Magnetic-field-sensitive bridge resistor arrangement and bridge circuit with PMA layer structure and corresponding production method

Abstract

The invention relates to a magnetic-field-sensitive bridge resistor arrangement (20) composed of at least two bridge resistors (14) arranged adjacently on a substrate (12) for a bridge circuit (10) that is magnetic-field-sensitive in a main axis direction (SA). Each bridge resistor (14) comprises a series circuit composed of multiple TMR layer structures (22, 70, 72). Each TMR layer structure (22, 70, 72) comprises an antiferromagnetic layer (24), at least one first fixed ferromagnetic layer (26) having a first fixed magnetization direction (28), fixed substantially in the direction of the main axis direction (SA), in a plane of the TMR layer structure (22, 70, 72), and a free ferromagnetic layer (30) having a free magnetization direction (32), wherein a non-magnetic intermediate layer (34) is arranged between the free ferromagnetic layer (30) and the at least first fixed ferromagnetic layer (24). The invention proposes that the free magnetization direction (32) for forming a PMA (perpendicular magnetic anisotropy) layer structure is oriented perpendicular to the plane of the TMR layer structure (22, 70, 72) in the magnetic-field-free state, and the first fixed magnetization directions (28) of TMR layer structures (22, 70, 72) of the bridge resistors (14) arranged adjacently on the substrate (12) are different to one another. For this purpose, a temperature of at least 260°C to at most 350° over a predeterminable period of at least 1 h to at most 12 h and a field strength of a coupled pretreatment magnetic field (Hz) with a magnetic flux density strength of less than 500 mT can be used during production. Secondary aspects propose a bridge circuit for measuring a weak magnetic field and a method for producing the bridge resistor arrangement (20).

Description

[0001] Magnetic field sensitive bridge resistor arrangement and bridge circuit with PMA layer structure and related manufacturing method

[0002] The invention relates to a magnetic-field-sensitive bridge resistor arrangement comprising at least two TMR bridge resistors arranged adjacently on a substrate for a bridge circuit that is magnetically sensitive in a main axis direction, as well as to such a bridge circuit, in particular for a current sensor or angle sensor, and preferably for the vectorial measurement of a weak magnetic field of up to 50 mT. A free magnetization direction in a free ferromagnetic layer of a TMR layer structure of the bridge resistor arrangement is oriented perpendicular to a first defined magnetization direction and to the plane of the TMR layer structure to form a PMA layer structure (Perpendicular Magnetic Anisotropy) in the magnetic-field-free state.

[0003] In a secondary aspect, the invention relates to a manufacturing method of such a bridge resistor arrangement and such a bridge circuit.

[0004] STATE OF THE ART

[0005] Magnetoresistive magnetic field sensors are used for the resistance-based measurement of magnetic fields. Through suitable geometric arrangements, other physical quantities such as displacement, angle, or current can be measured. Magnetoresistive magnetic field sensors are based on a magnetoresistive effect. This describes a change in the electrical resistance of a material due to the application or variation of an external magnetic field. Magnetic field sensors with a comparatively high magnetoresistive effect, which can be described by the quotient of the change in resistance (AR = RMSX - resistance) and the minimum resistance RMin, are based on the giant magnetoresistance effect (GMR effect) or the tunnel magnetoresistance effect (TMR effect). Alternatively, materials are available that exhibit the AMR effect (anisotropic magnetoresistance).These effects are also collectively referred to as the xMR effect. TMR magnetic field sensors comprise a thin-film construction of non-magnetic and magnetic materials in a layered structure, in which a magnetic coupling or spin effect through the layers influences the electrical resistance. In TMR-based magnetoresistive layered structures, a change in electrical resistance of up to 600% can be achieved based on an external magnetic field. A layered structure is a structure that can be described as a sequence of thin layers along one axis, typically perpendicular to the substrate surface, and has a geometric shape along the other orthogonal axes.

[0006] To manufacture TMR magnetic field sensors, a layered structure of at least two ferromagnetic layers and an electrically insulating barrier layer, which serves as a tunnel barrier and is also referred to as an intermediate layer, is formed in a TMR layer structure so that a tunnel current can flow between the two ferromagnetic layers. In the case of a TMR magnetic field sensor, the barrier layer consists of Al2O3 or MgO, for example. The electrical resistance of a tunnel element depends, in addition to geometric parameters such as the area, on how the two ferromagnetic layers are magnetized to each other. If the two ferromagnetic layers are magnetized parallel to each other, the resistance R M in minimal. If, however, they are magnetized antiparallel to each other, the resistance R Ma x maximum.

[0007] In practice, the magnetization direction of one of the two ferromagnetic layers is often fixed or pinned, so that the magnetization of this layer reacts only weakly or not at all to external fields. This layer is referred to as the reference layer or pinned layer. In the following, the reference layer will be referred to as the first fixed ferromagnetic layer. The other layer, however, is designed so that its magnetization can follow the external field in a defined manner. This layer is also called the detection layer or free ferromagnetic layer. In the following, the detection layer will be referred to as the free ferromagnetic layer.

[0008] Thin-film technologies are used to manufacture such structures or resistance elements. During the manufacturing process, the direction of magnetization of the fixed ferromagnetic layer can be permanently adjusted, a process often referred to as pinning. To pin the fixed ferromagnetic layer, the ferromagnetic layer is typically coupled to a neighboring antiferromagnetic layer. To adjust the magnetization direction, the resistance element, i.e., the layer structure, is heated above the so-called blocking temperature, at which the exchange coupling between the antiferromagnetic layer and the ferromagnetic layer disappears. This temperature is usually lower than the Curie temperature of the ferromagnetic layers.After reaching the desired temperature above the blocking temperature and below the Curie temperature, the ferromagnetic layers are exposed to an external pinning magnetic field, which forces these layers into a defined magnetization direction. This requires that the applied pinning magnetic field be large enough to align the ferromagnetic layer completely parallel to the pinning field. This magnetization direction is maintained when the layer structure cools down again with the pinning magnetic field applied and the temperature falls below the blocking temperature.

[0009] In this context, a pinning magnetic field is referred to as a locally acting magnetic field that penetrates a ferromagnetic layer of the layer structure in a desired pinning direction, perpendicular to the layer sequence, i.e., tangential to the substrate surface, and represents a local magnetic field component. This must be distinguished from the so-called pretreatment magnetic field, which is a global alignment magnetic field from which the pinning magnetic field is derived by guiding the magnetic field, e.g., by ferromagnetic structuring elements. The global pretreatment magnetic field is generally stronger and can be aligned in a different direction than the local pinning magnetic field.

[0010] To set pinning directions, it is known to selectively heat spatially limited regions of a substrate bearing layered structures using selective heating methods, in particular using lasers, and to apply an external magnetic field in a desired direction parallel to the substrate surface for pinning. This makes it possible to pin locally heated regions with layered structures in an identical direction. If different pinning directions are to be created on a substrate, the process must be repeated several times with different external magnetic field orientations. However, it is not possible to pin spatially closely adjacent layered structures in different directions.On the other hand, the construction of conventional direction-selective magnetic field sensors requires layer structures that have different preferred directions and are subject to the same process-technical properties; thus, pinning layer structures in different directions is desirable for closely adjacent layer structures.

[0011] Furthermore, laser pinning in less than one second is disadvantageous for antiferromagnetic materials, such as PtMn or NiMn, which can only recrystallize into the antiferromagnetic ordered L1 o phase during the pinning process. The recrystallization process typically takes several hours and is not achievable in practice with localized laser heating.

[0012] WO 2016 / 078793 A1 discloses a method and device for multidirectional pinning of magnetic field sensors. Soft magnetic structuring elements are arranged adjacent to the layer structures, coupling a pretreatment magnetic field into the layer structures. The method presented therein enables coupling of the pretreatment magnetic field perpendicular to the substrate surface, allowing any desired pinning direction to be set tangential to the substrate surface in the sense of multidirectional spinning. Such multidirectional spinning makes it possible, for example, to produce high-precision angle sensors with harmonic filtering of the sensor signal, as described, for example, in WO 2016 / 083420 A1.However, in practical use, this method can only achieve low pinning flux densities in ranges far below 1 T, so that this method cannot be used for multilayer stack structures with strong magnetic couplings.

[0013] By dividing the layer into a fixed ferromagnetic layer (reference layer) and a free ferromagnetic layer (detection layer), which react differently to external fields, it is possible to obtain resistance changes when external fields change, thus creating a sensor device. The resistance dependence correlates with the angle between the magnetization direction of the free layer (also referred to as the "free layer") and the magnetization direction of the fixed ferromagnetic layer (also referred to as the "pinned layer"). A disadvantage of a layer structure with only one fixed ferromagnetic layer, also referred to as a "simple spin valve" (SSV), is its low thermal stability. In particular, there is a risk that the pinning direction will be reversed in an application due to the occurrence of high temperatures and magnetic fields.This effect causes a drift in the behavior of a sensor using these reference layers. The smaller the magnetic moment of the reference layer, the weaker the magnetic fields can couple in and rotate the layer. Therefore, it is advantageous to keep the thickness of the reference layer small to minimize potential drift. However, the magnetoresistive effect in such SSV structures is comparatively small. One advantage, however, is that only low magnetic field strengths are required to align the reference layer.

[0014] In an improved reference layer structure, in addition to a first fixed ferromagnetic layer arranged on top of the antiferromagnetic layer, a second fixed ferromagnetic layer is provided. A coupling layer is provided between these two fixed ferromagnetic layers, which creates an antiparallel RKKY coupling (Ruderman-Kittel-Kasuya-Yoshida interaction) between the two ferromagnetic layers. Such layer structures are also referred to as "antiparallel coupled pinned layer spin valve (APP-SV)" or "synthetic antiferromagnet."Since the magnetic moments of the two fixed ferromagnetic layers are approximately equal, and the total magnetic moment of the ferromagnetic layers cancels out to almost zero due to their antiparallel alignment, external magnetic fields cause only a slight change in the magnetization direction of the reference layer system during operation, so that such an APP-SV is stable even at higher temperatures. Compared to an SSV, the magnetoresistive effect of an APP-SV is also greater.

[0015] A significant disadvantage, however, is that due to the canceling magnetic moments of the two fixed ferromagnetic layers (total magnetic moment approximately zero), pinning this layered structure is only possible if the magnetic flux density is so large that the RKKY coupling between the fixed ferromagnetic layers is overcome. This requires magnetic flux densities of more than 1 T. This requires a significant amount of effort for the pinning process. Magnetic field sensors that incorporate multiple layer stacks or resistance elements with different magnetic orientations are either impossible or very difficult to manufacture.

[0016] In the absence of a magnetic field, the free ferromagnetic layer typically exhibits a magnetization direction that lies in the layer plane and is usually antiparallel to the magnetization direction of the fixed ferromagnetic layer at the end of the magnetic circuit. The properties of the resulting magnetization direction in the free layer are strongly determined by the material thickness and geometry, particularly the anisotropy of the layer shape. An in-plane magnetization direction of the free layer limits both the linearity and dynamic range of the field strength to be measured, as well as the accuracy with regard to angle measurements, and requires extremely precise alignment of the layers, thus being disadvantageous.In many sensor applications, particularly for angle measurement tasks, it is necessary to arrange TMR layer structures with different in-plane magnetization directions in the free layer on different chip substrates. This requires at least two separate chip substrates to interconnect a sensor bridge circuit. These must be aligned and interconnected at a predefined angle, significantly increasing the space required and the manufacturing effort. The bond wires required for this increase the susceptibility to errors during assembly and are susceptible to capacitive and inductive error influences. This spatial separation provides a higher offset and tolerance range for the layer structures of the different chip substrates.

[0017] DE 10 2019 107 689 A1 describes a LAPP layer structure ((Leveraged) Antiparallel Coupled Pinned Layer Spin-Valve Layer Structure - synthetic antiferromagnet) with a horizontal magnetization direction in both the fixed layers and the free layer. With regard to a pinning step, it describes a required heating above the blocking temperature and proposes an arbitrarily long period for pinning at low magnetic field strengths. The duration should be at least 1 hour, preferably at least 5 hours, in particular at least 12 hours, with no upper time limit. This document teaches a horizontal orientation of the free magnetization, but not a vertical PMA orientation of the free layer.Another publication, US 2015 / 0 137 292 A1, discloses an MT J-layer structure (magnetic tunnel junction) with a free, relatively thin sensing layer with a vertical magnetization direction and a reference layer with horizontal magnetization defined by a pinning layer. An annealing process takes place at 300°C for 2 hours. There is no mention of adjacent layer structures aligned antiparallel in the reference layers, nor of a combined annealing and pinning step.

[0018] DE 10 2020 200 177 A1 and DE 10 2020 114 551 A1 disclose a layer structure of the same generic type as US 2015 / 0 137 292 A1 with a vertically magnetized free PMA layer and an artificial antiferromagnet with antiparallel horizontal magnetization, whereby no details on the manufacturing process, in particular temperatures, durations, bias fields, are shown.

[0019] US 2012 / 0 261 777 A1 describes a layer structure of the same type, in which both a free layer and pinned layers are vertically aligned. The free layer is crystallized (annealed) at 250°C, with the pinned layers losing their vertical magnetization at temperatures above 200°C. A common annealing process is used to crystallize all layers. An annealing temperature of 350°C can be used for one hour. No adjacent, antiparallel pinned layer structures are mentioned, nor are all magnetizations vertical to the layer plane. The time periods and combinations of pinning and annealing mentioned in this document are far from those of the invention.

[0020] US 2014 / 0 175 581 A1 also describes vertically aligned magnetizations of the free and pinned layers and indicates annealing temperatures of 250°C. Otherwise, the above statements regarding US 2012 / 0261 777 A1 apply.

[0021] US 2014 / 0 084 398 A1 generally refers to an annealing step at a temperature of 300-350°C for a PMA layer, although only a single pinned fixed layer is provided, so this document does not go beyond the disclosure content of US 2014 / 0 175 581 A1.

[0022] DE 10 2021 110 733 A1 is silent about a specific layer structure design and specifications of the layer structure according to the invention and merely describes a meandering and nested arrangement of TMR layer structures of each bridge resistor.

[0023] The aforementioned publications are silent about specific process conditions for pinning adjacent, antiparallel aligned layer structures, and at best describe isolated features of an annealing step for setting a PMA orientation of the thin free layer, without proposing a combined formation of a LAPP structure and PMA orientation by combining suitable process parameters.

[0024] It is the object of the present invention to provide a magnetic field sensitive bridge resistor arrangement for a magnetosensitive magnetic field sensor, a magnetic field sensitive bridge circuit and a method for producing the magnetic field sensitive bridge resistor arrangement of the magnetic field sensor, which are improved over the prior art.

[0025] In particular, the introduction of perpendicular magnetic anisotropy (PM A) in TMR sensors can increase the measurable magnetic field range from a few hundred Oe to several kOe, i.e., from a few tens of mT to several hundred mT. The integration of all TMR layer structures on a common chip substrate is also intended for angle measurement tasks. The sensor components envisaged here can close a gap between established TMR and Hall-effect-based sensors with regard to their compromise between sensitivity and magnetic field range. Through a dominant PMA orientation of the magnetization in the free layer in the magnetic field-free state, the magnetic easy axis of the free layer can be oriented out-of-plane (OOP), while that of the fixed layer lies in-plane (IP).The aim is to reduce magnetic anisotropy errors and increase the measurable magnetic field ranges.

[0026] This object is achieved by a bridge resistor arrangement, a bridge circuit, and related manufacturing methods according to the independent claims. Advantageous embodiments of the invention are the subject of the dependent claims.

[0027] DISCLOSURE OF THE INVENTION According to the invention, a magnetic field-sensitive bridge resistor arrangement of at least two bridge resistors arranged adjacently on a substrate for a bridge circuit that is magnetic field-sensitive in a main axis direction SA is proposed, wherein each bridge resistor comprises a series connection of a plurality of TMR layer structures. Each TMR layer structure comprises an antiferromagnetic layer, at least one first fixed ferromagnetic layer with a first fixed magnetization direction, essentially in the direction of the main axis direction SA, in a plane of the TMR layer structure, wherein an exchange coupling exists between the antiferromagnetic layer and the first fixed ferromagnetic layer, and a free ferromagnetic layer with a free magnetization direction.A non-magnetic intermediate layer is arranged between the free ferromagnetic layer and the at least first fixed ferromagnetic layer in such a way that a resistance behavior of the bridge resistor arrangement depends on an angular deviation between the first fixed magnetization direction and that of an external magnetic field H to be measured. ex t following the free magnetization direction.

[0028] According to the invention, it is proposed that the free magnetization direction for forming a PMA layer structure (Perpendicular Magnetic Anisotropy) in the magnetic field-free state is oriented perpendicular to the first defined magnetization direction and to the plane of the TMR layer structure, ie is oriented out-of-plane and at right angles to the layer plane, and the first defined magnetization directions of adjacent TMR layer structures of the at least two bridge resistors arranged on the substrate differ from one another, in particular are oriented substantially 180° opposite to one another.

[0029] Furthermore, the invention proposes that, in order to produce the magnetic field-sensitive bridge resistor arrangement, a combined annealing of the free ferromagnetic layer to form the free magnetization direction of the PMA layer structure and pinning of the first defined layers to form differing first defined magnetization directions of the adjacent bridge resistors takes place at a temperature of at least 260°C to a maximum of 350°C, above a blocking temperature of the first defined layers, for a predeterminable period of time of at least 1 h to a maximum of 12 h, and a field strength of a coupled pretreatment magnetic field with a magnetic flux density of less than 500 mT.

[0030] In other words, an arrangement of adjacent bridge resistors, each with a combination of a PMA orientation with, in the magnetic field-free state, a perpendicular magnetic field orientation of the free layer on the plane of the layer structure with a simple spin valve structure or APP / LAPP structure, i.e. synthetic antiferromagnetic magnet of the fixed ferromagnetic layers, is proposed, wherein the fixed ferromagnetic layer(s) located therein have a different fixed magnetic field orientation in the layer plane in the main axis direction SA, in particular a magnetic field orientation deviating by 180°.

[0031] Within the scope of this invention, a simultaneous combination of an annealing process and a pinning process is proposed: The annealing process serves to establish a PMA orientation of the magnetic field perpendicular to the layer plane of the layer structure in the free ferromagnetic layer by producing a crystal structure conducive to this, or to "anneal" the crystal structure to this end. The pinning process serves to establish a fixed magnetization direction in the fixed ferromagnetic layer(s) in a predefinable direction in the layer plane of the layer structure. This is achieved by pinning the magnetization direction of a ferromagnetic layer by coupling it to an antiferromagnetic layer.Both the annealing process to provide the PMA orientation of the free ferromagnetic layer and the pinning process to fix the magnetization in the fixed ferromagnetic layer are carried out simultaneously under identical temperature and time conditions.

[0032] The invention teaches a combination of precise annealing and pinning conditions with regard to time, temperature and strength of the pretreatment magnetic field, which are to be selected so that: both a stable PMA is formed and a strong synthetic antiferromagnet of the fixed layers is formed.

[0033] This combination was discovered through lengthy and laborious development work and is not suggested by the prior art, as the skilled person cannot derive any suggestion from it to combine these individual features in this way. In particular, the prior art does not teach a process time window with a maximum annealing process duration of 12 hours or less.

[0034] The proposed bridge resistor arrangement offers a number of advantages:

[0035] The introduction of a PMA orientation in the free ferromagnetic layer enables the provision of a high dynamic measuring field range with high temperature stability. In the state-of-the-art in-plane orientation, the measuring range is hampered by a relatively high magnetic anisotropy field Hk, which characterizes an influence on the free rotation of the magnetization in the free layer. Research has shown that by providing a PMA orientation, the measuring range can be increased by at least four to five times, reaching ranges previously only achievable with Hall sensors. The bridge resistor arrangement is advantageously suited for measuring weak fields up to 100 mT, preferably also up to 30 mT or 300 Oe, whereby ranges up to 100 mT and beyond can be measured with high linearity.

