JP5491080B2 - microphone - Google Patents

Description

  The present invention relates to a microphone for detecting vibration caused by sound.

  The present inventors have proposed a technique described in Patent Document 1 as a small microphone capable of sound source localization.

  In this technique, the direction of the sound source can be specified by detecting tilt vibration in the XY plane of the circular diaphragm.

  By the way, in this technique, a device is required for the support structure of the circular diaphragm so that the circular diaphragm can vibrate corresponding to the direction of movement. For example, a structure has been proposed in which the center of the lower surface of the circular diaphragm is supported so that the circular diaphragm can be tilted, or the circular diaphragm is supported using a gimbal mechanism.

However, adopting such a support structure
• The manufacturing process tends to be complex and difficult;
The mechanical structure of the microphone itself tends to be fragile;
・ There are significant restrictions on the detection mechanism of the circular diaphragm;
・ Problems such as difficulty in increasing sensitivity and frequency characteristics occur.

  On the other hand, the present inventors have obtained a theoretical finding that the optimum load function for a so-called mistletoe type acoustic sensor is a Gaussian function (the following Non-Patent Document 1).

      JP 2006-345130 A

  Ando, Ono, "Optimum structure of mistletoe type acoustic sensor and direct algebra solution of short-time sound source localization," Applied Acoustical Auditory Joint Study Group, IEICE Technical Report, Vol. 107, No. 7, EA2007-52, H-2007 -101, 2007.

  As a result of studying various sensor structures that satisfy the conditions obtained by the theoretical analysis described above, the present inventors can satisfy such conditions by applying a cantilever structure, The knowledge that the structure of can be simplified was obtained.

  Therefore, the present invention provides a microphone having a relatively simple structure that can perform sound source localization or sound source separation.

  Means for solving the above-described problems can be described as follows.

(Item 1)
A support frame, a first diaphragm, a second diaphragm, and a coupling body;
One end of each of the first diaphragm and the second diaphragm is elastically supported by the support frame,
The other end of the first diaphragm and the other end of the second diaphragm are disposed to face each other.
And the other end of the first diaphragm and the other end of the second diaphragm are connected by the connecting body,
The microphone is characterized in that the connecting body is displaceable with respect to the other end of the first diaphragm and the other end of the second diaphragm.

  An extending direction of the first diaphragm and the second diaphragm is set as an X axis, and a direction orthogonal to the diaphragm is set as a Z axis. When a sound wave comes from a direction inclined in the X-axis direction with respect to the Z-axis (generally, the inclination angle θ is 0 ° <θ <180 °), the first diaphragm and the second diaphragm are in accordance with the inclination angle. Vibrates with a large phase difference. When sound waves come from the Z-axis direction, the first diaphragm and the second diaphragm vibrate in phase. Therefore, the direction of the sound source can be known by detecting the phase difference of the vibration. By using a plurality of sets of diaphragms that vibrate with a phase difference, it is possible to know the inclination angle in the Y-axis direction and the Z-axis direction in addition to the X-axis direction. The tilt vibration of the coupled body corresponds to the phase difference of vibration in each diaphragm. Therefore, sound source localization and sound source separation can be performed by detecting the vibration of the coupled body.

(Item 2)
A weakening portion that facilitates deformation between the connecting body and the other end of the first diaphragm and between the connecting body and the other end of the second diaphragm is provided. Item 1. The microphone according to item 1.

  By providing the weakening portion, it is possible to smoothly generate the tilt vibration of the coupled body when the first diaphragm and the second diaphragm vibrate in opposite phases.

(Item 3)
Furthermore, a third diaphragm and a fourth diaphragm are provided,
One end of each of the third diaphragm and the fourth diaphragm is elastically supported by the support frame,
The other end of the third diaphragm and the other end of the fourth diaphragm are disposed to face each other.
And the other end of the third diaphragm and the other end of the fourth diaphragm are connected by the connecting body,
The coupling body is displaceable with respect to the other end of the third diaphragm and the other end of the fourth diaphragm.
The microphone according to item 1 or 2, wherein the third diaphragm and the fourth diaphragm are extended in a direction crossing an extension direction of the first diaphragm and the second diaphragm.

  As described above, by further including the third diaphragm and the fourth diaphragm, sound source localization in a two-dimensional direction becomes possible.

(Item 4)
The first diaphragm, the second diaphragm, and the coupling body are configured by forming a slit in a single plate that can be elastically deformed with respect to sound pressure,
The microphone according to item 1, wherein one end of the first diaphragm and one end of the second diaphragm and the support frame are integrated.

