JP2006235195A - Method for manufacturing member with antireflective structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a member with an antireflective structure by which the antireflective structure with antireflection effect can easily be manufactured by X-ray lithography. <P>SOLUTION: An X-ray mask 1 and the member 2 are arranged at such a distance D that X-rays passing through different regions of the X-ray mask 1 are diffracted to cause interference, and the member 2 which has at least its structure forming surface made of a photosensitive material is exposed to the X rays through the X-ray mask 1. Then the exposed member 2 is developed. Consequently, the antireflective structure can be formed which has superior antireflection effect over the entire range of wavelength needed for optical equipment under an influence of the interference and chemical operation during the development. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a member having an antireflection structure, and more specifically, to a method for manufacturing a member having an antireflection structure formed using X-ray lithography.

  Optical elements such as lenses and optical components such as camera barrels that have been subjected to antireflection treatment for incident light are used in various applications. The optical functional surfaces of these optical elements and optical components are generally subjected to antireflection treatment by techniques such as vapor deposition, sputtering, and coating, and are provided with a single layer film or a low refractive index layer comprising a low refractive index layer. And an antireflective film such as a multilayer film in which a high refractive index layer is laminated (for example, Patent Document 1).

  Such an antireflection film has been widely used because it can be formed by a general method such as vapor deposition or sputtering, but a complicated process is required to control the optical film thickness of the antireflection film with high accuracy. Therefore, improvements in productivity and cost have been desired. In addition, since such an antireflection film has wavelength dependency, the antireflection effect at a wavelength other than a predetermined wavelength is reduced, and good antireflection is achieved over the entire visible light region required in the imaging optical apparatus. In addition, since there is an angle dependency problem that the antireflection effect decreases as the incident angle increases, an antireflection method with improved wavelength dependency and angle dependency is desired. It was.

  Therefore, as a method for solving these problems, in recent years, a technology for forming a structure called an antireflection structure on which the surface of an optical element or optical component is arranged in a very fine conical uneven shape is arranged in an array. Has attracted attention. More specifically, the antireflection structure is a structure in which conical uneven shapes are arranged in an array at a pitch equal to or smaller than the wavelength of incident light (for example, submicron pitch in the case of visible light). The aspect ratio, which is the ratio of the pitch and height of the concavo-convex shape, is 1 or more.

  When such an antireflection structure is formed on the surface of an optical element or optical component, the refractive index distribution on the surface changes very smoothly, and incident light having a wavelength longer than the arrangement pitch of the conical concavo-convex shape is not received. , Almost all enter the inside of the optical element or optical component. Therefore, reflection of light from the surface of the optical element or optical component can be prevented. Moreover, even if the incident angle of incident light increases, the antireflection effect does not decrease so much. Thus, if the antireflection structure can be formed on the surface of the optical element or optical component, the wavelength dependency and the incident angle dependency, which are problems in the antireflection film, can be solved.

  In order to form the antireflection structure, an ultrafine processing technique of a submicron level or less is required. For example, in the method described in Patent Document 2, first, a resist pattern is formed by patterning on the surface of an optical element made of quartz glass or the like by an electron beam (EB) drawing method. Next, a chromium (Cr) mask having a submicron pitch is formed directly on the surface of the optical element based on the resist pattern. Then, the portion other than the portion covered with the mask of the optical element material is finely processed by dry etching, thereby forming an antireflection structure.

  As in Patent Document 2, the EB drawing method is generally used to form a very fine pattern with a submicron pitch. However, if the EB drawing method is used for patterning the submicron pattern, a very long drawing time is required. Depending on the pattern shape and conditions to be drawn, for example, it takes about 5 hours to draw a circular pattern (diameter 0.2 μm) at a pitch of 0.25 μm in a 5 mm square region. Accordingly, drawing on an area (50 mm square) corresponding to the entire inner surface of the camera barrel requires 500 hours of drawing time, and it is a reality that an antireflection structure is directly formed on an optical material for mass production. Is impossible.

  Furthermore, in the method using the EB drawing method, it is very difficult to draw a fine pattern on a curved surface such as a lens, and an electron beam drawing apparatus provided with a stage capable of very special three-dimensional position control. Is required.

  On the other hand, recently, a technique for forming a submicron-level fine structure using an X-ray lithography technique has been proposed (for example, Patent Document 3 and Patent Document 4). Since X-rays have a short wavelength and excellent straightness, they are suitable for processing a submicron-level fine structure that has been difficult in the past. FIG. 12A is a schematic diagram illustrating a method for manufacturing a fine structure by X-ray lithography. In FIG. 12A, an X-ray mask 1 has a mask pattern in which an X-ray absorption region 3 and an X-ray transmission region 4 are arranged corresponding to a fine structure to be formed. The X-ray absorption region 3 is formed by forming a membrane on a substrate constituting the X-ray mask 1 and disposing an X-ray absorber on the membrane. The member 2 is formed of a photosensitive material. The X-ray mask 1 and the member 2 are arranged with a certain distance L, and X-ray exposure is performed toward the member 2 through the X-ray mask 1.

In X-ray lithography, the provision of a certain distance L between the X-ray mask 1 and the member 2 is because the X-ray mask 1 uses a membrane that is very thin and easily broken. This is because the X-ray mask 1 may be destroyed if the mask and the substrate are brought into close contact with each other as in photolithography using a mask. Since the X-ray has a short wavelength and excellent straightness, the X-ray can be exposed on the member 2 with a desired pattern intensity even if the distance L is provided between the X-ray mask 1 and the member 2. it can. Therefore, X-ray lithography avoids the occurrence of a portion where the distance between the X-ray mask 1 and the member 2 becomes large, as in the case where an antireflection structure is formed on the surface of a non-planar member such as a lens surface. This is particularly effective when it is not possible.
JP 2001-127852 A JP 2001-272505 A JP 2000-035500 A Japanese Patent No. 3521205

  By the way, as described above, since X-rays are light excellent in straightness, the X-rays 5 that have passed through the X-ray mask 1 go straight as they are as shown in FIG. The member 2 is exposed to the vertical direction to move straight inside the member 2 to expose the member 2 to light. A photosensitive portion having an X-ray intensity distribution corresponding to the mask pattern is formed on the surface of the member 2 after exposure. And the recessed part of the shape corresponding to a mask pattern is formed in the surface of the member 2 after image development, and as shown in FIG.12 (b), the fine structure 13 which made the column shape the structural unit is formed. Thus, in the fine structure 13 having the columnar shape as the structural unit, the smooth refractive index distribution change on the surface as described above cannot be obtained, and thus the antireflection effect cannot be obtained. Therefore, as described in Patent Document 3, a method of performing X-ray exposure a plurality of times while moving at least one of the X-ray mask 1 or the member 2 and changing the relative positional relationship between them, or Patent Document 4 As described in the above, the X-ray intensity distribution of the exposed portion of the member 2 is mechanically adjusted so that the side wall portion of the columnar structure is inclined by using a double exposure method in which partial exposure and full exposure are combined. A method of changing is proposed.

  If such an exposure method is applied, as shown in FIG. 12C, an antireflection structure 14 having a cone shape as a unit can be obtained. However, the double exposure method and the X-ray mask 1 can be used with high accuracy. However, since the exposure method while moving to a position requires a plurality of exposure processes, the manufacturing process is complicated, and precise management is required when moving the X-ray mask 1 and the member 2.

  Therefore, an object of the present invention is to provide a method for producing a member having an antireflection structure, which can easily produce an antireflection structure excellent in antireflection effect using X-ray lithography. .

  This invention which solves the said subject is a manufacturing method of the member which has an antireflection structure which consists of the following processes. That is, first, an exposure process is performed in which X-rays are irradiated toward a member having at least a structure forming surface made of a photosensitive material through an X-ray mask in which a plurality of X-ray transmission regions are formed. Next, a developing process for developing the exposed member is performed. Here, the exposure step exposes the X-rays in a state in which the X-ray mask and the member are arranged apart from each other by a distance that causes interference between the X-rays that have passed through different X-ray transmission regions. Specifically, X-rays are light excellent in straightness as described above, but strictly speaking, X-rays travel toward the irradiation surface with a certain extent. At the time of X-ray exposure, X-rays transmitted through the X-ray mask travel to the irradiation surface with a very gentle spread, and there is interference due to diffraction by X-rays passing through different X-ray transmission regions at a certain distance. appear.

  In the present invention, X-ray exposure is performed with the X-ray mask and the member separated by a distance where such interference occurs, so that the shape of the mask pattern is transferred as it is to the exposed member. Rather than forming a columnar X-ray intensity distribution, a cone-shaped X-ray intensity distribution with a thin tip with an obscure outline is generated. As a result, on the surface of the member after development, a structure is formed in which the outline is ambiguous and the tip is thin and cone-shaped due to the influence of interference and chemical action during development. Thus, an antireflection structure having an excellent antireflection effect can be obtained. Further, since the antireflection structure can be easily formed by performing only one exposure process, the manufacturing process can be simplified.

  The X-ray mask preferably has a mask pattern in which cylindrical or polygonal X-ray absorption regions or X-ray transmission regions are arranged in an array at a pitch equal to or less than the wavelength of light that should be prevented from being reflected. . Examples of the member on which the antireflection structure is formed include an optical element or an optical component. Specifically, the optical element includes a lens, a microlens array, a prism, a filter, an optical sheet, a diffraction grating, and the like. The optical component is a mechanical component for holding an optical element such as a lens barrel. As the photosensitive material, polymethyl methacrylate or fluorine-based resin can be preferably used. The antireflection structure has a cone shape with an aspect ratio of 1 or more as a structural unit, and this cone shape is arranged in an array on the structure forming surface of the member at a pitch equal to or less than the wavelength of light that should be prevented from being reflected. Is preferred.

  In addition, when the photosensitive material is a photosensitive resist, an etching process for dry etching the member may be further provided after the developing process using the photosensitive resist patterned by the developing process as a mask. Further, when the photosensitive material is a photosensitive resist and an etching mask layer made of a material for an etching mask is provided under the layer made of the photosensitive resist, the photosensitive film patterned by the developing step is formed after the developing step. A first etching step in which the etching mask layer is wet-etched or dry-etched using the conductive resist as a mask, and a second etching step in which the member is dry-etched using the etching mask layer patterned by the first etching step as a mask It is preferable to further provide.

  In addition, after the development process, a replication mold forming process for forming a replication mold by electroforming or press molding using a member on which the antireflection structure is formed may be further provided. Thereby, the type | mold for mass-producing the member in which the reflection preventing structure was formed can be obtained easily. Then, after the replica mold forming process, the replica mold is further provided with a molding process of molding a molding material made of a resin material or a glass material. It becomes possible.

  When the electroforming process is performed in the replica mold forming step, a water repellent process step of performing water repellent treatment on the replica mold forming surface may be included. In addition, when press molding is performed in the replica mold forming step, a mold release processing step of performing a mold release process on the molding surface of the replica mold may be included. Specifically, it is desirable to use an injection molding method or a press molding method in the molding process.

