JPH06250373A - Transmittance modulation type photomask and production of optical parts by using the same - Google Patents

Abstract

PURPOSE:To produce the optical parts having ruggedness in biaxial directions by one time of exposing. CONSTITUTION:The transmittance modulation type photomask 3 having patterns alternately arranging first and second rows Ra1, Rb1 and Ra2, Rb2 at prescribed intervals a, b along respective first and second directions A, B is constituted. The first row Ra1, Rb1 alternately have light shielding parts 3B and half opening parts 3C and the second rows Ra2, Rb2 alternately have opening parts 3A and half-opening parts 3C. The ruggedness arranged at the prescribed intervals a, b along the first and second directions A, B is formed by once exposing the photosensitive material film on a base material surface by using such photomask 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uneven pattern in a biaxial direction.
Modulation type photomask capable of manufacturing an optical component having an optical component, and a method of manufacturing an optical component such as a diffraction grating or a hologram by exposing a known photosensitive material using the photomask And about.

[0002]

2. Description of the Related Art As a method for manufacturing an optical component having a concavo-convex structure such as a sine wave grating, a trapezoidal wave grating, and a rectangular wave grating in a biaxial direction, a manufacturing method by the steps shown in FIG. 8 is generally used. That is, according to this manufacturing method, as shown in FIG. 8 (1), the surface of the base material 22 coated with the photosensitive material film 21 such as a negative photoresist is applied in the first direction as shown in FIG. 8 (2). A first row Ra1, Rb1 and a second row R along A and a second direction B orthogonal thereto, respectively.
It is exposed by ultraviolet rays 24 or the like from a light source through a photomask 23 having a pattern in which a2 and Rb2 are alternately arranged.

As a result, a photomask 23 is formed on the substrate 22 coated with the photosensitive material film 21 as shown in FIG. 8C.
The uneven pattern 25 corresponding to the pattern is formed. The first row Ra1 in the pattern of the photomask 23,
Rb1 is a column in which the light shielding portion 23A and the opening portion 23B alternate, and the second columns Ra2 and Rb2 are columns including only the opening portion 23B. In the concavo-convex pattern 25 of FIG. 8C, the cross section taken along the line IX-IX along the portion corresponding to the first row Ra1 of the photomask 23 has a shape in which convex portions and concave portions alternate as shown in FIG. The cross section taken along the line XX of the photomask 23 along the portion corresponding to the second row Ra2 has a flat shape as shown in FIG.

That is, in the concavo-convex pattern 25 formed by this manufacturing method, the second pattern of the photomask 23 is formed.
The portions corresponding to the columns Ra2 and Rb2 of No. 3 do not have a concavo-convex structure, and only the structure in which the concave portions are monotonically arranged in a matrix is obtained as a whole. That is, in the exposure using the photomask 23, the unevenness is arranged in each row facing the first direction A, and
It is not possible to form a concavo-convex structure in which concavities and convexities are lined up even in each row facing the second direction.

Therefore, conventionally, when manufacturing an optical component having such a concavo-convex structure, a base material coated with a photosensitive material film 21 such as a negative photoresist as shown in FIG. 11 (1). As shown in FIG. 11B, the surface of 22 is covered with a strip-shaped light shielding portion 26A and an opening portion 26B along one direction C.
Photomask 26 having a pattern in which
And a second photomask 2 having a similar pattern of light-shielding portions 27A and openings 27B as shown in FIG. 11C.
7 and 2 are arranged in two directions, and ultraviolet rays from the light source 24
And so on.

As a result, a large amount of the unreacted portion of the photosensitive material film 21 where the exposure is never limited by the light shielding portions 26A and 27A of the photomasks 26 and 27 is removed, and the opening portions 26B and 27B are again provided. The part where the exposure is not restricted by is left as it is, and the part where the exposure is restricted by the light shielding parts 26A and 27A is removed by a small amount, and the concavo-convex pattern in which the concavities and convexities are arranged in each row in two directions as shown in FIG. 11 (4). 28 is formed.

