WO2022006999A1 - 一种mems麦克风 - Google Patents

一种mems麦克风 Download PDF

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Publication number
WO2022006999A1
WO2022006999A1 PCT/CN2020/103723 CN2020103723W WO2022006999A1 WO 2022006999 A1 WO2022006999 A1 WO 2022006999A1 CN 2020103723 W CN2020103723 W CN 2020103723W WO 2022006999 A1 WO2022006999 A1 WO 2022006999A1
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Prior art keywords
diaphragm
main body
mems microphone
inner cavity
body portion
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PCT/CN2020/103723
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English (en)
French (fr)
Inventor
赵转转
柏杨
但强
王凯杰
李杨
张睿
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瑞声声学科技(深圳)有限公司
瑞声科技（南京）有限公司
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Publication of WO2022006999A1 publication Critical patent/WO2022006999A1/zh

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    • 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
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
    • H04R1/222—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only  for 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
    • H04R1/20—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
    • 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

Definitions

  • the invention relates to the technical field of acoustics, in particular to a MEMS microphone.
  • a MEMS (Micro Electro Mechanic System, Micro Electro Mechanical System) microphone in the prior art is provided with a vibrating membrane at intervals on the base, and a back plate is provided above the vibrating membrane and further apart from the inner cavity.
  • the diaphragm and the back plate are parallel to each other, forming a flat capacitive system.
  • the sound wave airflow enters the cavity between the back plate and the diaphragm, the sound pressure acts on the diaphragm and causes the diaphragm to move. This movement changes the distance between the film and the back plate, thereby changing the capacitance and finally converting it into an electrical signal.
  • the corresponding function of the microphone is realized.
  • the air velocity near the edge of the diaphragm and the back plate is smaller than the air velocity in the central area of the inner cavity when the air flows, that is, the air flows between the diaphragm and the back plate.
  • Laminate damping The compression film damping has a great influence on the dynamic response of the MEMS chip. The greater the damping, the greater the mechanical noise.
  • the purpose of the present invention is to provide a MEMS microphone.
  • the MEMS microphone includes a base with a back cavity, a diaphragm arranged at intervals from the base, and a back plate covering the diaphragm and spaced from the diaphragm with an inner cavity
  • the back plate comprises a fixed part and a main body part surrounded by and connected with the fixed part, the central area of the main body part is raised in a direction away from the vibrating film to form a convex part.
  • the distance from the main body portion to the diaphragm gradually decreases from the central position of the main body portion to the direction of the fixing portion.
  • the raised portion is in the shape of an arc surface.
  • a plurality of spaced acoustic holes are formed through the main body.
  • a first insulating layer is provided between the diaphragm and the back plate, and the fixing portion is fixedly connected to the first insulating layer.
  • a second insulating layer and a plurality of etching barrier walls are arranged between the diaphragm and the base.
  • the beneficial effect of the present invention is that the central area of the main body portion of the back plate is raised to form a convex portion in the direction away from the vibrating film, so that the distance between the position where the back plate has the convex portion and the vibrating film is greater than that between the back plate and the vibrating film. Average distance between membranes.
  • FIG. 1 is a cross-sectional view of a MEMS microphone according to Embodiment 1 of the present invention.
  • the MEMS microphone includes a base 1 having a back cavity 11 , a diaphragm 2 and a back plate 4 sequentially arranged on the surface of the base 1 .
  • the backplane 4 includes a fixed portion 46 and a main body portion 45 surrounded by and connected to the fixed portion 46 .
  • the fixed portion 46 of the backplane is the edge of the backplane 4 , wherein the main body portions 45 are arranged at intervals.
  • a first insulating layer 6 is provided between the back plate 4 and the vibrating membrane 2 , so as to isolate the back plate 4 from the vibrating membrane 2 , and the fixing portion 46 is fixedly connected to the first insulating layer 6 .
  • a second insulating layer 21 is disposed between the diaphragm 2 and the base 1 to isolate the diaphragm 2 from the base 1 , and the first insulating layer 6 at least partially covers the second insulating layer 21 .
