JPH05257261A - Transmittance modulation type photomask and production of optical parts by using the same - Google Patents

Abstract

PURPOSE:To obtain the transmittance modulation-type photomask which can produce optical parts having bidirectional rugged patterns by exposing once and the process for production of the optical parts by using this photomask. CONSTITUTION:Apertures 6 and light shielding parts 7 are alternately arranged at prescribed intervals (a), (b) along first and second directions A, B. The width W1 along the first direction A of the light shielding part 7A existing between the apertures 6A and 6A changes along the second direction B in correspondence to the prescribed shape of the ruggedness 16 of a diffraction grating (optical part) 1. The two-dimensional diffraction grating 1 having the rugged patterns in the two directions A, B is produced by one time of exposing when this photomask 5 is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmittance modulation type photomask capable of producing an optical component having a concavo-convex pattern in biaxial directions, and a known photosensitizing material exposed to light using the photomask. The present invention relates to a method of manufacturing an optical component such as a diffraction grating and a hologram.

[0002]

2. Description of the Related Art In order to obtain an optical component in which irregularities such as a sine wave grating and a rectangular wave grating are arranged in a biaxial direction, a photomask having a biaxial pattern is used and a photomask and a resist are used. Generally, a method of disturbing the parallelism of light is controlled by controlling the distance between the light source and the photomask or inserting a light diffusion plate between the light source and the photomask.
However, according to such a method, as shown in FIG. 13, the cross-sectional shape of the optical component formed is a predetermined concave-convex shape (rectangular shape in this example) in the convex portion 2, but the concave portion 3
Then it becomes almost flat. That is, it is merely a structure in which the convex portions 2 are arranged along the biaxial directions A and B. Therefore, an optical component having a concavo-convex pattern in the uniaxial direction is combined with the concavo-convex pattern in the biaxial direction, and has an optical characteristic different from the desired optical component as shown in FIG. 14, for example.

That is, in FIG. 14, a diffraction grating 1A which is an optical component has a convex portion 2 and a concave portion 3 arranged along the first and second directions A and B, and the concave portion 3 also has an uneven shape. It has a middle portion 31 and a bottom portion 32, and thereby a desired so-called two-dimensional diffraction grating 1 having a concavo-convex pattern in the biaxial direction is obtained.

[0004]

Therefore, in order to obtain an optical component in which the cross-sectional shape of the recess is also a predetermined uneven shape,
A photomask having a uniaxial lattice pattern can be produced by exposing the photomask so that its axial direction matches with each of the two directions. However, since this method requires two exposure processes, the productivity is low and the optical components are inevitably expensive.

The present invention has been made in view of the above points, and it is possible to inexpensively mass-produce an optical component provided with a biaxial concavo-convex pattern, and the concavo-convex pattern has various cross-sectional shapes. It is an object of the present invention to provide a mold photomask and a method for manufacturing an optical component using the photomask.

[0006]

In order to achieve the above object, in a transmittance modulation type photomask of the present invention, openings and light shielding portions are alternately arranged at predetermined intervals along the first and second directions. The light-shielding portion located between the openings arranged along the first direction has a width in the first direction that corresponds to a predetermined shape of the unevenness to be formed on the surface of the optical component by exposure. And changes along the second direction.

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. Asperities having a predetermined shape are formed at predetermined intervals.

[0008]

According to the photomask of the present invention and the method of manufacturing an optical component using the photomask, the width of the light shielding portion located between the openings lined up along the first direction in the first direction is , The light-shielding portion corresponding to, for example, a concave portion of the concavo-convex pattern of the optical component changes its area along the second direction. Therefore, the light transmittance of the portion of the photomask corresponding to the recess changes in the second direction, so that when the photomask is used for exposure, the sectional shape of the recess also becomes a predetermined uneven shape. That is, it is possible to manufacture an optical component having a concavo-convex pattern in the biaxial direction by one exposure.

Further, by appropriately setting the shape and spacing of the openings of the photomask, and the rate of change of the width of the light shielding portion, it is possible to obtain unevenness of various cross-sectional shapes.

