JPH0447542A - Manufacture of optical master disk - Google Patents

Abstract

PURPOSE:To reduce the influence of etching on an unexposed part and to obtain a pre-groove part with rectangular cross-section by performing exposure by setting the light intensity on a photosensitive material layer at a specific range, and performing developing for a time less than ten seconds by using developer of constant temperature. CONSTITUTION:A laser beam with prescribed light intensity is projected on the surface of a photoresist 2 by an exposure device equipped with an argon laser oscillator in which the numerical aperture (NA) of an objective lens is set at a value less than a constant value. The light intensity I(mw) at that time is set so as to satisfy the next condition i.e. to satisfy 3.8 X linear velocity (m/sec)>=I>=2.3 X linear velocity (m/sec). Thence, alkaline developer is jetted at a temperature of around 22 deg.C and for a time <=ten seconds, and the developing is performed, and a groove 3 for a pre-groove part is formed. In such a way, the progression of the etching on the unexposed part can be suppressed without increasing the NA of the objective lens, and the cross-section of the pre-groove part can be formed in rectangular shape.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing an optical disc master, particularly a resist master disc for a pregroup optical disc.

[Conventional technology]

In general, data is written on playback-only optical discs such as video discs using a combination of pits formed on the disc surface, and a laser beam is projected onto the optical disc surface and the presence or absence of reflected light from the focused area is detected to perform playback. It is supposed to be done.

In manufacturing such optical discs, a master disc called a so-called standber is manufactured, and mass production is performed using this master disc as a main mold.

By the way, the production of such master discs is usually done by coating a glass plate with photoresist to form a photoresist layer, exposing it to a laser beam, developing it and buttering it to produce a resist master disc. A metal master is manufactured by filling a resist master with a metal material. During the manufacturing process of the master as described above, it is desirable that the shape of the pre-group part in the resist master is formed into a rectangular cross-section with predetermined width and depth dimensions, but this shape depends on the laser beam profile and light intensity during laser exposure. , is determined as a function of the type of photoresist, type of developer, development time, etc.

For example, development utilizes the difference in etching speed of photoresist between exposed and unexposed areas, and the etching speed increases as the exposure amount increases. Therefore, when etching a certain amount, if the light intensity is lowered, it will take a longer time to develop, and the difference in etching speed between the exposed and unexposed areas will become smaller, and the etching speed for the unexposed areas will become relatively higher. As a result, the width of the pre-group portion becomes wider relative to the depth.

By the way, conventionally, the shape control of the pre-group part was carried out at around 20°C by using an organic alkaline developer, which is a developer to widen the groove width, and an inorganic alkaline developer, which is a developer to deepen only the groove depth. Development is performed for about 60 seconds (Japanese Patent Application Laid-Open No. 59-229754).

[Problem to be solved by the invention]

However, with this conventional method, due to the long development time, etching progresses rapidly in the unexposed areas, making it difficult to narrow the groove width of the group, resulting in the problem that the cross-sectional shape does not become rectangular as shown in Figure 4. there were.

FIG. 5(a) is a graph showing the relationship between light intensity (1) and development time, with light intensity (I) plotted on the horizontal axis and development time (1) plotted on the vertical axis. As is clear from this graph, as the light intensity increases, the development time decreases.

Figure 5 (bl is a graph showing the relationship between development time (1) and pre-group width; the horizontal axis represents development time (1), and the vertical axis represents pre-group width (W). It is.

As is clear from this graph, as the development time becomes longer, the width of the pregroup portion becomes wider.

As a countermeasure to this problem, a method has been adopted in which exposure is performed by increasing the NA of the objective lens and decreasing the diameter of the laser beam, but this method has a problem in that the depth of focus becomes shallow, which causes a decrease in yield.

The present invention was developed in view of the above circumstances, and its purpose is to maintain appropriate light intensity during exposure, shorten development time, and reduce the effect of etching on unexposed areas. It is an object of the present invention to provide a method for manufacturing an optical disc master in which a pregroup portion having a rectangular cross section can be obtained.

[Means to solve the problem]

In the method for manufacturing an optical disc master according to the present invention, the light intensity (■) during exposure by a laser beam when forming a pre-group portion is set to 3.
．． 8 X-ray velocity (m/sec)≧■≧2.3×linear velocity (m/sec), and the development time is 10 seconds or less.

[Effect]

In the present invention, this makes it possible to suppress the progress of etching on the unexposed area without increasing the NA of the objective lens.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof.

FIG. 1 is a schematic diagram showing the main manufacturing process of the method of the present invention, in which a photoresist layer 2 is laminated to a required thickness on a glass substrate 1, and the NA (aperture ratio) of the objective lens is set to 0.6. A laser beam with a predetermined light intensity (2) is projected onto the surface of the photoresist 2 by an exposure apparatus equipped with an argon laser oscillator as described below.

The light intensity (■) at this time is set so as to satisfy the following conditions.

3.8X-ray velocity (m/sec)≧I≧2.3X-ray velocity (m/sec)
(Second) Next, an alkaline developer is sprayed at about 22° C. for 10 seconds or less to perform development and form grooves 3 for the pregroup portions.

As the developer, either an organic alkali (tetramethylammonium, hydroxide, 0.265N) or an inorganic alkali (NaOtl, KOH, 0.232N) may be used.

Figure 2 (a) is a graph showing the relationship between energy density and development time, where the horizontal axis shows energy density (exposure amount (mW)).
/linear velocity (m/sec)), and the vertical axis represents development time (sec). FIG. 2('b) is a graph showing the relationship between pre-group width and development time, with the horizontal axis representing the pre-group width (nm) and the vertical axis representing the development time (seconds).
This is an indication.

As is clear from this graph, the energy density is 2, 3
It can be seen that the desired pregroup width of 580 to 600 nm can be obtained with a development time of 10 seconds or less.

FIG. 3 is a schematic diagram showing the cross-sectional shape of the pre-group part when the method of the present invention is used. In the figure, the solid line shows the case where the method of the present invention is used, and the broken line shows the case where the conventional method is used. ing.

As is clear from a comparison of Figures 3 and 4, the ratio of depth to width is significantly improved when the method of the present invention is used compared to when the conventional method is used. I understand.

〔Effect of the invention〕

As described above, in the method of the present invention, it is possible to perform exposure with a small aperture ratio of the objective lens, and it is possible to set the objective depth of focus deep, which can greatly improve the yield of master production. The present invention has excellent effects.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the main steps of the method of the present invention, Fig. 2 is a graph showing the relationship between energy density and development time, and the relationship between pregroup part width and development time, and Fig. 3 is a graph showing the relationship between energy density and development time. FIG. 4 is a cross-sectional view of the pre-group portion after development obtained by the conventional method;
Figure 5 (al is a graph showing the general relationship between light intensity and development time, Figure 5 (bl is a graph showing the general relationship between development time and pregroup width). 1... Glass plate 2...Photoresist layer 3...Groove In the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] (1) For the photosensitive material layer laminated on the substrate, use an argon laser to set the light intensity I to 3.8 x linear velocity (m/sec) ≧ I ≧ 2.3 x linear velocity (m/sec) A method for producing an optical disc master, comprising: exposing the light-sensitive material layer to a temperature within the range of 22° C.; and developing the photosensitive material layer using a developer at 22° C. for 10 seconds or less.