JP2019075704A - Acoustic wave device and method of manufacturing the same - Google Patents

Acoustic wave device and method of manufacturing the same Download PDF

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JP2019075704A
JP2019075704A JP2017200752A JP2017200752A JP2019075704A JP 2019075704 A JP2019075704 A JP 2019075704A JP 2017200752 A JP2017200752 A JP 2017200752A JP 2017200752 A JP2017200752 A JP 2017200752A JP 2019075704 A JP2019075704 A JP 2019075704A
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film
electrode fingers
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piezoelectric substrate
additional film
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JP6957306B2 (en
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今須　誠士
Seishi Imasu
誠士 今須
史弥 松倉
Fumiya Matsukura
史弥 松倉
中村　健太郎
Kentaro Nakamura
中村　　健太郎
松田　隆志
Takashi Matsuda
隆志 松田
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Taiyo Yuden Co Ltd
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Abstract

To improve a coverage of an insulating film.SOLUTION: The acoustic wave device includes: a piezoelectric substrate 10; a pair of comb-tooth electrodes 20a, 20b provided on the piezoelectric substrate, each having a plurality of electrode fingers 21a, 21b, at least a portion of each of the electrode fingers being alternately arranged in an arrangement direction; an additional film 14 provided on the piezoelectric substrate between adjacent electrode fingers, a film thickness being smaller than a film thickness of the plurality of electrodes, and separated from the adjacent electrode fingers; and an insulator film 16 covering the plurality of electrode fingers and the additional film.SELECTED DRAWING: Figure 4

Description

本発明は、弾性波デバイスおよびその製造方法に関し、例えば櫛歯電極を有する弾性波デバイスおよびその製造方法に関する。   The present invention relates to an elastic wave device and a method of manufacturing the same, for example, an elastic wave device having a comb electrode and a method of manufacturing the same.

弾性波を利用した弾性波デバイスとして、圧電基板上に一対の櫛歯電極からなるＩＤＴ（Interdigital Transducer）を含む弾性表面波（ＳＡＷ：Surface acoustic wave）デバイスが知られている。弾性表面波デバイスは、例えば４５ＭＨｚから２ＧＨｚの周波数の無線信号を処理する各種回路におけるバンドパスフィルタとして用いられている（例えば特許文献１）。櫛歯電極をリフトオフ法を用い形成することが知られている（例えば特許文献２−４）。櫛歯電極の電極指の間の圧電基板上に付加膜を設けることが知られている（例えば特許文献５−７）。   As an elastic wave device utilizing an elastic wave, a surface acoustic wave (SAW) device including an IDT (Interdigital Transducer) consisting of a pair of comb electrodes on a piezoelectric substrate is known. A surface acoustic wave device is used, for example, as a band pass filter in various circuits that process wireless signals with a frequency of 45 MHz to 2 GHz (for example, Patent Document 1). It is known that a comb-tooth electrode is formed by using a lift-off method (for example, Patent Documents 2-4). It is known to provide an additional film on the piezoelectric substrate between the electrode fingers of the comb electrode (for example, Patent Documents 5-7).

特開２０１５−８９０６９号公報JP, 2015-89069, A 特開２００１−２６７８６８号公報JP 2001-267868 A 特開２００９−１４７８１８号公報JP, 2009-147818, A 特開２００７−２６７１１７号公報JP 2007-267117 A 特開２０１１−７８０７２号公報JP, 2011-78072, A 特開２０１１−１２４７４５号公報JP 2011-124745 A 再表２０１０／１００９６７号公報Re-listed 2010/1009967

櫛歯電極をリフトオフ法を用い形成するため、圧電基板とマスク層との間に付加膜を設ける。櫛歯電極を形成した後に付加膜を除去すると圧電基板の表面にダメージが導入されることがある。付加膜を除去せずに、櫛歯電極および付加膜上に保護膜として絶縁膜を設けると、絶縁膜の被覆性が悪くなることがある。   In order to form the comb-tooth electrode by the lift-off method, an additional film is provided between the piezoelectric substrate and the mask layer. If the additional film is removed after forming the comb electrode, damage may be introduced to the surface of the piezoelectric substrate. If the insulating film is provided as a protective film on the comb electrode and the additional film without removing the additional film, the covering property of the insulating film may be deteriorated.

本発明は、上記課題に鑑みなされたものであり、絶縁膜の被覆性を向上させることを目的とする。   The present invention has been made in view of the above problems, and has an object to improve the coverage of an insulating film.

本発明は、圧電基板と、前記圧電基板上に設けられ、各々複数の電極指を有し、少なくとも一部において各々の電極指が互い違いに配列方向に配列する一対の櫛歯電極と、隣接する電極指の間における前記圧電基板上に設けられ、膜厚が前記複数の電極指の少なくとも１つの膜厚より小さく、前記隣接する電極指から離間する付加膜と、前記複数の電極指および前記付加膜を覆う絶縁体膜と、を備える弾性波デバイスである。   The present invention is adjacent to a piezoelectric substrate, and a pair of comb-like electrodes provided on the piezoelectric substrate, each having a plurality of electrode fingers, in which at least a portion of the electrode fingers are alternately arranged in the arrangement direction. An additional film provided on the piezoelectric substrate between the electrode fingers and having a thickness smaller than that of at least one of the plurality of electrode fingers and spaced from the adjacent electrode finger, the plurality of electrode fingers, and the addition And an insulator film covering the film.

上記構成において、前記一対の櫛歯電極は、各々対応する複数の電極指が接続されたバスバーを有し、前記一対の櫛歯電極の一方の電極指の前記配列方向の両側に設けられた付加膜は、前記一対の櫛歯電極の一方の電極指と前記一対の櫛歯電極の他方のバスバーとの間を経由して接続する構成とすることができる。   In the above configuration, the pair of comb electrodes includes bus bars to which a plurality of corresponding electrode fingers are respectively connected, and the addition is provided on both sides in the arrangement direction of one electrode finger of the pair of comb electrodes The film may be connected via one of the electrode fingers of the pair of comb electrodes and the other bus bar of the pair of comb electrodes.

上記構成において、前記付加膜は前記一対の櫛歯電極を囲むように設けられている構成とすることができる。   In the above configuration, the additional film may be provided to surround the pair of comb electrodes.

上記構成において、前記付加膜と前記一対の櫛歯電極との離間距離は略一定である構成とすることができる。   In the above configuration, the separation distance between the additional film and the pair of comb electrodes can be substantially constant.

