WO2021088401A1 - 一种基于双层电极高机电耦合系数的声表面波器件及其制备方法 - Google Patents

一种基于双层电极高机电耦合系数的声表面波器件及其制备方法 Download PDF

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WO2021088401A1
WO2021088401A1 PCT/CN2020/101804 CN2020101804W WO2021088401A1 WO 2021088401 A1 WO2021088401 A1 WO 2021088401A1 CN 2020101804 W CN2020101804 W CN 2020101804W WO 2021088401 A1 WO2021088401 A1 WO 2021088401A1
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acoustic wave
surface acoustic
wave device
electrode
preparation
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French (fr)
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潘峰
苏荣宣
曾飞
沈君尧
傅肃磊
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清华大学
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02535—Details of surface acoustic wave devices
    • H03H9/02543—Characteristics of substrate, e.g. cutting angles
    • H03H9/02574—Characteristics of substrate, e.g. cutting angles of combined substrates, multilayered substrates, piezoelectrical layers on not-piezoelectrical substrate
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/24—Vacuum evaporation
    • C23C14/28—Vacuum evaporation by wave energy or particle radiation
    • C23C14/30—Vacuum evaporation by wave energy or particle radiation by electron bombardment
    • 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
    • C—CHEMISTRY; METALLURGY
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    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/0021—Reactive sputtering or evaporation
    • C23C14/0036—Reactive sputtering
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/08—Oxides
    • C23C14/086—Oxides of zinc, germanium, cadmium, indium, tin, thallium or bismuth
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/10—Glass or silica
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/14—Metallic material, boron or silicon
    • C23C14/18—Metallic material, boron or silicon on other inorganic substrates
    • 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
    • H03H3/02—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 piezoelectric or electrostrictive resonators or networks
    • 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
    • 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
    • H03H9/02535—Details of surface acoustic wave devices
    • H03H9/02543—Characteristics of substrate, e.g. cutting angles
    • H03H9/02582—Characteristics of substrate, e.g. cutting angles of diamond substrates
    • 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
    • H03H9/14544—Transducers of particular shape or position
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/64—Filters using surface acoustic waves
    • 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
    • H03H3/02—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 piezoelectric or electrostrictive resonators or networks
    • H03H2003/023—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 piezoelectric or electrostrictive resonators or networks the resonators or networks being of the membrane type
    • 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
    • H03H9/02228—Guided bulk acoustic wave devices or Lamb wave devices having interdigital transducers situated in parallel planes on either side of a piezoelectric layer

Definitions

  • the invention relates to a surface acoustic wave device based on a double-layer electrode with high electromechanical coupling coefficient and a preparation method thereof, belonging to the field of information and electronic materials.
  • Surface acoustic wave devices are electronic devices that encode and decode radio frequency signals for information transmission based on the piezoelectric effect. They have developed rapidly in the past few decades. With the opening of the 5G era, the demand for surface acoustic wave devices with zero temperature drift, small size, and large bandwidth is becoming stronger.
  • the surface acoustic wave device based on piezoelectric film has the advantages of wide frequency range and simple preparation, which can better meet the requirements of miniaturization and integration of surface acoustic wave devices.
  • the frequency and electromechanical coupling of the device can be adjusted by selecting substrate materials with different sound speeds. coefficient.
  • the current mainstream piezoelectric film materials include zinc oxide and aluminum nitride. Compared with aluminum nitride, zinc oxide has the advantages of small temperature drift, large electromechanical coupling coefficient, and simpler preparation.
  • the current surface acoustic wave mode based on zinc oxide film is mainly the Sisava wave mode.
  • the electromechanical coupling coefficient of the Sisava wave is currently reported to be relatively low, which is still slightly inadequate compared with single crystal materials.
