JP7393904B2 - Imprint mold manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing an imprint mold used to form a fine three-dimensional structural pattern.

Imprint molds are known in which a specific fine three-dimensional structural pattern is formed on a base material (eg, glass, resin, metal, silicon, etc.). Imprint molds are used in semiconductor devices, optical elements, wiring circuits, recording devices such as hard disks and DVDs, medical test chips used for DNA analysis, display panels, microchannels, and the like.

Etching using a mask is known as a method of forming a fine three-dimensional structural pattern (see, for example, Patent Document 1).

JP2009-72956A

By filling the recesses of an imprint mold with resin, metal, etc., fine structures can be transferred, but since the fine recesses have a large surface area per volume, the filled material may stick. Sticking complicates the molding process and reduces the quality of the molded product.
As a countermeasure, a mold release agent may be applied to the inner surface of the recess, but this often does not provide a sufficient effect.

In view of the above circumstances, an object of the present invention is to provide an imprint mold in which sticking of a molding material to a fine structure is suppressed.

A first aspect of the present invention is an imprint mold that includes a substrate in which a plurality of fine recesses are opened on one surface, and has a plurality of protrusions on the inner surface that is continuous with the opening edge of the fine recesses.
Another imprint mold of the present invention includes a substrate on which a plurality of fine convex portions are formed on one surface, and has a plurality of protrusions on the outer surface of the fine convex portions.

The second aspect of the present invention is a method for manufacturing an imprint mold.
In this manufacturing method, a photoresist having multiple openings is placed on one side of the substrate, the substrate exposed in the openings is isotropically etched to form a primary recess, and the inner surface of the primary recess is covered with a protective film. and performing isotropic etching on the primary recess at least partially covered with the protective film to form a secondary recess below the primary recess.
In another method of manufacturing an imprint mold of the present invention, the fine recesses of the imprint mold described above are filled with a molding material, the molding material is hardened to transfer the inner shape of the fine recesses to the molding material, and the imprint mold is is removed to obtain a second imprint mold made of molding material.

According to the present invention, it is possible to provide an imprint mold in which sticking of a molding material to a fine structure is suppressed.

FIG. 1 is a schematic cross-sectional view showing an imprint mold according to an embodiment of the present invention. FIG. 3 is a diagram showing a process during manufacturing of the same imprint mold. FIG. 3 is a diagram showing a process during manufacturing of the same imprint mold. FIG. 3 is a diagram showing a process during manufacturing of the same imprint mold. FIG. 3 is a diagram showing a process during manufacturing of the same imprint mold. FIG. 3 is a diagram showing a process during manufacturing of the same imprint mold. FIG. 3 is a schematic cross-sectional view showing a second imprint mold manufactured using the same imprint mold. It is a schematic sectional view showing a modification of the same imprint mold. It is a schematic sectional view showing a modification of the same imprint mold. It is a schematic plan view which shows the modification of the same imprint mold.

One embodiment of the present invention will be described with reference to FIGS. 1 to 10.
FIG. 1 is a schematic cross-sectional view showing an imprint mold 1 according to this embodiment. The imprint mold has fine recesses 20 opening in the surface of the substrate 10.
Examples of the material of the substrate 10 include silicon (Si), nickel (Ni), resin, and the like. Among these, silicon is suitable as a material for a master mold (original plate), which is an imprint mold for producing imprint molds made of nickel and resin.

The number, dimensions, arrangement mode, pitch, etc. of the fine recesses 20 opened on the surface of the substrate 10 can be set as appropriate depending on the use of the structure to be created. For example, the opening diameter of the fine recess 20 is about several μm to several tens of μm.
The fine recess 20 may penetrate the substrate 10 or may have a bottom.

The spatial shape of the fine recess 20 is approximately cylindrical. Therefore, the fine recess 20 has an inner surface 22 that is continuous with the opening edge 21 and extends in the thickness direction of the substrate 10 .
The inner surface 22 has a plurality of protrusions (protrusions) 23 that protrude toward the inner space of the fine recess 20 . The protrusions 23 are arranged at approximately equal intervals (pitch) in the thickness direction of the substrate 10. The pitch of the protrusions 23 can be, for example, about 50 nm to 20 μm.
Each protrusion 23 is continuous over the entire circumference of the inner surface 22 and has a substantially annular shape in a plan view of the substrate 10, but it is not essential that it be completely annular; It may be partially discontinuous due to certain reasons.

The tips of the protrusions 23 of the imprint mold 1 are sharp in the cross-sectional view shown in FIG. 1, and curved grooves 24 are formed between adjacent protrusions 23 in the thickness direction of the substrate 10. There is. The grooved line 24 is also generally continuous over the entire circumference of the inner surface 22.

A method for manufacturing the imprint mold 1 according to this embodiment will be described.
First, a substrate 10 made of a desired material is prepared. In the following, a case will be described in which a silicon substrate 10 is used.

Next, as shown in FIG. 2, a photoresist 101 having openings 101a corresponding to the minute recesses 20 is formed on the surface of the substrate 10 (Step A). The opening diameter of the opening 101a of the photoresist 101 is approximately the same as the diameter D1 of the effective area R1 (see FIG. 1) defined by the apex of the protrusion 23 in the fine recess 20 to be formed.

Next, isotropic dry etching is performed on the photoresist 101 to etch the substrate 10 exposed within the opening 101a (step B). As shown in FIG. 3, the primary recess 200 formed by isotropic etching expands below the photoresist 101, and a connecting portion 203 between the bottom surface 201 and the side wall 202 is formed in a curved shape.
Isotropic dry etching can be performed by a known method.

Next, as shown in FIG. 4, the inner surface of the primary recess 200 is covered with a protective film 102 (Step C). In step C, the photoresist 101 may be covered with a protective film 102.
Subsequently, anisotropic dry etching is performed from above the substrate 10 to remove a portion of the protective film 102 (Step D). Since the etching is anisotropic, the protective film 102 located below the photoresist 101 remains without being removed, as shown in FIG.

Subsequently, isotropic dry etching is performed to further dig into the substrate 10 (step E). In step E, as shown in FIG. 6, a secondary recess 210 is formed below the primary recess 200, and a protrusion 23 is formed at the boundary between the primary recess 200 and the secondary recess 210.

Thereafter, steps C to E are repeated until the set depth of the fine recesses is reached. Steps C to E correspond to one cycle of the known Bosch process.
Finally, when the photoresist 101 and the protective film 102 are removed by cleaning or the like, the imprint mold 1 shown in FIG. 1 in which the fine recesses 20 having the protrusions 23 are formed is completed.

In the fine recesses 20 of the completed imprint mold 1, the plurality of protrusions 23 create a lotus effect on the inner surface, increasing liquid repellency. Therefore, the molding material such as resin filled in the fine recesses 20 remains within the effective region R1 and does not come into contact with the grooves 24.
As a result, the molding material filled in the fine recesses 20 is molded into a substantially cylindrical shape corresponding to the effective region R1. Furthermore, since the molding material after molding and the inner surface of the fine recess 20 are in contact with each other only at the tips of the protrusions 23, the contact area between the two is significantly smaller than in conventional imprint molds. Therefore, the molding material is less likely to stick to the inner surface of the fine recess 20, and can be easily released from the mold without damaging the shape.

In conventional imprint molds, processing was performed to smooth the inner surfaces of minute recesses in order to improve mold releasability. The inventor questioned such conventional practices and completed the present invention by discovering that mold releasability was improved by deliberately leaving the unevenness on the inner surface that was generated in the process of forming minute recesses.

