JPH0610122A - Target material for magnetic thin film and its manufacture, fe-m-c soft magnetic film and its manufacture, magnetic head using the film and magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain a target for a magnetic thin film capable of obtaining a uniform Fe-M-C base film by constituting it of specified atomic ratios of metal M (one or more kinds among Ti, Zr, Hf or the like), carbon and Fe and forming the specified ratio of the carbon in the strucdture into a compound with the metal M. CONSTITUTION:This target has a compsn. constituted of, by atom, 5 to 20% metal M (one or moer kinds among Ti, Zr, Hf, V, Nb, Ta, Mo and W) and 6 to 20% carbon, and the balance Fe, and >=75% of the carbon present in the strucdture is present as a compound with the metal M. As for this target, the carbon is taken in the target by forming the carbon into the powder in the state of the compound or alloy with the metal without using the carbon as a simple substance such as graphite and executing sintering. For example, the powder of the compound of the metal M and carbon is blended with the powder of the alloy of Fe and carbon or the alloy in which the metal M enters into solid solution in this or, in addition to the same, is blended with carbon powder with <=5% atomic ratio, and sintering is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic thin film target material for providing a magnetic thin film used for a magnetic head and the like, a method for producing the same, a Fe-MC soft magnetic film and a method for producing the same, and a magnetic material using the same. The present invention relates to a head and a magnetic recording / reproducing device.

[0002]

2. Description of the Related Art In recent years, the magnetic recording technology has made remarkable progress, 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
It must generate a recording magnetic field that can be sufficiently written on a recording medium having a high coercive force. For this reason, it is required to form a magnetic film having a higher saturation magnetic flux density in the magnetic head. Further, the material for the magnetic head needs to have a high magnetic permeability from the viewpoint of improving the recording / reproducing efficiency, and it is desirable to control the magnetostriction constant to near zero in order to stabilize the recording / reproducing characteristics. 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 Japanese Patent Laid-Open No. 60-74110, etc.). Also,
Recently, Fe-N-based multilayer films, Co-based and Fe-based modulation nitride films, Co-TaC films, and Fe-MC films (M is T
Materials such as i, Zr, Hf, V, Nb, Ta, Mo, and W, which are one or more selected from each other: hereinafter referred to as M), are being actively searched. Among these magnetic films, the above-mentioned Fe-M-C based composition, which is disclosed in JP-A-2-229406 or JP-A-3-20444.
The magnetic film having a microcrystalline structure described in U.S. Pat. No. 5,698,639 is a very promising material in the future because it has low coercive force, high magnetic permeability, and thermally stable magnetic properties.

[0004]

The above-mentioned Fe-M-C
In order to obtain a thin film having a particularly high carbon content in a magnetic thin film of the system, a method of arranging graphite pellets on a target of an Fe-M alloy and sputtering, or a Fe-M alloy target containing no carbon is used. Used,
A method of introducing a mixed gas of methane (CH ₄ ) into an inert gas such as Ar and performing reactive sputtering to heat-treat the obtained film to precipitate fine crystals and obtain a thin film with high saturation magnetic flux density. It has been known. Among them, the method using reactive sputtering has been considered to have an advantage that the carbon concentration in the film can be easily controlled. However, in the above-mentioned reactive sputtering, the reaction rate of gas and sputtered particles is rate-determining, so that there is a problem that the film forming rate must be slowed down.

On the other hand, the method of arranging carbon as graphite pellets has a problem that graphite is likely to be selectively sputtered and it is difficult to control the carbon concentration in the thin film. In addition, the method of mixing carbon powders alone has a problem that it is difficult to manufacture a uniform target because the difference in specific gravity between the target base material and carbon is large. Further, when carbon is added by itself, there is a problem that the gas adsorbing the gas of carbon is high and the gas adsorbed during the sputtering is released to change the film composition. An object of the present invention is Fe-
An M-C type alloy thin film is formed by an ordinary sputtering method.
(EN) Provided are a target material for a magnetic thin film capable of obtaining a uniform film and a manufacturing method thereof, a Fe-MC soft magnetic film and a manufacturing method thereof, and a magnetic head and a magnetic recording / reproducing apparatus using the same.

