JPH0664736B2 - Method for manufacturing magnetic thin film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a magnetic thin film that enables high density perpendicular magnetic recording.

2. Description of the Related Art In recent years, magnetic recording is progressing toward higher density and digitization. Conventionally, a magnetic recording method based on so-called in-plane magnetization, which has an easy axis of magnetization in the plane of the magnetic recording medium, has been mainly used as a magnetic recording method. However, in this method, as the recording density is increased, the magnetization directions in the magnetic recording medium are arranged so as to repel each other, which makes it difficult to achieve high density. Therefore, as a new method of magnetic recording, a so-called perpendicular magnetic recording method having an easy axis of magnetization in the direction perpendicular to the in-plane of the magnetic recording medium has recently been developed [eg S Iwasaki and Wai Nakayama; high density recording. For magnetic mode analysis,
EE, Trance, Magazine, MAG-13, No. 5, 1272, 1977 (Ar analysis for the magnetization mod
e for high density magnetic recording.IEEE Trans.
Magn. MAG-13.No.5, p.1272 (1977))] It has become possible to dramatically increase the recording density. The recording medium used in this perpendicular magnetic recording system is cobalt-
Chromium (Co-Cr) alloy film is mainly used for the spatter method [eg S. Iwasaki and K. Ouchi: Cobalt-chrome recording film with perpendicular magnetization anisotropy, I.E.
E, Transformer, Magazine, MAG-14, 849, 197
8 years (K.Ouchi: Co-Cr recording film with perpendicular magnetic anisotr
opy, IEEE Trans.Magn.MAG-14,5,849 (1978)], vacuum deposition method [eg Ryuji Sugita; Co-Cr vertical anisotropic film by vacuum deposition method, IEICE Technical Report, MR81-5 (1981)] ] Etc. are being developed. The barium ferrite other than _{Co-Cr (BaO · 6Fe 2} O 3) is a sputtering method [for example star, Matsuoka, Naoe, Yamanaka; C axis by facing target sputtering orientation Ba
-Structure and magnetic properties of ferrite film, Theory of theory (C), J66-
C, 1, p. 9-16 (Showa 58-01)] Problems to be Solved by the Invention In these perpendicular magnetic recording media, the Co--Cr alloy film is
It can be prepared at low temperature, but its perpendicular magnetic anisotropy, which is a measure of the magnitude of perpendicular magnetization, is smaller than barium ferrite. Therefore, there is a problem that a perfect perpendicular magnetization film is not formed, and the in-plane magnetization component is hampered to some extent.

On the other hand, with barium ferrite, a film with almost perfect C-axis orientation can be obtained, so that an almost perfect perpendicular magnetization film can be formed. However, it is difficult to form Ba ferrite or hexagonal ferrite on polyimide or aluminum because a substrate temperature of 500 ° C. or higher is required to form barium ferrite or hexagonal ferrite film.
Also, barium ferrite alone has a large perpendicular magnetic anisotropy and a coercive force (coercive force) of 2000 to 30 as a magnetic recording medium.
Since it becomes as high as 00 Oersted (Oe), for example, in a ferrite head (Mn-Zn ferrite head), it is difficult to sufficiently magnetize the medium because the saturation magnetic flux density (Bs) is small. [For example, recording on a high coercive force medium by a sputtered alloy film head, IEICE Technical Report MR77-2 (1977) p. 11] Means for Solving Problems The present invention is directed to solving the above problems. Instead of the conventional sputter vacuum deposition method, a plasma CVD method is used, in which the reaction gas is flowed in the plasma and the plasma activity is utilized.
Provided is a method for producing a perpendicular magnetization film composed of a hexagonal ferrite single phase having a coercive force (coercive force) smaller than that of a barium ferrite single phase at a low temperature of ℃ or less.

Working inventors have found that by using the plasma CVD method
It has been found that hexagonal ferrite having a small coercive force can be obtained at the following low temperatures. That is, a metal alkoxide containing Fe, Ba, Co, Ti, such as Fe (O.C.
₂ H _{5) 3} (diethoxy _{iron) Ba (O · C 2 H} 5) 2 ( diethoxy _{barium) Co (O · C 2 H} 5) 3 ( diethoxy _{cobalt) Ti (O · C 2 H} 5) 4, (Diethoxytitanium) is dissolved in ethyl alcohol, argon is used as a carrier gas, oxygen is used as a reaction gas, and these gases are introduced into high-frequency plasma (frequency 13.56 MHz). Hexagonal ferrite is produced by decomposition and precipitation.

In this way, it is possible to deposit hexagonal ferrite at low temperatures because in plasma there are many chemical species such as active radicals and ions that cause chemical reactions at low temperatures, and the usual CVD (decomposition and deposition by heat) This is because a reaction that cannot occur energetically in the plasma CVD is possible in the plasma. [For example, 225 pages of thin film handbook, Ohmsha, Dec. 10, 1983] In addition, plasma CVD method is generally compared with ordinary thermal CVD method.
Not only can high-melting substances such as oxides, carbides, and nitrides be synthesized at low temperatures, but a high-purity film with good crystallinity can be obtained even at low temperatures because of the thermal decomposition and precipitation reaction. Therefore, it is necessary to have good crystal orientation such as hexagonal ferrite, and it is considered to be the optimum method for synthesizing it at low temperature.

Embodiment One embodiment of the present invention will be described below with reference to the drawings. The figure shows a schematic view of a plasma CVD apparatus in an embodiment of the present invention. In FIG. 1, 11 is a reaction chamber, 12 is a high frequency electrode, 13 is a high frequency power supply, 14 is a substrate heating holder, 15 is a substrate, 16 is a bubbler of Fe (OR) ₃ , 17 is a bubbler of Ba (OR) ₂ , 18 is a Co (OR) ₃ bubbler, 19 is a Ti (OR) ₄ bubbler, 20 is a carrier gas (Ar) cylinder, 21 is a reaction gas (O ₂ ) cylinder, and 22 is a rotary pump.

First diethoxy iron _{[Fe (O · C 2 H 5} ) 3 ], diethoxy barium _{[Ba (O · C 2 H 5} ) 2 ], diethoxy cobalt _{[Co (O · C 2 H 5} ) 3 ], diethoxy Titanium (Ti
(O · C ₂ H ₅ ) ₄ ] 30% alcohol (C ₂ H ₅ OH)
Argon gas 20 for bubbles is added to the bubblers 16, 17, 18, and 19 containing the solution, respectively 200 cc / min, 50 cc / min, 10 cc / min, 10 cc
The flow rate of these vapors is increased by the rotary pump 22
345 ℃ in the reaction chamber 11 which was depressurized by
Introduced onto a heated polyidal substrate. Then again,
Oxygen 21 which is a reaction gas is flown on the polyimide substrate at a flow rate of 200 cc / min. The gas pressure at this time was 10 Torr. Next, high frequency power (13.56MHz) 500W (5W / cm ² )
Was applied for 60 minutes to react.

Next, the film thickness of the hexagonal ferrite deposited on the polyimide substrate at this time was about 2.5 μm. Next, the magnetic characteristics of this film were measured by X-ray analysis and VSM (vibrating sample magnetometer). The results are shown in Table 1, Sample No. 1
Shown in.

Similarly, the substrate temperature, Ba (OR) ₂ , Fe (OR) ₃ , Co
(OR) ₃ Ti (OR) ₄ bubbler amount (Ar flow rate), pressure in reaction chamber, film thickness when changing high frequency power, X-ray analysis, VSM results 2-9.
Further, sample numbers 10 to 16 are comparative examples other than the present invention. Here, X-ray analysis examined whether or not C-axis orientation was obtained in a single phase of hexagonal ferrite. Also, from the results of VSM, the saturation magnetization and hysteresis curve of hexagonal ferrite (B
-H curve) was obtained to obtain remanent magnetization in the vertical direction (direction perpendicular to the film surface of the thin film) of hexagonal ferrite, and remanent magnetization in the horizontal direction and coercive force (remanent magnetization in the vertical direction was remanent in the horizontal direction). The larger the size, the better the perpendicular magnetization film.) In the present invention, the substrate temperature is limited to 350 ° C. or lower because thermal deformation or deterioration occurs in polyimide or Al used as the substrate material at 350 ° C. or higher, and a good quality hexagonal ferrite film cannot be obtained. Is.

Also, the plasma power was limited to 0.5W to 10W by 0.5W / cm
^This is because single-phase hexagonal ferrite cannot be synthesized sufficiently in the gas phase with a plasma power of ² or less.
This is because at m ² or more, the electric power is too strong and the hexagonal ferrite formed in the gas phase is redissolved and the phases other than hexagonal ferrite (Fe ₃ O ₄ etc.) precipitate.

Moreover, the reason why the pressure for maintaining the plasma is limited to 0.1 to 10 Torr is that the film formation speed of the reaction product (hexagonal ferrite) is slow at 0.1 Torr or less and there is a problem in practical use. This is because it does not grow as a film and becomes a powdery substance in space.

EFFECTS OF THE INVENTION As described above, according to the present invention, by making good use of the activity of plasma, the remanent magnetization in the vertical direction is large and the coercive force in the vertical direction is relatively high at a relatively low temperature of 350 ° C. or less. It is a method capable of forming a small hexagonal ferrite film, and is a very useful invention for achieving high density magnetic recording.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a plasma CVD apparatus in one embodiment of the present invention. 11 …… Reaction chamber, 12 …… High frequency electrode, 13 …… High frequency power supply, 14 …… Substrate heating holder, 15 …… Substrate, 16 ……
Fe (OR) ₃ bubbler, 17 …… Ba (OR) ₂ bubbler,
18 …… Co (OR) ₃ bubbler, 19 …… Ti (OR) ₄ bubbler, 20 …… Ar carrier gas cylinder, 21 …… Reaction gas (O ₂ ) cylinder, 22 …… Rotary pump.

Claims (5)

[Claims] 1. Iron (Fe), barium (Ba), cobalt (C)
o) and titanium (Ti) -containing metal alcohol oxide alcohol solutions, and from these alcohol solutions,
Argon (Ar) as a gas for transporting the vapor of metal alcooxide and oxygen (O ₂ ) as a reaction gas are decomposed in plasma to form a perpendicular magnetization film composed of a hexagonal ferrite single phase on a heated substrate. A method for producing a magnetic thin film, which comprises depositing. 2. The hexagonal ferrite single phase according to claim 1, wherein the chemical formula of the iron-containing alcohol compound is represented by Fe (OR) ₃ (where R is an alkyl group). Of manufacturing a magnetic thin film comprising. 3. A barium-containing alcohol compound having a chemical formula of Ba (OR) ₂ (wherein R is an alkyl group)
The method for producing a magnetic thin film comprising a single phase of hexagonal ferrite according to claim 1, characterized in that: 4. An alcooxide compound containing cobalt has a chemical formula of Co (OR) ₃ (where R is an alkyl group).
The method for producing a magnetic thin film comprising a single phase of hexagonal ferrite according to claim 1, characterized in that: 5. The titanium-containing alcohol compound has a chemical formula of Ti (OR) ₄ (where R is an alkyl group).
The method for producing a magnetic thin film comprising a single phase of hexagonal ferrite according to claim 1, characterized in that: