WO2021253501A1 - 绝对压力感测微机电系统麦克风、麦克风单体及电子设备 - Google Patents

绝对压力感测微机电系统麦克风、麦克风单体及电子设备 Download PDF

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Publication number
WO2021253501A1
WO2021253501A1 PCT/CN2020/099439 CN2020099439W WO2021253501A1 WO 2021253501 A1 WO2021253501 A1 WO 2021253501A1 CN 2020099439 W CN2020099439 W CN 2020099439W WO 2021253501 A1 WO2021253501 A1 WO 2021253501A1
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Prior art keywords
diaphragm
gap
vacuum
absolute pressure
pressure sensing
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PCT/CN2020/099439
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English (en)
French (fr)
Inventor
邹泉波
王德信
方华斌
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歌尔微电子有限公司
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Priority to US18/010,935 priority Critical patent/US20230234833A1/en
Publication of WO2021253501A1 publication Critical patent/WO2021253501A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B3/00—Devices comprising flexible or deformable elements, e.g. comprising elastic tongues or membranes
    • B81B3/0018—Structures acting upon the moving or flexible element for transforming energy into mechanical movement or vice versa, i.e. actuators, sensors, generators
    • B81B3/0021—Transducers for transforming electrical into mechanical energy or vice versa
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R19/00—Electrostatic transducers
    • H04R19/005—Electrostatic transducers using semiconductor materials
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R19/00—Electrostatic transducers
    • H04R19/04—Microphones
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/02—Casings; Cabinets ; Supports therefor; Mountings therein
    • H04R1/04—Structural association of microphone with electric circuitry therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B2201/00—Specific applications of microelectromechanical systems
    • B81B2201/02—Sensors
    • B81B2201/0257—Microphones or microspeakers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B2201/00—Specific applications of microelectromechanical systems
    • B81B2201/02—Sensors
    • B81B2201/0264—Pressure sensors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B2203/00—Basic microelectromechanical structures
    • B81B2203/01—Suspended structures, i.e. structures allowing a movement
    • B81B2203/0127—Diaphragms, i.e. structures separating two media that can control the passage from one medium to another; Membranes, i.e. diaphragms with filtering function
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B2203/00—Basic microelectromechanical structures
    • B81B2203/03—Static structures
    • B81B2203/0315—Cavities
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B2203/00—Basic microelectromechanical structures
    • B81B2203/04—Electrodes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2201/00—Details of transducers, loudspeakers or microphones covered by H04R1/00 but not provided for in any of its subgroups
    • H04R2201/003—Mems transducers or their use
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2499/00—Aspects covered by H04R or H04S not otherwise provided for in their subgroups
    • H04R2499/10—General applications
    • H04R2499/11—Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's

Definitions

  • This specification relates to the technical field of MEMS microphones, and more specifically, to an absolute pressure sensing MEMS microphone, a microphone unit, and electronic equipment.
  • one side of the pressure sensing membrane is the vacuum, and the other side is the pressure environment to be sensed.
  • the vacuum here refers to an approximate vacuum, which can be an environment where the pressure is much lower than the standard atmospheric pressure.
  • FIG. 1 shows the different states of a micro-electromechanical system (MEMS) absolute pressure sensor.
  • MEMS absolute pressure sensor shown in FIG. 1 may be a capacitive sensor.
  • the pressure sensing film 11, the electrode plate 12 and the spacer 13 form a vacuum chamber 14.
  • Figure 1(A) shows the state of the MEMS absolute pressure sensor in a vacuum environment without applying a working bias. As shown in FIG. 1(A), the pressure sensing film 11 is located at the flat position P. Fig. 1(A) may be the state when the MEMS absolute pressure sensor is manufactured.
  • Figure 1(B) shows the state of the MEMS absolute pressure sensor in an atmospheric pressure environment without applying a working bias. As shown in FIG. 1(B), due to the action of atmospheric pressure, the pressure sensing film 11 deviates from the flat position P and dents downward. Figure 1(B) may be the state when the MEMS absolute pressure sensor is not in use.
  • Figure 1(C) shows the state of the MEMS absolute pressure sensor under the condition of applying a working bias in an atmospheric pressure environment. As shown in FIG. 1(C), due to the atmospheric pressure and the working bias, the pressure sensing film 11 deviates from the flat position P and further dents downward. Figure 1(C) can be the state of the MEMS absolute pressure sensor when it is used.
