JPH025255A - Production of magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic film having the angle of Kerr rotation and perpendicular magnetic anisotropy required as the magneto-optical recording medium even if substrate heating is not executed by producing the magnetic metal oxide film by an ion assist film forming method. CONSTITUTION:The formation of the magnetic metal oxide film on a substrate 2 is executed by an ion beam assisted film forming method, by which the substrate 2 is irradiated with the ions 20 of an oxygen-contg. gas or inert gas at the time of forming the magnetic metal oxide film on the substrate 2. The atom layer to the surface is excited by the kinetic energy possessed by the ions 10 at the time of film formation and the reaction rate constant of the metal atoms and the oxygen atoms or oxygen ions is substantially improved by the reactivity possessed by the ions 10 in this case. The film which has the good magneto-optical characteristics, particularly the large angle of Kerr rotation in spite of a low temp. on the surface of the substrate 2 and the excellent perpendicular magnetic anisotropy is obtd. in this way.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for manufacturing a metal oxide magnetic film mainly used in a recording layer of a magneto-optical recording medium, and in particular, to The present invention relates to a method of forming a film on a low-temperature substrate using an assisted method.

[Prior art and its problems]

Magneto-optical recording media have been actively developed and put into practical use as recording materials with large recording capacities in recent years. The most promising recording materials for magneto-optical disks that are about to be put into practical use are amorphous rare earth transition metals such as TbFeCo and GdCo. This material has an excellent magneto-optic effect and can provide a magneto-optical disk with good sensitivity and C/N. However, amorphous rare earth transition metals are chemically unstable, and magneto-optical disks using this material have problems such as poor weather resistance and high cost. On the other hand, metal oxide magnetic films such as cobalt ferrite are relatively chemically stable and inexpensive, do not have the problems of the amorphous rare earth transition metal materials mentioned above, and have excellent magneto-optical effects. Therefore, research is being conducted as a material for magneto-optical recording media.

The method for producing the metal oxide magnetic film is, for example, a sputtering method using a metal oxide such as cobalt ferrite as a target, as disclosed in JP-A-60-12490, or 1986-
As disclosed in Publication No. 47359, Fe and Co
There is a sputtering method in an oxidizing gas atmosphere using a target mainly composed of an alloy of

In the former method, the crystallinity of the thin film formed on the substrate is low and sufficient magnetic and magneto-optical properties cannot be obtained.
As disclosed in No. 202, it was necessary to heat at a high temperature of 500° C. or higher.

Therefore, heat resistance is required for the substrate, and the selection of the substrate is severely restricted, especially polycarbonate (hereinafter abbreviated as PC),
This has been a major obstacle to the use of resin substrates such as polymethyl methacrylate (hereinafter abbreviated as PMMA). On the other hand, the latter method allows film formation at relatively low temperatures;
Although we were able to obtain a certain degree of magnetic properties, the squareness ratio in the magnetic hysteresis curve was still only about 0.7 at most, and the squareness ratio of the recording layer was too high for practical use as a recording layer of a magneto-optical recording medium. is required to be at least 0.95, so the thin film disclosed in JP-A-63-47359 was not sufficiently practical as a recording layer for a magneto-optical recording medium.

On the other hand, as a film forming method for iron nitride, which is an internally magnetized film, iron atoms are evaporated by an oblique thin deposition method while nitrogen ions are irradiated onto the substrate, and the ions are efficiently reacted on the substrate to form a film. It is known that by using assisted vapor deposition, it is possible to improve the film formation rate and the squareness ratio (SQ, ) of the in-plane M-H characteristics of the film (JP-A-6O-28028).
However, there is no known effect on improving the optical properties of magneto-optical thin films that require perpendicular magnetization properties as the object of the present invention.

[Problems to be Solved by the Invention] As mentioned above, metal oxide magnetic films can also be produced by sputtering metal oxides such as cobalt ferrite as targets, as well as by targeting metals or alloys in an oxidizing gas atmosphere. In the conventional technology, there was no method for imparting magnetic properties and magneto-optical properties without requiring treatment at high temperatures. Therefore,
Although metal oxide magnetic films are considered promising as recording materials for magneto-optical recording media, they have not been fully put into practical use.

The present invention was made in order to solve the problems of the prior art, and it is possible to improve the magneto-optical properties such as the Kerr rotation angle (θK) and the perpendicular magnetic anisotropy without subjecting the substrate to high-temperature heat treatment. This patent is characterized in that it provides a method for forming an excellent metal oxide magnetic film.

[Means for Solving the Problems] An object of the present invention is to provide a method for manufacturing a magneto-optical recording medium in which a metal oxide magnetic film is formed as a recording layer on a substrate, in which an oxygen-containing gas or an inert gas is used. It is clear that the light beam characterized by forming the metal oxide magnetic film on the substrate by vacuum evaporation or sputtering while irradiating the substrate with ions can be achieved by a method for producing a recording medium. It became.

