JP2001277522A - Method for manufacturing ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute good patterning at an overall etching face by suppressing a surface roughness of the overall etching face and generation of micropyramids in a method for manufacturing ink jet heads of an electrostatic driving form. SOLUTION: A first substrate 1 to which a second substrate 2 is joined is uniformly etched by an 80 deg. and 38 wt.% potassium hydroxide aqueous solution until an Si substrate 31 of an initial thickness 400 μm becomes 160 μm thick. Then the substrate is uniformly etched by an 80 deg. and 32 wt.% potassium hydroxide aqueous solution until the Si substrate 31 becomes a desired thickness of 140 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an ink-jet head, which is a main part of an ink-jet head recording apparatus for ejecting ink droplets only when recording is necessary and attaching the ink droplets to a recording sheet.

[0002]

2. Description of the Related Art An ink jet recording apparatus has many advantages, such as extremely low noise during recording, high-speed printing, and the use of inexpensive plain paper with high ink freedom. Among them, the so-called ink-on-demand method, in which ink droplets are ejected only when recording is necessary, has become mainstream at present because it does not require collection of ink droplets unnecessary for recording.

[0003] In the ink-on-demand type recording, an ink-jet head recording apparatus uses an electrostatic force as a driving means as a method of ejecting ink (Japanese Patent Laid-Open No. 6-71882).
This method has the advantages of small size, high density, high printing quality and long life. On the other hand, when the density of the ink jet head is increased, the thickness of the partition wall separating the discharge chamber becomes thin, and the rigidity of the partition wall decreases. for that reason,
The partition wall is deformed by the pressure generated in the ejection chamber due to the deformation of the vibration plate during ink ejection, and the amount of this deformation is sufficient to push out the ink in the adjacent non-drive ejection chamber from the nozzle. In order to prevent the deformation of the partition, it is necessary to reduce the height of the partition and improve the rigidity of the partition, and a thin Si substrate has been used to reduce the height of the partition.

However, such a thin Si substrate is not only expensive but also difficult to handle and has low productivity. Therefore, as described in Japanese Patent Application Laid-Open No. 9-94445, a low-cost and easy-to-handle thick Si substrate is used. A method of joining a glass substrate and etching the Si substrate in that state to obtain a desired thickness of the Si substrate has come to be used.

[0005]

However, no consideration has been given to the surface roughness that occurs when wet etching, particularly etching with an aqueous solution of potassium hydroxide, leading to a deterioration in the patterning accuracy of the discharge chamber due to the surface roughness.
In addition, when the surface roughness is large, the thickness of the resist at the time of patterning locally varies, so that a thick portion of the resist is not sufficiently exposed, and an oxide film serving as an etching mask remains in that portion, which is a discharge chamber. There is a problem that the discharge chamber is not formed when it is generated in the forming portion. In general, when the concentration of an aqueous solution of potassium hydroxide, which is an etching solution, is high, minute protrusions (hereinafter, referred to as micropyramids) of about 10 μm are generated on the etched surface, and the micropyramids have poor patterning and may have a problem with the first substrate. There has been a problem that this may cause poor bonding in the bonding process with the third substrate.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems. It is an object of the present invention to eliminate patterning defects by suppressing the surface roughness of the entire etched surface.
An object of the present invention is to provide a method for manufacturing an ink jet head having high productivity.

[0007]

SUMMARY OF THE INVENTION A method of manufacturing an ink jet head according to the present invention is a method of manufacturing an ink jet head having a first substrate on which a vibration plate is formed and a second substrate on which electrodes are formed. A step of joining a first substrate and a second substrate; a step of wet-etching the first substrate with a first aqueous solution of potassium hydroxide; and a step of etching the first substrate with the first potassium hydroxide. Etching with a second aqueous potassium hydroxide solution having a concentration different from that of the acid aqueous solution. Also,
The inkjet manufacturing method of the present invention is characterized in that the concentration of the first aqueous solution of potassium hydroxide is higher than the concentration of the second aqueous solution of potassium hydroxide. In particular, the concentration of the first aqueous solution of potassium hydroxide is 37% by weight or more, and the concentration of the second aqueous solution of potassium hydroxide is 32% by weight.
less than wt%. By adopting such a manufacturing method, the surface roughness of the etched surface can be suppressed to a level at which good patterning can be performed, and the micropyramid generated on the etched surface can be reduced. Further, the surface of the first substrate is washed with a mixed solution of sulfuric acid and hydrogen peroxide, a mixed solution of ammonia and hydrogen peroxide, or nitric acid.
By making the surface of the substrate hydrophilic, the occurrence of micro pyramids on the etched surface can be further suppressed. Note that it is also possible to oxidize the surface of the Si substrate by irradiating the surface of the first substrate with ultraviolet light,
A similar effect of hydrophilizing the surface of the Si substrate can be obtained.

