JPH0548281B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing a sputtering target made of a sintered alloy, which is suitable for producing a magnetic metal thin film of a magneto-optical recording medium by sputtering. .

[Conventional technology]

In recent years, magneto-optical recording media have been developed as recording media that can record information at high density and that can be easily reproduced, erased, and re-recorded.The magnetic metal thin film that forms the recording layer is made of rare earth elements and transition metals. amorphous alloys (Tb−Fe−Co, Gd−Tb
-Fe, etc.) are attracting attention for practical use because they have many advantages, such as requiring less energy for recording, no grain boundary noise, and the ability to relatively easily produce large-sized materials. .

In this way, in magneto-optical recording media, rare earth
Transition metal alloy thin films are attracting attention, and methods for forming them include chemical plating methods, sputtering methods, ion plating methods, vacuum evaporation methods, and the like. Among these methods, the sputtering method is superior because the quality of the obtained magnetic thin film is good.

Although a target is required in the sputtering method, an alloy type target is advantageous in that it has a good yield, little change in composition, and it is easy to obtain an alloy thin film having the desired composition.

Now, as a method for producing a rare earth element-transition metal alloy used as a target, there is a conventional method of melting rare earth elements and transition metals by arc discharge etc., but since rare earth elements are highly active, it is difficult to process In addition, the property of intermetallic compounds such as poor retention, segregation, and pore-containing ingots, which are extremely brittle of alloys of rare earth elements and transition metals, appears, especially in large alloy lumps. There is a problem in that cracks and cracks are likely to occur during production.

On the other hand, if a mixture of rare earth element powder and transition metal powder or an alloy powder containing the required composition of rare earth element and transition metal is used as a raw material and the raw material powder is sintered using a powder metallurgy method, cracks and cracks may occur. can be avoided.

[Problem that the invention seeks to solve]

However, the raw material alloy powder used in the above-mentioned powder metallurgy method is conventionally manufactured by crushing an alloy ingot obtained by melting component metals, as described in Japanese Patent Application Laid-open No. 60-230903. However, since rare earth elements have the property of being easily oxidized in the air, the oxygen content of the alloy powder obtained during crushing increases, and as a result, the oxygen content of the sintered body also increases. is unavoidable. There is a problem in that oxygen in this sintered alloy significantly deteriorates the magneto-optical properties of a thin film produced by sputtering. In order to reduce the oxygen content in the sintered metal, it is necessary to perform the above-mentioned pulverization process in an organic solvent or in an inert atmosphere, but this has the drawbacks that the process is complicated and the manufacturing cost is extremely high. There is.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above problems and to provide a sintered alloy with a low oxygen content that is useful for forming a metal thin film having good properties as a recording layer of a magneto-optical recording medium by a sputtering method. An object of the present invention is to provide a method for manufacturing a manufactured target.

[Means for solving problems]

The present invention includes praseodymium (Pr), neodymium (Nd), samarium (Sm), gadolinium (Gd),
Rare earth element oxide powder containing at least one of terbium (Tb), dysprosium (Dy), holmium (Ho) and erbium (Er); and at least one of iron (Fe), nickel (Ni) and cobalt (Co). A mixture of at least one selected from a metal powder of a transition metal containing a species, an oxide powder thereof, and a chloride powder thereof; and at least one selected from an alkali metal, an alkaline earth metal, and a hydride thereof; magneto-optical method, which consists of wet-processing the reaction product mixture after heating in an active gas atmosphere or under vacuum to obtain a rare earth-transition metal alloy powder, and sintering the metal powder containing the powder by powder metallurgy. The present invention provides a method for manufacturing a sintered alloy target for sputtering used in the manufacture of recording media.

The present invention also provides a method for producing a sintered alloy target, in which the mixture subjected to heating in the production method further contains at least one selected from alkali metal chlorides and alkaline earth metal chlorides. It is.

