JP3070193B2 - Method of manufacturing magnetoresistive element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetoresistive element comprising a ferromagnetic thin film of a nickel alloy, which is used in a magnetic phase / displacement detector.

[0002]

2. Description of the Related Art Among rotation detection devices currently mainly used, an optical rotation detection device using an optical semiconductor and a magnetic rotation detection device using a Hall IC have a heat resistant temperature of 125.
It is below ℃, which is a major obstacle when used for industrial equipment. Therefore, the use of ferromagnetic magnetoresistive elements having a heat-resistant temperature of 200 ° C. or more for industrial equipment is increasing. Especially in the field of electrical components,
There are many electronic components that require heat resistance of 180 ° C. or higher, and it is clear from the physical properties of the detector that rotation detection devices other than ferromagnetic magnetoresistive elements cannot be used. .

On the other hand, a ferromagnetic magnetoresistive element is formed on a glass or ceramic substrate or the like by a nickel alloy having a thickness of about 5 mm.
The ferromagnetic thin film is formed by patterning a ferromagnetic thin film having a thickness of 00 ° and coating a protective film such as SiN thereon. Since a ferromagnetic thin film exhibits strong shape anisotropy in all directions, in the case of a magnetoresistive element used by generating anisotropy in the longitudinal direction of a pattern, the surface state of the substrate must be mirror-finished.

A ferromagnetic magnetoresistive element converts a change in resistance (magnetoresistive effect) due to a magnetic field into an electric signal. At this time, the magnetoresistive change characteristic has the greatest influence on the electric signal output. . The magnetoresistance characteristics are influenced by the following factors. 1. 1. Surface smoothness of substrate 2. Shape anisotropy of ferromagnetic magnetoresistive thin film 3. Crystal anisotropy of ferromagnetic magnetoresistive thin film Electron spin orientation of the ferromagnetic magnetoresistive thin film Among these, factors 1 and 2 can be expected at the time of selecting a material to be used or at the stage of pattern design.

On the other hand, the factors 3 and 4 are considered to be determined when the ferromagnetic magnetoresistive thin film is formed. Therefore, these phenomena are controlled by the following method. 1. 1. Deposition in a magnetic field 2. Oblique deposition at a certain angle of 90 ° or less with respect to the substrate. High-temperature annealing in a magnetic field The improvement of the magnetoresistance effect by the above method is extremely susceptible to external influences. Therefore, the control of crystal anisotropy and electron spin orientation of ferromagnetic magnetoresistive thin films is currently an industrial issue. It is not currently considered.

In addition, when the magnetoresistive element is used as a magnetic sensor, it is extremely difficult to use the magnetic sensor unless the resistance change rate is 2% or less and the midpoint potential change is 5 mV or less when applied at 5 V in continuous use. It is.

[0007]

Hereinafter, a conventional magnetoresistive element will be specifically described.

In the conventional method, as shown in FIG. 5, a magnetoresistive thin film made of a nickel alloy is formed on an alkali glass, borosilicate glass, or glazed alumina substrate, and a protective film such as SiN is formed thereon. It was done. Here, 2 is a ferromagnetic magnetoresistive element, 4 is a substrate, and 3 is a protective film.

The rate of change of the resistance value of this magnetoresistive element Δρ / ρ
Is about 3.5% at room temperature, and the only way to obtain further characteristics is as follows. 1. 1. Deposition in a magnetic field Oblique deposition 3. Annealing in a magnetic field These methods have the following disadvantages. 1. 1. Stable characteristics cannot be obtained. 2. There are difficulties in the construction method, and mass production equipment cannot be designed. FIG. 3 shows the amount of change in the midpoint potential due to continuous use at 200 ° C. in the conventional method. FIG. 3 shows that all the methods are shifted to the minus side by 10 mV or more.

From the above, the following problems are conceivable in the conventional substrate. 1. 1. Diffusion of alkali components or halogen molecules contained in a substrate into a nickel alloy by electrophoresis. 2. Heat transfer at the interface between the substrate material and the nickel alloy thin film Movement of crystal grains in magnetoresistive thin film In view of the above problems, a magnetoresistive element that easily improves the magnetoresistive effect by 0.5% or more and has a midpoint potential change of 1 mV or less when used at 200 ° C. for 3000 hours or more. The purpose is to provide a low-cost.