上記構成において、前記付加膜の膜厚は前記複数の電極指の少なくとも１つの膜厚の１／２以下である構成とすることができる。   In the above configuration, the film thickness of the additional film may be half or less of the film thickness of at least one of the plurality of electrode fingers.

上記構成において、前記絶縁体膜を覆うように設けられた誘電体膜を備え、前記絶縁体膜は前記複数の電極指より薄く、前記誘電体膜は前記複数の電極指より厚い構成とすることができる。   In the above configuration, the dielectric film is provided to cover the insulator film, the insulator film is thinner than the plurality of electrode fingers, and the dielectric film is thicker than the plurality of electrode fingers. Can.

上記構成において、前記付加膜は前記絶縁体膜と同じ材料からなる構成とすることができる。   In the above configuration, the additional film can be made of the same material as the insulator film.

上記構成において、前記付加膜の音響インピーダンスは、前記複数の電極指の音響インピーダンスより前記絶縁体膜の音響インピーダンスに近い構成とすることができる。   In the above configuration, the acoustic impedance of the additional film may be closer to the acoustic impedance of the insulator film than the acoustic impedance of the plurality of electrode fingers.

本発明は、圧電基板上に付加膜を形成する工程と、前記付加膜上に第１開口を有するマスク層を形成する工程と、前記付加膜が前記マスク層より小さくなるように、前記マスク層をマスクに付加膜を除去し前記第１開口に連通する前記付加膜の第２開口を形成する工程と、前記第１開口および前記第２開口内の前記圧電基板上および前記マスク層上に前記付加膜の膜厚より大きい膜厚を有する金属膜を形成する工程と、前記マスク層を除去することにより前記マスク層上の前記金属膜を除去し、前記圧電基板上の金属膜から、各々複数の電極指を有し、少なくとも一部において各々の電極指が互い違いに配列方向に配列する一対の櫛歯電極を形成する工程と、前記圧電基板上に、前記複数の電極指および前記付加膜を覆うように、絶縁体膜を形成する工程と、を含む弾性波デバイスの製造方法である。   The present invention comprises the steps of forming an additional film on a piezoelectric substrate, forming a mask layer having a first opening on the additional film, and making the additional film smaller than the additional mask layer. Removing an additional film using a mask to form a second opening of the additional film communicating with the first opening; and forming the second opening of the additional film on the piezoelectric substrate and the mask layer in the first opening and the second opening. Forming a metal film having a film thickness larger than the film thickness of the additional film, and removing the metal film on the mask layer by removing the mask layer; Forming a pair of comb-teeth electrodes having the electrode fingers of which at least a part of the electrode fingers are alternately arranged in the arranging direction, and on the piezoelectric substrate, the plurality of electrode fingers and the additional film. Insulator film to cover A step of forming a method for manufacturing the acoustic wave device comprising a.

本発明によれば、絶縁膜の被覆性を向上させることができる。   According to the present invention, the coverage of the insulating film can be improved.

図１（ａ）から図１（ｄ）は、実施例１に係る弾性波デバイスの製造方法を示す断面図（その１）である。1 (a) to 1 (d) are cross-sectional views (part 1) showing a method of manufacturing an acoustic wave device according to the first embodiment. 図２（ａ）から図２（ｃ）は、実施例１に係る弾性波デバイスの製造方法を示す断面図（その２）である。2 (a) to 2 (c) are cross-sectional views (part 2) showing a method of manufacturing an acoustic wave device according to the first embodiment. 図３は、図１（ｄ）に相当するＳＥＭ画像の模式図である。FIG. 3 is a schematic view of an SEM image corresponding to FIG. 1 (d). 図４は、実施例１に係る弾性波共振器の平面図である。FIG. 4 is a plan view of the elastic wave resonator according to the first embodiment. 図５（ａ）は、図４のＡ−Ａ断面図、図５（ｂ）は、図４の拡大図である。5 (a) is a cross-sectional view taken along the line A-A of FIG. 4, and FIG. 5 (b) is an enlarged view of FIG. 図６（ａ）および図６（ｂ）は、比較例１および比較例２における弾性波デバイスの製造方法を示す断面図である。6 (a) and 6 (b) are cross-sectional views showing a method of manufacturing an acoustic wave device in Comparative Example 1 and Comparative Example 2. FIG. 図７は、実施例１の変形例１に係る弾性波デバイスの断面図である。FIG. 7 is a cross-sectional view of an elastic wave device according to a first modification of the first embodiment. 図８（ａ）は、実施例２に係るフィルタの回路図、図８（ｂ）は、実施例２の変形例１に係るデュプレクサの回路図である。Fig.8 (a) is a circuit diagram of the filter based on Example 2, FIG.8 (b) is a circuit diagram of the duplexer based on the modification 1 of Example 2. As shown in FIG.

以下図面を参照し、本発明の実施例について説明する。   Hereinafter, embodiments of the present invention will be described with reference to the drawings.

図１（ａ）から図２（ｃ）は、実施例１に係る弾性波デバイスの製造方法を示す断面図である。図１（ａ）に示すように、圧電基板１０上に付加膜１４を形成する。圧電基板１０は、例えばタンタル酸リチウム基板またはニオブ酸リチウム基板である。圧電基板１０は支持基板に接合されていてもよい。付加膜１４は、例えば酸化シリコン膜、窒化シリコン膜、炭化シリコン膜、酸化タンタル膜もしくは酸化ニオブ膜等の絶縁膜、アルミニウム膜等の金属膜またはシリコン膜等の導電体膜である。付加膜１４は、例えば真空蒸着法、スパッタリング法またはＣＶＤ（Chemical Vapor Deposition）法を用い形成する。   FIGS. 1A to 2C are cross-sectional views showing a method of manufacturing an acoustic wave device according to the first embodiment. As shown in FIG. 1A, the additional film 14 is formed on the piezoelectric substrate 10. The piezoelectric substrate 10 is, for example, a lithium tantalate substrate or a lithium niobate substrate. The piezoelectric substrate 10 may be bonded to a support substrate. The additional film 14 is, for example, an insulating film such as a silicon oxide film, a silicon nitride film, a silicon carbide film, a tantalum oxide film or a niobium oxide film, a metal film such as an aluminum film, or a conductive film such as a silicon film. The additional film 14 is formed using, for example, a vacuum evaporation method, a sputtering method, or a CVD (Chemical Vapor Deposition) method.

図１（ｂ）に示すように、付加膜１４上に開口５２を有するマスク層５０を形成する。マスク層５０は、例えばフォトレジストであり、塗布、露光および現像を行うことにより形成する。   As shown in FIG. 1B, a mask layer 50 having an opening 52 is formed on the additional film 14. The mask layer 50 is, for example, a photoresist, and is formed by applying, exposing, and developing.

図１（ｃ）に示すように、マスク層５０をマスクに付加膜１４を除去する。付加膜１４の除去は、例えばウェットエッチング法またはドライエッチング法を用いる。このとき、付加膜１４をサイドエッチングする。これにより、付加膜１４の開口５３は開口５２より大きくなる。付加膜１４の側面はマスク層５０の側面より内側に設けられる。マスク層５０の両端部には、マスク層５０と圧電基板１０との間に付加膜１４が設けられていないオーバーハング５４が形成される。   As shown in FIG. 1C, the additional film 14 is removed using the mask layer 50 as a mask. The removal of the additional film 14 uses, for example, a wet etching method or a dry etching method. At this time, the additional film 14 is side-etched. Thus, the opening 53 of the additional film 14 becomes larger than the opening 52. The side surface of the additional film 14 is provided inside the side surface of the mask layer 50. Overhangs 54 in which the additional film 14 is not provided between the mask layer 50 and the piezoelectric substrate 10 are formed at both ends of the mask layer 50.

図１（ｄ）に示すように、開口５２および５３内の圧電基板１０上およびマスク層５０上に金属膜１２および１３を形成する。金属膜１２および１３の形成は例えば真空蒸着法を用いる。金属膜１２および１３は、例えばアルミニウム膜または銅膜を含む膜であり、付加膜１４より厚い。オーバーハング５４が形成されているため、領域５６のように、開口５２および５３内の圧電基板１０上に形成された金属膜１２とマスク層５０上に形成された金属膜１３とは接続されずに分断される。   As shown in FIG. 1D, metal films 12 and 13 are formed on the piezoelectric substrate 10 and the mask layer 50 in the openings 52 and 53, respectively. The formation of the metal films 12 and 13 uses, for example, a vacuum evaporation method. The metal films 12 and 13 are films including, for example, an aluminum film or a copper film, and are thicker than the additional film 14. Since overhang 54 is formed, metal film 12 formed on piezoelectric substrate 10 in openings 52 and 53 and metal film 13 formed on mask layer 50 are not connected like region 56. Divided into

実施例１に係る弾性波デバイスの製造方法の一例について、図１（ｄ）に相当するＳＥＭ（Scanning Electron Microscope）画像を取得した。図３は、図１（ｄ）に相当するＳＥＭ画像の模式図である。図３に示すように、マスク層５０の側面に形成された金属膜１３と金属膜１２とは領域５６において分断されている。金属膜１２は、ルテニウム膜１２ａおよび銅膜１２ｂを有している。   About an example of a manufacturing method of an elastic wave device concerning Example 1, a SEM (Scanning Electron Microscope) image equivalent to Drawing 1 (d) was acquired. FIG. 3 is a schematic view of an SEM image corresponding to FIG. 1 (d). As shown in FIG. 3, the metal film 13 and the metal film 12 formed on the side surface of the mask layer 50 are divided at the region 56. The metal film 12 has a ruthenium film 12a and a copper film 12b.

図２（ａ）に示すように、マスク層５０を除去することにより、マスク層５０上に形成されていた金属膜１３がリフトオフされる。金属膜１２と１３とが分断されているため、金属膜１３は容易に除去できる。例えば金属膜１２と１３とが一部接続されていると、金属膜１２端にバリ等が形成される。   As shown in FIG. 2A, by removing the mask layer 50, the metal film 13 formed on the mask layer 50 is lifted off. Since the metal films 12 and 13 are separated, the metal film 13 can be easily removed. For example, when the metal films 12 and 13 are partially connected, a burr or the like is formed at the end of the metal film 12.

図２（ｂ）に示すように、圧電基板１０上に金属膜１２および付加膜１４を覆うように絶縁体膜１６を形成する。絶縁体膜１６は、例えば窒化シリコン膜または酸化シリコン膜である。絶縁体膜１６は、例えば真空蒸着法またはＣＶＤ法を用い形成する。絶縁体膜１６は例えば金属膜１２より薄い。   As shown in FIG. 2B, an insulator film 16 is formed on the piezoelectric substrate 10 so as to cover the metal film 12 and the additional film 14. The insulator film 16 is, for example, a silicon nitride film or a silicon oxide film. The insulator film 16 is formed using, for example, a vacuum evaporation method or a CVD method. The insulator film 16 is thinner than, for example, the metal film 12.

図２（ｃ）に示すように、絶縁体膜１６上に誘電体膜１８を形成する。誘電体膜１８は、例えば酸化シリコン膜である。誘電体膜１８は、例えば真空蒸着法またはＣＶＤ法を用い形成する。誘電体膜１８は例えば金属膜１２より厚い。誘電体膜１８の上面を例えばＣＭＰ（Chemical Mechanical Polishing）法を用い平坦化する。   As shown in FIG. 2C, the dielectric film 18 is formed on the insulator film 16. The dielectric film 18 is, for example, a silicon oxide film. The dielectric film 18 is formed using, for example, a vacuum evaporation method or a CVD method. The dielectric film 18 is thicker than, for example, the metal film 12. The upper surface of the dielectric film 18 is planarized using, for example, a CMP (Chemical Mechanical Polishing) method.

図４は、実施例１に係る弾性波共振器の平面図である。図５（ａ）は、図４のＡ−Ａ断面図、図５（ｂ）は、図４の拡大図である。図４および図５（ｂ）では、金属膜１２および付加膜１４を図示している。弾性波の伝搬方向（すなわち電極指の配列方向）をＸ方向、電極指の延伸方向をＹ方向、圧電基板１０の上面の法線方向をＺ方向とする。Ｘ方向、Ｙ方向およびＺ方向は、圧電基板１０の結晶方位のＸ軸方向、Ｙ軸方向およびＺ軸方向とは必ずしも対応しない。   FIG. 4 is a plan view of the elastic wave resonator according to the first embodiment. 5 (a) is a cross-sectional view taken along the line A-A of FIG. 4, and FIG. 5 (b) is an enlarged view of FIG. In FIG. 4 and FIG. 5 (b), the metal film 12 and the additional film 14 are illustrated. The propagation direction of the elastic wave (that is, the arrangement direction of the electrode fingers) is taken as the X direction, the extension direction of the electrode fingers as the Y direction, and the normal direction of the upper surface of the piezoelectric substrate 10 as the Z direction. The X direction, the Y direction, and the Z direction do not necessarily correspond to the X axis direction, the Y axis direction, and the Z axis direction of the crystal orientation of the piezoelectric substrate 10.

