WO2019049893A1 - 弾性波装置 - Google Patents
弾性波装置 Download PDFInfo
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- WO2019049893A1 WO2019049893A1 PCT/JP2018/032884 JP2018032884W WO2019049893A1 WO 2019049893 A1 WO2019049893 A1 WO 2019049893A1 JP 2018032884 W JP2018032884 W JP 2018032884W WO 2019049893 A1 WO2019049893 A1 WO 2019049893A1
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- H03H9/46—Filters
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Definitions
- the present invention relates to an elastic wave device.
- Patent Document 1 listed below describes an example of an elastic wave device that uses Rayleigh waves.
- suppression of transverse mode ripple is achieved by lowering the speed of sound in the edge region. More specifically, in the region where the first and second electrode fingers overlap in the elastic wave propagation direction, edge regions are provided at both ends of the electrode finger in the extension direction.
- the film thickness of the dielectric film in the edge region is made thicker than the film thickness of the dielectric film in the central region sandwiched between the edge regions. Thereby, the speed of sound in the edge region is reduced.
- the mass applied to the IDT electrode has been increased by thickening the film thickness of the dielectric film laminated on the IDT electrode. It was thought that the speed of sound could be lowered thereby.
- the inventors of the present invention found that the sound speed becomes higher when the film thickness of the dielectric film in the edge region is increased. If the velocity of sound in the edge region is relatively higher than the velocity of sound in the central region, the transverse mode ripple can not be suppressed.
- An object of the present invention is to provide an elastic wave device capable of suppressing the transverse mode ripple by reliably reducing the sound speed in the edge region when utilizing Love waves.
- a piezoelectric substrate having a piezoelectric layer whose reverse speed surface is elliptical, an IDT electrode provided on the piezoelectric substrate, and the IDT electrode are covered.
- the IDT electrode has the first electrode finger.
- the film thickness of the dielectric film in the first edge region and the film thickness of the dielectric film in the second edge region are the films of the dielectric film in the central region. Thinner than thick.
- a piezoelectric substrate having a piezoelectric layer whose reverse speed surface is elliptical, an IDT electrode provided on the piezoelectric substrate, and the IDT electrode are covered.
- the IDT electrode has two electrode fingers, the elastic wave propagation direction is a first direction, and the direction orthogonal to the first direction is a second direction, the IDT electrode is the first electrode finger.
- a portion where the second electrode finger and the second electrode finger overlap in the first direction A central region located at the center side in the second direction, and a first edge region located on the first bus bar side of the central region. And a second edge region located on the second bus bar side of the central region, wherein the IDT electrode is made of Pt, Au, W, Ta, Mo or Cu, and the IDT electrode is When the wavelength determined by the electrode finger pitch is ⁇ , the film thickness of the IDT electrode is h, and the wavelength normalized film thickness of the IDT electrode h / ⁇ ⁇ 100 (%) is x (%), the wavelength of the IDT electrode
- the normalized film thickness x is not less than the value shown in Table 1 below according to the material of the IDT electrode, and the film thickness of the dielectric film in the first edge region and the thickness in the second edge region The thickness of the dielectric film is in the central region. That is thinner than the thickness of the dielectric film. In this case, even when the thickness of the IDT electrode is large, the speed of sound in the
- the sound speed in the edge region can be reliably lowered to suppress the transverse mode ripple.
- FIG. 1 is a schematic cross-sectional view of an elastic wave device according to a first embodiment of the present invention.
- FIG. 2 is a schematic plan view showing an electrode structure of the elastic wave device according to the first embodiment of the present invention.
- FIG. 3 is a view showing the relationship between the wavelength normalized film thickness of the dielectric film, the acoustic velocity of the elastic wave, and the wavelength normalized film thickness of the IDT electrode when the IDT electrode is made of Pt.
- FIG. 4 is a view showing the relationship between the wavelength normalized film thickness of the dielectric film, the acoustic velocity of the elastic wave, and the wavelength normalized film thickness of the IDT electrode when the IDT electrode is made of Mo.
- FIG. 1 is a schematic cross-sectional view of an elastic wave device according to a first embodiment of the present invention.