  • the absolute pressure sensor Since the pressure referenced by the absolute pressure sensor for sensing is the vacuum pressure, the absolute pressure sensor is not susceptible to changes in atmospheric pressure and/or temperature.
  • the absolute pressure sensor needs to resist the atmospheric pressure Po, and will be deformed greatly. Therefore, the absolute pressure sensor is generally used for pressure sensing, and is not suitable for use as a microphone.
  • the initial vacuum gap of the absolute pressure sensor (the pressure sensing membrane 11 and the electrode plate shown in Figure 1(A))
  • the gap between 12, where the inside and outside of the pressure sensing membrane 11 are both vacuum) needs to be set to be larger, about 15-20um or more. This not only greatly increases the difficulty of process manufacturing, but also makes the area of the diaphragm (pressure sensing membrane) very large due to the requirement of matching the effective capacitance Cmic of the MEMS microphone with the MEMS microphone, which further increases the cost of the MEMS microphone.
  • the center of the diaphragm has the maximum deflection, and the large-area surrounding diaphragm part contributes little to the performance of the microphone, which increases the difficulty of improving the performance.
  • the embodiments of this specification provide a new technical solution for the microphone of the microelectromechanical system.
  • an absolute pressure sensing MEMS microphone including: a diaphragm; a back plate; a spacer located between the diaphragm and the back plate, wherein the diaphragm, The back electrode plate and the spacer form a vacuum chamber, and the air pressure in the vacuum chamber is the first air pressure.
  • the gap separating the diaphragm and the back electrode plate by the spacer is a production gap.
  • a microphone unit including a unit housing, the absolute pressure sensing MEMS microphone and an integrated circuit chip disclosed herein, wherein the absolute pressure sensing MEMS microphone and The integrated circuit chip is arranged in the single housing.
  • an electronic device including the microphone monomer disclosed herein.
  • a thinner diaphragm can be used in the absolute pressure sensing MEMS microphone, thereby improving the sensitivity of the microphone.
  • any one of the embodiments of the present specification does not need to achieve all the above-mentioned effects.
  • Figure 1 shows the state of the absolute pressure sensor under different conditions.
  • Fig. 2 shows the state change of the absolute pressure sensing MEMS microphone under different conditions according to an embodiment.
  • FIG. 3 shows the state of the absolute pressure sensing MEMS microphone under different conditions according to an embodiment.
  • Fig. 4 shows a schematic diagram of an absolute pressure sensing MEMS microphone according to an embodiment.
  • Fig. 5 shows a schematic diagram of an absolute pressure sensing MEMS microphone according to another embodiment.
  • Fig. 6 shows a schematic diagram of an absolute pressure sensing MEMS microphone according to yet another embodiment.
  • Fig. 7 shows a schematic diagram of an absolute pressure sensing MEMS microphone according to yet another embodiment.
  • Fig. 8 shows a schematic diagram of a microphone monomer according to an embodiment disclosed herein.
  • Fig. 9 shows a schematic diagram of an electronic device according to an embodiment disclosed herein.
  • the diaphragm is pre-bent to improve the sensitivity of the microphone.
  • the absolute pressure sensing MEMS microphone includes: a diaphragm, a back plate 32 and a spacer 33.
  • the curves indicated by the icons 311, 312, and 313 are the positions of the diaphragm under different conditions.
  • the curve 311 indicates the position of the diaphragm when the air pressure inside and outside the diaphragm is the first air pressure.
  • the inner side of the diaphragm refers to the side of the diaphragm located on the vacuum chamber 34.
  • the curve 312 indicates the position of the diaphragm when the air pressure outside the diaphragm is 1 standard atmospheric pressure.
  • the curve 313 indicates the position of the diaphragm when the air pressure outside the diaphragm is 1 standard atmospheric pressure and the working bias is applied between the diaphragm and the back plate 32.
  • the spacer 33 is located between the diaphragm and the back plate 32.
  • the spacer 33 may be a separate spacer layer or a part of the chip substrate.
  • the diaphragm, the back plate 32 and the spacer 33 form a vacuum chamber 34.
  • the air pressure in the vacuum chamber 34 is the first air pressure.
