JPH09216357A - Ink jet head and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method for forming high concentration impurity layer of necessary depth to obtain the thickness of a desired diaphragm by forming high concentration p-type impurity layers on both side surfaces of an Si board, and using either one of the layers as the diaphragm. SOLUTION: The opposite side 44 of the surface formed with a B-doped layer 46 is coated with resist, and a diffusion agent 45 is removed by etching with hydrofluoric acid water solution. Since the boron compound 47 present on a board surface has high etching resistance and is impossible to remove it by wet etching, next means is adopted. After the resist of the board 41 is released, the board 41 is set in an oxidizing furnace, and the compound 47 is oxidized for one hour under the conditions of oxygen and steam atmosphere at 600 deg.C. to chemically change it to B2 O3 +SiO2 50 making it possible to be etched with the hydrofluoric acid water solution. Since the temperature of the oxidation is low, the diffusion is not proceeded, but the compound 47 can be removed by dry etching.

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 which is a main part of an ink jet head recording apparatus for ejecting ink droplets and adhering the ink droplets onto a recording paper surface only when recording is required, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Print heads for ink jet printers are required to have fine and precise processing and complicated desired shapes due to the demand for high-definition printing, and in particular, JP-A-6-7188.
In an ink jet head using an electrostatic force as a drive source as disclosed in Japanese Patent Laid-Open No. 2 (1993), the mechanical deformation characteristics of the diaphragm have a great influence on the ink ejection characteristics, and it is necessary to control the thickness of the diaphragm with high accuracy. is there. Conventionally, when a diaphragm is formed by etching a Si substrate, a method of controlling the etching time to control the thickness of the diaphragm has been used. However, as the size of the inkjet head becomes smaller and the performance becomes higher, the diaphragm becomes thinner, and the thickness accuracy is required. Therefore, JP-A-6-71882, page 20, 15
A method of forming a thin film to be a diaphragm by using an etch stop technique as described in the row and utilizing the slow etching rate of the p-type impurity layer and leaving only the p-type impurity layer by etching is used. It's starting to happen.

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

[0004]

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

In the case of the ion implantation method, there is a problem that an expensive implanting device is required or the concentration and depth at which doping can be performed are limited. Further, in the vapor phase diffusion method, since the gas is in contact with the substrate, the concentration of the diffusion source on the surface of the substrate 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 the solid high-concentration diffusion source is in contact with the Si substrate, the high-concentration and short-time diffusion is possible as compared with the gas-phase diffusion method in which the 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 vapor-phase diffusion method, the diffusion source is a diffusion agent coated on the substrate before diffusion, and the diffusion ability of the diffusion agent is limited. Is. That is, the thickness of the diffusing agent that can be coated is limited for the reason of ensuring uniformity. Therefore, if diffusion is performed for a long time in order to form a deep diffusion region, there is a problem that the diffusion source in the finite diffusion agent is exhausted, the diffusion ability of the diffusion agent decreases, and it is difficult to diffuse deep high concentration. It was

Further, when the high-concentration impurity layer is formed only on one side of the substrate, when the thickness of the substrate is small, a tensile stress of the high-concentration impurity layer causes a concave warp toward the high-concentration impurity layer formation side. was there.

An object of the present invention is to provide a method for 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 the diaphragm.

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

[0009]

An ink jet head of the present invention has a single or a plurality of nozzle holes for ejecting ink droplets, an ejection chamber connected to each of the nozzle holes, and at least one wall of the ejection chamber. An ink jet head comprising a vibrating plate and a driving unit that causes deformation of the vibrating plate, the driving unit including electrodes that deform the vibrating plate by electrostatic force, and the substrate on which the vibrating plate is formed is a Si substrate, Forming a high concentration p-type impurity layer on both sides of the Si substrate,
It is characterized in that either one of the p-type impurity layers is used as a diaphragm.

Further, in the method for manufacturing an ink jet head of the present invention, a single or a plurality of nozzle holes for ejecting ink droplets, an ejection chamber connected to each of the nozzle holes, and at least one wall of the ejection chamber are formed. A vibration plate and a drive unit that causes the vibration plate to deform. The driving unit includes an electrode that deforms the vibration plate by an electrostatic force, and a substrate on which the vibration plate is formed is an Si substrate. The plate is made of a high-concentration p-type impurity layer, and the p-type impurity layer is formed by coating the Si substrate with an impurity diffusion source and performing thermal diffusion. The diffusion method is performed a plurality of times. And

[0011]

As a vibrating plate forming method in the method of manufacturing the ink jet head, the highly doped p-type region is
It is formed by leaving the high-concentration impurity diffusion layer as a vibrating plate by utilizing the fact that the etching rate in Si etching with alkali is very small. Therefore, the thickness of the high-concentration impurity diffusion layer becomes the thickness of the diaphragm. In the method of forming the high-concentration impurity layer, by performing the impurity diffusion a plurality of times to increase the thickness of the high-concentration impurity diffusion layer, the diaphragm having a desired thickness can be formed in a short time.

