JP4215076B2 - Condenser microphone and manufacturing method thereof - Google Patents

Description

The present invention relates to a condenser microphone and a manufacturing method thereof, and more particularly to a condenser microphone that can be manufactured by applying a manufacturing process of a semiconductor device and a manufacturing method thereof.

  Conventionally, a capacitor-type pressure sensor that can be manufactured by applying a manufacturing process of a semiconductor device is known. The capacitor-type pressure sensor includes a diaphragm that vibrates due to a pressure change, a plate that faces the diaphragm with a dielectric such as air interposed therebetween, and an air chamber. The capacitance between the diaphragm and the plate changes due to the vibration of the diaphragm. The capacitor-type pressure sensor converts the change in capacitance into an electrical signal and outputs it. On the other hand, the air chamber relieves changes in internal pressure that hinder diaphragm vibration. Therefore, the output characteristics of the pressure sensor can be enhanced by increasing the capacity of the air chamber.

  Patent Document 1 discloses a condenser microphone that forms an air chamber with a recess formed in a substrate and a diaphragm covering the recess. However, in Patent Document 1, the inner wall of the recess is formed perpendicular to the diaphragm. The opening of such a recess cannot be made larger than the thin film constituting the diaphragm, and a large-capacity air chamber cannot be formed. Patent Document 2 discloses a condenser microphone in which an air chamber is constituted by an inner wall of a through hole formed in a substrate and a diaphragm. In Patent Document 2, the inner wall of the through hole is formed in a tapered shape whose diameter increases from the plate side toward the opposite side. Therefore, the volume of the air chamber can be made larger than that of the condenser microphone described in Patent Document 1. However, since such a tapered through hole is formed using a silicon lattice plane, the taper angle is constant. As a result, since the capacity of the air chamber is limited by the size of the thin film constituting the diaphragm, the capacity of the air chamber cannot be increased without increasing the size of the pressure sensor.

JP-T-2004-537182 JP 2004-356707 A

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a condenser microphone having a large air chamber capacity and a method for manufacturing the same.

(1) A condenser microphone for achieving the above object includes a plate having a fixed electrode, a movable electrode opposed to the fixed electrode, a diaphragm that is displaced by a pressure change, and an end portion of the plate fixed to the inside. A first inner wall forming a first air chamber, a step in the plate thickness direction of the diaphragm with respect to the first inner wall, and a cross-sectional area in the plate surface direction of the diaphragm on the inner side. And a support portion having a second inner wall forming a second air chamber larger than the chamber.
The cross-sectional area of the diaphragm of the second air chamber in the plate surface direction is discontinuously enlarged with respect to the cross-sectional area of the diaphragm of the first air chamber in the plate surface direction. And the edge part of the plate is being fixed to the 1st inner wall which forms a 1st air chamber. Accordingly, without being limited to the size of the plate surface direction of the plate, and without increasing the size of the condenser microphone, it is possible to increase the capacitance of the air chamber of the condenser microphone.

(2) The second inner wall may form a step in the plate thickness direction of the diaphragm, and the cross-sectional area of the second air chamber in the plate surface direction of the diaphragm may expand toward the opposite side of the plate. .
The cross-sectional area in the plate surface direction of the diaphragm of the second air chamber expands discontinuously toward the side opposite to the plate. Therefore, the capacity of the air chamber of the condenser microphone can be increased.

(3) A condenser microphone manufacturing method for achieving the above object includes a plate having a fixed electrode, a diaphragm having a movable electrode opposed to the fixed electrode and displaced by a pressure change, and supporting the plate inside. A condenser microphone including a support portion having an air chamber, wherein a thin film constituting the plate and a thin film constituting the diaphragm are formed on the first surface of the substrate by deposition, and the first of the substrate is formed. A first mask having a first opening is formed on a second surface opposite to the one surface, and the first mask is covered on the second surface of the substrate and inside the first opening. Forming a second mask having a second opening for exposing a portion of the thin film constituting the plate of the substrate, and exposing the base to the second opening using the second mask; The recess is formed in the substrate by anisotropic etching, the second mask is removed, and the bottom of the recess is removed from the substrate exposed to the first opening using the first mask. Forming through holes in the substrate by anisotropic etching to the substrate.
When the substrate exposed to the second opening is anisotropically etched using the second mask, a recess is formed in the substrate. Then, using the first mask, anisotropic etching is performed on the concave portion of the substrate exposed to the first opening and its peripheral portion until the bottom of the concave portion is removed, thereby forming a stepped through hole in the thickness direction of the substrate. Is done. Here, the second opening is patterned so as to expose a portion on a part of the thin film constituting the plate of the substrate. Therefore, the remainder of the thin film constituting the plate is stacked on the substrate even after the through holes are formed. By forming the stepped through hole in the substrate in this manner, a condenser microphone having a large air chamber capacity can be manufactured.

(4) A condenser microphone manufacturing method for achieving the above object includes a plate having a fixed electrode, a diaphragm having a movable electrode opposed to the fixed electrode and displaced by a pressure change, and supporting the plate inside. A condenser microphone including a support portion having an air chamber, wherein a thin film constituting the plate and a thin film constituting the diaphragm are formed on the first surface of the substrate by deposition, and the first of the substrate is formed. On the second surface opposite to the one surface, a first opening that exposes a portion on a part of the thin film constituting the plate of the substrate, and a slit-shaped second along the outer edge of the first opening. Forming a mask having an opening, and anisotropically etching the substrate exposed to the first opening and the second opening using the mask. The air chamber is configured by forming a hole corresponding to the first opening and a recess corresponding to the second opening, and removing a wall portion between the hole and the recess of the substrate. Forming a through hole in the substrate.
When the substrate is anisotropically etched until a hole is formed in the first opening using a mask having the first opening and the second opening, a recess corresponding to the second opening is formed in the substrate. . This is due to the aspect-dependent etching effect. Then, when the wall portion between the hole portion and the concave portion of the substrate is removed, a stepped through hole is formed in the substrate. Here, the first opening is patterned so as to expose a portion on a part of the thin film constituting the plate of the substrate. Therefore, the remainder of the thin film constituting the plate is stacked on the substrate even after the through holes are formed. By forming the stepped through hole in the substrate in this manner, a condenser microphone having a large air chamber capacity can be manufactured.

(5) The second opening is narrowly formed so as to be separated from the first opening on the outside of the first opening, and the wall between the recesses adjacent to the substrate is formed as the hole. You may remove with the said wall part between the said recessed parts.
Since the width of the second opening is narrower as it is farther from the first opening, the depth of the concave portion corresponding to the second opening in the thickness direction of the substrate is smaller as it is farther from the first opening. Therefore, when the wall portion between adjacent concave portions of the substrate is removed, a multi-stepped through hole is formed in the substrate. In this way, a capacitor microphone having a large capacity of the air chamber can be manufactured by forming the multi-stage stepped through hole in the substrate in this manner.
(6) The hole and the recess may be formed in a reverse taper shape from the second surface of the substrate toward the first surface.
By forming such a reverse tapered hole and recess in the substrate, the wall portion described above becomes thinner from the second surface of the substrate toward the first surface. As a result, the wall portion can be easily removed by separating the wall portion from the substrate at the thin portion of the wall portion.

(7) A condenser microphone manufacturing method for achieving the above object includes a plate having a fixed electrode, a diaphragm having a movable electrode opposed to the fixed electrode and displaced by a pressure change, and supporting the plate inside. A condenser microphone including a support portion having an air chamber, wherein a thin film constituting the plate and a thin film constituting the diaphragm are formed on the first surface of the substrate by deposition, and the first of the substrate is formed. On the second surface opposite to the one surface, a first opening that exposes a portion of the thin film that constitutes the plate of the substrate, and a slit-shaped second connected to the first opening. Forming a mask having an opening, and anisotropically etching the substrate exposed to the first opening and the second opening using the mask. The hole constituting the forming on the substrate, comprising.
When the substrate is anisotropically etched until a hole is formed in the first opening using a mask having the first opening and the second opening, the substrate corresponds to the second opening due to an aspect-dependent etching effect. A slit-like recess is formed. The concave portion of the substrate is connected to the hole portion, and the hole portion and the concave portion form a stepped through hole. Here, the first opening is patterned so as to expose a portion on a part of the thin film constituting the plate of the substrate. Therefore, the remainder of the thin film constituting the plate is stacked on the substrate even after the through holes are formed. By forming the stepped through hole in the substrate in this manner, a condenser microphone having a large air chamber capacity can be manufactured.

In the present specification, “... formed on” means “... formed directly on” and “... on the intermediate” unless there is a technical impediment. It is meant to include both “formed through”.
In addition, the order of each operation of the method described in the claims is not limited to the order of description unless there is a technical impediment, and may be executed in any order, and may be executed simultaneously. Also good.

Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings. In each embodiment, the component to which the same code | symbol was attached | subjected corresponds to the component of the other embodiment to which the code | symbol was attached | subjected.
(First embodiment)
A condenser microphone 1 according to the first embodiment shown in FIG. 1 is a so-called silicon microphone manufactured using a semiconductor manufacturing process, and is a pressure sensor that converts a sound wave arriving from the plate 21 side into an electric signal.

1. Configuration of Sound Sensing Unit The sound sensing unit of the condenser microphone 1 has a laminated structure including the substrate 10, the first film, the second film, the third film, and the fourth film.
The substrate 10 is, for example, a single crystal silicon substrate. A stepped through hole 12 is formed in the substrate 10 in the thickness direction.

The first film is an insulating thin film made of silicon dioxide or the like. The first film supports the second film on the substrate 10 so that a gap is formed between the diaphragm 20 and the substrate 10. A circular opening 13 is formed in the first film.
The second film is a conductive thin film made of polysilicon to which, for example, P (phosphorus) is added as an impurity. The portion of the second film that is not fixed to the third film constitutes the diaphragm 20. The diaphragm 20 is not fixed to the first film or the third film, and functions as a movable electrode that vibrates by sound waves. The diaphragm 20 has a circular shape covering the opening 13 of the first film.

Similar to the first film, the third film is an insulating thin film made of, for example, silicon dioxide. The third film insulates the conductive second film and the fourth film and supports the fourth film on the second film. A circular opening 15 is formed in the third film.
The fourth film is a conductive thin film made of polysilicon to which, for example, P is added as an impurity, like the second film. The portion of the fourth membrane that is not fixed to the third membrane constitutes the plate 21. A plurality of through holes 22 are formed in the plate 21.

  The substrate 10, the first film, the third film, the second film, and the part of the fourth film that is not fixed to the third film constitute a support part 23. A back air chamber 40 including a first air chamber 41 and a second air chamber 42 is formed in the support portion 23. The back air chamber 40 relieves the pressure received by the diaphragm 20 from the opposite side of the traveling direction of the sound wave. The first air chamber 41 is formed inside the inner wall 12 a of the substrate 10 on the plate 21 side and the inner wall 13 a of the opening 13 of the second film. The second air chamber 42 is formed inside the inner wall 12 b opposite to the plate 21 of the substrate 10. The cross-sectional area in the plate surface direction of the diaphragm 20 of the second air chamber 42 is larger than that of the first air chamber 41. The inner wall 12a of the substrate 10 and the inner wall 13a of the second film correspond to the “first inner wall” described in the claims, and the inner wall 12b of the substrate 10 corresponds to the “second inner wall”.

2. Configuration of Detection Unit An example of the detection unit of the condenser microphone 1 will be described based on the circuit diagram shown in FIG. The diaphragm 20 is connected to a bias power source. Specifically, the lead 104 and the lead 106 connected to the terminal 102 of the bias power source are connected to the second thin film and the substrate 10, respectively. As a result, the diaphragm 20 and the substrate 10 have substantially the same potential. The plate 21 is connected to the input terminal of the operational amplifier 100. Specifically, the lead 108 connected to the input terminal of the operational amplifier 100 is connected to the fourth film. The input impedance of the operational amplifier 100 is high.

3. Operation of Capacitor Microphone When a sound wave passes through the through hole 22 of the plate 21 and propagates to the diaphragm 20, the diaphragm 20 vibrates due to the sound wave. When the diaphragm 20 vibrates, the vibration causes the distance between the diaphragm 20 and the plate 21 to change, and the capacitance formed by the diaphragm 20 and the plate 21 changes.

  Here, the plate 21 is connected to the operational amplifier 100 having a high input impedance as described above. For this reason, even if the capacitance formed by the diaphragm 20 and the plate 21 changes, the amount of charge existing on the plate 21 moves to the operational amplifier 100 is very small. Therefore, it can be considered that the electric charge which exists in the plate 21 and the diaphragm 20 does not change. As a result, a change in capacitance formed by the diaphragm 20 and the plate 21 can be taken out as a change in potential of the plate 21. In this way, the condenser microphone 1 outputs an extremely slight change in the capacitance formed by the diaphragm 20 and the plate 21 as an electric signal. That is, the condenser microphone 1 converts the change in sound pressure applied to the diaphragm 20 into a change in capacitance, and converts the change in capacitance into a change in voltage, thereby generating an electrical signal correlated with the change in sound pressure. Output.

4). Method for Manufacturing Capacitor Microphone First, as shown in FIG. 2A1, a first film 51 is formed by deposition on a wafer 50 to be a substrate 10 (see FIG. 1). For example, the first film 51 is formed by depositing silicon dioxide on the single crystal silicon wafer 50 by plasma CVD (Chemical Vapor Deposition).

Next, the second film 52 is formed on the first film 51 by deposition. Specifically, for example, it is as follows. The second film 52 is formed by depositing polysilicon doped with P on the first film 51 by using a low pressure CVD method. Next, after a photoresist film is applied to the entire surface of the second film 52, a resist pattern is formed by photolithography that performs exposure and development using a predetermined resist mask. Then, the second film 52 is selectively removed by anisotropic etching such as RIE (Reactive Ion Etching) to form a circular second film 52.
Next, as shown in FIG. 2A2, a third film 53 is formed on the second film 52 by deposition. For example, the third film 53 is formed by depositing silicon dioxide on the second film 52 using plasma CVD.

