Three axis magnetic field sensor

Abstract

Three bridge circuits ( 101, 111, 121 ), each include magnetoresistive sensors coupled as a Wheatstone bridge ( 100 ) to sense a magnetic field ( 160 ) in three orthogonal directions ( 110, 120, 130 ) that are set with a single pinning material deposition and bulk wafer setting procedure. One of the three bridge circuits ( 121 ) includes a first magnetoresistive sensor ( 141 ) comprising a first sensing element ( 122 ) disposed on a pinned layer ( 126 ), the first sensing element ( 122 ) having first and second edges and first and second sides, and a first flux guide ( 132 ) disposed non-parallel to the first side of the substrate and having an end that is proximate to the first edge and on the first side of the first sensing element ( 122 ). An optional second flux guide ( 136 ) may be disposed non-parallel to the first side of the substrate and having an end that is proximate to the second edge and the second side of the first sensing element ( 122 ).

The invention claimed is: 
     
       1. A ferromagnetic thin-film based magnetic field sensor comprising:
 a substrate having a planar surface; and   a first magnetoresistive sensor comprising:
 a first sensing element having a first side lying parallel to the planar surface of the substrate, the first sensing element having a second side opposed to the first side and having first and second opposed edges; and 
 a first flux guide comprising a soft ferromagnetic material disposed non-parallel to the first side of the first sensing element and having an end that is proximate to the first edge and the first side of the first sensing element. 
   
     
     
       2. The ferromagnetic thin-film based magnetic field sensor of  claim 1  wherein the first magnetoresistive sensor further comprises:
 a second flux guide comprising a soft ferromagnetic material disposed non-parallel to the first side of the first sensing element and having an end that is proximate to the second edge and the second side of the first sensing element. 
 
     
     
       3. The ferromagnetic thin-film based magnetic field sensor of  claim 1  wherein the first magnetoresistive sensor comprises one of an array of ferromagnetic thin-film based magnetic field sensors. 
     
     
       4. The ferromagnetic thin-film based magnetic field sensor of  claim 1  wherein the first flux guide comprises a high aspect ratio structure non-parallel to the first sense element. 
     
     
       5. The ferromagnetic thin-film based magnetic field sensor of  claim 1  wherein the first flux guide comprises a U shaped element. 
     
     
       6. The ferromagnetic thin-film based magnetic field sensor of  claim 1  wherein the first flux guide includes a flared end. 
     
     
       7. The ferromagnetic thin-film based magnetic field sensor of  claim 1  further comprising a material disposed adjacent the first flux guide and comprising one of the group consisting of a high conductivity metal and a dielectric material. 
     
     
       8. The ferromagnetic thin-film based magnetic field sensor of  claim 1  wherein the first flux guide comprises a box shaped structure. 
     
     
       9. The ferromagnetic thin-film based magnetic field sensor of  claim 1  wherein at least one of the first and second flux guides is disposed substantially orthogonal to the plane of the substrate. 
     
     
       10. The ferromagnetic thin-film based magnetic field sensor of  claim 1  wherein at least one of the first and second flux guides is disposed at an angle of between 45 degrees and 90 degrees to the plane of the substrate. 
     
     
       11. The ferromagnetic thin-film based magnetic field sensor of  claim 1  further comprising:
 a second magnetoresistive sensor having a second sensing element for detecting a magnetic field in a second direction orthogonal to the first direction; and 
 a third magnetoresistive sensor having a third sensing element orthogonal to the second sensing element for detecting a magnetic field in a third direction orthogonal to the first and second directions, 
 wherein the third sensing element is in a plane with the first and second sensing elements. 
 
     
     
       12. The ferromagnetic thin-film based magnetic field sensor of  claim 11 , wherein the first, second, and third sensor elements each comprise an imbalanced synthetic antiferromagnet formed with first and second ferromagnetic layers separated by a spacer layer, where the first and second ferromagnetic layers have different magnetic moments. 
     
     
       13. The ferromagnetic thin-film based magnetic field sensor of  claim 1  further comprising:
 the first magnetoresistive sensor comprising:
 a first pinned layer; 
 
 a second magnetoresistive sensor comprising:
 a second pinned layer; and 
 a second sensing element formed on the second pinned layer; 
 
 a third magnetoresistive sensor comprising:
 a third pinned layer; and 
 a third sensing element formed on the third pinned layer and orthogonal to the second sensing element; 
 wherein the second and third pinned layers are oriented about 45 degrees to the first pinned layer. 
 
 
     
     
       14. The ferromagnetic thin-film based magnetic field sensor of  claim 13  wherein the first magnetic tunnel junction further comprises:
 a second flux guide disposed non-parallel to the first side of the first sensing element and having an end that is proximate to the second edge and the second side of the first sensing element. 
 
     
     
       15. The ferromagnetic thin-film based magnetic field sensor of  claim 14  wherein the first and second flux guides each comprise an aspect ratio greater than 10. 
     
     
       16. A ferromagnetic thin-film magnetic field sensor comprising:
 a first bridge circuit comprising first, second, third, and fourth magnetic tunnel junction sensors coupled as a Wheatstone bridge for sensing a magnetic field orthogonal to the plane of the sensors;   the first magnetic tunnel junction sensor comprising:
 a first reference layer; and 
 a first sensing element formed on the first reference layer, the first sensing element having first and second edges and first and second sides; and 
 a first flux guide comprising a soft ferromagnetic material disposed orthogonal to and spaced from the first edge and the first side of the first sensing element; 
   the second magnetic tunnel junction sensor comprising:
 a second reference layer; and 
 a second sensing element formed on the second reference layer, the second sensing element having first and second edges and first and second sides; and 
 a second flux guide comprising a soft ferromagnetic material disposed orthogonal to and spaced from the first edge and the first side of the second sensing element; 
   the third magnetic tunnel junction sensor comprising:
 a third reference layer; and 
 a third sensing element formed on the third reference layer, the third sensing element having first and second edges and first and second sides; and 
 a third flux guide comprising a soft ferromagnetic material disposed orthogonal to and spaced from the first edge and the first side of the third sensing element; 
   the fourth magnetic tunnel junction sensor comprising:
 a fourth reference layer; and 
 a fourth sensing element formed on the fourth reference layer, the fourth sensing element having first and second edges and first and second sides; and 
 a fourth flux guide disposed orthogonal to and spaced from the first edge and the first side of the fourth sensing element. 
   
     
     
       17. The ferromagnetic thin-film based magnetic field sensor of  claim 16  wherein the first, second, third, and fourth magnetic tunnel junction sensors further comprise fifth, sixth, seventh, and eighth flux guides disposed orthogonal to and spaced from the second edge and the second side of the first, second, third, and fourth sensing elements, respectively. 
     
     
       18. The ferromagnetic thin-film based magnetic field sensor of  claim 16  further comprising:
 a second bridge circuit comprising fifth, sixth, seventh, and eighth magnetic tunnel junction sensors coupled as a second Wheatstone bridge for sensing a magnetic field in a second direction orthogonal to the first direction; and 
 a third bridge circuit comprising ninth, tenth, eleventh, and twelfth magnetic tunnel junction sensors coupled as a third Wheatstone bridge for sensing a magnetic field in a third direction orthogonal to the first and second directions. 
 
     
     
       19. The ferromagnetic thin-film based magnetic field sensor of  claim 16  wherein each of the first, second, third, and fourth sensors comprises an array of sense elements. 
     
     
       20. A method of testing the functionality and sensitivity of a response of the Z axis of a ferromagnetic thin-film magnetic field sensor including a substrate having a planar surface, and a first magnetoresistive sensor comprising a sensing element having a first side lying parallel to the planar surface of the substrate, the sensing element having a second side opposed to the first side and having first and second opposed edges, a first flux guide comprising a soft ferromagnetic material disposed non-parallel to the first side of the substrate and having an end that is proximate to the first edge and the first side of the sensing element, and a metal line formed adjacent contiguous to the flux guide, the method comprising:
 applying a current through the metal line to provide a magnetic field with a component parallel to the plane of the flux guides.   
     
