JPH0229955A - Production of optical disk - Google Patents

Abstract

PURPOSE:To suppress the fluctuation of depth in a substrate plane by providing an upper layer photoresist having high exposing sensitivity and a lower layer photoresist having low sensitivity onto the substrate and setting the exposing sensitivity of the upper layer at specific times of the exposing sensitivity of the lower layer. CONSTITUTION:The surface of the disk-shaped substrate 1 is coated with the lower layer photoresist 2 having the film thickness corresponding to the difference between the depth of deep patterns 5 and the depth of shallow patterns 4. The upper layer photoresist having the film thickness corresponding to the depth of the pattern 4 on the layer 2. The exposing sensitivity of the layer 3 to laser light used for exposing is then set at >=1.5 times the exposing sensitivity of the layer 2. The layer 2 having the low exposing sensitivity is not subjected to such exposing that the photoresist is removed by a development processing even if there are some fluctuations in the laser exposing sensitivity to the pattern 4 forming parts, the control of the depth of the shallow patterns is regulated by the film thickness of the upper layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disc manufacturing method, and particularly to an optical disc manufacturing method in which patterns with different depths are formed on a substrate.

[Conventional technology]

In the conventional optical disc manufacturing method, a photoresist layer is formed on a substrate, and in the step of forming an information signal as a pattern on the substrate by laser exposure and development processing, a single hot resist layer 6 is formed as shown in FIG. A shallow pattern 4 and a deep pattern 5 are formed.

As a means of forming patterns with different depths in the photoresist layer using the single-layer photoresist 6, exposure is performed by changing the intensity of laser light depending on the depth of the pattern to be formed.

That is, the depth when forming the shallower pattern 4 in the photoresist layer is controlled by controlling the depth of the photoresist layer removed in the development process after exposure by adjusting the intensity of laser exposure. In order to control the depth of the deeper pattern, the photoresist layer is exposed to light at a sufficient intensity to be completely removed in the development process, and the depth of the deeper pattern is determined by controlling the depth of the coated single-layer photoresist layer 6. This is done in a way that makes the thickness equal to the film thickness.

[Problem to be solved by the invention]

However, with the above-mentioned conventional optical disc manufacturing method, it is difficult to form patterns with different depths on almost the entire surface of the substrate so that there is no variation in the respective depths. Depth control of shallow patterns, which is controlled by the depth of the photoresist layer removed by processing, is limited to ±5 variations in the depth within the substrate plane due to variations in laser exposure intensity or variations in the exposure sensitivity of the photoresist layer. It has the disadvantage that it is extremely difficult to suppress it within %.

[Means to solve the problem]

The optical disc manufacturing method of the present invention uses upper and lower photoresist layers with different exposure sensitivities as photoresist layers forming patterns on a substrate, the upper layer is a photoresist with higher exposure sensitivity, and the lower layer has a higher exposure sensitivity than the upper layer. Constructed using low photoresist.

That is, in the optical disc manufacturing method of the present invention, the photoresist layer coated on the substrate to form patterns with different depths on the substrate by laser exposure consists of two layers, an upper layer and a lower layer, and the film thickness of the upper layer photoresist is determined by the depth. The thickness of the lower photoresist is such that the sum of the thicknesses of the upper and lower photoresist corresponds to the depth of the shallow pattern, and the thickness of the lower photoresist is such that the sum of the thicknesses of the upper and lower photoresists corresponds to the depth of the deep pattern. The multilayer photoresist layer has an exposure sensitivity that is 1.5 times or more that of the underlying photoresist.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the present invention.

In the optical disc manufacturing method shown in FIG.
Then, about 700 people formed an upper layer photoresist 3 having an exposure sensitivity about twice that of the lower layer photoresist 2,
Shallow pattern 4 using laser light with a wavelength of 4570
5mW as the laser light intensity to expose the part forming the
, the portion where the deep pattern 75 is to be formed is exposed with a laser light intensity of 15 mW, and then a development process is performed,
formed a pattern.

A depth of approximately 70 mm formed by the optical disc manufacturing method shown in Figure 1.
The variation in depth within the plane of the substrate 10 for shallow pattern 4 with 0 people and deep pattern 5 with about 1400 people is about ±3.
It was within %.

In addition, in the above-mentioned example, an example was explained in which the ratio of the laser exposure sensitivity of the upper layer photoresist and the lower layer photoresist was doubled, but this laser exposure sensitivity ratio is not limited to twice, and substantially It is sufficient if the sensitivity ratio is 1.5 or more, which is the sensitivity ratio at which the effect of the present invention is produced.

〔Effect of the invention〕

In the optical disc manufacturing method of the present invention, in the step of forming patterns with different depths on a substrate, a photoresist layer with high laser exposure sensitivity and a thickness corresponding to the depth of the shallow pattern is formed as an upper layer, and an upper layer photoresist layer is formed as a lower layer. The sum of the film thickness and the film thickness of the lower layer photoresist corresponds to the depth of the deep pattern, and the exposure sensitivity is 1/2 compared to the upper layer photoresist.
By using a multilayer photoresist layer composed of the following photoresist layers, even if there is some variation in the laser exposure intensity for shallow pattern forming areas, the lower layer photoresist with low exposure sensitivity can be used as a material that can be removed by the development process. This has the effect that the depth of the shallow pattern is almost determined by the thickness of the upper photoresist layer even if there is some variation in the laser exposure intensity.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view showing an example of the conventional technology. 1...Substrate, 2. ...Lower layer photoresist, 3...Top layer photoresist, 4,5...
...Pattern, 6...Single layer photoresist. Agent Patent Attorney Susumu Uchihara

Claims (1)

[Claims] A lower photoresist layer with a film thickness corresponding to the difference between the depth of the deep pattern and the depth of the shallow pattern is applied to the substrate, and the exposure sensitivity is equal to that of the lower photoresist layer. A method for manufacturing an optical disc, characterized in that an upper layer photoresist is coated with a film thickness corresponding to the depth of a shallow pattern that is 1.5 times or more deep.