JPH11293453A - Production of high purity alloy sputtering target - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alloy sputtering target small in the intrusion of impurities and having a uniform compsn. small in dispersion. SOLUTION: This method for producing the high purity alloy sputtering target comprises a stage where at least >= two kinds of raw material metals are prepd., and weighing and charging are executed, a stage where the raw material metals are charged to a floating and melting crucible and are subjected to floating and melting, a stage where the molten alloy is cast into a preheated mold, a stage in which the cast ingot as the stock of a sputtering target alloy is subjected to machining and a stage where the alloy sputtering target is bonded with a backing plate. A stage where the cast ingot being the sputtering target alloy stock is rolled is added before the stage where machining is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of a sputtering target made of an alloy, and more particularly to a display device, a recording medium, and a material suitable for forming a magnetic thin film by sputtering on a material used for the recording device. It relates to the production of a high purity alloy target.

[0002]

2. Description of the Related Art In recent years, in various fields such as display devices, recording media, and recording devices, development of various alloy targets for forming a magnetic thin film having an alloy composition on an electronic element, an integrated circuit, and an optical component by a PVD method. Is thriving.

In general, a magnetic thin film material is formed by a PVD method using a sputtering apparatus. In sputtering, an alloy target is placed in a vacuum vessel, a substrate is placed so as to face the target, an argon gas is added into the vacuum vessel, and a high-frequency current flows to discharge. Then, argon ions in the plasma generated by the discharge are caused to collide with the alloy target, and the alloying element is beaten by the collision energy to reach the substrate to form a thin alloy film. In order to form a magnetic thin film of usually several microns or less on a substrate by using the sputtering method, it is necessary to use a high-purity alloy target having a composition substantially equal to the composition of the magnetic thin film.

There are many types of alloy sputtering targets, and the alloy composition differs depending on the application field. That is, in the recording media field, the recording film of the hard disk is made of Co-Cr-Pt or Co-Cr-T.
a, a Co alloy target such as Co-Ni-Cr, and a Tb-Fe-based alloy target of Tb-Fe-Co are used for the recording film of the magneto-optical recording disk. Further, in the field of recording devices, a magnetic head, particularly a MIG head, has a magnetic head, such as Fe-Ta, Fe-Al-Si,
e-alloy target, thin film head and MR head
An Fe-N alloy target is used for the Fe-based alloy target and GMR. Further, in the field of display devices, ITO (In ₂
O ₃ + SnO ₂ ) target and electrodes are Al-N
An Al alloy target such as d, Al-Ti, Al-Nb, or Al-Ta, or a Ti metal target is used.

There are several methods for manufacturing an alloy sputtering target, and the vacuum melting and casting method described below is generally used. That is, a raw material metal is prepared, weighed and charged, melted in a vacuum, and then subjected to machining processing through a forging step and / or a rolling step or without a forging step and / or a rolling step to obtain a target material. Then, the product is bonded to a backing plate and finished to give a product.

However, in the conventional vacuum melting step, a raw material is melted by induction heating using a ceramic crucible having a composition of MgO, Al ₂ O ₃ , CaO or the like. As a result, impurities are eluted and mixed in from the ceramic crucible, so that it has been difficult to obtain a high-purity, uniform-quality alloy sputtering target.

An alloy target using several kinds of metal materials having a large difference in specific gravity, for example, Al—Ni, Al—T
i, Al-based alloys such as Al-W and Ti-Si alloys do not have a large stirring power in the conventional method, so that an element having a large specific gravity sinks to the bottom during melting. There was a problem that it was not possible.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide an alloy sputtering target having a small amount of impurities, a uniform composition and a small variation. It aims to provide a manufacturing method.

[0009]

Means for Solving the Problems The present inventors have paid attention to the fact that in order to produce a high-purity alloy material, it is only necessary to dissolve it without contact with a ceramic crucible which causes contamination. Then, it has been found that a desired alloy sputtering target can be obtained by employing a levitation melting method in which the alloy is completely and stably floated and melted, since the stirring force of the molten metal by the electromagnetic force is large.

The present invention has the following features. (1) Steps of preparing, weighing and charging raw metal, charging raw metal into a floating melting crucible, and floating and melting.
Casting a molten alloy in a preheated mold, machining a cast ingot of a sputtering target alloy material, and bonding an alloy sputtering target to a backing plate, a high-purity alloy. A method for manufacturing a sputtering target.

(2) A high-purity alloy sputtering target according to (1), wherein a step of forging and / or rolling a cast ingot of a sputtering target alloy material is added before the step of performing machining. Manufacturing method. (3) A high-purity alloy sputtering target characterized in that the content of gas and metal impurities is small, the distribution of the added metal is uniform, and the raw metal is produced by fusing and melting.

