JP2003300326A - Electrostatic actuator and process for making ink jet head utilizing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control the direction and the amount of deflection of a diaphragm even if the diaphragm is 1 μm thick or less. <P>SOLUTION: TEOS films are formed on the opposite sides of a diaphragm 9 by plasma CVD. TEOS films of different thickness are formed independently on the opposite sides or TEOS films are formed independently on the opposite sides under different film deposition conditions. Since the TEOS films formed on the opposite sides have different film stress, deflection of the diaphragm 9 can be controlled easily by the difference of film stress. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic actuator used as a drive mechanism for an inkjet head and the like, and a method for manufacturing an inkjet head using the electrostatic actuator. More specifically, the present invention relates to a method of forming an insulating film in an electrostatic actuator in which an insulating film is formed on the surface of a member that is relatively displaced by electrostatic force.

[0002]

2. Description of the Related Art An electrostatic drive type ink jet head which employs an electrostatic actuator as a drive mechanism for ejecting ink droplets is disclosed in, for example, Japanese Patent Application Laid-Open No. 5-50.
It is proposed in Japanese Patent No. 601.

In this type of ink jet head, the bottom surface of the ink flow path communicating with the ink nozzle is formed as a vibrating plate which is elastically deformable in the out-of-plane direction. Further, the vibrating plate has a structure in which glass substrates are arranged to face each other at regular intervals, and counter electrodes are respectively arranged on the vibrating plate and the glass substrate. Furthermore, an insulating film is applied to the surface of this diaphragm. This insulating film is a film for preventing dielectric breakdown and short circuit when the diaphragm is electrostatically attracted. When a voltage is applied between the opposing electrodes, the diaphragm is electrostatically attracted to the substrate side and vibrates due to the electrostatic force generated between them. Due to fluctuations in the internal pressure of the ink flow path (ink pressure chamber) caused by the vibration of this diaphragm,
Ink droplets are ejected from the ink nozzle.

The insulating film on the surface of the diaphragm is 100
A thermal oxide film formed by thermal oxidation at a high temperature of 0 ° C. or higher, which is applied after forming the diaphragm.

[0005]

However, when an insulating film made of a thermal oxide film is applied to a diaphragm having a thickness of 1 μm or less, the thermal oxidation is performed at a high temperature of 1000 ° C. or more as described above. However, there is a problem in that the bending direction and the bending amount cannot be controlled due to the large bending due to the high temperature and the stress of the thermal oxide film itself.

The present invention has been made to solve the above problems, and utilizes an electrostatic actuator capable of controlling the bending direction and the bending amount even if the thickness of the diaphragm is 1 μm or less, and the electrostatic actuator. Another object of the present invention is to propose a method for manufacturing the inkjet head.

[0007]

In order to solve the above-mentioned problems, an electrostatic actuator according to the present invention comprises a diaphragm, a counter electrode arranged to face the diaphragm, the diaphragm and the counter electrode. In an electrostatic actuator having a vibration chamber formed by, a plasma CVD (Chemical Vapor Depo) is formed on both surfaces of the vibration plate.
TEOS (Tetra ethyl o)
It is characterized by forming an rthosilicate film. When the TEOS film is formed by plasma CVD, the film formation temperature is considerably lower than that of the conventional film formation by thermal oxidation at a high temperature, and therefore a large change in the bending amount of the diaphragm can be suppressed.

The electrostatic actuator to which the present invention is applicable is an ink jet head used in an ink jet recording apparatus. In this case, it is configured to have a nozzle and an ink flow path that communicates with the nozzle and is partially formed with the vibrating plate, and generates static electricity between the vibrating plate and the counter electrode to generate the vibrating plate. A driving means for displacing the nozzle, the driving means being configured to include a voltage applying means for applying an electric pulse between the diaphragm and the counter electrode, and the nozzle according to the application of the electric pulse. Ink droplets may be ejected from.

In order to control the bending direction and the bending amount of the diaphragm to the desired bending direction and bending amount, the film stress of the TEOS film formed on one surface of the diaphragm and the other surface of the TEOS film are adjusted. The film stress may be changed in the formed TEOS film. When forming a TEOS film by plasma CVD, TE
The film stress can be easily changed by changing the film forming conditions such as the OS flow rate, the O2 flow rate, the RF power, the pressure, and the temperature.

As another method of controlling the bending direction and the bending amount of the diaphragm, the thickness of the TEOS film formed on one surface of the diaphragm and the TEOS film formed on the other surface of the diaphragm are controlled. The films may be formed so that the film thicknesses are different.

[0011]

1 is a diagram showing an example of an ink jet head formed by a manufacturing method of the present invention. As shown in FIG. 1, it comprises a nozzle plate 3 having a nozzle 2 formed in a thin portion 1, a cavity plate 4 and a wiring board 5.

FIG. 2 is a sectional view seen from the direction of arrow 6 in FIG. In the cavity plate 4, a pressure chamber 8 is formed, one of which communicates with the nozzle 2 and the other of which communicates with the supply port 7.
A vibrating plate 9 is integrally formed with the other one of the pressure chambers 8. An air chamber 10 is formed on the wiring plate 5 side of the vibration plate 9, and an electrode 11 is provided at a position facing the vibration plate 9 of the air chamber 10. Further, the diaphragm 9 shown in the figure is formed by anisotropically etching the cavity plate 4 to a thickness of about 0.8 μm, and is formed on the surface facing the electrode 11 arranged on the wiring board 5. Is provided with an insulating film 13. Also, the pressure chamber 8
Is a flow path for ink, and therefore a protective film 14 is provided on the surface of the vibration plate 9 on the pressure chamber 8 side.

When a voltage is applied to the electrode 11 and the diaphragm 9,
The vibrating plate 9 is bent by the generated electrostatic attraction force, and when the application of the voltage is stopped, the bending is restored, and the vibration operation is performed. Occurs. By the pressure vibration,
Ink is pushed out from the nozzle 2 to eject an ink droplet 12.

Next, a method of manufacturing the diaphragm 9 will be described. First, the cavity plate 4 is put in a potassium hydroxide aqueous solution,
(KOH), TMAH (Tetra methyl A
thickness of about 0.8μ by anisotropic etching using an etching solution such as mmmonium Hydroxide).
The diaphragm 9 of m is formed. Next, the air chamber 10 of the diaphragm 9
A TEOS film is formed on the side surface at a temperature of 500 ° C. or lower to form an insulating film 13.

At this time, if the surface of the diaphragm 9 is cleaned by O ₂ plasma treatment before the TEOS film is formed, the insulating film 13 having a good withstand voltage is formed. Furthermore, after forming the TEOS film, by performing an annealing treatment at a high temperature of 600 ° C. or higher, the withstand voltage can be further improved.

The apparatus used for forming the TEOS film is a CVD apparatus manufactured by Japan ASM Co.
When the film is formed by D, the stress of the film can be easily changed by changing the film forming conditions. Therefore, it was investigated how the deflection amount of the diaphragm 9 changes by changing the film forming conditions and changing the film stress. as a result,
In order to reduce the amount of bending, the TEOS flow rate is increased. Reduce the O2 flow rate. Lower RF Power. Increase pressure. Lower the temperature. By doing so, it was found that the amount of bending can be controlled to a desired value.

For example, TEOS flow rate: 100 cc / min O 2 flow rate: 800 cc / min RF Power: 300 W Pressure: 2.0 Torr Temperature: 390 ° C. Under the film forming conditions, a film having a thickness of 0.1 μm TE is formed on the surface of the diaphragm 9.
When the OS film is formed, the bending amount of the diaphragm 9 is about 0.01.
In addition, the bending direction was convex toward the air chamber 10 side.

Next, a TEOS film is formed again on the surface of the vibration plate 9 having a thickness of about 0.8 μm on the pressure chamber 8 side at a temperature of 500 ° C. or lower to form a protective film 14. Even when the protective film 14 is formed, as in the case of forming the insulating film 13, before the TEOS film is formed, the O ₂ on the surface of the diaphragm 9 is formed.
Cleaning is performed by plasma treatment, and then T
After forming the EOS film, by performing annealing treatment at a high temperature of 600 ° C. or higher, a more dense film can be formed,
Ink resistance can be improved. In addition, the protective film 1
4 not only protects the flow path of the ink, but also the protective film 14
The amount of bending of the diaphragm 9 can also be controlled by forming the.

