Patent Publication Number: US-2023135336-A1

Title: Magnetic sensor and its manufacturing method

Description:
RELATED APPLICATIONS 
     This application is a Continuation of U.S. patent application Ser. No. 17/131,142, filed Dec. 22, 2020, which claims the benefit of Japanese Patent Application No. 2020-057483, filed Mar. 27, 2020. The disclosure of the prior applications is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a magnetic sensor including a magnetoresistive element and its manufacturing method. 
     2. Description of the Related Art 
     Magnetic sensors have been used for a variety of applications. Examples of known magnetic sensors include one that uses a spin-valve magnetoresistive element provided on a substrate. The spin-valve magnetoresistive element includes a magnetization pinned layer having a magnetization whose direction is fixed, a free layer having a magnetization whose direction is variable depending on the direction of an applied magnetic field, and a gap layer located between the magnetization pinned layer and the free layer. In many cases, the spin-valve magnetoresistive element provided on a substrate is configured to have sensitivity to a magnetic field in a direction parallel to the surface of the substrate. Such a magnetoresistive element is thus suitable to detect a magnetic field that changes in direction within a plane parallel to the substrate surface. 
     On the other hand, a system including a magnetic sensor may be intended to detect a magnetic field containing a component in a direction perpendicular to the surface of a substrate by using a magnetoresistive element provided on the substrate. In such a case, the magnetic field containing the component in the direction perpendicular to the surface of the substrate can be detected by providing a soft magnetic body for converting a magnetic field in the direction perpendicular to the surface of the substrate into a magnetic field in the direction parallel to the surface of the substrate or locating the magnetoresistive element on an inclined surface formed on the substrate. 
     JP 2001-102659 A describes a magnetoresistive element that is formed on a substrate and includes a plurality of magnetic tunnel junction structures connected in series. In this magnetoresistive element, lower and upper electrodes connect a pair of adjoining magnetic tunnel junction structures. JP 2001-102659 A also describes formation of a layered structure including lower electrodes on the substrate by etching off outer peripheral ends of the lower electrodes by ion beam etching (ion milling) using an ion milling apparatus. 
     EP 3199965 A1 describes a magnetic sensor including a magnetic detection unit that includes a plurality of magnetoresistive elements formed on a substrate and has a magnetic sensing axis in a direction parallel to the plane of the substrate. In this magnetic sensor, lower and upper electrodes connect two adjoining magnetoresistive elements. This magnetic sensor further includes a magnetic converging unit including a plurality of magnetic converging members made of a soft magnetic material. This magnetic sensor detects magnetic fields in X-, Y-, and Z-axis directions by converting the direction of an external magnetic field into the direction of the magnetic sensing axis with the plurality of magnetic converging members. 
     US 2008/0169807 A1 describes a magnetic sensor including X-, Y-, and Z-axis sensors located on a thick substrate film. In this magnetic sensor, a plurality of magnetic sensing portions of a giant magnetoresistive element constituting the Z-axis sensor are located on midsections of inclined surfaces of a V-shaped groove formed in the thick substrate film. This magnetic sensor also includes a bias magnet portion that connects two magnetic sensing portions formed on two adjoining inclined surfaces. US 2008/0169807 A1 also describes formation of the bias magnet portion by depositing a magnet film for making the bias magnet portion over the entire substrate surface and then removing unneeded portions by etching. 
     Like the Z-axis sensor described in US 2008/0169807 A1, a magnetic sensor including a magnetoresistive element located on an inclined surface can increase the occupation area of the magnetoresistive element per unit area, compared to the magnetic sensor described in EP 3199965 A1. Suppose that a magnetic sensor includes a plurality of magnetoresistive elements located on an inclined surface. In this magnetic sensor, the plurality of magnetoresistive elements located on the one inclined surface are connected by lower and upper electrodes. The occupation area of the magnetoresistive elements per unit area can be increased by reducing a dimension (hereinafter, referred to as a width) of the inclined surface in a direction (hereinafter, referred to as a width direction) orthogonal to the direction of arrangement of the plurality of magnetoresistive elements. 
     However, the smaller the width of the inclined surface, the smaller the width of the lower electrodes. On the other hand, in view of increasing the occupation area of the magnetoresistive elements per unit area, the width of the magnetoresistive elements is not much reduced with the reduction in the width of the inclined surface. In other words, the smaller the width of the inclined surface, the smaller the width of the lower electrodes becomes relative to the width of the magnetoresistive elements. As a result, the distances from both ends of the lower electrodes in the width direction to the magnetoresistive elements decrease. 
     As described in JP 2001-102659 A and US 2008/0169807 A1, the lower electrodes are formed by etching a metal film by ion milling, for example. If the metal film is etched by ion milling, etched and scattered substances of the metal film can adhere to the metal film and the like to form re-deposition films on the surface of the lower electrodes etc. The re-deposition films are formed in regions within a predetermined range from both ends of the lower electrodes. If the distances from both ends of the lower electrodes to the magnetoresistive elements decrease as described above, there occur problems such as formation of the magnetoresistive elements on the re-deposition films and a short circuit caused by contact of the re-deposition films with the upper electrodes. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a magnetic sensor that includes a magnetoresistive element located on an inclined portion and is configured so that the occurrence of the problems due to a reduction in the width of the inclined portion can be prevented, and its manufacturing method. 
     A magnetic sensor according to the present invention includes a magnetoresistive element whose resistance changes with an external magnetic field, and a support member that supports the magnetoresistive element. The support member includes a top surface opposed to the magnetoresistive element and a bottom surface located on a side opposite to the top surface. The top surface of the support member includes an inclined portion inclined relative to the bottom surface. 
     The magnetoresistive element includes a main body, and a lower electrode and an upper electrode that supply a current to the main body. The main body is located on the inclined portion. The lower electrode is interposed between the main body and the inclined portion. The upper electrode is located on the main body. 
