JP2006121465A - Acoustic sensor and method for manufacturing acoustic sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acoustic sensor for improving noise tolerance to an acoustic signal. <P>SOLUTION: This acoustic sensor 100 is provided with a vibrating electrode 16 formed on a silicon substrate 52 and a fixed electrode 14 arranged with a predetermined interval oppositely to the vibrating electrode 16, and a capacitor is configured of the vibrating electrode 16 and the fixed electrode 14. Central direction width T2 in the acoustic sensor 100 of a film (insulating film 55, reinforced film 60, protecting film 12) fixing the fixed electrode 14 to the silicon substrate 52 is made larger than film thickness T1 of a film (protecting film 12, fixed electrode 14, insulating film 55) covering the fixed electrode 14 and both faces of the fixed electrode 14. Also, the film fixing the fixed electrode 14 to the silicon substrate 52 is formed of the film (strengthened film 60, insulating film 55, protecting film 12) constituted of two or more types of materials. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an acoustic sensor and a method for manufacturing the acoustic sensor.

Conventionally, a capacitor-type silicon microphone has been proposed as a semiconductor sensor for detecting acoustic vibration (see, for example, Patent Document 1 and Patent Document 2). This microphone
A vibration electrode and a fixed electrode facing the vibration electrode and arranged at a predetermined interval are provided, and a capacitor is formed by the vibration electrode and the fixed electrode.

When the sound pressure is applied to the microphone, the vibration electrode vibrates, and the capacitance changes due to a change in the distance between the vibration electrode and the fixed electrode due to the vibration. Furthermore, an acoustic signal is obtained by electrically reading a change in voltage between the two electrodes accompanying a change in capacitance.
JP-T 60-500841 JP 2002-328117 A

In the microphone described above, noise countermeasures are important in order to measure changes in capacitance due to vibration. In particular, when the fixed electrode is displaced due to vibration or the like, there is a problem that an accurate capacitance change cannot be measured, and noise is added to the obtained acoustic signal.

Then, an object of this invention is to provide the manufacturing method of the acoustic sensor which improves the noise tolerance with respect to an acoustic signal, and an acoustic sensor in view of said subject.

In order to achieve the above object, a first feature of the present invention includes a vibration electrode formed on a semiconductor substrate, and a fixed electrode opposed to the vibration electrode and disposed at a predetermined interval. And a fixed electrode, a sensor comprising a capacitor, wherein the width in the center direction of the film sensor that fixes the fixed electrode to the semiconductor substrate is larger than the film thickness of the film that covers both surfaces of the fixed electrode and the fixed electrode It is a summary.

The force due to internal stress of the fixed electrode and a film covering both surfaces of the fixed electrode (hereinafter referred to as “film A”) is applied to a film (hereinafter referred to as “film B”) that fixes the fixed electrode to the semiconductor substrate. This force decreases as the film thickness of the film A decreases. On the other hand, when the width of the film B increases, the area where the film B is in contact with the semiconductor substrate increases, and as a result, the force due to the internal stress of the film A per unit area decreases.

Therefore, according to the acoustic sensor according to the first feature, since the width of the film B is larger than the film thickness of the film A, the force due to the internal stress of the film A per unit area in contact with the semiconductor substrate of the film B is reduced. And
It has a high strength structure. For this reason, a fixed electrode does not displace and it can improve the noise tolerance with respect to an acoustic signal.

In the acoustic sensor according to the first feature, the film for fixing the fixed electrode to the semiconductor substrate is 2
It is preferable that the film is formed of different kinds of materials. Also, as a film made of different materials,
It is preferable to use films having different internal stress states with respect to the semiconductor substrate.

A second feature of the present invention includes a vibrating electrode formed on a semiconductor substrate and a fixed electrode facing the vibrating electrode and arranged at a predetermined interval, and a capacitor is configured by the vibrating electrode and the fixed electrode. The gist of the present invention is that the film for fixing the fixed electrode to the semiconductor substrate is an acoustic sensor formed of two or more types of different films.

According to the acoustic sensor according to the second feature, since the film surrounding the fixed electrode is formed of a film made of a different material, vibration of a frequency that is easily absorbed by the other material with respect to vibration propagating through one material. Since it absorbs, it becomes a structure which a vibration does not propagate easily. For this reason, the fixed electrode is not displaced,
Noise resistance against acoustic signals can be improved.

