JPH06111403A - Film forming method for transition metal / noble metal artificial lattice multilayer film recording medium - Google Patents

Abstract

(57) [Summary] [Objective] To establish a method for easily and stably forming a transition metal / noble metal artificial lattice multilayer film for a recording medium having a high coercive force without corrosion resistance and deterioration of the film structure. [Configuration] Transition metal (Co, Fe, Ni, etc.) / Noble metal (Pt, Pd, etc.) artificial lattice multilayer film for magneto-optical or perpendicular magnetic recording medium is formed by sputtering as shown in FIG. In addition, the transition metal / noble metal artificial lattice multilayer film having a high coercive force is formed by increasing the “sputtering gas pressure when depositing the noble metal layer” higher than the “sputtering gas pressure when depositing the transition metal layer”. Preferably, the sputter gas pressure during deposition of the noble metal layer is set to 0.5 to 5.0 Pa, and the sputter gas pressure during deposition of the transition metal layer is set to 0.01 to 1.0 Pa. By setting the ratio of "sputtering gas pressure during deposition of precious metal layer" to "pressure" to 1.2 to 100, the film characteristics and deposition stability of the multilayer film are further improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a transition metal / noble metal artificial lattice multilayer film for a magneto-optical recording medium or a perpendicular magnetic recording medium.

[0002]

2. Description of the Related Art In recent years, as a substitute for read-only optical disc systems such as CDs and laser discs, next-generation optical disc systems having a "rewritable function using laser light" have been developed. Magneto-optical disk system has been developed and has been partially commercialized.

A rare earth / transition metal amorphous alloy film typified by TbFeCo is currently used as a recording medium for a commercially available magneto-optical disk having such a high recording density and a rewritable function. This is because the rare earth / transition metal amorphous alloy film has a) a high rotation angle of 0.3 ° or more with respect to the wavelength of the infrared laser disk light source, b) large perpendicular magnetic anisotropy, c) amorphous This is because it has many advantages such as small surface noise because it is amorphous, d) the coercive force can be adjusted by controlling the composition ratio, and e) high mass productivity because it can be produced by sputtering.

However, in this rare earth / transition metal amorphous alloy film, when the laser disk light source has a shorter wavelength so as to be more advantageous for high density, the car rotation angle becomes gradually smaller, and therefore, the reading characteristic. There was a problem that was worse.

From the above, as a next-generation recording medium, a Co / Pt film or a Co film which exhibits excellent magneto-optical properties even for a laser disk light source in the short wavelength region and has good corrosion resistance.
"Transition metal / noble metal artificial lattice multilayer film" such as / Pd film has come to the fore. That is, this transition metal / noble metal artificial lattice multilayer film, for example, Co / Pt multilayer film, has a ratio of the Co film thickness to the Pt film thickness of the non-magnetic layer: 1/1 to 1/4, Co film thickness: 15Å or less, all layers Number: 10 layers or more is a general structure, but it has excellent corrosion resistance as compared with the rare earth / transition metal amorphous alloy film, which is a currently available magneto-optical recording medium material. Even when a wavelength laser is used, the curve rotation angle (θ _k ) is large and the light reflectance (R) is also high (ie, the magneto-optical performance index (θ _k · √R) is very high). This is because it has become clear that it has desirable characteristics.

On the other hand, however, the above-mentioned transition metal / noble metal artificial lattice multilayer film has a drawback that it has a small coercive force as compared with a rare earth / transition metal amorphous alloy film and it is difficult to draw a clean pit. First of all, overcoming this drawback was an indispensable issue.

However, as a measure for improving the coercive force of the Co / Pt artificial lattice multilayer film, the following proposals have been seen so far. (1) Xe gas is used as a sputtering gas when forming a Co / Pt artificial lattice multilayer film [Appl. Phys. Lett.] 56
(1990), p. 2345], (2) Co / Pt artificial lattice multi-layered film with TbFeCo having a large coercive force exchange coupled with TbFeCo [J. Magn. Soc. Jpn.] 15 (1991) ), P. 49 twist], (3) Increasing the sputtering gas pressure (Ar gas pressure) when forming a Co / Pt artificial lattice multilayer film by sputtering [J. Appl. Phys.] 70 (1991) ), P. 6044).

However, each of the measures has advantages and disadvantages,
The following evaluations were made respectively. (1) Sputtering with Xe gas The coercive force of the obtained multilayer film is high and the characteristics for magneto-optical disks are excellent, but Xe is extremely expensive and is not suitable for mass production. (2) Exchange-coupling with TbFeCo TbFeCo, which is the current recording material, was made to bear the coercive force characteristic, and the Co / Pt artificial lattice multilayer film was made to bear the curve rotation angle characteristic when using a short wavelength laser. The coercive force can also be increased by this, but since TbFeCo, which is easily corroded, is bonded, the high corrosion resistance characteristic of the Co / Pt multilayer film cannot be utilized, and the film structure is Since it becomes complicated, film formation and handling are troublesome. (3) Increasing sputter gas pressure (Ar gas pressure) Although the coercive force can be increased by forming a Co / Pt artificial lattice multilayer film with a relatively high Ar gas pressure during sputtering, the film density is rough. Therefore, the decrease of the curve rotation angle and the reflectance, and consequently the magneto-optical performance index (θ _k · √R)
Cause a drop in. In addition, the film structure also becomes severely uneven, which is not preferable in terms of noise. For example, in FIG.
Is a graph showing the results of investigating the relationship between the coercive force of the Co / Pt multilayer film and the curve rotation angle and the sputtering gas pressure (Ar gas pressure). The coercive force increases as the sputtering gas pressure increases. However, it can be seen that the car rotation angle tends to decrease. Further, FIG. 3 is a graph showing the results of investigating the relationship between the surface roughness of the Co / Pt multilayer film and the sputter gas pressure (Ar gas pressure). When the sputter gas pressure becomes high, a film structure with severe irregularities is formed. I understand.

Therefore, it is an object of the present invention to provide a transition metal / noble metal artificial lattice multilayer film for a recording medium having a high coercive force (Hc) without deterioration of corrosion resistance and film structure. Was to establish a method capable of easily and stably forming a film.

[0010]

The inventors of the present invention have made extensive studies in order to achieve the above object, and as a result, have obtained the following findings.

That is, a transition metal / noble metal artificial lattice multilayer film,
For example, a Co / Pt artificial lattice multilayer film is usually formed using a sputtering target of pure Co and pure Pt, and the gas pressure is
1) Co (or Pt) is sputtered on the substrate in Ar gas of 0.01 to 1.0 Pa (0.08 to 7.52 mTorr), and Co (or Pt)
t) form a thin layer, 2) sputter Pt (or Co),
The process of forming a thin layer of o) is repeated for the number of times of lamination,
The sputtering gas pressure during film formation by this sputtering is
Co / Pt multilayer film that exhibits high coercive force without adversely affecting other properties when adjusted to a relatively low level when forming a Co thin layer and a relatively high level when forming a Pt thin layer Can be obtained easily and stably, and the film formed in this way
It has been clarified that the Co / Pt multilayer film has excellent performance even when used as a perpendicular magnetic recording medium.

The present invention has been completed after further studies based on the above-mentioned findings and the like. "The transition metal / noble metal artificial lattice multilayer film for a magneto-optical or perpendicular magnetic recording medium is formed by sputtering. Therefore, by increasing the "sputtering gas pressure during deposition of the noble metal layer" higher than the "sputtering gas pressure during deposition of the transition metal layer", a transition metal / noble metal artificial lattice multilayer film recording medium with high coercive force can be formed. The feature is that the film can be formed stably and easily. Furthermore, the sputter gas pressure during deposition of the precious metal layer is 0.5 to 5.0 Pa.
In addition, the sputtering gas pressure at the time of forming the transition metal layer is 0.01 to
By setting each to 1.0 Pa or setting the ratio of "sputtering gas pressure during deposition of noble metal layer" to "sputtering gas pressure during deposition of transition metal layer" to 1.2 to 100, film characteristics and deposition stability Is further improved ”.

Here, Co is preferable as a constituent material of the transition metal layer which is a magnetic layer, but Fe, Ni, and
Co-Pt alloy etc. are mentioned. Further, Pt or Pd is preferable as the constituent material of the noble metal layer which is the non-magnetic layer, but good results can be obtained with other platinum group metals and palladium group metals. Therefore, exemplifying the transition metal / noble metal artificial lattice multilayer film to be formed by the method of the present invention, Co / Pt, Fe / Pt, Ni /
Examples include multilayer films of Pt, Co / Pd, Fe / Pd, Ni / Pd, Co-Pt / Pt, and the like.

On the other hand, as the sputtering gas applied in the present invention, Ar which is generally used is preferable.
Any inert gas such as He, Xe, Kr and N can be used.

Incidentally, as the particularly preferable sputtering gas pressure in the present invention, the numerical values of 0.5 to 5.0 Pa for forming the noble metal layer and 0.01 to 1.0 Pa for forming the transition metal layer are given for the following reasons. . First, if a precious metal film is formed under a gas pressure of less than 0.5 Pa, a sufficiently high coercive force cannot be obtained.
On the contrary, when the film is formed under the condition of exceeding, the problem of the decrease in coercive force cannot be ignored. When the transition metal film is formed under a gas pressure of less than 0.01 Pa, the sputtering cannot be continuously continued continuously, and on the contrary, when the film is formed under the condition of more than 1.0 Pa, the reflectance and thus the magneto-optical performance are improved. The problem of index drop cannot be ignored.

Further, as a particularly preferable ratio of the "sputtering gas pressure at the time of film formation of the transition metal layer" to the "sputtering gas pressure at the time of film formation of the transition metal layer", a numerical value of "1.2 to 100" is mentioned. When the film is formed under the condition of less than 1.2, it is almost the same as the film property by the conventional method that does not make a difference in gas pressure, and a high magneto-optical figure of merit cannot be obtained. This is because, if the film is formed under the condition that exceeds the above conditions, the problem that the sputtering cannot be continuously continued continuously and that the reflectance and thus the magneto-optical performance index are lowered cannot be ignored.

By the way, FIG. 1 is a schematic explanatory view of an example of a film forming process of a "transition metal (Co) / noble metal (Pt) artificial lattice multilayer recording medium" according to the present invention. According to the method of the present invention as described above, the coercive force can be improved only by relatively increasing the sputter gas pressure during the formation of the noble metal layer. Film cost is relatively low, b) Film structure is the same as general transition metal / noble metal artificial lattice multilayer film, and corrosion resistance is not sacrificed. C) Sputtering gas pressure when forming transition metal layer By making the value low, it is possible to secure industrially very favorable effects such as improvement in coercive force without sacrificing the car rotation angle and reflectance.

Next, the effects of the present invention will be described more specifically by way of examples.

Example A Co / Pt artificial lattice multilayer film was formed on a substrate by sputtering under the following "common conditions" and the conditions shown in "Table 1".

[Common Sputtering Conditions] Power: 50 W (0.274 W / cm ² ) DC Sputtering, Sputtering gas: Ar, Sputtering gas flow rate: 100 SCCM, Substrate: Corning 7059 glass (0.7 mm thick), Co film thickness: 5Å per layer, Pt film thickness: 10Å per layer, total film thickness: 310Å (41 layers in total starting from Pt and ending at Pt).

[0020]

[Table 1]

Next, the surface of the obtained Co / Pt multilayer film was observed, and "magnetic characteristics", "optical characteristics" and "magneto-optical characteristics" were investigated. In addition, "reflectance", "curve rotation angle"
The "light transmittance" was measured using a light source having a wavelength of 500 nm. These results are also shown in "Table 1".

As is clear from the results shown in "Table 1", the Co / Pt multilayer film obtained according to the method of the present invention has a smooth surface state, and has "magnetic characteristics", "optical characteristics", "magneto-optical characteristics". It can be seen that both the characteristics are excellent, and the characteristics are excellent as a magneto-optical recording medium or a perpendicular magnetic recording medium.

[0023]

As described above, according to the present invention, a magneto-optical recording medium or a perpendicular magnetic recording medium which has a high coercive force and is also excellent in other magnetic characteristics, optical characteristics, magneto-optical characteristics and corrosion resistance. It is possible to easily and stably form a "transition metal / noble metal artificial lattice multi-layer film" for use, which brings extremely useful effects in industry.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of an example of a film forming process of a “transition metal (Co) / noble metal (Pt) artificial lattice multilayer film recording medium” according to the present invention.

FIG. 2 is a graph showing the results of an examination of the relationship between the coercive force and the curl rotation angle of a Co / Pt multilayer film and the sputtering gas pressure (Ar gas pressure).

[Fig. 3] Surface roughness of Co / Pt multilayer film and sputtering gas pressure (Ar
It is a graph which shows the result of having investigated the relationship with (gas pressure).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeo Ohashi Sanban No.3, Kurami, Takaza-gun, Takaza-gun, Kanagawa Nippon Mining Co., Ltd., Kurami Plant

Claims (5)

[Claims] 1. When forming a transition metal / noble metal artificial lattice multilayer film for a magneto-optical or perpendicular magnetic recording medium by sputtering, the "sputtering gas pressure at the time of forming the noble metal layer" is set to "at the time of forming the transition metal layer." The method for forming a transition metal / noble metal artificial lattice multi-layer recording medium having a high coercive force, which is characterized by increasing the sputtering gas pressure. 2. The sputtering gas pressure during film formation of the noble metal layer is 0.5.
To 5.0 Pa, and the sputter gas pressure during the transition metal layer deposition is set to 0.01 to 1.0 Pa, respectively.
A method for forming a transition metal / noble metal artificial lattice multilayer film recording medium having a high coercive force according to claim 1. 3. "Sputtering gas pressure when forming a transition metal layer"
To the ratio of "sputtering gas pressure during deposition of the noble metal layer"
3. The method for forming a transition metal / noble metal artificial lattice multi-layer recording medium having a high coercive force according to claim 1, wherein the film thickness is set to 1.2 to 100. 4. The method for forming a transition metal / noble metal artificial lattice multilayer film recording medium having a high coercive force according to claim 1, wherein the transition metal is Co. 5. The method for forming a transition metal / noble metal artificial lattice multilayer recording medium having a high coercive force according to claim 1, wherein the noble metal is Pt or Pd.