CN108622846B - MEMS microphone and forming method thereof - Google Patents
MEMS microphone and forming method thereof Download PDFInfo
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- CN108622846B CN108622846B CN201710176077.8A CN201710176077A CN108622846B CN 108622846 B CN108622846 B CN 108622846B CN 201710176077 A CN201710176077 A CN 201710176077A CN 108622846 B CN108622846 B CN 108622846B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
- B81B7/02—Microstructural systems; Auxiliary parts of microstructural devices or systems containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS]
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
- B81C1/00015—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems
- B81C1/00134—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems comprising flexible or deformable structures
- B81C1/00158—Diaphragms, membranes
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R19/00—Electrostatic transducers
- H04R19/04—Microphones
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B2201/00—Specific applications of microelectromechanical systems
- B81B2201/02—Sensors
- B81B2201/0257—Microphones or microspeakers
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2400/00—Loudspeakers
- H04R2400/11—Aspects regarding the frame of loudspeaker transducers
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- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Manufacturing & Machinery (AREA)
- Computer Hardware Design (AREA)
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Signal Processing (AREA)
- Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
- Micromachines (AREA)
- Pressure Sensors (AREA)
Abstract
The invention provides an MEMS microphone and a forming method thereof, the MEMS microphone comprises: a back electrode film comprising a first face and a second face, the back electrode film comprising a functional region and a support region surrounding the functional region; the diaphragm membrane is positioned on the first surface of the back electrode membrane, the mechanical strength of the diaphragm membrane is greater than that of the back electrode membrane, the diaphragm membrane in the functional area is provided with a diaphragm hole, and the diaphragm hole penetrates through the diaphragm membrane; and the support is positioned between the back pole membrane and the vibrating piece membrane of the support area. The mechanical strength of the diaphragm membrane is greater than that of the back electrode membrane, so that the diaphragm membrane can bear larger stress, and the MEMS microphone is not easy to break in the use process, so that the service life of the MEMS can be prolonged.
Description
Technical Field
The invention relates to the technical field of semiconductor manufacturing, in particular to an MEMS microphone and a forming method thereof.
Background
MEMS, that is, micro electro Mechanical Systems (micro electro Mechanical Systems), is a leading-edge research field of multidisciplinary crossing developed on the basis of microelectronic technology. Over forty years of development, it has become one of the major scientific and technological fields of world attention. It relates to various subjects and technologies such as electronics, machinery, materials, physics, chemistry, biology, medicine and the like, and has wide application prospect.
MEMS (micro-electro-mechanical systems) microphones are microphones manufactured on the basis of MEMS technology, in short a capacitor integrated on a micro-silicon wafer. MEMS microphones are capable of withstanding high reflow temperatures, are easily integrated with CMOS devices and other audio circuitry, and have low noise performance, thereby making their use more and more widespread.
The MEMS microphone is generally composed of a MEMS micro-capacitance sensor, a micro-integrated conversion circuit, an acoustic cavity and an RF anti-interference circuit. The MEMS micro-capacitance electrode head comprises a silicon diaphragm and a silicon back electrode which are used for receiving sound, the silicon diaphragm can directly receive audio signals and transmit the audio signals to the micro-integrated circuit through the MEMS micro-capacitance sensor, the micro-integrated circuit converts and amplifies high-resistance audio electrical signals into low-resistance electrical signals, and meanwhile, the low-resistance electrical signals are filtered by the RF anti-noise circuit and output electrical signals matched with a front-end circuit, so that the acousto-electric conversion is completed. And the electric signals are read, so that the voice is identified.
MEMS microphones formed by the prior art have short service life.
Disclosure of Invention
The invention provides an MEMS microphone and a forming method thereof, which can prolong the service life of the MEMS microphone.
