JP3728906B2 - Through-hole forming method for inkjet head - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a through hole in an inkjet head of an inkjet printer. More specifically, the present invention relates to a method for forming a through hole by etching from both sides of a silicon single crystal substrate.
[0002]
[Prior art]
An ink jet head used in an ink jet printer has been proposed in which a plurality of ink nozzles that eject ink droplets to the outside and an ink supply path that communicates with these ink nozzles are formed on a semiconductor substrate. . In recent years, more precise and finer processing is required for inkjet heads in order to be able to print high-definition characters. For this reason, various methods for manufacturing an inkjet head have been developed.
[0003]
For example, in Japanese Patent Laid-Open No. 5-50601 by the present applicant, an ink nozzle and an ink supply are provided by applying a photolithographic technique and wet crystal anisotropic etching to a silicon single crystal substrate in an electrostatic drive type inkjet head. An ink jet head manufacturing method for forming a path with high accuracy is disclosed.
[0004]
The ink jet head disclosed in the publication includes a plurality of ink nozzles, ink cavities communicating with the ink nozzles, and a common ink reservoir that supplies ink to the ink cavities. The ink supplied from the external ink supply source to the ink reservoir of the inkjet head is supplied from the ink reservoir to the corresponding ink cavity via each ink supply port. The bottom surface of each ink cavity functions as a diaphragm, and ink droplets are directed outward from the ink nozzles communicating with the ink cavity by utilizing the volume variation of the ink cavity that fluctuates when the diaphragm is vibrated by electrostatic force. It is possible to discharge.
[0005]
The inkjet head includes a nozzle plate on which ink nozzles are formed, an ink supply path such as a reservoir and a cavity, a silicon single crystal substrate on which a vibration plate is formed, and an electrode for deflecting the vibration plate by electrostatic force. Adopted a structure in which glass substrates formed with are bonded together.
[0006]
By adopting such a structure, each ink jet head pattern (nozzle, ink supply path, electrode) is formed on each substrate, then the substrate is joined, and the joined substrate is cut to form each ink jet head. A manufacturing method of separating (so-called multi-blocking) can be adopted, and an inkjet head can be manufactured at low cost.
[0007]
In the nozzle plate which is the uppermost substrate among these three substrates, in addition to ink nozzles, through holes for connecting FPCs to, for example, electrodes separated into individual inkjet heads are formed by using, for example, etching. There is a need to. For ease of manufacturing, it is desirable to form the through hole and the ink nozzle by etching at the same time, but a minute hole for an ink nozzle that requires extremely high accuracy and high accuracy are not required so much. Simultaneously forming the through-holes having a large opening area by etching may cause a decrease in etching speed and a large variation in etching depth in the substrate (wafer) plane.
[0008]
[Problems to be solved by the invention]
The ink nozzle and the through hole of the ink jet head are formed by etching a silicon single crystal substrate as shown in the above prior art. However, during the anisotropic etching by plasma discharge, Since the total etching area including the etching area and the etching area of the nozzle is very large, the etching rate is lowered, and at the same time, the variation of the etching depth in the wafer surface is deteriorated. Here, since the etching depth of the ink nozzle is an important parameter for stable ejection, it is necessary to suppress variations in the etching depth as much as possible.
[0009]
In view of these points, the present invention is capable of forming ink nozzles and forming through-holes without decreasing the etching rate and without deteriorating the variation in etching depth in the wafer surface. The present invention proposes a method for forming a through hole of an ink jet head.
