JP2007038452A - Electrostatic actuator, its manufacturing method, liquid droplet delivering head, its manufacturing method, device and liquid droplet delivering apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic actuator which can control a driving form and a connection order of a diaphragm, and can improve an electrostatic force while avoiding dielectric breakdown, and to provide a liquid droplet delivering head, a liquid droplet delivering apparatus, etc. <P>SOLUTION: The electrostatic actuator comprises the diaphragm 4 driven by the electrostatic force, and a counter electrode 11 opposed with a gap to the diaphragm 4. An insulating film 30 is formed on a surface of the counter electrode 11 side of the diaphragm 4. The insulating film 30 has a plurality of regions (a first region 31 and a second region 32) formed of different materials. The plurality of regions are on the same plane. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrostatic actuator and a manufacturing method thereof, a droplet discharge head and a manufacturing method thereof, a device, and a droplet discharge device, and in particular, can control a position where an actuator unit such as a diaphragm starts driving, and is insulated. Electrostatic actuator capable of improving electrostatic force while avoiding destruction and method for manufacturing the same, droplet discharge head using the electrostatic actuator and method for manufacturing the same, device equipped with the electrostatic actuator, and the liquid The present invention relates to a droplet discharge device equipped with a droplet discharge head.

  In a conventional electrostatic actuator, a plate-shaped diaphragm and an individual electrode (counter electrode) are opposed to each other in a parallel state, a voltage is applied to both, and the diaphragm is driven by electrostatic force (for example, patents) Reference 1). Note that in an inkjet head to which an electrostatic actuator is applied, the diaphragm and the individual electrodes are generally brought into contact when the diaphragm is driven.

In order to improve the performance of the electrostatic actuator, it is necessary to improve the electrostatic force applied to the diaphragm and to improve the withstand voltage of the insulating film formed on the surface of the diaphragm etc. in order to apply a high voltage. . For this reason, some conventional electrostatic actuators have an insulating film formed by combining a material with a high relative dielectric constant and silicon oxide, which is a common material.
Japanese Patent Laid-Open No. 11-165413 (FIG. 1) Japanese Patent Laid-Open No. 9-39235 (FIGS. 1, 4, and 5) Japanese Patent Laid-Open No. 10-286952 (FIGS. 21 and 23)

  However, in the conventional electrostatic actuator (see, for example, Patent Document 1), the part from which the diaphragm starts to be driven and the part from which the diaphragm and the individual electrode start to contact is determined by a slight surface step in the manufacturing process. Depending on the deflection of the diaphragm, etc., it differs depending on the chip or actuator part of the electrostatic actuator (here, the diaphragm and the individual electrodes), and there is a problem that the drive mode and contact sequence of the diaphragm cannot be controlled. .

  For this reason, in the conventional inkjet head (for example, refer patent document 2), the step was provided in the glass groove | channel in which an individual electrode is formed in order to control the drive mode etc. of an actuator part. In other inkjet heads (see, for example, Patent Document 3), a step is provided in the thickness of the diaphragm. However, when a step is provided in a glass groove or the like in which individual electrodes are formed, there is a problem that the manufacturing process becomes complicated.

  In addition, when an insulating film is formed by combining tantalum oxide with high relative permittivity and silicon oxide, a high voltage is applied because there is a risk of dielectric breakdown if tantalum oxide with low insulation resistance contacts an individual electrode. There was a problem that it was not possible. In order to solve such problems, for example, there is a method of increasing insulation resistance by laminating silicon oxide on tantalum oxide, but when silicon oxide is laminated with a thickness that can ensure insulation resistance, There has been a problem that the effect of improving the electrostatic force by the high dielectric constant material is diminished.

  The present invention relates to an electrostatic actuator that can control the driving mode and contact sequence of the diaphragm and can improve electrostatic force while avoiding dielectric breakdown, a method for manufacturing the same, and a liquid to which the electrostatic actuator is applied. It is an object of the present invention to provide a droplet discharge head and a manufacturing method thereof, a device equipped with the electrostatic actuator, and a droplet discharge apparatus equipped with the droplet discharge head.

An electrostatic actuator according to the present invention includes a diaphragm driven by electrostatic force and a counter electrode facing the diaphragm with a gap therebetween, and the surface of the diaphragm on the counter electrode side is made of different materials. An insulating film having a plurality of regions and having the plurality of regions on the same plane is formed.
Since an insulating film having a plurality of regions made of different materials on the surface on the counter electrode side of the diaphragm and having these regions on the same plane is formed, for example, these regions are made of materials having different relative dielectric constants. In this way, it becomes possible to control the drive mode and the contact order of the diaphragm. Further, by forming a part of the insulating film in a region having a high relative dielectric constant, it is possible to increase the electrostatic force applied to the diaphragm.

In the electrostatic actuator according to the present invention, the insulating film has two regions in a portion facing the diaphragm, and the relative dielectric constant of one of the two regions is the ratio of the other region. It is higher than the dielectric constant.
The insulating film has two regions facing the diaphragm, and the relative dielectric constant of one of the two regions is higher than the relative dielectric constant of the other region. The diaphragm starts to be driven from the portion where the insulating film having a high thickness is formed, and it is possible to control the drive mode and contact sequence of the diaphragm, and to improve the electrostatic force applied to the diaphragm. Become.

