WO2011105317A1 - Acoustic wave device and manufacturing method therefor - Google Patents

Acoustic wave device and manufacturing method therefor Download PDF

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Publication number
WO2011105317A1
WO2011105317A1 PCT/JP2011/053631 JP2011053631W WO2011105317A1 WO 2011105317 A1 WO2011105317 A1 WO 2011105317A1 JP 2011053631 W JP2011053631 W JP 2011053631W WO 2011105317 A1 WO2011105317 A1 WO 2011105317A1
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dielectric film
idt electrode
wave device
sound velocity
acoustic wave
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PCT/JP2011/053631
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French (fr)
Japanese (ja)
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三浦　道雄
卓 藁科
松田　隆志
松田　聡
井上　和則
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太陽誘電株式会社
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Publication of WO2011105317A1 publication Critical patent/WO2011105317A1/en

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
    • H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
    • H03H3/08—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of resonators or networks using surface acoustic waves
    • H03H3/10—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of resonators or networks using surface acoustic waves for obtaining desired frequency or temperature coefficient
    • 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
    • H03H9/125—Driving means, e.g. electrodes, coils
    • H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
    • H03H9/14538—Formation

Definitions

  • the present invention relates to an acoustic wave device that can be used for a filter element or an oscillator in, for example, a TV, a mobile phone, or a PHS.
  • a surface acoustic wave element (SAW device: Surface Acoustic Wave Device) is well known as one of the devices that apply elastic waves. This SAW device is used for various circuits in devices that process radio signals in the frequency band of 45 MHz to 2 GHz, for example, transmission bandpass filters, reception bandpass filters, local oscillation filters, antenna duplexers, IF filters, FM modulators, etc. It is done.
  • FIG. 1 is a diagram illustrating an example of pass characteristics of a 1-port resonator of a Love wave device.
  • FIG. 2 is a cross-sectional view illustrating a configuration example of a Love wave device.
  • the Love wave device shown in FIG. 2 includes a piezoelectric substrate 102 and an interelectrode dielectric layer 104 between the IDT electrode 103 (Cu) and the IDT electrode 103 provided on the piezoelectric substrate 102. Further, a diffusion prevention layer 106 and a dielectric layer 107 are provided so as to cover the IDT electrode 103 and the interelectrode dielectric layer 104.
  • FIG. 3 is a graph showing the result of calculating the Rayleigh wave response in the Love wave device shown in FIG. 2 by the finite element method. In the graph of FIG.
  • the horizontal axis represents the film thickness of Cu used as an electrode material
  • the vertical axis represents the magnitude of the Rayleigh wave response.
  • the substrate material at this time is Y-cut X-propagating LiNbO 3 .
  • the graph shows that when the Cu film thickness (the film thickness of the IDT electrode 103) is about 150 nm, the magnitude of the Rayleigh wave response becomes zero. That is, the graph shows that the magnitude of the Rayleigh wave response suddenly increases regardless of whether the Cu film thickness is thicker or thinner than 150 nm.
  • the thickness of the IDT electrode By increasing the thickness of the IDT electrode, the cross-sectional area of the electrode increases, and the electrode resistance can be reduced.
  • the Cu film thickness is fixed to 150 nm in the Love wave device having the structure shown in FIG. That is, it is difficult to use a means for reducing the loss by increasing the thickness of the IDT electrode 103.
  • the optimum film thickness of the IDT electrode that can suppress the Rayleigh wave response varies depending on the substrate used, the material of the IDT electrode, etc.
  • the Rayleigh wave response is the same as in FIG. 3 even when other materials are used. You can draw a graph with values.
  • the film thickness of the IDT electrode is limited by the Rayleigh wave response characteristics as well in the elastic wave device other than the Love wave device. The unnecessary response that limits the film thickness of the IDT electrode is not limited to the Rayleigh wave response.
  • an object of the present invention is to provide an elastic wave device capable of increasing the film thickness of the IDT electrode while suppressing an unnecessary wave response.
  • the acoustic wave device disclosed in the present application includes a piezoelectric substrate, an IDT electrode including a plurality of electrode fingers arranged side by side on the piezoelectric substrate, and a first dielectric film formed between the plurality of electrode fingers. A second dielectric film covering the IDT electrode and the first dielectric film, and the first dielectric formed between the plurality of electrode fingers and on the first dielectric film. And a high sound velocity layer that is a medium having a higher sound velocity than the body.
  • an elastic wave device capable of increasing the film thickness of the IDT electrode while suppressing unnecessary wave response.
  • FIG. 4B is a top perspective view of the acoustic wave device according to the present embodiment. It is a graph which shows the result of having calculated the magnitude of the Rayleigh wave response of the elastic wave device in this embodiment by the finite element method.
  • 3 is a graph showing pass characteristics of a resonator when the Love wave device having the configuration shown in FIG.
  • FIG. 2 is operated as a one-port resonator. It is a figure which shows the example of a manufacturing method of the elastic wave device of this embodiment.
  • FIG. 3 is a diagram showing an example of a method for manufacturing the acoustic wave device shown in FIG. It is a figure which shows the structural example of a communication apparatus.
  • FIG. 4A is a cross-sectional view showing a configuration example of an acoustic wave device in the present embodiment.
  • FIG. 4B is a top perspective view of the acoustic wave device according to the present embodiment.
  • FIG. 4A shows a part of a cross section taken along line AA of FIG. 4B.
  • an IDT electrode 3 including a plurality of electrode fingers arranged side by side on a piezoelectric substrate 2 and a first dielectric formed between the plurality of electrode fingers.
  • a body membrane 4 is provided.
  • a high sound velocity layer 5 is formed between the plurality of electrode fingers and on the first dielectric film 4.
  • the high sound velocity layer 5 is formed on the upper portion of the first dielectric film 4.
  • the high sound velocity layer 5 is a medium having a higher sound velocity than the first dielectric 4.
  • a second dielectric film 7 is provided so as to cover the IDT electrode 3 and the first dielectric film 4.
  • a diffusion prevention layer 6 (an example of an additional layer) is provided between the second dielectric 7 and the IDT electrode 3 and the high sound velocity layer 5.
  • the diffusion prevention layer 6 is a medium having a higher sound velocity than the second dielectric 7.
  • a high acoustic velocity layer 5 is provided on the first dielectric film 4 between a plurality of electrode fingers of the IDT electrode 3, thereby allowing an unnecessary wave response such as a Rayleigh wave to respond.
  • the inventors have found that the properties change. That is, it is found that the thickness value of the IDT electrode 3 most suitable for suppressing the unwanted wave response is shifted by inserting the high sound velocity layer 5 that is a medium having a higher sound velocity than the first dielectric film 4. It was done. That is, in the space sandwiched between the electrode fingers of the IDT electrode 3, a medium having a higher sound speed than the first dielectric is provided on the first dielectric film 4, thereby balancing the sound speed near the IDT electrode 3. Can take. As a result, in the acoustic wave device 1, it is possible to increase the film thickness of the IDT electrode 3 while suppressing the unwanted wave response. As a result, low loss can be realized.
  • the total thickness of the first dielectric film 4 and the high sound velocity layer 5 is preferably the same as the thickness of the IDT electrode 3.
  • the upper surface of the high sound velocity layer 5 and the upper surface of the IDT electrode 3 are formed to be the same surface. Therefore, the layer formed on the IDT electrode 3 can be easily flattened.
  • the same thickness does not need to be exactly the same, and for example, manufacturing errors are allowed.