Using the above-described imprint mold 1 as a master mold, an imprint mold (second imprint mold) having fine protrusions corresponding to the shape of the fine recesses 20 can be manufactured.
In this case, a lyophilic material that increases wettability is applied to the inner surface of the fine recess 20, and then the desired material is filled into the fine recess 20. When filling, the molding material is heated to a high temperature to lower its viscosity, evacuated, or pressure is applied as necessary to sufficiently fill the micro recesses 20 with the molding material. After the molding material is cured, the master mold is destroyed and removed, and as shown in FIG. 7, an imprint mold 51 having fine protrusions 60 on a substrate 50 made of the molding material is completed. Examples of molding materials include resin and metal. When the molding material is resin, the curing method can be heat curing, electron beam curing, or the like.

In the imprint mold 51 , the fine convex portion 60 has a plurality of protrusions 63 on the side surface 62 . The protruding end portion of the protruding strip 63 has a curved surface shape corresponding to the inner surface shape of the concave strip 24. The surface of the fine convex portion 60 exhibits a lotus effect due to the plurality of convex stripes 63, and has improved liquid repellency. When the fine protrusions 60 of the imprint mold 51 are molded while immersed in a liquid resin or the like, the molded product is formed with a fine concave portion having a shape corresponding to the fine convex portion 60, that is, a space having the same shape as the fine concave portion 20. You can get a body. In this molded article, since the inner surface of the fine recesses has excellent liquid repellency, it can be suitably used, for example, as an ejection opening of a nozzle of an inkjet printer.

Although one embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and modifications and combinations of the configuration may be made without departing from the gist of the present invention. included. Some changes are illustrated below, but these are not all, and other changes are also possible. Two or more of these changes may be combined as appropriate.

- In the present invention, the surface shape of the fine recesses and the fine protrusions formed by transferring the fine recesses can be changed in various ways.
In the fine recess 20A of the modified example shown in FIG. 8, the tips of the protrusions 23A are flat. Such a shape can be formed, for example, by performing step D for a long time. The protrusions 23A are not easily damaged during filling with molding material, and their shape is stably maintained and the liquid repellent effect is easily maintained.
The diameter of the fine recess 20B of the modified example shown in FIG. 9 becomes smaller as it approaches the bottom. Such a shape can be formed, for example, by gradually shortening the time of each step when repeating steps C to E. In the case of this shape, a straight line connects the bottom to the opening edge, and the greater the angle that the straight line makes with the bottom in the recess, the better the mold releasability, so by setting the angle it is possible to remove the master mold without destroying it. becomes easier.

・The opening shape of the minute recess can also be changed. FIG. 10 shows a plan view of a modified fine recess 20C. The opening edge of the fine recess 20C has a plurality of protrusions 27 extending toward the center of the fine recess 20C in plan view. Such an opening shape can be easily formed by the shape of the photoresist 101 in step A. Further, when the fine recesses 20C are formed by the above-described manufacturing method, the protrusions formed on the inner surface have a discontinuous substantially annular shape depending on the arrangement of the protrusions 27. As a result, the contact area with the molding material is reduced compared to the fine recesses 20 described above, and the liquid repellent effect is further enhanced.

- The releasability of the imprint mold of the present invention may be further improved by applying a mold release agent to the inner surfaces of the fine concave portions and fine convex portions.
- In the manufacturing method of the present invention, step D may be omitted. That is, step E may be performed after step C, and the protective film may be removed by isotropic dry etching.

1 Imprint mold 10 Substrate 20, 20A, 20B, 20C Fine recess 21 Opening edge 22 Inner surface 23, 23A, 63 Projection (protrusion)
51 Imprint mold (second imprint mold)
60 Fine convex portion 101 Photoresist 102 Protective film 200 Primary recess 210 Secondary recess

Claims (1)

A photoresist having a plurality of openings is placed on one side of the substrate,
isotropically etching the substrate exposed in the opening to form a primary recess;
covering the inner surface of the primary recess with a protective film;
isotropically etching the primary recess at least partially covered with the protective film to form a secondary recess below the primary recess;
A method for manufacturing an imprint mold.

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