Magnetic thin film chip, magnetism measurement device, and method for manufacturing magnetic thin film chip

Abstract

To provide a magnetic thin film chip with a high AMR ratio.SOLUTION: The magnetic thin film chip according to the present invention includes: an organic substrate; and a magnetic thin film of a rectangular flat shape, provided in the main surface of the organic substrate. The arithmetic average roughness Ra of the surface of the magnetic thin film is 0.65 nm at a maximum.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a magnetic thin film chip, a magnetic measurement device, and a method for manufacturing a magnetic thin film chip.

Background Art

[0002] A magnetic thin film chip having a magnetic thin film on a substrate utilizes an effect (magnetoresistance effect) in which a change in electrical resistance (magnetoresistance) due to a magnetic field occurs in the magnetic thin film, such as an anisotropic magnetoresistance (AMR) effect, a giant magnetoresistance (GMR) effect, or a tunnel magnetoresistance (TMR) effect, and is widely used in sensors, information recording media, displays, and the like.

[0003] Among magnetic thin film chips, development of a magnetic thin film chip that uses a flexible organic substrate as a substrate and exhibits an AMR effect as a magnetoresistance effect with a single-layer magnetic thin film has been studied. A magnetic thin film chip using an organic substrate as a substrate is easy to bend along the shape of a subject and is easy to deform its shape flexibly, and thus is expected to be applied to various uses as a flexible magnetic sensor.

[0004] As a magnetic thin film chip that uses an organic substrate as a substrate and utilizes the AMR effect of a magnetic thin film, for example, on a polycarbonate substrate, a magnetic thin film such as Ni or Ni 78 Fe 22 is formed, and an AMR sensor is disclosed in which the AMR ratio of the magnetic thin film shows a maximum of about 0.42% (see, for example, Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Here, in order to further enhance the sensitivity of a magnetic thin film chip that utilizes the AMR effect of a magnetic thin film formed on an organic substrate, such as the AMR sensor of Non-Patent Document 1, a magnetic thin film chip having a higher AMR ratio in the magnetic thin film is desired.

[0007] One aspect of the present invention aims to provide a magnetic thin film chip that can have a high AMR ratio.

Means for Solving the Problems

[0008] One aspect of the present invention is an organic substrate, a magnetic thin film having a rectangular planar shape provided on a main surface of the organic substrate, having a magnetic thin film chip in which an arithmetic mean roughness Ra of a surface of the magnetic thin film is 0.65 nm or less.

[0009] Another aspect of the present invention is a method for manufacturing a magnetic thin film chip including a magnetic thin film forming step of forming a magnetic thin film having a rectangular planar shape on a main surface of an organic substrate, wherein an arithmetic mean roughness Ra of a surface of the magnetic thin film is 0.65 nm or less.

Advantages of the Invention

[0010] The magnetic thin film chip according to one aspect of the present invention can have a high AMR ratio.

Brief Description of the Drawings

[0011]

Figure 1

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Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described in detail. For ease of understanding of the description, the same reference numerals are given to the same components in each drawing, and duplicate descriptions are omitted. Also, the scales of the members in the drawings may be different from the actual ones. In this specification, "~" indicating a numerical range means including the numerical values described before and after it as the lower limit value and the upper limit value, unless otherwise specified.

[0013] <Magnetic Detection Device> A magnetic detection device including a magnetic thin film chip according to an embodiment of the present invention will be described. Here, the case where the magnetic detection device is a magnetic sensor will be described. FIG. 1 is a schematic diagram showing an example of the configuration of a magnetic detection device including a magnetic thin film chip according to the present embodiment. As shown in FIG. 1, the magnetic sensor 1 includes a magnetic thin film chip 10, a power supply unit 20, and a measurement unit 30. The magnetic sensor 1 is used by installing the magnetic thin film chip 10 on a subject or the like.

[0014] In FIG. 1, a three-dimensional orthogonal coordinate system in three axial directions (X-axis direction, Y-axis direction, Z-axis direction) is used. The short axis direction of the magnetic sensor 1 is the X direction, the long axis direction is the Y direction, and the thickness direction is the Z direction. In FIG. 1, the direction from the bottom to the top of the magnetic sensor 1 is the +Z axis direction, and the opposite direction is the -Z axis direction. In the following description, the +Z axis direction may be referred to as up or upward, and the -Z axis direction may be referred to as down or downward, but it does not represent a universal up and down relationship.

[0015] [Magnetic thin film chip] As shown in FIG. 1, the magnetic thin film chip 10 has an organic substrate 11 and a magnetic thin film 12 formed on the main surface 11a of the organic substrate 11.

[0016] Among the magnetoresistance effects, the magnetic thin film chip 10 utilizes the anisotropic magnetoresistance (AMR) effect that can be realized with a relatively simple structure in particular. The AMR effect is such that the resistance changes depending on the relative angle between the current and the magnetization, and the resistance is maximum when the current and the magnetization are substantially parallel, and the resistance is minimum when the current and the magnetization are substantially perpendicular. The AMR effect is represented by the magnitude of the AMR ratio. The larger the value of the AMR ratio, the better the magnetic performance of the magnetic thin film chip 10. In order to increase the AMR ratio, it is important that the in-plane magnetization of the magnetic thin film 12 points in the same direction as much as possible, that is, the magnetic anisotropy MA is high. Note that the magnetic anisotropy MA may be, for example, induced magnetic anisotropy or shape magnetic anisotropy.

