JPH1044406A - Ink jet head and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic ink jet head using a structural material capable of being formed into a vibration plate having an accurate thickness dimension and not requiring a special alkali anisotropic etching process apparatus. SOLUTION: A substrate 1 having an SOI structure wherein an oxide film 2a is held between single crystal silicon substrates 1a, 1b is used. At first, the oxide film 2a becoming a vibration plate 3 and a single crystal silicon substrate 1b are ground so as to obtain the desired thickness t1 of the vibration plate 3. Thereafter, oxide films 2b, 2c are formed on the entire surface of the substrate 1. Next, patterning is applied to the substrate by photolithographic technique and the oxide film 2b on the silicon surface of the single crystal silicon substrate 1a is etched at a place desired to be etched by a hydrofluoric acid etching soln. Thereafter, the exposed part 1d of the single crystal silicon substrate is etched by using a heated alkali anisotropic etching soln.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head and a method of manufacturing the same, and more particularly to an ink jet head of an ink jet recording apparatus for applying ink to a recording paper surface by using electrostatic force and a method of manufacturing the same. The present invention also relates to a manufacturing method suitable for use in manufacturing a microactuator using the same.

[0002]

2. Description of the Related Art When manufacturing a microactuator using single crystal silicon, an alkali anisotropic etching technique has been conventionally used. In etching,
Utilizing the property that the etching rate depends on the impurity concentration, only a specific layer can be selectively etched. In the case of silicon, isotropic and crystal anisotropic etching can be performed.

As an etching method, there is a method in which a desired etching amount is etched by time management. For example, a film (layer) containing a P-type impurity such as boron at a high concentration (10 ¹⁹ / cm ³ or more) is used. Thus, a film (layer) having the property of being extremely insoluble in the crystal anisotropic etching solution is obtained, whereby a substantially self-supporting film (etching stop film) structure can be formed.

In addition, when electrochemical etching is performed by using a pn junction, only the n-type side is anodized in a crystal anisotropic etching solution, so that it can be prevented from being etched. Japanese Patent Application Laid-Open No. 6-71882 also discloses a method of forming an inkjet head using an anisotropic etching process that leaves a P-type high-concentration self-supporting film or an n-type film by electrochemical etching using a crystalline anisotropic etching solution. Have been.

[0005] In the ink jet recording apparatus, there are a method in which the driving means is a piezoelectric element and a method in which the ink is heated to generate bubbles to discharge the ink. In the former method using a piezoelectric element, it takes a lot of time and effort to finely process the piezoelectric element, and the piezoelectric element must be finely processed for high density. There has been a problem that the dimensional and shape accuracy in processing has a large variation in printing quality.

The latter is not formed by the above problem because it is formed by a resistance heating element. However, the resistance heating element is damaged by repeated heating and cooling of the driving means. Has a short life span.

[0007] In order to solve the above problems,
Ink jets utilizing electrostatic force as a driving means have been proposed, and have the advantages of small size, high density, high printing quality, and long service life with respect to the above problems. However, in order to further enhance these advantages, it is necessary to keep the gap dimension between the diaphragm and the electrode for driving the diaphragm at a very high accuracy within a predetermined range. It is said that "ejection pressure is proportional to the cube of the thickness of the diaphragm." Since the dimensional variation of the diaphragm has a very significant effect on the ink ejection characteristics, the diaphragm is finished with high dimensional accuracy. What you need. And other issues remain.

As a method for solving such a problem, there is, for example, a method disclosed in Japanese Patent Laid-Open Publication No. Hei 6-71882, which discloses an etching process method using a high-concentration P layer using an etching stop film (layer). And an electrochemical etching process using an n-type film as an etching stop film (layer).

In the former method, in forming a diaphragm, an np junction layer is provided by doping boron (B) with 5 × 10 ²⁰ / cm ³ by vapor phase, solid phase, ion implantation or the like in a layer which can be a diaphragm. Then, the etching surface is patterned, and the silicon surface is etched with an alkali anisotropic etching solution (KOH). 10 ²⁰ / cm ³ B-doped (P)
At which point the etching rate drops sharply, which means that the etching has been substantially stopped.

