JP2002299985A - Production method for surface acoustic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method for surface acoustic wave(SAW) device by which an electrode or resist is hardly damaged by heating in an electrode forming process and a piezoelectric substrate is hardly cracked in flip chip bonding, etc., without increasing a production process. SOLUTION: When producing a SAW device in which first and second SAW elements having different electrode thickness are constituted on a piezoelectric substrate 1, an IDT electrode 2 of the first SAW element, electrode pad layers 8a and 9a, electrode pad layers 10a and 11a of the second SAW element and wiring 16 for short-circuiting are simultaneously formed and when forming an IDT electrode 3 of the second SAW element, the electrode pad layers 8a, 9a, 10a and 11a are made into two layers and after electrodes are completely formed, wiring 16 and 17 for short-circuiting are disconnected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a surface acoustic wave device in which first and second surface acoustic wave elements having different electrode thicknesses are formed on a piezoelectric substrate.
The present invention relates to a method for manufacturing a surface acoustic wave device in which at least an electrode pad has a two-layer structure.

[0002]

2. Description of the Related Art Conventionally, various types of surface acoustic wave devices in which surface acoustic wave elements having different characteristics are formed on one piezoelectric substrate have been proposed.

[0003] For example, WO 99/05788 discloses a method for manufacturing a surface acoustic wave device in which first and second surface acoustic wave elements having different electrode thicknesses are formed on a piezoelectric substrate. . When this type of surface acoustic wave device is used in a high frequency band, the electrode film thickness becomes small and the IDT
(Inter digital transducer) The line width of the electrode is reduced. Therefore, the mechanical strength of the electrode tends to decrease. Therefore, when the surface acoustic wave device is packaged by flip-chip bonding, the piezoelectric substrate tends to crack when the metal bumps are formed.

Therefore, in the manufacturing method described in the above-mentioned prior art, the thickness of the electrode pad and the bus bar is made larger than the thickness of the IDT electrode. Has been done. Therefore, the manufacturing process was complicated.

On the other hand, when packaging is performed by the flip chip method, it is necessary to heat the piezoelectric substrate in the metal bump forming step to promote the mutual diffusion of metal in order to increase the bump strength. In addition, when the resist was cured, it was necessary to heat it. However, when the above method is applied to the manufacture of a surface acoustic wave device using a piezoelectric substrate having a pyroelectric property, the first and the second due to a temperature change during heating.
A potential difference occurs between the IDT electrodes of the second surface acoustic wave element,
Discharge occurs. As a result, pyroelectric breakdown of the IDT electrode occurs, and the yield rate must be reduced.

On the other hand, Japanese Patent Application Laid-Open No. 11-321943 discloses another method of manufacturing a surface acoustic wave device having first and second surface acoustic wave elements having different electrode thicknesses. Here, a first conductive film is formed on the entire surface of the piezoelectric substrate,
Next, a resist is applied on the entire surface of the first conductive film. Then, this resist is patterned, and FIG.
Is obtained. In addition, 10
Reference numeral 1 denotes a piezoelectric substrate, and 102 denotes a first conductive film. The resist pattern 103 is patterned to form an IDT electrode and an electrode pad of the first surface acoustic wave device and an electrode pad of the second surface acoustic wave device.

Next, as shown in FIG. 11B, the IDT electrode 104 of the first surface acoustic wave element is etched by etching.
, An electrode pad 105 and an electrode pad 106 of the second surface acoustic wave element are formed. Next, the entire surface is covered with the second resist 107 (FIG. 11C), and thereafter, on the portion where the IDT electrode of the second surface acoustic wave element is formed and on the electrode of the second surface acoustic wave element. The resist is removed on a part of the pad (FIG. 11D). Thereafter, the second conductive film 111 is applied to the entire surface (FIG. 11).
(E)) Next, the second resist and the conductive film 111 on the second resist are removed by a lift-off method (FIG. 11F). Thus, in the second surface acoustic wave device, the conductive film 111 is partially formed on the upper surface of the electrode pad 106.
a are laminated to form two layers. Note that 111b
Indicates an IDT electrode.

In the prior art described in Japanese Patent Application Laid-Open No. 11-312943, the electrode pad 106 of the second surface acoustic wave element is formed at the time of forming the electrode of the first surface acoustic wave element as described above. That is, the second electrode pad 106
It is formed before the surface of the piezoelectric substrate is contaminated with a resist step or a developing solution. Therefore, the bonding strength between the electrode pad of the second surface acoustic wave element and the piezoelectric substrate is said to be increased.

[0009]

As described above, WO9
In the prior art described in Japanese Patent Application Laid-Open No. 9/05788, exposure and development must be performed three times, and the production method is complicated.
In addition, since the number of times of exposure and development is large, the number of heating steps for curing the resist is increased, and as a result,
There has been a problem that pyroelectric breakdown of the DT electrode occurs and the yield rate decreases.

On the other hand, in the manufacturing method described in JP-A-11-321943, exposure and development need only be performed twice. However, if the piezoelectric substrate has pyroelectricity,
Again, the heating step for curing the resist
Pyroelectric breakdown of the DT electrode sometimes occurred.

