MEMS acoustic sensing chip, microphone and electronic equipment

Abstract

The embodiment of the invention discloses an MEMS acoustic sensing chip, a microphone and electronic equipment, the MEMS acoustic sensing chip comprises a substrate, and the substrate is provided with a back cavity; the first vibrating diaphragm, the second vibrating diaphragm and the back polar plate are arranged on one side of the substrate through the supporting structure, an inner cavity is formed between the first vibrating diaphragm and the second vibrating diaphragm, and the back polar plate is located in the inner cavity; each of the first vibrating diaphragm and the second vibrating diaphragm comprises a suspension area, the air leakage hole penetrates through the suspension area of the first vibrating diaphragm and the suspension area of the second vibrating diaphragm, the isolation structure surrounds the air leakage hole and divides the inner cavity into a sealing cavity and an air leakage cavity, and the air leakage cavity is communicated with the back cavity; at least one of the first vibrating diaphragm and the second vibrating diaphragm is provided with a release hole, and the release hole is communicated with the sealing cavity. The air leakage cavity is communicated with the back cavity, and the pressure balance between the inner cavity and the outside can be adjusted through an air leakage channel formed by the air leakage hole and the air leakage cavity.

Description

Technical Field

[0001] This application belongs to the field of acoustic-electric technology. Specifically, this application relates to a MEMS acoustic sensing chip, a microphone, and an electronic device. Background Art

[0002] With the rapid development of portable electronic devices such as smart phones, wearable devices, and Internet of Things terminals, miniaturized and high-performance acoustic sensors have become key technological requirements. Among them, MEMS (Micro-Electro-Mechanical Systems) acoustic sensing chips have gradually become the mainstream technical solution in the field of acoustic sensors due to their advantages such as small size, high integration, and low power consumption.

[0003] In order to further improve acoustic performance, currently, dual-diaphragm MEMS acoustic sensing chips are mostly used, which include two diaphragms, and a backplate with through holes is provided between the two diaphragms. However, the inner cavity between the two diaphragms is mostly a sealed structure, and the change in sound pressure will cause pressure fluctuations in the inner cavity, and when the sound pressure difference is large, it will also affect the vibration stability of the diaphragm. Summary of the Invention

[0004] The purpose of the embodiments of this application is to provide a new technical solution for MEMS acoustic sensing chips, microphones, and electronic devices.

[0005] According to the first aspect of the embodiments of this application, a MEMS acoustic sensing chip is provided, including:

[0006] A substrate, with a back cavity opened on the substrate;

[0007] A first diaphragm, a second diaphragm, a backplate, and a support structure. The first diaphragm, the second diaphragm, and the backplate are arranged on one side of the substrate through the support structure, and an inner cavity is formed between the first diaphragm and the second diaphragm, and the backplate is located in the inner cavity;

[0008] A vent hole and an isolation structure. Both the first diaphragm and the second diaphragm include a suspended area. The vent hole penetrates through the suspended areas of the first diaphragm and the second diaphragm. The isolation structure surrounds the vent hole and divides the inner cavity into a sealed cavity and a venting cavity, and the venting cavity is communicated with the back cavity;

[0009] At least one of the first diaphragm and the second diaphragm is provided with a release hole, and the release hole is communicated with the sealed cavity.

[0010] Optionally, the isolation structure is an isolation ring, and both sides of the isolation ring are circumferentially sealed with the first diaphragm and the second diaphragm respectively.

[0011] Optionally, it further includes a connection structure disposed in the sealing cavity, and the connection structure is connected between the first diaphragm and the second diaphragm.

[0012] Optionally, the connection structure includes a plurality of independent connection columns, and the plurality of connection columns are spaced apart.

[0013] Optionally, the distance from the connection column to the center of the first diaphragm is not less than the radius of the first diaphragm.

[0014] Optionally, the aperture of the air vent hole is 5μm - 20μm.

[0015] Optionally, the aperture of the air vent hole is 12μm - 16μm.

