JP2017198484A - Thin-film magnetic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin-film magnetic sensor that can accurately detect a change in an external magnetic field even when there is a temperature change, but does not cause increased manufacturing costs.SOLUTION: A thin-film magnetic sensor 10a comprises a magnetic field detection element 20, a temperature compensation element 30a connected in series to the magnetic field detection element 20, and a magnetic shield 40a enclosing the periphery of the temperature compensation element 30a. The magnetic field detection element 20 is provided with a TMR film (A) 22 and a pair of thin-film yokes (A) 24, 26 consisting of a soft magnetic material electrically connected to both ends of the TMR film (A) 22. The temperature compensation element 30a is provided with a TMR film (B) 32 and a pair of thin-film yokes (B) 34, 36 consisting of a soft magnetic material electrically connected to both ends of the TMR film (B) 32. It is desirable that the magnetic field sensitivity of the temperature compensation element 30a is lower than that of the magnetic field detection element 20. Furthermore, the magnetic shield 40a consists of the same material as the thin-film yokes (B) 34, 36.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a thin film magnetic sensor, and more particularly to a thin film magnetic sensor capable of accurately detecting a change in an external magnetic field even when a temperature change occurs.

  A magnetic sensor is an electromagnetic force (eg, current, voltage, power, magnetic field, magnetic flux, etc.), a mechanical quantity (eg, position, velocity, acceleration, displacement, distance, tension, pressure, torque, temperature, humidity, etc.), An electronic device that converts a detected amount such as a biochemical amount into a voltage via a magnetic field. Magnetic sensors are classified into Hall sensors, Anisotropic Magneto-Resistiity (AMR) sensors, Tunnel Magneto Resistance (TMR) sensors, etc., depending on the detection method of the magnetic field.

Among these, the TMR sensor
(1) Maximum value of change rate of electrical resistivity compared to AMR sensor (ie MR ratio = Δρ / ρ ₀ (Δρ = ρ _H −ρ ₀ : ρ _H is electrical resistivity in external magnetic field H, ρ ₀ is an extremely large electrical resistivity at zero external magnetic field)),
(2) The temperature change of the resistance value is small compared to the Hall sensor.
(3) Since the material having the TMR effect is a thin film material, it is suitable for microfabrication.
There are advantages such as. Therefore, the TMR sensor is expected to be applied as a high-sensitivity micromagnetic sensor used in computers, electric power, automobiles, home appliances, portable devices, and the like.

  As a material exhibiting the TMR effect, a multilayer film of a ferromagnetic layer (for example, permalloy or the like) and a nonmagnetic layer (for example, Cu, Ag, Au, or the like), an antiferromagnetic layer, a ferromagnetic layer (a fixed layer), A metal artificial lattice composed of a multilayer film (so-called “spin valve”) having a four-layer structure of a non-magnetic layer and a ferromagnetic layer (free layer); nanometer-sized fine particles composed of a ferromagnetic metal (for example, permalloy); , Metal-metal nanogranular material having a grain boundary phase made of nonmagnetic metal (for example, Cu, Ag, Au, etc.), tunnel junction film in which MR (Magneto-Resistivity) effect is produced by spin-dependent tunnel effect, nm size A metal-insulator nanogranular material having a ferromagnetic metal alloy fine particle and a grain boundary phase made of a nonmagnetic / insulating material is known.

  Among these, a multilayer film represented by a spin valve is generally characterized by high sensitivity in a low magnetic field. However, the multilayer film needs to be laminated with high accuracy with thin films made of various materials, so that the stability and yield are poor, and there is a limit in suppressing the manufacturing cost. For this reason, this type of multilayer film is used only for high value-added devices (for example, magnetic heads for hard disks), and is applied to magnetic sensors that are forced to compete with AMR sensors and Hall sensors with low unit prices. Is considered difficult. In addition, diffusion between the multilayer films is likely to occur, and the TMR effect is likely to be lost.

On the other hand, nano-granular materials are generally easy to produce and have good reproducibility. Therefore, if this is applied to a magnetic sensor, the cost of the magnetic sensor can be reduced. In particular, metal-insulator nanogranular materials
(1) If the composition is optimized, a high MR ratio exceeding 10% is exhibited at room temperature.
(2) Since the electrical resistivity ρ is an order of magnitude higher, it is possible to simultaneously achieve the miniaturization and low power consumption of the magnetic sensor.
(3) Unlike spin valve films including antiferromagnetic films with poor heat resistance, they can be used in high-temperature environments.
There are advantages such as. However, the metal-insulator nanogranular material has a problem that the magnetic field sensitivity in a low magnetic field is very small. Therefore, in such a case, yokes made of a soft magnetic material are disposed at both ends of the TMR film to increase the magnetic field sensitivity of the TMR film.

  In general, the resistance value of a magnetic sensor varies with temperature. Therefore, when an external magnetic field is detected using only a single element, there is a problem that the detection accuracy of the external magnetic field decreases when a temperature change occurs. In order to solve this problem, various proposals have heretofore been made.

For example, in Patent Documents 1 and 2, two magnetic tunnel effect elements having the same structure are connected in series to form a half-bridge circuit, and the upper surface of one magnetic tunnel effect element is covered with a soft magnetic material. A sensor is disclosed.
In Patent Document 2,
(A) When one of the magnetic tunnel effect elements is magnetically shielded by a soft magnetic material, the resistance value becomes a constant value regardless of the external magnetic field, and
(B) The magnetic sensor having such a configuration describes that the output voltage is substantially constant even when the environmental temperature changes.

