JP2001237473A - Composite magnetic thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly sensitive composite magnetic thin film having various kinds of functions. SOLUTION: The composite magnetic thin film has a backing magnetic substance film that is formed on a substrate and an upper-layer magnetic body film that is formed on the ground magnetic body film. The saturation magnetic field strength of the upper-layer magnetic body film is at least ten times larger than the saturation magnetic field strength of the backing magnetic substance film, and the backing magnetic substance film is constituted so as to have an irregular structure having directionality within the surface of the thin film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic thin film such as a magnetoresistive thin film whose resistance changes due to an external magnetic field and a magnetostrictive film whose size changes, and which has high sensitivity by adopting the structure of the present invention. It is possible to realize a simple magnetic field sensor, a low magnetic field operation actuator, and the like.

[0002]

2. Description of the Related Art A granular alloy magnetic film can be used as a single layer film among giant magnetoresistance effect films (GMR films) used for a magnetic field sensor. Therefore, the method of forming the granular alloy magnetic film is extremely simple as compared with other GMR films.

[0003] Such a granular alloy magnetic film is disclosed in Japanese Patent Application Laid-Open No. 8-316548 and Japanese Patent Application Laid-Open
In a thin film in which magnetic metal fine particles are dispersed in a nonmagnetic insulator matrix as disclosed in Japanese Patent No. 308320 or the like, electric conduction is generated by a tunnel effect of conduction electrons between the magnetic metal particles, and many tunnel junctions are connected. Multiplex structure. For example, in a CoAlO film,
It is known that Co having a particle size of 2 to 3 nm is dispersed, and the thickness of the Al oxide between Co particles is about 1 nm. Such a granular film has a magnetoresistance change (MR) of about 8%.
Ratio). However, the magnetic field required to change the resistance was as large as about 1 MA / m, and the magnetic field sensitivity was low.

As a method for increasing the magnetic field sensitivity of such a GMR film, Mitani et al. Use a photolithography technique in JP-A-11-274599 and in "Materia", Vol. 37, No. 9, page 745. A method is disclosed. That is, as shown in FIG. 5, a soft magnetic film structure 120 having a gap G1 (gap G1) substantially equal to the film thickness (several μm) is formed on a base 110, and a granular film 130 is formed thereon. ing. This composite structure includes the granular film 130 in the gap G1 of the soft magnetic film 120.
Is called Granular-In-Gap (GIG). In the "Materia" document, the CoYO granular film formed in the NiFe soft magnetic film gap is saturated by an external magnetic field of 0.2 kA / m, and the magnetic field sensitivity is improved to 200 times that of the CoYO single layer film. Has been reported.

On the other hand, the 21st Annual Meeting of the Japan Society of Applied Magnetics, 307 (1997), IEICE Magnetics Research Group, MAG-96-84, page 61 (1996), describes the oblique sputtering method. The magnetic film formed by the method has a directional fibrous structure in the plane, and the electrical resistance and anisotropy of the magnetic film formed by such a fine structure, and the magnetoresistance effect characteristics Have been reported by researchers including the present inventors.

[0006] A rare earth-transition metal alloy is known as a magnetostrictive material which shows a large dimensional change due to an external magnetic field. The rare earth-transition metal alloy is disclosed in, for example,
As described in Japanese Patent Application Laid-Open No. 308980 and Japanese Patent Application Laid-Open No. 4-99006, the operating magnetic field is large. That is, a large problem is that the anisotropic magnetic field is large. In order to solve such a problem, Japanese Patent Application Laid-Open No. 63-308980 proposes that a low magnetic field operation can be realized by using a laminated structure with a soft magnetic film.
However, the improvement is marginal. Also,
Japanese Patent Application Laid-Open No. Hei 4-99006 proposes to select a material exhibiting relatively large magnetostriction in a low magnetic field, rather than a material exhibiting large magnetostriction in a high magnetic field.

[0007] These magnetostrictive films have a strong force generated due to dimensional changes and are easy to miniaturize, and thus are expected to be used as power sources for ultra-compact machines and micromachines.

