WO2010131607A1 - Elastic boundary wave device - Google Patents

Elastic boundary wave device Download PDF

Info

Publication number
WO2010131607A1
WO2010131607A1 PCT/JP2010/057824 JP2010057824W WO2010131607A1 WO 2010131607 A1 WO2010131607 A1 WO 2010131607A1 JP 2010057824 W JP2010057824 W JP 2010057824W WO 2010131607 A1 WO2010131607 A1 WO 2010131607A1
Authority
WO
WIPO (PCT)
Prior art keywords
medium
thickness
acoustic wave
wave device
boundary acoustic
Prior art date
Application number
PCT/JP2010/057824
Other languages
French (fr)
Japanese (ja)
Inventor
昌和 三村
大志 田中
Original Assignee
株式会社村田製作所
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 株式会社村田製作所 filed Critical 株式会社村田製作所
Publication of WO2010131607A1 publication Critical patent/WO2010131607A1/en

Links

Images

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/0222—Details of interface-acoustic, boundary, pseudo-acoustic or Stonely wave devices

Definitions

  • the present invention relates to a boundary acoustic wave device using a boundary acoustic wave, and more particularly to a three-medium type boundary acoustic wave device having first and second dielectric layers formed on a piezoelectric substrate.
  • elastic wave devices have been used for RF filters and IF filters for mobile phones, VCO resonators, television VIF filters, and the like.
  • a surface acoustic wave device a surface acoustic wave device using a surface acoustic wave has been generally used.
  • the following patent document The boundary acoustic wave device as described in No. 1 has been used.
  • Patent Document 1 a polycrystalline silicon oxide film as a first medium and a polycrystalline silicon film as a second medium are arranged in this order on a piezoelectric substrate on which an IDT electrode is formed.
  • the boundary acoustic wave device formed by is described.
  • the piezoelectric substrate and the polycrystalline silicon film have a function of confining the boundary acoustic wave generated in the IDT electrode in the polycrystalline silicon oxide film.
  • the thickness of the first medium normalized by the wavelength ( ⁇ ) of the boundary acoustic wave generated in the IDT electrode is preferably 0.2 ⁇ or more, and the wavelength standard of the second medium It is described that the thickness is preferably 0.25 ⁇ or more.
  • the boundary acoustic wave device described in Patent Document 1 does not consider any higher-order modes that cause spurious responses.
  • the present inventors set the wavelength normalized thickness of the first medium to 0.2 ⁇ or more and the wavelength normalized thickness of the second medium. It has been found that even when the thickness is 0.25 ⁇ or more, a higher-order mode that becomes a spurious response may not be sufficiently suppressed. Conventionally, it is known that the excitation strength of the higher-order mode depends on the thickness of the first medium, and the higher-order mode is weakened as the thickness of the first medium is decreased. In the case where the wavelength normalized thickness of the medium No. 2 was 0.25 ⁇ , the higher-order mode that caused the spurious response could not be sufficiently suppressed even if the thickness of the first medium was reduced.
  • the present invention has been made in view of such a point, and an object thereof is to suppress a higher-order mode that becomes a spurious response in a boundary acoustic wave device.
  • the boundary acoustic wave device includes a piezoelectric substrate, a first medium, a second medium, and an IDT electrode.
  • the first medium is formed on the piezoelectric substrate.
  • the second medium is formed on the first medium.
  • the IDT electrode is formed at the boundary between the piezoelectric substrate and the first medium.
  • the sound speed of the first medium is lower than the sound speed of the piezoelectric substrate and the second medium.
  • the thickness of the second medium is 0.56 ⁇ or more when the wavelength of the boundary acoustic wave generated in the IDT electrode is ⁇ .
  • the thickness of the second medium is 4.6 ⁇ m or less.
  • the piezoelectric substrate is a rotating Y-cut LiNbO 3 substrate having a cut angle in a range of 0 ° to 37 °.
  • the second medium is made of silicon nitride.
  • the first medium is made of silicon oxide.
  • the second medium is a film formed by sputtering, vapor deposition, CVD, spin coating, or screen printing.
  • the thickness of the second medium is 0.56 ⁇ or more, it is possible to effectively suppress higher-order modes that are spurious responses. As a result, good resonator characteristics, filter characteristics, and the like can be realized.
  • FIG. 1 is a schematic plan view showing an electrode structure of a boundary acoustic wave device.
  • FIG. 2 is a schematic cross-sectional view in which a part of the boundary acoustic wave device is enlarged.
  • FIG. 3 is a graph showing impedance characteristics when the thickness of the second medium is 0.33 ⁇ .
  • FIG. 4 is a graph showing phase characteristics when the thickness of the second medium is 0.33 ⁇ .
  • FIG. 5 is a graph showing impedance characteristics when the thickness of the second medium is 0.44 ⁇ .
  • FIG. 6 is a graph showing phase characteristics when the thickness of the second medium is 0.44 ⁇ .
  • FIG. 7 is a graph showing impedance characteristics when the thickness of the second medium is 0.56 ⁇ .
  • FIG. 8 is a graph showing phase characteristics when the thickness of the second medium is 0.56 ⁇ .
  • FIG. 9 is a graph showing impedance characteristics when the thickness of the second medium is 1.05 ⁇ .
  • FIG. 10 is a graph showing phase characteristics when the thickness of the second medium is 1.05 ⁇ .
  • FIG. 11 shows the thickness of the second medium and the piezoelectric substrate when a single crystal piezoelectric substrate made of disc-shaped LiNbO 3 having a diameter of 10.16 cm (4 inches) and a thickness of 0.7 mm is used. It is a graph showing the relationship with curvature.
  • FIG. 12 is a diagram illustrating impedance characteristics when the cut angle is 0 °.
  • FIG. 13 is a diagram illustrating phase characteristics when the cut angle is 0 °.
  • FIG. 12 is a diagram illustrating impedance characteristics when the cut angle is 0 °.
  • FIG. 14 is a diagram showing impedance characteristics when the cut angle is 10 °.
  • FIG. 15 is a diagram illustrating phase characteristics when the cut angle is 10 °.
  • FIG. 16 is a diagram showing impedance characteristics when the cut angle is 37 °.
  • FIG. 17 is a diagram illustrating phase characteristics when the cut angle is 37 °.
  • the boundary acoustic wave resonator shown in FIG. 1 is given as an example of a preferable boundary acoustic wave device embodying the present invention.
  • the boundary acoustic wave device according to the present invention has a boundary acoustic wave resonance. Not limited to children.
  • the boundary acoustic wave device according to the present invention may be, for example, a boundary acoustic wave filter.
  • FIG. 1 is a schematic plan view showing an electrode structure of a boundary acoustic wave device according to this embodiment.
  • the boundary acoustic wave device 1 includes an input terminal 11 and an output terminal 12.
  • An IDT electrode 13 is connected between the input terminal 11 and the output terminal 12.
  • First and second grating reflectors 14 and 15 are arranged on both sides of the IDT electrode 13 in the boundary acoustic wave propagation direction.
  • 1 is a schematic diagram of the boundary acoustic wave device 1. In FIG. 1, the number of electrode fingers of the IDT electrode 13 and the first and second grating reflectors 14 and 15 is larger than the actual number. Less is drawn.
  • FIG. 2 is a schematic cross-sectional view in which a part of the boundary acoustic wave device according to this embodiment is enlarged.
  • the boundary acoustic wave device 1 is a so-called three-medium type boundary acoustic wave device.
  • the boundary acoustic wave device 1 includes a piezoelectric substrate 20.
  • the piezoelectric substrate 20 can be formed of an appropriate piezoelectric material. Specific examples of the piezoelectric substrate 20 include a LiNbO 3 substrate and a LiTaO 3 substrate.
  • the IDT electrode 13 and the first and second grating reflectors 14 and 15 are formed on the piezoelectric substrate 20.
  • the IDT electrode 13 and the first and second grating reflectors 14 and 15 can be formed of an appropriate conductive material such as a metal such as Au, Pt, Al, Cu, Ni, or Ti, or an alloy such as AlCu. .
  • the IDT electrode 13 and the first and second grating reflectors 14 and 15 may be formed of a single conductive layer, or may be formed of a stacked body of a plurality of conductive layers.
  • the thicknesses of the IDT electrode 13 and the first and second grating reflectors 14 and 15 are not particularly limited, and can be appropriately set according to the required characteristics of the boundary acoustic wave device 1.
  • the base layer 23 is formed on the surface of the piezoelectric substrate 20, and the IDT electrode 13 and the first and second grating reflectors 14 and 15 are formed on the base layer 23.
  • the underlayer is not essential, and an IDT electrode or the like may be formed directly on the piezoelectric substrate.
  • the material of the underlayer 23 is not particularly limited, but the underlayer 23 can be formed of tantalum oxide such as Ta 2 O 5 , for example.
