JPH02197559A - Method and device for producing magnetite film - Google Patents

Abstract

PURPOSE:To form a homogeneous magnetite film on the surface of a substrate by reactive sputtering by feeding a gaseous mixture into each vacuum chamber and exhausting it parallel to the transfer direction of the substrate in a film forming region. CONSTITUTION:Each vacuum chamber 10 is continuously evacuated, a gaseous Ar and O2 mixture is introduced from a feed member 14 and an RF magnetron cathode 13 is allowed to act to generate Ar ions. These Ar ions bombard the surface of an iron alloy target 2 to emit iron ions and these iron ions pass through an opening 16 in a correcting plate 15, approach a substrate 11 travelling through a pallet 12 and react with O2 to form a magnetite film on the surface of the substrate 11. The feed member 14 is composed of parallel broad upper and lower plates 30, 31, parallel low side plates 34, 35, a low side plate 33 on the upper stream side and a gas feed pipe 36 connected to the plate 33 so that the member 14 has an opening 32 on the down-stream side and gives a uniformly diffused flow. The gaseous mixture is fed into the film forming region and exhausted parallel to the transfer direction of the substrate 11 and uniform film formation is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method and apparatus for manufacturing a magnetite film.

(Prior Art) Various methods have been proposed for manufacturing magnetic recording media by forming a film of magnetite or magnetic iron oxide such as gamma iron oxide on the surface of a nonmagnetic substrate such as metal or glass. In particular, the RF magnetron sputtering method, which has a fast film formation rate, is attracting attention. A typical method is to introduce low-pressure argon and oxygen into a vacuum, ionize the argon, and convert the ions to iron or a small amount of Co. A target made of an iron alloy is bombarded, and the sputtered iron atoms react with oxygen on the surface of the substrate to form a film of α-iron oxide on the surface of the substrate.Then, the substrate is heated in a reducing atmosphere such as hydrogen. Heat treatment is performed to convert α iron oxide into a magnetite film, and further heat treatment is performed in an oxidizing atmosphere to obtain a γ iron oxide film. This method has problems such as the need to generate α-iron oxide and then a step of reducing it to magnetite (Japanese Patent Application Laid-Open No. 62-943819, U.S. Patent No. 45
44612, etc.), on the other hand, it has also been proposed to directly form a magnetite film by sputtering and then treat it in an oxidizing atmosphere to form gamma iron oxide. However, as described below, the conventional method film cannot be formed (in the thickness direction).

A typical example of an RF magnetron sputtering device is as shown in FIG. 1, in which a magnet 5 is placed in a tunnel-shaped vacuum chamber 1.
A target 2 made of iron or iron alloy supported by a backing plate 7 is placed, a metal or glass substrate 3 is positioned opposite to it and is fed at a constant speed in the direction of the arrow, and low-pressure argon and Oxygen gas is introduced, and the argon gas is ionized by electrons generated and restrained by the RF electric field applied between the earth shield electrode 6 and the target 2 and the magnetic field of the magnet 5, and the target is made to have a strong negative potential by the RF electric field. 2, and the iron or iron alloy particles that are knocked out are directed to the substrate and react with oxygen on the surface of the substrate to form a magnetite film. Note that 8 is a correction plate having an opening for correction, and is basically not important.The correction plate 8 is supported by a support 9, and when the substrate receives sputtering while being sent in the direction of the arrow, it It has an elongated opening that is narrow in the center and widens outwardly, extending in the transverse direction. This is because there are generally many iron atoms ejected from the center of the target in the width direction.
This is necessary to equalize the amount.

The present inventor attempted to directly form a film of magnetite using the above-mentioned apparatus and was successful. The present invention uses such a technique, but the obtained magnetite film is heat-treated in an oxidizing atmosphere to convert it into gamma iron oxide. It has been found that in this case, the surface layer acts as a barrier and oxidation is not performed uniformly in the thickness direction, resulting in fluctuations in magnetic properties.

