MEMS Microphone

Abstract

The present invention discloses a micro-electro-mechanical system (MEMS) microphone. The MEMS microphone includes a substrate, a back plate, an insulating layer and a diaphragm. The substrate has an opening. The back plate is arranged on one side of the substrate and has a protrusion protruding toward the substrate. The diaphragm is movably arranged between the substrate and the back plate and is spaced from the back plate by a spacing distance. The protrusion is configured to limit deformation of the diaphragm when air flows through the opening.

Description

Technical Field

[0001] The present invention relates to an acoustic transducer, and more particularly to a micro-electro-mechanical system (MEMS) microphone. Background Art

[0002] The current trend is to manufacture thin, small, light and high-performance electronic devices, including microphones. Microphones can be used to receive sound waves and convert sound signals into electrical signals. Microphones are widely used in daily life and installed in electronic products such as telephones, mobile phones and voice recorders. In a capacitive microphone, the change in acoustic pressure (i.e., the local pressure deviation of the ambient atmospheric pressure caused by the sound wave) causes the diaphragm to deform accordingly, thereby causing a change in capacitance. Therefore, the change in sound pressure of the sound wave can be obtained by measuring the voltage change caused by the change in capacitance.

[0003] Unlike conventional electret condenser microphones (ECM), the mechanical and electronic components of a microelectromechanical system (MEMS) microphone can be integrated on a semiconductor material using integrated circuit (IC) technology to create a miniature microphone. MEMS microphones have advantages such as small size, light weight, and low power consumption, and have therefore become the mainstream of miniature microphones.

[0004] Although existing MEMS microphones are sufficient to meet general usage requirements, they have not yet fully met other aspects. For example, the compatible sound pressure range (i.e., dynamic range) of detectable sound waves in MEMS microphones still needs to be improved. The dynamic range is related to the maximum compatible sound pressure (i.e., acoustic overload point, hereinafter referred to as "AOP"), and the maximum compatible sound pressure is determined by the harmonic distortion rate (total harmonic distortion, hereinafter referred to as "THD") of the MEMS microphone. On the other hand, if the diaphragm has a lower elastic modulus (i.e., lower rigidity), it can be used to sense smaller sound pressures (i.e., has higher sensitivity), but the THD of the vibration mode will be sacrificed (i.e., the AOP will be reduced). Therefore, it is impossible to simultaneously achieve the high AOP of the MEMS microphone, high air pressure reliability, and enhance the sensitivity of the MEMS microphone at low frequencies (i.e., it is impossible to achieve a wider dynamic range). Summary of the invention

[0005] In view of the above problems, an object of the present invention is to provide a MEMS microphone which can achieve high AOP and high air pressure reliability.

[0006] One embodiment of the present invention provides a micro-electromechanical system (MEMS) microphone. The MEMS microphone includes a substrate, a back plate, an insulating layer, and a diaphragm. The substrate has an opening. The back plate is disposed on one side of the substrate and has a protrusion protruding toward the substrate. The diaphragm is movably disposed between the substrate and the back plate and is spaced from the back plate by a spacing distance. The protrusion is configured to limit deformation of the diaphragm when air flows through the opening.

[0007] In some embodiments, the height of the protrusion is greater than one third of the separation distance.

[0008] In some embodiments, the thickness of the back plate is greater than the height of the protrusions.

[0009] In some embodiments, the MEMS microphone further includes an island structure located on the upper surface of the vibration mode.

[0010] In some embodiments, the thickness of the island structure is equal to or greater than the thickness of the mode.

[0011] In some embodiments, the island structure includes a plurality of island blocks aligned with respective protrusions.

[0012] In some embodiments, the island structure spans more than one protrusion when viewed from a direction perpendicular to the diaphragm.

[0013] In some embodiments, the diaphragm extends across the opening of the substrate.

[0014] In some embodiments, the substrate, the back plate and the diaphragm are connected via a dielectric layer.

[0015] In some embodiments, the MEMS microphone further includes a center post connected between the back plate and the diaphragm.

[0016] In some embodiments, the MEMS microphone further includes an island structure located on the upper surface of the diaphragm, and the island structure is symmetrically arranged around the central column.

[0017] In some embodiments, the island structure includes a plurality of island blocks aligned with each protrusion, and each island block spans more than one protrusion when viewed from a direction perpendicular to the diaphragm.

[0018] In some embodiments, a plurality of slots are defined in an annular region of the diaphragm and are spaced apart from one another.

[0019] In some embodiments, a plurality of vents are defined in the diaphragm and are spaced apart from one another.

