JPS6286778A - Magnetoresistance effect element - Google Patents

Abstract

PURPOSE:To avoid deterioration in the characteristics of a thin film magnetoresistance element caused by thermal factors by providing a diffusion prohibiting layer between an insulating layer and a ferromagnetic metal thin film which has magnetoresistance effect. CONSTITUTION:A Ti layer is provided between an NiFe alloy film and an SiO2 insulating film which constitute a thin film MR element. With this constitution, mutual diffusion between the NiFe alloy film and the SiO2 insulating film can be prohibited so that a thin film MR element which has sufficient thermal stability can be obtained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a thin film magnetic head for reproduction that detects signals recorded on a magnetic recording medium using the magnetoresistive effect of a metal ferromagnetic thin film, and The present invention relates to a thin film magnetoresistive element (hereinafter referred to as a thin film MR element) used in magnetic rotary encoders and the like that detect changes in magnetic field strength.

(Prior art) In a thin film MR element, the magnetization direction inside the thin film MR element changes due to an external signal magnetic field, and the change in electrical resistance of the thin film MR element corresponding to the change in the magnetization direction is output as an external output. be. When this thin film MR element is used in a magnetic reproduction head, high integration and multi-element technology can be easily realized using semiconductor microfabrication technology, and the head is a magnetic flux responsive type that does not depend on the moving speed of the magnetic recording medium. It is seen as a promising magnetic head for playback in multi-channel fixed head type PCM recorders. Furthermore, it has already been put into practical use as an element for detecting rotation angle in magnetic rotary encoders.

An example of the structure of a thin film MR element is shown in FIGS. 1 and 2.

This thin film MR element is composed of a metal ferromagnetic thin film l made of NiFe alloy, etc., and current terminals 2, 2 for signal detection.The metal ferromagnetic thin film l is processed into a predetermined shape by etching, etc. The current terminal 2.2 is formed by forming and etching a conductor layer such as Aβ on the portion. When constructing a magnetic head using a thin film MR element having such a configuration, a magnetic core (not shown) made of a NiFe alloy or the like is formed on one or both sides of the thin film MR element. Insulating layers such as SiO□ are formed on both sides of the thin film MR element because it is necessary to insulate it from the ferromagnetic thin film l.

Furthermore, even when a magnetic core is not formed like in a magnetic rotary encoder, thin film Ml? S as a protective layer on the element
Insulating layers 4 and 5 such as iot are formed. 3 in the figure is a substrate.

(Problems to be Solved by the Invention) By the way, the thickness of the metal ferromagnetic thin film used in the thin film MR element is very thin by 300 to 500 mm, and therefore a slight amount of diffusion etc. may occur between the insulating layers on both sides. Even if this happens, it will significantly affect the characteristics of the thin film MR element. Regarding the deterioration of the characteristics of the thin film MR element due to this diffusion, the present inventors investigated the change in the magnetic properties of the NiFe film when a sample in which the NiFe film was formed to a thickness of 350 mm was annealed at 200°C and 300°C in vacuum. It was confirmed. The results are shown in FIG. In the figure, the characteristics deteriorate significantly in 2 hours at 300°C, and in particular, the saturation magnetization also decreases, so this characteristic deterioration is caused by the underlying Sin.

This is thought to be due to mutual diffusion with On the other hand, even if the annealing temperature is lowered to 200°C, the characteristics deteriorate considerably, so there is a possibility that the characteristics of the thin-film MR element may already deteriorate due to temperature increase during the manufacturing process of the thin-film magnetic head or magnetic rotary encoder. Furthermore, there is a problem that the heat resistance of the product itself is also deteriorated.

The present invention improves the heat resistance of thin-film MR elements used in thin-film magnetic heads or magnetic rotary encoders, thereby improving the heat resistance of thin-film MR elements used in thin-film magnetic heads or magnetic rotary encoders. The purpose is to prevent deterioration of the characteristics of

(Means for Solving the Problems) According to the present invention, a diffusion prevention layer is provided between a metal ferromagnetic thin film having a magnetoresistive element and an insulating layer.

(Function) The diffusion prevention layer prevents mutual diffusion between the metal ferromagnetic thin film and the insulating layer, thereby preventing deterioration of the characteristics of the thin film MR element.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

First, an experimental example using TiN as the base layer of the NiFe alloy film will be described below.

After forming a Ti layer with a thickness of about 100 layers on a glass substrate by EB evaporation, a Ti layer with a thickness of about 350 layers is formed on a glass substrate. F.