(Objective of the Invention) An object of the present invention is to provide a method and apparatus, particularly a reactive sputtering method and apparatus, capable of producing a magnetite film that is easily converted into gamma iron oxide of uniform film quality in an oxidizing atmosphere.

In this specification, magnetite refers to magnetite (Fe3
04), as well as intermediate forms between wustite (Fed) and magnetite (Fe304), as well as magnetite (F
e.

04) and γ-magnetite (γ-Few Os), the so-called bertholed form.

(Summary of the Invention) The present invention provides a film forming area in which iron or alloy particles are released by bombarding a target made of iron or an iron-based alloy with ions of an ion-forming gas such as argon by RF magnetron sputtering. In a method for forming a magnetite film on a substrate by directing the iron or alloy particles to a substrate being continuously transported through the substrate and reacting the iron or alloy particles with oxygen on the surface of the substrate, the oxygen to the deposition location is or the supply of the oxygen-ion-forming gas mixture and the evacuation of the deposition region are in a direction that produces a cocurrent flow of oxygen or oxygen-ion-forming gas mixture in the direction of transport of the substrate in the deposition region. The present invention provides a method for manufacturing a magnetite film.

The present invention also provides a vacuum chamber, a target made of iron or an iron-based alloy disposed in the chamber, and a transfer means for continuously transferring a substrate through a film forming region opposite to the target. An apparatus comprising an inlet for introducing an ion-forming gas such as argon and oxygen, wherein the inlet is arranged so as to produce a cocurrent oxygen flow or an oxygen + argon flow in the substrate transport direction close to the trajectory of the substrate. A magnetite manufacturing apparatus is provided, wherein an opening is provided on the upstream side of the film forming region, and a vacuum chamber or a means for evacuating the film forming region is provided on the downstream side of the film forming region.

(Summary of Effects) According to the present invention, oxygen flows through the film-forming region along the substrate surface in parallel with the substrate transport direction, so that the magnetite film grown on the substrate surface has a higher oxygen concentration on the side closer to the substrate, and the oxygen concentration on the surface is higher. The oxygen concentration is lower on the side, and therefore, by the subsequent heat treatment step under oxidizing conditions, -like oxidation can be easily performed in the thickness direction, and a homogeneous γ iron oxide film can be obtained.

(Specific Description of Configuration) Hereinafter, the present invention will be described in detail in connection with embodiments of the present invention with reference to the drawings.

In this example, a disk with a precisely finished glass surface chemically strengthened is used as a base, and a row of multiple bases is sent to a film forming location, and a magnetite film is formed on both sides of the bases. Although the manufacturing method and manufacturing apparatus of the medium will be described, the present invention generally applies to modifications such as forming a magnetite film on one or both sides of a metal substrate or glass substrate, or forming a film on two or more rows of multiple substrates at the same time. is possible.

FIG. 2 is a plan sectional view showing the main parts of an RF magnetron sputtering apparatus according to an embodiment of the present invention. Figure 3 is the second
FIG. 2 is an enlarged view of the substrate viewed from line 2-m in the figure, indicated by a chain line.

As shown in the figure, the RF magnetron sputtering apparatus includes a horizontally extending vacuum chamber 10 and a substrate 1 such as a metal or glass disk.
1, and an RF magnetron cathode 13 that supports an iron or iron alloy target 2 placed opposite to the substrate 11.
, a supply member 14 (this structure will be described in detail later) and an exhaust means for generating an oxygen flow parallel to the substrate transport direction along the substrate surface in the film forming region, and ionizing the introduced argon. It basically consists of an RF power source (not shown) for impacting the target.

The magnetron cathode 13 is composed of a magnet 21, a backing plate 22 that supports the target 2, and an earth shield electrode 23 that is spaced apart from the backing plate 22 and placed near the periphery of the target.
F power is applied between the earth shield electrode and the target, and electrons generated near the surface of the target due to the electric field are confined near the surface of the target by the magnetic field of the magnet 21, thereby efficiently ionizing argon. The RF'li magnetic field also brings the target 22 to a high negative potential, accelerating argon ions toward the target surface. Also,
In order to make the growth of the magnetite film uniform, a correction plate 15 is provided with two openings 16 of the same shape, narrow at the center and wide at the side ends, extending in the vertical direction. The correction effect of this correction plate is similar to the conventional one, but the difference is that two apertures are provided.