In the electrostatic actuator according to the present invention, the dielectric constant of the portion of the insulating film that does not face the counter electrode is equal to or less than the dielectric constant of the portion of the insulating film that faces the counter electrode.
Since the diaphragm (including the insulating film) and the counter electrode form a kind of capacitor, the time constant of the actuator can be reduced by lowering the relative permittivity of the portion of the insulating film that does not face the counter electrode. The responsiveness of the diaphragm can be improved.

In the electrostatic actuator according to the present invention, at least a part of the insulating film comes into contact with the counter electrode when the diaphragm is driven.
Since a part of the insulating film comes into contact with the counter electrode when the diaphragm is driven, the driveable range of the diaphragm can be increased. For example, when the electrostatic actuator of the present invention is applied to a droplet discharge head, the effect is particularly great because the amount of droplet discharge increases.

In the electrostatic actuator according to the present invention, the first region is formed in a portion of the insulating film that contacts the counter electrode, and the second region of the insulating film is opposed to the counter electrode and does not contact the counter electrode. The dielectric constant of the second region is higher than that of the first region.
A first region having a low relative dielectric constant is formed in a portion of the insulating film that contacts the counter electrode, and a second region having a high relative dielectric constant is formed in the portion of the insulating film that faces the counter electrode and does not contact the counter electrode. Thus, even when the second region is formed of a material having a high relative dielectric constant and low insulation resistance such as tantalum oxide, it is possible to improve electrostatic force while avoiding dielectric breakdown.

In the electrostatic actuator according to the present invention, at least one of the plurality of regions is made of aluminum oxide, hafnium oxide, or zirconium oxide.
By forming at least one of the plurality of regions of the insulating film from aluminum oxide, hafnium oxide, or zirconium oxide, a region having a high relative dielectric constant can be easily formed.

In the electrostatic actuator according to the present invention, at least one of the plurality of regions is made of silicon oxide.
By forming at least one region of the plurality of regions of the insulating film from silicon oxide, a region having a low relative dielectric constant and high insulation resistance can be easily formed.

In the electrostatic actuator according to the present invention, the second region is made of tantalum oxide.
By forming the second region of the insulating film from tantalum oxide, a region having a high relative dielectric constant can be easily formed. Note that since tantalum oxide has low insulation resistance, it is desirable to form an insulating film in combination with silicon oxide.

The droplet discharge head according to the present invention is one to which any of the electrostatic actuators described above is applied.
By applying any one of the electrostatic actuators described above, it is possible to control the drive mode and contact order of the diaphragm, and a liquid droplet ejection head with high ejection accuracy can be obtained.

The droplet discharge head according to the present invention is applied with any of the electrostatic actuators described above, has a nozzle hole for discharging a droplet, and the insulating film has a first region and a second region. The second region is formed in a portion farther from the nozzle hole than the first region in the portion where the insulating film faces the counter electrode, and the relative dielectric constant of the second region is that of the first region. It is higher than the relative dielectric constant.
Since the second region having a high relative dielectric constant is formed in a portion farther from the nozzle hole than the first region in the portion where the insulating film faces the counter electrode, the diaphragm is separated from the portion away from the nozzle hole. The liquid droplets flow smoothly by being sequentially driven to the portion close to the nozzle hole, and the discharge performance of the liquid droplet discharge head can be improved.

The method for manufacturing an electrostatic actuator according to the present invention includes a step of forming a first insulating film on a silicon substrate, a step of forming an opening in the first insulating film, and the opening on the first insulating film. Forming a second insulating film, a step of removing the second insulating film formed on the first insulating film, and a silicon substrate on which the first insulating film and the second insulating film are formed And forming a diaphragm driven by electrostatic force.
After the opening is formed in the first insulating film, the second insulating film is formed on the first insulating film and the opening, and the second insulating film formed on the first insulating film is removed. Thus, an insulating film composed of two regions on the same plane can be easily formed.

In the method for manufacturing an electrostatic actuator according to the present invention, the relative dielectric constant of the second insulating film is higher than that of the first insulating film.
Since the relative dielectric constant of the second insulating film is higher than the relative dielectric constant of the first insulating film, the vibration plate starts to be driven from the portion where the insulating film having a high relative dielectric constant is formed. It is possible to control the driving mode and the contact order of the plates, and it is possible to improve the electrostatic force applied to the diaphragm.

A method for manufacturing a droplet discharge head according to the present invention is a method for manufacturing a droplet discharge head by applying the method for manufacturing an electrostatic actuator described above.
By manufacturing the droplet discharge head by applying the above-described electrostatic actuator manufacturing method, it becomes possible to control the drive mode and contact order of the diaphragm, and to obtain a droplet discharge head with high discharge performance. it can.

A device according to the present invention is equipped with any one of the electrostatic actuators described above.
By mounting any one of the electrostatic actuators described above, it is possible to control the driving mode and contact order of the diaphragm, and to obtain a device with high driving performance.

