JP2002212716A - Sintered sputtering target material for forming recording layer of magneto-optical recording medium exhibiting excellent cracking resistance under high sputtering power - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sintered sputtering target material for forming a recording layer of a magneto-optical recording medium which exhibits excellent cracking resistance under high sputtering power. SOLUTION: The sintered sputtering target material consists of a press sintered body. The press sintered body has (a) a composition containing rare earth metals consisting of 41 to 49 mass% of one or more kinds selected from Tb, Gd and Dy, and the balance transition metals consisting of Fe or essentially consisting of Fe and containing Co or essentially consisting of Fe and containing Co and Cr with inevitable impurities. The press sintered body has (b) a structure consisting of: dispersed phases essentially consisting of an intermetallic compound satisfying the compositional formula of RT3 by atomic ratio wherein the rare earth metals are expressed by R, and the transition metals are expressed by T by structural observation with a scanning electron microscope; and continuous phases (skeletal structural phases) existing among the dispersed phases and essentially consisting of an intermetallic compound satisfying the compositional formula of R6T23. In the dispersed phases, a fine intermetallic compound satisfying the compositional formula of R2T17 is dispersedly distributed simultaneously with the intermetallic compound satisfying the compositional formula of R6T23. The press sintered body also has a theoretical density ratio of >=90%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered sputtering target material for forming a recording layer of a magneto-optical recording medium, which does not cause breakage even when a high sputtering power is applied, in order to perform high-speed film formation with a sputtering apparatus. (Hereinafter, simply referred to as target material).

[0002]

2. Description of the Related Art In general, a magneto-optical recording medium such as a magneto-optical disk for recording, reproducing, and erasing information using a light beam such as a semiconductor laser and an electromagnetic coil is basically made of, for example, a polycarbonate substrate, It is known that each of the layers has a lower dielectric protection layer, a recording layer, an upper dielectric protection layer, and constituent layers of a reflection layer formed on the surface thereof by a sputtering method.

Further, as a target material used for forming a recording layer (hereinafter, simply referred to as a recording layer) among the constituent layers of the above-described magneto-optical recording medium, for example, JP-A-8-30246.
As described in Japanese Patent Publication No. 3 (No. 3), (a) rare earth metal: 4
(B) a rare earth metal-transition metal alloy powder phase and a rare earth metal-transition metal alloy grain boundary interposed therebetween. 2. Description of the Related Art A target material having a structure composed of a diffusion phase, a composition and a structure described in (a) and (b) above, and a pressure sintered body having a theoretical density ratio of 90% or more is known.

Further, as the above-mentioned target material, a rare earth metal-transition metal alloy powder powdered by an atomizing method is used as a raw material powder, and for example, when the theoretical density ratio is less than 90 to 97%, The hot press treatment is performed at a temperature of 30 to 100 ° C. and a pressure of 10 to 40 MPa below the liquid: appearance temperature of the liquid phase. 100
It is also known that it is manufactured by performing HIP (Hot Isostatic Pressing) treatment under conditions of ° C. and pressure: 50 to 120 MPa.

Further, generally, the recording layer is formed by, for example, using a direct current magnetron sputtering apparatus as a sputtering apparatus, and first soldering the target material to, for example, an oxygen-free copper backing plate cooled by cooling water circulating inside. After the inside of the apparatus is evacuated by a vacuum exhaust device, Ar gas is introduced and maintained at a predetermined sputter gas pressure, and in this state, sputter power is applied to the target material by a DC power supply, and the target A glow discharge is generated between the substrate and a substrate made of, for example, polycarbonate, which is disposed in parallel with a predetermined distance therebetween, and causes Ar ions in plasma forming the glow discharge to collide with the surface of the target material. Formed by depositing sputtered particles on the surface of the substrate. There.

[0006]

On the other hand, there is a strong demand for improvement in productivity of magneto-optical recording media such as the above-mentioned magneto-optical disk in recent years, and accordingly, the film forming speed of constituent layers tends to be increased. However, in order to perform high-speed film formation, it is necessary to increase the plasma density of glow discharge generated between the target material and the substrate, and for this purpose, it is essential to increase the sputtering power applied to the target material. But,
In the above-mentioned conventional target material, if a high sputtering power is applied thereto, the breakage is likely to occur.
At present, it is impossible to perform one-step high-speed film formation satisfactorily.

[0007]

Means for Solving the Problems Accordingly, the present inventors have:
From the above point of view, we focused on the above-mentioned conventional target materials and conducted research to improve their breakage resistance.
In addition to specifying the rare earth metals which are the constituent components of the above-mentioned conventional target materials to Tb, Gd, and Dy, the transition metals were also specified to be Fe, mainly containing Co, and Fe mainly containing Co and Cr. Above, (b) the target material of (a) is subjected to a vacuum (normal furnace cooling) process from a heating temperature of a hot pressing process or a HIP process in a manufacturing process of the target material, or a separate heating furnace. Alternatively, if the heat treatment is performed under the condition of furnace cooling after holding at a temperature of 750 to 950 ° C. for 20 to 50 hours in an inert gas atmosphere, (c) the target material after the heat treatment of the above (b) becomes a scanning electron microscope. When the above-mentioned rare earth metal is represented by R and the transition metal is represented by T, the disperse phase of the intermetallic compound which satisfies the composition formula: RT ₃ in both atomic ratios and the disperse phase Intervening Formula: continuous phase of an intermetallic compound which satisfies the R ₆ T ₂₃ consists (skeleton tissue phase), and in the dispersed phase in the fine composition formula: R ₂ T ₁₇
As fine as the intermetallic compound satisfying the formula: R
Intermetallic compound which satisfies the ₆ T ₂₃ becomes to have a dispersed distribution organization, target material having a tissue (d) above (c), upon sputtering, a high robust to sputter power applied thereto It exhibits excellent breakage resistance even when a high sputtering power is applied to it, so that it is possible to form a film at a much higher rate than the above-mentioned conventional target material. That's the research result.

The present invention has been made on the basis of the above research results, and (a) rare earth metals consisting of one or more of Tb, Gd and Dy: 41 to 41
49% by mass, with the balance being Fe, mainly Fe, and Co
Content, and a composition consisting of a transition metal composed of any one of Co and Cr containing Fe as a main component and unavoidable impurities,
(B) When the rare earth metal is represented by R and the transition metal is represented by T in the structure observation by a scanning electron microscope, an intermetallic compound which satisfies the composition formula: RT ₃ in an atomic ratio is mainly used. It is composed of a dispersed phase and a continuous phase (skeleton structure phase) mainly composed of an intermetallic compound satisfying the composition formula: R ₆ T ₂₃ , interposed between the dispersed phases, and is finely divided into the dispersed phase. A structure in which the intermetallic compound satisfying the formula: R ₆ T ₂₃ is dispersed and distributed as in the case of the intermetallic compound satisfying the formula: R ₂ T ₁₇ , and has the composition and structure described in (a) and (b) above. Further, the present invention is characterized in that the target material is made of a pressurized sintered body having a theoretical density ratio of 90% or more and exhibits excellent cracking resistance with high sputtering power.

The reason why the content of the rare earth metal in the pressure sintered body constituting the target material of the present invention is set to 41 to 49% by mass is as follows.
That is, the recording layer generally formed by vapor deposition on the surface of the substrate by sputtering the surface of the target material needs to have predetermined saturation magnetization and coercive force in terms of characteristics. A recording layer made of a transition metal is used. In this case, even if the content of the rare earth metal is less than 41% by mass (the content of the transition metal relatively increases) or exceeds 49% by mass (the content of the transition metal decreases conversely), While the saturation magnetization provided by increases, the coercive force decreases,
Since the small recording magnetic domain cannot be stably held, the content of the rare earth metal relative to the transition metal is 41%.
Therefore, the sputtering method forms a recording layer having substantially the same composition as that of the target material. Therefore, the content of the rare earth metal in the target material is also 41 to 41% by mass. It is set at 49% by mass. The reason why the theoretical density ratio of the pressed sintered body constituting the target material is set to 90% or more is that when the theoretical density ratio becomes less than 90%, the sputtering power applied to the surface of the target sintered material is increased. This is because no significant improvement in the film formation rate is exhibited, and it is preferable to have a theoretical density ratio of 98% or more.

[0010]

Next, the target material of the present invention will be specifically described with reference to examples. Using a normal high-frequency vacuum melting furnace, while maintaining the inside of the furnace at a vacuum of 1 × 10 −2 Pa or less, alloy melts having the component compositions shown in Table 1 were prepared, and the melts were powdered by Ar gas atomization and sieved. As a result, raw material powders A to Z having the average particle diameters shown in Table 1 were produced.

Then, the resulting raw material powders A to Z
One, or two or three, is selected as a sintering furnace, using a graphite mold when using a hot press apparatus (HP), and using a hot isostatic sintering apparatus (HIP). Are charged in the state of being filled in mild steel capsules, respectively.
When two or three types of raw material powders are used in combination at the time of this charging, one of the raw material powders is located in a circular shape at the center, and the remaining raw material powders are located in a ring shape on the outer peripheral portion thereof. In the hot press apparatus (HP), the heating temperature (sintering temperature) is set to a predetermined temperature in the range of 30 to 100 ° C. below the liquid phase appearance temperature (in this case, two kinds or three kinds). In the case of charging the raw material powder, the liquid phase appearance temperature of the raw material powder occupying the central circular portion is set as a reference. This is the same in the following HIP), and the pressure is set to a predetermined pressure in the range of 10 to 40 MPa. In the HIP, the heating temperature (sintering temperature) is set to a predetermined temperature within a range of 30 to 100 ° C. or lower than the liquid phase appearance temperature, and the pressure is set to 80 to 100 ° C. As a predetermined pressure in the range of 100 MPa, Was treated with a predetermined time retained condition within the range of 3 hours to sinter, further cooling process from the heating temperature in the sintering furnace or in a conventional furnace separately provided,
A single phase as shown in Table 2 is obtained by holding in an Ar gas atmosphere at a predetermined temperature in a range of 800 to 950 ° C. for a predetermined time in a range of 25 to 40 hours and then performing a heat treatment under furnace cooling conditions. (The center circular portion, the intermediate ring portion, and the outer ring portion have the same raw material powder symbol), two concentric phases (consisting of the central circular portion and the outer ring portion), or three concentric phases (the central circular portion, the intermediate ring portion, and the like). (Consisting of an outer ring portion), a pressed sintered body having the same theoretical density ratio (center measurement) as shown in Table 2, and having a diameter of 127 m.
Each of the target materials 1 to 18 of the present invention having a dimension of mx thickness: 12 mm was manufactured. For the above-mentioned target materials 1 to 18 of the present invention, the respective arbitrary cross sections were observed for the structure of each constitutive phase in the case of concentric two-phase and concentric three-phase using a scanning electron microscope. RT
A dispersed phase mainly composed of an intermetallic compound that satisfies ₃ and a continuous phase (skeleton structure phase) that is interposed between the dispersed phases and mainly composed of an intermetallic compound that satisfies the composition formula: R ₆ T _23. And the dispersion phase is finely divided into the composition formula: R ₂ T
Finely divided like the intermetallic compound satisfying ₁₇ , the composition formula:
A structure in which an intermetallic compound satisfying R ₆ T ₂₃ was dispersed and distributed was shown.

For comparison purposes, comparative target materials 1 to 12 were produced under the same conditions except that the heat treatment was not performed on the pressure-sintered body as shown in Table 3.