[0016] Optionally, the aperture of the release hole is 0.15μm - 0.5μm.

[0017] Optionally, the aperture of the release hole is 0.3μm - 0.5μm.

[0018] Optionally, on the first diaphragm and / or the second diaphragm, the distance between adjacent release holes is 10μm - 30μm.

[0019] Optionally, there is a first gap between the first diaphragm and the back plate electrode, and the two form a first capacitor structure; there is a second gap between the second diaphragm and the back plate electrode, and the two form a second capacitor structure.

[0020] Optionally, a plurality of through holes are formed in the back plate electrode, and the plurality of through holes communicate the first gap with the second gap;

[0021] When the second diaphragm moves towards the first diaphragm under the action of sound pressure, the air in the sealing cavity flows, and the air can pass through the second gap, the through hole and the first gap in sequence to generate pressure on the first diaphragm, so that the first diaphragm and the second diaphragm vibrate synchronously.

[0022] Optionally, at least one of the first diaphragm and the second diaphragm is provided with a conductive part, and the support structure is provided with a first metal through hole in the thickness direction, and the conductive part leads out a first electrical connection part through the first metal through hole.

[0023] Optionally, the back plate electrode includes a conductive layer and insulating layers respectively disposed on both sides of the conductive layer;

[0024] The support structure is provided with a second metal through hole in the thickness direction, and the conductive layer leads out a second electrical connection part through the second metal through hole.

[0025] According to a second aspect of the embodiments of the present application, there is also provided a microphone, including a packaging structure; and the MEMS acoustic sensing chip as described above, and the MEMS acoustic sensing chip is disposed within the packaging structure.

[0026] According to a third aspect of the embodiments of the present application, there is also provided an electronic device, including the microphone as described above.

[0027] One technical effect of the embodiments of the present application is that:

[0028] For the MEMS acoustic sensing chip provided by the present application, by connecting the air release cavity with the back cavity, during the operation of the MEMS acoustic sensing chip, the pressure balance between the inner cavity and the outside can be adjusted through the air release channel formed by the air release hole and the air release cavity, reducing the influence of pressure changes on the vibration of the first diaphragm and the second diaphragm, which helps to improve the stability and reliability of the MEMS acoustic sensing chip. Moreover, it can also maintain the air pressure balance inside and outside the MEMS acoustic sensing chip, reducing the high-temperature or high-pressure impact on the back cavity, thereby realizing the protection of the MEMS acoustic sensing chip.

[0029] Other features and advantages of the present application will become clear through the following detailed description of the exemplary embodiments of the present application with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings incorporated in the specification and constituting a part of the specification illustrate the embodiments of the present application and, together with the description, are used to explain the principles of the present application.

[0031] Figure 1 FIG. 1 is one of the schematic structural diagrams of the MEMS acoustic sensing chip provided by the embodiments of the present application;

[0032] Figure 2 FIG. 2 is another schematic structural diagram of the MEMS acoustic sensing chip provided by the embodiments of the present application;

[0033] Figure 3 FIG. 3 is a comparison diagram of the low-frequency cut-off points of the release holes of different sizes of the MEMS acoustic sensing chip provided by the embodiments of the present application;

[0034] Figure 4 FIG. 4 is a comparison diagram of the signal-to-noise ratios of the release holes of different sizes of the MEMS acoustic sensing chip provided by the embodiments of the present application;

[0035] Figure 5 FIG. 5 is a comparison diagram of the noise power spectral densities of the release holes of different sizes of the MEMS acoustic sensing chip provided by the embodiments of the present application.

[0036] Description of the reference numerals:

[0037] 1. Substrate; 111. Back cavity; 2. First diaphragm; 3. Second diaphragm; 4. Back plate; 41. Through hole; 5. Support structure; 6. Inner cavity; 61. Sealing cavity; 62. Air leakage cavity; 7. Air leakage hole; 8. Isolation structure; 9. Release hole; 10. Connection structure; 11. First electrical connection part; 12. Second electrical connection part. Detailed implementation manners

[0038] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that: unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions and values set forth in these embodiments do not limit the scope of the present application.

