JPS59148319A - Formation of magnetic layer - Google Patents

Abstract

PURPOSE:To obtain an iron oxide group magnetic layer of excellent characteristics for vertical magnetization with a high speed and a low electric power consumption and at low temperature by a method wherein the thickness of a target of a magnetic layer composing material is less than 14mm. when the iron oxide group magnetic layer suitable for vertical magnetization is formed by sputtering. CONSTITUTION:A substrate 6, on which a magnetic thin film is to be formed, is held vertically to the side between facing targets by a holder 5. The thickness of the targets made of a magnetic layer composing material is less than 14mm.. In a sputtering equipment composed like this, a magnetic field is formed to the direction perpendicular to each surface of the targets T1, T2, facing each other in parallel, and sputtered gas ions, accelerated by this magnetic field in an electric field of a cathode-drop portion, give impact against the surface of the target to emit gamma-electrons so that a high density plasma is formed in a space between the targets T1-T2. As a result, target material is sufficiently sputtered and accumulated on the substrate 6 at the side as a magnetic material.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Industrial Application Field The present invention relates to a method for forming magnetic rfI (especially a magnetic layer for a magnetic recording medium).

2. Prior Art Conventionally, magnetic recording media have been widely used for recording various types of signals such as video, audio, and digital signals. These have been developed as a system that uses magnetization in the in-plane longitudinal direction of a magnetic Ii (magnetic recording layer) formed on a substrate. However, in recent years, with the increase in the density of magnetic recording, recording methods that use magnetization in the longitudinal direction in the plane have a tendency to increase the demagnetizing field within the medium as the recording signal becomes shorter in wavelength, resulting in attenuation and rotation of the residual magnetization. This causes a significant decrease in playback output.

For this reason, it is extremely difficult to reduce the recording wavelength to submicron or less.

On the other hand, a perpendicular magnetization recording method that uses magnetization in the thickness direction of the magnetic layer of a magnetic recording medium (so-called perpendicular magnetization) has recently been proposed (for example, [Nikkei Electronics J
August 7, 197'8 issue No.

192). According to this recording method, as the recording wavelength becomes shorter, the demagnetizing field that acts on the residual magnetization in the medium decreases, so it has favorable characteristics for increasing density, and is essentially suitable for high-density recording. This is considered to be a method.

By the way, in order to perform this kind of perpendicular recording efficiently,
The recording layer of the magnetic recording medium is perpendicular (thickness direction of the magnetic layer)
It must have an axis of easy magnetization. Such a magnetic recording medium is a coated type in which a magnetic coating mainly composed of magnetic powder and a binder is coated on a substrate (support), and the axis of easy magnetization is oriented in the perpendicular direction of the magnetic layer. The medium is known. This coated media includes Co, F
e5ox, r -FezOx Co-added Fes Oy
Co-added TF e2 Qs, hexagonal ferrite (e.g. barium ferrite), Mn Bt, etc. are used as magnetic powders (JP-A-52-46803, JP-A-52-46803).
3-! No. 67406, No. 52-78403, No. 55-861
No. 03, No. 52-78403, No. 54-87202). However, in these coated media, there is a limit to increasing the packing density of magnetic powder due to the presence of a non-magnetic binder in the magnetic layer, and therefore the S
/N ratio cannot be made high enough. Furthermore, the magnitude of the recorded signal is limited by the size of the magnetic particles, and thus a medium having a magnetic layer made of a magnetic coating is unsuitable for perpendicular magnetization recording.

Therefore, continuous thin-film magnetic recording media, in which a perpendicularly magnetized magnetic layer is formed by continuously depositing a magnetic material on a support without using a binder or inder, are suitable for high-density recording. Attention has been paid.

This continuous thin film type perpendicular magnetization recording medium has a magnetic recording layer made of an alloy film of cobalt and chromium, as disclosed in Japanese Patent Publication No. 57-17282, and has a particularly high chromium content. states that a Co--Cr alloy film containing 5 to 25% by weight is superior. Further, a magnetic recording medium having a magnetic layer formed by adding 30% by weight or less of rhodium to a Co-Cr alloy film is disclosed in JP-A-55-111110, and furthermore, a cobalt-vanadium alloy film (for example, Communication Society: Abbreviation: IEEE academic journal “T”
transaction on Magnetism″1
982 Vol. 18 No. 016. 111 Annual Tribute Vol. 18 No. 016
Ruthenium alloy film (for example, the 18th meeting held in March 1982)
Magnetic recording media using the Tohoku University Research Institute Symposium ``Perpendicular Magnetic Recording'' are known.

Among these, the Co--Cr alloy film has been shown to be promising for perpendicular magnetization, but it has been found that it has the following drawbacks.

(1) In order to orient the axis of easy magnetization perpendicular to the surface of the magnetic layer, it is necessary to create the magnetic layer in a high vacuum of 10 Torr or more, and the substrate must be subjected to advanced cleaning treatment and a low sputtering speed. etc., and the control factors for vertical alignment become extremely complex.

(2) During signal recording and reproduction, since the magnetic recording medium and the perpendicular recording/reproducing groove are caused to slide relative to each other, the interface between the groove and the medium is poor, and the medium It is easy to generate scratches, and the head may also be damaged.

(3) Since the magnetic layer is hard, cracks tend to occur when the magnetic layer is provided on a flexible substrate. It is necessary to provide a protective film.

(5) The raw material, carp, is difficult to obtain stably and is expensive.

3. Purpose of the Invention In view of the above-mentioned circumstances, the present inventor has made intensive studies and has aimed to obtain at high speed a magnetic layer suitable for high-density perpendicular magnetic recording and excellent in mechanical strength, chemical stability, etc. I found a way to do this.

4. Structure of the invention, that is, the method according to the invention consists of a continuous layer mainly composed of iron oxide, and the residual magnetization (MH) in the in-plane direction of the magnetic layer and the residual magnetization (MH) in the direction perpendicular to the plane of the magnetic layer. A magnetic layer with a ratio of magnetization (Mv) (MV/MH) of 0.5 or more is
When forming the magnetic layer on the substrate by the vine ring method, a target made of the material constituting the magnetic layer is used, and the thickness of the target nodule is set to 14 mm or less.

5. Examples Hereinafter, examples of the present invention will be explained in detail with reference to the drawings.
I will clarify.

First, referring to FIG. 1, a facing target sputtering apparatus suitable for forming a magnetic layer for perpendicular magnetization recording containing iron oxide as a main component will be described.

In the drawing, 1 is a vacuum chamber, 2 is an exhaust system consisting of a vacuum pump etc. for evacuating the vacuum chamber 1, and 3 is a gas introduction system for introducing a predetermined gas into the vacuum chamber 1 and setting the gas pressure. The target electrodes are configured as opposed target electrodes in which a pair of targets (1) are separated from each other by a target holder 4 and are arranged facing each other in parallel. The target material may consist of Fe, Fe5OII, T-Fe201, and a bertholed compound (of intermediate composition between FesOll and γ-Fe20). A magnetic field is generated between these targets by magnetic field generating means (not shown).

On the other hand, the substrate 6 on which the magnetic thin film is to be formed is held in the substrate holder 5.
is arranged vertically laterally between the opposing targets.

In the sputtering apparatus configured in this manner, a magnetic field is formed in a direction perpendicular to each surface of both targets T1 and n that face each other in parallel, and this magnetic field generates a magnetic field between the cathode falling part (i.e., target layer) Tt and T2. The γ electrons emitted by the impact of the sputtering gas ions accelerated by the electric field on the target surface in the region between the plasma atmosphere and each target T1 and T2 are trapped in the space between the targets, and the γ electrons are trapped in the space between the targets and move in the direction. The γ electrons that have moved to the other target surface are reflected at the cathode fall section nearby. In this way, the γ electrons are transferred to the target T+
-T! In between, the reciprocating motion is repeated while being constrained by a magnetic field. During this reciprocation, the γ electrons collide with the neutral atmospheric gas to generate ions and electrons of the atmospheric gas, and these products promote the release of the γ electrons from the target and the ionization of the atmospheric gas. Therefore, a high-density plasma is formed in the space between T2 and T2, and the target material is sufficiently sputtered and deposited as a magnetic material on the side substrate 6. .

Compared to other flying methods, this facing target sputtering device enables film formation at a high deposition rate through high-speed sputtering, and the substrate is not directly exposed to plasma, allowing film formation at low substrate temperatures. It is advantageous to form a perpendicularly magnetized film because it is possible. In addition, the energy incident on the substrate of the magnetic film material that is ejected by the facing target sputtering device is smaller than that of a normal sputtering device, so the material is easily deposited directionally in the desired direction, making it possible to record perpendicular magnetization. It becomes easier to obtain a membrane with a structure suitable for

Next, a specific example of producing a magnetic recording medium using the above sputtering apparatus will be described.

The conditions for this preparation were as follows.

Target material Iron (contains 1 atomic% Co) base
Distance between glass facing targets 100mm Magnetic field in sputtering space 1400e Target shape 100mm diameter Distance between substrate and target end 30III11 Back pressure in vacuum chamber
10 Torr Introduced gas: Ar+Oz Introduced gas pressure: 4 x 10 Torr Sputter input power: 420 W In this way, as shown in FIG. 2, a magnetic recording medium having an iron oxide magnetic layer 10 on the base film 6 was obtained. Regarding this medium, the characteristics of the magnetic layer were evaluated by identifying the composition using an X-ray microanalyzer (XMA), the state of iron oxide using an X-ray diffraction method, and the magnetic properties using a vibrating sample magnetic needle. The characteristics of the obtained magnetic recording medium were as follows.

First, the ratio of the residual magnetization (MH) in the in-plane direction of the magnetic layer to the residual magnetization (MV) in the perpendicular direction to the plane of the magnetic layer is Mv
/MH≧0.5. That is, as illustrated in FIG. 3, a hysteresis curve during magnetization in the in-plane direction shown by the broken line and a hysteresis curve during magnetization in the perpendicular direction shown by the solid line were obtained, but when the applied magnetic field is zero The amounts of magnetization at this time were defined as MH and MV. According to this, the former hysteresis curve is smaller than the latter hysteresis curve, and Mv/
It is clear that Ivb+≧0.5, and it can be seen that a magnetic layer suitable for perpendicular magnetization is formed. This is a surprising fact for iron oxide-based magnetic layers.

In addition, the composition of this magnetic recording medium was analyzed using XMA (X-ray microanalyzer: rX-556JKEVEX, newly manufactured by Hitachi).
-700Q type), it was found that Fe was the main peak, with a small amount of Co present. Furthermore, in order to examine the state of iron oxide, measurements were taken using an X-ray diffraction device (rJDX-10RAj manufactured by JEOL Ltd., using a CuKα tube). As shown in the table below, the magnetic layer mainly consisted of iron oxide. It turned out that it was an ingredient. Moreover, it was observed using an electron microscope that this magnetic layer had an ordered structure in the direction perpendicular to the in-plane direction.

This perpendicularly magnetizable magnetic layer is fundamentally different from conventional coated magnetic layers in that it is made of non-stoichiometric amounts of iron oxide (e.g. Fe The bertolide compound (having a theoretical composition) itself consists of a continuous thin film. In this magnetic layer, the sum of both elements iron and oxygen is 5
The content is preferably 0% by weight or more, and more preferably 70% by weight or more.

Also, the ratio of iron and oxygen is the number of oxygen atoms/the number of iron atoms=
The ratio is preferably 1 to 3, more preferably 4/3 to 2, and the iron oxides listed above are suitable. However, metals other than iron and oxygen or their oxides, nonmetals, semimetals, or compounds thereof are added to the magnetic layer, thereby improving the magnetic properties of the magnetic layer (e.g. coercive force, saturation magnetization, residual magnetization). amount), its crystallinity, and the orientation of the crystal in a specific axial direction. These additive elements or compounds may be mixed into the target in advance, and their types include Co, Co-Mn, Zn, Co-Zn, Li, and C
r, Ti, Li-Cr, Mg-, Mg-Ni', Mn
-Zn, Ni, Ni -Ass Ni-Zn
, CuSCu-Mn, Cu-Zn, etc., but other elements and compounds may also be used.

Further, as the base material that can be used in the magnetic recording medium having the magnetic layer, various materials can be used as long as a magnetic material can be attached thereto. For example, plastics such as polyethylene terephthalate, polyvinyl chloride, cellulose triacetate, polycarbonate, polyimide, polyamide, and polymethyl methacrylate, ceramics such as glass, and metals can be used. The shape of the substrate may be a sheet, a card, a disk, a drum, or a long tape.

If the magnetic layer is formed by the sputtering method according to this embodiment, it can be formed at a much higher speed than a conventional thin film type magnetic layer (or even a magnetic layer by electroless plating). For example, the film forming speed is 10 to 5 μm/min (preferably 200 to 2 μm/n+in), and the film structure has a columnar structure that provides good orientation during crystal growth and good perpendicular magnetization. can be formed.

When forming the iron oxide-based magnetic layer as described above by the sputtering method, it is extremely important to set the thickness of the targets T1, Tp, (see Figure 1) to 14 mm or less. found. This will be explained in detail below.

In manufacturing recording media using the conventional sputtering method, the film formation rate is slow, so in order to increase the formation speed, it is necessary to raise the substrate temperature, but this does not allow the formation of a high-quality magnetic film. Moreover, only heat-resistant substrates can be used, and there are restrictions on the types of substrates that can be used.

On the other hand, it has been found that, based on the method of the present invention, the above drawbacks can be effectively eliminated by reducing the thickness of the target to 14 mm or less. In other words, by setting the target thickness thinner, the leakage magnetic flux from the target increases, which traps electrons in the magnetic flux between the targets and generates high-density plasma. Film formation becomes possible. Furthermore, since high-density plasma is generated by the leakage magnetic flux, it is possible to form a film with low power, and it is possible to prevent the temperature of the substrate from rising.

Thus, in order to obtain a film with good characteristics at high speed, low power, and low substrate temperature, the target thickness should be 14 mm or less.

Figure 4 shows an iron oxide target and an iron oxide target as targets.
This figure shows the residual magnetization ratio (Mν/M+-1) of the magnetic layer obtained when using G and G, respectively (however, the magnetic field generation during sputtering was done by a permanent magnet attached inside the target). . From this result, a film with good characteristics (i.e., Mv
/MH of 0.5 or more), when using an iron oxide target, the target thickness should be 14 m.
m or less (preferably 12 mm or less), and when using an iron target, the target thickness should be 1 mm or less.
It can be seen that it should be 2 mm or less (preferably lQmm or less). However, if the target thickness is too thin, M
Although it does not affect V/MH, it causes a decrease in the mechanical strength of the target and wear, so the target thickness is set to 0.5.
It is appropriate that the thickness be equal to or larger than mm.

The sputtering method described above is not limited to the facing target method, and can be performed using a planar magnetron sputtering device.

6. Effects of the Invention As described above, in the present invention, when forming an iron oxide magnetic layer suitable for perpendicular magnetization by sputtering, the thickness of the target 7) of the magnetic layer constituent material is set to 14 mm or less.
An iron oxide magnetic layer for perpendicular magnetization with excellent properties can be obtained at high speed, low power, and low temperature.

[Brief explanation of the drawing]

The drawings illustrate the present invention, and FIG. 1 is a schematic sectional view of a facing target sputtering apparatus, FIG. 2 is a sectional view of a magnetic recording medium, FIG. 3 is a hysteresis curve diagram of the magnetic recording medium, and FIG. The figure is a graph showing the relationship between target thickness and residual magnetization ratio. In addition, the symbols shown in the drawings are 1---- Vacuum chamber 2--- Exhaust system 3-- Gas introduction system 4.5-- -Holder 6---Substrate 10---One magnetic layer T, Tz---One target. Agent Patent attorney Hiroshi Aisaka (1 other person) = 105 @10

Claims (1)

[Claims] 1. It consists of a continuous layer mainly composed of iron oxide, and the ratio of the residual magnetization (MH>) in the in-plane direction of the magnetic layer to the residual magnetization (Mν) in the direction perpendicular to the plane of the magnetic layer (Mν/MH ) is 0.5
A method for forming a magnetic layer, which comprises using a target made of the constituent material of the magnetic layer and controlling the thickness of the target to 14 mm or less when forming the above magnetic layer on a substrate by sputtering.