JP2002240299A - Method for manufacturing ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an ink jet head in which a diaphragm to be formed by an etching stop technique is formed highly accurately up to a sub micrometer thickness. SOLUTION: A boron dope layer 4 is formed to a Dope face of an Si substrate 1 under conditions of a diffusion temperature of 1025-1200 deg.C and a diffusion time of 0.5 hr or shorter. SiO2 films 5a are formed to both faces of the Si substrate 1 at a low temperature. The SiO2 film 5 formed to a Cav face 2 of the Si substrate 1 is patterned, and thereafter the boron dope layer 4 is formed by the etching stop technique as the diaphragm 4a.

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 A conventionally known ink jet head has a face ink jet type in which ink droplets are ejected from nozzle holes provided in a surface portion of a substrate, and ink droplets are supplied from nozzle holes provided in an end portion of a substrate. There is an edge ink jet type for discharging, and each type has a laminated structure in which three substrates are overlapped and joined. An intermediate substrate of the three laminated substrates is made of Si, and has a plurality of concave discharge chambers having a bottom wall as a diaphragm,
A concave reservoir for supplying ink to each discharge chamber and a narrow groove-shaped orifice connecting this reservoir and each discharge chamber are formed. Then, a thermal oxide film by thermal oxidation is applied as an insulating film on the entire surface of the substrate, and is a film for preventing dielectric breakdown and short circuit at the time of inkjet driving. The diaphragm of this conventional inkjet head is formed through the steps shown in FIG. FIG. 5 is a process chart showing a method for manufacturing an intermediate substrate of a conventional inkjet head. (A) First, Cav surface 2 on both surfaces of Si substrate 1 and Dope
The surface 3 is mirror-polished to produce a substrate having a thickness of 180 μm. (B) Then, a boron diffusion plate (not shown) is made to face the Dope surface of the Si substrate 1 and the Si substrate 1 is heated at a temperature of 1100 degrees C.
Boron (B) is diffused into the Dope surface 3 of the Si substrate 1 by performing a heat treatment for a time to form a boron doped layer 4. In addition, as another means for forming a high-concentration boron-doped layer, there is a method of performing thermal oxidation. (C) The Si substrate 1 having the boron doped layer formed on the Dope surface is set in a thermal oxidation furnace to be in an oxygen and water vapor atmosphere,
Thermal oxidation treatment at a temperature of 1100 degrees Celsius for 4 hours
1.2 μm thermal oxide film (SiO ₂ film) 5 on the surface of substrate 1
To form (D) Then, a resist 6 is coated on both surfaces of the Si substrate 1, and a resist patterning for forming a discharge chamber or the like is performed on the Cav surface 2 side. (E) The SiO ₂ film 5 is patterned by etching the resist-patterned Cav surface 2 with a hydrofluoric acid aqueous solution, and the resists 6 on both surfaces of the Si substrate 1 are peeled off. At this time, the SiO ₂ film coated with the resist 6 remains. (F) The Si substrate 1 is immersed in a 35% by weight aqueous solution of potassium hydroxide at a high concentration to perform Si etching, and the etching is continued until the thickness of the etched portion Si becomes 10 μm. Thereafter, the Si substrate 1 is immersed in a 3 wt% aqueous solution of potassium hydroxide at a low concentration to perform Si etching. When the Si substrate 1 reaches the boron doped layer 4, the etching is stopped and the boron doped layer 4 remains. The thickness of this boron-doped layer is 2 μm, and it becomes the diaphragm 4a. (G) Then, the SiO ₂ film remaining on the Si substrate 1 is removed by etching with a hydrofluoric acid aqueous solution. Thereafter, a 0.1 μm SiO ₂ film is formed on the surface of the Si substrate 1 by thermal oxidation.
This is used as an insulating film. As shown in FIG. 6, for example, in the case of a face ink jet type, it has a diaphragm 4a manufactured through the above-described steps, and further has a reservoir 7
The nozzle hole 12 and the reservoir 7 communicating with the discharge chamber 8 are provided on the upper surface of the Si substrate 1 on which the discharge chamber 8 and the through hole 9 are formed.
(Si) 11 having an ink supply port 13 communicating with the substrate and a narrow groove for communicating the discharge chamber 8 with the reservoir 7, and a substrate (on the lower surface, on which an electrode 22 facing the diaphragm 4 a is mounted) (Made of glass) 21 is joined. The through-hole 9 formed in the Si substrate 1 has an electrode 22 of a glass substrate 21 bonded to the lower surface of the Si substrate 1 and a drive circuit (not shown) for applying a pulse to the electrically connected 22.
And for electrically connecting the

