Magnetic field sensor with MTJ elements arranged in series

Abstract

Magnetic field sensor (100; 300; 400), including: a first plurality of magnetic tunnel contact elements, MTJ elements (102), wherein each MTJ element of the first plurality of MTJ elements (102) has a state (114) indicated by the direction of the magnetic moment (112) of a sensing layer (110) relative to a pinned reference layer (122) in the absence of an external magnetic field (116), wherein the first plurality of MTJ elements (102) is arranged in two substantially identical sets (170, 172) of at least two MTJ elements, each MTJ element (102) in each respective set (170; 172) having a different state (114), wherein the two substantially identical sets (170, 172) and the at least two MTJ elements in each set (170; 172) are electrically connected in series, where each set (170, 172) includes at least two MTJ elements; a first MTJ element (102) with state (114) in a first direction; and a second MTJ element (102) whose state (114) is in a second direction that is oriented approximately perpendicular to the first direction.

Description

background

[0001] The present invention relates to magnetic field sensors and, more particularly, to a magnetic field sensor using magnetic tunnel junction (MTJ) elements.

[0002] Magnetic field sensors in the form of magnetoresistive transducers are used in the electronics industry to detect an external magnetic field in conjunction with measuring a range of parameters such as current, position, direction, and motion. One type of sensor uses tunneling magneto-resistivity (TMR). A TMR sensor uses a type of sensing element called a magnetic tunnel junction (MTJ) element. MTJ elements have the advantage of being more sensitive to resistance changes in response to an applied magnetic field, especially compared to other types of transducers such as Hall effect, anisotropic magnetoresistance (AMR), or giant magnetoresistance (GMR) sensors. MTJ elements can also consume less power, are smaller, and have better resolution than other types of sensors.

[0003] An MTJ element comprises a multilayer structure with, from top to bottom: a sensing layer (also called the free ferromagnetic layer), a tunnel barrier layer, and a pinned reference layer. The sensing layer has a magnetic moment that can easily move, e.g., rotate, in the presence of a relatively small external magnetic field; hence the term "free" in reference to the magnetic nature of the layer. The tunnel barrier layer is an insulator, e.g., an oxide. The pinned reference layer may comprise a synthetic antiferromagnetic (SAF) pinning layer beneath a ferromagnetic layer. The pinned reference layer has a magnetic field with a fixed direction that does not move when exposed to an external magnetic field; hence the term "pinned" or "reference" in reference to the magnetic nature of the layer.A non-magnetic, conductive electrode is connected to both the sensing layer and the reference layer. A parameter to be measured, e.g., an electric current, generates an external magnetic field that causes a rotation of the magnetic moment in the sensing layer. The rotation of the magnetic moment in the sensing layer causes a change in resistance (e.g., measured as a voltage change) in the MTJ element, which can be quantified to enable the measurement of the parameter.

[0004] A large number of MTJ elements are typically arranged in a two-dimensional Wheatstone bridge to create a TMR magnetic field sensor. A Wheatstone bridge uses a large number of MTJ elements in each arm of a symmetrical bridge arrangement, i.e., with the MTJ elements in an electrically parallel arrangement. In an MTJ element, the response curve of resistance (R) versus magnetic field (H) (i.e., R versus H) is non-linear. A maximum response (change in resistance) is measured in an MTJ element when the external magnetic field in the sensing layer is oriented perpendicular to the magnetic moment. However, if the external magnetic field in the sensing layer is parallel to the magnetic moment, no response is measured. Therefore, to achieve good sensitivity, different types of MTJ elements with opposite R versus H response curves are used in the Wheatstone bridge, e.g.,those whose resistance increases with increasing magnetic field, and others whose resistance decreases with increasing magnetic field. One problem with this arrangement is that the measurement may be incorrect and / or ambiguous if the direction of the external magnetic field is unknown. To overcome this problem, current Wheatstone bridges use arms with hundreds of MTJ elements arranged in X and Y alignments to attempt to accurately measure the external magnetic field by adding the two components. The area of ​​the magnetic field sensor can therefore be very large. Another challenge is that external magnetic fields that are not orthogonal to the sensing layers in the sensor, e.g., at a 45° angle, produce ambiguous results.For example, with current Wheatstone bridge designs, there is no difference in the measured resistance for a magnetic field that deviates by +45° from the direction of the magnetic field in the sensor layer and for a magnetic field that deviates by -45° from the direction of the magnetic field in the sensor layer. Accordingly, sensor positioning is critical to ensure accurate measurement.

[0005] Another difficulty with current Wheatstone bridge designs is that the two types of MTJ elements with different response curves use a different number of layers and different materials within the layers. For example, the MTJ element with one response curve may use a four-layer reference layer, while the MTJ element with the opposite response curve may use a six-layer reference layer. Therefore, manufacturing the magnetic field sensor can be very complex and expensive.

[0006] Document DE 10 2016 104 285 A1 discloses a magnetic sensor comprising a magnetic field detection unit and a calculation unit, wherein the magnetic sensor is configured to generate a value of a detected angle that has a correspondence relationship to an angle formed by the direction of a magnetic field to be detected at a reference position with respect to a reference direction. The magnetic field detection unit comprises a plurality of magnetoresistive elements for detecting the magnetic field, and the magnetic field detection unit outputs a first signal and a second signal, wherein the first signal has a correspondence relationship to the angle formed by the direction of the magnetic field with respect to a first direction, and the second signal has a correspondence relationship to the angle formed by the direction of the magnetic field with respect to a second direction.Each of the plurality of magnetoresistive elements includes a fixed magnetization layer whose magnetization direction is fixed, a free layer whose magnetization direction changes depending on the direction of the magnetic field, and a non-magnetic layer disposed between the fixed magnetization layer and the free layer. The calculation unit calculates the value of the detected angle based on the first signal and the second signal. The value of the detected angle when the direction of the magnetic field rotates at a predetermined period includes an angle error component that changes at a period of 1 / 4 of the predetermined period.A maximum amount of the angular error component changes by 0.1° or less when the strength of the magnetic field at the magnetic field detection unit changes within a sub-range that is part of a range of 20 to 150 mT and has an upper limit and a lower limit that differ from each other by 30 mT or more.