  • the diffusion prevention layer 6 mainly composed of a material with a higher sound velocity than the second dielectric 7, the IDT electrode 3 and the first The dielectric film 4 or the high sound velocity layer 5 can be protected.
  • the diffusion prevention layer 6 can be omitted.
  • the material of the high sound velocity layer 5 can include, for example, SiC, AlN, alumina, or diamond.
  • the material of the diffusion preventing layer 6 can also include, for example, SiC, AlN, alumina, or diamond. Note that the material of the high sound velocity layer 5 is not limited to a specific material as long as the sound velocity of the elastic waves in the high sound velocity layer 5 is higher than the sound velocity of the elastic waves in the first dielectric film 4. Similarly, the material of the diffusion preventing layer 6 is not limited to a specific material. Further, the sound velocity of the high sound velocity layer 5, the sound velocity of the first dielectric film 4, and the sound velocity of the diffusion prevention layer 6 are not necessarily determined only by the material, and may be affected by the structure, temperature, and the like. In the present embodiment, as an example, the high sound velocity layer 5 is formed by disposing a high sound velocity material on the first dielectric film 4 at a position sandwiched between the electrode fingers of the IDT electrode. .
  • the IDT electrode 3 can be mainly composed of Cu, for example, and the first dielectric film 4 and the second dielectric film 7 can be composed mainly of SiO 2 , for example.
  • the piezoelectric substrate 2 can be a LiNbO 3 substrate, for example.
  • the IDT electrode 3 has alternating electrode fingers (strip) connected to the input IN side electrode and electrode fingers (strip) connected to the output OUT side electrode. Are arranged at equal intervals. Reflectors 8 are disposed on both sides of the IDT electrode 3 in a direction perpendicular to the direction in which the electrode fingers extend.
  • the elastic wave device 1 operates as a resonator because the elastic wave propagates between the reflectors 8 in a direction perpendicular to the electrode fingers.
  • An IDT Inter Digital Transducer
  • the elastic wave device shown in FIGS. 4A and 4B can be used, for example, as a device that uses a Love wave, which is a type of surface acoustic wave.
  • the said acoustic wave device is an example of a 1 port type
  • the arrangement of the electrode fingers is not limited to the example shown in FIG. 4B. For example, a configuration in which the intersection width between adjacent electrode fingers is weighted with an apodization may be used.
  • the elastic wave device according to the present invention is not limited to a device using a Love wave, and can be used as a device using a boundary acoustic wave.
  • FIG. 5 is a graph showing the result of calculating the magnitude of the Rayleigh wave response of the acoustic wave device in this embodiment shown in FIGS. 4A and 4B by the finite element method. This calculation is based on the assumption that SiC is formed as the high sound velocity layer 5 with a film thickness of 20 nm. This calculation assumes that the piezoelectric substrate 2 is a rotating Y-plate LiNbO 3 substrate and the Cu IDT electrode 3 is formed on the piezoelectric substrate 2.
  • the plot of the Rayleigh wave response of the elastic wave device in the present embodiment is indicated by a triangle.
  • the Rayleigh wave response plot of the Love wave device shown in FIG. 2 is indicated by a diamond.
  • the plot representing the magnitude of the Rayleigh wave response of the acoustic wave device of the present embodiment is shifted to the right as a whole compared to the comparative example.
  • the magnitude of the Rayleigh wave response is 0 when the Cu film thickness is about 200 nm. That is, by introducing the high sound velocity layer 5, the thickness of the IDT electrode 3 can be increased by about 50 nm.
  • the electrode resistance of the IDT electrode 3 can be reduced, and consequently, the loss as an acoustic wave device can be reduced.
  • the current density at the IDT electrode 3 can be reduced, a device that is strong against application of high power can be realized.
  • the thickness of the entire acoustic wave device can be reduced.
  • FIG. 6 is a graph showing the pass characteristics of a resonator when the Love wave device having the configuration shown in FIG. 2 is operated as a one-port resonator.
  • the high-order unnecessary response suddenly increases.
  • the configuration of the present embodiment is more desirable than the configuration of FIG. 2 from the viewpoint of suppressing unnecessary responses.
  • FIG. 7 is a diagram showing an example of a method for manufacturing the acoustic wave device of the present embodiment.
  • the first dielectric film 4 is formed on the entire upper surface of the piezoelectric substrate 2.
  • the substrate material of the piezoelectric substrate 2 for example, Y-cut X propagation LiNbO 3 can be used.
  • the substrate material LiNbO 3 having another crystal orientation may be used, or another piezoelectric single crystal may be used.
  • transparent SiO 2 can be used for example.
  • a high sound velocity layer 5 is formed on the entire upper surface of the first dielectric film 4.
  • a SiC layer is formed.
  • a method such as printing, vapor deposition, or sputtering can be used.
  • a resist pattern 11 is formed on the high sound velocity layer 5 by using a photolithography technique.
  • the resist pattern 11 is a pattern for forming the IDT electrode 3.
  • the resist pattern is formed in the remaining area of the upper surface of the piezoelectric substrate 2 except for the area where the IDT electrode 3 is formed.
  • the high sound velocity layer 5 is etched. Thereby, the high sound velocity layer 5 other than the region located under the resist pattern 11 is removed. Further, as shown in FIG. 7 (e), the first dielectric film 4 is also removed by etching except for the region located under the resist pattern 11.
  • an electrode film for forming the IDT electrode 3 is formed.
  • the electrode film can be formed by sputtering or vapor deposition, for example.
  • the electrode film is applied to the region where the first dielectric film 4 is removed, that is, the region where the IDT electrode 3 is formed, and the resist pattern 11.
  • the film thickness of the electrode film is preferably formed so as to be substantially the same as the total thickness of the first dielectric film 4 and the high acoustic velocity layer 5.
  • the resist pattern 11 is removed by lift-off.
  • the remaining IDT electrode 3 and the surface of the high sound velocity layer 5 may be surface-treated so as to be flat. In this way, the IDT electrode 3 is formed by the lift-off method. Further, a structure in which the first dielectric film 4 whose upper surface is covered with the high sound velocity layer 5 is located between the electrode fingers of the IDT electrode 3 is obtained.
  • a diffusion preventing film 6 made of SiC and a second dielectric film 7 made of SiO 2 are formed so as to cover the IDT electrode 3 and the high sound velocity layer 5. Thereby, the acoustic wave device having the configuration shown in FIGS. 4A and 4B is obtained.
  • the first dielectric film 4 of the acoustic wave device when transparent SiO 2 is used for the first dielectric film 4 of the acoustic wave device, the first dielectric film 4 is formed on the piezoelectric substrate 2 as shown in FIG. In this state, a fine resist pattern cannot be formed by photolithography. Therefore, as shown in FIG. 2, when an acoustic wave device having a configuration in which the high sound velocity layer 5 is not formed is formed, a light shielding film such as Si or metal is formed on the first dielectric film 4. It is necessary to form a resist pattern thereon.
  • FIG. 8 is a diagram showing an example of a method for manufacturing the acoustic wave device shown in FIG.
  • a light shielding film 112 such as Si is formed on the entire upper surface of the dielectric film 3 (see FIG. FIG. 8 (b)).
  • a resist pattern 111 is formed on the light shielding film 112 (FIG. 8C), and the light shielding film 112 etching (FIG. 8D) and the first dielectric layer 104 etching (FIG. 8E) are performed. .