On the other hand, the latter is a method in which electrochemical alkali anisotropic etching is performed on a P-type substrate using, for example, a pn junction substrate grown by n-epitaxial growth. − ”Potential DC voltage is applied,
Etching by immersing the silicon substrate in KOH solution,
As a result, the exposed portion of the P-type silicon layer is removed by etching, and the n-type silicon layer is inactivated by the "+" DC voltage, so that the etching does not proceed and the etching is completed. .

[0011]

However, in the former high-concentration doping process, if a concentration distribution occurs due to a process variation or the like, there is a possibility that the diaphragm and the etching time will vary, and the latter will not. In addition, the etching stop layer is limited to the n-type layer, the selection of the stop layer is narrow, and there is a problem that an electrochemical anisotropic etching apparatus is required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and is capable of accurately forming the thickness of a diaphragm, and furthermore, a structural material which does not require a special alkali anisotropic etching process apparatus. An object of the present invention is to provide an electrostatic ink jet head using the same and a method for manufacturing the same.

[0013]

According to a first aspect of the present invention, there is provided an ink jet head for ejecting ink droplets by deforming a vibrating plate by electrostatic force.
con on Insulator) It is characterized by using a structural material, and can drive the electrostatic ink jet head at a low voltage, so that the ink ejection amount is stable and high quality printing can be performed. It is like that.

According to a second aspect of the present invention, in the first aspect of the present invention, the SOI structural material has a laminated structure in which an insulator is sandwiched between single crystal silicons. Item 2 is the invention according to Item 2, wherein the insulator is made of an oxide film or a nitride film, so that the etching process management can be reduced, and any type of substrate can be used. This is to prevent the silicon surface from being roughened by ink or the like.

According to a fourth aspect of the present invention, in the second or third aspect, a thickness of the laminated structure of the single crystal silicon and the insulator is a desired thickness of the diaphragm. In addition, it is possible to obtain a highly accurate diaphragm with little variation in film thickness.

According to a fifth aspect of the present invention, in the second aspect of the present invention, the insulator has a film thickness of 0.1 to 0.1 mm.
It is characterized by having a thickness of 0.5 μm, which can sufficiently withstand over-etching and does not cause inconvenience such as generation of residual stress of the diaphragm.

[0017]

1 and 2 show an SOI used in an ink jet head and a method of manufacturing the same according to the present invention.
FIG. 2 is a diagram for explaining a (Silicon on Insulator) technique.

FIG. 1 is a table showing classifications of various SOI technologies, and a method of forming a silicon crystal layer on an insulator is generally defined as an SOI technology. The usefulness of this method is that complete isolation between elements by an insulator is easy.

There are various methods for forming the SOI structure. As a typical example, a method in which silicon is grown on sapphire and an SOS structure, and furthermore, an amorphous film or a polycrystalline film is CVD-deposited on an insulating film (oxide film), and then the film is irradiated with a laser to make it a single crystal. As shown in FIG. 2 (A), the method is repeated to obtain a thick film single crystal by a melt recrystallization method.
As shown in FIG. 2B, a laminating method of directly laminating and integrating two mirror-finished wafers each having an oxide film on at least one surface, and then mirror-finishing one of the wafers to a desired thickness. Etc.

FIG. 3 is a schematic diagram showing a main part of an embodiment of an ink jet head according to the present invention.
Is a substrate, 1a and 1b are single crystal silicon substrates, 2a is an oxide film, 3 is a vibration plate, 4 is an upper substrate, 5 is a lower substrate, 6 is a nozzle hole, 7 is an insulating film, 8 is an electrode, and 9 is a discharge chamber. It is.

