JP2986291B2 - Sputtering target for magneto-optical recording medium and method for producing 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 sputtering target used for producing a magnetic recording layer of a magneto-optical recording medium and a method for producing the same.

[0002]

2. Description of the Related Art Magneto-optical recording media have been actively researched and developed recently as media capable of recording, reproducing and erasing. As these magneto-optical recording medium materials, amorphous materials made of an alloy of a rare earth element and a transition metal have attracted attention because they have the following features. That is, (1) since it is amorphous, there is no grain boundary noise seen in a crystalline medium such as MnBi. (2) It is relatively easy to prepare a film, and a uniform film can be obtained over a large area.
(3) The temperature rise of the medium during recording may be about 100 ° C.,
Therefore, a semiconductor laser can be used, and the size of the device can be reduced. These amorphous alloys are formed into a thin film on a substrate by a sputtering method.

Therefore, various alloy (Tb-Fe-Co, Gd-Tb-Fe) targets of rare earth elements and transition metals have been proposed in the past. For example, Japanese Patent Laid-Open No. 2-10
No. 7762 discloses an alloy target having a fine mixed phase of the intermetallic compound phase and the rare earth element and a mixed structure of the intermetallic compound phase.

However, the alloy target described in the above publication is composed of a fine mixed phase of an intermetallic compound phase and a rare earth element, a fine mixed phase of an intermetallic compound phase and a rare earth element, and a mixed phase of a rare earth element. Since a large amount of rare earth elements are present and the rare earth elements are easily oxidized, it is difficult to obtain a target film composition, and since the film contains a relatively large amount of oxygen, film characteristics as a memory may be deteriorated. A problem arises in long-term storage of information as a recording medium. In addition, since the sputtering rates of the rare earth element and the intermetallic compound are different, the rare earth element phase is preferentially sputtered, and the film composition changes greatly with the sputtering time (hereinafter referred to as aging). Furthermore,
As is clear from the above-mentioned publications, and particularly from the examples, when preparing this alloy target, in the phase diagram of the rare earth element and the transition metal, an alloy powder having a composition rich in the rare earth element from the eutectic point is used. Therefore, mechanical pulverization is difficult, and it is necessary to use a method such as the PREP method which is expensive and has a high oxygen content.

The present invention solves the above-mentioned conventional problems and provides an alloy target which does not deteriorate in film characteristics and has little change with time. In addition, mechanical pulverization is possible, powder preparation is easy, and production is easy. An object of the present invention is to provide a method for manufacturing a simple alloy target.

[0006]

Means for Solving the Problems The magneto-optical target of the present invention has a component composition of at least one rare earth element selected from Gd, Tb and Dy in an amount of 10 to 40 at%, and the balance substantially consisting of Fe, Co is composed of one or two transition metals of Co, and its structure is an intermetallic compound a phase of a rare earth element and a transition metal, an intermetallic compound a having the same composition as the intermetallic compound a, a rare earth element and a trace It is characterized by comprising a fine mixed phase composed of a solid solution of a transition metal element and an intermetallic compound b phase of a rare earth element and a transition metal having different compositions from each other. Then, a composite structure is constituted by the intermetallic compound a phase and the fine mixed phase around the intermetallic compound a comprising the intermetallic compound a and a solid solution of a rare earth element and a trace amount of a transition metal element. Is composed of a structure in which the intermetallic compound b is formed in the solid. The method of manufacturing this target is based on the alloy powder a of a rare earth element having a composition of an intermetallic compound b having a particle size of 1000 μm or less and a transition metal, and the alloy phase diagram of a rare earth element and a transition metal having a particle size of 1000 μm or less. It is obtained by mixing an alloy powder b of a rare earth element having a transition metal element-rich composition from the crystal point and a transition metal, and hot-pressing the mixture. In addition, at least the alloy powder b among the alloy powders a and b may be obtained by a rapid quenching solidification method.

