JP6930230B2 - Metal-Insulation System Nanogranular Thin Film and Thin Film Magnetic Sensor - Google Patents

Description

The present invention relates to a metal-insulation system nanogranular thin film and a thin film magnetic sensor, and more particularly to a metal-insulation system nanogranular thin film having excellent heat resistance and a thin film magnetic sensor using the same.

Magnetic sensors include electromagnetic forces (eg, current, voltage, power, magnetic field, magnetic flux, etc.), dynamics (eg, position, speed, acceleration, displacement, distance, tension, pressure, torque, temperature, humidity, etc.), It is 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-Resistance (AMR) sensors, Giant Mangneto-Resistance (GMR) sensors, and the like, depending on the method of detecting the magnetic field.

Among these, the GMR sensor is
(1) The maximum value of the rate of change of the electrical specific resistance compared to the AMR sensor (that is, MR ratio = Δρ / ρ ₀ (Δρ = ρ _{H −ρ 0} : ρ _H is the electrical specific resistance in the external magnetic field H, ρ ₀ is the electrical specific resistance)) at zero external magnetic field,
(2) The temperature change of the resistance value is smaller than that of the Hall sensor.
(3) Since the material having a giant magnetoresistive effect is a thin film material, it is suitable for micronization.
There are advantages such as. Therefore, the GMR 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.

Examples of the material exhibiting the GMR effect include a multilayer film of a ferromagnetic layer (for example, Permaloi) and a non-magnetic layer (for example, Cu, Ag, Au, etc.), an antiferromagnetic layer, a ferromagnetic layer (fixed layer), and the like. Metal artificial lattice consisting of a multilayer film (so-called "spin valve") having a four-layer structure of a non-magnetic layer and a ferromagnetic layer (free layer), and nm-sized fine particles made of ferromagnetic metal (for example, Permalloy) , Metal-metal nanogranular material with grain boundary phase made of non-magnetic metal (eg Cu, Ag, Au, etc.), tunnel junction film in which MR (Magneto-Resistance) effect is produced by spin-dependent tunnel effect, nm size There are known metal-insulation system nanogranular materials including fine ferromagnetic metal alloy fine particles and an insulation matrix made of a non-magnetic / insulating material.

Of these, multilayer films typified by spin valves are generally characterized by high sensitivity in low magnetic fields. However, since it is necessary to laminate thin films made of various materials with high accuracy, the multilayer film has poor stability and yield, and there is a limit in suppressing the manufacturing cost. Therefore, this type of multilayer film is used exclusively for high value-added devices (for example, magnetic heads for hard disks), and is applied to magnetic sensors that are forced to compete with low-priced AMR sensors and Hall sensors. Is considered difficult. In addition, diffusion between the multilayer films is likely to occur, and the GMR effect is likely to disappear, so that there is a major drawback that heat resistance is poor.

On the other hand, nanogranular materials are generally easy to manufacture 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-insulation system 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 realize ultra-miniaturization and low power consumption of the magnetic sensor at the same time.
(3) Unlike spin valve membranes containing antiferromagnetic membranes with poor heat resistance, they can be used even in high temperature environments.
There are advantages such as. However, the metal-insulation system nanogranular material has a problem that the magnetic field sensitivity in a low magnetic field is very small. Therefore, soft magnetic thin films are arranged at both ends of the giant magnetoresistive thin film to increase the magnetic field sensitivity of the giant magnetoresistive thin film.

Various proposals have been made conventionally for such a metal-insulation system nanogranular material and a thin film magnetic sensor using the same.
For example, Patent Document 1 discloses a nanogranular alloy thin film in which nanometer-sized magnetic granules are dispersed in an insulating matrix made of fluoride.
The same document, such nano-granular alloy thin film showed more than 3% magnetoresistance ratio at room temperature, it has been described that it has an electrical resistivity of more than 10 ⁵ .mu..OMEGA.cm.

Patent Document 2, the general formula _{(Fe lab Co a Ni b)} 100-wxyz L w M x O y F z ( where, L is selected Ru, Rh, Pd, Os, Ir, and from the group consisting of Pt Any one or more elements, M is from the group consisting of Be, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Sr, Zr, Nb, Mo, Ba, Hf, Ta, W, and rare earth elements. Any one or more selected elements, 0 ≦ a ≦ 1, 0 <b ≦ 0.5, 0 ≦ w ≦ 50, 10 ≦ x ≦ 40, 0 ≦ y ≦ 50, 0 ≦ z ≦ 50, 30 ≦ x + y + z The granular film represented by ≦ 70) is disclosed.
The same document, such granular film has been described that it has a 3% or more has a magnetic resistance effect, and 10 ⁴ .mu..OMEGA.cm higher than the electrical resistivity at room temperature.