  • An electrode film of the IDT electrode 103 is formed on the region where the first dielectric layer 104 has been removed by etching and on the resist pattern 111 (8 (f)). Then, the resist pattern 111 and the electrode film placed thereon are removed by lift-off (FIG. 8 (g)). Here, a step of removing the light shielding film 112 (FIG. 8H) is required. After removing the light shielding film 112, the second dielectric layer 107 is formed (FIG. 8 (i)).
  • the light shielding film 112 provided for forming the resist pattern is not necessary in an actual device, and therefore needs to be removed before the second dielectric layer 107 is formed.
  • a light-shielding material such as SiC is used as the high acoustic velocity layer 5 formed on the first dielectric film 4, for example.
  • a filter, a module, or a communication device including the above acoustic wave device is also one embodiment of the present invention.
  • FIG. 9 is a diagram illustrating a configuration example of a communication device.
  • a communication module 60 for example, the elastic wave device shown in the above embodiment can be used.
  • the transmission terminal Tx of the communication module 60 is connected to the RFIC 53, and the reception terminal Rx is also connected to the RFIC 53.
  • the RFIC 53 is connected to the baseband IC 54.
  • the RFIC 53 can be formed of a semiconductor chip and other components.
  • the RFIC 53 is integrated with a reception circuit for processing a reception signal input from a reception terminal and a circuit including a transmission circuit for processing a transmission signal.
  • the baseband IC 54 can also be realized by a semiconductor chip and other parts.
  • the baseband IC 54 includes a circuit for converting the reception signal received from the reception circuit included in the RFIC 53 into an audio signal and packet data, and a transmission circuit included in the RFIC 53 that converts the audio signal and packet data into a transmission signal. Is integrated with the circuit for output.
  • output devices such as speakers and displays are connected to the baseband IC 54, for example, and output audio signals and packet data converted from reception signals by the baseband IC 54 to the user of the communication device 50. Can be recognized.
  • input devices included in the communication device 50 such as a microphone and a button are also connected to the baseband IC 54, and the baseband IC 54 can convert voice and data input from the user into transmission signals. . Note that the configuration of the communication device 50 is not limited to the example illustrated in FIG.

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)

Abstract

Provided is an acoustic wave device that allows the film thickness of an IDT electrode to be made thicker while suppressing unwanted wave responses. The acoustic wave device is equipped with: a piezoelectric substrate (2); an IDT electrode (3) containing multiple electrode fingers arranged in a line on the piezoelectric substrate (2); a first dielectric film (4) formed between the multiple electrode fingers; a second dielectric film (7) covering the IDT electrode (3) and the first dielectric film (4); and a high-velocity layer (5), which is a medium with a higher velocity than the first dielectric film (4), and which is formed between the multiple electrode fingers on the first dielectric layer (4).

Description

弾性波デバイスおよびその製造方法Elastic wave device and manufacturing method thereof
　本発明は、例えば、TVや携帯電話、PHS等におけるフィルタ素子や発振子に用いることができる弾性波デバイスに関する。 The present invention relates to an acoustic wave device that can be used for a filter element or an oscillator in, for example, a TV, a mobile phone, or a PHS.
　弾性波を応用したデバイスの1つとして弾性表面波素子(SAWデバイス:Surface Acoustic Wave Device)が以前より良く知られている。このSAWデバイスは例えば45MHz～2GHzの周波数帯における無線信号を処理する装置における各種回路、例えば送信バンドパスフィルタ、受信バンドパスフィルタ、局発フィルタ、アンテナ共用器、IFフィルタ、FM変調器等に用いられる。 A surface acoustic wave element (SAW device: Surface Acoustic Wave Device) is well known as one of the devices that apply elastic waves. This SAW device is used for various circuits in devices that process radio signals in the frequency band of 45 MHz to 2 GHz, for example, transmission bandpass filters, reception bandpass filters, local oscillation filters, antenna duplexers, IF filters, FM modulators, etc. It is done.
　近年、携帯電話などの高性能化に伴い、例えばバンドパスフィルタに用いられるSAWデバイスに対して、通過帯域内での低ロス化、通過帯域外での高抑圧化、温度安定性の向上など、諸特性の改善やデバイスサイズの小型化が求められている。中でも、温度安定性の向上については、デバイスサイズの小型化、デバイスへの入力パワーの増大などを原因とするデバイスのパワー密度の増大を背景として、喫緊の課題である。この温度安定性に関して、近年従来のSAWデバイスとは異なる構造のデバイスによる改善が提案されている。圧電性基板上にIDT電極を形成し、さらにIDT電極を覆うように厚い誘電体層を形成したラブ波デバイス、境界波デバイスなどがその例である（例えば、特許文献１および２参照）。 In recent years, with the improvement in performance of mobile phones and the like, for example, for SAW devices used in bandpass filters, low loss within the passband, high suppression outside the passband, improved temperature stability, etc. Improvement of various characteristics and miniaturization of device size are demanded. Above all, improvement of temperature stability is an urgent issue against the backdrop of an increase in device power density due to a reduction in device size and an increase in input power to the device. With respect to this temperature stability, an improvement with a device having a structure different from that of a conventional SAW device has been proposed in recent years. Examples thereof include a Love wave device and a boundary wave device in which an IDT electrode is formed on a piezoelectric substrate and a thick dielectric layer is formed so as to cover the IDT electrode (see, for example, Patent Documents 1 and 2).
特開2004-112748号公報JP 2004-112748 A 国際公開第98/52279号パンフレットInternational Publication No. 98/52279 Pamphlet
　例えば、ラブ波デバイスのように、圧電性基板上のIDT電極を覆うよう誘電体層を備える弾性波デバイスにおいては、不要応答としてレイリー波と高次不要応答が励振されることが多い。レイリー波は、スプリアス応答などとなって損失を増加させるなどの影響をもたらす。一方、高次不要応答は、ラブ波の周波数よりかなり高周波な周波数帯で励振される。こちらは、フィルタの抑圧を悪化させる原因となる場合がある。レイリー波応答の大きさは、弾性波デバイスの電極種、膜厚、誘電体層厚によって変化する。図１は、ラブ波デバイスの1ポート共振器の通過特性の一例を示す図である。ラブ波の***振周波数より低周波側にレイリー波応答が出現している。図２は、ラブ波デバイスの構成例を示す断面図である。図２に示すラブ波デバイスは、圧電性基板102と、圧電性基板102上に設けられるIDT電極103（Cu）とIDT電極103の間の電極間誘電体層104と備える。さらに、IDT電極103と電極間誘電体層104を覆うように拡散防止層106および誘電体層107が設けられる。図３は、図２に示すラブ波デバイスにおけるレイリー波応答を有限要素法で計算した結果を示すグラフである。図３のグラフは、横軸に電極材として用いているCuの膜厚を、縦軸にレイリー波応答の大きさをとっている。このときの基板材料は、YカットX伝播のLiNbO3である。グラフはCu膜厚（IDT電極103の膜厚）が約150 nmの時に、レイリー波応答の大きさが0となることを示している。すなわち、グラフは、Cu膜厚が150 nmより厚くなっても、薄くなっても、急激にレイリー波応答の大きさが大きくなってしまうことを示している。 For example, in an acoustic wave device including a dielectric layer so as to cover an IDT electrode on a piezoelectric substrate, such as a Love wave device, a Rayleigh wave and a higher-order unnecessary response are often excited as unnecessary responses. Rayleigh waves cause spurious responses and the like to increase losses. On the other hand, the high-order unnecessary response is excited in a frequency band considerably higher than the frequency of the Love wave. This may cause the filter suppression to worsen. The magnitude of the Rayleigh wave response varies depending on the electrode type, film thickness, and dielectric layer thickness of the acoustic wave device. FIG. 1 is a diagram illustrating an example of pass characteristics of a 1-port resonator of a Love wave device. A Rayleigh wave response appears on the lower frequency side than the anti-resonance frequency of the Love wave. FIG. 2 is a cross-sectional view illustrating a configuration example of a Love wave device. The Love wave device shown in FIG. 2 includes a piezoelectric substrate 102 and an interelectrode dielectric layer 104 between the IDT electrode 103 (Cu) and the IDT electrode 103 provided on the piezoelectric substrate 102. Further, a diffusion prevention layer 106 and a dielectric layer 107 are provided so as to cover the IDT electrode 103 and the interelectrode dielectric layer 104. FIG. 3 is a graph showing the result of calculating the Rayleigh wave response in the Love wave device shown in FIG. 2 by the finite element method. In the graph of FIG. 3, the horizontal axis represents the film thickness of Cu used as an electrode material, and the vertical axis represents the magnitude of the Rayleigh wave response. The substrate material at this time is Y-cut X-propagating LiNbO 3 . The graph shows that when the Cu film thickness (the film thickness of the IDT electrode 103) is about 150 nm, the magnitude of the Rayleigh wave response becomes zero. That is, the graph shows that the magnitude of the Rayleigh wave response suddenly increases regardless of whether the Cu film thickness is thicker or thinner than 150 nm.
