JPH09257833A - Electret applied device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electret applied device having little nonuniformity in performance, and a manufacture thereof. SOLUTION: This device is prepared by joining a fixed piece 20 having a fixed electrode with a movable piece 10 having a movable part 10a' functioning also as a movable electrode. The fixed piece 20 has an electrode 25 for charging formed in a portion opposite to the movable part 10a' and a contact 42 formed at a portion opposite to a contact 41 with an insulating film 27a interlaid. A surface potential of an electret 3 is regulated by impressing a high voltage on the electrode 25 for charging to generate a corona discharge and by charging the electret 3 therewith, after the fixed piece 20 is joined with the movable piece 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electret application device and a manufacturing method thereof.

[0002]

2. Description of the Related Art As a known example of a conventional electret application device, there is an electrostatic drive type relay disclosed in Japanese Patent Application Laid-Open No. 2-100224. This electrostatic drive type relay has an electret on a fixed electrode made of a silicon substrate. The fixed piece on which is formed is joined to the movable piece having the movable electrode formed of the cantilever portion formed by anisotropically etching the silicon substrate. Here, the electret is electrified by corona discharge, electron beam irradiation, ion irradiation, or the like before joining the fixed piece and the movable piece.

[0003]

By the way, in the manufacture of the electrostatic drive type relay, a temperature of about 200 ° C. to 500 ° C. is applied when joining the fixed piece and the movable piece.
When the fixed piece made of a glass substrate and the movable piece made of a silicon substrate are joined by the anodic bonding technique, the substrate needs to be heated to about 400 ° C. Such a joining process is the same for other electret applied devices, for example, for joining a fixed piece and a movable piece such as an acceleration sensor or a pressure sensor. However, in any electret application device, since the electret is formed before joining the fixed piece and the movable piece, the equivalent voltage of the electret is lowered by the joining step, and at this time, the joining temperature, the joining time, etc. may be slightly different. However, there is a problem in that the value of the equivalent voltage of the electret is different due to the difference between the two, and the variation of the equivalent voltage, that is, the surface potential increases. For this reason,
There is a problem that the electrostatic drive type relay has a large variation in driving voltage between products, and the acceleration sensor, the pressure sensor, and the like have a large variation in sensor output between products.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an electret application device having a small performance variation and a manufacturing method thereof.

[0005]

In order to achieve the above object, the invention according to claim 1 has a fixed piece having a fixed electrode, and a movable portion facing the fixed electrode with a gap therebetween. A movable piece that is swingably supported and joined to the fixed piece, an electret formed on one of the fixed electrode and the movable portion, and a charging electrode formed on a portion facing the electret. Since it is possible to charge the electret by corona discharge even after joining the fixed piece and the movable piece, there is little variation in surface potential by charging after joining and variation in performance. It is possible to provide a small electret application device.

According to a second aspect of the present invention, there is provided a fixed piece having a fixed electrode, and a movable portion facing the fixed electrode with a gap therebetween. The movable portion is swingably supported and joined to the fixed piece. In the manufacturing method of the electret application device having a movable piece, an electret formed on any one of the fixed electrode and the movable portion, and a charging electrode formed on a portion facing the electret, the charging electrode It is characterized in that it has a charging step of charging the electret by applying a high voltage to generate a corona discharge, which is charged by corona discharge after joining the fixed piece and the movable piece. Since the surface potential of the electret can be adjusted with, the performance variation of the electret application device can be reduced.

According to the invention of claim 3, in the invention of claim 2, since the charging step is performed after the fixed piece and the movable piece are joined, it is possible to prevent a decrease in the surface potential of the electret due to the influence of heating at the time of joining. You can The invention of claim 4 is
In the invention of claim 1, since the charging electrode also serves as the detection electrode or the drive voltage application electrode, it is not necessary to separately provide the detection electrode or the drive voltage application electrode, and the manufacturing process can be simplified. .

The invention of claim 5 is the invention of claim 1 or claim 4.
In the invention, since the mesh-shaped electrode is formed on the surface of the electret, the mesh-shaped electrode can be used as a grid electrode when the electret is charged by corona discharge, and the surface potential of the electret can be adjusted with good controllability. Therefore, the performance variation of the electret application device can be reduced.

According to a sixth aspect of the present invention, there is provided a fixed piece having a fixed electrode, and a movable portion facing the fixed electrode with a gap therebetween. The movable portion is swingably supported and joined to the fixed piece. A movable piece, an electret, a charging electrode formed in a portion facing the electret, and a electret application device having a mesh-shaped electrode formed at a position sandwiching the electret on the surface side on which the electret is formed In the manufacturing method, a high voltage is applied to the charging electrode to generate a corona discharge, and the mesh-shaped electrode is used as a grit electrode to charge the electret, and the electret is electrified by corona discharge. The surface potential can be adjusted with good controllability when electrifying the surface of the electret application device. It can be reduced.

According to the invention of claim 7, in the invention of claim 6, since the charging step is carried out after the fixed piece and the movable piece are joined together, it is possible to prevent the surface potential from being lowered due to the influence of heating during joining. . According to an eighth aspect of the present invention, a fixed piece having a fixed electrode, and a movable piece having a movable portion facing the fixed electrode via a gap, the movable portion being swingably supported and joined to the fixed piece. An electret formed on one of the fixed electrode and the movable portion, a charging electrode formed on a portion facing the electret, and a mesh formed on a surface side of the electret facing the charging electrode. In a method for manufacturing an electret application device having a striped electrode, a charging step of charging the electret by applying a high voltage to the charging electrode to generate corona discharge and using the mesh electrode as a grit electrode is included. The feature is to reduce the variation of the surface potential of the electret and adjust the value of the surface potential of the electret. Kill.

