JPH06201907A - Production of blaze grating - Google Patents

Abstract

PURPOSE:To easily provide the ideal blaze grating with high accuracy by inclining a substrate in the state of paralleling the ridge lines of the grating patterns formed by exposing and developing a positive type resist with a horizontal plane, then applying an energy-curing type resin to the substrate while rotating the substrate. CONSTITUTION:The positive type photoresist 12 having a high resolution is uniformly applied on the substrate 1 consisting of glass and is exposed by irradiation with UV rays 25 by using a chromium mask 3 having patterns formed and developed by using an aq. alkaline soln., thereby diffraction gratings 13 are produced on the substrate 1. The substrate 1 is thereafter fixed to a spin coater in such a manner that the ridgelines 17 are parallel with a plane 18 of rotation and has an angle theta with the plane 18 of rotation. The sufficient resist is applied on the substrate 1 while this spin coater is kept rotated, to form the planes 20 of the photoresist and a photoresist layer 27 having a blaze shape is produced. The photoresist is subjected in the as-inclined state to baking to be cured, thereby, the blaze grating having the planes 20 as slopes is produced.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for optically producing a blazed grating.

[0002]

2. Description of the Related Art Micro optical systems are widely used, including laser pickups, and photolithography is generally used as a manufacturing method thereof.
For example, when light enters a hologram that utilizes the diffraction phenomenon, not only the required + 1st-order diffracted light but also the −1st-order diffracted light and higher-order diffracted light are generated. Becomes non-uniform, and the diffraction efficiency of + 1st order diffracted light can be improved. in this case,
A diffraction efficiency of almost 100% can be realized by forming an ideal right-angled triangular sawtooth shape at an appropriate height.

As a method of manufacturing this blazed hologram, conventionally, the method shown in FIGS. 13 to 17 has been performed.
That is, as shown in FIG. 13, a photoresist 2 is applied to the surface of the substrate 1, the photoresist 2 is covered with a chrome mask 3a, exposed, and developed to form a pattern 4a shown in FIG. Then, the photoresist 2 is applied again, and as shown in FIG. 15, the chrome mask 3b is formed.
And then exposed to light, as shown in FIG.
A step-shaped pattern 4b is manufactured. Then, by repeating the series of steps up to this point, a stepwise blaze pattern is formed as shown in FIG.

On the other hand, in FIGS. 18 to 21, since drawing is performed by an electron beam without using a mask, the method disclosed in JP-A-60-1
Another conventional method disclosed in Japanese Patent No. 68104 is shown. First, as shown in FIG. 18, after applying the photoresist 2 on the surface of the substrate 1, the electron beam 6 is sequentially scanned while being changed in a linear function, so that the dose to the resist is increased as shown in FIG. The quantity distribution is formed in a sawtooth shape, and after development, a blaze pattern 7 is formed on the substrate 1 by the electron beam 6 as shown in FIG. Alternatively, by changing the electron beam shape itself and sequentially scanning not the circular shape but the triangular electron beam 8 having a triangular shape as shown in FIG. 21, the dose distribution of the resist is sawtooth shape as shown in FIG. As a result, the blaze pattern 7 is formed on the substrate 1 by the electron beam.

[0005]

However, as shown in FIG.
It has been difficult to manufacture an ideal sawtooth shape by the former method shown in FIGS. This is because, when the exposure phenomenon is repeated using a plurality of masks, it is very difficult to align the masks. That is, since the blazed shape itself has a size of several μm, the alignment accuracy is required to be as high as 0.1 μm or less.
This is because a series of steps for aligning the position in the horizontal and vertical directions in one horizontal plane needs to be repeated a plurality of times, so that the displacement due to the alignment inevitably occurs.

Secondly, in the accuracy of the mask itself, in-plane variation of one sheet and displacement of each mask due to use of a plurality of sheets occur, and in addition, variation caused by repeating the exposure step. Is caused. Then, such variations increase as the number of exposure steps increases, and finally the slopes of the blaze obtained from these steps have a step shape instead of a straight line.
As a result, even if the number of processes is increased, the slope does not have a linear shape. As described above, there is a problem that the former conventional method is difficult to manufacture, and since the manufactured blazes are step-shaped blazes, it is not possible to sufficiently obtain the intensity of the conjugate diffracted light.