  • a first medium 21 is formed on the piezoelectric substrate 20 so as to cover the IDT electrode 13 and the first and second grating reflectors 14 and 15. That is, the IDT electrode 13 and the first and second grating reflectors 14 and 15 are formed at the boundary between the piezoelectric substrate 20 and the first medium 21.
  • a second medium 22 is formed on the first medium 21. The sound speed of the first medium 21 is lower than both the sound speed of the piezoelectric substrate 20 and the sound speed of the second medium 22.
  • the material of the first medium 21 and the second medium 22 is not particularly limited as long as the sound speed of the first medium 21 is lower than the sound speed of the piezoelectric substrate 20 and the sound speed of the second medium 22.
  • the first medium 21 and the second medium 22 can be formed of a dielectric.
  • the first medium 21 is formed by a silicon oxide such as SiO 2
  • the second medium 22 may be formed of silicon nitride, such as SiN.
  • the formation method of the first and second media 21 and 22 is not particularly limited, and the first and second media 21 and 22 can be formed by an evaporation method such as a sputtering method or a CVD method.
  • the thickness of the first medium 21 is not particularly limited, and can be appropriately set according to characteristics required for the boundary acoustic wave device 1.
  • the thickness of the second medium 22 is 0.56 ⁇ or more when the wavelength of the boundary acoustic wave generated in the IDT electrode 13 is ⁇ . For this reason, as can be seen from the results of the following experimental examples, it is possible to effectively suppress higher-order modes that are spurious responses.
  • a boundary acoustic wave device having the configuration shown in FIGS. 1 and 2 was manufactured with the following design parameters, and the resonator characteristics were measured.
  • Piezoelectric substrate 20 25 ° YX LiNbO 3 substrate Material of underlayer 23: Ta 2 O 5 Underlayer 23 thickness: 12 nm (0.007 ⁇ ) Film configuration of IDT electrode 13 and first and second grating reflectors 14 and 15: Ti layer (thickness 10 nm (0.006 ⁇ )) / Pt layer (thickness 31 nm (0.017 ⁇ )) / Ti layer (thickness) 10 nm (0.006 ⁇ )) / Al layer (thickness 300 nm (0.167 ⁇ )) / Ti layer (thickness 10 nm (0.006 ⁇ )) / Pt layer (thickness 31 nm (0.017 ⁇ )) / Ti layer (Thickness 10 nm (0.006 ⁇ )) Wavelength ( ⁇ ) determined by the pitch of the electrode fingers of the IDT electrode 13: 1.8 ⁇ m Number of electrode finger pairs in IDT electrode 13: 60 Duty of IDT electrode 13: 0.50 Cross width of IDT electrode 13 (interval of bus bars facing each other):
  • FIG. 3 to 10 show the measurement results of the resonator characteristics.
  • FIG. 3 is a graph showing impedance characteristics when the thickness of the second medium is 0.33 ⁇ .
  • FIG. 4 is a graph showing phase characteristics when the thickness of the second medium is 0.33 ⁇ .
  • FIG. 5 is a graph showing impedance characteristics when the thickness of the second medium is 0.44 ⁇ .
  • FIG. 6 is a graph showing phase characteristics when the thickness of the second medium is 0.44 ⁇ .
  • FIG. 7 is a graph showing impedance characteristics when the thickness of the second medium is 0.56 ⁇ .
  • FIG. 8 is a graph showing phase characteristics when the thickness of the second medium is 0.56 ⁇ .
  • FIG. 9 is a graph showing impedance characteristics when the thickness of the second medium is 1.05 ⁇ .
  • FIG. 10 is a graph showing phase characteristics when the thickness of the second medium is 1.05 ⁇ .
  • a response in the basic mode is indicated by A and a response in the higher order mode is indicated by B.
  • the resonator characteristics of the fundamental mode do not change greatly even if the thickness of the second medium 22 changes.
  • the intensity of the higher-order mode is large when the thickness of the second medium 22 is less than 0.56 ⁇ , and is small when the thickness of the second medium 22 is 0.56 ⁇ or more.
  • FIGS. 9 and 10 showing the case where the thickness of the second medium 22 is 1.05 ⁇ . It can be seen that when the thickness of the second medium 22 is 0.56 ⁇ or more, the intensity of the higher-order mode does not change so much even if the thickness of the second medium 22 changes.
  • a boundary acoustic wave filter having good characteristics can be created by using the boundary acoustic wave device 1 of the present embodiment.
  • the fundamental mode does not greatly correlate with the thickness of the second medium 22, whereas the strength of the higher-order mode increases as the thickness of the second medium 22 decreases. This is considered to be because of a wider displacement distribution in the substrate thickness direction than That is, when the thickness of the second medium 22 is less than 0.56 ⁇ , the fundamental mode does not reach the surface of the second medium 22, but the higher-order mode reaches the surface of the second medium 22. On the other hand, when the thickness of the second medium 22 is 0.56 ⁇ or more, the higher-order mode is also confined in the second medium 22 and does not reach the surface of the second medium 22. It is considered that the spurious response due to the higher order mode is reduced.
  • a boundary acoustic wave device is manufactured in the same manner as the boundary acoustic wave device created in the above experimental example, except that a sound absorbing layer made of polyimide and having a thickness of 8 ⁇ m is formed on the second medium. It was measured. As a result, when the thickness of the second medium 22 was 0.56 ⁇ or 1.05 ⁇ , there was no significant change in the resonator characteristics with and without the sound absorbing layer. On the other hand, when the thickness of the second medium 22 is 0.44 ⁇ or 0.33 ⁇ , the intensity of the higher-order mode response is smaller by providing the sound absorbing layer than when the sound absorbing layer is not provided. .
  • the thickness of the second medium 22 is 0.44 ⁇ or 0.33 ⁇ .
  • the thickness of the second medium 22 is 0.56 ⁇ or more.
  • the response of the higher order mode did not become so small. From this result, it is difficult to sufficiently suppress the higher-order mode only by providing the sound absorption layer, and in order to sufficiently suppress the higher-order mode, the thickness of the second medium 22 is set to 0.56 ⁇ or more. I know you need to do that.
  • the thickness of the second medium 22 is increased, for example, if the second medium 22 is formed by sputtering, vapor deposition, CVD, spin coating, or screen printing, the film stress of the second medium As a result, the piezoelectric substrate 20 is warped. If the piezoelectric substrate 20 is warped, it may be difficult to carry out the conveying process, or the piezoelectric substrate 20 may be cracked or chipped. For this reason, from the viewpoint of reducing the warpage generated in the piezoelectric substrate 20, it is preferable that the thickness of the second medium 22 is small.
  • FIG. 11 shows a first medium on a disk-shaped piezoelectric substrate (cut angle 25 ° rotated Y-cut LiNbO 3 substrate) 20 having a diameter of 10.16 cm (4 inches) and a thickness of 0.7 mm. 21, when a SiO 2 film having a thickness of 600 nm is formed by RF sputtering, and then a SiN film is formed by RF sputtering as the second medium 22, the thickness of the SiN film and the piezoelectric substrate 20 It is a graph showing the relationship with the curvature of.
  • the thickness of the second medium 22 is 4.6 ⁇ m or less, the warp amount of the piezoelectric substrate 20 can be 500 ⁇ m or less that can be handled in the transport process. From this result, it can be seen that the thickness of the second medium 22 is preferably 4.6 ⁇ m or less. Furthermore, the thickness of the second medium 22 is more preferably 2.8 ⁇ m or less because the amount of warpage of the piezoelectric substrate can be 300 ⁇ m or less.
  • FIGS. 12 to 17 show boundary acoustic wave devices in the case of using a rotated Y-cut LiNbO 3 substrate having a second medium thickness of 0.56 ⁇ or more and cut angles ⁇ of 0 °, 10 °, and 37 °. The impedance characteristic and the phase characteristic of are shown.
  • the response by the fundamental mode of the SH type boundary acoustic wave device is indicated by A, and the response by the higher order mode is indicated by B.
  • the impedance ratio of the fundamental mode that is, the ratio of the impedance at the anti-resonance frequency to the impedance at the resonance frequency is The impedance ratio is equal to or greater than 60 dB, which is equivalent to the impedance ratio in the above-described embodiment, that is, the 25 ° rotated Y-cut LiNbO 3 substrate. Therefore, if the cut angle ⁇ is in the range of 0 ° to 37 °, it can be seen that the response in the fundamental mode is sufficiently large as in the above embodiment.
  • the cut angle ⁇ of LiNbO 3 is in the range of 0 ° to 37 °, higher-order mode spurious can be suppressed and a response with a sufficiently large fundamental mode can be obtained. I understand that I can do it.
  • the horizontal axis in FIGS. 12 to 17 is the speed of sound.
  • Sound speed (m / sec) frequency (MHz) ⁇ wavelength ( ⁇ m).
  • the speed range of 3000 m / sec to 5000 m / sec is equivalent to the frequency range of 1700 MHz to 2700 MHz.

