JP2001308414A - Huge magnetoresistance effect film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a tunnel current magnetoresistance effect film excellent in magnetic field sensitivity by a simple method. SOLUTION: This huge magnetoresistance effect film is provided with a base magnetic material film formed on a substrate and an insulating film formed on the base magnetic material film, which has uneven structure having directivity in the plane of a thin film. On the substrate, the portions are formed in which a tunnel current flows between protruding parts of the base magnetic material film which are adjacent to each other via the insulating film buried in the recessed parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a giant magnetoresistive thin film whose resistance is changed by an external magnetic field, and it is possible to realize a highly sensitive magnetic field sensor and the like by using these magnetic thin films. .

[0002]

2. Description of the Related Art As a highly sensitive magnetic field sensor, a tunnel effect magnetoresistive element (TMR) in which two ferromagnetic thin films are joined via a thin insulating film is known. In this tunnel effect magnetoresistive element, when a constant tunnel current flows between two ferromagnetic materials and different magnetic fields are applied in parallel to the surface of the ferromagnetic thin film in this state, a huge resistance change occurs in the element. Utilizes the phenomenon that occurs.

For example, Japanese Patent Application Laid-Open No. 8-316548 discloses that such a device is particularly large when Miyazaki et al. Have no anisotropy in the film plane and the coercive force of the upper and lower magnetic films is different. It is disclosed that a resistance change occurs.

[0004] However, it is extremely difficult to stably produce a thin insulating film.
JP-A-8-316548 and JP-A-10-308
No. 320 discloses a granular giant magnetoresistive film. The granular type giant magnetoresistive film is a thin film in which magnetic metal particles are dispersed in a non-magnetic insulator matrix, and electric conduction in the thin film is caused by a tunnel effect of conduction electrons between the magnetic metal particles. A large number of tunnel junctions form a multi-layered structure. For example, a CoAlO film has a particle size of 2
It is known that ３3 nm of Co is dispersed, and the thickness of Al oxide between Co particles is about 1 nm.

It has been reported that such a granular film exhibits a magnetoresistance change (MR ratio) of about 8%. However, the magnetic field required for the resistance to change is 1
It was very large at about MA / m, and the magnetic field sensitivity was low.

[0006] Such a giant magnetoresistive film (GMR)
As a method for improving the magnetic field sensitivity of
No. 4599, Mitani et al. Discloses a method using a photolithography technique. That is, a soft magnetic film structure having a gap (gap) of the same thickness as the film thickness is formed on a substrate, and a granular film is formed thereon. This composite structure is called Granular-In-Gap (GIG) because a granular film is placed in the gap of the soft magnetic material. Co formed in NiFe soft magnetic film gap
It is reported that the YO granular film is saturated by an external magnetic field of 0.2 kA / m, and the magnetic field sensitivity is improved up to 200 times that of the CoYO single layer film.

On the other hand, the 21st Annual Meeting of the Japan Society of Applied Magnetics, 307 pages (1997), IEICE Magnetics Research Group, MAG-96-84, page 61 (1996), describes the oblique sputtering method. In the magnetic film formed by the above, a fibrous structure having directionality in the plane is formed, and furthermore, the electric resistance, anisotropy, and magnetoresistance effect characteristics of the magnetic film formed by such a fine structure are improved. Changes have been reported by researchers including the present inventors.

[0008]

However, it has been difficult for the above-mentioned conventional TMR film to form a thin insulating film sandwiched between two magnetic films.

[0009] Also in the granular GMR film, the above-mentioned GIG structure using the photolithography technique is as follows.
Fine processing is required for its production. Therefore, the original great advantage of the granular GMR film that it can be easily manufactured has been reduced by half.

Further, it has been known that the granular GMR having a fibrous structure formed by the oblique sputtering method can increase the magnetic field sensitivity by the effect of controlling anisotropy caused by its structure. Was slight.

