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).

Description

(not shown) (e.g., 200, 201, 202, and 203 shown in FIG. 2) may be disposed between the sense elements 102-105, 112-125, 122-125 and the pinned layers 106-109, 116-119, and 126-129. The pinned and sense electrodes are desirably magnetic materials whose magnetization direction can be aligned. Suitable electrode materials and arrangements of the materials into structures commonly used for electrodes of magnetoresistive random access memory (MRAM) devices and other magnetic tunnel junction (MTJ) sensor devices are well known in the art. For example, pinned layers 106-109, 116-119, and 126-129 may be formed with one or more layers of ferromagnetic and antiferromagnetic materials to a combined thickness in the range 10 to 1000 Å, and in selected embodiments in the range 250 to 350 Å. In an exemplary implementation, each of the pinned layers 106-109, 116-119, and 126-129 is formed with a single ferromagnetic layer and an underlying anti-ferromagnetic pinning layer. In another exemplary implementation, each pinned layer 106-109, 116-119, and 126-129 includes a synthetic anti-ferromagnetic stack component (e.g., a stack of CF (Cobalt Iron), Ruthenium (Ru) and CFB) which is 20 to 80 Å thick, and an underlying anti-ferromagnetic pinning layer that is approximately 200 Å thick. The lower anti-ferromagnetic pinning materials may be re-settable materials, such as IrMn, though other materials, such as PtMn, can be used which are not readily re-set at reasonable temperatures. As formed, the pinned layers 106-109, 116-119, and 126-129 function as a fixed or pinned magnetic layer when the direction of its magnetization is pinned in one direction that does not change during normal operating conditions. As disclosed herein, the heating qualities of the materials used to pin the pinned layers 106-109, 116-119, and 126-129 can change the fabrication sequence used to form these layers.

One of each of the sense elements 102-105, 112-125, 122-125 and one of each of the pinned layers 106-109, 116-119, 126-129 form a magnetic tunnel junction (MTJ) sensor. For example, for bridge circuit 121, sense element 122 and pinned layer 126 form an MTJ sensor 141. Likewise, sense element 123 and pinned layer 127 form an MTJ sensor 142, sense element 124 and pinned layer 128 form an MTJ sensor 143, and sense element 125 and pinned layer 129 form an MTJ sensor 144.

The pinned layers 106-109, 116-119, and 126-129 may be formed with a single patterned ferromagnetic layer having a magnetization direction (indicated by the arrow) that aligns along the long-axis of the patterned reference layer(s). However, in other embodiments, the pinned reference layer may be implemented with a synthetic anti-ferromagnetic (SAF) layer which is used to align the magnetization of the pinned reference layer along the short axis of the patterned reference layer(s). As will be appreciated, the SAF layer may be implemented in combination with an underlying anti-ferromagnetic pinning layer, though with SAF structures with appropriate geometry and materials that provide sufficiently strong magnetization, the underlying anti-ferromagnetic pinning layer may not be required, thereby providing a simpler fabrication process with cost savings.

The sense elements 102-105, 112-125, 122-125 may be formed with one or more layers of ferromagnetic materials to a thickness in the range 10 to 5000 Å, and in selected embodiments in the range 10 to 60 Å. The upper ferromagnetic materials may be magnetically soft materials, such as NiFe, CoFe, Fe, CFB and the like. In each MTJ sensor, the sense elements 102-105, 112-125, 122-125 function as a sense layer or free magnetic layer because the direction of their magnetization can be deflected by the presence of an external applied field, such as the Earth's magnetic field. As finally formed, sense elements 102-105, 112-125, 122-125 may be formed with a single ferromagnetic layer having a magnetization direction (indicated with the arrows) that aligns along the long-axis of the patterned shapes.

The pinned layers 106-109, 116-119, 126-129 and sense elements 102-105, 112-125, 122-125 may be formed to have different magnetic properties. For example, the pinned layers 106-109, 116-119, 126-129 may be formed with an anti-ferromagnetic film exchange layer coupled to a ferromagnetic film to form layers with a high coercive force and offset hysteresis curves so that their magnetization direction will be pinned in one direction, and hence substantially unaffected by an externally applied magnetic field. In contrast, the sense elements 102-105, 112-125, 122-125 may be formed with a magnetically soft material to provide different magnetization directions having a comparatively low anisotropy and coercive force so that the magnetization direction of the sense electrode may be altered by an externally applied magnetic field. In selected embodiments, the strength of the pinning field is about two orders of magnitude larger than the anisotropy field of the sense electrodes, although different ratios may be used by adjusting the respective magnetic properties of the electrodes using well known techniques to vary their composition.

The pinned layers 106-109, 116-119, 126-129 in the MTJ sensors are formed to have a shape determined magnetization direction in the plane of the pinned layers 106-109, 116-119, 126-129 (identified by the vector arrows for each sensor bridge labeled “Pinning direction” in FIG. 1). As described herein, the magnetization direction for the pinned layers 106-109, 116-119, 126-129 may be obtained using shape anisotropy of the pinned electrodes, in which case the shapes of the pinned layers 106-109, 116-119, 126-129 may each be longer in the pinning direction for a single pinned layer. Alternatively, for a pinned SAF structure, the reference and pinned layers may be shorter along the pinning direction. In particular, the magnetization direction for the pinned layers 106-109, 116-119, 126-129 may be obtained by first heating the shaped pinned layers 106-109, 116-119, 126-129 in the presence of a orienting magnetic field which is oriented non-orthogonally to the axis of longest orientation for the shaped pinned layers 106-109, 116-119, 126-129 such that the applied orienting field includes a field component in the direction of the desired pinning direction for the pinned layers 106-109, 116-119, 126-129. The magnetization directions of the pinned layers are aligned, at least temporarily, in a predetermined direction. However, by appropriately heating the pinned layers during this treatment and removing the orienting field without reducing the heat, the magnetization of the pinned layers relaxes along the desired axis of orientation for the shaped pinned pinned layers 106-109, 116-119, 126-129. Once the magnetization relaxes, the pinned layers can be annealed and/or cooled so that the magnetic field direction of the pinned electrode layers is set in the desired direction for the shaped pinned layers 106-109, 116-119, 126-129.

The exemplary embodiments described herein may be fabricated using known lithographic processes as follows. The fabrication of integrated circuits, microelectronic devices, micro electro mechanical devices, microfluidic devices, and photonic devices involves the creation of several layers of materials that interact in some fashion. One or more of these layers may be patterned so various regions of the layer have different electrical or other characteristics, which may be interconnected within the layer or to other layers to create electrical components and circuits. These regions may be created by selectively introducing or removing various materials. The patterns that define such regions are often created by lithographic processes. For example, a layer of photoresist material is applied onto a layer overlying a wafer substrate. A photomask (containing clear and opaque areas) is used to selectively expose this photoresist material by a form of radiation, such as ultraviolet light, electrons, or x-rays. Either the photoresist material exposed to the radiation, or that not exposed to the radiation, is removed by the application of a developer. An etch may then be applied to the layer not protected by the remaining resist, and when the resist is removed, the layer overlying the substrate is patterned. Alternatively, an additive process could also be used, e.g., building a structure using the photoresist as a template.

Referring to FIG. 2 and in accordance with an exemplary embodiment of the present invention, the structure of the MTJ devices 141-144 of the third bridge circuit 121 include the pinned layers 126-129, the sense elements 122-125, and the flux guides 132-139, all formed within the dielectric material 140. The flux guide 136 is positioned adjacent a line 145 and has an end positioned below an edge of the sensor element 122. The flux guides 133 and 138 are positioned on opposed sides of a line 146 and have ends positioned below edges of the sensor elements 123 and 124, respectively. The flux guide 135 is positioned adjacent a line 147 and has an end positioned below an edge of the sensor element 125. The flux guides 132 and 137 are spaced apart by an upper line 148 and have ends positioned above edges of the sensor elements 122 and 123, respectively, and the flux guides 134 and 139 are spaced apart by an upper line 149 and have ends positioned above edges of the sensor elements 134 and 139, respectively. The lines 145-149, are preferably copper, but in some embodiments may be a dielectric. A metal stabilization line 150 is positioned above the MTJ devices 141-144 for providing a stabilization field to the sense elements. The ends of the flux guides may be brought as close as possible to the sensor elements, with a preferable spacing of less than or equal to 250 nm between the two. The sense elements are brought as close as possible for the tightest density array, preferably less than 2.5 um apart.

FIG. 3 is a view of flux lines as calculated by finite element simulation of MTJ devices 141, 142 of FIG. 2 with a magnetic field in the z direction imparted upon the sense elements 122-123. FEM modeling shows the resultant magnetic flux lines 160, exhibiting a component in the plane of the sensor. MTJ device 141 is represented by flux guides 132 and 136 on opposed ends of the sensing element 122. MTJ device 142 is represented by flux guides 133 and 137 on opposed ends of the sensing element 123. Stated otherwise, sensing element 122 extends from flux guides 132 and 136, and sensing element 123 extends from flux guides 133 and 137. The magnetic field 160 in the Z-axis 130 produces an asymmetric response in the sensing elements 122, 123 along the X-axis 120 as indicated by the arrows 170. In this manner, for a field 160 in the Z direction 130 directed towards the bottom of the page, the magnetization of sense element 122 rotates away from the pinning direction (and to higher resistance) of the pinned layer 126, while the magnetization of sense element 123 rotates towards the pinning direction (and to lower resistance) of pinned layer 127. For a field in the X direction 120, both elements 122, 123 show induced magnetization in the same direction (towards higher or lower resistance). Therefore, by wiring MTJ elements 141, 142 in a Wheatstone bridge for differential measurement and subtracting the resistances of MTJ devices 141, 142, the X field response is eliminated and twice the Z field response is measured.

Referring again to FIG. 2, in the case of an exposure to a large magnetic field which may induce magnetization disturbances and domain structure in the flux guides 132-139, a large current pulse may be introduced along metal lines 145-149 to reset the flux guide domain structure.

In another exemplary embodiment (shown in FIG. 4), each of the cladded lines 145-149 are divided into two independent metal lines, and additional non-flux guiding cladding (161-168 and 191-198) is placed in between these two metal lines at the interior edges. For sensor 141, the flux guide 161 on the left edge of the left metal line, 148 guides Z field flux into the sense element 122 to its left, and the flux guide 192 on the right most edge of the right metal line 145 guides Z field flux into the sense element 122 on its right. Sensors 142-144 function similarly, with the cladded edge of the metal line adjacent to each sense element serving the active flux guiding function. As these lines are separated, a current may be made to pass through cladded lines 145, 146, 182 and 183 into the page, and 181, 147, 148, and 149 out of the page to create a magnetic field along the cladded line edges with a Z component pointing in a consistent direction (down in this example). These current orientations can serve to create a magnetic field with a strong component in the Z direction, which, through a calibration for the geometry can serve as a self test for the functionality and sensitivity of the Z axis response.

Another exemplary embodiment (see FIG. 5) includes extensions 152-159 integrally formed with the flux guides 132-139. The extensions 152-159 extend along the same axis as the sensor elements 122-125 and accentuate the horizontal component of the flux guide and move the horizontal component more to the center of the appropriate sense element 122-125.

While various exemplary embodiments have been shown for the flux guides, including the vertical elements 132-139 of FIG. 2, and the “L” shaped flux guides including extensions 152-159 of FIG. 5, other exemplary embodiments may be used for both upper and lower flux guides, such as box shaped or “U” shaped flux guides. In the “U” shaped structure (FIG. 6), a horizontal NiFe segment 171 connects the two vertical segments 161, 162 along the bottom metal line, while in the box shaped structure (FIG. 7), a horizontal segment 172 connects the two vertical segments both above the metal line as well. A horizontal segment helps to couple the magnetic structure of the two vertical segments, increasing the field conversion factor by 10-20% over that of two isolated vertical flux guides. Two horizontal segments of the box like structure provide better coupling and increase the field conversion factor by twenty to forty percent over a simple vertical flux guide. Additionally, the vertical segments of the “U” shaped structure of FIG. 6 may be flared 173, 174 (FIG. 8) out so that the region near the sense element edge has a horizontal component. Similar to the L shaped guides, the flared segments guide the magnetic flux so that there is a component directly in the plane of the magnetic sensor to further amplify the field conversion factor. However, care must be taken that the overlay is not too great or the magnetic flux will be shielded from the sensor.

FIG. 9 is a graph showing the Z/X sensitivity ratio versus the cladding/sensor spacing for a 25 nm wide, 500 nm tall vertical segments placed above and below the sense element. The Z/X sensitivity increases, to about 75 percent, as the cladding is brought to 25 nanometers of distance. Additional factors may be gained through cross sectional changes such as those highlighted above, or through aspect ratio improvements in the flux guide, for example, making the guide taller and increasing the aspect ratio will linearly increase the Z/X sensitivity ratio. Therefore, it is important to bring the flux guide as close as possible to the sense element, and increase its aspect ratio as much as is possible without adversely impacting the magnetic microstructure.

Although the described exemplary embodiments disclosed herein are directed to various sensor structures and methods for making same, the present invention is not necessarily limited to the exemplary embodiments which illustrate inventive aspects of the present invention that are applicable to a wide variety of semiconductor processes and/or devices. Thus, the particular embodiments disclosed above are illustrative only and should not be taken as limitations upon the present invention, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, the relative positions of the sense and pinning layers in a sensor structure may be reversed so that the pinning layer is on top and the sense layer is below. Also the sense layers and the pinning layers may be formed with different materials than those disclosed. Moreover, the thickness of the described layers may deviate from the disclosed thickness values. Accordingly, the foregoing description is not intended to limit the invention to the particular form set forth, but on the contrary, is intended to cover such alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims so that those skilled in the art should understand that they can make various changes, substitutions and alterations without departing from the spirit and scope of the invention in its broadest form.

Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or element of any or all the claims. As used herein, the terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.

Claims

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).