[0020] In some embodiments, the MEMS microphone further includes a dynamic valve layer disposed between the substrate and the back plate, wherein the dynamic valve layer includes a flap portion that covers at least one vent of the diaphragm when viewed from a direction perpendicular to the diaphragm, and the flap portion deforms when air flows through the vent. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The following will be described in detail with reference to the accompanying drawings. It should be noted that, in accordance with standard practice in the industry, various features are not drawn to scale and are only used for illustration. In fact, the size of the components can be arbitrarily enlarged or reduced to clearly show the features of the embodiments of the present invention.

[0022] Figure 1 For some embodiments of the present invention, a cross-sectional view of a micro-electromechanical system microphone is shown;

[0023] Figure 2 For other embodiments of the present invention, a cross-sectional view of a micro-electromechanical system microphone is shown;

[0024] Figure 3A and Figure 3B For some embodiments of the present invention, a top view of a MEMS microphone is shown;

[0025] Figure 4A to Figure 4D For some other embodiments of the present invention, a cross-sectional view of a micro-electromechanical system microphone is shown;

[0026] Figure 5 For still other embodiments of the present invention, cross-sectional views of MEMS microphones are shown.

[0027] Explanation of symbols

[0028] 10: MEMS structure

[0029] 11:Substrate

[0030] 11A, 12A: Opening

[0031] 12: Dielectric layer

[0032] 13: Back panel

[0033] 131: Conductive layer

[0034] 132: Insulation layer

[0035] 1321: first insulating layer

[0036] 1322: Second insulation layer

[0037] 134: Protrusion

[0038] 13A: Sound hole

[0039] 14: Diaphragm

[0040] 141: Ventilation hole

[0041] 142: Slot

[0042] 15: Electrode layer

[0043] 16: Isolation structure (island structure)

[0044] 161: Island Block

[0045] 17:Central column

[0046] 30: Enlarged image

[0047] DV: Dynamic Valve Layer

[0048] DV1: flap

[0049] G: Air Gap

[0050] M:MEMS microphone

[0051] S: spacing distance

[0052] S1: First side

[0053] S2: Second side DETAILED DESCRIPTION

[0054] The following disclosure provides many different embodiments or examples to show different components of the embodiments of the present invention. The following will disclose specific examples of the components of this specification and their arrangement to simplify the description of the present invention. Of course, these specific examples are not intended to limit the present invention. For example, if the following invention content of this specification describes forming a first component on or above a second component, it means that it includes an embodiment in which the first and second components formed are in direct contact, and also includes an embodiment in which an additional component can be formed between the above-mentioned first and second components, and the first and second components are not in direct contact. In addition, the various examples in the description of the present invention may use repeated reference symbols and / or words. The purpose of these repeated symbols or words is to simplify and clarify, and is not used to limit the relationship between the various embodiments and / or the configurations.

[0055] Furthermore, in order to conveniently describe the relationship between one element or component and another element or component in the drawings, spatially relative terms such as "under", "below", "lower", "above", "upper" and the like may be used. In addition to the orientations shown in the drawings, spatially relative terms also cover different orientations of the device in use or operation. When the device is turned to a different orientation (for example, rotated 90 degrees or other orientations), the spatially relative adjectives used therein will also be interpreted according to the orientation after the rotation.

[0056] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meanings as commonly understood by those skilled in the art to which the present invention belongs. It is understood that these terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning consistent with the background or context of the relevant technology and the present invention, and should not be interpreted in an idealized or overly formal manner unless specifically defined in the embodiments of the present invention.

[0057] In the present invention, according to various illustrative embodiments, a micro-electromechanical system (MEMS) microphone for detecting sound waves and converting sound waves (acoustic signals) into electrical signals is provided. Specifically, by configuring a protrusion on the back plate to limit the deformation of the diaphragm when the air flows through the opening, the micro-electromechanical system microphone in various embodiments can prevent the diaphragm from breaking. The various features described below can simultaneously achieve high reliability of air pressure and improve sensitivity at low frequencies. In this way, the micro-electromechanical system microphone of the present invention can achieve high reliability of air pressure. Changes in some embodiments are also discussed below. In the various figures and illustrative embodiments, the same reference symbols are used to represent the same elements.

[0058] Figure 1 FIG. 1 is a cross-sectional view of a MEMS microphone M according to some embodiments of the present invention. It should be understood that for the sake of clarity, Figure 1 The MEMS microphone M depicted in the figure is simplified to better understand the inventive concept of the present invention. Other additional features may be added to the MEMS microphone M, and some of the features described below may also be replaced or deleted in other embodiments of the MEMS microphone M. Figure 1 As shown, the MEMS microphone M is a capacitive microphone and includes a MEMS structure 10 . The MEMS structure 10 includes a substrate 11 , a dielectric layer 12 , a back plate 13 , a diaphragm 14 and an electrode layer 15 .