  As described above, according to the present invention, X-ray exposure is performed in a state where the X-ray mask and the member are arranged at a distance such that interference by X-rays is positively generated. Due to the influence of the chemical action, it is possible to easily form an antireflection structure with a cone-shaped unit as a single exposure process, and it has an excellent antireflection effect over the entire wavelength range required for optical equipment. A member having an antireflection structure can be easily manufactured.

(First embodiment)
Below, the manufacturing method of the member which has the reflection preventing structure which concerns on the 1st Embodiment of this invention is demonstrated. FIG. 1A is a schematic diagram for explaining a manufacturing method of an antireflection structure by X-ray lithography. In FIG. 1A, an X-ray mask 1 has a mask pattern in which an X-ray absorption region 3 and an X-ray transmission region 4 are arranged corresponding to an antireflection structure to be formed. The member 2 is formed of a photosensitive material. The X-ray mask 1 and the member 2 are arranged with a certain distance D, and X-ray exposure is performed toward the member 2 through the X-ray mask 1.

  Here, the characteristic part of this embodiment is that the distance D between the X-ray mask 1 and the member 2 is set to a distance at which X-rays that have passed through different X-ray transmission regions 4 cause interference due to diffraction. The X-ray exposure is performed on the member 2 through the X-ray mask 1. FIG.1 (b) is a schematic diagram which shows the irradiation state of the X-ray 5 at the time of X-ray exposure. As shown in FIG. 1B, the X-ray 5 is light having excellent straightness, but strictly speaking, the X-ray 5 advances toward the irradiation surface with a certain extent. Since this spread is very gradual, when the member 2 is within the range of the distance P from the X-ray mask 1 as indicated by an imaginary line 2a in FIG. X-rays 5 that have passed through 4 do not overlap each other due to diffraction. Accordingly, a concave portion having a shape corresponding to the mask pattern of the X-ray mask 1 is formed on the surface of the member 2 after exposure, and as described in the conventional example, the columnar structure as shown in FIG. Thus, the fine structure 13 is formed.

  1B, when the distance from the X-ray mask 1 exceeds the range P and the member 2 is in the range M, as shown by the phantom line 2b in FIG. Interference due to diffraction occurs between the lines 5, and an X-ray intensity distribution having a conical shape with a thin tip and an unclear outline is generated on the surface of the member 2. As a result, on the surface of the member 2 after development, a structure having a fuzzy outline and a united cone shape with a thin tip is formed due to the influence of interference and chemical action during development. Is done.

  FIG. 1C is a schematic diagram showing a state of the member 2 when it is exposed and developed when the distance between the member 2 and the X-ray mask 1 is in the range of M. FIG. In FIG.1 (c), many convex parts 15 close | similar to a cone shape are formed in the surface of the member 2, and the antireflection structure 6 which uses this cone-shaped convex part 15 as a structural unit is obtained. This antireflection structure 6 is much more excellent in the antireflection effect as compared with the microstructure 13 having the columnar structure as a unit. Note that the antireflection structure 6 shown in FIG. 1C schematically shows an ideal shape. In practice, the edge portion of each structural unit is formed by a chemical action during development. It may be distorted. Further, since the antireflection structure 6 is formed by the interference of the X-rays 5, depending on the value of the distance D, an antireflection structure having the pattern shape of the X-ray mask 1 and an inversion distribution is formed. There is also. However, even with the antireflection structure formed by the inversion distribution, the antireflection effect remains maintained.

  As described above, in the present embodiment, the distance D between the X-ray mask 1 and the member 2 is set to a value that is positively affected by interference, thereby moving the X-ray mask 1 and the member 2. Therefore, the antireflection structure 6 having an excellent antireflection effect can be formed on the member 2 by a simple process of a single exposure process.

  Hereinafter, the present embodiment will be described more specifically. In the antireflection structure 6 according to the present embodiment, structural units having an aspect ratio of 1 or more, which is a ratio of pitch to height, are arranged in an array at a pitch equal to or less than the wavelength of light to be prevented from being reflected. It is what. The shape of the structural unit having such an arrangement is a cone shape as described above. In this embodiment, the cone shape refers to the cone shape shown in FIG. 12C in the conventional example, the antireflection structure 6a having a polygonal cone shape as a structural unit as shown in FIG. Further, the antireflection structures 6b and 6c having a bell shape as a structural unit as shown in FIGS. 3 (a) and 3 (b) and the tip portions are flattened as shown in FIGS. 3 (c) and 3 (d). Also included are antireflection structures 6d and 6e having a frustum shape as a structural unit. However, each structural unit does not have to be a strict geometric shape such as a cone shape, a polygonal pyramid shape, a bell shape and a frustum shape, and is substantially in a cone shape, a polygonal pyramid shape, a bell shape and a frustum shape. I just need it. Each structural unit may be constituted by not only the convex portion having the above-mentioned cone shape but also a concave portion that is an inverted shape of this cone shape.

  The X-ray mask 1 according to the present embodiment has an X-ray absorption region 3 and an X-ray transmission region 4, and reflection should be prevented using one X-ray absorption region 3 or X-ray transmission region 4 as a structural unit. Those having a mask pattern arranged at a pitch equal to or less than the wavelength of light can be applied. The shape of the structural unit is not particularly limited, and may be appropriately selected according to the shape of the antireflection structure 6 to be formed. However, those having a cylindrical or polygonal columnar structural unit are preferable. For example, as shown in FIG. 4A, if the X-ray mask 1 has a cylindrical X-ray absorption region 3, the antireflection structure having a conical shape as a structural unit as shown in FIG. 14 is formed. Conversely, in the case of the X-ray mask 1 having the columnar X-ray transmission region 4, an antireflection structure having a concave portion in which the conical shape is inverted as a structural unit is formed. Further, as shown in FIG. 4B, if the X-ray mask 1 has a polygonal columnar X-ray absorption region 3, an antireflection structure 6a having a hexagonal pyramid shape as a structural unit as shown in FIG. It is formed.