[0007]

However, in the manufacturing method using such photomasks 26 and 27, it is necessary to perform the exposure twice, and the steps are complicated and the manufacturing cost is high. .

The present invention has been made in view of the above points, and it is possible to easily form a concavo-convex pattern in which concavities and convexities are arranged in each row along the first and second directions on a substrate. It is an object of the present invention to provide a mold photomask and a method for manufacturing an optical component using the photomask.

[0009]

In order to achieve the above object, the transmittance modulation type photomask of the present invention comprises a combination of an opening portion, a light shielding portion, and a half opening portion having a light transmittance between them. In order to change the transmittance of a light beam for exposure, first and second parallel columns extending along the first direction and parallel to each other are alternately arranged at a predetermined interval, and Parallel first and second rows extending along the intersecting second direction are alternately arranged at a predetermined interval, and the first rows alternately have the light shielding portion and the half-opening portion. However, the second row has alternating openings and half openings.

Further, in the method for manufacturing an optical component of the present invention, the photosensitive material film on the surface of the substrate is exposed by using the above-mentioned transmittance modulation type photomask, and the above-mentioned first and second directions are followed. It is intended to form irregularities arranged at a predetermined interval.

[0011]

According to the photomask of the present invention, as the rows along the first direction in the pattern of the photomask, the first rows in which the shielding portions and the half openings alternate, and the half openings and the openings alternate. The second rows are alternately arranged, and as the rows along the second direction, the first rows in which the light blocking portions and the half openings are alternated and the second rows in which the half openings and the opening are alternated. The pattern is alternating. Therefore, when an optical component is manufactured using this photomask, the concavo-convex pattern of the optical component corresponds to the above-mentioned pattern of the photomask, and has a convex portion and a semi-concave portion along each of the first and second directions. Has a concavo-convex structure in which first columns alternating with and second columns alternating with semi-recesses and recesses are alternately arranged. That is, it is possible to manufacture an optical component having a concavo-convex pattern in which concavities and convexities are arranged in each of two rows by one exposure.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an enlarged plan view of an essential part showing an example of a photomask according to the present invention. The photomask 3 is used to form a large number of irregularities having a predetermined shape, for example, a rectangular shape, on the surface of a diffraction grating that is an optical component.
It is a transmittance modulation type photomask that changes the transmittance of a light beam for exposure by a combination of A, a light shielding portion 3B, and a half aperture portion 3C having a light transmittance between them.

In the photomask 3, along the first direction A, the first row Ra1 in which the light shielding portions 3B and the half openings 3C alternate, and the openings 3A and the half openings 3C alternate. Second
Row Ra2 of the first row and the second row Ra2 of the second row Ra2 are arranged alternately at a predetermined interval a and in parallel with each other, and along the second direction B orthogonal to the first direction A. A pattern is formed in which Rb2 are arranged alternately at predetermined intervals b and in parallel with each other.

The light-shielding portion 3B is a rectangular area formed by entirely forming a chromium film on a transparent glass plate, which is the base material of the photomask 3, and is a rectangle on the transparent glass plate corresponding to the opening 3A. Nothing is formed in the area. The half-opening portion 3C is a rectangular area formed by forming a chrome film on a transparent glass plate like the light-shielding portion 3B, but the thickness thereof is thinner than that of the light-shielding portion 3B to allow light transmission. Set to limit rates. The light transmittance of the semi-opening portion 3C is preferably 30 to 60% of that of the opening portion 3A as described later. When the light transmittance of the half-opening portion 3C is set to 50%, the film thickness of the half-opening portion 3C may be set to 80 to 100 Å while the film thickness of the light shielding portion 3B is 900 to 1100 Å.

When using this photomask 3 to manufacture a diffraction grating (optical component) having a concavo-convex pattern as shown in FIG. 9, the photomask 3 is exposed to ultraviolet rays 7 from a light source 6 as shown in FIG. Through it, the photosensitive material film 1 formed on the main surface of the base material 2 which becomes the diffraction grating is exposed. Specifically, as shown in FIG. 2 (1), the main surface of the substrate 2 on which the photosensitive material film 1 is formed is exposed to ultraviolet rays 7 as shown in FIG. 2 (2) through the photomask 3. . In the case where a negative photoresist is used as the photosensitive material film 1 in this case, it is shown in FIG.
The uneven pattern 8 like this is formed.

