JP2006243633A - Manufacturing method of member having antireflection structure body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an antireflection structure body which has a high antireflection effect using hologram exposure caused by luminous flux interference. <P>SOLUTION: In the manufacturing method of a member having antireflection structure body, the antireflection structure body comprises a prescribed shape body as a structural unit and is formed by arranging a plurality of prescribed shape bodies in an array state with at most a pitch of wavelength of the light whose reflectance should be reduced. The manufacturing method of the member having antireflection structure body comprises: a first exposure process in which a light intensity distribution composed of interference fringe pattern formed by directly superimposing two luminous fluxes to each other is generated on a substrate as the member above mentioned of which at least the structure body formation surface is made of photosensitive material and the substrate is exposed; a second exposure process including at least two times of exposure process in which the relative positional relation between the substrate and the interference fringe pattern is changed so that the interference fringe pattern formed on the substrate has such a relation as to form a prescribed angle with the interference fringe pattern exposed on the first exposure process and, thereafter, the substrate is exposed; and a development process in which the exposed substrate is developed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a member having an antireflection structure, and more particularly, to a method for manufacturing a member having an antireflection structure formed using hologram exposure by two-beam interference.

  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, improvement in productivity and cost has 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 on the surface of an optical element made of quartz glass or the like by patterning using an electron beam (EB) drawing method. Then, a submicron pitch chromium (Cr) mask is formed directly on the surface of the optical element material. Then, the portion other than that covered with the mask of the optical element material is finely processed by a dry etching process to form 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.

In Patent Document 3, a light-induced surface relief material is formed on the surface of a sample, and a laser beam is caused to interfere with the light-induced surface relief material to generate a light intensity distribution, whereby a relief (antireflection structure) is formed. The forming technique is disclosed. In Patent Document 3, after exposing a sample (substrate) using a one-dimensional periodic light intensity distribution generated by two-beam interference of a laser, the sample (substrate) is rotated by 90 degrees, and the two-beam interference of the laser is again performed. Discloses a technique for manufacturing a two-dimensional periodic structure by exposing a sample using the one-dimensional periodic light intensity distribution generated by the above (for example, description of [0023] and [0024]) .
JP 2001-127852 A JP 2001-272505 A JP 2004-170631 A

  9A and 9B show an interference fringe pattern generated by two-beam interference of a conventional laser, that is, a line and space pattern (hereinafter referred to as an L / S pattern) formed by repeating light intensity. It is a front view showing. FIG. 10A is a schematic diagram showing a light intensity distribution formed on a substrate after two hologram exposures in a conventional method for producing a member having an antireflection structure. FIG. 10B is an enlarged perspective view showing a three-dimensional view of the light intensity distribution irradiated onto the substrate after two hologram exposures in the conventional method for manufacturing a member having an antireflection structure. .

  The L / S pattern is an interference fringe generated by two-beam interference, and is composed of a portion 91 where the light beam interferes and strengthens and a portion 92 where the light beam interferes and weakens the strength. In a conventional method for manufacturing a member having an antireflection structure, hologram exposure is performed so as to have the L / S pattern of FIG. 9A using two-beam interference, and then the substrate is oriented in the normal direction of the substrate. Is rotated 90 degrees around the axis, and the arrangement shown in FIG. 9B is performed. When exposed in this way, a square lattice pattern superimposed on a state where the L / S pattern forms an angle of 90 degrees is irradiated onto the substrate.

  As shown in FIG. 10A, the pattern exposed on the substrate has a three-dimensional structure in which approximately three levels of square lattices with large, medium and small exposure amounts are arranged. That is, the region with the smallest exposure amount (denoted as “0” in FIG. 10A), the region with the largest exposure amount (denoted as “2” in FIG. 10A), and an intermediate between them. A region which is an exposure amount (denoted as “1” in FIG. 10A) is formed.

  As described above, a light intensity distribution corresponding to a shape in which the unit structure shown in FIG. 10B is periodically formed can be obtained. By developing a substrate exposed with light having such a light intensity distribution, a shape in which the unit structure shown in FIG. 10B is inverted, that is, a periodic structure in which a portion with a large exposure amount is developed more deeply. It is possible to get a body.

  A desired antireflection structure can be obtained by using a periodic structure obtained as a result of development as it is or by performing dry etching or the like. Thus, the method of directly patterning the substrate by hologram exposure does not require the preparation of a photomask, and the pattern pitch can be changed by changing the angle of the light beam to be irradiated. There is a merit that it is easy. However, the antireflection structure manufactured by rotating the substrate as described in Patent Document 3 by 90 degrees has an exposure amount distribution as shown in FIG. The exposure amount accounts for more than half. Accordingly, since the portions having the same exposure amount are developed to substantially the same depth, the portions having the antireflection effect in the shape shown in FIG. 10A are only the areas “0” and “2”. There is a problem that the antireflection effect is less than half.

  An object of the present invention is to provide a method for manufacturing an antireflection structure having a high antireflection effect using hologram exposure by two-beam interference.

  The object is achieved by a method for manufacturing a member having an antireflection structure having the following configuration. A method for manufacturing a member having an antireflection structure in which a predetermined shape is a structural unit and the predetermined shape is arranged in an array at a pitch equal to or less than the wavelength of light whose reflectance is to be reduced, and at least the structure forming surface A first exposure step of generating a light intensity distribution composed of an interference fringe pattern formed by superimposing two light beams directly on a substrate serving as the member made of a photosensitive material, and exposing the substrate And the interference fringe pattern generated on the substrate is in a relationship with the interference fringe pattern exposed in the first exposure step to form a predetermined angle between the substrate and the interference fringe pattern. After changing the relative positional relationship, the method includes a second exposure process including an exposure process for exposing the substrate at least twice, and a development process for developing the exposed substrate.

  In this specification and claims, the antireflection structure is a fine structure formed on the surface of the optical functional surface in order to suppress reflection of light having a predetermined wavelength. It means a set of shapes and includes not only an aspect that does not completely reflect light that should be suppressed at a predetermined wavelength, but also an aspect that has an effect of suppressing reflection of light that should be suppressed at a predetermined wavelength.

  Moreover, in this specification and the column of a claim, a member contains all the members which need an antireflection effect. Examples of members include, for example, optical elements such as lens elements, prism elements, and mirror elements that are disposed in the optical path and have an optical function surface, and protect the entire device including the structural members and optical elements used to hold these optical elements. Antireflection in housing members, various optical devices (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, etc.) Examples include structural portions that require treatment, display portions of display panels such as liquid crystal display panels, organic electroluminescence panels, and plasma light emitting panels.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the antireflection structure body with the high antireflection effect using the hologram exposure by two-beam interference can be provided, and the optical element provided with the antireflection structure body of a very cheap and large area Such a member can be provided.

(Embodiment 1)
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. 1 is a configuration diagram of a hologram exposure apparatus used in a method for manufacturing a member having an antireflection structure according to a first embodiment. In FIG. 1, the hologram exposure apparatus includes a light source S that emits parallel light rays including a laser and a lens, a half mirror HM1, and reflection mirrors M1 and M2.

  The parallel light emitted from the light source S is incident on the half mirror HM1, and the incident light beam is split substantially in a one-to-one relationship. The first light beam (shown by a solid line) that has passed through the half mirror HM1 is reflected by the mirror M1 and guided to the photoresist 11 formed on the substrate Q1. On the other hand, the second light beam reflected by the half mirror HM1 (indicated by a broken line) is reflected by the mirror M2 and is similarly guided to the photoresist 11 formed on the substrate Q1. At this time, when the light transmitted through the half mirror HM1 of the first light beam and the light reflected from the half mirror HM1 of the second light beam are superimposed on the substrate Q1 at the same incident angle θ, they are formed on the substrate Q1. An interference fringe pattern having an L / S pattern with a pitch of λ / (2 × sin θ) is formed on the photoresist 11. (Λ is the wavelength)

  2A, 2B, and 2C are front views showing L / S patterns generated by light beam interference in the first embodiment. 2A shows an L / S pattern used for the first exposure, FIG. 2B shows an L / S pattern used for the second exposure, and FIG. The L / S pattern used for the third exposure is shown. The L / S pattern is an interference fringe generated by two-beam interference, and represents a portion 1 where the light beam interferes and strengthens, and a portion 2 where the light beam interferes and weakens the strength.