Patent Document 3 does not aim to compensate for fluctuations in resistance value caused by temperature changes, but includes a giant magnetoresistive (GMR) film and a thin film yoke. A thin film magnetic sensor including a sensitivity portion is disclosed.
This document describes that when a high-sensitivity part and a low-sensitivity part are provided in a thin film yoke, both a high magnetic field and a low magnetic field can be measured simultaneously with an appropriate resolution.

  As described in Patent Documents 1 and 2, when the upper surface of the magnetic tunnel effect element is covered with a soft magnetic material, the sensitivity of the magnetic tunnel effect element can be reduced. Therefore, if a half-bridge circuit is configured using an element that is magnetically shielded and an element that is not magnetically shielded, it is possible to compensate for a variation in resistance value caused by a temperature change. As a result, it is possible to accurately detect a change in the external magnetic field regardless of the environmental temperature.

However, in order to coat the upper surface of the magnetic tunnel effect element with the soft magnetic material, a film forming process of the soft magnetic thin film is required separately, which increases the manufacturing cost. In addition, since the herb bridge circuit is configured using magnetic tunnel effect elements having the same structure, if the magnetic shielding by the soft magnetic material is insufficient, the compensation of the fluctuation of the resistance value is also insufficient. Become.
Furthermore, when two elements are connected in series to form a half-bridge circuit, it is necessary to join wires to both ends of each element. However, there has never been proposed an example of a thin film magnetic sensor that can compensate both for fluctuations in resistance value and facilitate wiring connection.

Special table 2014-508286 gazette JP 2001-345498 A JP 2009-204435 A

The problem to be solved by the present invention is to provide a thin film magnetic sensor that can accurately detect a change in an external magnetic field even when a temperature change occurs, and that does not increase the manufacturing cost. It is in.
Another object of the present invention is to provide a thin film magnetic sensor that can compensate for a variation in resistance value caused by a temperature change and that can be easily connected to a wiring.

In order to solve the above problems, a thin film magnetic sensor according to the present invention is summarized as having the following configuration.
(1) The thin film magnetic sensor
A substrate,
A magnetic field detection element for detecting a change in an external magnetic field formed on the substrate;
A temperature compensation element formed on the substrate and connected in series to the magnetic field detection element for compensating for a variation in resistance value caused by a temperature change;
And a magnetic shield formed on the substrate and surrounding the temperature compensation element.
(2) The magnetic field detecting element is
A TMR film (A) having a tunnel magnetoresistance effect;
A pair of thin film yokes (A) made of a soft magnetic material electrically connected to both ends of the TMR film (A).
(3) The temperature compensation element is
A TMR film (B) having a tunnel magnetoresistance effect;
A pair of thin film yokes (B) made of a soft magnetic material electrically connected to both ends of the TMR film (B).
(4) The magnetic shield is made of the same material as the thin film yoke (B).

The thin film magnetic sensor is
The magnetic shield is divided into two shield pieces by a slit;
Each of the divided shield pieces is preferably electrically connected to the pair of thin film yokes (B).

Even if the ambient temperature changes, the outside of the temperature compensation element is surrounded by a magnetic shield made of the same material as the thin film yoke. It is possible to accurately detect a change in the magnetic field. Further, since the magnetic shield surrounding the temperature compensation element can be formed simultaneously with the formation of the thin film yoke, an increase in manufacturing cost can be suppressed.
Furthermore, when the magnetic shield is divided into two parts and the divided shield pieces are integrated with the pair of thin film yokes (B) of the temperature compensation element, it is easy to pass through the shield pieces having a larger area than the thin film yoke (B). Wiring connection is possible.

It is a top view (Drawing 1 (A)) of a thin film magnetic sensor concerning a 1st embodiment of the present invention, and an enlarged plan view (Drawing 1 (B)) of a temperature compensation element and a magnetic shield. It is the top view (FIG. 2 (A)) of the thin film magnetic sensor which concerns on the 2nd Embodiment of this invention, and the enlarged plan view (FIG. 2 (B)) of a temperature compensation element and a magnetic shield. It is a figure which shows the relationship between an externally applied magnetic flux density and the magnetic flux density in a TMR element position.

Hereinafter, an embodiment of the present invention will be described in detail.
[1. Thin Film Magnetic Sensor (1)]
FIG. 1A shows a plan view of a thin film magnetic sensor according to the first embodiment of the present invention. FIG. 1B shows an enlarged plan view of the temperature compensation element and the magnetic shield. In FIG. 1, hatching is partially applied for easy viewing.

In FIG. 1, the thin film magnetic sensor 10a is
A substrate (not shown);
A magnetic field detection element 20 for detecting a change in an external magnetic field formed on the substrate;
A temperature compensation element 30a formed on the substrate and connected in series to the magnetic field detection element 20 to compensate for a variation in resistance value caused by a temperature change;
And a magnetic shield 40a surrounding the periphery of the temperature compensation element 30a formed on the substrate.

[1.1. substrate]
The substrate is for forming the magnetic field detection element 20, the temperature compensation element 30a, and the magnetic shield 40a on the surface thereof. The material and shape of the substrate are not particularly limited, and an optimal material and shape can be selected according to the purpose.

[1.2. Magnetic field detection element]
The magnetic field detection element 20 includes a TMR film (A) 22 having a tunnel magnetoresistive effect, and a pair of thin film yokes (A) 24 and 26 made of a soft magnetic material electrically connected to both ends of the TMR film (A) 22. And.

