the excitation electrode 3, the area of the cover body 6 in contact with the wiring 5 in the vibration space Sp is increased, so that the temperature rise around the excitation electrode 3 is further increased. Can be reduced.

  In the SAW element of this embodiment, the protrusion 7 is in contact with a part of the wiring 5, whereby the heat of the wiring 5 can be released to the outside. Thereby, since the heat generated in the excitation electrode 3 can be released to the outside through the wiring 5, the temperature rise of the excitation electrode 3 can be reduced. As a result, since the occurrence of stress migration in the excitation electrode 3 can be reduced, hillocks or voids can be hardly generated in the excitation electrode 3. As a result, the destruction of the excitation electrode 3 can be reduced, so that the temperature resistance characteristics of the SAW element can be improved.

  Further, since the cover body 6 has the protrusions 7 in this way, it is possible to reduce the collision of the cover body 6 with the excitation electrode 3 when the cover body 6 is mounted on the piezoelectric substrate 2. it can. Further, since the protrusion 7 is in contact with the wiring 5, the lid 6b can be made difficult to be deformed when the SAW element 1 is mounted on a circuit board or the like, so that the shock resistance of the SAW element 1 is improved. Can be made.

(Modification 1 of SAW element)
As shown in FIG. 4, the protrusion 7 may be provided so that the width increases as the distance from the piezoelectric substrate 2 increases. Specifically, the protrusion 7 is provided in a trapezoidal shape in the cross section in the thickness direction (z direction). By configuring the protruding portion 7 in this way, it is possible to set the width to increase as the distance from the lid portion 6b approaches, while reducing the portion in contact with the wiring 5. Thereby, it is possible to easily transfer the heat transferred from the wiring 5 to the lid portion 6b side while making contact with the wiring 5 having a narrow line width (reducing the contact area with the wiring 5). In addition, the SAW element 1 of this modification is a case where the frame part 6a and the cover part 6b are comprised with a different material.

(Modification 2 of the SAW element)
As the external connection terminal 13 of the cover body 6, as shown in FIG. 5, a bump 13c may be used instead of the second columnar electrode 13b. FIG. 5 shows a case where the SAW element 1 is mounted on the circuit board 14 via the second bump 14 ′, and the through hole 6c is inclined so as to expand toward the upper surface 6bA side of the lid 6b. It is. Thus, the columnar electrodes 13a of the cover body 6 are electrically connected to the electrode pads 4 of the piezoelectric substrate 2 via the bumps 13c, so that the electrical connection is reliably made when the cover body 6 is mounted. be able to. As a result, the reliability of the SAW element 1 can be improved. For the bump 13c and the second bump 14 ′, for example, a conductive material made of tin can be used.

(Modification 3 of the SAW element)
As shown in FIG. 6, the electrode pad 4 may be disposed outside the frame portion 6 a of the cover body 6 (on the outer peripheral side of the piezoelectric substrate 2). With this arrangement, when mounting on a circuit board or the like, it can be directly mounted with bumps or the like, and the height can be reduced. In particular, the impact resistance of the SAW element 1 can be improved by using silicon as the cover body 6. In this case, since the structure of the cover body 6 is simple, processing can be facilitated and productivity can be improved.

  FIG. 6 shows a case where the frame portion 6 a is in contact with the wiring 5 and also functions as the projection portion 7. By arranging the cover body 6 in this way, the SAW element can be miniaturized in the plane direction. FIG. 6 shows a case where a protective film Hg is formed on a part of the excitation electrode 3, the wiring 5 and the electrode pad 4, and the protrusion 7 (frame portion 6a) is connected to the wiring 5 via the protective film Hg. This is the case when touching.

(Modification 4 of the SAW element)
In the above description, the case where the inner wall surface 6bB of the cover body 6 is in contact with the wiring 5 or the piezoelectric substrate 2 has been the case where the projections 7 are provided on the cover body 6, but as shown in FIG. 5 may have the 2nd protrusion part 5a which protruded to the inner wall face 6bB side. Since part of the wiring 5 has the second protrusion 5a, the wiring 5 and the inner wall surface 6bB are in contact with each other. In this modification, in order to bring the wiring 5 into contact with the inner wall surface 6aB, the protruding body 5b is disposed between the wiring 5 and the piezoelectric substrate 2 and the wiring 5 is projected.