[0036] The PMA layer structure also enables linearization of the measuring range characteristic over a wide measuring range, something that was not possible with previous in-plane oriented layer structures. Hysteresis-free characteristic curves are achievable, particularly in field ranges up to 100 mT. The temperature-dependent slope characteristic behavior has also been significantly improved, making the sensor temperature-invariant over a wide range. The temperature slope characteristic describes the dependence of a signal response sensitivity in % on a temperature variation, with the TC_Slope characteristic value characterizing a gradient of the temperature slope characteristic.Furthermore, the shape of the free layer is no longer a dominant factor in a PMA layer structure of the free ferromagnetic layer, allowing the design of the TM R resistance elements to be freely selected, in contrast to in-plane layer structures, where the shape anisotropy of the layer structure has a dominant influence. Thus, PMA layer structures can be manufactured more cost-effectively due to their lower geometric requirements. In particular, the significantly reduced thickness of the free layer, for example, from more than 50 nm in in-plane layer structures to approximately 1 nm or less, provides a cost advantage.The integration of all TMR layer structures on a common chip substrate due to the possibility of multipinning eliminates the need for bonding connections between different chip substrates for sensor construction, resulting in fewer manufacturing errors, reduced layer structure offset, and improved signal quality due to the spatial proximity of the layer structures. Finally, a PMA layer structure can also be used to measure so-called out-of-plane (OOP) fields, making a PMA layer structure advantageous over a 2D in-plane layer structure, particularly for 3D measurement tasks where space is limited.

[0037] By providing different pinning directions for adjacent TMR layer structures, effective harmonic filtering is possible to reduce field strength-dependent angle errors in angle sensors. Integrating all layer structures for all sensor tasks, especially for angle measurement, on a common chip substrate enables integration of the entire sensor with low component tolerance due to multi-pinning capability. Finally, by ensuring identical PMA orientation of the free ferromagnetic layer, all TMR layer structures of a sensor bridge circuit can be provided on a common chip substrate. The free magnetic layer is not coupled to any other layer in the TMR layer system.

[0038] In an advantageous development, a coupling layer and a second fixed ferromagnetic layer can be arranged between the first fixed ferromagnetic layer and the intermediate layer to form an APP or LAPP layer structure ((Leveraged) Antiparallely Coupled Pinned Layer Spin-Valve layer structure - synthetic antiferromagnet). A LAPP layer structure is a subset of an APP layer structure and has different magnetic moments of the fixed ferromagnetic layers. If an APP / LAPP layer structure of the reference layer is provided instead of an SSV layer structure, there is a second fixed ferromagnetic layer with generally opposite magnetization direction to the first fixed ferromagnetic layer. Both orientations lie in the plane. The magnetization direction of the free magnetic layer is perpendicular to this, i.e. it has a PMA orientation.

[0039] In an advantageous development of the aforementioned embodiment, the first fixed ferromagnetic layer can have a first magnetic moment and the second fixed ferromagnetic layer can have a second magnetic moment of the APP layer structure. Preferably, the quotient of the first and second magnetic moments of each LAPP layer structure can be unequal to 1, in particular between 1.3 and 2.3, preferably 1.6. This results in a leveraged anti-parallel coupled pinned layer, a so-called LAPP layer structure. Furthermore, the material composition and / or the layer thickness of the first and second fixed ferromagnetic layers can preferably be different.In this development, it is proposed that the quotient of the first magnetic moment of the first fixed ferromagnetic layer coupled to the antiferromagnetic layer and the second magnetic moment of the second fixed ferromagnetic layer, which is coupled antiparallel to the first ferromagnetic layer, is between 1.3 and 2.3, preferably 1.6. Thus, the first fixed ferromagnetic layer coupled to the antiferromagnetic layer by exchange coupling has a magnetic moment approximately twice as high as the second fixed ferromagnetic layer, which is located on the side of the first ferromagnetic layer facing away from the antiferromagnetic layer and which is coupled antiparallel to the first ferromagnetic layer via a non-magnetic coupling layer.The antiferromagnetic layer, the first and second fixed ferromagnetic layers, and the coupling layer thus form a reference layer stack that can be pinned at very low magnetic field strengths. The resulting total magnetic moment M_APP_SV of the two ferromagnetic layers MFM1 and MFM2 of the layered structure is given by:

[0040] M_APP_SV = MFM1 - ​​MFM2 < M SSV, and is significantly smaller than the resulting moment MSSV of a simple spin valve layer structure (SSV) with comparable magnetoresistive properties. This layer structure can be referred to as a (leveraged) antiparallel coupled pinned layer structure ((L)APP - (leveraged) antiparallel coupled pinned layer spinvalve).

[0041] The formation of the different magnetic moments of the specified ferromagnetic layers of the reference layer stack is altered by different material compositions, which can differ in terms of the chemical elements they contain and / or their proportions. Thus, the first specified ferromagnetic material composition can be a CoFe alloy, wherein in particular the molar fraction or the atomic percentage of Fe is between 5% and 15%, preferably 10%. The second specified ferromagnetic material composition can be a CoFeB alloy, wherein, within the scope of a respective tolerance deviation, the molar fraction or the atomic percentage of Co and Fe is 40% each and the proportion of B is 20%, wherein the tolerance deviation comprises that a respective proportion deviates from the respective stated value for the proportion by no more than 5 percentage points, preferably by no more than 2.5 percentage points.

[0042] Furthermore, the first fixed ferromagnetic layer can have a first layer thickness AH and the second fixed ferromagnetic layer AI2 can have a second layer thickness, wherein the quotient AI1 / AI2 of the first and the second layer thickness is between 1.2 and 2.5.

[0043] Compared to the layered structure mentioned above, especially compared to APP structures, the required pinning magnetic field strength in LAPP structures is reduced by a factor of 10 in this embodiment. Thus, this LAPP refinement of the layered structure represents an optimization with regard to the feasibility of the pinning process, the thermal and magnetic stability, and the magnitude of the TMR effect.

[0044] The antiferromagnetic layer can be made of FeMn, IrMn, PtMn, NiMn, for example, and have a thickness between 5 nm and 30 nm.

[0045] According to an advantageous embodiment, the coupling layer comprises, in particular exclusively, Ru and has a thickness between 0.3 nm and 1.5 nm, preferably between 0.35 nm and 0.85 nm, preferably 0.5 nm. The coupling layer, which effects an antiparallel alignment of the second ferromagnetic layer with respect to the first ferromagnetic layer, can, for example, consist of a metallic, non-magnetic material, for example Ru, and have a thickness between 0.3 nm and 1.5 nm.

[0046] In an advantageous development, the plurality of TMR layer structures of a bridge resistor can be arranged as a row, in particular as an angled row, on the substrate. Furthermore, rows of bridge resistors can preferably be arranged adjacently on the substrate, in particular in a meandering pattern and nested within one another, specifically in an interdigitally interlocking arrangement in which rows of different bridge resistor positions are arranged alternately next to one another. Thus, a compact chip design can be achieved with largely identical magnetoresistive behavior of the adjacent bridge resistor arrangements.

[0047] In an advantageous development, a center-to-center distance Ad between adjacent TMR layer structures of different bridge resistances can be 50 pm or less, preferably 20 pm or less, in particular 12 pm or less. Advantageously, two identically constructed and adjacent TMR elements can thus be arranged on a substrate, and the magnetization directions of the corresponding first fixed ferromagnetic layers and optionally also second corresponding fixed ferromagnetic layers can differ from one another, in particular be oriented opposite to one another. The adjacent TMR elements comprise identical layer packages and are produced in an identical deposition process, in particular simultaneously. The center-to-center distance Ad of the adjacent TMR elements can preferably be 50 pm or less, in particular 20 pm or less.Here, by at least temporarily arranging a ferromagnetic, preferably soft magnetic, structuring element between the two TMR elements, a pretreatment magnetic field can be coupled into the structuring element, preferably perpendicular to the substrate surface. Stray fields of the structuring element, which contain field components aligned parallel to the substrate surface and perpendicular to the lateral surface profile of the structuring element, act as an effective pinning magnetic field along the edges of the structuring element to align the magnetic orientation of the first ferromagnetic layer. For this purpose, a relatively small center-to-center distance Δd between the layer structures or the TMR elements on the substrate can be selected, and the structuring element can be either built up on the substrate or temporarily introduced between them, for example, in the form of a stamp.The pretreatment magnetic field can act over the entire surface of the substrate, whereby pinning in different directions parallel to the substrate surface can be achieved at the positions of the structuring elements according to their edge alignments by the locally acting pinning magnetic fields derived from the pretreatment magnetic field. In contrast to conventional laser pinning processes, in which an in-plane pinning magnetic field is coupled parallel to the surface of the substrate – whereby the pretreatment magnetic field is thus equal to the pinning magnetic field – and the blocking temperature is exceeded by short-term laser heating, this further development enables holistic pinning in different directions of virtually all layer structures on a substrate over an arbitrarily long period of time at low magnetic field strengths.In practice, this means that all TMR elements of all sensors can be pinned on a chip substrate in one step.

[0048] As a rule, the pinning direction of the first defined ferromagnetic layer lies in the principal axis direction. In an advantageous development, at least three, in particular four or more, TMR layer structures of adjacent bridge resistors can be arranged adjacent to one another in rows. Their first defined magnetization directions can differ from one another, wherein, in particular, the first defined magnetization directions of pairs of opposing layer structures of adjacent bridge resistors can be aligned substantially 180° opposite to one another in a principal axis direction SA in order to provide multipinning and achieve harmonic filtering with respect to the measurement of a magnetic field in the principal axis direction.Preferably, the series connection of a plurality of TMR layer structures of a bridge resistor can comprise several groups of TMR layer structures, the first fixed magnetization directions of which can be angled relative to one another symmetrically to the main axis direction SA, preferably by 90°, 45°, 36°, 30° or 15°.

[0049] In an advantageous development, in each layer structure, the at least first defined ferromagnetic layer can consist of a first ferromagnetic material composition, preferably a CoFe / CoFeB material composition. Furthermore, the free ferromagnetic layer, before carrying out an annealing process, can consist of a second, boron-containing ferromagnetic material composition, preferably a boron-containing cobalt-iron compound, in particular CoFeB. The layer thickness of the free ferromagnetic layer can be less than the layer thickness of the first defined ferromagnetic layer and can be a maximum of 1.5 nm or less. The defined ferromagnetic layer, ie the reference layer orthe antiferromagnet can have a larger layer thickness to receive more external magnetic field signal and so that the magnetization lies in the layer plane according to the orientation of the antiferromagnet and not perpendicular to it.