図５（ａ）に示すように、圧電基板１０上に金属膜１２が設けられている。金属膜１２の間の圧電基板１０上に付加膜１４が設けられている。金属膜１２および付加膜１４を覆うように絶縁体膜１６が設けられている。絶縁体膜１６上に誘電体膜１８が設けられている。付加膜１４の膜厚Ｈ２は、金属膜１２の膜厚Ｈ１より小さい。すなわち、付加膜１４の上面の圧電基板１０からの高さは、金属膜１２の上面の圧電基板１０からの高さより低い。   As shown in FIG. 5A, the metal film 12 is provided on the piezoelectric substrate 10. An additional film 14 is provided on the piezoelectric substrate 10 between the metal films 12. An insulator film 16 is provided to cover the metal film 12 and the additional film 14. A dielectric film 18 is provided on the insulator film 16. The film thickness H 2 of the additional film 14 is smaller than the film thickness H 1 of the metal film 12. That is, the height from the piezoelectric substrate 10 of the upper surface of the additional film 14 is smaller than the height from the piezoelectric substrate 10 of the upper surface of the metal film 12.

誘電体膜１８は、例えば圧電基板１０の弾性率の温度係数と逆符号の弾性率の温度係数を有する。これにより、弾性波デバイスの周波数温度係数を小さくできる。圧電基板１０がタンタル酸リチウム基板またはニオブ酸リチウム基板の場合、絶縁体膜１６は、例えば酸化シリコン膜である。酸化シリコン膜に弗素を添加することで、弾性波デバイスの周波数温度係数をより小さくできる。絶縁体膜１６は、圧電基板１０の上面および金属膜１２を保護する保護膜である。例えば金属膜１２の原子の誘電体膜１８への拡散を抑制する。   The dielectric film 18 has, for example, a temperature coefficient of elastic modulus that has the opposite sign to that of the elastic substrate of the piezoelectric substrate 10. Thereby, the temperature coefficient of frequency of the elastic wave device can be reduced. When the piezoelectric substrate 10 is a lithium tantalate substrate or a lithium niobate substrate, the insulator film 16 is, for example, a silicon oxide film. By adding fluorine to the silicon oxide film, the temperature coefficient of frequency of the acoustic wave device can be further reduced. The insulator film 16 is a protective film that protects the upper surface of the piezoelectric substrate 10 and the metal film 12. For example, diffusion of atoms of the metal film 12 to the dielectric film 18 is suppressed.

図４および図５（ｂ）に示すように、圧電基板１０上にＩＤＴ２４および反射器２６が設けられている。ＩＤＴ２４および反射器２６は、金属膜１２により形成される。ＩＤＴ２４は、対向する一対の櫛歯電極２０ａおよび２０ｂを備える。櫛歯電極２０ａは、複数の電極指２１ａ（櫛歯）と、複数の電極指２１ａが接続されたバスバー２２ａを備える。櫛歯電極２０ｂは、複数の電極指２１ｂ（櫛歯）と、複数の電極指２１ｂが接続されたバスバー２２ｂを備える。一対の櫛歯電極２０ａおよび２０ｂは、少なくとも一部において電極指２１ａおよび２１ｂがほぼ互い違いとなるように、対向して設けられている。   As shown in FIGS. 4 and 5B, the IDT 24 and the reflector 26 are provided on the piezoelectric substrate 10. The IDT 24 and the reflector 26 are formed by the metal film 12. The IDT 24 includes a pair of opposing comb electrodes 20a and 20b. The comb-tooth electrode 20a includes a plurality of electrode fingers 21a (comb teeth) and a bus bar 22a to which the plurality of electrode fingers 21a are connected. The comb-tooth electrode 20 b includes a plurality of electrode fingers 21 b (comb teeth) and a bus bar 22 b to which the plurality of electrode fingers 21 b are connected. The pair of comb-tooth electrodes 20a and 20b are provided opposite to each other so that the electrode fingers 21a and 21b are substantially staggered at least in part.

一対の櫛歯電極２０ａおよび２０ｂの電極指２１ａおよび２１ｂが交差する領域が交差領域である。交差領域において電極指２１ａおよび２１ｂが励振する弾性波は、主にＸ方向に伝搬する。反射器２６は、弾性波を反射する。これにより、ＩＤＴ２４の交差領域内に弾性波が閉じ込められる。同じ櫛歯電極２０ａおよび２０ｂにおける電極指２１ａおよび２１ｂのピッチλがほぼ弾性波の波長となる。   A region where the electrode fingers 21a and 21b of the pair of comb electrodes 20a and 20b intersect is a crossing region. The elastic waves excited by the electrode fingers 21a and 21b in the intersection region mainly propagate in the X direction. The reflector 26 reflects the elastic wave. Thereby, the elastic wave is confined within the crossing region of the IDT 24. The pitch λ of the electrode fingers 21a and 21b in the same comb-tooth electrode 20a and 20b is approximately the wavelength of the elastic wave.

付加膜１４は、電極指２１ａと２１ｂとの間に設けられている。電極指２１ａのＸ方向の両側に設けられている付加膜１４は、電極指２１ａとバスバー２２ｂとの間において接続されている。電極指２１ｂのＸ方向の両側に設けられている付加膜１４は、電極指２１ｂとバスバー２２ａとの間において接続されている。反射器２６内の電極指間の付加膜１４は孤立している。付加膜１４はＩＤＴ２４および反射器２６を囲むように設けられている。隣接する電極指２１ａと２１ｂとの間における付加膜１４の幅Ｗ２は、隣接する電極指２１ａと２１ｂとの間の幅Ｗ１より小さい。   The additional film 14 is provided between the electrode fingers 21a and 21b. The additional films 14 provided on both sides of the electrode finger 21a in the X direction are connected between the electrode finger 21a and the bus bar 22b. The additional films 14 provided on both sides in the X direction of the electrode finger 21 b are connected between the electrode finger 21 b and the bus bar 22 a. The additional film 14 between the electrode fingers in the reflector 26 is isolated. The additional film 14 is provided to surround the IDT 24 and the reflector 26. The width W2 of the additional film 14 between the adjacent electrode fingers 21a and 21b is smaller than the width W1 between the adjacent electrode fingers 21a and 21b.

圧電基板１０は、例えば回転ＹカットＸ伝搬ニオブ酸リチウム基板である。金属膜１２は、例えば圧電基板１０側から膜厚が２０ｎｍのルテニウム膜および膜厚が１２５ｎｍの銅膜である。絶縁体膜１６は、例えば膜厚が２０ｎｍの窒化シリコン膜である。   The piezoelectric substrate 10 is, for example, a rotating Y-cut X-propagating lithium niobate substrate. The metal film 12 is, for example, a ruthenium film having a film thickness of 20 nm and a copper film having a film thickness of 125 nm from the piezoelectric substrate 10 side. The insulator film 16 is, for example, a silicon nitride film having a film thickness of 20 nm.

［比較例］
図６（ａ）および図６（ｂ）は、比較例１および比較例２における弾性波デバイスの製造方法を示す断面図である。図６（ａ）に示すように、比較例１では、付加膜１４の幅とマスク層５０の幅は同程度である。金属膜１２と付加膜１４とは離間しない。マスク層５０の側面の金属膜１３と圧電基板１０上の金属膜１２とが分断されない。よって、金属膜１３をリフトオフすることが難しくなる。さらに、金属膜１２（電極指２１ａおよび２１ｂ）と付加膜１４とが接触すると、弾性波の励振効率が悪くなる。 [Comparative example]
6 (a) and 6 (b) are cross-sectional views showing a method of manufacturing an acoustic wave device in Comparative Example 1 and Comparative Example 2. FIG. As shown in FIG. 6A, in Comparative Example 1, the width of the additional film 14 and the width of the mask layer 50 are substantially the same. The metal film 12 and the additional film 14 are not separated. The metal film 13 on the side surface of the mask layer 50 and the metal film 12 on the piezoelectric substrate 10 are not divided. Therefore, it becomes difficult to lift off the metal film 13. Furthermore, when the metal film 12 (the electrode fingers 21a and 21b) contacts the additional film 14, the excitation efficiency of the elastic wave is degraded.

図６（ｂ）に示すように、比較例２では、付加膜１４の膜厚Ｈ２は金属膜１２の膜厚Ｈ１より大きい。金属膜１２および付加膜１４を覆うように絶縁体膜１６を形成すると、絶縁体膜１６の被覆性が悪くなる。例えば、絶縁体膜１６は、金属膜１２の側面、付加膜１４の側面、および/または圧電基板１０上面の被覆性が悪くなる。よって、絶縁体膜１６の保護膜としての機能が低下する。   As shown in FIG. 6B, in Comparative Example 2, the film thickness H2 of the additional film 14 is larger than the film thickness H1 of the metal film 12. If the insulator film 16 is formed so as to cover the metal film 12 and the additional film 14, the coverage of the insulator film 16 is deteriorated. For example, in the insulator film 16, the coverage of the side surface of the metal film 12, the side surface of the additional film 14, and / or the upper surface of the piezoelectric substrate 10 is deteriorated. Thus, the function of the insulator film 16 as a protective film is reduced.

［実施例１の効果］
実施例１によれば、図１（ａ）のように、圧電基板１０上に付加膜１４を形成する。図１（ｂ）のように、付加膜１４上に開口５２（第１開口）を有するマスク層５０を形成する。図１（ｃ）のように、付加膜１４がマスク層５０より小さくなるように、マスク層５０をマスクに付加膜１４を除去し開口５２に連通する付加膜１４の開口５３（第２開口）を形成する。図１（ｄ）のように、開口５２および５３内の圧電基板１０上およびマスク層５０上に付加膜１４の膜厚より大きい膜厚を有する金属膜１２および１３を形成する。図２（ａ）に示すように、マスク層５０を除去することによりマスク層５０上の金属膜１３を除去する。図４のように、圧電基板１０上の金属膜１２から、各々複数の電極指２１ａおよび２１ｂを有し、少なくとも一部において各々の電極指２１ａおよび２１ｂが互い違いに配列方向に配列する一対の櫛歯電極２０ａおよび２０ｂを形成する。図２（ｂ）のように、圧電基板１０上に、金属膜１２および付加膜１４を覆うように、絶縁体膜１６を形成する。 [Effect of Example 1]
According to the first embodiment, the additional film 14 is formed on the piezoelectric substrate 10 as shown in FIG. As shown in FIG. 1B, a mask layer 50 having an opening 52 (first opening) is formed on the additional film 14. As shown in FIG. 1C, the additional film 14 is removed using the mask layer 50 as a mask so that the additional film 14 is smaller than the mask layer 50, and the opening 53 of the additional film 14 communicated with the opening 52 (second opening) Form As shown in FIG. 1D, metal films 12 and 13 having a film thickness larger than that of the additional film 14 are formed on the piezoelectric substrate 10 and the mask layer 50 in the openings 52 and 53. As shown in FIG. 2A, by removing the mask layer 50, the metal film 13 on the mask layer 50 is removed. As shown in FIG. 4, a pair of combs each having a plurality of electrode fingers 21a and 21b from the metal film 12 on the piezoelectric substrate 10 and in which the electrode fingers 21a and 21b are alternately arranged in the arrangement direction at least partially. The tooth electrodes 20a and 20b are formed. As shown in FIG. 2B, the insulator film 16 is formed on the piezoelectric substrate 10 so as to cover the metal film 12 and the additional film 14.