According to the invention of claim 9, the member facing the electret through the gap is formed in a mesh shape, so that when the electret is charged by corona discharge, the mesh member is used as a grid electrode. Therefore, it is possible to adjust the surface potential with good controllability, and it is possible to provide an electret application device with small performance variations.

According to a tenth aspect of the present invention, there is provided a fixed piece having a fixed electrode, and a movable portion facing the fixed electrode with a gap therebetween. The movable portion is swingably supported and joined to the fixed piece. In the manufacturing method of the electret application device having a movable piece, an electret formed on any one of the fixed electrode and the movable portion, and a mesh-shaped charging electrode formed on a portion facing the electret, It is characterized by having a charging step of charging the electret by an external corona discharge device using the charging electrode as a grit electrode, and the surface potential of the electret can be adjusted with good controllability. Performance variations can be reduced.

According to an eleventh aspect of the present invention, in the tenth aspect of the invention, since the charging step is performed after the fixed piece and the movable piece are joined, it is possible to prevent a decrease in the surface potential of the electret due to the influence of heating during joining. You can According to a twelfth aspect of the present invention, in the invention according to any one of the first, fourth, fifth, and ninth aspects, the movable portion has a movable electrode facing the fixed electrode, and between the fixed electrode and the movable electrode. The other end is supported and fixed so that the one end moves to the fixed electrode side by the electrostatic force generated by the external voltage applied to the one end of the movable part. It is characterized in that it is formed at the end of the fixed piece corresponding to this one end, and these contacts constitute an electrostatic drive type relay connected to an external electric circuit. It is possible to provide an electrostatic drive type relay that is small and has a small variation in drive voltage.

The invention of claim 13 relates to claims 1, 4, 5,
9. The invention according to any one of 9 above, wherein the movable piece is a weight portion, one end is a flexure portion integrally connected to the weight portion, and the other end of the flexure portion is integrally connected to swing the weight portion. A support portion that is movably supported is formed, and the fixed piece is an acceleration sensor that is joined to the movable piece and has a fixed electrode that faces the weight portion at a distance. It is possible to provide an acceleration sensor with a small variation in the surface potential of the electret and a small variation in the sensor output.

The invention of claim 14 is the invention of claim 1, 4, 5,
In the invention described in any one of 9 above, the movable portion is composed of a diaphragm portion to form a pressure sensor, and the pressure sensor has a small variation in surface potential of the electret and a small variation in sensor output. Can be provided. The invention of claim 15 is the invention according to any one of claims 1, 4, 5, and 9,
The movable part is composed of a diaphragm part, and a microphone having a vent hole for communicating the space between the diaphragm part and the fixed part with the outside is formed in at least one of the movable part and the fixed part. Is what
It is possible to provide a microphone with a small variation in the surface potential of the electret and a small variation in the output.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) An electret application device according to the present embodiment has a fixed piece having a fixed electrode, a movable piece having a movable portion facing the fixed electrode with a gap, an electret, and the electret facing each other. And a charging electrode formed on a portion thereof.

FIG. 1 shows a sectional view of an electrostatic drive type relay.
This electrostatic drive type relay has a fixed piece 20 having a fixed electrode.
And a movable part (cantilever part) which also serves as a movable electrode 10
The movable piece 10 having a ′ is joined to the movable piece 10 via the metal thin film layer 30 made of AuGe—Au eutectic. Movable part 10
The electret 3 and the contact point 41 are formed on the surface side of the a ′ facing the fixed piece 20. Also, the fixing piece 2
In 0, the charging electrode 25 is provided at a portion facing the movable portion 10a ′.
Is formed, and the contact 42 is formed at a portion facing the contact 41 via the insulating film 27a. In this electrostatic drive relay, an electrostatic force is generated by applying a drive voltage to the fixed electrode (that is, the charging electrode 25) of the fixed piece 20 and the movable piece 10 to bring the contacts 41 and 42 into contact with and separate from each other. Activate the relay. In this electrostatic drive type relay, the charging electrode 25 also serves as a fixed electrode. By the way, the surface potential (equivalent voltage) of the electret 3 can be obtained by charging the electret 3 by applying a high voltage to the charging electrode 25 after the fixed piece 20 and the movable piece 10 are joined to generate a corona discharge. Has been adjusted. Therefore, it is possible to prevent a decrease in the surface potential of the electret due to the influence of heating at the time of joining, and it is possible to provide an electret application device in which the variation in the surface potential of the electret is small and the variation in performance is small.

The method of manufacturing the electrostatic drive type relay will be described below. First, a method of manufacturing the fixed piece 20 will be described. A concave portion 23a is formed by forming a mask in which a predetermined region is opened on one surface side of the insulating film 23 and etching the insulating substrate 23 to a predetermined depth. Then, the mask is removed, and then EB (Electron Bea) is performed.
m) By vapor deposition, for example, chromium (C
The charging electrode 25 composed of r) is formed. At this time, a plating base is also formed at the same time. Next, a contact 42 is formed on the insulating film 27a by a plating technique, and Au for bonding is formed at a position corresponding to the bonding portion 30 of FIG.
The fixed piece 20 having the structure shown in FIG. Since the charging electrode 25 also serves as the fixed electrode, it is not necessary to separately form the fixed electrode, the manufacturing process can be reduced, and the cost can be reduced.

Next, a method of manufacturing the movable piece 10 will be described. The movable piece 10 and the fixed piece 20 are not manufactured first. A silicon oxide film is formed on the entire surface of the silicon substrate 11 by a so-called thermal oxidation method, and the silicon oxide film in a predetermined region is etched by, for example, a photolithography technique and a dry etching technique to form insulating films 17 and 18 made of the silicon oxide film. To do. After that, the movable portion 10a ′ is formed by etching the silicon substrate 11 using the insulating films 17 and 18 as a mask. Subsequently, the oxide film 3 for the electret was formed on one surface of the movable portion 10a ′ by, for example, the plasma CVD method, and was etched into a predetermined shape. Here, the oxide film 3 is formed by, for example, a plasma CVD method using monosilane (SiH ₄ ) gas and nitrous oxide (N ₂ O) gas as source gases. The frequency of the high frequency voltage applied to the electrodes of the plasma CVD apparatus is preferably 13.56 MHz.

