JPH10124941A - Production of optical recording medium and film forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the constitution and mechanism of a film forming device by executing sputtering at the plural film forming sections successively installed in a sputtering chamber, thereby forming multilayered structures. SOLUTION: Disks 1 are continuously carried via a load locking chamber 2 for vacuum maintenance from the inside of the atm. into a sputtering chamber 3. This sputtering chamber 3 is internally provided with targets 4a to 4d for forming the respective layers of the four-layered structures. The disks are successively transported to these film forming sections, by which the desired film thickness layers are formed by sputtering and the four layers are formed. Since the disks 1 are continuously supplied, the sputtering is executed simultaneously or in overlap in time at the film forming sections of the four points. The respective layers of the four-layered structures are formed with the substantially the same sputtering gases under the same pressure. The disks are ejected out of an unload locking chamber 6 after the formation of the four-layered structures. As a result, the vacuum production by the one sputtering chamber is made possible and the improvement in the reliability and maintenance is resulted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for forming a film on an optical recording medium, and more particularly to a composition of a sputtering gas, a sputtering pressure, and a structure of a sputtering chamber in film formation by sputtering.

[0002]

2. Description of the Related Art Rewritable optical disks that are currently in practical use have a multilayer structure by sputtering such as a protective layer, a recording layer, and a reflective layer in both the magneto-optical system and the phase change system. It is formed by suitable different sputtering gas conditions (sputtering gas type, sputtering gas pressure, sputtering gas flow rate, etc.).

In particular, in the case of a magneto-optical disk, the protective layer (enhancement layer) is often formed by using a Si nitride layer formed by reactive sputtering of Si using a mixed gas of argon and nitrogen as a sputtering gas. . For this reason, the formation of the recording layer and the reflective layer using only argon as a sputtering gas is independent of each other so as not to be affected by the mixed gas of argon and nitrogen used for forming the protective layer (enhancement layer). A sputtered chamber is indispensable.

In the case of a phase change disk, a protective layer,
In forming the recording layer and the reflective layer, optimal sputtering gas and sputtering pressure are generally selected for obtaining good recording characteristics and the like.

Therefore, in the optical disk sputtering apparatus for mass production, a plurality of vacuum-independent sputtering chambers each having an evacuation system and a gas introduction system are connected by an isolation valve mechanism or the like in order to form each layer. It has a structure. Then, the disk is transported between the respective sputtering chambers and is sequentially formed into a film to form a multilayer structure.

In a small-scale experiment / development application, a protective layer, a recording layer, a reflective layer, and the like are sequentially formed in one sputtering chamber.
Evacuation / introduction of sputtering gas is performed every time one layer is formed, and sputtering gas conditions are completely switched each time each layer is formed, even though one sputtering chamber is used.

[0007]

However, the conventional film forming method and apparatus as described above have the following problems. First, a plurality of independent sputtering chambers are required to form a multilayer structure.Each chamber has a vacuum evacuation system, a sputtering gas introduction system, a vacuum degree measurement system, and a disk substrate for transferring the disk substrate between the chambers. A valve mechanism for vacuum-isolating the transfer mechanism and the chamber, and a control mechanism (hard / soft) for controlling these are required.

Therefore, the configuration / mechanism of the entire apparatus becomes complicated, resulting in a decrease in reliability of the apparatus, a decrease in maintenance, and the like. In order to increase productivity, it is necessary to increase the number of processed disks per time.However, an isolation mechanism is required between each chamber, and the transport mechanism does not interfere with the isolation mechanism. In some cases, the transfer speed between the discs is limited, and the number of processed disks is limited. In addition, many various devices as described above,
Since a mechanism or the like is required, the sputtering apparatus becomes expensive.

An object of the present invention is to eliminate the need for an independent sputtering chamber for each layer, focusing on the above-mentioned problems.

[0010]

In order to solve the above-mentioned problems, the present invention provides a method for forming a plurality of different sputtering layers, which is provided in a single sputtering chamber in a vacuum. The method comprises forming each layer of a sputtered multilayer structure with substantially the same sputtering gas composition and substantially the same sputtering pressure.

Hereinafter, the contents of the present invention will be described in detail. The optical recording medium according to the present invention has at least a recording layer and a protective layer on a substrate. Preferably, for example, a multilayer structure in which a first layer (first protective layer) / second layer (recording layer) / third layer (second protective layer) / fourth layer (reflective layer) is provided in this order on a substrate; Or a first layer (first protective layer) / second layer (recording layer) / third layer (second protective layer) / fourth layer (light absorbing layer) / fifth layer (reflective layer) and the like.

