JP5275488B2 - Directional microphone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a directional microphone which is excellent in directing quality and durability. <P>SOLUTION: The directional microphone has a base 31 having an opening 311 in its central part, each bridge 11 extended over each opening 311 of the base 31, a vibrating plate 32 supported elastically through a supporting axis 321 in the central part of the bridge 11, a plurality of stationary electrodes 13A-13D disposed oppositely to the vibrating plate 32 in the opening 311 across a gap and supported by the base 31, and a plurality of elastic parts 12 provided in the central parts of the bridges 11 which support elastically the supporting axis 321 of the vibrating plate 32 from the lateral sides so that the incident surface of the vibrating plate 32 is inclined by the incidence of an acoustic wave according to a sound-source direction. Thereby, the directional microphone wherein its sound collecting quality relative to the acoustic wave of its sound-source direction is improved and it has a high directing quality is obtained. Also, it can automatically adjust the directing orientation according to the sound-source direction without changing the entire direction of the microphone. Further, the vibrating plate 32 is supported by the plurality of elastic parts 12, thereby the durability of the supporting part can be improved. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a directional microphone.

  2. Description of the Related Art Conventionally, there is known a microphone that identifies a sound source direction by detecting a distribution of vibration amplitude when a diaphragm around the axis is vibrated by sound pressure and supporting a central point of the diaphragm with a shaft. . However, when the diaphragm is vibrated for a long time, the shaft is deformed due to fatigue, and the diaphragm is inclined even when no sound wave is received.

  Therefore, in the invention described in Patent Document 1, an electrode that suppresses the inclination of the diaphragm is provided, a voltage is applied to the electrode to suppress the inclination, and the sound source direction is specified from the voltage.

JP 2006-345130 A

  However, in the invention described in Patent Document 1, although the direction of the sound source can be specified, there is a problem that the directivity of the microphone is hindered because the inclination of the diaphragm is suppressed.

According to a first aspect of the present invention, there is provided a base substrate having a space in the central portion, a diaphragm in which a first comb electrode is formed, and a support portion for supporting the diaphragm on the base substrate in the space of the base substrate. A directivity comprising: a plurality of divided electrodes held on a base substrate; and a fixed electrode in which each of the divided electrodes has a second comb-shaped electrode meshed with the first comb-shaped electrode. The support unit includes a plurality of elastic portions that elastically support the diaphragm such that the position of the first comb electrode is changed with respect to the second comb electrode when the diaphragm is displaced according to the sound source direction. The diaphragm, the support portion, and the fixed electrode are formed of the same Si layer of an SOI (Silicon on Insulator) substrate.
Further, as in the invention of claim 6, the capacitance between the plurality of divided electrodes and the diaphragm is individually detected by the detection unit corresponding to each of the divided electrodes, and each detected by the detection unit is detected. The direction of the sound source may be specified by the calculation unit based on the capacitance.

  ADVANTAGE OF THE INVENTION According to this invention, the directional microphone excellent in directivity and durability can be obtained.

It is a front view of the microphone 1 of this Embodiment. It is D1-D1 sectional drawing of FIG. It is a figure explaining generation | occurrence | production of the inclination of the diaphragm 32 by a sound source direction. It is a figure explaining basic formula derivation of a parallel plate type microphone. It is a figure explaining an output voltage. It is a figure which shows the equivalent circuit of FIG. It is a figure explaining sound source direction specification. It is a figure explaining process (a)-(d) of a manufacturing process. It is a figure explaining the process (e) of a manufacturing process. It is a figure explaining process (f), (g) of a manufacturing process. It is a figure explaining process (h)-(k) of a manufacturing process. It is a figure explaining process (l)-(o) of a manufacturing process. It is a figure which shows the microphone of 2nd Embodiment, (a) is a front view, (b) is D1-D1 sectional drawing. It is a figure which shows the mode of the diaphragm 32 when the sound wave from a sound source is received. It is a figure which shows the microphone of 3rd Embodiment, (a) is a front view, (b) is D1-D1 sectional drawing. FIG. 6 is a diagram for explaining the relationship between the direction of a sound source and the displacement of a diaphragm. It is a figure which shows the modification of 3rd Embodiment, (a) shows a 1st modification, (b) shows a 2nd modification. It is a figure which shows the modification of 3rd Embodiment, (a) shows a 3rd modification, (b) shows a 4th modification. It is a figure which shows the modification of the elastic part. It is a figure which shows the structure at the time of dividing | segmenting the diaphragm 32 shown in FIG. 1 into four division | segmentation diaphragms 32A-32D. It is a top view which shows the modification of the microphone shown in FIG. It is a figure which shows the modification of a comb-tooth electrode, (a) shows a 1st modification, (b) shows a 2nd modification, respectively. It is a figure explaining a pressure difference, (a) The case where the back surface side of the diaphragm 230 is sealed space is shown, (b) shows the case where the space of the diaphragm back surface side is a semi-sealed state. It is a figure explaining propagation of the pressure difference in a gap. It is a figure which shows the relationship between a gap width and a fluctuation | variation volume.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
-First embodiment-
1 and 2 are diagrams showing a schematic configuration of a directional microphone according to the present embodiment. 1 is a front view of the microphone 1, and FIG. 2 is a cross-sectional view taken along the line D1-D1 of FIG. The microphone 1 uses an SOI (Silicon on Insulator) substrate having a three-layer structure of a lower Si layer 30, an SiO ₂ layer 20, and an upper Si layer 10, as shown in FIG. 2, by a micromachining technique or a photolithography technique. Produced.

  A base 31 formed by the lower Si layer 30 is formed so that a circular opening 311 passes therethrough. On the upper surface side of the base 31, four bridges 11 are arranged in a cross shape so as to be bridged over the circular opening 311. One end of each bridge 11 is fixed on the base 31. An elastic portion 12 is provided at the other end of each bridge 11. Each elastic portion 12 elastically connects between the bridge 11 and a support shaft 321 provided on the diaphragm 32. The support shaft 321 is formed so as to protrude vertically from the center (that is, the center of gravity) of the disc-shaped diaphragm 32. As a result, the bridge 11 elastically supports the central portion thereof in such a form that the diaphragm 32 is suspended.