[0003]

As described in the step (C) of the conventional manufacturing method described above, the Do
After the boron doped layer 4 is formed on the pe surface 3, an SiO ₂ film 5 serving as an etching protection film is formed on the surface of the Si substrate 1 by thermal oxidation. The temperature at which the SiO ₂ film is applied is 1100 degrees Celsius. High temperature, the Do of Si substrate 1
Boron diffused at a high concentration on the pe surface 3 is further thermally diffused into the Si substrate 1, so that it was not possible to manufacture a highly accurate submicron-thick diaphragm 4a.
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and is intended to prevent the thermal diffusion of boron due to thermal oxidation at the time of forming an etching protective film, and to manufacture an ink jet head capable of providing a diaphragm with high accuracy up to a submicron thickness. The aim is to get the method.

[0004]

(1) A method of manufacturing an ink jet head according to the present invention includes a step of forming an etching protective film at a low temperature, and a method of forming a silicon substrate on which a boron-doped layer is formed at a predetermined concentration of hydroxylation. In a method of manufacturing an ink jet head in which a boron-doped layer is formed as a vibration plate by an etching stop technique by immersing in a potassium aqueous solution, the boron-doped layer has a diffusion temperature of 1025 ° C. to 12 ° C.
It is formed at a diffusion time of 0.5 hours or more at 00 degrees. By diffusing B in this temperature and time range, a diaphragm having a thickness suitable for an inkjet head can be formed. (2) According to the present invention, the thickness of the diaphragm formed by the etching stop technique can be set to 0.4 μm or more and 16 μm or less. Further, in the present invention, it is possible to form a considerably thin diaphragm having a thickness of up to 0.4 μm as compared with a conventional diaphragm, so that it is possible to provide a more accurate inkjet head. (3) In the method for manufacturing an ink jet head according to the present invention, the formation temperature of the etching protection film is 800 ° C. or less. This low temperature can suppress the diffusion of boron in the boron-doped layer, so that a thin diaphragm can be formed by the etching stop technique.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 In the first embodiment of the present invention, a boron-doped layer is formed on the Dope surface of the Si substrate 1, and then an etching protection film is formed on both surfaces so that a diaphragm having a predetermined thickness can be obtained.

Hereinafter, steps until a diaphragm is formed will be described with reference to FIG. FIG. 1 is a process chart showing a method for manufacturing an intermediate substrate of an inkjet head according to Embodiment 1 of the present invention. Note that the same or corresponding parts as those of the conventional example described with reference to FIG.

(A) First, the Cav surface 2 of the Si substrate 1 and D
Each of the ope surfaces 3 is mirror-polished to a thickness of, for example, 140 μm.
m substrates are prepared.

(B) A boron diffusion plate (not shown) is opposed to the Dope surface 3, and is heated at, for example, a temperature of 1050 degrees Celsius for 8 hours to diffuse boron (B) into the Dope surface 3, thereby forming a boron doped layer 4. To form

(C) The Si substrate 1 is set in a plasma CVD apparatus, and a film forming process is performed at a temperature of, for example, 360 degrees Celsius, and the surface of the boron-doped layer 4 is made of, for example, 2 μm SiO _2.
The film 5a is formed as an etching protection film.

(D) Thereafter, a resist 6 is coated on both surfaces of the Si substrate 1, and resist patterning is performed on the two surfaces of the Cav surface to form a discharge chamber.

(E) Ca with resist patterning
The v surface 2 is etched with a hydrofluoric acid aqueous solution to pattern the SiO ₂ film, and the resists 6 on both surfaces of the Si substrate 1 are peeled off.

(F) Then, the Si substrate 1 is immersed in a 35% by weight aqueous solution of potassium hydroxide to carry out Si etching. At this time, the substrate is etched from the Si exposed on the Cav surface of the Si substrate 1. Then, the etching is continued until the thickness of the etched portion Si becomes 10 μm. Next, the Si substrate 1 is immersed in a 3 wt% aqueous solution of potassium hydroxide having a low concentration to perform Si etching. When the Si substrate 1 reaches the boron doped layer 4, the etching is stopped and the boron doped layer 4 remains. The thickness of this boron doped layer is 2
When it is μm, it becomes the diaphragm 4a.

