JP5195443B2 - Elastic wave device - Google Patents

Description

  The present invention relates to an elastic wave device, and more particularly, to an elastic wave device having an IDT electrode and using an elastic wave such as a surface acoustic wave or a boundary acoustic wave.

  In recent years, there has been an increasing demand for lower loss for acoustic wave devices such as elastic surface filters used in the RF stage of communication devices such as mobile phones. Along with this, for example, in the following Patent Documents 1 to 3 and the like, various techniques for reducing the loss of the acoustic wave device by suppressing the transverse mode spurious have been proposed.

  For example, the following Patent Document 1 discloses a surface acoustic wave device shown in FIG. 21 as an acoustic wave device capable of suppressing transverse mode spurious. As shown in FIG. 21, the surface acoustic wave device 100 includes an IDT electrode 101, and first and second reflectors 102 and 103 disposed on both sides of the IDT electrode 101 in the surface acoustic wave propagation direction. Yes. The IDT electrode 101 of the surface acoustic wave device 100 is a regular IDT electrode in which the crossing width of the electrode fingers is shortened by providing the dummy electrode 104. The IDT electrode 101 is formed such that a line L100 formed by connecting the intersections of the bus bar and the electrode fingers is inclined with respect to the surface acoustic wave propagation direction, and the length of the adjacent dummy electrode 104 changes. Has been.

  Patent Document 2 below also describes that transverse mode spurious can be suppressed by providing a dummy electrode and changing the crossing width of the electrode fingers, as in Patent Document 1 described above. In Patent Document 2 below, W / W0 is set to 0.65 or more and 0.75 or less, particularly when the waveguide length of the waveguide portion of the IDT electrode is W0 and the cross width of the electrode fingers is W. Thus, it is described that the transverse mode spurious can be effectively suppressed.

Further, Patent Document 3 below describes that transverse mode spurious can be suppressed by applying cross width weighting to the IDT electrode. Specifically, Patent Document 3 describes a surface acoustic wave device having an IDT electrode 200 shown in FIG. Patent Document 3 describes that transverse mode spurious can be suppressed by applying cross width weighting to the IDT electrode 200 so that the cross width weighting envelope L200 satisfies the following expression.
Y = ± cos ⁻¹ (| αX |) · cos (βX)
However,
X axis: surface acoustic wave propagation direction,
Y axis: intersecting width direction perpendicular to the surface acoustic wave propagation direction X,
Of the IDT electrodes _{ranges: -X 0/2 ≦ X ≦} X 0/2,
0 <α ≦ π / X ₀ ,
0 <β ≦ π / X ₀ ,
It is.

WO2006 / 078001 A1 JP 2006-35264 A Japanese Patent Application Laid-Open No. 07-22898

  However, as a result of earnest research by the present inventors, it is merely a normal IDT electrode in which the cross width of the electrode fingers is shortened by providing a dummy electrode, and the length of the adjacent dummy electrode is changed, or the IDT electrode It has been found that the transverse mode spurious cannot be sufficiently suppressed or the insertion loss is deteriorated only by applying the cross width weighting.

  An object of the present invention is to provide an acoustic wave device in which transverse mode spurious is sufficiently suppressed and insertion loss is low.

  An elastic wave device according to the present invention relates to an elastic wave device including a piezoelectric substrate and a regular IDT electrode formed on the piezoelectric substrate. In the acoustic wave device according to the present invention, the normal IDT electrode includes first and second bus bars, a plurality of first electrode fingers, a plurality of second electrode fingers, and a first dummy electrode. And a second dummy electrode. The plurality of first electrode fingers extend from the first bus bar toward the second bus bar. The plurality of second electrode fingers extend from the second bus bar toward the first bus bar. The plurality of second electrode fingers are interleaved with the plurality of first electrode fingers. The first dummy electrode is opposed to the tip of the second electrode finger via a gap. The first dummy electrode is connected to the first bus bar. The second dummy electrode is opposed to the tip of the first electrode finger via a gap. The second dummy electrode is connected to the second bus bar. The elastic wave device according to the present invention includes a first film and a second film. The first film is formed so as to cover at least a part of the first dummy electrode and at least a part of the first electrode finger so as not to reach the gap. The second film is formed so as to cover at least a part of the second dummy electrode and at least a part of the second electrode finger so as not to reach the gap. Each of the end face on the second bus bar side of the first film and the end face on the first bus bar side of the second film is inclined with respect to the elastic wave propagation direction.