     
       21. The method of  claim 20 , further comprising:
 applying a current pulse through the metal line to reset the flux guide domain structure.   
     
     
       22. A ferromagnetic thin-film based magnetic field sensor comprising:
 a plurality of magnetoresistive sensors connected in a first circuit to sense a magnetic field orthogonal to a plane of the plurality of magnetoresistive sensors, wherein the plurality of magnetoresistive sensors includes first, second, third, and fourth magnetoresistive sensors;   the first magnetoresistive sensor comprising in an order in a direction:
 a reference layer, 
 an intermediate layer, and 
 a sensing element, and 
   wherein the first magnetoresistive sensor further comprises a first flux guide comprising a soft ferromagnetic material, wherein the first flux guide is (i) adjacent to the sensing element of the first magnetoresistive sensor and (ii) above or below the sensing element of the first magnetoresistive sensor in the direction;   the second magnetoresistive sensor comprising in the direction:
 a reference layer, 
 an intermediate layer, and 
 a sensing element, and 
   wherein the second magnetoresistive sensor further comprises a second flux guide comprising a soft ferromagnetic material, wherein the second flux guide is (i) adjacent to the sensing element of the second magnetoresistive sensor and (ii) above or below the sensing element of the second magnetoresistive sensor in the direction;   the third magnetoresistive sensor comprising in the direction:
 a reference layer, 
 an intermediate layer, and 
 a sensing element, and 
   wherein the third magnetoresistive sensor further comprises a third flux guide comprising a soft ferromagnetic material, wherein the third flux guide is (i) adjacent to the sensing element of the third magnetoresistive sensor and (ii) above or below the sensing element of the third magnetoresistive sensor in the direction; and   the fourth magnetoresistive sensor comprising in the direction:
 a reference layer, 
 an intermediate layer, and 
 a sensing element, and 
   wherein the fourth magnetoresistive sensor further comprises a fourth flux guide comprising a soft ferromagnetic material, wherein the fourth flux guide is (i) adjacent to the sensing element of the fourth magnetoresistive sensor and (ii) above or below the sensing element of the fourth magnetoresistive sensor in the direction.   
     
     
       23. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first circuit is a bridge circuit. 
     
     
       24. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the plurality of magnetoresistive sensors are connected in the first circuit to provide a differential measurement. 
     
     
       25. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein each of the first, second, third, and fourth magnetoresistive sensors is a magnetic tunnel junction sensor. 
     
     
       26. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein each of the first, second, third, and fourth flux guides is a bar comprising a soft ferromagnetic material. 
     
     
       27. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first circuit is electrically coupled to a voltage meter. 
     
     
       28. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first circuit includes input terminals configured to connect to an electrical source. 
     
     
       29. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein each of the sensing elements of the first, second, third, and fourth magnetoresistive sensors includes a sense axis parallel to the plane of the plurality of magnetoresistive sensors. 
     
     
       30. A ferromagnetic thin-film based magnetic field sensor comprising:
 a first plurality of magnetoresistive sensors electrically connected into a first circuit to sense a first magnetic field orthogonal to a plane of the first plurality of magnetoresistive sensors, wherein each magnetoresistive sensor of the first plurality of magnetoresistive sensors comprises in an order in a direction:
 a reference layer, 
 an intermediate layer, and 
 a sensing element, and 
   wherein each magnetoresistive sensor further comprises a flux guide (i) adjacent to an associated sensing element and (ii) above or below the associated sensing element in the direction, wherein the flux guide comprises a soft ferromagnetic material; and   a second plurality of magnetoresistive sensors electrically connected into a second circuit to sense a second magnetic field orthogonal to the first magnetic field.   
     
     
       31. The ferromagnetic thin-film based magnetic field sensor of claim 30, wherein the first and second circuits are located on or in a single substrate. 
     
     
       32. The ferromagnetic thin-film based magnetic field sensor of claim 30, wherein each magnetoresistive sensor of the first and second pluralities of magnetoresistive sensors is a magnetic tunnel junction sensor. 
     