付加膜１４を除去せずに絶縁体膜１６を形成するため、付加膜１４を除去する工程に起因した圧電基板１０および電極指２１ａおよび２１ｂのダメージを抑制できる。図１（ｂ）において付加膜１４がマスク層５０より小さいため、比較例１よりも図２（ａ）のリフトオフを容易に行うことができる。また、付加膜１４が電極指２１ａおよび２１ｂから離間するため、電極指２１ａおよび２１ｂの励振効率の低下を抑制できる。さらに、付加膜１４の体積（重量）を小さくできるため、付加膜１４が弾性波に影響することを抑制できる。さらに、付加膜１４の膜厚が複数の電極指２１ａおよび２１ｂの少なくとも１つの膜厚より小さいため、比較例２の図６（ｂ）のような絶縁体膜１６の被覆性の劣化を抑制できる。   Since the insulator film 16 is formed without removing the additional film 14, damage to the piezoelectric substrate 10 and the electrode fingers 21 a and 21 b due to the process of removing the additional film 14 can be suppressed. Since the additional film 14 is smaller than the mask layer 50 in FIG. 1B, the lift-off of FIG. 2A can be performed more easily than in Comparative Example 1. In addition, since the additional film 14 is separated from the electrode fingers 21a and 21b, it is possible to suppress a decrease in the excitation efficiency of the electrode fingers 21a and 21b. Furthermore, since the volume (weight) of the additional film 14 can be reduced, the influence of the additional film 14 on the elastic wave can be suppressed. Furthermore, since the film thickness of the additional film 14 is smaller than the film thickness of at least one of the plurality of electrode fingers 21 a and 21 b, the deterioration of the coverage of the insulator film 16 as shown in FIG. .

一対の櫛歯電極２０ａおよび２０ｂに大電力を加えると、電極指２１ａと２１ｂとの間の圧電基板１０と絶縁体膜１６との界面において電極指２１ａおよび２１ｂの原子がマイグレーションする。これにより、櫛歯電極２０ａおよび２０ｂが破壊されることがある。実施例１では、付加膜１４を設けることで、電極指２１ａと２１ｂとの間の原子のマイグレーションを抑制できる。   When a large electric power is applied to the pair of comb electrodes 20a and 20b, atoms of the electrode fingers 21a and 21b migrate at the interface between the piezoelectric substrate 10 and the insulator film 16 between the electrode fingers 21a and 21b. As a result, the comb electrodes 20a and 20b may be broken. In the first embodiment, by providing the additional film 14, migration of atoms between the electrode fingers 21 a and 21 b can be suppressed.

実施例１のように櫛歯電極２０ａおよび２０ｂを形成すると、図４および図５（ｂ）のように、付加膜１４は、隣接する電極指２１ａおよび２１ｂの間における圧電基板１０上に設けられ、隣接する電極指２１ａおよび２１ｂから離間する。   When the comb-tooth electrodes 20a and 20b are formed as in the first embodiment, the additional film 14 is provided on the piezoelectric substrate 10 between the adjacent electrode fingers 21a and 21b as shown in FIGS. 4 and 5B. , Separate from the adjacent electrode fingers 21a and 21b.

また、櫛歯電極２０ａの電極指２１ａのＸ方向の両側に設けられた付加膜１４は、電極指２１ａと櫛歯電極２０ｂのバスバー２２ｂとの間を経由して接続する。付加膜１４は、櫛歯電極２０ａおよび２０ｂを囲むように設けられる。付加膜１４と一対の櫛歯電極２０ａおよび２０ｂの離間距離は製造誤差程度に略一定となる。   The additional films 14 provided on both sides in the X direction of the electrode finger 21a of the comb electrode 20a are connected via the electrode finger 21a and the bus bar 22b of the comb electrode 20b. The additional film 14 is provided so as to surround the comb electrodes 20a and 20b. The distance between the additional film 14 and the pair of comb electrodes 20a and 20b is substantially constant to the extent of manufacturing error.

絶縁体膜１６の被覆性を高めるため、付加膜１４の膜厚Ｈ２は電極指２１ａおよび２１ｂの少なくとも１つの膜厚Ｈ１の５０％（１／２）以下が好ましく２５％（１／４）以下がより好ましい。マスク層５０と圧電基板１０との間に隙間を設けるため、膜厚Ｈ２はＨ１の１０％（１／１０）以上が好ましい。   In order to enhance the coverage of the insulator film 16, the film thickness H2 of the additional film 14 is preferably 50% (1/2) or less of the film thickness H1 of at least one of the electrode fingers 21a and 21b, and preferably 25% (1/4) or less Is more preferred. In order to provide a gap between the mask layer 50 and the piezoelectric substrate 10, the film thickness H2 is preferably 10% (1/10) or more of H1.

金属膜１２のリフトオフを容易に行うため、付加膜１４の幅Ｗ２は電極指２１ａと２１ｂとの間の幅Ｗ１の９０％（９／１０）以下が好ましく、７５％（３／４）以下がより好ましい。図１（ｂ）においてマスク層５０を機械的に補強するように、幅Ｗ２はＷ１の３０％以上が好ましい。   In order to easily lift off the metal film 12, the width W2 of the additional film 14 is preferably 90% (9/10) or less of the width W1 between the electrode fingers 21a and 21b, and 75% (3/4) or less More preferable. The width W2 is preferably 30% or more of W1 so as to mechanically reinforce the mask layer 50 in FIG. 1 (b).

付加膜１４の音響インピーダンスが絶縁体膜１６および／または誘電体膜１８と大きく異なると、弾性波に影響してしまう。よって、付加膜１４の音響インピーダンスは、複数の電極指２１ａおよび２１ｂの音響インピーダンスより絶縁体膜１６および／または誘電体膜１８の音響インピーダンスに近いことが好ましい。   If the acoustic impedance of the additional film 14 is significantly different from that of the insulator film 16 and / or the dielectric film 18, it affects the elastic wave. Therefore, the acoustic impedance of the additional film 14 is preferably closer to the acoustic impedance of the insulator film 16 and / or the dielectric film 18 than the acoustic impedance of the plurality of electrode fingers 21 a and 21 b.

