MEMS Microphone

Abstract

The present invention provides a micro-electromechanical microphone comprising: a substrate, which includes a back cavity arranged in the substrate and a sound inlet arranged on the substrate and connected to the back cavity; a sensor device, which is arranged on the inner side wall of the back cavity; a first cantilever, which is arranged in the back cavity and includes an end coupled to the sensor device; a first diaphragm, which is arranged at the sound inlet, wherein one side of the first diaphragm is connected to the first cantilever and the other side is used to receive external force; a second diaphragm, which is arranged in the back cavity; and a plurality of second cantilevers, wherein each of the cantilevers includes a first end for mechanically supporting the first cantilever and a second end connected to the second diaphragm. By suspending the first cantilever beam on the second cantilever beam, the end of the first cantilever beam is always coupled to the preset position of the sensor device. The micro-electromechanical microphone of the present invention can prevent the DC offset of the displacement of the diaphragm.

Description

Technical Field

[0001] The present invention relates to the technical field of acoustic-electric conversion, and more particularly to a micro-electromechanical microphone. Background Art

[0002] Currently, commercially available micro-electro-mechanical system (MEMS) microphones have a back cavity behind the diaphragm. The back cavity is a semi-sealed air containment chamber in which the air compresses and expands when sound waves are input. The back cavity can provide a space for the vibration of the diaphragm. However, the containment chamber is the largest source of noise, which greatly limits the signal-to-noise ratio (SNR) of the MEMS microphone. The smaller the volume of the back cavity, the greater the noise from the back cavity. Therefore, unless the package size is very large, it is impossible to achieve a microphone with a signal-to-noise ratio higher than about 74dB. If the back cavity is a vacuum containment chamber, the sensing part of the MEMS is replaced by the sensing part inside the vacuum containment chamber, which can effectively eliminate not only the noise from the back cavity, but also the damping noise related to the movement of the diaphragm, such as the back plate noise. The only way to achieve a high signal-to-noise ratio in an ordinary or smaller package is to form a vacuum environment in the back cavity.

[0003] However, there are two major challenges for microphones with such vacuum back chambers. First, the 1atm pressure difference between air and vacuum will cause a normal diaphragm to collapse. Therefore, a diaphragm with high stiffness is required, which will result in low sensitivity. Second, when the ambient pressure changes greatly, displacement of the diaphragm may occur, and the direct current (DC) offset of the diaphragm will also change.

[0004] like Figure 1 and Figure 2 As shown, the micro-electromechanical microphone of the related art includes a substrate 1, a cantilever 2, a support arm 6, a diaphragm 4, a plunger 5 and a sensor device 3. An inner cavity 7 is provided in the substrate 1, and the sensor device 3 and the cantilever 2 are arranged in the inner cavity 7. The end 21 of the cantilever 2 is coupled to the sensor device 3. Each support arm 6 includes one end fixedly connected to the bottom of the inner cavity 7 and the other end hinged to the cantilever 2. The diaphragm 4 is connected to the center of the cantilever 2 through the plunger 5. The diaphragm 4 is arranged on one side of the cantilever 2, and the support arm 6 is arranged on the other side of the cantilever 2.

[0005] When the diaphragm 4 is not subjected to force, Figure 1 As shown, the diaphragm 4 is in a flat state, the cantilever 2 is straight, and is coupled to the middle position of the sensor device 3.

[0006] When the diaphragm 4 is subjected to external force, such as Figure 2As shown, the diaphragm 4 is recessed in the direction of the inner cavity 7. The plunger 5 moves downward, and the portion of the cantilever 2 connected to the connector 5 is recessed in the direction away from the diaphragm 4. The cantilever 2 is supported by the support arm 6, and forms a lever structure with the support arm 6. In this case, when the center of the cantilever 2 is subjected to a downward force through the plunger 5, the end 21 of the support arm 2 coupled to the sensor device 3 will tilt upward, so that the end 21 of the cantilever 2 has an upward displacement relative to the sensor device 3, deviating from the middle position of the sensor device 3. Figure 2 As shown, a slight deformation of the center of the cantilever 2 will cause a large displacement of the end 21 of the cantilever 2. Therefore, the related art micro-electromechanical microphone cannot handle changes in ambient pressure. When the ambient pressure changes, the change of the diaphragm within a range of 3 μm may significantly cause excessive changes in the DC offset of the end 21 of the cantilever 2, making the sensor device 3 unable to work properly. Summary of the invention

[0007] The present invention provides a micro-electromechanical microphone, aiming to solve the problem of displacement of the end of the diaphragm of the micro-electromechanical microphone in the related art.

[0008] To solve the above technical problems, an embodiment of the present invention provides a micro-electromechanical microphone including: a substrate, which includes a back cavity arranged in the substrate and a sound inlet arranged on the substrate and connected to the back cavity; a sensor device, which is arranged on the inner side wall of the back cavity; a first cantilever, which is arranged in the back cavity and includes an end coupled to the sensor device; a first diaphragm, which is arranged at the sound inlet, wherein one side of the first diaphragm is connected to the first cantilever, and the other side is used to receive external force; a second diaphragm, which is arranged in the back cavity; and a plurality of second cantilevers, wherein each of the cantilevers includes a first end that mechanically supports the first cantilever and a second end connected to the second diaphragm.

[0009] Preferably, the micro-electromechanical microphone further comprises a connecting rod, wherein the connecting rod comprises one end connected to the first cantilever and the other end connected to the center of the first diaphragm.

[0010] Preferably, the base is further provided with a flange which is arranged around the sound inlet and faces the back cavity, and the edge of the first diaphragm abuts against the flange.

[0011] Preferably, the first diaphragm and the second diaphragm are respectively located on both sides of the flange, and the edge of the second diaphragm abuts against the inner wall of the back cavity and the flange respectively.

[0012] Preferably, a limiting protrusion is provided on the inner side wall of the back cavity, and the edge of the second diaphragm abuts against the limiting protrusion and the flange respectively.

[0013] Preferably, the second diaphragm is spaced apart from the upper surface of the substrate to form an auxiliary cavity between the upper surface of the substrate and the second diaphragm.

[0014] Preferably, a plurality of pressure relief holes are provided on the upper surface of the substrate and are opposite to the second diaphragm to connect the auxiliary cavity with the atmosphere.

[0015] Preferably, each of the second cantilevers includes a first connecting rod and a second connecting rod, wherein the first connecting rod includes a first rod connecting end connected to the second connecting rod and the second end connected to the second diaphragm, and the second connecting rod includes a second rod connecting end connected to the first rod connecting end of the first connecting rod and the first end hinged to the first cantilever.

[0016] Preferably, the first cantilever comprises a hinge connected to the first end of the second connecting rod, wherein the first end of the second connecting rod is connected to a stator portion of the hinge.

[0017] Preferably, the first diaphragm, the second diaphragm and the plurality of second cantilevers are all located on the same side of the first cantilever.

[0018] In view of this, a micro-electromechanical microphone is provided according to an embodiment of the present invention, aiming to solve the problem of displacement of the end of the diaphragm and the problem of DC offset variation caused by changes in ambient pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of the state of a micro-electromechanical microphone of the related art when no external force is applied;

[0020] Figure 2 is a state diagram of a micro-electromechanical microphone of the related art under an external force;

[0021] Figure 3 is a state schematic diagram I of a micro-electromechanical microphone according to an embodiment of the present invention;

[0022] Figure 4 Schematic diagram II of the state of a micro-electro-mechanical microphone according to an embodiment of the present invention.

[0023] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, explain the principles of the invention. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention will be described below with reference to the accompanying drawings. It should be noted that the described embodiments are merely exemplary embodiments of the present invention and should not be construed as limiting the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

[0025] In an embodiment of the present invention, a micro-electromechanical microphone is provided. Figure 3 and Figure 4 As shown, in this embodiment, the micro-electromechanical microphone includes a substrate 100, a sensor device 200, a first cantilever 300, a first diaphragm 400, a second cantilever 500 and a second diaphragm 600. Here, a back cavity 140 is provided in the substrate 100. A sound inlet 110 is provided on the upper surface of the substrate and communicates with the back cavity 140. The sensor device 200 is arranged on the inner side wall of the back cavity 140. The first cantilever 300 is arranged in the back cavity 140, and includes an end 310 coupled to the sensor device. The first diaphragm 400 is arranged at the sound inlet 110, one side of the first diaphragm 400 is connected to the first cantilever 300, and the other side of the first diaphragm 400 is used to receive external force. The second diaphragm is arranged in the back cavity 140. Each second cantilever 500 includes a first end that mechanically supports the first cantilever 300, and a second end that is connected to one side of the second diaphragm 600.

[0026] In one embodiment, the micro-electromechanical microphone is a vacuum microphone with a back chamber.