  • the edge of the diaphragm 2 is connected to the base 1 through the second insulating layer 21 , only the edge end of the diaphragm 2 is connected to the second insulating layer 21 , and the position where the diaphragm 2 is not fixedly connected to the second insulating layer 21 can be Free vibration is performed, that is to say, the central area of the diaphragm 2 can vibrate freely, and the vibration effect of the diaphragm 2 is maintained. Since the second insulating layer 21 is disposed between the diaphragm 2 and the base 1 , a gap is formed between the diaphragm 2 and the base 1 . The displacement space for the vibration of the diaphragm 2 is increased.
  • An inner cavity 3 is formed between the back plate 4 (ie, the main body portion 45 ) and the diaphragm 2 , and a capacitor exists in the inner cavity 3 .
  • the diaphragm 2 vibrates, the height of the inner cavity 3 in the direction perpendicular to the diaphragm 2 is changed, thereby changing the capacitance value of the inner cavity 3, and the change of the capacitance is converted into a digital signal, and finally the function of the microphone is realized.
  • a plurality of etching barrier walls 5 may also be arranged between the diaphragm 2 and the base 1, and the etching barrier walls 5 can ensure a reliable stop of the etching process that may occur in the manufacturing process, thereby protecting the second The insulating layer 21 is not etched away.
  • a plurality of etching stop walls 5 are arranged at intervals, and a second insulating layer 21 is provided between every two etching stop walls 5 .
  • the second insulating layer 21 and the etching barrier wall 5 jointly support the diaphragm 2 , so that the diaphragm 2 and the base 1 are spaced to form a gap.
  • the etch stop wall 5 can typically be made of, for example, oxide, thermal oxide, or TEOS. Its thickness can be between 0.1 and 1 ⁇ m.
  • the back plate 4 has at least one raised portion 41 that is raised in a direction away from the diaphragm 2 .
  • a raised portion 41 is formed in the central area of the main body portion 45 in a direction away from the vibrating membrane 2;
  • the central axis of the protruding portion 41 coincides with the central axis of the main body portion 45 , and the distance from the main body portion 45 to the diaphragm 2 gradually decreases from the central position of the main body portion 45 toward the fixing portion 46 .
  • the back plate 4 protrudes from the connection position with the first insulating layer 6 to the direction away from the diaphragm 2 to form a convex portion 41 .
  • the convex portion is in the shape of an arc surface. The vertex of the central area.
  • the distance between the center of the convex portion 41 and the diaphragm 2 is the farthest, that is, the inner cavity 3 has the greatest height on the central axis.
  • the central volume of the inner cavity 3 increases due to the upward bulge of the central area of the main body portion 45 , and the flow velocity of the acoustic air flow at the center of the inner cavity 3 is not greater than that in the inner cavity 3
  • the average flow rate of so that the squeeze film damping in the inner cavity 3 can be reduced to negligible, thereby reducing the mechanical noise of the MEMS microphone.
  • the main body 45 of the back plate 4 is evenly provided with acoustic holes 42 penetrating the back plate 4 , the acoustic holes 42 communicate with the atmosphere of the inner cavity 3 and the external environment, and the acoustic holes 42 are small through holes, so that The acoustic air flow can enter or flow out of the cavity 3 , and the acoustic holes 42 are evenly distributed on the back plate 4 .
  • the acoustic air flow is transmitted, the acoustic air flow enters the cavity 3 through the acoustic holes 42 .
  • the cross section of the back cavity 11 is an inverted isosceles trapezoid.
  • the back cavity 11 has atmospheric pressure. When the vibrating membrane 2 vibrates, the pressure in the back cavity 11 does not change, so that the free vibration of the vibrating membrane 2 is maintained.
  • the vibrating membrane 2 is disposed on the base 1 with the back cavity 11 spaced by the second insulating layer 21 , so that there is a gap between the vibrating membrane 2 and the base 1 , so as to ensure that the vibrating membrane 2 has sufficient vibration space.
  • a back plate 4 with acoustic holes 42 is arranged above the diaphragm 2 with an interval of the inner cavity 3 , and a raised portion 41 is formed on the back plate 4 . Since there is an inner cavity 3 between the diaphragm 2 and the back plate 4 , the raised portion 41 increases the height of the inner cavity 3 along the direction perpendicular to the diaphragm 2 on the central axis.
  • the acoustic air flow flows in the inner cavity 3, and the height of the central area of the inner cavity 3 increases to be greater than the average height of the inner cavity 3, thereby reducing the airflow velocity in the central area of the inner cavity 3, thereby reducing the pressure in the central area of the inner cavity 3.
  • the mechanical noise of the MEMS microphone is also reduced.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Pressure Sensors (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)