To solve the above problems, the present invention provides a MEMS microphone, including: a back polar film comprising opposing first and second faces, the back polar film comprising a functional region and a support region surrounding the functional region; the diaphragm membrane is positioned on the first surface of the back pole membrane, the mechanical strength of the diaphragm membrane is greater than that of the back pole membrane, the functional area diaphragm membrane is provided with a diaphragm hole, the diaphragm hole penetrates through the diaphragm membrane, and a gap is formed between the functional area diaphragm membrane and the back pole membrane; and the support is positioned between the back pole membrane and the vibrating piece membrane of the support area.
Optionally, the diaphragm membrane is made of graphene.
Optionally, the thickness of the diaphragm film is 90nm to 110 nm.
Optionally, the diaphragm hole is a circular hole, and the diameter of the diaphragm hole is greater than 0.2 μm; the distance between adjacent diaphragm holes is 20-100 μm.
Optionally, the second face of the back electrode film functional region has a back cavity therein; the back pole film at the bottom of the back cavity is provided with a back pole hole which penetrates through the back pole film.
Correspondingly, the invention also provides a forming method of the MEMS microphone, which comprises the following steps: providing a back plate comprising opposing first and second faces, the back plate comprising a functional region and a support region surrounding the functional region; forming a support layer on the first surface of the back plate; forming a diaphragm membrane on the supporting layer, wherein the mechanical strength of the diaphragm membrane is greater than that of the back plate, and a diaphragm hole is formed in the functional region diaphragm membrane and penetrates through the diaphragm membrane; after the diaphragm membrane is formed, thinning the second surface of the back plate of the functional area to form a back plate membrane of the back plate; after the back pole film is formed, the support layer of the functional area is removed, and a support member is formed between the back pole film and the vibrating piece film of the support area.
Optionally, the diaphragm membrane is made of graphene.
Optionally, the thickness of the diaphragm film is 90nm to 110 nm.
Optionally, the step of forming the diaphragm membrane includes: forming an initial diaphragm membrane on the support layer; and carrying out first patterning treatment on the initial diaphragm membrane to form a diaphragm membrane and a diaphragm hole in the diaphragm membrane.
Optionally, the initial diaphragm membrane is made of graphene; the step of forming the initial diaphragm membrane includes: forming a sacrificial layer on the support layer; forming an initial diaphragm film on the sacrificial layer; forming a cover layer on the preliminary diaphragm film; after forming a covering layer, removing the sacrificial layer, and transferring the initial vibrating piece film to the surface of the supporting layer; and removing the covering layer after removing the sacrificial layer.
Optionally, the sacrificial layer is made of copper, and the process for forming the sacrificial layer includes a physical vapor deposition process.
Optionally, the process for forming the initial diaphragm film includes a chemical vapor deposition process, and the process parameters for forming the initial diaphragm film include: the reaction gas comprises hydrogen and methane, and the flow ratio of the hydrogen to the methane is 14-16; the radio frequency power is 900W-1100W, and the pressure is 45 mtorr-55 mtorr.
Optionally, the covering layer is made of polymethyl methacrylate, and the process for forming the covering layer includes a spin coating process.
Optionally, the step of removing the sacrificial layer and transferring the initial vibrating piece film to the surface of the support layer includes: and soaking the sacrificial layer and the initial vibrating sheet film by etching liquid.
Optionally, the etching liquid includes: ammonium persulfate or ferric chloride solution.
Optionally, the diaphragm hole is a circular hole, and the diameter of the diaphragm hole is greater than 0.2 μm; the distance between adjacent diaphragm holes is 20-100 μm.
Optionally, after the patterning process, the method further includes: and forming a protective layer covering the diaphragm membrane and the side wall of the diaphragm hole.
Optionally, the protective layer is made of silicon oxide or silicon nitride; the thickness of the protective layer is 1000-10000 angstrom.
Optionally, the thinning process forms a back cavity in the second surface of the functional region back electrode film.