[0039] The following description of at least one exemplary embodiment is merely illustrative in nature and in no way limits the present application, its application or use.

[0040] Technologies, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such technologies, methods and devices should be regarded as part of the specification.

[0041] In all the examples shown and discussed here, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values.

[0042] It should be noted that: like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0043] Refer to Figure 1 and Figure 2 , the present application discloses a MEMS acoustic sensing chip, comprising:

[0044] Substrate 1, the substrate 1 is provided with a back cavity 111;

[0045] A first diaphragm 2, a second diaphragm 3, a back plate 4 and a support structure 5, the first diaphragm 2, the second diaphragm 3 and the back plate 4 are arranged on one side of the substrate 1 through the support structure 5, and an inner cavity 6 is formed between the first diaphragm 2 and the second diaphragm 3, and the back plate 4 is located in the inner cavity 6;

[0046] An air leakage hole 7 and an isolation structure 8, both the first diaphragm 2 and the second diaphragm 3 include a suspended area, the air leakage hole 7 penetrates through the suspended areas of the first diaphragm 2 and the second diaphragm 3, and the isolation structure 8 surrounds the air leakage hole 7 and divides the inner cavity 6 into a sealing cavity 61 and an air leakage cavity 62, and the air leakage cavity 62 is communicated with the back cavity 111;

[0047] At least one of the first diaphragm 2 and the second diaphragm 3 is provided with a release hole 9, and the release hole 9 communicates with the sealing cavity 61.

[0048] Referring to Figure 1 and Figure 2 , the MEMS acoustic sensing chip includes a substrate 1, and a back cavity 111 is formed at the central position of the substrate 1. The substrate 1 is the basic support structure of the MEMS acoustic sensing chip, and its material is usually selected from semiconductor materials such as silicon. A back cavity 111 is formed on the substrate 1, and the formation of the back cavity 111 can adopt processes such as ion etching. The back cavity 111 can provide space for the subsequent vibration of the first diaphragm 2 and the second diaphragm 3, and communicates with the air leakage cavity 62, which helps to adjust the pressure balance inside the MEMS acoustic sensing chip.

[0049] A support structure 5 is provided on the substrate 1, and the first diaphragm 2, the back plate 4 and the second diaphragm 3 can be sequentially stacked on the substrate 1 through the support structure 5. Among them, the first diaphragm 2 and the second diaphragm 3 are spaced apart on both sides of the back plate 4, and an inner cavity 6 is formed between the first diaphragm 2 and the second diaphragm 3, and the back plate 4 is located in the inner cavity 6.

[0050] Among them, the support structure 5 can adopt insulating materials such as silicon oxide and silicon nitride, and is formed by processes such as deposition, photolithography and etching.

[0051] The first diaphragm 2 and the second diaphragm 3 are the sensing components of the MEMS acoustic sensing chip. They are usually made of conductive materials such as polysilicon and have certain elasticity and mechanical strength. When a sound signal acts on the MEMS acoustic sensing chip, it will cause the vibration of the first diaphragm 2 and the second diaphragm 3, thereby changing the capacitance value in the inner cavity 6 and realizing the conversion of the sound signal to the electrical signal.

[0052] Referring to Figure 1 and Figure 2 , both the first diaphragm 2 and the second diaphragm 3 include a support area and a suspended area. The support area is connected to the support structure 5, and the suspended area is opposite to the back cavity 111. Air discharge holes 7 are formed through the suspended areas of the first diaphragm 2 and the second diaphragm 3, so that the gas in the inner cavity 6 can be discharged to the outside through the air discharge holes 7, avoiding the deformation or damage of the first diaphragm 2 and the second diaphragm 3 caused by gas expansion or contraction during use, which helps to improve the reliability and stability of the MEMS acoustic sensing chip, and also enables the MEMS acoustic sensing chip to work stably under various environmental conditions.