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.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An inkjet head according to a preferred example of the present invention will be described in detail below.

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

The ink jet head of this embodiment has a laminated structure in which three substrates 1, 2 and 3 having the structure described in detail below are stacked 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. First
An oxide film 12 of 0.1 μm is formed on the entire surface of the substrate 1 of FIG.
An insulating film is formed to form a film for preventing dielectric breakdown and short circuit when the inkjet is driven.

The second substrate 2 bonded to the lower surface of the first substrate 1 is made of borosilicate glass, and the recess 14 for mounting the electrode 13 on the substrate 2 is etched by 0.3 μm. A gap G is formed between the diaphragm 5 and the electrode 13 arranged to face the diaphragm 5, that is, a gap G. The concave portion 14 has the electrode 13 and the lead portion 1 inside thereof.
The pattern is formed in a slightly larger shape similar to the shape of the electrode portion so that the terminal 5 and the terminal portion 16 can be mounted. Electrode 1
In No. 3, ITO is sputtered in the recess 14 by 0.1 μm,
It is manufactured by forming an O pattern.

Therefore, the gap G after the anodic bonding of the first substrate 1 and the second substrate 2 in this embodiment is 0.
It is 2 μm.

A Si substrate having a thickness of 100 μm is used as the third substrate 3 bonded to the upper surface of the first substrate 1, and the surface portion of the substrate 3 communicates with the recess 7 for the discharge chamber 6. Nozzle holes 17 are provided in each of the
An ink supply port 18 is provided so as to communicate with the concave portion 11 for use.

The operation of the ink jet head configured as described above will be described. When a pulse potential of 0V to 35V is applied to the electrode 13 by the oscillator circuit 19 and the surface of the electrode 13 is positively charged, the lower surface of the corresponding diaphragm 5 is negatively charged. Therefore, the diaphragm 5 bends downward due to the electrostatic attraction. Next, turn off the electrode 13.
Then, the diaphragm 5 is restored. Therefore, the pressure in the ejection chamber 6 rapidly rises, and the ink droplets 2 are discharged from the nozzle holes 17.
0 is ejected toward the recording paper 21. Next, when the diaphragm 5 bends downward again, ink is supplied from the ink cavity 10 into the ejection chamber 6 through the orifice 8. The substrate 1 and the oscillator circuit 19 are connected to each other through a window (not shown) of the oxide film 12 formed in a part of the substrate 1 by dry etching.

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

In the method of manufacturing the first substrate 1 of the ink jet head in this embodiment, referring to the manufacturing process diagram of the first substrate in FIG. 4, B (boron) is used as an impurity diffusion source and 4 μm is used.
The case of forming the diaphragm 5 of m will be described in detail.

First, both surfaces of a Si substrate having (110) plane orientation are mirror-polished to prepare a substrate 41 having a thickness of 180 μm (FIG. 4A). The Si substrate 41 is set in a thermal oxidation furnace, and the temperature is set to 1100 degrees Celsius in an atmosphere of oxygen and water vapor.
A thermal oxidation process is performed for a period of time to form an oxide film 42 of 1 μm on the surface of the substrate 41 (FIG. 4B). Next, in order to remove the oxide film 42 on the surface 43 on which the B-doped layer is formed, the substrate 41
A surface 44 opposite to the surface 43 on which the B-doped layer is formed is coated with a resist, and the oxide film 42 on the surface 43 on which the B-doped layer is formed is removed by etching with an aqueous hydrofluoric acid solution using the resist as a protective film to remove the resist. (FIG. 4 (c)). A diffusion agent 45 in which 3.15% by weight of B ₂ O ₃ as a diffusion source is dispersed in an organic solvent is applied to the surface 43 from which the oxide film 42 is removed by 2000.
Spin coating is performed under the conditions of rpm and 1 minute, and baking is performed in a clean oven at a temperature of 140 degrees Celsius for 30 minutes (FIG. 4D). At this time, the thickness of the diffusing agent is 1.2 μm
Becomes It is desirable that the diffusing agent 45 can be coated thickly, and a method of increasing the film thickness by lowering the spin rotation number and increasing the concentration of B ₂ O ₃ in the diffusing agent can be considered, but the former is a film in the substrate. Variation in thickness will increase,
The latter has a problem that the uniformity of dispersion is deteriorated, and the above-mentioned coating conditions are the best conditions among 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 a temperature of 600 ° C. to oxidize and remove the organic binder in the diffusing agent 45 and bake B ₂ O ₃ . . Then, the inside of the furnace is made into a nitrogen atmosphere, the temperature is raised to 1100 degrees Celsius, the temperature is kept as it is for 6 hours, B is diffused into the Si substrate, and the 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. 4 (e)).
When the furnace temperature is lowered, the substrate 41 is taken out and the diffusing agent coating is repeated to form the diffusing agent second layer 48 on the diffusing agent 45. Further, firing and diffusion are performed to thicken the B-doped layer 46 (FIG. 4 (f)). Similarly, a diffusing agent coating is performed to form a diffusing agent third layer 49, which is baked and diffused to further thicken the B dope layer 46 (FIG. 4G).