The effects of the first and second protective layers are as follows: prevention of corrosion of the recording layer, prevention of deterioration of recording characteristics caused by heat deformation of the substrate and the recording layer during recording, and signal contrast during reproduction due to an optical interference effect. Has the effect of improving. In this case, the thickness of the first protective layer is usually 50 nm to 400 nm. The “quenching structure” in which the thickness of the second protective layer is as thin as about 20 nm has less deterioration of the recording characteristics due to repetition of rewriting and the erasing power as compared with the “slow cooling structure” in which the dielectric layer is thick as about 200 nm. Has been reported to be superior in that it has a wide power margin (T. Ohota et a
l., SPIE Proc. Vol. 1316 (1990) pp367-373). Therefore, it is preferable that the thickness of the second protective layer be 10 nm to 100 nm.

As such a protective layer, ZnS, Si
An inorganic film such as O ₂ , Ta ₂ O ₅ , ZrC, TiC, MgF ₂ or a mixed film thereof can be used. Especially ZnS and SiO
₂ and a mixed film of ZnS and MgF ₂ are preferable because they have excellent wet heat resistance and further suppress deterioration at the time of recording / erasing. A mixture of these and carbon is also preferable because the residual stress of the film is small. Especially mixed film or of ZnS and SiO _2, ZnS and SiO ₂ and mixed film of carbon,
By repeating recording and erasing, recording sensitivity, C / N,
This is preferable because deterioration such as the erasing rate hardly occurs.

As the recording layer, it is preferable to use an alloy containing at least three elements Ge, Sb, and Te as constituent elements from the viewpoint that overwriting can be performed at high speed. Further, the composition is preferably within the range represented by the following formula, from the viewpoint of excellent thermal stability and repetition stability.

M _z (Sb _x Te _1-x ) _1-yz (Ge _0.5 Te _0.5 ) _y 0.35 ≦ x ≦ 0.5 0.2 ≦ y ≦ 0.5 0.0005 ≦ z ≦ 0.01 Here, M represents at least one metal selected from palladium, niobium, platinum, silver, gold and cobalt, Sb represents antimony, Te represents tellurium, and Ge represents germanium. In addition, x, y, z, and numbers represent the number of atoms of each element (the number of moles of each element). In particular, palladium and niobium preferably contain at least one kind.

The light reflecting layer formed on the second protective layer or the light absorbing layer improves the signal contrast at the time of reproduction by an optical interference effect, and also has a cooling effect of an amorphous recording mark. There are known techniques for facilitating formation and improving erasing characteristics and repetition characteristics. The thickness of the recording layer is preferably from 10 to 100 nm.

As a material of the reflection layer, a metal such as Al or Au having light reflectivity, or a material containing these as a main component,
an alloy containing additional elements such as i, Cr, Hf, and Al;
Examples include a mixture of a metal such as Au and a metal compound such as a metal nitride such as Al and Si, a metal oxide, and a metal chalcogenide. Metals such as Al and Au and alloys containing these as main components are preferable because of their high light reflectivity and high thermal conductivity. As an example of the above-mentioned alloy, Al, Si, Mg, Cu, Pd, Ti, Cr, H
At least one element such as f, Ta, Nb, Mn and the like added in a total of 5 at% or less and 1 at% or more, or at least one of Au, Cr, Ag, Cu, Pd, Pt, and Ni Element total 20 atomic% or less 1 atomic%
These are the ones added above. Particularly, an alloy containing Al as a main component is preferable because the price of the material can be reduced.
at least one metal selected from the group consisting of r, Ta, Hf, Zr, Mn, and Pd in a total of 5 atomic% or less and 0.5 atomic%.
The alloys added above are preferred. In particular, because corrosion resistance is good and hillocks do not easily occur,
Containing a total of 0.5 atomic% or more and less than 3 atomic% of additional elements,
Al-Hf-Pd alloy, Al-Hf alloy, Al-Ti alloy, Al-Ti-Hf alloy, Al-Cr alloy, Al-T
An alloy containing Al as a main component, such as an alloy a, an Al—Ti—Cr alloy, or an Al—Si—Mn alloy, is preferable as the material of the reflective layer. The thickness of the reflective layer is not particularly limited, but is preferably 30 to 200 nm.

As the absorbing layer, for example, Ti, Zr, or an alloy thereof is used. The thickness of the absorbing layer is not particularly limited, but is preferably 3 to 50 nm.

