CN105704622A

CN105704622A - Support Apparatus for Microphone Diaphragm

Info

Publication number: CN105704622A
Application number: CN201610104597.3A
Authority: CN
Inventors: 贾森.W.魏戈尔德
Original assignee: InvenSense Inc
Current assignee: Analog Devices Inc; InvenSense Inc
Priority date: 2006-01-20
Filing date: 2007-01-22
Publication date: 2016-06-22
Also published as: JP2009524368A; JP5215871B2; CN101371614A; WO2007085017A1

Abstract

A microphone includes a diaphragm assembly supported by a substrate. The diaphragm assembly includes at least one carrier, a diaphragm, and at least one spring coupling the diaphragm to the at least one carrier such that the diaphragm is spaced from the at least one carrier. An insulator (or separate insulators) between the substrate and the at least one carrier electrically isolates the diaphragm and the substrate.

Description

Support equipment for condenser microphone diaphragm

Technical field

Present invention relates in general to microphone, more particularly, the present invention relate to the support of microphone diaphragm。

Background technology

MEMS (" MEMS ", hereinafter referred to as " MEMS " device) is widely used in various application。Such as, currently generally realize MEMS sound signal to be converted to the signal of telecommunication as microphone, carrys out the angle of pitch of sense aircraft as gyroscope and optionally launch the air bag in automobile as accelerometer。Say with the term simplified, this MEMS typically has the movable structure being suspended on substrate, and associated circuit, the exercise data perceived also is sent to one or more external devices (such as, outer computer) by the motion of this associated circuit perception suspended structure。External device processes perception data is to calculate measured feature (such as, the angle of pitch or acceleration)。

MEMS microphone is increasingly utilized for greater number of application。Such as, MEMS microphone is frequently used for portable phone and other such devices。But, more market to be permeated, it is important to acquire satisfied sensitivity and the signal to noise ratio mated with more traditional microphones。

MEMS microphone typically comprises thin membrane electrode and is positioned at the fixing sensing electrode on thin membrane electrode side。The pole plate of septum electrode and fixing sensing electrode and variable condenser similarly works。During microphone operation, charge placement is on septum electrode and fixing sensing electrode。When septum electrode responds acoustic vibration, the distance change between septum electrode and fixing sensing electrode causes the capacitance variations corresponding with sound wave。Therefore change in these electric capacity produces to represent the electronic signal of sound wave。Finally, can process to reproduce sound wave for example, on a speaker to this electronic signal。

Fig. 1 illustrates the population structure of micro-microphone well known in the art。Wherein, this micro-microphone includes barrier film 102 and bridge electrode (i.e. backboard) 104。Barrier film 102 and backboard 104 work as the electrode for condenser network。As it can be seen, backboard 104 can be perforated to allow for sound wave arrives barrier film 102。Alternatively, or in addition, sound wave can be made to pass through other passages arrive barrier film。In any situation, sound wave all can cause barrier film to vibrate, and this vibration can be sensed as the capacitance variations between barrier film 102 and bridge 104。This micro-microphone typically comprises barrier film 102 substantial cavity 106 below to allow barrier film 102 to move freely。

Many MEMS microphone adopt the barrier film being anchored completely around its periphery, similar with the head of drum。This barrier film there will be a lot of problem。Such as, when there being sound wave, this barrier film tends to bend without unanimous between the higher and lower levels mobile, as shown in Figure 2 A。This bending can negatively affect the sensitivity of microphone, especially because the distance between internal tension and membrane portions and fixing sensing electrode part changes the limited displacement of the barrier film caused。This barrier film can be influenced by the sensitivity impact to stress (such as, thermal expansion), and described stress can distort the shape of barrier film and can affect the mechanical integrity of barrier film and the sound quality of microphone generation。

Some MEMS microphone have by multiple springs in a movable manner with its underlying stationary member (hereinafter referred to as " bracket ") barrier film that is connected。Spring with tending to make barrier film unanimous between the higher and lower levels mobile (that is, similar to plunger), as shown in Figure 2 B。

