JP4120317B2 - Inkjet head manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet head for discharging various solutions such as ink droplets and a recording apparatus equipped with the ink jet head.
[0002]
[Prior art]
Ink jet recording apparatuses have been increased in number of nozzles in order to cope with high-speed printing, and minute actuators have been required due to the demand for higher resolution. For this reason, an ink jet head using an electrostatic force as an actuator has been proposed.
As disclosed in Japanese Patent Laid-Open No. 11-993, an electrostatically driven ink jet head includes a Si cavity substrate on which a discharge chamber and a reservoir are formed, an electrode glass substrate provided with electrodes, and a nozzle provided with nozzle holes. Three substrates are stacked and configured. The Si cavity substrate needs to be thinned to prevent so-called crosstalk, which causes ink to be ejected from the adjacent non-driven nozzles, but if it is made thin from the beginning, cracks are likely to occur during handling. In addition, it is difficult to increase the diameter of the Si substrate from which the Si cavity substrate is taken out. Therefore, in the manufacture of the electrostatic drive type ink jet head, the Si cavity substrate and the electrode glass substrate are joined, and then the Si cavity substrate is thinned, and then a discharge chamber and the like are formed.
[0003]
[Problems to be solved by the invention]
However, in the process of thinning the Si cavity substrate by wet etching, there is a problem in that the etchant enters the bonding interface between the Si cavity substrate and the glass substrate to cause a diaphragm defect. Further, in the case where the thin plate is not formed by wet etching, there is a problem that the manufacturing cost increases because grinding or the like is performed.
Further, when the Si cavity substrate is thinned, the surface of the substrate becomes rough, and the patterning accuracy of the discharge chamber and the reservoir is deteriorated.
The present invention has been made in view of the above problems, and prevents the occurrence of a diaphragm defect caused by an etching solution. Further, the surface of the thinned Si cavity substrate is made as flat as possible to improve productivity and manufacture. An object is to improve the reliability of the inkjet head. Another object of the present invention is to provide a recording apparatus using the inkjet head.
[0004]
[Means for Solving the Problems]
The method according to the first aspect of the present invention includes an ink discharge chamber, a nozzle hole and an ink supply port communicating with the discharge chamber, a vibration plate formed on a lower surface of the discharge chamber, and a space facing the vibration plate. An inkjet head manufacturing method, wherein a voltage is applied between the diaphragm and the electrode to deform the diaphragm and eject ink droplets from the nozzle holes. After the first substrate and the second substrate having the electrode and the ink supply port are joined, the thickness of the first substrate is reduced by wet etching, and the discharge chamber and the diaphragm In this method, after the first substrate and the second substrate are bonded, the inner region of the ink supply port is formed with a SiO ₂ film or a SiN film before etching the first substrate. It is characterized by.
According to this, since the surface where the first substrate and the second substrate are joined does not come into contact with the etching solution, the etching solution does not enter from the surface, and the occurrence of the diaphragm defect is suppressed. . In addition, the SiO2 film or SiN film formed in the inner region of the ink supply port prevents the etching liquid from entering the bonding interface between the first substrate and the second substrate from the ink supply port. Also from this point, the occurrence of diaphragm defects is suppressed.
In addition, an insulating film is formed by plasma CVD on a bonding surface between the first substrate and the second substrate before the bonding between the first substrate and the second substrate. By this plasma CVD, an insulating film with a more uniform breakdown voltage can be formed. The SiO ₂ film or SiN film is formed by plasma CVD. Since TEOS (tetraethoxysilane) that can be used as these raw materials is less ignitable than other materials, it is easy to handle.
[0005]
According to a second aspect of the present invention, there is provided an ink discharge chamber, a nozzle hole and an ink supply port communicating with the discharge chamber, a vibration plate formed on a lower surface of the discharge chamber, and facing the vibration plate with a gap. An inkjet head manufacturing method, wherein a voltage is applied between the diaphragm and the electrode to deform the diaphragm and eject ink droplets from the nozzle holes. After joining the first substrate and the second substrate having the electrode and the ink supply port, the thickness of the first substrate is reduced by wet etching to reduce the discharge chamber and the vibration. In the method of forming a plate, a potassium hydroxide solution having a different concentration is used, and the first substrate is roughly processed by a potassium hydroxide solution having a higher concentration, and then the potassium hydroxide having a lower concentration is used. Wherein the solution performs finishing etching the first substrate.
