JP4433969B2 - Microphone with thin film coil - Google Patents

Description

  The present invention relates to a microphone provided with a diaphragm that responds to changes in sound pressure, and more particularly to a microphone provided with a thin film coil suitable for miniaturization.

  Various types of microphones that convert sound pressure into electrical signals have been known, such as a dynamic type that uses magnetic induction (inductive type), a piezoelectric type that uses distortion of piezoelectric elements, and a condenser type that uses static electricity. It has been. By the way, in recent years, in applications such as mobile phones and hearing aids, there has been a demand for higher sensitivity and ultra-miniaturization of this type of microphone. However, the inductive type currently has to be large because it is necessary to wind a coil, and there is a limit to downsizing. In addition, the piezoelectric type has a high acoustic impedance due to its high rigidity and is suitable for capturing vibrations such as water, but has a drawback that it is not suitable for detecting air vibrations.

  On the other hand, the miniaturization of a microphone using a micromachine technology (MEMS: Micro Electro Mechanical System) has been studied. In this case, many of the operating principles are of the capacitor type, and are proposed in, for example, Patent Document 1 and Patent Document 2. Here, in Patent Document 1, as shown in FIG. 34, an oscillation / modulation circuit 85 is obtained by changing the capacitance of a capacitor composed of a vibrating electrode 81 and a back electrode 82 in response to a change in sound pressure. The oscillation frequency of the LC oscillation circuit changes. The oscillation output signal of the LC oscillation circuit is FM modulated in response to a change in sound pressure and transmitted from the antenna 86. Thus, it is not necessary to apply a large bias voltage to the IC microphone by reading the change in the capacitance of the capacitor caused by the sound pressure as the change in the oscillation frequency of the LC oscillation circuit having the capacitor as a part of C. By reducing the distance between the electrodes, the sensitivity can be increased.

In Patent Document 2, as shown in FIG. 35, the condenser microphone 90 has a pair of electrodes 92 and 93 formed on a single crystal silicon substrate 91 so as to form a capacitor. Is a diaphragm that is movable with respect to the other electrode 93, and the other electrode 93 is a condenser microphone 90 that is a back plate in which a plurality of through holes 94 are formed. In this case, the diaphragm 92 and the back plate 93 are part of a single crystal silicon substrate and are doped with boron. As a result, a compact and high-performance condenser microphone 90 having a highly accurate diaphragm in which internal stress is appropriately adjusted can be obtained.
Japanese Patent Laid-Open No. 2001-39796 JP 2002-95093 A

  However, in the microphone proposed in Patent Document 1 described above, when the microphone is miniaturized, C of the diaphragm portion becomes smaller. For this reason, there is a problem that the C of the diaphragm is buried in the capacitance of the circuit and the signal processing, and the ratio of the change of C contributing as the change rate of the entire inductance becomes very small. As a result, the sensitivity deteriorates and the problem that it is not suitable for miniaturization has arisen. Further, when the size is reduced, C of the diaphragm portion is reduced and the oscillation frequency is increased, which causes a problem that the loss in the circuit due to the high frequency increases. Furthermore, an external inductor is required to form an oscillation circuit. However, when the microphone is miniaturized, both L and C become smaller and the oscillation frequency becomes very high, so that the electromagnetic wave emitted to the outside is reduced. As a result, there was a problem that the signal was greatly lost in the circuit and the sensitivity was lowered. In addition, there is a problem that this external inductor does not contribute to the output increase and the efficiency is low.

  On the other hand, the microphone proposed in Patent Document 2 described above has a problem that the output of the microphone is small. Here, in order to increase the output of the microphone, it is necessary to increase the area of the condenser (diaphragm). However, if the area of the condenser (diaphragm) is increased, the microphone becomes larger, and miniaturization is not possible. It caused the problem of being unsuitable. In order to increase the output, it is necessary to reduce the distance between the electrodes of the capacitor. However, if the distance between the electrodes of the capacitor (diaphragm) is reduced, the problem arises that the electrodes of the capacitor tend to stick together. Furthermore, in order to increase the output, it is necessary to increase the bias voltage. However, if the bias voltage of the capacitor (diaphragm) is increased, the capacitor electrode tends to stick. For this reason, it was not suitable for the purpose of making it small and highly sensitive.

  Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide an ultra-small microphone having improved sensitivity as an element having a large inductance even when being miniaturized.

  In order to achieve the above object, a microphone according to the present invention includes a diaphragm that responds to a change in sound pressure, and at least a part of the diaphragm is formed of a magnetic material to become an upper yoke. And a thin film coil formed in the lower yoke. The upper yoke and the lower yoke serve as a magnetic path for the magnetic flux generated in the thin film coil. When the diaphragm is displaced by the external sound pressure, the upper yoke and the lower yoke formed on the diaphragm are formed. The inductance is changed so that the distance between and changes.

  As described above, since the microphone of the present invention includes the magnetic path composed of the upper yoke and the lower yoke and the thin film coil that generates magnetic flux, it can be an ultra-small element having a large inductance. . This is because, according to the semiconductor technology, it is possible to simultaneously form a multi-turn coil with a fine pattern at a time. Here, if the number of turns (N) of the coil is increased, the inductance of this element increases in proportion to the square of N. Therefore, the inductance can be increased by increasing the number of turns. On the other hand, the smaller the yoke, the lower the magnetic path resistance and the greater the inductance of this element.

  For this reason, even if this microphone is made small, it can be an element whose inductance is sufficiently larger than the stray inductance of other circuit units, so that the inductance of this element can be reduced by other electronic circuits and signal processing circuits. It is not buried in the stray inductance. Therefore, even if it is very small, since the overall inductance change is large, it is possible to obtain an ultra-small microphone with improved sensitivity.

  The microphone of the present invention can incorporate a capacitor therein. In this case, the diaphragm has conductivity and becomes one electrode of the capacitor, and at least a part of the diaphragm is made of a magnetic material and becomes an upper yoke, and is opposed to the upper yoke through an air layer. A lower yoke formed on the substrate at the position and a thin film coil formed in the lower yoke are provided. The upper yoke and the lower yoke serve as a magnetic path for the magnetic flux generated in the thin film coil. The upper yoke and the lower yoke are opposed to one electrode of the capacitor via an air layer. A conductive plate serving as the other electrode of the capacitor.

  When the diaphragm is displaced by the external sound pressure, both the distance between the upper yoke and the lower yoke formed on the diaphragm and the distance between one electrode and the other electrode of the capacitor change. , Both inductance and capacitance are changed. As a result, it is possible to obtain a microphone with improved sensitivity efficiently, and it is not necessary to store a large charge in the diaphragm unlike a condenser microphone, so the diaphragm and the electrode are attracted by the applied charge. There is no problem of sticking together.

  In this case, the lower yoke is integrally formed with three parts: a bottom part disposed at the lower part of the thin film coil, a cylindrical part disposed at the outer peripheral part of the thin film coil, and a cylindrical part disposed at the center part of the thin film coil. It is desirable that this type of lower yoke and thin film coil can be easily formed. When the outer peripheral portion of the diaphragm is fixed on the cylindrical portion of the lower yoke disposed on the outer peripheral portion of the thin film coil, the external sound pressure fluctuates, so that the center of the diaphragm is deflected and the thin film The distance between the cylindrical portion of the lower yoke arranged at the center of the coil changes. On the other hand, if the center part of the diaphragm is fixed to the cylindrical part of the lower yoke arranged at the center part of the thin film coil, the external sound pressure fluctuates, so that the periphery of the diaphragm is bent and the thin film coil The distance between the cylindrical portion of the lower yoke arranged on the outer peripheral portion of the lower yoke changes.

  It is desirable that the thin film coil and the lower yoke are insulated from each other and between the thin film coils by an insulating layer in which the resist is cured. The magnetic body forming the upper yoke and the lower yoke is preferably formed of any one metal selected from Ni, Fe, and Co, or an alloy composed of two or more of these metals. . The magnetic material is preferably formed by any one of vacuum film forming methods such as vapor deposition and sputtering, liquid phase film forming methods such as electroplating and electroless plating, or a combination thereof. In addition, the diaphragm excluding the magnetic material may be a simple substance of Al, Ti, Be, Mg, Si, B, or C, or a mixture thereof, or an oxide film, a nitride film, or a carbide film of these metals, or a combination thereof. It is desirable to be formed by a mixture of

  In addition, the diaphragm formed of the above-described magnetic body and serving as the upper yoke is formed to extend outward from the cylindrical portion of the lower yoke, and the outermost periphery of the diaphragm is supported or fixed. When the diaphragm is displaced by the external sound pressure, the inductance varies as the distance between the diaphragm and the cylindrical portion of the lower yoke and the distance between the diaphragm and the cylindrical portion of the lower yoke vary simultaneously. This is desirable because the variation in inductance increases.

  Further, a diaphragm made of a magnetic material and serving as an upper yoke is formed to extend outward from the cylindrical portion of the lower yoke, and the outermost periphery of the diaphragm is supported or fixed. A soft magnetic material is provided at a portion where a magnetic path on the lower surface facing the cylindrical portion of the lower yoke is to be formed, and when the diaphragm is displaced by an external sound pressure, between the diaphragm and the cylindrical portion of the lower yoke, and the diaphragm The inductance may be changed by simultaneously changing both distances between the upper yoke and the cylindrical portion of the lower yoke.

  Hereinafter, embodiments of a microphone having a thin film coil according to the present invention will be described with reference to the drawings as a microphone according to a first embodiment, a microphone according to a second embodiment, and a microphone according to a modification thereof. The present invention is not limited to these examples, and can be appropriately modified and implemented without changing the object of the present invention. 1 to 12 are diagrams schematically showing the microphone of the first embodiment and the manufacturing method thereof. FIGS. 13 to 28 are views schematically showing the microphone of the second embodiment and the manufacturing method thereof. Further, FIG. 29 to FIG. 33 are diagrams schematically showing microphones of those modifications.