[0007] DE 11 2010 003 775 T5 describes a magnetic field sensor based on a ferromagnetic thin film, comprising: a substrate with a planar surface, and a first magnetoresistive sensor. The magnetoresistive sensor comprises: a first sensing element having a first side parallel to the planar surface of the substrate, the first sensing element having a second side opposite the first side and having first and second edges opposite each other, and a first flux guide arranged non-parallel to the first side of the first sensing element and having an end close to the first edge and the first side of the first sensing element. Summary

[0008] Aspects of the invention relate to a magnetic field sensor according to independent claim 1 or independent claim 2.

[0009] More advantageous embodiments are defined in dependent claims 3 to 10.

[0010] The above features and other features of the invention will become apparent from the following more detailed description of embodiments of the invention. Short description of the drawings

[0011] The embodiments of this invention are described in detail with reference to the following figures, wherein like reference numerals denote like elements and wherein: Fig. 1 shows a schematic plan view of a magnetic field sensor according to embodiments of the invention. Fig. 2A shows a cross-sectional view of an illustrative magnetoresistive contact (MTJ) element. Fig. Figure 2B shows a schematic plan view of an illustrative MTJ element. Fig. 3A shows a cross-sectional view of another illustrative MTJ element. Fig. Figure 3B shows a schematic plan view of another illustrative MTJ element. Fig. Figure 3C shows a cross-sectional view of another illustrative MTJ element. Fig. 4 shows a schematic plan view of a magnetic field sensor according to other embodiments of the invention. Fig. 5 shows a schematic plan view of a magnetic field sensor according to further embodiments of the invention. Fig. 6 a cross-sectional view of the magnetic field sensor of Fig. 5 along the view line 6-6. Fig. 7 shows a schematic plan view of a magnetic field sensor using a Wheatstone bridge arrangement according to embodiments of the invention. Fig. 8 shows a schematic plan view of a magnetic field sensor with a Wheatstone bridge arrangement according to another embodiment of the invention. Fig. 9 shows a graph illustrating a response curve (R versus H) of a magnetic field sensor according to embodiments of the invention. Fig. 10-13 show schematic plan views of a magnetic field sensor to which external magnetic fields of different directions are applied, according to further embodiments of the invention. Fig. 14 shows a schematic plan view of an illustrative arrangement of MTJ elements coupled to form a magnetic field sensor, according to embodiments of the invention.

[0012] Please note that the drawings of the invention are not necessarily to scale. The drawings are intended to illustrate only typical aspects of the invention and should therefore not be considered limiting the scope of the invention. Like reference numerals represent like elements throughout the drawings. Detailed description

[0013] In the following description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the present invention may be practiced.

[0014] When an element, such as a layer, region, or substrate, is described as being "on" or "over" another element, it may be directly on top of the other element, or there may be intervening elements. On the other hand, when an element is described as being "directly on" or "directly over" another element, there may not necessarily be intervening elements. When an element is described as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intervening elements. On the other hand, when an element is described as being "directly connected" or "directly coupled" to another element, there are no intervening elements.

[0015] Reference in the specification to "one embodiment" of the present invention, as well as other variations thereof, means that a particular feature, structure, characteristic, etc., described in connection with the embodiment, is included in at least one embodiment of the present invention. Therefore, the phrases "in an embodiment" or "in an embodiment," as well as any other variations appearing at various points in the specification, do not necessarily all refer to the same embodiment. It is to be understood that the use of " / ," "and / or," and "at least one of," e.g., in the cases "A / B," "A and / or B," and "at least one of A and B," is intended to encompass only the selection of the first listed option (a), only the selection of the second listed option (B), or the selection of both options (A and B).Another example: In the cases of "A, B and / or C" and "at least one of options A, B and C", this wording is intended to cover only the first listed option (A), or only the selection of the second listed option (B), or only the selection of the third listed option (C), or the selection of the first and second listed options (A and B), or the selection of the first and third listed options (A and C), or the selection of the second and third listed options (B and C), or the selection of all three options (A and B and C). This can be extended to any number of listed options, as will be readily apparent to a person skilled in the art.

[0016] Embodiments of the invention include a magnetic field sensor. The magnetic field sensor can be used to measure a variety of parameters that generate an external magnetic field, e.g., current, position, direction, movement, etc. The magnetic field sensor takes the form of a magnetoresistive transducer using tunneling magneto-resistivity (TMR) technology, and in particular, magnetic tunnel junction (MTJ) elements. As previously mentioned, TMR and MTJ elements are advantageous because, for example, they exhibit greater sensitivity to resistance changes due to an applied magnetic field, particularly compared to other forms of transducer, e.g., Hall effect, anisotropic magnetoresistance (AMR), or giant magnetoresistance (GMR) sensors. The magnetic field sensor can comprise a variety of MTJ elements.Each MTJ element is described as having a “state” indicated by the direction of the magnetic moment of a sensing layer relative to a pinned reference layer in the absence of an external magnetic field.

