JP2003178918A - Rare-earth thin film magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a constitution that can improve the productive efficiency of a rare-earth thin film magnet by reducing the thickness of a protective film, while the conventional constitution makes the productive efficiency of the magnet lower due to the long forming time of the protective film and, at the same time, to improve the corrosion resistance of the magnet even when the thickness of the protective film is reduced. <P>SOLUTION: The magnetic film of the rare-earth thin film magnet is constituted by successively forming a nonmagnetic base film, a rare-earth magnet film, and a nonmagnetic protective film on a substrate. The nonmagnetic protective film is composed of a nitride film containing Ti as the main component. The nonmagnetic base film is also constituted of a nitride film containing Ti as the main component, and the rare-earth magnet film contains Nd, Fe and B as main components. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a micromotor,
A thin film magnet used for a micro device such as a microactuator, particularly a rare earth thin film magnet having excellent magnet characteristics. In a magnetic film formed by sequentially forming a nonmagnetic undercoat film, a rare earth magnet film, and a nonmagnetic protective film on a substrate, The present invention relates to a rare earth thin film magnet characterized by preventing oxidation of a film and improving magnetic properties.

[0002]

2. Description of the Related Art In recent years, motors and actuators have been required to be downsized in accordance with the miniaturization and high performance of electronic devices, and hence the magnets used have been required to be thin.

At present, rare earth magnets having excellent magnet characteristics are mainly used for those applications, and particularly, when the rare earth is R, a magnet having a composition represented by R-Fe-B is often used. However, since the magnet is manufactured by the powder metallurgy method, there is a limit to further reduction in thickness.

Against this background, the above-mentioned R-Fe has been recently used.
-Research on thinning of B-based magnets has been activated. For example, Cadieu et al. Reported for the first time that an Nd-Fe-B thin film was formed and magnetic properties were exhibited (Vac.Sci.Techno.
L., A6, 1688 (1988)).

Further, for the purpose of higher performance, at room temperature substrate temperature, on a Mo substrate or a substrate on which a Mo film is formed,
A magnet film in which a rare earth magnet film and a Ti protective film are sequentially formed has also been reported (JP-A-11-288812). There is a need for a protective film for a magnet film, the characteristics of which tend to deteriorate due to oxidation.

[0006]

However, in the above method, the practical thickness of the protective film is 10 nm to 100 n.
m is needed. Such a film thickness means that the film forming time becomes long, and there is a problem that the production efficiency is low.

It is an object of the present invention to provide a method for thinning a protective film used for suppressing oxidation of a rare earth magnet film so as to improve not only production efficiency but also touch resistance with the same film thickness. To do.

[0008]

To achieve the above object, the present invention is characterized in that a nitride film containing titanium as a main component is formed on the surface of a magnet film as a protective film. That is, the rare earth thin film magnet of the present invention is a magnetic film in which a nonmagnetic undercoat film, a rare earth magnet film, and a nonmagnetic protective film are sequentially formed on a substrate, and the nonmagnetic protective film contains titanium as a main component. It is characterized by being composed of a nitride film. Even if the film is thinner than the conventional film made of titanium or the like, it has the same or more effects. More preferably, the nonmagnetic protective film is made of titanium nitride.

Further, when the non-magnetic underlayer film provided at the interface between the substrate and the rare earth magnet film in the present invention is composed of a nitride film containing titanium as a main component, oxidation of the magnet film due to oxygen diffusion from the substrate can be suppressed, It is effective for further thinning.
Further, in the present invention, the magnet film can be composed of a rare earth magnet having neodymium iron boron (Nd-Fe-B) as a main component, which has large saturation magnetization and coercive force.

When the rare earth thin film magnet of the present invention is applied to an actuator, since the protective film is thin, the distance (magnetic gap) between the member for applying the magnetic field of the magnet film and the magnet can be reduced. For example, MEMS (Micro-Electro Mechanical System) using microfabrication technology or integration technology.
With regard to (s), if the rare earth thin film magnet of the present invention is used to self-hold the driving member (cantilever or mirror supporting member), the magnetic gap is small and the force of the magnet to attract the driving member can be increased. When a constant attracting force is required, the thickness of the rare earth thin film magnet can be reduced, which contributes to thinning and downsizing of the MEMS. The MEMS includes an optical switch, an optical path switching device,
Includes micromachine devices and the like.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION When metallic Ti is formed as a thin film, its surface is likely to be oxidized immediately because of its active property.
Oxidation proceeds from the surface in the film thickness direction, and when the film thickness is thin, the rare earth magnet film is also oxidized. In order to suppress the influence, it is necessary to increase the film thickness.

On the other hand, the material used as the protective film for the magnet film in the present invention is a nitride containing Ti as a main component. T
The i-nitride is not easily oxidized and does not react with the Nd-Fe-B film, so that its magnetic characteristics are not deteriorated. However, in order to realize denseness and crystallinity as a thin film, the film thickness must be a certain value or more.
The present invention requires a thickness of 10 nm or more. The upper limit is not particularly specified, but there is no significant difference in the effect when the thickness is 100 nm or more. However, when applied to an actuator such as MEMS, the upper limit is set to 100 from the viewpoint of thinning the film.
nm is desirable. Therefore, in the present invention, the preferable film thickness is 10 nm or more and 100 nm or less.

The protective film according to the present invention is formed by a vacuum film forming method such as sputtering, ion beam deposition or pulse laser ablation. In the case of the sputtering or ion beam deposition method, the film is formed by using an ordinary inert gas as a discharge medium, and in the case of the pulse laser ablation method, the film is formed in a vacuum, but both methods are performed in a nitrogen atmosphere. May be.

The Ti nitride is not particularly limited to the binary Ti-N alloy, but a small amount of Ti, such as Ta, Si,
Even if the composition is replaced with a metal such as Al, the effect is the same.

