WO2021090705A1

WO2021090705A1 - Microstructure and method for producing same

Info

Publication number: WO2021090705A1
Application number: PCT/JP2020/039860
Authority: WO
Inventors: 水谷康弘; 高谷裕浩; 中西弘樹; 江崎隆; 牧浦良彦
Original assignee: 国立大学法人大阪大学; 倉敷紡績株式会社
Priority date: 2019-11-08
Filing date: 2020-10-23
Publication date: 2021-05-14
Also published as: JPWO2021090705A1

Abstract

The present invention is a microstructure which is a sheet 20 comprising an energy ray active resin 21. The microstructure has inclined holes 22 that are shaped so as to at least reach the interior. The holes 22 of the structure interior make a modeled pattern shape where the Talbot distance is stipulated by formula 1; the relational expression with an adjacent Talbot structure satisfies formula 2 and formula 3; and the shape of the microstructure has periodicity in the planar direction. Where Z_T is Talbot distance (nm), n is refractive index, d is pitch distance (nm), λ = light wavelength (nm), and ΔX is horizontal distance (nm) between an irradiation spot portion of a column 1 as seen from an irradiation surface and an irradiation spot portion of an adjacent column 3. Due to the foregoing, provided is a three-dimensional structure enabling periodic micromolding such that control is carried out up to to the interior of the structure.

Description

Microstructure and its manufacturing method

The present invention relates to a microstructure to be processed using the Talbot effect and a method for producing the same.

In recent years, attention has been focused on three-dimensional structures on the order of submicrons. It consists of microstructured parts in semiconductor devices and microelectromechanical systems (MEMS), biomimetic structures that imitate the functional microstructures of living organisms, and substances with different refractive indexes arranged at intervals similar to the wavelength of light. Examples include nanostructured photonic crystals. These submicron-order three-dimensional structures, particularly those having a periodic structure, are attracting attention as functional materials. Techniques for producing microstructures include lithography, etching, nanoimprint, laser microfabrication, atomic manipulation with an atomic force microscope (AFM), and self-assembling techniques. In these methods, as the structure becomes multidimensional, the time required for processing becomes longer, and it is required to improve the processing efficiency. Further, the production of a complicated structure is also required, and a high degree of freedom in processing and a processing accuracy in which the periodicity can be arbitrarily controlled are also required. However, there is a trade-off relationship between machining efficiency and machining freedom, and although it is a simple method, a technique for realizing multidimensional machining and molding has not been established, and a structure is being developed. Further, in order to manufacture a structure, it is required not only to improve the processing accuracy but also to set the processing area to a wide area on the order of millimeters.

As a method for easily manufacturing a fine structure, there is a method of manufacturing a resist resin as a material by using a three-dimensional lithography technique. In particular, a three-dimensional lithography process using a Talbot effect has a specific wavelength. By using a diffraction grating, it becomes easy to form a periodic pattern in a large area at once, and the processing efficiency is extremely high. However, lithography using the Talbot effect has a problem that the degree of freedom of processing is low because the parameters for controlling the period are wavelength and lattice pitch and the period control is limited to two dimensions, and the processing area is a three-dimensional structure. No technology has been established for processing arbitrary shapes without limiting to the "surface" and "inside" of.

Patent Document 1 discloses a technique for lithography processing using the Talbot effect, but since it is a technique for processing a screen mask for etching, internal processing of the structure is not performed. Patent Document 2 discloses a mask capable of forming a highly accurate pattern using the Talbot effect and a method for forming the pattern, but this is not a technique for producing a structure. In Patent Document 3, recesses or holes having a periodic structure are formed by etching, but it is difficult to easily produce a microstructure. Non-Patent Document 1 proposes a structure in which metal nanoparticles are dispersed by applying a stereolithography method based on the Talbot effect, but has not actually produced a clear hierarchical structure by the Talbot effect. Non-Patent Document 2 discloses that a wide range of nanostructures in a one-dimensional layer structure and a two-dimensional periodic structure are produced, but there are problems in the accuracy and structure maintenance of the structure, and the structure has periodicity. Has not been reached. Non-Patent Document 3 and Non-Patent Document 4 suggest that a three-dimensional nanoperiodic structure can be produced from the results of numerical analysis of multiple exposures, but there are problems in the accuracy and structure maintenance of the structure, and it is practically used. It has not reached the level structure.

WO 2016-190247 Japanese Unexamined Patent Publication No. 2015-169803 Japanese Unexamined Patent Publication No. 2006-343671

As described above, a three-dimensional structure made of a resin for resist has been focused on as a useful technique and has been studied conventionally, but it has not been put into full-scale practical use. This is because it is difficult to control the periodicity of the three-dimensional structure.
In order to solve these conventional problems, the present invention provides a three-dimensional structure capable of micromolding in which the periodicity of the surface and the inside of the structure is controlled.

The present invention is a microstructure having holes inside, the structure is a sheet containing an energy ray active resin, and holes having an inclination are formed at least to the inside, and the holes inside the structure. Has a shape of a modeling pattern in which the Talbot distance is defined by the following (Equation 1), the relational expression with the adjacent Talbot structure satisfies the following (Equation 2) and (Equation 3), and is periodic in the plane direction. It is a microstructure having a certain shape.

However, in (Equation 1) to (Equation 3),
Z _T : Talbot distance (nm)
n: Refractive index d: Pitch distance (nm)
λ: Light wavelength (nm)
ΔX: Horizontal distance (nm) between the irradiation spot portion in the first row and the irradiation spot portion in the adjacent third row when viewed from the irradiation surface.

The method for producing a microstructure of the present invention is
(1) A process of applying an energy ray active resin on a substrate to a uniform thickness, and
(2) A step of prebaking (heating) the coated energy ray active resin layer and
(3) A step of installing a diffraction grating on the upper surface of the resin layer obtained in (2) above and irradiating energy rays from an oblique direction to generate a pattern on the resin layer.
(4) A step of chemically reacting the resin layer obtained in (3) above with a developing solution, dissolving a portion that has been irradiated with energy rays exceeding the curing threshold, and curing a portion that does not meet the energy ray curing threshold. Alternatively, a step of curing a portion that has been irradiated with energy rays exceeding the curing threshold value and dissolving a portion that does not meet the energy ray curing threshold value.
(5) The present invention includes a step of eluting the dissolved portion by washing the substrate obtained in (4) above with pure water to obtain a fine structure.

The microstructure of the present invention can be perforated on the surface and inside of the structure by adjusting the incident angle of exposure and the Talbot distance, and the microstructure can be microformed by controlling the periodicity to the surface and inside of the structure.

FIG. 1A is a schematic cross-sectional view in which an exposure mask is placed on the upper surface of the photoresist resin and irradiated with ultraviolet rays (UV) in order to explain the basic concept of the present invention. FIG. It is a schematic cross-sectional view explaining the part. FIG. 2A is a schematic cross-sectional view showing an exposure of a conventional example, and FIG. 2B is a schematic cross-sectional view of an exposure according to an embodiment of the present invention. 3A-E are schematic cross-sectional views showing a manufacturing method according to an embodiment of the present invention, and FIG. 3F is a schematic perspective view. FIG. 4A is a schematic perspective view showing the inside of the microstructure of Example 1 of the present invention, and FIG. 4B is a photograph of the same. FIG. 5A is a schematic perspective view showing the inside of the microstructure of the comparative example, and FIG. 5B is a photograph of the same.

In the present invention, a hole having an inclination is formed in a sheet containing an energy ray active resin. The inclined hole is preferably inclined in the range of 15 to 30 ° from the vertical direction. More preferably, the range is 16 ° to 27 °. As a result, continuous holes can be formed. The holes inside the structure have the shape of a modeling pattern in which the Talbot distance is specified in (Equation 1) above, and the relational expressions with the adjacent Talbot structures (holes) are as follows (Equation 2) and (Equation 3). ), And has a shape with periodicity in the plane direction.

The energy ray active resin is preferably a resin for resist, and more preferably a resin for positive resist. The resin for positive resist has a property that the exposed portion dissolves in a solution when exposed to energy rays, and is suitable for microfabrication. Since the negative resist resin is exposed to a high temperature due to the post-baking treatment, the resin is distorted and it is difficult to obtain a fine structure having accurate periodicity.

The periodic shape preferably has a lattice pitch: wavelength λ ≤ lattice pitch d and a pitch duty ratio of 0.2 to 0.7. As a result, finer processing can be performed. The periodic shape is preferably a regular shape. As a result, a fine structure having high uniformity is obtained.

The holes inside the structure may exist from the front surface to the inside, or may penetrate the front and back surfaces. This hole is a concept that includes a groove and / or a hole.

The method for producing a microstructure of the present invention includes the following steps.
(1) A step of applying an energy ray active resin on a substrate to a uniform thickness.
(2) A step of prebaking (heating) the coated energy ray active resin layer.
(3) A step of installing a diffraction grating on the upper surface of the resin layer obtained in (2) above, irradiating an energy ray capable of obtaining a talbot effect from an oblique direction, and generating a pattern on the resin layer.
(4) The resin layer obtained in (3) above is chemically reacted with a developing solution to dissolve the resin portion that has been irradiated with energy rays exceeding the curing threshold, and cure the resin portion that does not meet the energy ray curing threshold. A step, or a step of curing a portion that has been irradiated with energy rays exceeding the curing threshold and dissolving a portion that does not meet the energy ray curing threshold.
(5) A step of eluting the dissolved portion by washing the resin obtained in (4) above with pure water to obtain a fine structure.

As an example, the spin coating method can be used as the means for applying the energy ray-active resin of the above (1) to a uniform thickness. The spin coating method can be applied in a relatively small area with a thin and uniform film thickness.
The prebaking (heating) condition of (2) is preferably about 1 to 5 minutes at 0 to 100 ° C., which is a value recommended by the manufacturer.
The irradiation of the energy rays in the process of generating the pattern (3) from an oblique direction is preferably at an angle of 30 to 50 ° from the vertical direction, and more preferably at an angle of 35 to 45 °. As a result, continuous holes can be formed. The exposure amount is preferably 100 to 300 mJ / cm ² , and the number of exposures is preferably once.
It is preferable to post-bake (heat) between (3) and (4) in order to stabilize the resist after exposure. The post-baking condition is preferably about 1 to 60 minutes at 30 to 100 ° C.
As an example, the spin coating method can be used for the cleaning treatment of (5).

An example of the microstructure of the present invention is as follows.
(1) The processing area can be up to an area of 20 mm on a side with one exposure. When processing a wider area, it is possible by repeating the exposure.
(2) The thickness of the structure can be 500 nm to 100 μm. It is more preferably 700 nm to 50 μm, still more preferably 1 to 20 μm.
(3) The length (length in the depth direction) of the holes that can be microfabricated is preferably 10 nm to 3000 nm. More preferably, it is 100 to 1500 nm.
(4) The periodicity can be from 1 to 20 cycles, preferably about 2 to 10 laps.

The Talbot effect used in the present invention is as follows.
(1) When a plane wave is incident on a diffraction grating, the diffracted light in the Fresnel region interferes with each other, so that a periodic light intensity distribution is repeated three-dimensionally.
(2) By generating a periodic light intensity distribution with a diffraction grating and using it for lithography exposure, it is possible to process a large area of periodic microstructures in a batch in three dimensions.

The following will be explained using drawings. In the drawings below, the same reference numerals indicate the same thing. FIG. 1A is a drawing for explaining the basic concept of the present invention, and is a schematic cross-sectional view in which an optical filter (exposure mask) 2 is installed on the upper surface of the photoresist resin 3 and ultraviolet rays (UV) 1 are irradiated. The photoresist resin 3 uses a positive photoresist resin, and the optical filter (exposure mask) 2 uses a polycarbonate diffraction grating as an example. The distance between the photoresist resin 3 and the optical filter (exposure mask) 2 is set to l. X and Y are in the plane direction, and Z is in the depth direction. Details are as shown in the drawings. FIG. 1B is a schematic cross-sectional view illustrating the exposed portion 4 in which the photoresist resin 3 is irradiated with light. The exposed light intensity distribution is shown by a dot pattern, and the larger the number of dots, the higher the exposure intensity. The exposure intensity is an arbitrary unit (denoted as a.u.) because it is standardized with the strongest light intensity.

FIG. 2A is a schematic cross-sectional view showing the exposure of a conventional example. When the surface of the photoresist resin 3 is irradiated with ultraviolet rays (UV) 1 from a vertical direction, exposed

portions

5a and 5b are formed. Z _T is the Talbot distance (nm). That is, it is the vertical distance (nm) between the center point of the irradiation spot portion in the first row and the center point of the irradiation spot portion in the third row when viewed from the irradiation surface.

FIG. 2B is a schematic cross-sectional view of the exposure of one embodiment of the present invention. _{The irradiation angle Θ i} of ultraviolet (UV) 1 is preferably 30 to 50 °. When irradiated in this range, a continuous exposed portion 6 is formed inside the photoresist resin 3. When the exposed portion 6 is later melted, this portion becomes a continuous hole. Δx is the horizontal distance (nm) between the center point P1 of the irradiation spot portion in the first row and the center point P2 of the irradiation spot portion in the third row adjacent to each other when viewed from the irradiation surface.

