JPH0593270A - Crystalline thin film and its manufacture - Google Patents

Abstract

PURPOSE:To provide a thin film excellent in magnetic properties. CONSTITUTION:A crystalline thin film shown by Sm2-deltalFe17-delta2X3=delta3(X denotes nitrogen, carbon and hydrogen as well as delta1, delta2 and delta3 satisfy-1 to +1) and a target shown by Sm2-deltalFe17-delta2Xdelta4(delta4 satisfies 0 to 3) are irradiated with ion beams, and sputtered atoms from the target are allowed to arrive on a heated substrate. Simultaneously, the heated substrate is irradiated with ion beams among crystal lattices constituted of nitrogen, carbon and hydrogen in a power level at which sputtering does not occur to form a thin film contg. the atoms of both the target and ion beams among crystal lattices. In this way, the film excellent in magnetic properties and applicable to a medium for magnetic recording or photomagnetic recording can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film and a manufacturing method thereof, and more particularly to a solid thin film having magnetic properties and a manufacturing method thereof.

[0002]

2. Description of the Related Art The method of forming a thin film by an ion beam is the most effective method for obtaining a solid thin film because of its excellent controllability and reproducibility. Various ion beam sputtering methods are used for Ion Beam Assisted Field G
rowth, T .; Itoh, Ed. , Elsevie
r, New York, pp. 1-8 (1989).

Nagakubo, M .; The IEEE T
rans. Magn. , 25 (5) 3892-3895.
Has obtained an ion nitride thin film having semi-hard magnetic characteristics by using two ion beam sputterings and further annealing. Naoe et al. Appl. P
hys. , 64 (10) 5449-51 (1988) discloses that an iron thin film having a low nitrogen content is obtained by periodically irradiating nitrogen ions during two ion beam sputtering.

US Pat. No. 4,484,995 teaches thermally controlled sputtering of highly magnetic anisotropic materials. Two targets of Sm and Fe are deposited on the heated substrate to obtain a Sm2 Fe2 thin film. Materials useful for application in magneto-optical recording devices for magnetic data recording generally have high Curie temperature, spontaneous magnetization moment per unit volume and easy uniaxial anisotropy. Y2 Fe1
7, iron-based intermetallic compounds such as Sm2 Fe17 and Nd2 Fe17 have been investigated for such applications, but have not been realized due to their extremely low Curie temperature. X
iang-Zhong et al. Mater. Sci. ，
23 (1), 329-331 (1988) introduce hydrogen into the crystal lattice (interstitial) to raise the Curie temperature (Tc), but the uniaxial anisotropy is strong enough for practical applications. It states that there is no. The same applies to introducing carbon between crystal lattices.

It has been found that the introduction of crystalline interstitial nitrogen into the lattice of certain rare earth metal intermetallic compounds increases Tc while maintaining strong uniaxial anisotropy. Coey et al. Phys. condensed Matter, 2
(30), 6465 (1990), Sm and YF
The e-nitride powder is obtained by heating fine powder of an iron compound, which is the corresponding intermetallic compound, at 450 to 650 ° C. in the presence of ammonia or nitrogen in a thermal piezo analyzer.

However, for many applications powdered form is not suitable and thin films are preferred. For example, in a magnetic disk for magneto-optical recording, the magnetic substance is desired to be in the form of a thin film having a thickness of 5 microns or less. It is well known that the presence of other interstitial impurities such as nitrogen or hydrogen or carbon is not desirable for the production of thin films.

[0007]

An object of the present invention is to obtain an intermetallic compound crystalline thin film having nitrogen, hydrogen or carbon between crystal lattices, and to obtain such a thin film by an ion beam sputtering method. It is in.

[0008]

The gist of the present invention is a crystalline thin film characterized by the following composition formula (1).

Embedded image Sm2-δ1 Fe17-δ2 X3-δ3 (1) (wherein X represents nitrogen, carbon or hydrogen, and δ1, δ2
, Δ3 are independently -1 to +1. ) And a) irradiating the target represented by the following composition formula (2) with an ion beam to allow sputtered atoms from the target to reach the heated substrate,

## STR00004 ## Sm2-.delta.1 Fe17-.delta.2 X.delta.4 (2) (wherein X represents nitrogen, carbon or hydrogen, and .delta.1, delta2
Are independently -1 to +1 and δ4 is 0 to 3. B) At the same time, the heating substrate is irradiated with a crystal interstitial ion beam of nitrogen, carbon, or hydrogen at a power level that does not cause sputtering to contain atoms from both the target and the crystal interstitial ion beam. A method for producing a crystalline thin film is characterized by forming a thin film on a substrate.

The crystalline thin film of the present invention has a composition represented by the above composition formula (1), that is, Sm2-δ1 Fe17-δ2 X3-δ3, wherein δ1, δ2 and δ3 are independently -1 to -1. It can have a value of +1. Of these, δ1 and δ2 are preferably about 0, and δ3 is Sm2 Fe17
It varies within the range shown according to the amount of nitrogen, carbon or hydrogen introduced interstitialally into the basic structure of.

The minimum film thickness of the thin film is typically about 0.1 micron, but the film thickness can vary from about 0.01 micron to about 1 micron. The most preferable practical thickness is about 0.05.
~ About 0.1 micron. The thin film has an in-plane coercive force of 1.0 KOe or more. The best combination of high Curie temperature, eg, 200 ° C. or higher and strong uniaxial magnetic anisotropy is when X in equation (1) is N. The preferred composition for optimum magnetic properties is Sm2 Fe17 N3.

The present invention is also a method for producing the above-mentioned thin film. The crystalline thin film of the present invention is produced by modifying and applying a technique known in the art as ion beam sputtering in which atoms are emitted from a target upon irradiation with inert gas ions. General methods of ion beam deposition and apparatus useful therefor are known, for example, "Ion Beam Assisted".
Film Groth ", T.W. Itoh, Ed. , El
Sevier, New York, pp. 1-8, 19
89.

According to the invention, the crystalline thin film allows the ion beam to undergo Sm2-δ1Fe17- under at least partial decompression.
δ2 X δ4 (X represents nitrogen, carbon or hydrogen, δ1,
.delta.2 is independently -1 to +1 and .delta.4 is about 0 to 3). Sm and Fe atoms are sputtered on the heated substrate, and at the same time, a thin film of Sm2-δ1Fe17-δ2X3-δ3 is formed on the substrate by the crystal lattice interstitial ion beam irradiated on the heated substrate.

FIG. 1 is a schematic diagram showing an outline of an ion beam apparatus for carrying out the present invention. Referring to FIG. 1, according to the method of the present invention for producing a crystalline thin film, an ion beam 1 under reduced pressure is fed from an ion beam source 2 to Sm2-δ1 Fe.
It is performed by irradiating the target 3 made of 17-δ2 Xδ4, preferably made of pressed powder. S
The m ions 4 and the Fe ions 5 are sputtered and Sm2-
δ1 Fe17− δ2 Xδ4 is emitted onto the surface of the substrate 6. The substrate 6 is preheated to a temperature of about 550 to 650 ° C., and at the same time, a nitrogen, carbon or hydrogen crystal interstitial ion beam 7 is irradiated from a corresponding ion beam source 8. Thus Sm2-δ1 Fe17-δ2X3-δ3 (X
Form a crystalline thin film 9 having a composition of N, C or H).

The ion beam for releasing metal ions from the target is preferably an inert gas ion beam, and argon is preferable from the viewpoint of convenience and economy. The target must have a Sm and Fe source,
N, C or H is required as an optional component. Other rare earth elements may hinder the formation of the thin film composition of the present invention and should be avoided. Typical targets are Sm and Fe
To easily obtain a powder represented by Sm2-δ1 Fe17-δ2 Xδ4 (where X is N and δ4 is almost 0 in the presence of nitrogen) by heating the mixed powder at 600 ° C., for example, in a nitrogen atmosphere. You can When the Sm and Fe powders are pre-reacted in this way, almost the same amount of Sm and Fe as the desired thin film
A target containing atoms is obtained.

The ion beam is a commercially available Kaufman (Kau
fman) source. The ion beam power level is about 500 to 1000 eV and the ion beam current is about 15 to 25 mA. A crystal interstitial ion beam can be obtained similarly, and the power level is about 50 to 35
The ion beam current is about 5 to 10 mA. The power of the crystal interstitial ion beam is adjusted so that the crystal interstitial ion beam itself does not cause sputtering, that is, there is no scattering of Sm or Fe from the substrate surface. Therefore, the power of the crystal interstitial ion beam is maintained at a level lower than the power of the sputtering ion beam.

The substrate on which the thin film is deposited may be any material that can withstand the reaction temperature used and does not react with the deposit. Representative substrates include tantalum, magnesium oxide, quartz and glass. Of these, tantalum is preferable. The method of the present invention is carried out under reduced pressure, for example, at about 1 × 10 ⁻⁶ to 1 × 10 ⁻⁷ Torr, and the atmosphere in which the ions and sputtered atoms are transferred is maintained relatively pure. Sputtering pressure is typically 10 ^-3
Torr, preferably 10 ⁻⁴ Torr. In contrast to typical conventional sputtering, which uses an inert gas plasma between the target and the substrate, the process of the present invention does not yield useful thin films of the composition of the present invention. Different from sputtering. The method of the present invention does not require an inert gas plasma. Two beams of different power are carefully irradiated under reduced pressure in a radius range of less than 3 cm, one beam of which is used for sputtering. The comparative example described below is a method of sputtering with a single ion beam, and a single inert gas ion beam is used to sputter Sm, Fe and N atoms from a target powder on a substrate and is substantially crystalline. It produces a nitrogen-free thin film of interstitials. It is believed that the known methods do not allow nitrogen atoms to penetrate deep enough into the Sm / Fe based structure to the depth required to obtain the desired magnetic properties.