  Four fixed electrodes 13 </ b> A to 13 </ b> D are provided on the upper surface of the base 31 so as to cover the upper surface of the opening 311. Each of the fixed electrodes 13A to 13D has a fan shape with a central angle of 90 degrees, and is provided with a wiring portion 131 and a terminal portion 132, respectively. The bridge 11 and the fixed electrodes 13 </ b> A to 13 </ b> D are formed of the upper Si layer 10 of the SOI substrate, and a polycrystalline silicon film 40 and an aluminum film 50 are sequentially formed on the upper surface of the upper Si layer 10. As described above, the microphone 1 of the present embodiment constitutes a condenser microphone including the diaphragm 32 and the plurality of fixed electrodes 13A to 13D arranged to face each other in parallel.

  The diaphragm 32 which is a diaphragm vibrates when receiving sound pressure, and the gap between the fixed electrodes 13A to 13D and the diaphragm 32 changes according to the period of sound waves. In addition, since the support shaft 321 and the bridge 11 are connected by the elastic portion 12, the elastic portion 12 is bent when an external force is applied to the diaphragm 32 by sound pressure. For example, when the sound source is in the axial direction of the microphone 1 (that is, the axial direction of the circular opening 311), the elastic portions 12 are bent almost uniformly and the entire diaphragm 32 is in the axial direction of the microphone 1 (that is, the circular opening). 311 (axial direction of 311) is displaced (vibrated) in a parallel state. The capacitance between each fixed electrode 13 </ b> A to 13 </ b> D and the diaphragm 32 changes according to the vibration or displacement of the diaphragm 32.

  On the other hand, as shown in FIG. 3, when the sound source is inclined with respect to the central axis J of the microphone 1, the arrival time and sound pressure of the sound wave from the sound source differ depending on the position on the diaphragm 32. The diaphragm 32 is tilted so that the normal line of the diaphragm 32 faces the sound source direction. And the diaphragm 32 vibrates according to the output of a sound wave in the inclined state.

Here, the capacitance C in the parallel plate is expressed by the following equation (1). In Equation (1), Q is an electric charge, V is a voltage, ε is a dielectric constant, S is an electrode area, and d is an interelectrode distance.

  In the microphone 1, the inter-electrode distance d corresponds to the distance between the fixed electrodes 13 </ b> A to 13 </ b> D and the diaphragm 32. Strictly speaking, since the diaphragm 32 does not always move in parallel, the expression (1) cannot be applied as it is, and the expression needs to be changed to an expression according to the shape of the diaphragm 32. However, the capacitance increases as the distance between the fixed electrodes 13A to 13D and the diaphragm 32 decreases, and conversely, as the distance increases, the capacitance decreases as in the case of the parallel plate electrodes. Therefore, when the sound source is in an oblique direction, the diaphragm 32 is inclined and the distances from the fixed electrodes 13A to 13D are different, so that the capacitances of the fixed electrodes 13A to 13D have different values.

  When the diaphragm 32 is inclined as shown in FIG. 3, the capacitance Ca related to the fixed electrode 13A closer to the sound source tends to be small, and the capacitance Cc related to the fixed electrode 13C farther from the sound source tends to increase. The diaphragm 32 vibrates according to the output of the sound wave with the tilted state as the center. In addition, the period of change in capacitance also varies between the fixed electrodes 13A to 13D depending on the position of the sound source. This is because the vibration plate 32 is not rigid but strictly elastic, and does not always follow the sound wave immediately. The time difference in the change depends on the position on the plane between the position where the sound wave reaches first and the position where it finally reaches. This is because.

  Next, a signal detection method in the microphone 1 will be described. In the capacitance type microphone as in the present embodiment, the change in the capacitance value due to the fluctuation of the diaphragm is extracted in the form of a voltage signal applied to the load resistance. With respect to the microphone functioning as an electrostatic transducer in this manner, the derivation of the basic formula of a general electrostatic transducer and its output voltage will be described below.

[1. Derivation of basic formula]
Here, as shown in FIG. 4, consider parallel plate electrodes facing each other across a narrow gap. In this case, if a plurality of fixed electrodes 13 </ b> A to 13 </ b> D are used as one fixed-side electrode 100, the electrode 101 displaced by an external force corresponds to the diaphragm 32.

The DC voltage applied between the electrodes is E ₀ , the AC voltage is e, the external force acting on the electrode 101 is f, and the electrode interval before the displacement is generated is d ₀ . Further, when the DC voltage E ₀ is applied, the displacement of the electrode 101 is X, the minute displacement is x, and the capacitance generated between the electrodes is C (x). At this time, if the Lagrangian equation of motion is used for the model system shown in FIG. 4, the Lagrangian and the dissipation function are expressed by the following equations (2) and (3), respectively. Incidentally, m is applied mass of the electrode 101, v is the speed of displacement of the electrode 101, k is a spring constant of the portion of the electrode 101 elastically supports (corresponding to the elastic part 12), _{Q 0} is a direct-current voltage _{E 0} It is assumed that q is a charge generated by the alternating voltage e. R _f is the mechanical resistance in the system.

Assuming that the area of the opposing surface of the parallel plate electrodes is S, the equation of the capacitance generated between the parallel plate electrodes is expressed as the following equation (4). The Lagrangian equations of motion of the mechanical system and the electrical system are expressed by the equations (5) and (6) in this order.

Substituting the expressions (2) and (3) into the expression (5) and expanding, the following expression (7) is obtained. Further, the third term on the right side of Equation (7) is expanded as in Equation (8).

Furthermore, the following equation (9) is obtained by Taylor expansion of equation (8).

Since the first term of equation (9) is a static term, when this is removed and substituted into equation (7), the final equation (10) is obtained as the basic equation of the mechanical system. In the equation (10), A, B, C (0) are represented by the following equations (11) to (13).

Similarly, when Expressions (2) and (3) are substituted into Expression (6) and expanded, Expression (14) is obtained.

Expression (15) is obtained by Taylor expansion of Expression (14), and Expression (16) is obtained by eliminating Q ₀ = C ₀ E ₀ as a static term. Therefore, the basic equation of the electric system is Equation (17). When Expression (17) is phasor-displayed, Expression (18) is obtained.

[2. Output voltage]
In general, in a state of actual use, the DC voltage Ep applied between the parallel plate electrodes is supplied through some impedance as shown in FIG. This impedance usually has a large value in applications such as condenser microphones. Therefore, when the capacitance changes due to the displacement of the electrode 101, the DC voltage Ep also changes. Further, since the time constant due to the capacitance C ₀ and the resistance R _{0 of} the parallel plate electrode is also a considerably large value, the charge is hardly transferred in the frequency range used as a microphone.

…（２１） At this time, in the basic formula of the electric system,
e = −R ₀ i (19)
Since the following equation (20) holds, the following equation (21) is obtained by substituting the equations (19) and (20) into the equation (18). This equivalent circuit can be expressed as shown in FIG.
v = jω · x (20)

... (21)

  Thus, according to the microphone of the first embodiment, the following operational effects can be obtained.

  (1) According to the microphone of the present invention, it is possible to read the change in the capacitance according to the vibration of the diaphragm 32 due to the sound wave as the voltage e using electrostatic conversion. As shown in FIG. 3, the diaphragm 32 automatically tilts so that the normal line faces the sound source direction according to the direction of the sound source. Therefore, it is possible to receive a sound wave of a sound source more efficiently and to obtain a microphone with very high directivity. In addition, the directivity can be automatically adjusted according to the position of the sound source without changing the direction of the entire microphone.

  (2) In the present embodiment, the position close to the center (center of gravity) of the diaphragm 32 is supported by the plurality of elastic parts 12, so that when the sound pressure acts on the diaphragm 32, the elastic part 12 Easy to deform. For this reason, the diaphragm 32 tilts in the direction of the sound source in response to the sound wave, and the directivity sensitivity is improved. Furthermore, the durability of the diaphragm support structure can be improved by providing a plurality of elastic portions 12.

  The positions of the elastic portions 12 are preferably formed at positions that are evenly spaced on the concentric circles from the center of the diaphragm 32. The vicinity here is not limited to the position where it is directly coupled to the support shaft 321 as shown in FIG. 1, but the position of the elastic portion 12 is a position approximately half or less of the radius of the diaphragm 32 when viewed from the center of the diaphragm 32. It points to something.

  On the other hand, in the case of the microphone described in Patent Document 1, the diaphragm is supported in the normal direction at only one central point. Therefore, when the direction of the sound source is on the normal line, the axial deformation of the support portion cannot be expected, and the change in capacitance depends only on the elastic deformation of the diaphragm. As a result, measurement is difficult because the change in capacitance is small. In addition, when control is not performed so that the diaphragm does not tilt, repeated stress due to tilting concentrates on one point, and there is a risk of causing repeated fatigue and damage.

In the description of the basic equation and the output voltage described above, a change in capacitance is taken out as a change in output voltage as one capacitor having a plurality of fixed electrodes 13A to 13D as one fixed electrode. However, assuming that four capacitors corresponding to the fixed electrodes 13A to 13D are connected in parallel, a change in capacitance of each capacitor may be taken out as a change in output voltage. In that case, instead of the above-described capacitance C ₀ , the capacitances C _A0 , C _B0 , C _C0 , and C _D0 of each capacitor are considered.

As shown in FIG. 7, a resistor R ₀ is provided in series with each of the fixed electrodes 13 </ b> _{A to} 13 </ b> _D, and voltages e _{A to} e _D of the resistors are detected by the voltage detection circuit 200 of the sound source direction specifying unit 2. Each of the voltages e _{A to} e _D can be obtained by replacing the capacitance C ₀ in the equation (21) with each capacitance C _A0 , C _B0 , C _C0 , C _D0 . Since the capacitance change and change period of each fixed electrode 13A to 13D are reflected in these voltages e _{A to} e _D , the direction specifying circuit 201 specifies the direction of the sound source based on these voltages e _{A to} e _D. To do. For example, when comparing the magnitude of the average value of the voltages e _A to e _D, since the distance between the electrodes mean voltage increases as the small fixed electrode, the specific sound source direction by comparing the magnitude of their average value can do.

Next, the manufacturing process of the microphone shown in FIG. 1 will be described with reference to FIGS. First, in a step (a) shown in FIG. 8A, an SOI wafer 100 having a three-layer structure of a lower Si layer 30, an SiO ₂ layer 20, and an upper Si layer 10 is prepared. The thickness of each layer 30, 20, 10 is set to 500 μm, 1 μm, and 25 μm in order, for example. In step (b) of FIG. 8B, a resist 41 is applied to the surface of the upper Si layer 10. The resist 41 is applied, for example, by a spin coater under the conditions of 3000 rpm and 30 seconds, and baked under the conditions of 90 ° C. and 5 minutes.

In the step (c) shown in FIG. 8C, the resist 41 is exposed to ultraviolet rays for 4.0 sec and developed for 1.5 min using a mask having patterns 15 corresponding to the four corners of the support shaft 321. Then, the resist 41 in the pattern 15 portion is removed. Thereafter, the upper Si layer 10 in the pattern 15 portion is etched by ICP-RIE (inductively coupled plasma-reactive ion etching) to expose the surface of the SiO ₂ layer 20. ICP-RIE etches a sample under a relatively low pressure of 0.05 to 1 Pa using a chemical reaction between ions of a process gas in a high-density plasma and the sample surface. High etching processing is possible. As the process gas, an oxidizing gas such as CCl ₂ F ₂ or CF ₄ is used.

In the step (d) shown in FIG. 8D, the resist 41 is removed by washing at 90 ° C. for 5 min with sulfuric acid / hydrogen peroxide (H ₂ SO ₄ + H ₂ O ₂ ), and SiO ₂ exposed by strong hydrofluoric acid. Layer 20 is etched away. Thereafter, a polycrystalline silicon film 40 is deposited by 600 nm by LPCVD (low pressure chemical vapor deposition). FIG. 8D is a view showing a cross section of the substrate after the LPCVD process, and shows a cross section corresponding to the D2-D2 cross section of FIG. A groove is formed by etching in the Si layer 10 and the SiO ₂ layer 20 in the pattern 15 portion, and the polycrystalline silicon film 40 is also formed on the surface in the groove.

LPCVD is a film forming method in which a sample is heated under a reduced pressure of 10 to 10 ³ Pa, and a film is generated on the sample surface by a gas phase chemical reaction by thermal energy. This method has an advantage that a uniform film thickness can be obtained with excellent film adhesion. In film formation of polycrystalline silicon, SiCl ₄ + H ₂ or SiH ₄ is used as a process gas. The reason why the polycrystalline silicon film 40 is formed is to strengthen the coupling between the support shaft 321 and the diaphragm 32. Furthermore, if a contact hole is provided at the coupling position and a polycrystalline silicon film is formed, an anchor effect can be expected.