  In the method for manufacturing a member having an antireflection structure according to the first embodiment, three patterns are superimposed on a substrate by exposing light beams so that L / S patterns form an angle of 60 degrees with each other. The intensity distribution of the light flux is formed. That is, in the manufacturing method of this member, after the L / S pattern is first exposed in the arrangement of FIG. 2 (A), the substrate is rotated 60 degrees clockwise and exposed in the arrangement of FIG. 2 (B). It is characterized in that the substrate is rotated 60 degrees to the right and exposed in the arrangement shown in FIG.

  FIG. 3A is a schematic diagram illustrating the intensity distribution of a light beam formed on the substrate after exposure in the method for manufacturing a member having the antireflection structure according to the first embodiment. FIG. 3B is an enlarged perspective view showing the intensity distribution of the light beam irradiated on the substrate after exposure in a three-dimensional manner in the method for manufacturing the member having the antireflection structure according to the first embodiment. is there.

  Hereinafter, the principle of the first embodiment will be described. After the exposure is performed using the L / S pattern of FIG. 2A, the substrate Q1 is subjected to the substrate method at the boundary portion between the portion 1 where the two light beams are strengthened and the portion 2 where the two beams are weakened in the intensity distribution of the L / S pattern. Rotating 60 degrees around the line direction as an axis, the arrangement shown in FIG. 2B is carried out, and the substrate Q1 is formed at the boundary portion between the strengthening portion 1 and the weakening portion 2 of the L / S pattern. Rotation is performed 60 degrees around the line direction as an axis, and the arrangement shown in FIG. When exposed in this way, the L / S pattern is formed so that the width of the part 1 where the light flux strengthens and the part 2 where the light flux weakens are 1: 1, so that the three L / S patterns have an angle of 60 degrees. A triangular lattice pattern superimposed on the formed state is irradiated onto the substrate.

  As shown in FIG. 3A, the pattern exposed on the substrate is a triangular lattice with an exposure amount of 4 levels. That is, on the substrate after exposure, a region with the minimum exposure amount (denoted as “0” in FIG. 3A) and a region where the light beam is exposed only once (in FIG. 3A, “ 1 ”), a region where the light beam is exposed only twice (indicated as“ 2 ”in FIG. 3A), and a region with the maximum exposure amount (in FIG. 3A,“ 3 ”). To be formed). As a result, the intermediate region (“1” in FIG. 10A) existing at the time of the three-level shape formed by the conventional two-time superposition is eliminated, and most of the portions are slanted with a steep inclination angle. It becomes an area.

  When the substrate exposed in this way is developed, the entire area where the light beam is exposed becomes a recess by development. At this time, the formation depth of the concave portion becomes deep when the intensity of the irradiated light beam is large. Accordingly, the recesses become deeper in the order of the region where the light beam is exposed, the region where the light beam is exposed only once, and the region where the light beam is exposed only once. As described above, it is possible to obtain an antireflection structure having an inverted shape of the intensity distribution of the light beam corresponding to the shape in which the four-level unit structure shown in FIG. 3B is periodically formed. In this structure, four-level unit structures are arranged in an array with a pitch equal to or less than the wavelength of light whose reflectance is to be reduced, and an antireflection effect of being incident on the surface is achieved.

  Hereinafter, the manufacturing method of the member which has the reflection preventing structure concerning Embodiment 1 demonstrated above is demonstrated concretely. FIG. 4 is a schematic diagram illustrating a method for manufacturing a member having an antireflection structure according to the first embodiment.

A plano-convex lens having a diameter of 15 mm, a curvature radius of 40 mm, and a thickness of 5 mm made of quartz glass is processed with high precision by grinding to obtain a quartz glass substrate Q1. The substrate Q1 has a surface polished to a centerline surface roughness Ra of about 2 nm. A photoresist 11 is formed to a thickness of 0.5 μm on the surface of the quartz glass substrate Q1 by using a spin coating method, and ultraviolet rays having a wavelength of 248 nm are incident using the apparatus shown in FIG. 1 with a KrF laser as a light source. Hologram exposure by two-beam interference was performed at an angle of 30 degrees, and exposure was performed for 5 seconds at an illuminance of 7.7 mW / cm ² (first exposure step: FIG. 4A).

Next, the quartz glass substrate Q1 is rotated about the normal direction of the apex of the curved surface as an axis so that the L / S pattern forms an angle of 60 degrees before and after the rotation, and similarly the apparatus shown in FIG. Using this, hologram exposure was performed (second exposure step: FIG. 4B). The hologram exposure time is 5 seconds at an illuminance of 7.7 mW / cm ² . Further, the quartz glass substrate Q1 was rotated again about the normal direction of the apex of the curved surface as an axis, and the hologram exposure was performed so that the L / S pattern formed an angle of 60 degrees before and after the rotation (second phase) Exposure process: FIG. 4 (C)). The hologram exposure time is 5 seconds at an illuminance of 7.7 mW / cm ² .

After the exposure, the quartz glass substrate Q1 is immersed in an alkali developer for 1 minute without stirring and subjected to a post-baking treatment, and the photoresist 11 has a height of 480 nm and a pitch of 240 nm having an inverted structure as shown in FIG. To a fine shape 13 (development process: FIG. 4D). Thereafter, the quartz glass substrate Q1 on which the fine shape 13 is formed is put into an RF dry etching apparatus, and the surface of the quartz glass substrate Q1 is etched using CHF ₃ + O ₂ gas, and the shape shown in FIG. A quartz glass substrate 16 having an antireflection structure 15 in which structural units having a shape close to a triangular pyramid having a height of 240 nm, which is an inverted shape, is arranged at a pitch of 240 nm was formed (structure formation step: FIG. 4E). . Therefore, the antireflection structure 15 having an aspect ratio of 1 was formed on the surface of the quartz glass substrate 16. In this case, the etching rate ratio between the photoresist 11 and the quartz glass Q1 was 2: 1. When the reflectance of the surface of the quartz glass substrate 16 on which the antireflection structure 15 was formed was measured, it showed an average value of about 0.15% for light having a wavelength of 250 nm or more.

  As described above, in the manufacturing method of the antireflection structure according to the first embodiment, the L / S pattern generated as a result of the two-beam interference is used when patterning is performed by performing hologram exposure using two-beam interference. Since the exposure is performed three times, the formed antireflection structure has a small number of flat portions, and a structure having a high antireflection effect can be obtained. In addition, since the manufacturing method of the antireflection structure according to the first embodiment requires high-precision manufacturing and does not use an expensive photomask, it is possible to manufacture an antireflection structure having a very low cost and a large area. it can.

  In the first embodiment, an example is shown in which the substrate is rotated by 60 degrees for exposure, the substrate is further rotated by 60 degrees, and the L / S pattern is superimposed. However, the present invention is not limited to this. For example, the exposure is performed by rotating the substrate by 120 degrees, the rotation is further rotated by 120 degrees, the L / S pattern is superimposed, the exposure is performed by rotating the substrate by 60 degrees, and the rotation is further rotated by 120 degrees in the reverse direction. Exposure may be performed to superimpose an L / S pattern, or exposure may be performed by rotating the substrate by 120 degrees, and exposure may be performed by rotating the substrate by 60 degrees in the opposite direction, and the L / S pattern may be superimposed. In short, the substrate may be finally rotated so that the L / S patterns form an angle of 60 degrees with each other. Further, instead of rotating the substrate, the light beam irradiation portion of the hologram exposure apparatus may be made movable so that the L / S pattern rotates.

  Further, if the substrate is rotated by 45 degrees or rotated by 30 degrees, the exposure level can be changed in small increments, and it goes without saying that the antireflection effect is further improved. That is, in the first embodiment, the L / S pattern to be exposed after the rotation is exposed when the L / S pattern exposed in the first exposure step has an angle of 60 degrees. However, the present invention is not limited to this, and the exposure may be performed a plurality of times by further generalization.

As an example, when the second exposure process includes n (n = 2, 3, 4...) Rotational exposure processes, the interference fringe pattern and the substrate each satisfy the following relational expression. To expose.
θi = {180 / (n + 1)} * i
However,
i: an integer from 1 to n,
θi: the angle formed by the interference fringe pattern after rotation with the interference fringe pattern exposed in the first exposure step, the i-th angle formed in ascending order,
It is.

  By exposing the substrate at a position satisfying the above relational expression, it is possible to form an intensity distribution of a light beam for obtaining a shape having a level difference of (n + 1) levels. For this reason, as the number of exposures increases, the side slope becomes steeper and a three-dimensional shape with a large aspect ratio can be obtained. However, the manufacturing process is complicated by that amount, and the performance and manufacturing of the antireflection structure are easy. The number of times may be determined in view of the balance.