Since the Ti nitride film is stable without being oxidized, it can be used not only as a protective layer but also as a base film between the substrate and the magnet film. The Nd-Fe-B magnet film exhibits magnetic properties by being formed at a high substrate temperature or after being formed into a predetermined film structure and then heat-treated in a vacuum. Therefore, the substrate is made of an oxide such as glass. In that case, the magnet film is prevented from being oxidized by oxygen diffusion from the substrate.

The magnet film Nd-Fe-B has Nd of 13 to 15
It is represented by a composition in which atomic%, B is 7 to 11 atomic% and the balance is Fe. When other rare earth elements are added, the structure is replaced with Nd, and the composition of the rare earth elements does not change at this time.
Here, the composition is analyzed by EPMA using a powder magnet sample as a calibration standard.

A sample, which is sequentially formed on the substrate at a substrate temperature of room temperature as in the present invention, exhibits magnet characteristics by being heat-treated at a high temperature of 600 ° C. or higher in a vacuum or in an anaerobic atmosphere. It is disclosed in Japanese Patent Application Laid-Open No. HEI-1 that the magnetic properties of the magnet film are exhibited by forming a protective film and then heat-treating the sample.
No. 1-288812. However, this method is already a technique that is apparent from the embodiment disclosed in Japanese Patent Laid-Open No. 9-237714, and is not special as a process for exhibiting magnetic characteristics. Hereinafter, the present invention will be described in more detail with reference to specific examples.

[0018]

(Example) (Example 1) 10 chambers in the film forming apparatus
^{Evacuate to −8} Pa or less. By irradiating the target mounted in the chamber with the KrF excimer laser, the underlying Ti layer and N are formed on the Si substrate facing the target.
A d-Fe-B magnetic layer and a TiN protective layer are sequentially formed. T
As iN, a target composition having a composition containing approximately 50 atomic% of nitrogen was used. Nd-Fe-B is 13, 70,
A target having a composition of 17 atomic% was used. Irradiation energy of excimer laser is 200m for all film formation
The frequency of J and pulse generation was controlled to 10 Hz. The substrate temperature was room temperature, and the substrate was a 10 mm × 10 mm square MgO single crystal. Here, the underlying Ti layer has a film thickness of 50 n
The thickness of the TiN protective layer was changed to 10 to 200 nm by setting the m and Nd-Fe-B layers to 1 μm. After film formation, the sample was taken out and heat-treated at 700 ° C. for 1 hour in a vacuum environment of 10 ⁻⁴ Pa or less. The results of measuring the magnetic characteristics of the obtained sample with a vibrating magnetometer are shown in FIG. The graph of FIG. 1 shows a sample in which a base film, a magnet film, and a protective film are sequentially formed on a substrate when a Ti protective film is provided and when TiN according to the present invention is used.
Saturation magnetization Bs and coercive force H when a protective film is provided
The film thickness dependence of the magnetic property of c is shown. The circles represent Example 1 of the present invention, and the triangles represent Comparative Example 1.

Comparative Example 1 A sample was prepared under the same conditions as in Example 1 except that the protective layer was Ti. The magnetic characteristics of the obtained sample are shown in FIG.

(Example 2) TiN as a base layer on a substrate
The layer was formed to a thickness of 50 nm, an Nd-Fe-B film was then formed to a predetermined thickness, and a TiN protective film was formed to a thickness of 80 nm. Nd
Different samples were prepared by changing the film thickness of the —Fe—B film within the range of 100 nm to 1.5 μm. Other conditions were the same as in Example 1, and the sample was manufactured. The measurement results of the magnetic properties of the obtained sample are shown in the same FIG. FIG. 2 shows that, in the above film structure, the base film is the T film of the present invention.
The film thickness dependence of the Nd-Fe-B magnet film of the magnetic characteristics is shown for the case of iN and the case of providing the Ti film of the comparative example together with 50 nm. The circles represent Example 2 and the triangles represent Comparative Example 2.

Comparative Example 2 A sample was prepared under the same conditions as in Example 2 except that Ti was used as the underlayer.
The magnetic characteristics of the obtained sample are shown in FIG.

As shown in FIG. 1, when the results of Example 1 and Comparative Example 1 are compared, the sample having the TiN protective film has excellent magnetic properties in the range where the protective film is obviously thin. However, when the film thickness is 100 nm or more, the magnetic properties are almost the same. When the TiN film is also provided on the underlayer, as is apparent from FIG. 2 showing the results of Example 2 and Comparative Example 2, the magnetic characteristics are improved when the film thickness of the Nd-Fe-B magnet film is thin. The effect is remarkable.

[0023]

From these results, it is understood that the TiN protective film is more effective than the conventionally known Ti film. Further, it can be understood that it is effective not only as a protective film but also as a base film. With the configuration of the present invention, the protective film is thinned,
It is possible to improve production efficiency and also improve touch resistance.

[Brief description of drawings]

FIG. 1 is a graph showing the dependence of magnetic properties of saturation magnetization Bs and coercive force Hc on a protective film thickness.

FIG. 2 is a graph showing the dependence of magnetic characteristics on the film thickness of an Nd—Fe—B magnet film.

Claims (3)

[Claims] 1. A nonmagnetic underlayer film, a rare earth magnet film, and
A rare-earth thin-film magnet, wherein the non-magnetic protective film is a magnetic film sequentially formed, and the non-magnetic protective film is composed of a nitride film containing titanium as a main component. 2. The rare earth thin-film magnet according to claim 1, wherein the non-magnetic underlayer film is also composed of a nitride film containing titanium as a main component. 3. The rare earth thin film magnet according to claim 1, wherein the rare earth magnet film has a composition containing neodymium iron boron as a main component.