JP2010060681A - Method for manufacturing lithographic mask, surface processing method, method for manufacturing metal mold for molding optical element, and method for manufacturing optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a lithographic mask, which makes exposure even on a curved surface. <P>SOLUTION: The method for manufacturing a lithographic mask 10 used to process a surface of a processing object having a surface shape at least the part of which is a curved surface includes steps of: forming a nickel film 14 having a predetermined pattern as a light shielding layer on a transparent film 11 as a substrate of polyethylene terephthalate (PET) or the like, which transmits emitted light when performing lithography; and deforming the transparent film 11 with the nickel film 14 formed thereon by pressing into a shape laid along the shape of at least the part of the surface of the processing object. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a mask for lithography, a surface processing method, a method for manufacturing a mold for molding an optical element, and a method for manufacturing an optical element.

  In recent years, the demand for optical elements has increased rapidly. As an application using an optical element for visible light, for example, it may be used for optical communication or a digital camera. In order to use an optical element for such an application, it is desired to develop a technique for manufacturing a high-performance optical element at a lower cost. In applications where optical elements are used for infrared rays, commercialization of products for mounting on automobiles, for human body detection sensors for home security, and for thermography cameras is in full swing. Similarly, high performance and low cost are required. Many of these optical elements are often manufactured by a press molding method in which an optical material is pressed by a mold and a method in which the optical material is ground and polished to be shaped. In particular, the press molding method is an excellent production method in that it can produce a large number of optical elements of the same shape and provide them at low cost.

  The surface of these optical elements is usually treated to prevent reflection of incident light. As one technique for this purpose, a technique for forming a structure in which very fine uneven structures called antireflection structures are periodically arranged on the surface of an optical element has been proposed. This utilizes the phenomenon that when light is incident on the surface of a concavo-convex structure having an aspect ratio of about 1 or more at a pitch shorter than the wavelength of light, light having a wavelength longer than the pitch of the structure is almost transmitted. is there. If this structure can be formed at the same time as the press molding of the optical element, the process of forming the antireflection film becomes unnecessary, and the production cost is greatly reduced. In addition, since the antireflection structure provides an antireflection effect in a wide wavelength range and a wide incident angle range, application to various optical elements is expected.

Here, in order to form the antireflection structure on the optical element by press molding, it is necessary to form the transfer structure of the antireflection structure on the mold surface as the shape transfer source. The transfer structure of this antireflection structure is, for example, a concavo-convex structure having a very fine pitch.
This concavo-convex structure needs to be adjusted in pitch according to the wavelength of light used. For example, in the case of visible light having a wavelength of about 400 nm to 800 nm, an uneven structure with a pitch of about 300 nm or less is required. Further, in the case of infrared light having a wavelength of 8 μm to 12 μm used in thermography or the like, it is necessary to have a concavo-convex structure with a pitch of about 3 μm or less.

As a method for forming such a fine concavo-convex structure, for example, Patent Document 1 describes a method of forming a concavo-convex shape on the surface of an optical element using electron beam drawing.
Patent Document 2 discloses a preparation step of preparing either a substrate made of a material sensitive to X-rays or a substrate on which a layer made of an X-ray resist sensitive to X-rays is formed on the surface; An exposure step of exposing an X-ray through an X-ray mask to form an X-ray intensity distribution according to the pattern of the X-ray mask, and a development step of developing the exposed substrate to form an antireflection structure The X-ray mask includes a transmission part that transmits X-rays and an absorption part that absorbs X-rays, and the transmission part has a polygonal shape corresponding to the bottom surface of the antireflection structure to be manufactured. In addition, there is described a method of manufacturing a member including an antireflection structure arranged in an array so that the transmissive portions share the vertices without sharing each other's sides.

JP 2001-272505 A JP 2006-317807 A

However, the method using electron beam drawing requires a very long drawing time, and the drawing apparatus is very expensive, resulting in a significant increase in production cost. Therefore, there is a problem that it is not suitable for production of an optical element for which cost reduction is desired.
In addition, an optical element such as a lens usually has a curved surface shape. However, in the method using electron beam drawing, the surface on which a fine pattern can be formed is limited to a flat surface. Therefore, this method can be applied only to the production of a very limited optical element having a flat shape. Furthermore, when manufacturing a member having an antireflection structure using an X-ray mask, the surface that can be exposed using the X-ray mask is limited to a flat surface, and thus limited in the same manner. Applicable only to the manufacture of optical elements.

