WO2024063030A1

WO2024063030A1 - Method for manufacturing nozzle plate

Info

Publication number: WO2024063030A1
Application number: PCT/JP2023/033794
Authority: WO
Inventors: 光横山; 幸一鮫島
Original assignee: コニカミノルタ株式会社
Priority date: 2022-09-22
Filing date: 2023-09-15
Publication date: 2024-03-28

Abstract

This method for manufacturing a nozzle plate 110 comprises: a first step for forming a first hole 305 that is longer in the [100] direction as compared with in the [010] direction and that is connected to a first surface Bb of a monocrystalline silicon substrate B in which the surface crystal orientation is in the (100) plane, and a second hole 306 that is connectable to the first hole 305 and to a second surface Ba of the monocrystalline silicon substrate B; and a second step for enlarging the first hole 305 and the second hole 306 by performing anisotropic wet etching on the monocrystalline silicon substrate B to form a nozzle flow path 100 that comprises a nozzle taper portion 20 having the (111) plane and a straight connecting portion 10 contiguous to the nozzle taper portion 20.

Description

Manufacturing method of nozzle plate

The present invention relates to a method for manufacturing a nozzle plate.

Conventionally, as shown in Patent Document 1, it is known that a nozzle plate of a droplet ejection head of a droplet ejection device is manufactured from a single crystal silicon substrate. Nozzle channels are formed in this nozzle plate by anisotropic wet etching.

Patent No. 5519263

By the way, when performing anisotropic wet etching on a single crystal silicon substrate whose surface crystal orientation is {100} plane, the corrosion action progresses in a fixed direction. Therefore, it is only possible to form a nozzle flow path in which the opening on the surface facing the droplet ejection surface has a square shape. If such a nozzle plate is joined to another plate whose ink flow path has a rectangular cross-sectional shape, for example, the shape of the joint between the ink flow path and the nozzle flow path will be mismatched. Therefore, the resistance during ink ejection becomes strong, and it is necessary to increase the driving voltage. In addition, the meniscus becomes unstable and injection defects occur, resulting in deterioration of injection characteristics. Further, since there are restrictions on the shape of the nozzle flow path, it is difficult to increase the density of the nozzle openings arranged in a row on the single crystal silicon substrate in order to secure the volume of the nozzle flow path.

In order to solve these problems, the present invention aims to provide a method for manufacturing a nozzle plate that can achieve both high density nozzle openings and suitable injection characteristics.

The invention according to claim 1 is a method for manufacturing a nozzle plate of a droplet ejection head, comprising:
a first hole that communicates with a first surface of a single crystal silicon substrate whose surface crystal orientation is {100} plane and is longer in the [100] direction than in the [010] direction; and the first hole and the single crystal. a first step of forming a second hole that can communicate with the second surface of the silicon substrate;
By enlarging the first hole and the second hole by anisotropic wet etching on the single crystal silicon substrate, a nozzle taper portion having a {111} plane and a straight communication portion continuous to the nozzle taper portion are formed; and a second step of forming a nozzle flow path.

The invention according to claim 2 is a method for manufacturing the nozzle plate according to claim 1, comprising:
In the first step, the length of the second hole in the [001] direction is the length from the end of the second hole on the first surface side to the end of the first hole in the [100] direction. They are formed so that they are approximately equal.

The invention according to claim 3 is a method for manufacturing the nozzle plate according to claim 1, comprising:
In the first step, the length of the second hole in the [001] direction is longer than the length from the end of the second hole on the first surface side to the end of the first hole in the [100] direction. Form it so that it is also long,
A step surface is formed in the nozzle taper portion.

The invention described in claim 4 is a method for manufacturing the nozzle plate described in any one of claims 1 to 3, comprising the steps of:
The first hole and the second hole are centered.

The invention according to claim 5 is a method for manufacturing the nozzle plate according to any one of claims 1 to 3,
In the first step, the bottom of the first hole is formed into a stepped shape.

The invention according to claim 6 is a method for manufacturing the nozzle plate according to any one of claims 1 to 3,
The first step is
forming a third hole by deep-drilling the single-crystal silicon substrate halfway from the first surface by dry etching;
Next, forming a nozzle mask layer along the inner surface of the third hole,
Next, the step of removing the nozzle mask layer formed at the bottom of the third hole,
The first hole is formed by further digging the third hole,
In the second step, a nozzle flow path including a nozzle straight portion continuous from the end of the nozzle tapered portion on the second surface side is formed.

The invention according to claim 7 is a method for manufacturing the nozzle plate according to any one of claims 1 to 3,
A non-wet etching layer is formed on the second surface of the single crystal silicon substrate.

The invention according to claim 8 is a method for manufacturing the nozzle plate according to any one of claims 1 to 3,
The method includes a third step of enlarging the diameter of the opening on the first surface side and/or the second surface side of the nozzle flow path.

According to the present invention, it is possible to provide a method for manufacturing a nozzle plate that can achieve both high density nozzle openings and suitable injection characteristics.

