CN111131987A

CN111131987A - MEMS microphone and manufacturing method thereof

Info

Publication number: CN111131987A
Application number: CN201911216592.XA
Authority: CN
Inventors: 周延青; 潘华兵; 郑泉智; 胡铁刚
Original assignee: Hangzhou Silan Microelectronics Co Ltd
Current assignee: Hangzhou Silan Microelectronics Co Ltd
Priority date: 2019-12-02
Filing date: 2019-12-02
Publication date: 2020-05-08

Abstract

Disclosed are a MEMS microphone and a method of manufacturing the same. The MEMS microphone includes: a substrate; a diaphragm and a backplate electrode on the first surface of the substrate, the diaphragm and the backplate electrode being spaced apart from each other, the first surface of the diaphragm and the first surface of the backplate electrode opposing each other; and an acoustic cavity penetrating through the substrate to the second surface of the diaphragm, wherein the back electrode plate electrode is located above the movable region of the diaphragm, and an area of the back electrode plate electrode is equal to or smaller than an area of the movable region of the diaphragm. The MEMS microphone adopts the pattern of the back electrode plate electrode to limit the effective capacitance area so as to inhibit the adverse effect of parasitic capacitance and process fluctuation on the capability of the device and improve the working sensitivity of the device.

Description

MEMS microphone and manufacturing method thereof

Technical Field

The invention belongs to the technical field of miniature microphones, and particularly relates to an MEMS microphone and a manufacturing method thereof.

Background

The MEMS microphone is a MEMS (Micro-Electro-Mechanical System) device manufactured by using a Micro-machining process. Due to the advantages of small volume, high sensitivity and good compatibility with the existing semiconductor technology, the MEMS microphone is more and more widely applied to mobile terminals such as mobile phones. The structure of the MEMS microphone includes a diaphragm and a backplate electrode that are opposed to each other, and both are connected to the respective electrodes via leads, respectively. An isolating layer is also included between the diaphragm and the back plate electrode. The isolation layer is used for separating the diaphragm and the back electrode plate electrode, and a cavity is formed in the isolation layer to provide a vibration space required by the diaphragm.

With the development of micro-fabrication processes, MEMS microphones are being miniaturized more and more, wherein the distance between the membrane and the back electrode plate electrode is less than 1.5 microns, for example, and the process requirements during the manufacturing and application of the MEMS microphone are also being increased more and more. 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 in the application environment to be sharply deteriorated. For example, in the manufacturing process of a MEMS microphone, etching is used to form a cavity between the diaphragm and the backplate electrode. Process variations of this etching step affect the effective area of the MEMS microphone, causing fluctuations in the performance of the MEMS microphone. In addition, the existing MEMS microphones have complicated patterns, and employ photolithography for multiple alignment to form the patterns. Process variations of this patterning step may also cause fluctuations in the performance of the MEMS microphone. In addition, the capacitance change caused by the diaphragm vibration of the MEMS microphone according to the air vibration generated by the sound signal includes not only an effective portion but also an ineffective portion, and the ineffective capacitance component generates an unfavorable parasitic capacitance. Further improvements in the structure of the MEMS microphone are expected to suppress parasitic capacitance and suppress adverse effects of process variations of etching and photolithography on device performance to improve yield and device reliability.

Disclosure of Invention

An object of the present invention is to provide a MEMS microphone and a method of manufacturing the same, in which an effective capacitance area is defined using a pattern of a back electrode plate electrode to suppress adverse effects of parasitic capacitance and process fluctuation on device capability and to improve operating sensitivity of the device.

According to an aspect of the present application, there is provided a MEMS microphone including: a substrate; a diaphragm and a backplate electrode on the first surface of the substrate, the diaphragm and the backplate electrode being spaced apart from each other, the first surface of the diaphragm and the first surface of the backplate electrode opposing each other; and an acoustic cavity penetrating through the substrate to reach the second surface of the diaphragm, wherein the back electrode plate electrode is located above the movable region of the diaphragm, and an area of the back electrode plate electrode is equal to or smaller than an area of the movable region of the diaphragm.

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

Preferably, the area of the back electrode plate electrode is 70% to 100% of the movable region.

Preferably, the radius of the smallest cross section of the acoustic cavity is 385 microns to 415 microns.

Preferably, the spacing between the back electrode plate electrode and the membrane is from 1 micron to 5 microns.

Preferably, the diaphragm comprises a central portion and a peripheral portion, and a spring structure connecting the two, the movable area of the diaphragm comprising an area of the central portion and an area of the spring structure.

Preferably, the sensitivity V of the microphone_o|ACComprises the following steps:

where Δ C represents the amount of capacitance change caused by vibration of the diaphragm, C_moAn effective capacitance component, C, representing an effective deformation of the middle portion of the diaphragm_p2An ineffective capacitance component representing an ineffective deformation of a region of the spring structure of the diaphragm or no deformation of a region of the peripheral portion of the diaphragm, CL represents a load capacitance of the MEMS microphone, V_BIASRepresenting the bias voltage.

Preferably, the bias voltage V_BIASComprises the following steps:V_BIAS＝VDD-V_dc|inwherein VDD represents a voltage applied between the diaphragm and the back electrode plate electrode, V_dc|inRepresenting a voltage of a reference plate of the MEMS microphone.

Preferably, the spring structure of the diaphragm is a concentric annular corrugated portion, or a spiral corrugated portion.

Preferably, the diaphragm further comprises a reinforcing rib at a peripheral portion of the diaphragm.

Preferably, the stiffening ribs of the membrane are radial strip beams or a parapet structure at the peripheral portion.

Preferably, the female reinforcing structure comprises a plurality of annular sections, and the shape of each annular section is rectangular and wavy.

Preferably, the reinforcing rib includes a plurality of ring-shaped cut surfaces, and corners of the ring-shaped cut surfaces are shaped as circular arcs or trapezoidal waves or sine waves having an inclination.

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

Preferably, a partial area of the peripheral portion of the diaphragm is a discontinuous area.

Preferably, the edge of the peripheral portion of the membrane sheet is discontinuous, the edge of the peripheral portion is serrated, and the plurality of indentations of the serrations form the discontinuous region.

Preferably, the discontinuous region of the peripheral portion includes a hollow structure, the hollow structure includes a plurality of through holes, and the through holes are circular, trapezoidal, or polygonal in shape.

Preferably, the method further comprises the following steps: a first isolation layer between the diaphragm and the substrate, the acoustic cavity extending through the first isolation layer such that a movable area of the second surface of the diaphragm is exposed; and a second isolation layer located between the back electrode plate electrode and the diaphragm, wherein at least a partial area of a peripheral portion of the diaphragm is sandwiched between the first isolation layer and the second isolation layer.

Preferably, the method further comprises the following steps: the back plate electrode is positioned between the first protective layer and the second protective layer, and the first protective layer is positioned between the second isolation layer and the back plate electrode.

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

Preferably, the second protective layer serves as a mechanical support layer for the back electrode plate electrode to provide rigidity so that the back electrode plate electrode is maintained in a non-deformed state in an operating state.

Preferably, the method further comprises the following steps: a plurality of release holes penetrating the first protective layer, the back electrode plate electrode, and the second protective layer; and a cavity in the second isolation layer, the cavity being in communication with the release hole and exposing the first surface of the diaphragm.

Preferably, the plurality of release holes are circular in shape, and have a diameter of 1 to 15 micrometers.

Preferably, the plurality of release holes have a shape of any one of a polygon and a cross-flower hole.

Preferably, a maximum value of a distance between two apexes of the plurality of release holes is 1 to 15 micrometers.

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

Preferably, the method further comprises the following steps: a first lead passing through the second protective layer, the first protective layer, and the second isolation layer to the first surface of the diaphragm; and a second lead passing through the second protective layer to a second surface of the back electrode plate electrode.

Preferably, the helical spring structure includes at least one spiral thread radiating outwardly from a middle portion of the diaphragm.

According to another aspect of the present application there is provided a method of manufacturing a silicon microphone, comprising: sequentially forming a diaphragm and a back plate electrode 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; and forming an acoustic cavity penetrating through the substrate to the second surface of the diaphragm, wherein the back electrode plate electrode is located above the movable region of the diaphragm, and an area of the back electrode plate electrode is equal to or smaller than an area of the movable region of the diaphragm.

Preferably, the method further comprises the following steps: forming a first isolation layer between the diaphragm and the substrate, the acoustic cavity extending through the first isolation layer such that a movable area of the second surface of the diaphragm is exposed; forming a second isolation layer between the back electrode plate electrode and the diaphragm, wherein at least a partial area of a peripheral portion of the diaphragm is sandwiched between the first isolation layer and the second isolation layer.

Preferably, the method further comprises the following steps: a second isolation layer formed between the second isolation layer and the back electrode plate electrode; a first protective layer; and forming a second protective layer over the back electrode plate electrode.

Preferably, the method further comprises the following steps: a plurality of release holes are formed through the first protective layer, the back electrode plate electrode and the second protective layer; and forming a cavity in the second isolation layer, the cavity being in communication with the release hole and exposing the first surface of the diaphragm.

Preferably, the method further comprises the following steps: forming a first lead through the second protective layer, the first protective layer, and the second isolation layer to a first surface of the diaphragm; and forming a second lead through the second protective layer to a second surface of the back electrode plate electrode.

According to the MEMS microphone of the embodiment of the present invention, the back plate electrode is located above the movable region of the diaphragm, and the area of the back plate electrode is equal to or smaller than the area of the movable region of the diaphragm, so that the influence of parasitic capacitance that does not contribute to the sensitivity of the MEMS microphone can be reduced. Even if there is process fluctuation, since the back plate electrode only needs to be aligned with the movable region of the diaphragm, it is possible to easily align the two.

In a preferred embodiment, the area of the back electrode plate electrode is smaller than or equal to the minimum cross-sectional area of the acoustic cavity, so that the problem of reliability reduction of the MEMS microphone caused by process fluctuation in batch production is avoided, and the overall performance of the product is improved.

In a preferred embodiment, the area of the back electrode plate electrode is 70% to 100% of the movable area of the diaphragm. The MEMS microphone adopts the pattern of the back electrode plate electrode to limit the effective capacitance area, can reduce the influence of parasitic capacitance which does not contribute to the sensitivity of the MEMS microphone, inhibit the adverse influence of the parasitic capacitance and process fluctuation on the device capability, and improve the working sensitivity of the device.

In a preferred embodiment, the backplate 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 a surface facing the first surface of the diaphragm to prevent adhesion between the back electrode plate electrode and the diaphragm. The second protective layer serves as a mechanical support layer for the back electrode plate electrode to provide rigidity so that the back electrode plate electrode is maintained in an undeformed state in an operating state. Since the second protective layer serves as a mechanical support layer, the degree of freedom in device design can be improved. The pattern design of the back electrode plate electrode of the MEMS microphone only needs to be designed based on electrical performance, and the requirement of mechanical rigidity is not considered, so that the effective capacitance area can be limited by adopting the pattern of the back electrode plate electrode, and the influence of parasitic capacitance which does not contribute to the sensitivity of the MEMS microphone can be reduced.

In a preferred embodiment, the membrane of the MEMS microphone comprises a spring structure of concentric annular corrugated portions, or spiral corrugated portions. The spring structure of the diaphragm effectively releases the stress of the diaphragm and improves the sensitivity of the MEMS microphone.

In a preferred embodiment, the diaphragm further comprises a reinforcing rib located at the peripheral part of the diaphragm, so that the elastic property of the diaphragm can be improved, the vibration area can be controlled, the elastic coefficient of the membrane structure can be improved, the resonance frequency of the mechanical structure can be improved, and the requirement of performance design of the MEMS microphone can be met.

In a preferred embodiment, the partial area of the peripheral portion of the membrane is a discontinuous area. The discontinuous area is discontinuous at the edge of the peripheral part or a hollow structure of the peripheral part. A capacitor structure cannot be formed between the discontinuous area of the diaphragm and the upper and lower dielectric layers, so that the parasitic capacitance which is unfavorable for the sensitivity of the microphone is reduced. Meanwhile, the discontinuous area can release part of the membrane stress, and the sensitivity of the membrane is effectively improved.

In a preferred embodiment, the MEMS microphone further includes a plurality of release holes penetrating the first protective layer, the back electrode plate electrode, and the second protective layer. The release holes not only serve as supply channels for the etchant during processing, but also reduce the acoustic resistance in the operating state of the MEMS microphone.

Drawings

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

FIG. 1 illustrates an exploded view of a MEMS microphone in accordance with an embodiment of the present invention;

fig. 2 shows a flow diagram of a method of manufacturing a MEMS microphone according to an embodiment of the invention;

fig. 3a to 3l show cross-sectional views of different stages of a method of manufacturing a MEMS microphone according to an embodiment of the invention;

FIG. 4a shows a schematic structural diagram of a diaphragm of a MEMS microphone in accordance with an embodiment of the present invention; FIG. 4b shows a schematic structural diagram of another diaphragm of a MEMS microphone in accordance with an embodiment of the invention;

FIG. 5a shows a schematic structural diagram of a diaphragm of a MEMS microphone according to another embodiment of the present invention; fig. 5b shows a schematic structural view of another diaphragm of a MEMS microphone according to another embodiment of the invention;

FIG. 6a shows a schematic structural diagram of a diaphragm of a MEMS microphone according to yet another embodiment of the present invention; fig. 6b shows a schematic structural view of another diaphragm of a MEMS microphone according to yet another embodiment of the invention;

FIG. 7 shows a detail according to C in FIG. 1;

FIG. 8 illustrates different deformation regions of a MEMS microphone according to an embodiment of the present invention; and

fig. 9 shows an equivalent circuit diagram of a MEMS microphone according to an embodiment of the present invention.

Detailed Description

Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by the same or similar reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale.

The present invention may be embodied in various forms, some examples of which are described below.

Fig. 1 shows an exploded view of a MEMS microphone according to an embodiment of the present invention.

The MEMS microphone 100 includes a substrate 101, a diaphragm 103 on the substrate 101, and a backplate electrode 106. The diaphragm 103 and the back plate electrode 106 are spaced apart from each other, and a first surface of the diaphragm 103 and a first surface of the back plate electrode 106 are opposite to each other. The acoustic cavity 115 extends through the substrate 101 to the second surface of the diaphragm 103. The back plate electrode 106 is located above the movable region of the diaphragm 103, and the area of the back plate electrode 106 is equal to or smaller than the area of the movable region of the diaphragm 103. In some preferred embodiments, the area of the back plate electrode 106 is 70% to 100% of the movable area.

In some preferred embodiments, the area of the backplate electrode 106 is equal to or less than 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 obtained at different levels are all the same, and the only cross-sectional area is the minimum cross-sectional area of the acoustic cavity 121. When the opening of the acoustic cavity 115 has an inverted trapezoidal or trapezoidal shape, the area of the cross-section of the acoustic cavity 115 at the first surface or the second surface of the substrate 101 is the smallest. In some embodiments, the smallest cross-section has a radius of 385 microns to 415 microns.

Further, the diaphragm 103 comprises a middle portion and a peripheral portion, and a spring structure connecting the two, and the movable area of the diaphragm 103 comprises an area of the middle portion and an area of the spring structure. The spring structure of the diaphragm 103 is, for example, a concentrically annular corrugated portion, or a spiral corrugated portion. Further, the helical spring structure includes at least one helical thread radiating outwardly from a middle portion of the diaphragm.

In an alternative embodiment, the membrane 103 further comprises a stiffening rib at said peripheral portion, for example a radial strip beam or a rib structure at the peripheral portion, and further the rib structure comprises a plurality of ring-shaped cut-outs, the shape of the ring-shaped cut-outs being rectangular wave-like. Alternatively, the reinforcing rib includes a plurality of ring-shaped cut surfaces, and the shape of the corners of the plurality of ring-shaped cut surfaces is a circular arc or a trapezoidal wave with inclination or a sine wave. 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, and further, the parapet structure includes a plurality of annular sections, and the shape of the annular sections is rectangular wave-shaped. Alternatively, the reinforcing rib includes a plurality of ring-shaped cut surfaces, and the shape of the corners of the plurality of ring-shaped cut surfaces is a circular arc or a trapezoidal wave with inclination or a sine wave.

In an alternative embodiment, a partial region 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 plurality of indentations of the serrations form discontinuous regions. In an alternative embodiment, the discontinuous region of the peripheral portion of the membrane 103 comprises a hollow structure, and further, the hollow structure comprises a plurality of through holes, and the through holes are polygonal and circular.

Further, the MEMS microphone 100 further includes a first isolation layer 102 and a second isolation layer 104. At least a partial area of the peripheral portion of the diaphragm 103 is sandwiched between the first release layer 102 and the second release layer 104. The first isolation layer 102 is located between the substrate 101 and the membrane 103, and the acoustic cavity 115 penetrates the substrate 101 and the first isolation layer 102 to expose an area of the middle portion of the second surface of the membrane 103 and an area of the spring structure, and optionally also at least a partial area of the peripheral portion of the second surface of the membrane 103. 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 a region of the middle portion of the first surface of the diaphragm 103, a region of the spring structure, and at least a partial region of the peripheral portion. Thus, the middle portion of the diaphragm 103 can freely vibrate in the cavity 114 and the acoustic cavity 115. The thickness of the second isolation layer 104 defines the spacing between the diaphragm 103 and the back-plate electrode 106, for example 1 to 5 microns.

Further, the MEMS microphone 100 further includes a first protection layer 105 and a second protection layer 107. The back plate electrode 106 is, for example, integrally sandwiched between the first protective layer 105 and the second protective layer 107. A first surface of the back plate electrode 106 is in contact with the first protective layer 105, a second surface of the back plate electrode 106 is in contact with 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 form a back plate structure.

Further, the first protective layer 105 forms a plurality of protrusions on a surface facing the first surface of the diaphragm 103 to prevent adhesion between the back electrode 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 an operating state.

Further, the MEMS microphone 100 further includes a plurality of release holes 113. The release hole 113 penetrates the first protective layer 105, the back plate electrode 106, and the second protective layer 107, and communicates with a cavity 114 in the second isolation layer 104. The release hole 113 has a shape of, for example, any one of a circle, a cross-flower hole, and a polygon. The diameter of the release holes 113 is 1 to 15 micrometers when the shape of the release holes 113 is circular. The maximum value of the distance between the two vertexes of the release hole 113 is 1 to 15 micrometers when the shape of the release hole 113 is any one of a polygon or a cross-flower hole. In this embodiment, the plurality of release holes 113 are arranged in a honeycomb structure array (staggered rectangular array) having different row and/or column pitches, the entire array being confined within a circular area, for example. In alternative embodiments, the plurality of release holes 113 may be arranged in a rectangular array, a circular array, or the like.

Further, the MEMS microphone 100 further includes a contact 121 connected to the diaphragm 103, a contact 122 connected to the backplate electrode 106, and a first lead 123 and a second lead 124 connected to the

contacts

121 and 122, respectively. The first lead 123 reaches the first surface of the diaphragm 103 through the second protective layer 107, the first protective layer 105, and the second isolation layer 104, thereby being connected to the first contact 121. And a second lead 124 passing through the second protective layer 107 to the second surface of the back electrode 106 to be connected to the second contact 122.

Fig. 2 shows a flow chart of a method of manufacturing a MEMS microphone according to an embodiment of the present invention, and fig. 3a to 3l show cross-sectional views of different stages of the method of manufacturing a MEMS microphone according to an embodiment of the present invention, in which the cross-sectional views are taken in a direction indicated by a line AA shown in fig. 2.

In step S01, a first isolation layer 102 is formed on the substrate 101, as shown in fig. 3 a.

In this embodiment, the substrate 101 is, for example, a substrate silicon wafer of <100> crystal orientation. Optionally, the substrate is doped N-type. The first isolation layer 102 is, for example, a silicon oxide layer. For example, a silicon oxide layer is formed as the first isolation layer 102 on the substrate 101 by a thermal oxidation or Chemical Vapor Deposition (CVD) method.

A portion of the first isolation layer 102 will act as a sacrificial layer for forming part of the acoustic cavity below the diaphragm. The thickness of the first isolation layer 102 is, for example, 0.5 to 2 micrometers.

In step S02, a groove 131 is formed on the surface of the first isolation layer 102, as shown in fig. 3 b.

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 using a photolithography process. The exposed portions of the first isolation layer 102 are removed using a selective etchant with the resist layer as a mask, thereby forming the recesses 131. By controlling the etching time, the etching can be stopped at a predetermined depth to the first isolation layer 102. After etching, the resist layer may be removed by ashing or dissolution in a solvent.

The recess 131 is open at the surface of the first isolation layer 102 and extends downward. The shape of the recess 131 is a concentric ring shape, for example, including 1 to 6 nested circular ring shapes, as viewed from the surface of the first insulating layer 102. The shape of the groove 131 is substantially trapezoidal or V-shaped with a bottom dimension smaller than an opening dimension when viewed in cross section of the first separator 102, and in a preferred embodiment, the shape of the groove 131 is square when viewed in cross section of the first separator 102. The depth of the grooves 131 is, for example, 0.5 to 0.8 micrometers. The recess 131 serves to define a spring structure of the diaphragm to be formed in a subsequent step.

Preferably, the opening surface of the groove 131 and the surface of the first isolation layer 102 form a smooth transition curved surface. To this end, an additional deposition step may be used to form a conformal capping layer, such as a thin oxide layer, to improve the topography of the recess 131 to obtain a rounded transition curve. The thickness of the cover layer is, for example, 0.1 to 2 micrometers.

Preferably, the groove 131 is used not only to define the spring structure of the diaphragm, but also to form a helical structure in the spring structure area of the diaphragm and to define a reinforcing rib in the periphery of the diaphragm.

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, as shown in fig. 3 c.

In this embodiment, the membrane 103 is for example composed of doped polysilicon. For example, Low Pressure Chemical Vapor Deposition (LPCVD) is used to deposit polysilicon on the first isolation layer 102, for example, at a temperature of 570 to 630 degrees celsius. Further, the polysilicon layer is patterned using photolithography and etching steps to pattern the diaphragm 103 and the contact 121 in different regions of the polysilicon layer, respectively.

The diaphragm 103 comprises a central 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 continuously and conformally covers the bottom surface and the sidewalls of the recess 131 with the middle portion 103a and the peripheral portion 103 c. The spring structure 103b is a concentric ring-shaped corrugated portion, in conformity with the shape of the groove 131. The thickness of the membrane 103 is for example 0.3 to 1 micrometer, preferably 0.4 micrometer.

In this embodiment, the central 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 corrugated portion. The middle portion 103a of the diaphragm 103 and the spring structure 103b are the movable area of the diaphragm 103. In an alternative embodiment, the spring structure of the membrane 103 is a helically corrugated portion (as shown in fig. 4a, 4 b). In both embodiments, the spring structure of fig. 4a has a dense thread, with the radius of curvature of the spiral thread being invariant with position. The spring structure in fig. 4b has sparse threads, and the curvature radius of the spiral thread varies with the position, and the two embodiments can be selected according to the requirements of practical application. Compared with a diaphragm with a flat surface, the diaphragm 103 with a spring structure formed on the surface can improve the elastic characteristic of the diaphragm, control the vibration area, improve the elastic coefficient of the diaphragm structure, and meet the requirement of performance design of the MEMS microphone. In an alternative embodiment, the middle portion of the diaphragm 103 is recessed downward to the same depth as the spiral threads of the spring structure. In a preferred embodiment, the radius of curvature of each spiral is the same. In an alternative embodiment, the spring structure is located in the entire diaphragm 103, i.e. the middle and peripheral portions of the diaphragm 103 are provided as spring structures. The stress of the diaphragm is effectively released, and the sensitivity of the MEMS microphone is improved.

In an alternative embodiment, the diaphragm 103 further includes reinforcing ribs formed at the peripheral portion 103c (as shown in fig. 5a, 5 b). As shown in fig. 5a, the stiffening 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 ring-shaped sections, and the ring-shaped sections have equal radii and have a rectangular wave-shaped appearance. In an alternative embodiment, the diaphragm 103 further includes a reinforcing rib 1032 (as shown in FIG. 5 b) formed at the peripheral portion 103 c. The stiffener 1032 of the diaphragm 103 includes a plurality of ring-shaped sections having equal radii and corners having circular arcs, trapezoidal waves having inclinations, sinusoidal waves, and the like. Compared with the diaphragm 103 with a flat surface, the diaphragm 103 with the spring structure 103b and the reinforcing rib 1031 formed on the surface can improve the elastic characteristics of the diaphragm, control the vibration region, improve the elastic coefficient of the diaphragm structure, improve the resonance frequency of the mechanical structure, and meet the requirements of the performance design of the MEMS microphone. In a preferred embodiment, the reinforcing rib formed on the peripheral portion 103c of the diaphragm 103 is a parapet structure including a plurality of ring-shaped cut surfaces, and the plurality of ring-shaped cut surfaces may include at least two of a rectangular wave shape, a circular arc shape at a corner of the ring-shaped cut surface, or a trapezoidal wave shape with an inclination, or a sine wave shape.

In an alternative embodiment, a partial area of the peripheral portion 103c of the diaphragm 103 is a discontinuous area (as shown in fig. 6a, 6 b). As shown in fig. 6a, the edge of the peripheral portion of the membrane 103 is discontinuous. Specifically, the edge of the peripheral portion 103c is serrated, and the plurality of indentations 1033 of the serrated form a discontinuous area. In an alternative embodiment, as shown in fig. 6b, the discontinuous region of the peripheral portion 103c of the membrane 103 comprises an openwork structure. Specifically, the hollow structure includes a plurality of through holes 1034, and the through holes 1034 are circular, trapezoidal, or polygonal, wherein in this embodiment, the through holes 1034 are shaped like a sector, and the plurality of through holes 1034 are formed in a peripheral portion of the membrane 103 in a crossed arrangement, further, the membrane 103 is shaped like a sunflower, and more specifically, the edges of the membrane 103 are connected by a plurality of circular arc edges.

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, as shown in fig. 3 d.

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 as the second isolation layer 104 by a method of Low Pressure Chemical Vapor Deposition (LPCVD) or Plasma Enhanced Chemical Vapor Deposition (PECVD). After forming the second isolation layer 104, the surface of the second isolation layer 104 is planarized, for example, using chemical mechanical planarization.

A portion of the second isolation layer 104 will act as a sacrificial layer for forming a cavity above the diaphragm 103 and also define the spacing between the diaphragm and the back electrode plate electrode by the thickness of the second isolation layer 104. The thickness of the second isolation layer 104 is chosen according to the electrical and acoustic properties of the MEMS microphone, for example 2 to 4 microns.

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. The exposed portions of second isolation layer 104 are removed with a selective etchant using the resist layer as a mask, thereby forming openings 132. By controlling the etching time, the etching can be stopped at a predetermined depth to the second isolation layer 104. After etching, the resist layer may be removed by ashing or dissolution in a solvent.

The opening 132 is open at the surface of the second isolation layer 104 and extends downward. The openings 132 are shaped as a plurality of circular holes, a plurality of square holes, or a plurality of triangular holes, as viewed from the surface of the second separator layer 104. The shape of the opening 132 is a substantially trapezoidal or V-shape having a bottom surface size smaller than an opening surface size when viewed from a cross section of the second separator 104. The openings 132 are, for example, 0.5 to 1.5 microns in diameter and 0.5 to 1.5 microns deep. The openings 132 serve to define protrusions that will be formed in a subsequent step to prevent adhesion of the back plate electrode.

In step S05, a first protection layer 105 is formed on the second isolation layer 104, as shown in fig. 3 e.

The first protective layer 105 is composed of, for example, any one selected from a silicon nitride layer, a boron nitride layer, and a silicon carbide layer. In this embodiment, the first protection layer 105 is, for example, a boron nitride layer. For example, a boron nitride layer, in which N is used, is formed on second isolation layer 104 by filament-assisted Plasma Enhanced Chemical Vapor Deposition (PECVD)₂、H₂And from H₂Diluted B₂H₆As the reaction gas, the substrate temperature is 400 to 500 degrees Celsius, and the reaction pressure is about 100 Pa. The thickness of the first protective layer 105 is, for example, 800 to 1500 angstroms.

The first protection layer 105 fills the opening 132 on the surface of the second isolation layer 104, thereby forming the protrusion 105 a. The shape of the protrusion 105a conforms to the shape of the opening 132, such as any of: polygonal pyramid, polygonal prism, cylinder. The diameter of the protrusions 105a is, for example, 0.5 to 1.5 micrometers, and the depth is, for example, 0.5 to 1.5 micrometers.

In step S06, the back plate electrode 106 is formed on the first protection layer 105, and the contact 122 to which the back plate electrode 106 is connected is formed, as shown in fig. 3 f.

The back plate electrode 106 is a conductive layer, and is composed of, for example, any one selected from Al, Cu, Au, Ti, Ni, Wu, and alloy-doped polysilicon thereof. For example, a doped polysilicon layer is formed on the first protective layer 105 using Low Pressure Chemical Vapor Deposition (LPCVD). The polysilicon layer is then patterned using photolithography and etching steps to pattern the back plate electrode 106. The back electrode plate electrode 106 has a thickness of, for example, 0.3 to 1 μm.

In this embodiment, the back plate electrode 106 and the diaphragm 103 constitute the two plates of the capacitor. As described above, the diaphragm 103 includes the middle portion 103a, the peripheral portion 103c, and the 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 defining an effective capacitance area, which is advantageous for reducing the parasitic capacitance of the finally formed MEMS microphone.

In this embodiment, the back plate electrode 106 has a flat surface, and the surface shape viewed 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, a spiral shape at a middle portion and/or a reinforcing rib at a peripheral portion, for example, a radial strip beam or a cross strip beam or a parapet structure. In some preferred embodiments, the reinforcing structure extends through the entire back plate electrode 106. The surface shape of the back electrode 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 the reinforcing structure formed on the surface can improve the rigidity of the back plate electrode, so that the back plate electrode does not deform in the working state of the MEMS microphone.

In some preferred embodiments, this step is followed by etching through the first protective layer 105 by conventional semiconductor processing to form the recess 191 on the second isolation layer.

In step S07, a second protective layer 107 is formed on the back plate electrode 106, as shown in fig. 3 g.

The second protective layer 107 is composed of, for example, 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 filament-assisted Plasma Enhanced Chemical Vapor Deposition (PECVD), in which N is used₂、H₂And from H₂Diluted B₂H₆As the reaction gas, the substrate temperature is 400 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 to 1 μm. The first protective layer 105, the back plate electrode 106, and the second protective layer 107 form a back plate structure.

Since the back plate electrode 106 is patterned, a first portion of the second protective 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 protective layer 105.

It should be noted that, if the groove 191 is formed by etching through the first protection layer 105 before forming the second protection layer 107 on the second isolation layer, the step further includes forming a third portion of the second protection layer 107 in the groove 191.

In step S08, via holes 111 reaching the contacts 121 of the diaphragm 103 and via holes 112 reaching the contacts 122 of the back plate electrode 106, respectively, are formed, as shown in fig. 3 h.

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 using a photolithography process. The via holes 111 and 112 are formed using a selective etchant with the resist layer as a mask. In the first partial region of the second protective layer 107, the etching removes the portion of the second protective layer 107 exposed through the mask opening to form the via hole 112 reaching the contact 122 of the back plate electrode 106. In the second partial region of the second protective layer 107, the etching removes, from top to bottom, the portions of the second protective layer 107, the first protective layer 105, and the second isolation layer 104, each exposed through the mask opening, in order to form a via hole 111 reaching the contact 121 of the membrane 103. After etching, the resist layer may be removed by ashing or dissolution in a solvent.

Due to the patterning step of the back electrode plate electrode 106 described above, the second portion of the second protective layer 107 is in direct contact with the corresponding portion of the first protective layer 105. At least one via hole 111 extends from the second partial surface of the second protective layer 107, via the second protective layer 107, the first protective layer 105 and the second isolation layer 104, to a contact 121 of the membrane 103 below the back plate electrode 106.

In step S09, leads 123 reaching the contacts 121 of the diaphragm 103 and leads 124 reaching the contacts 122 of the back plate electrode 106, respectively, are formed as shown in fig. 3 i.

In this embodiment, the

leads

123 and 124 are composed of a conductive material, for example, any one selected from aluminum, gold, silver, copper, nickel, titanium, chromium, or an alloy thereof. The aluminum alloy for the lead wire 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 metal layer is, for example, 1 to 2 micrometers thick and fills the via holes 111 and 112.

A resist layer is formed on the surface of the metal layer, and a pattern including an opening is formed in the resist layer by a photolithography process. The exposed portions of the metal layer are removed with a selective etchant using the resist layer as a mask. The etching uses the second protective layer 107 as a stop layer due to the selectivity of the etchant. After etching, the resist layer may be removed by ashing or dissolution in a solvent.

In the first partial region of the second protective layer 107, at least one lead 124 passes through the second protective layer 107 to reach the back 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, the second isolation layer 104 in this order to reach the membrane 103.

Back electrode plate electrode in step S10, a release hole 113 is formed through the second protective layer 107, the back electrode plate electrode 106, and the first protective layer 105, as shown in fig. 3 j.

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 using a photolithography process. The second protective layer 107, the back plate electrode 106, and the first protective layer 105 are each removed from the exposed portion thereof with a selective etchant using the resist layer as a mask, thereby forming the release holes 113. Due to the selectivity of the etchant, the second isolation layer 104 acts as a stop layer. After etching, the resist layer may be removed by ashing or dissolution in a solvent.

This step forms the release holes 113, for example, using a special deep trench etcher. The release hole 113 serves not only as a supply channel of an etchant in the manufacturing process but also as a sound hole in the finally formed MEMS microphone to reduce acoustic resistance. The shape of the release hole 113 is, for example, any one of a circle, a cross-flower hole, and a polygon, as viewed from the surface of the second protective layer 107. The diameter of the release holes 113 is 1 to 15 micrometers when the shape of the release holes 113 is circular. The maximum value of the distance between the two vertexes of the release hole 113 is 1 to 15 micrometers when the shape of the release hole 113 is any one of a polygon or a cross-flower hole. In this embodiment, the shape of the release holes 113 is hexagonal (a partial enlarged view at C in fig. 1 as shown in fig. 7), and a plurality of the release holes 113 are arranged in a honeycomb structure array (a staggered rectangular array). In alternative embodiments, the plurality of release holes 113 may be arranged in a rectangular array, a circular array, or the like.

In step S11, an acoustic cavity 115 is formed through the substrate 101 below the diaphragm 103, as shown in fig. 3 k.

In this embodiment, the thickness of the substrate 101 is reduced to a design value, for example 350 microns to 450 microns, preferably 400 microns, by a chemical mechanical planarization or thinning process. For example, a first surface and a second surface of the substrate 101, which are opposite to each other, are used for forming the above-described first isolation layer 102 and are free surfaces, respectively, and the second surface is polished 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 including an opening is formed in the resist layer by a photolithography process. The exposed portions of the substrate 101 are removed with a selective etchant using the resist layer as a mask, thereby forming the acoustic cavity 115. In this embodiment, the acoustic chamber is a square opening, alternatively, it may be an inverted trapezoidal opening. The first isolation layer 102 acts as a stop layer due to the selectivity of the etchant. After etching, the resist layer may be removed by ashing or dissolution in a solvent.

Wherein the area of the back plate electrode 106 is smaller 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 obtained at different levels are all the same, and the only cross-sectional area is the minimum cross-sectional area of the acoustic cavity 115. When the opening of the acoustic cavity 115 has an inverted trapezoidal or trapezoidal shape, the area of the cross-section of the acoustic cavity 115 at the first surface or the second surface of the substrate 101 is the smallest. In some embodiments, the smallest cross-section has a radius of 385 microns to 415 microns.

This step forms the acoustic cavity 115, for example using a conventional Bosch process in MEMS technology and a special deep trench etcher.

In step S12, a portion of the first isolation layer 102 is removed via the acoustic cavity 115 and a portion of the second isolation layer 104 is removed via the release hole 113 to release the membrane 103, as shown in fig. 3 l.

In this embodiment, for example, HF acid is used as an etchant, and the acoustic chamber 115 and the release hole 113 formed in the above-described step are used as an access passage for the etchant. The first protective layer 105 and the second protective layer 107 each function as a protective film for the back plate electrode 106, so that the back plate electrode 106 is not etched in this etching step.

A portion of each of first barrier layer 102 and second barrier layer 104 is removed by a vapor phase fumigation with HF acid or a wet etching with HF acid, respectively, so that a portion of each of first and second surfaces of diaphragm 103 facing each other is re-exposed, thereby releasing 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 protection layer 105 and the first surface of the membrane 103. The release hole 113 and the cavity 114 communicate with each other, providing an air flow passage during vibration of the diaphragm 103.

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

Fig. 8 and 9 respectively show different deformation regions of a MEMS microphone and an equivalent circuit diagram according to an embodiment of the present invention.

In the MEMS microphone 100 shown in fig. 1, the back plate electrode 106 and the diaphragm 103 constitute two plates of a capacitor. As described above, the diaphragm 103 includes the middle portion 103a, the peripheral portion 103c, and the spring structure 103c therebetween, the area of the back plate electrode 106 is a portion of the effective deformation, and the back plate electrode 106 corresponds to the middle portion 103a of the diaphragm 103, thereby defining an effective capacitance area for effective deformation, which is beneficial for reducing the parasitic capacitance of the finally formed MEMS microphone.

Sensitivity V of MEMS microphone 100_o|ACExpressed as:

V_BIAS＝VDD-V_dc|in(2)，

where Δ C represents the amount of change in capacitance due to the diaphragm of the MEMS microphone vibrating in response to air vibration generated by the sound signal, C_moAn effective capacitance component, C, representing the effective deformation of the diaphragm of the MEMS microphone in response to an acoustic signal_p2An ineffective capacitance component representing ineffective deformation or no deformation of the diaphragm of the MEMS microphone in response to the acoustic signal, VDD represents a voltage applied between the diaphragm and the back plate electrode of the MEMS microphone, e.g., generated by a charge pump structure in an ASIC circuit, V_dc|inRepresenting the voltage of the reference plate of the MEMS microphone, e.g. the operating point voltage of the ASIC signal input in conjunction therewith, CL representing the load capacitance, e.g. consisting of the parasitic capacitances of the wiring and the pads, e.g. of the order of 1pF, V_BIASRepresenting a bias voltage, V_BIAS＝VDD-V_dc|in。

The area of the backplate 106 is an effective deformation area, and in this embodiment, the middle portion 103a of the diaphragm 103 of the MEMS microphone 100 is, for example, an effective deformation area corresponding to a portion of the backplate electrode opposite to the middle portion, and the spring structure 103b is, for example, an ineffective deformation area, and the effective deformation area and the ineffective deformation area belong to a free surface of the peripheral portion 103c and a portion of the peripheral portion 103c sandwiched between the first spacer 102 and the second spacer 104 is, for example, an undeformed portion.

The area of the back electrode plate electrode 106 of the MEMS microphone 100 is equal to or smaller than the area of the movable region of the diaphragm 103. Therefore, the MEMS microphone 100 according to an embodiment of the present invention employs the pattern of the back plate electrode 106 to actually remove the ineffective capacitance component from the detection signal, so that the sensitivity of the detection signal is related to only 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 smaller than or equal to the minimum cross-sectional area of the acoustic cavity 115, so that the problem of reliability reduction of the MEMS microphone caused by process fluctuation in mass production is avoided, and the overall performance of the product is improved.

While embodiments in accordance with the invention have been described above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The scope of the invention should be determined from the following claims.

Claims

1. A MEMS microphone, comprising:

a substrate;

a diaphragm and a backplate electrode on the first surface of the substrate, the diaphragm and the backplate electrode being spaced apart from each other, the first surface of the diaphragm and the first surface of the backplate electrode opposing each other; and

an acoustic cavity extending through the substrate to the second surface of the diaphragm,

wherein the back electrode plate electrode is located above the movable region of the diaphragm, and an area of the back electrode plate electrode is equal to or less than an area of the movable region of the diaphragm.

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

3. The MEMS microphone of claim 1, wherein the area of the back electrode plate electrode is 70-100% of the movable region.

4. The MEMS microphone of claim 2, wherein the smallest cross-sectional area of the acoustic cavity has a radius of 385 to 415 microns.

5. The MEMS microphone of claim 1, wherein a spacing between the back electrode plate electrode and the diaphragm is 1-5 microns.

6. The MEMS microphone of claim 1, wherein the diaphragm comprises a middle portion and a peripheral portion, and a spring structure connecting the two, the movable region of the diaphragm comprising a region of the middle portion and a region of the spring structure.

7. The MEMS microphone of claim 6, wherein the sensitivity V of the microphone_o|ACComprises the following steps:

8. The MEMS microphone of claim 7, wherein the bias voltage V_BIASComprises the following steps: v_BIAS＝VDD-V_dc|inWherein VDD represents a voltage applied between the diaphragm and the back electrode plate electrode, V_dc|inRepresenting a voltage of a reference plate of the MEMS microphone.

9. The MEMS microphone of claim 6, wherein the spring structure of the diaphragm is a concentric annular corrugated portion, or a spiral corrugated portion.

10. The MEMS microphone of claim 1, wherein the diaphragm further comprises a stiffening rib located at a peripheral portion of the diaphragm.

11. The MEMS microphone of claim 10, wherein the stiffening ribs of the diaphragm are radial ribbon beams or a parapet structure at the perimeter portion.

12. The MEMS microphone of claim 11, wherein the female stiffener structure comprises a plurality of circular sections, the circular sections having a rectangular wave shape in profile.

13. The MEMS microphone of claim 10, wherein the reinforcement rib comprises a plurality of ring-shaped cut surfaces, and the shape of corners of the ring-shaped cut surfaces is a circular arc or a trapezoidal wave or a sine wave having an inclination.

14. The MEMS microphone of claim 1, wherein the back electrode plate electrode comprises a protrusion or groove shaped reinforcement structure.

15. The MEMS microphone of claim 1, wherein a partial area of the peripheral portion of the diaphragm is a discontinuous area.

16. The MEMS microphone of claim 15, wherein an edge of the peripheral portion of the diaphragm is discontinuous, the edge of the peripheral portion being serrated, the plurality of indentations of the serrations forming the discontinuous region.

17. The MEMS microphone of claim 15, wherein the discontinuous region of the peripheral portion comprises a hollowed-out structure comprising a plurality of through holes, the through holes being circular, trapezoidal, or polygonal in shape.

18. The MEMS microphone of claim 6, further comprising:

a first isolation layer between the diaphragm and the substrate, the acoustic cavity extending through the first isolation layer such that a movable area of the second surface of the diaphragm is exposed; and

a second isolation layer between the back electrode plate electrode and the diaphragm,

wherein at least a partial area of the peripheral portion of the diaphragm is sandwiched between the first and second spacer layers.

19. The MEMS microphone of claim 18, further comprising:

the back plate electrode is positioned between the first protective layer and the second protective layer, and the first protective layer is positioned between the second isolation layer and the back plate electrode.

20. The MEMS microphone of claim 19, wherein 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 electrode plate electrode and the diaphragm.

21. The MEMS microphone of claim 19, wherein the second protective layer acts as a mechanical support layer for the back electrode plate electrode to provide rigidity such that the back electrode plate electrode is maintained in an undeformed state in an operating state.

22. The MEMS microphone of claim 19, further comprising:

a plurality of release holes penetrating the first protective layer, the back electrode plate electrode, and the second protective layer; and

a cavity in the second isolation layer, the cavity in communication with the release hole, and the cavity exposing the first surface of the diaphragm.

23. The MEMS microphone of claim 22, wherein the plurality of release holes are circular in shape and have a diameter of 1-15 microns.

24. The MEMS microphone of claim 22, wherein the plurality of release holes are any one of polygonal or cross-hatched in shape.

25. The MEMS microphone of claim 24, wherein a maximum of two vertex distances of the plurality of release holes is 1 to 15 micrometers.

26. The MEMS microphone of claim 22, wherein the plurality of release holes are arranged in a rectangular array or a staggered rectangular array or a circular array.

27. The MEMS microphone of claim 19, further comprising:

a first lead passing through the second protective layer, the first protective layer, and the second isolation layer to the first surface of the diaphragm; and

a second lead through the second protective layer to a second surface of the back electrode plate electrode.

28. The MEMS microphone of claim 9, wherein the helical spring structure comprises at least one spiral thread radiating outward from a middle portion of the diaphragm.

29. A method of manufacturing a MEMS microphone, comprising:

sequentially forming a diaphragm and a back plate electrode 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; and

forming an acoustic cavity through the substrate to the second surface of the diaphragm,

30. The method of claim 29, wherein the area of the back electrode plate electrode is equal to or less than the smallest cross-sectional area of the acoustic cavity.

31. A method according to claim 29 wherein the area of the back electrode plate electrode is 70% to 100% of the moveable region.

32. The method of claim 30, wherein the smallest cross-section of the acoustic cavity has a radius of 385 to 415 microns.

33. The method of claim 29, further comprising:

forming a first isolation layer between the diaphragm and the substrate, the acoustic cavity extending through the first isolation layer such that a movable area of the second surface of the diaphragm is exposed;

forming a second isolation layer between the back electrode plate electrode and the diaphragm,

34. The method of claim 33, further comprising:

forming a first protective layer between the second isolation layer and the back electrode plate electrode; and

a second protective layer is formed over the back electrode plate electrode.

35. The method of claim 34, further comprising:

a plurality of release holes are formed through the first protective layer, the back electrode plate electrode and the second protective layer; and

a cavity is formed in the second release layer, the cavity being in communication with the release hole, and the cavity exposing the first surface of the diaphragm.

36. The method of claim 34, further comprising:

forming a first lead through the second protective layer, the first protective layer, and the second isolation layer to a first surface of the diaphragm; and

a second lead is formed through the second protective layer to a second surface of the back electrode plate electrode.

37. The method of claim 29, wherein the diaphragm includes a middle portion and a peripheral portion, and a spring structure connecting the two, the movable region of the diaphragm including a region of the middle portion and a region of the spring structure.

38. The method of claim 37, wherein the spring structure of the diaphragm is a concentric annular corrugated portion, or a spiral corrugated portion.

39. The method of claim 29, wherein the diaphragm further comprises a stiffening rib located at a peripheral portion of the diaphragm.

40. A method according to claim 39, wherein the stiffening ribs of the diaphragm are radial strip beams or a parapet structure at the peripheral portion.

41. The method of claim 29, wherein the back electrode plate electrode comprises a protrusion or groove shaped reinforcing structure.

42. The method of claim 29, wherein the partial area of the peripheral portion of the diaphragm is a discontinuous area.

43. The method of claim 35, wherein the plurality of release holes are any one of polygonal or cross-hatched in shape.

44. The method of claim 35, wherein the plurality of release holes are arranged in a rectangular array or a staggered rectangular array or a circular array.