Here, the most important point for the present invention is as follows.
Each of the above-described layers such as the protective layer, the recording layer, and the reflective layer is basically an Ar gas or a mixed gas of Ar and N ₂ , and the same layer such as a gas having N ₂ of 10% or less. In a sputtering gas atmosphere, a desired layer can be obtained by ordinary DC sputtering or RF sputtering using a target having a composition suitable for a desired sputtering layer composition. Therefore, it is not necessary to perform sputtering that requires a special sputtering gas in forming a specific layer.

The sputtering gas is preferably Ar gas or a mixed gas of Ar and N ₂ , and N ₂ is 10% or less. In a mixed gas N ₂ exceeds 10%, the recording characteristics and storage stability of the optical recording medium is deteriorated. Further, in order to improve the characteristics as an optical recording medium, a gas obtained by mixing a small amount of O ₂ , H ₂ O, or the like with the above gas may be used. Further, an inert gas such as Ne, Kr, or Xe may be used instead of Ar.

The sputtering pressure is 0.05 P
a to 5 Pa is preferable, and more preferably 0.1 Pa to
1 Pa. If it is less than 0.05 Pa, the discharge of sputtering may be unstable, and if it exceeds 5 Pa, the repetition characteristics of the optical recording medium may be deteriorated.

When a plurality of film forming units are installed in a single sputtering chamber in a vacuum, it is necessary to prevent interference of plasma during sputtering between the film forming units and to prevent unnecessary portions of sputtered particles. It is desirable to provide a suitable shielding plate around the sputtering target in order to prevent sneaking around. Alternatively, in a case where the wraparound of sputtered particles is positively used, it is desirable to provide an appropriate shielding plate for preventing plasma interference. The film forming section referred to here is a so-called cathode section and its peripheral portion, and includes a target, a power introduction section,
A target cooling water system, an earth shield, a magnet, a substrate holding unit, and the like, and a part where film formation is actually performed by sputtering. The number of film forming units is determined by a desired number of layers. Generally, at least the same number as the number of layers is necessary. However, when one layer is formed by being divided into a plurality of film forming units, the number of divisions is The required number of film forming units is determined accordingly.

As a method for introducing the sputtering gas into the sputtering chamber, it may be introduced from one place, but it is preferable to provide a nozzle covering a plurality of film forming sections so that the gas distribution inside the chamber becomes constant. Although the equipment is slightly complicated, it is also effective to provide a plurality of independent gas introduction systems and actively control the gas distribution inside the chamber to be constant. When an independent gas introduction system is provided for each film forming unit, it is possible to locally and minutely change the sputtering gas composition or the sputtering gas pressure.

As a substrate for an optical recording medium, it is preferable to use a material through which laser light can be transmitted in order to perform recording and reproduction from the substrate side. For example, polymethyl methacrylate resin, polycarbonate resin, polyolefin resin, epoxy resin Organic polymer resins such as these, mixtures thereof, and copolymers can be used. Among them,
A polycarbonate resin can be most preferably used from the viewpoint of optical characteristics and heat resistance.

Using this thermoplastic resin, a disk-shaped substrate (disk) is manufactured by, for example, injection molding or injection compression molding. At the time of molding the substrate, a stamper having a predetermined groove or pit male mold formed on the surface is mounted in a mold, and a substrate having a desired track formed on the surface by transfer from the stamper is molded.

The size of the substrate needs to conform to the standard required by the optical recording medium drive. For example, the diameter is 80 mm, 90 mm, 120 mm or 130 mm
Substrates are defined. As the thickness, both 1.2 mm and 0.6 mm can be used.

A sputtering layer having a multilayer structure is formed on such a substrate. An organic resin protective layer may be provided on this layer. As the organic resin protective layer, a photocurable resin composition containing a polymerizable monomer or oligomer as a main component or a thermosetting resin composition is used, and is generally formed by a spin coating method. In addition, a protective layer made of a similar organic resin composition is provided on the substrate on the light incident surface side, with abrasion resistance,
It can also be provided for the purpose of protecting the substrate, for example, for improving the printing durability, or for providing antistatic properties for preventing dust adhesion.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a film forming method and a film forming apparatus for an optical recording medium according to an embodiment of the present invention.