[0053] In this embodiment, the air discharge holes 7 are formed in the suspended areas of the first diaphragm 2 and the second diaphragm 3, so that the formation process of the air discharge holes 7 is simple and controllable, which helps to reduce the processing difficulty and processing cost of the MEMS acoustic sensing chip.

[0054] An isolation structure 8 is disposed around the outer periphery of the air vent 7. The isolation structure 8 can divide the inner cavity 6 into a sealed cavity 61 and a deflation cavity 62. The deflation cavity 62 is communicated with the air vent 7, and the sealed cavity 61 is a closed chamber. Among them, the isolation structure 8 can also be made of the same material as the support structure 5 and formed by photolithography and etching processes.

[0055] Among them, the setting of the isolation structure 8 makes the sealed cavity 61 and the deflation cavity 62 independent of each other, that is, the gases in the sealed cavity 61 and the deflation cavity 62 do not flow into each other. For example, the gas flowing in the sealed cavity 61 will not enter the deflation cavity 62, which helps to ensure that the two diaphragms can vibrate under the action of the external sound pressure, and thus can improve the sensing sensitivity of the MEMS acoustic sensing chip.

[0056] The deflation cavity 62 is communicated with the back cavity 111, so that during the operation of the MEMS acoustic sensing chip, the pressure balance between the inner cavity 6 and the outside can be adjusted through the deflation channel formed by the air vent 7 and the deflation cavity 62, reducing the influence of pressure changes on the vibration of the first diaphragm 2 and the second diaphragm 3, which helps to improve the stability and reliability of the MEMS acoustic sensing chip. Moreover, it can also maintain the air pressure balance inside and outside the MEMS acoustic sensing chip, reducing the high temperature or high pressure impact on the back cavity 111, thus realizing the protection of the MEMS acoustic sensing chip.

[0057] In addition, at least one of the first diaphragm 2 and the second diaphragm 3 is provided with a release hole 9. For example, the release hole 9 can be provided only on the first diaphragm 2, or only on the second diaphragm 3, or on both the first diaphragm 2 and the second diaphragm 3. The release hole 9 is communicated with the sealed cavity 61 to release the stress in the sealed cavity 61, avoiding the rupture or deformation of the first diaphragm 2 and the second diaphragm 3 caused by stress concentration, and also reducing the performance fluctuations caused by environmental changes and mechanical stress, providing a reliable guarantee for practical applications. Among them, the size and number of the release holes 9 can be adjusted according to actual design requirements and are usually formed by photolithography and etching processes.

[0058] In this MEMS acoustic sensing chip, an inner cavity 6 is formed between the first diaphragm 2 and the second diaphragm 3, and the back electrode plate 4 is located in the inner cavity 6. When a sound signal acts on the MEMS acoustic sensing chip, it will cause the vibration of the first diaphragm 2 and the second diaphragm 3.

[0059] Due to the existence of the inner cavity 6 and the specific positional relationship between the two diaphragms and the back plate 4, the minute vibrations of the first diaphragm 2 and the second diaphragm 3 can also change the capacitance value in the inner cavity 6. This capacitance change is closely related to the intensity and frequency of the sound signal, enabling this MEMS acoustic sensing chip to accurately convert the sound signal into an electrical signal, greatly improving the sensitivity and accuracy of acoustic sensing. Thus, the MEMS acoustic sensing chip has good response characteristics to sound signals of different frequencies. Whether it is a low-frequency deep sound or a high-frequency sharp sound, the MEMS acoustic sensing chip can effectively sense and convert them.

[0060] Optionally, the first diaphragm 2 is disposed on a side of the back plate 4 close to the substrate 1, and a first cavity is provided between the first diaphragm 2 and the substrate 1. The first cavity communicates the air vent hole 7 with the back cavity 111.

[0061] Optionally, the isolation structure 8 is an isolation ring, and both sides of the isolation ring are circumferentially sealed to the first diaphragm 2 and the second diaphragm 3 respectively.