  • an absolute vacuum cannot be achieved. Therefore, an environment where the pressure is much lower than the atmospheric pressure is usually called a vacuum environment. In this vacuum environment, there is still an air pressure approaching zero.
  • the air pressure approaching zero is defined as the first air pressure.
  • the gap Gf separating the diaphragm and the back plate 32 by the spacer 33 is a manufacturing gap.
  • the production gap Gf can be the distance between the back plate 32 and the flat position P of the diaphragm.
  • the diaphragm When the air pressure inside and outside the diaphragm is the first air pressure, the diaphragm is at the position of the curve 311, and the effective vacuum gap (for example, the average vacuum gap) between the diaphragm position curve 311 and the back plate 32 is The first vacuum gap.
  • the first vacuum gap is larger than the production gap Gf.
  • the vacuum pressure sensing device is used for the MEMS microphone, so that the advantages of the vacuum pressure sensing device can be used.
  • the diaphragm is pre-bent, so that a softer diaphragm can also be used to form a vacuum cavity, so that the absolute pressure sensor can be used as a microphone to provide a microphone similar to ordinary MEMS microphones.
  • the sensitivity is pre-bent, so that a softer diaphragm can also be used to form a vacuum cavity, so that the absolute pressure sensor can be used as a microphone to provide a microphone similar to ordinary MEMS microphones.
  • the first vacuum gap is greater than or equal to twice the manufacturing gap. In addition, the first vacuum gap is less than or equal to 10 times the manufacturing gap.
  • the effective vacuum gap between the diaphragm (curve 312) and the back plate 32 is the second vacuum gap.
  • the second vacuum gap is larger than the production gap Gf. In this way, the degree of downward bending of the diaphragm (curve 313) when the operating bias is applied can be reduced.
  • FIG. 3(A), (B), (C) respectively show the state of the diaphragm 31 under different conditions.
  • the diaphragm 31, the back plate 32 and the spacer 33 form a vacuum cavity 34.
  • the air pressure inside and outside the diaphragm 31 are both vacuum air pressure.
  • the pressure on both sides of the diaphragm 31 is the same, and the diaphragm 31 is in a free state.
  • the diaphragm 31 is pre-bent to deviate from the flat position P.
  • the air pressure outside the diaphragm 31 is all atmospheric pressure. In this case, the pressure on the outside of the diaphragm 31 is greater than the pressure on the inside.
  • the diaphragm 31 is pressed toward the back plate 32 by the atmospheric pressure.
  • the diaphragm 31 is still located outside the flat position P.
  • the air pressure on the outside of the diaphragm 31 is atmospheric pressure, and a working bias is applied between the back plate 32 and the diaphragm 31.
  • the diaphragm 31 is attracted by the back electrode plate 32 and further approaches the back electrode plate 32.
  • the degree of deviation of the diaphragm 31 from the flat position P is small.
  • the diaphragm 31 is located on the side of the flat position P close to the back plate 32.
  • the diaphragm 31 can still be located outside the flat position P when the working bias is applied.
  • the effective vacuum gap between the diaphragm (curve 313) and the back plate 32 is the third vacuum gap under the condition of applying the working bias voltage.
  • the third vacuum gap is greater than or equal to 80% of the production gap and less than or equal to 120% of the production gap. In this way, it can be ensured that the diaphragm (curve 313) is in a proper working position, so as to ensure that the diaphragm is in a better working state.
  • the diaphragm can be pre-tensioned by the stress structure, so that the first vacuum gap is larger than the manufacturing gap.
  • the pressure Po on the outside of the diaphragm 31 is 1 atm (ie, a standard atmospheric pressure)
  • the gap Go between the diaphragm 31 (curve 312) and the back plate 32 is relatively large, and the microphone's VP (sagging down) can be increased. Voltage), thereby improving the sensitivity of the MEMS microphone.
  • the third vacuum gap is Ge, that is, the effective vacuum gap between the curve 313 and the back plate 32 in FIG. 1.
  • the maximum value of the VB/VP ratio is 75%, therefore, k ⁇ 75%.
  • " ⁇ " means approximately or approximately equal to.
  • VP (8Go 3 /27 ⁇ 0 Sm 0 ) 0.5 , where ⁇ 0 is the vacuum dielectric constant.
  • the degree of pre-pull can be increased to make Gi>>Gf, so that the sensitivity and SNR (signal-to-noise ratio) of the MEMS microphone are greatly improved.