Further, since the light transmittance of the photomask can be determined by a simple area ratio, the rate of change of the width of the light shielding portion in the photomask of the present invention, that is, the curved shape of the edge of the light shielding portion can be determined from the area ratio. Easy to determine. In addition, since the mask pattern can be formed by a method such as usual chrome etching, the photomask can be manufactured very easily.

[0011]

FIG. 1 shows an example of a photomask according to the present invention. This photomask 5 is used to form a large number of irregularities of a predetermined shape, for example, a sinusoidal shape, on the surface of a diffraction grating that is an optical component. It is a transmittance modulation type that changes the rate.

As shown in the enlarged plan view of FIG. 2, in the photomask 5, openings 6 and light-shielding portions 7 are alternately arranged at predetermined intervals a along the first direction A, and
Even along the second direction B, they are alternately arranged at a predetermined interval b. The openings 6A arranged along the first direction A,
The width W1 in the first direction A of the light-shielding portion 7A located between 6A changes along the second direction B. The change curve, that is, the curved shape of the edge 71 of the light shielding portion 7A is
It has an elliptical shape that changes corresponding to the sine shape of the unevenness to be formed. Similarly, the light-shielding portion 7B located between the openings 6B and 6B arranged along the second direction B is also the second portion.
The width W2 in the direction B of is changed along the first direction A, and the edge 72 thereof has an elliptical shape.

When a diffraction grating having a sinusoidal concavo-convex pattern is to be formed using this photomask 5, as shown in FIG. 3, a light beam 11 from a light source 10 causes the diffraction grating to pass through the photomask 5. The photosensitive material film 15 formed on the main surface 14 of the first base material 13 is exposed.
As a result, the sine wave-shaped irregularities 16 are formed at predetermined intervals a and b along the first and second directions A and B of FIG. At this time, the photomask 5 and the photosensitive material film 1
5 is adjusted, or a light diffusing plate 17 such as frosted glass is arranged between the light source 10 and the photomask 5 to disturb the parallelism of light rays and then perform exposure.

Here, as the photosensitive material film 15,
Besides a general photoresist film, a special photosensitive resin film made of a mixture of a copolymer of methyl methacrylate and 2-butenyl methacrylate and m-benzoylbenzophenone (composition described in Japanese Patent Application No. 1-132286). Is used. This special photosensitive resin film is used for the photomask 5
The unreacted unreacted m-benzoylbenzophenone is removed by exposing the film through the film and further heating it in vacuum to form unevenness.

The photomask 5 of the present invention as described above can be easily manufactured by using an ordinary photomask manufacturing method. That is, a method may be used in which a pattern is formed on a photosensitive material film with an electron beam or an ultraviolet ray, and then a light shielding metal film such as chromium is removed by etching to form an opening, or a plate coated with a silver salt emulsion or the like. Alternatively, the pattern may be written on the film with light to be developed.

The present invention will be specifically described below with reference to examples. Example 1 The photomask of this example has the shape shown in FIG.
The predetermined intervals a and b along the first and second directions A and B are both set to 20 μm, and the widths W1 and W2 of the light shielding portions 7A and 7B are gradually changed at the pitch of 20 μm. However, the widths W1c and W2c of the central portion are 5 μm, and the widths W1e and W2e at the start end and the end of the opening 6 are 10 μm.
The edges 71 and 72 of the light-shielding portions 7A and 7B are formed in an elliptical shape so as to be m.

Using this photomask 5, as shown in FIG. 3, a photosensitive material formed by spin-coating the above-mentioned special photosensitive resin on a glass substrate (base material) 13 in a film thickness of about 3 μm. A mask aligner is used for the material film 15, and the gap L between the photomask 5 and the surface of the photosensitive material film 15 is set to 10
It was set to μm and exposed for 500 seconds. Obtained unevenness 16
4 has a cross-sectional shape as shown in FIG. 4, and the second direction B in FIG.
The convex portion 2 appearing in the convex portion cross section S1 passing through the openings 6B, 6B arranged in parallel, and the light shielding portions 7A, 7 arranged in the second direction B.
The recesses 3 appearing in the recess section S2 passing through A were both substantially sinusoidal in cross section.

