JP4088787B2 - Disc manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a disk such as a magneto-optical disk whose recording density is improved by magnetic super-resolution.

  In recent years, various types of information such as sound, images, and moving images have been recorded on and reproduced from disk-type recording media, and the data size of these information continues to increase. ing.

  Therefore, the recording density is improved by devising the configuration and reproducing method of the magneto-optical disk. For example, even if the track pitch is higher than the optical cut-off frequency of the spot light, a method for generating a racking error and enabling recording and reproduction is to pits in the radial direction with a period twice as long as the track pitch. There is a sample servo system that detects the tracking error signal by periodically providing the arranged servo areas in the circumferential direction of the disk. If this method is used, data can be reproduced even if the pitch of the recording track is higher than the optical cutoff frequency.

  In addition, a magnetic super-resolution method that is not limited by the spatial frequency of an optical slot is known as an effective method for increasing the density in the linear density direction of an area where recorded information is recorded. In particular, in recent years, DWDD (Domain Wal1 Disp1ace Detection) is considered the most effective method. In one of these methods, a domain wall moving layer having a small domain wall coercive force is provided on the reproducing light incident side, and the domain wall of the magnetic moving layer is moved to the high temperature side by using the temperature gradient in the reproducing spot. There is a method of expanding and reproducing the magnetic domain. In this method, even if the recording mark size is reduced, the signal is reproduced while enlarging the magnetic domain. Therefore, the reproduction light can be used effectively, and the resolution can be increased without reducing the signal amplitude.

  FIG. 6 is a diagram for explaining the reproducing operation of the magnetic super-resolution method. FIG. 6 (A) is a cross-sectional view showing a recording track portion of the magneto-optical disk, and FIG. 6 (B) is a diagram of the magneto-optical disk. It is the top view which showed the recording track part. The recording track 8 has a three-layer structure including a memory layer 2, a blocking layer 4, and a domain wall motion layer 6. Data is recorded in the memory layer 2 by the minute magnetic domains 200 smaller than the diameter of the spot 102 of the light beam 100 of the reproduction light.

  The minute magnetic domain 200 recorded in the memory layer 2 moves into the reproduction spot 102 of the domain wall moving layer 6 where the temperature is high due to the reproduction light and expands as indicated by 202. By reading out the enlarged magnetic domain, the signal recorded in the micro magnetic domain 200 can be reproduced. Therefore, it is necessary for the magnetic domains to move quickly into the reproduction spot 102, and in order to obtain high mobility of the magnetic domains there, the both sides of the recording track 8 are thermally annealed to be nonmagnetic or always magnetized. The domain wall can move smoothly without receiving interference from adjacent tracks. Subsequent reports have confirmed that an equivalent effect can be obtained by the groove shape of the substrate without performing this annealing treatment.

  That is, by optimizing the groove shape parameters of the substrate in land / groove recording, a discontinuous portion of the recording film is generated at the boundary between the groove and the land where the recording film is adhered, and thereby the magnetic field between the land and the groove Since the characteristics can be cut, the mobility of the magnetic domains can be increased. In order to cut the continuity of the recording film, it is effective to increase the slope angle of the groove, and a method for manufacturing a magneto-optical disk (generally an optical disk) having such a groove will be described below.

  The process of creating an optical disk master is called a mastering process. In this mastering process, a metal master called a stamper is finally created. This stamper is used as a mold in a later molding process, and a large number of optical disks are produced by molding. FIG. 7 shows a manufacturing method of this stamper. An outline of a manufacturing method using reactive ion etching (RIE) capable of realizing fine processing in order to make the slope of the groove steep will be outlined.

  First, a photoresist 12 is applied to the surface of the quartz master 10 that has been sufficiently cleaned after polishing. Next, an exposure apparatus (cutting machine) using a laser or the like as a light source irradiates a predetermined region with a light beam 104 as shown in FIG. Thereafter, development is performed with a developing solution to remove the photosensitive portion 14. The quartz master 10 thus treated is put into a chamber of a reactive ion etching apparatus and evacuated, and then an etching gas 106 is introduced and reactive ion etching is performed as shown in FIG. A concave portion as shown by a broken line is formed in the quartz master 10 in a portion where 12 is removed.

  Thereafter, the residual resist on the glass master 20 is peeled off to obtain an optical disk master (glass master) 20 as shown in FIG. The concave portion of the glass master 20 is a groove (groove) 16 and a land 18 is formed between the concave portion and the concave portion. Next, a Ni conductive film is formed on the surface of the glass master 20 to make it conductive, further Ni electroforming is performed, the Ni electroformed layer is peeled off from the glass master 20, and a plating stamper as shown in FIG. (Hereinafter simply referred to as a stamper) 22 is created (see, for example, Patent Document 1).

Here, combining the sample servo for increasing the track pitch and DWDD is one effective combination for increasing the density, and the conventional optical disk having the mark / group arrangement of the sample servo format shown in FIG. The stamper is generated using the RIE process as described above.
JP 2001-14742 A (page 2-3, FIG. 1)

  However, in the conventional optical disk with the mark / groove arrangement of the sample servo format shown in FIG. 8A, the servo mark 302 is used under the condition that the slope shape of the data area 32 is steep when the RIE process as described above is used. On the end face of the groove 16 in contact with the servo region 30 having the thickness, the density of the etching target is reduced, so that the etching is concentrated, and a recess 34 called a sub-trench as shown in FIG. 8C is generated. The reason why the concave portion 34 is generated is that etching progresses intensively in the vicinity of the servo mark 302 having a relatively small etching surface in the data area due to etching particles in the RIE process. Therefore, in the data region 32 as shown in FIG. 8A where there are many etched surfaces, a normal groove 16 with no occurrence of sub-trench is formed as shown in FIG. 8B.

  When the stamper 22 is peeled from the glass master 20 having the sub-trench, the protrusion 24 (see FIG. 7D) of the stamper 22 formed by the sub-trench 34 is likely to be rubbed off. If this peeling occurs partially or remains on the stamper 22, the signal of the servo mark 302 is given nonuniformity, which causes a reduction in servo accuracy.

  The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a disk manufacturing method capable of manufacturing an optical disk free of sub-trench generation.

In order to achieve the above object, the present invention provides a disk manufacturing method including a step of exposing a predetermined region of a photoresist coated on a quartz master disk by exposing it to an exposure beam, and developing the photoresist after the exposure. In the region where the etching target density is high when etching the quartz master after being removed, the exposure beam rise and fall times are shortened, and in the region where the etching target density is small, the exposure beam rise and fall times are lengthened. characterized in that it.

  As described above, in the disk manufacturing method of the present invention, when the region where the photoresist is exposed is a region where there is little etching target after removing the resist exposed portion, the rising and falling times at the time of exposure beam irradiation are determined as the etching target. In comparison with the case of irradiating a large area, the resist is exposed to the boundary between the exposed and unexposed portions of the resist, and the resist end surface formed by removing the resist exposed portion is inclined toward the exposure direction of the quartz master. Sub-trenching due to the concentration of etching in the etching process of the exposed portion of the quartz master performed thereafter can be prevented.

  As described above in detail, according to the present invention, when the region where the photoresist coated on the quartz master disk is exposed by the exposure beam is a region where there are few etching objects after removing the resist photosensitive portion, the exposure beam The rise and fall times at the time of irradiation are made longer than when irradiating a region where there is a lot of etching target, and the resist end surface formed by removing the resist photosensitive portion is inclined to the exposure direction of the quartz master disk, and then the process is performed. By creating a glass master that prevents the generation of sub-trench due to the concentration of etching in the RIE etching process of the exposed portion of the quartz master, it is possible to eliminate the protrusions formed by the sub-trench from the stamper generated from this glass master. Because it is possible, the optical disk that is duplicated from this stamper It can be eliminated subtrenches from the substrate. Therefore, the shape of the servo mark on the optical disk substrate can be made constant, so that the servo signal becomes uniform and stable servo accuracy can be obtained. Further, the slope of the groove formed on the optical disk substrate can be made steep by RIE etching. When a recording film is formed on such an optical disk substrate, the recording film is formed at the boundary between the groove and the land. A discontinuous portion can be generated, thereby cutting the magnetic characteristics between the land and the groove and increasing the mobility of the magnetic domain.

  The purpose of the present invention is to manufacture an optical disc without generating sub-trench, where the region where the photoresist applied to the quartz master disk is exposed by the laser beam is a region where the etching target after removing the resist exposed portion is small. The rise and fall time at the time of laser beam irradiation is longer than that when irradiating a region where there are many etching targets, and the resist photosensitive part is removed by inclining the boundary between the photosensitive part and the unexposed part of the resist. By forming a glass master that has a shape in which the edge of the resist to be inclined in the exposure direction of the quartz master and prevents the occurrence of sub-trench due to the concentration of etching in the etching process of the exposed portion of the quartz master that is subsequently performed Realize.

  FIG. 1 is a block diagram showing a configuration of a cutting machine (exposure apparatus) according to a disk manufacturing method according to an embodiment of the present invention. The cutting machine 60 includes a gas laser 62, an acousto-optic modulator (AOM) 64, an optical system 66, a laser condensing unit 68, a turntable 70 on which a quartz master coated with a photoresist is placed, and a spindle motor that rotates the turntable 70. 72 and a signal generator 74 for controlling the AOM 64.

  Next, the operation of the present embodiment will be described. A quartz master (not shown) coated with a photoresist is placed on a turntable 70 that is rotated at a predetermined speed by a spindle motor 72, and a laser beam emitted from a gas laser 62 is irradiated onto the quartz master. Make it light. The laser beam passes through the AOM 64 and the optical system 66 and is focused on the quartz master by the laser focusing unit 68. The AOM 64 modulates the optical output and optical path of the laser beam irradiated on the quartz master disk in accordance with the information signal supplied from the signal generator 74. At that time, the laser condensing unit 68 is moved at a constant speed in the radial direction of the quartz master.

  The signal generator 74 of the cutting machine 60 controls not only the modulation (on / off) of the optical output of the laser beam applied to the quartz master and the modulation of the optical path of the laser beam, but also the rotational speed of the spindle motor 72 and the laser. Control of the feeding speed of the light condensing unit 68 and the like is also performed.

  Here, a case will be described in which an optical disk having a sample servo format mark and groove arrangement as shown in FIG. As shown in FIG. 3A, the intensity of the laser beam when exposing the photoresist so as to form the data region 32 with a large etching surface changes to a rectangular shape, and the rise and fall are approximately 90 degrees. It has become. As a result, when the photoresist of the quartz master is exposed and the exposed portion is etched by the RIE process, the end portion of the remaining portion of the photoresist 82 is cut off as shown in FIG. Yes.

  On the other hand, as shown in FIG. 3B, the rise and fall of the intensity of the laser beam when exposing the photoresist so as to form the servo area 30 with a small etching surface is prolonged by the signal generator 74 and the AOM 64. To make it so-called dull. As a result, when the photoresist on the quartz master disk is exposed and the exposed portion is developed and removed with a developer, the end of the remaining portion of the photoresist 82 on the quartz master disk 80 is removed as shown in FIG. The concave portion opened by removing the photoresist 82 becomes a shape that becomes smaller as it goes down.

  When the quartz master 80 shown in FIGS. 4A and 4B as described above is etched by the RIE process, there are many etched surfaces in the data region 32 of FIG. 2, so that no sub-trench is generated as shown in FIG. A groove 84 having a steep slope is formed. Further, in the servo region 30 of FIG. 2, even if the etching of the RIE process is concentrated on the groove end face, the end of the remaining portion of the photoresist 82 is inclined as shown in FIG. The quartz master 80 is etched so as to reflect the shape, and as shown in FIG. 5, a groove 84 having no steep slope and having a steep slope can be generated.

  According to the present embodiment, the intensity of the laser beam 104 when the photoresist is exposed to form the servo region 30 with a small etching surface is determined by the signal generator 74 and the AOM 64 as shown in FIG. In order to expose the quartz master disk 80 coated with the photoresist 82 in a so-called dull state, the rise and fall times are increased and inclined, and the photosensitive portion is developed and removed with a developer. As shown in B), the end portion of the remaining portion of the photoresist 82 has a shape that is not steep and inclined, and after that, even if etching is performed by the RIE process, the formation of a sub-trench is prevented by the shape and a steep slope is formed. The held groove 84 can be generated.

  For this reason, when a stamper is generated from the glass master created by the above etching and an optical disk substrate is formed using this stamper, the groove of the optical disk substrate has a steep slope. In addition, a discontinuous portion of the recording film is formed at the boundary between the slope and the groove, and the magnetic characteristics between the land and the groove can be cut. Thereby, the mobility of the magnetic domain in the DWDD method can be increased. In addition, since the sub-trench is not generated in the groove in all regions of the optical disk substrate, the non-uniformity of the groove shape due to the generation, non-generation or deformation of the sub-trench does not occur, and the servo mark signal can be made uniform. And stable servo accuracy can be obtained.

  In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the summary, it can implement also with another various form in a concrete structure, a function, an effect | action, and an effect. For example, in the above-described embodiment, the disk manufacturing method with the sample servo format and the recording density improved by the DWDD method has been described. However, the etching target by RIE differs depending on the area of the quartz master, and there is a possibility that a sub-trench may be generated. In some cases, the same effect can be obtained by applying the present invention to the manufacture of various optical disks. Further, the exposure beam for exposing the photoresist is not limited to laser light, and the same effect can be obtained by applying the present invention to any exposure beam that can be exposed.

It is the block diagram which showed the structure of the cutting machine (exposure apparatus) which concerns on the disc manufacturing method concerning one embodiment of this invention. It is the partial top view which showed the structure of the optical disk of the mark servo arrangement of the sample servo format manufactured with the disk manufacturing method of this embodiment. It is a wave form diagram which showed the intensity | strength change of the laser beam radiate | emitted from the laser condensing part 68 shown in FIG. It is sectional drawing which showed the quartz original disk 80 after removing the resist photosensitive part after having been exposed with the cutting machine shown in FIG. It is sectional drawing which showed the glass master manufactured with the disc manufacturing method of this embodiment. It is sectional drawing which showed the recording track part of the magneto-optical disk reproduced | regenerated by the conventional magnetic super-resolution system. It is a figure explaining the method to manufacture a stamper by the conventional RIE process. It is the figure which showed the state of the glass master at the time of manufacturing the optical disk of the mark servo group arrangement | positioning of a sample servo format with the conventional disc manufacturing method.

Explanation of symbols

30 ... Servo area, 32 ... Data area, 60 ... Cutting machine, 62 ... Gas laser, 64 ... AOM, 66 ... Optical system, 68 ... Laser focusing unit, 70 ... Turntable, 72 ... spindle motor, 74 ... signal generator, 80 ... quartz master, 82 ... photoresist, 84 ... groove, 302 ... servo mark.

Claims (5)

A method of manufacturing a disk including a step of exposing a predetermined region of a photoresist applied to a quartz master disk by irradiating with a light beam with an exposure beam,
In the region where the etching target density is high when etching the quartz master after developing and removing the exposed photoresist, the rise and fall times of the exposure beam are shortened, and in the region where the etching target density is low, the exposure is performed. Increase the rise and fall times of the beam,
A method of manufacturing a disc. Disc manufacturing method according to claim 1, wherein said etching is reactive ion etching. Disc manufacturing method according to claim 1, wherein the pattern to be produced and exposed the photoresist is patterned to create disk Mark Guru part arrangement of the sample servo format. Developing and removing the photoresist after exposure;
Etching the quartz master after the development;
Producing a stamper from the quartz master after the etching;
Replicating a disk substrate from the stamper;
Forming a recording film on the replicated disk substrate;
Disc manufacturing method according to claim 1, characterized by including the. The exposure beam is disc manufacturing method according to claim 1, characterized in that it is a laser beam.

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