Next, a contact 41 is formed by plating on the surface of the movable portion 10a 'on which the oxide film 3 is formed,
AuGe is formed on it. After that, the anisotropic dry etching technique (for example, reactive ion etching) is cut into a U-shape around the movable portion 10a ′, as shown in FIG.
The movable piece 10 having the structure shown in FIG.
The oxide film 3 is prevented from being charged when 0a 'is separated).

Next, the electret 3 is formed by charging the oxide film 3 by corona discharge (oxide film 3).
To electret). Then, for example, about 350 ℃
The fixed piece 20 and the movable piece 10 are placed on the heated sample table
And is heated for 1 minute to form a metal thin film layer 30 of AuGe—Au eutectic, thereby joining the fixed piece 20 and the movable piece 10 through the metal thin film layer 30.

By the way, by this joining step, the equivalent voltage of the electret becomes lower than the value when it is charged by corona discharge. However, in this electrostatic drive type relay, a high voltage (for example, 5 k) is applied to the charging electrode 25 after the joining process.
The surface potential of the electret 3 is adjusted by applying (approx. V) to generate corona discharge. For this reason,
It is possible to reduce variations in the drive voltage of the electrostatic drive type relay.

FIG. 2 shows a sectional view of the acceleration sensor. This acceleration sensor includes a weight portion 13, a bending portion 14 whose one end is integrally connected to the weight portion 13, and the other end of the bending portion 14 which is integrally connected and which supports the weight portion 13 swingably by the bending portion 14. A movable piece 10 on which the charging electrode 25 is formed, a fixed piece 20 on which a charging electrode 25 that also functions as a detection electrode is formed facing the weight portion 13 at a distance, and the charging electrode 2 on the weight portion 13.
5 and the electret 3 formed on the side facing the surface. In this electrostatic drive type relay, the fixed piece 20 and the movable piece 1
0 is joined by anodic bonding, and then the charging electrode 25
A high voltage is applied to the electret 3 to generate a corona discharge, thereby charging the electret 3 and adjusting the surface potential.
This acceleration sensor detects acceleration by a change in capacitance between the electret 3 and the detection electrode (that is, the charging electrode 25).

The method of manufacturing the acceleration sensor will be described below. First, a method of manufacturing the fixed piece 20 will be described. The recess 4 is provided in the insulating substrate 23 by etching the insulating substrate 23 which is a glass substrate. After that, the fixing piece 20 having the structure shown in FIG. 2 is obtained by forming the charging electrode 25 made of, for example, Cr on the bottom of the inner peripheral surface of the recess 4.

Next, a method of manufacturing the movable piece 10 will be described. A silicon oxide film is formed on the entire surface of the silicon substrate 11 by a so-called thermal oxidation method, and the silicon oxide film in a predetermined region is etched by, for example, a photolithography technique and a dry etching technique to form a mask made of the silicon oxide film. After that, the exposed silicon substrate 11 is anisotropically etched so that the weight portion 13, the bending portion 14,
The support 12 is formed. After that, the oxide film 3 for the electret is formed on one surface of the weight portion 13 by the plasma CVD method or the like. Subsequently, the weight portion 13 is separated at a portion other than the bending portion 14 by anisotropic dry etching using, for example, a reactive dry etching device (hereinafter referred to as an RIE device). Either the fixed piece 20 or the movable piece 10 may be manufactured first.

Next, the movable piece 10 and the fixed piece 20 are subjected to the anodic bonding technique on a heated sample table heated to 400 ° C., for example.
And join. Then, a high voltage is applied to the charging electrode 25 to generate corona discharge, thereby charging the electret oxide film 3 to form the electret 3 and adjusting the surface potential. Therefore, it is possible to reduce variations in the sensor output of the acceleration sensor.

FIG. 3 shows a sectional view of the pressure sensor. The present pressure sensor includes a fixed piece 20 having a charging electrode 25 formed on an insulating substrate 23, a movable piece 10 having a movable portion 10a made of a diaphragm portion formed by providing a recess 4 in a silicon substrate 11, and a movable piece 10 movable. Charging electrode 2 in the portion 10a
5 and an electret 3 formed on the side facing the surface. Here, in the present pressure sensor, after the fixed piece 20 and the movable piece 10 are joined by the anodic joining technique, a high voltage is applied to the charging electrode 25 to electret 3.
The surface potential (equivalent voltage) of is adjusted. Therefore, it is possible to obtain a pressure sensor with a small variation in the surface potential of the electret 3 and a small variation in the sensor output. Further, in this pressure sensor, the charging electrode 25 is
Since it also serves as a detection electrode (fixed electrode) for detecting a signal, it is not necessary to separately form a detection electrode, the number of manufacturing steps can be reduced, and the cost can be reduced. The pressure sensor detects pressure by a change in capacitance between the electret 3 and the detection electrode (that is, the charging electrode 25).