1. First Embodiment A microphone 10 according to a first embodiment of the present invention is shown in FIG. 1 (note that FIG. 1A is a plan view schematically showing a state in which the inside is watermarked, and FIG. As shown in FIG. 2, the lower yoke (core) 12 made of a magnetic material formed on the substrate 11, and the thin film coil 13 formed so as to be surrounded by the lower yoke 12, The upper yoke 14 made of a magnetic layer is disposed on the lower yoke 12 via a gap made of an air layer, and the diaphragm 15 is formed on the upper yoke 14 and is formed integrally with the upper yoke 14. It consists of. In this case, an inductor L is formed by the lower yoke 12, the thin film coil 13, and the upper yoke 14, and an LC oscillation circuit is formed by connecting a capacitor (capacitor) (not shown) to the thin film coil 13.

Here, as the substrate 11, a silicon (Si) substrate, a ceramic substrate such as alumina (Al ₂ O ₃ ) or zirconia (ZrO ₂ ), a glass substrate, a resin substrate, a metal substrate, or the like can be used. When a substrate such as Si or GaAs is used, it is desirable to use a substrate in which a signal processing circuit is formed in advance in the substrate 11 as an LSI. As a material of the lower yoke 12, it is desirable to use an FeNi alloy (permalloy: 20% Fe-80% Ni alloy) having a relative permeability of 1000 or more. The lower yoke 12 has a disk-shaped bottom portion 12a, a cylindrical portion 12b protruding from the periphery of the bottom portion 12a, a columnar portion 12c protruding from the center portion of the bottom portion 12a, and an outward extension from the cylindrical portion 12b. And a lead portion 12d serving as a lead.

  The thin-film coil (inductor) 13 is made of a copper (Cu) plating layer having a width of 1 to 10 μm and a thickness of 1 to 10 μm, and is formed in a cylindrical shape within the cylindrical portion 12 b on the disk-shaped bottom portion 12 a of the lower yoke 12. It is wound a predetermined number of times N around the part (core) 12c. One end portion of the thin film coil 13 is connected to the cylindrical portion 12c of the lower yoke 12, and the other end portion of the thin film coil 13 extends outward to form a coil lead portion 13d. In this case, the thin film coil 13 may be a single stage or a plurality of stages of two or more stages. The upper yoke 14 is preferably made of an FeNi alloy (permalloy: 20% Fe-80% Ni alloy) having a thickness of 0.1 to 3 μm and a relative permeability of 1000 or more similar to the material of the lower yoke 12. In this case, an amorphous magnetic material such as CoZrNi or CoTa may be used.

The diaphragm 15 is formed of a thin film made of a light and highly rigid material having a density of 5 g / cm ³ or less and a Young's modulus of 7000 Kg / mm ² or more. Light, high-rigidity materials having a density of 5 g / cm ³ or less and a Young's modulus of 7000 Kg / mm ² or more include Al, Ti, Be, C, B, Mg alone or their alloys, SiO ₂ , Al ₂ O. Oxides such as ₃ , carbides such as TiC and SiC, and nitrides such as AlN and TiN are used. In this case, the outer peripheral portion of the diaphragm 15 is fixed to the upper portion of the cylindrical portion 12b of the lower yoke 12, but the upper yoke 14 is lg (in this case 0) from the upper end of the cylindrical portion (core) 12c of the lower yoke 12. It is preferable that the gap (air gap) is formed so that only .5 μm ≦ lg ≦ 50 μm is satisfied. Thus, when sound pressure is applied to the diaphragm 15, the diaphragm 15 vibrates at a predetermined resonance frequency.

  Here, a capacitor (capacitor) (not shown) has one end connected to a lead portion 12 d extending outward from the cylindrical portion 12 b of the lower yoke 12, and the other end extending outward from the thin film coil 13. By connecting to the lead portion 13d, a magnetic circuit in which a capacitor (capacitor) is connected in parallel to the inductor formed by the lower yoke 12, the thin film coil 13, and the upper yoke 14 is formed. A capacitor (capacitor) may be connected in series to the inductor formed by the lower yoke 12, the thin film coil 13, and the upper yoke 14.

Next, the oscillation frequency of the microphone 10 configured as described above and the rate of change (sensitivity) thereof are obtained as follows. Here, as shown in FIG. 2, the number of turns of the thin film coil 13 is N (times), the magnetic path resistance is Rm, and the core length (the total length of the closed magnetic circuit formed by the upper and lower yokes 14 and 12) is lc. The cross sectional area of the core (the cross sectional area of the upper and lower yokes 14 and 12) is Sc, the magnetic permeability of the core (the magnetic permeability of the upper and lower yokes 14 and 12) is μc, and the gap length (the upper end of the cylindrical portion 12c of the lower yoke 12). From the upper yoke 14 to lg, the gap cross-sectional area Sg, and the air permeability μ ₀ .

In this case, the inductance L of the magnetic circuit of FIG. 2 is L = N ² / Rm, and the magnetic path resistance Rm is Rm = (lc / μcSc) + (lg / μ ₀ Sg). Here, if (lc / μcSc) is sufficiently smaller than (lg / μ ₀ Sg) (μ ₀ << μc), Rm≡lg / μ ₀ Sg. As a result, L = N ² μ ₀ Sg / lg is obtained. When the capacitance C of the capacitor (not shown) is combined, the oscillation frequency f is expressed by the following equation (1).

Here, when the oscillation frequency f is differentiated by lg, the following equation (2) is obtained.

When the change (sensitivity) of the oscillation frequency due to the displacement of the upper yoke 14 formed integrally with the diaphragm 15 is obtained as (df / dlg) / f from the above equation (2), the following equation (3) is obtained. .

  The above expression (3) represents the following. That is, (1) the sensitivity (change rate of oscillation frequency) of the microphone 10 depends only on the gap length lg. (2) In order to increase the sensitivity (change rate of oscillation frequency) of the microphone 10, the gap length lg is decreased. (3) The sensitivity (change rate of oscillation frequency) of the microphone 10 does not depend on the area of the diaphragm (upper yoke) 14 and the number of coil turns (N times) of the thin film coil 13, and is suitable for downsizing.

  Next, a method for manufacturing the microphone 10 according to the first embodiment having the above-described configuration will be described in detail with reference to FIGS. First, a substrate 11 such as Si or GaAs is prepared, and a resist is applied to the entire surface of the substrate 11. In this case, either a positive type or a negative type may be used as the resist, but in the case of a positive type, for example, it is desirable to use OFPR800 manufactured by Tokyo Ohka Co., Ltd. or the like. Next, the resist is exposed by irradiating ultraviolet rays through a photomask on which a predetermined pattern is formed. In addition to ultraviolet rays, the resist may be exposed by irradiation with electron beams or X-rays.

  Next, the resist is patterned into a predetermined shape by dipping in a developer (when the above-mentioned OFPR800 is used as a resist, DE-6 manufactured by Tokyo Ohka Co., Ltd. is preferably used). Here, when the resist is a positive type, the exposed portion is dissolved and removed in alkali, and the unexposed portion remains. Next, as shown in FIG. 3, etching was performed using the remaining resist 11 a as a mask to form a recess 11 b having a depth of 5 to 50 μm in the substrate 11. In this case, as the etching, a plasma etching method in a gas phase or a solution etching method using an etchant (etching solution) in a liquid layer can be applied.

Next, the resist 11a is removed and the surface is cleaned. In this case, a method of dissolving the resist with an alkali or an organic solvent and removing it in a liquid phase, or an ashing method of removing in a gas phase using plasma can be applied. In the case of using a Si substrate, it is necessary to obtain an insulating surface in advance by oxidizing this surface or depositing (depositing) an insulating film such as SiO ₂ or Al ₂ O _3. There is.

  Next, in order to form the magnetic material by electroplating, a plating base film 11c having a thickness of 0.1 to 0.3 μm is formed. Here, a 20% Fe80% Ni alloy (permalloy) was formed by sputtering as the plating base film 11c. In this case, in addition to the 20% Fe80% Ni alloy (Permalloy), a metal containing Ni, Fe, Co, or an alloy thereof may be used. In addition to sputtering, the film may be formed by vapor deposition or electroless plating.

  Next, a resist similar to that described above is applied to the entire surface. Also in this case, for example, it is desirable to use OFPR800 manufactured by Tokyo Ohka Co., Ltd. Next, the applied resist is exposed to ultraviolet rays through a photomask having a predetermined pattern formed thereon. In addition to ultraviolet rays, the resist may be exposed by irradiation with electron beams or X-rays. Next, the resist is patterned into a predetermined shape by dipping in a developer (when the above-mentioned OFPR800 is used as a resist, DE-6 manufactured by Tokyo Ohka Co., Ltd. is preferably used).

  Then, a magnetic material is electroplated on the plating base film 11 c to form a magnetic material layer that becomes the bottom 12 a of the lower yoke 12. In this case, the magnetic body is preferably an alloy mainly composed of Ni, Fe, Co or the like having a relative permeability of 1000 or more, for example, 20% Fe80% Ni alloy (permalloy). And it is desirable to form into a film so that a film thickness may be set to 2-10 micrometers. Next, the resist is removed and the surface is cleaned. Also in this case, a method of dissolving the resist with an alkali or an organic solvent and removing it in a liquid phase, or an ashing method of removing in a gas phase using plasma is used. As a result, as shown in FIG. 4, a magnetic layer serving as the bottom 12a of the lower yoke 12 is formed on the plating base film 11c.

  Next, the exposed plating base film 11c is removed by ion milling that irradiates the surface with accelerated ions. In this case, a liquid phase etching method in which metal is dissolved may be used instead of ion milling. Next, a resist similar to that described above is applied to the entire surface. Also in this case, for example, it is desirable to use OFPR800 manufactured by Tokyo Ohka Co., Ltd. Next, the resist is exposed by irradiating ultraviolet rays through a photomask on which a predetermined pattern is formed. Next, the resist is patterned into a predetermined shape by dipping in a developer (when the above-mentioned OFPR800 is used as a resist, DE-6 manufactured by Tokyo Ohka Co., Ltd. is preferably used). As the resist, either a positive type or a negative type may be used. However, in the case of a positive type, a positive type resist is used because a slope is likely to be formed at the corner by flowing during heating in a later process. Is desirable.

  Next, the resist patterned by development is heated to 150 to 230 ° C. to perform resist flow processing. As a result, as shown in FIG. 5, the hardened resist (insulating layer) 13 a does not adhere to and peel off from the magnetic layer serving as the bottom 12 a of the lower yoke 12. Next, in order to form a coil by electroplating, a Cu base film 13b is formed by sputtering. Here, after this sputtering, in order to improve adhesion, a Cr (or Ti) film (for example, a thickness of 0.03 μm) is formed, and then a Cu film (for example, a thickness of 0.01 to 0.3 μm) is formed. It is desirable to form. In this case, when a positive resist is used and slopes are formed at the corners by the flow during heating, the Cu thin film can be continuously applied during the sputtering of the Cu base film 13b. The film may be formed by vapor deposition or electroless plating instead of sputtering.

  Next, a resist similar to that described above is applied to the entire surface. In this case as well, in the case of the positive type, it is desirable to use, for example, OFPR800 manufactured by Tokyo Ohka Co., Ltd. Next, the resist is exposed by irradiating ultraviolet rays through a photomask on which a predetermined pattern is formed. Next, the resist 13c is patterned into a predetermined coil shape by dipping in a developing solution (when the above-mentioned OFPR800 is used as a resist, DE-6 manufactured by Tokyo Ohka Co., Ltd. is preferably used). As the resist, either a positive type or a negative type may be used.

  Next, Cu micro-plating is performed on the Cu base film 13b to form a Cu coil 13 and a coil lead portion 13d on the Cu base film 13b as shown in FIG. Next, the resist 13c is removed and the surface is cleaned. Also in this case, a method of dissolving the resist with an alkali or an organic solvent and removing it in a liquid phase, or an ashing method of removing in a gas phase using plasma is used. Next, the Cu base film 13b exposed on the surface is removed by ion milling that irradiates the entire surface with accelerated ions.

  Next, as shown in FIG. 7, a yoke forming resist 12e for forming the cylindrical portion 12b, the columnar portion 12c and the lead portion 12d of the lower yoke 12 is applied to the entire surface. In this case as well, in the case of the positive type, it is desirable to use, for example, OFPR800 manufactured by Tokyo Ohka Co., Ltd. Next, the resist 12e is exposed by irradiating ultraviolet rays through a photomask on which a predetermined yoke pattern is formed. Next, the resist 12e is patterned so as to have a predetermined yoke shape by dipping in a developing solution (when the above-mentioned OFPR800 is used as a resist, DE-6 manufactured by Tokyo Ohka Co., Ltd. is preferably used). . As the resist, either a positive type or a negative type may be used.

  Next, on the magnetic body forming the bottom 12a of the lower yoke 12, a magnetic body that forms the cylindrical portion 12b, the column portion 12c, and the lead portion 12d of the yoke is formed by electroplating. In this case, the same magnetic material as in the case of the bottom portion 12a, that is, an alloy mainly composed of Ni, Fe, Co or the like having a relative permeability of 1000 or more, for example, a 20% Fe80% Ni alloy (Permalloy) is used. desirable. Next, the resist 12e is removed and the surface is cleaned. Also in this case, a method of dissolving the resist with an alkali or an organic solvent and removing it in a liquid phase, or an ashing method of removing in a gas phase using plasma is used.

  Next, as shown in FIG. 8, an insulating resist for forming an insulating layer 13e between the Cu coils 13 is applied to the entire surface. In this case, the applied insulating resist is heated and cured at 150 to 230 ° C. so that the insulating layer 13e is in close contact with the resist (insulating layer) 13a. After that, the portion of the magnetic body that becomes the cylindrical portion 12b, the cylindrical portion 12c, and the lead portion 12d and the portion that protrudes from the surface of the substrate 11 of the resist that becomes the insulating layer 13e are polished with a lapping machine or the like, and protruded from the surface of the substrate 11 The portion is removed so that the entire surface is the same as the surface of the substrate 11.

  Next, as shown in FIG. 9, a Cu film to be the sacrificial film 14a is formed on the entire surface by sputtering. In this case, sputtering is performed so that the thickness of the Cu film becomes 3 μm. The sacrificial film 14a is not limited to Cu as long as it can be removed later by etching, but sputtering or vapor deposition of a metal thin film such as Sn or Si thin film, metal plating, or spin coating such as resin is preferable. It is desirable to form the film so that its thickness is 0.5 to 50 μm.

  Next, a sacrificial film forming resist 14b for forming a pattern of the sacrificial film 14a is applied to the entire surface. In this case as well, in the case of the positive type, it is desirable to use, for example, OFPR800 manufactured by Tokyo Ohka Co., Ltd. Next, the resist 14b is exposed by irradiating ultraviolet rays through a photomask on which a predetermined pattern is formed. Next, the sacrificial film 14a is formed in a predetermined shape by dipping in a developer (DE-6 manufactured by Tokyo Ohka Kogyo Co., Ltd. is preferably used when the above-mentioned OFPR800 is used as a resist). As shown, the resist 14b is patterned into a predetermined shape. As the resist, either a positive type or a negative type may be used.

  Next, the extra sacrificial film 14a is removed by etching using the resist 14b as a mask. Here, as the etching, ion milling, etching with plasma in a gas phase, dissolution etching with an etchant in a liquid phase, and the like can be applied. When the sacrificial film 14a is Si, RIE (Reactive Ion Etching) method using reactive plasma, milling method using non-reactive acceleration ions, liquid phase etching that dissolves Si with potassium hydroxide (KOH). Laws can also be used. In the case where the sacrificial film 14a is made of a metal other than Cu, etching is performed using an etchant that can dissolve the metal. Further, when the sacrificial film 14a is a resin, a method of dissolving the resin with a solvent or a method of hydrolyzing with an alkali or the like can be applied.

  Next, the resist 14b is removed and the surface is cleaned. Also in this case, a method of dissolving the resist with an alkali or an organic solvent and removing it in a liquid phase, or an ashing method of removing in a gas phase using plasma is used. Next, as shown in FIG. 11, a magnetic layer to be the upper yoke 14 is formed. In this case, an alloy mainly composed of Ni, Fe, Co or the like having a relative magnetic permeability of 1000 or more, for example, a 20% Fe80% Ni alloy (Permalloy) is formed by sputtering so as to have a thickness of 0.1 to 3 μm. To do. An amorphous magnetic material such as CoZrNi or CoTa, or an iron-based soft magnetic material such as FeAl, FeSiAl, or FeSi may be used. In addition to sputtering, the film may be formed by vapor deposition or electroless plating.

Next, on the upper yoke (magnetic layer) 14 formed as described above, the density for similarly forming the diaphragm 15 is 5 g / cm ³ or less, and the light weight and rigidity is Young's modulus of 7000 Kg / mm ² or more. A thin film made of a material (in this case, an aluminum film) is formed by sputtering. In addition to aluminum, Ti, Be, C, B, Mg alone or their alloys, SiO ₂ , Al, other than aluminum, are light weight and highly rigid materials having a density of 5 g / cm ³ or less and a Young's modulus of 7000 Kg / mm ² or more. Oxides such as ₂ O ₃ , carbides such as TiC and SiC, and nitrides such as AlN and TiN may be used. In addition to sputtering, the film may be formed by vapor deposition or electroless plating.

  Next, a diaphragm forming resist for forming the pattern of the diaphragm 15 is applied to the entire surface. In this case as well, in the case of the positive type, it is desirable to use, for example, OFPR800 manufactured by Tokyo Ohka Co., Ltd. Next, after exposing the resist by irradiating ultraviolet rays through a photomask on which a predetermined pattern is formed, a developer (when the above-mentioned OFPR800 is used as a resist, DE-6 manufactured by Tokyo Ohka Co., Ltd.) is used. The resist is patterned into a predetermined shape of the diaphragm 15 by immersing in a preferable manner. As the resist, either a positive type or a negative type may be used.

  Next, using the resist as a mask, the unnecessary portions other than the magnetic layer to be the upper yoke 14 and the aluminum film to be the vibration plate 15 are removed by etching by ion milling. In this case, as shown in FIG. 12, the magnetic layer and the aluminum film not covered with the resist are removed, and the magnetic layer serving as the upper yoke 14 and the aluminum film serving as the vibration plate 15 covered with the resist remain. It becomes. Next, the resist is removed and the surface is cleaned. Also in this case, a method of dissolving the resist with an alkali or an organic solvent and removing it in a liquid phase, or an ashing method of removing in a gas phase using plasma is used.