     The inclined portion includes a lower end closest to the bottom surface and an upper end farthest from the bottom surface. The lower electrode includes a first end closest to the lower end of the inclined portion and a second end closest to the upper end of the inclined portion. The main body is located at a position closer to the second end of the lower electrode than to the first end of the lower electrode. 
     In the magnetic sensor according to the present invention, a distance from the upper end of the inclined portion to the first end of the lower electrode may be smaller than or greater than a distance from the upper end of the inclined portion to the lower end of the inclined portion. 
     In the magnetic sensor according to the present invention, the upper electrode may include a third end closest to the lower end of the inclined portion. A distance from the main body to the third end of the upper electrode may be smaller than a distance from the main body to the first end of the lower electrode. 
     A manufacturing method for a magnetic sensor according to the present invention includes a step of forming the magnetoresistive element and a step of forming the support member. The step of forming the magnetoresistive element includes a step of forming the main body, a step of forming the lower electrode, and a step of forming the upper electrode. 
     The step of forming the lower electrode includes a step of forming a metal film on the support member, a step of forming an etching mask, and an etching step of etching the metal film by using the etching mask so that the metal film makes the lower electrode. The etching mask has an undercut that forms a space between the etching mask and an underlayer of the etching mask. 
     In the manufacturing method for a magnetic sensor according to the present invention, the undercut may form a first space closest to the lower end of the inclined portion and a second space closest to the upper end of the inclined portion. A maximum dimension of the first space in a first direction perpendicular to the bottom surface of the support member may be greater than a maximum dimension of the second space in the first direction. A dimension of the first space in a second direction parallel to a direction from the lower end to the upper end of the inclined portion may be greater than a dimension of the second space in the second direction. 
     In the manufacturing method for a magnetic sensor according to the present invention, the step of forming the etching mask may include forming the etching mask on the metal film. In such a case, the step of forming the main body may be performed after the etching step. 
     In the magnetic sensor and its manufacturing method according to the present invention, the magnetoresistive element includes the main body, the lower electrode, and the upper electrode. The lower electrode includes the first end closest to the lower end of the inclined portion and the second end closest to the upper end of the inclined portion. The main body is located at a position closer to the second end of the lower electrode than to the first end of the lower electrode. According to the present invention, the magnetic sensor including the magnetoresistive element located on the inclined portion can thus prevent the occurrence of the problems due to a reduction in the width of the inclined portion. 
     Other and further objects, features and advantages of the present invention will appear more fully from the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view showing a schematic configuration of a magnetic sensor system of an embodiment of the invention. 
         FIG.  2    is a perspective view showing a magnetic sensor according to the embodiment of the invention. 
         FIG.  3    is a plan view showing a magnetic sensor according to the embodiment of the invention. 
         FIG.  4    is a sectional view showing a cross section of the magnetic sensor according to the embodiment of the invention. 
         FIG.  5    is a circuit diagram showing the circuit configuration of the magnetic sensor according to the embodiment of the invention. 
         FIG.  6    is a cross-sectional view illustrating a step of a manufacturing method for the magnetic sensor according to the embodiment of the invention. 
         FIG.  7    is a cross-sectional view illustrating a step that follows the step in  FIG.  6   . 
         FIG.  8    is a cross-sectional view illustrating a step that follows the step in  FIG.  7   . 
         FIG.  9    is a cross-sectional view illustrating a step that follows the step in  FIG.  8   . 
         FIG.  10    is a cross-sectional view illustrating a step that follows the step in  FIG.  9   . 
         FIG.  11    is a cross-sectional view showing a cross section of a modification example of the magnetic sensor according to the embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A preferred embodiment of the present invention will now be described in detail with reference to the drawings. An outline of a magnetic sensor system including a magnetic sensor according to the embodiment of the present invention will initially be described with reference to  FIG.  1   . A magnetic sensor system  100  according to the present embodiment includes a magnetic sensor  1  according to the present embodiment and a magnetic field generator  5 . The magnetic field generator  5  generates a target magnetic field MF that is a magnetic field for the magnetic sensor  1  to detect (magnetic field to be detected). 
     The magnetic field generator  5  is rotatable about the rotation axis C. The magnetic field generator  5  includes a pair of magnets  6 A and  6 B. The magnets  6 A and  6 B are arranged at symmetrical positions with a virtual plane including the rotation axis C at the center. The magnets  6 A and  6 B each have an N pole and an S pole. The magnets  6 A and  6 B are located in an orientation such that the N pole of the magnet  6 A is opposed to the S pole of the magnet  6 B. The magnetic field generator  5  generates the target magnetic field MF in the direction from the N pole of the magnet  6 A to the S pole of the magnet  6 B. 
     The magnetic sensor  1  is located at a position where the target magnetic field MF at a predetermined reference position can be detected. The reference position may be located on a rotation axis C. In the following description, the reference position is located on the rotation axis C. The magnetic sensor  1  detects the target magnetic field MF generated by the magnetic field generator  5 , and generates a detection value Vs. The detection value Vs has a correspondence with a relative position, or rotational position in particular, of the magnetic field generator  5  with respect to the magnetic sensor  1 . 
     The magnetic sensor system  100  can be used as a device for detecting the rotational position of a rotatable moving part in an apparatus that includes the moving part. Examples of such an apparatus include a joint of an industrial robot.  FIG.  1    shows an example where the magnetic sensor system  100  is applied to an industrial robot  200 . 
     The industrial robot  200  shown in  FIG.  1    includes a moving part  201  and a support unit  202  that rotatably supports the moving part  201 . The moving part  201  and the support unit  202  are connected at a joint. The moving part  201  rotates about a rotation axis C. For example, if the magnetic sensor system  100  is applied to the joint of the industrial robot  200 , the magnetic sensor  1  may be fixed to the support unit  202 , and the magnets  6 A and  6 B may be fixed to the moving part  201 . 