Abstract

Provided is an elastic boundary wave device wherein high-order mode which causes spurious response is suppressed. An elastic boundary wave device (1) is provided with a piezoelectric substrate (20), a first medium (21), a second medium (22), and an IDT electrode (13). The first medium (21) is formed on the piezoelectric substrate (20). The second medium (22) is formed on the first medium (21). The IDT electrode (13) is formed on the boundary between the piezoelectric substrate (20) and the first medium (21). The sound speed of the first medium (21) is lower than the sound speeds of the piezoelectric substrate (20) and the second medium (22). The thickness of the second medium (22) is 0.56λ or more, where λ represents the wavelength of the elastic boundary waves generated in the IDT electrode (13).

Description

弾性境界波装置Boundary acoustic wave device
　本発明は、弾性境界波を利用した弾性境界波装置に関し、詳細には、圧電基板の上に形成された第１及び第２の誘電体層を有する３媒質型の弾性境界波装置に関する。 The present invention relates to a boundary acoustic wave device using a boundary acoustic wave, and more particularly to a three-medium type boundary acoustic wave device having first and second dielectric layers formed on a piezoelectric substrate.
　従来、携帯電話用のＲＦフィルタやＩＦフィルタ、ＶＣＯ用共振子、テレビジョン用ＶＩＦフィルタなどに弾性波装置が用いられている。弾性波装置としては、従来、弾性表面波を利用した弾性表面波装置が一般的に用いられていたが、近年、弾性表面波装置よりも小型化が可能であることより、例えば下記の特許文献１に記載されているような、弾性境界波装置が用いられるようになってきている。 Conventionally, elastic wave devices have been used for RF filters and IF filters for mobile phones, VCO resonators, television VIF filters, and the like. As a surface acoustic wave device, a surface acoustic wave device using a surface acoustic wave has been generally used. However, in recent years, since it can be made smaller than a surface acoustic wave device, for example, the following patent document The boundary acoustic wave device as described in No. 1 has been used.
　具体的には、特許文献１には、ＩＤＴ電極が形成された圧電基板の上に、第１の媒質としての多結晶酸化珪素膜と、第２の媒質としての多結晶珪素膜とをこの順番で形成した弾性境界波装置が記載されている。この弾性境界波装置において、圧電基板と、多結晶珪素膜とは、ＩＤＴ電極において発生した弾性境界波を多結晶酸化珪素膜内に閉じ込める機能を有している。特許文献１には、ＩＤＴ電極において発生する弾性境界波の波長（λ）により規格化された第１の媒質の厚さは、０．２λ以上であることが好ましく、第２の媒質の波長規格化厚さは、０．２５λ以上であることが好ましい旨が記載されている。 Specifically, in Patent Document 1, a polycrystalline silicon oxide film as a first medium and a polycrystalline silicon film as a second medium are arranged in this order on a piezoelectric substrate on which an IDT electrode is formed. The boundary acoustic wave device formed by is described. In this boundary acoustic wave device, the piezoelectric substrate and the polycrystalline silicon film have a function of confining the boundary acoustic wave generated in the IDT electrode in the polycrystalline silicon oxide film. In Patent Document 1, the thickness of the first medium normalized by the wavelength (λ) of the boundary acoustic wave generated in the IDT electrode is preferably 0.2λ or more, and the wavelength standard of the second medium It is described that the thickness is preferably 0.25λ or more.
ＷＯ９８／５２２７９　Ａ１号公報WO98 / 52279 A1 Publication
　しかしながら、特許文献１に記載の弾性境界波装置では、スプリアス応答となる高次モードについては一切考慮されていなかった。本発明者らは、弾性境界波装置におけるスプリアス応答となる高次モードについて鋭意研究した結果、第１の媒質の波長規格化厚さを０．２λ以上とし、第２の媒質の波長規格化厚さを０．２５λ以上とした場合であっても、スプリアス応答となる高次モードを十分に抑圧できない場合があることを見出した。また、従来、高次モードの励振の強さは、第１の媒質の厚さに依存し、第１の媒質の厚さを小さくするほど高次モードが弱まることが知られているが、第２の媒質の波長規格化厚さを０．２５λとした場合は、第１の媒質の厚さを小さくしてもスプリアス応答となる高次モードを十分に抑圧できなかった。 However, the boundary acoustic wave device described in Patent Document 1 does not consider any higher-order modes that cause spurious responses. As a result of diligent research on higher-order modes serving as spurious responses in the boundary acoustic wave device, the present inventors set the wavelength normalized thickness of the first medium to 0.2λ or more and the wavelength normalized thickness of the second medium. It has been found that even when the thickness is 0.25λ or more, a higher-order mode that becomes a spurious response may not be sufficiently suppressed. Conventionally, it is known that the excitation strength of the higher-order mode depends on the thickness of the first medium, and the higher-order mode is weakened as the thickness of the first medium is decreased. In the case where the wavelength normalized thickness of the medium No. 2 was 0.25λ, the higher-order mode that caused the spurious response could not be sufficiently suppressed even if the thickness of the first medium was reduced.
　本発明は、かかる点に鑑みてなされたものであり、その目的は、弾性境界波装置において、スプリアス応答となる高次モードを抑圧することにある。 The present invention has been made in view of such a point, and an object thereof is to suppress a higher-order mode that becomes a spurious response in a boundary acoustic wave device.
　本発明に係る弾性境界波装置は、圧電基板と、第１の媒質と、第２の媒質と、ＩＤＴ電極とを備えている。第１の媒質は、圧電基板の上に形成されている。第２の媒質は、第１の媒質の上に形成されている。ＩＤＴ電極は、圧電基板と第１の媒質との境界に形成されている。第１の媒質の音速は、圧電基板及び第２の媒質の音速よりも低い。第２の媒質の厚さは、ＩＤＴ電極において生じる弾性境界波の波長をλとしたときに、０．５６λ以上である。 The boundary acoustic wave device according to the present invention includes a piezoelectric substrate, a first medium, a second medium, and an IDT electrode. The first medium is formed on the piezoelectric substrate. The second medium is formed on the first medium. The IDT electrode is formed at the boundary between the piezoelectric substrate and the first medium. The sound speed of the first medium is lower than the sound speed of the piezoelectric substrate and the second medium. The thickness of the second medium is 0.56λ or more when the wavelength of the boundary acoustic wave generated in the IDT electrode is λ.
　本発明に係る弾性境界波装置のある特定の局面において、第２の媒質の厚さが４．６μｍ以下である。 In a specific aspect of the boundary acoustic wave device according to the present invention, the thickness of the second medium is 4.6 μm or less.
　本発明に係る弾性境界波装置の他の特定の局面において、圧電基板は、カット角が０°～３７°の範囲内にある回転ＹカットＬｉＮｂＯ３基板である。 In another specific aspect of the boundary acoustic wave device according to the present invention, the piezoelectric substrate is a rotating Y-cut LiNbO 3 substrate having a cut angle in a range of 0 ° to 37 °.
　本発明に係る弾性境界波装置の別の特定の局面において、第２の媒質が窒化珪素からなる。 In another specific aspect of the boundary acoustic wave device according to the present invention, the second medium is made of silicon nitride.
　本発明に係る弾性境界波装置のさらに他の特定の局面において、第１の媒質が酸化珪素からなる。 In yet another specific aspect of the boundary acoustic wave device according to the present invention, the first medium is made of silicon oxide.
　本発明に係る弾性境界波装置のさらに別の特定の局面において、第２の媒質は、スパッタ法、蒸着法、ＣＶＤ法、スピンコート法またはスクリーン印刷法により形成された膜である。 In yet another specific aspect of the boundary acoustic wave device according to the present invention, the second medium is a film formed by sputtering, vapor deposition, CVD, spin coating, or screen printing.
　本発明では、第２の媒質の厚さが０．５６λ以上とされているため、スプリアス応答となる高次モードを効果的に抑圧できる。その結果、良好な共振子特性や、フィルタ特性等を実現することができる。 In the present invention, since the thickness of the second medium is 0.56λ or more, it is possible to effectively suppress higher-order modes that are spurious responses. As a result, good resonator characteristics, filter characteristics, and the like can be realized.
