JP2002131407A - Thin film magnetic field sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic field sensor having a simple constitution and high magnetic field detection sensitivity and no error due to temperature variation and capable of detecting the absolute value of impressed magnetic field intensity. SOLUTION: A conductive film 6 is arranged on both sides of a large magnetic field resistance thin film, an element 10 provided with electric terminals 8 and 9 is introduced and a bridge circuit consisting of an element 5 and the element 10 as two arms is formed. Although the sensitivity for a magnetic field of electric value of the element 10 is practically zero in a small magnetic field, electric resistance value variation due to a cause other than magnetic field impression is equal to the element 5. The output voltage of the bridge is proportional to the difference of the electric resistance values of the element 5 and 10 and so variation causes other than those of magnetic field impression such as temperature variation of the large magnetic resistance thin film are cancelled from the output voltage of the bridge. Thus an exact impressed magnetic field value can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film magnetic field sensor for measuring a magnetic field in a space, and more particularly to a thin film magnetic field sensor for accurately measuring a magnetic field using a giant magnetoresistive thin film, for example, a nanogranular giant magnetoresistive thin film. It is about.

[0002]

2. Description of the Related Art FIG. 1 shows a magnetic field sensor described in JP-A-11-87804 and JP-A-11-274599. In the figure, the part written as giant magnetoresistive thin film is
This is a metal-insulator nanogranular giant magnetoresistive thin film that exhibits a change in electric resistance of about 10% when a magnetic field of 10 kOe is applied. As in this example, in the case of a giant magnetoresistive thin film, the change width of the electric resistance value is larger than that of a general magnetoresistive material, but as described above, the applied magnetic field for causing the electric resistance change is generated. When only a giant magnetoresistive thin film is used alone, a change in electric resistance value in a small magnetic field generally used as a magnetic field sensor cannot be expected. The configuration of FIG. 1 complements this. That is,
The soft magnetic thin film plays a role of collecting the magnetic flux around it, and by selecting appropriate dimensions of the soft magnetic thin film, in principle, regardless of the magnitude of the magnetic field around the soft magnetic thin film, the giant magnetoresistive thin film part However, it is possible to apply an extremely large magnetic flux density within the saturation magnetic flux density of the soft magnetic thin film. In addition, from the viewpoint of electric resistance, the electric resistance between the soft magnetic thin films is the sum of the electric resistance of the soft magnetic thin film portion and the giant magnetoresistive thin film portion.
Since the electric resistivity of the giant magnetoresistive thin film is 100 times or more larger than that of the soft magnetic thin film, the electric resistance between the soft magnetic thin films is substantially equal to the value of the giant magnetoresistive thin film portion. That is, a change in the electric resistance of the giant magnetoresistive thin film directly appears in the electric resistance between the soft magnetic thin films. FIG. 2 shows an example of such a change in the electric resistance of the configuration shown in FIG. 1. A change in electric resistance of about 6% is realized in a small magnetic field of several Oe.

[0003]

However, the present invention aims at realizing a magnetic field sensor for measuring an absolute value of an applied magnetic field based on a measured electric resistance of a giant magnetoresistive thin film. It has been found that the configuration of FIG. 1 has a serious problem. This is a problem of a change in electric resistance value of the giant magnetoresistive thin film depending on the temperature. As described above, in the case of the configuration shown in FIG. 1, there is room to select the magnitude of the magnetic field to be detected. However, no matter how high the sensitivity is, it is a choice for the magnetic field to be impressed, and in principle, it is impossible to obtain a variation width larger than the electrical resistance variation of the giant magnetoresistive thin film. Actually, the electric resistance change width in the case of the configuration of FIG. 1 is further reduced to about 6% including other factors. If there is a change due to the temperature of the giant magnetoresistive thin film with respect to the electric resistance change of 6%, only the electric resistance change becomes an uncertain factor in estimating the applied magnetic field. FIG. 3 shows an example of the temperature characteristic. As is clear from this figure, the resistance change of the giant magnetoresistive thin film due to the temperature is larger than the resistance change caused by the application of the magnetic field, and the structure shown in FIG. Is difficult.

