JPH0462814A - Method for producing artificial grid film - Google Patents

Abstract

PURPOSE:To enable an artificial grid film with a sharp interface of a lamination film, a high orientation property of a crystal orientation, and a vertical magnetization by using the ion beam sputter method and specifying acceleration energy of the ion in the artificial grid layer where a specific magnetic metal layer and a non-magnetic layer consisting of a non-magnetic transition metal are alternately laminated. CONSTITUTION:In an artificial grid film where a magnetic metal layer consisting of Co1-xFex (0<x<1) and a non-magnetic metal layer of precious metals Pt, Pd, Ru, Au, and Ag or at least one type of Al and Cu are laminated alternately, the ion beam sputtering is used as a manufacturing method and an acceleration energy of ion is 600 eV or less. Ions which are generated by an ion gun (1) are accelerated and are radiated to a target, sputter atoms constituting the target, and the sputtered atoms are deposited on a substrate(S). The target is rotated alternately to enable a lamination film to be produced. An ion gun (2) is used to emit ions during cleaning or formation of film of the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for producing a superlattice film, particularly a superlattice film having perpendicular magnetic anisotropy.

(Prior art) Generally, a magnetic thin film that has an axis of easy magnetization perpendicular to the film surface and a Curie temperature higher than room temperature records information of several micrometers or less by irradiating it with a light beam such as a laser beam. , and can be used as a high-density magnetic recording medium.

Such recording media include polycrystalline metal thin films such as MnBi, compound single crystal thin films such as Gd1G (gadolinium iron garnet), Tb-Fe, and Gd-Co.

Examples include rare earth-iron group amorphous alloy films such as Tb-Co and Tb-Fe-Co.

Writing is performed on polycrystalline metal thin films such as MnB1 using the Curie temperature (Tc), but since Tc is as high as about 360° C., there is a drawback that writing requires a large amount of energy. In addition, since it is a polyurethane material, it is necessary to create a thin film with a stoichiometric composition, which makes it difficult to manufacture.

Furthermore, since films such as Gd1G are formed on a GGG (gadolinium gallium garnet) single crystal substrate, there are drawbacks such as the fact that the magnetic properties are easily influenced by the condition of this substrate and that it is difficult to obtain a large-area substrate.

On the other hand, rare earth iron group amorphous alloy thin films (RE-TM films) such as GdCo and Tb-Fe have the following advantages: a magnetic thin film of any size can be formed, composition can be easily controlled, and grain boundaries It has advantages such as a good reproduced S/N ratio because of the low temperature, and has been actively researched in recent years. However, this RE-
TM films generally exhibit magneto-optical Faraday effect and Kerr effect (
Kerr effect) was small, the C/N ratio, etc. was insufficient, and the corrosion resistance was poor.

On the other hand, Co/Pt has recently been developed as a new perpendicular magnetization film.
.

Artificial lattice films such as Co/Pd are attracting attention.

These are produced by ordinary sputtering or ultra-high vacuum evaporation, and are coated with co and Pt or Pd to an appropriate film thickness (4 to 1
It is known that the film becomes perpendicularly magnetized when the magnetic field is about 0. Furthermore, this film has a large Kerr effect of 0.3 to 0.4 degrees at short wavelengths of 400 to 500 nm, and is expected to be used as a high-density magneto-optical recording medium compatible with short wavelengths.

Since the cause of perpendicular magnetization in such a superlattice film is surface anisotropy, it is necessary to sharply control the interface in the multilayer film. To achieve this, it is necessary to make the surface of the film as clean as possible and to increase the epitaxial film length. For this purpose, M'BE and ultra-high vacuum evaporation methods are desirable, but these methods have drawbacks such as expensive equipment and excessive time required to operate the equipment.

On the other hand, the sputtering method is simple, but the vacuum level during film formation is not high (0 to 10" Torr), the substrate is exposed to plasma, the temperature of the substrate rises, diffusion at the interface is likely to occur, and sharp There is also a drawback that it is difficult to obtain an excellent epitaxial film with controlled crystal orientation.

(Problems to be Solved by the Invention) An object of the present invention is to provide an artificial lattice film that has a sharp interface between laminated films, has high crystal orientation, and exhibits perpendicular magnetization.

[Composition of the invention (means and operation for solving the problem) The present invention is Co1
-xFe (o≦X≦1) magnetic metal layer (preferably 3 to 15 people) and, for example, Pt, Pd, Ru, Au,
Noble metal of Ag or Aj2. At least one type of Cu□
It is an artificial lattice film in which 4L magnetic metal layers (preferably 6 to 45 layers) are alternately laminated, and the ion beam sputtering method is used to manufacture it, and the acceleration energy of ions is increased to 600%.
This is a method for producing an artificial lattice film, characterized in that it is carried out at eV or less.

In the present invention, Co 1x Fe X (0≦X≦1
) and M are essential elements to obtain perpendicular magnetization,
In addition, a film thickness of 3 to 15 and 6 to 45 is preferable for obtaining perpendicular magnetization. Ion beam sputtering allows film formation in a high vacuum compared to normal sputtering, and since the substrate is not exposed to plasma, it is expected to reduce the temperature rise of the substrate and suppress interfacial reactions in the superlattice film. However, when we actually produced a superlattice film, we found that controlling the accelerating voltage is very important, leading to the present invention.

FIG. 2 is a schematic diagram of the ion beam sputtering (IBS) apparatus of FIG. 1; The ions generated by the ion gun (1) are accelerated and irradiated onto the target, and the atoms constituting the target are thrown off, and the thrown off atoms are deposited on the substrate (S). To produce a laminated film, the targets are rotated alternately.

The ion can (2) is for irradiating ions during substrate cleaning or film formation.

If the acceleration energy of the ions is too large, the energy of the atoms that make up the repelled target will also be large, and as a result, atoms will easily move on the substrate, causing mixing of atoms in the laminated film, resulting in sharp interfaces. This makes it difficult to obtain an artificial lattice film.

As a result of various experiments, it was found that a superlattice film with a sharp interface can be produced when the acceleration energy E is 600 eV or less. Of course, if the acceleration energy is too small, the sputtered atoms will not fly away from the target, so it must not be too small. A preferred range is 50-600eV, more preferably 200-500eV.

The degree of sharpness of the interface can be confirmed by the presence or absence of higher-order peaks in small-angle X-rays, and it can be said that the higher the peaks, the sharper the interface. It can also be seen from the behavior of the magnetization curve. In other words, the narrower the interface, the more perpendicular magnetization is likely to occur.

(Example) Hereinafter, the present invention will be explained in detail using Examples.

Example 1 Using the ion beam sputtering apparatus shown in FIG.
An artificial lattice film made of /Pt was prepared. Co and p
A laminated film was produced by rotating the target using each target consisting of t.

The substrate used was quartz glass.

After evacuation to a vacuum level of 4X10 7 Torr in advance, Ar gas (9999% purity) was introduced into the main gun (ion gun 1) until the partial pressure reached 5X10 4 Torr.
Ar was ionized and the target was irradiated as an ion beam with various acceleration voltages.

The Co and PT targets were alternately rotated at predetermined intervals to produce an artificial lattice film in which the thicknesses of each of the Co and PT films were varied. Hereinafter, the film thickness of CO is t. . .

Let the film thickness of Pt be t, the number of repetitions t of the Co layer and PT layer be n, and this artificial lattice film will be expressed as (tco/1Pt)n.

By changing the acceleration voltage V (too/l, t) - (5/15
) The X-ray pattern at VB of 300 V and 100 OV when the superlattice film of No. 7 was prepared is shown in FIG. 3
At 00V, diffraction lines up to the 3rd order due to the artificial period can be seen, whereas at 1000V, only 2nd order diffraction lines can be seen.

This shows that in the case of VBloooV, there is a mixture of Pt and Co atoms at the interface, and the degree of this is small at 300V. When VB=600V or less, peaks up to third order were observed.

FIG. 3 shows the Kerr hysteresis (measured at a wavelength of 400 nm) of the above films prepared at VB-300 and 100OV. The 300V film is a perfect perpendicular magnetization film, but the 100OV film has a poor squareness ratio and shows that the interface is considerably disordered. 300■ for membranes below 600V
It was similar to the membrane of

As described above, the artificial lattice film produced at an accelerating voltage of 600 V or less had a sharp interface, and an excellent perpendicularly magnetized film was obtained. Further, as a physical property value quantitatively indicating the sharpness of the interface, there is surface anisotropy energy Ks obtained from measurement of magnetic anisotropy.

The larger Ks means that the interface is sharper. Regarding the films produced at 600 V or less, magnetic anisotropy was measured using a torque meter and Ks was determined, and all were in the range of Ks = 0.35 to 0.42 erg/cJ. On the other hand, those made by normal sputtering have 0
It was as small as 2 to 0.25 erg/cJ. This shows that the superlattice film of the present invention has a sharper interface.

Similar results were obtained for superlattice films having other compositions.

[Effects of the Invention] As described above, according to the manufacturing method of the present invention, an artificial lattice film with a sharp interface can be produced, and as a result, an excellent perpendicular magnetization film can be provided, which can be used for new recording media such as magneto-optical devices. This makes a great contribution to industry, such as being able to provide the following.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of an apparatus for producing the artificial lattice film of the present invention. FIGS. 2 and 3 are diagrams showing the X-ray pattern and magnetization curve of the artificial lattice film, respectively.

Claims (1)

[Claims] Co_1_-_x. ．． Fe_x. ．． An artificial lattice film in which magnetic metal layers made of (0≦x≦1) and nonmagnetic layers made of nonmagnetic transition metals are alternately laminated is created using the ion beam sputtering method, and the acceleration energy of the ions is reduced to 600%.
A method for producing an artificial lattice film, characterized in that the voltage is below eV.