JPH10124935A - Production of stamper for optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to reduce the thickness of a photoresist layer and to form low-height pits by preparing a photoresist soln. to a low viscosity. SOLUTION: The photoresist soln. diluted to a viscosity of <=4cP is applied by a spin coater on a glass master disk 1. This photoresist is baked at <=100 deg.C after application to form the photoresist layer 2 of a prescribed film thickness. The photoresist layer 2 is subjected to laser cutting by using an He-Cd laser or Kr laser. Next, the exposed parts 2a of the photoresist layer 2 are eluted by an alkaline developer to form groove parts which are pits. While the film thickness of the spin coated photoresist layer 2 is determined by the number of revolutions of the spin coater, the photoresist soln. has the viscosity as low as <=4cP and, therefore, the photoresist layer 2 is formable to the thinner layer in spite of the low number of revolutions of the spin coater. Then, the low- height pits are formed and the manufacture of the stamper for optical disks dealing with a trend toward higher densities is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical disk stamper used for molding an optical disk substrate.

[0002]

2. Description of the Related Art Photoresists are mainly used in the production of semiconductors and the like, and the viscosity thereof has hardly been studied so far.

For example, commercially available photoresists include:
Even those with low viscosity are only about 5 cp, for the following reasons.

[0004] The main application of the semiconductor is a mask for dry etching and ion implantation at the time of fine processing, and the used film thickness is about 200 to 2000 nm. In this semiconductor manufacturing process, generally, the diameter is 125 to 125.
A silicon substrate having a thickness of about 200 mm and a thickness of about 0.4 to 0.7 mm is vacuum-adsorbed and held, and is coated with a photoresist.
Since the photoresist layer is shaken off at a rate of 00 to 6000 revolutions / minute, a very low viscosity is not required for the photoresist layer to have the desired film thickness.

[0005]

On the other hand, when producing a stamper for an optical disk, a diameter of 200 mm is generally used.
A glass master having a thickness of about 360 mm and a thickness of about 5 to 7 mm is used, and its weight can be as large as 500 to 1500 g. Therefore, the load on the spin coater is larger than that of the silicon substrate.
It is desired that the rotation be performed at a rotation speed of 000 rotations / minute or less.

In optical disk applications, the thickness of the photoresist is equivalent to the height of the pit as it is, and in the case of a so-called compact disk (CD), it is about 130 to 160 nm. This height is used to detect a signal by utilizing the fact that the amount of light that returns to the objective lens when the reading beam is diffracted at the pit portion when reading the disk is small, and corresponds to １ ／ of the reading laser wavelength. For example, in the case of an optical disc, pits are formed on a substrate (refractive index: about 1.5) made of polycarbonate or acrylic resin, and a laser beam having a wavelength of about 0.78 μm is used for reading light. 1 / 1.5 = 1.3 (μm) Basically, this calculation formula is the basis for setting the pit height of the optical disk, that is, the thickness of the photoresist.

[0007] In the optical disc, further densification is required, and in order to realize this, the wavelength of the reading laser beam is shortened. Accordingly, the photoresist layer corresponding to the height of the pits is required to be thinner.

However, as described above, when manufacturing a stamper for an optical disk, the rotational speed of the spin coater cannot be increased so much, and if a commercially available photoresist is used as it is, a thin film of the photoresist layer is formed. There is a limit to the conversion.

Accordingly, the present invention has been proposed in view of such a conventional situation, and a method of manufacturing a stamper for an optical disk capable of reducing the thickness of a photoresist layer and responding to an increase in the density of an optical disk. The purpose is to provide.

[0010]

In order to achieve the above object, a method of manufacturing a stamper for an optical disc according to the present invention comprises spinning a photoresist solution adjusted to have a viscosity of 4 cp or less by diluting with a solvent. It is characterized by forming a photoresist layer on a substrate by coating, forming unevenness on the photoresist layer by exposure and development, and then forming a plating film.

By reducing the viscosity of the photoresist solution, the thickness of the photoresist layer can be reduced without increasing the rotation speed of the spin coater. For example, by reducing the viscosity of a photoresist solution to 2 cp or less, 1
A photoresist film thickness of about 160 nm or less can be obtained by spin coating at 000 rpm.

Therefore, a pit having a low height can be formed, and a stamper for an optical disk which is compatible with high density can be manufactured.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing an optical disk stamper according to the present invention will be described below in detail with reference to the drawings.

A method of manufacturing a stamper for an optical disk according to the present invention is characterized in that a photoresist solution adjusted to have a viscosity of 4 cp or less by diluting with a solvent is used.

The solvent used for diluting the photoresist solution is not particularly limited, but propylene glycol monomethyl ether acetate (hereinafter referred to as P
Called GMEA. ), Butyl acetate (hereinafter, referred to as BA), 2-heptanone (hereinafter, referred to as MAK), ethyl lactate (hereinafter, referred to as EL) and the like are preferably used. EL has a high viscosity of 2.6 cp itself,
PGMEA having a viscosity of 1.1 cp and MAK having a viscosity of 0.8 cp are more suitable as diluting solvents.

As these solvents, the above-mentioned solvents may be used alone, or a plurality of kinds may be used in combination.

Specifically, as shown in FIG. 1, a glass master 1 which is first washed with an alkali or an acid, and further with running water ultrasonic waves is prepared.

Next, as shown in FIG. 2, a photoresist solution diluted to 4 cp or less with a solvent is applied on the glass master 1 using a spin coater. After application, 1
Baking is performed at a temperature of 00 ° C. or less to form a photoresist layer 2 having a predetermined thickness.

As the photoresist solution, a commercially available photoresist having a high viscosity of 5 cp or more diluted with a solvent to reduce the viscosity to 4 cp or less is used.

Next, as shown in FIG. 3, in order to expose the photoresist layer 2, for example, He having a wavelength of 442 nm is used.
Using a Cd laser or a Kr laser with a wavelength of 412 nm,
Laser cutting (recording exposure) is performed.

Next, as shown in FIG. 4, the exposed portion 2a of the photoresist layer 2 is eluted with an alkaline developing solution (in the case of a positive type photoresist) to form a groove serving as a pit.

Next, as shown in FIG. 5, a conductive layer made of nickel, silver, or the like is formed on the photoresist layer 2 having the groove formed by the previous exposure and development by electroless plating, sputtering, or the like. A nickel electroplating (electroforming) film of about 0.3 mm is formed to a thickness of about 30 to 100 nm, and a stamper 3 for an optical disk is manufactured.

Finally, as shown in FIG.
, And the photoresist remaining on the surface of the stamper 3 is removed by washing with an alkali or an organic solvent to obtain a stamper for an optical disk.

The photoresist solution diluted with a solvent to a viscosity of 4 cp or less is spin-coated on the glass master 1. The thickness of the spin-coated photoresist layer 2 is determined by the rotation speed of the spin coater.

In the method of manufacturing a spanter for an optical disk according to the present invention, a photoresist solution having a viscosity of 2 cp can obtain a photoresist film thickness of about 160 nm at 400 rpm and a photoresist film thickness of about 100 nm at 1000 rpm. can get. In addition, a photoresist solution having a viscosity of 1.5 cp can provide a photoresist film thickness of about 80 to 90 nm.

As described above, in the method for manufacturing a spanter for optical disks according to the present invention, the photoresist solution is
Since the viscosity is reduced to cp or less, the thickness of the photoresist layer can be reduced without increasing the rotation speed of the spin coater. Therefore, a pit having a low height can be formed, and a stamper for an optical disc corresponding to high density can be manufactured.

In the following, photoresist solutions having various viscosities were prepared, and the relationship between the viscosity of the photoresist, the rotation speed of the spin coater, and the thickness of the photoresist layer was examined.

First, a commercially available photoresist (trade name: TSMR-, manufactured by Tokyo Ohka Kogyo Co., Ltd.) was placed in a clean room under a yellow fluorescent lamp so that the photoresist was not exposed to light.
V50) was collected with a measuring cylinder and transferred to a brown quart bottle for preventing light exposure. In addition to this, commercially available PGMEA
(Manufactured by Hoechst; trade name: AZ5200) was collected by another measuring cylinder and added, followed by stirring with a stirrer. Here, by changing the dilution ratio of PGMEA, the viscosity was 1.5 cp,
A 2 cp, 3 cp, 4 cp, 5 cp, 10 cp photoresist solution was prepared.

Then, the photoresist solutions having different viscosities are spin-coated for 2 minutes at a set number of rotations.
It was pre-baked by a hot plate method at 0 ° C. for 30 minutes. FIG. 7 shows the relationship between the rotation speed of the spin coater and the thickness of the photoresist layer.

As can be seen from FIG. 7, if the photoresist solution has a viscosity of 2 cp, a photoresist film thickness of about 160 nm is obtained at a rotation speed of 400 rpm, and
A photoresist film thickness of about 100 nm can be obtained at a rotation speed of pm. Further, in the case of a photoresist solution having a viscosity of 1.5 cp, about 80 to 90 at a rotation speed of 1000 rpm or less.
A photoresist thickness of nm is obtained.

As described above, even at a rotation speed of 1000 rpm or less, the thickness of the photoresist layer can be reduced by diluting the photoresist with a solvent such as PGMEA to have a viscosity of 4 cp or less. Thus, for example, by formulating a photoresist solution having a viscosity of 2 cp or less, digital video
It is possible to obtain a photoresist film having a thickness of about 100 to 130 nm corresponding to a disk (DVD). Further, even when the density is further increased in the future and miniaturization is required, a photoresist film having a viscosity of 1.5 cp or less can be prepared to obtain a photoresist film having a viscosity of 100 nm or less.

[0032]

As is clear from the above description, in the method for manufacturing a spanter for an optical disk according to the present invention, since the viscosity of the photoresist solution is reduced to 4 cp or less, the rotational speed of the spin coater does not increase. However, the thickness of the photoresist layer can be reduced. Therefore,
It is possible to form a pit having a low height, and it is possible to provide a stamper for an optical disk that is compatible with high density.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for manufacturing an optical disk stamper to which the present invention is applied.

FIG. 2 is a process chart showing a method for manufacturing an optical disk stamper to which the present invention is applied.

FIG. 3 is a process chart showing a method for manufacturing an optical disk stamper to which the present invention is applied.

FIG. 4 is a process chart showing a method for manufacturing an optical disk stamper to which the present invention is applied.

FIG. 5 is a process chart showing a method for manufacturing an optical disk stamper to which the present invention is applied.

FIG. 6 is a process chart showing a method for manufacturing an optical disk stamper to which the present invention is applied.

FIG. 7 is a characteristic diagram showing the relationship between the number of rotations of a spin coater, the viscosity of a photoresist solution, and its film thickness.

[Explanation of symbols]

1 glass master, 2 photoresist layer, 3 stamper for optical disc

Claims (3)

[Claims] 1. A viscosity of 4 cp by dilution with a solvent.
An optical disc, comprising: forming a photoresist layer on a substrate by spin-coating a photoresist solution adjusted to be as follows; forming unevenness on the photoresist layer by exposure and development; and then forming a plating film. Method of manufacturing a stamper. 2. The photoresist solution has a viscosity of 2 cp.
2. The method for manufacturing an optical disk stamper according to claim 1, wherein: 3. The method according to claim 1, wherein the solvent is at least one selected from propylene glycol monomethyl ether acetate, butyl acetate, and 2-heptanone.