JPH05249211A - Magnetic sensor - Google Patents

Abstract

PURPOSE:To obtain a magnetic sensor which can measure strength of a magnetic field accurately at a low cost and easily by performing temperature compensation fully even if a surrounding temperature changes. CONSTITUTION:A magnetic sensor 1 is constituted by a deposition thin film of a ferromagnetic metal, is constituted by the deposition thin film of the above ferromagnetic metal apart from magnetoresistance elements R1 and R2 with magnetoresistance effect, and has a temperature detection circuit R3 which is formed by a pattern whose line width is 6mum or less. Therefore, temperature of the magnetoresistance elements R1 and R2 can be measured accurately with improved response. thus measuring strength of a magnetic field B accurately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic sensor utilizing the magnetoresistive effect of a magnetoresistive element formed of a thin film of ferromagnetic metal.

[0002]

2. Description of the Related Art Conventionally, magnetic sensors have been widely used as proximity switches, position detectors, electronic lock devices, keyboards, thin film magnetic heads, pressure switching sensors, pattern recognition sensors and the like. A magnetoresistive element having a magnetoresistive effect is widely used as a magnetic sensor for measuring the strength of a magnetic field.

Here, the magnetoresistive effect means a phenomenon in which the internal electrical resistance in a conductor changes when an element such as a ferromagnetic metal thin film is placed in a magnetic field. As a magnetoresistive element utilizing the magnetoresistive effect, one using a compound semiconductor such as indium antimony or gallium arsenide, Ni, Ni—C
Two types are used, one using a magnetically sensitive thin film formed of a ferromagnetic metal such as o or permalloy.

In general, in a semiconductor magnetoresistive element, the internal resistance increases when a magnetic field is applied. That is, the semiconductor magnetoresistive element has a positive magnetic characteristic. On the other hand, in a ferromagnetic magnetoresistive element, its internal resistance decreases when a magnetic field is applied. That is, the ferromagnetic magnetoresistive element has a negative magnetic characteristic.

On the other hand, conventionally, a magnetic sensitive thin film formed of a ferromagnetic metal has a thickness of about 1000 and a ferromagnetic metal such as permalloy on a glass substrate or the like by using a vacuum deposition method or a sputtering method. It is formed by depositing a thin film of angstrom. A magnetoresistive element formed of a ferromagnetic metal thin film is widely used because it has better frequency characteristics than a semiconductor magnetoresistive element. The magnetoresistive element is formed by etching the magnetically sensitive thin film into a zigzag pattern.

However, the magnetoresistive element formed by the pattern of the ferromagnetic metal thin film has a large temperature dependency, and there is a practical problem as it is. That is, the ferromagnetic metal generally has a property that the internal resistance changes depending on the temperature, and the magnetoresistive element has a thin film pattern, and thus is easily affected by the temperature change. Therefore, the internal resistance of the magnetoresistive element changes not only with the strength of the magnetic field but also with the ambient temperature.

As a means for solving this problem, conventionally, two magnetoresistive elements have been provided on the same substrate to differentially perform temperature compensation. An example of a conventional magnetic sensor 16 using a ferromagnetic metal thin film is shown in FIG.
The same magnetoresistive elements 11 and 12 are each about 10 to 20 μm.
Is formed as a pattern having a line width of. The patterns of the magnetoresistive elements 11 and 12 are formed so as to have a quadrature phase difference.

The magnetoresistive elements 11 and 12 have the property that the internal resistance value decreases when a magnetic field is applied at right angles to the longitudinal direction of the pattern lines. When a magnetic field is applied to, the internal resistance value does not change. Therefore, as shown in FIG. 5, when the magnetic field A is applied in the longitudinal direction of the pattern line of the magnetoresistive element 11, the internal resistance value of the magnetoresistive element 12 decreases, but the internal resistance value of the magnetoresistive element 11 decreases. It does not change depending on the magnetic field A.

Therefore, the change in the internal resistance value of the magnetoresistive element 11 directly represents only the change in temperature. On the other hand, the internal resistance value of the magnetoresistive element 12 changes depending on both the strength of the magnetic field A and the ambient temperature. Therefore, the change in the internal resistance value of the magnetoresistive element 12 can be temperature-compensated by the change in the internal resistance value of the magnetoresistive element 11. That is, the strength of the temperature-compensated magnetic field A is measured by measuring the DC voltage at both terminals 13 and 14 of the magnetoresistive element 11 in which the DC current that fluctuates due to the change in the internal resistance value of the magnetoresistive element 12 flows. Can be measured.

[0010]

However, in order to differentially perform temperature compensation using the two magnetoresistive elements 11 and 12 as in the conventional case, the dimensions of the two magnetoresistive elements are accurately measured. It was necessary to manage. In order to temperature-compensate the change of the internal resistance value due to the temperature change of the magnetoresistive element 12, if the dimensional accuracy of the two magnetoresistive elements 11 and 12 is poor, an extra experiment for determining a complicated calculation or a constant is required. This is because

Here, with respect to the dimensions of the magnetoresistive element, the film thickness is determined by vapor deposition, and the line width of the pattern is determined by etching. Among them, the wet etching process greatly varies depending on the concentration of the etching liquid, the liquid temperature, etc., and it is difficult to accurately process the line width of the pattern to a predetermined width.

