JPH11287669A - Magnetic field sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic field sensor which has high resolution, provides large outputs, and can be made compact. SOLUTION: This magnetic field sensor has 2n (n>=3; n is an integer) magnetoresistance effect elements. Of the 2n magnetoresistance effect elements, Am and Bm ' which make a pair satisfy the positional relation ships represented by the equations: Am = P(m-1)/n} (m=1, 2, 3,..., n) Bm =Am ±P/2 The elements Am and Bm ' are arranged parallel to each other within a width P corresponding to the magnetization pitch P of the subject of detection and are connected in series with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic field sensor for converting a change in an external magnetic field into an electric signal.

[0002]

2. Description of the Related Art A magnetic field sensor is a sensor for converting a change in an external magnetic field into an electric signal. To convert a change in an external magnetic field into an electric signal. Here, the magnetoresistive element refers to an element portion formed by patterning, and the magnetic field sensor refers to an entire element including two or more magnetoresistive elements.

Incidentally, a ferromagnetic magnetoresistive sensor is
This sensor measures the magnetic field intensity using a phenomenon (magnetic resistance effect, MR effect) in which the electric resistance of a ferromagnetic metal changes due to an external magnetic field. In the case of a single-layer film, a magnetic anisotropic magnetoresistance effect (hereinafter simply referred to as A
Recently, for example, as disclosed in Japanese Patent Application Laid-Open No. 5-259530, a coupled giant magnetoresistance effect (GMR effect) using a film having a multilayer structure is used. Sensors have also been developed.

A magnetic film exhibiting the GMR effect has a larger MR change rate than a conventional film exhibiting the MR effect. Therefore, for example, when used for rotation or the like, the output becomes large. As a result, it is possible to increase the tolerance for the gap runout, which is extremely advantageous in terms of mechanical design. That is, if a magnetic film exhibiting the GMR effect is used, a stable output can be obtained even if the gap between the detection target and the sensor slightly changes. In a magnetic film exhibiting the GMR effect, the change in resistance is isotropic irrespective of the relative angle between the magnetic field and the current. Therefore, even if the direction of the applied magnetic field changes, the magnitude of the magnetic field does not change. Unless the output is stable, it can be maintained.

A giant magnetoresistive film is generally of an antiferro (coupling) type having a (ferromagnetic / non-magnetic conductor) structure,
(High coercivity ferromagnetic / non-magnetic conductor / low coercivity ferromagnetic) Inductive ferri (non-coupling) type, (antiferromagnetic /
It is roughly classified into a spin valve type having a (ferromagnetic material / non-magnetic conductor / ferromagnetic material) structure and a non-solid solution type granular type of Co / Ag system. These giant magnetoresistive films differ greatly in the detectable magnetic field strength, that is, the saturation magnetic field strength of the magnetoresistive effect, depending on the structure and composition. For example, (Fe / Cr)
10 KOe or more in the antiferro-type (CoNiFe
/ Cu) -based antiferro type, from 0.1 to 1 KOe, (NiFe / Cu / Co / Cu) -based induced ferri type, about 5 to 20 Oe, (FeMn / NiFe / Cu /
A magnetic field of several Oe can be detected in a NiFe) spin valve type, and a magnetic field of about 100 to 5 KOe can be detected in a granular type.

[0006]

By the way, there have been various types of magnetic field sensors in which a plurality of magnetoresistive elements are sequentially arranged on a substrate in order to increase resolution and detection accuracy. Proposed.

For example, Japanese Unexamined Patent Publication No. 3-221814 discloses a specific method of arranging magnetoresistive elements with respect to a magnetic field pitch. According to this proposal, the magnetoelectric conversion device arranges a total of 2N magnetoresistive elements for detecting an object to be detected which is periodically magnetized at the pitch P between the magnetic poles, and is shifted by a phase of P / N. Since the configuration in which signals are obtained from the N pairs of elements is adopted, the resolution of the magnetoelectric conversion device can be increased N times.
However, in this proposal, when the number of magnetoresistive elements is increased in order to increase the resolution, a pair
Becomes smaller, and the amplitude of the output signal becomes smaller.

Japanese Patent Application Laid-Open No. 61-99816 discloses that n pairs (2n magnetoresistive elements) are represented by (P
(P / n) are disclosed, and sensors that realize high resolution are disclosed. In Japanese Patent Application Laid-Open No. 4-282417, k sensors composed of four magnetoresistive elements are configured, and (L + m / 2 + 1 / 2k) P (L, m is 0).
It has been proposed to increase the resolution by arranging sensors at intervals of (an integer; k is an integer). However, in these cases, the size of the sensor is increased in order to increase the resolution, and thus the sensor cannot be reduced in size and size.

