JPS6356831A - Method for grooving glass substrate for optical disk - Google Patents

Abstract

PURPOSE:To improve etching accuracy by projecting a halogen ion beam directly to a glass substrate for an optical disk, and forming grooves or pits thereon. CONSTITUTION:The moving speed of the glass substrate and the scanning speed of an ion source are controlled by a computer and the pattern of grooves is formed on the glass substrate by direct drawing using the halogen ion beam. Since the glass sbustrate is directly drawn and etched by the halogen ion beam accelerated by a high acceleration voltage, the accuracy of the etching is extremely enhanced. As a result, the optical disk substrate formed with the grooves or pits having sharp edges is obtd. and the high C/N is obtd. The excellent characteristics are exhibited as well when the substrate is used as a master disk for mastering.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides an optical disk substrate or an optical disk master (the above-mentioned The present invention relates to a method for grooving a glass substrate for an optical disc to obtain an optical disc master (when the optical disc substrate is used as a master for a mask ring).

[Prior Art] The conventional optical disc master production process includes (1) coating a photoresist on a glass substrate, (2) performing beam exposure and recording using a laser recording device, and (3) developing the resist. It consists of A metal mold is then created from the obtained disc master, and a resin optical disc substrate is manufactured through a mask ring process (Encyclopedia of Electrical and Electronic Engineering 1, published by Denkishoin Co., Ltd. in 1984, Vol. 25). (See page 370).

In recent years, due to the demand for improved signal quality, after the resist development process described above, the exposed glass surface of the exposed area is subjected to reactive ion etching (proceeding by chemical reaction with highly chemically active radicals and ions using the resist pattern as a mask). Etching: Electrical and Electronic Engineering Encyclopedia 2 Published by Denkishoin Co., Ltd. 1984, Vol. 5, p. 243) to perform grooving directly on the glass substrate to form pits and grooves. As a result, a method for obtaining an optical disc substrate or an optical disc master is being realized. By putting this into practical use, it will be possible to reduce the noise from the master surface to the level of the glass surface and improve its quality, and it will be possible to create many metal molds from one glass master ( (Please refer to page 69 of the Proceedings of the Optical Memory Symposium 85)
.

Furthermore, it is also being considered to use a glass substrate with pits and grooves directly as an optical disk substrate for rewritable disks for computers that require a high degree of reliability.

[Problems to be Solved by the Invention] However, with the reactive ion etching method, it is difficult to obtain high precision in the shape of the groove or pit, the surface roughness within the groove, the groove depth, etc. For example, when a glass substrate with an outer diameter of 130 mm was used, the groove depth varied by about ±20%. These problems are due to the fact that the reactive ion etching method is an indirect patterning process using a photoresist, and that reactive ion etching etches glass irregularly. When such variations in groove depth etc. occur, the signal-to-noise ratio of the optical disc becomes inconsistent, which is a problem.

Furthermore, recently there has been a demand for recording ``grooves of varying depth'' as sector marks and for using multiple types of grooves to shorten seek time, and conventional reactive ion etching is no longer able to meet these demands. It's coming.

The second invention was made to solve the above-mentioned problems, and it is possible to create grooves that have sharp edges, flat sides, and "adjusted depth" by directly grooving the glass substrate for optical discs. Another object of the present invention is to provide a method for preparing an optical disc substrate or an optical disc master having pits.

[Means for Solving the Problems] The present invention is a method for grooving a glass substrate for an optical disc, in which an optical disc substrate or an optical disc master is obtained by forming predetermined grooves or pits in the glass substrate. The method is characterized in that the grooves or pits are formed by directly irradiating the glass substrate for an optical disk with a halogen ion beam.

[Function] The grooving method of the present invention performs etching by direct writing on the glass substrate with a halogen ion beam accelerated at a high acceleration voltage, so the etching accuracy is higher than that of reactive ion etching.

Furthermore, since a halogen ion beam is used, the reactivity toward glass is high.

Furthermore, the scanning speed of the halogen ion beam ion source and the moving speed of the glass substrate can be modulated by computer control.

[Example] Examples of the present invention will be shown below.

Example 1 and Comparative Example 1 Chemically strengthened soda glass having an outer diameter of 130 mm was used as a glass substrate. This soda glass was etched with a pitch of 1. 6um, groove width 0
．． Grooving was performed to form grooves of 8 μm and an average depth of 0° and 10 μm.

Note that this groove pattern was formed on a glass substrate using a resist pattern using a reactive ion etching method.

In the halogen ion beam etching method, the moving speed of the glass substrate and the scanning speed of the ion source were controlled by a computer, and a pattern of grooves was formed on the glass substrate by direct writing with the halogen ion beam.

The following halogen ion beams were used in the present invention.

Ion source: Field emission type ion source ion type 2F- Ion current: 200 pA Acceleration voltage: 30 keV Ion optical system: Electrostatic cylindrical lens and electrostatic polarizer Beam diameter: 0.2 μm On a glass substrate with grooves formed According to the conventional method for magneto-optical rewritable disks, AαN100OA and G were laminated, and various characteristics were investigated.

Table 1 shows the results of various characteristic investigations of a glass substrate grooved by the halogen ion beam etching method of the present invention (Example 1) and a glass substrate grooved by reactive ion etching (Comparative Example 1). .

Table 1 As is clear from Table 1, the groove depth, groove width within one cross section, and groove width variations of the grooves of the glass substrate obtained by grooving by halogen ion beam etching of the present invention are the same as those obtained by grooving by reactive ion etching. The in-groove reflectance and C/N (
The carrier to noise ratio is also excellent.

In addition, since the present invention uses halogen ions in the beam and has high reactivity to glass, other ion sources (Ar
etc.), it is possible to perform etching at high speed, and the surface inside the groove can be formed to be extremely smooth. And this advantage can be further emphasized by slight etching with dilute hydrogen fluoride after grooving.

In this example, an example of grooving to form a simple groove was shown to clarify the difference from Comparative Example 1, but by applying this grooving to the formation of pits and grooves, optical disk substrates and optical disks Get the master.

Further, in the method of the present invention, the scanning speed of the ion source and the moving speed of the glass substrate can be modulated by computer control, and the depth of the pits and grooves can be easily varied. In this case, the pit size and groove width do not change even if the depth changes.

In this example, an example using fluorine ions, which is preferable as the ion species, was given, but the present invention is not limited to this, and other halogen species (chlorine ions, etc.) are used.

bromine ion, etc.).

Further, in this embodiment, a case where the accelerating voltage of the halogen ion beam is set to 30 keV is shown as a preferable example, but the present invention is not limited to this, and the accelerating voltage can be used within the range of 5 to 50 keV. Acceleration voltage is 5keV
If it is less than 50 keV, the etching efficiency will deteriorate, and if it is more than 50 keV, the halogen ion beam will be injected into the glass substrate, causing a problem.

Further, in this example, a preferable beam diameter of the halogen ion beam is 0.2 μm, but the present invention is not limited to this, and the beam diameter is 0.05 μm.
to 0.5 μm. Generally, the groove width of a groove formed on a glass substrate is about 0.8 μm, and if the beam diameter is less than 0.05 μm, it is too small to form a groove width of 0.8 μm, which is inefficient. Beam diameter is 0
゜0.5μm or more. It is too large to form a groove width of 8 μm, which is a problem.

[Effects of the Invention] Since the grooving method of the present invention performs etching by directly writing a halogen ion beam accelerated at a high acceleration voltage onto a glass substrate, the etching accuracy is significantly increased. As a result, an optical disk substrate having grooves or pits with sharp edges can be obtained, and an excellent C/N ratio can be obtained. Therefore, even when the optical disc substrate is used as a mastering mastering disc (an optical disc master), it can exhibit excellent characteristics.

Further, since a halogen ion beam is used, the reactivity with glass is high, high-speed etching is possible, and grooves or pits can be formed with extremely smooth surfaces.

Furthermore, since the scanning speed of the halogen ion beam ion source and the moving speed of the glass substrate can be modulated by computer control, the depth of the groove can be adjusted in various ways. As a result, the demand for changing the depth of the groove and using it as a sector mark, and for shortening the seek time by using various types of jumpers can be appropriately satisfied.

(2 others)

Claims (4)

[Claims] (1) A method for grooving a glass substrate for an optical disk in which an optical disk substrate or an optical disk master is obtained by forming predetermined grooves or pits on a glass substrate, characterized in that the grooves or pits are formed by irradiation with a halogen ion beam. Grooving method for glass substrates for optical discs. (2) The beam diameter of the halogen ion beam is 0.05
2. The method of grooving a glass substrate for an optical disk according to claim 1, wherein the halogen ion beam has an acceleration voltage of 5 to 50 keV. (3) The method for grooving a glass substrate for an optical disk according to claim 1 or 2, wherein the halogen ion beam is a fluorine ion beam. (4) The method for grooving a glass substrate for an optical disc according to any one of claims 1 to 3, wherein the glass is soda glass.