The present invention has been made in view of such circumstances, and its object is to provide a simple and easy method without using a method of manufacturing a thin insulating film, which is extremely difficult to manufacture, or a method such as photolithography. It is an object of the present invention to provide a tunnel current magnetoresistive film which can be manufactured by a simple method and has good magnetic field sensitivity.

[0012]

SUMMARY OF THE INVENTION In order to solve such problems, the present invention provides a base magnetic film formed on a substrate, and an insulating film formed on the base magnetic film. A giant magnetoresistive film having:
The substrate has a concavo-convex structure having directionality in the plane of the thin film, and a portion that acts so as to allow a tunnel current to flow between adjacent protrusions of the underlying magnetic film via the insulator film embedded in the recess is formed on the substrate. It is configured as formed above.

In the present invention, the surface resistivity of the underlayer magnetic film has direction dependency in a plane, and when the maximum surface resistivity is (ρmax) and the minimum surface resistivity is (ρmin), The direction indicating (ρmax) and the direction indicating (ρmin) are configured to be substantially orthogonal.

In the present invention, (ρmax) /
The ratio of (ρmin) is configured to be 1.10.

In the present invention, when the maximum film thickness is (Tmax) and the minimum film thickness is (Tmin) based on a surface profile measured in the width direction of the uneven structure, the maximum film thickness ( Tmax) is 3 to 30 nm, and the minimum thickness (Tmin) is zero because the underlying magnetic film is partially interrupted to include a portion where the substrate is exposed. Average width of 0.
It is configured to be 5 nm to 50 nm.

The present invention also provides a giant magnetoresistive film having a base magnetic film formed on a substrate and an insulating film formed on the base magnetic film, The body film is configured to be a magnetic film vacuum-formed so that the deposited particles constituting the base magnetic film can be incident on the substrate surface at an incident angle of 50 to 80 degrees. .

Further, in the present invention, the underlayer magnetic film is vacuum-deposited in such a state that deposited particles constituting the underlayer magnetic film can be incident on the substrate surface at an incident angle of 50 to 80 degrees. Then, the surface is etched.

In the present invention, electrodes are formed at both ends of the underlying magnetic film and a detection current is caused to flow therethrough so as to be adjacent to the underlying magnetic film via the insulating film buried in the concave portion of the uneven structure. There are a plurality of locations where a tunnel current flows between the protruding portions of the underlying magnetic film (close to the substrate).

The uneven structure of the underlying magnetic film has a random ridge-like structure, and each ridge has a slightly different coercive force Hc depending on the condition of the ridge. Therefore, the magnetized state of the concavo-convex structure of the underlying magnetic film changes due to the change of the external magnetic field (the state of magnetization equilibrium and the state of anti-equilibrium change locally), thereby changing the tunnel current flowing between the electrodes. Act like so.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail.

FIG. 1 shows a giant magnetoresistive film 1 of the present invention.
Is shown. As shown in FIG. 1, the giant magnetoresistive film 1 of the present invention includes a base magnetic film 20 formed on a substrate 10 and a base magnetic film 20.
As a giant magnetoresistive film having an insulator film 30 formed thereon.

The structure and method of forming the underlying magnetic film 20, the structure of the insulator film 30, the laminated structure of these films, and the like will be sequentially described below.

Configuration of Underlayer Magnetic Film 20 As shown in FIG. 1, the underlayer magnetic film 20 has an uneven structure having directionality in the plane of the thin film. That is,
A concavo-convex structure (a concavo-convex structure having directionality) in which concave portions 21 and convex portions 22 are alternately repeated in the (α)-(α) direction (left-right direction on the paper surface) in FIG. By the way,
If the shape of the concave portion 21 and the convex portion 22 in FIG. 1 in the depth direction of the paper surface is expressed as an ideal shape, as shown in FIG. It is in a form extending in the depth direction of the paper while maintaining it.