[0017] In manufacturing the magnetic thin film chip 10 that uses the organic substrate 11 and utilizes the AMR effect in the magnetic thin film 12, the inventors of the present application focused on the relationship between the surface roughness of the magnetic thin film 12 and the magnetic anisotropy of the magnetic thin film 12. The inventors of the present application found that in the magnetic thin film chip 10 with the magnetic thin film 12 formed on the organic substrate 11, by enhancing the flatness of the magnetic thin film 12 and reducing the surface roughness, the magnetic anisotropy MA of the magnetic thin film 12 can be enhanced, and the AMR ratio in the magnetic thin film 12 can be improved. And the inventors of the present application found that by suppressing the arithmetic mean roughness Ra of the surface of the magnetic thin film 12 to 0.65 nm or less, a magnetic thin film chip 10 having a magnetic thin film 12 that exhibits a high AMR effect and has a high AMR ratio can be obtained.

[0018] Note that the AMR ratio is the rate of change of AMR due to an external magnetic field (hereinafter, also simply referred to as "magnetic field") H, and is obtained from the following formula (1). AMR ratio = (R2 - R1) / R1 ···(1) (In formula (1), R2 is the resistance when the current and magnetization are parallel, and R1 is the resistance when the current and magnetization are perpendicular.)

[0019] Also, in order to increase the AMR ratio in the magnetic thin film 12, it is important to enhance the flatness of the magnetic thin film 12. However, in the magnetic thin film chip 10 with the magnetic thin film 12 formed on the organic substrate 11, it is difficult to control the surface roughness of the magnetic thin film 12 formed on the organic substrate 11, and it is difficult to enhance the flatness of the magnetic thin film 12. The inventors of the present application found that by using an organic substrate 11 whose arithmetic mean surface roughness Ra is a predetermined value or less in advance, the flatness of the magnetic thin film 12 can be surely enhanced, and the AMR ratio in the magnetic thin film 12 can be further increased.

[0020] As shown in FIG. 1, the organic substrate 11 is a plate-like member having a rectangular planar shape. As the organic substrate 11, a substrate or film (plastic substrate or plastic film) formed using a non-conductive organic material can be used. By forming the organic substrate 11 using a plastic substrate or a plastic film, a flexible magnetic thin film chip 10 can be obtained, and the applicable range of the magnetic sensor 1 can be expanded.

[0021] The thickness and size of the organic substrate 11 may be appropriately and arbitrarily selected according to the application.

[0022] The shape of the organic substrate 11 is not limited to a rectangular shape, and may be an arbitrary shape as appropriate according to the application or the like.

[0023] As the material of the organic substrate 11, an organic material is used. Examples of the organic material include polyimide (PI)-based resins, polycarbonate (PC) resins, polyester-based resins (polyethylene terephthalate (PET), polyethylene naphthalate (PEN)), acrylic resins, cycloolefin-based resins (cycloolefin polymer (COP), etc.), polypropylene-based resins, polymethyl methacrylate (PMMA), polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), polystyrene (PS), cellulose-based resins (cellulose triacetate, etc.), polyether-based resins (polyethersulfone, etc.), polysulfide-based resins (polyphenylene sulfide, etc.). Among these, polyimide-based resins are preferred in terms of high surface smoothness and ease of forming a substrate having high heat resistance.

[0024] When the organic substrate 11 is formed using a polyimide-based resin, it may be a polyimide film having a polyimide-based resin layer on the main surface, or a polyimide film made of a polyimide-based resin layer. As the polyimide film, for example, commercially available products such as Zenomax (registered trademark) can be used.

[0025] The surface of the organic substrate 11 is preferably as smooth as possible. The arithmetic mean roughness Ra of the surface of the organic substrate 11 is preferably 0.8 nm or less, more preferably 0.5 nm or less, and even more preferably 0.35 nm or less. If the arithmetic mean roughness Ra of the surface of the organic substrate 11 is 0.8 nm or less, it is easy to reduce the surface roughness of the magnetic thin film 12 formed on the surface of the organic substrate 11.

[0026] The Young's modulus of the organic substrate 11 is preferably 3000 MPa or more, more preferably 5000 MPa or more, still more preferably 8000 MPa or more, and most preferably 9000 MPa or more. If the Young's modulus of the organic substrate 11 is 3000 MPa or more, the organic substrate 11 can have sufficient bending characteristics.

[0027] Note that the Young's modulus is the ratio of the force (stress) acting per unit cross-sectional area of an object to the deformation rate (strain) when an external force is applied in a uniaxial direction within the elastic range of the object, and is the initial slope in the stress-strain curve. The Young's modulus is a value representing the difficulty of deformation of a material, and the larger the Young's modulus, the more difficult it is to deform. The Young's modulus in the major axis direction or minor axis direction of the organic substrate 11 may be measured using a general measurement method. For example, it can be measured in accordance with JIS P8113:2006, the second part, constant speed stretching method, etc.

[0028] The heat-resistant process temperature of the organic substrate 11 is preferably 300 °C or more, more preferably 400 °C or more, and still more preferably 500 °C or more. If the heat-resistant process temperature of the organic substrate 11 is 300 °C or more, even when the organic substrate 11 is heated up to 300 °C, the coefficient of thermal expansion is almost constant, and it is possible to reduce the deformation of the organic substrate 11 and the generation of minute irregularities on the surface. Also, if the organic substrate 11 is a polyimide film (ZENOMAX (registered trademark)), it is particularly preferable because the coefficient of thermal expansion is almost constant up to about 500 °C.

[0029] Note that in this specification, the heat-resistant process temperature refers to the temperature at which the organic substrate 11 does not deform when heated during the manufacturing process of the magnetic thin film chip 10 and the shape of the organic substrate 11 can be maintained, and means the heat-resistant temperature of the organic substrate 11.