[0011] In addition, in the manufacturing method described in Japanese Patent Application Laid-Open No. 11-321943, only the electrode pad 106 of the second surface acoustic wave element has two layers. Therefore,
Since the electrode pad 105 of the first surface acoustic wave element was a single layer, the die shear strength was low. Therefore, when packaging by flip chip bonding is attempted,
Cracks tend to occur in the piezoelectric substrate.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, not only to reduce the number of exposure and development steps, but also to provide the first and second surface acoustic wave elements with respect to both of the piezoelectric substrates. It is an object of the present invention to provide a method of manufacturing a surface acoustic wave device in which the adhesion strength is increased and a crack is less likely to occur in a piezoelectric substrate during flip chip bonding.

[0013]

According to a first aspect of the present invention, there is provided an IDT electrode having a plurality of interdigital electrodes on a piezoelectric substrate and the IDT electrode.
A method for manufacturing a surface acoustic wave device comprising an electrode pad connected to a T electrode and first and second surface acoustic wave elements having different electrode thicknesses, wherein the first surface acoustic wave An electrode pad layer that is a part of the IDT electrode and the electrode pad of the element; an electrode pad layer that is at least a part of the electrode pad of the second surface acoustic wave element;
Forming a short-circuit wiring for connecting the plurality of comb-shaped electrodes of the IDT electrode of the surface acoustic wave device; and forming a region where the IDT electrode and the electrode pad layer of the first surface acoustic wave device are formed and a second region. Applying a resist to at least a region including a portion on which the electrode pad layer is formed of the surface acoustic wave element, heating the resist, and forming a resist on a region where the second surface acoustic wave element is formed; Removing the resist on at least the region of the surface acoustic wave element where the electrode pad layer is formed, and forming a conductive film having a thickness equal to the electrode thickness of the IDT electrode of the second surface acoustic wave element. A step of lifting off the resist and a conductive film provided on the resist; and a step of cutting the short-circuit wiring.

In the first invention, at least the electrode pad layer of the second surface acoustic wave element and the short-circuit wiring are formed together with the IDT electrode and the electrode pad layer of the first surface acoustic wave element. Therefore, before the surface of the piezoelectric substrate is contaminated by the resist, the electrode pad layers of the first and second surface acoustic wave elements are formed. Next, after the resist is applied and heated, the resist on the region where the second surface acoustic wave element is formed and the resist on the region where at least the electrode pad layer of the first surface acoustic wave element is formed Is removed, a conductive film having a thickness equal to the electrode thickness of the IDT electrode of the second surface acoustic wave element is formed, and the resist and the conductive film provided on the resist are removed by a lift-off method. Therefore, since a conductive film for forming the IDT electrode of the second surface acoustic wave element is laminated on both of the electrode pad layers of the first and second surface acoustic wave elements, each electrode pad has two layers. Having a structure. Therefore, not only the adhesion of the electrode pads to the piezoelectric substrate is excellent, but also cracking of the piezoelectric substrate during flip chip bonding is prevented.

Further, since the short-circuit wiring is formed in advance, and finally the short-circuit wiring is cut, a resist heating step is performed when forming the IDT electrodes and the electrode pads for the first and second surface acoustic wave devices. Pyroelectric breakdown is reliably prevented.

According to a second aspect of the present invention, there is provided a piezoelectric element comprising an IDT electrode having a plurality of comb-shaped electrodes and an electrode pad connected to the IDT electrode on a piezoelectric substrate and having different electrode thicknesses.
A method of manufacturing a surface acoustic wave device having a second surface acoustic wave element, wherein a step of applying a first resist over the entire surface of the piezoelectric substrate, and an IDT of the first surface acoustic wave element At the same time as removing the resist in the region where the electrodes and the electrode pads are formed and at least the region where the electrode pads of the second surface acoustic wave element are formed, a plurality of IDT electrodes of the first surface acoustic wave element are removed. Removing the resist on the portion where the short-circuit wiring connecting the first and second electrodes is provided; forming a conductive film having a thickness equal to the electrode thickness of the IDT electrode of the first surface acoustic wave element; And the conductive film provided on the first resist are lifted off, the IDT electrode of the first surface acoustic wave element, the electrode pad layer which is a part of the electrode pad, and the electrode of the second surface acoustic wave element. Part of pad Forming a certain electrode pad layer, and the short-circuit wire, I of the first surface acoustic wave device
A step of applying a second resist on a region including at least a portion of the DT electrode and the electrode pad layer and the electrode pad layer of the second surface acoustic wave element, and heating the second surface acoustic wave element; Removing the second resist on the region where is formed and the region where at least the electrode pad layer of the first surface acoustic wave element is formed; and removing the IDT electrode of the second surface acoustic wave element. Forming a conductive film having a thickness equal to the thickness of the electrode;
A step of lifting off the conductive film formed on the resist, and a step of cutting the short-circuit wiring.

Also in the second invention, first, the IDT electrode and the electrode pad layer of the first surface acoustic wave element, the electrode pad layer of the second surface acoustic wave element, and the short circuit are formed on the piezoelectric substrate by exposure and development. Wiring is formed, and then the second wiring
Is applied and heated to form a first surface acoustic wave element on the region where the IDT electrode and the electrode pad are formed, and a first surface acoustic wave element on the region where at least the electrode pad layer is formed. After the second resist is removed, a conductive film having a thickness equal to the electrode thickness of the IDT electrode of the second surface acoustic wave element is formed, and is formed on the second resist and the second resist by a lift-off method. The conductive film is removed.