[1.2.1. TMR film (A)]
The TMR film (A) 22 is for sensing a change in the external magnetic field as a change in the electric resistance R and consequently detecting it as a change in the voltage, and is made of a material having a tunnel magnetoresistance (TMR) effect. In order to detect a change in the external magnetic field with high sensitivity, the absolute value of the MR ratio of the TMR film (A) 22 is preferably as large as possible. Specifically, the absolute value of the MR ratio of the TMR film (A) 22 is preferably 5% or more, and more preferably 10% or more.

Further, since the TMR film (A) 22 is directly electrically connected to the thin film yokes (A) 24 and 26, the TMR film (A) 22 has a higher electrical ratio than the thin film yokes (A) 24 and 26. Those having a resistance ρ are used. Generally, if the electrical resistivity ρ of the TMR film (A) 22 is too small, the thin film yokes (A) 24 and 26 are electrically short-circuited, which is not preferable. On the other hand, when the electrical specific resistance ρ of the TMR film (A) 22 is too high, noise increases and it becomes difficult to detect a change in the external magnetic field as a voltage change.
Specifically, the electrical specific resistance ρ of the TMR film (A) 22 is preferably 10 ³ μΩcm or more and 10 ¹² μΩcm or less, more preferably 10 ⁴ μΩcm or more and 10 ¹¹ μΩcm or less.

  There are various materials that satisfy such conditions, and among them, the above-described metal-insulator nanogranular material is particularly suitable. Metal-insulator nanogranular materials not only have high MR ratio and high electrical resistivity ρ, but also MR ratio does not fluctuate greatly due to slight composition fluctuations, so that thin films with stable magnetic properties can be reproduced. There is an advantage that it can be manufactured at low cost.

As a metal-insulator system nano granular material used as the TMR film (A) 22, specifically,
_{(1) Co-Y 2 O} 3 system nano granular alloy, Co-Al ₂ O ₃ system nano granular alloy, Co-Sm ₂ O ₃ system nano granular alloy, Co-Dy ₂ O ₃ system nano granular alloy, FeCo-Y ₂ O ₃ system Oxide nanogranular alloys such as nanogranular alloys,
(2) Fluoride-based nanogranular alloys such as Fe—MgF ₂ , FeCo—MgF ₂ , Fe—CaF ₂ , FeCo—AlF ₃ ,
and so on.

[1.2.2. Thin-film yoke (A)]
The thin film yokes (A) 24 and 26 are opposed to each other through a gap, and the TMR film (A) 22 is electrically connected to the thin film yokes (A) 24 and 26 in or near the gap.
Here, “near the gap” means a region affected by a large amplified magnetic field generated at the tips of the thin film yokes (A) 24 and 26. Since the magnetic field generated between the thin film yokes (A) 24 and 26 is the largest in the gap, the TMR film (A) 22 is most preferably formed in the gap, but acts on the TMR film (A) 22. When the magnetic field to be applied is sufficiently large in practice, it means that all or part of the magnetic field may be outside the gap (for example, the upper surface side or the lower surface side of the thin film yoke (A) 24, 26).

  The thin film yokes (A) 24 and 26 are for increasing the magnetic field sensitivity of the TMR film (A) 22 and are made of a soft magnetic material. In order to obtain a high magnetic field sensitivity to a weak magnetic field, it is preferable to use a material having high permeability μ and / or saturation magnetization Ms for the thin film yokes (A) 24 and 26. The material of the thin-film yokes (A) 24 and 26 is preferably one that does not have magnetic saturation in the range of the external magnetic field to be used. On the other hand, the magnetic permeability μ of the soft magnetic material is preferably as high as possible. For example, 5000 or more is preferable.

As a soft magnetic material satisfying such conditions, specifically,
(A) 40-90% Ni-Fe alloy, Fe ₇₄ Si ₉ Al ₁₇ , Fe ₁₂ Ni ₈₂ Nb ₆ , Fe _75.6 Si _13.2 B _8.5 Nb _1.9 Cu _0.8 , Fe ₈₃ Hf ₆ C ₁₁ , Fe ₈₅ Zr ₁₀ B ₅ Alloy, Fe ₉₃ Si ₃ N ₄ alloy, Fe ₇₁ B ₁₁ N ₁₈ alloy,
(B) 40-90% Ni—Fe alloy / SiO ₂ multilayer film,
(C) Fe _71.3 Nd _9.6 O _19.1 nano granular alloy, Co ₇₀ Al ₁₀ O ₂₀ nano granular alloy, Co ₆₅ Fe ₅ Al ₁₀ O ₂₀ nano granular alloy,
(D) Co ₃₅ Fe ₃₅ Mg ₁₀ F ₂₀ nano granular alloy.

[1.2.3. Shape and dimensions of magnetic field detection element]
The magnetic field detection element 20 is for detecting a change in the external magnetic field. Therefore, the larger the magnetic field sensitivity in the magnetic sensing direction, the better.
Here, the “magnetic direction” refers to the direction in which an external magnetic field is applied when the magnetic field sensitivity of the TMR film (A) 22 is maximized.

The shape and size of each part of the magnetic field detection element 20 affects the magnetic field sensitivity in the magnetic sensitive direction. Generally, the shorter the gap length (the length of the TMR film (A) 22 in the magnetic sensing direction) g ₁ , the higher the sensitivity because the leakage magnetic flux decreases. Further, as the length of the thin film yokes (A) 24, 26 in the magnetic sensing direction becomes longer, the demagnetizing factor of the thin film yokes (A) 24, 26 becomes smaller, so that the sensitivity becomes higher. Therefore, it is preferable to select the optimal shape and size of each part of the magnetic field detection element 20 so that the desired sensitivity can be obtained.

[1.3. Temperature compensation element]
The temperature compensation element 30a includes a TMR film (B) 32 having a tunnel magnetoresistive effect, and a pair of thin film yokes (B) 34, 36 made of a soft magnetic material electrically connected to both ends of the TMR film (B) 32. And. The temperature compensation element 30a may have a magnetic field sensitivity equal to or higher than that of the magnetic field detection element 20 when the magnetic shield 40a is not provided. However, in order to reduce the error due to the temperature change, it is preferable that the temperature compensation element 30a has a lower magnetic field sensitivity than the magnetic field detection element 20 when the magnetic shield 40a is not provided.

[1.3.1. TMR film (B)]
The material of the TMR film (B) 32 may be a material different from the TMR film (A) 22 of the magnetic field detection element 20 or the same material. If the same material is used for the TMR film (B) 32 and the TMR film (A) 22, both TMR films can be formed simultaneously in one step, and thus the manufacturing cost can be reduced.
The other points regarding the material of the TMR film (B) 32 are the same as those of the TMR film (A) 22, and thus the description thereof is omitted.

[1.3.2. Thin-film yoke (B)]
The material of the thin film yokes (B) 34 and 36 may be different from the material of the thin film yokes (A) 24 and 26 of the magnetic field detection element 20 or may be the same material. If the same material is used for the thin-film yokes (B) 34 and 36 and the thin-film yokes (A) 24 and 26, both thin-film yokes can be formed at the same time in one step, so that the manufacturing cost can be reduced.
Since the other points regarding the material of the thin film yokes (B) 34 and 36 are the same as those of the thin film yokes (A) 24 and 26, description thereof will be omitted.

[1.3.3. Magnetic field sensitivity]
The temperature compensation element 30a is for compensating for a change in resistance value caused by a temperature change. For this reason, the smaller the magnetic field sensitivity of the temperature compensation element 30a, the better.
As a method of reducing the magnetic field sensitivity of the temperature compensation element 30a, there are a method of reducing the magnetic field sensitivity itself of the temperature compensation element 30a and a method of indirectly reducing it using a magnetic shield 40a described later. In the present invention, the magnetic shield 40a is used, but it is difficult to completely block the external magnetic field only by the magnetic shield 40a. Therefore, in addition to using the magnetic shield 40a, it is preferable to reduce the magnetic field sensitivity itself of the temperature compensation element 30a.

As will be described later, when the dimensions of each part of the temperature compensation element 30a are optimized, the magnetic field sensitivity of the temperature compensation element 30a (magnetic field sensitivity in the absence of the magnetic shield 40a) is ½ or less of that of the magnetic field detection element 20. can do. The magnetic field sensitivity of the temperature compensation element 30a is preferably 1/5 or less, more preferably 1/10 or less that of the magnetic field detection element 20.
Here, “magnetic field sensitivity” refers to the ease with which the electrical resistivity of an element changes due to a change in an external magnetic field (strictly, an external magnetic field of a component in the direction of magnetic sensing of the element). Therefore, “low magnetic field sensitivity” means that the electrical resistivity is difficult to change even if the external magnetic field changes greatly. On the other hand, “high magnetic field sensitivity” means a property in which the electrical resistivity easily changes even with a slight change in the external magnetic field. In the present invention, by using both, a high-performance magnetic sensor can be obtained even when the environmental temperature changes.

The method for changing the magnetic field sensitivity is not particularly limited. For example, the gap length (the length in the magnetic sensing direction of the TMR film), the thin film yoke length (the length in the direction parallel to the magnetic sensing direction), and the thin film yoke are used. There is a method of changing the aspect ratio represented by length / thin film yoke width.
Since the magnetic field sensitivity decreases as the gap length increases, the gap length of the temperature compensation element is preferably longer than the gap length of the magnetic field detection element.
Further, since the magnetic field sensitivity decreases as the length of the thin film yoke becomes shorter, the thin film yoke length of the temperature compensation element is preferably shorter than the thin film yoke length of the magnetic field detection element.
Furthermore, since the magnetic field sensitivity decreases as the aspect ratio decreases, the aspect ratio of the temperature compensation element is preferably smaller than the aspect ratio of the magnetic field detection element.
Although only one of the three methods described above may be used, the magnetic field sensitivity can be changed by using a plurality of methods. Therefore, in FIG. 1, all the three methods described above are employed.

[1.3.4. Temperature compensation element shape and dimensions]
The shape and size of each part of the temperature compensation element 30a affects the magnetic field sensitivity in the magnetic sensing direction. In general, as the gap length (the length in the magnetic sensing direction of the TMR film (B) 32) g ₂ increases, the leakage magnetic flux increases, resulting in a low sensitivity. Further, as the length A _{1 of} the thin film yokes (B) 34, 36 in the magnetic sensing direction becomes shorter, the demagnetizing field coefficient of the thin film yokes (B) 34, 36 becomes larger, so the sensitivity becomes lower. For this reason, it is preferable to select the optimum shape and size of each part of the temperature compensation element 30a so that the desired magnetic field sensitivity can be obtained.

Furthermore, since the electric resistance of the TMR film (B) 32 is much larger than that of the thin film yokes (B) 34 and 36, the electric resistance of the temperature compensation element 30 a is almost equal to that of the TMR film (B) 32. This also applies to the magnetic field detection element 20.
The thin film magnetic sensor 10a outputs a potential (middle point potential) between the magnetic field detection element 20 and the temperature compensation element 30a, and obtains the strength of the magnetic field by calculation using the middle point potential. In order to facilitate the calculation, it is preferable that the electric resistances of the temperature compensation element 30a and the magnetic field detection element 20 are close to each other.

