JPH06101150B2 - Disk blank manufacturing method and device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a guide groove (hereinafter simply referred to as a guide groove) formed by a spiral or concentric concavo-convex pattern on a substrate surface of a disk-shaped storage medium such as an optical disk or a magneto-optical disk. The present invention relates to a method and an apparatus for forming a disc blank on which such a fine pattern is formed.

There are various materials for the disc blank, for example, a magneto-optical disc in which a guide groove or a prepit is directly provided on one side of a disc-shaped glass, and an optical disc in a disc-shaped aluminum substrate or a disc-shaped glass substrate. There is a plastic disk having guide grooves and pits engraved on its surface, which is bonded to the surface opposite to the engraved surface with an adhesive.

(Background of the Invention) A disk-shaped storage medium such as an optical disk or a magneto-optical disk is provided with a spiral or concentric guide groove for increasing the recording density of information in the radial direction, and tracking is performed by the guide groove. . 2 is a plan view of the disk blank, and FIG. 3 is a partial sectional view of the disk blank, which is a sectional view taken along the line AA in FIG.

In the following description, the disc blank will be described in which the guide groove is directly formed on one surface of the transparent disc glass.

In FIGS. 2 and 3, 6 is a disk blank made of transparent glass, and G is a guide groove. Conventionally, in the case of manufacturing such a disk blank, in the case of a spiral guide groove, as shown in FIG. 4, a photoresist 11 is formed on one surface of a disk-shaped glass substrate (disk blank original plate) 60.
Is applied by spin coating or the like and then rotated at a constant speed, a light beam of a laser light source is irradiated onto the surface of the photoresist 11 in a spot shape, and the spot is exposed while moving at a constant speed in the radial direction. Further, in the case of the concentric guide groove, as shown in FIG. 4, the photoresist 11 is applied on one surface of the disk blank original plate 60 by spin coating or the like, and then is rotated at a constant speed to make the photoresist 11 The surface is irradiated with the light beam of the laser light source in a spot shape and exposed, the irradiation of the laser beam is stopped after each round irradiation, and the irradiation position of the laser beam is moved by one pitch in the radial direction, and then again as described above. Laser beam is irradiated, and this is repeated for the number of tracks to complete the exposure. The thus exposed product is developed to prepare a master plate as shown in FIG. In FIG. 5, 11a is the photoresist remaining after the development. After that, the removal portion 61 shown by the diagonal lines is removed by a known etching method such as dry etching, and the remaining photoresist 11a is removed by a known asher process, so that the spiral shape or concentric shape shown in FIG. The disk blank 6 having the guide groove G of 1 is manufactured.

Conventionally, since the disk blank is manufactured as described above, the width W of the guide groove G is 1 μm and the pitch P is 1.
6 μm, depth H 700 Å, disk diameter D 130 mm, guide groove formation range L 42 mm, disk rotation speed 1800 rpm, the exposure time is about 15 minutes for the spiral guide groove, and for the concentric guide groove In some cases, it took an extremely long time of about 30 to 40 minutes. This drawback is common to guide grooves and other fine patterns.

(Object of the Invention) It is an object of the present invention to solve the above-mentioned drawbacks and to obtain a disk blank manufacturing method and apparatus capable of shortening the exposure step for forming a fine pattern in the disk blank manufacturing step.

(Summary of the invention) The present invention, while performing projection exposure of a pattern of a fine pattern mask in which a fine pattern is formed of a light-transmitting portion and a non-light-transmitting portion onto a partial area of a disc blank original plate coated with a photoresist in advance, The technical point is to perform the exposure process for forming a fine pattern by moving the region continuously or discontinuously and rotating once.

The disc blank manufactured according to the present invention can also be used as a mold (mold or stamper).

(Embodiment) FIG. 1 shows an embodiment of a disk blank manufacturing apparatus of the present invention.

In FIG. 1, reference numeral 1 is a light source for exposure, such as a mercury lamp. An exposure optical system 2 is provided to obtain an exposure light flux having a uniform light intensity distribution. Reference numeral 3 is a guide groove pattern mask in which a guide groove pattern is formed by a light-transmitting portion and a non-light-transmitting portion. For example, the pattern is an opaque thin film (for example, a chromium thin film vapor-deposited) deposited on a transparent glass disk. What is formed is used. Here, the groove width W and the pitch P are as described above. Then, it is necessary to use the projection lens 4 having a larger N than λ / NA ² . In that case, the depth of focus is about 1 μm, which is very short, and the surface accuracy of the disk blank original plate is required to be very high. As such a projection lens, for example, a projection lens used in a projection exposure apparatus of a semiconductor manufacturing apparatus can be used. A plane parallel glass 5 is fixed so that the lower surface thereof coincides with the focal plane of the projection lens 4. The flatness is a thick glass that is polished to within 0.1 μm in the depth of focus of the projection lens 4, that is, both the upper surface and the lower surface and has good parallelism. 6
Is a disk blank original plate made of a transparent glass disk or an opaque aluminum disk on which a SiO ₂ thin film is vapor-deposited, and the exposed surface (the upper surface in FIG. 1)
A photoresist is applied by a method such as spin coating to a uniform thickness (for example, a thickness of 1.2 μm) to form a photoresist application surface 6a. Generally, a blank disc blank has a warp of about 2 minutes, a flatness of about 20 to 30 μm, and a parallelism of 10
It is about μm. Therefore, if the projection lens used in the projection exposure apparatus of the semiconductor manufacturing apparatus is used as the projection lens 4, the flatness is low and the focal depth of the projection lens 4 deviates from 1 μm. 8 is a mounting table of a disk blank manufacturing apparatus with a guide groove, which can be controlled to move up and down, and the upper surface thereof has unevenness, and a ring-shaped convex portion (ring-shaped mounting portion) 8a and a circular convex portion (circular mounting portion). Section) 8b, and the portion sandwiched between the ring-shaped mounting portion 8a and the circular mounting portion 8b forms a ring-shaped recess 8c. O-rings 7a and 7b are provided on the upper surfaces of the mounting portions 8a and 8b, respectively. Reference numeral 9 is a communication hole that opens into the ring-shaped recess 8c, and communicates the central portion of the circular mounting portion 8b with an air hole 10 provided vertically. Reference numeral 12 denotes a processing hole which is provided for punching the communication hole 9. After the communication hole 9 is drilled, a screw 13 is screwed in for airtightness.

Here, the batch exposure method has a problem that the resolution of the peripheral portion is lowered due to the performance limit of the projection lens, and the edge portion of the guide groove in the peripheral portion is not formed sharply. Therefore, in the present invention, the original disk blank plate is partially subjected to equal-magnification or reduction projection exposure, and the position of the projection exposed portion on the original disk blank plate is relatively moved to expose the entire surface of the original disk blank plate 6.

At this time, the relative movement may be continuous or discontinuous.

The relative movement between the projection exposure unit and the disc blank original plate may be performed by rotating the disc blank original plate.
In that case, the shape of the partial projection exposure is preferably a fan-shaped partial projection exposure shape 14 as shown in FIG.

In order to continuously move the partial exposure to expose the entire surface of the disk blank original plate 6, both are continuously rotated while the positional relationship between the guide groove pattern mask 3 and the disk blank original plate 6 is fixed. . This method is hereinafter referred to as a continuous rotation exposure method.

On the other hand, in order to move the partial exposure in a discontinuous manner to expose the entire surface of the disc blank original plate 6, both are intermittently rotated while the positional relationship between the guide groove pattern mask 3 and the disc blank original plate 6 is fixed. Constitute. This method is hereinafter referred to as an intermittent rotation exposure method.

The continuous rotation exposure method and the intermittent rotation exposure method will be described in detail below.

[Continuous Rotation Exposure Method] The disk blank original plate 6 is mounted on the mounting table 8 with the photoresist coating surface 6a facing upward.

The mounting table is raised and pressed with a constant pressure on the lower surface of the parallel flat glass 5 which is prepositioned so that the lower surface thereof coincides with the focal plane of the projection lens 4.

After that, air is forced in at a constant pressure through the air hole 10. At this time, the photoresist coating surface 6a, which is the upper surface of the disk blank original plate 6, follows the lower surface of the plane-parallel glass 5 and has the same degree of flatness as the lower surface.

As a result, the upper surface of the original disc blank 6 is within the depth of focus of the projection lens, and a sharp projected image is obtained.

While projecting and exposing the pattern of the guide groove pattern mask 3 onto the fan-shaped exposure area 14 as shown in FIG. 2, both of them are rotated at a constant speed while the positional relationship between the guide groove pattern mask 3 and the disc blank original plate 6 is fixed. Then, by performing one rotation (synchronous rotation), uniform exposure of the entire surface of the photoresist coating surface 6a of the original disc blank 6 is completed.

The exposed disc blank master plate 6 is subjected to a publicly known etching process to form guide grooves to complete the disc blank.

According to the above method, it is possible to perform exposure with any of the spiral and concentric guide groove patterns.

[Intermittent Rotation Exposure Method] is exactly the same as in the above continuous rotation exposure method.

The pattern of the guide groove pattern mask 3 is projected and exposed in a fan-shaped exposure area 14 as shown in FIG.

When the exposure is completed, both the guide groove pattern mask 3 and the disc blank original plate 6 are rotated by a predetermined angle and stopped while the positional relationship between the guide groove pattern mask 3 and the disc blank original plate 6 is stopped. Project and expose the pattern.

For example, if the angle of the fan-shaped exposure range 14 is set to 7 to 8 degrees,
By repeating the above-described exposure and movement steps about 50 times, the exposure of the entire photoresist coated surface 6a of the disc blank original plate 6 is completed. If one exposure and movement time is about 0.2 sec., One rotation is about 10 sec.

The exposed disc blank master plate 6 is subjected to a publicly known etching process to form guide grooves to complete the disc blank.

According to the above method, it is possible to perform exposure with any of the guide groove patterns having a spiral shape or a concentric circle shape. In particular, in the case of the concentric guide groove pattern, the pattern mask 3 may be a partial one, that is, a minimum pattern mask sufficient to cover the fan-shaped exposure area 14, instead of the entire disk blank. In this case, the pattern mask is moved relative to the disc blank original plate 6 while keeping the positional relationship with the exposure light flux fixed, and the above exposure and movement are repeated to repeat the exposure and the photoresist coated surface 6a of the disc blank original plate 6.
The exposure on the entire surface is completed.

Here, according to the intermittent rotation exposure method, since the boundary of each exposure range is double-exposed, that portion is overexposed and the shape of the formed guide groove is destroyed. However, if this section is used by formatting by dividing the track into sectors, there will be no inconvenience if it is arranged so as to correspond to the gap.

This will be described in more detail below.

FIG. 6 shows a disk blank manufactured by the intermittent rotation exposure method, 14a is an overlapping portion of each exposure, and the guide groove shape is broken in this double exposure portion.

In the currently used optical disc, one round is divided into about 50 sectors, and each sector is divided as shown in FIG.

In FIG. 7, 20 is a sync signal recording area of a sector, 12
Is a data recording area, 13 is a gap area, 21 and 23 are synchronization signal recording areas, and 22 is an address etc. recording area.

The gap 13 is provided in order to avoid double recording of data due to a rotation error of the optical disc driver, and there is no problem even if the shape of the guide groove is broken in the gap region 13.

Therefore, if the format is set so that the circumferential length of the overlapping portion 14a of the exposure is within the circumferential length of the gap region 13, there will be no problem due to the overlapping exposure.

FIG. 8 is a view showing the main part of another embodiment of the method and apparatus for manufacturing a disc blank. In FIG. 8, the case where the disc blank original plate 6 is made of a transparent material will be described.

In FIG. 8, the same symbols as in FIG. 1 represent the same effect members.

The present embodiment is different from the embodiment shown in FIG. 1 in that it is a table on which a disc blank original plate is placed, and the other configurations are the same.
In this embodiment, 17 is a mounting table made of an opaque material such as metal and having a flat upper surface, and the groove 16 is provided on the flat upper surface. The groove 16 communicates with the air hole 10.

Next, the process according to this embodiment will be described in detail.

The disc blank original plate 6 is placed on the placing table 17 so that the photoresist coating surface 6a faces downward.

Air is drawn from the air hole 10 with a vacuum pump. At this time, the lower surface of the disk blank original plate 6, that is, the photoresist coating surface 6a is sucked by the groove 16 of the mounting table 17 and follows the upper surface of the mounting table 17, and has the same degree of flatness as the upper surface of the mounting table 17.

As a result, the upper surface of the original disc blank 6 is within the depth of focus of the projection lens, and a sharp projected image is obtained.

Any of the following steps may be applied by the steps following the description of the step by the continuous rotation exposure method or by the steps after the description of the step by the intermittent rotation exposure method.

In this embodiment, it was explained that the present invention can be applied to the case where the disc blank original plate 6 is transparent, but when the parallelism of the upper and lower surfaces of the disc blank original plate 6 is secured (for example, the precision of 1 μm or less), Photoresist coated surface 6a
It is also possible that the photoresist coating surface 6a is exposed by mounting it on the mounting table 17 so that it becomes the upper surface.

(Effects of the Invention) As described above, according to the method and apparatus of the present invention, the disk blank original plate is pressed or sucked by static pressure on the reference flat surface so that the photoresist coated surface of the disk blank original plate follows the flat surface. In this way, a very high plane accuracy is achieved, and a mask pattern is exposed on a part of the photoresist coated surface of the disc blank master plate, and the partially exposed portion on the disc blank master plate is relatively moved. As a result, the entire surface of the disc blank is exposed, so that the exposure process for forming the guide groove in the process of manufacturing the disc blank can be drastically shortened.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a disk blank manufacturing apparatus according to an embodiment of the present invention, FIG. 2 is a plan view of a disk blank, FIG. 3 is a partial sectional view of a disk blank, and FIG.
5 and 5 are partial cross-sectional views showing a disk blank manufacturing process, FIG. 6 is a plan view of a disk blank manufactured by the intermittent exposure method, and FIG. 7 is a view showing a division state within one sector, and FIG. FIG. 6 is a sectional view showing a main part of a structure of a disk blank manufacturing apparatus according to another embodiment of the present invention. (Explanation of symbols for main parts) 1 ... Exposure light source 2 ... Certification optical system 3 ... Guide groove pattern mask 4 ... Projection lens 5 ... Parallel flat glass 6 ... Disc blank original plate 6a ... Photoresist Coating surface 7a, 7b …… O-ring 8a …… ring-shaped mount 8b …… circular mount 8c …… ring-shaped recess

Claims (6)

[Claims] 1. A pattern of a fine pattern mask in which a fine pattern is formed of a light-transmitting portion and a non-light-transmitting portion is projected and exposed onto a region of a part of a photosensitizer-coated surface of a disc blank original plate to which a photosensitizer is previously coated, Projection exposure of the fine pattern on the entire surface of the disk by relative movement of the projection exposure and the disk,
A method of manufacturing a disk blank, which is characterized by performing photoetching treatment thereafter. 2. A projection optical system for projecting and exposing a pattern of a fine pattern mask in which a fine pattern is formed of a light-transmitting portion and a non-light-transmitting portion onto a part of an original disc blank plate, and a projection surface provided by the projection optical system. A reference plane member having a reference plane, a disc blank original plate holding member including pneumatic means for causing the reference blank member to follow the original disc blank plate by air pressure, and a projection exposure portion by the projection optical system is held by the holding member. A disk blank manufacturing apparatus, comprising: a moving unit that is relatively movable on a held disk blank original plate. 3. The method of manufacturing a disc blank according to claim 1, wherein the movement is continuous movement. 4. The method of manufacturing a disk blank according to claim 1, wherein the movement is intermittent movement. 5. The disk blank manufacturing apparatus according to claim 2, wherein the movement is continuous movement. 6. The disc blank manufacturing apparatus according to claim 2, wherein the movement is intermittent movement.