JP3262695B2 - Magnetoresistive body and manufacturing method thereof - Google Patents

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 an uncoupled artificial lattice which can be used as a magnetoresistive element such as a magnetic sensor, a magnetic head, a position sensor, a rotation sensor, and the like.

[0002]

2. Description of the Related Art Materials whose electrical resistance changes in response to changes in an external magnetic field are known as magnetoresistive (MR) effect materials. As this MR effect material, NiFe
An alloy (permalloy) thin film is known, but the permalloy thin film has a magnetoresistance ratio of at most about 2% to 3%. Therefore, in order to realize a narrower track of a magnetic head and a higher resolution of a magnetic sensor by applying the MR effect, an MR effect material having a larger magnetoresistance ratio (MR ratio) is required in the future.

In recent years, a phenomenon called the so-called giant magnetoresistance (GMR) effect has been discovered in an artificial lattice made of a multilayer thin film of Fe / Cr or Co / Cu system (MNBaibich et al., Physical Review Letter, 61 (1)
988) 2472, DHMosca 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 mechanism of occurrence, and it is said that the anti-ferromagnetic exchange coupling between the magnetic films works, and the anti-parallel magnetic structures are aligned in parallel by the magnetic field, thereby reducing the electrical resistance. ing.

[0004]

It is said that GMR elements using an artificial lattice made of the above-mentioned multilayer thin film can be roughly classified into three types depending on the configuration. That is, Co / C
u, Co / Ag, an antiferromagnetic system having a combined artificial lattice of NiFe / Cu, a spin valve system of NiFe / Cu / Co / FeMn, and Cu / Co / Cu / NiF
Non-bonding type such as e. Among them, the coupling type artificial lattice such as the Co / Cu type can obtain an MR ratio several times or more higher than the magnetoresistance change rate of a permalloy thin film or the like.
To generate the R effect requires a large external magnetic field,
There have been difficulties in applying it to small devices. Recently,
Research on GMR materials using multilayer thin film structures has progressed,
It has been found that the MR effect on the current in the direction perpendicular to the film can be expected to have a larger effect than the MR effect on the current in the in-plane direction of the multilayer artificial lattice 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, and a large-scale superconducting device is required to eliminate the peripheral resistance. It seemed difficult to put it to practical use.

[0005] In order to solve this problem, attempts have been made to cut out a fine column from the multilayer film and measure the MR effect from the resistance change at both ends of the column (MAMGijs et al., Phys.
v. Lett. 70 (1993) 3343). However, extremely precise processing technology is required for the preparation of this sample, and it is considered that practical use is difficult. As shown in FIG. 7, Shinjo et al. (The Japan Society of Applied Magnetics, 88th Workshop, “Recent Progress in Giant Magnetoresistance Research,” Jan. 26-27, 1995) A magnetoresistive element of a system in which a triangular wave-like surface is formed by lithography on 20 and a non-bonded multilayer 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 55 °, compared to 0 °. As a result, the measurement result reports that an MR effect clearly larger than that of the in-plane current type was obtained.

However, this method has a problem in working such as forming a triangular wave surface on the substrate, and is difficult to manufacture. The present invention has been made in order to solve the above-described problems, and accordingly, has as its object to provide a magnetoresistive element made of a non-coupled artificial lattice which is highly sensitive to external magnetic field fluctuations and is easy to manufacture, and a magnetic resistor comprising the same. It is to provide a manufacturing method.

[0007]

The object of the present invention is to provide a large number of pillars made of one of two types of magnetic materials having different coercive forces, projecting perpendicularly to the substrate surface, and surrounding each pillar with a non-magnetic material. This problem can be solved by providing a magnetic resistor 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 the columnar bodies on which the isolation film is formed.

[0008] Among the magnetic materials having different coercive forces, one magnetic material is preferably a hard magnetic material selected from the group consisting of Co or a Co alloy. Further, one magnetic material 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 an alloy containing at least one of them.

According to the present invention, when manufacturing any one of the above magnetic resistors, a large number of columnar bodies made of any one of the above magnetic materials are grown on a substrate in a direction perpendicular to the substrate surface. Provided is a method for manufacturing a magnetoresistive element, wherein an isolation film made of a nonmagnetic conductive material is formed around a body, and then a filling layer made of the other magnetic material is formed in a gap between the columnar bodies on which the isolation film is formed. I do.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described by way of an embodiment with reference to the drawings. FIG. 1 is a cross-sectional view illustrating a magnetic resistor according to an embodiment of the present invention. In FIG. 1, the magnetoresistive element 10 includes a substrate 1, a non-magnetic initial layer 2 formed on the substrate 1 along the substrate surface,
And the MR layer 3 formed on the upper surface of the substrate. This M
The R layer 3 has a large number of pillars 4 made of one of two types of magnetic materials having different coercive forces, each of which protrudes perpendicularly to the substrate 1 continuously from the initial layer 2. An isolation film 5 made of a conductive material is formed, and a layer (hereinafter referred to as a “filled layer”) 6 of the other magnetic material is formed in a gap between the pillars 4.

In the MR layer 3, one of the two magnetic materials having different coercive forces (columnar body 4) is CoPt.
And the other (filled layer 6) is made of NiFe
It is made of a 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 with oxygen added. The substrate 1 may be made of any non-magnetic material such as Si or glass. In this case, the substrate 1 is made of Si.

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

When the external magnetic field is zero, the magnetization direction of the columnar body 4 and the magnetization direction of the magnetic film 6 of the magnetic resistor 10 are
It is displaced perpendicularly and antiparallel to the substrate. When an external magnetic field is applied to the MR layer 3 with a current flowing between both ends of the MR layer 3 to change the external magnetic field in a vertical and / or horizontal direction, 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 in response to a change in the external magnetic field, and the internal electrical resistance of the MR layer 3 changes accordingly. Therefore, an MR effect (magnetoresistive effect) in which the amount of current changes is exhibited. This is because even if a current flows in the film surface, the CPP type (Current Perpendicu
lar to Plane, that is, a type in which a current flows vertically in a film plane).

The magnetic resistor 10 of this embodiment can be manufactured by the method shown in FIGS. As shown in FIG. 2, first, CoP is formed on an Si substrate 1 in an oxygen atmosphere.
The initial layer 2 is formed by sputtering t. CoPt is modulated by the 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 manufacture or use.

Next, as shown in FIG. 3, when the addition of oxygen is stopped and the sputtering conditions are switched to high argon pressure sputtering and CoPt is subsequently sputtered, the growth seeds of CoPt microcrystals continue from the initial layer 2, but A large number of columnar bodies 4 which are generated and grown separately from each other in the form of islands and project perpendicularly to the substrate 1 are formed. When an external magnetic field is applied during the high argon pressure sputtering, the direction of magnetization 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 pillar 4 using Cu which is a non-magnetic conductive material. It is preferable to use a plating technique for forming the isolation film 5.

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

At the stage when the filling layer 6 is formed, a continuous skin layer of the filling layer 6 and the separator 5 is formed on the surface layer.
This skin layer obstructs the MR effect and must be removed. Therefore, as a final step, as shown in FIG. 6, the skin layer is removed by a technique such as dry etching. Thereby, the MR layer 3 without the skin layer is formed,
The magnetic resistor 10 is manufactured. The above-mentioned skin layer becomes non-magnetic when oxidized, and thus may be used as a protective layer without being removed by surface oxidation.

The above-described manufacturing method is a combination of a conventionally known thin-film technique, and has an advantage that a CPP type magnetic resistor 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 materials are known as the hard magnetic material, and any of them may be used.
It is selected from the group consisting of Co or a Co alloy. Examples of Co alloys include CoPt, CoCrTa,
CoCrNb and the like can be mentioned. These form good pillars by high argon pressure sputtering.

In the magnetic resistor of the present invention, the magnetic material used as the filling layer is preferably a soft magnetic material. Various kinds of soft magnetic materials are known, and any of them may be used.
e or CoNiFe.

In the magnetic resistor of the present invention, any of Cu, Au, Ag, and an alloy containing at least one of these can be used as the nonmagnetic conductive material forming the isolation film. These are non-magnetic and highly conductive, and do not hinder current measurement. Further, a film can be easily formed by a simple method such as plating.

In the magnetic resistor 10 shown in FIG.
The effective thickness H of the R layer 3 is preferably in 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 the thickness H exceeds 1 μm, the surface of the columnar body 4 is connected, so that the subsequent formation of the isolation film 5 and the filling layer 6 becomes difficult.

The outer diameter a of the columnar body 4 formed perpendicular 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
If the thickness c is less than 1 nm, magnetic coupling occurs between the columnar body 4 and the filling layer 6, and if the thickness c exceeds 10 nm, the probability that an in-plane current passes through the interface between the columnar body 4 / separating film 5 / filling layer 6 is low. 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 or more.
It is particularly preferable that the thickness be 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 are degraded, and if it exceeds 10 nm, the probability that the in-plane current passes through the interface between the columnar body 4 / separation film 5 / filled layer 6 decreases, which is not preferable. From this viewpoint, it is particularly preferable that the thickness b of the isolation film 5 be 3 nm to 5 nm.

The magnetoresistive element 1 of the present invention having the above configuration
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. In addition to providing a magnetoresistor that is sensitive to minute fluctuations in the external magnetic field,
Since the length of the R layer 3 can be increased until the electric resistance reaches a desired value, a small-sized magnetoresistive element for a magnetoresistive element that can detect the MR effect at room temperature without using a superconducting circuit or the like can be obtained.

[0027]

According to the magnetoresistive element of the present invention, a large number of pillars made of one of two kinds of magnetic materials having different coercive forces project vertically from the substrate, and around each of these pillars,
An isolation film made of a nonmagnetic conductive material is formed, and a layer of the other magnetic material is formed in a gap between the pillars on which the isolation film is formed. Thus, a magnetoresistive element having high sensitivity to an external magnetic field fluctuation and having an appropriate electric resistance can be obtained.

According to the method of manufacturing a magnetic resistor 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 perpendicular to the substrate by a high argon sputtering method. An isolation film made of a non-magnetic conductive material is formed around the columnar body, and then a layer of the other magnetic material is formed in the gap between the columnar bodies. By the combination, a magnetic resistor can be easily produced industrially.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a magnetic resistor according to the present invention.

FIG. 2 is a cross-sectional view showing one process of manufacturing the above magnetic resistor.

FIG. 3 is a sectional view showing another process of manufacturing the magnetic resistor.

FIG. 4 is a sectional view showing still another process of manufacturing the above magnetic resistor.

FIG. 5 is a sectional view showing still another process of manufacturing the above magnetic resistor.

FIG. 6 is a sectional view showing still another process of manufacturing the magnetic resistor.

FIG. 7 is a sectional view showing an example of a conventionally proposed magnetic resistor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 3 ... MR layer 4 ... Columnar body 5 ... Isolation film 6 ... Filling layer 10 ... Magnetic resistance

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) H01L 43/08 G01R 33/09 G11B 5/39 H01F 10/08 H01L 43/12 JICST file (JOIS)

Claims (6)

(57) [Claims] 1. A large number of columnar bodies made of one of two types of magnetic materials having different coercive forces project perpendicularly to a substrate surface, and an isolation film made of a non-magnetic conductive material is formed around each columnar body. A magnetic resistor, wherein a filling layer made of the other magnetic material is formed in a gap between the columnar bodies on which the isolation film is formed. 2. The magnetic resistor according to claim 1, wherein one of the magnetic materials having different coercive forces is a hard magnetic material selected from the group consisting of Co or a Co alloy. 3. The magnetic resistor 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 nonmagnetic 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 columnar bodies each made of one of two types of magnetic materials having different coercive forces project perpendicularly to a substrate surface, and an isolation film made of a nonmagnetic conductive material is formed around each columnar body. When manufacturing a magnetoresistive element in which a filling layer made of the other magnetic material is formed in a gap between the columnar bodies on which the isolation film is formed, a plurality of magnetic materials made of any one of the above magnetic materials are formed on a substrate. Are grown perpendicular to the substrate surface, an isolation film made of a non-magnetic conductive material is formed around these pillars, and the other magnetic material is placed in the gap between the pillars on which the isolation film is formed. A method of manufacturing a magnetoresistive element, comprising forming a filling layer made of: 6. The method according to claim 5, wherein the means for growing a large number of columnar bodies made of any one of the magnetic materials on the substrate in a direction perpendicular to the substrate surface is a high argon sputtering method. Manufacturing method of resistor.