JPS61214250A - Formation of substrate for plane plate-shaped information recording carrier - Google Patents

Abstract

PURPOSE:To form easily grooves and pit arrays different in depth on the same substrate by providing a mask having aperture parts different in width on the substrate and allowing a gas in the plasma state to act upon this substrate. CONSTITUTION:A photoresist 2 is applied onto a glass substrate 1 and is exposed to light while changing the spot diameter of a laser light 3 to form a mask pattern having aperture part different in width. This glass substrate 1 is placed on the cathode electrode of a dry etching device, and CHF3 is used as the etching gas to allow the gas in the plasma state to act upon the substrate by discharge. If the discharging power of plasma generation, the action time of plasma, etc. are selected properly at this time, etching different in depth is performed in accordance with aperture parts of the mask. Thus, grooves and pit arrays different in depth are formed easily on the same substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing a substrate for a flat information recording carrier having grooves and pit rows of different depths.

Conventional technology Optical discs are capable of recording and reproducing information using a minute laser spot with a diameter of 1 μm or less, allowing for large-capacity and high-density recording. It has been put into practical use as a file system for files such as files and documents.

Concentric or spiral grooves and pit rows are formed on the information recording surface of this optical disk, and information is read out by irradiating the laser spot along these. On read-only optical discs such as video discs, information is recorded as unevenness of minute bits, and on write-once optical discs that allow additional information to be recorded, information is recorded as physical changes in the film on the recording surface. However, even in this case, guide grooves are formed on the recording surface so that information can be recorded at regular intervals and with high density. Recording density can be increased by narrowing the spacing between pit rows and guide grooves, but if the spacing approaches the size of the laser spot, the light flux of the groove (or part of the pit) that is being read when reading information is applied to one adjacent groove (or pit row), and its influence appears as crosstalk in the reproduced signal.In order to reduce this crosstalk, the depth of adjacent grooves or focus rows is alternated. This is attracting attention as a method for increasing the density of optical discs.(Refer to Japanese Patent Application Laid-Open No. 136303/1983) The conventional method of creating grooves and pitch rows of different depths on a single disc is The method will be explained with reference to FIG.

First, a photoresist 2 is uniformly applied to the surface of a highly precisely polished glass plate 1 (FIG. 2a).

Thereafter, the photoresist 2 is exposed to laser light 3 modulated in accordance with the desired structure of pit rows and grooves (FIG. 2b). At this time, when exposure is performed while changing the laser intensity, the photoresist 2 that is removed during the development stage is
Since the amount of irradiation varies depending on the exposure amount, the depth of the groove formed varies accordingly (FIG. 2C). By transferring this uneven pattern onto a metal plate 4 (Fig. 2 d) and further transferring it onto a substrate 5 such as acrylic (Fig. 2 e), an optical disk substrate with a desired structure and depth can be created. 0 Problems to be solved by the invention However, in such conventional production methods,
Since the amount of development of the photoresist is very sensitive to changes in the state of the developer and the external environment, there has been a problem in that it is very difficult to control the amount of development to obtain a predetermined groove depth.

Means for Solving the Problems In order to solve the above problems, the present invention reacts plasma gas to a substrate provided with masks having different widths to form grooves and pit rows having different depths. The feature is that it is designed to do the following.

Effect The effect of this method is as follows. When a plasma-like gas is applied to a substrate whose surface has been masked with photoresist or the like, the unmasked portions of the substrate surface are etched due to plasma collisions and chemical reactions between the substrate and the plasma. The shape of this etched pattern actually differs greatly from the original mask pattern, but this is due to the effects of isotropy of the reaction process and changes in the amount of etching with respect to the incident angle of the plasma ion beam. .

These effects vary depending on the type and pressure of the gas used as the plasma, the discharge power used to generate the plasma, the time for which the plasma is applied, etc., but by appropriately selecting these factors, changes in the mask pattern can be controlled. Etching conditions can be found such that the depth of the etched pattern formed with respect to the etching pattern changes. By utilizing this, grooves and pit rows with different depths can be created on the same substrate by changing the width of the mask pattern formed on the substrate.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIG.

Laser light 3 is applied to glass plate 1 coated with photoresist 2.
The process of irradiating is the same as the conventional method (Fig. 1a,
b). However, in this example, the width of the exposed area is changed by changing the spot diameter of the irradiated laser beam. If a positive type photoresist is used as the photoresist 2, the exposed portion will be removed by development. A mask pattern with a width of is formed.

Next, this glass plate with a mask pattern is placed on a cathode electrode in a dry etching apparatus, and after creating a vacuum state, gas is introduced and discharged to perform etching. In this embodiment, CHF3 is used as the etching gas. In this case, the plasma generated by the dissociation of CHF3 due to the discharge collides with the surface of the glass plate 1 and sputters the glass, while at the same time sputtering S10, which is the main component of the glass.
It has the effect of selectively reacting with 2 and decomposing it. Therefore, the etching speed of the glass plate 1 can be made higher than the etching speed of the photoresist 2, making it possible to create deeper grooves. Note that the glass plate 1 used in this embodiment is made of ordinary soda glass material, and even in this case, a sufficient etching rate can be obtained.

After etching has progressed to a predetermined depth (FIG. 1d), the remaining photoresist 2 is removed by plasma ashing using 02 gas, creating grooves and pit rows with different depths on the surface of the glass plate 1. (Fig. 1e).

As the substrate of the flat information recording carrier, instead of using this glass plate 1 as it is, it is also possible to use a substrate with a concavo-convex pattern transferred from this glass plate 1 as in the conventional method.

Note that the etching gas used in this example was CHF.
In addition, CF4. C2F6. C3F8. NF3 or the like can be used. Further, when an inert gas such as Ax is used, since there is no effect of decomposing 5iO20, the etching rate of the glass plate 1 becomes low, but it is possible to form a pattern.

Furthermore, as the glass plate 1, inexpensive soda glass can be used as in this embodiment, and in order to form deeper grooves, quartz glass or the like having a high etching rate can also be used.

Effects of the Invention As described above, the present invention enables plasma gas to act on a flat substrate provided with masks having different widths to form grooves and focus rows with depths corresponding to the mask widths. , it is possible to easily create optical disk substrates having grooves and bit rows of different depths on the same substrate.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing a method for manufacturing a substrate for a flat information recording carrier according to an embodiment of the present invention, and FIG. 2 is a process diagram showing a conventional method for manufacturing a substrate for a flat information recording carrier. 1...Glass plate, 2...Photoresist, 3...Laser light, 4...Metal plate, 5...Acrylic substrate 0 Name of agent: Patent attorney Toshio Nakao and 1 other person
Glass plate Z Photo cyst ° Goni 1 translation.

Claims (6)

[Claims] (1) A gas in a plasma state is applied to a flat substrate provided with a mask having continuous or intermittent openings of different widths, and grooves or pit rows having different depths corresponding to the widths of the openings are formed. 1. A method for producing a substrate for a flat information recording carrier, the method comprising: forming a substrate for a flat information recording carrier; (2) A method for producing a substrate for a flat information recording carrier according to claim 1, characterized in that a positive photoresist is used as a mask. (3) The flat information recording carrier according to claim 1, wherein the flat substrate is formed of a material whose main component is SiO_2 at least at the portion where the groove or pit row is formed. How to create a board. (4) The planar information according to claim 1, wherein the planar substrate is formed of a material whose main components are SiO_2 and Na_2O at least in the portion where the grooves or pit rows are formed. A method for producing a record carrier substrate. (5) CHF_3 and CF_4 as gases in plasma state
, C_2F_6, C_3F_8, and NF_3.
A method for producing a substrate for a flat information recording carrier as described in 2. (6) A method for producing a substrate for a flat information recording carrier according to claim 1, characterized in that Ar is used as the gas in a plasma state.