JP2010052398A - Mold, method for manufacturing the same, and method for manufacturing optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold capable of obtaining a fine one-dimensional periodic structure with a preferred height, the method for manufacturing the same, and the method for manufacturing an optical element having a fine one-dimensional periodic structure. <P>SOLUTION: In the mold, projection parts 12 extending in one direction on the surface 11a of a base plate 11 are formed periodically, at a predetermined interval in a direction B perpendicular to an extending direction A. In the projection parts 12, there is no flat portion parallel to the surface 11a of the base plate 11 in the tip portion thereof and the cross sections perpendicular to the extending direction A have a tapered shapes. The mold is manufactured, by forming a metal mask layer on the surface of the base plate, drawing the periodic structure by applying a resist on the metal mask layer, developing, and dry-etching the base plate. Furthermore, a glass material or a resin material is press molded by using the mold. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a mold, particularly a mold for molding an optical element having a fine one-dimensional periodic structure in the order of the wavelength of light, a manufacturing method thereof, and a manufacturing method of the optical element.

  In general, optical elements such as aspheric lenses and lens arrays are often mass-produced by a precision press molding technique (hereinafter also referred to as a molding method). On the other hand, a micro optical element having a diffraction function having a fine one-dimensional periodic structure in the order of the wavelength of light is manufactured by forming a fine structure pattern on the surface of a glass substrate by lithography and directly processing it by an etching method or the like. Therefore, high cost was required for mass production.

  Therefore, in recent years, development has been advanced in which the mold method is applied to the production of optical elements having these fine structures (see, for example, Patent Document 1). As shown in FIG. 14, a mold conventionally proposed in Patent Document 1 or the like is formed by forming a fine convex 112 on a surface 111 a of a substrate 111 so as to extend in one direction, and the period of the convex 112. P is 500 nm, height H is 440 nm, space width S is 300 nm, line width L is 200 nm, and the sidewall angle α of the convex portion 112 is 84 °.

However, when a glass material is press-molded using such a mold 100, the glass material 20 is not sufficiently filled between the convex portions 112 as shown in FIG. 15, and is necessary for a fine periodic structure of a molded product. There is a problem that a high height cannot be obtained. The reason for this is considered to be that the tip of the convex portion 112 is flat, so that a sufficient force to push (fill) the glass material 20 between the convex portions 112 cannot be obtained.
Japanese Patent No. 2992596

  Accordingly, an object of the present invention is to provide a mold capable of obtaining a fine one-dimensional periodic structure having a preferable height, a method for producing the mold, and a method for producing an optical element having a fine one-dimensional periodic structure. .

In order to achieve the above object, the first aspect of the present invention provides:
A mold having a one-dimensional periodic structure in which convex portions extending in one direction on the surface of the substrate are periodically formed at predetermined intervals in a direction perpendicular to the extending direction of the convex portions,
The convex part has a tapered shape in a cross section perpendicular to the extending direction without a flat part parallel to the surface of the substrate at the tip part,
It is characterized by.

  In the mold according to the first aspect, the convex portion periodically formed at a predetermined interval has a cross section orthogonal to the extending direction without a flat portion parallel to the surface of the substrate at the tip portion. Because of its tapered shape, when a glass material or a resin material is press-molded, the force for filling the molding material between the convex portions acts greatly on the molding material. A fine periodic structure can be formed at a required height.

The second aspect of the present invention is:
A method for manufacturing a mold according to the first embodiment,
Forming a metal mask on the surface of the substrate;
Applying a resist on the metal mask;
Drawing and developing a periodic structure on the resist; and
Dry etching the substrate using a reactive gas or a mixed gas of a reactive gas and an inert gas;
It is provided with.

The third aspect of the present invention is:
Using a mold that is the first form or a mold that is manufactured by the method that is the second form, press molding a glass material or a resin material to form an optical element having a fine one-dimensional periodic structure. It is characterized by.

  Hereinafter, examples of the mold according to the present invention, the manufacturing method thereof, and the manufacturing method of the optical element will be described.