The acoustic sensor according to the second feature preferably uses films having different internal stress states with respect to the semiconductor substrate as films made of different materials. According to this acoustic sensor, the internal stress can be effectively canceled by combining materials having tensile stress that contracts with respect to the semiconductor substrate and yield stress that expands with respect to the semiconductor substrate.

A third feature of the present invention is a method of manufacturing an acoustic sensor in which a capacitor is constituted by a vibrating electrode and a fixed electrode, wherein (a) a step of forming an etch stopper on a semiconductor substrate, and (b) an etch stopper Forming a vibrating electrode thereon; (c) forming a sacrificial film on the vibrating electrode and a reinforcing film disposed at a predetermined distance outside the sacrificial film; and (d) a sacrificial film and the reinforcing film. Forming an insulating film that insulates the vibration electrode and the fixed electrode on the film and burying between the sacrificial film and the reinforcing film; and (e) forming a conductive film that forms the fixed electrode on the insulating film; Patterning the conductive film to form an acoustic hole; (f) forming a protective film on the fixed electrode; patterning the protective film to remove the protective film from the acoustic hole; and (g) Selectively etch from the back side of the semiconductor substrate to expose the vibrating electrode. A step of, and summarized in that through (h) sound hole, a manufacturing method of the acoustic sensor and a step of selectively etching the sacrificial layer.

According to the method for manufacturing an acoustic sensor according to the third feature, since the reinforcing film disposed with a predetermined distance is formed outside the sacrificial film, the periphery of the fixed electrode can be firmly held. . For this reason, a fixed electrode does not displace and it can improve the noise tolerance with respect to an acoustic signal. Further, in the acoustic sensor manufacturing method according to the third feature, the sacrificial film is formed at the same time as the reinforced film is formed. Therefore, the acoustic sensor can be manufactured with the same number of steps as in the prior art.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the acoustic sensor which improves the noise tolerance with respect to an acoustic signal, and an acoustic sensor can be provided.

Next, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings below,
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 ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like 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.

(Acoustic sensor)
As shown in FIGS. 1 and 2, the acoustic sensor 100 according to the present embodiment includes a silicon substrate 52.
A vibration electrode 16 formed above and a fixed electrode 14 facing the vibration electrode 16 and arranged at a predetermined interval are provided, and the vibration electrode 16 and the fixed electrode 14 constitute a capacitor. or,
FIG. 1 is a top view illustrating the configuration of the acoustic sensor 100 according to the present embodiment, and FIG. 2 is a cross-sectional view taken along the line AA ′ of the acoustic sensor 100 of FIG.

The acoustic sensor 100 includes an air gap layer 10, a protective film 12, an insulating film 55, a reinforcing film 60, a fixed electrode 14, a vibrating electrode 16, a substrate opening 20, an acoustic hole 22, and a vibrating electrode pad electrode 2.
4, a fixed electrode pad electrode 26, an etch stopper 50, a silicon substrate 52, and the like. still,
As is apparent from FIG. 2, the air gap layer 10 and the like cannot be directly seen from the upper surface in FIG. However, in order to facilitate the understanding of the structure, portions that are not directly visible are shown so that they can be seen as appropriate.

The silicon substrate 52 is a substrate for the acoustic sensor 100. As shown in FIG. 2, sound holes are formed in the silicon substrate 52 from the upper side to the lower side of the silicon substrate 52. Also, as shown in FIGS. 1 and 2, the sound hole substrate opening 20 on the upper surface of the silicon substrate 52 is used.
Has a quadrangular shape. The upper surface of the silicon substrate 52 includes an etch stopper 50.

As shown in FIG. 2, the vibrating electrode 16 is formed so as to cover the sound hole in the cross section of the silicon substrate 52. A sound pressure is inputted from the lower side of the sound hole, and the vibrating electrode 16 can be vibrated by the sound pressure, that is, can be moved.

As shown in FIG. 2, the fixed electrode 14 is provided above the vibration electrode 16, and the vibration electrode 16.
Together with this, a capacitor is formed. The capacitor has a characteristic that the capacitance value changes when the vibrating electrode 16 vibrates due to sound pressure. The fixed electrode 14 is designed to have a size that occupies at least a part of the substrate opening 20, that is, the sound hole.

As illustrated in FIG. 2, the protective film 12 is formed so as to cover the vibration electrode 16 and the fixed electrode 14. Here, a space formed between the protective film 12 and the fixed electrode 14 and the vibration electrode 16 is referred to as an air gap layer 10. Further, the protective film 12 and the fixed electrode 14 form a plurality of acoustic holes 22.

The vibration electrode pad electrode 24 and the fixed electrode pad electrode 26 are respectively connected to the vibration electrode 16 and the fixed electrode 14 to apply a predetermined voltage. Further, if the capacitance of the capacitor by the vibrating electrode 16 and the fixed electrode 14 changes, the potential difference between the vibrating electrode pad electrode 24 and the fixed electrode pad electrode 26 also changes. Output as.
That is, the vibration electrode pad electrode 24 and the fixed electrode pad electrode 26 indirectly detect a change in capacitance of the capacitor. For example, the output audio signal is output by a speaker or converted into a digital signal and stored.

In the acoustic sensor 100 according to the present embodiment, as shown in FIG. 2, the acoustic sensor 100 of a film (insulating film 55, reinforcing film 60, protective film 12) that fixes the fixed electrode 14 to the silicon substrate 52.
The width T2 in the center direction (radial direction when the acoustic sensor 100 is circular) is larger than the film thickness T1 of the fixed electrode 14 and the film (protective film 12 and insulating film 55) covering both surfaces of the fixed electrode 14. . For this reason, the amount per unit area of the portion where the film that fixes the fixed electrode 14 to the silicon substrate 52 is in contact with the silicon substrate 52 due to the internal stress generated by the insulating film 55, the fixed electrode 14, and the protective film 12 is reduced.

In FIG. 2, the film for fixing the fixed electrode 14 to the silicon substrate 52 includes the reinforcing film 60 and the insulating film 55.
The protective film 12 is a laminated film. The reinforcing film 60 is a film formed at the same time as a sacrificial film for forming the air gap layer 10 later, and is formed of the same material as the sacrificial film, for example, a silicon oxide film. The insulating film 55 serves to embed between the sacrificial film and the reinforcing film 60 as well as to insulate the vibration electrode 16 and the fixed electrode 14. The insulating film 55 and the protective film 12 are formed of, for example, a silicon nitride film.

The film for fixing the fixed electrode 14 to the silicon substrate 52 is formed of two or more different materials such as a silicon oxide film and a silicon nitride film. At this time, it is preferable to use films having different internal stress states with respect to the silicon substrate 52 as films of different materials.

Here, the internal stress state will be described. As shown in FIG. 3, when the film 65 is formed on the silicon substrate 52, there are a film on which contracting tensile stress works and a film on which expanding yield stress works. That is, the “internal stress state” indicates whether a tensile stress is applied or a yield stress is applied. FIG. 4 shows a material on which tensile stress works and a material on which yield stress works. A positive value indicates tensile stress, and a negative value indicates yield stress. Note that “LP−” in FIG. 4 indicates that it is formed by a low-pressure CVD method, and “Pe−” indicates that it is formed by a plasma CVD method. Examples of the material having a tensile stress include SiN, Cu, and SiOC, and examples of the material having a yield stress include polysilicon, SiO ₂ , Al, and SiC.

The film for fixing the fixed electrode 14 to the silicon substrate 52 is preferably formed by combining a film made of a material having a tensile stress and a film made of a material having a yield stress as shown in FIG. In particular, as described above, it is preferable to combine a silicon nitride film generally used as the insulating film 55 and the protective film 12 with a silicon oxide film generally used as a sacrificial film.

(Manufacturing method of acoustic sensor)
Next, a method for manufacturing the acoustic sensor 100 according to the present embodiment will be described with reference to FIGS. 5 to 7 correspond to the AA ′ cross section in the acoustic sensor 100 of FIG. 1, similarly to FIG. 2.

First, in Step 1 shown in FIG. 5A, an etch stopper 50 is deposited on the double-side polished silicon substrate 52 to a thickness of 200 nm. The etch stopper 50 becomes a stopper when the silicon substrate 52 is etched later from the back surface. For the etch stopper 50, a silicon nitride film is generally used. Gases used for forming the silicon nitride film are monosilane and ammonia, dichlorosilane and ammonia, and the film formation temperature is 300 to 600 ° C.

Next, in step 2 shown in FIG. 5B, the vibrating electrode 16 is placed on the etch stopper 50.
A μm film is formed. Polysilicon is generally used for the vibrating electrode 16, but other conductive materials may be used. Then, unnecessary portions of the vibrating electrode 16 are removed using a normal photolithography technique and an etching technique.

Next, in step 3 shown in FIG. 5C, a sacrificial film 56 of about 3 μm is formed on the vibrating electrode 16.
A reinforcing film 60 is formed outside the sacrificial film 56 so as to be disposed at a predetermined distance. Sacrificial film 5
6, it is common to use a silicon oxide film containing phosphorus (P), but hydrofluoric acid (HF
Any membrane may be used as long as it is soluble in (). The sacrificial film 56 is a film that does not remain in the final structure because it is removed later by etching with HF. The peripheral portion of the sacrificial film 56 is removed using a normal photolithography technique and an etching technique. Since the film thickness of the sacrificial film 56 is the final air gap distance between the electrodes, the capacitance (C = e * S / t, e: dielectric constant, S: electrode area, t: air gap distance), that is, In addition to being reflected in the sensitivity, the structure of the acoustic sensor 100 is strongly affected. For example, if the air gap layer is too narrow, the vibrating electrode 16 and the fixed electrode 14 come into contact with each other and sensing becomes impossible.

The reinforcing film 60 is a film made of the same material as the sacrificial film 56. The reinforcing film 60 is formed as a film that reinforces the film that fixes the fixed electrode 14 to be formed later to the silicon substrate 52, and the distance from the sacrificial film 56 may be less than twice the film thickness of the insulating film 55. desirable.

FIGS. 6A to 6C show a method for manufacturing the acoustic sensor 100 following FIGS. 5A to 5C.

In Step 4 shown in FIG. 6A, an insulating film 55 that insulates the vibrating electrode 16 and the fixed electrode 14 is formed on the sacrificial film 56 and the reinforcing film 60 by 200 nm. The insulating film 55 is formed of the sacrificial film 5.
6 and the reinforcing film 60 are embedded. As the insulating film 55, a silicon nitride film is generally used. Then, unnecessary portions are removed using a normal photolithography technique and an etching technique.

Next, in Step 5 shown in FIG. 6B, a conductive film for forming the fixed electrode 14 is formed on the insulating film 55. From the viewpoint of mechanical strength, the conductive film is preferably polysilicon. Then, unnecessary portions are removed using a normal photolithography technique and an etching technique. At the time of this patterning, the acoustic hole 22 for moving the air in the air gap according to the displacement of the vibrating electrode 16 is patterned at the same time.

Next, in step 6 shown in FIG. 6C, a silicon nitride film that is the protective film 12 is formed on the fixed electrode 14. Then, unnecessary portions of the silicon nitride film are removed using a normal photolithography technique and an etching technique. Here, the unnecessary portion includes not only the peripheral portion but also the pad portion and the acoustic hole 22. At this time, the fixed electrode 14 and the fixed electrode 1
4 is a film (protective film 12, insulating film 55) having a thickness T1 of about 2 μm, but a film for fixing the fixed electrode 14 to the silicon substrate 52 (insulating film 55, reinforcing film 60, protective film 12). The width T2 in the center direction of the acoustic sensor 100 is easily larger than 2 μm. That is, T1 <T
A film thickness of 2 can be obtained.

Further, when the protective film 12 is patterned, the position of the acoustic hole 22 that has been processed earlier is aligned, and an acoustic hole having a smaller diameter than that formed by the conductive film is formed at the same time. As a result, the fixed electrode 14 is not exposed and is not etched when the silicon substrate 52 is etched later.

FIGS. 7A to 7C show a method for manufacturing the acoustic sensor 100 following FIGS. 6A to 6C.

In step 7 shown in FIG. 7A, pad electrodes for the vibration electrode pad electrode 24 and the fixed electrode pad electrode 26 are formed in the pad portion. A low resistance metal film such as aluminum, copper, or gold is particularly suitable for the pad electrode. As a formation method, there is a method using a normal photolithography technique and an etching technique, but a technique such as a so-called plating resist method or a resist etch-off method may be applied.

Next, in step 8 shown in FIG. 7B, an etching mask is formed on the back surface of the silicon substrate 52, and using this etching mask, an aqueous potassium hydroxide solution (KOH) or an aqueous tetramethylammonium hydroxide solution (TMAH). Isotropic etching is performed with an alkaline etching solution such as This isotropic etching is automatically stopped by the etch stopper 50 formed in step 1. Thereafter, the etch stopper 50 in the opened portion from the back side is removed by an etching solution (for example, phosphoric acid) or dry etching.

Next, in step 9 shown in FIG. 7C, the sacrificial film 56 is completely removed by selectively etching the sacrificial film 56 using HF from the acoustic hole 22 and the back surface side. Thus, the air gap layer 10 is finally formed.

(Modification)
Next, modified examples of the acoustic sensor 100 according to the present embodiment will be described with reference to FIGS.

In FIG. 2, the reinforced film 60 is formed by a single piece, but as shown in FIG. 8, the reinforced film 60a,
A plurality of 60b may be formed side by side on the silicon substrate 52.

In FIG. 2, the periphery of the reinforcing film 60 is covered with the insulating film 55 and the protective film 12. However, as shown in FIG. 9, the insulating film 55 and the protective film 12 may be stacked on the reinforcing film 60. I do not care.

In FIG. 2, the periphery of the reinforcing film 60 is covered with the insulating film 55 and the protective film 12.
And as shown in FIG. 11, you may form the reinforcement | strengthening film | membrane 60, the insulating film 55, and the protective film 12 so that it may adjoin.

Further, the arrangement of the reinforcing film 60 may cover the entire periphery of the fixed electrode as shown in FIG. 12, or may be divided so as to cover a part of the periphery of the fixed electrode as shown in FIG. May be. 12 and 13 show portions that are not directly visible from the upper surface as in FIG.

(Function and effect)
In the acoustic sensor 100 according to the present embodiment, a film (a protective film 12, an insulating film 12) having a center-direction width T <b> 2 in the acoustic sensor 100 of the film that fixes the fixed electrode 14 to the silicon substrate 52 covers both the fixed electrode 14 and the fixed electrode 14. It is larger than the total film thickness T1 of the film 55). For this reason, the fixed electrode 1
The force due to the internal stress of the fixed electrode 14 per unit area and the film covering both surfaces of the fixed electrode 14 (protective film 12, insulating film 55) in contact with the silicon substrate 52 of the film that fixes 4 to the silicon substrate 52 decreases, It has a high strength structure. Therefore, according to the acoustic sensor 100 according to the present embodiment, the fixed electrode is not displaced, and noise resistance against the acoustic signal can be improved.

In the acoustic sensor 100 according to the present embodiment, the film for fixing the fixed electrode 14 to the silicon substrate 52 is formed of two or more different types of films. Thus, since the film surrounding the fixed electrode 14 is formed of a film made of different materials, the structure has a high strength. For this reason, the fixed electrode 14 is not displaced, and noise resistance against an acoustic signal can be improved. In addition, by using two or more kinds of different films, vibrations with a frequency that easily propagates to the film can be absorbed by different films, and displacement of the fixed electrode 14 can be suppressed.

Moreover, it is preferable to use films having different internal stress states with respect to the silicon substrate 52 as the films made of different materials. As described above, the internal stress can be effectively canceled by combining the materials having the tensile stress that contracts with respect to the silicon substrate 52 and the yield stress that expands with respect to the silicon substrate 52.

Further, in the method for manufacturing the acoustic sensor 100 according to the present embodiment, the reinforcing film 60 disposed with a predetermined distance is formed outside the sacrificial film 56, so that the periphery of the fixed electrode 14 is firmly held. can do. For this reason, the fixed electrode 14 is not displaced, and noise resistance against an acoustic signal can be improved. In addition, in this manufacturing method, since the sacrificial film 56 is formed and the reinforcing film 60 is formed at the same time, the acoustic sensor 100 can be manufactured with the same number of steps as in the prior art.

(Other embodiments)
Although the present invention has been described according to the above-described embodiments, 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.