[0006]

Means for Solving the Problems The present inventor has proposed that carbon is not a simple substance such as graphite but is a powder of a compound or alloy with a metal, which is sintered and incorporated into the target material structure by sintering. It has been found that it is possible to suppress the variation in the composition of the formed thin film due to the difference in specific gravity from the target base material or the gas adsorption property, which was a problem with carbon alone. That is, the present invention is based on the atomic ratio of metal M (M is Ti, Zr, Hf, V, Nb, T).
1 or 2 or more types selected from a, Mo, W) is 5
20%, carbon 6 to 20%, balance Fe and unavoidable impurities, and 75% of carbon present in the structure.
% Or more is present as a compound particle with the metal M, or in addition to this, is present as an alloy particle with Fe, which is a target material for a magnetic thin film. The less free carbon is present in the target material, the better, and 75% or more of the total amount of carbon present in the structure may be present in the target structure as compound particles with the metal M or alloy particles with Fe in addition thereto. preferable.

In the present invention, the metal M is 5 to 2 in atomic ratio.
0%, 6 to 20% carbon, the balance Fe and inevitable impurities, and the structure is composed of at least one of metal M and a carbide of metal M and at least one of a carbide of Fe and Fe. It is a characteristic target material for magnetic thin films. In the target material structure of the present invention, since carbon exists as a carbide of metal M or a carbide of Fe, the difference in specific gravity generated between free carbon and other elements when carbon simple substance is added is almost eliminated, and carbon is generated. It is possible to prevent variations in thin film composition. Further, in the present invention, the less the free carbon is, the better, but the free carbon may be included in an amount of 5 atom% or less.

In the magnetic thin film target of the present invention, a compound powder of metal M and carbon is mixed with an alloy of Fe and carbon or a metal alloy powder in which metal M is solid-solved, or In addition to the above, a carbon powder having an atomic ratio of 5% or less is blended and then sintered. For example, when an Fe-Ta-C-based target is created, (1) when the carbon content is less than the equivalent value relative to the Ta content with respect to the target composition of the target, Fe- It can be manufactured by mixing Ta alloy powder. (2) When the amount of carbon is larger than the equivalent value with respect to the content of Ta, the powder can be produced by mixing TaC powder and Fe—C alloy powder with an adjusted amount of C. Since any element of the metal M defined in the present application is likely to bond with oxygen, it is not preferable to use the metal M alone, and the metal M is preferably used in the state of a carbide or an alloy with Fe. In the present invention, the metal M and carbon are not used alone,
All can be used in the form of compounds or alloys, but carbon may be added to the extent that there is no problem such as segregation, that is, up to 5% in atomic ratio for the purpose of adjusting the components of the target. In the present invention, a target having a higher density and almost no pores inside is obtained by performing pressure sintering after pressure-hardening a mixture in which each powder is mixed, or performing pressure sintering while performing consolidation. Therefore, it is possible to prevent abnormal discharge during sputtering due to holes inside the target.

Next, the reasons for limiting the composition of the present invention will be described. In the present invention, the metal M is an element that improves the soft magnetic properties of the alloy of the thin film to be formed, and is also an element that combines with carbon to precipitate fine carbides and improve the soft magnetic properties. If the atomic ratio of the metal M is less than 5%, the effect of improving the soft magnetic properties is small, and if it exceeds 20%, the saturation magnetic flux density decreases, so the content is limited to 5 to 20%. Carbon is an element necessary for improving soft magnetic properties and heat resistance, but if the atomic ratio is less than 6%, the effect of improving soft magnetic properties is small, and if it exceeds 20%, the saturation magnetic flux density is increased. Therefore, it is limited to 6 to 20%.

[0010]

【Example】

(Example 1) TaC having a purity of 99.9% and an average particle size of 3 μm
The powder was degassed at 1200 ° C. for 2 hours at 10 −3 torr to prepare a TaC powder raw material.
Further, in an induction-type vacuum induction melting furnace, pure Fe having a purity of 99.9% was refined using a zirconial crucible, carbon powder was added, and cast into a carbon steel ingot containing 1.42% by weight of carbon. . After removing the oxide scale on the surface of the ingot of this carbon steel, it was made into powder by an argon gas atomizing device, and this powder was further pulverized by a ball mill to collect powder of 150 mesh or less. The carbon content of the obtained carbon steel powder was 1.33% by weight. F
Target composition of 77 atomic% of e, 9 atomic% of Ta and 14 atomic% of C, ie, Fe 70.55% by weight, Ta 26.7
Aiming at a target composition of 0 wt% and C 2.75 wt%, TaC powder is 28.47 wt% and carbon steel powder is 7 wt%.
1.50% by weight and 0.03% by weight of carbon powder for adjusting the amount of carbon were mixed in a ball mill for 24 hours, and then filled in a capsule for hot isostatic pressing with an inner diameter of 180 mm and a depth of 11 mm. This capsule was degassed at 400 ° C. to a reduced pressure atmosphere of 10 −6 torr and then sealed.