  • the bandwidth of the SAW filter directly depends on the electromechanical coupling coefficient of the device. Therefore, in order to broaden the application of film materials in surface acoustic wave devices, it is necessary to use zinc oxide film materials for surface acoustic wave devices. In the process, the electromechanical coupling coefficient of the device must be improved.
  • the purpose of the present invention is to provide a surface acoustic wave device and a preparation method thereof.
  • the present invention realizes a high electromechanical coupling coefficient through a double-layer electrode.
  • the structure of the surface acoustic wave device provided by the present invention is as follows:
  • the signal terminal of the copper electrode is opposite to the ground terminal of the aluminum electrode, and the ground terminal of the copper electrode is opposite to the signal terminal of the aluminum electrode, so that the electric field in the thickness direction can be excited.
  • the thickness of the copper electrode may be 50-100 nm, such as 75 nm, 50-75 nm or 75-100 nm;
  • the thickness of the aluminum electrode may be 50-100 nm, such as 75 nm, 50-75 nm or 75-100 nm.
  • the piezoelectric film may be at least one of a zinc oxide film, an aluminum nitride film, a doped zinc oxide film, and a doped aluminum nitride film, and is preferably a zinc oxide film.
  • the thickness of the piezoelectric film may be 100-1500 nm, such as 300 nm, 100-300 nm, 300-1500 nm.
  • the substrate may be a c-plane sapphire substrate, SiC or diamond.
  • the gap provided between the substrate and the piezoelectric film (that is, the gap excluding the copper electrode) is filled with a silicon oxide film.
  • the surface acoustic wave device of the present invention can be prepared according to the following method 1) or 2):
  • the gap between the piezoelectric film and the substrate is filled with a silicon oxide film
  • the copper electrode and the silicon oxide film are sequentially deposited on the substrate, and the silicon oxide film is chemically mechanically polished After correcting the surface, continue to deposit the piezoelectric film and the aluminum electrode.
  • the copper electrode and the aluminum electrode are prepared by means of electron beam evaporation
  • the evaporation source is small particles of elemental aluminum metal or small particles of elemental copper metal, with a purity of 99.999%;
  • the vacuum degree is 10 -6 ⁇ 10 -5 Pa;
  • the temperature is 10 ⁇ 100°C;
  • the distance between the target and the substrate is 50-100 cm;
  • the evaporation rate is
  • the evaporation After the evaporation is completed, it further includes filling nitrogen into the vacuum chamber of the electron beam evaporation until the pressure in the vacuum chamber becomes atmospheric pressure, and then taking out the prepared metal film.
  • the silicon oxide film is prepared by means of radio frequency magnetron sputtering
  • the conditions of the radio frequency magnetron sputtering are as follows:
  • the target material is a silicon target, the diameter of the silicon target may be 75mm, and the purity may be 99.999%;
  • the flow rate of the working gas can be 10-30mL/min, specifically it can be 18mL/min for argon and 12mL/min for oxygen;
  • the magnetron sputtering source is a planar target magnetron sputtering source
  • the power is 1000W;
  • the temperature is 20 ⁇ 400°C;
  • the pressure of the system is 0.5 ⁇ 1.2Pa
  • the distance between the target and the substrate is 60-80 mm.
  • the zinc oxide film is prepared by means of radio frequency magnetron sputtering
  • the conditions of the radio frequency magnetron sputtering are as follows:
  • the target material may be a zinc target, the diameter of the metal target may be 75mm, and the purity may be 99.999%;
  • the flow rate of the working gas can be 10-30mL/min, specifically it can be 18mL/min for argon and 12mL/min for oxygen;
  • the magnetron sputtering source is a planar target magnetron sputtering source
  • the power is 140W;
  • the temperature is 20 ⁇ 400°C;
  • the pressure of the system is 0.5 ⁇ 1.2Pa
  • the distance between the target and the substrate is 60-80 mm.
  • Figure 1 is a schematic cross-sectional view of a double-electrode surface acoustic wave device of the present invention; in which 1-c plane sapphire; 2-SiO 2 ; 3-Cu; 4-ZnO; 5-Al.