[0008]

(Embodiment 1) FIG. 1 is an exploded perspective view of an ink jet head according to a first embodiment of the present invention, which is partially shown in a sectional view. This embodiment shows an example of a face ink jet head that discharges ink droplets from nozzle holes provided in the upper flat portion of the ink jet head. FIG. 2 is a side sectional view of the assembled overall device. 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 overlapped and joined.

The intermediate first substrate 1 is a Si substrate,
A concave portion 7 that forms a discharge chamber 6 having a bottom wall as a vibration plate 5, a narrow groove 9 for an ink inlet that forms an orifice 8 provided at a rear portion of the concave portion 7, It has a concave portion 11 that constitutes a common ink cavity 10 for supplying ink to the ejection chamber 6. The third substrate 3 is a Si substrate, and the nozzle hole 12 is formed on the side of the discharge chamber 6 facing the narrow groove 9 for the ink inlet.
And an ink supply port 13 for supplying ink to the ink cavity 10. On the surface of the first substrate 1 facing the second substrate, an oxide film is formed to a thickness of 0.1 μm by thermal oxidation to form an insulating film. This is 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 uses borosilicate glass.
The concave portion 14 for mounting the electrode 15 is etched by 0.3 μm, so that the gap between the diaphragm 5 and the electrode 15 arranged opposite thereto, that is, the gap G
Is formed. The recess 14 has an electrode 15 therein.
The pattern is formed in a slightly larger shape similar to the shape of the electrode portion so that the lead portion 16 and the terminal 17 can be mounted. The electrode 15 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. The operation of the inkjet head configured as described above will be described. When a pulse electrode of 0 V to 35 V is applied to the electrode 15 by the transmission circuit 23 and the surface of the electrode 15 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, the electrode 15 is turned off.
Then, the diaphragm 5 is restored. As a result, the pressure in the ejection chamber 6 rapidly rises, and the ink droplet 2
1 is ejected toward the recording paper 22.

Next, when the diaphragm 5 bends downward again, the ink is moved from the ink cavity 10 into the orifice 8.
Is supplied to the inside of the discharge chamber 6. The connection between the substrate 1 and the transmission circuit 23 is made in a window (not shown) of an oxide film opened in a part of the substrate 1 by dry etching. Further, the supply of the ink to the inkjet head is performed through the ink supply port 13 above the ink cavity 10.

In the ink jet head of this embodiment,
The diaphragm is a Si thin film in which P-type impurities are diffused at a high concentration.
You. This Si thin film is etched by an alkaline aqueous solution.
Etching rate in the case of dopant is boron
In the case of high concentration (about 5 × 10 ¹⁹cm^-3Above)
And the fact that the etching rate becomes very small
It is produced. In other words, the diaphragm formation area is
Ron doped layer, and alkali anisotropic etching,
When forming the discharge chamber and ink cavity,
The etching rate is extremely small when the layer is exposed.
The so-called etch stop technology, the diaphragm is
It is manufactured to a desired thickness.

The manufacturing method of the ink jet head according to the present embodiment will be described with reference to the diffusion process diagram of FIG. 3, the overall etching process diagram of the first substrate of FIG. 4, and the diaphragm etching process diagram of FIG. The case of forming a plate will be described in detail.

First, one surface of a Si substrate 31 having a plane orientation of (110) is mirror-polished to produce a substrate having a thickness of 400 microns (FIG. 3A). Next, a boron diffusion plate is opposed to the Si substrate 31, and heat treatment is performed at a temperature of 1100 degrees Celsius for 2 hours to diffuse boron on the surface of the Si substrate 31 to form a boron doped layer 32 (FIG. 3B). . As another means for forming a high-concentration doped layer, there is a method in which a boron dopant is applied to the surface of a Si substrate and thermal diffusion is performed.

Next, an oxidation temperature of 100 is applied to the Si substrate 31.
Oxidation with dry oxygen is performed under the conditions of 0 ° C. and an oxidation time of 2 hours and 15 minutes to form an oxide film 33 serving as an insulating film of 0.12 μm (FIG. 3C). After protecting the oxide film 33 on the surface on the boron dope layer 32 side with a resist, it is immersed in a hydrofluoric acid aqueous solution,
The oxide film 33 on the opposite surface on which the boron doped layer 32 is formed is removed, and the resist is finally stripped (FIG. 3D). The electrode forming surface of the second substrate 1 on which the electrodes 15 are formed and the boron-doped layer of the first substrate 1 are overlapped (FIG. 4).
(A)) The two substrates are anodically bonded (FIG. 4 (b)).
The first substrate 1 to which the second substrate 2 is bonded is heated to a liquid temperature of 80 degrees Celsius.
The Si substrate 31 having an initial thickness of 400 μm is uniformly etched with a 38 wt% aqueous solution of potassium hydroxide until the thickness becomes 160 μm. Next, 32wt of liquid temperature 80 degrees Celsius
The Si substrate 31 is uniformly etched with a 100% aqueous solution of potassium hydroxide until the thickness becomes a desired 140 μm (FIG. 4).
(C)). Subsequently, an oxide film 51 is formed to a thickness of 1 micron by a CVD apparatus (FIG. 5A), and a resist pattern is formed on the oxide film 51 side to form a discharge chamber and an ink cavity. Etched oxide film 51
After patterning the resist, the resist is removed (FIG. 5).
(B)).

Next, a method of manufacturing a diaphragm by etching will be described.

A boron doped layer 32 is formed, and an oxide film 5 is formed.
35% by weight of a patterned Si substrate 31
The etching is performed with a potassium hydroxide aqueous solution until the etching reaches the boron doped layer (about 10 microns remaining) (FIG. 5).
(C)). Subsequently, etching is performed with a 3 wt% aqueous solution of potassium hydroxide until a predetermined thickness of 1 μm is obtained. After the oxide film 51 is removed by etching with hydrofluoric acid, the Si substrate or the SUS substrate in which a portion corresponding to the electrode extraction portion is punched is superimposed on the first substrate using an etching mask, and the Si of the electrode extraction portion 52 is removed by dry etching. Etching is removed, and an electrode extraction portion is opened. (FIG. 5 (e)) By the method described above, good patterning on the etched surface could be performed, and the productivity of the head could be increased by eliminating defective etching of the discharge chamber.

(Embodiment 2) The selection of the concentration of the aqueous potassium hydroxide solution in the overall etching step of the above embodiment will be described in detail. First, when the surface roughness of the first substrate after the entire surface is etched is 2 μm or more, etching failure due to patterning failure occurs. Therefore, the surface roughness at which no etching failure occurs needs to be 2 μm or less. Furthermore, when the concentration of an aqueous solution of potassium hydroxide, which is generally an etching solution, is high, micro-pyramids are generated on the etched surface, and the micro-pyramids cause poor patterning and poor bonding in the bonding process between the first and third substrates. Therefore, it is necessary to eliminate the occurrence of micropyramids.

The etching amount is 180 microns and 260
FIG. 6 shows a change in the surface roughness depending on the concentration of the etching solution at the time of micron, and FIG. 7 shows a change in the number of generated micropyramids according to the concentration of the etching solution.

Looking at the relationship between the surface roughness due to the concentration of the etching solution and the state of occurrence of the micropyramid, the surface roughness is 2%.
The concentration of the etchant at or below the micron is 37 wt% or more, and the number of occurrences of the micropyramid becomes 0 at the concentration of 32 wt% or less. That is, when the entire surface is etched with a single etching solution, there is no optimum concentration of the etching solution that does not generate micro pyramids and can suppress the surface roughness to 2 μm or less. Therefore, using two kinds of etching solutions of etching concentration,
Etching is performed to near the target plate thickness while suppressing the surface roughness with an etching solution of 37 wt% or more, allowing the surface roughness to increase and generating no micro pyramid 32 w
It suffices to perform etching with an etching solution of t% or less.

As an example, a description will be given of a case where the first overall etching is performed with a 38 wt% aqueous solution of potassium hydroxide and the second overall etching is performed with a 32 wt% aqueous solution of potassium hydroxide. S with 38wt% potassium hydroxide aqueous solution
FIG. 8 shows the change in the surface roughness according to the etching time when the i-substrate surface was etched with an etching amount of 260 μm and then further etching with a 32 wt% aqueous solution of potassium hydroxide. Is shown in FIG.

As the etching time in a 32 wt% aqueous potassium hydroxide solution becomes longer, the number of micropyramids decreases. When the etching time is 10 minutes or more, the generation of micropyramids is suppressed to a low level. On the other hand, the longer the etching time, the higher the surface roughness, but within 15 minutes, the surface roughness can be suppressed to within 2 microns. The first whole surface etching is performed with a 38 wt% aqueous solution of potassium hydroxide, and the subsequent whole surface etching is performed with a 32 wt% aqueous solution of potassium hydroxide in an etching time of 10 to 15 minutes. The entire surface can be etched while suppressing the occurrence of the occurrence.

(Embodiment 3) In the method of the above embodiment,
It is desirable to change the cleaning method before the second etching because the micropyramid may not be completely zero and the appearance of the etching surface may be fogged (slightly rough). . 38wt%
The etching time in an aqueous solution of potassium hydroxide and an aqueous solution of 32 wt% potassium hydroxide is fixed at 78 minutes and 10 minutes,
Table 1 shows the results of the surface state obtained by changing the cleaning method before etching with a 32 wt% aqueous potassium hydroxide solution.

