CN108810776B - Capacitive MEMS microphone and manufacturing method thereof - Google Patents
Capacitive MEMS microphone and manufacturing method thereof Download PDFInfo
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- CN108810776B CN108810776B CN201810631510.7A CN201810631510A CN108810776B CN 108810776 B CN108810776 B CN 108810776B CN 201810631510 A CN201810631510 A CN 201810631510A CN 108810776 B CN108810776 B CN 108810776B
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Abstract
The invention discloses a capacitive MEMS microphone and a manufacturing method thereof. Since the edge of the diaphragm is not easy to vibrate, the capacitance formed by the edge part of the back electrode and the edge of the diaphragm has a great influence on sensitivity. The invention relates to a capacitive MEMS microphone, which comprises a substrate, a vibrating diaphragm, a back electrode, a wiring assembly, an etching stop ring, a vibrating diaphragm supporting ring, a first insulating ring and a second insulating ring. The substrate, the etching stop ring, the vibrating diaphragm support ring, the first insulating ring and the second insulating ring are sequentially arranged and fixed together. The vibrating diaphragm is fixed on the vibrating diaphragm support ring. A plurality of annular grooves are arranged on both side surfaces of the vibrating diaphragm. All annular grooves are arranged coaxially with the vibrating diaphragm. The passivation protection layer of silicon nitride is composed of a protection ring and a protection disk. The side face of the protection disc, which is close to the vibrating diaphragm, is arranged in a convex mode, and the side face of the protection disc is arranged in a concave mode. The conductive layer is composed of a conductive ring and a conductive sheet. The invention realizes high sensitivity of the microphone by manufacturing the vibrating diaphragm into the annular structure.
Description
Technical Field
The invention belongs to the technical field of sensors and micro-electromechanical systems, and particularly relates to a capacitive MEMS microphone and a manufacturing method thereof.
Background
Voice communication is the most direct way for human communication, and thus microphones have played an important role in the traditional consumer electronics field of communication and entertainment. A microphone is essentially an acoustic sensor, which is a transducer that converts an external acoustic signal into an electrical signal. Microphones can be broadly classified into three types of capacitive type, piezoelectric type and photoelectric type according to a signal conversion principle or manner, wherein the capacitive type microphone is dominant in the market.
Electret Condenser Microphones (ECM) and microelectromechanical systems (MEMS) condenser microphones are the most common two types of condenser microphones. Over decades of development, conventional ECMs have been widely used in various fields. However, the vibration film of ECM is made of polymeric material having permanent charges, and cannot withstand high temperature treatment, and a large number of automated surface mounting processes at present need to be soldered at 260 ℃ and therefore ECM has lost the advantage of mass production in consumer electronics. Compared with ECM, the capacitive MEMS microphone has better noise elimination performance, wider temperature range, high expandability, good sound quality, small volume and stable product performance, and is beneficial to mass automatic production.
Capacitive MEMS microphones are miniature transducers that can convert acoustic signals into electrical signals. The two polar plates (namely the vibrating diaphragm and the back electrode) of the capacitor are basic structures, the vibrating diaphragm is movable in general, the back electrode is fixed, the vibrating diaphragm can generate corresponding vibration due to the input of different sounds, the capacitance value is correspondingly changed, and corresponding electric signals can be obtained after the subsequent circuit processing.
The sensitivity is the most important parameter for measuring whether the microphone performance is good, and can be used for qualitative analysis from the aspects of electrical sensitivity and mechanical sensitivity. From the aspect of electrical sensitivity, the sensitivity can be improved by improving the capacitance value and the DC bias voltage of the capacitive element; from the viewpoint of mechanical sensitivity, the sensitivity can be improved by reducing the stress of the diaphragm. Reducing the distance between the diaphragm and the back electrode or increasing the surface area of the diaphragm and the back electrode can improve the capacitance value of the capacitor, but too small a distance between the diaphragm and the back electrode easily causes the diaphragm and the back electrode to adhere together when the microphone works, and too large a surface area easily causes the diaphragm and the back electrode to be broken and damaged; when the direct-current bias voltage is too large and is larger than the pull-in voltage, the vibrating diaphragm and the back electrode can be adsorbed together under the action of electrostatic force. The reduction in film stress results in a reduced film stiffness, which is susceptible to film cracking or dishing. Therefore, it is desirable to balance the electrical sensitivity with the mechanical sensitivity to further enhance the performance of the microphone. In addition, since the edge of the diaphragm is not easy to vibrate, the size of capacitance formed by the edge portion of the back electrode and the edge of the diaphragm has a great influence on sensitivity.