As a result, the processed surface of the first substrate is further flattened, and as a result, variations in ink discharge characteristics can be reduced, thereby improving the reliability of the inkjet head. In addition, since a potassium hydroxide solution is used as an etching solution, it is possible to reduce the thickness at a low cost.
Note that, when the top surface and the diaphragm surface of the first substrate are formed by wet etching, potassium hydroxide solutions having different concentrations are used to switch from roughing to finishing. According to this, since the processing surface is further flattened, patterning accuracy and adhesion between the first substrate and the nozzle substrate are improved, and surface roughness of the vibration plate surface is suppressed, resulting in variations in ink ejection characteristics. Since this can be reduced, the reliability of the inkjet head is improved.
The first concentration value is selected from a range of 36 wt% to 40 wt% aqueous solution of potassium hydroxide, and the second concentration value is 30 wt% to less than 36 wt% aqueous solution of potassium hydroxide. It is characterized by selecting from the range of the range. In addition, after the first substrate and the second substrate are bonded, the inner region of the ink supply port is formed with a SiO ₂ film before the first substrate is etched. This prevents the etchant from entering the bonding interface between the first substrate and the second substrate from the ink supply port, and can also reduce the occurrence of diaphragm defects.
[0006]
The above method also has the following advantages. That is, since the first substrate is thinned after the first substrate is bonded to the second substrate, the Si substrate that is the first substrate is not easily broken, and a relatively thick Si substrate can be handled. The diameter of the Si substrate can be increased. Further, since the number of heads is increased by increasing the diameter of the Si substrate, the cost of the inkjet head can be reduced.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an exploded perspective view of an inkjet head manufactured by a method according to an embodiment of the present invention, which will be described later, and a part thereof is shown in a sectional view. FIG. 1 shows an example of a face inkjet head that ejects ink droplets from nozzle holes provided on the surface of the substrate, but the present invention is not particularly limited to that type. 2 is a side sectional view of the assembled entire apparatus, and FIG. 3 is a view taken along the line AA ′ in FIG. This ink jet head has a laminated structure in which three sheets of a first substrate 1, a second substrate 2, and a third substrate 3 having a structure described in detail below are overlapped and joined.
[0009]
The intermediate first substrate 1 is called a cavity substrate and is made of Si or the like. The first substrate 1 constitutes a recess 6 that constitutes a discharge chamber 5 whose bottom wall is a diaphragm 4 and a common reservoir 9 for supplying ink to each discharge chamber 5. A recess 10 is provided. A TEOS film is formed on the entire surface of the first substrate 1 by plasma CVD so as to form an insulating film. This is to prevent dielectric breakdown and short-circuit during ink-jet driving and to prevent etching of the cavity substrate by ink.
[0010]
The second substrate 2 bonded to the lower surface of the first substrate 1 is a glass substrate and is made of borosilicate glass or the like. On the second substrate 2, a recess 13 for mounting the electrode 12 is etched by 0.3 μm, thereby forming a gap between the diaphragm 4 and the electrode 12 disposed opposite thereto, that is, a gap G. It has come to be. The concave portion 13 is patterned in a slightly larger shape similar to the electrode portion shape so that the electrode 12, the lead portion 14, and the terminal portion 15 can be mounted therein. Therefore, the gap G after the anodic bonding of the first substrate 1 and the second substrate 2 in this example is 0.2 microns.
[0011]
The third substrate 3 bonded to the upper surface of the first substrate 1 is called a nozzle substrate, and a Si substrate having a thickness of 100 microns is used. Nozzle holes 16 are provided in the surface portion of the third substrate 3 so as to communicate with the discharge chamber recess 6 of the first substrate 1, and an orifice 7 is formed to communicate the discharge chamber recess 6 and the reservoir recess 10. A narrow groove 8 is provided for the ink inlet to be used.
