JP2008216610A - Method of manufacturing optical component for laser beam machining - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical component for laser beam machining, by which fine ruggedness can be formed on substrate surface having insulation properties simply and in a short period to impart nonreflective function to a substrate. <P>SOLUTION: The method of manufacturing the optical component, which transmits laser beams at laser beam machining, comprises a process (a) of directly forming a photoresist film 3, 13 on the surface of substrate 4, 14 having insulation properties; a process (b) of forming an un-photosensitive part 2, 12 presenting a fine rugged shape by exposing the photoresist film 3, 13 with laser beams L; and a process (c) of transferring the rugged shape of the un-photosensitive part 2, 12 to the substrate 4, 14 by etching and thereby, forming fine ruggedness on the surface of the substrate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing an optical component for laser processing. More specifically, the present invention relates to a method of manufacturing an optical component that transmits laser light during laser processing and has a surface having a non-reflection function.

  In an optical component used for transmitting laser light and condensing the laser light in laser processing, it is necessary to suppress reflection on the surface of the optical component on which the laser light is incident as much as possible in order to increase the transmittance of the laser light. There is. Therefore, conventionally, in order to provide an AR function (antireflection function) to an optical component, a surface having a refractive index different from that of the substrate is coated on the surface of the substrate constituting the optical component to form an antireflection film. Has been done.

  However, since the substrate and the antireflection film absorb laser light, although slightly, the temperature rises due to laser light irradiation. The substrate and the antireflection film differ not only in refractive index but also in thermal expansion coefficient, but depending on the degree of temperature rise, the antireflection film may peel off from the substrate due to the difference in thermal expansion.

  Further, when the substrate is coated with the substance, the surface of the substrate is cleaned.If this cleaning is insufficient and even a slight amount of residual impurities exist between the substrate and the antireflection film, the laser beam is irradiated. Absorption of laser light occurs in the portion where residual impurities exist. As a result, the substrate or the antireflection film may be destroyed starting from this portion.

  Furthermore, since the antireflection film generally has a larger absorption coefficient of laser light than the substrate, the temperature of the optical component increases when the substrate coated with the antireflection film is used as an optical component rather than when the substrate is used alone. Is likely to occur. Laser processing condenses laser light with an optical component and heats and melts the workpiece. When the temperature of the optical component rises, its refractive index changes, and the focal position changes accordingly. If the focal position fluctuates, sufficient focusing cannot be performed and laser processing cannot be performed.

  Therefore, as a method for giving an AR function to an optical component without using such an antireflection film, it has been proposed to form minute irregularities having an inclined surface on the surface of the substrate (see Patent Document 1).

  The method described in Patent Document 1 is a method in which a mask is provided on the surface of silicon, and the exposed surface of silicon is processed by etching. A mask made of a material that is etched at a slower rate than the silicon is used. A plurality of two-dimensional arrays are provided, and reactive ion etching is performed until the mask has a predetermined size. The mask is formed by drawing a positive type electronic resist coated on the surface of a silicon substrate so as to form a predetermined two-dimensional array by an electron beam, and removing the drawn portion by development, and then removing the resist and exposing it. The metal is deposited on the substrate surface and the remaining resist, and finally the metal on the resist is removed together with the resist by a lift-off method, leaving only the metal on the substrate.

JP 2004-107765 A

  However, in the method described in Patent Document 1, since a mask having a predetermined shape is drawn using an electron beam, it takes a long time to draw a pattern capable of forming minute irregularities. As a result, the manufacturing cost is high.

  When an insulating substrate is used, electrons accumulate in the substrate and are charged up. This prevents the electron beam from entering straight and makes it impossible to draw as desired. In order to avoid this, it is necessary to form a conductive film on the substrate and form a resist on the conductive film. And it is necessary to let an electron escape from the contact provided in the said electrically conductive film. The formation of such a conductive film and contact takes time and causes further cost increase.

  The present invention has been made in view of such circumstances, and a laser capable of easily forming fine irregularities on a surface of an insulating substrate in a short time and imparting a non-reflective function to the substrate. It aims at providing the manufacturing method of the optical component for a process.

The method for producing an optical component for laser processing according to the present invention is a method for producing an optical component that transmits laser light during laser processing,
(A) a step of directly forming a photoresist film on the surface of an insulating substrate;
(B) exposing the photoresist film with a laser beam to form an unexposed portion exhibiting a fine uneven shape; and (c) transferring the uneven shape of the unexposed portion to a substrate by etching to form a surface of the substrate. It includes a step of forming fine irregularities.

  In the method for manufacturing an optical component for laser processing according to the present invention, fine irregularities are formed by exposing a photoresist film on an insulating substrate to a laser beam. There is no need to provide a film between the substrate and the photoresist film. Further, it is not necessary to form a contact for releasing electrons from the conductive film. Therefore, the manufacturing process can be simplified.