Disclosure of Invention
The invention aims to provide a capacitive MEMS microphone and a manufacturing method thereof.
The invention relates to a capacitive MEMS microphone, which comprises a substrate, a vibrating diaphragm, a back electrode, a wiring assembly, an etching stop ring, a vibrating diaphragm supporting ring, a first insulating ring and a second insulating ring. The substrate, the etching stop ring, the vibrating diaphragm support ring, the first insulating ring and the second insulating ring are sequentially arranged and fixed together. The vibrating diaphragm is fixed on the vibrating diaphragm support ring. A plurality of annular grooves are arranged on both side surfaces of the vibrating diaphragm. All annular grooves are arranged coaxially with the vibrating diaphragm. The edge of the vibrating diaphragm is provided with a vent hole.
The back electrode is fixed with the inner side wall of the second insulating ring. The back electrode is arranged at intervals with the vibrating diaphragm. The back electrode comprises a blocking insulating layer, a conducting layer and a silicon nitride passivation protection layer. The passivation protection layer of silicon nitride is composed of a protection ring and a protection disk. The guard ring is fixed with the second insulating ring. The side face of the protection disc, which is close to the vibrating diaphragm, is arranged in a convex mode, and the side face of the protection disc is arranged in a concave mode.
The conductive layer consists of a conductive ring and a conductive sheet. The conducting ring and the conducting strip are fixed with the protective disc. The inner diameter of the conductive ring is greater than or equal to the diameter of the conductive sheet. The conducting strip and the conducting ring are both fixed with the protection disc. The distance between the conductive ring and the vibrating diaphragm is larger than the distance between the conductive sheet and the vibrating diaphragm. The barrier insulating layer is composed of a barrier insulating ring and a barrier insulating sheet. The blocking insulating ring is fixed with the conducting ring. The blocking insulating sheet is fixed with the conductive sheet. The blocking insulating ring and the conducting ring are fixed with the protecting ring. The back electrode is provided with a plurality of sound holes. All sound holes extend through the back electrode. A plurality of anti-adhesion convex blocks are arranged on the side surface of the blocking insulating layer, which is close to the vibrating diaphragm.
The wiring assembly comprises a first wiring terminal and a fourth wiring terminal. The first binding post and the fourth binding post are respectively connected with the vibrating diaphragm and the conductive layer.
Further, the vibrating diaphragm, the noise reduction belt, the noise reduction ring and the conductive layer are all made of polysilicon. The isolation insulating layer and the silicon nitride passivation protective layer are made of silicon nitride. The etching stop ring, the vibrating diaphragm support ring, the first insulating ring and the second insulating ring are all made of silicon dioxide.
Further, a back cavity penetrating through the substrate is formed in the outer end face of the substrate.
Further, a noise reduction belt is arranged between the outer edge of the vibrating diaphragm and the inner side wall of the first insulating ring. And a noise reduction ring is arranged between the etching stop ring and the vibrating diaphragm support ring. The wiring assembly also comprises a second wiring terminal and a third wiring terminal. The second binding post is connected with the noise reduction belt. The third binding post is connected with the noise reduction ring.
Further, the inner diameters of the annular grooves on the same side face of the vibrating diaphragm are sequentially equal-difference gradually increased along the direction from the center of the vibrating diaphragm to the edge.
The manufacturing method of the MEMS microphone specifically comprises the following steps:
and step one, electrodepositing a layer of silicon dioxide with the thickness of 300-500 nm on a substrate to obtain an etching stop annular embryonic body.
And step two, electrodepositing a layer of amorphous silicon material with the thickness of 300-500 nm on the etching stop annular embryonic body to obtain a first amorphous silicon layer. The first amorphous silicon layer is divided into a third binding post, a noise-reduction annular rudiment and a plurality of auxiliary processing rings, wherein the noise-reduction annular rudiment and the auxiliary processing rings are mutually independent and coaxially arranged in a photoetching mode. And annealing the noise-reducing ring blank to obtain the noise-reducing ring.
And thirdly, electrodepositing a layer of silicon dioxide with the thickness of 500-800 nm on the noise reduction ring to obtain the vibrating diaphragm support ring embryonic body.
And step four, electrodepositing a layer of amorphous silicon material with the thickness of 300-500 nm on the vibrating diaphragm support annular embryonic body to obtain a second amorphous silicon layer.