Therefore, it is difficult to improve the processing accuracy of the two magnetoresistive elements, and for that reason, extra cost is generated. This is especially a problem when the magnetic sensor is used in an environment in which the ambient temperature changes within a range of several tens of degrees.

As a means for solving this problem, a temperature detector for measuring the ambient temperature is provided separately from the magnetic sensor, and the temperature of the magnetic sensor is compensated based on the ambient temperature obtained from the temperature detector. Was also done. However, in this case, it is difficult to measure the temperature of the magnetoresistive element itself, and the ambient temperature is measured at a position distant from the magnetoresistive element by a temperature detector having a different response from the magnetoresistive element. , The temperature of the magnetic sensor could not be compensated accurately.

The present invention has been made to solve the above-mentioned problems, and provides a magnetic sensor capable of accurately measuring the strength of a magnetic field by performing sufficient temperature compensation even if the ambient temperature changes. The purpose is to provide it easily and at low cost.

[0015]

In order to achieve this object, the magnetic sensor of the present invention is a magnetic sensor using a magnetoresistive element having a magnetoresistive effect, which is composed of an evaporated thin film of a ferromagnetic metal. Separately from the magnetoresistive element, the line width is 6 μm and is composed of the evaporated thin film of the ferromagnetic metal.
It has a temperature detection circuit formed in the following pattern.

[0016]

In the magnetic sensor of the present invention having the above construction, when placed in a magnetic field, the electrical resistance value decreases according to the strength of the magnetic field. The strength of the magnetic field is measured by measuring the change in the resistance value and converting it into the strength of the magnetic field.

For example, when the magnetic sensor is used as a rotation speed detector, a permanent magnet is attached to the rotating body, and the magnetic sensor is attached at a position where the permanent magnet can be detected. As the permanent magnet rotates, the internal resistance value of the magnetoresistive element of the magnetic sensor changes periodically. Here, if the ambient temperature changes,
The internal resistance value of the magnetoresistive element also changes according to the ambient temperature.

On the other hand, since the temperature detection circuit is formed of a ferromagnetic metal of the same material as the magnetoresistive element in a pattern with a line width of 6 μm or less, the temperature detection circuit has the same ambient temperature as that of the magnetoresistive element. Although affected by the change, it is hardly affected by the change in the magnetic field strength as compared with the magnetoresistive element. Therefore, by performing temperature compensation of the magnetoresistive element using the output of this temperature detector, it is possible to obtain an accurate magnetic sensor that is not affected by the ambient temperature.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic sensor 1 according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a magnetic sensor 1 using the magnetoresistive elements R1 and R2. On the magnetic sensor 1, two zigzag patterns of the magnetoresistive elements R1 and R2 are formed so as to each have a phase difference of a right angle.

Here, the magnetoresistive elements R1 and R2 are both formed as a zigzag pattern having a line width of about 10 to 20 μm. In addition, the temperature detection circuit R3 is about 4μ
Is formed as a meandering pattern having a line width of. In this embodiment, permalloy (Ni-Fe, 83:17) is used as the ferromagnetic metal as the material of the magnetoresistive elements R1 and R2 and the temperature detection circuit R3.

The magnetoresistive elements R1 and R2 have a property that the resistance value decreases when a magnetic field is applied at right angles to the longitudinal direction of the pattern lines, and the magnetic field is applied in the longitudinal direction of the pattern lines. When received, the resistance value does not change. Terminals 2 and 3 are arranged at both ends of the magnetoresistive element R1, and terminal parts 3 and 4 are arranged at both ends of the magnetoresistive element R2. Terminals 5 and 6 are arranged at both ends of the temperature detection circuit R3.

Next, the detection circuit of the magnetic sensor 1 will be described. FIG. 2 shows a detection circuit of the magnetic sensor 1. A DC voltage E is applied between the terminals 2 and 4. Then, the DC voltage between the terminals 3 and 4 is output as the output A17.

On the other hand, the external resistor S1 is connected to the terminal portion 6 of the temperature detector R3, and the other terminal portion 7 of the external resistor S1 is connected to the DC power source. In this embodiment, the external resistance S1 has a TCR of several tens of ppm / degree. A DC voltage E is applied between the terminals 5 and 7. Then, the DC voltage between the terminals 6 and 7 is output as the output B18.

Next, the case where the ambient temperature changes will be described. First, the temperature detection circuit R3 will be described. The data that the present inventor conducted an experiment are shown in FIG. The horizontal axis shows the line width of the pattern in micron units, and the vertical axis shows the magnetoresistance change rate when the pattern is used as a magnetoresistive element. The data obtained by experimenting the magnetic field strength at 100 gauss is shown by the dotted line 8, the data obtained by experimenting at the magnetic field strength at 50 gauss is shown by the alternate long and short dash line 9, and the magnetic field strength is 25
The data experimented with Gauss is shown by the solid line 10.

