JP2007308804A - ZnS-SiO2 SPUTTERING TARGET - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ZnS-SiO<SB>2</SB>sputtering target for depositing an optical disk protection film, which contains fine SiO<SB>2</SB>crystal grains, has a high density of ≥95% and can be produced stably at a low cost, and with which the uniformity of a deposited film can be enhanced and the production efficiency can be increased, and to provide an optical recording medium in which a ZnS-SiO<SB>2</SB>phase-change type optical disk protective film is deposited by using the same. <P>SOLUTION: The ZnS-SiO<SB>2</SB>sputtering target contains, as additive, one or more selected from alkaline earth metals or their oxides in an amount of 0.001-5 wt.%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

In the present invention, when forming a film by sputtering, particles (dust generation) and nodules generated at the time of sputtering can be reduced, mass variation can be improved, and mass productivity can be improved. Particularly, ZnS-SiO _{The present invention} relates to a ZnS—SiO ₂ sputtering target useful for forming a _two- phase change optical disc protective film and an optical recording medium having a ZnS—SiO ₂ phase change optical disc protective film formed using the target.

In recent years, high-density recording optical disc technology capable of recording / reproducing without the need of a magnetic head has been developed, and interest is rapidly increasing. These optical discs are classified into three types: read-only type, write-once type, and rewritable type. In particular, the phase change method used in the write-once type or the rewritable type is attracting attention. The principle of recording and reproduction using this phase change type optical disk will be briefly described below.
A phase-change optical disc records and reproduces information by heating the recording thin film on the substrate by laser irradiation and causing a crystallographic phase change (amorphous crystal) in the structure of the recording thin film. More specifically, information is reproduced by detecting a change in reflectance caused by a change in optical constant between the phases.

The above phase change is performed by laser light irradiation with a diameter of about 1 to several μm. In this case, for example, when a 1 μm laser beam passes at a linear velocity of 10 m / s, the time during which light is irradiated to a certain point on the optical disk is 100 ns, and the phase change and reflectance are detected within this time. There is a need.
In order to realize the crystallographic phase change, that is, the phase change between amorphous and crystal, the melting and rapid cooling are applied not only to the phase change recording layer of the optical disc but also to the surrounding dielectric protective layer and the reflective film of the aluminum alloy. It will be given repeatedly.

For this reason, the phase change optical disk is a four-layer structure in which both sides of a Ge—Sb—Te-based recording thin film layer are sandwiched between protective layers of ZnS / SiO ₂ -based high-melting dielectric, and an aluminum alloy reflective film is further provided. It has a structure.
Among them, the reflective layer and the protective layer are required to have an optical function that increases absorption between the amorphous part and the crystalline part and has a large difference in reflectance, as well as the moisture resistance of the recording thin film and the function of preventing deformation due to heat, A function of thermal condition control during recording is required (see “Optical”, Vol. 26, No. 1, pages 9 to 15).
In this way, the protective layer of the high melting point dielectric is resistant to the repeated heat stress caused by heating and cooling, and further prevents these thermal effects from affecting the reflective film and other parts. The film itself must be thin, have low reflectivity, and do not deteriorate. In this sense, the dielectric protective layer has an important role.

  The dielectric protective layer is usually formed by a sputtering method. In this sputtering method, a target composed of a positive electrode and a negative electrode is opposed to each other, and an electric field is generated by applying a high voltage between the substrate and the target in an inert gas atmosphere. Ionized electrons collide with inert gas to form a plasma, and cations in the plasma collide with the target (negative electrode) surface to strike out target constituent atoms, and the surface of the substrate where the ejected atoms face each other This is based on the principle that a film is formed by adhering to the film.

Conventionally, since the protective layer is required to have transparency in the visible light range, heat resistance, and the like, a thin film of about 500 to 2000 mm is formed by sputtering using a ceramic target such as ZnS—SiO ₂ .
These materials are formed using a DC (direct current) sputtering apparatus after a special treatment is performed on a high frequency sputtering (RF) apparatus, a magnetron sputtering apparatus, or a target material.
By making the crystal grains of the ZnS-SiO ₂ target finer and densified, it is possible to make the sputtering surface of the target uniform and smooth, reduce particles and nodules, and further increase the target life. Has characteristics. As a result, it is known that the productivity of optical disks is improved.
However, SiO ₂ used in the conventional ZnS-SiO ₂ target, the average grain size 4N or more high purity are used those 0.1 to 20 [mu] m, the sintering between the normal 800 to 1200 ° C However, in such a temperature range, deformation of SiO ₂ itself does not occur, and reaction with ZnS does not occur.
Therefore, it is easy thus ZnS-SiO ₂ target produced by causes a gap between the ZnS and SiO _2, as the SiO ₂ to refine it becomes conspicuous, since the densification of ZnS is inhibited, the target There was a problem that the density decreased.

For this reason, conventionally, in order to increase the density, it has been necessary to set the production conditions such as hot pressing to a higher temperature and a higher surface pressure. However, for example, when manufacturing by the hot press method, the time required for one process becomes longer as the temperature becomes higher, and the higher the surface pressure, the greater the thickness of the outer periphery and the load area portion in order to maintain the strength of the graphite mold. Must be reduced. This resulted in a problem that the production volume per batch of hot press was significantly reduced.
Conversely, it is conceivable to increase the size of the hot press apparatus and the graphite mold itself so as not to reduce the production volume, but the cost of the hot press apparatus, the graphite mold, etc. increases.
For this reason, conventionally, it has been impossible to obtain a high-density ZnS-SiO ₂ phase change optical disk protective film sputtering target at low cost.
Therefore, in general, a low-density target must be used, and as a result, when forming a film by sputtering, particles (dust generation) and nodules generated during sputtering are generated. There was a problem that the productivity was lowered and the productivity was poor.

The present invention provides a sputtering target for forming an optical disk protective film that can stably produce a high-density target having a crystal grain size of 90% or more at a low cost, and can further improve the uniformity of film formation and increase the production efficiency. And an optical recording medium having a ZnS-SiO ₂ phase change optical disc protective film formed thereon using the sputtering target.

In order to solve the above-mentioned problems, the present inventors have conducted intensive research. As a result, by adding an additive to ZnS-SiO ₂ , the gap with ZnS is reduced, and the density can be easily increased even when miniaturized. It has become possible to reduce the number of particles and nodules generated during sputtering and improve the film thickness uniformity without impairing the properties as a protective film.
The present invention is based on this finding,
1. 1. ZnS—SiO ₂ sputtering target characterized by containing 0.001 to 5 wt% of one or more selected from alkaline earth metals or their oxides as additives. The ZnS- of item 1, wherein the additive contains at least one selected from alkali metals or oxides thereof in an amount of 0.001 to 5 wt% in total with the alkaline earth metal or oxides thereof. 2. SiO ₂ sputtering target 3. ZnS—SiO ₂ sputtering target according to 1 or 2 above, containing 0.001 to 10 wt% of one or more selected from boron, aluminum, phosphorus, arsenic or oxides thereof as an additive. ZnS-SiO ₂ sputtering target 5 as described in any one of the above 1 to 3, characterized in that a relative density of 95% or more. The ZnS—SiO ₂ sputtering target according to any one of 1 to 4 above, wherein the average grain size of the crystal grains of the SiO ₂ part is 0.1 to 30 μm.

By adding the additive of the present invention, it is possible to reduce the gap with ZnS, easily increase the density even if the SiO ₂ is miniaturized, and the properties generated as a protective film are not impaired. Sputtering target for forming an optical disk protective film that can suppress generation of dust (dust generation) and nodules, improve film formation uniformity, and increase production efficiency, and a ZnS-SiO ₂ phase change optical disk using the sputtering target The optical recording medium having a protective film can be obtained.

The ZnS—SiO ₂ -based sputtering target of the present invention contains 0.001 to 5 wt% of one or more selected from an alkaline earth metal or an oxide thereof as an additive. By adding an alkaline earth metal or an oxide thereof, a ZnS—SiO ₂ -based sputtering target having a high density and a high corrosion resistance can be obtained.
Further, the ZnS-SiO ₂ sputtering target containing 0.001 to 5 wt% of one or more selected from the above alkaline earth metals or their oxides, and further one or more selected from alkali metals or these oxides Can be contained in an amount of 0.001 to 5 wt%. The alkali metal includes Li, Na, K, Rb, Cs, and Fr, and the alkaline earth metal includes Be, Mg, Ca, Sr, Ba, and Ra.
In addition to the above, 0.001 to 10 wt% of boron, aluminum, phosphorus, arsenic, or an oxide thereof may be further contained. In addition of these materials, it is particularly desirable that the amount is not more than twice that of the above-mentioned additive selected from Na, K or alkaline earth metals or oxides thereof.

