JP3534264B2 - Target material for magnetic thin film and method for manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a target material for providing a magnetic thin film used for a magnetic head or the like and a method for manufacturing the target material.

[0002]

2. Description of the Related Art In recent years, the progress of magnetic recording technology has been remarkable, and the recording density has been increased in order to increase the capacity of magnetic disks and the like, or to reduce the size and weight of VTR devices. The magnetic head used for this high-density recording is required to have a magnetic film having a recording magnetic field capable of sufficiently writing on a recording medium having a high coercive force. Also, the material for the magnetic head needs to have a high magnetic permeability from the viewpoint of improving the efficiency of recording and reproduction, and the magnetostriction constant should be controlled to near zero in order to stabilize the recording and reproduction characteristics. Is desirable. Further, in the manufacturing process of the magnetic head, glass welding or the like is often used in order to ensure reliability, so it is also necessary to improve stability at high temperature so that the characteristics are not deteriorated by heat treatment.

As such a material, Fe--
Al-Si alloys (so-called sendust), Co amorphous alloys, etc. have been developed and applied to magnetic heads. (See JP-A-60-74110, etc.).
Recently, Japanese Patent Laid-Open No. 3-20444 discloses Fe- (T) as a thin film for a magnetic head having excellent magnetic characteristics.
One or more elements selected from i, Zr, Hf, Nb and Ta: hereinafter referred to as M) -C based alloys are shown. Also,
Japanese Unexamined Patent Publication (Kokai) No. 4-68009 discloses a Fe- (M) -N-based alloy as a thin film for a magnetic head that provides excellent magnetic characteristics. As described in JP-A-3-20444 and JP-A-4-6809, Fe- (M)
The (C, N) -based thin film can have a microcrystalline structure, has a small coercive force, a high magnetic permeability, and has excellent characteristics that the magnetic characteristics are thermally stable. Therefore, it can be said that it is a very promising material for thin films for magnetic heads.

Of the above thin films for magnetic heads, Fe-
In order to obtain a (M) -C alloy film, the method disclosed in JP-A-3-204
As described in Japanese Patent Publication No. 44-44, a target material in which graphite is arranged on an Fe-M based target material is used, or the Fe-M based target material is subjected to reactive sputtering in a methane-containing atmosphere in a film. A method of introducing carbon into is known. Further, when an Fe- (M) -N-based alloy film is obtained, as described in JP-A-4-68009, a spalling target material in which pellets of metal M are arranged on Fe is used to contain nitrogen. By carrying out reactive sputtering in an atmosphere, an Fe-MN system alloy thin film was obtained.

[0005]

The above-mentioned Fe- (M)
Among the methods for producing a thin film of a (C, N) -based alloy, the method using the reactive sputtering method has an advantage that it is easy to control the introduction amount of carbon and nitrogen, and is considered to be a main production method. . Since the present inventor applies it to the above-mentioned reactive sputtering method, among the alloy systems proposed above, the Fe-Ta system, which is said to have particularly high thermal stability and excellent magnetic properties, is selected. And Fe and Ta for the purpose of obtaining a magnetic thin film by reactive sputtering.
An attempt was made to obtain the target material of the binary alloy of No. 1 by the casting method.

However, the alloy of Fe and Ta is F during casting.
It was found that since a compound of e and Ta is formed, the structure has a large segregation portion at the time of casting, and this segregation portion causes variation in the composition of the thin film formed by sputtering. An object of the present invention is to provide an Fe—Ta based target material for a magnetic thin film, which can reduce variations in composition of a film obtained by sputtering, and a method for producing the same.

[0007]

The inventor of the present invention has found that Fe--Ta
In the system-based alloy target material, the composition is set to Ta amount of 5 to
By setting the content to be in the atomic% range, the composition near the eutectic point in the phase diagram of the binary system of Fe and Ta can be obtained. Further, by setting the casting temperature just above the melting point of the alloy, the cooling during casting is accelerated, It was found that a target material in which the compound of Ta and Ta is finely dispersed can be obtained, and that a thin film having a small variation in composition distribution can be obtained by sputtering using a target material having this structure, and the present invention was reached.