In view of the above problems, an object of the present invention is to provide a method of manufacturing a lithography mask that can perform exposure even if the surface shape of a workpiece is a curved surface.
Another object of the present invention is to provide a surface processing method capable of forming a concavo-convex structure even if the surface shape of the workpiece is a curved surface.
Furthermore, another object is to provide a method for producing a mold for molding an optical element in which a concavo-convex structure is formed on a molding surface by a simple method.
Still another object is to provide a method for manufacturing a large amount of an optical element having an antireflection structure on its surface at a low cost.

  As a result of intensive studies, the inventors have formed a light-shielding layer having a predetermined pattern on a substrate, and adopting a technique for deforming the substrate by pressing the substrate on which the light-shielding layer is formed. It has been found that it is possible to manufacture a lithography mask that can be exposed with high positional accuracy even if the shape is a curved surface, and the present invention has been completed based on such knowledge. That is, the gist of the present invention is as follows.

  The lithography mask manufacturing method of the present invention is a method of manufacturing a lithography mask used for processing a surface of a workpiece in which at least a part of a surface shape is a curved surface. Forming a light-shielding layer having a predetermined pattern on a substrate that transmits light irradiated to the substrate, and deforming the substrate by pressing the substrate on which the light-shielding layer is formed, along the shape of at least a part of the surface of the workpiece And a step of forming the shape.

  Here, the substrate is preferably made of a thermoplastic resin, and the thermoplastic resin is more preferably polyethylene terephthalate (PET). The light shielding layer is preferably made of a metal material.

  Further, the surface processing method of the present invention is a method of forming a concavo-convex structure on the surface of a workpiece whose surface shape is a curved surface, the step of forming a resist layer on the surface of the workpiece, A mask manufactured by forming a light shielding layer having a predetermined pattern on a substrate and deforming the substrate by pressing the substrate on which the light shielding layer is formed so as to conform to the shape of at least a part of the surface of the workpiece. A step of placing on the surface of the resist layer, a step of exposing the resist layer by performing exposure, a step of transferring the pattern to the resist layer, a step of removing the exposed resist layer by performing development, and dry etching And a step of forming an uneven structure corresponding to the pattern on the surface of the workpiece.

  Here, the mask is preferably a film mask, and the dry etching is preferably reactive ion etching. Then, between the step of removing the exposed resist layer and the step of forming the concavo-convex structure corresponding to the pattern on the surface of the workpiece, the step of forming the metal layer and the resist layer other than the exposed resist layer are removed. It is preferable to further include a step of removing a part of the metal layer.

  Furthermore, the method for producing a mold for molding an optical element of the present invention is a method for producing a mold for molding an optical element by forming a concavo-convex structure on a molding surface having a curved surface, wherein a resist layer is provided on the molding surface. It was produced by forming a light shielding layer having a predetermined pattern on the substrate, forming the light shielding layer into a shape that conforms to at least a part of the molding surface by pressing the substrate on which the light shielding layer is formed. A step of placing a mask on the surface of the resist layer; a step of exposing the resist layer by performing exposure; a step of transferring the pattern to the resist layer; a step of removing the exposed resist layer by performing development; Forming a concavo-convex structure corresponding to the pattern on the molding surface by performing dry etching.

  Here, the uneven structure is preferably a transfer structure having an antireflection structure, and the dry etching is more preferably reactive ion etching. Then, between the step of removing the exposed resist layer and the step of forming the concavo-convex structure corresponding to the pattern on the molding surface, the step of forming the metal layer and removing the resist layer other than the exposed resist layer It is preferable to further include a step of removing a part of the layer.

  Furthermore, the optical element manufacturing method of the present invention is an optical element by press-molding an optical element base material using an optical element manufacturing apparatus to which an optical element molding die manufactured by the above method is attached. An uneven structure is formed on the surface of the base material.

  Here, the optical element is preferably made of chalcogenide glass, and the uneven structure is preferably an antireflection structure.

  ADVANTAGE OF THE INVENTION According to this invention, even if the surface shape of a to-be-processed object is a curved surface, the mask for lithography which can perform exposure can be manufactured.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIGS. 1A to 1G are diagrams for explaining an example of a method for manufacturing a mask for lithography to which the present embodiment is applied. 1A to 1G show a method of manufacturing a lithography mask in the order of manufacturing steps.

  Here, first, a resist layer 12 is formed on a transparent film 11 as a substrate (FIG. 1A). The transparent film 11 is not particularly limited as long as it is transparent to the light irradiated for exposure when performing lithography in the step of FIG. 2B to be described later. In the step of FIG. 1 (f), a film made of a thermoplastic resin is preferable because it needs to be heat-deformed into a desired shape. Moreover, it is preferable that it is a film which has flexibility. Specifically, for example, polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polystyrene (PS), polymethyl methacrylate (PMMA), polyphenylene ether (PPE), polyamide (PA), polycarbonate (PC ), Polyacetal (POM), polybutylene terephthalate (PBT) and the like can be used. In this embodiment, a film made of polyethylene terephthalate (PET) and having a thickness of 100 μm is used.