[0011]

Means for Solving the Problems The present invention to achieve the above ^{object, Na +, K +, Cl} - content 10ppm of
Form a ferromagnetic thin film of nickel alloy on the following substrate surface,
Aging by high temperature load is performed.

[0012]

According to the present invention, to heat by a nickel alloy thin film Na ^+, K ^+, Cl ^- to eliminate the influence of diffusion, such as the Na ^+, K ^+, Cl ^- content 10ppm or less of
By using a lower substrate and applying a high temperature load, the nickel alloy thin film pattern self-heats and ages, thereby relaxing the stress of the nickel alloy thin film with the substrate and further reducing the anisotropy of the crystal grains of the magnetoresistive thin film. Orient in the longitudinal direction of the magnetoresistive thin film pattern. In addition, the transfer of a trace amount of alkali contained in the substrate is terminated by heat and electrons in the metal thin film so that the resistance of the nickel alloy thin film does not change at all during continuous use at 200 ° C. for 3000 hours or more. did.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a magnetoresistive element according to one embodiment of the present invention will be described below. FIG. 1 shows the structure of a magnetoresistive element according to one embodiment of the present invention, where 1 is a substrate, 2
Is a ferromagnetic thin film of a nickel alloy, and 3 is a protective film made of SiN. Note that sapphire or the like is used as an example of the substrate 1.
A substrate made of such a material can be used.

In this embodiment, aging was performed by applying a 5 V voltage to a 1000 Ω magnetoresistive element at 200 ° C. for 100 hours. FIGS. 2A and 2B are characteristic diagrams showing the resistance change rate Δρ / ρ representing the magnetoresistance effect of the elements of the present embodiment and the conventional example, where the vertical axis represents the magnetoresistance change rate, The horizontal axis indicates the magnetic field strength. According to this, it was found that in the device according to the present example, Δρ / ρ was improved by about 0.75% from the conventional 3.5% to 4.25%. FIG. 3 shows the result of the midpoint potential drift amount after continuous use at 200 ° C. using the device of the present example. The horizontal axis represents time, and the vertical axis represents the drift amount of the midpoint potential. . In the figure, conventional examples 1, 2, and 3 respectively use borosilicate glass, alkali glass, and glazed alumina for the substrate. According to this, the conventional example is 1
In contrast to the drift of 0 mV or more, in the present embodiment, the drift is 0.1 mV.
It can be seen that only 5 mV drifts. FIG. 4 shows the change over time of the resistance value when 5 V is applied at 200 ° C. using the device according to the present embodiment and the devices according to the conventional examples 1, 2, and 3. According to this, compared to the conventional example,
It can be seen that the embodiment of the present invention has hardly changed.
In addition, although sapphire was explained as an example of the substrate 1,
As mentioned in the description of the action that ^{predicate, Na +, K +, Cl} - of
A substrate having a content of 10 ppm or less may be used.

Further, compared with the conventional oblique deposition, magnetic field deposition, or magnetic field annealing, the number of substrates processed per process is about 2 times.
It turned out to be 0 times. As described above, according to the present embodiment, 2. The magnetoresistance effect Δρ / ρ is improved by 0.5% or more 2. In continuous use at 200 ° C., there is no drift of the midpoint potential. The effect is obtained that a large number of high-output, thermally stable magnetoresistive elements can be obtained easily and easily.

[0016]

As described above, according to the present invention, the magnetoresistance effect is easily improved by 0.5% or more,
When used for 0 hours or more, a magnetoresistive element having a midpoint potential change of 1 mV or less can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view of a magnetoresistive element according to one embodiment of the present invention.

FIG. 2A is a characteristic diagram showing a magnetoresistive effect of the present embodiment; FIG. 2B is a characteristic diagram showing a conventional magnetoresistive effect;

FIG. 3 is a characteristic diagram showing a midpoint potential drift amount of the present embodiment and a conventional example.

FIG. 4 is a characteristic diagram showing resistance value change rates of the present embodiment and a conventional example.

FIG. 5 is a sectional view of a conventional magnetoresistive element.

[Explanation of symbols]

1 substrate 2 ferromagnetic thin film 3 protective film

Claims (1)

(57) [Claims] 1. A Na ^+, K ^+, Cl ^- content of 10pp
2. A method for manufacturing a magnetoresistive element, comprising forming a ferromagnetic thin film of a nickel alloy on a substrate surface of not more than m and performing aging under a high temperature load.