  • the diaphragm can also be smaller, thereby reducing the cost of the chip.
  • Figures 4-7 show various implementations of using the stress structure to pull the diaphragm to the desired state.
  • the gap that is, the thickness of the sacrificial layer in the MEMS microphone
  • the back plate and the diaphragm form a vacuum cavity.
  • Gi/Gf>>1 for example, Gi is 2-10 times Gf
  • the diaphragm 314, the back plate 320, and the spacers 331 and 332 form a vacuum cavity 340.
  • the stress structure includes a diaphragm 314 and a compressive stress component 315.
  • the diaphragm 314 has a tensile stress along the surface of the diaphragm.
  • the compressive stress component 314 is attached to the outside of the diaphragm 314 with respect to the vacuum cavity 340 and has a compressive stress along the surface direction of the diaphragm 314.
  • the diaphragms 316, 317, the back plate 320, and the spacer 331 form a vacuum cavity 340.
  • the fixing member 332 fixes the diaphragms 316 and 317 to the spacer 331.
  • the stress structure includes composite layers 316, 317 of the diaphragm.
  • the composite layers 316 and 317 include an inner film 317 located inside the vacuum chamber and an outer film 316 located outside.
  • the inner diaphragm 317 has a tensile stress along the surface of the diaphragm and the outer diaphragm 316 has a compressive stress along the surface of the diaphragm.
  • the diaphragm 318, the back plate 320 and the spacer 331 form a vacuum cavity 340.
  • the fixing part 332 fixes the diaphragm 318 to the spacer 331.
  • the fixing member 332 has a tensile stress in the direction of the diaphragm surface and is attached to the upper surface (i.e., outer surface) of the diaphragm.
  • the spacer 331 has a compressive stress in the direction of the diaphragm surface and is attached to the lower surface (ie, the inner side surface) of the diaphragm.
  • the stress structure includes a ridge structure 319 on the diaphragm, so that the diaphragm bulges outward with respect to the vacuum cavity.
