JP4576961B2 - Method for manufacturing replica diffraction grating - Google Patents

Description

  The present invention relates to a replica diffraction grating used in various optical instruments such as a spectrophotometer.

  Conventionally, a method of manufacturing a replica diffraction grating from a master diffraction grating has been widely adopted when mass-producing diffraction gratings. The method will be schematically described based on the description in Patent Document 1 and the like.

  First, a thin film of a metal such as aluminum is vapor-deposited on one surface of a glass substrate, and a grating groove is formed in the thin film to manufacture a master diffraction grating. Using this master diffraction grating as a mother mold, a thin oil film is formed as a release agent on the grating surface, and a metal thin film is formed thereon by vacuum deposition. Thereafter, the replica substrate is bonded onto the metal thin film via an adhesive, and when the adhesive is cured, the replica substrate is peeled off from the mother die. As a result, the metal thin film on which the grating grooves are formed moves to the replica substrate side in an inverted state, and the replica diffraction grating is completed.

  Such a diffraction grating is mainly used in a spectroscope, but the surface roughness of the grating surface of the diffraction grating causes stray light. Therefore, it is desirable that this surface roughness be as small as possible. Conventionally, glass (soda glass), quartz glass, etc. have been used as replica substrates, and in order to increase the adhesion area for the purpose of improving the adhesion of the adhesive, the surface to which the adhesive is applied has a fine uneven surface. The one that is used is used. However, when a metal thin film is affixed to such a replica substrate via an adhesive, the adhesive shrinks with curing such as thermosetting, so that the effect of the surface roughness of the groove surface is the replica surface, that is, the replica diffraction grating. It also appears on the lattice plane.

  In a spectroscope, if the surface roughness of the grating surface of the diffraction grating is large, the scattering of incident light increases, and the scattered light is reflected in the same direction as the regular diffracted light and becomes stray light. For example, when analyzing a sample in the spectral mode of a spectroscope, the monochromatic light wavelength-separated by the diffraction grating is incident on the sample and the degree of absorption is measured. However, the incident light has a wavelength other than the monochromatic light, that is, stray light. When it is mixed, it becomes noise, which becomes a major factor that lowers analysis sensitivity and analysis accuracy. Such stray light is not a problem when the wavelength of light to be handled is relatively long, specifically, when it is infrared light or visible light. In particular, when the wavelength to be handled is shortened, for example, soft X-rays, etc. This is a big problem when performing spectroscopy.

Japanese Patent Laid-Open No. 7-261010

  The present invention has been made in view of such points, and an object of the present invention is to provide a replica diffraction grating capable of reducing the generation of stray light by suppressing the surface roughness of the grating surface. is there.

According to a first aspect of the present invention for solving the above problems, a metal thin film is formed on a grating surface of a master diffraction grating, the metal thin film and a replica substrate are brought into close contact with each other through an adhesive, and then the replica substrate is mastered. In the method of manufacturing a replica diffraction grating , which is separated from the diffraction grating and forms a grating surface by reversing and bonding the metal thin film to the replica substrate.
Together with the adhesive roughness of the surface to be bonded to the metal thin film through the replica substrate is polished in advance so as to be less shiny surface 1 nm RMS, as characterized by the incorporation of a coupling agent to the adhesive Yes.

Further, the second invention made to solve the above-mentioned problem is that the metal thin film is formed on the grating surface of the master diffraction grating, and the metal thin film and the replica substrate are brought into close contact with each other through an adhesive. In the method of manufacturing a replica diffraction grating , which is separated from the master diffraction grating and forms a grating surface by reversing and bonding the metal thin film to the replica substrate,
With the surface to be bonded to the metal thin film through the adhesive of the replica substrate surface roughness polished in advance so as to be less shiny surface 1 nm RMS, as characterized by applying a coupling agent to the adhesive surface Yes.

The method for manufacturing a replica diffraction grating according to the present invention may be applied to either a planar diffraction grating or a concave diffraction grating.

In the replica diffraction grating manufacturing method according to the first aspect of the invention, the surface of the replica substrate on which the metal thin film is reversely bonded via the adhesive, that is, the surface serving as the foundation of the grating groove is a glossy surface and the surface roughness is Since it is small, the influence of the curing shrinkage of the adhesive can be suppressed even after the adhesive is cured, and the surface roughness of the lattice surface can be reduced. Also, since the adhesive is mixed with, for example, a coupling agent typified by a silane coupling agent that improves the bondability between the organic component and the inorganic component, the above-mentioned reversal adhesion surface is a ground surface in the replica substrate. Even if it is a glossy surface, high adhesion can be ensured, and a metal thin film can be firmly attached to the replica substrate to ensure high reliability.

In the replica diffraction grating manufacturing method according to the second aspect of the invention, the coupling agent is applied to the adhesive surface of the replica substrate, which is a glossy surface, instead of previously mixing the coupling agent with the adhesive. The master diffraction grating on which the metal thin film is formed is adhered. Also by this, since a coupling agent improves adhesiveness, a metal thin film can be firmly stuck on a replica board | substrate.

Here, the better the surface roughness of the shiny side of the replica substrate is small of course, in the present invention the surface roughness is less 1 nm RMS. Since the surface roughness of the reverse surface of the reverse adhesion surface of the metal thin film of the conventional general replica substrate is about 50 nmRms, by reducing this to 1 nmRms or less, the surface roughness is much higher than the stray light generated in the conventional replica diffraction grating. The level can be kept low.

That is, according to the method for manufacturing a replica diffraction grating according to the present invention, it is possible to achieve the same surface roughness as that of the master diffraction grating, and greatly reduce stray light due to unwanted scattering when used in a spectrometer. can do. Thereby, analysis accuracy and analysis sensitivity can be improved, and it contributes to a significant improvement in analysis accuracy particularly in a short wavelength region such as soft X-rays.

  Hereinafter, a manufacturing method of an embodiment of a replica diffraction grating according to the present invention will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing the manufacturing procedure of the replica diffraction grating of this embodiment.

  First, a glass substrate (float glass) 11 having a size of 30 mm × 33 mm × 6.8 mm is coated with OFPR5000 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) with a thickness of 0.4 μm as a photoresist, and holographic exposure method is applied thereto. A resist pattern of lattice grooves (density: 1600 lines / mm) is formed by (laser wavelength: 441.6 nm). Next, a lattice groove having a sawtooth shape with a groove cross section of 4 ° is formed by ion beam etching using the resist pattern as a mask, and a metal such as aluminum, gold, or platinum having a film thickness of 0.2 μm is formed thereon. The thin film 12 is formed by vacuum deposition. In this way, the master diffraction grating 10 having a grating groove whose surface is coated with the metal thin film 12 is completed (state shown in FIG. 1A).

  Next, a thin release agent film 13 having a thickness of about 1 nm is formed on the grating surface of the master diffraction grating 10 by using silicon grease or the like (the state shown in FIG. 1B), and then the film thickness is formed by vacuum deposition. An aluminum thin film 23 having a thickness of 0.2 μm is formed (state shown in FIG. 1C). This aluminum thin film 23 later covers the grating surface of the replica diffraction grating.

  Next, a replica substrate (float glass, size: 30 mm × 33 mm × 6.8 mm) 21 having a glossy surface by polishing the adhesive surface 21a is prepared (the state shown in FIG. 1 (d)), and the surface is made of a fluorinated solvent. After washing with AK-255 (manufactured by Asahi Glass Co., Ltd.) or the like, an adhesive (thermosetting epoxy resin) 22 mixed with a silane coupling agent is applied (state of FIG. 1 (e)). Then, the replica substrate 21 and the master diffraction grating 10 in the state shown in FIG. 1C are bonded to each other through the adhesive 22 and pressed with an appropriate pressure. As a result, the adhesive 22 spreads so as to fill a groove having a sawtooth cross section in the aluminum thin film 23 (the state shown in FIG. 1 (f)). At this time, the film thickness of the adhesive 22 is about 10 μm.

  The replica substrate 21 is preferably made of a low-expansion material in order to suppress the change in the groove interval due to the temperature rise. Examples of the replica substrate 21 include quartz glass, Zerodur (manufactured by SCHOTT, Zerodur: Low expansion crystal glass such as registered trademark of Carl Zeiss). However, when using a diffraction grating in an environment with a small temperature rise, use cheaper materials such as BK7 (a kind of synthetic quartz), Pyrex (registered trademark of Corning) glass, soda glass, etc. Can do.

  Furthermore, this is accommodated in a baking furnace, and heat is applied under conditions of 60 ° C. and about 24 hours to accelerate the curing of the adhesive 22. When the adhesive 22 is sufficiently cured, the replica substrate 21 is peeled off from the master diffraction grating 10 with the release agent film 13 as a boundary. Then, the aluminum thin film 23 formed in a sawtooth shape in cross section is peeled off in a state where it is fixed to the replica substrate 21 via the adhesive 22 (the state shown in FIG. 1 (g)). After the peeling, the release agent film 13 remaining on the grating surface of the replica diffraction grating 20 is removed by washing with the above-described fluorinated solvent. In this way, the replica diffraction grating 20 in which the grating grooves are formed by reversing and transferring the grating grooves of the master diffraction grating 10 is obtained.

