JP3511363B2 - Electrostatic actuator and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic actuator and a method of manufacturing the same, and more particularly to a head for an on-demand ink jet printer.

[0002]

2. Description of the Related Art In an ink-jet printer that ejects ink droplets directly from a nozzle onto a recording medium to record the ink, an on-demand system that ejects ink only when necessary does not require a mechanism for collecting the ink and is therefore inexpensive. ， It has the features that it can be downsized and that it can easily handle colorization. Among them, the mainstream as a personal printer is
A pressure wave is generated in the ink chamber by the displacement of the piezo element,
There are two types, an electromechanical conversion method in which ink is ejected from a nozzle, and an electrothermal conversion method in which bubbles are generated in an ink chamber by a heater heated to a high temperature in a short time and ink is ejected due to volume expansion of the bubbles.

On the other hand, since the electrostatic ink jet head can be manufactured by a wafer process, it is easy to increase the density and a large number of stable elements can be manufactured. Since it is a basic structure, it has the advantage that it can be easily downsized, and it is disclosed in JP-A-2-289351, JP-A-5-50601, and JP-A-6-718.
Many structures are disclosed in Japanese Patent Publication No. 82 and the like. In these electrostatic heads, parallel plate electrodes are formed at opposite positions of a diaphragm that forms the bottom of the liquid chamber, and ink is sucked and ejected by electrostatic attraction and vibration caused by the rigidity of the diaphragm.

[0004]

In order to perform high-speed, high-quality printing with an inkjet head, it is essential to increase the density of nozzles. In an inkjet head that drives a diaphragm by a piezo element or electrostatic attraction, in order to narrow the nozzle pitch and increase the density, it is necessary to shorten the short side length of each diaphragm in the nozzle pitch direction. Here, since the displacement amount of the diaphragm due to the electrostatic attraction is proportional to the fourth side of the short side length of the diaphragm from the equation (1), if the short side length of the diaphragm is shortened for the purpose of increasing the density, the displacement amount becomes Noticeably smaller Therefore, in order to increase the displacement and secure the required ejection amount of the ink droplets, equations (1) and (2)
Therefore, it becomes necessary to reduce the thickness of the diaphragm, reduce the distance between the electrodes, or increase the drive voltage. The minimum value of the distance between the electrodes is determined due to restrictions in the manufacturing method such as processing accuracy. Moreover, if the voltage setting value is increased, the cost of the power supply and the drive circuit increases. Therefore, in this case, it becomes necessary to reduce the thickness of the diaphragm.

[0005]

[Equation 1]

As a method for forming a thin diaphragm from a Si wafer, a method of etching the Si wafer from one side and stopping the etching at a desired thickness by time management can be considered. The variation in thickness is directly reflected in the variation in thickness of the diaphragm, making it difficult to make many uniform diaphragms. On the other hand, a method of providing an etching stop layer can be considered. As one of the methods, there is a method that utilizes the fact that the etching rate is slow in a high-concentration boron diffusion layer. Since there are many, there is concern about the reliability of the diaphragm and its change over time.

In addition, an N-type layer is formed on the P-type substrate,
There is an electrochemical etching stop method in which a voltage is applied so that an oxide film is formed when the N-type layer is exposed to an etching solution by etching away the P-type substrate, but the etching apparatus is complicated, When trying to obtain a thin film of several μm, the substrate concentration may be restricted due to the depletion layer near the pn junction. As another method, a method of etching and removing the supporting substrate of the SOI substrate can be considered, but the substrate is expensive.

As described above, forming a thin diaphragm from a Si substrate causes a problem that a uniform thickness cannot be obtained in a wide area, there is a concern about the use of a high-concentration impurity layer, the apparatus becomes complicated, and the cost is high. There was a problem.

The present invention solves the above problems,
It enables the formation of a Si thin film diaphragm that can be used in an electrostatically driven high density inkjet head.

[0010]

According to a first aspect of the present invention, there is provided a vibrating plate made of a polycrystalline Si thin film, an electrode substrate bonded to the vibrating plate via a gap, and the vibrating plate on the electrode substrate. In an electrostatic actuator having an electrode provided to face a plate and applying a drive voltage between the diaphragm and the electrode to deform the diaphragm by an electrostatic force, a polycrystal forming the diaphragm. It is characterized in that each crystal grain of Si constitutes a part of at least one of the two surfaces of the vibration plate.