[Means for Solving the Problems]

The features of the present invention are as follows. According to the first invention, a gap having a predetermined gap length has
The divided soft magnetic thin film 1 having a predetermined thickness and a predetermined width in contact with a gap, a giant magnetoresistive thin film 2 formed so as to fill the gap, and a soft magnetic thin film 1 divided into two sections are electrically connected to each other. The connected terminals 3 and 4 are divided into two by a gap having a gap length substantially equal to the gap length,
A conductor film 6 having a thickness substantially equal to the film thickness and a width substantially equal to the width in contact with the gap, a giant magnetoresistive thin film 7 formed so as to fill the gap, and two divided conductors A thin-film magnetic field sensor comprising a terminal 8 and a terminal 9 electrically connected to each of the membranes 6, wherein the terminals 3 and 4 and the terminals 8 and 9 each form two arms of a bridge circuit. About.

The second invention is a soft magnetic thin film 1 divided into two by a gap having a predetermined gap length, having a predetermined thickness and a predetermined width in contact with the gap, and a giant magnetoresistance formed to fill the gap. The thin film 2, the terminal 3 and the terminal 4 electrically connected to each of the divided soft magnetic thin film 1, and a gap having a gap length substantially equal to the gap length are divided into two, and the thickness is substantially equal to the film thickness. A conductive film 6 having a thickness equal to that of the conductive film 6 and a width substantially equal to the width in contact with the gap, a giant magnetoresistive thin film 7 formed so as to fill the gap, and electrically connected to each of the two divided conductive films 6. The connected terminals 8 and 9 are divided into two by a gap having a gap length substantially equal to the gap length, and have a thickness substantially equal to the film thickness and a width substantially equal to the width in contact with the gap. Soft magnetic thin film 21 A giant magnetoresistive thin film 22 formed to fill the gap, terminals 23 and 24 electrically connected to each of the two divided soft magnetic thin films 21, and a gap having a gap length substantially equal to the gap length. A conductive film 26 having a thickness substantially equal to the film thickness and a width substantially equal to the width in contact with the gap, a giant magnetoresistive thin film 27 formed to fill the gap, and 2 A terminal 28 and a terminal 29 are electrically connected to each of the divided conductor films 26, and the terminals 3 and 4, the terminals 8 and 9, the terminals 23 and 24, the terminals 28 and 29 The invention relates to a thin-film magnetic field sensor characterized by forming four arms of a circuit.

A third invention is a soft magnetic thin film 1 divided into two by a gap having a predetermined gap length, having a predetermined thickness and a predetermined width in contact with the gap, and a giant magnetoresistance formed to fill the gap. The thin film 2, the terminal 3 and the terminal 4 electrically connected to each of the divided soft magnetic thin film 1, and a gap having a gap length substantially equal to the gap length are divided into two, and the thickness is substantially equal to the film thickness. A soft magnetic thin film 31 having a thickness equal to and a width substantially equal to the width in contact with the gap;
Giant magnetoresistive thin film 3 formed to fill the void
A terminal 33 and a terminal 34 electrically connected to each of the two and the two divided soft magnetic thin films 31;
And terminal 4, terminal 33 and terminal 34 each form two arms of a bridge circuit, and
1 relates to a thin-film magnetic field sensor characterized in that the area on the plane is 1/10 or less of the area on the plane of the soft magnetic thin film 1.

According to a fourth aspect of the present invention, at least a part of the width dimension of the soft magnetic thin film 1 measured along a line parallel to the line contacting the gap is larger than the width of the line where the soft magnetic thin film 1 contacts the gap. The present invention relates to a thin-film magnetic field sensor according to any one of the first to third inventions.

According to a fifth aspect of the present invention, the magnetic properties of the soft magnetic thin film 1 are uniaxially anisotropic, and the direction of the axis of easy magnetization is substantially parallel to a line in contact with the air gap. The present invention relates to a thin-film magnetic field sensor according to any one of the first to third inventions.

[Action]

The operation of the present invention is as follows. The configuration of the first invention is a high-precision magnetic field sensor by extracting only changes due to a magnetic field, excluding changes due to temperature, humidity, and time-dependent factors in changes in electric resistance of a giant magnetoresistive thin film. Is realized. In other words, a bridge is formed by a giant magnetoresistive thin film and two systems of elements having the same structure, and one of the two elements is arranged with soft magnetic thin films on both sides of the giant magnetoresistive thin film to increase sensitivity to a magnetic field. The other element has a sensitivity to a magnetic field of substantially zero by using a giant magnetoresistive thin film as it is. Since the output voltage of the bridge is proportional to the difference in the electrical resistance of these elements, consequently the temperature change of the giant magnetoresistive thin film, as well as other factors such as humidity and aging, are excluded from the output voltage. As a result, only a change in the electric resistance due to the magnetic field appears in the output. Therefore, the absolute value of the magnetic field can be accurately detected, and at the same time, an extremely small magnetic field can be detected.