Patent Document 3 discloses a granular film represented by the composition formula Co _48.7 Al _12.2 Mn _13.8 O _25.3.
The same document, the MR ratio of the granular film is 4.8%, the point electrical resistivity is 1.38 × 10 ⁵ μΩcm is described.

Patent Document 4 describes a free layer made of a Co-Fe-B alloy film, a tunnel insulating layer made of MgO, a Co-Fe-B alloy film / Ru film / Co-Fe alloy film / A magnetoresistive sensor composed of a laminate of a fixed layer made of an Ir—Mn alloy film, in which the projection components of the magnetization of the free layer and the fixed layer on the film surface are orthogonal to each other in a state where no magnetic field is applied from the outside. Is disclosed.
The document describes that such a configuration can suppress hysteresis.

Patent Document 5 states that although it is not a nanogranular film, it is a ferromagnetic tunnel junction having a structure in which a tunnel barrier layer is sandwiched between two ferromagnetic layers, and the tunnel barrier layer is a ferromagnetic material made of a non-magnetic material having a spinel structure. Tunnel junctions are disclosed.
In the same document, such a ferromagnetic tunnel junction is described.
(A) The _{resistance is considerably smaller than when the amorphous AlO x} barrier layer is used, and a larger TMR can be obtained.
(B) It is described that a high quality tunnel barrier and tunnel junction can be obtained by the sputtering method as compared with the case where the MgO barrier is used.

Patent Document 6 _{describes ferromagnetic particles having a composition represented by Co 2} Fe (Al _1-x Si _x ) (however, 0 <x <1) and Al _{2 filled around the ferromagnetic particles.} A metal-insulation system nanogranular thin film with an insulation matrix consisting of O _{3 is disclosed.}
The document describes that such metal-insulation system nanogranular materials exhibit a relatively high MR ratio.

Further, Patent Document 7 states that (Fe _1-x Co _x ) _100-z (B _{1-y S y} ) _z (where 0 ≦ x ≦ 1, 0 <y ≦ 0.5, 7 ≦ z ≦ 15). ), And a metal-insulation system nanogranular material including an insulating matrix composed of Mg—F compounds packed around the ferromagnetic particles is disclosed.
The document describes that in a (Mg-F) -FeCo-based nanogranular material, when a predetermined amount of B and / or Si is added, the rate of increase in electrical resistivity after heating becomes relatively small. ..

_{Magnetic sensors using MgF 2-} FeCo nanogranular films that are currently in practical use exhibit high characteristics at room temperature, but when exposed to high temperatures, characteristic changes such as an increase in resistivity and a decrease in output occur. On the other hand, as described in Patent Document 7, when a predetermined amount of B and / or Si is added to the (Mg-F) -FeCo-based nanogranular material, the change in characteristics when exposed to a high temperature can be reduced. can. However, even if the (Mg-F) -FeCo-based nanogranular material to which B and / or Si is added is used for industrial machines and in-vehicle parts used in a harsher environment, the characteristic change becomes large. ..

Japanese Unexamined Patent Publication No. 2001-094175 JP-A-2002-344042 Japanese Unexamined Patent Publication No. 10-092639 Japanese Unexamined Patent Publication No. 2013-229444 International Publication No. 2010/11992 Japanese Unexamined Patent Publication No. 2012-015221 Japanese Patent No. 5447996

An object to be solved by the present invention is to provide a novel metal-insulation system nanogranular thin film having high heat resistance, and a thin film magnetic sensor using the same.

In order to solve the above problems, the metal-insulation system nanogranular thin film according to the present invention is
With ferromagnetic particles
It is summarized as that and an insulating matrix in which the consist is filled around the ferromagnetic particles were _{MgAl x O y (1.6 ≦ x} ≦ 2.4,3.2 ≦ y ≦ 4.8).
It is a gist that the thin film magnetic sensor according to the present invention includes the metal-insulation system nanogranular thin film according to the present invention.

Metal-insulation system nanogranular thin films using fluoride such as _{MgF 2 or oxides such as Al 2} O ₃ and MgO as the insulation matrix have low heat resistance, and their characteristics change in the temperature range exceeding 200 ° C. Becomes larger. On the other hand, when Mg Al _x O _y is used as the insulation matrix, there is little change in characteristics even in a temperature range exceeding 400 ° C.

