CN211152207U - MEMS microphone - Google Patents

Abstract

A MEMS microphone is disclosed. The MEMS microphone includes: a substrate; a diaphragm and a back plate electrode on the first surface of the substrate, the diaphragm and the back plate electrode being spaced apart from each other, the first surface of the diaphragm and the first surface of the back plate electrode being opposite to each other; and an acoustic cavity extending through the substrate to the second surface of the diaphragm, the diaphragm including a spring structure, the spring structure of the diaphragm being a concentric annular or spiral corrugated portion. The MEMS microphone is provided with a spring structure in a movable area of the diaphragm, and the stress of the diaphragm can be released. And further, the yield and the reliability of the MEMS microphone device are improved.

Description

MEMS microphone

Technical Field

The utility model belongs to the technical field of the microphone, more specifically relates to MEMS microphone.

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.

Further improvements in the structure of MEMS microphones are desired to improve yield and device reliability and sensitivity.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a MEMS microphone, wherein, the spring structure of MEMS microphone's diaphragm is concentric annular fold part, perhaps spiral helicine fold part to release the stress of diaphragm effectively, improved MEMS microphone's sensitivity.

According to an aspect of the utility model, a MEMS microphone is provided, include: 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, the diaphragm including a spring structure, the spring structure of the diaphragm being a concentric ring or spiral folded portion.

Preferably, the helical spring structure comprises at least one spiral thread radiating from the middle portion of the membrane sheet to the outside.

Preferably, the middle portion of the diaphragm is recessed downward, and the depth of the downward recess of the middle portion is the same as the depth of the spiral thread.

Preferably, the spiral thread is rotationally symmetric around the middle portion of the membrane sheet.

Preferably, the radius of curvature of the spiral is invariant with position.

Preferably, the radius of curvature of the spiral thread varies with position.

Preferably, the center of curvature of the spiral does not change with position.

Preferably, the center of curvature of the spiral is varied with position.

Preferably, the spring structure is located in the entire membrane.

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; 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 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 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 concentric rings comprise 1 to 6 circular rings.

According to the utility model discloses MEMS microphone, the spring structure of MEMS microphone's diaphragm is concentric annular fold part, perhaps spiral helicine fold part. The diaphragm and the spring structure are integrated, so that the stress of the diaphragm is effectively released, and the sensitivity of the MEMS microphone is improved. In particular, the helical spring structure comprises at least one helical thread radiating from the middle portion of the membrane towards the outside, the helical thread being rotationally symmetric around the middle portion of the membrane.

In a preferred embodiment, the central portion of the diaphragm is recessed downward, improving the reliability of the diaphragm. Furthermore, the spring structure is positioned in the whole diaphragm, so that the stress of the diaphragm is effectively released, and the sensitivity of the MEMS microphone is 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 shows an exploded view of a MEMS microphone according to an embodiment of the present invention;

fig. 2 shows a schematic 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. 4 shows a schematic structural diagram of a diaphragm of a MEMS microphone according to an embodiment of the present invention.

Fig. 5 shows a schematic structural diagram of another diaphragm 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 presented in a variety of forms, some 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.

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, such as concentric annular corrugated portions or spiral corrugated portions, effectively relieves the stress of the diaphragm and improves the sensitivity of the MEMS microphone. Further, the concentrically annular corrugated portions include, for example, nested 1 to 6 annular rings. Further, the helical spring structure comprises at least one helical thread radiating from the middle part of the membrane 103 to the outside, the depth of the helical thread can be specifically set according to actual requirements, and the helical thread is rotationally symmetric around the middle part of the membrane 103. The spiral threads of the spiral spring structure have a radial characteristic, and the shape of the spiral threads includes a straight line, a curve with a variable or non-variable curvature radius according to the position, and a curve with a variable or non-variable curvature center according to the position. Such curves include, but are not limited to, bezier curves, archimedes spirals, cartesian log spirals, fermat spirals, equiangular spirals, interlocking spirals, euler spirals.

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 whole membrane, i.e. the middle and peripheral portions of the membrane 103 are provided as spring structures. The stress of the diaphragm is effectively released, and the sensitivity of the MEMS microphone is improved.

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 schematic flow diagram of a method for 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 a method for manufacturing a MEMS microphone according to an embodiment of the present invention, wherein the cross-sectional views are obtained along 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 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 at least one concentric ring, for example comprising nested 1 to 6 ring shapes, as viewed from the surface of the first spacer 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 define a helical structure in the middle portion 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.

The membrane 103 is for example comprised of doped polysilicon in this embodiment polysilicon is deposited on the first isolation layer 102, for example using low Pressure Chemical Vapor Deposition (L ow Pressure Chemical Vapor Deposition, L PCVD), at a Deposition temperature of for example 570 to 630 degrees celsius further the polysilicon layer is patterned using photolithography and etching steps to pattern the membrane 103 and the contacts 121, respectively, in different areas of the polysilicon layer.

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 at least one concentric annular corrugated portion, in conformity with the shape of the recess 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 flat surfaces, and the spring structure 103b of the diaphragm 103 is a concentric annular corrugated portion or a spiral corrugated portion. Wherein the concentric rings comprise 1 to 6 circular rings. As shown in fig. 4 and 5, there are two embodiments of the spiral-shaped corrugated portion of the spring structure 103 b. In the two embodiments, the threads of the spring structure in fig. 4 are dense, and the threads of the spring structure in fig. 5 are sparse, 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 whole membrane, i.e. the middle and peripheral portions of the membrane 103 are provided as spring structures. The stress of the diaphragm is effectively released, and the sensitivity of the MEMS microphone is improved.

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.

For example, a silicon oxide layer is formed on the film 103 as the second isolation layer 104 by a method of low Pressure Chemical Vapor Deposition (L PCVD, &tttttransfer = L "&tttl &ttt/t &tttow Pressure Chemical Vapor Deposition) or Plasma Enhanced Chemical Vapor Deposition (PECVD). after the second isolation layer 104 is formed, the surface of the second isolation layer 104 is planarized using, for example, 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 silicon nitride, boron nitride, and silicon carbide. In this embodiment, the first protection layer 105 is, for example, a boron nitride layer. For example, a boron nitride layer is formed on the second isolation layer 104 by filament-assisted Plasma Enhanced Chemical Vapor Deposition (PECVD), wherein N is used as the boron nitride layer₂、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, for example, composed of any one selected from Al, Cu, Au, Ti, Ni, Wu, and alloys thereof doped polysilicon, for example, a doped polysilicon layer is formed on the first protective layer 105 using low Pressure chemical vapor Deposition (L PCVD, &lttttranslation = L "&tttl &ttt &tttgtt ow Pressure chemical vapor Deposition).

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 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 silicon nitride, boron nitride, and silicon carbide. 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 electrode 106 by a filament-assisted Plasma Enhanced Chemical Vapor Deposition (PECVD) method, in which N is used as the N₂、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 constitute 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, a plurality of conductive paths reaching the surfaces of the diaphragm and the back plate electrode, respectively, are formed. Further, the leads 123 reaching the contacts 121 of the diaphragm 103 and the leads 124 reaching the contacts 122 of the back plate electrode 106, respectively, are formed in the present embodiment, 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 a 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, and in a second partial region 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 sequence to reach the diaphragm 103. Thereby forming a plurality of conductive paths to the surfaces of the diaphragm 103 and the back plate electrode 107, respectively.

In step S10, a release hole 113 is formed through the second protective layer 107, the back 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 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 plurality of release holes 113 are arranged in a honeycomb structure array (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. 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.

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.

In accordance with the embodiments of the present invention as set forth above, these embodiments are not exhaustive and do not 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 its practical application, to thereby enable others skilled in the art to best utilize the invention and its various embodiments with various modifications as are suited to the particular use contemplated. The protection scope of the present invention should be subject to the scope defined by the claims of the present invention.

Claims (15)

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,

the diaphragm comprises a spring structure, and the spring structure of the diaphragm is a concentric ring-shaped or spiral folded part.

2. The MEMS microphone of claim 1, wherein the helical spring structure comprises at least one spiral thread radiating outward from a middle portion of the diaphragm.

3. The MEMS microphone of claim 2, wherein a middle portion of the diaphragm is recessed downward, and a depth of the depression of the middle portion is the same as a depth of the spiral.

4. The MEMS microphone of claim 2, wherein the spiral pattern is rotationally symmetric about the middle portion of the diaphragm.

5. The MEMS microphone of claim 2, wherein a radius of curvature of the spiral is invariant with position.

6. The MEMS microphone of claim 2, wherein a radius of curvature of the spiral is varied with position.

7. The MEMS microphone of claim 2, wherein a center of curvature of the spiral is invariant with position.

8. The MEMS microphone of claim 2, wherein a center of curvature of the spiral varies with position.

9. The MEMS microphone of claim 1, wherein the spring structure is located throughout the diaphragm.

10. The MEMS microphone of claim 1, further comprising:

a first isolation layer between the diaphragm and the substrate, the acoustic cavity extending through the first isolation layer; 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.

11. The MEMS microphone of claim 10, 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.

12. The MEMS microphone of claim 11, 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.

13. The MEMS microphone of claim 12, wherein the plurality of release holes are arranged in a rectangular array or a staggered rectangular array or a circular array.

14. The MEMS microphone of claim 11, 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.

15. The MEMS microphone of claim 1, wherein the concentric rings comprise 1 to 6 circular rings.

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