JP3974114B2 - Diaphragm integrated substrate, acoustoelectric transducer, acoustoelectric conversion system, and method for manufacturing diaphragm integrated substrate - Google Patents

Description

  The present invention relates to an acoustoelectric conversion element, and further relates to a diaphragm integrated base serving as an element of the acoustoelectric conversion element, an acoustoelectric conversion system using the acoustoelectric conversion element, and a method of manufacturing the acoustoelectric conversion element. .

  An acoustoelectric conversion element called an optical microphone is known as a microphone having a sharp directivity. Since the optical microphone does not require an element such as an electrode for blocking the arrival of sound waves such as electrodes on the back surface of the diaphragm, it has a feature that it cancels sound waves from the lateral direction and does not show sensitivity to sound waves from the lateral direction.

  In addition, microphone array technology that uses multiple condenser microphones to achieve unidirectionality by utilizing the delay sum, and pipes are added to a part of the originally sealed container, behind the diaphragm A method has also been proposed in which outside air is supplied and the sound wave from the front is delayed to reach the back of the diaphragm to give it a “speed-type” action and to make it “unidirectional” as a whole. Yes.

Furthermore, a vertical surface-emitting light emitting device having a substantially uniform light emission intensity distribution and a structure in which light receiving devices are arranged concentrically around the light emitting device are adopted, and outputs from a plurality of light receiving devices are used as differential signals. There has also been proposed an optical microphone that detects and outputs a difference (see Patent Document 1). In the invention described in Patent Document 1, the influence of the temperature change or drive current change of the light emitting element is reduced and a stable signal output is obtained as compared with the case of using a single light receiving element as an output signal. .
JP 2001-169394 A

  Conventional directional microphones are excellent for identifying a sound source only in a direction facing the diaphragm, but it is difficult to identify a sound source from a direction other than the direction facing the diaphragm. For this reason, in order to separate and collect sound sources in a sound field having a plurality of sound sources, a plurality of microphones corresponding to the respective sound sources are required, resulting in an enormous system and an increase in cost.

  The present invention relates to an acoustoelectric transducer capable of specifying a plurality of sound source directions with a single integrated substrate, a diaphragm integrated substrate serving as an element of the acoustoelectric transducer, and an acoustoelectric using the acoustoelectric transducer. It is an object of the present invention to provide a conversion system and a method for manufacturing the acoustoelectric conversion element.

  In order to achieve the above object, a first feature of the present invention is a diaphragm integrated base including a plurality of diaphragms each having a diffraction grating and vibrating by sound pressure. The gist of the invention is a diaphragm integrated substrate including a diaphragm whose surface is parallel to the main surface of the diaphragm integrated substrate and a diaphragm whose main surface is inclined with respect to the main surface of the diaphragm integrated substrate.

  The second feature of the present invention is (b) a plurality of diaphragms each having a diffraction grating, which vibrates due to sound pressure, and whose principal plane directions are different from each other; and (b) light is transmitted to each of the diffraction gratings. Acoustoelectric conversion comprising a plurality of light sources for irradiation and (c) a plurality of photodetectors for detecting and diffracting the light diffracted by the diffraction grating, respectively, and converting the displacements of the plurality of diaphragms into electric signals, respectively. The gist is that the element.

  The third feature of the present invention is (a) a plurality of diaphragms each having a diffraction grating, which are vibrated by sound pressure, and whose principal surfaces are different from each other, and (b) light is transmitted to each of the diffraction gratings. A plurality of light sources to be irradiated; (c) a plurality of photodetectors for detecting and diffracting light diffracted by the diffraction grating; and (d) time-series signals output by the plurality of photodetectors on the frequency axis. The gist of the present invention is an acoustoelectric conversion system that includes a Fourier transform unit that converts a signal into a signal, converts the displacement of a plurality of diaphragms into a spectrum for each of a plurality of corresponding sound sources, and identifies the plurality of sound sources.

The fourth feature of the present invention is (a) a fixed frame, a fixed beam connected to the fixed frame, a plurality of elastic beams having one end connected to the fixed frame, and fixed via the elastic beams. Forming a first diaphragm supported on the frame by a cantilever beam structure, and forming a second diaphragm supported on the fixed frame by a cantilever beam structure via the elastic beam; (b) first and second Forming a diffraction grating on the diaphragm, and
Forming a cavity at the bottom of each of the first and second diaphragms; and (c) bending the elastic beam connecting the second diaphragms by the weight of the second diaphragm, so that the main surface of the second diaphragm is And a method of manufacturing a diaphragm integrated base, comprising the step of attaching the end of the second diaphragm not supported by the elastic beam to a part of the substrate. To do.

  According to the present invention, an acoustoelectric transducer capable of specifying a plurality of sound source directions with one integrated substrate, a diaphragm integrated substrate serving as an element of the acoustoelectric transducer, and the acoustoelectric transducer are used. The acoustoelectric conversion system and a method for manufacturing the acoustoelectric conversion element can be provided.

  Next, first to third embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  The first to third embodiments described below exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention is the component parts. The material, shape, structure, arrangement, etc. are not specified below. The technical idea of the present invention can be variously modified within the scope of the claims.

(First embodiment)
As shown in FIG. 1, the diaphragm integrated base according to the first embodiment of the present invention has a plate-shaped integrated base in which _five diaphragms X _{1 to} X ₅ are arranged inside a fixed frame 11. Is configured. The periphery of the fixed frame 11 is supported by the support frame 10. Center of the diaphragm (first diaphragm) X ₅ has parallel main surface to the main surface of the vibration plate integrated substrate, connected to the rectangular frame-shaped anchor 13 by four elastic beams (springs) 23 a to 23 d Has been. Here, the “main surface of the diaphragm integrated base” is a surface parallel to the upper surface of the fixed frame 11 appearing in the bird's-eye view of FIG. The rectangular frame-shaped anchor 13 is fixed to the fixed frame 11 by four fixed beams 12a to 12d. In a broad sense, the anchor 13 is also a kind of fixed beam. The fixed beams 12a to 12d are ridge-shaped beams extending in the diagonal direction of the rectangular (square) fixed frame 11.