The method of manufacturing the pressure sensor will be described below, but either the fixed piece 20 or the movable piece 10 may be manufactured first. The fixing piece 20 has the structure shown in FIG. 3 when the charging electrode 25 made of Cr is formed on one surface of the insulating substrate 20 by, for example, EB vapor deposition. on the other hand,
The movable piece 10 forms a thermal oxide film on the silicon substrate 11,
This thermal oxide film is processed into a predetermined shape, and the exposed silicon substrate 11 is anisotropically etched using the thermal oxide film as a mask to form a recess 4 in the silicon substrate 11 to form a movable portion 10a made of a diaphragm portion. . Next, plasma CVD is performed from the surface side of the silicon substrate on which the recess 4 is formed.
The oxide film 3 for the electret is formed by a method or the like, and is processed by etching so as to remain only in the movable portion 10a. Subsequently, for example, the fixed piece 20 is placed on a heated sample table heated to 400 ° C., and the fixed electrode 25 and the electret 3 are arranged so as to face each other via the recess 4 and moved by the anodic bonding technique. The piece 10 and the fixed piece 20 are joined. Next, a high voltage is applied to the charging electrode 25 to generate corona discharge, thereby charging the electret oxide film 3 and adjusting the surface potential of the electret 3. Therefore, since the surface potential of the electret is not lowered in the joining process as in the conventional example, it is possible to reduce the variation in the sensor output of the pressure sensor.

(Embodiment 2) The electret application device according to the present embodiment has a fixed piece having a fixed electrode, a movable piece having a movable portion facing the fixed electrode via a gap, and a fixed piece in the movable piece. And an electret formed on a surface facing each other, a mesh-shaped grid electrode, and a charging electrode formed on a portion of the fixed piece facing the electret.

FIG. 4 shows a sectional view of the electrostatic drive type relay.
The basic structure of the electrostatic drive type relay is substantially the same as that of the first embodiment shown in FIG. 1, and is characterized in that a mesh-shaped grid electrode 15 is formed on the surface of the electret 3. Therefore, the fixed piece 20 and the movable piece 10
After joining and, a high voltage (for example,
(About 5 kV) to generate corona discharge and adjust the voltage applied to the grid electrode 15 to adjust the oxide film 3
Adjusts the surface potential of the electret 3 charged with. In this electrostatic drive type relay, the surface potential of the electret 3 can be adjusted with good controllability by the voltage applied to the grid electrode 15 when the oxide film 3 is electretized by corona discharge.

The method of manufacturing the electrostatic drive type relay will be described below. Since the method of manufacturing the electrostatic drive relay is substantially the same as the method of manufacturing the electrostatic drive relay according to the first embodiment, only characteristic steps will be described. In the method of manufacturing the electrostatic drive type relay, the mesh-shaped grid electrode 15 is formed on the surface of the oxide film 3 after forming the electret oxide film 3 on the movable portion 10a ′. In addition, after joining the fixed piece 20 and the movable piece 10 to each other, a high voltage is applied to the charging electrode 25 to generate corona discharge and the grid electrode 1
The surface potential of the electret 3 is adjusted by applying a voltage to 5. Also, after that, the grid electrode 15
It is also possible to apply heat to the electret to adjust the surface potential of the electret 3.
Therefore, the surface potential can be adjusted with good controllability by controlling the current value and the current supply time on the power supply side.

FIG. 5 shows a sectional view of the acceleration sensor. The basic structure of this acceleration sensor is substantially the same as that of FIG. 2 of the first embodiment, and is characterized by the movable portion 1 of the movable piece 10.
The mesh-shaped grid electrode 15 is formed on the electret 3 formed at 0a, and after the fixed piece 20 and the movable piece 10 are joined, a high voltage is applied to the charging electrode 25 to corona discharge the electret 3 and This is because the surface potential is controlled by the voltage of the grid electrode 15 when the surface potential is adjusted.

The method of manufacturing the acceleration sensor will be described below. Since the method of manufacturing the acceleration sensor of the present embodiment is substantially the same as the method of manufacturing the acceleration sensor of the first embodiment, only the characteristic steps will be described. In the method of manufacturing the acceleration sensor according to the first embodiment, after the oxide film 3 for the electret is formed, the EB
A mesh-shaped grid electrode 15 is formed on the oxide film 3 by vapor deposition or the like. Further, after joining the fixed piece 20 and the movable piece 10, a high voltage is applied to the charging electrode 25 to generate corona discharge and the voltage applied to the grid electrode 15 is controlled to charge the oxide film 3. Electret 3
And the surface potential is adjusted. In this manufacturing method, the surface potential of the electret 3 can be adjusted with good controllability by the voltage applied to the grid electrode 15. Therefore, it is possible to reduce variations in the sensor output of the acceleration sensor.

FIG. 6 shows a sectional view of the pressure sensor. The basic structure of this pressure sensor is substantially the same as that of the first embodiment shown in FIG. 3, and is characterized in that the mesh-shaped grid electrode 15 is formed on the surface of the electret 3 facing the charging electrode. To be there. Therefore, after the fixed piece 20 and the movable piece 10 are joined together, the electret 3
Since the surface potential of the can be adjusted with good controllability, it is possible to provide a pressure sensor with a small variation in sensor output.

The method of manufacturing the pressure sensor will be described below. Since the method of manufacturing the pressure sensor of the present embodiment is substantially the same as the method of manufacturing the pressure sensor of the first embodiment, only the characteristic steps will be described. In the manufacturing method of the present pressure sensor, the mesh-shaped grid electrode 15 is formed after the electret 3 is formed on the concave portion 4 side of the movable portion 10a of the movable piece 10. In addition, after joining the fixed piece 20 and the movable piece 10,
A high voltage is applied to the charging electrode 25 to generate corona discharge, and the voltage applied to the grid electrode 15 is controlled to charge the oxide film 3 to form the electret 3 and adjust its surface potential. In this manufacturing method, the surface potential of the electret 3 can be adjusted with good controllability by the voltage applied to the grid electrode 15. Therefore, it is possible to reduce variations in the sensor output of the pressure sensor.

(Third Embodiment) FIG. 7 shows a sectional view of an electrostatic drive relay. In this electrostatic drive type relay, a movable portion (cantilever portion) 10a ″ is attached to a fixed piece 20 having a fixed electrode.
The movable piece 10 having is bonded to the metal thin film layer 30 made of AuGe-Au eutectic. The fixed piece 20 and the movable piece 10 are electrically insulated and separated by the insulating film 27 and the insulating film 18. In this electrostatic drive type relay, the movable portion 10a also serves as the movable electrode. Here, the movable part 10a "
Since the mesh is processed into a mesh shape, after the fixed piece 20 and the movable piece 10 are joined, the wire-type electrode 51 and the wire-type electrode 5 separately provided as shown in FIG.
1 cover 54, high voltage power supply 52, grid power supply 5
In the electrification device including the electret 3 of FIG. 3, the movable portion 10a ″ is also used as a grid electrode, and the electric charge generated by corona discharge from the wire-type electrode 51 is adjusted by the voltage of the grid power source of the movable portion 10a. In addition, the movable portion 10a is provided on the surface side facing the fixed piece 10 with the electret 3 and the contact 41.
Are formed. The fixed piece 20 is the silicon substrate 2
The contact 42 is formed of two and also serves as a fixed electrode, and a contact 42 is formed at a portion facing the contact 41 via an insulating film 27a. In this electrostatic drive type relay, the fixed piece 20 and the movable piece 1
By applying a driving voltage to 0 and 0, an electrostatic force is generated to bring the contacts 41 and 42 into contact with and separate from each other to operate the relay.

By the way, in the conventional electrostatic drive type relay,
Although the drive voltage between products varies due to the influence of heat in the process of joining the fixed piece 20 and the movable piece 10, in the present electrostatic drive type relay, after the fixed piece 20 and the movable piece 10 are joined, the electret Since the surface potential can be adjusted, the variation in drive voltage is smaller than in the past. Hereinafter, a method of manufacturing the electrostatic drive type relay will be briefly described.

First, a method of manufacturing the fixed piece 20 will be described. A silicon oxide film is formed on the entire surface of the silicon substrate 22 by a so-called thermal oxidation method, and a part of the silicon oxide film formed on one surface side of the silicon substrate 22 is etched by, for example, a photolithography technique and a dry etching technique to etch the silicon oxide film. Forming a mask consisting of. afterwards,
The recess 22a is formed by anisotropically etching the exposed silicon substrate 22 by a predetermined depth. After that, thermal oxidation is performed again to form a silicon oxide film on the entire surface of the silicon substrate 22, and the silicon oxide film is removed only in a predetermined region by a photolithography technique and a dry etching technique.
27a and 28 are formed. After that, the contact 42 is formed on the insulating film 27a by the plating technique, and the contact portion 30 of FIG.
Au is formed at a position corresponding to. Then, plasma C
By forming the oxide film 3 for the electret by the VD method or the like and etching it into a predetermined shape, the fixed piece 20 having the structure shown in FIG. 7 is obtained.

Next, a method of manufacturing the movable piece 10 will be described. The movable piece 10 and the fixed piece 20 are not manufactured first. A silicon oxide film is formed on the entire surface of the silicon substrate 11 by a so-called thermal oxidation method, and the silicon oxide film in a predetermined region is etched by, for example, a photolithography technique and a dry etching technique to form insulating films 17 and 18 made of the silicon oxide film. To do. After that, the movable portion 10a ″ is formed by etching the silicon substrate 11 using the insulating films 17 and 18 as a mask. Subsequently, on the surface side of the movable portion 10a ″ on which the oxide film 3 is formed,
Contact 41 is formed by plating technology, and AuG is formed on it.
e is formed. Then, the anisotropic dry etching technique (for example, reactive ion etching) is used to separate the periphery of the movable part 10a ″ into a U-shape and to form the movable part 10a ″ into a mesh shape to move the structure shown in FIG. A piece 10 is obtained.

Next, the fixed piece 20 and the movable piece 10 are placed on a heating sample table heated to, for example, about 350 ° C. and heated for 1 minute to form a metal thin film layer 30 of AuGe—Au eutectic. The fixed piece 20 and the movable piece 10 are joined via the metal thin film layer 30. Then, as shown in FIG.
Corona discharge is generated outside by using the movable portion 10a ″ as a grid electrode, and the voltage applied to the movable portion 10a ″ is controlled to electretize the oxide film 3 to form the electret 3 having a desired surface potential. At this time, the voltage applied to the wire electrode 51 is, for example, about 6 kV, while the voltage applied to the grid electrode is, for example, 100 to 25.
It is about 0V.

FIG. 9 shows a sectional view of the acceleration sensor. This acceleration sensor includes a weight portion 13, a bending portion 14 whose one end is integrally connected to the weight portion 13, and the other end of the bending portion 14 which is integrally connected and which supports the weight portion 13 swingably by the bending portion 14. A movable piece 10 on which the charging electrode 25 is formed, a fixed piece 20 integrally formed with a charging electrode 25 that also faces the weight portion 13 at a distance and also serves as a detection electrode, and a surface of the weight portion 13 that faces the charging electrode 25. And an electret 3 formed on the side. Here, the charging electrode 25 is processed into a mesh shape. In this electrostatic drive type relay, after the fixed piece 20 and the movable piece 10 are joined by anodic bonding, as shown in FIG.
1, a cover 54 for the wire-type electrode 51, and a high-voltage power source 52
And a power source 53 for the grid,
Wire type electrode 5 using charging electrode 25 as a grid electrode
The charge generated by the corona discharge from 1 is charged by the charging electrode 25.
The amount of electric charge can be adjusted by the voltage of the power supply for the grid to be supplied to the electret 3.
That is, the surface potential of the electret 3 can be adjusted with good controllability by the voltage applied to the charging electrode 25. This acceleration sensor detects acceleration by a change in capacitance between the electret 3 and the detection electrode (that is, the charging electrode 25).