[0030] As shown in FIG. 1, the magnetic thin film 12 may be provided on at least a part of the main surface 11a of the organic substrate 11. The magnetic thin film 12 has a soft magnetic material. Since the soft magnetic material has a small coercive force and a large magnetic permeability, the magnetization M becomes zero where there is no external magnetic field H, but the soft magnetic material is easily magnetized where there is an external magnetic field H, so the presence of the external magnetic field H can be detected. In FIG. 1, the direction of the magnetization M of the magnetic thin film 12 due to the external magnetic field H is the long axis direction (Y-axis direction) of the magnetic thin film 12 (see the white arrow in FIG. 1).

[0031] Examples of the soft magnetic material include Ni-Fe-based alloys such as permalloy, supermalloy, mu-metal, and soft ferrite, pure iron, Fe-Si-based alloys such as silicon steel, Fe-Co-based alloys such as permendur, Fe-Si-Al-based alloys such as sendust, Fe-Cr-Si-based alloys, Fe-Cr-Al-based alloys, etc. Supermalloy is an alloy obtained by adding Mo to permalloy to increase the magnetic permeability. Mu-metal is an alloy obtained by adding Cu or Cr to permalloy to increase the magnetic permeability. Among these, from the viewpoints of magnetic properties such as magnetic permeability and magnetic flux density and cost, Fe-based alloys are preferred. Among Fe-based alloys, Ni-Fe-based alloys are preferred. Among Ni-Fe-based alloys, permalloy is preferably used.

[0032] The Ni content of the magnetic thin film 12 is preferably 75 atomic % (at%) to 85 at%. If the Ni content is 75 at% to 85 at%, the magnetic thin film 12 is easily magnetized where there is an external magnetic field H, and the presence of the external magnetic field H can be easily detected.

[0033] Note that the Ni content can be measured using a general measurement method. For example, it is determined with respect to all the atoms present in the sample of the magnetic thin film 12 and can be determined by X-ray photoelectron spectroscopy using an Al-Kα source.

[0034] The magnetic thin film 12 has a rectangular planar shape that is long in the major axis direction (Y-axis direction). The aspect ratio of the width d in the minor axis direction (X-axis direction) to the length l in the major axis direction (Y-axis direction) of the magnetic thin film 12 is preferably 1:5 to 1:15, more preferably 1:8 to 1:12. The length of the magnetic thin film 12 in the major axis direction (Y-axis direction) may be any length necessary for the magnetic thin film 12 to be magnetized by the external magnetic field H, for example, a length that can ensure an electrode distance of 10 mm or more.

[0035] The magnetic thin film 12 having a shape that is long in one direction like a rectangular shape generally has magnetization aligned in the longitudinal direction and exhibits magnetic anisotropy MA (especially shape magnetic anisotropy). Therefore, the magnetic thin film 12 has an easy axis of magnetization in the major axis direction (Y-axis direction). When the magnetic thin film 12 is formed on the organic substrate 11 by vapor deposition or the like during the manufacture of the magnetic thin film chip 10, magnetic anisotropy MA is imparted in the major axis direction (Y-axis direction) of the magnetic thin film 12. The method of imparting the magnetic anisotropy MA will be described later. When a current i is passed through the magnetic thin film 12 along the major axis direction of the magnetic thin film 12 and an external magnetic field H is applied in a direction substantially perpendicular to the direction of the current i flow, the anisotropic magnetoresistance (AMR) effect is exhibited. AMR can be changed by the relative angle between the current i and the magnetization M changing according to the magnitude of the external magnetic field H and the electrical resistance of the magnetic thin film 12 changing. The AMR effect is represented by the magnitude of the AMR ratio as described above, and the AMR ratio is obtained from the above formula (1).

[0036] FIG. 2 is a diagram showing an example of imparting magnetic anisotropy MA to the magnetic thin film 12. As shown in FIG. 2, when manufacturing the magnetic thin film chip 10 or the like, magnets 40 such as ferrite magnets are arranged on both end sides in the major axis direction (Y-axis direction) of the organic substrate 11. The magnets 40 are arranged such that the N pole and the S pole face each other. In this state, when a magnetic thin film material such as a NiFe alloy is vacuum-deposited on the main surface 11a of the organic substrate 11, magnetic anisotropy MA (especially, induced magnetic anisotropy) is imparted in the major axis direction (Y-axis direction) of the magnetic thin film 12 formed on the organic substrate 11.

[0037] The thickness of the magnetic thin film 12 may be appropriately selected according to the shape and size of the magnetic thin film chip 10, the type of material of the magnetic thin film 12, etc., but it is preferably 10 nm to 150 nm. The lower limit value of the thickness of the magnetic thin film 12 is more preferably 15 nm or more, and even more preferably 20 nm or more. The upper limit value of the thickness of the magnetic thin film 12 is more preferably 120 nm or less, even more preferably 100 nm or less, and most preferably 80 nm or less. If the thickness of the magnetic thin film 12 is 10 nm or more, the magnetic thin film 12 can sufficiently exhibit the characteristics of the soft magnetic material. If the thickness of the magnetic thin film 12 is 150 nm or less, a high AMR effect can be exhibited.

[0038] In addition, in this specification, the thickness of the magnetic thin film 12 refers to the length in the direction perpendicular to the main surface of the magnetic thin film 12. The thickness of the magnetic thin film 12 may be, for example, the thickness when measured at an arbitrary location in the cross-section of the magnetic thin film 12, or may be measured at several locations at arbitrary locations and used as the average value of these measurement values.