[0010]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a method for forming a through hole in a silicon single crystal substrate used in an inkjet head, wherein a first resist film is formed on the surface of the silicon single crystal substrate. A step of forming a silicon oxide film; a first patterning step of half-etching the silicon oxide film to form a half-etched region; and a first portion of the half-etched region formed by the first patterning step. The second groove located in the outer peripheral portion of the region where the through hole is formed is fully etched at a position away from the half-etched region, and an exposed portion of the surface of the silicon single crystal substrate, respectively. A second patterning step to be formed; and the exposed portion corresponding to the first groove and the second groove of the silicon single crystal substrate. A first dry etching step of performing anisotropic dry etching by plasma discharge, a full etching of the half etching region, the silicon single crystal substrate corresponding to the half etching region, and the second groove The silicon single crystal substrate corresponding to the region is subjected to anisotropic dry etching by plasma discharge to further etch the first groove, outside the position where the first groove is formed, A second dry etching step of forming a third groove having a width wider than one groove and further etching the silicon single crystal substrate corresponding to the region of the second groove; and the silicon single crystal substrate Forming a second silicon oxide film as a resist film on the surface of the silicon single crystal substrate, the first groove and the silicon monocrystal substrate Etching is performed on a position corresponding to the first groove and the second groove of the silicon single crystal substrate from the surface opposite to the surface on which the second groove is formed, and the first groove and the third groove are etched. Forming a nozzle having a plurality of grooves, and penetrating through the second groove to form the through hole.
[0013]
According to the through hole forming method of the present invention, not all the through holes are etched in the first dry etching step. The outer periphery of the area where the through hole is formed Since only etching is performed, the total area subjected to anisotropic dry etching can be greatly reduced. Therefore, according to the through hole forming method of the present invention, it is possible to easily form without reducing the etching rate and without deteriorating the variation of the etching depth in the wafer surface.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
(An example of an inkjet head to which the present invention is applied)
FIG. 1 shows a schematic cross section of an inkjet head to which the method of the present invention can be applied.
[0015]
Referring to FIG. 1, the ink jet head 1 of this example is an electrostatic drive type ink jet head similar to the ink jet head disclosed in Japanese Patent Laid-Open No. 5-50601 by the present applicant. A nozzle plate 2 made of a crystal substrate, a cavity plate 3 made of a silicon single crystal substrate, and a glass substrate 4 are bonded together.
[0016]
The cavity plate 3 is formed with a plurality of ink cavities 31 and a common ink reservoir 32 that supplies ink to each ink cavity 31. On the nozzle plate 2 side, a plurality of ink nozzles 21 communicating with each ink cavity 31 and an ink supply port 22 communicating each ink cavity 31 with a common ink reservoir 32 are formed. The ink supply port 22 has a cross-sectional shape in which a deep groove portion 22a is formed on one side and a shallow groove portion 22b is formed on the other side. The nozzle plate 2 is also formed with a through hole 23 for electrode wiring.
[0017]
In the glass substrate 4 attached to the back surface of the cavity plate 3, a concave portion 41 is formed in a portion facing the vibration plate 33 defining the bottom surface of the cavity 31, and the vibration plate 33 is formed on the bottom surface of the concave portion. Opposing individual electrodes 42 are formed. An ink supply hole 34 is formed in the bottom surface of the ink reservoir 32, and the ink supply hole 34 communicates with an ink supply path 43 formed in the glass substrate 4. Ink can be supplied to the ink reservoir 32 from an external ink supply source via the ink supply path 43 and the ink supply hole 34.
[0018]
The diaphragm 33 that defines the bottom surface of each cavity 31 formed on the cavity plate 3 functions as a common electrode, and a voltage is applied between the cavity plate 3 and the individual electrode 42 facing each diaphragm 33. When applied, the diaphragm 33 facing the individual electrode 42 to which a voltage is applied vibrates due to electrostatic force, and accordingly, the volume of the cavity 31 changes, and ink droplets are ejected from the ink nozzles 21.
[0019]
Here, the ink nozzle 21 is an ink nozzle having a stepped cross section. That is, a circular small cross-section nozzle portion 21a (small cross-section side portion) is formed on the front side in the ink droplet ejection direction, and a circular large cross-section nozzle portion 21b (large cross-section side portion) is formed on the rear side. These boundary portions are annular step surfaces 21c. Therefore, the cross-sectional shape cut along the axial direction of the ink nozzle 21 is reduced stepwise toward the tip side. The tip opening 21 d of the ink nozzle 21 opens at the bottom surface of the recess 24 formed on the opposite surface of the nozzle plate 2.
