JPH07111791B2 - Method for manufacturing magneto-optical recording medium - Google Patents

Description

The present invention relates to a method for manufacturing a magneto-optical recording medium.

(Prior Art) In recent years, as a high-density and large-capacity recording method, a magneto-optical recording method that performs thermomagnetic recording by laser light is drawing attention.
As a recording medium used in this recording method, an amorphous magnetic thin film made of a rare earth-transition metal is considered promising. This is because it is easy to manufacture a large area and read noise is small. An alloy thin film of TbFe, GdCo or the like is given as a typical material of this type.

By the way, one method for producing this kind of magnetic thin film,
There is a high frequency sputtering method. This is 10 ^-3 to 10 ^-1 Torr
In this method, a negative high-frequency voltage is applied to a metal target as a material in an argon gas atmosphere to produce a film.

However, according to this method, since the operating gas pressure during sputtering is high, a large amount of argon gas and residual impurity gas (nitrogen, oxygen, etc.) may be mixed in the magnetic film. Further, due to the nonuniformity of the electric field in the vicinity of the substrate, a difference occurs in the composition along the radial direction of the substrate, and the uniformity of magnetic characteristics is regarded as a problem.

Another method for producing the thin film is a bias sputtering method. In this method, high frequency sputtering is performed while applying a bias of negative (or positive in some cases) DC voltage or high frequency voltage to the substrate.

In this method, the magnetic film on the substrate is sputter-cleaned during film formation, whereby uniformity of film composition and reduction of residual impurity gas are achieved. However, this method does not improve the amount of argon gas mixed in at all, and requires a pretreatment for imparting conductivity to the substrate (usually a transparent material such as glass or plastic).

(Problems to be Solved by the Invention) The present invention has excellent characteristics of a magnetic thin film, and film uniformity,
It is an object to obtain a magneto-optical recording medium having good reproducibility.

(Means for Solving Problems) The present invention targets a metal of a TbFeCo alloy, and ion-beam sputters this in an atmosphere having an argon gas pressure of 10 ⁻⁵ to 10 ⁻⁴ Torr to form a film surface on a substrate. It is characterized by forming a TbFeCo ternary amorphous alloy thin film having an easy axis of magnetization in the perpendicular direction.

The ion beam sputtering method usually uses Ar
⁺ Ions were irradiated on the target surface, the sputtered particles in a manner that a thin film is deposited on the substrate, ^10-5
-4 Torr Argon atmosphere. By using this method, the film is formed under a gas pressure of one digit or more lower than in the case of the sputtering method as described above, so that the amount of argon gas, impurity gas, etc. mixed into the film is significantly reduced. Like

Furthermore, since Ar ⁺ ions are generated by the ion source, there is no plasma or potential difference between the target and substrate, and the target surface is sputtered almost uniformly, so the film composition is uniform. Will be good. Therefore, the substrate bias is unnecessary, and the pretreatment for imparting conductivity to the substrate can be omitted.

The metal used here is Co, which is slightly added instead of Fe in order to improve the Kerr rotation angle of the thin film, raise the Curie point, and improve the corrosion resistance.

(Embodiment) An embodiment method of the present invention will be described with reference to the drawings. In the apparatus shown in FIG. 1, 1 is a vacuum chamber, 2 is an ion source for generating Ar ⁺ ions, 3 is a target, 4 is a substrate holder, and 5 is a substrate made of glass or the like supported by the substrate holder 4. . The surface of the target 3 is arranged at an angle of 45 ° with respect to the beam from the ion source 2, and the fine particles of the target sputtered by the ions are deposited on the substrate 5 to form a thin film. is there.

An example of the structure of the target 3 is shown in FIG. 2 and FIG. 3, in which a target surface 6 made of a composition of Fe: Co = 95: 5 (atom%) has a concave portion 7 having a side of 8 mm. Provide a plurality of (25 in the example in the figure), and set Tb small pieces 8 on each side of 7 mm, 5 mm, and 3 mm with an appropriate number of Fe, Fe,
Co and Tb were constructed as the desired area ratio.

Using the above apparatus and the target 3, the pressure of Ar gas in the vacuum chamber 1 is 6.0 × 10 ⁻⁵ Torr, the amount of Ar ⁺ ion beam (on the target surface) is 50 to 70 mA, the beam energy is 200 to 1000 eV. A thin film was formed under the conditions that the pre-sputtering time was 2 hours and the main sputtering time was 20 to 60 minutes. The following table shows the characteristics of the 17 samples prepared. Further, FIG. 4 is a graph showing the holding power with respect to the Tb area ratio (%).

In each of the above samples, the magnetic properties in the perpendicular direction of the film were investigated by the polar Kerr effect measuring device, and it was found that
It was confirmed that the perpendicular magnetization film was formed reliably for 15 types of samples except for, if the area ratio of Tb is 31% or more and 40% or less and the beam energy is 400 eV or more. did it.

Among the magnetic films exhibiting perpendicular magnetic anisotropy, the coercive force is preferably 1 KOe or more in order to make a practical magneto-optical recording medium. In such a case, the area ratio of the Tb pieces needs to be 34% or more of the target surface when the beam energy is 400 eV or more, based on the above-mentioned experimental results.

In the experiment described above, the composite target was used, but since it can be considered similarly in the case of an alloy target, when the amorphous magnetic thin film using Tb as a rare earth is formed by the ion beam sputtering method, the beam energy is Is 400 eV and the target surface Tb occupying area or composition ratio is 34% or more.

If the beam energy is lower than 400 eV, the film formation rate will be slow and the production efficiency will be reduced. The beam current should be increased to increase the deposition rate, but the beam energy should be 40%.
Below 0 eV, it becomes difficult to increase the beam current.

(Effects of the Invention) As described in detail above, according to the present invention, the amount of argon gas and other impurity gases mixed in the thin film is significantly reduced, plasma is generated between the target and the substrate, and a potential difference is generated. Since the target surface is almost uniformly sputtered, the uniformity of the film composition becomes good,
Therefore, the bias sputtering of the substrate is unnecessary, and the pretreatment for imparting conductivity to the substrate can be omitted.

[Brief description of drawings]

FIG. 1 is a sectional view of an apparatus used to carry out a method of an embodiment of the present invention, FIG. 2 is a front view of a target, FIG. 3 is an enlarged perspective view of the same portion, and FIG. 4 shows holding force. It is a characteristic diagram. 1 ... Vacuum chamber, 2 ... Ion source, 3 ... Target, 5 ... Substrate,

Claims (1)

[Claims] 1. TbFe with an area ratio of Tb of 34% or more and 40% or less
Target the Co alloy metal and set the argon gas pressure to this.
Beam energy of 40 in an atmosphere of 10 ^-5 to 10 ^-4 Torr
A method of manufacturing a magneto-optical recording medium, which comprises ion-beam sputtering at 0 eV or more to form a TbFeCo ternary amorphous alloy thin film having an easy axis of magnetization in a direction perpendicular to a film surface.