The embodiment shown in FIG. 3 has a structure in which an intermediate substrate 1 composed of single-crystal silicon substrates 1a and 1b and an oxide film 2a, an upper substrate 4 and a lower substrate 5 are overlapped and joined. When a pulse voltage is applied to the electrode 8 and the surface of the electrode 8 is positively charged, the corresponding lower surface of the diaphragm 3 is charged to a negative potential, whereby the diaphragm 3 moves downward due to the electrostatic attraction. Deflection, then the electrode 8
When the FF is set, the diaphragm 3 is restored and the pressure in the discharge chamber 9 rises rapidly, so that ink droplets are discharged from the nozzle holes 6 toward the recording paper.

FIG. 4 is a view for explaining an embodiment of a method of manufacturing a diaphragm of an ink jet head according to the present invention. In the figure, 1c is a polished portion, 1d is an exposed portion of a single crystal silicon substrate 1a, 2b , 2c oxide film, t ₁ is the vibrating plate 3
, T ₂ is the thickness of the substrate 1, t ₃ is the thickness of the oxide films 2 b and 2 c, and other portions that operate in the same manner as in FIG. 3 are given the same reference numerals as in FIG. 3.

As the substrate 1, a substrate having an SOI structure in which an oxide film 2a is sandwiched between a single crystal silicon substrate (first substrate) 1a and a single crystal silicon substrate (second substrate) 1b is used. A silicon wafer substrate 1a having a plane orientation of SOI structure is mirror-polished on both sides, and an oxide film 2
The lower surface (polished portion 1c) of the single-crystal silicon substrate (second substrate) 1b is polished so that the desired thickness of the diaphragm including the a layer (t ₁ = 20 μm) is obtained, and the entire substrate thickness t ₂ Is 2
A silicon substrate 1 having a thickness of 00 μm is manufactured (FIG. 4A).

Thermal oxide films 2b and 2c having a thickness of t ₃ are applied to both sides of the SOI substrate 1 by 2 μm (FIG. 4 (B)).
A photoresist pattern (not shown) is formed on the upper surface of the first substrate 1a of the OI substrate 1 in a shape to be subjected to silicon etching, and the thermal oxide film 2b is etched with a hydrofluoric acid-based etchant (BHF).
To expose the silicon surface (exposed portion 1d) (FIG. 4C). The thermal oxide films 2b and 2c are
This is a mask material using an alkali etching solution.

Next, the exposed portion 1d of the single-crystal silicon substrate 1a is etched using an alkali anisotropic etching solution heated to EDP, KOH, TMAH or the like. As is well known, when etching with single crystal silicon using an alkali such as EDP, potassium hydroxide solution (KOH), or TMAH, anisotropic etching becomes possible because of a large difference in etching rate depending on the crystal plane. In particular,
Since the etching of the (111) crystal plane is the smallest, a structure is obtained in which the (111) plane remains as a smooth surface as the etching proceeds. In the anisotropic etching, etching is performed by time management. However, when the etching rate varies due to process variation or the like, the thickness of the diaphragm 3 is affected.

In the embodiment shown in FIG. 4, an SOI structure silicon substrate 1 masked with oxide films 2b and 2c in an etching solution heated to 80 ° C. using an aqueous solution of 40% by weight of KOH as an anisotropic etching solution is used. It was immersed and anisotropically etched. Since the thickness t ₁ of the diaphragm 3 was 20 μm, 180 μm was removed from the total thickness t ₂ of the silicon substrate 1 = 200 μm.

The etching rate of silicon is 1.
Although the etching proceeds at 3 μm / min, the oxide film 2a has a selectivity of 0.009 μm / min, and the etching sharply decreases. Even if the etching oxide film 2a reaches the layer of the etching oxide film 2a faster than the predetermined time and is over-etched for 5 minutes, the oxide film 2a is etched only 0.045 μm, and the diaphragm 3 is formed without substantially proceeding the etching of the oxide film 2a. be able to. (FIG. 4 (D)).