[0017] The plurality of MTJ elements are arranged in two substantially identical sets of at least two MTJ elements, with each MTJ element in each respective set having a different state. That is, each MTJ element in each set has a different direction of the magnetic field in its sensing layer. The term "substantially identical" as used herein means that the said structures are as similar in all details (e.g., material layers, dimensions / size, configuration, function, etc.) as manufacturing tolerances would suggest. The states of the MTJ elements are arranged to measure the external magnetic field regardless of its direction. More specifically, the sensor generates a unique signal (e.g., a unique change in resistance, measured by voltage) regardless of the direction of the external magnetic field, thereby eliminating any ambiguity regarding the direction of the external magnetic field.The magnetic field sensor can be arranged as a two-dimensional sensor or a three-dimensional sensor. The two essentially identical groups, with two or more MTJ elements in each group, are electrically connected in series. The magnetic field sensor thus solves the problems of a Wheatstone bridge arrangement. The magnetic field sensor also exhibits a unique response curve (R versus H) with less noise and variability. The sensor can be manufactured with much less effort and at a much lower cost compared to conventional sensors. In particular, the sensor can be manufactured using thin-film technology using MTJ elements that are all essentially identical, thus eliminating the challenges of manufacturing two types of MTJ elements with, for example, a different number of layers and different materials. The sensor also uses a significantly smaller number of MTJ elements, e.g.only four compared to hundreds.

[0018] With reference to Fig. Figure 1 shows a schematic plan view of a magnetic field sensor 100 according to embodiments of the invention. The magnetic field sensor 100 (hereinafter referred to as "sensor 100" for brevity) may include a (first) plurality of magnetic tunnel junction (MTJ) elements 102 electrically connected in series. The electrical connection is represented by the circular line 104. The plurality of MTJ elements 102 includes at least four MTJ elements 102A-D.

[0019] Fig. Figure 2A shows a cross-sectional view of an illustrative MTJ element 102 that can be used in a sensor 100 according to embodiments of the invention. Each MTJ element 102 has a "state" 114, which is indicated by the direction of the magnetic moment of a free sensing layer 110 (hereinafter "sensing layer 110") relative to a pinned reference layer 122 in the absence of an external magnetic field 116. To ensure that the resistance changes linearly when the magnetic moment of the sensing layer 110 is rotated by the external magnetic field 116, the relative orientation of the magnetic moment between the reference layer 122 and the sensing layer 110 is adjusted to be perpendicular to each other. Therefore, the "state" 114 for each MTJ element 102 is the direction of the magnetic moment 112 in the sensing layer 110 in the absence of the external magnetic field 116.A state 114 of an MTJ element 102 is indicated by black arrows in the drawings, and the external magnetic field(s) 116 are indicated by gray arrows in the drawings. The magnetic moment 112 is only visible in . Fig. 2A with double arrows to indicate that it is easily movable / rotatable. According to the illustration in Fig. 2B, the sensing layer 110 and the reference layer 122 of the MTJ elements 102 have a long axis (LA) and a short axis (SA). In the example of Fig. In Figure 2B, layers 110 and 122 are arranged one above the other. The direction of the magnetic moment 112 of the sensing layer 110, and thus its state 114, extend along the long axis LA, which is the natural state in the absence of an external magnetic field 116. In this way, the state 114 of each MTJ element 102 can be adjusted in a desired direction depending on how the MTJ element 102, i.e., layers 110, 112, are arranged during manufacture.

[0020] According to the presentation in Fig. 2A, MTJ elements 102 each include at least a pinned reference layer 122, a tunnel barrier layer 120, and a sensing layer 110. Each MTJ element 102 thus has a multilayer structure. The sensing layer 110 may include one or more ferromagnetic layers 130, 132 (two shown) that generate a magnetic field 112 that is relatively easy to move, e.g., rotate, in the presence of a relatively small external magnetic field 116. In one non-limiting example, the sensing layer 110 may include ferromagnetic metals and / or compounds such as the nickel-iron (NiFe) layer 130 and a cobalt-iron-boron-tantalum (CoFeBTa) layer 132. The NiFe layer 130 is a ferromagnetic alloy known as a mu-metal. The tunnel barrier layer 120 comprises one or more insulator layers (one of which is shown), including but not limited to, for example, an oxide such as magnesium oxide (MgO), silicon oxide (SiO2), or aluminum oxide (Al2O3).The pinned or fixed reference layer 122 (hereinafter "reference layer 122") has a magnetic moment 136 with a pinned or fixed direction. In . Fig. 2A, the magnetic moment 136 extends within a plane of the reference layer 122. The reference layer 122, which may also be referred to as a pinned antiferromagnetic layer, may, for example, comprise a synthetic antiferromagnetic (SAF) pinning layer. The SAF pinning layer may, for example, comprise a CoFeBTa layer 140, a ruthenium layer 142, a cobalt iron (CoFe) layer 144, and a platinum manganese (PtMn) layer 146. The reference layer 122 may thus comprise a ferromagnetic layer, e.g., the CoFeBTa layer 140, over one or more bulkier antiferromagnetic layers 142, 144, 146, the latter serving to fix ("pin") the direction of the magnetic moment 136. A non-magnetic conductive electrode 150 may be connected to the sensing layer 110 and a non-magnetic conductive electrode 152 may be connected to the pinning layer 120.Each conductive electrode 150, 152 may comprise any non-magnetic electrode known today or later developed, such as a ruthenium layer 156 and a tantalum layer 158.