A droplet discharge apparatus according to the present invention is equipped with the above-described droplet discharge head.
By mounting the above-described droplet discharge head, it is possible to obtain a droplet discharge device with high printing performance and the like.

Embodiment 1. FIG.
FIG. 1 is an exploded perspective view showing a droplet discharge head according to Embodiment 1 of the present invention. The droplet discharge head according to the first embodiment is of an electrostatic drive type, and is of a face eject type that discharges droplets in a direction perpendicular to the nozzle substrate 3. The ejection method may be a side eject type that ejects droplets in parallel to the nozzle substrate 3. In FIG. 1, two nozzle holes 20 are provided in the nozzle substrate 3 and the discharge chamber 5 and the counter electrode 11 are also provided in two rows, but these are provided in one row or three or more rows. You may do it. In the first embodiment, an electrostatic drive type droplet discharge head will be described as an example of an electrostatic actuator.

  The droplet discharge head according to the first embodiment is mainly configured by bonding a cavity substrate 1, an electrode substrate 2, and a nozzle substrate 3. The cavity substrate 1 is made of, for example, single crystal silicon having a thickness of 50 μm, and is subjected to the following predetermined processing. In FIG. 1, single crystal silicon having (110) plane orientation is used as the cavity substrate 1. In the cavity substrate 1, single crystal silicon is subjected to anisotropic wet etching to store droplets discharged from the plurality of discharge chambers 5 and the nozzle holes 20 whose bottom wall is the diaphragm 4. A reservoir 7 is formed.

  In addition, an insulating film 30 is formed on the cavity substrate 1 on the electrode substrate 2 side to prevent a short circuit between the diaphragm 4 and the counter electrode 11 and breakdown of the insulating film (not shown in FIG. 1, see FIG. 2). . In the first embodiment, the insulating film 30 is formed by, for example, TEOS-CVD (Tetraethylorthosilicate Tetraethoxysilane-Chemical Vapor Deposition), a first region 31 made of silicon oxide, and a second region made of aluminum oxide and formed of CVD or the like. 32. The first region 31 and the second region 32 are not stacked and are formed on the same plane. The insulating film 30 will be described later.

  The electrode substrate 2 is made of, for example, borosilicate glass having a thickness of 1 mm, and is joined to the diaphragm 4 side of the cavity substrate 1. In this electrode substrate 2, an electrode recess 10 having a depth of 0.2 μm, for example, is formed by etching in accordance with the positions of the diaphragm 4 and the discharge chamber 5 of the cavity substrate 1. A counter electrode 11 is formed inside the electrode recess 10 and is connected to the lead portion 12 and the terminal portion 13. In addition, the recessed part 10 for electrodes shall be formed to the part of the lead part 12 at least. The counter electrode 11, the lead portion 12, and the terminal portion 13 are made of ITO (Indium Tin Oxide) doped with tin oxide or the like, and are formed with a thickness of 0.1 μm, for example, by sputtering inside the electrode recess 10. Has been. A hole 17 for supplying a droplet to the reservoir 7 is provided in a portion of the electrode substrate 2 where the counter electrode 11 is not formed.

  The nozzle substrate 3 is made of, for example, a silicon substrate having a thickness of 180 μm, and is bonded to the surface of the cavity substrate 1 opposite to the surface to which the electrode substrate 2 is bonded. A nozzle hole 20 communicating with the discharge chamber 5 is formed in the nozzle substrate 3, and droplets are discharged from the surface opposite to the surface to which the cavity substrate 1 is bonded. An orifice 21 for communicating the discharge chamber 5 and the reservoir 7 is provided on the surface of the nozzle substrate 3 to which the cavity substrate 1 is bonded. The orifice 21 may be provided in the cavity substrate 1.

2 is a longitudinal sectional view and a transverse sectional view of the droplet discharge head shown in FIG. 2A is a longitudinal sectional view in the longitudinal direction of the discharge chamber 5, and FIG. 2B is a bb sectional view of FIG. 2A (transverse sectional view of the insulating film 30). . 2 shows only the right half of the droplet discharge head of FIG. As described above, the insulating film 30 of the droplet discharge head according to the first embodiment includes the first region 31 made of silicon oxide (SiO ₂ , relative dielectric constant 3.9) and aluminum oxide (Al ₂ O ₃ , ratio). The first region 31 and the second region 32 are formed on the same plane. The second region 32 has a dielectric constant of 7.0. Note that the second region 32 may be formed of hafnium oxide (HfO ₂ , relative dielectric constant 30) or zirconium oxide (ZrO ₂ , relative dielectric constant 30) having a relative dielectric constant higher than that of silicon oxide. 2, the second region 32 is farther from the nozzle hole 20 than the first region 31 in the portion where the insulating film 30 faces the counter electrode 11 (the portion below the discharge chamber 5 in FIG. 2A). It is formed in the part. The portion of the insulating film 30 that does not face the counter electrode 11 is made of silicon oxide having a low relative dielectric constant. In addition, the part which does not oppose the counter electrode 11 here shall mean the part which opposes the lead | read | reed part 12, and the part to which the cavity substrate 1 and the electrode substrate 2 between the some discharge chambers 5 are joined.

