JP2000178723A - Aluminum-titanium alloy sputtering target for forming reflective film of optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a reflective film small in the frequency of the generation of abnormal discharge in the process of sputtering and uniform in the distribution of Ti concn. by using a target for forming a reflective film of an optical recording medium composed of an Al-Ti alloy contg. a specified ratio of carbon. SOLUTION: The content of carbon in an Al-Ti alloy is controlled to 100 to 5000 ppm, preferably to 500 to 2000 ppm. Elements are blended so as to obtain a compsn. contg. high purity Ti, Al and graphite by 0.5 to 10%, 100 to 5000 ppm C, and the balance Al with inevitable impurities, and it is charged to an aluminum crucible or a magnesia crucible, is melted in a high vacuum or in an atmosphere of inert gas and is cast to form an ingot, which is hot- worked and is thereafter subjected to machining. When the melting is executed by using a carbon crucible, C in the crucible enters into solid solution in the Al-Ti alloy, by which a sputtering target contg. 100 to 5000 ppm C can be produced. In the refrective film, variation in the concn. of Ti according to places is small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magneto-optical recording disk (MD, MO) and an optical recording disk (CD-RW, D
The present invention relates to an Al-Ti alloy sputtering target for forming a reflection film of an optical recording medium such as a VD-RAM.

[0002]

2. Description of the Related Art Conventionally, magneto-optical recording disks (MD, M
O), optical recording disk (CD-RW, DVD-RAM)
As a sputtering target for forming a reflective film of an optical recording medium, such as 0.1 to 10 at%, one or two of Hf and Ta: 0.1 to 10 at%.
%, An Al-Ti alloy sputtering target comprising an Al-based alloy containing 0.1% by weight is known (JP-A-4-267).
No. 57).

[0003]

However, the conventional Al-
When a reflective film is formed using a Ti alloy sputtering target, abnormal discharge frequently occurs during sputtering, and many particles and splashing occur, and the concentration of Ti contained in the obtained reflective film becomes uneven in some places. There were problems such as.

[0004]

Accordingly, the present inventors have developed an Al-Ti alloy capable of obtaining a reflective film having a small number of abnormal discharges during sputtering and having a uniform Ti concentration distribution in the obtained reflective film. While research was conducted to develop a sputtering target, the amount of carbon (hereinafter referred to as C) contained in a conventional Al—Ti alloy sputtering target for forming a reflective film of an optical recording medium was 80 ppm or less. When the amount of C contained in the Ti alloy sputtering target is increased to 100 to 5000 ppm, the number of occurrences of abnormal discharge during sputtering that causes the generation of particles and splashing can be reduced. The reflective film formed using the 5000 ppm Al-Ti alloy sputtering target Variation in Ti concentration is smaller by, is the finding that were obtained.

[0005] The present invention has been made based on the results of such research, and (1) C: 100 to 5000 pp
Al-Ti alloy sputtering target for forming a reflective film of an optical recording medium made of an Al-Ti alloy having a composition containing m: (2) Ti: 0.5 to 10%, C: 100 by weight%
An Al-Ti alloy sputtering target for forming a reflection film of an optical recording medium comprising an Al-Ti alloy having a composition containing 5,000 ppm and a balance of Al and unavoidable impurities.

[0006] The Al-Ti alloy sputtering target of the present invention is obtained by converting high-purity Ti, Al and graphite as raw materials into Ti: 0.5 to 10% and C: 100 to 5000 pp
m, with the balance being Al, loaded into an alumina crucible or a magnesium crucible, melted in a high vacuum or inert gas atmosphere, and then cast in a vacuum or inert gas atmosphere. Then, an ingot is manufactured, and the obtained ingot is manufactured by hot working and then machining. In addition, Ti of the present invention:
An Al—Ti alloy sputtering target containing 0.5 to 10%, C: 100 to 5000 ppm, and the balance being Al is prepared by loading high-purity Ti and Al into a carbon crucible and adding no graphite. It can also be manufactured by dissolving in a high vacuum or an inert gas atmosphere, casting it in a vacuum or an inert gas atmosphere to produce an ingot, hot working the obtained ingot, and then machining. When dissolving using a carbon crucible, C of the crucible is dissolved in the Al-Ti alloy, and the Al-Ti alloy sputtering target for forming a reflective film of the optical recording medium of the present invention containing 100 to 5000 ppm of C can be produced. it can.

[0007] The Al for forming a reflective film of the optical recording medium of the present invention
When the -Ti alloy sputtering target is used, the reason why the number of abnormal discharges during sputtering is small and the Ti concentration distribution of the obtained reflective film becomes uniform is that C is 1
This is because when Al is added in an amount of from 0.00 to 5000 ppm, the crystal grains of the Al-Ti intermetallic compound of the obtained target become finer, segregation is reduced, and cracking of the Al-Ti intermetallic compound during processing is suppressed.

[0008] The Al for forming a reflective film of the optical recording medium of the present invention
The reason for limiting the C content in the Ti alloy sputtering target to 100 to 5000 ppm will be described.
If the C content is less than 100 ppm, coarse TiAl ₃ intermetallic compounds are crystallized by melting and casting, and segregation is liable to occur. The coarse TiAl ₃ intermetallic compound in the ingot is liable to be cracked during processing, and if a target made from this ingot is subjected to pattering, abnormal discharge is induced and particles and splashing are undesirably generated. . In addition, a reflective film obtained by sputtering a target having segregation of an intermetallic compound is not preferable because the Ti concentration distribution becomes non-uniform in some places.
On the other hand, if the content of C exceeds 5000 ppm, the reflectance and corrosion resistance required for the reflective film are undesirably reduced. Therefore, the C content of the Al-Ti alloy sputtering target for forming a reflective film of the optical recording medium of the present invention was set to 100 to 5000 ppm. A more preferable range of the content of C is 500 to 2000 ppm.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As a raw material, graphite, purity: 99.
High-purity Ti of 99% or more and high-purity Al of 99.999% or more were prepared. The prepared graphite, high-purity Ti and high-purity Al were charged into an alumina crucible and melted in a high-frequency induction heating furnace in a vacuum atmosphere having a degree of vacuum of 2 × 10 ⁻⁴ Torr. Diameter: 150mm, length by casting in Ar atmosphere:
An ingot having a size of 400 mm and having the composition shown in Table 1 was prepared, and the ingot was cut into a slice to form a disk having a size of 150 mm in diameter and 30 mm in thickness. The plate was forged and rolled to produce a rolled plate having a diameter of 230 mm and a thickness of 10 mm, and was machined to have a diameter of 200 mm and a thickness of 7 mm, as shown in Table 1. Inventive Al—Ti alloy sputtering targets (hereinafter referred to as “inventive targets”) 1 to 7 having the following compositions were produced.

Further, for comparison, the high-purity Ti and high-purity Al were charged into an alumina crucible, and the degree of vacuum: 2
It is melted by a high frequency induction heating furnace in a vacuum atmosphere of × 10 ^-4 Torr, and the obtained molten metal is cast in an Ar atmosphere of 0.5 Pa to obtain a diameter of 150 mm and a length of 400.
An ingot having the dimensions shown in Table 1 was produced, and the ingot was cut into a ring shape to produce a disk having the dimensions of 150 mm in diameter and 30 mm in thickness. The plate is forged and rolled to produce a rolled plate having a diameter of 230 mm and a thickness of 10 mm, which is machined to obtain a diameter of 2 mm.
A conventional Al-Ti alloy sputtering target (hereinafter, referred to as a conventional target) having a size of 00 mm and a thickness of 7 mm and having the composition shown in Table 1 was produced. The C amount of the conventional target is obtained by measuring the amount of C contained as an unavoidable impurity, and the result is shown in Table 1.

[0011]

[Table 1]

The target 1 of the present invention thus obtained
7 and the cross section of the conventional target were polished, etched, and observed with an optical microscope.
7 showed that the crystal grains and precipitates were smaller than those of the conventional target, and the precipitates were uniformly dispersed.

Example 1 The targets 1 to 7 of the present invention and the conventional targets having the compositions shown in Table 1 were each soldered to an oxygen-free copper cooling plate having a thickness of 10 mm using In-Sn eutectic solder. Sputtering was performed for 35 hours under the following conditions: substrate: transparent polycarbonate resin plate; sputtering gas: 5 mm Torr Ar gas; DC power: 800 w 5 hours later, 1
0 hour, 15 hours, 20 hours, 25 hours, 30 hours
The cumulative number of arc occurrences after and after 35 hours was measured, and the results are shown in Table 2.

[0014]

[Table 2]

From the results shown in Tables 1 and 2, the cumulative number of arc occurrences increases when long-lasting sputtering is performed using a conventional target having a C content of 70 ppm.
C: The targets 1 to 7 of the present invention containing 100 to 5000 ppm show the number of accumulated arcs immediately after the start of sputtering and 3
Since there is almost no difference in the number of accumulated arcs generated after 5 hours, it can be seen that the generation of particles and splashing is small even when long-lasting sputtering is performed using the targets 1 to 7 of the present invention. In some of the targets 1 to 7 of the present invention, the number of arcs generated immediately after the start of sputtering is larger than that of the conventional target. This is due to contamination of the surface of the target and adhesion of oxides. When the film is formed, the number of arcs generated immediately after the start of the sputtering may be ignored since the main sputtering is performed after performing the empty sputtering for about 5 minutes.

Example 2 The targets 1 to 7 of the present invention and the conventional targets having the compositions shown in Table 1 were each soldered to an oxygen-free copper cooling plate having a thickness of 10 mm using In-Sn eutectic solder. Attached to a DC magnetron sputtering apparatus, and started sputtering under the same conditions as in Example 1.
0 mm, 20 mm, 40 mm, 60 mm, 80 mm in the radial direction from just above the target center of the reflective film obtained after 10 hours.
mm and 100 mm away from the Ti concentration by ICP
(Inductively coupled high frequency plasma spectroscopy)
The results are shown in Table 3, and the value obtained by dividing the difference between the Ti concentration at the 0 mm point and the Ti concentration at the 100 mm point by the Ti concentration at the 100 mm point was obtained as a variation in the Ti concentration.
Table 3 shows the results.

[0017]

[Table 3]

From the results shown in Tables 1 and 3, C:
Targets 1 to 7 of the present invention containing 100 to 5000 ppm
The reflective film formed by the method of the present invention has a significantly smaller variation in Ti concentration than the reflective film formed by the conventional target containing 70 ppm of C:
7 show that a reflective film having a more uniform Ti concentration can be obtained than the conventional target.

[0019]

As described above, the Al-Ti alloy sputtering target for forming a reflective film of an optical recording medium according to the present invention has no particles or splashing,
A reflective film having a uniform concentration can be formed, the incidence of defective products can be reduced more than before, an optical recording medium can be manufactured efficiently, and it can greatly contribute to the development of the media industry.

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Claims (2)

[Claims] 1. An Al-Ti alloy sputtering target for forming a reflection film of an optical recording medium, comprising an Al-Ti alloy having a composition containing 100 to 5000 ppm of C. 2. Ti: 0.5 to 10% by weight, C: 100
An Al-Ti alloy sputtering target for forming a reflective film of an optical recording medium, comprising an Al-Ti alloy containing 5,000 ppm and a balance of Al and unavoidable impurities.