If the additive amount selected from the above-mentioned Na, K or alkaline earth metals or their oxides is less than 0.001 wt%, there is no effect of addition, and if it exceeds 5 wt%, the film characteristics change greatly. Since corrosion resistance deteriorates and is not preferable, the total amount is set to 0.001 to 5 wt%.
Addition of boron, aluminum, phosphorus, arsenic or an oxide thereof is more effective in improving the corrosion resistance. If it is less than 0.001 wt%, the effect of addition is not obtained, and if it exceeds 10 wt%, the film properties are greatly changed, which is not preferable. Therefore, when the corrosion resistance is improved by addition, the total amount is 0.001 to 10 wt%. The above additives and addition amounts are appropriately selected and adjusted according to the required characteristics of the sputtering target for forming a ZnS-SiO ₂ phase change optical disc protective film.
In the production of the target, the above additive elements are uniformly dispersed and mixed in the ZnS powder and the SiO ₂ powder, and this is molded by hot pressing or the like. Preferably, the additive element or a salt thereof and SiO ₂ powder are mixed and heated, and then mixed with the remaining ZnS powder and molded by hot pressing.
Thereby, a sputtering target for forming a ZnS-SiO ₂ phase change optical disc protective film having a small gap between ZnS and SiO ₂ and a relative density of 95% or more can be obtained.

Furthermore, since the crystal grains of the ZnS-SiO ₂ target can be refined and densified simply by adding the above materials, the sputtering surface of the target can be made uniform and smooth. Particles and nodules can be reduced, and the target life can be lengthened. As a result, the productivity of the optical recording medium on which the ZnS—SiO ₂ phase change optical disc protective film is formed is improved, and a material with excellent quality can be obtained.
The above characteristics can be further improved by setting the average grain size of the SiO ₂ crystal grains to 0.1 to 30 μm.

  Hereinafter, description will be made based on Examples and Comparative Examples. In addition, a present Example is an example to the last, and is not restrict | limited at all by this example. In other words, the present invention is limited only by the scope of the claims, and includes various modifications other than the examples included in the present invention.

(Reference Example 1)
A SiO ₂ powder having a purity of 99.99% or more was mixed at a ratio of 20 mol% with respect to ZnS, and 0.1 wt% Na ₂ O was further added thereto and mixed.
This mixed powder was filled in a graphite die and hot pressed under conditions of an Ar atmosphere, a surface pressure of 150 kg / cm ² , and a temperature of 1000 ° C. The relative density of the target thus obtained was 99%. A surface micrograph of this target is shown in FIG.
The black spherical portion in FIG. 1 indicates SiO ₂ , and the average particle diameter of the SiO ₂ crystal grains is 10 μm or less, and almost no void is observed on the surface between ZnS and SiO ₂ . As a result, a high-density ZnS—SiO ₂ phase change optical disk protective film forming sputtering target was obtained.

Example 1
SiO ₂ -based powder having a purity of 99.99% or more was mixed at a ratio of 20 mol% with respect to ZnS, and 0.1 wt% Na ₂ O and 0.01 wt% MgO were further added and mixed.
This mixed powder was filled in a graphite die in the same manner as in Example 1, and hot pressed under conditions of an Ar atmosphere, a surface pressure of 150 kg / cm ² , and a temperature of 1000 ° C. The relative density of the target thus obtained was 97%.
Similar to Example 1, the average grain size of the SiO ₂ crystal grains was 10 μm or less, and almost no voids were observed on the surface between ZnS and SiO ₂ . As a result, a high-density sputtering target suitable for forming a ZnS—SiO ₂ phase change optical disc protective film was obtained.

(Reference Example 2)
A SiO ₂ powder having a purity of 99.99% or more was mixed at a ratio of 20 mol% with respect to ZnS, and 1.0 wt% Na ₂ O and 0.3 wt% Al ₂ O ₃ were further added and mixed.
This mixed powder was filled in a graphite die in the same manner as in Example 1, and hot pressed under conditions of an Ar atmosphere, a surface pressure of 150 kg / cm ² , and a temperature of 1000 ° C. The relative density of the target thus obtained was 97%.
Similar to Example 1, the average grain size of the SiO ₂ crystal grains was 10 μm or less, and almost no voids were observed on the surface between ZnS and SiO ₂ . As a result, a high-density sputtering target suitable for forming a ZnS—SiO ₂ phase change optical disc protective film was obtained.