     
       33. The ferromagnetic thin-film based magnetic field sensor of claim 30, wherein each of the first and second circuits is a bridge circuit. 
     
     
       34. The ferromagnetic thin-film based magnetic field sensor of claim 30, wherein the first circuit is electrically coupled to a voltage meter. 
     
     
       35. The ferromagnetic thin-film based magnetic field sensor of claim 30, wherein each magnetoresistive sensor of the first and second pluralities of magnetoresistive sensors includes a sense axis parallel to the plane of the first plurality of magnetoresistive sensors. 
     
     
       36. The ferromagnetic thin-film based magnetic field sensor of claim 30, wherein the flux guide of each magnetoresistive sensor of the first plurality of magnetoresistive sensors is a bar comprising a soft ferromagnetic material. 
     
     
       37. The ferromagnetic thin-film based magnetic field sensor of claim 30, wherein the reference layer of each magnetoresistive sensor of the first plurality of magnetoresistive sensors includes a first pinning direction, and wherein each magnetoresistive sensor of the second plurality of magnetoresistive sensors includes a reference layer having a second pinning direction orthogonal to the first pinning direction. 
     
     
       38. The ferromagnetic thin-film based magnetic field sensor of claim 30, wherein the first circuit includes input and output terminals, and wherein the magnetic field sensor further includes:
 an electrical source electrically coupled to the input terminals, and   a voltage meter electrically coupled to the output terminals.   
     
     
       39. The ferromagnetic thin-film based magnetic field sensor of claim 30, wherein the intermediate layer of each magnetoresistive sensor of the first plurality of magnetoresistive sensors is an insulating dielectric layer. 
     
     
       40. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein at least one of the first, second, third, and fourth flux guides is directly above or directly below a portion of the sensing element of the first, second, third, and fourth magnetoresistive sensors, respectively. 
     
     
       41. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the order in the direction includes:
 the sensing element of each of the first, second, third, and fourth magnetoresistive sensors being formed on or above the intermediate layer of each of the first, second, third, and fourth magnetoresistive sensors, respectively, and   the intermediate layer of each of the first, second, third, and fourth magnetoresistive sensors being formed on or above the reference layer of each of the first, second, third, and fourth magnetoresistive sensors, respectively.   
     
     
       42. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the order in the direction includes:
 the reference layer of each of the first, second, third, and fourth magnetoresistive sensors being formed on or above the intermediate layer of each of the first, second, third, and fourth magnetoresistive sensors, respectively, and   the intermediate layer of each of the first, second, third, and fourth magnetoresistive sensors being formed on or above the sensing element of each of the first, second, third, and fourth magnetoresistive sensors, respectively.   
     
     
       43. The ferromagnetic thin-film based magnetic field sensor of claim 30, wherein the flux guide is directly above or directly below a portion of the associated sensing element. 
     
     
       44. The ferromagnetic thin-film based magnetic field sensor of claim 30, wherein the order in the direction includes:
 the sensing element of each magnetoresistive sensor of the first plurality of magnetoresistive sensors being formed on or above the associated intermediate layer of each magnetoresistive sensor, and   the intermediate layer of each magnetoresistive sensor of the first plurality of magnetoresistive sensors being formed on or above the associated reference layer of each magnetoresistive sensor.   
     
     
       45. The ferromagnetic thin-film based magnetic field sensor of claim 30, wherein the order in the direction includes:
 the reference layer of each magnetoresistive sensor of the first plurality of magnetoresistive sensors being formed on or above the associated intermediate layer of each magnetoresistive sensor, and   the intermediate layer of each magnetoresistive sensor of the first plurality of magnetoresistive sensors being formed on or above the associated sensing element of each magnetoresistive sensor.   
     