[0050] In an advantageous development, an at least single-layer structure of a third material composition, preferably comprising Ta, Hf, W, Mo, TaN, or TaO, can be arranged as an anneal process layer directly adjacent to the free ferromagnetic layer on a side of the free ferromagnetic layer facing away from the non-magnetic intermediate layer. This third material composition of the anneal process layer can be suitable for extracting boron from the second, boron-containing ferromagnetic material composition of the free ferromagnetic layer in an anneal process and preventing it from diffusing into the free ferromagnetic layer. The structure of the anneal process layer can preferably have a layer thickness in the range of 5 to 10 nm.The third material composition acts like a sponge, absorbing boron from the free ferromagnetic layer during the crystallization process from amorphous CoFeB to crystalline CoFe, without itself diffusing into the free ferromagnetic layer. The proposed structure for forming the free ferromagnetic layer containing CoFeB and an annealing layer containing a boron-absorbing material thus forms the following material and layer structure based on the fixed ferromagnetic layer, the reference layer: a non-magnetic intermediate layer (MgO or AlOx) + free ferromagnetic layer (CoFeB) + annealing layer with material that can extract the boron from the CoFeB without itself "migrating" into the CoFeB. This can be Ta, Hf, W, Mo, TaN, or TaO.

[0051] In an advantageous development, the non-magnetic intermediate layer can consist of a non-ferromagnetic metal oxide, in particular MgO or AlOx, especially Al2O3, and can have a layer thickness between 1 nm and 3 nm, preferably 1.8 nm to 2.2 nm, in particular 2 nm. Additionally or alternatively, the non-magnetic intermediate layer can have a sheet resistance Ra in the range of 200 Ω pm 2 up to 200 kQ pm 2 , especially 400 Q pm 2 up to 3 kQ pm 2The resistance R of a non-magnetic intermediate layer is given by R=Ra / A, where Ra is the surface resistance and A is the surface area of ​​the intermediate layer. The unit of resistance is [Q]=[Q pm2] / [pm2]. The surface resistance is thus Ra=R*A, and thus [Ohmpm2]=[Ohm]*[[pm2]. Since measuring layer thicknesses can be difficult, the specified values ​​for the surface resistance Ra correspond to the corresponding layer thicknesses. For non-magnetic intermediate layers, this is advantageously in the range of 200–200,000 Q pm. 2 , especially 400-3000 Q pm 2 The sheet resistance Ra describes the electrical resistance during a vertical current flow related to the thickness of the non-magnetic intermediate layer and the specific resistance value, which is a material constant.

[0052] In an advantageous development, the TMR layer structures can be arranged on the substrate such that each TMR layer structure can be formed with a lower base electrode, preferably a lower base electrode formed as a seed layer, and an upper terminal electrode. In this case, the first fixed magnetization direction can be imprinted in a pinning direction in the at least first fixed ferromagnetic layer, and the second magnetization direction, oriented orthogonally thereto, can be freely established in the free ferromagnetic layer in the magnetic field-free state. The layer structure is thus advantageously applied to a substrate, wherein a so-called seed layer can be applied between the substrate and the antiferromagnetic layer, which can promote the growth of the antiferromagnetic layer and can serve as a base electrode.In principle, the layer structure between the seed and the cover or terminal electrode layer can be applied to a substrate in the reverse order to that described here.

[0053] In an advantageous embodiment, a change behavior of a temperature slope characteristic of an output signal S of the bridge resistor arrangement over the temperature can remain essentially constant at least in a temperature range from -40°C to 120°C, and preferably in a range less than or equal to ±0.2% / K, in particular ±0.1% / K. The temperature slope characteristic characterizes a change in a signal sensitivity S in % over a variation of the ambient temperature in Kelvin K. The behavior of this characteristic thus describes the influence of the measuring ambient temperature on the sensor signal behavior. A change behavior, i.e. a gradient of the temperature slope characteristic, is specified as a TC_Slope characteristic value. In this embodiment, it is suggested that the change behavior is constant, i.e., over the temperature, the signal behavior behaves linearly to the temperature change, i.e.The TC_Slope characteristic remains constant over temperature, and the temperature-slope characteristic curve forms a straight line over the temperature profile. Furthermore, a very small gradient of + / - 0.2% / K, particularly + / - 0.1% / K, i.e., a very small change in sensitivity over temperature, is proposed, making the bridge resistor arrangement extremely robust against temperature fluctuations. This can be achieved by appropriately selecting the manufacturing parameters, such as the duration and magnitude of the manufacturing process temperature and a suitable material selection.

[0054] In a subordinate aspect, a magnetic field-sensitive bridge circuit is proposed, in particular for a current sensor or angle sensor, and preferably for the vectorial measurement of a weak magnetic field up to 30 mT, comprising a substrate, an arrangement of at least two or more bridge resistors of a bridge resistor arrangement according to one of the aforementioned embodiments, arranged adjacently on the substrate, and at least one ferromagnetic, in particular soft magnetic, structuring element that can be introduced at least temporarily and is arranged adjacent to or partially overlapping a respective TMR layer structure, preferably overlapping between two or more adjacently arranged TMR layer structures. The structuring element can be designed and arranged to generate a pretreatment magnetic field Hz, which is introduced into or into thepenetrating the structuring elements in such a way that, at least in the first defined ferromagnetic layer of adjacent TMR layer structures, differently aligned magnetic field components act as a stray magnetic field of the structuring element as a pinning field M. o which run parallel to a layer plane of the TMR layer structure. The pretreatment magnetic field Hz can be coupled into the structuring element, preferably perpendicular to the surface of the substrate, and can be pinned by a resulting pinning field M o in an annealing process, the first fixed magnetization direction of the at least first fixed ferromagnetic layer can be pinned, and simultaneously the PMA layer structure of the free ferromagnetic layer of the TMR layer structures can be formed.

[0055] The ferromagnetic, preferably soft-magnetic structuring element, which is made, for example, from a lithographically structured nickel-iron alloy, is arranged such that a pretreatment magnetic field is coupled into the structuring element(s) simultaneously and perpendicular to the surface of the respective layer structure. At the location of the layer structure, magnetic field components parallel to the surface of the respective layer structure are also generated, which penetrate the first and second ferromagnetic layers at least in some regions. Adjacent layer structures can thus be penetrated by differently oriented, preferably opposing, pinning magnetic fields.The pretreatment magnetic field can be a homogeneous magnetic field that impinges perpendicularly on the surface of the layer structure. Due to the magnetic field guidance properties and the geometric design of the structuring element, this field also emerges in the form of an inhomogeneous stray field parallel to the layer structure surface at the boundary edges, pinning the neighboring layer structures. This allows for any desired pinning direction within a given layer structure, with a single structuring element also being able to pin multiple layer structures simultaneously and in different directions. The different pinning directions depend essentially on the contour shape of the structuring element, which defines the boundary between the structuring element and the substrate surface.

[0056] The pinning process is carried out at a pinning temperature above the blocking temperature between the antiferromagnetic layer and the first fixed ferromagnetic layer for a predeterminable pinning time. This time period and process temperature are advantageously used simultaneously for the annealing process in the free ferromagnetic layer to crystallize the amorphous CoFeB into CoFe, simultaneously providing a PMA orientation of the free ferromagnetic layer.

[0057] It has been shown that ferromagnetic, preferably soft magnetic, structuring elements are particularly suitable for pinning layer structures to a substrate. This is due to the fact that pinning the layer structure according to the invention requires only a pretreatment magnetic field in the substrate plane with a relatively low strength, less than 500 mT, preferably less than 130 mT. The resulting pinning magnetic fields, which are generally less than 80%, usually less than 50%, of the strength of the pretreatment magnetic field, are even significantly lower. In particular, it is possible to provide several layer structures according to the invention on a magnetic field sensor, which are magnetized in different spatial directions and, in particular, form a Wheatstone bridge.In a further subordinate aspect, a method for producing a bridge resistor arrangement according to one of the preceding embodiments is proposed, comprising the steps:.

[0058] - applying the adjacent TMR layer structures to a substrate in the said order, or in reverse order, between a seed layer and a cover layer;

[0059] - applying at least one, preferably temporarily arranged, ferromagnetic structuring element between adjacent TMR layer structures;

[0060] - Heating the TMR layer structures to a temperature of at least 260°C to a maximum of 350°C, above a blocking temperature to start an annealing process, whereby the exchange coupling between the antiferromagnetic layer and the first fixed ferromagnetic layer is eliminated and formation of a PMA layer structure in the free ferromagnetic layer begins;

[0061] - Coupling a pretreatment magnetic field Hz, in particular aligned perpendicular to the surface of the substrate, with a magnetic flux density of less than 500 mT into the heated TMR layer structures during the annealing process for simultaneously setting a pinning field M o with different first specified magnetization directions of at least the first specified ferromagnetic layer of adjacent TMR layer structures at least during a predeterminable period of time of at least 1 h to a maximum of 12 h, during which the temperature of the TMR layer structures is greater than the blocking temperature; and

[0062] - Cooling the TMR layer structures to a temperature below a blocking temperature in the presence of the pretreatment magnetic field Hz after the predetermined time period to terminate the annealing process; whereby the free magnetization direction in the free ferromagnetic layer forms as a PMA layer structure simultaneously with the deviating first fixed magnetization directions within the adjacent TMR layer structures.

[0063] Optionally and preferably, the temporarily introduced ferromagnetic, preferably soft magnetic, structuring elements can be removed again following the annealing process.

[0064] In a first step, at least one, in particular a plurality of, magnetoresistive layer structures are applied to a chip substrate, which have a layer construction according to one or more of the aforementioned aspects. To align a pinning direction in the first fixed ferromagnetic layer or the first and second fixed ferromagnetic layers, a temperature higher than the blocking temperature is applied, so that the exchange interaction between the first fixed ferromagnetic layer and the antiferromagnetic layer is canceled. The fixed layer is now no longer pinned by the adjacent antiferromagnetic layer and behaves similarly to a free ferromagnetic layer.Subsequently, an external magnetic field is coupled in, which is also referred to as a pretreatment magnetic field, whereby the field lines of the magnetic field are guided through the ferromagnetic, preferably soft magnetic structuring elements in such a way, ie in a stray field with magnetic field lines aligned parallel to the substrate plane, that these enter the layer structure at a suitable point as a pinning magnetic field parallel to the layer plane and there cause an adjustable magnetization of the first ferromagnetic layer.