  Here, the operation of the droplet discharge head according to the first embodiment will be described with reference to FIG. The discharge chamber 5 stores droplets to be discharged from the nozzle hole 20, and the pressure in the discharge chamber 5 is increased by bending the vibration plate 4 that is the bottom wall of the discharge chamber 5. Let the drops be ejected. In order to bend the diaphragm 4, an oscillation circuit 23 (schematically shown in FIG. 2A) is connected to the terminal portion 13 connected to the counter electrode 11 and the cavity substrate 1, and the counter electrode 11 is vibrated. A potential difference is generated between the plates 4. In this way, a mechanism for generating a potential difference between two objects and driving them by electrostatic force is generally called an electrostatic actuator.

ここで、Ｆは振動板４にかかる静電気力、ε₀は真空中の誘電率、Ｅは振動板４と対向電極１１の間の電位差、ｇは絶縁膜３０から対向電極１１までの距離、ｈは絶縁膜３０の厚さ、ε₁は絶縁膜３０（第１の領域３１又は第２の領域３２）の比誘電率、Ｓは振動板４の面積である。 In the first embodiment, the insulating film 30 comes into contact (contact) with the counter electrode 11 when the diaphragm 4 is driven. At this time, the portion of the diaphragm 4 in which the second region 32 having a high relative dielectric constant is formed has a stronger electrostatic force than the portion in which the first region 31 having a low relative dielectric constant is formed. The portion of the diaphragm 4 where the region 32 is formed starts to drive first, and comes into contact with the counter electrode 11 earlier than the portion where the first region 31 is formed. Then, the diaphragm 4 in the portion where the first region 31 is sequentially formed starts to drive and comes into contact with the counter electrode 11. At this time, since the bending of the vibration plate 4 sequentially moves from a position away from the nozzle hole 20 (reservoir 7 side) to a position close to the nozzle hole 20, a droplet such as ink flows smoothly from the reservoir 7 to the nozzle hole 20. . The electrostatic force applied to the diaphragm 4 is expressed by the following formula (1).

Here, F is an electrostatic force applied to the diaphragm 4, ε ₀ is a dielectric constant in vacuum, E is a potential difference between the diaphragm 4 and the counter electrode 11, g is a distance from the insulating film 30 to the counter electrode 11, h Is the thickness of the insulating film 30, ε ₁ is the relative dielectric constant of the insulating film 30 (the first region 31 or the second region 32), and S is the area of the diaphragm 4.

  As described above, the portion of the insulating film 30 that does not face the counter electrode 11 is made of silicon oxide having a low relative dielectric constant. This is because the diaphragm 4 (including the insulating film 30) and the counter electrode 11 form a kind of capacitor, so that the relative dielectric constant of the portion of the insulating film 30 that does not face the counter electrode 11 is lowered to reduce the actuator portion ( This is because the time constant between the diaphragm 4 and the counter electrode 11) can be reduced, and the response of the diaphragm 4 can be improved. Here, the time constant τ is represented by τ = C × R, where C is the capacitance and R is the electrical resistance. The portion of the insulating film 30 that does not face the counter electrode 11 may be formed of another material having a relative dielectric constant lower than that of silicon oxide.

Further, the vibration plate 4 of the droplet discharge head according to the first embodiment includes an insulating film 30 and a boron-doped layer 34 (see FIG. 2A). The boron-doped layer 34 is formed by doping boron at a high concentration (about 5 × 10 ¹⁹ atoms / cm ³ or more). For example, when single crystal silicon is etched with an alkaline aqueous solution, the etching rate is extremely high. This is a so-called etching stop layer that becomes slower. Since the boron-doped layer 34 functions as an etching stop layer, the thickness of the diaphragm 4 and the volume of the discharge chamber 5 can be formed with high accuracy. The gap between the diaphragm 4 and the counter electrode 11 is sealed with a sealing material 22.

  3 and 4 are longitudinal sectional views showing manufacturing steps of the droplet discharge head according to Embodiment 1 of the present invention. 3 and 4 show a process of manufacturing the droplet discharge head shown in FIGS. 1 and 2, and particularly show a process of manufacturing the electrode substrate 2 shown in FIG. 3 and 4 show a longitudinal section of the discharge chamber 5 in the longitudinal direction (the section of FIG. 2A). Further, FIG. 3 and FIG. 4 show the periphery of the portion to be the chip of each droplet discharge head. A method for manufacturing a droplet discharge head using the method for manufacturing an electrostatic actuator according to the present invention will be described below with reference to FIGS.

  First, a glass substrate 2a made of, for example, a borosilicate heat-resistant hard glass is polished on both sides to a thickness of 1 mm (FIG. 3A), and then, for example, chromium having a thickness of 0.1 μm is sputtered on one surface of the glass substrate 2a. A film 40 is formed (FIG. 3B). Next, resist patterning for forming the electrode recess 10 on the surface of the chromium film 40 is performed (see FIG. 1), and the electrode recess 10 is formed using a mixture of a ceric ammonium nitrate aqueous solution and a perchloric acid aqueous solution. A portion of the chromium film 40 is removed (FIG. 3C). FIG. 3C shows a state in which the chromium film 40 in the portion that becomes the electrode recess 10 is removed.