Summary of the invention

According to an aspect of the present invention, it is provided that a kind of microphone, have: substrate；The diaphragm assembly supported by described substrate, described diaphragm assembly includes at least one bracket, barrier film and couples the diaphragm at least one spring of at least one bracket described, and described barrier film and at least one bracket described separate；And at least one insulator, described insulator between described substrate and at least one bracket described so that described barrier film and described substrate electric insulation。

In various optional embodiments, described substrate and barrier film can Capacitance Coupled to form fixing plate and the movable platen of variable condenser。Each bracket may be coupled to insulator, and described insulator couples with described substrate。Described barrier film can be perforated and/or corrugated。Space between described barrier film and at least one bracket described can in the nominal plane of described barrier film。Described barrier film can with at least one bracket stress isolation described。At least one bracket described can include maybe can including multiple different bracket around the single integral bracket of described barrier film。At least one insulator described can include oxide。Described diaphragm assembly can include polysilicon。At least one insulator described can be formed directly or indirectly on described substrate, and at least one bracket described can be formed directly or indirectly at least one insulator described。Described substrate can be formed by the silicon layer of silicon-on-insulator wafer。Described substrate can include multiple through hole, and in this situation, described through hole can allow sound wave to arrive described barrier film from the dorsal part of described substrate。This microphone can include the electronic circuit producing signal in response to diaphragm movement。This electronic circuit can be formed directly or indirectly on described substrate。

According to a further aspect in the invention, it is provided that a kind of microphone, this microphone includes: substrate；Barrier film；For coupling the diaphragm to support arrangement of described substrate in a movable manner, this support arrangement includes the bracket system for being fixedly connected with described substrate and for coupling the diaphragm to described bracket system the suspension arrangement described barrier film and described bracket system separated in a movable manner；And for making described barrier film and the dielectric body device of described substrate electric insulation。

In various optional embodiments, described microphone can farther include the device for described substrate and described diaphragm capacitance couple fixing plate and movable platen to form variable condenser。Described microphone can additionally or alternatively include for allowing sound wave to arrive the device of described barrier film from the dorsal part of described substrate。Described microphone can additionally or alternatively include the device for producing signal in response to diaphragm movement。

Accompanying drawing explanation

From the aforementioned advantages that referring to accompanying drawing, the further instruction of the present invention can be more fully understood by the present invention, wherein:

Fig. 1 illustrates the population structure of micro-microphone well known in the art；

Fig. 2 A schematically shows the flexure operation of drum type MEMS microphone barrier film；

Fig. 2 B schematically shows the plunger type action of the MEMS microphone barrier film with spring；

Fig. 3 schematically shows the MEMS microphone that can produce according to the illustrative embodiment of the present invention；

Fig. 4 schematically shows the plane graph of the microphone of Fig. 3 of the illustrative embodiment configuration according to the present invention；

Fig. 5 illustrates the plan view photograph of the concrete microphone according to illustrative embodiments configuration；

Fig. 6 illustrates the close-up plan view picture of the spring that figure 5 illustrates；

Fig. 7 schematically shows viewgraph of cross-section and the partial top view of the microphone of the illustrative embodiment configuration according to the present invention, and described barrier film is in non-release conditions；And

Fig. 8 schematically shows viewgraph of cross-section and the partial top view of the microphone of the illustrative embodiment configuration according to the present invention, and described barrier film is in release conditions。

For the ease of explaining the black and white copying part of specific pattern, with the different material of following legend identification: " S " represents monocrystal silicon；" O " represents oxide；" P " represents polysilicon；" M " represents metal；And " Pass " represents passivating material such as nitride。

Unless the context otherwise suggests, similar components like numeral represents。Equally, unless otherwise stated, accompanying drawing is not necessarily drawn to scale。