[0020]
(Comparative example)
2 to 5 show comparative examples of the manufacturing process of the nozzle plate 2. The manufacturing procedure of the nozzle plate 2 will be described with reference to these drawings.
[0021]
(Step 1: first thermal oxide film forming step)
First, as shown in FIG. 2A, a silicon wafer 200 having a thickness of 180 microns is prepared, the silicon wafer 200 is thermally oxidized, and a thickness of a resist film on its surface is 1.2 microns or more. The SiO2 film 210 is formed.
[0022]
(Step 2: First patterning step of SiO2 film)
Next, as shown in FIG. 2B, half-etching is performed on the portion of the SiO2 film 210 covering the surface 200a of the silicon wafer 200, so that the large cross-section nozzle portion 21b of the ink nozzle 21 and the ink supply port 22 are formed. Patterns 201b and 202b for forming the shallow groove portion 22b are formed. As an etchant, ammonium fluoride (HF: NH4F = 880 ml: 5610 ml) can be used. The etching depth can be set to 0.5 microns, for example.
[0023]
(Step 3: Second patterning step of SiO2 film)
Thereafter, as shown in FIG. 2C, the patterns 201a and 202a for forming the small section nozzle portion 21a of the ink nozzle 21 and the deep groove portion 22a of the ink supply port 22 are formed in the half-etched region of the SiO2 film 210. Are formed in the portions of the patterns 201b and 202b. That is, these half-etched regions are completely etched to form patterns 201a and 202a that expose the silicon wafer surface. Along with these patterns, a pattern 203 for forming the electrode through holes 23 is also formed by full etching of the SiO2 film 210. The etching liquid used in this case can also use the same ammonium fluoride as described above.
[0024]
(Step 4: first dry etching step)
In this way, after patterning the SiO2 film 210 twice, anisotropic dry etching by plasma discharge is performed on the silicon wafer 200 as shown in FIG. As a result, the surface of the silicon wafer 200 is vertically etched in a shape corresponding to the patterns 201b, 202b and 203 formed in Step 3, and grooves 221, 222 and 223 having the same depth are formed, respectively. The As an etching gas in this case, for example, a CF-based gas and SF6 are used, and these etching gases may be used alternately. Here, the CF-based gas is used to protect the groove side face so that the etching does not proceed to the side face of the groove to be formed, and SF6 is used to promote the etching of the silicon wafer in the vertical direction.
[0025]
Thus, for example, after the grooves 221, 222, and 223 having an etching depth of 35 microns are formed, the SiO2 film 210 is removed by etching with a hydrofluoric acid solution to a thickness of 0.7 microns. As a result, as shown in FIG. 3B, the portions of the patterns 201b and 202b formed in Step 2 are completely removed, and the surface of the silicon wafer 200 is exposed.
[0026]
(Step 5: second dry etching step)
Next, as shown in FIG. 3C, anisotropic dry etching by plasma discharge is performed again. As a result, the surface portion of the silicon wafer exposed from the patterns 201b, 202b, and 203 proceeds vertically in the thickness direction while maintaining its cross-sectional shape. The etching gas in this case is also the same as Step 4 described above, and the etching depth is set to 55 microns, for example. As a result, a nozzle groove 231 having a cross-sectional shape corresponding to the stepped ink nozzle 21 and a groove 232 having a cross-sectional shape corresponding to the ink supply port 22 are formed. Further, a groove 233 having a depth half that of the through hole 23 for electrode arrangement is also formed.
[0027]
Thereafter, the SiO2 film 210 is completely peeled off with a hydrofluoric acid aqueous solution (for example, HF: H2 O = 1: 5 vol, 25 ° C.). FIG. 3D shows this state.
[0028]
(Step 6: second thermal oxide film forming step)
Thereafter, the surface of the silicon wafer 200 is again thermally oxidized to form a SiO2 film 240 as a resist film. Even in this case, the thickness of the SiO2 film 240 may be 1.2 microns.