     Now, we define X, Y, and Z directions as shown in  FIG.  1   . The X, Y, and Z directions are orthogonal to one another. In the present embodiment, a direction parallel to the rotation axis C (in  FIG.  1   , a direction out of the plane of the drawing) will be referred to as the X direction. In  FIG.  1   , the Y direction is shown as a rightward direction, and the Z direction is shown as an upward direction. The opposite directions to the X, Y, and Z directions will be referred to as −X, −Y, and −Z directions, respectively. The direction of the target magnetic field MF rotates within the YZ plane, about the reference position on the rotation axis C. 
     Next, a configuration of the magnetic sensor  1  according to the present embodiment will be described with reference to  FIGS.  2  to  5   .  FIG.  2    is a perspective view showing a magnetic sensor  1 .  FIG.  3    is a plan view showing a magnetic sensor  1 .  FIG.  4    is a sectional view showing a cross section of the magnetic sensor  1 .  FIG.  5    is a circuit diagram showing the circuit configuration of the magnetic sensor  1 . 
     The magnetic sensor  1  includes at least one magnetoresistive element whose resistance changes with an external magnetic field, and a support member  60  that supports the at least one magnetoresistive element. A magnetoresistive element will hereinafter be referred to as an MR element. The at least one MR element is each configured to be able to detect the target magnetic field MF. In the present embodiment, the magnetic sensor  1  includes four MR elements  10 ,  20 ,  30 , and  40  as the at least one MR element. 
     As shown in  FIGS.  2  and  4   , the support member  60  includes a top surface  60   a  opposed to the MR elements  10 ,  20 ,  30 , and  40 , and a bottom surface  60   b  located on a side opposite to the top surface  60   a . The top surface  60   a  is located at an end of the support member  60  in the Z direction. The bottom surface  60   b  is located at an end of the support member  60  in the −Z direction. The bottom surface  60   b  is parallel to the XY plane. 
     The top surface  60   a  of the support member  60  includes at least one inclined portion inclined relative to the bottom surface  60   b . In the present embodiment, the top surface  60   a  of the support member  60  includes two inclined portions  60   a   1  and  60   a   2  symmetrical about a ZX plane. The entirety of each of the inclined portions  60   a   1  and  60   a   2  is perpendicular to the YZ plane and inclined relative to the XY plane. 
     As shown in  FIG.  4   , the inclined portion  60   a   1  includes a lower end Ea closest to the bottom surface  60   b  and an upper end Eb farthest from the bottom surface  60   b . The lower end Ea of the inclined portion  60   a   1  is located at an end of the inclined portion  60   a   1  in the Y direction. The upper end Eb of the inclined portion  60   a   1  is located at an end of the inclined portion  60   a   1  in the −Y direction. 
     As shown in  FIG.  4   , the inclined portion  60   a   2  includes a lower end Ec closest to the bottom surface  60   b  and an upper end Ed farthest from the bottom surface  60   b . The lower end Ec of the inclined portion  60   a   2  is located at an end of the inclined portion  60   a   2  in the −Y direction. The upper end Ed of the inclined portion  60   a   2  is located at an end of the inclined portion  60   a   2  in the Y direction. 
     The top surface  60   a  of the support member  60  further includes three flat portions  60   a   3 ,  60   a   4 , and  60   a   5 . The flat portion  60   a   3  is connected to the lower end Ea of the inclined portion  60   a   1 . The flat portion  60   a   4  is connected to the lower end Ec of the inclined portion  60   a   2 . The flat portion  60   a   5  is connected to the upper end Eb of the inclined portion  60   a   1  and the upper end Ed of the inclined portion  60   a   2 . All the flat portions  60   a   3  to  60   a   5  are parallel to the XY plane. 
     In view of the manufacturing precision and the like of the magnetic sensor  1 , the inclined portions  60   a   1  and  60   a   2  may be curved. In such a case, the upper end Eb of the inclined portion  60   a   1  and the upper end Ed of the inclined portion  60   a   2  may be connected to each other. 
     The MR elements  10  and  20  are located on the inclined portion  60   a   1 . The MR elements  30  and  40  are located on the inclined portion  60   a   2 . As shown in  FIGS.  2    and  3 , the MR elements  10  and  20  are arranged in a row in this order along the −X direction. The MR elements  30  and  40  are arranged in a row in this order along the −X direction, at positions in front of the MR elements  10  and  20  in the −Y direction. The set of MR elements  10  and  20  and the set of MR elements  30  and  40  may be located symmetrically about the XZ plane. 
     Each of the MR elements  10 ,  20 ,  30 , and  40  includes at least one MR element main body, and at least one lower electrode and at least one upper electrode that supply a current to the at least one MR element main body. In the present embodiment, each of the MR elements  10 ,  20 ,  30 , and  40  includes two MR element main bodies, one lower electrode, and two upper electrodes as the at least one MR element main body, the at least one lower electrode, and the at least one upper electrode. 
     The MR elements  10  and  20  have the same configuration. The following description serves as both a description of the MR element  10  (with reference numerals before parentheses) and a description of the MR element  20  (with parenthesized reference numerals). The MR element  10  ( 20 ) includes MR element main bodies  11  and  12  ( 21  and  22 ), a lower electrode  13  ( 23 ), and upper electrodes  14  and  15  ( 24  and  25 ), and is located on the inclined portion  60   a   1 . The lower electrode  13  ( 23 ) is interposed between the MR element main bodies  11  and  12  ( 21  and  22 ) and the inclined portion  60   a   1 . The upper electrode  14  ( 24 ) is located on the MR element main body  11  ( 21 ). The upper electrode  15  ( 25 ) is located on the MR element main body  12  ( 22 ). Each of the MR element main bodies  11  and  12  ( 21  and  22 ) has a bottom surface facing the lower electrode  13  ( 23 ) and a top surface on the opposite side. 