  Next, the sacrificial film 14a formed under the diaphragm (aluminum film) 15 and the upper yoke (magnetic layer) 14 is removed. In this case, an etchant enters from a part of the diaphragm (aluminum film) 15 and the upper yoke (magnetic layer) 14 or a hole (intrusion port) (not shown) previously formed in the substrate 11, and the sacrificial film 14a is dissolved and etched. Is used. When the sacrificial film 14a is Si, a liquid phase etching method in which Si is dissolved with KOH is used. If the sacrificial film 14a is made of another metal, etching is performed using an etchant that dissolves the metal. Further, when the sacrificial film 14a is a resin, a method of dissolving with a solvent or hydrolyzing with an alkali or the like is employed.

  Note that the number of entrances for the etchant is not limited to one, and it can be provided at a plurality of locations to facilitate entry of the etchant. You can also use ultrasonics to increase the rate of etchant penetration and renewal. Here, the entrance releases the back pressure of the diaphragm 15, and when the diaphragm 15 is vibrated by air vibration from the upper surface, the vibration of the diaphragm 15 is suppressed by the back pressure in the closed space. This is preferable because it acts to prevent the above.

  Next, the lead portion 12d extending outward from the cylindrical portion 12b of the lower yoke 12 is connected to one end portion of a capacitor (capacitor) (not shown), and the other end portion of the capacitor (capacitor) is connected outwardly from the thin film coil 13. The lead portion 13d extending to is connected. As a result, the microphone 10 of the first embodiment shown in FIG. 1 is formed. The capacitor (capacitor) may be formed in the substrate 11 in advance, or may be formed in another part of the same substrate at the same time when the upper and lower yokes 14 and 12 and the thin film coil 13 are formed. Good. In addition, it is desirable to use a substrate in which a signal processing circuit made of LSI is formed in advance in the substrate and pads are formed in advance so as to extend from the signal processing circuit and be exposed.

2. Second Embodiment A microphone 20 according to a second embodiment of the present invention is shown in FIG. 13 (note that FIG. 13A is a plan view schematically showing a state where the inside is seen through, and FIG. A lower yoke (core) 22 made of a magnetic material formed on the substrate 21, a thin film coil 23 formed so as to be surrounded by the lower yoke 22, as shown in FIG. A capacitor metal film 24 disposed on the lower yoke 22, an upper yoke 25 composed of a magnetic layer disposed on the capacitor metal film 24 via a gap composed of an air layer, and the upper yoke 25 The diaphragm 26 is disposed above and is formed integrally with the upper yoke 25. In this case, the inductor L is formed by the lower yoke 22, the thin film coil 23 and the upper yoke 25, and the capacitor C is formed by the capacitor metal film 24 and the upper yoke 25.

Here, as in the first embodiment, the substrate 21 is a silicon (Si) substrate, a ceramic substrate such as alumina (Al ₂ O ₃ ) or zirconia (ZrO ₂ ), a glass substrate, a resin substrate, or a metal substrate. Etc. can be used. When a substrate such as Si or GaAs is used, it is desirable to use a substrate in which a signal processing circuit is formed in advance in the substrate 21 as an LSI. Further, as a material of the lower yoke (core) 22, it is desirable to use an FeNi alloy (permalloy: 20% Fe-80% Ni alloy) having a relative magnetic permeability of 1000 or more. In this case, the lower yoke 22 includes a disk-shaped bottom portion 22a, a cylindrical portion 22b protruding from the periphery of the bottom portion 22a, a columnar portion 22c protruding from the center portion of the bottom portion 22a, and a lead portion 22d. Yes. A cutout portion is formed in a part of the cylindrical portion 22b, and a lead portion 22d extends outward from the cutout portion.

  The thin film coil 23 is made of a copper (Cu) plating layer having a width of 1 to 10 μm and a thickness of 1 to 10 μm, and a cylindrical portion 22 c is formed in the cylindrical portion 22 b on the disc-shaped bottom portion 22 a of the lower yoke 22. It is wound a predetermined number N around the center. One end portion of the thin film coil 23 is connected to the cylindrical portion 22c of the lower yoke 22, and the other end portion of the thin film coil 23 extends outward to form a coil lead portion 23d. In this case, the thin film coil 23 may be a single stage or a plurality of stages of two or more stages. The capacitor metal film 24 is formed of a metal thin film (thickness: 0.05 to 10 μm) made of Cr, Ti, Au, Pt or the like. The upper yoke 25 is preferably made of an FeNi alloy (permalloy: 20% Fe-80% Ni alloy) having a thickness of 0.1 to 3 μm and a relative permeability of 1000 or more similar to the material of the lower yoke 22. In this case, an amorphous magnetic material such as CoZrNi or CoTa may be used.

The diaphragm 26 is formed of a thin film made of a light and highly rigid material having a density of 5 g / cm ³ or less and a Young's modulus of 7000 Kg / mm ² or more. Light, high-rigidity materials having a density of 5 g / cm ³ or less and a Young's modulus of 7000 Kg / mm ² or more include Al, Ti, Be, C, B, Mg alone or their alloys, SiO ₂ , Al ₂ O. Oxides such as ₃ , carbides such as TiC and SiC, and nitrides such as AlN and TiN are used. In this case, the upper yoke 25 has a gap (air gap) of only lg (in this case, preferably 0.5 μm ≦ lg ≦ 50 μm) above the cylindrical portion 22 b and the column portion c of the lower yoke 22. Are arranged to form. Thus, when sound pressure is applied to the diaphragm 26, the diaphragm 26 vibrates at a predetermined resonance frequency.

  In the microphone 20 of the second embodiment, the coil lead portion 23d extending outward from the thin film coil 23 → the thin film coil coil 23 → the cylindrical portion 22c of the lower yoke 22 → the capacitor metal film 24 → the upper yoke 25 → The diaphragm 26 is electrically connected through a path 22 d of the lower yoke 22. For this reason, a capacitor (capacitor) formed of the capacitor metal film 24 and the upper yoke 25 is connected in series to the inductor formed of the lower yoke 22, the thin film coil 23, and the upper yoke 25. In this case, not only the series connection but also the inductor (L) and the capacitor (C) may be connected in parallel.

Next, the oscillation frequency of the microphone 20 configured as described above and the rate of change (sensitivity) thereof are obtained as follows. Here, as shown in FIG. 14, the number of turns of the thin film coil 23 is N (times), the magnetic path resistance is Rm, and the core length (the total length of the closed magnetic circuit formed by the upper and lower yokes 25 and 22) is lc. , Sc is the cross-sectional area of the core (cross-sectional area of the upper and lower yokes 25 and 22), μc is the magnetic permeability of the core (permeability of the upper and lower yokes 25 and 22), and the gap length is from the upper end of the cylindrical portion 22c to the upper yoke. Lg), the gap cross-sectional area is Sg, the air permeability is μ _{0, and} the area of _the diaphragm 26 (the area facing the capacitor metal film 24) is Sp.

In this case, the inductance L of the magnetic circuit of FIG. 14 is L = N ² μ ₀ Sg / lg, as in the first embodiment described above. On the other hand, the capacitance C is C = ε ₀ Sp / lg. Therefore, the oscillation frequency f of the magnetic circuit of FIG. 14 is expressed by the following equation (4).

Here, when the oscillation frequency f is differentiated by lg, the following equation (5) is obtained.

From the above equation (5), when the change (sensitivity) of the oscillation frequency due to the displacement of the upper yoke 25 formed integrally with the diaphragm 26 is obtained as (df / dlg) / f, the following equation (6) is obtained. .

  The above equation (6) represents the following. That is, (1) the sensitivity (change rate of oscillation frequency) of the microphone 20 depends only on the gap length lg. (2) In order to increase the sensitivity (change rate of oscillation frequency) of the microphone 20, the gap length lg is decreased. (3) The sensitivity (change rate of oscillation frequency) of the microphone 20 does not depend on the area of the upper yoke 25 formed integrally with the diaphragm 26 and the number of coil turns (N times) of the thin film coil 23, and is suitable for downsizing. ing.

  Next, a method for manufacturing the microphone 20 according to the second embodiment having the above-described configuration will be described in detail below with reference to FIGS. First, a substrate 21 such as Si or GaAs is prepared, and a resist is applied to the entire surface of the substrate 21. In this case, either a positive type or a negative type may be used as the resist, but in the case of a positive type, for example, it is desirable to use OFPR800 manufactured by Tokyo Ohka Co., Ltd. or the like. Next, the resist is exposed by irradiating ultraviolet rays through a photomask on which a predetermined pattern is formed. In addition to ultraviolet rays, the resist may be exposed by irradiation with electron beams or X-rays.

  Next, the resist is patterned into a predetermined shape by dipping in a developer (when the above-mentioned OFPR800 is used as a resist, DE-6 manufactured by Tokyo Ohka Co., Ltd. is preferably used). Here, when the resist is a positive type, the exposed portion is dissolved and removed in alkali, and the unexposed portion remains. Next, as shown in FIG. 15, etching was performed using the remaining resist 21 a as a mask to form a recess 21 b having a depth of 5 to 50 μm in the substrate 21. In this case, as the etching, a plasma etching method in a gas phase or a solution etching method using an etchant (etching solution) in a liquid layer can be applied.

Next, the resist is removed and the surface is cleaned. In this case, a method of dissolving the resist with an alkali or an organic solvent and removing it in a liquid phase, or an ashing method of removing in a gas phase using plasma can be applied. In the case of using a Si substrate, it is necessary to obtain an insulating surface in advance by oxidizing this surface or depositing (depositing) an insulating film such as SiO ₂ or Al ₂ O _3. There is.

  Next, in order to form the magnetic material by electroplating, a plating base film 21c having a film thickness of 0.1 to 0.3 μm is formed. Here, a 20% Fe80% Ni alloy (permalloy) was formed as a plating base film 21c by sputtering. In this case, in addition to the 20% Fe80% Ni alloy (Permalloy), a metal containing Ni, Fe, Co, or an alloy thereof may be used. In addition to sputtering, the film may be formed by vapor deposition or electroless plating.

