WO2019223071A1 - 一种电容式超声换能器及其制造方法 - Google Patents

一种电容式超声换能器及其制造方法 Download PDF

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WO2019223071A1
WO2019223071A1 PCT/CN2018/094768 CN2018094768W WO2019223071A1 WO 2019223071 A1 WO2019223071 A1 WO 2019223071A1 CN 2018094768 W CN2018094768 W CN 2018094768W WO 2019223071 A1 WO2019223071 A1 WO 2019223071A1
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layer
ultrasonic transducer
cavity
graphene layer
lower electrode
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PCT/CN2018/094768
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English (en)
French (fr)
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崔开宇
朱鸿博
蔡旭升
黄翊东
刘仿
冯雪
张巍
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清华大学
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B9/00—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B9/00—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00
    • B32B9/005—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00 comprising one layer of ceramic material, e.g. porcelain, ceramic tile
    • B32B9/007—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00 comprising one layer of ceramic material, e.g. porcelain, ceramic tile comprising carbon, e.g. graphite, composite carbon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B9/00—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00
    • B32B9/04—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00 comprising such particular substance as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/20—Properties of the layers or laminate having particular electrical or magnetic properties, e.g. piezoelectric
    • B32B2307/206—Insulating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2313/00—Elements other than metals
    • B32B2313/04—Carbon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2457/00—Electrical equipment

Definitions

  • the invention relates to the field of electronic technology, and in particular to a capacitive ultrasonic transducer and a manufacturing method thereof.
  • Photoacoustic imaging as a new type of medical imaging method in recent years, has the characteristics of human body safety, small size, low cost, adjustable imaging depth, and higher resolution. Wide application prospects.
  • the ultrasonic transducer is a component that realizes the exchange of acoustic energy and electrical energy, and is the most critical sensing unit for photoacoustic imaging.
  • traditional piezoelectric ceramic ultrasonic transducers have been widely used due to their advantages such as high electromechanical conversion efficiency, easy matching with circuits, stable performance, easy processing, and low cost.
  • due to the high acoustic impedance of piezoelectric ceramic materials it is not easy to match the acoustic impedance of human soft tissues and water, and has high mechanical quality factor, narrow bandwidth, large brittleness, low tensile strength, high-density array elements, and ultra-thin high-frequency switching.
  • the energy-saving device is not easy to be processed.
  • the present invention provides a capacitive ultrasonic transducer and a manufacturing method thereof.
  • the present invention provides a capacitive ultrasonic transducer, which includes a substrate, an insulating isolation layer, and a graphene layer arranged in order from bottom to top, and is disposed on the substrate at a position corresponding to the graphene layer.
  • a lower electrode is provided with a cavity between the graphene layer and the lower electrode, and the graphene layer, the lower electrode and the cavity form a flat capacitor structure.
  • the graphene layer is 1 to 10 layers of graphene films.
  • the cavity is a circular hole, and the radius of the circular hole is 0.5-200 ⁇ m.
  • the thickness of the cavity is 0.1-10 ⁇ m.
  • the substrate is made of silicon dioxide or a flexible organic material.
  • the lower electrode is a germanium and gold composite metal electrode, a polysilicon electrode, or a transparent conductive glass.
  • the insulating isolation layer is made of silicon dioxide or a flexible organic insulating material.
  • the present invention provides a method for manufacturing a capacitive ultrasonic transducer, including:
  • a graphene layer is transferred onto the insulation layer and covers the cavity.
  • the method before the transferring the graphene layer to the insulation layer and covering the cavity, the method further includes:
  • transferring the graphene layer onto the insulation layer and covering the cavity includes:
  • the capacitive ultrasonic transducer and the manufacturing method thereof provided by the present invention include a substrate, an insulating isolation layer, and a graphene layer in order from bottom to top.
  • a lower electrode is provided at a position corresponding to the graphene layer on the substrate.
  • a cavity is provided between the ene layer and the lower electrode, and the graphene layer, the lower electrode and the cavity form a flat capacitor structure, which improves the sensitivity of the ultrasonic transducer.
  • FIG. 1 is a schematic structural diagram of a capacitive ultrasonic transducer according to an embodiment of the present invention
  • FIG. 2 is a schematic structural diagram of a capacitive ultrasonic transducer according to another embodiment of the present invention.
  • FIG. 3 is a schematic flowchart of a method for manufacturing a capacitive ultrasonic transducer according to an embodiment of the present invention
  • FIG. 4a is a schematic diagram of forming a lower electrode according to another embodiment of the present invention.
  • 4b is a schematic diagram of forming an insulating isolation layer according to another embodiment of the present invention.
  • 4c is a schematic diagram of forming an electrode contact on another embodiment of the present invention.
  • 4d is a schematic diagram of forming a circular hole according to another embodiment of the present invention.
  • FIG. 4e is a schematic diagram of forming a graphene layer according to another embodiment of the present invention.
  • the capacitive ultrasonic transducer provided by the present invention is made of graphene, and graphene can be made into a graphene film. Because the graphene film has a small vibration mass and high sensitivity to external forces, it is suitable for high-precision sensing; graphene It has the characteristics of high Young's modulus. By designing the suspended structure, a wide spectrum response can be achieved. Graphene can also be combined with a flexible substrate to make a flexible device to suit different application scenarios of photoacoustic imaging; graphene itself can be used as a good conductive material to form the electrode plate structure of a capacitor. Therefore, based on the above characteristics of graphene, the present invention proposes a capacitive ultrasonic transducer.
  • Graphene is applied to a capacitive ultrasonic transducer that conforms to photoacoustic imaging.
  • the instrument using the above-mentioned capacitive ultrasonic transducer can Detection of biological tissue signals from 1 to 20 MHz.
  • FIG. 1 is a schematic structural diagram of a capacitive ultrasonic transducer according to an embodiment of the present invention.
  • the capacitive ultrasonic transducer provided by the present invention includes a substrate 1 and an insulation layer disposed in order from bottom to top. 2 and graphene layer 5, a lower electrode 3 is provided on the substrate 1 at a position corresponding to the graphene layer 5, a cavity 4 is provided between the graphene layer 5 and the lower electrode 3, and the graphene layer 5, the lower electrode 3, and the space The cavity 4 forms a flat capacitor structure.
  • the substrate 1 is used to carry the structure of the entire device of the capacitive ultrasonic transducer, and silicon dioxide or a flexible organic material may be used; an insulating isolation layer 2 is provided on the substrate 1 to support the graphene layer. 5 and play an insulating role, silicon dioxide or flexible organic insulating materials can be used; the graphene layer 5 is provided on the insulating isolation layer 2 as the upper electrode plate of the ultrasonic sensor and the flat capacitor structure; the lower electrode 3 is provided on The substrate 1 is disposed opposite to the graphene layer 5 as the lower electrode plate of the flat capacitor structure; a cavity 4 is provided between the graphene layer 5 and the lower electrode 3, and the graphene layer 5 and the lower electrode 3 and The cavity 4 forms the flat capacitor structure.
  • the suspended graphene layer 5 can vibrate under the action of the ultrasonic wave, thereby changing the capacitance of the flat capacitor structure, and finally detecting the ultrasonic wave by detecting the change in the capacitance.
  • the capacitive ultrasonic transducer and the manufacturing method thereof provided by the present invention include a substrate, an insulating isolation layer, and a graphene layer in order from bottom to top.
  • a lower electrode is provided at a position corresponding to the graphene layer on the substrate.
  • a cavity is provided between the olefin layer and the lower electrode, and the graphene layer, the lower electrode and the cavity form a flat-plate capacitor structure, which improves the sensitivity of the ultrasonic transducer, thereby improving the accuracy of ultrasonic detection.
  • the graphene layer 5 is 1 to 10 layers of graphene films.
  • the cavity 4 is a circular hole, and the radius of the circular hole is 0.5-200 ⁇ m.
  • the radius of the circular hole is 0.5-200 ⁇ m.
  • the thickness of the cavity is 0.1 to 10 ⁇ m.
  • the substrate 1 is made of silicon dioxide or a flexible organic material.
  • silicon dioxide is a transparent material, which can improve the transparency of the ultrasonic transducer and facilitate the passage of light.
  • the use of flexible organic materials is conducive to improving the overall flexibility of the ultrasonic transducer, which is convenient for practical applications.
  • the lower electrode 3 is a germanium and gold composite metal electrode, a polysilicon electrode, or a transparent conductive glass.
  • the lower layer of the germanium and gold composite metal electrode is germanium and the upper layer is gold.
  • the thickness of germanium may be 50 nm, and the thickness of gold is 50-200 nm.
  • the insulating isolation layer 2 is made of silicon dioxide or a flexible organic insulating material.
  • FIG. 2 is a schematic structural diagram of a capacitive ultrasonic transducer according to another embodiment of the present invention.
  • the capacitive ultrasonic transducer provided by the present invention further includes an upper electrode contact 6, and the upper electrode contact 6 is disposed at The insulating isolation layer 3 is connected to the graphene layer 5.
  • the graphene layer 5 covers a part of the upper electrode contact 6 provided on the insulating isolation layer 3.
  • the electrode contact 6 is used to connect the graphene layer 5 externally.
  • the electrode contact 6 may be a germanium and gold composite metal electrode, a polysilicon electrode, or a transparent conductive glass.
  • the upper electrode contact 6 is a germanium and gold composite metal electrode
  • the lower layer of the germanium and gold composite metal electrode is germanium and the upper layer is gold.
  • the thickness of germanium may be 50 nm and the thickness of gold is 50-200 nm.
  • FIG. 3 is a schematic flowchart of a method for manufacturing a capacitive ultrasonic transducer according to an embodiment of the present invention. As shown in FIG. 3, a method for manufacturing a capacitive ultrasonic transducer according to an embodiment of the present invention includes:
  • a lower electrode can be fabricated on a substrate by using processes such as ultraviolet lithography and sputtering.
  • the substrate can be silicon dioxide or a flexible organic material.
  • the lower electrode can be a germanium and gold composite metal electrode, polysilicon Electrodes or transparent conductive glass. Wherein, when a germanium and gold composite metal electrode is used, the lower layer of the germanium and gold composite metal electrode is germanium and the upper layer is gold.
  • the thickness of germanium can be 50 nm and the thickness of gold is 50-200 nm.
  • An insulating isolation layer is formed on the substrate, and the insulating isolation layer covers the lower electrode.
  • an insulating isolation layer may be formed on the substrate by a plasma enhanced chemical vapor deposition method or a chemical spin coating method, and the insulating isolation layer may be silicon dioxide or a flexible organic insulating material. Wherein, the insulating isolation layer covers the lower electrode formed in the previous step.
  • the thickness of the insulation isolation layer is set according to actual needs, which is not limited in the embodiment of the present invention.
  • a cavity penetrating the insulation isolation layer may be fabricated on the insulation isolation layer above the lower electrode through processes such as ultraviolet lithography and chemical etching, and the cavity may be a circular hole with a diameter of the circular hole. It is set according to different ultrasonic signal frequency ranges, which are not limited in the embodiment of the present invention.
  • the height of the cavity may be 0.1 to 10 ⁇ m.
  • a graphene dry imprint transfer method is used to transfer a graphene layer onto the insulating isolation layer and cover the cavity, so that the graphene layer, the cavity, and the lower electrode Forming a flat capacitor structure, the graphene layer serves as an upper electrode plate of the capacitor structure, and the lower electrode serves as a lower electrode plate of the capacitor structure.
  • the graphene layer may use 1 to 10 graphene films.
  • a lower electrode is produced at a position corresponding to the graphene layer on the substrate, and A cavity is formed between the ene layer and the lower electrode, and the graphene layer, the lower electrode and the cavity form a flat capacitor structure, which improves the sensitivity of the ultrasonic transducer.
  • the method further includes:
  • transferring the graphene layer onto the insulation layer and covering the cavity includes:
  • the upper electrode contact may be fabricated by using processes such as ultraviolet lithography, sputtering, wet etching, or lift-off, and the upper electrode contact may be germanium and gold composite metal. Electrode, polysilicon electrode or transparent conductive glass. When the germanium and gold composite metal electrode is used as the upper electrode contact, the lower layer of the germanium and gold composite metal electrode is germanium and the upper layer is gold. The thickness of germanium may be 50 nm and the thickness of gold is 50-200 nm.
  • the graphene layer After the upper electrode contact is manufactured, when the graphene layer is transferred to the insulating isolation layer, the graphene layer will cover at least a part of the upper electrode contact, thereby realizing the graphite
  • the olefin layer is electrically connected to the upper electrode contact, so that the graphene layer is externally connected through the upper electrode contact.
  • Step 1 and FIG. 4a are schematic diagrams of forming a lower electrode according to another embodiment of the present invention.
  • a germanium and gold composite metal electrode is formed on a silicon dioxide substrate 41 by processes such as ultraviolet lithography and sputtering.
  • the lower layer of the germanium and gold composite metal electrode is germanium, and the upper layer is gold.
  • the thickness of germanium may be 50 nm and the thickness of gold is 100 nm.
  • FIG. 4b is a schematic diagram of forming an insulating isolation layer according to another embodiment of the present invention. As shown in FIG. 4b, a 1 ⁇ m thick precipitate is formed on the silicon dioxide substrate 41 and the lower electrode 43 by a plasma enhanced chemical vapor deposition method.
  • the insulating isolation layer 42 is made of silicon dioxide.
  • FIG. 4c is a schematic diagram of forming an upper electrode contact in another embodiment of the present invention.
  • the upper electrode contact 46 is fabricated on the insulating isolation layer 42 by using ultraviolet lithography, sputtering, and wet etching.
  • the upper electrode contact 46 is made of transparent conductive glass.
  • FIG. 4d is a schematic diagram of forming a circular hole according to another embodiment of the present invention. As shown in FIG. The diameter of the hole 44 and the circular hole 44 is 10 ⁇ m, and the height of the circular hole 44 is 850 nm.
  • FIG. 4e is a schematic diagram of forming a graphene layer according to another embodiment of the present invention.
  • a graphene dry imprint transfer method is used to transfer 5 layers of graphene film 45 to the insulating isolation layer 42, The entire circular hole 44 and a part of the upper electrode contact 46 are covered, so that the graphene film 45, the circular hole 44 and the lower electrode 43 constitute a flat capacitor structure, and the graphene film 45 is externally connected through the upper electrode contact 46.