[0065] Simultaneously with the pinning process, the annealing process in the free layer occurs as follows: During annealing, for example, the tantalum of the third material composition can extract boron from the amorphous CoFeB in the free layer. The remaining CoFe then adopts the bcc structure of the cubic crystal system of MgO, which in turn leads to high interfacial anisotropies. The origin of a high PMA lies in the hybridization of the Co and Fe 3d orbitals with the p orbitals of oxygen. A charge transfer to the oxygen orbitals occurs, while the out-of-plane 3d orbitals become depleted of electrons compared to the 3d in-plane orbitals. This ultimately leads to an increased out-of-plane orbital moment and ultimately to PMA. In CoFe(B), two effects are now present simultaneously: First, the out-of-plane PMA, which is formed at the interface, and second, the bulk anisotropy, which lies in the plane.Which effect predominates depends on the CoFeB composition, the annealing or pinning temperature, and the layer thickness of the CoFeB. The annealing and pinning conditions, in terms of time and temperature, must be selected so that:

[0066] • the PMA is trained;

[0067] • a strong and stable coupling is established between the antiferromagnetic layer and the first ferromagnetic layer taking into account the multipinning process.

[0068] The exchange coupling between the antiferromagnetic layer and the first ferromagnetic layer only occurs upon cooling below the blocking temperature in a magnetic field. The first ferromagnetic layer aligns itself according to the external magnetic field. Upon cooling below the blocking temperature of the antiferromagnetic layer, the spins of the antiferromagnetic layer at the interface between the antiferromagnetic layer and the first fixed ferromagnetic layer follow the spins of the first fixed ferromagnetic layer and remain aligned below this temperature. When the external magnetic field is removed, the pinning magnetization of the first fixed ferromagnetic layer is held in its alignment by the antiferromagnetic layer, provided the temperature is below the blocking temperature. Above this temperature, the antiferromagnetic layer loses its antiferromagnetic properties.The annealing process of the free layer must be designed in such a way that boron is extracted from the free ferromagnetic layer through diffusion processes, and the transformation of amorphous CoFeB into crystalline CoFeB is modified in such a way that the perpendicular magnetization develops simultaneously with the pinning process. After completion of the manufacturing process, the ferromagnetic, preferably soft magnetic, structuring element(s) that were introduced to individually adjust the pinning directions in the specified ferromagnetic layers are regularly removed.

[0069] In an advantageous development of the manufacturing process, the arrangement of the TMR layer structures can be heated to a temperature of at least 270°C to 290°C, in particular 280°C, for pinning the fixed ferromagnetic layer(s) and for annealing the free layer. The temperature can preferably depend on the thickness of the free ferromagnetic layer. This is because there is a relationship between the annealing temperature and the thickness of the free layer, which is crucial for the magnetic alignment, via the dead layer formed by diffusion and the degree of crystallization of the CoFeB.

[0070] In an advantageous development of the manufacturing process, the strength of the magnetic flux density of the coupled pretreatment magnetic field Hz can be less than 200 mT, in particular less than 100 mT. This allows TMR elements based on antiparallel coupled spin valve layer structures (LAPP - leveraged antiparallel coupled pinned layer spin valve) to be manufactured easily and cost-effectively.

[0071] In an advantageous development of the manufacturing process, the time required for pinning the fixed ferromagnetic layer(s) and for annealing the free layer can be between 3 and 7 hours, in particular 5 hours. By selecting the coupling time at high temperatures, an ordered L1 o layer alignment of the antiferromagnetic layer can be achieved, thus significantly improving the antiferromagnetic properties and optimizing the crystallization process in the free layer for PMA orientation.

[0072] The annealing time and temperature required to form the PMA orientation of the free layer, which simultaneously serve as the pinning time and pinning temperature, significantly influence the temperature sensitivity of the bridge resistor arrangement. It has been shown that the temperature-slope characteristic can be precisely tuned by varying the annealing temperature and time, respectively.

[0073] In a further subordinate aspect, a method for producing an aforementioned magnetic field-sensitive bridge circuit is proposed, comprising the steps:

[0074] - Manufacturing the bridge resistor arrangement according to the aforementioned and related manufacturing method; with

[0075] - at least temporary application of the at least one ferromagnetic, preferably soft magnetic structuring element, wherein

[0076] - the pretreatment magnetic field Hz is coupled via the structuring element as a pinning field Mo into the TMR layer structures with deviating magnetization directions in an annealing process in which the PMA layer structure is formed simultaneously in the free ferromagnetic layer, and after which preferably

[0077] - the structuring element is removed after completion of the annealing process.

[0078] In this inventive method for producing a magnetic field-sensitive bridge circuit according to the invention, which according to the aspect described above comprises at least one ferromagnetic, preferably soft magnetic structuring element, the above-described inventive method for producing a layer structure, including the advantageous embodiments of the method for simultaneously pinning the fixed ferromagnetic layer and annealing the free ferromagnetic layer to produce the PMA orientation, and an at least temporary application of the at least one structuring element. According to the invention, the pretreatment magnetic field is coupled into the layer structure as a pinning magnetic field via the structuring element. During the pinning process, crystallization of the material composition of the free layer occurs through an annealing process.Preferably, the structuring element can be removed again after pinning is complete, so that it can be temporarily applied to the substrate using conventional lithographic and galvanic processes, for example, and removed again using etching or material-removing processes. It is also conceivable to temporarily lower the structuring elements over the substrate in the form of a stamp and couple the pretreatment magnetic field in this way. Alternatively, the ferromagnetic structuring elements can also be retained, at least in part, as flux guides for the external magnetic field.

[0079] In an advantageous development of the aforementioned method for producing an aforementioned magnetic field-sensitive bridge circuit, an arrangement of at least two adjacent and spaced-apart bridge resistors can be applied to the substrate, and the structuring element can be applied at least temporarily to the substrate between adjacent rows of TMR layer structures forming the bridge resistors. During the combined pinning and annealing process, which establishes a magnetization direction in the established ferromagnetic layer(s) and imparts a PMA property to the free ferromagnetic layer, the pretreatment magnetic field Hz can be coupled into the structuring element perpendicular to the surface of the substrate, so that a stray magnetic field generated by the structuring element acts as a pinning field M oessentially parallel to the surface of the substrate a different orientation of the pinning field M o adjacent TMR layer structures can be provided, the orientation of which depends on the side geometry of the structuring element, so that the orientation of the pinning field M othe neighboring TMR layer structures can differ from one another, in particular can be aligned essentially oppositely, while simultaneously the PMA layer structure can form in the free layer. The alignment of the pinning-effective magnetic field components parallel to the substrate surface from the pretreatment magnetic field depends on the edge geometry of the structuring element, so that preferably the alignment of the pinning magnetic field of the neighboring layer structures can differ from one another, in particular can be aligned oppositely. By means of this development of the manufacturing method, TMR elements in a spatially closely adjacent arrangement can be pinned in different preferred directions using a relatively weak pretreatment magnetic field, less than 500 mT, preferably less than 200 mT, in particular less than 100 mT, even if the reference layers of the TMR elements contain two antiparallel coupled fixed ferromagnets.

[0080] By combining the processes, in particular the possibility of long-term pinning and simultaneous annealing and the special sequence of layer structures with closely spaced arrangements and materials (material selection), it is possible to produce thermally particularly robust antiferromagnetic materials such as IrMn, PtMn and NiMn in an optimized L1 o Phase with additional thermally robust antiferromagnetic coupled first and second fixed ferromagnetic layers and a PMA orientation in the free ferromagnetic layer in sensors, and additionally to place various TMR elements in a small space, which are identically designed and manufactured except for the pinning directions of the reference layer, which deviate arbitrarily in the direction and are preferably oppositely aligned.

[0081] Further advantageous embodiments of the layer structure, the magnetoresistive bridge circuit, and the manufacturing method are evident from the description, the figures, and the dependent claims. DRAWINGS

[0082] Further advantages will become apparent from the accompanying drawing description. The drawings illustrate exemplary embodiments of the invention. The drawing, the description, and the claims contain numerous features in combination. A person skilled in the art will expediently consider the features individually and combine them into further meaningful combinations.

[0083] They show:

[0084] Figs. 1a-1c schematically show a structure of adjacent bridge resistor arrangements according to two embodiments of the invention, with detailed representation;

[0085] Fig. 2 schematically shows a signal behavior of an embodiment of a bridge resistor arrangement with respect to the strength variation of an external magnetic field H e xt;

[0086] Fig. 3 schematically shows a further signal behavior of an embodiment of a bridge resistor arrangement in an angle sensor with respect to a rotational behavior of an external magnetic field H ex t;

[0087] Fig. 4 schematically shows a pinning arrangement for pinning the first fixed ferromagnetic layer of an embodiment of two adjacent bridge resistor arrangements;

[0088] Figs. 5a, b Diagram showing the temperature dependence of a sensor sensitivity at different temperature levels during the annealing and pinning process;

[0089] Figs. 6a,b,c Circuit diagram and chip substrate configuration of bridge resistor arrangements of the prior art and an embodiment of the invention.

[0090] In the figures, similar elements are numbered with the same reference numerals. The figures are merely examples and are not to be construed as limiting.

[0091] Figs. 1a and 1b show two alternative embodiments of adjacently arranged TMR layer structures 22 of a bridge resistor arrangement 20. Fig. 1a shows an SSV layer structure 70 with a fixed ferromagnetic layer 26, and Fig. 1b shows a LAPP layer structure 72 with two fixed ferromagnetic layers 26, 27 of the TMR layer structures 22, wherein their thicknesses AH, AI2, which influence the magnetic moment of the fixed ferromagnetic layers, are different. A series connection of several of these TMR layer structures 22 results in a bridge resistor, wherein Figs. 1a, 1b each schematically shows TMR layer structures 22 of adjacent bridge resistors of a bridge resistor arrangement 20. An annealing process layer 33 advantageous for the annealing process is not shown in Figs. 1a, 1b for reasons of clarity and is explained in more detail in Fig. 1c.

[0092] The various layers of the TMR layer structures 22 are applied by coating processes which are generally known and commonly used in semiconductor technology, for example processes for chemical or physical vapor deposition or common sputtering processes.

[0093] One or more TMR layer structures 22 are applied to a semiconductor substrate or chip substrate 12. First, a seed layer 40 is applied to the chip substrate 12, which is selected so that a subsequently applied antiferromagnetic layer 24 grows with optimal properties. The seed layer 40 is characterized by sufficiently high electrical conductivity and the lowest possible surface roughness, so that it forms a first electrical connection point as the base electrode 38.

[0094] The antiferromagnetic layer 24 is applied to the seed layer 40; this layer consists, for example, of FeMn, NiMn, IrMn or PtMn with a typical layer thickness between 5 nm and 30 nm.

[0095] A first ferromagnetic layer 26 is subsequently applied to the antiferromagnetic layer 24. This first ferromagnetic layer 26 is made of a CoFe alloy, typically Co90Fe10 (data in mass percentages) or CoFeB, with a thickness of 1 nm to 3 nm, typically 2.3 nm. A pinning process imprints a fixed magnetization 28 in one direction in the layer plane of the reference layer stack. The antiferromagnetic layer 24 and the first ferromagnetic layer 26 form a reference layer stack in the case of an SSV layer structure according to Fig. 1a.

[0096] When forming a LAPP layer structure 72 according to Fig. 1b, the first ferromagnetic layer 26 is followed by a coupling layer 25, which is made, for example, of Ru with a thickness between 0.35 nm and 1.0 nm, typically 0.5 nm. The coupling layer 25 effects an antiparallel magnetic alignment of a second ferromagnetic layer 27 with respect to the first ferromagnetic layer 26 via the RKKY coupling. The second ferromagnetic layer 27, which is made of a CoFeB alloy, typically Co40Fe40B20, is deposited onto the coupling layer 25. The layer thickness of the second ferromagnetic layer 27 is selected such that the magnetic moments of the deposited, not yet pinned ferromagnetic layers 26, 27 assume a desired ratio.Advantageously, this ratio, or more precisely the quotient of the magnetic moment M1 of the first ferromagnetic layer 26 and the magnetic moment M2 of the second ferromagnetic layer 27, M1 / M2, can assume a value between 1.3 and 2.3, preferably between 1.6 and 2.0. Based on the above-mentioned material compositions of the ferromagnetic layers 26, 27, this corresponds to a ratio or quotient AI1 / AI2 of the physical thickness A1 of the first ferromagnetic layer 26 and the physical thickness A2 of the second ferromagnetic layer 27 in a range between 1.36 and 1.94, typically 1.6. By means of a pinning process, a fixed magnetization 28 is impressed in the first fixed ferromagnetic layer 26 in one direction in the layer plane of the reference layer stack and a magnetization 29 antiparallel thereto and scaled in the ratio of the magnetic moments in the second fixed ferromagnetic layer 27.The antiferromagnetic layer 24, the first ferromagnetic layer 26, the coupling layer 25, and the second ferromagnetic layer 27 together form a reference layer stack in the case of a LAPP layer structure 72 according to Fig. 1b. The two ferromagnetic layers 26, 27 can have different material compositions and / or different layer thicknesses to achieve the different magnetic moments. For this purpose, the first ferromagnetic layer 26 is shown with a thickness of Al11 and the ferromagnetic layer 27 with a thickness of Al2, with a reduced thickness indicating a reduced magnetic moment.

[0097] Furthermore, a non-magnetic intermediate layer 34 in the form of a non-conductive layer made of preferably MgO, but also AlOx, in particular Al2O3, is applied to the reference layer stack or to the top side of the second ferromagnetic layer 27, the thickness of which is selected such that the magnetoelectric tunneling effect, which is typically between 20% and 200%, and the tunneling resistance of the TMR layer structure, which can typically be between 100 Ω and 30 kΩ, are optimized for the respective application. The layer thickness can be between 1 nm and 3 nm, preferably 1.8 nm to 2.2 nm, in particular 2 nm. Additionally or alternatively, the non-magnetic intermediate layer can have a sheet resistance Ra in the range of 200 Ω.m 2 up to 200 kΩ n 2 , especially 400 sq.m 2 up to 3 kΩ .m 2 have.

[0098] Finally, a free ferromagnetic layer 30 is applied to the non-magnetic intermediate layer 34. This free ferromagnetic layer contains a boron-containing cobalt-iron compound, in particular a CoFeB material composition, wherein one or more further elements can be alloyed in so that the TMR effect is maximized. The layer thickness of the free ferromagnetic layer should be less than the layer thickness of the first defined ferromagnetic layer and should be a maximum of 1.5 nm or less. As part of the pinning process for imprinting the defined magnetizations 28, 29 in the first and optionally second ferromagnetic layer 26, 27, a crystallization process takes place in the free layer by means of an annealing process, whereby a PMA orientation of the free magnetization direction 32 occurs in the field-free state.The free magnetization direction 32 is perpendicular to the X / Y plane of the TMR layer structure 22 and is aligned in the Z direction. The annealing process is performed simultaneously with the pinning process.

[0099] On the free ferromagnetic layer 30, a further, at least single-layer structure of a third material composition, preferably comprising Ta, Hf, W, Mo, TaN or TaO, is arranged as an anneal process layer 33; in this regard, see a detailed illustration of an individual TMR layer structure 22 in Fig. 1c as part of the arrangement of the SSV layer structures 70 in Fig. 1a. For reasons of clarity, the anneal process layer 33 is not shown in Figs. 1a, 1b and the thickness of the free ferromagnetic layer 30 is greater than shown in reality in order to be able to represent the PMA orientation of the free magnetization direction 32. This third material composition of the anneal process layer 33 is designed to extract boron from the second, boron-containing ferromagnetic material composition of the free ferromagnetic layer in an anneal process and not to diffuse into the free ferromagnetic layer itself.The structure of the annealing process layer 33 can have a layer thickness in the range of 5 to 10 nm. The annealing process layer 33 acts like a sponge to convert amorphous CoFeB into crystalline CoFe during the crystallization process triggered by the annealing process by absorbing boron from the free ferromagnetic layer.

[0100] Furthermore, one or more non-magnetic layers such as a metallic electrode layer 42 or cover layer 44 are provided on the layer structure 22 in order to be able to electrically contact the layer structure 22 and to delimit it against environmental influences or overlying or adjacent elements.

[0101] The layers 24 to 44 mentioned can also be applied in reverse order between cover layer 44 and seed layer 40 on the chip substrate 12.

[0102] Furthermore, Figs. 1a and 1b schematically show an arrangement of two adjacent bridge resistors 14 with TMR layer structures 22 of the bridge resistor arrangements 20 with a distance Ad of the center axes in the size range of 5 pm to 50 pm. For application in a magnetic field sensor, different pinning directions of magnetoresistive resistors 14 of a measuring bridge are required, which are ideally constructed identically and spatially closely spaced to homogenize the resistance behavior. This is achieved in Figs. 1a, 1b by the center-to-center distance Ad of the reference layer stacks being between 5 pm and 50 pm, and the pinning directions 28, 29 of the adjacent reference layer stacks being oriented in opposite directions. Thus, the resistance behavior of the adjacent TMR layer structures 22 of the bridge resistor arrangements 20 is opposite in the presence of an external magnetic field.In order to be able to align the two pinning directions 28 / 29 differently, a ferromagnetic structuring element 50 can advantageously be temporarily introduced between the two TMR elements 22 and can be flooded in the Z direction by a pretreatment magnetic field Hz, wherein the structuring element 50 forms stray magnetic fields which are referred to as pinning field M. o a pinning of the first and possibly second fixed ferromagnetic layer 26, 27 is effected, this is shown schematically in Fig. 4.

[0103] During the manufacture of the bridge resistor arrangement 20, the TMR layer structures 22 are subjected to a pinning process of the fixed layers 26, 27 and an annealing process of the free layer 30. For this purpose, the adjacent TMR layer structures 22 are heated to a temperature above the blocking temperature of the TMR layer structure 22, preferably to more than 260°C, typically 280°C. The layer structure 70, 72 is then exposed to a pretreatment magnetic field Hz with a relatively low magnetic field strength of no more than 500 mT, preferably no more than 200 mT, in particular less than 130 mT, especially less than 100 mT, wherein the field lines of the pinning magnetic field Mo derived therefrom, scattered by structuring elements, run parallel to the X / Y layer surfaces of the TMR layer structures 22.Simultaneously and in parallel, the heating of the bridge resistor arrangement 22 above the blocking temperature triggers an annealing process in the free ferromagnetic layer 30 to adjust the PMA orientation of the free magnetic field orientation 32.

[0104] The advantageous effect of a PMA orientation of the free ferromagnetic layer 30 is shown in Fig. 2. Even in weak field ranges up to 30 mT, a sensor signal is essentially perfectly linear to an external magnetic field H to be measured. e xt so that further compensation processes can be dispensed with.

[0105] Furthermore, Fig. 3 shows signal curves for an increasing or decreasing external magnetic field H to be measured. ext, as occurs, for example, in current sensors, for example for use in converters in energy technology, or rotation angle sensors, for example a steering wheel angle sensor in automotive technology, where first an increase and then a decrease of the external field strength H to be measured ex t is recorded. The linear sensor field strength range AH ​​is defined between Hmin=-60 mT and Hmax=+60 mT. The two signal characteristics – dashed for an increase, dotted for a decrease of the external magnetic field H ex t are almost superimposed in the linear range, which is due to the PMA property of the free ferromagnetic layer 30, whereby anisotropy errors can be largely suppressed.

[0106] As illustrated in Fig. 4, a structuring element 50 guides a pretreatment magnetic field Hz in a Z-axis device such that it is applied to the boundary edges of the structuring element 50 largely parallel to the surface of the chip substrate 12 as a pinning magnetic field M oemerges and penetrates the spaced-apart TMR layer structures 22 of the bridge resistor arrangement 20 in the desired antiparallel direction in the layer structure plane. Pinning of the fixed ferromagnetic layer 26 of the TMR layer structures 22 is achieved in particular by setting a temperature above the blocking temperature of the antiferromagnetic layers of the TMR layer structures 22, wherein further advantageously improved flux guidance through the first and optionally second fixed ferromagnetic layers 26, 27 can be achieved, for example, by appropriately shaping the boundary edges of the structuring element 50 or arranging a counterpole surface (not shown). Simultaneously in time and combined with the pinning process, an annealing process takes place in the free ferromagnetic layer 30, wherein boron is removed from the free ferromagnetic layer 30 through an annealing process layer 33, e.g. in Fig.1c, thus causing a phase change between an amorphous phase to a crystalline phase, which provides a PMA orientation of the free magnetic field direction 32.