As the above-mentioned photosensitive material film 1, in addition to a general photoresist film, a special photosensitive resin made of a mixture of a polymer of methyl methacrylate and 2-butenyl methacrylate and m-benzoylbenzophenone (Japanese Patent Application No. Hei 10-135,049). 1
The composition described in -132286) is used.
This special photosensitive resin film is exposed through a photomask 3 and further heated in vacuum to remove unreacted unreacted m-benzoylbenzophenone,
Unevenness is formed.

By the exposure, the rectangular area corresponding to the opening 3A of the photomask 3 in the photosensitive material film 1 is exposed and remains, so that it becomes a convex portion, and the rectangular area corresponding to the half opening 3C has a light transmittance. Since the exposure is limited to some extent, it is partially removed and becomes a semi-recessed portion. Since the rectangular region corresponding to the light-shielding portion 3B is not exposed, a larger amount than the semi-recessed portion is removed to be a recessed portion. Thereby, along the first and second two directions A and B, the first row Ra in which the recesses and the semi-recesses alternate with each other.
1, Rb1 and the second row Ra2, Rb in which the semi-recessed portion and the raised portion alternate
Diffraction grating (optical component) with an uneven structure in which 2 and 2 are alternately arranged
9 is produced.

At this time, the distance L between the photomask 3 and the photosensitive material film 1 is adjusted as shown in FIG. 3, or a light diffusion plate 10 such as frosted glass is arranged between the light source 6 and the photomask 3, By exposing the ultraviolet rays 7 while disturbing the parallelism, the biaxial grating shape of the diffraction grating (optical component) 9, that is, the cross-sectional shape of the unevenness can be made into a sine wave shape or a rectangular shape. Figure 4
Shows a cross section taken along the line VI-VI along the second row Ra2 of the diffraction grating (optical component) 9 in FIG. 2 (3) when the irregularities have a sinusoidal shape, and FIG. 5 shows along the first row Ra1 VII. -VII shows a cross section taken along the arrow.

Further, the unevenness to be formed can be adjusted also by the exposure sensitivity of the photosensitive material film 1. That is, when the exposure sensitivity of the photosensitive material film 1 is high, the unevenness becomes a rectangle as shown in FIG.
When the photosensitivity is low, the unevenness is sinusoidal as shown in FIGS.

Half opening 3C in the photomask 3
When the light transmittance of is less than 30% of the opening 3A,
The height difference between the corresponding semi-recessed portion of the concavo-convex pattern 8 and the recessed portion corresponding to the light-shielding portion 3B becomes too small. Since the height difference between the semi-recessed portion and the convex portion corresponding to the opening 3A becomes too small, the light transmittance of the semi-opened portion 3C is preferably 30 to 60%.

Instead of forming the semi-opening 3C by adjusting the film thickness as described above, the linear chromium film 4 is formed in the rectangular area on the transparent glass plate which becomes the semi-opening 3C as shown in FIG. May be thinned to limit the light transmittance, and as shown in FIG. 7, the chromium film 4A in which the dot-shaped openings 5 are dispersed is formed in the rectangular area on the transparent glass plate which becomes the half-opening 3C. Then, the light transmittance may be limited. In that case, make sure that the shadows of lines and dots do not appear.
Chromium film 4 line pitch (Fig. 6), dot-shaped openings 5
(FIG. 7) or the exposure sensitivity of the photosensitive material film 1 is appropriately set.

The photomask 3 of the present invention as described above can be easily produced by using a usual photomask producing method. That is, by a method of forming an opening or a semi-opening by removing the light shielding metal film by etching after forming a pattern on the photosensitive material film with an electron beam or ultraviolet rays on the surface of the light shielding metal film such as chromium. Alternatively, a plate or film coated with a silver salt emulsion or the like may be used to write a pattern with light to be developed.