  The protruding body 5b is made of a photosensitive resin such as polyimide or epoxy resin. Such a protrusion 5b is formed by applying a photosensitive resin to the piezoelectric substrate 2 by a spin coating method or the like with a film thickness of about 1.0 μm to 2.0 μm, and then exposing and developing with a reduction projection exposure machine (stepper). By processing, a predetermined pattern can be formed. After forming a conductor layer so as to cover the protruding body 5b, the conductor layer can be patterned into a predetermined pattern to form the wiring 5 having a predetermined shape.

  By making a part of the wiring 5 protrude and contact the cover body 6 in this way, the heat generated in the excitation electrode 3 can be released to the cover body 6 side, thereby reducing the temperature rise of the excitation electrode 3. can do. Further, since the second protrusion 5a is constituted by a part of the wiring, the heat generated in the excitation electrode 3 is further released to the cover body 6 side as compared with the case where the thermal conductivity is formed of resin or the like. It can be made easier.

  Further, the protruding body 5b may be provided on the wiring 5 as shown in FIG. In this case, the on-wiring conductor 5c is laminated on the wiring 5 and the protruding body 5b to form the second protrusion 5a. The on-wiring conductor 5c is disposed so as to cover the protruding body 5b. Further, as shown in FIG. 8, the protrusion 5 b may have a width that decreases as the distance from the piezoelectric substrate 2 increases. That is, since the protrusion 5b becomes wider toward the piezoelectric substrate 2, the angle formed between the side surface of the protrusion 5b and the upper surface of the wiring 5 becomes an obtuse angle. As a result, the coverage of the on-wiring conductor 5c disposed on the wiring 5 and the protruding body 5b can be improved, and the adhesion of the on-wiring conductor 5c can be improved. When a protective film is provided so as to cover the excitation electrode 3 and the wiring 5, the protruding body 5b and the on-wiring conductor 5c may be provided on the protective film.

  The on-wiring conductor 5c can be formed, for example, by laminating and patterning an alloy of aluminum and copper or an alloy of titanium and aluminum by a sputtering method. The thickness of the on-wiring conductor 5c can be set to 3.0 μm or more and 4.0 μm, for example. In addition, what is necessary is just to adjust the height of the protrusion 5b and the conductor 5c on wiring so that it may contact | connect the inner wall surface 6bB according to the height of the vibration space Sp. In addition, the thickness of the protrusion 5b and the conductor 5c on wiring may be substantially the same.

(Modification 5 of the SAW element)
As shown in FIG. 9, the SAW element 1 may have a protrusion 7 that partially protrudes from the cover body 6 and may have a second protrusion 5 a that protrudes part of the wiring 5. In this case, the inner wall surface 6bB and the wiring 5 come into contact with each other when the projecting portion 7 and the second projecting portion 5a are in contact with each other. As a result, the temperature rise of the excitation electrode 3 can be reduced. Further, since the protrusions 7 and the second protrusions 5a are provided in this way, the heights of the respective protrusions 7, 5a can be reduced, so that the protrusions can be easily manufactured.

  As shown in FIG. 9, the portions with which the protrusions 7 and 5a are in contact may be different. Thus, the impact resistance of the SAW element 1 can be further improved, for example, because the areas of the top surfaces, which are the contact portions of the protrusion 7 and the second protrusion 5a, are different. Specifically, the top surfaces of the protrusion 7 and the second protrusion 5a may have a larger area in the protrusion 7 than in the second protrusion 5a, or in the second protrusion 5a. The area may be larger than the protrusion 7.

(Modification 6 of the SAW element)
Further, as shown in FIG. 10, the SAW element 1 may have a through conductor 6 d in contact with the second protrusion 5 a in the cover body 6. The through conductor 6d is disposed in the cover body 6. Since the through conductor 6d and the second protrusion 5a are in contact with each other, the wiring 5 and the inner wall surface 6bB are in contact with each other. Can be reduced.

  For example, copper or the like can be used for the through conductor 6d. As a method for forming the through conductor 6d in the cover body 6, for example, a CVD method, a vacuum deposition method, a sputtering method, a plating method, or the like can be used. Such a through conductor 6d may be electrically connected to a reference potential or an input / output signal line.