  Further, unlike the electron beam, the laser light can form fine irregularities in a short time, and thus the manufacturing cost can be greatly reduced.

  In the step (b), it is preferable to form a plurality of cones in the unexposed portion by controlling the output of the photoresist film while scanning the laser beam. In this case, a concavo-convex structure composed of a plurality of cones can be formed on the surface of the substrate through a subsequent transfer process by etching. The concavo-convex structure composed of a plurality of cones has an extremely low reflectance and is ideal as a non-reflective structure, and can reliably prevent reflection of laser light on the substrate surface.

  The substrate is made of a group 2-6 compound such as ZnSe or ZnS, a group 3-5 compound such as GaAs or GaN, a group 4 element such as Si or Ge, diamond such as natural diamond, synthetic diamond or CVD diamond, quartz or alumina. It can consist of oxides, such as. The substrate is quartz in the case of a carbon dioxide laser with a wavelength of 9.3 to 10.6 μm, ZnSe or CVD diamond, an LD laser of about 0.5 to 1.1 μm, a YAG laser, or a fiber laser. Is preferred. In this case, these materials have a large transmittance in each wavelength region, and a thermal lens effect (a phenomenon in which the refractive index changes due to the heat generation of the substrate and the optical characteristics such as the focal length change) is generated. Hard to do. In particular, diamond such as CVD diamond has a good thermal conductivity and is suitable for a high-power carbon dioxide laser.

  The etching is preferably performed by an IPC dry etching method. In this case, since etching with high anisotropy (perpendicularity) is possible, it is effective to transfer the shape of the photoresist as it is to the substrate.

  According to the method for producing an optical component for laser processing of the present invention, it is possible to easily form fine irregularities on an insulating substrate surface in a short time and to impart a non-reflective function to the substrate.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a method for manufacturing an optical component for laser processing of the present invention (hereinafter also simply referred to as “manufacturing method”) will be described in detail with reference to the accompanying drawings. In addition, in order to make it intelligible, in FIG. 1-3, the dimension of the thickness direction of a component, etc. is drawn exaggeratingly.

  The manufacturing method of the present invention forms fine irregularities on the surface of an insulating substrate constituting an optical component used for condensing laser light in laser processing, and a photoresist film is directly formed on the surface of the substrate. Forming a non-exposed portion exhibiting a fine uneven shape by exposing the photoresist film with a laser beam, and transferring the uneven shape of the unexposed portion to a substrate by etching to form a fine surface A step of forming a rough surface.

  The insulating substrate is not particularly limited in the present invention, and a substrate made of a material having a function of transmitting laser light can be widely used. For example, 2-6 such as ZnSe and ZnS can be used. Group III compounds, Group 3-5 compounds such as GaAs and GaN, Group 4 elements such as Si and Ge, diamonds such as natural diamond, synthetic diamond and CVD diamond, and oxides such as quartz and alumina can be used. . Among these, when the laser beam transmittance is larger, the temperature rise due to absorption of the laser beam is less and the thermal lens effect is less likely to occur. Therefore, when the laser beam is a carbon dioxide laser with a wavelength of 9.3 to 10.6 μm, ZnSe or In the case of diamond, an LD laser of about 0.5 to 1.1 μm, a YAG laser, and a fiber laser, it is preferable to use one made of quartz. Further, the shape of the substrate is not particularly limited in the present invention, and at least a part of the surface that becomes the incident surface or the emitting surface of the laser light is configured by a plane, a spherical surface, an aspherical surface, a free curved surface, or the like. can do.

  A photoresist is coated on the surface of the substrate by a spin coater or the like, and then the substrate coated with the photoresist is heated at 80 to 110 ° C. for about 2 to 30 minutes, thereby forming a photoresist film directly on the substrate. This heating can be performed, for example, by placing it on a hot plate heated to the temperature. The coating thickness of the photoresist is selected based on the height difference of fine irregularities formed on the surface of the substrate, the wavelength used, and the like, but generally 0.5 to 20 μm is a standard. In the present invention, since drawing is performed using a laser beam, it is not necessary to use a dedicated resist such as an electron beam, and a commonly used photoresist such as AZP4620 (manufactured by AZ Electronics Materials) is used. Can be adopted as appropriate. Further, it is not necessary to provide a conductive film between the insulating substrate and the photoresist film as in the case of drawing using an electron beam, and it is not necessary to form a contact for releasing electrons from the conductive film. Therefore, the manufacturing process can be simplified.

  The photoresist film formed on the substrate is exposed with a laser beam to form an unexposed portion having a fine uneven shape on the photoresist film. This uneven shape can be formed by controlling the output (exposure intensity) while scanning a laser beam on the photoresist film. For example, in a partially enlarged view of FIG. 1C, reference numeral 1 denotes a photosensitive portion exposed by the laser light L, and 2 denotes an unexposed portion not exposed by the laser light L. In this figure, the output of the laser beam L when it reaches the point indicated by x of the photoresist film 3 is set to a size that can be exposed by the thickness h of the photoresist film 3, and at the point indicated by y of the photoresist film 3. By controlling the speed at which the laser beam L is scanned and the output so that the output of the laser beam L is zero, the sawtooth-shaped unexposed portion 2 as shown in FIG. Can be formed. In order to perform such control, a correlation between the intensity of the laser beam used and the photosensitive thickness of the photoresist film is grasped in advance. Although the unevenness shown in FIGS. 1 and 2 is expressed as a flat surface, the actual unevenness has a three-dimensional shape as shown in FIG. Therefore, the scanning speed of the laser beam and its output are changed not only in the horizontal direction in FIGS. In the present invention, since drawing is performed using laser light, fine irregularities can be formed in an extremely short time compared to the case of using an electron beam, and the manufacturing cost can be significantly reduced.

  In addition, in order for the substrate surface to have a non-reflecting function with respect to incident light, it is necessary to form fine irregularities smaller than the wavelength of the laser light used on the surface of the substrate. Specifically, for the case of forming irregularities on the substrate surface with a plurality of cones 10 as shown in FIG. 3 for processing laser light having a wavelength of 0.5 to 10.6 μm, for example, the height of the cones By setting h (see (f) in FIG. 1) to 0.5 to 20 μm and the diameter d of the circle on the bottom surface of the cone to 0.4 to 20 μm, a non-reflective function can be imparted to the substrate surface. it can.

  The substrate exposed by the laser light is cleaned after being developed. The development of the substrate can be performed by, for example, using an AZ developer (manufactured by AZ Electronic Materials) to swing the substrate for about 1 to 5 minutes. The substrate can be cleaned by, for example, rocking the substrate for about 1 to 5 minutes in ultrapure water (resistivity ≧ 18 MΩcm). The exposed portion exposed by the laser beam is removed from the photoresist film in the development process.

  The cleaned substrate is heated at 80 to 110 ° C. for about 2 to 30 minutes. This heating can be performed, for example, by leaving it on a hot plate heated to the temperature.

Next, the substrate is etched to transfer the uneven shape of the unexposed portion of the photoresist film to the substrate. As the etching method, a dry etching method or a wet etching method can be used. However, since the resist shape needs to be transferred to the substrate as it is, it is preferable to use the IPC dry etching method. Although depending on the type of the substrate and the photoresist film, when the IPC dry etching method is used, the IPC input power and the bias input power can be set to, for example, 100 to 800 W and 100 to 700 W, respectively. Further, the pressure can be 0.1 to 10 Pa, and the flow amount of gas can be BCl ₃ 1 to 50 sccm and Ar 1 to 100 sccm. Through the above steps, fine unevenness providing a non-reflective function can be formed on the surface of the insulating substrate.

  Next, although the Example of the manufacturing method of this invention is described, this invention is not limited only to this Example from the first.

[Example 1]
Both surfaces were flat, and an optical component having fine irregularities formed on both the surfaces was manufactured.
AZP4620 (Clariant Japan Photoresist) is applied to one surface of a circular substrate 4 (see FIG. 1A) made of ZnSe (zinc selenide) having a diameter of 50 mm and a thickness of 5 mm so as to have a thickness of 6 μm. Then, the substrate 4 coated with the photoresist was placed on a hot plate and heated at 90 ° C. for 10 minutes to form a photoresist film 3 on the substrate 4 (see FIG. 1B).

  Next, the photoresist film 3 was exposed by scanning the laser beam L while changing the intensity of the laser beam L (see FIG. 1C). Based on the correlation between the exposure laser intensity obtained in advance and the photosensitive thickness of the photoresist film, the intensity of the laser beam is controlled so that an unexposed portion 2 composed of a plurality of cones (see FIG. 3) is formed. did. The scanning speed and intensity of the laser beam were controlled so that cones having a height H of 6 μm and a bottom circle having a diameter d of 3 μm were continuously formed without gaps. The diameter of the used laser beam was about 0.4 μm, and the intensity of the laser beam was controlled within a range of 0.1 to 20 mW.

  Next, the exposed substrate 4 was developed with AZ-Developer (manufactured by AZ Electronic Materials) for 4 minutes, and the photosensitive portion 1 of the photoresist film 3 was removed. After the development, the substrate 4 was washed by shaking in ultrapure water (resistivity ≧ 18 MΩcm) for 2 minutes, and then the washed substrate 4 was placed on a hot plate and heated at 100 ° C. for 5 minutes (FIG. 1). (See (d)).