  Next, as shown in FIG. 2 (A3), a fourth film 54 is formed on the third film 53 by deposition. Specifically, for example, it is as follows. A fourth film 54 is formed by depositing polysilicon doped with P on the third film 53 using a low pressure CVD method. Next, after a photoresist film is applied to the entire surface of the fourth film 54, a resist pattern is formed by photolithography that performs exposure and development using a predetermined resist mask. Then, by selectively removing the fourth film 54 by anisotropic etching such as RIE, a circular fourth film 54 having a large number of through holes 22 is formed (see FIG. 2 (A3)).

  Next, as shown in FIG. 3A4, a first opening 55a is provided on the second surface 50b opposite to the first surface 50a on which the first film 51 to the fourth film 54 of the wafer 50 are laminated. A first mask 55 is formed. For example, a metal first mask 55 is attached to the wafer 50 using an adhesive. The adhesive is preferably an organic adhesive, and the first mask 55 is preferably nickel, chromium, or the like. The first mask 55 may be formed of any material as long as it can be selectively removed from the second mask 56 described later. Alternatively, the first mask 55 may be formed by plating the wafer 50 with a metal.

  Next, a second mask 56 having a second opening 56 a is formed on the second surface 50 b of the wafer 50 and the first mask 55. For example, after a photoresist film is applied to the entire surface of the second surface 50b of the wafer 50 and the first mask 55, the second mask 56 is formed by photolithography that performs exposure and development using a predetermined resist mask. The second opening 56a exposes a part of the second film 52 and the fourth film 54 of the wafer 50 inside the first opening 55a.

Next, as shown in FIG. 3A5, the recess 50 is formed in the wafer 50 by anisotropically etching the wafer 50 exposed to the second opening 56a using the second mask 56. For example, the recesses 60 are formed in the wafer 50 by selectively removing the wafer 50 by deep-RIE.
Next, as shown in FIG. 3A6, the second mask 56 is removed. For example, a resist stripping solution such as NMP (N-methyl-2-pyrrolidone) is used to remove the second mask 56.

  Next, the stepped through-hole 12 is formed in the wafer 50 by anisotropically etching the wafer 50 exposed to the first opening 55 a using the first mask 55. For example, the stepped through holes 12 are formed in the wafer 50 by selectively removing the wafer 50 until the bottom of the recess 60 is removed by Deep-RIE. As a result, portions of the second film 52 and the fourth film 54 of the first film 51 are exposed to the through holes 12. The remaining portions of the second film 52 and the fourth film 54 are stacked around the opening on the second surface 50 b side of the wafer 50 even after the through holes 12 are formed.

Next, the first film that is a silicon oxide film is formed by isotropic wet etching using an etching solution such as buffered hydrofluoric acid (Buffered HF) or a combination of isotropic etching and anisotropic etching. 51 and the third film 53 are selectively removed. At this time, the etching solution enters from the through hole 22 of the fourth film 54 and the through hole 12 of the wafer 50 to dissolve the first film 51 and the third film 53. By appropriately designing the shape and arrangement of the through holes 22 and the through holes 12, the openings 13 and 15 are formed in the first film 51 and the third film 53, respectively. As a result, the diaphragm 20, the plate 21, and the support part 23 of the sound sensing part are formed (see FIG. 1).
The condenser microphone 1 is completed through subsequent processes such as dicing and packaging.

(Second embodiment)
1. Sound Sensing Section The sound sensing section of the condenser microphone 2 of the second embodiment shown in FIG. 4 is different from the sound sensing section of the capacitor microphone 1 of the first embodiment in the shape of the substrate 10. A multi-stage stepped through hole 212 is formed in the substrate 10 of the condenser microphone 2. The substrate 10, the first film, the third film, the second film, and the part of the fourth film that is not fixed to the third film constitute a support part 223.

The support portion 223 is formed with a back air chamber 240 including a first air chamber 241 and a second air chamber 242. The first air chamber 241 is formed inside the inner wall 212 a on the plate 21 side of the substrate 10 and the inner wall 13 a of the opening 13 of the second film. The second air chamber 242 is formed inside the inner wall 212 b opposite to the plate 21 of the substrate 10. The inner wall 212 b of the substrate 10 forms a step in the thickness direction of the diaphragm 20. Thereby, the cross-sectional area in the plate thickness direction of the diaphragm 20 of the second air chamber 242 is discontinuously enlarged from the plate 21 side toward the opposite side. The inner wall 212a of the substrate 10 and the inner wall 13a of the second film correspond to the “first inner wall” recited in the claims, and the inner wall 212b of the substrate 10 corresponds to the “second inner wall”.
The detection unit of the condenser microphone 2 is substantially the same as the detection unit of the condenser microphone 1 of the first embodiment. The operation of the condenser microphone 2 is substantially the same as the operation of the condenser microphone 1 of the first embodiment. Therefore, these descriptions are omitted.