[0021] Fig. 3A to 3C show variations of MTJ elements 102 that may also be used in accordance with embodiments of the invention. Fig. 3A shows a cross-sectional view and Fig. Figure 3B shows a schematic plan view of another illustrative MTJ element 102 that may be used in a sensor 100. The MTJ element 102 of Fig. 3A-B is essentially similar to that of the Fig. 2A-B, except that, as in Fig. 3B, the longitudinal axis of the reference layer 122 is rotated perpendicular to that of the sensing layer 110. Therefore, the magnetic moment 112 of the sensing layer 110 is oriented perpendicular to the magnetic moment 136 of the reference layer 122. Fig. Figure 3A shows a magnetic moment 136 (arrowhead or tail) extending into or out of the page. Fig. Figure 3C shows a cross-sectional view of another illustrative MTJ element 102 that can be used in a sensor 100. The MTJ element 102 of Fig. 3C is similar to that of Fig. 2A-B and Fig. 3A-B, except that the magnetic moment 136 of the reference layer 122 extends vertically (shown upwards, but could also extend downwards), which may be easier to manufacture.

[0022] MTJ elements 102 can be fabricated over any known or newly developed semiconductor substrate 160 as part of a thin-film process. The MTJ elements 102 can be embedded in any known or advanced dielectric material 162 ( Fig. 2A). It is emphasized that, although exemplary layers of an MTJ element 102 are described herein, the invention is not limited to any particular type of MTJ element 102, and that a wide variety of alternatives are known and applicable to embodiments of the present invention. However, in accordance with embodiments of the invention, the MTJ elements 102 used in the sensor 100 may be substantially identical. Among other things, the MTJ elements 102 used in the sensor 100 may use the same material layers. Accordingly, the sensor 100 eliminates the challenges of manufacturing a sensor that uses different types of MTJ elements with, for example, a different number of layers and different materials.

[0023] With respect to individual MTJ elements 102, a parameter to be measured, such as an electric current, generates an external magnetic field 116 during operation, which causes a rotation of the magnetic field 112 in the sensing layer 110 and changes its state 114. The rotation of the magnetic field 112 in the sensing layer 112 causes a change in resistance (R) (e.g., measured as a voltage change) in the respective MTJ element 102, which can be quantified to enable a measurement of the parameter in a known manner. Since the manner of quantifying the measurement is known, further description is not required.

[0024] With further reference to Fig. 1, a plurality of MTJ elements 102A-D may be arranged in two substantially identical sets 170, 172 (marked with dashed boxes) of at least two MTJ elements, e.g., 102A-B and 102C-D, respectively. Each MTJ element 102A and 102B, or 102C and 102D, in each set 170, 172 has a different state 114. That is, MTJ element 102A has a different state 114 (from left to right on the page) than MTJ element 102B (from bottom to top on the page) in set 170. Similarly, MTJ element 102C has a different state 114 (from left to right on the page) than MTJ element 102D (from bottom to top on the page). The sets 170, 172 are also essentially identical in that the states 114 of the series-connected MTJ elements 102A-B and 102C-D are repeated.As already mentioned, the two substantially identical sets 170, 172 and the two or more MTJ elements 102A-B, 102C-D in each set 170, 172 are electrically connected in series, that is, across the conductors shown in . Fig. 1 schematically shown connecting line 104.

[0025] Each of the MTJ elements 102 in the sensor 104 comprises the same material layers. (See, for example, layers in the illustrative MTJ element 102 in Fig. 2A). This means they all have the same number of layers with the same materials, so they can be formed simultaneously. Using MTJ elements 102 with the same material layers makes manufacturing easier than sensors that use two different types of MTJ elements.

[0026] The number of MTJ elements 102 in each set 170, 172 may vary. In one embodiment, there may be any even number of MTJ elements 102 to ensure accurate measurement of the external electric field 116 (an example in Fig. 1). In Fig. 1, each set 170, 172 comprises two MTJ elements, creating a sensor with four MTJ elements 102. More specifically, each set 170, 172 comprises a first MTJ element 102A, 102C having state 114 in a first direction. In the example shown, the first direction is from left to right in the page, but it can be any direction. As will be described, the first direction serves as the reference direction for describing the states of the other MTJ elements 102. In Fig. 1, each set 170, 172 also includes a second MTJ element 102B, 102D whose state 114 is approximately perpendicular to the first reference direction in a second direction (e.g., from bottom to top of the page). As used herein with reference to the directions of the states 114, "approximately" means + / - 2°.

[0027] As shown, multiple MTJ elements 102A-D function together in a floral pattern 176, i.e., as if they were centered around a center point CP and extend radially from that point. In this regard, it is recognized that the MTJ elements 102 may be physically arranged in any desired manner using thin-film technology. For example, as in the example in Fig. 14, MTJ elements 102 may be constructed in rows, columns, or arrays of MTJ elements 102 having the same state 114, but electrically connected in series by line 104 to collectively act as in a floral pattern 176.

[0028] With reference to Fig. 4 is a schematic view of another embodiment of the sensor 100. In this embodiment, the sensor 100 includes MTJ elements 102A-D as shown in Fig. 1, but each set 170, 172 further comprises a third and fourth MTJ element 102, forming an eight-membered flower pattern 176 and not a four-membered flower pattern as in Fig. 1 is generated. In this way, the sensor 100 can Fig. 4 detect a wider variety of external magnetic fields 116 (in Fig. 4 (only one is shown), e.g., over a wider variety of external magnetic field directions. Set 170 includes a third MTJ element 102E disposed in series between MTJ element 102A and MTJ element 102B, and a fourth MTJ element 102F disposed in series downstream of MTJ element 102B. Similarly, set 172 includes a third MTJ element 102G disposed in series between MTJ element 102C and MTJ element 102D, and a fourth MTJ element 102H disposed in series downstream of MTJ element 102D. The angles of the MTJ elements 102E-H with respect to the reference direction (i.e., the first reference direction of the MTJ elements 102A, 102C) may be chosen such that pairs of MTJ elements 102 are perpendicular to an expected external magnetic field 116.For example, the third MTJ element 102E may have a state 114 in a third direction between 10° and 80° relative to the first reference direction (left to right in the example shown). In the non-limiting example shown, the third MTJ element 102E of the set 170 has a state 114 in a third direction at an angle of approximately 45° relative to the first reference direction of the MTJ element 102A. Similarly, the third MTJ element 102G of the set 172 has a state 114 in a third direction between 10° and 80° relative to the first reference direction of the MTJ element 102C. In the non-limiting example shown, the third MTJ element 102G of the set 172 has a state 114 in a third direction at an angle of approximately 45° relative to the first reference direction of the MTJ element 102C.