Exposure temperature of MgAl ₂ O _4- Fe ₆₀ Co ₄₀ thin film (Example 1, no heat treatment, heat treatment temperature 200 ° C., heat treatment temperature 400 ° C.) and MgF _2- Fe ₆₀ Co ₄₀ thin film (Comparative example 1, no heat treatment) It is a figure which shows the relationship with the electrical resistivity change rate (ρ (@T ° C) / ρ _0). Exposure temperature of MgAl ₂ O _4- Fe ₆₀ Co ₄₀ thin film (Example 1, no heat treatment, heat treatment temperature 200 ° C., heat treatment temperature 400 ° C.) and MgF _2- Fe ₆₀ Co ₄₀ thin film (Comparative example 1, no heat treatment) It is a figure which shows the relationship with the magnetic resistance ratio (MR ratio) (H = 10 [koe], 23 degreeC). MR curves of the metal-insulation system nanogranular thin film obtained in Example 1 (heat treatment temperature 400 ° C.), Example 3 (heat treatment temperature 600 ° C.), Example 4 (heat treatment temperature 600 ° C.) and Comparative Example 1 (no heat treatment). Is.

Hereinafter, an embodiment of the present invention will be described in detail.
[1. Metal-Insulation System Nano Granular Thin Film]
The metal-insulation system nanogranular thin film according to the present invention is
With ferromagnetic particles
And an insulating matrix in which the consist is filled around the ferromagnetic particles were _{MgAl x O y (1.6 ≦ x} ≦ 2.4,3.2 ≦ y ≦ 4.8).

[1.1. Ferromagnetic particles]
In the present invention, the composition of the ferromagnetic particles is not particularly limited.
As ferromagnetic particles, for example
_{(A) (Fe 1-x} Co x) 100-y Z y alloy (where, Z = B and / or Si, 0 ≦ x ≦ 1,0 ≦ y ≦ 20),
(B) Co ₂ Fe (Al _1-x Si _x ) alloy (however, 0 ≦ x ≦ 1),
(C) Co ₂ MnZ alloy (provided that any one or more elements selected from the group consisting of Z = Al, Si, and Ge) and
(D) Fe ₂ CrSi alloy and the like. The metal-insulation system nanogranular thin film may contain any one of these ferromagnetic particles, or may contain two or more of them.
Among these, the ferromagnetic particles are preferably a (Fe _1-x Co _x ) _100-y Z _y alloy or a Co ₂ Fe (Al _1-x Si _x ) alloy. These, when dispersed in MgAl _x O _y, it exhibits a high MR ratio.

[1.1.1. _{(Fe 1-x Co x)} 100-y Z y Alloy
The first specific example of ferromagnetic particles consists of a (Fe _1-x Co _x ) _100-y Z _y alloy. x represents the atomic ratio of Co to Fe and Co contained in the ferromagnetic particles. The ferromagnetic particles may contain only Fe or only Co, or may be an Fe—Co alloy. In order to obtain a high MR ratio, x is preferably 0 or more and 0.9 or less. x is more preferably 0.2 or more and 0.6 or less.

y represents (Fe _1-x Co x) The total amount of B and Si contained in the _100-y Z _y alloy (at%). When B and / or Si is added to the Fe—Co alloy, the increase in resistivity due to heating can be suppressed. z is more preferably 5 at% or more, still more preferably 7 at% or more.
On the other hand, when z becomes excessive, the MR ratio decreases. Therefore, z is preferably 20 at% or less. z is more preferably 15 at% or less.

The atomic ratio of Si to B and Si contained in the ferromagnetic particles (= Si / (B + Si)) is not particularly limited and can be arbitrarily selected depending on the intended purpose. That is, the ferromagnetic particles may contain only B or Si only, or may contain both B and Si. Both B and Si have an effect of suppressing an increase in resistivity due to heating. In particular, B has a greater effect of suppressing an increase in electrical resistance than Si, so that a large effect can be obtained by adding a small amount. In order to obtain a high effect with a small amount of addition, the Si / (B + Si) ratio is preferably 0.5 or less. The Si / (B + Si) ratio is preferably 0.3 or less, more preferably 0.

Since B and Si have a small atomic radius, they easily penetrate into the gap between the ferromagnetic particles and the insulating matrix. It is considered that the reason why the grain growth of the ferromagnetic particles is suppressed by adding B and Si is that these elements invade the interface between the ferromagnetic particles and the insulating matrix and prevent the aggregation of the ferromagnetic particles. .. Examples of elements other than B and Si having the same functions as these include C, Al, P and the like.
Further, in order to suppress the grain growth of the ferromagnetic particles, an element that is difficult to diffuse even if the surface of the ferromagnetic particles is heat-treated may be present instead of the element having a small atomic radius. If there is an element that is difficult to diffuse on the surface of the ferromagnetic particles, it becomes difficult for the ferromagnetic particles to move in the insulating matrix, and the aggregation of the ferromagnetic particles is hindered. Examples of elements having such a function include Ti, V, Zr, Nb, Mo, Hf, Ta, and W.