As a result, 0.03% by weight, which is the amount of added carbon, is present as free carbon, and atomic%
Is about 0.2%. In addition, 1% of the total amount of carbon is present as free carbon. The encapsulated capsule was pressure-sintered while being consolidated by a hot isostatic press at 1200 kgf / cm ² for 1180 ° C. × 2.5 hours, and then a target material of 150φ × 6 mm was obtained by cutting. Collect an analytical sample from this target material,
2 from the outer and center of the target material surface
The composition analysis of the part was performed. The results are shown in Table 1. Table 1
As shown in FIG. 5, it was confirmed that the obtained target material was uniform with almost no compositional variation depending on the position of the target.

[0012] ↓

[Table 1] ↑

The structure of this target material was observed with an optical microscope. Photographs of the metal structure of the target material surface before and after etching are shown in FIGS. 1 and 2, respectively. From FIG. 1 and FIG. 2, it was confirmed that this target material was a structure in which grains having a pearlite structure composed of an α solid solution of Fe and Fe ₃ C and TaC grain aggregation regions were present between these grains. This target was deposited on 10 aluminum substrates using an RF-magnetron sputtering apparatus using high frequency, and when the compositional variation of Ta for each substrate was evaluated by an EPMA apparatus, Ta was 2
It was confirmed that it was within a very narrow range of 6.2 ± 0.3 wt%.

(Example 2) Purity 99.9%, average particle size 3
12 μm NbC powder at 10 −3 torr
Degassing treatment was carried out at 00 ° C. for 2 hours to prepare a NbC powder raw material. In an induction-type vacuum induction melting furnace, purity 9
9.9% pure Fe was refined using a zirconial crucible,
Carbon powder was added and cast into a carbon steel ingot containing 2.18 wt% carbon. After removing the oxide scale on the surface of the ingot of this carbon steel, it was made into powder by an argon gas atomizing device, and this powder was further pulverized by a ball mill to collect powder of 150 mesh or less. The carbon content of the obtained carbon steel powder was 2.06% by weight. Aiming at a target composition of 71 atomic% of Fe, 11 atomic% of Nb, and 18 atomic% of C, that is, target composition of 76.19% by weight of Fe, 19.65% by weight of Nb, and 4.16% by weight of C, 22.19% by weight of NbC powder and carbon 77.79% by weight of steel powder and 0.02% by weight of carbon powder for adjusting the amount of carbon were added, mixed for 24 hours in a ball mill, and then filled in a capsule for hot isostatic pressing with an inner diameter of 250 mm and a depth of 11 mm. . The capsule was degassed at 500 ° C. to a reduced pressure atmosphere of 10 −5 mm Hg, and then sealed.

As a result, 0.02% by weight, which is the amount of added carbon, is present as free carbon.
Is about 0.1%. In addition, the total amount of carbon is 0.5
% Will be present as free carbon. Sealed capsule at 1180 ° C for 2.5 hours, 1000 kgf / cm
^{In step 2} , pressure sintering was performed while consolidating with a hot isostatic press, and then a target of 204φ × 6 mm was obtained by cutting. This target is RF-
A magnetron sputtering device is used to form a film on 10 aluminum substrates, and an EPMA device is used to form N films for each substrate.
When the variation of the composition of b was evaluated, Nb was 19.5 ±
It was confirmed that the content was within a very narrow range of 0.3 wt%.

(Embodiment 3) The magnetic characteristics of the soft magnetic film obtained by the target material of the present invention will be described below (Ta was used as M). Fig. 3 shows the target structure and Fe-Ta- in the portion facing the substrate at each position of A, B, and C in the figure.
FIG. 4 is a diagram showing a BH curve (after heat treatment in a magnetic field) of a C sputtered film, and FIG. 4 is a relational diagram of the sputter time and the composition ratio of Fe and Ta in the sputtered film. It can be seen from FIG. 3 that the use of the target of the present invention improves the variation in the magnetic characteristics as compared with the conventional method (pellet method), and that there is no change over time in the composition of the sputtered film. Further, the present inventors have found the influence of these targets on the soft magnetic properties of the sputtered film, and will be described in detail below with reference to FIGS. 5 to 8. FIG. 5 is a frequency characteristic of BH curve (hard axis direction after heat treatment in a magnetic field) and relative permeability, and FIG. 6 is an observation view of a magnetic domain structure using the Microker effect. As shown in FIG. 5, when the target of the present invention is used, an Fe-Ta-C film having good uniaxial anisotropy can be obtained, and in the conventional (pellet method) composite target, coercive force of 1 esterted or less, It was found that good uniaxial anisotropy was difficult to obtain although soft magnetic characteristics with a relative magnetic permeability of about 1000 were obtained. Further, as shown in FIG. 6, Fe-Ta- using the target of the present invention
The C film had a difference between the hard axis and the easy axis, and domain wall movement was observed, but it was found that the conventional film is magnetically almost isotropic. This difference in magnetic characteristics will be described with reference to FIGS. 7 and 8.

