JP2811457B2 - 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) A magnetite film is formed on the surface of a nonmagnetic substrate such as metal or glass and then oxidized, or a nonmagnetic film such as α-iron oxide is formed and then reduced to a magnetite film and further oxidized. Various methods have been proposed for producing an iron oxide recording medium by such a method, and in particular, an RF magnetron sputtering method having a high film forming speed has been attracting attention. A typical method is to introduce a low-pressure ion-forming gas such as argon and oxygen into a vacuum, ionize argon, bombard the ions with a target made of iron or an iron alloy, and sputter iron or iron alloy particles. Is reacted with oxygen on the surface of the substrate to deposit a metal oxide film on the surface of the substrate (JP-A-62-943819, U.S. Pat. No. 4,446,612).
No. etc.). However, in these methods, it is difficult to uniformly supply the reactive gas over the front surface of the substrate, and the thickness and composition of the formed oxide film vary depending on the location, and required properties such as magnetic properties vary depending on the location. There's a problem.

There are various causes for this, but one of the important causes is that the oxidation conditions in the vicinity of the substrate surface fluctuate in a direction transverse to the substrate feeding direction. Conventionally, various gas supply devices have been used to solve this problem.

A typical example of the RF magnetron sputtering apparatus is as shown in FIG. 1, in which a magnetic right 5 is arranged 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 a support post 9 and has an elongated opening that extends transversely to the direction of movement of the substrate when it is subjected to sputter while being sent in the direction of the arrow, and is narrow at the center and widened toward the outside. . This is generally necessary in order to equalize the amount of iron atoms, which are generally blown out at a central portion in the target axis direction.

Various types of gas inlets 4 have been proposed in the above-described apparatus. FIG. 6 shows a conventional distribution type gas inlet. That is, the gas supply pipe 42 is connected to a distribution member 40 in which a number of holes 41 are perforated at regular intervals, and the diameter of the holes 41 is
The distance increases from the connection point of 42.
However, in this method, the gas discharge speed varies depending on the location, and a flowing pattern is formed on the substrate even if the substrate position is considerably apart.

Another conventional example is shown in FIG. In this example, the supply pipe 50 is connected to a distribution pipe 53 having a large number of holes 52, and gas is discharged through a slit 54 of a second distribution pipe 51 surrounding the distribution pipe 53. This example is an improvement over the example of FIG. 6, but the flow pattern is not sufficiently eliminated. As will be understood from the present invention described below, this is because the inner and outer distribution pipes are too close.

(Object of the Invention) It is an object of the present invention to provide a method and an apparatus capable of uniformly producing a magnetite film, in particular, a reactive sputtering method and an apparatus.

In this specification, magnetite is magnetite (Fe ₃ O
₄ ) Not only wustite (FeO) and magnetite (Fe
Intermediate form of ₃ O _4), as well as an intermediate form of magnetite (Fe ₃ O ₄₎ and gamma maghemite _{(γ-Fe 2 O 3)} , is intended to include so-called berthollide form.

(Summary of the Invention) The present invention directs particles of iron or an iron alloy to a substrate by bombarding a target made of iron or an iron alloy mainly composed of iron with ions of an ion-forming gas such as argon by a reactive sputtering method. Forming a magnetite film on the surface of the substrate by reacting with the oxygen, the flat and wide long supply member having an upstream end and an open downstream end connected to a gas supply pipe, and Disposing the supply member having a shape and length sufficient to obtain a substantially constant diffusion flow, in the vicinity of the substrate, and introducing the oxygen or oxygen and an ion-forming gas through the supply member; And a method for producing a magnetite film.

The present invention also comprises a vacuum chamber, a target made of iron or an alloy mainly composed of iron, a substrate arranged opposite to the target, and an inlet for introducing an ion-forming gas such as argon and oxygen. In an apparatus for forming a magnetite film on a substrate surface by a reactive sputtering method, the inlet is provided near the substrate, and has an upstream end connected to a gas supply pipe and an open downstream end. An apparatus for manufacturing a magnetite film, comprising: a flat and wide long supply member, the supply member having a shape and a length sufficient to obtain a substantially constant diffusion flow over the entire downstream end. I do.

(Summary of Effect) The feature of the present invention resides in that the length of the supply member is sufficiently long so that the supply gas has a uniform diffusion flow throughout the outlet of the supply member. This allows the oxygen gas or the argon oxygen gas to flow uniformly in the transverse direction along the substrate surface (the direction perpendicular to the substrate feeding direction), so that it reacts uniformly with the sputtered iron or iron alloy particles. A uniform magnetite film can be formed over the front surface of the substrate.

(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.

Magnetite film forming apparatus In this example, a disk in which the surface of a precision-finished glass is chemically strengthened 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. Although a method and apparatus for manufacturing a magnetic recording medium to be formed are described, the present invention generally forms a magnetite film on one or both surfaces of a metal substrate or a glass substrate, or simultaneously forms a magnetite 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.
A magnetron cathode 13 supporting an iron or iron alloy target 2 on a surface arranged opposite to the substrate 11; and a member 14 for introducing argon and oxygen configured according to the features of the present invention (this point And an RF power supply (not shown) for ionizing the introduced argon and bombarding the target 2.

The magnetron cathode 13 has a magnet 21, a backing plate 22 for supporting the target 2, and a backing plate.
An RF power is applied between the earth shield electrode 23 and the target 2 and generated near the surface of the target by an electric field. Electron to magnet 21
Is confined near the surface of the target, thereby ionizing argon. Further, the target 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 having two openings 16 of the same shape, which is preferably narrow at the center and wide at the side end and extending in the vertical direction, is provided. The correction effect of this correction plate is the same as the conventional one, but
The difference is that two openings are provided.

Further, preferably, an electrode 20 is provided at a central portion of the correction plate by a column 19. This electrode is provided close to the target 2 facing the center of the magnet 21. 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 this interval is too wide, a discharge will occur,
Oxide adhering to the target surface is hit by argon ions and scattered on the substrate surface, causing granular iron oxide to adhere to the magnetite film in a dotted manner, thereby deteriorating the film quality. Further, the area of the electrode 20 is set so as to cover almost the entire area where the iron oxide particles would otherwise adhere. 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, the correction plate 15 and the support are made of a conductor. Although a magnetite film can be formed without the electrode 20, the quality of the film deteriorates due to the attachment of the oxide particles. Therefore, it is necessary to clean the target surface every time a film is formed on several substrates. Become.

Preferably, the peripheral part of the target 2 is completely or almost completely surrounded by the surrounding wall 24 except for the opening of the correction plate 15. The correction plate 15 is fixed in close contact with the top of the surrounding wall 24. By doing so, oxidation of the target surface is suppressed, so that Fe is easily beaten out by argon ions, and the productivity of the magnetite film is improved.

The inlet or supply member 14 for the mixed gas of argon and oxygen is provided outside the correction plate when viewed from the target, and is provided so as to generate a flow close to and parallel to the substrate. 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. Note that argon may be introduced into the space between the correction plate 15 and the target 2, and oxygen or an oxygen-argon mixed gas may be introduced from the illustrated member 14.

According to the invention, the gas inlet is configured as 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 a supply member having an opening 32 formed on the downstream side, and one piece connected to the side plate 33. It comprises the above gas conduit 36. The width w of the opening and the height h are designed so that a uniform diffusion flow can be obtained. When it is desired to make the width w of the gas supply member sufficiently large, the number of branches or the number of inlets of the gas conduit 36 is increased.

If a gas reservoir as shown in FIG. 8 is attached to the supply member, the uniformity can be further improved. In this figure, a gas reservoir 37 is further added to the lower plate 31 of the supply member shown in FIG. According to this embodiment, the gas flowing from the gas inlet 14 enters the gas reservoir 37, spreads in the width direction, and flows downstream at a constant flow rate from there. In this case, the length l required for diffusion may be relatively short.

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. An iron or iron alloy target 2 is mounted at a predetermined position, the vacuum chamber 10 is continuously evacuated, and a mixed gas of, for example, about 90% argon and about 10% oxygen is introduced from the member 14. The magnetron cathode 13 is operated 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 as magnetite to the surface of the substrate 11 to grow a magnetite film.

In this film forming process, the electrode 20 is provided close to the surface of the target 2, thereby preventing the oxide from adhering to the target surface. Therefore, this oxide is bombarded with argon ions and directed to the substrate. Is no longer possible.

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 thickness and film quality, and iron oxide particles are deposited on the magnetite film derived from iron oxide deposited on the target. Almost no adhesion. Further, this eliminates the need for a step of cleaning the target surface. The reason why a uniform magnetite film is formed is that the gas introduced into the supply member has a laminar flow due to its initial viscosity and has a constant flow pattern as shown in FIG. This is because the light is diffused in the width direction and eventually becomes uniform in a direction in a cross section perpendicular to the flow path. Therefore, by making the length l of the supply member sufficiently long, a substantially uniform reactive gas density can be obtained at the member opening 32. The uniform flow thus formed flows on the surface of the substrate which is moving parallel to and close to the upper and lower plates 30 and 31, and performs a uniform oxidation reaction.

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 magnetron magnetic field 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. This figure shows the magnetic flux density distribution along the point ABC in FIG.

It has been found that the magnetite film can be made into magnetite (Fe ₂ O ₄ ) itself or a belt-ride form deviating therefrom by controlling the film forming conditions. The obtained magnetite film can be converted into γ-iron oxide suitable for a magnetic recording medium by performing a heat treatment in an oxidizing atmosphere.

 Examples will be described below.

Example A magnetite film was formed using the apparatus and method shown in FIG. 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 about 270 mm in the transverse direction was arranged and placed at a position 5 mm from the surface of the target at the center of the target. The RF power supply was 13.56 MHz and 700-1500 W. A mixed gas of 90% argon and 10% oxygen is supplied to the supply member of the present invention (about 5 mm away from the locus of the substrate surface, w55.0 cm, h0.4 cm, l40.0c
m) and introduced at a flow rate of 30 to 60 SCCM, and the operating pressure was set to 5 × 10 ^-1 Pa or less. An ultra-precision polished (Rmax about 100μ) surface-reinforced glass plate with a diameter of about 13.0cm and a thickness of 1.9mm (R _max about 100μ) is fed at a constant speed at a distance of about 75mm from the target surface for about 0.
A film was formed to have a thickness of 2 μm. During the film formation, the temperature of the substrate was 100 to 200 ° C. The obtained film was confirmed by analysis to be substantially a magnetite film.

For comparison, an experiment was carried out using the conventional member shown in FIG. 7 (the width was the same as in the example, the width of the slit 54 was 0.2 cm), and the other conditions were the same as in the example.

(Specific action and effect) When the films obtained in Examples and Comparative Examples were analyzed, they were magnetite films. In the transverse direction perpendicular to the substrate transfer direction when the thickness is measured, the present invention has a constant about 0.2.
It was about 0.25μ at the center, and about 0.25μ at both ends.
2μ. Also, when the specific resistance was measured, in the example, all the portions were about 0.01 Ωcm, but in the comparative example, about
It was 0.03-0.07Ωcm at both ends of 0.01Ωcm. FIG. 9 shows the distribution of the specific resistance of the magnetite film formed on the disk-shaped substrate according to the example and the comparative example. In the figure, the angle θ is the angle in the rotational direction of the disk with the center line in the feed direction of the disk being 0 or 180 degrees,
r is the radius from the center of the disk. It can be seen that the effect of the supply member of the present invention is remarkable.

[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, FIG. 5 is a perspective view showing the structure of the reaction gas supply device of the present invention, and FIG. 6 is a diagram showing the conventional reaction gas supply device. FIG. 7 is a perspective view showing another conventional reaction gas supply device, FIG. 8 is a perspective view showing the structure of another embodiment of the reaction gas supply device of the present invention, and FIG. 9 is the present invention. 7 is a graph showing the effects of the example and the comparative example.

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masataka Yamaguchi 1-1-13 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation (72) Inventor Muneto Goto 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside DK Corporation (72) Inventor Akinori Sasaki 1-13-1 Nihombashi, Chuo-ku, Tokyo TDK 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) (58) Fields investigated (Int. Cl. ⁶ , DB name) C23C 14/00-14 / 58

Claims (3)

(57) [Claims] 1. A target made of iron or an iron alloy mainly composed of iron is bombarded with ions of an ion-forming gas such as argon by a reactive sputtering method so that iron or iron alloy particles are directed to a substrate and reacted with oxygen. The method of forming a magnetite film on a substrate surface by causing a flat and wide long supply member having an upstream end connected to a gas supply pipe and an open downstream end, and having a substantially constant diffusion throughout the downstream end The supply member having a shape and a length sufficient to obtain a flow is disposed close to the substrate, and the oxygen or the oxygen and the ion-forming gas are introduced through the supply member. Manufacturing method of magnetite film. 2. A vacuum chamber, comprising a target made of iron or an alloy mainly composed of iron, a substrate arranged opposite to the target, and an inlet for introducing an ion-forming gas such as argon and oxygen. In an apparatus for forming a magnetite film on a substrate surface by a reactive sputtering method, the inlet is provided near the substrate, and has an upstream end connected to a gas supply pipe and an open downstream end. An apparatus for manufacturing a magnetite film, comprising: a flat and wide supply member having a shape and a length sufficient to obtain a substantially constant diffusion flow over the entire downstream end. 3. The apparatus for manufacturing a magnetite film according to claim 2, wherein the flat surface of the supply member is provided in parallel with the surface of the substrate.