JP2010221528A - Method for manufacturing electrostatic actuator, method for manufacturing liquid droplet discharging head, and method for manufacturing liquid droplet discharging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an electrostatic actuator, for accurately forming a high lubricant hard film in an optional dimension on a diaphragm part. <P>SOLUTION: The method for manufacturing the electrostatic actuator includes: a step of forming the high lubricant hard film (DLC film 20) on a surface position of an insulating film 19 corresponding to the diaphragm 8; a step of forming an etching protection film 21 protecting the insulating film 19 and the high lubricant hard film; and a step of performing etching from a surface on an opposite side to a surface where the diaphragm 8 is formed of a silicon substrate 3'. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a manufacturing method of an electrostatic actuator used for an electrostatic drive type inkjet head or the like, a manufacturing method of a droplet discharge head to which the manufacturing method of the electrostatic actuator is applied, and a manufacturing method of the droplet discharge head The present invention relates to a method of manufacturing a droplet discharge device to which the above is applied.

  As an ink discharge method in an ink jet head type recording apparatus, a so-called electrostatic driving type ink jet recording apparatus using electrostatic force as a driving means is known. This electrostatic drive type ink jet recording apparatus generally includes a counter electrode (fixed electrode) formed on an electrode glass substrate, and a silicon-made vibration disposed opposite to the counter electrode via a predetermined gap (gap). An electrostatic actuator composed of a plate (movable electrode) is provided. The electrostatic drive type ink jet recording apparatus performs an operation of attracting / isolating the diaphragm to the counter electrode by supplying / cutting off a voltage between the diaphragm and the counter electrode, and a pressure change caused thereby. Ink is ejected using the.

  Therefore, the vibration plate and the counter electrode act as an electrostatic actuator that varies the pressure in the pressure chamber in which the ink droplets are stored. In an apparatus to which such an electrostatic actuator is applied, in order to ensure high reliability, generally, a silicon oxide film for preventing dielectric breakdown or short-circuiting between a charged diaphragm and a counter electrode is used. An insulating film is formed. As this insulating film, a thermal oxide film of silicon is generally used. The reason is that the silicon thermal oxide film is excellent in the simplicity of the manufacturing process and the insulating film characteristics. In addition, an insulating film is often formed on the opposing surface of the diaphragm by a silicon oxide film using TEOS (tetraethoxysilane) as a source gas by a plasma CVD (Chemical Vapor Deposition) method.

  However, this insulating film has a problem that the electrostatic suction pressure is not stabilized due to the influence of the residual charge on the surface of the insulating film, and the stable driving of the actuator cannot be ensured. As a countermeasure, a highly lubricated hard film (for example, a film made of a carbon material such as DLC (diamond-like carbon)) is used as a surface layer on at least one of the opposing surfaces of the diaphragm on which the insulating film is formed and the counter electrode. It has been proposed to form.

  As such, there has been proposed a manufacturing method in which a DLC film is formed on the diaphragm (on the counter electrode side), and after anodic bonding with the electrode glass substrate, a flow path is formed using a potassium hydroxide aqueous solution. (For example, see Patent Document 1). Further, when the DLC film is formed on the diaphragm (on the counter electrode side), after the cavity substrate is formed, the DLC film is formed by aligning and fixing the cavity substrate using an arbitrarily opened Si mask or the like. A manufacturing method has been proposed (see, for example, Patent Document 2).

JP 2007-136856 (9th, 10th page, FIG. 6) JP 2007-190730 A (pages 10, 11 and 6)

In the technique described in Patent Document 1, after anodically bonding a silicon substrate on which a DLC film is formed and an electrode glass substrate, a flow path is formed using an aqueous potassium hydroxide solution. Although the subsequent process is not described in Patent Document 1, the silicon substrate is used for alignment and fixing to the cavity substrate, and then the fixed electrode portion and the sealing hole serving as the FPC connection portion are opened by dry etching. There is a need. This necessitates the production of a silicon mask, which increases the number of steps required. In addition, SF ₆ is used as the silicon etching gas, and CF _{4 or} CHF ₃ is used as the SiO ₂ etching gas. However, etching of the electrode substrate after opening occurs due to in-plane variation in the silicon thickness of the etched portion or variation in the dry etching plane, Thereby, there is a possibility that the airtightness of the sealing by the inorganic sealing or the like is prevented.

  In the technique described in Patent Document 2, a mask substrate made of silicon is used, pin alignment or camera alignment is performed with the cavity substrate, and the cavity substrate and the mask substrate are fixed with a tape or the like to form a DLC film. It was. If the adhesion between the cavity substrate and the mask substrate is poor, the wafer may be displaced when the tape is fixed, or if there is a warp of the cavity substrate or the mask substrate, a gap will be generated between the substrates, resulting in DLC during subsequent DLC film formation. Problems such as wrapping around the membrane occur. In addition, if the adhesion between the cavity substrate and the mask substrate is good, there is a problem that when the mask substrate is peeled off from the cavity substrate after the DLC film is formed, the thin plate portion such as the vibration plate is broken.

  That is, when the DLC film is formed by the technique described in Patent Document 1, the number of processing steps is increased in the etching process after anodic bonding, and a problem remains in productivity. Further, when the DLC film is formed by the technique described in Patent Document 2, it is difficult to ensure alignment accuracy if the adhesion between the silicon mask and the cavity substrate is low, and conversely, if the adhesion between the silicon mask and the cavity substrate is high. When the silicon mask is peeled off, there remains a problem that a defect such as cracking of the cavity substrate occurs.

