JPH0620835A - Amorphous magnetic thin film - Google Patents

Abstract

PURPOSE:To obtain the amorphous magnetic thin film having high specific resistance, low coersive force and excellent permeability as well as extremely efficient high-frequency characteristics in permeability. CONSTITUTION:Magnetic thin films of Fe, B and N have multiple metallographical phases and a thickness not exceeding 500Angstrom . An intermediate non- magnetic film is sandwiched between the magnetic films and has a thickness not exceeding 60% of the thickness of the magnetic films.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amorphous magnetic thin film suitable for magnetic core materials such as inductors and transformers used in a high frequency band.

[0002]

2. Description of the Related Art With the progress of weight reduction and high integration of electronic equipment parts, miniaturization of inductors and transformers is required.
Mn-Zn ferrite and Ni-Zn ferrite have been conventionally used as the magnetic core material for such inductors and transformers, and efforts have been made in that range to cope with recent miniaturization. However, in particular for use in 100 MHz _z about more frequency ranges in a ferrite low saturation magnetic flux density, since the magnetic permeability is extremely small, it is necessary to increase the volume of the magnetic material to meet the electrical and magnetic properties, miniaturization Is limited.

[0003]

When used in a high frequency band, it is inevitable to make the material thinner. Ferrite has problems as described above, and further, when it is made thin, the structure required for soft magnetism cannot be obtained. On the other hand, the amorphous alloy has a specific resistance ρ that is inferior to that of ferrite, but is one digit larger than that of a crystalline alloy, and the saturation magnetic flux density Bs is considerably larger than that of flight, so that it is suitable for thinning.

With respect to such an amorphous magnetic alloy thin film, literatures on many component systems have been published so far, and in particular, an amorphous alloy thin film having a high specific resistance ρ is disclosed in JP-A-54- Japanese Patent No. 94428 and Japanese Patent Laid-Open No. 60-152651 refer to an alloy film composed of a transition metal element (Co, Fe) and a semimetal element B and nitrogen N. However, in JP-A-54-94428, the effect of improving the specific resistance ρ, the change of the saturation magnetic flux density Bs and the increase of the perpendicular anisotropy magnetic field Hk are exclusively mentioned, and although the ρ is improved, the anisotropy of It can be seen that the increase in the vertical direction necessarily brings about characteristics that are incompatible with the soft magnetic material of the present invention, and that this component system does not include all but naturally aims at a different material. . Further, in Japanese Patent Laid-Open No. 60-152651, although the improvement of the specific resistance ρ and the saturation magnetic flux density Bs are similarly mentioned, the soft magnetic material intended by the present invention has an extremely large coercive force Hc. is not.

The present invention has been made in view of the above circumstances, and provides an amorphous magnetic thin film having a high specific resistance, a low coercive force, and an excellent magnetic permeability, and yet having an excellent high frequency characteristic of the magnetic permeability. The purpose is to

[0006]

In order to solve the above-mentioned problems, the present invention is composed of a plurality of phases metallurgically in an ingredient system consisting of three elements Fe, B and N (amorphous composite dispersion). Film), a magnetic thin film having a thickness of less than 500 Å is laminated with an intermediate non-magnetic film having a thickness not exceeding 60% of that of the magnetic thin film.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The present invention by the means, has a high specific resistance and a low coercive force and excellent magnetic permeability, those yet obtain very good multilayer amorphous magnetic thin film of the high frequency characteristics of permeability, frequency 100 MHz _z A soft magnetic thin film suitable for high-frequency micro-inductors and transformer magnetic cores having excellent soft magnetism and magnetic permeability of a degree or more is obtained.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings.

The thin film of the present invention is formed by the sputtering method. For the magnetic thin film, a composite target in which boron nitride BN is arranged on an Fe target having a high saturation magnetic flux density is sputtered in a mixed gas atmosphere of Ar + N _2. By doing so, an amorphous composite dispersion film is formed, and the intermediate non-magnetic insulating film is formed by a ceramic such as a nitride system. There is no particular limitation on the composition ratio of Fe and BN in the magnetic thin film, but when Fe / BN <1, the specific resistance ρ is high but the saturation magnetic flux density decreases, which is not desirable, and the BN-rich non-magnetic phase It is desirable that the Fe and Fe-rich magnetic phases are dispersed in a good state. Figure 1
Shows the hysteresis curve of the produced single-layer thin film in the case of the Fe-BN thin film having the content ratio of Fe / BN = 1. The single-layer film has a high specific resistance but does not show such soft magnetism. 2 is shown in FIG.
AIN thin film is sandwiched between the magnetic film and the AIN film as the intermediate insulating layer, that is, the AIN thin film is formed as an intermediate insulating layer on the Fe-BN thin film having the content ratio of Fe / BN = 1, and each film thickness is 1000 angstrom / This is a hysteresis curve of a multilayer film with a thickness of 200 Å and a stacking period of 20. Thus, when the thickness of the magnetic film is 1000 Å, the perpendicular magnetic anisotropy component still exists and soft magnetism is not obtained. The inventors of the present invention have repeatedly studied the thickness of this magnetic film, and by making the thickness of the magnetic film thinner than 500 angstroms, a thin film having excellent soft magnetism and high specific resistance as shown in FIG. 3 is obtained. I got it successfully. That is, FIG. 3 shows that the content ratio of Fe is Fe / BN = 1.
Fig. 3 is a characteristic diagram showing a hysteresis curve of a multilayer film in which each AIN thin film has a film thickness of 120 angstroms / 30 angstroms as a middle insulating layer in a BN thin film and a stacking period is 200. In FIG. 3, H is the hard axis direction (hard).
and E is the direction of the easy axis of magnetization (easy).
It is shown that the measurement magnetic field is applied to the (axis). Figure 4 shows the frequency of the magnetic permeability of a multilayer film with a film thickness of 120 angstroms / 30 angstroms per layer and an AIN thin film as an intermediate insulating layer in a Fe-BN thin film with a content ratio of Fe / BN = 1. It is a figure which shows a characteristic.

The magnetic film / AIN film thickness ratio must not exceed 5/3, that is, the AIN film thickness must not exceed 60% of the magnetic film. Saturation magnetic flux density Bs cannot be obtained. The intermediate insulating layer is not limited to AIN, but a non-magnetic metal nitride film is preferable in terms of magnetic characteristics, and a semi-metal nitride film such as aluminum or silicon is preferable. Specific examples of the present invention will be shown below. Specific Example-1 A multilayer thin film was formed under the following conditions using a high frequency sputtering device. Target: Magnetic substance: Fe Sintered BN chips were arranged on a target and uniformly arranged so that the Fe / BN area ratio was 1/1. Insulator: AIN Sputtering condition: Atmosphere gas: Ar + N ₂ Substrate temperature: 100 ℃ Film thickness: Fe-BN: 120 Å / layer AIN: 30 Å / layer Stacking period: 200 Total film thickness: 3 μm It has a high specific resistance and a low coercive force as shown in FIG. 3, and it is obvious that the magnetic permeability and its frequency characteristic are excellent as shown in FIG. Specific Example-2

The sputtering conditions for the target, the atmosphere gas, and the substrate temperature were the same as those of the concrete example-1, and Fe-
The film thickness per layer of BN and AIN was set as follows, the film thickness ratio was kept constant at 5/1, and the total film thickness was set to 3.0 to 3.8 μm: Fe-BN (Angstrom) / AIN (Angstrom): 500 / 100,200 / 40,100 / 20,50 / 10,20 / 4.

[0012] frequency is shown in FIG. 5 the relationship between the ratio _{μ (50MH z) / μ (} 5MH z) and Fe-B-N film thickness per layer of the permeability at 5MH _z and 50 mH _z. From this, it is understood that the stability with respect to frequency is particularly excellent when the Fe-BN film thickness is in the range of 500 to 100 Å. The frequency is the permeability in 5MH _z was 900 (500 Angstroms) to 1500 (20 angstroms).

[0013]

As described above, according to the present invention, an amorphous alloy magnetic thin film whose component is Fe-BN and has a thickness of less than 500 angstroms is used.
Multilayer amorphous magnetic thin film with high specific resistance, low coercive force and excellent magnetic permeability, and excellent high frequency characteristics of magnetic permeability can be obtained by stacking intermediate non-magnetic films that do not exceed 60%. I understand, this industrial significance,
The effect on the industrial world is great.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing a hysteresis curve of a single-layer thin film in the case of a content ratio of Fe / BN = 1.

[Fig. 2] Hysteresis curve of a multi-layered film in which each AIN thin film has a thickness of 1000 angstroms / 200 angstroms as a middle insulating layer in a Fe-BN thin film having a content ratio of Fe / BN = 1 and a stacking period is 20. It is a characteristic view to show.

FIG. 3 is a characteristic diagram showing a hysteresis curve of a multilayer amorphous magnetic thin film according to a sample of the present invention.

FIG. 4 is a characteristic diagram showing the frequency of magnetic permeability of the multilayer amorphous magnetic thin film according to the sample of the present invention.

[5] The present invention specific mu (50) of each of the magnetic permeability when the frequency of multi-layer amorphous magnetic thin film according to the sample 5MH _z and 50MH _z / μ (5) and a more per Fe-BN film It is a characteristic view which shows the relationship with a film thickness.

[Explanation of symbols]

 H: hard axis of magnetization, E: easy axis of magnetization.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Shinji Furukawa, 6-6 Minamiyoshinari, Minamiyoshinari, Aoba-ku, Sendai-shi, Miyagi 3 Amorphous / Electronic Device Laboratory, Inc. 6-chome 3 Amorphous / Electronic Devices Co., Ltd. (72) Inventor Keiyasu Fujimori 2-20-3 Yoshinari Aoba-ku, Sendai-shi, Miyagi Prefecture (72) Ken Ken Masumoto 3-8-Uesugi, Aoba-ku, Sendai-shi, Miyagi Prefecture twenty two

Claims (1)

[Claims] 1. A magnetic thin film composed of Fe, B and N elements and constituting a plurality of phases in a metallographical manner and having a thickness of less than 500 angstroms. An amorphous magnetic thin film characterized by being laminated with a magnetic film sandwiched therebetween.