The method of manufacturing the acceleration sensor will be described below. First, a method of manufacturing the fixed piece 20 will be described. A silicon oxide film is formed on the entire surface of the silicon substrate 22 by a so-called thermal oxidation method, an oxide film mask having a predetermined shape is formed, and a recess 4 is provided. Next, the charging electrode 25 is formed by processing the thin portion 29 of the silicon substrate 22 into a mesh shape by reactive dry etching or the like. After that, the oxide film mask is removed to obtain the fixing piece 20 having the structure shown in FIG.

The method of manufacturing the movable piece 10 is the same as that of the acceleration sensor of the first embodiment. The fixed piece 20 and the movable piece 1
Either 0 may be manufactured first. After the fixed piece 20 and the movable piece 10 are formed, the movable piece 10 and the fixed piece 20 are joined by an anodic bonding technique on a heating sample table heated to 400 ° C., for example. Then, as shown in FIG. 10, a corona discharge is generated outside by using the charging electrode 25 as a grid electrode, the voltage applied to the charging electrode 25 is controlled, and the oxide film 3 is electretized to obtain a desired surface potential. The electret 3 is formed. That is, by applying a high voltage to the charging electrode 25 to generate corona discharge, the oxide film 3 for the electret is charged to form the electret 3 and the surface potential is adjusted. Therefore, it is possible to reduce variations in the sensor output of the acceleration sensor.

FIG. 11 shows a sectional view of the pressure sensor. In this pressure sensor, a movable piece 10 having a movable portion 10a formed by providing the recess 4 and a charging electrode 25 which is opposed to the movable portion 10a with a space therebetween and also serves as a detection electrode are integrally formed. It has a piece 20 and an electret 3 formed on the surface of the movable portion 10a opposite to the surface on which the recess 4 is provided. Here, the charging electrode 25 is processed into a mesh shape. In this pressure sensor, the fixed piece 20 and the movable piece 1
0 is joined by anodic bonding, and then the wire-type electrode 51 is separately provided as shown in FIG.
In the charging device including the cover 54 of the wire-type electrode 51, the high-voltage power source 52, and the grid power source 53, the charge electrode 25 is used as a grid electrode, and the charge generated by the corona discharge from the wire-type electrode 51 is charged. The charge amount can be adjusted by the voltage of the grid power supply supplied to the electrode 25 and introduced into the electret 3. That is, the surface potential of the electret 3 can be adjusted with good controllability by the voltage applied to the charging electrode 25. Therefore, it is possible to obtain a pressure sensor with a small variation in the surface potential of the electret 3 and a small variation in the sensor output. Further, in the present pressure sensor, since the charging electrode 25 also serves as a detection electrode (fixed electrode) for detecting a signal, it is not necessary to separately form a detection electrode, and the manufacturing process can be reduced, and the cost can be reduced. Can be realized. The pressure sensor detects pressure by a change in capacitance between the electret 3 and the detection electrode (that is, the charging electrode 25).

The method of manufacturing the pressure sensor will be described below. The method of manufacturing the movable piece 10 of the present pressure sensor is the same as the method of manufacturing the movable piece of the pressure sensor of the first embodiment, and the method of manufacturing the fixed piece 20 is the same as the method of manufacturing the fixed piece of the acceleration sensor described above. The description of the manufacturing method of each of the piece 10 and the fixed piece 20 is omitted.

In the manufacturing method of this pressure sensor, the fixed piece 20 is used.
After joining the movable piece 10 and the movable piece 10, as shown in FIG.
Corona discharge is generated outside by using the charging electrode 25 as a grid electrode, the voltage applied to the charging electrode 25 is controlled, and the oxide film 3 is electretized to form the electret 3 having a desired surface potential. That is, by applying a high voltage to the charging electrode 25 to generate corona discharge, the oxide film 3 for the electret is charged to form the electret 3 and the surface potential is adjusted. Therefore, it is possible to reduce variations in the sensor output of the pressure sensor.

(Embodiment 4) FIG. 13 shows a sectional view of a microphone. This microphone is provided with a recess 4 and the recess 4
A movable piece 10 having an electret 3 formed on the ceiling of
The fixing piece 20 is formed integrally with a charging electrode 25 facing the electret 3 with a space therebetween and also serving as a detection electrode. Here, the charging electrode 25 is processed into a mesh shape. The electret 3 also serves as the movable portion 10a of the movable piece 10. In this microphone, the sound pressure is detected by the change in capacitance between the electret 3 and the charging electrode 25.

In this microphone, after the fixed piece 20 and the movable piece 10 are joined by anodic bonding, the wire-type electrode 51 is separately provided as shown in FIG.
And a cover 54 for the wire-type electrode 51 and a high-voltage power supply 52.
And a power source 53 for the grid,
Wire type electrode 5 using charging electrode 25 as a grid electrode
The charge generated by the corona discharge from 1 is charged by the charging electrode 25.
The amount of electric charge can be adjusted by the voltage of the power supply for the grid to be supplied to the electret 3.
That is, the surface potential of the electret 3 can be adjusted with good controllability by the voltage applied to the charging electrode 25. Therefore, it is possible to obtain a microphone in which variations in the surface potential of the electret 3 are small and variations in the output are small. Further, in the present microphone, since the charging electrode 25 also serves as a detection electrode (fixed electrode) for detecting a signal, it is not necessary to separately form a detection electrode, and the manufacturing process can be reduced and the cost can be reduced. Can be achieved.

The method of manufacturing the above microphone will be described below. Since the method for manufacturing the fixed piece 20 of the present microphone is the same as the method for manufacturing the fixed piece of the acceleration sensor according to the third embodiment, the description thereof will be omitted and the method of manufacturing the movable piece 10 will be described.
The silicon substrate 11 is thermally oxidized to form a silicon oxide film on the entire surface of the silicon substrate 11. Then, the silicon oxide film on one surface is removed, and the oxide film 3 for electret is formed on the exposed silicon substrate 11 by the plasma CVD method or the like. Next, the silicon oxide film on the surface of the silicon substrate 11 opposite to the surface on which the oxide film 3 is formed is processed into a predetermined shape, and the silicon substrate 11 is used as a mask to reach a depth reaching the oxide film 3. By etching and removing the silicon oxide film, the movable piece 10 having the structure shown in FIG. 13 is obtained.