  The present invention has been made in order to solve the above-described problems. An electrostatic actuator manufacturing method capable of accurately forming a highly lubricated hard film with an arbitrary dimension on a diaphragm portion, and droplet discharge It is an object of the present invention to propose a method for manufacturing a head and a method for manufacturing a droplet discharge device.

  The method for manufacturing an electrostatic actuator according to the present invention includes a step of forming a fixed electrode in a recess formed in a first substrate and a movable electrode that operates by electrostatic force generated between the second substrate and the fixed electrode. Forming an insulating film on the movable electrode forming surface of the second substrate, forming a highly lubricated hard film at a surface position corresponding to the movable electrode of the insulating film, and insulating film and highly lubricated A step of forming a protective film for protecting the hard film, a step of etching from a surface opposite to the movable electrode forming surface at a position corresponding to the fixed electrode of the second substrate, and a protection from the second substrate Removing the film, and anodic bonding the first substrate and the second substrate so that the fixed electrode of the first substrate and the movable electrode of the second substrate face each other with a gap therebetween. It is characterized by having.

  Therefore, since a highly lubricated hard film can be formed without using a mask, problems in using the mask (for example, alignment accuracy, wraparound of the highly lubricated hard film, wafer cracking, etc.) can be solved. . Moreover, the subject of the process (for example, the inorganic sealing defect by the electrode part glass etching, a process increase, etc.) which etches a pressure chamber etc. with potassium hydroxide liquid after anodic bonding can be solved. Therefore, stabilization of the high voltage drive and high reliability of the electrostatic actuator can be ensured.

  The manufacturing method of the electrostatic actuator according to the present invention is characterized in that the protective film is a silicon nitride film, an aluminum film, or a laminated film of these and silicon oxide. Therefore, the insulating film and the highly lubricated hard film can be effectively protected from etching.

  The manufacturing method of the electrostatic actuator according to the present invention is characterized in that the highly lubricated hard film is a carbon-based hard film. This makes it possible to ensure stable driving of the electrostatic actuator.

  The method for manufacturing an electrostatic actuator according to the present invention is characterized in that the carbon-based hard film is diamond-like carbon, carbon nanotube, or fullerene C60. This makes it possible to effectively ensure stable driving of the electrostatic actuator.

  In the method for manufacturing an electrostatic actuator according to the present invention, the insulating film is made of silicon oxide or a dielectric material having a relative dielectric constant higher than that of silicon oxide. Accordingly, the ejection characteristics are stabilized and improved while ensuring insulation, and the low-temperature film-formability, film homogeneity, process adaptability, and the like are improved.

  A manufacturing method of a droplet discharge head according to the present invention includes a manufacturing process of an electrostatic actuator by the above-described manufacturing method of an electrostatic actuator. Accordingly, the manufacturing method of the droplet discharge head has the same effect as the above-described manufacturing method of the electrostatic actuator.

  A manufacturing method of a droplet discharge device according to the present invention includes a manufacturing step of a droplet discharge head according to the method of manufacturing a droplet discharge head described above. Therefore, the method for manufacturing the droplet discharge device has the same effect as the method for manufacturing the droplet discharge head described above.

FIG. 3 is an exploded perspective view illustrating a state in which the droplet discharge head according to Embodiment 1 is disassembled. It is a longitudinal cross-sectional view which shows the BB longitudinal cross-section of the state by which the droplet discharge head was assembled. It is a longitudinal cross-sectional view which expands and shows the schematic cross section of the contact part of a cavity board | substrate. It is a flowchart which shows the flow of the manufacturing process of a droplet discharge head. It is AA longitudinal cross-sectional view which shows a part of manufacturing process example of a droplet discharge head. It is an AA longitudinal cross-sectional view which shows a part of manufacturing process of the droplet discharge head of the prior art as a comparative example. It is an AA longitudinal cross-sectional view which shows a part of etching process after joining as a comparative example. FIG. 2 is a perspective view showing an example of a droplet discharge device equipped with the droplet discharge head according to the first embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is an exploded perspective view showing a state in which the droplet discharge head 100 according to Embodiment 1 of the present invention is disassembled. FIG. 2 is a longitudinal sectional view showing a BB longitudinal section in a state where the droplet discharge head 100 is assembled. Based on FIGS. 1 and 2, the configuration and operation of the electrostatic actuator will be described together with the configuration and operation of the droplet discharge head 100. In addition, in the following drawings including FIG. 1, the relationship of the size of each component may be different from the actual one.

  The droplet discharge head 100 is a representative of electrostatic actuators driven by electrostatic force, and is a face-eject type droplet discharge that discharges droplets from nozzle holes provided on the surface side of a nozzle substrate. Represents the head. As shown in FIGS. 1 and 2, the droplet discharge head 100 includes a nozzle substrate 1, a cavity substrate 3 as a second substrate, and an electrode glass substrate 4 as a first substrate in this order. It has a three-layer structure joined so as to be laminated. That is, in the droplet discharge head 100, the nozzle substrate 1 is bonded to one surface (upper surface) of the cavity substrate 3, and the electrode glass substrate 4 is bonded to the other surface (lower surface). The electrode glass substrate 4 and the nozzle substrate 1 are sandwiched from above and below.

  The droplet discharge head 100 includes a counter electrode 17 (fixed electrode) formed on the electrode glass substrate 4 and a vibration plate 8 of the cavity substrate 3 disposed to face the counter electrode 17 with a predetermined gap 18 therebetween. An electrostatic actuator composed of (movable electrode) is provided. Further, in the droplet discharge head 100 according to the first embodiment, the electrode glass substrate 4 and the cavity substrate 3 are joined by anodic bonding, and the cavity substrate 3 and the nozzle substrate 1 are bonded with an adhesive such as epoxy resin. It demonstrates as what is used and joined. Further, a driving signal (pulse voltage) is supplied to the counter electrode 17 which is a fixed electrode formed on the electrode glass substrate 4 of the droplet discharge head 100 by an oscillation circuit 50 which is a power supply means such as a driver IC shown in FIG. It has come to be.

[Cavity substrate 3]
The cavity substrate 3 is composed of, for example, a (110) plane silicon single crystal substrate (hereinafter simply referred to as a silicon substrate (second substrate)) having a thickness of about 180 μm (micrometer) as a main material. Either or both of dry etching and anisotropic wet etching are performed on the silicon substrate, and each member (discharge chamber 7, reservoir 29, etc.) of the cavity substrate 3 is formed. A discharge chamber (pressure chamber) 7 which is one of the members of the cavity substrate 3 is a diaphragm 8 having a flexible bottom wall, and a plurality of discharge chambers (pressure chambers) are formed.

  The discharge chamber 7 is formed corresponding to the electrode row of the counter electrode 17 and is adapted to hold a droplet of ink or the like and apply a discharge pressure. The discharge chamber 7 is formed in parallel from the front side to the back side of the drawing. The reservoir 29 which is one of the members of the cavity substrate 3 functions as a common ink chamber for supplying droplets such as ink to the discharge chambers 7. An ink supply hole 27 penetrating the bottom surface of the reservoir 29 is formed on the bottom surface of the reservoir 29. The ink supply hole 27 communicates with the ink supply hole 28 of the electrode glass substrate 4.

The diaphragm 8 is composed of a high-concentration boron-doped layer. In order to form the diaphragm 8 having a desired thickness, a boron-doped layer having the same thickness, for example, 2 μm is formed. The etching rate in etching single crystal silicon with an alkaline solution such as an aqueous potassium hydroxide solution is very small in a high concentration region of about 5 × 10 ¹⁹ atoms / cm ³ or more when the dopant is boron. For this reason, when the diaphragm 8 is made of a high-concentration boron-doped layer and the discharge chamber 7 is formed by anisotropic etching with an alkaline solution, the boron-doped layer is exposed and the etching rate becomes extremely small, so-called etching stop. By using the technique, the thickness of the diaphragm 8 and the volume of the discharge chamber can be formed with high accuracy.

On the lower surface of the cavity substrate 3 (the surface facing the electrode glass substrate 4, the lower surface of the diaphragm 8), a TEOS film (here, tetraethyl orthosilicate) for electrically insulating the diaphragm 8 and the counter electrode 17 is provided. An insulating film 19 that is a tetraethoxysilane (referred to as an SiO ₂ film formed using tetraethoxysilane (ethyl silicate)) is formed, for example, to a thickness of several hundreds of nanometers using a plasma CVD (also referred to as Chemical Vapor Deposition: TEOS-pCVD) method. is doing. This is for preventing dielectric breakdown and short-circuit when the diaphragm 8 is driven, and for preventing etching of the cavity substrate 3 by droplets of ink or the like.

Here, a case where the insulating film 19 is a TEOS film will be described as an example. However, the present invention is not limited to this, and any material that improves the insulating performance may be used. For example, a dielectric material having a relative dielectric constant higher than that of silicon oxide such as Al ₂ O ₃ (aluminum oxide (alumina)) or silicon oxynitride may be used. In addition, the insulating film may be formed by an ALD (Atomic Layer Deposition) method, ECR sputtering, or the like, without being limited to the case where the film is formed by plasma CVD.

Furthermore, an SiO ₂ film (including a TEOS film) that serves as a liquid protective film (not shown) may be formed on the upper surface of the cavity substrate 3 by a plasma CVD method or a sputtering method. This is because by forming such a liquid protective film, it is possible to prevent the flow path from being corroded by ink droplets. There is also an effect that the stress of the liquid protective film and the stress of the insulating film 19 are offset and the warpage of the diaphragm 8 can be reduced.

  A DLC film 20 that is a highly lubricious hard film is formed on the surface of the insulating film 19 (the surface of the insulating film 19 on the electrode glass substrate 4 side) and in contact with the counter electrode 17. The DLC film 20 is preferably formed with a thickness of about several nm to several tens of nm, for example, by RF plasma CVD or the like. In the first embodiment, the case where the highly lubricated hard film is the DLC film 20 will be described as an example. However, the present invention is not limited to this, and the highly lubricated hard film may be a carbon-based hard film such as carbon nanotube or fullerene C60. Any film may be used.