図１は、弾性境界波装置の電極構造を示す略図的平面図である。FIG. 1 is a schematic plan view showing an electrode structure of a boundary acoustic wave device. 図２は、弾性境界波装置の一部を拡大した略図的断面図である。FIG. 2 is a schematic cross-sectional view in which a part of the boundary acoustic wave device is enlarged. 図３は、第２の媒質の厚さが０．３３λである場合のインピーダンス特性を表すグラフである。FIG. 3 is a graph showing impedance characteristics when the thickness of the second medium is 0.33λ. 図４は、第２の媒質の厚さが０．３３λである場合の位相特性を表すグラフである。FIG. 4 is a graph showing phase characteristics when the thickness of the second medium is 0.33λ. 図５は、第２の媒質の厚さが０．４４λである場合のインピーダンス特性を表すグラフである。FIG. 5 is a graph showing impedance characteristics when the thickness of the second medium is 0.44λ. 図６は、第２の媒質の厚さが０．４４λである場合の位相特性を表すグラフである。FIG. 6 is a graph showing phase characteristics when the thickness of the second medium is 0.44λ. 図７は、第２の媒質の厚さが０．５６λである場合のインピーダンス特性を表すグラフである。FIG. 7 is a graph showing impedance characteristics when the thickness of the second medium is 0.56λ. 図８は、第２の媒質の厚さが０．５６λである場合の位相特性を表すグラフである。FIG. 8 is a graph showing phase characteristics when the thickness of the second medium is 0.56λ. 図９は、第２の媒質の厚さが１．０５λである場合のインピーダンス特性を表すグラフである。FIG. 9 is a graph showing impedance characteristics when the thickness of the second medium is 1.05λ. 図１０は、第２の媒質の厚さが１．０５λである場合の位相特性を表すグラフである。FIG. 10 is a graph showing phase characteristics when the thickness of the second medium is 1.05λ. 図１１は、直径が１０．１６ｃｍ（４インチ）で、厚さが０．７ｍｍである円板状のＬｉＮｂＯ３からなる単結晶圧電基板を用いた場合の第２の媒質の厚さと圧電基板の反りとの関係を表すグラフである。FIG. 11 shows the thickness of the second medium and the piezoelectric substrate when a single crystal piezoelectric substrate made of disc-shaped LiNbO 3 having a diameter of 10.16 cm (4 inches) and a thickness of 0.7 mm is used. It is a graph showing the relationship with curvature. 図１２は、カット角が０°である場合のインピーダンス特性を示す図である。FIG. 12 is a diagram illustrating impedance characteristics when the cut angle is 0 °. 図１３は、カット角が０°である場合の位相特性を示す図である。FIG. 13 is a diagram illustrating phase characteristics when the cut angle is 0 °. 図１４は、カット角が１０°である場合のインピーダンス特性を示す図である。FIG. 14 is a diagram showing impedance characteristics when the cut angle is 10 °. 図１５は、カット角が１０°である場合の位相特性を示す図である。FIG. 15 is a diagram illustrating phase characteristics when the cut angle is 10 °. 図１６は、カット角が３７°である場合のインピーダンス特性を示す図である。FIG. 16 is a diagram showing impedance characteristics when the cut angle is 37 °. 図１７は、カット角が３７°である場合の位相特性を示す図である。FIG. 17 is a diagram illustrating phase characteristics when the cut angle is 37 °.
　以下、図面を参照しつつ、本発明の具体的な実施形態を説明することにより、本発明を明らかにする。なお、本実施形態では、本発明を実施した弾性境界波装置の好ましい例の一例として、図１に示す弾性境界波共振子を挙げるが、本発明に係る弾性境界波装置は、弾性境界波共振子に限定されない。本発明に係る弾性境界波装置は、例えば、弾性境界波フィルタなどであってもよい。 Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings. In the present embodiment, the boundary acoustic wave resonator shown in FIG. 1 is given as an example of a preferable boundary acoustic wave device embodying the present invention. However, the boundary acoustic wave device according to the present invention has a boundary acoustic wave resonance. Not limited to children. The boundary acoustic wave device according to the present invention may be, for example, a boundary acoustic wave filter.
　図１は、本実施形態に係る弾性境界波装置の電極構造を示す略図的平面図である。図１に示すように、弾性境界波装置１は、入力端子１１と出力端子１２とを備えている。入力端子１１と出力端子１２との間には、ＩＤＴ電極１３が接続されている。ＩＤＴ電極１３の弾性境界波伝搬方向の両側には、第１及び第２のグレーティング反射器１４，１５が配置されている。なお、図１は、弾性境界波装置１の模式図であって、図１において、ＩＤＴ電極１３並びに第１及び第２のグレーティング反射器１４，１５の電極指の本数は、実際の本数よりも少なく描画されている。 FIG. 1 is a schematic plan view showing an electrode structure of a boundary acoustic wave device according to this embodiment. As shown in FIG. 1, the boundary acoustic wave device 1 includes an input terminal 11 and an output terminal 12. An IDT electrode 13 is connected between the input terminal 11 and the output terminal 12. First and second grating reflectors 14 and 15 are arranged on both sides of the IDT electrode 13 in the boundary acoustic wave propagation direction. 1 is a schematic diagram of the boundary acoustic wave device 1. In FIG. 1, the number of electrode fingers of the IDT electrode 13 and the first and second grating reflectors 14 and 15 is larger than the actual number. Less is drawn.
　図２は、本実施形態に係る弾性境界波装置の一部を拡大した略図的断面図である。図２に示すように、弾性境界波装置１は、所謂３媒質型の弾性境界波装置である。弾性境界波装置１は、圧電基板２０を備えている。圧電基板２０は、適宜の圧電材料によって形成することができる。圧電基板２０の具体例としては、例えば、ＬｉＮｂＯ３基板や、ＬｉＴａＯ３基板などが挙げられる。 FIG. 2 is a schematic cross-sectional view in which a part of the boundary acoustic wave device according to this embodiment is enlarged. As shown in FIG. 2, the boundary acoustic wave device 1 is a so-called three-medium type boundary acoustic wave device. The boundary acoustic wave device 1 includes a piezoelectric substrate 20. The piezoelectric substrate 20 can be formed of an appropriate piezoelectric material. Specific examples of the piezoelectric substrate 20 include a LiNbO 3 substrate and a LiTaO 3 substrate.
　圧電基板２０の上には、ＩＤＴ電極１３並びに第１及び第２のグレーティング反射器１４，１５が形成されている。ＩＤＴ電極１３並びに第１及び第２のグレーティング反射器１４，１５は、Ａｕ、Ｐｔ、Ａｌ、Ｃｕ、Ｎｉ、Ｔｉなどの金属や、ＡｌＣｕなどの合金等の適宜の導電材料により形成することができる。ＩＤＴ電極１３並びに第１及び第２のグレーティング反射器１４，１５は、ひとつの導電層により構成されていてもよいし、複数の導電層の積層体により形成されていてもよい。 The IDT electrode 13 and the first and second grating reflectors 14 and 15 are formed on the piezoelectric substrate 20. The IDT electrode 13 and the first and second grating reflectors 14 and 15 can be formed of an appropriate conductive material such as a metal such as Au, Pt, Al, Cu, Ni, or Ti, or an alloy such as AlCu. . The IDT electrode 13 and the first and second grating reflectors 14 and 15 may be formed of a single conductive layer, or may be formed of a stacked body of a plurality of conductive layers.
　また、ＩＤＴ電極１３並びに第１及び第２のグレーティング反射器１４，１５の厚さも、特に限定されず、弾性境界波装置１の要求特性などに応じて適宜設定することができる。 Also, the thicknesses of the IDT electrode 13 and the first and second grating reflectors 14 and 15 are not particularly limited, and can be appropriately set according to the required characteristics of the boundary acoustic wave device 1.
　なお、本実施形態においては、圧電基板２０の表面上に、下地層２３が形成されており、その下地層２３の上にＩＤＴ電極１３並びに第１及び第２のグレーティング反射器１４，１５が形成されている。しかしながら、本発明において、下地層は必須ではなく、圧電基板の直上にＩＤＴ電極等を形成してもよい。下地層２３の材料は特に限定されないが、下地層２３は、例えば、Ｔａ２Ｏ５などの酸化タンタルにより形成することができる。 In the present embodiment, the base layer 23 is formed on the surface of the piezoelectric substrate 20, and the IDT electrode 13 and the first and second grating reflectors 14 and 15 are formed on the base layer 23. Has been. However, in the present invention, the underlayer is not essential, and an IDT electrode or the like may be formed directly on the piezoelectric substrate. The material of the underlayer 23 is not particularly limited, but the underlayer 23 can be formed of tantalum oxide such as Ta 2 O 5 , for example.
　圧電基板２０の上には、ＩＤＴ電極１３並びに第１及び第２のグレーティング反射器１４，１５を覆うように第１の媒質２１が形成されている。すなわち、ＩＤＴ電極１３並びに第１及び第２のグレーティング反射器１４，１５は、圧電基板２０と第１の媒質２１との境界に形成されている。第１の媒質２１の上には、第２の媒質２２が形成されている。第１の媒質２１の音速は、圧電基板２０の音速及び第２の媒質２２の音速のいずれよりも低い。 A first medium 21 is formed on the piezoelectric substrate 20 so as to cover the IDT electrode 13 and the first and second grating reflectors 14 and 15. That is, the IDT electrode 13 and the first and second grating reflectors 14 and 15 are formed at the boundary between the piezoelectric substrate 20 and the first medium 21. A second medium 22 is formed on the first medium 21. The sound speed of the first medium 21 is lower than both the sound speed of the piezoelectric substrate 20 and the sound speed of the second medium 22.
　第１及び第２の媒質２１，２２の材料は、第１の媒質２１の音速が圧電基板２０の音速及び第２の媒質２２の音速よりも低くなる材料であれば特に限定されない。例えば、第１の媒質２１及び第２の媒質２２は、誘電体により形成することができる。具体的には、例えば、第１の媒質２１をＳｉＯ２などの酸化珪素により形成し、第２の媒質２２をＳｉＮなどの窒化珪素により形成することができる。 The material of the first medium 21 and the second medium 22 is not particularly limited as long as the sound speed of the first medium 21 is lower than the sound speed of the piezoelectric substrate 20 and the sound speed of the second medium 22. For example, the first medium 21 and the second medium 22 can be formed of a dielectric. Specifically, for example, the first medium 21 is formed by a silicon oxide such as SiO 2, the second medium 22 may be formed of silicon nitride, such as SiN.
　第１及び第２の媒質２１，２２の形成方法も特に限定されず、第１及び第２の媒質２１，２２は、例えば、スパッタ法や、ＣＶＤ法等の蒸着法により形成することができる。 The formation method of the first and second media 21 and 22 is not particularly limited, and the first and second media 21 and 22 can be formed by an evaporation method such as a sputtering method or a CVD method.
　第１の媒質２１の厚さは、特に限定されず、弾性境界波装置１に要求される特性などに応じて適宜設定することができる。一方、第２の媒質２２の厚さは、ＩＤＴ電極１３において生じる弾性境界波の波長をλとしたときに、０．５６λ以上である。このため、下記の実験例の結果からも分かるように、スプリアス応答となる高次モードを効果的に抑圧することができる。 The thickness of the first medium 21 is not particularly limited, and can be appropriately set according to characteristics required for the boundary acoustic wave device 1. On the other hand, the thickness of the second medium 22 is 0.56λ or more when the wavelength of the boundary acoustic wave generated in the IDT electrode 13 is λ. For this reason, as can be seen from the results of the following experimental examples, it is possible to effectively suppress higher-order modes that are spurious responses.
　具体的には、以下のような実験を行った。 Specifically, the following experiment was conducted.
　以下の設計パラメータで、図１及び図２に示す構成の弾性境界波装置を作製し、共振子特性を測定した。 A boundary acoustic wave device having the configuration shown in FIGS. 1 and 2 was manufactured with the following design parameters, and the resonator characteristics were measured.
　圧電基板２０：２５°Ｙ－Ｘ　ＬｉＮｂＯ３基板
　下地層２３の材料：Ｔａ２Ｏ５
　下地層２３の厚さ：１２ｎｍ（０．００７λ）
　ＩＤＴ電極１３及び第１及び第２のグレーティング反射器１４，１５の膜構成：Ｔｉ層（厚さ１０ｎｍ（０．００６λ））／Ｐｔ層（厚さ３１ｎｍ（０．０１７λ））／Ｔｉ層（厚さ１０ｎｍ（０．００６λ））／Ａｌ層（厚さ３００ｎｍ（０．１６７λ））／Ｔｉ層（厚さ１０ｎｍ（０．００６λ））／Ｐｔ層（厚さ３１ｎｍ（０．０１７λ））／Ｔｉ層（厚さ１０ｎｍ（０．００６λ））
　ＩＤＴ電極１３の電極指のピッチによって決定される波長（λ）：１．８μｍ
　ＩＤＴ電極１３における電極指対数：６０対
　ＩＤＴ電極１３のデューティー：０．５０
　ＩＤＴ電極１３の交叉幅（対向しあうバスバーの間隔）：３０λ
ＩＤＴ電極のアポダイズ比（最小交叉幅Ｗ０／最大交叉幅Ｗ１）：０．４０
　第１及び第２のグレーティング反射器１４，１５における電極指の本数：各５１本
　第１の媒質２１の材料：ＳｉＯ２
　第１の媒質２１の厚さ：１１１８ｎｍ（０．６２１λ）
　第２の媒質２２の材料：ＳｉＮ
　第２の媒質２２の厚さ：６００ｎｍ（０．３３λ）、８００ｎｍ（０．４４λ）、１０００ｎｍ（０．５６λ）、１８９０ｎｍ（１．０５λ） Piezoelectric substrate 20: 25 ° YX LiNbO 3 substrate Material of underlayer 23: Ta 2 O 5
Underlayer 23 thickness: 12 nm (0.007λ)
Film configuration of IDT electrode 13 and first and second grating reflectors 14 and 15: Ti layer (thickness 10 nm (0.006λ)) / Pt layer (thickness 31 nm (0.017λ)) / Ti layer (thickness) 10 nm (0.006λ)) / Al layer (thickness 300 nm (0.167λ)) / Ti layer (thickness 10 nm (0.006λ)) / Pt layer (thickness 31 nm (0.017λ)) / Ti layer (Thickness 10 nm (0.006λ))
Wavelength (λ) determined by the pitch of the electrode fingers of the IDT electrode 13: 1.8 μm
Number of electrode finger pairs in IDT electrode 13: 60 Duty of IDT electrode 13: 0.50
Cross width of IDT electrode 13 (interval of bus bars facing each other): 30λ
IDT electrode apodization ratio (minimum crossover width W 0 / maximum crossover width W 1 ): 0.40
Number of electrode fingers in first and second grating reflectors 14 and 15: 51 each Material of first medium 21: SiO 2
Thickness of the first medium 21: 1118 nm (0.621λ)
Material of the second medium 22: SiN
Thickness of the second medium 22: 600 nm (0.33λ), 800 nm (0.44λ), 1000 nm (0.56λ), 1890 nm (1.05λ)
　図３～図１０に共振子特性の測定結果を示す。具体的には、図３は、第２の媒質の厚さが０．３３λである場合のインピーダンス特性を表すグラフである。図４は、第２の媒質の厚さが０．３３λである場合の位相特性を表すグラフである。図５は、第２の媒質の厚さが０．４４λである場合のインピーダンス特性を表すグラフである。図６は、第２の媒質の厚さが０．４４λである場合の位相特性を表すグラフである。図７は、第２の媒質の厚さが０．５６λである場合のインピーダンス特性を表すグラフである。図８は、第２の媒質の厚さが０．５６λである場合の位相特性を表すグラフである。図９は、第２の媒質の厚さが１．０５λである場合のインピーダンス特性を表すグラフである。図１０は、第２の媒質の厚さが１．０５λである場合の位相特性を表すグラフである。なお、基本モードによる応答をＡ、高次モードによる応答をＢで示す。 3 to 10 show the measurement results of the resonator characteristics. Specifically, FIG. 3 is a graph showing impedance characteristics when the thickness of the second medium is 0.33λ. FIG. 4 is a graph showing phase characteristics when the thickness of the second medium is 0.33λ. FIG. 5 is a graph showing impedance characteristics when the thickness of the second medium is 0.44λ. FIG. 6 is a graph showing phase characteristics when the thickness of the second medium is 0.44λ. FIG. 7 is a graph showing impedance characteristics when the thickness of the second medium is 0.56λ. FIG. 8 is a graph showing phase characteristics when the thickness of the second medium is 0.56λ. FIG. 9 is a graph showing impedance characteristics when the thickness of the second medium is 1.05λ. FIG. 10 is a graph showing phase characteristics when the thickness of the second medium is 1.05λ. A response in the basic mode is indicated by A and a response in the higher order mode is indicated by B.
　図３～図１０に示すように、基本モードの共振子特性は、第２の媒質２２の厚さが変化しても大きく変化しないことがわかる。それに対して、高次モードの強度は、第２の媒質２２の厚さが０．５６λ未満である場合は大きく、第２の媒質２２の厚さが０．５６λ以上の場合は小さくなった。 As shown in FIGS. 3 to 10, it can be seen that the resonator characteristics of the fundamental mode do not change greatly even if the thickness of the second medium 22 changes. On the other hand, the intensity of the higher-order mode is large when the thickness of the second medium 22 is less than 0.56λ, and is small when the thickness of the second medium 22 is 0.56λ or more.
　また、第２の媒質２２の厚さが０．５６λである場合を表す図７，８と、第２の媒質２２の厚さが１．０５λである場合を表す図９，１０との比較により、第２の媒質２２の厚さが０．５６λ以上では、第２の媒質２２の厚さが変化しても、高次モードの強度がそれほど大きくは変化しないことが分かる。 7 and 8 showing the case where the thickness of the second medium 22 is 0.56λ, and comparison with FIGS. 9 and 10 showing the case where the thickness of the second medium 22 is 1.05λ. It can be seen that when the thickness of the second medium 22 is 0.56λ or more, the intensity of the higher-order mode does not change so much even if the thickness of the second medium 22 changes.
　これらの結果から、第２の媒質２２の厚さを０．５６λ以上とすることによって、基本モードの特性を変化させることなく、高次モードを効果的に抑圧できるため、高次モードに起因するスプリアスを効果的に低減することができる。従って、例えば、本実施形態の弾性境界波装置１を用いることによって特性が良好な弾性境界波フィルタを作成することができる。 From these results, by setting the thickness of the second medium 22 to 0.56λ or more, it is possible to effectively suppress the higher order mode without changing the characteristics of the fundamental mode. Spurious can be effectively reduced. Therefore, for example, a boundary acoustic wave filter having good characteristics can be created by using the boundary acoustic wave device 1 of the present embodiment.
　なお、基本モードが第２の媒質２２の厚さに大きく相関しないのに対して、第２の媒質２２の厚さが小さくなると高次モードの強度が高くなるのは、高次モードは基本モードに比べて基板厚み方向に広い変位分布を持つためであると考えられる。すなわち、第２の媒質２２の厚さが０．５６λ未満の場合は、基本モードは第２の媒質２２の表面にまで達しないものの、高次モードが第２の媒質２２の表面にまで達しているのに対して、第２の媒質２２の厚さが０．５６λ以上である場合は、高次モードも第２の媒質２２内に閉じ込められ、第２の媒質２２の表面にまで達しなくなるため、高次モードに起因するスプリアス応答が小さくなったものと考えられる。 Note that the fundamental mode does not greatly correlate with the thickness of the second medium 22, whereas the strength of the higher-order mode increases as the thickness of the second medium 22 decreases. This is considered to be because of a wider displacement distribution in the substrate thickness direction than That is, when the thickness of the second medium 22 is less than 0.56λ, the fundamental mode does not reach the surface of the second medium 22, but the higher-order mode reaches the surface of the second medium 22. On the other hand, when the thickness of the second medium 22 is 0.56λ or more, the higher-order mode is also confined in the second medium 22 and does not reach the surface of the second medium 22. It is considered that the spurious response due to the higher order mode is reduced.
　ところで、高次モードに起因するスプリアスを抑圧する方法としては、従来、第２の媒質２２の表面に、高次モードを吸音する吸音層を設ける方法が知られている。しかしながら、第２の媒質２２の表面に吸音層を設けたとしても、高次モードの強度を十分に小さくすることはできない。このことを確認するために、以下の実験を行った。 By the way, as a method of suppressing spurious due to the higher order mode, a method of providing a sound absorbing layer for absorbing the higher order mode on the surface of the second medium 22 is conventionally known. However, even if a sound absorbing layer is provided on the surface of the second medium 22, the strength of the higher-order mode cannot be sufficiently reduced. In order to confirm this, the following experiment was conducted.
　すなわち、第２の媒質の上にポリイミドからなる厚さ８μｍの吸音層を形成したこと以外は、上記実験例において作成した弾性境界波装置と同様に弾性境界波装置を作製し、共振子特性を測定した。その結果、第２の媒質２２の厚さが０．５６λまたは１．０５λである場合は、吸音層がある場合とない場合とで、共振子特性に大きな変化は見られなかった。一方、第２の媒質２２の厚さが０．４４λまたは０．３３λである場合は、吸音層を設けることにより、吸音層を設けない場合よりも、高次モードの応答の強度が小さくなった。しかしながら、吸音層を設けた場合であっても、第２の媒質２２の厚さが０．４４λまたは０．３３λである場合は、第２の媒質２２の厚さが０．５６λ以上である場合ほどは高次モードの応答が小さくならなかった。この結果から、吸音層を設けたのみでは高次モードを十分に抑圧することは困難であり、高次モードを十分に抑圧するためには、第２の媒質２２の厚みを０．５６λ以上にする必要があることがわかる。 That is, a boundary acoustic wave device is manufactured in the same manner as the boundary acoustic wave device created in the above experimental example, except that a sound absorbing layer made of polyimide and having a thickness of 8 μm is formed on the second medium. It was measured. As a result, when the thickness of the second medium 22 was 0.56λ or 1.05λ, there was no significant change in the resonator characteristics with and without the sound absorbing layer. On the other hand, when the thickness of the second medium 22 is 0.44λ or 0.33λ, the intensity of the higher-order mode response is smaller by providing the sound absorbing layer than when the sound absorbing layer is not provided. . However, even when the sound absorbing layer is provided, when the thickness of the second medium 22 is 0.44λ or 0.33λ, the thickness of the second medium 22 is 0.56λ or more. The response of the higher order mode did not become so small. From this result, it is difficult to sufficiently suppress the higher-order mode only by providing the sound absorption layer, and in order to sufficiently suppress the higher-order mode, the thickness of the second medium 22 is set to 0.56λ or more. I know you need to do that.
　ところで、第２の媒質２２の厚さを厚くした場合、例えば、第２の媒質２２をスパッタ法や蒸着法、ＣＶＤ法、スピンコート法、スクリーン印刷法で形成すると、第２の媒質の膜応力により圧電基板２０に反りが発生する。圧電基板２０が反ると、搬送工程が行いづらくなったり、圧電基板２０に割れや欠けが生じたりする場合がある。このため、圧電基板２０に生じる反りを小さくする観点からは、第２の媒質２２の厚さは、小さい方が好ましい。 By the way, when the thickness of the second medium 22 is increased, for example, if the second medium 22 is formed by sputtering, vapor deposition, CVD, spin coating, or screen printing, the film stress of the second medium As a result, the piezoelectric substrate 20 is warped. If the piezoelectric substrate 20 is warped, it may be difficult to carry out the conveying process, or the piezoelectric substrate 20 may be cracked or chipped. For this reason, from the viewpoint of reducing the warpage generated in the piezoelectric substrate 20, it is preferable that the thickness of the second medium 22 is small.
　図１１は、直径が１０．１６ｃｍ（４インチ）で、厚さが０．７ｍｍである円板状の圧電基板（カット角２５°回転ＹカットＬｉＮｂＯ３基板）２０の上に、第１の媒質２１として、厚さ６００ｎｍのＳｉＯ２膜をＲＦスパッタ法により成膜した後に、第２の媒質２２として、ＳｉＮ膜をＲＦスパッタ法により成膜した場合の、ＳｉＮ膜の膜厚と、圧電基板２０の反りとの関係を表すグラフである。 FIG. 11 shows a first medium on a disk-shaped piezoelectric substrate (cut angle 25 ° rotated Y-cut LiNbO 3 substrate) 20 having a diameter of 10.16 cm (4 inches) and a thickness of 0.7 mm. 21, when a SiO 2 film having a thickness of 600 nm is formed by RF sputtering, and then a SiN film is formed by RF sputtering as the second medium 22, the thickness of the SiN film and the piezoelectric substrate 20 It is a graph showing the relationship with the curvature of.
　図１１に示すように、第２の媒質２２の厚みが４．６μｍ以下であれば、圧電基板２０の反り量を、搬送工程において取り扱いが可能な５００μｍ以下にできることが分かる。この結果から、第２の媒質２２の厚みは、４．６μｍ以下であることが好ましいことが分かる。さらに、圧電基板の反り量が３００μｍ以下にすることが可能であることより、第２の媒質２２の厚みは、２．８μｍ以下であることがより好ましい。 As shown in FIG. 11, it can be seen that if the thickness of the second medium 22 is 4.6 μm or less, the warp amount of the piezoelectric substrate 20 can be 500 μm or less that can be handled in the transport process. From this result, it can be seen that the thickness of the second medium 22 is preferably 4.6 μm or less. Furthermore, the thickness of the second medium 22 is more preferably 2.8 μm or less because the amount of warpage of the piezoelectric substrate can be 300 μm or less.
　図１２～図１７に、第２の媒質の厚さが０．５６λ以上であり、カット角θが０°、１０°、３７°の回転ＹカットＬｉＮｂＯ３基板を用いた場合の弾性境界波装置のインピーダンス特性及び位相特性を示す。 FIGS. 12 to 17 show boundary acoustic wave devices in the case of using a rotated Y-cut LiNbO 3 substrate having a second medium thickness of 0.56λ or more and cut angles θ of 0 °, 10 °, and 37 °. The impedance characteristic and the phase characteristic of are shown.
　図１２及び図１３が、θ＝０°の場合の結果を、図１４及び図１５が、θ＝１０°の結果を、図１６及び図１７が、θ＝３７°の場合の結果をそれぞれ示す。 12 and 13 show the results when θ = 0 °, FIGS. 14 and 15 show the results when θ = 10 °, and FIGS. 16 and 17 show the results when θ = 37 °, respectively. .
　ＳＨ型弾性境界波装置の基本モードによる応答をＡ、高次モードによる応答をＢで示す。 The response by the fundamental mode of the SH type boundary acoustic wave device is indicated by A, and the response by the higher order mode is indicated by B.
　図１２～図１７から明らかなように、カット角θが０°、１０°または３７°の場合のいずれにおいても、基本モードのインピーダンス比、すなわち反共振周波数におけるインピーダンスの共振周波数におけるインピーダンスに対する比は６０ｄＢ以上であり、上記実施形態すなわち２５°回転ＹカットＬｉＮｂＯ３基板の場合のインピーダンス比と同等である。従って、カット角θが、０°～３７°の範囲であれば、上記実施形態と同様に、基本モードの応答は充分な大きさとなることがわかる。 As is apparent from FIGS. 12 to 17, regardless of whether the cut angle θ is 0 °, 10 °, or 37 °, the impedance ratio of the fundamental mode, that is, the ratio of the impedance at the anti-resonance frequency to the impedance at the resonance frequency is The impedance ratio is equal to or greater than 60 dB, which is equivalent to the impedance ratio in the above-described embodiment, that is, the 25 ° rotated Y-cut LiNbO 3 substrate. Therefore, if the cut angle θ is in the range of 0 ° to 37 °, it can be seen that the response in the fundamental mode is sufficiently large as in the above embodiment.
　また、カット角θが、０°～３７°の範囲では、高次モードによるスプリアスの応答が大きいことが問題であることがわかる。第２の媒質を構成するＳｉＮからなる誘電体層の膜厚が０．５６λより小さい場合は、高次モードのスプリアス応答がさらに大きくなる。 Also, it can be seen that when the cut angle θ is in the range of 0 ° to 37 °, the spurious response due to the higher-order mode is large. When the film thickness of the dielectric layer made of SiN constituting the second medium is smaller than 0.56λ, the spurious response of the higher-order mode is further increased.
　よって、本発明においては、好ましくは、ＬｉＮｂＯ３のカット角θは０°～３７°の範囲内であれば、高次モードスプリアスを抑圧し、充分な大きさの基本モードによる応答を得ることができることがわかる。 Therefore, in the present invention, preferably, when the cut angle θ of LiNbO 3 is in the range of 0 ° to 37 °, higher-order mode spurious can be suppressed and a response with a sufficiently large fundamental mode can be obtained. I understand that I can do it.
　なお、図１２～１７の横軸は音速とした。音速（ｍ／秒）＝周波数（ＭＨｚ）×波長（μｍ）である。音速の３０００ｍ／秒から５０００ｍ／秒の範囲は、周波数の１７００ＭＨｚから２７００ＭＨｚの範囲と等価である。 The horizontal axis in FIGS. 12 to 17 is the speed of sound. Sound speed (m / sec) = frequency (MHz) × wavelength (μm). The speed range of 3000 m / sec to 5000 m / sec is equivalent to the frequency range of 1700 MHz to 2700 MHz.
　１…弾性境界波装置
１１…入力端子
１２…出力端子
１３…ＩＤＴ電極
１４…第１のグレーティング反射器
１５…第２のグレーティング反射器
２０…圧電基板
２１…第１の媒質
２２…第２の媒質
２３…下地層 DESCRIPTION OF SYMBOLS 1 ... Elastic boundary wave apparatus 11 ... Input terminal 12 ... Output terminal 13 ... IDT electrode 14 ... 1st grating reflector 15 ... 2nd grating reflector 20 ... Piezoelectric substrate 21 ... 1st medium 22 ... 2nd medium 23 ... Underlayer

Claims (6)

  1. 　圧電基板と、
    　前記圧電基板の上に形成されている第１の媒質と、
    　前記第１の媒質の上に形成されている第２の媒質と、
    　前記圧電基板と前記第１の媒質との境界に形成されているＩＤＴ電極とを備え、
    　前記第１の媒質の音速は、前記圧電基板及び前記第２の媒質の音速よりも低い弾性境界波装置であって、
    　前記ＩＤＴ電極において生じる弾性境界波の波長をλとしたときに、前記第２の媒質の厚さが０．５６λ以上である、弾性境界波装置。     A piezoelectric substrate;
    A first medium formed on the piezoelectric substrate;
    A second medium formed on the first medium;
    An IDT electrode formed at a boundary between the piezoelectric substrate and the first medium;
    The acoustic velocity of the first medium is a boundary acoustic wave device that is lower than the acoustic velocity of the piezoelectric substrate and the second medium,
    A boundary acoustic wave device in which the thickness of the second medium is 0.56λ or more, where λ is the wavelength of the boundary acoustic wave generated in the IDT electrode.
  2. 　前記第２の媒質の厚さが４．６μｍ以下である、請求項１に記載の弾性境界波装置。 The boundary acoustic wave device according to claim 1, wherein the thickness of the second medium is 4.6 µm or less.
  3. 　前記圧電基板は、カット角が０°～３７°の範囲内にある回転ＹカットＬｉＮｂＯ３基板である、請求項１または２に記載の弾性境界波装置。 3. The boundary acoustic wave device according to claim 1, wherein the piezoelectric substrate is a rotating Y-cut LiNbO 3 substrate having a cut angle in a range of 0 ° to 37 °.
  4. 　前記第２の媒質が窒化珪素からなる、請求項１～３のいずれか一項に記載の弾性境界波装置。 The boundary acoustic wave device according to any one of claims 1 to 3, wherein the second medium is made of silicon nitride.
  5. 　前記第１の媒質が酸化珪素からなる、請求項１～４のいずれか一項に記載の弾性境界波装置。 The boundary acoustic wave device according to any one of claims 1 to 4, wherein the first medium is made of silicon oxide.
  6. 　前記第２の媒質は、スパッタ法、蒸着法、ＣＶＤ法、スピンコート法またはスクリーン印刷法により形成された膜である、請求項１～５のいずれか一項に記載の弾性境界波装置。 6. The boundary acoustic wave device according to claim 1, wherein the second medium is a film formed by sputtering, vapor deposition, CVD, spin coating, or screen printing.
PCT/JP2010/057824 2009-05-12 2010-05-07 Elastic boundary wave device WO2010131607A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2009-115551 2009-05-12
JP2009115551A JP2012169692A (en) 2009-05-12 2009-05-12 Elastic boundary wave device