- FIG. 2 is a schematic plan view showing an electrode structure of the elastic wave device according to the first embodiment of the present invention.
- FIG. 3 is a view showing the relationship between the wavelength normalized
- FIG. 5 is a view showing the relationship between the wavelength normalized film thickness of the dielectric film, the acoustic velocity of the elastic wave, and the wavelength normalized film thickness of the IDT electrode when the IDT electrode is made of Au.
- FIG. 6 is a view showing the relationship between the wavelength normalized film thickness of the dielectric film, the acoustic velocity of the elastic wave, and the wavelength normalized film thickness of the IDT electrode when the IDT electrode is made of W.
- FIG. 7 is a view showing the relationship between the wavelength normalized film thickness of the dielectric film, the acoustic velocity of the elastic wave, and the wavelength normalized film thickness of the IDT electrode when the IDT electrode is made of Ta.
- FIG. 8 is a view showing the relationship between the wavelength normalized film thickness of the dielectric film, the acoustic velocity of the elastic wave, and the wavelength normalized film thickness of the IDT electrode when the IDT electrode is made of Cu.
- FIG. 9 is a graph showing the relationship between the lower limit value of the wavelength-normalized film thickness of the IDT electrode and the electrode density of the IDT electrode, in which the sound velocity increases as the film thickness of the dielectric film increases.
- FIG. 10 is a graph showing the relationship between the wavelength normalized film thickness of the dielectric film, the acoustic velocity of the elastic wave, and the wavelength normalized film thickness of the IDT electrode when the IDT electrode is composed of a laminated metal film of Pt film and Al film. is there.
- FIG. 9 is a graph showing the relationship between the lower limit value of the wavelength-normalized film thickness of the IDT electrode and the electrode density of the IDT electrode, in which the sound velocity increases as the film thickness of the dielectric film increases.
- FIG. 10 is a graph
- FIG. 11 is a graph showing the relationship between the wavelength normalized film thickness of the dielectric film, the acoustic velocity of the elastic wave, and the wavelength normalized film thickness of the IDT electrode when the IDT electrode is composed of a laminated metal film of Pt film and Cu film. is there.
- FIG. 12 is a graph showing the relationship between the wavelength normalized film thickness of the dielectric film, the acoustic velocity of the elastic wave, and the wavelength normalized film thickness of the IDT electrode when the IDT electrode is formed of a laminated metal film of Mo film and Al film. is there.
- FIG. 13 is a cross-sectional view corresponding to the cross-section shown in FIG. 1 of an elastic wave device according to a modification of the first embodiment of the present invention.
- FIG. 14 is a front cross-sectional view of an elastic wave device according to a second embodiment of the present invention.
- FIG. 1 is a schematic cross-sectional view of an elastic wave device according to a first embodiment of the present invention.
- FIG. 2 is a schematic plan view showing an electrode structure of the elastic wave device according to the first embodiment.
- FIG. 1 is a cross-sectional view taken along the line II in FIG. In FIG. 2, a dielectric film described later is omitted.
- the elastic wave device 1 has a piezoelectric substrate 2.
- the piezoelectric substrate 2 has a piezoelectric layer whose reverse speed surface is elliptical.
- the piezoelectric layer of the piezoelectric substrate 2 is made of LiNbO 3.
- the piezoelectric substrate 2 of the elastic wave device 1 is a piezoelectric substrate consisting of only a piezoelectric layer.
- the piezoelectric substrate 2 may be a laminated substrate including a piezoelectric layer.
- the IDT electrode 3 shown in FIG. 2 is provided on the piezoelectric substrate 2.
- an elastic wave is excited.
- Love waves are used as elastic waves.
- the Euler angles ( ⁇ , ⁇ , ⁇ ) of the piezoelectric substrate 2 are not particularly limited, but are the Euler angles ( ⁇ , range of ⁇ 90 ° ⁇ 30 °, ⁇ ). Thereby, the love wave can be suitably excited.
- ⁇ in the Euler angles includes an upper limit value and a lower limit value indicated by ⁇ .
- the elastic wave propagation direction is taken as a first direction
- the direction orthogonal to the elastic wave propagation direction is taken as a second direction.