FIG. 7 is a transmission electron beam diffraction pattern (negative diagram) of the Fe-Ta-C film, and FIG. 8 is a model diagram of the jumping atom distribution. 1 is the jumping distribution of Ta and C, and 2 is the jumping of Fe. Jump distribution, 1
0 is Ta and C, and 20 is Fe. As shown in FIG. 7A, in the Fe-Ta-C film using the target of the present invention and having good uniaxial anisotropy, TaC is randomly oriented and the diffraction intensity is weak. On the other hand, in the case of using the conventional (pellet method) composite target, as shown in FIG. 7B, the preferential orientations of TaC (200) and TaC (111) are observed in the film plane, and the diffraction intensities are compared. Strong. This is considered as follows. That is, the migration of Ta and C on the substrate is almost the same (because the sputtering conditions and the substrate temperature are the same), but as can be seen from FIG. 8B, when the conventional (pellet method) composite target is used. Causes microscopic Ta and C rich layers on the substrate, and when the target of the present invention is used, the microscopic composition unevenness is small as shown in FIG. That is, favorable uniaxial anisotropy can be obtained because the exchange interaction between Fe fine crystal grains, which is considered to be a factor for softening the Fe—Ta—C film, works more uniformly in the film. Here, for the jump distribution of atoms, c
Although various laws such as os law, cos ² law, and Gauss law have been proposed, it is qualitatively understood that the use of the target of the present invention enables film formation without microscopic composition unevenness. At this time, for the purpose of improving the corrosion resistance of the film, Fe, T
Elements other than a and C (for example, W, Al, Si, B, Ga,
Ge, Co, Ni, Ir, Pt, Au, Rh, Ru, etc.) may be mixed in the mixture and sputtered to obtain the effect of the present invention. However, as shown in FIGS. 9 and 10, even in the target of the present invention, if the constituent grains are large, the above-mentioned good characteristics cannot be obtained, so that the constituent grain size is preferably 5 mm or less.

Next, the knowledge about the influence of the substrate temperature during film formation on the magnetic characteristics has been obtained. FIG. 11 shows the substrate temperature of 300 ° C. or less, 400
It is a frequency characteristic of BH curve (hard axis direction after heat treatment in a magnetic field) and relative permeability when the temperature is set to ° C. As shown in the figure, when the substrate temperature is 300 ° C. or lower, good uniaxial anisotropy is obtained, but when the substrate temperature is 400 ° C., the coercive force increases and the anisotropic magnetic field decreases. That is, the substrate temperature during film formation is preferably 300 ° C. or lower. The lower limit is the temperature of water, air or liquid nitrogen for cooling the substrate used during sputtering, that is, -200 ° C. The film forming method using the target of the present invention, which has been described in detail above, does not generate combustible or explosive gas, so there is no safety problem.

[0019]

According to the present invention, a target material having a sintered structure in which carbon is uniformly dispersed can be obtained, and a uniform magnetic film can be formed by a usual sputtering method. Therefore, the problem that the film forming rate is slow, which is a problem with the conventional reactive sputtering, is eliminated, and mass productivity is significantly improved. further,
In the target of the present invention, carbon does not disperse as a simple substance but exists as an alloy or a compound. Therefore, there is no problem of variation in film forming composition for each sputtering lot due to selective sputtering of carbon, and it is extremely reliable. A high quality magnetic film can be obtained. The target material of the present invention has the effect of preventing variations in the magnetic properties of the Fe-Ta-C soft magnetic film to be formed and changes over time. Furthermore, there is an effect that an Fe-Ta-C soft magnetic film having good uniaxial anisotropy can be obtained.

[Brief description of drawings]

FIG. 1 is a photograph of a metal structure of a target material of the present invention before etching.

FIG. 2 is a photograph of a metal structure of a target material of the present invention after etching.

FIG. 3 is a target configuration and a BH curve diagram.

FIG. 4 is a graph showing the relationship between the sputtering time and the composition ratio of Fe and Ta in the sputtered film.