[0062] Specifically, the setting of the isolation ring can conveniently divide the inner cavity 6 between the first diaphragm 2 and the second diaphragm 3 into a sealed cavity 61 and a venting cavity 62, and ensure the independence of the two functional regions of the sealed cavity 61 and the venting cavity 62, which helps to improve the sensing sensitivity of the MEMS acoustic sensing chip.

[0063] Among them, setting both sides of the isolation ring to be circumferentially sealed to the first diaphragm 2 and the second diaphragm 3 respectively can ensure the independence of the two functional regions of the sealed cavity 61 and the venting cavity 62. When the internal pressure of the MEMS acoustic sensing chip changes, the gas can flow between the back cavity 111 and the outside through the air vent hole 7 and the venting cavity 62 to achieve pressure balance and regulation. And the outside gas will not flow into the sealed cavity 61 from the air vent hole 7 and the venting cavity 62, which helps to ensure that the two diaphragms can vibrate under the action of the external sound pressure, and thus can improve the sensing sensitivity of the MEMS acoustic sensing chip.

[0064] Moreover, the sealed connection of the isolation ring can also prevent the outside gas and impurities from entering the inside of the MEMS acoustic sensing chip, so as to prevent the pollution and damage of components such as the two diaphragms and the back plate 4 by impurities, and thus can extend the service life of the MEMS acoustic sensing chip.

[0065] In addition, the isolation ring can also provide additional structural support for the first diaphragm 2 and the second diaphragm 3. When the first diaphragm 2 and the second diaphragm 3 are excited by a sound signal and vibrate, the presence of the isolation ring can limit the excessive deformation of the first diaphragm 2 and the second diaphragm 3, preventing the first diaphragm 2 and the second diaphragm 3 from colliding with or being damaged by other components due to excessive vibration amplitude, helping to maintain the shape and position stability of the first diaphragm 2 and the second diaphragm 3, and ensuring the performance consistency of the MEMS acoustic sensing chip during long-term operation.

[0066] In another embodiment, the isolation structure 8 may further include a plurality of sequentially connected isolation posts, and the plurality of isolation posts form a circumferential seal with the first diaphragm 2 and the second diaphragm 3.

[0067] Optionally, a connection structure 10 is further included, and the connection structure 10 is disposed in the sealed cavity 61, and the connection structure 10 is connected between the first diaphragm 2 and the second diaphragm 3.

[0068] Referring to Figure 2 , the connection structure 10 is connected between the first diaphragm 2 and the second diaphragm 3, so that the connection structure 10 can provide additional mechanical support for the two diaphragms to limit the excessive deformation of the two diaphragms, preventing the two diaphragms from colliding with or being damaged by other components due to excessive vibration amplitude. Moreover, the setting of the connection structure 10 can also enhance the interaction between the first diaphragm 2 and the second diaphragm 3, and further ensure the consistency of the vibration of the two diaphragms.

[0069] In the absence of the connection structure 10, the first diaphragm 2 and the second diaphragm 3 may generate relative displacement during vibration, resulting in a change in the structure of the inner cavity 6, thus affecting the sensing performance of the MEMS acoustic sensing chip. The connection function of the connection structure 10 enables the two diaphragms to maintain a relatively fixed positional relationship during vibration, reducing the generation of relative displacement, thereby ensuring the stability of the structure of the inner cavity 6, which is beneficial to improving the sensing accuracy and consistency of the MEMS acoustic sensing chip. Moreover, the constraint function of the connection structure 10 makes the vibration of the two diaphragms more linear, reducing the generation of non-linear noise. The connection structure 10 can also absorb the mechanical energy generated by the vibration of the two diaphragms, further reducing the noise level, which helps to improve the signal-to-noise ratio of the MEMS acoustic sensing chip.

[0070] Among them, by reasonably designing parameters such as the size, shape, and material of the connection structure 10, the natural frequencies of the two diaphragms can be adjusted, so that the MEMS acoustic sensing chip has good sensing performance in a wider frequency range.