　一般に携帯電話などに用いられる弾性波デバイスに対しては、低消費電力化、つまりデバイスの低ロス化が強く求められている。低ロス化の手段の一つとして、IDT電極を厚くすることが挙げられる。IDT電極を厚くすることによって、電極の断面積が大きくなり、電極抵抗を低減することができる。しかし、前述のレイリー波応答の大きさの挙動からわかるように、図２に示した構造のラブ波デバイスにおいては、Cu膜厚は150 nmに固定されてしまう。つまり、IDT電極103の膜厚を厚くすることによって、低ロス化を図るという手段を用いることが困難である。なお、使用する基板やIDT電極の材料等によって、レイリー波応答を抑圧できる最適なIDT電極の膜厚は異なるが、他の材料を用いた場合も、レイリー波応答は、図３と同様の極値を持つグラフを描き得る。また、レイリー波応答特性によって、IDT電極の膜厚が制限されることは、ラブ波デバイス以外の弾性波デバイスでも同様である。また、IDT電極の膜厚を制限する不要応答は、レイリー波応答に限られない。 Generally, for acoustic wave devices used for mobile phones and the like, low power consumption, that is, low device loss is strongly demanded. One way to reduce loss is to increase the thickness of the IDT electrode. By increasing the thickness of the IDT electrode, the cross-sectional area of the electrode increases, and the electrode resistance can be reduced. However, as can be seen from the behavior of the magnitude of the Rayleigh wave response, the Cu film thickness is fixed to 150 nm in the Love wave device having the structure shown in FIG. That is, it is difficult to use a means for reducing the loss by increasing the thickness of the IDT electrode 103. Although the optimum film thickness of the IDT electrode that can suppress the Rayleigh wave response varies depending on the substrate used, the material of the IDT electrode, etc., the Rayleigh wave response is the same as in FIG. 3 even when other materials are used. You can draw a graph with values. In addition, the film thickness of the IDT electrode is limited by the Rayleigh wave response characteristics as well in the elastic wave device other than the Love wave device. The unnecessary response that limits the film thickness of the IDT electrode is not limited to the Rayleigh wave response.
　そこで、本発明は、不要波応答を抑圧しつつ、IDT電極の膜厚を厚くすることが可能な弾性波デバイスを提供することを目的とする。 Therefore, an object of the present invention is to provide an elastic wave device capable of increasing the film thickness of the IDT electrode while suppressing an unnecessary wave response.
　本願開示の弾性波デバイスは、圧電性基板と、前記圧電性基板上に並んで配置される複数の電極指を含むＩＤＴ電極と、前記複数の電極指間に形成される第１の誘電体膜と、前記ＩＤＴ電極と前記第１の誘電体膜を覆う第２の誘電体膜と、前記複数の電極指間であって前記第１の誘電体膜上に形成される、前記第１の誘電体より高音速の媒質である高音速層とを備える。 The acoustic wave device disclosed in the present application includes a piezoelectric substrate, an IDT electrode including a plurality of electrode fingers arranged side by side on the piezoelectric substrate, and a first dielectric film formed between the plurality of electrode fingers. A second dielectric film covering the IDT electrode and the first dielectric film, and the first dielectric formed between the plurality of electrode fingers and on the first dielectric film. And a high sound velocity layer that is a medium having a higher sound velocity than the body.
　本願開示によれば、不要波応答を抑圧しつつ、IDT電極の膜厚を厚くすることが可能な弾性波デバイスを提供することができる。 According to the present disclosure, it is possible to provide an elastic wave device capable of increasing the film thickness of the IDT electrode while suppressing unnecessary wave response.
ラブ波デバイスの1ポート共振器の通過特性の一例を示す図である。It is a figure which shows an example of the passage characteristic of the 1 port resonator of a Love wave device. ラブ波デバイスの構成例を示す断面図である。It is sectional drawing which shows the structural example of a Love wave device. 図２に示すラブ波デバイスにおけるレイリー波応答を有限要素法で計算した結果を示すグラフである。It is a graph which shows the result of having calculated the Rayleigh wave response in the Love wave device shown in FIG. 2 by the finite element method. 本実施形態における弾性波デバイスの構成例を示す断面図である。It is sectional drawing which shows the structural example of the elastic wave device in this embodiment. 図4Bは、本実施形態における弾性波デバイスの上面透視図である。FIG. 4B is a top perspective view of the acoustic wave device according to the present embodiment. 本実施形態における弾性波デバイスのレイリー波応答の大きさを有限要素法で計算した結果を示すグラフである。It is a graph which shows the result of having calculated the magnitude of the Rayleigh wave response of the elastic wave device in this embodiment by the finite element method. 図2に示す構成のラブ波デバイスを1ポート共振器として動作させたときの共振器の通過特性に示すグラフである。3 is a graph showing pass characteristics of a resonator when the Love wave device having the configuration shown in FIG. 2 is operated as a one-port resonator. 本実施形態の弾性波デバイスの作製方法例を示す図である。It is a figure which shows the example of a manufacturing method of the elastic wave device of this embodiment. 図2に示す弾性波デバイスの作製方法例を示す図である。FIG. 3 is a diagram showing an example of a method for manufacturing the acoustic wave device shown in FIG. 通信機器の構成例を示す図である。It is a figure which shows the structural example of a communication apparatus.