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Abstract

一种电容式超声换能器，包括：从下到上依次设置的衬底（1）、绝缘隔离层（2）和石墨烯层（5），在衬底（1）上与石墨烯层（5）对应的位置设置下电极（3），石墨烯层（5）和下电极（3）之间设置空腔（4），石墨烯层（5）、下电极（3）和空腔（4）形成平板式电容结构。该电容式超声换能器提高了超声换能器的灵敏度。还提供一种电容式超声换能器的制造方法。

Description

一种电容式超声换能器及其制造方法
交叉引用
本申请引用于2018年05月22日提交的专利名称为“一种电容式超声换能器及其制造方法”的第2018104970113号中国专利申请，其通过引用被全部并入本申请。
技术领域
本发明涉及电子技术领域，具体涉及一种电容式超声换能器及其制造方法。
背景技术
光声成像作为一种近年来新型的医疗成像手段，具有对人体安全、体积小、成本较低、成像深度可调节、分辨率更高等特点，在医学诊断与治疗、遥感与遥控等技术领域有着广泛的应用前景。
超声换能器是实现声能与电能互换的部件，是实现光声成像最关键的传感单元。现有技术中，传统压电陶瓷超声换能器因具有机电转换效率高、易与电路匹配、性能稳定、易加工和成本低等优点得到广泛的应用。但是由于压电陶瓷材料存在声阻抗高，不易与人体软组织及水的声阻抗匹配，并且具有机械品质因数高，带宽窄，脆性大、抗张强度低、高密度阵元及超薄高频换能器不易加工等缺陷。
因此，如何提出一种超声换能器，能够提高超声换能器的灵敏度成为业界亟待解决的重要课题。
发明内容
针对现有技术中的缺陷，本发明提供一种电容式超声换能器及其制造方法。
一方面，本发明提出一种电容式超声换能器，包括从下到上依次设置的衬底、绝缘隔离层和石墨烯层，在所述衬底上与所述石墨烯层对应的位置设置下电极，所述石墨烯层和所述下电极之间设置空腔，所述石墨烯层、 所述下电极和所述空腔形成平板式电容结构。
其中，所述石墨烯层为1～10层石墨烯薄膜。
其中，所述空腔为圆孔，所述圆孔的半径为0.5～200μm。
其中，所述空腔的厚度为0.1～10μm。
其中，所述衬底采用二氧化硅或者柔性有机材料。
其中，所述下电极采用锗和金复合金属电极、多晶硅电极或者透明的导电玻璃。
其中，所述绝缘隔离层采用二氧化硅或者柔性有机绝缘材料。
其中，还包括上电极触点，所述上电极触点设置在所述绝缘隔离层上，并与所述石墨烯层相连。
另一方面，本发明提供一种电容式超声换能器制造方法，包括：
在衬底上形成下电极；
在所述衬底上形成绝缘隔离层，所述绝缘隔离层覆盖所述下电极；
在所述下电极上方的绝缘隔离层制作出贯通所述绝缘隔离层的空腔；
将石墨烯层转移到所述绝缘隔离层上，并覆盖所述空腔。
其中，在所述将石墨烯层转移到所述绝缘隔离层上，并覆盖所述空腔之前还包括：
在所述绝缘隔离层上形成上电极触点；
相应地，将石墨烯层转移到所述绝缘隔离层上，并覆盖所述腔体包括：
将所述石墨烯层转移到所述绝缘隔离层上，并至少覆盖所述上电极触点的一部分，以实现所述石墨烯层与所述上电极触点的电连接。
本发明提供的电容式超声换能器及其制造方法，由于从下到上依次设置衬底、绝缘隔离层和石墨烯层，在衬底上与石墨烯层对应的位置设置下电极，在石墨烯层和下电极之间设置空腔，石墨烯层、下电极和空腔形成平板式电容结构，提高了超声换能器的灵敏度。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作一简单地介绍，显而易见地，下面描述中的附图是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附 图。
图1为本发明一实施例电容式超声换能器的结构示意图；