Abstract

本发明提供了一种MEMS麦克风，包括具有背腔的基座，与所述基座间隔设置的振膜，和覆盖于所述振膜上且与所述振膜间隔有内腔的背板；所述背板包括固定部和由所述固定部围绕并与之相连的主体部，所述主体部的中心区域向远离所述振膜的方向隆起形成凸起部。凸起部的存在，增大了主体部与振膜的距离，当声波气流通过声学孔进入内腔后，声波气流在凸起对应的内腔中流速小于内腔的平均气流流速，从而减小了压膜阻尼，进而减少了MEMS麦克风的机械噪声。

Description

一种MEMS麦克风 技术领域
本发明涉及声学技术领域，特别涉及一种MEMS麦克风。
 背景技术
现有技术的MEMS（Micro Electro Mechanic System，微型机电系统）麦克风在基座上间隔设置有振膜，在振膜上方再间隔内腔设置有背板。振膜和背板相互平行，构成了平板电容系统。当声波气流进入背板和振膜之间的内腔时，声压作用于振膜引起振膜运动，这种运动改变薄膜与背板之间的距离，进而改变电容并最终转化为电信号，最终实现麦克风的相应功能。
 技术问题
然而，由于振膜与背板间的内腔较小，空气流动时靠近振膜与背板边缘的气流速度小于内腔中心区域的气流速度，即空气在振膜与背板之间流动时存在压膜阻尼。而压膜阻尼对MEMS芯片的动态响应影响很大，阻尼越大，则机械噪声越大。
因此，有必要提供一种MEMS麦克风，解决MEMS芯片中压膜阻尼较大的情况。
 技术解决方案
本发明的目的在于提供一种MEMS麦克风。
本发明的技术方案如下：该MEMS麦克风包括具有背腔的基座，与所述基座间隔设置的振膜，和覆盖于所述振膜上且与所述振膜间隔有内腔的背板；所述背板包括固定部和由所述固定部围绕并与之相连的主体部，所述主体部的中心区域向远离所述振膜的方向隆起形成凸起部。
更优地，所述主体部到所述振膜的距离自所述主体部的中心位置向所述固定部方向逐步递减。
更优地，该凸起部为圆弧面状。
更优地，所述主体部上贯穿开设有多个间隔的声学孔。
更优地，所述振膜与所述背板之间设有第一绝缘层，所述固定部与所述第一绝缘层固定连接。
更优地，所述振膜与所述基座之间设有第二绝缘层以及若干刻蚀阻挡墙。
 有益效果
本发明的有益效果在于：背板主体部的中心区域向远离所述振膜的方向隆起形成凸起部，使得该背板具有凸起部的位置与振膜之间的距离大于背板与振膜之间的平均距离。此设计使得凸起部所对应的内腔中的空气流速小于内腔的平均气流，进而降低内腔中的压膜阻尼，降低MEMS芯片的机械噪声。
 附图说明
图1为本发明实施例一提供的一种MEMS麦克风的剖面图。
 本发明的最佳实施方式
下面结合附图和实施方式对本发明作进一步说明。
参见图1，在本发明的实施例一中，该MEMS麦克风包括具有背腔11的基座1和依次设置于基座1表面上的振膜2、背板4。
背板4包括固定部46和由固定部46围绕并与之连接的主体部45，背板的固定部46即背板4的边缘，其中，主体部45间隔设置。背板4与振膜2之间设有第一绝缘层6，从而将背板4与振膜2隔离开，固定部46与第一绝缘层6固定连接。
振膜2与基座1之间设置有第二绝缘层21，从而将振膜2与基座1隔离开，第一绝缘层6至少部分覆盖第二绝缘层21。振膜2的边缘通过第二绝缘层21与该基座1相连接，振膜2只有边缘端与该第二绝缘层21连接，振膜2未与第二绝缘层21固定连接的位置都可以进行自由振动，也就是说振膜2的中心区域可以自由振动，保持振膜2的振动效果。由于第二绝缘层21设置在振膜2与基座1之间，使得振膜2与基座1间隔形成间隙。增大了振膜2振动的位移空间。
背板4（即主体部45）与振膜2之间形成内腔3，内腔3中存在电容。当振膜2振动时，改变内腔3在垂直于该振膜2方向的高度，进而改变内腔3的电容值，电容的变化转化为数字信号，最终实现麦克风的功能。
在变更实施例中，振膜2与基座1之间还可以设置有若干刻蚀阻挡墙5，刻蚀阻挡墙5可以确保可能出现在制造工艺中的蚀刻工艺的可靠停止，从而保护第二绝缘层21不会被刻蚀掉。若干个刻蚀阻挡墙5间隔设置，每两个刻蚀阻挡墙5之间设有第二绝缘层21。第二绝缘层21与刻蚀阻挡墙5共同支撑振膜2，使振膜2与基座1间隔形成间隙。刻蚀阻挡墙5通常可由例如氧化物、热氧化物、或TEOS制成。其厚度可以在0.1至1μm之间。
进一步地，背板4具有至少一个朝远离振膜2的方向隆起的凸起部41。在一实施方式中，主体部45的中心区域向远离振膜2的方向隆起形成有一个凸起部41；背板4与振膜2之间的内腔3中存在电容，当振膜2发生振动时，振膜2与背板4之间的距离发生变化，使得内腔3中的电容发生变化，构成内腔3电容的振膜2上的电位就会发生变化，变化的电位转换成电信号。
具体的，凸起部41的中心轴与主体部45的中心轴相重合，主体部45到振膜2的距离自主体部45的中心位置向固定部46方向逐步递减。背板4从与第一绝缘层6的连接位置处开始向远离振膜2的方向隆起形成凸起部41，凸起部为圆弧面状，凸起部41的隆起直至达到主体部45的中心区域的顶点。由于凸起部41的中心轴与该主体部45的中心轴相重合，使得凸起部41的中心与振膜2的距离达到最远，即内腔3在中心轴上具有最大高度。当声波气流经过声学孔42进入内腔3后，由于主体部45的中心区域向上隆起，使得内腔3的中心容积增大，声波气流在内腔3中心处的流速不大于在内腔3内的平均流速，使得内腔3中的压膜阻尼减小到可以忽略，进而减少MEMS麦克风的机械噪声。
更优地，在该背板4的主体部45上均匀设置有贯通背板4的声学孔42，声学孔42连通内腔3与外界环境的大气，声学孔42是较小的通孔，使得声波气流可以进入或流出内腔3，声学孔42均匀的分布在该背板4上，当声波气流传输过来，声波气流穿过声学孔42进入内腔3。
更优地，该背腔11的截面为倒等腰梯形。背腔11内具有大气压强，当振膜2振动后背腔11内的压力不变，保持振膜2的自由振动。
通过在具有背腔11的基座1上间隔第二绝缘层21而设置振膜2，使得振膜2与基座1之间存在空隙，保证振膜2具有足够的振动空间。在振膜2上方间隔内腔3而设置带声学孔42的背板4，在背板4上隆起形成的凸起部41。由于振膜2和背板4之间具有内腔3，凸起部41增大了内腔3在中心轴上沿垂直于振膜2方向的高度，当声波气流通过声学孔42进入内腔3后，声波气流在内腔3中流动，在内腔3的中心区域由于高度增加至大于内腔3的平均高度，从而降低内腔3中心区域的气流流速，进而减少内腔3中心区域的压膜阻尼内腔3中的压膜阻尼被降低后，MEMS麦克风的机械噪声也被降低。
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 (6)

  1. 一种MEMS麦克风，所述MEMS麦克风包括具有背腔的基座，与所述基座间隔设置的振膜，和覆盖于所述振膜上且与所述振膜间隔有内腔的背板；其特征在于，所述背板包括固定部和由所述固定部围绕并与之相连的主体部，所述主体部的中心区域向远离所述振膜的方向隆起形成凸起部。
  2. 根据权利要求1所述的MEMS麦克风，其特征在于，所述主体部到所述振膜的距离自所述主体部的中心位置向所述固定部方向逐步递减。
  3. 根据权利要求2所述的MEMS麦克风，其特征在于，所述凸起部为圆弧面状。
  4. 根据权利要求2所述的MEMS麦克风，其特征在于，所述主体部上贯穿开设有多个间隔的声学孔。
  5. 根据权利要求1所述的MEMS麦克风，其特征在于，所述振膜与所述背板之间设有第一绝缘层，所述固定部与所述第一绝缘层固定连接。
  6. 根据权利要求1所述的MEMS麦克风，其特征在于，所述振膜与所述基座之间设有第二绝缘层以及若干刻蚀阻挡墙。
PCT/CN2020/103723 2020-07-06 2020-07-23 一种mems麦克风 WO2022006999A1 (zh)

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