  The exposure may be performed at a position where the interference fringe pattern and the substrate each satisfy the above relational expression, and it goes without saying that the process for making the relation does not matter. Therefore, the direction and angle of rotation performed during exposure may be determined as appropriate. Note that the three-time exposure described in the first embodiment corresponds to the case where n = 2 in the above relational expression.

(Embodiment 2)
Next, a specific example for further enhancing the antireflection effect will be described with reference to FIG. FIG. 5 is a schematic diagram illustrating a method for manufacturing a member having an antireflection structure according to the second embodiment.

A plano-convex lens having a diameter of 15 mm, a curvature radius of 40 mm, and a thickness of 5 mm made of quartz glass is processed with high precision by grinding to obtain a quartz glass substrate Q1. The substrate Q1 has a surface polished to a centerline surface roughness Ra of about 2 nm. On the surface of this quartz glass substrate Q1, a Cr film 12 as an etching mask was formed with a thickness of 0.1 μm by sputtering. Further, a photoresist 11 having a thickness of 0.5 μm is formed on the Cr film 12 by using a spin coating method, and an ultraviolet ray having a wavelength of 248 nm is used with the KrF laser as a light source using the apparatus shown in FIG. Hologram exposure by two-beam interference was performed at an incident angle of 30 degrees, and exposure was performed for 5 seconds at an illuminance of 7.7 mW / cm ² (first exposure step: FIG. 5A).

Next, the quartz glass substrate Q1 is rotated about the normal direction of the apex of the curved surface as an axis so that the L / S pattern forms an angle of 60 degrees before and after the rotation, and similarly the apparatus shown in FIG. Using this, hologram exposure was performed (second exposure step: FIG. 5B). The hologram exposure time is 5 seconds at an illuminance of 7.7 mW / cm ² . Further, the quartz glass substrate Q1 was rotated again about the normal direction of the apex of the curved surface as an axis, and the hologram exposure was performed so that the L / S pattern formed an angle of 60 degrees before and after the rotation (second phase) Exposure process: FIG. 5 (C)). The hologram exposure time is 5 seconds at an illuminance of 7.7 mW / cm ² .

After the exposure, the quartz glass substrate Q1 is immersed in an alkali developer for 1 minute without stirring and subjected to a post-baking process, and the photoresist 11 has a height of 480 nm and a pitch of 240 nm having an inverted structure as shown in FIG. To a fine shape 13 (development process: FIG. 5D). Thereafter, the fine shape 14 made of Cr was formed as an etching mask by dry etching using an ion milling apparatus using Ar gas with the fine shape 13 as a mask (structure formation step: FIG. 5E). At this time, the fine shape 14 had a height of 80 nm and a pitch of 240 nm. Therefore, in this case, the etching rate ratio between the photoresist 11 and the Cr film 12 was 6: 1. Finally, the quartz glass substrate Q1 on which the fine shape 14 is formed is put into an RF dry etching apparatus, and the surface of the quartz glass substrate Q1 is etched using CHF ₃ + O ₂ gas to form a triangular pyramid having a height of 480 nm. A quartz glass substrate 16 having an antireflection structure 15 in which structural units having similar shapes are arranged at a pitch of 240 nm was formed (structure formation step: FIG. 5F). In this case, the etching rate ratio between the Cr film 12 and the quartz glass substrate Q1 was 1: 6. Therefore, the antireflection structure 15 having an aspect ratio of 2 was formed on the surface of the quartz glass substrate 16. When the reflectance of the surface of the quartz glass substrate 16 at this time was measured, the average value of light having a wavelength of 250 nm or more was about 0.07%.

  In addition, although the Cr film was specifically mentioned as an etching mask material, it is not restricted to this. Any material that has a high selectivity in etching with the final member such as quartz may be used. For example, the etching mask may be any film such as Cr, Ni, Al, C, Ta, Mo, Fe, Pt, or Au.

  As described above, in the method for manufacturing the antireflection structure according to the second embodiment, the L / S pattern generated as a result of two-beam interference is used when patterning is performed by performing hologram exposure using two-beam interference. Since the exposure is performed three times, the formed antireflection structure has a small number of flat portions, and a structure having a high antireflection effect can be obtained. In addition, since the manufacturing method of the antireflection structure according to the second embodiment requires high-precision manufacturing and does not use an expensive photomask, it is possible to manufacture an antireflection structure having a very low cost and a large area. it can.