And fifthly, dividing the second amorphous silicon layer into a first binding post, a second binding post, a vibrating diaphragm embryonic body and a noise reduction belt embryonic body in a photoetching mode. The vibrating diaphragm embryonic body and the noise reduction belt embryonic body are mutually independent. The first binding post is connected with the vibrating diaphragm. The second binding post is connected with the noise reduction belt. The vibrating diaphragm prototype is provided with a vent hole. The noise-reducing belt blank surrounds the diaphragm blank. And (5) annealing the vibrating diaphragm blank and the noise reduction belt to the vibrating diaphragm and the noise reduction belt.
And step six, electrodepositing a layer of silicon dioxide insulating material with the thickness of 500-800 nm on the vibrating diaphragm to obtain a first insulating annular embryonic body.
And seventhly, forming a plurality of adhesion-preventing auxiliary holes in the first insulating annular embryonic body in a photoetching mode.
And step eight, electrodepositing a layer of silicon dioxide insulating material with the thickness of 1000 nm-2000 nm on the first insulating annular embryonic body to obtain a second insulating annular embryonic body.
And step nine, forming a blind hole on the second insulating ring blank in a photoetching mode.
And step ten, electrodepositing a layer of silicon nitride insulating material with the thickness of 100-200 nm on the second insulating annular embryonic body to obtain the insulating layer embryonic body. The insulating layer performs are composed of insulating ring performs and insulating sheets. A plurality of anti-adhesion convex blocks are formed on the side surface of the insulating layer blank close to the vibrating diaphragm.
And step eleven, electrodepositing a layer of amorphous silicon material with the thickness of 500-1000 nm on the insulating layer embryonic body to obtain the conducting layer embryonic body. The conducting layer embryonic body consists of a conducting ring embryonic body and a conducting sheet positioned in the blind hole.
And step twelve, removing edge parts of the insulating ring blank and the conducting ring blank by means of etching after photoetching, and obtaining a fourth binding post. The fourth binding post is connected with the conducting layer embryonic body. And annealing the conducting layer embryonic body to obtain the barrier insulating layer and the conducting layer.
And thirteenth step, removing the silicon dioxide insulating materials covered on the first binding post, the second binding post and the third binding post in a photoetching mode. And then coating metal on the first binding post, the second binding post, the third binding post and the fourth binding post through a sputtering process.
And fourteen, electrodepositing a layer of silicon nitride with the thickness of 500-1000 nm on the side surface of the conducting layer, which is far away from the substrate and the second insulating ring, so as to obtain the passivation protection layer of the silicon nitride. The silicon nitride insulating ring, the conducting layer and the silicon nitride passivation protection layer form a back electrode.
Fifteen, forming a plurality of sound holes on the back electrode in a photoetching mode, and removing silicon nitride covered on the first binding post, the second binding post, the third binding post and the fourth binding post.
Sixthly, etching a back cavity on the outer end face of the substrate in a photoetching mode. The back cavity penetrates the substrate.
Seventeenth, etching the middle parts of the etching stop ring blank and the vibrating diaphragm supporting ring blank by using hydrofluoric acid to obtain the etching stop ring and the vibrating diaphragm supporting ring.
Eighteenth, corroding central parts of the first insulating ring blank and the second insulating ring blank by using hydrofluoric acid through the sound holes to obtain the first insulating ring and the second insulating ring.
Further, in the second step, ions are doped in a bit doping mode while the first amorphous silicon layer is electrodeposited. In the fourth step, ions are doped in a bit doping mode while the second amorphous silicon layer is electrodeposited. In step eleven, ions are incorporated by means of in-situ doping while electrodepositing the conductive layer preform.
The invention has the beneficial effects that:
1. the invention realizes high sensitivity of the microphone by manufacturing the vibrating diaphragm into the annular structure.
2. The back electrode of the invention presents a state that the central part is close to the vibrating diaphragm and the edge part is far away from the vibrating diaphragm. Since the edge of the diaphragm is not easy to vibrate, the capacitance formed by the edge part of the back electrode and the edge of the diaphragm has a great influence on sensitivity. After the edge part of the back electrode is far away from the vibrating diaphragm, the capacitance formed by the edge part of the back electrode and the edge of the vibrating diaphragm can be effectively reduced, and the sensitivity of the microphone is effectively improved.
3. The invention further reduces the influence of noise on signals by arranging the noise reduction belt and the noise reduction ring, thereby realizing higher signal-to-noise ratio.