The structure of the second invention realizes a thin film magnetic field sensor having higher accuracy and higher magnetic field sensitivity. In other words, the bridge output voltage can be reduced by forming a bridge circuit using two elements each having a soft magnetic thin film disposed on both sides of the giant magnetoresistive thin film and two elements each having a conductor film disposed on both sides of the giant magnetoresistive thin film. Therefore, the thickness can be made twice as large as that of the configuration of the first invention, and a thin-film magnetic field sensor with higher accuracy and higher magnetic field sensitivity can be realized.

The structure of the third invention is to further enhance the accuracy of the thin-film magnetic field sensor from the viewpoint of the material used. In other words, even if the material and structure of the giant magnetoresistive thin film part in the elements constituting the bridge are exactly the same, if the material sandwiching the giant magnetoresistive thin film is different, the minute electric potential due to the contact potential difference or the thermoelectromotive force etc. There may be differences in resistance values. According to the configuration of the third invention, it is possible to strictly cancel the electric resistance change of the giant magnetoresistive thin film due to factors other than the resistance change due to the application of the magnetic field of the two structures, including these problems. Thus, a more accurate thin-film magnetic field sensor can be realized.

The structure of the fourth invention realizes a smaller and more accurate thin film magnetic field sensor in terms of structure. In order to increase the sensitivity as a magnetic field sensor and reduce the size, the soft magnetic thin film is arranged on both sides of the giant magnetoresistive thin film. It is necessary to reduce the size of the magnetic thin film portion.
According to the configuration of the fourth invention, it is possible to realize a magnetic field sensor having high sensitivity and a smaller shape.

A fifth aspect of the present invention is to further enhance the accuracy of the thin-film magnetic field sensor in view of the residual magnetization. In other words, after the measurement of the applied magnetic field is completed and the magnetization remains in the soft magnetic thin film after the external magnetic field is removed,
The remanent magnetization has the same effect on the giant magnetoresistive thin film as the application of an external magnetic field, resulting in a decrease in magnetic field detection accuracy. For this reason, in the configuration of the fifth invention, the soft magnetic thin film is magnetized in a direction orthogonal to the detection magnetic field of the giant magnetoresistive thin film, thereby reducing the residual magnetization in the soft magnetic thin film and measuring the magnetic field with higher accuracy. be able to.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the present invention will be described below with reference to the drawings. In each of the drawings, the same elements are denoted by the same reference numerals, to avoid duplication of description.

[First Embodiment] FIG. 4 shows a first embodiment of the present invention. In this figure and the following figures, the giant magnetoresistive thin film portion is distinguished by dots, the soft magnetic thin film portion is indicated by oblique lines, and the conductor thin film portion is blanked out for easy understanding. Reference numeral 5 denotes an element including the soft magnetic thin film 1, the giant magnetoresistive thin film 2, and the electric terminals 3 and 4, which is the same as the configuration shown in FIG. A description of the operation of element 5 is given in the text.

As described above, only the specific contents of the present invention will be described here without duplication. 1 is a soft magnetic thin film
It is a permalloy having a high saturation magnetic flux density of 5 kG or more and a low coercive force of 0.5 Oe or less. Table 1 shows specific material names and typical characteristics of the soft magnetic thin film 1 including other materials.

[0016]

[Table 1]

The thickness of the soft magnetic thin film 1 is t = 1 μm.
In the soft magnetic thin film 1, a gap indicated by a gap length g is formed. The dimension of the gap length g is g = 1 μm. The dimension of the width w of the soft magnetic thin film 1 in contact with the gap is w = 100 μm.
A giant magnetoresistive thin film 2 is formed so as to fill the gap of the soft magnetic thin film 1. The material of the giant magnetoresistive thin film 2 is
Co ₃₉ Y ₁₄ O ₄₇ . Table 2 shows the names of materials that can be used as the giant magnetoresistive thin film 2 including these materials and their typical characteristics.

[0018]

[Table 2]

Here, the thickness t of the soft magnetic thin film 1 and the gap length g
The dimension of the width w of the soft magnetic thin film 1 in contact with the gap needs to be selected so as to satisfy the required characteristics from both the magnetic and electrical conditions, but the features of the present invention are wide. The objective is to obtain the desired performance over a range. That is, the range of dimension selection is very wide. As a magnetic condition, when the air gap length g is too wide, for example, when the thickness t of the soft magnetic thin film is several times or more, the soft magnetic thin film 1 collects the magnetic flux around and sufficiently supplies the magnetic flux to the air gap. I can't concentrate. On the other hand, as for the thickness t of the soft magnetic thin film, the function of the present invention is exhibited no matter how thick the function is, but the deposition capability per unit time possessed by the apparatus for forming the soft magnetic thin film,
Alternatively, the thickness of the soft magnetic thin film is formed on the substrate, and the thickness of the soft magnetic thin film is separated from the substrate. Conversely, if the thickness t of the soft magnetic thin film is 10 nm or less, the magnetic properties of the soft magnetic thin film deteriorate, so that the lower limit of the thickness is substantially 10 nm. As the electrical conditions, the width w of the soft magnetic thin film 1 is a value that is easy to handle by peripheral circuits as the absolute value of the miniaturization of the magnetic sensor and the electric resistance, for example, several tens kΩ to several hundreds MΩ
It is necessary to set in consideration of the range. The absolute value of the electric resistance is proportional to the electric resistivity and the gap length g of the giant magnetoresistive thin film, and is inversely proportional to the width w of the soft magnetic thin film and the thickness t of the soft magnetic thin film. The width g of the soft magnetic thin film is large, and there is a possibility that the width g can be realized in a wide range from a maximum of several mm to a minimum of several μm.

Electric terminals 3 and 4 made of Cu are connected to the soft magnetic thin films 1 on both sides which are divided into two with a gap therebetween. Since the material of the electric terminal portion does not have a large magnetic effect, the material may be determined based on electrical conductivity, and the material of the soft magnetic thin film can be commonly used. It is also possible to form a Cu film on the surface only in a portion provided for connection with the outside.
Reference numeral 5 denotes an element including the soft magnetic thin film 1, the giant magnetoresistive thin film 2, and the electric terminals 3 and 4. Electric terminal 3
The electric resistance value between and 4 is denoted by Ra. FIG. 5 shows an example of the relationship between the applied magnetic field of the element 5 and the change in the electric resistance value, using the length dimension L of the soft magnetic thin film 1 as a parameter.
It can be seen that by increasing the length L, it is possible to impress with a smaller magnetic field. FIG.
Shows a change in resistance value of the element 5 depending on the temperature.
The relationship between the applied magnetic field and the electric resistance value in FIG. 5 shows that the absolute value of the applied magnetic field changes almost linearly up to a magnetic field of a certain magnitude. The change in the electric resistance value with the temperature in FIG. 6 is regarded as a linear relationship near room temperature. Therefore,
If the resistance value when the applied magnetic field is zero and the temperature is 22 ° C. is R ₀ , the absolute value of the applied magnetic field is H, and the temperature is T, the resistance value Ra can be expressed as Expression 1.

[0021]

Ra = R ₀ (1 + r _M H + r _T (T−25)) (1) where r _M is a differential coefficient of a change in electric resistance due to an applied magnetic field, and r _T is a temperature coefficient of the electric resistance. is there. Table 3 shows the value of r _M , the range of the magnetic field H where Expression 1 is satisfied, and the value of r _T for each length L of the soft magnetic thin film.

[0022]

[Table 3]

Reference numeral 6 denotes a conductor film having substantially the same thickness t 'as the soft magnetic thin film 1. The material of the conductor film 6 is Cu. The Cu material shows extremely weak diamagnetism, but is almost magnetically regarded as transparent. The conductor film 6 has a gap length g ′ substantially equal to the gap length g of the soft magnetic thin film 1. The width w 'of the conductor film 6 in contact with the gap is substantially the same as the width w of the soft magnetic thin film 1 in contact with the gap. The length dimension corresponding to L of the element 5 is arbitrary. A giant magnetoresistive thin film 7 is formed so as to fill the voids in the conductor film 6. The material of the giant magnetoresistive thin film 7 is the giant magnetoresistive thin film 2
Is the same as Electrical terminals 8 and 9 are respectively connected to the conductor films 6 on both sides which are divided into two with the gap therebetween. 1
0 represents an element including the conductor film 6, the giant magnetoresistive thin film 7, and the electric terminals 8 and 9. The electric resistance between the electric terminals 8 and 9 is represented by Rb.

