JP6780466B2 - Nozzle plate manufacturing method and inkjet head manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a nozzle plate and a method for manufacturing an inkjet head using the manufacturing method.

Conventionally, in order to improve the ejection accuracy of an inkjet head that ejects ink from a nozzle, a nozzle plate that processes only the vicinity of the outlet of a tapered nozzle to be straight has been proposed. By forming the straight portion on the nozzle, the dimensional accuracy of the hole diameter at the time of processing the nozzle is stabilized, so that the effect of keeping the ink ejection amount in each nozzle constant can be expected.

Methods for manufacturing such nozzle plates are disclosed, for example, in Patent Documents 1 and 2. In the manufacturing method of Patent Document 1, as shown in FIG. 16, first, a high concentration of boron is injected into the surface layer portion of one surface of the silicon substrate 101 to form the boron layer 102. Subsequently, the mask layer 103 is formed on the surface on which the boron layer 102 is not formed on the silicon substrate 101 to perform patterning, and wet etching is performed from the patterned mask layer 103 side to taper the silicon substrate 101. Part 104a is formed. At this time, the boron layer 102 functions as an etching stopper layer and is not etched. After the etching of the tapered portion 104a is completed and the mask layer 103 is removed, the mask layer 105 is formed on the high-concentration boron layer 102 to perform patterning. Then, the straight portion 104b is attached to the boron layer 102 by performing dry etching on the boron layer 102 from the mask layer 105 side, that is, from the side opposite to the side where the wet etching is performed (the side where the tapered portion 104a is formed). Form. Finally, by removing the mask layer 105, the nozzle plate 100 having the nozzle 104 in which the tapered portion 104a and the straight portion 104b communicate with each other is completed.

On the other hand, in the manufacturing method of Patent Document 2, as shown in FIG. 17, first, an etching stopper layer (for example, a silicon oxide layer) 202 is formed on one surface of the silicon substrate 201. Subsequently, a mask layer 203 is formed on the other surface of the silicon substrate 201 to perform patterning, and dry etching is performed on the silicon substrate 201 from the patterned mask layer 203 side, whereby the tapered portion 204a is formed on the silicon substrate 201. To form. After that, the same mask layer 203 is used, and the etching stopper layer 202 is dry-etched from the mask layer 203 side to form a straight portion 204b on the etching stopper layer 202. Finally, by peeling off the mask layer 203, the nozzle plate 200 having the nozzle 204 in which the tapered portion 204a and the straight portion 204b communicate with each other is completed.

Japanese Patent No. 3269618 (see claim 10, paragraphs [0033] to [0039], FIG. 3, etc.) Japanese Patent No. 4706850 (see claim 1, paragraphs [0024] to [0030], FIG. 1, etc.)

However, in the manufacturing method of Patent Document 1, since the tapered portion 104a and the straight portion 104b of the nozzle 104 are formed by etching from opposite sides to the silicon substrate 101, the tapered portion 104a and the straight portion 104b are formed. The center positions of the holes tend to shift, and these cannot be formed with good position accuracy. The misalignment of the tapered portion 104a and the straight portion 104b affects the ink ejection characteristics, and if the misalignment is large, the ink ejection direction is bent and the ejection characteristics are deteriorated.

On the other hand, in the manufacturing method of Patent Document 2, since the tapered portion 204a and the straight portion 204b are formed on the silicon substrate 201 by processing from the same surface side (mask layer 203 side) with respect to the silicon substrate 201, the tapered portion The misalignment of the 204a and the straight portion 204b can be suppressed. However, since the same mask layer 203 is used when the tapered portion 204a is processed and when the straight portion 204b is processed, deterioration of the processing accuracy of the straight portion 204b occurs as a new problem.

That is, when the tapered portion 204a is processed, the edge portion 203a of the patterned mask layer 203 is also slightly etched, and the edge portion 203a recedes. Therefore, when the straight portion 204b is formed by using the mask layer 203 in the next step, it becomes difficult to form the straight portion 204b in a desired shape. Further, in general, in processing a processing target using a mask layer, it is necessary to bring the mask layer into close contact with the processing target in order to improve the processing accuracy. However, in the manufacturing method of Patent Document 2, the patterned mask layer 203 is separated from the etching stopper layer 202, which is the processing target of the straight portion 204b, by the thickness of the silicon substrate 201, and is not in close contact with the mask layer 203. Therefore, the processing accuracy of the etching stopper layer 202 deteriorates, and it becomes difficult to process the straight portion 204b with high accuracy. If the processing accuracy of the straight portion 204b deteriorates, the hole diameter of the straight portion 204b will vary widely among the nozzles 204, and the amount of ink ejected will vary among the nozzles 204.

The present invention has been made to solve the above problems, and an object of the present invention is to improve both the positional accuracy of the tapered portion and the straight portion of the nozzle and the machining accuracy of the straight portion. It is an object of the present invention to provide a manufacturing method and a manufacturing method of an inkjet head including the manufacturing method.

The method for manufacturing a nozzle plate according to one aspect of the present invention includes a first pattern forming step of forming a first mask pattern having a first opening on one surface of a nozzle forming substrate, and the first pattern forming step. The first opening has a second opening having an opening diameter smaller than that of the first opening of the mask pattern of the above, and the second opening is located inside the first opening. The nozzle forming substrate is placed on the one surface side of the nozzle forming substrate through the second pattern forming step of forming the second mask pattern covering the mask material of the mask pattern and the second opening of the second mask pattern. A taper portion forming step of forming a tapered portion having a reverse taper shape in which the opening width increases as the nozzle forming substrate advances from one surface side in the thickness direction of the nozzle forming substrate by dry etching from the nozzle forming substrate. After forming the tapered portion, the second pattern removing step of removing the second mask pattern to expose the first mask pattern and the first opening of the exposed first mask pattern are formed. By dry-etching the nozzle-forming substrate straight from one surface side in the thickness direction of the nozzle-forming substrate, a straight portion communicating with the tapered portion is formed on the nozzle-forming substrate. Includes a straight portion forming step.

In the taper portion forming step, a step (a) of forming a protective film so as to cover the surface of the nozzle forming substrate exposed through the inside of the second opening, and a step (a) of forming the protective film on the nozzle. A step (b) of selectively removing the substrate by anisotropic etching in the thickness direction of the substrate and a step (c) of isotropic etching of the substrate for forming a nozzle exposed by the selective removal of the protective film. By repeating the above steps and changing the etching conditions of the step (c) for each repetition of the steps (a) to (c), the tapered portion is formed on the nozzle forming substrate. May be good.

In the taper portion forming step, the tapered portion is formed on the nozzle forming substrate by lengthening the etching time in the step (c) each time the steps (a) to (c) are repeated. You may.

The first pattern forming step is a step of forming the mask material on the entire surface of the one surface of the nozzle forming substrate, and a resist having an opening corresponding to the first opening on the mask material. A step of forming the pattern and a step of forming the first mask pattern having the first opening by patterning the mask material using the resist pattern as a mask may be included.

The first mask material may be a silicon oxide film.

When the mask material of the first mask pattern is used as the first mask material, the second pattern forming step is performed on the inside of the first opening in the first mask pattern and the first mask. A step of applying a second mask material different from the first mask material on the material, and removing a part of the second mask material applied to the inside of the first opening. Thereby, the step of forming the second mask pattern having the second opening inside the first opening so as to cover the first mask material may be included.

It is desirable that the opening center of the first opening and the opening center of the second opening coincide with each other in a plane perpendicular to the thickness direction of the nozzle forming substrate.

The second mask material may be a photosensitive resin.

The first pattern forming step may include a step of forming an etching stopper layer on the other surface of the nozzle forming substrate.

The nozzle-forming substrate is an SOI substrate in which two silicon substrates are bonded via an oxide film, and in the taper portion forming step, the tapered portion is formed on one silicon substrate of the nozzle-forming substrate, and the tapered portion is formed. In the straight portion forming step, the straight portion is formed on the one silicon substrate of the nozzle forming substrate, and in the manufacturing method, after the straight portion forming step, the other silicon substrate and the oxide film are formed on the one. A step of forming a communication passage portion for forming a communication passage portion communicating with the tapered portion on the nozzle forming substrate by dry etching from the side opposite to the silicon substrate of the above may be further included.

After the straight portion forming step, a first pattern removing step of removing the first mask pattern may be further included.

It is desirable that the length of the straight portion along the thickness direction of the nozzle forming substrate is 10 μm or less.

It is desirable that the length of the tapered portion along the thickness direction of the nozzle forming substrate is 10 μm or more.

The method for manufacturing an inkjet head according to another aspect of the present invention is a method for manufacturing an inkjet head using the above-described method for manufacturing a nozzle plate, in which the tapered portion and the straight portion are formed into the nozzle. The step includes joining the nozzle plate formed on the substrate for use and the substrate on which the piezoelectric element is supported and the pressure chamber is formed so that the pressure chamber and the tapered portion communicate with each other.

According to the above manufacturing method, both the positional accuracy of the tapered portion and the straight portion of the nozzle and the processing accuracy of the straight portion can be improved.

It is explanatory drawing which shows the schematic structure of the inkjet printer which concerns on one Embodiment of this invention. It is a top view which shows the schematic structure of the actuator of the inkjet head included in the said inkjet printer. 2A is a cross-sectional view taken along the line AA'in FIG. 2A. It is sectional drawing of the said inkjet head. It is a flowchart which shows the process flow at the time of manufacturing the said inkjet head. It is sectional drawing which shows the manufacturing process of the said inkjet head. It is sectional drawing which shows the nozzle plate applied to the said inkjet head in an enlarged manner. It is a flowchart which shows the flow at the time of manufacturing of the said nozzle plate. It is sectional drawing which shows the manufacturing process of the said nozzle plate. It is sectional drawing which shows the manufacturing process of the said nozzle plate. It is a top view of the substrate for forming a nozzle used for manufacturing the said nozzle plate. It is sectional drawing which shows the detail of the taper part forming process included in the manufacturing process of the nozzle plate. It is sectional drawing which shows the detail of the said taper part forming process. It is sectional drawing which shows the detail of the said taper part forming process. It is sectional drawing which shows the other structure of the said nozzle plate. It is a flowchart which shows the flow at the time of manufacturing of the nozzle plate of FIG. It is sectional drawing which shows the manufacturing process of the nozzle plate of Patent Document 1. FIG. It is sectional drawing which shows the manufacturing process of the nozzle plate of Patent Document 2. FIG.

An embodiment of the present invention will be described below with reference to the drawings. In this specification, when the numerical range is expressed as A to B, the numerical range includes the values of the lower limit A and the upper limit B.

[Configuration of Inkjet Printer]
FIG. 1 is an explanatory diagram showing a schematic configuration of the inkjet printer 1 of the present embodiment. The inkjet printer 1 is a so-called line head type inkjet recording device in which the inkjet head 21 is provided in a line shape in the width direction of the recording medium in the inkjet head unit 2.

The inkjet printer 1 has the above-mentioned inkjet head portion 2, a feeding roll 3, a take-up roll 4, two back rolls 5.5, an intermediate tank 6, a liquid feeding pump 7, a storage tank 8, and fixing. It is equipped with a mechanism 9.

The inkjet head unit 2 ejects ink from the inkjet head 21 toward the recording medium P to form (draw) an image based on the image data, and is arranged in the vicinity of one of the back rolls 5. The details of the inkjet head 21 will be described later.

The feeding roll 3, the winding roll 4, and each back roll 5 are members having a cylindrical shape that can rotate around an axis. The feeding roll 3 is a roll in which a long recording medium P wound around the peripheral surface in a number of layers is fed toward a position facing the inkjet head portion 2. The feeding roll 3 is rotated by a driving means (not shown) such as a motor, so that the recording medium P is fed in the X direction of FIG. 1 and conveyed.

The take-up roll 4 is unwound from the pay-out roll 3 and winds up the recording medium P on which the ink is ejected by the inkjet head unit 2 on the peripheral surface.

Each back roll 5 is arranged between the feeding roll 3 and the winding roll 4. One of the back rolls 5, which is located on the upstream side in the transport direction of the recording medium P, winds the recording medium P, which is unwound by the feeding roll 3, around a part of the peripheral surface to support the recording medium P, and faces the inkjet head portion 2. Transport towards. The other back roll 5 carries the recording medium P around a part of its peripheral surface while supporting it from a position facing the inkjet head portion 2 toward the take-up roll 4.

The intermediate tank 6 temporarily stores the ink supplied from the storage tank 8. Further, the intermediate tank 6 is connected to a plurality of ink tubes 10 and adjusts the back pressure of the ink in each of the inkjet heads 21 to supply the ink to each of the inkjet heads 21.

The liquid feed pump 7 supplies the ink stored in the storage tank 8 to the intermediate tank 6, and is arranged in the middle of the supply pipe 11. The ink stored in the storage tank 8 is pumped up by the liquid feed pump 7 and supplied to the intermediate tank 6 via the supply pipe 11.

The fixing mechanism 9 fixes the ink ejected to the recording medium P by the inkjet head unit 2 to the recording medium P. The fixing mechanism 9 is composed of a heater for heating and fixing the discharged ink to the recording medium P, a UV lamp for curing the discharged ink by irradiating the discharged ink with UV (ultraviolet rays), and the like. There is.

In the above configuration, the recording medium P fed out from the feeding roll 3 is conveyed to a position facing the inkjet head unit 2 by the back roll 5, and ink is ejected from the inkjet head unit 2 to the recording medium P. After that, the ink ejected to the recording medium P is fixed by the fixing mechanism 9, and the recording medium P after the ink is fixed is wound up by the take-up roll 4. In this way, in the line head type inkjet printer 1, ink is ejected while conveying the recording medium P while the inkjet head portion 2 is stationary, and an image is formed on the recording medium P.

The inkjet printer 1 may be configured to form an image on a recording medium by a serial head method. The serial head method is a method in which an image is formed by ejecting ink by moving an inkjet head in a direction orthogonal to the conveying direction while conveying a recording medium. Further, as the recording medium, a sheet-like medium pre-cut to a predetermined size (shape) may be used in addition to the long-shaped one.

[Structure of inkjet head]
Next, the configuration of the above-mentioned inkjet head 21 will be described. FIG. 2A is a plan view showing a schematic configuration of an actuator 21a (piezoelectric actuator) of the inkjet head 21, and FIG. 2B is a cross-sectional view taken along the line AA in FIG. 2A. The inkjet head 21 has a thermal oxide film 23, a lower electrode 24, a piezoelectric thin film 25, and an upper electrode 26 on the substrate 22 in this order.

The substrate 22 is composed of a semiconductor substrate or an SOI substrate made of a single crystal Si (silicon) element having a thickness of, for example, about 50 to 300 μm. Note that FIG. 2B shows a case where the substrate 22 is composed of an SOI substrate. The substrate 22 is adjusted to the above thickness by, for example, polishing a Si substrate or an SOI substrate having a thickness of about 750 μm. The thickness of the substrate 22 may be appropriately adjusted according to the device to be applied. A plurality of pressure chambers 22a (openings) are formed in the substrate 22, and ink supplied from the intermediate tank 6 (see FIG. 1) is supplied to the pressure chamber 22a via an ink supply path (not shown). It is housed there.

The SOI substrate is formed by joining two Si substrates via an oxide film. The upper wall of the pressure chamber 22a (the wall located closer to the piezoelectric thin film 25 than the pressure chamber 22a) in the substrate 22 constitutes a vibrating plate 22b serving as a driven film, and is accompanied by the drive (expansion and contraction) of the piezoelectric thin film 25. It is displaced (vibrated) and pressure is applied to the ink in the pressure chamber 22a. The substrate 22 on which the pressure chamber 22a is formed is also a support substrate that supports the piezoelectric element 27 described later.

The thermal oxide film 23 is made of SiO ₂ (silicon oxide) having a thickness of, for example, about 0.1 μm, and is formed for the purpose of protecting and insulating the substrate 22.

The lower electrode 24 is a common electrode commonly provided in a plurality of pressure chambers 22a, and is configured by laminating a Ti (titanium) layer and a Pt (platinum) layer. The Ti layer is formed to improve the adhesion between the thermal oxide film 23 and the Pt layer. The thickness of the Ti layer is, for example, about 0.02 μm, and the thickness of the Pt layer is, for example, about 0.1 μm. A layer made of TIOx (titanium oxide) may be used instead of the Ti layer.

The piezoelectric thin film 25 is made of a ferroelectric thin film having a perovskite-type structure, such as lead zirconate titanate (PZT), and is provided corresponding to each pressure chamber 22a. The film thickness of the piezoelectric thin film 25 can be, for example, 1 μm or more and 10 μm or less, but as a piezoelectric actuator for an inkjet head, it is 2 μm or more and 6 μm or less from the viewpoint that ink can be reliably ejected in the thin film configuration. Desirable from. Further, in the inkjet head, as the piezoelectric material constituting the piezoelectric thin film 25, a material having lead (Pb), that is, a piezoelectric material having a lead-based perovskite type structure is desirable in that good piezoelectric characteristics can be obtained. The piezoelectric thin film 25 may be made of a lead-free, so-called lead-free piezoelectric material (for example, sodium potassium niobate (KNN)).

The upper electrode 26 is an individual electrode provided corresponding to each pressure chamber 22a, and is configured by laminating a Ti layer and a Pt layer. The Ti layer is formed to improve the adhesion between the piezoelectric thin film 25 and the Pt layer. The thickness of the Ti layer is, for example, about 0.02 μm, and the thickness of the Pt layer is, for example, about 0.1 to 0.2 μm. The upper electrode 26 is provided so as to sandwich the piezoelectric thin film 25 with the lower electrode 24 from the film thickness direction. A layer made of gold (Au) may be formed instead of the Pt layer. The upper electrode 26 is connected to the upper electrode drawing portion and is pulled out above the substrate 22 outside the pressure chamber 22a, but the upper electrode drawing portion is not essential in the present embodiment. , In order to simplify the drawings, the drawings are omitted in FIGS. 2A and 2B.

The lower electrode 24, the piezoelectric thin film 25, and the upper electrode 26 constitute a piezoelectric element 27 for ejecting ink in the pressure chamber 22a to the outside. The piezoelectric element 27 is driven from the drive circuit 28 based on the voltage (drive signal) applied to the lower electrode 24 and the upper electrode 26. The inkjet head 21 is formed by arranging the piezoelectric element 27 and the pressure chamber 22a vertically and horizontally.

FIG. 3 is a cross-sectional view of the inkjet head 21 provided with the actuator 21a of FIG. A nozzle plate 31 is joined to the substrate 22 of the actuator 21a on which the pressure chamber 22a is formed, on the side opposite to the forming side of the piezoelectric thin film 25. A plurality of nozzles 32 for ejecting ink stored in the pressure chamber 22a to the outside are formed on the nozzle plate 31 corresponding to each pressure chamber 22a. The details of the nozzle 32 will be described later. The nozzle 32 communicates with the pressure chamber 22a of the substrate 22.

In the above configuration, when a voltage is applied from the drive circuit 28 to the lower electrode 24 and the upper electrode 26, the piezoelectric thin film 25 is in a direction perpendicular to the thickness direction (substrate) according to the potential difference between the lower electrode 24 and the upper electrode 26. It expands and contracts in the direction parallel to the surface of 22). Then, due to the difference in length between the piezoelectric thin film 25 and the diaphragm 22b, the diaphragm 22b is curved, and the diaphragm 22b is displaced (curved, vibrated) in the thickness direction. Due to such displacement of the diaphragm 22b, a pressure wave is propagated to the ink in the pressure chamber 22a, and the ink in the pressure chamber 22a is ejected from the nozzle 32 as ink droplets D to the outside.

[Manufacturing method of inkjet head]
Next, the method of manufacturing the inkjet head 21 of the present embodiment will be described below. FIG. 4 is a flowchart showing a processing flow at the time of manufacturing the inkjet head 21. In this embodiment, a substrate preparation step (S1), a thermal oxide film forming step (S2), a lower electrode forming step (S3), a piezoelectric thin film forming step (S4), an upper electrode forming step (S5), and a pressure chamber forming The inkjet head 21 is manufactured by sequentially performing the step (S6) and the nozzle plate joining step (S7). The details of each step will be described below. FIG. 5 is a cross-sectional view showing a manufacturing process of the inkjet head 21.

(S1; Substrate preparation process)
First, the substrate 22 is prepared. As the substrate 22, crystalline silicon (Si), which is often used in MEMS (Micro Electro Mechanical Systems), can be used, and here, two Si substrates 22c and 22d are bonded via an oxide film 22e. The one with SOI structure is used.

(S2; thermal oxide film film forming process)
The substrate 22 is placed in a heating furnace and held at about 1500 ° C. for a predetermined time to form thermal oxide films 23a and 23b made of SiO _{2 on} the surfaces of the Si substrates 22c and 22d, respectively.

(S3; lower electrode forming step)
Next, the layers of Ti and Pt are sequentially formed on one of the thermal oxide films 23a by a sputtering method to form the lower electrode 24. As a result, a base layer composed of the substrate 22, the thermal oxide film 23a, and the lower electrode 24 is formed. That is, the lower electrode 24 is located on the outermost layer on the opposite side of the substrate 22 in the above-mentioned base layer.

(S4; Piezoelectric thin film film forming process)
Subsequently, a piezoelectric thin film 25 having a perovskite-type structure such as PZT is formed on the lower electrode 24. More specifically, the substrate 22 is reheated to about 600 ° C., and the PZT layer 25a to be a displacement film is formed by a sputtering method. Next, the photosensitive resin 35 is applied onto the layer 25a by a spin coating method, exposed and etched through a mask to remove unnecessary portions of the photosensitive resin 35, and the shape of the piezoelectric thin film 25 to be formed is transferred. To do. Then, using the photosensitive resin 35 as a mask, the shape of the layer 25a is processed by a reactive ion etching method to obtain a piezoelectric thin film 25.

(S5; upper electrode forming step)
Next, layers of Ti and Pt are sequentially formed on the lower electrode 24 by a sputtering method so as to cover the piezoelectric thin film 25 to form the layer 26a. Subsequently, the photosensitive resin 36 is applied onto the layer 26a by a spin coating method, and an unnecessary portion of the photosensitive resin 36 is removed by exposure and etching through a mask, and the shape of the upper electrode 26 to be formed is transferred. To do. Then, using the photosensitive resin 36 as a mask, the shape of the layer 26a is processed by a reactive ion etching method to form the upper electrode 26.

(S6; pressure chamber forming step)
Next, the photosensitive resin 37 is applied to the back surface (thermal oxide film 23b side) of the substrate 22 by a spin coating method, and exposed and etched through a mask to remove unnecessary parts of the photosensitive resin 37. The shape of the pressure chamber 22a to be formed is transferred. Then, using the photosensitive resin 37 as a mask, the substrate 22 is removed by using a reactive ion etching method to form a pressure chamber 22a to form an actuator 21a.

(S7; Nozzle plate joining process)
After that, the substrate 22 of the actuator 21a and the nozzle plate 31 having the nozzle 32 are joined by using an adhesive or the like so that the pressure chamber 22a formed in the substrate 22 and the nozzle 32 of the nozzle plate 31 communicate with each other. To do. As a result, the inkjet head 21 is completed. In FIG. 5, the substrate 22 and the nozzle plate 31 are joined via the thermal oxide film 23b while leaving the thermal oxide film 23b on the back surface of the substrate 22, but after removing the thermal oxide film 23b, The substrate 22 and the nozzle plate 31 may be directly bonded with an adhesive or the like.

Further, even if an intermediate glass having a through hole at a position corresponding to the nozzle 32 is used and the thermal oxide film 23b is removed, the substrate 22 and the intermediate glass, and the intermediate glass and the nozzle plate 31 are anodically bonded to each other. Good. In this case, the three parties (the substrate 22, the intermediate glass, and the nozzle plate 31) can be joined without using an adhesive.

[Details of nozzle]
Next, the details of the nozzle 32 of the nozzle plate 31 described above will be described. FIG. 6 is an enlarged cross-sectional view of the nozzle plate 31. The nozzle 32 of the nozzle plate 31 has a tapered portion 32a and a straight portion 32b. The tapered portion 32a and the straight portion 32b communicate with each other to form a discharge hole for discharging the ink supplied from the pressure chamber 22a (see FIG. 3) of the substrate 22 to the outside.

The tapered portion 32a communicates with the pressure chamber 22a of the substrate 22, and as the opening width W in the direction perpendicular to the thickness direction of the nozzle plate 31 goes from the pressure chamber 22a side to the ink ejection side (straight portion 32b side). It has a tapered shape that narrows. In this way, since the nozzle 32 has the tapered portion 32a, the ink from the pressure chamber 22a smoothly flows into the nozzle 32 through the tapered portion 32a, so that the ink is ejected from the nozzle 32 to the outside. It can be stabilized.

At this time, assuming that the length of the tapered portion 32a in the thickness direction of the nozzle plate 31 is L1 (μm), it is desirable that the length L1 is 10 μm or more. When the length L1 of the tapered portion 32a is 10 μm or more, when the tapered portion 32a is formed at a predetermined angle, that is, the inclination angle of the side surface of the tapered portion 32a with respect to the surface perpendicular to the thickness direction of the nozzle plate 31 is When the tapered portion 32a is formed so as to have an optimum angle, a sufficient opening width on the communication side of the tapered portion 32a with the pressure chamber 22a can be secured. As a result, the ink can be reliably and smoothly supplied from the pressure chamber 22a to the inside of the nozzle 32, and the above-mentioned effect of stably ejecting the ink can be enhanced.

The straight portion 32b has an opening width W0 that is the same as the minimum opening width of the tapered portion 32a, and is formed straight in the thickness direction of the nozzle plate 31. By providing the straight portion 32b in communication with the tapered portion 32a, it is possible to suppress variations in the opening diameter of each nozzle 32. That is, if the nozzle 32 is composed of only the tapered portion 32a, it is difficult to accurately process the tip of the tapered portion 32a (the portion having the narrowest opening width), so that the opening diameter varies among the plurality of nozzles 32. It will be easier. Since the straight portion 32b can be easily formed with a constant opening width by dry etching or the like, it is possible to form the nozzle 32 with suppressed variation in the opening diameter. As a result, it is possible to suppress variations in the amount of ink ejected from each nozzle 32.

When the length of the straight portion 32b in the thickness direction of the nozzle plate 31 is L2 (μm), the length L2 is preferably 10 μm or less (greater than 0 μm). In this case, the above-mentioned effect of suppressing the variation in the opening diameter can be obtained by forming the straight portion 32b while facilitating the processing (etching) of the straight portion 32b. In particular, it is desirable that the length L2 of the straight portion 32b is 5 μm or less from the viewpoint of facilitating the processing of the straight portion 32b. Further, the opening width W0 of the straight portion 32b is set to, for example, 15 to 30 μm, but is not limited to this range.

[Manufacturing method of nozzle plate]
Next, the method for manufacturing the nozzle plate 31 described above will be described. FIG. 7 is a flowchart showing a flow during manufacturing of the nozzle plate 31. As shown in the figure, in the present embodiment, the first mask material forming step (S11), the etching stopper layer forming step (S12), the resist pattern forming step (S13), the first mask pattern forming step (S14), Resist pattern removing step (S15), second mask material forming step (S16), second mask pattern forming step (S17), taper portion forming step (S18), second mask pattern removing step (S19), straight The nozzle plate 31 is manufactured by performing the portion forming step (S20), the first mask pattern removing step (S21), and the etching stopper layer removing step (S22). Hereinafter, details of each step will be described with reference to FIGS. 8 and 9. 8 and 9 are cross-sectional views showing a manufacturing process of the nozzle plate 31.

(S11; first mask material forming step)
(S12; etching stopper layer forming step)
First, a silicon wafer is prepared as a nozzle forming substrate 31a, and the nozzle forming substrate 31a is set in a thermal oxidation furnace and heated in an oxygen gas or steam atmosphere to heat both sides of the nozzle forming substrate 31a. Form an oxide film. Here, since one of the thermal oxide films is used as a mask when forming the tapered portion 32a described later, it is referred to as a first mask material 41a. Further, since the other thermal oxide film is used as an etching stopper for stopping the progress of etching of the tapered portion 32a, it is referred to as an etching stopper layer 42. Therefore, the steps of forming the thermal oxide film on both sides of the nozzle forming substrate 31a include the step of forming the first mask material 41a on the entire surface of one surface of the nozzle forming substrate 31a (S11) and the nozzle forming substrate. It can be said that the step (S12) of forming the etching stopper layer 42 on the other surface of 31a is included. At this time, since the first mask material 41a and the etching stopper layer 42 are formed by thermal oxidation of the silicon wafer, they are composed of a silicon oxide film (SiO ₂ film).

The method using oxygen gas is called dry oxidation, and the method using water vapor is called wet oxidation, but either method may be adopted as the above thermal oxidation. The heating temperature is about 900 to 1200 ° C. in the case of dry oxidation and about 800 to 1100 ° C. in the case of wet oxidation. For example, when wet oxidation is used, a 1 μm-thick thermal oxide film (first mask material 41a, etching stopper layer 42) is formed on both sides of the nozzle-forming substrate 31a by heating at 1000 ° C. for about 4 hours. can do.

The first mask material 41a and the etching stopper layer 42 may be formed by using a method such as thin film deposition or sputtering instead of thermal oxidation. In this case, the first mask material 41a and the etching stopper layer 42, in addition to the SiO ₂ film, it is possible to configure a film other than SiO ₂ film (e.g., chromium (Cr) metal film, etc.).

The thickness of the nozzle-forming substrate 31a to be used may be any thickness as long as it can form the tapered portion 32a and the straight portion 32b on the nozzle-forming substrate 31a with desired lengths, and may be appropriately adjusted by polishing the substrate or the like. ..

(S13; resist pattern forming step)
Next, an HMDS treatment is performed to make the surface of the wafer hydrophobic. The HDMS treatment is a treatment in which the surface of the substrate is hydrophobized using hexamethyldisilazane (HMDS). This HMDS treatment can be carried out by applying, for example, "OAP" manufactured by Tokyo Ohka Co., Ltd. on the first mask material 41a using a spin coater under the conditions of, for example, 2500 rpm and 15 sec.

Subsequently, a positive resist (OFPR-800LB manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied onto the first mask material 41a using a spin coater under the conditions of, for example, 3000 rpm and 30 sec. Then, prebaking is performed at 110 ° C. for 90 sec, and the resist is exposed with a contact aligner with a light intensity of about 50 mJ / cm ² . Then, the wafer is immersed in a developing solution at 25 ° C. (NMD-3 manufactured by Tokyo Ohka Co., Ltd.) for 60 to 90 seconds to remove the photosensitive portion of the resist, whereby the opening 43a is provided on the first mask material 41a. The resist pattern 43 is formed. The opening 43a is formed in a size corresponding to the opening 41a ₁ formed in the first mask material 41a in the next step. For example, the opening diameter of the opening 43a is 15 to 30 μm.

(S14; first mask pattern forming step)
Next, by patterning the first mask material 41a using the resist pattern 43 as a mask, the first mask pattern 41 (first opening) having an opening 41a ₁ (first opening) having the same shape as the opening 43a is formed. (Also referred to as one pattern) is formed. The patterning of the first mask material 41a at this time can be performed by dry etching using CHF ₃ (trifluoromethane) gas or CH ₄ (methane) gas. For example, by using Samco's RIE-100C and patterning the first mask material 41a under dry etching conditions of CHF ₃ gas flow rate; 80 sccm, pressure; 3 Pa, RF power; 90 W, etching time: about 1 hour. , A first mask pattern 41 having an opening 41a ₁ can be formed. The opening diameter of the opening 41a _{1 is the same as} the opening diameter of the opening 43a (for example, 15 to 30 μm).

The steps S11 to S14 described above correspond to the first pattern forming step (S100) of forming the first mask pattern 41 having the opening 41a ₁ on one surface of the nozzle forming substrate 31a.

(S15; resist pattern removing step)
Subsequently, the resist pattern 43 used in S14 is removed. For example, the resist pattern 43 can be removed by a wet process using acetone, an alkaline solution, or the like, or a dry process using oxygen plasma or the like.

(S16; second mask material forming step)
Next, in order to make the surface of the wafer hydrophobic, the same HMDS treatment as in S13 is performed. After that, a positive resist (OFPR-800LB manufactured by Tokyo Ohka Kogyo Co., Ltd.), which is a photosensitive resin, is applied to the inside of the opening 41a ₁ in the first mask pattern 41 and on the first mask material 41a, for example, using a spin coater. It is applied under the conditions of 3000 rpm and 30 sec to form a second mask material 44a made of the above-mentioned photosensitive resin.

(S17; second mask pattern forming step)
Subsequently, prebaking is performed at 110 ° C. for 90 sec, and the second mask material 44a is exposed with a contact aligner with a light intensity of about 50 mJ / cm ² . Then, the wafer is immersed in a developing solution at 25 ° C. (NMD-3 manufactured by Tokyo Ohka Co., Ltd.) for 60 to 90 seconds to remove the photosensitive portion of the second mask material 44a. More specifically, the exposure and development of the second mask material 44a removes a part of the second mask material 44a formed inside the opening 41a ₁ of the first mask pattern 41. As a result, a second mask pattern 44 (also referred to as a second pattern) having an opening 44a ₁ (second opening) inside the opening 41a ₁ is formed so as to cover the first mask material 41a. ..

Here, FIG. 10 is a plan view of the nozzle forming substrate 31a on which the first mask pattern 41 and the second mask pattern 44 are formed. In a plane perpendicular to the thickness direction of the nozzle forming substrate 31a, the opening center O ₁ of the opening 41a ₁ of the first mask pattern 41 and the opening center O ₂ of the opening 44a ₁ of the second mask pattern 44. The above-mentioned exposure and development are performed so that the above-mentioned second mask pattern 44 is formed. It should be noted that the above-mentioned "match" includes not only an exact match but also a substantially match within a range in which a positional deviation can be tolerated. The opening diameter of the opening 44a ₁ of the second mask pattern 44 is, for example, 10 μm, which is smaller than the opening diameter of the opening 41a ₁ of the first mask pattern 41.

The steps S16 to S17 described above have an opening 44a ₁ having an opening diameter smaller than that of the opening 41a _{1 of} the first mask pattern 41, so that the opening 44a ₁ is located inside the opening 41a _1. Corresponds to the second pattern forming step (S200) of forming the second mask pattern 44 covering the first mask material 41a of the first mask pattern 41.

(S18; taper portion forming step)
Next, the nozzle-forming substrate 31a is dry-etched from one surface side (second mask pattern 44 side) through the opening 44a ₁ of the second mask pattern 44 to form the nozzle-forming substrate 31a. The tapered portion 32a is formed. The shape of the tapered portion 32a is a reverse taper shape in which the opening width increases as the nozzle forming substrate 31a advances from one surface side toward the thickness direction (toward the etching stopper layer 42). The reverse taper processing can be performed using a dry etching apparatus such as a RIE (Reactive Ion Etching) apparatus or an ICP-RIE etching apparatus which is a dry etching apparatus that employs an inductively coupled plasma as a discharge type. it can. Further, as the process gas, SF ₆ (sulfur hexafluoride) gas, C ₄ F ₈ (octafluorocyclobutane) gas, or the like can be used. When the etching proceeds to the etching stopper layer 42, the etching is stopped there. By such etching, the length of the tapered portion 32a along the thickness direction of the nozzle forming substrate 31a is secured to be 10 μm or more. The details of the method of forming the tapered portion 32a having the reverse taper shape will be described later.

(S19; second mask pattern removing step)
Subsequently, the second mask pattern 44 used in S18 is removed. As a result, the first mask pattern 41, which is the base of the second mask pattern 44, is exposed. For example, as in S15, the second mask pattern 44 can be removed by a wet process using acetone, an alkaline solution, or the like, or a dry process using oxygen plasma or the like. The step S19 corresponds to the second pattern removing step of forming the tapered portion 32a on the nozzle forming substrate 31a and then removing the second mask pattern 44 to expose the first mask pattern 41.

(S20; straight portion forming step)
Next, the nozzle forming substrate 31a is dry-etched straight from one surface side in the thickness direction of the nozzle forming substrate 31a through the opening 41a ₁ of the exposed first mask pattern 41. As a result, the straight portion 32b communicating with the tapered portion 32a is formed on the nozzle forming substrate 31a. The processing of the straight portion 32b at this time can be performed by, for example, a Bosch process using an ICP device. The Bosch process is a method of performing etching while repeating etching in the thickness direction and protection of the side wall by a protective film. For example, by repeating etching with SF ₆ gas and protection of the side wall with C ₄ F ₈ gas or the like, a thin and deep hole can be dug. The opening diameter of the straight portion 32b is the same as the opening diameter of the opening 41a ₁ (for example, 15 to 30 μm). Further, the straight portion 32b is formed so that the length of the nozzle forming substrate 31a along the thickness direction is 10 μm or less. In this way, the nozzle 32 including the tapered portion 32a and the straight portion 32b is obtained.