That is, the present invention contains Ta as an alloy composition in an amount of 5 to 15 atomic%, and balances Fe and unavoidable impurities.
Which is a target material composed of Fe, and a lumpy compound of Fe and Ta having a maximum particle diameter of 50 μm or less and a long-granular compound of Fe and Ta having a maximum length of 50 μm or less. A target material for a magnetic thin film having a dispersed structure. Further, the present invention is an alloy composition
5 to 15 atomic% Ta and 10 atomic% or less Cr
And a target consisting of the balance Fe and unavoidable impurities.
It is a tough material and has a maximum content of Fe-based matrix.
Fe and Ta lumps with particle size less than 50 μm
Fe particles with a length of 50 μm or less and long granular compounds of Ta are dispersed.
Target for magnetic thin film characterized by having different texture
It is a material.

Another aspect of the present invention is to provide a target material for magnetic thin film according to the present invention, which is characterized in that the molten alloy having the above composition is cast at a casting temperature of a melting point + 50 ° C. which is higher than the liquidus temperature of the alloy. it is a manufacturing method.

[0010]

One of the characteristics of the target material of the present invention is that the composition near the eutectic in the phase diagram of the binary system of Fe and Ta is T
It is defined to be 5 to 15 atom%. According to the binary phase diagram of Fe and Ta, the eutectic point is Ta 7.9 atom%, and the eutectic structure can be expressed in the range of Ta 2.5 to 28 atom%. A composition matching the eutectic point is preferable in order to make the structure of the target material uniform and fine, but it is possible to obtain a fine structure even in the vicinity of the eutectic point composition. It was defined as 15 atom%. Preferably, it is Ta7-10%.

The lower limit of Ta is 5 atomic%
If it is less than 5 atomic%, it is not possible to achieve improvement in magnetic properties such as grain refinement in the case of a magnetic thin film used for a magnetic head or the like, and if it is less than 5%, the Ta content is small, so Fe and Ta This is because the compound itself becomes less and the problem of variation in thin film composition due to segregation of the compound is less likely to occur. On the other hand, if it exceeds 15 atomic%, it is separated from the eutectic composition and a large amount of an intermetallic compound of Fe and Ta is generated and the target material structure cannot be refined.

In the present invention, although it is based on a binary system of Fe and Ta, it is known as an element having a function of forming a fine structure by becoming a carbide or a nitride at the time of forming a thin film like Ta. Ti, Zr, Hf, V,
It does not exclude that Nb is substituted with a part of Ta and contained. Since these elements are inferior to Ta in heat resistance of the thin film to be formed, it is necessary to make the content less than Ta.

Further, in the present invention, it is desirable to add a corrosion-resistant element such as Cr, Al, Pt, Ru or the like in order to ensure the corrosion resistance of the thin film. The target material of the present invention is one that is reacted with carbon or nitrogen during the sputtering period,
T, which is a 4A, 5A group element that strongly binds to carbon and nitrogen
Since i, Zr, Hf, V, and Nb exist as a carbide or a nitride in a thin film state, the effect of improving the corrosion resistance of the thin film is small. Therefore, other Fe
Therefore, it is desirable to add an element that enhances corrosion resistance. In particular, Cr is effective as an element with little deterioration in magnetic characteristics. The above-mentioned corrosion-resistant element deteriorates the magnetic characteristics when added in a large amount, so the addition amount needs to be limited, and is preferably 10 atomic% or less.

Further, according to the present invention, in a matrix containing Fe as a main component, an agglomerate compound containing Fe and Ta as a main component having a maximum particle size of 50 μm or less and a long-granular compound containing Fe and Ta as a main component having a maximum length of 50 μm or less as a main component. Defined in a dispersed organization.
In the Fe—Ta— (C, N) -based alloy thin film used for a magnetic head or the like, T introduced from the target material is used.
a combines with C or N introduced from the vapor phase by sputtering to form a carbide or a nitride, and acts as a nucleus for suppressing crystal growth in the thin film structure.
By this action, the thin film becomes a fine structure and excellent magnetic properties are obtained. Therefore, in order to stably obtain a thin film having a uniform fine structure and little variation in magnetic characteristics, it is necessary to suppress the variation in the structure in the target material.