Further, an electrode 20 is preferably installed in the center of the correction plate by a support 19. This electrode is magnetron cathode 1
The magnet 21 is provided close to the target 2 and facing the center of the magnet 21 of No. 3. The distance between the electrode 20 and the target 2 is 5 mm or less. This interval can be easily determined through optimization experiments. If this distance is too wide, discharge will occur and the effect of suppressing the adhesion of particulate oxides to the substrate surface as intended by the present invention will be reduced. Further, the area of the electrode 20 is set so as to cover almost the entire region where iron oxide is deposited. This point can also be easily determined through optimization experiments. The electrode 20 is grounded or has a positive potential with respect to the target. For example, if the electrode 20 is grounded, the correction plate 15 and the pillar are made of a conductor.

Preferably, all parts of the peripheral part of the target 2 other than the opening of the correction plate 15 are almost completely surrounded by the surrounding wall 24.

Therefore, the correction plate 15 is fixed in close contact with the top of the surrounding wall 24. This makes it easier to generate argon ions and improves the productivity of magnetite.

An inlet or supply member 14 for a mixed gas of argon and oxygen is provided so as to create a flow close to and parallel to the substrate on the outside of the correction plate when viewed from the target. This makes it easier for argon to form dense argon ions near the target as described above, while oxygen tends to preferentially react with iron atoms on the substrate surface to generate magnetite.

Preferably, the gas inlet is configured as shown in FIG. The inlet 14 is composed of parallel wide upper and lower plates 30, 31, parallel low side plates 34, 35, and an upstream low side plate 33, and includes a supply member with an opening 32 formed on the downstream side, and one piece connected to the side plate 33. It consists of the gas conduit 36 described above. The width W and height h of the opening and the length β of the supply member are determined to be at least the shortest length that allows a uniform diffusion flow to be obtained. When it is desired to make the gas conduit width W sufficiently large, the number of branches of the gas conduit 36 is increased.

The film forming method of the present invention will be explained using the magnetite film forming apparatus having the above configuration. It is assumed that the substrate 11 is transported at a constant speed in the direction of the arrow. A target 2 made of iron or iron alloy is attached to a predetermined position, the vacuum chamber 10 is continuously evacuated,
On the other hand, from the supply member 14, for example, argon 90%, oxygen 10%
% of the mixed gas is continuously introduced into the film forming region.

Oxygen flows along the substrate surface in the same direction as the substrate movement direction (cocurrent direction). Exhaust is performed to achieve this parallel flow, and an RF magnetron is activated to form argon ions. The argon ions bombard the surface of the target 2 to release iron atoms. The iron atoms pass through the opening 16 of the correction plate 15 and react with oxygen near the surface of the base 11, and adhere to the surface of the base 11 as magnetite to grow a magnetite film.

In this film-forming process, by providing the electrode 20 close to the surface of the target 2, the oxide deposited on the target surface is bombarded by argon ions and directed to the substrate as particulate oxide, forming a magnetite film. There is no possibility that the film quality will deteriorate due to foreign matter adhering in spots.

As shown in the following examples, according to the present invention, the magnetite film formed on the surface of the substrate 11 is uniform in both thickness and film quality in the plane direction, and the oxygen concentration is gradually reduced from the substrate to the surface in the thickness direction. . In addition, the gas introduced into the supply member shown in FIG. 5, which has almost no adhesion of iron oxide particles derived from the oxide deposited on the target 2, initially forms a laminar flow due to its viscosity and has a constant flow pattern. As it flows, it diffuses in the width direction and eventually becomes uniform in the direction within the cross section perpendicular to the flow path. Therefore, by making the length of the supply member sufficiently long (°C), an almost completely uniform density can be obtained in the supply member opening 32.
It flows to the surface of the substrate which is moving parallel to 0.31 and close to the surface, and performs a uniform oxidation reaction in the in-plane direction.