[0008]

However, the above-mentioned GIG structure using the photolithography technique requires fine processing for its fabrication. Therefore, the original great advantage of the granular GMR film that it can be easily manufactured has been reduced by half. Also, the size of the gap is as large as several microns.

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

Also, as described above, a magnetic material exhibiting a large magnetostriction generally has a problem that its characteristics are not exhibited unless a large magnetic field is applied.

The present invention has been made under such circumstances, and an object of the present invention is to provide a highly sensitive composite magnetic thin film having various functions without using a method such as photolithography. .

[0012]

In order to solve the above problems, the present invention provides an underlayer magnetic film formed on a substrate, and an overlayer magnetic film formed on the underlayer magnetic film. A composite magnetic thin film having a film, wherein the upper magnetic film has a saturation magnetic field strength of at least 10 times the saturation magnetic field strength of the underlying magnetic film, and the underlying magnetic film is oriented in the plane of the thin film. It is configured to have a concave-convex structure having a property.

The surface resistivity of the underlayer magnetic film is
It has direction dependence in the plane, and the maximum surface resistivity is (ρma
x), when the minimum surface resistivity is (ρmin), (ρma
It is configured such that the direction indicating (x) and the direction indicating (ρmin) are substantially orthogonal.

The ratio (ρmax) / (ρmin) is configured to be 1.10.

The value of (ρmax) is set to be 50 Ω / □ or more.

Further, the upper magnetic film is configured so that its specific resistance is at least 100 times the specific resistance of the underlying magnetic film and exhibits a giant magnetoresistance effect (GMR effect).

The upper magnetic film is formed as a magnetoresistive film.

The upper magnetic film has an absolute value (1 ×
^10-5 ) The magnetic film (magnetostrictive film) exhibiting the above-mentioned saturation magnetostriction.

The underlying magnetic film having the uneven structure is vacuum-formed in such a state that the deposited particles constituting the underlying magnetic film can be incident on the substrate surface at an incident angle of 50 to 80 degrees. It is configured as a coated magnetic film.

The underlying magnetic film having the uneven structure is formed under vacuum in such a state that the deposited particles constituting the underlying magnetic film can be incident on the substrate surface at an incident angle of 50 to 80 degrees. After the film is formed, the surface thereof is subjected to an etching treatment, and the underlying magnetic film located in the concave portion is at least partially removed.

The present invention also relates to a composite magnetic thin film having a base magnetic film formed on a substrate and an upper magnetic film formed on the base magnetic film. The film is a magnetic film formed in a vacuum so that the deposited particles constituting the base magnetic film can be incident on the substrate surface within an incident angle range of 50 to 80 degrees, and the upper magnetic film is Are configured such that the saturation magnetic field strength is at least 10 times the saturation magnetic field strength of the underlying magnetic film.

By using the above-mentioned present invention, a magnetic thin film having high magnetic field sensitivity can be obtained because an external magnetic field is concentrated on an extremely small nano-order gap. The gap forming method is also very simple.

[0023]

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

FIG. 1 shows the first composite magnetic thin film 1 of the present invention.
Is shown. FIG. 2 shows a second embodiment of the composite magnetic thin film 2 of the present invention. The second embodiment shown in FIG. 2 is a more preferable embodiment than the first embodiment shown in FIG. 1. However, in understanding the present invention, the concept of the film thickness in FIG. Since it is easy to understand, description will be made mainly on FIG.

As shown in FIG. 1, a composite magnetic thin film 1 of the present invention comprises a base magnetic film 20 formed on a substrate 10.
And a composite magnetic thin film having an upper magnetic film 30 formed on the underlying magnetic film 20.

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

Configuration of Underlayer Magnetic Film 20 As shown in FIG. 1, the underlayer magnetic film 20 has a concavo-convex structure having directivity 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,
When the shape of the concave portion 21 and the convex portion 22 in FIG. 1 in the depth direction of the paper surface is schematically represented, the shape of the concave portion 21 and the convex portion 22 is substantially maintained as shown in FIG. In this state, it extends in the depth direction of the paper.