The rare earth elements used in the present invention include Pr, Nd,
It must contain at least one of Sm, Gd, Tb, Dy, Ho and Er, especially Gd,
It is preferable to contain at least one of Tb, Dy, Ho and Er. As the rare earth element, rare earth elements other than these may be contained, and in terms of the magneto-optical properties of the resulting metal thin film, Pr,
The total amount of Nd, Sm, Gd, Tb, Dy, Ho and Er used is 20 to 80% by weight based on the total of rare earth elements and transition metal elements used, especially
It is preferably 30 to 60% by weight. Pr, Nd,
Rare earth elements other than Sm, Gd, Tb, Dy, Ho and Er include lanthanum (La), cerium (Ce),
These include europium (Eu), thulium (Tm), ytterbium (Yb), lutetium (Lu), promethium (Pm), yttrium (Y), and scandium (Sc). These rare earth element oxide powders can be used alone or as a mixture of two or more. The particle size of these powders is not particularly limited, but the average particle size is 1 to 50 μm (Fitscher subsieve sizer method, the same applies hereinafter).
is preferred.

Furthermore, the transition metal element used in the present invention must contain at least one of Fe, Co, and Ni. Transition metals include Fe, Co
and may contain transition metals other than Ni. Fe,
The types of transition metals other than Co and Ni are not particularly limited (excluding the rare earth elements mentioned above), but typical examples include manganese (Mn), chromium (Cr),
Examples include vanadium (V) and titanium (Ti).

These transition metals can be used alone or as a mixture or alloy of two or more. The forms of transition metals are metal powders (including alloy powders),
Either oxide powder or chloride powder may be used,
A mixture of these may also be used (hereinafter simply referred to as "transition metal powder etc."). It is usually preferable to use it as a metal powder. When using an oxide or chloride, it is preferable to use it as part of the metal powder, but if the amount of the metal used is small, it is preferable to use the entire amount of the metal as the oxide and/or chloride. can. The particle size of the transition metal powder, etc. is not particularly limited, but it is desirable to have a particle size of 100 mesh (Tyler, hereinafter the same) or less in view of the particle size of the obtained alloy powder and the uniformity of the alloy composition. Furthermore, it is generally desirable that the particle size of the raw metal powder is 1/2 or less of the target particle size.
Therefore, for example, in order to produce a fine alloy powder with a particle size of 100 mesh or less, which is preferable as a raw material for powder metallurgy, it is preferable to use metal powder with a particle size of 200 mesh or less.

The alkali metals, alkaline earth metals, and hydrides thereof (hereinafter simply referred to as "alkali metals, etc.") used in the present invention also function as reducing agents. Specific examples include lithium, sodium, potassium, magnesium, and their hydrides, but calcium is preferred from the viewpoint of handling safety and cost. These metals or metal hydrides may be used in granular or powdered form, but from the viewpoint of cost, granular metallic calcium having a particle size of 4 mesh or less is preferred. The amount of these reducing agents used is based on the reaction equivalent (the stoichiometric amount required to reduce rare earth oxides and other metal components when oxides and chlorides are used as raw materials). 1.1 to 3.0 times the amount is preferable,
Particularly preferred is 1.5 to 2.0 times the amount.

In the production method of the present invention, alkali metal chlorides and alkaline earth metal chlorides (hereinafter referred to as "alkali metal chlorides" etc.) that may be contained in the mixture to be heated are metal powders used as raw materials and It prevents particles of alloy powder from welding and bonding with each other and particles of by-product oxides such as alkali metals, and also works to promote disintegration of the reaction product obtained as a lumpy mixture during wet processing. It is something. Also, alkali metals, etc.
The content of impurities such as oxygen and carbon can be reduced at any time. Examples of the alkali metal chlorides include chlorides of lithium, sodium, potassium, and magnesium, and anhydrous ones that do not contain hydrates are preferred. Among these, anhydrous calcium chloride is particularly preferred because it exhibits almost no volatility when heated and is advantageous in terms of cost. The amount of these alkali metal chlorides, etc. used is
The amount is preferably 1 to 30% by weight based on the amount of rare earth oxide, and in particular, the content of alkali metals such as calcium and oxygen content in the rare earth-transition metal alloy powder, which is a product component, should be as low as possible, and 3 to 20% by weight is particularly preferred if it is desired to produce a fine alloy powder.