  The resist layer 12 can be formed, for example, by applying a positive type photoresist solution to the transparent film 11 with a thickness of 2 μm by spin coating and solidifying by heating at 110 ° C.

Next, the glass photomask 13 is placed on the resist layer 12 and exposed to transfer the pattern of the glass photomask 13 (FIG. 1B).
In the glass photomask 13, circular holes with a diameter of 2 μm (not shown) are arranged in a hexagonal lattice pattern with a pitch of 3 μm. When exposure is performed, light is transmitted through the circular hole portion, and light is blocked between the holes. Therefore, by light irradiation by exposure, the pattern is transferred onto the resist layer 12 in a circular pattern with a diameter of 2 μm and a pattern arranged in a hexagonal lattice pattern with a pitch of 3 μm. The exposure can be performed by using a batch exposure machine using an ultrahigh pressure mercury lamp as a light source and setting the exposure time to 30 seconds.

Next, an exposure developer is immersed in the exposed resist layer 12, and development is performed (FIG. 1C).
As a result of development, the exposed resist layer 12 is removed, and the other portions remain. Therefore, the resist layer 12 has circular shapes with a diameter of 2 μm, and holes 12 a arranged in a hexagonal lattice pattern with a pitch of 3 μm. The hole 12a penetrates the resist layer 12, and the transparent film 11 is exposed at the bottom.

Next, a nickel film 14 is formed as a light shielding layer (FIG. 1D). By this step, the nickel film 14 is formed on the surface of the remaining resist layer 12 and on the bottom of the hole 12a. The nickel film 14 may be a film made of another material as long as it shields exposure light irradiated when performing lithography in FIG. 2B described later. However, a metal layer formed of a metal material is preferable from the viewpoint of easiness of film formation. Specific examples of the metal material include nickel (Ni), simple substance such as iron (Fe), cobalt (Co), chromium (Cr), or an alloy containing these.
The nickel film 14 can be formed, for example, by forming a film with a thickness of 100 nm using a sputtering method.

Next, the remaining resist layer 12 is removed using a resist removing solution (FIG. 1E). As a result, the nickel film 14 formed on the bottom of the hole 12a remains, but the nickel film 14 formed on the resist layer 12 is removed together with the remaining resist layer 12 because it is removed. . As a result, the nickel film 14 has a circular shape with a diameter of 2 μm, and remains on the transparent film 11 in a form arranged in a hexagonal lattice pattern with a pitch of 3 μm.
As the resist removing solution, for example, acetone can be used. Then, the remaining resist layer 12 can be removed more easily by immersing in acetone and applying ultrasonic waves.
1A to 1E can be grasped as a process of forming a light-shielding layer having a predetermined pattern on a substrate that transmits light irradiated when performing lithography.

Next, a transparent film 11 having a nickel film 14 formed thereon is used by using a concave mold base material 15a having a pressing surface processed into the shape of an optical element molding die described later and a convex mold base material 15b. The mold base materials 15a and 15b are sandwiched and pressed (FIG. 1 (f)). At this time, the surface on which the nickel film 14 is formed is directed toward the convex mold base material 15b.
In the present embodiment, the pressing surface of the concave mold base material 15a has a spherical shape with a radius of curvature of 20.1 mm, and the convex mold base material 15b has a spherical shape with a curvature radius of 20.0 mm. Can be formed. By pressing, the transparent film 11 has a concave shape on the side on which the nickel film 14 is formed, and is deformed into the shape of the pressing surface of the mold base materials 15a and 15b. Since this deformation is plastic deformation, the deformed shape is maintained even if the pressing by the mold base materials 15a and 15b is released. In addition, since it is easy to deform | transform the transparent film 11, it is preferable to heat at the time of a press. In the present embodiment, the heating temperature is 140 ° C., and the heating time is 5 minutes. In addition, this process is a process in which the substrate on which the light-shielding layer is formed is deformed by pressing, and is formed into a shape that conforms to the shape of at least a part of the surface of an optical element molding die, which will be described later. I can grasp it.

  Further, after heating, cooling is performed and the transparent film 11 is peeled off from the mold base materials 15a and 15b, whereby a lithography mask 10 to which the present embodiment is applied can be manufactured (FIG. 1 (g)).