Detailed description of the invention

In embodiments of the present invention, MEMS microphone includes the diaphragm assembly supported by substrate。This diaphragm assembly includes at least one bracket, barrier film and at least one spring, and described spring couples the diaphragm at least one bracket described and described barrier film and at least one bracket described are separated。Insulator (or the insulator separated) between described substrate and at least one bracket described makes described barrier film and described substrate electric insulation。Described bracket can be attached directly to described insulator and described insulator can be attached directly to described substrate；Alternatively, described insulator can be separated by one or more other materials with described substrate and/or described bracket。When described barrier film and described substrate are electrically insulated from one another, described barrier film and described substrate can Capacitance Coupled therefore can be used as two pole plates of variable condenser so that sound signal is converted to the signal of telecommunication。

Fig. 3 schematically shows the unencapsulated MEMS microphone 10 (also referred to as " microphone chip 10 ") of the illustrative embodiment according to the present invention。Wherein, microphone 10 includes supporting and forming the backboard 12 (joint detail of described diaphragm assembly and backboard 12 is discussed below) fixed of variable condenser with the diaphragm assembly including barrier film 14。In illustrative embodiment, backboard 12 is formed by monocrystal silicon, and the diaphragm assembly including barrier film 14 is formed by the polysilicon deposited, and the insulator between backboard 12 and described diaphragm assembly is formed by oxide。In this example, backboard 12 is formed so leaning against in basic oxide layer and base silicon layer by the top silicon layer of SOI (SOI) wafer 20。For the ease of operation, backboard 12 has multiple through hole 16, and through hole 16 leads to the backside cavity 18 formed through described basic oxide layer and base silicon layer。Using and encapsulate microphone 10 makes sound wave arrive barrier film 14 through backside cavity 18 and through hole 16。

Audio signal causes barrier film 14 to vibrate, and therefore produces the electric capacity of change。The electric capacity of this change is converted to the signal of telecommunication that can process further by on-chip circuit or chip circuitry。It should be noted that to the discussion of the microphone 10 shown in Fig. 3 solely for the purpose of illustration。Therefore other MEMS microphone with the structure similar or not similar with the microphone 10 shown in Fig. 3 can be adopted together with the illustrative embodiment of the present invention。

Fig. 4 schematically shows the plane graph of the microphone 10 according to illustrative embodiment configuration。This exemplary microphone 10 has the feature that many and shown in Fig. 3 features are identical。Specifically, as it can be seen, microphone 10 includes substrate 20, substrate 20 has multiple bracket 22 (being four brackets in this example), and bracket 22 supports barrier film 14 via multiple springs 24。Dissimilar with barrier film 14, each bracket 22 is fixedly connected with substrate 20。In illustrative embodiment, each bracket 22 is attached to substrate 20 and makes each bracket 22 and substrate 20 electric insulation by electrically insulating material (such as, oxide) layer。

Wherein, this formation expansion space 26 it is arranged between at least one bracket 22 and barrier film 14。Therefore, if subjected to stress, barrier film 14 can freely expand in this space 26。Correspondingly, under anticipated stresses, barrier film 14 will not with bracket 22 Mechanical Contact (this contact can reduce systematic function)。

Fig. 5 illustrates the plan view photograph of the concrete microphone 10 according to illustrative embodiment configuration, and Fig. 6 illustrates the close-up plan view picture of shown in Fig. 5 a spring 24。It should be noted that concrete microphone 10 is the example of the various embodiments of the present invention。Correspondingly, it is not considered that shape and quantity to the discussion such as spring 24 of concrete assembly are the restrictions to the various embodiment of the present invention。

As it can be seen, microphone 10 has a circular diaphragm 14 and four radially extend but circumferentially shaped spring 24, spring 24 forms space 26 between (multiple) bracket 22 and the outer peripheral edge of barrier film 14。In this example, described diaphragm assembly includes the single integral bracket 22 around barrier film 14。In addition to providing the noted expansion space 26, spring 24 also should alleviate diaphragm flexes (that is, at barrier film 14 from time in terms of its top concavely) when moving down。Correspondingly, thus, barrier film 14 should move to substrate 20 in a more consistent way compared with the prior art without space 26 or spring 24。Such as, barrier film 14 can move up and down close to the mode of plunger。Correspondingly, barrier film 14 Ying Kegeng moves up and down freely, and the more multizone of the inner surface of barrier film 14 should can be used to produce basis signal。

Fig. 7 schematically shows viewgraph of cross-section and the partial top view of the microphone 10 of the illustrative embodiment configuration according to the present invention, and described barrier film is in non-release conditions。This schematically illustrates above-mentioned multiple features, the space between the such as space between barrier film 14 and substrate 20, and barrier film 14 and bracket 22。In this figure, it is shown that described barrier film has oxide underlayer, this oxide underlayer is removed to discharge described barrier film later。Fig. 8 schematically shows viewgraph of cross-section and the partial top view of the microphone of the illustrative embodiment configuration according to the present invention, and described barrier film is in release conditions (that is, being removed by described oxide underlayer)。

In only certain exemplary embodiments of this invention, micro-microphone can be formed by silicon or SOI (SOI) wafer。As it is known in the art, SOI wafer includes being commonly referred to the top silicon layer of device layer, intermediate insulator (oxide) layer and typically thick than described top silicon layer a lot (such as, about 650 microns) bottom silicon layer。The top layer formed by silicon or SOI wafer In some embodiments of the present invention can relatively thin (such as, about 10 microns of thickness) or thicker (such as, about 50 microns of thickness) in other embodiments。In only certain exemplary embodiments of this invention, described fixing sensing electrode (at this also referred to as " backboard ") can be formed by the top silicon layer of described wafer, and described barrier film is formed as being suspended on described top silicon layer。Perforation may be formed in described fixing sensing electrode to allow sound wave to arrive described barrier film from the bottom of described wafer。Insulating barrier on the dorsal part of described top silicon layer is (such as, oxide skin(coating)), can be used as etching stopping layer for controlling the processing of described fixing sensing electrode, this insulating barrier can be intrinsic oxide skin(coating) or the deposition oxide skin(coating) on silicon of SOI wafer。

Illustrative processes for forming micro-microphone from SOI wafer includes the top silicon layer through blank SOI wafer in described intermediate oxide layer and optionally pass through the etching groove to described bottom silicon layer。Then with groove described in oxide pad。Then by polycrystalline silicon material deposition to be filled with lining groove and to cover described top silicon。Described polycrystalline silicon material is patterned and etches to form the various sacrifice structure being removed later。By other oxide material deposition。Polycrystalline silicon material is deposited and is patterned to form the diaphragm assembly including microphone diaphragm and pendulum spring。By oxide deposition also etch-hole to expose described back board part and diaphragm assembly part。Metal deposit composition are used for arranging the electrode of electric charge and multiple adhesive covered pads with formation on described barrier film for arranging the electrode of electric charge, being formed on described backboard。Multiple electrical connection can be had between adhesive covered pads and described electrode。Then by passivation layer (such as, being nitridized the oxide skin(coating) that nitride layer covers, described nitride layer is the standard passivation layer for integrated circuit) deposition。Etch described passivation layer to expose described adhesive covered pads and to expose described barrier film。Photo anti-corrosion agent material is deposited then composition to expose future pedestal area。Then pass through the oxide that etching removes on described future pedestal area。Remaining photo anti-corrosion agent material is removed, and makes described bottom silicon layer be thinned to about 350 microns from about 650 microns alternatively by any one including in the several method etching, mill and polishing。Photo anti-corrosion agent material is deposited on the front side of described wafer to form photoresist base。Also photo anti-corrosion agent material is deposited on the dorsal part of described wafer and composition is to draw the profile of backside cavity。Described backside cavity is by etching away the part formation to described intermediate oxide layer of the described bottom silicon layer。In exemplary embodiment, the described backside cavity volume after encapsulation is about 1 cubic millimeter。Remove to expose described sacrificial polysilicon structures by a described intermediate oxide layer part in described cavity。Such as by described polysilicon is exposed to XeF through described backside cavity₂In gas or in the another kind of silicon etching agent being suitable for, described sacrificial polysilicon structures is removed。It should be noted that XeF₂Gas is likely to remove the bottom silicon layer that part exposes, and even now is usually less desirable。Such as by being placed in suitable liquid by the oxide removal after described barrier film。Then, for instance in dry ecthing agent (on-liquid), remove the photo anti-corrosion agent material (including described pedestal) of front side。So substantially described barrier film and relevant structure are released。It should be noted that described base is for supporting fragile microphone construction at deenergized period and not being be required in all embodiments, particularly when be remove described oxide with steam HF rather than liquid。