According to a second aspect of the present invention, in the first aspect of the invention, the polycrystalline Si forming the diaphragm has a columnar structure in which the grain boundaries are approximately perpendicular to the surface of the diaphragm. Is.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the polycrystalline Si thin film forming the vibration plate is an amorphous Si thin film and is then recrystallized to form polycrystalline Si thin film.
The feature is that it is a thin film.

According to a fourth aspect of the invention, in the first or second aspect of the invention, the electrode substrate bonded to the diaphragm is a single crystal S.
i formed from SiO _{2 and} formed in advance on at least one surface of the joint between the vibration plate and the electrode substrate.
It is characterized in that the film is used as a gap spacing maintaining means.

According to a fifth aspect of the invention, in the fourth aspect of the invention, the SiO ₂ film is a thermal oxide film of Si.

According to the invention of claim 6, in the invention of claim 4, the SiO ₂ film is formed by a sputtering method, a vapor deposition method, an ion plating method, a sol / gel method, a CVD method or a sintering method of an organic Si compound. It is characterized by being.

According to a seventh aspect of the invention, in the first or second aspect of the invention, the electrode substrate joined to the diaphragm is made of single crystal Si, and the gap between the diaphragm and the electrode substrate vibrates. It is characterized in that it is held by a concave shape formed on at least one of the plate side and the electrode substrate.

According to an eighth aspect of the present invention, in the seventh aspect of the present invention, the concave shape formed on at least one of the vibrating plate side and the electrode substrate that holds the gap between the vibrating plate and the electrode substrate is a Si selective oxidation method. It is characterized by being formed by.

According to a ninth aspect of the present invention, in the first or second aspect of the present invention, the electrode substrate bonded to the diaphragm has a linear expansion coefficient close to that of the single crystal Si, and is made of a glass material capable of anodic bonding with Si. The gap between the vibrating plate and the electrode substrate is held by the concave shape formed in the vibrating plate.

According to a tenth aspect of the invention, in the ninth aspect of the invention, the concave shape formed on the side of the diaphragm that holds the gap between the diaphragm and the electrode substrate is formed by a selective oxidation method of Si. It is characterized by.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a view showing a constitutional example of an electrostatic actuator according to claim 1, and FIG. 1A is a sectional view of the electrostatic actuator of the present invention (a dotted line portion in FIG. 1B). FIG. 1B is a sectional view taken along the dotted line in FIG. 1A. 1 (C) is an enlarged schematic view of the polycrystalline Si diaphragm of the present invention, and FIG. 1 (D) is an enlarged sectional view of the polycrystalline Si diaphragm, in which 11 is a polycrystalline Si diaphragm. 12 is an electrode substrate, 13 is an electrode, 14 is a gap, 15 is a crystal grain, 1
6 indicates a crystal grain boundary. As shown in FIGS. 1A and 1B, a polycrystalline Si diaphragm 11 is bonded to an electrode substrate 12 on which an electrode 13 is formed via a gap 14. In the electrostatic actuator of the present invention, the crystal grains 15 of polycrystalline Si used for forming the diaphragm are shown in FIGS.
As shown in (D), two surfaces of the diaphragm 11 (surface /
It is characterized in that it constitutes at least one surface of the back surface).

Another feature of the present invention is that the polycrystalline Si constituting the polycrystalline Si vibrating plate 11 has a columnar structure in which the crystal grain boundaries 26 are substantially perpendicular to the surface of the vibrating plate as shown in FIG. There is. As a result, when the diaphragm 11 is displaced, shear stress does not act on the grain boundaries 26 of polycrystalline Si, so that material fatigue due to repeated actions of shearing force does not occur, the life of the diaphragm is extended, and reliability is improved. improves.

The polycrystalline Si diaphragm of the present invention is characterized in that it is formed on the substrate in a state of amorphous Si, and then the amorphous Si is transformed into polycrystalline Si by thermal annealing. . When the polycrystalline Si film is formed, irregularities reflecting the grain size of the polycrystalline 80 are formed on the surface (FIG. 8).
(A)). When such a polycrystalline Si film 81 is bonded to Si or glass which is the electrode substrate material 82, the unevenness of the surface of the polycrystalline film 81 narrows the margin of bonding conditions, leading to a reduction in yield. Therefore, the present invention has devised a method for obtaining a flat surface. Since the amorphous film 83 has no crystal grain boundaries, the formed film is extremely flat (FIG. 8B). By subjecting this film 83 to a heat treatment, it is recrystallized while maintaining the flatness of the surface, and the polycrystalline S
The i film 84 can be obtained (FIG. 8C). Polycrystalline Si can be formed by heat treatment at a temperature of 450 ° C. or higher, but the surface properties of the obtained polycrystalline Si film are better as the heating temperature is lower. Also, the grain size of recrystallized polycrystalline Si can be increased as the heating temperature is lowered. However, the lower the heating temperature is, the longer the time required for recrystallization is. Therefore, an optimum combination of various conditions is selected in practice.

As a specific example, a heating temperature of 500 is used on a quartz glass substrate using disilane gas (Si ₂ H ₆ ) as a source gas.
An amorphous Si film having a thickness of 3 μm was formed at ℃. afterwards,
This film was polycrystallized by heating at 600 ° C. for 40 hours in a nitrogen atmosphere. The surface property of the film is maintained as it was formed of an amorphous film, and grain boundary etching (seco etching)
The average particle size was 1.3 microns. Further, in the cross section of the film, individual particles of polycrystal Si constituted the film surface, and the polycrystal Si film was described in claim 1 of the present invention (Example 1).

The amorphous Si film formed in the same manner was polycrystallized by heating at 550 ° C. for 80 hours in a nitrogen atmosphere. The grain size of the polycrystalline Si film obtained at this time is 4 microns on average, and the cross-section shows that the individual grains grow in columns as shown in the structural diagram of FIG. 2 to form a polycrystalline film Si film. The polycrystalline Si film was described in claim 2 of the present invention (Example 2).

Further, according to the present invention, the electrode substrate is made of single crystal Si, and the polycrystalline Si diaphragm and the SiO ₂ film previously formed on at least one surface of the bonding portion of the electrode substrate,
It constitutes a gap holding means. The SiO ₂ film is Si
Can be formed of a thermal oxide film. In addition, the SiO ₂
The film can also be formed by a sputtering method, a vapor deposition method, an ion plating method, a sol-gel method, a CVD method, or a sintering method of an organic Si compound. When the electrode substrate is formed of single crystal Si, the electrode can be formed by diffusing p-type or n-type impurities in the Si substrate.

Another feature of the present invention is that a concave structure formed on the diaphragm or the electrode substrate is used as a gap maintaining means between the polycrystalline Si diaphragm and the electrode formed on the electrode substrate made of single crystal Si. I am trying. In such a configuration, since the diaphragm and the electrode substrate are electrically connected after the joining, the structure is advantageous for electrically driving the diaphragm. Diaphragm,
The concave structure of the electrode substrate can be formed by etching Si (both wet etching and dry etching), but in addition, Si in the concave structure is selectively oxidized to form S.
It is also possible to use iO ₂ and then form the SiO ₂ oxide film by removing it. Since the oxidation rate of Si can be controlled accurately by the oxidation temperature, this method for forming a concave structure can form a concave structure with a highly accurate gap size.

In the present invention, a glass material having a linear expansion coefficient close to that of single crystal Si and capable of anodic bonding with Si can be used for the electrode substrate. For example, Pyrex glass # 7740 manufactured by Corning, SW3 manufactured by Iwaki Glass, and SD2 manufactured by Hoya can be used. When glass is used as the electrode substrate material, the substrate size can be freely selected, so that a long actuator array can be formed.

FIG. 3 is a view for explaining an embodiment (embodiment 3) of claims 1, 3 and 5 of the present invention. This embodiment is a case where the electrostatic actuator of the present invention is applied to an ink jet head. Is an example of. (A): 31 is a (110) wafer of single crystal silicon. In this embodiment, this silicon (110) wafer is used as a substrate for forming a polycrystalline silicon diaphragm and at the same time used as a member for forming a pressurized liquid chamber of an inkjet head (FIG. 3A).

(B): A thermal oxide film 33 having a thickness of 500 nm is formed on the single crystal silicon 31, and an amorphous Si film is formed thereon at a heating temperature of 500 ° C. using disilane gas (Si ₂ H ₆ ) as a source gas. Formed to a thickness of 3 microns. Then, polycrystallized 32 by heating at 550 ° C. for 80 hours in a nitrogen atmosphere. At this time, the film thickness was 2.7 μm (FIG. 3 (B)). (C): (110) wafer is potassium hydroxide (KOH)
The solution was etched into a liquid chamber 34 of the inkjet head (FIG. 3C). Anisotropic etching technology of potassium hydroxide is used for processing. The potassium hydroxide solution has an extremely low etching rate of silicon with respect to the (111) plane as compared with the rate of etching with other planes. When etching is performed with this solution, the etching plane becomes a plane composed of the (111) plane. This method is the same as the method described in the related art and the like, and is not an essential point of the present invention, and therefore detailed description thereof will be omitted.

(D): As the electrode substrate 35, a silicon (100) substrate (p type, resistivity 10 Ω · cm) was used. First, an oxide film as a means for maintaining the gap between the diaphragm 32 and the electrode 36 was formed by thermal oxidation of silicon in a hydrogen gas atmosphere. Oxidation temperature is 1000 ° C, oxidation time is 95
In this case, the oxide film thickness at this time was 510 nm. The oxide film is removed into a gap shape by photolithography and an oxide film 37 as a gap holding means is formed.
Further, the electrode 36 is formed on the electrode substrate 35 by the impurity diffusion method. In this embodiment, it is formed by a method of implanting phosphorus P ions into the substrate. The implantation conditions are a dose of 4E15 cm.
² , acceleration voltage is 50 KeV. Then, the electrode substrate 35
Is bonded to the polycrystalline silicon diaphragm 32. Bonding was performed by the method of silicon / silicon direct bonding. Before bonding, wash both substrates with a mixed solution of (ammonia / hydrogen peroxide),
It is possible to bond the two substrates by stacking them and heat-treating them at 800 ° C. in a nitrogen atmosphere (FIG. 3D).

(E): Finally, a stainless steel lid 38 is adhered on the liquid chamber 34 to complete an ink jet head using the electrostatic actuator of the present invention (FIG. 3 (E)). (F): FIG. 3 (F ₁ ), (F ₂ ) shows a front view and a side view of the inkjet head of this embodiment formed as described above.

FIG. 4 is a front cross-sectional view (FIG. 4 (A)) and a front vertical cross-sectional view for explaining an embodiment of claim 4 of the present invention. The manufacturing method of the polycrystalline silicon diaphragm 41 has already been described. It is similar to the embodiment described above. A silicon (100) wafer (p-type, resistivity 10 Ω · cm) was used as the electrode substrate 42. An oxide film 45 was formed on this wafer by thermal oxidation in a hydrogen gas atmosphere. The oxidation temperature was 1000 ° C., the oxidation time was 140 minutes, and the oxide film thickness at this time was 750 nm.
The oxide film in the gap between the vibrating plate and the electrode was etched to 700 nm with buffered hydrofluoric acid to form the gap 43. Next, a platinum thin film having a thickness of 200 nm was formed as an electrode 44 in this gap portion by a sputtering method. Then, the polycrystalline Si diaphragm 41 is attached to the electrode substrate 42.
Was directly bonded to the substrate to complete the electrostatic actuator of the present invention (Example 4).

FIG. 5 illustrates an embodiment of claim 6 of the present invention.
Front cross-sectional view (FIG. 5A) and front vertical cross-section for
In the figure, the manufacturing method of the polycrystalline silicon diaphragm 51 has already been described.
It is similar to the embodiment described above. Silicon as the electrode substrate 52
Using (110) wafer (p type, resistivity 10 Ω · cm)
It was This wafer is treated with silane (SiH_Four), Nitrous oxide (N
_TwoO) is used as the source gas to form the oxide film 55 by the CVD method.
I made it. The film formation temperature is 800 ° C and the film formation time is 14 minutes.
At that time, the oxide film thickness was 800 nm. Of diaphragm and electrode
The oxide film in the part that becomes the gap is formed with buffered hydrofluoric acid.
Etching was performed at 00 nm to form the gap 53. Next
Then, a nickel thin film is used as an electrode 54 in this gap portion.
It was formed to a thickness of 150 nm by the putter method. Then on
The polycrystalline Si vibration plate 51 is directly bonded to the electrode substrate 52,
The electrostatic actuator of the present invention was completed (Example 5).

6A and 6B are a front cross-sectional view (FIG. 6A) and a front vertical cross-sectional view for explaining the embodiments of claims 7 and 8 of the present invention. This is similar to the embodiment already described. A silicon (100) wafer (p-type, resistivity 10 Ω · cm) was used as the electrode substrate 62. An oxide film was formed by thermal oxidation in a hydrogen gas atmosphere on the portion of the wafer where the gap is formed by a selective oxidation method. In the selective oxidation, the portion of the wafer surface that prevents
_The masking was performed with a ₃ N ₄ film. This selective oxidation of silicon by the Si ₃ N ₄ mask is widely used as an element isolation method in a semiconductor manufacturing process. The oxide film may be formed prior to the formation of the Si ₃ N ₄ mask. The oxidation temperature was 1000 ° C., the oxidation time was 280 minutes, and the oxide film thickness at this time was 1500 nm. When this oxide film is removed by etching, a gap portion is formed at a depth of 750 nm in the electrode substrate.

Next, the electrode 64 is formed in this gap portion by the impurity diffusion technique. In this embodiment, it is formed by a method of implanting phosphorus (P) ions into the substrate. The implantation conditions are a dose amount of 4E15 / cm ² and an acceleration voltage of 50 keV. Then, the polycrystalline Si diaphragm 61 is attached to the electrode substrate 62.
Was directly bonded to the above to complete the electrostatic actuator of the present invention (Example 6).

FIG. 7 is a front cross-sectional view (FIG. 7A) and a front vertical cross-sectional view for explaining the embodiments of claims 9 and 10 of the present invention. This is the same as the above-described embodiment, but in this embodiment, since the gap is formed on the diaphragm side, the diaphragm thickness is set to 3.5 μm considering the gap portion. An oxide film was formed by thermal oxidation in a hydrogen gas atmosphere at the portion forming the gap on the diaphragm side by the selective oxidation method. The selective oxidation was performed by a method of masking a portion of the wafer surface that prevents oxidation with a Si ₃ N ₄ film. This selective oxidation of silicon by the Si ₃ N ₄ mask is widely used as an element isolation method in a semiconductor manufacturing process.

In some cases, an oxide film may be formed prior to the formation of the Si ₃ N ₄ film mask. Oxidation temperature is 1000 ℃,
The oxidation time is 280 minutes and the oxide film thickness at this time is 1500 nm
Met. When this oxide film is removed by etching, a gap portion is formed in the vibration plate 71 with a depth of 750 nm. Pyrex glass # 7740 manufactured by Corning was used as the electrode substrate 72. On this glass substrate, a platinum thin film having a thickness of 200 is formed as an electrode 74 by a sputtering method.
nm. After that, the polycrystalline Si vibrating plate 71 was anodically bonded to the electrode substrate 72 to complete the electrostatic actuator of the present invention (Example 7).

[0038]

According to the electrostatic actuator of the first aspect, since the grain size of the polycrystalline Si forming the diaphragm is large, the electrostatic actuator having a large Young's modulus and high strength can be obtained.

According to the electrostatic actuator of claim 2, since the shearing force does not act on the grain boundary of the polycrystalline Si forming the vibrating plate even if the vibrating plate is deformed, the electrostatic actuator has a long life and high reliability. can do.

In the method of manufacturing an electrostatic actuator according to the third aspect, since the polycrystalline Si thin film has a good surface property, the yield of bonding with the electrode substrate can be increased.

In the electrostatic actuator of the fourth aspect, since the electrode substrate is made of single crystal Si, the electrode can be formed by diffusing impurities into Si, so that the electrode substrate can be formed with high productivity.

In the electrostatic actuator of the fifth aspect, since the gap holding means is the thermal oxide film of Si, it is possible to obtain a gap with high dimensional accuracy.

In the electrostatic actuator of claim 6, the gap forming means is a low temperature process such as a sputtering method, a vapor deposition method, an ion plating method, a sol / gel method, a CVD method or a sintering method of an organic Si compound. A low-cost manufacturing method can be obtained.

According to the electrostatic actuator of claim 7,
Since the vibration plate and the electrode substrate can be formed at the same potential, a simple actuator having a wiring structure can be obtained.

According to the electrostatic actuator of claim 8,
Since the concave shape that holds the gap is formed by the selective oxidation of Si, it is possible to obtain a method of manufacturing an actuator with high dimensional controllability.

According to the electrostatic actuator of claim 9,
Since the electrode substrate can be formed of glass, a long electrostatic head can be obtained.

According to the electrostatic actuator of the tenth aspect, since the concave shape for holding the gap is formed by the selective oxidation method of Si, it is possible to obtain a method of manufacturing an electrostatic actuator having high dimensional controllability.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of an electrostatic actuator according to the present invention.

FIG. 2 is a diagram showing an example of a columnar structure of polycrystalline Si.

FIG. 3 is a diagram for explaining an example of a manufacturing process of the electrostatic actuator according to the present invention.

FIG. 4 is a configuration diagram for explaining another example of the electrostatic actuator according to the present invention.

FIG. 5 is a configuration diagram for explaining still another example of the electrostatic actuator according to the present invention.

FIG. 6 is a configuration diagram for explaining still another example of the electrostatic actuator according to the present invention.

FIG. 7 is a configuration diagram for explaining still another example of the electrostatic actuator according to the present invention.

FIG. 8 is a diagram for explaining an uneven surface reflecting the grain size of a polycrystalline film.

[Explanation of symbols]

11 ... Si diaphragm, 12 ... Electrode substrate, 13 ... Electrode, 14
... gap, 15 ... crystal grain, 16, 26 ... crystal grain boundary, 3
1 ... Single crystal silicon, 32 ... Polycrystal silicon, 33 ...
Thermal oxide film, 34 ... Liquid chamber, 35 ... Electrode substrate, 36 ... Electrode,
37 ... Gap holding means, 38 ... Lid, 41, 51, 6
1, 71 ... Vibration plate, 42, 52, 62, 72 ... Electrode substrate, 43, 53, 63, 73 ... Gap, 44, 54,
64, 74 ... Electrodes, 45, 55 ... Oxide films.

Claims (10)

(57) [Claims] 1. A vibrating plate made of a polycrystalline Si thin film, and an electrode substrate bonded to the vibrating plate via a gap,
An electrostatic actuator that has an electrode provided on the electrode substrate so as to face the diaphragm, applies a driving voltage between the diaphragm and the electrode, and deforms the diaphragm by an electrostatic force. An electrostatic actuator, wherein each crystal grain of polycrystalline Si that constitutes the diaphragm constitutes a part of at least one surface of the two surfaces of the diaphragm. 2. The electrostatic actuator according to claim 1, wherein the polycrystalline Si forming the vibration plate has a columnar structure in which grain boundaries are substantially perpendicular to the surface of the vibration plate. Actuator. 3. The method of manufacturing an electrostatic actuator according to claim 1, wherein the vibrating plate is made of polycrystalline Si.
A method for manufacturing an electrostatic actuator, comprising forming an amorphous Si thin film and then recrystallizing the thin film into a polycrystalline Si thin film. 4. The electrostatic actuator according to claim 1, wherein the electrode substrate bonded to the diaphragm is a single crystal S.
i formed from SiO _{2 and} formed in advance on at least one surface of the joint between the vibration plate and the electrode substrate.
An electrostatic actuator characterized in that a film is used as a gap spacing maintaining means. 5. The electrostatic actuator according to claim 4, wherein the SiO ₂ film is a thermal oxide film of Si. 6. The electrostatic actuator according to claim 4, wherein the SiO ₂ film is formed by a sputtering method, a vapor deposition method, an ion plating method, a sol / gel method, a CVD method or a sintering method of an organic Si compound. Electrostatic actuator characterized by 7. The electrostatic actuator according to claim 1 or 2, wherein the electrode substrate joined to the diaphragm is made of single crystal Si, and the gap between the diaphragm and the electrode substrate is on the diaphragm side. And an electrostatic actuator held by a concave shape formed on at least one of the electrode substrate and the electrode substrate. 8. The electrostatic actuator according to claim 7, wherein the concave shape formed on at least one of the vibrating plate side that holds the gap between the vibrating plate and the electrode substrate and the electrode substrate is formed by a selective oxidation method of Si. Electrostatic actuator characterized by being used. 9. The electrostatic actuator according to claim 1, wherein the electrode substrate bonded to the vibration plate is made of a glass material having a linear expansion coefficient close to that of the single crystal Si and capable of anodic bonding with Si, The electrostatic actuator, wherein a gap between the vibrating plate and the electrode substrate is held by a concave shape formed in the vibrating plate. 10. The electrostatic actuator according to claim 9, wherein the concave shape formed on the diaphragm side holding the gap between the diaphragm and the electrode substrate is formed by a selective oxidation method of Si. And electrostatic actuator.