[0029]
(Step 7: Third patterning step of SiO2 film)
Next, as shown in FIG. 4B, a portion of the SiO2 film 240 that covers the surface 200b on the opposite side of the silicon wafer 200 is etched to form a pattern corresponding to the recess 24 in which the ink nozzles 21 are open. 204 and a turn 203A corresponding to the through hole 23 is formed. In this case, the etching solution used in Step 2 can be used.
[0030]
(Step 8: Wet etching process)
Next, as shown in FIG. 4C, the silicon wafer 200 is immersed in an etching solution and anisotropic wet etching is performed on the exposed portion of the silicon wafer 200 to form a groove 244 corresponding to the recess 24. The nozzle 21 is penetrated. In addition, a groove 233 </ b> A corresponding to the through hole 23 is formed to penetrate the through hole 23. The etching solution used in this case is an aqueous potassium hydroxide solution having a concentration of 2 wt% and a solution temperature of 80 ° C. The etching depth is, for example, 110 microns. After the etching is completed, as shown in FIG. 4D, the SiO2 film 240 is completely removed with a hydrofluoric acid aqueous solution.
[0031]
(Step 9: Final thermal oxidation process)
Finally, as shown in FIG. 5, in order to ensure the ink resistance of the silicon wafer and the adhesion of the water repellent treatment of the nozzle surface, the silicon wafer is again thermally oxidized to form a SiO2 film. Thus, the nozzle plate 2 is obtained.
[0032]
In the case where the nozzle and the through hole are formed by the above method, when the etching area of the through hole 23 becomes very large in the dry etching process of Step 4 and Step 5, the etching rate is lowered and at the same time the etching depth in the wafer surface is reduced. There was a case where the variation of the thickness became large.
[0033]
(Example of embodiment of the present invention)
6 to 9 show the manufacturing process of the nozzle plate 2. The manufacturing procedure of the nozzle plate 2 will be described with reference to these drawings.
[0034]
(Step 1: first thermal oxide film forming step)
First, as shown in FIG. 6A, a silicon wafer 300 having a thickness of 180 microns is prepared, the silicon wafer 300 is thermally oxidized, and the thickness of the resist film on the surface is 1.2 microns or more. The SiO2 film 310 is formed.
[0035]
(Step 2: First patterning step of SiO2 film)
Next, as shown in FIG. 6B, half-etching is performed on the portion of the SiO2 film 310 covering the surface 300a of the silicon wafer 300, so that the large-section nozzle portion 21b of the ink nozzle 21 and the ink supply port 22 are formed. Patterns 301b and 302b for forming the shallow trench portion 22b are formed. As an etchant, ammonium fluoride (HF: NH4F = 880 ml: 5610 ml) can be used. The etching depth can be set to 0.5 microns, for example.
[0036]
(Step 3: Second patterning step of SiO2 film)
Thereafter, as shown in FIG. 6C, patterns 301a and 302a for forming the small section nozzle portion 21a of the ink nozzle 21 and the deep groove portion 22a of the ink supply port 22 are formed in the half-etched region of the SiO2 film 310. Are formed in the portions of the patterns 301b and 302b. That is, these half-etched regions are completely etched to form patterns 301a and 302a that expose the silicon wafer surface. Along with these patterns, a pattern 303 for forming the through hole 23 for the electrode is also formed by fully etching the SiO2 film 310. The etching liquid used in this case can also use the same ammonium fluoride as described above.