[0029] A similar arrangement is provided, respectively, for the fourth MTJ elements 102F and 102H of each set 170 and 172. For example, the fourth MTJ element 102F may have a state 114 in a fourth direction between 110° and 170° relative to the first reference direction (left to right in the example shown). In the illustrated, non-limiting example, the fourth MTJ element 102F of set 170 has a state 114 in a third direction at an angle of approximately 135° relative to the first reference direction of MTJ element 102A. Similarly, the fourth MTJ element 102H of set 172 has a state 114 in a fourth direction between 110° and 170° relative to the first reference direction of MTJ element 102C. In the non-limited example shown, the fourth MTJ element 102H of the set 172 has a state 114 in a fourth direction at an angle of approximately 135° relative to the first reference direction of the MTJ element 102C.

[0030] The angles of the states 114 of all MTJ elements 102A-H in a given sensor 100 with respect to the reference direction (i.e., the first reference direction of the MTJ elements 102A, 102C) can be selected to ensure that pairs of MTJ elements 102 are perpendicular to an expected external magnetic field 116 to ensure maximum response from at least one pair of MTJ elements 102. As will be further described, using a number of MTJ elements 102 at non-orthogonal state angles relative to the external magnetic field 116 also contributes to the response to enable identification of the direction of the external magnetic field 116.

[0031] As shown, multiple MTJ elements 102A-H function together in a floral pattern 178, i.e., as if they were centered around a central point CP and extending radially from that point. As previously mentioned, the MTJ elements 102A-H can be arranged in any desired manner using thin-film technology. For example, the MTJ elements 102A-H can be constructed in rows, columns, or arrays of MTJ elements 102 having the same state 114, but electrically connected in series by line 104 to collectively function as if in a floral pattern 178.

[0032] The Fig. 5-8 show alternative embodiments of the magnetic field sensor 100 according to embodiments of the invention.

[0033] In the previously described embodiments, the MTJ elements 102 of the sensor 100 are arranged in two dimensions, e.g., in a plane of an integrated circuit. Fig. 5 shows a schematic plan view and Fig. 6 shows a cross-sectional view along the view line 6-6 in Fig. 5 of a sensor 100 in which the MTJ elements 102 are also arranged two-dimensionally. In these embodiments, however, the sensor 100 also includes a magnetic field deflector 200 arranged to deflect an external magnetic field 216 (only Fig. 6), which has a direction outside the two dimensions of the MTJ elements 102, into the two dimensions for detection by a plurality of MTJ elements 102. The magnetic field deflection 200 thus converts a Z component of an external magnetic field 216 ( Fig. 6) into an XY field that can be measured by the sensor 100. The magnetic field deflector 200 can comprise any paramagnetic material known today or later developed, such as a mu-metal. In a non-limiting example, the magnetic field deflector 200 can deflect up to 70% of the Z of the external magnetic field 216. It should be noted that the sensor 100 cannot distinguish the Z component of the external magnetic field 216 from the regular X or Y components of the external magnetic field 116 (an example is shown in Fig. 5). The magnetic field deflection 200 can have any shape to deflect the external magnetic field 216 ( Fig. 6) into the MTJ elements 102. In the example shown, the magnetic field deflection 200 has a truncated cone shape; however, other shapes are also conceivable. Fig. 5-6, the sensor 100 has MTJ elements 102, which are arranged as in Fig. 4. It is recognized that the lessons learned from the Fig. 5-6 may be used with one or more sensors according to any embodiment described herein.

[0034] Fig. 7 and Fig. 8 show schematic views of embodiments in which the magnetic field sensor(s) 100 described herein, each having a plurality of MTJ elements 102, is / are arranged in a Wheatstone bridge magnetic field sensor 300 or 400. Fig. Figure 7 shows a Wheatstone bridge magnetic field sensor 300 (hereinafter "sensor 300") with a plurality of MTJ elements 102 of sensor 100 in a first quarter arm 304 of a Wheatstone bridge 302. Here, Wheatstone bridge 302 includes a second quarter arm 310, a third quarter arm 312, and a fourth quarter arm 314, each including a resistor 320 with a fixed value. Sensor 300 may be referred to as a quarter-bridge circuit. The MTJ elements 102 in sensor 100 are electrically connected in series in the first quarter arm 304, while arms 304, 310, 312, 314 of the bridge are electrically connected in parallel in a known manner. The sensor 300 offers the advantages of the MTJ elements 102 described herein, but with resistors 320 that reduce the number of MTJ elements required compared to conventional Wheatstone bridge arrangements.The resistors 320 may include any thin-film technology resistors known today or later developed, such as metal resistors, polysilicon resistors, etc.