The surface resistivity of the underlayer magnetic film of the present invention has direction dependence in the plane. That is, taking FIG. 4 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 reliably improve the magnetic field sensitivity of the upper magnetic film, which is the object of the present invention. The value of (ρmax) / (ρmin) is preferably 1.20 or more, more preferably 1.30 or more.

The maximum value (ρmax) of the surface resistivity of the underlayer magnetic film is 50Ω / □ or more, preferably 1Ω / □.
If it is 00Ω / □ or more, the effect of the present invention can be maximized. The upper limit of this value is not particularly limited, but is usually about 1 million Ω / □.

When an oxide magnetic film is selected and formed as the upper magnetic film, the underlying magnetic film is oxidized when the upper magnetic film is formed, and its surface resistivity is increased. May increase. That is, when the surface resistivity was 120Ω / □ when only the base magnetic film was evaluated, an oxide magnetic layer was formed thereon, and then a composite magnetic thin film was formed.
The surface resistivity may be 500,000 Ω / □.
In such a case, it is indicated that the specific resistance of the underlying magnetic film has increased. However, in the present invention, the surface resistivity of the underlying magnetic film can be substantially evaluated. The surface resistivity at the time of completion of the film formation is used.

As shown in FIG. 1, the uneven structure having the concave portions 21 and the convex portions 22 preferably has a maximum film thickness (Tmax) based on a surface profile measured in the width direction (α direction) in which the uneven structure is formed. ), Minimum film thickness (Tmi
n), the maximum film thickness (Tmax) is 3 to 100 n
m, preferably 5 to 50 nm.

In a preferred embodiment, the ratio of the maximum film thickness (Tmax) to the minimum film thickness (Tmin) is (Tma).
x) / (Tmin) exceeds 5 ((T
max) / (Tmin)> 5), preferably more than 10 ((Tmax) / (Tmin)> 10).

Further, according to the present invention, as shown in the second embodiment shown in FIG.
0 is completely removed, and the state where the substrate 10 is exposed is also recognized as a preferred concavo-convex structure of the present invention.
When n) = 0, the upper limit of (Tmax) / (Tmin) is infinite.

When the maximum film thickness (Tmax) is less than 3 nm, the underlying film itself has no value, and its influence on the upper magnetic film 30 formed thereon as the underlying film 20 is reduced. There is a tendency that the effect of the present invention of reducing the magnetic field is reduced.
When the maximum film thickness (Tmax) exceeds 100 nm,
In the manufacturing process for forming the desired concavo-convex structure in the present application, there is a tendency that the self-shading effect, which will be described later, is reduced and a desired concavo-convex structure cannot be obtained.

When the value of (Tmax) / (Tmin) is 5 or less, the uneven structure is insufficient, and the magnetic flux flowing between the so-called gaps G (FIGS. 1 and 2) formed by the uneven structure is reduced. It tends to be weak. Therefore, the effect of the present invention of reducing the operating magnetic field is reduced, and when the film is used as a magnetoresistive effect film, the current tends to flow around the underlying layer, so that the so-called MR effect tends to be reduced. .

In a preferred embodiment, the uneven structure having the directivity has a peak-to-peak average length (Tpp) of the protrusions of the unevenness based on the surface profile measured in the width direction of the underlying magnetic film. 0.2 × (Tmax) <(Tp
p) <20 × (Tmax). Particularly preferably, (Tmax) <(Tpp) <5 × (Tma
x). The value of the average length between peaks (Tpp) of the projections is
If the value is 0.2 × (Tmax) or less, the gap structure is unstable, and there are many short circuits between the gaps G, and the function as the gap G tends to be lost. Further, the value of the average length between peaks (Tpp) of the convex portions is 0.2 ×
When it exceeds (Tmax), the magnetic flux flowing between the gaps G becomes weak, and the effect of the present invention of reducing the operating magnetic field tends to decrease.

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 to form such a base magnetic film 20 in the following manner.