In the present invention, when forming the metal oxide magnetic film on the substrate, a so-called ion beam assisted film formation method is used, in which ions of the oxygen-containing gas or the inert gas are irradiated onto the substrate. The method is characterized in that a metal oxide magnetic film is formed by the following steps.

According to the present invention, when a metal oxide magnetic film is fabricated by optimizing the conditions of the ion beam assisted film formation method, the kinetic energy of the ions excites the atomic layer on the surface during film formation, and the reaction in which the ions exist. By effectively improving the reaction rate constant between metal atoms and oxygen atoms or oxygen ions, the substrate surface exhibits good crystallinity magneto-optical properties even at low temperatures below 150°C, especially when the Kerr rotation angle is large and the perpendicular magnetic anomaly is improved. It was found that it is possible to obtain a film with excellent orientation.

The method of the present invention will be explained based on the evaporation apparatus using the ion beam assist method shown in FIG.

An ion gun and an evaporation source are arranged with shutters 3 and 4 sandwiched between them for controlling an evaporation atom flow 9 and an ion flow 10 toward a substrate 2 fixed on a substrate holder 1 through which cooling water is passed. ing.

After adjusting the inside of the M deposition tank 8 to a degree of vacuum of 10-' Torr or less, for example, oxygen-containing gas is introduced into the ion generation chamber of the ion gun to generate plasma.

Meanwhile, for example, Fe1-x Cox placed in the evaporation source is heated by an electron beam gun. Thereafter, the shutter 4 is opened and ions are irradiated onto the substrate from the ion gun at a certain angle.

Next, the shutter 3 is opened and metal or metal oxide is evaporated onto the substrate from the evaporation source, for example,
A metal oxide magnetic film of cobalt ferrite is formed on the substrate.

In the present invention, in addition to the above-mentioned Fe1-x Cox, materials used for the metal oxide magnetic film as a vapor deposition source in the evaporation method and as a target in the sputtering method include Cox Fe3-, Me, 04 (however, Me is Bt, Sl, Ge+ Mn, Ni+ Tt+ Z
n+AI+ Sn+ Cr, Cu, Mgt Rh,
V, Ga+ In, 5b+ Sc+Y, Ss,
IEu, Tb, Gd, elements of at least syam or higher) R3-JzFe5-yMyO+z (R is rare earth or yttrium, A is Bi+ Sr
, Ca, Ba+ CdlPb, M is AI+ Ga
, Sc+ In+ Cr+ Cu+ Zn+ Mgt
At least one element among NiSi, Ge)
A', Fe3-, Co, Me' w 04 (However, A' is Ba.

At least one element among Sr, pb, and Ca.

Me' is Ga, AI, Inn Sc, Ti
+ Zn, Sn, Cr+ Ta.

(At least one element selected from among Sb, Bi, ν, Y, Sl, and Mn) [Description of constituent elements] The ion gun used in the present invention is preferably a high-efficiency ion gun represented by the Kaufmann type, but this is not necessarily the case. There are several types of plasma ion sources that use gas discharge, such as high frequency discharge type, microwave discharge type, electron impact type, PIG type,
Electron vibration type, electron beam incidence type, duoplasmatron type, sputter type, and laser irradiation type are used as surface effect ion sources that utilize the interaction between the metal surface and atoms, such as surface ionization type, thermionic emission type, and strong electric field application. The electron impact type and the electrostatic field application type can be used as an ion source that utilizes a mass of atoms.

A feature of the present invention is that resins with low heat resistance such as PC and PMMA can be used as the substrate, but of course conventionally used quartz glass, non-alkali glass, oxides such as alumina, aluminum, stainless steel, etc. Heat-resistant substrates such as metals can also be used.

As the gas to be ionized and irradiated onto the substrate, in addition to oxygen, reactive gases, oxidizing gases, and inert gases such as hydrogen, nitrogen oxide (NOx), argon, helium, and neon can be used. It is also possible to use a mixture of two or more types of gas. Further, even when the above-mentioned gas that is not ionized is used simultaneously with the ionized gas, the effects of the present invention can be obtained. The conditions for the ion irradiation are an accelerating voltage of 50 V or more and 1 KV or less (preferably 200 V or less; below the lower limit, the operation of the ion gun is unstable; above the upper limit, film formation will not proceed due to the etching effect of reverse sputtering). Beam current Density is IO
It is desirable that it be A/rrr or less.

The angle of incidence with respect to the substrate is typically 60@ or less.

Furthermore, if necessary, it is also possible to irradiate as a beam of high-energy atoms or molecules whose ions are neutralized using thermal electrons. The amount of gas to be supplied varies depending on the size of the reaction chamber and the pumping speed, but in order to obtain good film quality, the pressure during film formation must be 5 x 10"4 Torr or less. If performed before Wi, the adhesion between the film and the substrate can be improved by cleaning and modifying the substrate surface.