Table 1 shows the change in magnetostriction constant when a sample of an alloy film formed by resistance heating in a magnetic field was annealed in vacuum at 200° C. for 2 hours in the same magnetic field. For comparison, Table 1 also shows changes in the magnetostriction constant of the NiFe alloy film formed on the conventionally used 3,02 underlayer.

[Table 1] The magnetostriction constant in this table is N due to external stress.

It can be easily measured from changes in the uniaxial anisotropy magnetic field of the F0 alloy film, and is extremely sensitive to the composition of the NiFe alloy film, making it suitable for detecting compositional changes due to diffusion between the NiFe alloy film and the underlying layer.

As can be seen from Table 1, when a Ti layer is used as the underlayer, the magnetostriction constant does not change due to annealing, but on the other hand, when a 5=Oz underlayer is used, the magnetostriction constant decreases due to annealing. NiFe alloy film and S, O
□ This shows that the F0 structure in the NiFe alloy film was reduced due to diffusion with the underlying layer. Therefore, N and F become thin film MR elements.

By providing a Ti layer between the alloy film and the S,0□ insulating film, it is possible to prevent diffusion between the NiFe alloy film and the StO2 insulating layer due to temperature rise during normal processing processes, and to ensure sufficient heat. It is possible to obtain a thin film MR element that is economically stable.

Next, an experimental example in which a Ti layer is used as the upper protective layer of the NiFe alloy film will be described below.

As the underlayer, a Ti layer having a thickness of about 100 nm was used, which was formed on a glass substrate by EB evaporation based on the experimental results described above. On this base layer, a NiFe alloy film with a thickness of approximately 350 mm was formed using a resistance heating method in a magnetic field, and then a NiFe alloy film with a thickness of approximately 100 mm was formed using a resistance heating method in a magnetic field.
Table 2 shows the change in magnetostriction constant when a sample with a Ti layer formed thereon was annealed in a vacuum at 200° C. for 2 hours in a magnetic field. For comparison, S was used as an insulating layer directly on the NiFe alloy film.
Table 2 also shows the change in the magnetostriction constant of the sample in which the iO□ layer was formed by the RF bipolar sputtering method.

[Table 2] As shown in Table 2, when the S10□ layer, which serves as an insulating layer, is formed directly on the NiFe alloy film, the magnetostriction constant changes from positive to negative due to annealing, and the experiments shown in Table 1 As in the example, N is caused by diffusion between the NiFe alloy film and the S, O
F in the iFe alloy film.

This indicates that the components have decreased. On the other hand, N and F.

When the T1 layer is formed on the alloy film, the change in the magnetostriction constant is extremely small. Therefore, by providing T4 layers on both sides of the NiFe alloy film that will become the thin film MR element, it is possible to prevent diffusion with the Si ox layer that will become the insulating layer.

As shown in the above experimental example, Ni
T serves as a diffusion prevention layer on both sides of the Fe alloy film.

By providing a layer, 8.0□ insulation and N, F.

Diffusion with the alloy film can be prevented, and deterioration of the characteristics of the thin film MR element due to thermal factors such as temperature increase during processing or temperature history during product use can be prevented. In the above experimental example, a T8 layer is used as a diffusion prevention layer between the thin film MR element and an insulating layer such as 5=Oz, but other than Ti, other materials such as M, W, Ti, etc. can be used as a diffusion prevention layer. High melting point metals or alloys thereof can also be used. Furthermore, although the above experimental example shows the case where a NiFe alloy film is used as the thin film MR element,
It is clear that similar effects can be obtained when other metal ferromagnetic films such as NiF, C, Ni00, etc. are used in addition to the iFe alloy film.

(Effects of the Invention) As described above, according to the present invention, the heat resistance of the thin film MR element can be improved, and deterioration of characteristics due to temperature increase during the processing process or use in a high-temperature atmosphere can be prevented. I can do it.

[Brief explanation of drawings]

Figure 1 is a plan view showing the configuration of a conventionally used thin film MR element, Figure 2 is a cross-sectional view of the element, and Figure 3 is a St O2
FIG. 4 is a characteristic diagram showing changes in magnetic properties of a NiFe alloy film formed directly on an insulating layer to serve as a thin film MR element.

Claims (1)

[Scope of Claims] 1) A magnetoresistive element characterized in that a diffusion prevention layer is provided between a metal ferromagnetic thin film having a magnetoresistive effect and an insulating layer. 2) The magnetoresistive element according to claim 1, wherein the metal ferromagnetic thin film is a NiFe alloy film, the insulating layer is a SiO_2 layer, and the diffusion prevention layer is a Ti layer.