Magnetic sensor and manufacturing method therefor

A magnetic sensor includes a plurality of giant magnetoresistive elements, each of which includes a free layer, a conductive layer, and a pin layer sequentially laminated on a substrate, wherein the pin layer formed by sequentially laminating a first magnetic layer, an Ru layer, a second magnetic layer, and an antiferromagnetic layer is subjected to magnetization heat treatment so as to fix the magnetization direction thereof. The first and second magnetic layers differ from each other in thickness and magnetic moment thereof, and the thickness of the Ru layer ranges from 4 Å to 10 Å. The magnetization heat treatment is performed so as to maintain an anti-parallel state between the first and second magnetic layers. In order to detect magnetic fields in three-axial directions, one giant magnetoresistive element is formed using a planar surface, and the other giant magnetoresistive elements are formed using respective slopes on the substrate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to magnetic sensors, each of which includes a plurality of giant magnetoresistive elements formed on a single substrate so as to detect magnetic field intensities (or magnetic field strengths) in two-axial directions or three-axial directions. The present invention also relates to manufacturing methods of magnetic sensors.

The present application claims priority on Japanese Patent Application No. 2007-110475, the content of which is incorporated herein by reference.

2. Description of the Related Art

As elements used for magnetic sensors, giant magnetoresistive elements (GMR elements) and tunnel magnetoresistive elements (TMR elements) have been conventionally known. Each of the conventionally-known magnetoresistive elements includes a pin layer whose magnetization direction is pinned (or fixed) and a free layer whose magnetization direction varies in response to an external magnetic field, wherein it shows a resistance to suit the mutual relationship between the magnetization direction of the pin layer and the magnetization direction of the free layer. Magnetic sensors using magnetoresistive elements have been disclosed in various documents such as Patent Document 1 and Patent Document 2.Patent Document 1: Japanese Unexamined Patent Application Publication No. 2005-260064.Patent Document 2: Japanese Unexamined Patent Application Publication No. 2006-261400.

Patent Document 1 teaches a magnetic sensor that is constituted using a plurality of giant magnetoresistive elements each having a synthetic antiferromagnetic (SAF) structure, in which a Ru layer (where Ru stands for ruthenium) is inserted into a magnetic layer of a pin layer formed on the surface of a substrate. Each of the giant magnetoresistive elements detects a magnetic field intensity lying in one direction on the surface of the substrate. A plurality of giant magnetoresistive elements, which detect magnetic field intensities in different directions, is formed on the surface of the substrate. This makes it possible for the magnetic sensor to detect magnetic field intensities in two-axis directions.

In magnetization heat treatment (or pinning) for fixing magnetization directions of pin layers during manufacturing of magnetic sensors, substrates are each heated up to a prescribed temperature while a magnet away is positioned opposite to the surface of the substrate, wherein an intense magnetic field (whose value is 10 T or more, for example) is applied to the pin layer so as to allow two magnetic layers to be positioned in parallel with each other. Herein, the magnetic field applied to the pin layer occurs in a slit (e.g., a rectangular through-hole) of a yoke forming the magnet array, wherein the magnetization direction of the pin layer depends upon polarities of permanent magnets adjoining together in the magnet array. After heat treatment, the magnetic sensor is produced such that the magnetization directions of two magnetic layers are directed opposite to each other, in other words, two magnetic layers are placed in an anti-parallel state of magnetization.

Patent Document 2 teaches a small-size magnetic sensor in which planar surfaces and slopes (i.e., inclined surfaces inclined to planar surfaces) are formed on the surface of a single substrate, wherein giant magnetoresistive elements are formed on the planar surface and the slopes respectively, thus making it possible to detect magnetic field intensities in three-axial directions.

The slopes are formed by way of V-shaped channels formed on the surface of the substrate and are thus positioned opposite to each other in each channel. This magnetic sensor is formed using giant magnetoresistive elements, in which Ru layers are not inserted into magnetic layers of pin layers.

The magnetic sensor of Patent Document 2 is capable of detecting magnetic field intensities in three-axial directions, wherein magnetization directions of pin layers of giant magnetoresistive elements are affected and varied due to an excessively intense external magnetic field. When the external magnetic field becomes zero in intensity, magnetization directions are varied and fixed in wrong directions. That is, this magnetic sensor may suffer from a relatively weak resistance in ferromagnetism.

The giant magnetoresistive elements of synthetic antiferromagnetic structures used in the magnetic sensor of Patent Document 1 are each designed such that two magnetic layers forming a pin layer are placed in an anti-parallel state of magnetization, which may increase the resistance in ferromagnetism but which cannot detect magnetic field intensities in three-axial directions. For this reason, the inventor of this application modifies the magnetic sensor of Patent Document 2 such that giant magnetoresistive elements of synthetic antiferromagnetic structures are formed on planar surfaces and slopes of a substrate.

Suppose that three giant magnetoresistive elements having pin layers of different magnetization directions are formed on a planar surface and two slopes (i.e., paired slopes positioned opposite to each other via a channel) respectively. In magnetization heat treatment for fixing magnetization directions of pin layers, the overall area projecting the paired slopes having giant magnetoresistive elements whose pin layers are placed under a magnetic field becomes larger than the other area projecting the planar surface having a giant magnetoresistive element whose pin layer is also placed under the magnetic field. Herein, the width dimensions of giant magnetoresistive elements formed on the opposite slopes become larger than the width dimensions of a giant magnetoresistive element formed on the planar surface.

As described above, even when giant magnetoresistive elements of synthetic antiferromagnetic structures are applied to the magnetic sensor of Patent Document 2, it is necessary to apply an intense magnetic field whose value is 10 T or more to pin layers of giant magnetoresistive elements during heat treatment; hence, it is necessary to use a magnet array having slits. Herein, the width dimensions of a slit for applying a magnetic field to giant magnetoresistive elements formed on slopes are increased by differences of width dimensions between the slopes and the planar surface in comparison with the width dimensions of another slit for applying a magnetic field to a giant magnetoresistive element formed on the planar surface.

This may weaken the magnetic field applied to giant magnetoresistive elements formed on the slopes; hence, it becomes very difficult to apply an intense magnetic field to all the giant magnetoresistive elements during heat treatment. When a magnetic field having an inadequate intensity is applied to giant magnetoresistive elements in heat treatment, it becomes very difficult to place two magnetic layers in an anti-parallel state of magnetization after heat treatment.

In heat treatment in which an intense magnetic field is applied to giant magnetoresistive elements, variations of the intensity of the magnetic field applied to giant magnetoresistive elements become very large relative to variations of the distance between the substrate and the magnet array, which are positioned opposite to each other with a prescribed gap therebetween. That is, it is necessary to adjust the relative positioning and the distance between the substrate and the magnet array with very high precision. This may cause trouble in the manufacturing of magnetic sensors.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a magnetic sensor including a plurality of giant magnetoresistive elements in which magnetization directions of pin layers can be easily controlled in heat treatment.

It is another object of the present invention to provide a manufacturing method of the magnetic sensor.

In a first aspect of the present invention, a manufacturing method of a magnetic sensor includes a GMR component forming step and a magnetization heat treatment step. In the GMR component forming step, a plurality of GMR components each including a plurality of giant magnetoresistive elements are formed on the surface of a substrate, wherein each giant magnetoresistive element includes a free layer, a conductive layer, and a pin layer that are sequentially laminated together on the substrate, and wherein the pin layer includes a first magnetic layer, an Ru layer, a second magnetic layer, and an antiferromagnetic layer that are sequentially laminated together on the conductive layer. In the magnetization heat treatment, magnetization heat treatment is performed on the substrate arranging the GMR components, wherein a magnetic field is applied to the pin layer so as to fix its magnetization direction, and wherein the first and second magnetic layers are magnetized while maintaining the magnetization directions thereof in an anti-parallel state of magnetization.