     The MR elements  30  and  40  have the same configuration. The following description serves as both a description of the MR element  30  (with reference numerals before parentheses) and a description of the MR element  40  (with parenthesized reference numerals). The MR element  30  ( 40 ) includes MR element main bodies  31  and  32  ( 41  and  42 ), a lower electrode  33  ( 43 ), and upper electrodes  34  and  35  ( 44  and  45 ), and is located on the inclined portion  60   a   2 . The lower electrode  33  ( 43 ) is interposed between the MR element main bodies  31  and  32  ( 41  and  42 ) and the inclined portion  60   a   2 . The upper electrode  34  ( 44 ) is located on the MR element main body  31  ( 41 ). The upper electrode  35  ( 45 ) is located on the MR element main body  32  ( 42 ). Each of the MR element main bodies  31  and  32  ( 41  and  42 ) has a bottom surface facing the lower electrode  33  ( 43 ) and a top surface on the opposite side. 
     As shown in  FIGS.  2  and  3   , the MR element main bodies  11 ,  12 ,  21  and  22  are arranged in a row in this order along the −X direction. The MR element main bodies  31 ,  32 ,  41  and  42  are arranged in a row in this order along the −X direction, at positions in front of the MR element main bodies  11 ,  12 ,  21  and  22  in the −Y direction. The set of MR element main bodies  11 ,  12 ,  21  and  22  and the set of MR element main bodies  31 ,  32 ,  41  and  42  may be located symmetrically about the XZ plane. 
     The magnetic sensor  1  further includes a lead electrode  51  connected to the border of the upper electrodes  15  and  24 , and a lead electrode  52  connected to the border of the upper electrodes  35  and  44 . The lower electrodes  13 ,  23 ,  33 , and  43 , the upper electrodes  14 ,  15 ,  24 ,  25 ,  34 ,  35 ,  44 , and  45 , and the lead electrodes  51  and  52  are made of a conductive material such as Cu, for example. In  FIG.  2   , the upper electrodes  14 ,  15 ,  24 ,  25 ,  34 ,  35 ,  44 , and  45  and the lead electrodes  51  and  52  are omitted. 
     As shown in  FIGS.  2  and  4   , the support member  60  includes a substrate  61  and an insulating layer  62  located on the substrate  61 . The substrate  61  is a semiconductor substrate made of a semiconductor such as Si, for example. The substrate  61  has a top surface located at an end of the substrate  61  in the Z direction, and a bottom surface located at an end of the substrate  61  in the −Z direction. The bottom surface  60   b  of the support member  60  is constituted by the bottom surface of the substrate  61 . The substrate  61  has a constant thickness (dimension in the Z direction). 
     The insulating layer  62  is made of an insulating material such as SiO 2 , for example. The insulating layer  62  includes a top surface located at an end in the Z direction. The top surface  60   a  of the support member  60  is constituted by the top surface of the insulating layer  62 . The insulating layer  62  has a minimum thickness (dimension in the Z direction) near the ends of the insulating layer  62  in the Y and −Y directions, and a maximum thickness near the center of the insulating layer  62  in a direction parallel to the Y direction. 
     The lower electrodes  13 ,  23 ,  33 , and  43  are located on the top surface  60   a  of the support member  60 , i.e., on the top surface of the insulating layer  62 . As shown in  FIG.  4   , the magnetic sensor  1  further includes insulating layers  63 ,  64  and  65 . The insulating layer  63  is located on the top surface of the insulating layer  62 , around the lower electrodes  13 ,  23 ,  33 , and  43 . As shown in  FIG.  2   , the MR element main bodies  11 ,  12 ,  21 ,  22 ,  31 ,  32 ,  41 , and  42  are located on the lower electrodes  13 ,  23 ,  33 , and  43 . 
     The insulating layer  64  is located on the lower electrodes  13 ,  23 ,  33 , and  43  and the insulating layer  63 , around the MR element main bodies  11 ,  12 ,  21 ,  22 ,  31 ,  32 ,  41 , and  42 . The upper electrodes  14 ,  15 ,  24 ,  25 ,  34 ,  35 ,  44 , and  45  are located on the MR element main bodies  11 ,  12 ,  21 ,  22 ,  31 ,  32 ,  41 , and  42 , respectively (see  FIG.  3   ), and on the insulating layer  64  (see  FIG.  4   ). 
     The lead electrodes  51  and  52  are located on the insulating layer  64 . The insulating layer  65  is located on the insulating layer  64 , around the upper electrodes  14 ,  15 ,  24 ,  25 ,  34 ,  35 ,  44 , and  45  and the lead electrodes  51  and  52 . In  FIGS.  2  and  3   , the insulating layers  63  to  65  are omitted. 
     The magnetic sensor  1  may further include a non-shown insulating layer covering the foregoing upper electrodes, the lead electrodes  51  and  52 , and the insulating layer  65 . The insulating layers  63  to  65  and the non-shown insulating layer are made of an insulating material such as SiO 2 , for example. 
     As shown in  FIG.  5   , the magnetic sensor  1  further includes power supply nodes V 1  and V 2 , ground nodes G 1  and G 2 , and signal output nodes E 11  and E 12 . Predetermined magnitude of power supply voltages are applied to the power supply nodes V 1  and V 2 . The ground nodes G 1  and G 2  are grounded. 
     The MR element  10  is arranged between the power supply node V 1  and the signal output node E 1 . The MR element main bodies  11  and  12  are connected in series in this order from the power supply node V 1  side. The upper electrode  14  is electrically connected to the power supply node V 1 . The upper electrode  15  is electrically connected to the signal output node E 1  via the lead electrode  51 . 
     The MR element  20  is arranged between the signal output node E 1  and the ground node G 1 . The MR element main bodies  21  and  22  are connected in series in this order from the signal output node E 1  side. The upper electrode  24  is electrically connected to the signal output node E 1  via the lead electrode  51 . The upper electrode  25  is electrically connected to the ground node G 1 . 
     The MR element  30  is arranged between the power supply node V 2  and the signal output node E 2 . The MR element main bodies  31  and  32  are connected in sense in this order from the power supply node V 2  side. The upper electrode  34  is electrically connected to the power supply node V 2 . The upper electrode  35  is electrically connected to the signal output node E 2  via the lead electrode  52 . 
     The MR element  40  is arranged between the signal output node E 2  and the ground node G 2 . The MR element main bodies  41  and  42  are connected in series in this order from the signal output node E 2  side. The upper electrode  44  is electrically connected to the signal output node E 2  via the lead electrode  52 . The upper electrode  45  is electrically connected to the ground node G 2 . 
     In terms of circuit configuration, the MR element main bodies  12  and  21  are connected in series. The signal output node E 1  outputs a signal corresponding to the potential of the connection point between the MR element main bodies  12  and  21  as a detection signal S 1 . 
     In terms of circuit configuration, the MR element main bodies  32  and  41  are connected in series. The signal output node E 2  outputs a signal corresponding to the potential of the connection point between the MR element main bodies  32  and  41  as a detection signal S 2 . 
     The magnetic sensor  1  further includes a detection value generation circuit  53  that generates the detection value Vs on the basis of the detection signals S 1  and S 2 . The detection value Vs depends on the detection signals S 1  and S 2 . The detection value generation circuit  53  includes an application specific integrated circuit (ASIC) or a microcomputer, for example. 
     The substrate  61  and the portions of the magnetic sensor  1  stacked on the substrate  61  are referred to collectively as a detection unit.  FIGS.  1  to  4    can be said to show the detection unit. The detection value generation circuit  53  may be integrated with or separate from the detection unit. 
     The configuration of the MR elements  10 ,  20 ,  30  and  40  will now be described in detail. In the present embodiment, in particular, each of the MR elements  10 ,  20 ,  30  and  40  is a spin-valve MR element. Each of the MR element main bodies  11 ,  12 ,  21 ,  22 ,  31 ,  32 ,  41 , and  42  includes a magnetization pinned layer having a magnetization whose direction is fixed, a free layer having a magnetization whose direction is variable depending on the direction of an external magnetic field, and a gap layer located between the magnetization pinned layer and the free layer. Each of the MR elements  10 ,  20 ,  30  and  40  may be a tunneling magnetoresistive element (TMR) element or a giant magnetoresistive element (GMR) element. In the TMR element, the gap layer is a tunnel barrier layer. In the GMR element, the gap layer is a nonmagnetic conductive laver. The resistances of the MR elements  10 ,  20 ,  30  and  40  change with an angle that the direction of the magnetization of the free layer forms with respect to the direction of the magnetization of the magnetization pinned layer. The resistance is minimized if the angle is 0°. The resistance is maximized if the angle is 180°. In each of the MR elements  10 ,  20 ,  30 , and  40 , the free layer has a shape anisotropy that sets the direction of the magnetization easy axis to be orthogonal to the magnetization direction of the magnetization pinned layer. In  FIG.  5   , the filled arrows indicate the directions of the magnetizations of the magnetization pinned layers included in the respective MR element main bodies  11 ,  12 ,  21 ,  22 ,  31 ,  32 ,  41 , and  42 . 
     Next, an electrical connection relationship between the MR element main bodies, the lower electrodes, and the upper electrodes in the MR elements  10 ,  20 ,  30 , and  40  will be described. The following description serves as both a description of the electrical connection relationship in the MR elements  10  and  20  (with reference numerals before parentheses) and a description of the electrical connection relationship in the MR elements  30  and  40  (with parenthesized reference numerals). The lower electrode  13  ( 33 ) electrically connects the bottom surfaces of the respective MR element main bodies  11  and  12  ( 31  and  32 ). The upper electrodes  15  and  24  ( 35  and  44 ) electrically connect the top surfaces of the respective MR element main bodies  12  and  21  ( 32  and  42 ). The lower electrode  23  ( 43 ) electrically connects the bottom surfaces of the respective MR element main bodies  21  and  22  ( 41  and  42 ). 
     Next, a positional relationship between the MR element main bodies, the lower electrode, and the upper electrodes in each of the MR elements  10 ,  20 ,  30 , and  40  will be described. The positional relationship between the MR element main bodies  11  and  12  and the lower electrode  13  in the MR element  10  will initially be described with reference to  FIG.  4   . The lower electrode  13  includes a first end  13   a  closest to the lower end Ea of the inclined portion  60   a   1  and a second end  13   b  closest to the upper end Eb of the inclined portion  60   a   1 . 
     The entire lower electrode  13  is located on the inclined portion  60   a   1 . The distance from the upper end Eb of the inclined portion  60   a   1  to the first end  13   a  of the lower electrode  13  is smaller than that from the upper end Eb to the lower end Ea of the inclined portion  60   a   1 . 
     The MR element main body  11  is located at a position closer to the second end  13   b  than to the first end  13   a . The distance from the second end  13   b  to the MR element main body  11  is smaller than that from the first end  13   a  to the MR element main body  11 . The same applies to the MR element main body  12 . 
     The description of the positional relationship between the MR element main bodies  1 I and  12  and the lower electrode  13  in the MR element  10  also applies to the positional relationship between the MR element main bodies  21  and  22  and the lower electrode  23  in the MR element  20  if the reference numerals  11 ,  12 , and  13  are replaced with the reference numerals  21 ,  22 , and  23 , respectively. 
     Next, the positional relationship between the MR element main bodies  31  and  32  and the lower electrode  33  in the MR element  30  will be described with reference to  FIG.  4   . The lower electrode  33  has a first end  33   a  closest to the lower end Ec of the inclined portion  60   a   2  and a second end  33   b  closest to the upper end Ed of the inclined portion  60   a   2 . The description of the positional relationship between the MR element main bodies  11  and  12  and the lower electrode  13  in the MR element  10  also applies to the positional relationship between the MR element main bodies  31  and  32  and the lower electrode  33  in the MR element  30  if the reference numerals  11 ,  12 ,  13 ,  13   a ,  13   b ,  60   a   1 , Ea and Eb are replaced with the reference numerals  31 ,  32 ,  33 ,  33   a ,  33   b ,  60   a   2 , Ec and Ed, respectively. The description of the positional relationship between the MR element main bodies  31  and  32  and the lower electrode  33  in the MR element  30  also applies to the positional relationship between the MR element main bodies  41  and  42  and the lower electrode  43  in the MR element  40  if the reference numerals  31 ,  32 , and  33  are replaced with the reference numerals  41 ,  42 , and  43 , respectively. 
     Now, a manufacturing method for the magnetic sensor  1  according to the present embodiment will be described with reference to  FIG.  6    to  FIG.  10   . The manufacturing method for the magnetic sensor  1  includes steps of forming the portions of the magnetic sensor  1  shown in  FIGS.  1  to  4   , i.e., the detection unit, and steps of completing the magnetic sensor  1  by using the detection unit.  FIGS.  6  to  10    show the steps of forming the detection unit. 
     As shown in  FIG.  6   , in the steps of forming the detection unit, the insulating layer  62  is initially formed on the substrate  61 . The insulating layer  62  may be formed by forming a photoresist mask on the substrate  61  and then forming an insulating film. The insulating layer  62  may be formed by forming an insulating film on the substrate  61  and then etching a part of the insulating film. The formation of the insulating layer  62  completes the support member  60 . Next, a metal film  71  for eventually making the lower electrodes  13 ,  23 ,  33 , and  43  is formed on the insulating layer  62 , i.e., on the support member  60 . The metal film  71  is formed to cover the entire top surface of the insulating layer  62 . 
       FIG.  7    shows the next step. In this step, first to fourth etching masks  81  are initially formed on the metal film  71 . The first, second, third, and fourth etching masks  81  are used to form the lower electrodes  13 ,  23 ,  33 , and  43 , respectively.  FIG.  7    shows the first etching mask  81 . 
     Each of the first to fourth etching masks  81  has an undercut  81 C. The undercut  81 C forms a space between the etching mask  81  and an underlayer of the etching mask  81 . In the present embodiment, each of the first to fourth etching masks  81  includes a lower layer  81 A located on the metal film  71  and an upper layer  81 B located on the lower layer  81 A. The upper layer  81 B is made of a photoresist patterned by photolithography. The lower laver  81 A is made of a material that dissolves in a developing agent used in patterning the upper layer  81 B, for example. The undercut  81 C is formed by removing a part of the lower layer  81 A in patterning the upper layer  81 B. 
     In the step shown in  FIG.  7   , an etching step of etching the metal film  71  is then performed by ion milling, for example, using the first to fourth etching masks  81  so that the metal film  71  makes the lower electrodes  13 ,  23 ,  33 , and  43 . As described above, each of the first to fourth etching masks  81  has the undercut  81 C. In the etching step, etched and scattered substances of the metal film  71  enter the space formed by the undercut  81 C to form a re-deposition film on the surface of each of the lower electrodes  13 ,  23 ,  33 , and  43 . In  FIG.  7   , the reference numeral  91  represents the re-deposition film formed on the surface of the lower electrode  13 , near the first end  13   a  of the lower electrode  13 . The reference numeral  92  represents the re-deposition film formed on the surface of the lower electrode  13 , near the second end  13   b  of the lower electrode  13 . 
     Although not shown in the drawings, re-deposition films similar to the re-deposition films  91  and  92  are also formed on the surface of each of the lower electrodes  23 ,  33 , and  43 . A re-deposition film formed on the surface of a lower electrode near the first end of the lower electrode will hereinafter be referred to as a first re-deposition film. A re-deposition film formed near the second end of the lower electrode will be referred to as a second re-deposition film. 
     In the step shown in  FIG.  7   , the insulating layer  63  is then formed with the first to fourth etching masks  81  left unremoved. The insulating layer  63  is also formed on the surfaces of the first to fourth etching masks  81 . In  FIG.  7   , the portion of the insulating layer  63  formed on the surface of the first etching mask  81  is omitted. The first to fourth etching masks  81  are then removed. 
       FIG.  8    shows the next step. In this step, films for eventually making the layers constituting the MR element main bodies  11 ,  12 ,  21 ,  22 ,  31 ,  32 ,  41 , and  42  of the MR elements  10 ,  20 ,  30 , and  40  are formed in order. A layered film  72  for eventually making the MR element main bodies  11 ,  12 ,  21 ,  22 ,  31 ,  32 ,  41 , and  42  is thereby formed on the lower electrodes  13 ,  23 ,  33 , and  43  and the insulating layer  63 . 
       FIG.  9    shows the next step. In this step, non-shown eight etching masks for forming the MR element main bodies  11 ,  12 ,  21 ,  22 ,  31 ,  32 ,  41 , and  42  are initially formed on the layered film  72 . Like the first to fourth etching masks  81 , the eight etching masks may have undercuts. Next, the layered film  72  is etched by ion milling, for example, using the eight etching masks. The layered film  72  is thereby made into the MR element main bodies  11 ,  12 ,  21 ,  22 ,  31 ,  32 ,  41 , and  42 . The etching also removes the first and second re-deposition films formed on the surfaces of the lower electrodes  13 ,  23 ,  33 , and  43  in the etching step. Next, the insulating layer  64  is formed with the eight etching masks left unremoved. Next, the eight etching masks are removed. 
