JPH0718003B2 - Sputtering target for optical media Ingot material - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering target material for optical media, and more specifically, an optical disk, a magneto-optical disk, etc. for reading or writing information using laser light. The present invention relates to a sputtering target material for forming a reflective film used for optical media.

(Prior Art) Optical media such as optical disks and magneto-optical disks are required to have high reliability, and it is particularly important to secure the storability of recorded data. The deterioration of the reflection film on the substrate, which constitutes the main part of the medium, particularly the deterioration of the reflectance over time due to the oxidation of the reflection film has a great influence on the data storability. Prevention is an important issue.

Conventionally, pure Al has been used for the reflective film, which is a thin film of pure Al formed on a substrate. The thin film forming method includes a sputtering method and a vapor deposition method, but the sputtering method is often adopted from the viewpoint of improving the adhesion to the substrate. As the above-mentioned pure Al, 99.9% (3N) purity was used at the beginning, but the higher the purity, the better the corrosion resistance,
Since it is difficult for the reflectance to decrease over time,
99.99% (4N) purity is used.

However, the reflection film made of pure Al has a limit in corrosion resistance and cannot satisfy the recent demand for higher reliability, and a drastic countermeasure is required.

Therefore, it was attempted to improve the corrosion resistance by alloying Al, and as a result, a reflective film made of an Al alloy containing a metal of the group Va of the periodic table of elements was proposed, for example, in JP-A-64-4938, Al- T
a Alloy film is described. Such an alloy film is formed on the substrate by the following sputtering method. That is,
(A) A small piece of a Va group metal placed on a target of pure Al, (b) a block of pure Al and Va group metals arranged in a mosaic pattern, or (c) a pure Al and Va group metal This is performed by a method in which powders are mixed and sintered and used as a sputtering target material, and sputtering is performed on a substrate.

(Problems to be Solved by the Invention) However, the methods (a) and (b) can be obtained because the sputtering rate and the emission angle of Al and the Va group metal are different.
The composition of the reflective film made of Al-based alloy (hereinafter referred to as alloy film) is smaller than the composition of the target (area ratio of Al and Va group metal), and this difference changes depending on the sputtering conditions and equipment. It is difficult to adjust the composition, and it is extremely difficult to always obtain a predetermined alloy film stably. In addition, since the area ratio continuously changes during use of the target material, it is difficult to obtain an alloy film having a predetermined composition.

In the method (c), since the Al powder and the Va group metal powder have large specific gravities, it is difficult to mix them uniformly, and the composition of the target material becomes non-uniform, so that the composition of the alloy film tends to become non-uniform. There is a point. Also, both of the above powders are active,
Since it easily absorbs oxygen, the alloy film contains a large amount of oxygen,
Therefore, there is a problem that the reflectance becomes low.

The present invention has been made in view of such circumstances, and its purpose is to solve the above-mentioned problems of the conventional one and to stably obtain an alloy film having a predetermined composition. It is intended to provide a sputtering target material for optical media.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the ingot-sputtering material for optical media according to the present invention has the following structure.

That is, the sputtered cage material according to claim 1 contains one or more of Ta, Nb, and V of the Va group of the periodic table of elements.
In addition to being composed of Al-based molten alloy containing 0.5-10 at%,
An intermetallic compound of the Va group element with Al is uniformly dispersed in an Al matrix, which is a material for melting a sputtering target for optical media.

The sputtering target ingot material according to claim 2,
The ingot-melting material for optical media according to claim 1, wherein the size of the intermetallic compound is 100 μm or less.

The ingot material for sputtering target according to claim 3 is
The sputter target ingot material for optical media according to claim 1, wherein the oxygen content of the Al-based ingot alloy is 200 ppm or less.

(Operation) As described above, the melted material for the sputtering target for optical media according to the present invention contains one or more of Ta, Nb, and V in the Va group of the periodic table (hereinafter referred to as Ta) in an amount of 0.5 to 0.5. 10at%
Al-based ingot alloy containing, that is, Al produced through the ingot process
Since it is composed of a base alloy, only a small part of Ta or the like exists as a solid solution in the Al matrix, and most of it exists as an intermetallic compound with Al. The distribution of the solid solution Ta and the like in the former is uniform, and the intermetallic compound in the latter is usually also dispersed uniformly, and such a uniform dispersion state can be easily obtained. Therefore, the Ta and the like exist uniformly dispersed in the Al-based alloy, and form a target material together with Al in the matrix.

Since such a target material has a uniform composition, the composition does not change with time during use, and since the sputtering rate and the emission angle are uniform, the composition of the target and the composition of the obtained alloy film are substantially the same. To do. Therefore, the composition of the alloy film can be easily adjusted, and as a result, an alloy film having a predetermined composition can be stably obtained. In addition, since the target material is manufactured through a melting process, the oxygen content can be set to a low level, so that an alloy film having a low oxygen content and a high reflectance can be reliably obtained.

The content of Ta and the like is 0.5 to 10 at% because 0.5 at
This is because if it is less than 10%, the effect of improving the corrosion resistance is small and it is not possible to sufficiently prevent the deterioration of the reflectance over time, and if it exceeds 10 at%, the required reflectance of 70% cannot be secured as shown in FIG.

If the oxygen content of the Al-based ingot-made alloy exceeds 200 ppm, the reflectance tends to decrease, so it is desirable to set it to 200 ppm or less.

When the size of the intermetallic compound is more than 100 μm, there is a difference between the target composition and the alloy film composition.
When the thickness is less than or equal to μm, the difference is almost eliminated, and the alloy film composition can be adjusted more easily.

In order to reduce the thickness to 100 μm or less, the molten metal obtained by the melting method and having a homogeneous mixture of Al and Ta may be rapidly cooled. As the method of quenching, the molten metal is cast in a water-cooled copper mold or a mold having a large cooling capacity, continuously cast in a water-cooled copper mold, poured between two rotating rolls to form a thin plate, or Examples thereof include a method of atomizing with an inert gas.

(Example) Example 1 3 kg of alloy was induction-melted under vacuum and cast in a water-cooled copper mold to obtain an Al-based alloy ingot containing Ta and the like. Table 1 shows the contents of Ta and the like in the ingot. When the microstructure of the ingot was observed, it was confirmed that the intermetallic compounds were fine particles of 100 μm or less and were uniformly dispersed.

A sputtering target was taken from the ingot and sputtered using this to obtain the thickness on the substrate of the optical disc.
A 1000 Å reflective film was formed. Table 1 shows the Ta content and oxygen content of the target, and the Ta content in the reflective film. It can be seen that the composition of the target and the composition of the alloy film are substantially the same.

Regarding the above-mentioned reflective film forming materials, those of Experiment Nos. 1, 5 and 8 were manufactured into optical disks and subjected to an environmental accelerated test (temperature: 105 ° C,
Pressure: 1.5 atm, humidity: 100%). Also, pure Al with a purity of 4N
The same reflective film formation, optical disc production, and test as described above were carried out using the target made of.

The results of these tests are shown in FIGS. When a pure Al target is used, the reflectance sharply decreases and the elalate significantly increases as the test time elapses. On the other hand, in Experiment Nos. 1, 5 and 8, the decrease in reflectance was extremely gentle, and the increase in elalate was hardly observed, indicating a constant value.

Comparative Example 1 After mixing pure Al powder and Ta powder with a V mixer, HIP
A sputtering target material was manufactured by sintering at 400 ° C. by the method, and using this, the same reflection film formation as in Example 1 was performed.

Table 2 shows the Ta amount and oxygen amount of the target material and the Ta amount of the reflective film. As can be seen from the table, the amount of Ta in the alloy film is extremely smaller than that in the target.

Comparing the reflective film of Experiment No. 11 with the reflective film of Experiment No. 2 of Example 1, the Ta amounts are the same, but the reflectance of the former is 83
%, The reflectance of the latter is 71%, The two are significantly different. This is due to the difference in oxygen content between the two.

Example 2 10 kg of Al-3 at% Nb alloy was induction-melted, and the melt was subjected to twin roll type strip casting.
A thin plate having a structure in which fine precipitates of ₃ Nb were uniformly dispersed was obtained. When this was processed into a target plate and used for sputtering, a reflective film in which Al-Nb was uniformly distributed was obtained.

Example 3 10 kg of Al-3 at% Nb alloy was induction-melted, and a quenching powder obtained by gas atomizing this molten metal was deposited to obtain a thin plate having a structure in which fine Al ₃ V precipitates were uniformly dispersed. Was given. When this was processed into a target plate and used for sputtering, a reflective film in which Al-V was uniformly distributed was obtained.

(Effect of the Invention) According to the sputtering target material for optical media of the present invention, an alloy film having a predetermined composition (a reflective film made of an Al-based alloy)
Will be able to get stable. Therefore, it is possible to obtain a reflective film that is excellent in corrosion resistance, is not easily deteriorated, and is unlikely to cause a decrease in reflectance over time. Therefore, it is possible to improve the storability of data on an optical medium and enhance the reliability.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the Ta, Nb, and V contents of a sputtering target material made of an Al-based alloy and the reflectance of a reflective film obtained by sputtering the target material, and FIG. FIG. 3 is a diagram showing the relationship between the test time in the environmental acceleration test of the optical disk according to Example 1 and the reflectance of the reflective film, and FIG. 3 is a diagram showing the relationship between the test time in the acceleration test and the error rate. .

Claims (3)

[Claims] 1. An intermetallic compound comprising an Al-based melted alloy containing 0.5 to 10 at% of one or more of Ta, Nb, and V of the Va group of the periodic table of elements, and an intermetallic compound with Al of the Va group of elements. Is a sputtering target ingot for optical media, in which is uniformly dispersed in the Al matrix. 2. The material for melting a sputtering target for optical media according to claim 1, wherein the size of the intermetallic compound is 100 μm or less. 3. The material for melting a sputtering target for optical media according to claim 1, wherein the oxygen content of the Al-based melted alloy is 200 ppm or less.