  • Fig. 8 shows a schematic diagram of a microphone monomer according to an embodiment disclosed herein.
  • the microphone unit 40 includes a unit housing 41, the absolute pressure sensing MEMS microphone 42 described above, and an integrated circuit chip 43.
  • the absolute pressure sensing MEMS microphone 42 and the integrated circuit chip 43 are arranged in the single housing 42.
  • the absolute pressure sensing MEMS microphone 42 corresponds to the air inlet of the single housing 41.
  • the circuits in the absolute pressure sensing MEMS microphone 42, the integrated circuit chip 43 and the unit housing 41 are connected by leads 44.
  • Fig. 14 shows a schematic diagram of an electronic device according to an embodiment disclosed herein.
  • the electronic device 50 may include the microphone unit 51 shown in FIG. 8.
  • the electronic device 50 may be a mobile phone, a tablet computer, a wearable device, or the like.

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  • Acoustics & Sound (AREA)
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  • Chemical & Material Sciences (AREA)
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Abstract

本说明书实施例提供绝对压力感测微机电系统麦克风、麦克风单体及电子设备。该绝对压力感测微机电系统麦克风，包括：振膜；背极板；位于振膜和背极板之间的间隔件，其中，所述振膜、背极板和间隔件形成真空腔，真空腔中的气压是第一气压，其中，通过所述间隔件将振膜和背极板间隔开的间隙是制作间隙，其中，在振膜内侧和外侧的气压都是第一气压的状态下，振膜与背极板之间的有效真空间隙是第一真空间隙，以及其中，第一真空间隙大于制作间隙。

Description

绝对压力感测微机电系统麦克风、麦克风单体及电子设备 技术领域
本说明书涉及微机电系统麦克风技术领域，更具体地，涉及一种绝对压力感测微机电系统麦克风、麦克风单体及电子设备。
背景技术
在绝对压力感测器中，压力感测膜的一侧是真空，另一侧是待感测的压力环境。这里的真空指的是近似真空，可以是气压远低于标准大气压的环境。
图1示出了一种微机电系统(MEMS)绝对压力感测器的不同状态。图1所示的MEMS绝对压力感测器可以是电容型感测器。在图1中，压力感测膜11、极板12和间隔件13形成真空腔14。
图1(A)示出的是在真空环境中在未施加工作偏压的情况下MEMS绝对压力感测器的状态。如图1(A)所示，压力感测膜11位于平整位置P。图1(A)可以是制造MEMS绝对压力感测器时的状态。
图1(B)示出的是在大气压环境中在未施加工作偏压的情况下MEMS绝对压力感测器的状态。如图1(B)所示，由于大气压的作用，压力感测膜11偏离平整位置P并向下凹陷。图1(B)可以是MEMS绝对压力感测器未被使用时的状态。
图1(C)示出的是在大气压环境中在施加工作偏压的情况下MEMS绝对压力感测器的状态。如图1(C)所示，由于大气压和工作偏压的作用，压力感测膜11偏离平整位置P并进一步向下凹陷。图1(C)可以是MEMS绝对压力感测器在被使用时的状态。
由于绝对压力感测器进行感测所参考的压力是真空压力，因此，绝对压力感测器不易受大气压变化和/或温度变化的影响。
然而，绝对压力感测器的压力感测膜11需要抵抗大气压Po，并会产生较大的形变。因此，绝对压力感测器一般用于压力感测，而不适于用做麦克风。
如果希望达到和传统MEMS麦克风同等的灵敏度(例如，5-10mV/Pa左右)，那么，绝对压力感测器的初始真空间隙(图1(A)中所示的压力感测膜11和极板12之间的间隙，其中，压力感测膜11的内侧和外侧均为真空)需要被设置得较大，约15-20um以上。这不但大大增加了工艺制造的难度，还因为MEMS麦克风的有效电容Cmic与MEMS麦克风匹配的要求而使得振膜(压力感测膜)面积变得非常大，这进一步增加了MEMS麦克风的成本。另外，在平整的振膜朝向背极板方向位移/翘曲时，振膜的中心具有最大挠度，而周围大面积的振膜部分对麦克风性能贡献微弱，这增加了提高性能的难度。
因此，需要提供一种新的MEMS麦克风。
发明内容
本说明书的实施例提供用于微机电系统麦克风的新技术方案。
根据本说明书的第一方面，提供了一种绝对压力感测微机电系统麦克风，包括：振膜；背极板；位于振膜和背极板之间的间隔件，其中，所述振膜、背极板和间隔件形成真空腔，真空腔中的气压是第一气压，其中，通过所述间隔件将振膜和背极板间隔开的间隙是制作间隙，其中，在振膜内侧和外侧的气压都是第一气压的状态下，振膜与背极板之间的有效真空间隙是第一真空间隙，以及其中，第一真空间隙大于制作间隙。
根据本说明书的第二方面，提供了一种麦克风单体，包括单体外壳、这里公开的绝对压力感测微机电系统麦克风以及集成电路芯片，其中，所述绝对压力感测微机电系统麦克风以及集成电路芯片被设置在所述单体外壳中。
根据本说明书的第三方面，提供了一种电子设备，包括这里公开的麦克风单体。
在不同实施例中，可以在绝对压力感测微机电系统麦克风中使用较薄的振膜，从而提高麦克风的灵敏度。
应当理解的是，以上的一般描述和后文的细节描述仅是示例性和解释性的，并不能限制本说明书实施例。
此外，本说明书实施例中的任一实施例并不需要达到上述的全部效果。
通过以下参照附图对本说明书的示例性实施例的详细描述，本说明书的实施例的其它特征及其优点将会变得清楚。
附图说明
为了更清楚地说明本说明书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简单地介绍，显而易见地，下面描述中的附图仅仅是本说明书实施例中记载的一些实施例，对于本领域普通技术人员来讲，还可以根据这些附图获得其他的附图。
图1示出了绝对压力感测器在不同条件下的状态。
图2示出了根据一个实施例的绝对压力感测MEMS麦克风在不同条件下的状态变化。
图3示出了根据一个实施例的绝对压力感测MEMS麦克风在不同条件下的状态。
图4示出了根据一个实施例的绝对压力感测MEMS麦克风的示意图。
图5示出了根据另一个实施例的绝对压力感测MEMS麦克风的示意图。
图6示出了根据又一个实施例的绝对压力感测MEMS麦克风的示意图。
图7示出了根据又一个实施例的绝对压力感测MEMS麦克风的示意图。
图8示出了根据这里公开的一个实施例的麦克风单体的示意图。
图9示出了根据这里公开的一个实施例的电子设备的示意图。
具体实施方式
现在将参照附图来详细描述各种示例性实施例。
以下对至少一个示例性实施例的描述实际上仅仅是说明性的，决不作为对本发明及其应用或使用的任何限制。
应注意到：相似的标号和字母在下面的附图中表示类似项，因此，一旦某一项在一个附图中被定义，则在随后的附图中不需要对其进行进一步讨论。
下面，参照附图描述本说明书的不同实施例和例子。
在这里提出，在绝对压力感测MEMS麦克风中，将振膜预弯曲，以提高麦克风的灵敏度。
例如，参见图2，示出了根据一个实施例的绝对压力感测MEMS麦克风在不同条件下的状态变化。绝对压力感测MEMS麦克风包括：振膜、背极板32和间隔件33。
图标311、312、313所指示的曲线是振膜在不同条件下所处的位置。曲线311指示在振膜内侧和外侧的气压均为第一气压时振膜所处的位置。振膜内侧指的是振膜位于真空腔34的一侧。曲线312指示在振膜外侧的气压为1个标准大气压时振膜所处的位置。曲线313指示在振膜外侧的气压为1个标准大气压且在振膜和背极板32之间施加工作偏压时振膜所处的位置。
间隔件33位于振膜和背极板32之间。间隔件33可以是单独的间隔层，也可以是芯片衬底的一部分。
振膜、背极板32和间隔件33形成真空腔34。真空腔34中的气压是第一气压。在现实中，无法实现绝对的真空。因此，通常将气压远低于大气压的环境称为真空环境。在这种真空环境中仍然存在趋近于零的气压。在这里，将这种趋近于零的气压定义为第一气压。
如图2所示，通过间隔件33将振膜和背极板32间隔开的间隙Gf是制作间隙。制作间隙Gf可以背极板32与振膜平整位置P的距离。
在振膜内侧和外侧的气压都是第一气压的状态下，振膜处于曲线311的位置，并且振膜位置曲线311与背极板32之间的有效真空间隙(例如，平均真空间隙)是第一真空间隙。第一真空间隙大于制作间隙Gf。
在这里，将真空压力感测器件用于MEMS麦克风，从而可以利用真空压力感测器件的优势。