Next, a method for performing surface processing of a workpiece using the lithography mask 10 manufactured by the process described in FIG. 1 will be described.
FIGS. 2A to 2G are diagrams illustrating a method for performing surface processing of a workpiece using a lithography mask (film mask) 10 manufactured by the process described in FIG. .
2A to 2G, an optical element molding die is taken as an example of a workpiece. As an example of the surface processing, an antireflection structure transfer structure is formed on an optical element molding die. That is, a method for manufacturing a mold for forming an optical element having a transfer structure having an antireflection structure is shown in the order of manufacturing steps.

First, a resist layer 22 is formed on a mold 21 where a transfer structure having an antireflection structure is to be formed (FIG. 2A).
For example, as shown in FIG. 3, the mold 21 includes a base material 31 and a coating layer 32 formed on the molding surface 33 of the mold 21. The base material 31 includes, for example, a cemented carbide whose main component is tungsten carbide (WC). Moreover, you may be comprised by the raw material with high heat resistance, such as silicon carbide (SiC) and glassy carbon. Further, it may be made of inconel, stubbax, die steel or the like. Further, the coating layer 32 is a layer that is formed in order to realize a suitable release when the optical element is press-molded. For example, it is formed of a platinum (Pt) -iridium (Ir) alloy. In addition, materials having low chemical reactivity such as noble metal alloys other than platinum-iridium alloys, alloys of noble metals and transition metals, alloys of noble metals and general purpose metals, carbon, or DLC (diamond-like carbon) are preferably used. Is done. In the present embodiment, a silicon carbide (SiC) material produced by a sintering method is used as the base material 31, and silicon carbide (SiC) formed by a CVD (Chemical Vapor Deposition) method is used as the coating layer 32. . Here, the convex mold 21 will be described as an example of the mold for molding the optical element. The molding surface 33 of the mold 21 has a spherical shape with a curvature of 20.0 mm.

  The resist layer 22 is formed by, for example, using a positive type photoresist liquid, applying the photoresist liquid to the molding surface 33 of the mold 21 with a thickness of 2 μm by spin coating, and heating and solidifying at 110 ° C. can do.

Next, exposure is performed by placing a lithography mask 10 on the surface of the resist layer 22 (FIG. 2B). Here, the mask 10 is placed so that the side on which the nickel film 14 is formed is in contact with the resist layer 22. Since this mask 10 is manufactured in accordance with the shape of the molding surface 33 (see FIG. 3) of the mold 21 for molding an optical element, the mask 10 is placed in close contact with the molding surface 33 of the mold 21 which is a curved surface. Can do. In the present embodiment, when exposure is performed in this state, light is transmitted through the transparent film 11, but is shielded by the nickel film 14 formed on the mask 10, and the portion where the nickel film 14 is formed is exposed to light. Not transparent. That is, the nickel film 14 serves as a light shielding layer. However, since the light is transmitted through the portion where the nickel film 14 is not formed, the resist layer 22 can be exposed at the portion where the light is transmitted. Since the nickel film 14 is formed so as to be arranged in a circular shape on the transparent film 11, the resist layer 22 is in a state in which a portion not exposed to the circular shape and a portion exposed around it are mixed. . Here, when performing exposure, the mask 10 is in close contact with the optical element molding die 21. Therefore, exposure can be performed even if the molding surface 33 of the mold 21 is a curved surface. Further, it is possible to increase the position accuracy of the location where the exposure is performed, and to reduce the distortion of the pattern of the array where the transfer is performed.
Here, the exposure can be performed, for example, by using a batch exposure machine using an ultrahigh pressure mercury lamp as a light source and setting the exposure time to 30 seconds.

Next, the mask 10 is removed, and an exposure developer is immersed in the exposed resist layer 22 for development (FIG. 2C).
As a result of the development, the resist layer 22 in the exposed part is removed and the other part remains, so the molding surface 33 of the mold 21 has a circular shape with a diameter of 2 μm and a hexagonal lattice shape with a pitch of 3 μm. The arranged resist remaining portions 22a are arranged. The resist is removed around the circular resist remaining portion 22a, and the molding surface 33 of the mold 21 is exposed at the bottom.

Next, the nickel film 24 is formed (FIG. 2D). By this step, the nickel film 24 is formed on the surface of the remaining resist portion 22a and around the remaining resist portion 22a. The nickel film 24 may be a film made of another material as long as it has resistance when dry etching is performed in the process of FIG. However, a metal layer formed of a metal material is preferable from the viewpoint of easiness of film formation. Specific examples of the metal material include nickel (Ni), simple substance such as iron (Fe), cobalt (Co), chromium (Cr), or an alloy containing these.
The nickel film 24 can be formed by, for example, forming a film with a thickness of 100 nm using a sputtering method.