More specifically, it is preferable that the temperature compensation element 20 and the magnetic field detection element 20 satisfy the relationship of the following formula (1). When the electrical resistances are close to each other, the resistance difference between the two can be ignored, so that calculation (correction processing) becomes unnecessary. The difference in resistance between the two is preferably 10% or less, more preferably 1% or less.
| R _H −R _L | / R _H ≦ 0.1 (1)
However,
R _H is the resistance value of the TMR film (A) at room temperature,
R _L is the resistance value of the TMR film (B) at room temperature.

In the case where the same material is used for the TMR film (B) 32 and the TMR film (A) 22, since these are formed simultaneously in one process, the film thicknesses of both are generally the same. Therefore, the gap length g _{2 of} the TMR film (B) 32 and the length perpendicular to the magnetic sensing direction (equal to the width B ₁ of the thin film yoke (B) in the example shown in FIG. 1) are optimized. Then, only the magnetic field sensitivity can be lowered while maintaining the electrical resistance of the TMR film (B) 32 to be the same as that of the TMR film (A) 22. Further, when the shape of the TMR film (B) 32 is optimized, an increase in the size of the temperature compensation element 30a can be avoided.

For example, when the shape of the TMR film (B) 32 is the same as that of the TMR film (A) 22, the relationship of the formula (1) is automatically satisfied. In this case, the temperature compensation element 30a is lowered in sensitivity only by increasing the demagnetizing factor of the thin film yokes (B) 34, 36.
On the other hand, when the shape of the TMR film (B) 32 is changed so as to satisfy the expression (1), both the increase in the gap length g _{2 and} the increase in the demagnetizing factor of the thin film yokes (B) 34 and 36 are used. Thus, the temperature compensation element 30a can be further reduced in sensitivity.

The length A _{1 in the} direction parallel to the magnetic sensing direction of the thin-film yokes (B) 34 and 36 is not particularly limited, and is at least a length that ensures electrical connection with the TMR film (B) 32. I need it. However, in the present embodiment, wiring is connected to the thin film yokes (B) 34 and 36. Therefore, it is preferable that the length A ₁ in the magnetic sensing direction of the thin film yokes (B) 34 and 36 is set to a length that facilitates the connection of the wiring.

[1.4. Magnetic shield]
The magnetic shield 40a is for suppressing the inflow of the magnetic flux to the temperature compensation element 30a by inducing the magnetic flux therein. In the present invention, the magnetic shield 40a is formed on the substrate so as to surround the temperature compensation element 30a. This is different from the conventional one.

[1.4.1. Magnetic shield material]
In the present invention, the same material as the thin film yokes (B) 34 and 36 is used as the material of the magnetic shield 40a. This is because the thin-film yokes (B) 34 and 36 and the magnetic shield 40a are formed simultaneously to simplify the manufacturing process. The materials for the thin-film yokes (B) 34 and 36 are as described above, and will not be described.

[1.4.2. Magnetic shield shape]
The shape of the magnetic shield 40a is not particularly limited as long as it can suppress the inflow of magnetic flux to the temperature compensation element 30a. In FIG. 1, the shape of the magnetic shield 40a is a hollow rectangular shape in which both the outer peripheral shape and the inner peripheral shape are rectangular, but this is merely an example.
As the shape of the magnetic shield 40a, for example,
(A) The outer peripheral shape and the inner peripheral shape are both circular or elliptical,
(B) The outer peripheral shape and the inner peripheral shape are both polygons such as pentagons, hexagons, octagons,
(C) The outer peripheral shape is a circle or an ellipse, and the inner peripheral shape is a polygon.
(D) The outer peripheral shape is a polygonal shape, and the inner peripheral shape is a circle or an ellipse,
and so on.

[1.4.3. Magnetic shield dimensions]
The size of each part of the magnetic shield 40a affects the magnetic shield effect.

[A. Magnetic shield thickness]
If the thickness of the magnetic shield 40a is too thin with respect to the thickness of the thin film yokes (B) 34, 36, the magnetic flux easily flows into the thin film yokes (B) 34, 36, and the magnetic shielding effect is reduced. On the other hand, even if the thickness of the magnetic shield 40a is increased more than necessary, there is no difference in effect and there is no actual benefit. In order to suppress the inflow of magnetic flux to the temperature compensation element 30a, the average thickness of the magnetic shield 40a is preferably substantially the same as that of the thin film yokes (B) 34 and 36.

  The magnetic shield 40a may be formed separately from the thin film yokes (A) 24, 26 and the thin film yokes (B) 34, 36. However, in order to reduce the manufacturing cost, it is preferable to simultaneously form the magnetic shield 40a and the thin film yokes (B) 34 and 36 (and the thin film yokes (A) 24 and 26) in one step. When the magnetic shield 40a and the thin film yokes (B) 34 and 36 are formed simultaneously, the average thickness of the two is generally the same (the difference in film thickness is, for example, 10% or less). In addition, what is necessary is just to calculate an average value by performing the film thickness measurement by SEM observation several times about the cross section of arbitrary places.

[B. Magnetic shield planar dimensions]
In order to obtain a high magnetic shielding effect, it is preferable to determine the dimensions of each part so that the inflow of magnetic flux in the direction of magnetic sensing of the temperature compensation element 30a is suppressed. Specifically, the magnetic shield 40a preferably satisfies the following expressions (11) to (14).
100 nm ≦ a _ALL <20 μm (11)
100 nm ≦ b _ALL <20 μm (12)
(B ₁ + 2b) _{MAX / 2} * _0.75 ≦ A _2MIN (13)
(B ₁ + 2b) _MAX / 2 _* 0.75 _≦ B _2MIN (14)
However,
a _ALL is the length (a) of the gap between the thin-film yoke (B) and the magnetic shield in the direction parallel to the magnetic sensing direction of the temperature compensation element,
b _ALL is the length (b) of the gap between the thin-film yoke (B) and the magnetic shield in the direction perpendicular to the magnetic sensing direction of the temperature compensation element,
B ₁ is the width of the thin film yoke (B),
(B ₁ + 2b) _MAX is the maximum value of the distance (B ₁ + 2b) between the magnetic shields in the direction perpendicular to the magnetic sensing direction of the temperature compensation element,
A _2MIN is the minimum value of the length (A ₂ ) of the magnetic shield in the direction parallel to the magnetic sensing direction of the temperature compensation element,
B _2MIN is the minimum value of the length (B ₂ ) of the magnetic shield in the direction perpendicular to the magnetic sensing direction of the temperature compensation element.

Here, it is preferable that the expressions (11) and (12) hold for “a” and “b” everywhere, even when “a” and “b” differ from place to place. Represent.
Moreover, Formula (13) and Formula (14) _show that it is preferable that A _2MIN and B _2MIN are satisfied at least even when A ₂ and B ₂ are different depending on locations.
As will be described later, when the thin film yoke is extended and connected to the magnetic shield, “b _ALL ” does not include a portion where the thin film yoke and the magnetic shield are connected. This also applies to “a _ALL ”.

Formula (11) represents the allowable range of a _ALL . If a _ALL is too short, the magnetic shield 40a and the temperature compensation element 30a may be short-circuited. Accordingly, a _ALL is preferably 100 nm or more. a _ALL is preferably 1 μm or more, more preferably 3 μm or more.
On the other hand, if a _ALL becomes too large, the magnetic shielding effect is reduced and the thin film magnetic sensor 10a is also enlarged. Therefore, a _ALL is preferably 20 μm or less. a _ALL is more preferably 10 μm or less.

Equation (12) represents the allowable range of b _ALL . If b _ALL is too short, the magnetic shield 40a and the temperature compensation element 30a may be short-circuited. Therefore, b _ALL is preferably 100 nm or more. b _ALL is preferably 1 μm or more, more preferably 3 μm or more.
On the other hand, if b _ALL becomes too large, not only will there be no profit, but the thin-film magnetic sensor 10a will become large. Therefore, b _ALL is preferably 20 μm or less. b _ALL is more preferably 10 μm or less.

Equation (13) represents the allowable range of A _2. The smaller A ₂ is, the less the magnetic shielding effect is. Therefore, A _2MIN is preferably (B ₁ + 2b) _MAX /2*0.75 or more. A _2MIN is more preferably (B ₁ + 2b) _MAX /2*1.0 or more.
On the other hand, even if A ₂ is increased more than necessary, there is no difference in the magnetic shielding effect and there is no actual benefit. Further, if A ₂ is increased more than necessary, the thin film magnetic sensor 10a is increased in size. Therefore, the maximum value of A ₂ (A _2MAX ) is preferably (B ₁ + 2b) _{MAX / 2} * 37.5 or less. A _2MAX is more preferably (B ₁ + 2b) _MAX /2*18.75 or less.

Equation (14) represents the tolerance of B _2. The smaller the B ₂ , the less the magnetic shielding effect. Therefore, B _2MIN is preferably (B ₁ + 2b) _MAX /2*0.75 or more. B _2MIN is more preferably (B ₁ + 2b) _MAX /2*1.0 or more.
On the other hand, even if B ₂ is increased more than necessary, there is no difference in the magnetic shielding effect and there is no actual benefit. Further, if B ₂ is increased more than necessary, the thin film magnetic sensor 10a is increased in size. Therefore, the maximum value of B ₂ (B _2MAX ) is preferably (B ₁ + 2b) _MAX /2*37.5 or less. B _2MAX is more preferably (B ₁ + 2b) _MAX /2*18.75 or less.

  The outer peripheral width W and the outer peripheral length L of the magnetic shield 40a are uniquely determined when the dimensions of the other portions of the magnetic shield 40a and the size of the temperature compensation element 30a are determined.

[1.5. Arrangement and connection]
The arrangement of the magnetic field detection element 20 and the temperature compensation element 30b is not particularly limited. For example, as shown in FIG. 1, they may be arranged so that the magnetic sensing directions of the magnetic field detection element 20 and the temperature compensation element 30a are parallel to each other. Alternatively, although not shown, they may be arranged so that the magnetic sensing directions of the magnetic field detection element 20 and the temperature compensation element 30a are non-parallel.

  Further, in the example shown in FIG. 1, the thin film magnetic sensor 10a includes a half bridge circuit in which a magnetic field detection element 20 and a temperature compensation element 30a are connected in series. A combination of two half bridge circuits results in a full bridge circuit. The present invention can be applied to both a half bridge circuit and a full bridge circuit. In the case of a full bridge circuit, the difference between the midpoint potentials of the half bridge circuits is output.

[2. Thin-film magnetic sensor (2)]
FIG. 2A shows a plan view of a thin film magnetic sensor according to the second embodiment of the present invention. FIG. 2B shows an enlarged plan view of the temperature compensation element and the magnetic shield. In FIG. 2, hatching is partially applied for easy viewing.

In FIG. 2, the thin film magnetic sensor 10b is
A substrate (not shown);
A magnetic field detection element 20 for detecting a change in an external magnetic field formed on the substrate;
A temperature compensation element 30b formed on the substrate and connected in series to the magnetic field detection element 20 to compensate for a variation in resistance value caused by a temperature change;
A magnetic shield 40b formed on the substrate and surrounding the temperature compensation element 30b.

