Tunnel magnetoresistive element for detecting out-of-plane changes in magnetic field strength

Abstract

A method in one embodiment includes the step of manufacturing a tunnel magnetoresistance (TMR) element for sensing out-of-plane changes in magnetic field strength in a magnetic field. The manufacturing step includes depositing a plurality of antiferromagnetic layers having magnetization directions that alternate layer by layer between a first direction and a second direction opposite to the first direction. The uppermost layer of the plurality of antiferromagnetic layers has a magnetization direction in the first direction. The manufacturing step further includes the steps of directly depositing a ferromagnetic layer on the uppermost layer, directly depositing a first multilayer structure on the ferromagnetic layer, directly depositing a metallic layer on the first multilayer structure, and directly depositing a second multilayer structure on the metallic layer. The ferromagnetic layer, the first multilayer structure, and the second multilayer structure are each parallel to the xy plane, and the first direction is either the z direction or the -z direction.

Description

Background Art

[0001]

[0001] A magnetic field sensor may include a bridge (e.g., a Wheatstone bridge). The bridge usually includes four or more magnetoresistive elements. The magnetoresistive elements of the bridge may include tunnel magnetoresistive (TMR) elements. Each TMR element may include a plurality of pillars.

Summary of the Invention

[0002]

[0002] A method in one aspect includes manufacturing a tunnel magnetoresistive (TMR) element for sensing an out-of-plane change in magnetic field strength in a magnetic field. The manufacturing step includes depositing an antiferromagnetic material on a seed layer. The antiferromagnetic material includes a plurality of antiferromagnetic layers having magnetization directions that alternate layer by layer between a first direction and a second direction opposite to the first direction. The uppermost layer of the plurality of antiferromagnetic layers has a magnetization direction in the first direction. The manufacturing step further includes directly depositing a ferromagnetic layer on the uppermost layer of the plurality of antiferromagnetic layers, directly depositing a first multilayer structure on the ferromagnetic layer, directly depositing a metal layer on the first multilayer structure, and directly depositing a second multilayer structure on the metal layer. The ferromagnetic layer, the first multilayer structure, and the second multilayer structure are each parallel to the xy plane. The first direction is either the z direction or the -z direction. The magnetization direction of the second multilayer structure is the second direction, which is determined by the magnetization direction of the uppermost layer of the plurality of antiferromagnetic layers, is opposite to the magnetization direction of the uppermost layer of the plurality of antiferromagnetic layers, and the magnetization direction of the second multilayer structure is the reference direction of the TMR element.

[0003]

[0003] The features may include one or more of the following individually or in combination with other features. The ferromagnetic layer is a first magnetic layer, and further comprises the steps of depositing a second ferromagnetic layer on a second multilayer structure, directly depositing an insulating layer on the second ferromagnetic layer, and depositing a free layer on the insulating layer. The magnetization direction of the free layer is in the xy plane. The method further comprises depositing a striped magnetic domain structure on the free layer. The step of depositing a striped magnetic domain structure on the free layer comprises the step of depositing a striped magnetic domain structure including one or more sublayers. Each sublayer includes at least one heavy metal and at least one ferromagnetic material. Each sublayer includes at least one oxide layer and at least one ferromagnetic layer. Each sublayer further includes at least one heavy metal. Each sublayer further includes a buffer layer. The metal layer is a first metal layer, and further includes the step of depositing a second metal layer on a second multilayer structure before the step of depositing a second ferromagnetic layer. The magnetization direction of the first multilayer structure is a first direction, determined by the magnetization direction of the top layer of a plurality of antiferromagnetic layers. The magnetization direction of the top layer of a plurality of antiferromagnetic layers is formed using a laser or by a current pulse passing through a TMR element. The step of depositing the first multilayer structure includes the step of depositing sublayers, each sublayer comprising a first heavy metal layer and a first ferromagnetic material layer. The step of depositing the second multilayer structure includes the step of depositing sublayers, each sublayer comprising a second heavy metal layer and a second ferromagnetic material layer. The total number of sublayers in the first multilayer structure is not equal to the total number of sublayers in the second multilayer structure. The total number of sublayers in the first multilayer structure is equal to the total number of sublayers in the second multilayer structure. The first heavy metal layer and / or the second heavy metal layer is a platinum layer, and the first ferromagnetic material layer and / or the second ferromagnetic material layer contains the element cobalt. The step of depositing the antiferromagnetic material includes the step of depositing iridium manganese, platinum manganese, or iron manganese.

