JP2002096475A - Method for manufacturing ink-jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce damage to an Si substrate by uniforming thermal diffusion of boron during boron doping in a vertical furnace and to realize formation of an insulating film with high insulation withstand pressure on a surface of the Si substrate, when an ink-jet head is formed with use of anisotropic etching and a high-density boron etching stop to the Si substrate. SOLUTION: In the vertical furnace, a solid diffusion source 51 based on B2O3 is superposed on a supporting substrate 52 contacting the diffusion source only by an outer peripheral part, and the high-density boron is diffused thermally to the Si substrate 41 arranged opposite to the diffusion source.

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 only when recording is required and attaching the ink droplets to a recording sheet, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A conventionally known ink jet head using electrostatic force as a driving source has a face eject type in which ink droplets are ejected from nozzle holes formed in a surface portion of a substrate joined to an upper surface of an intermediate substrate. There is an edge eject type in which ink droplets are ejected from a nozzle hole provided at an end of an intermediate substrate.
It has a laminated structure in which two substrates are overlapped and joined.

For example, in the case of the face eject type, an intermediate substrate is made of a Si substrate, and has a concave discharge chamber having a bottom wall as a vibration plate and a concave reservoir for supplying ink to each discharge chamber. An insulating film is formed on the surface of the substrate. The insulating film is a film for preventing dielectric breakdown and short circuit during inkjet driving.

The substrate to be bonded to the lower surface of the intermediate substrate is made of borosilicate glass, and the diaphragm is provided with electrodes facing each other with a gap. This electrode is electrically connected to a pulse transmission circuit that outputs a predetermined pulse potential. Further, a Si substrate is used as a substrate bonded to the upper surface, and a plurality of nozzle holes communicating with the discharge chamber, an orifice for an ink inflow port communicating the discharge chamber with the reservoir, and a reservoir communicate with the surface of the substrate. And an ink supply port.

The above-mentioned diaphragm is a high-concentration boron-doped layer formed by thermally diffusing boron at a high temperature on a doped surface of a Si substrate, and is an etching stop technology described in JP-A-9-234873, page 5, line 1. Is formed by making use of the fact that the etching rate of the boron-doped layer is low and leaving only the boron-doped layer by anisotropic etching.

[0006] The boron doped layer is formed on a quartz boat using B ₂ O ₃
And a supporting substrate having the same area as the diffusion source and made of SiC, and the solid diffusion source mainly composed of
It is formed by disposing a Si substrate at a distance of 3 mm from the substrate and thermally diffusing it at a high temperature of 1000 ° C. or higher.

[0007]

However, in the above-described method for forming a boron-doped layer, since thermal diffusion is performed at a high temperature of 1000 ° C. or more, Si is thermally diffused from the supporting substrate made of SiC into the diffusion source. As a result, the thermal diffusion of boron becomes non-uniform, causing damage to the Si substrate, which causes a problem that the withstand voltage of the insulating film formed on the surface of the substrate is reduced.

Accordingly, the present invention has been made to solve the above-mentioned problems, and has an object to make the thermal diffusion of boron uniform and to improve the Si content.
An object of the present invention is to provide a method for manufacturing an ink jet head capable of forming an insulating film with a high withstand voltage without causing damage to a substrate.

[0009]

According to a method of manufacturing an ink jet head of the present invention, a single or a plurality of nozzle holes for discharging ink droplets, a discharge chamber connected to each of the nozzle holes, What is claimed is: 1. A method for manufacturing an ink jet head comprising: a diaphragm constituting at least one wall; and driving means for causing deformation of the diaphragm, comprising: a solid diffusion source containing B ₂ O ₃ as a main component; and the diffusion source. A supporting substrate in contact with only the outer peripheral portion is disposed in a vertical furnace, a Si substrate is disposed facing the diffusion source, and high-concentration boron is thermally diffused into the Si substrate.

[0010] According to the above structure, the thermal diffusion of impurities from the supporting substrate is suppressed as compared with the conventional technique in which the supporting substrate in contact with the entire surface of the diffusion source is overlapped with the diffusion source, so that the thermal diffusion of boron becomes uniform. This has the effect of reducing the damage to the Si substrate placed opposite to the diffusion source.