3A-E are schematic cross-sectional views showing a manufacturing method according to an embodiment of the present invention, and FIG. 3F is a schematic perspective view.
(1) In FIG. 3A, a sheet obtained by curing a photoresist resin having a thickness of 10 μm is placed on the substrate 10 as a buffer layer 11, and the photoresist resin liquid 13 is coated on the sheet by spin coating. The state in which the photoresist resin layer 12a is formed is shown.
(2) FIG. 3B shows a state in which the coated photoresist resin layer 12a is prebaked (heated) on the hot plate 14 to form the photoresist resin layer 12b.
(3) In FIG. 3C, an optical filter (exposure mask) 15 is placed on the photoresist resin layer 12b obtained in (2) above, and ultraviolet rays (UV) 16 are irradiated from an oblique direction to form a photoresist resin layer 12c. The state in which the exposure pattern 17 is formed is shown in 1.
(4) FIG. 3D shows a state in which the photoresist resin layer 12c obtained in (3) above is post-baked (heated) in order to stabilize it. Next, in FIG. 3E, the post-baked (heated) photoresist resin layer 12d is chemically reacted with a developing solution by spin coating to dissolve the portion 17 irradiated with ultraviolet rays (UV) exceeding the curing threshold, and energy ray curing is performed. The state which cures the resin part 19 which did not meet the threshold is shown. The photoresist resin layer 12e is in a state where the holes 18 are open.
(5) FIG. 3F shows a state in which the resin 19 obtained in (4) above is washed with pure water to elute the dissolved portion to form a fine structure.

The preferred processing conditions of the present invention are as follows.
(1) Resin material It is preferable to use a positive resist. For example, a positive UV curable resin is preferable. When the negative type is used, a step of arranging the Bacher layer is required. Further, when the negative type is used, since it is exposed to a high temperature due to the post-baking treatment, the resin is distorted, and it is difficult to manufacture a fine structure having accurate periodicity. The resin processing temperature (prebake) is preferably 0 to 100 ° C. This is the resin curing temperature range recommended by the resin manufacturer.
(2) Cleaning liquid: Any liquid that is non-invasive to the resin is possible. It is preferable to use pure water.
(3) Light wavelength: UV light from a laser is used. For example, λ = 360 nm. As the wavelength region, 0.1 nm to 380 nm can be used. As the energy beam, ultraviolet rays (UV-A, B, C), X-rays, electron beams and the like are used.
(4) Diffraction grating: Use one or more optical filters. For example, a polycarbonate optical filter is used. Lattice pitch: Specified by wavelength λ ≤ lattice pitch d. Pitch duty ratio: 0.2 to 0.7, preferably 0.4 to 0.6. As an example, a grid pitch of 747 nm and a grid height of 150 nm are used. It can utilize the DVD surface. As the diffraction grating other than DVD, the one shown in Table 1 can be used.

(5) Machining pattern A regular groove structure can be formed. It has periodicity and can be arbitrarily changed from 1 to 20 cycles. The surface can be shaped at an acute angle or on a flat surface.
(6) Machining features (a) Perform one-shot exposure and perform precise machining without phase shift.
(B) The processing state can be changed depending on the exposure state and time. When the optical threshold is exceeded, resin curing occurs. Curing is controlled by the exposure time.
(C) The irradiation light has an incident angle of 30 to 50 ° from the vertical direction of the base material surface.
(D) The Talbot distance is calculated by the formula specified in (Equation 1) above. This is the range of the Talbot effect. The processing characteristics are specified in (Equation 2) and (Equation 3) above.
As a result, it becomes as follows.
(I) By extending the distance between adjacent Talbots, adjacent processing regions are combined.
(Ii) By controlling the adjacent wavelength distances X, the front and rear processing regions are combined.

Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention is not limited to the following examples.
(Example 1)
The experiment was conducted as follows.
(1) Using a spin coater, a uniform thickness UV curable resin SIPR-3251-6.0 (manufactured by ShinEtsu MicroSi) resin layer 12a was formed on the Bacher layer 11 on the substrate 10. The thickness was 6 μm (Fig. 3A).
(2) The resin layer 12a formed in (1) was placed on a hot plate 14 and prebaked (heated) at 100 ° C. for 2 minutes to volatilize the solvent contained in the resin layer 12a to obtain a resin layer 12b (2). FIG. 3B).
(3) A diffraction grating 15 (pitch width: 747 nm) made of polycarbonate and having a refractive index of n = 1.59 was placed on the upper surface of the resin layer 12b obtained in (2). Light 16 of an ultraviolet LED surface light source (wavelength λ = 360 nm) was exposed to one shot at an angle of 40 ° from the vertical direction to generate a pattern on the resin layer 12c (FIG. 3C). At this time, the above formulas 1 to 3 were satisfied.
(4) The resin layer 12c obtained in (3) was chemically reacted with a developer for SIPR-3251 (the developer was attached at the time of purchasing the resin), and the portion subjected to light irradiation exceeding the photocuring threshold of SIPR-3251 was subjected to light irradiation. It was dissolved to form a resin layer 12d (FIG. 3D). Next, the resin layer 12d was chemically reacted with a developing solution by spin coating to dissolve the portion 18 irradiated with ultraviolet rays (UV) exceeding the curing threshold, and cured the resin portion 19 that did not meet the energy ray curing threshold. .. The photoresist resin layer 12e is in a state in which holes 18 are formed in the resin portion 19 (FIG. 3E).
(5) The resin 19 obtained in (4) above was washed with pure water to elute the dissolved portion to obtain a fine structure (FIG. 3F).

