JPH02244440A - Production of optical master disk - Google Patents

Abstract

PURPOSE:To control the width of broad grooves with high accuracy by adjusting the condensing position of a light beam for exposing so that the light beam exposes a photoresist on a master disk in the position exclusive of a beam west position. CONSTITUTION:The condensing position of the light beam 14 is adjusted to irradiate the photoresist 12 on the master disk with the beam in the position exclusive of the condensed beam waist position 20 and the beam spot formed on this photoresist 12 is made into a large diameter in the exposing operation for forming the broad grooves 21. The exposing of the broad grooves 21 is, therefore, executed by one time of the exposing operation using one light beam. The need for relaying on the exposing operations of using plural pieces of the beam spots with which the accuracy is hardly obtainable is eliminated and, therefore, the control of the width of the groove 21 to a desired value with high accuracy is possible.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing an optical disk master, and more specifically, in order to form grooves on the optical disk master, a light beam is used to form a photocoat on the master optical disk. The present invention relates to a method of exposing a resist.

(Prior Art) Many optical disks, particularly write-once and rewritable optical disks, are formed with grooves that serve as guide tracks for guiding a pickup during information recording and reproduction. In general, there are grooves with a width of about 0.4 μm, which are called narrow grooves, and grooves with a width of about 1.2 μm, which are called wide grooves. This kind of groove is
It is formed through a cutting operation in which a focused laser beam is irradiated onto a master coated with photoresist, and a predetermined position of the photoresist is exposed. However, since the focused laser beam forms a small diameter beam spot on the photoresist, it is difficult to use it as it is as an exposure beam for forming the wide groove. The exposure method for forming such wide grooves is to irradiate the photoresist layer of the optical disc master with two laser beams, and to create two light spots that overlap each other. A method of irradiation can be considered in relation to
3-10500).

(Problem to be Solved by the Invention) However, such a method requires high precision because the precision of the groove width dimension depends on the precision of the positional interval between the two light spots, that is, the mechanical precision of the optical jig of the exposure device. There is a problem in that the groove width cannot be precisely controlled.

The present invention was made in view of the above circumstances, and it is an object of the present invention to provide a method for manufacturing an optical disc master, which allows the width of a wide groove of an optical disc to be controlled with high precision.

(Means for Solving the Problems) The method for manufacturing an optical disk master of the present invention adjusts the focusing position of the exposure light beam for cutting the optical disk master, so that this light beam is at the beam waist position (focusing position ) is characterized in that the photoresist on the master is set to be exposed at a position other than ( ).

(Function) In the master cutting process, efforts are being made to narrow down the beam diameter of the exposure light beam as much as possible in order to achieve high-density recording, and this narrowed beam is used to expose wide grooves. Because I was trying to do 1
It has been difficult to form a wide groove with a desired width by a single exposure operation using a light beam. Therefore, in the above configuration, the idea was changed, and when exposing a wide groove, the light beam was irradiated onto the photoresist layer on the master at a position other than the focused beam waist position of the light beam. By making the spot diameter on the resist layer larger, a desired wide groove can be formed in one exposure operation. As a result, it is possible to perform an exposure operation corresponding to a sufficiently wide groove without using a plurality of light beams for exposure, so that the groove width can be easily controlled during this exposure operation.

(Example) An example of the present invention will be described below with reference to the drawings.

In general, the manufacturing process of an optical disc can be broadly divided into a mastering process up to the formation of a stamper necessary for duplicating the disc, and a replication process up to the formation of a replica disc (see FIG. 2). The mastering process begins with processing and polishing the original glass plate (Sl),
Next, photoresist coating (S2) and laser beam exposure (cutting) are performed (S3). Thereafter, development is performed (S4), the surface is made conductive with a nickel thin film, and nickel electroforming is performed (S5) to produce a stamper necessary for copying and transferring. After this, the replication process involves duplicating the disc using this stamper.

Here, the structure of the glass master exposure apparatus (cutting apparatus) according to the present invention will be explained.

As shown in FIG. 3, the light intensity of the laser beam 14 emitted from the light source 13 is controlled by the EO modulator 15.
The beam is reflected by a reflection mirror 16 and is made incident on a beam expander 17, where the beam diameter is expanded to an appropriate effective NA value. After this, the laser beam 14 is
The light is made incident on the condensing lens 18, the focus is controlled by the focus control device 19, and the surface of the photoresist layer 12 of the resist master disk 11 which is being rotated is irradiated. As a result, a predetermined position of this photoresist layer 12 is exposed.

Incidentally, the exposure of the photoresist layer 12 with the laser beam 14 is normally performed at the most narrowed point of the focused laser beam (beam waist position). However, when forming a wide tracking groove (for example, about 1.2 μm wide),
A desired groove width cannot be obtained by exposing the laser beam 14 at the beam waist position.

Therefore, in the method according to the present invention, as shown in FIG. 1A, when performing exposure for a wide groove, a position other than beam waist position 20 (beam waist position 2
The photoresist layer 12 is irradiated with the beam at a position shifted from 0 in the optical axis direction, and a wide beam spot is exposed with a large diameter beam spot. The direction of deviation from the beam waist position 2α on the optical axis may be either a direction toward or away from the condensing lens I8, but a groove having a cross-sectional shape with better reflectivity is obtained by shifting in the direction away from the condensing lens I8. be able to.

As shown in FIG. 1(B), the light intensity distribution of the laser beam 14 has a gentle curved shape at the bottom, so that the exposure amount changes gradually at the edge of the groove 21. Become. As a result, the groove 21 after development
As shown in FIG. 1(C), the cross-sectional shape of the groove 21 is formed such that the shoulder portion 22 at the edge of the groove 21 draws a gentle curve. Since the shoulder portion 22 at the edge of the groove 21 has a gently curved shape, the groove reflectance of the optical disk formed by the method of this embodiment is higher than that of the conventional product, and the tracking servo characteristics It becomes possible to improve the

In addition, in the above embodiment method, the width of the formed groove 21 is controlled by irradiating the optical disc with parallel light during development and monitoring the diffracted light from the groove 21, so that the desired width can be achieved. It becomes possible to form the groove 21 with even higher precision. Note that the diffracted light may be either reflected or transmitted.

Note that the material of the master disk 11 to which the photoresist layer 12 described above is applied is not limited to glass, and various materials with which the photoresist can be easily applied can be used.

Note that the method of the present invention is applicable not only to the production of writable discs such as write-once discs and rewritable discs, but also to
For example, it can be applied to the production of read-only optical discs having wide grooves.

(Effects of the Invention) As explained above, according to the method for manufacturing an optical disc master of the present invention, in the exposure operation for forming a wide groove, the focusing position of the light beam is adjusted and The photoresist layer on the master is irradiated with a beam at the position, and the beam spot formed on the photoresist layer has a large diameter, so that one
A wide groove can be exposed by multiple exposure operations. This eliminates the need to rely on exposure operations that are difficult to obtain with precision, such as using a plurality of beam spots, making it possible to control the width of the groove to a desired value with high precision.

[Brief explanation of drawings]

Figures 1 (A), (B), and (C) are schematic diagrams for explaining a method for manufacturing an optical disc master according to an embodiment of the present invention, and Figure 2 shows each manufacturing process for manufacturing an optical disc. FIG. 3 is a block diagram showing an apparatus for carrying out an embodiment method of the present invention. DESCRIPTION OF SYMBOLS 11... Resist master disk 12... Photoresist layer 13... Light source 14... Laser beam 18... Condensing lens 19... Focus control part 20... Condensed beam waist position 21...・Groove (C) Figure, /11

Claims (1)

[Claims] While rotating a master disc having a photoresist layer formed on a substrate, a light beam is irradiated onto the photoresist layer to expose a predetermined position on the layer, and then the photoresist layer is exposed at a predetermined position on the layer. A method of manufacturing an optical disc master in which a groove is formed by developing a resist, the method comprising: setting the light beam to expose the photoresist at a position other than a focused beam waist position. .