[0027] In one embodiment, the sensing device 200 may be a comb sensing device including a plurality of first comb fingers. A plurality of second comb fingers are provided at the end 310 of the first cantilever 300. The first comb fingers and the second comb fingers engage with each other to operate as a comb sensing device.

[0028] When no external force is applied, Figure 3 As shown, the first diaphragm 400 and the second diaphragm 600 are in a flat state, and the first cantilever 300 is straight.

[0029] Figure 4 1 shows a state diagram of a micro-electromechanical microphone according to an embodiment of the present invention. Figure 4As shown, when external pressure is applied to the first diaphragm 400 through the sound inlet 110, the first diaphragm 400 is recessed in the direction toward the back cavity 140. In one embodiment, the external pressure is a DC ambient pressure, and its full range is 0.5atm to 1atm. Due to the connection between the first cantilever 300 and the first diaphragm 400, the first cantilever 300 is recessed downward as the first diaphragm 400 is recessed. By suspending the first cantilever 300 on the second cantilever 500, the first cantilever 300 is indirectly hinged to the second diaphragm 600. Therefore, the second diaphragm 600 is recessed downward together with the first cantilever 300. Therefore, as shown in Figure 3 and Figure 4 As shown, when the first diaphragm 400 is subjected to a DC environmental pressure, the end 310 of the first cantilever 300 is always coupled to the preset position of the sensor device 200 without any displacement. Therefore, the DC offset of the displacement of the diaphragm can be prevented.

[0030] In one embodiment, the first diaphragm 400, the second diaphragm 600 and the second cantilever 500 are located on the same side of the first cantilever 300. When the first cantilever 300 is recessed downward, under the horizontal principle, the end 310 of the first cantilever 300 will not have a large DC displacement relative to the comb sensor device 200.

[0031] In one embodiment of the present invention, the second diaphragm 600 is spaced apart from the upper surface of the substrate 100 to form an auxiliary cavity between the upper surface of the substrate 100 and the second diaphragm 600. The upper surface of the substrate 100 is provided with a plurality of pressure relief holes 130 to allow the auxiliary cavity to communicate with the atmosphere. The pressure relief holes 130 are arranged opposite to the second diaphragm 600.

[0032] In one embodiment, the base 100 is provided with pressure relief holes 130 around the sound inlet 110. Figure 4 As shown, when both the first diaphragm 400 and the second diaphragm 600 are exposed to a DC ambient pressure, after receiving pressure at the pressure relief hole 130, the second diaphragm 600 is recessed downward. In this way, the function of an acoustic low-pass filter can be achieved through the combined action of the pressure relief hole 130, the second diaphragm 600 and the back cavity 140. In addition, the alternating current (AC) pressure is allowed to be converted into an AC displacement at the end of the second cantilever 500, and the DC pressure is prevented from being transmitted to the end 310 of the first cantilever 300 to cause a DC displacement. By adjusting the compliance of the second diaphragm 600, a zero DC displacement of the end 310 of the first cantilever 300 can be achieved. In one embodiment, the diameter of the second diaphragm 600 can be adjusted to achieve a zero DC displacement of the end 310.

[0033] In one embodiment, the micro-electromechanical microphone further includes a connecting rod 700, which includes one end connected to the first cantilever 300 and the other end connected to the center of the first diaphragm 400. Figure 4 As shown, when the first diaphragm 400 is recessed toward the back cavity 140 , the first cantilever 300 may be recessed downward at the same time under the action of the connecting rod 700 .

[0034] In one embodiment, the base 100 is further provided with a flange 120 surrounding the edge of the sound inlet 110, and the flange 120 extends toward the back cavity 140. The edge of the first diaphragm 400 abuts against the flange 120. Therefore, the position of the first diaphragm 400 can be limited by the flange 120, thereby preventing the first diaphragm 400 from deviating in the radial direction.

[0035] In one embodiment, the first diaphragm 400 and the second diaphragm 600 are respectively located on both sides of the flange 120. The edges of the second diaphragm 600 are respectively in contact with the inner wall of the back cavity 140 and the flange 120. The auxiliary cavity is formed by the inner wall of the back cavity 140, the flange 120, the substrate 100, and the second diaphragm 600, thereby realizing the function of an acoustic low-pass filter.

[0036] In one embodiment, the second cantilever 500 includes a first connecting rod 510 and a second connecting rod 520. The first connecting rod 510 includes a first rod connecting end connected to the second connecting rod 520, and a second end connected to the center of the second diaphragm 600. The second connecting rod 520 includes a second rod connecting end connected to the first rod connecting end of the first connecting rod 510 and a first end hinged to the first cantilever 300.