[0012]
The ink jet head configured as described above operates as follows. That is, when a pulse electrode of 0 V to 35 V is applied to the electrode 12 by the transmission circuit 18 and the surface of the electrode 12 is positively charged, the lower surface of the corresponding diaphragm 4 is charged to a negative potential. Therefore, the diaphragm 4 bends downward due to electrostatic attraction. Next, when the electrode 12 is turned off, the diaphragm 4 is restored. For this reason, the pressure in the discharge chamber 5 rapidly increases, and the ink droplet 19 is discharged from the nozzle hole 16 toward the recording paper 20. Next, the vibration plate 4 bends downward again, whereby ink is supplied from the reservoir 9 into the discharge chamber 5 through the orifice 7. Note that the connection between the first substrate 1 and the transmission circuit 18 is made in a window (not shown) of an oxide film opened in a part of the first substrate 1 by dry etching. Ink supply to the ink jet head is performed from an ink supply port 17 penetrating the first substrate 1 and the second substrate 2 from the bottom surface of the reservoir 9.
[0013]
Next, a method for manufacturing the inkjet head will be described. FIG. 4 is a process diagram showing an example of a manufacturing process of the ink jet head shown in FIG. 1, and will be described along the illustrated processes (a) to (j).
[0014]
(A) ITO electrode 12 is formed by sputtering ITO (Indium Tin Oxide) into the recess 13 of the second substrate 2 which is a glass substrate by 0.1 micron to form an ITO pattern. Thereafter, a hole is drilled in the second substrate 2 to form an ink supply port 17.
[0015]
(B) One surface of the first substrate 1 which is a Si substrate having a plane index of (110) and a low oxygen concentration is mirror-polished to produce a substrate having a thickness of 525 microns. In order to remove fine particles and metal adhering to the mirror-polished surface (the surface on which the boron dope layer is formed), SC-1 cleaning (cleaning with a mixed solution of ammonia water and hydrogen peroxide solution), SC- Perform combination cleaning of 2 cleaning (cleaning with a mixture of hydrochloric acid and hydrogen peroxide).
Next, the surface on which the boron doped layer 41 of the first substrate 1 is formed is set on a quartz boat so as to face a solid diffusion source mainly composed of B2O3. A quartz boat is set in a vertical furnace, the inside of the furnace is made into a nitrogen atmosphere, the temperature is raised to 1050 degrees Celsius, the temperature is maintained as it is for 8 hours, and boron is diffused into the Si substrate to form the boron doped layer 41. In this boron doped layer generating step, the first substrate 1 is charged at 800 ° C. and the substrate 1 is taken out at 800 ° C. Thereby, since it can pass through a region (600 ° C. to 800 ° C.) where the growth rate of oxygen defects is high, generation of oxygen defects can be suppressed. A boron compound is formed on the surface of the boron doped layer 41, but it is chemically changed to B2O3 + SiO2 which can be etched with a hydrofluoric acid aqueous solution by oxidizing for 1 hour 30 minutes in an oxygen and water vapor atmosphere at 600 degrees Celsius. Can do. Then, B2O3 + SiO2 is removed by etching with a hydrofluoric acid aqueous solution in a state where it is chemically changed to B2O3 + SiO2.
Further, a TEOS insulating film 11 is formed on the surface of the boron doped layer 41 of the first substrate 1 by CVD (chemical vapor deposition). In this film formation, a 0.1 micron film is formed under the conditions of a processing temperature of 360 ° C., a high frequency output of 250 W, a pressure of 500 mTorr, a gas flow rate of TEOS flow rate of 100 sccm, and an oxygen flow rate of 1000 sccm. Before forming the TEOS insulating film 11, oxygen plasma treatment is performed under the conditions of a pressure of 0.5 torr, an oxygen flow rate of 1000 sccm, a high frequency output of 250 W, a treatment temperature of 360 ° C., and a treatment time of 1 minute. As a result, the surface of the first substrate 1 is cleaned, and the uniformity of the withstand voltage of the TEOS insulating film 11 can be improved.
[0016]
(C) After heating the first substrate 1 and the second substrate 2 to 360 ° C., the negative electrode is connected to the second substrate 2 and the positive electrode is connected to the first substrate 1, and a voltage of 800 V is applied, The first substrate 1 and the second substrate 2 are anodically bonded.
[0017]
(D) A TEOS protective film 42 is formed on the surface of the second substrate 2 opposite to the surface bonded to the first substrate 1, including the inner region of the ink supply port 17. In this film formation, a film of 3 microns is formed under the conditions of a processing temperature of 360 ° C., a high frequency output of 700 W, a pressure of 250 mTorr, a gas flow rate of TEOS flow rate of 100 sccm, and an oxygen flow rate of 1000 sccm. As a result, the inner region of the ink supply port 17, that is, the inner peripheral surface of the ink supply port 17 and the TEOS insulating film surface facing the ink supply port 17 of the first substrate 1 are covered with the TEOS protective film 42.