2. First, as shown in FIG. 5A1, the first film 51 to the fourth film 54 are formed on the first surface 50a of the wafer 50 by deposition as shown in FIG. 5A1. To do.
Next, a mask 255 having openings 255 a to 255 d is formed on the second surface 50 b of the wafer 50. For example, after a photoresist film is applied to the entire second surface 50b of the wafer 50, the mask 255 is formed by photolithography that performs exposure and development using a predetermined resist mask. The opening 255 a has a circular shape that exposes portions of the second film 52 and the fourth film 54 of the wafer 50. The opening 255b to the opening 255d have an annular shape along the outer periphery of the opening 255a, and have a slit shape whose radial width is smaller than the diameter of the opening 255a. The radial width of the opening 255c is smaller than the radial width of the opening 255b. The radial width of the opening 255d is smaller than the radial width of the opening 255c.

  Next, as illustrated in FIG. 5A2, the wafer 50 is anisotropically etched using a mask 255, so that a hole 260 and recesses 261 to 263 are formed in the wafer 50. Specifically, the wafer 50 exposed from the mask 255 is selectively removed by anisotropic etching such as Deep-RIE. This anisotropic etching is performed until a hole 260 is formed in a portion corresponding to the opening 255a of the wafer 50. Here, the width in the radial direction of the openings 255b to 255d is smaller than the diameter of the opening 255a. Therefore, due to the aspect-dependent etching effect, concave portions 261 to 263 are formed in portions corresponding to the opening portions 255b to 255d of the wafer 50, respectively. Further, since the width in the radial direction of the opening 255 c is smaller than the width in the radial direction of the opening 255 b, the size (depth) of the recess 262 in the plate thickness direction of the wafer 50 is smaller than that of the recess 261. Since the radial width of the opening 255d is smaller than the radial width of the opening 255c, the size (depth) of the recess 263 in the plate thickness direction of the wafer 50 is smaller than that of the recess 262.

Next, the wall portion 271 between the hole portion 260 and the concave portion 261, the wall portion 272 between the concave portion 261 and the concave portion 262, and the wall portion 273 between the concave portion 262 and the concave portion 263 are removed. Specifically, for example, it is as follows. By thermally oxidizing the second surface 50b of the single crystal silicon wafer 50, the wall portions 271 to 273 are transformed into silicon oxide. Next, the wall portions 271 to 273 are selectively removed together with the surface portion of the altered second surface 50b of the wafer 50 by wet etching using an etchant such as buffered hydrofluoric acid. As a result, multi-stepped through holes 212 are formed in the wafer 50, and portions of the second film 52 and the fourth film 54 of the first film 51 are exposed in the through holes 212. The remaining portions of the second film 52 and the fourth film 54 are stacked around the opening on the second surface 50b side of the wafer 50 even after the through holes 212 are formed.
Subsequent steps are substantially the same as the manufacturing method of the first embodiment.

(Third embodiment)
In the manufacturing method of the second embodiment, the wall portions 271 to 273 of the wafer 50 are altered to selectively remove them. However, the method for removing the wall portion is not limited to this. Hereinafter, a manufacturing method according to a third embodiment, which is different from the manufacturing method according to the second embodiment, and the wall removing method will be described.
First, as shown in FIG. 6A1, the first film 51 to the fourth film 54 are formed by deposition on the first surface 50a of the wafer 50 in the same manner as in the manufacturing method of the first embodiment.
Next, a mask 355 having an opening 355 a and an opening 355 b is formed on the second surface 50 b of the wafer 50. For example, after a photoresist film is applied to the entire second surface 50b of the wafer 50, a mask 355 is formed by photolithography that performs exposure and development using a predetermined resist mask. The opening 355a has a circular shape that exposes portions on the second film 52 and the fourth film 54 of the wafer 50. The opening 355b has an annular shape along the outer periphery of the first opening, and has a slit shape in which the radial width is smaller than the diameter of the opening 355a.