[0039] 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. For this reason, the size of the gap G takes a nano-order size and structure that exceeds the technical limits of conventional photolithography and the like. The “irregular structure having directionality” in the present invention is as described above, but if further described, as shown in FIG. 4, “fibrous”, “ It is a nanostructure in which a large number of irregularities expressed as "streaks" and "ridges" are formed in parallel.

However, since the structure is basically formed naturally, the structure is not perfect. For example, if one convex portion 22 is viewed, the direction is disturbed and the other convex portion becomes oblique. There are many parts that are in contact with and integrated with the part 22, and parts that are interrupted on the way. Further, a structure in which particles are combined in one direction to form a convex portion is also included. The projection may be interrupted in the middle. That is, when viewed microscopically, the case where the structure having no in-plane directivity 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 an extremely fine structure is handled, it is 100 to 1 even if it is macroscopic.
It refers to the surface profile in the range of about 000 nm.

As described above, the actual fine structure of the present invention is extremely complicated (the structures shown in FIGS. 1 to 4 are schematically shown for easy understanding of the structure and effect of the present invention. ).

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 relatively clear directionality as shown in FIG. 4, when scanning in the (α)-(α) direction, large irregularities are seen in a short period. 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 from a diagonal direction in a vacuum are
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. 3A, the concavo-convex structure of the present invention formed by sputtering 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.

When 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.

As the material of the base magnetic film 20 used in the present invention, various metal thin films having a small saturation magnetic field, that is, generally known as a soft magnetic material are used. For example, Ni, Fe, Co, NiFe, NiFeP, CoF
e, CoNiFe, CoFeP, NiFeMo, FeZ
rN, FeN, FeSiAl and the like can be used. The saturation magnetic field of these soft magnetic thin films is about 20 to 800 A / m.

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 the magnetic field intensity at which the magnetization is 90% saturated when an external magnetic field is applied.

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.

Further, for example, in the sputter film formation by the sputtering method, the shape of the concavo-convex structure formed differs depending on various factors such as the type of atmospheric gas to be used, gas pressure, input power, and 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 having the concavo-convex structure having the gap G structure according to the present invention is at least 750 μΩcm, particularly preferably at least 1000 μΩcm. The underlying magnetic film 20 having the concavo-convex structure of the present invention has directionality in the plane, but the gap G varies, and the magnetic film is formed in the concave portion 21 which partially forms the gap G. Normally, a short circuit occurs at the concave portions of the underlying magnetic film on both sides of the remaining gap. For this reason, the specific resistance does not become infinite,
Indicates a finite value. The specific resistance in the present invention is calculated using the average film thickness of the magnetic film, and is a value measured in a direction in which the value becomes highest.

In the present invention, as shown in FIG. 3A, 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. 3A) that has been slightly formed in the concave portion 21 forming the gap of the concave-convex structure.
According to the GIG effect of the present invention, the shape of the underlying magnetic film having a preferable gap is produced. The composite magnetic thin film having the final uneven structure formed by the etching process is shown in FIG.
Is shown in

Depending on the conditions for forming the underlying magnetic film 20,
Before the etching process, as shown in FIG. 3A, since the magnetic film is slightly formed between the gaps G, that is, the portions where the concave portions 21 are formed, the base magnetic film 20 is formed. Has a low specific resistance. Also in this case, as shown in FIG. 3B, 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, and further, 1000 μΩcm or more can be easily and reliably achieved. And the effect of the present invention can be maximized.

Configuration of Upper Magnetic Film 30 The upper magnetic film 30 is formed substantially on the underlying magnetic film 20 having the above-mentioned uneven structure.

As described above, it is preferable to form a portion where the magnetic film is not present in the concave portion 21 of the underlying magnetic film 20 in order to form a good gap G (FIG. 2). Therefore, strictly speaking, the magnetic film may not exist in the concave portion of the underlying magnetic film 20 even though it has an uneven structure, but the underlying magnetic film 20 having the uneven structure also includes this mode. Called. Therefore, the upper magnetic film 30 may be formed directly on the substrate partially located in the concave portion. Therefore, in the present invention, "formation of the upper magnetic film on the underlying magnetic film" naturally includes this aspect.