[0018]
(E) Subsequently, the entire bonded substrate is immersed in a potassium hydroxide solution, and the entire surface of the first substrate 1 is etched by 385 microns. This etching process is performed in two steps. First, etching is performed for 164 minutes with a 38 wt% aqueous solution of potassium hydroxide, and then etching is performed for 10 minutes with a 32 wt% aqueous solution of potassium hydroxide. In this way, by performing etching using two types of aqueous potassium hydroxide solutions having different concentrations, it is possible to suppress surface roughness of the etched processed surface and to suppress the occurrence rate of minimal protrusions. Thereby, the patterning accuracy on the first substrate 1 is improved, and the adhesion between the first substrate 1 and the third substrate 3 is also improved.
[0019]
(F) A TEOS etching mask 43 is formed on the etching surface of the first substrate 1. The film is formed at a processing temperature of 360 ° C., a high frequency output of 700 W, a pressure of 250 mTorr, a gas flow rate of TEOS flow rate of 100 sccm, and an oxygen flow rate of 1000 sccm.
Subsequently, resist patterning for forming the discharge chamber 5 and the reservoir 9 is performed on the TEOS etching mask 43, and the TEOS etching mask 43 is patterned by etching with a hydrofluoric acid aqueous solution. Thereafter, the resist is peeled off.
Further, the bonded substrate is immersed in a 35 wt% potassium hydroxide aqueous solution, and etching is performed until the thickness of the first substrate 1 becomes 10 microns. Subsequently, the substrate is immersed in a 3 wt% potassium hydroxide aqueous solution, and etching is continued until an etching stop due to a decrease in the etching rate in the boron doped layer 41 is sufficiently effective. Here, the term “etching stop” is defined as a state in which bubbles generated from the etching surface are stopped, and it is determined that etching is stopped when bubbles are stopped in actual etching. In this case as well, by performing etching using two types of potassium hydroxide solutions having different concentrations, the surface roughness of the diaphragm 4 can be suppressed and the thickness accuracy can be made 0.80 ± 0.05 microns or less. it can. Thereby, the discharge performance of an inkjet head can be stabilized.
[0020]
(G) After the Si etching on the first substrate 1 is completed, the entire substrate is immersed in a hydrofluoric acid aqueous solution, and the TEOS etching mask 43 on the surface of the first substrate 1 and the TEOS protective film 42 on the surface of the second substrate 2 are peeled off. To do. Thereafter, a TEOS film 45 is formed on the surface of the first substrate 1 by plasma CVD. The film is formed at a processing temperature of 360 ° C., a high frequency output of 250 W, a pressure of 500 mTorr, a gas flow rate of TEOS flow rate of 100 sccm, and an oxygen flow rate of 1000 sccm.
[0021]
(H) The ink supply port 17 is penetrated to the reservoir 9 by drilling. Thereafter, a silicon substrate having a thickness of 100 microns is used, nozzle holes 16 are respectively provided so as to communicate with the ejection chamber 5, and an orifice 7 that communicates with the ejection chamber 5 and the reservoir 9 is formed. The third substrate 3 provided with the narrow groove and further provided with the electrode extraction hole 44 is bonded to the first substrate 1 with an epoxy adhesive.
[0022]
(I) After bonding the third substrate 3 to the first substrate 1, in order to take out the electrode wiring, dry etching is performed to remove Si on the lower surface of the electrode take-out hole 44, and an electrode take-out port is opened. . Thereafter, the edge of the electrode outlet is sealed with an epoxy resin 46 for the purpose of preventing moisture and foreign matter from entering the actuator.
(J) Finally, each head is cut by dicing.
[0023]
By the way, the diaphragm 4 in the ink jet head obtained through the above steps is a high-concentration boron-doped layer 41, and the boron-doped layer has the same thickness as the desired diaphragm thickness. When the dopant is boron, the etching rate of Si etching with an alkaline solution is very low in a high concentration region (about 5 × 10 ¹⁹ cm ⁻³ or more). In this manufacturing method, using this fact, the diaphragm forming region is made a high-concentration boron-doped layer, and etching is performed when the boron-doped layer is exposed when forming the discharge chamber 5 and the reservoir 9 by alkali anisotropic etching. The diaphragm 4 is manufactured to a desired plate thickness by a so-called etching stop technique in which the rate becomes extremely small.
[0024]
In addition, since the first substrate 1 is thinned and the discharge chamber 5 and the like are formed after the first substrate 1 and the second substrate 2 are bonded together, a relatively thick Si substrate is formed on the first substrate 1. Can be used. For this reason, the handling of the first substrate 1 becomes easy, and the cracks can be reduced. In addition, since the diameter of the Si substrate, which is the material of the first substrate 1, can be increased, many inkjet heads can be taken out from a single Si substrate, and the productivity of the inkjet head can be improved. .
[0025]
In the thinning process of the first substrate 1, prior to the wet etching, the inner peripheral surface of the ink supply port 17 and the TEOS insulating film surface facing the ink supply port 17 of the first substrate 1 are TEOS protective films. Since it is covered, the potassium hydroxide solution as an etching solution is prevented from entering the bonding interface. Furthermore, in the thinning process of the first substrate 1, since the two-step etching process using two different concentrations of potassium hydroxide solution is performed, the surface roughness of the Si substrate after thinning is reduced at a low cost. Is reduced, and the surface is flattened.
[0026]
Next, an etching process using potassium hydroxide (KOH) solutions having different concentrations in the thinning process of the Si cavity substrate as the first substrate 1 will be described. In this step, since the entire surface of the Si substrate is etched by about 385 microns, a high-concentration potassium hydroxide aqueous solution that increases the etching rate is used. In wet etching using a potassium hydroxide aqueous solution, as shown in the graph of FIG. 6, the surface roughness decreases as the concentration of potassium hydroxide increases. However, when the concentration exceeds 40 wt%, this is a very small protrusion called a micropyramid. The rate of occurrence increases rapidly. Therefore, first, etching is performed with a potassium hydroxide aqueous solution in a concentration range that reduces the incidence of micropyramids while preventing an increase in surface roughness, and then a potassium hydroxide aqueous solution in a concentration range that hardly generates micropyramids. Etching is performed. In the present specification, for the sake of convenience, the former processing performed while preventing the increase in surface roughness and suppressing the occurrence rate of the micropyramid is referred to as rough processing etching, and the subsequent processing that hardly generates the micropyramid is performed for convenience. This is referred to as finish processing etching.
[0027]
The concentration range of the potassium hydroxide solution that reduces the incidence of micropyramids while preventing the increase in surface roughness is considered to be approximately 36 wt% or more and 40 wt% or less, preferably 37 wt% or more and 38 wt% or less. Further, the concentration range of the potassium hydroxide solution in which micropyramids hardly occur is considered to be less than about 36 wt%, but considering the processing speed, it is 30 wt% or more and less than 36 wt%, preferably 30 wt% or more and 32 wt%. It is as follows. The ratio between the rough etching and the finishing etching amount may be determined as appropriate. However, if the rough etching is performed about 90% of the total etching amount, the processing speed can be increased. In the experiment, after etching for 164 minutes with a 38 wt% potassium hydroxide aqueous solution, etching is performed for 10 minutes with a 32 wt% potassium hydroxide aqueous solution, thereby reducing the surface roughness and generating little micropyramids. Could be formed.
[0028]
By the way, the ink jet head 600 manufactured by the above method is assembled as shown in FIG. 7, for example, when it is mounted on an ink jet recording apparatus. That is, the inkjet head 600 is attached to a carriage 601 that is movable on the guide rail 602, and the position of the inkjet head 600 is controlled in the width direction of the paper 604 fed by the roller 603.
The ink jet head of the present invention is not limited to a recording apparatus, but can also be applied to a color filter, a filter material or organic EL material ejection device in manufacturing an organic EL, and other various solution ejection devices.
[0029]
In addition, each value related to the thickness of the substrate or etching, each value related to various film thicknesses, and other various condition values shown in the inkjet head manufacturing process described in the above embodiment are merely examples, The present invention is not limited to these values. Further, the TEOS film mentioned as the insulating film or the protective film is used as a general term for the SiO ₂ film or the SiN film. Needless to say, another film having properties equivalent to those of the SiO ₂ film or the SiN film may be formed. Furthermore, although the TEOS film is formed by plasma CVD in the above embodiment, the film forming method is not limited to this, and other possible methods may be used.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing the structure of an inkjet head manufactured by an embodiment according to the method of the present invention.
2 is a cross-sectional side view of the inkjet head in FIG.
3 is a view taken along the line AA ′ in FIG.
FIG. 4 is a manufacturing process diagram of an inkjet head showing an embodiment of the present invention.
FIG. 5 is a manufacturing process diagram of an inkjet head showing a process following FIG. 4;
FIG. 6 is a graph showing surface roughness and micropyramid (protrusion) generation rate with respect to a change in concentration of a potassium hydroxide solution.
FIG. 7 is a partial configuration diagram of a recording apparatus including the inkjet head according to the invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... 1st board | substrate (Si cavity board | substrate), 2 ... 2nd board | substrate (electrode glass substrate), 3 ... 3rd board | substrate (nozzle board | substrate), 4 ... Vibration plate, 5 ... Discharge chamber, 6 ... Recessed part, 7 ... Orifice, 8 ... Narrow groove, 9 ... Reservoir, 10 ... Recess, 11 ... TEOS insulating film, 12 ... Electrode, 13 ... Recess, 14 ... Lead part, 15 ... Terminal part, 16 ... Nozzle hole, 17 ... Ink supply port , 18 ... Transmitter circuit, 19 ... Ink droplet, 20 ... Recording paper, 41 ... Boron doped layer, 42 ... TEOS protective film, 43 ... TEOS etching mask, 44 ... Electrode extraction hole, 45 ... TEOS insulating film, 46 ... Epoxy resin.

Claims (7)

An ink discharge chamber, a nozzle hole and an ink supply port communicating with the discharge chamber, a vibration plate formed on a lower surface of the discharge chamber, and an electrode facing the vibration plate with a gap, the vibration plate and the A method of manufacturing an ink jet head that applies a voltage between an electrode and deforms the diaphragm to discharge ink droplets from the nozzle hole,
After joining the first substrate constituting the diaphragm and the second substrate having the electrode and the ink supply port, the thickness of the first substrate is reduced by wet etching, and the discharge chamber and In the method of forming the diaphragm,
An ink jet characterized in that an inner region of the ink supply port is formed with a SiO ₂ film or a SiN film after the first substrate and the second substrate are bonded and before the first substrate is etched. Manufacturing method of the head.   2. An insulating film is formed by plasma CVD on a bonding surface between the first substrate and the second substrate before the bonding between the first substrate and the second substrate. The manufacturing method of the inkjet head of description. The SiO ₂ film or the production method according to claim 1 or 2 inkjet head wherein a is formed by a plasma CVD using the SiN film. An ink discharge chamber, a nozzle hole and an ink supply port communicating with the discharge chamber, a vibration plate formed on a lower surface of the discharge chamber, and an electrode facing the vibration plate with a gap, the vibration plate and the A method of manufacturing an ink jet head that applies a voltage between an electrode and deforms the diaphragm to discharge ink droplets from the nozzle hole,
After the first substrate that constitutes the diaphragm and the second substrate having the electrode and the ink supply port are joined, the thickness of the first substrate is reduced by wet etching, and the discharge chamber is formed. And a method of forming the diaphragm,
Using the potassium hydroxide solutions having different concentrations, rough etching of the first substrate is performed with the higher concentration potassium hydroxide solution, and then the first substrate is performed with the lower concentration potassium hydroxide solution. A method of manufacturing an ink-jet head, comprising performing a finishing etching process.   5. The formation of the top surface and the diaphragm surface of the first substrate by wet etching is switched from rough processing to finishing processing using potassium hydroxide solutions having different concentrations. Manufacturing method of the inkjet head.   The value of the first concentration is selected from a range of 36 wt% to 40 wt% aqueous solution of potassium hydroxide, and the value of the second concentration is a range of 30 wt% to 30 wt% aqueous solution of potassium hydroxide. 6. The method of manufacturing an ink jet head according to claim 4, wherein the method is selected from a range. 5. The inner region of the ink supply port is formed with a SiO ₂ film after the first substrate and the second substrate are bonded and before the first substrate is etched. 7. A method for producing an ink jet head according to any one of 6 above.

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