The oxygen released with the argon becomes oxygen-depleted by reacting with the sputtered iron or alloy particles while flowing along the substrate to form magnetite, so that as the substrate is transported it initially becomes an oxygen-rich layer of magnetite. The oxygen content gradually decreases, and the magnetite layer on the surface has a low oxygen concentration. Therefore, the produced magnetite film has a high oxygen concentration in the lower layer.

According to this example, the deposition efficiency of the magnetite film is almost the same as when the electrode 20 is not used. This is because the strength distribution of the magnetron's magnetic field is generally twin-shaped as shown in Figure 4. This is because the magnetic field 20 is located in the central portion of the weak magnetic field. Note that this figure shows the magnetic flux density distribution along the point ABC in FIG. 3.

Examples will be described below.

1. Magnetite film formation was performed using the apparatus and method described above. A pure iron target was manufactured to have a length of approximately 127 mm in the substrate feeding direction and approximately 381 mm in the transverse direction, and was supported at the center of the backing plate. An electrode having a length of about 35 mm in the substrate feeding direction and a length of 270 mm in the transverse direction was arranged and installed at a position 5 mm from the surface at the center of the target. The RF power source is 13.56MHz.

The power was 7oo to 150oW. 90% argon, 10% oxygen
% mixed gas was introduced at a flow rate of 30-60 SCCM, and the operating pressure was below 5×10 −′ Pa. Approximately 13.0cm in diameter
, 1.9mm thick ultra-precision polished (R,, approx. 10
0μ) Place the surface tempered glass plate approximately 75mm from the target surface.
A film was continuously formed at a distance of about 0.2 μm by feeding at a constant speed. Note that the temperature of the substrate during film formation was 100 to 200°C.

Analysis confirmed that the obtained film was a magnetite film.

(Specific Effects) Analysis confirmed that the obtained film was a magnetite film with a ratio of oxygen concentration between the substrate surface and the surface of the film of 1:0.8.

This was further heated in air at 300°C for 2 hours to obtain γ iron oxide.

FIG. 2 is a cross-sectional plan view of a magnetite film forming apparatus according to an embodiment of the present invention, FIG. 3 is a view taken from ■-■ in FIG. 2, and FIG. A graph showing the magnetic flux density distribution and FIG. 5 are perspective views showing the structure of the reaction gas supply device.

4. t' B Figure 1 is a map created by RF magnetron sputtering Figure 3 Figure 1 ↑ Ar+02

Claims (1)

[Claims] 1) A target made of iron or an iron-based alloy is bombarded with ions of an ion-forming gas such as argon by reactive sputtering, and the released particles of iron or iron alloy are used in a film forming area. A method for forming a magnetite film on a substrate by reacting the iron or alloy particles with oxygen on the surface of the substrate by directing the iron or alloy particles to the substrate being continuously transported through the or the supply of the oxygen-ion-forming gas mixture and the evacuation of the deposition region are carried out in such a way as to produce a cocurrent flow of oxygen or oxygen-ion-forming gas mixture in the direction of transport of the substrate in the deposition region. A method for producing a magnetite film. 2) a vacuum chamber, a target made of iron or an iron-based alloy disposed in the chamber, a transfer means that faces the target and continuously transfers the substrate through a film forming region, and a vacuum chamber containing argon or the like. An apparatus comprising an inlet for introducing an ion-forming gas and oxygen, wherein the inlet and exhaust means produce a cocurrent flow of oxygen or an oxygen-ion-forming gas mixture in the direction of substrate transport in the deposition region. A magnetite production device characterized by being located at. 3) The inlet is a flat, wide, and long supply member with an open outlet end, and the length and shape of the supply member are determined to be sufficient to obtain a substantially constant diffusion flow throughout the outlet. and at least one gas supply pipe opened at the upstream end of the supply member. 4) The metal oxide film manufacturing apparatus according to item 3, wherein the flat surface of the supply member is provided parallel to the surface of the substrate.