此外，为了提高MEMS麦克风的灵敏度，对振膜进行预弯曲，使得较软的振膜也能够用于形成真空腔，从而使得绝对压力感测器能够用做麦克风，以提供与普通MEMS麦克风相类似的灵敏度。
例如，第一真空间隙大于或等于制作间隙的2倍。此外，第一真空间隙小于或等于制作间隙的10倍。
另外，在标准大气压下，振膜(曲线312)与背极板32之间的有效真空间隙是第二真空间隙。第二真空间隙大于制作间隙Gf。通过这种方式，可以减小在施加工作偏压时振膜(曲线313)向下弯曲的程度。
图3(A)、(B)、(C)分别示出了在不同条件下振膜31的状态。在图3中，振膜31、背极板32和间隔件33形成真空腔34。
在图3(A)所示的状态下，振膜31的内侧和外侧的气压均为真空气压。在这种情况下，振膜31两侧的压力相同，振膜31处于自由状态。振膜31被预弯曲以偏离平整位置P。
在图3(B)所示的状态下，振膜31的外侧的气压均是大气压。在这种情况下，振膜31外侧的压力大于它的内侧的压力。振膜31被大气压向着背极板32方向按压。在图3(B)中，由于预弯曲的因素，振膜31仍然位于平整位置P的外侧。
在图3(C)所示的状态下，振膜31的外侧的气压均是大气压并且在背极板32和振膜31之间施加工作偏压。在这种情况下，由于工作偏压的作用，振膜31被背极板32所吸引，并进一步向着背极板32靠近。在图3(B)中，由于预弯曲的因素，振膜31偏离平整位置P的程度较小。在图3(B)中，振膜31位于平整位置P的靠近背极板32的一侧。但是，通过设置振膜31预弯曲的程度，可以使得在施加工作偏压的情况下，振膜31仍然位于平整位置P的外侧。
在振膜31工作时，尽量将振膜31设置在平整位置P附近，可以提供较好的MEMS麦克风性能。例如，在标准大气压下，在施加工作偏压的状态下，振膜(曲线313)与背极板32之间的有效真空间隙是第三真空间隙。 第三真空间隙大于或等于制作间隙的80％且小于或等于制作间隙的120％。通过这种方式，可以保证振膜(曲线313)位于适当的工作位置，以保证振膜处于较好的工作状态。
可以通过应力结构，对振膜进行预拉偏，以使得第一真空间隙大于制作间隙。
通过利用振膜(薄膜)的应力把振膜31预拉偏，以偏离背极板32，可以在不增加工艺制造难度(例如，制造间隙Gf)的情况下，获得较高的灵敏度所需的较大初始间隙Gi(即，在振膜31外侧的气压Po＝0时，振膜曲线311与背极板32之间的有效真空间隙)。这样，在振膜31的外侧气压Po＝1atm(即，一个标准大气压)时，振膜31(曲线312)和背极板32之间的间隙Go较大，并且可以提高麦克风的VP(下塌电压)，由此提高MEMS麦克风的灵敏度。
关于这种麦克风的性能的具体分析如下。在这里，假设这种MEMS麦克风的机械灵敏度是线性。
假设在Po＝0时，第一真空间隙是Gi，即，图1中的曲线311与背极板32之间的有效真空间隙；在Po＝1atm下，振膜31的机械灵敏度的有效值是Sm 0，第二真空间隙是Go，即，图1中的曲线312与背极板32之间的有效真空间隙；在Po＝1atm下，并且在振膜31和背极板32之间施加工作偏压VB时，第三真空间隙是Ge，即，图1中的曲线313与背极板32之间的有效真空间隙。
麦克风最大开路灵敏度Soc.max～(k·VP/Ge)·Sm 0。通常，VB/VP比值的最大值是75％，因此，k～75％。这里，“～”表示近似或约等于。
VP＝(8Go 3/27ε 0Sm 0) 0.5,其中ε 0为真空介电常数。
Wo＝Sm 0Po＝(Gi-Go)/Po,其中Wo为大气压Po所导致的振膜有效变形。
于是，MEMS麦克风的最大灵敏度Soc.max～(Go 3Sm 0/6ε 0Ge 2) 0.5＝[Go 3(Gi-Go)/12ε 0PoGe 2] 0.5。
在保证Ge以使得MEMS能够稳定工作的情况下，MEMS麦克风的灵敏度Soc的最大值位于Go＝3/4Gi处。此时的灵敏度Soc.max～(9/16)Gi 2/[Ge(12ε 0Po) 0.5]。它和预拉偏后的初始间隙Gi直接相关。
在现有的绝对压力感测器中，不对压力感测膜执行预拉偏。这也就是说，在现有的绝对压力感测器中，上式中的Gi等于制作间隙Gf，即Gi＝Gf。
在这里，可以加大预拉偏的程度，使得Gi>>Gf，从而使得MEMS麦克风的灵敏度和SNR(信噪比)大幅提高。
另外，由于对振膜进行预拉偏，因此，可以采用较小的制作间隙小，这样，振膜也可以较小，从而降低芯片成本。
图4-7示出了利用应力结构把振膜拉偏到期望状态的各种实现方式。在这里，制作间隙(即，MEMS麦克风中的牺牲层厚度)Gf＝0.1-2um。在MEMS麦克风释放后，背极板和振膜形成真空腔。在真空腔内外均为真空时，振膜和背极板的有效间隙与在标准大气压下的第二真空间隙G分的比值Gi/Gf>>1(比如，Gi是Gf的2-10倍)。
在图4的实施例中，振膜314、背极板320、间隔件331、332形成真空腔340。