[0035] Fig. 8 shows a Wheatstone bridge magnetic field sensor 400 (hereinafter "sensor 400") having a first plurality of MTJ elements 102 (i.e., sensor 100A) in a first quarter arm 404 of a Wheatstone bridge 402. The Wheatstone bridge 402 of the sensor 400 also includes a second quarter arm 410 having a second plurality of MTJ elements 102 (i.e., sensor 100B), a third quarter arm 412 having a third plurality of MTJ elements 102 (i.e., sensor 100C), and a fourth quarter arm 414 having a fourth plurality of MTJ elements 102 (i.e., sensor 100D). Thus, a sensor 100, as described herein, is disposed in each arm of the Wheatstone bridge 402 of the sensor 400. The sensor 400 offers the advantages of the MTJ elements 102 as in the sensor 100 and greater sensitivity to different directions of the external electric fields 116, but with a smaller number of MTJ elements compared to conventional Wheatstone bridge arrangements.Each plurality of MTJ elements 102 may be arranged as described in any embodiment herein. In sensor 400, the MTJ elements 102 in each of the first plurality of MTJ elements, the second plurality of MTJ elements, the third plurality of MTJ elements, and the fourth plurality of MTJ elements are electrically connected in series, while the arms 404, 410, 412, 414 of the bridge are electrically connected in parallel in a known manner. As shown, the first plurality of MTJ elements 102 (sensor 100A) and the third plurality of MTJ elements 102 (sensor 100C) are located in opposite quarter arms 404, 412 of the Wheatstone bridge 402 and have substantially similar arrangements, e.g., with their first reference directions in the same direction.Furthermore, the second plurality of MTJ elements 102 (sensor 100B) and the fourth plurality of MTJ elements 102 (sensor 100D) are located in opposite quarter arms 410, 414 of the Wheatstone bridge 402 and have substantially similar arrangements, e.g., with their first reference directions in the same direction. However, as can be seen by comparing the directions of the states 114 in each sensor 100A-D in FIG. Fig. 8, the second plurality of MTJ elements 102 (sensor 100B) and the fourth plurality of MTJ elements 102 (sensor 100D) have different arrangements than the first plurality of MTJ elements 102 (sensor 100A) and the third plurality of MTJ elements 102 (sensor 100C), e.g., they have different reference directions. In the Fig. 7-8, the sensors 100 comprise MTJ elements 102, which as in Fig. 4. It is recognized that the lessons learned from the Fig. 7-8 are applicable with sensors 100 according to any embodiment described herein.

[0036] Fig. Figure 9 shows a graph illustrating a response curve of magnetic field sensors 100, 300, or 400 according to embodiments of the invention. As shown in Fig. 9, a response curve of resistance (R) versus magnetic field (H) (i.e., R versus H) for the MTJ element 102 is non-linear. With reference to the Fig. 4 and Fig. 9, the sensors 100, 300, 400 with MTJ elements 102 according to the embodiments of the invention generate for each direction of the external magnetic field 116 applied to them ( Fig. 4) a clear signal (e.g., a change in resistance across the sensor). The response curves (R versus H) exhibit less noise and variability compared to conventional magnetic field sensors.

[0037] As already mentioned, one would normally obtain two extreme values ​​of the response curve: one with maximum resistance change when the external magnetic field is perpendicular to the free direction of the MTJ elements in the Wheatstone bridge, and one with no resistance change when the external magnetic field is parallel to the free direction of the MTJ elements in the Wheatstone bridge. External magnetic fields that are not orthogonal to the sensing layers in the sensor, e.g., at an angle of 45°, would also not lead to clear results (see, for example, fields 116B or 116C in Fig. 10). For example, when using the current Wheatstone bridge, there is no difference in the measured resistance for a magnetic field that deviates by +45° from the direction of the magnetic field in the sensing layer and a magnetic field that deviates by -45° from the direction of the magnetic field in the sensing layer.

[0038] The MTJ elements 102 of the sensor 100, 300, 400 generate a unique resistance for each direction of the external magnetic field 116 applied to them. In particular, the sensor 100, 300, 400 can be configured such that a pair of MTJ elements 102 within each set 170, 172 is perpendicular or nearly perpendicular to the external magnetic field 116 to elicit maximum response from these MTJ elements 102. Those MTJ elements 102 that are not perpendicular and not parallel to the external magnetic field 116 also contribute to the resistance change and generate the unique signal.

[0039] With reference to the Fig. 10-11, the application of illustrative external magnetic fields 116 to the sensor 100 of Fig. 4 to explain the operation of the sensors 100, 300, 400. In operation, a parameter to be measured, such as an electric current, generates an external magnetic field 116, which causes a rotation of the magnetic field 112 ( Fig. 2A) in the detection layer 110 ( Fig. 2A) of the MTJ elements 102 in a sensor, causing their states 114 to change. The rotation of the magnetic field 112 ( Fig. 2A) in the sensing layer 110 causes a change in the resistance (R) ( Fig. 2A) (e.g., measured as a voltage change) in the series-connected MTJ elements 102, which can be quantified to enable the measurement of the parameter. The quantification of the parameter can be achieved using any technique known today or later developed, e.g., by calibration. Since the method of quantifying the measurement is well known, further details are not required.

[0040] Fig. Figure 10 shows an applied external magnetic field 116A (from left to right on the page) and its effect on the states 114 of the MTJ elements 102 in the sensor 100. (Note that the original states of the MTJ elements 102A-H are shown in dashed lines behind the black arrows, which indicate the current states 114 rotated by the external magnetic field 116A.) As shown, the external magnetic field 116A causes a maximum response (i.e., a maximum rotation of the magnetic field 112 ( Fig. 2A) and a maximum change in resistance) in the MTJ elements 102B, 102D, since they are perpendicular to the external magnetic field 116A. No change is registered in the MTJ elements 102A and 102C, since they are parallel to the external magnetic field 116A. The external magnetic field 116A also causes a rotation of the magnetic field 112 ( Fig. 2A) in the MTJ elements 102E, 102F, 102G, and 102H, i.e., in the MTJ elements 102 that are not orthogonal and not parallel to the external magnetic field 116A. The resistance change at the sensor 100, 300, or 400 caused by these MTJ elements generates a signal that, due to its direction, is uniquely associated with the external magnetic field 116A. This means that the resistance change is uniquely attributable to the direction of the external magnetic field 116A, allowing the field direction to be measured and identified.