  • Figure 2 is a schematic diagram of the velocity of sound as a function of the thickness-wavelength ratio of the piezoelectric film obtained by calculation and simulation.
  • Figure 3 is a schematic diagram showing the variation of the electromechanical coupling coefficient with the piezoelectric film thickness-wavelength ratio obtained by calculation and simulation.
  • the c-plane sapphire substrate with the interdigital electrode pattern with a period of 2 microns is prepared by photolithography. After the primer is applied, the substrate is placed in the electron beam coater. Start the vacuum system to evacuate to 9 ⁇ 10 -6 Pa; adjust the power of the electron gun to 20%, and clean the target (purity: 99.999%) for 5 minutes.
  • the vacuum chamber of the electron beam evaporation coating machine is filled with nitrogen until the pressure in the vacuum chamber becomes atmospheric pressure, and the cavity is opened to take out the sapphire substrate on which the copper electrode has been evaporated.
  • the upper electrode pattern is made by engraving so that the ground terminals of the upper and lower electrodes are opposite to the signal terminals.
  • the upper electrode aluminum electrode is prepared by electron beam evaporation.
  • the specific process is similar to step (1).
  • the evaporation rate of Al is Deposition of 75nm.
  • step (7) The thin film prepared in step (7) is peeled off in acetone to obtain the desired surface acoustic wave device.
  • the schematic diagram of the structure is shown in FIG. 1.
  • a surface acoustic wave device with a single electrode (Al electrode with the same thickness as the Al electrode of the double-layer electrode structure) was prepared according to the steps 1), 6) and 7) in Example 1.
  • the performance of the surface acoustic wave device with the double-layer electrode and the single-layer electrode prepared above was predicted by comsol finite element simulation calculation method.
  • the obtained sound velocity vs. piezoelectric film thickness-wavelength ratio change diagram is shown in Figure 2.
  • the schematic diagram of the variation of the electromechanical coupling coefficient with the thickness-wavelength ratio of the piezoelectric film is shown in Fig. 3. It can be seen that the maximum electromechanical coupling coefficient of the double-electrode surface acoustic wave device of the present invention is about 7.5% when the thickness-wavelength ratio is 0.175.
  • the single-layer electrode surface acoustic wave device has a higher sound velocity, the maximum electromechanical coupling coefficient is only half of that of the double-layer electrode device. Therefore, the double-layer electrode structure provided by the present invention can greatly improve the acoustic surface under the premise of ensuring high sound velocity.
  • the electromechanical coupling coefficient of the wave device provides a practical solution for the future large-bandwidth filter.
  • the present invention is characterized in that the longitudinal electric field (the film thickness direction) and the transverse electric field (the propagation direction of surface acoustic waves) are excited by the double-layer electrode, and the electric field is changed by changing the electric field.
  • the coupling method with the piezoelectric film improves the electromechanical coupling coefficient of the surface acoustic wave device.