[1.1.2. Co ₂ Fe (Al _1-x Si _x ) alloy]
A second specific example of ferromagnetic particles consists of a Co ₂ Fe (Al _1-x Si _x ) alloy. _{Co 2 Fe (Al 1-x} Si x) ( hereinafter, also referred to as "CFAS"), one of the electronic spin has a metallic band structure, the other electron spin has an insulating body specific band structure, so-called It is a "half-metal ferromagnet".
The CFAS unit cell has a structure in which eight body-centered cubic lattices are superposed. In a CFAS unit cell having a regular structure, Co (X atom) occupies the position of the body center of each body-centered cubic lattice, and Fe or (Si, Al) occupies the position of the apex of each body-centered cubic lattice. Occupy.

For the crystal structure of CFAS,
(A) A2 structure in which Co (X atom), Fe (Y atom) and (Si, Al) (Z atom) occupy the positions of each body-centered cubic lattice irregularly.
(B) Co (X atom) occupies the position of the body center of each body-centered cubic lattice, and Fe (Y atom) and (Si, Al) (Z atom) do not have the vertices of each body-centered cubic lattice. The B2 structure (XY) occupied by the rules and
(C) Co (X atom) occupies the position of the body center of each body centered cubic lattice, and Fe (Y atom) and (Si, Al) (Z atom) form each body center so as to form a rock salt structure. _{L2 1} type structure (X ₂ YZ, so-called "Whisler alloy" or "Full Whistler alloy") that regularly occupies the apex of the cubic lattice,
It has been known.
The _{Whistler alloy having an L2 1} type structure is generally regarded as a promising half-metal ferromagnet because the Curie temperature is above room temperature. In the present invention, CFAS may have any of the crystal structures (a) to (c).

x represents the atomic ratio of Si and Al contained in the ferromagnetic particles. Reference: As described in TM Nakatani et al., Journal of Applied Physics 102, 033916 (2007), when x = 0 or 1, a relatively large MR ratio cannot be obtained.
Generally, the larger x is, the higher the MR ratio is obtained. This is because the spin polarizability becomes large. Therefore, x is preferably 0.3 or more.
On the other hand, if x becomes too large, the MR ratio will rather decrease. This is because the spin polarizability becomes small. Therefore, x is preferably 0.7 or less.
Among these, Co ₂ Fe (Si _0.5 Al _0.5 ) is suitable as ferromagnetic particles. This is because the spin polarizability becomes the largest at x = 0.5.

[1.1.3. Co ₂ MnZ alloy]
A third specific example of ferromagnetic particles is made of a Co ₂ MnZ alloy. The Co ₂ MnZ alloy is a type of Whistler alloy having an L2 ₁ type structure. As the Co ₂ MnZ alloy, for example, Co ₂ MnGe, Co ₂ MnSn, Co ₂ MnSi, Co ₂ MnGa, Co ₂ MnAl, Co 2 MnSb and the like are known. Among these, the Co ₂ MnZ alloy is preferably Co ₂ MnAl, Co ₂ MnSi, and Co ₂ MnGe, and a solid solution or mixture composed of two or more of these. This is because the MR ratio is relatively high.

[1.1.4. Fe ₂ CrSi alloy]
A fourth specific example of ferromagnetic particles is made of a Fe ₂ CrSi alloy. Fe ₂ CrSi alloy is a kind of half metal ferromagnet.

[1.2. Insulation matrix]
The insulating matrix is packed around the ferromagnetic particles. In the present invention, the insulation matrix is made of MgAl _x O _y . MgAl _x O _y, compared to other materials, metal - a large effect of improving the heat resistance of the insulator system nano granular thin film. The MgAl _x O _y, is a oxide based spinel (MgAl ₂ O _4), the deposition conditions may not become crystalline and / or stoichiometric composition.

x represents the atomic ratio of Al to Mg. If x becomes too small, the MR ratio becomes small or the resistivity change rate becomes large. Therefore, x needs to be 1.6 or more. x is preferably 1.8 or more, more preferably 1.9 or more.
On the other hand, if x becomes too large, the MR ratio becomes small or the electrical resistivity change rate becomes large. Therefore, x needs to be 2.4 or less. x is preferably 2.2 or less, more preferably 2.1 or less.

y represents the atomic ratio of O to Mg. If y becomes too small, the MR ratio becomes small or the resistivity change rate becomes large. Therefore, y needs to be 3.2 or more. y is preferably 3.6 or more, more preferably 3.8 or more.
On the other hand, if y becomes too large, the MR ratio becomes small or the electrical resistivity change rate becomes large. Therefore, y needs to be 4.8 or less. y is preferably 4.4 or less, more preferably 4.2 or less.

