JPH0756324A - Diffusion type photomask and method of manufacturing optical component using the same - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to collect optical components such as a diffraction grating with a uniform pattern shape and steps over the entire surface without using an expensive exposure apparatus that uses special components for the optical system. To be able to manufacture efficiently and at low cost. A diffusion type photomask 1 having a light diffusing member 5 for diffusing transmitted light, such as frosted glass, is used on a surface opposite to a surface on which a mask pattern 4 is formed. The entire exposed surface of the photosensitive resin film 7 is uniformly irradiated with transmitted light to form a pattern of an optical component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask used for manufacturing an optical component such as a diffraction grating having a uniform shape and a level difference over the entire surface such as a triangular shape or a sine wave shape by exposure. The present invention also relates to a method of manufacturing an optical component in which a photosensitive resin film is irradiated with a mask pattern through the photomask to form a predetermined pattern.

[0002]

2. Description of the Related Art Photomasks generally used in the past have only formed a lattice-shaped mask pattern on one surface of a transparent substrate such as glass. When manufacturing an optical component such as a diffraction grating using such a photomask, a photosensitive resin material is spin-coated on the surface of a glass substrate, and a desired resin is spin-coated on the photosensitive resin film. By disposing the above-mentioned photomask having a mask pattern, exposing through the photomask, and developing with a developing solution, an optical component having a predetermined pattern shape is manufactured.

In the optical component manufactured by the manufacturing method using the conventional photomask as described above, in order to make the step and the pattern shape uniform over the entire area and have the same optical characteristics, conventionally, in general, For example, a special lens component such as a fly's eye lens or a condenser lens is incorporated into an optical system of an exposure apparatus to make the illuminance distribution on the entire exposure surface uniform and to make the light parallel.

When manufacturing a triangular or sinusoidal diffraction grating having a uniform pattern shape and a step difference among the optical parts, the photomask and the surface of the photosensitive resin film are combined with each other. It is general to manufacture while controlling the distance (print gap) to appropriately control the amount of diffracted light that wraps around.

[0005]

However, as described above, when a special lens component is incorporated in the optical system to form an exposure apparatus having a uniform illuminance distribution and parallel light, the exposure apparatus itself It will be very expensive. Therefore, in the case of an optical component manufactured by using such an expensive exposure apparatus, an increase in the manufacturing cost cannot be avoided.

Further, an exposure apparatus which does not have perfect parallel light and uniform illuminance distribution is used while controlling the distance between the photomask and the surface of the photosensitive resin film to control the amount of diffracted light that wraps around. In the case of manufacturing an optical component such as a diffraction grating, it is very difficult to manufacture an optical component having a uniform pattern shape and steps over the entire exposed surface, and the diffraction intensity of the ± 1st order light with respect to the 0th order light is I
+1, I-1, ± 1 order light balance (I + 1-I-1)
There is a problem that / (I + 1 + I-1) becomes large, that is, the intensity difference of the ± 1st order light becomes large, and the yield is significantly reduced.

The present invention has been made in view of the above circumstances, and can be easily manufactured by a normal photomask manufacturing method, but can effectively improve the illuminance distribution over the entire exposed surface. An optical component whose main purpose is to provide a diffusion-type photomask, and by using the diffusion-type photomask, an optical component having a uniform pattern shape and steps over the entire area can be manufactured at high yield and at low cost. Another purpose is to provide a manufacturing method of.

In order to achieve the above main object, a diffusion type photomask according to the present invention comprises a light diffusing member for diffusing transmitted light on a surface of a transparent substrate opposite to a mask pattern forming surface. ing.

In order to achieve the above-mentioned other objects, in the method of manufacturing an optical component according to the present invention, the above-mentioned diffusion type photomask is arranged on a photosensitive resin film, and exposure is performed through the diffusion type photomask. By this, the entire area of the photosensitive resin film is uniformly irradiated with randomly transmitted light having directivity to form a pattern of the optical component.

[0010]

According to the diffusion type photomask according to the present invention,
When a photosensitive resin film spin-coated on the surface of a light-transmitting substrate in an optical component is irradiated with a mask pattern, the light-diffusing member provided on the surface of the photomask diffuses the transmitted light to direct the light. Are randomized, and as a result, random light having directivity is uniformly irradiated to the photosensitive resin film. Further, such a photomask having a light diffusion function can be easily manufactured by a normal photomask manufacturing method.

Here, the ordinary photomask manufacturing method means
A method of forming a predetermined pattern on a photoresist with an electron beam or ultraviolet rays and then removing the light-shielding metal film such as chromium by etching, or writing a predetermined pattern by light on a plate or film coated with silver salt emulsion etc. It is a method of developing afterwards, and by only attaching a light diffusing member such as frosted glass to the surface opposite to the mask pattern forming surface of the photomask manufactured by such a method by adhesion or the like, A diffusion photomask can be manufactured.

Further, according to the method of manufacturing an optical component according to the present invention, the photosensitive resin film in the optical component is irradiated with the mask pattern through the diffusion type photomask described above, so that the exposed surface is exposed by the light diffusion function described above. The directionality of the light rays irradiated toward the entire area becomes random, and the random light with the directionality is uniformly applied over the entire exposed surface on the photosensitive resin film.

In particular, in an optical component having a step such as a triangular or sinusoidal diffraction grating, a state in which a print gap is provided between the photomask and the photosensitive resin film, not in contact with each other. Since the method of exposure is adopted, the direction of the light beam tends to vary between the central portion and the end portion of the exposure surface (the surface of the photosensitive resin film) due to the diffracted light wraparound. That is, the light beam spreads from the center of the exposure surface toward the end, and it becomes impossible to obtain an optical component having a predetermined step and pattern shape over the entire surface. Here, as in the present invention, by using the diffusion type photomask having the above-mentioned light diffusion function, the directionality of the light rays is made random, and the random light rays having the directionality are made uniform over the entire surface of the photosensitive resin film. It is possible to irradiate the surface with the light, and it is possible to obtain an optical component having a predetermined step and pattern shape over the entire surface.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view of a diffusion photomask according to the present invention. This diffusion-type photomask 1 has a grid pattern composed of a light-shielding portion 4a and an opening portion (transparent portion) 4b formed on a photoresist 3 on one surface of a transparent substrate 2 such as a transparent glass or a transparent resin by an electron beam or ultraviolet rays. Mask pattern 4
And a plate-like light diffusing member 5 such as frosted glass is bonded to the surface of the photomask 1 opposite to the mask pattern forming surface by adhesion or the like.

Next, an embodiment of a manufacturing method for manufacturing an optical component such as a diffraction grating using the diffusion type photomask 1 will be described. Example 1 First, a diffusion type photomask 1 was produced by forming a mask pattern 4 with a photoresist 3 on one surface of a transparent glass 2 and adhering a ground glass 5 to the other surface. Next, as shown in FIG. 2, a special photosensitive resin made of a mixture of a copolymer of methyl methacrylate and 2-butenyl methacrylate and m-benzoylbenzophenone was formed on the surface of a disk-shaped glass substrate 6 having a diameter of 5 inches. A film (see Japanese Patent Laid-Open No. 3-15070) 7 is spin-coated, and the diffusion photomask 1 is placed on the photosensitive resin film 7 via a mask aligner. At this time, the distance (print gap) g between the diffusion type photomask 1 and the surface of the photosensitive resin film 7
Was set to 10 μm, and ultraviolet UV was exposed for 500 seconds through the diffusion type photomask 1. Then, by vacuum heating, unreacted m-benzoylbenzophenone was removed, and the pattern formed on the photosensitive resin film 7 was solidified.

In the optical component (diffraction grating) having the grating pattern manufactured by the above manufacturing method, the diffraction efficiency of the ± first-order light with respect to the 0th-order light of the grating is 38.0 on average.
%, Standard deviation 2.3, ± 1st order diffraction intensity balance (I
The average of (+ 1-I-1) / (I + 1 + I-1) was 0.61 and the standard deviation was 0.34.

Comparative Example 1 As shown in FIG. 3, a normal (conventional) photomask 1A having a grating pitch P of 50 μm, which is the same as the grating pitch P in the diffusion type photomask 1 shown in Example 1, was used. The mask 1A is placed on the photosensitive resin film 7 having the same specifications as those of the above-mentioned Embodiment 1 via a mask aligner,
Exposure was performed under the same conditions as in Example 1.

In the optical component (diffraction grating) manufactured in Comparative Example 1 above, the diffraction efficiency of ± 1st-order light with respect to the 0th-order light of the grating is 38.0% on average, standard deviation 2.1, ± 1st-order light. The diffraction intensity balance of (I + 1-I-1) / (I + 1 + I-1) was 1.52 on average and the standard deviation was 1.3.

Comparing Example 1 and Comparative Example 1 described above, Example 1 is much better than Comparative Example 1 in terms of the diffraction intensity balance of the ± 1st order light with respect to the 0th order light of the grating. It can be seen that the yield of optical components manufactured using the diffusion photomask is significantly improved.

The exposure apparatus used in the method of manufacturing an optical component according to the present invention may be, for example, a mirror projection exposure apparatus or a projection type exposure apparatus such as a stepper.

[0021]

As described above, according to the diffusion type photomask of the first aspect, the transmitted light is sufficiently diffused at the time of manufacturing the optical component, and the directional random light is made uniform with respect to the photosensitive resin film. It is possible to effectively improve the illuminance distribution over the entire exposed surface of the optical component by irradiating the light. Moreover, this diffusion type photomask can be easily manufactured by a normal photomask manufacturing method.

Further, according to the manufacturing method of the second aspect, it is not necessary to use an expensive exposure apparatus incorporating a special optical system lens, and by using the above-mentioned diffusion type photomask having a light diffusion function, Randomize the direction of
It is possible to uniformly irradiate the entire surface of the photosensitive resin film with a random light beam, and it is possible to manufacture an optical component having a predetermined step and a pattern shape over the entire surface with high yield. Moreover, since no special lens parts are required, the cost is low.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a diffusion photomask according to the present invention.

FIG. 2 is a sectional view showing an embodiment of a method for manufacturing an optical component according to the present invention.

FIG. 3 is a cross-sectional view showing a comparative example of the same manufacturing method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Diffusion type photomask, 2 ... Translucent substrate, 4 ... Mask pattern, 5 ... Light diffusing member, 7 ... Photosensitive resin film.

Claims (2)

[Claims] 1. A photomask in which a grid-shaped mask pattern is formed on one surface of a translucent substrate, wherein transmitted light is applied to the surface of the translucent substrate opposite to the mask pattern forming surface. A diffusion type photomask provided with a light diffusion member for diffusing. 2. A diffusion type photomask according to claim 1 is disposed on a photosensitive resin film, and light is exposed through the diffusion type photomask, whereby directional random transmission is performed over the entire area of the photosensitive resin film. A method of manufacturing an optical component, which comprises uniformly irradiating light to form a pattern of the optical component.