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WO2023017780A1 - Dispositif à ondes élastiques - Google Patents

Dispositif à ondes élastiques Download PDF

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Publication number
WO2023017780A1
WO2023017780A1 PCT/JP2022/029970 JP2022029970W WO2023017780A1 WO 2023017780 A1 WO2023017780 A1 WO 2023017780A1 JP 2022029970 W JP2022029970 W JP 2022029970W WO 2023017780 A1 WO2023017780 A1 WO 2023017780A1
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WO
WIPO (PCT)
Prior art keywords
layer
elastic wave
wave device
silicon nitride
piezoelectric layer
Prior art date
Application number
PCT/JP2022/029970
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English (en)
Japanese (ja)
Inventor
泰伸 林
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株式会社村田製作所
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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 WO2023017780A1 publication Critical patent/WO2023017780A1/fr

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/25—Constructional features of resonators using surface acoustic waves

Definitions

  • the present invention relates to an acoustic wave device in which a dielectric film is provided between a piezoelectric layer and an IDT electrode.
  • Acoustic wave devices are conventionally known in which a dielectric film is provided between an IDT electrode and a piezoelectric layer.
  • a dielectric film is provided between an IDT electrode and a piezoelectric layer.
  • a thin silicon nitride film or aluminum nitride film is formed on a piezoelectric layer made of LiTaO 3 .
  • An IDT electrode is provided on the silicon nitride film or the aluminum nitride film.
  • An object of the present invention is to provide an elastic wave device whose characteristics are less likely to deteriorate.
  • An acoustic wave device includes a piezoelectric layer, a silicon nitride film provided on the piezoelectric layer, and an IDT electrode provided on the silicon nitride film, wherein the IDT electrode is made of Cu
  • the silicon nitride film has a metal layer made of a Cu alloy
  • the refractive index of the silicon nitride film is 2.15 or more
  • the film thickness of the silicon nitride film is 10 nm or more and 75 nm or less.
  • FIG. 1 is a front cross-sectional view of an elastic wave device according to a first embodiment of the invention.
  • FIG. 2 is a partially cutaway front cross-sectional view showing an enlarged main part of the elastic wave device according to the first embodiment of the present invention.
  • FIG. 3 is a circuit diagram of a ladder-type filter as an elastic wave filter having the elastic wave device of the first embodiment of the present invention.
  • FIG. 4 is a diagram showing the relationship between the film thickness of the silicon nitride film and the fractional bandwidth of the acoustic wave device.
  • FIG. 5 is a diagram showing the relationship between the refractive index of a silicon nitride film and the amount of characteristic variation in a moisture resistance test.
  • FIG. 6 is a front cross-sectional view of an elastic wave device according to a second embodiment of the invention.
  • FIG. 7 is a front cross-sectional view of an elastic wave device according to a third embodiment of the invention.
  • FIG. 8 is a front cross-sectional view of an elastic wave device according to a fourth embodiment of the invention.
  • FIG. 1 is a front cross-sectional view of an elastic wave device according to the first embodiment of the present invention.
  • An elastic wave device 1 has a support substrate 2 .
  • the support substrate 2 is made of Si.
  • the material of the support substrate 2 is not limited to Si, and various insulators and semiconductors can be used.
  • the intermediate layer 3 is laminated on the support substrate 2 .
  • the intermediate layer 3 has a high acoustic velocity film 4 as a high acoustic velocity material layer laminated on the support substrate 2 and a low acoustic velocity film 5 laminated on the high acoustic velocity film 4 .
  • a piezoelectric layer 6 is laminated on the intermediate layer 3 .
  • the piezoelectric layer 6 is made of LiTaO 3 . Therefore, the supporting substrate 2 is laminated on the surface of the intermediate layer 3 opposite to the side on which the piezoelectric layer 6 is provided.
  • the piezoelectric layer 6 has first and second main surfaces 6a and 6b facing each other.
  • the second main surface 6b is located on the intermediate layer 3 side.
  • a silicon nitride film 7 is laminated on the first main surface 6a.
  • the silicon nitride film 7 is represented by SiNx . where x is a positive number. Therefore, the intermediate layer 3 is provided on the side of the second main surface 6b opposite to the side of the piezoelectric layer 6 on which the silicon nitride film 7 is laminated.
  • An IDT electrode 8 is provided on the silicon nitride film 7 .
  • the IDT electrode 8 has an adhesion layer 8b and a metal layer 8a made of Cu as a main electrode layer provided on the adhesion layer 8b.
  • the adhesion layer 8b is made of Ti. However, instead of Ti, other metals or alloys such as NiCr may be used.
  • the metal layer 8 a is made of Cu and is the main electrode layer of the IDT electrode 8 . It should be noted that the main electrode layer refers to a predominant electrode layer among portions functioning as electrodes.
  • the metal layer 8a may be made of a copper alloy mainly containing Cu instead of Cu.
  • Reflectors 10 and 11 are provided on both sides of the IDT electrode 8 in the elastic wave propagation direction. An elastic wave resonator is thereby configured.
  • a protective layer 9 is laminated so as to cover the IDT electrodes 8 .
  • the protective layer 9 is provided not only on the top and side surfaces of the electrode finger portions of the IDT electrodes 8 but also on the regions between the electrode fingers.
  • the protective layer 9 is made of suitable insulating ceramics.
  • the protective layer 9 is made of silicon oxide.
  • the intermediate layer 3 is provided to confine the energy of elastic waves in the piezoelectric layer 6 .
  • the high acoustic velocity film 4 described above is made of a high acoustic velocity material.
  • a high acoustic velocity material is a material in which the acoustic velocity of a propagating bulk wave is higher than the acoustic velocity of an elastic wave propagating through the piezoelectric layer 6 .
  • Such high sonic materials include aluminum oxide, silicon carbide, silicon nitride, silicon oxynitride, silicon, sapphire, lithium tantalate, lithium niobate, quartz, alumina, zirconia, cordierite, mullite, steatite, fort.
  • the high acoustic velocity film 4 is made of silicon nitride.
  • the low sound velocity film 5 is made of a low sound velocity material.
  • a low sound velocity material is a material in which a propagating bulk wave has a lower acoustic velocity than a bulk wave propagating through the piezoelectric layer 6 .
  • Such low sound velocity materials include silicon oxide, glass, silicon oxynitride, tantalum oxide, compounds obtained by adding fluorine, carbon, boron, hydrogen, or silanol groups to silicon oxide, and media containing the above materials as main components. and various other materials.
  • the low sound velocity film 5 is made of silicon oxide.
  • the low sound velocity film 5 is laminated on the second main surface 6 b of the piezoelectric layer 6 .
  • a high acoustic velocity film 4 is laminated on the surface of the low acoustic velocity film 5 opposite to the piezoelectric layer 6 . Therefore, the energy of the elastic wave can be effectively confined on the piezoelectric layer 6 side.
  • the silicon nitride film 7 is provided between the piezoelectric layer 6 and the IDT electrode 8 .
  • the refractive index of the silicon nitride film 7 is 2.15 or more, and the film thickness of the silicon nitride film 7 is in the range of 10 nm or more and 75 nm or less. Therefore, deterioration of the characteristics of the acoustic wave device is less likely to occur. That is, in the elastic wave resonator, deterioration of resonance characteristics such as a fractional bandwidth is less likely to occur. This will be explained more specifically.
  • a silicon nitride film 7 of SiNx was formed on the piezoelectric layer 6 by sputtering.
  • the refractive index was adjusted by adjusting the SiN 2 gas flow rate during film formation.
  • the film thickness of the silicon nitride film 7 was set to 15 nm.
  • a copper alloy of Cu-0.02Ag was used for the metal layer 8a of the IDT electrode 8 .
  • Cu-0.02Ag means a Cu alloy containing Ag in a proportion of 2% by weight.
  • the adhesion layer 8b was a Ti film with a thickness of 10 nm.
  • FIG. 4 is a diagram showing the relationship between the film thickness (nm) of the silicon nitride film 7 and the fractional bandwidth of the acoustic wave device 1 as a resonator.
  • the specific bandwidth is required to be 2% or more. Therefore, as is clear from FIG. 4, a sufficiently large fractional bandwidth can be realized if the film thickness of the silicon nitride film 7 is 75 nm or less.
  • the film thickness of the silicon nitride film 7 is required to be 10 nm or more in order to obtain a sufficient anti-diffusion effect. As described above, in the present embodiment, the thickness of the silicon nitride film 7 is 10 nm or more and 75 nm or less.
  • FIG. 5 is a diagram showing the relationship between the refractive index of the silicon nitride film 7 and the amount of characteristic variation in a moisture resistance test.
  • the elastic wave device 1 was maintained in an environment of 93° C. and 81% RH for 1200 hours.
  • the amount of characteristic variation (%) after this moisture resistance test was determined.
  • the amount of variation in the center frequency of the passband of the elastic wave filter using a plurality of elastic wave devices 1 shown in FIG. 1 was defined as the amount of characteristic variation (%).
  • the refractive index of the silicon nitride film 7 is 2.15 or more.
  • the refractive index is 2.8 or less. If the refractive index exceeds 2.8, filter characteristics may deteriorate.
  • Optical constants refractive index, extinction coefficient
  • film thickness is calculated by fitting with the model formula from the change in the polarization state due to the incidence and reflection of light (ratio of amplitude reflectance tan ( ⁇ ) and phase difference ⁇ ). Method. Specifically, the refractive index was determined using an ellipsometer.
  • the refractive index can be increased when the SiNx becomes rich in Si.
  • the value of the refractive index can be controlled.
  • FIG. 3 is a circuit diagram of a ladder-type filter as an elastic wave filter having the elastic wave device according to the first embodiment of the present invention.
  • the acoustic wave filter 12 has a plurality of series arm resonators S1-S4 and a plurality of parallel arm resonators P1-P3.
  • the acoustic wave device 1 of the present embodiment for at least one of the series arm resonators S1 to S4 and the parallel arm resonators P1 to P3, deterioration of filter characteristics can be suppressed.
  • the elastic wave device according to the present invention can be used not only for such ladder-type filters having a plurality of elastic wave resonators, but also for various band-pass filters.
  • the supporting substrate 2A is a high acoustic velocity supporting substrate made of the above high acoustic velocity material.
  • FIG. 7 is a front cross-sectional view of an elastic wave device according to a third embodiment of the invention.
  • the support substrate 2A is laminated on the second main surface 6b of the piezoelectric layer 6 with the bonding layer 22 interposed therebetween.
  • the support substrate 2A is made of Si. However, it may be made of other semiconductors or insulators.
  • the support substrate 2A has a concave portion 2a open on the upper surface. This concave portion 2 a is positioned below the IDT electrode 8 . Therefore, the excitation region having the IDT electrodes 8 is positioned above the recess 2a.
  • the second main surface 6b of the piezoelectric layer 6, the inner side surface of the bonding layer 22, and the concave portion 2a of the support substrate 2A form a cavity 23 for preventing vibration. No protective layer is provided.
  • FIG. 8 is a front cross-sectional view of an elastic wave device according to a fourth embodiment of the invention.
  • the intermediate layer 32 has a structure in which high acoustic impedance layers 32a, 32c, 32e and low acoustic impedance layers 32b, 32d, 32f are alternately laminated.
  • the high acoustic impedance layers 32a, 32c, 32e are made of a high acoustic impedance material with relatively high acoustic impedance.
  • the low acoustic impedance layers 32b, 32d, 32f are made of a low acoustic impedance material with relatively low acoustic impedance.
  • the elastic wave device 31 is configured in the same manner as the elastic wave device 1 except that the intermediate layer 32 is different from the intermediate layer 3 and no protective layer is provided.
  • the intermediate layer for confining the energy of elastic waves may be an acoustic reflection layer having high acoustic impedance layers 32a, 32c, 32e and low acoustic impedance layers 32b, 32d, 32f. good.
  • the silicon nitride film 7 is formed on the piezoelectric layer 6, so that deterioration of characteristics hardly occurs.

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)

Abstract

L'invention concerne un dispositif à ondes élastiques dont les caractéristiques n'ont pas tendance à s'altérer.　Le dispositif à ondes élastiques 1 comprend : une membrane en nitrure de silicium 7 disposée sur une couche piézoélectrique 6 ; et une électrode IDT 8 disposée sur la membrane en nitrure de silicium 7. L'électrode IDT 8 comprend une couche métallique 8a comprenant du Cu ou un alliage de Cu. L'indice de réfraction de la membrane en nitrure de silicium 7 est d'au moins 2,15 et l'épaisseur de la membrane en nitrure de silicium 7 est de 10 à 75 nm.
PCT/JP2022/029970 2021-08-11 2022-08-04 Dispositif à ondes élastiques WO2023017780A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2021-131225 2021-08-11
JP2021131225 2021-08-11

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WO2023017780A1 true WO2023017780A1 (fr) 2023-02-16

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005530924A (ja) * 2002-05-29 2005-10-13 インフィネオン テクノロジーズ アクチエンゲゼルシャフト 窒化シリコンまたは酸窒化シリコンを蒸着するためのプラズマ化学蒸着方法、および層構造の製造方法、並びに、層構造
JP2008078739A (ja) * 2006-09-19 2008-04-03 Fujitsu Media Device Kk 弾性波デバイスおよびフィルタ
JP2011114826A (ja) * 2009-11-30 2011-06-09 Taiyo Yuden Co Ltd フィルタ、分波器、通信モジュール
JP2019145886A (ja) * 2018-02-16 2019-08-29 株式会社村田製作所 弾性波装置、高周波フロントエンド回路及び通信装置
WO2020175234A1 (fr) * 2019-02-27 2020-09-03 株式会社村田製作所 Dispositif à ondes de surface élastiques
JP6819834B1 (ja) * 2019-02-18 2021-01-27 株式会社村田製作所 弾性波装置
WO2021060513A1 (fr) * 2019-09-27 2021-04-01 株式会社村田製作所 Dispositif à ondes élastiques

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005530924A (ja) * 2002-05-29 2005-10-13 インフィネオン テクノロジーズ アクチエンゲゼルシャフト 窒化シリコンまたは酸窒化シリコンを蒸着するためのプラズマ化学蒸着方法、および層構造の製造方法、並びに、層構造
JP2008078739A (ja) * 2006-09-19 2008-04-03 Fujitsu Media Device Kk 弾性波デバイスおよびフィルタ
JP2011114826A (ja) * 2009-11-30 2011-06-09 Taiyo Yuden Co Ltd フィルタ、分波器、通信モジュール
JP2019145886A (ja) * 2018-02-16 2019-08-29 株式会社村田製作所 弾性波装置、高周波フロントエンド回路及び通信装置
JP6819834B1 (ja) * 2019-02-18 2021-01-27 株式会社村田製作所 弾性波装置
WO2020175234A1 (fr) * 2019-02-27 2020-09-03 株式会社村田製作所 Dispositif à ondes de surface élastiques
WO2021060513A1 (fr) * 2019-09-27 2021-04-01 株式会社村田製作所 Dispositif à ondes élastiques

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