  In the second embodiment, the example in which the exposure is performed by rotating the substrate by 60 degrees, the exposure is performed by rotating the substrate by 60 degrees, and the L / S pattern is superimposed is shown, but the present invention is not limited thereto. For example, the exposure is performed by rotating the substrate by 120 degrees, the rotation is further rotated by 120 degrees, the L / S pattern is superimposed, the exposure is performed by rotating the substrate by 60 degrees, and the rotation is further rotated by 120 degrees in the reverse direction. Exposure may be performed to superimpose an L / S pattern, or exposure may be performed by rotating the substrate by 120 degrees, and exposure may be performed by rotating the substrate by 60 degrees in the opposite direction, and the L / S pattern may be superimposed. In short, the substrate may be finally rotated so that the L / S patterns form an angle of 60 degrees with each other. Further, instead of rotating the substrate, the light beam irradiation portion of the hologram exposure apparatus may be made movable so that the L / S pattern rotates.

  Further, if the rotation angle is rotated by 45 degrees or 30 degrees, the exposure level can be changed in small increments, and it goes without saying that the antireflection effect is further enhanced. That is, in the above-described second embodiment, the exposure is performed when the L / S pattern to be exposed after the rotation has a relationship of 60 degrees with the L / S pattern exposed in the first exposure step. However, the present invention is not limited to this, and the exposure may be performed a plurality of times by further generalization.

As an example, when the second exposure process includes n (n = 2, 3, 4...) Rotational exposure processes, the interference fringe pattern and the substrate each satisfy the following relational expression. To expose.
θi = {180 / (n + 1)} * i
However,
i: an integer from 1 to n,
θi: the angle formed by the interference fringe pattern after rotation with the interference fringe pattern exposed in the first exposure step, the i-th angle formed in ascending order,
It is.

  By exposing the substrate at a position satisfying the above relational expression, it is possible to form an intensity distribution of a light beam for obtaining a shape having a level difference of (n + 1) levels. For this reason, as the number of exposures increases, the side slope becomes steeper and a three-dimensional shape with a large aspect ratio can be obtained. However, the manufacturing process is complicated by that amount, and the performance and manufacturing of the antireflection structure are easy. The number of times may be determined in view of the balance.

  The exposure may be performed at a position where the interference fringe pattern and the substrate each satisfy the above relational expression, and it goes without saying that the process for making the relation does not matter. Therefore, the direction and angle of rotation performed during exposure may be determined as appropriate. Note that the three-time exposure described in the second embodiment corresponds to the case where n = 2 in the above relational expression.

(Embodiment 3)
In the present embodiment, a method for manufacturing a replica mold by electroforming using a member having an antireflection structure produced by the method according to the first or second embodiment will be described. FIG. 6 is a schematic diagram for explaining a method for producing an electroforming mold used in a method for producing a member having an antireflection structure according to the third embodiment. The method for manufacturing a member having an antireflection structure according to the third embodiment is characterized in that the mold is electroformed and duplicated. Hereinafter, a process of electroforming and duplicating the quartz glass substrate 16 on which the antireflection structure formed by the manufacturing method of Embodiment 1 is formed will be described as an example.

  First, a lens master 61 made of quartz glass having an antireflection structure 62 manufactured by the same manufacturing method as that described in Embodiment 1 was prepared (FIG. 6A). First, since the lens master 61 made of quartz glass is not conductive, it is subjected to sensitization treatment, activation treatment with Pd, and then immersed in the Ni / B solution 63 for electroless plating to reflect it. An electroless plating layer 64 was formed on the surface of the prevention structure 62 (FIG. 6B). The electroless Ni / B plating layer 64 formed on the antireflection structure 62 of the lens master 61 made of quartz glass had a thickness of 40 nm.

  Subsequently, the lens master 61 made of quartz glass on which the electroless plating layer 64 is formed is immersed in a nickel sulfamate electrolyte 65 and electroplated to form a Ni plating layer 66 on the surface of the lens master 61 made of quartz glass. (FIG. 6C). Thereafter, the lens master 61 made of Ni-plated quartz glass is taken out of the plating solution (FIG. 6D), and the Ni replica mold 68 is mechanically separated from the lens master 61 made of quartz glass (FIG. 6E). . The thickness of the Ni replication mold 68 was 4.0 mm.