[0037]
(Step 4: first dry etching step)
After the patterning of the SiO2 film 310 is performed twice in this way, anisotropic dry etching by plasma discharge, for example, ICP discharge is performed on the silicon wafer 300 as shown in FIG. As a result, the surface of the silicon wafer 300 is vertically etched in a shape corresponding to the patterns 301b, 302b and 303 formed in Step 3, and grooves 321, 322 and 323 having the same depth are formed, respectively. The At this time, since the groove 323 is only the outer peripheral groove for forming the through hole, the etching area can be greatly reduced, and the etching rate can be improved and the variation in the etching depth in the wafer surface can be improved. It becomes. Here, FIG. 10 shows an example of the relationship between the etching rate and the aperture ratio. The aperture ratio here is the ratio of the area of the etched portion to the area of the wafer. As shown in FIG. 10, for example, when the aperture ratio is 30%, the etching rate is 1.4 μm per minute, and when the aperture ratio is 7%, the etching rate is 1.9 μm per minute. That is, when the aperture ratio is decreased from 30% to 7%, the etching rate increases by about 36%. Further, the etching depth variation within the wafer surface is uniform within the wafer surface when the aperture ratio is 30%, whereas the uniformity within the wafer surface is 6% when the aperture ratio is 7%. The uniformity is significantly improved at 4%. As an etching gas in this case, for example, a CF-based gas and SF6 are used, and these etching gases may be used alternately. Here, the CF-based gas is used to protect the groove side face so that the etching does not proceed to the side face of the groove to be formed, and SF6 is used to promote the etching of the silicon wafer in the vertical direction. Here, as other anisotropic dry etching methods, ECR (electron cyclotron resonance) discharge, HWP (helicon wave plasma) discharge, RIE (reactive ion etching), or the like may be used. Thus, for example, after the grooves 321, 322, and 323 having an etching depth of 35 μm are formed, the SiO 2 film 310 is etched away to a thickness of 0.7 μm with a hydrofluoric acid aqueous solution. As a result, as shown in FIG. 7B, the portions of the patterns 301b and 302b formed in Step 2 are completely removed, and the surface of the silicon wafer 300 is exposed.
[0038]
(Step 5: second dry etching step)
Next, as shown in FIG. 7C, anisotropic dry etching by plasma discharge, for example, ICP discharge is performed again. As a result, the surface portions of the silicon wafer exposed from the patterns 301b, 302b, and 303 are etched vertically in the thickness direction while maintaining the cross-sectional shape. In this case as well, since only the outer peripheral grooves for forming the through holes are formed as in Step 4 described above, the etching area can be greatly reduced, and the etching rate is improved and the etching depth variation in the wafer surface is improved. It becomes possible. The etching gas in this case is also the same as Step 4 described above, and the etching depth is set to 55 microns, for example. Here, as other anisotropic dry etching methods, ECR (electron cyclotron resonance) discharge, HWP (helicon wave plasma) discharge, RIE (reactive ion etching) or the like may be used as in Step 4 described above. As a result, a nozzle groove 331 having a cross-sectional shape corresponding to the stepped ink nozzle 21 and a groove 332 having a cross-sectional shape corresponding to the ink supply port 22 are formed. Further, a groove 333 having a half depth of the through hole 23 for electrode arrangement is also formed.
[0039]
Thereafter, the SiO2 film 310 is completely peeled off with a hydrofluoric acid aqueous solution (for example, HF: H2 O = 1: 5 vol, 25.degree. C.). FIG. 7D shows this state.
[0040]
(Step 6: second thermal oxide film forming step)
Thereafter, the surface of the silicon wafer 200 is again thermally oxidized to form a SiO2 film 340 as a resist film. Even in this case, the thickness of the SiO2 film 340 may be 1.2 microns.
[0041]
(Step 7: Third patterning step of SiO2 film)
Next, as shown in FIG. 8B, the portion of the SiO2 film 340 covering the surface 300b on the opposite side of the silicon wafer 300 is etched, and a pattern corresponding to the recess 24 where the ink nozzles 21 are opened. 304 and a pattern 303A corresponding to the through hole 23 are formed. In this case, the etching solution used in Step 2 can be used.