As described above, the soft magnetic thin film used as the underlying magnetic film 20 exhibits a relatively small saturation magnetic field. The soft magnetic thin film (underlying magnetic film 20) having a concavo-convex structure having directionality in the plane is magnetized by an external magnetic field Hex from a direction perpendicular to the so-called ridge-like muscle structure (α direction in FIG. 1). Then, a magnetic field corresponding to the magnetization of the soft magnetic alloy thin film acts on the concave portion 21. Therefore, the upper magnetic film 30 formed so as to be buried in the recess 21 is magnetized by a strong magnetic field acting from the soft magnetic thin film (the underlying magnetic film 20). That is, the upper magnetic film 30
Is magnetized with the same magnetic field intensity as the saturation magnetic field of the soft magnetic thin film (underlying magnetic film 20).

For this reason, when the functional film constituted as the upper magnetic film 30 is constituted, for example, as a magnetic thin film exhibiting a giant magnetoresistance effect or a magnetic thin film exhibiting a large saturation magnetostriction, each of these films is used. Can be driven with a small magnetic field. That is, high sensitivity can be achieved.

In order for the effect of the present invention to be remarkable, the saturation magnetic field strength of the upper magnetic film 30 should be at least 10 times, preferably 20 times, the saturation magnetic field strength of the underlying magnetic film 20.
It is preferably at least twice, particularly preferably at least 100 times.
There is no particular upper limit in this case.

In the present invention, as the giant magnetoresistance effect film (GMR film) suitably used as the upper magnetic film 30, films having various known compositions and structures can be used. Among them, a film that is easy to form, such as a granular film, is particularly preferable. In the case of such a giant magnetoresistive film (GMR film), "simple" which is one of the main points of the present invention is exhibited. In particular, a metal-oxide based granular GMR film is preferable, and the specific resistance of the film is 100 times smaller than that of the underlying magnetic film 20.
It is desirable that the number be twice or more. The upper limit is not particularly limited, but if it is less than the lower limit, the current is shunted to the underlying magnetic film 20 and the GMR effect tends to be unable to be used effectively.

In the present invention, the upper magnetic film 30
As the magnetostrictive film preferably used as the above, a magnetostrictive film having a particularly large magnetostriction, particularly a saturated magnetostriction having an absolute value of 1 × 10 ⁻⁵ or more is preferable. If the absolute value of the saturation magnetostriction is less than 1 × 10 ⁻⁵ , the range of industrial use is limited. There is no particular upper limit on the absolute value of the saturation magnetostriction.

Particularly preferred compositions for such a magnetostrictive film include Ni, NiFe, FeB and various alloys known as giant magnetostrictive materials, for example, RTx (R: one or more rare earth elements, T: Transition metal element, x = 1.5-
This is a rare earth-transition metal alloy film represented by 3). For example, TbFe ₃ and Tb _0.3 Dy _0.7 Fe _1.9 are well known.

The upper magnetic film 3 used in the present invention
The value of 0 is not limited to the giant magnetoresistive film and the magnetostrictive film described above (these are exemplified as preferred examples), and can be applied to various functional magnetic films having a large operating magnetic field. That is, the present invention is also effective for reducing the operating magnetic field of various functional magnetic thin films such as a magneto-optical thin film having a large operating magnetic field. Further, since there is a nano-scale gap, driving at a low voltage can be realized by using the base film structure of the present invention as a piezoelectric electrode.

Laminated Structure of Film In the composite magnetic thin film of the present invention, in addition to the above-described laminated structure of a simple two-layer magnetic layer, a two-layer laminated magnetic film is considered as one repetitive unit. Thus, a composite magnetic thin film may be formed. That is, from the substrate side, the soft magnetic film 20 having an uneven structure / the upper magnetic film 30
/ A soft magnetic film 20 having an uneven structure / an upper magnetic film 30 / a soft magnetic film 20 having an uneven structure / an upper magnetic film layer 30 /... As a result, the total thickness of the upper magnetic film 30 can be increased. Although the number of laminations (repeating unit) is not particularly limited, generally, the basic structure (the soft magnetic film 2 having an uneven structure) is generally used.
0 / upper magnetic film 30) is preferably repeated about 500 times. If it exceeds 500 times, it becomes difficult to form the fine structure of the soft magnetic film 20 having desired irregularities, and the function as the composite magnetic thin film of the present invention may not be sufficient.