The present invention will be specifically described below with reference to examples. Example 1 In this example, a transparent glass substrate was used as the substrate of the photomask 3, and the special photosensitive resin described in Japanese Patent Application No. 1-132286 was applied by a spin coat to a film thickness of 3 μm. The photomask 3 has the same shape as that shown in FIG. 1, and has a first row Ra1 and Rb1 and a second row Ra2 and Rb2 arranged along the first direction A and the second direction B. The distances a and b are both 20 μm, and the light transmittance of the half opening 3C is 50% of that of the opening 3A. Further, the first direction A and the second direction B are set to intersect each other at right angles.

Using this photomask 3, as shown in FIG. 2, a photosensitivity formed by spin-coating the above-mentioned special photosensitive resin on a transparent glass substrate (base material) 2 in a thickness of about 3 μm. The material film 1 was exposed. At this time, the distance L between the photomask 3 and the surface of the photosensitive material film 1 was set to 10 μm using a mask aligner, and the exposure time was 500 seconds. The cross-sectional shape of the obtained concavo-convex pattern 8 was substantially sinusoidal as shown in FIGS. 4 and 5.

Although the special photosensitive resin used in the above embodiments is a negative type, a positive type photoresist may be used. In this case, the relationship between the unevenness formed and the openings 3A, the light shields 3B, and the half openings 3C of the photomask 3 is opposite to that in the above embodiment. Further, the intersection angle between the first row A and the second row B is 9 as in the case of the above embodiment.
The angle is not limited to 0 degree, and may be any angle.

[0026]

As described above, by using the transmittance modulation type photomask of the present invention, it is possible to manufacture an optical component having a concavo-convex pattern in two directions by a single exposure, so that the productivity is remarkably increased. It can be improved and the manufacturing cost can be significantly reduced.

Furthermore, since the pattern of the photomask of the present invention can be formed by a method such as ordinary chrome etching, it is extremely easy to prepare.

[Brief description of drawings]

FIG. 1 is an enlarged plan view of an essential part showing a transmittance modulation type photomask according to an embodiment of the present invention.

FIG. 2 is a process drawing showing the manufacturing method of the optical component using the same photomask.

FIG. 3 is a side view showing a configuration of an optical system in the manufacturing method.

FIG. 4 is a cross-sectional view of a portion along one row in the optical component obtained by the manufacturing method.

FIG. 5 is a cross-sectional view of a portion of the same optical component along another row.

FIG. 6 is an enlarged plan view showing an example of a configuration of a half opening in the photomask.

FIG. 7 is an enlarged plan view showing another example of the configuration of the half-opening.

FIG. 8 is a process chart showing an example of a conventional manufacturing method.

FIG. 9 is a sectional view of a portion along one row in an optical component obtained by the manufacturing method.

10 is a cross-sectional view of a portion of the optical component along the other row in FIG.

FIG. 11 is a process drawing showing another example of the conventional manufacturing method.

[Explanation of symbols]

1 ... Photosensitive material film, 2 ... Base material, 3 ... Photomask, 3A
... Apertures, 3B ... Shading sections, 3C ... Semi-openings, 7 ... UV rays, 8 ... Concavo-convex pattern, Ra1, Rb1 ... First row, Ra2,
Rb2 ... second row.

Claims (2)

[Claims] 1. A transmittance modulation type photomask for changing the transmittance of an exposure light beam by a combination of an opening portion, a light shielding portion and a half opening portion having a light transmittance between them, which is a first aspect. First and second parallel to each other extending in the direction
Of rows are alternately arranged at a predetermined interval, and first and second rows parallel to each other extending along a second direction intersecting the first direction are alternately arranged at a predetermined interval. The rows of have alternating light-shielding portions and half-opening portions,
The transmittance modulation type photomask in which the second row has openings and half openings alternately. 2. A method of manufacturing an optical component having a large number of irregularities on a base material, which comprises exposing a photosensitive material film on the surface of the base material using the transmittance-modulated photomask according to claim 1. Then
A method for manufacturing an optical component, characterized in that the irregularities arranged at the predetermined intervals are formed along the first and second directions.