在图4的实施例中，应力结构包括振膜314以及压应力部件315。振膜314具有沿振膜表面方向的张应力。压应力部件314相对于真空腔340附着在振膜314外侧，并具有具有沿振膜314的表面方向的压应力。
在图5的实施例中，振膜316、317、背极板320、间隔件331形成真空腔340。固定部件332将振膜316、317固定到间隔件331。
在图5的实施例中，应力结构包括振膜的复合层316、317。
复合层316、317包括位于真空腔内侧的内侧膜317以及位于外侧的外侧膜316。内侧膜317具有沿振膜表面方向的张应力以及外侧膜316具有沿振膜表面方向的压应力。
在图6的实施例中，振膜318、背极板320、间隔件331形成真空腔340。固定部件332将振膜318固定到间隔件331。固定部件332具有沿振 膜表面方向的张应力并附着到振膜的上表面(即，外侧表面)。间隔件331具有沿振膜表面方向的压应力并附着到振膜的下表面(即，内侧表面)。
在图7到实施例中，应力结构包括振膜上的纹膜结构319，以使得振膜相对于真空腔向外凸起。
图8示出了根据这里公开的一个实施例的麦克风单体的示意图。
如图8所示，麦克风单体40包括单体外壳41、上面描述的绝对压力感测MEMS麦克风42以及集成电路芯片43。绝对压力感测MEMS麦克风42以及集成电路芯片43被设置在所述单体外壳42中。绝对压力感测MEMS麦克风42与单体外壳41的进气口对应。绝对压力感测MEMS麦克风42、集成电路芯片43和单体外壳41中的电路通过引线44连接。
图14示出了根据这里公开的一个实施例的电子设备的示意图。
如图14所示，电子设备50可以包括图8所示的麦克风单体51。电子设备50可以是手机、平板电脑、可穿戴设备等。
以上所述仅是本说明书实施例的具体实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本说明书实施例原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也应视为本说明书实施例的保护范围。

Claims (12)

  1. 一种绝对压力感测微机电系统麦克风，包括：
    振膜；
    背极板；
    位于振膜和背极板之间的间隔件，
    其中，所述振膜、背极板和间隔件形成真空腔，真空腔中的气压是第一气压，
    其中，通过所述间隔件将振膜和背极板间隔开的间隙是制作间隙，
    其中，在振膜内侧和外侧的气压都是第一气压的状态下，振膜与背极板之间的有效真空间隙是第一真空间隙，以及
    其中，第一真空间隙大于制作间隙。
  2. 根据权利要求1所述的绝对压力感测微机电系统麦克风，其中，第一真空间隙大于或等于制作间隙的2倍。
  3. 根据权利要求2所述的绝对压力感测微机电系统麦克风，其中，第一真空间隙小于或等于制作间隙的10倍。
  4. 根据权利要求1所述的绝对压力感测微机电系统麦克风，其中，在标准大气压下，振膜与背极板之间的有效真空间隙是第二真空间隙，以及第二真空间隙大于制作间隙。
  5. 根据权利要求1所述的绝对压力感测微机电系统麦克风，其中，在标准大气压下，在施加工作偏压的状态下，振膜与背极板之间的有效真空间隙是第三真空间隙，以及第三真空间隙大于或等于制作间隙的80％且小于或等于制作间隙的120％。
  6. 根据权利要求1所述的绝对压力感测微机电系统麦克风，其中，通过应力结构，对振膜进行预拉偏，以使得第一真空间隙大于制作间隙。
  7. 根据权利要求6所述的绝对压力感测微机电系统麦克风，其中，所述应力结构包括所述振膜以及压应力部件，
    其中，所述振膜具有沿振膜表面方向的张应力，以及
    其中，所述压应力部件相对于真空腔附着在振膜外侧，并具有具有沿振膜表面方向的压应力。
  8. 根据权利要求6所述的绝对压力感测微机电系统麦克风，其中，所述应力结构包括所述振膜的复合层，
    其中，所述复合层包括位于真空腔内侧的内侧膜以及位于外侧的外侧膜，
    其中，所述内侧膜具有沿振膜表面方向的张应力以及所述外侧膜具有沿振膜表面方向的压应力。
  9. 根据权利要求6所述的绝对压力感测微机电系统麦克风，其中，所述应力结构包括所述间隔件和将振膜固定到所述间隔件的固定部件，
    其中，该固定部件具有沿振膜表面方向的张应力并附着到振膜的上表面，所述间隔件具有沿振膜表面方向的压应力并附着到振膜的下表面。
  10. 根据权利要求6所述的绝对压力感测微机电系统麦克风，其中，所述应力结构包括振膜上的纹膜结构，以使得振膜相对于真空腔向外凸起。
  11. 一种麦克风单体，包括单体外壳、根据权利要求1所述的绝对压力感测微机电系统麦克风以及集成电路芯片，其中，所述绝对压力感测微机电系统麦克风以及集成电路芯片被设置在所述单体外壳中。
  12. 一种电子设备，包括根据权利要求11所述的麦克风单体。
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