　以下、本発明の実施形態について図面を参照して具体的に説明する。 Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
　（第１の実施形態）
　［弾性波デバイスの構成例］
　図4Aは、本実施形態における弾性波デバイスの構成例を示す断面図である。図4Bは、本実施形態における弾性波デバイスの上面透視図である。図4Aは、図4BのA-A線断面の一部を示している。図4Aおよび図4Bに示す弾性波デバイス１では、圧電性基板2の上に、並んで配置される複数の電極指を含むＩＤＴ電極3と、複数の電極指間に形成される第１の誘電体膜4が設けられる。複数の電極指間であって第1の誘電体膜4上には、高音速層5が形成される。すなわち、第１の誘電体膜4の上部部分上に高音速層5が形成されている。高音速層5は、第１の誘電体4より高音速の媒質である。ＩＤＴ電極3と第１の誘電体膜4を覆うように第2の誘電体膜7が設けられる。この第2の誘電体7と、ＩＤＴ電極3および高音速層5の間には、拡散防止層6（付加層の一例）が設けられている。拡散防止層6は、第2の誘電体7より高音速の媒体としている。 (First embodiment)
[Configuration example of elastic wave device]
FIG. 4A is a cross-sectional view showing a configuration example of an acoustic wave device in the present embodiment. FIG. 4B is a top perspective view of the acoustic wave device according to the present embodiment. FIG. 4A shows a part of a cross section taken along line AA of FIG. 4B. 4A and 4B, an IDT electrode 3 including a plurality of electrode fingers arranged side by side on a piezoelectric substrate 2 and a first dielectric formed between the plurality of electrode fingers. A body membrane 4 is provided. A high sound velocity layer 5 is formed between the plurality of electrode fingers and on the first dielectric film 4. That is, the high sound velocity layer 5 is formed on the upper portion of the first dielectric film 4. The high sound velocity layer 5 is a medium having a higher sound velocity than the first dielectric 4. A second dielectric film 7 is provided so as to cover the IDT electrode 3 and the first dielectric film 4. A diffusion prevention layer 6 (an example of an additional layer) is provided between the second dielectric 7 and the IDT electrode 3 and the high sound velocity layer 5. The diffusion prevention layer 6 is a medium having a higher sound velocity than the second dielectric 7.
　図4Aに示す構成のように、IDT電極3の複数の電極指間において、第1の誘電体膜4の上に高音速層5が設けられることにより、例えばレイリー波のような不要波の応答特性が変化することが発明者らによって見出された。すなわち、第1の誘電体膜4より音速が高い媒質である高音速層5の挿入により、不要波応答を抑圧するのに最も適したIDT電極3の膜厚の値がシフトすることが見出された。すなわち、IDT電極3の電極指に挟まれた空間において、第1の誘電体膜4の上に、第1の誘電体より音速が高い媒質を設けることにより、IDT電極3付近の音速のバランスを取ることができる。その結果、弾性波デバイス1では、不要波応答を抑圧しつつ、IDT電極3の膜厚を厚くすることが可能になる。ひいては、低ロス化を実現することができる。 As shown in FIG. 4A, a high acoustic velocity layer 5 is provided on the first dielectric film 4 between a plurality of electrode fingers of the IDT electrode 3, thereby allowing an unnecessary wave response such as a Rayleigh wave to respond. The inventors have found that the properties change. That is, it is found that the thickness value of the IDT electrode 3 most suitable for suppressing the unwanted wave response is shifted by inserting the high sound velocity layer 5 that is a medium having a higher sound velocity than the first dielectric film 4. It was done. That is, in the space sandwiched between the electrode fingers of the IDT electrode 3, a medium having a higher sound speed than the first dielectric is provided on the first dielectric film 4, thereby balancing the sound speed near the IDT electrode 3. Can take. As a result, in the acoustic wave device 1, it is possible to increase the film thickness of the IDT electrode 3 while suppressing the unwanted wave response. As a result, low loss can be realized.
　上記構成において、第１の誘電体膜4の厚みと高音速層5の厚みの合計は、IDT電極3の厚みと同じであることが好ましい。これにより、高音速層5の上面およびIDT電極3の上面が同一面になるように形成される。そのため、IDT電極3の上に形成される層の平坦化が容易になる。なお、ここで、厚みが同じであるとは、厳密に厚みが同じである必要はなく、例えば、製造上の誤差は許容される。 In the above configuration, the total thickness of the first dielectric film 4 and the high sound velocity layer 5 is preferably the same as the thickness of the IDT electrode 3. Thereby, the upper surface of the high sound velocity layer 5 and the upper surface of the IDT electrode 3 are formed to be the same surface. Therefore, the layer formed on the IDT electrode 3 can be easily flattened. Here, the same thickness does not need to be exactly the same, and for example, manufacturing errors are allowed.
　また、図4Aに示すように、第2の誘電体7より高音速の材質を主成分とする拡散防止層6を設けることにより、不要波応答を抑圧しつつも、IDT電極3、第1の誘電体膜4あるいは高音速層5を保護することができる。なお、拡散防止層6は、省略することもできる。 In addition, as shown in FIG. 4A, by providing the diffusion prevention layer 6 mainly composed of a material with a higher sound velocity than the second dielectric 7, the IDT electrode 3 and the first The dielectric film 4 or the high sound velocity layer 5 can be protected. The diffusion prevention layer 6 can be omitted.
　高音速層5の材質は、例えば、SiC、AlN、アルミナあるいはダイヤモンドを含むものとすることができる。拡散防止層6の材質も、例えば、SiC、AlN、アルミナあるいはダイヤモンドを含むものとすることができる。なお、高音速層5における弾性波の音速が、第1の誘電体膜4における弾性波の音速より高い構成であれば、高音速層5の材料は特定のものに限定されない。同様に、拡散防止層6の材質も特定のものに限定されない。また、高音速層5の音速、第1の誘電体膜4の音速および拡散防止層6の音速は、材料のみによって決まるとは限らず、構造や温度などの影響を受ける場合もある。本実施形態では、一例として、第1の誘電体膜4の上でIDT電極の電極指にはさまれた位置に、高音速の材料を配置することによって、高音速層５を形成している。 The material of the high sound velocity layer 5 can include, for example, SiC, AlN, alumina, or diamond. The material of the diffusion preventing layer 6 can also include, for example, SiC, AlN, alumina, or diamond. Note that the material of the high sound velocity layer 5 is not limited to a specific material as long as the sound velocity of the elastic waves in the high sound velocity layer 5 is higher than the sound velocity of the elastic waves in the first dielectric film 4. Similarly, the material of the diffusion preventing layer 6 is not limited to a specific material. Further, the sound velocity of the high sound velocity layer 5, the sound velocity of the first dielectric film 4, and the sound velocity of the diffusion prevention layer 6 are not necessarily determined only by the material, and may be affected by the structure, temperature, and the like. In the present embodiment, as an example, the high sound velocity layer 5 is formed by disposing a high sound velocity material on the first dielectric film 4 at a position sandwiched between the electrode fingers of the IDT electrode. .
　IDT電極3は、例えば、Cuを主成分とし、第１の誘電体膜4および第２の誘電体膜7は、例えば、SiO2を主成分とすることができる。また、圧電性基板2は、例えば、LiNbO3基板を用いることができる。 The IDT electrode 3 can be mainly composed of Cu, for example, and the first dielectric film 4 and the second dielectric film 7 can be composed mainly of SiO 2 , for example. The piezoelectric substrate 2 can be a LiNbO 3 substrate, for example.
　図4Bに示すように、弾性波デバイス1において、IDT電極3は、入力IN側電極に接続される複数電極指（ストリップ）と、出力OUT側電極に接続される電極指（ストリップ）とが交互に等間隔で並んで配置される。電極指の延びる方向に垂直な方向において、IDT電極3の両側に、反射器8が配置される。弾性波が、反射器8間を、電極指に垂直な方向に伝播することで、弾性波デバイス1は、共振器として動作する。なお、IDT(Inter Digital Transducer)は、櫛形電極または櫛歯型電極とも称されることがある。 As shown in FIG. 4B, in the acoustic wave device 1, the IDT electrode 3 has alternating electrode fingers (strip) connected to the input IN side electrode and electrode fingers (strip) connected to the output OUT side electrode. Are arranged at equal intervals. Reflectors 8 are disposed on both sides of the IDT electrode 3 in a direction perpendicular to the direction in which the electrode fingers extend. The elastic wave device 1 operates as a resonator because the elastic wave propagates between the reflectors 8 in a direction perpendicular to the electrode fingers. An IDT (Inter Digital Transducer) may also be referred to as a comb-shaped electrode or a comb-shaped electrode.
　図4Aおよび図4Bに示す弾性波デバイスは、例えば、弾性表面波の一種であるラブ波を利用するデバイスとして用いることができる。なお、上記弾性波デバイスは、1ポート型弾性波共振器の例であるため、１つのIDT電極3が反射器に挟まれて配置されていたが、弾性波デバイスの用途に応じて、複数のIDT電極が形成されてもよい。また、反射器8を設けなくてもよい。電極指の配置も図4Bに示す例に限れず、例えば、隣り合う電極指の交差幅にアポタイズ重み付けがなされた構成であってもよい。また、本発明にかかる弾性波デバイスは、ラブ波を利用するデバイスに限られず、弾性境界波を利用するデバイスとして利用することも可能である。 The elastic wave device shown in FIGS. 4A and 4B can be used, for example, as a device that uses a Love wave, which is a type of surface acoustic wave. In addition, since the said acoustic wave device is an example of a 1 port type | mold elastic wave resonator, although one IDT electrode 3 was arrange | positioned between reflectors, according to the use of an acoustic wave device, several An IDT electrode may be formed. Further, the reflector 8 may not be provided. The arrangement of the electrode fingers is not limited to the example shown in FIG. 4B. For example, a configuration in which the intersection width between adjacent electrode fingers is weighted with an apodization may be used. The elastic wave device according to the present invention is not limited to a device using a Love wave, and can be used as a device using a boundary acoustic wave.
　図5は、図4Aおよび図4Bに示す本実施形態における弾性波デバイスのレイリー波応答の大きさを有限要素法で計算した結果を示すグラフである。この計算は、高音速層5として、SiCを20 nmの膜厚で形成した場合を想定した計算である。また、この計算は、圧電性基板2は、回転Y板のLiNbO3基板とし、圧電性基板2上にCuのIDT電極3が形成された場合を想定している。 FIG. 5 is a graph showing the result of calculating the magnitude of the Rayleigh wave response of the acoustic wave device in this embodiment shown in FIGS. 4A and 4B by the finite element method. This calculation is based on the assumption that SiC is formed as the high sound velocity layer 5 with a film thickness of 20 nm. This calculation assumes that the piezoelectric substrate 2 is a rotating Y-plate LiNbO 3 substrate and the Cu IDT electrode 3 is formed on the piezoelectric substrate 2.
　図5のグラフでは、本実施形態における弾性波デバイスのレイリー波応答のプロットが三角で示されている。比較例として、図2に示すラブ波デバイスのレイリー波応答のプロットが、ひし形で示されている。図5のグラフにおいては、本実施形態の弾性波デバイスのレイリー波応答の大きさを表すプロットが、比較例に比べて全体的に右にシフトしている。その結果、本実施形態の構造では、Cu膜厚が約200 nmの場合にレイリー波応答の大きさが0となっていることが分かる。つまり、高音速層5を導入することによって、IDT電極3の厚みを約50nm厚くできることになる。その結果、IDT電極3での電極抵抗の低減をでき、ひいては、弾性波デバイスとしてのロスの低減を実現することができる。また、IDT電極3での電流密度を低減することができるため、高電力の印加に対して強いデバイスを実現することができる。さらに、弾性波デバイス全体の厚みを薄くすることができる。 In the graph of FIG. 5, the plot of the Rayleigh wave response of the elastic wave device in the present embodiment is indicated by a triangle. As a comparative example, the Rayleigh wave response plot of the Love wave device shown in FIG. 2 is indicated by a diamond. In the graph of FIG. 5, the plot representing the magnitude of the Rayleigh wave response of the acoustic wave device of the present embodiment is shifted to the right as a whole compared to the comparative example. As a result, it can be seen that in the structure of this embodiment, the magnitude of the Rayleigh wave response is 0 when the Cu film thickness is about 200 nm. That is, by introducing the high sound velocity layer 5, the thickness of the IDT electrode 3 can be increased by about 50 nm. As a result, the electrode resistance of the IDT electrode 3 can be reduced, and consequently, the loss as an acoustic wave device can be reduced. In addition, since the current density at the IDT electrode 3 can be reduced, a device that is strong against application of high power can be realized. Furthermore, the thickness of the entire acoustic wave device can be reduced.
　本願の発明者らの検討において、レイリー波応答の大きさは、IDT電極付近の音速に影響されていることが分かりつつある。この知見に基づけば、レイリー波応答を抑圧しつつ、櫛型電極厚を厚くする手段として、図2に示す構成において、拡散防止層106に高音速材料を用いて、その拡散防止層106を厚くすることによって、IDT電極付近の音速のバランスを取る方法も考えられる。図6は、図2に示す構成のラブ波デバイスを1ポート共振器として動作させたときの共振器の通過特性に示すグラフである。図6のグラフでは、高次不要応答が急激に大きくなってしまう。このため、本実施形態の構成の方が、図2の構成に比べて、不要応答抑制の観点から望ましいと言える。 In the examination by the inventors of the present application, it is becoming clear that the magnitude of the Rayleigh wave response is influenced by the sound speed near the IDT electrode. Based on this finding, as a means for increasing the comb-shaped electrode thickness while suppressing the Rayleigh wave response, in the configuration shown in FIG. By doing so, a method of balancing the speed of sound near the IDT electrode is also conceivable. FIG. 6 is a graph showing the pass characteristics of a resonator when the Love wave device having the configuration shown in FIG. 2 is operated as a one-port resonator. In the graph of FIG. 6, the high-order unnecessary response suddenly increases. For this reason, it can be said that the configuration of the present embodiment is more desirable than the configuration of FIG. 2 from the viewpoint of suppressing unnecessary responses.
　［弾性波デバイスの製造方法］
　図7は、本実施形態の弾性波デバイスの作製方法例を示す図である。まず、図7(a)に示すように、圧電性基板2の上面全面に第1の誘電体膜4を形成する。圧電性基板2の基板材料は、例えば、YカットX伝播のLiNbO3を用いることができる。なお、基板材料としては、他の結晶方位のLiNbO3を用いてもよく、あるいは、他の圧電単結晶を用いてもよい。第１の誘電体膜4には、例えば、透明のSiO2を用いることができる。 [Method for Manufacturing Elastic Wave Device]
FIG. 7 is a diagram showing an example of a method for manufacturing the acoustic wave device of the present embodiment. First, as shown in FIG. 7A, the first dielectric film 4 is formed on the entire upper surface of the piezoelectric substrate 2. As the substrate material of the piezoelectric substrate 2, for example, Y-cut X propagation LiNbO 3 can be used. As the substrate material, LiNbO 3 having another crystal orientation may be used, or another piezoelectric single crystal may be used. For the first dielectric film 4, for example, transparent SiO 2 can be used.
　図7(b)において、第1の誘電体膜4の上面全面に高音速層5が形成される。高音速層5として、例えば、SiC層が形成される。第1の誘電体膜4および高音速層5の形成には、印刷、蒸着、またはスパッタリングなどの方法を用いることができる。 In FIG. 7B, a high sound velocity layer 5 is formed on the entire upper surface of the first dielectric film 4. As the high sound velocity layer 5, for example, a SiC layer is formed. For the formation of the first dielectric film 4 and the high acoustic velocity layer 5, a method such as printing, vapor deposition, or sputtering can be used.
　図7(c)に示すように、フォトリソグラフィ技術を用いて、高音速層5上にレジストパターン11を形成する。レジストパターン11は、IDT電極3を形成するためのパターンであり、例えば、圧電性基板2の上面においてIDT電極3を形成する領域を除いた残りの領域にレジストパターンが形成される。 As shown in FIG. 7 (c), a resist pattern 11 is formed on the high sound velocity layer 5 by using a photolithography technique. The resist pattern 11 is a pattern for forming the IDT electrode 3. For example, the resist pattern is formed in the remaining area of the upper surface of the piezoelectric substrate 2 except for the area where the IDT electrode 3 is formed.
　図7(d)に示すように、レジストパターン11形成後に、高音速層5がエッチングされる。これにより、レジストパターン11の下に位置する領域以外の高音速層5が除去される。さらに、図7(e)に示すように、第1の誘電体膜4も、エッチングにより、レジストパターン11の下に位置する領域以外が除去される。 As shown in FIG. 7 (d), after the resist pattern 11 is formed, the high sound velocity layer 5 is etched. Thereby, the high sound velocity layer 5 other than the region located under the resist pattern 11 is removed. Further, as shown in FIG. 7 (e), the first dielectric film 4 is also removed by etching except for the region located under the resist pattern 11.
　図7(f)では、IDT電極3を形成する電極膜が成膜される。電極膜は、例えば、スパッタリングまたは蒸着等により成膜することができる。電極膜は、第1の誘電体膜4が除去された領域、すなわちIDT電極3が形成される領域と、レジストパターン11上とに付与される。ここで、電極膜の膜厚は、第1の誘電体膜4の厚みと高音速層5の厚みの合計とほぼ同じになるよう、成膜されることが好ましい。 In FIG. 7 (f), an electrode film for forming the IDT electrode 3 is formed. The electrode film can be formed by sputtering or vapor deposition, for example. The electrode film is applied to the region where the first dielectric film 4 is removed, that is, the region where the IDT electrode 3 is formed, and the resist pattern 11. Here, the film thickness of the electrode film is preferably formed so as to be substantially the same as the total thickness of the first dielectric film 4 and the high acoustic velocity layer 5.
　次に、図7(g)に示すように、リフトオフにより、レジストパターン11は除去される。残ったIDT電極3と高音速層5の表面がフラットになるように表面処理されてもよい。このようにして、IDT電極3は、リフトオフ法によって形成される。また、IDT電極3の電極指間に、上面が高音速層5で被覆された第1の誘電体膜4が位置する構造が得られる。 Next, as shown in FIG. 7 (g), the resist pattern 11 is removed by lift-off. The remaining IDT electrode 3 and the surface of the high sound velocity layer 5 may be surface-treated so as to be flat. In this way, the IDT electrode 3 is formed by the lift-off method. Further, a structure in which the first dielectric film 4 whose upper surface is covered with the high sound velocity layer 5 is located between the electrode fingers of the IDT electrode 3 is obtained.
　そして、IDT電極3と高音速層5を覆うように、例えば、SiCの拡散防止膜6、およびSiO2の第2の誘電体膜7が形成される。これにより、図4Aおよび図4Bに示した構成の弾性波デバイスが得られる。 Then, for example, a diffusion preventing film 6 made of SiC and a second dielectric film 7 made of SiO 2 are formed so as to cover the IDT electrode 3 and the high sound velocity layer 5. Thereby, the acoustic wave device having the configuration shown in FIGS. 4A and 4B is obtained.
　上記のように、弾性波デバイスの第１の誘電体膜4に透明のSiO2を用いた場合、図7(a)に示すように圧電性基板2上に第１の誘電体膜4を形成した状態では、フォトリソグラフィによって微細なレジストパターンを形成することができない。そのため、図2に示すように、高音速層5を形成しない構成の弾性波デバイスを作成する場合には、第１の誘電体膜4の上にSiや金属などの遮光膜を形成してから、その上にレジストパターンを形成することが必要になる。 As described above, when transparent SiO 2 is used for the first dielectric film 4 of the acoustic wave device, the first dielectric film 4 is formed on the piezoelectric substrate 2 as shown in FIG. In this state, a fine resist pattern cannot be formed by photolithography. Therefore, as shown in FIG. 2, when an acoustic wave device having a configuration in which the high sound velocity layer 5 is not formed is formed, a light shielding film such as Si or metal is formed on the first dielectric film 4. It is necessary to form a resist pattern thereon.
　図8は、図2に示す弾性波デバイスの作製方法例を示す図である。図8(a)に示すように、圧電性基板102上に第1の誘電体層104が形成されると、その誘電体膜3の上面全面に、Si等の遮光膜112が形成される(図8(b))。遮光膜112の上にレジストパターン111が形成され(図8(c))、遮光膜112エッチング(図8(d))および第1の誘電体層104エッチング(図8(e))がなされる。IDT電極103の電極膜が、第1の誘電体層104がエッチング除去された領域とレジストパターン111上とに成膜される(8(f))。そして、リフトオフにより、レジストパターン111とその上に載っていた電極膜が除去される(図8(g))。ここで、遮光膜112を除去する工程(図8(h))が必要となる。遮光膜112を除去した後に、第2の誘電体層107が形成される(図8(i))。 FIG. 8 is a diagram showing an example of a method for manufacturing the acoustic wave device shown in FIG. As shown in FIG. 8 (a), when the first dielectric layer 104 is formed on the piezoelectric substrate 102, a light shielding film 112 such as Si is formed on the entire upper surface of the dielectric film 3 (see FIG. FIG. 8 (b)). A resist pattern 111 is formed on the light shielding film 112 (FIG. 8C), and the light shielding film 112 etching (FIG. 8D) and the first dielectric layer 104 etching (FIG. 8E) are performed. . An electrode film of the IDT electrode 103 is formed on the region where the first dielectric layer 104 has been removed by etching and on the resist pattern 111 (8 (f)). Then, the resist pattern 111 and the electrode film placed thereon are removed by lift-off (FIG. 8 (g)). Here, a step of removing the light shielding film 112 (FIG. 8H) is required. After removing the light shielding film 112, the second dielectric layer 107 is formed (FIG. 8 (i)).
　このように、図8に示す例では、レジストパターン形成するために設けられた遮光膜112は実デバイスでは不要となるため、第2の誘電体層107を形成する前に除去する必要がある。これに対して、本実施形態の弾性波デバイスでは、図7に示すように、第1の誘電体膜4の上に形成される高音速層5として例えば、SiCのような遮光性の材料を用いることにより、遮光膜を特に形成しなくても、リソグラフィで微細なレジストパターンの形成が可能となる。また、高音速層5は、弾性波デバイスでそのまま利用されるため、その後の除去工程も不要である。そのため、工程の簡略化も可能となり、弾性波デバイスの低コスト化が可能となる。 As described above, in the example shown in FIG. 8, the light shielding film 112 provided for forming the resist pattern is not necessary in an actual device, and therefore needs to be removed before the second dielectric layer 107 is formed. In contrast, in the acoustic wave device of the present embodiment, as shown in FIG. 7, a light-shielding material such as SiC is used as the high acoustic velocity layer 5 formed on the first dielectric film 4, for example. By using it, it is possible to form a fine resist pattern by lithography without particularly forming a light shielding film. Further, since the high sound velocity layer 5 is used as it is in an elastic wave device, a subsequent removal step is not necessary. Therefore, the process can be simplified, and the cost of the acoustic wave device can be reduced.