In the element 10, since the conductor film 6 has no magnetic effect, the magnetic flux density applied to the giant magnetoresistive thin film 7 is the magnetic flux density of the environment where the giant magnetoresistive thin film 7 is placed. FIG. 7 shows the change in Rb due to the applied magnetic field, and the change in the electric resistance value due to the applied magnetic field is regarded as substantially zero. On the other hand, as the change with respect to the temperature, the same temperature coefficient as that shown in FIG. 6 is shown. Therefore, the expression of the resistance value Rb in the case of the element 10 corresponding to Expression 1 is as shown in Expression 2.

[0025]

Rb = R ₀ (1 + r _T (T−25)) (2)

Reference numeral 11 denotes a first resistor having a resistance value Rc. The first resistor 11 is connected to electric terminals 12 and 13. Reference numeral 14 denotes a second resistor having a resistance value Rd. The second resistor 14 has electrical terminals 15 and 16
Is connected. As for the first resistor and the second resistor, those having a precisely matched resistance value and temperature coefficient between them are used. Assuming that the temperature coefficient of the resistance is r _T ′ in the same manner as in Expressions 1 and 2, Expressions 3 and 4 are obtained.

[0027]

Rc = R ₀ (1 + r _T ′ (T−25)) (3)

[0028]

Equation 4] _{Rd = R 0 (1 + r} T '(T-25)) (4)

Between terminals 4, 8 and 20, between terminals 3, 12 and 17, between terminals 9, 16 and 18, terminals 13, 1
5 and 19 are electrically interconnected. FIG.
Represents the configuration of FIG. 4 as an electrical equivalent circuit, and forms one bridge circuit as a whole. Element 5 and element 10 form the two arms of the bridge circuit. A drive voltage is applied between the terminals 17 and 18, and an output voltage of the bridge appears between the terminals 19 and 20. In the circuit of FIG. 8, the voltage V ₀ is applied between the terminals 17 and 18.
Is applied, the voltage V ₂ that appears between the terminals 19 and 20
Is represented by Expression 5.

[0030]

V ₂ = (RaRd−RbRc) V ₀ / ((Ra + Rb) · (Rc + Rd)) (5)

By substituting Equations 1, 2, 3, and 4 for Ra, Rb, Rc, and Rd in Equation 5, respectively, and omitting the second-order minute amount,
Term relating to the temperature of the V ₂ are all offset to obtain Equation 6.

[0032]

[6] _{V 2 = r T HV 0/} 4 (6)

Here, V ₀ , r _T , and R ₀ are constants that can be determined in advance. If a measured value of V ₂ is obtained, the target magnetic field can be determined as shown in Expression 7.

[0034]

H = 4V ₂ / (V ₀ r _T ) (7)

The level to which the bridge circuit output V ₂ can be stably detected with respect to V ₀ is determined by the stability of the amplifier of the bridge circuit output voltage, etc. In general, V ₂ / V ₀ = 1 × 10 ⁻⁵ is easily feasible.
Therefore, in Expression 7, if V ₂ / V ₀ = 1 × 10 ⁻⁵ and the value of r _T in Table 3 are substituted, the resolution of the magnetic field possible by the present invention is obtained. Table 4 shows the results.

[0036]

[Table 4]

The resolution shown in Table 4 is based on the flux Ga of the prior art.
Comparable with the resolution of the te sensor. This FluxGate
The sensor uses the saturation characteristics of a magnetic material, and is considerably complicated and large in both the sensor structure and the configuration of the peripheral circuit. The configuration of the present invention is extremely simple, small, and lightweight as compared with these magnetic field sensors, and the utility of the present invention is extremely high.

[Embodiment 2-1] FIG. 9 shows a second embodiment of the present invention. In the drawing, the element 25 is an element equivalent to the element 5 described in FIG. 4, and the element 30 is an element equivalent to the element 10. As a whole circuit, the element 25 is a first resistor,
The element 30 is in the form of replacing each of the second resistors. If FIG. 9 is expressed as an equivalent circuit, FIG.
The circuit shown in FIG. 9 is the same as that shown in FIG.
= Ra and Rc = Rb hold. Equation 8 is obtained by substituting Equations 1 and 2 into Equation 5 as in Equation 6.

[0039]

[Equation 8] _{V 2 = r T HV 0/} 2 (8)

Here, the value of equation (8) is twice that of equation (6). Therefore, according to the configuration of FIG. 9, it is possible to more accurately estimate the magnitude of the magnetic field as compared with the configuration of FIG. 4, and it is possible to further increase the resolution of the detectable magnetic field to half.

Embodiment 2-2 FIG. 10 shows a second embodiment of the present invention.
Another embodiment of the present invention is shown. In FIG. 10, the element 5 and the element 25 are arranged in parallel, and the element 10 and the element 30 are arranged between them to effectively use the occupied area as a whole. Further, the terminals 4 and 8, the terminal 24 and the terminal 28, the terminal 3 and the terminal 9, and the terminal 23 and the terminal 29 are common, and the connection between these terminals is omitted to simplify the structure. I'm measuring. Regarding the connection terminals 17, 18, 19, and 20 to the external circuit, terminals 3 and 9, terminals 23 and 29, terminals 4 and 8, and terminals 24 and 28 are not directly connected. 25, and has the same electrical function as that of FIG. In the case of FIG.
The angle at which the giant magnetoresistive thin film is placed is orthogonal to the element 5 and the element 10 and the element 25 and the element 30. As shown in FIG. 7, the sensitivity to the magnetic field of the element 10 and the element 30 is almost zero, but the arrangement as shown in FIG. Thus, the change in electric resistance of the element 10 and the element 30 can be made zero.

Embodiment 3 FIG. 11 shows a third embodiment of the present invention. The difference between this embodiment and the first embodiment is that FIG.
The same material as that of the soft magnetic thin film 1 is used as the conductive film 6 indicated by. In FIG. 4, it is necessary to equalize as much as possible the change in electric resistance of the element 5 and the element 10 other than the change due to the magnetic field, and to cancel them out in the bridge circuit. To achieve this, first, the material and structure of the giant magnetoresistive thin film itself must be shared, but even if the giant magnetoresistive thin film itself is exactly the same, a minute electrical resistance value may be reduced depending on the material in contact with it. There may be differences. The cause is a contact potential difference or a thermoelectromotive force. In Example 3 shown in FIG. 11, the material to be brought into contact with the giant magnetoresistive thin film is the element 5
This problem is avoided by using a common soft magnetic thin film for the element 35 and the element 35. However, the soft magnetic thin film 3 of the element 35
When the size of 1 is increased, the giant magnetoresistive thin film 3
The magnetic flux density applied to the element 2 also increases, and the sensitivity of the magnetic field sensor as a difference between the resistance values of the element 5 and the element 32 decreases. In the third embodiment, this problem is avoided by setting the area of the soft magnetic thin film 31 of the element 35 to 1/10 or less of the area of the soft magnetic thin film 1 of the element 5. According to this configuration,
An output voltage of at least 90% or more of the bridge output voltage when the conductor portion of the element 35 is a non-magnetic material can be secured.
The elements 5 and 35 can exactly cancel each other, and a highly accurate thin-film magnetic field sensor can be realized.

[Embodiment 4] FIG. 12 shows a fourth embodiment of the present invention. In the first embodiment, it has been described that the sensitivity of the impressed magnetic field can be increased by increasing the L dimension of the soft magnetic thin film for the element 5. The function of the soft magnetic thin film 1 is to collect the peripheral magnetic flux and concentrate it on the giant magnetoresistive thin film portion.
It is almost proportional to the area of the soft magnetic thin film. Therefore, in the case of the configuration shown in FIG. 4, in order to provide sensitivity with a small magnetic field, it is necessary to increase the L dimension, and it is inevitable that the overall dimension of the magnetic field sensor will increase. . According to the configuration of FIG. 12, by providing a portion having a width of wx larger than the width w of the soft magnetic thin film in contact with the giant magnetoresistive thin film, effective use of the occupation area of the soft magnetic thin film is achieved, and the overall size is reduced. In addition, a magnetic sensor having high magnetic field sensitivity can be realized.

Embodiment 5 FIG. 13 shows a fifth embodiment of the present invention. In a soft magnetic thin film, even when an external magnetic field is applied, magnetization is unlikely to remain after the external magnetic field is removed, but magnetization may remain within the range of the coercive force Hc. Since this residual magnetization is a direct error of the magnetic field to be detected, a material having no residual magnetization is desirable. As shown in Table 1, the Co ₇₇ Fe ₅ Si ₉ B ₈ material has a low Hc of about 1/6 as compared with Permalloy, and this value is obtained when excited in the direction of the hard magnetization axis. Generally, the magnetization process in the hard axis direction of a magnetic material having uniaxial anisotropy is caused by magnetization rotation, so that no hysteresis occurs and Hc becomes almost zero. Therefore, no residual magnetization occurs in the hard axis direction. According to the fifth aspect of the present invention, since the hard axis direction of the material having uniaxial anisotropy is used as the magnetic field detection direction, the residual magnetization remains in the soft magnetic thin film even after the externally applied magnetic field is removed. Therefore, accurate measurement of the magnetic field becomes possible.

[0045]

As described above, according to the present invention, the following effects can be obtained.

All changes other than the change in the electric resistance due to the application of the magnetic field, such as the change in the electric resistance of the giant magnetoresistive thin film due to the temperature change, are canceled out in the bridge circuit and are not output as the bridge output. The change in electric resistance due to the temperature or the like of the giant magnetoresistive thin film is excluded, and the change due to the application of a magnetic field can be detected purely.

Since the function of detecting a minute change in electric resistance value of the bridge circuit can be used, it is possible to detect a magnetic field with a high resolution corresponding to an extremely small change.

In order to avoid a minute difference in resistance value caused by a difference in the materials arranged on both sides of the two giant magnetoresistive thin films, the same material is arranged on both sides of the two giant magnetoresistive thin films, thereby reducing the magnetic field. Changes in electrical resistance due to factors other than the above are more strictly offset.

By reducing the length of the soft magnetic thin film disposed on both sides of the giant magnetoresistive thin film and, instead, increasing the width thereof, it is possible to reduce the size of the magnetic field sensor as a whole without lowering the sensitivity of the magnetic field sensor. It is.

By applying a material having uniaxial anisotropy with little residual magnetization as the soft magnetic thin film disposed on both sides of the giant magnetoresistive thin film, the accuracy of magnetic field detection by residual magnetization after excluding the magnetic field to be detected Can be prevented from decreasing.

The thin-film magnetic field sensor of the present invention has a simple structure, can be miniaturized, and has excellent magnetic field sensitivity. Therefore, it has a great industrial significance as a next-generation high-performance magnetic field sensor.

[Brief description of the drawings]

FIG. 1 shows a conventional thin film magnetic field sensor.

FIG. 2 Changes in resistance value due to application of a magnetic field

FIG. 3 is a temperature characteristic of the same resistance value.

FIG. 4 shows a first embodiment of the present invention.

FIG. 5 shows a relationship between a magnetic field and a change in resistance of the element 5 according to the first embodiment of the present invention.

FIG. 6 shows elements 5 and 1 according to the first embodiment of the present invention.
Resistance temperature characteristics of 0

FIG. 7 shows a relationship between a magnetic field and a resistance change of the element 10 according to the first embodiment of the present invention.

FIG. 8 is an electrical equivalent circuit of the above.

FIG. 9 shows a second embodiment of the present invention.

FIG. 10 shows a second embodiment of the present invention.

FIG. 11 shows a third embodiment of the present invention.

FIG. 12 shows a fourth embodiment of the present invention.

FIG. 13 shows a fifth embodiment of the present invention.

[Explanation of symbols]