Structure of the Substrate 10 The material of the substrate 10 on which the base magnetic film 20 and the upper magnetic 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 was provided on a semiconductor circuit for signal processing in advance, and a substrate subjected to planarization was used as a substrate, and the composite magnetic thin film of the present invention was used thereon. It is also possible to provide a magnetic field sensor element.

Incidentally, various known protective layers may be formed on the upper magnetic film 30.

[0064]

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

[0065] 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 or CoZrNb as a target material for forming the base magnetic film 20, the base magnetic film 20 is formed on a glass substrate by a multi-target high-frequency magnetron sputtering apparatus (HSR-551 type, Shimadzu Corporation). A film was formed. During the film formation, the Ar gas pressure during the film formation was 0.3 Pa (2 mTorr), 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 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 maximum of 25 minutes at mA, a beam voltage of 400 V, an acceleration voltage of 250 V, and a gas thickness of 0.3 Pa (2 mTorr). As described above, the configuration of the underlying magnetic film is shown in Table 1 below.

Giant magnetoresistance effect as the upper magnetic film 30
Formation of Film (GMR Film) A granular GMR film made of a CoSmO composition was formed on a glass substrate with a base magnetic film formed under the above-described various conditions. That is, on the Co target,
Using a composite target on which an Sm ₂ O ₃ chip is placed, Co
An SmO magnetic film was formed by sputtering on a glass substrate provided with a base magnetic film. At this time, the angle between the composite target and the substrate is parallel, and the Ar gas pressure is 1.2 Pa (9 mTo
rr), the input power was 300 W. As other granular GMR films, CoAlO magnetic films and CoYO magnetic films were prepared in the same manner.

In this way, various composite magnetic thin film samples functioning as GMR films (Example samples I-1 to I-1)
-3, Comparative Example Samples I-1 to I-3). In addition, the comparative sample having no underlying magnetic film (Comparative Sample I-1) was also manufactured. The structure of the upper magnetic film is shown in Table 2 below.

Formation of Magnetostrictive Film as Upper Magnetic Film 30 A magnetostrictive film having an SmFe composition was formed on a glass substrate with a base magnetic film formed under the above-described various conditions. At this time, the angle between the target and the substrate was set to be parallel, and the Ar gas pressure was 2.0 Pa (15 mTorr).
r), the input power was 400 W. Thus, various composite magnetic thin film samples (Example samples II-1 to II-2, Comparative example sample II-1) functioning as a magnetostrictive film were produced. The comparative sample was not provided with a base magnetic film. The structure of the upper magnetic film is shown in Table 2 below.

For these various composite magnetic thin film samples, (1) film thickness of each layer, (2) surface profile of the underlying magnetic film (unevenness), (3) alloy composition, and (4) resistance Evaluation and MR evaluation, and (5) magnetostriction evaluation were performed.

(1) Film thickness of each layer, 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 as necessary 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 upper magnetic layer, depending on the sample form.

The film thickness of the upper magnetic film was a film thickness formed on a glass substrate having no underlying film under the same conditions.

(3) Alloy composition The alloy composition was determined by an energy dispersive X-ray spectrometer (EDX).
And electron probe microanalyzer (EMP
It evaluated using A). The alloy composition of the upper magnetic film was determined by the composition when the film was formed on a glass substrate having no underlayer under the same conditions.

(4) Resistance Evaluation and MR Evaluation Resistance evaluation was performed by a DC four-terminal method, and MR evaluation was similarly performed at room temperature by 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.

(5) Evaluation of magnetostriction The magnetostriction was evaluated by the optical lever method. The results were expressed in terms of magnetostriction and magnetostriction sensitivity as shown in Table 3 below.

Tables 1 to 3 show the results of the above evaluations. In particular, Table 3 shows the evaluation of characteristics as a composite magnetic thin film.

[0078]

[Table 1]

[0079]

[Table 2]

[0080]

[Table 3]

Although not shown in Table 3, a comparison between the composite magnetic thin film of the present invention and a composite magnetic thin film obtained by a conventional photolithography method showed that the MR sensitivity of the composite magnetic thin film of the present invention was The magnetostriction sensitivity was twice as high as that of a composite magnetic thin film formed by a conventional photolithography method. The time required for manufacturing the composite magnetic thin film of the present invention is 1/5 of that of the conventional method, and the cost required for manufacturing the composite magnetic thin film of the present invention is 1/5 as compared with that of the conventional method.
/ 3.

[0082]

The effects of the present invention are clear from the above results. That is, the present invention is a composite magnetic thin film having a base magnetic film formed on a substrate and an upper magnetic film formed on the base magnetic film, wherein the upper magnetic film is The saturation magnetic field strength is at least 10 times the saturation magnetic field strength of the underlying magnetic film, and the underlying magnetic film is configured to have a concavo-convex structure having directionality in the plane of the thin film. In addition, it is possible to increase the sensitivity of various functional magnetic thin films. The production method is also very simple.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a first embodiment of a composite magnetic thin film of the present invention.

FIG. 2 is a sectional view schematically showing a second embodiment of the composite magnetic thin film of the present invention.

FIGS. 3A and 3B are schematic cross-sectional views for explaining a method of manufacturing a composite magnetic thin film of the present invention.

FIG. 4 is a perspective view drawn so that the general concept of the underlying magnetic film of the composite magnetic thin film of the present invention can be understood.

FIG. 5 is a sectional view for explaining a conventional example.

[Explanation of symbols]

 1, 2 ... composite magnetic thin film 10: substrate 20: base magnetic film 21: concave portion 22: convex portion 30: upper magnetic film G: gap

Claims (10)

[Claims] 1. A composite magnetic thin film having a base magnetic film formed on a substrate and an upper magnetic film formed on the base magnetic film, wherein the upper magnetic film is The composite magnetic thin film, wherein the saturation magnetic field strength is at least 10 times the saturation magnetic field strength of the underlying magnetic film, and the underlying magnetic film has an uneven structure having directionality in the plane of the thin film. . 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 composite magnetic thin 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 composite magnetic thin film according to claim 2, which is 0 or more. 4. The composite magnetic thin film according to claim 2, wherein the value of (ρmax) is 50 Ω / □ or more. 5. The upper magnetic film has a specific resistance which is 100 times or more the specific resistance of the underlying magnetic film and exhibits a giant magnetoresistance effect (GMR effect). 5. The composite magnetic thin film according to any one of 4. 6. The composite magnetic thin film according to claim 1, wherein said upper magnetic film is a magnetoresistive film. 7. The method according to claim 1, wherein the upper magnetic film has an absolute value (1 × 10
^-5 ) The composite magnetic thin film according to any one of claims 1 to 5, which is a magnetic film (magnetostrictive film) exhibiting the above-described saturation magnetostriction. 8. The underlayer magnetic film having the uneven structure,
8. A magnetic film formed in a vacuum state in such a manner that deposited particles constituting the underlying magnetic film can be incident on the substrate surface at an incident angle of 50 to 80 degrees.
A composite magnetic thin film according to any one of the above. 9. The magnetic underlayer film having the uneven structure,
After a vacuum film is formed in such a state 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, the surface is etched.
9. The composite magnetic thin film according to claim 1, wherein the underlying magnetic film located in the recess is at least partially removed. 10. A base magnetic film formed on a substrate,
A composite magnetic thin film having an upper magnetic film formed on the underlying magnetic film, wherein the deposited particles forming the underlying magnetic film have an incident angle of 50 with respect to a substrate surface. A magnetic film formed in a vacuum so that light can be incident within a range of up to 80 degrees, wherein the upper magnetic film has a saturation magnetic field strength of 10 times or more the saturation magnetic field strength of the base magnetic film. A composite magnetic thin film characterized by the following.