The actual shapes of the concave portions 21 and the convex portions 22 forming the concave-convex structure are regularly arranged and regularly arranged as shown in the drawings, as can be seen from the manufacturing method described later. However, the convex portion 21 has a complicated shape in which large and small convex shapes having different shapes are mixed. In other words, in the drawing,
It is drawn as a relatively regular uneven structure to facilitate understanding of the present invention.

The surface resistivity of the underlying magnetic film of the present invention has direction dependence in the plane. That is, taking FIG. 3 as an example, the maximum value is shown in the (α)-(α) direction, and the minimum value is shown in a direction substantially perpendicular thereto (an angle of about 90 ° ± 10 °). This phenomenon is attributable to the fact that the underlying magnetic film has a directional uneven structure, which is a major feature of the present invention. Then, the maximum value of the surface resistivity is defined as (ρmax:
When the minimum value of the surface resistivity is (ρmin: minimum surface resistivity) and the value of (ρmax) / (ρmin) is 1.10 or more, the directional uneven structure base has a directionality. It is desirable to use a magnetic film. This is to ensure the improvement of the magnetic field sensitivity, which is the object of the present invention. The above (ρma
The value of (x) / (ρmin) is preferably 1.20 or more, more preferably 1.30 or more.

If the maximum value (ρmax) of the surface resistivity of the underlying magnetic film is 200 Ω / □ or more, preferably 500 Ω / □ or more, the effect of the present invention can be maximized. Become. There is no particular upper limit for this value,
Usually, it is about 1,000,000Ω / □.

As shown in FIG. 1, the concave and convex structure having the concave portion 21 and the convex portion 22 has a maximum film thickness (Tmax) based on a surface profile measured in the width direction (α direction) for forming the concave and convex structure, and a minimum film thickness. When the thickness is (Tmin), the maximum thickness (Tmax) is 3 to 30 nm, preferably 5 to 20 nm.
nm. The minimum film thickness (Tmin) in the present invention is:
The value is zero because the base magnetic film 20 includes a part where the surface of the substrate 10 is exposed by being partially interrupted. In the present invention, the insulator film 30 buried in the recess 21 is used.
A portion is formed on the substrate through which a tunnel current flows between the protrusions 22 of the underlying magnetic film adjacent to each other. That is, the insulator film 30 buried in the concave portion 21 according to the present invention functions as a barrier film for a tunnel current flowing between the adjacent convex portions 22 of the base magnetic film formed on both sides thereof. It is.

The average of the width Wr (measured in the α direction) of the concave portion 21 in the uneven structure having directivity is 0.5 nm to
It is 50 nm, preferably 5 to 30 nm. The average of the width Wp (measured in the α direction) of the convex portion 22 in the concave-convex structure is 0.5 nm to 50 nm, preferably 5 nm to 30 nm.
It is said. Here, the width Wr of the concave portion 21 and the width Wp of the convex portion 22
The term “width” refers to the width of a convex portion at a position of 50% of the maximum height and the width of a concave portion at a position of 50% of the maximum depth in the surface profile. If the width Wp of the convex portion 22 is less than the above range, the effect of concentrating magnetic flux as a magnetic substance is weak, and the saturation magnetic field becomes large. When the ratio exceeds the above range, a portion contributing to the TMR effect decreases, so that the rate of change becomes small. If the width Wr of the concave portion 21 is less than the above range, contact between the magnetic bodies occurs frequently, and if the width Wr exceeds the above range, it becomes difficult for a tunnel current to flow.

The location where the tunnel current actually flows is where the width Wr of the concave portion 21 is the narrowest, in many cases near the surface of the substrate 10, and 50% of the maximum height (depth) as described above. Not in a place. This is because the cross-sectional shape of the convex portion 22 is inclined as can be seen from a manufacturing method described later.

When the maximum film thickness (Tmax) is less than 3 nm, the existence value of the underlying film itself is lost, the influence on the insulating film 30 formed thereon as the underlying film 20 is reduced, and the operating magnetic field is reduced. , The effect of the present application of reducing the amount of light is reduced. In addition, the maximum film thickness (Tma
If x) exceeds 100 nm, in the manufacturing process for forming the desired uneven structure, the disadvantage that the self-shading effect described later becomes small and the desired uneven structure cannot be obtained occurs.

As will be described later, the concavo-convex structure in the present invention is formed substantially spontaneously, and its variation is large. For this reason, the numerical value relating to the uneven surface shape in the present invention indicates the average value of the ten points, and the individual measurement may deviate significantly from the average value. As a specific method for evaluating the concavo-convex structure, surface state (two-dimensional) observation by an atomic force microscope (AFM) is performed, and cross-sectional profile data of a representative place is used.

It is preferable that such a base magnetic film 20 is formed in the following manner.

[0033] In the film formation present invention the underlying magnetic layer 20, without using a method such as expensive photolithography laborious, utilizes an uneven structure having a directional in a plane which is naturally formed. Therefore, the size of the gap (concave portion) has a nano-order size and structure that exceeds the technical limit of conventional photolithography and the like. The “irregular structure having directionality” in the present invention is:
As already described above, if it is further described, as schematically shown in FIG. 3, along a certain specific direction in the plane, "fibrous", "streak", "ridge", etc. It is a nanostructure in which a large number of expressed irregularities are formed in parallel.

However, since the structure is basically formed naturally, the structure is not perfect as shown in FIG.
There are many parts where the directionality is disturbed and becomes oblique and in contact with and integrated with other convex parts 22, and there are many parts that are interrupted on the way. Further, a structure in which the particles are combined in one direction to form the protrusions 22 is also included. The convex part 22 may be interrupted on the way.

That is, when viewed microscopically, the case where the structure having no directionality in the plane is never seen is also included in the uneven structure of the present invention. However, macroscopically, a concavo-convex structure having directionality in a plane is recognized. However, in the present invention, since a very fine structure is handled, macroscopic means a surface profile in a range of about 100 to 1000 nm.

As described above, the actual concave / convex fine structure of the present invention is extremely complicated (the concave / convex structure shown in FIGS. 1 to 3 is a schematic diagram for easy understanding of the configuration and effect of the present invention as described above. It is a regular expression in).

For this reason, when the surface profile of the underlying magnetic film 20 is evaluated using, for example, an atomic force microscope,
In a structure having a relatively clear directionality as shown in FIG. 3, when scanning in the (α)-(α) direction, large irregularities are seen in a short cycle. On the other hand, (α) −
When scanning at right angles to the (α) direction, no irregularities are seen.
However, in the case of a structure in which the projections 22 are not completely parallel and are partially bent, large irregularities are observed even when scanning is performed at right angles to the (α)-(α) direction. The maximum film thickness and the minimum film thickness of the unevenness are exactly the same as in the case of scanning in the (α)-(α) direction, but the average length of the peak of the projection is scanned in the (α)-(α) direction. It becomes longer than the case where it did, and becomes a long cycle. That is, there is a phenomenon that the period of the unevenness differs depending on the scanning direction.

Such a concavo-convex structure having directionality in a plane has a structure in which particles incident obliquely in a vacuum form the substrate 10.
It can be formed by the so-called self-shading effect in the initial stage when depositing on the top. For example, as shown in FIG. 2A, the concavo-convex structure of the present invention formed by sputter deposition forms an arrangement angle θ between the plane of the substrate 10 and the plane of the target 50 (the incident angle with respect to the vertical direction of the plane of the substrate 10). (same as θ) is 50 to 80 degrees, preferably 55 to 70 degrees.

If the incident angle θ is less than 50 degrees, the self-shading effect is weak, and a good directional structure cannot be obtained. If the incident angle θ exceeds 80 degrees, the film forming efficiency is poor and the in-plane distribution is large, which is not suitable for practical use.

