JP2010252321A - Surface acoustic wave device, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface acoustic wave device capable of reducing resistance loss, and to provide a method for manufacturing the surface acoustic wave device which is capable of preventing damage of an IDT electrode during a manufacturing process. <P>SOLUTION: The surface acoustic wave device 1 includes a piezoelectric substrate 7, the IDT electrode 9 formed on the piezoelectric substrate 7, an electrode pad 11 formed on the piezoelectric substrate 7 to connect the IDT electrode 9 to an external terminal, and a connection interconnect 13 formed on the piezoelectric substrate 7 to connect the IDT electrode 9 and the electrode pad 11. The IDT electrode 9 has a first thickness. The electrode 11 has a second thickness greater than the first thickness. The connection interconnect 13 has a thickness larger than the first thickness and smaller than the second thickness. Also, a method for manufacturing the surface acoustic wave device 1 includes the steps of applying a resist R3 onto the IDT electrode 9 and the connection interconnect 13, and patterning the resist R3 to cover at least a portion connecting the IDT electrode 9 and the connection interconnect 13. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface acoustic wave device and a method for manufacturing the same.

  Conventionally, various surface acoustic wave devices in which an IDT electrode is formed on a piezoelectric substrate have been proposed. For example, the surface acoustic wave device described in Patent Document 1 includes an IDT electrode and an electrode pad for connecting the IDT electrode to an external terminal. The IDT electrode and the electrode pad are electrically connected by a connection wiring. Connected. The IDT electrode and the connection wiring are formed of a thin film having a constant thickness.

JP 2008-271354 A

  However, since the thin film forming the IDT electrode and the connection wiring is very thin, the electric resistance is large and the resistance loss is large. Further, since the IDT electrode is formed of such a very thin thin film, there is a problem that it is easily damaged in the manufacturing process and is easily disconnected.

  The present invention has been made in order to solve the above-described problem, and a first object thereof is to provide a surface acoustic wave device capable of reducing resistance loss. A second object of the present invention is to provide a method of manufacturing a surface acoustic wave device that can suppress damage to the IDT electrode in the manufacturing process.

  The surface acoustic wave device according to the present invention includes a piezoelectric substrate, an IDT electrode formed on the piezoelectric substrate, an electrode pad formed on the piezoelectric substrate for connecting the IDT electrode to an external terminal, A connection wiring formed on the piezoelectric substrate and connecting the IDT electrode and the electrode pad. The IDT electrode has a first thickness, and the electrode pad has a second thickness greater than the first thickness. A thickness of the connection wiring is larger than the first thickness and smaller than the second thickness.

  The surface acoustic wave device manufacturing method according to the present invention includes a piezoelectric substrate, an IDT electrode formed on the piezoelectric substrate, an electrode pad for connecting the IDT electrode to an external terminal, the IDT electrode, A method of manufacturing a surface acoustic wave device including a connection wiring for connecting an electrode pad. In the manufacturing method, the IDT electrode having a first thickness is formed on the piezoelectric substrate, and the connection wiring having a thickness larger than the first thickness is formed on the piezoelectric substrate. Applying a resist on the IDT electrode and the connection wiring, patterning the resist so as to cover at least a connection portion between the IDT electrode and the connection wiring, and using the patterned resist And a step of forming the electrode pad on the piezoelectric substrate.

  In the step of patterning the resist, the applied resist may be patterned with a developer.

  According to the surface acoustic wave device according to the present invention, it is possible to reduce the resistance loss in the connection wiring connecting the IDT electrode and the electrode pad. Moreover, according to the manufacturing method of the surface acoustic wave device according to the present invention, it is possible to suppress damage to the IDT electrode in the manufacturing process.

1 is a plan view of a surface acoustic wave device according to an embodiment of the present invention. It is the II-II sectional view taken on the surface acoustic wave apparatus of FIG. FIG. 3 is a cross-sectional view of the surface acoustic wave device of FIG. 1 taken along the line III-III. It is a figure which shows the manufacturing process of the surface acoustic wave apparatus of FIG. It is a figure which shows the manufacturing process of the surface acoustic wave apparatus of FIG. It is a figure which shows the comparative example of the manufacturing process of the surface acoustic wave apparatus of FIG. It is sectional drawing of the surface acoustic wave apparatus which concerns on other embodiment of this invention. It is a graph which shows the frequency characteristic of the insertion loss of the surface acoustic wave element of an Example and a comparative example. It is a top view which expands and shows the edge part of a connection wiring, (a) is an Example, (b) is a comparative example.

  Hereinafter, an embodiment of a surface acoustic wave device according to the present invention will be described with reference to the drawings.

  As shown in FIGS. 1 to 3, the surface acoustic wave device 1 according to the present embodiment includes a surface acoustic wave element 3 and a base substrate 5 to which the surface acoustic wave element 3 is bonded. In FIG. 1, the base substrate 5 and solder bumps 25 to be described later are not shown for convenience of explanation.

  The surface acoustic wave element 3 is, for example, a surface acoustic wave filter or a surface acoustic wave resonator, and includes a piezoelectric substrate 7, an IDT electrode 9, an electrode pad 11, and a frame body 17 formed on the piezoelectric substrate 7. Yes. The piezoelectric substrate 7 is made of a piezoelectric material such as a lithium tantalate single crystal, a lithium niobate single crystal, or a lithium tetraborate single crystal.

  Two IDT electrodes 9 are arranged side by side in the direction of arrow Y in FIG. Each IDT electrode 9 is composed of two electrodes (hereinafter referred to as comb-shaped electrodes) 19 and 19 formed in a comb-tooth shape. The comb-shaped electrodes 19 and 19 are arranged so as to face each other and the electrode fingers 19a and 19a mesh with each other.

  The electrode pad 11 is connected to the IDT electrode 9 by a connection wiring 13 and is connected to a connection terminal 21 described later provided on the base substrate 5 as shown in FIG.

  As shown in FIG. 2, the frame body 17 is provided along the peripheral edge portion of the piezoelectric substrate 7 so as to collectively surround the two IDT electrodes 9, the electrode pads 11, and the connection wirings 13.

  The base substrate 5 is made of an insulating material such as ceramic or glass ceramic, and its peripheral portion is bonded to the upper surface of the frame 17 by solder bumps 25 as shown in FIGS. By doing so, the IDT electrode 9 formed on the piezoelectric substrate 7 is sealed by the frame body 17 and the base substrate 5.

As shown in FIG. 2, a through hole 5 a penetrating the base substrate 5 is formed at a position corresponding to the electrode pad 11 in the base substrate 5. Connection terminals 21 are provided in the through holes 5 a, and the connection terminals 21 are joined to the corresponding electrode pads 11 by solder bumps 25. Each connection terminal 21 can be connected to an external terminal connected to an external drive circuit (not shown). Thereby, the electrode pad 11 connected to the IDT electrode 9 via the connection wiring 13 can be electrically connected to the external terminal of the external drive circuit (not shown) via the connection terminal 21.

  Next, the cross-sectional configurations of the IDT electrode 9, the electrode pad 11, the connection wiring 13, and the frame body 17 configured as described above will be described in detail.

  As shown in FIGS. 2 and 3, the IDT electrode 9 includes a first conductive film 31 and a second conductive film 32. The frame body 17 is formed by laminating a first conductive film 31, a second conductive film 32, a third conductive film 33, and a fourth conductive film 34 in this order. By doing so, the height of the frame body 17 becomes higher than the height of the IDT electrode 9, and a gap is secured between the IDT electrode 9 and the base substrate 5.

  As shown in FIG. 2, the electrode pad 11 is formed by laminating a first conductive film 31, a second conductive film 32, a third conductive film 33, and a fourth conductive film 34 in this order, like the frame 17. Yes. In this way, the height of the electrode pad 11 becomes the same as the height of the frame body 17, and the electrode pad 11 is provided on the base substrate 5 when the surface acoustic wave element 3 is bonded to the base substrate 5. It can be joined to the connection terminal 21.

  The connection wiring 13 is formed by laminating a first conductive film 31, a second conductive film 32, and a third conductive film 33 in this order. By doing so, the thickness of the connection wiring 13 is larger than the thickness of the IDT electrode 9.

  The first conductive film 31, the second conductive film 32, the third conductive film 33, and the fourth conductive film 34 are formed at different film formation timings as will be described later. In the present embodiment, as described above, the IDT electrode 9 is formed of the first conductive film 31 and the second conductive film 32, and the electrode pad 11 is formed of the first conductive film 31, the second conductive film 32, and the third conductive film. By forming the film 33 and the fourth conductive film 34, the IDT electrode 9 has the first thickness in the present invention, and the electrode pad 11 has the second thickness in the present invention. Then, by forming the connection wiring 13 with the first conductive film 31, the second conductive film 32, and the third conductive film 33, the thickness of the connection wiring 13 is larger than the first thickness and smaller than the second thickness. It has become.

  The first conductive film 31, the second conductive film 32, the third conductive film 33, and the fourth conductive film 34 are made of, for example, Al or an Al alloy (for example, Al—Cu based, Al—Ti based), Cu or Cu alloy ( For example, Cu—Mg, Cu—Ti, Cu—Rd), Ag and Ag alloys (eg, Ag—Mg, Ag—Ti, Ag—Rd), Ti and Ti alloys (eg, Ti— (Al-based, Ti-Cu-based) or the like.

Although not shown, a protective film made of a highly insulating material such as Si, SiO ₂ , SiN _x , or Al ₂ O ₃ may be provided on the exposed surface of the IDT electrode 9. As a result, it is possible to prevent a short circuit due to conductive foreign matter adhering between the electrode fingers 19 a of the IDT electrode 9.

  Next, a method for manufacturing the surface acoustic wave device 1 configured as described above will be described with reference to FIGS. Here, the first conductive film 31, the third conductive film 33, and the fourth conductive film 34 are formed of any one of Al, Al alloy, Cu, Cu alloy, Ag, and Ag alloy, and the second conductive film. A case where the film 32 is formed of Ti will be described.

First, a piezoelectric substrate 7 is prepared. As shown in FIG. 4A, an evaporation method,
A first conductive film 31, a second conductive film 32, and a third conductive film 33 are sequentially formed by using a crystal growth method such as a sputtering method or a CVD method, and a stacked body L formed of these conductive films is formed. .

  Next, as shown in FIG. 4B, a resist R1 is applied on the third conductive film 33, a desired pattern is exposed by a photolithography method, and then this pattern is developed with a developer. At this time, as the resist R1, for example, a photosensitive resist material containing a novolac resin can be used. Further, as the developer, for example, an alkali developer containing tetramethylammonium hydroxide can be used.

  Next, as shown in FIG. 4C, the third conductive film 33 is selectively etched by a wet etching method. At this time, an etching agent having a lower etching rate of the second conductive film 32 than that of the third conductive film 33 can be used, and includes, for example, tetramethylammonium hydroxide, which is the same as the developer of the resist R1. By using the alkaline developer, only the third conductive film 33 can be removed. After the etching of the third conductive film 33, the resist R1 is removed as shown in FIG.

  Subsequently, as shown in FIG. 4E, a resist R2 is applied on the laminate L, a desired pattern is exposed by a photolithography method, and then the pattern is developed with a developer. At this time, as the resist R2 and the developer, for example, the same ones as exemplified for the resist R1 can be used.

And as shown in FIG.4 (f), the laminated body L is etched by the dry etching method, and a part of piezoelectric substrate 7 is exposed. At this time, for example, a mixed gas of BCl ₃ , Cl ₂ , and N ₂ can be used as the etching agent. After completion of the etching of the stacked body L, the resist R2 is removed as shown in FIG. Thus, the IDT electrode 9 and the connection wiring 13 are formed.

  Next, as shown in FIG. 5H, a resist R3 is applied onto the laminate L and the piezoelectric substrate 7, and a desired pattern is exposed by a photolithography method, and then this pattern is developed with a developer. At this time, as the resist R3, for example, a photosensitive resist material containing a novolak resin and naphthoquinonediazide can be used. Moreover, as a developing solution, the same thing as illustrated with respect to resist R1 can be used, for example. At this time, the resist R3 is patterned so as to cover the IDT electrode 9 and the connection wiring 13. Therefore, it is possible to prevent the IDT electrode 9 from being eroded and damaged by the developer.

  In other words, for example, as shown in FIG. 6, a case where the connection wiring 13 is not covered with the resist R3 is considered. In this case, the boundary surface E between the third conductive film 33 constituting the connection wiring 13 and the resist R3 is exposed. Therefore, when the resist R3 is developed with the developer, the developer enters the boundary surface E, and the first conductive film 31 constituting the IDT electrode 9 is easily eroded. This is because the second conductive film 32 is made of Ti and has high resistance to the developer, but the developer can reach the first conductive film 31 through the surface of the second conductive film 32. Therefore, the IDT electrode 9 is easily damaged by the developer. Since the film thickness of the IDT electrode 9 is very thin, problems such as disconnection are likely to occur due to this damage. Note that the connection wiring 13 is formed by the first conductive film 31, the second conductive film 32, and the third conductive film 33, and is formed thicker than the IDT electrode 9, so that even if it is eroded by the developer. It is hard to reach disconnection.

On the other hand, when the connection wiring 13 is covered in addition to the IDT electrode 9 as in the present embodiment shown in FIG. 5H, the connection portion of the connection wiring 13 with the IDT electrode 9 is covered with the resist R3. Therefore, the boundary surface E between the third conductive film 33 (side surface thereof) and the resist R3 constituting the connection wiring 13 is not exposed. Therefore, it is difficult for the developer to reach the first conductive film 31 constituting the IDT electrode 9, and damage to the IDT electrode 9 can be suppressed.

  Next, as shown in FIG. 5I, a fourth conductive film 34 is formed by a sputtering method or the like. Then, as shown in FIG. 5J, the resist R3 is peeled off, and the fourth conductive film 34 formed on the resist R3 is removed. By doing so, the electrode pads 11 each composed of a laminate composed of the first conductive film 31, the second conductive film 32, the third conductive film 33, and the fourth conductive film 34 using the patterned resist R3. And the frame 17 is formed.

  As described above, the surface acoustic wave device 3 according to this embodiment is manufactured. Although not shown, the above steps are performed at the wafer level, and after forming a plurality of surface acoustic wave elements 3 on the wafer, the wafer is cut to separate the plurality of surface acoustic wave elements 3. Use a chip shape.

  As shown in FIG. 2, the chip-shaped surface acoustic wave element 3 is disposed to face the base substrate 5, and the peripheral portion of the base substrate 5 and the frame body 17 are joined by the solder bumps 25. The connection terminal 21 provided on the substrate 5 and the electrode pad 11 are joined. Thus, the surface acoustic wave device 1 according to this embodiment is manufactured.

  According to the surface acoustic wave device 1 according to the present embodiment, the thickness of the connection wiring 13 is larger than the thickness of the IDT electrode 9 and smaller than the thickness of the electrode pad 11. Therefore, for example, compared to the case where the thickness of the connection wiring 13 is the same as the thickness of the IDT electrode 9, the electrical resistance of the connection wiring 13 can be reduced, and the connection between the electrode pad 11 and the IDT electrode 9 can be reduced. Resistance loss can be reduced.

  Further, according to the method for manufacturing the surface acoustic wave device 1 according to the present embodiment, the IDT electrode 9 and the connection wiring are covered by covering the IDT electrode 9 and the connection wiring 13 with the resist R3 as shown in FIG. 13 is covered with the resist R3, the developing solution of the resist R3 hardly reaches the IDT electrode 9, and damage caused by the developing solution eroding the IDT electrode 9 can be suppressed. Therefore, disconnection of the thin IDT electrode 9 can be suppressed.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible unless it deviates from the meaning. For example, in the above embodiment, as shown in FIG. 5H, the entire connection wiring 13 is covered with the resist R3, but at least the connection portion of the connection wiring 13 with the IDT electrode 9 is covered with the resist R3. As long as it is not limited to this.

  Moreover, in the said embodiment, although it is comprised so that the thickness of IDT electrode 9, the connection wiring 13, and the electrode pad 11 may become large in this order, as long as it is comprised in such a relationship, IDT electrode 9, connection The wiring 13 and the electrode pad 11 may include one or more conductive films in addition to the conductive film layers constituting them. The layer configuration of the IDT electrode 9, the connection wiring 13, and the electrode pad 11 is not limited to the above embodiment. For example, the IDT electrode 9 is composed of two layers of a first conductive film 31 and a second conductive film 32, and the connection wiring 13 is composed of three layers of a first conductive film 31, a second conductive film 32, and a third conductive film 33. The electrode pad 11 and the frame body 17 are composed of four layers of a first conductive film 31, a second conductive film 32, a third conductive film 33, and a fourth conductive film 34, but the IDT electrode 9 and the connection wiring 13 are formed. The electrode pad 11 and the frame body 17 may each be composed of a single conductive film or other multiple conductive films.

In the above embodiment, the present invention has been described by exemplifying a surface acoustic wave device having a so-called chip size package. However, the present invention is not limited to this. For example, the present invention can be applied to a surface acoustic wave device of a so-called wafer level package. In general, in the case of a surface acoustic wave device of a wafer level package, for example, as shown in FIG. 7, a frame body 17 is formed of resin, and a lid body 6 made of resin is provided on the frame body 17. A sealing structure for the IDT electrode 9 is formed. In FIG. 7, the same reference numerals are given to the same types of components as those of the surface acoustic wave device 1 shown in FIG. 2, and detailed description thereof is omitted. In the surface acoustic wave device 10 of FIG. 7, since the frame body 17 and the lid body 6 are made of resin, for example, when an external force in the lateral direction of FIG. The lid 6 is easily deformed. When the frame body 17 and the lid body 6 are deformed, an external force is also applied to the IDT electrode 9 as a result. At this time, if the developer is damaged by the erosion of the IDT electrode 9 as described above, there may be a problem that stress is concentrated on the damaged portion and the IDT electrode 9 is destroyed. On the other hand, the surface acoustic wave device manufacturing method according to the present invention is more effective for a surface acoustic wave device of a wafer level package because it can suppress such damage to the IDT electrode.

  The surface acoustic wave element 3 described above was actually manufactured and the electrical characteristics were measured. Specifically, the surface acoustic wave device 3 was manufactured as follows in accordance with the processes shown in FIGS.

  First, a first conductive film 31, a second conductive film 32, and a third conductive film 33 are laminated in this order on the main surface of a wafer-like piezoelectric substrate 7 made of a 38.7 ° Y-cut X-propagating lithium tantalate single crystal. A laminated body L was formed. Al was used for the first conductive film 31 and the third conductive film, and Ti was used for the second conductive film 32.

  Next, a photoresist R1 was applied to a thickness of about 0.5 μm using a resist coating apparatus. And the photoresist pattern corresponding to the part used as the IDT electrode 9 was formed with the reduction projection exposure apparatus (stepper). Further, an unnecessary portion of the photoresist R1 was dissolved with a developing solution using a developing device. Note that a novolak resin was used for the photoresist R1, and an alkaline developer containing tetramethylammonium hydroxide was used for the developer.

  Next, the third conductive film 33 was selectively etched by a wet etching method. An alkaline developer containing tetramethylammonium hydroxide was used as the etchant. Thereafter, the resist R1 was peeled off.

  Subsequently, a resist R2 was applied on the laminate L, a desired pattern was exposed by a photolithography method, and then this pattern was developed with a developer. Note that the same novolak resin as the resist R1 was used for the resist R2. The same developer as that used for developing the resist R1 was used.

And the laminated body L was etched by the dry etching method, and a part of piezoelectric substrate 7 was exposed. As the etching agent, a mixed gas of BCl ₃ , Cl ₂ , and N ₂ was used. After the etching of the laminated body L, the resist R2 was peeled off, and the IDT electrode 9 and the connection wiring 13 were formed.

  Next, a resist R3 was applied on the laminate L and the piezoelectric substrate 7, and a desired pattern was exposed by a photolithography method, and then this pattern was developed with a developer. For the resist R3, a photosensitive resist material containing a novolak resin and naphthoquinone diazide was used. Further, the same developer as that used for the resist R1 was used. At this time, the resist R3 was patterned so as to cover the IDT electrode 9 and the connection wiring 13.

  Subsequently, after forming the 4th electrically conductive film 34 by sputtering method etc., the electrode pad 11 and the frame 17 were formed by peeling resist R3. The fourth conductive film 34 has a three-layer structure of Cr / Ni / Au.

  Thereafter, the wafer-like piezoelectric substrate 3 was cut to obtain individual surface acoustic wave elements 3. The dimensions of the piezoelectric substrate 3 after cutting are 1.1 mm in length, 0.9 mm in width, and 0.45 mm in thickness.

  The thickness of the first conductive film 31 is 200 nm, the thickness of the second conductive film 32 is 5 nm, the thickness of the third conductive film 33 is 1.2 μm, and the thickness of the fourth conductive film is 10 nm for the Cr layer and 1 for the Ni layer. .2 μm, Au layer is 50 nm.

  That is, the surface acoustic wave element 3 of the example has a first thickness (the thickness of the IDT electrode 3) of 0.205 μm and a second thickness (the thickness of the electrode pad 11) of 2.665 μm. The thickness of the connection wiring 13 is 1.405 μm larger than the first thickness and smaller than the second thickness.