FIG. 2 is a perspective view of a droplet ejection device equipped with a droplet ejection head formed by stacking nozzle plates. FIG. 3 is a plan view of the nozzle plate viewed from the [0 0 1] direction. FIG. 3 is a plan view of the nozzle plate viewed from the [0 0 -1] direction. FIG. 2 is a cross-sectional view of the nozzle plate according to the first embodiment, viewed from the [0 1 0] direction. FIG. 3 is a perspective cross-sectional view showing a nozzle flow path formed by the nozzle plate manufacturing method according to the first embodiment. They are a cross-sectional view as seen from the [0 1 0] direction and a plan view as seen from the [0 0 1] direction of the nozzle plate manufacturing method according to the first embodiment. FIG. 3 is a cross-sectional view of the progress of etching in the second step, viewed from the [1 0 0] direction. FIG. 3 is a cross-sectional view of the progress of etching in the second step, viewed from the [0 1 0] direction. FIG. 3 is a cross-sectional view of a nozzle flow path formed by shifting the centers of the opening hole and the nozzle hole in the [1 0 0] direction, as seen from the [0 1 0] direction. This is a cross-sectional view, viewed from the [0 0 1] direction, of a nozzle flow path formed so that the length of the nozzle hole in the [0 0 1] direction is longer than the length from the end of the opening hole in the [1 0 0] direction to the end of the nozzle hole on the adhesive surface side. This is a cross-sectional view, viewed from the [0 0 1] direction, of a nozzle flow path formed so that the length of the nozzle hole in the [0 0 1] direction is shorter than the length from the end of the opening hole in the [1 0 0] direction to the end of the nozzle hole on the adhesive surface side. They are a cross-sectional view seen from the [0 1 0] direction and a plan view seen from the [0 0 1] direction of a method for manufacturing a nozzle plate according to the second embodiment. FIG. 7 is a cross-sectional view of a nozzle plate according to a third embodiment when viewed from the [0 1 0] direction. A cross-sectional view of a nozzle plate relating to a modified example of the third embodiment, viewed from the [0 1 0] direction. FIG. 7 is a perspective cross-sectional view showing a nozzle flow path formed by a nozzle plate manufacturing method according to a third embodiment. They are a cross-sectional view seen from the [0 1 0] direction and a plan view seen from the [0 0 1] direction of the nozzle plate manufacturing method according to the third embodiment. FIG. 2 is a cross-sectional view of one nozzle flow path and an intermediate structure serving as the nozzle flow path according to Example 1, viewed from the [0 1 0] direction. FIG. 2 is a plan view of one nozzle flow path and an intermediate structure serving as the nozzle flow path according to Example 1, viewed from the [0 0 1] direction. FIG. 3 is a cross-sectional view of one nozzle flow path and an intermediate structure serving as the nozzle flow path according to Example 2, viewed from the [0 1 0] direction. FIG. 7 is a plan view of one nozzle flow path and an intermediate structure serving as the nozzle flow path according to Example 2, viewed from the [0 0 1] direction. FIG. 7 is a cross-sectional view of one nozzle flow path and an intermediate structure serving as the nozzle flow path according to Example 3, viewed from the [0 1 0] direction. FIG. 7 is a plan view of one nozzle flow path and an intermediate structure serving as the nozzle flow path according to Example 3, viewed from the [0 0 1] direction.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the illustrated example. Furthermore, in the following description, parts having the same functions and configurations will be denoted by the same reference numerals, and the description thereof will be omitted.

Furthermore, regarding Miller indices that describe crystal planes and directions, there are generally the following conventions, and this specification also conforms to them.
(h k l): Specific surface [h k l]: Equivalent surface [h k l]: Specific direction <h k l>: Equivalent direction

In addition, unless otherwise specified, in the examples in the specification,
Adhesion side surface of wafer surface: (0 0 1) surface Discharge side surface of wafer surface: (0 0 -1) surface,
Four tapered surfaces of the surfaces that make up the nozzle taper part: (1 1 1) plane, (-1 1 1) plane, (1 -1 1) plane, and (-1 -1 1) plane. Among the vertical surfaces that form the straight communication section, the two opposing surfaces with long sides among the four side surfaces that form the straight communication section: (0 1 0) surface and (0 -1 0) surface The four side surfaces that form the straight communication section The two opposing faces with the shortest sides are described as the (1 0 0) face and the (-1 0 0) face. However, as a matter of course, the description is not limited to this as long as the surface and direction are equivalent to the contents of the description.

In addition, in the display method of the Miller index, as in (1) and (2) of Equation 1 below, the code representing a negative index is generally marked with a bar above the index. However, in this specification, for convenience, they are expressed as (1') and (2') below.

(h -k l)...(1')
[h -k l]...(2')

[First embodiment]
A method for manufacturing the nozzle plate 110 according to the first embodiment of the present invention will be explained.
The method for manufacturing the nozzle plate 110 according to the first embodiment is a method for manufacturing the nozzle plate 110 (see FIG. 2) of the droplet ejection head 2 attached to the droplet ejection device 1 as shown in FIG.

(nozzle plate)
The nozzle plate 110 is formed from a single crystal silicon substrate B whose surface has a {100} crystal orientation. 2A is a plan view showing the (001) plane of the nozzle plate 110, and FIG. 2B is a plan view showing the (00-1) plane of the nozzle plate 110.

As shown in FIG. 2B, the nozzle plate 110 is provided with a plurality of nozzle openings N arranged in a row along the [010] direction on the discharge surface (second surface) Ba ((00-1) plane). It is being
The nozzle plate 110 is provided with a plurality of nozzle channels 100 penetrating from the adhesive surface (first surface) Bb ((001) surface) to the discharge surface Ba.
The nozzle plate 110 is bonded to its adhesive surface Bb with another plate having an ink flow path using an adhesive or the like. Then, the liquid that has flowed in from the ink flow path is discharged from the nozzle opening N via the nozzle flow path 100.

Although FIG. 2B shows only one row of nozzle openings N, a plurality of nozzle openings N may be arranged in the [100] direction.

FIG. 3 is a cross-sectional view of the nozzle plate 110 viewed from the [010] direction. Further, FIG. 4 is a perspective cross-sectional view of one nozzle flow path 100.
As shown in FIGS. 3 and 4, the nozzle channel 100 includes a straight communication section 10, a nozzle taper section 20, and a nozzle opening N in this order from the adhesive surface Bb.

{Straight communication part}
The straight communication portion 10 is provided from the adhesive surface Bb to the end of the nozzle tapered portion 20 on the adhesive surface Bb side. That is, the straight communication portion 10 constitutes an opening on the adhesive surface Bb side of the nozzle flow path 100.
The straight communication portion 10 is constituted by a portion of four {100} crystal planes ((100) plane, (-100) plane, (010) plane, and (0-10) plane). Further, in the straight communication portion 10, as shown in FIGS. 2A and 4, a pair of opposing surfaces 10a are substantially parallel.

As shown in Figures 2A and 4, the faces that constitute the straight communicating portion 10 have, among the sides that intersect with the adhesive surface Bb, a length in the [100] direction along a pair of opposing faces 10a that is longer than the length in the [010] direction.
That is, the side formed by the surface constituting the straight communicating part 10 and the surface constituting the adhesive surface Bb has an elongated shape as shown in Figures 2A and 4. By forming the straight communicating part 10 in this manner, it is possible to arrange the nozzle openings N at a narrow pitch in the short side length of the elongated shape while ensuring the volume of the nozzle flow path 100. That is, the density of the nozzle openings N in the nozzle plate 110 can be increased.