  The frame portion 6a that joins the cover body 6 and the piezoelectric substrate 2 may be made of the same photosensitive resin as the protruding body 5b. In this case, since the frame part 6a and the protruding body 5b can be manufactured in the same process, the productivity of the SAW element 1 can be improved. Further, the frame portion 6a may be formed and bonded to both the cover body 6 side and the piezoelectric substrate 2 side by the same method as the protruding body 5b.

  Further, the SAW element 1 may use a piezoelectric substrate 2 as the cover body 6 as shown in FIG. In this case, the excitation electrode 3 may be formed on the main surface of the cover body 6 on the vibration space Sp side. By forming the excitation electrodes 3 on the cover body 6 side in this way, the number of excitation electrodes 3 provided on the piezoelectric substrate 2 can be reduced, and the size in the plane (xy) direction can be reduced. Further, when the second protrusion 5a is connected to the reference potential, it is electrically connected to both the piezoelectric substrate 2 side and the excitation electrode 3 on the cover body 6 side, thereby comparing with the case where the reference potential is connected separately. Thus, the SAW element 1 can be reduced in size.

The SAW element 1 shown in FIG. 11 has a wall-shaped resin 6da that surrounds the second protrusion 5a. By disposing the wall-shaped resin 6da around the second protrusion 5a, it is possible to reduce, for example, a part of the second protrusion 5a being chipped and scattered around the second protrusion 5a. As a result, it is possible to reduce the short circuit of the excitation electrode 3. Alternatively, the second protrusion 5a
When the (on-wiring conductor 5c) is formed by a plating method, it can be used as a molding member when the wall-shaped resin 6da is formed by a plating method.

(Demultiplexer)
The SAW element 1 may be applied to a duplexer 1 ′ having an antenna terminal 8, a transmission filter 9, and a reception filter 10, as shown in FIG. The antenna terminal 8 is a terminal connected to the antenna. The transmission filter 9 is a filter that filters the transmission signal TS input from the transmission terminal 9 a and outputs the filtered signal to the antenna terminal 8. The reception filter 10 is a filter that filters the reception signal RS input from the antenna terminal 8. The filtered reception signal RS is output from the output terminal 10a. The transmission filter 9 and the reception filter 10 are electrically connected to the antenna terminal 8. In FIG. 12, G indicates the ground, and L indicates the inductor. The reception filter 10 is a double mode SAW filter D.

  The transmission filter 9 is a ladder type having series resonators S1 to S3 connected in series to the antenna terminal 8 and the transmission terminal 9a, and parallel resonators P1 to P3 connected in parallel to the antenna terminal 8 and the transmission terminal 9a. Consists of filters. Although an example of a three-stage ladder filter is used, the present invention is not limited to this, and any number of ladder filters may be used. When the transmission filter 9 is configured by a ladder filter, the protruding portion 7 may be disposed in contact with the wiring 5 connected to the excitation electrode 3 configuring the series resonators S1 to S3.

  Since the ladder type filter in the transmission filter 9 easily generates heat from the series resonators S1 to S3, the protrusion 7 is provided on the piezoelectric substrate 2 so as to surround the wiring 5 near the series resonators S1 to S3 or the series resonators S1 to S3. By making the contact, the temperature rise of the excitation electrode 3 can be effectively reduced.

  Above all, as a result of the simulation, it was found that the series resonator S1 on the antenna terminal 8 side where the reception signal RS and the transmission signal TS are filtered generates a large amount of heat. Therefore, the protrusion 7 may bring the protrusion 7 into contact with the wiring 5 positioned between the series resonator S1 closest to the antenna terminal 8 and the antenna terminal 8 among the series resonators S1 to S3. Thereby, the temperature rise of the excitation electrode 3 can be reduced more effectively. Furthermore, the temperature rise of the series resonator S2 can be reduced by bringing the protrusion 7 into contact with the wiring 5 located between the series resonator S1 and the series resonator S2.

  When the protrusion 7 is disposed in contact with the piezoelectric substrate 2 so as to surround the series resonators S1 to S3, the protrusion 7 may be disposed so as to surround the plurality of series resonators S1 to S3. You may arrange | position so that child S1-S3 may be enclosed. Moreover, the protrusion part 7 should just be in contact with the piezoelectric substrate 2 around the series resonators S1 to S3. Furthermore, the protrusion 7 may be in contact with the piezoelectric substrate 2 via a protective film or the like.

