Same chip implementation of full-bridge and dual-axis magnetic sensor

Abstract

This invention discloses a magnetic sensor that integrates full-bridge and dual-axis configurations on a single chip. The magnetic sensor comprises two antiferromagnetic tunnel junction full-bridge structures formed on the same chip with mutually perpendicular magnetic sensing directions. Each arm of the full-bridge structure has an antiferromagnetic tunnel junction unit, comprising, from bottom to top, a heavy metal layer, an antiferromagnetic reference layer, a tunneling barrier layer, an antiferromagnetic free layer, and a ferromagnetic layer. During the initialization phase of the antiferromagnetic tunnel junction unit, the Néel vector direction of the antiferromagnetic reference layer is set by applying an in-plane write current to the heavy metal layer. The Néel vector directions of the antiferromagnetic reference layers in the antiferromagnetic tunnel junction units corresponding to the two pairs of diagonal arms are opposite, and the in-plane write current directions corresponding to the two full-bridge structures are orthogonal. This invention integrates the reverse-direction configuration and the dual-axis orthogonal-direction configuration of the antiferromagnetic tunnel junction full-bridge on the same chip through current initialization.

Description

Technical Field

[0001] This invention relates to the fields of spintronics, tunneling magnetoresistance (TMR) sensors, orientation control technology for antiferromagnetic / interlaced magnetic materials, and the fabrication technology of on-chip integrated magnetic field sensing chips. Specifically, it relates to a scheme for selectively writing the antiferromagnetic Néel vector direction using the current direction, thereby realizing the on-chip integration of antiferromagnetic tunnel junction units into full-bridge and biaxial structures. Background Technology

[0002] Magnetoresistive sensors (such as GMR / TMR) generate magnetoresistive changes under the influence of a magnetic field, but their output is easily affected by temperature drift, bias voltage fluctuations, and process variations. To improve linearity and suppress temperature drift and noise, the industry commonly uses a Wheatstone bridge structure to form a differential output system. However, a full-bridge structure requires that the magnetic response directions of the magnetoresistive units between the bridge arms be opposite, that is, the magnetization directions of their reference layers (pinning layers) must be aligned in opposite directions (resulting in opposite output curves). However, wafer-level thin film deposition is usually completed under a uniform magnetic field direction, resulting in all devices having the same pinning direction, making it difficult to naturally form the reverse structure required for a full-bridge.

[0003] Current methods for achieving directional differences in full-bridge or biaxial structures of magnetoresistive sensors include: sorting and splicing full-bridge structures, local annealing, partitioned photolithography with multiple deposition stages, and single-stage annealing directional control relying on shape anisotropy. While these methods can achieve directional differences to some extent, existing processes generally suffer from the following core limitations:

[0004] 1. It is impossible to simultaneously achieve the "output reverse direction" required by the full bridge and the "orthogonal direction" required by the dual axes on the same wafer.

[0005] 2. The reference layer orientation depends on high-temperature annealing, cannot be rewritten, and does not support electrical programmability.

[0006] 3. Localized annealing causes severe thermal damage and has a narrow process window, making it difficult to use in high-reliability TMR devices.

[0007] 4. The partitioned deposition process is complex and prone to film contamination and parameter inconsistencies, making mass production difficult.

[0008] 5. None of the existing methods can achieve independent orientation control of on-chip regions, nor are they suitable for arrayed, scalable orientation writing.

[0009] Therefore, how to achieve a reference layer orientation control mechanism that does not require multiple magnetic field annealing, is reversible and rewritable, and is electrically programmable on-chip, so as to integrate full-bridge and dual-axis structures on the same wafer, is a key problem that urgently needs to be solved. Summary of the Invention

[0010] To address at least one of the technical problems mentioned in the background art, this invention proposes a magnetic sensor that implements full-bridge and dual-axis magnetic properties on the same chip. The magnetic sensor comprises two antiferromagnetic tunnel junction full-bridge structures formed on the same chip with mutually perpendicular magnetic sensing directions. Each arm of the antiferromagnetic tunnel junction full-bridge structure is provided with an antiferromagnetic tunnel junction unit. The antiferromagnetic tunnel junction unit comprises, from bottom to top, a heavy metal layer, an antiferromagnetic reference layer, a tunneling barrier layer, an antiferromagnetic free layer, and a ferromagnetic layer.

[0011] During the initialization phase of the antiferromagnetic tunnel junction unit, the Néel vector direction of the antiferromagnetic reference layer is set by applying an in-plane write current to the heavy metal layer. For each antiferromagnetic tunnel junction full-bridge structure, an in-plane write current along a first direction is applied to the antiferromagnetic tunnel junction unit corresponding to one pair of diagonal bridge arms during the initialization phase, and an in-plane write current along a second direction is applied to the antiferromagnetic tunnel junction unit corresponding to another pair of diagonal bridge arms during the initialization phase. The first direction and the second direction are opposite, so that the Néel vector directions of the antiferromagnetic reference layer in the antiferromagnetic tunnel junction units corresponding to the two pairs of diagonal bridge arms are opposite. The in-plane write current directions corresponding to the two antiferromagnetic tunnel junction full-bridge structures are orthogonal to each other.