Note that although FIGS. 2A and 4 illustrate a case where the opening on the adhesive surface Bb side of the nozzle flow path 100 in the nozzle plate 110 is rectangular, the shape is not limited to this. When the opening on the bonding surface Bb side of the nozzle flow path 100 is expanded by performing the third step (removal process) described later, the opening will always have a rectangular shape. However, in the present invention, the third step is not an essential step. Therefore, the opening on the adhesive surface Bb side of the nozzle flow path 100 in the nozzle plate 110 may have any shape that corresponds to the shape of the opening pattern 303, which will be described later, as long as it is elongated.

{Nozzle taper part}
The nozzle tapered portion 20 includes a tapered surface 20a having a substantially constant angle and whose flow path area gradually increases from the discharge surface Ba toward the adhesive surface Bb. More specifically, the nozzle taper part 20 has four crystal planes whose crystal planes are {111} planes ((111) plane, (-111) plane, (1-11) plane, and (-1-11) plane). It is constituted by a tapered surface 20a which is , and a portion 20b of the four surfaces whose crystal planes are {100} planes.
Note that the "flow path area" in the present invention refers to a cross-sectional area in a direction perpendicular to the ink ejection direction.

The tapered surface 20a of the nozzle tapered portion 20 has an angle θ ₁ (see FIG. 3) of 15° or more with an axis parallel to the nozzle central axis. In the present invention, the tapered surface 20a is formed by performing anisotropic wet etching on the single crystal silicon substrate B. Therefore, due to the etching characteristics of Si, the angle θ ₁ is 45°.

By providing the nozzle tapered portion 20, even when the liquid meniscus retreats deep into the nozzle flow path 100 due to high-speed driving, the meniscus shape and droplet discharge can be stabilized.

{Nozzle opening}
The nozzle opening N is a circular, elliptical, or polygonal hole provided on the ejection surface Ba and through which droplets are ejected. The nozzle opening N communicates with the end of the nozzle tapered portion 20 on the discharge surface Ba side.

(Method for manufacturing nozzle plate)
The method for manufacturing the nozzle plate 110 includes, for example, the first to third steps shown in FIG.
In the first step, an intermediate structure 300 including an opening hole (first hole) 305 and a nozzle hole (second hole) 306, which will be described later, is formed. Furthermore, in the second step, the nozzle channel 100 is formed by performing anisotropic wet etching on the intermediate structure 300 formed in the first step. Furthermore, in the third step, the nozzle plate 110 formed in the second step is appropriately removed.

{First step: intermediate structure formation step}
(Step 1-1)
As shown in FIG. 5, the first step is further subdivided into a plurality of steps.
First, in step 1-1, a mask layer is formed on the surface of single crystal silicon substrate B. Specifically, a surface mask layer 301 is formed on the bonding surface Bb of single crystal silicon whose surface crystal orientation is the {100} plane. Further, a back mask layer 302 is formed on the ejection surface Ba.
In the following, unless a particular distinction is made between the front mask layer 301 and the back mask layer 302, they will be collectively referred to as "mask layers" as described above.

The single crystal silicon substrate B is a plate-like member with a thickness of approximately 100 μm to 725 μm. By using single crystal silicon as the base material of the nozzle plate 110, highly accurate processing is possible. As a result, the nozzle plate 110 can be formed with fewer errors in position and less variation in shape.

Further, the material for forming the mask layer may be any material as long as it can stop the progress of etching during anisotropic wet etching, which will be described later. Further, any material may be used as long as it cannot be removed by etching.
The material of the mask layer is not particularly limited as long as it satisfies these conditions, but for example, an oxide such as SiO ₂ (silicon oxide) can be used for the mask layer. Further, a metal film made of Al (aluminum), Cr (chromium), etc., resin, or the like can be used for the mask layer.
In the present invention, SiO ₂ is used as a mask layer.

The thickness of the mask layer is not particularly limited, but is preferably 0.1 μm to 50 μm, and more preferably 0.5 μm to 20 μm. When the mask layer has a thickness of 0.5 μm or more, the etching stop effect is enhanced. When the mask layer has a thickness of 20 μm or less, it can be easily formed.
However, when the mask layer is formed by the above-mentioned thermal oxidation method, the thickness of the mask layer is preferably set to 1 μm to 5 μm. Furthermore, the mask layer is not limited to the single layer structure as shown in the figure, but may have a multi-layer structure.

(Step 1-2)
Next, as a 1-2 step, an elongated opening pattern 303 is formed in the front mask layer 301 to become an opening on the bonding surface Bb side of the nozzle channel 100.
Note that in this embodiment, the shape of the opening pattern 303 is a hexagonal shape having long sides along the <100> direction, but the shape is not limited to this. The shape of the opening pattern 303 may be an elongated shape that is longer in the [100] direction than in the [010] direction. Therefore, the shape of the opening pattern 303 may be, for example, a rectangular shape, an elliptical shape, or a shape in which a short side of a rectangle is combined with a semicircle with a diameter having the same width as the short side.
Specifically, first, a resist pattern is formed on the surface mask layer 301 using a well-known photolithography technique.

<Resist pattern>
A positive photoresist or a negative photoresist can be used to form the resist pattern. Known materials can be used as the positive photoresist and the negative photoresist. For example, ZPN-1150-90 manufactured by Zeon Corporation can be used as the negative photoresist. Furthermore, as the positive photoresist, OFPR-800LB and OEBR-CAP112PM manufactured by Tokyo Ohka Kogyo Co., Ltd. can be used.

The resist layer is formed by applying it to a predetermined thickness using a spin coater or the like. Thereafter, a prebaking process is performed at 110° C. for 90 seconds.

In order to improve adhesion, HMDS treatment may be performed before resist coating. The HMDS treatment uses an organic material called hexamethyldisilazane, such as OAP (hexamethyldisilazane, manufactured by Tokyo Ohka Kogyo Co., Ltd.). HMDS may be applied using a spin coater, similar to resist application. Further, HMDS can be expected to have an effect of improving adhesion even when exposed to hexamethyldisilazane vapor.

