JP2001228229A - Magnetic impedance effect element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic impedance effect element with high sensitivity in detecting external magnetic fields capable of suppressing the lifting of both sides of a magnetic thin film in the widthwise direction of the magnetic thin film. SOLUTION: The magnetic impedance effect element is provided with both a substrate 2 made of a non-magnetic body and a band-shaped magnetic thin film 3 provided on the thin film 2. The film thickness of both side parts of the magnetic thin film 3 is formed more thinly than the film thickness of the center part of the magnetic thin film 3 in the widthwise direction B of the magnetic thin film 3, so that the width Wa of the lower surface 3a of the magnetic thin film 3 closely adhering to the substrate 2 may be larger than the width Wb of the upper surface 3b of the magnetic thin film 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-impedance effect element for detecting an external magnetic field using a magneto-impedance effect.

[0002]

2. Description of the Related Art Magneto-impedance effect elements have a high external magnetic field detection sensitivity, and therefore have begun to be applied to azimuth sensors, motor rotation sensors and the like as magnetic detection elements. 8 to 10 are for explaining the prior art of such a magneto-impedance effect element. This magneto-impedance effect element 21 has a high magnetic permeability formed on a substrate 22 made of a non-magnetic material. The first and second electrodes 24 and 25 for leading out a lead made of a conductive film are laminated on both ends in the longitudinal direction of a strip-shaped magnetic thin film 23 having a magnetic thin film 23 as shown in FIG. It is formed in such a rectangular cross section. Also, the magnetic thin film 23 is formed such that the direction of the axis of easy magnetization is perpendicular to the longitudinal direction of the magnetic thin film 23 (the direction of arrow A) in the film plane.
3 has magnetic anisotropy in the width direction (the direction of arrow B).

[0003] The magneto-impedance effect element 21 having the above-described configuration is arranged such that the longitudinal direction of the magnetic thin film 23 is arranged along an external magnetic field H generated from a detection object (not shown). When a high-frequency current in the MHz band is applied to the magnetic thin film 23 through the electrodes 24 and 25, the impedance between both ends in the longitudinal direction of the magnetic thin film 23 changes.
This change is converted into an electric signal, and a detection output of the external magnetic field H is obtained.

[0004] As shown in FIG. 10A, the production of the magneto-impedance effect element 21 is carried out in a static magnetic field.
Alloy thin film 26 in an amorphous state to be a magnetic thin film 23 on the top surface
Is formed by a sputtering method.
As shown in (b), a strip-shaped photoresist 27 is formed on the alloy thin film 26. Then, the alloy thin film 26 is wet-etched to a state shown in FIG. 10C, and then, as shown in FIG. 10D, the photoresist 27 is removed, and the alloy thin film 26 and the substrate 22 are exposed to a static magnetic field. A heat treatment (annealing) is performed to change the alloy thin film 26 into a crystalline state to form a magnetic thin film 23 (see FIG. 10E).
By forming electrodes 24 and 25 at both ends in the longitudinal direction of the magnetic thin film 23, the magneto-impedance effect element 21 shown in FIGS. 8 and 9 is manufactured.

[Problems to be solved by the invention]

However, in the above-described conventional magneto-impedance effect element 21, when the alloy thin film 26 formed in a strip shape by etching is heated together with the substrate 22, the difference in the thermal expansion coefficient between the two occurs. , Substrate 22
The lower surface of the alloy thin film 26 adhered to the metal thin film 26 is pulled toward the upper surface of the alloy thin film 26, and as shown in FIG.
In the width direction of the magnetic thin film 23 (direction of arrow B), both sides of the alloy thin film 26 are turned up. As a result, as shown in FIG. The magnetic domain of the turned up portion disappears during the heat treatment, the portion of the magnetic thin film 23 where the magnetic domain 28 is formed decreases, the change in impedance with respect to the external magnetic field H decreases, and the external magnetic field detection sensitivity of the magnetic impedance effect element 21 increases. However, there was a problem that was reduced.

The phenomenon that both sides of the magnetic thin film are turned up and the magnetic domain disappears appears particularly remarkably when a material which undergoes a phase change from an amorphous state to a crystalline state by heat treatment is used for the alloy thin film 26.