Next, the resist remaining portion 22a is removed using a resist removing solution (FIG. 2E). As a result, the nickel film 24 formed around the remaining resist portion 22a remains, but the nickel film 24 formed on the remaining resist portion 22a is removed together with the remaining resist portion 22a. The As a result, the nickel film 24 has a circular shape with a diameter of 2 μm, and remains on the optical element molding die 21 in a form in which holes 25 arranged in a hexagonal lattice pattern with a pitch of 3 μm are arranged.
As the resist removing solution, for example, acetone can be used. Then, the resist remaining portion 22a can be more easily removed by immersing acetone and applying ultrasonic waves.
This step can be grasped as a step of removing a part of the metal layer by removing the resist layer 22 other than the exposed resist layer.

  Next, dry etching is performed on the mold 21 in which the nickel film 24 remains, using the nickel film 24 as a mask (FIG. 2F). By this dry etching, portions other than the portion where the nickel film 24 of the mold 21 is formed are removed preferentially, and an uneven structure can be formed on the molding surface 33 which is the surface of the mold 21. Actually, the surface of the coating layer 32 made of silicon carbide (SiC) formed on the molding surface 33 of the mold 21 is etched to form an uneven structure. This uneven structure is a transfer structure of an antireflection structure in the present embodiment. Further, the depth of the concave portion of the concave-convex structure can be controlled by the time for performing dry etching.

As the dry etching, reactive ion etching (RIE) is preferable as described in detail later. Further, the processing gas used at this time is preferably a mixed gas of CF ₄ and O ₂ . In this embodiment, the flow rate of CF ₄ gas is 90 SCCM (SCCM is cm ³ / min when the gas is 25 ° C. and 1 atm), the O ₂ gas flow rate is 10 SCCM, and capacitively coupled RF plasma is used. The reactive ion etching used was performed. In addition, the RF power at this time can be 500 W.
In the present embodiment, by this reactive ion etching, for example, a concavo-convex structure with a pitch of 3 μm and a depth of 3 μm can be formed on the molding surface 33 of the mold 21. Note that the depth and the shape of the concavo-convex structure can be controlled by the etching conditions. The shape of the concavo-convex structure can be, for example, a sawtooth shape, a conical shape, a cylindrical shape, or the like.

  Finally, when the mold 21 is immersed in a nitric acid solution and the remaining nickel film 24 is removed, the mold 50 to which the present embodiment in which the transfer structure of the antireflection structure is formed on the molding surface 33 is applied. Can be manufactured. (FIG. 2 (g)). Through the above series of steps, even if the molding surface 33 of the mold 50 is a curved surface, a transfer structure having an antireflection structure can be formed by lithography. In addition, the transfer structure of this antireflection structure has good positional accuracy of the concave and convex portions, and can also reduce the distortion of the array pattern.

  In the present embodiment, a convex mold has been described as an example of the mold 21. However, the mold 21 is not limited to a convex mold, and may be a concave mold. In this case, the lithography mask 10 can be dealt with by forming the transparent film 11 having a convex shape on the side on which the nickel film 14 is formed in the step described with reference to FIG.

  In addition, the process demonstrated in the said FIG.2 (d) and FIG.2 (e) is not necessarily required. That is, when dry etching is performed, under the etching conditions that the resist remaining portion 22a can withstand, the dry etching can be directly performed using the resist remaining portion 22a as a mask in the process of FIG. In that case, by dry etching, a portion other than the portion where the resist remaining portion 22a of the mold 21 is formed is removed preferentially, and an uneven structure can be formed on the molding surface 33 of the mold 21. That is, since the resist remaining portion 22a replaces the nickel film 24, it is not necessary to form the nickel film 24, and the steps described in FIGS. 2D and 2E are not required.

(Reactive ion etching)
Next, a processing apparatus that performs reactive ion etching will be described.
FIG. 4 is a diagram illustrating an example of a processing apparatus that performs reactive ion etching using capacitively coupled RF plasma.
A processing apparatus 60 for performing reactive ion etching shown in FIG. 4 includes an installation table 62 on which an object to be processed 61 is installed, and a counter electrode 63 arranged to face the installation table 62. Further, the processing apparatus 60 includes a processing gas introduction valve 64 that introduces a predetermined processing gas into the environment around the workpiece 61, a high-frequency power source 65 that applies a high-frequency voltage between the installation table 62 and the counter electrode 63, It has an exhaust valve 66 and an exhaust pump 67 for exhausting air or process gas from the surrounding environment. Here, the workpiece 61 corresponds to, for example, the mold 21 in which the nickel film 24 described with reference to FIG.

  The installation base 62 is made of a conductive material such as stainless steel having a strength capable of mounting the workpiece 61. The installation table 62 is connected to the high frequency power supply 65 together with the counter electrode 63.

  The counter electrode 63 is made of a conductor such as stainless steel, for example. The counter electrode 63 is disposed opposite to the installation table 62 so that the counter electrode 63 is substantially parallel to the installation table 62 on which the workpiece 61 is mounted.

  The processing gas introduction valve 64 is configured such that an exhaust valve 66 and an exhaust pump 67, which will be described later, exhaust air from the environment around the workpiece 61 formed between the installation table 62 and the counter electrode 63 to obtain a predetermined degree of vacuum. After reaching, process gas is introduced.

  The high frequency power supply 65 applies a high frequency voltage between the installation table 62 and the counter electrode 63. The applied high frequency has such a frequency and voltage that the processing gas introduced by the processing gas introduction valve 64 is excited to generate plasma.

  The exhaust valve 66 and the exhaust pump 67 exhaust air from the environment around the workpiece 61 formed between the installation table 62 and the counter electrode 63 until a predetermined degree of vacuum is reached. The exhaust valve 66 and the exhaust pump 67 are used when exhausting the processing gas after the processing is completed.

A method of performing reactive ion etching using the processing apparatus 60 having the above configuration will be described below.
First, after the workpiece 61 is mounted at a predetermined position on the installation table 62, the exhaust valve 66 and the exhaust pump 67 cooperate to release air from the environment around the workpiece 61 until a predetermined degree of vacuum is reached. Discharge. After reaching a predetermined degree of vacuum, the processing gas is introduced from the processing gas introduction valve 64.

  A high frequency voltage is applied between the installation table 62 and the counter electrode 63 by the high frequency power source 65. The processing gas is decomposed by the applied high-frequency voltage, and radicals and ions are generated. Etching is performed by the generated radicals and ions colliding with the object to be processed 61, causing a chemical reaction with surface atoms to be vaporized and removed.

  Next, an apparatus and a method for press-molding an optical element using the mold 50 manufactured in the process described in FIG. 2 will be described below.

(Press molding equipment)
FIG. 5 is a configuration diagram showing an example of a press molding apparatus using a mold 50 to which the present embodiment is applied.
The press molding apparatus 100 shown in FIG. 5 is an apparatus that manufactures a glass lens as an example of an optical element by press molding in a vacuum using a pair of molds. The press molding apparatus 100 includes a lower mold 50a and an upper mold 50b, a lower soaking plate 114 and an upper soaking plate 116 that maintain the lower mold 50a and the upper mold 50b at predetermined temperatures, and a lower mold 50a. And a lower heater 118 and an upper heater 120 for raising the temperature of the upper mold 50b. The press molding apparatus 100 also includes a pressure cylinder 124 that moves the upper mold 50b, a gas introduction port 126 and a vacuum exhaust port 128 that control the molding environment of the optical glass lens, a lower mold 50a, and an upper mold 50b. And the like, and a sleeve 132 for restricting the operation of the upper mold 50b.

Both the lower mold 50a and the upper mold 50b are the mold 50 described above. In the present embodiment, the lower mold 50a is a concave mold, and the upper mold 50b is a convex mold. However, this is an example, for example, a double-concave mold. Also good. Then, the lower mold 50a and the upper mold 50b are molded by pressing and softening the optical element base material 122 to produce a glass lens.
Lower soaking plate 114 and upper soaking plate 116 are mounted on lower heater 118 and upper heater 120, respectively. The lower soaking plate 114 and the upper soaking plate 116 serve as a thermal buffer (thermal buffer) so that the heat received from the lower heating heater 118 and the upper heating heater 120 does not interfere with the production of the glass lens. A uniform state is transmitted to the lower mold 50a and the upper mold 50b. Here, the lower heater 118 and the upper heater 120 are controlled using control means (not shown) so that the surfaces of the lower mold 50a and the upper mold 50b have temperatures suitable for press molding.

As the optical element base material 122, for example, chalcogenide glass that transmits infrared light can be used as long as the manufactured glass lens is used for infrared light. Moreover, as long as it is used for uses other than infrared light, a low melting point glass containing silica as a main component and added with alumina, sodium, lanthanum oxide, or the like is exemplified. The optical element base material 122 may be, for example, a low-melting glass that is a glass having a softening temperature of 600 ° C. or lower, or an ultra-low melting glass that is a glass having a softening temperature of 400 ° C. or lower.
The pressure cylinder 124 is a drive system that moves the upper mold 50b fixed to the upper heater 120 and the upper soaking plate 116 up and down. The operation is controlled by a control means (not shown).
The vacuum exhaust port 128 prevents the oxidation at a high temperature by making the atmosphere of the mold at the time of molding a vacuum. This vacuum atmosphere is necessary for accurately transferring the uneven structure on the surfaces of the lower mold 50a and the upper mold 50b to the optical element base material 122.

A manufacturing process in which the press molding apparatus 100 having the above configuration press-molds the optical element base material 122 to manufacture a glass lens will be described below.
First, the optical element base material 122 is placed between the lower mold 50 a and the upper mold 50 b, and the optical element base material 122 is placed in the press molding apparatus 100.

Next, air is exhausted from the vacuum exhaust port 128 using an exhaust pump and a processing gas introduction pump (not shown), and the inside of the press molding apparatus 100 is evacuated. Then, the temperature of the lower heater 118 and the upper heater 120 is increased, and the optical element base material 122 is sufficiently heated to the transition point (transition temperature) Tg of the optical element base material 122 under vacuum. Temperature) The temperature is raised to At and the optical element base material 122 is softened.
Then, when the temperature reaches the yielding temperature At, the upper die 50b is moved by the pressure cylinder 124, and the optical element base material 122 is pressed by the lower die 50a and the upper die 50b.

The optical element base material 122 spreads outward by the pressure applied by the lower mold 50a and the upper mold 50b during pressing, and is accommodated in a gap formed between the lower mold 50a and the upper mold 50b, and is press-molded. Is done.
Thereafter, the press molding apparatus 100 is cooled to near the transition temperature Tg while pressure is applied, and then the pressure of the upper mold 50b is released, for example, cooled to room temperature, and the glass lens is taken out.
Through this series of steps, the concavo-convex structure on the surfaces of the lower mold 50a and the upper mold 50b is transferred to the optical element base material 122, and a glass lens having a concavo-convex structure such as an antireflection structure on the surface is manufactured.

As described in detail above, an optical element molding die is exemplified as a workpiece to be subjected to surface processing using the lithography mask of the present embodiment, and the optical element molding die is antireflective as a concavo-convex structure. Although the case where the transfer structure of the structure is formed has been described, the present invention is not limited to this. For example, a circuit board can be used as the workpiece. In this case, a circuit pattern having a concavo-convex structure can be manufactured by performing lithography using the lithography mask of this embodiment on the surface of a circuit board having a curved shape. Moreover, an optical element can be mentioned as another workpiece. In this case, an uneven structure such as an antireflection structure can be directly formed on the optical element. In addition, by changing the concavo-convex structure, it is possible to produce not only the antireflection structure but also a microlens, a wave plate, a diffraction grating (grating), a diffraction element, and the like.
In addition, the lithography mask of the present embodiment is manufactured in a shape that conforms to the entire molding surface of the optical element molding die, but is not limited to this. A shape is sufficient. In other words, a mask for lithography may be formed in a shape along a part of the shape to be subjected to lithography for a workpiece.

  In this embodiment, the method of performing capacitive coupling type reactive ion etching as dry etching has been described. However, the present invention is not limited to this, and for example, a two-wavelength capacitive coupling type plasma etching method or a magnetic field is used. Reactive ion etching method, ECR (Electron Cyclotron Resonance) etching method, inductively coupled plasma etching (ICP: Inductively Coupled Plasma), a method of irradiating a reactive ion or radical to a sample such as an ion processing apparatus having an independent ion gun All of these are available.

  A lithography mask 10 in which nickel films 14 having a circular shape with a diameter of 2 μm and arranged in a hexagonal lattice pattern with a pitch of 3 μm are formed on a transparent film 11 made of polyethylene terephthalate (PET) by the process described in FIG. Was made. Using this mask 10, a lower mold 50 a and an upper mold 50 b for forming an optical element were manufactured by the process described with reference to FIG. 2. The lower mold 50a produced here is a concave mold, and the upper mold 50b is a convex mold. The lower mold 50a and the upper mold 50b have a concavo-convex structure with a pitch of 3 μm and a depth of 3 μm.

Then, press molding of the optical element was performed using the press molding apparatus 100 described in FIG.
As the optical element base material 122, chalcogenide glass, which is an infrared light transmitting material, was used. The lower mold 50a, the upper mold 50b, and the optical element base material 122 were set in the press molding apparatus 100. After the inside of the press molding apparatus 100 was evacuated, the lower mold 50a and the upper mold 50b were heated. After the temperature of the lower mold 50a and the upper mold 50b reached 270 ° C., press molding was started. The molding pressure was 7 MPa, and after holding for 20 minutes, the molding pressure was released. Then, it cooled to room temperature and took out the lens which is an optical element. Thus, an infrared lens having a fine concavo-convex structure having a meniscus shape with a convex radius of curvature of 20 mm and a concave radius of curvature of 20.1 mm, a pitch of about 3 μm on the surface, and a depth of about 3 μm. Got. When the reflectance of the infrared light of this lens was measured, the reflectance in the wavelength range of 8 μm to 12 μm was less than 2%, and it was confirmed that a good antireflection structure was formed on the lens surface.

(A)-(g) is a figure explaining an example of the manufacturing method of the mask for lithography to which this Embodiment is applied. (A)-(g) is the figure explaining the method of performing the surface process of a to-be-processed object using the mask for lithography manufactured by the process demonstrated in FIG. It is a figure explaining the metal mold | die for optical element shaping | molding. It is a figure explaining an example of the processing apparatus which performs reactive ion etching with capacitive coupling type RF plasma. It is a block diagram which shows an example of the press molding apparatus using the metal mold | die to which this Embodiment is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Mask, 11 ... Transparent film, 12 ... Resist layer, 12a ... Hole, 13 ... Glass photomask, 14 ... Nickel film, 15a, 15b ... Mold base material, 50 ... Mold, 60 ... Processing apparatus, 100 ... Press forming equipment

Claims (15)

A method for producing a lithographic mask used for processing a surface of a workpiece, at least part of which is a curved surface,
Forming a light-shielding layer having a predetermined pattern on a substrate that transmits light irradiated when performing the lithography;
Deforming by pressing the substrate on which the light-shielding layer is formed, and forming the shape along the shape of at least a part of the surface of the workpiece;
A method of manufacturing a mask for lithography.   2. The method for manufacturing a mask for lithography according to claim 1, wherein the substrate is made of a thermoplastic resin.   3. The method for manufacturing a mask for lithography according to claim 2, wherein the thermoplastic resin is polyethylene terephthalate (PET).   The method of manufacturing a mask for lithography according to claim 1, wherein the light shielding layer is made of a metal material. A method of forming a concavo-convex structure on the surface of a workpiece, wherein at least a part of the surface shape is a curved surface,
Forming a resist layer on the surface of the workpiece;
A light shielding layer having a predetermined pattern is formed on a substrate, and the substrate on which the light shielding layer is formed is deformed by pressing to form a shape along at least a part of the surface of the workpiece. Installing a mask on the surface of the resist layer;
Exposing the resist layer by exposing and transferring the pattern to the resist layer; and
Removing the exposed resist layer by developing; and
Forming a concavo-convex structure corresponding to the pattern on the surface of the workpiece by performing dry etching;
A surface processing method comprising:   The surface processing method according to claim 5, wherein the mask is a film mask.   The surface processing method according to claim 5, wherein the dry etching is reactive ion etching.   A step of forming a metal layer between a step of removing the exposed resist layer and a step of forming an uneven structure corresponding to the pattern on the surface of the workpiece; and a resist layer other than the exposed resist layer The surface processing method according to claim 5, further comprising a step of removing a part of the metal layer by removing the metal. A method of forming a concavo-convex structure on a molding surface having a curved surface, and manufacturing a mold for optical element molding,
Forming a resist layer on the molding surface;
A mask manufactured by forming a light-shielding layer having a predetermined pattern on a substrate and deforming the substrate on which the light-shielding layer is formed by pressing to form a shape along at least a part of the shape of the molding surface. Installing on the surface of the resist layer;
Exposing the resist layer by exposing and transferring the pattern to the resist layer; and
Removing the exposed resist layer by developing; and
Forming a concavo-convex structure corresponding to the pattern on the molding surface by performing dry etching;
The manufacturing method of the metal mold | die for optical element shaping | molding characterized by including these.   The method for producing a mold for molding an optical element according to claim 9, wherein the uneven structure is a transfer structure having an antireflection structure.   The method for producing a mold for molding an optical element according to claim 9 or 10, wherein the dry etching is reactive ion etching.   Between the step of removing the exposed resist layer and the step of forming an uneven structure corresponding to the pattern on the molding surface, removing the resist layer other than the exposed resist layer The method for producing a mold for molding an optical element according to claim 9, further comprising a step of removing a part of the metal layer.   An uneven structure is formed on the surface of the optical element base material by press-molding the optical element base material using the optical element manufacturing apparatus to which the optical element molding die manufactured by the method according to claim 12 is attached. Forming an optical element.   The method of manufacturing an optical element according to claim 13, wherein the optical element base material is made of chalcogenide glass.   15. The method of manufacturing an optical element according to claim 13, wherein the uneven structure is an antireflection structure.

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