Illustrative processes for forming micro-microphone from well-regulated silicon wafer includes oxide layer deposition at described silicon wafer。Then, by polycrystalline silicon material composition and etch to form described diaphragm assembly。Oxide material is deposited, and etch-hole is to expose described substrate portion and described diaphragm assembly part。By metal deposit and be patterned to form adhesive covered pads and for arranging the electrode of electric charge on described microphone diaphragm and backboard。Electrical connection can be had between described adhesive covered pads and one or more described electrode。By passivation layer (such as, nitride layer the oxide skin(coating) covered, described nitride layer is the standard passivation layer for integrated circuit) deposition。Described passivation layer is etched to expose described adhesive covered pads。Described passivation layer part above described microphone construction is removed and by above described polysilicon structure and part oxide removal below described polysilicon structure to form resist base area。By including etching, mill and polish in the several method of described dorsal part any one make the dorsal part of described silicon wafer be thinned to about 350 microns from about 650 microns alternatively, and one layer of oxide is deposited on the dorsal part of described wafer。Photo anti-corrosion agent material is deposited on the front side of described wafer, and by the oxide composition in described wafer backside。Photo anti-corrosion agent material is deposited and is patterned on the dorsal part of described wafer, and trench etch is to described silicon wafer。Described photo anti-corrosion agent material is removed from described front side and dorsal part, and on described front side, forms new layer of photoresist material for protecting。Then with already present oxide as the hard mask back side etch cavity at described wafer。It is then passed through described silicon layer further by the resist base area of described trench etch to described microphone region。Such as by being exposed in HF gas the oxide removal that will expose through described cavity。Remaining photo anti-corrosion agent material is removed from the front side of described wafer, thus discharging described microphone construction。Finally, Pyrex alignment anode can be bonded to the dorsal part of described wafer。Before bonding, in described glass, microphone holes can be carried out ultrasonic cut。

It will also be noted that the technique of these descriptions is illustrative of。For concrete implementation, less, other or different step or technique can be adopted。In some cases, different from the material having described that materials is likely to be suited for concrete step or technique。It is practically impossible to describe each combination and permutation of material and the technique that can use in the various embodiments of the present invention。Therefore, it is contemplated that include this type of materials all and technique, described material and technique include the suitable variant of material and the technique having described that。Additionally, the micro-microphone of the above-mentioned type can collectively form on the same wafer together with inertial sensor and/or electronic circuit and can various shape factor encapsulate。

It will also be noted that the invention is not restricted to the microphone diaphragm of any concrete shape, structure or combination。Described microphone can be such as circular or square, solid or be installed with one or more hole and/or flat or corrugated。Different membrane configurations be likely to need from have described that the different or other technique of technique。Such as, other technique can be used for being formed hole or ripple in described barrier film。In above-mentioned various embodiment, described diaphragm assembly is polysilicon, but can also use other materials。

It will also be noted that the invention is not restricted to the spring for coupling the diaphragm at least one bracket described of any particular type or quantity。Embodiments of the present invention can use dissimilar and quantity spring。

