JP2000203023A - Electrostatic actuator, manufacture thereof and ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive electrostatic actuator, and a manufacturing method thereof, in which high density can be realized. SOLUTION: A diaphragm substrate 1 and an electrode substrate 2 are bonded directly without using any adhesive and a silicon oxide 9 for forming a gap is provided on the diaphragm substrate 1 side. Alternatively, a silicon oxide of having a thickness becoming a gap is formed by thermal oxidation on a silicon wafer where impurities are implanted heavily to the diaphragm substrate 1 on the side being bonded to the electrode substrate 2 and then it is patterned into a desired shape before being bonded to the electrode substrate 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic actuator, a method of manufacturing the same, and an ink jet head.

[0002]

2. Description of the Related Art An ink jet head used in an ink jet recording apparatus used as an image recording apparatus such as a printer, a facsimile, a copying apparatus, etc. has a nozzle hole for discharging ink droplets and a discharge chamber (liquid chamber, pressure chamber) communicating with the nozzle hole. Chamber, pressurized liquid chamber, ink channel, etc.)
And an energy generating means (actuator) for generating energy for pressurizing the ink in the discharge chamber, and driving the actuator to pressurize the ink in the discharge chamber to discharge ink droplets from the nozzle holes. The ink-on-demand type that ejects ink droplets only when recording is necessary is the mainstream. The method is roughly classified into several methods according to a method of generating ink droplets (recording liquid) and a control method for controlling a flying direction.

Here, as an ink jet head using an electrostatic actuator, for example, Japanese Patent Laid-Open No. 4-522
No. 14, JP-A-3-293141, etc., a diaphragm which forms a liquid chamber and one wall surface of this liquid chamber by etching a first substrate (diaphragm substrate) made of a silicon substrate Is formed, and a second substrate (electrode substrate) on which electrodes are formed is disposed below the first substrate, and the electrodes are opposed to each other with a predetermined gap between the diaphragm and the electrostatic actuator. By applying a voltage between the diaphragm and the electrodes of this actuator, the diaphragm is flexed by electrostatic force to change the internal volume of the liquid chamber and eject ink droplets from nozzles communicating with the liquid chamber. It has been known.

[0004] In an ink jet head using such an electrostatic actuator, gap accuracy for utilizing electrostatic force is important. In particular, when manufacturing an ink jet head for obtaining a high-definition image, high-density dots must be realized, and the pitch that can be used as a diaphragm is reduced. When the size of the diaphragm is reduced, a large force for deforming the diaphragm is required. To generate a large force by the electrostatic actuator, a driving voltage applied between the diaphragm and the electrode is required. There is no alternative but to increase the electric field by increasing it or to increase the electric field by reducing the gap.

In this case, increasing the driving voltage requires
The drive circuit becomes expensive, and in some cases, general-purpose products cannot be used, which leads to higher costs and more problems such as an increase in power consumption. It is desired to control the gap with high precision and drive the actuator with a smaller gap.

However, in order to manufacture a high-density ink-jet head exceeding 150 dpi, for example, the gap between the diaphragm and the electrode must be 1 μm or less. In addition, when a non-contact drive, that is, a method in which the diaphragm is driven in a state where the diaphragm and the electrode do not contact each other is adopted as a driving method of the diaphragm, the diaphragm and the electrode do not contact due to deformation of the diaphragm. Must be manufactured. In order to form such a high-precision gap, it is preferable to use a semiconductor manufacturing technique such as LSI.

In this case, a method of bonding the electrode substrate and the diaphragm substrate becomes important in controlling the gap. That is, using a semiconductor manufacturing technology, the electrode substrate and
Even if a diaphragm is manufactured, a high-density ink-jet head cannot be put to practical use if the gap accuracy is deviated by the joining. Therefore, it is known to perform direct bonding using a silicon substrate.

In this direct bonding, after the surfaces of the substrates are subjected to a hydrophilization treatment, the two substrates are gently bonded to each other and heat-treated to bond the two substrates. Since the direct bonding does not require any special treatment, the surface properties of the substrate are very important. For example, surface roughness, surface undulations, etc. have a large effect on bondability, and in general,
It is said that if the surface roughness is about 15 nm or more, the bondability deteriorates (for example, Applied Physics Vol. 60, No. 8 (199).
1) P.I. 790).

That is, when performing direct bonding of silicon substrates, the process must not be such that the bonding surface is roughened. However, in the semiconductor manufacturing process,
During this process, processes that may damage the bonding surface, such as ion implantation, photoresist ashing, cleaning with chemicals, and etching, are repeated, so that process design becomes important.

[0010] Therefore, for example, Japanese Patent Application Laid-Open No. 5-50601
As described in Japanese Patent Application Laid-Open No. 6-71882, a method is used in which anisotropic etching is performed on a silicon substrate to form an electrode groove, and the diaphragm substrate and the electrode substrate are joined by anodic bonding. ing. Anodic bonding is 300-4
In an environment heated to about 50 ° C., a voltage of several hundred volts is applied between substrates to be bonded to perform bonding.

[0011]

However, when the diaphragm and the electrode substrate are bonded by anodic bonding as described above, when a voltage is applied at a high temperature to the semiconductor substrate on which the bonding diffusion layer is formed, a junction is generated. There is a problem that the substrate is destroyed, or one of the substrates is almost limited to a glass substrate. If the substrate is limited to glass,
Due to the problem of processing accuracy, it is difficult to form a minute gap.

The present invention has been made in view of the above points, and has as its object to provide an inexpensive and high-density electrostatic actuator, a method of manufacturing the same, and an ink jet head.

[0013]

According to a first aspect of the present invention, there is provided an electrostatic actuator in which a diaphragm substrate on which a diaphragm is formed and an electrode substrate on which individual electrodes are formed are formed as insulating films. In an electrostatic actuator in which a gap is formed by a silicon oxide film and joined, and the diaphragm is deformed by applying a voltage between the electrode and the diaphragm, the diaphragm substrate and the electrode substrate are bonded with an adhesive. And a silicon oxide film for forming the gap is provided on the diaphragm substrate side.

According to a second aspect of the present invention, there is provided a method of manufacturing an electrostatic actuator according to the first aspect, further comprising joining the electrode substrate of a semiconductor substrate to the diaphragm substrate. A silicon oxide film having a thickness corresponding to the gap is formed on the silicon wafer by thermal oxidation using a silicon wafer into which high-concentration impurities are implanted on the surface side, and then the silicon oxide film on the bonding surface side has a desired shape. And bonded to the electrode substrate.

According to a third aspect of the present invention, there is provided a method of manufacturing an electrostatic actuator according to the first aspect, wherein a semiconductor substrate having an SOI structure is used as the diaphragm substrate. After forming a silicon oxide film having a thickness corresponding to a required gap of the actuator by a thermal oxidation method on a bonding surface side of the semiconductor substrate with the electrode substrate, the silicon oxide film on the bonding surface side is patterned into a desired shape. And the electrode substrate.

According to a fourth aspect of the present invention, there is provided a method of manufacturing an electrostatic actuator according to the first aspect, further comprising using a silicon substrate as the diaphragm substrate. After a silicon nitride film having the thickness of the vibration plate is formed on the entire surface of the substrate at the joint surface with the electrode substrate, a silicon oxide film is formed on the nitride film to a thickness that is necessary for the actuator. After that, the silicon oxide film on the bonding surface side was patterned into a desired shape, and the silicon oxide film was bonded to the electrode substrate.

According to a fifth aspect of the present invention, there is provided the electrostatic actuator manufacturing method for manufacturing the electrostatic actuator according to the first aspect, wherein a silicon wafer is used as the diaphragm substrate. After forming a silicon nitride film having a thickness of the vibration plate on a bonding surface of the wafer with the electrode substrate, patterning the silicon nitride film only in a region where the vibration plate is formed, and then masking the nitride film Then, thermal oxidation is performed to selectively oxidize the silicon substrate, grow an oxide film to a thickness that becomes a necessary gap of the actuator, and then bond the silicon substrate to the electrode substrate.

According to a sixth aspect of the present invention, there is provided a method of manufacturing an electrostatic actuator according to the first aspect of the present invention, wherein the vibration plate is connected to a semiconductor substrate and the electrode substrate. After masking the region to be the vibration plate on the bonding surface side of the silicon wafer using a silicon wafer into which high-concentration impurities are implanted on the surface side, the region to be the vibration plate is oxidized by thermal oxidation. Other than selectively oxidizing, after forming the required thickness of the actuator gap, the mask is removed,
It was configured to be bonded to the electrode substrate.

According to a seventh aspect of the present invention, in the method of manufacturing an electrostatic actuator according to the first aspect, a semiconductor substrate having an SOI structure is used as the diaphragm substrate. Then, after masking the region to be the vibration plate on the bonding surface of the semiconductor substrate with the electrode substrate, by oxidizing by thermal oxidation,
After selectively oxidizing a region other than the region serving as the vibration plate and forming an oxide film to a thickness that is necessary for the actuator, the mask is removed and the structure is joined to the electrode substrate.

According to an eighth aspect of the present invention, there is provided the method of manufacturing an electrostatic actuator according to the second or third aspect, wherein the silicon oxide film is formed on the bonding surface of the diaphragm substrate during the patterning of the oxide film. After the patterning was completed, thermal oxidation was performed again to form an oxide film on the back side of the diaphragm.

According to a ninth aspect of the present invention, in the method of manufacturing an electrostatic actuator according to the first aspect, the electrode substrate corresponds to the electrode on a silicon substrate. A resist pattern is formed, and using this resist pattern as a mask,
A step of forming an active layer by performing heat treatment after performing ion implantation, and configured to completely remove an oxide film on a bonding surface before bonding to the diaphragm substrate before bonding to the diaphragm substrate. .

According to a tenth aspect of the present invention, in the method of manufacturing an electrostatic actuator according to the first aspect, the electrode substrate is formed by implanting impurities on a silicon substrate. After depositing a polysilicon film or a metal-based conductive film, a silicon oxide film serving as an insulating film is formed, a protective film having a shape covering the electrode pattern is formed, and etching is performed using the protective film as a mask to form a bonding surface. After exposing the silicon substrate, the silicon substrate was joined to the diaphragm substrate.

According to the eleventh aspect of the present invention, the diaphragm substrate on which the diaphragm and the individual electrodes are formed and the electrode substrate on which the common electrode is formed are joined by forming a gap with a silicon oxide film serving as an insulating film. An electrostatic actuator in which the diaphragm is deformed by applying a voltage between the individual electrode and the common electrode, wherein the diaphragm substrate is a low-resistance silicon substrate, and the diaphragm substrate and the electrode The substrate was directly bonded without using an adhesive, and a silicon oxide film for forming a gap was provided on the diaphragm substrate side.

According to a twelfth aspect of the present invention, in the method for manufacturing an electrostatic actuator according to the eleventh aspect, the semiconductor substrate forming the diaphragm has an SOI structure. And
After a silicon oxide film is formed on the silicon surface of the first conductivity type, which is the bonding surface, by a thermal oxidation method to a thickness that will be the required gap for the actuator. After ion-implantation of the second conductivity type is performed using this pattern film as a mask to form individual electrodes for each of the diaphragms, ions implanted by the heat of direct bonding at the time of bonding with the silicon substrate are used. It was configured to be activated.

According to a thirteenth aspect of the present invention, in the method for manufacturing an electrostatic actuator according to the eleventh aspect, the semiconductor substrate forming the diaphragm is a silicon wafer. After forming a silicon nitride film having a thickness of a diaphragm on a silicon surface serving as a bonding surface, a silicon oxide film is deposited and formed on the nitride film to a thickness required for a necessary gap of an actuator. After patterning with a resist into a desired shape, a conductive film is deposited on the diaphragm substrate with the resist, and the resist film and the conductive film in portions other than the diaphragm are removed, thereby individually forming the diaphragm. After the individual electrodes are formed on the silicon substrate, they are directly bonded to the silicon substrate.

According to a fourteenth aspect of the present invention, there is provided an ink jet head comprising: a nozzle for discharging ink droplets; a discharge chamber communicating with the nozzle; a vibration plate forming a wall surface of the discharge chamber; 12. An electrostatic ink jet head comprising: an actuator formed of an electrode formed by applying a voltage between the vibration plate and the electrode to discharge ink droplets from the nozzle. It was configured as an electric actuator.

According to a fifteenth aspect of the present invention, there is provided an ink-jet head comprising: a nozzle for discharging ink droplets; a discharge chamber communicating with the nozzle; a vibration plate forming a wall surface of the discharge chamber; 13. An electrostatic ink jet head comprising: an actuator formed of an electrode formed by applying a voltage between the vibration plate and the electrode to discharge ink droplets from the nozzle. To 14 comprising an electrostatic actuator manufactured by any one of the manufacturing methods.

[0028]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic sectional view showing a first embodiment of an ink jet head provided with an electrostatic actuator according to the present invention. This ink jet head includes the electrostatic actuator according to the first aspect of the present invention.

This ink jet head includes a diaphragm substrate 1, an electrode substrate 2 provided below the diaphragm substrate 1,
A plurality of nozzles 5 for discharging ink droplets, comprising: a nozzle plate 3 provided above the diaphragm substrate 1;
Form a discharge chamber (liquid chamber) 6 and the like.

The vibrating plate 1 has a concave portion 7 forming a liquid chamber 6 and a vibrating plate 8 forming a bottom of the concave portion 7 and serving as a common electrode.
And a silicon oxide film 9 for forming a gap between the electrode and the electrode substrate 2. The common ink chamber for supplying ink to the liquid chamber 6 and the common ink chamber and the liquid chamber 6 are connected to the vibrating plate substrate 1 or a common liquid chamber member interposed between the vibrating plate substrate 1 and the nozzle plate 3. A fluid resistance portion and the like that communicate with each other are formed.

The electrode substrate 2 is provided with an individual electrode 10 facing the diaphragm 8 of the diaphragm substrate 1 via a gap formed by the silicon oxide film 9. The ink in the liquid chamber 6 is pressurized by the vibrating plate 8 and the individual electrodes 10 to
An actuator for discharging from the liquid is constituted.

Here, the diaphragm substrate 1 and the electrode substrate 2 are directly joined without using an adhesive, and the silicon oxide film 9 forming a gap between the diaphragm 8 and the individual electrode 10 is attached to the diaphragm substrate 1 side. Is provided. Thereby, when manufacturing the actuator using the semiconductor process, the diaphragm substrate 1
Without causing the joint surface between the electrode substrate 2 and the
Actuator part by direct joining can be obtained,
The gap accuracy is improved, and a higher density inkjet head can be obtained.

Next, FIG. 2 is a schematic sectional view showing a second embodiment of an ink jet head provided with an electrostatic actuator according to the present invention. This ink jet head includes the electrostatic actuator according to claim 11.

This ink jet head includes a diaphragm substrate 11 and an electrode substrate 1 provided below the diaphragm substrate 11.
2 and a nozzle plate 1 provided above the diaphragm substrate 11
3, a plurality of nozzles 15 for discharging ink droplets,
A discharge chamber (liquid chamber) 16 to which each nozzle 15 communicates is formed.

The vibrating plate substrate 11 has a concave portion 17 forming a liquid chamber 16, a vibrating plate 18 forming the bottom of the concave portion 17, an individual electrode 20 provided on the vibrating plate 18 corresponding to each liquid chamber 16,
A silicon oxide film 19 for forming a gap with the electrode substrate 12 serving as a common electrode is provided. The diaphragm plate 11 or the diaphragm plate 11 and the nozzle plate 1
3, a common ink chamber for supplying ink to the liquid chamber 16 to a common liquid chamber member interposed between the common ink chamber and the common ink chamber and the liquid chamber 16.
To form a fluid resistance portion or the like that communicates with.

The individual electrodes 20 and the electrode substrate 12 of the diaphragm substrate 11 face each other via a gap formed by the silicon oxide film 19 of the diaphragm substrate 11, and the diaphragm 18 including these individual electrodes 20 and the electrode substrate 12 This constitutes an actuator for pressurizing the ink in the liquid chamber 16 and discharging the ink from the nozzle 15.

Here, the diaphragm substrate 11 and the electrode substrate 12 are directly joined without using an adhesive, and
A silicon oxide film 19 that forms a gap between the individual electrode 20 and the electrode substrate 12 is provided on the diaphragm substrate 11 side. Accordingly, when an actuator is manufactured using a semiconductor process, an actuator portion can be obtained by direct bonding without causing a deviation in a bonding surface between the diaphragm substrate 11 and the electrode substrate 12, and gap accuracy can be improved. Thus, it is possible to obtain a higher density inkjet head.

Next, a first embodiment of a method for manufacturing an electrostatic actuator according to the present invention will be described with reference to FIGS. FIG. 3 is an explanatory view illustrating a manufacturing process of a diaphragm substrate to which the invention according to claim 2 is applied, and FIG. 4 is an explanatory view illustrating a manufacturing process of an electrode substrate to which the invention according to claim 9 is applied. FIG. 5 is an explanatory view illustrating a process of manufacturing the electrostatic actuator by bonding the diaphragm substrate of FIG. 3 and the electrode substrate of FIG.

First, as shown in FIG. 3A, a silicon substrate 31 serving as a diaphragm substrate is a substrate having a P-type polarity and a crystal plane orientation of <110>. I have. Such a silicon substrate is used in order to obtain an accurate processed shape by utilizing the plane anisotropy of the wet etching rate of silicon.

A high-concentration boron layer 32 is formed by injecting high-concentration boron into the surface of the silicon substrate 31 on the side to be joined to the electrode substrate by a solid diffusion method or the like.
The thickness of the high-concentration boron layer 32 is diffused so as to be equal to the thickness of the diaphragm. This silicon substrate is used as a starting material.

Then, as shown in FIG. 2B, the silicon substrate 31 is oxidized by a pyro-oxidation (wet oxidation) method or a thermal oxidation method such as dry oxidation.
A silicon oxide film 34 is formed on the surface of the substrate 1. At this time, the thickness of the silicon oxide film 34 is equal to the gap of the electrostatic actuator. In this embodiment, about 4
It was formed to a thickness of 00 μm.

Next, as shown in FIG. 2C, a photoresist film 35 is applied on both sides of the silicon substrate 31 and then, as shown in FIG. An opening pattern 37 serving as a gap between the diaphragm and the individual electrode on the bonding surface side of the photoresist film 35, and a pattern 3 serving as an etching opening for forming the diaphragm.
6 is formed. Here, the use of the double-sided exposure machine is to ensure the positioning accuracy of the opening pattern 37 serving as a gap portion and the pattern 36 serving as an etching opening portion.

Then, using the photoresist film 35 as a mask, the silicon oxide film 34 is etched using a hydrogen fluoride solution having a concentration of about 5% to form a silicon oxide film 4 as shown in FIG. After forming the etching opening 38 and the gap opening 39, the photoresist film 35 is removed.

The removal of the photoresist film 35 is preferably performed by a process using a remover specified by a photoresist maker. A photoresist ashing device using oxygen plasma may be used, but in this case, it is necessary to prevent the silicon oxide film 34 from being damaged (surface roughness, resist ash residue, etc.).

On the other hand, as shown in FIG. 4A, the silicon substrate 41 serving as an electrode substrate is a substrate having P-type polarity and having a crystal plane orientation of <110>. The surface side is mirror-finished.

