JPH09107136A - Magnetoresistive element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetoresistive element consisting of a non-coupled artificial lattice which is highly sensitive to an external magnetic field fluctuation and can be easily manufactured. SOLUTION: In a magnetoresistive element, a number of column-shaped bodies 4 made of Co hard magnetic material vertically project from a substrate 1, an isolating film 5 made of Cu is formed around each column-shaped body 4, and a filling layer of NiFe soft magnetic material is formed at the gap of the column-shaped body 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive element composed of a non-coupling type artificial lattice which can be used as a magnetoresistive effect element such as a magnetic sensor, a magnetic head, a position sensor and a rotation sensor.

[0002]

2. Description of the Related Art A material whose electric resistance changes in response to a change in an external magnetic field is known as a magnetoresistive (MR) effect material. This MR effect material has conventionally been NiFe.
Although alloy (permalloy) thin films are known, the magnetoresistance change rate of permalloy thin films is about 2% to 3% at most. Therefore, in the future, in order to realize a narrower track of the magnetic head and a higher resolution of the magnetic sensor by applying this MR effect, an MR effect material having a larger magnetoresistance change rate (MR ratio) is required.

In recent years, a phenomenon called the so-called giant magnetoresistive (GMR) effect has been discovered in artificial lattices composed of multi-layer thin films such as Fe / Cr or Co / Cu (MN Baibich et al., Physical Review Letter, 61 (1).
988) 2472, DH Mosca et al., Journal of Magnetis
m and Magnetic Materials, 94 (1991) L1). In these artificial lattices, it is said that the spin-dependent scattering of conduction electrons at the interface between Fe and Cr or the interface between Co and Cu contributes to the GMR effect. The effect is fundamentally different in the generation mechanism, and it is said that antiferromagnetic exchange coupling works between the magnetic films and the antiparallel magnetic structures are aligned in parallel by the magnetic field, so that the electric resistance is reduced. ing.

[0004]

It is said that the GMR element using the artificial lattice composed of the above-mentioned multi-layered thin film can be roughly classified into three types according to its structure. That is, Co / C
u, Co / Ag, antiferromagnetic system having a combined artificial lattice of NiFe / Cu, spin valve system by NiFe / Cu / Co / FeMn, etc., and Cu / Co / Cu / NiF
It is a non-bonded type such as e. Among them, the combined artificial lattice of Co / Cu or the like can obtain an MR ratio several times higher than the magnetoresistive change rate of a permalloy thin film, but M
A large external magnetic field is required to cause the R effect,
It was difficult to apply to small devices. Recently,
Research on GMR materials using multi-layer thin film structure has progressed,
It has been found that the MR effect with respect to the current in the direction perpendicular to the film can be expected to be larger than the MR effect with respect to the current in the in-plane direction of the multilayer artificial lattice that has been performed so far (for example, WPPratt Jr. et al. Phys. Rev. Lett. 6
6 (1991) 3060). However, since the electric resistance is very small in the direction perpendicular to the film surface, the current change due to the MR effect is buried in the contact resistance of the wiring, etc., and a large-scale superconducting device or the like is required to eliminate the peripheral resistance. Therefore, it was difficult to put it into practical use.

In order to solve this problem, an attempt was made to cut out a fine pillar from the multilayer film and measure the MR effect from the resistance change at both ends of the pillar (MAMGijs et al., Phys. Re.
v. Lett. 70 (1993) 3343). However, this sample preparation requires extremely precise processing technology, and it seems difficult to put it into practical use. In addition, Shinjo et al. (Japan Applied Magnetics Society, 88th Research Group sample “Recent Progress in Giant Magnetoresistance Effect Research” January 26-27, 1995) is a Si substrate as shown in FIG. A magnetoresistive element of the type in which a triangular wave-shaped surface is formed on 20 to form a triangular wave-shaped surface and a non-bonding type multi-layered film artificial lattice 21 is formed thereon is proposed.
According to this magnetoresistive element, when a current is applied to the film, the angle of the current direction with respect to the film surface of the conventional in-plane current type magnetoresistive element is 0 °, whereas the angle of 55 ° is obtained. It is reported that the measurement result clearly has a larger MR effect than the in-plane current type.