[0041] Fig. Figure 11 shows the application of the external magnetic field 116B (e.g., at an angle of 45° from left to right on the page) and its effect on the states 114 of the MTJ elements 102 in the sensor 100. As shown, the external magnetic field 116B causes a maximum response (i.e., a maximum rotation of the magnetic field 112 ( Fig. 2A) and a maximum change in resistance) in the MTJ elements 102E, 102G, since they are perpendicular to the external magnetic field 116B. No change is registered in the MTJ elements 102F and 102H, since they are parallel to the external magnetic field 116B. The external magnetic field 116B also causes a rotation of the magnetic field 112 ( Fig. 2A) in the MTJ elements 102A, 102B, 102C, and 102D, i.e., in the MTJ elements 102 that are not orthogonal and not parallel to the external magnetic field 116B. The resistance change at the sensor 100, 300, or 400 caused by these MTJ elements generates a signal that, due to its direction, is only valid for the external magnetic field 116B. Other external magnetic fields, e.g., 116C in Fig. 4, generate clear signals in a similar way.

[0042] For descriptive purposes only, it is assumed that the resistance contribution of each MTJ element 102 is between 0 and 10 units. For the external magnetic field 116A in Fig. 10, the MTJ elements 102B, 102D each contribute a maximum of 10 units, while the MTJ elements 102E, 102H each contribute +5 units and the MTJ elements 102F, 102G each contribute -5 units. The MTJ elements 102A and 102C do not contribute because the external magnetic field 116A is parallel to their magnetic moment. The external magnetic field 116A generates 20 units, which is a unique signal corresponding to the direction of the external magnetic field 116A. For the external magnetic field 116B in Fig. 11, the MTJ elements 102E, 102G each contribute a maximum of 10 units, while the MTJ elements 102A, 102D each contribute +2.2 units, and the MTJ elements 102B, 102C each contribute -0.8 units. The MTJ elements 102B and 102F do not contribute because the external magnetic field 116B is parallel to their magnetic moment. The external magnetic field 116B thus generates a unique signal of 22.4 units. For the external magnetic field 116C in Fig. 12, the MTJ elements 102F, 102H each contribute a maximum of 10 units, while the MTJ elements 102A, 102B each contribute +3 units and the MTJ elements 102C, 102H each contribute -1.5 units. The MTJ elements 102E and 102G do not contribute because the external magnetic field 116C is parallel to their magnetic moment. The external magnetic field 116C generates 23 units, which is a unique signal corresponding to the direction of the external magnetic field 116C. Regarding the external magnetic field 116D in Fig. 13, all MTJ elements 102 contribute due to the direction of the field. For example, MTJ elements 102F and 102H each contribute almost a maximum of 9.4 units, while the following MTJ elements contribute the following units: 102A +5, 102B +4.9, 102C -2.5, 102D -2.2, 102E +1.2, 102G -1.1. The external magnetic field 116D generates 24.1 units, which is a unique signal corresponding to the direction of the external magnetic field 116D. Differently oriented external magnetic fields 116 generate similar unique and identifying signals.

[0043] Although embodiments with four or eight MTJ elements 102 in a sensor 100 have been described herein, any number of MTJ elements 102 may be used, e.g., 10, 16, 18, etc.

[0044] As mentioned here, several MTJ elements 102 function together in a floral pattern 176 ( Fig. 1 and Fig. 4), ie, as if they were centered around a center point CP and extending radially therefrom. In this context, it is recognized that the MTJ elements 102 can be physically arranged in any desired manner using thin-film technology. For example, MTJ elements 102, as in the example in Fig. 14, may be constructed in rows, columns, or arrays of MTJ elements 102 having the same state 114, but electrically connected in series by line 104 to collectively act as in a floral pattern 176.

[0045] Embodiments of the invention provide a magnetic field sensor 100, 300, 400 for measuring a plurality of parameters that generate an external magnetic field, e.g., current, position, direction, movement, etc. The sensor can arrange the states of its MTJ elements in any desired manner to measure the external magnetic field regardless of the direction of the external magnetic field. Advantageously, each direction of an external magnetic field applied to the sensor generates a unique signal, e.g., a change in resistance measured by a voltage, in the sensor, thereby eliminating any ambiguity regarding the direction of the external magnetic field. As described, the magnetic field sensor can be arranged as a two-dimensional sensor or as a three-dimensional sensor. The magnetic field sensor also exhibits a unique response curve (R versus H) with less noise and variability.The sensor can be formed using thin-film technology using MTJ elements that are all essentially identical, eliminating the challenges of manufacturing two types of MTJs. The sensor also uses a significantly smaller number of MTJ elements, for example, only four compared to hundreds.

[0046] The resulting integrated circuit chips, including the sensors 100, 300, 400 described herein, may be distributed by the manufacturer in unprocessed wafer form (i.e., a single wafer containing multiple unpackaged chips), as a bare chip, or in packaged form. In the latter case, the chip is mounted in a single-chip package (e.g., a plastic carrier with leads attached to a motherboard or other higher-level carrier) or in a multi-chip package (e.g., a ceramic carrier with surface interconnects and / or buried interconnects). In either case, the chip is then integrated with other chips, discrete circuit elements, and / or other signal processing devices as part of either (a) an intermediate product, such as a motherboard, or (b) a final product.The end product can be any product containing integrated circuit chips, ranging from toys and other simple applications to advanced computer products with a display, keyboard or other input device, and a central processor.

[0047] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an,” and “the” include the plural forms unless the context clearly indicates otherwise. It is further understood that the terms “comprises” and / or “comprising,” when used in this description, specify the presence of certain features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. “Optional” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not occur.

[0048] Vague language, as used herein in the description and claims, may be used to modify any quantitative representation that may permissibly vary without altering the basic function to which it relates. Accordingly, a value modified by one or more terms such as "approximately" and "substantially" is not limited to the precise value stated. The term "approximately" has been expressly defined herein as it relates to the states of the MTJ elements 102. In at least some cases, the vague language may correspond to the accuracy of a measuring device. Here and throughout the description and claims, range limitations may be combined and / or interchanged; such ranges are identified and include all subranges contained therein unless the context or language indicates otherwise.The term "approximately" applied to a specific value of a range refers to both values ​​and, unless otherwise dependent on the accuracy of the measuring instrument, may mean + / - 10% of the stated value(s).

[0049] The corresponding structures, materials, acts, and equivalents of all means or step-plus-function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed.

Claims

[1] Magnetic field sensor (100; 300; 400), comprising: a first plurality of magnetic tunnel contact elements, MTJ elements (102), wherein each MTJ element of the first plurality of MTJ elements (102) has a state (114) indicated by the direction of the magnetic moment (112) of a sensing layer (110) relative to a pinned reference layer (122) in the absence of an external magnetic field (116), wherein the first plurality of MTJ elements (102) is arranged in two substantially identical sets (170, 172) of at least two MTJ elements, wherein each MTJ element (102) in each respective set (170; 172) has a different state (114), wherein the two substantially identical sets (170, 172) and the at least two MTJ elements in each set (170; 172) are electrically connected in series, wherein each set (170, 172) comprises the at least two MTJ elements; a first MTJ element (102) having the state (114) in a first direction; and a second MTJ element (102) whose state (114) is in a second direction oriented approximately perpendicular to the first direction. [2] Magnetic field sensor (300), comprising: a first plurality of magnetic tunnel contact elements, MTJ elements (102), wherein each MTJ element of the first plurality of MTJ elements (102) has a state (114) indicated by the direction of the magnetic moment (112) of a sensing layer (110) relative to a pinned reference layer (122) in the absence of an external magnetic field (116), wherein the first plurality of MTJ elements (102) is arranged in two substantially identical sets (170, 172) of at least two MTJ elements, wherein each MTJ element (102) in each respective set (170; 172) has a different state, wherein the two substantially identical sets (170, 172) and the at least two MTJ elements in each set are electrically connected in series, wherein the first plurality of MTJ elements (102) are arranged in a first quarter arm (304) of a Wheatstone bridge (302), and wherein the Wheatstone bridge (302) comprises a second quarter arm (310), a third quarter arm (312), and a fourth quarter arm (314), each comprising a resistor (320) having a fixed value. [3] The magnetic field sensor (100; 300; 400) of claim 2, wherein each set (170, 172) comprises the at least two MTJ elements, comprising: a first MTJ element (102) having the state (114) in a first direction; and a second MTJ element (102) whose state (114) is in a second direction oriented approximately perpendicular to the first direction. [4] Magnetic field sensor (100; 300; 400) according to claim 1 or 3, wherein each set (170, 172) further comprises: a third MTJ element (102) whose state is oriented in a third direction between 10° and 80° relative to the first direction; and a fourth MTJ element (102) whose state is oriented in a fourth direction between 110° and 170° with respect to the first direction. [5] The magnetic field sensor (100; 300; 400) of claim 4, wherein the first plurality of MTJ elements (102) function together in a floral pattern. [6] The magnetic field sensor (100; 300; 400) of claim 1 or 2, wherein each of the first plurality of MTJ elements (102) comprises the same material layers. [7] The magnetic field sensor (300) of claim 1, wherein the first plurality of MTJ elements (102) are arranged in a first quarter arm (304) of a Wheatstone bridge (302), and wherein the Wheatstone bridge (302) comprises a second quarter arm (310), a third quarter arm (312), and a fourth quarter arm (314), each comprising a resistor (320) having a fixed value. [8] The magnetic field sensor (400) of claim 1, wherein the first plurality of MTJ elements (102) is arranged in a first quarter arm (404) of a Wheatstone bridge (402), and wherein the Wheatstone bridge (402) further comprises a second quarter arm (410) with a second plurality of MTJ elements (102), a third quarter arm (412) with a third plurality of MTJ elements (102), and a fourth quarter arm (414) with a fourth plurality of MTJ elements (102), wherein the MTJ elements (102) in each of the first plurality of MTJ elements (102), the second plurality of MTJ elements (102), the third plurality of MTJ elements (102), and the fourth plurality of MTJ elements (102) are electrically connected in series, and wherein the first plurality of MTJ elements (102) and the third plurality of MTJ elements (102) are located in opposite quarter arms of the Wheatstone bridge (402) and are arranged substantially similarly, and the second plurality of MTJ elements (102) and the fourth plurality (102) of MTJ elements are located in opposite quarter arms of the Wheatstone bridge (402) and are arranged substantially similarly, wherein the second plurality of MTJ elements (102) and the fourth plurality of MTJ elements (102) have a different arrangement than the first plurality of MTJ elements (102) and the third plurality of MTJ elements (102). [9] The magnetic field sensor (100) of claim 1 or 2, wherein the first plurality of MTJ elements (102) are arranged in two dimensions and further comprises a magnetic field deflector (200) positioned to direct an external magnetic field (216) having a direction outside the two dimensions into the two dimensions for detection by the first plurality of MTJ elements (102). [10] Magnetic field sensor (100) according to claim 9, wherein the magnetic field deflection (200) has a frustoconical shape.

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