After forming the resist layer, the resist layer is exposed to light using an aligner or the like using a predetermined mask. For example, in the case of contact aligners, exposure is performed with a light intensity of approximately 50 mJ/cm ² . Thereafter, the resist layer is immersed in a developer (for example, NMD-3 manufactured by Tokyo Ohka Kogyo Co., Ltd. for 60 to 90 seconds) to remove the exposed areas of the resist layer. As a result, a resist pattern is formed on the surface mask layer 301.

After forming the resist pattern, the opening pattern 303 is formed by dry etching the surface mask layer 301 using the resist pattern as a mask. After forming the opening pattern 303, the resist pattern is removed.

<Dry etching>
A RIE (Reactive Ion Etching) device is used for dry etching. Further, a dry etching apparatus such as an ICP (Inductively Coupled Plasma)-RIE etching apparatus, which is a dry etching apparatus that employs an inductive coupling method as a discharge type, is used. Further, as a process gas, CHF ₃ (trifluoromethane), CF ₄ (tetrafluoromethane), etc. are used.

As an example, RIE-100C, a dry etching apparatus manufactured by Samco Corporation, is used. The opening pattern 303 can be formed by etching for a predetermined time under the conditions of CHF ₃ gas flow rate of 80 sccm, pressure of 3 Pa, and RF power of 90 W.

<Removal of resist pattern>
Furthermore, examples of methods for removing the resist pattern include a wet process using acetone or an acid solution, and a dry process using oxygen plasma.

(Step 1-3)
Next, as a 1-3 step, the single crystal silicon substrate B under the opening pattern 303 is deeply etched by dry etching to form an opening hole 305.

(Step 1-4)
Next, in step 1-4, a nozzle pattern 304 which becomes the nozzle opening N is formed.
The method for forming the nozzle pattern 304 is substantially the same as the method for forming the opening pattern 303 in step 1-2. Note that the nozzle pattern 304 in this embodiment is a square (diamond) having sides in the <110> direction.
The nozzle pattern 304 is formed so that, when viewed from the adhesive surface Bb or the ejection surface Ba, its center approximately coincides with the center of the opening pattern 303. In the following, this condition is referred to as "Condition 1."

(Step 1-5)
Next, in a 1-5 step, the single crystal silicon substrate B under the nozzle pattern 304 is deeply etched by dry etching to form a nozzle hole 306.
The nozzle hole 306 is formed so that its length a in the [001] direction approximately matches the length b of the end of the opening hole 305 in the [100] direction from the end of the nozzle hole 306 on the adhesive surface Bb side. do. In the following, this condition will be referred to as "Condition 2."

In the 1-5th step, as shown in FIG. 5, it is preferable to form a nozzle hole 306 so as to communicate with the opening hole 305. By forming the intermediate structure 300 in which the opening hole 305 and the nozzle hole 306 communicate with each other in the first step, the fluidity of the anisotropic wet etching solution used in the second step is improved. Therefore, anisotropic wet etching is always performed using a fresh chemical solution. Furthermore, hydrogen gas generated during anisotropic wet etching can escape uniformly and efficiently through each nozzle channel 100. As a result, the wet etching progresses in the same manner in each nozzle channel 100, and a uniform nozzle channel 100 can be formed.

However, it is not essential to form the intermediate structure 300 in which the opening hole 305 and the nozzle hole 306 communicate with each other at the time of the first step. The opening hole 305 and the nozzle hole 306 only need to be able to communicate with each other when anisotropic wet etching is performed in the second step.

In addition, although the case where the first step is carried out in the order of step 1-1, step 1-2, step 1-3, step 1-4, and step 1-5 is illustrated above, the present invention is not limited to this. I can't do it. At least three steps are to be taken: performing step 1-1 first, performing step 1-2 before step 1-3, and performing step 1-4 before step 1-5. All you have to do is meet the conditions.

Therefore, condition 1 may be rephrased as "the opening pattern 303 is formed so that its center substantially coincides with the center of the nozzle pattern 304 when viewed from the adhesive surface Bb or the ejection surface Ba".

Condition 2 is such that "the length b of the end of the nozzle hole 306 on the adhesive surface Bb side from the end in the [100] direction is approximately equal to the length a of the nozzle hole 306 in the [001] direction. It may also be stated as "forming an opening hole 305".

{Second step: anisotropic wet etching step}
Next, in a second step, anisotropic wet etching is performed on both the adhesive surface Bb and the ejection surface Ba of the intermediate structural body 300 formed in the first step.
Fig. 6A is a cross-sectional view showing the progress of etching in the second step as viewed from the [100] direction which constitutes the short side of the opening hole 305. Fig. 6B is a cross-sectional view showing the progress of etching in the second step as viewed from the [010] direction which constitutes the long side of the opening hole 305.
6A and 6B, in the second step, the opening hole 305 provided in the first-3 step and the nozzle hole 306 provided in the first-5 step are enlarged, thereby forming a nozzle flow path 100 including a nozzle taper portion 20 and a straight communicating portion 10.

<Anisotropic wet etching>
An alkaline aqueous solution is used for anisotropic wet etching. Specifically, they include KOH (potassium hydroxide), TMAH (tetramethylammonium hydroxide), and EDP (ethylenediamine pyrocatechol).

In the second step, as shown in FIG. 6A, when viewed from the [100] direction, the surfaces forming the opening hole 305 and the nozzle hole 306 are aligned in the [010] direction and the [0-10] direction. Etching progresses.
Therefore, the distance between the (010) plane and the (0-10) plane after anisotropic wet etching is (diameter of nozzle pattern 304+2×etching amount) μm (3).

Further, as shown in FIG. 6B, when viewed from the [010] direction, etching progresses in the [100] direction and the [-100] direction with respect to each surface forming the opening hole 305. Further, etching progresses in the [100] direction or the [-100] direction with respect to each surface forming the nozzle hole 306.
Therefore, the distance between the (100) plane and the (-100) plane after anisotropic wet etching is (diameter of nozzle pattern 304 + 6 x etching amount) μm (4).

Here, specifically, the diameter of the nozzle pattern 304 is 10 μm, and the etching amount is 20 μm. Then, the distance between the (010) plane and the (0-10) plane after the anisotropic wet etching is 10 μm+2×20 μm=50 μm from the above equation (3).
Further, the distance between the (100) plane and the (-100) plane after the anisotropic wet etching is 10 μm+6×20 μm=130 μm from the above equation (4).
On the other hand, the diameter of the nozzle pattern 304 is 30 μm, and the distance between the (010) plane and the (0-10) plane after anisotropic wet etching is 50 μm. Then, from the above equation (3), the etching amount x becomes 10 μm since 30 μm+2×x μm=50 μm.
Then, the distance between the (100) plane and the (-100) plane after the anisotropic wet etching is 30 μm+6×10 μm=90 μm from the above equation (4).

As described above, the nozzle flow path 100 formed according to the present invention has an elongated shape in which the opening on the adhesive surface Bb side has a different dimension between the long side and the short side. This is preferable from the viewpoint of increasing the density of the nozzle openings N.
As will be described later, when removing the straight communication portion 10 in the third step after the second step so that it becomes approximately vertical, the distance between the (010) plane and the (0-10) plane is the same as the nozzle flow path. This is the short side dimension of the opening on the bonding surface Bb side of 100. Further, the distance between the (100) plane and the (-100) plane is the dimension on the long side.
Therefore, based on the above calculation, it is preferable to form the nozzle pattern 304 with a diameter as small as possible.
However, in this embodiment, the ratio of the interval between the (010) plane and the (0-10) plane and the interval between the (100) plane and the (-100) plane, that is, the ratio of the interval between the (100) plane and the (-100) plane, that is, the The theoretical limit value of the ratio of the short side dimension to the long side dimension of the opening on the adhesive surface Bb side is 1:3.

{Third process: Removal process}
Returning to FIG. 5, after the second step, as a third step, removal processing such as etching, grinding, or polishing is performed on the nozzle plate 110. Specifically, for example, the removal process is performed so that the straight communication portion 10 becomes substantially vertical, and the diameter of the opening on the bonding surface Bb side of the nozzle channel 100 after anisotropic wet etching is expanded. Alternatively, the thickness of the nozzle plate 110 is adjusted to a desired dimension. Alternatively, the mask layer is removed.
In particular, even if the diameter of the nozzle pattern 304 is formed small as described above, the nozzle pattern 304 can be removed by performing removal processing such as photolithography, transfer to the back mask layer 302, and etching again from the ejection surface Ba side. The diameter of the opening N can be expanded.
Note that the third step is not an essential step, and may be performed as needed.

[Technical effect]
As described above, the method for manufacturing the nozzle plate 110 according to the first embodiment includes an opening hole (first hole) 305 that is elongated in the [100] direction, and a nozzle that can communicate with the opening hole 305 and the discharge surface Ba. The method includes a first step of forming an intermediate structure 300 having a hole (second hole) 306 . The method also includes a second step of enlarging the opening hole 305 and the nozzle hole 306 by anisotropic wet etching to form the nozzle flow path 100.

The reason why condition 1 and condition 2 are described as "approximately the same" above is because they may not be completely the same due to manufacturing errors. Fig. 7A shows a case where condition 1 is not satisfied. Fig. 7B shows a case where condition 2 is not satisfied, with a>b. Fig. 7C shows a case where condition 2 is not satisfied, with a<b. All of Figs. 7A to 7C include a step in tapered surface 20a.
As can be seen from a comparison of FIG. 5 with FIG. 7A to FIG. 7C, by satisfying condition 1 and condition 2, a nozzle flow channel 100 with a smooth tapered surface 20a is formed.

On the other hand, as shown in FIGS. 7A to 7C, even if a manufacturing error related to condition 1 or condition 2 occurs in the first step, the nozzle opening N is the same as the nozzle opening N of the tapered surface 20a. Located at the symmetrical center of the plane between the steps. This is because at least the portion of the nozzle taper portion 20 that communicates with the nozzle opening N is enlarged from the nozzle hole 306 .

As described above, according to the above manufacturing method, even if there is a manufacturing error under Condition 1 or Condition 2, the nozzle tapered portion 20 is always formed from the nozzle hole 306. The nozzle opening N is arranged without any positional deviation at the symmetrical center of the surface between the nozzle opening N and the step of the tapered surface 20a. Therefore, even if there is a manufacturing error in Condition 1 or Condition 2, it is possible to form a nozzle plate 110 that has no eccentricity, maintains the symmetry of the liquid flow, and has the nozzle flow path 100 with a stable injection angle. .

Furthermore, according to the above manufacturing method, it is possible to form a nozzle plate 110 having a nozzle flow path 100 with an elongated opening on the adhesive surface Bb. Therefore, the nozzle openings N can be made denser in the nozzle plate 110. Furthermore, when the nozzle plate 110 is joined to another plate having an elongated cross-sectional shape of the ink flow path, the joint between the nozzle flow path 100 and the ink flow path matches in shape, resulting in favorable ejection characteristics.

[Other preferred configurations]
As described above, the opening pattern 303 is not limited to a hexagon having a long side along the <100> direction, and the nozzle pattern 304 is not limited to a square having a side along the <110> direction.
However, in consideration of the crystal orientation dependency of anisotropic wet etching, it is particularly preferable that the opening pattern 303 and the nozzle pattern 304 have the above shapes, which makes it easier for anisotropic wet etching such as that shown in FIG.

Further, FIGS. 7A to 7C illustrate cases where a manufacturing error related to condition 1 or condition 2 occurs in the first step. Among these, as shown in FIG. 7B, there is a nozzle flow path in which a>b and a hanging surface with a step in the nozzle taper portion 20 or an inclined surface (step surface) having an inclination steeper than the angle θ ₁ is formed. 100 has better meniscus stability.
This is because when the step surface is formed, even if the meniscus returns to the back side of the nozzle flow path 100, the expansion in the [100] direction is suppressed, and the width in the [100] direction and the width in the [010] direction are This is because the width and length can be made the same.

It is preferable to form the step surface so that the length from the ejection surface Ba to the end of the step surface on the adhesive surface Bb side is 20 μm or more and 60 μm or less.
This is because it is rare for the liquid to be drawn in greater than 20 μm, and if the length is greater than 60 μm, the nozzle flow path 100 will not be able to ensure a sufficient volume.

[Second embodiment]
Next, a method for manufacturing the nozzle plate 110 according to the second embodiment will be described.
In the second embodiment, after forming the opening pattern 303, patterns with different sizes and thicknesses are further formed to form the opening hole 305 with a stepped bottom.

FIG. 8 illustrates a method for manufacturing the nozzle plate 110 according to the second embodiment.
Note that since the step 1-1 is the same as that in the first embodiment, detailed explanation thereof will be omitted.

(Step 1-2a)
In this embodiment, resist pattern formation and dry etching are performed twice as the 1-2a step. Specifically, after the opening pattern 303 is formed, a resist pattern having a size that surrounds the opening pattern 303 is formed. Further, dry etching is performed with an etching amount smaller than that of the opening pattern 303 to form the sub-pattern 303a.
After forming the opening pattern 303 and the sub-pattern 303a, the resist pattern is removed.

(Step 1-3)
After the opening pattern 303 and the sub-pattern 303a are formed, the opening hole 305 is formed by deep drilling using dry etching.
At this time, in the sub-pattern 303a, the surface mask layer 301 is first etched. Then, when the etching of the surface mask layer 301 is completed, the single crystal silicon substrate B is etched. On the other hand, in the opening pattern 303, there is no surface mask layer 301. Therefore, the single crystal silicon substrate B is immediately etched.

Therefore, even if etching is performed for the same time, the amount of etching of the single crystal silicon substrate B is different between the opening pattern 303 and the sub-pattern 303a. That is, the single crystal silicon substrate B under the opening pattern 303 is etched more deeply. As a result, an open hole 305 with a stepped bottom is formed as shown in FIG.
In addition, for the steps formed in the 1-3 steps, it is preferable to design the length c in the [001] direction and the length d in the [100] direction so that a≒b≒c≒d. . Similar to the first embodiment, when the conditions are met, a nozzle flow path 100 with a smooth tapered surface 20a is formed.

(Step 1-4, Step 1-5, Step 2, Step 3)
After the opening hole 305 is formed, the nozzle hole 306 is formed in the 1-4th step and the 1-5th step. Then, in a second step, the nozzle channel 100 is formed by anisotropic wet etching.
After the second step, appropriate removal processing is performed as a third step.

[Technical effect]
As described above, the method for manufacturing the nozzle plate 110 according to the second embodiment is to form the sub-pattern 303a having a different size and thickness from the opening pattern 303, thereby forming the opening holes 305 with stepped bottoms. Form.
According to this configuration, the ratio of the short dimension to the long dimension of the opening on the bonding surface Bb side of the nozzle flow path 100 can be made even larger than 1:3. Therefore, it becomes possible to further increase the density of the nozzle openings N.

[Modified example]
Note that in the above description, the sub-pattern 303a is formed after the opening pattern 303 is formed, but the order is not limited to this, and the order may be reversed.
Moreover, although the case where formation of a resist pattern and dry etching are performed twice is illustrated above, it is not limited to this. That is, the opening hole 305 having a plurality of steps may be formed by performing resist pattern formation and dry etching two or more times.
Moreover, although the case where formation of a resist pattern and dry etching are performed multiple times is illustrated above, the present invention is not limited to this. That is, the aperture pattern 303 and the sub-pattern 303a may be formed at the same time by using a gray tone mask.

[Third embodiment]
Next, a method for manufacturing the nozzle plate 110 according to the third embodiment will be explained based on FIG. 11.
In the method for manufacturing a nozzle plate 110 according to the third embodiment, a nozzle flow path 100 including a nozzle straight portion 30 as shown in FIGS. 9 and 10 is formed.

{Nozzle straight part}
The nozzle straight portion 30 is a flow path where the discharge surface Ba side is continuous with the nozzle opening N and the adhesive surface Bb side is continuous with the nozzle tapered portion 20.

In the following, a nozzle straight portion 30 formed by a surface that forms an angle of 0° with an axis parallel to the nozzle central axis as shown in FIG. 9A will be exemplified, but the present invention is not limited to this.
As shown in FIG. 9B , it is sufficient that the angle θ ₂ between the surface constituting the nozzle straight section 30 and an axis parallel to the nozzle central axis is approximately constant at every point and is in the range of 0°≦θ ₂ <15°.

In the present embodiment, steps 1-A to 1-C are sequentially executed after at least step 1-4 and before step 1-5. In this embodiment, if the above conditions and the following three conditions are met: 1-1 step is executed first, and 1-2 step is executed before 1-3 step, the step The order is not particularly limited.
However, in practice, it is preferable to perform steps 1-A to 1-C before step 1-3. This is because when step 1-B, which will be described later, is performed after step 1-3, a mask layer is also formed in the opening hole 305, and a step of removing the mask layer is required.
Therefore, in the following, 1-1 process → 1-4 process → 1-A process → 1-B process → 1-C process → 1-5 process → 1-2 process → 1-1 process -Proceed in the order of 3rd process → 2nd process → 3rd process.
Further, since the steps 1-1 to 1-5 are the same as those in the first embodiment, detailed explanation thereof will be omitted.

(Step 1-A)
After forming the nozzle pattern 304 in step 1-4, in step 1-A, the single crystal silicon substrate B below the nozzle pattern 304 is dry etched by a predetermined amount. This forms a nozzle straight hole (third hole) 307. In this step, it is sufficient to etch only the length of the planned nozzle straight portion 30.

(Step 1-B)
After the nozzle straight hole 307 is formed, in step 1-B, a nozzle mask layer 308 is formed along the inner surface of the nozzle straight hole 307. The nozzle mask layer 308 is formed using the same material and method as the mask layer.

(Step 1-C)
After forming the nozzle mask layer 308, the nozzle mask layer 308 formed at the bottom of the nozzle straight hole 307 is removed as a 1-C step. The nozzle mask layer 308 at the bottom of the nozzle straight hole 307 can be removed by dry etching using an RIE apparatus or the like. However, due to the vertical nature of the etchant in dry etching using an RIE apparatus, the nozzle mask layer 308 formed on the side surfaces is more difficult to remove than the bottom portion. Therefore, of the nozzle mask layer 308, the layer formed at the bottom of the nozzle straight hole 307 is etched first, and the layer formed at the side surface remains.

Note that the etching conditions in this step may be set to low pressure or high bias to make it more difficult for the nozzle mask layer 308 on the side surfaces to be etched.

(Step 1-5, Step 1-2, Step 1-3)
After the 1-C process, as a 1-5 process, the single crystal silicon substrate B is dry etched to further dig the nozzle straight hole 307 to form a nozzle hole 306. Then, an opening hole 305 is provided in the 1-2nd step and the 1-3rd step.

(2nd process, 3rd process)
Then, anisotropic wet etching is performed as a second step. At this time, the side surface of the nozzle straight hole 307 is protected by a nozzle mask layer 308. Therefore, the progress of etching on the side surface portion of the nozzle straight hole 307 is suppressed, and the side surface portion remains as the nozzle straight portion 30.
After the second step, appropriate removal processing is performed as a third step. Note that in this embodiment, the nozzle mask layer 308 may also be removed together with the mask layer in the third step.

[Technical effect]
As described above, the method for manufacturing the nozzle plate according to the third embodiment includes steps 1-A to 1-C for forming the nozzle straight hole 307 and the nozzle mask layer 308 .
According to this configuration, it is possible to form a nozzle flow path 100 that includes a nozzle straight section 30. The nozzle straight section 30 increases the resistance when droplets are ejected, suppresses the vibration of the meniscus, and makes the meniscus shape more stable. Therefore, it is possible to form a nozzle plate 110 that includes a nozzle flow path 100 with improved ejection stability.

[Modified example]
In addition, although the case where the nozzle straight part 30 is formed by forming the nozzle straight hole 307 and the nozzle mask layer 308 was illustrated above, it is not limited to this.
The nozzle straight portion 30 can also be formed using a single crystal silicon substrate B provided with a non-wet etching layer having etching resistance.

The non-wet etching layer refers to a layer having etching resistance that can be formed, for example, by masking, thermal oxidation processing, or doping with high concentration B (boron). In addition, a quartz layer formed by a method other than the above-mentioned thermal oxidation may be provided on the single crystal silicon substrate B, and the quartz layer may be used as the non-wet etching layer.

Specifically, first, a non-wet etching layer having the same thickness as the nozzle plate 110 is provided on at least the ejection surface Ba side of the single crystal silicon substrate B. Then, when a nozzle hole 306 is formed using such a single crystal silicon substrate B and anisotropic wet etching is performed, the non-wet etching layer plays the same role as the nozzle mask layer 308.
Therefore, the nozzle straight portion 30 can be formed in the nozzle flow path 100 even by using the single crystal silicon substrate B having a non-wet etching layer.

Note that the "length a of the nozzle hole 306 in the [001] direction" according to condition 2 includes the length in the [001] direction of parts that have etching resistance, such as the nozzle mask layer 308 and non-wet etching layers. Of course not.

Further, in the manufacturing process according to each embodiment, a step of forming at least one protective film may be added in order to use the nozzle plate 110 for a long period of time.
In this case, a step of forming a protective film covering at least a portion of the surface including the inside of the nozzle flow path 100 is performed after the second step or the third step.

The protective film is mainly made of a material that does not dissolve upon contact with the ink, such as a metal oxide film (tantalum pentoxide, hafnium oxide, niobium oxide, titanium oxide, zirconium oxide, etc.) or a metal oxide film containing silicon. The materials used to form the mask layer include metal silicate films (tantalum silicate, hafnium silicate, niobium silicate, titanium silicate, zirconium silicate, etc.), SiC (silicon carbide) films, DLC (diamond-like carbon) films, etc. It can be used selectively. Further, as the protective film, an organic film such as polyimide, polyamide, parylene, etc. may be used.
The thickness of the protective film is not particularly limited, but may be, for example, 0.05 μm to 20 μm.

Next, the results of evaluating preferred configurations for Examples and Comparative Examples of the present invention will be described. EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

[Sample creation]
A nozzle plate 110 having 1280 nozzle channels 100 formed according to the following Examples and Comparative Examples was manufactured. Then, the inkjet head, which is the droplet ejection head 2, is bonded to a piezoelectric plate having an ink flow path whose opening on the adhesive surface has the same shape as the opening on the adhesive surface Bb side of the nozzle flow path 100. Formed. Then, the inkjet head was mounted on an inkjet recording device, which is the droplet ejection device 1.

12 to 14 are diagrams showing one nozzle flow path 100 in the nozzle plate 110 according to each embodiment. In each figure, the dotted line portion indicates the intermediate structure 300 formed in the first step. In addition, the solid line portion is anisotropic wet etching performed on the intermediate structure 300 in the second step, and removal processing is performed in the third step so that the straight communication portion 10 becomes approximately vertical, so that the bonding surface Bb side is A nozzle flow path 100 with a rectangular opening is shown.

(Example 1)
The nozzle plate 110 was formed based on the manufacturing method according to the second embodiment. That is, as shown in FIGS. 12A and 12B, an intermediate structure 300 was formed in which the bottom of the opening hole 305 was stepped. Then, a nozzle flow path 100A including a nozzle tapered portion 20A, a straight communication portion 10A, and a nozzle opening N was formed.

Note that, as shown in FIG. 12B, the shape of the opening pattern 303 is hexagonal in plan view. Further, the dimensions of the opening on the adhesive surface Bb side of the nozzle flow path 100A are 50 μm×130 μm, and the nozzle opening N is circular with a diameter of 30 μm. Further, the intermediate structure 300 formed in the first step was designed so that a≒b≒c≒d.

(Example 2)
The nozzle plate 110 was formed based on the manufacturing method according to the third embodiment. That is, as shown in FIGS. 13A and 13B, a nozzle flow path 100B including a nozzle straight section 30B, a nozzle tapered section 20B, a straight communication section 10B, and a nozzle opening N was formed.

Note that, as shown in FIG. 13B, the shape of the opening pattern 303 is a combination of a short side of a rectangle and a semicircle with a diameter that is the same width as the short side. Further, the dimensions of the opening on the adhesive surface Bb side of the nozzle flow path 100B are 50 μm×130 μm. Further, the length of the nozzle straight portion 30B in the [001] direction is 30 μm. Further, as shown in FIGS. 13A and 13B, in this example, a circular nozzle pattern 304 with a diameter of 10 μm is formed in the 1st-4th process, and the nozzle opening N is formed in a circular shape with a diameter of 30 μm in the 3rd process. Expanded to take shape.

Also, for condition 2, it was designed so that a>b. Therefore, a vertical surface (stepped surface) with a length of 10 μm in the [001] direction was formed, which provided a step on the tapered surface 20aB of the nozzle tapered portion 20B.

(Example 3)
The nozzle plate 110 was formed based on the manufacturing method according to the third embodiment. That is, as shown in FIGS. 14A and 14B, a nozzle flow path 100C including a nozzle straight section 30C, a nozzle tapered section 20C, a straight communication section 10C, and a nozzle opening N was formed.

Note that, as shown in FIG. 14B, the opening pattern 303 has a rectangular shape in which the length in the [010] direction is longer than the length in the [100] direction. Further, the dimensions of the opening of the nozzle flow path 100C on the adhesive surface Bb side are 50 μm×130 μm. Further, as shown in FIGS. 14A and 14B, in this example, a diamond-shaped nozzle pattern 304 with a diameter of 10 μm is formed in the 1st-4th process, and the nozzle opening N is formed in a circle with a diameter of 30 μm in the 3rd process. Expanded to take shape.

Furthermore, for condition 2, it was designed so that a=b. Therefore, no stepped surface is formed on the tapered surface 20aC of the nozzle tapered portion 20C.
Further, for the nozzle straight portion 30C, etching conditions were appropriately set in the nozzle opening expansion step. Therefore, the nozzle straight portion 30C had a tapered surface with an angle θ ₂ of 8°, a length in the [001] direction of 35 μm, and a diameter at the end on the adhesive surface Bb side of 40 μm.

(Comparative example 1)
The nozzle flow path 100 was formed by a conventionally known method. That is, although the nozzle tapered part 20 and the straight communication part 10 are provided, the opening of the nozzle flow path 100 on the adhesive surface Bb side has a square shape of 50 μm×50 μm.

Using an inkjet recording device equipped with an inkjet head equipped with the nozzle plate 110 of Examples 1-3 and Comparative Example 1, the following

Tests

1 and 2 were conducted.

[Test 1. Injection angle test]
UV ink heated to a viscosity of 8 cP was injected at a driving voltage such that the average droplet velocity was about 6 m/s. At this time, the injection angle, which is the angle between the nozzle central axis and the injection liquid, was evaluated for 1280 nozzles to see if it was within ± degrees.

[Test 2. Upper limit speed test]
At a driving frequency of 40 kHz, the ejection speed of UV ink heated to a viscosity of 8 cP was increased from 5 m/s. Then, the injection speed at which the number of nozzle openings N at which injection failure occurred occurred in 5 or more out of 100 nozzles was measured. Note that when the injection speed is 9 m/s or more, injection failure is unlikely to occur even if the injection speed is high. Further, it is preferable that the injection speed is 11 m/s because injection failure is less likely to occur. Therefore, the meniscus stability was evaluated as "C" if it was less than 9 m/s, "B" if it was 9 m/s or more and less than 11 m/s, and "A" if it was 11 m/s or more.

The results of Test 1 and Test 2 are shown in Table I.

[evaluation]
Comparing Example 1 and Comparative Example 1, Example 1 has better meniscus stability and is less likely to cause injection failure. This is because in the first embodiment, the nozzle tapered portion 20A is formed such that the center of the nozzle opening N is located at the symmetrical center of the tapered surface 20aA.

Furthermore, when comparing Example 1 with Examples 2 and 3, Examples 2 and 3 have improved injection angles and improved injection characteristics. This is because the nozzle

straight portions

30B and 30C are formed in the nozzle flow path 100.

Further, when comparing Example 2 and Example 3, Example 2 has better meniscus stability and is less likely to cause injection defects. This is because a stepped surface is formed on the tapered surface 20aB of the nozzle tapered portion 20B.

The present invention can be used in a method for manufacturing a nozzle plate that can achieve both high density nozzle openings and suitable injection characteristics.

2 Droplet discharge head 10 Straight communication part 20 Nozzle tapered part 30 Nozzle straight part 100 Nozzle channel 110 Nozzle plate 305 Opening hole (first hole)
306 Nozzle hole (second hole)
307 Nozzle straight hole (3rd hole)
308 Nozzle mask layer N Nozzle opening B Single crystal silicon substrate Ba Ejection surface (second surface)
Bb Adhesive side (first side)

Claims

A method for manufacturing a nozzle plate of a droplet ejection head, the method comprising:
a first hole that communicates with a first surface of a single crystal silicon substrate whose surface crystal orientation is {100} plane and is longer in the [100] direction than in the [010] direction; and the first hole and the single crystal. a first step of forming a second hole that can communicate with the second surface of the silicon substrate;
By enlarging the first hole and the second hole by anisotropic wet etching on the single crystal silicon substrate, a nozzle taper portion having a {111} plane and a straight communication portion continuous to the nozzle taper portion are formed; a second step of forming a nozzle flow path.
In the first step, the length of the second hole in the [001] direction is the length from the end of the second hole on the first surface side to the end of the first hole in the [100] direction. 2. The method of manufacturing a nozzle plate according to claim 1, wherein the nozzle plates are formed to be substantially equal.
In the first step, the length of the second hole in the [001] direction is longer than the length from the end of the second hole on the first surface side to the end of the first hole in the [100] direction. Form it so that it is also long,
2. The method of manufacturing a nozzle plate according to claim 1, wherein a stepped surface is formed in the nozzle tapered portion.
The method for manufacturing a nozzle plate according to any one of claims 1 to 3, wherein the centers of the first hole and the second hole coincide.
The method for manufacturing a nozzle plate according to any one of claims 1 to 3, wherein in the first step, the bottom of the first hole is formed in a stepped shape.
The first step comprises:
The single crystal silicon substrate is deep-drilled from the first surface to a middle portion thereof by dry etching to form a third hole;
Next, a nozzle mask layer is formed along the inner surface of the third hole;
Then, removing the nozzle mask layer formed on the bottom of the third hole,
The first hole is formed by further deepening the third hole,
The method for manufacturing a nozzle plate according to claim 1 , wherein the second step forms a nozzle flow path including a nozzle straight portion continuing from an end of the nozzle tapered portion on the second surface side.
The method for manufacturing a nozzle plate according to any one of claims 1 to 3, wherein the single crystal silicon substrate has a non-wet etching layer formed from the second surface.
The method for manufacturing a nozzle plate according to any one of claims 1 to 3, including a third step of enlarging the diameter of the opening on the first surface side and/or the second surface side of the nozzle flow path.