JPH0572015B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method of manufacturing a magnetic recording medium, and more particularly, to a method of manufacturing a magnetic recording medium having a high coercive force. [Background Art] In recent years, with the development of information processing technology for computers and the like, there has been an increasing demand for high-density recording in magnetic recording media such as magnetic disks used in external storage devices. Currently, Co-based alloy thin films epitaxially formed on Cr underlayer thin films by sputtering or the like are becoming mainstream as magnetic layers of magnetic recording media used in longitudinal recording magnetic disks.
However, regarding this Co-based alloy thin film magnetic layer,
In response to the demand for high-density recording, it is necessary to provide magnetic properties with higher coercive force, and there have been many reports regarding this property. (For example, “New longitudinal
recording media Co _x Ni _y Cr _z from high
rate static magnetron sputter−ing system”
IEEE Trans.Magn.Mag−22, No5, (1986),
334; JP-A-63-79233; JP-A-63-79968
Publication No. ) [Problems to be Solved by the Invention] As previously reported, the coercive force of a Co-based alloy thin film magnetic layer increases with the thickness of the Cr underlayer thin film. However, when a certain upper limit is exceeded, saturation characteristics are exhibited, and it is difficult to increase the coercive force further. For example, in Japanese Patent Application Laid-open No. 63-79968, it is recognized that when the thickness of the Cr underlayer thin film is 1500 Å or more, the coercive force of the magnetic layer tends to saturate and the coercive force of the magnetic layer does not increase any further. It has been shown that there is a problem in practical use. Moreover, this coercive force increases as the thickness of the Co-based alloy thin film is reduced. However, since reducing the film thickness leads to a decrease in the reproduction output value, it is practically difficult to reduce the film thickness to a predetermined thickness or less. Furthermore, although it is possible to improve the coercive force to some extent by selecting sputtering conditions such as the film forming gas pressure and substrate temperature during film formation of the magnetic layer, the improvement effect is small. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and provide a method for manufacturing a magnetic recording medium having an extremely high coercive force. [Means for Solving the Problems] The method for manufacturing a magnetic recording medium of the present invention is a method for manufacturing a magnetic recording medium in which a chromium underlayer thin film and a cobalt-based alloy magnetic thin film are sequentially formed on a substrate by sputtering. After forming a thin film of chromium underlayer with a thickness of 10 to 1200 Å on top, a film containing cobalt (Co) as the main component, chromium (Cr) and tantalum (Ta) is coated with a negative bias voltage applied to the substrate side. It is characterized by forming a magnetic thin film containing a cobalt-based alloy. That is, in view of the above-mentioned conventional situation, the present inventors have
As a result of intensive studies to maintain the coercive force of the magnetic recording medium at a high level even when the thickness of the Cr underlayer is 1200 Å or less, we have developed a method to form a Cr underlayer thin film on the substrate with a thickness of 1200 Å or less. , then
The present inventors have discovered that the coercive force of a magnetic recording medium can be maintained at a high level by sputtering and forming a thin magnetic layer consisting of Co, Cr, and Ta under specific conditions, leading to the completion of the present invention. Hereinafter, the present invention will be explained in detail. The substrate used in the present invention is generally a disc-shaped substrate made of aluminum or an aluminum alloy. Usually, after processing the aluminum substrate to a predetermined thickness, the surface of the aluminum substrate is mirror-finished, and then a first base layer is applied. as hard non-magnetic metals, e.g.
Ni-P alloy is formed by electroless plating or anodic oxidation treatment, and then used as a second base layer.
Sputtered Cr is used. As the substrate 3, without forming the above-mentioned first base layer,
It is also possible to use a material in which Cr is sputtered directly onto a mirror-finished aluminum substrate as an underlayer. In the present invention, the film thickness of the Cr underlayer is 10 to 1200
Å, preferably 50 to 1000 Å, more preferably 100
~400Å range. If the film thickness is less than 10 Å, the coercive force of the magnetic layer will decrease significantly, and if it is thicker than 1200 Å, the coercive force of the magnetic layer will not increase any further.
On the contrary, this is not desirable because it leads to an increase in costs. There are no particular restrictions on the sputtering conditions for forming the Cr underlayer, and the sputtering conditions employed when forming a normal Cr underlayer, the sputtering conditions for forming a magnetic layer thin film, etc., which will be described later, can be adopted. In the present invention, such a predetermined thickness of Cr
After forming the underlayer on the substrate, a Co-based alloy magnetic thin film containing Co as a main component and Cr and Ta is formed by sputtering under specific conditions. The method for forming this magnetic thin film will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram showing an example of a sputtering apparatus suitable for implementing the present invention. In the figure, reference numeral 1 indicates a target, and a substrate holder 2 is provided at a position opposite to the target, and a substrate 3 is mounted on the substrate holder 2. The substrate holder 2 is movable so that the substrates 3 can be continuously deposited. 4 is a sputtering power source connected to the target 1. Reference numeral 5 denotes a bias power supply for applying a negative bias voltage to the substrate holder 2. As these sputtering power source 4 and bias power source 5, DC power sources are preferable, but RF power sources can also be used. As a sputtering device, ordinary DC
A magnetron sputter device or an RF magnetron sputter device is used. As target 1, the main component is Co, and Cr
An alloy consisting of Ta and Ta is used. This Co−Cr
-Ta alloy: Co: 70 to 95 atomic%, Cr:
A composition having a composition of 520 atomic % and Ta: 0.1 to 10 atomic % is preferable. In order to manufacture a magnetic recording medium according to the method of the present invention using the sputtering apparatus shown in FIG. Co−Cr
- Sputtering is performed using Ta alloy target 2 in the presence of a rare gas such as argon.
At this time, a negative bias voltage is applied to the substrate holder 2, that is, the bias power supply 5 applies a voltage of -1000 V or more to the substrate holder 2, preferably -
Perform sputtering while applying a voltage of 50 to -500V, more preferably -100 to -400V,
A magnetic thin film made of Co, Cr and Ta is formed on the substrate 3. In the present invention, as the sputtering conditions, conditions normally employed when forming a magnetic layer of a magnetic recording medium can be employed. For example, the pressure inside the evacuated chamber is 1×10 ^-6
Torr or less, rare gas pressure such as Ar is 0.5×10 ^-3 to 2×
10 ^-2 Torr, preferably 1×10 ^-3 to 5×10 ^-3 Torr
Keep the substrate temperature above 150°C, preferably 200°C.
Sputtering can be carried out under conditions ranging from ~300°C. The thickness of the magnetic thin film layer formed by such sputtering is such that the product (Br・t) of the residual magnetic density (Br) and the film thickness (t) of the magnetic thin film layer is 300 to 300.
It is preferable to set the film thickness to 700G·μm. [Function] Through a Cr underlayer with a thickness of 10 to 1200 Å,
A Co--Cr--Ta based 1 alloy magnetic thin film layer formed by sputtering with a negative bias voltage applied to the substrate side forms a high-performance magnetic layer having a high coercive force. [Examples] The present invention will be described in more detail with reference to Examples and Comparative Examples below, but the present invention is not limited to the following Examples unless it exceeds the gist thereof. Examples 1-4, Reference examples 1-2, Comparative examples 1-
5 Using the apparatus shown in FIG. 1, using the aluminum substrate 3 on which a Cr thin film with the thickness shown in Table 1 was formed by sputtering as an underlayer and the Co-Cr-Ta alloy target 1, a bias power source 4 was connected to the aluminum substrate 3. 1
With the voltage shown in the table applied, the ultimate pressure inside the chamber is 1 x 10 ^-6 Torr or less, and the argon pressure is 2 x
Sputtering was performed under conditions of 10 ^-3 Torr and a substrate temperature of 250°C, and 86 atomic% Co-12 atomic% was deposited on the substrate.
A Cr-2 atomic % Ta magnetic layer (550G·μm) was formed. The coercive force of the obtained magnetic disk was measured using a sample vibrating magnetometer, and the results are shown in Table 1. Comparative Examples 6 to 14 In Example 1, a Co-Ni-Cr alloy target was used instead of the Co-Cr-Ta alloy target,
70 atomic% Co-20 on the substrate at the voltage shown in Table 1.
A magnetic disk was obtained in the same manner except that a magnetic layer of 550 G.mu.m in atomic % Ni-10 atomic % Cr was formed, and the coercive force measurement results are shown in Table 1.

【table】

[Table] [Effects of the Invention] As detailed above, according to the method for manufacturing a magnetic recording medium of the present invention, a high-performance magnetic recording medium having a high coercive force can be easily manufactured, and the magnetic recording medium can be improved. It is possible to achieve even higher density recording.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a sputtering apparatus suitable for implementing the present invention. 1...Target, 2...Substrate holder, 3...
...Substrate, 4...Power supply for sputtering, 5...Bias power supply.

Claims (1)

[Claims] 1. In a method for manufacturing a magnetic recording medium in which a chromium underlayer thin film and a cobalt-based alloy magnetic thin film are sequentially formed on a substrate by sputtering, after forming a chromium underlayer thin film on the substrate with a film thickness of 10 to 1200 Å, A method for manufacturing a magnetic recording medium, comprising forming a cobalt-based alloy magnetic thin film mainly composed of cobalt and containing chromium and tantalum while applying a negative bias voltage to a substrate side.