  Since each diaphragm and coupling body can be formed by the slits, the manufacturing process can be simplified. Further, by reducing the slit width, the amount of medium (for example, air) that escapes to the back side of each diaphragm can be reduced, and the efficiency of the microphone can be increased.

(Item 5)
Furthermore, the microphone of any one of the items 1-4 provided with the detection part which detects the parallel vibration and inclination vibration of the said coupling body.

  By analyzing the output from the detection unit, for example, sound source localization and sound source separation can be performed.

(Item 6)
Item 5. The microphone according to item 4, wherein the first diaphragm and the second diaphragm have the same thickness as a whole.

  By making the thickness uniform, the processing cost can be reduced.

(Item 7)
The said 1st diaphragm and the said 2nd diaphragm are any one of the items 1-6 whose thickness or width is changed with the place so that it may have a Gaussian type sensitivity distribution. microphone.

  By making the sensitivity distribution obtained by each diaphragm close to an ideal Gaussian distribution, the accuracy as a microphone can be improved.

(Item 8)
8. A sound source analyzing apparatus that performs sound source localization by analyzing vibration of the connected body in the microphone according to items 1 to 7.

  A sound source analyzing apparatus capable of sound source localization using any of the microphones described above can be provided.

  The microphone of the present invention has a relatively simple structure and can perform sound source localization or sound source separation.

It is explanatory drawing of the microphone which concerns on 1st Embodiment of this invention. FIG. 1 (a) shows a plan view of the microphone. Fig. (B) shows a half sectional view of Fig. (A). It is an enlarged plan view which shows the connection body part in the microphone which concerns on 1st Embodiment of this invention. It is a graph which shows the example of calculation of load distribution in the microphone concerning a 1st embodiment of the present invention. The figure (a) shows a common mode (in-phase vibration). FIG. 5B shows the differential mode (phase difference vibration). It is a model for demonstrating the vibration mode of the coupling body in the microphone which concerns on 1st Embodiment of this invention. It is explanatory drawing of the microphone which concerns on 2nd Embodiment of this invention. FIG. 1 (a) shows a plan view of the microphone. Fig. (B) shows a half sectional view of Fig. (A). It is an enlarged plan view which shows the connection body part in the microphone which concerns on 2nd Embodiment of this invention. It is explanatory drawing of the microphone which concerns on 3rd Embodiment of this invention, Comprising: The top view of the support plate arrange | positioned facing a coupling body is shown. It is explanatory drawing of the microphone which concerns on 4th Embodiment of this invention, Comprising: The optical system used for the vibration detection of a coupling body is shown. It is explanatory drawing of the manufacturing process of the microphone which concerns on 5th Embodiment of this invention. It is explanatory drawing for demonstrating the cutting location corresponding to the cross section shown in FIG. It is explanatory drawing of the manufacturing process of the microphone which concerns on 6th Embodiment of this invention. It is explanatory drawing of the manufacturing process of the microphone which concerns on 6th Embodiment of this invention. It is explanatory drawing for demonstrating the cutting location corresponding to the cross section shown in FIG.

(First embodiment)
A microphone according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. This microphone alone enables sound source localization in the XY plane. In the following description, a microphone means a detector or a detection device that can detect a dense wave propagating in a medium. In the following, air will be described as an example of the medium. In addition, an audible range is assumed as the frequency band of the dense wave, but application to other bands is also possible.

  The microphone of the present embodiment includes the first diaphragm 1, the second diaphragm 2, the third diaphragm 3, the fourth diaphragm 4, the support frame 5, and the coupling body 6 as main elements. ing.

  Each of the first to fourth diaphragms 1 to 4 is formed in a substantially isosceles triangle shape (see FIG. 1A). Each of the ends 11 to 41 of the diaphragms 1 to 4 is formed in a thin plate shape and is elastically supported by the support frame 5 (see FIG. 1B). Specifically, each diaphragm 1-4 is formed integrally with the support frame 5, and is supported by the support frame 5 so that it can be elastically deformed by the elastic force of each diaphragm 1-4. Yes. Moreover, each diaphragm 1-4 of this embodiment cut | disconnects the thin plate integrally formed with the support frame 5 by the very narrow slits 7a-7d (refer FIG. 1A). It is formed. Therefore, the first to fourth diaphragms 1 to 4 have the same thickness as a whole (see FIG. 1B). For example, the thickness of each diaphragm indicated by the symbol “a” in FIG. 1B can be 2 to 5 μm, for example, but is not limited to this thickness.