The diaphragms (second diaphragms) X ₁ , X ₂ , X ₃ , and X ₄ other than the central diaphragm (first diaphragm) X ₅ are respectively connected to the fixed beams 12 a to 12 d and the anchor 13. The diaphragms are connected to each other by two elastic beams (springs) 21a, 22b; 21b, 22c; 21c, 22d; 21d, 22a, and have a principal surface that is oblique to the principal surface of the diaphragm integrated base.

For example, as shown in FIG. 7, the fixed frame 11 includes a buried insulating film 42, a single crystal Si layer 43, and a protective film 44 that are sequentially deposited on a support substrate 41 made of single crystal Si. The anchor 13 and the fixed beams 12a to 12d are each composed of a buried insulating film 42, a single crystal Si layer 43, and a protective film 44. Similarly, the diaphragms X _{1 to} X ₅ have a laminated structure including the buried insulating film 42, the single crystal Si layer 43, and the protective film 44. Further, the elastic beams 23a to 23d; 21a, 22b; 21b, 22c; 21c, 22d; 21d, 22a are composed of a buried insulating film 42, a single crystal Si layer 43, and a protective film 44.

Although described later with reference to FIGS. 5 to 7, a cavity (cavity) Q ₁ is formed below the surrounding four diaphragms X ₁ , X ₂ , X ₃ , and X ₄ by using a semiconductor integrated circuit manufacturing process. , Q ₂ , Q ₃ , Q ₄ , the four diaphragms X ₁ , X ₂ , X ₃ , X ₄ are elastic beams (springs) 21a, 22b; 21b, 22c; 21c, 22d; Since only one end is supported by 22a, the end without elastic beams 21a, 22b; 21b, 22c; 21c, 22d; 21d, 22a descends by its own weight. At this time, sticking by intentional sticking (sticking) is generated between the lowered ends of the _four diaphragms X ₁ , X ₂ , X ₃ , and X ₄ and the inner wall surface of the fixed frame 11. Thus, diaphragms X ₁ , X ₂ , X ₃ , and X ₄ having a structure equivalent to a substantial both-end beam (pseudo both-end beam structure) are formed.

  The sticking phenomenon in which the movable part of the MEMS device becomes stuck (sticking) to the surrounding substrate or the like and does not move is considered as one of the major factors that limit the life of a general MEMS device. For example, in a micromirror array device, a phenomenon in which a tilted micromirror adheres to a landing surface due to some time signature and does not return is a problem as a sticking phenomenon. The cause of the sticking phenomenon is moisture in the cleaning process at the time of manufacturing the MEMS device, and it is said that when moisture entering between the substrate and the movable part dries, it attracts each other due to surface tension and the like, resulting in a sticking phenomenon. In particular, in most cases, the movable part once attached cannot be repaired due to the sticking phenomenon. In the diaphragm integrated substrate according to the first embodiment, the sticking phenomenon is positively used.

Since these four diaphragms X ₁ , X ₂ , X ₃ , and X ₄ have an oblique angle with respect to the main surface of the diaphragm integrated substrate, they are inclined with respect to the main surface of the diaphragm integrated substrate. Sensitive to directional sound waves. On the other hand, the central diaphragm X ₅ varies greatly with respect to the sound pressure from the sound source from the direction of the normal direction of the main surface of the diaphragm integrated base and exhibits sensitivity. Here, the number of the elastic beams 21a, 22b; 21b, 22c; 21c, 22d; 21d, 22a connected to the connecting portion between the fixed beams 12a to 12d and the anchor 13 can be varied at the design level, as shown in FIG. It is not limited to the two shown.

The transmission type diffraction grating provided on the diaphragms X _{1 to} X ₅ in FIG. 1 may be the two-dimensional diffraction grating shown in FIG. 2A or the one-dimensional diffraction grating shown in FIG. In FIG. 2A, a plurality of holes (through holes) H _i−1,1 ,..., H _{i, 1} , H ₁ arranged in a matrix in each of the vibration plates X _{1 to} X _{5. , 2} , H _1,3 ,..., H _{i + 2,6} shows an example of forming a two-dimensional diffraction grating. Further, in FIG. 2 (b), the diaphragm X ₁ to X _5, a plurality of through-grooves are periodically arranged _{(slit) G 1, G 2, G} 3, ·····, the G ₆ The example which comprises a one-dimensional diffraction grating is shown.

As shown in FIG. 3, the electroacoustic transducer according to the first embodiment of the present invention vibrates due to sound pressure and has five diaphragms X _{1 to} X ₅ whose main surfaces are different from each other, and vibrations. five light sources _LD 1 to Ld ₅ for applying light to the diffraction grating plate X ₁ to X _5, and five photodetectors _PD 1 -PD ₅ for converting an electric signal to detect the light diffracted by the diffraction grating A multidirectional identification optical microphone provided.

A fixed frame 11 that houses and fixes _five diaphragms X _{1 to} X ₅ whose main surfaces are different from each other is supported by the support frame 10, and between the housing upper side wall 31 a and the housing lower side wall 31 b. It is fixed. The five light sources LD _{1 to} LD ₅ are arranged on a case top plate 39 disposed at the upper end of the case upper side wall 31a. The housing top plate 39 includes an upper opening 37 into which a sound wave can be incident at the center, and the five light sources LD _{1 to} LD ₅ have different positions on the housing top plate 39 so as to surround the upper opening 37. Are two-dimensionally arranged. In the electroacoustic transducer according to the first embodiment shown in FIG. 3, the light irradiated from the light sources LD _{1 to} LD ₅ is respectively near the central portion of the main surface of the _five diaphragms X _{1 to} X _5. The optical axes of the light sources LD _{1 to} LD ₅ are adjusted so as to be incident. The adjustment of the optical axis can be set according to the mount angle of the light sources LD _{1 to} LD ₅ .