According to the present invention, first, a mixture of raw materials such as the rare earth oxide powder described above is heated in an inert gas atmosphere or under vacuum, for example, at 10 ^-5 Torr or less.

Each raw material is thoroughly mixed, but this handling is carried out under conditions where moisture absorption does not occur, such as in a dry inert gas atmosphere. The resulting mixture is heated under an inert gas atmosphere or under vacuum as described above.
Here, the inert gas atmosphere used is:
Examples include argon and nitrogen. Also, the heating temperature at this time is 900 to 1300℃, especially 950℃.
The heating time is preferably in the range of 1100°C to 1100°C, and although the heating time is not particularly limited, the heating time is preferably 1 to 10 hours in order to obtain an alloy powder with a uniform composition. The reaction product obtained by this heat treatment is a lumpy mixture containing the target rare earth-transition metal alloy, by-product oxides such as alkali metals, unreacted alkali metals, and the like.

Next, the obtained lump mixture is subjected to wet processing. Here, in the wet treatment, the reaction product mixture may be left in steam if necessary, and then brought into contact with water by a method such as pouring into water and stirring, and acid treatment is performed if necessary. When the reaction product mixture is brought into contact with water, residual alkali metals, etc. and by-product oxides contained therein react with water, such as Ca(OH) ₂
Since hydroxides of alkali metals and the like are generated and dissolved, the lumpy mixture disintegrates. After stirring the slurry produced by the disintegration, the suspension of hydroxides such as alkali metals at the top is removed by decantation, and the slurry is removed by repeating the operations of water injection, stirring, and decantation. Hydroxide can be removed from the resulting alloy powder. In addition, some remaining hydroxide can be removed using acetic acid or hydrochloric acid to
6, preferably by washing at pH 4 to 5. The alloy powder obtained through such a wet treatment may be washed with water, washed with an organic solvent such as alcohol or acetone, dehydrated, and dried in vacuum, for example. The disintegration of a lumpy mixture, which is a reaction product, during wet processing differs as follows depending on the presence or absence of an alkali metal chloride. If there is no mixture of alkali metal chlorides, etc., it takes 20 to 30 minutes for almost complete disintegration.
Although it takes time, when an alkali metal chloride or the like is mixed, the disintegration is completed in 5 to 30 minutes.

In addition, in terms of the impurity content (wt%) in the obtained alloy powder, for example, taking the case where calcium is used as a reducing agent, if an alkali metal chloride etc. is not mixed, Ca: 0.1 ~ 0.2%,
It has a low impurity content of 0.05 to 0.15% for C and 0.2 to 0.4% for O ₂ , and has a good purity as a raw material powder for sputtering targets used to create metal thin films for magneto-optical recording media. On the other hand, when alkali metal chlorides etc. are mixed, Ca: 0.1% or less, C:
The impurity content is extremely low, 0.02% or less, O ₂ : 0.2% or less, and the alkali metal chloride has an excellent effect on impurities, making it possible to obtain a particularly excellent raw material powder for the sputtering target.

The alloy powder thus obtained or the metal powder containing the alloy powder is then subjected to sintering by a powder metallurgy method to produce a sintered alloy.

At this time, the metal powder to be subjected to sintering may be the alloy powder obtained above alone, or may be used as necessary.
A metal powder whose composition is adjusted by mixing an appropriate amount of transition metal powder such as Fe, Ni, or Co may also be used.

Sintering of metal powder by powder metallurgy is, for example,
Alloy powder or metal powder containing alloy powder at room temperature.
Simple compression with a pressure of 0.5-5t/ ^cm2 or 0.5-2t/cm2
After molding with a hydrostatic press at a pressure of ^cm2 , it is molded at a temperature of 900 to 1300℃ in a vacuum or Ar atmosphere for 1 to 5
Pressureless sintering method for time sintering, in vacuum, 0.1-0.5t/cm ²
Hot pressing method involves sintering at a pressure of 800 to 1200℃ for 1 to 5 hours, and furthermore, after sintering in an elastic body,
Sintering can be carried out by a hot isostatic pressing method in which sintering is performed at a temperature of 1200° C. and a pressure of 0.1 to 2 t/cm ² for 1 to 5 hours.