In the method of manufacturing an ink jet head according to the present invention, the surface of the diffusion source facing the Si substrate is a surface opposite to the surface of the diffusion source facing the Si substrate during the previous thermal diffusion. It is characterized by.

According to the above configuration, since the warpage of the diffusion source can be suppressed, there is an effect that the change in the facing distance between the diffusion source and the Si substrate is suppressed and the diffusion amount of boron is made constant.

[0013] A method of manufacturing an ink jet head according to the present invention is characterized in that the material of the supporting substrate is SiC.

According to the above configuration, there is an effect that sticking between the diffusion source and the support substrate or sticking between the diffusion source and the quartz boat are prevented.

[0015]

(Embodiment 1) FIG. 1 is an exploded perspective view of an ink jet head according to the present invention, which is partially shown in a sectional view. This embodiment shows an example of a face ink jet head for discharging ink droplets from nozzle holes provided on the surface of a substrate. FIG. 2 is a side sectional view of the assembled overall device, 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,
It has a concave portion 6 that constitutes a discharge chamber 5 whose bottom wall is the vibration plate 4, and a concave portion 10 that constitutes a common reservoir 9 for supplying ink to each discharge chamber 5. TE on the entire surface of the first substrate by plasma CVD.
The OS film is formed as an insulating film by forming 0.1 μm. 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 is made of borosilicate glass.
The concave portion 13 for mounting the electrode 12 is etched by 0.3 μm, so that the opposing interval between the diaphragm 4 and the electrode 12 disposed opposite thereto, that is, the gap G
Is formed. The recess 13 has the electrode 12 therein,
The pattern is formed in a slightly larger shape similar to the shape of the electrode portion so that the lead portion 14 and the terminal portion 15 can be mounted. The electrode 12 is manufactured by sputtering ITO into the recess 13 by 0.1 μm to form an ITO pattern.

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

The third substrate joined to the upper surface of the first substrate
The substrate 3 is a 100 micron thick Si substrate,
Nozzle holes 16 are provided in the surface portion of the substrate 3 so as to communicate with the concave portions 6 for the discharge chambers 5, and the orifices 7 that connect the concave portions 6 for the discharge chambers 5 and the concave portions 10 for the reservoirs 9 are formed. A narrow groove 8 for the ink inlet is provided, and an ink supply port 17 is provided so as to communicate with the concave portion 10 for the reservoir 9.

The operation of the ink jet head configured as described above will be described. 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 corresponding lower surface of the diaphragm 4 is charged to a negative potential. Therefore, the diaphragm 4 bends downward due to the electrostatic attraction. Next, the electrode 12 is turned off.
Then, the diaphragm 4 is restored. As a result, the pressure in the discharge chamber 5 rises rapidly, and the ink droplet 1
9 is ejected toward the recording paper 20. Next, when the diaphragm 4 bends downward again, ink is supplied from the reservoir 9 into the ejection chamber 5 through the orifice 7. In addition,
The connection between the substrate 1 and the transmission circuit 18 is made in a window (not shown) of an oxide film opened in a part of the substrate 1 by dry etching. The supply of the ink to the ink jet head is performed through the ink supply port 17 at the end of the reservoir 9.

The diaphragm 4 in the ink-jet head of this embodiment is a high-concentration boron-doped layer, and the boron-doped layer has a thickness equal to a desired diaphragm thickness. When the dopant is boron, the etching rate in Si etching with alkali is high (about 5 ×
In the region of 10 ¹⁹ cm ^-3 or more), the etching rate becomes very small. In this embodiment, taking advantage of this fact, the diaphragm forming region is made of a high-concentration boron-doped layer, and the discharge chamber 5 and the reservoir 9 are formed by alkali anisotropic etching.
When forming the vibration plate 4, the diaphragm 4 is manufactured to have a desired thickness by a so-called etching stop technique in which the etching rate becomes extremely small when the boron doped layer is exposed.

