Magnetic sensor and magnetic sensor manufacturing method

A magnetic sensor 1 includes: a nonmagnetic substrate 10; a sensitive element 31 laminated on the substrate 10, the sensitive element 31 being made of a soft magnetic material, the sensitive element 31 having a longitudinal direction and a transverse direction and having uniaxial magnetic anisotropy in a direction intersecting the longitudinal direction, the sensitive element 31 being configured to sense a magnetic field by a magnetic impedance effect; and a pair of thin-film magnets 20a, 20b laminated on the substrate 10 and disposed to face each other in the longitudinal direction across the sensitive element 31, the pair of thin-film magnets 20a, 20b being configured to apply a magnetic field in the longitudinal direction of the sensitive element 31.

TECHNICAL FIELD

The present invention relates to a magnetic sensor and a magnetic sensor manufacturing method.

BACKGROUND ART

Some publications in this field disclose a magnetic impedance effect element including: a thin-film magnet composed of a hard magnetic film formed on a nonmagnetic substrate; an insulating layer covering the thin-film magnet; and a magneto-sensitive part composed of one or more rectangular soft magnetic films formed on the insulating layer and imparted with uniaxial anisotropy (see Patent Document 1).

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

A magnetic sensor may include an insulating layer interposed between a sensitive element that senses a magnetic field by a magnetic impedance effect and a thin-film magnet that applies a bias magnetic field to the sensitive element. When high-frequency electric current is supplied to the sensitive element of such a magnetic sensor, the magnetic sensor may act as a capacitor with capacitance due to polarization of the insulating layer. In this case, the high-frequency electric current supplied to the sensitive element is used for the capacitor, which may reduce the amount of impedance change as a function of the amount of magnetic field change.

An object of the present invention is to provide a magnetic sensor that exhibits a large amount of impedance change as a function of the amount of magnetic field change as compared to cases where an insulating layer is interposed between the sensitive element and the thin-film magnet.

Solution to Problem

An aspect of the present invention is a magnetic sensor including: a nonmagnetic substrate; a sensitive element laminated on the substrate, the sensitive element being made of a soft magnetic material, the sensitive element having a longitudinal direction and a transverse direction and having uniaxial magnetic anisotropy in a direction intersecting the longitudinal direction, the sensitive element being configured to sense a magnetic field by a magnetic impedance effect; and a pair of thin-film magnets laminated on the substrate and disposed to face each other in the longitudinal direction across the sensitive element, the pair of thin-film magnets being configured to apply a magnetic field in the longitudinal direction of the sensitive element.

The above magnetic sensor may further include a pair of yokes laminated on the substrate, each of the pair of yokes being disposed between the sensitive element and a corresponding one of the pair of thin-film magnets, the pair of yokes being configured to induce magnetic flux generated by the pair of thin-film magnets such that the magnetic flux passes through the sensitive element in the longitudinal direction.

In the above magnetic sensor, each of the pair of yokes may be in contact with a magnetic pole of the corresponding one of the pair of thin-film magnets, the magnetic pole facing the sensitive element in the longitudinal direction thereof.

In the above magnetic sensor, each of the pair of yokes may be disposed continuously over an area from a position between the sensitive element and the corresponding one of the pair of thin-film magnets to a top side of the corresponding one of the pair of thin-film magnets.

In the above magnetic sensor, the sensitive element may be composed of a plurality of soft magnetic layers antiferromagnetically coupled to each other across a demagnetizing field suppressing layer composed of Ru or an Ru alloy.

Another aspect of the present invention is a method for manufacturing a magnetic sensor, the method including: forming, on a nonmagnetic substrate, a pair of thin-film magnets whose magnetic anisotropy is controlled in an in-plane direction thereof, the pair of thin-film magnets being disposed such that different magnetic poles face each other with a space in between; and forming a sensitive part including a sensitive element on the substrate, the sensitive element having uniaxial magnetic anisotropy in a direction intersecting a direction in which magnetic flux generated by the pair of thin-film magnets passes, the sensitive element being configured to sense a magnetic field by a magnetic impedance effect.

Advantageous Effects of Invention

The present invention provides a magnetic sensor that exhibits a large amount of impedance change as a function of the amount of magnetic field change as compared to cases where an insulating layer is interposed between the sensitive element and the thin-film magnet.

DESCRIPTION OF EMBODIMENTS

A magnetic sensor as discussed herein is one that uses a so-called magnetic impedance effect element.

Below a detailed description will be given of an exemplary embodiment of the present invention with reference to the attached drawings.