In the method of the present invention, the deposition is hot, ie preheated, preferably from about 550 ° C. to about 65.
Done on a substrate heated to 0 ° C, more preferably about 580 ° C to about 610 ° C. This causes the deposition to be at a sufficiently high temperature to ensure an adequate crystalline interstitial content and consequently the desired magnetic properties. However, if it is too high, the thin film will decompose. Comparative Example 2 described below is 550.
This is an example when performed at a temperature of less than ° C, and both the nitrogen content and the magnetic properties are low. Below 550 ° C,
The complete reaction between Sm / Fe and nitrogen does not occur. If sufficient nitrogen is not introduced, the thin film will have poor magnetic properties.

The thin film of the present invention is useful as a medium for magnetic recording and magneto-optical recording. Further, the manufacturing method of the present invention is useful as a method for manufacturing a thin film having desired magnetic properties.

[0019]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples unless it exceeds the gist of the present invention. General Procedure In the examples and comparative examples, thin films were produced using a two ion beam sputtering system of the type shown in the schematic diagram of FIG. The system had a turbopump vacuum chamber and operated at a base pressure of 10 ^-7 to 10 ^-8 Torr.
The target is obtained by heating Sm and Fe powder in a nitrogen atmosphere at 600 ° C. to obtain a bulk powder containing Sm, Fe and a small amount of adsorbed nitrogen, and pressing the powder. It was pressed into a disk having a diameter of 7.5 cm and a thickness of 0.5 cm. The disc was placed on a copper backing plate fitted with a water cooler. During sputtering, the pressed powder target was maintained at ambient temperature with a copper backing plate water cooler. A commercially available 1 cm square tantalum foil was used as the substrate. The substrate was attached to a copper heating block heated to 550-650 ° C and maintained at this temperature during sputtering.

The sputtering of the target was carried out by using an argon ion beam source having a focus of 3 cm (manufactured by Cammon Wells Scientific Co., USA). The argon ion beam source was 15 cm from the target. 100
An ion current of 20 mA was used with an ion energy of 0 eV. The excitation part of the target was about 4 cm. Nitrogen was introduced into the thin film by irradiating the substrate with a commercially available 1 cm ion beam source (manufactured by Cammon Wells Scientific Co., USA) 15 cm away from the substrate and irradiating the substrate with generated nitrogen ions. Nitrogen ion energy has an ion current of 5 m
A was kept constant and varied from 50 to 350 eV. The thin film deposition rate was about 15 to 25 Å / min (0.0015-0.0025 μm / min). The thickness of the thin film is 1000 to 2000 angstroms (0.
1 to 0.2 μm).

The thin film was analyzed by using a commercially available X-ray diffractometer (Rigaku X-ray diffractometer manufactured by Waltham, USA) using Cuk α rays (wavelength λ = 1.54 Å). The composition of the thin film was measured using a commercially available X-ray X-ray photoelectron spectrometer (XPS, Surface Science Instrument XPS system manufactured by Mountain View, Inc. in the US).
Analysis was performed by irradiating the sample with a 1 mm diameter beam using alpha rays (1465 eV). The energy and intensity of the emitted core level photoelectrons were detected. The energy / intensity of the emitted photoelectrons emitted from each component of the sample is related to the concentration of each sample component. The magnetic properties of the thin film were measured using a commercially available vibrating sample magnetometer.

Example 1 The apparatus according to the above general procedure was set to a reference pressure of 2 × 10 ⁻⁷ Torr, a chamber pressure of Argon only of 9 × 10 ⁻⁵ Torr, a chamber pressure of Nitrogen of 9 × 10 ⁻⁵ Torr, and a sputtering pressure of 2 × 10 ⁻⁴ Torr. 5 tantalum foil substrates
Heated to 90 ° C. Argon ion beam source is ion beam energy 1000 eV, ion beam current 20 m
It was set to A. The nitrogen ion beam source had an ion beam energy of 100 eV and an ion beam current of 5 mA. Sputtering was carried out for 60 minutes, and a thin film having a thickness of 1550 angstrom (0.155 micron) was obtained.

The obtained thin film was analyzed by XPS, and as a result, Sm 12.94 atomic% and Fe7 based on the total Sm / Fe / N.
7.03 atomic% and N 10.03 atomic%, that is, Sm
It was 2.87Fe17.0N2.22. The coercive force is 0 in the vertical direction.
It was 248 kOe and 1.02 kOe in the in-plane direction. The magnetization, σ _S, is 16 emu / g in the vertical direction and 5 in the in-plane direction.
It was 4 emu / g.

COMPARATIVE EXAMPLE 1 The apparatus having the above general procedure was used with a reference pressure of 1 × 10 ⁻⁶ Torr, a chamber pressure of Argon only of 9 × 10 ⁻⁵ Torr, and a chamber pressure of Nitrogen only, since no nitrogen beam was used.
Torr and sputtering pressure were set to 9 × 10 ⁻⁵ Torr. The tantalum foil substrate was heated to 580 ° C. Argon ion beam source has ion beam energy of 1000e
V and ion beam current were 20 mA. No nitrogen ion beam source was used. Sputtering was carried out for 70 minutes, and a thin film having a thickness of 1590 angstrom (0.159 micron) was obtained.

The obtained thin film was analyzed by XPS, and as a result, Sm25.6 atomic% and Fe7 with respect to the total Sm / Fe / N were obtained.
4.4 atomic%, N is 0 atomic%, that is, Sm 5.8 Fe
It was 17.0 N0.0. Coercive force is 0.298k in vertical direction
Oe was 0.073 kOe in the in-plane direction. Magnetization, σ
_S is 12 emu / g in the vertical direction and 20 em in the in-plane direction
It was u / g.

In Comparative Example 1, even if nitrogen was present in the pressed powder of the target, nitrogen of crystal interstitials would not be sputtered into the thin film unless a nitrogen ion beam was used according to the present invention. Indicates. Comparative Example 2 The apparatus in the general procedure described above was used with a standard pressure of 2 × 10 ⁻⁷ torr, chamber pressure of argon only 9 × 10 ⁻⁵ torr, chamber pressure of nitrogen only 9 × 10 ⁻⁵ , sputtering pressure 2 × 1.
Set to ^0-4 torr. Tantalum foil substrate at 525 ℃
Heated to. The argon ion beam source had an ion beam energy of 1000 eV and an ion beam current of 20 mA. The nitrogen ion beam source has an ion beam energy of 20.
It was operated at 0 eV and an ion beam current of 5 mA. Sputtering was carried out for 60 minutes, and a thin film having a thickness of 1540 Å (0.154 micron) was obtained.

The obtained thin film was analyzed by XPS, and as a result, based on the total Sm / Fe / N, Sm 9.61 atomic% and Fe 8
3.8 atom%, N is 6.59 atom%, that is, Sm1.
95Fe17.0N1.41 was out of the composition range of the present application. Coercive force is 0.578 kOe in the vertical direction and 0.170 in the in-plane direction.
It was kOe. The magnetization, σ _S, is 14 emu in the vertical direction.
/ G and 40 emu / g in the in-plane direction.

Comparative Example 2 shows that at a lower temperature used in the process of the present invention, a sufficient amount of nitrogen, which is a crystal interstitial atom, is not sputtered into the thin film, and the thin film has poor magnetic properties. Show.

[0029]

The thin film of the present invention has excellent magnetic properties and can be applied to a medium for magnetic recording or magneto-optical recording.
Further, according to the manufacturing method of the present invention, a thin film having excellent magnetic properties can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an ion beam apparatus used for carrying out a thin film manufacturing method of the present invention.

[Explanation of symbols]

 1 Ion beam for sputtering 2 Ion beam source 3 Target 6 Substrate 7 Crystal interstitial ion beam 9 Crystal thin film

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01F 10/14 7371-5E 41/18 7371-5E // G11B 11/10 A 9075-5D

Claims (2)

[Claims] 1. A crystalline thin film represented by the following composition formula (1): ## STR1 ## Sm2-δ1 Fe17-δ2 X3-δ3 (1) (wherein X represents nitrogen, carbon or hydrogen, and δ1, δ2
, Δ3 are independently -1 to +1. ) 2. A) A target represented by the following composition formula (2) is irradiated with an ion beam to allow sputtered atoms from the target to reach a heating substrate, and Sm2-δ1 Fe17-δ2 Xδ4. .. (2) (In the formula, X represents nitrogen, carbon or hydrogen, and δ1, δ2
Are independently -1 to +1 and δ4 is 0 to 3. B) At the same time, the heating substrate is irradiated with a crystal interstitial ion beam of nitrogen, carbon, or hydrogen at a power level that does not cause sputtering to contain atoms from both the target and the crystal interstitial ion beam. A method for producing a crystalline thin film, which comprises forming a thin film on a substrate.