Next, in the latter conventional method, the electron beam is exposed while making it strong and weak, but since the spot diameter of this electron beam has a spatial region, an intensity distribution is generated. That is, in the intensity distribution 10 of the electron beam spot diameter 9, as shown in FIG. 22, the intensity distribution in the central portion is larger than the intensity distribution in the peripheral portion. Therefore, after development, as shown in FIG. 23, minute unevenness 11 is formed on the slope of the photoresist 2 on the substrate 1. Since the unevenness 11 scatters the focused light, there is a problem that the diffraction efficiency is deteriorated.
The present invention has been made in consideration of the above circumstances, and an object thereof is to easily and highly accurately manufacture a blazed grating having a cross-sectional shape close to an ideal sawtooth shape.

[0008]

According to the manufacturing method of the present invention, a step of exposing and developing a positive type resist applied on a substrate to form a predetermined grating pattern on the substrate, and the ridge line of the grating pattern is a horizontal plane. Inclining the substrate in a state of maintaining the parallel state, and applying the energy curable resin while rotating the substrate in this state to form a pattern corresponding to the slope of the blaze, and the ridge line of the grating pattern is a horizontal plane. And a step of curing the energy curable resin in a state parallel to the above.

[0009]

In the above structure, by using the positive type resist in the patterning process, the tip of the portion forming the sawtooth-shaped vertical wall surface can be sharpened. By rotating the substrate in a tilted state and applying the energy-curable resin, the surplus resin is blown off by the centrifugal force, and the slope of the blazed lattice can be formed by the surface tension of the remaining resin. Then, by curing the resin while the substrate is tilted, the sawtooth-shaped blaze grating can be manufactured with high accuracy.

[0010]

1 to 10 show a manufacturing process of an embodiment of the present invention. First, as shown in FIG. 1, a positive photoresist 12 having high resolution is formed on a glass substrate 1.
Is applied to have a uniform film thickness, and then ultraviolet rays 25 are irradiated and exposed using a chrome mask 3 having a pattern with a line width of 0.5 μm or less and a pitch of about several μm. Then, the substrate is developed using an alkaline aqueous solution, and is developed on the substrate 1 as shown in FIGS.
A diffraction grating 13 having an acute tip as shown in (3) is produced.

The tip of the diffraction grating 13 is thin and has an acute angle as compared with the substrate side, for the following reason. When light is used to perform very high resolution fine processing, the contrast of the exposure image is low. When such high-resolution and low-contrast exposure is performed, the cross-sectional shape of the resist formed by development is different between the positive type and the negative type. FIG. 4 shows the cross-sectional formation of a positive photoresist, and FIG. 5 shows that of a negative photoresist, and the portion exposed by the photoresist is indicated by a horizontal line segment 14. Since both the positive type and the negative type are exposed with low contrast, they are absorbed by the resist, and the proportion of the exposed portion is smaller toward the portion closer to the substrate. When the resist exposed under such conditions is developed, the positive type melts the resist from the surface where the light is most intense, whereas the negative type melts from the surface where the light is the weakest. As a result, in the negative type, the shape 15 having the plane portion on the diffraction grating upper portion is used.
Is obtained (see FIG. 5), but in the positive type, a shape 16 in which the upper portion of the diffraction grating has an acute angle is obtained (see FIG. 4).

For the above reasons, the positive photoresist 1
When 2 is used, a thin and sharp diffraction grating 13 can be formed. The grating pattern thus obtained finally constitutes the wall surface of the blazed grating. That is, the side surface of the grating pattern constitutes the vertical plane of the blazed grating, and the sharp tip of the grating pattern constitutes the sharp tip of the blazed grating.

After forming the diffraction grating 13, as shown in FIG. 6, the substrate 1 is spun so that its ridge line 17 is parallel to the rotating surface 18 and has a specific angle θ with respect to the rotating surface 18. Fix it on the coater. FIG. 7 shows the spin coater 26, and the side surface 27 is inclined at an angle θ with respect to the rotation surface. This angle θ is defined by tan θ = h / t from the height h of the diffraction grating 13 and the pitch t. After the substrate 1 is set on the side surface 27 of the spin coater 26 so that the ridge line 17 is parallel to the rotation surface, air is sucked through the suction holes 28 as shown in FIG. After the spin coater 26 is mounted in this manner, the substrate 1 is coated with sufficient resist while rotating the spin coater 26. At this time, the spin coater was operated to apply the photoresist, and the excess photoresist was removed by centrifugal force to form a flat surface 20 of the photoresist to have a blaze shape as shown in FIGS. 9 and 10. The photoresist layer 27 is produced. Then, while maintaining the inclination of the substrate 1 with respect to the horizontal plane, baking is performed to cure the photoresist, and a blazed grating having the plane 20 as an inclined surface is manufactured.