In a second aspect of the present invention, a magnetic sensor is produced using a substrate and a plurality of GMR components each including a plurality of giant magnetoresistive elements, wherein each giant magnetoresistive element includes a free layer, a conductive layer, and a pin layer sequentially laminated on the surface of the substrate. Herein, the pin layer includes a first magnetic layer, an Ru layer, a second magnetic layer, and an antiferromagnetic layer, which are sequentially laminated together on the conductive layer, and the first and second magnetic layers differ from each other in magnetic moment thereof.

In the above, the first and second magnetic layers differ from each other in thickness and magnetic moment thereof. Herein, the thickness of the first magnetic layer is larger than the thickness of the second magnetic layer, and the thickness of the Ru layer ranges from 4 Å to 10 Å. In the magnetization heat treatment, a magnet array producing the magnetic field is positioned in proximity to the backside of the substrate whose surface arranges the GMR components.

A planar surface and at least one slope are formed on the substrate in advance. The GMR components having sensitivities in different axial directions are formed on the substrate in such a way that one GMR component is formed using the planar surface, and the other GMR component is formed using the slope. By arranging two GMR components using the planar surface and the slope of the substrate, it is possible to detect magnetism in two-axial directions. By arranging three GMR components using the planar surface and the slopes of the substrate, it is possible to detect magnetism in three-axial directions.

As described above, the present invention provides the following effects.(1) In the magnetization heat treatment, it is necessary to apply a magnetic field having a relatively low intensity that allows the first and second magnetic layers to be magnetized in an anti-parallel state. Since the first and second magnetic layers differ from each other in magnetic moment thereof, they are magnetized in opposite directions due to the antiferromagnetic connection therebetween under the magnetic field.(2) In the magnetization heat treatment, it is possible to fix desired magnetization directions and desired magnetization intensities to the first and second magnetic layers. This eliminates the necessity of applying a relatively high magnetic field to magnetic layers by use of yokes in order to maintain a parallel state of magnetization therebetween in the conventionally-known technology. In other words, the present invention simply requires a relatively low magnetic field applied to the magnetic layers in the magnetization heat treatment. This reduces variations of the magnetic field relative to variations of the distance between the magnet array and the substance; hence, it is unnecessary to precisely adjust the positioning and distance with respect to the magnet array and the substrate at a high precision. Thus, it is possible to easily control the magnetization direction of the pin layer in the magnetization heat treatment.(3) Even when GMR components are formed using the planar surface and slopes of the substrate, it is possible to fix desired magnetization directions to the magnetic layers of the pin layers thereof without applying a relatively high magnetic field thereto. That is, it is possible to easily produce magnetic sensors that are capable of detecting magnetism in two-axial directions and in three-axial directions.(4) Since the first and second magnetic layers have different thicknesses, it is possible for the first and second magnetic layers to reliably produce different magnetic moments. This makes it possible to fix desired magnetization directions to the first and second magnetic layers while maintaining the anti-parallel state of magnetization therebetween in the magnetization heat treatment.(5) when the thickness of the first magnetic layer is larger than the thickness of the second magnetic layer, the magnetic moment of the first magnetic layer becomes higher than the magnetic moment of the second magnetic layer. In this case, the first magnetic layer is magnetized in the same direction as the magnetic field, while the second magnetic layer is magnetized in the direction opposite to the direction of the magnetic field.(6) Magnetic forces of the first and second magnetic layers are exerted on the free layer, wherein they include the exchange coupling force of the first magnetic layers and the magnetostatic forces of the first and second magnetic layers. By increasing the magnetic moment of the first magnetic layer to be higher than the magnetic moment of the second magnetic layer, it is possible to easily reduce the sum of the exchange coupling force and magnetostatic forces exerted on the free layer.(7) By appropriately adjusting, the thickness of the conductive layer, the exchange coupling force may substantially match the magnetostatic force of the first magnetic layer exerted on the free layer. Since the magnetic moment of the second magnetic layer is lower than the magnetic moment of the first magnetic layer, it is possible to reduce the magnetostatic force of the second magnetic layer exerted on the free layer to be smaller than the exchange coupling force and magnetostatic force of the first magnetic layer.(8) Since the direction of the exchange coupling force is opposite to the direction of the magnetostatic force in the first magnetic layer but is identical to the magnetostatic force of the second magnetic layer, it is possible to easily reduce the sum of the exchange coupling force and the magnetostatic forces exerted on the free layer. In other words, it is possible to reduce the influence of the magnetization of the first and second magnetic layers with respect to the magnetization direction of the free layer; therefore, it is possible to set a desired magnetization direction to the free layer.(9) By reducing the thickness of the Ru layer (which ranges from 4 Å to 10 Å), it is possible to easily maintain the anti-parallel state of magnetization between the first and second magnetic layers even when the magnetic field used in the magnetization heat treatment is increased. This increases the range of the intensity of the magnetic field maintaining the anti-parallel state of magnetization between the first and second magnetic layers, making it possible to easily control the intensity of the magnetic field in the magnetization heat treatment; hence, it is possible to easily control the magnetization direction of the pin layer.(10) Since the magnet array is positioned in proximity to the backside of the substrate whose surface arranges the GMR components in the magnetization heat treatment of manufacturing of a magnetic sensor, even when a relatively high magnetic field occurs in proximity to the magnet array, it is possible to weaken the intensity of the magnetic field reaching the first and second magnetic layers of the pin layer because the magnet array is distanced from the GMR component by the thickness of the substrate, wherein it is possible to reduce variations of the intensity of the magnetic field relative to variations of the distance between the magnet array and the GMR component; hence, it is possible to easily adjust the intensity of the magnetic field applied to the GMR component.(11) As described above, the present invention is designed to easily control the magnetization direction of the pin layer without applying a high magnetic field collapsing the anti-parallel state of magnetization between the first and second magnetic fields in the magnetization heat treatment; thus, it is possible to easily produce magnetic sensors that are capable of detecting magnetism in two-axial directions and in three-axial directions.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will be described in further detail by way of examples with reference to the accompanying drawings.

A three-axial magnetic sensor10will be described in accordance with a preferred embodiment of the present invention with reference toFIGS. 1A,1B,2A,2B,3A,3B,4A,4B,4C,5A,5B, and5C.

As shown inFIG. 1A, the three-axial magnetic sensor10has a square shape in plan view having two sides lying in an X-axis and another two sides lying in a Y-axis and includes a substrate11, which is composed of quartz or silicon and which has a small thickness in a Z-axis perpendicular to the X-axis and the Y-axis. In total, twelve sets of giant magnetoresistive elements are formed and positioned at prescribed positions on the surface of the substrate11. Specifically, four X-axis GMR components (denoted as first, second, third, and fourth X-axis GMR components)12ato12deach including four giant magnetoresistive elements are formed at prescribed positions on the surface of the substrate11along the Y-axis; four Y1-axis GMR components (denoted as first, second, third, and fourth Y1-axis GMR components)12eto12heach including four giant magnetoresistive elements (designated by solid line segments representing GMR bars) are formed at prescribed positions on the surface of the substrate11along the X-axis; and four Y2-axis GMR components (denoted as first, second, third, and fourth Y2-axis GMR components)12ito12leach including four giant magnetoresistive elements (designated by dotted line segments representing GMR bars) are formed at prescribed positions on the surface of the substrate11along the X-axis. In addition, pads (i.e., parts for exacting output signals from wires to an external device, not shown), vias (i.e., portions for establishing connections between giant magnetoresistive elements and wires, not shown), which are not exposed in the final stage of manufacturing, and wires (not shown) are fabricated into the substrate11. In addition, LSI components with wiring layers or wiring layers can be further fabricated into the substrate11. When the LSI components with wiring layers are incorporated into the substrate11, the three-axial magnetic sensor10can serve as a digital magnetic sensor for outputting digital signals. When only the wiring layers are incorporated into the substrate11, the three-axial magnetic sensor10serves as an analog magnetic sensor for outputting analog signals.

InFIG. 1A, the left end along the X-axis is designated as a reference point of the X-axis, wherein a rightward direction from the reference point is denoted as a positive X-axis direction, and a leftward direction from the right end opposite to the reference point is denoted as a negative X-axis direction. Similarly, the lower end along the Y-axis is designated as a reference point of the Y-axis, wherein an upward direction from the reference point is denoted as a positive Y-axis direction, and a downward direction from the upper end opposite to the reference point is denoted as a negative Y-axis direction.

In the above, the first X-axis GMR component12aand the second X-axis GMR component12b, which adjoin together along the Y-axis, are positioned substantially in the center portion of the Y-axis in proximity to the right end of the X-axis. The third X-axis GMR component12cand the fourth X-axis GMR component12d, which adjoin together along the Y-axis, are positioned substantially in the center portion of the Y-axis in proximity to the left end of the X-axis.

The first Y1-axis GMR component12eand the second Y1-axis GMR component12f, which adjoin together along the X-axis, are positioned substantially in the center portion of the X-axis in proximity to the upper end of the Y-axis. The third Y1-axis GMR component12gand the fourth Y1-axis GMR component12h, which adjoin together along the X-axis, are positioned substantially in the center portion of the X-axis in proximity to the lower end of the Y-axis.

The first Y2-axis GMR component12iand the second Y2-axis GMR component12j, which adjoin together along the X-axis, are positioned substantially in the center portion of the X-axis in proximity to the lower end of the Y-axis. The third Y2-axis GMR component12kand the fourth Y2-axis GMR component12l, which adjoin together along the X-axis, are positioned substantially in the center portion of the X-axis in proximity to the upper end of the Y-axis.

Each of the twelve GMR components12a-12d,12e-12h, and12i-12lincludes a plurality of GMR bars (i.e., elongated band-shaped giant magnetoresistive elements), which are positioned in parallel. Specifically,FIG. 1Ashows that each GMR component is constituted of four GMR bars, which is not a restriction, wherein it is preferable that each of the X-axis GMR components12ato12dinclude an even number of GMR bars. GMR bars are connected in series via lead films. At ends of connected GMR bars, lead films serving as terminals are formed.FIG. 2Ashows an example of the constitution of the first X-axis GMR component12a, which is similarly applied to the other X-axis GMR components12bto12d. Herein, four GMR bars (or giant magnetoresistive elements)12a-1,12a-2,12a-3, and12a-4are connected in series via three lead films12a-6,12a-7and12a-8. In addition, a lead film12a-5serving as a terminal is connected to one terminal end of the series connection of the GMR bars12a-1to12a-4, and another lead film12a-9serving as a terminal is connected to the other terminal end of the series connection of the GMR bars12a-lto12a-4. The GMR bars (e.g., the GMR bars12a-1to12a-4) included in the X-axis GMR components12ato12dare formed on the planar surfaces, which are parallel to the overall surface of the substrate11, wherein the longitudinal directions thereof are each parallel to the Y-axis, in other words, they are each perpendicular to the X-axis.

A plurality of projections (or banks)15each having a trapezoidal shape in its cross section are formed on the substrate11, wherein each projection15has two slopes, namely, a first slope15aand a second slope15b. Each of the Y1-axis GMR components12eto12hand the Y2-axis GMR components12ito12lincludes a prescribed number of GMR bars, which are formed on slopes of projections of the substrate11.

The arrangements of the first Y1-axis GMR component12e(including GMR bars12e-1,12e-2,12e-3, and12e4) and the third Y2-axis GMR component12k(including GMR bars12k-1,12k-2,12k-3, and12k-4), which are coupled together in a prescribed section of the substrate11(seeFIG. 1A), will be described with reference toFIG. 1BandFIG. 4B. The GMR bars12e-1to12e-4of the first Y1-axis GMR component12eare formed on the first slopes15aof the projections15, while the GMR bars12k-1to12k-4of the third Y2-axis GMR component12kare formed on the second slopes15bof the projections15. The longitudinal directions of the GMR bars12e-lto12e-4and the GMR bars12k-1to12k-4run in parallel with the ridgelines of the projections15. Both the slopes15aand15bare inclined with the same inclination angle θ (where 20°≦θ≦60°) relative to the planar surfaces of the substrate11.

One GMR bar of the Y1-axis GMR component12eis positioned opposite to the corresponding GOU bar of the Y2-axis GMR component12kwith respect to a single projection15. For example, the GMR bar12e-1and the GMR bar12k-1are formed on the slopes15aand15bof one projection15, while the GMR12e-2and the GMR bar12k-2are formed on the slopes15aand15bof another projection15. The longitudinal directions of the (my bars of the Y1-axis GMR components12eto12hand the GMR bars of the Y2-axis GMR components12ito12lrun in parallel with the X-axis, in other words, they run perpendicular to the Y-axis.

The constitution of the GMR bar will be described with respect to the GMR bar12a-2of the first X-axis GMR component12a, for example, with reference toFIG. 2BandFIGS. 3A and 3B. The same constitution is applied to the other GMR bars12a-1,12a-3, and12a-4, the descriptions of which are thus omitted. In addition, the same constitution is similarly applied to the other X-axis GOU components12bto12d, the Y1-axis GMR components12eto12h, and the Y2-axis GMR components12ito12l, the descriptions of which are thus omitted.

As shown inFIG. 2B, the GMR bar12a-2of the first X-axis GMR component12aincludes a spin-valve film SV whose longitudinal direction lies perpendicular to the X-axis (or in parallel with the Y-axis). Both ends of the spin-valve film SV are connected to the lead films12a-6and12a-7formed therebelow. The lead films12a-6and12a-7are each formed using a non-magnetic metal film composed of chromium (Cr) and the like, wherein the thickness thereof is set to 130 nm (1300 Å), for example.

As shown inFIG. 3A, the spin-valve film SV is constituted of a free layer (i.e., a free magnetization layer) F, a conductive spacer layer (i.e., a conductive layer) composed of copper (Cu) whose thickness is 2.8 nm (28 Å), a pin layer (i.e., a fixed layer or a fixed magnetization layer) P, and a capping layer C composed of tantalum (Ta) or titanium (Ti) whose thickness is 2.5 nm (25 Å). The free layer A, the spacer layer S, the pin layer P, and the capping layer C are sequentially laminated and formed on the substrate11.

The magnetization direction of the free layer F varies in response to the direction of an external magnetic field. The free layer F is composed of a CoZrNb amorphous magnetic layer12a-21whose thickness is 8 nm (80 Å), a NiFe magnetic layer12a-22whose thickness is 3.3 nm (33 Å), and a CoFe layer12a-23whose thickness is 1.2 nm (12 Å). These layers are sequentially laminated together in such a way that the CoZrNb amorphous magnetic layer12a-21is formed just above the substrate11; the NiFe magnetic layer12a-22is formed on the CoZrNb amorphous magnetic layer12a-21; and the CoFe layer12a-23is formed on the NiFe magnetic layer12a-22.

The CoZrNb amorphous magnetic layer12a-21, the NiFe magnetic layer12a-22, and the CoFe layer12a-23are laminated together to form a soft ferromagnetic thin film. The CoFe layer12a-23is provided to avoid the Ni diffusion of the NiFe layer12a-22and the Cu diffusion of a Cu layer12a-24forming the spacer layer S.

The pin layer P is constituted of a first CoFe magnetic layer12a-25whose thickness is 3.2 nm (32 Å), a Ru layer12a-26whose thickness is 0.5 nm (5 Å), a second CoFe magnetic layer12a-27whose thickness is 2.2 nm (22 Å), and an antiferromagnetic layer12a-28whose thickness is 24 nm (240 Å), which is composed of a PtMn alloy including Pt whose content ranges from 45 mol % to 55 mol %. These layers are sequentially laminated together in such a way that the first CoFe magnetic layer12a-25is formed on the Cu layer12a-24; the Ru layer12a-26is formed on the first CoFe magnetic layer12a-25; the second CoFe magnetic layer12a-27is formed on the Ru layer12a-26; and the antiferromagnetic layer12a-28is formed on the second CoFe magnetic layer12a-27.

The aforementioned values of thickness of the layers forming the free layer F and the pin layer P as well as the aforementioned values of thickness of the spacer layer S and the capping layer C are determined with respect to the X-axis GMR components12ato12d. With respect to the other GMR components such as the Y1-axis GMR components12eto12hand the Y2-axis GMR components12ito12l, the thickness of their layers are reduced in a range between 70% and 80% as the aforementioned values of thickness determined with respect to the X-axis GMR components12ato12d.

As shown inFIG. 3B, the second CoFe magnetic layer12a-27is lined with the antiferromagnetic layer12a-28in a exchange coupling manner, wherein the magnetization direction (or magnetization vector) thereof is fixed (or pinned) in the negative X-axis direction. The first CoFe magnetic layer12a-25is connected to the second CoFe magnetic layer12a-27in an antiferromagnetic manner, wherein the magnetization direction thereof is fixed in the positive X-axis direction. That is, the magnetization direction of the pin layer P depends upon the magnetization directions of the CoFe magnetic layers12a-25and12a-27.

As shown inFIGS. 2A,3B, and4A, the sensitivity direction of the first X-axis GMR component12alies in parallel with the planar surface of the substrate11and perpendicular to the magnetization direction of the free layer F, in other words, it lies in a direction perpendicular to the longitudinal directions of the GMR bars and in the positive X-axis direction (see an arrow a1shown inFIG. 4A). Similar to the first X-axis GMR component12a, the sensitivity direction of the second X-axis GMR component12blies in the positive X-axis direction (see an arrow b1shown inFIG. 4A).

When a magnetic field is applied to the three-axial magnetic sensor10in the directions a1and b1, the resistance of the first X-axis GMR component12aand the resistance of the second X-axis GMR component12bare reduced in proportion to the intensity of the magnetic field. When a magnetic field is applied to the three-axial magnetic sensor10in the directions opposite to the directions a1and b1, the resistance of the first X-axis GMR component12aand the resistance of the second X-axis GMR component12bare increased in proportion to the intensity of the magnetic field.

As shown inFIG. 4A, the sensitivity directions of the third X-axis GMR component12cand the fourth X-axis GMR component12dlie in the directions perpendicular to the longitudinal directions of the GMR bars and are thus reverse to the sensitivity directions of the first X-axis GEM component12aand the second X-axis GMR component12bby 180°. In the third X-axis GMR component12cand the fourth X-axis GMR component12d, the pin layers are formed in such a way that the magnetization directions (or magnetization vectors) thereof are fixed (or pinned) in the negative X-axis direction (see arrows c1and d1shown inFIG. 4A), which is reverse to the magnetization directions of the pin layers included in the GMR bars of the first X-axis GMR component12aand the second X-axis GMR component12bby 180°.

Therefore, when a magnetic field is applied to the three-axial magnetic sensor10in the directions c1and d1, the resistances of the third X-axis GMR component12cand the fourth X-axis GMR component12dare reduced in proportion to the intensity of the magnetic field. When a magnetic field is applied in the directions opposite to the directions c1and d1, the resistances of the third X-axis GMR component12cand the fourth X-axis GMR component12dare increased in proportion to the intensity of the magnetic field.

As shown inFIG. 4B, the sensitivity directions of the first Y1-axis GMR component12eand the second Y1-axis GMR component12flie perpendicular to the longitudinal directions of their GMR bars (e.g., GMR bars12e-2and12e-3and GMR bars12f-2and12f-3) along the tint slopes15a(each having the inclination angle θ) of the projections15in the positive Y-axis direction and negative Z-axis direction; that is, they lie in directions e1and f1shown inFIGS. 4A and 4B.

When a magnetic field including magnetic components directed to the directions e1and f1is applied to the three-axis magnetic sensor10shown inFIG. 4A, the resistances of the first Y1-axis NMR component12eand the second Y1-axis GMR component12fare reduced in proportion to the intensity of the magnetic field. When a magnetic field including magnetic components lying in the directions opposite to the directions e1and f1is applied to the three-axial magnetic sensor10, the resistances of the first Y1-axis GMR component12eand the second Y1-axis GMR component12fare increased in proportion to the intensity of the magnetic field.

As shown inFIG. 4C, the sensitivity directions of the third Y1-axis GMR component12gand the fourth Y1-axis GMR component12hlie perpendicular to the longitudinal directions of their GMR bars (e.g., GMR bars12e-2and12e-3and GMR bars12h-2and12h-3) along the first slopes15aof the projections15in the negative Y-axis direction and negative Z-axis direction; that is, they lie in directions g1and h1shown inFIGS. 4A and 4C. That is, the sensitivity directions of the third Y1-axis GMR component12gand the fourth Y1-axis GMR component12hare reverse to the sensitivity directions of the first Y1-axis GMR component12eand the second Y1-axis GMR component12fby 180°.

Therefore, when a magnetic field including magnetic components lying in the directions g1and h1is applied to the three-axial magnetic sensor10shown inFIG. 4A, the resistances of the third Y1-axis GMR component12gand the fourth Y1-axis GMR component12hare reduced in proportion to the intensity of the magnetic field. When a magnetic field including magnetic components lying in the directions opposite to the directions g1and h1is applied to the three-axial magnetic sensor10, the resistances of the third Y1-axis GMR component12gand the fourth Y1-axis GMR component12hare increased in proportion to the intensity of the magnetic field.

As shown inFIG. 4C, the sensitivity directions of the first Y2-axis GMR component12iand the second Y2-axis GMR component12jlie perpendicular to the longitudinal directions of their GMR bars (e.g., GMR bars12i-2and12i-3, and GMR bars12j-2and12j-3) along the second slopes15b(having the inclination angle θ) of the projections15in the negative Y-axis direction and positive Z-axis direction; that is, they lie in directions i1and j1shown inFIGS. 4A and 4C.

Therefore, when a magnetic field including magnetic components lying in the directions i1and j1is applied to the three-axial magnetic sensor10shown inFIG. 4A, the resistances of the first Y2-axis GMR component12iand the second Y2-axis GMR component12jare reduced in proportion to the intensity of the magnetic field. When a magnetic field including magnetic components lying in the directions opposite to the directions i1and j1is applied to the three-axial magnetic sensor10, the resistances of the first Y2-axis GMR component12iand the second Y2-axis GMR component12jare increased in proportion to the intensity of the magnetic field.

As shown inFIG. 4B, the sensitivity directions of the third Y2-axis GMR component12kand the fourth Y2-axis GMR component12llie perpendicular to the longitudinal directions of their GMR bars (e.g., GMR bars12k-2and12k-3, and GMR bars12l-2and12l-3) along the second slopes15bof the projections15in the positive Y-axis direction and positive Z-axis direction; that is, they lie in directions k1and l1shown inFIGS. 4A and 4B.

Therefore, when a magnetic field including magnetic components lying in the directions k1and l1is applied to the three-axial magnetic sensor10shown inFIG. 4A, the resistances of the third Y2-axis GMR component12kand the fourth Y2-axis GMR component12lare reduced in proportion to the intensity of the magnetic field. When a magnetic field including magnetic components lying in the directions opposite to the directions k1and l1is applied to the three-axial magnetic sensor10, the resistances of the third Y2-axis GMR component12kand the fourth Y2-axis GMR component12lare increased in proportion to the intensity of the magnetic field.

FIGS. 5A to 5Cshow equivalent circuits with respect to the X-axis GMR components12ato12d, the Y1-axis GMR component12eto12h, and the Y2-axis GMR components12ito12l, the magnetization directions of which are designated by arrows, wherein upward arrows correspond to the GMR components whose pin layers P are each pinned in the negative Y-axis direction.

FIG. 5Ashows an equivalent circuit in which the four X-axis GMR components12ato12dfor detecting magnetic components lying in the directions a1, b1, c1, and d1along the X-axis are connected in a fall bridge circuit. A pad13acoupled to the X-axis GMR components12aand12cis connected to a positive electrode of a constant voltage source14and is thus applied with a potential Vxin+(e.g., 3V). A pad13bcoupled to the X-axis GMR components12band12dis connected to a negative electrode of the constant current source14and is thus applied with a potential Vxin−(e.g., 0V). In addition, a potential Vxout+is extracted from a pad13ccoupled to the X-axis GMR components12band12c, while a potential Vxout−is extracted from a pad13dcoupled to the X-axis GMR components12aand12d. Thus, it is possible to produce a sensor output Vxout corresponding to a potential difference (Vxout+−Vxout−).

FIG. 5Bshows an equivalent circuit in which the four Y1-axis GMR components12eto12hfor detecting magnetic components lying in the directions e1, f1, g1, and h1along the Y-axis are connected in a full bridge circuit. A pad13ecoupled to the Y1-axis GMR components12eand12gis connected to the positive electrode of the constant voltage source14and is thus applied with a potential Vy1in+(e.g. 3V). A pad13fcoupled to the Y1-axis GM components12fand12his connected to the negative electrode of the constant current source14and is thus applied with a potential Vy1in−(e.g., 0V). Thus, it is possible to produce a sensor output Vy1out corresponding to a potential difference between a pad13gcoupled to the Y1-axis GMR components12fand12gand a pad13hcoupled to the Y1-axis GMR components12eand12h.

FIG. 5Cshows an equivalent circuit in which the four Y2-axis GMR components12ito12lfor detecting magnetic components lying in the directions i1, j1, k1, and l1along the Y-axis are connected in a full bridge circuit. A pad13icoupled to the Y2-axis GMR components12iand12kis connected to the positive electrode of the constant voltage source14and is thus applied with a potential Vy2in+(e.g., 3V). A pad13jcoupled to the Y2-axis GMR components12jand12lis connected to the negative electrode of the constant current source14and is thus applied with a potential Vy2in−(e.g., 0V). Thus, it is possible to produce a sensor output Vy2out corresponding to a potential difference between a pad13kcoupled to the Y2-axis GMR components12jand12kand a pad13lcoupled to the Y2-axis GMR components12iand12l.

Based on the sensor outputs Vxout, Vy1out, and Vy2out, it is possible to calculate three magnetic components of a magnetic field applied to the three-axial magnetic sensor10, i.e., an X-axis magnetic component Hx, a Y-axis magnetic component Hy, and a Z-axis magnetic component Hz in accordance with equations (1), (2), and (3). Calculations are implemented by an LSI component formed in the substrate11in advance or an individual LSI chip electrically connected to the three-axial magnetic sensor10.

In the above, θ denotes the inclination angle of the slopes15aand15bof the projection15, where 20°≦θ≦60°; and kx, ky, and kz denote proportional constants, wherein kx=ky=kz when the same sensitivity is achieved by all the GMR components12ato12l.

Next, a manufacturing method of the three-axial magnetic sensor10having the aforementioned constitution will be described in detail with reference toFIGS. 6A-6C,FIGS. 7A-7C,FIGS. 8A-8C,FIGS. 9A-9C,FIGS. 10A-10C,FIGS. 11A-11C,FIGS. 12A-12C,FIGS. 13A-13C,FIGS. 14A-14C, andFIGS. 15A-15C, wherein “A” appended to each figure number indicates an illustration of a via, “B” appended to each figure number indicates an illustration of a pad, and “C” appended to each figure number indicates a Y1-axis or Y2-axis GMR component. As the substrate11, it is preferable to use a substrate fabricated with an LSI component or a substrate fabricated with only a wiring layer in advance by way of CMOS manufacturing processes.

In a first step of the manufacturing method of the three-axial magnetic sensor10as shown inFIGS. 6A to 6C, an interlayer insulating film11b, e.g., a SOG (Spin On Glass) film11b, is applied to the substrate11(e.g., a quartz substrate or a silicon substrate), in which a wiring layer11ais formed in advance, thus forming a planar surface on the substrate11.

In a second step of the manufacturing method as shown inFIGS. 7A to 7C, a prescribed portion of the interlayer insulating film11bis removed via etching so as to form an opening11c(seeFIG. 7A), thus exposing the wiring layer11ain the via; and a prescribed portion of the interlayer insulating film11bis removed via etching so as to form an opening11d(seeFIG. 7B), thus exposing the wiring layer11ain the pad.

In a third step of the manufacturing method as shown inFIGS. 8A to 8C, an oxide film11ecomposed of SiO2(or SiOx) having a 1500 Å thickness and a nitride film11fcomposed of Si3N4(or SiNx) having a 5000 Å thickness are sequentially formed via plasma CVD (Chemical Vapor Deposition); a resist is fiercer applied thereon; then, cutting is performed to form a prescribed pattern having openings in the via and pad.

In a fourth step of the manufacturing method as shown inFIGS. 9A to 9C, the nitride film11fis partially removed from the via and the pad, whereby an opening11g(seeFIG. 9A) is formed so as to expose the oxide film11ein the via, and an opening11h(seeFIG. 9B) is formed so as to expose the oxide film11ein the pad. The openings11gand11hare formed in such a way that the oxide film11eis not completely etched and still remains. The diameters of the opening11gand11hare smaller than the diameters of the openings11cand11dso as to prevent the interlayer insulating film11bfrom being exposed in the openings11cand11dand to thereby prevent water content from entering into the wiring layer11aand the LSI component (not shown).

In fifth and sixth steps of the manufacturing method as shown inFIGS. 10A to 10CandFIGS. 11A to 11C, a planar surface elongated perpendicular to the thickness direction of the substrate11is formed, and slopes (i.e., the first slope15aand the second slope15b, seeFIG. 1BandFIGS. 4B and 4C) inclined relative to the planar surface are formed on the surface of the substrate. These steps will be collectively referred to as a mount surface forming step.

In the fifth step of the manufacturing method as shown inFIGS. 10A to 10C(which will be referred to as a resist forming step), an upper oxide film11j(serving as a base film) is formed on the surface of the substrate11; then, a resist film11jhaving a trapezoidal projection having slopes is formed on the upper oxide film11i. Specifically, the upper oxide film11icomposed of SiO2(or SiOx) and having a 5 μm thickness is formed on the oxide film11eand the nitride film11fvia plasma CVD. Then, a resist is applied to the upper oxide film11ivia a spin-coat method or a dip-coat method so as to form the resist film11jhaving a 5 μm thickness. In this state, the surface of the resist film11jis a planar surface elongated perpendicular to the thickness direction of the substrate11.

The resist film11jis subjected to cutting so as to form a prescribed pattern forming the openings of the via and pad in connection with the upper oxide film11iand to form another pattern forming the slopes in the upper oxide film11i, in other words, another pattern forming the projections for arranging the Y1-axis GMR component and the Y2-axis GMR component.

After completion of cutting, the substrate11is subjected to heat treatment at a temperature of 150° C. for a prescribed time ranging from one minute to ten minutes so as to soften the resist film11f, which is thus formed in a tapered shape as shown inFIGS. 11A and 11B. Thus, it is possible to form projections having slopes for mounting the Y1-axis GMR component and the Y2-axis GMR component.FIGS. 11A to 11Cdo not precisely show that the surface of the resist film11jfor mounting the X-axis GMR component is still maintained in the original planar surface thereof.

In the mount surface forming step, after completion of the resist forming step, the upper oxide film11iand the resist film11jare subjected to anisotropic etching so as to form slopes in the upper oxide film11iin conformity with the resist film11jforming the projection. This will be referred to as an anisotropic etching step. Specifically, both the upper oxide film11iand the resist film11jare subjected to dry etching at substantially the same etching rate such that, after completion of dry etching, the remaining portion of the upper oxide film11ihas a maximum thickness of approximately 0.5 μm (approximately 5000 Å). In addition, dry etching is performed in such a way that the diameters of the openings formed in the upper oxide film11ido not become larger than the diameters of the openings formed in the nitride film11fin connection with the via and pad.

In a seventh step of the manufacturing method as shown inFIGS. 12A to 12C, after completion of dry etching, the remaining portion of the resist film11jis completely removed so as to form the projections15using the upper oxide film11ifor mounting the Y1-axis GMR component and the Y2-axis GMR component (seeFIG. 11C). That is, slopes are formed in the upper oxide film11i.FIGS. 12A to 12Cdo not precisely show that the other portion of the resist film11jis subjected to dry etching so as to form the planar surface of the upper oxide film11ifor mounting the X-axis GMR component.

In an eighth step of the manufacturing method as shown inFIGS. 13A to 13C, a resist is applied to the upper oxide film11iand is then subjected to cutting so as to form a pattern forming an opening in the via; thereafter, it is subjected to etching. The remaining portion of the resist, which still remains irrespective of etching, is completely removed so that an opening11k(seeFIG. 13A) is formed in the via so as to expose the wiring layer11a(which corresponds to an uppermost layer of the substrate11). Herein, the prescribed portions of the oxide film11eand the upper oxide film11iabove the wiring layer11amay still remain in the pad irrespective of etching. Alternatively, etching is performed such that the oxide film11eand the upper oxide film11iare simultaneously removed so as to expose the wiring layer11ain the pad similar to the via.

In a ninth step of the manufacturing method as shown inFIGS. 14A to 14C, a lead film11mcomposed of Cr (which may form the lead films12a-5,12a-6,12a-7,12a-8, and12a-9shown inFIG. 2Ain the latter step) is formed on the upper oxide film11iand the exposed portion of the wiring layer11ain the via (seeFIG. 14A) by way of sputtering, vacuum evaporation, or ion plating. Next, a resist is applied to the upper oxide film11iand the lead film11mand is then subjected to cutting in a prescribed pattern corresponding to the lead film11m, which is ten subjected to etching.

In the above, the resist can be formed in a tapered shape in such a way that etching is appropriately performed on the slopes15aand15bof the projection15, then, heat treatment is performed so as to reshape the cross-sectional shape of the projection15. After completion of etching, the remaining portion of the resist, which still remains on the upper oxide film11i, is removed.

Next, a GMR multilayered film11n(which may form the GMR components12ato12d,12eto12h, and12ito12lin the latter step) is formed on the upper oxide film11iand the lead film11mby way of sputtering. This will be referred to as a GMR element forming step.

In the GMR element forming step, the GMR multilayered film11nis formed by way of the formation of the laminated structure ofFIG. 3A, in which the free layer (or free magnetic layer) F, the conductive spacer layer S composed of Cu having a 2.8 nm (28 Å) thickness, the pin layer (i.e., the fixed layer or fixed magnetization layer) P, and the capping layer C are sequentially laminated on the substrate11.

In the above, the free layer F is constituted of the CoZrNb amorphous magnetic layer12a-21having a 8 nm (80 Å) thickness, the NiFe magnetic layer12a-22having a 3.3 nm (33 Å) thickness, and CoFe layer12a-23having a 1.2 nm (12 Å) thickness, which are sequentially laminated on the substrate11.

In addition, the pin layer F is constituted of the first CoFe magnetic layer12a-25having a 3.2 nm (32 Å) thickness, the Ru layer12a-26having a 0.5 nm (5 Å) thickness, the second CoFe magnetic layer12a-27having a 2.2 nm (22 Å) thickness, and the antiferromagnetic layer12a-28having a 24 nm (240 Å) thickness (composed of a PtMn alloy including Pt ranging from 45 mol % to 55 mol %), which are sequentially laminated above the free layer F via the spacer layer S composed of Cu.

Thereafter, a permanent bar magnet array16shown inFIG. 16is moved close to the substrate11having the GMR multilayered film11nso as to perform magnetization heat treatment (or pinning), thus fixing the magnetization direction of the pin layer P. This will be referred to as a magnetization heat treatment step.

Then, a resist is applied to the surface of the GMR multilayered film11nwith a prescribed thickness, which is set to 2 μm in connection with the planar surface. A mask is placed on the surface of the resist and is then subjected to burning and development so as to remove unnecessary portions of the resist, thus forming a resist film whose pattern matches the pattern of the GMR multilayered film11n(which will be formed in the latter step). In this case, the resist is formed in a tapered shape so as to appropriately perform etching of the projection15and to reshape the cross-sectional shape of the projection15. Thereafter, the prescribed portion of the GMR multilayered film11n, which is not protected by the resist film, is removed via ion milling and is thus formed in a prescribed shape (e.g., a plurality of thin band-like shapes).

Ion milling is performed such that both the GMR multilayered film11nand the lead film11mstill remain in the via. This makes it possible to prevent the lead film11mfrom being broken at the edge of the via.

In a tenth step of the manufacturing method as shown inFIGS. 15A to 15C, a silicon passivation film11o, which includes an oxide film composed of SiO2having a 1500 Å thickness and a nitride film composed of Si3N4having a 5000 Å thickness, are formed on the exposed portion of the oxide film11e, the upper oxide film11i, the lead film11m, and the GMR multilayered film11nby way of plasma CVD. A polyimide film11pis flirter formed on the silicon passivation film11o. Thus, it is possible to completely form a passivation film composed of the silicon passivation film11oand the polyimide film11p.

Using the polyimide film11pas a mask, the silicon passivation film11oand the oxide film11eabove the wiring layer11aare removed by way of etching in the pad, which is thus opened so as to form an electrode pad using the exposed portion of the wiring layer11a. Lastly the substrate11is subjected to cutting, thus completing the production of the three-axial magnetic sensor10shown inFIG. 1A.

The formation of the passivation film and electrode pad is not necessarily limited to the aforementioned procedures. For example, after the formation of the silicon passivation film11o, the silicon passivation film11ois removed by way of etching in the pad, which is thus opened so as to expose the prescribed portion of the wiring layer11a. Next, the polyimide film11pis formed on the silicon passivation film11oand the wiring layer11aso as to form the passivation film. Lastly the polyimide film11pis removed by way of etching so as to expose the wiring layer11aagain in the pad, thus forming the electrode pad using the exposed portion of the wiring layer11a.

FIG. 17is a cross-sectional view taken along line G-G inFIG. 16, which shows only five permanent bar magnets16ato16ein the permanent bar magnet array (or simply referred to as a magnet array)16.

In the magnetization heat treatment (or pitting), the permanent bar magnet array16is positioned in proximity to the backside of the substrate11which is opposite to the GMR multilayered film11nformed on the surface of the substrate11; then, the substrate11and the permanent bar magnet array16are heated at a prescribed temperature ranging from 260° C. to 290° C. in the vacuum state, in which they are left alone for four hours.

In the permanent bar magnet array16shown inFIG. 16, the permanent bar magnets16ato16eare positioned in a lattice form in such a way that the polarity of the upper end of one permanent bar magnet differs from the polarity of the upper end of its adjacent permanent bar magnet. Herein, the permanent bar magnet16ahaving N polarity on its upper end is positioned close to the center portion of the substrate11, and the other permanent bar magnets16b,16c,16d, and16eeach having S polarity on its upper end are positioned to surround the permanent bar magnet16ain prescribed regions outside of the overall area range of the substrate11.

Due to the aforementioned positioning of the permanent bar magnets16ato16ein the permanent bar magnet array16positioned relative to the substrate11, four magnetic fields H are formed due to lines of magnetic forces, which are directed from the N polarity of the permanent bar magnet16a(positioned just below the center portion of the substrate11) to the S polarities of the permanent bar magnets16b,16c,16d, and16ein four directions (see dotted arrows inFIG. 16), which are shifted from each other in phase by 90°. The magnetic fields H are directed from the N polarity of the permanent bar magnet16aso as to reach the backside of the substrate11and to be transmitted through the inside of the substrate11, thus reaching the GMR components (e.g., the X-axis GMR components12ato12d, seeFIG. 17).

The intensity of the magnetic field H to be transmitted through each GMR component will be described with reference toFIG. 18, which substantially shows the pin layer P included in the first X-axis GMR component12a. That is, the intensity of the magnetic field H is set to a prescribed value (e.g., 10 mT or more, 200 mT or less, preferably, 20 mT or more, 80 mT or less) so that the magnetization direction of the first CoFe magnetic layer12a-25substantially matches the magnetization direction of the second CoFe magnetic layer12a-27so as to maintain the anti-parallel state of magnetization between the first and second CoFe magnetic layers12a-25and12a-27, for example.

The first and second CoFe magnetic layers are composed of the same material, whereas the thickness of the first CoFe magnetic layer (32 Å) is larger than the thickness of the second CoFe magnetic layer (22 Å); hence, the magnetic moment of the first CoFe magnetic layer is higher than the magnetic moment of the second CoFe magnetic layer. For this reason, upon application of the aforementioned magnetic field, the first CoFe magnetic layer is magnetized in the same direction as the magnetic field H, while the second CoFe magnetic layer is magnetized in the direction opposite to the direction of the magnetic field H due to antiferromagnetic coupling with the first CoFe magnetic layer.

The Ru layer (e.g.,12a-26, seeFIG. 18) sandwiched between the first and second CoFe magnetic layers is formed with a small thickness of 5 Å, which makes it possible to maintain the anti-parallel state of magnetization between the first and second CoFe magnetic layers even when the magnetic field H is increased in intensity. In other words, as the thickness of the Ru layer is reduced, it is possible to increase the intensity of the magnetic field H while maintaining the anti-parallel state of magnetization between the first and second CoFe magnetic layers.

The substrate11applied with the magnetic field H is heated at a temperature ranging from 260° C. to 290° C. for four hours in the vacuum state, whereby, as shown inFIG. 3B, the magnetization direction of the second CoFe magnetic layer12a-27is lined with the antiferromagnetic layer12a-28in a exchange coupling manner and is thus fixed to be opposite to the direction of the magnetic field H. The magnetization direction of the first CoFe magnetic layer12a-25is fixed in the same direction as the magnetic field H due to the antiferromagnetic connection with the second CoFe magnetic layer12a-27. In short, the magnetization directions of the first and second CoFe magnetic layers12a-25and12a-27are fixed to their original directions that are established due to the magnetic field H applied thereto in the magnetization heat treatment.

InFIG. 19, a region (I) indicates the range of the intensity of the magnetic field H maintaining the anti-parallel state of magnetization between the first and second CoFe magnetic layers12a-25and12a-27in the magnetization heat treatment. The graph ofFIG. 19shows the relationship between the intensity of the magnetic field H (see horizontal axis) and the saturation magnetization of the pin layer P (see vertical axis, which shows the sum of the magnetization intensities of the first and second CoFe magnetic layers12a-25and12a-27applied with the magnetic field H) in the condition in which the thickness of the Ru layer (e.g.,12a-26) is set to 8 Å. Herein, the magnetization intensity regarding each of the first and second CoFe magnetic layers12a-25and12a-27is represented in a positive value when its magnetization direction matches the direction of the magnetic field H but is represented in a negative value when its magnetization direction is opposite to the direction of the magnetic field H.

In the graph ofFIG. 19, when the intensity of the magnetic field H lies in the region (I), the first and second CoFe magnetic layers12a-25and12a-27are magnetized in respective directions while the anti-parallel state of magnetization is maintained between the magnetization directions of the first and second CoFe magnetic layers12a-25and12a-27. Herein, the magnetization vectors of the first and second CoFe magnetic layers12a-25and12a-27form an angle of 180° therebetween, wherein the magnetization intensity of the first CoFe magnetic layer12a-25is higher than the magnetization intensity of the second CoFe magnetic layer12a-27in the region (I). In short, the region (I) shows the preferable range of the intensity of the magnetic field H in the magnetization heat treatment in accordance with the present embodiment.

In a region (III) that is higher than the region (I) in terms of the intensity of the magnetic field H, both the first and second CoFe magnetic layers12a-25and12a-27are magnetized in the same direction as the magnetic field H so that the magnetization directions of the first and second CoFe magnetic layers12a-25and12a-27are set to a parallel state of magnetization. In short, the magnetization vectors of the first and second CoFe magnetic layers12a-25and12a-27form an angle of 0° therebetween in the region (III). The region (III) shows the range of the magnetic field H applied to the GMR component of the synthetic antiferromagnetic structure.

A region (II), which is higher than the region (I) but is lower than the region (III) in terms of the intensity of the magnetic field H, shows the transition from the anti-parallel state to the parallel state and the transition from the parallel state to the anti-parallel state with respect to the magnetization directions of the first and second CoFe magnetic layers12a-25and12a-27. In the region (II), the magnetization vectors of the first and second CoFe magnetic layers12a-25and12a-27form an angle, which is more than 0° and less than 180°.

FIG. 20is a graph showing the relationship between the thickness of the Ru layer and the intensity of the magnetic field H applied to the pin layer P in connection with the graph ofFIG. 19, wherein B1designates variations of the upper-limit value of the intensity of the magnetic field H maintaining the anti-parallel state of magnetization in connection with the boundary between the regions (I) and (II) inFIG. 19, and B2designates variations of the lower-limit value of the intensity of the magnetic field H maintaining the parallel state of magnetization in connection with the boundary between the regions (II) and (III) shown inFIG. 19. As shown inFIG. 20, the anti-parallel state upper-limit value B1and the parallel state lower-limit value B2vary in response to the thickness of the Ru layer, wherein as the thickness of the Ru layer becomes large, the values of both B1and B2become small.

Variations of the anti-parallel state upper-limit value B1are smaller than variations of the parallel state lower-limit value B2with respect to variations of the thickness of the Ru layer. In the conventionally-known technology in which the magnetization heat treatment is performed using the magnetic field H whose intensity lies in the region (III), transition from the region (III) to the region (II) may easily occur due to small variations of the thickness of the Ru layer. In the present embodiment in which the magnetization heat treatment is performed using the magnetic field H whose intensity lies in the region (I), the magnetization directions of the first and second CoFe magnetic layers12a-25and12a-27still remain in the region (I) irrespective of small variations of the thickness of the Ru layer, wherein transition from the region (I) to the region (II) may hardly occur due to small variations of the thickness of the Ru layer. That is, by performing the magnetization heat treatment using the magnetic field H whose intensity lies in the region (I), it is possible to easily form desired GMR components without controlling the thickness of the Ru layer at high precision.