[0107] In an advantageous embodiment, the boundary edges of the structuring element 50 overlap the boundary edges of the TMR layer structures 22, as shown in Fig. 4. The TMR layer structures 22 are thus penetrated across their entire width by magnetic fields, which also have a component parallel to the surface of the chip substrate 12. Ultimately, the magnetic field lines are directed through the chip substrate 12 to a counterpole surface (not shown), which is arranged, for example, in a ring around the chip substrate 12, so that different pinning magnetic field directions 28 / 29 can be set depending on the orientation of the boundary edges of the structuring elements 50 in the fixed ferromagnetic layer 26, 27. Figs. 5a, 5b represent a series of investigations into the influence of the annealing temperature on the dependence of a sensor sensitivity S on temperature variations.A LAPP layer structure 72 of a bridge resistor arrangement 22 with a ratio of the thicknesses of the two fixed ferromagnetic layers 26, 27 with AI1 / AI2=1.6 was considered. The quality of the PMA orientation generated by the annealing process at different annealing temperatures is expressed by the temperature slope characteristic curve of the sensor sensitivity S versus a temperature variation shown in Fig. 5b. This shows the dependence of a sensor sensitivity S in mV / V / mT on a temperature variation T in °C during the measuring process. Ideally, the TC_Slope characteristic value, which is given in % / K and describes the slope or gradient of the temperature slope characteristic curve, is at best 0, or at least very small and runs parallel to the temperature axis, so that a sensor sensitivity S is largely temperature invariant, i.e. essentially constant orchanges only slightly with temperature, and temperature-related errors are very easily compensated or do not occur at all. The characteristic curves shown are examples; the curves do not always have to be perfectly linear, but can have slight fluctuations and nonlinearities.

[0108] Fig. 5a shows three different configurations and process temperatures for the pinning and annealing process, with the annealing process adjusting the PMA orientation in the free ferromagnetic layer 30. Fig. 5b shows a temperature slope characteristic curve of the sensor sensitivity S over a measurement temperature, where the TC_Slope characteristic value indicates the gradient of the temperature slope characteristic curve in % / K with respect to the temperature T:

[0109] - 1st test: 5 h @ 280°C -> TC_Slope = 0 % / K

[0110] - 2nd test: 5 h @ 265°C -> TC_Slope = 0.2 % / K

[0111] - 3rd test: 5 h @ 300°C -> TC_Slope = -0.35 % / K

[0112] It has been shown that a low temperature of 265°C leads to a positively increasing temperature slope, while a higher temperature of 300°C leads to a negatively increasing or decreasing temperature slope. A preferred parameter configuration appears to be an anneal time of 5 hours at an anneal temperature of 280°C, which leads to a temperature-invariant behavior of the sensor sensitivity S with respect to temperature. Other parameters, such as longer times at lower temperatures or shorter times at higher temperatures, can also be considered.

[0113] Finally, Figs. 6a, 6b and 6c show a bridge circuit diagram in Fig. 6a, a chip layout of a bridge circuit 100 of a uniaxial magnetic field sensor of the prior art and Fig. 6b a chip layout of a bridge circuit 10 according to an embodiment of the invention.

[0114] Fig. 6a shows a circuit diagram of a magnetic field-sensitive bridge circuit 10 for a single-axis magnetic field sensor. The bridge circuit 10 comprises four magnetic field-sensitive bridge resistors 14. Bridge resistors R1-R4 and R2-R3 define a half-bridge of the bridge circuit 10, wherein a sensor signal S+, S- can be tapped between the center taps of the half-bridges. Each bridge resistor 14 has a magnetic field-sensitive main axis direction SA, in which the bridge resistor 14 is oscillated upon application of an external magnetic field H to be measured. ext has a resistance maximum or minimum. The orientation of a vectorial addition of the principal axis directions SA defines the sensor-active measuring axis of bridge circuit 10. Bridge circuit 10 comprises two bridge branches; in each bridge branch, two bridge resistors 14 with opposing principal axis directions SA are connected in series. Parallel bridge resistors 14 of the bridge branches also have opposing principal axis directions SA. A sensor signal S can be recorded at signal taps S+ and S- of the bridge branches.

[0115] Figs. 6b and 6c show chip arrangements of TMR layer structures connected to bridge resistors 14 and to a bridge circuit.

[0116] Fig. 6b shows a bridge resistor arrangement 100 of the prior art. For this purpose, those bridge resistors 14 R1 and R3 which are oriented in the positive main axis direction SA+ are arranged on a common chip substrate 12, visible in the upper half of the image. On a separate chip substrate 12 in the lower half of the image, those bridge resistors 14 R2 and R4 are arranged whose main axis direction SA- is oriented antiparallel thereto, which is achieved by rotating the chip substrate by 180°. On each chip substrate 12, TMR layer structures 22 are interconnected in rows 46 to form bridge resistors 14, which can be contacted by connection pads 52. Thus, a bridge resistor arrangement 20 with two bridge resistors 14 is arranged on each chip substrate 12. In the prior art, it is currently only possible to pin TMR layer structures 22 of a chip substrate 12 in a common main axis direction SA.Therefore, two chip substrates 12 were required, which had to be connected by bonding wires to form a full bridge 10, as shown in Fig. 6a. This entails various disadvantages, such as increased space requirements, susceptibility to errors in the bonding wire connection, scattering of the magnetosensitive properties of the TMR layer structures 22, and increased manufacturing costs.

[0117] In contrast, Fig. 6c shows an embodiment of a uniaxial magnetic field sensor according to the invention. The magnetic field-sensitive bridge circuit 10 is arranged on a single chip substrate 12 by integrating two bridge resistor arrangements 20 and each comprises bridge resistors 14 that are pinned in the positive and negative main axis directions SA. Rows 46 of antiparallel TMR layer structures 22 are arranged adjacent to one another with a very small spacing Ad<50 .m, so that no further functional or structural element can be placed between them, apart from a ferromagnetic, preferably soft-magnetic structuring element 50, which can be at least temporarily introduced during the manufacturing process. The connection pads 52 are already provided for connecting a supply voltage VCC-GND and the signal tap S+ / S-. The disadvantages of the prior art with regard to the bridge resistor arrangement shown in Fig.The disadvantages of the prior art magnetic field-sensitive bridge circuit 100 shown in Figure 6b are thus completely overcome. Furthermore, the PMA property of the free layer 30 provides a linear characteristic curve, which is suitable for weak-field measurements for fields up to 100 mT and even up to 30 mT, and enables temperature-invariant sensor operation.

[0118] The proposed PMA property of the free layer in combination with a multi-pinning process for creating different pinning directions on a chip substrate, which can be produced by a temporally simultaneous and combined annealing and pinning process, makes it possible to provide a magnetic field-sensitive bridge resistor arrangement that is more cost-effective and energy-efficient to manufacture, requires less installation space, has a lower error tolerance, especially against temperature fluctuations, enables a linear characteristic curve, and offers the possibility of effective harmonic filtering through a free choice of pinning directions by specifying the geometry of the structuring elements.

[0119] List of reference symbols

[0120] 10 Magnetic field sensitive bridge circuit

[0121] 12 Chip substrate

[0122] 14 Bridge resistance

[0123] 20 Magnetic field sensitive bridge resistor arrangement

[0124] 22 TM R-layer structures

[0125] 24 antiferromagnetic layer

[0126] 25 Coupling layer

[0127] 26 first fixed ferromagnetic layer

[0128] 27 second fixed ferromagnetic layer

[0129] 28 first fixed magnetization direction

[0130] 29 second fixed magnetization direction

[0131] 30 free ferromagnetic layer / PMA layer

[0132] 32 free magnetization direction

[0133] 33 Annealing process layer

[0134] 34 non-magnetic intermediate layer

[0135] 38 Lower base electrode

[0136] 40 seed layer

[0137] 42 Upper connection electrode

[0138] 44 Top layer

[0139] 46 series of TM R layer structures

[0140] 48 Meandering row arrangement of TMR-

[0141] Layer structures

[0142] 50 ferromagnetic, preferably soft magnetic structuring element

[0143] 52 Connection pad of a bridge resistor arrangement

[0144] 70 TMR-SSV (Simple Spin-Valve) layer stacks

[0145] 72 TMR-APP (Antiparallelly Coupled Pinned Layer) spin valve

[0146] Layer stack

[0147] 100 bridge resistor arrangement of the state of the art

[0148] Mo Pinning field external magnetic field to be measured

[0149] Hz pretreatment magnetic field

[0150] SA principal axis direction

[0151] S Signal tap

[0152] Vcc supply voltage

[0153] GND reference voltage

[0154] Ad Center distance of adjacent TM R layer structures

[0155] AI1 Thickness of the first fixed ferromagnetic layer

[0156] AI2 Thickness of the second specified ferromagnetic layer Hmin, Hmax Minimum and maximum field strength for a linear sensor value curve

[0157] AH Linear sensor field strength range

[0158] R1, R2, R3, R4 bridge resistors R1-R4., R2-R3 half-bridge resistors S sensor signal

[0159] S+, S- signal taps of the bridge circuit

Claims

Patent claims 1. A magnetic field-sensitive bridge resistor arrangement (20) comprising at least two bridge resistors (14) arranged adjacently on a substrate (12) for a magnetic field-sensitive bridge circuit (10) in a principal axis direction (SA), wherein each bridge resistor (14) comprises a series connection of a plurality of TMR layer structures (22, 70, 72), and each TMR layer structure (22, 70, 72) comprises an antiferromagnetic layer (24), at least one first fixed ferromagnetic layer (26) with a first fixed magnetization direction (28) in a plane of the TMR layer structure (22, 70, 72), substantially in the direction of the principal axis direction (SA), wherein an exchange coupling exists between the antiferromagnetic layer (24) and the first fixed ferromagnetic layer (26), and a free ferromagnetic layer (30) with a free magnetization direction (32),wherein a non-magnetic intermediate layer (34) is arranged between the free ferromagnetic layer (30) and the at least first fixed ferromagnetic layer (24) such that a resistance behavior of the bridge resistor arrangement (20) depends on an angular deviation between the first fixed magnetization direction (28) and the, an external, magnetic field H to be measured, ext following free magnetization direction (32), characterized in that the free magnetization direction (32) for forming a PMA layer structure (Perpendicular Magnetic Anisotropy) in the magnetic field-free state is oriented perpendicular to the first fixed magnetization direction (28) and to the plane of the TMR layer structure (22, 70, 72), and the first fixed magnetization directions (28) of adjacent TMR layer structures (22, 70, 72) of the at least two bridge resistors (14) arranged on the substrate (12) differ from one another, in particular are oriented substantially 180° opposite to one another,wherein a combined annealing of the free ferromagnetic layer (30) to form the free magnetization direction (32) of the PMA layer structure and pinning of the first fixed layer (26) to form mutually differing first fixed magnetization directions (28) of the adjacent bridge resistors (24) takes place at a temperature of at least 260°C to a maximum of 350°C, above a blocking temperature of the first fixed layer (26), during a predeterminable period of time of at least 1 h to a maximum of 12 h, and a field strength of a coupled pretreatment magnetic field (Hz) with a magnetic flux density strength of less than 500 mT.