The material of the underlying magnetic film 20 used in the present invention is composed mainly of at least one element selected from Ni, Fe and Co. In particular, it is preferable to use various metal thin films having a small saturation magnetic field, that is, various kinds of metal thin films generally known as soft magnetic materials, from the viewpoint of improving the magnetic field sensitivity. For example, Ni, Fe, Co, NiFe,
NiFeP, CoFe, CoNiFe, CoFeP, N
iFeMo, FeZrN, FeN, FeSiAl, Co
ZrNb or the like can be used. The saturation magnetic field of these soft magnetic thin films is about 20 to 2000 A / m, and 3000
A / m or less. For a material having a saturation magnetic field exceeding 3000 A / m, the saturation magnetic field of the giant magnetoresistive film is too large and the magnetic field sensitivity is reduced.

Although the saturation magnetic field can be measured by various methods, an approximate value can be easily obtained by measuring using a vibrating sample magnetometer (VSM). The saturation magnetic field in the present invention is defined as a magnetic field intensity at which the magnetization is 90% saturated as compared with a case where a sufficiently strong magnetic field is applied from the outside.

In order to obtain a large magnetoresistance effect change rate, it is preferable to use a material having a large polarization as the material of the base magnetic film 20 in the present invention.
In a magnetic material mainly containing one or more elements selected from Fe and Co, the higher the saturation magnetic flux density material, the larger the polarization. However, high saturation magnetic flux density materials generally have a large saturation magnetic field, so the magnetic field sensitivity is low.
It is applicable when the purpose is to obtain a large change rate.

The uneven structure having directivity according to the present invention can be formed by various vacuum film forming methods such as a DC sputtering method, an ion beam sputtering method and an evaporation method other than the high-frequency magnetron sputtering method. . Among them, a sputtering method is particularly preferable. This is because the energy of the film-forming particles in the sputtering method is particularly suitable for forming the uneven structure of the present invention. In other words, this is because a concavo-convex structure due to the self-shading effect preferable in the present invention is easily developed.

Furthermore, for example, in the sputter deposition by the sputtering method, the shape of the concavo-convex structure formed differs depending on various factors such as the type of the atmospheric gas to be used, the gas pressure, the input power, and the substrate temperature. For example, when the arrangement angle θ between the substrate and the target is set to 60 degrees using an argon gas, the most effective and favorable uneven structure is formed when the gas pressure is 2.67 Pa (2 mTorr).

The resistivity of the underlying magnetic film 20 having the concavo-convex structure having the gap structure according to the present invention is 750 μΩcm or more.
Particularly preferably, it is 1000 μΩcm or more. In the gap structure formed by conventional photolithography,
Since the underlying magnetic films on both sides of the gap are completely separated, the theoretical specific resistance becomes infinite. On the other hand, the underlying magnetic film 20 having the concavo-convex structure of the present invention has directionality in the plane, but the gap thereof varies, and the magnetic material film is formed in the concave portion 21 which partially forms the gap. Normally, the film is short-circuited at the concave portions 21 of the underlying magnetic film on both sides of the remaining gap. For this reason, the specific resistance does not become infinite, but shows a certain finite value. In the present invention, since the specific resistance is a film having irregularities, the film thickness is calculated from the measured resistance value using the maximum film thickness (Tmax).

In the present invention, as shown in FIG. 2A, a base magnetic film is deposited on the substrate 10 by oblique sputtering at a desired angle to form an uneven structure.
It is preferable to perform an etching treatment as shown in (b), that is, an operation of uniformly removing a film having a desired thickness from the surface. The etching process may be performed by, for example, an ion milling device using an argon gas in a vacuum. This etching process makes it possible to completely remove the magnetic film (the state shown in FIG. 2A) that has been slightly formed in the concave portion 21 forming the gap of the concave-convex structure.
A base film shape having a more preferable gap for manifesting the tunnel current effect of the present invention is produced.

Depending on the conditions for forming the underlying magnetic film 20,
Before the etching process, as shown in FIG. 2A, the magnetic film is slightly formed between the gaps, that is, the portion where the concave portion 21 is formed.
0 indicates a low specific resistance. Also in this case, as shown in FIG. 2B, by performing an etching process for uniformly removing a film having a desired thickness from the surface, a high specific resistance of 750 μΩcm or more can be obtained easily and reliably. The effects of the invention can be maximized.

[0048]Configuration of insulator film 30 The insulator film 30 is substantially a base having the above-described uneven structure.
It is formed on the magnetic film 20. As a thin insulator film
It is possible to use films having various known compositions and structures.
However, preferably, 100 times or more of the underlying magnetic film 20,
Particularly preferred is a material having a specific resistance of 1000 or more.
You. Below the range (less than 100 times), the tunnel current
It is difficult to flow and the MR ratio becomes small. Specifically
Is SiO _Two, TiO_Two, Ta_TwoO_Five, Al_TwoO_Three, Sm
_TwoO_Three, Hf_TwoO_Three, CeO_Two, Y_TwoO_Three, SiN, AlN
It is particularly preferable that at least one material selected from the group consisting of
Good.

As described above, it is preferable to form a portion in which the magnetic film is not present in the concave portion 21 of the base magnetic film 20 in order to form a favorable tunnel film structure. For this reason, strictly speaking, a concave portion of the underlying magnetic film 20 needs a portion where the magnetic film does not exist even though it has an uneven structure. This is referred to as a magnetic film 20. Therefore, the insulator film 30 is formed directly on the substrate partially located in the concave portion. Therefore, in the case of "forming an insulating film on a base magnetic film" in the present invention, this mode is of course included.

In such a giant magnetoresistive film of the present invention, the electrodes are formed at both ends (left and right ends in FIG. 1) of the base magnetic film 20 and a detection current is caused to flow, so that the unevenness of the base magnetic film 20 is obtained. Through the insulator film 30 buried in the concave portion 21 of the structure (particularly, the portion where the substrate surface is exposed), a tunnel current flows between the convex portions 22, 22 of the adjacent base magnetic film 20 (close to the substrate) between the adjacent convex portions 22, 22. There are a plurality of places where flows. Further, the uneven structure of the underlying magnetic film 20 has a random ridge-like structure or the like, and each ridge has a slightly different coercive force Hc depending on the condition of the ridge. Therefore, the magnetized state of the concavo-convex structure of the underlying magnetic film changes due to the change of the external magnetic field (the state of magnetization equilibrium and the state of anti-equilibrium change locally), thereby changing the tunnel current flowing between the electrodes. It works like that.

Laminated Structure of Film The giant magnetoresistive film of the present invention, in addition to the above-described laminated structure of a two-layer magnetic film, further considers a two-layer laminated magnetic film as one unit of repetition, Alternatively, a giant magnetoresistive film may be formed by stacking. That is, from the substrate side, the soft magnetic film 20 having the uneven structure / the insulator film 30 / the soft magnetic film 20 having the uneven structure / the insulator film 30 /
This is a giant magnetoresistive film having a structure in which the soft magnetic film 20 / insulator film 30 /...

Although the number of laminations (repeating unit) is not particularly limited, generally, the basic structure (the soft magnetic film 20 having an uneven structure) is generally used.
/ Insulator film 30) is preferably repeated about 500 times. If it exceeds 500 times, it becomes difficult to form a fine structure of the soft magnetic film 20 having desired irregularities, and the function as the giant magnetoresistive film of the present invention may not be sufficient.

Structure of Substrate 10 The material of the substrate 10 on which the base magnetic film 20 and the insulating film 30 are laminated is not particularly limited, regardless of an organic material or an inorganic material. Preferred specific examples include organic materials such as polyimide, polycarbonate, and polyethylene terephthalate, and inorganic materials such as silicon, glass, titanium, and aluminum. Further, a film of alumina, silicon oxide, polyimide or the like may be formed on these substrates. For example, when used as a magnetic field sensor, a silicon oxide film is provided on a semiconductor circuit for signal processing in advance, and a substrate subjected to planarization processing is used as a substrate, and a giant magnetoresistive film of the present invention is formed thereon. It is also possible to provide the used magnetic field sensor element.

Note that various known protective films may be formed on the insulator film 30.

Various compositions used in a film formed by laminating two magnetic films via an insulating film, known as a tunnel current magnetoresistive film, are also effectively utilized in the present invention. For example, the half metallic ferromagnetic material N
iMnSb and LaSrMnO are used as the base magnetic film 20 and Al ₂ O ₃ and SrTiO ₃ are used as the upper insulating film 30.
It is also possible to create a structure using the present invention according to the present invention. That is, in the present invention, a structure that has been stacked in the conventional substrate surface direction can be regarded as a structure that is stacked in the vertical direction of the substrate.

[0056]

The present invention will be described in more detail with reference to specific examples below.

[0057] In the deposition procedure follows the underlying magnetic layer 20, on a glass substrate (Matsunami Glass S1225), thereby forming a base magnetic film 20.

Using a target of Ni80-Fe20 as a target material for forming the base magnetic film 20, the base magnetic film 20 was formed on a glass substrate by a multi-target high-frequency magnetron sputtering apparatus (HSR-551, Shimadzu Corporation). A film was formed. During the film formation, the Ar gas pressure during the film formation was 0.3 Pa to 0.6 Pa, and the input power was 300 W. As shown in Table 1 below, the glass substrate 10 was tilted at various angles from 20 to 70 degrees with respect to the target in accordance with the target sample production, and the film forming time was varied to change the inclination. A substrate sample with a base magnetic film having a shape was prepared.

As shown in Table 1 below, the surface of the base magnetic film was further subjected to an etching treatment for these substrate samples with the base magnetic film. That is, an argon gas is used as an etching gas,
Milling treatment (etching treatment) was performed at a predetermined time shown in Table 1 at mA, a beam voltage of 400 V, an acceleration voltage of 250 V, and a gas thickness of 0.3 Pa (2 mTorr).

[0060]Formation of insulator film 30 Gas with a base magnetic film produced under the above various conditions
Al on the glass substrate _TwoO_ThreeThe insulator film 30 having the composition
A film was formed by sputtering. At this time, the angle between the target and the substrate
Are parallel, and the Ar gas pressure is 1.2 Pa (9 mTorr).
r), the input power was 300 W. Average of insulator film 30
The thickness was about 10 nm. Also, on a substrate with a smooth surface
The specific resistance of only the insulator film 30 formed under the same conditions
It was very high and could not be evaluated.

In this manner, various giant magnetoresistive film samples (Example samples 1 to 4 and Comparative example samples 1 to 4)
3) was produced. The sample 4 of the embodiment is obtained by changing the composition of the magnetic underlayer film 20 of the sample 1 of the embodiment from NiFe to CoZrNb.

With respect to these various giant magnetoresistive film samples, (1) film thickness of each film, (2) surface profile of the underlying magnetic film (unevenness), and (3) resistance evaluation and MR evaluation was performed.

(1) Film thickness of each film, and (2) underlying magnetism
Measurement of Surface Profile (Unevenness) of Body Film The measurement of the film thickness and the surface profile was performed using an atomic force microscope (AFM) (AFM observation). These measurements were performed after the formation of the underlying magnetic film, after the etching treatment of the surface of the underlying magnetic film, and after the formation of the insulator film, as required depending on the sample form.

The thickness of the insulator film was determined from the film thickness formed on a glass substrate having no base film under the same conditions.

(3) Resistance Evaluation and MR Evaluation Resistance evaluation was performed by a DC four-terminal method, and MR evaluation was similarly performed at room temperature while applying a magnetic field from the outside by a DC four-terminal method. The results were expressed as specific resistance, surface resistivity, MR change rate, and MR sensitivity as shown in the table below.

Tables 1 and 2 show the evaluation results. In particular, the evaluation of characteristics as a giant magnetoresistive film is shown in Table 2.

[0067]

[Table 1]

[0068]

[Table 2]

[0069]

The effects of the present invention are clear from the above results. That is, the present invention is a giant magnetoresistive film having a base magnetic film formed on a substrate and an insulator film formed on the base magnetic film, wherein the base magnetic film is A concave / convex structure having directionality in the plane of the thin film, and a portion that acts so that a tunnel current flows between adjacent convex portions of the underlying magnetic film via the insulator film buried in the concave portion. Since it is configured to be formed on a substrate, it is a simple method without using a method of manufacturing a thin insulating film, which is said to be extremely difficult to manufacture, or a method such as photolithography. A good tunnel current magnetoresistive film can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing an embodiment of a giant magnetoresistive film of the present invention.

FIGS. 2A and 2B are schematic cross-sectional views for explaining a method of manufacturing a giant magnetoresistive film according to the present invention.

FIG. 3 is a perspective view of the giant magnetoresistive film of the present invention, which is drawn so that the general concept of the underlying magnetic film can be understood.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Giant magnetoresistive film 10 ... Substrate 20 ... Base magnetic film 21 ... Concave part 22 ... Convex part 30 ... Insulator film

Claims (8)

[Claims] 1. A giant magnetoresistive film having a base magnetic film formed on a substrate and an insulator film formed on the base magnetic film, wherein the base magnetic film is The substrate has a concavo-convex structure having directivity in the plane of the thin film, and a portion that acts so that a tunnel current flows between adjacent protrusions of the underlying magnetic film via the insulator film embedded in the recess is formed on the substrate. A giant magnetoresistive film, which is formed thereon. 2. The surface resistivity of the underlayer magnetic film has direction dependency in a plane, and when the maximum surface resistivity is (ρmax) and the minimum surface resistivity is (ρmin), (ρmax) The giant magnetoresistive film according to claim 1, wherein the direction indicating (ρmin) is substantially orthogonal to the direction indicating (ρmin). 3. The ratio of (ρmax) / (ρmin) is 1.1.
3. The giant magnetoresistive film according to claim 2, wherein the value is 0 or more. 4. When the maximum film thickness (Tmax) and the minimum film thickness (Tmin) according to the surface profile measured in the width direction of forming the concave-convex structure are defined as the maximum film thickness (Tmax), 3 to 30 nm, minimum film thickness (Tmin)
Is zero because the underlying magnetic film partially includes the exposed part of the substrate due to interruption, and the average of the width of the concave portion in the uneven structure having directivity is 0.5 nm to 50 nm. The giant magnetoresistive film according to claim 3. 5. A giant magnetoresistive film having a base magnetic film formed on a substrate and an insulator film formed on the base magnetic film, wherein the base magnetic film is A giant magnetoresistive effect, wherein the magnetic film is formed in a vacuum state in such a manner that deposited particles constituting the base magnetic film can be incident on the substrate surface at an incident angle of 50 to 80 degrees. film. 6. The magnetic underlayer film, wherein the deposited particles constituting the magnetic underlayer film have an incident angle of 50 to 8 with respect to the substrate surface.
6. The giant magnetoresistive film according to claim 5, wherein the surface is etched after a vacuum film is formed in a state where the light can be incident within a range of 0 degrees. 7. The surface resistivity of the underlayer magnetic film has direction dependency in the plane, and when the maximum surface resistivity is (ρmax) and the minimum surface resistivity is (ρmin), (ρmax) The giant magnetoresistive film according to claim 6, wherein the direction indicating (ρmin) is substantially orthogonal to the direction indicating (ρmin). 8. The ratio of (ρmax) / (ρmin) is 1.1.
The giant magnetoresistive film according to claim 7, wherein the value is 0 or more.