(Example 2)
A SiO ₂ powder having a purity of 99.99% or more is uniformly mixed at a ratio of 20 mol% with respect to ZnS. Further, 0.1 wt% of Na ₂ O, 0.01 wt% of CaO and 0.1 wt% of Al ₂ O ₃ were added and mixed.
This mixed powder was filled in a graphite die and hot pressed under conditions of an Ar atmosphere, a surface pressure of 150 kg / cm ² , and a temperature of 1000 ° C. The relative density of the target thus obtained was 97%. As a result, a high-density ZnS—SiO ₂ phase change optical disk protective film forming sputtering target was obtained. This SEM photograph is shown in FIG.
The black spherical portion in FIG. 2 shows SiO ₂ , and the average particle diameter is 10 μm or less, and it can be seen that there are few voids between ZnS and SiO ₂ .

(Example 3)
A SiO ₂ powder having a purity of 99.99% or more was mixed at a ratio of 20 mol% with respect to ZnS, and 1.0 wt% Na ₂ O, 0.5 wt% BaO, and 0.1 wt% P ₂ O ₅ were further added thereto. Added and mixed.
This mixed powder was filled in a graphite die in the same manner as in Example 1, and hot pressed under conditions of an Ar atmosphere, a surface pressure of 150 kg / cm ² , and a temperature of 1000 ° C. The relative density of the target thus obtained was 97%.
Similar to Example 1, the average grain size of the SiO ₂ crystal grains was 10 μm or less, and almost no voids were observed on the surface between ZnS and SiO ₂ . As a result, a high-density sputtering target suitable for forming a ZnS—SiO ₂ phase change optical disc protective film was obtained.

(Reference Example 3)
An SiO ₂ powder having a purity of 99.99% or more was mixed at a ratio of 20 mol% with respect to ZnS, and 0.1 wt% K ₂ O was further added thereto and mixed.
This mixed powder was filled in a graphite die in the same manner as in Example 1, and hot pressed under conditions of an Ar atmosphere, a surface pressure of 150 kg / cm ² , and a temperature of 1000 ° C. The relative density of the target thus obtained was 99%, and the density improvement was particularly remarkable.
As in Example 1, the average grain size of SiO ₂ crystal grains was 10 μm or less, and almost no voids were observed on the surface between ZnS and SiO ₂ . As a result, a high-density sputtering target suitable for forming a ZnS—SiO ₂ phase change optical disc protective film was obtained.

(Reference Example 4)
A SiO ₂ powder having a purity of 99.99% or more was mixed at a ratio of 20 mol% with respect to ZnS, and 0.1 wt% K ₂ O and 0.1 wt% Al ₂ O ₃ were further added thereto and mixed.
This mixed powder was filled in a graphite die in the same manner as in Example 1, and hot pressed under conditions of an Ar atmosphere, a surface pressure of 150 kg / cm ² , and a temperature of 1000 ° C. The relative density of the target thus obtained was 97%.
Similar to Example 1, the average grain size of the SiO ₂ crystal grains was 10 μm or less, and almost no voids were observed on the surface between ZnS and SiO ₂ . As a result, a high-density sputtering target suitable for forming a ZnS—SiO ₂ phase change optical disc protective film was obtained.

Example 4
A SiO ₂ -based powder having a purity of 99.99% or more was mixed at a ratio of 20 mol% with respect to ZnS, and 2.0 wt% K ₂ O, 0.1 wt% MgO and 0.1 wt% Al were further added thereto. Mixed.
This mixed powder was filled in a graphite die in the same manner as in Example 1, and hot pressed under conditions of an Ar atmosphere, a surface pressure of 150 kg / cm ² , and a temperature of 1000 ° C. The relative density of the target thus obtained was 97%.
Similar to Example 1, the average grain size of the SiO ₂ crystal grains was 10 μm or less, and almost no voids were observed on the surface between ZnS and SiO ₂ . As a result, a high-density sputtering target suitable for forming a ZnS—SiO ₂ phase change optical disc protective film was obtained.

(Example 5)
A SiO ₂ -based powder having a purity of 99.99% or more was mixed at a ratio of 20 mol% with respect to ZnS, and 0.2 wt% MgO and 0.01 wt% CaO were further added thereto and mixed.
This mixed powder was filled in a graphite die in the same manner as in Example 1, and hot pressed under conditions of an Ar atmosphere, a surface pressure of 150 kg / cm ² , and a temperature of 1000 ° C. The relative density of the target thus obtained was 98%.
Similar to Example 1, the average grain size of the SiO ₂ crystal grains was 10 μm or less, and almost no voids were observed on the surface between ZnS and SiO ₂ . As a result, a high-density sputtering target suitable for forming a ZnS—SiO ₂ phase change optical disc protective film was obtained.

(Example 6)
SiO ₂ -based powder having a purity of 99.99% or more was mixed at a ratio of 20 mol% with respect to ZnS, and 0.5 wt% CaO and 0.1 wt% Al ₂ O ₃ were further added and mixed.
This mixed powder was filled in a graphite die in the same manner as in Example 1, and hot pressed under conditions of an Ar atmosphere, a surface pressure of 150 kg / cm ² , and a temperature of 1000 ° C. The relative density of the target thus obtained was 97%.
Similar to Example 1, the average grain size of the SiO ₂ crystal grains was 10 μm or less, and almost no voids were observed on the surface between ZnS and SiO ₂ . As a result, a high-density sputtering target suitable for forming a ZnS—SiO ₂ phase change optical disc protective film was obtained.

(Comparative Example 1)
With a purity of 99.99% or more SiO ₂ powder, homogeneously mixing 20 mol% of the ratio SiO ₂ powder to ZnS.
This mixed powder was filled in a graphite die and hot pressed under conditions of an Ar atmosphere, a surface pressure of 150 kg / cm ² , and a temperature of 1000 ° C. The relative density of the target thus obtained was 94%. As a result, a ZnS—SiO ₂ phase change optical disk protective film forming sputtering target having a density lower than that of the example of the present invention was obtained.
A surface micrograph of this target is shown in FIG. Similarly to the above, the black spherical portion in FIG. 3 shows SiO ₂ , the average particle diameter is 10 to 20 μm, and many voids are observed between ZnS and SiO ₂ .

(Comparative Example 2)
With a purity of 99.99% or more SiO ₂ powder, homogeneously mixing 20 mol% of the ratio SiO ₂ powder to ZnS. Further, 0.5 wt% Al ₂ O ₃ was added to this and mixed.
This mixed powder was filled in a graphite die and hot pressed under conditions of an Ar atmosphere, a surface pressure of 150 kg / cm ² , and a temperature of 1000 ° C. The relative density of the target thus obtained was 91%. As a result, a ZnS—SiO ₂ phase change optical disk protective film forming sputtering target having a density lower than that of the example of the present invention was obtained. The average particle diameter of the target is 10 to 20 [mu] m, many voids between ZnS and SiO ₂ were observed.

By adding the additive of the present invention, it is possible to reduce the gap with ZnS, easily increase the density even if the SiO ₂ is miniaturized, and the properties generated as a protective film are not impaired. It is useful as a sputtering target for forming an optical disk protective film that can suppress the generation of dust (dust generation) and nodules, increase the uniformity of film formation, and increase the production efficiency. Using this sputtering target, ZnS-SiO It can be used for a _two- phase change type optical disc protective film.

2 is a photomicrograph of the target surface obtained in Example 1. 6 is a photomicrograph of the target surface obtained in Example 4. 2 is a photomicrograph of the target surface obtained in Comparative Example 1.

Claims (5)

ZnS-SiO ₂ sputtering target, characterized in that it contains 0.001 to 5% one or more selected from alkaline earth metals or oxides thereof as additives. 2. The ZnS according to claim 1, wherein the additive contains at least one selected from an alkali metal or an oxide thereof as 0.001 to 5 wt% in total with an alkaline earth metal or an oxide thereof. -SiO ₂ sputtering target. 3. The ZnS—SiO ₂ sputtering target according to claim 1, wherein the additive contains 0.001 to 10 wt% of one or more selected from boron, aluminum, phosphorus, arsenic, or oxides thereof. ZnS-SiO ₂ sputtering target according to any one of claims 1 to 3, characterized in that a relative density of 95% or more. ZnS-SiO ₂ sputtering target according to claim 1, average particle diameter of the crystal grains of SiO ₂ parts is characterized in that a 0.1 to 30 [mu] m.

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