JP2004249743A - Manufacturing method for inkjet head and inkjet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture an inkjet head that can efficiently form a high precision vibrating plate and can achieve stable high quality printing. <P>SOLUTION: The inkjet head, the component member of which is made of an Si substrate 41, discharges ink by the deformation of the vibration plate formed on the Si substrate. The vibrating plate 5 is made of a high density p-type impurity layer. The p-type impurity layer is formed by coating the surface of the Si substrate 41 with a diffusing agent 45 in which an impurity diffusion source is dispersed in an organic solvent and thermally diffusing the diffusion source. The diffusion treatment is repeated more than once. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an ink-jet head, which is a main part of an ink-jet head recording apparatus for ejecting ink droplets only when recording is required and attaching the ink droplets to a recording paper surface, and a method of manufacturing the same.

Print heads for ink jet printers require precision fine processing and complicated desired shapes due to the demand for high-definition printing. In particular, electrostatic force as disclosed in JP-A-6-71882 is used as a driving source. Inkjet head
In other words, the mechanical deformation characteristics of the diaphragm greatly affect the ink ejection characteristics, and it is necessary to control the thickness of the diaphragm with high accuracy. Conventionally, when a diaphragm is formed by etching a Si substrate, a method of controlling the thickness of the diaphragm by controlling the etching time has been adopted. However, as ink jet heads have become smaller and have higher performance, the diaphragm has become thinner, and when thickness accuracy is required, it has become difficult only by controlling the etching time. Therefore, using an etch stop technique as described in JP-A-6-71882, page 20, line 15, utilizing the fact that the etching rate of the p-type impurity layer is low, only the p-type impurity layer is left by etching. A method of forming a thin film serving as a diaphragm has been adopted.

  As a method for forming the p-type impurity layer, there are a vapor phase diffusion method using a liquid / solid as a source, an ion implantation method, and a coating method in which a diffusion source is directly coated on a Si substrate.

  However, the conventional p-type impurity layer forming method has the following problems.

  In the case of the ion implantation method, there is a problem that an expensive implantation apparatus is required or that there is a limit in the concentration and depth at which doping is possible. Further, in the vapor phase diffusion method, since the gas is in contact with the substrate, the concentration of the diffusion source on the substrate surface is low, and it is difficult to diffuse deeply to a high concentration. On the other hand, in the impurity diffusion by the coating method, since a solid high-concentration diffusion source is in contact with the Si substrate, high-concentration and short-time diffusion is possible as compared with the gas-phase diffusion method in which a gas is in contact. However, although it is a coating method that is more suitable as a high concentration diffusion method than the ion implantation method and the gas phase diffusion method, the diffusion source is a diffusion agent coated on the substrate before diffusion, and the diffusion capacity of the diffusion agent is limited. It is. That is, there is a limit to the thickness of the diffusing agent that can be coated due to the reason of ensuring uniformity. Therefore, if diffusion is performed for a long period of time to form a deep diffusion region, the diffusion source in the finite diffusion agent is depleted, and the diffusion capability of the diffusion agent is reduced. Was.

  Further, when a high-concentration impurity layer is formed only on one side of the substrate, when the thickness of the substrate is small, there is a problem that a concave type warpage is generated toward the high-concentration impurity layer formation side due to the tensile stress of the high-concentration impurity layer. .

  An object of the present invention is to provide a method of forming a deep high-concentration impurity layer necessary for obtaining a desired thickness of a diaphragm in an ink jet head using a p-type impurity layer as a diaphragm.

  It is another object of the present invention to provide a method for reducing substrate warpage caused by forming a high-concentration impurity layer.