 1: First soft magnetic thin film 2: First giant magnetoresistive thin film 3: One of the electric terminals connected to the first soft magnetic thin film 4: Other electric terminal connected to the first soft magnetic thin film 5: Element including above 1 to 4 6: First conductive film 7: Second giant magnetoresistive thin film 8: One of the electric terminals connected to the first conductive film 9: On the first conductive film Other electrical terminals to be connected 10: Elements including the above 6 to 9 11: First resistor 12: One of the electrical terminals connected to the first resistor 13: Connected to the first resistor Other electrical terminals 14: Second resistor 15: One of the electrical terminals connected to the second resistor 16: Other electrical terminal connected to the second resistor 17: Drive voltage is given One of the electric terminals 18: Another electric terminal to which a driving voltage is applied 19: One of the electric terminals of the bridge output 20: Other electrical terminals of ridge output 21: second soft magnetic thin film 22: third giant magnetoresistive thin film 23: one of electrical terminals connected to second soft magnetic thin film 24: second soft magnetic thin film Other electrical terminals to be connected 25: Elements including the above 21 to 24 26: Second conductive film 27: Fourth giant magnetoresistive thin film 28: One of the electrical terminals connected to the second conductive film 29 : Other electrical terminals connected to the second conductor film 30: Elements including the above 26 to 29 31: Third soft magnetic thin film 32: Fifth giant magnetoresistive film 33: Third soft magnetic thin film One of the electric terminals to be connected 34: Another electric terminal to be connected to the third soft magnetic thin film 35: An element including the above 31 to 34

Claims (5)

[Claims] A soft magnetic thin film having a predetermined thickness and a predetermined width in contact with the gap, a giant magnetoresistive thin film formed to fill the gap, Terminals 3 and 4 electrically connected to each of the two divided soft magnetic thin films 1, a film divided into two by a gap having a gap length substantially equal to the gap length, and substantially equal to the film thickness A conductive film 6 having a thickness and a width substantially equal to the width in contact with the space, a giant magnetoresistive thin film 7 formed so as to fill the space, and electrically connected to each of the two divided conductive films 6 The thin-film magnetic field sensor comprises terminals 8 and 9, wherein the terminals 3 and 4 and the terminals 8 and 9 each form two arms of a bridge circuit. 2. A soft magnetic thin film 1 divided into two by a gap having a predetermined gap length and having a predetermined thickness and a predetermined width in contact with the gap, a giant magnetoresistive thin film 2 formed so as to fill the gap, Terminals 3 and 4 electrically connected to each of the two divided soft magnetic thin films 1, a film divided into two by a gap having a gap length substantially equal to the gap length, and substantially equal to the film thickness A conductive film having a thickness and a width substantially equal to a width in contact with the gap, a giant magnetoresistive thin film formed to fill the gap, and electrically connected to each of the two divided conductive films; Terminals 8 and 9, two gaps having a gap length substantially equal to the gap length
A soft magnetic thin film 2 having a thickness substantially equal to the thickness and a width substantially equal to the width in contact with the gap;
1, a giant magnetoresistive thin film 22 formed so as to fill the gap, terminals 23 and 24 electrically connected to each of the divided soft magnetic thin films 21, and a gap length substantially equal to the gap length. A conductive film 26 having a thickness substantially equal to the film thickness and a width substantially equal to the width in contact with the gap, and a giant magnetoresistive thin film 27 formed so as to fill the gap , And a terminal 28 electrically connected to each of the two divided conductive films 26
And terminal 29, and terminals 3, 4 and 8
And a terminal 9, a terminal 23 and a terminal 24, a terminal 28 and a terminal 29 each form four arms of a bridge circuit. 3. A soft magnetic thin film 1 divided into two by a gap having a predetermined gap length and having a predetermined thickness and a predetermined width in contact with the gap, a giant magnetoresistive thin film 2 formed so as to fill the gap, Terminals 3 and 4 electrically connected to each of the two divided soft magnetic thin films 1, a film divided into two by a gap having a gap length substantially equal to the gap length, and substantially equal to the film thickness A soft magnetic thin film 31 having a thickness and a width substantially equal to the width in contact with the gap, a giant magnetoresistive thin film 32 formed to fill the gap, and 2
Each of the divided soft magnetic thin films 31 is composed of a terminal 33 and a terminal 34 electrically connected thereto, and the terminals 3 and 4, the terminals 33 and 34 are connected to the bridge circuit 2 respectively.
And the area of the soft magnetic thin film 31 on the plane is 1/1 of the area of the soft magnetic thin film 1 on the plane.
A thin film magnetic field sensor characterized by being 0 or less. 4. At least a part of the width dimension of the soft magnetic thin film 1 measured along a line parallel to a line contacting the gap is larger than the width of the soft magnetic thin film 1 in contact with the gap. The thin-film magnetic field sensor according to claim 1, wherein: 5. The magnetic property of the soft magnetic thin film 1 is uniaxial anisotropy, and the direction of the axis of easy magnetization is substantially parallel to a line in contact with the gap. The thin-film magnetic field sensor according to claim 3.