  After the polycrystalline silicon film 40 is formed, an OCD resist is applied with a spin coater under conditions of 4000 rpm and 30 seconds, baked under conditions of 150 ° C. and 30 minutes, and then thermal diffusion of phosphorus (P) under conditions of 1000 ° C. and 30 minutes. Process. Due to the thermal diffusion of phosphorus (P) into the polycrystalline silicon film 40, the electrical resistance of the polycrystalline silicon film 40 decreases. After the thermal diffusion treatment, the OCD resist is removed by washing with BHF solution for 5 minutes.

  In step (e) shown in FIG. 9, a resist pattern 42 is formed from a thick film resist. The thick film resist is applied by a spin coater under conditions of 2000 rpm and 25 sec, and then baked under conditions of 110 ° C. and 10 minutes. Then, the resist pattern 42 as shown in FIG. 9A is formed by performing ultraviolet exposure for 60 seconds and developing for 2 minutes. FIG. 9B is a sectional view taken along line D3-D3.

  In step (f) shown in FIG. 10A, the upper Si layer 10 and the polycrystalline silicon film 40 are etched by ICP-RIE to form the fixed electrode 13 and the hole 14 of the fixed electrode 13 of the bridge 11. In step (g) of FIG. 10B, the thick film resist 42 is removed by washing at 90 ° C. for 5 minutes with sulfuric acid / hydrogen peroxide. A polycrystalline silicon film 40 exists on the outermost surface. Thereafter, in order to protect the surface on the side etched in the step (f), the thick film resist 42 is applied again on the surface side and baked.

  Through the above series of steps, the upper structure of the condenser microphone 1 is completed, and then the lower structure is manufactured. In step (h) of FIG. 11A, an aluminum (Al) layer 31 is formed to a thickness of 0.1 μm on the lower Si layer 30 by vacuum deposition. In step (i) of FIG. 11B, a resist is applied to the surface of the Al layer 31 by a spin coater under the conditions of 3000 rpm and 30 sec. Then, after baking at 90 ° C. for 5 minutes, the resist pattern 43 is formed by performing ultraviolet exposure for 4.0 seconds and development for 1.5 minutes. The resist pattern 43 is a pattern in which a circular opening is formed.

In the step (j) of FIG. 11C, the Al layer 31 is etched for pattern formation by immersing in a mixed acid P solution (H ₃ PO ₄ + HNO ₃ + CH ₃ COOH + H ₂ O ₂ ) for 2 min. The resist 43 is removed by RIE, that is, ashing using oxygen gas.

  In the step (k) of FIG. 11D, a thick film resist is applied to the surface of the lower Si layer 30 from which the Al layer 31 has been removed with a spin coater under the conditions of 2000 rpm and 25 sec. Then, after baking at 110 ° C. for 5 minutes, a resist pattern 44 is formed by performing ultraviolet exposure for 60 seconds and development for 2 minutes. The resist pattern 44 is a circular pattern, and a ring-shaped gap region R is formed between the resist pattern 44 and the resist pattern 43.

  In step (l) shown in FIG. 12A, the lower Si layer 30 is etched in a ring shape by about 55 μm by ICP-RIE. This etching amount determines the thickness of the diaphragm 32. In the step (m) of FIG. 12B, the thick film resist 44 is removed by a remover (resist stripping solution). At this time, since the protective thick film resist (see FIG. 11) applied to the upper surface side of the substrate is also peeled off, the protective thick film resist is formed again.

In step (n) of FIG. 12C, the lower Si layer 30 is etched by about 445 μm by ICP-RIE using the Al layer 31 as a mask. As a result, a Si diaphragm 32 having a thickness of 55 μm is formed in a circular cavity formed in the lower Si layer 30. In the step (o) shown in FIG. 12D, the SiO ₂ layer 20 is removed with strong hydrofluoric acid after washing with sulfuric acid / hydrogen peroxide at 90 ° C. for 5 minutes. Thereby, the diaphragm 32 is completely separated from the fixed electrode 13. Finally, an Al metal layer 50 is formed on the upper surfaces of the bridge 11 and the fixed electrode 13.

  In general, in a microphone (acoustic transducer element) that detects sound by vibration of a diaphragm, a pressure difference generated between the front and back of the diaphragm as a diaphragm is important. In the present embodiment, a diaphragm 32 formed of the same lower Si layer is disposed in a circular opening 311 of a base 31 composed of the lower Si layer 30, and the diaphragm 32 vibrates due to sound pressure. ing. As described above, in the structure in which the front side space and the back side space of the diaphragm 32 communicate with each other through the gap between the diaphragm 32 and the base 31, in order to generate a sufficient pressure difference between the front and back of the diaphragm 32. Therefore, it is necessary to set the gap dimension of the gap to an optimum value.

  For example, when the back surface side of the diaphragm 230 is a sealed space as shown in FIG. 23A, and the hole 230a is formed in the diaphragm 230 as shown in FIG. 23B, the space on the back surface side of the diaphragm Consider the case where is semi-sealed.

  Since air is a fluid and has viscosity, the velocity of air is equal to 0 on the surface of the material, and it can be considered that the velocity gradually returns to the original sound velocity as the distance from the surface increases. The region where the air drops below the speed of sound (99% or less of the speed of sound) when viewed from the material surface is called the velocity boundary layer. When the surface of an object placed in a fluid sound field is not perpendicular to the vibration velocity of a fluid particle, a velocity boundary layer with a thickness of δ = (2ν / ω) ^ 0.5 is generated on the surface of the object. Here, the velocity boundary layer is a region where the sound velocity is slowed by the influence of the wall. ν is the kinematic viscosity coefficient of air, and ω is the angular frequency of the sound wave.

  As shown in FIG. 23 (b), in the case of a semi-open system in which a sufficiently large hole or gap is opened acoustically, the pressure fluctuation is transmitted to the front and back at the speed of sound. The pressure difference between the front and back surfaces of the flat plate that receives the sound wave in one cycle of the sound wave contributes only to the thickness of the flat plate with respect to the degree of sound density, and is very weak as a force. Assuming that the air pressure fluctuation P due to sound pressure is 1 Pa (at 94 dB), the pressure applied to the flat plate will remain as it is when it is sealed or close as shown in FIG. Shows quasi-sinusoidal fluctuation up to 1 Pa. However, in the case of a semi-open system with a sufficiently large gap as shown in FIG. 23B, the pressure difference between the front and back is simply the difference that the sound wave moves through the thickness.

For example, at room temperature and normal pressure, if a sound wave has a sound pressure of 2 Pa and a frequency of 1 kHz, the sound is 1 ms per cycle, during which the pressure fluctuation advances by one wavelength, that is, approximately 34 cm. The time required for the pressure fluctuation of the sonic wave to pass through the plate thickness of 20 μm is 59 ns. Assuming that pressure fluctuation fluctuates sinusoidally, each frequency of density fluctuation is ω, and time is t,
δP = (P0 + Psinω (t + 59ns))-(P0 + Psinωt)
It is represented by Since the value of 59 ns is about 17000th of a cycle of 1ms and is about 0.021 ° in phase, δP is less than about 2500th of the maximum for P under this condition and is in a semi-open state It can be seen that the pressure difference is clearly small with respect to the sealed state. Therefore, in general, when a hole is opened, the sensitivity of the vibrating body that receives sound waves is too low, and it reacts only in a special state where the input sound waves are at the resonance frequency.

  On the other hand, if 1/2 of the radius of the hole on the flat plate or the gap interval is equal to or less than the velocity boundary layer, it can be said that the sound wave passing through the gap propagates slower than originally intended. FIG. 24 is a diagram for explaining the propagation of the pressure difference in the gap. The fixed portion 241 corresponds to the base 31 and the movable portion 242 corresponds to the diaphragm 32. When this gap (gap) d10 is sufficiently narrow and the thickness h of the flat plate is sufficiently thick relative to the gap, the propagation of the pressure difference in the gap is delayed with respect to a wide free space. Is not transmitted at the speed of sound.

  Therefore, the pressure difference between the front and back of the flat plate when receiving a sound wave can be regarded as a difference between the sound pressure of the sound wave itself and the equilibrium state, not the difference in thickness. At least the viscous resistance generated when air passes through the gap is greater than when there is a sufficiently large hole or gap, so that the force due to the sound wave is easily transmitted to the movable electrode. In addition, due to the squeeze film damping effect, the movable electrode becomes difficult to move in the direction parallel to the plane and moves in the vertical direction. When this gap is 3 μm or less and the thickness is 5 times or more, a perforated flat plate as shown in FIG. 23 (b) blocks air without gaps in the so-called audible band of 20 Hz to 20 kHz. As with the sealed diaphragm, it was confirmed that it vibrates under sound pressure.

  For example, if the acoustic boundary layer thickness is about 15.7 μm at 20 kHz and the width of the gap is 3 μm, the propagation speed of the sound wave through the gap is 3.18 m / s at the maximum at 25 ° C. Decrease to 1/100 or less. If the width of the gap is 1 μm, the propagation speed of the sound wave is reduced to 0.35 m / s and is about 1/1000. When this speed is reached, the arrival position of the pressure fluctuation is about 17 μm at 20 kHz per cycle, and even if the electrode thickness is 17 μm or more, it does not even reach the back surface. As a result, an acoustic resistance of an order that cannot be ignored in practice occurs.

  Furthermore, it was found that the sound velocity changes depending on the gap width, and as shown in FIG. 25, the volume affected by the pressure fluctuation of the sound wave also changes depending on the gap width. If the range of influence of pressure fluctuation per cycle is sufficiently larger than the volume of the original gap, it can be considered that the sound wave penetrates the gap. When the gap width d10 is 4 μm or more, the pressure fluctuation due to the sound wave exceeds twice, so that the sound wave blocking effect is reduced. Therefore, in the present invention, the gap width capable of obtaining a sufficient effect is set to 3 μm or less. If the gap is too narrow, there is a possibility of contact with the wall surface. When general ICP-RIE processing is used, the wall surface roughness is about 200 nm or less, so it is desirable to have a gap of 0.5 μm or more if possible.

  That is, the flat plate is divided into a movable part and a fixed part, the gap between the movable part and the fixed part is 0.5 μm or more and 3 μm or less, and the thickness of the edge part constituting the gap between the movable part and the fixed part is 5 times or more of the gap. It is desirable to improve sensitivity. With such a structure, it is possible to configure a sensor that can sufficiently read the sound pressure.

-Second Embodiment-
FIG. 13 is a diagram showing a second embodiment of the directional microphone 1 according to the present invention. The microphone 1 shown in FIG. 1 constitutes a parallel plate type condenser microphone in which the fixed electrodes 13A to 13D and the diaphragm 32 are arranged to face each other in parallel. On the other hand, the microphone 1 shown in FIG. 13 constitutes a comb electrode type condenser microphone. In addition, the same code | symbol was attached | subjected to the component similar to the case of FIG.

  In FIG. 13, (a) is a plan view of the microphone 1, and (b) is a D1-D1 sectional view. In the present embodiment, the diaphragm is constituted by four substantially fan-shaped divided diaphragms 32A to 32D, each formed by the upper Si layer 10 of the SOI substrate, while the bridge 11 has a cross shape, Each tip portion is fixed on the base 31. The bridge 11 is provided with a terminal portion 11d. Four elastic portions 12 are provided radially on the side surface of the central portion 111 of the bridge 11, and the divided diaphragms 32 </ b> A to 32 </ b> D are supported by the elastic portions 12. Comb electrodes 322 and 323 each having a plurality of projections and depressions are formed on the arc-shaped portions of the divided diaphragms 32A to 32D.

  On the other hand, fixed electrodes 23A to 23C are formed on the base 31 so as to face the comb electrodes 322 and 323. As in the case of the microphone 1 shown in FIG. 1, the fixed electrodes 23 </ b> A to 23 </ b> D are formed by the upper Si layer 10. Comb electrodes 232 and 233 are also formed on the fixed electrodes 23A to 23D. The fixed electrodes 23A to 23D are arranged so that the comb electrodes 232 and 233 and the comb electrodes 322 and 323 of the diaphragm 32 mesh with each other through a gap. Each fixed electrode 23 </ b> A to 23 </ b> D is provided with a terminal portion 132 via a wiring portion 131.

  Note that the gap dimensions between the comb-tooth electrodes 232 and 233 and the comb-tooth electrodes 322 and 323 can be said to be the same as the gap described in the first embodiment. That is, the gap dimension between the comb electrodes 232 and 233 and the comb electrodes 322 and 323 is set to 0.5 μm or more and 3 μm or less. Further, the thickness of the comb electrode portion is also set to 5 times or more of the gap.

  FIG. 14 is a diagram schematically illustrating a state of the diaphragm when receiving a sound wave from a sound source. As in the case shown in FIG. 3, the sound source is in a direction inclined obliquely with respect to the central axis J of the microphone 1. When each divided diaphragm 32A to 32D receives sound pressure due to sound waves, each elastic portion 12 bends according to the magnitude of the received sound pressure, and the divided diaphragms 32A to 32D are displaced with the central portion 111 of the bridge 11 as a fulcrum. Then vibrate. As a result, the pair of comb electrodes facing each other are displaced upward, the meshing area is changed, and the capacitance is changed. This corresponds to a change in the electrode area S in the above-described equation (1). In the case of a comb electrode, since the electrode facing surface has an irregular shape, the electrode area can be increased and the sensitivity can be improved.

  In the case shown in FIG. 14, the divided diaphragm 32A is closer to the sound source than the divided diaphragm 32C, so that the acting sound pressure is larger and the change in capacitance is larger. Thus, since the electrostatic capacitance regarding each divided diaphragm 32A-32D changes according to the direction of a sound source, by comparing the magnitude of the change of the electrostatic capacity regarding each divided diaphragm 32A-32D, The direction can be specified. Furthermore, since the diaphragm is divided into a plurality of divided diaphragms 32A to 32D so as to receive sound waves independently, the sound source can be specified more accurately than in the case of one diaphragm 32 as shown in FIG. It can be carried out. In addition, the directivity can be automatically adjusted according to the position of the sound source without changing the direction of the entire microphone.

  Note that the audio signal detection method is the same as in the first embodiment, and a description thereof is omitted here. In the present embodiment, the diaphragm is divided into four. However, the number of divisions is not limited to four, and may be plural. Although the number of fixed electrodes is the same as the number of divided diaphragms, signals can be output by the number of fixed electrodes, and may be larger than the number of divided diaphragms. The direction of the sound source can be specified more precisely by increasing the number of divided diaphragms and increasing the number of fixed electrodes.

  In the case of a parallel plate type microphone in which a diaphragm and a fixed electrode are arranged in parallel via a gap, the area of the diaphragm is increased to ensure capacitance, and the fixed electrode and diaphragm (diaphragm) are as much as possible. It is necessary to make the diaphragm into a thin film diaphragm in order to reduce the gap between the diaphragm and the film. However, sticking is caused when gaps are formed, resulting in a decrease in yield, sacrificial layer etching, cleaning techniques, and the like, and a large amount of masks.

  On the other hand, in the second embodiment, instead of the parallel plate diaphragm structure, the capacitance portion is a comb-teeth electrode structure, so that the capacitance is reduced without forming a thin film narrow gap structure. It becomes possible to secure. Further, the divided diaphragms 32 </ b> A to 32 </ b> D, the bridge 11, the elastic portion 12, and the fixed electrodes 23 </ b> A to 23 </ b> D are simultaneously formed by the same upper Si layer 10. Therefore, the machining process is simplified as compared with the microphone of the first embodiment. These components are simultaneously formed by etching in step (c) shown in FIG. 8C, and then the lower Si layer 30 is etched from the back side to form a circular opening 31.

  In addition, since the capacitance change with respect to the tilt displacement is larger than that of the parallel plate type, the tilt detection sensitivity is improved. In a comb-type electrode sensor, the gap can be easily changed, and the probability of yield failure such as sticking is lower than that of a thin film. A narrow gap can be easily formed by the recent development of Deep-RIE technology. Sensors with high changes can be created.

-Third embodiment-
In the first and second embodiments described above, when the sound source is in an oblique direction, the diaphragm is displaced to be inclined with respect to the surface of the base 31. On the other hand, in the present embodiment, the configuration is such that the diaphragm is displaced parallel to the surface of the base 31.

  FIG. 15 is a diagram showing a third embodiment of the microphone, and the microphone 1 constitutes a comb electrode condenser microphone similar to the second embodiment. However, the diaphragm is not a divided diaphragm but a single diaphragm 32 having a circular shape. Four fixed electrodes 23 </ b> A to 23 </ b> D having comb-tooth electrodes 232 and 233 are provided on the base 31 so as to face the comb-tooth electrodes 322 and 323 of the diaphragm 32. The diaphragm 32 is elastically supported on the opening 311 by the four elastic portions 12. The elastic portion 12 has an oval beam structure so that the diaphragm 32 is easily displaced in parallel with the base 31.

  A groove 325 like a Fresnel lens is formed on the sound wave incident surface of the diaphragm 32, that is, the surface opposite to the opening 311. The cross-sectional shape of the circular groove 325 is a sawtooth shape, and a plurality of grooves 325 are formed concentrically around the center of the diaphragm 32. In FIG. 15, the surface 325a on the center side of the groove 325 is an inclined surface and the outer surface 325b is a vertical surface. On the other hand, the center surface 325a is a vertical surface and the outer surface 325a is an outer surface. The surface 325b may be a slope.

  When a sound wave enters perpendicularly to the inclined surface 325 a in the left region of the diaphragm 32 and a sound pressure acts, a leftward force F acts on the diaphragm 32. On the contrary, when a sound wave is applied to the slope 325 a in the right region and a sound pressure is applied, a rightward force is applied to the diaphragm 32. Therefore, as shown in FIG. 16A, when sound waves are incident on the diaphragm 32 from a sound source obliquely upward to the right with respect to the central axis J of the diaphragm 32, the diaphragm 32 receives a leftward force as a whole. It will be displaced to the left. Conversely, when the light source is on the left side of the central axis as shown in FIG. 16B, the diaphragm 32 receives a force in the right direction as a whole and is displaced to the right side.

  As a result, the gap between the comb electrode portions in the direction opposite to the sound source direction is narrowed, and the capacitance of the region is increased. For example, in FIG. 15A, when the diaphragm 32 is displaced leftward, the capacitance related to the fixed electrodes 23C and 23D increases, and conversely, the capacitance related to the fixed electrodes 23A and 23B decreases. Therefore, the capacitance change of the fixed electrodes 23C and 23D greatly depends on the sound wave from the sound source direction, and the microphone has directivity in the sound source direction. However, since the force component due to the sound pressure is not only in the horizontal direction but also in the vertical direction, the diaphragm 32 is inclined according to the distribution state of the vertical direction component. Therefore, the change in capacitance is slightly different from that described above. In FIG. 15, the inclined surface 325 is formed on the sound wave incident surface of the diaphragm 32, but the incident surface may be a flat surface. That is, even if it is a plane, the diaphragm 32 is inclined by the sound pressure distribution, and as a result, a lateral (horizontal) force is applied, and the diaphragm 32 moves in the lateral direction. In any case, directivity is automatically adjusted in the direction of the sound source. Further, in the case of the comb-teeth electrode, the change in capacitance is larger when the comb teeth are displaced in the opposite direction as in the present embodiment rather than being displaced in the vertical direction as in the second embodiment. . Therefore, the detection sensitivity can be improved.

  Further, the direction of the sound source can be specified by comparing the difference in capacitance between the fixed electrodes 23A to 23D. Further, as in the case described above, when the diaphragm is displaced in the direction opposite to the comb electrode, the change in capacitance increases, so that the direction resolution for specifying the sound source direction can be further increased.

  In the example shown in FIG. 15, the elastic part 12 elastically supports the four portions around the diaphragm 32, but the elastic part 12 supports the part near the center of the diaphragm 32 as shown in FIG. 21. May be. In FIG. 21, the elastic portion 12 is provided at the tip portion of the bridge 11, and the diaphragm 32 is supported by the elastic portion 12. Other structures are the same as those shown in FIG. By supporting the portion close to the center in this way, not only the diaphragm 32 moves in parallel due to the sound pressure, but also the diaphragm 32 tends to tilt obliquely. The structure of the elastic part 12 may be the same as that shown in FIG. 15, or may be a structure as shown in FIGS.

  The planar shape of the groove 325 is not limited to the concentric circular shape as shown in FIG. 15, and various forms are possible. For example, you may arrange | position squarely like the modification 1 shown to Fig.17 (a). It is also possible to increase the sensitivity to sound waves from a specific direction by directing the normal direction of the slope 325a to the specific direction. The sawtooth-shaped groove can be formed by making a difference in etching rate by a gray mask technique. Further, when only a slope facing in a specific direction is formed, it can be formed by wet etching.

  FIG. 17B is a diagram showing a second modification example. The diaphragm 32 is divided into four divided diaphragms 32 </ b> A to 32 </ b> D, and these are individually supported by the elastic portion 12. From the cross-shaped bridge 11, two elastic portions 12 are connected to the divided diaphragms 32A to 32D, respectively. The pair of elastic portions 12 are configured such that the divided diaphragms 32A to 32D are easily displaced in the radial direction.

  In Modification 3 shown in FIG. 18A, a sound wave enters from the base 31 side, contrary to the microphone shown in FIG. That is, sound waves are incident on the bottom surface 326 side of the diaphragm 32. Other configurations are the same as those in the third embodiment described above. The bottom surface 326 is formed of a slope in order to increase directivity with respect to the sound source direction. The bottom surface 326 has a convex surface with a convex shape at the center. Therefore, for example, even if there is an air flow from below to above, the bottom shape is such that the air resistance is reduced, and the influence of the air flow can be reduced.

  In Modification 3 shown in FIG. 18A, the inclination of the inclined surface gradually increases from the central portion to the peripheral portion, but it may be a bottom surface 326 such as a conical surface.

  In the modified example 4 shown in FIG. 18B, the bottom surface 326 is concave. Therefore, the sound collection effect can be improved.

  As the form of the elastic portion 12, a beam structure as shown in FIG. 19 is conceivable in addition to the beam structure as shown in FIG. 1 and the elliptical beam structure as shown in FIG. The elastic part 12 shown in FIG. 19A is composed of two linear beams 121. The elastic portion 12 has a structure that is easily bent in the y direction in the figure. In the elastic portion 12 shown in FIG. 19B, the thickness (z-direction dimension) of the beam is reduced to reduce the spring constant. In the case of this configuration, it is easy to bend in the vertical direction (z direction), so it is suitable for supporting the diaphragm 32 configured to tilt up and down.

  The elastic part 12 shown in FIG. 19C has a configuration in which the beam constituting the elastic part 12 shown in FIG. 1 and the beam shown in FIG. 19B are connected in series. Therefore, the structure is easy to bend in both the z direction and the y direction. The elastic portion 12 shown in FIG. 19D has a bellows-like beam structure folded in the y direction. Therefore, it has the advantage that it is easy to bend in the y direction and is easily displaced in the x direction. Note that if the folding direction of the bellows is the z direction, it is easy to bend in the z direction and easily deform in the x direction.

The embodiment described above has the following operational effects.
(1) A base 31 having an opening 311 at the center, a bridge 11 spanning the opening 311 of the base 31, and a diaphragm 32 elastically supported at the center of the bridge 11 via a support shaft 321. And a plurality of fixed electrodes 13A to 13D which are arranged opposite to each other with an opening 311 and a diaphragm 32 provided in the opening 311, and are provided at the center of the bridge 111. A plurality of elastic members 32 that elastically support the support shaft 321 of the diaphragm 32 from the side so that the incident surface is inclined according to the sound source direction. As a result, the sound collection characteristic relating to the sound wave in the sound source direction is improved, and a microphone with high directivity can be obtained. In addition, the directivity can be automatically adjusted according to the position of the sound source without changing the direction of the entire microphone. Furthermore, since the diaphragm 32 is supported by the plurality of elastic portions 12, the durability of the support portion can be improved as compared with the conventional one-point support structure.
(2) The directional microphone includes a base 31 having an opening 311 at the center, a bridge 11 spanning on the opening 311 of the base 31, and a plurality of divided diaphragms 32A to 32D. 11 is provided with a plurality of electrodes 13A to 13D held by a base plate 31 and a diaphragm 32 elastically supported by the central portion of the eleventh plate, an opening 311 which is opposed to the divided diaphragms 32A to 32D with a gap. The split vibration is generated on the side periphery of the central portion 111 provided in the central portion of the bridge 11 so that the incident surfaces of the plurality of split diaphragms 32A to 32D are inclined according to the sound source direction by the incidence of the sound wave. And a plurality of elastic portions 12 that elastically support the plates 32A to 32D. Directivity is further improved by tilting the plurality of divided diaphragms 32A to 32D.
(3) Comb-shaped electrodes 322 and 323 are formed on the diaphragm 32, and the diaphragm 32 has a plurality of elastic portions on the opening 311 of the base 31 so as to be displaced according to the direction of the incident sound wave. 12 is elastically supported. The fixed electrode is composed of a plurality of divided electrodes 23A to 23D held by the base 31, and comb-shaped electrodes 232 and 233 that mesh with the comb-shaped electrodes 322 and 323 with gaps are respectively provided for the divided electrodes 23A to 23D. Is formed. By using a comb-tooth electrode, the change in capacitance can be increased, and the detection sensitivity can be improved. Furthermore, since the diaphragm 32, the elastic portion 12, and the fixed electrode are formed of the same Si layer of an SOI (Silicon on Insulator) substrate, the etching process is simplified and the microphone can be miniaturized.
(4) As shown in FIG. 13, the diaphragm 32 may be divided into a plurality of parts so that they are inclined by the sound pressure, or as shown in FIGS. 15 and 17B. You may comprise so that 32, 32a-32d may displace to a surface direction (namely, direction parallel to a surface). In the case of the configuration of FIG. 17B, the directivity can be further improved by dividing the diaphragm into a plurality of divided diaphragms 32a to 32d.
(5) The vibration plate 32 is elastically supported so as to be movable in the surface direction, and the inclined surface 325 is formed on the sound wave incident surface of the vibration plate 32. It may be displaced. As a result, the capacitance change with respect to the displacement of the diaphragm can be increased, and the directivity of the microphone and the sound source direction specifying performance can be improved.
(6) The electrostatic capacitance between the plurality of fixed electrodes 23A to 23D and the diaphragm 32 is individually detected as a voltage by the voltage detection circuit 200 corresponding to each of the fixed electrodes 23A to 23D, and based on the voltage The walking specifying circuit 201 specifies the direction of the sound source. With this configuration, it is possible to specify a sound source with a single microphone.

  It is also possible to combine one or more of the above-described embodiments and modifications. Any combination of the modified examples is possible. For example, the diaphragm 32 in FIG. 1 may be divided into four diaphragms 32A to 32D that are opposed to the fixed electrodes 13A to 13D as shown in FIG. In FIG. 20, the configuration of the microphone is shown by omitting the fixed electrodes 13 </ b> A to 13 </ b> D so that the shape of the diaphragm 32 can be easily understood. The center portion 111 of the bridge 11 constitutes a support shaft for the divided diaphragms 32A to 32D, and the elastic portions 12 are provided radially on the side periphery thereof. The divided diaphragms 32A to 32D are elastically supported by the elastic part 12, respectively.

  Further, the number of bridges 11 is not limited to four and may be two or three. The number of divisions of the fixed electrode and the diaphragm is not limited to 4, and may be 2, 3 or 5 or more. In that case, the resolution of sound source identification improves as the number of divisions increases.

  Furthermore, the extending direction of the comb electrodes 232, 233, 322, and 323 is not limited to the above-described radial direction, and the comb electrodes 232, 233, 322, and 323 are arranged in the circumferential direction as shown in FIG. You may employ | adopt the thing of the form extended to. FIG. 22 is a view showing a modification of the shape of the comb-teeth electrode. A part of the diaphragm 32 and the fixed electrodes 23A to 23D, that is, the comb-teeth electrode of the fixed electrode 23A and the comb-teeth on the diaphragm 32 side facing it The electrode is shown. In the example shown in FIG. 22A, two rows of comb-shaped electrodes 233 extending in the circumferential direction are formed on both sides of the shaft portion 234 extending radially from the fixed electrode 23A. A plurality of shaft portions 234 are formed on the fixed electrode 23A.

  On the other hand, a plurality of radially extending shaft portions 324 are formed on the outer peripheral surface of the diaphragm 32, and two rows of comb-shaped electrodes 322 extending in the circumferential direction are formed on both sides of each shaft portion 324 in the radial direction. The comb-tooth electrode 232 enters the concave portion (comb electrode 323) on the diaphragm 32 side, and the comb electrode 322 enters the concave portion (comb electrode 233) on the fixed electrode 23A side. By adopting such a comb electrode structure, the capacitance change can be increased, and the sensitivity of sound wave detection can be improved.

  FIG. 22B is a diagram showing another example, in which the shaft portions 324 of the comb-tooth electrodes 322 and 323 extend radially from a portion near the center of the diaphragm 32 and extend in the circumferential direction. Eight rows of 322 and 323 are provided in the radial direction. The comb electrode structure on the fixed electrode 23A side is the same as that on the diaphragm side. Thus, most of the diaphragm 32 may be a comb electrode region, and the sensitivity can be improved by increasing the capacitance change.

  The above description is merely an example, and the present invention is not limited to the configuration of the above embodiment as long as the characteristics of the present invention are not impaired.

  1: microphone, 2: sound source direction specifying part, 11: bridge, 12: elastic part, 13A to 13D, 23A to 23D: fixed electrode, 31: base, 32: diaphragm, 32A to 32D: divided diaphragm, 111: Central part, 200: voltage detection circuit, 201: direction specifying circuit, 232, 233, 322, 323: comb electrode, 311: opening, 321: support shaft, 325: groove, 325a: slope, 325b: vertical surface, 326 : Bottom

Claims (6)

A base substrate having a void in the center, and
A diaphragm on which a first comb electrode is formed;
A support portion for supporting the diaphragm on the base substrate in a space in the base substrate;
A fixed electrode formed of a plurality of divided electrodes held on the base substrate and having a second comb-shaped electrode meshing with the first comb-shaped electrode with a gap formed on each of the divided electrodes; A directional microphone comprising:
The support portion includes a plurality of elastic portions that elastically support the vibration plate such that the vibration plate is displaced according to a sound source direction and the position of the first comb electrode relative to the second comb electrode changes. Have
The directional microphone characterized in that the diaphragm, the support portion, and the fixed electrode are formed of the same Si layer of an SOI (Silicon on Insulator) substrate. The directional microphone according to claim 1,
The directional microphone is characterized in that the support portion elastically supports the diaphragm via the plurality of elastic portions so that the support portion can move in a direction parallel to the surface of the diaphragm by the incidence of sound waves. The directional microphone according to claim 2,
A directional microphone, wherein a slope is formed on a sound wave incident surface of the diaphragm. The directional microphone according to claim 2 or 3,
The diaphragm is composed of a plurality of divided plates corresponding to the divided electrodes,
The directional microphone is characterized in that the support portion elastically supports each of the plurality of divided plates. The directional microphone according to claim 1,
The diaphragm is divided into a plurality of divided plates,
The support portion includes a beam structure spanned over a space in the base substrate, and each of the plurality of divided plates such that the plurality of divided plates are individually inclined according to a sound source direction by incidence of sound waves. A directional microphone comprising: a plurality of elastic parts that individually and elastically support at a central part of the beam structure. In the directional microphone as described in any one of Claims 1-5,
A detection unit that individually detects the capacitance between the plurality of divided electrodes and the diaphragm, corresponding to each of the divided electrodes;
A directional microphone comprising: a calculation unit that specifies a sound source direction based on each capacitance detected by the detection unit.

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