[0024]

[Table 1]

Example 1 in Table 1 is a mixture of ammonia water and hydrogen peroxide at 70 ° C. for 10 minutes, and Example 2 is a mixture of sulfuric acid and hydrogen peroxide at 90 ° C. In this case, the surface appearance was not clouded and micropyramids were not generated. on the other hand,
When the cleaning shown in Comparative Example 1 was not performed, and when the substrate was washed with a hydrofluoric acid aqueous solution at 25 degrees Celsius shown in Comparative Example 2, cloudiness and micro pyramids were generated. Observation of the wettability of the substrate surface reveals that the surface washed well with the mixed solution of sulfuric acid / hydrogen peroxide and the mixed solution of ammonia / hydrogen peroxide is well wetted and hydrophilic. The surface is rendered hydrophobic in the washing of. That is, in order to further suppress the fogging of the etched surface and the occurrence of micro pyramids, cleaning with a mixed solution of ammonia water and hydrogen peroxide solution is performed before the second etching, and the substrate surface is weakly oxidized to oxidize the surface. Need to be made hydrophilic. Similarly, as a method of oxidizing the substrate surface, washing with nitric acid and ozone oxidation by ultraviolet irradiation are also effective.

[0026]

According to the method for manufacturing an ink jet head, in the step of joining the first substrate and the second substrate and the step of reducing the thickness of the Si substrate of the first substrate by wet etching, the wet etching has a low concentration. By performing the etching in two stages using two different types of potassium hydroxide aqueous solutions, the surface roughness of the etched surface can be suppressed to a level that allows good patterning, and the micropyramid generated on the etched surface can be reduced. .

In the two-stage etching, before the second etching, the surface of the first substrate is washed with a mixed solution of sulfuric acid / hydrogen peroxide, a mixed solution of ammonia / hydrogen peroxide, nitric acid, or the like. By making the surface of the substrate hydrophilic, the occurrence of micro pyramids on the etched surface can be further suppressed.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a structure of an inkjet head according to a first embodiment of the present invention.

FIG. 2 is a sectional side view of the ink jet head according to the first embodiment of the present invention.

FIG. 3 is a process sectional view of a diffusion step in the first embodiment of the present invention.

FIG. 4 is a process cross-sectional view of the entire surface etching step in the first embodiment of the present invention.

FIG. 5 is a process sectional view of a diaphragm forming step according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a change in surface roughness depending on the concentration of an etching solution in a second embodiment of the present invention.

FIG. 7 is a diagram showing a change in the number of generated micropyramids depending on the concentration of an etching solution in a second embodiment of the present invention.

FIG. 8 is a diagram showing a change in surface roughness according to an etching time in a 32% aqueous potassium hydroxide solution in a third example of the present invention.

FIG. 9 is a diagram showing a change in the number of generated micropyramids according to an etching time in a 32% aqueous potassium hydroxide solution in a third example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st board | substrate 2 2nd board | substrate 3 3rd board | substrate 5 Vibration plate 6 Discharge chamber 7 Depression 8 Orifice 9 Narrow groove 10 Ink cavity 11 Depression 12 Nozzle hole 13 Ink supply port 14 Depression 15 Electrode 16 Lead part 17 Terminal 18 Oxide film 21 Ink droplet 22 Recording paper 23 Oscillation circuit 31 Si substrate 32 Boron-doped layer 51 Oxide film 52 Electrode take-out part G gap

Claims (7)

[Claims] A first substrate on which a diaphragm is formed;
In a method for manufacturing an ink jet head having a second substrate on which electrodes are formed, a step of joining the first substrate and the second substrate; and a step of wet-treating the first substrate with a first aqueous solution of potassium hydroxide. Manufacturing an inkjet head, comprising: a step of etching; and a step of etching the first substrate with a second aqueous solution of potassium hydroxide having a concentration different from that of the first aqueous solution of potassium hydroxide. Method. 2. The method according to claim 1, wherein the concentration of the first aqueous solution of potassium hydroxide is higher than the concentration of the second aqueous solution of potassium hydroxide. 3. The method according to claim 1, wherein the concentration of the first aqueous solution of potassium hydroxide is 37 wt% or more. 4. The method according to claim 1, wherein the concentration of the second aqueous solution of potassium hydroxide is less than 32% by weight. 5. The method according to claim 1, wherein the surface of the substrate is treated to be hydrophilic.
The method according to any one of claims 1 to 4, wherein the substrate is etched with the second aqueous solution of potassium hydroxide. 6. A mixture of sulfuric acid and hydrogen peroxide, ammonia
The method according to claim 5, wherein the surface of the first substrate is made hydrophilic by a cleaning liquid such as a mixed solution of hydrogen peroxide or nitric acid. 7. The method according to claim 5, wherein the surface of the first substrate is treated to be hydrophilic with ozone gas generated by ultraviolet irradiation.