Due to the magnetization heat treatment of the present embodiment, it is possible to fix the magnetization directions of the pin layers P included in the X-axis GMR components12ato12das shown inFIG. 4Ain such a way that the magnetization directions of the X-axis GMR components12aand12bare each fixed to the positive X-axis direction, i.e., the directions a1and b1, while the magnetization directions of the X-axis GMR components12cand12dare each fixed to the negative X-axis direction, i.e., the directions c1and d1.

The magnetization directions of the pin layers P included in the Y1-axis GMR components12eand12fare each fixed to the positive Y-axis direction along the first slopes15aof the projections15(seeFIG. 4B), i.e., the directions e1and f1. The magnetization directions of the pin layers P included in the GMR components12gand12hare each fixed to the negative Y-axis direction along the first slopes15aof the projections15(seeFIG. 4C), i.e., the directions g1and h1.

The magnetization directions of the pin layers P included in the Y2-axis GMR components12iand12jare each fixed to the negative Y-axis direction along the second slopes15bof the projections15(seeFIG. 4C), i.e., the directions i1and j1.

The magnetization directions of the pin layers P included in the GMR components12kand12lare each fixed to the positive Y-axis direction along the second slopes15bof the projections15(seeFIG. 4B), i.e., the directions k1and l1.

Unlike the conventionally-known technology, the manufacturing method of the three-axial magnetic sensor10does not need an intense magnetic field that is applied to GMR components and that is high enough to break the anti-parallel state of magnetization between the first and second CoFe magnetic layers. In the magnetization heat treatment of the present embodiment, a relatively weak magnetic field, which is lower than the conventionally-known magnetic field, is applied to GMR components so that variations of the magnetic field applied to GMR components become small relative to variations of the distance between the substrate11and the permanent bar magnet array16; hence, it is unnecessary to precisely control the positioning of the permanent bar magnet array16relative to the substrate11at high precision and to precisely adjust the distance therebetween at high precision. This makes it possible to easily control the magnetization directions of the pin layers P in the magnetization heat treatment.

As described above, it is possible to easily fix the magnetization directions of the first and second CoFe magnetic layers to desired directions with respect to each of the pin layers P of the GMR components formed on the planar surfaces, and the first slopes15aand the second slopes15bof the projections15on the substrate11; hence, it is possible to easily produce the three-axial magnetic sensor10.

Since the thickness of the first CoFe magnetic layer is larger than the thickness of the second CoFe magnetic layer, it is possible to reliably increase the magnetic moment of the first CoFe magnetic layer to be higher than the magnetic moment of the second CoFe magnetic layer. That is, it is possible to fix the magnetization directions of the first and second CoFe magnetic layers to desired directions while maintaining the anti-parallel state of magnetization therebetween in the magnetization heat treatment.

Magnetic forces of the first and second CoFe magnetic layers included in the pin layer P are exerted on the free layer F, wherein they may include a exchange coupling force of the first CoFe magnetic layer and magnetostatic forces due to magnetic fields of the first and second CoFe magnetic layers. Since the magnetic moment of the first CoFe magnetic layer is increased to be higher than the magnetic moment of the second CoFe magnetic layer, it is possible to easily reduce the sum of the exchange coupling force and magnetostatic forces applied to the free layer F.

The intensities of the exchange coupling force and magnetostatic force of the first CoFe magnetic layer exerted on the free layer F can be made substantially identical to each other by appropriately adjusting the thickness of the spacer layer S, for example. When the magnetic moment of the second CoFe magnetic layer is decreased to be smaller than the magnetic moment of the first CoFe magnetic layer, it is possible to reduce the magnetostatic force of the second CoFe magnetic layer exerted on the free layer F to be lower than the exchange coupling force and magnetostatic force of the first CoFe magnetic layer.

The direction of the exchange coupling force of the first CoFe magnetic layer is opposite to the direction of the magnetostatic force of the first CoFe magnetic layer and is identical to the direction of the magnetostatic force of the second CoFe magnetic layer; hence, it is possible to easily reduce the sum of the exchange coupling force and magnetostatic force of the first CoFe magnetic layer exerted on the free layer F. That is, it is possible to reduce the influence of the magnetic forces of the first and second CoFe magnetic layers with respect to the magnetization direction of the free layer F; thus, it is possible to set a desired magnetization direction of the free layer F.

By reducing the thickness of the Ru layer, it is possible to increase the range of the intensity of the magnetic field H applied to the pin layer P while maintaining the anti-parallel state of magnetization between the first and second CoFe magnetic layers (seeFIG. 20). This makes it possible to easily control the intensity of the magnetic field H in the magnetization heat treatment; hence, it is possible to easily control the magnetization directions with respect to the pin layer P.

In the magnetization heat treatment in which the permanent bar magnet array16is positioned close to the backside of the substrate11, even when a relatively high magnetic field H is produced in proximity to the permanent bar magnet array16, it is possible to easily reduce the intensity of the magnetic field H reaching the first and second CoFe magnetic layers of the pin layer P included in each GMR component because the permanent bar magnet array16is distanced from each GMR component by the thickness of the substrate11.

Since the present embodiment is designed to reduce variations of the magnetic field H relative to variations of the distance between the substrate11and the permanent bar magnet away16(seeFIG. 20), it is possible to easily control the intensity of the magnetic field H applied to each GMR component.

The present embodiment is not necessarily limited to the aforementioned values with regard to the thickness of the first and second CoFe magnetic layers and the Ru layer, wherein it is simply required that the thickness of the first CoFe magnetic layer be larger than the thickness of the second CoFe magnetic layer. In addition, it is possible to set different thicknesses to the first and second CoFe magnetic layers when the magnetic forces of the first and second CoFe magnetic layers exerted on the free layer F are not necessarily considered in manufacturing of the three-axial magnetic sensor10. It is simply required that the thickness of the Ru layer be set to a prescribed value as long as it increases the range of the intensity of the magnetic field H maintaining the anti-parallel state of magnetization between the first and second CoFe magnetic layers. That is, it is preferable that the thickness of the Ru layer ranges from 4 Å to 10 Å.

The present embodiment is designed such that the Ru layer is directly sandwiched between the first and second CoFe magnetic layers both composed of the same material in the pin layer P; but this is not a restriction. That is, it is possible to form first and second magnetic layers composed of different materials. In this case, it is necessary to select appropriate materials such that the magnetic moment of the first magnetic layer differs from the magnetic moment of the second magnetic layer, wherein it is possible to set the same thickness to the first and second magnetic layers.

The present embodiment is designed such that the Y1-axis GMR component and Y2-axis GMR component are formed on the first slope15aand the second slope15bof the same projection15; but this is not a restriction. It is simply required that the Y1-axis GMR component and Y2-axis GMR component be formed on different slopes, which are inclined in different directions; hence, it is possible to individually form them using different projections.

The present embodiment is designed such that the GMR components are formed on the planar surfaces of the substrate11as well as the first slopes15aand the second slopes15bof the projections15on the substrate11, thus producing the three-axial magnetic sensor10sensing magnetic fields in three axial directions; but this is not a restriction. That is, the present embodiment can be adapted to two-axial magnetic sensors or one-axial magnetic sensors.

Lastly, the present invention is not necessary limited to the present embodiment, which can be further modified in a variety of ways without departing from the essentials thereof and within the scope of the invention as defined in the appended claims.