JPH05224425A - Evaluation method of photoresist for optical disk - Google Patents

Abstract

PURPOSE:To efficiently evaluate the characteristics of a photoresist to be used in a short time in a step before an optical disk of a final product is obtained. CONSTITUTION:A resist film 20 is formed on a glass substrate 10 (resist film forming process 1), after that, the resist film 20 is exposed while changing exposure stepwise and a stair like semi-exposed part 30 is formed by developing processing (semi-exposed part forming process 2), next, the surface roughness of the semi-exposed part 30 is measured (surface roughness measuring process 3).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating a photoresist for an optical disk, and more specifically, it can evaluate the characteristics of the photoresist, which influences the characteristics of the optical disk product, in a short time, thereby improving the production efficiency of the optical disk. The present invention relates to a method for evaluating a photoresist for an optical disk, which can improve the above.

[0002]

2. Description of the Related Art Optical discs are usually manufactured by the following process. As shown in FIG. 5A, first,
A positive type photoresist is applied to a well-polished glass substrate 100 to a uniform thickness, and as shown in FIG.
A photoresist layer 101 is formed. Then, FIG.
As shown in (c), laser light is applied to the pit corresponding portions of the photoresist layer 101. A portion of the photoresist layer 101 irradiated with the laser light is more easily dissolved in the alkali developing solution than a non-irradiated portion. Therefore, when the photoresist layer 101 is coated with the alkaline developing solution and developed, the result shown in FIG. As shown in d), a recess corresponding to a pit is formed in the portion irradiated with the laser beam. Then, as shown in FIG. 5E, the photoresist layer 101
A metal film 102 that imparts conductivity is formed thereover. Then, as shown in FIG. 5 (f), electroforming is performed to form the metal film 10.
2, a nickel (Ni) electroformed body 103 is formed, and the nickel (Ni) electroformed body 103 is formed on the metal film 102.
With photoresist layer 101 and glass substrate 10
What is obtained by peeling from 0 is a metal master (stamper) 104 as shown in FIG. Next, a resin disc 105 as shown in FIG. 5 (h) is formed from the metal master 104, and then a metal film 106 for reflection is further formed on the disc 105 as shown in FIG. 5 (i). An optical disc product is manufactured by forming a transparent protective layer 107 that protects the metal film 106 as shown in FIG. 5 (j).

Since the characteristics of the photoresist used in the manufacturing process of such an optical disk have a great influence on the performance of the final product, the optical disk, the characteristics of the photoresist to be used determine the required performance of the optical disk. Evaluating whether it is suitable to obtain is extremely important in the manufacture of optical discs.

Conventionally, evaluation of a photoresist used for manufacturing an optical disk has been performed by evaluating whether or not the final product, an optical disk, satisfies required performance. That is, when the optical disc finally obtained as a product through the above manufacturing process satisfies the required performance, the photoresist used has desirable characteristics, and the optical disc requires When the performance was not satisfied, the photoresist was evaluated as being not suitable for the photoresist used.

[0005]

However, in the conventional evaluation method as described above, the characteristics of the photoresist used satisfy the required performance unless the final product, the optical disk, is manufactured. There is a problem in that it is not possible to know whether or not it is suitable for manufacturing an optical disc to be evaluated, and it takes time before the evaluation. Also,
If it is found that the characteristics of the photoresist that was used after the final product optical disk was obtained were not appropriate, the processes up to that point will be wasted, improving the efficiency of optical disk production. There is also a drawback that it is not preferable in terms of Further, since the performance of the optical disk depends on the cumulative influence of each process in the manufacturing process, it is necessary to evaluate the photoresist while repeating many trial manufactures.

Therefore, as a result of various studies conducted by the present inventor on a method for evaluating a photoresist for an optical disk, the quality of the reproduced signal, which is the most important factor in the performance of the optical disk, that is, the CN ratio (carrier to noise ratio). ) Depends on the uniformity of the pit shape of the optical disc, and the uniformity of the pit shape has a close relationship with the uniformity of the development of the resist film, and the uniformity of the development of the resist film is It was found that there is a correlation with the surface roughness of the semi-exposed portion of the resist film, that is, the resist film is exposed while the exposure amount is changed stepwise, and development processing is performed to form a stepwise portion.

The present invention has been made on the basis of such findings, and an object of the present invention is to provide a photoresist for an optical disk, which enables efficient evaluation of the photoresist in a short time during the manufacturing process of the optical disk. To provide an evaluation method.

[0008]

The constitution of the present invention for achieving the above object is to form a resist film on a glass substrate, and then expose the resist film while changing the exposure amount stepwise. A method for evaluating a photoresist for an optical disk, characterized in that the photoresist is evaluated by measuring the surface roughness of a stepwise semi-exposed portion formed by performing a development process. The method for evaluating a photoresist for an optical disk according to claim 1, wherein the semi-exposed portion to be measured is a portion where the thickness of the resist film is reduced to about 1/2.

[0009]

In the method for evaluating a photoresist for an optical disk of the present invention, the resist film formed on the glass substrate is
Exposure is performed while changing the exposure amount stepwise, development processing is performed to form a stepwise semi-exposed area, and the uniformity of the development reaction in the resist film is measured by measuring the surface roughness of this semi-exposed area. evaluate. That is, the smaller the surface roughness of the semi-exposed portion, the more uniformly the development reaction of the resist film progresses. When the development reaction of the resist film progresses uniformly, the pit-shaped A high-performance optical disc with a small variation and thus a high CN ratio (carrier-to-noise ratio) will be manufactured. Therefore, according to this photoresist evaluation method for optical disks, it is possible to efficiently evaluate the suitability of the photoresist used in the optical disk manufacturing process in a short time without making a prototype of the final optical disk. Is.

[0010]

Embodiments of the present invention will now be described with reference to the drawings. As shown in FIG. 1, this method includes a resist film forming step 1 on a glass substrate, a semi-exposed portion forming step 2 following the step, and a surface roughness measuring step for measuring the surface roughness of the semi-exposed portion. 3, and the photoresist is evaluated based on the surface roughness of the semi-exposed portion measured in the surface roughness measuring step 3.

The glass substrate used in the resist film forming step 1 is the same as that used for making a master disc of an optical disc, and its surface is sufficiently polished.
A photoresist is coated on this glass substrate to form a resist film, and the photoresist can be coated using, for example, a spinner. The thickness of the resist film may be about the same as the depth of the pits formed on the optical disc, specifically about 0.1 μm.

Next, in the semi-exposure portion forming step 2, the resist film is exposed while the exposure amount is changed stepwise,
By performing a developing process, as shown in FIG. 2, the resist film 20 on the glass substrate 10 is removed stepwise in the thickness direction to form the semi-exposed portion 30. Here, in order to change the exposure amount stepwise, a step tablet can be preferably used. That is, when a step tablet is brought into close contact with the resist film to gradually select the intensity of light and the exposure time is appropriately selected, a development process is performed using an alkali developing solution, as shown in FIG. Then, the resist film 20 is removed stepwise to form a stepwise semi-exposure portion 30.

The half-exposure portion 30 and the pit cross section of the finally obtained optical disc have a relationship as shown in FIG. 3, and the surface roughness of the step-like half-exposure portion 30 is measured to obtain the final product. CN of the reproduction signal of the optical disc
It is possible to know the uniformity of the pit shape that affects the ratio (carrier-to-noise ratio).

Here, the semi-exposure section 30 for measuring the surface roughness.
The depth from the resist film surface is preferably about 1/2 of the initial thickness. This is because the surface roughness of this portion can be regarded as an average value or a typical value of the surface roughness of the pit sidewall.

The surface roughness can be measured by a conventional method such as a stylus method, a light cutting method, a light spot displacement method, a phase difference method, or a light wave interference method. It is desirable to use a scanning tunneling microscope or an atomic force microscope.

Next, an experimental example will be shown, and the method for evaluating the photoresist for the optical disk will be described more specifically. Experimental example Several kinds of samples were prepared by coating various kinds of photoresist on a glass substrate and forming a resist film with a thickness of about 0.1 μm. Each sample was exposed to light using a step tablet and then developed. The semi-exposed portion was formed by performing the above, and the surface roughness of the portion where the thickness from the surface of the resist film was reduced to about ½ of the initial thickness was measured using a scanning tunneling microscope.

The relationship between the surface roughness and the reproduction signal level (C), noise level (N), and CN ratio (carrier-to-noise ratio) of the optical disk obtained by using each photoresist was investigated. The relationship shown in 4 was obtained. In addition,
An optical system with a wavelength of 441 nm and a numerical aperture of 0.5 was used for reproduction.

As is clear from FIG. 4, the smaller the surface roughness of the semi-exposed portion, the smaller the noise level of the reproduced signal of the obtained optical disk and the better the CN ratio. It was confirmed that the performance of the obtained optical disk can be predicted by measuring the height, and thus the suitability of the photoresist for the optical disk can be accurately evaluated by this method.

[0019]

EFFECTS OF THE INVENTION According to the present invention, because of the above constitution, the photoresist used is suitable for manufacturing an optical disk satisfying the required performance before the final optical disk is obtained. It is possible to efficiently evaluate whether or not the optical disk has a short time, and it is possible to provide a method for evaluating a photoresist for an optical disk, which can improve the production efficiency of the optical disk.

[Brief description of drawings]

FIG. 1 is a flow chart showing steps of a method for evaluating a photoresist for an optical disc of the present invention.

FIG. 2 is an explanatory view schematically showing a semi-exposed portion formed by the method of the present invention.

FIG. 3 is an explanatory diagram showing a relationship between a half-exposure portion formed by the method of the present invention and a cross-sectional shape of a pit of an optical disc.

FIG. 4 is a graph showing the relationship between the surface roughness of the semi-exposed portion, the reproduction signal level (C), the noise level (N), and the CN ratio (carrier-to-noise ratio) of the optical disc.

FIG. 5 is an explanatory view showing the manufacturing process of the optical disc in the order of steps.

[Explanation of symbols]

 1 ... Resist film forming step 2 ... Semi-exposure part forming step 3 ... Surface roughness measuring step 10 ... Glass substrate 20 ... Resist film 30 ... Semi-exposure part

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kunizo Ogoshi 6-1, 1-1 Fujimi, Tsurugashima City, Saitama Pioneer Co., Ltd.

Claims (2)

[Claims] 1. A surface roughness of a stepwise semi-exposed portion formed by forming a resist film on a glass substrate, then exposing the resist film while changing the exposure amount stepwise, and developing the resist film. A method for evaluating a photoresist for an optical disk, characterized in that the photoresist is evaluated by measuring the height. 2. The method for evaluating a photoresist for an optical disk according to claim 1, wherein the semi-exposed portion for measuring the surface roughness is a portion where the thickness of the resist film is reduced to about 1/2.