Atoms, which are the raw materials for the oxide magnetic film, are evaporated by electron beam heating or resistance heating, or evaporated by a spackle method using plasma or ion beams, and oxygen (ions, excited molecules, atoms) are evaporated on or near the substrate. , ozone) to form a metal oxide magnetic film.

Although the present invention has been described above in detail mainly using the vapor deposition method, the method of the present invention can also be carried out using the spuck method, and a metal oxide magnetic film with excellent opto-magnetic properties can be obtained.

The spuck method includes high frequency magnetron sputtering method,
Although an ion beam spattering method or the like can be used, the ion beam sputtering method is particularly preferred in the present invention.

The novel features of the present invention will be specifically explained using the following Examples and Comparative Examples.

[Example-1] A cobalt ferrite thin film was produced using a vapor deposition apparatus using the ion assist method shown in FIG.

As the evaporation source, a cobalt ferrite sintered body of Fe@Co0a is used, and the evaporation is performed by electron beam heating. At this time, the evaporation is performed at a 60@ angle with respect to a 1 to 2 inch thick polycarbonate substrate fixed above the evaporation source. 5M1 per minute from the direction of
While irradiating the substrate with an ion beam obtained by ionizing argon gas with a Kauffman type ion gun,
Vapor deposition was performed at a deposition rate of about 10 people per second. The ion acceleration voltage was 50 V, and the current density was varied from 0.1 to 10 A/i. The pressure in the film forming chamber was 1 xto-' Torr. In addition, the substrate holder was water-cooled. The cobalt ferrite thin film produced by this method has the -C formula (
Ff! The composition was expressed as +-xCO,)sOs□. In addition, the Kerr rotation angle and vertical anisotropy (ratio of SQ without and with ion assist) varied as shown in Figures 2 and 3 depending on the current density of the irradiated ions. . The Kerr hysteresis was measured using a semiconductor laser with a wavelength of 830 nm, the maximum applied magnetic field was 16 koe, and the film thickness was 4000-6000. Both Kerr rotation angle and vertical anisotropy are increased by ion irradiation.
The effect of ion irradiation was observed. Further, when the ion current density is 10 people/+Tr or more, the substrate surface temperature increases, making it difficult to form a uniform film on the resin substrate. This indicates that the ion irradiation of the present invention can have the same effect on crystallization of the cobalt ferrite 'fgJ film as substrate heating during film formation or annealing after film formation.

[Comparative Example 1] Using a normal magnetron sputtering device, FezCo
Using an O4 cobalt ferrite sintered body as a target, a cobalt ferrite thin film was sputtered on a glass substrate using argon gas, and then annealed at 550°C in the air for a sufficient time for crystallization. Excellent membrane,
The Kerr rotation angle and vertical anisotropy are shown in FIGS. 2, 3, 5, and 6. Kerr hysteresis was measured under the same conditions as in Example 1.

[Example 2] A cobalt ferrite thin film was produced in the same manner as in Example 1 above, except that the ion acceleration voltage was 50-1100 V and the ion current density was 2 persons/vo. FIG. 4 shows the relationship between the ion acceleration voltage and the film formation rate of the obtained film. As a result, at an accelerating voltage of 1 kV or higher, the etching effect due to ions is large, and the film formation rate drops rapidly. Moreover, the surface of the obtained film is rough, which lowers the reflectance and the perpendicular anisotropy, making it unsatisfactory as a magneto-optical recording medium.

[Example 3] Cobalt was evaporated in the same manner as in Example 1 above, except that an iron-cobalt alloy of Fe and Co was used as the evaporation source, and ionized oxygen gas of sufficient amount for oxidation was used. A ferrite thin film was fabricated.

The Kerr rotation angle and vertical anisotropy changed as shown in FIGS. 5 and 6 depending on the current density of irradiated ions.

The Kerr hysteresis was measured using a semiconductor laser with a wavelength of 8301 m, and the maximum applied m field was 16 koe. Both Kerr rotation angle and SQ increased by ion irradiation, and the effect of ion irradiation was observed. this is,
It has been shown that the ion irradiation of the present invention has the same effect on crystallization of cobalt ferrite thin films as substrate heating during film formation or annealing after film formation.

[Example 4] B
An i-substituted yttrium-iron garnet (BiHYIG) thin film was prepared. A sintered body of BitYFesO4 is used as the evaporation source, and evaporation is performed using an electron beam heating method. At this time, from a direction forming a certain angle with the evaporation source with respect to the PET film substrate fixed above the evaporation source, Vapor deposition was performed at a constant evaporation rate while irradiating the substrate with an ion beam obtained by ionizing a constant flow of argon gas with a Kauffman ion gun. In addition, the Kerr rotation angle and vertical anisotropy change as shown in Figure 7.8 depending on the current density of irradiated ions. The Kerr hysteresis was measured under the same conditions as in Example 1 except that a Cr reflective film was provided. Both the Kerr rotation angle and the vertical anisotropy were increased by ion irradiation, and the effect of ion irradiation was observed. This indicates that the ion irradiation of the present invention has the same effect on crystallization of the garnet thin film as substrate heating during film formation or annealing after film formation.