First Embodiment

(Structure of the Magnetic Sensor1)

FIGS.1A and1Billustrate an example of the magnetic sensor1in accordance with an exemplary embodiment;FIG.1Ais a plan view of the magnetic sensor1, andFIG.1Bis a sectional view taken along a line IB-IB inFIG.1A.

As shown inFIGS.1A and1B, the magnetic sensor1in accordance with the present embodiment includes a nonmagnetic substrate10and a sensitive part30disposed on the substrate10. The sensitive part30senses a magnetic field and is composed of two layers of a soft magnetic material (lower soft magnetic layer105aand upper soft magnetic layer105b) with a demagnetizing field suppressing layer106interposed in between. The magnetic sensor1further includes yokes40disposed on the substrate10. The yokes40are each composed of the two layers of the soft magnetic material (soft magnetic layers105a,105b) with the demagnetizing field suppressing layer106interposed in between and face sensitive elements31(described later) of the sensitive part30in a longitudinal direction thereof. In the following description, the two layers of the soft magnetic material (lower soft magnetic layer105aand upper soft magnetic layer105b) are simply referred to as soft magnetic layers105unless their distinction is particularly needed. The magnetic sensor1further includes thin-film magnets20disposed on the substrate10. The thin-film magnets20are each composed of a hard magnetic material (hard magnetic layer103) and applies a bias magnetic field to the sensitive elements31of the sensitive part30.

Details about the magnetic sensor1including its sectional structure will be detailed later.

The hard magnetic material refers to a so-called high coercivity material that, once being magnetized by an external magnetic field, keeps its magnetized state even after removal of the external magnetic field. The soft magnetic material refers to a so-called low coercivity material that is easily magnetizable by an external magnetic field but quickly returns to a non-magnetized or low magnetized state after removal of the external magnetic field.

In the present specification, elements constituting the magnetic sensor1(e.g., thin-film magnet20) is denoted by two-digit reference numerals, and layers processed into these elements (e.g., hard magnetic layer103) are denoted by reference numerals in the 100s. And the reference numeral for each layer processed into a corresponding element may be placed in parentheses following the reference numeral for the corresponding element. For example, the thin-film magnet20may be denoted like “the thin-film magnet20(hard magnetic layer103)”. In the figures, the reference numerals may be presented like “20(103)”. This holds for other elements.

A description will be given of a planar structure of the magnetic sensor1, with reference toFIG.1A. By way of example, the magnetic sensor1has a rectangular planar shape.

As described above, the magnetic sensor1includes the sensitive part30. The sensitive part30includes: a plurality of sensitive elements31each being of a long strip shape having longitudinal and transverse directions; connecting portions32connecting each adjacent sensitive elements31in series in a zigzag form; and terminal portions33connected with electric wires for electric current supply. In the shown example, four sensitive elements31are arranged such that their longitudinal directions are parallel to each other. In the magnetic sensor1of the present embodiment, the sensitive elements31are magnetic impedance effect elements.

By way of example, each sensitive element31has a longitudinal length of about 1 mm, a transverse width of about several hundreds of micrometers, a thickness (total thickness of the soft magnetic layers105and the demagnetizing field suppressing layer106) of 0.5 μm to 5 μm. A distance between each adjacent sensitive elements31is 50 μm to 150 μm.

The connecting portions32are disposed between ends of each adjacent sensitive elements31to connect each adjacent sensitive elements31in series in a zigzag form. As the magnetic sensor1shown inFIG.1Aincludes four sensitive elements31arranged in parallel to each other, there are three connecting portions32. The number of the sensitive elements31is set as a function of the magnitude of the magnetic field to be sensed (measured), for example. Accordingly, in the case where there are two sensitive elements31, there will be one connecting portion32. In the case where there is one sensitive element31, there will be no connecting portion32. The width of the connecting portion32may be set as a function of electric current to be supplied to the sensitive part30. By way of example, the connecting portion32may have the same width as that of the sensitive element31.

The terminal portions33are provided to two respective ends of the sensitive elements31that are not connected with the connecting portions32. Each terminal portion33includes a lead-out portion led out from the sensitive element31and pad portions to be connected with electric wires for electric current supply. The lead-out portion is provided to arrange the two pad portions in the transverse direction of the sensitive element31. The pad portions may be arranged continuous to the sensitive element31without the lead-out portion. The pad portions may have a size that allows for connection of electric wires. Since there are four sensitive elements31, the two terminal portions33are arranged on the left side inFIG.1A. In the case where the sensitive elements31are odd in number, the two terminal portions33may be arranged respectively on the right and left sides.