On the other hand, T which is an element constituting the target material
a forms a compound with Fe and exists in the target material. Since this compound has a sputtering rate and a sputtering direction different from those of Fe that is a matrix, if Ta is segregated, the Ta concentration greatly changes, and the magnetic characteristics of the obtained thin film greatly change. In the present invention, segregation in the target material is reduced, microstructure refinement is attempted, the composition is limited to the vicinity of the eutectic composition, and casting is performed within the range of + 50 ° C. above the liquidus temperature of the alloy. A microstructure with less segregation was obtained. Specifically, the fine structure is a structure in which a lump compound mainly composed of Fe and Ta having a maximum particle size of 50 μm or less and a long granular compound mainly composed of Fe and Ta having a maximum length of 50 μm or less are dispersed. Since the abundance ratio of the lump compound and the long particulate compound can be changed by the Ta amount, it is possible to adjust the sputtering rate and the Ta concentration distribution according to the characteristics of the sputtering device by the Ta amount.

An important feature of the manufacturing method of the present invention is that
Casting is performed at a casting temperature of the melting point + 50 ° C, which exceeds the liquidus temperature. In the present invention, the casting temperature is set just above the melting point so that solidification starts quickly after pouring, whereby fine crystallization of the Fe and Ta compounds occurs, and at the same time the Fe and Ta compounds crystallized during the casting process. Segregation due to the difference in specific gravity between the compound and the matrix can be prevented, and the target material having the structure of the present invention described above can be obtained. Further, in the production method of the present invention, it is not excluded that another means for preventing segregation is also used. For example, forced cooling may be performed to obtain a finer structure, or soaking may be performed by heating to 1100 to 1300 ° C. and holding for 1 hour or more.

[0017]

【Example】

(Example 1) Fe = 92.1% in atomic%, Ta 7.9
% Alloy having a eutectic point composition was cast at 10 to the third power Torr while controlling the melting point temperature of 1442 ° C. to +20 to 25 ° C. The structure of this target material was observed with an optical microscope. FIG. 1 shows a 400 times metal microstructure photograph. As is clear from FIG. 1, the microstructure of the target material has a structure in which a lump compound in which one particle occupies a large area in the cross section of the structure and a fine long granular compound are dispersed. Observation of this structure revealed that the maximum particle size of the lump compound was 21 μm and the maximum length of the long compound was 24 μm. In addition, it was confirmed by X-ray diffraction analysis that both the lump compound and the long-grain compound were Fe ₃ Ta ₇ compounds. As a comparative example, an alloy having the same composition was cast by controlling the casting temperature to a melting point +70 to 80 ° C.
FIG. 2 shows a photograph of the metal microstructure of the obtained target material of Comparative Example at 400 times. The maximum particle size of the massive compound of Fe and Ta present in the target material of the comparative example was 64 μm.

Next, using these target materials, sputtering is performed in a mixed atmosphere of nitrogen and argon,
Introduction of 16 atomic% nitrogen was performed. Other conditions are as follows. Degree of exhausted vacuum <1 × 10 minus 6th power input 4.5 W / cm ² Substrate Crystallized glass film thickness 2 μm plus / minus 0.2 μm Target material was sputtered for 40 hours to obtain Ta concentration in the obtained thin film. The variation was 0.1 atom% in the target material of the present invention, but was as large as 0.9 atom% in the target material of the comparative example, and the target material of the present invention can obtain a magnetic thin film more stably. I found that

(Example 2) An alloy having a composition of Fe = 88.0 % and Ta = 12.0% in atomic% has a liquidus temperature of 15 under 10 ^ 3 Torr.
Casting was performed while controlling at +20 to 25 ° C with respect to 20 ° C. The structure of this target material was observed with an optical microscope. Fig. 3 shows a photograph of the metal microstructure of 400 times.
As is clear from FIG. 3, as in Example 1, the microstructure of the target material has a structure in which a lump compound having a large area of one particle occupying the structure cross section and a fine long granular compound are dispersed. You can see that Maximum particle size of the bulk compound the tissue observation 26 .mu.m, the maximum length of long grain-like compound was 13 .mu.m. The addition X-ray diffraction analysis, it was confirmed with mass compounds and Nagatsubu like compound is a compound of Fe ₃ Ta _7. In addition, as compared with Example 1, the ratio of the lump compound was increased.