图2为本发明另一实施例电容式超声换能器的结构示意图；
图3为本发明一实施例电容式超声换能器的制造方法的流程示意图；
图4a为本发明另一实施例下电极的形成示意图；
图4b为本发明另一实施例绝缘隔离层的形成示意图；
图4c为本发明另一实施例上电极触点的形成示意图；
图4d为本发明另一实施例圆孔的形成示意图；
图4e为本发明另一实施例石墨烯层的形成示意图；
附图标记说明：
1-衬底；           2-绝缘隔离层；
3-下电极；         4-空腔；
5-石墨烯层；       6-上电极触点；
41-衬底；          42-绝缘隔离层；
43-下电极；        44-圆孔；
45-石墨烯薄膜；    46-上电极触点。
。
具体实施方式
为使本发明的目的、技术方案和优点更加清楚，下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚地描述，显然，所描述的实施例是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。
本发明提供的电容式超声换能器采用石墨烯制作，石墨烯可以制作成石墨烯薄膜，由于石墨烯薄膜振动质量很小，对于外力作用灵敏度高，很适合用于高精度传感；石墨烯具有高杨氏模量的特点，通过设计悬空结构，可以实现宽频谱响应。石墨烯也可与柔性衬底相结合，可制作成柔性器件，以适应光声成像的不同应用场景；石墨烯本身可作为良好的导电材料，用于构成电容的极板结构。所以，基于石墨烯的上述特点，本发明提出一种电容式超声换能器，将石墨烯应用在符合光声成像的电容式超声换能器 中，采用上述电容式超声换能器的仪器可探测1～20MHz的生物组织信号。
图1为本发明一实施例电容式超声换能器的结构示意图，如图1所示，本发明提供的电容式超声换能器，包括从下到上依次设置的衬底1、绝缘隔离层2和石墨烯层5，在衬底1上与石墨烯层5对应的位置设置下电极3，石墨烯层5和下电极3之间设置空腔4，石墨烯层5、下电极3和空腔4形成平板式电容结构。
具体地，衬底1用于承载所述电容式超声换能器的整个器件的结构，可以采用二氧化硅或柔性有机材料；绝缘隔离层2设置在衬底1上，用于支撑石墨烯层5和起到绝缘作用，可以采用二氧化硅或柔性有机绝缘材料；石墨烯层5设置在绝缘隔离层2上，作为超声波传感器和所述平板式电容结构的上电极板；下电极3设置在衬底1上，并与石墨烯层5相对设置，作为所述平板式电容结构的下电极板；石墨烯层5和下电极3之间设置空腔4，石墨烯层5、下电极3和空腔4形成所述平板式电容结构。在接收到超声波时，悬空的石墨烯层5可在超声波的作用下，发生振动，从而改变所述平板式电容结构的电容，通过检测所述电容的变化最终可以实现对超声波的检测。
本发明提供的电容式超声换能器及其制造方法，由于从下到上依次设置衬底、绝缘隔离层和石墨烯层，在衬底上与石墨烯层对应的位置设置下电极，在石墨烯层和下电极之间设置空腔，石墨烯层、下电极和空腔形成平板式电容结构，提高了超声换能器的灵敏度，从而提高了对超声波探测的精度。
在上述各实施例的基础上，进一步地，石墨烯层5为1～10层石墨烯薄膜。
在上述各实施例的基础上，进一步地，空腔4为圆孔，所述圆孔的半径为0.5～200μm。通过更改所述圆孔的半径可以实现对特定频带范围超声波的强度、频率等信息的探测。
在上述各实施例的基础上，进一步地，所述空腔的厚度为0.1～10μm。
在上述各实施例的基础上，进一步地，衬底1采用二氧化硅或者柔性有机材料。其中，二氧化硅为透明材料，可以提高所述超声换能器的透明度，便于光线穿过。采用柔性有机材料有利于提高所述超声换能器整体的 柔性，便于实际应用。
在上述各实施例的基础上，进一步地，下电极3采用锗和金复合金属电极、多晶硅电极或者透明的导电玻璃。其中，当采用锗和金复合金属电极时，所述锗和金复合金属电极的下层为锗，上层为金，锗的厚度可以为50nm，金的厚度为50～200nm。
在上述各实施例的基础上，进一步地，绝缘隔离层2采用二氧化硅或者柔性有机绝缘材料。
图2为本发明另一实施例电容式超声换能器的结构示意图，如图2所示，本发明提供的电容式超声换能器还包括上电极触点6，上电极触点6设置在绝缘隔离层3上，并与石墨烯层5相连，例如，石墨烯层5覆盖设置在绝缘隔离层3上的上电极触点6的一部分。电极触点6用于将石墨烯层5外接，电极触点6可以采用锗和金复合金属电极、多晶硅电极或者透明的导电玻璃。其中，当上电极触点6采用锗和金复合金属电极时，所述锗和金复合金属电极的下层为锗，上层为金，锗的厚度可以为50nm，金的厚度为50～200nm。
图3为本发明一实施例电容式超声换能器的制造方法的流程示意图，如图3所示，本发明实施例提供的电容式超声换能器制造方法，包括：
S301、在衬底上形成下电极；
具体地，可以采用紫外光刻和溅射等工艺在衬底上制作出下电极，所述衬底可以采用二氧化硅或柔性有机材料，所述下电极可以采用锗和金复合金属电极、多晶硅电极或者透明的导电玻璃。其中，当采用锗和金复合金属电极时，所述锗和金复合金属电极的下层为锗，上层为金，锗的厚度可以为50nm，金的厚度为50～200nm。
S302、在所述衬底上形成绝缘隔离层，所述绝缘隔离层覆盖所述下电极；
具体地，可以在所述衬底上通过等离子体增强化学的气相沉积法或化学旋涂法沉淀形成绝缘隔离层，所述绝缘隔离层可以采用二氧化硅或柔性有机绝缘材料。其中，所述绝缘隔离层覆盖上一步骤形成的所述下电极。所述绝缘隔离层的厚度根据实际需要进行设置，本发明实施例不做限定。
S303、在所述下电极上方的绝缘隔离层制作出贯通所述绝缘隔离层的 空腔；
具体地，可以通过紫外光刻和化学腐蚀等工艺在所述下电极上方的绝缘隔离层制作出贯通所述绝缘隔离层的空腔，所述空腔可以为圆孔，所述圆孔的直径根据不同的超声波信号频率范围进行设置，本发明实施例不做限定。其中，所述空腔的高度可以为0.1～10μm。
S304、将石墨烯层转移到所述绝缘隔离层上，并覆盖所述空腔。
具体地，采用石墨烯干法压印转移的方法，将石墨烯层转移到所述绝缘隔离层上，并覆盖所述空腔，使得所述石墨烯层、所述空腔和所述下电极构成平板式电容结构，所述石墨烯层作为所述电容结构的上电极板，所述下电极作为所述电容结构的下电极板。其中，所述石墨烯层可以采用1至10层石墨烯薄膜。
本发明提供的电容式超声换能器的制造方法，由于从下到上依次形成衬底、绝缘隔离层和石墨烯层，在衬底上与石墨烯层对应的位置制作出下电极，在石墨烯层和下电极之间形成空腔，石墨烯层、下电极和空腔形成平板式电容结构，提高了超声换能器的灵敏度。
在上述各实施例的基础上，进一步地，在所述将石墨烯层转移到所述绝缘隔离层上，并覆盖所述空腔之前还包括：
在所述绝缘隔离层上形成上电极触点；
相应地，将石墨烯层转移到所述绝缘隔离层上，并覆盖所述腔体包括：
将所述石墨烯层转移到所述绝缘隔离层上，并至少覆盖所述上电极触点的一部分，以实现所述石墨烯层与所述上电极触点的电连接。
具体地，在形成所述绝缘隔离层之后，可以采用紫外光刻、溅射和湿法腐蚀，或者抬离等工艺制作出上电极触点，所述上电极触点可以采用锗和金复合金属电极、多晶硅电极或者透明的导电玻璃。其中，当所述上电极触点采用锗和金复合金属电极时，所述锗和金复合金属电极的下层为锗，上层为金，锗的厚度可以为50nm，金的厚度为50～200nm。在所述上电极触点制作完成之后，在将所述石墨烯层转移到所述绝缘隔离层上时，所述石墨烯层至少会覆盖所述上电极触点的一部分，从而实现所述石墨烯层与所述上电极触点的电连接，以便于通过所述上电极触点将所述石墨烯层外接。
下面来详细说明本发明另一实施例的电容式超声换能器的制造方法的具体实现过程。