In order to control the desired bending direction and the desired bending amount, the film forming conditions and film thickness of the TEOS film on the air chamber 10 side of the diaphragm 9 and the pressure chamber 8 side of the diaphragm 9 are controlled. TEO
The film forming conditions and film thickness of the S film may be changed.

For example, the bending direction of the diaphragm 9 is set to the air chamber 1
When it is desired to form a convex shape on the 0 side, the TEOS film on the side of the pressure chamber 8 of the diaphragm 9 is affected by the stress of the TEOS film on the side of the air chamber 10 of the diaphragm 9.
The stress of the OS film is reduced. Specifically, the film thickness of the TEOS film on the pressure chamber 8 side of the diaphragm 9 is made smaller than the film thickness of the TEOS film on the air chamber 10 side of the diaphragm 9, or the diaphragm 9 is formed under film forming conditions. The TEOS flow rate is increased, the O2 flow rate is decreased, the RF power is lowered, and the pressure is increased, depending on the film forming conditions of the TEOS film on the side of the air chamber 10
The film stress can be reduced by lowering the temperature.

On the contrary, when it is desired that the bending direction of the diaphragm 9 is convex toward the pressure chamber 8, the TE on the pressure chamber 8 side of the diaphragm 9 is TE.
Due to the stress of the OS film, TEOS on the air chamber 10 side of the diaphragm 9
Reduce the stress on the film. Specifically, the film thickness of the TEOS film of the diaphragm 9 on the side of the air chamber 10 is made smaller than the film thickness of the TEOS film of the diaphragm 9 on the side of the pressure chamber 8, or the diaphragm 9 is formed under film forming conditions. The TEOS flow rate is increased, the O2 flow rate is decreased, depending on the film formation conditions of the TEOS film on the pressure chamber 8 side of
The film stress can be lowered by lowering RF Power, raising pressure, lowering temperature, and the like. By the above method, the bending direction and the bending amount of the diaphragm 9 can be easily controlled.

(Other Embodiments) In the above example, the present invention is applied to an ink jet head using an electrostatic actuator. However, the present invention can be similarly applied to an electrostatic actuator other than the inkjet head, for example, an electrostatically driven sensor.

[0023]

As described above, according to the present invention, the TEOS films having different film stresses are formed on both surfaces of the diaphragm by the plasma CV.
Since the films are separately formed according to D, the bending amount of the diaphragm can be easily controlled.

Further, in the present invention, since the thickness of the TEOS film formed on one surface and the thickness of the TEOS film formed on the other surface can be made different, the diaphragm The amount of bending can be easily controlled.

[Brief description of drawings]

FIG. 1 is an external view of an inkjet head of the present invention.

FIG. 2 is a cross-sectional explanatory view of an inkjet head of the present invention.

[Explanation of symbols]

1 Thin part 2 nozzles 3 nozzle plate 4 cavity plate 5 wiring board 6 arrows 7 supply port 8 pressure chambers 9 diaphragm 10 air chambers 11 electrodes 12 ink drops 13 Insulating film: TEOS film 14 Protective film: TEOS film

Claims (4)

[Claims] 1. An electrostatic actuator having a vibrating plate, a counter electrode arranged to face the vibrating plate, and a vibrating chamber formed by the vibrating plate and the counter electrode, wherein both sides of the vibrating plate are provided. TEOS by plasma CVD
An electrostatic actuator characterized by forming a film. 2. A drive for displacing a nozzle, an ink flow path communicating with the nozzle and having the vibration plate formed in a part thereof, and generating static electricity between the vibration plate and the counter electrode. The driving means includes a voltage applying means for applying an electric pulse between the diaphragm and the counter electrode, and ink droplets are ejected from the nozzle in response to the application of the electric pulse. The method of manufacturing an inkjet head using an electrostatic actuator according to claim 1, wherein: 3. The electrostatic capacitor according to claim 1, wherein the film stress of the TEOS film formed on one surface of the diaphragm is different from the film stress of the TEOS film formed on the other surface. Actuator. 4. The electrostatic capacitor according to claim 1, wherein the film thickness of the TEOS film formed on one surface of the diaphragm is different from the film thickness of the TEOS film formed on the other surface. Actuator.