  Next, as shown in FIG. 6A 2, the wafer 50 is anisotropically etched using a mask 355, thereby forming a hole 360 and a recess 361 in the wafer 50. The hole 360 and the recess 361 are formed in a reverse taper shape from the second surface 50b of the wafer 50 toward the first surface 50a. Specifically, the wafer 50 exposed from the mask 355 is selectively removed by deep-RIE. This anisotropic etching is performed until a hole 360 is formed in a portion corresponding to the opening 355a of the wafer 50. At this time, the reversely tapered hole 360 and the recess 361 can be formed by adjusting the etching conditions. For example, the wafer 50 is etched under the condition that the depositing property to the sidewall protective film is low, or the wafer 50 is etched while adjusting the formation time and the etching time of the sidewall protective film. As a result, the wall portion 371 between the hole portion 360 and the concave portion 361 of the wafer 50 becomes thinner from the second surface 50b toward the first surface 50a.

  Next, as shown in FIG. 6A3, the wall portion 371 of the wafer 50 is removed. Specifically, the wafer 50 is wet-etched using an etchant such as potassium hydroxide (KOH) or tetramethylammonium hydroxide (TMAH). At this time, the thin portion of the wall portion 371 is dissolved before the other portion, and the wall portion 371 is separated from the wafer 50. The wall portion 371 separated from the wafer 50 is completely dissolved in the etching solution. As a result, a stepped through hole 12 is formed in the wafer 50. Note that the method of separating the wall portion 371 from the wafer 50 is not limited to the method described above. For example, the wall 371 may be separated from the wafer 50 by applying ultrasonic waves or mechanical vibrations to the wall 371. Subsequent steps are substantially the same as the manufacturing method of the first embodiment.

(Fourth embodiment)
1. Sound Sensing Part The sound sensing part of the condenser microphone 4 of the fourth embodiment shown in FIG. 7 is different from the sound sensing part of the capacitor microphone 1 of the first embodiment in the shape of the substrate 10. The substrate 10 of the condenser microphone 2 has a stepped through-hole 412 including a cylindrical hole 400 and a plurality of recesses 401 radially arranged on the outer periphery of the hole 400 and connected to the hole. Is formed. The substrate 10, the first film, the third film, the second film, and the part of the fourth film that is not fixed to the third film constitute a support part 423.

A back air chamber 440 including a first air chamber 441 and a second air chamber 442 is formed in the support portion 423. The first air chamber 441 is formed inside the inner wall 412a on the plate 21 side of the hole 400 and the inner wall 13a of the opening 13 of the second film. The second air chamber 442 is formed inside the inner wall 412 b formed by the inner wall of the hole 400 opposite to the plate 21 and the inner wall of the recess 401. The inner wall 412a of the substrate 10 and the inner wall 13a of the second film correspond to the “first inner wall” described in the claims, and the inner wall 412b of the substrate 10 corresponds to the “second inner wall”.
The detection unit of the condenser microphone 4 is substantially the same as the detection unit of the condenser microphone 1 of the first embodiment. The operation of the condenser microphone 4 is substantially the same as the operation of the condenser microphone 1 of the first embodiment. Therefore, these descriptions are omitted.

2. First, as shown in FIG. 8, the first film 51 to the fourth film 54 are formed on the first surface 50a of the wafer 50 by deposition, as shown in FIG.
Next, a mask 455 having an opening 455a and a plurality of openings 455b is formed on the second surface 50b of the wafer 50. For example, after a photoresist film is applied to the entire second surface 50b of the wafer 50, a mask 455 is formed by photolithography that performs exposure and development using a predetermined resist mask. The opening 455a has a circular shape that exposes portions on the second film 52 and the fourth film 54 of the wafer 50. The opening 455b has a slit shape extending radially from the opening 455a. The circumferential width of the opening 455a of the opening 455b is smaller than the diameter of the opening 455a.

Next, through holes 412 are formed in the wafer 50 by anisotropically etching the wafer 50 using the mask 455. Specifically, the wafer 50 exposed from the mask 455 is selectively removed by anisotropic etching such as Deep-RIE. This anisotropic etching is performed until a hole 400 (see FIG. 7) is formed in a portion corresponding to the opening 455a of the wafer 50. Here, the radial width of the opening 455a of the opening 455b is smaller than the diameter of the opening 455a. Therefore, a recess 401 is formed at a portion corresponding to the opening 455b of the wafer 50 due to the aspect-dependent etching effect. As a result, a stepped through hole 412 including a hole 400 and a plurality of concave portions 401 is formed in the wafer 50, and the second film 52 of the first film 51 and a part of the fourth film 54 are formed in the through hole 412. The part of is exposed. The remaining portions of the second film 52 and the fourth film 54 are stacked around the opening on the second surface 50b side of the wafer 50 even after the through holes 412 are formed.
Subsequent steps are substantially the same as the manufacturing method of the first embodiment.