(Communication device)
As shown in FIG. 13, the communication device 17 includes an antenna 15, a duplexer 1 ′ electrically connected to the antenna 15, and an RF-IC 16 electrically connected to the duplexer 1 ′. May be. According to the communication device 17, it is possible to reduce the temperature rise of the excitation electrode 3.

<Method for producing acoustic wave element>
Next, a method for manufacturing the SAW element 1 according to the embodiment of the present invention described above will be described separately for each step.

(Process for forming excitation electrodes on the piezoelectric substrate)
Excitation electrodes 3, electrode pads 4, and wirings 5 are formed on the upper surface 2 </ b> A of the piezoelectric substrate 2. As a method of forming the excitation electrode 3, the electrode pad 4, and the wiring 5, first, a metal film is formed on the upper surface 2A by a thin film forming method such as a sputtering method, a vapor deposition method, or a CVD (Chemical Vapor Deposition) method. Then, the excitation electrode 3, the electrode pad 4, and the wiring 5 can be formed by patterning the metal film by a photolithography method using a microprojection exposure machine (stepper) or an RIE (Reactive Ion Etching) apparatus. In the case of forming a protective film, it can be formed by patterning a film formed by a thin film forming method such as a CVD method or a sputtering method by a photolithography method.

  When the columnar electrode 13a provided on the cover body 6 side and the second columnar electrode 13b provided on the piezoelectric substrate 2 side are electrically connected as the external connection terminal 13, the second columnar electrode 13b is disposed on the piezoelectric substrate 2 side. 6 is prepared before mounting. As shown in FIG. 14A, the second columnar electrode 13 b forms a resist pattern that exposes the electrode pad 4. Then, as shown in FIG.14 (b), it can produce by performing electroless plating. And as shown in FIG.14 (c), the 2nd columnar electrode 13b can be provided on the electrode pad 4 by removing a resist pattern.

(Process of forming the cover body)
Since the SAW element 1 of this embodiment uses a substrate made of silicon as the cover body 6, for example, anisotropic etching by a wet method is performed with the silicon (100) surface and the (110) surface as the main surface. Thereby, the frame part 6a and the cover part 6b can be formed. When such a surface is used as the main surface, the frame portion 6a or the protruding portion 7 can be formed because the etching rate is different from that of the (111) surface. Moreover, the frame part 6a or the protrusion part 7 can also be inclined by using the difference in etching rate.

  As an etchant used for anisotropic etching, for example, an alkaline aqueous solution such as potassium hydroxide (KOH), sodium hydroxide (NaOH), or tetramethylammonium hydroxide (TMAH) can be used. At that time, for example, a silicon oxide film can be used as an etching mask. For patterning the etching mask, for example, a method can be used in which a resist pattern is formed by photolithography, and an oxide film at an opening of the resist pattern is etched away with buffered hydrofluoric acid (BHF).

  The through-hole 6c can be formed by dry etching silicon while alternately switching the etching process and the deposition process by DEEP-RIE using a resist pattern by photolithography as a mask. The through hole 6c inclined with respect to the electrode pad 4 can be created by adjusting the process time of the etching process and the deposition process. FIG. 15A shows a cover body 6 provided with a frame portion 6a, a protruding portion 7, and a through hole 6c.

  As shown in FIG. 15B, the columnar electrode 13a can fill the through hole 6c with copper by electroplating. Titanium and copper are sequentially formed by sputtering or the like as a base layer for electroplating. Thereafter, the columnar electrode 13a made of copper can be formed on the underlayer by electroplating copper. At this time, a wiring pattern 19 such as a coil is formed on the inner wall surface 6bB of the lid portion 6b, or a frame member made of ring-shaped copper for the purpose of hermetic sealing on the outer peripheral portion of the excitation electrode 3 is attached to the lower surface of the frame portion 6a. Or may be formed. Nickel may be used as the columnar electrode 13a.