  The mold replicated as described above can be used as a mold for directly molding a heat-softened resin or glass. According to the third embodiment, it is possible to manufacture a mold used for molding the antireflection structure without using a high-cost and low-productivity method such as electron beam drawing.

(Embodiment 4)
In the present embodiment, a member having an antireflection structure formed on the surface is manufactured by press molding using a member having the antireflection structure formed by the method according to the first or second embodiment as a mold. A method will be described.

FIG. 7A is a cross-sectional view illustrating a configuration of a molding machine that performs press molding. In FIG. 7A, the interior of the chamber 76 is entirely replaced with nitrogen (N ₂ ) gas, and the upper mold 72 and the lower mold 73 are arranged to face each other. The upper mold 72 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 73 is made of a material whose main component is tungsten carbide (WC), and has a recess formed so as to hold a lens molding material. A mold release film 71 is formed on the molding surface of the upper mold 72 and the recess of the lower mold 73 in order to improve mold release properties. The release film 71 is an Ir—Rh alloy thin film formed by sputtering, the release film 71 formed on the upper mold 72 has a thickness of 0.01 μm, and the release film formed on the lower mold 73. The thickness of 71 is 0.03 μm.

  A glass substrate 74 serving as a lens molding material is placed in the recess of the lower mold 73. The glass substrate 74 is made of crown-based borosilicate glass (transition point Tg: 501 ° C., yield point At: 549 ° C.), and a release agent 75 mainly composed of boron nitride (BN) is formed on the surface thereof. Is formed.

  FIG. 7B shows a state where the glass substrate 74 is pressed. In FIG. 7 (B), the upper die 72 descends and press-molds the glass substrate 74 under the conditions of 590 ° C. and 1000 N for 3 minutes. When the press work is completed, the upper die 72 is raised as shown in FIG. 7C without performing a cooling process. Thereby, an antireflection structure having an inverted shape with respect to the antireflection structure formed on the upper mold 72 is formed on the surface of the molded glass lens 74.

  FIG. 7D is a cross-sectional view showing the lens 77 taken out from the chamber 76. When the surface reflectance of the lens 77 was measured, it showed an average value of about 0.07% for light having a wavelength of 250 nm or more. If there is no surface protective thin film, the glass material will be in direct contact with the mold, causing fusion and making it impossible to release from the mold. If you try to release the mold forcibly, the glass material or mold will break.

  As described above, according to the fourth embodiment, an antireflection structure is formed by directly molding a heat-softened resin or glass using the member produced by the method shown in the first or second embodiment as a mold. It is possible to easily and mass-produce a member such as an optical element having a very low cost.

(Embodiment 5)
Next, another method for manufacturing a member having an antireflection structure will be described with reference to FIG. FIG. 8 is a schematic diagram illustrating a method for manufacturing a member having an antireflection structure according to the fifth embodiment. The fifth embodiment is characterized in that a member made of an optical resin is molded using an electroformed and duplicated mold manufactured by the method described in the third embodiment.

  The electromold 83 described above is used as an insert mold and incorporated in the base mold 81, and a silane coupling agent is applied to the entire cavity inner surface filled with resin to form a surface protective release layer 82 (FIG. 8A). )). Next, the electroforming mold 83 was heated to 80 ° C., and a polyolefin resin 84 in a fluid state was injected into the mold (FIG. 8B) and filled (FIG. 8C). When the resin was solidified by cooling, the mold was opened and the resin was taken out to obtain a resin 85 on which an antireflection structure was formed. When the reflectance of the surface of the resin 85 on which the antireflection structure was formed was measured, the average value of light having a wavelength of 250 nm or more was about 0.15%. In this embodiment mode, acrylic, Teflon (registered trademark), polyethylene, polyolefin, or the like can be used as a resin material.

(Embodiment 6)
The sixth embodiment is characterized in that a member made of an optical resin is molded using an electroformed replication mold produced by the method described in the third embodiment. The optical resin material was press-molded using the same molding machine (FIG. 7) as in Embodiment 4 using an electroformed replication mold in which a surface protective film was formed with a silane coupling agent. An electroformed replication mold having a surface protective film formed thereon was used as an upper mold, and a cemented carbide containing WC as a main component was used as a lower mold. The upper mold, the lower mold, and the PMMA resin substrate were set and press molded at 180 ° C. and 20 MPa to form an antireflection structure on the surface of the resin substrate. When the reflectance of the resin surface on which the antireflection structure was formed was measured, the average value of light having a wavelength of 250 nm or more was about 0.15%. In this embodiment mode, acrylic, Teflon (registered trademark), polyethylene, polyolefin, or the like can be used as the resin substrate.