For example, as shown in FIG. 2, a film (insulating film 5) that fixes the fixed electrode 14 to the silicon substrate 52.
5, the central direction width T2 of the acoustic film 100 of the reinforcing film 60 and the protective film 12) is larger than the film thickness T1 of the film (protective film 12, insulating film 55) covering both surfaces of the fixed electrode 14 and the fixed electrode 14, In addition, the film for fixing the fixed electrode 14 to the silicon substrate 52 is a film made of a different material (reinforced film 6
Although the acoustic sensor 100 formed of 0, the insulating film 55, and the protective film 12) has been described, the acoustic sensor 100 according to the present embodiment may satisfy any one of these conditions. That is, the acoustic sensor 100 according to the present embodiment may satisfy the film thickness condition of T1 <T2 or may be formed from films made of different materials.

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 top view which shows the structure of the acoustic sensor which concerns on this embodiment. FIG. 2 is a cross-sectional view taken along the line A-A ′ of FIG. 1. It is a figure explaining the internal stress state of the acoustic sensor which concerns on this embodiment. It is a graph explaining the internal stress state for every material. It is sectional drawing which shows the manufacturing method of the acoustic sensor which concerns on this embodiment (the 1). It is sectional drawing which shows the manufacturing method of the acoustic sensor which concerns on this embodiment (the 2). It is sectional drawing which shows the manufacturing method of the acoustic sensor which concerns on this embodiment (the 3). It is sectional drawing which shows the modification of the acoustic sensor which concerns on this embodiment (the 1). It is sectional drawing which shows the modification of the acoustic sensor which concerns on this embodiment (the 2). It is sectional drawing which shows the modification of the acoustic sensor which concerns on this embodiment (the 3). It is sectional drawing which shows the modification of the acoustic sensor which concerns on this embodiment (the 4). It is a top view which shows arrangement | positioning of the reinforcement film | membrane of the acoustic sensor which concerns on this embodiment (the 1). It is a top view which shows arrangement | positioning of the reinforcement film | membrane of the acoustic sensor which concerns on this embodiment (the 2).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Air gap layer 12 ... Protective film 14 ... Fixed electrode 16 ... Vibrating electrode 20 ... Substrate opening 22 ... Acoustic hole 24 ... Vibrating electrode pad electrode 26 ... Fixed electrode pad electrode 50 ... Etch stopper 52 ... Silicon substrate 55 ... Insulating film 56 ... Sacrificial film 60, 60a, 60b ... Reinforcement film 100 ... Acoustic sensor

Claims (6)

An acoustic sensor comprising: a vibration electrode formed on a semiconductor substrate; and a fixed electrode facing the vibration electrode and arranged at a predetermined interval, and constituting a capacitor by the vibration electrode and the fixed electrode. ,
The width in the center direction of the acoustic sensor of the film for fixing the fixed electrode to the semiconductor substrate is
The acoustic sensor characterized by being larger than the film thickness of the said fixed electrode and the film | membrane which covers both surfaces of the said fixed electrode. The acoustic sensor according to claim 1, wherein the film for fixing the fixed electrode to the semiconductor substrate is formed of two or more different types of films. The acoustic sensor according to claim 2, wherein films having different internal stress states with respect to the semiconductor substrate are used as the films having different materials. An acoustic sensor comprising: a vibration electrode formed on a semiconductor substrate; and a fixed electrode facing the vibration electrode and arranged at a predetermined interval, and constituting a capacitor by the vibration electrode and the fixed electrode. ,
The acoustic sensor according to claim 1, wherein the film for fixing the fixed electrode to the semiconductor substrate is formed of two or more kinds of different films. The acoustic sensor according to claim 4, wherein films having different internal stress states with respect to the semiconductor substrate are used as the films having different materials. A method of manufacturing an acoustic sensor that constitutes a capacitor with a vibrating electrode and a fixed electrode,
Forming an etch stopper on the semiconductor substrate;
Forming the vibrating electrode on the etch stopper;
Forming on the vibrating electrode a sacrificial film and a reinforcing film disposed at a predetermined distance outside the sacrificial film;
Forming an insulating film on the sacrificial film and the reinforcing film to insulate the vibration electrode and the fixed electrode and fill the gap between the sacrificial film and the reinforcing film;
Forming a conductive film for forming the fixed electrode on the insulating film, and patterning the conductive film to form an acoustic hole;
Forming a protective film on the fixed electrode, patterning the protective film, and removing the protective film of the acoustic hole;
Selectively etching from the back side of the semiconductor substrate to expose the vibrating electrode;
And a step of selectively etching the sacrificial film through the acoustic hole.

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