The sensitive elements31, the connecting portions32, and the terminal portions33of the sensitive part30are integrally formed of the two soft magnetic layers105(lower soft magnetic layer105aand upper soft magnetic layer105b) and the demagnetizing field suppressing layer106. As the soft magnetic layers105and the demagnetizing field suppressing layer106are conductive, electric current can be supplied from one terminal portion33to the other terminal portion33.

Note that the length and width of each sensitive element31and the number of sensitive elements31arranged in parallel described above are merely exemplary, and these parameters may be modified according to factors such the value of the magnetic field to be sensed (measured) and the soft magnetic material to be used.

The magnetic sensor1further includes the yokes40facing the longitudinal ends of the sensitive elements31. In this example, the magnetic sensor1includes two yokes40a,40bfacing respective longitudinal ends of the sensitive elements31. Hereinafter, the yokes40a,40bmay be simply referred to as the yokes40unless their distinction is particularly needed. The yokes40induce magnetic lines of force to the longitudinal ends of the sensitive elements31. Hence, the yokes40include a soft magnetic material (soft magnetic layer105) that easily transmits magnetic lines of force. In this example, the sensitive part30and the yokes40are composed of the two soft magnetic layers105(lower soft magnetic layer105aand upper soft magnetic layer105b) and the demagnetizing field suppressing layer106. It should be noted that the yokes40may be eliminated when magnetic lines of force can sufficiently pass through the sensitive elements31in the longitudinal direction thereof.

The magnetic sensor1further includes the two thin-film magnets20facing each other in the longitudinal direction across the sensitive part30and the yokes40. In this example, the magnetic sensor1includes a thin-film magnet20aspaced from and adjacent to the yoke40aand a thin-film magnet20bspaced from and adjacent to the yoke40b. The thin-film magnets20a,20bapply a magnetic field (bias magnetic field described later) in the longitudinal direction of the sensitive elements31. The thin-film magnets20a,20bare composed of a hard magnetic material (hard magnetic layers103a,103b). In this example, each of the thin-film magnets20a,20bhas a rectangular planar shape. By way of example, each of the thin-film magnets20a,20bhas a longitudinal length of about 4 mm and a transverse length of about 2 mm.

Hereinafter, the thin-film magnets20a,20bmay be simply referred to as thin-film magnets20unless their distinction is particularly needed. Likewise, the hard magnetic layers103a,103bmay be simply referred to as hard magnetic layers103unless their distinction is particularly needed.

From the above, the magnetic sensor1is several millimeters square in planar shape. It should be noted that the size of the magnetic sensor1is not limited to this value.

Now a detailed description will be given of a sectional structure of the magnetic sensor1, with reference toFIG.1B. The magnetic sensor1is composed of the nonmagnetic substrate10, and the sensitive part30and the yokes40, which consist of the soft magnetic layers105and the demagnetizing field suppressing layer106, and the thin-film magnets20, which consist of the hard magnetic layers103, disposed (laminated) on the substrate10. In other words, the sensitive part30, the yokes40, and the thin-film magnets20are provided on the same substrate10in the magnetic sensor1. The magnetic sensor1further includes an adhesive layer101and a control layer102laminated between the substrate10and each thin-film magnet20. To further illustrate, an adhesive layer101aand a control layer102aare laminated between the substrate10and the thin-film magnet20a(hard magnetic layer103a), and an adhesive layer101band a control layer102bare laminated between the substrate10and the thin-film magnet20b(hard magnetic layer103b).

The substrate10is made of a nonmagnetic material. Example of the substrate10includes an oxide substrate such as glass and sapphire, a semiconductor substrate such as silicon, and a metal substrate such as aluminum, stainless steel, and metal plated with nickel phosphorus.

Each sensitive element31of the sensitive part30is imparted with uniaxial magnetic anisotropy in a direction intersecting the longitudinal direction, e.g., in the transverse direction (width direction) perpendicular to the longitudinal direction. It should be noted that the direction intersecting the longitudinal direction may be a direction at an angle of 45 degrees or more with respect to the longitudinal direction.

As the soft magnetic material (lower soft magnetic layer105aand upper soft magnetic layer105b) constituting the sensitive element31, use may be made of an amorphous alloy that contains Co as a main component and is doped with high melting point metal such as Nb, Ta, and W (hereinafter referred to as a Co alloy constituting the sensitive element31). Examples of the Co alloy constituting the sensitive element31include CoNbZr, CoFeTa, and CoWZr. Each soft magnetic material (lower soft magnetic layer105aand upper soft magnetic layer105b) constituting the sensitive element31is 0.2 μm to 2 μm thick, for example.

The demagnetizing field suppressing layer106constituting the sensitive element31is made of Ru or an Ru alloy. Here, setting a film thickness of the demagnetizing field suppressing layer106made of Ru or an Ru alloy in the range of 0.4 nm to 1.0 nm or in the range of 1.6 nm to 2.6 nm results in the lower soft magnetic layer105aand the upper soft magnetic layer105bhaving an antiferromagnetically coupled (AFC) structure. This reduces the demagnetization field and improves sensitivity of the sensitive elements31.

The adhesive layer101increases adhesiveness of the control layer102to the substrate10. As the adhesive layer101, use may be made of an alloy containing Cr or Ni. Examples of the alloy containing Cr or Ni include CrTi, CrTa, and NiTa. The adhesive layer101is 5 nm to 50 nm thick, for example. It should be noted that the adhesive layer101may be eliminated when the control layer102has sufficient adhesiveness to the substrate10. It should be noted that in the present specification, the composition ratio of the alloy containing Cr or Ni will not be presented. This holds for other alloys given below.

The control layer102controls the magnetic anisotropy of the thin-film magnet20, which is composed of the hard magnetic layer103, such that the magnetic anisotropy develops in an in-plane direction. As the control layer102, use may be made of Cr, Mo, W, or an alloy containing at least one of these metals (hereinafter referred to as an alloy containing Cr or the like constituting the control layer102). Examples of the alloy containing Cr or the like constituting the control layer102include CrTi, CrMo, CrV, and CrW. Also, the alloy containing Cr or the like constituting the control layer102has a body-centered cubic (bcc) structure. The control layer102is 10 nm to 300 nm thick, for example.

As the hard magnetic layer103constituting the thin-film magnet20, use may be made of an alloy that contains Co as a main component and one or both of Cr and Pt (hereinafter referred to as a Co alloy constituting the thin-film magnet20). Examples of the Co alloy constituting the thin-film magnet20include CoCrPt, CoCrTa, CoNiCr, and CoCrPtB. The Co alloy constituting the thin-film magnet20may also contain Fe. The hard magnetic layer103is 500 nm to 1500 nm thick, for example.

The alloy containing Cr or the like constituting the control layer102has a body-centered cubic (bcc) structure. Thus, the hard magnetic material (hard magnetic layer103) constituting the thin-film magnet20preferably has a hexagonal close-packed (hcp) structure, which allows crystal growth to easily take place on the control layer102composed of the alloy containing Cr or the like with the bcc structure. Such crystal growth of the hard magnetic layer103with the hcp structure on the bcc structure can easily cause a c-axis of the hcp structure to be oriented in the in-plane direction. Consequently, the thin-film magnet20, which is composed of the hard magnetic layer103, can easily have the magnetic anisotropy in the in-plane direction. The hard magnetic layer103is a polycrystal composed of a group of differently oriented crystallites, and each crystallite has the magnetic anisotropy in the in-plane direction. This magnetic anisotropy is derived from magneto-crystalline anisotropy.

To facilitate the crystal growth of the alloy containing Cr or the like constituting the control layer102and the Co alloy constituting the thin-film magnet20, the substrate10may be heated to 100° C. to 600° C. This heating facilitates the crystal growth of the alloy containing Cr or the like constituting the control layer102and thus facilitates the crystal orientation that yields an easy axis of magnetization in the plane of the hard magnetic layer103with the hcp structure. In other words, the heating facilitates impartation of the in-plane magnetic anisotropy to the hard magnetic layer103.

The adhesive layers101a,101b, the control layers102a,102b, and the hard magnetic layers103(thin-film magnets20a,20b) are processed to have a rectangular planar shape (seeFIG.1A).

The thin-film magnets20a,20bare disposed such that different magnetic poles face each other in the longitudinal direction via the yokes40and the sensitive part30. In this example, the north pole of the thin-film magnet20aand the south pole of the thin-film magnet20bface each other in the longitudinal direction via the yokes40and the sensitive part30. To further illustrate, a line connecting the north pole of the thin-film magnet20aand the south pole of the thin-film magnet20bis oriented in the longitudinal direction of the sensitive element31of the sensitive part30. The phrase “oriented in the longitudinal direction” means that the line connecting the north pole and the south pole is angled from 0 to 45 degrees with respect to the longitudinal direction. A smaller angle between the line connecting the north and south poles and the longitudinal direction is preferable.

In the magnetic sensor1, magnetic lines of force emanating from the north pole of the thin-film magnet20apass through the sensitive elements31via the yoke40aand reach the south pole of the thin-film magnet20bvia the yoke40b. In other words, the thin-film magnets20a,20bapply the magnetic field in the longitudinal direction of the sensitive elements31. This magnetic field is called a bias magnetic field.