FIG. 5 is a frequency characteristic diagram of BH curve and relative permeability.

FIG. 6 is an observation view of a magnetic domain structure using the Microker effect.

FIG. 7 is a transmission electron beam diffraction pattern diagram of the Fe—Ta—C film.

FIG. 8 is a model diagram of a jumping atom distribution.

FIG. 9 is a BH curve difference diagram according to the constituent grain size of the target of the present invention.

FIG. 10 is a model diagram of jumping atom distribution.

FIG. 11 is a frequency characteristic diagram of BH curve and relative permeability.

[Explanation of symbols]

 1 Ta, C jump distribution 2 Fe jump distribution 10 Ta, C 20 Fe

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location H01F 10/14 (72) Inventor Masaya Yasukochi 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Stock company (72) Inventor Shigeo Aoki 1410 Inada, Katsuta-shi, Ibaraki Hitachi Ltd. Tokai Plant, Hitachi Ltd.

Claims (12)

[Claims] 1. A metal M (M is Ti, Zr, H in atomic ratio).
f, V, Nb, Ta, Mo, W, one or more selected from 5 to 20%, carbon to 6 to 20%, and balance Fe.
And a target material for a magnetic thin film having a composition of unavoidable impurities, wherein 75% or more of carbon present in the structure is present as compound particles with the metal M. 2. A metal M in atomic ratio (M is Ti, Zr, H
f, V, Nb, Ta, Mo, W, one or more selected from 5 to 20%, carbon to 6 to 20%, and balance Fe.
And a target material for a magnetic thin film having a composition of unavoidable impurities, wherein 75% or more of carbon present in the structure exists as compound particles with the metal M and alloy particles with Fe. 3. A metal M in atomic ratio (M is Ti, Zr, H
f, V, Nb, Ta, Mo, W, one or more selected from 5 to 20%, carbon to 6 to 20%, and balance Fe.
And an unavoidable impurity and having a structure of at least one of metal M and carbide of metal M, and Fe.
A target material for a magnetic thin film, which comprises at least one of Fe and Fe carbide. 4. A metal M (M is Ti, Zr, H) in atomic ratio.
f, V, Nb, Ta, Mo, W, one or more selected from 5 to 20%, carbon to 6 to 20%, and balance Fe.
And a target material for a magnetic thin film having a composition of unavoidable impurities and having an atomic ratio of free carbon of 5% or less. 5. A metal M (M is Ti, Zr, Hf, V, N
(1 or 2 or more selected from b, Ta, Mo and W)
A method for producing a target material for a magnetic thin film, which comprises mixing a compound of carbon and carbon, an alloy of Fe and carbon or an alloy powder in which a metal M is solid-solved, and sintering the mixture. 6. A metal M (M is Ti, Zr, Hf, V, N
(1 or 2 or more selected from b, Ta, Mo and W)
A target for a magnetic thin film, which comprises compounding and sintering a compound of carbon and carbon, an alloy of Fe and carbon or an alloy powder in which a metal M is dissolved in solid solution, and carbon powder of 5 atomic% or less. Method of manufacturing wood. 7. A metal M (M is Ti, Zr, Hf, V, N
(1 or 2 or more selected from b, Ta, Mo and W)
A mixture of a powder of a compound of carbon and carbon and an alloy of Fe and carbon or an alloy powder in which a metal M is solid-solved is compacted and then pressure-sintered, or pressure is applied while compacting. A method for manufacturing a target for a magnetic thin film, which comprises performing sintering. 8. A metal M (M is Ti, Zr, Hf, V, N
(1 or 2 or more selected from b, Ta, Mo and W)
A mixture of a powder of a compound of carbon and carbon, an alloy of Fe and carbon or an alloy powder in which a metal M is dissolved in solid solution, and carbon powder of 5 atomic% or less is consolidated and then pressure-sintered. Or a method for producing a target for a magnetic thin film, which comprises performing pressure sintering while consolidating. 9. An F formed by sputtering the target according to any one of claims 1 to 4.
e-MC Soft magnetic film (M is Ti, Zr, Hf, V, N
at least one of b, Ta, Mo and W). 10. The Fe-MC soft magnetic film according to claim 9, wherein M is Ti, Zr, Hf, V, Nb, Ta, Mo or W.
At least one of the above), the substrate temperature during film formation is 300 ° C. or lower, and a method for manufacturing an Fe-MC soft magnetic film. 11. A magnetic head using the Fe-M-C soft magnetic film according to claim 9. 12. A magnetic recording / reproducing apparatus using the magnetic head according to claim 11.