  Next, a resist 21d similar to that described above is applied to the entire surface. Also in this case, for example, it is desirable to use OFPR800 manufactured by Tokyo Ohka Co., Ltd. Next, the applied resist is exposed to ultraviolet rays through a photomask having a predetermined pattern formed thereon. In addition to ultraviolet rays, the resist may be exposed by irradiation with electron beams or X-rays. Next, the resist 21d is patterned into a predetermined shape by dipping in a developer (when the above-mentioned OFPR800 is used as a resist, DE-6 manufactured by Tokyo Ohka Co., Ltd. is preferably used).

  Subsequently, a magnetic material is electroplated on the plating base film 21c to form a magnetic material layer that becomes the bottom portion 22a and the lead portion 22d of the yoke. In this case, the magnetic body is preferably an alloy mainly composed of Ni, Fe, Co or the like having a relative permeability of 1000 or more, for example, 20% Fe80% Ni alloy (permalloy). And it is desirable to form into a film so that a film thickness may be set to 2-10 micrometers. As a result, as shown in FIG. 16, a magnetic layer serving as the bottom portion 22a and the lead portion 22d of the lower yoke is formed on the plating base film 21c. Next, the resist 21d is removed and the surface is cleaned. Also in this case, a method of dissolving the resist with an alkali or an organic solvent and removing it in a liquid phase, or an ashing method of removing in a gas phase using plasma is used.

  Next, the exposed plating base film 21c is removed by ion milling that irradiates the surface with accelerated ions. In this case, a liquid phase etching method in which metal is dissolved may be used instead of ion milling. Next, as shown in FIG. 17, a resist to be the insulating layer 23a is applied to the entire surface. Also in this case, for example, it is desirable to use OFPR800 manufactured by Tokyo Ohka Co., Ltd. Next, the resist is exposed by irradiating ultraviolet rays through a photomask on which a predetermined pattern is formed. Next, the resist is patterned into a predetermined shape by dipping in a developer (when the above-mentioned OFPR800 is used as a resist, DE-6 manufactured by Tokyo Ohka Co., Ltd. is preferably used). Note that either a positive type or a negative type resist may be used as the insulating layer 23a. However, in the case of the positive type, since a slope is likely to be formed at the corners by flowing during heating in a later process, It is desirable to use a type resist.

  Subsequently, the resist to be the insulating layer 23a patterned by development is heated to 150 to 230 ° C. to perform a resist flow process. As a result, the hardened resist does not adhere to and peel off from the magnetic layer serving as the bottom 22a of the lower yoke 22. Next, in order to form the coil by electroplating, a Cu base film (not shown) is formed by sputtering. Here, after this sputtering, in order to improve adhesion, a Cr (or Ti) film (for example, a thickness of 0.03 μm) is formed, and then a Cu film (for example, a thickness of 0.01 to 0.3 μm) is formed. It is desirable to form. In this case, if a positive resist is used and slopes are formed at the corners by the resist flow during heating, the Cu thin film can be continuously deposited during sputtering of the Cu underlayer. The film may be formed by vapor deposition or electroless plating instead of sputtering.

  Next, a resist 23b similar to that described above is applied to the entire surface. In this case as well, in the case of the positive type, it is desirable to use, for example, OFPR800 manufactured by Tokyo Ohka Co., Ltd. Next, the resist 23b is exposed by irradiating ultraviolet rays through a photomask on which a predetermined pattern is formed. Next, the resist 23b is patterned into a predetermined coil shape by dipping in a developing solution (when the above-mentioned OFPR800 is used as a resist, DE-6 manufactured by Tokyo Ohka Co., Ltd. is preferably used). As the resist, either a positive type or a negative type may be used.

  Next, Cu micro-plating is performed on the Cu plating base film to form a Cu coil 23 and a coil lead portion 23d on the Cu base film as shown in FIG. In this case, micro plating was performed so that the film thickness of the Cu coil 23 was 1 to 10 μm. Next, the resist 23b is removed and the surface thereof is cleaned. Also in this case, a method of dissolving the resist with an alkali or an organic solvent and removing it in a liquid phase, or an ashing method of removing in a gas phase using plasma is used. Next, the exposed plating base film is removed by ion milling that irradiates the surface with accelerated ions.

  Next, a lower yoke forming resist 23c for forming the cylindrical portion 22b, the columnar portion 22c and the lead portion 22d of the lower yoke 22 is applied to the entire surface. In this case as well, in the case of the positive type, it is desirable to use, for example, OFPR800 manufactured by Tokyo Ohka Co., Ltd. Next, the resist 23c is exposed by irradiating ultraviolet rays through a photomask having a predetermined lower yoke pattern. Next, it is immersed in a developer (when the above-mentioned OFPR800 is used as a resist, DE-6 manufactured by Tokyo Ohka Kogyo Co., Ltd. is preferably used), and as shown in FIG. Patterning into the shape of the yoke 22. As the resist, either a positive type or a negative type may be used.

  Next, the magnetic body is electroplated on the magnetic body forming the bottom portion 22a of the lower yoke 22 to form the cylindrical portion 22b, the cylindrical portion 22c, and the lead portion 22d of the lower yoke 22. In this case, the same magnetic material as in the case of the bottom 22a, that is, an alloy mainly composed of Ni, Fe, Co or the like having a relative permeability of 1000 or more, for example, a 20% Fe80% Ni alloy (permalloy) is used. desirable.

  Next, as shown in FIG. 20, the resist 23c is removed and the surface thereof is cleaned. Also in this case, a method of dissolving the resist with an alkali or an organic solvent and removing it in a liquid phase, or an ashing method of removing in a gas phase using plasma is used. Next, in order to form the insulating layer 23e between the Cu coils 23, as shown in FIG. 21, a resist for forming the insulating layer 23e is applied over the entire surface. In this case, the resist for forming the applied insulating layer 23e is heated and cured at 150 to 230 ° C. so that the insulating layer 23e is in close contact with the insulating layer (resist) 23a. Thereafter, the surface of the lower yoke 22 that protrudes from the surface of the substrate 21 of the magnetic body or insulating layer (resist) 23e, which becomes the cylindrical portion 22b, the cylindrical portion 22c, and the lead portion 22d, is polished with a lapping machine or the like. The protruding portion is removed so that the entire surface is the same as the surface of the substrate 21 as shown in FIG.

  Next, a capacitor metal film 24 made of Ti is formed on the entire surface by sputtering. In this case, sputtering is performed so that the thickness of the Ti film becomes 1 μm. In addition to Ti, a conductive material such as Cr, Au, Pt is used as a material for the capacitor metal film 24, and it is formed by sputtering, vapor deposition, or plating so that the film thickness becomes 0.05 to 10 μm. It is desirable to film. Thereafter, a resist is applied and patterned to have a predetermined shape of the capacitor metal film 24. Next, the capacitor metal film is etched into a predetermined shape of the capacitor metal film 24 by ion etching using the resist as a mask. Thereby, as shown in FIG. 23, the capacitor metal film 24 is formed on the Cu coil 23 layer. In this case, the capacitor metal film 24 is electrically connected to the cylindrical portion 22 c of the lower yoke 22.

  Next, as shown in FIG. 24, a Cu film to be a sacrificial film 24a is formed on the entire surface by sputtering. In this case, sputtering is performed so that the thickness of the Cu film becomes 3 μm. The sacrificial film 24a is not limited to Cu as long as it can be removed later by etching, but sputtering or vapor deposition of a metal thin film such as Sn or Si thin film, metal plating, spin coating such as resin, etc. is preferable. It is desirable to form the film so that its thickness is 0.5 to 50 μm.

  Next, a sacrificial film forming resist for forming a pattern of the sacrificial film 24a is applied to the entire surface. In this case as well, in the case of the positive type, it is desirable to use, for example, OFPR800 manufactured by Tokyo Ohka Co., Ltd. Next, the resist is exposed by irradiating ultraviolet rays through a photomask on which a predetermined pattern is formed. Subsequently, the resist is patterned into a predetermined sacrificial film 24a by dipping in a developer (when the above-mentioned OFPR800 is used as a resist, DE-6 manufactured by Tokyo Ohka Co., Ltd. is preferably used). As the resist, either a positive type or a negative type may be used. Next, the extra sacrificial film 24a is removed by etching using the resist as a mask. Here, as the etching, ion milling, etching with plasma in a gas phase, dissolution etching with an etchant in a liquid phase, and the like can be applied.

  When the sacrificial film 24a is Si, RIE (Reactive Ion Etching) method using reactive plasma, milling method using non-reactive acceleration ions, liquid phase etching that dissolves Si with potassium hydroxide (KOH). Laws can also be used. When the sacrificial film 24a is made of a metal other than Cu, chemical etching is performed using an etchant that can dissolve the metal. Furthermore, when the sacrificial film 24a is a resin, a method of dissolving the resin with a solvent or a method of hydrolyzing with an alkali or the like can be applied. Next, the resist is removed and the surface is cleaned. Also in this case, a method of dissolving the resist with an alkali or an organic solvent and removing it in a liquid phase, or an ashing method of removing in a gas phase using plasma is used.

  Next, as shown in FIG. 25, a magnetic layer to be the upper yoke 25 is formed. In this case, an alloy mainly composed of Ni, Fe, Co or the like having a relative magnetic permeability of 1000 or more, for example, a 20% Fe80% Ni alloy (Permalloy) is formed by sputtering so as to have a thickness of 0.1 to 3 μm. To do. An amorphous magnetic material such as CoZrNi or CoTa, or an iron-based soft magnetic material such as FeAl, FeSiAl, or FeSi may be used. In addition to sputtering, the film may be formed by vapor deposition or electroless plating.