However, this method is difficult to manufacture because of problems in working such as forming a triangular wave surface on the substrate. The present invention has been made to solve the above problems, and therefore an object thereof is to provide a magnetoresistive body composed of a non-coupling type artificial lattice, which is highly sensitive to an external magnetic field fluctuation and is easy to manufacture, and a method thereof. It is to provide a manufacturing method.

[0007]

The above-mentioned problems are solved by the fact that a large number of columnar bodies made of one of two kinds of magnetic materials having different coercive force are projected perpendicularly to the substrate surface, and non-magnetic material is formed around each columnar body. The problem can be solved by providing a magnetoresistor in which an isolation film made of a conductive material is formed, and a filling layer made of the other magnetic material is formed in a gap between columnar bodies in which the isolation film is formed.

Of the above magnetic materials having different coercive forces, one magnetic material is preferably a hard magnetic material selected from the group consisting of Co and Co alloys. Further, one of the magnetic materials is preferably a soft magnetic material made of NiFe or CoNiFe. The nonmagnetic conductive material is preferably selected from the group consisting of Cu, Au, Ag and alloys containing at least one of these.

According to the present invention, in manufacturing any one of the magnetoresistive bodies described above, a large number of columnar bodies made of any one of the above magnetic materials are grown on a substrate perpendicularly to the substrate surface, and these columnar bodies are grown. Provided is a method for manufacturing a magnetoresistive body, wherein an isolation film made of a non-magnetic conductive material is formed around a body, and then a filling layer made of another magnetic material is formed in a gap between columnar bodies having the isolation film formed therein. To do.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to the drawings according to an embodiment. FIG. 1 is a sectional view showing a magnetoresistive element according to an embodiment of the present invention. In FIG. 1, the magnetoresistive body 10 includes a substrate 1, a nonmagnetic initial layer 2 formed on the substrate 1 along the substrate surface, and the initial layer 2.
Of the MR layer 3 formed on the upper surface of the. This M
In the R layer 3, a large number of columnar bodies 4 made of one of two kinds of magnetic materials each having different coercive force are continuously projected from the initial layer 2 perpendicularly to the substrate 1 and non-magnetic around the columnar bodies 4. An isolation film 5 made of a conductive material is formed, and a layer 6 of the other magnetic material (hereinafter referred to as “filling layer”) 6 is formed in the gap between the columnar bodies 4.

In the MR layer 3, one of the two kinds of magnetic materials (columnar bodies 4) having different coercive force is CoPt.
Made of Ni-based hard magnetic material, the other (filling layer 6) is NiFe
It is made of soft magnetic material. Further, the isolation film 5 in the MR layer 3 is made of Cu, and the initial layer 2 on the substrate 1 is made of a CoPt alloy forming the columnar body 4 to which oxygen is added. The substrate 1 may be any non-magnetic material such as Si or glass, but in this case, it is made of Si.

Here, the hard magnetic material is generally a permanent magnetic material having a large coercive force even when the external magnetic field is removed, and the soft magnetic material is also called a high magnetic permeability material. It is a magnetic material that changes its magnetization sensitively to changes in strength.

In the magnetic resistor 10, when the external magnetic field is zero, the magnetization direction of the columnar body 4 and the magnetization direction of the magnetic film 6 are
It is offset vertically and anti-parallel to the substrate. When an external magnetic field is applied to the MR layer 3 while changing the external magnetic field in a vertical and / or horizontal direction with a current flowing between both ends of the MR layer 3, the columnar body 4 is a hard magnetic material. Since the direction of magnetization does not change and the filling layer 6 is a soft magnetic material, the direction of magnetization changes according to the change of the external magnetic field, and the internal electric resistance of the MR layer 3 changes accordingly. Therefore, the MR effect (magnetoresistive effect) in which the amount of current changes is exhibited. This is because the CPP type (Current Perpendicu
lar to Plane, that is, a type in which a current flows vertically in the film plane), which is a novel magnetoresistive element.

The magnetoresistive element 10 of this embodiment can be sequentially manufactured by the methods shown in FIGS. As shown in FIG. 2, first, on the Si substrate 1, CoP was performed in an oxygen atmosphere.
The initial layer 2 is formed by sputtering t. CoPt is modulated by addition of oxygen and becomes non-magnetic and has high electric resistance. This layer is interposed between the substrate 1 and the MR layer 3 and serves as a buffer layer during manufacturing or use.

Next, as shown in FIG. 3, when oxygen addition was stopped, the sputtering conditions were switched to high argon pressure sputtering, and CoPt was subsequently sputtered, growth seeds of CoPt microcrystals continued from the initial layer 2, but A large number of pillars 4 are formed on the substrate 1 which are generated and grown separately from each other in the shape of islands and are vertically projected on the substrate 1. By applying an external magnetic field during this high argon pressure sputtering, the magnetization direction of the columnar body 4 can be made uniform and fixed.

Next, as shown in FIG. 4, an isolation film 5 is formed around each columnar body 4 using Cu, which is a nonmagnetic conductive material. It is preferable to use a plating technique for forming the isolation film 5.

Next, as shown in FIG. 5, a NiFe-based soft magnetic material is filled in the gap between the columnar bodies 4 on which the isolation film 5 is formed to form a filling layer 6. A plating technique or a selective CVD technique can be used for this filling.

At the stage where the filling layer 6 is formed, a continuous skin layer of the filling layer 6 and the isolation film 5 is formed on the surface layer.
This skin layer impedes the MR effect and must be removed. Therefore, as a final step, as shown in FIG. 6, this skin layer is removed by a technique such as dry etching. As a result, the MR layer 3 having no skin layer is formed,
The magnetic resistor 10 is manufactured. Since the above-mentioned skin layer becomes non-magnetic when oxidized, it may be used as a protective layer without being surface-oxidized and removed.

The above manufacturing method is a combination of conventionally known thin film technologies, and has an advantage that a CPP type magnetoresistive element can be easily manufactured even by an in-plane current.

In the magnetic resistor of the present invention, one of the magnetic materials used as the columnar body is preferably a hard magnetic material. Various hard magnetic materials are known, and any of them may be used.
It is selected from the group consisting of Co and Co alloys. Examples of Co alloys include CoPt, CoCrTa,
CoCrNb etc. can be mentioned. These form good columnar bodies by high argon pressure sputtering.

In the magnetoresistive element of the present invention, the magnetic material used as the filling layer is preferably a soft magnetic material. Various soft magnetic materials are known, and any of them may be used, but NiF is particularly preferable.
Either e or CoNiFe.

In the magnetoresistive element of the present invention, the nonmagnetic conductive material forming the isolation film may be Cu, Au, Ag or an alloy containing at least one of these. They are non-magnetic and have good electrical conductivity, and do not interfere with current measurement. Further, it is possible to easily form a film by a simple method such as plating.

In the magnetic resistor 10 shown in FIG. 1, M
The effective thickness H of the R layer 3 is preferably within the range of 10 nm to 1 μm. When the thickness H is less than 10 nm, the growth of the columnar body is incomplete, and when it exceeds 1 μm, the surfaces of the columnar body 4 are connected to each other, which makes it difficult to subsequently form the isolation film 5 and the filling layer 6.

The outer diameter a of the columnar body 4 formed perpendicularly to the substrate 1 in the MR layer 3 and the thickness c of the filling layer 6 are preferably 1 nm to 10 nm, respectively. Thickness a
And / or if the thickness c is less than 1 nm, magnetic coupling occurs between the columnar body 4 and the filling layer 6, and if it exceeds 10 nm, the in-plane current is likely to pass through the interface of the columnar body 4 / isolation film 5 / filling layer 6. It is not preferable because it decreases. From this viewpoint, the thickness a and the thickness c of the columnar body 4 and the filling layer 6 are each 2 nm to
It is particularly preferable that the thickness is 5 nm.

The thickness b of the isolation film 5 formed around the columnar body 4 is preferably 2 nm to 10 nm. If the thickness b is less than 2 nm, the soft magnetic properties deteriorate, and if it exceeds 10 nm, the probability that the in-plane current passes through the interface of the columnar body 4, the isolation film 5, and the filling layer 6 decreases, which is not preferable. From this viewpoint, the thickness b of the isolation film 5 is particularly preferably 3 nm to 5 nm.

The magnetoresistive element 1 of the present invention having the above structure.
0 is a CPP type in a broad sense in which the angle of the current direction with respect to the magnetization direction is 90 °, and since the magnetization directions of the hard magnetic layer and the soft magnetic layer can be made antiparallel, an extremely high MR effect occurs. However, not only is it possible to obtain a magnetoresistive body that is sensitive to minute changes in the external magnetic field, but
Since the length of the R layer 3 can be increased until the electric resistance reaches a desired value, it is possible to obtain a small magnetoresistive element for a magnetoresistive element capable of detecting the MR effect at room temperature without using a superconducting circuit or the like.

[0027]

In the magnetoresistive body of the present invention, a large number of columnar bodies made of one of two kinds of magnetic materials having different coercive forces are vertically projected from the substrate, and the periphery of each of these columnar bodies is
An isolation film made of a non-magnetic conductive material is formed, and a layer of the other magnetic material is formed in the gap between the columnar bodies on which the isolation film is formed. And a high MR effect can be obtained, and a magnetoresistive effect element having high sensitivity to an external magnetic field fluctuation and having an appropriate electric resistance can be obtained.

In the method for manufacturing a magnetoresistive element of the present invention, a large number of columnar bodies made of any one of the above magnetic materials are grown on a substrate, preferably by a high argon sputtering method, and grown vertically to the substrate. Since the isolation film made of a non-magnetic conductive material is formed around the columnar body, and then the layer of the other magnetic material is formed in the gap between the columnar bodies, the conventional microfabrication technology is used. The combination makes it possible to industrially easily produce the magnetoresistive body.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a magnetoresistive body of the present invention.

FIG. 2 is a sectional view showing a process of manufacturing the magnetoresistive body.

FIG. 3 is a cross-sectional view showing another process of manufacturing the magnetoresistive body.

FIG. 4 is a sectional view showing still another process of manufacturing the magnetoresistive body.

FIG. 5 is a sectional view showing still another process of manufacturing the magnetoresistive body.

FIG. 6 is a sectional view showing still another process of manufacturing the magnetoresistive body.

FIG. 7 is a cross-sectional view showing an example of a conventionally proposed magnetoresistive body.

[Explanation of symbols]

 1 ... Substrate 3 ... MR layer 4 ... Columnar body 5 ... Isolation film 6 ... Filling layer 10 ... Magnetoresistive body

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 43/12 G01R 33/06 R

Claims (6)

[Claims] 1. A large number of columnar bodies made of one of two kinds of magnetic materials each having different coercive force are projected perpendicularly to the substrate surface, and an isolation film made of a nonmagnetic conductive material is formed around each columnar body. A magnetoresistive element characterized in that a filling layer made of the other magnetic material is formed in a gap between the columnar bodies in which the isolation film is formed. 2. The magnetic resistor according to claim 1, wherein among magnetic materials having different coercive forces, one magnetic material is a hard magnetic material selected from the group consisting of Co and Co alloys. 3. The magnetoresistive element according to claim 1, wherein one of the magnetic materials having different coercive forces is a soft magnetic material made of NiFe or CoNiFe. 4. The magnetoresistive element according to claim 1, wherein the non-magnetic conductive material is selected from the group consisting of Cu, Au, Ag and an alloy containing at least one of these. 5. A large number of pillars made of one of two kinds of magnetic materials having different coercive forces are projected perpendicularly to the substrate surface, and an isolation film made of a non-magnetic conductive material is formed around each pillar. When manufacturing a magnetoresistor in which a filling layer made of the other magnetic material is formed in the gap between the columnar bodies in which the isolation film is formed, a large number of one of the above magnetic materials is formed on the substrate. Columnar bodies are grown vertically to the substrate surface, an isolation film made of a non-magnetic conductive material is formed around these columnar bodies, and then the other magnetic material is formed in the gap between the columnar bodies where the isolation film is formed. A method of manufacturing a magnetoresistive element, which comprises forming a filling layer made of. 6. The magnetic material according to claim 5, wherein the means for growing a large number of columnar bodies made of one of the magnetic materials on the substrate perpendicularly to the substrate surface is a high argon sputtering method. Resistor manufacturing method.