JPH04280960A - Thin al alloy film and al alloy sputtering target - Google Patents

Abstract

PURPOSE:To produce a thin Al alloy film which is used for reflecting film, etc., for optical recording medium and has high reflectivity, superior corrosion resistance, and low thermal conductivity and also has excellent uniformity of composition and superior productivity. CONSTITUTION:The film is a thin film of an Al alloy which has a composition containing, as alloy component, 0.1-15atomic% Mn or further 0.1-10atomic% of Hf and/or Ta. This thin Al alloy film is produced by forming the thin Al alloy film on a substrate by means of sputtering by using a refined Al alloy target which has a composition containing 0.1-15atomic% Mn or further 0.1-10 atomic% of Hf and/or Ta. This thin film can suitably be used for reflecting film for optical recording medium, and a recording medium excellent in recording sensitivity and durability and capable of maintaining high sensitiviey and high precision for a long period can stably be constituted with superior economic efficiency.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an Al alloy thin film and an Al alloy thin film.
The present invention relates to an alloy sputtering target, and specifically relates to an aluminum alloy thin film (Al alloy thin film) used as a reflective film of an optical recording medium such as a magneto-optical disk, and an Al alloy sputtering target for forming an Al alloy thin film.

0002

[Background Art] Optical recording media have a higher information recording density than magnetic recording media, and the information can be reproduced without contact, so their use has expanded in recent years. It is being done.

Among optical recording media, read-only optical discs have traditionally been provided with a light reflective layer (reflection film), and in recent years, rewritable optical recording media such as magneto-optical discs have also been improved in signal quality (i.e. For the purpose of improving the C/N ratio, etc., devices equipped with a reflective film have been proposed, and the use of reflective films has been increasing year by year.

Since such a reflective film is required to have a high reflectance, a pure Al thin film formed on a substrate has conventionally been used. However, pure Al thin films have poor corrosion resistance and will corrode if left in the atmosphere for a long time, causing a decrease in reflectivity and pitting corrosion, resulting in an increase in the reading error rate (error rate) when reproducing information (signals). There are some difficulties. Further, pure Al thin films have high thermal conductivity, and when used in magneto-optical recording media, there is a drawback that recording sensitivity is significantly reduced.

[0005] Al alloy thin films of various compositions have been proposed as a measure to improve these difficulties. For example, Al alloy thin films containing Si, Mg and/or Cu, and Al alloy thin films containing Pt or Pd have been proposed.

[0006]

[Problems to be Solved by the Invention] However, although the conventional Al alloy thin films proposed above have better corrosion resistance than pure Al thin films, they still do not have sufficient corrosion resistance and are difficult to use for optical recording media. There is a problem in that long-term reliability regarding information recording and reproduction cannot be ensured. Also, pure A
Although the thermal conductivity is lower than that of a thin film, there is a problem in that the recording sensitivity is not sufficient when used in a magneto-optical recording medium.

[0007] Furthermore, when forming an Al alloy thin film, it is necessary to ensure uniformity of the alloy composition of the film, and for this purpose it is preferable to employ a sputtering method rather than a vapor deposition method. However, the sputtering method has a lower film formation rate than the vapor deposition method and takes a longer time to form a thin film, which reduces the throughput of the thin film formation process in mass production.
This can easily become an obstacle to improving productivity. Therefore, the conventional Al
The alloy thin film also has the problem that it takes a long time to form the thin film and the productivity is low.

[0008] Therefore, measures to improve the above-mentioned problems were further investigated, and as a result, 2.
Elemental or ternary Al alloy thin films have been developed and proposed. However, these methods have the following problems.

That is, such an Al alloy thin film is formed on a substrate by sputtering using one of the following sputtering targets. ■ A target with a small piece of additive element (metal) placed on a pure Al target. ■ A target consisting of blocks of pure Al and small pieces of additive metal arranged in a mosaic pattern. ■ A target made by mixing pure Al and additive metal powder and sintering it. ■ Melting and casting pure Al and additive metals (or further forging)
A melt-made Al alloy sputtering target.

However, in the cases of ■ and ■, Al
Since the sputtering yield and emission angle of the aluminum alloy and the additive elements are different, the film composition varies depending on the sputtering conditions and equipment, making it difficult to adjust the composition and making it extremely difficult to stably obtain a predetermined Al alloy thin film.

In the case of (2), since the specific gravities of Al and the additive metal are greatly different, it is difficult to mix them uniformly, and the composition of the target becomes non-uniform, which tends to result in non-uniform composition of the Al alloy thin film. In addition, since both powders are active and easily absorb oxygen, the Al alloy thin film contains a large amount of oxygen,
Therefore, there is also the problem that the reflectance decreases.

[0012] In the case of (2), since the melting points of Al and the additive element are greatly different, when the concentration of the additive element is high, it is difficult to melt the melt itself, and it is also difficult to control the composition of the molten metal, making it difficult to ensure the composition uniformity of the Al alloy thin film. It's difficult. In addition, since intermetallic compounds crystallize and disperse during casting, it is difficult to stably obtain an Al alloy thin film having a predetermined composition and uniformity, resulting in a problem of lower manufacturing yield and lower economic efficiency. There is a point.

[0013] The present invention was made in view of these circumstances, and its purpose is to solve the above-mentioned problems of the conventional products, and to provide a material with high reflectance, excellent corrosion resistance, and excellent thermal conductivity. It is an object of the present invention to provide an Al alloy thin film and an Al alloy sputtering target for forming an Al alloy thin film, which have a low yield rate, excellent compositional uniformity, and excellent productivity.

[0014]

Means for Solving the Problems In order to achieve the above object, an Al alloy thin film and an Al alloy sputtering target for forming an Al alloy thin film according to the present invention have the following configuration.

That is, the Al alloy thin film according to claim 1 is
This is an Al alloy thin film characterized by containing 0.1 to 15 at% of Mn as an alloy component.

[0016] The Al alloy thin film according to claim 2 contains 0.1 to 15 at% of Mn as an alloy component, and Hf.
, 0.1 to 10 at of one or more of Ta
%, and the total amount of these alloy components is 0.2
This is an Al alloy thin film characterized by a concentration of ~20 at%.

The Al alloy thin film according to claim 3 is the Al alloy thin film according to claim 1 or 2, which is used as a reflective film of an optical recording medium such as a read-only or write-once optical disc.

The Al alloy thin film according to claim 4 is the Al alloy thin film according to claim 1 or 2, which is formed by sputtering.

[0019] The sputtering target according to the fifth aspect of the present invention is a melted Al alloy sputtering target for forming an Al alloy thin film containing 0.1 to 15 at% Mn as an alloy component.

The sputtering target according to claim 6 contains Mn as an alloy component in an amount of 0.1 to 15 at%, and one or more of Hf and Ta in an amount of 0.1 to 15 at%.
This is a melted Al alloy sputtering target for forming an Al alloy thin film, which contains 1 to 10 at% and the total amount of these alloy components is 0.2 to 20 at%.

[0021]

[Operation] The present invention manufactures molten Al alloy targets of various compositions, examines the uniformity of the alloy composition, and uses these targets to produce Al by sputtering.
This is based on the following findings obtained by forming alloy thin films and examining the composition, reflectance, corrosion resistance, and thermal conductivity of these Al alloy thin films.

That is, Al containing Mn as an alloy component
The alloy thin film has a high reflectance equivalent to that of a pure Al thin film, and
It was found that this film has extremely excellent corrosion resistance and low thermal conductivity compared to other Al alloy thin films. At this time, Mn
It is necessary for the content to be 0.1 at% or more; if it is less than 0.1 at%, the corrosion resistance will be insufficient and the thermal conductivity will be high, which is not good. However, the Mn content is 15
If it exceeds at%, the reflectance will decrease, and during storage under high-temperature conditions, precipitates larger than the recording bit may occur, leading to information reading errors, and the alloy's melting point and Due to the increase in plasticity, problems such as a decrease in compositional uniformity and the occurrence of cracks during ingot processing occur during the production of molten Al alloy targets. Therefore, the Mn content needs to be 0.1 to 15 at%.

[0023] Since Mn does not affect the film formation rate during sputtering, the productivity of the above-mentioned Mn-containing Al alloy thin film is equivalent to that of a pure Al thin film. Also, Al
Since the melting point difference between Mn and Mn is relatively small, the IVa group,
Compared to the case of adding Va group transition elements, melting and composition control of the molten metal are easier, and therefore the composition uniformity of the molten Al alloy target is excellent, and an Al alloy thin film having a predetermined composition and excellent composition uniformity can be obtained. It is easy to obtain stably.

[0024] Therefore, an Al alloy thin film containing 0.1 to 15 at% Mn has high reflectance, excellent corrosion resistance, low thermal conductivity, and has excellent composition uniformity and excellent productivity. .

Furthermore, when one or more of Hf and Ta (hereinafter referred to as Hf, etc.) is contained in an amount of 0.1 to 10 at %, the film formation rate during sputtering is more significantly improved. This improvement effect is hardly observed when Hf, etc.: less than 0.1 at%, and it is necessary to make Hf, etc.: 0.1 at% or more. However, if Hf etc. exceeds 10 at % and/or the total content of Mn and Hf etc. exceeds 20 at %, the reflectance decreases and reading errors due to precipitates occur. Therefore, it was found that it is necessary to keep Hf etc. at 0.1 to 10 at% and to keep the total amount of Mn, Hf etc. at 20 at% or less.

Therefore, as mentioned above, the Al alloy thin film according to the present invention contains Mn as an alloy component in an amount of 0.1 to 15 at%.
Therefore, based on the above findings,
The Al alloy thin film according to claim 1 has a high reflectance, excellent corrosion resistance, low thermal conductivity, and excellent compositional uniformity, so that it can be produced with excellent productivity.

[0027] Furthermore, it contains Mn in an amount of 0.1 to 15 at%,
Furthermore, it contains 0.1 to 10 at% of Hf, etc., and the total amount of these alloy components is 0.2 to 20 at%. In this way, the film formation rate during sputtering is significantly improved, resulting in even better productivity (Al alloy thin film according to claim 2).

Since the Al alloy thin film according to the present invention has excellent properties as described above, it can be suitably used as a reflective film for optical recording media such as read-only or write-once optical discs, and has high recording sensitivity and A recording medium having both a high C/N ratio can be constructed.

It is preferable that the Al alloy thin film is formed by sputtering because the uniformity of the alloy composition of the film is better (the Al alloy thin film according to claim 4).

On the other hand, the Al alloy sputtering target according to the present invention contains Mn as an alloy component, as described above.
A molten Al alloy sputtering target containing 0.1 to 15 at%, or a sputtering target containing 0.1 to 15 at% Mn and 0.1 to 10 at% Hf, etc.
It is a melted Al alloy target in which the total amount of these alloy components is 0.2 to 20 at% (Claim 5 or Claim 6)
sputtering target).

[0031] Since such a melt-made Al alloy sputtering target is an Al alloy produced through a melt-making process, it is uniform in composition, and therefore the composition does not change over time during use, and the sputtering rate and emission angle are uniform. is uniform, so
The composition of the target and the composition of the obtained alloy film substantially match. Therefore, it becomes possible to reliably and stably obtain an Al alloy thin film (as defined in claims 1 and 2) according to the present invention having the above composition.

Furthermore, since the target material is manufactured through a melting process, the oxygen content can be kept at a low level, and therefore an Al alloy thin film with a high reflectance can be reliably obtained with a low oxygen content.

[0033]

Examples (Example 1) 4 kg of an alloy was induction melted under vacuum and cast in a water-cooled copper mold to obtain a binary Al alloy ingot containing 2 to 15 at% Mn. A sputtering target was taken from the ingot and used to form an Al alloy thin film (reflection film) with a thickness of 500 Å on a transparent polycarbonate resin substrate with a thickness of 1.27 mm by DC magnetron sputtering. A protective film (thickness: 10 μm) made of acrylic resin was applied on the reflective film by spin coating to prepare a sample.

The reflectance of the above sample using a laser beam having a wavelength of 780 nm was measured from the transparent polycarbonate resin substrate side. As a result, as shown in FIG. 1, all the samples showed a high reflectance (initial reflectance) of 60% or more.

Next, the above sample was subjected to PCT (Pressure Cooker Te) as an environmental accelerated test.
temperature: 105° C., pressure: 1.2 atm, humidity: 100% RH) to evaluate the corrosion resistance of the reflective film. Corrosion resistance was evaluated based on the amount of decrease in reflectance caused by laser light at a wavelength of 780 nm. PCT: Figure 2 shows the amount of decrease in reflectance after 30 hours. It can be seen that by adding 0.1 at% or more of Mn, the amount of decrease in reflectance is significantly reduced, resulting in excellent corrosion resistance.

(Example 2) Using the same target as in Example 1 and using the same sputtering method, the thickness:
Al thickness: 10 μm on a 150 μm glass substrate
An alloy thin film was formed. The thermal conductivity of this sample was measured using the optical alternating current method. As shown in FIG. 3, the addition of Mn significantly reduced the thermal conductivity.

When 3 at % of Ta was added, the thermal conductivity further decreased as shown in FIG. In this way, Ta also has the effect of lowering thermal conductivity, and in a ternary Al alloy thin film containing Mn and Ta, the thermal conductivity can be significantly lowered due to the synergistic effect of Mn and Ta.

(Example 3) 4 kg of alloy was induction melted under vacuum and cast in a water-cooled copper mold to obtain a plate-shaped Al alloy ingot containing 2 at% Mn. Also, for comparison, Mo is 2a
A plate-shaped Al alloy ingot containing t% was obtained. Analytical samples were taken from various positions of these ingots and analyzed by ICP method to investigate the alloy composition distribution within the ingots. As a result, the maximum, minimum and average concentrations of Mo were 2.53, 1.82 and 2.0
40at%, maximum, minimum and average concentration of Mn is 2.22
, 2.05 and 2.096 at%, and Mo-containing Al
It was found that the Mn-containing Al alloy has superior compositional uniformity compared to the alloy.

(Example 4) Mn was used as an evaporation source at 2at
5mm x 5m on the melted Al alloy target containing %
Sputtering is performed for a certain period of time using a DC magnetron sputtering method using a composite target with a predetermined amount of Ta chips (purity: 99.9%) or a melted Al alloy target containing 2 at% Mn and a predetermined amount of Ta. Various Al-Mn-Ta alloy thin films were formed on glass substrates.

The composition of the above thin film was analyzed by ICP, and the film formation rate was calculated by measuring the film thickness. Figure 4 shows the relationship between the amount of Ta in the thin film and the film formation rate obtained as a result.
Shown below. Both the composite target and the molten Al alloy target are made by adding Ta to the Al-Mn alloy.
The film formation rate during sputtering increases significantly, and the film formation rate increases as the amount of Ta increases. Also, melting A
In the l alloy target, the effect of Ta addition on the film formation rate is greater than in the composite target. The reason for this is that molten A
The l-alloy target has Ta throughout the target material.
This is because they are uniformly distributed.

Note that the same effect as above can be obtained when Hf is used instead of Ta. Moreover, such effects of Ta and Hf are observed regardless of the magnitude of the Mn concentration.

(Example 5) Al-0.6at%Mn,
Using a melted Al alloy target having a composition of Al-0.6at%Mn-2.0at%Ta, an Al alloy thin film was formed by sputtering in the same manner as in Example 1, and then Example 1 was performed on the thin film. A corrosion resistance test using PCT was conducted in the same manner as above. The relationship between the PCT test time and the amount of decrease in reflectance obtained as a result is shown in FIG. Al-0.6at%
Mn-2.0at%Ta alloy thin film is Al-0.6at
%Mn alloy thin film, and has excellent corrosion resistance, and due to the additivity of the Mn and Ta addition effects, it is found that the corrosion resistance is superior to an alloy thin film to which Mn is added alone. Furthermore, the additivity of the elemental addition effect on improving corrosion resistance is as follows:
This holds true for all alloy compositions and component ranges in the present invention.

[0043]

[Effects of the Invention] The Al alloy thin film according to the present invention has high reflectance, excellent corrosion resistance, low thermal conductivity, and excellent compositional uniformity, resulting in excellent productivity. Therefore, it can be suitably used as a reflective film for optical recording media, has excellent C/N ratio, recording sensitivity, and durability, and is unlikely to cause a decrease in reflectance or pitting corrosion over a long period of time, making it difficult to increase error rate. It becomes possible to stably and economically configure a recording medium.

Furthermore, according to the ingot Al alloy sputtering target for forming an Al alloy thin film according to the present invention, the Al alloy thin film according to the present invention described above can be produced reliably and stably. Furthermore, productivity can be greatly improved, resulting in increased economic efficiency, and an Al alloy thin film with a low oxygen content and high reflectance can be reliably obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the Mn content and reflectance of an Al alloy thin film according to Example 1.

FIG. 2 is a diagram showing the relationship between the amount of Mn in the Al alloy thin film according to Example 1 and the amount of decrease in reflectance in an accelerated environmental test.

FIG. 3 is a diagram showing the relationship between the Mn content and thermal conductivity of the Al alloy thin film according to Example 2.

FIG. 4 T of Al-2at%Mn alloy according to Example 4
FIG. 3 is a diagram showing the relationship between the amount of a and the film formation rate during sputtering.

FIG. 5 is a diagram showing the relationship between the accelerated environmental test time and the amount of decrease in reflectance for the Al alloy thin film according to Example 5.

Claims (6)

[Claims] [Claim 1] Mn is 0.1 to 15 as an alloy component.
An Al alloy thin film characterized by containing at%. [Claim 2] Mn is 0.1 to 15 as an alloy component.
Al containing 0.1 to 10 at% of one or more of Hf and Ta, and the total amount of these alloy components is 0.2 to 20 at%. Alloy thin film. 3. The Al alloy thin film according to claim 1 or 2, which is used as a reflective film of an optical recording medium such as a read-only or write-once optical disc. 4. The Al alloy thin film according to claim 1 or 2, which is formed by sputtering. [Claim 5] Mn is 0.1 to 15 as an alloy component.
A melt-produced Al alloy sputtering target for forming an Al alloy thin film containing at%. [Claim 6] Mn is 0.1 to 15 as an alloy component.
at% and one or more of Hf and Ta at 0.1 to 10 at%, and the total amount of these alloy components is 0.2 to 20 at%. Made of aluminum alloy sputtering target.