The method of manufacturing an ink jet head according to the present invention includes a nozzle hole for discharging ink droplets, a discharge chamber connected to each of the nozzle holes, a diaphragm constituting at least one wall of the discharge chamber, and the diaphragm And a driving means for causing deformation of the diaphragm, wherein the driving means comprises an electrode for deforming the vibration plate by electrostatic force, wherein the substrate on which the vibration plate is formed is a Si substrate, the method of manufacturing an inkjet head,
A high concentration p-type impurity layer is formed on both surfaces of the Si substrate, and a layer in which the concentration of the p-type impurity changes steeply is provided by performing diffusion of the p-type impurity a plurality of times on both surfaces or one surface. Forming a high concentration p-type impurity layer,
Forming a thermal oxide film on the Si substrate on which the p-type impurity layer is formed;
Forming a pattern as a mask on the thermal oxide film,
By etching the Si substrate, the discharge chambers connected to each of the nozzle holes are formed, and the p-type impurity layer is left to form a diaphragm having a reduced surface roughness of the etched surface. It is characterized by the following.
A nozzle hole for discharging the ink droplets, a discharge chamber connected to each of the nozzle holes, a vibration plate constituting at least one wall of the discharge chamber, and a driving means for causing deformation of the vibration plate. Wherein the driving means comprises an electrode for deforming the diaphragm by electrostatic force, and wherein the substrate on which the diaphragm is formed is a Si substrate.
Forming a high concentration p-type impurity layer on both surfaces of the Si substrate,
Forming a thermal oxide film on the Si substrate on which the p-type impurity layer is formed;
In order to form the discharge chamber connected to each of the nozzle holes, a pattern serving as a mask is formed on the thermal oxide film,
Etching the Si substrate with the pattern of the thermal oxide film, digging the Si substrate to form the discharge chamber, and leaving the p-type impurity layer as a diaphragm,
In the etching step, a jig for protecting a surface serving as the diaphragm from etching is used.
Further, the thickness of the high-concentration p-type impurity layer formed on both surfaces of the Si substrate is changed depending on each surface.
Further, by performing the step of forming the p-type impurity layer a plurality of times, the thickness of the high-concentration p-type impurity layer formed on both surfaces of the Si substrate is made uniform.

  Further, an ink jet printer of the present invention is characterized in that a head manufactured by the method for manufacturing an ink jet head is used.

  As a method of forming a diaphragm in a method of manufacturing an ink jet head, utilizing the fact that a highly doped p-type region has a very low etching rate in Si etching with alkali, a high concentration impurity diffusion layer is left as a diaphragm. It forms by doing. Therefore, the thickness of the high-concentration impurity diffusion layer becomes the thickness of the diaphragm. In the method for forming the high-concentration impurity layer, the diaphragm having a desired thickness can be formed in a short time by performing impurity diffusion plural times and increasing the thickness of the high-concentration impurity diffusion layer.

  Further, by forming the high-concentration impurity diffusion layers on both surfaces of the substrate, the substrate can be relaxed due to the stress of the high-concentration impurity diffusion layers.

  Hereinafter, an inkjet head according to a preferred example of the present invention will be described in detail.

  FIG. 1 is an exploded perspective view of the ink jet head according to the first embodiment, which is shown in a partial sectional view. This embodiment shows an example of a face ink jet type in which ink droplets are ejected from nozzle holes provided on the surface of a substrate. FIG. 2 is a cross-sectional side view of the assembled overall apparatus, and FIG. 3 is a view taken along line AA of FIG.

  The ink jet head of this embodiment has a laminated structure in which three substrates 1, 2, and 3 having a structure described in detail below are stacked and joined.

The intermediate first substrate 1 is a Si substrate, and has a concave portion 7 for forming a discharge chamber 6 having a bottom wall as a vibration plate 5 and an orifice 8 provided at a rear portion of the concave portion 7. And a concave portion 11 which forms a common ink cavity 10 for supplying ink to each ejection chamber 6. An oxide film 12 is formed on the entire surface of the first substrate 1 by thermal oxidation to a thickness of 0.1 μm to form an insulating film.
A film is formed to prevent dielectric breakdown and short circuit during ink jet driving.

  The second substrate 2 bonded to the lower surface of the first substrate 1 is made of borosilicate glass, and the concave portion 14 for mounting the electrode 13 on the substrate 2 is etched by 0.3 μm to form the diaphragm 5. A gap G is formed between the electrode 13 and the electrode 13 disposed opposite thereto. The recess 14 is formed in a slightly larger pattern similar to the shape of the electrode so that the electrode 13, the lead 15 and the terminal 16 can be mounted therein. The electrode 13 is manufactured by sputtering ITO into the recess 14 by 0.1 μm to form an ITO pattern.