After the fixed piece 20 and the movable piece 10 are formed, the movable piece 10 and the fixed piece 20 are joined together by an anodic bonding technique on a heating sample table heated to 400 ° C., for example.
Next, as shown in FIG. 14, the charging electrode 25 is used as a grid electrode to externally generate corona discharge, the voltage applied to the charging electrode 25 is controlled, and the oxide film 3 is electretized to obtain a desired surface potential. To form an electret 3 having That is, by applying a high voltage to the charging electrode 25 to generate corona discharge, the oxide film 3 for the electret is charged to form the electret 3 and the surface potential is adjusted. Therefore, it is possible to reduce variations in the output of the microphones. In each of the embodiments, the electrostatic drive type relay, the acceleration sensor, the pressure sensor, and the microphone have been described.
The device is not limited to these devices and may have the same configuration.

[0051]

According to the first aspect of the present invention, since the charging electrode is formed at the portion facing the electret, the electret can be charged by corona discharge even after the fixed piece and the movable piece are joined. As a result of charging after joining, there is an effect that it is possible to provide an electret application device in which variations in surface potential are small and variations in performance are small.

According to the second aspect of the present invention, the electret is charged by applying a high voltage to the charging electrode to generate corona discharge. Therefore, after the fixed piece and the movable piece are joined, the electret is charged by corona discharge. There is an effect that the surface potential of the electret can be adjusted and the performance variation of the electret application device can be reduced.

According to the invention of claim 3, in the invention of claim 2, since the charging step is performed after the fixed piece and the movable piece are joined, it is possible to prevent the surface potential of the electret from being lowered due to the influence of heating at the time of joining. There is an effect that can be. According to the invention of claim 4, in the invention of claim 1, since the charging electrode also serves as the detection electrode or the drive voltage application electrode,
Since it is not necessary to separately provide a detection electrode and a drive voltage application electrode, there is an effect that the manufacturing process can be simplified.

The invention of claim 5 is claim 1 or claim 4.
In the invention, since the mesh-shaped electrode is formed on the surface of the electret, the mesh-shaped electrode can be used as a grid electrode when the electret is charged by corona discharge, and the surface potential of the electret can be adjusted with good controllability. Therefore, there is an effect that the performance variation of the electret application device can be reduced.

According to the sixth aspect of the present invention, a high voltage is applied to the charging electrode to generate corona discharge and the mesh-shaped electrode is used as a grit electrode to charge the electret. Therefore, the surface potential is controlled when the electret is charged by corona discharge. It is possible to adjust with good performance, and it is possible to reduce variations in performance of the electret application device.

According to the invention of claim 7, in the invention of claim 6, the charging step is performed after the fixed piece and the movable piece are joined together, so that the surface potential can be prevented from lowering due to the influence of heating during joining. There is an effect. The invention of claim 8 is
Since a high voltage is applied to the charging electrode to generate corona discharge and the mesh-shaped electrode is used as a grit electrode to charge the electret, it is possible to reduce the variation in the electret surface potential and adjust the value of the electret surface potential. The effect is that you can do it.

In the ninth aspect of the present invention, since the member facing the electret via the gap is formed in a mesh shape, the mesh member is used as a grid electrode when the electret is charged by corona discharge. It is possible to adjust the surface potential with good controllability, and it is possible to provide an electret application device with a small variation in performance.

According to the tenth aspect of the invention, since the electret is charged by the external corona discharge device using the charging electrode as the grit electrode, the surface potential of the electret can be adjusted with good controllability, and the performance variation of the electret application device can be controlled. There is an effect that can be reduced. According to the eleventh aspect of the invention, in the tenth aspect of the invention, since the charging step is performed after the fixed piece and the movable piece are joined together, it is possible to prevent a decrease in the surface potential of the electret due to the influence of heating during joining. effective.

The invention of claim 12 relates to claims 1, 4, 5,
9. The invention according to any one of 9 above, wherein the movable portion has a movable electrode facing the fixed electrode, and the fixed electrode is generated by an electrostatic force generated by an external voltage applied between the fixed electrode and the movable electrode. The other end is supported and fixed so that the one end moves toward the side, and contacts that come in contact with and separate from each other by the movement of the movable part are formed at the one end of the movable part and the end of the fixed piece corresponding to the one end. An electrostatic drive type relay in which these contacts are connected to an external electric circuit is provided, and an electrostatic drive type relay having a small variation in surface potential of the electret and a small variation in driving voltage is provided. The effect is that you can.

The invention of claim 13 is the same as claims 1, 4, 5,
9. The invention according to any one of 9 above, wherein the movable piece is a weight portion, one end is a flexure portion integrally connected to the weight portion, and the other end of the flexure portion is integrally connected to swing the weight portion. A support portion that is movably supported is formed, and the fixed piece is an acceleration sensor that is joined to the movable piece and has a fixed electrode that faces the weight portion at a distance. There is an effect that it is possible to provide an acceleration sensor in which the variation in the surface potential of the electret is small and the variation in the sensor output is small.

The fourteenth aspect of the present invention includes the first, fourth, fifth and sixth aspects.
In the invention described in any one of 9 above, the movable portion is composed of a diaphragm portion to form a pressure sensor, and the pressure sensor has a small variation in surface potential of the electret and a small variation in sensor output. Can be provided. According to a fifteenth aspect of the invention, in the invention according to any one of the first, fourth, fifth and ninth aspects, the movable portion is a diaphragm portion, and the diaphragm portion is provided on at least one of the movable piece and the fixed piece. A microphone having a ventilation hole that communicates the space between the fixed piece and the outside is provided, and a microphone having a small variation in the surface potential of the electret and a small variation in the output is provided. There is an effect that can be.

[Brief description of drawings]

FIG. 1 is a sectional view of an electrostatic drive type relay according to a first embodiment.

FIG. 2 is a sectional view of the acceleration sensor according to the first embodiment.

FIG. 3 is a cross-sectional view of the pressure sensor according to the first embodiment.

FIG. 4 is a sectional view of an electrostatic drive type relay according to a second embodiment.

FIG. 5 is a sectional view of an acceleration sensor according to a second embodiment.

FIG. 6 is a sectional view of a pressure sensor according to a second embodiment.

FIG. 7 is a sectional view of an electrostatic drive type relay according to a third embodiment.

FIG. 8 is an explanatory diagram of the manufacturing method.

FIG. 9 is a sectional view of an acceleration sensor according to a third embodiment.

FIG. 10 is an explanatory diagram of the above manufacturing method.

FIG. 11 is a cross-sectional view of the pressure sensor according to the embodiment.

FIG. 12 is an explanatory diagram of the above manufacturing method.

FIG. 13 is a cross-sectional view of the microphone of the embodiment.

FIG. 14 is an explanatory diagram of the above manufacturing method.

[Explanation of symbols]

 3 Electret 10 Movable piece 10a 'Movable part 17, 18 Insulating film 20 Fixed piece 23 Insulating substrate 25 Charging electrode 27 Insulating film 30 Joining part 41, 42 Contact

Claims (15)

[Claims] 1. A fixed piece having a fixed electrode, a movable piece which has a movable portion facing the fixed electrode with a gap, and the movable portion is swingably supported and joined to the fixed piece, An electret application device comprising: an electret formed on either one of the fixed electrode and the movable portion, and a charging electrode formed on a portion facing the electret. 2. A fixed piece having a fixed electrode, a movable piece which has a movable portion facing the fixed electrode via a gap, and which is joined to the fixed piece so that the movable portion is swingably supported. In a method of manufacturing an electret application device having an electret formed on either one of a fixed electrode and the movable portion, and a charging electrode formed on a portion facing the electret, a high voltage is applied to the charging electrode. A method of manufacturing an electret application device, comprising a charging step of charging the electret by generating a corona discharge. 3. The method of manufacturing an electret application device according to claim 2, wherein the charging step is performed after the fixed piece and the movable piece are joined. 4. The electret application device according to claim 1, wherein the charging electrode also serves as a detection electrode or a drive voltage application electrode. 5. The electret application device according to claim 1, wherein a mesh-shaped electrode is formed on the surface of the electret. 6. A fixed piece having a fixed electrode, a movable piece which has a movable portion facing the fixed electrode via a gap, the movable portion is swingably supported, and is joined to the fixed piece, An electret formed on either one of the fixed electrode and the movable portion, a charging electrode formed on a portion facing the electret, and a mesh-like formed on the surface side of the electret facing the charging electrode. In a method of manufacturing an electret application device having an electrode,
A method of manufacturing an electret application device, comprising: a charging step of applying a high voltage to the charging electrode to generate a corona discharge to charge the electret using the mesh electrode as a grit electrode. 7. The method of manufacturing an electret application device according to claim 6, wherein the charging step is performed after joining the fixed piece and the movable piece. 8. A fixed piece having a fixed electrode, a movable piece having a movable portion facing the fixed electrode with a gap, and the movable portion being swingably supported and joined to the fixed piece, An electret formed on one of the fixed electrode and the movable portion, a charging electrode formed on a portion facing the electret, and a mesh shape formed on a surface side of the electret facing the charging electrode. The method for manufacturing an electret application device, comprising: applying a current to the mesh-shaped electrode to heat the electret application device. 9. The electret application device according to claim 1, wherein a member facing the electret via a gap is formed in a mesh shape. 10. A fixed piece having a fixed electrode, and a movable piece having a movable portion facing the fixed electrode with a gap therebetween, the movable portion being swingably supported and joined to the fixed piece.
In the method for manufacturing an electret application device, comprising: an electret formed on either one of the fixed electrode and the movable portion, and a mesh-shaped charging electrode formed at a portion facing the electret, the charging electrode A method for manufacturing an electret application device, comprising a charging step of charging the electret with an external corona discharge device using the grit electrode as a grit electrode. 11. The method of manufacturing an electret application device according to claim 10, wherein the charging step is performed after joining the fixed piece and the movable piece. 12. The movable part has a movable electrode facing the fixed electrode, and one end thereof is moved to the fixed electrode side by an electrostatic force generated by an external voltage applied between the fixed electrode and the movable electrode. As described above, the other end is supported and fixed, and the contacts that come into contact with and separate from each other by the movement of the movable part are formed at one end of the movable part and the end of the fixed piece corresponding to this one end, and these contacts are connected to the external electric circuit. The electret application device according to any one of claims 1, 4, 5, and 9, characterized in that an electrostatic drive type relay connected to is configured. 13. The movable piece includes a weight portion, a bending portion whose one end is integrally connected to the weight portion, and the other end of the bending portion which is integrally connected and which supports the weight portion swingably by the bending portion. And the fixed piece has a fixed electrode facing the weight portion with a space therebetween to constitute an acceleration sensor joined to the movable piece.
The electret application device according to any one of 1. 14. The pressure sensor according to claim 1, wherein the movable portion comprises a diaphragm portion.
The electret application device according to any one of 5 and 9. 15. A microphone in which the movable portion is a diaphragm portion, and at least one of the movable piece and the fixed piece is provided with a ventilation hole for communicating the space between the diaphragm portion and the fixed piece with the outside. The electret application device according to claim 1, 4, 5, or 9.