4. The manufacturing method of the invention is easy to operate and is beneficial to mass production.
Drawings
FIG. 1 is a schematic diagram of the overall structure of the present invention;
FIG. 2 is a schematic top view of the present invention;
FIG. 3 is a schematic cross-sectional view of the present invention;
FIG. 4 is a partial cross-sectional view of a diaphragm according to the present invention;
FIG. 5 is a schematic diagram of the manufacturing method of the present invention after the completion of step one;
FIG. 6 is a schematic diagram of the manufacturing method of the present invention after the second step is completed;
FIG. 7 is a partial cross-sectional view of the combination of an auxiliary processing ring and an etch stop ring blank after completion of step two of the manufacturing method of the present invention;
FIG. 8 is a schematic diagram of the manufacturing method of the present invention after the completion of step three;
FIG. 9 is a schematic diagram of the manufacturing method of the present invention after the completion of step four;
FIG. 10 is a schematic diagram of the manufacturing method of the present invention after the fifth step;
FIG. 11 is a schematic view of a vent hole after the completion of step five of the manufacturing method of the present invention;
FIG. 12 is a schematic diagram of the manufacturing method of the present invention after the completion of step six;
FIG. 13 is a schematic diagram of the manufacturing method of the present invention after completion of step seven;
FIG. 14 is a schematic diagram of the manufacturing method of the present invention after step eight;
FIG. 15 is a schematic diagram of the manufacturing method of the present invention after step nine;
FIG. 16 is a schematic diagram of the manufacturing method of the present invention after step ten;
FIG. 17 is a schematic diagram of the manufacturing method of the present invention after completion of step eleven;
FIG. 18 is a schematic diagram of a manufacturing method according to the present invention after the step twelve;
FIG. 19 is a schematic diagram of the manufacturing method of the present invention after the step fourteen;
FIG. 20 is a schematic diagram of a manufacturing method of the present invention after fifteen steps are completed;
FIG. 21 is a schematic diagram of the manufacturing method of the present invention after step sixteen;
FIG. 22 is a schematic diagram of the manufacturing method of the present invention after seventeen steps are completed;
fig. 23 is a schematic diagram of the manufacturing method of the present invention after the eighteen steps are completed.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
Referring to fig. 1, 2 and 3, the capacitive MEMS microphone includes a substrate 1, a diaphragm 2, a back electrode, a noise reduction band 4, a noise reduction ring 5, a wiring assembly, an etching stop ring 9, a diaphragm support ring 10, a first insulating ring 11, and a second insulating ring 12.
The outer end surface of the substrate 1 is provided with a back cavity 6 penetrating through the substrate 1. The substrate 1, the etching stop ring 9, the diaphragm support ring 10, the first insulating ring 11, and the second insulating ring 12 are stacked in this order and coaxially fixed together. A noise reduction ring 5 is arranged between the etching stop ring 9 and the vibrating diaphragm support ring 10. The diaphragm 2 is fixed to the diaphragm support ring 10 at a side remote from the substrate 1. A noise reducing belt 4 is arranged between the outer edge of the diaphragm 2 and the inner side wall of the first insulating ring 11.
Referring to fig. 1 and 4, a plurality of annular grooves are formed on both side surfaces of the diaphragm 2. All annular grooves are arranged coaxially with the diaphragm 2. The inner diameters of the annular grooves on the same side surface of the diaphragm 2 are sequentially equal-difference gradually increased along the direction from the center of the diaphragm 2 to the edge. The surface of the vibrating diaphragm is of an annular structure, so that the sensitivity of the device can be improved, and the noise reduction belt is connected into a signal processing circuit to reduce the influence of noise. The edge of the diaphragm 2 is provided with a vent hole 21 to prevent the microphone from forming a sealed space after encapsulation.
The back electrode is fixed to the inner side wall of the second insulating ring 12. The back electrode is disposed at a distance from the diaphragm 2 to form a vibration cavity 7 (a space surrounded by the back electrode, the diaphragm 2, the first insulating ring 11, and the second insulating ring 12). The back electrode comprises a blocking insulating layer, a conducting layer and a silicon nitride passivation protection layer.
The passivation protection layer of silicon nitride is composed of a guard ring 316 and a guard disk 313. The guard ring 316 is fixed with the second insulating ring. The side surface of the protection disk 313, which is close to the diaphragm, is arranged in a convex manner, and the side surface of the other side is arranged in a concave manner, so that a near film part 33 positioned at the center of the protection disk 313 and a far film part 34 positioned at the edge of the protection disk 313 are formed.
The conductive layer is comprised of conductive ring 312 and conductive sheet 315. The conductive ring 312 is fixed to the side of the protective disk 313, which is close to the diaphragm 2, of the distal film portion 34, and surrounds the proximal film portion 33. The conductive sheet 315 is fixed to the side of the protective disk 313 near the diaphragm 2 near the diaphragm portion 33. The distance between the conductive ring 312 and the diaphragm 2 is larger than the distance between the conductive sheet 315 and the diaphragm 2.
The barrier insulating layer is composed of a barrier insulating ring 311 and a barrier insulating sheet 314. The insulating ring 311 and the conductive ring 312 are fixed to the side surface of the diaphragm 2, and encircle the membrane-proximal portion 33. The blocking insulating sheet 314 is fixed to the side of the conductive sheet 315 close to the diaphragm 2. The blocking insulating ring and the conducting ring are fixed with the protecting ring.
The back electrode is provided with a plurality of sound holes 32. All acoustic holes 32 extend through the back electrode. The side of the insulating barrier layer close to the diaphragm 2 is provided with a plurality of anti-adhesion bumps 31. The back electrode assumes a state in which the center portion is close to the diaphragm 2 and the edge portion is far from the diaphragm 2. Because the vibrating diaphragm edge is not easy to vibrate, the size of the capacitor formed by the edge part of the back electrode and the vibrating diaphragm edge has great influence on the sensitivity, so that after the edge part of the back electrode is far away from the vibrating diaphragm 2, the capacitor formed by the edge part of the back electrode and the vibrating diaphragm edge can be effectively reduced, and the sensitivity of a microphone is effectively improved.
The wiring assembly includes a first terminal 84, a second terminal 81, a third terminal 83, and a fourth terminal 82. The first binding post 84, the second binding post 81, the third binding post 83, and the fourth binding post 82 are all fixed to the protection ring 316, and are connected to the diaphragm 2, the noise reduction belt 4, the noise reduction ring 5, and the conductive layer, respectively.
The vibrating diaphragm 2, the noise reduction belt 4, the noise reduction ring 5 and the conducting layer are all made of polysilicon. The material of the barrier insulating layer and the silicon nitride passivation protective layer is silicon nitride. The etching stop ring 9, the diaphragm support ring 10, the first insulating ring 11 and the second insulating ring 12 are all made of silicon dioxide.
Referring to fig. 5 to 23, the method for manufacturing the MEMS microphone is specifically as follows:
step one, referring to fig. 5, a layer of silicon dioxide insulating material with the thickness of 300-500 nm is electrodeposited on the inner end face of the substrate, so as to obtain an etching stop ring 9 embryonic body. The function of the etch stop ring 9 preform is to prevent over etching damage to the microphone during formation of the back cavity.
Step two, referring to fig. 6, a layer of amorphous silicon material (amorphous silicon α -Si, also called amorphous silicon) with a thickness of 300 nm-500 nm is electrodeposited on the side surface of the embryonic body of the etching stop ring 9, which is far from the substrate 1, to obtain a first amorphous silicon layer. Ions are incorporated by means of in-situ doping at the same time as the electrodeposition of the first amorphous silicon layer. The first amorphous silicon layer is divided into a third binding post, a noise reduction ring 5 blank and a plurality of auxiliary processing rings which are mutually independent and coaxially arranged in a photoetching mode. The plurality of auxiliary processing rings are respectively corresponding to the plurality of annular grooves on the vibrating diaphragm 2 in position. The noise reduction ring 5 prototype ring is provided with an auxiliary processing ring. The positional relationship between the noise reduction ring 5 blank and the plurality of auxiliary processing rings is shown in fig. 7.
And annealing the noise reduction ring 5 blank in a rapid annealing furnace to convert amorphous silicon into polycrystalline silicon, thereby obtaining the noise reduction ring 5. The noise reduction ring 5 is connected into the signal processing circuit to eliminate the noise of the device. The plurality of auxiliary processing rings will drop through the back cavity of the substrate 1 after step fourteen, in addition, the auxiliary processing rings can fix the silicon dioxide corrosion area to eliminate the alignment error in step fourteen;
step three, referring to fig. 8, a layer of silicon dioxide insulating material with the thickness of 500 nm-800 nm is electrodeposited on the side surface of the noise reduction ring 5, which is far away from the substrate 1, so as to obtain a vibrating diaphragm support ring 10 prototype. Since the thickness of the diaphragm support ring 10 blank obtained by electrodeposition is uniform throughout, a plurality of annular protrusions having the same shape as the respective auxiliary processing rings are present on the diaphragm support ring 10 blank.
Fourth, referring to fig. 9, a layer of amorphous silicon material with a thickness of 300 nm-500 nm is electrodeposited on the side surface of the diaphragm support ring 10 blank far from the substrate 1, so as to obtain a second amorphous silicon layer. Since the thickness of the second amorphous silicon layer obtained by electrodeposition is uniform throughout, a plurality of annular grooves are present on both sides of the second amorphous silicon layer. Ions are incorporated by means of in-situ doping at the same time as the electrodeposition of the second amorphous silicon layer.
And fifthly, referring to fig. 10 and 11, dividing the second amorphous silicon layer into a first binding post, a second binding post, a vibrating diaphragm 2 blank and a noise reduction belt 4 blank by means of etching after photoetching. The vibrating diaphragm 2 prototype and the noise reduction belt 4 prototype are independent of each other. The first terminal is connected with the vibrating diaphragm 2. The second binding post is connected with the noise reduction belt 4. The diaphragm 2 prototype is provided with a vent 21. The sound-reducing belt 4 blank surrounds the vibrating diaphragm 2 blank. And annealing the vibrating diaphragm 2 blank and the noise reduction belt 4 in a rapid annealing furnace to convert amorphous silicon into polycrystalline silicon, thereby obtaining the vibrating diaphragm 2 and the noise reduction belt 4.
Step six, referring to fig. 12, a layer of silicon dioxide insulating material with a thickness of 500 nm-800 nm is electrodeposited on the side surface of the diaphragm 2, which is far from the substrate 1, by a Tetraethylorthosilicate (TEOS) thermal decomposition method, so as to obtain a first insulating ring 11 blank.
Step seven, referring to fig. 13, a plurality of adhesion-preventing auxiliary holes 111 are formed in the first insulating ring 11 blank by means of post-lithography etching.
Step eight, referring to fig. 14, a layer of silicon dioxide insulating material with a thickness of 1000 nm-2000 nm is electrodeposited on the side surface of the first insulating ring 11 blank far from the substrate 1, so as to obtain a second insulating ring 12 blank. Since the thickness of the electrodeposited second insulating ring 12 preform is uniform throughout, the second insulating ring 12 preform has auxiliary processing holes similar to the adhesion preventing auxiliary holes 111 in the first insulating ring 11 preform.
Step nine, referring to fig. 15, a blind hole 121 is formed in a central position of the second insulating ring 12 blank away from the side surface of the substrate 1 by means of etching after photolithography. The processing depth of the etching after the photoetching is consistent, so that auxiliary processing holes remain at the bottoms of the blind holes 121.
Step ten, referring to fig. 16, a layer of silicon nitride insulating material with a thickness of 100nm to 200nm is electrodeposited on the side of the second insulating ring 12 blank away from the substrate 1 by a Tetraethylorthosilicate (TEOS) thermal decomposition method, to obtain a barrier insulating layer blank. The insulating layer blank is composed of an insulating ring 311 blank and insulating sheets 314 in the blind holes. A plurality of anti-adhesion convex blocks 31 are formed on the side surface of the insulating layer blank close to the vibrating diaphragm. The anti-sticking bumps 31 can prevent the diaphragm from sticking to the back electrode.
Step eleven, referring to fig. 17, a layer of amorphous silicon material with a thickness of 500-1000 nm is electrodeposited on the side surface of the insulating layer blank far from the substrate 1, to obtain a conductive layer blank. Ions are incorporated by means of in-situ doping while electrodepositing the conductive layer preform. The conductive layer preform is comprised of a conductive ring 312 preform and conductive pads 315 located within the blind holes.
Step twelve, referring to fig. 18, edge portions of the insulating ring 311 blank and the conductive ring 312 blank are removed by post-lithography etching, and a fourth post is obtained. The fourth binding post is connected with the conducting layer embryonic body. And annealing the conducting layer embryonic body in a rapid annealing furnace to convert the amorphous silicon into polycrystalline silicon to obtain a blocking insulating layer and a conducting layer, thereby forming a back electrode structure.
And thirteenth, removing the silicon dioxide insulating materials covered on the first binding post 84, the second binding post 81 and the third binding post 83 in a photoetching mode to expose the polysilicon conductive material. The first, second, third and fourth posts 84, 81, 83 and 82 are then covered with metal for lead encapsulation by a sputtering process.
Fourteen, referring to fig. 19, a layer of silicon nitride insulating material with a thickness of 500 nm-1000 nm is electrodeposited on the side surface of the conductive layer away from the substrate 1 and the second insulating ring 12, so as to obtain a passivation protection layer of silicon nitride. The silicon nitride insulating ring, the conducting layer and the silicon nitride passivation protection layer form a back electrode.
Fifteen, referring to fig. 20, a plurality of sound holes are formed in the back electrode by etching after photolithography, and silicon nitride covering the first post 84, the second post 81, the third post 83, and the fourth post 82 is removed. All sound holes extend through the back electrode.
Step sixteen, referring to fig. 21, the back cavity 6 is etched on the outer end surface of the substrate 1 by means of etching after photolithography. The back cavity 6 extends through the substrate 1.
Seventeenth, referring to fig. 22, the silicon dioxide insulating material in the center of the prototype of the etching stop ring 9 and the prototype of the diaphragm support ring 10 is etched away by hydrofluoric acid to expose the diaphragm 2. An etch stop ring 9 and a diaphragm support ring are obtained, at which time a plurality of auxiliary processing rings all fall out of the back chamber 6 of the substrate 1.
Eighteenth, referring to fig. 23, the center portions of the first insulating ring 11 and the second insulating ring 12 are etched away by hydrofluoric acid through the sound holes to obtain the first insulating ring 11 and the second insulating ring 12, and the vibration cavity 7 is formed. The back electrode plate 3 and the vibrating diaphragm 2 form two electrodes of a capacitor.
Claims (5)
1. The capacitive MEMS microphone comprises a substrate, a vibrating diaphragm, a back electrode, a wiring assembly, an etching stop ring, a vibrating diaphragm supporting ring, a first insulating ring and a second insulating ring; the method is characterized in that: the substrate, the etching stop ring, the vibrating diaphragm support ring, the first insulating ring and the second insulating ring are sequentially arranged and fixed together; the vibrating diaphragm is fixed on the vibrating diaphragm support ring; a plurality of annular grooves are formed in both side surfaces of the vibrating diaphragm; all annular grooves are coaxially arranged with the vibrating diaphragm; the edge of the vibrating diaphragm is provided with a vent hole;
the back electrode is fixed with the inner side wall of the second insulating ring; the back electrode is arranged at intervals with the vibrating diaphragm; the back electrode comprises a blocking insulating layer, a conducting layer and a silicon nitride passivation protective layer; the silicon nitride passivation protection layer consists of a protection ring and a protection disc; the protection ring is fixed with the second insulation ring; the side surface of the protection disc, which is close to the vibrating diaphragm, is arranged in a convex manner, and the side surface of the other side is arranged in a concave manner; forming a near membrane part positioned at the central part of the protective disc and a far membrane part positioned at the edge part of the protective disc;
the conductive layer consists of a conductive ring and a conductive sheet; the conducting ring is fixed with the side surface of the far membrane part on the protection disc, which is close to the vibrating diaphragm, and the near membrane part is looped; the conducting strip is fixed with the side surface of the membrane approaching part on the protection disc, which is close to the vibrating diaphragm; the conducting rings and the conducting strips are fixed with the protective disc; the inner diameter of the conductive ring is larger than or equal to the diameter of the conductive sheet; the distance between the conducting ring and the vibrating diaphragm is larger than the distance between the conducting plate and the vibrating diaphragm; the barrier insulating layer consists of a barrier insulating ring and a barrier insulating sheet; the blocking insulating ring is fixed with the conducting ring; the blocking insulating sheet is fixed with the conducting strip; the blocking insulating ring and the conducting ring are fixed with the protecting ring; a plurality of sound holes are formed in the back electrode; all sound holes penetrate through the back electrode; a plurality of anti-adhesion convex blocks are arranged on the side surface of the barrier insulating layer, which is close to the vibrating diaphragm;
the wiring assembly comprises a first wiring terminal and a fourth wiring terminal; the first binding post and the fourth binding post are respectively connected with the vibrating diaphragm and the conducting layer;
the vibrating diaphragm, the noise reduction belt, the noise reduction ring and the conducting layer are all made of polysilicon; the isolation insulating layer and the silicon nitride passivation protective layer are made of silicon nitride; the etching stop ring, the vibrating diaphragm support ring, the first insulating ring and the second insulating ring are all made of silicon dioxide;
the outer end face of the substrate is provided with a back cavity penetrating through the substrate.
2. A capacitive MEMS microphone as claimed in claim 1, wherein: a noise reduction belt is arranged between the outer edge of the vibrating diaphragm and the inner side wall of the first insulating ring; a noise reduction ring is arranged between the etching stop ring and the vibrating diaphragm support ring; the wiring assembly also comprises a second wiring terminal and a third wiring terminal; the second binding post is connected with the noise reduction belt; the third binding post is connected with the noise reduction ring.
3. A capacitive MEMS microphone as claimed in claim 1, wherein: the inner diameters of the annular grooves on the same side surface of the vibrating diaphragm are sequentially increased in an equal difference mode along the direction from the center of the vibrating diaphragm to the edge.