[0071] In addition, in application scenarios such as mobile devices, the MEMS acoustic sensing chip may be subject to external impacts and vibrations. The setting of the connection structure 10 can also enhance the overall rigidity of the two diaphragms, enabling the MEMS acoustic sensing chip to better maintain its structural integrity when subjected to impacts and reducing the risk of damage to the MEMS acoustic sensing chip due to impacts.

[0072] Optionally, the connection structure 10 includes a plurality of independent connection posts, and the plurality of connection posts are spaced apart.

[0073] Referring to Figure 2 , according to actual requirements, a plurality of discrete connection posts can be provided between the first diaphragm 2 and the second diaphragm 3 to enhance the interaction between the first diaphragm 2 and the second diaphragm 3, and thus ensure the consistency of the vibrations of the two diaphragms while avoiding a reduction in the mechanical sensitivity of the MEMS acoustic sensing chip caused by an excessive number of connection posts.

[0074] Optionally, the distance from the connection post to the center of the first diaphragm 2 is not less than the radius of the first diaphragm 2.

[0075] Specifically, a plurality of connection posts are arranged in the area outside the radius of the first diaphragm 2 of , or a plurality of connection posts are arranged in the area outside the radius of the second diaphragm 3 of , so that the plurality of connection posts can be arranged in the low-stress areas of the two diaphragms, thereby enhancing the interaction between the first diaphragm 2 and the second diaphragm 3 and thus ensuring the consistency of the vibrations of the two diaphragms.

[0076] Optionally, the aperture of the air vent 7 is 5 μm - 20 μm.

[0077] Specifically, the aperture of the air vent 7 is set between 5 μm and 20 μm to be able to discharge the gas in the inner cavity 6 to the outside through the air vent 7, avoid the deformation or damage of the first diaphragm 2 and the second diaphragm 3 caused by gas expansion or contraction during use, contribute to improving the reliability and stability of the MEMS acoustic sensing chip, and at the same time ensure that the MEMS acoustic sensing chip has good acoustic performance.

[0078] Optionally, the aperture of the air vent 7 is 12 μm - 16 μm, which can facilitate the formation of the air vent 7 on the first diaphragm 2 and the second diaphragm 3, reduce the processing difficulty, and ensure that the MEMS acoustic sensing chip has good acoustic performance.

[0079] Optionally, the aperture of the release hole 9 is 0.15 μm - 0.5 μm.

[0080] Specifically, the diameter of the release hole 9 is set to be 0.15 - 0.5 μm, which is much smaller than the size of the air vent hole 7. The size of environmental dust particles is about 1 μm - 5 μm, that is, the diameter of the release hole 9 in the present application is smaller than the size of environmental dust particles. Therefore, the MEMS acoustic sensing chip provided in the present application is not sensitive to environmental dust particles and has good dust and water protection capabilities.

[0081] Optionally, the aperture of the release hole 9 is 0.3 μm - 0.5 μm, which can facilitate the formation of the release hole 9 on the first diaphragm 2 and / or the second diaphragm 3 and reduce the processing difficulty. As Figures 3 to 5 shown, when the aperture of the release hole 9 is 0.3 μm - 0.5 μm, that is, the radius of the release hole 9 is 0.15 μm - 0.25 μm, the formed MEMS acoustic sensing chip has better acoustic performance.

[0082] Optionally, on the first diaphragm 2 and / or the second diaphragm 3, the distance between adjacent release holes 9 is 10 μm - 30 μm.

[0083] Specifically, controlling the distance between two adjacent release holes 9 within 10 μm - 30 μm can correspondingly reduce the concentration of the hydrofluoric acid-based etching solution used in the etching process and reduce the etching time. In this way, the high mechanical reliability of the first diaphragm 2, the back plate 4, and the second diaphragm 3 can be ensured, and the damage to the first diaphragm 2, the back plate 4, and the second diaphragm 3 caused by the long-term etching of the high-concentration etching solution can be reduced, thereby ensuring that the MEMS acoustic sensing chip has good acoustic performance.

[0084] Optionally, referring to Figure 1 and Figure 2 , there is a first gap between the first diaphragm 2 and the back plate 4, and the two form a first capacitor structure. There is a second gap between the second diaphragm 3 and the back plate 4, and the two form a second capacitor structure.

[0085] Optionally, a plurality of through holes 41 are formed on the back plate 4, and the plurality of through holes 41 communicate the first gap with the second gap;

[0086] When the second diaphragm 3 is subjected to sound pressure and moves towards the first diaphragm 2, the air in the sealed cavity 61 flows. The air can sequentially pass through the second gap, the through hole 41, and the first gap and then generate pressure on the first diaphragm 2, causing the first diaphragm 2 and the second diaphragm 3 to vibrate synchronously.

[0087] The above is the working principle during forward sound transmission. At this time, the second diaphragm 3 can be set to be closed and the first diaphragm 2 has the release hole 9, which can improve the sensitivity of the MEMS sound sensing chip.

[0088] When using a back-incoming sound, the sound enters the back cavity 111 from the back cavity 111 on the substrate 1. The first diaphragm 2 moves upward under the action of the sound pressure. The air in the sealing cavity 61 is pressured to flow, and after passing through the first gap, the through hole 41 provided on the back plate 4, and the second gap in sequence, the sound pressure is transmitted to the second diaphragm 3 to cause the second diaphragm 3 to move upward. During this process, the first diaphragm 2 and the second diaphragm 3 are connected to move together through the air flow in the sealing cavity 61. The back plate 4 remains stationary due to its high mechanical strength, and the MEMS sound sensing chip forms a differential capacitive microphone, which has characteristics such as low THD (Total Harmonic Distortion) and high AOP (Acoustic Overload Point).

[0089] Optionally, at least one of the first diaphragm 2 and the second diaphragm 3 is provided with a conductive portion. The support structure 5 is provided with a first metal through hole in the thickness direction, and the conductive portion leads out a first electrical connection portion 11 through the first metal through hole.

[0090] Optionally, the back plate 4 includes a conductive layer and insulating layers respectively provided on both sides of the conductive layer;

[0091] The support structure 5 is provided with a second metal through hole in the thickness direction, and the conductive layer leads out a second electrical connection portion 12 through the second metal through hole.

[0092] Referring to Figure 1 and Figure 2 , conductive portions are provided on both the first diaphragm 2 and the second diaphragm 3. A third electrical connection portion is provided on the surface of the second diaphragm 3, and the third electrical connection portion is electrically connected to the conductive portion on the surface of the second diaphragm 3. The support structure 5 is provided with a first metal through hole in the thickness direction, and the conductive portion on the first diaphragm 2 can be led out through the metal through hole to form a first electrical connection portion 11.

[0093] The back plate 4 includes a conductive layer and insulating layers respectively provided on both sides of the conductive layer. The support structure 5 is provided with a second metal through hole extending to the conductive layer in the thickness direction, and the conductive layer is led out through the second metal through hole to form a second electrical connection portion 12. In this way, when under the action of an external sound pressure, the capacitance value change of the differential capacitive microphone can be detected through the first electrical connection portion 11, the second electrical connection portion 12, and the third electrical connection portion, and further the conversion of the sound signal to the electrical signal can be realized.

[0094] This application also discloses a microphone, including:

[0095] A packaging structure;

[0096] And the above-mentioned MEMS acoustic sensing chip, and the MEMS acoustic sensing chip is disposed within the packaging structure.

[0097] The present application also discloses an electronic device, including the microphone described above. Among them, the electronic device can be a mobile phone, a tablet, a head-mounted display device, etc.