[0022] The first method of manufacturing the substrate 1 of the ink jet head of this embodiment, the first manufacturing step view of the substrate 1 in FIG. 4, the boron diffusion process of FIG. 5, boron diffusion source B ₂ O ₃ The case where the diaphragm 4 having a thickness of 0.8 μm is formed will be described in detail.

First, both surfaces of a Si substrate 41 having a plane orientation of (110) are mirror-polished to produce a substrate having a thickness of 140 microns (FIG. 4A). The Si substrate 41 is set in a thermal oxidation furnace, and is heated to 1100 degrees Celsius in an atmosphere of oxygen and water vapor.
A thermal oxidation process is performed for 4 hours, and an oxide film 42 is formed to a thickness of 1.2 μm on the surface of the Si substrate 41 (FIG. 4B). Next, in order to remove the oxide film 42 on the surface 43 on which the boron-doped layer is formed, a resist is coated on the surface 44 of the Si substrate 41 opposite to the surface 43 on which the boron-doped layer is formed, and a boron-doped layer is formed using the resist as a protective film. The oxide film 42 on the surface 43 is removed by etching with a hydrofluoric acid aqueous solution, and after the etching, the resist is removed (FIG. 4C).

A solid diffusion source 51 mainly composed of B ₂ O ₃
Is overlapped with a support substrate 52 made of SiC and in contact with the diffusion source only at the outer peripheral portion, and set on a quartz boat 54. The silicon substrate 41 is separated from the diffusion source 51 by 2.5 mm to form a surface 43 on which a boron-doped layer is formed. Is set to face the diffusion source 51. A dummy Si substrate 53 is set above the Si substrate 41 in order to prevent boron from wrapping around. A quartz boat 54 was set in a vertical furnace, the inside of the furnace was set to a nitrogen atmosphere, the temperature was raised to 1050 degrees Celsius, the temperature was maintained for 8 hours, and boron was diffused into the Si substrate 41 to form a boron doped layer 45. (FIG. 4D). A boron compound is formed on the surface of the Si substrate 41 of the boron doped layer 45 (not shown).
By oxidizing for 1 hour and 30 minutes under the above conditions, it can be chemically changed to B ₂ O ₃ + SiO ₂ which can be etched with a hydrofluoric acid aqueous solution. In a state chemically changed to B ₂ O ₃ + SiO ₂ , a resist is coated on the surface 44 opposite to the surface 43 on which the boron doped layer is formed, and the resist is used as a protective film to form a B film.
₂ O ₃ + SiO ₂ is removed by etching with hydrofluoric acid aqueous solution,
After the etching, the resist is removed.

After the boron doping step of the Si substrate, a TEOS film is formed on the surface of the boron-doped layer by plasma CVD at a processing temperature of 360 degrees Celsius and a high-frequency output of 7 degrees.
00W, pressure is 250mTorr, gas flow rate is TEOS
A 1.2 micron film is formed under the conditions of a flow rate of 100 sccm and an oxygen flow rate of 1000 sccm (FIG. 4E).

The discharge chamber 5 is provided on the oxide film side 44 of the Si substrate 41.
The resist patterning for forming the reservoir 9 is performed, and the oxide film 42 is patterned by etching with a hydrofluoric acid aqueous solution. Then, the resist is peeled off (FIG. 4
(F)).

The Si substrate 41 is immersed in an aqueous solution of potassium hydroxide having a concentration of 35% by weight, and is subjected to Si etching to a Si plate thickness of 10%.
The process is performed until the thickness reaches a micron (FIG. 4G). Subsequently, the Si substrate 41 is immersed in a 3% by weight aqueous solution of potassium hydroxide,
The etching is continued until the etching stop due to the decrease in the etching rate in the boron doped layer 45 is sufficiently effective (FIG. 4F). Here, the term “etching stop” is defined as a state in which bubbles generated from an etching surface have stopped during etching, and the stop of bubbles in actual etching is determined to be an etching stop.

By performing the etching using the two kinds of aqueous potassium hydroxide solutions having different concentrations, the surface roughness of the diaphragm 4 can be suppressed, and the thickness accuracy can be reduced to 0.8 ± 0.05 μm or less. As a result, the ejection performance of the inkjet head can be stabilized.

After the Si etching step, the oxide film is etched with a hydrofluoric acid aqueous solution (FIG. 4 (i)), and the plasma C
The TEOS film 46 is formed on the entire surface of the Si substrate 41 by VD, the processing temperature during the film formation is 360 degrees Celsius, the high frequency output is 250 W,
The pressure is 500 mTorr and the gas flow rate is TEOS flow rate 10
0.1 sccm under the condition of 0 sccm and oxygen flow rate of 1000 sccm.
A micron film is formed (FIG. 4 (j)). Before forming the TEOS film, the pressure is 0.5 torr and the O ₂ flow rate is 1000
sccm, high frequency output 250 W, processing temperature 36 degrees Celsius
O ₂ plasma processing is performed under the conditions of 0 ° and processing time of 1 minute. Thereby, the surface of the Si substrate 41 is cleaned, and the uniformity of the withstand voltage of the TEOS film is improved.
After the TEOS film is formed, the processing temperature is 1000 degrees Celsius and the processing time is 1 hour in a nitrogen atmosphere on the TEOS film.
Annealing is performed under the condition of time. By performing this annealing treatment, the denseness of the TEOS film is improved, and the withstand voltage is further improved.

The surface condition of the Si substrate facing the electrode 12 disposed on the glass substrate 2 depends on the shape of the support substrate 52 supporting the diffusion source 51 in the boron doping step as shown in Table 1 below. Diffusion source 5
When a ring-shaped SiC substrate contacting with only 1 at the outer peripheral portion of 0.5 mm was used, no fogging was observed on the Si substrate surface,
No damage was occurring. Further, when a circular SiC substrate in contact with the entire surface of the diffusion source 51 is used, as in the conventional technique, the surface of the Si substrate is observed to be fogged and damaged.

The insulating film 1 formed by the above method
In the case of using a ring-shaped SiC substrate that is in contact with the diffusion source 51 only at the outer peripheral portion of 0.5 mm, a dielectric withstand voltage of 10.0 MV / cm on the average in the Si substrate surface is obtained.
In addition, when a circular SiC substrate in contact with the entire surface of the diffusion source 51 was used, an average withstand voltage of 3.0 MV / cm in the Si substrate surface was obtained.

By a thermal diffusion method using a supporting substrate such that the diffusion source 51 contacts only the outer periphery, damage to the Si substrate generated in the boron doping process is reduced, and the withstand voltage of the TEOS film formed on the boron diffusion surface is reduced. Could be kept high.

[0033]

[Table 1]

(Embodiment 2) In the boron doping step according to the second embodiment of the present invention, the surface of the diffusion source facing the Si substrate was changed to the surface of the diffusion source facing the Si substrate during the previous thermal diffusion. The case where heat diffusion is performed on the opposite surface will be described with reference to FIG. 6 showing a method for setting a diffusion source.

First, the new diffusion source 51 is set on a quartz boat with the surface 61 facing the Si substrate 41 and the surface 62 facing the ring-shaped support substrate 52 that is in contact with the diffusion source 51 only at the outer periphery. (FIG. 6A). The central portion of the diffusion source 51 that is not supported by the support substrate 52 during thermal diffusion is warped downward.

Therefore, if thermal diffusion is repeated many times in the same set state, the amount of warpage at the central portion of the diffusion source increases, the facing distance with the Si substrate 41 increases, and the amount of boron diffusion becomes uniform within the Si substrate surface. The sex worsens.

Therefore, in the thermal diffusion after the second use of the diffusion source, the surface 61 facing the Si substrate 41 at the time of the previous thermal diffusion is diffused toward the support substrate 52 (FIG. 6).
(B)).

According to this method, the amount of warpage at the center of the diffusion source is increased in one direction, so that the boron diffusion amount
It was possible to prevent the in-plane uniformity of the substrate from deteriorating.

