JP2507034B2 - Original plate for information storage disk and method for manufacturing substrate for information storage disk - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate used for a magnetic disk, an optical disk, a magneto-optical disk capable of high-density storage, and a method for manufacturing a master plate (stamper) for manufacturing these substrates. Is.

Conventional technology For optical disks and magnetic disks, one of the important points is to secure the reliability of data for long-term storage and to secure the stability and reliability of the substrate for high-speed writing and reading.
For this purpose, it is necessary to use a substrate that does not deform as a disk substrate, and it is desirable to use a glass substrate.
For example, when glass is used for the substrate, it has been customary in the past to provide a guide groove by a photopolymer method (eg, Kanamaru optical video disk system, Journal of the Television Society, Vol. 32, No. 1, 1978, 15 pp.). Since nickel (Ni) original plates are used for these original plates (stampers) for optical disks, it is common that the guide groove cannot be transferred to a heat-resistant hard material such as glass. In addition, recently, a method has been developed in which an uneven guide groove is directly provided on the glass substrate by a reactive ion etching method (for example, Kenji Ohta et al., Vacuum,
28 (2) 77 (1985)).

The process of forming a guide groove in a typical conventional glass substrate is shown below.

After cleaning the glass disk, apply a positive resist with a spin coater to a thickness of 200 to 300 nm, pre-bak it,
Argon (Ar) laser light is focused, and a spiral guide groove with a groove width of about 800 nm and a pitch of 1600 nm is recorded by moving the laser light in the radial direction of the disk while rotating the disk at a constant speed. . Next, after developing this, using the remaining resist as a mask, reactive ion etching using CHF ₃ gas was performed to etch the glass to a depth of about 70 nm, and the unnecessary resist was removed by ashing with oxygen gas. By doing so, a guide groove is formed in the glass substrate for an optical disc. This is a method that does not use an original plate (stamper) and is said to be extremely poor in production. Further, since a substrate for a magnetic disk generally does not have a guide groove unlike an optical disk, it is delayed in achieving a high track density like an optical disk.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the conventional photopolymer method, a substrate for an optical disk can be manufactured with a certain degree of productivity, but since the original plate (stamper) for the optical disk is made of nickel, it is manufactured by the photopolymer method or the injection method. The optical disc substrate made of resin was made of resin. However, there is a drawback that the guide groove cannot be formed in the glass excellent in heat resistance and reliability by using the nickel stamper. In addition, the method of directly forming concave and convex guide grooves on the glass substrate by the reactive ion etching method is a complicated process such as applying a resist to each glass substrate and developing a guide groove pattern on the resist and a reactive ion etching process. However, there is a drawback that the productivity is extremely poor and the quality of the guide groove is not good.

The present invention has been made to overcome such drawbacks and uses an original disk for an information storage disk, which has extremely excellent heat resistance and poor reactivity with glass, and has a very small number of steps and a high-quality optical disk, An object of the present invention is to provide a method for producing a guide groove for a magneto-optical disk and a magnetic disk substrate.

Means for Solving the Problems In order to solve the above problems, the present invention uses a cemented carbide mainly composed of tungsten carbide (WC) or a cermet mainly composed of chromium carbide (Cr ₃ C ₂ ) as a base material. As the above, after forming an aluminum (Al) film on the base material, a resist is applied, the guide groove for the tracking servo is patterned, and a guide groove for the tracking servo is formed on the aluminum film by etching using the resist as a mask. Unevenness is formed. After that, the resist is removed, nitrogen ion implantation is performed, and the aluminum film is changed to an aluminum nitride film, thereby providing a method for easily producing a high-precision information storage disk original plate (stamper). A method for producing a substrate for an information storage disk by inserting glass between a pair of original disks for an information storage disk prepared by the method, heating, press-molding, and transferring the guide groove shape of the original plate onto the glass. Is intended to be provided.

Action The present invention is a method of forming a guide groove by hot press forming a glass material with a master plate (stamper) having a pair of guide groove patterns, as if press-forming a record disk. The guide groove pattern can be formed with high accuracy. In this way, the guide groove can be formed on the glass with high accuracy by forming the aluminum film on the surface of the original plate (stamper), then patterning the guide groove with high accuracy, and ion-implanting the aluminum film at high temperature with the glass. This is due to the original plate manufacturing method of changing into an aluminum nitride film that does not react.

Example Hereinafter, a configuration and a manufacturing method of an original plate for an information storage disk and a manufacturing method of an optical disk substrate using the original plate of one example of the present invention will be described with reference to the drawings.

Example 1 Hereinafter, an example of the present invention will be described with reference to FIG. First, as shown in Fig. 1 (a), W with a diameter of 90 nm and a thickness of 5 mm is used.
The cemented carbide base material 11 containing C as a main component is mirror-polished to finish its surface roughness to RMS = 8 to 10Å, and then an aluminum film 12 is sputtered by a sputtering method as shown in FIG. 0.5
The film was formed to a thickness of μm.

Next, as shown in FIG. 1 (c), a positive type resist 13 is spin coated on the alloy film to a thickness of 2000 to 3000Å,
As shown in FIG. 1D, a spiral guide groove having a width of 800 nm and a pitch of 1600 nm is patterned. Then, FIG. 1 (e) shows the spiral guide groove formed on the aluminum film by wet etching using the remaining resist as a mask to remove the resist. Next, FIG. 1 (f) shows that an original plate for an information storage disk was produced by changing the aluminum into aluminum nitride 14 by ion-implanting nitrogen into the original plate with an energy of about 1 M electron volt.

Although cemented carbide was used as the base material in this example, the base material of the original plate (stamper) is not limited to cemented carbide, and mainly Cr ₃ C ₂ excellent in heat resistance and high temperature strength is used. Cermet as a component can also be used. Further, the etching method of the aluminum film coated on the base material is not limited to wet etching, but dry etching such as electron cyclotron plasma etching can also be used.

Second Embodiment A second embodiment of the present invention will be described with reference to FIG. An information storage disk original plate (stamper) and an original plate having no guide groove prepared in Example 1 were prepared to form a pair of upper and lower molds. Then, as shown in FIG. 2 (a), the composition was SiO ₂ 73 wt.
%, Na ₂ O 16.5 wt%, Al ₂ O ₃ 1 wt%, CaO ₅ wt%, and MgO 3.5 w
A glass disk 23 with a diameter of 90 mm and a thickness of 1.2 mm consisting of t% is sandwiched between a pair of upper and lower stampers 21 and 22, and 78
After heating to 0 ° C, pressure molding is performed at a pressure of 20 kg / cm ² . FIG. 2 (b) shows the place where the glass disk 24 having the guide groove transferred thereto was taken out after being cooled to 500 ° C. as it was.

After that, the inner diameter hole was processed, and the surface and half surface of the glass substrate were evaluated using a scanning electron microscope.As a result, the shape of the stamper molding surface was accurately transferred, and the glass substrate had a width
A spiral guide groove with 800 nm, a pitch of 1600 nm, and a depth of 70 nm was formed. The surface roughness of the flat part of the glass substrate is also RM.
It was found that S = 10Å and the molding surface of the stamper was transferred cleanly.

Next, the glass substrate was rotated at 900 rpm, and the signal quality (CN ratio) of the substrate was measured using an optical head. As a result, the low roughness when the glass substrate having a mirror surface with a surface roughness RMS of 10Å or less was not rotated was When the CN ratio in the frequency range is taken as the reference (0 dB), the CN ratio is reduced by -1.0 dB, which is better than the substrate prepared using the stamper coated with the iridium alloy of the comparative example shown in Table 1. The result was obtained.

In addition, Table 1 collectively shows the experimental results when the composition of the glass serving as the substrate was changed.

EFFECTS OF THE INVENTION As described above, according to the present invention, a highly reliable and highly accurate original plate (stamper) for an information storage disk and an optical disk having a highly accurate guide groove very easily using this original plate It is possible to manufacture a magneto-optical disk or a substrate for a magnetic disk, and it is possible to supply a large amount of these substrates at low cost, which is an extremely useful invention in industry.

[Brief description of drawings]

1 (a) to 1 (f) are cross-sectional views showing a manufacturing process of a master plate (stamper) for an information storage disk, and FIG. 2 (a) is a vertical stamper and a space between them when manufacturing a substrate (disk). FIG. 2 (b) is a cross-sectional view of the installed material to be molded (glass disk), and FIG. 2 (b) is a cross-sectional view of an optical disk, a magneto-optical disk, or a magnetic disk substrate having a guide groove on its surface. 11 …… Base material, 12 …… Aluminum film, 13 …… Positive type resist, 14 …… Aluminum nitride, 21 …… Master plate with guide groove (stamper), 22 …… Flat upper mold, 23 …… Molding material (Glass plate), 24: A substrate that is molded and has guide grooves on the surface.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masaki Aoki 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Hideo Torii, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Eiji Fujii 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

(57) [Claims] 1. A cemented carbide mainly composed of tungsten carbide (WC) or a cermet mainly composed of chromium carbide (Cr ₃ C ₂ ) is used as a base material, and an aluminum (Al) film is formed on the base material. After the formation, a resist is applied, the guide groove for the tracking servo is patterned, and the resist is used as a mask to form concavities and convexities to be the guide groove for the tracking servo on the aluminum film by etching. After that, the resist is removed, nitrogen ions are implanted, and the aluminum film is changed to an aluminum nitride film to prepare a master plate for an information storage disk. 2. A cemented carbide mainly composed of tungsten carbide (WC) or a cermet mainly composed of chromium carbide (Cr ₃ C ₂ ) is used as a base material, and an aluminum (Al) film is formed on the base material. After the formation, a resist is applied, the guide groove for the tracking servo is patterned, and the resist is used as a mask to form concavities and convexities to be the guide groove for the tracking servo on the aluminum film by etching. After that, the resist is removed, nitrogen ion implantation is performed, and the aluminum film is changed to an aluminum nitride film to prepare an information storage disk original plate, and the glass is heated and pressure-molded to guide the unevenness of the original plate. A method for manufacturing an information storage disk substrate, which comprises manufacturing an information storage disk substrate by transferring the groove shape onto glass.