The five photodetectors PD _{1 to} PD ₅ are arranged on a housing bottom plate (mounting substrate) 32 disposed at the lower end of the housing lower side wall 31b. The housing bottom plate 32 includes a bottom opening 35 through which a sound wave can be incident at the center, and the five photodetectors PD _{1 to} PD ₅ are two-dimensional on the housing bottom plate 32 so as to surround the bottom opening 35. They are arranged in spatially different positions. In FIG. 3, the positions of the photodetectors PD _{1 to} PD ₅ are optically arranged so that light transmitted through the _five diaphragms X _{1 to} X ₅ enters the photodetectors PD _{1 to} PD ₅ , respectively. It has been adjusted. That is, the positions of the photo detectors PD _{1 to} PD ₅ are determined in consideration of the diffraction angle by the transmission type diffraction grating provided on the vibration plates X _{1 to} X ₅ . On the housing bottom plate 32, drive and control circuits 33a to 33d for _five light sources LD _{1 to} LD ₅ and five photodetectors PD _{1 to} PD ₅ are further arranged. Although not shown, the drive / control circuits 33 a to 33 d of the _five light sources LD _{1 to} LD ₅ may be separately arranged on the housing top plate 39.

An image sensor such as a photodiode array is preferably used for the photodetectors PD _{1 to} PD ₅ shown in FIG. That is, the photodetectors PD _{1 to} PD ₅ do not detect the difference in light intensity, but detect two-dimensional images of diffraction images, thereby detecting five diaphragms X ₁ to X 5 having different principal plane directions. the detection of displacement of the X _5. Therefore, the photodiode arrays PD _{1 to} PD ₅ have a sufficiently wide area for the diffracted light so that the diffraction images can be detected without omission.

In the electroacoustic transducer according to the first embodiment, since the transmissive diffraction gratings are formed on the _five diaphragms X _{1 to} X ₅ having different main surface directions, the five light sources LD are provided. _The light waves irradiated from _{1 to} LD ₅ are diffracted while passing through the corresponding diffraction gratings X _{1 to} X ₅ , respectively, to produce diffraction images on the surfaces of the _five photodiode arrays PD _{1 to} PD ₅ . Then, the displacement of the diaphragm X ₁ to X ₅ optically detected by a photodetector PD ₁ -PD ₅ as a diffraction image, further which, as in FIG. 4, is converted into an electric signal.

In the electroacoustic transducer according to the first embodiment shown in FIG. 3, in addition to the diaphragm (first diaphragm) X ₅ facing the main surface of the diaphragm integrated base, the same diaphragm is integrated. A plurality (four) of diaphragms (second diaphragms) X _{1 to} X ₄ having angles in various directions on the substrate are arranged, and corresponding light sources LD ₁ to LD ₅ and photodetectors PD _{1 to} PD ₅ are arranged. The vibration displacements of the diaphragms X _{1 to} X ₅ are individually detected by. In each of the photodetectors PD ₁ to PD _5, it corresponds to the extension of the normal line of the main surface of the diaphragms X _{1 to} X ₅ corresponding to the photodetectors PD _{1 to} PD ₅ with the maximum output. It is possible to identify the sound source to be played.

Furthermore, according to the electroacoustic transducer according to the first embodiment, since the vibration displacement of each of the diaphragms X _{1 to} X ₅ is individually detected, a clear sound can be obtained even in a sound field where there are many sound sources. It becomes possible to extract.

FIG. 4 is a block diagram showing the configuration of the electroacoustic conversion system according to the first embodiment of the present invention, and shows how the displacements of the plurality of diaphragms X _{1 to} X _n are detected. The case of n = 5 corresponds to the electroacoustic transducer using the _five diaphragms X _{1 to} X ₅ illustrated in FIG. 3, but is not limited to n = 5, and n is 2 or more. It can be designed to any value. Therefore, in FIG. 4, a more generalized, it is indicated by a diaphragm X ₁ to X _n.

In the electroacoustic conversion system shown in FIG. 4A, n diaphragms X _{1 to} X _n are prepared corresponding to _n sound sources (sound waves) S _{1 to} S _n . The diaphragm X ₁ to X n number of light sources _LD 1 to Ld _n corresponding to each of _n, the n photodetectors _PD 1 -PD _n, are n amplifiers _A 1 to A _n, independently of one another The n parallel circuits are connected to each other, and the outputs of the n parallel circuits are input to a single Fourier transform means. In FIG. 4A, a fast Fourier transform (FFT) analyzer is used as an example of Fourier transform means. The FFT analyzer is a Fourier transform unit that performs a transform related to the discrete Fourier transform at a high speed, and converts the time-series signals output from the _n amplifiers A ₁ to An into frequency axis signals. The FFT analyzer generally includes a low-pass filter, an AD converter, an FFT arithmetic circuit, a display unit, and the like. The continuous signal voltage output from the _n amplifiers A _{1 to An} is sampled at a certain time interval, AD (analog-digital) converted by an AD converter, and then subjected to FFT calculation by an FFT calculation circuit. Do. At this time, in order to prevent an aliasing phenomenon in which a frequency component that does not exist in the original signal appears, a low-pass filter is used before sampling. The signals subjected to the FFT processing by the FFT operation circuit are combined into one frequency spectrum _fΣ and aggregated. According to the system shown in FIG. 4 (a), the sound source is in many sound field of (n) exists, clearly the each sound wave S ₁ to S _n from each sound source to identify, can be recorded.

Similarly to the system shown in FIG. 4A, the electroacoustic conversion system shown in FIG. 4B corresponds to _n sound sources (sound waves) S _{1 to} Sn, and n diaphragms X ₁ to _Xn is prepared. The diaphragm X ₁ to X n number of light sources _LD 1 to Ld _n corresponding to each of _n, the n photodetectors _PD 1 -PD _n, are n amplifiers _A 1 to A _n, independently of one another N parallel circuits are connected. However, in FIG. 4 (b), (in parallel) separately from n parallel circuit is output to the plurality of the Fourier transform means (FFT _analyzer) FFT 1 _{~FFT n.} Each Fourier transform means (FFT analyzer) FFT _{1 to} FFT _n converts the time series signals output from the _n amplifiers A ₁ to An into frequency axis signals, respectively, and converts the frequency spectra f _{1 to} f _n respectively. Output. According to the system shown in FIG. 4 (b), even sound field sound source number (n pieces) are present, the frequency spectrum f ₁ ~f plurality of (n) corresponding to sound waves S ₁ to S _n from the sound source Each _n can be identified and clearly recorded.

In the electroacoustic conversion system according to the first embodiment shown in FIG. 4, assuming that the diaphragm (first diaphragm) facing the main surface of the diaphragm integrated base is, for example, the diaphragm X _n . _(N-1) other diaphragms (second diaphragms) X _{1 to} X _(n-1) having angles in various directions on the same diaphragm integrated base are arranged, and the corresponding light sources LD ₁ to LD ₁ are arranged. LD _n, it detects the vibration displacement of individually diaphragm X ₁ to X _n by the photodetector _PD 1 -PD _n. The output of each photodetector _PD 1 -PD _n Fourier transform, the maximum of the frequency spectrum _f 1 ~f _n photodetector intensities were obtained of _PD 1 -PD corresponding to _n diaphragm X ₁ to X _n It is possible to identify that there is a corresponding sound source on an extension of the normal of the main surface.

Furthermore, according to the electroacoustic conversion system according to the first embodiment, since the vibration displacement of each of the diaphragms X _{1 to} X _n is individually detected, even in a sound field where there are a large number (n) of sound sources, A clear sound can be extracted.

As described above, according to the electro-acoustic transducer system according to the first embodiment, can be of one diaphragm integrated substrate, detecting the sound waves S ₁ to S _n from the multi-azimuth (n azimuth) Thus, it becomes possible to provide a low-cost and space-saving multidirectional identification optical microphone system.

  A method for manufacturing the diaphragm integrated substrate according to the first embodiment of the present invention shown in FIG. 1 will be described with reference to FIGS. It should be noted that the manufacturing method of the diaphragm integrated substrate described below is an example, and it is needless to say that the method can be realized by various other manufacturing methods including this modification.

(A) First, a so-called SOI substrate is prepared in which a buried insulating film (SOI oxide film) 42 and a single crystal Si layer (SOI layer) 43 are sequentially stacked on a support substrate 41 made of single crystal Si. Next, as shown in FIG. 5A, a protective film 44 such as a silicon oxide film (SiO ₂ film) or a silicon nitride film (Si ₃ N ₄ film) is deposited on the SOI substrate by a CVD method or the like. The silicon oxide film (SiO ₂ film) may be formed by thermal oxidation, or may be CVD or coating of TEOS.

(B) Next, a photoresist film (hereinafter simply referred to as “photoresist”) is spin-coated on the surface of the protective film 44. Then, the photoresist is patterned by a photolithography technique. Then, using this photoresist as a mask, the protective film 44 is etched by the RIE method or the like. Thereafter, the photoresist is removed, and the single crystal Si layer 43 is separated by the RIE method or the like using the protective films 44a, 44b, 44c, 44l, 44m, 44q, and 44r patterned by the RIE method or the like as a mask. (b), the single-crystal Si layer 43c that defines the area of the first diaphragm X ₅ and the second diaphragm X _1, X _3, 43 b, cut out 43a (in front and back of the paper is shown The region of the diaphragm (second diaphragm) X ₂ and X ₄ from which is omitted is also cut out. At this time, as shown in FIG. 5B, the single crystal Si layers 43l and 43m are similarly separated under the protective films 44l and 44m, and the anchor (fixed beam) 13 is formed. Further, as shown in FIG. 5B, the single crystal Si layers 43q and 43r are similarly separated under the protective films 44q and 44r, and a pattern corresponding to the fixed frame 11 is formed. Although not shown in the sectional view, patterns of elastic beams (springs) 23a to 23d; 21a, 22b; 21b, 22c; 21c, 22d; 21d, 22a shown in FIG. That is, on the surface of the SOI substrate, a fixed frame 11, a fixed beam 13 connected to the fixed frame 11; 11a to 11d, and a plurality of elastic beams 23a to 23d connected at one end to the fixed frame 11, 21a, 22b; 22c; 21c, 22d; 21d, 22a, elastic beams 23a-23d; 21a, 22b; 21b, 22c; 21c, 22d; 21d, 22a. Diaphragm X ₅ , second elastic plates X _{1 to} X supported by cantilever structure on fixed frame 11 via elastic beams 23a to 23d; 21a, 22b; 21b, 22c; 21c, 22d; ₄ and are formed.

(C) Thereafter, a new photoresist is spin-coated on the surfaces of the protective films 44a, 44b, 44c, 44l, 44m, 44q, and 44r. That is, using the photolithography technique and the RIE method or the like, as shown in FIG. 5C, the protective films 44a, 44b, 44c, the single crystal Si layers 43a, 43b, 43c, and the buried insulating film 42 are selectively formed. In addition, a fine pattern that forms a transmission type two-dimensional diffraction grating on the surfaces of the first diaphragm X ₅ and the second diaphragms X _{1 to} X ₄ is continuously removed by RIE or ECR ion etching. Holes H _i1 , H _i2 ,..., H _i6 are formed (see FIG. 6). Thereafter, the photoresist is removed. The diffraction grating is not limited to a two-dimensional diffraction grating, and may be a one-dimensional diffraction grating as shown in FIG.

(D) minute holes H _i1, H _i2, · · · · ·, after forming the H _i6, by thermal oxidation, minute holes H _i1, H _i2, · · · · ·, exposed on the side walls of the H _i6 As shown in FIG. 6, a silicon oxide film is formed as an etching protection film 48 on the surfaces of the single crystal Si layers 43a, 43b, and 43c. In FIG. 6, the entire region of the first diaphragm X ₅ and only the partial region of the second diaphragms X ₁ and X ₃ are shown, but the second diaphragm that is present in front of and behind the page is omitted. Similarly, an etching protective film 48 is formed on the surface of the single crystal Si layer exposed on the side walls of the fine holes H _i1 , H _i2 ,..., H _{i6 in} the X ₂ and X ₄ regions.

(E) Thereafter, a new photoresist is spin-coated on the surfaces of the first diaphragm X ₅ and the second diaphragms X _{1 to} X ₄ . By photolithography to form a window portion to expose the surface of each region of the diaphragm X ₁ to X _5. This window is an opening including the entire arrangement of the fine holes H _i1 , H _i2 ,..., H _i6 . Then, using this photoresist as a mask, the etching protection film 48 formed on the bottom of the diaphragms X _{1 to} X ₅ exposed to the window is selectively removed by RIE having high directivity. As a result, the support substrate 41 made of single crystal Si is exposed at the bottoms of the fine holes H _i1 , H _i2 ,..., H _i6 of the respective vibration plates X _{1 to} X ₅ .

(F) The difference between the single crystal Si through the fine holes H _i1 , H _i2 ,..., H _i6 of the first diaphragm X ₅ and the second diaphragms X _{1 to} X _4. If a anisotropic etchant, for example, a chemical solution such as tetramethylammonium hydroxide (TMAH) is introduced and selective anisotropic etching of the support substrate 41 is performed, as shown in FIG. ₅ is formed below the first diaphragm X ₅ , and cavities Q ₁ and Q ₃ are formed below the second diaphragm X ₁ and X ₃ , respectively. Similarly, cavities Q ₂ and Q _{4 (not shown)} are formed below the second diaphragms X ₂ and X ₄ (not shown). As a result, the diaphragm (first diaphragm) X ₅ parallel to the main surface of the SOI substrate has a doubly supported beam structure supported by the anchor (fixed beam) 13 with four elastic beams. On the other hand, the second diaphragms X ₁ and X ₃ (and the second diaphragms X ₂ and X _{4 not shown} ) have an anchor (fixed beam) 13 and elastic beams 21a and 22b; 21b and 22c only at one end. 21c, 22d; 21d, 22a, the opposite ends become free (free ends) as etching progresses, and the elastic beams 21a, 22b; 21b, 22c; 21c, 22d; 21d, 22a Bend. Here, the end of the free diaphragm (second diaphragm) X _{1 to} X ₄ is lowered by its own weight, and the Si wall exposed to the cavities Q _{1 to} Q ₄ obtained by anisotropic etching Are attached (sticked) as shown in FIG. That, is part cavity Q ₁ to Q ₄ of the wall of the supporting substrate 41 is a stopper, thereby supporting the end portion of the lowered towards the four second diaphragm X ₁ to X _4. As a result, the diaphragms (second diaphragms) X _{1 to} X ₄ are actually realized, and the main surfaces of the second diaphragms X _{1 to} X ₄ are in relation to the surface (main surface) of the SOI substrate. And become slanted.

(G) Finally, the support substrate 41 is etched from the back surface to form the cavity 47, whereby the diaphragm integrated base according to the first embodiment of the present invention is completed. As shown in FIG. 1, five diaphragms X _{1 to} X ₅ having different main surface directions are formed in the fixed frame 11 of the microphone.

As described above, according to the manufacturing method of the diaphragm integrated base according to the first embodiment of the present invention, the film stress and the sticking (adhesion) phenomenon generated during the selective anisotropic etching of the support substrate 41. Are used, the pseudo-dual-supported diaphragms (second diaphragms) X _{1 to} X ₄ are formed obliquely with respect to the main surface of the diaphragm integrated base. That is, in addition to the first diaphragm X ₅ facing the main surface of the diaphragm integrated substrate, the second diaphragms X ₁ to X 2 having angles of the main surface in various directions on the same diaphragm integrated substrate. A diaphragm integrated substrate in which a plurality (four) of X ₄ are arranged can be easily manufactured.

(Second Embodiment)
In the first embodiment, the diaphragm integrated base including the diaphragms X _{1 to} X ₅ having the transmission type diffraction grating, the electroacoustic transducer using the same, and the like have been described. In the second embodiment of the present invention, as shown in FIG. 8, a diaphragm integrated substrate including diaphragms X _{1 to} X ₅ having reflective diffraction gratings and an electroacoustic transducer using the same. explain.

Similar to the first embodiment, the reflection type diffraction grating according to the second embodiment is the two-dimensional diffraction grating shown in FIG. 8A or the one-dimensional diffraction grating shown in FIG. Of course, it does not matter. In FIG. 8 (a), a plurality of holes (concave portions) H _i−1,1 ,..., H _{i, 1} arranged in a matrix on the diaphragms X _{1 to} X ₅ , respectively. , H _1,2 , H _1,3 ,..., H _{i + 2,6} shows an example of forming a two-dimensional diffraction grating. Further, in FIG. 8B, a plurality of U grooves G ₁ , G ₂ , G ₃ ,..., G ₆ having a fixed depth that are periodically arranged in the diaphragms X _{1 to} X ₅ , respectively. Thus, an example of configuring a one-dimensional diffraction grating is shown.

As shown in FIG. 9, the electroacoustic transducer according to the second embodiment of the present invention vibrates due to sound pressure and has five reflective diffraction gratings whose principal surfaces are different from each other. The plates X _{1 to} X ₅ , the five light sources LD _{1 to} LD 5 that irradiate the diffraction gratings of the vibration plates X _{1 to} X ₅ , and the _five lights that detect the light diffracted by the diffraction grating and convert it into electrical signals It is a multidirectional identification optical microphone provided with detectors PD _{1 to} PD ₅ .

A fixed frame 11 that houses and fixes _five diaphragms X _{1 to} X ₅ having different main surface directions is supported by the support frame 10 and fixed to the upper end of the housing side wall 31. Each of the _five diaphragms X _{1 to} X ₅ shown in FIG. 9 is a two-dimensional diffraction grating shown in FIG. 8A or a one-dimensional diffraction grating shown in FIG. 8B. These reflection-type diffraction grating surfaces are facing downward (in FIG. 9, the diffraction grating surfaces are schematically illustrated as if facing upward, but this is intended to image the diffraction grating, In reality, holes (recesses) H _i-1,1 , ..., H _{i, 1} , H _1,2 , H _1,3 , ..., H _{i + 2,6} are formed. The diffraction grating surface is facing downward, and a flat bottom surface appears in FIG. 9).

The five light sources LD _{1 to} LD ₅ and the five photodetectors PD _{1 to} PD ₅ are arranged on a housing bottom plate (mounting substrate) 32 disposed at the lower end of the housing side wall 31. The housing bottom plate (mounting substrate) 32 includes a bottom opening 35 at the center, and the five light sources LD _{1 to} LD ₅ and the five photodetectors PD _{1 to} PD ₅ surround the bottom opening 35. Arranged on the casing bottom plate 32. In Figure 9, two-dimensional spatially different positions arranged five light sources _LD 1 to Ld ₅ is, light emitted from the light source _LD 1 to Ld ₅ is vibration direction of the main surface is different from five mutually The optical axis is adjusted so that it can enter each of the plates X _{1 to} X ₅ . Further, the five light reflected by the diaphragm X ₁ to X _5, respectively so as to be incident on the photodetector _PD 1 -PD _5, is optically adjusted, is the photodetector _PD 1 -PD ₅ Has been placed. On the housing bottom plate 32, drive and control circuits 33a to 33d for _five light sources LD _{1 to} LD ₅ and five photodetectors PD _{1 to} PD ₅ are further arranged.

For the photodetectors PD _{1 to} PD ₅ shown in FIG. 9, it is preferable to use an image sensor such as a photodiode array, similarly to the electroacoustic transducer according to the first embodiment. In the electroacoustic transducer according to the second embodiment, the reflection plates are formed on the _five diaphragms X _{1 to} X ₅ having different principal surface directions, so that the five light sources LD are provided. _The light waves irradiated from _{1 to} LD ₅ are reflected by the corresponding diffraction gratings X _{1 to} X ₅ , respectively, and produce diffraction images on the surfaces of the _five photodiode arrays PD _{1 to} PD ₅ . The optical detectors PD _{1 to} PD ₅ optically detect the displacements of the _five diaphragms X _{1 to} X ₅ each having a reflection type diffraction grating and having different principal plane directions. It converts into an electric signal using the system similar to FIG. 4 demonstrated with the electroacoustic transducer which concerns on a form of. According to the electro-acoustic transducer according to the second embodiment, of one diaphragm integrated substrate, it is possible to detect the sound waves S ₁ to S _n from the multi-orientation, low-cost, space-saving An electroacoustic transducer can be provided.

As shown in FIG. 10, the electroacoustic transducer according to the modification (first modification) of the second embodiment of the present invention vibrates by sound pressure and has five vibrations whose principal surfaces are different from each other. The plates X _{1 to} X ₅ , the five light sources LD _{1 to} LD 5 that irradiate the diffraction gratings of the vibration plates X _{1 to} X ₅ , and the _five lights that detect the light diffracted by the diffraction grating and convert it into electrical signals The configuration is the same as that shown in FIG. 9 in that the multidirectional identification optical microphone includes the detectors PD _{1 to} PD ₅ .

However, the fixed frame 11 that houses and fixes the _five diaphragms X _{1 to} X ₅ having different main surface directions is supported by the support frame 10, and is formed between the housing upper side wall 31 a and the housing lower side wall 31 b. The point fixed in between is different from FIG. The housing top plate 39 includes an upper opening 37 at the center.

The five light sources LD _{1 to} LD ₅ , the five photodetectors PD _{1 to} PD ₅ , and the drive / control circuits 33a to 33d of these light sources LD _{1 to} LD ₅ and the photodetectors PD _{1 to} PD ₅ The (arrangement) on the (mounting substrate) 32 is the same as the configuration of FIG.

As in the case of FIG. 9, the electroacoustic transducer according to the modification of the second embodiment also includes five diaphragms X _{1 to} X ₅ having different principal surface directions to form a reflective diffraction grating. because there, light waves emitted from the light source _LD 1 to Ld ₅ is reflected by the diffraction grating X ₁ to X ₅ each corresponding results in diffraction image on the surface of the photodiode array _PD 1 -PD _5. Then, a reflective-type diffraction grating, the displacement of the vibrating plate X ₁ to X ₅ of 5 Like direction of the main surface are different from each other optically detected by a photodetector PD ₁ -PD _5, further to FIG. 4 this A similar system can be used to convert to an electrical signal.

By electro-acoustic transducer according to a modification of the second embodiment shown in FIG. 10, of one diaphragm integrated substrate, it is possible to detect the sound waves S ₁ to S _n from the multi-azimuth Thus, it is possible to provide a low-cost and space-saving electroacoustic transducer.

As an electroacoustic transducer according to another modified example (second modified example) of the second embodiment of the present invention, five light sources LD ₁ to LD are arranged on the lower surface of the casing top plate 39 in the configuration shown in FIG. LD _5, 5 one photodetector _PD 1 -PD ₅ and the light sources _LD 1 _{~LD 5,} multidirectional identified light microphones each drive and control circuit 33a~33d of the photodetector _PD 1 -PD ₅ arranged May be configured. In this case, the diffraction grating surfaces of the _five diaphragms X _{1 to} X ₅ shown in FIG. 10 are upward. Such, in configuration of arranging the light source _LD 1 to Ld ₅ and photodetectors _PD 1 -PD ₅ on the lower surface of the housing top plate 39, light emitted from the light source _LD 1 to Ld ₅ is the main surface direction of the Are adjusted so that they can be incident on _five diaphragms X _{1 to} X ₅ different from each other, and the light reflected by the diaphragms X _{1 to} X ₅ is incident on the photodetectors PD _{1 to} PD ₅ , respectively. If possible, the same operation as the configuration shown in FIG. 10 is possible by optical adjustment.

(Third embodiment)
In the description of FIG. 4 of the electroacoustic transducer according to the first embodiment, it has already been described that the number of diaphragms X _{1 to} X _n is not limited to n = 5. In the diaphragm integrated substrate according to the third embodiment, the case where n = 9 will be described. That is, as shown in FIG. 11, the diaphragm integrated substrate according to the third embodiment has nine diaphragms X _{1 to} X ₉ arranged in a 3 × 3 matrix.

In FIG. 11, the central diaphragm X ₉ is formed to face the main surface of the diaphragm integrated base and is connected by four elastic beams 21. The central diaphragm X ₉ varies greatly with respect to the sound pressure from the sound source from the direction facing the main surface of the diaphragm integrated base, and exhibits sensitivity.

The diaphragms X _{1 to} X ₈ other than the central diaphragm X ₉ form a cantilever shape connected at two points from the anchors (fixed beams) 12p, 12q, 12r, and 12s. When a cavity is formed in the lower part of the diaphragms X _{1 to} X ₉ using a processing process similar to the manufacturing process of the semiconductor integrated circuit, the surrounding eight diaphragms X _{1 to} X ₈ are cantilevered by the elastic beams 21. Due to the beam structure, the end on the side not connected to the elastic beam 21 descends. At this time, a vibration having a pseudo double-supported beam structure is generated by intentionally causing sticking between the end portion of the elastic beam 21 that is lowered due to the bending of the elastic beam 21 and the main surface of the vibration plate integrated base. to form an X ₁ ~X _8.

The peripheral eight diaphragms X _{1 to} X ₈ have an oblique angle with respect to the main surface of the diaphragm integrated base, and therefore have sensitivity to sound waves in an oblique direction. Here, the number of resilient beams 21 connected to the anchor (fixed beam) 12P～12s can varied in design level, four to the center of the diaphragm X _9, the eight peripheral diaphragm X ₁ ~ The number of two for X ₈ is not an essential matter, and other numbers can be flexibly adopted according to the design specifications.

Also by the electroacoustic transducer according to the modification of the third embodiment shown in FIG. 11, it is possible to detect the sound waves S _{1 to} S ₉ from nine directions with one diaphragm integrated substrate. Thus, a low-cost and space-saving electroacoustic transducer can be provided.

(Other embodiments)
As described above, the present invention has been described according to the first to third embodiments. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

FIG. 12 shows a state in which the free end of the beveled diaphragm (second diaphragm) X ₃ and the wall of the inner wall of the fixed frame 11 brought about by anisotropic etching of Si are attached (sticking). It is shown schematically. As shown in FIG. 12, in order to improve the accuracy and strength of adhesion between the free end of diaphragm X ₃ and Si, on the free end side of diaphragm X ₃ , the contact area is increased as shown in FIG. A pseudo double-supported beam structure may be realized by adding the contact member 19. Similarly, the contact member 19 of FIG. 12 is added to the free end side of the other diaphragms X ₁ , X ₂ , and X ₄ of the diaphragm integrated base according to the first embodiment, so that pseudo-both-end support is achieved. A beam structure may be realized. Further, in the second and third embodiments, the contact member 19 shown in FIG. 12 may be added to the inclined diaphragm.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

It is a typical bird's-eye view explaining the outline of the structure of the diaphragm integrated substrate which concerns on the 1st Embodiment of this invention. FIG. 2 is a schematic bird's-eye view for explaining the outline of the structure of a transmissive diffraction grating provided in each diaphragm of FIG. 1. It is a typical bird's-eye view explaining the outline of the structure of the electroacoustic transducer which concerns on the 1st Embodiment of this invention. In the electroacoustic conversion system which concerns on the 1st Embodiment of this invention, it is a block diagram explaining the outline of the structure which identifies each sound wave from each sound source. FIG. 6 is a schematic process cross-sectional view illustrating the manufacturing method of the diaphragm integrated base according to the first embodiment of the present invention (No. 1). FIG. 6 is a schematic process cross-sectional view illustrating the manufacturing method of the diaphragm integrated base according to the first embodiment of the present invention (No. 2). FIG. 6 is a schematic process cross-sectional view illustrating the manufacturing method of the diaphragm integrated substrate according to the first embodiment of the present invention (No. 3). It is a typical bird's-eye view explaining the outline of the structure of a reflection type diffraction grating provided in each diaphragm of the diaphragm integrated base concerning a 2nd embodiment of the present invention. It is a typical bird's-eye view explaining the outline of the structure of the electroacoustic transducer which concerns on the 2nd Embodiment of this invention. It is a typical bird's-eye view explaining the outline of the structure of the electroacoustic transducer which concerns on the modification of the 2nd Embodiment of this invention. It is a typical top view explaining the outline of the structure of the diaphragm integrated base which concerns on the 3rd Embodiment of this invention. It is a typical bird's-eye view explaining a part of structure of a diaphragm integrated base concerning other embodiments of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Support frame 11 ... Fixed frame 12a-12d ... Fixed beam 13 ... Anchor (fixed beam)
DESCRIPTION OF SYMBOLS 19 ... Contact member 21; 21a, 22b; 21b, 22c; 21c, 22d; 21d, 22a; 23a-23d ... Elastic beam 31 ... Housing side wall 31a ... Housing upper side wall 31b ... Housing lower side wall 32 ... Housing bottom plate 33a to 33d ... control circuit 35 ... bottom opening 37 ... top opening 39 ... housing top plate 41 ... support substrate 42 ... insulating film 43, 43a, 43b, 43c, 43l, 43m, 43q, 43r ... single crystal Si layer (SOI layer)
44,44a, 44b, 44c, 44l, 44m, 44q, 44r ... protective film 47 ... cavity 48 ... etching protection film A ₁ to A _n ... amplifier _{G 1, G 2, G 3} , ·····, G ₆ ... Groove (slit or U-groove)
H _i-1,1 ,..., H _{i, 1} , H _1,2 , H _1,3 ,..., H _{i + 2,6} .
Q ₁ , Q ₅ , Q ₃ ... cavity
S ₁ to S _n ... wave X ₁ to X _n ... diaphragm (diffraction grating)
_{f Σ,} f 1 ~f _n ... frequency spectrum _FFT, FFT 1 ~FFT _n ... fast Fourier transform (FFT) analyzer LD ₁ ~LD _n, ... light source PD ₁ -PD _n ... photodetector

Claims (13)

Each of the diaphragm integrated bases having a plurality of diaphragms each having a diffraction grating and vibrating by sound pressure, wherein the plurality of diaphragms are:
A first diaphragm whose main surface is parallel to the main surface of the diaphragm integrated base;
Second vibration in which the main surface is inclined at an oblique angle with respect to the main surface of the diaphragm integrated substrate so as to be sensitive to sound waves oblique to the main surface of the diaphragm integrated substrate. a plate seen including, the first and front and rear surfaces forming each of the main surface of the second diaphragm, the diaphragm integrated substrate, characterized in that it is both open to the waves. A diaphragm integrated base for an acoustoelectric transducer that converts displacement of a diaphragm that vibrates by sound pressure into an electrical signal via a diffraction image ,
A first diaphragm having a diffraction grating for forming the diffraction image, the principal surface of which is parallel to the principal surface of the diaphragm integrated base;
A diffraction grating for forming the diffraction image, and the main surface is sensitive to the main surface of the diaphragm integrated substrate so as to be sensitive to sound waves oblique to the main surface of the diaphragm integrated substrate. diaphragm integrated substrate, characterized in that it comprises a second diaphragm which is inclined with a bevel. A rectangular frame-shaped anchor surrounding the periphery of the first diaphragm;
A ridge-shaped fixed beam connected to each of the anchors and fixing the anchors so as not to vibrate due to sound pressure,
Further comprising a plurality of elastic beams having one end connected to the said anchor, said first and second diaphragm, claim 1, characterized in that connected to each of the anchor through a plurality of elastic beams Or the diaphragm integration | stacking base | substrate of 2. It further comprises a rectangular frame-shaped fixing frame for fixing the fixing beam,
The diaphragm integrated base according to claim 3 , wherein the second diaphragm has one end connected to the other end of the elastic beam and the other end attached to a part of the fixed frame. A plurality of diaphragms each having a diffraction grating, vibrated by sound pressure, and having different principal plane directions;
A plurality of light sources for irradiating each of the diffraction gratings,
A plurality of photodetectors that respectively detect diffraction images formed by the light diffracted by the diffraction grating and convert them into electrical signals, and the plurality of diaphragms are vibration plate integrated bases that integrate the plurality of diaphragms. The main surface of the diaphragm integrated substrate has a first surface having a main surface parallel to the main surface and a sensitivity to sound waves oblique to the main surface of the diaphragm integrated substrate. And a second diaphragm that is inclined at an oblique angle to each other , and the displacement of the plurality of diaphragms is converted into an electrical signal through the diffraction image, respectively.   The acoustoelectric transducer according to claim 5, wherein both the front surface and the back surface forming the main surface of each of the first and second diaphragms are open to sound waves.   The acoustoelectric conversion element according to claim 5, wherein the photodetector is an image sensor.   A rectangular frame-shaped anchor surrounding the periphery of the first diaphragm;
  A ridge-shaped fixed beam connected to each of the anchors and fixing the anchors so as not to vibrate due to sound pressure,
  A plurality of elastic beams having one end connected to the anchor
  The sound according to any one of claims 5 to 7, wherein each of the first and second diaphragms is connected to the anchor via the plurality of elastic beams. Electrical conversion element. A plurality of diaphragms each having a diffraction grating, vibrated by sound pressure, and having different principal plane directions;
A plurality of light sources for irradiating each of the diffraction gratings,
A plurality of photodetectors that respectively detect diffraction images formed by light diffracted by the diffraction grating and convert them into electrical signals;
Fourier transform means for converting time-series signals output from the plurality of photodetectors into frequency-axis signals, and the plurality of diaphragms are principal surfaces of a diaphragm-integrated substrate on which the plurality of diaphragms are integrated And a main surface with respect to the main surface of the diaphragm integrated substrate so as to be sensitive to sound waves oblique to the main surface of the diaphragm integrated substrate. A second diaphragm that is inclined at an oblique angle, and the displacement of the plurality of diaphragms is converted into a spectrum for each of a plurality of corresponding sound sources via the diffraction image, and the plurality of sound sources An acoustoelectric conversion system characterized by identifying.   The acoustoelectric conversion system according to claim 9, wherein a front surface and a back surface forming the main surfaces of the first and second diaphragms are both open to sound waves.   The acoustoelectric conversion system according to claim 9 or 10, wherein the photodetector is an image sensor.   A rectangular frame-shaped anchor surrounding the periphery of the first diaphragm;
  A ridge-shaped fixed beam connected to each of the anchors and fixing the anchors so as not to vibrate due to sound pressure,
  A plurality of elastic beams having one end connected to the anchor
  The sound according to any one of claims 9 to 11, wherein the first and second diaphragms are connected to the anchor via the plurality of elastic beams, respectively. Electrical conversion system. A rectangular frame-shaped anchor on the surface of the substrate, a ridge-shaped fixed beam that is connected to each of the anchors and fixes the anchor, a rectangular frame-shaped fixing frame that fixes the fixed beam, and a plurality of one ends connected to the anchor An elastic beam, a first diaphragm disposed inside the anchor and supported by the anchor in a doubly-supported beam structure via the elastic beam, and disposed on the outside of the anchor and separated from the anchor via the elastic beam. Forming a second diaphragm supported by a cantilever structure;
Forming a diffraction grating on each of the first and second diaphragms;
Forming cavities in the bottoms of the first and second diaphragms, respectively;
The elastic beam connecting the second diaphragm is bent by the weight of the second diaphragm, the main surface of the second diaphragm is inclined with respect to the surface of the substrate, and the second diaphragm is And a step of attaching an end portion on the side not supported by the elastic beam to a part of the substrate.

Images