JPH0321971B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a perpendicular magnetic recording medium, and in particular, the invention relates to a method for manufacturing a perpendicular magnetic recording medium, and in particular, a method for manufacturing a perpendicular magnetic recording medium, in which two layers consisting of a soft magnetic layer and a perpendicular magnetic layer are formed on a substrate by a sputtering method. The present invention relates to a method of manufacturing a structured recording medium.

[Prior art]

The perpendicular magnetic recording method is a recording method that has been actively researched and developed in recent years because it is capable of extremely high-density recording.

The recording medium used for this perpendicular magnetic recording has a two-layer structure in which a soft magnetic layer such as a nickel-iron (Ni-Fe) alloy, that is, permalloy, and a perpendicular magnetic layer such as cobalt-chromium (Co-Cr) are formed on a substrate. It has been reported that this recording medium has much better recording sensitivity than those with a single layer structure.

Generally, these recording media are manufactured by the sputtering method, but when forming the soft magnetic layer, it is best to keep the substrate surface at ground potential or in a floating state and perform sputtering. It was always hot.

A two-layer perpendicular magnetic recording medium formed by such a method has a problem in that the recording sensitivity in a high density region is not very good.

[Purpose of the invention]

The present invention was made in view of the above circumstances, and
The purpose of this invention is to improve the recording sensitivity in a high density region in a perpendicular magnetic recording medium having a two-layer structure consisting of a soft magnetic layer and a perpendicular magnetic layer.

[Structure of the Invention] In order to achieve the above object, the present invention makes the surface of the substrate a conductive region and exposes the conductive region to a plasma potential before forming a soft magnetic layer on the substrate by sputtering. This is characterized by maintaining the voltage at a negative potential.

As a result, a soft magnetic layer with low coercive force (low Hc), high magnetic permeability (high μ), and good soft magnetic properties is formed. A perpendicular magnetic recording medium with a layered structure can realize perpendicular magnetic recording with excellent high-density recording reproducibility characteristics without decreasing recording sensitivity even in a high-density region.

This is because by performing sputtering while keeping the substrate surface at a negative potential, the impurities in the film are knocked out by the discharge using sulfur ions (for example, argon ions Ar ^+, etc.), or the stress in the film is moderated. This is thought to be due to the fact that the strain inside is reduced.

Note that when a non-conductive substrate such as Mylar film is used as a substrate, even if the substrate holder is set to have a negative potential with respect to the plasma potential, discharge ions (Ar ⁺ etc.), the potential of the substrate surface exposed to the plasma increases and becomes equal to the plasma potential, making it impossible to obtain the effect of applying a negative bias to the substrate.

However, on a non-conductive substrate,
After forming a metal film with a thickness of approximately 0.05 to 0.1 μm to make the substrate surface conductive, a negative potential is applied using a metal brush, etc. to suppress the rise in potential on the substrate surface. However, by stably applying a negative bias, a soft magnetic layer with excellent soft magnetic properties can be obtained, and the above-mentioned problem can be solved.

〔Example〕

Hereinafter, a method for manufacturing a perpendicular magnetic recording medium according to the present invention will be described based on examples with reference to the drawings.

As shown in FIG. 1, the sputtering device used to carry out this manufacturing method includes a target 2 disposed in a vacuum chamber 1, and a
A substrate holder 4 for holding the substrate 3, a high frequency power source 5 for supplying power to the target 2, and a bias DC current for applying a bias to the substrate via the substrate holder 4. It is configured with a power source 6. As shown in FIG. 2, which is an enlarged view of the main part, the substrate holder has a metal brush 7 that can be attached and detached by operating from outside the vacuum chamber. A negative bias is applied.

First, a first example will be described.

First, the mylar film 3a as the substrate 3 is held on the substrate holder 4 with the metal brush 7 removed.

In this way, after introducing argon gas into the vacuum chamber 1 and setting the pressure inside the vacuum chamber, that is, the introduced argon pressure, to an appropriate value (for example, about 1 mmTorr), the output of the high frequency power source 5, that is, the RF power, is adjusted to an appropriate value. sputtering is performed while rotating the substrate 3 to form a permalloy film 3b with a thickness of 0.05 to 0.1 μm.

After that, as shown in Fig. 2, the metal brush 7 is set so as to be in contact with the permalloy film formed from the outside of the vacuum chamber, and then the bias power is turned on and the high frequency is applied again while applying a negative potential. While the power source 5 is set to the same value as in the previous step and the substrate is rotated, a permalloy thin film 8 of about 0.5 μm is further obtained as a soft magnetic layer. The coercive force of the soft magnetic layer at this time was 1 Oe (hereinafter referred to as Oe).

Furthermore, after changing the target 2 to a cobalt-chromium alloy, the same operation was repeated to make a cobalt-chromium alloy.
When the thickness of the chromium thin film reaches 0.2 to 0.5 .mu.m, sputtering is discontinued to obtain a cobalt-chromium thin film 9 as a perpendicular magnetization layer as shown in FIG. The coercive force of this perpendicular magnetization layer was 350 to 400 Oe.

The input/output characteristic curves of the two-layered recording medium thus formed are shown in solid lines 11, 12,
It is shown by 13. The vertical axis is the reproduction output (relative value), and the horizontal axis is the magnetomotive force (AT). For comparison, the input/output characteristics of a two-layer recording medium in which a soft magnetic layer is formed without applying a negative bias according to the conventional method are shown by dotted lines 14, 15, and 16. Solid lines 11, 12, 13
show the input/output characteristic curves at 2KBPI, 20KBPI, and 50KBPI, respectively, and similarly the dotted lines 14, 15, 1
6 also shows the input/output characteristic curves at 2KBPI, 20KBPI, and 50KBPI, respectively. Incidentally, the coercive force of the soft magnetic layer formed by the conventional method was 15 Oe.
As is clear from the comparison in FIG. 4, the recording sensitivity of the recording medium formed by the method of the embodiment of the present invention is significantly improved compared to the conventional one.
This is especially noticeable in high-density areas.

That is, in the conventional method, the recording sensitivity decreases in the high density region and saturation recording is not possible, but the recording medium formed by the method of the embodiment of the present invention can perform saturation recording even in the high density region. It can be seen that the playback output has also increased.

Incidentally, FIG. 5 shows a relationship curve between the negative bias potential applied during the formation of the soft magnetic layer and the coercive force Hc of the soft magnetic layer. The vertical axis is the coercive force Hc (Oe)
, the horizontal axis is the applied negative bias potential V _b (V)
It caught on. As is clear from this curve, when the negative bias potential is set to around -50V relative to the plasma potential, the soft magnetic properties are significantly improved.

Next, a second embodiment of the present invention will be described. The same sputtering equipment used in the previous example is used. First, as a substrate 3, a film of 500%
Using an aluminum thin film (Al thin film) of about 1000 Å, first, as shown in FIG.
hold it so that it is facing the Here, the substrate holder 4 applies a negative potential to the substrate surface via the metal brush 7.

In this way, while maintaining the substrate surface at a negative potential, argon gas is introduced into the vacuum chamber 1, and the pressure within the vacuum chamber, that is, the introduced argon pressure is set to an appropriate value (for example, about 2 mmTorr).

After that, the output of the high frequency power supply 5, that is, the RF
The power is set to an appropriate value and sputtering is performed while rotating the substrate 3. When the thickness of the permalloy alloy thin film reaches approximately 0.5 μm, sputtering is discontinued to obtain a permalloy alloy thin film as a soft magnetic layer.

Next, after changing the target 2 to a cobalt-chromium alloy, the same operation is repeated, and when the cobalt-chromium thin film has a thickness of 0.2 to 0.5 μm, sputtering is discontinued to obtain a cobalt-chromium thin film as a perpendicular magnetization layer.

Similarly to the recording medium shown in the first embodiment, the double-layered perpendicular magnetic recording medium thus formed also has a significantly improved recording sensitivity in the high-density region, achieving good results. I was able to do that.

In the examples, after forming a conductor layer such as permalloy thin film or aluminum thin film on the surface of the substrate, a negative bias was applied to the surface of the conductor layer. However, if the substrate is conductive, , there is no need to form a conductor layer.

In addition, in the first example, the soft magnetic layer was formed so that the coercive force Hc was about 1 O _e , and it was possible to obtain a practically sufficient recording sensitivity. It goes without saying that recording sensitivity can be further improved by improving .

〔Effect of the invention〕

As explained above, according to the method of the present invention, in manufacturing a perpendicular magnetic recording medium with a two-layer structure consisting of a soft magnetic layer and a perpendicular magnetic layer, in the sputtering step for forming the soft magnetic layer, By making the substrate surface a conductive region and maintaining this conductive region at a negative potential with respect to the plasma potential, a soft magnetic layer with good soft magnetic properties can be obtained, and recording sensitivity is maintained even in high density regions. It is possible to obtain a two-layer perpendicular magnetic recording medium capable of perpendicular magnetic recording with excellent high-density recording and reproducing characteristics without deterioration of performance.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a sputtering apparatus used in the method of the embodiment of the present invention, FIG. 2 is a diagram showing a state in which the metal brush of the substrate holder of the apparatus of FIG. 1 is set on a substrate, and FIG. FIG. 4 shows the input/output characteristics of the magnetic recording medium shown in FIG. 3. 5 are diagrams showing the relationship between negative bias potential and coercive force when a soft magnetic layer is formed by the method of the first embodiment of the present invention. 1... Vacuum chamber, 2... Target, 3... Substrate, 3a... Mylar film, 3b... Permalloy film (conductive film), 4... Substrate holder, 5... High frequency power supply, 6... Direct current for bias Power supply, 7... Metal brush, 8... Permalloy thin film (soft magnetic layer), 9
...Cobalt-chromium thin film, 11, 12, 13...
...Input/output characteristic curves of magnetic recording media formed by the method of the first embodiment of the present invention, 14, 15, 1
6... Input/output characteristic curve of a recording medium formed by a conventional method.

Claims (1)

[Claims] 1 The substrate surface is made into a conductive region, and the conductive region is held at a negative potential with respect to the plasma potential, and a soft magnetic layer and a perpendicular magnetization layer are sequentially formed by a plasma sputtering method. A method for manufacturing a perpendicular magnetic recording medium.