Optionally, after the thinning process, the method further includes: carrying out second graphical processing on the functional area back electrode film, and forming a back electrode hole in the functional area back electrode film, wherein the back electrode hole penetrates through the back electrode film; or, before forming the vibrating piece film, the method further comprises: performing second graphical processing on the first surface of the functional area back plate, and forming a back plate hole in the first surface of the functional area back plate; the thinning treatment enables the back electrode hole to penetrate through the back electrode film.
Compared with the prior art, the technical scheme of the invention has the following advantages:
in the MEMS microphone provided by the technical scheme of the invention, the bending deformation of the vibrating diaphragm membrane is larger than that of the back pole membrane in the working process of the MEMS microphone. The mechanical strength of the diaphragm membrane is greater than that of the back electrode membrane, so that the diaphragm membrane can bear larger stress, and the MEMS microphone is not easy to break in the use process, so that the service life of the MEMS can be prolonged.
Furthermore, the graphene has high electron mobility, so that the charging and discharging speed of a capacitor formed by the diaphragm membrane and the back electrode membrane is high, the working efficiency of the formed MEMS microphone can be improved, and the energy consumption is reduced; and the thickness of the graphene is the monoatomic size, so that the thickness of the graphene is smaller, the section moment of inertia of the diaphragm membrane in the direction perpendicular to the surface of the diaphragm membrane is smaller, the bending deformation of the diaphragm membrane can be increased, and the sensitivity of the formed MEMS microphone can be ensured.
Furthermore, the diameter of the diaphragm holes is 0.2-0.3 μm, and the distance between adjacent diaphragm holes is 20-100 μm. The diameter of the diaphragm hole and the distance between the adjacent diaphragm holes are larger, so that the section inertia moment of the diaphragm membrane in the direction perpendicular to the surface of the diaphragm membrane can be reduced, the bending deformation of the diaphragm membrane is further increased, and the sensitivity of the formed MEMS microphone can be ensured.
In the forming method of the MEMS microphone provided by the technical scheme of the invention, the bending deformation of the vibrating diaphragm membrane is larger than that of the back pole membrane in the working process of the MEMS microphone. The mechanical strength of the diaphragm membrane is greater than that of the back electrode membrane, so that the diaphragm membrane can bear larger stress, and the MEMS microphone is not easy to break in the use process, so that the service life of the MEMS can be prolonged.
Drawings
FIG. 1 is a schematic diagram of a MEMS microphone;
fig. 2 to 10 are schematic structural diagrams of steps of a method for forming a MEMS microphone according to an embodiment of the present invention.
Detailed Description
There are a number of problems with prior art MEMS microphones, such as: the MEMS microphone has a short lifetime.
Now, in connection with a MEMS microphone, the reason for the short lifetime of the MEMS microphone is analyzed:
fig. 1 is a schematic structural diagram of a MEMS microphone.
Referring to fig. 1, the MEMS microphone includes: the silicon vibration piece 11 and the silicon back electrode 12 are connected by a support piece 10; and the bonding pads 13 are respectively connected with the silicon vibrating plate 11 and the silicon back electrode 12.
When the MEMS microphone works, the silicon vibrating plate 11 bends under the pressure of sound waves, so that the distance between the silicon vibrating plate 11 and the silicon back electrode 12 changes, and the capacitance of the capacitor formed by the silicon vibrating plate 11 and the silicon back electrode 12 changes accordingly, thereby outputting an electrical signal. However, since the silicon diaphragm 11 has low mechanical strength and is easily broken, the MEMS microphone has a short lifetime.
In order to solve the technical problem, the present invention provides an MEMS microphone, including: a back polar film comprising opposing first and second faces, the back polar film comprising a functional region and a support region surrounding the functional region; the diaphragm membrane is positioned on the first surface of the back pole membrane, the mechanical strength of the diaphragm membrane is greater than that of the back pole membrane, the functional area diaphragm membrane is provided with a diaphragm hole, the diaphragm hole penetrates through the diaphragm membrane, and a gap is formed between the functional area diaphragm membrane and the back pole membrane; and the support is positioned between the back pole membrane and the vibrating piece membrane of the support area.