An etching protective film 21 is formed on the surface of the insulating film 19 (the portion from which the DLC film 20 has been removed (see FIG. 3)) and on the surface of the DLC film 20. The etching protective film 21 is preferably formed of silicon nitride (SiN) or aluminum (Al) to a thickness of about 0.1 μm by sputtering or plasma CVD. The etching protective film 21 may be a laminated film of a metal film and SiO ₂ . The laminated portion of the DLC film 20 and the etching protective film 21 becomes a contact surface during driving of the actuator.

  The cavity substrate 3 is formed with a common electrode terminal 16 as an external electrode terminal. The common electrode terminal 16 serves as a terminal when electric charges having a polarity opposite to that of the counter electrode 17 are supplied from the oscillation circuit 50 to the diaphragm 8 via an FPC (Flexible Printed Circuit) (not shown).

[Electrode glass substrate 4]
The electrode glass substrate 4 is preferably formed using a glass substrate (first substrate) such as a borosilicate heat-resistant hard glass having a thickness of 1 mm as a main material. Here, a case where the electrode glass substrate 4 is made of borosilicate heat-resistant hard glass is shown as an example, but the electrode glass substrate 4 may be made of single crystal silicon, for example. On the surface of the electrode glass substrate 4, a recess (glass groove) 12 is formed to a depth of about 0.2 μm by etching, for example, in accordance with the shape of the discharge chamber 7 of the cavity substrate 3 described above.

  In addition, inside the recess 12 (particularly at the bottom), a counter electrode 17 serving as a fixed electrode is opposed to each discharge chamber 7 (the diaphragm 8 serving as a movable electrode) of the cavity substrate 3 with a certain interval. It is made as follows. And this recessed part 12 demonstrates that the counter electrode 17, the lead part 14, and the terminal part 15 (the counter electrode 17 included the lead part 14 and the terminal part 15 unless it needs to distinguish in particular) in the inside. ) May be formed in a slightly larger shape similar to these shapes. Moreover, although the case where the depth of the recessed part 12 is about 0.2 micrometer is shown as an example, according to the thickness of the counter electrode 17 produced in the recessed part 12, it can change.

  The counter electrode 17 may be formed by sputtering, for example, transparent ITO (Indium Tin Oxide) doped with tin oxide as an impurity with a thickness of 0.1 μm. Thus, when the counter electrode 17 is made of ITO, there is an advantage that it is easy to confirm whether or not the discharge has occurred because it is transparent. The material of the counter electrode 17 is not limited to ITO, and a metal material such as chromium may be used. Further, the electrode glass substrate 4 is formed with an ink supply hole 28 penetrating through the ink supply hole 27 of the reservoir 29 and serving as a flow path for taking in liquid supplied from an external ink tank (not shown).

  Further, the FPC mounting portion 30 is formed on the electrode glass substrate 4 to a depth of about 0.2 μm by etching. An FPC (not shown) is mounted on the FPC mounting portion 30 so that one end (terminal portion 15) of the counter electrode 17 and the oscillation circuit 50 are connected. Therefore, a drive signal is supplied to the counter electrode 17 from the oscillation circuit 50 via the FPC.

  When the laminated body is formed by anodically bonding the electrode glass substrate 4 and the cavity substrate 3, a certain gap (between the diaphragm 8 and the counter electrode 17 can be deflected (displaced)). A gap 18 is formed by the recess 12 of the electrode glass substrate 4. The gap 18 is determined by the depth of the recess 12 and the thickness of the counter electrode 17. Since the gap 18 greatly affects the discharge characteristics of the droplet discharge head 100, strict accuracy control is required. The gap 18 is formed to be elongated and have a predetermined depth at a position facing each diaphragm 8. The gap 18 is hermetically sealed by the sealing portion 9 so that moisture, dust, and the like do not enter the inside.

  In addition, although the case where the depth of the FPC mounting part 30 is about 0.2 μm is shown as an example, the present invention is not limited to this, and may be changed according to the depth of the recess 12. The gap 18 may be hermetically sealed with the sealing portion 9 after performing a vapor phase process. The gas phase treatment is performed so as to perform a hydrophobic treatment after removing moisture in the gap 18. In addition, the gap 18 can be formed by forming a recess in the silicon substrate to be the cavity substrate 3 or sandwiching a spacer.

  In the droplet discharge head 100, a plurality of counter electrodes 17 are formed in a rectangular shape having long sides and short sides, and the counter electrodes 17 are arranged so that the long sides thereof are parallel to each other. FIG. 1 shows one electrode row extending in the short side direction of the counter electrode 17. In addition, when the short side of the counter electrode 17 is formed obliquely with respect to the long side and the counter electrode 17 has an elongated parallelogram shape, an electrode array extending in a direction perpendicular to the long side direction is formed. What should I do?

[Nozzle substrate 1]
The nozzle substrate 1 is composed of, for example, a silicon substrate having a thickness of about 180 μm as a main material. And it is joined to the upper surface of the cavity substrate 3 (the surface opposite to the surface to which the electrode glass substrate 4 is joined). A plurality of nozzle holes 5 communicating with each of the discharge chambers 7 are formed through the nozzle substrate 1. Each nozzle hole 5 discharges the droplets transferred from the discharge chamber 7 to the outside. In addition, when the nozzle hole 5 is formed in a plurality of stages (for example, two stages), it can be expected that straightness is improved when a droplet is ejected.