The present invention has been made in view of the above-mentioned circumstances of the prior art, and has as its object to suppress the disappearance of magnetic domains on both sides of a magnetic thin film in the width direction of the magnetic thin film, and to detect an external magnetic field. An object of the present invention is to provide a magneto-impedance effect element having high sensitivity.

[0008]

In order to achieve the above object, a magneto-impedance effect element according to the present invention comprises a substrate made of a non-magnetic material, and a strip-shaped magnetic thin film provided on the substrate. As the width of the lower surface of the magnetic thin film adhered to the substrate is larger than the width of the upper surface of the magnetic thin film,
The most characteristic feature is that the film thickness on both sides of the magnetic thin film in the width direction of the magnetic thin film is formed smaller than the film thickness on the central portion of the magnetic thin film.

Further, in the above configuration, tapered surfaces are provided on the both side portions of the magnetic thin film.

[0010] In the above structure, the both sides of the magnetic thin film are formed stepwise.

In the above structure, the magnetic thin film may have a uniform crystal grain size of 30 nm or less.
The soft magnetic alloy thin film was mainly composed of a simple substance or a mixture of FeCo and bccCo.

[0012] In the above structure, the magnetic thin film is represented by a compositional formula _{T 100-abcd X a M b} Z c Q d, element T
Is one or two elements of Fe and Co, X is one or two elements of Si and Al, and M is T
i, Zr, Hf, V, Nb, Ta, Mo, W are one or more elements selected from the group consisting of one or two elements of C and N; a ≦ 25, 1 ≦
b ≦ 10, 5 ≦ c ≦ 15, 0 ≦ d ≦ 10, and the crystal structure of the magnetic thin film has an average crystal grain size of 10 nm.
The structure was such that fine carbides or nitrides of the following element M precipitated around Fe or Co crystal grains.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of a magneto-impedance effect element according to the present invention will be described with reference to FIGS.

This magneto-impedance effect element 1 is provided on both ends in the longitudinal direction of a strip-shaped magnetic thin film 3 having a high magnetic permeability formed on a substrate 2 made of a non-magnetic material. The first and second electrodes 4 and 5 are arranged in a stacked manner.

The magnetic thin film 3 is made of Fe having a bcc structure and FeCo, b having a bcc structure having an average crystal grain size of 30 nm or less.
Consisting of a soft magnetic alloy thin film mainly composed of a simple substance or a mixture of Co having a cc structure, for example, the composition formula is Fe _71.4 Al _{5.8
Represented by} Si _13.1 Hf _3.3 C _4.5 Ru _1.9 (at%),
a microcrystalline soft magnetic alloy thin film having a crystal grain size of 5 to 30 nm mainly composed of Fe microcrystalline grains having a bcc structure and having HfC crystal grains deposited around the Fe microcrystalline grains by heat treatment,
The direction of the axis of easy magnetization is perpendicular to the longitudinal direction (the direction of arrow A) of the magnetic thin film 3 within the film plane.
Are provided with magnetic anisotropy in the width direction (arrow B direction).

Then, as shown in FIG. 2, the width Wa of the lower surface 3a of the magnetic thin film 3 adhered to the substrate 2 is larger than the width Wb of the upper surface 3b of the magnetic thin film 3, Are tapered surfaces 6 extending in the longitudinal direction of the magnetic thin film 3.
7, the thickness of the magnetic thin film 3 in the width direction at the center is larger than the thickness of the magnetic thin film 3 on both sides in the width direction. The magnetic thin film 3
When the width of the lower surface 3a of the magnetic thin film 3 is Wa, the width of the upper surface 3b of the magnetic thin film 3 is Wb, and the thickness of the lower surface 3a from the upper surface 3b is d, x = (Wa-Wb) / 2, x / D is 1
A value of about 5 is desirable.

The magnetic thin film 3 has a composition formula other than the above composition represented by T _100-abcd X _a M _b Z _c Q _d , and the element T is F
e is one or two of Co and X is S
i is one or two elements of Al, and M is T
i, Zr, Hf, V, Nb, Ta, Mo, W are one or more elements selected from the group consisting of one or two elements of C and N; a ≦ 25 (at
%), 1 ≦ b ≦ 10 (at%), 5 ≦ c ≦ 15 (at
%) And 0 ≦ d ≦ 10 (at%), and the fine carbide or nitride of the element M having an average crystal grain size of 10 nm or less in the crystal structure of the magnetic thin film 3 is made of Fe or Co by heat treatment. A microcrystalline soft magnetic alloy thin film precipitated around crystal grains may be used.

Next, the magneto-impedance effect element 1
First, as shown in FIG. 3A, an amorphous alloy thin film 8 represented by the above composition formula is formed on the upper surface of the substrate 2 by a sputtering method in a static magnetic field, as shown in FIG. Next, as shown in FIG.
A strip-shaped photoresist 9 is formed thereon. And FIG.
As shown in (c), the substrate 2 is etched by a wet etching method for a longer period of time than in the prior art (for example, an acidic aqueous solution containing hydrofluoric acid, hydrogen peroxide, or the like).
To perform an etching process on the alloy thin film 8, and then
As shown in FIG. 3D, when the photoresist 9 is removed, a strip-shaped alloy thin film 8 having tapered surfaces 6 and 7 formed on both sides can be formed.

Next, the alloy thin film 8 and the substrate 2 are subjected to a heat treatment in a static magnetic field to change the phase of the alloy thin film 8 from an amorphous state to a crystalline state, thereby forming a fine carbide or nitride of the element M described above. The alloy thin film 8 is changed to a magnetic thin film 3 having high magnetic permeability and magnetic anisotropy in the width direction by depositing a material around the Fe or Co crystal grains (FIG. 3).
(E)). Thereafter, the first and second electrodes 4 and 5 are formed on both ends in the longitudinal direction of the magnetic thin film 3, and the manufacture of the magneto-impedance effect element 1 is completed.

The magneto-impedance effect element 1 constructed and manufactured in this manner is arranged such that the longitudinal direction of the magnetic thin film 3 is arranged along the external magnetic field H emitted from the detection object (not shown). When a high-frequency current in the MHz band is applied to the magnetic thin film 3 through the second electrodes 4 and 5, the magnetic thin film 3
The impedance between both ends in the longitudinal direction changes, and this change is converted into an electric signal to obtain a detection output of the external magnetic field H.

In the magneto-impedance effect element 1, the alloy thin film 8 which becomes the magnetic thin film 3 is subjected to a heat treatment in the manufacturing process as in the prior art, as shown in FIG. As described above, the width Wa of the lower surface 8a of the alloy thin film 8 in close contact with the substrate 2 is equal to the width W of the upper surface 8b of the alloy thin film 8.
The tapered surfaces 6 and 7 extending in the longitudinal direction of the alloy thin film 8 are provided on both sides of the alloy thin film 8 so as to be larger than b. Is formed thicker than the film thickness on both sides of the alloy thin film 8, the lower surface 8 a of the alloy thin film 8 that adheres to the substrate 2 by the heat treatment is
As a result, the lower surface 3a of the magnetic thin film 3 is securely brought into close contact with the substrate 2 so that the magnetic domain 10 is spread over the entire magnetic thin film 3 as shown in FIG. Can be formed, and in the width direction of the magnetic thin film 3, the magnetic domains 1 on both sides of the magnetic thin film 3 during the heat treatment are formed.
It is possible to suppress the disappearance of 0 and completely prevent the external magnetic field detection sensitivity from being lowered.

Next, a second embodiment of the magneto-impedance effect element of the present invention will be described with reference to FIGS.

The magneto-impedance effect element 11 of the second embodiment is the same as the magneto-impedance effect element 1 described above.
The difference from the configuration is that the width Wa of the lower surface 3a of the magnetic thin film 3 adhered to the substrate 2 is larger than the width Wb of the upper surface 3b of the magnetic thin film 3, and the magnetic thin film 3 is provided on both sides of the magnetic thin film 3.
Steps 12 and 13 extending in the longitudinal direction of the magnetic thin film 3 are provided in place of the tapered surfaces 6 and 7, and both sides of the magnetic thin film 3 are formed in a step-like manner. .

In the manufacture of the magneto-impedance effect element 11, first, as shown in FIG. 7A, as in the first embodiment, the magneto-impedance effect element is expressed by the above composition formula on the upper surface of the substrate 2 in a static magnetic field. An alloy thin film 8 in an amorphous state is formed by a sputtering method, and then, as shown in FIG.
A strip-shaped photoresist 14 is formed thereon. Next, FIG.
As shown in FIG. 7C, after the substrate 2 is immersed in an etching solution to perform an etching process on the alloy thin film 8 by a wet etching method, and the photoresist 14 is removed, FIG.
As shown in (d), a strip-shaped photoresist 15 is formed on the alloy thin film 8 again.

Next, as shown in FIG. 7E, the substrate 2 is immersed in an etchant to perform an etching process on the alloy thin film 8 by a wet etching method.
As shown in FIG. 5, when the photoresist 15 is removed, a strip-shaped alloy thin film 8 having steps 12 and 13 formed on both sides can be formed. Then, the alloy thin film 8 and the substrate 2 are subjected to a heat treatment in a static magnetic field to change the phase of the alloy thin film 8 from an amorphous state to a crystalline state, so that the fine carbide or nitride of the above-described element M is changed to Fe or By precipitating around the Co crystal grains, the alloy thin film 8 is changed into the magnetic thin film 3 having high magnetic permeability and magnetic anisotropy in the width direction (see FIG. 7G). Thereafter, the first and second electrodes 4 and 5 are formed on both ends in the longitudinal direction of the magnetic thin film 3, and the manufacture of the magneto-impedance effect element 11 is completed. Note that the width of the lower surface 3a of the magnetic thin film 3 is Wa, the width of the upper surface 3b of the magnetic thin film 3 is Wb, the thickness from the lower surface 3a to the steps 12, 13 is d1, and the thickness of the lower surface 3a to the upper surface 3b is If x = (Wa−Wb) / 2 and Δd = d2−d1 when d2, x / Δd is preferably a value of about 1 to 5.

The magneto-impedance effect element 11 constructed and manufactured as described above is arranged so that the longitudinal direction of the magnetic thin film 3 is along the external magnetic field H emitted from the detection object (not shown). It operates similarly to the element 1.

Thus, in the magneto-impedance effect element 11 as well, in the manufacturing process, the alloy thin film 8 to be the magnetic thin film 3 is subjected to a heat treatment in the same manner as in the prior art, as shown in FIG. As described above, the width Wa of the lower surface 8a of the alloy thin film 8 in close contact with the substrate 2 is equal to the width W of the upper surface 8b of the magnetic thin film 8.
Steps 12 and 13 extending in the longitudinal direction of the alloy thin film 8 are provided on both sides of the alloy thin film 8 so as to be larger than the thickness of the alloy thin film 8. Is formed thicker than the film thickness on both sides of the alloy thin film 8, the lower surface 8 a of the alloy thin film 8 that adheres to the substrate 2 by the heat treatment is
As a result, the lower surface 3b of the magnetic thin film 3 is securely brought into close contact with the substrate 2 so that the magnetic thin film 3 is heated in the width direction of the magnetic thin film 3. The disappearance of the magnetic domains on both sides of the third magnetic field can be suppressed, and a decrease in external magnetic field detection sensitivity due to this can be completely prevented.

[0028]

The present invention is embodied in the form described above and has the following effects.

A substrate made of a non-magnetic material; and a strip-shaped magnetic thin film provided on the substrate, wherein the width of the lower surface of the magnetic thin film which is in close contact with the substrate is larger than the width of the upper surface of the magnetic thin film. Thus, in the width direction of the magnetic thin film,
Since the film thickness on both sides of the magnetic thin film was formed smaller than the film thickness at the center of the magnetic thin film, the lower surface of the magnetic thin film was securely adhered to the substrate, and in the width direction of the magnetic thin film, The disappearance of magnetic domains on both sides of the magnetic thin film can be suppressed, and a magneto-impedance effect element having high external magnetic field detection sensitivity can be provided.

Further, since the tapered surfaces are provided on the both sides of the magnetic thin film, the film thickness of both sides of the magnetic thin film can be easily made larger than the film thickness of the central part of the magnetic thin film in the width direction of the magnetic thin film. Can also be formed thin.

Also, since the both sides of the magnetic thin film are formed stepwise, the thickness of the both sides of the magnetic thin film can be easily made larger than the thickness of the center of the magnetic thin film in the width direction of the magnetic thin film. Can also be formed thin.

The magnetic thin film has an average crystal grain size of 30.
bccFe, bccFeCo, bccC of not more than nm
Since the magnetic thin film is made of a soft magnetic alloy thin film mainly composed of a simple substance or a mixture of o, the change of the impedance of the magnetic thin film with respect to an external magnetic field is large, and an excellent magnetic impedance effect element having high magnetic field detection sensitivity can be obtained.

The composition formula of the magnetic thin film is T
Expressed in _{100-abcd X a M b Z} c Q d, element T Fe, C
o is one or two elements, and X is Si, Al
And M is Ti, Zr,
One or more elements selected from Hf, V, Nb, Ta, Mo, W, and the element Z is composed of one or two elements of C and N, and 0 ≦ a ≦ 25 ( at%), 1 ≦
b ≦ 10 (at%), 5 ≦ c ≦ 15 (at%), 0 ≦ d
≦ 10 (at%), and fine carbides or nitrides of the element M having an average crystal grain size of 10 nm or less are precipitated around Fe or Co crystal grains in the crystal structure of the magnetic thin film. Therefore, the change of the impedance of the magnetic thin film with respect to an external magnetic field is further increased, and an excellent magneto-impedance effect element having higher magnetic field detection sensitivity can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view of a magneto-impedance effect element according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is an explanatory view showing a manufacturing process of the magneto-impedance effect element according to the first embodiment of the present invention.

FIG. 4 is an explanatory view showing a state of forming magnetic domains of a magnetic thin film provided in the magneto-impedance effect element according to the first embodiment of the present invention.

FIG. 5 is a plan view of a magneto-impedance effect element according to a second embodiment of the present invention.

FIG. 6 is a sectional view taken along the line 6-6 in FIG. 5;

FIG. 7 is an explanatory view showing a manufacturing process of the magneto-impedance effect element according to the second embodiment of the present invention.

FIG. 8 is a plan view of a conventional magneto-impedance effect element.

FIG. 9 is a sectional view taken along lines 9-9 in FIG. 8;

FIG. 10 is an explanatory view showing a manufacturing process of a conventional magneto-impedance effect element.

FIG. 11 is an explanatory diagram showing a problem of a conventional magneto-impedance effect element.

FIG. 12 is an explanatory view showing a state of forming magnetic domains of a magnetic thin film provided in a conventional magneto-impedance effect element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magneto-impedance effect element 2 Substrate 3 Magnetic thin film 3a Lower surface 3b Upper surface 4 First electrode 5 Second electrode 6 Tapered surface 7 Tapered surface 8 Alloy thin film 9 Photoresist 10 Magnetic domain 11 Magnetic impedance effect element 12 Step 13 Step 14 Photoresist 15 Photoresist

Claims (5)

[Claims] 1. A substrate made of a non-magnetic material, and a band-shaped magnetic thin film provided on the substrate, wherein a width of a lower surface of the magnetic thin film which is in close contact with the substrate is larger than a width of an upper surface of the magnetic thin film. A magneto-impedance effect element characterized in that the film thickness on both sides of the magnetic thin film is formed to be larger in the width direction of the magnetic thin film than the film thickness at a central portion of the magnetic thin film. 2. The magneto-impedance effect element according to claim 1, wherein tapered surfaces are provided on both sides of the magnetic thin film. 3. The magneto-impedance effect element according to claim 1, wherein said both side portions of said magnetic thin film are formed in a step shape. 4. The magnetic thin film has an average crystal grain size of 30 nm.
4. The magneto-impedance effect element according to claim 1, wherein the magneto-impedance effect element is made of a soft magnetic alloy thin film mainly composed of bccFe, bccFeCo, or bccCo as follows. 5. The magnetic thin film has a composition formula of T _100-abcd
X _a M _b Z _c is represented by Q _d, element T Fe, 1 of the Co
X is one or two elements of Si and Al, and M is Ti, Zr, Hf, V, N
b, Ta, Mo, W, one or more elements selected from the group consisting of one or two elements of C and N, and 0 ≦ a ≦ 25 (at%); 1 ≦ b ≦ 10 (a
t%), 5 ≦ c ≦ 15 (at%), 0 ≦ d ≦ 10 (at
%), Wherein fine carbides or nitrides of the element M having an average crystal grain size of 10 nm or less are precipitated around Fe or Co crystal grains in the crystal structure of the magnetic thin film. The magneto-impedance effect element according to claim 4.