例えば、電極指２１ａおよび２１ｂが主に銅膜の場合、銅の音響インピーダンスは３４．１ＭＰａ・ｓ／ｍ３である。絶縁体膜１６を窒化シリコン膜とすると、その音響インピーダンスは１５．２ＭＰａ・ｓ／ｍ３である。誘電体膜１８を弗素を添加した酸化シリコン膜とすると、その音響インピーダンスは１０．９ＭＰａ・ｓ／ｍ３である。この場合、電極指２１ａおよび２１ｂの音響インピーダンスより絶縁体膜１６および／または誘電体膜１８の音響インピーダンスに近い材料としては、窒化シリコン、酸化シリコン（ＳｉＯ２）、シリコンおよびアルミニウムがある。酸化シリコン、シリコンおよびアルミニウムの音響インピーダンスは、それぞれ１２．５ＭＰａ・ｓ／ｍ３、２０．８ＭＰａ・ｓ／ｍ３および１３．８ＭＰａ・ｓ／ｍ３である。 For example, when the electrode fingers 21a and 21b are mainly copper films, the acoustic impedance of copper is 34.1 MPa · s / m 3 . When the insulator film 16 is a silicon nitride film, its acoustic impedance is 15.2 MPa · s / m 3 . If the dielectric film 18 is a silicon oxide film doped with fluorine, its acoustic impedance is 10.9 MPa · s / m 3 . In this case, materials closer to the acoustic impedance of the insulator film 16 and / or the dielectric film 18 than the acoustic impedances of the electrode fingers 21a and 21b include silicon nitride, silicon oxide (SiO 2 ), silicon and aluminum. The acoustic impedances of silicon oxide, silicon and aluminum are 12.5 MPa · s / m 3 , 20.8 MPa · s / m 3 and 13.8 MPa · s / m 3 , respectively.

［実施例１の変形例１］
図７は、実施例１の変形例１に係る弾性波デバイスの断面図である。図７に示すように、電極指２１ａと２１ｂとの間の圧電基板１０上に付加膜１４が設けられている。付加膜１４と絶縁体膜１６とは同じ材料からなり、例えば窒化シリコン膜である。その他の構成は実施例１と同じであり説明を省略する。 Modification 1 of Embodiment 1
FIG. 7 is a cross-sectional view of an elastic wave device according to a first modification of the first embodiment. As shown in FIG. 7, an additional film 14 is provided on the piezoelectric substrate 10 between the electrode fingers 21a and 21b. The additional film 14 and the insulator film 16 are made of the same material, for example, a silicon nitride film. The other configuration is the same as that of the first embodiment, and the description is omitted.

実施例１の変形例１では、付加膜１４は絶縁体膜１６と同じ材料からなるため、付加膜１４の音響インピーダンスは絶縁体膜１６の音響インピーダンスとほぼ同じである。これにより、付加膜１４が弾性波に影響することを抑制できる。   In the first modification of the first embodiment, since the additional film 14 is made of the same material as the insulator film 16, the acoustic impedance of the additional film 14 is substantially the same as the acoustic impedance of the insulator film 16. Thereby, the additional film 14 can be inhibited from affecting the elastic wave.

実施例１の変形例１では、付加膜１４と絶縁体膜１６との界面が不明瞭となり、付加膜１４と絶縁体膜１６とが一体の膜として見える場合がある。電極指２１ａと２１ｂとの間においてはその中央部において付加膜１４と絶縁体膜１６とが一体となった膜の膜厚Ｈ４は、電極指２１ａと２１ｂとの間の両側部の絶縁体膜１６の膜厚Ｈ３より大きくなる。   In the first modification of the first embodiment, the interface between the additional film 14 and the insulator film 16 may be unclear, and the additional film 14 and the insulator film 16 may be viewed as an integral film. Between the electrode fingers 21a and 21b, the film thickness H4 of the film in which the additional film 14 and the insulator film 16 are integrated at the central portion thereof is the insulator film on both sides between the electrode fingers 21a and 21b. It becomes larger than the film thickness H3 of 16.

実施例２は、実施例１およびその変形例の弾性波共振器を用いたフィルタおよびデュプレクサの例である。図８（ａ）は、実施例２に係るフィルタの回路図である。図８（ａ）に示すように、入力端子Ｔ１と出力端子Ｔ２との間に、１または複数の直列共振器Ｓ１からＳ４が直列に接続されている。入力端子Ｔ１と出力端子Ｔ２との間に、１または複数の並列共振器Ｐ１からＰ４が並列に接続されている。１または複数の直列共振器Ｓ１からＳ４および１または複数の並列共振器Ｐ１からＰ４の少なくとも１つに実施例１およびその変形例の弾性波共振器を用いることができる。ラダー型フィルタの共振器の個数等は適宜設定できる。フィルタは、多重モードフィルタでもよい。   The second embodiment is an example of a filter and duplexer using the elastic wave resonators of the first embodiment and its modification. FIG. 8A is a circuit diagram of a filter according to the second embodiment. As shown in FIG. 8A, one or more series resonators S1 to S4 are connected in series between the input terminal T1 and the output terminal T2. One or more parallel resonators P1 to P4 are connected in parallel between the input terminal T1 and the output terminal T2. The elastic wave resonators according to the first embodiment and its modification can be used for at least one of the one or more series resonators S1 to S4 and the one or more parallel resonators P1 to P4. The number of resonators of the ladder type filter can be set as appropriate. The filter may be a multimode filter.

［実施例２の変形例１］
図８（ｂ）は、実施例２の変形例１に係るデュプレクサの回路図である。図８（ｂ）に示すように、共通端子Ａｎｔと送信端子Ｔｘとの間に送信フィルタ４０が接続されている。共通端子Ａｎｔと受信端子Ｒｘとの間に受信フィルタ４２が接続されている。送信フィルタ４０は、送信端子Ｔｘから入力された高周波信号のうち送信帯域の信号を送信信号として共通端子Ａｎｔに通過させ、他の周波数の信号を抑圧する。受信フィルタ４２は、共通端子Ａｎｔから入力された高周波信号のうち受信帯域の信号を受信信号として受信端子Ｒｘに通過させ、他の周波数の信号を抑圧する。送信フィルタ４０および受信フィルタ４２の少なくとも一方を実施例２のフィルタとすることができる。マルチプレクサとしてデュプレクサを例に説明したがトリプレクサまたはクワッドプレクサでもよい。 Modification 1 of Embodiment 2
FIG. 8B is a circuit diagram of a duplexer according to a first modification of the second embodiment. As shown in FIG. 8B, the transmission filter 40 is connected between the common terminal Ant and the transmission terminal Tx. A reception filter 42 is connected between the common terminal Ant and the reception terminal Rx. The transmission filter 40 passes the signal of the transmission band among the high frequency signals input from the transmission terminal Tx to the common terminal Ant as a transmission signal, and suppresses signals of other frequencies. The reception filter 42 passes the signal of the reception band among the high frequency signals input from the common terminal Ant to the reception terminal Rx as a reception signal, and suppresses signals of other frequencies. At least one of the transmission filter 40 and the reception filter 42 can be the filter of the second embodiment. Although the duplexer has been described as an example of the multiplexer, it may be a triplexer or quadplexer.