When using alkali metal chlorides, etc., this acts as an absorber for the heat generated in the thermal reduction reaction,
This prevents particles of raw metal powder and produced alloy powder from sintering with each other, and also prevents by-products from sintering.
It is thought that it dissolves in an oxide of an alkali metal such as CaO and improves the separation between the produced alloy powder and the oxide of an alkali metal such as CaO.

Examples of rare earth-transition metal alloy targets for forming metal thin films of magneto-optical recording media produced by the method of the present invention include Tb-Fe alloys, Dy-Fe alloys,
Gd-Tb-Fe alloy, Gd-Tb-Co alloy, Tb
-Fe-Co alloy, Tb-Co alloy, Tb-Dy-Fe
-Co alloy, Nd-Dy-Fe-Co alloy, etc., but are not limited to these.

〔Example〕

Next, the method of the present invention will be specifically explained using examples.

Example 1 Tb-Fe-Co alloy powder (target composition (weight%)
Tb ₄ O ₇ with a purity of 99.9% or more for the purpose of producing Tb: 55%, Fe: 42%, Co: 3%).
(average particle size 3μm or less) 407.4g, iron powder (particle size 200 mesh or less) 250.6g, cobalt powder (particle size 200 mesh or less) 20.4g, metallic calcium (particle size 4 mesh or less) 305.1g, and anhydrous calcium chloride (particle size 100 mesh or less). 40.7g of the following ingredients were added and mixed thoroughly. The mixture was placed in a stainless steel reaction vessel and heated for 1000 min in a stream of high-purity argon gas.
The temperature was raised to °C in about 1 hour, maintained at that temperature for 5 hours, and then cooled to room temperature. The resulting lumpy mixture
1012.3g was added to the water in Step 5. After the lumpy mixture was broken down, the upper Ca(OH) ₂ suspension was separated from the resulting slurry by decantation, water was added, the slurry was stirred for 5 minutes, and decantation was performed again. This operation of pouring water, stirring, and decanting was repeated to sufficiently separate calcium oxide from the alloy powder. Dilute acetic acid was added dropwise to a slurry of alloy powder and water with stirring until the pH reached 4.5, and this was maintained for 20 minutes. This was filtered, and the obtained alloy powder was washed with water and ethanol several times, and vacuum-dried at 50° C. and 1×10 ⁻² Torr for 12 hours. The composition (wt%) of the metal powder thus obtained was: Tb: 55.4%, Co: 3.4%, Fe:
The amount of O ₂ as an impurity was 0.10% by weight, which was extremely small. 540 g of the obtained alloy powder was charged into a graphite molded product with an inner diameter of 130 mm and hot pressed. As a condition for hot pressurization, the degree of vacuum is 5×
10 ^-5 Torr, and to pressurize the powder, 0.15t/
A pressure of cm ² was applied until the temperature rose to 1000° C. After the temperature was raised, the pressure was increased to 0.25 t/cm ² and that temperature was maintained for 1 hour.
After the obtained sintered body was cooled to room temperature, when it was taken out from the molding machine, there was almost no adhesion to the molding machine and it could be easily taken out. The sintered alloy was visually observed for cracks and cracks, but no cracks were found.The interior was inspected by irradiating transmitted X-rays, but no cracks or cracks were observed.

As a result of sampling the sintered alloy from several locations under a high-purity argon atmosphere and analyzing O ₂ ,
The _O2 content was 0.11±0.02% by weight.