  In a specific aspect of the present invention, each of the first and second films is a metal film. According to this configuration, the electrical resistance of the regular IDT electrode can be reduced. Therefore, the insertion loss can be further reduced.

  In another specific aspect of the present invention, each of the first and second films includes the first or second bus bar and at least a part of the first or second dummy electrode and the first or second electrode finger. The AlCu film made of an AlCu alloy, the AlCu film, the Ti film made of Ti, the Ti film, and the AlCu film made of AlCu. And an Al film.

  In another specific aspect of the present invention, each of the first and second films includes at least a part of the first or second bus bar and the first or second dummy electrode and the first or second electrode finger. And a Ti film made of Ti, and an AlCu film made of an AlCu alloy.

  In still another specific aspect of the present invention, the acoustic wave device is formed between the first electrode finger and the first film and between the second electrode finger and the second film. A first dielectric film is further provided.

  In still another specific aspect of the present invention, the acoustic wave device is substantially in plane with the first and second electrode fingers between the adjacent first electrode fingers and between the adjacent second electrode fingers. And a second dielectric layer formed to be unity.

  In another specific aspect of the present invention, a plurality of normal IDT electrodes are provided along the elastic wave propagation direction, and at least one normal IDT electrode among the plurality of normal IDT electrodes is an input-side IDT electrode. At least one IDT electrode of the normal type IDT electrodes other than the input side IDT electrode among the plurality of normal type IDT electrodes is set as the output side IDT electrode. According to this configuration, it is possible to provide a longitudinally coupled resonator type acoustic wave device in which transverse mode spurious is sufficiently suppressed and insertion loss is small.

  In still another specific aspect of the present invention, the surface acoustic wave device is a surface acoustic wave device that uses surface acoustic waves.

  In still another specific aspect of the present invention, the elastic wave device is a boundary acoustic wave device using a boundary acoustic wave.

  The elastic wave device according to the present invention is formed so as to cover at least a part of the first bus bar and the first dummy electrode and at least a part of the first electrode finger and not to reach the gap. The first film, the second bus bar and the second dummy electrode, and the second electrode finger are formed so as to cover at least a part of the second electrode bar and at least a part of the second electrode finger so as not to reach the gap. And an end face of the first film on the second bus bar side and an end face of the second film on the first bus bar side are inclined with respect to the elastic wave propagation direction. Therefore, the transverse mode is scattered, so that the transverse mode spurious can be sufficiently suppressed, and the insertion loss can be reduced.

1 is a schematic plan view of an acoustic wave device according to an embodiment. It is the II-II arrow line view in FIG. It is an III-III arrow line view in FIG. It is a typical top view for explaining the plane shape of the 1st and 2nd films. It is a top view which shows typically the excitation observation result in a 1st Example. It is a graph showing the impedance characteristic of the elastic wave apparatus of a 1st Example. It is a schematic plan view for demonstrating the planar shape of the 1st and 2nd film | membrane in a 2nd Example. It is a graph showing the impedance characteristic of the elastic wave apparatus of a 2nd Example. It is a schematic plan view for demonstrating the planar shape of the 1st and 2nd film | membrane in a 3rd Example. It is a graph showing the impedance characteristic of the elastic wave apparatus of a 3rd Example. It is a schematic plan view for demonstrating the planar shape of the 1st and 2nd film | membrane in a 4th Example. It is a graph showing the impedance characteristic of the elastic wave apparatus of a 4th Example. It is a schematic plan view of an elastic wave device according to a first comparative example. It is a XIV-XIV arrow line view in FIG. It is a top view which shows typically the excitation observation result in a 1st comparative example. It is a graph showing the impedance characteristic of the elastic wave apparatus of a 1st comparative example. It is a top view which shows typically the excitation observation result in the 2nd comparative example. It is a top view which shows typically the excitation observation result in the 2nd comparative example. It is a schematic sectional drawing of the elastic wave apparatus which concerns on a 1st modification. It is a typical top view of the elastic wave device concerning the 2nd modification. 1 is a schematic plan view showing a part of a surface acoustic wave device described in Patent Document 1. FIG. 10 is a schematic plan view showing an IDT electrode of a surface acoustic wave device described in Patent Document 3. FIG.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

  FIG. 1 is a schematic plan view of an elastic wave device according to the present embodiment, and FIGS. 2 and 3 are schematic cross-sectional views of the elastic wave device according to the present embodiment. FIG. 4 is a schematic plan view for explaining the planar shapes of the first and second films in the present embodiment. A surface acoustic wave device 1 shown in FIGS. 1 to 4 is a surface acoustic wave device as a 1-port resonator using surface acoustic waves. 1 to 3 are schematic diagrams, and the number of electrode fingers and the like are described fewer than the actual number. Further, in FIG. 1, the first and second films 23 and 24 are also schematically illustrated, and the actual planar shape of the first and second films 23 and 24 in this embodiment is shown in FIG. Have been described.