　　［通信機器］
　上記の弾性波デバイスを含むフィルタ、モジュールまたは通信機器も本発明の実施形態の一つである。 [Communication equipment]
A filter, a module, or a communication device including the above acoustic wave device is also one embodiment of the present invention.
　図9は、通信機器の構成例を示す図である。図9に示す通信機器50においては、モジュール基板51上に、通信モジュール60、RFIC53およびベースバンドIC54が設けられている。通信モジュール60には、例えば、上記実施形態で示した弾性波デバイスを用いることができる。 FIG. 9 is a diagram illustrating a configuration example of a communication device. In a communication device 50 shown in FIG. 9, a communication module 60, an RFIC 53, and a baseband IC 54 are provided on a module substrate 51. For the communication module 60, for example, the elastic wave device shown in the above embodiment can be used.
　通信モジュール60の送信端子TxはRFIC53に接続され、受信端子RxもRFIC53に接続されている。RFIC53はベースバンドIC54に接続されている。RFIC53は、半導体チップおよびその他の部品により形成することができる。RFIC53には、受信端子から入力された受信信号を処理するための受信回路および、送信信号を処理するための送信回路を含む回路が集積されている。 The transmission terminal Tx of the communication module 60 is connected to the RFIC 53, and the reception terminal Rx is also connected to the RFIC 53. The RFIC 53 is connected to the baseband IC 54. The RFIC 53 can be formed of a semiconductor chip and other components. The RFIC 53 is integrated with a reception circuit for processing a reception signal input from a reception terminal and a circuit including a transmission circuit for processing a transmission signal.
　また、ベースバンドIC54も半導体チップおよびその他の部品により実現することができる。ベースバンドIC54には、RFIC53に含まれる受信回路から受け取った受信信号を、音声信号やパッケットデータに変換するための回路と、音声信号やパッケットデータを送信信号に変換してRFIC53に含まれる送信回路に出力するため回路とが集積される。 The baseband IC 54 can also be realized by a semiconductor chip and other parts. The baseband IC 54 includes a circuit for converting the reception signal received from the reception circuit included in the RFIC 53 into an audio signal and packet data, and a transmission circuit included in the RFIC 53 that converts the audio signal and packet data into a transmission signal. Is integrated with the circuit for output.
　図示しないが、ベースバンドIC54には、例えば、スピーカ、ディスプレイ等の出力機器が接続されており、ベースバンドIC54で受信信号から変換された音声信号やパケットデータを出力し、通信機器50のユーザに認識させることができる。また、マイク、ボタン等の通信機器５０が備える入力機器もベースバンドIC54に接続されており、ユーザから入力された音声やデータをベースバンドIC54が送信信号に変換することができる構成になっている。なお、通信機器50の構成は、図9に示す例に限られない。 Although not shown, output devices such as speakers and displays are connected to the baseband IC 54, for example, and output audio signals and packet data converted from reception signals by the baseband IC 54 to the user of the communication device 50. Can be recognized. In addition, input devices included in the communication device 50 such as a microphone and a button are also connected to the baseband IC 54, and the baseband IC 54 can convert voice and data input from the user into transmission signals. . Note that the configuration of the communication device 50 is not limited to the example illustrated in FIG.
１　　　弾性波デバイス
２　　　基板
３　　　IDT電極
４　　　第1の誘電体膜
５　　　高音速層
６　　　拡散防止膜（付加膜）
７　　　第2の誘電体膜 1 Elastic wave device 2 Substrate 3 IDT electrode 4 First dielectric film 5 High sound velocity layer 6 Diffusion prevention film (additional film)
7 Second dielectric film

Claims (7)

  1. 　圧電性基板と、
    　前記圧電性基板上に並んで配置される複数の電極指を含むＩＤＴ電極と、
    　前記複数の電極指間に形成される第１の誘電体膜と、
    　前記ＩＤＴ電極と前記第１の誘電体膜を覆う第２の誘電体膜と、
    　前記複数の電極指間であって前記第１の誘電体膜上に形成される、前記第１の誘電体より高音速の媒質である高音速層とを備えた、弾性波デバイス。     A piezoelectric substrate;
    An IDT electrode including a plurality of electrode fingers arranged side by side on the piezoelectric substrate;
    A first dielectric film formed between the plurality of electrode fingers;
    A second dielectric film covering the IDT electrode and the first dielectric film;
    An acoustic wave device comprising: a high acoustic velocity layer that is a medium having a higher acoustic velocity than the first dielectric, and is formed on the first dielectric film between the plurality of electrode fingers.
  2. 　前記第１の誘電体膜の厚みと前記高音速層の厚みの合計が、前記ＩＤＴ電極の厚みと同じである、請求項１に記載の弾性波デバイス。 2. The acoustic wave device according to claim 1, wherein a total thickness of the first dielectric film and a thickness of the high sound velocity layer is the same as a thickness of the IDT electrode.
  3. 　前記ＩＤＴ電極および前記高音速層と、前記第２の誘電体との間に、前記第２の誘電体より高音速の媒質である付加層をさらに備える、請求項１または２に記載の弾性波デバイス。 The elastic wave according to claim 1, further comprising an additional layer that is a medium having a higher sound velocity than the second dielectric material, between the IDT electrode and the high sound velocity layer, and the second dielectric material. device.
  4. 　前記高音速層の材質は、SiC、AlN、アルミナあるいはダイヤモンドを含む、請求項１～３のいずれか１項に記載の弾性波素子。 4. The acoustic wave element according to claim 1, wherein the material of the high sound velocity layer includes SiC, AlN, alumina, or diamond.
  5. 　請求項１～４のいずれか１項に記載の弾性波デバイスを備えた、通信機器。 A communication device comprising the acoustic wave device according to any one of claims 1 to 4.
  6. 　圧電性基板上に、第１の誘電体膜を形成する工程と、
    　前記第１の誘電体膜を覆うように、前記第１の誘電体膜より高音速の媒質である高音速層を形成する工程と、
    　前記高音速層の上に、ＩＤＴ電極を形成するためのレジストパターンを形成する工程と、
    　前記レジストパターン形成後に、前記高音速層および前記第１の誘電体膜をエッチングする工程と、
    　前記エッチング後にＩＤＴ電極材料を成膜し、前記レジストパターンを除去する工程と、
    　前記ＩＤＴ電極および前記高音速層を覆うように、第２の誘電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 a first dielectric film on the piezoelectric substrate;
    Forming a high sound velocity layer that is a medium having a higher sound velocity than the first dielectric film so as to cover the first dielectric film;
    Forming a resist pattern for forming an IDT electrode on the high sound velocity layer;
    Etching the high sound velocity layer and the first dielectric film after forming the resist pattern;
    Forming an IDT electrode material after the etching and removing the resist pattern;
    Forming a second dielectric film so as to cover the IDT electrode and the high acoustic velocity layer.
  7. 　前記第1の誘電体膜は、透明な材質で形成され、
    　前記高音速層は、遮光性を有する材質で形成される、請求項６に記載の弾性波デバイスの製造方法。     The first dielectric film is formed of a transparent material,
    The method for manufacturing an acoustic wave device according to claim 6, wherein the high sound velocity layer is formed of a light-shielding material.
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