Therefore, also in the second invention, a conductive film equal to the electrode thickness of the IDT electrode of the second surface acoustic wave element is laminated on the electrode pad layers of the first and second surface acoustic wave elements. Thus, a two-layer electrode pad is formed. Therefore,
The occurrence of cracks in the piezoelectric substrate during flip chip bonding can be suppressed. Also, the first
As in the invention of the first aspect, the short-circuit wiring is formed first, and after the electrodes for the first and second surface acoustic wave elements are formed, the short-circuit wiring is cut, so that pyroelectric breakdown can be suppressed. .

In a specific aspect of the first and second inventions, the second aspect
In the step of removing the resist on the region where the surface acoustic wave element is formed and on the area where at least the electrode pad of the first surface acoustic wave element is formed, the IDT electrode of the second surface acoustic wave element is simultaneously removed. The resist on the portion where the short-circuit wiring connecting the plurality of comb-shaped electrodes is provided is removed, and the short-circuit wiring is formed also on the second surface acoustic wave element side by forming and lift-off of the conductive film. After the formation and lift-off of the conductive film on the surface acoustic wave element side, further comprising a step of forming a metal bump on each of the electrode pads, in the step of cutting the short-circuit wiring,
The short-circuit wiring provided on the second surface acoustic wave element side is also cut. This makes it easy to package the surface acoustic wave element by, for example, flip chip bonding. In this case, since each electrode pad has a two-layer structure, generation of cracks in the piezoelectric substrate can be reliably suppressed. The thickness of the electrodes of the first and second surface acoustic wave elements may be any. Heating is performed to promote diffusion with the electrode pads when forming the metal bumps. By providing short-circuiting wires also in the second surface acoustic wave element, the pyroelectric effect of the first and second surface acoustic wave elements can be improved. Destruction can be suppressed.

That is, the IDT of the first surface acoustic wave element
The thickness of the electrode may be smaller than the thickness of the IDT electrode of the second surface acoustic wave element. Conversely, the thickness of the IDT electrode of the first surface acoustic wave element may be smaller than the second surface acoustic wave. Element IDT
The electrode may be thicker than the electrode.

In a specific aspect of the present invention, the thickness of the IDT electrode of the first surface acoustic wave element is greater than the thickness of the IDT electrode of the second surface acoustic wave element.
The second surface acoustic wave element formed at the same time as the IDT electrode of the surface acoustic wave element has a shape in which the side surface is tapered so that at least the cross-sectional shape of the electrode pad layer becomes thinner upward. .

In another specific aspect of the present invention, the method further comprises the step of forming an insulating film on the piezoelectric substrate after the short-circuit wiring is cut, whereby the first and second wirings are formed.
The IDT electrode of the surface acoustic wave element can be protected.

In a more specific aspect of the present invention, the method further comprises, after the formation of the insulating film, a step of removing at least an insulating film in a region where the electrode pad is formed, whereby the metal wire is formed on the electrode pad. Such a conductive bonding material can be reliably bonded. Further, after the step of removing the insulating film on the electrode pad and the metal bump, at least the surface of the electrode pad is etched to remove, for example, the interface between the bump and the electrode pad, or the residue of the insulating film and the etchant on the electrode pad and the bump surface. can do. Therefore, the bondability between the electrode pad and the bump or between the bump and the external electrode can be improved.

Further, since the removal of the insulating film is performed by processing with plasma or the like immediately before flip chip bonding, contamination of the metal bump surface can be prevented, and the metal bump surface is cleaned with the plasma. I can do it. Therefore, it is possible to reduce the bonding failure of the metal bumps.

In another specific aspect of the present invention, the method further includes a step of adjusting the frequencies of the first and second surface acoustic wave elements by reducing the thickness of the insulating film. The thickness of the insulating film can be easily adjusted by controlling the thickness at the time of forming the insulating film, or by processing the insulating film so as to reduce the thickness after the formation. Thus, the frequency of at least one of the first and second surface acoustic wave elements can be easily adjusted after the electrodes are formed. Further, even if the frequency before the formation of the insulating film deviates from the target frequency range, a surface acoustic wave device having a desired frequency characteristic can be obtained by adjusting the thickness of the insulating film, and the yield rate can be reduced. Can increase.

A communication device according to the present invention includes a surface acoustic wave device obtained by a method of manufacturing a surface acoustic wave device configured according to the present invention as a bandpass filter. Therefore, according to the present invention, since the surface acoustic wave device which is obtained by a relatively simple process and has excellent reliability is provided as the bandpass filter, the cost of the communication device can be reduced and the reliability can be improved.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

(First Embodiment) A method for manufacturing a surface acoustic wave device according to a first embodiment will be described with reference to FIGS. FIGS. 1A and 1B to 3A and 3B are plan views showing an electrode structure on a piezoelectric substrate in each step of forming a surface acoustic wave device, and FIG. ) To (d) to FIG.
(A)-(c) is the typical sectional view which combined the side sectional view of the part in which the 1st, 2nd surface acoustic wave element is formed, respectively. For example, taking FIG. 4A as an example, FIG. 4A is a combination of cross-sectional views taken along lines AA and BB in FIG. 1A. 4 (b) to 5
(C) is a schematic cross-sectional view in which two cross-sectional portions are similarly combined.

