JPS6353721A - Preparation of thin oxide film - Google Patents

Abstract

PURPOSE:To enable high-density magnetic recording by subjecting a main target to oxidation reaction sputtering under the flow of an oxidizing gas thereto, subjecting an auxiliary target to sputtering under the flow of an inert gas thereto, regulating electric power to be thrown and adding a metallic element into a thin oxide film. CONSTITUTION:The main target 4 and the auxiliary target 5 are disposed to the lower side of a bell-jar 1 and an alumite coated aluminum alloy disk as a substrate 2 is held by a holder 3 installed in parallel with the target surface in the upper part of the bell-jar. An introducing pipe 6 for a gaseous mixture composed of argon and oxygen is installed near the main target and an introducing pipe 7 for gaseous Ar near the auxiliary target, respectively in the positions upper than the top ends of the targets 4, 5. The gaseous pressure in the bell-jar is maintained constant and the electric power is varied and thrown to the main target 4 and the auxiliary target 5, respectively by a high-frequency bipolar sputtering system to execute sputtering and to form hematite. Coercive force is thereby decreased in the bottom of the medium and an overlap writing characteristic is improved.

Description

Detailed Description of the Invention <Field of Industrial Application> The present invention relates to a method for producing an oxide thin film used as a magnetic recording thin film medium of a high recording density magnetic recording device. The present invention relates to a method for producing a thin film of maghemite (i.e., γ-FO203) containing

<Prior art> Maghemite film (γ-Fe203) is a magnetic disk,
It is used as a recording layer of magnetic recording media such as magnetic tape. In particular, patent application No. 59-54205, patent application No. 59-1
γ-F containing O8 proposed in 55140
e 203rA is the coercive force Hc and the square shape (residual magnetization M, , /
This is an iron oxide magnetic film with excellent saturation magnetization M,). Further O
The s-containing γ-Fe203 film is disclosed in Japanese Patent Application No. 59-27358. As shown in Japanese Patent Application No. 59-155140, its use as a perpendicular magnetic recording medium capable of high-density recording has also been proposed.

In order to produce the above Os-containing γ-Fe203 thin film, a conventional manufacturing method has been used.

i.e. (1) First, an alloy target of Fe and Os is placed on the substrate.

A thin film mainly composed of bematite (α-Fe2D3) containing O3 is formed by reactive sputtering using a sintered target of Fe and O8, a Fe target with an Os pellet, etc., and the resulting thin film is treated with a reducing agent such as H2. A method of producing a γ-Fe20 film containing Os by heating the Fc304 film in the atmosphere and reducing it to a thin film containing magnetite (Fc304 film rack). -164134, 59-542
(Related to 05), (2) Substrate - First, an alloy target of Fe and Os.

Reactive sputtering such as sintered Fe and Os targets, Fe targets with Os pellets, or Os
Fe3O4 target containing O
γ-F containing O8 is formed by forming a magnetite thin film containing O8 and heating the obtained thin film in the atmosphere.
There are two methods for producing an e2O3 film (related to Japanese Patent Application No. 155140/1983).

In both of these conventional manufacturing methods, the composition of Os element in the target is controlled before film formation by sputtering, and Fe and O8 or Fe, 04 and O8 are placed in the same sputtering atmosphere, sputtering is performed, and oxidation is performed. It involved adding O8 to iron.

<Problems to be Solved by the Invention> However, the additive element Os has (1) a high melting point and a high price per mass (1 g to 6,000 yen).

(2) It has a large atomic weight, (3) It is easily oxidized in an oxidizing atmosphere, and the boiling point of its oxide 0804 is extremely low, so conventional production methods have had the following problems. .

(b) Fe with Os pellet placed as a target
(Fe30.) or a sintered body of Fe and O8, the composition tends to change over time and cracks tend to occur.

To prevent this, there is a method of using an alloy target, but in order to produce an alloy target of Fe and Os having a high melting point, it is necessary to sinter the powder and perform electron beam or arc melting. For this reason, the yield is poor, the processing cost is high, and the actual manufacturing cost is increased.

(b) Since the Os element is easily oxidized during reactive sputtering, the Os element becomes an oxide as an inclusion in iron oxide, or is easily lost by evaporation during sputtering, resulting in poor reproducibility of magnetic properties. ) Since the O8 element has a large atomic weight, the energy of the sputtered particles is high, and the crystallinity of the iron oxide film, which is the main component, is deteriorated at the stage when the iron oxide film is formed on the substrate. In particular, the crystallinity in the thin film region is poor, causing saturation magnetization and a decrease in squareness.

The purpose of the present invention is to solve the above-mentioned drawbacks, and to produce a magnetic recording medium in which Us can be added to an iron oxide thin film at low cost without damaging the crystallinity of the iron oxide thin film, and which is capable of high-density magnetic recording. It is about providing law.

Furthermore, another object of the present invention is to oxidize the elements of one target while causing the elements of the other target to undergo an oxidation reaction when sputtering a plurality of targets having different components in the same sputtering apparatus. It is an object of the present invention to provide a method for forming a film without any involvement.

<Means for Solving the Problems> The configuration of the present invention to achieve the above object is to arrange a main target and a sub target having different components in a sputtering apparatus, and to cause an oxidation reaction by flowing an oxidizing gas to the main target. Sputtering is performed to form an oxide thin film on the substrate, while sputtering is performed by flowing an inert gas to the sub-target, and a metal element is added into the oxide thin film by independently adjusting the input power. It is characterized by

Effect> When sputtering is performed by flowing an oxidizing gas to the main target in a sputtering device, the elements of the main target form an oxide/thin film on the substrate. This is oxidation reaction sputtering. Furthermore, if sputtering is performed while flowing an inert gas to the sub-target, the elements of the sub-target will be added to the oxide thin film without participating in the oxidation reaction. Here, the oxide film may be formed by known reactive sputtering, the surface state of the sub-target is in a metallic state, and the amount added is controlled by the input power. Therefore, when using the Os element as the metal element of the sub-target and forming an iron oxide thin film as an oxide thin film on the substrate, it is possible to impart a concentration gradient of the Os element by controlling the predetermined input power. At the initial stage of deposition of iron oxide thin films, O8 is not added to prevent deterioration of crystallinity, but as the film thickness increases, the power input to the Os target is increased to increase the amount of addition, resulting in good crystallinity. Becomes iron oxide. A further advantage is that the iron oxide film thus obtained has a magnetic property gradient in the depth direction of the thin film. In other words, Hc is low at the bottom of the membrane, and Hc is low at the top,
allows for large composition media. The magnetic field of the head during recording is weaker at the bottom of the film, so if IIC is small at the bottom of the medium, it becomes possible to record on the entire medium, which has the effect of improving overwriting characteristics.

<Embodiment 1> FIGS. 1 and 2 are diagrams explaining the first embodiment of the present invention, in which 1 is a bell jar, 2 is a substrate, 3 is a substrate holder, 4 is a main target, and 5 is a sub-target. 6 is a gas introduction tube to the main target, 7 is a gas introduction tube to the sub target, 8 is a vacuum exhaust system, and 9.10 is a high frequency power source.

The main target (Fe, diameter 12cm) is placed under the belljar 1.
) 4 and an auxiliary target (O8, diameter 5cn+) 5 were arranged, and as the substrate 2, an 8-inch alumite-coated aluminum alloy disk was held by a holder 3 installed above the bell jar parallel to the target surface. A mixed gas introduction pipe 6 containing argon (Ar) and oxygen (0□) with 1=1 is installed near the main target, and an Ar gas introduction pipe 7 is installed near the secondary target.
Each was placed 1 cm above the upper end of target 4.5. Ar-02 mixed gas is 10cc/min, A
The r gas was set at 2 cc/min, and the gas pressure inside the bell jar was set at 2 cc/min.
While maintaining the X 10' Torr, the main target 4 was immersed with a power of 1.5 kll and the sub target 5 was immersed with a power of 1.5 kll and 0 to too, respectively, using the high frequency bipolar sputtering method.
α-Fe2 with a film thickness of 0.12 μm by sputtering
0. was formed.

In X-ray diffraction, no foreign phase was observed in the α-Fe203 structure, and when the amount of Os added was investigated by XFA, as shown in Figure 3, the content of O8 element (ratio of only metal elements) was It changed from 0 to 2.2at96 in proportion to. These thin films were heated to 310°C for 3 hours in a humidified hydrogen stream to obtain a magnetite (Fe304) film.
Furthermore, γ-F was oxidized by heating at 300°C for 3 hours in the air.
e20. It was made into a film. +1c at this time is shown in FIG. Hc increases almost proportionally with the immersion power of the sub-target, and the effect of Os addition becomes clear. In sputtering using this method, no blackening due to oxidation or the like was observed on the surface condition of the sub-target 5, and the reproducibility of the magnetic properties hardly changed even after sputtering for about 100 hours. In addition, while performing reactive sputtering of the main target 4, Os could be added by sputtering the sub target 5 with the same effect as in the conventional method, and moreover, the amount of Os added could be controlled by the input power.

Example 2> Next, the main target 4 was
sputtering was carried out in the same manner for 120 minutes, and the power was not turned on at the start of sputtering of the main target 4 for the sputtering of the sub-target 5 (the power was gradually increased at IW/min during the second 120 minutes, and α-F with varying O8 addition amount
An e203 thin film was produced. Composition analysis of this thin film by XFA revealed that the thin film as a whole contained approximately 0.83 at.
However, depth distribution measurements using ESCA show that a thin film is formed in which the amount of Os added increases from the substrate side to the surface side. For comparison, an α-Fe203 film containing 0.85 at % Os and with O3 uniformly distributed in the film thickness direction was fabricated using a conventional method. At this time, the sputtering conditions for the main target 4 are the same, and the O
The amount added was controlled by controlling the amount of S pellet. Both thin films were heat treated in the same manner as in Example 1, using a Mn-Zn ferrite head with gap length ('2g) = 0.27 μm, core width = 50 μm, number of coil turns = 20, and a circumferential speed of 20 m/s. (Flying height 0.2μm) When examining the overwriting characteristics, (2f=1000bpm,
O/W = If'/2f) 07W according to the conventional method is -20
At dB, a thin film with a concentration gradient of Os is -3
It was found that 1 dB and 1 ldB were also good. In this way, when controlling the O8 content in the iron oxide thin film by the Os composition of the target as in the past, the O8 content in the iron oxide thin film is
It has been impossible to adjust the depth distribution of s content, but it can be easily changed in the fabrication method of the present invention, and the overwriting characteristics are improved.

Embodiment Example 3 As shown in FIGS. 5 to 7, the main target 4, the sub target 5. Then, a magnetic Vill capable of applying a magnetic field in the circumferential direction of the substrate 2 during sputtering is placed in the bell jar, and a mixed gas of argon and oxygen at a ratio of 85:15 is introduced to increase the gas pressure to 3.5X 1O- The following two types of iron oxide thin films with a thickness of 0.1 μm were formed while maintaining the temperature at 2 Torr.

(1) Sputtering power for main target 4 is 3 kW.

Fe50.
Fe3O4 film was produced under the same sputtering conditions as Tll, using the magnetic pole 11 in bell jar 1, and applying a magnetic field of about 2 kOe in the disk circumferential direction during film deposition.These Fe3O4 films are about 1.2 at. ! It contained Osi of 1. These films were oxidized in the air at 320°C for 3 hours to form γ-Fe2O3, and their magnetic properties were evaluated using the conventional manufacturing method (using a Fe-1,2at!kos alloy target, gas pressure of 4 x 1O-2Torr, sputtering power 2.
Fe50. obtained at 8kW. Table 1 shows a comparison of the magnetic properties of a 1,2 atlOs-containing film obtained by oxidizing the film in the atmosphere.

Margin Table 1 below *However, in the case of thin film (2), as is clear from the value table when measured in the circumferential direction of the disk, in the production method of the present invention, coercive force,
The squareness ratio and saturation magnetization values are increased compared to the conventional method.

Furthermore, in the γ-Fe2O3 film formed while applying a magnetic field in the circumferential direction of the disk, the squareness ratio and coercive force in the circumferential direction change.

Furthermore, if the direction of application of this magnetic field is perpendicular to the film surface, it is also possible to form a perpendicular magnetic anisotropic film.

In this way, in forming an iron oxide thin film containing O3, the Os composition is not controlled by the target, but the iron oxide forming reaction is caused in the main target 4, and the sub target 5 is used.

By adding 0s to iron oxide in a metal state, it is possible to add O8 without damaging the crystallinity of the iron oxide thin film, and it is also possible to form a gradient in the amount of Os added in the film thickness direction, improving overwriting characteristics. There are advantages such as:

<Effects of the Invention> As described above in detail based on Examples, the present invention, when forming an oxide thin film by sputtering, oxidizes the main target element while subjecting the sub-target element to an oxidation reaction. It is possible to form a film without any involvement, and furthermore, it is possible to create a gradient in the amount of elements added to the sub-target in the direction of the film thickness.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram for explaining the first embodiment of the present invention, and FIG.
The figure is a view taken along the nn line in Figure 1, Figure 3 is a graph showing the relationship between the power input to the Os target and the amount of O3 added in iron oxide, and Figure 4 is a graph showing the relationship between the power input to the Os target and the amount of O3 added to the iron oxide. -Fe2
03 A graph showing the relationship with the holding force of the thin film, FIG. 5 is an explanatory diagram explaining another embodiment of the present invention, and FIG.
The I-VI line arrow view and FIG. 7 are enlarged views showing the vicinity of the Mi pole. In the drawing, 1 is a bell jar, 2 is a board, and 3 is a board holder. 4 is a main target, 5 is a sub target, 6 is a gas introduction pipe to the main target, 7 is a gas introduction pipe to the sub target,
8 is a vacuum exhaust system, 9.10 is a high frequency power source, and 11 is a magnetic pole.

Claims (4)

[Claims] (1) A thin oxide film is formed on the substrate by arranging main and sub targets having different components in a sputtering device and performing oxidation reaction sputtering by flowing an oxidizing gas to the main target, while forming an oxide thin film on the substrate. A method for producing an oxide thin film, characterized in that sputtering is performed by flowing an inert gas into the oxide thin film, and a metal element is added to the oxide thin film by independently adjusting input power. (2) The method for producing an oxide thin film according to claim 1, wherein the main target has Fe as a main component, and the sub target has Os as a main component. (3) In claim 2, the oxide thin film is an iron oxide thin film, and the metal element in the thin film is O.
A method for producing an oxide thin film characterized by adding an s element. (4) The method for producing an oxide thin film according to claim 1, characterized in that an Ar-O_2 mixed gas is used as the oxidizing gas, and Ar gas is used as the inert gas. (5) The method for producing an oxide thin film according to claim 1, characterized in that a magnetic field is applied in a direction perpendicular or parallel to the substrate during formation of the oxide thin film.