WO2022007016A1 - 一种压电式麦克风及其制备工艺 - Google Patents

一种压电式麦克风及其制备工艺 Download PDF

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Publication number
WO2022007016A1
WO2022007016A1 PCT/CN2020/104047 CN2020104047W WO2022007016A1 WO 2022007016 A1 WO2022007016 A1 WO 2022007016A1 CN 2020104047 W CN2020104047 W CN 2020104047W WO 2022007016 A1 WO2022007016 A1 WO 2022007016A1
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WIPO (PCT)
Prior art keywords
piezoelectric
layer
diaphragm
microphone
depositing
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Ceased
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PCT/CN2020/104047
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English (en)
French (fr)
Inventor
童贝
石正雨
沈宇
李杨
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AAC Technologies Holdings Shenzhen Co Ltd
AAC Technologies Holdings Nanjing Co Ltd
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AAC Acoustic Technologies Shenzhen Co Ltd
AAC Technologies Holdings Nanjing Co Ltd
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Publication of WO2022007016A1 publication Critical patent/WO2022007016A1/zh
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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers
    • H04R17/02—Microphones
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
    • H04R1/28—Transducer mountings or enclosures modified by provision of mechanical or acoustic impedances, e.g. resonator, damping means
    • H04R1/2807—Enclosures comprising vibrating or resonating arrangements
    • H04R1/283—Enclosures comprising vibrating or resonating arrangements using a passive diaphragm
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
    • H04R31/00—Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor
    • H04R31/003—Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor for diaphragms or their outer suspension
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
    • H04R2231/00—Details of apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor covered by H04R31/00, not provided for in its subgroups
    • H04R2231/003—Manufacturing aspects of the outer suspension of loudspeaker or microphone diaphragms or of their connecting aspects to said diaphragms

Definitions

  • the invention belongs to the technical field of microphones, and in particular relates to a piezoelectric microphone and a preparation process thereof.
  • MEMS Micro-Electro-Mechanical Micro-electromechanical system
  • MEMS microphones are more and more widely used in these devices.
  • Piezoelectric MEMS microphones have many advantages over traditional condenser MEMS microphones, including dust and water resistance and higher maximum sound pressure output (AOP).
  • the diaphragm of a piezoelectric MEMS microphone is composed of a plurality of diaphragms, and the plurality of diaphragms are fixed on a substrate with a back cavity through elastic connection, and the upper and lower parts of the diaphragm are air.
  • the airtight environment hinders the movement of the vibrating membrane, thereby reducing the output voltage of the piezoelectric unit and greatly reducing the sensitivity of the MEMS microphone.
  • the purpose of the present invention is to provide a piezoelectric microphone and a manufacturing process thereof, aiming at increasing the output voltage of the piezoelectric unit and improving the sensitivity of the piezoelectric microphone.
  • a piezoelectric microphone comprising a base having a back cavity and a piezoelectric vibrating film arranged on the base, the piezoelectric vibrating film comprising a vibrating film layer fixed on the base and a piezoelectric unit fixed on the diaphragm layer, characterized in that: the piezoelectric microphone further includes a casing covering the diaphragm layer, the casing and the diaphragm layer are enclosed An accommodating cavity for accommodating the piezoelectric unit is formed, and the accommodating cavity is a vacuum environment.
  • the casing is made of silicon, silicon nitride, polyethylene or glass.
  • the base includes a side wall enclosing the back cavity, the orthographic projection of the piezoelectric unit along the vibration direction of the diaphragm layer and the positive projection of the side wall along the vibration direction of the diaphragm layer. The projections partially overlap.
  • the diaphragm layer is an integral continuous structure.
  • the piezoelectric unit includes a plurality of piezoelectric sheets, the plurality of piezoelectric sheets are arranged symmetrically in the center, and two adjacent piezoelectric sheets are arranged at intervals.
  • the piezoelectric unit includes a first electrode layer, a piezoelectric layer and a second electrode layer stacked on the vibrating film layer in sequence, and the first electrode layer and the second electrode layer are made of aluminum, Molybdenum or titanium material, the piezoelectric layer is made of aluminum nitride, zinc oxide, scandium-doped aluminum nitride or lead zirconate titanate piezoelectric ceramic material.
  • the diaphragm layer is made of aluminum nitride, polysilicon, silicon dioxide or silicon nitride.
  • the invention also provides a preparation process of the piezoelectric microphone, comprising the following steps:
  • Step S1 providing a substrate, and depositing a first oxide layer on the surface of the substrate;
  • Step S2 depositing a diaphragm layer on the surface of the first oxide layer
  • Step S3 depositing a piezoelectric unit on the surface of the diaphragm layer
  • Step S4 etching the piezoelectric unit
  • Step S5 depositing on the surface of the piezoelectric unit a casing covering the vibrating membrane layer, the casing and the vibrating membrane are laminated to form an accommodation cavity for accommodating the piezoelectric unit;
  • Step S6 etching the other surface of the substrate away from the diaphragm layer to form a back cavity.
  • step S5 specifically includes:
  • Step S51 Cover the surface of the piezoelectric unit with a second oxide layer, and perform polishing and patterning treatment;
  • Step S52 depositing a first sealing layer on the surface of the second oxide layer
  • Step S53 etching the first sealing layer to form a release hole, and releasing the second oxide layer to form the receiving cavity;
  • Step S54 sealing the release hole.
  • step S5 specifically includes:
  • Step S501 depositing a peripheral wall layer on the edge of the diaphragm layer, the peripheral wall layer surrounding the piezoelectric unit;
  • Step S502 providing a second sealing layer
  • Step S503 bonding the peripheral wall layer and the second sealing layer to form the casing.
  • the beneficial effect of the present invention is that: by arranging a casing above the diaphragm layer, the casing and the diaphragm are laminated to form an accommodation cavity for accommodating the piezoelectric unit, and the accommodation cavity is a vacuum environment, so the diaphragm layer is subjected to vibration during vibration.
  • the air damping is greatly reduced, and the output voltage of the piezoelectric unit will increase under the same sound pressure, which effectively improves the sensitivity of the microphone.
  • FIG. 1 is a schematic diagram of the overall structure of a piezoelectric microphone provided by a first embodiment of the present invention
  • FIG. 2 is a schematic diagram of an exploded structure of the piezoelectric microphone provided by the first embodiment of the present invention
  • Fig. 3 is the A-A direction sectional schematic diagram of Fig. 1;
  • Fig. 4 is the preparation flow chart of the piezoelectric microphone provided by the second embodiment of the present invention.
  • 5 to 13 are schematic diagrams of the manufacturing process of the piezoelectric microphone provided by the second embodiment of the present invention.
  • FIG. 14 is a schematic diagram of a preparation process for depositing a peripheral wall layer on the edge of the diaphragm layer according to the third embodiment of the present invention.
  • 15 is a schematic diagram of a preparation process for providing a second sealing layer on the peripheral wall layer according to the third embodiment of the present invention.
  • FIG. 1 to FIG. 2 is a piezoelectric microphone provided by the first embodiment of the present invention, including a substrate 1 having a back cavity 4 and a piezoelectric vibrating membrane 2 disposed on the substrate 1 .
  • the piezoelectric vibrating membrane 2 It includes a diaphragm layer 21 fixed on the base 1 and a piezoelectric unit 22 fixed on the diaphragm layer 21 .
  • the piezoelectric unit 22 is pressed to drive the diaphragm layer 21 to deform in the space above the back cavity 4, thereby generating a voltage signal.
  • the piezoelectric microphone further includes a casing 3 covering the diaphragm layer 21 .
  • the casing 3 and the diaphragm layer 21 enclose a receiving cavity 5 for accommodating the piezoelectric unit 22 .
  • the containment cavity 5 is a vacuum environment.
  • the housing 3 includes a peripheral wall 31 disposed along the periphery of the diaphragm layer 21 and a top wall 32 covering the side of the peripheral wall 31 away from the diaphragm layer 21 .
  • the peripheral wall 31 and the diaphragm layer 21 are fixed and the peripheral wall 31 is connected to The edges of the diaphragm layer 21 are flush.
  • the peripheral wall 31 is flush with the edge of the diaphragm layer 21 , so that the piezoelectric microphone is balanced and stable as a whole and is more beautiful.
  • the diaphragm layer 21 in this embodiment has an overall continuous structure, and there is no fault or gap in the diaphragm layer 21 , so it can ensure that a completely vacuum vacuum chamber 5 is formed above the diaphragm layer 21 .
  • the casing 3 is made of silicon, silicon nitride, polyethylene or glass.
  • the casing 3 can also be a combination of silicon nitride, polyethylene or glass.
  • the substrate 1 includes a side wall 11 enclosing the back cavity 4 , and the orthographic projection of the piezoelectric unit 22 along the vibration direction of the diaphragm layer 21 partially overlaps with the orthographic projection of the side wall 11 along the vibration direction of the diaphragm layer 21 . That is to say, the edge of the piezoelectric unit 22 is at least partially laterally beyond the edge of the back cavity 4, so that when the diaphragm layer 21 vibrates, the part of the piezoelectric unit 22 corresponding to the edge of the back cavity 4 will be subjected to greater stress , thereby further increasing the output voltage of the piezoelectric unit 22 .
  • the piezoelectric unit 22 of this embodiment includes a first electrode layer 222 , a piezoelectric layer 223 and a second electrode layer 224 sequentially stacked on the diaphragm layer 21 , the first electrode layer 222 , the piezoelectric layer 223 and the second electrode The edges of layers 224 are flush with each other.
  • the substrate 1 is a micro-silicon substrate, the diaphragm layer 21 is disposed on the substrate 1, the first electrode layer 222 is disposed on the diaphragm layer 21, the piezoelectric layer 223 is disposed on the first electrode layer 222, and the second electrode layer 224 is disposed on the piezoelectric layer 223 .
  • the first electrode layer 222 and the second electrode layer 224 are made of aluminum, molybdenum or titanium, or a combination of the above materials
  • the piezoelectric layer 223 is made of aluminum nitride, scandium-doped aluminum nitride, zinc oxide, or zirconium titanate Lead piezoelectric ceramic material, or a combination of the above materials
  • the diaphragm layer 21 is made of aluminum nitride, polysilicon, silicon dioxide or silicon nitride, or a combination of the above materials.
  • the number of layers of the piezoelectric unit 22 is three. In other embodiments, the number of layers of the piezoelectric unit 22 may be four, five, six or more, which is not done in this embodiment. limit.
  • the piezoelectric unit 22 includes a plurality of piezoelectric sheets 221 , the plurality of piezoelectric sheets 221 are arranged symmetrically in the center, and two adjacent piezoelectric sheets 221 are arranged at intervals.
  • the piezoelectric unit 22 includes four piezoelectric sheets 221, and the four piezoelectric sheets 221 are all triangular in structure, and the sizes of the four piezoelectric sheets 221 are equal, and the four piezoelectric sheets 221 are enclosed to form a square structure.
  • the piezoelectric unit 22 is composed of a plurality of piezoelectric sheets 221 spaced apart from each other, and each piezoelectric sheet 221 extends from above the central position of the diaphragm layer 21 to above the edge of the diaphragm layer 21, so that the center of the piezoelectric region can be
  • the area has a larger deformation amount, thereby improving the sensitivity of the piezoelectric microphone and improving the uniformity of product performance, and the piezoelectric sheets 221 can be set to have equal intervals to improve the consistency and uniformity of the product structure.
  • the piezoelectric sheet 221 may also be a fan-shaped structure, and a plurality of fan-shaped piezoelectric sheets 221 are enclosed to form a circular structure.
  • the second embodiment of the present invention also provides a manufacturing process for a piezoelectric microphone, including the following steps:
  • Step S1 providing a substrate 1, and depositing a first oxide layer 6 on the surface of the substrate 1, as shown in FIG. 5;
  • the substrate 1 is a micro-silicon substrate, and before depositing the first oxide layer 6, the substrate 1 can be cleaned first.
  • the first oxide layer 6 can be silicon dioxide and is formed by a low pressure chemical vapor deposition method or a plasma enhanced chemical vapor deposition method.
  • Step S2 depositing a diaphragm layer 21 on the surface of the first oxide layer 6, as shown in FIG. 6;
  • the diaphragm layer 21 is made of aluminum nitride, polysilicon, silicon dioxide, polymer or silicon nitride material, or a combination of the above materials.
  • Step S3 depositing a piezoelectric unit 22 on the surface of the diaphragm layer 21, as shown in FIG. 7;
  • Step S31 depositing a first electrode layer 222 on the surface of the diaphragm layer 21 .
  • the first electrode layer 222 is made of aluminum, molybdenum, or titanium, or a combination of the above materials.
  • Step S32 depositing a piezoelectric layer 223 on the surface of the first electrode layer 222, the piezoelectric layer 223 is made of aluminum nitride, scandium-doped aluminum nitride, zinc oxide or lead zirconate titanate piezoelectric ceramic material, or a variety of the above materials. combination.
  • Step S33 depositing a second electrode layer 224 on the surface of the piezoelectric layer 223 .
  • the second electrode layer 224 is made of aluminum, molybdenum or titanium, or a combination of the above materials.
  • Step S4 etching the piezoelectric unit 22, as shown in FIG. 8;
  • dry etching is used to form a plurality of piezoelectric sheets 221 , the plurality of piezoelectric sheets 221 are arranged symmetrically in the center, and two adjacent piezoelectric sheets 221 are arranged at intervals.
  • Step S5 depositing a casing 3 covering the diaphragm layer 21 on the surface of the piezoelectric unit 22 , the casing 3 and the diaphragm layer 21 are enclosed to form an accommodation cavity 5 for accommodating the piezoelectric unit 22 ;
  • step S5 is prepared in a vacuum environment, so as to ensure that the finally formed containing cavity 5 is in a vacuum environment. Specifically, step S5 includes the following sub-steps:
  • Step S51 Cover the surface of the piezoelectric unit 22 with the second oxide layer 7 , and perform polishing and patterning treatment, as shown in FIG. 9 .
  • the second oxide layer 7 is silicon dioxide.
  • Step S52 depositing a first sealing layer 8 on the surface of the second oxide layer 7 , as shown in FIG. 10 ; the first sealing layer 8 is made of silicon nitride or polymer material.
  • Step S53 etching the first sealing layer 8 to form release holes 81 , releasing the second oxide layer 7 to form the receiving cavity 5 , as shown in FIG. 11 ;
  • the release hole 81 is used to remove the second oxide layer 7 located in the central main body region between the first sealing layer 8 and the diaphragm layer 21 until the diaphragm layer 21 is exposed, forming a receiving cavity 5 for accommodating the piezoelectric unit 22 .
  • Step S54 sealing the release hole 81 , as shown in FIG. 12 .
  • the same material as the first sealing layer 8 may be deposited in the area of the release hole 81 to seal the release hole 81 .
  • Step S6 etching the other surface of the substrate 1 away from the diaphragm layer 21 to form a back cavity 4 , as shown in FIG. 13 .
  • ICP deep etching is first performed on the other surface of the substrate 1 away from the diaphragm layer 21, and the etching stops at the first oxide layer 6 to form the back cavity 4 region, and then BOE solution or HF vapor phase etching technology is used to etch the first surface of the first oxide layer 6.
  • the oxide layer 6 is released, and finally the piezoelectric microphone of the embodiment of the present invention is formed.
  • the third embodiment of the present invention provides a manufacturing process of a piezoelectric microphone.
  • the only difference between the third embodiment and the second embodiment is that the method for depositing the casing 3 on the surface of the piezoelectric unit 22 is different. Specifically, it includes the following steps:
  • Step S11 providing a substrate 1, and depositing a first oxide layer 6 on the surface of the substrate 1;
  • Step S21 depositing a diaphragm layer 21 on the surface of the first oxide layer 6;
  • Step S31 depositing the piezoelectric unit 22 on the surface of the diaphragm layer 21;
  • Step S41 etching the piezoelectric unit 22;
  • Step S51 forming a casing 3 covering the diaphragm layer 21 on the surface of the piezoelectric unit 22 , and the casing 3 and the diaphragm layer 21 enclose a receiving cavity 5 for accommodating the piezoelectric unit 22 ;
  • Step S51 includes the following sub-steps:
  • Step S501 depositing a peripheral wall layer 70 on the edge of the diaphragm layer 21 , and the peripheral wall layer 70 surrounds the piezoelectric unit 22 , as shown in FIG. 14 .
  • Step S502 providing the second sealing layer 80 , as shown in FIG. 15 .
  • Step S503 bonding the peripheral wall layer 70 and the second sealing layer 80 to seal the top of the peripheral wall layer 70 and the second sealing layer 80 to form the accommodation cavity 5 for accommodating the piezoelectric unit 22 .