[1.3. Content of ferromagnetic particles]
The content of the ferromagnetic particles is not particularly limited. In general, if the content of ferromagnetic particles is too small, the electrical resistivity increases significantly, making it difficult to detect changes in the magnetic field as changes in current. Therefore, the content of ferromagnetic particles is preferably 10 vol% or more. The content of the ferromagnetic particles is preferably 20 vol% or more, more preferably 30 vol% or more.
On the other hand, if the content of the ferromagnetic particles becomes excessive, the ferromagnetic particles come into contact with each other and the tunnel magnetoresistive effect cannot be obtained. Therefore, the content of ferromagnetic particles is preferably 70 vol% or less. The content of the ferromagnetic particles is preferably 60 vol% or less, more preferably 50 vol% or less.

[1.4. Electrical resistivity change rate]
The metal-insulation system nanogranular thin film according to the present invention has higher heat resistance than conventional thin films. When the material composition and manufacturing conditions are optimized, the rate of change in resistivity becomes 10 or less. When the material composition and the like are further optimized, the rate of change in resistivity becomes 5 or less, or 2 or less.

Here, the "electric resistivity change rate" means a value represented by the following equation (1).
Electrical resistivity change rate = ρ (@ 400 ° C) / ρ ₀ ... (1)
However,
ρ (@ 400 ° C.) is the electrical resistivity at 23 ° C. and an external magnetic field H = zero [Oe] after an exposure treatment in which the metal-insulation system nanogranular thin film is heated at 400 ° C. for 0.5 hours.
ρ ₀ is the electrical resistivity of the metal-insulation system nanogranular thin film before the exposure treatment at 23 ° C. and an external magnetic field H = zero [Oe].

The "exposure treatment" here is not a heat treatment performed for the purpose of developing a nanogranular structure (heat treatment in the "heat treatment step" described later) or a heat treatment performed for the purpose of improving the magnetic properties of the yoke. A heat treatment performed on a thin film after the completion of a thin film exhibiting predetermined MR characteristics. This point is the same for the MR ratio and the electrical resistivity, which will be described later.

[1.5. MR ratio]
In the metal-insulation system nanogranular thin film according to the present invention, the MR ratio becomes 3% or more when the material composition and the production conditions are optimized. When the material composition and the like are further optimized, the MR ratio becomes 6% or more, or 9% or more.
The metal-insulation system nanogranular thin film according to the present invention exhibits such a high MR ratio not only immediately after film formation and after heat treatment, but also after an exposure treatment of heating at 400 ° C. for 0.5 hours. preferable.

Here, the "MR ratio" means a value (maximum MR ratio) represented by the equation (1).
MR ratio (%) = | ρ-ρ ₀ | × 100 / ρ ₀ ... (1)
However,
ρ ₀ is the electrical resistivity of the thin film when the external magnetic field H = zero [koe] at 23 ° C.
ρ is the electrical resistivity of the thin film when the external magnetic field H = 10 [koe] at 23 ° C.

[1.6. Electrical resistivity]
In general, the higher the content of ferromagnetic particles in a thin film, the higher the probability that the ferromagnetic particles will come into contact with each other, and the lower the resistivity of the thin film. To obtain a high tunneling magnetoresistance effect, the electrical resistivity of the thin film, or 1 × 10 ⁵ μΩ · cm is preferable.
On the other hand, if the content of the magnetic particles in the thin film becomes too small, the electrical resistivity increases remarkably, and it becomes difficult to detect the change in the magnetic field as the change in the current. Therefore, the electrical resistivity of the thin film ^{is preferably 5 × 10 11} μΩ · cm or less.
The metal-insulation system nanogranular thin film according to the present invention exhibits such an appropriate resistivity not only immediately after film formation and after heat treatment, but also after an exposure treatment of heating at 400 ° C. for 0.5 hours. Those are preferable.
Here, the "electric resistivity" means a value at 23 ° C. and an external magnetic field H = zero [koe].

[2. Thin film magnetic sensor]
The thin film magnetic sensor according to the present invention includes the metal-insulation system nanogranular thin film according to the present invention.
In a thin film magnetic sensor, a metal-insulation system nanogranular thin film is used as a magnetic layer for detecting a change in magnetism as a change in current.
The metal-insulation system nanogranular thin film is formed on the surface of the substrate. Further, electrodes for detecting an electric current are formed at both ends of the metal-insulation system nanogranular thin film. Further, in order to improve the magnetic field sensitivity in a low magnetic field, a thin film (thin film yoke) made of a soft magnetic material may be formed between the metal-insulation system nanogranular thin film and the electrode.

In the present invention, the structure of the thin film magnetic sensor and the material of each part are not particularly limited, and can be arbitrarily selected depending on the intended purpose.
For example, glass, Si with a thermal oxide film, or the like can be used as the substrate.
When forming a thin film yoke, the thin film yoke contains 40 to 90% Ni-Fe alloy, Fe ₇₄ Si ₉ Al ₁₇ , Fe ₁₂ Ni ₈₂ Nb ₆ , Co ₈₈ Nb ₆ Zr ₆ amorphous alloy, (Co ₉₄ Fe). ₆ ) ₇₀ Si ₁₅ B ₁₅ Amorphous Alloy, 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 Alloys, Fe _71.3 Nd _9.6 O _19.1 nanogranular alloys, Co ₇₀ Al ₁₀ O ₂₀ nanogranular alloys, Co ₆₅ Fe ₅ Al ₁₀ O ₂₀ alloys and the like can be used.

[3. Metal-Insulation System Manufacturing Method of Nanogranular Thin Film]
[3.1. Thin film formation process]
Metal-insulation system Nanogranular thin film
(A) A method of sputtering using a composite target in which an _{insulating chip (Al 2} O ₃ chip and Mg _{O chip or Mg Al 2} O ₄ chip) is placed on a metal disk having the same composition as the ferromagnetic particles.
(B) Simultaneous sputtering method, in which a ferromagnetic metal target and an insulator target are used and sputtered onto a substrate at the same time.
(C) Using a ferromagnetic metal target and an insulating target, it can be manufactured by a tandem method or the like in which a substrate, a shutter with a window, or the like is revolved and alternately sputtered onto the substrate.
By optimizing the film formation conditions such as the volume ratio of the metal and the insulator and the heating temperature of the substrate, a nanogranular structure can be obtained by the difference in the generation energy of the metal and the insulator only in the thin film forming step. However, if the film forming conditions such as the volume ratio of the metal and the insulator and the substrate heating temperature are not appropriate, a continuous film may be formed without adopting the nanogranular structure.

[3.2. Heat treatment process]
As described in the thin film forming step, if the film forming conditions are optimized, the nanogranular structure can be formed only by the film forming. However, if the heat treatment is performed after the film formation, the particle size of the ferromagnetic particles may be optimized, the crystallinity of the insulator may be improved, and the MR ratio may be improved. Further, when the thin film formed as a continuous film is heat-treated without taking a nanogranular structure in the thin film forming step, ferromagnetic particles are aggregated by heat to form a nanogranular structure, and the crystallinity of the insulator is improved. Therefore, the obtained thin film may be heat-treated because the MR ratio is improved. When the ferromagnetic metal is a Whistler alloy, if heat treatment is performed after the film formation, the regularity of the Whistler alloy is improved to form a B2 structure, an L2 ₁ structure, or the like, and the MR ratio may be improved.

Generally, if the heat treatment temperature is too low, the MR ratio cannot be improved within a practical time.
On the other hand, if the heat treatment temperature is too high, the ferromagnetic particles and the insulating material may mutually diffuse and the nanogranular structure may collapse. The heat treatment temperature is usually 150 ° C. to 800 ° C.

The optimum heat treatment time is selected according to the heat treatment temperature. Generally, the higher the heat treatment temperature, the shorter the MR ratio can be improved. The heat treatment time is usually 0.5 to 10 hours.

[4. Manufacturing method of thin film magnetic sensor]
Thin film magnetic sensor
(B) A step of forming a thin film having a predetermined composition on the surface of the substrate, and
(B) The process of removing unnecessary parts of the thin film by using the etching method, lift-off method, etc.
Can be manufactured by repeating.

Metal-Insulation System In the case of a thin film magnetic sensor in which yokes made of soft magnetic material are arranged at both ends of a nanogranular thin film, heat treatment is usually performed after forming the yoke in order to improve the magnetic properties of the yoke. Generally, the higher the heat treatment temperature, the better the characteristics of the yoke and the higher the MR ratio can be obtained. On the other hand, if the heat treatment temperature is too high, the electrical resistivity of the metal-insulation system nanogranular thin film increases extremely, and the MR ratio decreases.
The optimum heat treatment temperature depends on the composition of the yoke, the required characteristics, and the like. Generally, the heat treatment temperature is 150 to 800 ° C.
The optimum heat treatment time is selected according to the heat treatment temperature. Generally, the higher the heat treatment temperature, the shorter the magnetic properties can be improved. Usually, the heat treatment time is 0.5 to 10 hours.

[5. Action]
Metal-insulation system nanogranular thin films using fluoride such as _{MgF 2 or oxides such as Al 2} O ₃ and MgO as the insulation matrix have low heat resistance, and their characteristics change in the temperature range exceeding 200 ° C. Will increase. On the other hand, when Mg Al _x O _y is used as the insulation matrix, there is little change in characteristics even in a temperature range exceeding 400 ° C.

(Examples 1 to 5, Comparative Examples 1 to 3)
[1. Preparation of sample]
A metal-insulation nanogranular thin film was prepared on the surface of the substrate using the tandem method. After film formation, some thin films were heat-treated for the purpose of developing a nanogranular structure. The heat treatment temperature was 200 ° C. to 700 ° C., and the heat treatment time was 0.5 hours.
As the insulation matrix, MgAl ₂ O ₄ (Examples 1 to 5), MgF ₂ (Comparative Example 1), Al ₂ O ₃ (Comparative Example 2), or MgO (Comparative Example 3) was used.
The ferromagnetic particles include Fe ₆₀ Co ₄₀ (Example 1, Comparative Examples 1 to 3), Fe ₅₄ Co ₃₆ B ₁₀ alloy (Example 2), and Co ₂ FeAl _0.5 Si _0.5 (CFAS) alloy (Example 2). 3), Co ₂ MnSi alloy (Example 4), or Fe ₂ CrSi alloy (Example 5) was used.

[2. evaluation]
[2.1. Electrical resistivity change rate]
The obtained thin films were exposed to heating at various temperatures of T ° C. for 0.5 hours, and then the resistivity change rate (ρ (@T ° C.) / ρ ₀ ) was measured. FIG. 1 shows _{exposure of MgAl 2} O _4- Fe ₆₀ Co ₄₀ (Example 1, no heat treatment, heat treatment temperature 200 ° C., heat treatment temperature 400 ° C.) and MgF _2- Fe ₆₀ Co ₄₀ (Comparative Example 1, no heat treatment). The relationship between the temperature and the rate of change in electrical resistivity is shown.

In Comparative Example 1, the rate of change in electrical resistivity gradually increased up to about 200 ° C., but there was no significant change. However, when the exposure temperature exceeded 200 ° C., the rate of change in electrical resistivity increased sharply. On the other hand, in Example 1, the rate of change in electrical resistivity was only slightly increased even when the exposure temperature was 400 ° C. regardless of the presence or absence of heat treatment. It is considered that this is because MgAl ₂ O ₄ has high thermal stability and it is difficult for ferromagnetic particles to move and aggregate.

[2.2. MR ratio]
The obtained thin films were exposed to heating at various temperatures of T ° C. for 0.5 hours, and then the MR ratio at room temperature was measured. FIG. 2 shows _{exposure of MgAl 2} O _4- Fe ₆₀ Co ₄₀ (Example 1, no heat treatment, heat treatment temperature 200 ° C., heat treatment temperature 400 ° C.) and MgF _2- Fe ₆₀ Co ₄₀ (Comparative Example 1, no heat treatment). The relationship between the temperature and the magnetic resistance ratio (MR ratio) (H = 10k [Oe], 23 ° C.) is shown.

In Comparative Example 1, the MR ratio improved as the exposure temperature increased up to about 200 ° C. It is considered that this is because the particle size of the ferromagnetic particles was optimized by the exposure treatment and the crystallinity of the insulator was improved. However, when the exposure temperature exceeded 200 ° C., the MR ratio sharply decreased. On the other hand, in Example 1, the MR ratio did not decrease sharply even when the exposure temperature was set to 400 ° C. regardless of the presence or absence of heat treatment. It is considered that this is because MgAl ₂ O ₄ has high thermal stability and it is difficult for ferromagnetic particles to move and aggregate.

[2.3. Material dependence of electrical properties]
FIG. 3 shows the metal-insulation system nanogranular obtained in Example 1 (heat treatment temperature 400 ° C.), Example 3 (heat treatment temperature 600 ° C.), Example 4 (heat treatment temperature 600 ° C.) and Comparative Example 1 (no heat treatment). The MR curve of the thin film is shown. Table 1 shows the MR ratios (H = 10 [koe], 23 ° C.) of the metal-insulation system nanogranular thin films obtained in Examples 1 to 5 and Comparative Examples 1 to 3 and after exposure treatment at 400 ° C. The rate of change in electrical resistivity at 23 ° C. (= ρ (@ 400 ° C.) / ρ ₀ ) is shown. In Table 1, "S", "A", and "B" indicate pass, and "C" indicates fail. From FIG. 3 and Table 1, the following can be seen.

(1) When Fe ₆₀ Co _{40 or CFAS was used as the ferromagnetic particles and Mg Al 2} O ₄ was used as the insulating matrix, the MR ratio before the exposure treatment was 9% or more.
(2) Even when Fe ₆₀ Co ₄₀ is used as the ferromagnetic particles, the rate of change in electrical resistivity is large when _{Mg F 2} , Al ₂ O ₃ , or Mg O is used as the insulating matrix. It is considered that this is because the ferromagnetic particles move and aggregate and the distance between the ferromagnetic particles increases.
(3) In Example 1, the rate of change in electrical resistivity was reduced (heat resistance was improved) by appropriate heat treatment. It is considered that this is because the movement / agglutination of the ferromagnetic particles was performed in advance by the heat treatment, so that the movement / agglutination of the ferromagnetic particles was difficult to occur even if heat was applied again.
(4) For all the samples, the resistivity before and after exposure to 400 ° C. was in the range of ^{1 × 10 5} to 1 × 10 ^{11 μΩ · cm regardless of the presence or absence of heat treatment.}

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.

The metal-insulation system nanogranular thin film according to the present invention can be used as a material for a magnetic sensor, a magnetic memory, a magnetic head, or the like.
The thin-film magnetic sensor according to the present invention detects rotation information of automobile axles, rotary encoders, industrial gears, etc., stroke positions of hydraulic cylinders / pneumatic cylinders, position / speed information of machine tool slides, etc. It can be used for detecting current information such as arc current of industrial welding robots and for geomagnetic orientation compass.

Claims (8)

With ferromagnetic particles
It said metal and a dielectric matrix of packed around the ferromagnetic particles were _{MgAl x O y (1.6 ≦ x} ≦ 2.4,3.2 ≦ y ≦ 4.8) - insulator system nano granular thin film. The ferromagnetic particles are
_{(A) (Fe 1-x} Co x) 100-y Z y alloy (where, Z = B and / or Si, 0 ≦ x ≦ 1,0 ≦ y ≦ 20),
(B) Co ₂ Fe (Al _1-x Si _x ) alloy (however, 0 ≦ x ≦ 1),
(C) Co ₂ MnZ alloy (provided that any one or more elements selected from the group consisting of Z = Al, Si, and Ge) and
(D) The metal-insulation system nanogranular thin film according to claim 1, which is composed of any one or more alloys selected from the group consisting of _{Fe 2 CrSi alloys.} The ferromagnetic particles are Co ₂ The metal-insulation system nanogranular thin film according to claim 1, which comprises an MnZ alloy (provided that any one or more elements selected from the group consisting of Z = Al, Si, and Ge). The metal-insulation system nanogranular thin film according to any one of claims 1 to 3, wherein the resistivity change rate represented by the following formula (1) is 10 or less = ρ (@ 400). ℃) / ρ ₀・ ・ ・ (1)
However,
ρ (@ 400 ° C.) is the electrical resistivity at 23 ° C. and an external magnetic field H = zero [Oe] after an exposure treatment in which the metal-insulation system nanogranular thin film is heated at 400 ° C. for 0.5 hours.
ρ ₀ is the electrical resistivity of the metal-insulation system nanogranular thin film before the exposure treatment at 23 ° C. and an external magnetic field H = zero [Oe]. The metal-insulation system nanogranular thin film according to claim 4, wherein the resistivity change rate is 2 or less. The MR ratio at 23 ° C. before the exposure treatment of heating at 400 ° C. for 0.5 hour and after the exposure treatment is 3% or more.
The metal-insulation system nanogranular thin film according to any one of claims 1 to 5. The electrical resistivity at 23 ° C. before and after the exposure treatment of heating at 400 ° C. for 0.5 hours is 1 × 10 ⁵ μΩ · cm or more and 5 × 10 ¹¹ μΩ · cm or less.
The metal-insulation system nanogranular thin film according to any one of claims 1 to 6. A thin film magnetic sensor comprising the metal-insulation system nanogranular thin film according to any one of claims 1 to 7.

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