JP2811458B2 - Method and apparatus for manufacturing magnetite film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and an apparatus for producing a magnetite film.

(Prior Art) Various methods have been proposed for manufacturing a magnetic recording medium by forming a film of magnetic iron oxide such as magnetite or 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 high deposition rate, has attracted attention. A typical method is to introduce low-pressure argon and oxygen into a vacuum, ionize the argon, bombard the ions with a target made of iron or an iron alloy containing a small amount of Co, etc. Reacts with oxygen on the surface to form an α-iron oxide film on the surface of the substrate, and then heat-treats the substrate in a reducing atmosphere such as hydrogen to convert the α-iron oxide to a magnetite film. To obtain a gamma iron oxide film. In this method, it is necessary to once generate α-iron oxide, and there is a problem that a step of further reducing this to magnetite is required (JP-A-62-943819, US Pat. No. 4,446,612, etc.). On the other hand, it has also been proposed to directly form a magnetite film by a sputtering method and then treat the magnetite film in an oxidizing atmosphere to obtain γ-iron oxide. No film.

A typical example of the RF magnetron sputtering apparatus is as shown in FIG. 1, in which a magnet 5 is disposed in a tunnel-shaped vacuum chamber 1,
A target 2 made of iron or an iron alloy supported on a backing plate 7 is arranged, and a metal or glass substrate 3 fed in a direction of an arrow at a constant speed is positioned opposite thereto, and low-pressure argon and oxygen are supplied from a gas inlet 4. The gas is introduced, the argon gas is ionized by the RF electric field applied between the earth shield electrode 6 and the target 2 and the electrons generated and constrained by the magnetic field of the magnet 5, and the target 2 is set to a negative high potential by the RF electric field. To strike the blown-out iron or iron alloy particles to the substrate and react with oxygen on the surface to form a magnetite film. Reference numeral 8 denotes a correction plate having a correction opening, which is basically not important. The compensating plate 8 is supported by the columns 9 and has an elongated opening that extends transversely to the direction of movement when the substrate is sputtered while being sent in the direction of the arrow, and that is narrower at the center and wider toward the outside. . This is generally because many iron atoms are knocked out at the center in the target width direction,
It is necessary to make the amount uniform.

The inventor of the present invention has succeeded in directly forming a film of magnetite using the above-described apparatus. Although the present invention uses such a technique, when the obtained magnetite film is heat-treated in an oxidizing atmosphere to be converted to γ-iron oxide, the surface layer serves as a barrier and the oxidation in the thickness direction is sufficiently uniform. And the magnetic characteristics fluctuated.

(Object of the Invention) The present invention provides a method and an apparatus capable of producing a magnetite film which is easily converted to γ-iron oxide of uniform film quality in an oxidizing atmosphere.
In particular, it is to provide a reactive sputtering method and apparatus. In this specification, magnetite means magnetite (Fe
Not only ₃ O ₄ ), but also intermediate form between wustite (FeO) and magnetite (Fe ₃ O ₄ ), and intermediate form between magnetite (Fe ₃ O ₄ ) and γ-maghemite (γ-Fe ₂ O ₃ ), so-called belt ride Including form.

(Summary of the Invention) In the present invention, a target made of iron or an alloy mainly composed of iron is bombarded with ions of an ion-forming gas such as argon by RF magnetron sputtering, and the released iron or alloy particles are formed into a film forming region. A method of 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 oxygen or oxygen to the film-forming portion. Alternatively, the supply of the oxygen-ion forming gas mixture and the evacuation of the film formation region are directions in which an oxygen flow or an oxygen-ion formation gas mixture flow co-current to the substrate transfer direction in the film formation region. And a method for producing a magnetite film. Here, the co-current refers to a flow in the same direction as the substrate transfer direction.

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 unit that continuously transfers a substrate through a film formation region in opposition to the target, An inlet for introducing an ion-forming gas such as argon and oxygen, and an inlet for introducing an oxygen flow or an oxygen + argon flow in parallel with the substrate in the transfer direction in the vicinity of the trajectory of the substrate. An opening is provided on the upstream side of the film formation region, and a means for exhausting the vacuum chamber or the film formation region is provided on the downstream side of the film formation region.

(Summary of Effect) According to the present invention, since oxygen flows in the film formation region along the substrate surface in parallel with the direction of transport of the substrate, the magnetite film grown on the substrate surface has a high oxygen concentration near the substrate and has a high oxygen concentration. The oxygen concentration decreases on the side, so that a uniform heat treatment can be easily performed in the thickness direction by a subsequent heat treatment process under oxidizing conditions, and a uniform γ-iron oxide film can be obtained.

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

Oxide Film Deposition Apparatus In this example, a precision-finished glass surface is chemically strengthened and a disk is used as a substrate, and a plurality of substrates in a row are sent to a film-forming site, and a magnetite film is formed on both surfaces of the substrate. The present invention describes a method and apparatus for manufacturing a magnetic recording medium that forms a magnetite film on one or both sides of a general human metal substrate or a glass substrate, or simultaneously forms a film on a plurality of substrates in two or more rows. Deformation such as formation is possible.

FIG. 2 is a plan sectional view showing a main part of the RF magnetron sputtering apparatus according to the embodiment of the present invention. FIG. 3 shows the second
FIG. 3 is an enlarged view showing a substrate as viewed from a line III-III in the figure by a chain line.

As shown in the figure, an RF magnetron sputtering apparatus includes a horizontally extending vacuum chamber 10 and a pallet or holder 12 for transferring a substrate 11 such as a metal or glass disk in the direction of an arrow.
An RF magnetron cathode 13 supporting an iron or iron alloy target 2 disposed opposite to the substrate 11, and an oxygen flow for generating an oxygen flow parallel to the substrate transfer direction along the substrate surface in the film formation region. It basically comprises a supply member 14 (this structure will be described in detail later), an exhaust means, and an RF power supply (not shown) for ionizing the introduced argon and bombarding the target.

The magnetron cathode 13 comprises a magnet 21 and a target 2
A backing plate 22 that supports the target and an earth shield electrode 23 that is arranged near the periphery of the target at a distance from the backing plate 22.RF power is applied between the earth shield electrode and the target, Electrons generated in the vicinity of the surface of the target by the electric field are confined in the vicinity of the surface of the target by the magnetic field of the magnet 21, thereby ionizing argon efficiently. Further, the target 2 becomes negative high potential by the RF electromagnetic field, and accelerates argon ions to the target surface. Further, in order to make the growth of the magnetite film uniform, a correction plate 15 provided with two openings 16 of the same shape extending in the vertical direction which is narrow at the center and wide at the side ends is provided.
The correction effect of this correction plate is the same as the conventional one, but differs in that two openings are provided.

Further, preferably, an electrode 20 is provided by a support 19 at the center of the correction plate. This electrode is provided close to the target 2 facing the center of the magnet 21 of the magnetron cathode 13. The distance between the electrode 20 and the target 2 is 5 mm or less. This interval can be easily determined by optimization experiments. If the interval is too wide, a discharge occurs, and the effect of the present invention of suppressing the attachment of the particulate oxide to the substrate surface is reduced. The area of the electrode 20 covers almost the entire area where the iron oxide is deposited. This point can also be easily determined by an optimization experiment. The electrode 20 is grounded or at a positive potential with respect to the target. For example, when grounding, the correction plate 15 and the support 19 are made of a conductor.

Preferably, the peripheral portion of the target 2 is almost completely surrounded by the surrounding wall 24 except for the opening of the correction plate 15. For this reason, the correction plate 15 is fixed in close contact with the top of the surrounding wall 24.
By doing so, argon ions are easily generated, and the productivity of magnetite is improved.

The inlet or supply member 14 for the mixed gas of argon and oxygen is provided so as to be close to the substrate and parallel to the substrate outside the correction plate as 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.
Inlet 14 is parallel wide upper and lower plates 30, 31 and parallel low side plates
It comprises a supply member comprising 34, 35 and a lower side plate 33 on the upstream side and having an opening 32 formed on the downstream side, and one or more gas conduits 36 connected to the side plate 33. The width w of the opening and the height h The length l of the supply member is determined to be equal to or longer than the shortest length at which a uniform diffusion flow can 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.

Method for Forming a Magnetite Film A film forming method of the present invention will be described using the magnetite film forming apparatus having the above configuration. The substrate 11 is transferred at a constant speed in the direction of the arrow. The target 2 of iron or iron alloy is attached to a predetermined position, and the vacuum chamber 10 is continuously evacuated. Introduce. Oxygen flows along the substrate surface in the same direction (parallel flow direction) as the moving direction of the substrate. The exhaust is performed so as to realize this cocurrent. Activate the RF magnetron to form argon ions. The argon ions bombard the surface of the target 2 to release iron atoms. The iron atoms react with oxygen near the surface of the substrate 11 through the opening 16 of the correction plate 15 and adhere to the surface of the substrate 11 as magnetite to grow a magnetite film.

In this film formation process, the oxide deposited on the target surface is bombarded with argon ions and directed to the substrate as a granular oxide by providing the electrode 20 close to the surface of the target 2, and the oxide is deposited on the magnetite film. This eliminates the possibility that the film quality is degraded by adhering as a foreign matter.