       FIG.  10    shows the next step. In this step, a metal film for eventually making the upper electrodes  14 ,  15 ,  24 ,  25 ,  34 ,  35 ,  44 , and  45  and the lead electrodes  51  and  52  is initially formed on the MR element main bodies  11 ,  12 ,  21 ,  22 ,  31 ,  32 ,  41 , and  42  and the insulating layer  64 . Next, non-shown six etching masks for forming the upper electrodes  14 ,  15 ,  24 ,  25 ,  34 ,  35 ,  44 , and  45  are formed on the metal film. Next, the metal film is etched by ion milling, for example, using the six etching masks. The metal film is thereby made into the upper electrodes  14 ,  15 ,  24 ,  25 ,  34 ,  35 ,  44 , and  45  and the lead electrodes  51  and  52 . Next, the insulating layer  66  is formed with the six etching masks left unremoved. Next, the six etching masks are removed. After the removal of the etching masks, a non-shown insulating layer may be formed to cover the upper electrodes  14 ,  15 ,  24 ,  25 ,  34 ,  35 ,  44 , and  45 , the lead electrodes  51  and  52 , and the insulating layer  65 . 
     Next, a plurality of terminals constituting the power supply nodes V 1  and V 2  and the like are formed to complete the detection unit of the magnetic sensor  1 . 
     Now, the undercut  81 C of each of the first to fourth etching masks  81  will be described in detail. The undercut  81 C of the first etching mask  81  will initially be described with reference to  FIG.  7   . The undercut  81 C of the first etching mask  81  forms a first space SPa closest to the lower end Ea of the inclined portion  60   a   1  and a second space SPb closest to the upper end Eb of the inclined portion  60   a   1 . The lower layer  81 A is interposed between the first space SPa and the second space SPb. The first space SPa is a space located in front of the lower layer  81 A in the Y direction. The second space SPb is a space located in front of the lower layer  81 A in the −Y direction. 
     The lower layer  81 A of the first etching mask  81  is formed by applying a material having fluidity to the entire top surface of the stack. The material increases in thickness on the lower end Ea side of the inclined portion  60   a   1 , and decreases on the upper end Eb side of the inclined portion  60   a   1 . 
     Here, a direction perpendicular to the bottom surface  60   b  of the support member  60  will be defined as a first direction D 1 . The first direction D 1  is also parallel to the Z direction. A dimension in the first direction D 1  will hereinafter be referred to as a height. The closer to the lower end Ea of the inclined portion  60   a   1 , the greater the height of the lower layer  81 A of the first etching mask  81  before the patterning of the upper layer  81 B. As described above, the undercut  81 C is formed by removing apart of the lower layer  81 A in patterning the upper layer  81 B. Each of the first and second spaces SPa and SPb thus increases in height toward the lower end Ea of the inclined portion  60   a   1 . Moreover, the height of the first space SPa is greater than that of the second space SPb. Specifically, the maximum height of the first space SPa is greater than that of the second space SPb. The minimum height of the first space SPa may be greater than the maximum height of the second space SPb. 
     A direction parallel to a direction from the lower end Ea to the upper end Eb of the inclined portion  60   a   1  will be defined as a second direction D 2   u . As described above, the height of the first space SPa is greater than that of the second space SPb. In patterning the upper layer  81 B, the developing agent is therefore more likely to enter the first space SPa than the second space SPb. As a result, the dimension of the first space SPa in the second direction D 2   u  becomes greater than the dimension of the second space SPb in the second direction D 2   u.    
     The foregoing description of the undercut  81 C of the first etching mask  81  also applies to the undercut  81 C of the second etching mask  81 . 
     The first and second etching masks  81  and the third and fourth etching masks  81  are plane-symmetrical about the XZ plane therebetween. A direction parallel to a direction from the lower end Ec to the upper end Ed of the inclined portion  60   a   2  (see  FIG.  4   ) will be defined as a second direction D 2   v . The foregoing description of the undercut  81 C of each of the first and second etching masks  81  also applies to the undercut  81 C of each of the third and fourth etching masks  81  if the reference numeral and symbols  60   a   1 , Ea, Eb, and D 2   u  are replaced with the reference numeral and symbols  60   a   2 , Ec, Ed, and D 2   v , respectively. 
     A direction parallel to the inclined portion  60   a   1  and orthogonal to the X direction will be defined as a U direction. A direction parallel to the inclined portion  60   a   2  and orthogonal to the X direction will be defined as a V direction. In the present embodiment, the U direction is a direction rotated by α from the Y direction in the −Z direction. The V direction is a direction rotated by α from the Y direction in the Z direction. α is an angle of greater than 0° and smaller than 90°. As shown in  FIG.  7   , the second directions D 2   u  and D 2   v  are also parallel to the U and V directions, respectively. 
     The function and effect of the magnetic sensor  1  according to the present embodiment will now be described. In the present embodiment, each of the first to fourth etching masks  81  has the undercut  81 C. In the etching step, etched and scattered substances of the metal film  71  therefore enter the spaces formed by the undercut  81 C to form the first and second re-deposition films on the surface of each of the lower electrodes  13 ,  23 ,  33 , and  43 . 
     Consider now the lower electrode  13 . In the etching step, the first re-deposition film  91  is formed on the surface of the lower electrode  13 , near the first end  13   a  of the lower electrode  13 . The second re-deposition film  92  is formed on the surface of the lower electrode  13 , near the second end  13   b  of the lower electrode  13 . As shown in  FIG.  7   , the dimension of the first space SPa of the first etching mask  81  in the second direction D 2   u  is greater than the dimension of the second space SPb in the second direction D 2   u . The re-deposition film is therefore formed over a wider range in the first space SPa than in the second space SPb. As a result, the dimension of the first re-deposition film  91  in the second direction D 2   u  is greater than the dimension of the second re-deposition film  92  in the second direction D 2   u.    
     The dimension of each of the inclined portions  60   a   1  and  60   a   2  in a direction parallel to the Y direction (hereinafter, referred to as a width) can be reduced to increase the occupation area of the MR element main bodies per unit area. However, the smaller the width of the inclined portion  60   a   1 , the smaller the width of the lower electrode  13 . This reduces the distance from the first end  13   a  of the lower electrode  13  to the MR element main body  11 . With the reduced distance, the MR element main body  11  can overlap the first re-deposition film  91 . The same applies to the MR element main body  12 . If the MR element main bodies  11  and  12  overlap the first re-deposition film  91 , the MR element main bodies  11  and  12  are deformed. This causes a problem that the characteristics of the MR element main bodies  11  and  12 , i.e., the characteristics of the MR element  10  become different from desired ones. 
     By contrast, in the present embodiment, each of the MR element main bodies  11  and  12  is located at a position closer to the second end  13   b  of the lower electrode  13  than to the first end  13   a  of the lower electrode  13 . According to the present embodiment, the distance from the first end  13   a  to the MR element main body  11  and the distance from the first end  13   a  to the MR element main body  12  can thus be increased to prevent the occurrence of the foregoing problem. 
     In the present embodiment, the distance from the second end  13   b  to each of the MR element main bodies  11  and  12  is smaller than that from the first end  13   a  to each of the MR element main bodies  11  and  12 . According to the present embodiment, the width of the inclined portion  60   a   1  can thus be reduced compared to the case where the distance from the second end  13   b  to each of the MR element main bodies  11  and  12  is greater than or equal to that from the first end  13   a  to each of the MR element main bodies  11  and  12 , while the occurrence of the foregoing problem is prevented. Consequently, according to the present embodiment, the occupation area of the MR element main bodies per unit area can be increased. 
     Up to this point, a description has been given by taking the set including the MR element main bodies  11  and  12  and the lower electrode  13  as an example. The foregoing description also applies to the set including the MR element main bodies  21  and  22  and the lower electrode  23 , the set including the MR element main bodies  31  and  32  and the lower electrode  33 , and the set including the MR element main bodies  41  and  42  and the lower electrode  43 . In other words, in the present embodiment, the MR element main bodies are located at positions closer to the second ends of the lower electrodes than to the first ends of the lower electrodes. According to the present embodiment, the distances from the first ends to the MR element main bodies can be increased to prevent the occurrence of the problem that the characteristics of the MR element main bodies, i.e., the characteristics of the MR elements become different from desired ones. Moreover, according to the present embodiment, the widths of the inclined portions  60   a   1  and  60   a   2  can be reduced compared to the case where the distances from the second ends to the MR element main bodies are greater than or equal to the distances from the first ends to the MR element main bodies, while the occurrence of the foregoing problem is prevented. 
     Modification Example 
     Next, a modification example of the magnetic sensor  1  according to the present embodiment will be described with reference to  FIG.  11   . Consider now the MR element  10 . In the modification example, the distance from the upper end Eb of the inclined portion  60   a   1  to the first end  13   a  of the lower electrode  13  is greater than that from the upper end Eb to the lower end Ea of the inclined portion  60   a   1 . In particular, in the modification example, the lower electrode  13  is located to extend from the inclined portion  60   a   1  to the flat portion  60   a   3 . The first end  13   a  of the lower electrode  13  is located on the flat portion  60   a   3 . 
     In the modification example, the distance from the first end  13   a  of the lower electrode  13  to each of the MR element main bodies  11  and  12  of the MR element  10  is greater than in the case where the first end  13   a  is located on the inclined portion  60   a   1 . According to the modification example, the problem that the characteristics of the MR element main bodies  11  and  12 , i.e., the characteristics of the MR element  10  become different from desired ones can thereby be prevented more effectively. 
     The foregoing description of the MR element  10  also applies to the MR element  20  if the reference numerals  10 ,  11 ,  12 ,  13 , and  13   a  are replaced with the reference numerals  20 ,  21 ,  22 ,  23 , and  23   a , respectively. 
     The foregoing description of the MR elements  10  and  20  also applies to the MR elements  30  and  40  if the reference numerals and symbols  10 ,  11 ,  12 ,  13 ,  13   a ,  20 ,  21 ,  22 ,  23 ,  23   a ,  60   a   1 ,  60   a   3 , Ea, and Eb are replaced with the reference numerals and symbols  30 ,  31 ,  32 ,  33 ,  33   a ,  40 ,  41 ,  42 ,  43 ,  43   a ,  60   a   2 ,  60   a   4 , Ec, and Ed, respectively. 
     As shown in  FIG.  11   , the upper electrode  14  has a third end  14   a  closest to the lower end Ea of the inclined portion  60   a   1 . The distance from the MR element main body  11  to the third end  14   a  of the upper electrode  14  is smaller than that from the MR element main body  11  to the first end  13   a  of the lower electrode  13 . The description of the upper electrode  14  also applies to the upper electrodes  15 ,  24 , and  25 . 
     As shown in  FIG.  11   , the upper electrode  34  has a third end  34   a  closest to the lower end Ec of the inclined portion  60   a   2 . The distance from the MR element main body  31  to the third end  34   a  of the upper electrode  34  is smaller than that from the MR element main body  31  to the first end  33   a  of the lower electrode  33 . The description of the upper electrode  34  also applies to the upper electrodes  35 ,  44 , and  45 . 
     The present invention is not limited to the foregoing embodiment, and various modifications may be made thereto. The number and arrangement of MR elements, the numbers of MR element main bodies, lower electrodes, and upper electrodes, and the shape of the support member are not limited to the examples described in the embodiment, and may be freely set as far as the requirements set forth in the claims are satisfied. For example, the number of MR elements may be one. Alternatively, the number of MR elements may be eight. In such a case, a magnetic sensor according to the present invention may include a first Wheatstone bridge circuit including four MR elements and a second Wheatstone bridge circuit including four MR elements. 
     Each MR element may include only one MR element main body. In such a case, each MR element may include only one lower electrode and only one upper electrode. Alternatively, each MR element may include three or more MR element main bodies. In such a case, each MR element may include two or more lower electrodes and two or more upper electrodes. 
     The top surface of the support member  60  may include only one inclined portion, or three or more inclined portions. 
     Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. Thus, it is to be understood that, within the scope of the appended claims and equivalents thereof, the invention may be practiced in other embodiments than the foregoing most preferable embodiment.