The north and south poles of the thin-film magnets20a,20bare hereinafter collectively referred to as “both magnetic poles”, and each of the north and south poles is hereinafter referred to as a “magnetic pole” unless their distinction is particularly needed. While the description herein is made using the case where the right side of each of the thin-film magnets20a,20bis the north pole and the left side thereof is the south pole inFIGS.1A and1B, the north and south poles may be interchanged.

As shown inFIG.1A, when viewed from the top side of the substrate10, each of the yokes40(yokes40a,40b) has a shape that is tapered as it approaches the sensitive part30. This shape makes it possible to gather the magnetic lines of force into the sensitive part30. In other words, this shape helps increase the sensitivity by enhancing the magnetic field at the sensitive part30. It should be noted that the yokes40(yokes40a,40b) are not necessarily tapered on the portions thereof facing the sensitive part30.

A distance between each of the yokes40(yokes40a,40b) and the sensitive part30may be 1 μm to 100 μm, for example.

Also, a distance between each of the yokes40(yokes40a,40b) and the corresponding one of the thin-film magnets20(thin-film magnets20a,20b) may be 1 μm to 100 μm, for example. Alternatively, each of the yokes40(yokes40a,40b) and the corresponding one of the thin-film magnets20(thin-film magnets20a,20b) may be in contact with each other.

(Functions of the Magnetic Sensor1)

Now a description will be given of functions of the magnetic sensor1of the present embodiment.FIG.2illustrates a relationship between the magnetic field applied in the longitudinal direction of the sensitive elements31of the sensitive part30of the magnetic sensor1and impedance of the sensitive part30. InFIG.2, the horizontal axis represents the magnetic field H, and the vertical axis represents the impedance Z. The impedance Z of the sensitive part30is measured by applying high-frequency electric current between the two terminal portions33.

As shown inFIG.2, the impedance Z of the sensitive part30increases with increase in the magnetic field H applied in the longitudinal direction of the sensitive elements31. However, by use of a portion where an amount of change ΔZ of the impedance Z is steep as a function of an amount of change ΔH of the magnetic field H (i.e., a portion where ΔZ/ΔH is large) within the region where the applied magnetic field H is smaller than the anisotropic magnetic field Hk of the sensitive elements31, a slight change of the magnetic field H can be extracted as the amount of change ΔZ of the impedance Z. InFIG.2, the center of the portion of the magnetic field H where the ΔZ/ΔH is large is denoted as a magnetic field Hb. That is, the amount of change of the magnetic field H (ΔH) near the magnetic field Hb (in the region shown by the arrows inFIG.2) can be measured with high accuracy. The magnetic field Hb may also be called a bias magnetic field.

By the way, a magnetic sensor including a sensitive element as a magnetic impedance effect element and a thin-film magnet for applying a bias magnetic field to the sensitive element may have a structure in which the thin-film magnet and a sensitive part are laminated on a substrate with an insulating layer interposed between the thin-film magnet and the sensitive part.FIGS.6A and6Billustrate an example of a conventional magnetic sensor3;FIG.6Ais a plan view of the magnetic sensor3, and FIG.6B is a sectional view taken along the line VIB-VIB inFIG.6A. Similar components to those of the magnetic sensor1shown inFIGS.1A and1Bare denoted by the same reference numerals, and detailed description thereof has been omitted.

The magnetic sensor3shown inFIGS.6A and6Bincludes the adhesive layer101, the control layer102, a thin-film magnet21, and an insulating layer104laminated in this order on the substrate10, and the sensitive part30and the yokes40are formed on the insulating layer104. In other words, in the magnetic sensor3, the sensitive part30(sensitive elements31) and the thin-film magnet21face each other across the insulating layer104.

When high-frequency electric current is supplied to the sensitive part30of the above configured magnetic sensor3, the magnetic sensor3may act as a capacitor due to polarization of the insulating layer104interposed between the conductive thin-film magnet21and sensitive part30.

Thus, as a result of the high-frequency electric current supplied to the sensitive part30being used for the capacitor, the magnetic sensor3may have a smaller amount of change ΔZ of the impedance Z as a function of the amount of change ΔH of the magnetic field H.

In contrast, the magnetic sensor1of the present embodiment have the thin-film magnets20disposed on the substrate10similarly to the sensitive part30as described above, as opposed to disposing the thin-film magnets20between the sensitive part30and the substrate10. In other words, the magnetic sensor1of the present embodiment have the thin-film magnets20and the sensitive part30(sensitive elements31) laminated on the same substrate10. This allows for effective use of high-frequency electric current when it is applied to the sensitive part30, avoiding a decrease in the amount of change ΔZ of the impedance Z as a function of the amount of change ΔH of the magnetic field H.