(G) After that, S remaining on the Si substrate 1
iO₂The film 5 is removed by etching using a hydrofluoric acid aqueous solution,
The surface of the Si substrate 1 is coated with 0.1 μm S
iO ₂The film 5 is formed as an insulating film.

As described above, in the first embodiment, S
When the SiO ₂ film is applied to the boron-doped layer 4 of the i-substrate 1, the temperature is set to 800 ° C. or less, so that boron in the boron-doped layer can be suppressed, and therefore, the diaphragm formed by the etching stop technique 4a can be processed at a thickness of 0.8 μm. Hereinafter, the diffusion time and the diffusion temperature for forming the boron doped layer are shown in FIG.
It will be described in detail based on. FIG. 2 is a graph showing the relationship between the diffusion time and the diffusion temperature and the diaphragm thickness in the formation of the boron doped layer according to the first embodiment of the present invention.

When the thickness of the vibration plate is less than 0.4 μm, the thickness of the vibration plate is too small to obtain a sufficient repulsion force of the vibration plate required for ink ejection or to withstand vibration during driving of the ink jet head. The diaphragm will be damaged. Further, when SiO ₂ is formed as an insulating film on the diaphragm, the thinner the diaphragm is, the more easily the diaphragm is deformed by the film stress of SiO ₂ . From these facts, 0.4 μm is optimal as the lower limit of the diaphragm thickness.

As described above, the lower limit of the diaphragm thickness is set to 0.4 μm.
2, when the diffusion temperature is 1025 ° C., when the diffusion time is 8 hours or more, the lower limit of the diaphragm thickness is 0.4 μm.
Is exceeded, and a diaphragm can be formed. However, since the peak concentration of the B concentration itself is low, the effect of the etching stop is small and the accuracy of the diaphragm is low. When the diffusion temperature is lower than 1025 degrees Celsius, the peak concentration of B is further reduced and the accuracy of the diaphragm is deteriorated, and the diffusion takes a long time. Therefore, the lower limit of the diffusion temperature is 1025 degrees Celsius or more. Optimal.

Next, from the maximum operating temperature of the heating furnace and the B plate used for forming the boron doped layer, the upper limit of the diffusion temperature is 1 degree Celsius.
200 degrees. FIG. 2 shows that the diffusion temperature was 1200 ° C.
The diffusion time required to form a diaphragm having a thickness of 0.4 μm, which is the lower limit of the diaphragm thickness in degrees, is 0.5 hr. If the diffusion time is less than 0.5 hr, the thickness is 0.4 μm at any diffusion temperature.
It is impossible to form a diaphragm of m. Therefore, in order to form a diaphragm having a thickness of 0.4 μm or more,
A necessary condition is a diffusion time of 0.5 hr or more.

Next, the upper limit of the thickness of the diaphragm formed in the present invention will be described with reference to FIG. FIG. 3 is a diagram showing the relationship between the resolution (number of nozzles per inch (npi)) of the inkjet head formed according to the present invention and the required diaphragm thickness. The diaphragm thickness can be increased as long as the diffusion time is set longer, and the upper limit of the diaphragm thickness optimum for an inkjet head is set from the resolution of the inkjet head. The lower the resolution,
That is, as the width of the diaphragm increases, the diaphragm thickness increases as shown in FIG. 3 in order to obtain rigidity of the diaphragm suitable for electrostatic driving. Ink jets having a resolution of less than 50 npi have low practicality. In the present invention, it is sufficient to provide a method capable of forming a diaphragm having a thickness of 16 μm or less that can produce an ink jet head having a resolution of 50 npi or more. In addition, thickness 1
A diaphragm having a thickness of 6 μm or more can be sufficiently manufactured by the conventional technique, and the boron diffusion time required for forming the diaphragm becomes extremely long. Therefore, it is meaningless to apply the present invention. For these reasons, the upper limit of the diaphragm thickness is 16 μm.