Then, as shown in FIG. 2B, a silicon oxide film 44 serving as a buffer oxide film is formed on the surface of the silicon substrate 41 by a thermal oxidation method. At this time, the thickness of the silicon oxide film 44 needs to be large enough to withstand ion implantation. Here, it was formed to a thickness of about 1 μm.

Subsequently, as shown in FIG. 3C, after a photoresist film 45 is formed on the bonding surface (mirror side) of the silicon substrate 41, the photoresist film 45 is opened only in the region where the ion implantation is to be performed. Opening 4
6 is formed.

Thereafter, as shown in FIG. 4D, the silicon oxide film 1 is
4 is etched. Subsequently, the photoresist film 45 is removed, the silicon substrate 41 is immersed in a high concentration alkali metal hydroxide solution (for example, a 30% -KOH solution heated to 80 ° C.), and the silicon surface is selectively etched. Thus, a concave portion 47 is formed. Since the etching amount at this time is used for alignment at the time of bonding, it is sufficient that the etching is performed to a depth that can be visually recognized. Here, etching was performed to a depth of about 100 μm.

The concave portion 47 of the silicon substrate 41
Then, ion implantation for forming an electrode is performed. Here, since the P-type silicon substrate 41 is used, N-type impurity ions such as phosphorus are implanted, and the ion
To form The ion implantation was performed at 70 keV-3E18.
cm ³ .

Subsequently, as shown in FIG. 4E, the buffer oxide film 44 formed on the surface of the silicon substrate 41 is completely removed using a hydrogen fluoride solution having a concentration of about 5% to form an electrode substrate. .

Next, the silicon substrate 31 serving as the diaphragm substrate and the silicon substrate 41 serving as the electrode substrate formed as described above are directly joined. First, the above silicon substrate 3
10 and the electrode substrate 41 are washed. Here, cleaning using ammonia water + hydrogen peroxide water + water was performed to remove dust on the wafer surface. Next, a treatment for imparting hydrophilicity is performed for the purpose of improving the bonding property at room temperature. Here, a chemical solution treatment using sulfuric acid + hydrogen peroxide solution was performed.

Using the aligner, the pattern of the silicon oxide film 34 for forming the gap of the silicon substrate 31 (especially, the alignment pattern may be formed) and the ion-implanted region of the silicon substrate 41 are shown. Align using a carved pattern (especially an alignment pattern may be created) and glue gently.

Subsequently, after inspecting for the occurrence of initial voids using an IR inspection apparatus or the like, the wafer is placed in a heating furnace such as a diffusion furnace and heated, and as shown in FIG. Are bonded together. At this time, the ion layer 19 implanted into the silicon substrate 41 is simultaneously activated to be in a state where it can be used as the individual electrode 51. The conditions at this time were 850 ° C. for 2 hours. An etching protection film 52 is formed on the surface of the silicon substrate 41.

Next, as shown in FIG. 3B, using the silicon oxide film 34 on the surface except the etching opening 38 on the silicon substrate 31 as a mask, a high concentration alkali metal hydroxide solution is used. The silicon substrate is immersed in (for example, a 30% -KOH solution heated to 80 ° C.) and the silicon surface is selectively etched to form a concave portion 53 which becomes a liquid chamber to be pressurized by the vibration plate.

At this time, when the etching of the silicon substrate 31 reaches the region of the boron layer 32 implanted at a high concentration,
Since the etching stops spontaneously, an extremely thin diaphragm 54 can be produced with high accuracy. Here is about 2μ
The diaphragm 54 having a thickness of m was formed.

Thereafter, as shown in FIG. 5C, the silicon oxide film 34 of the silicon substrate 31 serving as the diaphragm substrate and the protective film 52 of the silicon substrate 41 serving as the electrode substrate were removed to obtain an electrostatic actuator. . In this electrostatic actuator, the thickness of the diaphragm 54 is 2 μm, and the gap distance between the diaphragm 54 and the individual electrode 51 is 500 nm (400 nm).
nm + 100 nm).

The electrostatic actuator thus obtained is composed of a diaphragm substrate 31 formed of a silicon substrate on which a diaphragm 54 formed of a high-concentration boron layer 32 is formed, and an electrode formed of a silicon substrate on which an individual electrode 51 is formed. A gap is formed between the substrate 41 and the silicon oxide film 34 serving as an insulating film and is directly joined without using an adhesive, and the silicon oxide film 34 for forming the gap is provided on the diaphragm substrate 31 side. is there.

As described above, a semiconductor manufacturing process is used by directly joining the diaphragm substrate and the electrode substrate without using an adhesive and providing a silicon oxide film for forming a gap on the diaphragm substrate side. Therefore, it is possible to obtain an electrostatic actuator by direct bonding without causing a change in the bonding surface, thereby improving the gap accuracy and obtaining a device with higher density.

In this case, as described above, using a silicon wafer in which a high-concentration impurity is implanted into the diaphragm substrate on the bonding surface side of the electrode substrate of the semiconductor substrate, the gap is formed by thermal oxidation on the silicon wafer. After forming a silicon oxide film of a certain thickness, the silicon oxide film on the bonding surface is patterned into a desired shape and bonded to the electrode substrate, so that the diaphragm substrate and the electrode substrate can be directly connected without using an adhesive. An electrostatic actuator in which a silicon oxide film for bonding and forming a gap is provided on the diaphragm substrate side can be manufactured.

Further, as described above, the electrode substrate forms a resist pattern corresponding to the electrode on the silicon substrate,
Using the resist pattern as a mask, a step of forming an active layer to be an electrode by performing heat treatment after performing ion implantation, and after removing an oxide film on a bonding surface completely before bonding with the diaphragm substrate, Manufactures an electrostatic actuator in which a diaphragm substrate and an electrode substrate are directly joined without using an adhesive by bonding to a plate substrate, and a silicon oxide film for forming a gap is provided on the diaphragm substrate side. can do.

Next, a second embodiment of the electrostatic actuator according to the present invention will be described with reference to FIGS. FIG. 6 is an explanatory view for explaining a manufacturing process of a diaphragm substrate to which the invention according to claim 3 is applied. FIG. 7 is a diagram illustrating a method of manufacturing an electrostatic actuator by bonding the diaphragm substrate of FIG. 6 and the electrode substrate of FIG. FIG. 4 is an explanatory view illustrating a step of performing

As shown in FIG. 1A, a silicon substrate 60 serving as a diaphragm substrate is formed by SOI (Silicon on Insulato).
A wafer having the structure of r) is used. The silicon surface 61 for engraving the diaphragm has P-type polarity and its crystal plane orientation is <110>.
The plate thickness is finished to the thickness of the diaphragm (here, about 2 μm), and its crystal plane orientation is <100>. The polarity may be either P-type or N-type, but P-type is cheaper in cost. The insulating layer sandwiched between the silicon surface 61 and the silicon surface 62 is a silicon oxide film 63, and an SOI substrate having a thickness of about 150 to 200 μm was used. Both surfaces of the silicon substrate 60 are mirror-polished. This silicon substrate 60 is used as a starting material.

As shown in FIG. 2B, the silicon substrate 60 is oxidized by a pyro-oxidation (wet oxidation) method or a thermal oxidation method such as dry oxidation to form a silicon oxide film 64 on the surface of the silicon substrate 60. I do. At this time, the thickness of the silicon oxide film 64 is equal to the gap of the electrostatic actuator. Here, it was formed to a thickness of about 400 μm.

Next, as shown in FIG. 2C, a photoresist film 65 is applied on both sides of the silicon substrate 60, and then, as shown in FIG. A pattern 67 to be a gap portion on the bonding surface side and a pattern 66 to be an etching opening portion for forming a diaphragm are formed on the photoresist film 65. Here, the use of the double-sided exposure machine is to ensure the positioning accuracy of the pattern to be the gap layer and the etching opening.

Then, as shown in FIG. 7E, the silicon oxide film 64 is etched using a photoresist film 65 as a mask and a hydrogen fluoride solution having a concentration of about 5% to form an etching opening 68 and a gap. Forming an opening 69,
The photoresist film 65 is removed.

The photoresist is preferably stripped using a stripping solution specified by a photoresist maker. A photoresist ashing device using oxygen plasma may be used, but in this case, it is necessary to prevent the silicon oxide film 64 from being damaged (surface roughness, resist ash residue, etc.).

Thereafter, the silicon substrate 60 serving as the diaphragm substrate and the electrode substrate 41 formed in the same manner as in FIG.
As shown in FIG. 7A, direct bonding is performed through the same steps as in the first embodiment described above. Then, as shown in FIG. 6B, using a silicon oxide film 64 formed on the surface of the silicon substrate 60 except for the etching opening 68 on the silicon surface 61 side as a mask, a high concentration alkali metal hydroxide is used. A silicon substrate is immersed in a solution, and a silicon surface 61 is selectively etched to form a concave portion 53 serving as a liquid chamber. In this case, a protective film 52 for etching is provided on the outer surface of the electrode substrate 41.

At this time, the etching of the silicon surface 61 of the silicon substrate 60 is stopped spontaneously when the insulating layer of the silicon oxide film 64 is etched. It can be produced with high accuracy. Thereafter, the silicon oxide film 64 of the silicon substrate 60 and the protective film 52 of the electrode substrate 41 are removed as shown in FIG. At this time, a portion of the silicon oxide film 63 as an insulating film corresponding to the vibration plate 54 formed by the silicon surface 62 is also removed.
Is formed, and an electrostatic actuator is obtained in which the individual electrode 51 facing the vibration plate 54 is opposed with a gap.

Using a semiconductor substrate having an SOI structure as the vibration plate substrate, a silicon oxide film having a thickness required to provide a necessary gap for the actuator is formed on the bonding surface side of the semiconductor substrate with the electrode substrate by a thermal oxidation method. After the formation, the silicon oxide film on the bonding surface side is patterned into a desired shape and bonded to the electrode substrate, thereby directly bonding the diaphragm substrate and the electrode substrate without using an adhesive, and forming a gap. Actuator in which a silicon oxide film is provided on the diaphragm substrate side for this purpose.

Next, a third embodiment of the electrostatic actuator according to the present invention will be described with reference to FIGS. FIG. 8 is an explanatory view illustrating a manufacturing process of a diaphragm substrate to which the invention according to claim 4 is applied, and FIG. 9 is a diagram illustrating a method of manufacturing an electrostatic actuator by bonding the diaphragm substrate of FIG. 8 and the electrode substrate of FIG. FIG. 4 is an explanatory view illustrating a step of performing

As shown in FIG. 7A, a silicon substrate 71 serving as a diaphragm substrate has a crystal plane orientation of <110>, and both surfaces are polished to a mirror surface. This silicon substrate 71
Is used as starting material. Then, a silicon nitride film 72 is deposited on the side of the silicon substrate 71 to be bonded to the electrode substrate by using the CVD method. At this time, the thickness of the silicon nitride film 72 is the thickness of the diaphragm.

Next, as shown in FIG. 7B, a silicon oxide film 74 is formed on the entire surface of the silicon substrate 71. Since a thermal oxide film hardly grows on the silicon nitride film 72,
A silicon oxide film 74 is formed by a method such as a CVD method. At this time, the thickness of the silicon oxide film 74 is equal to the gap of the electrostatic actuator. here,
It was formed to a thickness of about 400 nm.

Then, after a photoresist 75 is applied to both surfaces of the silicon substrate 71 as shown in FIG. 7C, the gap on the bonding surface side is applied using a double-sided exposure machine as shown in FIG. A pattern 77 to be a portion and a pattern 76 to be an etching opening for forming a diaphragm are formed. Here, the use of the double-sided exposure machine is to ensure the positioning accuracy of the pattern to be the gap layer and the etching opening.

Next, using the photoresist 75 as a mask, the silicon oxide film 74 is etched using a hydrogen fluoride solution having a concentration of about 5% to form an etching opening 78 and a gap opening 79. The photoresist is removed as shown in FIG. It is preferable that the photoresist is stripped by a process using a stripping solution specified by a photoresist maker. A photoresist ashing device using oxygen plasma may be used, but in that case, it is necessary to prevent the silicon oxide film from being damaged (rough surface, residual resist ash, etc.).

Thereafter, as shown in FIG. 9A, the diaphragm substrate 71 and the electrode substrate 41 shown in FIG. 4 are directly joined by the same method as in the first embodiment. Then, as shown in FIG. 4B, the silicon oxide film 74 on the surface is used as a mask except for the etching opening 78 on the silicon substrate 71 side, and the resultant is immersed in a high-concentration alkali metal hydroxide solution. The silicon substrate is immersed, and the silicon surface is selectively etched to form a concave portion 53 serving as a liquid chamber. In addition,
In this case, a protective film 52 for etching is provided on the outer surface of the electrode substrate 41.

At this time, when the silicon substrate 71 is etched down to the silicon nitride film 72, the etching stops spontaneously, so that the diaphragm 54 made of the extremely thin silicon nitride film 72 can be produced with high accuracy. . Thereafter, as shown in FIG.
1 silicon oxide film 74 and protective film 52 of electrode substrate 41
Is removed to obtain an electrostatic actuator in which the diaphragm 54 and the individual electrodes 51 facing the diaphragm 54 face each other with a gap therebetween.

As described above, the silicon substrate is used as the diaphragm substrate, and the silicon nitride film having the thickness of the diaphragm is formed on the entire surface of the bonding surface of the silicon substrate with the electrode substrate.
After forming a silicon oxide film on this nitride film to a thickness that is necessary for the actuator, the silicon oxide film on the bonding surface side is patterned into a desired shape, and bonded to an electrode substrate, thereby forming a diaphragm substrate. It is possible to manufacture an electrostatic actuator in which the substrate and the electrode substrate are directly bonded without using an adhesive, and a silicon oxide film for forming a gap is provided on the diaphragm substrate side.

Next, a fourth embodiment of the method for manufacturing an electrostatic actuator according to the present invention will be described with reference to FIG. FIG. 10 is an explanatory diagram for explaining a manufacturing process to which the invention according to claim 5 is applied. First, as shown in FIG. 1A, a silicon substrate 81 serving as a diaphragm substrate has a crystal plane orientation of <110>, and both surfaces are polished to a mirror surface.
This silicon substrate 81 is used as a starting material.

Then, a thin silicon oxide film serving as a buffer oxide film is formed on the silicon substrate 81 (not shown). A silicon nitride film 82 is deposited on the silicon substrate 81 by using the CVD method. At this time, the thickness of the silicon nitride film 82 is the thickness of the diaphragm.

Next, as shown in FIG. 9B, a photoresist 85 is formed on the side of the silicon substrate 81 which is to be bonded to the electrode substrate.
Is applied, and patterning is performed while leaving a diaphragm pattern portion 89 corresponding to the shape of the diaphragm as shown in FIG. Subsequently, using the diaphragm pattern portion 89 of the photoresist 85 as a mask, the silicon nitride film 82 is etched to make the silicon oxide film 82 into a diaphragm shape.

Then, as shown in FIG. 2D, after the photoresist 85 is removed, the silicon substrate 81 is thermally oxidized by a method such as pyro-oxidation. As a result, the oxide film does not grow in the region covered with the silicon nitride film 82, and the silicon oxide film 84 is selectively formed. At this time, the thickness of the silicon oxide film 84 is equal to the gap of the electrostatic actuator. Here, it was formed to a thickness of about 400 μm.

Next, as shown in FIG. 7E, after a photoresist 85 is applied on the upper surface of the silicon substrate 81, the pattern of the etched portion for forming the liquid chamber concave portion is formed by using a double-sided exposure machine. 86, the silicon oxide film 84 is etched to form an etching opening 88, and the photoresist 85 is removed to obtain a diaphragm substrate, as shown in FIG.

It is preferable that the photoresist is stripped by a process using a stripper specified by a photoresist maker. A photoresist ashing device using oxygen plasma may be used, but in that case, it is necessary to prevent the silicon oxide film from being damaged (rough surface, residual resist ash, etc.).

Thereafter, in the same manner as in each of the above-described embodiments, the silicon substrate 81 serving as the diaphragm substrate and the electrode substrate 41 are formed.
And the silicon oxide film 8 on the surface except the etching opening 88 on the silicon substrate 81 side.
Using the mask 4 as a mask, the silicon substrate is immersed in a high-concentration alkali metal hydroxide solution (for example, a 30% -KOH solution heated to 80 ° C.), and the silicon substrate 81 is selectively etched to form a liquid chamber. A recess 53 is formed. At this time, when the silicon substrate is etched down to the silicon nitride film 82 of the silicon substrate 81, the etching is stopped spontaneously, so that the diaphragm 54 made of an extremely thin silicon nitride film can be accurately produced.

Thereafter, the silicon oxide film 84 of the silicon substrate 81 and the protective film of the electrode substrate 41 are removed as shown in FIG.
Thus, an electrostatic actuator is obtained in which the individual electrode 51 facing 4 is opposed to the individual electrode 51 with a gap.

After using the silicon wafer as the diaphragm substrate and forming the silicon nitride film having the thickness of the diaphragm on the bonding surface of the silicon wafer with the electrode substrate, only the region where the diaphragm is to be formed is formed. After patterning while leaving the silicon nitride film, thermal oxidation is performed using this nitride film as a mask to selectively oxidize the silicon substrate and grow the oxide film to the thickness required for the actuator,
Manufactures an electrostatic actuator in which a diaphragm substrate and an electrode substrate are directly bonded without using an adhesive by bonding with an electrode substrate, and a silicon oxide film for forming a gap is provided on the diaphragm substrate side. can do.

Next, a fifth embodiment of the method of manufacturing an electrostatic actuator according to the present invention will be described with reference to FIG. FIG. 11 is an explanatory view for explaining a manufacturing process to which the invention according to claim 6 is applied. As shown in FIG.
The silicon substrate 91 serving as the diaphragm substrate has P-type polarity, has a crystal plane orientation of <110>, and has both surfaces mirror-polished. A high-concentration boron layer 92 is formed by injecting high-concentration boron into the surface of the silicon substrate 91 on the side that is to be bonded to the electrode substrate, using a solid diffusion method or the like. The thickness of the high-concentration boron layer 92 is diffused so as to be equal to the thickness of the diaphragm. This silicon substrate is used as a starting material.

First, a thin silicon oxide film serving as a buffer oxide film is formed on the silicon substrate 91 (not shown). Then, as shown in FIG. 6B, the silicon substrate 91 is bonded to the electrode substrate by using the CVD method on the bonding surface side.
A silicon nitride film 93 is deposited.

Then, a photoresist 95 is applied to the bonding surface side of the silicon substrate 91 and is patterned while leaving a diaphragm pattern portion 99 corresponding to the shape of the diaphragm. Subsequently, as shown in FIG. 3C, the silicon nitride film 93 and the high-concentration boron layer 92 are etched by using the diaphragm pattern portion 99 of the photoresist 95 as a mask, thereby forming the high-concentration boron layer 92 into the diaphragm. Shape.

Thereafter, as shown in FIG. 9D, after the photoresist 95 is removed, the silicon substrate 91 is thermally oxidized by a method such as pyro-oxidation. As a result, the oxide film does not grow in the region covered with the silicon nitride film 93, and the silicon oxide film 94 is selectively formed. At this time, the thickness of the silicon oxide film 94 is equal to the gap of the electrostatic actuator. Here, it was formed to a thickness of about 400 μm.

Next, as shown in FIG. 9E, a photoresist 95 is applied to an etching surface of the silicon substrate 91 for forming a concave portion, and then a diaphragm is formed by using a double-sided exposure machine. A pattern 96 to be an etching opening portion is formed, and the silicon oxide film 94 is etched to form an etching opening 98 as shown in FIG.
The photoresist 95 is removed, and the silicon nitride film 93 is removed to obtain a diaphragm substrate.

It is preferable that the photoresist is stripped by a process using a stripper specified by a photoresist maker. A photoresist ashing device using oxygen plasma may be used, but in that case, it is necessary to prevent the silicon oxide film from being damaged (rough surface, residual resist ash, etc.).

Thereafter, in the same manner as in each of the above-described embodiments, the silicon substrate 91 serving as a diaphragm substrate and the electrode substrate 41 are formed.
And the silicon oxide film 9 on the surface except for the etching opening 67 on the silicon substrate 91 side.
Using the mask 4 as a mask, the silicon substrate is immersed in a high-concentration alkali metal hydroxide solution, and the silicon surface is selectively etched to form a concave portion 53 serving as a liquid chamber. At this time,
In the etching of the silicon substrate, the etching is stopped spontaneously when the high-concentration boron layer 92 injected into the silicon substrate 91 is etched, so that the diaphragm 54 made of an extremely thin boron layer can be accurately produced.

Thereafter, the silicon oxide film 94 of the silicon substrate 91 and the protective film of the electrode substrate 41 are removed to remove the vibration plate 54 and the vibration plate 5 as shown in FIG.
Thus, an electrostatic actuator is obtained in which the individual electrode 51 facing 4 is opposed to the individual electrode 51 with a gap.

By using a silicon wafer in which a high-concentration impurity is implanted into the vibration plate on the bonding surface side of the semiconductor substrate with the electrode substrate, an area to be the vibration plate on the bonding surface side of the silicon wafer is masked. Later, by oxidizing by thermal oxidation, the region other than the region that becomes the diaphragm is selectively oxidized. After forming the thickness to be the necessary gap of the actuator, the mask is removed, and the vibration is formed by joining with the electrode substrate. It is possible to manufacture an electrostatic actuator in which a plate substrate and an electrode substrate are directly joined without using an adhesive, and a silicon oxide film for forming a gap is provided on the diaphragm substrate side.

Next, a sixth embodiment of the method for manufacturing an electrostatic actuator according to the present invention will be described with reference to FIG. FIG. 11 is an explanatory diagram for explaining a manufacturing process to which the invention according to claim 7 is applied.

As shown in FIG. 9A, a silicon substrate 100 serving as a diaphragm substrate uses a wafer having an SOI structure. The silicon surface 101 for engraving the diaphragm is P
It has the polarity of the mold, its crystal plane orientation is <110>, and the silicon surface 102 serving as the diaphragm is finished to the thickness of the diaphragm (about 2 μm here), and its crystal plane orientation is <
100>. The polarity may be either P-type or N-type, but P-type is cheaper in cost. The insulating layer sandwiched between the silicon surface 101 and the silicon surface 102 is a silicon oxide film 103 having a thickness of about 150 to
A 200 μm SOI substrate was used. Both surfaces of the silicon substrate 100 are mirror-polished. This silicon substrate 100 is used as a starting material.

First, a thin silicon oxide film serving as a buffer oxide film is formed on the silicon substrate 30 (not shown). Then, as shown in FIG.
On the substrate 0, a silicon nitride film 110 is deposited using a CVD method. Then, a photoresist 105 is applied to the bonding surface side of the silicon substrate 100, and patterning is performed while leaving a diaphragm pattern portion 109 in the shape of a diaphragm.

Subsequently, as shown in FIG. 9C, the silicon nitride film 110 and the silicon surface 102 are etched into the shape of the diaphragm by using the diaphragm pattern portion 109 of the photoresist 105 as a mask. Thereafter, as shown in FIG. 4D, after the photoresist 105 is peeled off, the silicon substrate 100 is thermally oxidized by a method such as pyro-oxidation. As a result, the oxide film does not grow in the region covered with the silicon nitride film 110, and the silicon oxide film 1 is selectively grown.
04 is formed. At this time, the thickness of the silicon oxide film 104 is equal to the gap of the electrostatic actuator. Here, it was formed to a thickness of about 400 μm.

Next, as shown in FIG. 10E, a photoresist 105 is applied to an etching surface for forming a concave portion on the silicon surface 101 of the silicon substrate 100,
Using a double-sided exposure machine, a pattern to be an etching opening 106 for forming a diaphragm is formed, and as shown in FIG. The resist 105 is removed, and the silicon nitride film 110 is removed to obtain a diaphragm substrate.

It is preferable that the photoresist is stripped by a process using a stripper specified by a photoresist maker. A photoresist ashing device using oxygen plasma may be used, but in that case, it is necessary to prevent the silicon oxide film from being damaged (rough surface, residual resist ash, etc.).

Thereafter, as shown in FIG. 10G, the silicon surface 101 of the silicon substrate 100 serving as the diaphragm substrate is directly bonded to the electrode substrate 41 in the same manner as in the first embodiment. In the next step, the silicon substrate is immersed in a high-concentration alkali metal hydroxide solution using the silicon oxide film 104 on the surface except for the opening 108 for etching on the silicon substrate 100 side as a mask. The concave portion 53 which becomes a liquid chamber by being selectively etched
To form At this time, when the etching of the silicon substrate 100 reaches the region of the silicon oxide film 103 which is an interlayer insulating film of the SOI substrate, the etching is stopped spontaneously. Can produce well.

As described above, by using a semiconductor substrate having an SOI structure as a diaphragm substrate and masking a region to be a diaphragm on a bonding surface of the semiconductor substrate with an electrode substrate, the substrate is oxidized by thermal oxidation. By selectively oxidizing the region other than the region that will become the diaphragm, forming an oxide film to a thickness that is necessary for the actuator, removing the mask, and joining the diaphragm to the electrode substrate, And an electrostatic actuator in which a silicon oxide film for forming a gap is provided on the diaphragm substrate side directly without using an adhesive.

Next, a seventh embodiment of the method of manufacturing an electrostatic actuator according to the present invention will be described with reference to FIG. FIG. 7A is an explanatory diagram showing another embodiment of the diaphragm substrate according to the first embodiment, and FIG. 7B is an explanatory diagram showing another embodiment of the diaphragm substrate according to the second embodiment. In this embodiment, leakage or sticking to the electrodes is prevented by leaving an insulating film on the electrode surface side of the diaphragm substrate 31 or 61. As the insulating film, a silicon oxide film may be formed by a method such as thermal oxidation, or the insulating film 111 may be formed by leaving the existing silicon oxide films 34 and 64 extremely thin.
This increases the degree of freedom in the method of manufacturing the electrode substrate.

Next, an eighth embodiment of the method of manufacturing an electrostatic actuator according to the present invention will be described with reference to FIG. FIG. 12 is an explanatory diagram for explaining a manufacturing process of an electrode substrate to which the invention according to claim 10 is applied. First, a silicon substrate 121 serving as an electrode substrate shown in FIG.
It is a substrate having the polarity of the mold and the crystal plane orientation of <110>, and the bonding surface side with the diaphragm substrate is mirror-finished.

Therefore, as shown in FIG. 2B, a silicon oxide film 124 serving as a buffer oxide film is formed on the surface of the silicon substrate 121 by a thermal oxidation method. At this time, the thickness of the silicon oxide film 124 needs to be large enough to withstand wet etching. Here is about 1μm
It was formed in thickness.

Subsequently, after a photoresist 125 is applied to the bonding surface (mirror side) of the silicon substrate 121, patterning is performed so that an opening 126 is formed only in a region where an electrode is to be formed, and the photoresist 125 is used as a mask. The silicon oxide film 124 is etched to form an opening 126.
To form

Then, as shown in FIG. 9C, the photoresist 125 is removed, the silicon substrate 121 is immersed in a high-concentration alkali metal hydroxide solution, and the silicon surface is selectively etched. The etching amount at this time is
Etching is performed to such a depth that the electrode material is embedded. Here, etching was performed to a depth of about 300 nm. Next, a silicon oxide film 127 serving as an insulating film between the electrode material and the silicon substrate 121 is formed. At this time, the thickness of the silicon oxide film 127 serving as an insulating film was about 100 μm.

Next, as shown in FIG. 4D, polysilicon 128 doped with impurities to be an electrode is deposited by a method such as CVD. At this time, the electrode material may be a high melting point metal material such as titanium nitride. The thickness of the electrode material was about 100 μm. Subsequently, a silicon oxide film 129 serving as a cap is deposited by a method such as CVD to secure the insulating properties of the electrodes.

Then, a photoresist is applied, and this is exposed and developed into an electrode shape to form an electrode-shaped pattern 130.
After the formation of the silicon oxide film 12 as shown in FIG.
9. Etching with polysilicon 128 and silicon oxide film 127, which are electrode materials, and removing the photoresist pattern 130 to obtain an electrode substrate on which individual electrodes 51 made of polysilicon are formed as shown in FIG. .

Here, the electrode shape is obtained by photoetching. However, as shown in FIG. 15, after a silicon oxide film 129 serving as a cap is deposited, as shown in FIG. 15E, a CMP (Chemical Mechanical Polishing) is performed as shown in FIG. The surface of the silicon substrate 121 may be polished by such a method. At this time, the surface of the silicon substrate (bonding interface) is finished to be flush, and there is an advantage that both surface accuracy and roughness are made uniform.

Thereafter, the electrostatic actuator can be obtained by directly bonding to the diaphragm substrate by the method described above.

As described above, the electrode substrate is formed by depositing the impurity-implanted polysilicon film on the silicon substrate, forming a silicon oxide film serving as an insulating film, and forming a protective film covering the electrode pattern. Etching is performed using this protective film as a mask to expose the silicon substrate serving as a bonding surface, and then bonding to the diaphragm substrate, so that a buried electrode structure can be obtained, and the contact to the electrode is made to the diaphragm substrate side Or from the electrode substrate side, which increases the degree of freedom in mounting the actuator on a functional device.

Next, a ninth embodiment of the method of manufacturing an electrostatic actuator according to the present invention will be described with reference to FIGS. FIG. 16 is an explanatory view for explaining a manufacturing process of the electrostatic actuator according to claim 11 to which the invention according to claim 12 is applied, and FIG. 17 is an explanatory view for explaining a bonding step between the diaphragm substrate and the electrode substrate.

The electrostatic actuator here is different from the above-mentioned electrostatic actuator in the way of taking individual electrodes. In the above-mentioned electrostatic actuator, a diaphragm substrate and an electrode substrate are provided separately. In the electrostatic actuator according to the eleventh aspect, the electrode substrate on which the conventional electrode is formed is a common electrode (ground level).
Thus, the configuration is such that a voltage can be individually applied to the diaphragm.

Therefore, as shown in FIG. 16A, a silicon substrate 140 serving as a diaphragm substrate uses a wafer having an SOI structure. The silicon surface 141 for engraving the diaphragm has P-type polarity and its crystal plane orientation is <110>, and the silicon surface 142 serving as the diaphragm has a thickness of about 2 μm (here, about 2 μm). ), The crystal plane orientation is <110>, and the polarity is P-type. Further, the insulating layer 143 sandwiched in the middle is a silicon oxide film,
An SOI substrate having a thickness of about 150 to 200 μm was used. Both sides are mirror-polished. This silicon substrate is used as a starting material.

First, as shown in FIG. 13B, the silicon substrate 140 is oxidized by a pyro-oxidation (wet oxidation) method or a thermal oxidation method such as dry oxidation.
A silicon oxide film 144 is formed on the surface of the substrate 40. At this time, the thickness of the silicon oxide film 144 is equal to the gap of the electrostatic actuator. Here, it was formed to a thickness of about 400 μm.

Next, as shown in FIG. 14C, a photoresist 145 is applied to both sides of the silicon substrate 140, and then, as shown in FIG. 12 to be the gap part on the joining surface side of
7 and a pattern 126 to be an etching opening for forming a diaphragm is formed. Here, the use of the double-sided exposure machine is to ensure the positioning accuracy of the pattern to be the gap layer and the etching opening.

Next, using the photoresist 145 as a mask, the silicon oxide film 144 is etched using a hydrogen fluoride solution having a concentration of about 5%. Thereafter, as shown in FIG. 3E, using the film of the photoresist 145 as a mask, ions 149 which become N-type after being implanted into the silicon substrate surface which becomes the vibration plate are removed, and the photoresist 145 is removed to oscillate. Obtain a plate substrate.

The photoresist is preferably stripped by a process using a stripper specified by a photoresist maker. A photoresist ashing device using oxygen plasma may be used, but in that case, it is necessary to prevent the silicon oxide film from being damaged (rough surface, residual resist ash, etc.).

Thereafter, as shown in FIG. 17A, the silicon substrate 140 serving as the diaphragm substrate is directly bonded to the electrode substrate 151 provided with the protective film 152. At this time, the ions 149 implanted into the silicon substrate 140 are activated by heat, and function as the individual electrodes 150.

Then, as shown in FIG. 12B, the silicon oxide film 144 on the surface except for the etching opening 148 on the silicon substrate 140 side is used as a mask.
The silicon substrate is immersed in a high-concentration alkali metal hydroxide solution, and the silicon surface is selectively etched to form a concave portion 153 serving as a liquid chamber. Then, as shown in FIG. Through a removing step, the silicon oxide film 143 and the like at the bottom of the concave portion 153 are removed to form the vibration plate 154.

At this time, since the etching of the silicon substrate 140 is stopped spontaneously when the insulating layer of the silicon oxide film 143 is etched, an extremely thin diaphragm 154 can be produced with high accuracy. In addition,
Since the silicon oxide film 143 on the vibration plate 154 is removed in the subsequent oxide film removing step as described above, the vibration characteristics are not affected.

As described above, the semiconductor substrate forming the diaphragm has the SOI structure, and the silicon substrate having the first conductivity type serving as the bonding surface is formed on the silicon surface having the thickness necessary for the necessary gap of the actuator by the thermal oxidation method. After the formation of the silicon oxide film, the silicon oxide film on the bonding surface side is patterned into a desired shape with a resist.
After forming individual electrodes for each diaphragm by performing ion implantation of the conductivity type of the diaphragm, the diaphragm substrate is activated by activating the implanted ions by heat of direct bonding at the time of bonding with a low-resistance silicon substrate. And the electrode substrate can be directly bonded without using an adhesive, and an electrostatic actuator in which a silicon oxide film for forming a gap is provided on the diaphragm substrate side can be manufactured.

Next, a tenth embodiment of the method of manufacturing an electrostatic actuator according to the present invention will be described with reference to FIGS.
This will be described with reference to FIG. FIG. 18 is an explanatory view illustrating a process of manufacturing a diaphragm substrate by applying the invention according to claim 13;
FIG. 19 is an explanatory view illustrating a process of manufacturing an electrostatic actuator by bonding a diaphragm substrate and an electrode substrate.

First, as shown in FIG. 18A, a silicon substrate 141 serving as a diaphragm substrate has a crystal plane orientation of <
110>, and both sides are mirror-polished. This silicon substrate 161 is used as a starting material.

Then, the silicon substrate 161 is
A silicon nitride film 162 is deposited using a method. The thickness of the silicon nitride film 162 at this time is the thickness of the diaphragm. Next, as shown in FIG.
A silicon oxide film 164 is formed on the entire surface of the substrate 1. At this time, since a thermal oxide film hardly grows on the silicon nitride film 162, the silicon oxide film 164 is formed by a method such as the CVD method. At this time, the thickness of the silicon oxide film 144 is
The thickness is set to be equal to the gap of the electrostatic actuator. Here, it was formed to a thickness of about 400 μm.

Next, as shown in FIG. 13C, a photoresist 165 is applied to both sides of the silicon substrate 161 and then, as shown in FIG.
A pattern 167 serving as a gap portion on the joining surface side and a pattern 166 serving as an etching opening portion for forming a diaphragm are formed. Here, the use of the double-sided exposure machine is to ensure the positioning accuracy of the pattern to be the gap layer and the etching opening.

Then, using the photoresist 165 as a mask, the silicon oxide film 164 is etched using a hydrogen fluoride solution having a concentration of about 5% to form openings 168 and 169. Thereafter, as shown in FIG. 3E, a thin film 170 of a high melting point metal such as titanium nitride is deposited by a method such as sputtering. At this time, the method of forming a thin film is preferably a method with poor step coverage such as sputtering.

Next, the photoresist 165 is removed to obtain a diaphragm substrate as shown in FIG. At this time, at the same time as the photoresist 165 is peeled, the electrode thin film 170 remaining on the photoresist film is also peeled (lift-off method). By using this method, an individual electrode can be formed on the back surface of the diaphragm.

Thereafter, as shown in FIG. 19A, the silicon substrate 161 serving as a diaphragm substrate and the electrode substrate 171 provided with the protective film 172 are directly bonded by the above-described method. In the next step, a silicon oxide film 164 on the surface is used as a mask while leaving an opening 168 for etching on the silicon substrate 161 side as shown in FIG. The silicon substrate is immersed, and the silicon surface is selectively etched to form a concave portion 173 serving as a liquid chamber.

At this time, when the silicon substrate is etched to the silicon nitride film 162 on the opposite side of the silicon substrate, the etching stops spontaneously.
The vibration plate 174 made of an extremely thin silicon nitride film can be accurately produced. Thereafter, the silicon oxide film 164 and the like are removed as shown in FIG.

As described above, the semiconductor substrate forming the diaphragm is a silicon wafer, a silicon nitride film having a thickness of the diaphragm is formed on a silicon surface serving as a bonding surface, and then a silicon oxide film is formed on the nitride film. The silicon oxide film is patterned into a desired shape with a resist, and then a conductive film is deposited on the diaphragm substrate with the resist. After removing the conductive film on the part other than the diaphragm, individual electrodes are formed for each diaphragm, and then directly bonded to a low-resistance silicon substrate, an adhesive is applied between the diaphragm substrate and the electrode substrate. It is possible to manufacture an electrostatic actuator in which a silicon oxide film for directly bonding and forming a gap is provided on the diaphragm substrate side without using it.

[0134]

As described above, according to the electrostatic actuator of the first aspect, the diaphragm substrate on which the diaphragm is formed and the electrode substrate on which the individual electrodes are formed are formed by the silicon oxide film serving as an insulating film. In an electrostatic actuator in which a diaphragm is deformed by applying a voltage between the electrode and the diaphragm, a diaphragm substrate and an electrode substrate are directly joined without using an adhesive. In addition, since a silicon oxide film for forming a gap is provided on the diaphragm substrate side, when manufacturing an actuator using a semiconductor process, the roughness of the joint surface between the diaphragm substrate and the electrode substrate is reduced. Direct bonding can be performed without causing the generation, and a low-cost and high-density electrostatic actuator can be obtained.