Additionally, as the magnetic sensor1eliminates the need for an insulating layer for insulation between the thin-film magnets20and the sensitive part30, the magnetic sensor1can be simple in structure.

It should be noted that the phrase “laminated on the substrate10” not only means a structure in which a relevant layer is directly laminated on the substrate10but also a structure in which a relevant layer is laminated on the substrate10through one or more intervening layers. For example, the phrase “the thin-film magnet20is laminated on the substrate10” not only means a structure in which the thin-film magnet20is directly laminated on the substrate10but also a structure in which the thin-film magnet20is laminated on the substrate10through the adhesive layer101and the control layer102as shown inFIG.1B.

(Method for Manufacturing the Magnetic Sensor1)

Now a description will be given of an exemplary method for manufacturing the magnetic sensor1.

FIGS.3A to3C and4A to4Dillustrate an exemplary method for manufacturing the magnetic sensor1.FIGS.3A to3C and4A to4Ddepict steps of the method for manufacturing the magnetic sensor1. It should be noted that the steps shown inFIGS.3A to3C and4A to4Dare representative in nature and may include other steps. The steps proceed sequentially fromFIG.3AthroughFIG.4D.FIGS.3A to3C and4A to4Dcorrespond to the sectional view taken along the line IB-IB inFIG.1A.

As described above, the substrate10is a substrate made of a nonmagnetic material, e.g., an oxide substrate such as glass and sapphire, a semiconductor substrate such as silicon, and a metal substrate such as aluminum, stainless steel, and metal plated with nickel phosphorus. The substrate10may be formed with linear grooves or linear protrusions and recesses with a curvature radius Ra of e.g., 0.1 nm to 100 nm by means of a polishing machine or the like. The direction of these linear grooves or linear protrusions and recesses may be aligned with the direction connecting the north and south poles of the thin-film magnets20composed of the hard magnetic layer103. This facilitates the crystal growth of the hard magnetic layer103in the direction of the grooves. This in turn helps to cause the easy axis of magnetization of the thin-film magnets20, each being composed of the hard magnetic layer103, to be oriented in the direction of the grooves (direction connecting the north and south poles of the thin-film magnets20). In other words, the thin-film magnets20can be magnetized easier.

By way of example, the substrate10discussed herein is assumed to be glass that is about 95 mm in diameter and about 0.5 mm thick. In the case where the magnetic sensor1is several millimeters square in planar shape, multiple magnetic sensors1are manufactured in batch on the substrate10and then divided (cut) into individual magnetic sensors1. WhileFIGS.3A to3C and4A to4Dfocus on one magnetic sensor1depicted at the center of the figures, the figures also depict portions of right and left adjacent magnetic sensors1. A boundary between two adjacent magnetic sensors1is shown by a dash-dotted line in the figures.

As shown inFIG.3A, after cleaning of the substrate10, a photoresist pattern (resist pattern)111is formed on one side (hereinafter referred to as a “top side”) of the substrate10by any known photolithography technique. The resist pattern111includes openings at positions where the thin-film magnets20(thin-film magnets20a,20b) are to be formed.

As shown inFIG.3B, the adhesive layer101, the control layer102, and the hard magnetic layer103are deposited (stacked) in this order.

Specifically, the adhesive layer101composed of the alloy containing Cr or Ni, the control layer102composed of the alloy containing Cr or the like, and the hard magnetic layer103composed of the Co alloy constituting the thin-film magnet20are successively deposited (stacked) in this order. This deposition may be done by a sputtering method or the like. The substrate10is moved to successively face multiple targets made of respective materials, whereby the adhesive layer101, the control layer102, and the hard magnetic layer103are laminated in this order on the substrate10. As described above, the substrate10may be heated to e.g., 100° C. to 600° C. during formation of the control layer102and the hard magnetic layer103to facilitate the crystal growth.

The substrate10may or may not be heated during deposition of the adhesive layer101. The substrate10may be heated prior to deposition of the adhesive layer101to remove moisture absorbed on the top side of the substrate10.

As shown inFIG.3C, the resist pattern111is removed, and also the adhesive layer101, the control layer102, and the hard magnetic layer103on the resist pattern111are removed (lifted off).

As shown inFIG.4A, a resist pattern112is formed that includes openings at positions where the sensitive part30and the yokes40(yokes40a,40b) are to be formed.

As shown inFIG.4B, the lower soft magnetic layer105acomposed of the Co alloy constituting the sensitive element31, the demagnetizing field suppressing layer106composed of Ru or the Ru alloy, and the upper soft magnetic layer105bcomposed of the Co alloy constituting the sensitive element31are deposited (stacked) in this order. The deposition of the soft magnetic layers105(lower soft magnetic layer105aand upper soft magnetic layer105b) and the demagnetizing field suppressing layer106may be done by a sputtering method, for example.

As shown inFIG.4C, the resist pattern112is removed, and also the soft magnetic layers105and the demagnetizing field suppressing layer106on the resist pattern112are removed (lifted off). As a result, the sensitive part30and the yokes40(yokes40a,40b) composed of the soft magnetic layers105and the demagnetizing field suppressing layer106are formed. In other words, the sensitive part30and the yokes40are simultaneously formed by deposition of the soft magnetic layers105and the demagnetizing field suppressing layer106.

Thereafter, the soft magnetic layers105are imparted with uniaxial magnetic anisotropy in the width direction of the sensitive elements31of the sensitive part30. This impartation of the uniaxial magnetic anisotropy to the soft magnetic layers105can be done by, for example, heat treatment (heat treatment in a rotating magnetic field) at 400° C. in a rotating magnetic field of 3 kG (0.3 T) and subsequent heat treatment (heat treatment in a static magnetic field) at 400° C. in a static magnetic field of 3 kG (0.3 T). At this time, similar uniaxial magnetic anisotropy is imparted to the soft magnetic layers105constituting the yokes40. However, the yokes40are not necessarily imparted with the uniaxial magnetic anisotropy because the yokes40are only required to serve as a magnetic circuit.

Then, the hard magnetic layer103constituting each thin-film magnet20is magnetized. This magnetization of the hard magnetic layer103can be done by applying a magnetic field larger than coercive force of the hard magnetic layer103in a static magnetic field or a pulsed magnetic field until the magnetization of the hard magnetic layer103is saturated. Thus, the magnetic pole of each thin-film magnet20(north pole of the thin-film magnet20aand south pole of the thin-film magnet20b) is formed on a lateral side of the corresponding hard magnetic layer103facing the sensitive part30with a gap in between. That is, the magnetized hard magnetic layer103becomes the thin-film magnet20.

The step of depositing the hard magnetic layer103constituting the thin-film magnet20and the step of magnetizing the hard magnetic layer103described above are those for forming the thin-film magnet20whose magnetic anisotropy is controlled in the in-plane direction, and thus these steps may be hereinafter collectively referred to as thin-film magnet forming steps.

Subsequently, as shown inFIG.4D, multiple magnetic sensors1formed on the substrate10are divided (cut) into individual magnetic sensors1. In other words, the substrate10, the adhesive layer101, the control layer102, and the hard magnetic layer103are cut such that each magnetic sensor1has a rectangular planar shape as shown in the plan view ofFIG.1A. This division (cutting) can be done by a dicing method, a laser cutting method, or the like.

It should be noted that an etching step of removing the adhesive layer101, the control layer102, and the hard magnetic layer103between adjacent magnetic sensors1on the substrate10so as to shape each magnetic sensor1into a rectangular planar shape (planar shape of the magnetic sensor1shown inFIG.1A) may take place after the step of laminating the adhesive layer101, the control layer102, and the hard magnetic layer103shown inFIG.3Band before the step of dividing the multiple magnetic sensors1into individual magnetic sensors1shown inFIG.4D. As such, the exposed substrate10may be divided (cut).

As compared to this method, the manufacturing method shown inFIGS.3A to3C and4A to4Drequires simplified steps.

Also, the steps of laminating the soft magnetic layers105and the demagnetizing field suppressing layer106to form the sensitive part30and the yokes40shown inFIGS.4A to4Cmay precede the step of laminating the adhesive layer101, the control layer102, and the hard magnetic layer103shown inFIG.3B.

The magnetic sensor1is thus manufactured. It should be noted that the impartation of the uniaxial magnetic anisotropy to the soft magnetic layers105and/or magnetization of the thin-film magnets20may be performed for each magnetic sensor1or multiple magnetic sensors1after the step of dividing the multiple magnetic sensors1into individual magnetic sensors1shown inFIG.4D.

Without the control layer102, it would be necessary to impart the magnetic anisotropy in the plane of the hard magnetic layer103by heating the hard magnetic layer103to 800° C. or more to bring about crystal growth after deposition thereof. In contrast, providing the control layer102, as in the magnetic sensor1of the present embodiment, eliminates the need for bringing about such crystal growth under high temperature of 800° C. or more because the control layer102can facilitate the crystal growth.

