JPH02247842A - Method for forming optical disk pattern - Google Patents

Abstract

PURPOSE:To obtain stable signal characteristics by forming a pattern of grooves and pits in a master disk with using two resist layers and then forming grooves and pits to a desired depth in a specified process. CONSTITUTION:On a glass substrate 1, the lower resist film 2, intermediate film 3 and upper resist film 4 are laminated. The resist film 2 dissolves in a developer when the main surface is given small quantity of light, while it becomes insoluble with large quantity of light. The resist film 4 dissolves in a developer and forms patterns by exposing to light. The pattern of grooves and pits in the optical master disk is formed by using the two resist layers 2, 4. Depth of grooves is determined only by the thickness of the resist film 4, while depth of pits is determined by the thickness of the resist films 2, 4. By this method, depth of grooves and pits can be accurately controlled with good reproductivity, which results in stable signal characteristics. The resist films 2, 4 are selectively removed by irradiating the substrate 1 with light 5d, 6d of different quantities.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an optical disc pattern forming method.

[Conventional technology]

Generally, optical disk media require two types of patterns to be formed on the plastic surface: a bead pattern for displaying address information and a group (guide groove) pattern for guiding a laser head for writing storage signals.

To manufacture such optical disc media, a mold called a nickel stamper is created from the optical disc master using electroforming technology, and the pattern of the optical disc medium is completed from this mold using plastic molding technology. do.

Therefore, since the pattern on the optical disk medium is transferred twice from the master process to the standby process, it is necessary to form a pattern on the optical disk master that has exactly the same shape as the optical disk medium.

A conventional optical disk pattern forming method will be explained using FIGS. 3(a) to 3(c).

First, as shown in Fig. 3(a), a positive photoresist (trade name: Microposit S-1400 manufactured by Shipley), for example, is applied to a thickness of 1500 mm on a flat soda-lime glass plate by a spin code method. A resist film 12 is formed by heat treatment at 90° C. for 30 minutes in a clean oven.

Next, as shown in FIG. 3(b), the laser beam irradiation portions 15.16 of the resist film 12 are irradiated with, for example, argon laser beams 15d and lad.

In this case, the ratio of the light amount of the laser beam 16d to the light amount of the laser beam 15d is set to about 40 to 60%.

Finally, as shown in FIG. 3(c), the glass substrate 11 is immersed for about 50 seconds in a developer whose main component is an aqueous solution of sodium silicate with a concentration of 0.21N to perform a development process.
All of the resist on the laser beam irradiation section 15 on the glass substrate 11 is removed to form a pit pattern 15A. On the other hand, the laser irradiation portion 16 of the resist film 12
resist film 1 because the light intensity of the laser beam LAD is small.
Approximately half of the pattern 2 is removed to form a group pattern 16A.

Through the above steps, an optical disc pattern to be used as an optical disc master is completed.

Such a conventional optical disc pattern forming method is based on a group pattern 1 formed for guiding a writing head.
In 6A, the thickness of the resist removed is the same as that of the resist film 12.
The thickness must be uniformly controlled at the exact midpoint.

However, it is difficult to stably realize a group pattern that meets the above requirements by setting the light intensity of the laser beam 16d to be relatively low compared to the light intensity of the pit pattern laser beam 15d. .

In other words, the currently used positive resists have the characteristic that the remaining film thickness changes rapidly in response to changes in the exposure amount at the exposure level where the remaining film thickness is about half. The relationship between exposure and remaining film thickness is shown in Figure 4, where the remaining film thickness is 15% of the initial film thickness.
At 750 people, which is half of 00 people, the slope of the characteristic curve is steep, and if the exposure amount changes by 10%, the residual film thickness will be ±2.
It can be seen that there is an extremely large change from 50 people.

From now on, it is extremely difficult to stably realize the group pattern 22A with good reproducibility due to the following fluctuation factors: ■ Fluctuations in laser beam light intensity ■ Changes in resist film sensitivity ■ Developer concentration ■ Development temperature reduction.

According to measurements, the actual residual film thickness in the group pattern 22A fluctuates between approximately 600 and 900 people due to the above-mentioned fluctuation factors.

Therefore, the signal characteristics obtained from this pattern are also subject to variations.

[Problem to be solved by the invention]

However, in the above-mentioned optical disk pattern forming method, when a single resist film is exposed with varying laser beam intensity, the remaining film thickness varies, resulting in poor reproducibility and stable signal characteristics. The disadvantage is that it cannot be obtained.

[Means to solve the problem]

The optical disk pattern forming method of the present invention is configured to form a pattern using a two-layer resist film made of two types of photoresist materials having different characteristics, instead of a single-layer film made of a single photoresist material. Ru.

〔Example〕

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

In the optical disc pattern forming method shown in FIGS. 1(a) to (g), 0.895% (by weight) of diphenyl sulfone oxide is added as a crosslinking agent to a positive resist 0FPR80050P manufactured by Tokyo Ohka Kogyo, for example, on a glass substrate 1. The resulting resist material is applied to a thickness of 800 mm using a spin foot method, and then heat treated at 90° C. for 30 minutes in a clean oven to form a lower resist film 2 as shown in FIG. 1(a).

Next, a solution of 2.58% (by weight) polyvinyl alcohol added to pure water was dropped onto the lower resist film 2, and then
It was spin-coded and heated in a clean oven at 80°C for 40 minutes to give it a thickness of 50 mm, as shown in Figure 1(b).
An interlayer film 3 of human polyvinyl alcohol is formed. This intermediate film 3 is formed to prevent mixing with the lower resist film 2 when applying a resist to the upper layer.

Next, on the intermediate film 3 made of polyvinyl alcohol, a positive resist microposit S made by Shipley was applied.
-1400 is coated to a thickness of 700 mm using a spin code method, and heated at 90° C. for 30 minutes in a clean oven to form an upper resist film 4 as shown in FIG. 1(c).

Next, predetermined portions of the upper resist film 4 are irradiated with argon laser beams 5d and 6d, respectively, using the laser beam irradiation sections 5 and 6 as shown in FIG. 1(d). In this case, the light intensity of the laser beam 5d is 25 Joule/aA
, the light intensity of the laser beam 6d is 55 Jou Ie/
Set to ad.

Subsequently, the glass substrate 1 is immersed in a developer containing a 0.21N solution of sodium silicate as a main component to perform a development process. When this development process is performed for 55 seconds, the laser beam irradiated parts 5 and 6 of the upper resist film 4 are removed, as shown in FIG. 1(e).
Upper resist patterns 5A and 6A are formed as shown in FIG.

Next, the glass substrate 1 is immersed for 50 seconds in a mixed solution of iso)° propyl alcohol and pure water at a ratio of 1=5 (volume ratio), and a thin layer of polyvinyl alcohol is formed between the laser beam irradiation parts 5 and 6. After removing the membrane 3, as shown in FIG.
Upper layer resist pattern 5A.

5B and intermediate film patterns 5B and 6B are formed.

Finally, the glass substrate 1 is immersed for 60 seconds in a developer containing the same 0.21 normal sodium silicate solution as the main component when developing the upper resist film 4 for development. As a result, the lower resist film 2 exhibits the exposure amount-residual film thickness characteristic as shown in FIG.

That is, in a region where the exposure amount is small, the resist has the characteristics of a positive resist, and there is no residual film at an exposure amount of about 15 Joule/aa. After that, the exposure amount was further increased to 35 Joul.
When the exposure amount exceeds e/aa, the lower resist film 2 exhibits characteristics as a nether type resist due to the crosslinking reaction of the resin component by the additive diphenyl sulfonoxide in the lower resist film 2, and when the exposure amount exceeds 5'O Joule/era, , the remaining film thickness is 750 people.

Therefore, by the above-mentioned development process, the laser beam irradiation section 5
The lower resist film 2 is completely removed to form a bit pattern 5C. On the other hand, in the laser beam irradiation section 6, the lower resist film 2 remains as it is, so only the upper layer is removed, as shown in FIG. 1(g). The horror group pattern 6C can be formed accurately.

If the optical disc pattern forming method of the present invention described above is used, the depth of the group pattern is determined by the reproducibility of the remaining film thickness of the lower resist film, so the reproducibility is significantly improved compared to the conventional optical disc pattern forming method. . That is, in the optical disk pattern forming method of the present invention, the remaining film of the group pattern is a lower resist film crosslinked by a laser beam with a large amount of light, and the film reduction rate during development is 1λ/
This is because the film reduction rate of 15 to 20 people/second during group pattern development in conventional optical disk pattern forming methods is much slower.

That is, according to measurements, the residual film thickness and reproducibility of group patterns obtained by the optical disc pattern forming method of the present invention are 73.
0 to 770 people, and the variation in residual film thickness is 17% compared to the conventional method.
It had improved to below 5.

〔Effect of the invention〕

The optical disc pattern forming method of the present invention uses two resist films, an upper resist film and a lower resist film, to form groups and pit patterns on an optical disc master, and the depth of the group pattern is determined by the thickness of the upper resist film. The depth of the pit pattern can be controlled by controlling the thickness of both the upper resist film and the lower resist film, allowing for accurate control with good reproducibility, making it possible to form optical disk masters with stable signal characteristics. There is an effect.

[Brief explanation of drawings]

FIGS. 1(a) to (g) are process sectional views for explaining an embodiment of the present invention, and FIG. 2 is a characteristic diagram for explaining the embodiment shown in FIGS. 1(a) to (g). Figure 3 (a) to (C)
4 is a process sectional view for explaining a conventional example, and FIG. 4 is a characteristic diagram for explaining the conventional example shown in FIGS. 3(a) to 3(c). 1.11...Glass substrate, 2...Lower resist film, 3...Intermediate film, 4...Upper resist film, 5d. 6d, 15d, 16d... Laser beam, 5
, 6°15.16. ...Laser beam irradiation section, 5A. 6A... Upper layer resist pattern, 12...
...Resist film, 5B, 6B...Intermediate film pattern, 50,15A...Pit pattern, 6C,
16A...Group pattern. Agent Patent Attorney Uchi Hara Shin Mei Amount → (Joule/(Layer 15 (l L-di beam 1tdL, -The: Beam (-&-2 Chijian Mei concave)

Claims (1)

[Claims] A first photosensitive resin film is formed on the main surface of a glass substrate having at least one main surface, the first photosensitive resin film having the property of becoming a developer-soluble type when the amount of irradiated light is small and becoming a developer-insoluble type when the amount of irradiated light is increased. a second step of forming a second photosensitive resin film having developer-soluble characteristics on the first photosensitive resin film by exposure, and forming a second photosensitive resin film on the glass substrate with different amounts of light. A third step of selectively irradiating a plurality of exposure lights, and a development process to remove only the first photosensitive resin film, the second photosensitive resin film, and the first photosensitive resin film in the exposure light irradiation area. and a fourth step of selectively removing one of the elements.