Sintered alloy obtained in the same manner as above (inner diameter 130
mm, thickness 4.5 mm) as a target, and sputtering method (argon gas pressure: 6×
10 ^-5 Torr, sputtering power: 4W/cm ² , substrate: soda glass) to form a thin film (film thickness: 3000Å)
When a film was prepared and its magneto-optical properties were measured, a film with the following good magneto-optical properties was obtained.

Polar magnetic force - rotation angle (θ _K ): 0.30° Coercive force (Hc): 400 kAm ^-1 Comparative example 1 Tb-Fe-Co alloy powder (target composition (weight %)
For the purpose of producing Tb-Fe master alloy (Tb: 75% by weight, Fe: 3%),
25% by weight) 680g, electrolytic iron 225g, electrolytic cobalt 27
g was charged into an aluminum crucible and melted and cast in a vacuum using a high frequency induction heating furnace. The ingot was coarsely pulverized in an argon atmosphere and then finely pulverized in a ball mill containing ethanol to obtain powder with an average particle size of 25 μm. The composition (wt%) of the alloy powder thus obtained was: Tb: 54.6%, Co: 2.98%, Fe:
41.8%, and O ₂ , an impurity, was 0.55%. The obtained alloy powder was hot pressed in the same manner as in Example 1. When the obtained sintered body was removed from the molding machine, some adhesion to the molding machine was observed, and when the surface of the sintered body was observed, some rough recesses were present. No cracks or cracks in the sintered alloy were observed either visually or by transmitted X-ray irradiation.

As a result of sampling from several locations of this sintered body in a high-purity argon atmosphere and analyzing O ₂ ,
The _O2 content was 0.58±0.03% by weight.

When a thin film was prepared in the same manner as in Example 1 using a sintered alloy separately obtained in the same manner as above as a target, it took a longer time than in Example 1. The magneto-optical properties of the obtained thin film were as follows.

Polar magnetic force - rotation angle (θ _k ): 0.27° Coercive force (Hc): 250 kAm ^-1 [Effects of the invention] According to the production method of the present invention, a rare earth-transition metal sintered alloy with an extremely low O ₂ content is produced. A target for sputtering can be manufactured, and the resulting alloy target is homogeneous without segregation of rare earth elements, pores, etc. Therefore, it is suitable as a target for sputtering when producing a magnetic metal thin film for a magneto-optical recording medium, and the resulting metal thin film has excellent magneto-optical properties.

According to the manufacturing method of the present invention, such a sintered alloy target for sputtering having any desired composition can be easily manufactured with good yield. Further, this method does not require a pulverization step, and a sintered alloy having a desired shape can be easily produced with a small number of steps.

Claims (1)

[Scope of Claims] 1. A rare earth element oxide powder containing at least one of praseodymium, neodymium, samarium, gadolinium, terbium, dysprosium, holmium, and eribium; and a transition metal oxide powder containing at least one of iron, nickel, and cobalt. A mixture of at least one selected from metal powder, oxide powder thereof, and chloride powder thereof; and at least one selected from alkali metals, alkaline earth metals, and hydrides thereof is heated in an inert gas atmosphere or in vacuum. wet processing the reaction product mixture to obtain a rare earth-transition metal alloy powder;
A method for producing a sintered alloy target for sputtering used in producing a magneto-optical recording medium, the method comprising sintering the powder or a metal powder containing the powder by a powder metallurgy method. 2 Rare earth element oxide powder containing at least one of praseodymium, neodymium, samarium, gadolinium, terbium, dysprosium, holmium and erbium; transition metal metal powder containing at least one of iron, nickel and cobalt, and its oxide At least one selected from powders and their chloride powders; At least one selected from alkali metals, alkaline earth metals, and hydrides thereof; At least one selected from alkali metal chlorides and alkaline earth metal chlorides.
After heating the mixture with seeds in an inert gas atmosphere or under vacuum, the reaction product mixture is wet-processed to obtain a rare earth-transition metal alloy powder, and the powder or a metal powder containing the powder is processed by powder metallurgy. A method of manufacturing a sintered alloy target for sputtering used in manufacturing a magneto-optical recording medium, the method comprising sintering the target.