JPS61271637A - Pattern forming method - Google Patents

Abstract

PURPOSE:To prevent generation of defect such as pin holes by using the X-ray exposure technology so as to form a pre-group of an optical disc base thereby constituting all processes by a dry process. CONSTITUTION:A cross-linked PMMA 2 is deposited onto the optical disc base 1 made of glass, an X-ray exposure mask 3 is placed on it, an X-ray is irradiated to the front face to bake a pattern 4 of a mask 3 to the PMMA layer 2. Then the pattern formed to the layer 2 is developed to leave behind a pattern 2' of an X-ray irradiated part on the base 1. In order to form directly the pre- group to the base 1, the base 1 is subject to plasma etching by using the PMMA pattern 2' as a mask to form pits 5 of the pattern corresponding to the X-ray unirradiated part. Thus, all processes are formed by the dry process, no solvent is required and the pre-group without defect such as pin holes is obtained.

Description

[Detailed Description of the Invention] [Summary] A pregroove of an optical disc is formed using X-ray exposure technology.

[Industrial application field]

The present invention relates to a pattern forming method, and more specifically, to a method for forming a pregroove on an optical disc substrate.

[Conventional technology]

Conventionally, methods for forming pregrooves on optical discs include a method in which they are formed directly on an acrylic substrate using a compression injection method, and a 2P method (photopolymer method) in which they are formed on a glass substrate using a photosensitive resin.

[Problem that the invention seeks to solve]

In all of the above methods, pregrooves are formed by molding liquid resin using a master disc. This liquid resin contains a solvent, and as a result, the cured resin inevitably has many defects such as pinholes (10
−' order of probability) occurs. Further, even in the 2P method in which pregrooves can be formed on a hard substrate, the substrate is limited to transparent glass, quartz, etc., and has the disadvantage that an opaque substrate such as aluminum cannot be used. Furthermore, in the 2P method, although pregrooves are formed on a hard substrate, the pregrooves are not directly formed on the hard substrate, but a resin layer having pregrooves is formed on the hard substrate.

[Means for solving problems]

In order to solve the above problems, the present invention forms pregrooves on a substrate using X-ray exposure technology.

[For production]

Conventionally, pattern formation using exposure technology has been commonly performed in the field of semiconductor device manufacturing, but it is only for small areas and has not yet been performed for large area items such as optical disks.However, if X-rays are used, It is possible to avoid interference of light, and it is possible to form a desired pattern as an optical disc even in a large area such as an optical disc. Therefore, if X-ray exposure technology is used, pregrooves can be formed directly on the surface of the substrate, if necessary, regardless of the type of substrate. Furthermore, all steps of the X-ray exposure technique can be performed as a dry process, thereby making it possible to form pregrooves with fewer defects.

〔Example〕

Formation of pregroove (see FIG. 1C) Crosslinkable PMMA 2 is deposited to a thickness of about 100 ns by vapor deposition on an optical disk substrate 1 made of glass, quartz, metal, etc. and having a diameter of, for example, 12 inches. A ready-made X-ray exposure mask 3 is placed on top of it, and the front surface is irradiated with xl.

For example, the X-ray exposure mask 3 has a width of 0.5 μm and an interval of 1.0 μm.
A mask pattern 4 made of an X-ray opaque material is formed concentrically or spirally on the μ sardine.

Therefore, by the above-mentioned X-ray exposure, the pattern is printed onto the PMMA layer 2 (the PMMA in the father-ray transmitting portion is crosslinked and hardened).

(See Figure 1C) When the X-ray exposure mask 3 is removed and the pattern formed on the PMMA layer 2 is developed by oxygen plasma etching, the non-X-ray irradiated areas, that is, the non-crosslinked areas, are selectively removed. Therefore, the pattern 2' of the xl irradiation part remains on the substrate 1.

This PHMA pattern can be used as it is as a pregroove.

(See Figure 1C.) In order to directly form a pregroove on the substrate 1, the substrate 1 must be CF
4 or CCLa to a depth of about 0.1 μm, for example. By this etching, a pattern of grooves 5 corresponding to the non-X-ray irradiated areas is formed on the surface of the substrate 1.

Although it is not necessary to remove PMMA 2', if necessary, it can be removed by oxygen plasma etching to obtain an optical disk substrate 1 having pregrooves 5 as shown in the third figure.

In this way, in either the state shown in FIG. 1 C or D, pregrooves can be formed on a hard substrate, regardless of the type of substrate, for example, on an aluminum substrate. In particular, in FIG. can be formed directly.

Further, in the above process, all the steps are dry processes and no solvent is required, so that excellent pregrooves without defects such as pinholes are provided.

The creation of an X-ray exposure mask used for the above-mentioned X-ray exposure of the X mask will be explained.

(See Figure 1C) Nickel is deposited on a substrate 7 several tensile thick, made of an X-ray transparent material such as glass, light metal, or plastic.

A heavy metal such as gold (X-ray opaque material) 8 is deposited to a thickness of about 110 ns by vapor deposition or sputtering, and then a photocrosslinkable resist (for example, polyvinyl alcohol or phenoxy resin with a sensitizer thiapyrylium salt added) 9) is deposited to a thickness of about 110 ns using a vapor deposition method.

A pregroove pattern is written on the master disk obtained in this way using, for example, an argon laser beam 10 having a wavelength of 458n+a. This pattern has a width of, for example, 0.5μ, as described above.
Heel, spacing 1. It is a concentric circle shape or a spiral shape of OIl+w. The portion 9' of the photocrosslinkable resist 9 that is irradiated with the laser beam is crosslinked and hardened.

(See FIG. 2B) When the resist 9 that has been written with the laser beam is subjected to oxygen plasma etching, the portions not irradiated with the laser beam are removed.

This etching is performed until the heavy metal layer 8 is exposed, and the pattern is developed.

(See FIGS. 2C and D) Using the obtained resist pattern 9' as a mask, the heavy metal layer 8 is plasma etched with CF# or CCl2. After etching is performed until the substrate 7 is exposed, oxygen plasma etching is performed to remove the resist pattern 9'.

In this way, a groove pattern 8' of heavy metal (X-ray opaque material) is obtained on the substrate (X-ray transparent material) 7, as shown in the second diagram, and the X-ray exposure mask is completed.

The entire process for making the X-ray exposure mask is a dry process, so a mask without defects such as pinholes can be obtained and can be used for forming the pregroove according to the present invention.

〔Effect of the invention〕

According to the present invention, a pregroove in an optical disc substrate is formed by an X-ray exposure technique. Thereby, pregrooves can also be formed in opaque materials such as aluminum. Furthermore, pregrooves can be formed directly on a hard substrate. In particular, according to this method, the entire process can be configured as a dry process, so that defects such as pinholes can be prevented from occurring.

[Brief explanation of the drawing]

1A to 1D are cross-sectional views of important parts of the process for explaining the method for forming pregrooves on an optical disc according to the present invention, and FIG. 2A
-D is a cross-sectional view of a main part of the process for explaining the method of forming an X-ray exposure mask. 1...Substrate, 2...PMMA. 3...X-ray exposure mask, 5t...group, 7...
- Substrate, 8... Heavy metal layer, 9... Resist, laser light.

Claims (1)

[Claims] 1. When forming a pregroove on the surface of an optical disc substrate, an X-ray resist layer is formed on the optical disc substrate,
placing a ready-made X-ray exposure mask on the X-ray resist layer;
irradiating the X-ray exposure mask with X-rays from above to print a groove pattern on the X-ray resist layer; and after removing the X-ray exposure mask, developing the baked pattern on the X-ray resist layer. Characteristic pattern formation method. 2. The pattern forming method according to claim 1, further comprising the step of selectively etching the optical disk substrate using the X-ray resist pattern obtained by the development as a mask.