Finally, the oxide films 2b and 2c are removed with a hydrofluoric acid-based etchant (BHF), and the vibration plate forming process is completed (FIG. 4E). The thickness t ₁ of the diaphragm 3 is
20 μm + 0.3 to −0.2. The insulating film sandwiched between the single crystal silicon substrates 1a and 1b is an oxide film 2
It can be easily understood that a nitride film may be used instead of a.

FIG. 5 shows the SO 2 used in the embodiment shown in FIG.
It is a figure for explaining evaluation of I structure material.

In the embodiment shown in FIG. 4, the P-type (100) is used as the substrate. However, as shown in FIG. 5, any of the pn substrates can be used as compared with other processes. There is an advantage that a substrate can be used.

[0031]

According to the first aspect of the present invention, in an ink jet head which discharges ink droplets by deforming a diaphragm by electrostatic force, an SOI (Silicon on Insulat) is provided on the diaphragm.
or) Since the structural material is used, the electrostatic ink jet head can be driven at a low voltage, thereby stabilizing the ink discharge amount and performing high quality printing.

According to a second aspect of the present invention, in the first aspect of the present invention, the SOI structural material has a laminated structure in which an insulator is sandwiched between single crystal silicons. Since the insulator is made of an oxide film or a nitride film, the etching selectivity between silicon and the oxide film (nitride film) is large, so that the etching is sharply reduced in the oxide film layer. Not etched. As a result, the management of the etching process can be reduced. As a further effect, any type of substrate can be used, and the silicon surface can be prevented from being roughened by ink or the like.

According to a fourth aspect of the present invention, in the second or third aspect of the present invention, since the thickness of the laminated structure of the single crystal silicon and the insulator is a desired thickness of the diaphragm, the insulator layer is etched. Is sharply reduced, so that a variation in film thickness is small and a highly accurate diaphragm can be obtained.

According to a fifth aspect of the present invention, in the second aspect of the present invention, the insulator has a thickness of 0.1 to 0.1.
Since it is 0.5 μm, it can sufficiently withstand over-etching, and there is no inconvenience such as generation of residual stress of the diaphragm.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an SOI technique used for an inkjet head and a method of manufacturing the same according to the present invention.

FIG. 2 is a diagram for explaining an SOI technique used in an inkjet head and a method of manufacturing the same according to the present invention.

FIG. 3 is a main part configuration diagram for explaining an embodiment of an ink jet head according to the present invention.

FIG. 4 is a view for explaining one embodiment of a method of manufacturing a diaphragm of an ink jet head according to the present invention.

FIG. 5 is a diagram for explaining evaluation of the SOI structure material used in the example shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 1a, 1b ... Single crystal silicon substrate, 1c ... Polished part, 1d ... Exposed part, 2a, 2b, 2c ... Oxide film,
Reference numeral 3 denotes a vibration plate, 4 denotes an upper substrate, 5 denotes a lower substrate, 6 denotes a nozzle hole, 7 denotes an insulating film, 8 denotes an electrode, 9 denotes a discharge chamber, t ₁ denotes a thickness of the vibration plate 3, and t ₂ denotes a thickness of the substrate 1. Thickness, t ₃ ... oxide films 2b, 2c
Thickness.

Claims (5)

[Claims] 1. An ink jet head for discharging ink droplets by deforming a diaphragm by electrostatic force, wherein an SOI (Silicon on Insulator) structural material is used for the diaphragm, and a method of manufacturing the same. 2. The ink-jet head according to claim 1, wherein the SOI structural material has a laminated structure in which an insulator is sandwiched between single-crystal silicon. 3. The ink-jet head according to claim 2, wherein the insulator is made of an oxide film or a nitride film. 4. The inkjet head according to claim 2, wherein the thickness of the laminated structure of the single crystal silicon and the insulator is a desired thickness of the diaphragm. 5. The insulator having a thickness of 0.1
The inkjet head according to any one of claims 2 to 4, wherein the thickness is from 0.5 to 0.5 m.