The reasons for limitation in the present invention will be described below. (1) Rare earth element 10 to 40 at% Both when using a target with a rare earth element of 10 at% or less and when using a target exceeding 40 at%, none of the sputtered films formed therefrom exhibit perpendicular magnetic anisotropy, Since the coercive force is low, characteristics required for the magneto-optical recording layer cannot be obtained. (2) Structure If the solid a composed of a eutectic phase of Tb + Fe and an intermetallic compound and the solid b composed of a different intermetallic compound do not coexist, the balance in the flight direction of Tb and Fe when sputtered is lost, and the solid a When the number is large, the amount of Tb flying at the center of the film is larger than that of Fe, and the amount of Tb at the outer periphery is smaller than that of Fe. As a result, the film composition has a higher Tb concentration at the center of the film and a lower concentration at the outer periphery. In addition, solid b
In contrast, the film composition has a lower Tb concentration toward the center as the content increases, and a stable recording film cannot be obtained in any case. (3) Particle Size When a target using a powder having a particle size of more than 1000 μm is produced, voids in the target are increased, the density is low, the use efficiency of the target is reduced, and the strength of the target is also reduced. If the particle size is too coarse, the uniformity of the film composition is adversely affected. (4) Use of an alloy richer in Fe than the eutectic point of Tb and Fe An alloy richer in Tb than the eutectic point is difficult to pulverize.
Although it is manufactured by the REP method, the oxidation proceeds and the cost increases. If the alloy is Fe-rich than the eutectic point, a ribbon is produced by a rapid quenching solidification method, and can be mechanically pulverized, has little oxidation, and has good workability.

[0008]

As described above, in the present invention, the particle size is 1000 μm
An alloy powder a of a rare earth element and a transition metal having a composition of the following intermetallic compound (hereinafter referred to as IMC) b,
In an alloy phase diagram of a rare earth element and a transition metal of 000 μm or less, an alloy powder b of a rare earth element and a transition metal having a composition rich in the transition metal element from the eutectic point is mixed, and this is obtained by hot pressing. Target is IM
A composite structure is composed of the Ca phase, its surrounding IMCa, and a fine mixed phase composed of a solid solution of a rare earth element and a trace amount of a transition metal element. The composite structure is a structure in which IMCb is formed in another solid. If this is represented schematically, IMCb + ｛IMC
a + [IMCa + αRE]}, and the number of single RE phases is smaller than that of the target having the structure of IMC + (IMC + RE) of the conventional example described in the above publication. Therefore, the degree of oxidation is reduced by that amount, deterioration of the film characteristics is prevented, and the change with time of the film composition is reduced.

In the present invention, the use of an alloy powder of a rare earth element and a transition metal having a composition richer than the eutectic point in the alloy phase diagram of the rare earth element and the transition metal in the alloy phase diagram of the rare earth element and the transition metal means, for example, In the Fe-Tb alloy phase diagram, a eutectic point is present at a composition of 72% Tb, and a powder having an Fe-Tb alloy composition richer than this eutectic point is used as a raw material. The powder b having such an alloy composition can be easily pulverized by producing a ribbon by, for example, a rapid quenching solidification method.

[0010] The ribbon obtained by the rapid quenching solidification method,
It is composed of amorphous or fine precipitated crystal grains partially containing amorphous. Therefore, the target produced by press-molding the target has a structure composed of much finer crystal grains than that obtained by pressure-forming a conventional ingot pulverized powder, and is formed at a high density. In addition, the maximum magnetic permeability of the target is considerably lower than that of the target obtained by the conventional method. Considering that this type of target is generally subjected to magnetron sputtering, this low maximum magnetic permeability greatly contributes to the improvement in sputtering efficiency as well as the effect of high density.

Since at least the alloy powder b used in the present invention is produced by the rapid quenching solidification method as described above, the powder is composed of fine crystal grains (phase). Therefore, the powder is rich in processability and can greatly reduce the molding temperature. Therefore, high-density molding can be performed at a low temperature so as to suppress the reaction of each phase constituting the structure. For example, T
In the case of a b-Fe-Co alloy, the temperature is 800 to 950 ° C.
Thus, it is possible to obtain a molded article having a sufficiently high density (relative density ≧ 95%). The molding conditions other than the temperature can be in accordance with a conventional method.

[0012] The resulting alloy target is then sputtered. A usual method can be directly applied to the means and conditions of sputtering. In the target of the present invention, the structure is fine and the reaction between the solids is suppressed, so that the composition difference between the solids is maintained. Therefore,
During sputtering, a magnetic recording layer is obtained in which the composition difference between the target and the film is small, there is no variation in the composition of the film formed on the substrate, and there is no variation in the magnetic recording characteristics.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 Terbume of 99.9% purity, electrolytic iron,
Alloy b, Tb: Fe = 8 using electrolytic cobalt as raw material
6:14 (% by weight), alloy a, Tb: Fe: Co = 2
5: 69: 6 (% by weight) was melted by an arc melting method, and the obtained alloys were melted in a quartz tube having an injection hole at the tip in an Ar atmosphere, and then placed on a copper roll rotating at 2000 RPM. A super-quenched ribbon was produced by injection.
Each alloy is pulverized and classified in an organic solvent to obtain a 100
A powder of 0 μm or less was prepared. b alloy powder 112g and a
After 239 g of the alloy powder was mixed in a ball mill in an Ar atmosphere, the mixture was filled into a carbon mold having an inner diameter of 102 mm,
After the temperature was raised to 950 ° C. in an atmosphere, the pressure was increased at 500 kg / cm ² for 1 hour, followed by cooling to room temperature.

No cracks, cracks, etc. were observed in the alloy target thus obtained. The composition of this target was Tb22, Fe72.4, Co5.6 (atomic%). The target organization is Tb ₂ (F
eCo) ₁₇ phase particles, a fine Tb (FeCo) ₂ phase around the Tb (FeCo) ₂ phase, and particles comprising a mixed phase of a fine αTb phase in which (FeCo) is dissolved in Tb. . Using this target (diameter: 102 mm, thickness: 5 mm), sputtering was performed under the conditions of a glass substrate, fixed directly above, an Ar gas pressure of 3 × (1/10 ³ ) Torr, and a power of 5 KW / cm ² . As a result of quantitative analysis of the film composition from the center position immediately above the substrate to 100 mm in the radial direction by EPMA, the variation was within 0.1 at% in Tb.
The difference between the target composition and the average value of the film composition is 0.2
The deviation of the average value of the film composition at the time of 1 hour and 10 hours after the sputtering was within 0.2 at%. And the relative density is 99% and the oxygen content is 400p
pm and the maximum magnetic permeability were 3.2.

[0015]

Embodiment 2 Alloy b, Tb: F in the same manner as in Embodiment 1.
e: Co = 65.5: 32: 2.5 (% by weight), powders of alloy a and Tb: Fe: Co = 25: 69.5: 5.5 (% by weight), each having 590 μm or less, are prepared. Mixing 225 g of alloy powder b and 122 g of alloy powder a
A target was prepared by hot pressing at 500 ° C. and 500 kg / cm ² . No cracks or cracks were found on the target. The target composition is Tb27, Fe68, C
At o5 (atomic%), the structure is Tb (FeCo) phase + αTb
The structure was the same as that of Example 1 except that there were many mixed phases. As a result of the sputtering, the variation in the film composition was 0.2 at%, and the composition deviation between the film and the target was 0.2 at%.
%, The change with time of the film composition is 0.2 at for 1 hour and 10 hours.
%Met. The relative density was 98.5%, the oxygen content was 350 ppm, and the maximum magnetic permeability was 3.0.

[0016]

Example 3 In the same manner as in Example 1, a ribbon was prepared from the alloy b, Tb: Fe = 86: 14 (% by weight) produced by the arc melting method by a super-quenching method, and pulverized and classified in an organic solvent. 2
A powder having a size of 00 μm or less was prepared. Also, alloys a, Tb:
Fe: Co = 25: 69.5: 5.5 (% by weight) was melted by an arc melting method, and pulverized and classified in an organic solvent to prepare a powder of 200 μm or less. Alloy powder b, 2
850 ° C. by mixing 25 g and alloy powder a, 122 g,
A target was produced by pressure molding at 220 kg / cm ² . No cracks or cracks were found on the target. Both the composition and the structure were the same as in Example 2. The variation in the film composition was 0.2 at%, the difference between the composition of the film and the target was 0.3 at%, and the change with time in the film composition was 0.3 at%.
And a good value. And its relative density is 98.8
%, The oxygen content is 350 ppm, and the maximum magnetic permeability is 3.1.
Met.

[0017]

Comparative Example 1 A target was prepared in the same manner as in Example 2 except that the hot working conditions were changed to 1100 ° C. No cracks or cracks were found on the target. The structure of the target was composed of a Tb (FeCo) ₂ phase and a Tb (FeCo) ₃ phase. When the target was sputtered in the same manner as in Example 1, the variation in the film composition showed a difference of about 2 at% in Tb value at a position 70 mm in the radial direction from the center immediately above. The relative density was 100%, the oxygen content was 480 ppm, and the maximum magnetic permeability was 5.5.

[0018]

Comparative Example 2 Alloy a, Tb: Fe: Co = 25: 69:
6 (% by weight) was melted by an arc melting method, and pulverized and classified in an organic solvent to prepare a powder a having a size of 300 μm or less. 0.266 g of the powder and 99.9% Tb powder of 250 μm or less produced by the PREP method were mixed in a ball mill in an argon atmosphere, and then filled in a carbon mold having an inner diameter of 102 mm, and then placed in an argon atmosphere at 1100 ° C. and 220 kg / cm ² for 1 hour. It was molded under pressure. No cracks or cracks were found on the target. The relative density of the target was 84%, which was lower than that of Example, and the impurity oxygen content was 1500 ppm, which was higher than that of Example 1. The maximum magnetic permeability of the film obtained by sputtering this target was 17.0.

[0019]

According to the present invention as described above, a single R
Since the amount of E is small, the oxidation is small, the deviation between the target composition and the film composition is very small, and the film characteristics do not deteriorate,
Further, the change with time of the film composition is extremely small. When producing this target, if the alloy b is obtained by the ultra-quick solidification method, the powder can be easily pulverized, the crystal grains thereof become fine, and molding can be performed at a low temperature at the time of molding. Density molding can be performed, and the manufacturing process can be simplified and cost can be reduced.

────────────────────────────────────────────────── ─── Continued on the front page (72) Katsuya Furumura, inventor 2081 Karafune, Omuta-shi, Fukuoka Mitsui Kinzoku Mining Co., Ltd. Thin Film Materials Division (56) References JP-A-2-107762 (JP, A) JP-A Sho64 -25977 (JP, A) JP-A-63-274764 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C23C 14/00-14/58 B22F 9/08 C22C 33/02 G11B 7/24 G11B 11/10 ECLA JOIS

Claims (4)

(57) [Claims] 1. A composition comprising at least one rare earth element selected from Gd, Tb and Dy in an amount of 10 to 40 at%, and the balance substantially consisting of one or two transition metals of Fe and Co. Is an intermetallic compound a phase of a rare earth element and a transition metal, a fine mixed phase comprising a solid solution of an intermetallic compound a having the same composition as the intermetallic compound a and a rare earth element and a trace amount of a transition metal element, A sputtering target for a magneto-optical recording medium, characterized in that the inter-compound a comprises an intermetallic compound b phase of a rare earth element and a transition metal having different compositions. 2. A composite structure is constituted by an intermetallic compound a phase, and a fine mixed phase around the intermetallic compound a phase comprising a solid solution of an intermetallic compound a, a rare earth element and a trace amount of a transition metal element. 2. The sputtering target for a magneto-optical recording medium according to claim 1, wherein the sputtering target has a structure in which the intermetallic compound b is formed in another solid. 3. An intermetallic compound b having a particle size of 1000 μm or less.
Powder a of a rare earth element having a composition of
And an alloy powder b of a rare earth element and a transition metal having a composition rich in the transition metal element from the eutectic point in the alloy phase diagram of the rare earth element and the transition metal having a particle diameter of 1000 μm or less, and hot-pressed. A method for producing a sputtering target for a magneto-optical recording medium according to claim 1. 4. The method according to claim 3, wherein at least the alloy powder b among the alloy powders a and b is obtained by a rapid solidification method.