In the first embodiment, the convex portion 2 appearing in the convex portion cross section S3 passing through the openings 6A, 6A arranged in the first direction A of FIG. 2 is the same as the cross section S1 of FIG. 4A. The concave portion 3 which has a substantially sinusoidal cross-sectional shape and which appears in the concave portion cross section S4 passing through the light shielding portions 7B, 7B arranged in the first direction A is also
The cross-sectional shape was substantially sinusoidal, which was the same as the cross-section S2 in FIG. Thus, the sinusoidal diffraction grating 1 having a grating pattern along the first and second directions A and B and having a grating pitch of 20 μm and a step of 0.6 μm was manufactured. This diffraction grating 1 is different from the diffraction grating 1A shown in FIG.
The protrusions 2 and the recesses 3 are different in that the cross-sectional shapes thereof are not rectangular but sinusoidal, and the concavities and convexities are the same.

Comparative Example 1 A schematic view of a photomask 50 of this Comparative Example 1 is shown in FIG.
Similar to the first embodiment, the pitches a and b of the opening 6 and the light shielding portion 7 are set to 20 μm, and the opening 6 and the light shielding portion 7 have the same line width. Using this photomask 50, a photosensitive material film made of the same special photosensitive resin as that used in Example 1 and a mask aligner were used for exposure under the same conditions to produce a diffraction grating. As a result, the cross-sectional shape of the pattern of the diffraction grating obtained after development was as shown in FIG. 6, and the cross-sectional shape of the convex portion 2 was substantially sinusoidal, but the concave portion 3 was substantially flat.

Comparative Example 2 FIG. 7 shows a schematic view of a photomask 51 of this comparative example. Here, a one-dimensional lattice pattern arranged with a pitch a = 20 μm along only the first direction A is drawn. Using this photomask 51, using the same photosensitive material film and mask aligner made of the same special photosensitive resin as in Example 1, the distance between the photomask 51 and the surface of the photosensitive material film was set to 10 μm, and 500 Second exposure. Further, the direction of the photomask 51 was changed by 90 degrees and exposure was performed for 500 seconds.
The uneven pattern obtained after development is as shown in FIG. 8, and a diffraction grating having a grating pitch of 20 μm and a step of 0.5 μm, in which both the convex portions 2 and the concave portions 3 have a substantially sinusoidal shape, could be manufactured. However, this method has low productivity because it requires two exposures.

Example 2 A schematic view of a photomask 5A of this example is shown in FIG. Here, a grid pattern having a pitch a of 5 μm along the first direction A and a pitch b of 3 μm along the second direction B is drawn. The light-shielding portion 7A located between the openings 6A and 6A arranged at a pitch of 5 μm along the first direction A is
The width W1 along the first direction A changes at the opening 6, W1c = 1.5 μm at the central portion, and W1e = 2.5 μm at the start and end of the opening 6. Second direction B
The width W2 in the second direction B of the light shielding portion 7B located between the openings 6B, 6B arranged along the direction is constant and does not change along the first direction A.

Using this photomask 5A, as shown in FIG. 3, a photosensitive material film 15 formed by spin-coating the above-mentioned special photosensitive resin with a film thickness of about 3 μm on a glass substrate 13, Using a mask aligner, the distance L between the photomask 5A and the surface of the photosensitive material film 15 was set to 0 μm (contact exposure), and exposure was performed for 500 seconds. After development,
The obtained cross-sectional shape is shown in FIG. The step of the convex portion 2 (convex section S3: FIG. 10A) in the first direction A having a lattice pitch of 5 μm, and the convex portion 2 (convex section in the second direction B having a lattice pitch of 3 μm Both the step S1) is 0.6 μm, and the recess 3 in the second direction B is
The step difference (recessed section S2: FIG. 10B) was also 0.6 μm. Thus, the sinusoidal diffraction grating 1 having a grating pattern along the first and second directions A and B was manufactured.

The recess 3 (recess section S4) in the first direction A is planar. That is, the concave portion 3 of the obtained diffraction grating 1 is different from the first embodiment in the first direction A.
Is flat along.

Comparative Example 3 FIG. 11 shows a schematic view of a photomask 52 of this comparative example.
Here, a = 5 along the first and second directions A, B.
A two-dimensional pattern with a grating pitch of μm and b = 3 μm is drawn. In both directions A and B, the opening 6 and the light shield 7 have a constant line width. This photomask 5
2 was exposed under the same conditions using a photosensitive material film made of the same special photosensitive resin and a mask aligner as in Example 2. As a result, the cross-sectional shape of the pattern obtained after development is as shown in FIG. 12, and is 3 μm pitch with respect to the step (projection section S3: FIG. 12A) in the first direction A with 5 μm pitch. The step (recessed section S2: FIG. 12B) in the second direction B is small, and the exposure time, the distance between the photomask and the surface of the photosensitive resin, the light diffusion plate such as frosted glass between the light source and the photomask. However, it was impossible to control by simply changing the exposure conditions, such as disposing the beam and disturbing the parallelism of the light rays.

In the above-described embodiment, the case where the sinusoidal unevenness is formed is shown. However, in the present invention, the shape and interval of the opening of the photomask, the rate of change of the width of the light shielding portion, etc. are appropriately set. By doing so, it is possible to form irregularities having various sectional shapes such as a rectangular wave and a trapezoidal wave.

Further, although the special photosensitive resin used in each of the above-mentioned embodiments is a negative type, a positive type photoresist may be used, and in that case, the opening portion and the light shielding portion of the photomask have the above-mentioned respective types. Contrary to the embodiment, it corresponds to each of the concave portion and the convex portion of the optical component.

The present invention can also be applied to the manufacture of other optical components such as holograms, in addition to diffraction gratings.

[0028]

As described above, by using the transmittance modulation type photomask of the present invention, it is possible to manufacture an optical component having a biaxial concave-convex pattern by a single exposure, so that the productivity is remarkably increased. improves. Further, by appropriately setting the shape and spacing of the openings of the photomask and the change rate of the width of the light shielding portion, it is possible to obtain irregularities having various cross-sectional shapes.

Further, since the mask pattern of the present invention can be formed by a usual method such as chromium etching, it is extremely easy to manufacture.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a transmittance modulation type photomask according to the present invention.

FIG. 2 is a plan view showing an enlarged part II of the photomask of FIG.

FIG. 3 is a side view showing a method of manufacturing an optical component using the photomask of FIG.

FIG. 4 is a cross-sectional view showing a concavo-convex shape of a diffraction grating manufactured using the photomask of FIG.

FIG. 5 is a plan view showing an example of a transmittance modulation type photomask according to a comparative example.

6 is a cross-sectional view showing an uneven shape of a diffraction grating manufactured using the photomask of FIG.

FIG. 7 is a plan view showing another example of the transmittance modulation type photomask according to the comparative example.

FIG. 8 is a cross-sectional view showing an uneven shape of a diffraction grating manufactured using the photomask of FIG.

FIG. 9 is a plan view showing another example of the transmittance modulation type photomask according to the present invention.

FIG. 10 is a cross-sectional view showing a concavo-convex shape of a diffraction grating manufactured using the photomask of FIG.

FIG. 11 is a plan view showing still another example of the transmittance modulation type photomask according to the comparative example.

12 is a cross-sectional view showing an uneven shape of a diffraction grating manufactured using the photomask of FIG.

FIG. 13 is a perspective view showing a diffraction grating in which unevenness is two-dimensionally arranged.

FIG. 14 is a perspective view showing a diffraction grating having a concavo-convex pattern in biaxial directions.

[Description of References] 1 ... Diffraction grating (optical component), 2 ... Convex portion, 3 ... Recessed portion, 5,
5A ... Transmittance modulation type photomask, 6, 6A, 6B ... Opening part, 7, 7A, 7B ... Shading part, 13 ... Base material, 15 ... Photosensitive material film, 16 ... Concavo-convex, A ... First direction, B ... second direction, a, b ... predetermined interval, W1 ... width.

Claims (2)

[Claims] 1. A transmittance modulation type photomask which changes the transmittance of an exposure light beam by a combination of an opening portion and a light shielding portion, wherein the opening portion and the light shielding portion are predetermined along the first and second directions. The light-shielding portions, which are arranged alternately at intervals and are located between the openings arranged in the first direction, have a width in the first direction that is equal to the unevenness to be formed on the surface of the optical component by exposure. A transmittance modulation type photomask that changes along a second direction in accordance with a predetermined shape 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, comprising forming irregularities of a predetermined shape arranged at the predetermined intervals along the first and second directions.