Publications (1)

Publication Number Publication Date
WO2010131607A1 true WO2010131607A1 (en) 2010-11-18

Family

ID=43084979

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2010/057824 WO2010131607A1 (en) 2009-05-12 2010-05-07 Elastic boundary wave device

Country Status (2)

Country Link
JP (1) JP2012169692A (en)
WO (1) WO2010131607A1 (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6964359B1 (en) * 2020-08-03 2021-11-10 三安ジャパンテクノロジー株式会社 Surface acoustic wave device

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998052279A1 (en) * 1997-05-12 1998-11-19 Hitachi, Ltd. Elastic wave device
WO2006114930A1 (en) * 2005-04-25 2006-11-02 Murata Manufacturing Co., Ltd. Boundary acoustic wave device

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998052279A1 (en) * 1997-05-12 1998-11-19 Hitachi, Ltd. Elastic wave device
WO2006114930A1 (en) * 2005-04-25 2006-11-02 Murata Manufacturing Co., Ltd. Boundary acoustic wave device

Also Published As

Publication number Publication date
JP2012169692A (en) 2012-09-06

Similar Documents

Publication Publication Date Title
US9035725B2 (en) Acoustic wave device
JP7377920B2 (en) surface acoustic wave device
WO2011158445A1 (en) Acoustic wave element
JP3885824B2 (en) Surface acoustic wave device
JP4337816B2 (en) Boundary acoustic wave device
JP5187444B2 (en) Surface acoustic wave device
JP2004112748A (en) Surface acoustic wave apparatus and manufacturing method therefor
JP5338914B2 (en) Elastic wave device, duplexer and electronic device using the same
US7876020B2 (en) Boundary acoustic wave device including idt electrodes including a plurality of conductive layers with different densities
JP4297139B2 (en) Surface acoustic wave device
JP2010193429A (en) Acoustic wave device
WO2010137279A1 (en) Acoustic wave resonator and duplexer using same
WO2009139108A1 (en) Boundary elastic wave device
WO2011132443A1 (en) Surface acoustic wave device and manufacturing method of same
WO2010052914A1 (en) Elastic wave element and electronic device using the same
US10951193B2 (en) Elastic wave device
US7705515B2 (en) Surface acoustic wave device
WO2020204045A1 (en) High-order mode surface acoustic wave device
JP5083469B2 (en) Surface acoustic wave device
JP5163805B2 (en) Surface acoustic wave device and manufacturing method thereof
WO2010131607A1 (en) Elastic boundary wave device
JPWO2005036744A1 (en) Boundary acoustic wave device
JP5299521B2 (en) Boundary acoustic wave device
JP2004172990A (en) Surface acoustic wave device
JP2004172991A (en) Surface wave instrument and its manufacturing method

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 10774864

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 10774864

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: JP