Next, the target materials 1 to 1 of the present invention described above are used.
8 and each of the comparative target materials 1 to 12 were soldered to a water-cooled backing plate made of oxygen-free copper, and mounted on a normal DC magnetron sputtering apparatus. After a vacuum atmosphere of 1 .mu.m, an Ar gas was introduced to set the atmosphere in the apparatus to a sputtering gas pressure of 0.7 Pa, and then a direct current power supply was applied to the target material at 1 KW (average power density: 7.0).
A sputter power of 9 w / cm ² ) is applied to the target material so that the glass substrate and the target material have a diameter of 6.5 cm × a thickness of 0.5 mm and are arranged in parallel with a spacing of 5 cm. A glow discharge is generated, Ar ions in the plasma forming the glow discharge collide with the surface of the target material to sputter the target material, and a recording layer is formed to deposit sputtered particles on the substrate surface. Then, while maintaining the respective additional powers for 5 minutes, the power is increased stepwise by 0.5 KW, and the sputter power at the time when the target material is cracked (hereinafter referred to as critical cracking spatter power) is measured. did. These measurement results are shown in Tables 2 and 3, respectively. The concentration distribution in the rare earth metal layer constituting the recording layer formed by vapor deposition on the substrate surface using the target materials 13 to 18 of the present invention having the concentric two-phase structure and the concentric three-phase structure was examined. However, center, radius: 15m from this center
The content at the position of m and the position of a radius of 30 mm from the center were almost the same, and the dispersion was extremely small.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

[0017]

According to the results shown in Tables 2 and 3, the target materials 1 to 18 of the present invention are comparative target materials 1 to 12 each having the same composition and structure as the conventional target material.
The cracking resistance to the applied sputtering power is remarkably higher than that of the target material. Therefore, even if a high sputtering power is applied, which was impossible with the conventional target material due to the occurrence of cracking, the occurrence of cracking is significantly suppressed. Thus, it is clear that the recording layer can be formed at a high film forming rate. As described above, the target material of the present invention enables the recording layer to be formed by a sputtering apparatus at a much higher speed than in the case of using a conventional target material, and greatly improves productivity and reduces costs. It will contribute.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shozo Omiyama 1-297 Kitabukurocho, Omiya City, Saitama Prefecture Inside Mitsubishi Materials Research Institute (72) Inventor Yoshiaki Takada 12-6 Techno Park, Mita City, Hyogo Prefecture Inside Terial Co., Ltd. Mita Plant (72) Inventor Hiroshi Nibuta 12-6 Techno Park, Mita City, Hyogo Prefecture Mitsubishi Materials Corporation Mita Plant F-term (reference) 4K018 AA27 BA18 DA11 EA02 EA13 EA14 KA29 4K029 BA21 BA24 BD12 CA05 DC04 DC09 5D075 FF04 GG03

Claims (1)

[Claims] 1. (a) a rare earth metal consisting of one or more of Tb, Gd, and Dy: 41 to 49% by mass, the balance being Fe, Fe being mainly contained and Co being contained,
And a composition consisting of a transition metal mainly composed of Fe and containing either Co or Cr and an unavoidable impurity. (B) Observation of the structure with a scanning electron microscope shows the rare earth metal as R and the transition metal as T. In this case, a dispersed phase mainly composed of an intermetallic compound satisfying the composition formula: RT ₃ in atomic ratio, and a metal interposed between the dispersed phases and satisfying the composition formula: R ₆ T ₂₃ are obtained. It is composed of a continuous phase (skeleton structure phase) mainly composed of a compound, and the dispersed phase is finely divided into a composition formula:
A structure in which the intermetallic compound satisfying the composition formula: R ₆ T ₂₃ is dispersed and distributed as finely as the intermetallic compound satisfying R ₂ T ₁₇ , and has the composition and structure of (a) and (b) above, And a sintered sputtering target material for forming a recording layer of a magneto-optical recording medium exhibiting excellent breakage resistance with high sputter power, characterized by comprising a pressed sintered body having a theoretical density ratio of 90% or more. .