Next, as shown in FIG. 26, on the upper yoke 25 made of the magnetic layer formed as described above, the density for forming the diaphragm 26 is 5 g / cm ³ or less and the Young's modulus is 7000 Kg / mm ^2. A thin film (in this case, an aluminum film) made of the above light and high rigidity material is formed by sputtering. In addition to aluminum (Al), Ti, Be, C, B, Mg alone or their alloys, SiO, as a lightweight and highly rigid material having a density of 5 g / cm ³ or less and a Young's modulus of 7000 Kg / mm ² or more, SiO 2 ₂ , oxides such as Al ₂ O ₃ , carbides such as TiC and SiC, and nitrides such as AlN and TiN may be used. In addition to sputtering, the film may be formed by vapor deposition or electroless plating.

  Next, a diaphragm forming resist 27 for forming the pattern of the diaphragm 26 is applied to the entire surface. In this case as well, in the case of the positive type, it is desirable to use, for example, OFPR800 manufactured by Tokyo Ohka Co., Ltd. Next, after exposing the resist 27 by irradiating ultraviolet rays through a photomask having a predetermined pattern formed thereon, a developer (when the above-mentioned OFPR800 is used as the resist, DE-6 manufactured by Tokyo Ohka Co., Ltd.) The resist 27 is patterned into a predetermined shape of the diaphragm 26 as shown in FIG. As the resist 27, either a positive type or a negative type may be used.

  Next, the excess portion of the diaphragm 26 is removed by etching by ion milling using the resist 27 as a mask. Next, the resist 27 is removed and the surface is cleaned. Also in this case, a method of dissolving the resist with an alkali or an organic solvent and removing it in a liquid phase, or an ashing method of removing in a gas phase using plasma is used.

  Next, as shown in FIG. 28, the sacrificial film 24a formed under the diaphragm 26 and the upper yoke 25 is removed. In this case, a method is often used in which an etchant enters through a part of the diaphragm 26 or a hole (intrusion port) (not shown) previously formed in the substrate 21 and the sacrificial film 24a is dissolved and etched. When the sacrificial film 24a is Si, a liquid phase etching method in which Si is dissolved with KOH is used. If the sacrificial film 24a is made of another metal, etching is performed using an etchant that dissolves the metal. Further, when the sacrificial film 24a is a resin, a method of dissolving with a solvent or hydrolyzing with an alkali or the like is employed.

Note that the number of entrances for the etchant is not limited to one, and it can be provided at a plurality of locations to facilitate entry of the etchant. You can also use ultrasonics to increase the rate of etchant penetration and renewal. Here, the entry port releases the back pressure of the diaphragm 26, and when the diaphragm 26 is vibrated by the air vibration from the upper surface, the vibration of the diaphragm 26 is suppressed by the back pressure of the closed space. This is preferable because it acts to prevent the above. Thereby, the microphone 20 of the second embodiment as shown in FIG. 13 is formed.
Also in the second embodiment, similarly to the first embodiment described above, a signal processing circuit made of LSI is formed in the substrate, and a pad is previously formed so as to extend from the signal processing circuit and be exposed. It is desirable to use a new substrate.

3. Modified Example (1) First Modified Example In the microphone 30 of the first modified example, FIG. 29 (FIG. 29A is a plan view schematically showing a state where the inside is watermarked, and FIG. ) Is a cross-sectional view showing the AA cross section), and a carved portion is formed in the central portion of the substrate 31, and a lower yoke 32 is formed in the carved portion. A vibration plate 35 that also serves as an upper yoke having a diameter larger than that of the lower yoke 32 is disposed above the lower yoke 32. A cylindrical holding member 36 is formed on the lower surface of the outer peripheral portion of the diaphragm 35. Thereby, the diaphragm 35 can be arranged in parallel to the surface of the substrate 31. The lower yoke 32 includes a bottom portion 32 a, a cylindrical portion 32 b, and a column portion 32 c, and a thin film coil 33 is formed in the lower yoke 32. The thin film coil 33 is formed on the insulating layer 33a, and the thin film coil 33 is insulated by the insulating layer 33b.

  In this case, the diaphragm 35 is supported or fixed to a cylindrical portion 32 c formed at the center of the lower yoke 32. A gap formed by an air layer with an interval of lg is formed between the diaphragm 35 and the cylindrical portion 32b formed on the outer peripheral portion of the lower yoke 32. Thereby, when the diaphragm 35 is displaced by the sound pressure, the distance between the diaphragm 35 serving also as the upper yoke and the cylindrical portion 32b of the lower yoke 32 is changed, so that the inductance of the magnetic path is changed.

(2) Second Modified Example In the microphone 40 of the second modified example, FIG. 30 (note that FIG. 30 (a) is a plan view schematically showing a state where the inside is watermarked, and FIG. As shown in the cross-sectional view of the AA cross section, a carved portion is formed in the center of the substrate 41, and a lower yoke 42 is formed in the carved portion. A vibration plate 45 also serving as an upper yoke having a diameter larger than that of the lower yoke 42 is disposed on the upper portion of the lower yoke 42. A cylindrical holding material 46 is formed on the lower surface of the outer peripheral portion of the diaphragm 45. Thereby, the diaphragm 45 can be arranged in parallel to the surface of the substrate 41. The lower yoke 42 includes a bottom portion 42 a, a cylindrical portion 42 b, and a column portion 42 c, and a thin film coil 43 is formed in the lower yoke 42. The thin film coil 43 is formed on the insulating layer 43a, and the thin film coil 43 is insulated by the insulating layer 43b.

  In this case, the diaphragm 45 is supported or fixed by a cylindrical holding member 46 formed on the lower surface of the outer peripheral portion thereof coming into contact with the surface of the substrate 41. A gap formed by an air layer having an interval of lg is formed between the diaphragm 45, the cylindrical portion 42b formed on the outer peripheral portion of the lower yoke 42, and the columnar portion 42c formed on the center portion thereof. It is made like that. Thus, when the diaphragm 45 is displaced by sound pressure, the distance between the diaphragm 45 serving also as the upper yoke, the cylindrical portion 42b formed on the outer peripheral portion of the lower yoke 42, and the column portion 42c formed at the center thereof. Simultaneously change, the rate of change in inductance of the magnetic path is twice that of the first modification described above.

(3) Third Modified Example In the microphone 50 of the third modified example, FIG. 31 (note that FIG. 31 (a) is a plan view schematically showing a state where the inside is watermarked, and FIG. As shown in the cross-sectional view of the AA cross section, a carved portion is formed in the center of the substrate 51, and a lower yoke 52 is formed in the carved portion. A diaphragm 55 having a diameter larger than that of the lower yoke 52 is disposed on the lower yoke 52. A cylindrical holding member 57 is formed on the lower surface of the outer peripheral portion of the diaphragm 55. Thereby, the diaphragm 55 can be arranged in parallel to the surface of the substrate 51. The lower yoke 52 includes a bottom portion 52a, a cylindrical portion 52b, and a column portion 52c, and a thin film coil 53 is formed in the lower yoke 52. The thin film coil 53 is formed on the insulating layer 53a, and the thin film coil 53 is insulated by the insulating layer 53b.

  In this case, the diaphragm 55 is made of a light and highly rigid material such as Be, B, C, Mg, Al, Ti. For this reason, the diaphragm 55 is provided with a soft magnetic material 56 serving as an upper core at a position facing the lower yoke 52 on the lower surface of the central portion. Thus, the cylindrical holding member 57 formed on the lower surface of the outer peripheral portion of the diaphragm 55 is supported or fixed by contacting the surface of the substrate 51. It should be noted that a light and highly rigid material (Be, B, C, Mg, Al, Ti, etc.) used as the diaphragm 55 can be formed by a method such as sputtering, vapor deposition, or plating.

  As described above, by using the light and rigid diaphragm 55 having a large area, it is possible to obtain a large amplitude response to the sound pressure. A magnetic path resistance can be lowered by attaching a sufficiently thick soft magnetic material 56 to a portion where a magnetic path is to be formed. As a result, the inductance of the main body element portion can be increased, and it is not buried in the floating inductance of other wiring portions.

(4) Fourth Modified Example In the microphone 60 of the fourth modified example, FIG. 32 (note that FIG. 32 (a) is a plan view schematically showing a state where the inside is watermarked, and FIG. As shown in the sectional view taken along the line AA, a plurality of sets of inductors are provided. In this case, three engraving portions are formed in the substrate 61, and the first lower yoke 62-1, the second lower yoke 62-2, and the third lower yoke 62-3 are respectively formed in these engraving portions. Is formed. The first lower yoke 62-1 includes a bottom portion (not shown), a cylindrical portion 62-1b, and a column portion 62-1c, and the second lower yoke 62-2 includes a bottom portion 62-2a, a cylindrical portion 62-2b, and the like. The third lower yoke 62-3 includes a column part 62-2c, and includes a bottom part (not shown), a cylindrical part 62-3b, and a column part 62-3c. Further, a first thin film coil 63-1 is formed in the first lower yoke 62-1 and a second thin film coil 63-2 is formed in the second lower yoke 62-2. A third thin film coil 63-3 is formed in the lower yoke 62-3. Each thin film coil is formed on an insulating layer 63-1a (not shown), 63-2a, 63-3a (not shown), and an insulating layer 63-1b (not shown) is provided between the coils. ), 63-2b, 63-3b (not shown).