It will also be noted that the invention is not restricted to the insulator between described substrate and at least one bracket described of any particular type。In above-mentioned various embodiment, described insulator is a kind of oxide, but is used as other kinds of insulator。

It will also be noted that the invention is not restricted to the encapsulation of any particular type。

Although the above discussion discloses various exemplary embodiments of the invention, but to those skilled in the art it is evident that can make when not necessarily departing from the true scope of the present invention and will realize the various modification of some advantage of the present invention。

Claims

1. a microphone, including:

Substrate, described substrate includes backboard and backside cavity, and described backboard includes some through holes, and wherein said backboard forms the fixing plate of variable condenser；

The diaphragm assembly supported by described substrate, described diaphragm assembly includes at least one bracket, conductive diaphragm and couples the diaphragm at least one spring of at least one bracket described, described barrier film and at least one bracket described separate, wherein said barrier film has a plane when not bending, at least one spring described in when not bending is positioned at described plane, and at least one spring described produces space on the direction of the plane of described barrier film between described barrier film and at least one bracket described；

At least one insulator, at least one insulator described is between described substrate and at least one bracket described, so that described barrier film and described substrate electric insulation, wherein said barrier film forms the movable platen of described variable condenser；

Wherein said backboard is between described backside cavity and described barrier film, and sound wave arrives described barrier film by the through hole of described backside cavity and described backboard through backboard。

2. microphone as claimed in claim 1, wherein each bracket is attached to insulator, and this insulator is attached to described substrate。

3. microphone as claimed in claim 1, wherein said barrier film is perforated。

4. microphone as claimed in claim 1, wherein said barrier film corrugated。

5. microphone as claimed in claim 1, at least one spring wherein said is arranged between described barrier film and described bracket。

6. microphone as claimed in claim 1, wherein said barrier film and at least one bracket stress isolation described。

7. microphone as claimed in claim 1, at least one bracket wherein said includes the single integral bracket around described barrier film。

8. microphone as claimed in claim 1, at least one bracket wherein said includes multiple different bracket。

9. microphone as claimed in claim 1, at least one insulator wherein said includes oxygen。

10. microphone as claimed in claim 1, wherein said diaphragm assembly includes polysilicon。

11. microphone as claimed in claim 1, at least one insulator wherein said is formed directly or indirectly on described substrate。

12. microphone as claimed in claim 11, at least one bracket wherein said is formed directly or indirectly at least one insulator described。

13. microphone as claimed in claim 1, wherein said substrate is formed by the silicon layer of silicon-on-insulator wafer。

14. microphone as claimed in claim 1, wherein said through hole allows sound wave to arrive described barrier film from the dorsal part of described substrate。

15. microphone as claimed in claim 1, farther include to produce the electronic circuit of signal in response to diaphragm movement。

16. microphone as claimed in claim 15, wherein said electronic circuit is formed directly or indirectly on described substrate。

17. a microphone, including:

Substrate, described substrate includes backboard and backside cavity, and described backboard includes some through holes；

Conductive diaphragm；

For coupling the diaphragm to a support arrangement of described substrate in a movable manner, described support arrangement includes bracket system and suspension arrangement, described bracket system is for being fixedly connected with described substrate, described suspension arrangement is for coupling the diaphragm to described bracket system in a movable manner and described barrier film and described bracket system being separated, wherein said barrier film has a plane when not bending, and described suspension arrangement is positioned at described plane when not bending；

Dielectric body device, described dielectric body device is used for making described barrier film and described substrate electric insulation；With

Wherein said barrier film forms variable condenser with described backboard, described backboard forms the fixing plate of variable condenser, described barrier film forms the movable platen of described variable condenser, described backboard is between described backside cavity and described barrier film, and sound wave arrives described barrier film by the through hole of described backside cavity and described backboard through backboard。

18. megaphone as claimed in claim 17, wherein said suspension arrangement is arranged between described barrier film and described bracket system。

19. microphone as claimed in claim 17, farther include the device for producing signal in response to diaphragm movement。