JPH0430171B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a sputter target used for forming an oxide magnetic thin film used as a magnetic recording medium in a magnetic disk device or the like. Improving the recording density in magnetic recording devices is a constant trend in this industry, and in order to achieve this, it is essential to make the magnetic recording medium thinner and thinner. Therefore, continuous thin film media, especially oxide magnetic thin films, which can be easily thinned, are attracting attention as high-performance magnetic recording media. The reasons for this are: (1) the residual magnetic flux density is low, (2) it has high mechanical strength and chemical stability, and does not require the protective film required for thin metal films; The advantage is that the space between the media can be made smaller, making it suitable for high density and low cost. Iron oxide thin films are mainly used as oxide magnetic thin films because they are easy to form, and there are various methods for manufacturing them, but by sputtering using magnetite (Fe ₃ O ₄ ) as a target, magnetite can be used as the main component. A simple and highly reproducible method for forming a ferromagnetic iron oxide thin film directly on a substrate has been proposed (see Japanese Patent Application Laid-Open No. 8200/1983). In this method, if cobalt is used as an additive to control the magnetic properties, the coercive force of the sputtered magnetite film can be controlled arbitrarily.
The formed film is then subjected to gamma treatment (processing to convert Fe ₃ O ₄ to γ-Fe ₂ O ₃ ) at a relatively high temperature in order to improve magnetic properties and stabilize the film. Usually, an aluminum alloy substrate coated with alumite is used as a substrate, but when this type of substrate is exposed to high temperatures, the flatness of the surface may be lost or the coated alumite layer may become stained with the base aluminum alloy. Since problems such as cracks occur due to differences in thermal expansion coefficients, it is preferable that the gamma treatment temperature be as low as possible. However, it is difficult to lower the gamma treatment temperature of the magnetite film formed by the above method to a temperature that does not impose a burden on the substrate, and in particular, the gamma treatment temperature of a magnetite film doped with cobalt tends to be even higher. As a method to solve this problem, the present inventors first used magnetite as a main component, which is formed directly on a substrate by sputtering in a neutral gas or a mixed atmosphere of a neutral gas and an oxidizing gas, using magnetite as a target. We propose the use of an oxide magnetic thin film that is characterized by containing copper as an additive, and that may also contain cobalt as an additive in order to control magnetic properties. did. The present invention provides a sputter target for forming an oxide magnetic thin film suitable for use in the above invention. The sputter target for forming a magnetic oxide thin film according to the present invention can be manufactured, for example, by the following method. Fe ₃ O ₄ at a given weight ratio,
After thoroughly mixing and pulverizing the CO ₂ O ₃ and CuO powders to obtain a uniform particle size, a binder is mixed and press-molded into a predetermined shape. By subjecting this molded body to a controlled heating and cooling process in an inert gas atmosphere and heat treatment at a maximum temperature of 1,250 to 1,300°C for several hours, a robust Co and Cu-added Fe ₃ O ₄ sintered body with no cracks is created. is obtained. The significance of the present invention will be explained in detail with reference to Examples below. Example 1 The metal iron ratio was 1.0 by the manufacturing method exemplified above.
Fe ₃ O ₄ sintered bodies containing 4.0% and 6.0% by weight of Cu as oxide were prepared, and these were used as targets at an argon pressure (P _Ar ) of 8×10 ^-2 Torr, a distance between the target and the substrate D = 30 mm, and a deposition rate. (SR) RF sputtering was performed at 250 Å/min to form Fe ₃ O ₄ films containing 1.5, 4.0, and 6.0 wt% Cu on an alumite-coated Al alloy substrate. These films are exposed to the atmosphere.
After performing the oxidation treatment for 1 hour, it was confirmed that all the films were converted into γ-Fe ₂ O ₃ films by the oxidation treatment at 250 to 275°C. On the other hand, as a comparative example, an Fe ₃ O ₄ film was formed under the same conditions using a pure Fe ₃ O ₄ sintered body to which no Cu was added, and a target containing 12% by weight of Cu as an oxide relative to metallic iron. Of these, in order to convert the pure Fe ₃ O ₄ film without adding Cu into a γ-Fe ₂ O ₃ film, oxidation treatment at 320°C or higher is required, which causes cracks in the substrate and reduces the fabrication margin by at least 0.5%. Cu addition by weight is preferred. Furthermore, Cu
In the doped γ-Fe ₂ O ₃ film, Hc is higher than in the pure γ-Fe ₂ O ₃ film.
Although there was a decrease, this was more noticeable as the amount of Cu added was larger, and as a comparative example, a γ-Fe ₂ O ₃ film containing 12 wt% Cu was less than 50 Oe, and the saturation magnetization (Ms) and squareness ratio (S , S ^* ) also decreases, and the amount of Cu added is preferably up to about 10% by weight. Example 2 Metallic iron ratio 2.0 to 3.0% by weight by the same manufacturing method
of Co, containing 2.2-4.4 wt% Cu as oxide
A Fe ₃ O ₄ sintered body was prepared and used as a target in an argon atmosphere at P _Ar =2×10 ^-3 to 5×10 ^-2 Torr,
Co and Cu-containing Fe ₃ O ₄ films of various compositions were deposited to a thickness of 1500 to 1700 Å on an alumite-coated aluminum alloy substrate as in Example 1 using the magnetron sputtering method under the conditions of D = 30 mm and SR = 1200 Å/min. Formed.
These films could be easily converted into Co and Cu-containing γFe ₂ O ₃ films by oxidation treatment in air at 250° to 300°C. Furthermore, their magnetic properties are Bs3000G, S0.7, S
(Coercive rectangularity) 0.8, Hc 500-800 Oe, suitable for density recording media (see table). Adding Co and Cu simultaneously in this way had the advantage of increasing Hc and promoting γFe ₂ O ₃ formation. Example 3 4.0-5.0% by weight of Co by the same manufacturing method as above,
Fe ₃ O ₄ sintered bodies containing 5 to 7.5% by weight of Cu as oxide were prepared, and P _Ar =
6×10 ^-4 ~8×10 ^-3 Torr, D=130mm, SR=100
Co was deposited on the same substrate under ~1000Å/min
A Cu alloy Fe ₃ O ₄ film was formed. These membranes are 275−
By oxidizing in air at 300℃
A high coercive force medium of Hc900−1300Oe was obtained (see table). As a comparative example, the coercive force of a γ-Fe ₂ O ₃ film containing 6 wt% Co and 7.5 wt% Cu was 1300 to 1500 Oe, which exceeded the limit of sufficient recording with a normal ferrite magnetic head. .

[Table] Targets shown in Example 2. A Co and Cu-containing Fe ₃ O ₄ film was formed on an alumite-coated aluminum alloy disk substrate with an outer diameter of 210 mm using sputtering conditions.
By oxidizing this, a Co and Cu-containing γ-Fe ₂ O ₃ film magnetic disk was fabricated. This disk is disk R/
Installed on W test machine, track width 20μm, recording density
When I observed the playback output on 24000FRP1,
It was confirmed that uniform reproduction output could be obtained in the circumferential direction over the entire surface of the disk. As described above, if the sputtering target for forming a magnetic oxide thin film according to the present invention is used, the oxide magnetic thin film used for magnetic disk media etc. can be formed at a lower γ-Fe ₂ O ₃ processing temperature than conventional ones. It becomes possible to uniformly, stably, and efficiently form an oxide magnetic thin film having a wide range of magnetic properties over the entire surface of the substrate while reducing the burden on the substrate.

Claims (1)

[Claims] 1. 1.0 to 7.5 weight percent of Cu based on metal iron
A sputter target for forming a magnetic oxide thin film made of a Fe 3 O ₄ sintered body containing Fe ₃ O 4 as an oxide. 2 1.0 to 7.5 weight percent Cu relative to metallic iron
A sputter target for forming a magnetic oxide thin film consisting of a Fe ₃ O ₄ sintered body containing 2.0 to 5.0 weight percent of Co as oxides.