     
       46. A ferromagnetic thin-film based magnetic field sensor comprising:
 a first plurality of magnetoresistive sensors electrically connected into a first circuit, wherein each magnetoresistive sensor of the first plurality of magnetoresistive sensors comprises in an order in a direction:
 a reference layer, 
 an intermediate layer, and 
 a sensing element, and 
   wherein each magnetoresistive sensor further comprises a flux guide (i) adjacent to an associated sensing element and (ii) in a plane that is above or below the associated sensing element in the direction and parallel to the associated sensing element, wherein the flux guide includes a soft ferromagnetic material.   
     
     
       47. The ferromagnetic thin-film based magnetic field sensor of claim 46, further comprising:
 a second plurality of magnetoresistive sensors electrically connected into a second circuit, wherein the first circuit is configured to sense a first magnetic field orthogonal to a plane of the first plurality of magnetoresistive sensors, and wherein the second circuit is configured to sense a second magnetic field orthogonal to the first magnetic field.   
     
     
       48. The ferromagnetic thin-film based magnetic field sensor of claim 46, wherein the intermediate layer of each magnetoresistive sensor of the first plurality of magnetoresistive sensors is an insulating dielectric layer. 
     
     
       49. The ferromagnetic thin-film based magnetic field sensor of claim 46, wherein each magnetoresistive sensor of the first plurality of magnetoresistive sensors is a magnetic tunnel junction sensor. 
     
     
       50. The ferromagnetic thin-film based magnetic field sensor of claim 46, wherein the first circuit is a Wheatstone bridge circuit. 
     
     
       51. The ferromagnetic thin-film based magnetic field sensor of claim 46, wherein the first circuit includes input conductors configured for connection to an electrical source. 
     
     
       52. The ferromagnetic thin-film based magnetic field sensor of claim 46, wherein the first circuit includes output conductors configured for connection to a voltage meter. 
     
     
       53. The ferromagnetic thin-film based magnetic field sensor of claim 46, wherein the order in the direction includes:
 the sensing element of each magnetoresistive sensor of the first plurality of magnetoresistive sensors being formed on or above the associated intermediate layer of each magnetoresistive sensor, and   the intermediate layer of each magnetoresistive sensor of the first plurality of magnetoresistive sensors being formed on or above the associated reference layer of each magnetoresistive sensor.   
     
     
       54. The ferromagnetic thin-film based magnetic field sensor of claim 46, wherein the order in the direction includes:
 the reference layer of each magnetoresistive sensor of the first plurality of magnetoresistive sensors being formed on or above the associated intermediate layer of each magnetoresistive sensor, and   the intermediate layer of each magnetoresistive sensor of the first plurality of magnetoresistive sensors being formed on or above the associated sensing element of each magnetoresistive sensor.   
     
     
       55. A ferromagnetic thin-film based magnetic field sensor comprising:
 a first plurality of magnetoresistive sensors electrically connected into a first Wheatstone bridge circuit to sense a first magnetic field in a direction orthogonal to a plane of the first plurality of magnetoresistive sensors, wherein each magnetoresistive sensor of the first plurality of magnetoresistive sensors includes a sensing element, and wherein each magnetoresistive sensor further comprises a flux guide (i) adjacent to an associated sensing element and (ii) in a plane that is above or below the associated sensing element in the direction and parallel to the associated sensing element, wherein the flux guide includes a soft ferromagnetic material; and   a second plurality of magnetoresistive sensors electrically connected into a second Wheatstone bridge circuit to sense a second magnetic field orthogonal to the first magnetic field.   
     
     
       56. The ferromagnetic thin-film based magnetic field sensor of claim 55, wherein the sensing element of each magnetoresistive sensor is disposed adjacent to a reference layer, and wherein an intermediate layer is disposed between the sensing element and the reference layer. 
     
     
       57. The ferromagnetic thin-film based magnetic field sensor of claim 55, wherein the sensing element of each magnetoresistive sensor is disposed adjacent to a reference layer, and wherein an insulating dielectric layer is disposed between the sensing element and the reference layer. 
     
     
       58. The ferromagnetic thin-film based magnetic field sensor of claim 55, wherein each magnetoresistive sensor of the first plurality of magnetoresistive sensors is a magnetic tunnel junction sensor. 
     
     
       59. The ferromagnetic thin-film based magnetic field sensor of claim 55, wherein the first circuit includes input conductors configured for connection to an electrical source. 
     
     
       60. The ferromagnetic thin-film based magnetic field sensor of claim 55, wherein the first circuit includes output conductors configured for connection to a voltage meter. 
     
     
       61. The ferromagnetic thin-film based magnetic field sensor of claim 55, further comprising:
 a third plurality of magnetoresistive sensors electrically connected into a third Wheatstone bridge circuit to sense a third magnetic field orthogonal to the first and second magnetic fields.   
     
     
       62. A ferromagnetic thin-film based magnetic field sensor comprising:
 a first plurality of magnetoresistive sensors connected in a first bridge circuit to sense a magnetic field in a first direction orthogonal to a plane of the first plurality of magnetoresistive sensors, wherein the first plurality of magnetoresistive sensors includes first, second, third, and fourth magnetoresistive sensors;   the first magnetoresistive sensor comprising:
 a sensing element, and 
 a first flux guide comprising a soft ferromagnetic material, wherein the first flux guide is (i) adjacent to the sensing element of the first magnetoresistive sensor and (ii) above or below the sensing element of the first magnetoresistive sensor in the first direction; 
   the second magnetoresistive sensor comprising:
 a sensing element, and 
 a second flux guide comprising a soft ferromagnetic material, wherein the second flux guide is (i) adjacent to the sensing element of the second magnetoresistive sensor and (ii) above or below the sensing element of the second magnetoresistive sensor in the first direction; 
   the third magnetoresistive sensor comprising:
 a sensing element, and 
 a third flux guide comprising a soft ferromagnetic material, wherein the third flux guide is (i) adjacent to the sensing element of the third magnetoresistive sensor and (ii) above or below the sensing element of the third magnetoresistive sensor in the first direction; and 
   the fourth magnetoresistive sensor comprising:
 a sensing element, and 
 a fourth flux guide comprising a soft ferromagnetic material, wherein the fourth flux guide is (i) adjacent to the sensing element of the fourth magnetoresistive sensor and (ii) above or below the sensing element of the fourth magnetoresistive sensor in the first direction. 
   
     
     
       63. The ferromagnetic thin-film based magnetic field sensor of claim 62, wherein each of the first, second, third, and fourth magnetoresistive sensors is a magnetic tunnel junction sensor. 
     
     
       64. The ferromagnetic thin-film based magnetic field sensor of claim 62, wherein the first bridge circuit includes output conductors configured for connection to a voltage meter. 
     
     
       65. The ferromagnetic thin-film based magnetic field sensor of claim 62, wherein the first bridge circuit includes input conductors configured for connection to an electrical source. 
     
     
       66. The ferromagnetic thin-film based magnetic field sensor of claim 62, further comprising:
 a second plurality of magnetoresistive sensors connected in a second bridge circuit to sense a magnetic field in a second direction orthogonal to the first direction.   
     
     
       67. The ferromagnetic thin-film based magnetic field sensor of claim 62, further comprising:
 a second plurality of magnetoresistive sensors connected in a second bridge circuit to sense a magnetic field in a second direction orthogonal to the first direction; and   a third plurality of magnetoresistive sensors connected in a third bridge circuit to sense a magnetic field in a third direction orthogonal to the first and second directions.   
     
     
       68. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein each of the soft ferromagnetic materials is nickel iron (NiFe). 
     
     
       69. The ferromagnetic thin-film based magnetic field sensor of claim 30, wherein the soft ferromagnetic material is nickel iron (NiFe). 
     
     
       70. The ferromagnetic thin-film based magnetic field sensor of claim 46, wherein the soft ferromagnetic material is nickel iron (NiFe). 
     
     
       71. The ferromagnetic thin-film based magnetic field sensor of claim 55, wherein the soft ferromagnetic material is nickel iron (NiFe). 
     
     
       72. The ferromagnetic thin-film based magnetic field sensor of claim 62, wherein each of the soft ferromagnetic materials is nickel iron (NiFe).