  The X-ray mask 1 includes, for example, an X-ray absorption region 3 in which a thin film made of an X-ray absorber material is formed on a silicon carbide (SiC) membrane using a silicon (Si) wafer as a substrate, and an X-ray absorber material. And an X-ray transmission region 4 on which no thin film is formed. Examples of the X-ray absorber material include tantalum (Ta), nickel (Ni), gold (Au), copper (Cu), silver (Ag), chromium (Cr), and iron (Fe). The X-ray absorber material is patterned into a desired shape by an EB drawing method, a dry etching method, or the like.

  The member 2 according to the present embodiment is an optical element or an optical component. Examples of the optical element include a lens, a microlens array, a prism, a filter, an optical sheet, and a diffraction grating. Examples of the optical component include a mechanism component for holding an optical element such as a lens barrel, a molding die used for molding the optical element and the optical component, and a master for obtaining the molding die. The member 2 only needs to have at least a structure-forming surface formed of a photosensitive material, and may be formed entirely of a photosensitive material. As the photosensitive material, an optical resin such as polymethyl methacrylate (PMMA) resin or fluorine resin can be preferably used.

  The shape of the member 2 is not particularly limited, and may be a flat plate or a lens having a curved surface. However, when the present embodiment is applied to a member 2 having a curved shape such as a lens, the distance D between the X-ray mask 1 and the member 2 is different between the central portion and the outer peripheral portion of the lens. Depending on the case, the antireflection structure 6 having an inverted shape may be formed due to interference. However, even in such a case, the function as the antireflection structure 6 is not impaired.

  Below, this embodiment is described based on a specific example. FIG. 5 is a diagram illustrating a process of forming the antireflection structure 6 on the member 2 made of PMMA resin. FIG. 5A is a diagram for explaining the X-ray exposure process. In FIG. 5A, the X-ray mask 1 has a hexagonal columnar X-ray transmission region 4 made of Ta with a thickness of 0.5 μm formed in an array of 30 mm × 30 mm in a pitch of 250 nm. The PMMA resin of 50 mm x 50 mm and thickness 2mm was used for the member 2 used. Then, X-ray exposure was performed at 15 A · min from the X-ray mask 1 side with the X-ray mask 1 and the member 2 facing each other with a distance D of 500 μm so as to cause interference by X-rays.

  FIG. 5B is a schematic diagram showing the state of the member 2 after development. In order to obtain the member 2 in such a state, the member 2 after X-ray exposure was immersed in a developer containing 2- (2-n-butoxyethoxy) ethanol as a main component and developed. As a result, an antireflection structure 6 in which hexagonal pyramid-shaped structural units having a pitch of 250 nm and a height of 300 nm are arranged in an array is formed on the surface of the member 2.

  Thus, when the surface reflectance of the member 2 on which the antireflection structure 6 was formed was measured, the average vertical reflectance was about 0.2% for light having a wavelength of 250 nm or more. Further, when the reflectance was measured by tilting the incident angle to 45 °, there was almost no change in the reflectance. As described above, according to the manufacturing method according to the present embodiment, the antireflection structure having an excellent antireflection effect in one exposure process without using a high-cost and low-productivity method such as the EB drawing method. The body could be easily obtained.

  FIG. 6 is a diagram illustrating a process of forming the antireflection structure 6 on the lens 7 made of PMMA resin molded by the injection molding method. FIG. 6A is a diagram for explaining the X-ray exposure process. In FIG. 6A, the X-ray mask 1 uses the aforementioned hexagonal column-shaped X-ray transmission region 4 formed at a pitch of 250 nm, and the lens 7 has a sag amount of 0.5 mm at maximum and a diameter. : Plano-convex lens with 3 mm and radius of curvature: 2 mm. Then, the X-ray mask 1 and the lens 7 were opposed to each other with a distance D of 500 μm so as to cause interference by X-rays, and X-ray exposure was performed at 20 A · min from the X-ray mask 1 side. Here, the distance D is the distance between the center of the lens 7 and the X-ray mask 1.

  FIG. 6B is a schematic diagram showing the state of the lens 7 after development. In order to obtain the member 2 in such a state, the lens 7 after X-ray exposure was immersed in a developer containing 2- (2-n-butoxyethoxy) ethanol as a main component and developed. As a result, the antireflection structure 6 in which hexagonal pyramid-shaped structural units having a pitch of 250 nm and a height of 300 nm are arranged in an array is formed on the surface of the lens 7. When the surface reflectance of the lens 7 on which the antireflection structure 6 was formed was measured, an average value of about 0.4% was obtained for light having a wavelength of 250 nm or more.

  As described above, according to the present embodiment, even when the lens 7 has a large amount of sag, reflection is prevented by a single exposure process without using a high-cost and low-productivity method such as the EB drawing method. The antireflection structure 6 excellent in effect could be easily formed on the entire surface of the lens 7. Here, the antireflection structure 6 having a uniform configuration can be formed on the entire surface of the lens 7. However, depending on the distance D between the X-ray mask 1 and the lens 7, the central portion and the outer periphery of the lens 7 can be obtained. In some cases, an antireflection structure having a shape different from each other, for example, an inverted shape between the central portion and the outer peripheral portion of the lens 7 may be formed. However, even in such a case, the antireflection effect of the antireflection structure is not impaired.

(Second Embodiment)
Hereinafter, a method for manufacturing a member having an antireflection structure according to the second embodiment of the present invention will be described with a specific example. In this embodiment, a member having a photosensitive resist on the surface is used, and an antireflection structure is formed on the member by performing an etching process after the development process. Since the other basic configuration is the same as that of the first embodiment, only the difference between them will be described in the following description.

  FIG. 7 is a diagram for explaining a manufacturing process of a member having the antireflection structure according to the present embodiment. FIG. 7A is a view for explaining the X-ray exposure process. In FIG. 7A, the X-ray mask 1 used is the one in which the hexagonal column-shaped X-ray absorption region 3 shown in FIG. 4A is formed with a pitch of 250 nm. As the member, a member in which an X-ray resist layer 9 was formed on the surface of a quartz glass substrate 8 was used. The quartz glass substrate 8 has a size of 20 mm × 20 mm × 5 mm, and the surface thereof is polished so that the center line surface roughness Ra is smooth to about 2 nm. The X-ray resist layer 9 is formed by applying an X-ray resist with a thickness of 0.3 μm to the surface of the quartz glass substrate 8 that has been subjected to the polishing process using a spin coating method. The X-ray mask 1 and the quartz glass substrate 8 on which the X-ray resist layer 9 is formed are opposed to each other with a distance D of 500 μm so as to cause interference by X-rays, and 15 A · min from the X-ray mask 1 side. The X-ray exposure was performed.

  FIG. 7B is a schematic diagram showing the state of the quartz glass substrate 8 after development. In order to obtain the quartz glass substrate 8 in such a state, the quartz glass substrate 8 after X-ray exposure is immersed in a developer containing 2- (2-n-butoxyethoxy) ethanol as a main component for development processing. went. As a result, the antireflection structure 10 in which hexagonal pyramid-shaped structural units having a pitch of 250 nm and a height of 500 nm formed of an X-ray resist are arranged in an array is formed on the surface of the quartz glass substrate 8.

In this embodiment, the quartz glass substrate 8 is etched using the antireflection structure 10 made of an X-ray resist as a mask. FIG. 7C is a schematic diagram showing a state of the quartz glass substrate 8 after the etching process. In order to obtain the quartz glass substrate 8 in such a state, first, the quartz glass substrate 8 on which the antireflection structure 10 was formed was put in an RF dry etching apparatus. Then, the surface of the quartz glass substrate 8 was etched using CHF ₃ gas and O ₂ gas as reaction gases. As a result, an antireflection structure 11 in which hexagonal pyramid-shaped structural units having a pitch of 250 nm and a height of 250 nm are arranged in an array is formed on the surface of the quartz glass substrate 8. In this case, the etching rate ratio between the X-ray resist layer 9 and the quartz glass substrate 8 was 2: 1. When the surface reflectance of the quartz glass substrate 8 on which the antireflection structure 11 was formed was measured, it showed an average value of about 0.2% for light having a wavelength of 250 nm or more.

  As described above, according to the present embodiment, if the surface is a member formed of a photosensitive resist, by performing an etching process after the development process, quartz glass that is more durable than the first embodiment, etc. The antireflection structure 11 having a high antireflection effect can be formed on the optical material.

(Third embodiment)
Hereinafter, a method for manufacturing a member having an antireflection structure according to the third embodiment of the present invention will be described with reference to specific examples. In this embodiment, an antireflection structure having a larger aspect ratio is formed on the surface of the member by performing the first and second etching processes using the member having the photosensitive resist layer and the etching mask layer. To do. In the following, the same components as those in the first and second embodiments are denoted by the same reference numerals and description thereof is omitted.

  FIG. 8 is a diagram illustrating a manufacturing process of a member having an antireflection structure according to the present embodiment. FIG. 8A is a diagram for explaining the X-ray exposure process. In FIG. 8A, the member has an etching mask layer 20 between the quartz glass substrate 8 and the X-ray resist layer 9. The etching mask layer 20 can be formed by sputtering using an etching mask material such as Cr, Ni, and Fe. Here, the etching mask layer 20 made of Cr and having a thickness of 200 nm will be described as an example. . A member having such a configuration is arranged facing the X-ray mask 1 with a distance D of 500 μm so that interference by X-rays occurs, and X-ray exposure is performed at 15 A · min from the X-ray mask 1 side. went.

  FIG. 8B is a schematic diagram showing the state of the member after development. In order to obtain a member in such a state, the member after X-ray exposure was immersed in a developer containing 2- (2-n-butoxyethoxy) ethanol as a main component and developed. As a result, an antireflection structure 21 in which hexagonal pyramid-shaped structural units having a pitch of 250 nm and a height of 500 nm formed of an X-ray resist are arranged in an array is formed on the surface of the member.

  In the present embodiment, the etching mask layer 20 is subjected to a first etching process using the antireflection structure 21 made of an X-ray resist as a mask. FIG. 8C is a schematic diagram showing the state of the member after the first etching process. In order to obtain a member in such a state, the member on which the antireflection structure 21 is formed is put in an RF dry etching apparatus, and Ar gas is used as an etching gas, and the etching mask layer 20 is subjected to the first etching process. gave. As a result, an antireflection structure 22 in which hexagonal pyramid-shaped structural units made of Cr having a pitch of 250 nm and a height of 150 nm are arranged in an array is formed on the surface of the quartz glass substrate 8. Here, the etching rate ratio between the X-ray resist and the etching mask made of Cr was 10: 3.