In this embodiment,
The magnetic shield 40b is divided into two shield pieces 46 and 48 by slits 42 and 44,
The divided shield pieces 46 and 68 are electrically connected to the pair of thin film yokes (B) 34 and 36, respectively. This is different from the first embodiment.

[2.1. substrate]
Since the details of the substrate are the same as those in the first embodiment, description thereof is omitted.

[2.2. Magnetic field detection element]
The magnetic field detection element 20 includes a TMR film (A) 22 having a tunnel magnetoresistive effect, and a pair of thin film yokes (A) 24 and 26 made of a soft magnetic material electrically connected to both ends of the TMR film (A) 22. And. The details of the magnetic field detection element 20 are the same as those in the first embodiment, and a description thereof will be omitted.

[2.3. Temperature compensation element]
The temperature compensation element 30b includes a TMR film (B) 32 having a tunnel magnetoresistive effect, and a pair of thin film yokes (B) 34, 36 made of a soft magnetic material electrically connected to both ends of the TMR film (B) 32. And. The temperature compensation element 30a preferably has a lower magnetic field sensitivity than the magnetic field detection element 20. Further, the thin film yokes (B) 34 and 36 are extended in the direction perpendicular to the magnetic sensing direction, and are integrated with the shield pieces 46 and 48, respectively. This point is different from the first embodiment.

Further, in the present embodiment, the wiring of the temperature compensation element 30 b is connected through the shield pieces 46 and 48. Therefore, the length A ₁ in the magnetic sensing direction of the thin-film yokes (B) 34 and 36 can be arbitrarily selected according to the purpose without considering the ease of wiring.
The other points of the temperature compensation element 30b are the same as those of the first embodiment, and thus description thereof is omitted.

[2.4. Magnetic shield]
The magnetic shield 40b is for suppressing the inflow of the magnetic flux to the temperature compensation element 30b by inducing the magnetic flux therein. The magnetic shield 40b is formed so as to surround the temperature compensation element 30b. Further, the magnetic shield 40 b is divided into two shield pieces 46 and 48 by slits 42 and 44.

The positions of the slits 42 and 44 are not particularly limited, and an optimum position is selected according to the shape of the magnetic shield 40b, the shape of the temperature compensation element 30b, the arrangement of the magnetic field detection element 20, the wiring connection method, and the like. be able to.
However, if the volumes of the shield pieces 46 and 48 are significantly different from each other, the magnetic flux cannot be evenly released. Therefore, it is preferable to determine the positions of the slits 42 and 44 so that the volume ratio between the shield piece 46 and the shield piece 48 is 30:70 to 70:30.

On the other hand, the width of the slits 42 and 44 affects the magnetic shield effect. Specifically, it is preferable that the widths of the slits 42 and 44 satisfy the relationship of the following formula (15).
100 nm ≦ c _ALL ≦ 2 μm (15)
However, c _ALL is the width (c) of the slit, and is the width at every point.
Here, the expression (15) indicates that it is preferable to hold for “c” everywhere, even when “c” varies from place to place.

Equation (15) represents the allowable range of c _ALL . If the c _ALL is too short, the shield pieces 46 and 48 may be short-circuited. Therefore, c _ALL is preferably 100 nm or more. c _ALL is preferably 1 μm or more.
On the other hand, if c _ALL becomes too large, the magnetic flux leakage increases and the magnetic shielding effect is reduced. Therefore, c _ALL is preferably 2 μm or less.

  Other points regarding the magnetic shield 40b are the same as those in the first embodiment, and thus the description thereof is omitted.

[2.5. Arrangement and connection]
In the present embodiment, the temperature compensation element 30 b is connected to the wiring via the shield pieces 46 and 48. Since the arrangement of the magnetic field detection element 20 and the temperature compensation element 30b and the other points of the wiring are the same as those in the first embodiment, description thereof will be omitted.

[3. Manufacturing method of thin film magnetic sensor]
The thin film magnetic sensors 10a and 10b according to the present invention can be manufactured by laminating thin films having a predetermined composition on a substrate surface in a predetermined order. At this time, if the magnetic shields 40a and 40b and the thin film yokes (B) 32 and 34 are formed at the same time, the manufacturing process can be simplified.

[4. Action]
In general, the resistance value of a magnetic sensor varies with temperature. Therefore, when an external magnetic field is detected using only a single element, there is a problem that the detection accuracy of the external magnetic field decreases when a temperature change occurs. In order to solve this problem, two elements having the same structure are connected in series to form a half-bridge structure, one is used as it is as a high-sensitivity element, and the other upper surface is covered with a magnetic shield made of a soft magnetic material. Making it a sensitivity element is performed. However, this method requires a magnetic shield film forming step, which increases the manufacturing cost.

In addition, in a magnetic sensor using a TMR film, it is conceivable to reduce the sensitivity by shortening the length of the thin film yoke in the magnetic sensing direction or increasing the length of the gap. However, this method has disadvantages such as insufficient sensitivity reduction, an increase in the absolute value of the resistance value, and a significant increase in the element size.
Furthermore, it is conceivable to use a non-magnetic material for the thin film yoke of the low sensitivity element. However, this method increases the number of steps of forming the nonmagnetic film, the masks accompanying it, and the processing steps.

  On the other hand, if a magnetic field detection element and a temperature compensation element are connected in series to form a bridge circuit and the temperature compensation element is surrounded by a magnetic shield made of the same material as the thin film yoke, the magnetic flux near the temperature compensation element is magnetized. Be actively guided to the shield. As a result, the magnetic flux flowing through the TMR film of the temperature compensation element is reduced and the sensitivity is further lowered. Further, even when the environmental temperature changes due to this, a change in the external magnetic field can be accurately detected.

Further, since the same material as the thin film yoke can be used as the material for the magnetic shield, the magnetic shield can be formed simultaneously with the formation of the thin film yoke. Therefore, there is no change in the number of steps associated with the reduction in sensitivity, and a low-sensitivity element can be easily obtained.
Furthermore, if the magnetic shield is divided into two parts and the divided shield pieces are connected to the pair of thin film yokes (B) of the temperature compensation element, wiring connection is facilitated.

(Example 1, Comparative Example 1)
[1. Preparation of sample]
A thin film magnetic sensor having the shape shown in FIG. 2 was produced (Example 1). A magnetic sensor having the same shape as that of Example 1 was prepared except that no magnetic shield was provided (Comparative Example 1).

[2. Test method and results]
An external magnetic field was applied to the obtained thin film magnetic sensor, and the magnetic flux density at the position of the TMR element (temperature compensation element 30b) was measured. FIG. 3 shows the relationship between the externally applied magnetic flux density and the magnetic flux density at the TMR element position. In the thin film magnetic sensor of Comparative Example 1, the magnetic flux density at the TMR element position was higher than the externally applied magnetic flux density. This is because the magnetic flux concentrates on the TMR element due to the magnetic flux collecting effect of the thin film yoke. On the other hand, in the thin film magnetic sensor of Example 1, the magnetic flux density at the TMR element position was lower than the externally applied magnetic flux density. This is because the external magnetic flux bypasses the TMR element via the magnetic shield.

  The embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention.

The thin film magnetic sensor according to the present invention detects rotation information of automobile axles, rotary encoders, industrial gears, etc., detects position / speed information of hydraulic cylinder / pneumatic cylinder stroke position, machine tool slide, etc. It can be used for detection of current information such as arc current of an industrial welding robot, a geomagnetic compass, and the like.
A magnetoresistive element having a TMR film and thin film yokes disposed at both ends thereof is particularly suitable as a magnetic sensor. However, the use of the magnetoresistive element is not limited to this, but a magnetic memory, magnetic It can also be used as a head or the like.

10a, 10b Thin film magnetic sensor 20 Magnetic field detection element 22 TMR film (A)
24, 26 Thin film yoke (A)
30a, 30b Temperature compensation element 32 TMR film (B)
34, 36 Thin-film yoke (B)
40a, 40b Magnetic shield 42, 44 Slit

Claims (7)

A thin film magnetic sensor having the following configuration.
(1) The thin film magnetic sensor
A substrate,
A magnetic field detection element for detecting a change in an external magnetic field formed on the substrate;
A temperature compensation element formed on the substrate and connected in series to the magnetic field detection element for compensating for a variation in resistance value caused by a temperature change;
And a magnetic shield formed on the substrate and surrounding the temperature compensation element.
(2) The magnetic field detecting element is
A TMR film (A) having a tunnel magnetoresistance effect;
A pair of thin film yokes (A) made of a soft magnetic material electrically connected to both ends of the TMR film (A).
(3) The temperature compensation element is
A TMR film (B) having a tunnel magnetoresistance effect;
A pair of thin film yokes (B) made of a soft magnetic material electrically connected to both ends of the TMR film (B).
(4) The magnetic shield is made of the same material as the thin film yoke (B).   The thin film magnetic sensor according to claim 1, wherein the magnetic field sensitivity of the temperature compensation element is lower than that of the magnetic field detection element.   3. The thin film magnetic sensor according to claim 1, wherein a magnetic field sensitivity of the temperature compensation element is ½ or less of that of the magnetic field detection element. The thin film magnetic sensor of any one of Claim 1 to 3 satisfy | filling the relationship of following Formula (1).
| R _H −R _L | / R _H ≦ 0.1 (1)
However,
R _H is the resistance value of the TMR film (A) at room temperature,
R _L is the resistance value of the TMR film (B) at room temperature. The thin film magnetic sensor of any one of Claim 1 to 4 which satisfy | fills the relationship of following Formula (11)-Formula (14).
100 nm ≦ a _ALL <20 μm (11)
100 nm ≦ b _ALL <20 μm (12)
(B ₁ + 2b) _{MAX / 2} * _0.75 ≦ A _2MIN (13)
(B ₁ + 2b) _MAX / 2 _* 0.75 _≦ B _2MIN (14)
However,
a _ALL is the length (a) of the gap between the thin-film yoke (B) and the magnetic shield in the direction parallel to the magnetic sensing direction of the temperature compensation element,
b _ALL is the length (b) of the gap between the thin-film yoke (B) and the magnetic shield in the direction perpendicular to the magnetic sensing direction of the temperature compensation element,
B ₁ is the width of the thin film yoke (B),
(B ₁ + 2b) _MAX is the maximum value of the distance (B ₁ + 2b) between the magnetic shields in the direction perpendicular to the magnetic sensing direction of the temperature compensation element,
A _2MIN is the minimum value of the length (A ₂ ) of the magnetic shield in the direction parallel to the magnetic sensing direction of the temperature compensation element,
B _2MIN is the minimum value of the length (B ₂ ) of the magnetic shield in the direction perpendicular to the magnetic sensing direction of the temperature compensation element. The magnetic shield is divided into two shield pieces by a slit,
6. The thin film magnetic sensor according to claim 1, wherein each of the divided shield pieces is electrically connected to a pair of the thin film yokes (B). The thin film magnetic sensor according to claim 6, satisfying a relationship of the following formula (15).
100 nm ≦ c _ALL ≦ 2 μm (15)
However, c _ALL is the width (c) of the slit, and is the width at every point.

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