[0042]
(Step 8: Wet etching process)
Next, as shown in FIG. 8C, the silicon wafer 300 is immersed in an etchant and anisotropic wet etching is performed on the exposed portion of the silicon wafer 300 to form a groove 344 corresponding to the recess 24. The nozzle 21 is penetrated. Further, a groove 333 </ b> A corresponding to the through hole 23 is formed to penetrate the through hole 23. The etching solution used in this case is an aqueous potassium hydroxide solution having a concentration of 2 wt% and a solution temperature of 80 ° C. The etching depth is, for example, 110 microns. After the etching is completed, as shown in FIG. 8D, the SiO2 film 340 is completely removed with a hydrofluoric acid aqueous solution.
[0043]
(Step 9: Final thermal oxidation process)
Finally, as shown in FIG. 9, in order to ensure the ink resistance of the silicon wafer and the adhesion of the water repellent treatment of the nozzle surface, the silicon wafer is thermally oxidized again to form a SiO2 film. Thus, the nozzle plate 2 is obtained.
[0044]
【The invention's effect】
As described above, in the method for forming a through hole of an ink jet head according to the present invention, when forming the nozzle and the through hole using anisotropic dry etching by plasma discharge, the through hole is not etched. By etching only the outer peripheral groove, the total etching area in the wafer surface can be greatly reduced, and the etching rate and the etching depth variation in the wafer surface can be improved. Therefore, the method of the present invention has the effect of being suitable for mass production because it can stabilize the ejection characteristics by reducing the variation in the etching depth of the nozzle and improve the processing speed.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an electrostatic drive type inkjet head to which the present invention is applicable.
2A is an explanatory view showing a first thermal oxide film forming process of a comparative example in the manufacturing process of the nozzle plate of the ink jet head of FIG. 1, and FIG. 2B is a first diagram of a SiO 2 film in the manufacturing process. An explanatory view showing a patterning step, (C) is an explanatory view showing a second patterning step of the SiO2 film in the manufacturing step.
3A is an explanatory view showing a first dry etching process for a silicon wafer of a comparative example in the manufacturing process of the nozzle plate of the ink jet head of FIG. 1, and FIG. 3B is a half-etching portion removed in the manufacturing process; (C) is an explanatory view showing a second dry etching process for the silicon wafer in the manufacturing process, and (D) is an explanatory view showing a state after removing the SiO2 film in the manufacturing process. FIG.
4A is an explanatory view showing a second thermal oxide film forming process of a comparative example in the manufacturing process of the nozzle plate of the inkjet head of FIG. 1, and FIG. 4B is a third diagram of a SiO 2 film in the manufacturing process. An explanatory view showing a patterning step, (C) is an explanatory view showing a wet etching step for a silicon wafer in the manufacturing step, and (D) is an explanatory view showing a state after removing the SiO2 film in the manufacturing step.
5 is an explanatory view showing a final thermal oxide film forming step of a comparative example in the manufacturing process of the nozzle plate of the ink jet head of FIG. 1. FIG.
6A is an explanatory view showing a first thermal oxide film forming step in the manufacturing process of the nozzle plate of the ink jet head of FIG. 1 according to the present invention, and FIG. 6B is a first view of a SiO2 film in the manufacturing step. (C) is an explanatory view showing a second patterning step of the SiO2 film in the manufacturing step.
7A is an explanatory view showing a first dry etching process for a silicon wafer in the manufacturing process of the nozzle plate of the inkjet head of FIG. 1 according to the present invention, and FIG. 7B is a half-etched portion in the manufacturing process; An explanatory view showing a state after removal, (C) is an explanatory view showing a second dry etching process for a silicon wafer in the same manufacturing process, and (D) is a state after removing the SiO2 film in the same manufacturing process. It is explanatory drawing.
8A is an explanatory view showing a second thermal oxide film forming step in the manufacturing process of the nozzle plate of the ink jet head of FIG. 1 according to the present invention, and FIG. 8B is a third diagram of a SiO2 film in the manufacturing step. (C) is an explanatory view showing a wet etching process for a silicon wafer in the manufacturing process, and (D) is an explanatory view showing a state after removing the SiO2 film in the manufacturing process.
9 is an explanatory view showing a final thermal oxide film forming step in the manufacturing process of the nozzle plate of the ink jet head of FIG. 1 according to the present invention.
FIG. 10 is a graph showing the relationship between the opening ratio of the silicon wafer and the etching rate in the dry etching process of the silicon wafer.
[Explanation of symbols]
1 Inkjet head
2 Nozzle plate
3 Cavity plate
4 Glass substrate
21 Ink nozzle
21a Front nozzle part
21b Rear nozzle part
21c An annular step surface
22 Ink supply port
22a Deep groove part
22b Shallow groove
23 Through hole
24 Nozzle groove
31 cavities
32 Ink reservoir
33 Diaphragm
34 Ink supply port
41 Glass groove
42 Individual electrodes
43 Ink supply path
200 Silicon wafer
201b Opening pattern by half-etching
202b Opening pattern by half etching
201a Open pattern by full etching
202a Open pattern by full etching
203 Opening pattern by full etching
204 Opening pattern by full etching
210 SiO2 film
221 first groove
222 First groove
223 first through hole outer peripheral groove
231 Second groove
232 second groove
233 Second through hole outer peripheral groove
240 SiO2 film
244 Nozzle groove
300 silicon wafer
301b Opening pattern by half-etching
302b Opening pattern by half etching
301a Open pattern by full etching
302a Open pattern by full etching
303 Opening pattern by full etching
304 Opening pattern by full etching
310 SiO2 film
321 first groove
322 first groove
323 1st through-hole outer periphery groove | channel
331 Second groove
332 second groove
333 second through hole outer peripheral groove
340 SiO2 film
344 Nozzle surface groove

Claims (5)

A method of forming a through hole in a silicon single crystal substrate used for an inkjet head,
Forming a first silicon oxide film as a resist film on the surface of the silicon single crystal substrate;
A first patterning step of half-etching the silicon oxide film to form a half-etched region;
A first groove is formed in a part of the half-etched region formed by the first patterning step, and a second groove located at a position away from the half-etched region and at an outer peripheral portion of the region where the through hole is formed. A second patterning step in which each of the grooves is fully etched to form an exposed portion of the surface of the silicon single crystal substrate;
A first dry etching step of performing anisotropic dry etching by plasma discharge on the exposed portions corresponding to the first groove and the second groove of the silicon single crystal substrate;
Full etching of the half etching region, and anisotropic dry etching of the silicon single crystal substrate corresponding to the half etching region and the silicon single crystal substrate corresponding to the region of the second groove by plasma discharge. To further etch the first groove to form a third groove outside the position where the first groove is formed and having a width wider than the first groove. A second dry etching step of further etching the silicon single crystal substrate corresponding to the groove region;
Forming a second silicon oxide film as a resist film on the surface of the silicon single crystal substrate;
Positions corresponding to the first groove and the second groove of the silicon single crystal substrate from the surface opposite to the surface on which the first groove and the second groove are formed of the silicon single crystal substrate. Etching, forming a nozzle having the first groove and the third groove, penetrating the second groove, and forming the through hole;
A method for forming a through hole of an ink jet head, comprising: The first dry etching step or in the second dry etching process, characterized by anisotropically dry etched by ICP (inductively coupled plasma) discharge to the exposed portion of the silicon single crystal substrate The method for forming a through hole in an ink jet head according to claim 1 . The first dry etching step or in the second dry etching step, and wherein the anisotropically dry etched by ECR (electron cyclotron resonance plasma) discharge to the exposed portion of the silicon single crystal substrate The method for forming a through hole in an ink jet head according to claim 1 . The first dry etching step or in the second dry etching process, characterized by anisotropically dry etching the HWP (helicon wave plasma) discharge to the exposed portion of the silicon single crystal substrate The method for forming a through hole in an ink jet head according to claim 1 . The first dry etching step or in the second dry etching process, characterized by anisotropically dry etched by RIE (reactive ion etching) to said exposed portion of said silicon single-crystal substrate The method for forming a through hole in an ink jet head according to claim 1 .

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