The impartation of the uniaxial magnetic anisotropy to the sensitive elements31of the sensitive part30may be done by a magnetron sputtering method during stacking of the soft magnetic layers105composed of the Co alloy constituting the sensitive element31, instead of the aforementioned heat treatment in a rotating magnetic field and heat treatment in a static magnetic field. The magnetron sputtering method forms a magnetic field using magnets and confines (concentrates) electrons generated by discharge to a surface of a target. The method thus increases the probability of collisions of the electrons with gas and facilitates ionization of the gas, thereby increasing film stacking speed (film deposition speed). This magnetic field formed by the magnets used in the magnetron sputtering method imparts the uniaxial magnetic anisotropy to the soft magnetic layers105at the same time as the stacking thereof. As such, the magnetron sputtering method allows the step of imparting the uniaxial magnetic anisotropy by the heat treatment in a rotating magnetic field and the heat treatment in a static magnetic field to be omitted.

Now a description will be given of a modification of the magnetic sensor1.

FIGS.5A and5Billustrate an example of a modified magnetic sensor2;FIG.5Ais a plan view, andFIG.5Bis a sectional view taken along a line VB-VB inFIG.5A. Similar components to those of the magnetic sensor1shown inFIGS.1A and1Bare denoted by the same reference numerals, and detailed description thereof has been omitted.

In the magnetic sensor1shown in FIGS. lA and1B, the sensitive part30and the yokes40are composed of the two soft magnetic layers105(lower soft magnetic layer105aand upper soft magnetic layer105b) disposed with the demagnetizing field suppressing layer106in between. Also, in the magnetic sensor1shown inFIGS.1A and1B, each of the yokes40(yokes40a,40b) is disposed between the sensitive part30and the corresponding one of the thin-film magnets20(thin-film magnets20a,20b) on the substrate10.

In contrast, in the magnetic sensor2as a modification of the magnetic sensor1, the sensitive part30and yokes41are each composed of a single soft magnetic layer105, as shown inFIGS.5A and5B.

Additionally, in the magnetic sensor2, each of the yokes41(yokes41a,41b) is formed continuously over an area from a position facing a longitudinal end of the sensitive element31to a top side of the corresponding one of the thin-film magnets20(thin-film magnets20a,20b), as shown inFIGS.5A and5B. To further illustrate, in the magnetic sensor2, each of the yokes41(yokes41a,41b) is disposed such that it contacts a lateral side of the corresponding one of the thin-film magnets20(thin-film magnets20a,20b) facing the sensitive element31and contacts the top side thereof.

Due to the yokes41(yokes41a,41b) of the magnetic sensor2having the shape as shown inFIGS.5A and5B, magnetic lines of force emanating from the north pole of the thin-film magnet20aare induced to the sensitive elements31via the yoke41a. Also, after emanating from the north pole of the thin-film magnet20aand passing through the sensitive elements31, the magnetic lines of force reach the south pole of the thin-film magnet20bvia the yoke41b.

To manufacture the magnetic sensor2, for example, the step of forming the resist pattern112in the above method for manufacturing the magnetic sensor1, as shown inFIG.4A, is modified such that the resist pattern112is shaped to include openings at positions where the sensitive part30and the yokes41(yokes41a,41b) are to be formed.

Also, the step of depositing the lower soft magnetic layer105a, the upper soft magnetic layer105b, and the demagnetizing field suppressing layer106shown inFIG.4Bis replaced with a step of depositing a single soft magnetic layer105. This results in the single soft magnetic layer105being deposited on the substrate10and on the hard magnetic layer103at positions corresponding to the openings in the resist pattern112.

Additionally, the above step of dividing multiple magnetic sensors into individual magnetic sensors shown inFIG.4Dis modified such that the soft magnetic layer105deposited on the hard magnetic layer103is also divided (cut) in addition to the substrate10, the adhesive layer101, the control layer102, and the hard magnetic layer103.

The above steps result in the manufacture of the magnetic sensor2shown inFIGS.5A and5B.

It should be noted that an etching step of removing the adhesive layer101, the control layer102, the hard magnetic layer103, and the soft magnetic layer105between adjacent magnetic sensors2on the substrate10so as to shape each magnetic sensor2into a rectangular planar shape (planar shape of the magnetic sensor2shown inFIG.5A) may take place after the step of laminating the adhesive layer101, the control layer102, the hard magnetic layer103, and the soft magnetic layer105and before the step of dividing the multiple magnetic sensors2into individual magnetic sensors2. As such, the exposed substrate10may be divided (cut).

The magnetic sensors2may be manufactured by other manufacturing steps.

While the exemplary embodiment of the present invention has been described above, the present invention is not limited to the above exemplary embodiment. Various modifications and combinations of embodiments may be made without departing from the spirit of the present invention.

REFERENCE SIGNS LIST