(Process of mounting the cover body on the piezoelectric substrate)
Thereafter, the cover body 6 manufactured in this way is fixed to the piezoelectric substrate 2 by using, for example, a heat bonding technique or a room temperature direct bonding technique. By using the room temperature direct bonding technique, it is possible to reduce warpage or the like caused by the difference in thermal expansion coefficient between the cover body 6 and the piezoelectric substrate 2. In the case of bonding, it is desirable to pre-process the bonding surface before bonding in order to remove the oxide film and activate the surface on the bonding surface of the cover body 6 and the piezoelectric substrate 2. For example, ion beam irradiation, atomic beam irradiation, or formic acid treatment can be used for the pretreatment of the bonding surface. In addition, when joining the lower surface of the frame part 6a with the piezoelectric substrate 2 via a copper ring, when joining, for example, joining so that it may contact with a ground line, it is isolation characteristics with the mounting of the cover body 6 Can be improved.

1 Elastic wave device (SAW device)
1 'duplexer 2 piezoelectric substrate 2A upper surface 3 excitation electrode 3a bus bar electrode 3b electrode finger 3c reflector 4 electrode pad 4' connection electrode 5 wiring 5a second protrusion 5b projection 5c wiring upper conductor 6 cover body 6a frame 6b Lid 6bA Upper surface 6bB Inner wall 6c Through-hole 6d Through-conductor 6da Wall-shaped resin 7 Projection 8 Antenna terminal 9 Transmission filter 10 Reception filter 11 Series resonator 12 Parallel resonator 13 External connection terminal 13a Columnar electrode 13b Second columnar electrode 13c Bump 14 Circuit board 14 'Second bump 15 Antenna 16 RF-IC
17 Communication device 18 Resist pattern 19 Wiring pattern

Claims (13)

A piezoelectric substrate;
An excitation electrode disposed on the piezoelectric substrate;
An electrode pad disposed on the piezoelectric substrate;
A wiring disposed on the piezoelectric substrate for electrically connecting the excitation electrode and the electrode pad;
A cover body disposed on the piezoelectric substrate and having a vibration space for sealing the excitation electrode between the piezoelectric substrate, and
An elastic wall element in which an inner wall surface of the cover body located in the vibration space is in contact with the wiring or the piezoelectric substrate. The cover body has a protrusion protruding from the inner wall surface,
2. The acoustic wave element according to claim 1, wherein the protruding portion is in contact with the wiring or the piezoelectric substrate and has a width that increases with distance from the piezoelectric substrate.   The acoustic wave element according to claim 2, wherein the protrusion is disposed so as to surround the excitation electrode.   The acoustic wave element according to claim 1, wherein the cover body is made of silicon. The wiring has a second protruding portion protruding toward the inner wall surface side,
The elastic wave device according to claim 1, wherein the second protrusion is in contact with the inner wall surface.   The acoustic wave element according to claim 5, wherein the second protrusion has a width that decreases with distance from the piezoelectric substrate. A protrusion between the wiring and the piezoelectric substrate;
The elastic wave device according to claim 5 or 6, wherein the protruding body is disposed at a position overlapping the second protrusion of the wiring. The cover body further includes a through conductor connecting the inner wall surface and the outside,
The lower surface of the through conductor constitutes a part of the inner wall surface of the cover body,
The acoustic wave device according to claim 5, wherein the lower surface is in contact with the wiring or the piezoelectric substrate. A wall-shaped resin disposed between the cover body and the piezoelectric substrate;
The acoustic wave element according to claim 5, wherein the wall-shaped resin is disposed around the second protrusion. A duplexer comprising an antenna terminal, a transmission filter that filters a transmission signal and outputs the filtered signal to the antenna terminal, and a reception filter that filters a reception signal from the antenna terminal,
The said transmission filter or the said reception filter is a duplexer which has an elastic wave element in any one of Claims 1-9. The acoustic wave element has a plurality of the excitation electrodes,
The acoustic wave element constituting the transmission filter is a ladder type filter having the excitation electrode connected in series to the antenna terminal and the excitation electrode connected in parallel to the antenna terminal. ,
The duplexer according to claim 10, wherein the protrusion is in contact with the wiring that electrically connects the excitation electrode connected in series with the antenna terminal.   The duplexer according to claim 11, wherein the protrusion is in contact with a portion of the wiring located between the antenna terminal and the excitation electrode. An antenna,
The duplexer according to any one of claims 10 to 12, electrically connected to the antenna;
A communication apparatus comprising: an RF-IC electrically connected to the duplexer.

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