  Then, the glass substrate 2a is etched using an aqueous solution of ammonium fluoride using the chromium film 40 as an etching mask to form the electrode recess 10 (FIG. 3D). Thereafter, the resist formed in the step of FIG. 3C is stripped using, for example, an organic stripping solution. Then, all of the chromium film 40 formed on the surface of the glass substrate 2a is removed using a mixed solution of a ceric ammonium nitrate aqueous solution and a perchloric acid aqueous solution (FIG. 3E). Next, ITO doped with tin oxide is sputtered to a thickness of, for example, 0.1 μm over the entire surface of the glass substrate 2a where the electrode recesses 10 are formed (FIG. 4F). ).

  Thereafter, a resist is patterned on the surface of the ITO film 41 in the shape of the counter electrode 11 (including the lead portion 12 and the terminal portion 13), and then the ITO film 41 is etched using a mixed solution of nitric acid and hydrochloric acid to counter the counter electrode 11. (Including the lead portion 12 and the terminal portion 13) is formed (FIG. 4G). And the hole 17 for supplying a droplet to the reservoir | reserver 7 using the sandblasting method is formed in the part in which the counter electrode 11 of the glass substrate 2a is not formed (FIG.4 (h)). In addition, although the hole part 17 may be formed by a drill process, in this Embodiment 1, it shall form by the sandblasting method. Thereby, the electrode substrate 2 as shown in FIG. 1 is completed.

  5, 6 and 7 are longitudinal sectional views showing the manufacturing process of the droplet discharge head according to Embodiment 1 of the present invention. 5 to 7 show the steps of manufacturing the droplet discharge head shown in FIGS. 1 and 2, and in particular, the steps of manufacturing the silicon substrate 1a to be the cavity substrate 1 and the silicon substrate 1a and the glass substrate 2a. A process of manufacturing a droplet discharge head after bonding is shown. 5 to 7 show a longitudinal section of the discharge chamber 5 in the longitudinal direction (the section of FIG. 2A). Further, FIG. 5 to FIG. 7 show peripheral portions of a portion that becomes a chip of each droplet discharge head.

First, for example, one side of a silicon substrate 1a having a surface orientation of (110) and a low oxygen concentration is mirror-polished to produce a silicon substrate 1a having a thickness of 220 μm, and boron is formed on the surface opposite to the surface on which the discharge chamber 5 and the like are formed. A dope layer 34 is formed (FIG. 5A). Specifically, the silicon substrate 1a is set on a quartz boat so as to face a solid diffusion source containing B ₂ O ₃ as a main component, and this quartz boat is placed in, for example, a vertical furnace. Then, the inside of the vertical furnace is maintained in a nitrogen atmosphere at a temperature of 1050 ° C. for 7 hours, and boron is diffused into the silicon substrate 1 a to form a boron-doped layer 34. At this time, the charging temperature of the silicon substrate 1a is set to 800 ° C., and after the temperature is raised to 1050 ° C., the temperature when the silicon substrate 1a is taken out is also set to 800 ° C. Thereby, it is possible to quickly pass through a region of 600 ° C. to 800 ° C. where the growth rate of oxygen defects of the silicon substrate 1a is fast, and the growth of oxygen defects can be suppressed.

In the above boron diffusion step, a SiB ₆ film (not shown) is formed on the surface of the boron doped layer 34, but it is oxidized in an oxygen and water vapor atmosphere at a temperature of 600 ° C. for about 1 hour 30 minutes. Thus, it can be chemically changed to B ₂ O ₃ and SiO ₂ which can be etched with a hydrofluoric acid aqueous solution. After the SiB ₆ film is chemically changed to B ₂ O ₃ and SiO ₂ in this way, B ₂ O ₃ and SiO ₂ are etched away with a buffered hydrofluoric acid solution.

Then, a first insulating film 31a made of silicon oxide having a thickness of 0.1 μm is formed on the surface of the silicon substrate 1a on the boron doped layer 34 side, for example, by TEOS-CVD (FIG. 5B). The film formation conditions of the first insulating film 31a at this time are, for example, a temperature of 360 ° C., a high frequency output of 250 W, a pressure of 66.7 Pa (0.5 Torr), a TEOS flow rate of 100 cm ³ / min (100 sccm), and an oxygen flow rate of 1000 cm ³ / Minutes (1000 sccm). The first insulating film 31 a becomes the first region 31 of the insulating film 30. Then, a resist is patterned in the shape of the opening 40 for forming the second region 32 on the surface on which the boron-doped layer 34 is formed (see FIG. 2B). Then, the first insulating film 31a in the opening 40 is removed by etching the silicon substrate 1a (FIG. 5C).

  Thereafter, a second insulating film 32a made of aluminum oxide is formed with a thickness of 0.1 μm on the first insulating film 31a and on the opening 40 by CVD or the like (FIG. 5D). The second insulating film 32 a becomes the second region 32 of the insulating film 30. As described above, the second insulating film 32a may be formed of hafnium oxide or zirconium oxide having a relative dielectric constant higher than that of silicon oxide. Then, after patterning a resist on the surface of the second insulating film 32a formed in the opening 40, the second insulating film 32a is etched to form the second insulating film 31a formed on the first insulating film 31a. The insulating film 32a is removed (FIG. 5E). Thereby, the insulating film 30 in which the first region 31 and the second region 32 are on the same plane is formed.

  Next, the silicon substrate 1a shown in FIG. 5 (e) and the electrode substrate 2 formed in the step of FIG. 4 (h) are joined by anodic bonding to form a joined substrate (FIG. 6 (f)). This anodic bonding is performed, for example, by heating the silicon substrate 1 a and the electrode substrate 2 to 360 ° C. and then applying a voltage of 800 V between the silicon substrate 1 a and the electrode substrate 2. In order to prevent damage to ITO or the like during anodic bonding, it is desirable to prevent a current of, for example, 10 mA or more from flowing. During the anodic bonding, the portion (gap) of the electrode recess 10 is sealed.

  After anodic bonding of the silicon substrate 1a and the electrode substrate 2, the silicon substrate 1a is thinned to a thickness of 60 μm, for example, by grinding. Then, for example, the silicon substrate 1a is etched by 10 μm using a 32 wt% potassium hydroxide aqueous solution, and the work-affected layer generated during the grinding process is removed (FIG. 6G). Thereby, the thickness of the silicon substrate 1a becomes 50 μm. In addition, you may make it perform the process of thinning the silicon substrate 1a of FIG.6 (g) all by an etching.

Then, a silicon oxide film 51 having a thickness of 1.5 μm is formed on the entire surface of the silicon substrate 1a by TEOS-CVD, for example (FIG. 6H). The film formation conditions of the silicon oxide film 51 by TEOS-CVD are, for example, a temperature of 360 ° C., a high frequency output of 700 W, a pressure of 33.3 Pa (0.25 Torr), a TEOS flow rate of 100 cm ³ / min (100 sccm), and an oxygen flow rate of 1000 cm ³ / Minutes (1000 sccm). This silicon oxide film 51 serves as an etching mask for subsequent etching with an aqueous potassium hydroxide solution.

  Then, a resist for forming a recess 5a serving as the discharge chamber 5, a recess 7a serving as the reservoir 7, and an electrode lead-out portion is patterned on the silicon substrate 1a on the silicon oxide film 51. The silicon oxide film 51 is removed by etching at the concave portion 5a to be formed, the concave portion 7a to be the reservoir 7 and the electrode extraction portion. In addition, an electrode extraction part means here the part which the terminal part 13 is exposed (refer Fig.2 (a)). Thereafter, the silicon substrate 1a is thinned with a 35% by weight aqueous potassium hydroxide solution until the thickness of the concave portion 5a serving as the discharge chamber 5 and the portion for forming the electrode lead-out portion become 10 μm. At this time, the etching of the portion of the recess 7 a that becomes the reservoir 7 is delayed by half-etching the silicon oxide film 51. Further, the silicon substrate 1a is etched with a 3% by weight potassium hydroxide aqueous solution, and the etching stop by the boron-doped layer 34 is sufficiently effective in the portion that becomes the recess 5a that becomes the discharge chamber 5 and the portion that forms the electrode extraction portion. Etching is continued until (FIG. 6 (i)).

  Here, the term “etching stop” refers to a state in which bubbles are no longer generated from the surface of the silicon substrate 1a to be etched, and etching is performed until no bubbles are actually generated. As a result, the concave portion 5a serving as the discharge chamber 5, the concave portion 7a serving as the reservoir 7, and the electrode extraction portion are formed. As described above, by performing etching using two types of aqueous potassium hydroxide solutions having different concentrations, the surface roughness of the diaphragm 4 which is the bottom wall of the discharge chamber 5 can be suppressed to 0.05 μm or less. The discharge performance of the droplet discharge head can be stabilized. Here, the thickness of the diaphragm 4 is 0.8 μm.

Then, all the silicon oxide film 51 formed on the silicon substrate 1a is removed using a hydrofluoric acid aqueous solution. Thereafter, the electrode extraction portion of the silicon substrate 1a is removed by RIE (Reactive Ion Etching) (FIG. 6 (j)). This RIE is a kind of dry etching, and is performed for 30 minutes using a silicon mask under conditions of an output of 200 W, a pressure of 40 Pa (0.3 Torr), and a CF ₄ flow rate of 30 cm ³ / min (30 sccm). At this time, the inside of the gap is released to the atmosphere.

  Then, a sealing material 22 such as an epoxy resin is poured along the end of the electrode extraction portion, and the gap between the diaphragm 4 and the counter electrode 11 (the portion of the electrode recess 10) is sealed (FIG. 7 ( k)). As a result, the gap between the diaphragm 4 and the counter electrode 11 is sealed again. Then, the nozzle substrate 3 is bonded to the silicon substrate 1a using an epoxy adhesive or the like (FIG. 7 (l)). Finally, dicing (cutting) is performed and divided into individual chips, thereby completing a plurality of droplet discharge heads (FIG. 7 (m)).

  In the first embodiment, since the insulating film 30 having a plurality of regions having different relative dielectric constants on the surface on the counter electrode 11 side of the diaphragm 4 and having the plurality of regions on the same plane is formed, the diaphragm 4 It is possible to control the driving form and the contact order of the above, and the electrostatic force applied to the diaphragm 4 can be increased. In addition, since the second region 32 having a high relative dielectric constant is formed in a portion farther from the nozzle hole 20 than the first region 31 in the portion where the insulating film 30 faces the counter electrode 11, the diaphragm 4 is It is sequentially driven from a part away from the nozzle hole 20 to a part close to the nozzle hole 20 so that the flow of droplets becomes smooth, and the ejection performance of the droplet ejection head can be improved. Furthermore, by forming the portion of the insulating film 30 that does not face the counter electrode 11 with a material having a low relative dielectric constant, the time constant of the actuator portion can be reduced, and the responsiveness of the diaphragm 4 can be improved.

Embodiment 2. FIG.
FIG. 8 is a longitudinal sectional view and a transverse sectional view of a droplet discharge head according to Embodiment 2 of the present invention. FIG. 9 is a view showing a cc cross section of FIG. 8A is a longitudinal sectional view of the discharge chamber 5 in the longitudinal direction, and FIG. 8B is a bb sectional view of FIG. 8A (transverse sectional view of a portion of the insulating film 30). . 8B and 9 show only a portion corresponding to one actuator portion (the vibration plate 4 and the counter electrode 11). Furthermore, FIG. 9 shall show the cc cross section when the electrostatic actuator which concerns on this Embodiment 2 is driving. The electrostatic actuator according to the second embodiment is the same as the electrostatic actuator according to the first embodiment except for the structure of the insulating film 30, and the same components are denoted by the same reference numerals and description thereof is omitted. In the second embodiment, as in the first embodiment, an electrostatic drive type droplet discharge head will be described as an example of the electrostatic actuator.

The insulating film 30 of the droplet discharge head according to the second embodiment includes a first region 31 made of silicon oxide (SiO ₂ , relative dielectric constant 3.9), tantalum oxide (Ta ₂ O ₅ , relative dielectric constant 25). ), And the first region 31 and the second region 32 are formed on the same plane. Tantalum oxide is a material having a high dielectric constant but low insulation resistance (5 MV / cm). Further, in the liquid droplet ejection head according to the second embodiment, the insulating film 30 comes into contact with the counter electrode 11 when the diaphragm 4 is driven, like the liquid droplet ejection head according to the first embodiment. (See FIG. 9). As shown in FIGS. 8B and 9, the first region 31 is formed in the portion of the insulating film 30 that contacts the counter electrode 11, and faces the counter electrode 11 of the insulating film 30 and counter electrode 11. A second region 32 is formed in a portion that does not come into contact with the second region 32. Here, the portion facing the counter electrode 11 is a portion below the discharge chamber 5 in FIGS. 8A and 9. Similarly to the droplet discharge head according to the first embodiment, the portion of the insulating film 30 that does not face the counter electrode 11 is a first region 31 (silicon oxide) having a low relative dielectric constant. In addition, the part which does not oppose the counter electrode 11 shall mean the part which opposes the lead | read | reed part 12, and the part to which the cavity substrate 1 and the electrode substrate 2 between the some discharge chambers 5 are joined here (FIG. 1).

  In the second embodiment, the first region 31 having a low relative dielectric constant is formed in the portion of the insulating film 30 that contacts the counter electrode 11, and faces the counter electrode 11 of the insulating film 30 and does not contact the counter electrode 11. Since the second region 32 having a high relative dielectric constant is formed in the portion, even when the second region 32 is formed of a material having a high relative dielectric constant and low insulation resistance such as tantalum oxide, dielectric breakdown is avoided. It is possible to improve the electrostatic force. In FIG. 8B, the second region 32 is formed in a square shape. For example, the second region 32 is formed only at the end on the nozzle hole 20 side and the end on the reservoir 7 side. You may do it. The droplet discharge head according to the second embodiment can be manufactured by changing the patterning shape of the resist in the step of FIG. 5C of the first embodiment.

Embodiment 3. FIG.
FIG. 10 is a diagram showing an example of a droplet discharge device according to Embodiment 3 of the present invention. A droplet discharge apparatus 100 shown in FIG. 10 is a general ink jet printer, and includes the droplet discharge head shown in the first or second embodiment. Since the droplet discharge head shown in the first or second embodiment is a droplet discharge head with high discharge accuracy, the droplet discharge apparatus 100 according to the third embodiment has high printing performance and the like. Note that the droplet discharge device 100 as shown in FIG. 10 can be manufactured using a known manufacturing method.