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  • Chemical & Material Sciences (AREA)
  • Acoustics & Sound (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
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Abstract

本发明公开了一种基于双层电极高机电耦合系数的声表面波器件及其制备方法。所述声表面波器件的结构如下：基片上依次为铜电极、压电薄膜和铝电极；铜电极的信号端与铝电极的接地端相对，铜电极的接地端与铝电极的信号端相对。由于所采用的西沙瓦波模式是薄膜厚度振动和横向振动耦合而成，本发明的特点在于通过双层电极激励纵向电场（薄膜厚度方向）和横向电场（声表面波传播方向），通过改变电场和压电薄膜的耦合方式从而提高声表面波器件的机电耦合系数。

Description

一种基于双层电极高机电耦合系数的声表面波器件及其制备方法 技术领域
本发明涉及一种基于双层电极高机电耦合系数的声表面波器件及其制备方法，属于信息电子材料领域。
背景技术
声表面波器件是基于压电效应对射频信号编码解码进行信息传输的电子器件，在过去几十年有着飞快的发展。目前随着5G时代的大幕拉开，对于零温漂、小尺寸、大带宽声表面波器件的需求越来越强烈。
传统声表面波器件是基于铌酸锂、钽酸锂等压电单晶材料，价格相对昂贵，并且对定向切割的要求很高。基于压电薄膜的声表面波器件具有频率范围广、制备简单等优点，更加满足声表面波器件微型化、集成化的要求，另外可以通过选择不同声速的衬底材料调控器件的频率和机电耦合系数。当前主流的压电薄膜材料有氧化锌和氮化铝两种，相比于氮化铝来说氧化锌具有温漂小、机电耦合系数大、制备更简单等优点，因此在制备高频低插损大带宽声表面波滤波器上具有更大的潜力。但目前基于氧化锌薄膜的声表面波模式主要是西沙瓦波模式，目前报导西沙瓦波的机电耦合系数相对较低，与单晶材料相比还是略有不足。作为声表面波器件的重要参数，声表滤波器带宽直接取决于器件机电耦合系数，因此为了拓宽薄膜材料在声表面波器件中的应用，要想将氧化锌薄膜材料真正用于声表面波器件中，必须提高器件的机电耦合系数。
发明内容
本发明的目的是提供一种声表面波器件及其制备方法，本发明通过双层电极实现高机电耦合系数。
本发明所提供的声表面波器件的结构如下：
基片上依次为铜电极、压电薄膜和铝电极；
所述铜电极的信号端与所述铝电极的接地端相对，所述铜电极的接地端与所述铝电极的信号端相对，从而能够激发厚度方向电场。
上述的声表面波器件中，所述铜电极的厚度可为50～100nm，如75 nm、50～75nm或75～100nm；
所述铝电极的厚度可为50～100nm，如75nm、50～75nm或75～100nm。
上述的声表面波器件中，所述压电薄膜可为氧化锌薄膜、氮化铝薄膜、掺杂氧化锌薄膜和掺杂氮化铝薄膜中的至少一种，优选为氧化锌薄膜。
上述的声表面波器件中，所述压电薄膜的厚度可为100～1500nm，如300nm、100～300nm、300～1500nm。
上述的声表面波器件中，所述基片可为c面蓝宝石基片、SiC或金刚石。
上述的声表面波器件中，所述基片与所述压电薄膜之间设置的空隙(即除铜电极之外的空隙)由氧化硅薄膜填充。
本发明所述声表面波器件可按照下述1)或2)的方法制备：
1)当所述压电薄膜与所述基片之间的空隙不填充氧化硅薄膜时，在所述基片上依次沉积所述铜电极、所述压电薄膜和所述铝电极即得；
2)当所述压电薄膜与所述基片之间的空隙填充氧化硅薄膜时，在所述基片上依次沉积所述铜电极和所述氧化硅薄膜，所述氧化硅薄膜经化学机械抛光修正表面后继续沉积所述压电薄膜和所述铝电极即得。
上述的制备方法中，采用电子束蒸镀的方式制备所述铜电极和所述铝电极；
所述电子束蒸镀的条件如下：
蒸镀源为单质铝金属小颗粒或单质铜金属小颗粒，纯度为99.999％；
真空度为10 -6～10 -5Pa；
温度为10～100℃；
靶材与所述基片的距离为50～100cm；
蒸镀速率为
Figure PCTCN2020101804-appb-000001
所述蒸镀完成后，还包括向所述电子束蒸镀的真空室中充入氮气至真空室内压力为大气压，取出所制备的金属薄膜。
上述的制备方法中，采用射频磁控溅射的方式制备所述氧化硅薄膜；
所述射频磁控溅射的条件如下：
靶材为硅靶，所述硅靶的直径可为75mm，纯度可为99.999％；
工作气体(氩气和氧气)的流量可为10～30mL/min，具体可为氩气18mL/min，氧气12mL/min；
磁控溅射源为平面靶磁控溅射源；
功率为1000W；
温度为20～400℃；
体系的压力为0.5～1.2Pa；
靶材与所述基片之间的距离为60～80mm。
上述的制备方法中，采用射频磁控溅射的方式制备所述氧化锌薄膜；
所述射频磁控溅射的条件如下：
靶材可为锌靶，所述金属靶的直径可为75mm，纯度可为99.999％；
工作气体(氩气和氧气)的流量可为10～30mL/min，具体可为氩气18mL/min，氧气12mL/min；
磁控溅射源为平面靶磁控溅射源；
功率为140W；
温度为20～400℃；
体系的压力为0.5～1.2Pa；
靶材与所述基片之间的距离为60～80mm。
附图说明
图1为本发明双层电极声表面波器件的剖面示意图；其中1-c面蓝宝石；2-SiO 2；3-Cu；4-ZnO；5-Al。
图2为计算模拟得到的声速随压电薄膜厚度波长比变化示意图。
图3为计算模拟得到的机电耦合系数随压电薄膜厚度波长比变化示意图。
具体实施方式
下述实施例中所使用的实验方法如无特殊说明，均为常规方法。
下述实施例中所用的材料、试剂等，如无特殊说明，均可从商业途径得到。
实施例1：
1)光刻做好周期2微米的叉指电极图形的c面蓝宝石基片。打底胶之后，将基片放入电子束镀膜机中。启动真空系统抽真空至9×10 -6Pa；调节电子枪功率为20％，清洗靶(纯度为99.999％)5min。
2)待电源示数稳定后，打开靶挡板，Cu电极材料的蒸镀速度为
Figure PCTCN2020101804-appb-000002
沉积75nm。
3)蒸镀完成后，关闭电源。向电子束蒸镀镀膜机的真空室中充入氮气至真空室内压力为大气压，开腔取出蒸镀好铜电极的蓝宝石基片。
4)将剥离好的基片放入磁控溅射腔体中生长二氧化硅薄膜，选择射频溅射模式，靶材与基片之间的距离为70mm，设定功率为1000W，氩气流量设为18ml/min，氧气流量为12ml/min，气压稳定在0.5Pa，在打开挡板之前预溅射180s左右，溅射时间控制在6s，沉积75nm。
5)溅射完成后，关闭电源。向磁控溅射的真空室中充入氮气至真空室内压力为大气压，开腔取出基片。通过化学机械抛光对二氧化硅薄膜进行修整表面从而保证氧化锌生长时基片的平整度。
6)在抛光过的基片表面溅射氧化锌薄膜，选择射频溅射模式，靶材与基片之间的距离为70mm，设定功率140W，氩气流量设为18ml/min，氧气流量为10ml/min，气压稳定在0.8Pa，温度稳定在350℃，在打开挡板之前预溅射180s左右，溅射时间控制在2250s，沉积300nm。
7)通过套刻做好上电极图形，使得上下电极的接地端和信号端相对。随后通过电子束蒸镀制备上电极铝电极，具体工艺与(1)步骤类似，Al的蒸镀速率为
Figure PCTCN2020101804-appb-000003
沉积75nm。
8)将步骤(7)中所制备薄膜在丙酮中剥离得到所需声表面波器件，结构示意图如图1所示。
制备单电极(Al电极，厚度与双层电极结构Al电极厚度相同)的声表面波器件，按照实施例1中步骤1)、6)和7)的步骤制备得到。
对上述制备得双层电极和单层电极的声表面波器件的性能通过comsol有限元模拟计算的方法进行了预测，得到的声速随压电薄膜厚度波长比变化示意图如图2所示，得到的机电耦合系数随压电薄膜厚度波长比变化示 意图如图3所示，可以看出，本发明双层电极的声表面波器件在厚度波长比为0.175时机电耦合系数最大值在7.5％左右。虽然单层电极的声表面波器件具有较高的声速但机电耦合系数最大值却只有双层电极器件的一半，因此本发明提供的双层电极结构能够在保证高声速的前提下大幅提升声表面波器件的机电耦合系数，对未来大带宽滤波器提出了一种切实可行的方案。
工业应用
本发明具有如下有益效果：
由于所采用的西沙瓦波模式是薄膜厚度振动和横向振动耦合而成，本发明的特点在于通过双层电极激励纵向电场(薄膜厚度方向)和横向电场(声表面波传播方向)，通过改变电场和压电薄膜的耦合方式从而提高声表面波器件的机电耦合系数。

Claims (15)

  1. 一种声表面波器件，其特征在于：基片上依次为铜电极、压电薄膜和铝电极；
    所述铜电极的信号端与所述铝电极的接地端相对，所述铜电极的接地端与所述铝电极的信号端位置相对。
  2. 根据权利要求1所述的声表面波器件，其特征在于：所述铜电极的厚度为50～100nm；
    所述铝电极的厚度为50～100nm。
  3. 根据权利要求1或2所述的声表面波器件，其特征在于：所述压电薄膜为氧化锌薄膜、氮化铝薄膜、掺杂氧化锌薄膜和掺杂氮化铝薄膜中的至少一种。
  4. 根据权利要求1-3中任一项所述的声表面波器件，其特征在于：所述压电薄膜的厚度为100～1500nm。
  5. 根据权利要求1-4中任一项所述的声表面波器件，其特征在于：所述基片为c面蓝宝石基片、SiC或金刚石。
  6. 根据权利要求1-5中任一项所述的声表面波器件，其特征在于：所述基片与所述压电薄膜之间设置的空隙由氧化硅薄膜填充。
  7. 权利要求1-6中任一项所述声表面波器件的制备方法，包括如下1)或2)的步骤：
    1)在所述基片上依次沉积所述铜电极、所述压电薄膜和所述铝电极即得权利要求1-5中任一项所述的声表面波器件；
    2)在所述基片上依次沉积所述铜电极和所述氧化硅薄膜，所述氧化硅薄膜经抛光修正表面后继续沉积所述压电薄膜和所述铝电极即得权利要求6所述声表面波器件。
  8. 根据权利要求7所述的制备方法，其特征在于：采用电子束蒸镀的方式制备所述铜电极和所述铝电极。
  9. 根据权利要求8所述的制备方法，其特征在于：所述电子束蒸镀的条件如下：
    温度为10～100℃；
    靶材与所述基片的距离为50～100cm。
  10. 根据权利要求7-9中任一项所述的制备方法，其特征在于：采用化学机械抛光的方式修正所述氧化硅薄膜表面。
  11. 根据权利要求7-10中任一项所述的制备方法，其特征在于：采用射频磁控溅射的方式制备所述氧化硅薄膜。
  12. 根据权利要求11所述的制备方法，其特征在于：所述射频磁控溅射的条件如下：
    磁控溅射源为平面靶磁控溅射源；
    功率为1000W；
    温度为20～400℃；
    体系的压力为0.5～1.2Pa；
    靶材与所述基片之间的距离为60～80mm。
  13. 根据权利要求7-12中任一项所述的制备方法，其特征在于：采用射频磁控溅射的方式制备所述氧化锌薄膜。
  14. 根据权利要求13所述的制备方法，其特征在于：所述射频磁控溅射的条件如下：
    磁控溅射源为平面靶磁控溅射源；
    功率为140W；
    温度为20～400℃；
    体系的压力为0.5～1.2Pa；
    靶材与所述基片之间的距离为60～80mm。
  15. 权利要求1-6中任一项所述声表面波器件在制备高声速、高机电耦合系数的声表面波滤波器中的应用。
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