  For example, KBM-403 (manufactured by Shin-Etsu Chemical Co., Ltd.) is useful as the silane coupling agent. Silane coupling agents have both reactive groups that chemically bond with organic materials such as amino groups, vinyl groups, and epoxy groups, and reactive groups that chemically bond with inorganic materials such as glass, metal, and silica in one molecule. It acts as a binder between an organic material and an inorganic material that are usually difficult to bond. Therefore, by mixing this silane coupling agent with the epoxy resin adhesive, it is possible to enhance the adhesion to both the replica substrate 21 and the aluminum thin film 23 which are glass. In particular, although the adhesive surface 21a of the replica substrate 21 is a glossy surface and is difficult to adhere an adhesive, sufficient adhesiveness can be ensured by the action of the silane coupling agent.

  The surface roughness of the grating surfaces of the master diffraction grating and replica diffraction grating actually produced by the above procedure was evaluated by stray light. With respect to the master diffraction grating 10 in the state of FIG. 1A, the stray light value at a wavelength of 220 nm was measured with a spectroscope, and as a result, it was 0.003%. On the other hand, as for the completed replica diffraction grating 20, the stray light value at a wavelength of 220 nm was measured with a spectroscope, and as a result, it was 0.003%, which was confirmed to be the same result as the master diffraction grating. Incidentally, the stray light value of the replica diffraction grating was 0.006% when the conventional method, that is, when the replica substrate had an adhesive surface and no adhesive was mixed with the adhesive. That is, it was confirmed that the stray light value was suppressed to about half in the replica diffraction grating of this example compared to the conventional replica diffraction grating.

  In the above description, the silane coupling agent is mixed with the adhesive itself in order to improve the adhesiveness between the replica substrate 21 and the aluminum thin film 23, but the main problem here is that the replica substrate is a glossy surface. It is difficult for the adhesive to adhere to the adhesive surface 21a. Therefore, instead of mixing the adhesive with the silane coupling agent, the adhesive surface 21a of the replica substrate 21 having a glossy surface is washed, and then the silane coupling agent is first applied thinly, and a thermosetting epoxy resin is applied thereon. A certain adhesive 22 may be applied. That is, if the adhesive 22 is heated and cured after the thin layer of the silane coupling agent is sandwiched between the adhesive surface 21a of the replica substrate 21 and the adhesive 22, the operation of the silane coupling agent is sufficient. Adhesiveness can be ensured.

  In addition, although the said Example is an example which applied this invention to the plane diffraction grating, it is clear that it is applicable also to the concave diffraction grating whose grating surface is a curved surface. In addition, it is apparent that other points are included in the scope of the claims of the present application even if appropriate changes or modifications are made within the scope of the present invention.

The schematic sectional drawing which shows the manufacturing process of the replica diffraction grating which is one Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Master diffraction grating 11 ... Glass substrate 12 ... Metal thin film 13 ... Release agent film 20 ... Replica diffraction grating 21 ... Replica substrate 21a ... Adhesive surface 22 ... Adhesive 23 ... Aluminum thin film

Claims (2)

A metal thin film is formed on the grating surface of the master diffraction grating, and after the metal thin film and the replica substrate are brought into close contact with each other through an adhesive, the replica substrate is peeled off from the master diffraction grating, and the metal thin film is inverted to the replica substrate. In the method of manufacturing a replica diffraction grating that forms a grating surface by bonding,
Together with the adhesive roughness of the surface to be bonded to the metal thin film through the replica substrate is polished in advance so as to be less shiny surface 1 nm RMS, and characterized by incorporating a coupling agent into the adhesive A method of manufacturing a replica diffraction grating. A metal thin film is formed on the grating surface of the master diffraction grating, and after the metal thin film and the replica substrate are brought into close contact with each other through an adhesive, the replica substrate is peeled off from the master diffraction grating, and the metal thin film is inverted to the replica substrate. In the method of manufacturing a replica diffraction grating that forms a grating surface by bonding,
With the surface to be bonded to the metal thin film through the adhesive of the replica substrate surface roughness polished in advance so as to be less shiny surface 1 nm RMS, and characterized by applying a coupling agent to the adhesive surface A method of manufacturing a replica diffraction grating.

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