In the present invention, in order to ensure the thickness accuracy of the diaphragm, it is necessary to form the etching protection film at a temperature at which the boron once diffused into the Si substrate does not re-diffuse and the concentration does not decrease. The diffusion coefficient of boron is 8 degrees Celsius.
It becomes 5 × 10 ¹⁷ cm ² / sec at 00 degrees, and it becomes 10 degrees Celsius.
Since the diffusion coefficient at 25 degrees is about 1 / 1,000 of 5 × 10 ¹⁴ cm ² / sec, the diffusion of boron can be almost ignored in the treatment at 800 degrees Celsius.

For example, a problem when the etching protection film is formed at a high temperature of 800 ° C. or more will be described. FIG. 4 is a diagram showing a change in the boron concentration depending on the diffusion depth of the boron-doped layer formed on the surface of the Si substrate, that is, a boron concentration profile.
After the boron diffusion, an etching protection film is formed at a temperature of 10 degrees Celsius.
These are boron concentration profiles when formed by a thermal oxidation method at 75 degrees.

When an etching protection film is formed by a thermal oxidation method requiring a high film forming temperature, boron re-diffuses at a high temperature during the thermal oxidation. Therefore, as shown in FIG. It can be seen that the position of the peak of the existing boron concentration is low and deeply shifted after the thermal oxidation. When such a shift occurs, the accuracy of the diaphragm deteriorates due to a decrease in the boron concentration. In order to ensure the accuracy of the diaphragm, it is necessary to form the etching protection film at 800 degrees Celsius or less at which boron does not re-diffuse. Therefore, the formation of the etching protection film may be performed at a temperature of 800 degrees Celsius or less. If the etching protection film can be formed at a temperature of not more than 800 degrees Celsius and has an etching resistance to potassium hydroxide, SiO ₂ ,
SiN or the like may be formed, or SiO ₂ may be formed by a sputtering method.

If a diaphragm is formed under the above-described method and conditions, a diaphragm with a high precision of a diaphragm thickness lower limit of 0.4 μm can be obtained by the etching stop technique.

[0023]

As described above, according to the present invention, when an etching protective film is applied to a Si substrate on which a boron-doped layer is formed, the etching protective film is formed at a low temperature, so that boron in the boron-doped layer can be suppressed and diffusion can be suppressed. Temperature 1025 degrees Celsius-1
Under conditions of 200 degrees and a diffusion time of 0.5 hr or more, the thickness of the diaphragm formed by the etching stop technique can be stably processed to a minimum of 0.4 μm with high precision.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for manufacturing a diaphragm of an inkjet head according to Embodiment 1 of the present invention.

FIG. 2 is a diagram showing a relationship between diffusion conditions and diaphragm thickness according to Embodiment 1 of the present invention.

FIG. 3 is a diagram showing the relationship between the resolution of an inkjet head formed according to the present invention and the required diaphragm thickness.

FIG. 4 is a diagram showing a change in boron concentration depending on the diffusion depth of a boron-doped layer formed on the surface of a Si substrate.

FIG. 5 is a process chart showing a conventional method for manufacturing a diaphragm of an inkjet head.

FIG. 6 is a cross-sectional view illustrating a configuration of an inkjet head.

[Explanation of symbols]

1 Si substrate 2 Cav surface 3 Dope surface 4 boron-doped layer 4a diaphragm 5 SiO ₂ (thermally oxidized) 5a SiO ₂ (CVD) 6 resist 7 reservoir 8 discharge chamber 9 through holes 10 narrow groove 11 Si substrate 12 nozzle holes 21 made of glass Substrate 22 electrode

Claims (3)

[Claims] A step of forming an etching protection film at a low temperature, immersing the Si substrate on which the boron-doped layer is formed in an aqueous solution of potassium hydroxide having a predetermined concentration, and forming the boron-doped layer as a diaphragm by an etching stop technique; A method for manufacturing an ink jet head, comprising: forming a boron-doped layer at a diffusion temperature of 1025 to 1200 degrees Celsius and forming a boron-doped layer for a diffusion time of 0.5 hr or more. 2. The thickness of the diaphragm is 0.4 μm or more and 16 μm or more.
The method according to claim 1, wherein: 3. The formation temperature of the etching protection film is 800 degrees Celsius.
2. The method according to claim 1, wherein the temperature is equal to or lower than the temperature.