MEMS microphone and method of manufacturing the same

Abstract

A MEMS microphone and a manufacturing method thereof are disclosed. The MEMS microphone comprises: a substrate; a diaphragm and a back plate electrode located on a first surface of the substrate, the diaphragm and the back plate electrode are separated from each other, and the first surface of the diaphragm and the first surface of the back plate electrode are opposite to each other; and a sound cavity penetrating the substrate to reach the second surface of the diaphragm, wherein the back plate electrode is located above the movable area of ​​the diaphragm, and the area of ​​the back plate electrode is smaller than the area of ​​the movable area of ​​the diaphragm. The MEMS microphone uses the pattern of the back plate electrode to define the effective capacitance area, so as to suppress the adverse effects of parasitic capacitance and process fluctuations on the device capability, and to improve the working sensitivity of the device.

Description

Technical Field

[0001] The present invention belongs to the technical field of micro-microphones, and more specifically, relates to a MEMS microphone and a manufacturing method thereof. Background Art

[0002] MEMS microphones are MEMS (Micro-Electro-Mechanical System) devices manufactured using micromachining technology. Due to the advantages of small size, high sensitivity, and good compatibility with existing semiconductor technology, MEMS microphones are increasingly used in mobile terminals such as mobile phones. The structure of a MEMS microphone includes a diaphragm and a back plate electrode facing each other, both of which are connected to corresponding electrodes via leads. An isolation layer is also included between the diaphragm and the back plate electrode. The isolation layer is used to separate the diaphragm and the back plate electrode, and a cavity is formed therein to provide the vibration space required by the diaphragm.

[0003] With the development of micro-machining technology, MEMS microphones are becoming more and more miniaturized, wherein the spacing between the diaphragm and the back plate electrode is, for example, less than 1.5 microns, and the process requirements in the manufacturing and application of MEMS microphones are becoming increasingly higher. The structural defects introduced by the process deviation not only affect the yield of the microphone, but also cause the performance of the MEMS microphone to deteriorate sharply in the application environment. For example, in the manufacturing process of the MEMS microphone, etching is used to form a cavity between the diaphragm and the back plate electrode. The process deviation of this etching step affects the effective area of ​​the MEMS microphone, causing the performance of the MEMS microphone to fluctuate. In addition, the pattern of the existing MEMS microphone is complex, and multiple aligned lithography is used to form the pattern. The process deviation of the patterning step may also cause the performance of the MEMS microphone to fluctuate. In addition, the capacitance change caused by the vibration of the diaphragm of the MEMS microphone according to the air vibration generated by the sound signal not only includes the effective part, but also the invalid part, and the invalid capacitance component will produce unfavorable parasitic capacitance. It is expected that the structure of the MEMS microphone will be further improved to suppress the parasitic capacitance and suppress the adverse effects of the process deviation of etching and lithography on the device performance, so as to improve the yield and device reliability. Summary of the invention

[0004] The object of the present invention is to provide a MEMS microphone and a manufacturing method thereof, wherein the pattern of the back plate electrode is used to define the effective capacitance area, so as to suppress the adverse effects of parasitic capacitance and process fluctuations on the device capability and improve the working sensitivity of the device.

[0005] According to one aspect of the present application, a MEMS microphone is provided, comprising: a substrate; a diaphragm and a back plate electrode located on a first surface of the substrate, the diaphragm and the back plate electrode being separated from each other, and the first surface of the diaphragm and the first surface of the back plate electrode being opposite to each other; and an acoustic cavity penetrating the substrate to reach the second surface of the diaphragm, wherein the back plate electrode is located above a movable region of the diaphragm, and an area of ​​the back plate electrode is smaller than an area of ​​the movable region of the diaphragm.

[0006] Preferably, the area of ​​the back plate electrode is less than or equal to the minimum cross-sectional area of ​​the acoustic cavity.

[0007] Preferably, the area of ​​the back plate electrode is 70% to 100% of the movable area.

[0008] Preferably, the radius of the minimum cross-section of the acoustic cavity is 385 microns to 415 microns.

[0009] Preferably, the distance between the back plate electrode and the diaphragm is 1 micron to 5 microns.

[0010] Preferably, the diaphragm includes a middle portion and a peripheral portion, and a spring structure connecting the middle portion and the peripheral portion, and the movable region of the diaphragm includes a region of the middle portion and a region of the spring structure.

[0011] Preferably, the sensitivity of the microphone for: ,in, represents the capacitance change caused by the vibration of the diaphragm, represents the effective capacitance component of the effective deformation of the middle part of the diaphragm, Invalid capacitance components indicating that the region of the spring structure of the diaphragm undergoes invalid deformation or the region of the peripheral portion of the diaphragm does not undergo invalid deformation, represents the load capacitance of the MEMS microphone, Indicates the bias voltage.

[0012] Preferably, the bias voltage for: , wherein VDD represents the voltage applied between the diaphragm and the back plate electrode, represents the voltage of the reference plate of the MEMS microphone.

[0013] Preferably, the spring structure of the diaphragm is a concentric annular fold portion, or a spiral fold portion.

[0014] Preferably, the diaphragm further comprises reinforcing ribs located at a peripheral portion of the diaphragm.

[0015] Preferably, the reinforcing ribs of the membrane are radial strip beams or parapet structures located at the peripheral portion.

[0016] Preferably, the parapet structure includes a plurality of annular sections, and the annular sections are in the shape of rectangular waves.

[0017] Preferably, the reinforcing rib comprises a plurality of annular sections, and the shape of the corners of the annular sections is an arc or a trapezoidal wave or a sine wave with an inclination.

[0018] Preferably, the back plate electrode comprises a reinforcement structure in the shape of a protrusion or a groove.

[0019] Preferably, a partial area of ​​the peripheral portion of the membrane is a discontinuous area.

[0020] Preferably, the edge of the peripheral portion of the membrane is discontinuous, and the edge of the peripheral portion is serrated, and a plurality of notches in the serrated shape form the discontinuous area.

[0021] Preferably, the discontinuous area of ​​the peripheral portion includes a hollow structure, the hollow structure includes a plurality of through holes, and the shape of the through holes is circular or polygonal.

[0022] Preferably, it also includes: a first isolation layer located between the diaphragm and the substrate, the acoustic cavity passes through the first isolation layer so that the movable area of ​​the second surface of the diaphragm is exposed; and a second isolation layer located between the back plate electrode and the diaphragm, wherein at least a portion of the peripheral portion of the diaphragm is clamped between the first isolation layer and the second isolation layer.

[0023] Preferably, it further comprises: a first protective layer and a second protective layer, the back plate electrode is located between the first protective layer and the second protective layer, and the first protective layer is located between the second isolation layer and the back plate electrode.

[0024] Preferably, the first protective layer forms a plurality of protrusions on a surface facing the first surface of the diaphragm to prevent adhesion between the back plate electrode and the diaphragm.

[0025] Preferably, the second protective layer serves as a mechanical support layer of the back plate electrode to provide rigidity, so that the back plate electrode is maintained in a non-deformed state in a working state.