As shown in FIG. 3, it can be seen that the target material structure of the present invention is extremely fine and has no segregation even when it contains 12 atomic% of Ta. The obtained target material was sputtered in the same manner as in Example 1 and the compositional variation was measured to be 0.3 atom%. With the target material of the present invention, the target of the present invention containing 12 atom% of Ta was used. It was found that the magnetic thin film can be stably obtained even in the material.

(Example 3) Fe = 92.1% in atomic% and 100% in Ta = 7.9 %
And Cr = 5.7% with respect to the total of Fe and Ta.
Fe and Ta alloy under 10 minus cube Torr with the addition of
+20 to 25 ° C against 1442 ° C which is the eutectic point temperature of
Casting was performed while controlling the temperature. This target material has Cr added as a corrosion resistant element. The structure of the target material was observed with an optical microscope. FIG. 4 shows a photograph of a metal microstructure of the target material at a magnification of 400 times. As is clear from FIG. 4, as in Example 1, the microstructure of the target material has a structure in which a lump compound in which one particle occupies a large area in the structure cross section and a fine long grain compound are dispersed. You can see that Maximum particle size of the bulk compound the tissue observation 20 [mu] m, the maximum length of long grain-like compound 13
was μm. The compounds of Fe ₃ Ta ₇ as mass compounds and Nagatsubu like compound was confirmed by X-ray diffraction analysis. Cr in the target material could not be detected as a compound, and it was confirmed that the Cr concentration in the matrix portion was higher than that in the compound portion.

Even when Cr is contained as shown in FIG.
It can be seen that the target material structure of the present invention is extremely fine and has no segregation. Sputtering was performed on the obtained target material in the same manner as in Example 1, and the variation in composition was measured to be 0.1 atom%, and the magnetic thin film was stable even in the target material of the present invention containing Cr as a corrosion resistance improving element. I found that I can get it.

[0023]

According to the present invention, the compound of Fe and Ta can be uniformly dispersed, and a thin film with little composition variation can be formed. Therefore, it is extremely effective as a target material used for forming a thin film for a magnetic head that requires extremely accurate recording or reproducing characteristics.

[Brief description of drawings]

FIG. 1 is an example of a metal microstructure photograph of a target material of the present invention.

FIG. 2 is an example of a metal microstructure photograph of a target material of a comparative example.

FIG. 3 is an example of a metal microstructure photograph of a target material of the present invention having a large amount of Ta.

FIG. 4 is an example of a metal microstructure photograph of a target material of the present invention containing Cr.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI G11B 5/31 G11B 5/31 C

Claims (3)

(57) [Claims] 1. A target material containing 5 to 15 atomic% of Ta as an alloy composition , the balance being Fe and unavoidable impurities, and having a Fe-based matrix with a maximum particle size of 50 μm. the following Fe and Ta bulk compound and a magnetic thin film target material and length particulate compound of the maximum length 50μm or less of Fe and Ta are characterized by having a distributed organization. 2. An alloy composition of 5 to 15 atomic% Ta,
Cr content of 10 atomic% or less, balance Fe and unavoidable
A target material composed of impurities , in which a Fe-based matrix has a maximum grain size of 50 μm or less and Fe and T
bulk compound a and the target material for a magnetic film characterized by having a structure in which the <br/> length particulate compounds of the maximum length 50μm or less of Fe and Ta are dispersed. 3. The set according to claim 1 or 2.
The method of manufacturing a magnetic thin film target material, characterized in that the molten alloy adult performing casting at casting temperature in the range of greater than + 50 ℃ liquidus temperature of the alloy.