  On the other hand, a surface acoustic wave device as a comparative example was also manufactured by the same manufacturing method using the same material as in the example. However, in the surface acoustic wave device of the comparative example, the thickness of the connection wiring 13 was made the same as the thickness of the IDT electrode 3. That is, in the surface acoustic wave element of the comparative example, the first thickness (the thickness of the IDT electrode 3) and the thickness of the connection wiring 13 are 0.205 μm, and the second thickness (the thickness of the electrode pad 11). Is 2.665 μm.

  Electrical characteristics were measured for the surface acoustic wave elements of Examples and Comparative Examples. The measurement results are shown in FIG. FIG. 8 is a graph showing frequency characteristics in the vicinity of the passband for the surface acoustic wave elements of the example and the comparative example, where the solid line indicates the surface acoustic wave element of the example and the broken line indicates the surface acoustic wave element of the comparative example. ing.

  From this result, it was found that the surface acoustic wave device of the example improved the insertion loss by 0.15 dB compared to the surface acoustic wave device of the comparative example.

  Moreover, when the connection wiring 13 of the surface acoustic wave element of an Example and a comparative example was image | photographed in the state expanded 200 times using the optical microscope, and they were compared, the difference was seen by both connection wiring. FIGS. 9A and 9B are enlarged plan views in which an edge portion of the photographed connection wiring 13 is copied. FIG. 9A is an example, and FIG. 9B is a comparative example. The edge portion of the connection wiring 13 of the surface acoustic wave element of the example was substantially linear, whereas a minute concave portion was seen in the edge portion of the connection wiring 13 of the surface acoustic wave element of the comparative example. . This concave portion is considered to have been formed by a phenomenon (migration) in which Al molecules as the constituent material move from the first electrode film 31 due to the influence of heat or the like applied during the process. When such a recess is formed in the connection wiring 13, the transmission distance becomes longer due to the edge skin effect, and the resistance value of the wiring increases.

  On the other hand, this phenomenon was not observed in the connection wiring 13 of the surface acoustic wave element of the example because the thickness of the connection wiring 13 was made larger than the film thickness of the IDT electrode, and migration was less likely to occur. It is estimated that From the results of the example, it can be seen that the thickness of the connection wiring 13 should be at least 7 times larger than the thickness of the IDT electrode in order to suppress the occurrence of migration.

  From the above, the surface acoustic wave device according to the example not only has the wiring resistance lowered due to the increase in the thickness of the connection wiring, but also the shape of the edge portion of the connection wiring 13 due to the suppression of the occurrence of migration. This is considered to be the reason why the wiring resistance has decreased. As a result, it can be said that the surface acoustic wave device of the example has improved insertion loss compared to the surface acoustic wave device of the comparative example.

DESCRIPTION OF SYMBOLS 1 Surface acoustic wave apparatus 3 Surface acoustic wave element 5 Base board 7 Piezoelectric board 9 IDT electrode 11 Electrode pad 13 Connection wiring 17 Frame 25 Solder bump 31 1st conductive film 32 2nd conductive film 33 3rd conductive film 34 4th conductive film

Claims (4)

A piezoelectric substrate;
An IDT electrode formed on the piezoelectric substrate;
An electrode pad formed on the piezoelectric substrate for connecting the IDT electrode to an external terminal;
A connection wiring formed on the piezoelectric substrate and connecting the IDT electrode and the electrode pad;
With
The IDT electrode has a first thickness;
The electrode pad has a second thickness greater than the first thickness;
The surface acoustic wave device according to claim 1, wherein a thickness of the connection wiring is larger than the first thickness and smaller than the second thickness.   2. The surface acoustic wave device according to claim 1, wherein a thickness of the connection wiring is 7 times or more of the first thickness. A surface acoustic wave comprising: a piezoelectric substrate; an IDT electrode formed on the piezoelectric substrate; an electrode pad for connecting the IDT electrode to an external terminal; and a connection wiring for connecting the IDT electrode and the electrode pad. A device manufacturing method comprising:
Forming the IDT electrode having a first thickness on the piezoelectric substrate;
Forming the connection wiring having a thickness larger than the first thickness on the piezoelectric substrate;
Applying a resist on the IDT electrode and the connection wiring, and patterning the resist so as to cover at least a connection portion between the IDT electrode and the connection wiring;
Forming the electrode pad on the piezoelectric substrate using the patterned resist;
A method for manufacturing a surface acoustic wave device.   4. The method of manufacturing a surface acoustic wave device according to claim 3, wherein in the step of patterning the resist, the applied resist is patterned with a developer.

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