In FIG. 1, reference numerals 1a to 1h indicate disks. Reference numeral 2 denotes a load lock chamber, which is provided to maintain a vacuum state of the sputtering chamber when a disk is continuously carried into the sputtering chamber from the atmosphere. 3 is a sputtering chamber, 4a to 4d are targets, 5a to 5c are shielding plates, and four film forming units provided with the targets and the shielding plates are installed. Reference numeral 6 denotes an unload lock chamber, which performs the same function as the load lock chamber 2 when the substrate is carried out of the sputtering chamber into the atmosphere. 7a to 7d are gate valves for isolating the vacuum state from the atmosphere, and open and close when the disk passes.
Reference numeral 8 denotes a sputtering gas introduction system, which is provided with nozzles that cover four film forming sections in order to control the gas flow rate by one mass flow controller and to make the distribution of the sputtering gas pressure in the sputtering chamber uniform. I have. Reference numerals 9, 10a, and 10b denote high vacuum pumps, and generally, a cryopump or a turbo molecular pump is used. Although not shown in FIG. 1, the sputtering chamber is provided with a set of vacuum measurement systems.

The discs are sequentially conveyed one by one from the load lock chamber 2 side and loaded into the sputtering chamber 3. Different targets 4a to 4c for forming the respective layers of the four-layer structure are set in advance in the four film forming units. The disk is sequentially transported to four film forming units, where a layer having a desired film thickness is formed by sputtering to form a four-layer structure. FIG. 1 shows a stationary facing type in which the substrate is stationary in the film forming unit. Of course, the substrate is rotated and / or revolved in the film forming unit in a passing type in which the film is formed while the substrate passes through the film forming unit. It is also possible to select various film forming methods such as a rotation type / revolution type / rotation type. Also, a plurality of disks may be conveyed as one set instead of one by one. Since disks are supplied continuously, 4
Sputtering is performed simultaneously or temporally in the film forming units at the four locations, and the respective layers of the four-layer structure are formed with substantially the same sputtering gas and substantially the same sputtering pressure. The disk on which the four-layer structure is formed is carried out from the unload lock chamber 6 to the atmosphere.

In FIG. 1, a plurality of film forming units are arranged on a straight line, but a layout arranged on a circumference is effective for making the apparatus compact. In the case of a layout arranged on such a circumference, the load lock chamber and the unload lock chamber can be shared by one chamber.

FIG. 2 shows a film forming method and a film forming apparatus based on the prior art for forming an optical recording medium having the same four-layer structure as described above. Each layer of the four-layer structure is formed by a different sputtering gas and sputtering pressure suitable for each layer. For this purpose, 3a, 3b, 3
c and 3d are required for the vacuum independent sputtering chambers, gate valves 7e, 7f and 7g for isolating each chamber, high vacuum pumps 9a, 9b, 9c and 9d for each chamber, and FIG. Although not shown, one set of vacuum degree measurement system or the like is required for each sputtering chamber.

For example, the sputtering chambers 3a and 3
If the sputtering gas used in b is different, when transporting the disk 1c from 3a to 3b, in order to prevent mutual sputtering gas contamination,
It may be necessary to evacuate both chambers 3a and 3b once to a high vacuum. The time required for such an operation results in a decrease in the number of processed disks per unit time, that is, a decrease in productivity.

[0034]

As described above, according to the method and apparatus for forming an optical recording medium of the present invention, an optical recording medium having a multilayered sputtering layer can be vacuum-produced even in mass production scale production. It can be manufactured in one sputtering chamber. For this reason, the configuration /
The mechanism is simplified, the reliability of the device is improved,
Maintenance is also improved. Further, the transfer mechanism between the chambers of the disk is simplified, so that the transfer speed can be increased. For this reason, the number of processed disks per unit time can be increased, and productivity is improved. Further, the device becomes inexpensive.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a film forming method and a film forming apparatus for an optical recording medium according to an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a film forming method and a film forming apparatus for an optical recording medium based on a conventional technique.

[Explanation of symbols]

 1a-1h Disc 2 Load lock chamber 3 Sputtering chamber 4a-4d Target 5a-5d Shielding plate 6 Unload lock chamber 7a-7d Gate valve 8 Sputtering gas introduction system 9, 10a, 10b High vacuum exhaust pump

Claims (6)

[Claims] 1. A method for manufacturing an optical recording medium, wherein a multilayer structure is formed by sputtering using a plurality of film forming units installed in a single sputtering chamber in a vacuum. 2. The method for manufacturing an optical recording medium according to claim 1, wherein the sputtering layers are formed simultaneously or temporally in at least two or more film forming sections so as to overlap each other. 3. The method according to claim 1, wherein the plurality of layers formed by sputtering comprise at least a protective layer, a recording layer, and a reflective layer. 4. The method according to claim 3, wherein the protective layer is mainly composed of ZnS and SiO ₂ . 5. The method according to claim 3, wherein the recording layer is a phase change recording layer mainly composed of Ge, Sb, and Te. 6. A film forming apparatus for an optical recording medium, wherein a film is formed by using the method according to claim 1.