以上、本発明の実施例について詳述したが、本発明はかかる特定の実施例に限定されるものではなく、特許請求の範囲に記載された本発明の要旨の範囲内において、種々の変形・変更が可能である。   As mentioned above, although the embodiment of the present invention has been described in detail, the present invention is not limited to such a specific embodiment, and various modifications may be made within the scope of the present invention described in the claims. Changes are possible.

１０ 圧電基板
１２、１３ 金属膜
１４ 付加膜
１６ 絶縁体膜
１８ 誘電体膜
２０ａ、２０ｂ 櫛歯電極
２１ａ、２１ｂ 電極指
２２ａ、２２ｂ バスバー
２４ ＩＤＴ
２６ 反射器
４０ 送信フィルタ
４２ 受信フィルタ
５０ マスク層
５２、５３ 開口 DESCRIPTION OF SYMBOLS 10 Piezoelectric substrate 12, 13 Metal film 14 Addition film 16 Insulator film 18 Dielectric film 20a, 20b Comb-tooth electrode 21a, 21b Electrode finger 22a, 22b Bus bar 24 IDT
26 reflector 40 transmit filter 42 receive filter 50 mask layer 52, 53 aperture

Claims (9)

圧電基板と、
前記圧電基板上に設けられ、各々複数の電極指を有し、少なくとも一部において各々の電極指が互い違いに配列方向に配列する一対の櫛歯電極と、
隣接する電極指の間における前記圧電基板上に設けられ、膜厚が前記複数の電極指の少なくとも１つの膜厚より小さく、前記隣接する電極指から離間する付加膜と、
前記複数の電極指および前記付加膜を覆う絶縁体膜と、
を備える弾性波デバイス。 A piezoelectric substrate,
A pair of comb-like electrodes provided on the piezoelectric substrate, each having a plurality of electrode fingers, in which at least a portion of each electrode finger is alternately arranged in the arrangement direction;
An additional film provided on the piezoelectric substrate between adjacent electrode fingers, the film thickness being smaller than the film thickness of at least one of the plurality of electrode fingers, and being separated from the adjacent electrode fingers;
An insulator film covering the plurality of electrode fingers and the additional film;
Acoustic wave device comprising: 前記一対の櫛歯電極は、各々対応する複数の電極指が接続されたバスバーを有し、
前記一対の櫛歯電極の一方の電極指の前記配列方向の両側に設けられた付加膜は、前記一対の櫛歯電極の一方の電極指と前記一対の櫛歯電極の他方のバスバーとの間を経由して接続する請求項１に記載の弾性波デバイス。 The pair of comb electrodes includes bus bars to which a plurality of corresponding electrode fingers are connected,
The additional film provided on both sides in the arrangement direction of one electrode finger of the pair of comb electrodes is between the one electrode finger of the pair of comb electrodes and the other bus bar of the pair of comb electrodes The elastic wave device according to claim 1 connected via. 前記付加膜は前記一対の櫛歯電極を囲むように設けられている請求項２記載の弾性波デバイス。   The elastic wave device according to claim 2, wherein the additional film is provided so as to surround the pair of comb electrodes. 前記付加膜と前記一対の櫛歯電極との離間距離は略一定である請求項３記載の弾性波デバイス。   The elastic wave device according to claim 3, wherein a separation distance between the additional film and the pair of comb electrodes is substantially constant. 前記付加膜の膜厚は前記複数の電極指の少なくとも１つの膜厚の１／２以下である請求項１から４のいずれか一項記載の弾性波デバイス。   The elastic wave device according to any one of claims 1 to 4, wherein the film thickness of the additional film is equal to or less than 1/2 of the film thickness of at least one of the plurality of electrode fingers. 前記絶縁体膜を覆うように設けられた誘電体膜を備え、
前記絶縁体膜は前記複数の電極指より薄く、前記誘電体膜は前記複数の電極指より厚い請求項１から５のいずれか一項記載の弾性波デバイス。 A dielectric film provided to cover the insulator film;
The elastic wave device according to any one of claims 1 to 5, wherein the insulator film is thinner than the plurality of electrode fingers, and the dielectric film is thicker than the plurality of electrode fingers. 前記付加膜は前記絶縁体膜と同じ材料からなる請求項１から６のいずれか一項記載の弾性波デバイス。   The elastic wave device according to any one of claims 1 to 6, wherein the additional film is made of the same material as the insulator film. 前記付加膜の音響インピーダンスは、前記複数の電極指の音響インピーダンスより前記絶縁体膜の音響インピーダンスに近い請求項１から７のいずれか一項記載の弾性波デバイス。   The elastic wave device according to any one of claims 1 to 7, wherein an acoustic impedance of the additional film is closer to an acoustic impedance of the insulator film than an acoustic impedance of the plurality of electrode fingers. 圧電基板上に付加膜を形成する工程と、
前記付加膜上に第１開口を有するマスク層を形成する工程と、
前記付加膜が前記マスク層より小さくなるように、前記マスク層をマスクに付加膜を除去し前記第１開口に連通する前記付加膜の第２開口を形成する工程と、
前記第１開口および前記第２開口内の前記圧電基板上および前記マスク層上に前記付加膜の膜厚より大きい膜厚を有する金属膜を形成する工程と、
前記マスク層を除去することにより前記マスク層上の前記金属膜を除去し、前記圧電基板上の金属膜から、各々複数の電極指を有し、少なくとも一部において各々の電極指が互い違いに配列方向に配列する一対の櫛歯電極を形成する工程と、
前記圧電基板上に、前記複数の電極指および前記付加膜を覆うように、絶縁体膜を形成する工程と、
を含む弾性波デバイスの製造方法。 Forming an additional film on the piezoelectric substrate;
Forming a mask layer having a first opening on the additional film;
Removing the additional film using the mask layer as a mask so as to make the additional film smaller than the mask layer to form a second opening of the additional film in communication with the first opening;
Forming a metal film having a film thickness larger than that of the additional film on the piezoelectric substrate and the mask layer in the first opening and the second opening;
The metal film on the mask layer is removed by removing the mask layer, and a plurality of electrode fingers are provided from the metal film on the piezoelectric substrate, and the electrode fingers are alternately arranged at least in part Forming a pair of comb electrodes arranged in a direction;
Forming an insulator film on the piezoelectric substrate so as to cover the plurality of electrode fingers and the additional film;
A method of manufacturing an acoustic wave device, including:
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