  In addition, an orifice 24 and a diaphragm 25 are formed on the lower surface of the nozzle substrate 1 (bonding surface with the cavity substrate 3). The orifice 24 allows the reservoir 29 and each discharge chamber 7 to communicate with each other in order to transfer droplets from the reservoir 29 to each discharge chamber 7. The diaphragm 25 is for buffering the pressure applied to the liquid on the reservoir 29 side by the diaphragm 8. Here, the nozzle substrate 1 is described as the upper surface and the electrode glass substrate 4 is described as the lower surface. However, when actually used, the nozzle substrate 1 is often lower than the electrode glass substrate 4.

  In the first embodiment, the case where the orifice 24 is formed in the nozzle substrate 1 is shown as an example, but the orifice 24 may be formed in the cavity substrate 3. Further, when the electrode glass substrate 4, the cavity substrate 3 and the nozzle substrate 1 are bonded, a silicon substrate and a borosilicate glass substrate are bonded (when the electrode glass substrate 4 and the cavity substrate 3 are bonded). In the case of bonding substrates made of silicon by anodic bonding (cavity substrate 3 and nozzle substrate 1), they can be bonded by bonding using an adhesive or direct bonding.

  The operation of the droplet discharge head 100 will be briefly described. The reservoir 29 of the cavity substrate 3 is supplied with droplets of ink or the like from the outside through the ink supply holes 28 and the ink supply holes 27. In addition, droplets are supplied from the reservoir 29 to the discharge chamber 7 of the cavity substrate 3 through the orifice 24. The oscillation circuit 50 is connected to the FPC mounting unit 30 via the FPC, and controls supply and stop of charge to the counter electrode 17. The oscillation circuit 50 oscillates at, for example, 24 kHz, applies a pulse potential of about 0 V to 40 V to the counter electrode 17 selected by the oscillation circuit 50 to supply charges, and charges the counter electrode 17 positively.

  At this time, a charge having a negative polarity is supplied to the cavity substrate 3 through the common electrode terminal 16, and the diaphragm 8 corresponding to the counter electrode 17 that is positively charged is relatively negatively charged. Therefore, an electrostatic force is generated between the selected counter electrode 17 and the diaphragm 8. If it does so, the diaphragm 8 will be drawn near to the counter electrode 17 side by an electrostatic force, and will bend. As a result, the volume of the discharge chamber 7 increases. That is, the counter electrode 17 is attracted to and contacts the counter electrode 17. As a result, the volume of the discharge chamber 7 increases.

  Thereafter, when the supply of electric charge to the counter electrode 17 is stopped, the electrostatic force between the diaphragm 8 and the counter electrode 17 disappears, and the diaphragm 8 is restored to the original state by the elastic force. At this time, since the volume of the discharge chamber 7 decreases rapidly, the pressure inside the discharge chamber 7 increases rapidly. Thereby, a part of the ink in the discharge chamber 7 is discharged from the nozzle hole 5 as an ink droplet. Printing or the like is performed when the ink droplets land on a recording sheet, for example. Thereafter, the droplets are replenished from the reservoir 29 into the discharge chamber 7 through the orifice 24, and the initial state is restored. Thus, the diaphragm 8 is driven to function as an electrostatic actuator. Such a method is called pulling, but there is also a method called pushing that discharges droplets using a spring or the like.

  FIG. 3 is an enlarged longitudinal sectional view showing a schematic cross section (AA cross section in FIG. 1) of the contact portion of the cavity substrate 3 (a laminated portion of the diaphragm 8, the insulating film 19, the DLC film 20, and the etching protective film 21). FIG. Based on FIG. 3, the contact portion of the cavity substrate 3, which is a feature of the droplet discharge head 100 according to the first embodiment, will be described in detail. By providing the DLC film 20 which is a highly lubricated hard film, stable driving of the electrostatic actuator can be realized. In addition, an etching protective film 21 for protecting the DLC film 20 from etching is formed on the surface of the insulating film 19 and the surface of the DLC film 20 in the droplet discharge head 100.

  As shown in FIG. 3, the DLC film 20 is formed in a portion corresponding to the contact portion with the counter electrode 17. The DLC film 20 has characteristics such as good adhesion to silicon, a dense film quality, and a small friction coefficient. Therefore, by forming the DLC film 20, it is possible to improve the driving durability and long-term stability of the electrostatic actuator. Since the DLC film 20 is formed at a portion corresponding to the contact portion with the counter electrode 17, a part of the insulating film 19 is exposed.

  Therefore, in the droplet discharge head 100, an etching protective film 21 is formed to protect the exposed portion of the insulating film 19 and the DLC film 20 from etching. That is, in the droplet discharge head 100, the etching protection film 21 is formed, so that the cavity substrate 3 and the electrode glass substrate 4 are anodically bonded, and then the cavity substrate 3 is etched with a potassium hydroxide solution ( It is possible to solve the problems such as process increase and inorganic sealing failure, and to form the cavity substrate alone.

  Next, the manufacturing process of the electrostatic actuator will be described together with the manufacturing process of the droplet discharge head 100. FIG. 4 is a flowchart showing the flow of the manufacturing process of the droplet discharge head 100. FIG. 5 is an AA longitudinal sectional view showing a part of a manufacturing process example of the droplet discharge head 100. FIG. 6 is an AA longitudinal sectional view showing a part of a manufacturing process of a conventional droplet discharge head as a comparative example. FIG. 7 is an AA longitudinal sectional view showing a part of the post-bonding etching process as a comparative example. Based on FIGS. 4 and 5, the manufacturing process of the droplet discharge head 100 will be described focusing on the features. In addition, after describing the manufacturing process of the droplet discharge head 100, the contents of FIG. 6 or FIG.