  Therefore, the gap G after the first substrate 1 and the second substrate 2 are anodically bonded in this embodiment is 0.2 μm.

  Further, as the third substrate 3 bonded to the upper surface of the first substrate 1, a 100 μm-thick Si substrate is used, and nozzles are formed on the surface of the substrate 3 so as to communicate with the recesses 7 for the discharge chamber 6. A hole 17 is provided, and an ink supply port 18 is provided so as to communicate with the concave portion 11 for the ink cavity 10.

  The operation of the inkjet head configured as described above will be described. When a pulse potential of 0 V to 35 V is applied to the electrode 13 by the transmission circuit 19 and the surface of the electrode 13 is positively charged, the corresponding lower surface of the diaphragm 5 is charged to a negative potential. Therefore, the diaphragm 5 bends downward due to the electrostatic attraction. Next, when the electrode 13 is turned off, the diaphragm 5 is restored. Therefore, the pressure in the ejection chamber 6 rapidly rises, and the ink droplet 20 is ejected from the nozzle hole 17 toward the recording paper 21. Next, the diaphragm 5 bends downward again, so that ink is supplied from the ink cavity 10 into the ejection chamber 6 through the orifice 8. The connection between the substrate 1 and the transmission circuit 19 is made in a window (not shown) of the oxide film 12 opened in a part of the substrate 1 by dry etching.

The diaphragm 5 in the ink-jet head of this embodiment is a high-concentration B (boron) doped layer, and the doped layer has the same thickness as the desired diaphragm thickness. When the dopant is B, the etching rate in Si etching with alkali is extremely small in a high concentration region (about 5 × 10 ¹⁹ cm ⁻³ or more) (FIG. 5). In this embodiment, taking advantage of this fact, the diaphragm forming region is a high-concentration B-doped layer, and when forming a discharge chamber and an ink cavity by alkaline anisotropic etching, etching is performed when the B-doped layer is exposed. The diaphragm 5 is manufactured to have a desired thickness by a so-called etch stop technique in which the rate becomes extremely small.

  The manufacturing method of the first substrate 1 of the ink jet head according to the present embodiment corresponds to the case where the 4 μm diaphragm 5 is formed by using B (boron) as an impurity diffusion source in the manufacturing process diagram of the first substrate of FIG. Will be described in detail.

First, both surfaces of a Si substrate having a plane orientation of (110) are mirror-polished to produce a substrate 41 having a thickness of 180 μm (FIG. 4A). The Si substrate 41 is set in a thermal oxidation furnace and subjected to a thermal oxidation treatment in an atmosphere of oxygen and water vapor at 1100 degrees Celsius for 4 hours to form an oxide film 42 of 1 μm on the surface of the substrate 41 (FIG. 4B). . Next, in order to peel off the oxide film 42 on the surface 43 on which the B-doped layer is formed, a resist is coated on the surface 44 of the substrate 41 opposite to the surface 43 on which the B-doped layer is formed, and the B-doped layer is formed using the resist as a protective film. The oxide film 42 on the surface 43 to be formed is removed by etching with a hydrofluoric acid aqueous solution, and the resist is stripped (FIG. 4C). A diffusion agent 45 in which 3.15 w% of B ₂ O _{3 serving} as a diffusion source is dispersed in an organic solvent is spin-coated on the surface 43 from which the oxide film 42 has been removed at 2,000 rpm for 1 minute, and then centrifuged in a clean oven. Bake at a temperature of 140 ° C. for 30 minutes (FIG. 4D). At this time, the thickness of the diffusing agent is 1.2 μm. It is desirable that the diffusing agent 45 can be coated thickly, and a method of increasing the film thickness by lowering the spin speed or increasing the concentration of B ₂ O ₃ in the diffusing agent can be considered. Thickness variation is large, the latter is the uniformity of dispersion
The above-mentioned coating conditions are the best conditions for the currently available diffusing agents.