  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.

1 is a configuration diagram of a hologram exposure apparatus used in a method for producing a member having an antireflection structure according to a first embodiment. The front view showing the interference fringe pattern produced | generated by light beam interference in Embodiment 1 (A) is the schematic diagram which shows intensity distribution of the light beam formed on the board | substrate after exposure in the manufacturing method of the member which has the reflection preventing structure concerning Embodiment 1, (B) is Embodiment 1. FIG. In the method of manufacturing a member having an antireflection structure according to the present invention, an enlarged perspective view showing a three-dimensional intensity distribution of a light beam irradiated on a substrate after exposure Schematic explaining the manufacturing method of the member which has the antireflection structure concerning Embodiment 1. Schematic explaining the manufacturing method of the member which has the reflection preventing structure concerning Embodiment 2. Schematic drawing explaining the manufacturing method of the electroforming mold used for the manufacturing method of the member which has the reflection preventing structure concerning Embodiment 3. Schematic drawing explaining the manufacturing method of the member which has the reflection preventing structure concerning Embodiment 4. Schematic drawing explaining the manufacturing method of the member which has the antireflection structure concerning Embodiment 5. Front view showing interference fringe pattern generated by light beam interference of conventional laser (A) is a schematic diagram showing a light intensity distribution formed on a substrate after two hologram exposures in a method for producing a member having a conventional antireflection structure, and (B) is a conventional antireflection structure. In the manufacturing method of the member which has a body, the perspective enlarged view which showed three-dimensionally the light intensity distribution irradiated on the board | substrate after two hologram exposures

Explanation of symbols

Q1 Substrate 1 Part 2 where the light beam interferes and strengthens the intensity 2 Part where the light beam interferes and weakens the intensity 11 Photoresist 12 Cr film 13 Fine shape 14 Fine shape 15 Antireflection structure 16 Quartz glass substrate 61 Quartz glass substrate Lens master 62 Antireflection structure 63 Ni / B solution 64 Electroless plating layer 65 Nickel sulfamate electrolyte 66 Ni plating layer 68 Ni replica mold 71 Release film 72 Upper mold 73 Lower mold 74 Molding material 75 Mold release agent 76 Chamber 77 Lens 81 Base mold 82 Surface protective release layer 83 Electroforming mold 84 Flowing polyolefin resin 85 Resin 91 A portion where the light beam interferes and strengthens strength 92 A portion where the light beam interferes and weakens strength

Claims (7)

A method of manufacturing a member having an antireflection structure in which a predetermined shape is a structural unit, and the predetermined shape is arranged in an array at a pitch equal to or less than a wavelength of light whose reflectance is to be reduced,
A light intensity distribution composed of an interference fringe pattern formed by superimposing two light beams directly on a substrate that is a member having at least a structure forming surface made of a photosensitive material is generated, and the substrate is exposed. A first exposure step;
Relative relation between the substrate and the interference fringe pattern so that the interference fringe pattern generated on the substrate forms a predetermined angle with the interference fringe pattern exposed in the first exposure step. An exposure step of exposing the substrate after changing the positional relationship, a second exposure step including at least twice,
The manufacturing method of the member which has an antireflection structure provided with the image development process which develops the exposed substrate. When the second exposure step includes n times (n = 2, 3, 4...) Of the exposure step, the interference fringe pattern and the substrate satisfy the following relational expressions, respectively. The manufacturing method of the member which has a reflection preventing structure of Claim 1 which exposes a board | substrate:
θi = {180 / (n + 1)} * i
However,
i: an integer from 1 to n,
θi: the angle formed by the interference fringe pattern after rotation with the interference fringe pattern exposed in the first exposure step, the angle formed by the i-th in ascending order,
It is. 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 method for producing a member having an antireflection structure according to claim 3, wherein an antireflection film is further formed under the photosensitive resist layer. 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.   The method for producing a member having an antireflection structure according to claim 5, further comprising an antireflection film formed under the photosensitive resist layer.   A method for manufacturing a member having an antireflection structure, wherein a replica mold is manufactured by electroforming or press molding from a member manufactured by the member manufacturing method according to claim 1, and the member is molded using the replica mold.

Images