In the plurality of embodiments described above, the cross-sectional area in the plate surface direction of the diaphragm 20 in the second air chamber is rapidly increased with respect to the cross-sectional area in the plate surface direction of the diaphragm 20 in the first air chamber. And the edge part of the thickness direction of the diaphragm 20 and the plate 21 is being fixed to the inner wall which forms the 1st air chamber. Therefore, the capacity of the back air chamber can be increased without being limited to the size of the diaphragm 20 or the plate 21 in the plate surface direction and without increasing the size of the condenser microphone.
Moreover, in 2nd embodiment, the cross-sectional area of the plate | board surface direction of the diaphragm 20 of the 2nd air chamber 242 is expanding in steps toward the opposite side to the plate 21. As shown in FIG. Thus, the capacity of the back air chamber 240 can be increased by discontinuously increasing the cross-sectional area in the plate surface direction of the diaphragm 20 of the second air chamber 242 toward the side opposite to the plate 21.

(Other embodiments)
In the above embodiments, a condenser microphone as a pressure sensor has been described. However, the present invention is also applicable to a pressure sensor that detects pressure changes other than sound pressure.
In the above embodiments, the condenser microphone including the circular diaphragm 20 and the plate 21 fixed to the support portion on the entire circumference has been exemplified. However, the configuration of the sensor unit including the diaphragm and the plate is not limited thereto. . For example, a part of the end of the diaphragm and the plate in the thickness direction may be fixed to the support portion. Specifically, the diaphragm may be fixed to the support portion in a doubly supported beam shape, or the diaphragm may be fixed to the support portion in a cantilever shape. Further, the shapes of the diaphragm and the plate are not limited to a circle. Specifically, the diaphragm and the plate may be polygonal. Further, the plate may be provided on the back air chamber side from the diaphragm. Further, the diaphragm may not be fixed directly to the support portion. Specifically, the diaphragm may be suspended from the plate, or the diaphragm may be supported on the plate.
In the above embodiments, the stepped through-hole having a right-angled step is formed in the substrate 10, but the step formed on the inner wall of the support portion may not be a right-angle.

Moreover, in said 1st embodiment-3rd embodiment, although the 2nd air chamber was expanded outside from the perimeter of the 1st air chamber, the 2nd air chamber was expanded outside from a part of 1st air chamber. Also good.
The manufacturing method of the first embodiment can also be applied to the manufacturing of the condenser microphone 2 of the second embodiment. In this case, a multilayer mask having the number of layers corresponding to the number of steps of the stepped through holes 12 may be formed. In the manufacturing method of the first embodiment, a multi-layer mask composed of the first mask 55 and the second mask 56 is used. However, a resist whose thickness is designed according to the shape of the stepped through hole 12 is used. A single layer mask made of may be used.

The manufacturing method of the second embodiment can also be applied to the manufacture of the condenser microphone 1 of the first embodiment. In this case, the openings 255b to 255d having the same radial width may be formed in the mask 255.
In the manufacturing method of the second embodiment, the mask 255 having the annular openings 255b to 255d is formed. However, the openings 255b to 255d may be strip-shaped.
In the manufacturing method of the second embodiment, other slit-shaped openings that intersect the openings 255b to 255d may be formed in the mask 255. In this case, the wall portion between the recesses corresponding to the openings 255b to 255d of the substrate 10 is divided by the recesses corresponding to the other openings described above. As a result, the wall can be easily removed by wet etching or the like.

In the third embodiment, the method for manufacturing the condenser microphone 1 of the first embodiment has been described. However, the manufacturing method of the third embodiment can also be applied to the manufacture of the condenser microphone 2 of the second embodiment.
Moreover, although the several recessed part 401 was formed in the said 4th embodiment, the recessed part 401 may be one.
In the fourth embodiment, the plurality of concave portions 401 are radially arranged outside the hole portion 400, but the concave portions 401 may be unevenly distributed outside the hole portion 400.

(A) is a top view which shows the condenser microphone of 1st embodiment, (B) is sectional drawing by the B1-B1 line | wire of (A). The schematic diagram which shows the manufacturing method of the capacitor | condenser microphone of 1st embodiment. The schematic diagram which shows the manufacturing method of the capacitor | condenser microphone of 1st embodiment. (A) is a top view which shows the condenser microphone of 2nd embodiment, (B) is sectional drawing by the B4-B4 line | wire of (A). The schematic diagram which shows the manufacturing method of the capacitor | condenser microphone of 2nd embodiment. The schematic diagram which shows the manufacturing method of the capacitor | condenser microphone of 3rd embodiment. (A) is sectional drawing by the A7-A7 line | wire of (B), (B) is a bottom view which shows the condenser microphone of 4th embodiment. The schematic diagram which shows the manufacturing method of the condenser microphone of 4th embodiment.