(S21; first mask pattern removing step)
(S22; Etching stopper layer removing step)
Finally, the thermal oxide films on both sides of the nozzle-forming substrate 31a, that is, the first mask pattern 41 and the etching stopper layer 42 are removed (S21, S22). As a result, the nozzle plate 31 is completed. As a method for removing the thermal oxide film, a wet process using a chemical such as HF (hydrofluoric acid) or a dry process using CF ₄ (carbon tetrafluoride) gas or CHF ₃ gas can be adopted.

The step of removing the first mask pattern 41 (S21) corresponds to the first pattern removing step of removing the first mask pattern 41 after the straight portion forming step of S20. Further, the step (S22) of removing the etching stopper layer 32 corresponds to the etching stopper layer removing step of removing the etching stopper layer 42 after forming the straight portion 32b.

After S22, the surface side of the obtained nozzle plate 31 from which the etching stopper layer 42 has been removed is joined to the substrate 22 so that the nozzle 32 and the pressure chamber 22a (see FIG. 3) communicate with each other. 21 can be obtained (nozzle plate joining step of S7 in FIG. 4).

As described above, the method for manufacturing the nozzle plate 31 of the present embodiment includes the above-mentioned first pattern forming step (S100), second pattern forming step (S200), taper portion forming step (S18), and second. The mask pattern removing step (S19) and the straight portion forming step (S20) are included. In S18 and S20, the tapered portion 32a and the straight portion 32b of the nozzle 32 use the second mask pattern 44 formed in S200 and the first mask pattern 41 formed in S100, respectively, to form the nozzle forming substrate 31a. It is formed by dry etching from the same side (one surface side (opposite side of the etching stopper layer 42) of the nozzle forming substrate 31a). That is, the second mask pattern 44 and the first mask pattern 41 are on the same side with respect to the nozzle forming substrate 31a. As a result, it becomes easy to ensure good mechanical accuracy when processing the second mask pattern 44 and the first mask pattern 41, and the openings of the second mask pattern 44 and the first mask pattern 41 are respectively opened. It becomes easy to form the portions 44a ₁ and 41a ₁ with high accuracy (while suppressing the deviation of the center position) by using the photolithography technique.

Therefore, by forming the tapered portion 32a and the straight portion 32b by using the second mask pattern 44 and the first mask pattern 41, the positional deviation (center of the hole) between the tapered portion 32a and the straight portion 32b is formed. Positional deviation) can be suppressed, and the accuracy of these positions can be improved.

Further, different masks (second mask pattern 44, first mask pattern 41) are used when the tapered portion 32a is formed and when the straight portion 32b is formed, and the same mask is not reused. Therefore, even if the edge portion of the second mask pattern 44 is retracted by etching when the tapered portion 32a is formed, the second mask pattern 44 is removed and not used when the straight portion 32b is formed, so that the straight portion is not used. It has no effect on the formation of 32b. Moreover, since the first mask pattern 41 used when forming the straight portion 32b is in close contact with the nozzle forming substrate 31a to be processed by the straight portion 32b, the processing deviation of the straight portion 32b with respect to the nozzle forming substrate 31a is large. It is less likely to occur. Therefore, it is possible to improve the processing accuracy of the straight portion 32b and reduce the variation in the hole diameter of the straight portion 32b. As a result, in the inkjet head 21, it is possible to reduce the variation in the amount of ink ejected from the straight portion 32b of each nozzle 32.

Further, the first pattern forming step (S100) includes a first mask material forming step (S11), a resist pattern forming step (S13), and a first mask pattern forming step (S14). A resist pattern 43 having an opening 43a corresponding to the opening 41a ₁ is formed on the first mask material 41a, and the opening is formed by patterning the first mask material 41a using the resist pattern 43 as a mask. The first mask pattern 41 having 41a ₁ can be reliably formed.

Further, the first mask material 41a is formed of a silicon oxide film (SiO ₂ film). The first mask material 41a can also be formed by a metal film (for example, a Cr film), but the silicon oxide film is very effective as the first mask material 41a because patterning by dry etching is easy. Further, when the nozzle forming substrate 31a is a silicon substrate as in the present embodiment, a SiO ₂ film can be easily formed by thermal oxidation of the silicon substrate, facilitates the first mask material 41a made of SiO ₂ film There is also a merit that can be realized.

Further, the first pattern forming step (S100) includes an etching stopper layer forming step (S12). By forming the etching stopper layer 42 on the other surface of the nozzle forming substrate 31a (on the surface opposite to the forming side of the first mask material 41a), the tapered portion 32a is formed in S18. Therefore, when the substrate is etched in the thickness direction, the etching can be stopped at a desired position (the position where the etching stopper layer 42 is formed).

Further, the second pattern forming step (S200) includes a second mask material forming step (S16) and a second mask pattern forming step (S17). A second mask material 44a, which is different from the first mask material 41a, is applied to the inside of the first opening 41a ₁ and on the first mask material 41a in the first mask pattern 41. By removing a part of the second mask material 44a applied to the inside of the opening 41a ₁ , the above-mentioned second mask pattern 44 can be reliably formed. That is, the second mask pattern 44 having the second opening 44a ₁ inside the first opening 41a ₁ can be reliably formed so as to cover the first mask material 41a.

Further, in a plane perpendicular to the thickness direction of the nozzle forming substrate 31a, a second mask with aperture center O ₁ of the opening 41a ₁ of the first mask pattern 41, is formed inside the opening 41a ₁ pattern It coincides with the opening center O ₂ of the opening 44a ₁ of 44. As a result, the tapered portion 32a formed by dry-etching the nozzle-forming substrate 31a through the opening 44a ₁ and the nozzle-forming substrate 31a formed by dry-etching the nozzle-forming substrate 31a through the opening 41a _1. The positional deviation from the straight portion 32b can be reliably eliminated, and the positional accuracy of the tapered portion 32a and the straight portion 32b can be reliably improved.

Further, since the second mask material 44a is a photosensitive resin, it is possible to easily form the second mask pattern 44 by patterning the second mask material 44a using a photolithography technique. ..

Further, the method for manufacturing the nozzle plate 31 of the present embodiment includes a first mask pattern removing step (S21) as a first pattern removing step. The nozzle plate 31 can be obtained by removing the first mask pattern 41 after the straight portion forming step of S20.

Further, the method for manufacturing the inkjet head 21 of the present embodiment is the method for manufacturing the inkjet head 21 using the method for manufacturing the nozzle plate 31 described above, in which the tapered portion 32a and the straight portion 32b are formed on the nozzle forming substrate 31a. (S7) includes a step (S7) of joining the nozzle plate 31 and the substrate 22 on which the piezoelectric element 27 is supported and the pressure chamber 22a is formed so that the pressure chamber 22a and the tapered portion 32a communicate with each other. ..

According to the manufacturing method of the nozzle plate 31 described above, the positional deviation between the tapered portion 32a and the straight portion 32b can be suppressed to improve the positioning accuracy, and the processing accuracy of the straight portion 32b can be improved to improve the straight portion 32b. It is possible to reduce the variation in the hole diameter of. Therefore, by configuring the inkjet head 21 using such a nozzle plate 31, it is possible to suppress bending of the ink ejection direction of the ink ejected from the nozzle 32, improve the ink ejection characteristics, and improve the ink ejection characteristics. It is possible to reduce variations in the amount of ink ejected from the nozzle 32.

[Details of taper part forming process]
Next, the details of the taper portion forming step of S18 will be described. As described above, the processing of the tapered portion 32a having a reverse taper shape can be performed by a RIE (reactive ion etching) process using ICP. Here, in order to improve the processing accuracy, a protective film forming step for protecting the side wall of the recess 32c (see FIG. 11) which will later become the tapered portion 32a, and anisotropic etching for selectively removing the protective film on the bottom surface of the recess 32c. A Bosch process was used to deeply dig the silicon by repeating the three steps of the step and the isotropic etching step of isotropically etching the silicon (nozzle forming substrate 31a). As the ICP apparatus, a SAMCO etching apparatus (RIE-800iPB) was used. Hereinafter, a more specific description will be given.

11 to 13 are cross-sectional views showing details of the taper portion forming step. First, a protective film is formed on the nozzle forming substrate 31a and on the second mask material 44a so as to cover the surface 31b of the nozzle forming substrate 31a exposed through the inside of the opening 44a ₁ of the second mask pattern 44. 45 is formed (step (a)). The protective film 45 is made of, for example, a fluorocarbon film (polyvinylidene fluoride), and is formed by using, for example, C ₄ F ₈ gas. As an example of the formation conditions of the protective film 45 at this time, ICP power; 3000 W, pressure; 10 Pa, C ₄ F ₈ flow rate; 200 sccm, O ₂ flow rate; 10 sccm.

Next, the protective film 45 is selectively removed by anisotropic etching in the thickness direction of the nozzle-forming substrate 31a (step (b)). That is, in the step (b), a part of the protective film 45 covering the surface 31b of the protective film 45 is removed by anisotropic etching in the thickness direction, and the upper side wall of the opening 44a ₁ and the second mask The protective film 45 on the material 44a remains. In the above anisotropic etching, in order to selectively remove the protective film 45 on the bottom surface, a negative bias voltage is applied to the nozzle forming substrate 31a of the ions generated from the SF ₆ gas under a low pressure condition. This is performed while accelerating to the nozzle forming substrate 31a. As an example of the anisotropic etching conditions at this time, ICP power; 750 W, bias; 350 W, pressure; 2 Pa, SF ₆ flow rate; 200 sccm, O ₂ flow rate; 10 sccm.

Subsequently, the nozzle-forming substrate 31a exposed by the selective removal of the protective film 45 in the step (b) is isotropically etched (step (c)). The isotropic etching is performed by isotropically etching the silicon of the nozzle forming substrate 31a with radicals generated from SF ₆ gas. As an example of the conditions for isotropic etching, ICP power; 3000 W, pressure: 30 Pa, SF ₆ flow rate; 600 sccm, O ₂ flow rate; 10 sccm. By this isotropic etching, silicon is etched in the thickness direction of the nozzle forming substrate 31a and in the direction perpendicular to the thickness direction, and the recess 32c is formed.

Hereinafter, these steps are repeated with the above-mentioned steps (a) to (c) as one cycle (see FIGS. 12 and 13). In the second and subsequent cycles, the inner surface of the recess 32c, that is, the "surface 31b of the nozzle forming substrate 31a exposed through the inside of the opening 44a ₁ of the second mask pattern 44" in the step (a). , Bottom surface 32c ₁ and side surface 32c ₂ . Further, in the step (b), since the protective film 45 is anisotropically etched in the thickness direction, in the second and subsequent cycles, a part of the protective film 45 on the bottom surface 32c _{1 of the} recess 32c of the protective film 45 Is selectively removed, and the protective film 45 on the side surface 32c ₂ remains unremoved.

In the present embodiment, the tapered portion 32a is formed on the nozzle forming substrate 31a by changing the etching conditions of the step (c) every time the steps (a) to (c) are repeated. For example, by lengthening the etching time of the step (c) in the second cycle rather than the first cycle, the recess 32c formed in the second cycle has a depth deeper than the recess 32c formed in the first cycle. And the width (opening diameter) both increase. Therefore, by repeating the steps (a) to (c) while changing the etching conditions in this way, the depth and width of the recess 32c can be gradually increased as the etching progresses in the thickness direction. Finally, a tapered portion 32a having a reverse taper shape can be obtained. Further, by controlling the etching time in the step (c), the side wall of the tapered portion 32a can be formed at a desired angle, and the tapered portion 32a having an inverted tapered shape can be formed without complicating the control. be able to.

As shown in FIG. 13, surface irregularities called scallops 32a ₁ remain on the side walls of the tapered portion 32a processed into an inverted tapered shape. The scallop 32a ₁ appears more prominently as the isotropic etching time increases. It is desirable to remove the scallop 32a ₁ because the electric charge tends to accumulate locally. Therefore, for example, after forming the tapered portion 32a having a reverse taper shape on the nozzle forming substrate 31a, a bias voltage is applied to the nozzle forming substrate 31a to perform anisotropic etching for a predetermined time. As a result, the tapered portion 32a from which the scallop 32a ₁ is selectively removed can be obtained.

[Other configurations of nozzle plate]
FIG. 14 is a cross-sectional view showing another configuration of the nozzle plate 31 of the present embodiment. The nozzle forming substrate 31a of the nozzle plate 31 may be the SOI substrate 50. The SOI substrate 50 is a substrate in which two silicon substrates 51 and 52 are bonded via an oxide film 53. On the other hand, the silicon substrate 51 is an active layer having a thickness of about 10 to 30 μm. The other silicon substrate 52 is a support layer having a thickness of about 50 to 500 μm (preferably about 100 to 200 μm). The oxide film 53 is a BOX (Buried Oxide) layer made of a SiO ₂ film having a thickness of 0.2 to 1 μm. The nozzle 32 including the tapered portion 32a and the straight portion 32b is formed on, for example, an active layer (silicon substrate 51).

In the SOI substrate 50, the layer on which the nozzle 32 is not formed, that is, the silicon substrate 52 and the oxide film 53, is formed with a communication passage portion 54 communicating with the nozzle 32 (particularly the tapered portion 32a). The communication passage portion 54 is a portion that communicates the pressure chamber of the substrate 22 with the nozzle 32 of the nozzle plate 31. In the communication passage portion 54, the width in the direction perpendicular to the substrate thickness direction is, for example, 100 to 200 μm, which is wider than the nozzle 32.

FIG. 15 is a flowchart showing a flow during manufacturing of the nozzle plate 31 of FIG. 14 using the SOI substrate 50. The nozzle plate 31 of FIG. 14 is manufactured by omitting the etching stopper layer forming step (S12) and the etching stopper layer removing step (S22) shown in FIG. 7 and newly adding a connecting passage portion forming step (S23). Can be done.

That is, in the first pattern forming step (S100) and the second pattern forming step (S200), the first mask pattern 41 and the second mask pattern 44 are on the surface opposite to the oxide film 53 with respect to the silicon substrate 51. (See FIGS. 8 and 9). Then, in the taper portion forming step of S18, the tapered portion 32a is formed on the silicon substrate 51 by dry etching the silicon substrate 51 through the opening 44a ₁ using the second mask pattern 44. After that, in the second mask pattern removing step of S19, the second mask pattern 44 is removed to expose the first mask pattern 41. Then, in the straight portion forming step of S20, the straight portion 32b is formed on the silicon substrate 51 by dry etching the silicon substrate 51 through the opening 41a ₁ using the exposed first mask pattern 41. After forming the straight portion 32b, the first mask pattern 41 is removed in the first pattern removing step of S21.