Hereinafter, the present invention will be described in detail. The manufacturing process of the alloy sputtering target of the present invention is as follows. First, preparing and weighing and charging the raw metal, then floating and dissolving the raw metal, casting, forging and / or rolling and machining as required, bonding, and finally finishing It consists of each step of the process. The atmosphere in the levitation melting step and the casting step is an argon gas atmosphere or preferably a vacuum atmosphere.

In the present invention, the raw material metal of the alloy for the sputtering target is melted by a levitation melting method as follows. First, put the solid metal that is the raw material in a water-cooled copper crucible with a slit that is vertically long, and apply an electric current,
An electromagnetic force is generated from the lower coil (for levitation), and an eddy current is induced in the metal and the crucible. Thereby, a repulsive force acts between the eddy currents, and the metal floats. Similarly, the electromagnetic force from the upper coil (for heating) causes the upper part of the metal to be in a completely levitated state without contacting the inner wall of the crucible. At the same time, when the metal is heated by the upper coil, the metal melts out, and impurities such as oxides inside are pushed out to the surface because the surface tension is weaker than that of the metal. The interior of the copper crucible is constantly cooled with water to prevent it from becoming hot and melting.

The metal levitated and melted in this way is carried to the next step, a casting step. The alloy sputtering target material cast into a predetermined shape is rolled as necessary for the purpose of densifying the structure, improving magnetic properties, and improving leakage magnetic flux, and then subjected to machining such as cutting.
Next, the alloy sputtering target material is subjected to a bonding process for bonding to the backing plate, and finally the process proceeds to a finishing process such as removal of dirt on the surfaces of the sputtering target and the backing plate.

The following various metallic targets can be applied to the production of the alloy sputtering target by levitation melting of the present invention. That is, a Co alloy,
Fe alloys, Ni-Fe alloys, Tb-Fe alloys, active metals such as Tb, Ti and Zr, and alloys having a large specific gravity difference such as Al-Ta, Al-Nd, Al-Ti and Al
—Nb, Al—Zr, and Ti—Si, whose types cover a wide range.

[0016]

The present invention will be further described below with reference to examples and comparative columns. Example 1 In order to obtain an alloy material for a sputtering target having an alloy composition of Co ₈₂ Cr ₁₃ Ta ₅ (mol%), a metal Co 75 was used.
35 g, metal 1054 g and metal 1411 g
A total of 10 kg was prepared. Raw metal is 99.9% pure
The above was used.

These raw materials are charged into a water-cooled copper crucible of a flotation melting apparatus (manufactured by Fuji Electric Co., Ltd.) and 2 × 10 ^-2.
The evacuation was performed to Torr or less. Next, argon gas is sealed up to 1 atm (zero gauge pressure), and the electric power is reduced to 150K.
When it was charged up to w, it dissolved in about 15 minutes. Then 1
It was held for 0 minutes, the power was adjusted, and when the temperature of the molten metal reached 1400 ° C., it was cast into a mold under an argon gas atmosphere.

The casting ingot of the obtained alloy material for a sputtering target is forged at 1300 ° C.
Hot rolling was performed at 100 ° C., and then cold rolling was performed at room temperature. Then, after machining to a predetermined shape, bonding to Co-Cr
A -Ta alloy sputtering target was obtained.

Example 2 In order to obtain an alloy material for a sputtering target having an alloy composition of Ni ₈₀ Fe ₂₀ (mol%), raw materials of Ni and Fe were weighed and prepared. These raw material metals were charged into a water-cooled copper crucible of a flotation melting apparatus (manufactured by Fuji Electric Co., Ltd.), and vacuuming was performed to 2 × 10 ⁻² Torr or less. Next, argon gas is sealed up to 1 atm (gauge pressure is zero),
When electric power was applied up to 150 Kw, it dissolved in about 15 minutes. Thereafter, the temperature was maintained for 10 minutes, the electric power was adjusted, and when the temperature of the molten metal reached 1350 ° C., casting was performed in a mold under an argon gas atmosphere.

The cast ingot of the obtained alloy material for a sputtering target was hot-rolled at 1100 ° C., machined into a predetermined shape, and bonded to a backing plate to obtain a Ni—Fe alloy sputtering target.

Example 3 In order to obtain an alloy material for a sputtering target having an alloy composition of Tb ₂₅ Fe ₆₅ Co ₁₀ (mol%), Tb, Fe, C
The raw material metal of o was weighed and prepared. These raw material metals were charged into a water-cooled copper crucible of a flotation melting apparatus (manufactured by Fuji Electric Co., Ltd.), and vacuuming was performed to 2 × 10 ⁻² Torr or less. Next, argon gas was sealed up to 1 atm (zero gauge pressure), and when electric power was applied up to 150 Kw, it dissolved in about 15 minutes. Thereafter, the temperature was maintained for 10 minutes, the electric power was adjusted, and when the temperature of the molten metal reached 1200 ° C., casting was performed in a mold under an argon gas atmosphere.

The casting ingot of the obtained alloy material for a sputtering target is machined into a predetermined shape,
Tb-Fe-C bonded to backing plate
An o alloy sputtering target was obtained.

Example 4 In order to obtain an alloy material for a sputtering target having an alloy composition of Ti ₈₀ Si ₂₀ (mol%), raw materials of Ti and Si were weighed and prepared. These raw material metals were charged into a water-cooled copper crucible of a flotation melting apparatus (manufactured by Fuji Electric Co., Ltd.), and vacuuming was performed to 2 × 10 ⁻² Torr or less. Next, argon gas is sealed up to 1 atm (gauge pressure is zero),
When electric power was applied up to 150 Kw, it dissolved in about 15 minutes. Thereafter, the temperature was maintained for 10 minutes, the power was adjusted, and when the temperature of the molten metal reached 1300 ° C., casting was performed in a mold under an argon gas atmosphere.

The casting ingot of the obtained alloy material for a sputtering target is machined into a predetermined shape,
Bonding to a backing plate gave a Ti-Si alloy sputtering target.

Example 5 In order to obtain an alloy material for a sputtering target having an alloy composition of Al-5% Zr (% by weight), raw materials of Al and Zr were weighed and prepared. These raw material metals were charged into a water-cooled copper crucible of a flotation melting apparatus (manufactured by Fuji Electric Co., Ltd.), and vacuuming was performed to 2 × 10 ⁻² Torr or less. Next, argon gas is sealed up to 1 atm (gauge pressure is zero),
When electric power was applied up to 150 Kw, it dissolved in about 15 minutes. Thereafter, the temperature was maintained for 10 minutes, the electric power was adjusted, and when the temperature of the molten metal reached 1200 ° C., casting was performed in a mold under an argon gas atmosphere.

The obtained cast ingot of the alloy material for a sputtering target is hot-rolled at 600 ° C., then machined into a predetermined shape, bonded to a backing plate, and sputtered on a 200 × 600 × 7 ton Al—Zr alloy. Got the target.

Comparative Examples 1 to 5 Comparative Examples 1 to 5 are contrasted with Examples 1 to 5 of the present invention, respectively. Examples 1 to 5 used a flotation melting apparatus using a copper crucible as a melting furnace, while Comparative Examples 1 to 4 used MgO.
In the crucible and Comparative Example 5, a high-frequency induction furnace was used as a carbon crucible. In Comparative Examples 1 to 5, alloy sputtering targets were obtained under the same conditions as in Examples 1 to 5, except for the above melting conditions.

Table 1 shows the amounts of impurity elements contained in the alloy sputtering targets obtained in Examples 1 to 5 and Comparative Examples 1 to 5. Further, with respect to the additional metal contained in the alloy sputtering targets obtained in Example 5 and Comparative Example 5, Zr at points A to D shown in FIG.
The distribution of the quantities is shown in Table 2.

[0029]

[Table 1]

[0030]

[Table 2]

As can be seen from Table 1, C, O, N, P,
It can be seen that the impurity amount of S is significantly reduced in the method of the present invention as compared with the conventional method shown as a comparative example. Co-based alloy, Ni-Fe-based alloy sputtering target is HD
Used for recording films of MR heads and MR heads.
If any of the elements such as N, P, S, etc. exceeds 100 ppm, the magnetic properties are remarkably deteriorated, so that the method of the present invention is useful.

Table 2 shows the variation in the component ratio of the added metal in the alloy sputtering target using a metal having a large difference in specific gravity. And the variation is small in the thickness direction.

[0032]

According to the present invention, unlike the conventional example, since a ceramic crucible is not used, there is no crack due to heat shock, so rapid heating is possible, and the melting / casting time is about 3 minutes as compared with the conventional example. Of 1 or less. In addition, in the production of the alloy sputtering target of the present invention, the inclusion of trace metal impurities and gas impurities from the crucible is reduced, so that an extremely high-purity sputtering target with a small amount of impurities can be obtained. Further, since the stirring power for the molten metal is larger than that of the conventional induction melting, the composition is uniform even when a metal material having a large difference in specific gravity is melted. Therefore, an alloy sputtering target made of a new kind of alloy can be manufactured, and the size of the target can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing a measurement position of a Zr content contained in an alloy sputtering target in Example 5 of the present invention.

Claims (3)

[Claims] 1. A step of preparing, weighing and charging a raw material metal, a step of charging a raw metal into a floating melting crucible, a step of floating and melting, a step of casting a molten metal alloy in a preheated mold, and a step of forming a sputtering target alloy material. A method for producing a high-purity alloy sputtering target, comprising: a step of machining a cast ingot; and a step of bonding an alloy sputtering target to a backing plate. 2. A method for forging and / or forging a cast ingot of a sputtering target alloy material before a step of machining.
The method for producing a high-purity alloy sputtering target according to claim 1, wherein a rolling step is added. 3. A high-purity alloy sputtering target characterized in that the content of gas and metal impurities is small, the distribution of the added metal is uniform, and the raw metal is produced by fusing and melting.