Explanation of symbols

1, 2, 4: Condenser microphone, 12, 212, 412: Through hole, 12a, 212a, 412a: Inner wall (first inner wall), 12b, 212b, 412b: Inner wall (second inner wall), 13a: Inner wall (first Inner wall), 20: diaphragm, 21: plate, 23, 223, 423: support part, 41, 241, 441: first air chamber, 42, 242 and 442: second air chamber, 50: wafer (substrate), 50a : First surface (first surface of the substrate), 50b: second surface (second surface of the substrate), 52: second film (thin film constituting the diaphragm), 54: fourth film (thin film constituting the plate) 55: first mask, 55a: first opening, 56: second mask, 56a: second opening, 60: recess, 255, 355, 455: mask, 255a, 355a, 455a: opening (first Opening), 255b-2 5d, 355b, 455b: opening (second opening), 260, 360: hole, 261 to 263, 361: recess, 271, 371: wall (wall between the hole and recess), 272 273: Wall (wall between adjacent recesses)

Claims (7)

A substrate having a through hole;
A plate having fixed electrodes;
A movable electrode facing the fixed electrode, and a diaphragm displaced by a pressure change;
An annular insulating portion that is connected to the substrate and fixes the end of the plate and the end of the diaphragm;
The through hole is composed of a first air chamber and a second air chamber formed by a step in the thickness direction of the substrate,
The cross-sectional area in the plate surface direction of the substrate of the second air chamber is larger than the cross-sectional area of the first air chamber,
A space inside the insulating portion located on the substrate side of the diaphragm constitutes a part of the first air chamber by connecting to the first air chamber,
The condenser microphone, wherein the first air chamber and the second air chamber form a back air chamber. A substrate having a through hole;
A plate having fixed electrodes;
A diaphragm having a movable electrode facing the fixed electrode and displaced by a pressure change;
An annular insulating portion that is connected to the substrate and fixes an end portion of the plate and an end portion of the diaphragm, and a method of manufacturing a condenser microphone ,
A thin film constituting the thin film and the insulating portion and the thin film constituting the plate on the first surface on constituting the diaphragm of the substrate is formed by depositing,
Forming a first mask having a first opening on a second surface opposite to the first surface of the substrate;
Covering the first mask, and forming a second mask having a second opening for forming the through hole so as to cover a part of the inside of the substrate of the first opening,
Forming a recess in the substrate by anisotropically etching the substrate exposed to the second opening using the second mask;
Wherein the second mask is removed, a portion of the bottom of said substrate said recess first using the mask to expose the first opening is removed the insulation portion is anisotropically etched until it exposed This forms the through hole consisting of the first air chamber and the second gas chamber to said substrate,
A method of manufacturing a condenser microphone . A substrate having a through hole;
A plate having fixed electrodes;
A diaphragm having a movable electrode facing the fixed electrode and displaced by a pressure change;
An annular insulating portion that is connected to the substrate and fixes an end portion of the plate and an end portion of the diaphragm, and a method of manufacturing a condenser microphone ,
A thin film constituting the thin film and the insulating portion and the thin film constituting the plate on the first surface on constituting the diaphragm of the substrate is formed by depositing,
On the opposite side of the second surface on said first surface of said substrate, a first opening, the second width greater than the diameter of Yan have the first opening is a narrow slit-shaped at the outer edge of the first opening forming a mask having an opening, a,
By anisotropic etching using the mask to form the hole having a plurality of air chambers in the substrate,
A method of manufacturing a condenser microphone . A plurality of recesses are formed in the substrate by using the mask in which a plurality of the second openings narrower toward the first opening are formed outside the first opening,
The method for manufacturing a condenser microphone according to claim 3 , comprising removing a wall portion between the concave portions adjacent to each other on the substrate. Forming the recess in the inversely tapered toward the first surface from said second surface of said substrate, a manufacturing method of the condenser microphone according to claim 3 or 4.   The method for manufacturing a condenser microphone according to claim 3, wherein the removal of the wall portion is performed after the wall portion is thermally oxidized. A substrate having a through hole;
A plate having fixed electrodes;
A diaphragm having a movable electrode facing the fixed electrode and displaced by a pressure change;
An annular insulating portion that is connected to the substrate and fixes an end portion of the plate and an end portion of the diaphragm, and a method of manufacturing a condenser microphone ,
A thin film constituting the thin film and the insulating portion and the thin film constituting the plate on the first surface on constituting the diaphragm of the substrate is formed by depositing,
On the opposite side of the second surface on said first surface of said substrate, a first opening, the first said Ri connected to the opening width than the diameter of the first opening is a plurality of slit-like narrow second forming a mask having an opening, a,
By anisotropically etching the substrate exposed to the first opening and the second opening by using said mask to form the hole constituting the air chamber to said substrate,
A method of manufacturing a condenser microphone .

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