[0026] Preferably, it also includes: a plurality of release holes, which penetrate the first protective layer, the back plate electrode and the second protective layer; and a cavity, which is located in the second isolation layer, the cavity is connected to the release holes, and the cavity exposes the first surface of the diaphragm.

[0027] Preferably, the plurality of release holes are circular in shape, and the diameter of the plurality of release holes is 1 micrometer to 15 micrometers.

[0028] Preferably, the plurality of release holes are in the shape of a polygon or a cross hole.

[0029] Preferably, the maximum value of the distance between two vertices of the plurality of release holes is 1 micrometer to 15 micrometers.

[0030] Preferably, the plurality of release holes are arranged in a rectangular array, a staggered rectangular array, or a circular array.

[0031] Preferably, it also includes: a first lead, passing through the second protective layer, the first protective layer, and the second isolation layer to reach the first surface of the diaphragm; and a second lead, passing through the second protective layer to reach the second surface of the back plate electrode.

[0032] Preferably, the helical spring structure comprises at least one helical pattern, and the helical pattern radiates outward from a middle portion of the diaphragm.

[0033] According to another aspect of the present application, a method for manufacturing a silicon microphone is provided, which includes: forming a diaphragm and a back plate electrode in sequence on a substrate, the diaphragm and the back plate electrode being separated from each other, and the first surface of the diaphragm and the first surface of the back plate electrode being opposite to each other; and forming a sound cavity that penetrates the substrate to reach the second surface of the diaphragm, wherein the back plate electrode is located above the movable region of the diaphragm, and the area of ​​the back plate electrode is smaller than the area of ​​the movable region of the diaphragm.

[0034] Preferably, the area of ​​the back plate electrode is less than or equal to the minimum cross-sectional area of ​​the acoustic cavity.

[0035] Preferably, the area of ​​the back plate electrode is 70% to 100% of the movable area.

[0036] Preferably, the radius of the minimum cross-section of the acoustic cavity is 385 microns to 415 microns.

[0037] Preferably, it also includes: forming a first isolation layer between the diaphragm and the substrate, the acoustic cavity penetrating the first isolation layer so that the movable area of ​​the second surface of the diaphragm is exposed; forming a second isolation layer between the back plate electrode and the diaphragm, wherein at least a portion of the peripheral portion of the diaphragm is clamped between the first isolation layer and the second isolation layer.

[0038] Preferably, the method further comprises: forming a first protective layer between the second isolation layer and the back plate electrode; and forming a second protective layer above the back plate electrode.

[0039] Preferably, it also includes: forming a plurality of release holes through the first protective layer, the back plate electrode and the second protective layer; and forming a cavity in the second isolation layer, the cavity being connected to the release holes and exposing the first surface of the diaphragm.

[0040] Preferably, it also includes: a first lead formed through the second protective layer, the first protective layer, and the second isolation layer to reach the first surface of the diaphragm; and a second lead formed through the second protective layer to reach the second surface of the back plate electrode.

[0041] Preferably, the diaphragm includes a middle portion and a peripheral portion, and a spring structure connecting the middle portion and the peripheral portion, and the movable region of the diaphragm includes a region of the middle portion and a region of the spring structure.

[0042] Preferably, the spring structure of the diaphragm is a concentric annular fold portion, or a spiral fold portion.

[0043] Preferably, the diaphragm further comprises reinforcing ribs located at a peripheral portion of the diaphragm.

[0044] Preferably, the reinforcing ribs of the membrane are radial strip beams or parapet structures located at the peripheral portion.

[0045] Preferably, the back plate electrode comprises a reinforcement structure in the shape of a protrusion or a groove.

[0046] Preferably, a partial area of ​​the peripheral portion of the membrane is a discontinuous area.

[0047] Preferably, the plurality of release holes are in the shape of a polygon or a cross hole.

[0048] Preferably, the plurality of release holes are arranged in a rectangular array, a staggered rectangular array, or a circular array.

[0049] According to the MEMS microphone of the embodiment of the present invention, the back plate electrode is located above the movable area of ​​the diaphragm, and the area of ​​the back plate electrode is equal to the area of ​​the movable area of ​​the diaphragm, thereby reducing the influence of parasitic capacitance that does not contribute to the sensitivity of the MEMS microphone. Even if there are process fluctuations, since the back plate electrode only needs to be aligned with the movable area of ​​the diaphragm, the two can be easily aligned.

[0050] In a preferred embodiment, the area of ​​the back plate electrode is less than or equal to the minimum cross-sectional area of ​​the acoustic cavity, thereby avoiding the problem of reduced reliability of the MEMS microphone due to process fluctuations in mass production and improving the overall performance of the product.

[0051] In a preferred embodiment, the area of ​​the back plate electrode is 70% to 100% of the movable area of ​​the diaphragm. The MEMS microphone uses the pattern of the back plate electrode to limit the effective capacitance area, which can reduce the influence of parasitic capacitance that does not contribute to the sensitivity of the MEMS microphone, suppress the adverse effects of parasitic capacitance and process fluctuations on device capabilities, and improve the working sensitivity of the device.

[0052] In a preferred embodiment, the back plate electrode of the MEMS microphone is sandwiched between a first protective layer and a second protective layer. The first protective layer forms a plurality of protrusions on the surface of the first surface facing the diaphragm to prevent adhesion between the back plate electrode and the diaphragm. The second protective layer serves as a mechanical support layer for the back plate electrode to provide rigidity so that the back plate electrode is maintained in an undeformed state in the working state. Since the second protective layer serves as a mechanical support layer, the freedom of device design can be improved. The pattern design of the back plate electrode of the MEMS microphone only needs to be designed based on electrical performance without taking into account the requirements of mechanical rigidity. Therefore, the pattern of the back plate electrode can be used to define the effective capacitance area, thereby reducing the influence of parasitic capacitance that does not contribute to the sensitivity of the MEMS microphone.

[0053] In a preferred embodiment, the diaphragm of the MEMS microphone includes a spring structure of concentric annular folded parts or spiral folded parts. The spring structure of the diaphragm effectively releases the stress of the diaphragm and improves the sensitivity of the MEMS microphone.

[0054] In a preferred embodiment, the diaphragm also includes reinforcing ribs located at the peripheral portion of the diaphragm, which can improve the elastic properties of the diaphragm, control the vibration area, improve the elastic coefficient of the membrane structure, and improve the resonant frequency of the mechanical structure to meet the performance design requirements of the MEMS microphone.

[0055] In a preferred embodiment, a portion of the peripheral portion of the diaphragm is a discontinuous region. The discontinuous region is a discontinuous edge of the peripheral portion or a hollow structure of the peripheral portion. The discontinuous region of the diaphragm and the upper and lower dielectric layers cannot form a capacitor structure, thereby reducing the parasitic capacitance that is detrimental to the sensitivity of the microphone. At the same time, the discontinuous region can release part of the diaphragm stress, effectively improving the sensitivity of the diaphragm.

[0056] In a preferred embodiment, the MEMS microphone further comprises a plurality of release holes, which penetrate the first protective layer, the back plate electrode and the second protective layer. The release holes not only serve as a supply channel for the etchant during the process, but also reduce the acoustic resistance when the MEMS microphone is in operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0058] Figure 1 An exploded structural diagram of a MEMS microphone according to an embodiment of the present invention is shown;

[0059] Figure 2 A schematic diagram showing a process of manufacturing a MEMS microphone according to an embodiment of the present invention;

[0060] Figures 3a to 3l sectional views showing different stages of a method for manufacturing a MEMS microphone according to an embodiment of the present invention;

[0061] Figure 4a A schematic structural diagram of a diaphragm of a MEMS microphone according to an embodiment of the present invention is shown; Figure 4b A schematic structural diagram of another diaphragm of a MEMS microphone according to an embodiment of the present invention is shown;

[0062] Figure 5a A schematic structural diagram of a diaphragm of a MEMS microphone according to another embodiment of the present invention is shown; Figure 5b A schematic structural diagram of another diaphragm of a MEMS microphone according to another embodiment of the present invention is shown;

[0063] Figure 6a A schematic structural diagram of a diaphragm of a MEMS microphone according to another embodiment of the present invention is shown; Figure 6b A schematic structural diagram showing another diaphragm of a MEMS microphone according to yet another embodiment of the present invention;

[0064] Figure 7 Show according to Figure 1 A partial enlarged view of point C in the middle;

[0065] Figure 8 shows different deformation regions of a MEMS microphone according to an embodiment of the present invention; and

[0066] Fig. 9 FIG. 4 shows an equivalent circuit diagram of a MEMS microphone according to an embodiment of the present invention. DETAILED DESCRIPTION

[0067] Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, the same elements are represented by the same or similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale.

[0068] The present invention may be embodied in various forms, some examples of which will be described below.

[0069] Figure 1 An exploded structural diagram of a MEMS microphone according to an embodiment of the present invention is shown.

[0070] The MEMS microphone 100 includes a substrate 101, a diaphragm 103 and a back plate electrode 106 located on the substrate 101. The diaphragm 103 and the back plate electrode 106 are separated from each other, and the first surface of the diaphragm 103 and the first surface of the back plate electrode 106 are opposite to each other. The acoustic cavity 115 penetrates the substrate 101 to reach the second surface of the diaphragm 103. The back plate electrode 106 is located above the movable area of ​​the diaphragm 103, and the area of ​​the back plate electrode 106 is smaller than the area of ​​the movable area of ​​the diaphragm 103. In some preferred embodiments, the area of ​​the back plate electrode 106 is 70% to 100% of the movable area.

[0071] In some preferred embodiments, the area of ​​the back plate electrode 106 is less than or equal to the minimum cross-sectional area of ​​the acoustic cavity 115. It should be noted that when the opening of the acoustic cavity 115 is square, the cross-sectional areas of the acoustic cavity at different horizontal planes are the same, and the unique cross-sectional area is the minimum cross-sectional area of ​​the acoustic cavity 121. When the opening of the acoustic cavity 115 is an inverted trapezoid or a trapezoid, the cross-sectional area of ​​the acoustic cavity 115 located at the first surface or the second surface of the substrate 101 is the smallest. In some embodiments, the radius of its minimum cross-sectional area is 385 microns to 415 microns.

[0072] Further, the diaphragm 103 includes a middle portion and a peripheral portion, and a spring structure connecting the two, and the movable area of ​​the diaphragm 103 includes the area of ​​the middle portion and the area of ​​the spring structure. The spring structure of the diaphragm 103 is, for example, a concentric annular fold portion, or a spiral fold portion. Further, the spiral spring structure includes at least one spiral pattern, and the spiral pattern radiates outward from the middle portion of the diaphragm.

[0073] In an alternative embodiment, the diaphragm 103 also includes reinforcing ribs located at the peripheral portion, for example, a radial strip beam or a parapet structure located at the peripheral portion, and further, the parapet structure includes a plurality of annular sections, and the morphology of the annular sections is a rectangular wave. Alternatively, the reinforcing ribs include a plurality of annular sections, and the shapes of the corners of the plurality of annular sections are circular arcs or inclined trapezoidal waves or sine waves. The back plate electrode 106 includes a reinforcing structure in the shape of a protrusion or a groove. Further, the reinforcing structure is, for example, a radial strip beam or a parapet structure. Further, the parapet structure includes a plurality of annular sections, and the morphology of the annular sections is a rectangular wave. Alternatively, the reinforcing ribs include a plurality of annular sections, and the shapes of the corners of the plurality of annular sections are circular arcs or inclined trapezoidal waves or sine waves.

[0074] In an alternative embodiment, a portion of the diaphragm 103 is a discontinuous region. Further, the edge of the peripheral portion of the diaphragm 103 is discontinuous, and further, the edge of the peripheral portion is serrated, and the multiple notches of the serrated form the discontinuous region. In an alternative embodiment, the discontinuous region of the peripheral portion of the diaphragm 103 includes a hollow structure, and further, the hollow structure includes multiple through holes, and the through holes are polygonal or circular.

[0075] Further, the MEMS microphone 100 also includes a first isolation layer 102 and a second isolation layer 104. At least a portion of the peripheral portion of the diaphragm 103 is sandwiched between the first isolation layer 102 and the second isolation layer 104. The first isolation layer 102 is located between the substrate 101 and the diaphragm 103, and the acoustic cavity 115 runs through the substrate 101 and the first isolation layer 102 to expose the middle portion of the second surface of the diaphragm 103 and the area of ​​the spring structure, and optionally, at least a portion of the peripheral portion of the second surface of the diaphragm 103 is also exposed. The second isolation layer 104 is located between the diaphragm 103 and the back plate electrode 106, and a cavity 114 is formed in the second isolation layer 104 to expose the middle portion of the first surface of the diaphragm 103, the area of ​​the spring structure, and at least a portion of the peripheral portion. Therefore, the middle portion of the diaphragm 103 can vibrate freely in the cavity 114 and the acoustic cavity 115. The thickness of the second isolation layer 104 defines the distance between the diaphragm 103 and the back plate electrode 106 , which is, for example, 1 micron to 5 microns.

[0076] Further, the MEMS microphone 100 further includes a first protective layer 105 and a second protective layer 107. The back plate electrode 106 is, for example, entirely sandwiched between the first protective layer 105 and the second protective layer 107. The first surface of the back plate electrode 106 contacts the first protective layer 105, the second surface of the back plate electrode 106 contacts the second protective layer 107, and the first protective layer 105 is located between the second isolation layer 104 and the back plate electrode 106. The first protective layer 105, the back plate electrode 106, and the second protective layer 107 constitute a back plate structure.

[0077] Further, the first protective layer 105 forms a plurality of protrusions on the surface of the first surface facing the diaphragm 103 to prevent adhesion between the back plate electrode 106 and the diaphragm 103. The second protective layer 107 serves as a mechanical support layer for the back plate electrode 106 to provide rigidity so that the back plate electrode 106 is maintained in a non-deformed state in the working state.

[0078] Further, the MEMS microphone 100 also includes a plurality of release holes 113. The release holes 113 penetrate the first protective layer 105, the back plate electrode 106 and the second protective layer 107, and are connected to the cavity 114 in the second isolation layer 104. The shape of the release hole 113 is, for example, any one of a circle, a cross hole and a polygon. When the shape of the release hole 113 is a circle, the diameter of the release hole 113 is 1 micron to 15 microns. When the shape of the release hole 113 is a polygon or any one of a cross hole, the maximum value of the distance between the two vertices of the release hole 113 is 1 micron to 15 microns. In this embodiment, the plurality of release holes 113 are arranged in a honeycomb structure array (staggered rectangular array), and the row and / or column spacing of the honeycomb structure array is different, and the entire array is, for example, limited to a circular area. In alternative embodiments, the plurality of release holes 113 can be arranged in a rectangular array, a circular array, and the like.

[0079] Furthermore, the MEMS microphone 100 further includes a contact 121 connected to the diaphragm 103, a contact 122 connected to the back plate electrode 106, and a first lead 123 and a second lead 124 respectively connected to the contacts 121 and 122. The first lead 123 passes through the second protective layer 107, the first protective layer 105, and the second isolation layer 104 to reach the first surface of the diaphragm 103, thereby connecting to the first contact 121. The second lead 124 passes through the second protective layer 107 to reach the second surface of the back plate electrode 106, thereby connecting to the second contact 122.

[0080] Figure 2 A schematic diagram showing a process of manufacturing a MEMS microphone according to an embodiment of the present invention is shown. Figures 3a to 3l The cross-sectional view shows different stages of a method for manufacturing a MEMS microphone according to an embodiment of the present invention, wherein Figure 2 The line AA shown indicates the direction in which the cross-sectional view is obtained.

[0081] In step S01, a first isolation layer 102 is formed on a substrate 101. Figure 3a shown.

[0082] In this embodiment, the substrate 101 is, for example, <100> The substrate 101 has a substrate silicon wafer with a crystal orientation. Optionally, the substrate is doped to an N-type. The first isolation layer 102 is, for example, a silicon oxide layer. For example, a silicon oxide layer is formed on the substrate 101 by thermal oxidation or chemical vapor deposition (CVD) as the first isolation layer 102.

[0083] A portion of the first isolation layer 102 will be used as a sacrificial layer to form a portion of the acoustic cavity below the diaphragm. The thickness of the first isolation layer 102 is, for example, 0.5 micrometers to 2 micrometers.

[0084] In step S02, a groove 131 is formed on the surface of the first isolation layer 102. Figure 3b shown.

[0085] In this embodiment, a resist layer is formed on the surface of the first isolation layer 102, and a pattern including an opening is formed in the resist layer by a photolithography process. With the resist layer as a mask, a selective etchant is used to remove the exposed portion of the first isolation layer 102, thereby forming a groove 131. By controlling the etching time, the etching can be stopped at a predetermined depth of the first isolation layer 102. After etching, the resist layer can be removed by ashing or dissolving in a solvent.

[0086] The groove 131 is open on the surface of the first isolation layer 102 and extends downward. When viewed from the surface of the first isolation layer 102, the shape of the groove 131 is a concentric ring, for example, including 1 to 6 nested circular rings. When viewed from the cross section of the first isolation layer 102, the shape of the groove 131 is a roughly trapezoidal or V-shaped shape with a bottom surface size smaller than the opening surface size. In a preferred embodiment, when viewed from the cross section of the first isolation layer 102, the shape of the groove 131 is a square. The depth of the groove 131 is, for example, 0.5 microns to 0.8 microns. The groove 131 is used to define the spring structure of the diaphragm to be formed in the subsequent steps.

[0087] Preferably, the opening surface of the groove 131 forms a smooth transition surface with the surface of the first isolation layer 102. To this end, an additional deposition step may be used to form a conformal cover layer, such as a thin oxide layer, to improve the morphology of the groove 131 and obtain a smooth transition surface. The thickness of the cover layer is, for example, 0.1 micrometer to 2 micrometers.

[0088] Preferably, the groove 131 is not only used to define the spring structure of the diaphragm, but also used to form a spiral structure in the spring structure region of the diaphragm, and used to define and form reinforcing ribs around the periphery of the diaphragm.

[0089] In step S03, a conformal membrane 103 is formed on the first isolation layer 102, and a contact 121 connected to the membrane 103 is formed, such as Figure 3c shown.

[0090] In this embodiment, the diaphragm 103 is composed of doped polysilicon, for example. For example, polysilicon is deposited on the first isolation layer 102 by low pressure chemical vapor deposition (LPCVD), and the deposition temperature is, for example, 570 degrees Celsius to 630 degrees Celsius. Further, the polysilicon layer is patterned by photolithography and etching steps, so that patterns of the diaphragm 103 and the contact 121 are respectively formed in different regions of the polysilicon layer.

[0091] The diaphragm 103 includes a middle portion 103a and a peripheral portion 103c, and a spring structure 103b connecting the two. The middle portion 103a and the peripheral portion 103c of the diaphragm 103 cover the surface of the first isolation layer 102, and the spring structure 103b, the middle portion 103a and the peripheral portion 103c continuously and conformally cover the bottom surface and sidewall of the groove 131. Consistent with the shape of the groove 131, the spring structure 103b is a concentric annular fold portion. The thickness of the diaphragm 103 is, for example, 0.3 microns to 1 micron, preferably 0.4 microns.

[0092] In this embodiment, the middle portion 103a and the peripheral portion 103c of the diaphragm 103 are both flat surfaces, and the spring structure 103b of the diaphragm 103 is a concentric annular folded portion. The middle portion 103a and the spring structure 103b of the diaphragm 103 are the movable areas of the diaphragm 103. In an alternative embodiment, the spring structure of the diaphragm 103 is a spiral folded portion (such as Figure 4a , 4b In these two implementation modes, Figure 4a The threads of the spring structure are dense, and the curvature radius of the spiral pattern does not change with position. Figure 4b The threads of the spring structure are sparse, and the radius of curvature of the spiral pattern changes with the position. These two implementation methods can be selected according to the needs of the actual application. Compared with a diaphragm with a flat surface, a diaphragm 103 with a spring structure formed on the surface can improve the elastic properties of the diaphragm, control the vibration area, improve the elastic coefficient of the membrane structure, and meet the performance design requirements of the MEMS microphone. In an alternative embodiment, the middle part of the diaphragm 103 is recessed downward, and the depth of the recessed middle part is the same as the depth of the spiral pattern of the spring structure. In a preferred embodiment, the radius of curvature of each spiral pattern is the same. In an alternative embodiment, the spring structure is located in the entire diaphragm 103, that is, the middle part and the peripheral part of the diaphragm 103 are set as a spring structure. The stress of the diaphragm is effectively released, and the sensitivity of the MEMS microphone is improved.

[0093] In an alternative embodiment, the diaphragm 103 further includes a reinforcing rib (e.g. Figure 5a , 5b As shown in Figure 5a As shown, the reinforcing rib 1031 of the diaphragm 103 is, for example, a radial strip beam or a parapet structure located at the peripheral portion 103c, and the parapet structure includes a plurality of annular sections, the plurality of annular sections have equal radius and the annular sections are rectangular wavy in shape. In an alternative embodiment, the diaphragm 103 further includes a reinforcing rib 1032 (such as Figure 5bAs shown). The reinforcing ribs 1032 of the diaphragm 103 include a plurality of annular sections, the plurality of annular sections have equal radius and the corners of the annular sections have arcs, trapezoidal waves with inclinations, sine waves, etc. Compared with the diaphragm 103 with a flat surface, the diaphragm 103 with a spring structure 103b and reinforcing ribs 1031 formed on the surface can improve the elastic properties of the diaphragm, control the vibration area, improve the elastic coefficient of the membrane structure, improve the resonant frequency of the mechanical structure, and meet the performance design requirements of the MEMS microphone. In a preferred embodiment, the reinforcing ribs formed on the peripheral portion 103c of the diaphragm 103 are parapet structures, and the parapet structures include a plurality of annular sections, and the plurality of annular sections can include at least two of rectangular waves, arcs at the corners of the annular sections, trapezoidal waves with inclinations, or sine waves.

[0094] In an alternative embodiment, a portion of the peripheral portion 103c of the diaphragm 103 is a discontinuous region (eg Figure 6a , 6b As shown in Figure 6a As shown, the edge of the peripheral portion of the diaphragm 103 is discontinuous. Specifically, the edge of the peripheral portion 103c is serrated, and the plurality of notches 1033 of the serrated shape form a discontinuous area. In an alternative embodiment, as Figure 6b As shown, the discontinuous area of ​​the peripheral portion 103c of the diaphragm 103 includes a hollow structure. Specifically, the hollow structure includes a plurality of through holes 1034, and the through holes 1034 are circular or polygonal. In this embodiment, the through holes 1034 are in a fan-shaped shape, and the plurality of through holes 1034 are cross-arranged and formed in the peripheral portion of the diaphragm 103. Further, the shape of the diaphragm 103 is a sunflower shape. More specifically, the edges of the diaphragm 103 are connected by a plurality of arc edges.

[0095] In step S04, a second isolation layer 104 is formed on the membrane 103, and a plurality of openings 132 are formed on the surface of the second isolation layer 104. Figure 3d shown.

[0096] In this embodiment, the second isolation layer 104 is, for example, a silicon oxide layer. For example, a silicon oxide layer is formed on the membrane 103 by a low pressure chemical vapor deposition (LPCVD) or plasma enhanced chemical vapor deposition (PECVD) method as the second isolation layer 104. After the second isolation layer 104 is formed, the surface of the second isolation layer 104 is flattened by, for example, chemical mechanical planarization.

[0097] A portion of the second isolation layer 104 will be used as a sacrificial layer to form a cavity above the diaphragm 103, and the distance between the diaphragm and the back plate electrode is also limited by the thickness of the second isolation layer 104. The thickness of the second isolation layer 104 is selected according to the electrical and acoustic performance of the MEMS microphone, for example, 2 to 4 microns.

[0098] Next, a resist layer is formed on the surface of the second isolation layer 104, and a pattern including an opening is formed in the resist layer by a photolithography process. With the resist layer as a mask, a selective etchant is used to remove the exposed portion of the second isolation layer 104, thereby forming an opening 132. By controlling the etching time, the etching can be stopped at a predetermined depth of the second isolation layer 104. After etching, the resist layer can be removed by ashing or dissolving in a solvent.

[0099] The opening 132 is open on the surface of the second isolation layer 104 and extends downward. Observed from the surface of the second isolation layer 104, the shape of the opening 132 is a plurality of circular holes, a plurality of square holes or a plurality of triangular holes. Observed from the cross section of the second isolation layer 104, the shape of the opening 132 is a roughly trapezoidal or V-shaped shape with a bottom surface size smaller than the opening surface size. The diameter of the opening 132 is, for example, 0.5 microns to 1.5 microns, and the depth is, for example, 0.5 microns to 1.5 microns. The opening 132 is used to define a protrusion that will be formed in a subsequent step to prevent the back plate electrode from adhering.

[0100] In step S05, a first protective layer 105 is formed on the second isolation layer 104. Figure 3e shown.

[0101] The first protective layer 105 is, for example, composed of any one selected from a silicon nitride layer, a boron nitride layer, and a silicon carbide layer. In this embodiment, the first protective layer 105 is, for example, a boron nitride layer. For example, a boron nitride layer is formed on the second isolation layer 104 by a hot wire-assisted plasma enhanced chemical vapor deposition (PECVD) method, wherein N2, H2, and B2H6 diluted by H2 are used as reaction gases, the substrate temperature is 400 degrees Celsius to 500 degrees Celsius, and the reaction pressure is about 100 Pa. The thickness of the first protective layer 105 is, for example, 800 angstroms to 1500 angstroms.

[0102] The first protective layer 105 fills the opening 132 on the surface of the second isolation layer 104, thereby forming a protrusion 105a. The shape of the protrusion 105a is consistent with the shape of the opening 132, for example, any one of the following: a polygonal pyramid, a polygonal column, and a cylinder. The diameter of the protrusion 105a is, for example, 0.5 microns to 1.5 microns, and the depth is, for example, 0.5 microns to 1.5 microns.

[0103] In step S06, a back plate electrode 106 is formed on the first protective layer 105, and a contact 122 connected to the back plate electrode 106 is formed. Figure 3f shown.

[0104] The back plate electrode 106 is a conductive layer, for example, composed of any one of polysilicon doped with Al, Cu, Au, Ti, Ni, Wu and alloys thereof. For example, a doped polysilicon layer is formed on the first protective layer 105 by low pressure chemical vapor deposition (LPCVD). Then, the polysilicon layer is patterned by photolithography and etching steps to form a pattern of the back plate electrode 106. The thickness of the back plate electrode 106 is, for example, 0.3 micrometers to 1 micrometer.

[0105] In this embodiment, the back plate electrode 106 and the diaphragm 103 form two plates of the capacitor. As described above, the diaphragm 103 includes a middle portion 103a, a peripheral portion 103c, and a spring structure 103b therebetween, and the back plate electrode 106 corresponds to the middle portion 103a and the spring structure 103b of the diaphragm 103, thereby limiting the effective capacitor area, which is beneficial to reducing the parasitic capacitance of the final MEMS microphone.

[0106] In this embodiment, the back plate electrode 106 has a flat surface, and the surface shape observed from the surface of the back plate electrode 106 is, for example, circular. In alternative embodiments, the back plate electrode 106 may also be formed with a reinforcement structure in the shape of a protrusion or a groove, for example, a plurality of concentric rings located in the middle part, a spiral and / or reinforcement ribs located in the peripheral part, for example, a radial strip beam or a crossed strip beam or a parapet structure. In some preferred embodiments, the reinforcement structure runs through the entire back plate electrode 106. The surface shape of the back plate electrode 106 is, for example, any one selected from a circle, a triangle, a square, and a hexagon. Compared with the back plate electrode 106 with a flat surface, the back plate electrode 106 with a reinforcement structure formed on the surface can improve the stiffness of the back plate electrode, so that the back plate electrode will not be deformed when the MEMS microphone is in the working state.

[0107] In some preferred embodiments, after this step, a conventional semiconductor process etching method is used to penetrate the first protection layer 105 to form a groove 191 on the second isolation layer.

[0108] In step S07, a second protective layer 107 is formed on the back plate electrode 106. Figure 3g shown.

[0109] The second protective layer 107 is, for example, composed of any one selected from a silicon nitride layer, a boron nitride layer, and a silicon carbide layer. In this embodiment, the second protective layer 107 is, for example, a boron nitride layer. For example, a boron nitride layer is formed on the back plate electrode 106 by a hot wire-assisted plasma enhanced chemical vapor deposition (PECVD) method, wherein N2, H2, and B2H6 diluted by H2 are used as reaction gases, the substrate temperature is 400 degrees Celsius to 500 degrees Celsius, and the reaction pressure is about 100 Pa. The thickness of the second protective layer 107 is, for example, 0.1 microns to 1 micron. Among them, the first protective layer 105, the back plate electrode 106, and the second protective layer 107 constitute a back plate structure.

[0110] Since the back plate electrode 106 is patterned, a first portion of the second protection layer 107 is formed on the surface of the back plate electrode 106 , and a second portion is formed on the surface of the first protection layer 105 .

[0111] It should be noted that, if the first protective layer 105 is penetrated to form the groove 191 on the second isolation layer by etching before forming the second protective layer 107 , this step also includes forming the third portion of the second protective layer 107 in the groove 191 .

[0112] In step S08, a channel hole 111 that reaches the contact 121 of the membrane 103 and a channel hole 112 that reaches the contact 122 of the back plate electrode 106 are formed, as shown in FIG. Figure 3h shown.

[0113] In this embodiment, a resist layer is formed on the surface of the second protective layer 107, and a pattern including an opening is formed in the resist layer by a photolithography process. The resist layer is used as a mask and a selective etchant is used to form channel holes 111 and 112. In the first partial area of ​​the second protective layer 107, the etching removes the portion of the second protective layer 107 exposed through the mask opening to form a channel hole 112 that reaches the contact 122 of the back plate electrode 106. In the second partial area of ​​the second protective layer 107, the etching removes the portions of the second protective layer 107, the first protective layer 105, and the second isolation layer 104 exposed through the mask opening from top to bottom to form a channel hole 111 that reaches the contact 121 of the diaphragm 103. After etching, the resist layer can be removed by ashing or dissolving in a solvent.

[0114] Due to the patterning step of the back plate electrode 106, the second portion of the second protection layer 107 is in direct contact with the corresponding portion of the first protection layer 105. At least one channel hole 111 starts from the second portion of the surface of the second protection layer 107, extends through the second protection layer 107, the first protection layer 105 and the second isolation layer 104 to the contact 121 of the diaphragm 103 below the back plate electrode 106.

[0115] In step S09, the leads 123 that reach the contact 121 of the diaphragm 103 and the leads 124 that reach the contact 122 of the back plate electrode 106 are formed. Figure 3i shown.

[0116] In this embodiment, the leads 123 and 124 are made of a conductive material, for example, selected from any one of aluminum, gold, silver, copper, nickel, titanium, chromium or an alloy thereof. The aluminum alloy used for the leads includes, for example, an aluminum silicon alloy (1% by weight of silicon), and the titanium alloy includes titanium nitride. For example, a metal layer is formed on the surface of the second protective layer 107 by sputtering or evaporation. The thickness of the metal layer is, for example, 1 micron to 2 microns, and fills the channel holes 111 and 112.

[0117] A resist layer is formed on the surface of the metal layer, and a pattern including an opening is formed in the resist layer using a photolithography process. The exposed portion of the metal layer is removed using a selective etchant with the resist layer as a mask. Due to the selectivity of the etchant, the etching uses the second protective layer 107 as a stop layer. After etching, the resist layer can be removed by ashing or dissolving in a solvent.

[0118] In the first partial area of ​​the second protective layer 107, at least one lead 124 passes through the second protective layer 107 to reach the back plate electrode 106. In the second partial area of ​​the second protective layer 107, at least one lead 123 passes through the second protective layer 107, the first protective layer 105, and the second isolation layer 104 in sequence to reach the diaphragm 103.

[0119] Back plate electrode Back plate electrode In step S10, a release hole 113 is formed penetrating the second protective layer 107, the back plate electrode 106 and the first protective layer 105, such as Figure 3j shown.

[0120] In this embodiment, a resist layer is formed on the surface of the second protective layer 107, and a pattern including an opening is formed in the resist layer by a photolithography process. With the resist layer as a mask, a selective etchant is used to remove the exposed portions of the second protective layer 107, the back plate electrode 106 and the first protective layer 105, thereby forming a release hole 113. Due to the selectivity of the etchant, the second isolation layer 104 serves as a stop layer. After etching, the resist layer can be removed by ashing or dissolving in a solvent.

[0121] This step, for example, uses a special deep groove etcher to form the release hole 113. The release hole 113 not only serves as a supply channel for the etchant in the manufacturing process, but also serves as a sound hole in the finally formed MEMS microphone to reduce the acoustic resistance. Observing from the surface of the second protective layer 107, the shape of the release hole 113 is, for example, any one of a circle, a cross hole and a polygon. When the shape of the release hole 113 is a circle, the diameter of the release hole 113 is 1 micron to 15 microns. When the shape of the release hole 113 is a polygon or any one of the cross holes, the maximum value of the distance between the two vertices of the release hole 113 is 1 micron to 15 microns. In this embodiment, the shape of the release hole 113 is a hexagon (such as Figure 7 shown Figure 1 (a partial enlarged view at C in FIG. 1 ), the plurality of release holes 113 are arranged in a honeycomb structure array (a staggered rectangular array). In an alternative embodiment, the plurality of release holes 113 may be arranged in a rectangular array, a circular array, etc.

[0122] In step S11, an acoustic cavity 115 penetrating the substrate 101 is formed below the diaphragm 103, as shown in FIG. Figure 3k shown.

[0123] In this embodiment, the thickness of the substrate 101 is reduced to a design value, such as 350 microns to 450 microns, preferably 400 microns, by chemical mechanical planarization or thinning process. For example, the first surface and the second surface of the substrate 101, which are opposite to each other, are used to form the above-mentioned first isolation layer 102 and as a free surface, respectively, and the second surface is ground to reduce the thickness of the substrate 101. Then, a resist layer is formed on the second surface of the substrate 101, and a pattern containing an opening is formed in the resist layer by a photolithography process. Using the resist layer as a mask, a selective etchant is used to remove the exposed portion of the substrate 101, thereby forming an acoustic cavity 115. In this embodiment, the acoustic cavity is a square opening, alternatively, it can also be an inverted trapezoidal opening. Due to the selectivity of the etchant, the first isolation layer 102 serves as a stop layer. After etching, the resist layer can be removed by ashing or dissolving in a solvent.

[0124] Among them, the area of ​​the back plate electrode 106 is less than or equal to the minimum cross-sectional area of ​​the acoustic cavity 115. It should be noted that when the opening of the acoustic cavity 115 is square, the cross-sectional areas of the acoustic cavity at different horizontal planes are the same, and the unique cross-sectional area is the minimum cross-sectional area of ​​the acoustic cavity 115. When the opening of the acoustic cavity 115 is an inverted trapezoid or a trapezoid, the cross-sectional area of ​​the acoustic cavity 115 located at the first surface or the second surface of the substrate 101 is the smallest. In some embodiments, the radius of its minimum cross-sectional area is 385 microns to 415 microns.

[0125] This step, for example, adopts a conventional Bosch process in MEMS technology and a special deep trench etching machine to form the acoustic cavity 115 .

[0126] In step S12, a portion of the first isolation layer 102 is removed through the acoustic cavity 115, and a portion of the second isolation layer 104 is removed through the release hole 113 to release the diaphragm 103, as shown in FIG. Figure 3l shown.

[0127] In this embodiment, for example, HF acid is used as an etchant, and the acoustic cavity 115 and the release hole 113 formed in the above steps are used as an entry channel for the etchant. The first protective layer 105 and the second protective layer 107 are respectively used as protective films for the back plate electrode 106, so that the back plate electrode 106 is not etched in the etching step.

[0128] By HF acid vapor fumigation or HF acid wet etching, a portion of each of the first isolation layer 102 and the second isolation layer 104 is removed, so that a portion of each of the first surface and the second surface opposite to each other of the diaphragm 103 is exposed again, thereby releasing the diaphragm 103. After removing a portion of the first isolation layer 102, the acoustic cavity 115 extends from the second surface of the substrate 101 to the second surface of the diaphragm 103. After removing a portion of the second isolation layer 104, a cavity 114 is formed between the first protective layer 105 and the first surface of the diaphragm 103. The release hole 113 and the cavity 114 are connected to each other, providing an air flow channel during the vibration of the diaphragm 103.

[0129] In this step, the spring structure 103 c of the diaphragm 103 is also exposed in the acoustic cavity 115 and the cavity 114 .

[0130] Figure 8 and 9 Different deformation areas and equivalent circuit diagrams of a MEMS microphone according to an embodiment of the present invention are respectively shown.

[0131] exist Figure 1 In the MEMS microphone 100 shown, the back plate electrode 106 and the diaphragm 103 form two plates of the capacitor. As described above, the diaphragm 103 includes a middle portion 103a, a peripheral portion 103c, and a spring structure 103c therebetween. The area of ​​the back plate electrode 106 is the effective deformation portion, and the back plate electrode 106 corresponds to the middle portion 103a of the diaphragm 103, thereby limiting the effective capacitance area where effective deformation occurs, which is beneficial to reducing the parasitic capacitance of the final MEMS microphone.

[0132] Sensitivity of MEMS microphone 100 It is expressed as:

[0133] (1),

[0134] (2),

[0135] in, It indicates the capacitance change caused by the vibration of the diaphragm of the MEMS microphone due to the air vibration generated by the sound signal. The effective capacitance component that represents the effective deformation of the diaphragm of the MEMS microphone in response to the sound signal. It indicates the invalid capacitance component of the diaphragm of the MEMS microphone that undergoes invalid deformation or no deformation in response to the sound signal. VDD indicates the voltage applied between the diaphragm and the back plate electrode of the MEMS microphone, for example, the voltage is generated by a charge pump structure in an ASIC circuit. represents the voltage of the reference plate of the MEMS microphone, such as the operating point voltage of the ASIC signal input terminal sealed with it, CL represents the load capacitance, such as the parasitic capacitance of the wiring and the pad, and the size is, for example, on the order of 1pF. represents the bias voltage, .

[0136] The area of ​​the back plate 106 is the effective deformation area. In this embodiment, the middle part 103a of the diaphragm 103 of the MEMS microphone 100 is, for example, the effective deformation area, and the effective deformation area corresponds to the part of the back plate electrode opposite to the middle part. The spring structure 103b is, for example, the invalid deformation area. The effective deformation area and the invalid deformation area belong to the free surface of the peripheral part 103c and the part of the peripheral part 103c sandwiched between the first isolation layer 102 and the second isolation layer 104 is, for example, the non-deformation part.

[0137] The area of ​​the back plate electrode 106 of the MEMS microphone 100 is smaller than the area of ​​the movable area of ​​the diaphragm 103. Therefore, the pattern of the back plate electrode 106 used in the MEMS microphone 100 according to the embodiment of the present invention actually removes the invalid capacitance component from the detection signal, so that the sensitivity of the detection signal is only related to the effective capacitance component, thereby improving the sensitivity of the MEMS microphone 100. In a preferred embodiment, the area of ​​the back plate electrode 106 is less than or equal to the minimum cross-sectional area of ​​the acoustic cavity 115, avoiding the problem of reduced reliability of the MEMS microphone caused by process fluctuations in mass production, and improving the overall performance of the product.

[0138] According to the embodiments of the present invention as described above, these embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and changes can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and the modified use based on the present invention. The scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. A MEMS microphone, comprising: substrate; A diaphragm and a back plate electrode are located on the first surface of the substrate, the diaphragm and the back plate electrode are separated from each other, and the first surface of the diaphragm and the first surface of the back plate electrode are opposite to each other; as well as an acoustic cavity extending through the substrate to the second surface of the diaphragm, The back plate electrode is located above the movable region of the diaphragm, and the area of ​​the back plate electrode is smaller than the area of ​​the movable region of the diaphragm. The diaphragm includes a middle portion and a peripheral portion, and a spring structure connecting the two, and the movable area of ​​the diaphragm includes an area of ​​the middle portion and an area of ​​the spring structure. The middle part is the effective deformation area, the spring structure is the ineffective deformation area, and the area of ​​the back plate electrode corresponds to the effective deformation area of ​​the diaphragm. The acoustic cavity penetrates the substrate to expose the middle portion of the second surface of the diaphragm and the spring structure.

2. The MEMS microphone according to claim 1, wherein: The area of ​​the back plate electrode is less than or equal to the minimum cross-sectional area of ​​the acoustic cavity.

3. The MEMS microphone according to claim 1, wherein: The area of ​​the back plate electrode is 70% to 100% of the movable area.

4. The MEMS microphone according to claim 2, wherein: The radius of the minimum cross-section of the acoustic cavity is 385 microns to 415 microns.

5. The MEMS microphone according to claim 1, wherein: The distance between the back plate electrode and the membrane is 1 micron to 5 microns.

6. The MEMS microphone according to claim 1, wherein: The sensitivity of the microphone for: ,in, represents the capacitance change caused by the vibration of the diaphragm, represents the effective capacitance component of the effective deformation of the middle part of the diaphragm, Invalid capacitance components indicating that the region of the spring structure of the diaphragm undergoes invalid deformation or the region of the peripheral portion of the diaphragm does not undergo invalid deformation, represents the load capacitance of the MEMS microphone, Indicates the bias voltage.

7. The MEMS microphone according to claim 6, wherein: The bias voltage for: , wherein VDD represents the voltage applied between the diaphragm and the back plate electrode, represents the voltage of the reference plate of the MEMS microphone.

8. The MEMS microphone according to claim 1, wherein: The spring structure of the diaphragm is a concentric annular fold part or a spiral fold part.

9. The MEMS microphone according to claim 1, wherein: The diaphragm further comprises a reinforcing rib located at a peripheral portion of the diaphragm.

10. The MEMS microphone according to claim 9, wherein: The reinforcing ribs of the membrane are radial strip beams or parapet structures located at the peripheral part.

11. The MEMS microphone according to claim 10, wherein: The parapet structure includes a plurality of annular sections, and the annular sections are in the shape of rectangular waves.

12. The MEMS microphone according to claim 9, wherein: The reinforcing rib includes a plurality of annular sections, and the shapes of the corners of the annular sections are circular arcs or trapezoidal waves or sine waves with an inclination.

13. The MEMS microphone according to claim 1, wherein: The back plate electrode includes a reinforcement structure in the shape of a protrusion or a groove.

14. The MEMS microphone according to claim 1, wherein: Part of the peripheral portion of the membrane is a discontinuous region.

15. The MEMS microphone according to claim 14, wherein: The edge of the peripheral portion of the membrane is discontinuous, and the edge of the peripheral portion is sawtooth-shaped, and a plurality of notches in the sawtooth shape form the discontinuous area.

16. The MEMS microphone of claim 14, wherein: The discontinuous area of ​​the peripheral portion includes a hollow structure, and the hollow structure includes a plurality of through holes, and the through holes are circular or polygonal in shape.

17. The MEMS microphone of claim 1, wherein: Also includes: a first isolation layer between the diaphragm and the substrate, the acoustic cavity penetrating the first isolation layer so that the movable area of ​​the second surface of the diaphragm is exposed; as well as a second isolation layer between the back plate electrode and the diaphragm, Wherein, at least a portion of the peripheral portion of the diaphragm is clamped between the first isolation layer and the second isolation layer.

18. The MEMS microphone of claim 17, wherein: Also includes: A first protective layer and a second protective layer, the back plate electrode is located between the first protective layer and the second protective layer, and the first protective layer is located between the second isolation layer and the back plate electrode.

19. The MEMS microphone of claim 18, wherein: The first protection layer forms a plurality of protrusions on a surface facing the first surface of the diaphragm to prevent adhesion between the back plate electrode and the diaphragm.

20. The MEMS microphone of claim 18, wherein: The second protective layer serves as a mechanical support layer of the back plate electrode to provide rigidity, so that the back plate electrode is maintained in a non-deformed state in a working state.

21. The MEMS microphone of claim 18, wherein: Also includes: A plurality of release holes, wherein the plurality of release holes penetrate the first protective layer, the back plate electrode and the second protective layer; as well as A cavity is located in the second isolation layer, the cavity is communicated with the release hole, and the cavity exposes the first surface of the membrane.

22. The MEMS microphone of claim 21, wherein: The plurality of release holes are circular in shape, and have a diameter of 1 micrometer to 15 micrometers.

23. The MEMS microphone of claim 21, wherein: The multiple release holes are in any shape of a polygon or a cross hole.

24. The MEMS microphone of claim 23, wherein: The maximum value of the distance between two vertices of the plurality of release holes is 1 micrometer to 15 micrometers.

25. The MEMS microphone of claim 21, wherein: The plurality of release holes are arranged in a rectangular array, a staggered rectangular array or a circular array.

26. The MEMS microphone of claim 18, wherein: Also includes: A first lead wire passes through the second protective layer, the first protective layer, and the second isolation layer to reach the first surface of the diaphragm; as well as The second lead passes through the second protective layer and reaches the second surface of the back plate electrode.

27. The MEMS microphone of claim 8, wherein: The helical spring structure includes at least one helical pattern, and the helical pattern radiates outward from a middle portion of the diaphragm.

28. A method of manufacturing a MEMS microphone, wherein: include: A diaphragm and a back plate electrode are sequentially formed on a substrate, wherein the diaphragm and the back plate electrode are separated from each other, and a first surface of the diaphragm and a first surface of the back plate electrode are opposite to each other; as well as forming an acoustic cavity penetrating the substrate to the second surface of the diaphragm, The back plate electrode is located above the movable area of ​​the diaphragm, and the area of ​​the back plate electrode is smaller than the area of ​​the movable area of ​​the diaphragm. The diaphragm includes a middle part and a peripheral part, and a spring structure connecting the two. The movable area of ​​the diaphragm includes the area of ​​the middle part and the area of ​​the spring structure. The middle part is the effective deformation area, the spring structure is the ineffective deformation area, and the area of ​​the back plate electrode corresponds to the effective deformation area of ​​the diaphragm. The acoustic cavity penetrates the substrate to expose the middle portion of the second surface of the diaphragm and the spring structure.

29. The method according to claim 28, wherein: The area of ​​the back plate electrode is less than or equal to the minimum cross-sectional area of ​​the acoustic cavity.

30. The method of claim 28, wherein: The area of ​​the back plate electrode is 70% to 100% of the movable area.

31. The method of claim 29, wherein: The radius of the minimum cross-section of the acoustic cavity is 385 microns to 415 microns.

32. The method of claim 28, wherein: Also includes: forming a first isolation layer between the diaphragm and the substrate, wherein the acoustic cavity penetrates the first isolation layer so that the movable area of ​​the second surface of the diaphragm is exposed; forming a second isolation layer between the back plate electrode and the diaphragm, Wherein, at least a portion of the peripheral portion of the diaphragm is clamped between the first isolation layer and the second isolation layer.

33. The method of claim 32, wherein: Also includes: forming a first protective layer between the second isolation layer and the back plate electrode; as well as A second protection layer is formed above the back plate electrode.

34. The method of claim 33, wherein: Also includes: forming a plurality of release holes through the first protective layer, the back plate electrode and the second protective layer; as well as A cavity is formed in the second isolation layer, the cavity being communicated with the release hole and exposing the first surface of the membrane.

35. The method of claim 33, wherein: Also includes: forming a first lead reaching the first surface of the diaphragm through the second protective layer, the first protective layer, and the second isolation layer; as well as A second lead is formed through the second protection layer and reaches the second surface of the back plate electrode.

36. The method of claim 28, wherein: The spring structure of the diaphragm is a concentric annular fold part or a spiral fold part.

37. The method of claim 28, wherein: The diaphragm further comprises a reinforcing rib located at a peripheral portion of the diaphragm.

38. The method of claim 37, wherein: The reinforcing ribs of the membrane are radial strip beams or parapet structures located at the peripheral part.

39. The method of claim 28, wherein: The back plate electrode includes a reinforcement structure in the shape of a protrusion or a groove.

40. The method of claim 28, wherein: Part of the peripheral portion of the membrane is a discontinuous region.

41. The method of claim 34, wherein: The multiple release holes are in any shape of a polygon or a cross hole.

42. The method of claim 34, wherein: The plurality of release holes are arranged in a rectangular array, a staggered rectangular array or a circular array.

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