Further, the quartz glass substrate 8 is subjected to a second etching process using the antireflection structure 22 made of Cr as a mask. FIG. 8D is a schematic diagram showing the state of the quartz glass substrate 8 after the second etching process. In order to obtain the quartz glass substrate 8 in such a state, the quartz glass substrate 8 on which the antireflection structure 22 made of Cr is formed is put into an RF dry etching apparatus, and CHF ₃ gas and O _{2 are used} as reaction gases. Etching was performed on the surface of the quartz glass substrate 8 using a gas. As a result, an antireflection structure 23 in which hexagonal pyramid-shaped structural units having a pitch of 250 nm and a height of 750 nm are arranged in an array is formed on the surface of the quartz glass substrate 8. The aspect ratio was 3. In this case, the etching rate ratio between the etching mask made of Cr and the quartz glass substrate 8 was 1: 5.

  When the surface reflectance of the quartz glass substrate 8 on which the antireflection structure 23 was formed was measured, it showed an average value of about 0.1% for light having a wavelength of 250 nm or more. As described above, the first and second etching processes are performed after the development process by using the member having the surface formed of the photosensitive resist and the etching mask layer formed thereunder, so that the aspect ratio is larger. The antireflection structure 23 having a structural unit can be obtained, and the antireflection effect can be enhanced.

  In this embodiment, the dry etching process is performed as the first etching process, but a wet etching process may be performed. Even with such a configuration, an antireflection structure having a structural unit with a large aspect ratio can be obtained in the same manner as described above.

  In each of the above embodiments, the method of forming the antireflection structure directly on the surface of the member by X-ray lithography has been described. A member having an antireflection structure manufactured by these methods can be used as a molding die for molding an optical element or an optical component or a master die for forming this molding die. When a member manufactured by the method according to each of the above embodiments is used as a mold, if the member is formed of a glass material or a metal material, it is used in a high temperature and high pressure atmosphere such as press molding or injection molding. It can also be applied to molds. However, when the member is formed of a resin material, it cannot be applied to press molding, injection molding, or the like. Therefore, it is necessary to create a replication mold using this member as a master mold. As described above, by using the member created in each of the above embodiments as a molding die or a master die, it becomes possible to mass-produce a member having an antireflection structure by a simple method such as injection molding or press molding. . The details will be described below.

(Fourth embodiment)
In the present embodiment, a method for manufacturing a replica mold by electroforming using a member having an antireflection structure created by the method according to the first embodiment will be described. FIG. 9 is a diagram for explaining a replication type manufacturing process according to the fourth embodiment of the present invention. FIG. 9A is a cross-sectional view of a lens 7 having an antireflection structure 6 produced by the method according to the first embodiment. Since the lens 7 is made of PMMA resin, it does not have conductivity. Therefore, an electroless Ni / B plating layer is formed on the lens 7 so as to perform electroforming, thereby imparting conductivity.

  FIG. 9B is a cross-sectional view illustrating a processing step for forming an electroless Ni / B plating layer. After the lens 7 having the antireflection structure 6 is subjected to sensitization processing and activation processing using Pd, the lens 7 subjected to the above processing is used for electroless plating as shown in FIG. 9B. Dipping in a Ni / B plating solution 60 of Thereby, an electroless Ni / B plating layer 61 having a thickness of 40 nm is formed on the surface of the lens 7 having the antireflection structure 6.

FIG. 9C and FIG. 9D are cross-sectional views for explaining an electroforming process for applying an electroplating process to the lens 7 on which the electroless Ni / B plating layer 61 is formed. As shown in FIG. 9C, the lens 7 on which the electroless Ni / B plating layer 61 is formed is immersed in a nickel sulfamate electrolytic solution 62 as a cathode, and a Ni electrode is used as a counter electrode. Electroplating was performed under the condition of dm ^{2 to} 5 A / dm ² . Thereby, the Ni plating layer 63 is formed with a thickness of 2 mm on the formation surface of the antireflection structure 6 covered with the electroless Ni / B plating layer 61. Next, as shown in FIG. 9D, the lens 7 on which the Ni plating layer 63 is formed is immersed in the basic solution 64. Thereby, the lens 7 is melt | dissolved and the replication type | mold 65 is formed.

  FIG. 9E is a cross-sectional view showing the replication mold 65 in a state of being taken out from the basic solution 64. The maximum thickness of the obtained replication mold 65 was 2.0 mm, and an antireflection structure 66 having a shape opposite to that of the antireflection structure 6 was formed on the melting surface of the lens 7.

  As described above, according to this embodiment, a mold that can be used for injection molding or press molding can be easily manufactured by electroforming. The molding surface of the replication mold 65 formed by electroforming may be subjected to water repellent treatment. A conventionally known material can be used for the water repellent treatment agent used for the water repellent treatment, and when the molding surface of the replication mold 65 is coated with such a water repellent treatment material, it is used for molding. The adhesion of the raw material, particularly the resin material can be prevented and the molding process can be performed at a low temperature, so that the molding cycle can be shortened. In the present embodiment, the replica mold 65 can function not only as a mold that is actually used for molding, but also as a member having an optical function.

(Fifth embodiment)
In the present embodiment, a method for manufacturing a lens having an antireflection structure formed on the surface thereof by injection molding using the replica mold 65 created in the fourth embodiment will be described. FIG. 10 is a diagram showing states at each stage in the process of manufacturing a lens according to the fifth embodiment of the present invention. Fig.10 (a) is sectional drawing which shows the structure of the molding machine which performs injection molding. In FIG. 10A, the molding machine has a cavity filled with a resin by incorporating a replica mold 65 in which an antireflection structure 66 is formed as an insert mold between base molds 67a and 67b. Has been. A surface protective release layer 68 is formed on the entire inner surface of the cavity by applying a silane coupling agent.

  FIG. 10B is a diagram illustrating a state in which a resin is filled in the cavity. In FIG. 10B, the replication mold 65 is heated to 80 ° C., and the polyolefin resin 69 in a fluid state is supplied into the cavity from the sides of the base molds 67a and 67b.

  FIG. 10C is a diagram showing a state in which the polyolefin resin 69 is filled in the cavity. In FIG. 10 (c), the polyolefin resin 69 is cooled until it is completely solidified. When the polyolefin resin 69 is completely solidified, the base molds 67a and 67b are opened and the resin is taken out.

  FIG. 10D is a cross-sectional view showing the configuration of the obtained lens 70. In the lens 70, an antireflection structure 71 having a shape opposite to that of the antireflection structure 66 formed in the replica mold 65 was formed. When the reflectance of the surface of the lens 70 on which the antireflection structure 71 is formed is measured, the same low reflectance as that of the lens 7 shown in the first embodiment is obtained, and light having a wavelength of 250 nm or more is obtained. An average value of about 0.4% was exhibited over the entire lens.

  As described above, according to this embodiment, the antireflection structure 71 can be easily formed on a curved surface such as the lens 70, and the lens 70 can be mass-produced with high productivity in a short time. In the above description, the injection molding is performed using the polyolefin resin 69. However, the present invention can also be applied to a material that can be heated and softened, such as a resin such as an acrylic resin, a fluorine resin, or a polyethylene resin, or glass. In the above description, the lens 70 having a convex surface on one side is described as an example of the member on which the antireflection structure 71 is formed. However, if the replica mold 65 is used for both the upper mold and the lower mold, both sides Even if the lens has a convex surface, the antireflection structure can be easily formed on the curved surface. Moreover, it can be applied to members that can be applied to various shapes and uses by appropriately changing the shape and arrangement of the replica mold 65. Furthermore, in the present embodiment, the mold that has been electroformed by the method according to the fourth embodiment is used as the replica mold 65, but if the mold satisfies the heat resistance and strength, the first embodiment is used. Even a mold manufactured by such a method can be applied as a mold used for injection molding.

(Sixth embodiment)
In the present embodiment, a method for producing a member having an antireflection structure formed on the surface thereof by press molding using a member having the antireflection structure formed by the method according to the second embodiment as a molding die will be described. To do. FIG. 11 is a diagram illustrating states at each stage in the process of manufacturing a lens according to the sixth embodiment of the present invention.

Fig.11 (a) is sectional drawing which shows the structure of the molding machine which performs press molding. In FIG. 11A, the interior of the chamber 80 is entirely replaced with nitrogen (N ₂ ) gas, and an upper mold 81 and a lower mold 82 are arranged to face each other. The upper mold 81 is a concave lens made of quartz glass on which an antireflection structure is formed by the manufacturing method according to the second embodiment, and is configured to be movable up and down by a drive shaft (not shown). The lower mold 82 is made of a material containing tungsten carbide (WC) as a main component, and has a recess formed so as to hold a lens molding material. A mold release film 83 is formed on the molding surface of the upper mold 81 and the recess of the lower mold 82 in order to improve the mold release property. The release film 83 is an Ir—Rh alloy thin film formed by a sputtering method, the release film 83 formed on the upper mold 81 has a thickness of 0.01 μm, and the release film formed on the lower mold 82. The thickness of 83 is 0.03 μm.

  A quartz glass substrate 84 serving as a lens molding material is placed in the recess of the lower mold 82. The quartz glass substrate 84 is made of a crown borosilicate glass (transition point Tg: 501 ° C., yield point At: 549 ° C.), and has a release agent 85 containing boron nitride (BN) as a main component on the surface thereof. Is applied.

  FIG. 11B shows a state where the quartz glass substrate 84 is pressed. In FIG. 11 (b), the upper die 81 descends and press-molds the quartz glass substrate 84 under conditions of 590 ° C. and 1000N for 3 minutes. When the press working is completed, the upper die 81 is raised as shown in FIG. 11C without performing a cooling process. As a result, an antireflection structure 87 having an inverted shape with respect to the antireflection structure formed on the upper mold 81 is formed on the surface of the molded lens 86.

  FIG. 10D is a cross-sectional view showing the lens 86 taken out from the chamber 80. When the surface reflectance of the lens 86 was measured, the average value of light having a wavelength of 250 nm or more was about 0.2%.

  As described above, according to the present embodiment, by using the member manufactured by the method according to the second embodiment as a molding die, a member having an antireflection structure can be easily manufactured. Can be easily mass-produced. Moreover, the obtained member can also be used as a mold for use in injection molding or press molding.

  In the above description, the release film 83 is formed on the molding surfaces of the upper mold 81 and the lower mold 82. However, if the release film 83 is not provided, the glass material constituting the quartz glass substrate 84 is partial. There is a case where the quartz glass substrate 84 cannot be released from the mold due to direct contact with the mold and fusion. At this time, if the glass material is forcibly released, the glass material or the mold may be broken. In this embodiment, the release film 83 is formed on the molding surfaces of the upper mold 81 and the lower mold 82. Is preferred.

  The present invention is suitable for an optical element having an optical function surface that requires antireflection processing for light rays in an optical path, such as a lens element and a prism element used in a digital camera, a printer device, and the like. In addition, the present invention can be applied to a structural member used for holding these optical elements or a casing member that protects the entire apparatus including the optical elements, thereby providing an antireflection surface that prevents unnecessary light. Furthermore, the present invention relates to various devices such as light emitting elements such as semiconductor laser elements and light emitting diodes, light receiving elements such as photodiodes, imaging elements such as CCD and CMOS, optical switches and branching devices used for optical communication, The function of each device can be improved by forming it in a portion requiring antireflection treatment. Furthermore, the present invention may be applied to a display portion of a display panel such as a liquid crystal display panel, an organic electroluminescence panel, or a plasma light emitting panel. In addition, the present invention can be widely applied to all members that require an antireflection treatment used in optical equipment.

The schematic diagram which shows the state of the X-ray exposure which concerns on the 1st Embodiment of this invention, the schematic diagram which shows the irradiation state of X-ray | X_line, and the schematic diagram which shows the structure of the member in which the reflection preventing structure was formed The perspective view which shows the structure of the reflection preventing structure which concerns on the same embodiment The perspective view which shows the structure of the reflection preventing structure which concerns on the same embodiment Plan view of the X-ray mask according to the embodiment The figure explaining the manufacturing process of the reflection preventing structure concerning the embodiment The figure explaining the manufacturing process of the reflection preventing structure concerning the embodiment The figure explaining the manufacturing process of the reflection preventing structure which concerns on the 2nd Embodiment of this invention. The figure explaining the manufacturing process of the reflection preventing structure which concerns on the 3rd Embodiment of this invention. The figure explaining the manufacturing process of the reflection preventing structure which concerns on the 4th Embodiment of this invention. The figure explaining the manufacturing process of the reflection preventing structure which concerns on the 5th Embodiment of this invention. The figure explaining the manufacturing process of the reflection preventing structure which concerns on the 6th Embodiment of this invention. Schematic diagram showing the state of conventional X-ray exposure, schematic diagram showing the X-ray irradiation state, and perspective view showing the configuration of the antireflection structure

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 X-ray mask 2 Member 3 X-ray absorption area | region 4 X-ray transmissive area | region 5 X-rays 6, 6a-6e Antireflection structure 7 Lens 8 Quartz glass substrate 9 X-ray resist layer 10, 11 Antireflection structure 15 Convex part 20 Etching mask layers 21, 22, 23 Antireflection structure 60 Ni / B plating solution 61 Electroless Ni / B plating layer 62 Nickel sulfamate electrolyte 63 Ni plating layer 64 Basic solution 65 Replica type 66 Antireflection structure 67a, 67b Base mold 68 Surface protective release layer 69 Polyolefin resin 70 Lens 71 Antireflection structure 80 Chamber 81 Upper mold 82 Lower mold 83 Release film 84 Quartz glass substrate 85 Release agent 86 Lens 87 Antireflection structure

Claims (14)

A method for forming an antireflection structure on the surface of a member by an X-ray exposure method,
An exposure step of exposing X-rays to a member having at least a structure forming surface made of a photosensitive material through a plurality of X-ray transmission regions formed in the X-ray mask;
A developing step for developing the exposed member,
In the exposure step, the X-ray is exposed in a state in which the X-ray mask and the member are arranged apart from each other by a distance in which X-rays passing through different X-ray transmission regions cause interference by diffraction. The manufacturing method of the member which has an antireflection structure.   The X-ray mask has a mask pattern in which cylindrical or polygonal X-ray absorption regions or X-ray transmission regions are arranged in an array at a pitch equal to or less than the wavelength of light to be prevented from being reflected. The manufacturing method of the member which has an antireflection structure of Claim 1.   The method for producing a member having an antireflection structure according to claim 1, wherein the member is an optical element or an optical component.   The method of manufacturing a member having an antireflection structure according to claim 3, wherein the optical element is a lens or a microlens array.   The method for producing a member having an antireflection structure according to claim 1, wherein the photosensitive material is polymethyl methacrylate or a fluorine-based resin.   The antireflection structure has a cone shape with an aspect ratio of 1 or more as a structural unit, and the cone shape is arranged in an array on the structure forming surface of the member at a pitch equal to or less than the wavelength of light that should be prevented from being reflected. The manufacturing method of the member which has the reflection preventing structure of Claim 1 characterized by the above-mentioned. The photosensitive material is a photosensitive resist,
2. The antireflection structure according to claim 1, further comprising, after the developing step, an etching step of dry etching the member using the photosensitive resist patterned by the developing step as a mask. Manufacturing method of member. The photosensitive material is a photosensitive resist, and has an etching mask layer made of a material for an etching mask under the layer made of the photosensitive resist.
After the development step, the etching resist layer is patterned by wet etching or dry etching using the photosensitive resist patterned by the development step as a mask, and by the first etching step. The method for manufacturing a member having an antireflection structure according to claim 1, further comprising a second etching step of dry etching the member using the etching mask layer as a mask.   2. The method according to claim 1, further comprising a replica mold forming step of forming a replica mold by performing an electroforming process using the member on which the antireflection structure is formed after the developing step. A method for producing a member having an antireflection structure.   2. The reflection according to claim 1, further comprising a replica mold forming step of forming a replica mold by performing press molding using a member on which the antireflection structure is formed after the developing step. A method for manufacturing a member having a prevention structure.   The method for producing a member having an antireflection structure according to claim 9, wherein the replica mold forming step includes a water repellent treatment step of performing a water repellent treatment on the molding surface of the replica mold.   11. The method for manufacturing a member having an antireflection structure according to claim 10, wherein the replica mold forming step includes a mold release processing step of performing a mold release process on a molding surface of the replica mold.   11. The method according to claim 9, further comprising a molding step of molding a molding material made of a resin material or a glass material using the replica mold after the replica mold forming step. A method for producing a member having an antireflection structure.   The method for manufacturing a member having an antireflection structure according to claim 13, wherein the molding step is performed by an injection molding method or a press molding method.

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