[0037] The second cantilever 500 has the purpose of connecting the anchor point of the hinge to the second diaphragm 600. Therefore, in order to hinge the second connecting rod 520 to the first cantilever 300, the first cantilever 300 includes a hinge connected to the first end of the second connecting rod 520. The first end of the second connecting rod 520 is connected to the stator part of the hinge.

[0038] In one embodiment, the second connecting rod 520 is connected to the stator portion of the hinge of the first cantilever 300 at a position adjacent to the connecting rod 700, and the first connecting rod 510 is vertically connected to the second connecting rod 520. Therefore, through the second connecting rod 520, the first connecting rod 510 and the second diaphragm 600 can be displaced at a position opposite to the pressure relief hole 130.

[0039] In one embodiment, a limiting protrusion 150 is formed on the inner wall of the back cavity 140. The limiting protrusion 150 can make the first cantilever 300 at a position above the first cantilever 300, thereby limiting the position of the first cantilever 300, thereby ensuring that the first cantilever 300 works normally in the back cavity 140.

[0040] The embodiments described above are only preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art may make various changes and modifications to the content of the present invention. Any modification, equivalent replacement and improvement made within the scope of the principle of the present invention shall belong to the protection scope of the present invention.

Claims

1. A micro-electromechanical microphone, characterized in that: The micro-electromechanical microphone comprises: A substrate, comprising a back cavity disposed in the substrate and a sound inlet disposed on the substrate and connected to the back cavity; A sensing device, arranged on the inner side wall of the back cavity, wherein the sensing device is a comb-shaped sensing device including a plurality of first comb-shaped fingers; A first cantilever, disposed in the back cavity, comprising an end coupled to the sensing device, a plurality of second comb fingers being provided at the end of the first cantilever, the first comb fingers and the second comb fingers being engaged with each other to operate as a comb sensing device; A first diaphragm is arranged at the sound inlet, wherein one side of the first diaphragm is connected to the first cantilever, and the other side is used to receive external force; A second diaphragm is disposed in the back cavity; and a plurality of second cantilevers, wherein each of the cantilevers comprises a first end mechanically supporting the first cantilever and a second end connected to the second diaphragm; Among them, the micro-electromechanical microphone also includes a connecting rod, which includes one end connected to the first cantilever and the other end connected to the center of the first diaphragm, and when the first diaphragm is recessed toward the back cavity, the first cantilever is recessed under the action of the connecting rod.

2. The micro-electromechanical microphone as claimed in claim 1, characterized in that The base is further provided with a flange which is arranged around the sound inlet and faces the back cavity, and the edge of the first diaphragm abuts against the flange.

3. The micro-electromechanical microphone as claimed in claim 2, characterized in that: The first diaphragm and the second diaphragm are respectively located on both sides of the flange, and the edge of the second diaphragm is respectively in contact with the inner wall of the back cavity and the flange.

4. The micro-electromechanical microphone as claimed in claim 3, characterized in that A limiting protrusion is arranged on the inner side wall of the back cavity, and the edge of the second diaphragm abuts against the limiting protrusion and the flange respectively.

5. The micro-electromechanical microphone as claimed in claim 1, characterized in that: The second diaphragm is spaced apart from the upper surface of the substrate to form an auxiliary cavity between the upper surface of the substrate and the second diaphragm.

6. The micro-electromechanical microphone as claimed in claim 5, characterized in that: A plurality of pressure relief holes are arranged on the upper surface of the substrate and are opposite to the second diaphragm to connect the auxiliary cavity with the atmosphere.

7. The micro-electromechanical microphone as claimed in claim 1, characterized in that: Each of the second cantilevers includes a first connecting rod and a second connecting rod, wherein the first connecting rod includes a first rod connecting end connected to the second connecting rod and the second end connected to the second diaphragm, and the second connecting rod includes a second rod connecting end connected to the first rod connecting end of the first connecting rod and the first end hinged to the first cantilever.

8. The micro-electromechanical microphone as claimed in claim 7, characterized in that: The first cantilever includes a hinge connected to the first end of the second connecting rod, wherein the first end of the second connecting rod is connected to a stator portion of the hinge.

9. The micro-electromechanical microphone as claimed in claim 1, characterized in that: The first diaphragm, the second diaphragm and the plurality of second cantilevers are all located on the same side of the first cantilever.

Images