[0059] The substrate 11 is configured to support the dielectric layer 12, the back plate 13, the diaphragm 14 and the electrode layer 15 on one side thereof. The substrate 11 may have an opening 11A that allows sound waves (e.g., such as a sound wave) received by the MEMS microphone M to pass through the substrate 11. Figure 1) through and / or into the MEMS structure 10. The substrate 11 may be made of silicon or similar materials.

[0060] The dielectric layer 12 is disposed between the substrate 11 and the diaphragm 14, and between the diaphragm 14 and the back plate 13, so that partial isolation can be provided between the substrate 11, the diaphragm 14, and the back plate 13. In addition, the dielectric layer 12 is disposed around the back plate 13 and the diaphragm 14, so that the back plate 13 and the diaphragm 14 can be supported by the dielectric layer 12 at their edges. Therefore, the substrate 11, the back plate 13, and the diaphragm 14 are connected through the dielectric layer 12. Furthermore, the dielectric layer 12 may have an opening 12A corresponding to the opening 11A of the substrate 11 to allow sound waves to pass through the diaphragm 14 and the back plate 13 and then leave the MEMS structure 10. The dielectric layer 12 may be made of silicon oxide or a similar material.

[0061] The back plate 13 is a fixed element disposed on one side of the substrate 11. The back plate 13 may have sufficient stiffness so that it does not bend or move when sound waves pass through the back plate 13. In some embodiments, the back plate 13 is a hard perforated element including a plurality of acoustic holes 13A, each of which passes through the back plate 13. Figure 1 As shown, the sound hole 13A is configured to allow sound waves to pass through.

[0062] In some embodiments, Figure 1 As shown, the back plate 13 includes a conductive layer 131 and an insulating layer 132 covering the conductive layer 131 for protection. The conductive layer 131 and the insulating layer 132 are respectively located on a first side S1 and a second side S2 of the back plate 13, the first side S1 faces the diaphragm 14, and the second side S2 is opposite to the first side S1. The conductive layer 131 can be made of polysilicon or a similar material, and the insulating layer 132 can be made of silicon nitride or a similar material.

[0063] In some embodiments, the MEMS structure 10 is electrically connected to a circuit (not shown) through a plurality of electrode pads of the electrode layer 15, and the electrode layer 15 is disposed on the back plate 13 and electrically connected to the conductive layer 131 and the diaphragm 14. In some embodiments, the electrode layer 15 includes copper, silver, gold, aluminum, or alloys thereof.

[0064] The diaphragm 14 can move or displace relative to the back plate 13, wherein the diaphragm 14 is movably disposed between the substrate 11 and the back plate 13 and is spaced apart from the back plate by a spacing distance S. Figure 1 As shown, the diaphragm 14 may extend across the opening 11A of the substrate 11. The diaphragm 14 is configured to sense sound waves received by the MEMS microphone M.

[0065] The displacement change of the diaphragm 14 relative to the back plate 13 causes the capacitance change between the diaphragm 14 and the back plate 13. Then, the capacitance change is converted into an electrical signal by a circuit connected to the diaphragm 14 and the back plate 13, and the electrical signal is transmitted from the MEMS microphone M through the electrode layer 15.

[0066] On the other hand, in order to increase the sensitivity of the diaphragm 14 , a plurality of vent holes 141 are provided in the diaphragm 14 , and the vent holes 141 function as springs in the diaphragm 14 to reduce the rigidity of the diaphragm 14 . Figure 3A FIG. 1 is a top view of a diaphragm 14 having a vent hole 141 according to some embodiments of the present invention. In some alternative embodiments, there may be more than two vent holes 141. With this structural feature, a high sensitivity of the micro-electromechanical system microphone M can be achieved. In addition, the vent holes 141 in the diaphragm 14 are also configured to relieve the high air pressure on the diaphragm 14.

[0067] In some embodiments, Figure 1 As shown, a plurality of protrusions 134 protruding toward the substrate 11 are provided or formed on the first side S1 of the back plate 13, and an air gap G is formed between the diaphragm 14 and each protrusion 134. In addition, the air gaps G between the diaphragm 14 and each protrusion 134 may have the same size (but not limited thereto).

[0068] Please continue reading Figure 1 In order to form the protrusion 134, the insulating layer 132 of the back plate 13 may include a first insulating layer 1321 and a second insulating layer 1322 stacked on the first insulating layer 1321. Figure 1 As shown, the protrusion 134 may be formed to protrude from the first insulating layer. In some embodiments, the first insulating layer 1321 and the second insulating layer 1322 may include the same material or different materials.