(Comparative Example 1)
The same procedure as in Example 1 was carried out except that the light 16 of the ultraviolet LED surface light source (wavelength λ = 360 nm) was irradiated from the vertical direction.
Table 2 summarizes the above conditions and results.

As shown in FIGS. 4A-B, in the microstructure (sheet) 20 obtained in Example 1, continuous holes 22 having an inclination were formed with periodicity up to the inside of the resin portion 21.
On the other hand, in the microstructure (sheet) 23 obtained in Comparative Example 1, as shown in FIGS. 5A-B, holes 25 in a closed cell state were formed inside the resin portion 24.

The microstructure of the present invention has grooves, through holes, open cells, etc. formed inside the resin layer, and can be applied to a photonic structure including a filter, a biomimetics structure, a functional member, and the like.

1,16 Ultraviolet rays (UV)
2,15 Optical filter (exposure mask)
3

Photoresist resin

4, 5a, 5b Exposed part 6 Continuous exposure part 10 Substrate 11 Bacher layer 12a-12f Photoresist resin layer 13 Photoresist resin liquid 14 Hot plate 17 Exposure pattern 18 Hole 19 Resin part 20, 23

Microstructure

21,24 Resin part (sheet)
22 Continuous holes with inclination 25 Holes in a closed cell state

Claims

It is a microstructure that contains holes inside.
The structure is a sheet containing an energy ray active resin, and is
At least to the inside, a hole with a slope is formed,
The holes inside the structure have the shape of a modeling pattern in which the Talbot distance is defined by the following (Equation 1).
The relational expression with the adjacent Talbot structure satisfies the following (Equation 2) and (Equation 3).
A microstructure characterized by having a shape with periodicity in the plane direction.

However, in (Equation 1) to (Equation 3),
Z T : Talbot distance (nm)
n: Refractive index d: Pitch distance (nm)
λ: Light wavelength (nm)
ΔX: Horizontal distance (nm) between the irradiation spot portion in the first row and the irradiation spot portion in the adjacent third row when viewed from the irradiation surface.
The microstructure according to claim 1, wherein the energy ray-active resin is a resin for resist.
The microstructure according to claim 1 or 2, wherein the energy ray-active resin is a resin for a positive resist.
The microstructure according to any one of claims 1 to 3, wherein the periodic shape has a lattice pitch: wavelength λ ≤ lattice pitch d and a pitch duty ratio: 0.2 to 0.7.
The microstructure according to any one of claims 1 to 4, wherein the hole inside the structure penetrates the front and back surfaces.
The microstructure according to any one of claims 1 to 5, wherein the hole inside the structure includes a groove and / or a hole.
The microstructure according to any one of claims 1 to 4, wherein the holes inside the structure are in a closed cell state.
The microstructure according to any one of claims 1 to 7, wherein the periodic shape is a regular shape.
The microstructure according to any one of claims 1 to 8, wherein the inclined hole is inclined by 15 to 30 ° from the vertical direction.
The method for producing a microstructure according to any one of claims 1 to 9.
(1) A process of applying an energy ray active resin on a substrate to a uniform thickness, and
(2) A step of prebaking (heating) the coated energy ray active resin layer and
(3) A step of installing a diffraction grating on the upper surface of the resin layer obtained in (2) above and irradiating energy rays from an oblique direction to generate a pattern on the resin layer.
(4) A step of chemically reacting the resin layer obtained in (3) above with a developing solution, dissolving a portion that has been irradiated with energy rays exceeding the curing threshold, and curing a portion that does not meet the energy ray curing threshold. Alternatively, a step of curing a portion that has been irradiated with energy rays exceeding the curing threshold value and dissolving a portion that does not meet the energy ray curing threshold value.
(5) A method for producing a microstructure, which comprises a step of eluting a dissolved portion by washing the substrate obtained in (4) with pure water to obtain a microstructure.
The method for manufacturing a fine structure according to claim 10, wherein the irradiation of the energy rays from the oblique direction is at an inclined position of 30 to 50 ° from the vertical direction.