- Reflectors 14 and reflectors 15 are provided on both sides of the IDT electrode 3 in the first direction, respectively.
- a one-port elastic wave resonator is configured.
- the IDT electrode 3 has a first bus bar 4 and a second bus bar 5 facing each other. One end of a plurality of first electrode fingers 6 is connected to the first bus bar 4. One end of a plurality of second electrode fingers 7 is connected to the second bus bar 5. The plurality of first electrode fingers 6 and the plurality of second electrode fingers 7 are mutually inserted. The first electrode finger 6 and the second electrode finger 7 extend parallel to the second direction.
- the IDT electrode 3 has a crossover region B in which the first electrode finger 6 and the second electrode finger 7 overlap in the first direction.
- the crossover region B includes a central region M located on the center side in the second direction and a first edge region X1 and a second edge region X2 located on both sides in the second direction of the central region M.
- the first edge area X1 is located on the first bus bar 4 side of the central area M.
- the second edge area X2 is located on the second bus bar 5 side of the central area M.
- the IDT electrode 3 is located on the side of the first gap region C1 located on the side of the first bus bar 4 of the first edge region X1 and on the side of the second bus bar 5 of the second edge region X2.
- the gap region C2 of Only the first electrode finger 6 of the first electrode finger 6 and the second electrode finger 7 is disposed in the first gap region C1.
- Only the second electrode finger 7 of the first electrode finger 6 and the second electrode finger 7 is disposed in the second gap region C2.
- the IDT electrode 3 has a plurality of first dummy electrode fingers 8 whose one end is connected to the first bus bar 4 and a plurality of second ones whose one end is connected to the second bus bar 5. And dummy electrode fingers 9.
- the plurality of first dummy electrode fingers 8 oppose the plurality of second electrode fingers 7 with the first gap region C1 therebetween.
- the plurality of second dummy electrode fingers 9 face each other across the plurality of first electrode fingers 6 and the second gap region C2.
- a dielectric film 13 is provided on the piezoelectric substrate 2 so as to cover the IDT electrode 3.
- the dielectric film 13 is made of SiO 2 .
- the dielectric film 13 is not limited to SiO 2, and may be made of silicon oxide which is represented by SiO x and x is an integer other than 2.
- the material forming dielectric film 13 may be another dielectric such as SiON.
- the wavelength determined by the electrode finger pitch of the IDT electrode 3 is ⁇
- the film thickness of the IDT electrode 3 is h
- the wavelength normalized film thickness h / ⁇ ⁇ 100 (%) of the IDT electrode 3 is x (%).
- the film thickness of the dielectric film 13 in the first edge region X1 and the film thickness of the dielectric film 13 in the second edge region X2 are thinner than the film thickness of the dielectric film in the central region M.
- FIG. 3 is a view showing the relationship between the wavelength normalized film thickness of the dielectric film, the acoustic velocity of the elastic wave, and the wavelength normalized film thickness of the IDT electrode when the IDT electrode is made of Pt.
- the dielectric film using a dielectric film made of SiO 2.
- the sound velocity becomes lower as the wavelength normalized film thickness of the dielectric film becomes thicker when the wavelength normalized film thickness of the IDT electrode is less than 1.8%. ing. However, when the wavelength normalized film thickness of the IDT electrode is 1.8% or more, the sound velocity increases as the wavelength normalized film thickness of the dielectric film increases.
- the wavelength-normalized film thickness x of the IDT electrode 3 is set to x or more which satisfies the above equation (1). Therefore, in the elastic wave device 1, as the film thickness of the dielectric film 13 becomes thicker, the sound velocity becomes higher.
- the film thickness of the dielectric film 13 in the first edge region X1 and the second edge region X2 is thinner than the film thickness of the dielectric film 13 in the central region M. Therefore, the speed of sound in the first edge area X1 and the second edge area X2 is lower than the speed of sound in the central area M.
- the sound velocity in the first edge region X1 and the second edge region X2 can be reliably lowered by using Love waves.
- a low sound velocity region having a lower sound velocity than the sound velocity in the central region M is configured in the first edge region X1 and the second edge region X2.
- a high sound velocity region having a higher sound velocity than the sound velocity in the central region M is configured in the first gap region C1 and the second gap region C2.
- the low sound velocity region is disposed outside the central region M in the second direction, and the high sound velocity region is disposed outside the low sound velocity region.
- the transverse mode ripple can be effectively suppressed by utilizing the piston mode.
- the IDT electrode 3 is made of Mo, Au, W, Ta, or Cu which is a metal other than Pt is shown.
- FIG. 4 is a view showing the relationship between the wavelength normalized film thickness of the dielectric film, the acoustic velocity of the elastic wave, and the wavelength normalized film thickness of the IDT electrode when the IDT electrode is made of Mo.
- FIG. 5 is a view showing the relationship between the wavelength normalized film thickness of the dielectric film, the acoustic velocity of the elastic wave, and the wavelength normalized film thickness of the IDT electrode when the IDT electrode is made of Au.
- FIG. 6 is a view showing the relationship between the wavelength normalized film thickness of the dielectric film, the acoustic velocity of the elastic wave, and the wavelength normalized film thickness of the IDT electrode when the IDT electrode is made of W.
- FIG. 7 is a view showing the relationship between the wavelength normalized film thickness of the dielectric film, the acoustic velocity of the elastic wave, and the wavelength normalized film thickness of the IDT electrode when the IDT electrode is made of Ta.
- FIG. 8 is a view showing the relationship between the wavelength normalized film thickness of the dielectric film, the acoustic velocity of the elastic wave, and the wavelength normalized film thickness of the IDT electrode when the IDT electrode is made of Cu.
- the IDT electrode is made of Mo
- the wavelength normalized film thickness x of the IDT electrode is 5.05% or more
- the wavelength normalized film thickness x of the IDT electrode is 5.05% or more
- the sound velocity becomes higher as the wavelength normalized film thickness of the dielectric film becomes thicker.
- the IDT electrode is made of Au
- the wavelength normalized film thickness x of the IDT electrode is 1.9% or more, according to FIG. 5, the larger the wavelength normalized film thickness of the dielectric film, the higher the sound velocity. I understand.
- the IDT electrode is made of W
- the wavelength normalized film thickness x of the IDT electrode is 2.2% or more, as shown in FIG. 6, the larger the wavelength normalized film thickness of the dielectric film, the higher the sound velocity.
- the IDT electrode is made of Ta
- the wavelength normalized film thickness x of the IDT electrode is 2.55% or more, as shown in FIG. 7, the larger the wavelength normalized film thickness of the dielectric film, the higher the sound velocity.
- the IDT electrode is made of Cu
- the wavelength normalized film thickness x of the IDT electrode is 5.25% or more, according to FIG. 8, the larger the wavelength normalized film thickness of the dielectric film, the higher the sound velocity. I understand.
- IDT electrode When the IDT electrode is made of Pt, W, Mo, Ta, Au or Cu, it is understood that x should be equal to or greater than the value shown in Table 2 according to the material of the electrode, as shown in Table 2 below.
- the wavelength standardized film thickness of the IDT electrode is preferably 25% or less. Thereby, the IDT electrode can be easily formed.
- FIG. 9 is a graph showing the relationship between the lower limit value of the wavelength-normalized film thickness of the IDT electrode and the electrode density of the IDT electrode, in which the sound velocity increases as the film thickness of the dielectric film increases.
- the curve shown in FIG. 9 is a curve shown by the equation (1) described above.
- the film thickness of the dielectric film is adjusted according to the present invention This makes it possible to lower the speed of sound in the first edge region and the second edge region. Therefore, by utilizing the piston mode as described above, the transverse mode ripple can be effectively suppressed.
- the IDT electrode may be made of a laminated metal film formed by laminating a plurality of metal films. In the following, an example in which the IDT electrode is formed of a laminated metal film is shown.
- FIG. 10 is a graph showing the relationship between the wavelength normalized film thickness of the dielectric film, the acoustic velocity of the elastic wave, and the wavelength normalized film thickness of the IDT electrode when the IDT electrode is composed of a laminated metal film of Pt film and Al film. is there.