(See mold, Fig. 1 and Fig. 2)
FIG. 1 shows a mold 10 according to an embodiment of the present invention. The mold 10 has a convex portion 12 extending in one direction (see arrow A) on a surface 11a of a substrate 11 made of silicon carbide, periodically in a direction orthogonal to the extending direction A (see arrow B) at predetermined intervals. Is formed. The convex portion 12 has a curved shape in which the cross section in the B direction perpendicular to the extending direction A is tapered without a flat portion parallel to the surface 11a at the tip portion. Details of the method for manufacturing the mold 10 and the curved shape will be described later.

  The period P of the convex part 12 is 500 nm, the height H is 440 nm, the space width S is 300 nm, the line width L is 200 nm, and the side wall angle α of the convex part 12 is 84 °.

  As shown in FIG. 2, the mold 10 is used as an upper mold, a glass material 20 or a resin material is sandwiched between the lower mold 15, and an optical element is press-molded while being heated and pressurized. In this case, the convex part 12 formed periodically at a predetermined interval has a curved shape with a tapered cross section perpendicular to the extending method A without a flat part parallel to the surface 11a at the tip part. Therefore, when the glass material 20 or the resin material is press-molded, a force (particularly a horizontal force) for filling the molding material with the molding material between the convex portions 12 acts greatly (arrow in FIG. 2). (Refer to the arrow in FIG. 15), and a fine periodic structure can be formed at a required height in the molded product (optical element).

  Examples of the glass material to be molded include high-softening point glass having a softening point of 300 ° C. or higher, which is often used for optical applications. As the resin material, polymethyl methacrylate, polycarbonate, polystyrene, and amorphous polyolefin can be used.

(Mold manufacturing method, see FIG. 3)
The mold 10 can be manufactured by the process shown in FIG. First, a substrate 11 made of silicon carbide is prepared (see FIG. 3A), and a metal mask layer 13 is formed on the surface thereof by sputtering or the like (see FIG. 3B). Subsequently, a resist 14 is applied on the metal mask layer 13 by spin coating or the like (see FIG. 3C), and a periodic structure is drawn on the resist 14 using an electron beam or ultraviolet rays (see FIG. 3D). ) And development using an ortho-xylene solution or the like (see FIG. 3E). Next, dry etching is performed using a reactive gas or a mixed gas of a reactive gas and an inert gas (see FIGS. 3F and 3G). Thereby, the convex part 12 is formed in the surface 11a of the board | substrate 11 as a fine one-dimensional periodic structure (refer FIG.3 (h)).

  In the dry etching process, the metal mask layer 13 is etched first, then the silicon carbide substrate 11 is etched, and the dry etching is continued to the extent that the metal mask layer 13 disappears, whereby the tip of the projection 12 The portion can be formed such that its cross section has a tapered curved shape.

As the substrate 11, in addition to silicon carbide (SiC), glassy carbon (GC), diamond, diamond-like carbon (DLC), carbide (WC), quartz (SiO ₂ ), noble metals such as platinum (Pt), stainless steel, etc. An alloy of

  When silicon carbide is used as the substrate 11, it is preferable to use polycrystalline silicon carbide or single crystal silicon carbide having a crystal grain size smaller than that of the periodic structure. Such silicon carbide has a dense and homogeneous composition, and can be produced by a chemical vapor deposition (CVD) method, a sputtering method, a vapor deposition method, or the like.

  As the metal mask layer 13, tungsten silicide (WSi) can be used. By using WSi, it is possible to adjust the speed at which the opening of the mask layer 13 is expanded by plasma during dry etching. As a result, the ratio of the etching rate of the mask layer 13 and the etching rate of the substrate 11 can be arbitrarily set to adjust the sidewall angle α of the convex portion 12.

The reactive gas used in the dry etching may be at least one gas selected from the group consisting of CBrCl, CCl ₂ F ₂ , CCl ₄ , CL ₂ , CHF ₃ , CF ₄ , SF ₆ , and O _2. Good. The inert gas may be at least one gas selected from the group consisting of Ar, Ne, and Kr. In particular, it is preferable to use a fluorine-containing gas or a mixed gas of fluorine-containing gas and oxygen gas as an etching gas. The etching rate of the mask layer 13 and the substrate 11 can be adjusted according to the ratio of the fluorine-containing gas and the oxygen gas, and as a result, the sidewall angle α of the convex portion 12 can be adjusted.