4. The method of manufacturing a capacitive MEMS microphone as claimed in claim 2, wherein:
firstly, electrodepositing a layer of silicon dioxide with the thickness of 300-500 nm on a substrate to obtain an etching stop annular embryonic body;
step two, electrodepositing a layer of amorphous silicon material with the thickness of 300-500 nm on the etching stop annular embryonic body to obtain a first amorphous silicon layer; dividing the first amorphous silicon layer into a third binding post, a noise-reduction annular rudiment and a plurality of auxiliary processing rings, wherein the noise-reduction annular rudiment and the auxiliary processing rings are mutually independent and coaxially arranged in a photoetching mode; annealing the noise-reducing ring blank to obtain a noise-reducing ring;
step three, electrodepositing a layer of silicon dioxide with the thickness of 500-800 nm on the noise reduction ring to obtain a vibrating diaphragm support ring blank;
step four, electrodepositing an amorphous silicon material with the thickness of 300-500 nm on the vibrating diaphragm support annular embryonic body to obtain a second amorphous silicon layer;
step five, dividing the second amorphous silicon layer into a first binding post, a second binding post, a vibrating diaphragm embryonic body and a noise reduction belt embryonic body in a photoetching mode; the vibrating diaphragm embryonic body and the noise reduction belt embryonic body are mutually independent; the first binding post is connected with the vibrating diaphragm; the second binding post is connected with the noise reduction belt; the vibrating diaphragm embryonic body is provided with a vent hole; the noise reduction belt rudiment surrounds the vibrating diaphragm rudiment; annealing the vibrating diaphragm blank and the noise reduction belt to the vibrating diaphragm and the noise reduction belt;
step six, electrodepositing a layer of silicon dioxide insulating material with the thickness of 500-800 nm on the vibrating diaphragm to obtain a first insulating annular embryonic body;
step seven, forming a plurality of anti-adhesion auxiliary holes on the first insulating annular embryonic body in a photoetching mode;
step eight, electrodepositing a layer of silicon dioxide insulating material with the thickness of 1000 nm-2000 nm on the first insulating annular embryonic body to obtain a second insulating annular embryonic body;
step nine, forming a blind hole on the second insulating ring blank in a photoetching mode;
step ten, electrodepositing a layer of silicon nitride insulating material with the thickness of 100 nm-200 nm on the second insulating annular embryonic body to obtain a barrier insulating layer embryonic body; the insulating layer performs are composed of insulating ring performs and insulating sheets; forming a plurality of anti-adhesion convex blocks on the side surface of the insulating layer blank close to the vibrating diaphragm;
step eleven, electrodepositing a layer of amorphous silicon material with the thickness of 500-1000 nm on the insulating layer embryonic body to obtain a conductive layer embryonic body; the conducting layer embryonic body consists of a conducting ring embryonic body and a conducting plate positioned in the blind hole;
removing edge parts of the insulating ring blank and the conducting ring blank by means of etching after photoetching, and obtaining a fourth binding post; the fourth binding post is connected with the conducting layer embryonic body; annealing the conducting layer embryonic body to obtain a blocking insulating layer and a conducting layer;
removing silicon dioxide insulating materials covered on the first binding post, the second binding post and the third binding post in a photoetching mode; then coating metal on the first binding post, the second binding post, the third binding post and the fourth binding post through a sputtering process;
fourteen, electrodepositing a layer of silicon nitride with the thickness of 500-1000 nm on the side surface of the conducting layer, which is far away from the substrate and the second insulating ring, so as to obtain a silicon nitride passivation protection layer; the silicon nitride insulating ring, the conducting layer and the silicon nitride passivation protection layer form a back electrode;
fifteen, forming a plurality of sound holes on the back electrode in a photoetching mode, and removing silicon nitride covered on the first binding post, the second binding post, the third binding post and the fourth binding post;
sixthly, etching a back cavity on the outer end surface of the substrate in a photoetching mode; the back cavity penetrates through the substrate;
seventeenth, corroding the middle parts of the etching stop ring blank and the vibrating diaphragm supporting ring blank by using hydrofluoric acid to obtain an etching stop ring and a vibrating diaphragm supporting ring;
eighteenth, corroding central parts of the first insulating ring blank and the second insulating ring blank by using hydrofluoric acid through the sound holes to obtain the first insulating ring and the second insulating ring.
5. The method of manufacturing a capacitive MEMS microphone as defined by claim 4, wherein: in the second step, doping ions in a bit doping mode while electrodepositing a first amorphous silicon layer; in the fourth step, ions are doped in an in-situ doping mode while the second amorphous silicon layer is electrodeposited; in step eleven, ions are incorporated by means of in-situ doping while electrodepositing the conductive layer preform.
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