  A single diaphragm 65 is disposed on the first lower yoke 62-1, the second lower yoke 62-2, and the third lower yoke 62-3 so as to cover them. Further, a first upper yoke (not shown) is provided at a position facing the first lower yoke 62-1, the second lower yoke 62-2, and the third lower yoke 62-3 on the lower surface of the diaphragm 65, A second upper yoke 64-2 and a third upper yoke (not shown) are formed. In this case, a cylindrical holding member 66 is formed on the lower surface of the outer peripheral portion of the diaphragm 65. As a result, a gap composed of an air layer with an interval of lg is formed between each lower yoke and each upper yoke.

  A pair of lead lines 67 and 68 are formed at the end of the microphone 60. The lead line 67 is connected to the outer peripheral end portion of the first thin film coil 63-1 via the wiring 67a, and the inner peripheral end portion of the first thin film coil 63-1 is the cylindrical portion 62 of the first lower yoke 62-1. -1c, and one end portion of the cylindrical portion 62-1b of the first lower yoke 62-1 is connected to the outer peripheral end portion of the second thin film coil 63-2 via the wiring 67b. On the other hand, the lead line 68 is connected to the outer peripheral end of the third thin film coil 63-3 via the wiring 68a, and the inner peripheral end of the third thin film coil 63-3 is a cylinder of the third lower yoke 62-3. Connected to the end 62-3c, one end of the cylindrical portion 62-3b of the third lower yoke 62-3 is connected to one end of the cylindrical portion 62-2b of the second lower yoke 62-2 via the wiring 68b. Yes.

  As a result, a magnetic circuit in which three inductors are connected in series is formed. For this reason, when the inductance of each inductor is L, an inductor having a large inductance of 3L in total can be configured, and it can be prevented from being buried in a floating inductance such as another wiring portion, and a highly sensitive microphone is formed. become able to. The material for the substrate, each yoke, and each thin film coil may be the same as that used when forming the microphones of the above-described embodiments.

(5) Fifth Modification In the microphone 70 of the fifth modification, FIG. 33 (note that FIG. 33 (a) is a plan view schematically showing a state in which the inside is watermarked, and FIG. 33 (b) is a plan view. As shown in the sectional view taken along the line AA, the substrate is provided with a plurality of through holes for releasing back pressure. Here, an engraved portion is formed in the central portion of the substrate 71, and a lower yoke 72 and a thin film coil 73 are formed in the engraved portion. The lower yoke 72 is composed of a bottom portion 72a, a cylindrical portion 72b, and a column portion 72c, and a thin film coil 73 is formed in the lower yoke 72. The thin film coil 73 is formed on the insulating layer 73a, and the thin film coil 73 is insulated by the insulating layer 73b.

  In this case, five through holes 77 for releasing the back pressure are formed so as to surround the periphery of the lower yoke 72 formed in the center of the substrate 71, and these through holes 77 for releasing the back pressure are covered. A diaphragm 75 is arranged as described above. An upper yoke 74 is formed at a position facing the lower yoke 72 on the lower surface of the diaphragm 75, and lg between the lower yoke 72 and the upper yoke 74 is formed on the lower surface of the outer peripheral portion of the diaphragm 75. A cylindrical holding member 76 is formed so as to form a gap made of an air layer.

The through-hole 77 for releasing the back pressure can be formed by a drilling method by machining such as a drill. However, when the material of the substrate 71 is Si, an etching method using a high density plasma of CF ₄ is applied. Is desirable. In addition, as the timing of drilling, a method of drilling holes in the middle of a series of processes, a method of drilling holes after the completion of all the processes, a substrate with holes previously prepared, and a sacrificial film embedded in these holes A method of etching and removing the sacrificial film after all the processes are completed can be applied. As described above, when the substrate 71 is provided with a plurality of through holes 77 for releasing back pressure, the back pressure of the diaphragm 75 is released by the through holes 77 when the diaphragm 75 is vibrated by air vibration. , It is possible to prevent the vibration of the diaphragm 75 from being suppressed by the back pressure in the closed space.

  In the above-described embodiment, an example in which a single-layer thin film coil is formed has been described. However, the thin-film coil used in the microphone of the present invention is not limited to one layer, and may be formed to have two or more layers. Good. In this case, two or more layers of thin film coils may be connected to each other at the center, and a pair of coil terminals may be formed from the outermost part of the thin film coil.

  Further, in the microphone of the present invention, the oscillation frequency generated by the LC resonance circuit changes, and the oscillation frequency is coupled to a signal processing circuit that detects the change in the oscillation frequency as FM modulation so that the oscillation frequency is superimposed on the oscillation frequency. Then, these signals may be taken out. Further, a wireless microphone can be formed by transmitting a radio wave having the oscillation frequency generated by the LC resonance circuit as a carrier wave.

  As described above, the microphone of the present invention is not limited to the microphone, but can be applied to a displacement meter, an acceleration sensor, a vibration pickup, and the like by utilizing the displacement of the diaphragm used in the microphone.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows typically the microphone of 1st Example of this invention, FIG. 1 (a) is a top view which shows the state through which the inside was watermarked, and FIG.1 (b) is the AA cross section. FIG. It is sectional drawing which shows the magnetic circuit of the microphone of FIG. 1 simplified. FIG. 3 is a diagram schematically showing a part of a process for manufacturing the microphone of FIG. 1, FIG. 3A is a plan view, and FIG. 3B is a cross-sectional view showing the AA cross section thereof. . FIG. 4 is a diagram schematically showing a part of a process for manufacturing the microphone of FIG. 1, FIG. 4 (a) is a plan view, and FIG. 4 (b) is a cross-sectional view showing the AA cross section. . FIG. 5 is a diagram schematically showing a part of a process for manufacturing the microphone of FIG. 1, FIG. 5 (a) is a plan view, and FIG. 5 (b) is a cross-sectional view showing the AA cross section. . FIGS. 6A and 6B are diagrams schematically showing a part of a process for manufacturing the microphone of FIG. 1, FIG. 6A is a plan view, and FIG. 6B is a cross-sectional view showing an AA cross section thereof. . FIG. 7 is a diagram schematically showing a part of a process for manufacturing the microphone of FIG. 1, FIG. 7A is a plan view, and FIG. 7B is a cross-sectional view showing the AA cross section. . FIG. 8 is a diagram schematically showing a part of a process for manufacturing the microphone of FIG. 1, FIG. 8A is a plan view schematically showing a state where the inside is watermarked, and FIG. It is sectional drawing which shows an AA cross section. FIG. 9 is a diagram schematically showing a part of a process for manufacturing the microphone of FIG. 1, FIG. 9A is a plan view schematically showing a state where the inside is watermarked, and FIG. It is sectional drawing which shows an AA cross section. FIG. 10 is a diagram schematically showing a part of a process for manufacturing the microphone of FIG. 1, FIG. 10A is a plan view schematically showing a state where the inside is watermarked, and FIG. It is sectional drawing which shows an AA cross section. FIG. 11 is a diagram schematically showing a part of a process for manufacturing the microphone of FIG. 1, FIG. 11A is a plan view schematically showing a state where the inside is watermarked, and FIG. It is sectional drawing which shows an AA cross section. FIG. 12 is a diagram schematically showing a part of a process for manufacturing the microphone of FIG. 1, FIG. 12A is a plan view schematically showing a state where the inside is watermarked, and FIG. It is sectional drawing which shows an AA cross section. It is a figure which shows typically the microphone of Example 2 of this invention, Fig.13 (a) is a top view which shows typically the state which watermarked the inside, FIG.13 (b) shows the AA cross section. FIG. 13C is a cross-sectional view showing the A-B cross section. It is sectional drawing which simplifies and shows the magnetic circuit of the microphone of FIG. FIG. 15 is a diagram schematically showing a part of a process for manufacturing the microphone of FIG. 13, FIG. 15 (a) is a plan view, and FIG. 15 (b) is a cross-sectional view showing the AA cross section thereof. . FIGS. 16A and 16B are diagrams schematically showing a part of a process for manufacturing the microphone of FIG. 13, FIG. 16A is a plan view, and FIG. 16B is a cross-sectional view showing the AA cross section. . It is a figure which shows typically a part of process for manufacturing the microphone of FIG. 13, Fig.17 (a) is a top view, FIG.17 (b) is sectional drawing which shows the AA cross section. . FIG. 18 is a diagram schematically showing a part of a process for manufacturing the microphone of FIG. 13, FIG. 18 (a) is a plan view, and FIG. 18 (b) is a cross-sectional view showing the AA cross section. . It is a figure which shows typically a part of process for manufacturing the microphone of FIG. 13, Fig.19 (a) is a top view which shows typically the state which watermarked the inside, FIG.19 (b) is the figure It is sectional drawing which shows an AA cross section. It is a figure which shows typically a part of process for manufacturing the microphone of FIG. 13, Fig.20 (a) is a top view which shows the state which watermarked the inside, FIG.20 (b) is the figure It is sectional drawing which shows an AA cross section. It is a figure which shows typically a part of process for manufacturing the microphone of FIG. 13, FIG.21 (a) is a top view which shows the state which watermarked the inside, FIG.21 (b) is the figure It is sectional drawing which shows an AA cross section. It is a figure which shows typically a part of process for manufacturing the microphone of FIG. 13, FIG.22 (a) is a top view which shows the state which watermarked the inside, FIG.22 (b) is the figure It is sectional drawing which shows an AA cross section. It is a figure which shows typically a part of process for manufacturing the microphone of FIG. 13, FIG.23 (a) is a top view which shows the state which watermarked the inside, FIG.23 (b) is the figure It is sectional drawing which shows an AA cross section. FIG. 24 is a diagram schematically illustrating a part of the process for manufacturing the microphone of FIG. 13, FIG. 24A is a plan view schematically illustrating a state in which the inside is watermarked, and FIG. It is sectional drawing which shows an AA cross section. It is a figure which shows typically a part of process for manufacturing the microphone of FIG. 13, FIG.25 (a) is a top view which shows the state which watermarked the inside, FIG.25 (b) is the figure It is sectional drawing which shows an AA cross section. It is a figure which shows typically a part of process for manufacturing the microphone of FIG. 13, Fig.26 (a) is a top view which shows typically the state which watermarked the inside, FIG.26 (b) is the figure It is sectional drawing which shows an AA cross section. It is a figure which shows typically a part of process for manufacturing the microphone of FIG. 13, Fig.27 (a) is a top view which shows the state which watermarked the inside, FIG.27 (b) is the figure It is sectional drawing which shows an AA cross section. FIG. 28 is a diagram schematically showing a part of the process for manufacturing the microphone of FIG. 13, FIG. 28A is a plan view schematically showing a state where the inside is watermarked, and FIG. It is sectional drawing which shows an AA cross section. It is a figure which shows typically the microphone of a 1st modification, Fig.29 (a) is a top view which shows the state which watermarked the inside, FIG.29 (b) is a cross section which shows the AA cross section FIG. It is a figure which shows typically the microphone of a 2nd modification, Fig.30 (a) is a top view which shows the state which watermarked the inside, FIG.30 (b) is a cross section which shows the AA cross section. FIG. It is a figure which shows typically the microphone of a 3rd modification, Fig.31 (a) is a top view which shows the state which watermarked the inside, FIG.31 (b) is the cross section which shows the AA cross section FIG. It is a figure which shows typically the microphone of a 4th modification, FIG. 32 (a) is a top view which shows the state which watermarked the inside, FIG.32 (b) is a cross section which shows the AA cross section. FIG. It is a figure which shows typically the microphone of a 5th modification, FIG.33 (a) is a top view which shows the state which watermarked the inside, FIG.33 (b) is a cross section which shows the AA cross section. FIG. It is a figure which shows typically the microphone of a prior art example. It is a figure which shows typically the microphone of another prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Microphone, 11 ... Board | substrate, 11a ... Resist, 11b ... Recessed part, 11c ... Plating base film, 12 ... Lower yoke, 12a ... Bottom part, 12b ... Cylindrical part, 12c ... Column part, 12d ... Lead part, 12e ... Yoke formation Resist, 13 ... Thin film coil, 13a ... Resist (insulating layer), 13b ... Cu base film, 13c ... Resist, 13d ... Coil lead, 13e ... Insulating layer, 14 ... Upper yoke (vibrating plate), 14a ... Sacrificial film , 14b... Sacrificial film forming resist, 15... Diaphragm (thin film made of lightweight high rigidity material), 20... Microphone, 21... Substrate, 21 a. ... Lower yoke, 22a ... Bottom, 22b ... Cylindrical part, 22c ... Column, 22d ... Coil lead part, 23 ... Thin film coil, 23a ... Insulating layer (resist ), 23b ... resist, 23c ... resist for forming yoke, 23d ... coil lead, 23e ... insulating layer (resist), 24 ... metal film for capacitor, 24a ... sacrificial film, 25 ... upper yoke, 26 ... vibrating plate, 27 Plate forming resist, 30 ... Microphone, 31 ... Substrate, 32 ... Lower yoke, 32a ... Bottom, 32b ... Cylindrical portion, 32c ... Column, 33 ... Thin film coil, 33a ... Insulating layer, 33b ... Insulating layer, 35 DESCRIPTION OF SYMBOLS ... Diaphragm, 36 ... Holding material, 40 ... Microphone, 41 ... Substrate, 42 ... Lower yoke, 42a ... Bottom part, 42b ... Cylindrical part, 42c ... Column part, 43 ... Thin film coil, 43a ... Insulating layer, 43b ... Insulating layer , 45 ... Diaphragm, 46 ... Holding material, 50 ... Microphone, 51 ... Substrate, 52 ... Lower yoke, 52a ... Bottom, 52b ... Cylindrical part, 52c ... Cylindrical part, 53 ... Thin film coil, 5 a ... insulating layer, 53b ... insulating layer, 55 ... diaphragm, 56 ... soft magnetic material, 57 ... holding material, 60 ... microphone, 61 ... substrate, 62-1 ... first lower yoke, 62-1b ... cylindrical part, 62-1c ... Cylindrical part, 62-2 ... Second lower yoke, 62-2a ... Bottom part, 62-2b ... Cylindrical part, 62-2c ... Cylindrical part, 62-3 ... Third lower yoke, 62-3b ... Cylinder Part, 62-3c ... cylindrical part, 63-1 ... first thin film coil, 63-2 ... second thin film coil, 63-3 ... third thin film coil, 64-2 ... second upper yoke, 65 ... diaphragm, 66 ... Holding material, 67 ... Lead line, 67a, 67b ... Wiring, 68 ... Lead line, 68a, 68b ... Wiring, 70 ... Microphone, 71 ... Substrate, 72 ... Lower yoke, 72a ... Bottom, 72b ... Cylindrical portion, 72c ... Cylinder part, 73 ... Thin film coil, 73a ... Insulating layer, 73b ... Edge layer, 74 ... upper yoke, 75 ... diaphragm, 76 ... holding material, 77 ... through hole