First, as shown in FIG. 1A, a piezoelectric substrate 1 is prepared. In this embodiment, the piezoelectric substrate 1 is made of a piezoelectric ceramic such as a lead zirconate titanate-based ceramic.

A first conductive film having the same thickness as the IDT electrode of the first surface acoustic wave device is formed on the entire upper surface of the piezoelectric substrate 1. In this embodiment, an Al alloy is used as a material for forming the conductive film. The formation of the conductive film is performed by vapor deposition,
It can be performed by an appropriate thin film forming method such as sputtering or plating, or another method of forming a conductive film.

Next, a positive resist is applied to the entire surface of the conductive film. A mask is overlaid on the resist, exposed, and then the exposed portions of the resist are removed. The mask has a shape in which an IDT electrode, a reflector, and an electrode pad of the first surface acoustic wave element, an electrode pad of the second surface acoustic wave element, a wiring electrode, and a bus bar portion are formed as a shielding portion. Having. Next, the conductive film is patterned by etching.

In this way, as shown in FIG. 1A, on the piezoelectric substrate 1, the IDT electrode 2 composed of a plurality of comb-shaped electrodes of the first surface acoustic wave element, the reflectors 4, 5 and The electrode pad layers 8a and 9a respectively connected to the pair of comb-shaped electrodes, the wiring electrode layers 12a and 13a, and the short-circuit wiring 16 are formed. The electrode pad layers 8a, 9a
Are formed so as to be connected to the bus bar layers 2a and 2b of the IDT electrode 2 by the wiring electrode layers 12a and 13a. The short-circuit wiring 16 is formed to short-circuit the electrode pad layers 8a and 9a on the IDT electrode 2 side, that is, to connect a plurality of comb-shaped electrodes. Both of the electrode pads 8a and 9a may constitute an input / output terminal, or one may constitute an input / output terminal of an IDT electrode and the other may constitute a ground terminal. In this embodiment,
The short-circuit wiring 16 is also connected to the reflectors 4 and 5.

On the other hand, in a position separated from the first surface acoustic wave element, that is, in a region where the second surface acoustic wave element is formed, the bus bar layers 3a and 3b of the second surface acoustic wave element are provided. The wiring electrode layers 14a and 15a and the electrode pad layers 10a and 11a are formed simultaneously so as to have the same thickness as the IDT electrode 2.

FIG. 4A shows a cross section taken along line AA and line BB in FIG. 1A. The etching may be either wet etching or dry etching using plasma or the like. Further, instead of etching, the electrode structure shown in FIG. 1A may be formed by a lift-off method.

In the second surface acoustic wave device, a conductive film having the same thickness as the IDT electrode of the second surface acoustic wave device is finally laminated on the electrode pad layers 10a and 11a according to the present invention. However, the conductive films do not necessarily have to be stacked on the bus bar layers 3a and 3b and the wiring electrode layers 14a and 15a so as to have a two-layer structure. In that case,
In the state shown in FIG. 1A, the electrode pad layers 10a,
It is sufficient to form only 11a, and the bus bar layers 3a and 3b and the wiring electrode layers 14a and 15a are not formed at this stage.

Next, a negative resist is applied to the entire upper surface of the piezoelectric substrate 1. Thereafter, the electrode pad layers 8a and 9a of the first surface acoustic wave element and the wiring electrode layer 12 are formed.
Exposure is performed using a mask in which a, 13a, the bus bar layers 2a, 2b of the IDT and the region where the various electrodes of the second surface acoustic wave element are formed are shielded portions. next,
By removing the unexposed portions of the resist, a patterned second resist 18 is formed as shown in FIGS. 1B and 4B. In FIG. 1B, the resist 18 does not reach the region where the electrode structure on the second surface acoustic wave element side is formed. FIG. 1 (b)
Then, on the second surface acoustic wave element side, the bus bar 3
Although it is illustrated as if a plurality of electrode fingers are arranged between a and 3b, in the state shown in FIG. 1B, only the resist 18 is removed at the positions where the electrode fingers are formed. At this stage, no electrode finger is formed. The same applies to the reflectors arranged on both sides of the IDT electrode. That is, the electrodes already formed on the second surface acoustic wave element side in FIG.
The busbar layers 3a, 3a shown in FIG.
b, wiring electrode layers 14a, 15a and electrode pad layer 10
a and 11a (the hatched portions in FIG. 1B).

Next, by subjecting the resist 18 to a heat treatment, the adhesiveness of the resist to the piezoelectric substrate 1 is increased, and the plasma resistance is enhanced. In this case, on the first surface acoustic wave element side, since the electrode pad layers 8a, 9a and the reflectors 4, 5 are short-circuited by the short-circuit wiring 16, they have the same potential, and the IDT due to the pyroelectric effect is generated.
The electrodes 2, the reflectors 4, 5 and the resist 18 are not damaged.

Next, a conductive film 19 having the same thickness as the electrode fingers of the IDT electrode of the second surface acoustic wave element is formed on the entire upper surface of the piezoelectric substrate 1 (see FIG. 4C). The second conductive film 19 is made of an Al alloy similarly to the first conductive film, and can be formed by an appropriate conductive film forming method such as evaporation, plating, or sputtering.

By forming the conductive film 19, the resist 1
In a portion where 8 is not provided, an electrode finger of the IDT electrode of the second surface acoustic wave element and a reflector are formed. Thereafter, the conductive film 19 provided on the resist 18 is lifted off together with the resist 18. In this way, as shown in FIGS. 2A and 4D, the electrode structures of the first and second surface acoustic wave elements 22 and 23 are formed on the piezoelectric substrate 1.

As shown in FIG. 2A,
In the second surface acoustic wave element 23, reflectors 6 and 7 are formed on both sides of the IDT electrode 3, and the short-circuit wiring 17
However, the electrode pads 10A and 11A are short-circuited so as to connect the plurality of comb-shaped electrodes of the IDT electrode 3, and the second conductive film is used to short-circuit these and the reflectors 6 and 7. Is formed. Also, the electrode pads 10A,
11A, bus bars 3A and 3B and wiring electrodes 14A and 15
A has a structure in which the first and second conductive films are stacked, that is, the electrode pad layer 10
a, 11a, bus bar layers 3a, 3b and wiring electrode layer 14
a, 15a, and a second conductive film is laminated thereon. Similarly, also on the first surface acoustic wave element 22 side, the bus bars 2A and 2B of the IDT electrode 2 and the electrode pad 8
A and 9A and the wiring electrodes 12A and 13A are configured to have a two-layer structure in which first and second conductive films are stacked.

The thickness of the electrode finger of the IDT electrode 3 on the side of the second surface acoustic wave element 23 is determined by the thickness of the second conductive film. The thickness of the film is made larger than the thickness of the first conductive film, whereby the thickness of the electrode of the IDT electrode 3 of the second surface acoustic wave element is smaller than the thickness of the IDT electrode of the first surface acoustic wave element. The finger thickness is increased.

When the second conductive film is formed, even if the piezoelectric substrate 1 is heated, the electrode pads 10A, 11A and the reflectors 6, 7 are short-circuited by the short-circuit wiring 17, that is, Since the plurality of interdigital electrodes are short-circuited, electrode destruction and resist damage due to the pyroelectric effect are unlikely to occur.

Next, as shown in FIG.
1, X2, Y1, Y2, short-circuit wiring 1
Cut 6,17. As a result, the electrode pad 8A, the electrode pad 9A, and the reflectors 4 and 5 are electrically separated. Similarly, also on the second surface acoustic wave element 23 side,
The electrode pad 10A, the electrode pad 11A, the reflector 6,
And 7 are electrically separated.

The cutting of the short-circuit wirings 16 and 17 can be performed by a photolithography-etching method. However, the method of cutting the short-circuit wirings 16 and 17 is not particularly limited. If it is necessary to package the surface acoustic wave device by flip-chip bonding, before cutting the short-circuit wirings 16 and 17, FIGS.
Metal bumps 20, 20, 20, 2 shown in (a)
0 is preferably formed on the electrode pads 8A, 9A, 10A, and 11A. In this case, even if the piezoelectric substrate 1 is heated to promote mutual diffusion of metal,
Pyroelectric breakdown in the T electrodes 2 and 3 can be prevented.

Next, as shown in FIG. 3A and FIG. 5B, an insulating film 21 is formed on the entire surface of the piezoelectric substrate 1. The insulating film 21 is formed of a suitable insulating material such as SiO ₂ . The method for forming the insulating film 21 is not particularly limited, but sputtering can be used, for example.

Preferably, the thickness of the insulating film 21 is set so that the frequency of the first surface acoustic wave element 22 and the frequency of the second surface acoustic wave element 23 have desired values. That is, the frequency can be adjusted by adjusting the thickness of the insulating film 21.

As shown in FIGS. 3 (b) and 5 (c), the metal bump 20 of the first surface acoustic wave element 22 and the second surface acoustic wave element 23
It is desirable to remove the insulating film 21 on the upper surfaces of the metal bumps 20 and the electrode pads 8A to 11A, whereby the die shear strength can be increased.

In the method of manufacturing the surface acoustic wave device according to the present embodiment, the bus bar layers 3a and 3b of the IDT electrode 3 of the second surface acoustic wave element 23 are formed simultaneously with the formation of the IDT electrode 2 of the first surface acoustic wave element 22. 3b, electrode pad layers 10a and 11a and wiring electrode layers 14a and 15a are formed. Further, at the same time when the electrode fingers of the IDT electrode 3 of the second surface acoustic wave element are formed, the electrode pad layers 8a, 9a, 10a, 11a and the wiring electrode layer 12 of the first and second surface acoustic wave elements 22 and 23 are formed.
a, 13a, 14a, 15a and busbar layers 2a, 2
b, 3a, 3b, a second conductive film is also laminated, and electrode pads 8A, 9A, 10A, 11A, wiring electrodes 12A, 13A, 14A, 15A and bus bars 2A, 2 of a two-layer structure are formed.
B, 3A and 3B are formed.

Therefore, as compared with the conventional surface acoustic wave device,
In both the first and second surface acoustic wave elements, the electrode pads 8A to 11A and the wiring electrode 12A with respect to the piezoelectric substrate 1 are provided.
~ 15A and the like. Further, the electrode pad 8 may be used for bonding to the outside by a metal bump or the like.
A, 9A, 10A, and 11A are not easily damaged, and cracks in the piezoelectric substrate 1 are hardly generated.

As described above, the first surface acoustic wave element 22
The short-circuit wiring 16 is formed simultaneously with the formation of the electrode finger of the IDT electrode 2, and the short-circuit wiring 17 is formed on the second surface acoustic wave element 23 simultaneously with the formation of the electrode finger of the IDT electrode 3.
Is formed, even if the piezoelectric substrate 1 is heated when the resist is heated, when the metal bumps are formed, or when the insulating film is formed, pyroelectric breakdown of the IDT and damage to the resist are unlikely to occur.
In addition, since such short-circuit wirings 16 and 17 are formed at the same time in the step of forming the IDT electrode 2 or 3, an extra step for forming the short-circuit wiring is not required.

Further, in the manufacturing method of the present embodiment, the frequency can be adjusted by controlling the thickness of the insulating film 21, so that the frequency variation of the surface acoustic wave device can be suppressed, whereby the elasticity can be reduced. The yield of the surface acoustic wave device can be increased.

Further, in the surface acoustic wave device of this embodiment, the patterning of the electrodes can be performed with high accuracy. Therefore, the filter characteristics can be improved as shown in FIG. In FIG. 6, the solid line indicates the attenuation frequency characteristic of the surface acoustic wave device configured according to the present embodiment, and the broken line indicates
7 shows frequency characteristics of a conventional surface acoustic wave device prepared for comparison.

In the conventional surface acoustic wave device, the electrode pads of the first and second surface acoustic wave devices, the bus bar of the IDT electrode, and the wiring electrode are respectively provided by the first and second surface acoustic wave devices. Except for the fact that the IDT electrode was formed of a single conductive film equal to the thickness of the electrode finger, a structure similar to that of the above example was prepared.

As is apparent from FIG. 6, according to the present embodiment, the variation of the insertion loss in the band is small, and the steepness of the filter characteristic near the pass band is improved.

(Modification) Next, a modification of the above embodiment will be described. In this modification, the method of electrically connecting the electrode fingers of the IDT electrode 3 and the bus bar on the second surface acoustic wave element 23 side is changed. Other points are the same as in the first embodiment.

First, in the first embodiment described above, the thickness of the electrode finger of the IDT electrode of the first surface acoustic wave element 22 is larger than the thickness of the electrode finger of the IDT electrode of the second surface acoustic wave element. Is also thinner. Therefore, as shown in FIG. 7, in the surface acoustic wave device obtained through the manufacturing method of the above embodiment,
The bus bar 3B on the second surface acoustic wave element side is
Structure in which the second bus bar layer 3b ₁ is equal to the thickness of the electrode fingers of the IDT electrode of the second surface acoustic wave elements are stacked in the same thickness of the bus bar layer 3b and the electrode fingers of the IDT electrode of the surface acoustic wave device has, in this case, the electrode fingers 3c, since that would continuous with the second bus bar layer 3b ₁ directly busbar 3B
And the electrode finger 3c can be reliably connected electrically.

On the other hand, as shown in FIG. 8, the thickness of the electrode finger of the IDT of the first surface acoustic wave element is larger than the thickness of the electrode finger of the IDT electrode of the second surface acoustic wave element. You may. In this case, the bus bar 3B of the second surface acoustic wave element
Is a second busbar layer having the same thickness as the electrode finger 3c of the IDT electrode of the second surface acoustic wave element on the busbar layer 3b having the same thickness as the electrode finger of the IDT electrode of the first surface acoustic wave element. 3b ₁ is laminated. Therefore, the end face of the electrode finger 3c of the IDT electrode 3 contacts the side surface of the bus bar layer 3b of the bus bar 3B, and conduction between the bus bar 3B and the electrode finger 3c is achieved.

FIG. 9 is a sectional view for explaining still another modified example of the first embodiment. In the second modification, similarly to the modification shown in FIG.
Is thicker than the electrode finger of the IDT electrode of the second surface acoustic wave element. However,
The side surface of the busbar layer 3b is tapered so that the width decreases as going upward. Accordingly, in the finally obtained surface acoustic wave device, the electrode fingers 3c, is chosen as shown in the second bus bar layer 3b ₁ Togazu 9. Therefore, the reliability of the electrical connection between the electrode finger 3c and the bus bar 3B is improved as compared with the case of the modification shown in FIG.

In the above-described embodiment, the piezoelectric ceramics is shown as a material constituting the piezoelectric substrate 1.
The piezoelectric substrate 1 may be made of a piezoelectric single crystal such as TaO ₃ , LiNbO ₃ , quartz, lithium tetraborate, or langasite. Further, the piezoelectric substrate 1 may be formed by forming a piezoelectric thin film such as a ZnO thin film on an insulating substrate such as alumina.

Further, in the above embodiment, the reflectors 4, 5,
Although 6, 7 are provided, in the present invention, the surface acoustic wave device may have a structure without a reflector, and the structures of the reflector and the IDT electrode are not particularly limited.

As the material for forming the metal bumps and the material for forming the electrodes, various metal materials can be used in addition to Al or Al alloy. Further, the material constituting the insulating film 21 formed for frequency adjustment is not limited to SiO ₂ .

The present invention is not particularly limited to the surface acoustic wave device manufactured according to the present invention, and the present invention is applicable to the manufacture of various surface acoustic wave devices such as surface acoustic wave resonators, surface acoustic wave filters, and duplexers. Can be applied.

FIG. 10 is a schematic block diagram for explaining a communication device 160 using the surface acoustic wave device according to the present invention. In FIG. 10, a duplexer 162 is connected to an antenna 161. Between the duplexer 162 and the reception-side mixer 163, a surface acoustic wave filter 164 and an amplifier 165 constituting an RF stage are connected.
Further, a surface acoustic wave filter 169 in the IF stage is connected to the mixer 163. Further, an amplifier 16 constituting an RF stage is provided between the duplexer 162 and the mixer 166 on the transmission side.
7 and the surface acoustic wave filter 168 are connected.

As the surface acoustic wave filters 164 and 168 in the communication device 160, a surface acoustic wave device configured according to the present invention can be suitably used.

[0065]

In the method of manufacturing a surface acoustic wave device according to the first and second aspects of the present invention, at least the electrode pad of the second surface acoustic wave element is formed at the same time as the formation of the IDT electrode of the first surface acoustic wave element. In order to complete the electrodes of the second surface acoustic wave element, the electrode pads of the first and second surface acoustic wave elements are formed in two layers simultaneously with the formation of the IDT electrode of the second surface acoustic wave element. You. Therefore, an electrode pad having a two-layer structure can be formed only by using two electrode forming processes. Since both of the electrode pads of the first and second surface acoustic wave devices have a two-layer structure, the flip-flop is used. Cracks of the piezoelectric substrate in chip bonding or the like can be suppressed.

In addition, a short-circuit wire is formed when the IDT electrode of the first surface acoustic wave element is formed, and a part of the short-circuit wire is cut after forming the electrodes of the first and second surface acoustic wave elements. Therefore, even if heated in the electrode forming step, pyroelectric breakdown of the electrode, damage to the resist, and the like hardly occur.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams for explaining an electrode structure formed on a piezoelectric substrate and a shape of a resist formed on the electrode structure in a manufacturing method according to an embodiment of the present invention; Plan view.

FIGS. 2A and 2B are a plan view showing a state in which an electrode of a second surface acoustic wave element is formed in the manufacturing method according to one embodiment of the present invention, and formation of a metal bump and wiring for short-circuiting; FIG. 6 is a plan view showing a state after cutting.

3A and 3B are a plan view showing a state in which an insulating film is formed and a plan view showing a state in which a part of the insulating film is removed in the manufacturing method according to one embodiment of the present invention.

FIGS. 4A to 4D are schematic cross-sectional views for explaining an electrode forming step in the manufacturing method according to one embodiment of the present invention, in which two parts are combined.

FIGS. 5A to 5C are schematic cross-sectional views showing a state in which a bump is formed, an insulating film is formed, and a part of the insulating film is removed in the manufacturing method according to one embodiment of the present invention. Yes,
The figure where two parts are combined.

FIG. 6 shows attenuation frequency characteristics of a surface acoustic wave device obtained according to an embodiment of the present invention and a conventional surface acoustic wave device.

FIG. 7 is a partially cutaway cross-sectional view for explaining an electrical connection structure between an electrode finger of an IDT of the second surface acoustic wave element and a bus bar in the first embodiment.

FIG. 8 is a partially cutaway cross-sectional view illustrating an electrical connection structure between an electrode finger of an IDT and a bus bar of a second surface acoustic wave element according to a first modification.

FIG. 9 is a partially cutaway cross-sectional view illustrating an electrical connection structure between an electrode finger of an IDT and a bus bar of a second surface acoustic wave element according to a second modification.

FIG. 10 is a schematic block diagram for explaining a communication device using the surface acoustic wave device according to the present invention.

11A to 11F are cross-sectional views illustrating an example of a conventional method for manufacturing a surface acoustic wave device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Piezoelectric substrate 2, 3 ... IDT electrode 2A, 2B, 3A, 3B ... Bus bar 2a, 2b, 3a, 3b ... Bus bar layer 4, 5, 6, 7 ... Reflector 8A, 9A, 10A, 11A ... Electrode pad 8a , 9a, 10a, 11a ... electrode pad layers 12A, 13A, 14A, 15A ... wiring electrodes 12a, 13a, 14a, 15a ... wiring electrode layers 16, 17 ... short-circuit wiring 18 ... first resist 19 ... second conductive Film 20 Bump 21 Insulating film 22 23 First and second surface acoustic wave elements 160 Communication device 161 Antenna 162 Duplexer 163 166 Mixer 164 Surface acoustic wave filter 165 Amplifier 167 Amplifier 168 ... Surface acoustic wave filter

Claims (10)

[Claims] An IDT electrode having a plurality of comb-shaped electrodes and an electrode pad connected to the IDT electrode and first and second surface acoustic wave elements having different electrode thicknesses are formed on a piezoelectric substrate. A method of manufacturing a surface acoustic wave device, comprising: an IDT electrode of the first surface acoustic wave element; an electrode pad layer that is a partial layer of an electrode pad; and at least the electrode of a second surface acoustic wave element. Forming an electrode pad layer that is a partial layer of a pad, and a short-circuit wiring that connects a plurality of comb-shaped electrodes of the IDT electrode of the first surface acoustic wave element; and the first surface acoustic wave element Applying a resist to a region where the IDT electrode and the electrode pad layer are formed and a region including at least a portion where the electrode pad layer is formed of the second surface acoustic wave element, and heating the second surface acoustic wave element; Surface acoustic wave device Removing the resist on the region where is formed and the region where at least the electrode pad layer of the first surface acoustic wave element is formed; and an electrode film of the IDT electrode of the second surface acoustic wave element Manufacturing a surface acoustic wave device, comprising: a step of forming a conductive film having a thickness equal to the thickness; a step of lifting off the resist and the conductive film provided on the resist; and a step of cutting the short-circuit wiring. Method. 2. An IDT electrode having a plurality of comb-shaped electrodes and first and second surface acoustic wave elements having electrode thicknesses different from each other and having electrode pads connected to the IDT electrodes are formed on a piezoelectric substrate. A method of applying a first resist to the entire surface of the piezoelectric substrate, wherein an IDT electrode and an electrode pad layer of the first surface acoustic wave element are formed. At the same time as removing the resist in the region and the region where at least the electrode pad layer of the second surface acoustic wave element is formed, the short-circuit wiring connecting the plurality of IDT electrodes of the first surface acoustic wave element is formed. Removing a resist on a portion to be provided; forming a conductive film having a thickness equal to the electrode thickness of the IDT electrode of the first surface acoustic wave element; and the first resist and the first resist Granted on Is lifted off the conductive film has, I of the first surface acoustic wave element
A DT electrode, an electrode pad layer which is a part of the electrode pad,
Forming an electrode pad layer that is a part of an electrode pad of the second surface acoustic wave element and the short-circuit wiring; and an IDT electrode and an electrode pad layer of the first surface acoustic wave element and a second step. Applying a second resist to a region including at least a portion where the electrode pad layer is formed of the surface acoustic wave element, and heating; and Removing a second resist on at least a region of the first surface acoustic wave element on which the electrode pad layer is formed; and a conductive film having a thickness equal to the electrode thickness of the IDT electrode of the second surface acoustic wave element. A method of manufacturing a surface acoustic wave device, comprising: a step of forming a film; a step of lifting off the second resist and a conductive film formed on the second resist; and a step of cutting the short-circuit wiring. . 3. In the step of removing the resist on the region where the second surface acoustic wave element is formed and on the region where at least the electrode pad of the first surface acoustic wave element is formed, The resist on the portion where the short-circuit wiring for connecting the plurality of IDT electrodes of the surface acoustic wave element is provided is removed, and the short-circuit wiring is also formed on the second surface acoustic wave element side by forming a conductive film and lifting off. Is formed, and further comprising a step of forming a metal bump on each of the electrode pads after the formation and lift-off of the conductive film on the second surface acoustic wave element side. In the step of cutting the short-circuit wiring, The method for manufacturing a surface acoustic wave device according to claim 1, wherein the short-circuit wiring provided on the surface acoustic wave element side is also cut. 4. The film thickness of the IDT electrode of the first surface acoustic wave device is smaller than the film thickness of the IDT electrode of the second surface acoustic wave device. Manufacturing method of a surface acoustic wave device. 5. An IDT electrode of the first surface acoustic wave element, wherein the thickness of the IDT electrode of the first surface acoustic wave element is greater than the thickness of the IDT electrode of the second surface acoustic wave element. The second surface acoustic wave element formed at the same time as the electrodes has a shape tapered on the side surface so that the cross section of at least the electrode pad layer of the second surface acoustic wave element becomes thinner upward. A method for manufacturing the surface acoustic wave device according to any one of the above. 6. The method for manufacturing a surface acoustic wave device according to claim 1, further comprising a step of forming an insulating film on the piezoelectric substrate after cutting the short-circuit wiring. 7. The method for manufacturing a surface acoustic wave device according to claim 6, further comprising, after forming the insulating film, removing a portion of the insulating film at least in a region where the electrode pad is formed. 8. The method for manufacturing a surface acoustic wave device according to claim 7, further comprising a step of etching at least an electrode pad surface after the step of removing the insulating film on the metal bump. 9. The method of manufacturing a surface acoustic wave device according to claim 6, further comprising a step of adjusting a frequency of the surface acoustic wave element by reducing a thickness of the insulating film. 10. A communication device comprising a surface acoustic wave device obtained by the method for manufacturing a surface acoustic wave device according to claim 1 as a bandpass filter.