  The following values of the substrate thickness, etching depth, temperature, pressure, etc. are merely examples, and the present invention is not limited to these values. In practice, a plurality of droplet discharge head members are generally formed simultaneously from a silicon wafer, but only a part of them is shown in a simplified manner in FIGS. Further, FIG. 7 illustrates a part of the post-bonding etching process (step (e ′) and step (f ′)) so as to branch from step (d) in FIG. 5.

Production of electrode glass substrate 4 (S0 shown in FIG. 4)
For the electrode glass substrate 4, for example, a double-sided mirror borosilicate glass substrate having a thickness of about 1 mm is prepared, and an upper surface is provided with an etching mask of gold / chromium, and etched with a hydrofluoric acid aqueous solution or the like to form the recess 12 (or groove portion) After the formation, the counter electrode 17 made of ITO is formed in the recess 12 by sputtering or the like. Then, the glass substrate is blasted to form ink supply holes 28. In this way, the electrode glass substrate 4 can be manufactured.

Fabrication of cavity substrate 3 (S1 to S8 shown in FIG. 4, FIGS. 5A to 5F)
For example, boron is doped on one side surface of a silicon substrate 3 ′ having a thickness of 180 μm whose both surfaces are mirror-polished to form a boron-doped layer 8 ′ having a thickness of about 2 μm. This boron doped layer 8 ′ will later become the diaphragm 8. Further, an insulating film 19 (or dielectric layer) is formed on the surface of the silicon substrate 3 ′ where the boron doped layer 8 ′ is formed (S1 shown in FIG. 4, FIG. 5A). As described above, the insulating film 19 may be formed by a plasma CVD method, an ALD method, an ECR sputtering method, or the like.

Subsequently, a DLC film 20 is formed on the surface of the insulating film 19 (S2 shown in FIG. 4, FIG. 5B). The DLC film 20 may be formed from several nm to several tens of nm by RF plasma CVD or the like. As source gases for film formation by RF plasma CVD, methane (CH ₄ ), ethane (C ₂ H ₆ ), propane (C ₃ H ₈ ), butane (C ₄ H ₁₀ ), acetylene (C ₂ H) ₂ ), benzene (C ₆ H ₆ ), toluene (C ₇ H ₈ ) and the like can be used.

  Next, after patterning the DLC film 20 with a resist 51 to protect the portion corresponding to the contact portion with the counter electrode 17 (S3 shown in FIG. 4, FIG. 5C), excess DLC is formed by oxygen plasma. The film 20 is oxidized and removed, and then the resist 51 is peeled off (S4 shown in FIG. 4, FIG. 5D). Then, an etching protective film 21 is formed on the entire surface on which the DLC film 20 is formed (S5 shown in FIG. 4, FIG. 5 (e)).

As this etching protective film 21, for example, silicon nitride (SiN) is preferably formed to a thickness of 0.1 μm by sputtering or CVD. Alternatively, a metal film such as Al may be formed by several hundred nm by sputtering or the like. In the case of forming a metal film, an S≡O ₂ film may be further formed thereon by using, for example, TEOS plasma CVD to have a thickness of 1.5 μm or more. The conditions for forming the silicon nitride film by the plasma CVD method are, for example, a temperature of 500 ° C. or less, a pressure of 1.3 kPa or less (10 Torr or less), and a gas flow rate ratio NH ₃ / SiH ₄ of 15 or more. In the following description, it is assumed that the etching protection film 21 is a silicon nitride film.

  Next, a silicon oxide film 52 having a thickness of, for example, 1.5 μm is formed on the entire surface of the silicon substrate 3 ′ opposite to the surface on which the DLC film 20 is formed (the flow path forming surface such as the discharge chamber 7 and the reservoir 29) by plasma CVD. Form. The silicon oxide film 52 is patterned with a resist (not shown) for forming a recess to be the discharge chamber 7, a recess to be the reservoir 29, and a recess to be the orifice 24, and the silicon oxide film 52 in this portion is etched. It is removed (S6 shown in FIG. 4).

  Thereafter, anisotropic wet etching is performed on the silicon substrate 3 'with a potassium hydroxide aqueous solution or the like (S7 shown in FIG. 4, FIG. 5 (f)). By doing so, a recess serving as the discharge chamber 7, a recess serving as the reservoir 29, and a recess serving as the orifice 24 are formed. Thereafter, the silicon oxide film 52 is removed. In this wet etching process, for example, it is preferable to perform two-stage etching using, for example, a 35% by weight potassium hydroxide aqueous solution first and then a 3% by weight potassium hydroxide aqueous solution. Thereby, surface roughness of the diaphragm 8 can be suppressed. In the above etching process, the previously formed boron doped layer 8 ′ acts as an etching stop, and the remaining boron doped layer 8 ′ is formed as the diaphragm 8.

  Thereafter, the silicon oxide film 52 used as an etching mask with an aqueous potassium hydroxide solution is removed using, for example, a hydrofluoric acid aqueous solution. Then, all of the silicon nitride film which is the etching protection film 21 formed on the silicon substrate 3 ′ is removed using a hot phosphoric acid aqueous solution. On the surface of the silicon substrate 3 ′ where the recesses to be the discharge chambers 7 are formed, a droplet-resistant protective film (not shown) made of silicon oxide or the like is formed with a thickness of 0.1 μm, for example, by CVD.

Then, the anti-droplet protective film is removed from the portion to be the common electrode terminal 16 of the silicon substrate 3 ′ by RIE (Reactive Ion Etching). This RIE is a kind of dry etching, and is performed 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). Thereafter, Pt is formed to a thickness of 0.1 μm on the common electrode terminal 16 by sputtering (S8 shown in FIG. 4). In this way, the cavity substrate 3 can be manufactured.

  The cavity substrate 3 and the electrode glass substrate 4 are aligned, and then heated to 360 ° C., a negative electrode is connected to the electrode glass substrate 4 and a positive electrode is connected to the cavity substrate 3, and anodic bonding is performed by applying a voltage of 800 V (FIG. S9) shown in FIG. After the anodic bonding, a sealing portion 9 is formed to hermetically seal the gap 18 to prevent foreign matter, moisture, etc. from entering the gap 18 (S10 shown in FIG. 4). Then, the nozzle substrate 1 in which the nozzle holes 5 are formed is bonded to the side surface opposite to the bonding surface of the cavity substrate 3 with the electrode glass substrate 4 using an adhesive such as an epoxy resin (S11 shown in FIG. 4). Finally, dicing (cutting) is performed on the bonding substrate to which the electrode glass substrate 4, the cavity substrate 3, and the nozzle substrate 1 are bonded, thereby completing individual droplet discharge heads 100 (S12 shown in FIG. 4).

The prior art shown in FIG. 6 will be described.
First, a boron doped layer 8a ′ is formed on one surface of the silicon substrate 3a (FIG. 6A), and an insulating film 19a is formed as an etching protection film on both surfaces of the silicon substrate 3a (FIG. 6B). Thereafter, a resist (not shown) is applied to the surface of the insulating film 19a, and patterning is performed by photolithography to form a recess or the like that becomes the discharge chamber 7a (FIG. 6C). And the recessed part used as the discharge chamber 7a is etched and produced.

  Then, the insulating film 19a is peeled from the entire surface of the silicon substrate 3a (FIG. 6D). Thereafter, the ink protective film 54 is formed on the flow path forming surface of the silicon substrate 3a, and the insulating film 55 is formed on the surface of the boron doped layer 8a '(FIG. 6E). At this time, a common electrode terminal is also formed. Thereafter, the DLC film 20a is formed by CVD or the like using a silicon mask (not shown) that masks the portions other than the portion where the DLC film 20a is to be formed (FIG. 6F). At this time, generally, the DLC film 20a is formed by fixing the silicon mask and the silicon substrate 3a with a tape or the like.

  If the adhesion between the silicon substrate 3a and the silicon mask is poor, wafer misalignment may occur during tape fixing. Further, if the silicon substrate 3a or the silicon mask warp is present, a gap between the substrates may be generated, and the DLC film 20a may wrap around. On the other hand, if the adhesion between the silicon substrate 3a and the silicon mask is good, the thin plate portion such as the boron doped layer 8a 'may be destroyed when the silicon mask is peeled off after the DLC film 20a is formed.

  However, in the manufacturing method of the electrostatic actuator according to the first embodiment (the manufacturing method of the droplet discharge head 100), the DLC film 20 is formed without using the silicon mask. There is no inconvenience. Therefore, in the manufacturing method of the electrostatic actuator according to the first embodiment, it is possible to accurately form the DLC film 20 with an arbitrary dimension, and to improve the disadvantages of the prior art.

The prior art shown in FIG. 7 will be described.
A DLC film 20 is formed as in FIG. 5D (FIG. 7D ′). Thereafter, the post-bonding etching process is performed. First, anodic bonding of the silicon substrate 3 ′ and the electrode glass substrate 4 is performed (FIG. 7 (e ′)). Then, the silicon substrate 3 ′ is ground to an arbitrary thickness. Thereafter, a hard mask 57 composed of a silicon oxide film or the like is formed on the flow path forming surface of the silicon substrate 3 ′ by CVD or the like (FIG. 7 (f ′)). After that, a recess or the like that becomes the discharge chamber 7 is formed in the silicon substrate 3 ′ by etching.

Thereafter, alignment and fixing are performed on the silicon substrate 3 ′ using a silicon mask, and a sealing hole for forming the FPC mounting portion 30 and the sealing portion 9 is opened by dry etching. In other words, it becomes necessary to manufacture a silicon mask separately, and the number of steps required for that increase. In addition, SF ₆ is generally used as the silicon etching gas and CF _{4 or} CHF ₃ is generally used as the SiO ₂ etching gas. However, due to the in-plane variation of the silicon thickness of the etched portion and the in-plane variation of the dry etching, the electrode glass substrate 4 after opening is formed. Etching may occur, thereby impeding sealing airtightness by inorganic sealing or the like. If it does so, productivity will fall and a yield will deteriorate.

  However, in the manufacturing method of the electrostatic actuator according to the first embodiment (the manufacturing method of the droplet discharge head 100), the flow path is formed in the silicon substrate 3 ′ without performing the post-bonding etching process. Therefore, it is not necessary to produce a silicon mask and productivity is not reduced. Moreover, since the etching of the electrode glass substrate 4 after opening does not occur, airtightness can be ensured and the DLC film 20 is not altered. Therefore, in the manufacturing method of the electrostatic actuator according to the first embodiment, unnecessary labor can be reduced, and the alteration of the DLC film 20 accurately formed with an arbitrary dimension can be prevented, thereby improving the disadvantages of the prior art. be able to.

Embodiment 2. FIG.
FIG. 8 is a perspective view showing an example of a droplet discharge device 150 on which the droplet discharge head 100 manufactured in the first embodiment is mounted. A droplet discharge device 150 shown in FIG. 8 is a general inkjet printer. The droplet discharge device 150 can be manufactured by a known manufacturing method. In addition to the droplet discharge device 150 shown in FIG. 8, the droplet discharge head 100 can produce various color droplets to produce a color filter for a liquid crystal display, form a light emitting portion of an organic EL display device, The present invention can also be applied to liquid discharge.

  The droplet discharge head 100 can also be used for a piezoelectric drive type droplet discharge device and a bubble jet (registered trademark) type droplet discharge device. For example, when the droplet discharge head 100 is used as a dispenser and is used for discharge onto a substrate that is a biomolecule microarray, DNA (Deoxyribo Nucleic Acids), other nucleic acids (for example, Ribo Nucleic Acid: ribonucleic acid, (Peptide Nucleic Acids: peptide nucleic acid, etc.) A liquid containing a probe such as a protein may be discharged.

  The electrostatic actuator mounted on the droplet discharge head 100 includes, for example, optical switches, mirror devices, and laser operation mirrors of laser printers used in optical communication, optical computation, optical storage devices, optical printers, video display devices, and the like. The present invention can also be applied to a drive unit, other microfabricated elements (devices), or apparatuses. In any case, it is possible to prevent charging at the interface of the multilayer insulating film, to prevent the vibration plate 8 from bending and sticking, and to improve the stability of ejection characteristics and drive durability. Can be planned.

  The electrostatic actuator, the droplet discharge head, and the droplet discharge device according to the embodiment of the present invention are not limited to the contents described in the above-described embodiment, and are within the scope of the idea of the present invention. Can be changed. Further, the case where the droplet discharge head 100 according to Embodiment 1 has a three-layer structure including the electrode glass substrate 4, the cavity substrate 3, and the nozzle substrate 1 has been described as an example, but the glass substrate, the cavity substrate, the reservoir substrate, A four-layer structure composed of nozzle plates may also be used.

  DESCRIPTION OF SYMBOLS 1 Nozzle substrate, 3 cavity substrate, 3 'silicon substrate, 3a silicon substrate, 4 electrode glass substrate, 5 nozzle hole, 7 discharge chamber, 7a discharge chamber, 8 diaphragm, 8' boron dope layer, 8a 'boron dope layer, 12 recessed part , 14 Lead part, 15 Terminal part, 16 Common electrode terminal, 17 Counter electrode, 18 Gap, 19 Insulating film, 19a Insulating film, 20 DLC film, 20a DLC film, 21 Etching protective film, 24 Orifice, 25 Diaphragm, 27 Ink Supply hole, 28 Ink supply hole, 29 Reservoir, 30 FPC mounting part, 50 Oscillator circuit, 51 Resist, 52 Silicon oxide film, 54 Ink protective film, 55 Insulating film, 57 Hard mask, 100 Droplet ejection head, 150 droplets Discharge device.

Claims (7)

Forming a fixed electrode in the recess formed in the first substrate;
Forming a movable electrode that operates by electrostatic force generated between the second substrate and the fixed electrode;
Forming an insulating film on the movable electrode forming surface of the second substrate;
Forming a highly lubricious hard film at a surface position corresponding to the movable electrode of the insulating film;
Forming a protective film for protecting the insulating film and the highly lubricated hard film;
Etching from a surface opposite to the movable electrode forming surface to a position corresponding to the fixed electrode of the second substrate to make a thin plate;
Removing the protective film from the second substrate;
And anodically bonding the first substrate and the second substrate so that the fixed electrode of the first substrate and the movable electrode of the second substrate face each other with a gap therebetween. A manufacturing method of an electrostatic actuator characterized by the above. The protective film,
The method for producing an electrostatic actuator according to claim 1, wherein the film is a silicon nitride film, an aluminum film, or a laminated film of these and silicon oxide. The highly lubricated hard film,
The method of manufacturing an electrostatic actuator according to claim 1, wherein the carbon-based hard film is used. The carbon-based hard film is
It is diamond-like carbon, a carbon nanotube, or fullerene C60. The manufacturing method of the electrostatic actuator of Claim 3 characterized by the above-mentioned. The insulating film is
It is comprised with the dielectric material whose dielectric constant is higher than silicon oxide or a silicon oxide. The manufacturing method of the electrostatic actuator in any one of Claims 1-4 characterized by the above-mentioned. A method for manufacturing a droplet discharge head, comprising: a manufacturing step of an electrostatic actuator according to the method for manufacturing an electrostatic actuator according to claim 1. A method for manufacturing a droplet discharge device, comprising the step of manufacturing a droplet discharge head according to the method for manufacturing a droplet discharge head according to claim 6.

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