[0069] In the present invention, the protrusion 134 is configured to restrict deformation of the diaphragm 14 when air flows through the opening 11A, and the MEMS microphone M can prevent the diaphragm 14 from breaking. Therefore, the MEMS microphone of the present invention can achieve high reliability of air pressure.

[0070] In some embodiments, for example, the height of the protrusion 134 is greater than one-third of the spacing distance S (i.e., the air gap G is less than two-thirds of the spacing distance S). Therefore, the elongated protrusion 134 can contact the diaphragm 14 when the air flows through the opening 11A, which further limits the deformation of the diaphragm 14 and prevents the diaphragm 14 from breaking.

[0071] In order to further limit any deformation of the diaphragm 14, in some embodiments, the back plate 13 is configured to prevent it from deforming under air pressure. For example, the toughness, stress, rigidity, or other properties of the back plate 13 are adjusted to limit the deformation of the back plate 13 and thus the deformation of the diaphragm 14 when air flows through the opening 11A. In some embodiments, the thickness of the back plate 13 is configured to be greater than the height of the protrusion 134 to increase the rigidity of the back plate 13. Therefore, the reinforced back plate 13 can limit the deformation of the diaphragm 14 and prevent the diaphragm 14 from breaking when air flows through the opening 11A.

[0072] Figure 2 FIG. 2 is a cross-sectional view of a micro-electromechanical system microphone M according to another embodiment of the present invention. Figure 2 The MEMS microphone M may further include a central column 17 connected between the back plate 13 and the diaphragm 14, thereby supporting the central area of ​​the diaphragm 14 and increasing the AOP of the diaphragm 14. In addition, the protrusion 134 surrounding the central column 17 may limit the deformation of the diaphragm 14 and prevent the diaphragm 14 from breaking when air flows through the opening 11A.

[0073] On the other hand, in order to increase the sensitivity of the diaphragm 14 , a plurality of grooves 142 may be provided in the diaphragm 14 . Figure 3B FIG. 1 is a top view of a diaphragm 14 having a groove 142 according to some embodiments of the present invention. Figure 3A Compared with the vent holes 141 in the vibrating mold 14, the plurality of grooves 142 are openings having a more elongated and curved shape. In some embodiments, the plurality of grooves 142 in the vibrating mold 14 are close to the dielectric layer 12 (for example, between the conductive layer 131 of the back plate 13 and the dielectric layer 12) and are arranged in concentric circles. Figure 3B As shown in the enlarged view 30 of the diaphragm 14 in FIG. 30 , the plurality of grooves 142 of adjacent circles can be arranged alternately, so that the plurality of grooves 142 can be used as springs in the diaphragm 14 to reduce the rigidity of the diaphragm 14. In some alternative embodiments, the number of concentric circles formed by the plurality of grooves 142 can be more than two. Through this structural feature, the high sensitivity of the micro-electromechanical system microphone M can be achieved.

[0074] Figure 4A to Figure 4D 2 is a cross-sectional view of a MEMS microphone according to some other embodiments of the present invention. In the following embodiments, the MEMS structure 10 further includes an isolation structure 16 (hereinafter also referred to as an island structure 16) located on the upper surface of the vibration mold 14. Figure 4A to Figure 4DAs shown, the thickness of the island structure 16 can be equal to or greater than the thickness of the diaphragm. It should be noted that in the presence of the isolation structure 16, the height of the protrusion can be shorter than in the absence of any isolation structure. By forming the isolation structure 16 on the upper surface of the diaphragm 14, the isolation structure 16 can contact the back plate 13 (in particular, contact the protrusion 134 of the back plate 13) when the air flows through the opening 11A, and the isolation structure 16 further limits the deformation of the diaphragm 14 and prevents the diaphragm 14 from breaking.

[0075] like Figure 4A As shown, the island structure 16 may include a plurality of island blocks 161 aligned with the respective protrusions 134. Figure 4B As shown, the island structure 16 may also span more than one protrusion 134 when viewed from a direction perpendicular to the diaphragm 14 .

[0076] Reference Figure 4C and Figure 4D The MEMS structure 10 may also include both the island structure 16 and the central column 17 between the back plate 13 and the diaphragm 14. In some embodiments, as Figure 4C and Figure 4D As shown, the island structure 16 is symmetrically arranged around the central column 17. Therefore, the protrusion 134, the island structure 16, and the central column 17 can simultaneously limit the deformation of the diaphragm 14 when the air flows through the opening 11A, and the central column 17 can also support the central area of ​​the diaphragm 14 and increase the AOP of the diaphragm 14.