From this data, it can be seen that the rate of change in magnetoresistance of the magnetoresistive element decreases as the pattern width decreases. Therefore, if a pattern having a line width smaller than the pattern width of the magnetoresistive elements R1 and R2 is used as the temperature detection circuit R3, the influence of the magnetic field strength of the temperature detection circuit R3 is small. It is possible to perform temperature compensation more accurately than the magnetoresistive element 11 which is a temperature compensation circuit using the.

That is, as compared with the case of the temperature compensating circuit using a pattern having a large line width, the temperature detecting circuit R3 using a pattern having a small line width is less affected by the strength of the magnetic field. However, even if there is an error in the line width manufacturing accuracy, accurate temperature detection can be performed.

Further, from this data, it is understood that the rate of change in magnetoresistance is remarkably reduced when the line width of the line forming the pattern of the magnetoresistance element is set to 6 μm or less. Therefore, if the pattern width is set to 6 μm or less, it is understood that even if a ferromagnetic metal thin film made of the same material as the magnetoresistive element is used, the internal resistance value of the thin film changes little depending on the strength of the magnetic field.

On the other hand, the change of the internal resistance value due to the change of the ambient temperature is not affected by the pattern width. Therefore, if the ferromagnetic metal thin film is formed with the pattern width of 6 μ or less, it has an excellent property as a temperature detecting circuit. I understand. That is, since the temperature detection circuit R3 is made of a ferromagnetic metal thin film made of the same material as the magnetoresistive elements R1 and R2 and has a pattern width of 6 μm or less, the temperature detection circuit R3 is resistant to changes in ambient temperature. And fluctuates with the same response as the magnetoresistive element. Therefore, if the temperature detection circuit R3 is used, the temperature of the metal under the same conditions as the magnetoresistive element itself is measured, and the temperature of the magnetoresistive element can always be accurately detected.

Next, a description will be given of a method of temperature-compensating a change in the internal resistance value, which is caused by a change in magnetic field strength of the magnetoresistive elements R1 and R2 and a change in temperature, by the measured temperature. FIG. 4 is a block diagram showing the temperature compensation circuit 19 for temperature compensation. The temperature compensation circuit 19 includes a CPU 2 which is an arithmetic processing unit.
1, an interface 20 which is an input / output relay, a ROM 23 for storing a calculation program, and a RAM 22 for temporarily storing data and the like are connected.

The ROM 23 stores a magnetic detection amount temperature correction program 24. The output A17, which is the output voltage of the magnetoresistive elements R1 and R2, and the output B18, which is the output voltage of the temperature detection circuit R3, are input to the interface 20. The output a25 is output.

The input output A17 contains change information of the internal resistance value due to the strength of the magnetic field and the temperature changes of the magnetoresistive elements R1 and R2. The input output B18 is
Only the change information of the internal resistance due to the temperature change of the temperature detection circuit R3 is included. The magnetic detection amount temperature correction program 24 corrects the value of the output A17 by the output B18 to calculate the strength of the magnetic field. Since the program is a general program, detailed description will be omitted.

In this embodiment, permalloy (Ni-Fe, 83:17) is used as the ferromagnetic metal material, but the same applies when the alloy component ratio is changed.
The same applies when Ni or Ni—Co is used as the material. Further, although the bias magnet is not used in this embodiment, the same effect can be obtained even when the bias magnet is used. Further, in the present embodiment, the temperature detection circuit R3 is used only for temperature compensation of the magnetic sensor, but by using the temperature detection circuit R3 as a temperature sensor, a composite sensor capable of measuring both temperature and magnetism can be obtained. You can

[0033]

As is apparent from the above description, according to the magnetic sensor of the present invention, in addition to the magnetoresistive element having the magnetoresistive effect, which is composed of the evaporated thin film of the ferromagnetic metal, Since the temperature detection circuit is composed of a vapor-deposited thin film of body metal and has a line width of 6 μm or less, the temperature of the magnetoresistive element can be accurately measured with high responsiveness. Can measure accurately.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a magnetic sensor using a magnetoresistive element according to an embodiment of the present invention.

FIG. 2 is a detection circuit diagram of a magnetic sensor according to an embodiment of the present invention.

FIG. 3 is a data diagram showing the relationship between the pattern width of a magnetoresistive element and the rate of change in magnetoresistance.

FIG. 4 is a control block diagram for temperature compensation of the magnetic sensor according to the embodiment of the present invention.

FIG. 5 is a detection circuit diagram of a conventional magnetic sensor.

[Explanation of symbols]

 1 Magnetic Sensor 2, 3, 4 Terminal 19 Temperature Compensation Circuit 24 Temperature Correction Program of Magnetic Detection Amount B Magnetic Field R1, R2 Magnetoresistive Element R3 Temperature Detection Circuit S1 External Resistance

Claims (1)

[Claims] 1. A magnetic sensor using a magnetoresistive element having a magnetoresistive effect, which is formed of a vapor-deposited thin film of ferromagnetic metal, and is formed of a vapor-deposited thin film of the ferromagnetic metal, separately from the magnetoresistive element. A magnetic sensor having a temperature detection circuit formed in a pattern having a line width of 6 μm or less.