JPH0664737B2 - 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 densities and digitalization. As a magnetic recording method, 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 heretofore been mainly used. 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 perpendicular to the in-plane of the magnetic recording medium has recently been developed [for example, S. Iwasaki and W. Nakayama;
Magnetic mode analysis for high-density recording, IEE, transformer, magazine, MAG-13, No. 5, page 1272,
1977 (Ar analysis for the magnetization mode for
high density magnetic recording. IEEE Trans. Mag
n. MAG-13.No.5, p.1272 (1977))] It has become possible to dramatically increase the recording density. As a recording medium used in this perpendicular magnetic recording system, a cobalt-chromium (Co-Cr) alloy film is mainly used as a sputtering method [for example, S. Iwasaki and Kei Ouchi: cobalt-chromium recording having perpendicular magnetization anisotropy. Film, iE, E, Trance, Magazine MAG-14, 849, 1978 (K.Ouchi: Co-Cr recording film with perpendicular
magnetic anisotropy, IEEE Trans. Magn. MAG-14,5,
849 (1978)]], vacuum evaporation method [eg Ryuji Sugita; Co-Cr vertical anisotropic film by vacuum evaporation method Technical Report, MR81-5 (1)
981)] and so on. The barium ferrite other than _{Co-Cr (BaO · 6Fe 2} O 3) is a sputtering method [for example star, Matsuoka, Naoe, Yamanaka; Structure and magnetic properties of C-axis oriented Ba- ferrite film by a facing target sputtering, IEICE Theory (C), J66-C, 1, p.9-16 (Showa 58-01)]
Has been obtained by.

Problems to be Solved by the Invention In these perpendicular magnetic recording media, the Co--Cr alloy film can be formed at a low temperature, but the perpendicular magnetic anisotropy that is a measure of the magnitude of perpendicular magnetization has barium ferrite or strontium. Smaller than ferrite. Therefore, there is a problem in that the film does not become a completely perpendicular magnetic film and the in-plane magnetization component is to some extent destroyed.

On the other hand, since barium ferrite or strontium ferrite can be obtained as a film with almost perfect C-axis orientation, it is possible to form an almost perfect perpendicular magnetization film. However, it is difficult to form strontium ferrite or Ba ferrite on polyimide or aluminum because a substrate temperature of 500 ° C. or higher is required to form a barium ferrite or strontium ferrite film.

Means for Solving the Problems In order to solve the above problems, the present invention does not use a conventional sputtering method or a vacuum deposition method, but a plasma CVD method utilizing a plasma CVD method in which a reactive gas is flowed in plasma to utilize 350
Provided is a method for producing a perpendicular magnetization film composed of a strontium ferrite single-phase C-axis oriented film having a large perpendicular magnetic anisotropy at a low temperature of ℃ or less.

Working inventors have found that by using the plasma CVD method
It has been found that strontium ferrite can be obtained at the following low temperatures. That is, a metal alcooxide containing Sr and Fe, for example, Sr (O.C ₂ H ₅ ) ₂ (diethoxystrontium) and Fe (O.C ₂ H ₅ ) ₃ (diethoxyiron) are dissolved in ethyl alcohol, Argon (Ar) as carrier gas, oxygen (O ₂ ) as reaction gas, high frequency plasma (frequency 13.56MHz), power
0.5W / cm ² or more) with these gases introduced at 350 ℃
The strontium ferrite is produced by decomposing and precipitating on the following substrate.

In this way, it is possible to deposit strontium 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 it is common for CVD (thermal decomposition and deposition) to occur. This is because a reaction that cannot occur energetically in the plasma CVD is possible in the plasma. [For example, page 225 of the thin film handbook, Ohmsha, Dec. 10, 1983] In general, plasma CVD is more efficient than ordinary thermal CVD.
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 strontium ferrite, and it is considered to be the optimum method for synthesizing it at low temperature.

Embodiment An 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 Sr (OR) ₂ bubbler, 17 is a Fe (OR) ₃ bubbler, 18 is an Ar carrier gas cylinder, 19 is an O ₂ reaction gas cylinder, and 20 is a rotary pump.

First, diethoxy strontium [Sr (O ・ C
₂ H ₅ ) ₂ ] and diethoxy iron [Fe (O · C)
₂ H ₅ ) ₃ ] in ethanol [C ₂ H ₅ OH] [Sr
(O · C ₂ H ₅ ) ₂ , Fe (O · C ₂ H ₅ ) ₃ 30 wt% solution] Bubblers 16 and 17 were respectively charged, and argon gas for bubbles was flowed at 20 cc / min and 200 cc / min, respectively. The steam is introduced by the rotary pump 20 onto the polyimide substrate heated to 350 ° C. in the reaction chamber 11 which has been depressurized. Next, the same reaction gas of oxygen 19
It is also flown on the glass substrate at a flow rate of 200 cc / min and introduced into the reaction chamber 11. The gas pressure at this time was 10 Torr. Next, the high frequency power (13.65MHz) is 500W (SW / c
m ² ) was applied for 60 minutes for reaction. .

Next, the film thickness of the strontium ferrite deposited on the polyimide substrate at this time was about 2.0 μm. Next, for this film, X-ray analysis and VSM (vibrating sample magnetometer)
The magnetic properties of the film according to The results are shown in Table 1, Sample No. 1. Substrate temperature, Sr (OR)
₂ 、 Fe (OR) ₃ bubbler amount (Ar flow rate), pressure in the reaction chamber, film thickness when changing high frequency power, X-ray analysis, VSM results are shown in Table 1 Sample Nos. 2-8 Shown in. Further, sample numbers 9 to 16 are comparative examples other than the present invention.

Here, the X-ray analysis investigated whether or not the C-axis orientation was obtained in the single phase of strontium ferrite. Further, the saturation magnetization and hysteresis curve (BH curve) of strontium ferrite were obtained from the results of VSM, and the remanent magnetization in the vertical direction and the remanent magnetization in the horizontal direction of strontium ferrite were obtained (the remanent magnetization in the vertical direction is the remanent magnetization in the horizontal direction). The larger the size, the better the perpendicular magnetization film.) In the scope of claims, the substrate temperature is limited to 350 ° C. or lower, because when the temperature is 350 ° C. or higher, polyimide or Al used as a substrate material is thermally deformed or deteriorated to obtain a high quality strontium ferrite film. Because there is no.

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

The pressure for maintaining the plasma was limited to 0.1 to 10 Torr because the film formation rate of the reaction product (strontium ferrite) was slow at 0.1 Torr or less, which was a problem in practice. Does not grow as a film in
This is because it becomes a powdery substance in the space.

As described above, according to the present invention, it is possible to form a strontium ferrite film excellent as a perpendicular magnetic recording medium at a relatively low temperature of 350 ° C. or less by skillfully utilizing the plasma activity. It is a very useful invention for achieving high density magnetic recording.

[Brief description of drawings]

The figure is a schematic view 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 ……
Sr (OR) ₂ bubbler, 17 …… Fe (OR) ₃ bubbler,
18 …… Ar carrier gas cylinder, 19 …… O ₂ reaction gas cylinder, 20 …… Rotary pump.

Claims (3)

[Claims] 1. Decomposition in a plasma of vapor of metal alkoxide containing strontium (Sr) and iron (Fe), an inert gas as a gas for transporting the vapor, and oxygen (O ₂ ) as a reaction gas. A method for producing a magnetic thin film, which comprises depositing a perpendicular magnetization film composed of a strontium ferrite single-phase C-axis orientation film on a substrate kept at 350 ° C. or lower. 2. The strontium ferrite single phase according to claim 1, wherein the strontium-containing alcohol compound has a chemical formula of Sr (OR) ₂ (where R is an alkyl group). A method for manufacturing a magnetic thin film comprising a C-axis alignment film. 3. The strontium ferrite single phase according to claim 1, characterized in that the iron-containing alkoxide compound has a chemical formula represented by Fe (OR) ₃ (where R is an alkyl group). A method for manufacturing a magnetic thin film comprising a C-axis alignment film.