[0039] The surface of the magnetic thin film 12 is desirably as smooth as possible, similar to the organic substrate 11. The arithmetic mean roughness Ra of the surface of the magnetic thin film 12 is 0.65 nm or less, preferably 0.50 nm or less, and more preferably 0.35 nm or less. By setting the arithmetic mean roughness Ra of the surface of the magnetic thin film 12 to 0.65 nm or less and making the surface as smooth as possible, it is possible to suppress the weakening of the magnetic anisotropy MA.

[0040] The ratio of the arithmetic mean roughness Ra of the surface of the magnetic thin film 12 to the arithmetic mean roughness Ra of the surface of the organic substrate 11 is preferably 1.0 or less, more preferably 0.95 or less, and even more preferably 0.90 or less. If the ratio of the arithmetic mean roughness Ra of the surface of the magnetic thin film 12 to the arithmetic mean roughness Ra of the surface of the organic substrate 11 is 1.0 or less, the surface of the magnetic thin film 12 is more likely to be made smoother, and the magnetic anisotropy MA is likely to be increased.

[0041] The magnetic thin film chip 10 can be manufactured by a general manufacturing method. An example of the manufacturing method of the magnetic thin film chip 10 will be described. When manufacturing the magnetic thin film chip 10, a magnetic thin film 12 having a rectangular planar shape is formed on the main surface 11a of the organic substrate 11 (magnetic thin film forming step).

[0042] For the magnetic thin film 12, general magnetic thin film forming methods such as vapor deposition and sputtering can be used. When using vapor deposition, for example, vacuum vapor deposition, high vacuum vapor deposition, or electron beam vapor deposition can be used.

[0043] Magnetic anisotropy MA is imparted to the magnetic thin film 12 simultaneously with the formation of the magnetic thin film 12. For imparting magnetic anisotropy MA to the magnetic thin film 12, generally known methods for imparting magnetic anisotropy MA can be used. As a method for imparting magnetic anisotropy MA to the magnetic thin film 12, for example, a method of forming the magnetic thin film 12 in a state where a magnetic field H is applied in the major axis direction (Y-axis direction) of the magnetic thin film 12 formed on the main surface 11a of the organic substrate 11 can be used.

[0044] For applying the magnetic field H to both sides of the organic substrate 11, generally known magnetic field application methods can be used. As a method for applying the magnetic field H to both sides of the organic substrate 11, for example, there is a method of forming the magnetic thin film 12 in a state where magnets, for example, are arranged on both sides of the organic substrate 11 in the major axis direction (Y-axis direction) of the magnetic thin film 12 formed on the main surface 11a of the organic substrate 11.

[0045] FIG. 2 is a diagram showing an example of imparting magnetic anisotropy MA to the magnetic thin film 12. As shown in FIG. 2, when forming the magnetic thin film 12 on the organic substrate 11 by vapor deposition or the like, in the chamber, magnets 40 such as ferrite magnets are arranged on both end sides in the major axis direction (Y-axis direction) of the organic substrate 11. The magnets 40 are arranged such that the N pole and the S pole face each other. In this state, when a magnetic thin film material such as an Ni—Fe alloy is vacuum-deposited on the main surface 11a of the organic substrate 11, magnetic anisotropy MA is imparted in the major axis direction (Y-axis direction) of the magnetic thin film 12 formed on the organic substrate 11.

[0046] As described above, the aspect ratio of the width d in the short-axis direction to the length l in the long-axis direction of the magnetic thin film 12 may be 1:5 to 1:15. Thereby, an easy axis of magnetization is formed in the long-axis direction of the magnetic thin film 12.

[0047] As a method for forming the magnetic thin film 12, vapor deposition is preferable, and among them, the high-vacuum vapor deposition method is more preferable.

[0048] When the magnetic thin film 12 is formed by vapor deposition, the film formation conditions of the magnetic thin film 12 are not particularly limited and may be appropriately selected according to the type of the magnetic thin film 12 and the like. When the high-vacuum vapor deposition method is used, for example, the vacuum deposition power is 200 W to 230 W, the growth rate is 1 nm / min to 3 nm / min, and the degree of vacuum during vapor deposition is 4.0×10 -5 Pa or less.

[0049] The magnetic field H applied in the XY plane by the magnet 40 can be appropriately selected. For example, it may be 300 Oe to 400 Oe, and may be about 360 Oe.

[0050] A magnetic thin film 12 having a rectangular planar shape is formed on the main surface 11a of the organic substrate 11, and magnetic anisotropy MA is imparted in the long-axis direction (Y-axis direction) of the magnetic thin film 12, whereby the magnetic thin film chip 10 is obtained.

[0051] The magnetic thin film chip 10 can be easily manufactured by simply forming the magnetic thin film 12 on the organic substrate 11. Therefore, by using the manufacturing method of the magnetic thin film chip 10, the manufacturing time of the magnetic thin film chip 10 can be shortened and the magnetic thin film chip 10 can be manufactured at low cost.

[0052] As described above, the magnetic thin film chip 10 includes the organic substrate 11 and the magnetic thin film 12 formed on the organic substrate 11. By setting the arithmetic mean roughness Ra of the surface of the magnetic thin film 12 to 0.65 nm or less, the AMR ratio can be increased.

[0053] If the arithmetic mean roughness Ra of the surface of the magnetic thin film 12 is large, the following reasons can be considered for the inability to increase the AMR ratio. That is, as shown in FIG. 3, when the arithmetic mean roughness Ra of the surface of the magnetic thin film 12 is large, magnetic poles are generated when an external magnetic field H is applied, and the magnetization M proceeds along the uneven shape of the surface of the magnetic thin film 12 (see FIG. 3(a)). Therefore, it is considered that the magnetization M is less likely to be oriented in a single direction. For this reason, the easy axis of magnetization is not determined in the long axis direction (Y-axis direction), and it is considered that the magnetic anisotropy MA is weakened. In addition, when the arithmetic mean roughness Ra of the surface of the magnetic thin film 12 is large, scattering on the surface of the magnetic thin film 12 is likely to occur frequently. If irregularities exist on the surface of the magnetic thin film 12, it is considered that the resistance due to electron scattering not caused by magnetoresistance increases on the surface of the magnetic thin film 12, and the AMR effect decreases (see FIG. 3(b)).

[0054] On the other hand, if the arithmetic mean roughness Ra of the surface of the magnetic thin film 12 is 0.65 nm or less, the surface of the magnetic thin film 12 is likely to form a short magnetic domain structure. Therefore, it can be said that the easy axis of magnetization is determined in the long axis direction (Y-axis direction), and the magnetic anisotropy MA of the magnetic thin film 12 is enhanced. As shown in FIG. 4, when an external magnetic field H is applied to the easy axis of magnetization of the magnetic thin film 12 (see FIG. 4(a)), the squareness ratio of the magnetization curve showing the relationship between the magnetic field H and the magnetization M is increased. Also, when an external magnetic field H is applied to the hard axis of magnetization that is substantially parallel to the direction orthogonal to the current flow direction (see FIG. 4(b)), the squareness ratio of the magnetization curve showing the relationship between the external magnetic field H and the magnetization M can be decreased. Therefore, the magnetic thin film 12 can increase the change rate of magnetoresistance with respect to the external magnetic field H. In addition, when the surface of the magnetic thin film 12 is flat, electron scattering on the surface can be suppressed, and the magnetic thin film 12 can minimize the resistance not caused by magnetoresistance. As a result, the magnetic thin film 12 can exhibit a highly sensitive AMR effect. Therefore, the magnetic thin film chip 10 can increase the AMR ratio.

[0055] In addition, the magnetic thin film chip 10 can have a high AMR ratio just by including a magnetic thin film 12 with an arithmetic mean roughness Ra of the surface of 0.65 nm or less on the organic substrate 11. Therefore, in order to enhance the magnetic anisotropy MA of the magnetic thin film 12, the burden such as performing microfabrication on the magnetic thin film 12 can be reduced. Generally, in a magnetic thin film chip, when using a magnetic thin film with a high surface roughness (for example, the arithmetic mean roughness Ra of the surface exceeds 0.65 nm), a method of performing microfabrication on the magnetic thin film to enhance the magnetic anisotropy may be used. Also in the magnetic thin film chip 10, if the magnetic thin film 12 is microfabricated, the magnetic anisotropy MA of the magnetic thin film 12 can be further enhanced. Therefore, the magnetic thin film chip 10 can have a higher AMR ratio and further higher magnetic sensitivity.

[0056] Furthermore, the magnetic thin film chip 10 is composed of only the organic substrate 11 and the magnetic thin film 12 and can be formed with a simple structure. Therefore, it can be manufactured by a simple method, shortening the manufacturing time and reducing the burden required for manufacturing.

[0057] It is preferable that the arithmetic mean roughness Ra of the surface of the organic substrate 11 of the magnetic thin film chip 10 is 0.8 nm or less. If the arithmetic mean roughness Ra of the surface of the organic substrate 11 is 0.8 nm or less, the surface roughness of the magnetic thin film 12 formed on the surface of the organic substrate 11 is likely to be formed low. Therefore, the arithmetic mean roughness Ra of the surface of the magnetic thin film 12 formed on the surface of the organic substrate 11 can be surely made 0.65 nm or less. Thus, the magnetic thin film chip 10 can surely have a higher AMR ratio.

[0058] In the magnetic thin film chip 10, the ratio of the arithmetic mean roughness Ra of the surface of the magnetic thin film 12 to the arithmetic mean roughness Ra of the surface of the organic substrate 11 is preferably 1.0 or less. Thereby, the arithmetic mean roughness Ra of the surface of the magnetic thin film 12 can be surely kept small. Thereby, since the magnetic thin film 12 can surely exhibit the magnetic anisotropy MA, the magnetic thin film chip 10 can surely have a high AMR ratio.

[0059] For the magnetic thin film chip 10, it is preferable that the Young's modulus of the organic substrate 11 is 3000 MPa or more. If the Young's modulus of the organic substrate 11 is 3000 MPa or more, the organic substrate 11 can have high flexibility, so that the magnetic thin film chip 10 can be easily and flexibly deformed along the shape of the subject on which the magnetic thin film chip 10 is installed, and the damage of the organic substrate 11 can be suppressed even if the surface of the subject is deformed. Therefore, the durability of the magnetic thin film chip 10 can be enhanced.

[0060] In the magnetic thin film chip 10, it is preferable that the heat-resistant process temperature of the organic substrate 11 is 300 °C or more. Thereby, since the organic substrate 11 can have high heat resistance, the organic substrate 11 and the magnetic thin film 12 can be heated to a high temperature during manufacturing. Therefore, the magnetic thin film chip 10 can have a magnetic thin film 12 containing various magnetic materials, and the applications of the magnetic thin film chip 10 can be expanded.

[0061] In the magnetic thin film chip 10, a polyimide film can be used for the organic substrate 11. Since the polyimide film can be used as a substrate for various types of sensors, the magnetic thin film chip 10 can expand the range of applications as a sensor by configuring the organic substrate 11 with the polyimide film. Further, for the magnetic thin film chip 10, by using a polyimide film having an arithmetic mean roughness Ra of the surface of 0.35 nm or less and heat resistance as the organic substrate 11, it becomes easy to form a magnetic thin film 12 having an arithmetic mean roughness Ra of the surface of 0.35 nm or less on the organic substrate 11. Therefore, the magnetic thin film chip 10 can surely have a magnetic thin film 12 with a higher AMR ratio.

[0062] In the magnetic thin film chip 10, the thickness of the magnetic thin film 12 is preferably 10 nm to 150 nm. If the thickness of the magnetic thin film 12 is 10 nm to 150 nm, the magnetic thin film 12 can surely exhibit high magnetic anisotropy MA, so that the AMR ratio of the magnetic thin film chip 10 can be further improved.

[0063] In the magnetic thin film chip 10, the magnetic thin film 12 preferably contains a soft magnetic material. Since the magnetic thin film 12 contains a soft magnetic material, magnetic anisotropy MA can be surely exhibited, so that the magnetic thin film chip 10 can surely exhibit the AMR effect.

[0064] In the magnetic thin film chip 10, the magnetic thin film 12 preferably contains a Ni-Fe based alloy. Since the magnetic thin film 12 contains a Ni-Fe based alloy, magnetic anisotropy MA can be more surely exhibited, so that the AMR effect can be more surely exhibited.

[0065] In the magnetic thin film chip 10, the Ni content of the magnetic thin film 12 is preferably 75 at% to 85 at%. Thereby, since the magnetic thin film 12 can surely exhibit magnetic anisotropy MA, the magnetic thin film chip 10 can surely exhibit the AMR effect.

[0066] [Power supply unit] As shown in FIG. 1, the power supply unit 20 is connected to the magnetic thin film chip 10 and applies a voltage to the magnetic thin film 12 of the magnetic thin film chip 10. The power supply unit 20 may use a generally used power supply.

[0067] [Measurement unit] As shown in FIG. 1, the measurement unit 30 is connected to the magnetic thin film chip 10, measures the current flowing through the magnetic thin film 12 of the magnetic thin film chip 10, and calculates the resistance. The measurement unit 30 only needs to be able to calculate the resistance of the magnetic thin film 12, and its device configuration is not particularly limited.

[0068] In the magnetic sensor 1, when the magnetic thin film chip 10 is disposed where there is no external magnetic field H, the magnetization M of the magnetic thin film 12 is in the Y-axis direction, and the relative angle between the current i and the magnetization M is zero. As shown in FIG. 1, when the magnetic thin film chip 10 is disposed where there is an external magnetic field H in the short-axis direction of the magnetic thin film 12, the magnetization M of the magnetic thin film 12 rotates in the X-axis direction, and the relative angle between the current i and the magnetization M is no longer zero and approaches 90 degrees. Thus, since the relative angle between the current i and the magnetization M changes depending on the magnitude of the external magnetic field H, the resistance changes. Thereby, the external magnetic field H can be detected.

[0069] As described above, the magnetic sensor 1 includes the magnetic thin film chip 10. The magnetic thin film chip 10 has a high AMR ratio as described above, and further has characteristics of being small, lightweight, highly durable, and usable even on a curved surface. Therefore, the magnetic sensor 1 can be suitably used as a flexible magnetic sensor or the like. For this reason, the magnetic sensor 1 can be suitably used for, for example, biosensors used in electrocardiograms, magnetoencephalograms, blood flow inspections, etc., heart valve monitoring smart implants, printed sensors, non-contact sensors, non-contact magnetic keyboards, electronic compasses, non-destructive inspections, sensors for automatic driving of automobiles, devices for observing magnetization states, information recording media, displays, electronic papers, and the like.

[0070] As described above, the embodiments have been described. However, the above embodiments are presented as examples, and the present invention is not limited by the above embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, replacements, changes, etc. can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalent scope.

Example

[0071] Hereinafter, examples of the present embodiment will be shown and described more specifically. However, the present embodiment is not limited by these examples.

[0072] <Example 1> [Manufacture of Magnetic Thin Film Chip] As an organic substrate, a PI substrate (PI film 1, ZENOMAX (registered trademark), manufactured by ZENOMAX, thickness: 38 μm, heat-resistant process temperature: 500 °C) made of polyimide (PI) having a rectangular planar shape was placed in a chamber. A pair of ferrite magnets were arranged on both sides in the major axis direction of the PI substrate so as to face each other through the PI substrate. The pair of ferrite magnets were arranged such that the N pole of one ferrite magnet faced the S pole of the other ferrite magnet. Thereafter, using a high-vacuum evaporation apparatus, by the high-vacuum evaporation method, under the following thin film formation conditions, on the main surface of the PI substrate, a magnetic thin film (permalloy, Ni 78 Fe 22 (Ni: 78 at%, Fe: 22 at%)) having a rectangular planar shape and showing magnetic anisotropy MA in the major axis direction was formed to a thickness of 26 nm. Thereby, the magnetic thin film chip shown in FIG. 5 was manufactured. (Thin film formation conditions) · Vacuum evaporation power: 284 W · Degree of vacuum: 4.0×10 -5 Pa or less · Applied magnetic field: 360 Oe

[0073] FIG. 6 is a three-dimensional AFM image of a part of the surface of the organic substrate and the magnetic thin film shown in FIG. 5. The observation range is the range indicated by the broken line in FIG. 5, which was set to 5×5 μm 2 . FIG. 6(a) is a three-dimensional AFM image of the organic substrate formed of the PI substrate (PI film 1), and FIG. 6(b) is a three-dimensional AFM image of the magnetic thin film formed of Ni 78 Fe 22 . As shown in FIG. 6(a), the arithmetic mean roughness Ra of the organic substrate formed of the PI substrate (PI film 1) is about 0.35 nm, and as shown in FIG. 6(b), the arithmetic mean roughness Ra of the magnetic thin film formed of Ni 78 Fe 22 is about 0.31 nm.

[0074] FIG. 7 is a cross-sectional TEM image of the magnetic thin film formed on the organic substrate. As shown in FIG. 7, at the interface between the organic substrate and the magnetic thin film, a clear interface without indentation was observed. Therefore, it was confirmed that both the organic substrate and the magnetic thin film have very smooth surfaces.

[0075] [Evaluation of Magnetic Properties of Magnetic Thin Film Chip] (Applying magnetic field H in the major axis direction) A magnetic field H of 100 Oe was applied in the major axis direction of the magnetic thin film chip shown in Fig. 5. Fig. 8 shows the magnetization curve indicating the relationship between the magnetic field H and the magnetization M at this time. In Fig. 8, the unit of the magnetization M was set as an arbitrary unit a.u. (arbitrary unit). As shown in Fig. 8, the squareness ratio of the magnetization curve of the magnetic thin film 12 of the magnetic thin film chip was 0.92, and the coercive force H C was 3.3 Oe.

[0076] (Applying magnetic field H in the minor axis direction) A magnetic field H of 100 Oe was applied in the minor axis direction of the magnetic thin film chip shown in Fig. 5. Fig. 9 shows the magnetization curve indicating the relationship between the magnetic field H and the magnetization M at this time. Also in Fig. 9, the unit of the magnetization M was set as an arbitrary unit a.u. As shown in Fig. 9, the anisotropy magnetic field H K was 9.4 Oe.

[0077] (Confirmation of AMR ratio) While changing the magnitude of the magnetic field H applied to the magnetic thin film chip shown in Fig. 5, the electrical resistance was measured, and the AMR ratio of the magnetic thin film chip was measured. The magnetic field H was applied so as to be substantially parallel to the minor axis direction of the magnetic thin film chip shown in Fig. 5. Fig. 10 shows the measurement results of the AMR ratio. Also, the maximum value (maximum AMR ratio) of the AMR ratio is shown in Table 1. When the maximum value of the AMR ratio was 0.45% or more, it was evaluated as good. As shown in Fig. 10, the AMR ratio changed depending on the magnitude of the magnetic field H. This is because by changing the magnitude of the external magnetic field H, the relative angle between the current i and the magnetization M changed, and the electrical resistance changed. When the magnetic field H was applied and the directions of the current i and the magnetization M were substantially perpendicular, the electrical resistance of the magnetic thin film with respect to the magnetic field H was small, and the AMR ratio of the magnetic thin film chip was small. When the magnetic field H was almost zero, the directions of the magnetization M and the current i were substantially parallel, and the AMR ratio of the magnetic thin film chip showed the maximum value. Therefore, when the directions of the magnetization M and the current i were substantially parallel, the electrical resistance of the magnetic thin film changed greatly with respect to the magnetic field H.

[0078] <Examples 2 to 5> In Example 1, a magnetic thin film chip was manufactured in the same manner as in Example 1 except that the thickness of the magnetic thin film was changed to the values shown in Table 1. In the same manner as the above "(Confirmation of AMR ratio)", the AMR ratio of the magnetic thin film chip was measured. In Examples 2 to 5, the thicknesses of the magnetic thin films were 20 nm, 49 nm, 60 nm, and 71 nm, respectively. The measurement results of the AMR ratios of the magnetic thin film chips using different magnetic thin films are shown in Fig. 11. Also, the relationship between the thickness of the magnetic thin film and the maximum value of the AMR ratio is shown in Fig. 12. As shown in Figs. 11 and 12, the AMR ratio was maximum when the thickness of the magnetic thin film was 60 nm. The maximum value of the AMR ratio is shown in Table 1.

[0079] <Comparative Examples 1 to 3> In Example 1, a magnetic thin film chip was manufactured in the same manner as in Example 1 except that the organic substrate and the magnetic thin film were changed to the materials shown in Table 1. In the same manner as the above "(Confirmation of AMR ratio)", the AMR ratio of the magnetic thin film chip was measured. As the organic substrate, PC (heat-resistant process temperature: 200 °C) was used in Comparative Examples 1 and 2, and PEN (heat-resistant process temperature: 120 °C) was used in Comparative Example 3. The maximum value of the AMR ratio is shown in Table 1. Also, the measurement results of the AMR ratio of the magnetic thin film chip of Comparative Example 2 are shown in Fig. 13. As shown in Fig. 13, when the magnetization M and the current i were substantially parallel, the AMR ratio of the magnetic thin film chip showed the maximum value.

[0080]

Table 1

[0081] From Table 1, in Examples 1 to 6, the maximum value of the AMR ratio was 0.67% or more. On the other hand, in Comparative Examples 1 to 3, the maximum value of the AMR ratio was 0.42% or less. Therefore, it can be said that if the arithmetic mean roughness Ra of the surface of the magnetic thin film formed on the main surface of the organic substrate is 0.31 nm or less, the magnetic thin film chip can have a high AMR ratio. Also, if the heat resistance of the organic substrate is high, the arithmetic mean roughness Ra of the surface of the organic substrate is likely to be kept lower, so it can be said that the magnetic thin film chip can have a high AMR ratio.

[0082] Also, as shown in FIGS. 10 to 12, when the thickness of the magnetic thin film is 26 nm to 71 nm, the maximum value of the AMR ratio is 0.50% or more. When the thickness of the magnetic thin film is 60 nm, the maximum value of the AMR ratio is the highest. Therefore, it can be said that the AMR ratio is maximized when the thickness of the magnetic thin film is around 60 nm.

[0083] Note that the embodiments of the present invention are as follows, for example. <1> An organic substrate, A magnetic thin film having a rectangular planar shape provided on the main surface of the organic substrate, having A magnetic thin film chip in which the arithmetic mean roughness Ra of the surface of the magnetic thin film is 0.65 nm or less. <2> The magnetic thin film chip according to <1>, wherein the arithmetic mean roughness Ra of the surface of the organic substrate is 0.8 nm or less. <3> The magnetic thin film chip according to <1> or <2>, wherein the ratio of the arithmetic mean roughness of the surface of the magnetic thin film to the arithmetic mean roughness of the surface of the organic substrate is 1.0 or less. <4> The magnetic thin film chip according to any one of <1> to <3>, wherein the Young's modulus of the organic substrate is 3000 MPa or more. <5> The magnetic thin film chip according to any one of <1> to <4>, wherein the heat-resistant process temperature of the organic substrate is 300 ° C or more. <6> The magnetic thin film chip according to any one of <1> to <5>, wherein the organic substrate is a polyimide film having a polyimide-based resin layer on the main surface. <7> The magnetic thin film chip according to any one of <1> to <6>, wherein the thickness of the magnetic thin film is 10 nm to 150 nm. <8> The magnetic thin film chip according to any one of <1> to <7>, wherein the magnetic thin film contains a soft magnetic material. <9> The magnetic thin film chip according to any one of <1> to <8>, wherein the magnetic thin film contains a Ni—Fe-based alloy. <10> The magnetic thin film chip according to <9>, wherein the Ni content of the magnetic thin film is 75 at% to 85 at%. <11> The magnetic thin film chip according to any one of <1> to <10>, and A power supply unit that applies a current to the magnetic thin film, and has, The magnetic thin film is a magnetic measurement device in which magnetic anisotropy is imparted in the major axis direction. <12> The magnetic measurement device according to <11> or <12>, which is a magnetic sensor. <13> including a magnetic thin film forming step of forming a magnetic thin film having a rectangular planar shape on the main surface of an organic substrate, A method for manufacturing a magnetic thin film chip in which the arithmetic mean roughness Ra of the surface of the magnetic thin film is 0.65 nm or less. <14> In the magnetic thin film forming step, the magnetic thin film is formed on the main surface of the organic substrate while applying a magnetic field in the major axis direction of the magnetic thin film to be formed on the organic substrate. The method for manufacturing a magnetic thin film chip according to <13>.

Description of reference numerals

[0084] 1 Magnetic sensor 10 Magnetic thin film chip 11 Organic substrate 12 Magnetic thin film 20 Power supply unit 30 Measurement unit 40 Magnet H External magnetic field (magnetic field) M Magnetization MA Magnetic anisotropy

Claims

1. An organic substrate, A magnetic thin film having a rectangular planar shape provided on the main surface of the organic substrate, Having, A magnetic thin film chip in which the arithmetic mean roughness Ra of the surface of the magnetic thin film is 0.65 nm or less.

2. The magnetic thin film chip according to claim 1, wherein the arithmetic mean roughness Ra of the surface of the organic substrate is 0.8 nm or less.

3. The magnetic thin film chip according to claim 1, wherein the ratio of the arithmetic mean roughness of the surface of the magnetic thin film to the arithmetic mean roughness of the surface of the organic substrate is 1.0 or less.

4. The magnetic thin film chip according to claim 1, wherein the Young's modulus of the organic substrate is 3000 MPa or more.

5. The magnetic thin film chip according to claim 1, wherein the heat-resistant process temperature of the organic substrate is 300 °C or more.

6. The magnetic thin film chip according to claim 1, wherein the organic substrate is a polyimide film having a polyimide-based resin layer on the main surface.

7. The magnetic thin film chip according to claim 1, wherein the thickness of the magnetic thin film is 10 nm to 150 nm.

8. The magnetic thin film chip according to claim 1, wherein the magnetic thin film contains a soft magnetic material.

9. The magnetic thin film chip according to claim 1, wherein the magnetic thin film contains a Ni—Fe-based alloy.

10. The magnetic thin film chip according to claim 9, wherein the Ni content of the magnetic thin film is 75 at% to 85 at%.

11. The magnetic thin film chip according to claim 1, A power supply unit for applying a current to the magnetic thin film, Having, The magnetic thin film is a magnetic measurement device in which magnetic anisotropy is imparted in the major axis direction.

12. The magnetic measurement device according to claim 11, which is a magnetic sensor.

13. A method for manufacturing a magnetic thin film chip, including a magnetic thin film forming step of forming a magnetic thin film having a rectangular planar shape on a main surface of an organic substrate, wherein an arithmetic mean roughness Ra of a surface of the magnetic thin film is 0.65 nm or less.

14. The method for manufacturing a magnetic thin film chip according to claim 13, wherein the magnetic thin film forming step forms the magnetic thin film on the main surface of the organic substrate while applying a magnetic field in a major axis direction of the magnetic thin film to be formed on the organic substrate.

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