(Optical element manufacturing method, see FIGS. 4 to 7)
A method for manufacturing an optical element using the mold 10 will be described. In the first example of the manufacturing method, as shown in FIG. 4, a glass material 20 is disposed on the lower mold 15 (see FIG. 4A), and the lower mold 15 is raised with respect to the upper mold (mold 10). And pressing at a predetermined temperature and pressure (see FIG. 4B). Thereafter, the lower mold 15 is lowered and the molded product 20 ′ is taken out (see FIG. 4C).

  In the second example of the manufacturing method, as shown in FIG. 5, the glass material 20 is disposed on the lower mold (mold 10) (see FIG. 5A), and the mold 10 is raised with respect to the upper mold 16. Press at a predetermined temperature and pressure (see FIG. 5B). Thereafter, the mold 10 is lowered and the molded product 20 'is taken out (see FIG. 5C).

  As shown in FIG. 6, the third example of the manufacturing method uses molds 10A and 10B for an upper mold and a lower mold, and a glass material 20 is disposed on a mold 10B as a lower mold (FIG. 6A). Reference), the mold 10B is raised relative to the upper mold 10A and pressed at a predetermined temperature and pressure (see FIG. 6B). Thereafter, the mold 10B is lowered, and the molded product 20 'is taken out (see FIG. 6C).

  Here, FIG. 7 shows the experimental results of the inventors regarding the height of the convex portion of the optical element molded by the first example. In FIG. 7, characteristic C1 is a result of using the mold 10 of the invention example shown in FIG. 1, and characteristic C2 is a result of using the mold 100 of the conventional example shown in FIG. Various conditions of the molds 10 and 100 are as follows. Further, the cross-sectional shape of the tip portion of the convex portion 12 of the mold 10 according to the present invention is a substantially quadratic function shape.

Substrate material: Silicon carbide by CVD method Height H: 440 nm
Period P: 500 nm
Space width S: 300nm
Line width L: 200 nm
Side wall angle α: 84 °
Glass material: K-PSK100 (phosphate glass)
Refractive index nd: 1.59, yield point At: 423 ° C
Molding conditions: Molding temperature 430 ° C, molding pressure 5MPa

  Under the above conditions, the molding time is set to 60 seconds, 120 seconds, 180 seconds, 240 seconds, and 300 seconds. As a result of performing press molding, when the mold 10 according to the present invention is used, the mold according to the conventional example is used. Compared with the case of using 100, an optical element having a convex portion with a height of about 50 nm or more could be obtained at any molding time.

(Cross-sectional shape of the tip portion, see FIGS. 8 to 13)
Next, the preferable shape of the cross section in the front-end | tip part of the convex part 12 of the mold 10 is demonstrated. As described above, the tip portion has a curved shape in which the cross section in the B direction orthogonal to the extending direction A is tapered without the presence of a flat portion parallel to the surface 11a of the substrate 11. The cross-sectional shape is, for example, a shape represented by a power function y = {(H / 2) / (S / 2) ^p } x ^p . In the power function y, H is the height of the convex part 12, and S is the space width of the convex part 12 (period of convex part P-width of convex part L).

  8 is p = 1, FIG. 9 is p = 1.5, FIG. 10 is p = 2, FIG. 11 is p = 3, FIG. 12 is p = 4, and FIG. 13 is p = 5. The convex part to be molded was simulated by setting from the start point (0, 0) to the end point (S / 2, H / 2). The conditions for press molding are the same as in the above experiment. As a comparative example, FIG. 16 shows a result of simulating a convex portion formed when the tip corner portion of the convex portion of the mold is an arc having a radius of 100 nm (a flat surface remains).

  In FIGS. 8 to 13 and 16, the shade of cross hatching represented on the convex portion to be molded indicates that the thinner the portion, the greater the fluidization. As is clear from these figures, the height of the convex part of the molded product shown in FIG. 16 in which the flat surface remains at the tip of the convex part 12 is 258 nm, whereas the exponent p of the function y 8 to 13 having a curved shape of 1 to 5 has a height of 265 to 345 nm, and can be formed high.

(Other examples)
In addition, the mold which concerns on this invention, its manufacturing method, and the manufacturing method of an optical element are not limited to the said Example, It can change variously within the range of the summary.

  For example, the materials and numerical values shown in the above embodiments are merely examples. The mold may be provided with a release film for preventing fusion with the molding material.

The perspective view which shows one Example of the mold which concerns on this invention. Explanatory drawing which shows the state which press-molds glass material using the said mold. Explanatory drawing which shows the manufacturing process of the said mold. Explanatory drawing which shows the 1st example of the manufacturing method of the optical element which concerns on this invention. Explanatory drawing which shows the 2nd example of the manufacturing method of the optical element which concerns on this invention. Explanatory drawing which shows the 3rd example of the manufacturing method of the optical element which concerns on this invention. The graph which shows the height of the convex part of the molded product press-molded with the mold which is an example of this invention, and the mold which is a prior art example. The schematic diagram which simulated the molding state using the mold which has the front-end | tip part cross-sectional shape of the power index p = 1. The schematic diagram which simulated the molding state using the mold which has the front-end | tip part cross-sectional shape of the power index p = 1.5. The schematic diagram which simulated the molding state using the mold which has the front-end | tip part cross-sectional shape of the power index p = 2. The schematic diagram which simulated the shaping | molding state using the mold which has the front-end | tip part cross-sectional shape of the power index p = 3. The schematic diagram which simulated the shaping | molding state using the mold which has the front-end | tip part cross-sectional shape of the power index p = 4. The schematic diagram which simulated the shaping | molding state using the mold which has the front-end | tip part cross-sectional shape of the power index p = 5. The perspective view which shows the conventional mold. Explanatory drawing which shows the state which press-molds glass material using the conventional mold. The schematic diagram which simulated the shaping | molding state using the mold which is a comparative example which left the flat surface in the front-end | tip part of a convex part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Mold 11 ... Board | substrate 11a ... Surface 12 ... Convex part 13 ... Metal mask layer 14 ... Resist

Claims (11)

A mold having a one-dimensional periodic structure in which convex portions extending in one direction on the surface of the substrate are periodically formed at predetermined intervals in a direction perpendicular to the extending direction of the convex portions,
The convex part has a tapered shape in a cross section perpendicular to the extending direction without a flat part parallel to the surface of the substrate at the tip part,
Mold characterized by. The cross-sectional shape of the tip portion of the convex portion is a shape represented by the function y = {(H / 2) / (S / 2) ^p } x ^p ;
H: Height of convex part S: Space width of convex part (period P of convex part-width L of convex part)
The mold according to claim 1.   The mold according to claim 2, wherein 1 ≦ p ≦ 5 in the function.   The mold according to any one of claims 1 to 3, wherein a periodic structure of the convex portions is formed on a surface of a substrate made of silicon carbide. A method for producing a mold according to any one of claims 1 to 4,
Forming a metal mask on the surface of the substrate;
Applying a resist on the metal mask;
Drawing and developing a periodic structure on the resist; and
Dry etching the substrate using a reactive gas or a mixed gas of a reactive gas and an inert gas;
A method for producing a mold, comprising:   The method for manufacturing a mold according to claim 5, wherein silicon carbide is used as the substrate.   The mold manufacturing method according to claim 5, wherein a periodic structure is drawn on the resist using an electron beam or ultraviolet rays. The reactive gas is at least one gas selected from the group consisting of CBrCl, CCl ₂ F ₂ , CCl ₄ , CL ₂ , CHF ₃ , CF ₄ , SF ₆ , and O _2. The manufacturing method of the mold of Claim 5 or Claim 6.   The method for producing a mold according to claim 5 or 6, wherein the inert gas is at least one gas selected from the group consisting of Ar, Ne, and Kr.   The mold manufacturing method according to claim 5 or 6, wherein a fluorine-containing gas or a mixed gas of a fluorine-containing gas and an oxygen gas is used as an etching gas.   Using a mold according to any one of claims 1 to 4 or a mold manufactured by the method according to any one of claims 5 to 10, a glass material or a resin material is press-molded to obtain a fine An optical element manufacturing method, comprising molding an optical element having a one-dimensional periodic structure.

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