2. Bridge resistor arrangement (20) according to claim 1, characterized in that a coupling layer (25) and a second fixed ferromagnetic layer (27) for forming an APP / LAPP layer structure ((Leveraged) Antiparallely Coupled Pinned Layer Spin-Valve layer structure) (72) are arranged between the first fixed ferromagnetic layer (26) and the intermediate layer (34).

3. Bridge resistor arrangement (20) according to claim 2, characterized in that the first fixed ferromagnetic layer (26) has a first magnetic moment and the second fixed ferromagnetic layer (27) has a second magnetic moment of the APP / LAPP layer structure, wherein preferably the quotient of the first and the second magnetic moment of each LAPP layer structure (74) is not equal to 1, in particular between 1.3 and 2.3, preferably 1.6, wherein furthermore preferably the material composition and / or the layer thickness of the first and second fixed ferromagnetic layers (26, 27) are different.

4. Bridge resistor arrangement (20) according to one of the preceding claims, characterized in that the plurality of TMR layer structures (22, 70, 72) of a bridge resistor is arranged as a row (46), in particular as an angled row (46) on the substrate (12), and rows (48) of bridge resistors (14), in particular meander-shaped and nested, are arranged adjacently on the substrate (12).

5. Bridge resistor arrangement (20) according to claim 4, characterized in that a center-to-center distance (Ad) of adjacent TMR layer structures (22, 70, 72) of different bridge resistors (14) is 50 pm or less, preferably 20 pm or less, in particular 12 pm or less.

6. Bridge resistor arrangement (20) according to one of the preceding claims, characterized in that at least three, in particular four or more TMR layer structures (22, 70, 72) of adjacent bridge resistors (14) are arranged in rows adjacent to one another, and their first defined magnetization directions (28) differ from one another, wherein in particular the first defined magnetization directions (28) of pairwise opposite layer structures (22) of adjacent bridge resistors (14) are aligned substantially by 180° opposite one another in a main axis direction (SA), and wherein preferably the series connection of a plurality of TMR layer structures (22, 70, 72) of a bridge resistor (14) comprises several groups of TMR layer structures (22, 70, 72), whose first defined magnetization directions (28) are symmetrical to the main axis direction (SA), preferably by 90°, 45°, 36°, 30° or 15°, angled against each other.

7. Bridge resistor arrangement (20) according to one of the preceding claims, characterized in that in each layer structure (22) the at least first fixed ferromagnetic layer (26) consists of a first ferromagnetic material composition, preferably a CoFe / CoFeB material composition, and the free ferromagnetic layer (30) before carrying out an annealing process consists of a second, boron-containing ferromagnetic material composition, preferably a boron-containing cobalt-iron compound, in particular CoFeB, wherein the layer thickness of the free ferromagnetic layer (30) is less than the layer thickness of the first fixed ferromagnetic layer (26) and is at most 1.5 nm or less.

8. Bridge resistor arrangement (20) according to claim 7, characterized in that immediately adjacent to the free ferromagnetic layer (30) on a side of the free ferromagnetic layer (30) facing away from the non-magnetic intermediate layer (34) there is arranged an at least single-layer structure of a third material composition as an anneal process layer (33), preferably comprising Ta, Hf, W, Mo, TaN or TaO, wherein the third material composition of the anneal process layer (33) is suitable for extracting boron from the second, boron-containing ferromagnetic material composition of the free ferromagnetic layer (30) in an anneal process and for not diffusing into the free ferromagnetic layer (30), and preferably the structure has a layer thickness in the range of 5 to 10 nm.

9. Bridge resistor arrangement (20) according to one of the preceding claims, characterized in that the non-magnetic intermediate layer (34) consists of a non-ferromagnetic metal oxide, in particular MgO or AlOx, in particular Al2O3 and a layer thickness between 1 nm to 3 nm, preferably 1.8 nm to 2.2 nm, in particular 2 nm, and / or a surface resistance Ra in the range 200 .m 2 up to 200 kΩ n 2 , especially 400 m 2 up to 3 kQ n 2 has.

10. Bridge resistor arrangement (20) according to one of the preceding claims, characterized in that the TMR layer structures (22, 70, 72) are arranged on the substrate (12) in such a way that each TMR layer structure (22, 70, 72) is formed with a lower base electrode (38), preferably a lower base electrode (38) designed as a seed layer (40), and an upper terminal electrode (42), wherein in the at least first fixed ferromagnetic layer (26), the first fixed magnetization direction (28) is impressed in a pinning direction, and in the free ferromagnetic layer (30), the second magnetization direction (32) aligned orthogonally thereto is freely established in the magnetic field-free state.

11. Bridge resistor arrangement (20) according to one of the preceding claims, characterized in that a change behavior of a temperature slope characteristic of an output signal S of the bridge resistor arrangement (20) over the temperature T remains substantially constant at least in a temperature range from -40°C to 120°C, and preferably lies in a range less than or equal to ±0.2% / K, in particular ±0.1% / K.

2. Magnetic field sensitive bridge circuit (10), in particular for a current sensor or angle sensor, and preferably for the vectorial measurement of a weak magnetic field up to 30 mT, comprising a substrate (12), an arrangement of at least two or more bridge resistors (14) of a bridge resistor arrangement (20) according to one of the preceding claims 1 to 11, which are arranged adjacently on the substrate (12), and at least one ferromagnetic, preferably soft magnetic structuring element (50) which can be introduced at least temporarily and is arranged adjacent to or partially overlapping a respective TMR layer structure (22, 70, 72), preferably overlapping between two or more adjacently arranged TMR layer structures (22, 70, 72), wherein the structuring element (50) is designed and arranged to introduce a pretreatment magnetic field (Hz) which is introduced into or partially overlapping a respective TMR layer structure (22, 70, 72).penetrating the structuring elements (50) in such a way that, at least in the first fixed ferromagnetic layer (26) of adjacent TMR layer structures (22, 70, 72), deviatingly aligned magnetic field components act as a stray magnetic field of the structuring element (50) as a pinning field (M. o ) which run parallel to a layer plane of the TMR layer structure (22, 70, 72), wherein the pretreatment magnetic field (Hz), preferably perpendicular to the surface of the substrate (12), can be coupled into the structuring element (50) and by a resulting pinning field (M o ) in an annealing process, the first fixed magnetization direction (28) of the at least first fixed ferromagnetic layer (26) is pinned, and simultaneously thereto the PMA layer structure of the free ferromagnetic layer (30) of the TMR layer structures (22, 70, 72) is formed.

3. A method for producing a bridge resistor arrangement (20) according to one of the preceding claims 1 to 11, comprising the steps: - applying the adjacent TMR layer structures (22, 70, 72) to a substrate (12) in the said, or in reverse order, between a seed layer (40) and a cover layer (44); - - applying at least one, preferably temporarily arranged, ferromagnetic structuring element (50) between adjacent TMR layer structures (22, 70, 72); Heating the TMR layer structures (22, 70, 72) to a temperature of at least 260°C to a maximum of 350°, above a blocking temperature to start an annealing process, wherein the exchange coupling between the antiferromagnetic layer (24) and the first fixed ferromagnetic layer (26) is eliminated and formation of a PMA layer structure in the free ferromagnetic layer (30) begins; Coupling a pretreatment magnetic field (Hz), in particular aligned perpendicular to the surface of the substrate (12), with a magnetic flux density of less than 500 mT into the heated TMR layer structures (22, 70, 72) during the annealing process for simultaneously setting a pinning field (M o ) with deviating first defined magnetization directions (28) of at least the first defined ferromagnetic layer (26) of adjacent TMR layer structures (22, 70, 72) at least during a predeterminable period of time of at least 1 hour to a maximum of 12 hours by the ferromagnetic structuring elements (50), during which the temperature of the TMR layer structures (22, 70, 72) is greater than the blocking temperature; and - Cooling the TMR layer structures (22, 70, 72) to a temperature below a blocking temperature in the presence of the pretreatment magnetic field (Hz) after the predetermined period of time to terminate the annealing process; whereby the free magnetization direction (32) in the free ferromagnetic layer (30) forms as a PMA layer structure simultaneously with the deviating first fixed magnetization directions (28) within the adjacent TMR layer structures (22, 70, 72).

14. The method according to claim 13, wherein the arrangement of the TMR layer structures (22, 70, 72) is heated to a temperature of at least 270°C to 290°C, in particular 280°C, wherein preferably the temperature depends on the thickness of the free ferromagnetic layer (30).

15. The method according to claim 13 or 14, wherein the strength of the magnetic flux density of the coupled pretreatment magnetic field (Hz) is less than 200 mT, in particular less than 100 mT.

16. The method according to any one of claims 13 to 15, wherein the duration of the annealing process is between 3 hours and 7 hours, in particular 5 hours. A method for producing a magnetic field-sensitive bridge circuit (10) according to claim 12, comprising the steps: - producing the bridge resistor arrangement (20) according to the method according to one of claims 13 to 16; with - at least temporarily applying the at least one ferromagnetic, preferably soft magnetic structuring element (50), wherein - the pretreatment magnetic field (Hz) via the structuring element (50) as a pinning field (M o ) is coupled into the TMR layer structures (22, 70, 72) with deviating magnetization directions in an annealing process in which the PMA layer structure is formed simultaneously in the free ferromagnetic layer (30), and after which the structuring element (50) is preferably removed again after completion of the annealing process.

7. The method according to claim 16, wherein an arrangement of at least two adjacent and spaced-apart bridge resistors (14) is applied to the substrate (12), and the structuring element (50) is applied at least temporarily to the substrate (12) between adjacent rows of TMR layer structures (22, 70, 72) forming the bridge resistors (14), and wherein the pretreatment magnetic field (Hz) is coupled into the structuring element (50) perpendicular to the surface of the substrate (12) during the annealing process, so that a stray magnetic field generated by the structuring element (50) as a pinning field (Mo) essentially parallel to the surface of the substrate (12) provides a deviating orientation of the pinning field (Mo) of adjacent TMR layer structures (22, 70, 72), the orientation of which depends on the side geometry of the structuring element (50), so that the orientation of the pinning field (Mo) of the neighboring TMR layer structures (22, 70,72) differ from each other, in particular are aligned substantially oppositely, while simultaneously the PMA layer structure forms in the free layer (30).

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