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. . Further, there is almost no adhesion of iron oxide particles derived from oxides deposited on the target 2. The gas introduced into the supply member shown in FIG. 5 initially forms a laminar flow due to viscosity, and has a constant flow pattern. Uniform in the direction. Therefore, by making the length l of the supply member sufficiently long, an almost completely uniform density can be obtained at the supply member opening 32. The uniform flow thus formed is the upper and lower plates 30,
It flows on the surface of the substrate that is moving parallel to and close to the surface of the substrate 31 to perform a uniform oxidation reaction in the in-plane direction.

Oxygen released with the argon becomes oxygen deficient by reacting with the sputtered iron or alloy particles while flowing along the substrate to produce magnetite, thus the substrate is initially transported with a high oxygen concentration in the magnetite layer. And the oxygen content is gradually reduced, and the surface magnetite layer has a low oxygen concentration. Therefore, the generated magnetite film has a higher oxygen concentration in the lower layer.

According to this example, the film formation efficiency of the magnetite film is almost the same as when the electrode 20 is not used. This is because the intensity distribution of the magnet magnetic field of the magnetron is generally of a twin type as shown in FIG. 4, so that the electrode 20 is located at the central weak magnetic field portion. Note that this figure is
7 shows a magnetic flux density distribution along a point ABC.

 Examples will be described below.

Example A magnetite film was formed using the apparatus and method described above. A pure iron target was manufactured to have a length of about 127 mm in the feed direction of the substrate and a length of about 381 mm in the transverse direction, and this was supported at the center position of the backing plate. An electrode having a length of about 35 mm in the feed direction of the substrate and a length of 270 mm in the transverse direction was arranged and placed at a position 5 mm from the surface at the center of the target. The RF power supply was 13.56 MHz and 700-1500 W. Argon 90
%, Oxygen 10% mixed gas at a flow rate of 30-60 SCCM,
The operating pressure was set to 5 × 10 ^-1 Pa or less. Approximately 13.0cm in diameter, 1.9m in thickness
m ultra-precision polished (R _max about 100μ) surface-reinforced glass plate at a constant speed of about 75mm from the target surface
A film was continuously formed at 0.2 μm. The temperature of the substrate during film formation is 100 to 20
It was 0 ° C. The obtained film was confirmed by analysis to be a magnetite film.

(Specific action and effect) It was confirmed by analysis that the obtained film was a magnetite film in which the ratio of the oxygen concentration between the substrate surface and the surface was 1: 0.8.
This was further heated in air at 300 ° C. for 2 hours to obtain γ iron oxide.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a magnetite film forming apparatus by RF magnetron sputtering, FIG. 2 is a plan sectional view of a magnetite film forming apparatus according to an embodiment of the present invention, and FIG.
FIG. 4 is a graph showing the magnetic flux density distribution of the magnetron, and FIG. 5 is a perspective view showing the structure of the reaction gas supply device.

Continuing on the front page (72) Inventor Masataka Yamaguchi 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation (72) Inventor Muneto Goto 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation (72) Inventor Akinori Sasaki 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC Corporation (72) Inventor Toshio Kubota 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation (56 References JP-A-60-237638 (JP, A) JP-A-58-199861 (JP, A) JP-A-61-94242 (JP, A) JP-A-59-215025 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C23C 14/00-14/58

Claims (4)

(57) [Claims] A target made of iron or an alloy mainly composed of iron is bombarded with ions of an ion-forming gas such as argon by a reactive sputtering method, and the released iron or iron alloy particles are continuously passed through a film formation region. In the method of forming a magnetite film on a substrate by reacting the iron or alloy particles with oxygen on the surface of the substrate toward the substrate being transferred to the substrate, the oxygen or oxygen-
The magnetite characterized in that the supply of the ion-forming gas mixture and the evacuation of the film-forming region are carried out in such a way that an oxygen flow or an oxygen-ion-forming gas mixture flow is produced in the film-forming region in the direction of transport of the substrate. Manufacturing method of membrane. 2. A vacuum chamber, a target made of iron or an iron-based alloy disposed in the chamber, and transfer means for continuously transferring a substrate through a film formation region in opposition to the target. In an apparatus comprising an ion-forming gas such as argon and an inlet for introducing oxygen, the inlet and the exhaust means are provided with an oxygen flow or an oxygen-ion-forming gas mixture flowing in the film formation region in the direction of transfer of the substrate. An apparatus for producing magnetite, characterized in that the apparatus is arranged so as to generate the following. 3. The inlet is a flat, wide, and long supply member having an open outlet end, and the length of the supply member is set to a length and a shape sufficient to obtain a substantially constant diffusion flow throughout the outlet. 3. The manufacturing apparatus according to claim 2, further comprising: a gas supply pipe, and at least one gas supply pipe opened at an upstream end of the supply member. 4. The apparatus for manufacturing a metal oxide film according to claim 3, wherein the flat surface of the supply member is provided in parallel with the surface of the substrate.