[Comparative Example 2] B iz
A garnet film with excellent opto-magnetic properties was obtained by sputtering a garnet thin film on a glass substrate using argon gas using a sintered body of YFes O+z as a target, and then annealing it in the air at 600"C for a sufficient time for crystallization. The Kerr rotation angle and vertical anisotropy of the film are shown in Figure 7.8.The Kerr hysteresis was measured under the same conditions as in Example 4.

[Effects of the present invention] As described above, if a metal oxide magnetic film is manufactured by the ion-assisted film formation method of the present invention, it can be used as a magneto-optical recording medium without the need for particular substrate heating due to the lower crystallization temperature. It is possible to obtain a magnetic film having a Kerr rotation angle and perpendicular anisotropy. This also makes it possible to use resin substrates such as PC and PMMA. Also, in terms of manufacturing,
It is possible to reduce material costs and manufacturing process costs.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a vapor deposition apparatus using the ion assist method used in the present invention. FIG. 2 is a diagram showing the relationship between ion current density and Kerr rotation angle in Example-1 and Comparative Example-1. Kerr hysteresis curve FIG. 3 is a diagram showing the relationship between ion current density and perpendicular magnetic anisotropy in Example-1 and Comparative Example-1. FIG. 4 is a diagram showing the relationship between ion current density and film formation rate in Example-2. FIG. 5 is a diagram showing the relationship between ion current density and Kerr rotation angle in Example-3 and Comparative Example-1. FIG. 6 is a diagram showing the relationship between ion current density and perpendicular magnetic anisotropy in Example-3 and Comparative Example-1. FIG. 7 is a diagram showing the relationship between ion current density and Kerr rotation angle in Example-4 and Comparative Example-2. FIG. 8 is a diagram showing the relationship between ion current density and perpendicular magnetic anisotropy in Example-4 and Comparative Example-2. 1 - Substrate holder 2 - Substrate 3 - Shutter 4 - Shutter 5 - Ion gun 6 - Evaporation source 7 - Electron beam gun 8 - Evaporation tank 9 - Evaporation atomic flow 10 - Ion flow Patent applicant Fuji Photo Film Co., Ltd. Figure ion gun 0 Note Voltage/kv Figure Figure Ion Yukishimaru Kotaka/A, Solution 2 Figure 8 Figure Procedure Amendment 1゜2゜3゜

Claims (8)

[Claims] (1) In a method of manufacturing a magneto-optical recording medium in which a metal oxide magnetic film is formed as a recording layer on a substrate, the substrate is irradiated with ions of an oxygen-containing gas or an inert gas while vacuum evaporation or sputtering is used. 1. A method of manufacturing a magneto-optical recording medium, comprising forming the metal oxide magnetic film on the substrate. (2) The metal oxide magnetic film is formed on the substrate by a single or multiple simultaneous evaporation method using a single metal oxide or a composite metal oxide as an evaporation source in an oxidizing gas or inert gas atmosphere. Characteristic claim 1
A method for manufacturing a magneto-optical recording medium as described in . (3) The metal oxide magnetic film is formed on the substrate by using a single metal oxide or a composite metal oxide as a target and performing sputtering in an oxidizing gas or inert gas atmosphere. A method for manufacturing a magneto-optical recording medium according to claim 1. (4) The metal oxide magnetic film is formed on the substrate by a single or multiple simultaneous evaporation method using a single metal or an alloy as the evaporation source in an oxidizing gas atmosphere. A method for manufacturing a magneto-optical recording medium according to item 1. (5) The metal oxide magnetic film is formed on the substrate by using a single metal or an alloy as the target and performing sputtering in an oxidizing gas or inert gas atmosphere. 2. A method for manufacturing a magneto-optical recording medium according to item 1. (6) A patent characterized in that the irradiation of ions of the oxygen-containing gas or the inert gas onto the substrate is performed at an accelerating voltage of 1 KV or less and an ion current density of 10 A/m^2 or less. A method for manufacturing a magneto-optical recording medium according to claims 2 to 5. (7) The method for manufacturing a magneto-optical recording medium according to claim 6, wherein the ions are irradiated onto the substrate after being neutralized. (8) Use a resin such as polycarbonate or polymethyl methacrylate for the substrate, and set the temperature of the substrate to 200°C.
A method for manufacturing a magneto-optical recording medium according to claims 6 and 7, characterized in that: