Magnetic field sensor with increased SNR

Abstract

The present disclosure relates to magnetic field sensors with increased SNR. Various means are disclosed for improving the signal-to-noise ratio (SNR) of magnetic field sensors for low power and high resolution magnetic sensing. Such improvements can be accomplished by reducing parasitic effects, increasing sensing element packaging density, staggering Z-axis layouts to reduce cancellation effects, and optimizing alignment between Z-axis sensing elements and flux guides, among others.

Description

[0001] This application is a divisional application of the Chinese invention patent application filed on April 29, 2016, with application number 201680023898.1 and invention name “Magnetic Field Sensor with Increased SNR”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of priority to U.S. Provisional Application No. 62 / 156,013, filed May 1, 2015; Provisional Application No. 62 / 154,210, filed April 29, 2015; and U.S. Non-Provisional Application No. 15 / 141,461, filed April 28, 2016, all of which are incorporated herein by reference. Technical Field

[0004] The present invention relates generally to the field of magnetic field sensors and, more particularly, to a method of increasing the signal-to-noise ratio (SNR) of a magnetic field sensor. Background Art

[0005] Magnetic field sensors have been widely used in various electronic devices such as computers, laptops, media players, smart phones, etc. There are several technologies / devices that can be used to detect magnetic fields. Tunneling Magnetoresistance (TMR) is a promising magnetic sensing technology for handheld applications because it has advantages in sensitivity, power, and process cost compared to other magnetic sensors. Another closely related technology in magnetic field sensing is Giant Magneto Resistance (GMR), and many of the disclosed embodiments are equally well suited for GMR-based sensing technology.

[0006] A TMR element consists of two ferromagnetic layers separated by a nonmagnetic insulating tunnel barrier. One layer has a magnetization direction that is "free" to rotate in a magnetic field. The other layer (the reference layer) has a "fixed" reference magnetization that does not rotate when in a magnetic field of moderate to low intensity that is of interest for sensing. If the magnetization directions of the two layers are parallel to each other, the resistance of the tunnel barrier is low. Conversely, when the magnetization directions are antiparallel, the resistance is high. Therefore, a TMR-based magnetic field sensor converts a magnetic field into an electrical signal by a change in resistance due to a change in the angle of the magnetization direction of the magnetic free layer in response to the field relative to the reference magnetization of the fixed layer.

[0007] The performance of a magnetic sensor can be defined by its signal-to-noise ratio (SNR). Magnetic sensors with high SNR require high power operation to achieve the desired output signal quality and are generally not suitable for situations where high-precision magnetic field measurements are required.

[0008] Therefore, it is desirable to have systems, devices, and methods that effectively increase the signal-to-noise ratio (SNR) of magnetic field sensors for lower power and high resolution magnetic sensing. Summary of the invention

[0009] Certain embodiments of the present invention provide systems, devices, and methods for effectively increasing the SNR of TMR magnetic field sensors for low-power, high-resolution magnetic sensing.

[0010] According to various embodiments of the present invention, various means for improving the SNR of TMR field sensors are disclosed. Such improvements can be achieved by reducing parasitic effects, increasing the packing density of sensing elements, staggering the Z-axis layout to reduce subtractive effects, and optimizing the alignment between the Z-axis sensing elements and the flux guides.

[0011] In some embodiments, the magnetic sensor is constructed with a Wheatstone bridge circuit, where each branch includes the same number of sensing elements. Such a design can avoid differential responses to planar fields because all elements respond in the same way. In addition, for balanced sensing current flow (e.g., for equal SNR weighting for each sensing element), an even number of sensing elements (preferably 4 sensing elements) per metal magnetic tunnel (MMT) is used, and the sensing current flows vertically through the magnetic tunnel junction (MTJ) sensing element and is perpendicular to the MMT orientation, which interconnects adjacent sensing elements to minimize resistive losses.

[0012] In certain embodiments, for Z-axis magnetic sensing, the Z-axis layout is staggered to utilize both sides of the flux guide. Preferably, dual flux guides are used for optimal trench width while maintaining the pitch and spacing constraints of the reference layer within the TMR sensing element. Sensing elements may also be used on both sides of the flux guide to eliminate the cancellation effect that exists when the inactive ferromagnetic side of one trench is close enough to interact with one side of an adjacent sensing element column. Adjacent sensing elements may be arranged to have opposite responses to out-of-plane fields, so that the Z-axis sensor branches become staggered with each other to allow for denser packaging, relatively higher sensing element footprint, and relatively higher SNR without compromising sensitivity due to the cancellation effect described above.

[0013] In some embodiments, the built-in reset line in the TMR sensor is routed at a 45 degree cross angle to the easy (long) axis of the magnetic sensing element, compared to a 90 degree cross angle reset line routing, to reduce the switching threshold by a factor of approximately two. In addition, the reset line in the TMR sensor can be used in combination with the above means in a bipolar chopping method to further reduce the sensor output signal noise.

[0014] Although the present invention is discussed below using a TMR magnetic field sensor with a TMR element, all aspects of the present invention will also be directly applicable to devices based on giant magnetoresistance (GMR) technology. The invention disclosed herein is also applicable to any magnetic sensing technology that utilizes a soft magnetic film to sense a magnetic field, such as, for example, anisotropic magnetoresistance (AMR), fluxgate, and Hall sensors with flux concentrators. For simplicity and clarity, the present invention will be described in more detail below using TMR technology as an example. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Reference will be made to the exemplary embodiments of the present invention illustrated in the accompanying drawings. These drawings are intended to be illustrative rather than restrictive. Although the present invention is generally described in the context of these embodiments, it is not intended that the scope of the present invention be limited to the specific features of the embodiments depicted and described by doing so.

[0016] Figure 1 Depicted are cross-sectional views of a single TMR element unit cell according to various embodiments of the present invention.

[0017] Figure 2 Depicted is an exemplary structural overview of a TMR sensor branch having multiple element units according to various embodiments of the present invention.

[0018] Figure 3 Depicted is an exemplary structural overview of a Z-axis TMR transducer branch having a plurality of Z-axis TMR element units according to various embodiments of the present invention.

[0019] FIG. 4 depicts a cross-sectional structural overview of a typical interconnection of a prior art X / Y-axis TMR element unit.

[0020] Figure 5 Depicted is an exemplary cross-sectional structural overview of the interconnection of an X / Y-axis TMR element unit according to various embodiments of the present invention.

[0021] FIG. 6 depicts a cross-sectional structural overview of a typical interconnection of a prior art Z-axis TMR element unit.

[0022] Figure 7 Depicted is an exemplary cross-sectional structural overview of the interconnection of a Z-axis TMR element unit according to various embodiments of the present invention.

[0023] 8A-8C illustrate cross-sectional views of a Z-axis TMR sensing element unit and a magnetic flux guide according to various embodiments of the present invention.

[0024] Fig. 9 An exemplary structural overview of a TMR magnetic field sensor including a bridge circuit with multiple TMR transducer branches according to various embodiments of the present invention is depicted.

[0025] Figures 10A-10B Depicted are exemplary schematic diagrams of bridge circuits for measuring the X-axis or Y-axis of a magnetic field according to various embodiments of the present invention.

[0026] Figures 11A-11B Depicted is an exemplary schematic diagram of a bridge circuit for measuring a Z-axis magnetic field according to various embodiments of the present invention.

[0027] Fig.12 Depicted are exemplary structural diagrams of arrays of X / Y-axis TMR element units according to various embodiments of the present invention.

[0028] Fig.13 A second exemplary structural diagram of an array of X / Y-axis TMR element units according to various embodiments of the present invention is depicted.

[0029] Fig.14 Depicted are exemplary structural diagrams of arrays of Z-axis TMR element units according to various embodiments of the present invention.

[0030] Figures 15A-15C Depicted are exemplary schematic diagrams of arrays of Z-axis TMR element units according to various embodiments of the present invention.

[0031] Fig.16 Depicted are exemplary schematic diagrams of an array of Z-axis TMR element cells with 45 degree reset current lines according to various embodiments of the present invention.

[0032] Those skilled in the art will recognize that various implementations and embodiments of the present invention can be practiced according to the description. All these implementations and embodiments are intended to be included within the scope of the present invention.

[0033] As used herein, the terms "comprises," "comprising," or any other variations thereof, are intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus that includes a list of elements includes not only those elements, but may also include other elements not expressly listed or inherent to those processes, methods, articles, or apparatuses. The term "exemplary" is used in the sense of an "example," rather than in the sense of an "ideal." DETAILED DESCRIPTION

[0034] In the following description, for the purpose of explanation, specific details are set forth in order to provide an understanding of the present invention. However, the present invention can be practiced without some or all of these details. The embodiments of the present invention described below can be incorporated into a plurality of different electrical components, circuits, equipment and systems. The structures and devices shown in the block diagrams are illustrations of exemplary embodiments of the present invention and are not used as an excuse to cover up the broad teachings of the present invention. The connection between the components in each figure is not intended to be limited to direct connection. On the contrary, the connection between the components can be modified, reformatted, rewired or otherwise changed by an intermediate component.

[0035] When this specification refers to "one embodiment" or "an embodiment", this means that a particular feature, structure, characteristic, or function described in connection with the embodiment in question is included in at least one contemplated embodiment of the present invention. Thus, the appearances of the phrase "in one embodiment" in various places in this specification do not constitute multiple references to a single embodiment of the present invention.

[0036] Various embodiments of the present invention are systems, devices, and methods for effectively increasing the SNR of a TMR magnetic field sensor and maintaining a desired measurement sensitivity. The TMR magnetic field sensor and (one or more) TMR elements therein can be integrated on a single component or include discrete components. In addition, embodiments of the present invention can be applied to a wide variety of techniques and method sets.

[0037] As described above, the magnetic field sensor claimed herein may mean one or more of a TMR magnetic field sensor, a GMR magnetic field sensor, an AMR magnetic field sensor, a fluxgate magnetic field sensor, and / or a Hall magnetic field sensor with a flux concentrator. In addition, the magnetoresistive sensing element claimed herein may mean one or more of a TMR element, a GMR element, an AMR element, a fluxgate element, and / or a Hall element with a flux concentrator.

[0038] Figure 1 A cross-sectional view of a single TMR element unit 100 according to various embodiments of the present invention is illustrated. The TMR element unit 100 consists of a first patterned ferromagnetic layer 112 and a second ferromagnetic layer 114 separated by a non-magnetic insulating tunnel barrier 116 (also referred to as a tunnel junction (TJ)). In one embodiment, the first layer 112 (also referred to as the sensing element) has a magnetization direction 132 that is free to rotate in a magnetic field. The second layer 114 (reference layer) has a fixed reference magnetization direction 134 that does not rotate when in a magnetic field. If the magnetization directions of the two layers are parallel to each other, the resistance of the tunnel barrier 116 is relatively low. In contrast, when the magnetization directions are anti-parallel, the resistance is relatively high.

[0039] Thus, the TMR element unit 100 converts a magnetic field into an electrical signal by a change in resistance due to a change in the magnetization direction 132 of the magnetic free layer in response to a field relative to a reference magnetization direction 134 of the fixed layer. The ferromagnetic layers 112 and 114 may be formed of any suitable ferromagnetic material, such as Ni, Fe, Co, or alloys thereof. The insulating tunnel barrier 116 may be composed of an insulator material such as AlOx, MgOx, ZrOx, TiOx, HfOx, or any combination thereof.

[0040] Typically, the first ferromagnetic layer 112 is connected to a first wire 124 via a first contact 122, and the second ferromagnetic layer 114 is connected to a second wire 128 via a second contact 126 that can be contacted from above and below the second ferromagnetic layer 114. The second wire 128 may also be referred to as a metal magnetic tunnel (MMT) layer. In one embodiment, the first wire 124 and the second wire 128 may be connected to other TMR element units 100 to form a TMR element unit array.

[0041] In one embodiment, the TMR element unit 100 includes a built-in current wire 410 located, deployed or deposited adjacent to the second ferromagnetic layer 114 to carry a reset current. The current wire 410 of one TMR element unit 100 can be coupled to the current wires of multiple other TMR element units. In another embodiment, the TMR element unit 100 also includes a second built-in current wire 420 located, deployed or deposited adjacent to the first ferromagnetic layer 112. The first ferromagnetic layer 112 is patterned into a shape having a long axis and a short axis. In a zero magnetic field, the magnetization direction of the first ferromagnetic layer 112 is arranged along the long axis of the element 100 and can be guided in either of the two directions along the axis. By applying a reset current signal to the current wire 410 and / or the current wire 420, an induced magnetic field is generated in the ambient area surrounding the corresponding current wire 410 / 420. Since the first layer 112 has a magnetization direction 132 that is free to rotate and switch, the magnetization direction 132 will switch to a direction along the direction projected on its axis by the induced magnetic field. As Figure 1 As shown in the exemplary illustration in , when the current in the current line 410 has a direction pointing outward (relative to the page) and the current in the current line 420 has a direction pointing inward (relative to the page), the magnetization direction 132 points to the left, which has a component aligned negatively with the reference magnetization direction 134, and the magnetization direction 132 of the free layer will be switched to the left; when the current in the current line 410 has a direction pointing inward and / or the current in the current line 420 has a direction pointing outward, the magnetization direction 132 points to the right, which has a component aligned positively with the reference magnetization direction 134, and the magnetization direction 132 of the free layer will be switched to the right.

[0042] In one embodiment, the TMR element unit 100 includes at least one built-in flux guide for Z-axis magnetic field sensing (for clarity of the figure, in Figure 1 ). The flux guide 118 is Figure 3 , 6 and 7, and will be described below.

[0043] Figure 2 An exemplary structural overview of a TMR transducer branch 210 having a plurality of element units 100 according to various embodiments of the present invention is depicted. The TMR sensor branch 210 comprises an array of a plurality of active sensing element units 100a-100d preferably arranged in a matrix layout. In one embodiment, each TMR transducer branch 210 comprises an array of 24×24 sensing element units 100, with an overall size of approximately 100×100 um 2 The current flows in the current lines 410a and 410b of each sensing element unit 100 may or may not be in the same direction. It should be understood that Figure 2 The structures shown are for general illustration purposes only. Figure 2 In addition to the patterns disclosed in , various sensing element coupling patterns can be implemented within the array. In one embodiment, the sensing element cells (e.g., cells 100a, 100c) can have opposite current directions relative to the current lines of adjacent sensing element cells (e.g., cells 100b and 100d). For the highest signal-to-noise ratio in a given chip area (most densely packed sensing element cells), multiple TMR element cells 100 can share a common reference layer (e.g., a common second ferromagnetic layer 114). In one embodiment, for balanced sensing current flow, four sensing element cells can share a common reference layer, with each TMR element cell having equal SNR weighting. This configuration is Fig.12 The diagram is shown in the circled area marked “one MMT”.

[0044] Figure 3 An exemplary structural overview of a Z-axis TMR transducer branch 310 having a plurality of element units 311 according to various embodiments of the present invention is depicted. Each Z-axis TMR transducer branch 310 includes an array of a plurality of active Z-axis TMR element units 311a-311d preferably arranged in a matrix layout. In one embodiment, each Z-axis TMR transducer branch 310 includes an array of 60×40 Z-axis sensing element units 311, with an overall size of approximately 150×200 um. 2 The Z-axis TMR element unit 311 has Figure 1 The structure of the TMR element unit 100 shown in FIG. 1 is similar to that of the TMR element unit 100 shown in FIG. 1 , except that the Z-axis TMR element unit 311 further includes at least one magnetic flux guide 118. Although the magnetic flux guide 118 is located, disposed or deposited on the Figure 3 The first ferromagnetic layer 312 (equivalent to Figure 1 and Figure 2 1 and 12. The Z-axis TMR element unit 311 is shown in FIG. ...

[0045] FIG4 depicts a cross-sectional structural overview of a typical interconnection of an X / Y axis TMR element unit of the prior art. Each second ferromagnetic layer 114 (MMT) is coupled to only one first ferromagnetic layer 112. TJ 116 is not explicitly shown in FIGS. 4-7. Therefore, a separate through hole 142 on the second ferromagnetic layer 114 (MMT) must be used for electrical connection between TMR sensing element units.

[0046] Figure 5 An exemplary cross-sectional structural overview of the interconnection of X / Y axis TMR element units according to various embodiments of the present invention is depicted. Compared to FIG. 4 , the second ferromagnetic layer 114 (MMT) and the upper conductor layer 124 are coupled to multiple first ferromagnetic layers 112 and directly serve as connecting conductors for series coupling between TMR sensing elements without the need for additional vias or interconnect lengths. By doing so, the electrical coupling path is significantly reduced and the parasitic effects from the coupling path are also significantly reduced. In a preferred embodiment, each second ferromagnetic layer 114 (MMT) is coupled to four first ferromagnetic layers 112. In one embodiment, all sensing element units are arranged in a single row or column on the MMT (see, e.g. Fig.12 ). In addition, the sense current flows vertically through the MTJ sense element unit and is oriented perpendicular to the MMT, which interconnects adjacent sense element units to minimize resistive losses.

[0047] Figure 6 depicts a cross-sectional structural overview of a typical interconnection of a prior art Z-axis TMR element unit. Similar to Figure 4, each second ferromagnetic layer 114 (MMT) is coupled to only one first ferromagnetic layer 112. Therefore, a separate through hole 142 on the second ferromagnetic layer 114 (MMT) must be used for electrical connection between the sensing element units.

[0048] Figure 7An exemplary cross-sectional structural overview of the interconnection of the Z-axis TMR element unit according to various embodiments of the present invention is depicted. Compared to Figure 6, the second ferromagnetic layer 114 (MMT) is coupled to multiple first ferromagnetic layers 112 and is directly used as a connecting conductor for series coupling between sensing element units. By doing so, the electrical coupling path is significantly reduced and the parasitic effects from the coupling path are also significantly reduced. In a preferred embodiment, each second ferromagnetic layer 114 (MMT) is coupled to two first ferromagnetic layers 112. Since each sensing element unit has an equal SNR weighting, this arrangement will be beneficial for balanced sensing current flow.