步骤一、图4a为本发明另一实施例下电极的形成示意图，如图4a所示，在二氧化硅衬底41上通过紫外光刻和溅射等工艺形成锗和金复合金属电极，作为下电极43。其中，所述锗和金复合金属电极的下层为锗，上层为金，锗的厚度可以为50nm，金的厚度为100nm。
步骤二、图4b为本发明另一实施例绝缘隔离层的形成示意图，如图4b所示，通过等离子体增强化学的气相沉积法在二氧化硅衬底41和下电极43上沉淀形成1μm厚的绝缘隔离层42，绝缘隔离层42采用二氧化硅。
步骤三、图4c为本发明另一实施例上电极触点的形成示意图，如图4c所示，采用紫外光刻、溅射和湿法腐蚀在绝缘隔离层42上制作出上电极触点46，上电极触点46采用透明的导电玻璃。
步骤四、图4d为本发明另一实施例圆孔的形成示意图，如图4d所示，通过紫外光刻和化学腐蚀等工艺在下电极43上方的绝缘隔离层42制作出贯通绝缘隔离层的圆孔44，圆孔44的直径为10μm，圆孔44的高度为850nm。
步骤五、图4e为本发明另一实施例石墨烯层的形成示意图，如图4e所示，采用石墨烯干法压印转移的方法将5层石墨烯薄膜45转移到绝缘隔离层42上，并覆盖整个圆孔44以及上电极触点46的一部分，从而使石墨烯薄膜45、圆孔44和下电极43构成平板式电容结构，石墨烯薄膜45通过上电极触点46进行外接。
本发明方法实施例的具体流程可以参照上述各系统实施例的介绍，此处不再赘述。
最后应说明的是：以上实施例仅用以说明本发明的技术方案，而非对其限制；尽管参照前述实施例对本发明进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本发明各实施例技术方案的精神和范围。

Claims (10)

  1. 一种电容式超声换能器，其特征在于，包括从下到上依次设置的衬底、绝缘隔离层和石墨烯层，在所述衬底上与所述石墨烯层对应的位置设置下电极，所述石墨烯层和所述下电极之间设置空腔，所述石墨烯层、所述下电极和所述空腔形成平板式电容结构。
  2. 根据权利要求1所述的超声换能器，其特征在于，所述石墨烯层为1～10层石墨烯薄膜。
  3. 根据权利要求1所述的超声换能器，其特征在于，所述空腔为圆孔，所述圆孔的半径为0.5～200μm。
  4. 根据权利要求1所述的超声换能器，其特征在于，所述空腔的厚度为0.1～10μm。
  5. 根据权利要求1所述的超声换能器，其特征在于，所述衬底采用二氧化硅或者柔性有机材料。
  6. 根据权利要求1所述的超声换能器，其特征在于，所述下电极采用锗和金复合金属电极、多晶硅电极或者透明的导电玻璃。
  7. 根据权利要求1所述的超声换能器，其特征在于，所述绝缘隔离层采用二氧化硅或者柔性有机绝缘材料。
  8. 根据权利要求1至7任一项所述的超声换能器，其特征在于，还包括上电极触点，所述上电极触点设置在所述绝缘隔离层上，并与所述石墨烯层相连。
  9. 一种电容式超声换能器制造方法，其特征在于，包括：
    在衬底上形成下电极；
    在所述衬底上形成绝缘隔离层，所述绝缘隔离层覆盖所述下电极；
    在所述下电极上方的绝缘隔离层制作出贯通所述绝缘隔离层的空腔；
    将石墨烯层转移到所述绝缘隔离层上，并覆盖所述空腔。
  10. 根据权利要求9所述的方法，其特征在于，在所述将石墨烯层转移到所述绝缘隔离层上，并覆盖所述空腔之前还包括：
    在所述绝缘隔离层上形成上电极触点；
    相应地，将石墨烯层转移到所述绝缘隔离层上，并覆盖所述腔体包括：
    将所述石墨烯层转移到所述绝缘隔离层上，并至少覆盖所述上电极触 点的一部分，以实现所述石墨烯层与所述上电极触点的电连接。
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