[0077] Similar to the embodiment without the central column 17, Figure 4C As shown, the symmetrically arranged island structure 16 may include a plurality of island blocks 161 aligned with each protrusion 134. Figure 4D As shown, when viewed from a direction perpendicular to the diaphragm 14 , the symmetrically arranged island structures 16 may also span more than one protrusion 134 .

[0078] Figure 5 1 is a cross-sectional view of a MEMS microphone M according to yet another embodiment of the present invention. In some embodiments, the MEMS structure 10 further includes a dynamic valve layer DV embedded in the dielectric layer 12 and having at least one flap portion DV1, and the flap portion DV1 protrudes from the dielectric layer 12 and is spaced apart from the diaphragm 14. When viewed from a direction perpendicular to the diaphragm 14, the flap portion DV1 may cover at least one vent hole 141 (or a groove) of the diaphragm 14. When the diaphragm 14 is affected by the sound pressure from the ambient sound wave, the air may pass through the opening portion 11A and the vent hole 141 in sequence, as shown in FIG. Figure 5 As shown by the arrow in , the flap portion DV1 of the dynamic valve layer DV is deformed to relieve the air pressure and bear the wind load on the diaphragm 14. Figure 5As shown, although the dynamic valve layer DV is disposed between the diaphragm 14 and the back plate 13, the present invention is not limited thereto. In some other embodiments, the dynamic valve layer DV is disposed between the diaphragm 14 and the substrate 11. Therefore, air can pass through the sound hole 13A and the vent hole 141 in sequence, so that the flap portion DV1 of the dynamic valve layer DV is deformed to reduce the air pressure and bear the wind load on the diaphragm 14.

[0079] In summary, according to various exemplary embodiments, a micro-electromechanical system (MEMS) microphone for detecting sound waves and converting sound waves (acoustic signals) into electrical signals is provided. Specifically, by configuring a protrusion on the back plate to limit the deformation of the diaphragm when air flows through the opening, the MEMS microphone in various embodiments can prevent the diaphragm from breaking. In this way, the MEMS microphone of the present invention can achieve high reliability of air pressure.

[0080] The features of several embodiments are summarized above so that those skilled in the art can more easily understand the concepts of the embodiments of the present invention. Those skilled in the art should understand that other manufacturing processes and structures can be easily designed or modified based on the embodiments of the present invention to achieve the same purposes and / or advantages as the embodiments introduced herein. Those skilled in the art should also understand that such equivalent manufacturing processes and structures do not deviate from the spirit and scope of the present invention, and can be variously changed, replaced and substituted without violating the spirit and scope of the attached claims.

Claims

1. A micro-electromechanical system microphone, comprising: A substrate having an opening; A back plate, disposed on one side of the substrate and having a plurality of protrusions protruding toward the substrate; as well as The diaphragm is movably disposed between the substrate and the back plate and is spaced apart from the back plate by a spacing distance. wherein the protrusion is configured to limit deformation of the diaphragm when air flows through the opening, A plurality of vent holes are defined in the diaphragm and are separated from each other. The micro-electromechanical system microphone further comprises a dynamic valve layer located between the substrate and the back plate, the dynamic valve layer comprises a flap portion, when viewed from a direction perpendicular to the diaphragm, the flap portion covers at least one vent hole of the diaphragm, and the flap portion is deformed when air flows through the vent hole, wherein the micro-electromechanical system microphone further comprises a central column connected between the back plate and the diaphragm, and an island structure located on the upper surface of the diaphragm, and the island structure is symmetrically arranged around the central column, The island structure includes a plurality of island blocks aligned with each of the protrusions, and when viewed from a direction perpendicular to the diaphragm, each of the island blocks spans across more than one protrusion. 2 . The MEMS microphone as claimed in claim 1 , wherein a height of the protrusion is greater than one third of the spacing distance. 3 . The MEMS microphone as claimed in claim 1 , wherein a thickness of the back plate is greater than a height of the protrusion. 4 . The MEMS microphone as claimed in claim 1 , wherein a thickness of the island structure is equal to or greater than a thickness of the diaphragm. The MEMS microphone as claimed in claim 1 , wherein the diaphragm extends across the opening of the substrate. 6 . The MEMS microphone as claimed in claim 1 , wherein the substrate, the back plate and the diaphragm are connected via a dielectric layer. 7 . The MEMS microphone as claimed in claim 1 , wherein a plurality of grooves are defined in the annular region of the diaphragm and are separated from each other.

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