The substrate 41 coated with the diffusing agent 45 is set in a thermal oxidation furnace, and heated in an oxygen atmosphere at 600 degrees Celsius to oxidize and remove the organic binder in the diffusing agent 45 and bake B ₂ O ₃ . Subsequently, the inside of the furnace is set to a nitrogen atmosphere, the temperature is increased to 1100 degrees Celsius, the temperature is maintained for 6 hours, B is diffused into the Si substrate, and a B-doped layer 46 is formed. A boron compound 47 is formed at the interface between B ₂ O ₃ and the B-doped layer on the substrate surface (FIG. 4E). When the furnace temperature is lowered, the substrate 41 is taken out and the diffusing agent coating is repeated to form the second diffusing agent layer 48 on the diffusing agent 45. Further, firing and diffusion are performed to increase the thickness of the B-doped layer 46 (FIG. 4F). Similarly, a diffusing agent coating is performed to form a third diffusing agent layer 49, which is baked and diffused, and the B-doped layer 46 is further thickened (FIG. 4 (g)).

A resist is coated on the side 44 opposite to the surface on which the B-doped layer 46 is formed, and the diffusing agent 45 is removed by etching with a hydrofluoric acid aqueous solution. Since the boron compound 47 appearing on the substrate surface has high etching resistance and cannot be removed by wet etching, the following means is employed. First, after the resist of the substrate 41 is removed, the substrate 41 is set in an oxidation furnace, and the boron compound 47 is oxidized for 1 hour under the conditions of oxygen and water vapor at 600 degrees Celsius, and B ₂ which can be etched with a hydrofluoric acid aqueous solution. It is chemically changed to O ₃ + SiO ₂ 50 (FIG. 4 (h)). Since the oxidation temperature is low, diffusion does not proceed, and the boron compound 47 can be removed by dry etching.

Subsequently, resist patterning for forming the ejection chamber 6 and the ink cavity 9 is performed on the oxide film side 44, and the oxide film 42 is patterned by etching with a hydrofluoric acid aqueous solution, and B ₂ O ₃ + SiO ₂ 50 is removed by etching. . Then, the resist on the substrate 41 is removed (FIG. 4 (i)).

  The substrate 41 is immersed in a 10% by weight aqueous solution of potassium hydroxide, and Si etching is performed. The substrate 41 is etched from the portion 51 where Si is exposed on the side where the oxide film 42 is patterned, and when the substrate 41 reaches the B-doped layer 46, the etching is stopped and the B-doped layer 46 is left. 46 becomes the diaphragm 5 (FIG. 4 (j)). At the time of the etching, the B-doped layer forming side 43 is protected by a jig so that the B-doped layer forming side 43 is not etched. Use an aqueous solution.

  Finally, after the oxide film 42 remaining on the substrate 41 is removed by etching using a hydrofluoric acid aqueous solution, the oxide film 12 is formed on the surface of the substrate 41 by thermal oxidation to a thickness of 0.1 μm, whereby the first substrate 1 is manufactured. .

  By the above method, a diaphragm having a thickness accuracy of 4 ± 0.2 μm can be manufactured.

The diffusion was completed without using a protective jig, and the boron compound 47 on the diffusion surface was oxidized to be chemically changed to B ₂ O ₃ + SiO ₂ 50 (FIG. 4 (h)), and further thermally oxidized. It is also possible to form a 1 μm oxide film on the B-doped layer side and perform Si etching using the oxide film as an etching-resistant film. However, in the above method, erosion of the substrate surface due to growth of the oxide film and thermal oxidation As the thickness of the high-concentration B-doped layer decreases due to the internal diffusion of B from the B-doped layer due to the heating, the thickness of the obtained diaphragm decreases.

  The effect of repeating diffusion a plurality of times in the method of manufacturing an ink jet head according to the present embodiment will be described with reference to FIGS. 5, 6, and 7. FIG.

FIG. 6 shows the results of measuring the change in the thickness of the obtained diaphragm while changing the number of times of diffusion while keeping the diffusion time constant. The thickness of the diaphragm obtained by two or three diffusions is greater than the thickness of the diaphragm obtained by one diffusion. In the case of diffusion for 18 hours, a diaphragm having a thickness of 3.4 μm is obtained by one diffusion for 18 hours, whereas a diaphragm having a thickness of 4.0 μm is obtained by three diffusions for 6 hours. I have. Therefore, increase the number of spreads
Thus, a diaphragm having a desired thickness can be manufactured with a shorter total diffusion time. On the other hand, when a diaphragm having a thickness exceeding 3.5 μm is to be obtained by one diffusion, it cannot be manufactured because the B supply capability of the diffusion source is significantly reduced.

