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 antiferromagnetic 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 8), 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 7) 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 first plurality of magnetoresistive sensors coupled 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 first sensing element, and

a first flux guide comprising a first soft ferromagnetic material, wherein the first soft ferromagnetic material is a first high permeability magnetic material, wherein (i) the first flux guide is above or below the first sensing element of the first magnetoresistive sensor in the first direction, (ii) the first flux guide is disposed non-parallel to a first side of the first sensing element, and (iii) the first flux guide includes an end that is proximate to a first edge and on the first side of the first sensing element;

the second magnetoresistive sensor comprising:

a second sensing element, and

a second flux guide comprising a second soft ferromagnetic material, wherein the second soft ferromagnetic material is a second high permeability magnetic material, wherein (i) the second flux guide is above or below the second sensing element of the second magnetoresistive sensor in the first direction, (ii) the second flux guide is disposed non-parallel to a first side of the second sensing element, and (iii) the second flux guide includes an end that is proximate to and on the first side of the second sensing element;

the third magnetoresistive sensor comprising:

a third sensing element, and

a third flux guide comprising a third soft ferromagnetic material, wherein the third soft ferromagnetic material is a third high permeability magnetic material, wherein (i) the third flux guide is above or below the third sensing element of the third magnetoresistive sensor in the first direction, (ii) the third flux guide is disposed non-parallel to a first side of the third sensing element, and (iii) the third flux guide includes an end that is proximate to and on the first side of the third sensing element; and

the fourth magnetoresistive sensor comprising:

a fourth sensing element, and

a fourth flux guide comprising a fourth soft ferromagnetic material, wherein the fourth soft ferromagnetic material is a fourth high permeability magnetic material, wherein (i) the fourth flux guide is above or below the fourth sensing element of the fourth magnetoresistive sensor in the first direction, (ii) the fourth flux guide is disposed non-parallel to a first side of the fourth sensing element, and (iii) the fourth flux guide includes an end that is proximate to and on the first side of the fourth sensing element,

wherein the sensor further includes a plurality of cladded lines, wherein each cladded line is positioned adjacent to one of the first, second, third, and fourth flux guides,

wherein each flux guide of the first, second, third, and fourth flux guides includes (i) a first vertical segment, (ii) a second vertical segment, and (iii) a horizontal segment connecting the first and second vertical segments, wherein a free end of the first vertical segment is flared away from a free end of the second vertical segment, each flux guide having the flared-away free ends at least partially enclosing the cladded line between the two vertical segments, and wherein the first vertical segment, the second vertical segment, and the horizontal segment define an opening, the opening having a width defined by a distance between inner walls of the first and second vertical segments, wherein the width of the opening between the inner walls at the flare-away free ends is larger than the width of the opening between the inner walls at connected ends of the first and second vertical segments, the first and second vertical segments being connected to the horizontal segment at the connected ends.

23. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein each of the first, second, third, and fourth high permeability magnetic materials is the same material.

24. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein at least one of the first, second, third, and fourth high permeability magnetic materials is nickel iron (NiFe).

25. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein each of the first, second, third, and fourth high permeability magnetic materials is nickel iron (NiFe).

26. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first plurality of magnetoresistive sensors is connected to form a circuit, and wherein the circuit includes input terminals configured to receive an electrical power and output terminals connected to a voltage meter.

27. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first plurality of magnetoresistive sensors is connected to form a circuit, and wherein the circuit is configured to detect the magnetic field in the first direction.

28. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first plurality of magnetoresistive sensors is connected into a bridge circuit having input terminals and output terminals.

29. The ferromagnetic thin-film based magnetic field sensor of claim 28, wherein the input terminals are configured to receive electrical power and the output terminals are connected to a voltmeter to measure an output signal.

30. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first and second magnetoresistive sensors are connected for differential measurement.

31. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first and second magnetoresistive sensors are connected to, in operation, subtract resistances of the first and second magnetoresistive sensors.

32. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first and second magnetoresistive sensors are connected to, in operation, produce a response when sensing a magnetic field in a second direction orthogonal to the first direction.

33. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first and second magnetoresistive sensors are connected to, in operation, eliminate a magnetic field response in a second direction orthogonal to the first direction.

34. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first and second magnetoresistive sensors are connected to, in operation, double a magnetic field measurement in the first direction.

35. 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.

36. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the ferromagnetic thin-film based magnetic field sensor is configured to generate a sensor signal, and wherein the magnetic field in the first direction is determined based on the sensor signal.

37. The ferromagnetic thin-film based magnetic field sensor of claim 22, further comprising:

a second plurality of magnetoresistive sensors configured to be electrically connected together to sense a magnetic field in a second direction orthogonal to the first direction.

38. The ferromagnetic thin-film based magnetic field sensor of claim 22, further comprising:

a second plurality of magnetoresistive sensors configured to be electrically connected together to sense a magnetic field in a second direction orthogonal to the first direction; and

a third plurality of magnetoresistive sensors configured to be electrically connected together to sense a magnetic field in a third direction orthogonal to the first and second directions.

39. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first magnetoresistive sensor further includes a first reference layer, the second magnetoresistive sensor further includes a second reference layer, the third magnetoresistive sensor further includes a third reference layer, and the fourth magnetoresistive sensor further includes a fourth reference 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 configured as a bar.

41. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first and third flux guides are above the first and third sensing elements, respectively, and wherein the second and fourth flux guides are below the second and fourth sensing elements, respectively.

42. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein each of the first, second, third, and fourth sensing elements includes a second side opposite to the first side, and wherein the first and third flux guides are above the first sides of the first and third sensing elements, respectively, and wherein the second and fourth flux guides are below the second sides of the second and fourth sensing elements, respectively.

43. A ferromagnetic thin-film based magnetic field sensor comprising:

a first plurality of magnetoresistive sensors coupled together, 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

one or more flux guides, wherein each flux guide of the one or more flux guides includes a soft ferromagnetic material, wherein the soft ferromagnetic material is a high permeability magnetic material, wherein at least one flux guide of the one or more flux guides is associated with at least one magnetoresistive sensor of the first plurality of magnetoresistive sensors, and wherein (i) the at least one flux guide is in a plane that is above or below the at least one magnetoresistive sensor and parallel to the sensing element of the at least one magnetoresistive sensor, (ii) the at least one flux guide is disposed non-parallel to a first side of the at least one magnetoresistive sensor, and (iii) the at least one flux guide includes an end that is proximate to a first edge and on the first side of the at least one magnetoresistive sensor,

wherein the sensor further includes a plurality of cladded lines, wherein each cladded line is positioned adjacent to a flux guide of the one or more flux guides,

wherein each flux guide of the one or more flux guides includes (i) a first vertical segment, (ii) a second vertical segment, and (iii) a horizontal segment connecting the first and second vertical segments, and wherein a free end of the first vertical segment is flared away from a free end of the second vertical segment, each flux guide having the flared-away free ends at least partially enclosing the cladded line between the two vertical segments, and wherein the first vertical segment, the second vertical segment, and the horizontal segment define an opening, the opening having a width defined by a distance between inner walls of the first and second vertical segments, wherein the width of the opening between the inner walls at the flare-away free ends is larger than the width of the opening between the inner walls at connected ends of the first and second vertical segments, the first and second vertical segments being connected to the horizontal segment at the connected ends.

44. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein each magnetoresistive sensor of the first plurality of magnetoresistive sensors is a magnetic tunnel junction sensor.

45. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the intermediate layer is an insulating dielectric layer.

46. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor, a second magnetoresistive sensor, a third magnetoresistive sensor, and a fourth magnetoresistive sensor,

wherein the one or more flux guides comprises a first flux guide, a second flux guide, a third flux guide, and a fourth flux guide, and

wherein the first flux guide is associated with the first magnetoresistive sensor, the second flux guide is associated with the second magnetoresistive sensor, the third flux guide is associated with the third magnetoresistive sensor, and the fourth flux guide is associated with the fourth magnetoresistive sensor.

47. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor, a second magnetoresistive sensor, a third magnetoresistive sensor, and a fourth magnetoresistive sensor,

wherein the one or more flux guides comprises a first flux guide, a second flux guide, a third flux guide, and a fourth flux guide, and

wherein the first flux guide is above the first magnetoresistive sensor, the second flux guide is below the second magnetoresistive sensor, the third flux guide is above the third magnetoresistive sensor, and the fourth flux guide is below the fourth magnetoresistive sensor.

48. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor, a second magnetoresistive sensor, a third magnetoresistive sensor, and a fourth magnetoresistive sensor, each of the first, second, third, and fourth magnetoresistive sensors including a first side and a second side opposite to the first side,

wherein the one or more flux guides comprises a first flux guide, a second flux guide, a third flux guide, a fourth flux guide, a fifth flux guide, a sixth flux guide, a seventh flux guide, and an eighth flux guide, and

wherein the first flux guide is below the first side of first magnetoresistive sensor, the second flux guide is above the second side of the first magnetoresistive sensor, the third flux guide is above the first side of the second magnetoresistive sensor, the fourth flux guide is below the second side of the second magnetoresistive sensor, the fifth flux guide is below the first side of the third magnetoresistive sensor, the sixth flux guide is above the second side of the third magnetoresistive sensor, the seventh flux guide is above the first side of the fourth magnetoresistive sensor, and the eighth flux guide is below the second side of the fourth magnetoresistive sensor.

49. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the high permeability magnetic material is nickel iron (NiFe).

50. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected for differential measurement.

51. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected to, in operation, subtract resistances of the first and second magnetoresistive sensors.

52. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected to, in operation, produce a response when sensing a magnetic field in a second direction orthogonal to the direction.

53. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected to, in operation, eliminate a magnetic field response in a second direction orthogonal to the direction.

54. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected to, in operation, double a magnetic field measurement in the direction.

55. The ferromagnetic thin-film based magnetic field sensor of claim 43, further comprising:

a second plurality of magnetoresistive sensors configured to be electrically connected together, wherein the first plurality of magnetoresistive sensors is configured to sense a first magnetic field in the direction, and wherein the second plurality of magnetoresistive sensors is configured to sense a second magnetic field in a second direction orthogonal to the direction.

56. The ferromagnetic thin-film based magnetic field sensor of claim 43, further comprising:

a second plurality of magnetoresistive sensors configured to be electrically connected together; and

a third plurality of magnetoresistive sensors configured to be electrically connected together,

wherein the first plurality of magnetoresistive sensors is configured to sense a first magnetic field in the direction, the second plurality of magnetoresistive sensors is configured to sense a second magnetic field in a second direction orthogonal to the direction, and the third plurality of magnetoresistive sensors is configured to sense a magnetic field in a third direction orthogonal to the direction and the second direction.

57. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors is connected to form a circuit, and wherein the circuit is configured to detect a magnetic field in the direction.

58. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors is connected to form a circuit, and wherein the circuit includes input terminals configured to receive an electrical power and output terminals connected to a voltage meter.

59. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors is connected into a bridge circuit having input terminals and output terminals.

60. The ferromagnetic thin-film based magnetic field sensor of claim 59, wherein the input terminals are configured to receive electrical power and the output terminals are connected to a voltmeter to measure an output signal.

61. The ferromagnetic thin-film based magnetic field sensor of claim 43, 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.

62. The ferromagnetic thin-film based magnetic field sensor of claim 43, 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.

63. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the reference layer of each magnetoresistive sensor includes a plurality of layers having a combined thickness in a range of 10 to 1000 Å.

64. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the reference layer of each magnetoresistive sensor includes a plurality of layers having a combined thickness in a range of 250 to 350 Å.

65. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the sensing element includes a thickness in a range of 10 to 5000 Å.

66. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the sensing element includes a thickness in a range of 10 to 60 Å.

67. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the ferromagnetic thin-film based magnetic field sensor is configured to generate a sensor signal, and wherein a magnetic field in the direction is determined based on the sensor signal.

68. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the reference layer of each magnetoresistive sensor includes:

a ferromagnetic layer; and

an antiferromagnetic layer.

69. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the reference layer of each magnetoresistive sensor includes:

a ferromagnetic layer having a thickness in a range of 20 to 80 Å; and

an antiferromagnetic layer having a thickness of approximately 200 Å.

70. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the reference layer of each magnetoresistive sensor includes:

a ferromagnetic layer; and

an antiferromagnetic layer including iridium-manganese (IrMn) alloy or platinum-manganese (PtMn) alloy.

71. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the reference layer of each magnetoresistive sensor includes:

a ferromagnetic layer including a three-layer structure; and

an antiferromagnetic layer.

72. A ferromagnetic thin-film based magnetic field sensor comprising:

a first plurality of magnetoresistive sensors coupled 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;

one or more flux guides, wherein each flux guide of the one or more flux guides includes a soft ferromagnetic material, wherein the soft ferromagnetic material is a high permeability magnetic material, wherein at least one flux guide of the one or more flux guides is associated with the sensing element of at least one magnetoresistive sensor of the first plurality of magnetoresistive sensors, and wherein (i) the at least one flux guide is in a plane that is above or below the associated sensing element in the direction and parallel to the associated sensing element, (ii) the at least one flux guide is disposed non-parallel to a first side of the at least one magnetoresistive sensor, and (iii) the at least one flux guide includes an end that is proximate to a first edge of the associated sensing element and on a first side of the associated sensing element; and

a second plurality of magnetoresistive sensors configured to be electrically connected together to sense a second magnetic field orthogonal to the first magnetic field;

wherein each flux guide of the one or more flux guides includes (i) a first vertical segment, (ii) a second vertical segment, and (iii) a horizontal segment connecting the first and second vertical segments, and wherein a free end of the first vertical segment is flared away from a free end of the second vertical segment, each flux guide having the flared-away free ends at least partially enclosing a cladded line between the two vertical segments, and wherein the first vertical segment, the second vertical segment, and the horizontal segment define an opening, the opening having a width defined by a distance between inner walls of the first and second vertical segments, wherein the width of the opening between the inner walls at the flare-away free ends is larger than the width of the opening between the inner walls at connected ends of the first and second vertical segments, the first and second vertical segments being connected to the horizontal segment at the connected ends.

73. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the high permeability magnetic material is nickel iron (NiFe).

74. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors is connected to form a circuit, and wherein the circuit includes input terminals configured to receive an electrical power and output terminals connected to a voltage meter.

75. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein first plurality of magnetoresistive sensors is connected into a bridge circuit having input terminals and output terminals.

76. The ferromagnetic thin-film based magnetic field sensor of claim 75, wherein the input terminals are configured to receive electrical power and the output terminals are connected to a voltmeter to measure an output signal.

77. The ferromagnetic thin-film based magnetic field sensor of claim 72, 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.

78. The ferromagnetic thin-film based magnetic field sensor of claim 72, 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.

79. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein each magnetoresistive sensor of the first plurality of magnetoresistive sensors is a magnetic tunnel junction sensor.

80. The ferromagnetic thin-film based magnetic field sensor of claim 72, further comprising:

a third plurality of magnetoresistive sensors electrically connected together to sense a third magnetic field orthogonal to the first and second magnetic fields.

81. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors is connected together to generate a sensor signal, and wherein the first magnetic field in the direction is determined based on the sensor signal.

82. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor, a second magnetoresistive sensor, a third magnetoresistive sensor, and a fourth magnetoresistive sensor,

wherein the one or more flux guides comprises a first flux guide, a second flux guide, a third flux guide, and a fourth flux guide, and

wherein the first flux guide is associated with the first magnetoresistive sensor, the second flux guide is associated with the second magnetoresistive sensor, the third flux guide is associated with the third magnetoresistive sensor, and the fourth flux guide is associated with the fourth magnetoresistive sensor.

83. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor, a second magnetoresistive sensor, a third magnetoresistive sensor, and a fourth magnetoresistive sensor,

wherein the one or more flux guides comprises a first flux guide, a second flux guide, a third flux guide, and a fourth flux guide, and

wherein the first flux guide is above the first magnetoresistive sensor, the second flux guide is below the second magnetoresistive sensor, the third flux guide is above the third magnetoresistive sensor, and the fourth flux guide is below the fourth magnetoresistive sensor.

84. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor, a second magnetoresistive sensor, a third magnetoresistive sensor, and a fourth magnetoresistive sensor, each of the first, second, third, and fourth magnetoresistive sensors including a first side and a second side opposite to the first side,

wherein the one or more flux guides comprises a first flux guide, a second flux guide, a third flux guide, a fourth flux guide, a fifth flux guide, a sixth flux guide, a seventh flux guide, and an eighth flux guide, and

wherein the first flux guide is below the first side of first magnetoresistive sensor, the second flux guide is above the second side of the first magnetoresistive sensor, the third flux guide is above the first side of the second magnetoresistive sensor, the fourth flux guide is below the second side of the second magnetoresistive sensor, the fifth flux guide is below the first side of the third magnetoresistive sensor, the sixth flux guide is above the second side of the third magnetoresistive sensor, the seventh flux guide is above the first side of the fourth magnetoresistive sensor, and the eighth flux guide is below the second side of the fourth magnetoresistive sensor.

85. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected for differential measurement.

86. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected to, in operation, subtract resistances of the first and second magnetoresistive sensors.

87. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected to, in operation, produce a response when sensing the second magnetic field.

88. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected to, in operation, eliminate a response generated when sensing the second magnetic field.

89. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected to, in operation, double a magnetic field measurement when sensing the first magnetic field.

90. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein each magnetoresistive sensor further includes a reference layer and an intermediate layer disposed between the sensing element and the reference layer.

91. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein each magnetoresistive sensor further includes a reference layer, and wherein the reference layer includes a plurality of layers having a combined thickness in a range of 10 to 1000 Å.

92. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein each magnetoresistive sensor further includes a reference layer, and wherein the reference layer includes a plurality of layers having a combined thickness in a range of 250 to 350 Å.

93. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein each magnetoresistive sensor further includes a reference layer, and wherein the reference layer comprises:

a ferromagnetic layer; and

an antiferromagnetic layer.

94. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein each magnetoresistive sensor further includes a reference layer, and wherein the reference layer comprises:

a ferromagnetic layer having a thickness in a range of 20 to 80 Å; and

an antiferromagnetic layer having a thickness of approximately 200 Å.

95. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein each magnetoresistive sensor further includes a reference layer, and wherein the reference layer comprises:

a ferromagnetic layer; and

an antiferromagnetic layer including iridium-manganese (IrMn) alloy or platinum-manganese (PtMn) alloy.

96. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein each magnetoresistive sensor further includes a reference layer, and wherein the reference layer comprises:

a ferromagnetic layer including a three-layer structure; and

an antiferromagnetic layer.

97. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the sensing element includes a thickness in a range of 10 to 5000 Å.

98. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the sensing element includes a thickness in a range of 10 to 60 Å.

99. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the ferromagnetic thin-film based magnetic field sensor is configured to generate a sensor signal, and wherein the first magnetic field is determined based on the sensor signal.