[0004]

[0004] In another embodiment, a tunnel magnetoresistance (TMR) element includes an antiferromagnetic material comprising a plurality of antiferromagnetic layers having a magnetization direction that alternates between a first direction and a second direction opposite to the first direction for each layer. The uppermost layer of the plurality of antiferromagnetic layers has a magnetization direction in the first direction. The TMR element further includes a ferromagnetic layer in direct contact with the uppermost layer of the plurality of antiferromagnetic layers, a first multilayer structure in direct contact with the ferromagnetic layer, a metal layer in direct contact with the first multilayer structure, and a second multilayer structure in direct contact with the metal layer, which is part of a reference layer. The ferromagnetic layer, the first multilayer structure, and the second multilayer structure are each parallel to the xy plane, and the first direction is either the z direction or the -z direction. The magnetization direction of the second multilayer structure is the second direction, determined by the magnetization direction of the uppermost layer of the multiple antiferromagnetic layers, and is opposite to the magnetization direction of the uppermost layer of the multiple antiferromagnetic layers; the magnetization direction of the second multilayer structure is the reference direction of the TMR element.

[0005]

[0005] The features may include one or more of the following individually or in combination with other features. The ferromagnetic layer is a first magnetic layer, and the TMR element further includes a second ferromagnetic layer on a second multilayer structure, an insulating layer in direct contact with the second ferromagnetic layer, and a free layer on the insulating layer. The magnetization direction of the free layer is in the xy plane. The TMR element further includes a striped magnetic domain structure on the free layer. The striped magnetic domain structure includes one or more sublayers. Each sublayer includes at least one heavy metal and at least one ferromagnetic material. Each sublayer includes at least one oxide layer and at least one ferromagnetic layer. Each sublayer further includes at least one heavy metal. Each sublayer includes a buffer layer. The metal layer is a first metal layer, and further includes a second metal layer between the second ferromagnetic layer and the second multilayer structure. The magnetization direction of the first multilayer structure is the first direction, determined by the magnetization direction of the uppermost layer of multiple antiferromagnetic layers. The first multilayer structure includes sublayers, each sublayer containing a first heavy metal layer and a first ferromagnetic material layer. The second multilayer structure includes sublayers, each sublayer containing a second heavy metal layer and a second ferromagnetic material layer. The first heavy metal layer and / or the second heavy metal layer is a platinum layer, and the first ferromagnetic material layer and / or the second ferromagnetic material layer contains the element cobalt. The total number of sublayers in the first multilayer structure is not equal to the total number of sublayers in the second multilayer structure. The total number of sublayers in the first multilayer structure is equal to the total number of sublayers in the second multilayer structure. The antiferromagnetic material includes iridium manganese, platinum manganese, or iron manganese.

[0006]

[0006] In a further embodiment, the magnetic field sensor includes a bridge comprising a power source and a first leg and a second leg. The first leg includes a first tunnel magnetoresistance (TMR) element and a second TMR element electrically in series with the first TMR element and electrically closer to the power source than the first TMR element. The second leg includes a third TMR element and a fourth TMR element electrically in series with the third TMR element and electrically closer to the power source than the third TMR element. The first TMR element, the second TMR element, the third TMR element, and the fourth TMR element each include an antiferromagnetic material comprising a plurality of antiferromagnetic layers having a magnetization direction that alternates layer by layer between a first direction and a second direction opposite to the first direction. The uppermost layer of the plurality of antiferromagnetic layers has a magnetization direction in the first direction. The first TMR element, the second TMR element, the third TMR element, and the fourth TMR element each further include a ferromagnetic layer in direct contact with the uppermost layer of a plurality of antiferromagnetic layers, a first multilayer structure in direct contact with the ferromagnetic layer, a metal layer in direct contact with the first multilayer structure, and a second multilayer structure in direct contact with the metal layer, which is part of the reference layer. The ferromagnetic layer, the first multilayer structure, and the second multilayer structure are each parallel to the xy plane, and the first direction is either the z direction or the -z direction. The magnetization direction of the second multilayer structure is the second direction, which is determined by the magnetization direction of the uppermost layer of the plurality of antiferromagnetic layers and is opposite to the magnetization direction of the uppermost layer of the plurality of antiferromagnetic layers. The magnetization direction of the second multilayer structure is the reference direction of the TMR element, with the first and fourth TMR elements each having a reference direction in the z direction, and the second and third TMR elements each having a reference direction in the -z direction.