FIG. 7 shows the result of measuring the thickness accuracy of a diaphragm manufactured by changing the number of times of diffusion. This shows that when the diaphragm is formed by performing the diffusion multiple times, the roughness of the etched surface of the diaphragm can be reduced. This is because the diffusion state of B changes due to the repetition of the diffusion, and the change in the B concentration near the threshold of 5 × 10 ¹⁹ cm ^{−3 of the} etching rate decrease shown in the H portion of FIG. is there.

  As described above, the effects of performing the diffusion multiple times in the coating method are summarized as follows.

  (1) The diffusion time in forming the doped layer can be reduced.

  (2) A thick doped layer that cannot be formed by one diffusion can be formed.

  (3) A diaphragm with high plate thickness accuracy can be formed.

  Next, a method of manufacturing the first substrate 1 of the inkjet head according to the second embodiment of the present invention will be described in detail with reference to a manufacturing process diagram shown in FIG. Note that a diffusion step that is the same as the manufacturing step in the first embodiment is partially omitted.

First, both surfaces of a Si substrate having a plane orientation of (110) are mirror-polished to produce a substrate 81 having a thickness of 180 μm (FIG. 8A). A diffusing agent 82 is spin-coated on both surfaces of the substrate 81 at 2000 rpm for 1 minute, and baked in a clean oven at a temperature of 140 degrees Celsius for 30 minutes (FIG. 8B). The substrate 81 coated with the diffusing agent 82 is set in a thermal oxidation furnace, baked, and diffused for 6 hours to form a B-doped layer 83. Similarly, repeat the diffusion agent coating, firing and diffusion twice,
Further, the B-doped layer 83 is formed thick. Then, the diffusing agent 82 is removed by etching with a hydrofluoric acid aqueous solution, and the boron compound formed on the surface is oxidized in the same manner as the method described in Example 1. Then, the boron compound is oxidized to form B ₂ O _3. + SiO ₂ is removed with a hydrofluoric acid aqueous solution (FIG. 8C). The substrate 81 is set in a thermal oxidation furnace, and thermally oxidized in an atmosphere of oxygen and water vapor at 1100 ° C. for 4 hours to form an oxide film 84 having a thickness of 1 μm on the surface of the substrate 81 (FIG. 8D).

  The diffusion time is extended in consideration of the erosion of the substrate surface due to the oxide film growth described in Example 1 and the decrease in the thickness of the high-concentration B-doped layer due to the internal diffusion of B from the B-doped layer due to heating during thermal oxidation. Needless to say.

  Next, resist patterning for forming the ejection chamber 6 and the ink cavity 9 is performed on one side of the substrate 81, and the oxide film 84 is etched and patterned using an aqueous hydrofluoric acid solution, and the resist is peeled off (FIG. 8). (E)). Subsequently, the Si substrate 81 is etched using a 10% by weight aqueous solution of potassium hydroxide to form the diaphragm 5 in the same manner as in Example 1 (FIG. 8F). Although the etching starts from the exposed portion 85 of Si, the etching does not proceed very much due to the presence of the B-doped layer 83, and the etching time becomes longer by the time required to etch the B-doped layer 83.

  Finally, the first substrate 1 is completed by removing the oxide film 84 remaining on the substrate 81 and forming a 0.1 μm-thick oxide film 84 on the substrate 81 by thermal oxidation.

  In the manufacturing method described above, since the high-concentration B-doped layers are formed on both surfaces of the Si substrate, the stress of the high-concentration B-doped layer cancels out on the front and back of the substrate to eliminate the warpage of the first substrate 1. Was completed. By eliminating the warpage of the first substrate 1, the bonding strength between the first substrate 1 and the second and third substrates 2 and 3 bonded to the first substrate 1 is increased.

  According to the present invention, in forming a diaphragm manufactured by the etch stop technique, a p-type impurity diffusion layer having a thickness required to obtain a desired diaphragm thickness and impossible in a single diffusion is required. Can be formed. Further, by performing the diffusion a plurality of times, the B concentration change can be made steep, and a diaphragm with high plate thickness accuracy can be formed.

  Furthermore, by forming a high-concentration impurity layer on both sides of the substrate, particularly when the substrate is thin, it is possible to prevent a concave-type warp generated toward the side where the high-concentration impurity layer is formed due to the tensile stress of the high-concentration impurity layer. Can be. By preventing the warpage of the substrate, the bonding strength with the borosilicate glass at the time of assembling the print head can be increased.

FIG. 2 is an exploded perspective view showing a structure of the inkjet head according to the first embodiment of the present invention. FIG. 2 is a cross-sectional side view of the method of manufacturing the inkjet head according to the first embodiment of the present invention. FIG. 3 is a view taken along line AA of FIG. 2. FIG. 5 is a manufacturing process diagram of the first substrate of the inkjet head according to the first embodiment of the present invention. FIG. 4 is a diagram illustrating a relationship between a B concentration and an etching rate in alkali anisotropic etching. FIG. 4 is a diagram illustrating a relationship between the number of times of diffusion and the thickness of the diaphragm in the method of manufacturing an ink jet head according to the first embodiment of the present invention. FIG. 4 is a diagram illustrating a relationship between the number of times of diffusion and the thickness accuracy of the diaphragm in the method of manufacturing an ink jet head according to the first embodiment of the present invention. FIG. 7 is a manufacturing process diagram of a first substrate according to a second embodiment of the present invention.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 1st board | substrate 2 2nd board | substrate 3 3rd board | substrate 5 Vibration plate 6 Discharge chamber 8 Orifice 10 Ink cavity 12 Oxide film 13 Electrode 17 Ink hole 18 Ink supply port 41 Substrate 42 Oxide film 45 Diffusing agent 46 B dope layer 47 Boron compound 81 Substrate 82 Diffusing agent 83 B-doped layer

Claims (5)

A nozzle hole for discharging ink droplets, a discharge chamber connected to each of the nozzle holes, a diaphragm constituting at least one wall of the discharge chamber, and a driving means for causing deformation of the diaphragm A manufacturing method of an inkjet head, wherein the driving unit includes an electrode that deforms the vibration plate by electrostatic force, and a substrate on which the vibration plate is formed is a Si substrate.
A high concentration p-type impurity layer is formed on both surfaces of the Si substrate, and a layer in which the concentration of the p-type impurity changes steeply is provided by performing diffusion of the p-type impurity a plurality of times on both surfaces or one surface. Forming a high concentration p-type impurity layer,
Forming a thermal oxide film on the Si substrate on which the p-type impurity layer is formed;
Forming a pattern as a mask on the thermal oxide film,
By etching the Si substrate, the discharge chamber connected to each of the nozzle holes is formed, and the p-type impurity layer is left to form a diaphragm having a reduced surface roughness of the etched surface. A method for manufacturing an ink-jet head, comprising: A nozzle hole for discharging ink droplets, a discharge chamber connected to each of the nozzle holes, a diaphragm constituting at least one wall of the discharge chamber, and a driving means for causing deformation of the diaphragm A manufacturing method of an inkjet head, wherein the driving unit includes an electrode that deforms the vibration plate by electrostatic force, and a substrate on which the vibration plate is formed is a Si substrate.
Forming a high concentration p-type impurity layer on both surfaces of the Si substrate,
Forming a thermal oxide film on the Si substrate on which the p-type impurity layer is formed;
In order to form the discharge chamber connected to each of the nozzle holes, a pattern serving as a mask is formed on the thermal oxide film,
Etching the Si substrate with the pattern of the thermal oxide film, digging the Si substrate to form the discharge chamber, and leaving the p-type impurity layer as a diaphragm,
A method for manufacturing an ink jet head, comprising using a jig for protecting a surface serving as the vibration plate from etching in the etching step. 3. The method according to claim 1, wherein the thickness of the high-concentration p-type impurity layer formed on both surfaces of the Si substrate is changed depending on each surface. The method according to claim 1, wherein the step of forming the p-type impurity layer is performed a plurality of times to make the thickness of the high-concentration p-type impurity layer formed on both surfaces of the Si substrate uniform. A method for manufacturing the inkjet head according to the above. An ink-jet printer using a head manufactured by the method for manufacturing an ink-jet head according to claim 1.

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