(Embodiment 3) The third embodiment of the present invention relates to whether or not the diffusion source is adhered to the support substrate due to a difference in the material of the support substrate of the diffusion source and whether or not the diffusion source is adhered to the quartz boat. It is as shown in Table 2 below.

When the material of the supporting substrate is SiC, the sticking of the diffusion source to the supporting substrate and the sticking of the diffusion source to the quartz boat are performed when the diffusion temperature is 1050 degrees Celsius.
Neither case occurred at 0 degrees. In addition, when the material of the support substrate is quartz, the diffusion temperature is 1050 degrees Celsius, and when the temperature is 1100 degrees, the diffusion source and the support substrate are stuck together. The quartz plate and the diffusion source were cracked due to the difference in thermal expansion coefficient between the diffusion source and the quartz plate. In addition, when the supporting substrate was not used, when the diffusion temperature was 1050 degrees Celsius, the adhesion between the diffusion source and the quartz boat did not occur, but when the diffusion temperature was 1100 degrees Celsius, the adhesion to the quartz boat did not occur. Sticking happened.

By using a supporting substrate made of SiC, it is possible to prevent the diffusion source from sticking to the supporting substrate and the diffusion source from sticking to the quartz boat, and to prevent the diffusion source and the supporting substrate from cracking. Was.

When the diffusion temperature is around 1050 degrees Celsius, the diffusion can be performed without using a support substrate by using a quartz boat in which the facing distance between the diffusion source and the Si substrate is adjusted.

[0043]

[Table 2]

[0044]

As described above, according to the method of manufacturing an ink jet head of the present invention, thermal diffusion of impurities from the supporting substrate can be suppressed by using the supporting substrate which is in contact with the diffusion source only at the outer peripheral portion. And the thermal diffusion of boron becomes uniform, the damage to the Si substrate disposed opposite to the diffusion source can be reduced, and the dielectric breakdown voltage of the TEOS insulating film formed on the diffusion surface of the Si substrate is kept high. be able to.

Further, by making the surface of the diffusion source facing the Si substrate opposite to the surface of the diffusion source facing the Si substrate in the previous thermal diffusion, the amount of warpage of the diffusion source is reduced in one direction. Thus, it is possible to prevent an increase in the amount of boron and prevent the in-plane uniformity of the amount of boron diffusion from deteriorating.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional side view of the inkjet head according to the embodiment of the present invention.

FIG. 3 is a view taken along the line AA ′ in FIG. 2;

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

FIG. 5 is a diagram showing a boron diffusion method according to the first embodiment of the present invention.

FIG. 6 is a view showing a method for setting a diffusion source to a quartz boat in a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st board | substrate 2 2nd board | substrate 3 3rd board | substrate 4 Vibration plate 5 Discharge chamber 6 Depression 7 Orifice 8 Narrow groove 9 Reservoir 10 Depression 11 Insulation film 12 Electrode 13 Depression 14 Lead part 15 Terminal part 16 Nozzle hole 17 Ink Supply port 18 Oscillation circuit 19 Ink droplet 20 Recording paper 41 Si substrate 42 Oxide film 43 Surface on which boron doped layer is formed 44 Opposite surface 45 Boron doped layer 46 TEOS film 51 Diffusion source 52 Support substrate 53 Dummy Si substrate 54 Quartz boat 61 Diffusion One side of source 62 Opposite side of diffusion source

Claims (3)

[Claims] 1. A single or plural nozzle holes 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 ink jet head, wherein a diffusion source of a solid containing B ₂ O ₃ as a main component and a support substrate contacting only the outer peripheral portion with the diffusion source are arranged in a vertical furnace. A method for manufacturing an ink jet head, comprising: disposing a Si substrate facing the diffusion source; and thermally diffusing high-concentration boron into the Si substrate. 2. The surface of the diffusion source facing the Si substrate is a surface opposite to the surface of the diffusion source facing the Si substrate during the previous thermal diffusion. Of manufacturing an inkjet head. 3. The method according to claim 1, wherein the support substrate is made of SiC.