And in the working process of the MEMS microphone, the bending deformation of the vibrating piece membrane is larger than that of the back pole membrane. The mechanical strength of the diaphragm membrane is greater than that of the back electrode membrane, so that the diaphragm membrane can bear larger stress, and the MEMS microphone is not easy to break in the use process, so that the service life of the MEMS can be prolonged.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
Fig. 2 to 10 are schematic structural diagrams of steps of a method for forming a MEMS microphone according to an embodiment of the present invention.
Referring to fig. 2, a back plate 100 is provided, the back plate 100 includes a first side 101 and a second side 102 opposite to each other, and the back plate 100 includes a functional region a and a supporting region B surrounding the functional region a.
The backplate 100 is used for subsequent formation of a backplate membrane of a MEMS microphone. The back plate 100 functional region a is used for the subsequent formation of a back hole. And the support region B is used for forming a support member subsequently.
In this embodiment, the material of the back plate 100 is silicon. In other embodiments, the material of the back plate may also be germanium or silicon germanium.
Referring to fig. 3, a support layer 110 is formed on the first side 101 of the back plate 100.
The support layer 110 is subsequently used to form a support.
In this embodiment, the material of the support layer 110 is silicon oxide.
In this embodiment, the process of forming the supporting layer 110 includes: a chemical vapor deposition process, a physical vapor deposition process, or an atomic layer deposition process.
And subsequently, a diaphragm membrane is formed on the support layer 110, the mechanical strength of the diaphragm membrane is greater than that of the back plate 100, and a diaphragm hole is formed in the diaphragm membrane 120 and penetrates through the diaphragm membrane.
The steps of forming the diaphragm membrane in this embodiment are shown in fig. 4 to 6.
Referring to fig. 4, an initial diaphragm film 120 is formed on the support layer 110, and the mechanical strength of the initial diaphragm film 120 is greater than that of the back plate 100.
The initial diaphragm membrane 120 is used for subsequent diaphragm membrane formation. The mechanical strength of the initial diaphragm membrane 120 is greater than that of the back plate 100, so that the mechanical strength of the formed diaphragm membrane is greater than that of the back plate 100, and the diaphragm membrane 120 is not easily broken in the working process, thereby prolonging the service life of the formed MEMS microphone.
In this embodiment, the initial diaphragm membrane 120 is made of graphene. The connection between the inside carbon atom of graphite alkene is very pliable and tough, and when applying external force in graphite alkene, the carbon atom face can bending deformation for the carbon atom needn't rearrange and adapt to external force, thereby keeps stable in structure, makes graphite alkene have very high mechanical strength, is difficult to the fracture.
The graphene has high electron mobility (more than 15000 cm)2V.s), and low resistivity (about 10)-6Ω · cm), thereby enabling the speed of charging and discharging the capacitor formed by the diaphragm membrane and the back electrode membrane to be faster, thereby improving the working efficiency and sensitivity of the formed MEMS microphone, and improving the signal-to-noise ratio (SNR); and the thickness of the graphene is monoatomic, and the thickness is small, so that the section inertia moment of the subsequently formed diaphragm membrane in the direction perpendicular to the surface of the diaphragm membrane 121 is small, the bending deformation of the diaphragm membrane can be increased, and the sensitivity of the formed MEMS microphone can be ensured. The diaphragm membrane is made of graphene, and the graphene has high mechanical strength and can bear high sound pressure, so that improvement of sound Overload points (AOP) of the MEMS microphone is facilitated.
In this embodiment, the thickness of the initial diaphragm film 120 is 90nm to 110 nm.
In this embodiment, the step of forming the initial diaphragm film 120 on the support layer includes: forming a sacrificial layer on the support layer; forming an initial diaphragm film on the sacrificial layer; forming a cover layer on the preliminary diaphragm film; after forming a covering layer, removing the sacrificial layer, and transferring the initial vibrating piece film to the surface of the supporting layer; and removing the covering layer after removing the sacrificial layer.
In this embodiment, the sacrificial layer is made of copper. The process of forming the sacrificial layer includes a physical vapor deposition process.
In this embodiment, the material of the cover layer is polymethyl methacrylate.
In this embodiment, the process of forming the sacrificial layer on the support layer includes a chemical vapor deposition process.
In this embodiment, the process parameters for forming the initial diaphragm membrane include: the reaction gas comprises hydrogen and methane, and the flow ratio of the hydrogen to the methane is 14-16; the radio frequency power is 900W-1100W, and the pressure is 45 mtorr-55 mtorr.
In this embodiment, the thickness of the sacrificial layer is 630nm to 770 nm.
In this embodiment, the step of removing the sacrificial layer and transferring the initial vibrating piece film to the surface of the support layer 110 includes: and soaking the sacrificial layer and the initial vibrating sheet film by etching liquid.
In this embodiment, the etching solution includes an ammonium persulfate or an iron chloride solution.
Referring to fig. 5, a first patterning process is performed on the initial diaphragm film 120 (shown in fig. 4) to form a diaphragm film 121 and a diaphragm hole 122 in the diaphragm film 121.
The diaphragm holes 122 are used to allow air to be discharged and sucked into a gap between the diaphragm membrane and a back electrode membrane to be formed later during the vibration of the diaphragm membrane 121.
In this embodiment, the first patterning step includes: forming a first graphic layer 130 on the initial diaphragm film 120, wherein the functional region a has an opening in the first graphic layer 130, and the opening penetrates through the first graphic layer 130; and performing first etching on the first graphic layer 130 and the initial diaphragm film 120 by using the first graphic layer 130 as a mask to form a diaphragm film 121 and a diaphragm hole 122 in the diaphragm film 121 in the functional region a.
In this embodiment, the first etching process includes a dry etching process.
In this embodiment, the first pattern layer 130 is made of silicon oxide, silicon oxynitride, or silicon nitride.
In this embodiment, the process of forming the first pattern layer 130 includes a chemical vapor deposition process.
In this embodiment, the diameter of the diaphragm holes 122 is 0.2 μm to 0.3 μm, and the distance between adjacent diaphragm holes 122 is 20 μm to 100 μm. The diameters of the diaphragm holes 122 and the distance between adjacent diaphragm holes 122 are large, so that the second moment of inertia of the diaphragm membrane 121 in the direction perpendicular to the surface of the diaphragm membrane 121 can be reduced, the bending deformation of the diaphragm membrane 121 is further increased, and the sensitivity of the formed MEMS microphone can be ensured. However, if the diameter of the diaphragm hole 122 is too large or the pitch is too small, the bending deformation of the diaphragm membrane 121 is easily too large, and the diaphragm membrane is easily broken.
Referring to fig. 6, a first pad 141 connected to the diaphragm film 121 is formed; a second pad 142 is formed to connect the back plate 100.
The first pad 141 is used for electrically connecting the diaphragm membrane 121 with an external circuit; the second pads 142 are used to electrically connect the subsequently formed back electrode film to an external circuit.
In this embodiment, the step of forming the first pad 141 and the second pad 142 includes: performing second etching on the first pattern layer 130 of the support region B, forming a first pad hole in the first pattern layer 130 of the support region B, wherein the bottom of the first pad hole exposes the diaphragm membrane 121; performing third etching on the first pattern layer 130, the vibrating piece film 121 and the supporting layer 110 in the supporting region B, and forming a second pad hole in the first pattern layer 130, the vibrating piece film 121 and the supporting layer 110 in the supporting region B, wherein the second pad hole exposes the back plate 100; a first pad 141 is formed in the first pad hole, and a second pad 142 is formed in the second pad hole.
In this embodiment, the material of the first pad 141 and the second pad 142 is copper or tungsten.
In this embodiment, the second etching process and the third etching process include a dry etching process.
Referring to fig. 7, a protection layer 132 is formed to cover the diaphragm film 121 and the side wall of the diaphragm hole 122.
The protective layer 132 serves to protect the diaphragm membrane 121 during subsequent removal of the functional region a support layer 110.
In this embodiment, the material of the protection layer 132 is silicon oxide.
If the thickness of the protection layer 132 is too large, the difficulty of subsequently removing the protection layer 132 is easily increased; if the thickness of the protective layer 132 is too small, it is not favorable for protecting the diaphragm membrane 121. Specifically, in this embodiment, the thickness of the protection layer 132 is 1000 angstroms to 10000 angstroms.
In this embodiment, the process of forming the protection layer 132 includes a chemical vapor deposition process or a physical vapor deposition process.
Referring to fig. 8, after the protective layer 132 is formed, the second surface 102 of the back plate 100 in the functional region a is thinned, so that the back plate 100 (as shown in fig. 7) forms a back plate film 104.
In this embodiment, the thinning process includes: carrying out planarization treatment on the second surface 102 of the functional area A of the back plate 100 and the second surface 102 of the support area B of the back plate 100, and reducing the thickness of the back plate 100; and thinning and etching the back plate 100 of the functional area A, and further reducing the thickness of the back plate 100 of the functional area A.
The thinning process forms a back cavity 105 in the second side 102 of the functional area a back electrode film 104. The functional region a back electrode film 104 is located at the bottom of the back cavity 105.
The back cavity 105 is used to contain sound waves.
In this embodiment, the planarization process includes a chemical mechanical polishing process.
In this embodiment, the thinning and etching process includes a dry etching process or a wet etching process.
Referring to fig. 9, after the back electrode film 104 is formed, a second patterning process is performed on the functional region a back electrode film 104, so that a back electrode hole 103 is formed in the functional region a back electrode film 104, and the back electrode hole 103 penetrates through the back electrode film 104.
The back pole holes 103 are used as channels for air to flow into and out of the gap between the back pole film 104 and the diaphragm film 121.
In this embodiment, the second patterning step includes: forming a second pattern layer on the second side 102 of the back electrode film 104; and performing fourth etching on the back electrode film 104 by taking the second pattern layer as a mask, and forming a back electrode hole 103 in the back electrode film 104 of the functional area A, wherein the back electrode hole 103 penetrates through the back electrode film 104.
In this embodiment, the fourth etching process includes a dry etching process.
In this embodiment, after the thinning process, the back electrode hole 103 is formed. In other embodiments, before the diaphragm film is formed, a second patterning process may be performed on the first surface of the functional region back plate, so as to form a back hole in the first surface of the functional region back plate; the thinning treatment enables the back electrode hole to penetrate through the back electrode film.
Referring to fig. 10, after the back electrode film 104 is formed, the support layer 110 of the functional region a is removed (as shown in fig. 9), and a support 111 is formed between the back electrode film 104 and the vibrating piece film 121 of the support region B.
The supporting member 111 makes a gap exist between the back electrode film 104 of the functional area a and the vibrating sheet film 121 of the functional area a, so that the back electrode film 104 can be bent during the operation of the formed MEMS microphone, and the distance between the back electrode film 104 of the functional area a and the vibrating sheet film 121 of the functional area a is changed, so that the capacitance between the back electrode film 104 of the functional area a and the vibrating sheet film 121 of the functional area a is changed, and further, the sound signal is converted into an electrical signal.
In this embodiment, the process of removing the support layer 110 in the functional region a includes a wet etching process.
It should be noted that, because the back electrode film 104 of the functional region a has a smaller thickness and the back electrode film 104 of the functional region a has the back electrode hole 103 therein, the support layer 110 of the functional region a is easy to be removed; however, since the back electrode film 104 of the support region B has a large thickness, the support layer 110 between the back electrode film 104 and the diaphragm film 121 of the support region B is not easily removed, thereby forming the support 111.
In this embodiment, after removing the support layer 110 of the functional region a, the method further includes: the protective layer 132 (shown in fig. 9) and the first graphic layer 130 (shown in fig. 9) are removed.
In this embodiment, the processes of removing the support layer 110 in the functional region a and removing the protection layer 132 and the first pattern layer 130 are performed in the same process.
In summary, in the method for forming the MEMS microphone provided by this embodiment, in the working process of the MEMS microphone, the bending deformation of the diaphragm membrane is greater than the bending deformation of the back electrode membrane. The mechanical strength of the diaphragm membrane is greater than that of the back electrode membrane, so that the diaphragm membrane can bear larger stress, and the MEMS microphone is not easy to break in the use process, so that the service life of the MEMS can be prolonged.
With continued reference to fig. 10, the present invention also provides an embodiment of a MEMS microphone comprising: a back electrode film 104, the back electrode film 104 including a first face 101 and a second face 102, the back electrode film 104 including a functional region a and a support region B surrounding the functional region a; the diaphragm membrane 121 is positioned on the first surface 101 of the back electrode membrane 104, the mechanical strength of the diaphragm membrane 121 is greater than that of the back electrode membrane 104, the functional region a diaphragm membrane 121 is provided with a diaphragm hole 122, the diaphragm hole 122 penetrates through the diaphragm membrane 121, and a gap is formed between the functional region a diaphragm membrane 121 and the back electrode membrane 104; and the support 111 is positioned between the back pole membrane 104 and the vibrating piece membrane 121 of the support area B.
In this embodiment, the back electrode film 104 of the functional region a has a back electrode hole 103 therein, and the back electrode hole 103 penetrates through the back electrode film 104.
The functional area a back pole film 104 has a back cavity 105 in the second side 102. The back electrode hole 103 is located in the back electrode film 104 at the bottom of the back cavity 105.
The back cavity 105 is used to contain sound waves.
In this embodiment, the diaphragm membrane 121 is made of graphene. The graphene has high electron mobility, so that the charging and discharging speed of a capacitor formed by the diaphragm membrane 121 and the back electrode membrane 104 is high, the working efficiency of the formed MEMS microphone can be improved, and the energy consumption is reduced; and the thickness of the graphene is a monoatomic size, so that the second moment of inertia of the section of the diaphragm membrane 121 in the direction perpendicular to the surface of the diaphragm membrane 104 is small, the bending deformation of the diaphragm membrane 121 can be increased, and the sensitivity of the formed MEMS microphone can be ensured.
In this embodiment, the thickness of the diaphragm film 121 is 90nm to 110 nm.
In this embodiment, the diaphragm hole 122 is a circular hole, and the diameter of the diaphragm hole 122 is 0.2 μm to 0.3 μm; the spacing between adjacent diaphragm holes 122 is 20 μm to 100 μm.
The diameter of the diaphragm holes 122 is 0.2-0.3 μm, and the distance between adjacent diaphragm holes 122 is 20-100 μm. The diameters of the diaphragm holes 122 and the distance between the adjacent diaphragm holes 122 are large, so that the section moment of inertia of the diaphragm film 123 in the direction perpendicular to the surface of the diaphragm film 123 can be reduced, the bending deformation of the diaphragm film 123 is further increased, and the sensitivity of the formed MEMS microphone can be ensured.
In this embodiment, the MEMS microphone has the same structure as the MEMS microphone formed by the forming method shown in fig. 2 to 10, and details thereof are not repeated herein.
In summary, in the MEMS microphone provided by this embodiment, in the working process of the MEMS microphone, the bending deformation of the diaphragm membrane is greater than the bending deformation of the back electrode membrane. The mechanical strength of the diaphragm membrane is greater than that of the back electrode membrane, so that the diaphragm membrane can bear larger stress, and the MEMS microphone is not easy to break in the use process, so that the service life of the MEMS can be prolonged.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (11)
1. A method of forming a MEMS microphone, comprising:
providing a back plate comprising opposing first and second faces, the back plate comprising a functional region and a support region surrounding the functional region;
forming a support layer on the first surface of the back plate;
forming a vibrating piece film on the supporting layer, wherein the mechanical strength of the vibrating piece film is greater than that of the back electrode plate, a vibrating piece hole is formed in the functional area vibrating piece film and penetrates through the vibrating piece film, the vibrating piece hole is a circular hole, and the diameter of the vibrating piece hole is greater than 0.2 mu m; the distance between adjacent vibrating piece holes is 20-100 mu m;
after the diaphragm membrane is formed, thinning the second surface of the back plate of the functional area to form a back plate membrane of the back plate;
after the back pole film is formed, removing the support layer of the functional area, and forming a support member between the back pole film and the vibrating piece film in the support area;
wherein the step of forming the diaphragm film comprises: forming an initial diaphragm membrane on the support layer; carrying out first graphical processing on the initial vibrating piece film to form a vibrating piece film and a vibrating piece hole in the vibrating piece film;
the initial vibrating piece film is made of graphene;
the step of forming the initial diaphragm membrane includes: forming a sacrificial layer on the support layer; forming an initial diaphragm film on the sacrificial layer; forming a cover layer on the preliminary diaphragm film; after forming a covering layer, removing the sacrificial layer, and transferring the initial vibrating piece film to the surface of the supporting layer; and removing the covering layer after removing the sacrificial layer.
2. The method of forming a MEMS microphone according to claim 1, wherein the thickness of the diaphragm film is 90nm to 110 nm.
3. The method of forming a MEMS microphone according to claim 1, wherein the material of the sacrificial layer is copper, and the process of forming the sacrificial layer includes a physical vapor deposition process.
4. The method of forming a MEMS microphone according to claim 1, wherein the process of forming the initial diaphragm membrane includes a chemical vapor deposition process, and the process parameters of forming the initial diaphragm membrane include: the reaction gas comprises hydrogen and methane, and the flow ratio of the hydrogen to the methane is 14-16; the radio frequency power is 900W-1100W, and the pressure is 45 mtorr-55 mtorr.
5. The method of forming a MEMS microphone according to claim 1, wherein the material of the cover layer is polymethyl methacrylate, and the process of forming the cover layer includes a spin coating process.
6. The method of forming a MEMS microphone according to claim 1, wherein the step of removing the sacrificial layer to transfer the initial diaphragm membrane to the surface of the support layer comprises: and soaking the sacrificial layer and the initial vibrating sheet film by etching liquid.
7. The method for forming the MEMS microphone according to claim 6, wherein the etching solution comprises: ammonium persulfate or ferric chloride solution.
8. The method of forming a MEMS microphone according to claim 1, further comprising, after the first patterning process: and forming a protective layer covering the diaphragm membrane and the side wall of the diaphragm hole.
9. The method of forming a MEMS microphone according to claim 8, wherein the material of the protective layer is silicon oxide or silicon nitride; the thickness of the protective layer is 1000-10000 angstrom.
10. The method of forming a MEMS microphone of claim 1 wherein the thinning forms a back cavity in the second side of the functional area backplate.
11. The method of forming a MEMS microphone according to claim 1, further comprising, after the thinning process: carrying out second graphical processing on the functional area back electrode film, and forming a back electrode hole in the functional area back electrode film, wherein the back electrode hole penetrates through the back electrode film;
or, before forming the vibrating piece film, the method further comprises: performing second graphical processing on the first surface of the functional area back plate, and forming a back plate hole in the first surface of the functional area back plate; the thinning treatment enables the back electrode hole to penetrate through the back electrode film.
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