[0049] 8A-8C show a comparison between a typical Z-axis TMR element unit and a cross-sectional view of a Z-axis TMR element unit according to various embodiments of the present invention. The cross-sectional view extends to multiple TMR element units. For clarity, some components such as the second ferromagnetic layer 114, the insulating tunnel barrier 116, etc. are not shown in FIG. 8A-8C. The flux guide 118 is a high aspect ratio vertical strip made of a high permeability magnetic material, and its ends terminate at the opposite edges close to the TMR sensing element (i.e., the first ferromagnetic layer 112). The flux guide 118 captures the magnetic flux from the applied field oriented in the Z-axis direction and bends the field lines into a horizontal component having a horizontal component close to the end of the flux guide 118. The first ferromagnetic layer 112 responds only to the in-plane magnetic field and therefore does not directly respond to the Z-axis magnetic field. The flux guide 118 bends the Z-axis magnetic field into a horizontal direction so that the first ferromagnetic layer 112 can respond accordingly.

[0050] FIG8A depicts a cross-sectional view of a TMR sensing element unit and a flux guide of two adjacent typical Z-axis TMR element units. Each TMR sensing element unit includes only one flux guide 118, which is asymmetrically placed between two adjacent sensing element units (i.e., the first ferromagnetic layer 112). Due to the asymmetry, a subtraction effect is generated between the flux guide 118 and the farther sensing element unit (this interaction is depicted with a (-) sign in FIG8A). Although the amplitude of the Z-axis field conversion (in-plane component) from the farther sensing element unit is smaller due to the distance from the edge of the flux guide, it is opposite to and subtracts from the in-plane component of the Z-axis field conversion of the adjacent sensing element unit.

[0051] Figure 8B and 8C 1 shows a cross-sectional view of a magnetic flux guide of a TMR sensing element unit and two different types of Z-axis TMR element units according to various embodiments of the present invention. Figure 8B In the embodiment, dual flux guide grooves 118a and 118b are used instead of a single wide flux guide 118c ( Figure 8C). The dual flux guide grooves 118a and 118b are symmetrically located, deployed or deposited between adjacent sensing element units (i.e., the first ferromagnetic layer 112). In addition, the dual flux guide grooves 118a and 118b (with gaps between the dual flux guide grooves) cover the entire spacing between adjacent sensing element units in the width direction. This arrangement decouples the requirements for sensing element pitch, MMT spacing, and groove width, thereby allowing optimal use of all of these. Figure 8C In the embodiment, the wide groove flux guide 118c is symmetrically located, disposed or deposited between adjacent sensing element units (ie, the first ferromagnetic layer 112), and covers the entire interval between adjacent sensing element units in the width direction. Figure 8B and 8C The dual flux guide grooves 118a and 118b and the wide groove flux guide 118 are shown below the first ferromagnetic layer 112, but the dual flux guide grooves 118a and 118b and the wide groove flux guide 118c can also be located, deployed or deposited above the first ferromagnetic layer 112. In one embodiment, the flux guide shown in Figures 8A-8C is made with a thin ferromagnetic material layer 119 coated on both sides of the groove to respond to the Z-axis magnetic field.

[0052] Fig. 9 A schematic diagram of a TMR magnetic field sensor 200 according to various embodiments of the present invention is shown. The magnetic field sensor 200 includes a first bridge circuit 220 powered by a voltage source 300 connected via a voltage source connection 300a and a second circuit 400 powered by an optional reset field source 500, which can be a current source connected via a reset field source connection 500a. The first bridge circuit 220 includes a plurality of TMR transducer branches 210 (or a plurality of Z-axis TMR transducer branches 310). The bridge circuit 220 can be a half-bridge circuit, a full-bridge circuit, or any combination thereof. In one embodiment, the bridge circuit 220 is a Wheatstone bridge circuit having two circuit branches, wherein the bridge output signal 260 between the two branches is at a certain midpoint along the branches. The TMR transducer branch 210 (or the Z-axis TMR transducer branch 310) is electrically used as a resistor, and its resistance value changes in response to the internal magnetic field and the external magnetic field. The current line 410 of each TMR element unit 100 (or the Z-axis TMR element unit 311 ) is wired in various wiring patterns to form the second circuit 400 .

[0053] Fig. 10A and 10B An exemplary schematic diagram of a bridge circuit for measuring the X-axis or Y-axis of a magnetic field with a current line energized according to various embodiments of the present invention is depicted. Figure 1When a reset current is applied to the current line 410, a magnetic field pulse having a magnetization direction 132 is generated on the first ferromagnetic layer 112. Depending on the polarity of the applied current pulse, the generated magnetic field switches the free layer direction 132 to have a component that is positively aligned or negatively aligned with the reference magnetization direction 134 of the second ferromagnetic layer. Fig. 10A shows a magnetization direction 132 that is substantially positively aligned in the first ferromagnetic layer 112, and Fig. 10B A substantially negatively aligned magnetization direction 132 in the first ferromagnetic layer 112 is shown.

[0054] Fig.11A and 11B Depicted is an exemplary schematic diagram of a bridge circuit with energized current lines for measuring the Z-axis of a magnetic field in accordance with various embodiments of the present invention. Fig.11A and 11B Two exemplary Z-axis bridge configurations with different sensing element magnetizations are shown. It should be understood that Fig.11A and 11B The magnetic flux guides 118 shown are for general illustration purposes only. It is referred to as a collection of magnetic flux guides within each Z-axis TMR transducer branch 310. Each Z-axis TMR transducer branch 310a, 310b, 310c, and 310d may also have a magnetic flux guide having ... Fig.11A and 11B The patterns shown are for different magnetizations.

[0055] Fig.12 An exemplary structural diagram of an array of X / Y axis TMR element units according to various embodiments of the present invention is depicted. The reset line 410 has a 45 degree crossing angle with the first ferromagnetic layer 112. Such reset line wiring will have a relatively low switching threshold, and only half the reset current is required to switch the magnetization direction of the first ferromagnetic layer 112 compared to the 90 degree reset line wiring. In one embodiment, in order to balance the flow of sensing current, four sensing element units can share a common reference layer (MMT), whereby each TMR element unit has an equal SNR weighting. The element units are connected via horizontal links (e.g., Figure 5 and Figure 7 Each horizontal link 124 couples a pair of elements in one row of elements to a pair of elements in an adjacent row.

[0056] Fig.13A second exemplary structural diagram of an array of X / Y axis TMR element units according to various embodiments of the present invention is shown. The reset line 410 has a 90 degree crossing angle with the first ferromagnetic layer 112. Compared with the 45 degree reset line wiring pattern, the 90 degree reset line wiring pattern requires a relatively high reset current threshold to switch the magnetization direction of the first ferromagnetic layer 112, but in some configurations, the 90 degree reset line wiring pattern is more robust. The 90 degree reset line wiring pattern can be used in applications with a relatively high power budget for the TMR sensor.

[0057] Fig.14 An exemplary block diagram of an array of Z-axis TMR element units according to various embodiments of the present invention is shown. Dual flux guide grooves 118a and 118b are used for optimal groove width while maintaining TJ pitch and spacing constraints. In one embodiment, a single wide flux guide 118c (not shown) may also be used instead of the configuration of dual flux guide grooves 118a and 118b. Similar to Figure 8B , the Z-axis TMR element units on each row are electrically connected to the second ferromagnetic layer 114 (MMT) via a horizontal link 124 through a sensing element (i.e., the first ferromagnetic layer 112), and the second ferromagnetic layer 114 (MMT) can be connected in a desired pattern to construct a final TMR sensor. In one embodiment, a row 1030 of Z-axis TMR element units has an opposite response to an out-of-plane field (Z-axis field) compared to an adjacent row 1040 of Z-axis TMR element units. For example, the TMR element units of row 1030 may have an increased resistance response, but the TMR element units of row 1040 may have a decreased resistance response. Therefore, the TMR element units of the same row can be bundled together and act as a bridge circuit 220 ( Fig. 9 A bridge branch (310) or a portion of a bridge branch) as shown.

[0058] Figures 15A-15C Schematic diagrams of arrays of Z-axis TMR element units according to various embodiments of the present invention are depicted. Fig.15A A Wheatstone bridge circuit 1100 is shown, wherein each bridge branch 1110, 1120, 1130, and 1140 represents a row (or rows) of a Z-axis TMR element unit. The Wheatstone bridge circuit 1100 is coupled between a voltage source Vdd and a ground GND, wherein the diagonal bridge branches have the same response to an out-of-plane field (Z-axis field). The voltage difference between the middle points m1 and m2 is the output of the Wheatstone bridge circuit 1100. The Wheatstone bridge circuit 1100 can be constructed by staggering patterns of different TMR element units. Fig. 15B shows a parallel staggered pattern, and Fig. 15C A parallel staggered pattern of longer serpentine paths is shown for optimum overall transducer resistance.

[0059] exist Fig. 15BIn the example, each bridge branch is connected to Fig.11A and 11B The first branch 1110 and the third branch 1130 form a path between the voltage source Vdd and the ground GND. The second branch 1120 and the fourth branch 1140 form another path between the voltage source Vdd and the ground GND. Each bridge branch corresponds to a row of TMR element units. The first branch 1110 and the third branch 1130 have opposite responses to the out-of-plane field (Z-axis field). The second branch 1120 and the fourth branch 1140 have opposite responses to the out-of-plane field (Z-axis field). In addition, the first branch 1110 and the second branch 1120 have opposite responses to the out-of-plane field (Z-axis field). The staggered pattern is designed to ensure maximum output and dense space filling between the midpoints m1 and m2 without the previously described attenuation effect from adjacent sensing element units and flux guides. In one embodiment, a TMR magnetic field sensor may include a plurality of such staggered patterns coupled in parallel between a voltage source and ground.

[0060] exist Fig. 15C In the embodiment, each bridge branch corresponds to multiple rows of TMR element units connected in series, and the number of rows included in each bridge branch is the same. In addition, the TMR element units in each bridge branch have the same response to the Z-axis magnetic field. Similar to Fig. 15B , the four bridge branches 1110-1140 establish a Wheatstone bridge circuit 1100 to ensure maximum output between the middle points m1 and m2. Fig. 15C As shown, each bridge branch is composed of three rows of TMR element units, but it should be understood that the bridge branch can be composed of any desired odd number of rows of TMR element units. In a preferred embodiment, the bridge branch can include rows of TMR element units for bridge circuit output resistances on the order of 10 kΩ to balance power consumption and Johnson noise.

[0061] Fig.16 An exemplary schematic diagram of an array of Z-axis TMR element units with a 45-degree reset current line according to various embodiments of the present invention is depicted. The reset line 410 has a 45-degree crossing angle with the first ferromagnetic layer 112. Compared to the 45-degree reset line wiring pattern, the 90-degree reset line wiring pattern requires a relatively high reset current threshold to switch the magnetization direction of the first ferromagnetic layer 112. However, for some configurations, the 90-degree reset line wiring pattern is more robust. The 90-degree reset line wiring pattern can be used for applications with a relatively high power budget for the TMR sensor.

[0062] Those skilled in the art will recognize that various implementations can be implemented within the described architecture, all of which fall within the scope of the present invention. For example, various reset current line wiring and / or power-on methods can be implemented in the TMR magnetic field sensor. For example, a bipolar reset current can be applied to the reset current line to reduce the 1 / f noise of the magnetic sensor. In addition to the reset current line wiring patterns disclosed in the above embodiments, a bipolar reset current can also be applied. In addition, the reset current line wiring patterns may not be limited to the above illustrated embodiments.

[0063] The foregoing description of the invention has been described for the sake of clarity and understanding. It is not intended to limit the invention to the precise form disclosed. Various modifications may be made within the scope and equivalence of the application.

Claims

1. A magnetic field sensor, comprising: a plurality of magnetoresistive sensing elements coupled together as a first circuit for sensing a magnetic field, wherein each of the plurality of magnetoresistive sensing elements comprises a first ferromagnetic layer and a second ferromagnetic layer separated by an insulating barrier layer, and A wire coupled to the first ferromagnetic layer of the first magnetoresistive sensing element and the first ferromagnetic layer of the second magnetoresistive sensing element such that portions of the first magnetoresistive sensing element and the second magnetoresistive sensing element are electrically connected, wherein a first magnetoresistive sensing element and a third magnetoresistive sensing element of the plurality of magnetoresistive sensing elements share a common second ferromagnetic layer, such that either (1) the common second ferromagnetic layer is above both the first ferromagnetic layer of the first magnetoresistive sensing element and the first ferromagnetic layer of the third magnetoresistive sensing element, or (2) the common second ferromagnetic layer is below both the first ferromagnetic layer of the first magnetoresistive sensing element and the first ferromagnetic layer of the third magnetoresistive sensing element, and The first magnetoresistance sensing element and the third magnetoresistance sensing element each include a separate first ferromagnetic layer and a separate insulating barrier layer, wherein the first ferromagnetic layers of the first magnetoresistance sensing element and the third magnetoresistance sensing element are spaced apart, and wherein the insulating barrier layers of the first magnetoresistance sensing element and the third magnetoresistance sensing element are spaced apart.

2. The magnetic field sensor according to claim 1, further comprising: At least one magnetic flux guide is positioned between two magnetoresistive sensing elements of the plurality of magnetoresistive sensing elements. 3 . The magnetic field sensor of claim 1 , further comprising at least one magnetic flux guide, and wherein the at least one magnetic flux guide is located above or below two of the plurality of magnetoresistive sensing elements.

4. The magnetic field sensor of claim 1, further comprising at least one magnetic flux guide, wherein the at least one magnetic flux guide comprises a thin layer of ferromagnetic material on both sides of the at least one magnetic flux guide. 5 . The magnetic field sensor of claim 1 , further comprising at least one magnetic flux guide, wherein the at least one magnetic flux guide is located between two magnetoresistive sensing elements of the plurality of magnetoresistive sensing elements. 6 . The magnetic field sensor of claim 5 , wherein the at least one magnetic flux guide is symmetrically located between the two magnetoresistive sensing elements of the plurality of magnetoresistive sensing elements. 7 . The magnetic field sensor of claim 6 , wherein a width of the at least one magnetic flux guide covers an entire width between the two magnetoresistive sensing elements of the plurality of magnetoresistive sensing elements.

8. The magnetic field sensor of claim 5, wherein the at least one magnetic flux guide is positioned relatively closer to one of the two magnetoresistive sensing elements in the plurality of magnetoresistive sensing elements than to the other of the two magnetoresistive sensing elements in the plurality of magnetoresistive sensing elements, and wherein the at least one magnetic flux guide comprises a high permeability magnetic material.

9. The magnetic field sensor of claim 1 , further comprising at least a first magnetic flux guide and a second magnetic flux guide, wherein the first magnetic flux guide is located above two of the plurality of magnetoresistive sensing elements, and wherein the second magnetic flux guide is located below the two of the plurality of magnetoresistive sensing elements.

10. The magnetic field sensor of claim 1 , further comprising at least one magnetic flux guide, wherein the at least one magnetic flux guide is configured to guide a portion of a magnetic field oriented orthogonal to a plane of the first magnetoresistive sensing element and the third magnetoresistive sensing element into the plane of the first magnetoresistive sensing element and the third magnetoresistive sensing element.

11. The magnetic field sensor of claim 1 , further comprising: A second circuit includes a plurality of current lines, wherein each current line of the plurality of current lines is adjacent to a corresponding magnetoresistive sensing element of the plurality of magnetoresistive sensing elements, and wherein at least one current line of the plurality of current lines is positioned above or below the corresponding magnetoresistive sensing element. 12 . The magnetic field sensor of claim 11 , wherein at least one of the plurality of current lines is positioned at a 45 degree crossing angle or a 90 degree crossing angle relative to a ferromagnetic layer of a magnetoresistive sensing element of the plurality of magnetoresistive sensing elements.

13. The magnetic field sensor according to claim 1, wherein: When the plurality of magnetoresistive sensing elements sense a magnetic field, a sensing current flows through the ferromagnetic layers of the magnetoresistive sensing elements, and a direction in which the sensing current flows is perpendicular to the conductive line.

14. The magnetic field sensor of claim 1, wherein the plurality of magnetoresistive sensing elements comprises four magnetoresistive sensing elements coupled together in a Wheatstone bridge.

15. The magnetic field sensor of claim 1, wherein the first ferromagnetic layer of each magnetoresistive sensing element includes a magnetization direction that is free to rotate in a magnetic field, and wherein each magnetoresistive sensing element includes the second ferromagnetic layer including a fixed magnetization direction.

16. The magnetic field sensor of claim 1, wherein the plurality of magnetoresistive sensing elements comprises one or more anisotropic magnetoresistive sensing elements. 17 . The magnetic field sensor of claim 1 , wherein the plurality of magnetoresistive sensing elements include one or more tunnel magnetoresistive sensing elements or one or more giant magnetoresistive sensing elements.

18. A magnetic field sensor, comprising: a plurality of magnetoresistive sensing elements coupled together as a first circuit for sensing a magnetic field, wherein each of the plurality of magnetoresistive sensing elements comprises a first ferromagnetic layer and a second ferromagnetic layer separated by an insulating barrier layer, wherein the plurality of magnetoresistive sensing elements comprises at least a first magnetoresistive sensing element and a second magnetoresistive sensing element located in one plane; a conductive line coupled to the first ferromagnetic layer of the first magnetoresistive sensing element and the first ferromagnetic layer of the second magnetoresistive sensing element; as well as at least one magnetic flux guide, wherein the at least one magnetic flux guide is located between the first magnetoresistive sensing element and the second magnetoresistive sensing element and above or below the first magnetoresistive sensing element, The first magnetoresistance sensing element and the third magnetoresistance sensing element among the plurality of magnetoresistance sensing elements only share a common second ferromagnetic layer, so that either (1) the common second ferromagnetic layer is above both the first ferromagnetic layer of the first magnetoresistance sensing element and the first ferromagnetic layer of the third magnetoresistance sensing element, or (2) the common second ferromagnetic layer is below both the first ferromagnetic layer of the first magnetoresistance sensing element and the first ferromagnetic layer of the third magnetoresistance sensing element.

19. The magnetic field sensor of claim 18, wherein the at least one magnetic flux guide is configured to guide a portion of the magnetic field oriented orthogonal to the plane of the first and second magnetoresistive sensing elements into the plane of the first and second magnetoresistive sensing elements, and in, When the plurality of magnetoresistive sensing elements sense a magnetic field, a sensing current flows through the first ferromagnetic layer, the insulating barrier layer, and the second ferromagnetic layer of the magnetoresistive sensing element, and The first magnetoresistive sensing element and the third magnetoresistive sensing element each include a separate first ferromagnetic layer and a separate insulating barrier layer.

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