According to the method of manufacturing an electrostatic actuator of claim 2, in the method of manufacturing an electrostatic actuator of claim 1, the bonding of the electrode substrate of the semiconductor substrate to the diaphragm substrate is performed. Using a silicon wafer into which high-concentration impurities are implanted on the surface side, a silicon oxide film having a thickness serving as a gap is formed on the silicon wafer by thermal oxidation, and then the silicon oxide film on the bonding surface side is formed into a desired shape. Since it is configured to be patterned and bonded to the electrode substrate, it is possible to obtain an electrostatic actuator by direct bonding without generating a roughness of a bonding surface by using a semiconductor manufacturing process, and improve a gap accuracy, Even higher density devices can be obtained.

According to a third aspect of the present invention, there is provided the method of manufacturing an electrostatic actuator according to the first aspect, wherein a semiconductor substrate having an SOI structure is used as a diaphragm substrate. Then, a silicon oxide film having a thickness that is necessary for the actuator is formed on the bonding surface side of the semiconductor substrate with the electrode substrate by a thermal oxidation method, and then the silicon oxide film on the bonding surface side is patterned into a desired shape. , Because it is configured to be bonded to the electrode substrate, it is possible to obtain an electrostatic actuator by direct bonding without causing a roughened bonding surface by using a semiconductor manufacturing process, and improve the gap accuracy,
Even higher density devices can be obtained.

According to the method of manufacturing an electrostatic actuator of the fourth aspect, in the method of manufacturing an electrostatic actuator of the first aspect, a silicon substrate is used as a diaphragm substrate. After a silicon nitride film having a thickness of a diaphragm was formed on the entire surface of the bonding surface of the silicon substrate with the electrode substrate, a silicon oxide film was formed on the nitride film to a thickness that required an actuator gap. After that, the silicon oxide film on the bonding surface was patterned into a desired shape and bonded to the electrode substrate. An actuator can be obtained, the gap accuracy can be improved, and an even higher density device can be obtained.

According to the method of manufacturing an electrostatic actuator of the fifth aspect, in the method of manufacturing an electrostatic actuator of the first aspect, a silicon wafer is used as a diaphragm substrate. After forming a silicon nitride film having a thickness of the diaphragm on the bonding surface of the silicon wafer with the electrode substrate, patterning is performed while leaving the silicon nitride film only in a region where the diaphragm is to be formed. Oxidation, selective oxidation of the silicon substrate, growth of an oxide film to the thickness required for the required actuator gap, and then bonding to the electrode substrate, the bonding surface using a semiconductor manufacturing process It is possible to obtain an electrostatic actuator by direct bonding without causing roughness, improving the gap accuracy and further increasing the density. It can be obtained device.

According to the method of manufacturing an electrostatic actuator of claim 6, in the method of manufacturing an electrostatic actuator of claim 1, the bonding of the vibration plate to the electrode substrate of the semiconductor substrate is performed. After using a silicon wafer in which high-concentration impurities are implanted on the surface side, a region to be a diaphragm on the bonding surface side of the silicon wafer is masked,
By oxidizing by thermal oxidation, it selectively oxidizes the area other than the area that will become the diaphragm, forms a thickness that will be the necessary gap of the actuator, removes the mask, and joins the electrode substrate It is possible to obtain an electrostatic actuator by direct bonding without causing the bonding surface to be rough due to the use of the manufacturing process, to improve the gap accuracy, and to obtain a higher density device.

According to the method of manufacturing an electrostatic actuator of claim 7, in the method of manufacturing an electrostatic actuator of claim 1, the semiconductor substrate having the SOI structure is used as the diaphragm substrate. After masking the area that will become the diaphragm on the joint surface of the semiconductor substrate with the electrode substrate using this, it is oxidized by thermal oxidation to selectively oxidize the area other than the area that will become the diaphragm, and the necessary gap for the actuator is obtained. After the oxide film is formed to the thickness required, the mask is removed and the structure is joined to the electrode substrate. A mold actuator can be obtained, the gap accuracy can be improved, and an even higher density device can be obtained.

According to the method of manufacturing an electrostatic actuator of claim 8, in the method of manufacturing an electrostatic actuator of claim 2 or 3, the silicon oxide is formed on the bonding surface side of the diaphragm substrate during the patterning of the oxide film. Since the thin film of the film is left, or the thermal oxidation is performed again after the patterning is completed to form an oxide film on the back side of the vibration plate, without causing the roughness of the bonding surface by using the semiconductor manufacturing process,
An electrostatic actuator by direct bonding can be obtained, the gap accuracy can be improved, and an even higher density device can be obtained.

According to the method of manufacturing an electrostatic actuator of claim 9, in the method of manufacturing an electrostatic actuator of claim 1, the electrode substrate corresponds to the electrode on the silicon substrate. Forming a resist pattern, using this resist pattern as a mask, performing a heat treatment after performing ion implantation and forming an active layer, and completely removes an oxide film on a bonding surface before bonding to a diaphragm substrate After that, it is configured to be joined to the diaphragm substrate, so that it is possible to obtain an electrostatic actuator by direct joining without causing a deviation of the joining surface by using a semiconductor manufacturing process, improving the gap accuracy,
Even higher density devices can be obtained.

According to a tenth aspect of the present invention, in the method of manufacturing an electrostatic actuator of the first aspect, the electrode substrate is formed by implanting impurities on a silicon substrate. After depositing a polysilicon film or a metal-based conductive film, a silicon oxide film serving as an insulating film is formed, a protective film having a shape covering the electrode pattern is formed, and etching is performed using the protective film as a mask to form a bonding surface. Since the silicon substrate is exposed and then joined to the diaphragm substrate, the electrodes can be contacted from any substrate side, and the degree of freedom in mounting the actuator functional device is increased.

According to the electrostatic actuator of the eleventh aspect, a gap is formed between the diaphragm substrate on which the diaphragm and the individual electrodes are formed and the electrode substrate on which the common electrode is formed by the silicon oxide film serving as an insulating film. An electrostatic actuator in which the diaphragm is deformed by applying a voltage between the individual electrode and the common electrode by bonding, the diaphragm substrate is a low-resistance silicon substrate, and the diaphragm substrate and the electrode substrate are Because the silicon oxide film for bonding directly and forming a gap was provided on the diaphragm substrate side without using an adhesive,
In the case of manufacturing an actuator using a semiconductor process, direct bonding can be performed without causing any deviation in the bonding surface between the diaphragm substrate and the electrode substrate, and a low-cost, high-density electrostatic actuator can be obtained.

According to the method of manufacturing an electrostatic actuator of claim 12, in the method of manufacturing an electrostatic actuator of manufacturing the electrostatic actuator of claim 11,
The semiconductor substrate forming the diaphragm has an SOI structure, and on a silicon surface having a first conductivity type serving as a bonding surface,
After forming a silicon oxide film having a thickness to be a necessary gap of the actuator by a thermal oxidation method, the silicon oxide film on the bonding surface side is patterned with a resist into a desired shape, and the second conductivity type is formed using the pattern film as a mask. After the individual electrodes are formed on each of the vibrating plates by performing ion implantation, the implanted ions are activated by the heat of direct bonding at the time of bonding with the silicon substrate. It can be taken from the side, and the degree of freedom in mounting the functional device of the actuator is increased.

According to the method of manufacturing an electrostatic actuator of claim 13, in the method of manufacturing an electrostatic actuator of claim 11,
The semiconductor substrate forming the diaphragm is a silicon wafer,
After forming a silicon nitride film having a thickness of a diaphragm on a silicon surface serving as a bonding surface, a silicon oxide film is deposited and formed on the nitride film to a thickness required for a necessary gap of an actuator, and the silicon oxide film is formed. After patterning with a resist into a desired shape, a conductive film is deposited on the diaphragm substrate with the resist, and the resist film and the conductive film in portions other than the diaphragm are removed. Since the individual electrodes are formed and then directly joined to the silicon substrate, the electrodes can be contacted from any substrate side, and the degree of freedom in mounting the actuator functional device is increased.

According to the fourteenth aspect of the present invention, there is provided a nozzle for discharging ink droplets, a discharge chamber to which the nozzle communicates, a diaphragm forming a wall surface of the discharge chamber, and a predetermined gap provided between the diaphragm and the diaphragm. 12. An electrostatic ink jet head comprising: an actuator having electrodes arranged opposite to each other; wherein a voltage is applied between the diaphragm and the electrodes to eject ink droplets from nozzles, wherein the actuator is an electrostatic ink jet head according to claim 1 or 11. Since the actuator is constituted by an actuator, a high-density inkjet head can be obtained at low cost.

According to the ink jet head of the fifteenth aspect, a nozzle for discharging ink droplets, a discharge chamber to which the nozzle communicates, a vibration plate forming a wall surface of the discharge chamber, and a predetermined gap between the vibration plate and the vibration plate. 15. An electrostatic ink jet head comprising: an actuator having electrodes arranged opposite to each other, wherein the actuator applies a voltage between the diaphragm and the electrodes to eject ink droplets from nozzles, wherein the actuators are used. Since the configuration is made of the electrostatic actuator manufactured by any one of the above manufacturing methods, a low-cost, high-density inkjet head can be obtained. .

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a first embodiment of an inkjet head including an electrostatic actuator according to the present invention.

FIG. 2 is a schematic cross-sectional view illustrating a second embodiment of an inkjet head including an electrostatic actuator according to the present invention.

FIG. 3 is an explanatory view illustrating a manufacturing process of a diaphragm substrate to which the invention according to claim 2 is applied.

FIG. 4 is an explanatory view illustrating a manufacturing process of an electrode substrate to which the invention according to claim 9 is applied.

FIG. 5 is an explanatory view illustrating a process of manufacturing an electrostatic actuator by bonding the diaphragm substrate of FIG. 3 and the electrode substrate of FIG. 4;

FIG. 6 is an explanatory view illustrating a manufacturing process of a diaphragm substrate to which the invention according to claim 3 is applied.

FIG. 7 is an explanatory view illustrating a process of manufacturing the electrostatic actuator by bonding the diaphragm substrate of FIG. 6 and the electrode substrate of FIG. 4;

FIG. 8 is an explanatory view illustrating a manufacturing process of a diaphragm substrate to which the invention according to claim 4 is applied.

FIG. 9 is an explanatory view illustrating a process of manufacturing the electrostatic actuator by bonding the diaphragm substrate of FIG. 8 and the electrode substrate of FIG. 4;

FIG. 10 is an explanatory view illustrating a manufacturing process to which the invention according to claim 5 is applied.

FIG. 11 is an explanatory view illustrating a manufacturing process to which the invention according to claim 6 is applied.

FIG. 12 is an explanatory view illustrating a manufacturing process to which the invention according to claim 7 is applied.

13A is an explanatory view showing another embodiment of the diaphragm substrate according to the first embodiment, and FIG. 13B is an explanatory view showing another embodiment of the diaphragm substrate according to the second embodiment.

FIG. 14 is an explanatory view illustrating a manufacturing process to which the invention according to claim 10 is applied.

FIG. 15 is an explanatory view illustrating another manufacturing process to which the invention according to claim 10 is applied.

FIG. 16 is an eleventh embodiment to which the invention according to the twelfth embodiment is applied.
Explanatory drawing explaining the manufacturing process of the electrostatic actuator of FIG.

FIG. 17 is an explanatory view illustrating a bonding step between a diaphragm substrate and an electrode substrate.

FIG. 18 is an eleventh embodiment to which the invention according to the thirteenth embodiment is applied.
Explanatory drawing explaining the manufacturing process of the electrostatic actuator of FIG.

FIG. 19 is an explanatory view illustrating a bonding step between a diaphragm substrate and an electrode substrate.

[Explanation of symbols]

1, 11: diaphragm substrate, 2, 12: electrode substrate, 3, 13
... Nozzle plate, 5, 15 ... Nozzle, 6, 16 ... Liquid chamber, 7, 17 ... Recess, 8, 18 ... Vibration plate, 9, 19 ... Silicon oxide film, 10, 20 ... Individual electrode.

Claims (15)

[Claims] 1. A diaphragm substrate on which a diaphragm is formed and an electrode substrate on which individual electrodes are formed are joined by forming a gap with a silicon oxide film serving as an insulating film, and a voltage is applied between the electrode and the diaphragm. In the electrostatic actuator in which the diaphragm is deformed by applying pressure, the diaphragm substrate and the electrode substrate are directly joined without using an adhesive, and the silicon oxide film for forming the gap is vibrated. An electrostatic actuator provided on a plate substrate side. 2. A method of manufacturing an electrostatic actuator according to claim 1, wherein the method includes the steps of:
Using a silicon wafer in which high-concentration impurities were implanted on the vibration plate substrate on the bonding surface side of the semiconductor substrate and the electrode substrate, a silicon oxide film having a thickness corresponding to the gap was formed on the silicon wafer by thermal oxidation. Thereafter, a method for manufacturing an electrostatic actuator, comprising: patterning a silicon oxide film on a bonding surface side into a desired shape and bonding the silicon oxide film to the electrode substrate. 3. The method for manufacturing an electrostatic actuator according to claim 1, wherein a semiconductor substrate having an SOI structure is used as the diaphragm substrate, and the semiconductor substrate is bonded to the electrode substrate. On the surface side, after forming a silicon oxide film having a thickness that becomes a necessary gap of the actuator by a thermal oxidation method, the silicon oxide film on the bonding surface side is patterned into a desired shape and bonded to the electrode substrate. Of manufacturing an electrostatic actuator. 4. The method of manufacturing an electrostatic actuator according to claim 1, wherein a silicon substrate is used as the diaphragm substrate, and a silicon substrate is provided on a bonding surface of the silicon substrate with the electrode substrate. After a silicon nitride film having the thickness of the vibration plate is formed on the entire surface, a silicon oxide film is formed on the nitride film to a thickness that is necessary for the actuator, and then a silicon oxide film on the bonding surface side is desired. A method for manufacturing an electrostatic actuator, comprising: 5. The method of manufacturing an electrostatic actuator according to claim 1, wherein a silicon wafer is used as the diaphragm substrate and the silicon wafer is provided on a bonding surface of the silicon wafer with the electrode substrate. After forming a silicon nitride film having a thickness of the diaphragm, patterning is performed while leaving a silicon nitride film only in a region where the diaphragm is to be formed. Then, thermal oxidation is performed using the nitride film as a mask, and the silicon substrate is selectively formed. And oxidizing the oxide film to grow an oxide film to a thickness required for a necessary gap of the actuator, and then bonding the oxide film to the electrode substrate. 6. The method for manufacturing an electrostatic actuator according to claim 1, wherein a high-concentration impurity is implanted into said vibration plate on a bonding surface side of said semiconductor substrate with said electrode substrate. After masking the region serving as the vibration plate on the bonding surface side of the silicon wafer using a wafer, the region other than the region serving as the vibration plate is selectively oxidized by oxidizing by thermal oxidation. The method of manufacturing an electrostatic actuator, further comprising removing the mask and bonding to the electrode substrate after forming the mask to a thickness of: 7. The method for manufacturing an electrostatic actuator according to claim 1, wherein a semiconductor substrate having an SOI structure is used as the diaphragm substrate, and the semiconductor substrate is bonded to the electrode substrate. After masking the area to be the diaphragm on the surface, by oxidizing by thermal oxidation, the area other than the area to be the diaphragm is selectively oxidized, and an oxide film is formed to a thickness that becomes a necessary gap of the actuator. And removing the mask and joining the mask to the electrode substrate. 8. The method for manufacturing an electrostatic actuator according to claim 2, wherein a thin film of a silicon oxide film is left on the bonding surface side of the diaphragm substrate during the patterning of the oxide film, or after the patterning is completed, A method for manufacturing an electrostatic actuator, wherein an oxide film is formed on the back side of a diaphragm by performing thermal oxidation. 9. The method of manufacturing an electrostatic actuator according to claim 1, wherein the electrode substrate forms a resist pattern corresponding to the electrode on a silicon substrate, and uses the resist pattern as a mask. Forming an active layer by performing a heat treatment after performing ion implantation, and completely bonding an oxide film on a bonding surface before bonding with the diaphragm substrate before bonding with the diaphragm substrate. A method for manufacturing an electrostatic actuator, which is characterized by the following. 10. The method for manufacturing an electrostatic actuator according to claim 1, wherein the electrode substrate is formed by depositing a polysilicon film or a metal-based conductive film into which impurities are implanted on a silicon substrate. Forming a silicon oxide film serving as an insulating film, forming a protective film having a shape covering the electrode pattern, performing etching using the protective film as a mask to expose a silicon substrate serving as a bonding surface, and then forming the diaphragm substrate And a method for manufacturing an electrostatic actuator. 11. A diaphragm substrate on which a diaphragm and an individual electrode are formed and an electrode substrate on which a common electrode is formed are joined by forming a gap with a silicon oxide film serving as an insulating film, and the individual electrode and the common electrode are connected to each other. An electrostatic actuator in which the diaphragm is deformed by applying a voltage between the diaphragm and the diaphragm substrate is a low-resistance silicon substrate, and the diaphragm substrate and the electrode substrate do not use an adhesive. An electrostatic actuator, wherein a silicon oxide film for directly bonding and forming a gap is provided on the diaphragm substrate side. 12. The method for manufacturing an electrostatic actuator according to claim 11, wherein the semiconductor substrate forming the vibration plate has an SOI structure and serves as a bonding surface. After a silicon oxide film having a thickness required for the actuator is formed on a silicon surface having a conductivity type by a thermal oxidation method, the silicon oxide film on the bonding surface is patterned into a desired shape with a resist. And ion implantation for forming the second conductivity type is performed using the mask as a mask to form individual electrodes for each of the vibration plates, and then the injected ions are activated by the heat of direct bonding at the time of bonding with the silicon substrate. Of manufacturing an electrostatic actuator. 13. The method of manufacturing an electrostatic actuator according to claim 11, wherein the semiconductor substrate forming the diaphragm is a silicon wafer, and a silicon nitride film having a thickness of the diaphragm is formed on a silicon surface serving as a bonding surface. After formation, a silicon oxide film is deposited on the nitride film to a thickness required for the necessary gap of the actuator, and the silicon oxide film is patterned into a desired shape with a resist. The method is characterized in that a conductive film is deposited on the substrate, and the resist film and the conductive film other than the diaphragm are removed to form individual electrodes for the diaphragm and then directly bonded to the silicon substrate. A method for manufacturing an electrostatic actuator. 14. An actuator comprising a nozzle for discharging ink droplets, a discharge chamber to which the nozzle communicates, a diaphragm forming a wall surface of the discharge chamber, and an electrode arranged opposite to the diaphragm with a predetermined gap. And an electrostatic inkjet head that ejects ink droplets from the nozzles by applying a voltage between the diaphragm and an electrode, wherein the actuator is the electrostatic actuator according to claim 1 or 11. An ink jet head, comprising: 15. An actuator comprising: a nozzle for discharging ink droplets; a discharge chamber communicating with the nozzle; a diaphragm forming a wall surface of the discharge chamber; and an electrode disposed to face the diaphragm with a predetermined gap therebetween. 11. An electrostatic ink jet head comprising: a nozzle for ejecting ink droplets by applying a voltage between the vibration plate and an electrode, wherein the actuator comprises the actuator.
An inkjet head comprising an electrostatic actuator manufactured by the manufacturing method according to any one of 2 to 14.