[0098] Although some specific embodiments of the present application have been described in detail by way of examples, those skilled in the art should understand that the above examples are only for illustration and not for limiting the scope of the present application. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A MEMS acoustic sensing chip, characterized in that, Comprising: A substrate (1), the substrate (1) being provided with a back cavity (111); A first diaphragm (2), a second diaphragm (3), a back plate (4) and a support structure (5), the first diaphragm (2), the second diaphragm (3) and the back plate (4) are arranged on one side of the substrate (1) through the support structure (5), and an inner cavity (6) is formed between the first diaphragm (2) and the second diaphragm (3), and the back plate (4) is located in the inner cavity (6); An air vent hole (7) and an isolation structure (8), both the first diaphragm (2) and the second diaphragm (3) include a suspended area, the air vent hole (7) penetrates through the suspended areas of the first diaphragm (2) and the second diaphragm (3), and the isolation structure (8) surrounds the air vent hole (7) and divides the inner cavity (6) into a sealed cavity (61) and a venting cavity (62), and the venting cavity (62) is communicated with the back cavity (111); At least one of the first diaphragm (2) and the second diaphragm (3) is provided with a release hole (9), and the release hole (9) is communicated with the sealed cavity (61).

2. The MEMS acoustic sensing chip according to claim 1, wherein The isolation structure (8) is an isolation ring, and both sides of the isolation ring are circumferentially sealed with the first diaphragm (2) and the second diaphragm (3) respectively.

3. The MEMS acoustic sensing chip according to claim 1, characterized in that, It further includes a connection structure (10), the connection structure (10) is arranged in the sealed cavity (61), and the connection structure (10) is connected between the first diaphragm (2) and the second diaphragm (3).

4. The MEMS acoustic sensing chip according to claim 3, wherein The connection structure (10) includes a plurality of independent connection posts, and the plurality of connection posts are distributed at intervals.

5. The MEMS acoustic sensing chip according to claim 4, wherein, The distance from the connecting column to the center of the first diaphragm (2) is not less than the radius of the first diaphragm (2).

6. The MEMS acoustic sensing chip according to claim 1, wherein, The aperture of the air vent hole (7) is 5μm - 20μm.

7. The MEMS acoustic sensing chip according to claim 6, wherein, The aperture of the air vent hole (7) is 12μm - 16μm.

8. The MEMS acoustic sensing chip according to claim 1, wherein The aperture of the release hole (9) is 0.15μm - 0.5μm.

9. The MEMS acoustic sensing chip according to claim 8, wherein The aperture of the release hole (9) is 0.3μm - 0.5μm.

10. The MEMS acoustic sensing chip according to claim 1, characterized in that, On the first diaphragm (2) and / or the second diaphragm (3), the distance between adjacent release holes (9) is 10μm - 30μm.

11. The MEMS acoustic sensing chip according to claim 1, wherein There is a first gap between the first diaphragm (2) and the back plate (4) and the two form a first capacitor structure, and there is a second gap between the second diaphragm (3) and the back plate (4) and the two form a second capacitor structure.

12. The MEMS acoustic sensing chip according to claim 11, wherein A plurality of through holes (41) are formed on the back plate (4), and the plurality of through holes (41) communicate the first gap with the second gap; When the second diaphragm (3) moves towards the first diaphragm (2) under the action of sound pressure, the air in the sealed cavity (61) flows, and the air can sequentially pass through the second gap, the through hole (41) and the first gap to generate pressure on the first diaphragm (2), so that the first diaphragm (2) and the second diaphragm (3) vibrate synchronously.

13. The MEMS acoustic sensing chip according to claim 1, characterized in that, At least one of the first diaphragm (2) and the second diaphragm (3) is provided with a conductive part, and a first metal through hole is provided on the support structure (5) along the thickness direction, and the conductive part leads out a first electrical connection part (11) through the first metal through hole.

14. The MEMS acoustic sensing chip according to claim 1, characterized in that, The back plate (4) includes a conductive layer and insulating layers respectively disposed on both sides of the conductive layer; The support structure (5) is provided with second metal through holes in the thickness direction, and a second electrical connection portion (12) is led out from the conductive layer through the second metal through holes.

15. A microphone, characterized in that, Comprising: A packaging structure; And the MEMS acoustic sensing chip according to any one of claims 1-14, wherein the MEMS acoustic sensing chip is disposed within the packaging structure.

16. An electronic device, characterized in that, Including the microphone according to claim 15.

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