The side 44 opposite to the surface on which the B-doped layer 46 is formed
Then, the resist is coated and the diffusing agent 45 is removed by etching with a hydrofluoric acid aqueous solution. The boron compound 47 appearing on the surface of the substrate has high etching resistance and cannot be removed by wet etching. Therefore, the following measures are taken. First, after removing the resist of the substrate 41, the substrate was set 41 to the oxidation reactor, the oxygen and water vapor atmosphere, boron compound 47 was oxidized for 1 hour under the conditions of 600 degrees Celsius, which can be etched by hydrofluoric acid aqueous solution B ₂ It is chemically changed to O ₃ + SiO ₂ 50 (FIG. 4 (h)). Since the oxidation temperature is low,
It is also possible to remove the boron compound 47 by dry etching without causing the diffusion to proceed.

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 formed. Remove by etching. Then, the resist on the substrate 41 is removed (FIG. 4 (i)).

The substrate 41 is dipped in an aqueous potassium hydroxide solution having a concentration of 10 w% and Si etching is performed. When the substrate 41 is etched from the exposed portion 51 of Si on the side where the oxide film 42 is patterned and reaches the B-doped layer 46, the etching is stopped and the B-doped layer 46 is left. 46 is the diaphragm 5 (see FIG. 4).
(J)). During the etching, the B-doped layer forming side 43
Side to prevent B from being etched
3 is used as the etching solution, and an aqueous solution of 10 w% potassium hydroxide in which the etching rate of the B-doped layer 46 is remarkably lowered is used.

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

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

The diffusion is completed without using a protective jig, and the boron compound 47 on the diffusion surface is oxidized to B ₂ O ₃ + S.
It is also possible to perform thermal oxidation in the state of chemically changing to iO ₂ 50 (FIG. 4 (h)) 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-mentioned method, the obtained diaphragm thickness is eroded by the growth of the oxide film, and the thickness of the high-concentration B-doped layer is decreased due to the internal diffusion of B from the B-doped layer due to the heating during the thermal oxidation. descend.

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

FIG. 6 shows the results of measuring the change in the thickness of the diaphragm obtained by 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 larger than the thickness of the diaphragm obtained by one diffusion. 1
In case of 8-hour diffusion, 18 hours, 3.4 μm in one diffusion
While a diaphragm having a thickness of 4 .mu.m is obtained, a diaphragm having a thickness of 4.0 .mu.m is obtained after three times of diffusion for 6 hours. Therefore, by increasing the number of times of diffusion, 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 of more than 3.5 μm is to be obtained by one diffusion, it cannot be produced because the B supply capability of the diffusion source is significantly reduced.

FIG. 7 shows the results of measuring the thickness accuracy of the diaphragm produced by changing the number of times of diffusion. It is shown that the surface roughness of the etching surface of the vibration plate can be reduced by forming the vibration plate by performing the diffusion a plurality of times. The above is because the diffusion state of B changes due to repeated diffusion, and the B concentration change becomes sharp near the threshold value 5 × 10 ¹⁹ cm ^{−3 of the} etching rate reduction shown in the H portion of FIG. is there.

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

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

(2) It is possible to form a thick doped layer that cannot be formed by one diffusion.

(3) A vibrating plate having a high plate thickness accuracy can be formed.

Next, a method of manufacturing the first substrate 1 of the ink jet head in the second embodiment of the present invention will be described in detail with reference to the manufacturing process chart shown in FIG. In addition, Example 1
A part of the diffusion process, which is the same as the manufacturing process in, is omitted.

First, both surfaces of a Si substrate having (110) plane orientation are mirror-polished to produce a substrate 81 having a thickness of 180 μm (FIG. 8A). The diffusion 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 ° C. 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, diffusing agent coating, baking, and diffusion are repeated twice, and then B
The dope layer 83 is formed thick. Then, the diffusing agent 82 is removed by etching with an aqueous solution of hydrofluoric acid, the boron compound formed on the surface is oxidized by the same method as that described in Example 1, and then the boron compound is oxidized to generate B ₂ O ₃ + S
iO ₂ is removed by a hydrofluoric acid aqueous solution (FIG. 8).
(C)). 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 of 1 μm on the surface of the substrate 81 (FIG. 8).
(D)).

In consideration of the erosion of the substrate surface due to the oxide film growth described in Example 1 and the reduction of the thickness of the high-concentration B-doped layer due to the internal diffusion of B from the B-doped layer due to the heating during the thermal oxidation, diffusion is performed. It goes without saying that you should extend the time.

Next, resist patterning for forming the discharge chamber 6 and the ink cavity 9 is performed on one side of the substrate 81, the oxide film 84 is etched and patterned using an aqueous solution of hydrofluoric acid, and then the resist is peeled off. (FIG.8 (e)). Subsequently, the Si substrate 81 was etched using a 10 w% potassium hydroxide aqueous solution,
The diaphragm 5 is formed in the same manner as in (FIG. 8 (f)). Although the etching starts from the exposed portion 85 of Si, the etching does not proceed so much due to the existence 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 oxide film 84 remaining on the substrate 81 is removed, and 0.1 μm to the substrate 81 by thermal oxidation treatment.
The first substrate 1 is completed by forming the oxide film 84 having a thickness of.

In the manufacturing method described above, since the high-concentration B-doped layers are formed on both sides of the Si substrate, the stress of the high-concentration B-doped layers cancels each other on the front and back of the substrate, and the warp of the first substrate 1 occurs. I was able to get rid of. By eliminating the warpage of the first substrate 1, the bonding strength between the first substrate 1 and the second substrate 3 and the third substrate 3 bonded to the first substrate 1 was increased.

[0044]

According to the present invention, a p-type impurity having a thickness required to obtain a desired thickness of a diaphragm in forming a diaphragm produced by an etch stop technique and which cannot be obtained by a single diffusion. The diffusion layer can be formed. Further, by performing the diffusion a plurality of times, it is possible to make the B concentration change steep, and it is possible to form a diaphragm with high plate thickness accuracy.

Further, by forming the high-concentration impurity layers on both sides of the substrate, particularly when the thickness of the substrate is thin, a concave warp that is generated toward the high-concentration impurity layer formation side due to the tensile stress of the high-concentration impurity layer is formed. Can be prevented. By preventing the warp of the substrate, the bonding strength with the borosilicate glass at the time of assembling the print head can be increased.

[Brief description of 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 method of manufacturing the inkjet head according to the first embodiment of the present invention.

FIG. 3 is a view taken along the line AA of FIG.

FIG. 4 is a manufacturing process diagram of the first substrate of the inkjet head according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between a B concentration and an etching rate in alkali anisotropic etching.

FIG. 6 is a diagram showing the relationship between the number of times of diffusion and the thickness of the diaphragm in the inkjet head manufacturing method according to the first embodiment of the present invention.

FIG. 7 is a diagram showing the relationship between the number of diffusions and the thickness accuracy of the diaphragm in the method for manufacturing an inkjet head according to the first embodiment of the present invention.

FIG. 8 is a manufacturing process drawing of the first substrate according to the second embodiment of the present invention.

[Explanation of symbols]

 1 First Substrate 2 Second Substrate 3 Third Substrate 5 Vibrating 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 (2)

[Claims] 1. A single or a plurality of nozzle holes for ejecting 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 the vibration plate. In an ink jet head in which the driving means includes an electrode for deforming the diaphragm by an electrostatic force, and the substrate on which the diaphragm is formed is a Si substrate, both surfaces of the Si substrate are provided. An ink jet head characterized in that a high-concentration p-type impurity layer is formed and one of the p-type impurity layers serves as a vibration plate. 2. A single or a plurality of nozzle holes for ejecting ink droplets, a discharge chamber connected to each of the nozzle holes, a vibration plate forming at least one wall of the discharge chamber, and the vibration plate. A driving means for causing deformation of the vibrating plate by an electrostatic force to deform the vibrating plate, and the substrate on which the vibrating plate is formed is a Si substrate. The plate is made of a high-concentration p-type impurity layer, and the method of forming the p-type impurity layer is a diffusion method of coating the Si substrate with an impurity diffusion source and performing thermal diffusion. The diffusion method is performed a plurality of times. A method for manufacturing an inkjet head, comprising: