JPS6370943A - Production of optical recording medium - Google Patents

Abstract

PURPOSE:To prevent the deterioration of a recording medium after repetition of recording and erasing of optical information by forming an underlying film on the recording medium, then subjecting the surface thereof to sputter etching to remove an oxide film, etc., thereby improving and uniformizing the adhesiveness of the recording medium. CONSTITUTION:The underlying film 12, the recording medium film 14 and a protective film 15 for said recording medium film are successively formed on a substrate 10. The boundary 13 of the underlying film is subjected to the sputter etching prior to the formation of the film 14 and while the vacuum at the time of the sputter etching is maintained, the film 14 is formed. The natural oxide layer formed on the surface of the underlying film and the impurities, etc., sticking thereto are completely removed if the underlying film is subjected to the sputter etching in the above-mentioned manner, by which the boundary of the underlying film of the recording medium is uniformized. Since the formation of the recording medium to be formed is continuously executed under the same vacuum conditions, the at mospheric pollution of the boundary is obviated and the adhesive power of the boundary is improved.

Description

[Detailed description of the invention] 〔(overview〕 Involved in the manufacture of optical discs used for recording optical information.

After forming the base film of the recording medium, the surface is spack-etched to remove the oxide film, etc.

The purpose is to improve the adhesion of the recording medium and to improve its adhesion, and to prevent deterioration of the recording medium due to repeated recording and erasure of optical information.

[Industrial application field]

The present invention relates to an optical disk medium that forms two optically different stable states by irradiating a recording medium on a substrate with pulses having different focused beam powers or irradiation times,
In particular, the present invention relates to a method of manufacturing a recording medium in which optical information is repeatedly recorded and erased.

Such optical disc media have a storage density of 106 to 107 (b
It is expected to be used as a mass storage disk for computers in the future because it is capable of recording at an order of magnitude higher density than conventional magnetic recording devices.

[Conventional technology]

The film structure of a conventional recording medium and the outline of a vacuum film forming apparatus for forming a recording medium film will be explained.

Using a carrier substrate such as glass that is transparent and has excellent flatness, its surface is first used as a base film for a recording medium film by vacuum evaporation or sputtering.

A metal oxide film such as 1IIBO, 5nOz, TiOz, or a zinc sulfide film ZnS is formed to a thickness of about 80 nm.

Subsequently, a thin alloy film of, for example, indium antimony In-5b is formed to a thickness of about 60 nm as a recording medium film.

Further, as a protective film for the In4b medium film, a film of ZnS or the like is formed to a thickness of about 50 nm.

A disk in which a base film, a recording medium film, and a protective film are sequentially applied in this manner is expected to be used as a phase change type rewritable optical storage disk.

Figure 2 shows the radio frequency (Radio Fr.
1 is a simplified cross-sectional view of a sputter etching apparatus (abbreviated as RP).

In the figure, the inside of the Pel jar 20 is once evacuated through an exhaust hole 23 connected to a vacuum system, and then filled with an ionizing argon line or the like to an appropriate pressure through a gas introduction hole 24. The disk substrate 10 to be film-formed is attached to the cathode 21, and the anode 22 side facing the cathode 21 is provided with one or more sputter target sources 26, 27 . For example, In-3b source or Z
An nS source etc. are arranged. - Then, if the space inside the Pelger 20 is plasma-excited by the RP source, the metal ions of the target source 26 will be transferred to the substrate 10 by the ionized Ar gas.
A thin film 11 is formed by the impact on the top. However, in this case.

The other cuget 'rA27 is closed by a shutter.

[Gateway point that the invention attempts to solve]

When an optical recording medium formed by stacking a base film, a recording medium film, and a protective film as described above is used, for example, in a large-capacity external storage device, one characteristic that must be provided is that the noise level of the recording signal is at a predetermined level. It is required that the noise level be below the noise level, and that the noise level be stable against repeated use of recording and erasing. However, conventional recording media suffer from so-called deterioration during long-term use, in which the reproduced CN ratio (carrier-to-noise ratio) of the recorded signal decreases in proportion to the number of repetitions of recording and erasing optical information. .

[Means for solving problems]

In the present invention, as shown in the cross-sectional view of a film-forming substrate for an optical recording medium in FIG. 1, a base film (12), a recording medium film (14), and a protective film (15 ) before the formation of the recording medium film (14), a means for sputter etching the base film interface (13), and a means for sputter etching the recording medium film (14) while maintaining the vacuum during the sputter etching. This method solves the above-mentioned problems as a method for manufacturing an optical recording medium including a means for forming a film.

[Effect]

Sputter etching of the base film completely removes the natural oxide layer generated on the surface of the base film and the attached impurities, thereby homogenizing the base film interface of the recording medium. However, after sputter etching, the film is formed on the recording medium continuously under the same vacuum conditions, so there is no atmospheric contamination of the interface, and the adhesion of the interface is improved.

In this way, the deterioration of rewritable optical storage media that involves repeated recording and erasing of optical signals, which were two problems in the past, is eliminated.
A stable optical disk substrate can be provided.

〔Example〕

FIG. 1 shows the formation of an optical recording medium t1 for explaining the details of the present invention.
FIG. 3 is a cross-sectional view of the substrate.

Using a sputter etching apparatus as shown in FIG. 2, zinc sulfide ZnS is spun-formed to a thickness of about 80 nm on the base film 12 under conditions of an Ar gas filling pressure of about 10-' Torr. Next, the sputter target source ZnS is closed with a shutter, and the zinc sulfide ZnS film surface 13 is sputter etched using Ar gas for 20 minutes. At this time, the power applied from the RF source 25 is 50 watts.

Immediately thereafter, without breaking the vacuum of the same apparatus, the sputtering target is switched to the In/sb source side, and an alloy film of indium (In) and antimony (sb) 1n4oSb6o is sputtered to a thickness of about 60 nm as the recording medium film 14. .

Further, as a protective film 15 for the recording medium film 14, ZnS is spun-formed to a thickness of approximately 50 nm.

FIG. 3 shows the deterioration characteristics of the CN ratio with respect to the number of recording/erasing repetitions (N) of the optical recording medium obtained in the above example and a conventional medium with the same laminated structure (dotted line) of the present invention. It is an actual measurement characteristic diagram showing the effect.

Recording on the optical recording medium is performed at a circumferential speed of the disk substrate of 14 m/s.
, recording frequency 6M1lz, recording laser power 8mW.

Also, recording erasure laser power 4mW, measurement bandwidth 3
This was measured under the condition of 0kt+z.

According to the measured characteristics, the CN ratio of a conventional optical recording medium without interface treatment is about 3 dB lower than that of a medium with interface treatment at the initial stage of repetition. This is because the noise level is 3 dB higher. After that, as the number of repetitions of recording and erasing increases, the dotted line characteristics deteriorate significantly, but the optical recording medium of the present invention that has been subjected to the interface treatment has stable characteristics.
f i = done.

In this way, by introducing the cleaning treatment for the base film interface of the recording medium film, the noise level can be reduced, and it is possible to prevent the noise level from increasing due to repeated recording and erasing.

〔Effect of the invention〕

As is clear from the above, according to the method for manufacturing an optical recording medium of the present invention, the interface of the base film of the recording medium is cleaned, thereby improving the adhesion of the medium to the substrate and making it homogeneous. A predetermined CN ratio for the disc will be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a film-forming substrate of an optical recording medium for explaining the present invention in detail. FIG. 2 is a simplified cross-sectional view of the recording medium film forming apparatus. FIG. 3 is a characteristic diagram showing the relationship between the number of recording/erasing repetitions (N) and the reproduction CN ratio. In the figure, 110 is a disk substrate. 12 is a base film, and 13 is an interface. 14 is the recording medium film, 15 is the protection i1 father 1.
2 Figure

Claims (1)

[Claims] Base film (12) and recording medium film (14) on the substrate (10)
, in forming the protective film (15) of the recording medium film,
The recording medium film (14) is formed by including means for sputter etching the base film interface (13) of the recording medium film (14) and means for forming the recording medium film (14) while maintaining the vacuum during the sputter etching. A method for manufacturing an optical recording medium.