Since the flat surface 20 thus obtained constitutes the slope of the blazed grating, the blazed grating can be manufactured by the steps described above. In this way, the obtained blazed grating can form the apex angle of the blazes because it forms the wall surface of the acute blazes using the positive photoresist. Further, the interface is formed by the surface tension of the photoresist in the air without forming the slope of the blazed by any medium such as the conventional formation by stacking or the physical removal by electron beam. It has excellent smoothness. Further, since the flatness of each blaze slope itself is excellent and the parallelism of each blaze slope is also excellent, it is possible to form an ideal right-angled triangular so-called sawtooth shape, so that a highly accurate blaze grating can be efficiently formed. Can be manufactured.

11 and 12 show a step of forming the stamper 24 using the blaze grating 27. First, the blazed grid 27 is washed with a neutral detergent or a weak alkaline detergent, and then an effective sensitizing activation treatment, that is, a sensitizer with a tin chloride aqueous solution and an activation with a palladium chloride aqueous solution are performed to activate the active metal on the activated surface. To form nuclei.

Next, the activated surface is electrolessly plated with Ni or Cr at about room temperature to form a conductive base layer 22 for electrolytic plating. At this time, the thickness of the conductive base layer 22 is about 1000Å. Then Ni
Alternatively, the electrolytic plating of Cr is performed to form the metal body 23, and at the interface between the metal body 23 and the activated surface,
Separated from the blazed grating 21, a metallic stamper 24 is manufactured. After manufacturing a mold for injection molding with this stamper 24 as a nest, PMMA (polymethylmethacrylate) is used as a molding resin, and the shape of the stamper 24 is reversed by the injection molding method. The molded article of is manufactured. By producing a molded product in this way, blazed gratings of the same shape can be produced rapidly, in large quantities, and at low cost, and mass productivity is excellent.

In this embodiment, a positive type resist hardening type, a resist similar to this is applied to obtain a blazed grating, but the present invention is not limited to this, and after hardening the positive type resist, for example, a negative type resist is used. The same effect can be obtained by using an energy type resin such as a resist, a UV curable resin, or a thermosetting resin.

[0018]

According to the present invention as described above, since a wall surface having a sharp blaze is formed using a positive photoresist,
The blaze apex angle can be made sharp. Further, since the interface is formed by the surface tension of the photoresist in the air, the smoothness is excellent, and the parallelism between the blaze slopes is excellent. From the above, it is possible to form an ideal right-angled triangular so-called sawtooth shape.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing exposure after applying a photoresist.

FIG. 2 is a cross-sectional view showing a diffraction grating.

FIG. 3 is a perspective view showing a diffraction grating.

FIG. 4 is a cross-sectional view showing development of a positive resist.

FIG. 5 is a cross-sectional view showing development of a negative resist.

FIG. 6 is a perspective view showing the inclination of the substrate.

FIG. 7 is a perspective view of a spin coater.

FIG. 8 is a perspective view of a spin coater.

FIG. 9 is a perspective view of a blazed grating.

FIG. 10 is a sectional view of a blazed grating.

FIG. 11 is a cross-sectional view of stamper fabrication.

FIG. 12 is a sectional view of a stamper.

FIG. 13 is a sectional view of a conventional method.

FIG. 14 is a sectional view of a conventional method.

FIG. 15 is a sectional view of a conventional method.

FIG. 16 is a sectional view of a conventional method.

FIG. 17 is a sectional view of a conventional method.

FIG. 18 is a cross-sectional view of another conventional method.

FIG. 19 is a sectional view of another conventional method.

FIG. 20 is a cross-sectional view of another conventional method.

FIG. 21 is a sectional view of another conventional method.

FIG. 22 is an explanatory diagram showing a problem of another conventional method.

FIG. 23 is an explanatory diagram showing a problem of another conventional method.

[Explanation of symbols]

 1 substrate 2 photoresist 3 chrome mask 13 diffraction grating

Claims (1)

[Claims] 1. A step of exposing and developing a positive resist applied on a substrate to form a predetermined grating pattern on the substrate, and a step of forming the substrate with the ridge line of the grating pattern kept in parallel with a horizontal plane. Inclining and applying the energy curable resin while rotating the substrate in this state to form a pattern corresponding to the slope of the blaze, and the energy curable resin with the ridge line of the grating pattern parallel to the horizontal plane. And a step of curing the blazed grating.