[0007]

[0007] The features described above can be better understood from the following brief description of the drawings. The drawings help to describe and understand the disclosed technology. Since it is often impractical or impossible to illustrate and describe all possible embodiments, the provided drawings depict one or more exemplary embodiments. Accordingly, the drawings are not intended to limit the scope of the broad concepts, systems, and technologies described herein. Similar figures in the drawings indicate similar elements. [Brief explanation of the drawing]

[0008] [Figure 1]

[0008] This is a diagram of an example of a tunnel magnetoresistance (TMR) element for detecting out-of-plane changes in a magnetic field. [Figure 2A]

[0009] This is a diagram illustrating an example of an antiferromagnetic material. [Figure 2B]

[0010] This is a diagram illustrating an example of a ferromagnetic material. [Figure 2C]

[0011] This is a diagram illustrating an example of the first multilayer structure. [Figure 2D]

[0012] This is a diagram illustrating an example of a second multilayer structure. [Figure 2E]

[0013] Figure 1 shows an example of a TMR element. [Figure 3A]

[0014] This is a diagram of another example of an antiferromagnetic material. [Figure 3B]

[0015] This is a diagram illustrating another example of a ferromagnetic material. [Figure 3C]

[0016] This is a diagram of another example of the first multilayer structure. [Figure 3D]

[0017] This is a diagram of another example of the second multilayer structure. [Figure 3E]

[0018] This is a diagram of another example of the TMR element shown in Figure 1. [Figure 4A]

[0019] Figures 2E and 3E illustrate examples of bridges using TMR elements. [Figure 4B]

[0020] Figures 2E and 3E show the lower TMR elements of the TMR element. [Figure 4C]

[0021] This is a diagram showing an example layout of a lower-level TMR element. [Modes for carrying out the invention]

[0009]

[0022] This specification describes techniques for manufacturing tunnel magnetoresistance (TMR) elements capable of detecting out-of-plane changes in the magnetic field strength. In particular, the magnetization direction of the uppermost layer of the antiferromagnetic material of the TMR element controls the magnetization direction of the reference layer of the TMR element, enabling out-of-plane detection of changing magnetic field strengths. The reference layer of the TMR element includes the magnetization direction which is the reference direction of the TMR element. The reference direction is the direction in which the TMR element is most sensitive to changes in the magnetic field strength (i.e., the direction in which a change in magnetic field strength results in the greatest change in the resistance value of the TMR element). Typically, magnetic field sensors using TMR elements are manufactured to detect changes in magnetic field strength within a plane (e.g., the xy plane in Figure 1) or to perform in-plane detection where the reference direction is within a plane (e.g., the xy plane in Figure 1). However, conventional manufacturing methods generally cannot produce TMR elements with a constant z-direction or a constant -z-direction as the reference direction, making the manufacturing of TMR elements in magnetic field sensors for out-of-plane detection (e.g., detection in the z-direction or -z-direction perpendicular to the xy-plane in Figure 1) unreliable. As will be further explained herein, TMR elements can be reliably manufactured with a z-direction as the reference direction or with a -z-direction as the reference direction to enable out-of-plane detection of changing magnetic field strengths.

[0010]

[0023] Referring to Figure 1, the TMR element 100 is in an external magnetic field H EXT A TMR-based magnetic field sensor is configured to detect changes in magnetic field strength in the z-direction or -z-direction, which is out-of-plane detection, whereas in-plane detection detects changes in magnetic field strength within the xy-plane. TMR-based magnetic field sensors are generally limited to in-plane sensing of changes in magnetic field strength.

[0011]

[0024] One of the main challenges in out-of-plane sensing of changes in detected magnetic field strength is obtaining a cross-anisotropic configuration that can provide a variable output in response to the magnetic field strength. In particular, the output of a TMR element is proportional to the angle between the magnetization direction of the reference layer and the magnetization direction of the free layer. In the case of TMR elements used in memory devices (e.g., magnetoresistive random access memory (MRAM) and hard drive disks (HDDs)), while the TMR element can detect out-of-plane magnetic fields, the TMR elements used in memory devices are essentially switches, meaning that the magnetization direction of the free layer abruptly changes from parallel to antiparallel to the magnetization direction of the reference layer, and therefore there are no measurable points between this parallel and antiparallel direction for measuring the resistance value that changes due to the changing magnetic field strength. Thus, abrupt changes in the magnetization direction of the free layer are not practical for use in magnetic field sensors.

[0012]

[0025] As described herein, a magnetic field sensor is desired in which the magnetization direction of the free layer exhibits a measurable change in response to changes in magnetic field strength between parallel and antiparallel. In this case, the resistance of the TMR element can be measured by continuously changing the orientation of the free layer such that a measurable angle is established between the magnetization direction of the free layer and the magnetization direction of the reference layer for a given magnetic field amplitude. The cross-anisotropy configuration allows for a starting point where the magnetization direction of the free layer is naturally perpendicular to the magnetization direction of the reference layer. Thus, the detected magnetic field rotates the magnetization direction of the free layer from perpendicular to the magnetization direction of the reference layer to either parallel or antiparallel to the magnetization direction of the reference layer (depending on the direction of the applied magnetic field), thereby allowing for several resistance measurement points in between.

[0013]

[0026] The TMR element 100 includes a bottom electrode 112, a seed layer on the bottom electrode 112, a pinning layer 120 on the seed layer 116, and a pinned layer 124 on the pinning layer 120. The pinning layer 120 includes an antiferromagnetic material 122. The pinned layer 124 includes a ferromagnetic layer 126 on the antiferromagnetic material 122 and a first multilayer structure 132 on the ferromagnetic layer 126. In one example, the ferromagnetic layer 126 may include cobalt alone or may include cobalt such as cobalt iron or cobalt iron boron.

[0014]

[0027] The TMR element 100 further includes a metal layer 136 on the pinned layer 124 and a reference layer 138 on the metal layer 136. In some cases, the metal layer 136 is called a spacer layer. In one example, the metal layer 136 is ruthenium. The reference layer 138 includes a second multilayer structure 142 on the metal layer 136, a metal layer 148 on the second multilayer structure 142, and a ferromagnetic layer 152. In one example, the ferromagnetic layer 152 may include cobalt alone or may include cobalt such as cobalt iron or cobalt iron boron.

[0015]

[0028] In one example, the metal layer 148 is tantalum. In one example, the metal layer 148 is called a space layer and enables the crystal structure of the ferromagnetic layer 152 to be separated from other underlying layers. In other examples, the metal layer 148 is not included in the TMR element 100 at all.

[0016]

[0029] The TMR element 100 further includes an insulating layer 156 on the reference layer 138, a free layer 162 on the insulating layer 156, another layer 168 on the free layer 162, and a cap layer 176 on the other layer 168. In one example, the insulating layer 156 includes magnesium oxide. In one example, the free layer 162 may include cobalt iron boron. In one example, the magnetization direction of the free layer 162 is completely in the xy plane.

[0017]

[0030] In one particular example, the ferromagnetic layer 152 is also cobalt iron boron. Cobalt iron boron is used in the ferromagnetic layer 152 because it is amorphous, and during annealing, it follows the crystalline structure of magnesium oxide (when used as the insulating layer 156), creating a consistent crystalline structure between the insulating layer 156 and the ferromagnetic layer 152, which has a higher magnetic field resistance (MR) ratio.

[0018]

[0031] In one example, the other layer 162 includes a striped magnetic domain structure containing multiple sub-layers. In one example, each sub-layer may include a heavy metal layer (e.g., platinum) and a metallic ferromagnetic layer (e.g., cobalt), with or without a buffer layer (e.g., a tantalum layer). In another example, each sub-layer may include a ferromagnetic layer (e.g., cobalt) and an oxide layer (e.g., magnesium oxide), with or without a buffer layer (e.g., a tantalum layer). In yet another example, each sub-layer may include a heavy metal layer (e.g., platinum), a ferromagnetic layer (e.g., cobalt), and an oxide layer (e.g., magnesium oxide), with or without a buffer layer (e.g., a tantalum layer). Movement of the domain walls within the striped magnetic domain structure allows for the detection of out-of-plane changes in magnetic field strength, but it is almost impossible to detect changes in in-plane magnetic field strength. In another example, the other layer 168 may include a bias layer.

[0019]

[0032] Referring to Figure 2A, an example of antiferromagnetic material 122 is antiferromagnetic material 122'. Antiferromagnetic material 122' includes antiferromagnetic layers (e.g., antiferromagnetic layer 222a, antiferromagnetic layer 222b, antiferromagnetic layer 222c, antiferromagnetic layer 222d, antiferromagnetic layer 222e, and antiferromagnetic layer 222f). Antiferromagnetic layer 222f is considered to be the top layer in this specification.

[0020]

[0033] In one example, the antiferromagnetic layers 222a to 222f are made of the same material. In another example, the antiferromagnetic layers 222a to 222f may be platinum-manganese, iridium-manganese, or iron-manganese.

[0021]

[0034] The antiferromagnetic layers 222a to 222f each have a magnetization direction that is opposite to that of the other antiferromagnetic layer. For example, antiferromagnetic layer 222a has a magnetization direction 224a in the -z direction, antiferromagnetic layer 222b has a magnetization direction 224b in the z direction, antiferromagnetic layer 222c has a magnetization direction 224c in the -z direction, antiferromagnetic layer 222d has a magnetization direction 224d in the z direction, antiferromagnetic layer 222e has a magnetization direction 224e in the -z direction, and antiferromagnetic layer 222f has a magnetization direction 224f in the z direction. As will be further described herein, the magnetization direction 224f controls the magnetization direction of the upper layer of the TMR element 100.

[0022]

[0035] In one example, the magnetization direction 224f is formed by heating the antiferromagnetic layer 222f using a laser focused only on the antiferromagnetic layer 222f and exposing the antiferromagnetic layer 222f to an external magnetic field. In another example, the magnetization direction 224f is formed by applying a current pulse through the TMR element 100 and exposing the antiferromagnetic layer 222f to an external magnetic field.

[0023]

[0036] Referring to Figure 2B, an example of the ferromagnetic layer 126 is the ferromagnetic layer 126'. The pinning layer 120 (Figure 1), specifically the magnetization direction 224f, pins the magnetization direction 228 of the ferromagnetic layer 126'. Therefore, the magnetization direction 228 is determined by the magnetization direction 224f and is the same as the magnetization direction 224f.

[0024]

[0037] Referring to Figure 2C, an example of the first multilayer structure 132 is the first multilayer structure 132'. The first multilayer structure 132' includes a first sublayer 230a, a second sublayer 230b, ..., and a Jth sublayer 230J, where J>2. In other examples, the first multilayer structure 132' may include one or two sublayers.

[0025]

[0038] The first sublayer 230a contains a heavy metal 232a on top of a ferromagnetic material 234a. The second sublayer 230b contains a heavy metal 232b on top of a ferromagnetic material 234b. The Jth sublayer 230J contains a heavy metal 232J on top of a ferromagnetic material 234J.

[0026]

[0039] For example, the heavy metal 232a-232J could be platinum. For example, the ferromagnetic material 234a-234J could be cobalt, or it could contain cobalt, for example, cobalt iron or cobalt iron boron.

[0027]

[0040] Referring to Figure 2D, an example of the second multilayer structure 142 is the second multilayer structure 142'. The second multilayer structure 142' includes a first sublayer 240a, a second sublayer 240b, ..., and a K sublayer 230K, where K > 2. In other examples, the second multilayer structure 142' may include one or two sublayers. In one example, J and K are not equal. In another example, J and K are equal.

[0028]

[0041] The first sublayer 240a contains a heavy metal 242a on top of a ferromagnetic material 244a. The second sublayer 240b contains a heavy metal 242b on top of a ferromagnetic material 244b. The K sublayer 240K contains a heavy metal 242K on top of a ferromagnetic material 244K.

[0029]

[0042] For example, heavy metals 242a to 242K could be platinum. For example, ferromagnetic materials 244a to 244K could be cobalt, or may contain cobalt, such as cobalt iron or cobalt iron boron.

[0030]

[0043] Referring to Figure 2E, the pinning layer 120 (Figure 1), specifically the magnetization direction 224f (Figure 2A), pins the magnetization direction 238 of the first multilayer structure 132'. Therefore, the magnetization direction 238 is determined by the magnetization direction 224f and is the same as the magnetization direction 224f.

[0031]

[0044] The magnetization direction 248 of the second multilayer structure 142' is opposite to the magnetization direction 238 of the first multilayer structure 132'. The thickness of the metal layer 136 (Figure 1) allows the RKKY (Ruderman-Kittel-Kasuya-Yosida) coupling mechanism to make the magnetization direction 248 opposite to the magnetization direction 238. Therefore, the magnetization direction 248 is determined by the magnetization direction 224f and is opposite to the magnetization direction 224f. The magnetization direction 248 is the reference direction of the TMR element 100a and is the -z direction.

[0032]

[0045] Referring to Figure 3A, another example of the antiferromagnetic material 122 is the antiferromagnetic material 122''. The antiferromagnetic material 122'' includes antiferromagnetic layers (e.g., antiferromagnetic layer 322a, antiferromagnetic layer 322b, antiferromagnetic layer 322c, antiferromagnetic layer 322d, antiferromagnetic layer 322e, and antiferromagnetic layer 322f). The antiferromagnetic layer 322f is considered to be the top layer in this specification.

[0033]

[0046] In one example, the antiferromagnetic layers 322a to 322f are made of the same material. In another example, the antiferromagnetic layers 322a to 322f may be platinum-manganese, iridium-manganese, or iron-manganese.

[0034]

[0047] The antiferromagnetic layers 322a to 322f each have a magnetization direction that is opposite for each antiferromagnetic layer. For example, antiferromagnetic layer 322a has a magnetization direction 324a in the z direction, antiferromagnetic layer 322b has a magnetization direction 324b in the -z direction, antiferromagnetic layer 322c has a magnetization direction 324c in the z direction, antiferromagnetic layer 322d has a magnetization direction 324d in the -z direction, antiferromagnetic layer 322e has a magnetization direction 324e in the z direction, and antiferromagnetic layer 322f has a magnetization direction 324f in the -z direction. As will be further described herein, the magnetization direction 324f controls the magnetization direction of the upper layer of the TMR element 100.

[0035]

[0048] In one example, the magnetization direction 324f is formed by heating the antiferromagnetic layer 322f using a laser focused only on the antiferromagnetic layer 322f and exposing the antiferromagnetic layer 322f to an external magnetic field. In another example, the magnetization direction 324f is formed by applying a current pulse through the TMR element 100 and exposing the antiferromagnetic layer 322f to an external magnetic field.

[0036]

[0049] Referring to Figure 3B, another example of the ferromagnetic layer 126 is the ferromagnetic layer 126''. The pinning layer 120 (Figure 1), specifically the magnetization direction 324f (Figure 3A), pins the magnetization direction 328. Thus, the magnetization direction 328 is determined by the magnetization direction 324f (Figure 3A) and is the same as the magnetization direction 324f.

[0037]

[0050] Referring to Figure 3C, another example of the first multilayer structure 132 is the first multilayer structure 132''. The first multilayer structure 132'' includes a first sublayer 330a, a second sublayer 330b, ..., and an Mth sublayer 330M, where M > 2. In other examples, the first multilayer structure 132'' may include one or two sublayers.

[0038]

[0051] The first sublayer 330a contains a heavy metal 332a on top of a ferromagnetic material 334a. The second sublayer 330b contains a heavy metal 332b on top of a ferromagnetic material 334b. The Mth sublayer 330M contains a heavy metal 332M on top of a ferromagnetic material 334M.

[0039]

[0052] For example, heavy metals 332a to 332M could be platinum. For example, ferromagnetic materials 334a to 334M could be cobalt, or may contain cobalt, such as cobalt iron or cobalt iron boron.

[0040]

[0053] Referring to Figure 3D, another example of the second multilayer structure 142 is the second multilayer structure 142''. The second multilayer structure 142'' includes a first sublayer 340a, a second sublayer 340b, ..., and an Nth sublayer 340N, where N > 2. In other examples, the second multilayer structure 142'' may include one or two sublayers. In one example, M and N are not equal. In another example, M and N are equal.

[0041]

[0054] The first sublayer 340a contains a heavy metal 342a on top of a ferromagnetic material 344a. The second sublayer 340b contains a heavy metal 342b on top of a ferromagnetic material 344b. The nth sublayer 340N contains a heavy metal 342N on top of a ferromagnetic material 344N.

[0042]

[0055] For example, heavy metals 342a to 342N could be platinum. For example, ferromagnetic materials 344a to 344N could be cobalt, or may contain cobalt, such as cobalt iron or cobalt iron boron.

[0043]

[0056] Referring to Figure 3E, the pinning layer 120 (Figure 1), specifically the magnetization direction 324f (Figure 3A), pins the magnetization direction 338 of the first multilayer structure 132''. Therefore, the magnetization direction 338 is determined by the magnetization direction 324f and is the same as the magnetization direction 324f.

[0044]

[0057] The magnetization direction 348 of the second multilayer structure 142'' is opposite to the magnetization direction 338 of the first multilayer structure 132''. The thickness of the metal layer 136 (Figure 1) allows the RKKY coupling mechanism to make the magnetization direction 348 opposite to the magnetization direction 338. Therefore, the magnetization direction 348 is determined by the magnetization direction 324f and is opposite to the magnetization direction 324f. The magnetization direction 348 is the reference direction of the TMR element 100b and is the z direction.

[0045]

[0058] Referring to Figure 4A, the bridge 400 (for example, a Wheatstone bridge) includes a first leg 402a containing a TMR element 100a (Figure 2E) electrically in series with a TMR element 100b (Figure 3E). At the first leg 402a, the TMR element 100a is closest to the power source, and the TMR element 100b is closest to ground. The bridge 400 also includes a second leg 402b containing a TMR element 100a (Figure 2E) electrically in series with a TMR element 100b (Figure 3E). At the second leg 402b, the TMR element 100b is closest to the power source, and the TMR element 100a is closest to ground. The bridge 400 generates differential outputs at nodes A and B to form an out-of-plane magnetometer or z-axis magnetometer.

[0046]

[0059] Referring to Figures 4B and 4C, the TMR element 102a (Figure 2E) may be divided into lower-level elements such as the lower-level TMR element 402a, and the TMR element 102b (Figure 3E) may be divided into lower-level elements such as the lower-level TMR element 402b. The lower-level TMR elements 402a and 402b may be arranged alternately in a checkerboard layout, such as layout 420.

[0047]

[0060] Elements of the different embodiments described herein can be combined to form other embodiments not specified in detail above. Various elements described in the context of a single embodiment can also be provided separately or in any suitable subcombination. Other embodiments not specified in detail herein are also within the scope of the following claims.

Claims

1. A method comprising the step of manufacturing a tunnel magnetoresistance (TMR) element for sensing out-of-plane changes in magnetic field strength in a magnetic field, The manufacturing step described above is: A step of depositing an antiferromagnetic material on a seed layer, wherein the antiferromagnetic material comprises a plurality of antiferromagnetic layers, each having a magnetization direction that alternates between a first direction and a second direction opposite to the first direction, and the uppermost layer of the plurality of antiferromagnetic layers has a magnetization direction in the first direction. The step of directly depositing a ferromagnetic layer on the uppermost layer of the plurality of antiferromagnetic layers, The steps include directly depositing a first multilayer structure on the ferromagnetic layer, The steps include directly depositing a metal layer on the first multilayer structure, The steps include directly depositing a second multilayer structure onto the aforementioned metal layer, Includes, The ferromagnetic layer, the first multilayer structure, and the second multilayer structure are each parallel to the xy plane. The first direction is either the z-direction or the -z-direction. The magnetization direction of the second multilayer structure is the second direction, determined by the magnetization direction of the uppermost layer of the plurality of antiferromagnetic layers, and is opposite to the magnetization direction of the uppermost layer of the plurality of antiferromagnetic layers. The magnetization direction of the second multilayer structure is the reference direction of the TMR element. method.

2. The ferromagnetic layer is the first magnetic layer, The steps include depositing a second ferromagnetic layer on the second multilayer structure, The steps include directly depositing an insulating layer on the second ferromagnetic layer, The method according to claim 1, further comprising the step of depositing a free layer on the insulating layer.

3. The method according to claim 2, wherein the magnetization direction of the free layer lies in the xy plane.

4. The method according to claim 2, further comprising the step of depositing a striped magnetic domain structure on the free layer.

5. The method according to claim 4, wherein the step of depositing the striped magnetic domain structure on the free layer includes the step of depositing the striped magnetic domain structure comprising one or more sublayers.

6. The method according to claim 5, wherein each sublayer comprises at least one heavy metal and at least one ferromagnetic material.

7. The method according to claim 5, wherein each sublayer comprises at least one oxide layer and at least one ferromagnetic layer.

8. The method according to claim 7, wherein each sublayer further comprises at least one heavy metal.

9. The method according to claim 5, wherein each sublayer further comprises a buffer layer.

10. The method according to claim 2, wherein the metal layer is a first metal layer, and further comprises the step of depositing a second metal layer on the second multilayer structure before the step of depositing the second ferromagnetic layer.

11. The method according to claim 1, wherein the magnetization direction of the first multilayer structure is the first direction and is determined by the magnetization direction of the uppermost layer of the plurality of antiferromagnetic layers.

12. The method according to claim 11, wherein the magnetization direction of the uppermost layer of the plurality of antiferromagnetic layers is formed using a laser or by a current pulse passing through the TMR element.

13. The step of depositing the first multilayer structure includes the step of depositing a sublayer, The method according to claim 1, wherein each sublayer comprises a first heavy metal layer and a first ferromagnetic material layer.

14. The step of depositing the second multilayer structure includes the step of depositing a sublayer, The method according to claim 13, wherein each sublayer comprises a second heavy metal layer and a second ferromagnetic material layer.

15. The method according to claim 14, wherein the total number of sublayers in the first multilayer structure is not equal to the total number of sublayers in the second multilayer structure.

16. The method according to claim 14, wherein the total number of sublayers in the first multilayer structure is equal to the total number of sublayers in the second multilayer structure.

17. The method according to claim 14, wherein the first heavy metal layer and / or the second heavy metal layer is a platinum layer, and the first ferromagnetic material layer and / or the second ferromagnetic material layer contains a cobalt element.

18. The method according to claim 1, wherein the step of depositing the antiferromagnetic material includes the step of depositing iridium manganese, platinum manganese, or iron manganese.

19. A tunnel magnetoresistance (TMR) element, An antiferromagnetic material comprising a plurality of antiferromagnetic layers having magnetization directions that alternate between a first direction and a second direction opposite to the first direction, and the uppermost layer of the plurality of antiferromagnetic layers having a magnetization direction in the first direction, A ferromagnetic layer in direct contact with the uppermost layer of the plurality of antiferromagnetic layers, A first multilayer structure in direct contact with the ferromagnetic layer, A metal layer in direct contact with the first multilayer structure, A second multilayer structure in direct contact with the aforementioned metal layer, the second multilayer structure being part of the reference layer, Equipped with, The ferromagnetic layer, the first multilayer structure, and the second multilayer structure are each parallel to the xy plane. The first direction is either the z-direction or the -z-direction. The magnetization direction of the second multilayer structure is the second direction, determined by the magnetization direction of the uppermost layer of the plurality of antiferromagnetic layers, and is opposite to the magnetization direction of the uppermost layer of the plurality of antiferromagnetic layers. The magnetization direction of the second multilayer structure is the reference direction of the TMR element. Tunnel magnetoresistance (TMR) element.

20. The ferromagnetic layer is the first magnetic layer, The second ferromagnetic layer on the second multilayer structure, The insulating layer in direct contact with the second ferromagnetic layer, The TMR element according to claim 19, further comprising a free layer on the insulating layer.

21. The TMR element according to claim 20, wherein the magnetization direction of the free layer lies in the xy plane.

22. The TMR element according to claim 20, further comprising a stripe-shaped magnetic domain structure on the free layer.

23. The TMR element according to claim 22, wherein the stripe-shaped magnetic domain structure comprises one or more sublayers.

24. The TMR element according to claim 23, wherein each sublayer comprises at least one heavy metal and at least one ferromagnetic material.

25. The TMR element according to claim 23, wherein each sublayer comprises at least one oxide layer and at least one ferromagnetic layer.

26. The TMR element according to claim 25, wherein each sublayer further comprises at least one heavy metal.

27. The TMR element according to claim 23, wherein each sublayer comprises a buffer layer.

28. The TMR element according to claim 20, wherein the metal layer is a first metal layer, and further comprises a second metal layer between the second ferromagnetic layer and the second multilayer structure.

29. The TMR element according to claim 19, wherein the magnetization direction of the first multilayer structure is the first direction and is determined by the magnetization direction of the uppermost layer of the plurality of antiferromagnetic layers.

30. The TMR element according to claim 19, wherein the first multilayer structure comprises sublayers, each sublayer comprising a first heavy metal layer and a first ferromagnetic material layer.

31. The TMR element according to claim 30, wherein the second multilayer structure comprises sublayers, each sublayer comprising a second heavy metal layer and a second ferromagnetic material layer.

32. The TMR element according to claim 31, wherein the first heavy metal layer and / or the second heavy metal layer is a platinum layer, and the first ferromagnetic material layer and / or the second ferromagnetic material layer contains a cobalt element.

33. The TMR element according to claim 31, wherein the total number of sublayers in the first multilayer structure is not equal to the total number of sublayers in the second multilayer structure.

34. The TMR element according to claim 31, wherein the total number of sublayers in the first multilayer structure is equal to the total number of sublayers in the second multilayer structure.

35. The TMR element according to claim 19, wherein the antiferromagnetic material includes iridium manganese, platinum manganese, or iron manganese.

36. A magnetic field sensor equipped with a bridge, The aforementioned bridge, Power source and The first leg, A first tunnel magnetoresistance (TMR) element, and The first leg comprises a second TMR element that is electrically in series with the first TMR element and is electrically closer to the power source than the first TMR element, The second leg, A third TMR element, and The second leg comprises a fourth TMR element that is electrically in series with the third TMR element and is electrically closer to the power source than the third TMR element, It is equipped with, The first TMR element, the second TMR element, the third TMR element, and the fourth TMR element are each, An antiferromagnetic material comprising a plurality of antiferromagnetic layers having magnetization directions that alternate between a first direction and a second direction opposite to the first direction, and the uppermost layer of the plurality of antiferromagnetic layers having a magnetization direction in the first direction, A ferromagnetic layer in direct contact with the uppermost layer of the plurality of antiferromagnetic layers, A first multilayer structure in direct contact with the ferromagnetic layer, A metal layer in direct contact with the first multilayer structure, A second multilayer structure in direct contact with the aforementioned metal layer, comprising a second multilayer structure which is part of the reference layer, The ferromagnetic layer, the first multilayer structure, and the second multilayer structure are each parallel to the xy plane. The first direction is either the z-direction or the -z-direction. The magnetization direction of the second multilayer structure is the second direction, determined by the magnetization direction of the uppermost layer of the plurality of antiferromagnetic layers, and is opposite to the magnetization direction of the uppermost layer of the plurality of antiferromagnetic layers. The magnetization direction of the second multilayer structure is the reference direction of the TMR element. The first TMR element and the fourth TMR element each have a reference direction in the z direction. The second TMR element and the third TMR element each have a reference direction in the -z direction. Magnetic field sensor.

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