  Here, in order to apply the manufacturing technology in the MEMS field, the thin plate is made of silicon single crystal, polycrystalline silicon, or metal such as Ni, Fe, W, Ti, Cr, Co, Cu, Pt, Au, and alloys thereof. It is preferable that it is comprised by. It is also preferable to use an insulator such as silicon oxide or silicon nitride for the material of the thin plate. Of course, the material of the thin plate may be any material that can be elastically deformed by sound pressure propagating in the medium, and the material is not limited to these, and for example, an organic material may be used.

  The other end 12 of the first diaphragm 1 and the other end 22 of the second diaphragm 2 are disposed to face each other. Similarly, the other end 32 of the third diaphragm 3 and the other end 42 of the fourth diaphragm 4 are disposed to face each other.

  The third diaphragm 3 and the fourth diaphragm 4 are extended in a direction intersecting with the extending directions of the first diaphragm 1 and the second diaphragm 2. Thus, in this embodiment, sound source localization in a two-dimensional direction is possible as will be described later. In this embodiment, the crossing angle between the extension direction of the third diaphragm 3 and the fourth diaphragm 4 and the extension direction of the first diaphragm 1 and the second diaphragm 2 is approximately 90 °. However, the crossing angle may be other than 90 °. The point is that, in principle, sound source localization in a two-dimensional plane is possible as long as tilt vibration having different direction components is performed according to sound waves from two different directions.

  The other ends 12 to 42 of the first to fourth diaphragms 1 to 4 are connected to each other by a connecting body 6. In this embodiment, the connecting body 6 has a thin flat plate shape. The other ends 12 to 42 of the first to fourth diaphragms 1 to 4 are integrated with the connecting body 6.

  The connecting body 6 can be displaced with respect to the other ends 12 to 42 of the first to fourth diaphragms 1 to 4. More specifically, weakened portions 8a to 8d that facilitate deformation between the connecting body 6 and the other ends 12 to 42 of the diaphragms 1 to 4 are formed (FIG. 2). reference). The weakening portions 8a to 8d are formed by cutting the vicinity of the other ends of the diaphragms 1 to 4 with a very narrow width, like the slits 7a to 7d. And the area | region between the weakening parts 8a-8d is called the connection beams 9a-9d in this specification. That is, each of the vibration plates 1 to 4 and the thin plate-like coupling body 6 are mechanically connected via the narrow coupling beams 9a to 9d.

  Piezoresistors 10a to 10d for detecting parallel vibrations and tilt vibrations of the coupling body 6 are formed in the coupling beams 9a to 9d. These piezoresistors 10a to 10d correspond to an example of the detection unit in the present invention. The piezoresistors 10a to 10d are deformed along with the deformation of the coupling beams 9a to 9d, and the resistance value is changed by the deformation. Therefore, by detecting the change in the resistance value using an appropriate detection circuit (not shown) such as a bridge circuit, for example, the deformation amounts of the coupled beams 9a to 9d can be known. Further, when the connecting beams 9a to 9d are formed of a silicon substrate, a piezoresistor can be easily created by thermal diffusion of boron (B), for example.

(Example)
Here, as an example, an example of specific dimensions of the microphone of the present embodiment will be described. In the example of FIGS. 1 and 2,
W = 5mm,
L = 1.25 mm,
Slit width = about 5 μm,
It has become. Such a structure can be created using, for example, a MEMS manufacturing technique. An example of the manufacturing method will be described later.

(Operation of microphone of this embodiment)
Next, the operation of the microphone of this embodiment will be described. First, as a premise for explanation, the principle of sound source localization will be explained.

(Exact theory of sound source localization and algebraic solution)
The spatial coordinates are vector r = (x, y, z), the unit direction vector of the sound source direction is vector n, and the sound speed is c. In addition, the distance to the sound source is assumed to be far enough that an incoming wave can be regarded as a plane wave in the observation region.

を満たす。逆も真で，この偏微分方程式の一般解は，その音源から発せられた任意の波形の音場の全体となる。ここで，観測平面上に任意の荷重関数w(ベクトルr) を導入すると，下記式（２）のように、偏微分方程式は等価な積分形式に変換される（参考： S. Ando and N. Ono, "Partial differential equation (PDE)-based theory of sound source localization," 4th Joint Meeting ASA and ASJ, Honolulu, 2006.）。 At this time, an arbitrary acoustic wave field f (vector r, t) generated by the sound source is expressed by the partial differential equation.

Meet. The reverse is true, and the general solution of this partial differential equation is the entire sound field of an arbitrary waveform emitted from the sound source. Here, when an arbitrary load function w (vector r) is introduced on the observation plane, the partial differential equation is converted into an equivalent integral form as shown in the following equation (2) (reference: S. Ando and N. Ono, "Partial differential equation (PDE) -based theory of sound source localization," 4th Joint Meeting ASA and ASJ, Honolulu, 2006.).

を導入する。ガウス関数は，その１階偏微分が

のように１次モーメントの形をもつことに注意する。そうすると，上式の積分形式は以下のような代数方程式に変換されることが分かる。 Here, Gaussian function as the load function

Is introduced. The Gaussian function has its first-order partial derivative

Note that it has the form of a first moment as Then, it turns out that the integral form of the above equation is converted into the algebraic equation as follows.

  Here, vector n = (nx, ny) is the x and y components of the direction vector of the sound source. Moreover, all the following unknowns in Formula (3) can be obtained by detecting the vibration of the coupling body 6 of this embodiment.

  That is, since these values are the 0th and 1st moments of the sound pressure distribution on the observation plane weighted by a Gaussian function, they are quantities that can be observed by a diaphragm (conjunction) placed on the observation plane. is there.

  On the other hand, according to the microphone having the structure of the present embodiment, a weighted distribution close to a Gaussian weighted distribution can be obtained. FIG. 3 shows a numerical calculation example of the weighted distribution obtained in the present embodiment. 3A shows a common mode, and FIG. 3B shows a differential mode. In these figures, the waveform of the Gaussian distribution is also shown for reference. In these calculation examples, there is still room for optimizing the design, but even in this state, a weighted distribution almost similar to a Gaussian weighted distribution is obtained.

  Therefore, the sound source direction (that is, the direction vector n) is determined strictly and uniquely by solving the equation (3) using the measured values of the parallel vibration and the tilt vibration of the coupled body 6 obtained in the present embodiment. Can do. Since this equation does not depend on the direction of arrival of the sound source or the spectrum of the incoming sound, in principle, sound source localization that is not related to these becomes possible.

  This detection principle can also be explained as follows. That is, when sound comes from a direction (Z axis) perpendicular to the surface of each diaphragm, the coupling body 6 performs parallel vibration. When sound comes from a direction tilted from the Z axis, the diaphragms vibrate with a phase difference, and thus the connecting body 6 tilts and vibrates. Since this tilt vibration corresponds to the direction of arrival of sound, detecting the tilt vibration enables sound source localization and sound source separation.

  If the direction of the sound source is known, directivity control and sound source separation can be performed. Since the analysis method for this is known, detailed description is omitted in this specification (for example, Ono, Ando, "Measurement of sound field and directivity control," 22nd Sensing Forum document, pp. 305-310, 9 May. 2005. Or Ono, Arita, Chiaki, Ando, "Directional control and sound source separation based on spatio-temporal gradient measurement," Proc. Of the Spring Meeting of the Acoustical Society of Japan 2005, 2-6- 13, pp. 607-608, Tokyo, March, 2005.).

  Therefore, according to the microphone of this embodiment, not only sound source localization but also directivity control and sound source separation can be performed. For example, in the case of voice recognition in a car, the position of the engine, which is the main noise source, is almost fixed with respect to the speaker, so directivity control is performed so that the gain at that position is close to zero. By doing so, the SN ratio can be improved.

  In the present embodiment, a microphone capable of sound source localization can be provided by a single element.

  Furthermore, in the present embodiment, the first to fourth diaphragms 1 to 4 are separated by narrow slits 7a to 7d. For this reason, it can prevent almost certainly that the air which propagates sound escapes to the back side of each diaphragm 1-4. When air that propagates sound escapes to the back side of each diaphragm 1 to 4, the sensitivity as a microphone deteriorates. In contrast, the present embodiment has an advantage that a highly sensitive microphone can be provided.

  Further, in the present embodiment, the vibration of the sound wave can be detected as the vibration of a minute component called the connecting body 6. For this reason, there is an advantage that high sensitivity can be obtained and the size of the entire microphone can be reduced.

  Furthermore, the microphone of this embodiment can be basically configured by forming a slit in a thin plate. Therefore, it is very easy to manufacture. In addition, the vibration characteristics can be easily changed by changing the slit shape or the weakened portion shape. Furthermore, there is an advantage that the operation is possible even if there is a fluctuation in static pressure (for example, a decrease in air pressure at a high place) or dust adhesion. That is, the microphone of the present embodiment can have strong environmental resistance.

  Since the back surface of each diaphragm 1 to 4 may basically be a cavity, sensitivity can be improved by forming an acoustic cavity. Also, viscous damping can be applied to the vibration of each diaphragm using the space on the back surface. Furthermore, it is also possible to arrange a capacitor for vibration detection using the space on the back side.

  In addition, the microphone according to the present embodiment can realize sound source localization with a wide band and high time resolution in principle.

  In addition, since the directivity can be controlled in the microphone of the present embodiment, it can be applied to sound collection and sound source separation under background noise.

  Furthermore, in this embodiment, since each diaphragm 1-4 and the support frame 5 can be made into the continuous structure, there also exists an advantage that it is easy to take out the wiring from detection elements, such as the piezo elements 10a-10d, outside. is there.

(Frequency characteristics of notched flat plate structure)
Here, an outline of a method for determining the optimum next resonance mode in the structure of the present embodiment will be described. The structural elements to be considered here are 1) the spring constant of a right triangle cantilever, 2) the spring constant of a finely coupled beam, and 3) the mass and moment of inertia of the central connecting plate.

で与えられる。ここでE は構造体のヤング率である。直角三角形に形成された片持ち梁においては，有限要素解析により，ほぼ

で表されるバネ定数をもつことが分かる。 1) Spring constant of right triangle cantilever beam First, if the thickness of the rectangular cantilever beam is a, the width is 2Wb, and the length is W, the spring constant for the bending of the tip is

Given in. Where E is the Young's modulus of the structure. For cantilever beams formed in a right triangle, finite element analysis

It can be seen that it has a spring constant represented by

のように表される。 2) Spring constant of coupled beam The width of the coupled beam of this embodiment is b and the length is d (see FIG. 2). Under the condition that both ends of the coupled beam are kept parallel, the spring constant related to the height difference in the direction perpendicular to their planes is

It is expressed as

3) Vibration mode of the central connecting plate (connecting body) Let ρ be the density of the sensor structure. A connecting plate supported at four points by four connecting beams can be modeled as a plate placed on a spring, as shown in FIG.

のバネ定数を有する。平行振動モードの運動方程式と共振周波数は

のように表される。傾き振動に関しては，その運動方程式と共振周波数は

で与えられる。ここでθは平板の基準面に対する傾き角である。二つの共振周波数の比は，比ｌ／Ｌの調整、すなわち、微細連結ビームの位置をどれだけ内側（中央側）へシフトさせるかによって調整可能である。そして、

に選ぶと、両モードでの共振周波数は等しくなる。 The mass of the plate is 4ρaL ² , and each spring corresponds to a series spring of a cantilever spring and a finely coupled beam spring.

The spring constant is The equation of motion and resonant frequency of the parallel vibration mode are

It is expressed as For tilt vibration, its equation of motion and resonance frequency are

Given in. Here, θ is an inclination angle with respect to the reference plane of the flat plate. The ratio of the two resonance frequencies can be adjusted by adjusting the ratio 1 / L, that is, how much the position of the finely coupled beam is shifted inward (center side). And

If selected, the resonant frequencies in both modes will be equal.

(Microphone according to the second embodiment)
Next, a microphone according to a second embodiment will be described with reference to FIGS. In addition, about the element which is fundamentally common with above-described 1st Embodiment, the duplication of description is avoided by attaching | subjecting the same code | symbol.

  In the first embodiment described above, sound source localization in an XY two-dimensional plane was possible. In contrast, the microphone of the second embodiment performs sound source localization in a one-dimensional direction. Therefore, in short, the microphone of the second embodiment corresponds to a structure in which the third diaphragm 3 and the fourth diaphragm 4 are removed from the microphone of the first embodiment.

  The microphone according to the second embodiment has a structure in which the first diaphragm 1 and the second diaphragm 2 are arranged to face each other, and their tips 12 and 22 are connected by a connecting body 6. The diaphragms 1 and 2 have a cantilever structure supported by the support frame 5 by forming slits 7e to 7h (see FIG. 5) with respect to the thin plate.

  Further, weakening portions 8 e to 8 h (see FIG. 6) are formed around the connecting body 6, so that the phase difference of vibration between the first diaphragm 1 and the second diaphragm 2 is made parallel to the connecting body 6. It can be detected as vibration or tilt vibration.

  Further, a detection unit (not shown) similar to that in the first embodiment is provided in the vicinity of the coupling body 6.

  As already described, the microphone according to the second embodiment can perform sound source localization in a one-dimensional direction. Therefore, for example, by combining with the microphone of the first embodiment, sound source localization in a three-dimensional direction becomes possible.

  Other configurations and advantages of the microphone according to the second embodiment are basically the same as those of the first embodiment, and thus further detailed description of the second embodiment is omitted.

(Third embodiment)
Next, a microphone according to a third embodiment will be described with reference to FIG. In addition, about the element which is fundamentally common with above-described 1st Embodiment, the duplication of description is avoided by attaching | subjecting the same code | symbol.

  In the microphone of the first embodiment, a piezoresistor is used as a detection unit for detecting the vibration of the coupling body 6. On the other hand, in the third embodiment, a capacitor is used as the detection unit.

  That is, in the third embodiment, four electrodes (not shown) are provided on one surface of the coupling body 6.

  In addition, a support plate 101 for fixing electrodes is provided at a position facing the connector 6. And the counter electrodes 101a-d for comprising a capacitor | condenser are provided in the surface of the support plate 101 (refer FIG. 7). Also, four through holes 102a to 102d are formed in the support plate 101 around the counter electrode in consideration of the acoustic effect.

  In this embodiment, a capacitance change in the same phase occurs in each capacitor with respect to the parallel vibration of the coupling body 6, and a capacitance change in the opposite phase occurs with respect to the tilt vibration. Using this characteristic, sound source localization and directivity control can be performed as in the first embodiment.

  Moreover, air exists in the space | gap which exists between the coupling body 6 and the support plate 101 of this embodiment. Therefore, it is possible to give a braking action to the connecting body 6 by using the viscous resistance of the air.

  Other configurations and advantages of the third embodiment are the same as those of the first embodiment described above, and thus detailed description of the third embodiment is omitted.

(Fourth embodiment)
Next, a microphone according to a fourth embodiment will be described with reference to FIG. In addition, about the element which is fundamentally common with above-described 1st Embodiment, the duplication of description is avoided by attaching | subjecting the same code | symbol.

  In the microphone of the first embodiment, a piezoresistor is used as a detection unit for detecting the vibration of the coupling body 6. In contrast, in the third embodiment, a heterodyne interference optical system is used as the detection unit.

  The optical system of the fourth embodiment includes a laser light source (laser), four photodiodes PD1 to PD4, lenses L1 to L5, plane mirrors M1 and M2, beam splitters BS1 and BS2, and an acoustooptic modulator AOM. It consists of and. And the back surface of the connection body 6 is made into the plane mirror.

  In the fourth embodiment, the distance change and the inclination change of the coupling body 6 can be detected by the heterodyne interference optical system using the reflected light and the input light from the coupling body 6. The reason why the four photodiodes PD1 to PD4 are used is to perform detection on an XY two-dimensional plane. As the vibration detection method using the heterodyne interference optical system, an existing method can be used, and thus further detailed description of this optical system is omitted.

  In this embodiment, there is an advantage that the vibration of the coupling body 6 can be accurately measured.

  Other configurations and advantages of the fourth embodiment are the same as those of the first embodiment described above, and thus detailed description thereof is omitted.

(Fifth embodiment)
Next, as a fifth embodiment, an example of a method for manufacturing the microphone of the present embodiment will be described with reference to FIGS. 9 and 10. In this example, an SOI substrate is used. Moreover, FIG. 10 represents the cutting location which obtains the cross section shown in FIG.

(Fig. 9 (a))
First, the structure of a substrate used for manufacturing will be described. As shown in the figure, this substrate is composed of a SiN layer 201, a SiO ₂ layer 202 on the lower side of an SOI (Silicon On Insulator) substrate comprising an Si substrate layer 203, an SiO ₂ layer 204, and an Si layer 205, and an SiO _{2 on} the upper side. _Two layers 206 are formed.

(Fig. 9 (b))
First, a photoresist film 207 is applied on the upper surface of the upper SiO ₂ layer 206, and a predetermined pattern is formed using a lithography technique. Next, the SiO ₂ layer 206 below the portion where the opening of the photoresist film 207 is formed is removed by RIE (reactive ion etching) using a gas such as CF ₄ . Next, the Si layer 205 is removed by RIE using a gas such as SF ₆ or Cl ₂ . By using RIE, narrow and deep etching becomes possible. Thereby, the slits 7a to 7d and the weakened portions 8a to 8d can be formed in the Si layer 205 with high accuracy.

  Next, the resist layer 207 is removed with a chemical solution.

(Fig. 9 (c))
Next, a photoresist is applied to the lower surface of the substrate, that is, the surface on the SiN layer 201 side, and another resist layer 208 having a predetermined pattern is formed. Next, unnecessary SiN layer 201 and SiO ₂ layer 202 are removed by RIE.

(Fig. 9 (d))
Next, a protective film 209 is formed on the upper surface of the substrate, that is, the surface of the SiO ₂ layer 206.

Then, using the SiN layer 201 and the SiO ₂ layer 202 as a mask, the Si substrate layer 203 is removed from the lower surface of the substrate by etching. At this time, the SiO ₂ layer 204 has an etching stop function. Further, the SiO ₂ layer 204 is removed using an appropriate etching agent. Thereafter, a portion corresponding to the support frame 5 is cut out from the substrate with a required size.

(Fig. 9 (e))
Next, the protective film 209 is removed. Thereby, the 1st-4th diaphragms 1-4 and the coupling body 6 of a very thin and fine structure can be obtained. As a result, very thin plate-like diaphragms 1 to 4 can be obtained by the Si layer 205, respectively. Further, the support frame 5 around the vibration plates 1 to 4 can be formed integrally with the vibration plates 1 to 4 by the Si substrate 203 and the Si layer 205.

  Then, the vibration of the coupling body 6 can be detected by attaching the detection unit by an appropriate method.

  According to the manufacturing method of the fifth embodiment, high-precision microfabrication can be performed using a so-called MEMS (Micro-Electro-Mechanical Systems) manufacturing technique. This makes it possible to manufacture a microphone having a small size and high detection accuracy.

  Moreover, in this manufacturing method, the widths of the slits 7a to 7d and the weakened portions 8a to 8d can be formed narrow. If it does in this way, air will hardly escape to the back of each diaphragm 1-4, and the detection accuracy as a microphone can be improved also from this point.

(Sixth embodiment)
Next, as a sixth embodiment, another example of a method for manufacturing the microphone of the present embodiment will be described with reference to FIGS. In the fifth embodiment described above, the detection unit is attached after the processing of the SOI substrate is completed. In contrast, the sixth embodiment includes a step of integrally forming a piezoresistor on an SOI substrate. Moreover, FIG. 13 represents the cutting location which obtains the cross section shown in FIG.11 and FIG.12. In the description of the sixth embodiment, the same reference numerals are used for the same steps as those described in the fifth embodiment, thereby avoiding complicated description.

(Fig. 11 (a))
First, the structure of a substrate used for manufacturing will be described. As shown in the figure, this substrate is composed of an SiO ₂ layer 202, an Si substrate layer 203, an SiO ₂ layer 204, an Si layer 205, and an SiO ₂ layer 206 from the bottom.

A mask 211 having a predetermined shape is formed on the upper surface of the SiO ₂ layer. Next, B ⁺ ions are implanted into the underlying Si layer 205 via the SiO ₂ layer 206. This implantation can be performed by a so-called ion implantation technique.

  Thus, in this embodiment, boron (B) can be added to two locations of the Si layer 205. The portion to which boron is added becomes the piezoresistive layer 212. The piezoresistive layer 212 is a portion corresponding to any of the piezoresistors 10a to 10d. Further, in this embodiment, one of the two piezoresistive layers 212 is formed at a position corresponding to the coupled beams 9a to 9d, and the other is formed at a position that is not easily subjected to stress (for example, a support frame). The This is because a change in resistance value is detected by a bridge circuit using a piezoresistor that is not subjected to stress as a reference resistor. As such a detection bridge circuit, since a conventionally known circuit can be used, detailed description is omitted.

(Fig. 11 (b))
Next, the resist layer 211 is removed.

(Fig. 11 (c))
Next, the SiN layer 201 is formed on the lower surface of the SiO ₂ layer 202. Further, a resist layer 213 is formed on the upper surface of the SiO ₂ layer 206. Next, the SiO ₂ layer 206 located on the upper surface of the piezoresistor is partially removed by etching. Thereby, the contact for wiring mentioned later can be formed.

(Fig. 11 (d))
Next, the resist layer 213 is removed. Thereafter, a metal layer 214 for wiring is formed so as to connect the piezoresistive layer 212. As the metal layer 214, for example, an Al—Si film containing about 1% Al can be used.

  Thereafter, a resist layer 215 is formed on the upper surface of the metal film 211, and the metal film 214 is etched, so that the metal film 214 has a predetermined shape.

(Fig. 11 (e))
Next, the resist layer 215 is removed. Further, a passivation film 216 is formed so as to cover the metal film 214 and the SiO ₂ layer 206. The passivation film 216 protects the metal film 214 and the piezoresistive layer 212 from subsequent processes. As the passivation film 216, in this embodiment, a stacked structure of SiN and PSG (Phospho-Silicate-Glass) is used.

(Fig. 12 (f))
Next, a resist layer 217 is disposed, and the passivation film 216 and the SiO ₂ layer 206 are partially removed by etching. Further, the Si layer 205 is partially removed using RIE. As a result, the slits 7a to 7d and the weakened portions 8a to 8d can be formed in the Si layer 205 as in the fifth embodiment.

(FIGS. 12 (g) to (i))
The steps of FIGS. 12G to 12I are substantially the same as the steps shown in FIGS. 9C to 9E in the fifth embodiment, and detailed description thereof is omitted.

  According to the manufacturing method of the sixth embodiment, the piezoresistors 10a to 10d can be accurately and easily formed on the coupling body 6.

  Other configurations and advantages of the sixth embodiment are the same as those of the fifth embodiment described above, and a detailed description thereof will be omitted.

  In addition, the structure of each above-mentioned embodiment is only the illustration of this invention, and is not the meaning of restrict | limiting the content of this invention.

  For example, in the above-described embodiment, the first to fourth diaphragms 1 to 4 have a flat plate shape. However, these thicknesses or widths can be appropriately changed so as to have a load distribution close to an ideal Gaussian shape.

DESCRIPTION OF SYMBOLS 1 1st diaphragm 11 One end of 1st diaphragm 12 The other end of 1st diaphragm 13 Coupled beam 2 2nd diaphragm 21 One end of 2nd diaphragm 22 The other end of 2nd diaphragm 23 Coupled beam 3 3rd vibration Plate 31 One end of the third diaphragm 32 Other end of the third diaphragm 33 Coupled beam 4 Fourth diaphragm 41 One end of the fourth diaphragm 42 Other end of the fourth diaphragm 43 Coupled beam 5 Support frame 6 Connected body 10a- 10d Piezoresistor (detector)
7a-7d Slit of the first embodiment 7e-7h Slit of the second embodiment 8a-8d Weaker part of the first embodiment 8e-8h Weaker part of the second embodiment 9a-9d Linked beam 101 Support plate 101a-101d Opposing Electrode (detector)
102a-102d through hole

Claims (8)

A support frame, a first diaphragm, a second diaphragm, and a coupling body;
One end of each of the first diaphragm and the second diaphragm is elastically supported by the support frame,
The other end of the first diaphragm and the other end of the second diaphragm are disposed to face each other.
And the other end of the first diaphragm and the other end of the second diaphragm are connected by the connecting body,
The coupling body, the other end of said first diaphragm, with respect to the other end of said second diaphragm, by Rukoto is a displaceable, the vibration of the first diaphragm and the second diaphragm Accordingly, the microphone is configured to perform parallel vibration or tilt vibration . A weakening portion that facilitates deformation between the connecting body and the other end of the first diaphragm and between the connecting body and the other end of the second diaphragm is provided. The microphone according to claim 1. Furthermore, a third diaphragm and a fourth diaphragm are provided,
One end of each of the third diaphragm and the fourth diaphragm is elastically supported by the support frame,
The other end of the third diaphragm and the other end of the fourth diaphragm are disposed to face each other.
And the other end of the third diaphragm and the other end of the fourth diaphragm are connected by the connecting body,
The coupling body is displaceable with respect to the other end of the third diaphragm and the other end of the fourth diaphragm.
The microphone according to claim 1 or 2, wherein the third diaphragm and the fourth diaphragm are extended in a direction intersecting with an extension direction of the first diaphragm and the second diaphragm. The first diaphragm, the second diaphragm, and the coupling body are configured by forming a slit in a single plate that can be elastically deformed with respect to sound pressure,
The microphone according to claim 1, wherein one end of the first diaphragm and one end of the second diaphragm and the support frame are integrated.   Furthermore, the microphone of any one of Claims 1-4 provided with the detection part which detects the parallel vibration and inclination vibration of the said coupling body.   The microphone according to claim 4, wherein the first diaphragm and the second diaphragm have the same thickness as a whole.   The thickness or width of the first diaphragm and the second diaphragm is changed depending on a location so as to have a Gaussian sensitivity distribution. Microphone.   The sound source analysis apparatus which performs sound source localization by analyzing the vibration of the said connection body in the microphone of Claims 1-7.

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