  Next, the substrate 4 was etched by the ICP dry etching method under the conditions shown in Table 1. The photoresist film 3 and the substrate 4 are etched at the same speed, and the concavo-convex shape formed of a plurality of cones formed on the unexposed portion 2 of the photoresist film 3 is transferred onto the substrate 4 (FIG. 1 (e), (Refer to (f)). FIG. 1E schematically shows a stage in the middle of the etching process, in which the upper part of the cone is constituted by the unexposed part 2 of the photoresist film 3 and the lower part of the cone is constituted by the substrate 4. Has been.

  An uneven shape composed of a plurality of cones was formed on the substrate 4 on the other surface of the substrate 4 under the same conditions as described above.

  As a result of measuring the surface shape of the obtained substrate 4 with an optical three-dimensional shape measuring instrument, it was confirmed that the substrate was finished with a surface accuracy of ± 0.2 μm. Further, the transmittance of the substrate 4 with respect to laser light having a wavelength of 10.6 μm was 99.0% or more.

[Example 2]
Fine irregularities were formed on the concave surface of the optical component in which one surface was a concave surface and the other surface was a single surface.

  AZP4620 is applied to a concave surface of a circular substrate 14 made of ZnSe having a concave surface and a flat surface shown in FIG. 2A and having a diameter of 25 mm so as to have a thickness of 6 μm. The photoresist film 13 was placed on the substrate 14 and heated at 90 ° C. for 10 minutes (see FIG. 2B).

  Subsequently, the photoresist film 13 was exposed by scanning the laser beam L while changing the intensity of the laser beam L (see FIG. 2C). As in the first embodiment, the laser beam L of the laser beam L is formed so that the unexposed portion 12 composed of a plurality of cones is formed based on the correlation between the exposure laser intensity obtained in advance and the photosensitive thickness of the photoresist film. Strength was controlled. The scanning speed and intensity of the laser light were controlled so that a cone having a height of 6 μm and a bottom circle with a diameter of 3 μm was continuously formed without a gap. The diameter of the used laser beam was about 0.4 μm, and the intensity of the laser beam was controlled within a range of 0.1 to 20 mW.

  Next, the exposed substrate 14 was developed by swinging for 4 minutes with an AZ-developer, and the exposed portion of the photoresist film 13 was removed. After the development, the substrate 14 was cleaned by shaking in ultrapure water (resistivity ≧ 18 MΩcm) for 2 minutes, and then the cleaned substrate 14 was placed on a hot plate and heated at 100 ° C. for 5 minutes.

  Next, the substrate 14 was etched by the ICP dry etching method under the conditions shown in Table 1. The photoresist film 13 and the substrate 14 were etched at the same speed, and the concavo-convex shape formed of a plurality of cones formed on the unexposed portion 12 of the photoresist film 13 was transferred onto the substrate 14.

  As a result of measuring the surface shape of the obtained substrate 4 with an optical three-dimensional shape measuring instrument, it was confirmed that the substrate was finished with a surface accuracy of ± 0.2 μm. Further, the transmittance of the substrate 4 with respect to laser light having a wavelength of 10.6 μm was 99.0% or more.

  It should be noted that the embodiment disclosed this time is merely an example in all respects and is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is sectional explanatory drawing which shows typically one Embodiment of the manufacturing method of this invention. It is sectional explanatory drawing which shows typically a part of other embodiment of the manufacturing method of this invention. It is perspective explanatory drawing of the uneven structure which consists of a cone formed in the board | substrate surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive part 2 Unexposed part 3 Photoresist film 4 Substrate 12 Unexposed part 13 Photoresist film 14 Substrate

Claims (4)

A method of manufacturing an optical component that transmits laser light during laser processing,
(A) a step of directly forming a photoresist film on the surface of an insulating substrate;
(B) a step of exposing the photoresist film with a laser beam to form an unexposed portion exhibiting a fine uneven shape; and (c) transferring the uneven shape of the unexposed portion onto the substrate by etching. A method for producing an optical component for laser processing, comprising the step of forming fine irregularities on the substrate.   2. The method of manufacturing an optical component for laser processing according to claim 1, wherein in the step (b), a laser beam is scanned on the photoresist film and an output thereof is controlled to form a plurality of cones in an unexposed portion.   The method for producing an optical component for laser processing according to claim 1, wherein the substrate is made of a 2-6 group compound, a 3-5 group compound, a 4 group element, diamond, or an oxide.   The method for producing an optical component for laser processing according to claim 1, wherein the etching is performed by an IPC dry etching method.

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