As shown in FIGS. 2 and 3, the acoustic wave device 100 includes a piezoelectric substrate 13. In the present embodiment, the piezoelectric substrate 13 is configured by a LiNbO ₃ substrate having a cut angle of 126 °. However, the piezoelectric substrate 13 may be formed by a piezoelectric material other than LiNbO _3, such as LiTaO _3.

  An electrode 17 shown in FIG. 1 is formed on the piezoelectric substrate 13. The electrode 17 includes a normal IDT electrode 10 and first and second reflectors 11 and 12 disposed on both sides of the normal IDT electrode 10 in the surface acoustic wave propagation direction x. Here, the “regular IDT electrode” is an IDT electrode in which the cross width of the electrode finger is constant in the propagation direction x of the surface acoustic wave.

  As shown in FIG. 1, the normal IDT electrode 10 includes first and second comb electrodes 10 a and 10 b that are interleaved with each other. The first comb electrode 10a includes a first bus bar 10c and a plurality of first electrode fingers 10d arranged along the surface acoustic wave propagation direction x. Each of the plurality of first electrode fingers 10d is connected to the first bus bar 10c. The plurality of first electrode fingers 10d extend from the first bus bar 10c toward the second bus bar 10f. Similarly, the second comb electrode 10b includes a second bus bar 10f and a plurality of second electrode fingers 10g arranged in the surface acoustic wave propagation direction x. Each of the plurality of second electrode fingers 10g is connected to the second bus bar 10f. The plurality of second electrode fingers 10g extend from the second bus bar 10f toward the first bus bar 10c. The plurality of second electrode fingers 10g and the plurality of first electrode fingers 10d are interleaved with each other.

  The first comb electrode 10a is provided with a plurality of first dummy electrodes 10e arranged along the surface acoustic wave propagation direction x and connected to the first bus bar 10c. . The first dummy electrode 10e faces the tip of the second electrode finger 10g via a gap. On the other hand, the second comb electrode 10b is provided with a plurality of second dummy electrodes 10h arranged along the surface acoustic wave propagation direction x and connected to the second bus bar 10f. . The second dummy electrode 10h is opposed to the tip of the first electrode finger 10d via a gap. Thus, in the present embodiment, the cross width of the electrode fingers is reduced by providing the first and second dummy electrodes 10e and 10h.

  The electrode 17 can be formed of an appropriate conductive material such as Cu, Al, Ag, Au, or Pt. For example, the electrode 17 may be formed of a laminated film in which a plurality of conductive films are laminated. Specifically, in the present embodiment, as shown in FIGS. 2 and 3, the electrode 17 is formed on the piezoelectric substrate 13, and includes a Ti film 14 as an adhesion layer made of Ti, and a Ti film 14. Formed of a laminated film of a Cu layer 15 as a main conductive film made of Cu, and an AlCu film 16 as a protective layer made of AlCu, formed on the Cu layer 15. Yes. For example, the thicknesses of the Ti film 14, the Cu film 15, and the AlCu film 16 are not particularly limited, but may be, for example, a Ti film 14:20 nm, a Cu film 15:48 nm, and an AlCu film 16:10 nm.

As shown in FIGS. 2 and 3, in the region where the electrode 17 is formed, a portion where the electrode 17 is not formed has a second dielectric layer 18 which is substantially flush with the electrode 17. Is formed. The second dielectric layer 18 fills the grooves between the electrode fingers. The second dielectric layer 18 is not particularly limited, but can be composed of, for example, a SiO ₂ film or a silicon nitride film.

A first dielectric layer 19 for improving the frequency temperature characteristic is formed on the electrode 17. Specifically, the first dielectric layer 19 is formed of a dielectric material such as SiO ₂ or silicon nitride, for example.

  Specifically, the first dielectric layer 19 is formed on a region of the IDT electrode 10 where a surface acoustic wave is excited. That is, the first dielectric layer 19 is formed so as to cover the first and second electrode fingers 10d and 10g and the second dielectric layer 18 between the first and second electrode fingers 10d and 10g. ing. Note that at least a part of the first and second bus bars 10 c and 10 f is not covered with the first dielectric layer 19.

  As shown in FIG. 1, the acoustic wave device 1 of the present embodiment covers at least a part of the first bus bar 10c and the first dummy electrode 10e and at least a part of the first electrode finger 10d. In addition, a first film 23 is formed. That is, the first film 23 may cover at least part of the first electrode finger 10d and at least part of the first bus bar 10c, or at least part of the first electrode finger 10d. Further, at least a part of the first dummy electrode 10e may be covered. Further, the first film 23 may cover at least a part of the first electrode finger 10d, at least a part of the first bus bar 10c, and at least a part of the first dummy electrode 10e. . The first film 23 is formed so as not to reach the gap between the electrode finger and the dummy electrode.

  The acoustic wave device 1 is formed so as to cover at least a part of the second bus bar 10f and the second dummy electrode 10h and at least a part of the second electrode finger 10g. That is, the second film 24 may cover at least a part of the second electrode finger 10g and at least a part of the second bus bar 10f, or at least one of the second electrode finger 10g. And at least a part of the second dummy electrode 10h may be covered. The second film 24 may cover at least a part of the second electrode finger 10g, at least a part of the second bus bar 10f, and at least a part of the second dummy electrode 10h. . The second film 24 is formed so as not to reach the gap between the electrode finger and the dummy electrode.

  The end face 23a on the second bus bar 10f side of the first film 23 and the end face 24a on the first bus bar 10c side of the second film 24 are inclined with respect to the surface acoustic wave propagation direction x. ing. Therefore, as will be supported in the following embodiments, the reflection of the surface acoustic wave becomes irregular in the region where the first and second films 23 and 24 are formed, and a transverse mode standing wave is generated. This can be suppressed. As a result, the transverse mode spurious can be sufficiently suppressed, and the insertion loss can be reduced.

  In the present embodiment, the portions of the end face 23a of the first film 23 and the end face 24a of the second film 24 facing each other in the cross width direction y orthogonal to the surface acoustic wave propagation direction x are non-parallel. It is. However, the portions of the end face 23a of the first film 23 and the end face 24a of the second film 24 facing each other in the cross width direction y orthogonal to the elastic wave propagation direction x may be parallel.

  The first and second films 23 and 24 are formed so as not to reach the gap. For this reason, the first and second films 23 and 24 do not exist at the intersections of the first and second electrode fingers 10d and 10g. For this reason, the first and second films 23 and 24 hardly affect the main modes of the surface acoustic waves concentrated at the intersections of the first and second electrode fingers 10d and 10g.

  The shape of the first and second films 23 and 24 is not particularly limited as long as it is a shape capable of irregularly reflecting a surface acoustic wave so as not to generate a transverse mode standing wave. Specifically, in the plan view, the shapes of the first and second films 23 and 24 are not particularly limited as long as the end faces 23a and 24a are inclined with respect to the propagation direction of the surface acoustic wave x.

  Specifically, in this embodiment, as shown in FIGS. 1 and 4, the end surfaces 23 a of the first film 23 are parallel to each other so as to face a predetermined angle with respect to the surface acoustic wave propagation direction x. The plurality of first end surface portions 23b that are positioned and the plurality of second end surface portions 23c that are positioned in parallel to each other so as to face different directions from the first end surface portion 23b. . The first and second end face portions 23b and 23c are alternately positioned in the surface acoustic wave propagation direction x.

  The end face 24a of the second film 24 includes a plurality of first end face parts 24b and first end face parts 24b that are positioned in parallel to each other so as to face a predetermined angle with respect to the surface acoustic wave propagation direction x. And a plurality of second end face portions 24c positioned in parallel to each other so as to face different directions. The first and second end face portions 24b and 24c are alternately positioned in the surface acoustic wave propagation direction x. The first end surface portion 24b of the second film 24 faces the first end surface portion 23b of the first film 23 in the cross width direction y. The first end surface portion 24b and the first end surface portion 23b are not parallel to each other. Further, the second end face portion 24 c of the second film 24 faces the second end face portion 23 c of the first film 23 in the cross width direction y. The second end surface portion 24c and the second end surface portion 23c are not parallel to each other.

  As shown in FIG. 2, since the first dielectric layer 19 is not formed on the first and second bus bars 10c and 10f, the first and second films 23 and 24 are formed as follows. And the second bus bars 10c and 10f.

  The first and second films 23 and 24 are not particularly limited as long as they can reflect the transverse mode. The first and second films 23 and 24 can be composed of one or more metal films, for example. By configuring the first and second films 23 and 24 with metal films, the electrical resistance of the first and second bus bars 10c and 10f can be reduced, and therefore the insertion loss can be further reduced. Because.

  As shown in FIG. 2, in the present embodiment, specifically, the first and second films 23 and 24 are formed on the electrode 17, and an AlCu film 20 made of an AlCu alloy and an AlCu film are formed. The Ti film 21 is made of Ti, and the Ti film 21 made of Ti and the Al film 22 made of Al are formed on the Ti film 21.

  The film thickness of the first and second films 23 and 24 is not particularly limited, but the transverse mode vibration below the first and second films 23 and 24 is caused by the first and second films 23 and 24. The thickness is preferably not transmitted to 24 surfaces. Specifically, the film thicknesses of the first and second films 23 and 24 can be set to about 500 nm to 1500 nm.

  Next, a method for manufacturing the acoustic wave device 1 of the present embodiment will be described. First, the piezoelectric substrate 13 is prepared. Next, a preceding film is formed on the entire surface of the piezoelectric substrate 13. The method for forming the preceding film can be appropriately selected depending on the material for forming the preceding film. The preceding film can be formed by, for example, a sputtering method or a vapor deposition method.

  Next, a resist film having an opening corresponding to the shape of the electrode 17 is formed on the preceding film. Then, the portion corresponding to the opening of the preceding film is removed by etching from above the resist film. Next, a conductive film is formed on the resist film. The method for forming the conductive film is not particularly limited. The conductive film can be formed by, for example, a sputtering method or an evaporation method. Next, the second dielectric layer 18 and the electrode 17 are formed by removing the resist film and the conductive film on the resist film by lift-off.

  Next, a dielectric film is formed on the piezoelectric substrate 13. Then, the first dielectric layer 19 is formed from the dielectric film by patterning the dielectric film into a desired shape. Specifically, a resist film having a predetermined pattern is formed on the dielectric film. After etching from above the resist film, the first dielectric layer 19 is formed by peeling the resist film.

  Finally, the first and second films 23 and 24 are formed on the piezoelectric substrate 13. Specifically, a resist film having an opening having a shape corresponding to the shape of the first and second films 23 and 24 is formed on the piezoelectric substrate 13. A film is formed on the resist film, and the first and second films 23 and 24 are formed by peeling the resist film. The elastic wave device 1 can be completed through the above steps.

  The elastic wave device 1 of the present embodiment described above can be used for, for example, a longitudinally coupled resonator type elastic wave filter, a shared antenna device such as a duplexer, a triplexer, and the like. In the acoustic wave device 1, the transverse mode spurious is suppressed. Therefore, by configuring the longitudinally coupled resonator type acoustic wave filter and the antenna duplexer using the acoustic wave device 1, it is possible to suppress the spurious in the passband. it can.

  In the present embodiment, the surface acoustic wave device is taken as an example of the surface acoustic wave device embodying the present invention, but the surface acoustic wave device according to the present invention is not limited to the surface acoustic wave device. For example, the elastic wave device according to the present invention may be a boundary acoustic wave device using a boundary acoustic wave. In that case, the first dielectric layer 19 shown in FIGS. 2 and 3 is formed to a thickness such that the boundary acoustic wave is excited.

  Hereinafter, the present invention will be specifically described with reference to examples. In the following description, members having substantially the same functions as those of the above-described embodiment are referred to by common reference numerals, and description thereof is omitted.

(First embodiment)
In this embodiment, the elastic wave device 1 shown in FIGS. 1 to 4 is manufactured according to the following design parameters, and a frequency (1005 MHz) corresponding to the spurious in the seventh-order transverse mode is generated using a laser micro displacement meter. The excitation was observed when applied to the device. Further, impedance (Z) measurement was performed at a frequency in the range of 980 MHz to 1060 MHz. The excitation observation result of the elastic wave device of the first example is shown in FIG. Moreover, the impedance measurement result is shown in FIG. The data shown in FIG. 5 and the following FIG. 15 and FIG. 18 is data when the crossover width is 6.4λ. Here, λ is the wavelength of the IDT electrode and is 3.74 μm in this embodiment. In FIG. 5 and FIGS. 15 and 18 described below, a thick solid line represents a large displacement in the positive direction, a thin solid line represents a small displacement in the positive direction, a thick broken line represents a large displacement in the negative direction, and a thin broken line represents a negative displacement. Represents a small displacement in direction. Moreover, the area | region where the continuous line and the broken line are not described represents the area | region where the standing wave was not observed. In FIG. 6 and the graphs shown in FIGS. 8, 10, 12 and 16 below, the solid line indicates a graph with a crossing width of 6.4λ, and the dashed line indicates a crossing width of 9.6λ. The two-dot broken line shows the graph when the crossover width is 11.2λ.

Piezoelectric substrate 13: LiNbO ₃ substrate with a cut angle of 126 ° Ti film 14 thickness: 20 nm
Cu film 15 thickness: 48 nm
The thickness of the AlCu film 16: 10 nm
First and second dielectric layers 19, 18: SiO ₂ film Thickness of first dielectric layer 19: 276 nm
IDT electrode 10 pitch: 1.87 μm
Aperture length: 16λ (where λ is the wavelength of the surface acoustic wave to be excited)
Number of electrode fingers: 321 Crossing width: 6.4λ, 9.6λ, 11.2λ
The thickness of the AlCu film 20: 500 nm
Ti film 21 thickness: 200 nm
Al film 22 thickness: 1140 nm
Number of peaks formed by the first end surface portions 23b, 24b and the second end surface portions 23c, 24c: 16 each

(Second embodiment)
FIG. 7 is a schematic plan view for explaining the planar shapes of the first and second films in the second embodiment. In the second embodiment, except that the shapes of the first and second films 23 and 24 are different, an elastic wave device similar to that in the first embodiment is manufactured, and the same as in the first embodiment. Thus, impedance (Z) measurement was performed. The impedance measurement results are shown in FIG.

  Specifically, in the second embodiment, as compared with the first embodiment described above, the peak portion constituted by the first end surface portions 23b and 24b and the second end surface portions 23c and 24c is formed. The quantity has been reduced. Specifically, the number of peaks formed by the first end surface portions 23b and 24b and the second end surface portions 23c and 24c in the second embodiment is four.

(Third embodiment)
FIG. 9 is a schematic plan view for explaining the planar shapes of the first and second films in the third embodiment. In the third embodiment, except that the shapes of the first and second films 23 and 24 are different, an elastic wave device similar to that in the first embodiment is manufactured, and the same as in the first embodiment. Thus, impedance (Z) measurement was performed. The impedance measurement result is shown in FIG.

  Specifically, in the third embodiment, the end surfaces 23a and 24a are constituted by a pair of first end surface portions 23b and 24b and second end surface portions 23c and 24c. In the third embodiment, the first end surface portions 23b and 24b and the second end surface portions 23c and 24c are spaced along the intersecting width direction y between the first film 23 and the second film 24. Is formed so as to be largest at the central portion in the elastic wave propagation direction x.

(Fourth embodiment)
FIG. 11 is a schematic plan view for explaining the planar shapes of the first and second films in the fourth embodiment. In the fourth embodiment, an elastic wave device similar to that of the first embodiment is manufactured except that the shapes of the first and second films 23 and 24 are different, and the same as the first embodiment. Thus, impedance (Z) measurement was performed. The impedance measurement result is shown in FIG.

  Specifically, in the fourth embodiment, the end surfaces 23a and 24a are constituted by a pair of first end surface portions 23b and 24b and second end surface portions 23c and 24c. In the fourth embodiment, the first end surface portions 23b and 24b and the second end surface portions 23c and 24c are spaced along the intersecting width direction y between the first film 23 and the second film 24. Is formed to be the smallest in the central portion in the elastic wave propagation direction x.

(First comparative example)
FIG. 13 is a schematic plan view of an acoustic wave device according to a first comparative example. FIG. 14 is a schematic cross-sectional view of an acoustic wave device according to a first comparative example. As shown in FIGS. 13 and 14, in the first comparative example, an elastic wave device similar to that in the first example is manufactured except that the first and second films 23 and 24 are not provided. In the same manner as in the first embodiment, excitation was observed using a laser micro displacement meter and impedance (Z) measurement was performed. FIG. 15 shows the excitation observation result of the elastic wave device of the first example. The results of impedance measurement are shown in FIG.

(Second comparative example)
FIG. 17 is a schematic plan view of an elastic wave device according to a second comparative example. As shown in FIG. 17, in the second comparative example, instead of providing the first and second films 23 and 24, the end surfaces of the first and second bus bars 10c and 10f are inclined with respect to the elastic wave propagation direction. An elastic wave device 300 was produced in the same manner as in the first example except that the above was performed. And about the produced elastic wave apparatus, it observed the excitation using the laser micro displacement meter like the said 1st Example. The excitation observation result of the elastic wave device of the second comparative example is shown in FIG.

  From the results shown in FIG. 16, in the first comparative example in which the first and second films 23 and 24 are not provided and the regular IDT electrode is used, the odd-orders of the third order to the eleventh order are used. It can be seen that the transverse mode is excited, and transverse mode spurs corresponding to these odd-order transverse modes are generated. As shown in FIG. 15, when a 7th-order transverse mode spurious frequency (1005 MHz) is applied, it has seven antinodes along the cross width direction y and is parallel to the elastic wave propagation direction. Since the extending 7th-order standing wave is observed, it can be seen from the observation result shown in FIG. 15 that the 7th-order odd-order transverse mode is excited.

  Similarly, from the result shown in FIG. 18, the first and second films 23 and 24 are not provided, and the end surfaces of the first and second bus bars 10c and 10f are inclined with respect to the elastic wave propagation direction. Also in the case of the comparative example, it can be seen that an odd-order transverse mode occurs.

  From this result, the first and second films 23 and 24 are not provided and a normal IDT electrode is used, or the first and second films 23 and 24 are not provided. It can be seen that when the end surfaces of the second bus bars 10c and 10f are inclined with respect to the elastic wave propagation direction, the transverse mode spurious due to the standing wave of the transverse mode cannot be sufficiently suppressed. Note that the even-order transverse mode is not excited because it is electrically canceled in the electrode.

  On the other hand, in the first to fourth embodiments in which the first and second films 23 and 24 are provided, the first and second results are obtained from the results shown in FIGS. It can be seen that odd-order transverse mode spurious is suppressed regardless of the shapes of the films 23 and 24. This is considered to be because the transverse mode is scattered and the vibration of the transverse mode is weakened at the end faces 23a and 24a inclined with respect to the elastic wave propagation direction. The fact that the transverse mode is scattered is supported by the fact that the transverse mode is along the direction inclined with respect to the elastic wave propagation direction in FIG.

  In FIG. 5, the transverse mode was not observed in the portion where the first and second films 23 and 24 existed. This is because the vibration on the surfaces of the first and second films 23 and 24 was observed. This is because the transverse mode vibrations are present below the first and second films 23 and 24. The transverse mode vibration below the first and second films 23 and 24 is attenuated as the distance from the piezoelectric substrate 13 increases in the thickness direction of the first and second films 23 and 24, and the first and second films 23. , 24 is not substantially transmitted to the surface.

(First modification)
In the above embodiment, the example in which the first and second films 23 and 24 are constituted by the AlCu film 20, the Ti film 21, and the Al film 22 has been described. However, in the present invention, the configuration of the first and second films 23 and 24 is not limited to this configuration. For example, as shown in FIG. 19, the first and second films 23 and 24 are formed on the electrode 17, are formed on the Ti film 25 made of Ti, and the Ti film 25, You may be comprised by the AlCu film | membrane 26 which consists of AlCu. The first and second films 23 and 24 may be formed of a single metal film or may be formed of a film other than the metal film.

  In the present embodiment, the first end surface portions 23b and 24b and the second end surface portions 23c and 24c are described as being linear in a plan view. However, the first end surface portions 23b and 24b and the second end surface portions 23b and 24b The end surface portions 23c and 24c may not be linear in a plan view, but may be curved.

(Second modification)
In the above embodiment, the surface acoustic wave device as a one-port resonator using surface acoustic waves has been described. However, the acoustic wave device of the present invention is not limited to a 1-port resonator. The present invention is also applicable to a longitudinally coupled resonator type acoustic wave filter. That is, the acoustic wave device of the present invention may be a longitudinally coupled resonator type acoustic wave filter as shown in FIG.

  A longitudinally coupled resonator type acoustic wave filter 1a shown in FIG. 20 has a plurality of regular IDT electrodes 10 shown in FIG. Specifically, the longitudinally coupled resonator type elastic wave filter 1a includes three normal IDT electrodes 10j, 10k, and 10l arranged along the elastic wave propagation direction x. Of the three normal type IDT electrodes 10j, 10k, 10l, the central normal type IDT electrode 10k is connected to the input terminal and constitutes an input side IDT electrode. Further, the regular IDT electrodes 10j and 10l are connected to the output terminal and constitute an output side IDT electrode.

  The first and second reflectors 11 and 12 are disposed on both sides of the elastic wave propagation direction x in the region where the regular IDT electrodes 10j, 10k, and 10l are provided.

  As described above, in the regular IDT electrode 10, the end face 23 a of the first film 23 on the second bus bar 10 f side and the end face 24 a of the second film 24 on the first bus bar 10 c side are elastic. It is inclined with respect to the surface wave propagation direction x. Therefore, in the region where the first and second films 23 and 24 are formed, it is possible to suppress the occurrence of transverse mode standing waves due to irregular reflection of surface acoustic waves. Therefore, it is possible to suppress the occurrence of transverse mode spurious and realize a longitudinally coupled resonator type acoustic wave filter 1a with a small insertion loss.

An example of the design parameters of the regular IDT electrodes 10j, 10k, 10l in this modification will be shown below. Design parameters other than the design parameters shown below are the same as the design parameters of the above embodiment.
Number of electrodes of normal type IDT electrode 10j: 22 Number of electrodes of normal type IDT electrode 10k: 39 Number of electrodes of normal type IDT electrode 10l: 22 First end face portions 23b and 24b and second end face portions Number of ridges composed of 23c and 24c: 6 each

DESCRIPTION OF SYMBOLS 1 ... Elastic wave apparatus 10 ... Regular type IDT electrode 10a ... 1st comb-tooth electrode 10b ... 2nd comb-tooth electrode 10c ... 1st bus-bar 10d ... 1st electrode finger 10e ... 1st dummy electrode 10f ... 1st Second bus bar 10g ... second electrode finger 10h ... second dummy electrode 11 ... first reflector 12 ... second reflector 13 ... piezoelectric substrate 14 ... Ti film 15 ... Cu film 16 ... AlCu film 17 ... electrode 18 ... 2nd dielectric layer 19 ... 1st dielectric layer 20 ... AlCu film 21 ... Ti film 22 ... Al film 23 ... 1st film 24 ... 2nd film | membrane 23a ... End surface 23b ... 1st end surface part 23c ... second end face 24 ... second film 24a ... end face 24b ... first end face 24c ... second end face 25 ... Ti film 26 ... AlCu film

Claims (9)

An acoustic wave device comprising a piezoelectric substrate and a regular IDT electrode formed on the piezoelectric substrate,
The regular IDT electrode includes first and second bus bars;
A plurality of first electrode fingers extending from the first bus bar toward the second bus bar;
A plurality of second electrode fingers extending from the second bus bar toward the first bus bar and interdigitated with the plurality of first electrode fingers;
A first dummy electrode facing the tip of the second electrode finger via a gap and connected to the first bus bar;
A second dummy electrode facing the tip of the first electrode finger via a gap and connected to the second bus bar;
A first film formed so as to cover at least part of the first dummy electrode and at least part of the first electrode finger and not to reach the gap;
A second film formed to cover at least a part of the second dummy electrode and at least a part of the second electrode finger and not to reach the gap;
Each of the end face on the second bus bar side of the first film and the end face on the first bus bar side of the second film is inclined with respect to the elastic wave propagation direction. .   The acoustic wave device according to claim 1, wherein each of the first and second films is a metal film.   Each of the first and second films includes at least a part of the first or second bus bar and the first or second dummy electrode and at least a part of the first or second electrode finger. An AlCu film made of an AlCu alloy; an Ti film made of Ti; a Ti film made of Ti; and an Al film made of Al formed on the Ti film; The elastic wave device according to claim 1, comprising:   Each of the first and second films includes at least a part of the first or second bus bar and the first or second dummy electrode and at least a part of the first or second electrode finger. The elastic wave device according to claim 1, further comprising: a Ti film made of Ti, and an AlCu film made of an AlCu alloy formed on the Ti film.   The apparatus further comprises a first dielectric film formed between the first electrode finger and the first film and between the second electrode finger and the second film. The elastic wave apparatus as described in any one of 1-4.   A second dielectric formed between the adjacent first electrode fingers and between the adjacent second electrode fingers so as to be substantially flush with the first and second electrode fingers. The elastic wave device according to claim 1, further comprising a body layer.   A plurality of the normal type IDT electrodes are provided along the elastic wave propagation direction, and at least one of the plurality of normal type IDT electrodes is an input side IDT electrode, and the plurality of normal type IDT electrodes are provided. The elastic wave according to any one of claims 1 to 6, wherein at least one of the regular IDT electrodes other than the input-side IDT electrode among the type-IDT electrodes is an output-side IDT electrode. apparatus.   The surface acoustic wave device according to claim 1, which is a surface acoustic wave device using a surface acoustic wave.   The elastic wave device according to any one of claims 1 to 7, wherein the elastic wave device is a boundary acoustic wave device that uses a boundary acoustic wave.

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