  • the peripheral wall layer 70 and the second sealing layer 80 may be bonded by eutectic bonding, anodic bonding or low temperature soldering.
  • Step S61 etching the other surface of the substrate 1 away from the diaphragm layer 21 to form the back cavity 4 .
  • the casing 3 is arranged above the diaphragm layer 21 , and the casing 3 and the diaphragm layer 21 enclose a vacuum cavity 5 for accommodating the piezoelectric unit 22 . Therefore, the air damping received by the diaphragm layer 21 during vibration is greatly reduced, and the output voltage of the piezoelectric unit 22 will increase under the same sound pressure, which effectively improves the sensitivity of the microphone.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
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  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)

Abstract

本发明提供了一种压电式麦克风及其制备工艺，压电式麦克风包括具有背腔的基底和设于所述基底上的压电振膜，所述压电振膜包括固定于所述基底上的振膜层以及固定于所述振膜层上的压电单元，所述压电式麦克风还包括罩盖在所述振膜层上方的壳体，所述壳体和所述振膜层合围形成容置所述压电单元的收容腔，所述收容腔为真空环境。本发明可以增大压电单元的输出电压，提高压电式麦克风的灵敏度。

Description

一种压电式麦克风及其制备工艺 技术领域
本发明属于麦克风技术领域，尤其涉及一种压电式麦克风及其制备工艺。
 背景技术
MEMS(Micro-Electro-Mechanical System，微机电系统)麦克风是一种利用微机械加工技术制作出来的电能换声器，其具有体积小、频响特性好、噪声低等特点。随着电子设备的小巧化、轻薄化发展，MEMS麦克风被越来越广泛地运用到这些设备上。压电式MEMS麦克风相比于传统的电容式MEMS麦克风具有很多优势，包括防尘性和防水性以及较高的最大输出声压（AOP）等。
相关技术中，压电式MEMS麦克风振膜由多个膜片组成，并且多个膜片通过弹性连接固定在开有背腔的基底上，振膜的上下部分都是空气。该压电式MEMS麦克风在进行封装后，密闭空气环境阻碍了振膜的运动，从而导致压电单元的输出电压减小，MEMS麦克风的灵敏度大幅下降。
 技术问题
本发明的目的在于提供一种压电式麦克风及其制备工艺，旨在增大压电单元的输出电压，提高压电式麦克风的灵敏度。
 技术解决方案
本发明的技术方案如下：一种压电式麦克风，包括具有背腔的基底和设于所述基底上的压电振膜，所述压电振膜包括固定于所述基底上的振膜层以及固定于所述振膜层上的压电单元，其特征在于：所述压电式麦克风还包括罩盖在所述振膜层上方的壳体，所述壳体和所述振膜层合围形成容置所述压电单元的收容腔，所述收容腔为真空环境。
进一步地，所述壳体为硅、氮化硅、聚乙烯或玻璃材质。
进一步地，所述基底包括合围形成所述背腔的侧壁，所述压电单元沿所述振膜层的振动方向的正投影与所述侧壁沿所述振膜层的振动方向的正投影部分重叠。
进一步地，所述振膜层为整体连续结构。
进一步地，所述压电单元包括多个压电片，多个所述压电片中心对称设置，相邻两个所述压电片之间间隔设置。
进一步地，所述压电单元包括依次叠设于所述振膜层上的第一电极层、压电层以及第二电极层，所述第一电极层和所述第二电极层为铝、钼或钛材质，所述压电层为氮化铝、氧化锌、掺钪氮化铝或锆钛酸铅压电陶瓷材质。
进一步地，所述振膜层为氮化铝、多晶硅、二氧化硅或氮化硅材质。
本发明还提供了一种压电式麦克风的制备工艺，包括以下步骤：
步骤S1：提供基底，在所述基底的表面沉积第一氧化层；
步骤S2：在所述第一氧化层的表面沉积振膜层；
步骤S3：在所述振膜层的表面沉积压电单元；
步骤S4：对所述压电单元进行刻蚀；
步骤S5：在所述压电单元的表面沉积形成罩盖在所述振膜层上方的壳体，所述壳体和所述振膜层合围形成容置所述压电单元的收容腔；
步骤S6：对所述基底背离所述振膜层的另一表面进行刻蚀，形成背腔。
进一步地，步骤S5具体包括：
步骤S51：在所述压电单元的表面覆盖第二氧化层，并进行抛光和图案化处理；
步骤S52：在所述第二氧化层表面沉积第一密封层；
步骤S53：刻蚀所述第一密封层形成释放孔，释放所述第二氧化层形成所述收容腔；
步骤S54：密封所述释放孔。
进一步地，所述步骤S5具体包括：
步骤S501：在所述振膜层的边缘沉积周壁层，所述周壁层环绕所述压电单元；
步骤S502：提供第二密封层；
步骤S503：将所述周壁层和所述第二密封层进行键合形成所述壳体。
 有益效果
本发明的有益效果在于：通过在振膜层的上方设置壳体，壳体和振膜层合围形成容置压电单元的收容腔，且收容腔为真空环境，因此振膜层在振动时受到的空气阻尼大大减少，相同声压作用下压电单元的输出电压会增大，有效提高了麦克风的灵敏度。
 附图说明
图1是本发明第一实施例提供的压电式麦克风的整体结构示意图；
图2是本发明第一实施例提供的压电式麦克风的分解结构示意图；
图3是图1的 A-A方向断面示意图；
图4是本发明第二实施例提供的压电式麦克风的制备流程图；
图5～图13是本发明第二实施例提供的压电式麦克风的制备工艺示意图；
图14是本发明第三实施例在振膜层的边缘沉积周壁层的制备工艺示意图；
图15是本发明第三实施例在周壁层上提供第二密封层的制备工艺示意图。
 本发明的实施方式
下面结合附图和实施方式对本发明作进一步说明。
实施例：
请参阅图1至图2，为本发明第一实施例提供的一种压电式麦克风，包括具有背腔4的基底1和设于基底1上的压电振膜2，压电振膜2包括固定于基底1上的振膜层21以及固定于振膜层21上的压电单元22。压电单元22受压带动振膜层21在背腔4上方的空间产生形变，进而产生电压信号。
本实施例中，如图2所示，压电式麦克风还包括罩盖在振膜层21上方的壳体3，壳体3和振膜层21合围形成容置压电单元22的收容腔5，收容腔5为真空环境。通过设置罩盖在振膜层21上方的壳体3，壳体3和振膜层21合围形成容置压电单元22的收容腔5，且收容腔5为真空环境，因此振膜层21在振动时受到的空气阻尼大大减少，相较于相关技术，相同声压作用下压电单元22的输出电压会增大，有效提高了麦克风的灵敏度。
具体的，壳体3包括沿振膜层21的边缘周向设置的周壁31以及盖接在周壁31远离振膜层21一侧的顶壁32，周壁31与振膜层21固定且周壁31与振膜层21的边缘平齐。周壁31与振膜层21的边缘平齐，使得压电式麦克风整体均衡稳定，也更加美观。本实施例的振膜层21为整体连续结构，振膜层21不存在断层或空隙，因此能够保证在振膜层21的上方形成完全真空的真空腔5。
优选的，壳体3为硅、氮化硅、聚乙烯或玻璃材质，当然，壳体3也可以为氮化硅、聚乙烯或玻璃材料的组合。
进一步地，基底1包括合围形成背腔4的侧壁11，压电单元22沿振膜层21的振动方向的正投影与侧壁11沿振膜层21的振动方向的正投影部分重叠。也就是说，压电单元22的边沿至少部分横向超出背腔4的边缘，如此设置，当振膜层21发生振动时，压电单元22对应背腔4的边缘的部分会受到更大的应力，从而进一步增大压电单元22的输出电压。
本实施例的压电单元22包括依次叠设于振膜层21上的第一电极层222、压电层223以及第二电极层224，第一电极层222、压电层223以及第二电极层224的边缘相互平齐。基底1为微硅基片，振膜层21设置于基底1上，第一电极层222设置在振膜层21上，压电层223设置在第一电极层222上，第二电极层224设置在压电层223上。其中，第一电极层222和第二电极层224为铝、钼或钛材质，或者上述多种材料的组合，压电层223为氮化铝、掺钪氮化铝、氧化锌或锆钛酸铅压电陶瓷材质，或者上述多种材料的组合，振膜层21为氮化铝、多晶硅、二氧化硅或氮化硅材质，或者上述多种材料的组合。本实施例中压电单元22的层数为三层，在其它实施例中，压电单元22的层数还可以为四层、五层、六层或更多，本实施例对此不做限制。
压电单元22包括多个压电片221，多个压电片221中心对称设置，相邻两个压电片221之间间隔设置。优选的，压电单元22包括四个压电片221，四个压电片221均为三角形结构，且四个压电片221的大小相等，四个压电片221合围形成正方形结构。压电单元22由多个相互间隔设置的压电片221组成，并且每一压电片221自振膜层21的中央位置上方延伸至振膜层21的边缘上方，可以使得压电区的中心区域具有更大的形变量，从而提高压电式麦克风的灵敏度，提升了产品性能的均匀性，并且压电片221之间可以设置为具有相等的间隔以提升产品结构的一致性和均匀性。在其他可能的实施方式中，压电片221也可以为扇形结构，多个扇形的压电片221合围形成圆形结构。
请参阅图4，本发明第二实施例还提供了一种压电式麦克风的制备工艺，包括以下步骤：
步骤S1：提供基底1，在基底1的表面沉积第一氧化层6，如图5所示；
具体地，基底1为微硅基片，在沉积第一氧化层6之前，可先对基底1进行清洗处理。第一氧化层6可以为二氧化硅，采用低压力化学气相沉积法或等离子体增强化学气相沉积法等工艺形成。
步骤S2：在第一氧化层6的表面沉积振膜层21，如图6所示；
具体地，振膜层21为氮化铝、多晶硅、二氧化硅、聚合物或氮化硅材质，或者上述多种材料的组合。
步骤S3：在振膜层21的表面沉积压电单元22，如图7所示；
具体地，包括以下子步骤：
步骤S31：在振膜层21的表面沉积第一电极层222，第一电极层222为铝、钼或钛材质，或者上述多种材料的组合。
步骤S32：在第一电极层222的表面沉积压电层223，压电层223为氮化铝、掺钪氮化铝、氧化锌或锆钛酸铅压电陶瓷材质，或者上述多种材料的组合。
步骤S33：在压电层223的表面沉积第二电极层224，第二电极层224为铝、钼或钛材质，或者上述多种材料的组合。
步骤S4：对压电单元22进行刻蚀，如图8所示；
具体地，采用干法刻蚀，形成多个压电片221，多个压电片221中心对称设置，相邻两个压电片221之间间隔设置。
步骤S5：在压电单元22的表面沉积形成罩盖在振膜层21上方的壳体3，壳体3和振膜层21合围形成容置压电单元22的收容腔5；
需要说明的是，步骤S5是在真空环境中制备的，从而保证最终形成的收容腔5处于真空环境中。具体地，步骤S5包括以下子步骤：
步骤S51：在压电单元22的表面覆盖第二氧化层7，并进行抛光和图案化处理，如图9所示。具体地，第二氧化层7为二氧化硅。
步骤S52：在第二氧化层7表面沉积第一密封层8，如图10所示；第一密封层8为氮化硅或聚合物材质。
步骤S53：刻蚀第一密封层8形成释放孔81，释放第二氧化层7以形成收容腔5，如图11所示；
释放孔81用于去除第一密封层8和振膜层21之间的位于中央主体区域的第二氧化层7，直至露出振膜层21，形成容置压电单元22的收容腔5。
步骤S54：密封释放孔81，如图12所示。可以在释放孔81的区域沉积与第一密封层8相同的材料，以对释放孔81进行密封。
步骤S6：对基底1背离振膜层21的另一表面进行刻蚀，形成背腔4，如图13所示。具体地，先对基底1背离振膜层21的另一表面进行ICP深刻蚀，刻蚀停止于第一氧化层6，形成背腔4区域，接着采用BOE溶液或HF气相刻蚀技术对第一氧化层6进行释放，最终形成本发明实施例的压电式麦克风。
本发明第三实施例提供了一种压电式麦克风的制备工艺，第三实施例与第二实施例的唯一不同点在于，在压电单元22的表面沉积壳体3的方法不同。具体地，包括以下步骤：
步骤S11：提供基底1，在基底1的表面沉积第一氧化层6；
步骤S21：在第一氧化层6的表面沉积振膜层21；
步骤S31：在振膜层21的表面沉积压电单元22；
步骤S41：对压电单元22进行刻蚀；
步骤S51：在压电单元22的表面形成罩盖在振膜层21上方的壳体3，壳体3和振膜层21合围形成容置压电单元22的收容腔5；
步骤S51包括以下子步骤：
步骤S501：在振膜层21的边缘沉积周壁层70，周壁层70环绕压电单元22，如图14所示。
步骤S502：提供第二密封层80，如图15所示。
步骤S503：将周壁层70和第二密封层80进行键合，从而将周壁层70顶部和第二密封层80进行密封，形成容置压电单元22的收容腔5。具体的，所述周壁层70和第二密封层80可以通过共晶键合、阳极键合或低温焊料键合。
步骤S61：对基底1背离振膜层21的另一表面进行刻蚀，形成背腔4。
综上所述，本发明实施例提供的压电式麦克风，通过在振膜层21的上方设置壳体3，壳体3和振膜层21合围形成容置压电单元22的真空腔5，因此振膜层21在振动时受到的空气阻尼大大减少，相同声压作用下压电单元22的输出电压会增大，有效提高了麦克风的灵敏度。
以上所述的仅是本发明的实施方式，在此应当指出，对于本领域的普通技术人员来说，在不脱离本发明创造构思的前提下，还可以做出改进，但这些均属于本发明的保护范围。

Claims (10)

  1. 一种压电式麦克风，包括具有背腔的基底和设于所述基底上的压电振膜，所述压电振膜包括固定于所述基底上的振膜层以及固定于所述振膜层上的压电单元，其特征在于：所述压电式麦克风还包括罩盖在所述振膜层上方的壳体，所述壳体和所述振膜层合围形成容置所述压电单元的收容腔，所述收容腔为真空环境。
  2. 根据权利要求1所述的压电式麦克风，其特征在于，所述壳体为硅、氮化硅、聚乙烯或玻璃材质。
  3. 根据权利要求1所述的压电式麦克风，其特征在于，所述基底包括合围形成所述背腔的侧壁，所述压电单元沿所述振膜层的振动方向的正投影与所述侧壁沿所述振膜层的振动方向的正投影部分重叠。
  4. 根据权利要求1所述的压电式麦克风，其特征在于，所述振膜层为整体连续结构。
  5. 根据权利要求1所述的压电式麦克风，其特征在于，所述压电单元包括多个压电片，多个所述压电片中心对称设置，相邻两个所述压电片之间间隔设置。
  6. 根据权利要求1所述的压电式麦克风，其特征在于，所述压电单元包括依次叠设于所述振膜层上的第一电极层、压电层以及第二电极层，所述第一电极层和所述第二电极层为铝、钼或钛材质，所述压电层为氮化铝、氧化锌、掺钪氮化铝或锆钛酸铅压电陶瓷材质。
  7. 根据权利要求1所述的压电式麦克风，其特征在于，所述振膜层为氮化铝、多晶硅、二氧化硅或氮化硅材质。
  8. 一种压电式麦克风的制备工艺，其特征在于，包括以下步骤：
    步骤S1：提供基底，在所述基底的表面沉积第一氧化层；
    步骤S2：在所述第一氧化层的表面沉积振膜层；
    步骤S3：在所述振膜层的表面沉积压电单元；
    步骤S4：对所述压电单元进行刻蚀；
    步骤S5：在所述压电单元的表面沉积形成罩盖在所述振膜层上方的壳体，所述壳体和所述振膜层合围形成容置所述压电单元的收容腔；
    步骤S6：对所述基底背离所述振膜层的另一表面进行刻蚀，形成背腔。
  9. 根据权利要求8所述的制备工艺，其特征在于，所述步骤S5具体包括：
    步骤S51：在所述压电单元的表面覆盖第二氧化层，并进行抛光和图案化处理；
    步骤S52：在所述第二氧化层表面沉积第一密封层；
    步骤S53：刻蚀所述第一密封层形成释放孔，释放所述第二氧化层以形成所述收容腔；
    步骤S54：密封所述释放孔。
  10. 根据权利要求8所述的制备工艺，其特征在于，所述步骤S5具体包括：
    步骤S501：在所述振膜层的边缘沉积周壁层，所述周壁层环绕所述压电单元；
    步骤S502：提供第二密封层；
    步骤S503：将所述周壁层和所述第二密封层进行键合形成所述壳体。
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