- FIG. 11 is a graph showing the relationship between the wavelength normalized film thickness of the dielectric film, the acoustic velocity of the elastic wave, and the wavelength normalized film thickness of the IDT electrode when the IDT electrode is composed of a laminated metal film of Pt film and Cu film. is there.
- FIG. 11 is a graph showing the relationship between the wavelength normalized film thickness of the dielectric film, the acoustic velocity of the elastic wave, and the wavelength normalized film thickness of the IDT electrode when the IDT electrode is composed of a laminated metal film of Pt film and Cu film. is there.
- FIG. 12 is a graph showing the relationship between the wavelength normalized film thickness of the dielectric film, the acoustic velocity of the elastic wave, and the wavelength normalized film thickness of the IDT electrode when the IDT electrode is formed of a laminated metal film of Mo film and Al film. is there.
- the sound velocity becomes larger as the film thickness of the dielectric film becomes thicker if the wavelength normalized film thickness x of the IDT electrode is 1.55% or more. Get higher.
- the sound velocity becomes larger as the film thickness of the dielectric film becomes thicker if the wavelength normalized film thickness x of the IDT electrode is 2.5% or more. Get higher.
- the IDT electrode is formed of a laminated metal film of Mo film and Al film, as shown in FIG. 12, if the wavelength normalized film thickness x of the IDT electrode is 5.5% or more, the film thickness of the dielectric film is large.
- the overall density of the laminated metal film is determined from the density and thickness of the electrode material constituting the laminated metal film.
- the electrode densities of the IDT electrodes for which the relationships shown in FIGS. 10 to 12 were obtained are 12.1 g / cm 3 , 15.2 g / cm 3 , and 6.5 g / cm 3 , respectively.
- the first edge region can be obtained by adjusting the film thickness of the dielectric film by setting the wavelength normalized film thickness x of the IDT electrode to a value satisfying the above equation (1) or more. And the speed of sound in the second edge region can be reliably reduced.
- the configuration of the present invention is preferable also in the case where an Al film or a Cu film having a low electric resistance is laminated on a Pt film, or in the case where an Al film having a low electric resistance is laminated on a Mo film.
- the laminated metal film shown in FIGS. 10, 11 and 12 is an example, and the laminated metal film may be made of a metal other than the above.
- the density of the whole laminated metal film changes with the film thickness ratio. Based on the density of the laminated metal film, the wavelength normalized film thickness x of the IDT electrode as the lower limit may be determined.
- FIG. 13 is a cross-sectional view corresponding to the cross section shown in FIG. 1 of the elastic wave device according to the modification of the first embodiment.
- the film thickness of dielectric film 33 in the region where the first dummy electrode finger and first bus bar 4 are provided is greater than the film thickness of dielectric film 33 in first edge region X1. It is thick and the same as the thickness of the dielectric film 33 in the central region M.
- the film thickness of the dielectric film 33 in the region where the second dummy electrode finger 9 and the second bus bar 5 are provided is thicker than the film thickness of the dielectric film 33 in the second edge region X2, And it is the same as the film thickness of the dielectric film 33 in the central region M. This can achieve simplification of the manufacturing process.
- the thickness of the dielectric film 33 in the region where the first dummy electrode finger and the first bus bar 4 are provided and in the region where the second dummy electrode finger 9 and the second bus bar 5 are provided is It may be different from the film thickness in the central region M.
- FIG. 14 is a front cross-sectional view of an elastic wave device according to a second embodiment of the present invention.
- the present embodiment differs from the first embodiment in that the piezoelectric substrate 22 is a laminated substrate.
- the elastic wave device of the present embodiment has the same configuration as the elastic wave device 1 of the first embodiment except for the above point.
- the piezoelectric substrate 22 has a structure in which a high sound velocity layer 22b, a low sound velocity layer 22c, and a piezoelectric layer 22d are stacked in this order on a support substrate 22a.
- the piezoelectric layer 22 d is made of LiTaO 3 . Also in this case, if the high sound velocity layer 22b is stacked directly or indirectly on the piezoelectric layer 22d, the reverse velocity surface of the piezoelectric substrate 22 is elliptical.
- the high sound velocity layer 22 b is made of a material in which the sound velocity of the bulk wave propagating is higher than the sound velocity of the elastic wave propagating in the piezoelectric layer 22 d.
- the high sound velocity layer 22 b is made of, for example, a material containing aluminum nitride, aluminum oxide, silicon carbide, silicon oxynitride, silicon, a DLC film, or a diamond as a main component.
- the material of the high sound velocity layer 22b may be a material having a relatively high sound velocity.
- the low sound velocity layer 22c is made of a material having a lower bulk acoustic velocity than that of the bulk wave propagating through the piezoelectric layer 22d.
- the low sound speed layer 22c is made of, for example, a material containing glass, silicon oxynitride, tantalum oxide or a compound obtained by adding fluorine or carbon or boron to silicon oxide as a main component.
- the material of the low sound velocity layer 22c may be a material having a relatively low sound velocity.
- the low sound velocity layer 22c is stacked between the piezoelectric layer 22d and the high sound velocity layer 22b, but the piezoelectric substrate 22 may not necessarily have the low sound velocity layer 22c.
- the support substrate 22a is made of an appropriate material such as silicon or alumina.
- the support substrate 22a may be a high sound velocity substrate made of a material having a relatively high sound velocity as described above. In this case, since the support substrate 22a is a high sound velocity layer, the piezoelectric substrate 22 may not have the high sound velocity layer 22b.
- the piezoelectric layer 22d is configured in the same manner as the first embodiment, even if the thickness of the IDT electrode 3 is large using Love waves, the first edge region is used. And the speed of sound in the second edge region can be reliably reduced. In addition, the transverse mode ripple can be effectively suppressed by utilizing the piston mode.
- an example of a 1-port-type elastic wave resonator is shown as an elastic wave device.
- the elastic wave device may be a longitudinally coupled resonator type elastic wave filter, a ladder type filter including the elastic wave resonator, or the like.
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Abstract
Description
y=0.0757x2-3.9023x+27.986…式(1)
を満たすx以上とされており、前記第1のエッジ領域における前記誘電体膜の膜厚及び前記第2のエッジ領域における前記誘電体膜の膜厚が、前記中央領域における前記誘電体膜の膜厚よりも薄い。
y=0.0757x2-3.9023x+27.986…式(1)
を満たすx以上とされている。3)第1のエッジ領域X1における誘電体膜13の膜厚及び第2のエッジ領域X2における誘電体膜13の膜厚が、中央領域Mにおける誘電体膜の膜厚よりも薄い。それによって、ラブ波を利用し、IDT電極3の膜厚が厚い場合においても、中央領域Mにおける弾性波の音速よりも、第1のエッジ領域X1及び第2のエッジ領域X2における弾性波の音速を確実に低くすることができる。以下において、この詳細を説明する。
2…圧電性基板
3…IDT電極
4,5…第1,第2のバスバー
6,7…第1,第2の電極指
8,9…第1,第2のダミー電極指
13…誘電体膜
14,15…反射器
22…圧電性基板
22a…支持基板
22b…高音速層
22c…低音速層
22d…圧電体層
33…誘電体膜
Claims (9)
- 逆速度面が楕円形である圧電体層を有する圧電性基板と、
前記圧電性基板上に設けられたIDT電極と、
前記IDT電極を覆うように前記圧電性基板上に設けられた誘電体膜と、
を備え、
ラブ波を利用しており、
前記IDT電極が、互いに対向し合う第1のバスバー及び第2のバスバーと、前記第1のバスバーに一端が接続された複数の第1の電極指と、前記第2のバスバーに一端が接続されており、かつ前記複数の第1の電極指と間挿し合っている複数の第2の電極指と、を有し、
弾性波伝搬方向を第1の方向とし、前記第1の方向に直交する方向を第2の方向としたときに、前記IDT電極が、前記第1の電極指と前記第2の電極指とが前記第1の方向において重なり合っている部分である交叉領域を有し、
前記交叉領域が、前記第2の方向における中央側に位置している中央領域と、前記中央領域の前記第1のバスバー側に位置している第1のエッジ領域と、前記中央領域の前記第2のバスバー側に位置している第2のエッジ領域と、を有し、
前記IDT電極の電極指ピッチにより定められる波長をλ、前記IDT電極の膜厚をh、前記IDT電極の波長規格化膜厚h/λ×100(%)をx(%)とし、前記IDT電極における電極密度をy(g/cm3)とした場合、前記IDT電極の電極密度yに応じて前記IDT電極の波長規格化膜厚xが、
y=0.0757x2-3.9023x+27.986…式(1)
を満たすx以上とされており、
前記第1のエッジ領域における前記誘電体膜の膜厚及び前記第2のエッジ領域における前記誘電体膜の膜厚が、前記中央領域における前記誘電体膜の膜厚よりも薄い、弾性波装置。 - 逆速度面が楕円形である圧電体層を有する圧電性基板と、
前記圧電性基板上に設けられたIDT電極と、
前記IDT電極を覆うように前記圧電性基板上に設けられた誘電体膜と、
を備え、
ラブ波を利用しており、
前記IDT電極が、互いに対向し合う第1のバスバー及び第2のバスバーと、前記第1のバスバーに一端が接続された複数の第1の電極指と、前記第2のバスバーに一端が接続されており、かつ前記複数の第1の電極指と間挿し合っている複数の第2の電極指と、を有し、
弾性波伝搬方向を第1の方向とし、前記第1の方向に直交する方向を第2の方向としたときに、前記IDT電極が、前記第1の電極指と前記第2の電極指とが前記第1の方向において重なり合っている部分である交叉領域を有し、
前記交叉領域が、前記第2の方向における中央側に位置している中央領域と、前記中央領域の前記第1のバスバー側に位置している第1のエッジ領域と、前記中央領域の前記第2のバスバー側に位置している第2のエッジ領域と、を有し、
前記IDT電極が、Pt、Au、W、Ta、MoまたはCuからなり、
前記IDT電極の電極指ピッチにより定められる波長をλ、前記IDT電極の膜厚をh、前記IDT電極の波長規格化膜厚h/λ×100(%)をx(%)とした場合、前記IDT電極の波長規格化膜厚xが、前記IDT電極の材料に応じて下記の表1に示す値以上とされており、
前記第1のエッジ領域における前記誘電体膜の膜厚及び前記第2のエッジ領域における前記誘電体膜の膜厚が、前記中央領域における前記誘電体膜の膜厚よりも薄い、弾性波装置。
- 前記IDT電極が複数の金属膜が積層されている積層金属膜からなり、前記IDT電極の電極密度yが、前記積層金属膜の密度である、請求項1に記載の弾性波装置。
- 前記IDT電極が、前記第1のエッジ領域の前記第1のバスバー側に位置しており、前記第1の電極指及び前記第2の電極指のうち前記第1の電極指のみが配置されている第1のギャップ領域と、前記第2のエッジ領域の前記第2のバスバー側に位置しており、前記第1の電極指及び前記第2の電極指のうち前記第2の電極指のみが配置されている第2のギャップ領域と、を有する、請求項1~3のいずれか1項に記載の弾性波装置。
- 前記IDT電極が、前記第1のバスバーに一端が接続されており、かつ前記複数の第2の電極指と前記第1のギャップ領域を隔てて対向している複数の第1のダミー電極指と、前記第2のバスバーに一端が接続されており、かつ前記複数の第1の電極指と前記第2のギャップ領域を隔てて対向している複数の第2のダミー電極指と、を有する、請求項4に記載の弾性波装置。
- 前記圧電体層がLiNbO3からなる、請求項1~5のいずれか1項に記載の弾性波装置。
- 前記圧電体層のオイラー角が、オイラー角(φ,-90°±30°の範囲,ψ)である、請求項6に記載の弾性波装置。
- 前記圧電性基板が、前記圧電体層に直接的または間接的に積層されており、前記圧電体層を伝搬する弾性波よりも伝搬するバルク波の音速が高い高音速層を有する、請求項1~7のいずれか1項に記載の弾性波装置。
- 前記圧電性基板が、前記圧電体層と前記高音速層との間に積層されており、前記圧電体層を伝搬するバルク波の音速よりも伝搬するバルク波の音速が低い低音速層を有する、請求項8に記載の弾性波装置。
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