Claims (12)

A microphone with a diaphragm that responds to changes in sound pressure,
At least a part of the diaphragm is made of a magnetic material to become an upper yoke,
A lower yoke formed on a substrate at a position facing the upper yoke with an air layer, and a thin film coil formed in the lower yoke,
The upper yoke and the lower yoke serve as a magnetic path of magnetic flux generated in the thin film coil,
A thin film coil characterized in that when the diaphragm is displaced by an external sound pressure, the distance between the upper yoke and the lower yoke formed on the diaphragm is changed to change the inductance. Microphone equipped with. A microphone with a diaphragm that responds to changes in sound pressure,
The diaphragm has conductivity and becomes one electrode of a capacitor, and at least a part thereof is made of a magnetic material and becomes an upper yoke.
A lower yoke formed on a substrate facing the upper yoke via an air layer; and a thin film coil formed in the lower yoke, wherein the upper yoke and the lower yoke The magnetic path of the generated magnetic flux
A conductive plate that is opposed to one electrode of the capacitor via an air layer between the upper yoke and the lower yoke, and serves as the other electrode of the capacitor;
When the diaphragm is displaced by external sound pressure, both the distance between the upper yoke and the lower yoke formed on the diaphragm and the distance between one electrode and the other electrode of the capacitor change. A microphone with a thin film coil characterized in that both inductance and capacitance are changed.   A conductive plate that faces the one electrode of the capacitor and serves as the other electrode of the capacitor is disposed on an insulating layer on the upper surface of the thin film coil, and the capacitor and the thin film coil are conductively connected. A microphone comprising the thin film coil according to claim 2.   The lower yoke has three parts, a bottom portion disposed at the lower portion of the thin film coil, a cylindrical portion disposed at the outer peripheral portion of the thin film coil, and a columnar portion disposed at the center of the thin film coil. The microphone provided with the thin film coil according to any one of claims 1 to 3, wherein the microphone is formed.   The outer peripheral part of the diaphragm is fixed on the cylindrical part of the lower yoke arranged on the outer peripheral part of the thin film coil, and the center of the diaphragm is bent due to the fluctuation of the external sound pressure, 5. The microphone with a thin film coil according to claim 4, wherein a distance between the cylindrical portion of the lower yoke arranged at the center of the thin film coil is changed.   The central portion of the diaphragm is fixed to the cylindrical portion of the lower yoke disposed at the central portion of the thin film coil, and the outer periphery of the diaphragm is bent due to fluctuations in the external sound pressure. 5. The microphone having a thin film coil according to claim 4, wherein a distance between the cylindrical portion of the lower yoke disposed on an outer peripheral portion of the thin film coil is changed. The diaphragm serving as the upper yoke is formed to extend outward from the cylindrical portion of the lower yoke, and the outermost periphery of the diaphragm is supported or fixed.
When the diaphragm is displaced by an external sound pressure, both the distance between the diaphragm and the cylindrical portion of the lower yoke and the distance between the diaphragm and the cylindrical portion of the lower yoke fluctuate simultaneously. The microphone provided with the thin film coil according to claim 4, wherein: The diaphragm serving as the upper yoke is formed to extend outward from the cylindrical portion of the lower yoke, and the outermost periphery of the diaphragm is supported or fixed,
A soft magnetic body is provided at a portion where a magnetic path on the lower surface of the diaphragm facing the cylindrical portion of the lower yoke is to be formed;
When the diaphragm is displaced by an external sound pressure, both the distance between the diaphragm and the cylindrical portion of the lower yoke and the distance between the diaphragm and the cylindrical portion of the lower yoke fluctuate simultaneously. The microphone provided with the thin film coil according to claim 4, wherein:   9. The thin film coil according to claim 1, wherein the thin film coil is insulated from the lower yoke and between the thin film coils by an insulating layer in which a resist is cured. Microphone.   The magnetic body forming the upper yoke and the lower yoke is formed of any one metal selected from Ni, Fe and Co, or an alloy composed of two or more of these metals. A microphone comprising the thin film coil according to any one of claims 1 to 9.   2. The magnetic material according to claim 1, wherein the magnetic material is formed by any one of a vacuum film formation method such as vapor deposition and sputtering, a liquid phase film formation method such as electroplating and electroless plating, or a combination thereof. Item 11. A microphone provided with the thin-film coil according to any one of items 10. The diaphragm excluding the magnetic material may be a simple substance of Al, Ti, Be, Mg, Si, B, C, or a mixture thereof, or an oxide film, a nitride film, a carbide film of these metals, or a combination thereof. The microphone provided with the thin-film coil according to any one of claims 1 to 11, wherein the microphone is formed of a mixture of the following.

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