  In addition to the ink jet printer as shown in FIG. 10, the droplet discharge heads shown in Embodiments 1 and 2 of the present invention are used for manufacturing an organic EL display device, a color filter for a liquid crystal display device, and a DNA device. It can also be used for the production of In addition, the electrostatic actuator according to the first and second embodiments of the present invention can be applied not only to the droplet discharge head but also to other devices such as a micropump, a capacitive pressure sensor, and an optical MEMS device. it can. For such a device, refer to, for example, Japanese Patent Application Laid-Open No. 2004-245753.

  The electrostatic actuator and the manufacturing method thereof, the droplet discharge head and the manufacturing method thereof, the device, and the droplet discharge apparatus according to the present invention are not limited to the above-described embodiments, and are within the scope of the idea of the present invention. Can be changed. For example, the insulating film 30 may be formed of not only the two regions of the first region 31 and the second region 32 but also a region made of three or more different materials.

1 is an exploded perspective view showing a droplet discharge head according to Embodiment 1 of the present invention. FIG. 2 is a longitudinal sectional view and a transverse sectional view of the droplet discharge head shown in FIG. 1. FIG. 3 is a longitudinal sectional view showing a manufacturing process of a droplet discharge head according to Embodiment 1 of the present invention. FIG. 4 is a longitudinal sectional view showing a step subsequent to the manufacturing step of FIG. 3. FIG. 3 is a longitudinal sectional view showing a manufacturing process of a droplet discharge head according to Embodiment 1 of the present invention. FIG. 6 is a longitudinal sectional view showing a step that follows the manufacturing step of FIG. 5. FIG. 7 is a longitudinal sectional view showing a step that follows the manufacturing step of FIG. 6. FIG. 6 is a longitudinal sectional view and a transverse sectional view of a droplet discharge head according to Embodiment 2 of the present invention. The figure which showed the cc cross section of Fig.8 (a). The figure which showed the example of the droplet discharge apparatus which concerns on Embodiment 3 of this invention.

Explanation of symbols

1 cavity substrate, 2 electrode substrate, 3 nozzle substrate, 4 diaphragm, 5 discharge chamber, 7 reservoir, 10 electrode recess, 11 counter electrode, 12 lead portion, 13 terminal portion, 17 hole portion, 20 nozzle hole, 21 orifice , 22 Sealing material, 23 Oscillator circuit, 30 Insulating film, 31 First region, 32 Second region, 34 Boron doped layer, 100 Droplet ejection device.

Claims (15)

A diaphragm driven by electrostatic force, and a counter electrode facing the diaphragm with a gap therebetween,
An electrostatic actuator having a plurality of regions made of different materials on an opposing electrode side surface of the diaphragm, and an insulating film in which the plurality of regions are on the same plane.   The insulating film has two regions in a portion facing the diaphragm, and one of the two regions has a relative dielectric constant higher than that of the other region. The electrostatic actuator according to claim 1.   3. The electrostatic actuator according to claim 1, wherein a relative dielectric constant of a portion of the insulating film that does not face the counter electrode is equal to or less than a relative dielectric constant of a portion of the insulating film that faces the counter electrode. .   The electrostatic actuator according to claim 1, wherein at least a part of the insulating film comes into contact with the counter electrode when the diaphragm is driven.   A first region is formed in a portion of the insulating film that contacts the counter electrode, and a second region is formed in a portion of the insulating film that faces the counter electrode and does not contact the counter electrode, The electrostatic actuator according to claim 4, wherein a relative dielectric constant of the second region is higher than a relative dielectric constant of the first region.   The electrostatic actuator according to claim 1, wherein at least one of the plurality of regions is made of aluminum oxide, hafnium oxide, or zirconium oxide.   The electrostatic actuator according to claim 1, wherein at least one of the plurality of regions is made of silicon oxide.   6. The electrostatic actuator according to claim 5, wherein the second region is made of tantalum oxide.   A liquid droplet ejection head, to which the electrostatic actuator according to claim 1 is applied.   5. The electrostatic actuator according to claim 1, wherein the electrostatic actuator is provided with a nozzle hole through which a droplet is discharged, and the insulating film has a first region and a second region, The region 2 is formed in a portion where the insulating film is opposed to the counter electrode, in a portion farther from the nozzle hole than the first region, and the relative permittivity of the second region is the first region A droplet discharge head characterized by being higher in relative dielectric constant than a region. Forming a first insulating film on a silicon substrate;
Forming an opening in the first insulating film;
Forming a second insulating film on the first insulating film and in the opening;
Removing the second insulating film formed on the first insulating film;
And a step of etching the silicon substrate on which the first insulating film and the second insulating film are formed to form a diaphragm driven by electrostatic force.   12. The method of manufacturing an electrostatic actuator according to claim 11, wherein a relative dielectric constant of the second insulating film is higher than a relative dielectric constant of the first insulating film.   13. A method for manufacturing a droplet discharge head, wherein the method for manufacturing an electrostatic actuator according to claim 11 or 12 is applied to manufacture a droplet discharge head.   A device comprising the electrostatic actuator according to claim 1. A droplet discharge apparatus, comprising the droplet discharge head according to claim 9.

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