In the step of forming the communication passage portion in S23, the silicon substrate 52 and the oxide film 53 are dry-etched from the side opposite to the silicon substrate 51 to form the communication passage portion 54 communicating with the taper portion 32a. The processing of the communication passage portion 54 can be performed by, for example, a Bosch process using an ICP device, as in the processing of the straight portion 32b. The step of forming the continuous passage portion in S23 may be performed after the step of forming the straight portion in S20, and may be performed before the first mask pattern removing step in S21. After forming the communication passage portion 54 and removing the first mask pattern 41, the nozzle plate 31 is joined by joining the substrate 22 and the nozzle plate 31a so that the communication passage portion 54 communicates with the pressure chamber 22a. Can be obtained.

As described above, even when the SOI substrate 50 is used, the nozzle plate 31 can be obtained by directly using the method of the present embodiment in which the tapered portion 32a and the straight portion 32b are formed by processing from the same side with respect to the substrate. it can.

Further, the ejection characteristics of the ink ejected from the nozzle 32 (particularly the bending in the ink ejection direction) are determined depending on the position accuracy of the tapered portion 32a and the straight portion 32b whose width (diameter) is narrowed to some extent, and the width is determined. It has little to do with the position accuracy of the wide passage portion 54 and the narrow nozzle 32. Therefore, in order to secure the desired ink ejection characteristics, the positional deviation between the communication passage portion 54 and the nozzle 32 is allowed to some extent. Therefore, the communication passage portion 54 is processed from the side opposite to the nozzle 32 of the SOI substrate 50. It becomes possible to form.

Further, since the oxide film 53 of the SOI substrate 53 functions as an etching stopper layer when etching the communication passage portion 54, a separate etching stopper layer 42 is formed on the nozzle forming substrate 31a as shown in FIG. Alternatively, a step such as removing the etching stopper layer 42 at the end becomes unnecessary.

The method for manufacturing a nozzle plate of the present invention can be used for manufacturing a nozzle plate having a tapered portion and a straight portion as nozzles.

21 Inkjet head 22 Substrate (support substrate)
22a Pressure chamber 27 Piezoelectric element 31 Nozzle plate 31a Nozzle forming substrate 32 Nozzle 32a Tapered part 32b Straight part 41 First mask pattern 41a First mask material 41a ₁ opening (first opening)
42 Etching stopper layer 43 Resist pattern 44 Second mask pattern 44a Second mask material 44a ₁ Opening (second opening)
45 Protective film 50 SOI substrate (nozzle forming substrate)
51 Silicon Substrate 52 Silicon Substrate 53 Oxide Film 54 Continuous Passage O ₁ Opening Center O ₂ Opening Center

Claims (14)

A first pattern forming step of forming a first mask pattern having a first opening on one surface of a nozzle forming substrate,
The second opening having a diameter smaller than that of the first opening of the first mask pattern is provided, and the second opening is located inside the first opening. A second pattern forming step of forming a second mask pattern covering the mask material of the first mask pattern, and
By dry etching the nozzle-forming substrate from the one surface side through the second opening of the second mask pattern, the thickness direction of the nozzle-forming substrate from the one surface side. A taper portion forming step of forming a tapered portion having a reverse taper shape in which the opening width increases as the nozzle is formed on the nozzle forming substrate.
A second pattern removing step of removing the second mask pattern to expose the first mask pattern after forming the tapered portion.
The nozzle-forming substrate is dry-etched straight from one surface side in the thickness direction of the nozzle-forming substrate through the first opening of the exposed first mask pattern. A method for manufacturing a nozzle plate, which comprises a straight portion forming step of forming a straight portion communicating with a tapered portion on the nozzle forming substrate. In the taper portion forming step, a step (a) of forming a protective film so as to cover the surface of the nozzle forming substrate exposed through the inside of the second opening, and a step (a) of forming the protective film on the nozzle. A step (b) of selectively removing the substrate by anisotropic etching in the thickness direction of the substrate and a step (c) of isotropic etching of the substrate for forming nozzles exposed by the selective removal of the protective film. The tapered portion is formed on the nozzle forming substrate by repeating the above steps and changing the etching conditions of the step (c) each time the steps (a) to (c) are repeated. The method for manufacturing a nozzle plate according to claim 1, wherein the nozzle plate is manufactured. In the taper portion forming step, the tapered portion is formed on the nozzle forming substrate by lengthening the etching time in the step (c) each time the steps (a) to (c) are repeated. The method for manufacturing a nozzle plate according to claim 2, wherein the nozzle plate is manufactured. The first pattern forming step is
A step of forming the mask material on the entire surface of the nozzle forming substrate, and
A step of forming a resist pattern having an opening corresponding to the first opening on the mask material, and
Any of claims 1 to 3, further comprising a step of forming the first mask pattern having the first opening by patterning the mask material using the resist pattern as a mask. The method for manufacturing a nozzle plate according to. The method for manufacturing a nozzle plate according to claim 4, wherein the mask material is a silicon oxide film. When the mask material of the first mask pattern is used as the first mask material,
The second pattern forming step is
A step of applying a second mask material different from the first mask material on the inside of the first opening and on the first mask material in the first mask pattern.
The second mask pattern having the second opening inside the first opening by removing a part of the second mask material applied to the inside of the first opening. The method for manufacturing a nozzle plate according to claim 4 or 5, wherein the step of forming the nozzle plate so as to cover the first mask material is included. The sixth aspect of claim 6 is characterized in that the opening center of the first opening and the opening center of the second opening coincide with each other in a plane perpendicular to the thickness direction of the nozzle forming substrate. Nozzle plate manufacturing method. The method for manufacturing a nozzle plate according to claim 6 or 7, wherein the second mask material is a photosensitive resin. The first pattern forming step is
The method for manufacturing a nozzle plate according to any one of claims 4 to 8, further comprising a step of forming an etching stopper layer on the other surface of the nozzle forming substrate. The nozzle-forming substrate is an SOI substrate in which two silicon substrates are bonded via an oxide film.
In the taper portion forming step, the tapered portion is formed on one silicon substrate of the nozzle forming substrate .
In the straight portion forming step, the straight portion is formed on the one silicon substrate of the nozzle forming substrate .
In the manufacturing method, after the straight portion forming step, the other silicon substrate of the nozzle forming substrate and the oxide film are dry-etched from the side opposite to the one silicon substrate to communicate with the tapered portion. The method for manufacturing a nozzle plate according to any one of claims 1 to 8, further comprising a step of forming a continuous passage portion to form a continuous passage portion on the nozzle forming substrate. The method for manufacturing a nozzle plate according to any one of claims 1 to 10, further comprising a first pattern removing step of removing the first mask pattern after the straight portion forming step. The method for manufacturing a nozzle plate according to any one of claims 1 to 11, wherein the length of the straight portion along the thickness direction of the nozzle-forming substrate is 10 μm or less. The method for manufacturing a nozzle plate according to any one of claims 1 to 12, wherein the length of the tapered portion along the thickness direction of the nozzle-forming substrate is 10 μm or more. A method for manufacturing an inkjet head, wherein the inkjet head is manufactured by using the method for manufacturing a nozzle plate according to any one of claims 1 to 13.
The pressure chamber and the tapered portion form a nozzle plate formed by forming the tapered portion and the straight portion on the nozzle forming substrate, and a support substrate on which the piezoelectric element is supported and the pressure chamber is formed. A method for manufacturing an inkjet head, which comprises a step of joining so as to communicate with each other.

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