The present invention has been made under such circumstances, and its object is to solve the conventional problems.
It is an object of the present invention to provide a magnetic field sensor having a high resolution, a large output, and a compact sensor itself.

[0010]

According to the present invention, there is provided a magnetic field sensor having 2n (n ≧ 3; n is an integer) magnetoresistive effect elements.
A _m and B _{m forming} a pair among the magnetoresistive elements
Satisfies the positional relationship of the following equations (1) and (2),
In addition, they are arranged in parallel within a width P corresponding to the magnetization pitch P of the detection target, and are connected in series.

A _m = (P (m−1) / n) (1) (where m = 1, 2, 3,..., N) B _m = A _m ± P / 2 (2) As a preferred embodiment of the magnetic field sensor of the present invention,
the installation position of _m and B _m, each further by adding a magnetoresistive element one another, the sum 4n (n ≧ 3;
n is integer) the magnetoresistive element is provided for by the A _m and B _m and the added magnetoresistive element in these installation position, configured such that constitute a bridge circuit.

In a preferred embodiment of the magnetic field sensor according to the present invention, the magnetoresistance effect element is a magnetic film formed in a predetermined pattern, and the magnetic film is a film exhibiting a giant magnetoresistance effect. It is composed of

In a preferred embodiment of the magnetic field sensor according to the present invention, six or more magnetoresistive elements are provided (n ≧ 3), and are configured to output signals of three or more phases. .

In a preferred embodiment of the magnetic field sensor according to the present invention, the number of the magnetoresistive elements is 6 or more and 30 or less (n = 3 to 15), and signals of 3 to 15 phases are provided. It is configured to output.

In a preferred embodiment of the magnetic field sensor according to the present invention, the magnetoresistance effect element is formed on a substrate, and the substrate is configured to have flexibility.

In a preferred embodiment of the magnetic field sensor according to the present invention, the substrate is a flexible resin substrate.

In a preferred aspect of the magnetic field sensor according to the present invention, the substrate is made of polyimide.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view showing a preferred first embodiment of a magnetic field sensor 1 according to the present invention. The arrangement pattern of magnetoresistive elements is mainly detailed in relation to an object to be detected. It is shown.

The magnetic field sensor 1 of the present invention has 2n (n ≧ 3;
n is an integer) number of magnetoresistive elements, and among the 2n magnetoresistive elements, a pair of _Am and _Bm is:
It satisfies the positional relationship of the following formulas (1) and (2), is arranged in parallel within a width P corresponding to the magnetized pitch P of the detected object, and is connected in series.

A _m = (P (m−1) / n) Expression (1) (where m = 1, 2, 3,..., N) B _m = A _m ± P / 2 Expression (2) In the case of the embodiment shown in FIG. 1, the magnetic field sensor 1 includes six magnetoresistive elements (A _{1 to} A ₃ ,
B ₁ -B ₃ ) are formed, and satisfy A ₁ and B ₁ , A ₂ and B ₂ , A
₃ and B ₃ constitute a magnetoresistive element (A _m and B _m ) which is a pair.

All of the 2n magnetoresistive elements of the present invention have a width P corresponding to the magnetized pitch P of the detection target to be detected (within the predetermined width P on the substrate).
They are arranged in parallel. Thereby, the size of the magnetic field sensor 1 is reduced.

[0023] If you leave described in detail the sequence method, first A ₁
To the left end of the drawing, and from this position (P / 2)
Installing a B ₁ to be paired to the right. Then A ₂ position
The position of A _1, is placed at the right of the (P / 3). Based on this A ₂ , a pair of B ₂ is set to the right (P / 2). Then A ₃ position, the position of A _2, is placed at the right of the (P / 3). This A ₃
Based on the, now installing B ₃ which is opposite to the (P / 2) pairs to the left. To the last, all the elements must be contained within the width P corresponding to the magnetization pitch P. That is, a method is required in which the installation direction is determined by using ± (P / 2) in the above equation (2), and is set within the width P.

As shown, the magnetoresistive effect elements A _m and B _m forming a pair are respectively arranged at intervals of (P / 2) and connected in series as shown in FIG. Output at a phase difference of every P / 3 by the element,
That is, three-phase signals are output (V ₁ , V ₂ , V
₃ ) Can be. Therefore, the resolution is extremely high (in the case of FIG. 1, it is three times that in the case where there is only one pair of elements), and the output can be large.

In the case of the embodiment shown in FIG.
The detection target 60 is an example of a detection target in which the S-N poles are alternately magnetized at the magnetization pitch P, and moves at a predetermined speed in the direction of the arrow and (α). The value of the magnetization pitch P applied in the present invention includes not only the pitch that can be clearly understood from the geometrical viewpoint but also the value of the magnetization pitch corrected in consideration of the operation conditions of the magnetic field detection and the like. I have. This can be easily understood from the following embodiment.

FIG. 2 is a diagram in which the circuit shown in FIG. 1 is changed to a specific configuration diagram of the magnetic field sensor 1. FIG.
, Each of the six magnetoresistive elements (A _{1 to} A ₃ , B
_{1 to} B ₃ ) are formed in a folded pattern on the substrate 20.
Conductor electrode films 11, 11 (electrode pads) are formed. The conductor electrode films 11 and 11 (electrode pads) are formed to allow a current to flow through the magnetoresistive film 10, and the conductor electrode films 11 and 11 are connected to an external circuit by soldering, wire bonding, or the like. Joining is performed.

The magnetoresistance effect element (magnetic film) for detecting a magnetic field used in the present invention is a film having a magnetoresistance effect, and may have any of a single-layer film structure and a multilayer film structure.
The magnetoresistance effect refers to a phenomenon in which electric resistance changes due to a change in a magnetic field. It is preferable to use a giant magnetoresistive film (GMR film), which has particularly high detection sensitivity and can greatly change the magnetic field strength to be detected, as the magnetic film constituting the element.

The giant magnetoresistive film is made of a metal artificial lattice (Kiyasu Fujimori, Agne Technology Center, issued in 1995) 347
As described on the page, it is a multilayer film of a ferromagnetic film and a non-magnetic film, and it is known that the resistance changes due to a change in interface scattering of the multilayer film.

As the giant magnetoresistive film, an antiferro (coupling) type having a (ferromagnetic / non-magnetic conductor) structure,
(High coercivity ferromagnetic / non-magnetic conductor / low coercivity ferromagnetic) Inductive ferri (non-coupling) type, (semi-ferromagnetic /
It is roughly classified into a spin valve type having a (ferromagnetic material / non-magnetic conductor / ferromagnetic material) structure and a non-solid solution type granular type of Co / Ag system.

Each of these giant magnetoresistive films has a detectable magnetic field strength, that is, a saturation magnetic field strength of the magnetoresistive effect greatly differs depending on its structure and composition. For example, (F
e / Cr) type antiferro type, 10KOe or more, (C
oNiFe / Cu) antiferro type is 0.1 Oe
To 1 KOe, (NiFe / Cu / Co / Cu) -based ferrielectric ferritypes have about 5 to 20 Oe, (FeMn /
NiFe / Cu / NiFe) spin valve type, several Oe, and granular type from 100 Oe to 5K
Magnetic field detection up to about Oe is possible. The magnetic field sensitivity is obtained by dividing the maximum magnetoresistance change rate by the saturation magnetic field strength. Even if the maximum magnetoresistance change rate is large, the magnetic field sensitivity is poor when the saturation magnetic field is large. Conversely, even when the maximum magnetoresistance ratio is small, the magnetic field sensitivity is good when the saturation magnetic field is very small. For this reason, a basic system is selected from the various giant magnetoresistive films described above so that the highest magnetic field sensitivity is obtained depending on the magnetic field strength to be detected, and further, a composition system is changed and a fine structure is optimized and used. .

Such a magnetoresistive film (magnetic film)
The film is formed by a vacuum film forming method, for example, a vapor deposition method, a sputtering method, or the like. More specifically, after a magnetoresistive film is formed on the entire surface of the substrate 20, it is patterned into a desired pattern to form a magnetoresistive element for detecting a magnetic field. Conductive electrode films 11, 1
1 is formed in a predetermined pattern. Conductor electrode film 11, 1
It is important that 1 has a smaller resistance than the magnetic film portion which is a magnetoresistive element. For this reason, the conductor electrode films 11 are made of a metal having high conductivity, for example, copper, gold, aluminum, or the like, and are relatively thick, for example, 0.3 mm.
To a thickness of 5.0 μm. Conductor electrode film 1
For forming the layers 1 and 11, a wet film formation method can be used in addition to the vacuum film formation method. First, the conductor electrode films 11, 1
After forming one conductive layer, the magnetoresistive effect element may be formed.

Further, as described above, the magnetoresistance effect element (A ₁
~A _3, B ₁ ~B ₃₎ and a conductive electrode film 11, 11 instead of constituting a material of individually different, integrally all the magnetoresistive element and the conductor electrode film 11 and 11 from the same material It may be formed (deposited). However, in this case, the magnetoresistive element and the conductor electrode film 11,
It is necessary to use the same material within a range in which each function of No. 11 can be exhibited. The portion of the magnetic film is the magneto-sensitive pattern portion, and the portion of the conductor electrode film does not need to be the magneto-sensitive pattern portion. Therefore, in order to change the current density between the magneto-sensitive pattern portion and the electrode portion, the width of the electrode portion is designed to be wider than the width of the magneto-sensitive pattern portion. That is, by increasing the width of both ends of the pattern made of the same material, a function as a conductor electrode film can be provided. By being made of the same material, the magnetoresistive element which is a magneto-sensitive part and the conductor electrode films 11 which are electrode parts are formed in one patterning step.
Can be formed at the same time, and extremely high productivity can be realized.

The magnetoresistance effect element is generally 200 nm
Since it is formed as the following thin film, corrosion resistance in a use environment often becomes a problem. For this reason, it is preferable to provide a protective film at least on the upper layer of the magnetoresistive element to protect the magnetoresistive element from the surrounding atmosphere. As the material of the protective film, it is preferable to use an inorganic material such as SiO ₂ or Al ₂ O ₃ or an organic material such as a polyimide resin or a novolak resin.

The material of the substrate 20 used in the present invention is not particularly limited, and any of inorganic materials such as glass, silicon and ceramic, and organic materials such as resin may be used. Among them, it is particularly preferable to use a thin and light one having excellent so-called flexibility. For example, a substrate similar to a plastic film widely used as a printed wiring board or the like can be suitably used. More specifically, various materials known as plastic film materials such as polyimide, polyethylene terephthalate (PET), polypropylene (PP), and Teflon can be used. In particular, it is preferable to use a polyimide film having high heat resistance in consideration of bonding by solder at the end of the conductor electrode film.

The thickness of the substrate 20 is not particularly limited, but is preferably 1 to 300 μm.

FIG. 3 shows a second embodiment of the present invention. The magnetic field sensor 2 shown in FIG. 3 is particularly different from the magnetic field sensor 1 shown in FIG. 1 in that eight magnetic resistance elements (A _{1 to} A ₄ and B _{1 to} B ₄ ) are formed. On the point.

In the case of the embodiment shown in FIG. 3, the magnetic field sensor 2 has eight magnetoresistive elements (A _{1 to} A ₄ and B _{1 to} B ₄ ) formed on a substrate 20. A ₁ and B ₁ satisfying the relationship between the above equations (1) and (2),
A and ₂ and B _2, A ₃ and B _3, A ₄ and B ₄ constitute pairs of magnetoresistance effect element comprising a (pair) (A _m and B _m), respectively.

Of course, also in this case, all of the eight magneto-resistive elements are within the width P (corresponding to the predetermined width P on the substrate) within the width P corresponding to the magnetization pitch P of the object to be detected. ) Are arranged in parallel.

[0039] If you leave described in detail the sequence method, first A ₁
To the left end of the drawing, and from this position (P / 2)
Installing a B ₁ to be paired to the right. Then A ₂ position
The position of A _1, is placed at the right of the (P / 4). Based on this A ₂ , a pair of B ₂ is set to the right (P / 2). Then A ₃ position, the position of A _2, is placed at the right of the (P / 4). This A ₃
Based on the, now installing B ₃ which is opposite to the (P / 2) pairs to the left. Next, the A ₄ position is changed from the A ₃ position to
Install at (P / 4) to the right. On the basis of this A ₄ , B ₄ which becomes a pair again in the opposite direction (P / 2)
Is installed. To the last, all the elements have the magnetization pitch P
Must be accommodated within the width P corresponding to. That is, as described above, ± (P / 2) in the above equation (2)
It is necessary to use a technique that determines the installation direction and fits within the width P.

The magnetoresistive effect elements A _m and B _m forming a pair are respectively arranged at an interval of (P / 2) and connected in series as shown in FIG. Output at a phase difference of every P / 4 by the effect element,
That is, four-phase signals are output (V ₁ , V ₂ , V
₃ , V ₄ ). Therefore, the resolution is extremely high (in the case of FIG.
Doubling the output).

FIG. 4 is a drawing in which the circuit shown in FIG. 3 is changed to a specific configuration diagram of the magnetic field sensor 2. FIG.
, The eight magnetoresistive elements (A _{1 to} A ₄ , B
_{1 to} B ₄ ) are formed in a folded pattern on the substrate 20.
Conductor electrode films 11, 11 (electrode pads) are formed. The description of the magnetoresistive element and the conductor electrode film has already been described above, and thus the description thereof is omitted here.

FIG. 5 shows a third embodiment of the present invention. The magnetic field sensor 3 shown in FIG. 5 is particularly different from the magnetic field sensor 1 shown in FIG. 1 in that ten magnetic resistance effect elements (A _{1 to} A ₅ , B _{1 to} B ₅ ) are formed. On the point.

In the case of the embodiment shown in FIG. 5, the magnetic field sensor 3 has ten magnetoresistive elements (A _{1 to} A ₅ and B _{1 to} B ₅ ) formed on a substrate 20. A ₁ and B ₁ satisfying the relationship between the above equations (1) and (2),
A and ₂ and B _2, A ₃ and B _3, A ₄ and B _4, A ₅ and B ₅ is a magnetoresistive element comprising a pair (pair), respectively (A _m and B _m).

Of course, also in this case, all of the ten magnetoresistive effect elements are within the width P corresponding to the magnetization pitch P of the detection target (the predetermined width P on the substrate).
Are arranged in parallel.

[0045] If you leave described in detail the sequence method, first A ₁
To the left end of the drawing, and from this position (P / 2)
Installing a B ₁ to be paired to the right. Then A ₂ position
The position of A _1, is placed at the right of the (P / 5). Based on this A ₂ , a pair of B ₂ is set to the right (P / 2). Then A ₃ position, the position of A _2, is placed at the right of the (P / 5). This A ₃
Based on the, placing the B ₃ to be paired to (P / 2) rightward. Then A ₄ position, from the position of A _3, it is placed at the right of the (P / 5). On the basis of this A ₄ , a pair B ₄ is installed in the opposite direction to the left (P / 2). The then A ₅ position, the position of A _4, placed at the right of the (P / 5). On the basis of this A ₅ , a pair B ₅ is installed in the opposite direction to the left (P / 2). To the last, all the elements must be contained within the width P corresponding to the magnetization pitch P.

As shown, the magnetoresistive effect elements A _m and B _m forming a pair (pair) are arranged at an interval of (P / 2) and connected in series, respectively, as shown in the figure. Output at a phase difference of every P / 5 by the element,
That is, a five-phase signal is output (V ₁ , V ₂ , V
₃ , V ₄ , V ₅ ). Therefore, the resolution is extremely high (in the case of FIG. 5, it is five times that in the case where there is only one pair of elements), and the output can be large.

FIG. 6 is a diagram in which the circuit shown in FIG. 5 is changed to a specific configuration diagram of the magnetic field sensor 3. FIG.
, 10 magnetoresistive elements (A _{1 to} A ₅ ,
B _{1 to} B ₅ ) are formed in a folded pattern on the substrate 20, and conductor electrode films 11, 11 (electrode pads) are formed on both ends thereof, respectively. The description of the magnetoresistive element and the conductor electrode film is as described above.

FIG. 7 shows an equivalent circuit in the arrangement of FIG.

As described above, in Embodiments 1 to 3, n = 3 to
Although the specific arrangement of the magnetoresistive elements in the case of No. 5 has been described, n = 6, 7, 8,.
It is clear that the present invention can be applied to the case of.

[0050] Figure 8 is an installation position of the A _m and B _m in the present invention, by adding a magnetic resistance effect element of one another each further sum 4n (n ≧ 3; n is an integer) number Of the above-described A _m and B _m
The magnetic field sensor 4 which forms a bridge circuit is shown by the magnetoresistive elements A _m ′ and B _m ′ added to these installation positions.

In FIG. 8, the arrangement of 2n elements that satisfy the equations (1) and (2), that is, the ten magnetoresistive elements (A _{1 to} A ₅ , B _{1 to} B ₅ ) are shown in the above-described diagram. 5 (Embodiment 3). Further, the arrangement positions of the added 2n, that is, the added ten magnetoresistive effect elements (A ₁ ′ to A ₅ ′, B ₁ ′ to B ₅ ′) are the same as the corresponding subscripts as shown in the drawing. (Eg, _Am and _Am ′; _Bm and _Bm ′). The twenty magnetoresistive elements thus formed and arranged form a bridge circuit by the four elements present at pairs (pairs). A specific bridge circuit is shown in FIG. Magnetic field sensor 4 shown in FIGS.
Compared with the magnetic field sensor 3 (Embodiment 3) shown in FIG. 5, the resolution is the same, but the output of the magnetic field sensor 4 is twice as large as that of the magnetic field sensor 3.

FIG. 10 shows an example of use of the magnetic field sensor 1 (magnetic field sensors 2 to 4) of the present invention. The magnetic field sensor 1 shown in FIG. 10 is installed at a distance of the gap G in order to detect the rotation speed of the rotating magnetized body, which is the detection target 60, in a non-contact manner. In this example, the rotating magnetized body (60) has a disk shape, and N-
The south poles are magnetized alternately (the width of the magnet of the north pole is defined as the magnetization pitch P). In this case, the magnetic field sensor 1 (substrate and magnetoresistive element) is given a curvature (by bending the substrate 20) in accordance with the curvature of the peripheral side surface of the rotating magnetized body (60) shown in FIG. Highly accurate detection becomes possible. That is, since the gap G can be kept constant, the output of the magnetic field sensor is stabilized. In consideration of this point, it is preferable to use a resin substrate having excellent flexibility as the substrate 20.

Further, as shown in FIG. 11, when the rotating object 61 is a disk gear-shaped object made of a soft magnetic material, the magnetic field sensor 1 of the present invention is, for example, Used in combination with the installed bias magnet 66. In this case, the total length of the concave and convex portions of the gear is defined as the magnetization pitch P. In the case shown in FIG. 11, similarly to the case of FIG. 10, it is preferable that the substrate 20 used for the magnetic field sensor is formed of a resin substrate having excellent flexibility and has a predetermined curved shape.

When compressive or tensile stress is applied to the magnetoresistive element formed on the flexible substrate 20, the value of the saturation magnetic field changes due to the anisotropy induced by the stress. Taking advantage of this property, for example, if the substrate is flattened after heat-treating the magnetoresistive film to which a compressive stress has been applied in advance at a high temperature to relax the stress, the tensile stress acts on the magnetoresistive film and the saturation magnetic field decreases. I do. That is, it is possible to manufacture a bendable magnetoresistive element having higher sensitivity than the intrinsic characteristics of the element while being flat.

FIG. 12 is a graph showing how the magnetoresistance effect curve (MR curve) changes when a stress is applied in the longitudinal direction of the stripe-shaped magnetoresistance effect element. 12A shows a state where no stress is applied, FIG. 12B shows a state where a compressive stress is applied, and FIG.
(C) is an MR curve in a state where a tensile stress is applied. Here, the stress is applied in the compression direction and the tension direction until the radius of curvature of the resin substrate becomes 5 mm.

FIG. 13 shows an MR curve that changes according to the processing operation when a GMR film as a magnetoresistive element formed on a polyimide film substrate is subjected to stress processing, heat treatment, or the like. . FIG. 13A shows an MR curve in a state where a stress is not forcibly applied to the film from the outside. Next, the film substrate is curved in a concave shape (compression stress application). The MR curve at this time is shown in FIG. 150 ° C. with the film substrate curved in a concave shape
When the heat treatment is performed for 1 hour, the MR curve returns to the state before the bending due to the stress relaxation (FIG. 13C). Next, when the film is flattened, a tensile stress is applied and some hysteresis is observed.
The saturation magnetic field can be reduced to about half of that before the heat treatment without deteriorating the R change rate (FIG. 13D). In this way, a highly sensitive and flexible magnetic field sensor can be manufactured, and the magnetic field sensor can be arranged along the surface of the detection target having a small curvature while keeping the gap constant.

[0057]

EXAMPLES Hereinafter, the present invention will be described in more detail by showing specific examples of the present invention.

Example 1 A polyimide film having a diameter of 3 inches and a thickness of 75 μm was used as a substrate. On this substrate, 200Å
-Ti (15 ° -NiFeCo / 20 ° -Cu) × 20
Was formed. Here, the membrane structure is initially 20
This is a multilayer film having a total thickness of 900 °, in which 0 ° Ti, then 15 ° NiFeCo alloy, and 20 ° Cu are sequentially stacked in 20 layers each. Note that, in order to improve the adhesion, ion milling of the substrate surface was performed with argon ions before forming the GMR film. Each of the targets used had a target composition of 99.9% or more in purity, and was evacuated to a final pressure of 4 × 10 ⁻⁷ Torr, and then an argon gas was introduced. The degree of vacuum during the film formation was 1.4 × 10 ^{−. 4} Torr. The acceleration voltage of argon ions during film formation is 300 V,
Beam current (proportional to the amount of argon ions) is 30 mA, N
The average deposition rate of iFeCo and Cu is 0.03 nm /
sec.

After the film formation, a pattern of a magnetoresistive element, which is a magnetically sensitive portion, was formed by photolithography. The pattern shapes were various shapes as shown below (Example samples 1 and 2; Comparative samples 1 to 5).

(1) Example Sample 1 As shown in FIGS. 5 and 6, ten magnetoresistive elements (n = 5) are arranged in parallel within a width P corresponding to the magnetized pitch P of the object to be detected. Example 1 was prepared by arranging. In FIG. 5, (P / 10) = 246 μm.

[0061] (2) Total of 4n (20; n = 5) As shown in Example Sample 2 8 a magnetoresistive element is provided for, added to A _m and B _m and their installation position An embodiment in which twenty magnetoresistive elements constituting a bridge circuit are arranged in parallel within a width P corresponding to a magnetized pitch P of a detection object by magnetoresistive elements A _m ′ and B _m ′ Sample 2 was produced. In FIG. 8, (P / 10) = 246 μm.

(3) Comparative Example Sample 1 As shown in FIG. 15, ten magnetoresistive elements (n
= 5) was prepared. This sample, while maintaining the pitch of A _m and B _m to (P / 2), in which the element to be these pairs were staggered in the right direction by P / 5. Therefore, all the elements do not fall within the width P corresponding to the magnetization pitch P, and the two elements B ₄ and B ₅ are out of the range of P. FIG.
In (P / 5) = 492 μm, (P / 10) = 2
It was 46 μm.

(4) Comparative Example Sample 2 This is of the same concept as the technology disclosed as the prior art in Japanese Patent Application Laid-Open No. 3-221814. As shown in FIG. 16, ten magnetoresistive elements are arranged in a width P corresponding to a magnetization pitch P. Pitch of A _m and B _m are a (P / 2), not originally were sequentially arranged A _m, then to satisfy equation (1) of the present invention to have sequentially arranged B _m .

(5) Comparative Example Sample 3 This is the same idea as the technique disclosed as the invention in Japanese Patent Application Laid-Open No. Hei 3-221814. As shown in FIG. 17, ten magnetoresistive elements are arranged in a width P corresponding to a magnetization pitch P. Pitch of A _m and B _m are not satisfy the equation (2) of the present invention does not become a (P / 2).

(6) Comparative Example Sample 4 This is the same idea as the technique disclosed in FIG. 4 in JP-A-4-282417. 18 (a) to 18 (f), the arrangement is shifted for each different set so that the arrangement format can be easily understood. This does not satisfy the formulas (1) and (2) of the present invention.

(7) Comparative Example Sample 5 This is the same idea as the technique disclosed in FIG. 1 in JP-A-61-99816. That is, as shown in FIG. 19, the detecting device includes two adjacent patterns A ₁ and B ₁ , A ₂ and B ₂ , A ₃ and B ₃ , A ₄ and B ₄ ,
A ₅ and B ₅ make a pair (n = 5), and patterns forming each pair are arranged at a pitch of (P−P / n). Pitch of A _m and B _m are the (P / 2), but the relationship of formula (1) of the present invention is not be satisfied. Also, the entire element does not fall within the pitch P.

For all of the above samples, a 1 μm gold film was separately formed by sputtering as a conductive electrode film (electrode pad). A tin-plated copper wire is joined to the conductor electrode film (electrode pad) by soldering, and a silicon resin is mainly formed on the magnetoresistive element in order to prevent self-heating of the magnetoresistive element (element). A material having good thermal conductivity as a component was formed.

In each of the above samples, the pattern width of the magnetoresistive element was 30 μm, the element length was 3.0 mm, and the total length was 9.0 mm. The resistance of each of the fabricated devices was 1.04 to 1.05 kΩ,
The rate of change (MR Ratio) was 14 to 15% in each case.

Each magnetic field sensor sample (symbol: MS) manufactured as described above is mounted on the outer peripheral surface of a rotating rotor 80 as shown in FIG. 14, and this rotor 80 is arranged inside a cylindrical magnetized body 90. Was evaluated as a rotational position sensor. The cylindrical magnetized body 90 is made of a ferrite rubber magnet,
The magnetization pitch P ′ of the rubber magnet was 2.58 mm, and the thickness was 1.5 mm. The inner diameter of the cylindrical rubber magnet (magnetized body 90) was 74 mm, and the gap G between the magnetic field sensor sample (code: MS) and the magnetized body 90 was 1.7 mm. When the period on the rotor is calculated in consideration of the gap G, the pitch P to be calculated by the equations (1) and (2) is P = 2.4.
6 mm is obtained. 5V when evaluating each sample
(= V _cc ) was applied and the output was measured.

The results are shown in Table 1 below.

[0071]

[Table 1] From the results shown in Table 1, the magnetic field sensor of the present invention can obtain many sensors from a 3-inch wafer in order to achieve compactness. In addition to high resolution,
Since the output is also large, it is possible to realize a significant cost reduction, high sensitivity and high output.

[0072]

The effects of the present invention are clear from the above results. That is, the magnetic field sensor according to the present invention has 2n (n ≧
3; n is an magnetic field sensor comprising a integer) of the magnetoresistive element, wherein among the 2n magnetoresistive element, a pair A _m and B _m are the following formulas (1) and (2 )
Are arranged in parallel within the width P corresponding to the magnetized pitch P of the object to be detected, and are connected in series.

A _m = (P (m−1) / n) Expression (1) (where m = 1, 2, 3,..., N) B _m = A _m ± P / 2 Expression (2) In the magnetic field sensor of the present invention having such a configuration, the sensor itself can be downsized, the resolution is high, and the output is large. Therefore, it is possible to realize significant cost reduction, high sensitivity, and high output.

[Brief description of the drawings]

FIG. 1 is a plan view showing a preferred first embodiment of a magnetic field sensor according to the present invention.

FIG. 2 is a plan view in which the circuit shown in FIG. 1 is changed to a specific configuration of a magnetic field sensor.

FIG. 3 is a plan view showing a second preferred embodiment of the magnetic field sensor of the present invention.

FIG. 4 is a plan view in which the circuit shown in FIG. 3 is changed to a specific configuration of a magnetic field sensor.

FIG. 5 is a plan view showing a third preferred embodiment of the magnetic field sensor of the present invention.

FIG. 6 is a plan view in which the circuit shown in FIG. 5 is changed to a specific configuration of a magnetic field sensor.

FIG. 7 is a diagram illustrating an equivalent circuit according to a third embodiment.

FIG. 8 is a plan view showing a fourth preferred embodiment of the magnetic field sensor of the present invention.

FIG. 9 is a diagram illustrating an equivalent circuit according to a fourth embodiment.

FIG. 10 is a schematic perspective view showing a usage example of the magnetic field sensor of the present invention.

FIG. 11 is a schematic side view showing another example of use of the magnetic field sensor of the present invention.

FIG. 12 is a graph showing how a magnetoresistive effect curve (MR curve) changes when a stress is applied in the longitudinal direction of a stripe-shaped magnetoresistive element. FIG.
2A shows an MR curve in a state where no stress is applied, FIG. 12B shows an MR curve in a state where a compressive stress is applied, and FIG. 12C shows an MR curve in a state where a tensile stress is applied.

FIGS. 13A to 13D show MR curves that change according to processing operations when a GMR film as a magnetoresistive element formed on a polyimide film substrate is subjected to stress processing, heat treatment, or the like. It is a graph shown.

FIG. 14 is a schematic plan view showing a state in which a magnetic field sensor is mounted on the outer peripheral surface of a rotating rotor, the rotor is arranged inside a cylindrical magnetized body, and the rotor is evaluated as a rotation position sensor.

FIG. 15 is a plan view showing an arrangement of elements in a conventional magnetic field sensor.

FIG. 16 is a plan view showing an arrangement of elements in a conventional magnetic field sensor.

FIG. 17 is a plan view showing an arrangement of elements in a conventional magnetic field sensor.

FIG. 18 is a plan view showing an arrangement of elements in a conventional magnetic field sensor.

FIG. 19 is a plan view showing an arrangement of elements in a conventional magnetic field sensor.

[Explanation of symbols]

1,2,3,4 ... magnetic field sensor 20 ... substrate _{A 1 ~A 5, B 1 ~B} 5 ... magnetoresistive element _{A 1 '~A 5', B} 1 '~B 5' ... magnetoresistive element

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takatoshi Oyama 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation (72) Inventor Koichi Kobayashi 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Inside the corporation

Claims (8)

[Claims] 1. A magnetic field sensor comprising 2n (n ≧ 3; n is an integer) magnetoresistive elements, wherein A _m and B _m forming a pair of the 2n magnetoresistive elements are: The width P that satisfies the positional relationship of the following equations (1) and (2) and that corresponds to the magnetized pitch P of the detection target
A magnetic field sensor, which is arranged in parallel and connected in series. A _m = (P (m-1) / n) Expression (1) (where m = 1, 2, 3,..., N) B _m = A _m ± P / 2 Expression (2) To 2. A set position of the A _m and B _m, each further by adding a magnetoresistive element one another, the total 4n; a (n ≧ 3 n is integer) of the magnetoresistive element provided by the a _m and B _m and a magnetic resistance effect element is added to these installation position, the magnetic field sensor of claim 1 formed by a bridge circuit. 3. The magnetic field sensor according to claim 1, wherein the magnetoresistance effect element is a magnetic film formed in a predetermined pattern, and the magnetic film is a film exhibiting a giant magnetoresistance effect. . 4. The magnetic field sensor according to claim 1, wherein six or more magnetoresistive elements are provided (n ≧ 3) and output three or more phase signals. . 5. The method according to claim 1, wherein the number of the magnetoresistive effect elements is 6 or more and 30 or more.
Or less (n = 3 to 15), 3 phases or more and 15
The magnetic field sensor according to any one of claims 1 to 3, wherein the magnetic field sensor outputs a signal of a phase or less. 6. The magnetic field sensor according to claim 1, wherein the magnetoresistive element is formed on a substrate, and the substrate has flexibility. 7. The magnetic field sensor according to claim 6, wherein the substrate is a flexible resin substrate. 8. The substrate according to claim 7, wherein said substrate is polyimide.
2. A magnetic field sensor according to claim 1.