[0012] Optionally, the Néel vector direction of the antiferromagnetic reference layer can be selectively set under the action of the write current and maintained after the write is completed, so as to provide a programmable reference direction in the device; the magnetic moment of the ferromagnetic layer changes under the action of an external magnetic field; the Néel vector of the antiferromagnetic free layer undergoes corresponding orientation modulation under the exchange coupling between the antiferromagnetic free layer and the ferromagnetic layer, thereby participating in the magnetic field sensitive output process.

[0013] Optionally, the heavy metal layer of the antiferromagnetic tunnel junction unit is electrically connected to a heavy metal write line to apply an in-plane write current to the heavy metal layer through the heavy metal write line.

[0014] Optionally, two sets of heavy metal writing lines are respectively provided for the two antiferromagnetic tunnel junction full bridge structures, wherein one set of heavy metal writing lines is arranged along the X direction and the other set of heavy metal writing lines is arranged along the Y direction, wherein the X direction and the Y direction are perpendicular to each other.

[0015] Optionally, the formation process of each of the antiferromagnetic tunnel junction units includes: depositing a magnetic thin film on a substrate for forming the antiferromagnetic tunnel junction unit; forming a hard mask layer on the magnetic thin film and patterning the magnetic thin film by photolithography and etching processes to define the device pattern of the antiferromagnetic tunnel junction unit; and forming an electrode structure electrically connected to the antiferromagnetic tunnel junction unit by dielectric layer deposition, via etching, and deposition and patterning of a top electrode.

[0016] Optionally, the antiferromagnetic tunnel junction unit further includes a seed layer disposed on a substrate, and the heavy metal layer disposed on the seed layer.

[0017] Optionally, the antiferromagnetic tunnel junction unit further includes a protective layer disposed on the ferromagnetic layer.

[0018] Optionally, the antiferromagnetic reference layer is made of RuO2.

[0019] Optionally, the material of the tunneling barrier layer is TiO2.

[0020] Optionally, the material of the antiferromagnetic free layer is RuO2.

[0021] The beneficial effects of this invention are as follows:

[0022] This invention integrates two sets of antiferromagnetic tunnel junction full-bridge structures with mutually perpendicular magnetic sensing directions on the same chip. During the initialization phase, an in-plane write current is applied to the heavy metal layer of each antiferromagnetic tunnel junction unit to set the Néel vector direction of the antiferromagnetic reference layer. This results in the reference layer Néel vector directions corresponding to the two pairs of diagonal bridge arms in each full-bridge being configured in opposite directions to form a differential output. At the same time, the in-plane write current directions corresponding to the two full-bridges are orthogonal to achieve dual-axis detection. Thus, under the same chip conditions, the reverse output direction configuration required by the full-bridge and the orthogonal direction configuration required by the dual axes are simultaneously satisfied. This reduces the dependence on complex process paths such as sorting and splicing, local annealing, or partitioned deposition, and enables on-chip directional configuration capability that can be initialized by current, facilitating array-based and scalable integrated applications. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0024] Figure 1 This is a schematic diagram of the antiferromagnetic tunnel junction unit membrane stack structure according to an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of the antiferromagnetic tunnel structure full bridge according to an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of the biaxial magnetic field detection formed by two antiferromagnetic tunnel junction full-bridge structures in an embodiment of the present invention;

[0027] Figure 4This is a cross-sectional view of the process in an embodiment of the present invention. Detailed Implementation

[0028] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0029] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0030] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products or devices.

[0031] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] Advantages of the interleaved magnetic (RuO2 / TiO2 / RuO2) system:

[0033] In existing technologies, antiferromagnetic materials with alternating magnetic order have been shown to have their Néel vector direction switched via the current-induced spin-orbit moment (SOT) effect. Literature reports that, under non-magnetic and non-thermal conditions, the Néel vector can be switched rapidly and reversibly under current control. The final Néel vector direction can be deterministically set to be orthogonal or collinear with the current direction, depending on the crystal symmetry of the material and the direction of the writing current.

[0034] These antiferromagnets lack a net magnetic moment, thus exhibiting strong robustness against external magnetic field interference. Furthermore, as metals, they possess high electrical conductivity, enabling efficient generation of spin-polarized currents, making them particularly suitable as substrates for programmable reference layers. Introducing a staggered magnetic structure similar to RuO2 / TiO2 / RuO2 into the magnetic tunnel junction system allows for independent control of the Néel vector direction of different regions of the reference layer through write currents in different directions, without altering the thin film deposition process. This provides a new approach for achieving "reverse" direction control of the full-bridge and "orthogonal" direction control of the dual-axis on the same wafer.

[0035] Therefore, in view of the problems of complex and low-yield multi-step magnetic field annealing process when constructing full-bridge or multi-axis integrated structures of existing magnetoresistive sensors, this application proposes a solution: This application utilizes an interlaced magnetic structure with Néel vector that can be controlled by current to construct an electrically programmable reference layer on the chip, thereby providing a method to achieve high-precision magnetization direction control without multi-step magnetic field annealing, and applies it to the fabrication of on-chip full-bridge and multi-axis integrated magnetoresistive sensors.

[0036] This application is based on the following physical principle: In antiferromagnetic or interlaced magnetic materials with significant spin polarization characteristics and capable of generating Néel spin-orbit torque, injecting current in different directions can drive the Néel vector inside the material to reorient, and maintain the set orientation state after the current is removed. Based on this physical property, this application sets heavy metal write lines in different directions on the chip, and applies in-plane current to the corresponding directions during the writing stage to achieve electrical setting of the Néel vector direction of the antiferromagnetic layer, thereby completing the on-chip programmable writing of the reference direction, providing a foundation for subsequent full-bridge configuration and dual-axis magnetic field detection.

[0037] In one embodiment of the present invention, the magnetic sensor that realizes full-bridge and dual-axis on the same chip proposed by the present invention includes: two antiferromagnetic tunnel junction full-bridge structures formed on the same chip and with magnetic sensing directions perpendicular to each other; each arm of the antiferromagnetic tunnel junction full-bridge structure is provided with an antiferromagnetic tunnel junction unit; the antiferromagnetic tunnel junction unit includes, from bottom to top, a heavy metal layer, an antiferromagnetic reference layer, a tunneling barrier layer, an antiferromagnetic free layer, and a ferromagnetic layer;

[0038] During the initialization phase of the antiferromagnetic tunnel junction unit, the Néel vector direction of the antiferromagnetic reference layer is set by applying an in-plane write current to the heavy metal layer. For each antiferromagnetic tunnel junction full-bridge structure, an in-plane write current along a first direction is applied to the antiferromagnetic tunnel junction unit corresponding to one pair of diagonal bridge arms during the initialization phase, and an in-plane write current along a second direction is applied to the antiferromagnetic tunnel junction unit corresponding to another pair of diagonal bridge arms during the initialization phase. The first direction and the second direction are opposite, so that the Néel vector directions of the antiferromagnetic reference layer in the antiferromagnetic tunnel junction units corresponding to the two pairs of diagonal bridge arms are opposite. The in-plane write current directions corresponding to the two antiferromagnetic tunnel junction full-bridge structures are orthogonal to each other.

[0039] In this application, "same-chip implementation" means that multiple antiferromagnetic tunnel junction units and their corresponding full-bridge structures used for full-bridge differential output and biaxial magnetic field detection are all formed on the same chip substrate through a unified thin film deposition and micro / nano fabrication process, rather than through sorting, splicing, or post-assembly. Specifically, the two sets of antiferromagnetic tunnel junction full-bridge structures in this application are fabricated on the same chip and arranged independently in spatial position. Their respective antiferromagnetic tunnel junction units share the same process platform and manufacturing process, thereby achieving highly consistent structural and parametric characteristics at the device level.

[0040] In terms of implementation, this application does not rely on multiple magnetic field annealings, partitioned depositions, or localized heat treatments at the wafer or chip level to obtain reference layer magnetization states in different directions. Instead, it sets up write structures with different directions on the same chip and applies directionally controllable in-plane write currents to different antiferromagnetic tunnel junction units during the initialization phase. This allows for independent setting of the Néel vector direction of the antiferromagnetic reference layer within the same chip area. Through this method, the difference in reference direction between different bridge arm units and different full-bridge structures is determined by the current writing process, rather than being fixed by the initial device fabrication conditions, thereby achieving programmable control of the direction within the on-chip region.

[0041] By implementing this method on a single chip, this application can simultaneously meet the requirements of a full-bridge structure for reversed reference direction configuration and a dual-axis detection requirement for orthogonal magnetic sensing direction configuration within a single chip. Compared to existing solutions that rely on sorting and splicing or multiple annealing, this application avoids parameter dispersion problems caused by differences in device sources, process batches, or inconsistent heat treatment. This allows the full-bridge and dual-axis structures to be fabricated, initialized, and work collaboratively on the same chip, making it more suitable for array integration and large-scale manufacturing.

[0042] In one embodiment of the present invention, the Néel vector direction of the antiferromagnetic reference layer can be selectively set under the action of the write current and maintained after the write is completed, so as to provide a programmable reference direction in the device; the magnetic moment of the ferromagnetic layer changes under the action of an external magnetic field; the Néel vector of the antiferromagnetic free layer undergoes corresponding orientation modulation under the exchange coupling between the antiferromagnetic free layer and the ferromagnetic layer, thereby participating in the magnetic field sensitive output process.

[0043] In one embodiment of the present invention, the antiferromagnetic tunnel junction unit is used to simultaneously complete the current writing setting of the reference direction and the resistance readout of the magnetic field signal. The heavy metal layer is used to carry the in-plane writing current. When the writing current flows in the heavy metal layer, it can generate an electrical writing effect on the antiferromagnetic reference layer above it, so that the Néel vector direction of the antiferromagnetic reference layer is set according to the writing current direction. After the writing is completed, the Néel vector direction of the antiferromagnetic reference layer remains in the set state and is used as the reference direction of the unit. The tunneling barrier layer is located between the antiferromagnetic reference layer and the antiferromagnetic free layer, and is used to form a tunneling conductive channel and provide a basis for resistance readout. The ferromagnetic layer is arranged adjacent to the antiferromagnetic free layer, and is used to provide an exchange bias to the antiferromagnetic free layer, so that the antiferromagnetic free layer produces a repeatable response under the action of an external magnetic field, thereby causing a change in the resistance of the antiferromagnetic tunnel junction unit.

[0044] In one embodiment of the present invention, the antiferromagnetic tunnel junction full-bridge structure comprises four bridge arms, each composed of four antiferromagnetic tunnel junction units. The units in each bridge arm are geometrically symmetrically arranged. During the initialization phase, the antiferromagnetic tunnel junction units of each bridge arm are written to. For the same full-bridge structure, a pair of diagonal bridge arms is selected as the first group, and an in-plane write current along a first direction is passed into the heavy metal layer of this first group. Another pair of diagonal bridge arms is selected as the second group, and an in-plane write current along a second direction is passed into the heavy metal layer of this second group. The first direction is opposite to the second direction. After writing, the Néel vector directions of the two antiferromagnetic reference layers in the first group of bridge arm units are aligned, and the Néel vector directions of the two antiferromagnetic reference layers in the second group of bridge arm units are aligned, but opposite in direction to each other. After the full bridge enters the readout phase, a measurement voltage is applied to the full bridge. The resistance changes of the four bridge arms are output differentially. Common-mode drift is canceled out in the bridge circuit. A differential voltage signal related to the external magnetic field is obtained at the output terminal.

[0045] In one embodiment of the present invention, the magnetic sensor comprises two sets of antiferromagnetic tunnel junction full-bridge structures. The two full-bridges are formed on the same chip. The two full-bridges are arranged perpendicularly to each other, and their magnetic sensing directions are perpendicular to each other. Initialization writing of the two full-bridges uses mutually orthogonal in-plane write current directions. The write current direction of the first full-bridge is used to set the Néel vector direction of its reference layer, making it more sensitive to changes in the external magnetic field in the first magnetic sensing direction. The write current direction of the second full-bridge is orthogonal to the first full-bridge, used to set the Néel vector direction of its reference layer, making it more sensitive to changes in the external magnetic field in the second magnetic sensing direction. During the readout phase, the two full-bridges output corresponding differential voltage signals respectively. The two output signals do not interfere with each other. This achieves dual-axis magnetic field detection on the same chip.

[0046] In one embodiment of the invention, initialization writing and normal readout are performed time-sharingly. Initialization writing is used to set the reference layer Néel vector direction for each bridge arm unit. After writing is completed, the writing current applied to the heavy metal layer is stopped. During the readout phase, the resistance of the antiferromagnetic tunnel junction unit is measured using tunneling current. The readout current is set to a small current to reduce disturbance to the reference layer state. When it is necessary to reset the reference direction, the initialization phase can be entered again, and the corresponding bridge arm unit can be written to according to the preset current direction to achieve adjustment and update of the direction configuration.

[0047] In one embodiment of the present invention, to achieve reliable writing and consistent reading, the amplitude and duration range of the writing pulse can be set for the writing process. Writing can be performed arm by arm, or simultaneously on the same group of diagonal bridge arms. After writing is complete, a verification read can be performed to determine whether the full-bridge differential output has reached the expected zero point or the expected bias level. If the verification fails, writing can be repeated or the writing parameters can be adjusted. Through the above method, the reverse reference direction configuration required for full-bridge differential output and the orthogonal direction configuration required for dual-axis detection can be implemented on the same chip.

[0048] In one embodiment of the present invention, the antiferromagnetic tunnel junction unit further includes a seed layer disposed on the substrate to improve the growth conditions of the functional thin films thereon, and the heavy metal layer is disposed on the seed layer. By disposing of the seed layer between the substrate and the heavy metal layer, the adhesion and flatness of the heavy metal layer can be improved, resulting in a more stable interface quality for the subsequently deposited antiferromagnetic layer and tunneling barrier layer, thereby facilitating the uniform formation of the antiferromagnetic tunnel junction unit. The heavy metal layer disposed on the seed layer enables stable conduction of the write current within the heavy metal layer and provides reliable current writing conditions for the antiferromagnetic reference layer.

[0049] In one embodiment of the present invention, the antiferromagnetic tunnel junction unit further includes a protective layer disposed on the ferromagnetic layer for encapsulating and protecting the underlying magnetic thin film structure. By providing a protective layer, the impact of subsequent process steps and environmental factors during device use on the ferromagnetic and antiferromagnetic layers can be reduced, and performance drift caused by oxidation, contamination, or mechanical damage can be minimized, thereby improving the long-term stability and reliability of the antiferromagnetic tunnel junction unit.

[0050] In one embodiment of the present invention, the antiferromagnetic reference layer is made of RuO2. RuO2 has antiferromagnetic properties, and its Néel vector direction can be set under the action of current, making it suitable for use as a reference layer in an antiferromagnetic tunnel junction unit. By selecting RuO2 as the antiferromagnetic reference layer material, current writing in the reference direction can be achieved during the initialization phase, and the set Néel vector direction can be maintained after the writing is completed, providing a stable reference for the full-bridge structure.

[0051] In one embodiment of the present invention, the tunneling barrier layer is made of TiO2. TiO2 is disposed between the antiferromagnetic reference layer and the antiferromagnetic free layer to form a stable tunneling conductive channel. By using TiO2, while ensuring controllable tunneling current, the antiferromagnetic tunnel junction unit can generate a resistance change related to the magnetic state during the readout phase, thereby achieving electrical detection of the external magnetic field.

[0052] In one embodiment of the present invention, the antiferromagnetic free layer is made of RuO2. Due to the exchange coupling with the ferromagnetic layer, the Néel vector of the antiferromagnetic free layer undergoes corresponding orientation modulation when the magnetic moment of the ferromagnetic layer changes with the external magnetic field. This enables the antiferromagnetic free layer to produce a stable and repeatable response under the action of the external magnetic field, thereby improving the sensitivity and output consistency of the antiferromagnetic tunnel junction unit to changes in the magnetic field.

[0053] In one embodiment of the present invention, the heavy metal layer of the antiferromagnetic tunnel junction unit is electrically connected to a heavy metal write line so as to apply an in-plane write current to the heavy metal layer through the heavy metal write line.

[0054] In one embodiment of the present invention, two sets of heavy metal writing lines are respectively provided for the two antiferromagnetic tunnel junction full bridge structures, wherein one set of heavy metal writing lines is arranged along the X direction and the other set of heavy metal writing lines is arranged along the Y direction, wherein the X direction and the Y direction are perpendicular to each other.

[0055] In one embodiment of the present invention, two sets of heavy metal write lines are respectively arranged for two antiferromagnetic tunnel junction full-bridge structures formed on the same chip. The two sets of heavy metal write lines are arranged in different directions in the chip plane, one set of heavy metal write lines extends along the X direction and the other set extends along the Y direction, and the X direction and the Y direction are perpendicular to each other. With the above arrangement, in-plane write currents can be applied to the antiferromagnetic tunnel junction units in the corresponding full-bridge structure along different directions during the initialization phase, thereby independently setting the Néel vector of the antiferromagnetic reference layer in different magnetic sensing directions. Since the two sets of heavy metal write lines are orthogonal to each other in spatial direction, the corresponding write currents do not interfere with each other during the initialization process, which is beneficial to realize independent writing and stable configuration of two full-bridge structures on the same chip, thereby providing a reliable writing basis for dual-axis magnetic field detection.

[0056] Figure 1 This is a schematic diagram of the membrane stack structure of an antiferromagnetic tunnel junction (AFMTJ) unit in one embodiment of the present invention, as shown below. Figure 1 As shown, in one embodiment of the present invention, the membrane stack structure of the antiferromagnetic tunnel junction unit includes, from bottom to top: a seed layer, a heavy metal layer, a reference layer RuO2 (i.e., the aforementioned antiferromagnetic reference layer), a TiO2 layer (i.e., the aforementioned tunneling barrier layer), a free layer RuO2 (i.e., the aforementioned antiferromagnetic free layer), a ferromagnetic layer, and a protective layer.

[0057] The seed layer is disposed on the substrate and is used to improve the adhesion, crystal orientation, and flatness of the heavy metal layer above it, thereby improving the growth quality and structural stability of the entire film stack structure. The seed layer material can be selected from metals such as Ta and Ru according to process requirements.

[0058] The heavy metal layer is disposed above the seed layer and serves as a current writing layer. This layer exhibits strong spin-orbit coupling characteristics; during the initialization phase, when an in-plane writing current is applied, a spin-orbit effect is generated, injecting spin angular momentum into the reference layer RuO2 above it, thereby achieving electrical setting of the Néel vector direction of the reference layer. The heavy metal layer material can be Pt, W, or their alloys.

[0059] The reference layer RuO2 is located above the heavy metal layer and is used as an antiferromagnetic reference layer. This layer is an interleaved magnetic material, and its Néel vector direction can be selectively set under the action of the write current and remains stable after the write operation is completed. It is used to provide a programmable reference direction in the device, forming a magnetization reference for full-bridge and biaxial structures.

[0060] The TiO2 layer is disposed between the reference layer RuO2 and the free layer RuO2, and is used as a tunneling barrier layer to realize the tunneling transmission characteristics of the antiferromagnetic tunnel junction and to provide electrical isolation between the upper and lower antiferromagnetic layers.

[0061] The free layer RuO2, located above the TiO2 layer, serves as a magnetic response layer. Due to the exchange coupling with the ferromagnetic layer, the Néel vector of this layer undergoes corresponding orientation modulation as the magnetic moment of the ferromagnetic layer changes with the external magnetic field, thereby enabling sensitive sensing of the external magnetic field.

[0062] The ferromagnetic layer is disposed on the free layer RuO2 and is used to apply an exchange bias field to the free layer to limit its magnetic response direction and improve the stability of the magnetoresistive readout signal, so that the antiferromagnetic tunnel junction unit has readable resistance change characteristics.

[0063] The protective layer is located on top of the membrane stack structure to prevent membrane oxidation and physical or chemical damage during subsequent processes, thereby improving the long-term reliability and environmental stability of the device.

[0064] Based on the aforementioned antiferromagnetic tunnel junction unit membrane stack structure, this application constructs a current-programmable antiferromagnetic tunnel junction Wheatstone full-bridge structure, as illustrated in the diagram below. Figure 2 As shown. The Wheatstone full-bridge structure includes four bridge arms, each of which is equipped with an antiferromagnetic tunnel junction unit. The four antiferromagnetic tunnel junction units together constitute the full-bridge differential detection structure.

[0065] In this structure, the heavy metal layer of each antiferromagnetic tunnel junction unit is electrically connected to the corresponding write end, enabling the Néel vector direction of the antiferromagnetic reference layer to be electrically set by the in-plane write current during the initialization phase. Specifically, the four antiferromagnetic tunnel junction units correspond to write ends 5–6, 7–8, 9–10, and 11–12, respectively.

[0066] During the initialization phase, an in-plane write current in the horizontal direction is applied between each write end pair to set the Néel vector direction of the antiferromagnetic reference layer in each bridge arm. The writing method for the four bridge arms is as follows:

[0067] 1) The first bridge arm corresponds to the write terminals 5–6, and the write current direction is defined as the + L direction;

[0068] 2) The second bridge arm corresponds to the write terminals 7–8, and the write current direction is defined as the -L direction;

[0069] 3) The third bridge arm corresponds to the write terminals 9–10, and the write current direction is defined as the -L direction;

[0070] 4) The fourth bridge arm corresponds to the write terminals 11–12, and the write current direction is defined as the + L direction.

[0071] By using the above writing method, the Néel vector direction of the antiferromagnetic reference layer in one pair of diagonal bridge arms is kept consistent, while the Néel vector direction of the antiferromagnetic reference layer in the other pair of diagonal bridge arms is opposite to it, thereby satisfying the requirements of the Wheatstone full bridge structure for the bridge arm orientation configuration.

[0072] The writing process can be performed by applying write current to each bridge arm individually, or by applying write pulses to multiple bridge arms simultaneously. After writing is completed, the Néel vector direction of each antiferromagnetic reference layer remains stable without continuous write current; this process is a one-time initialization operation.

[0073] After initialization, the full-bridge structure enters the measurement phase. During measurement, a measurement voltage is applied to the bridge circuit through electrode 13, and the differential voltage signal at the full-bridge output terminal is obtained through electrode 24; the reverse is also possible.

[0074] During the measurement phase, no writing current is passed through the heavy metal layer, and only the tunneling current used for reading passes through the antiferromagnetic tunnel junction unit, thereby avoiding disturbance to the Néel vector direction set in the antiferromagnetic reference layer and ensuring the stability of the measurement process.

[0075] like Figure 3 As shown, this application achieves dual-axis magnetic field detection by setting two sets of mutually perpendicular antiferromagnetic tunnel junction full-bridge structures on the same chip. The two sets of full-bridge structures are structurally independent and do not interfere with each other during writing and reading, thus corresponding to magnetic field detection in different magnetic sensing directions.

[0076] The biaxial structure includes a first antiferromagnetic tunnel junction full-bridge structure and a second antiferromagnetic tunnel junction full-bridge structure, with the magnetic susceptibility directions of the two full-bridge structures perpendicular to each other.

[0077] The first full-bridge structure comprises four antiferromagnetic tunnel junction units, each disposed on one of the four arms of the full-bridge structure. The heavy metal write lines of this full-bridge structure are arranged along the X-direction. During the initialization phase, by applying a controllable in-plane write current along the X-direction write lines, the Néel vector of the corresponding antiferromagnetic reference layer can be written as ±L. X The differential output of this full bridge is Vout. X .

[0078] The second full-bridge structure comprises four antiferromagnetic tunnel junction units, each disposed on one of the four arms of the full-bridge structure. The heavy metal write lines of this full-bridge structure are arranged along the Y-direction. During the initialization phase, by applying an in-plane write current along the Y-direction write lines, the Néel vector of the corresponding antiferromagnetic reference layer can be written as ±L. Y The differential output of this full bridge is Vout. Y .

[0079] The two sets of write lines are perpendicular to each other, and the writing process can be performed independently. A step-by-step writing method can be used to complete the write settings for the X and Y axes separately. The readout circuits of the two-axis full-bridge are independent of each other, thereby achieving separate detection and decoupled output of the X and Y axis magnetic fields.

[0080] In one embodiment of the present invention, the formation process of each of the antiferromagnetic tunnel junction units includes: depositing a magnetic thin film for forming the antiferromagnetic tunnel junction unit on a substrate; forming a hard mask layer on the magnetic thin film and patterning the magnetic thin film by photolithography and etching processes to define the device pattern of the antiferromagnetic tunnel junction unit; and forming an electrode structure electrically connected to the antiferromagnetic tunnel junction unit by dielectric layer deposition, via etching, and deposition and patterning of a top electrode.

[0081] The following describes the fabrication process of the antiferromagnetic tunnel junction unit in the magnetic sensor described in this application, taking the fabrication of a single antiferromagnetic tunnel junction unit as an example. A schematic cross-sectional view of the process is shown below. Figure 4 As shown.

[0082] First, the magnetic thin film structure required to form the antiferromagnetic tunnel junction unit is sequentially deposited on the substrate, including a heavy metal layer, an antiferromagnetic reference layer, a tunneling barrier layer, an antiferromagnetic free layer, and a ferromagnetic layer, thereby obtaining a continuous magnetic thin film stack structure, such as... Figure 4 As shown in step 1. Subsequently, a layer of silicon dioxide is deposited on the magnetic thin film stack as a hard mask layer for subsequent etching processes.

[0083] After forming a silicon dioxide hard mask layer, photoresist is coated on it, and a predetermined pattern is formed in the photoresist through photolithography exposure and development processes, such as... Figure 4 As shown in steps 3 and 4. Next, the silicon dioxide layer is etched using the photoresist pattern to form a hard mask structure corresponding to the shape of the antiferromagnetic tunnel junction unit device, and then the photoresist is removed.

[0084] After defining the hard mask pattern, the silicon dioxide hard mask is used as an etching mask to etch the underlying magnetic thin film stack, thereby forming an antiferromagnetic tunnel junction structure with an independent device profile in the magnetic thin film, such as... Figure 4 As shown in steps 5 to 7. Through the above process steps, the shape and size of the antiferromagnetic tunnel junction unit are defined.

[0085] Subsequently, after etching the antiferromagnetic tunnel junction unit body, a silicon dioxide layer is deposited again on the device surface for defining the pattern of the subsequent heavy metal layer current lines, such as... Figure 4As shown in step 8, the photolithography, development, and etching processes are repeated on the silicon dioxide layer to form a hard mask structure corresponding to the heavy metal layer current lines. After resist removal, the underlying heavy metal layer is etched to form a heavy metal layer current line structure for write current transmission, as shown in step 8. Figure 4 Steps 9 to 12 are shown in the middle section.

[0086] After forming the heavy metal layer current lines, a silicon dioxide dielectric layer is deposited again. Through-hole structures are then formed in the dielectric layer using photolithography and etching processes, enabling electrical connection between the top region of the antiferromagnetic tunnel junction unit and the subsequently formed top electrode. Figure 4 As shown in steps 13 and 14.

[0087] Finally, a top electrode layer is formed by depositing a metal material on the device surface using sputtering or evaporation processes. The top electrode material can be metals such as Ti, Au, or Al. Subsequently, the top electrode layer is patterned using photolithography and etching processes to obtain a top electrode structure electrically connected to the antiferromagnetic tunnel junction unit, such as... Figure 4 As shown in step 15.

[0088] Through the above fabrication process, a well-structured and dimensionally controllable antiferromagnetic tunnel junction unit can be formed on the same substrate, providing a basic device for the subsequent construction of an antiferromagnetic tunnel junction full-bridge structure and a biaxial magnetic sensor.

[0089] As can be seen from the above embodiments, the main inventive point of this application is:

[0090] 1. A programmable reference layer writing mechanism based on the Néel vector of current direction. This application sets a directional current writing line under the interlaced antiferromagnetic layer. By applying a pulse current, the Néel vector of the reference layer can be set, rotated and maintained along the current direction, thereby realizing reversible and programmable reference layer direction control without a magnetic field.

[0091] 2. Multi-directional reference layer setting capability of AFMTJ cells on the same wafer. Based on the above-mentioned programmable Néel vector mechanism, by applying write currents in different directions to different cells, multiple directions such as X-axis, Y-axis, reverse, and orthogonal can be achieved on the same wafer, so that each AFMTJ cell obtains an independent reference layer direction.

[0092] 3. Current line layout design for full-bridge and dual-axis structures enables directional on-chip integration. To achieve bridge-type differential output and multi-axis detection, this application arranges multi-directional heavy metal write lines (such as horizontal and vertical directions) on the chip plane, allowing AFMTJ units in different bridge arms or different axes to accept write currents in different directions. Programmable bridge arm structures and independent programmable initialization for X / Y axes can be implemented on the same chip. This allows on-chip full-bridge, dual-axis, and even multi-axis magnetic field sensors to be implemented using a unified AFMTJ film stack, eliminating the need for partitioned annealing, secondary deposition, or complex bridge splicing.

[0093] 4. Structural Implementation Path of Silicon Dioxide Hard Mask Pattern Transfer Method. To achieve high-precision and consistent AFMTJ patterning, this application uses a silicon dioxide hard mask for pattern transfer, enabling more reliable critical dimension (CD) control, sidewall morphology consistency, and film stack integrity, providing a stable process foundation for the rewritable orientation control of AFMTJ cells.

[0094] As can be seen from the above embodiments, this application utilizes an interlaced antiferromagnetic structure with an electrically programmable Néel vector to achieve on-chip electrical programmable reference layer orientation control, which can effectively solve the following key problems in the prior art:

[0095] 1. This application solves the problem that "full-bridge reverse direction + dual-axis orthogonal direction" cannot be simultaneously implemented on the same wafer. This application allows for independent setting of the Néel vector direction for different regions via write lines in different directions, enabling simultaneous multi-region, multi-directional writing on a single wafer.

[0096] 2. This application solves the problem of reference layer orientation relying on high-temperature annealing and being unable to be rewritten (this application provides reversible and programmable orientation). This application utilizes the SOT mechanism of interleaved magnetic materials such as RuO2 to achieve: no need for multiple magnetic field annealings; reversible writing and repeated modification of orientation; and independent programming of regions, providing magnetoresistive devices with unprecedented "on-chip reference layer programmability".

[0097] 3. This application solves the problems of thermal damage and uncontrollability in localized annealing. It employs electrically controlled Néel vectors, which avoids generating localized high temperatures and damage to the tunneling barrier layer, allowing for precise regional control and wafer-level compatibility.

[0098] 4. This application solves the problems of complex multi-stage deposition processes and inconsistent thin films caused by partitioned photolithography. It enables one-time deposition of the entire thin film, resulting in high device parameter consistency and a simple process suitable for mass production.

[0099] Therefore, this application achieves reference layer orientation control that is reversible, programmable, and regionally independent without the need for multiple annealing through an interlaced magnetic structure with an electrically adjustable Néel vector. This fundamentally solves the problems of difficulty in full-bridge integration, limited biaxial construction, uncontrollable heat treatment, and poor thin film consistency in the prior art.

[0100] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A magnetic sensor that integrates full-bridge and dual-axis operation on a single chip, characterized in that, It includes two antiferromagnetic tunnel junction full-bridge structures formed on the same chip with magnetic sensing directions perpendicular to each other; each arm of the antiferromagnetic tunnel junction full-bridge structure is provided with an antiferromagnetic tunnel junction unit; The antiferromagnetic tunnel unit includes, from bottom to top, a heavy metal layer, an antiferromagnetic reference layer, a tunneling barrier layer, an antiferromagnetic free layer, and a ferromagnetic layer; During the initialization phase of the antiferromagnetic tunnel junction unit, the Néel vector direction of the antiferromagnetic reference layer is set by applying an in-plane write current to the heavy metal layer. For each antiferromagnetic tunnel junction full-bridge structure, an in-plane write current along a first direction is applied to the antiferromagnetic tunnel junction unit corresponding to one pair of diagonal bridge arms during the initialization phase, and an in-plane write current along a second direction is applied to the antiferromagnetic tunnel junction unit corresponding to another pair of diagonal bridge arms during the initialization phase. The first direction and the second direction are opposite, so that the Néel vector directions of the antiferromagnetic reference layer in the antiferromagnetic tunnel junction units corresponding to the two pairs of diagonal bridge arms are opposite. The in-plane write current directions corresponding to the two antiferromagnetic tunnel junction full-bridge structures are orthogonal to each other.

2. The magnetic sensor that realizes full-bridge and dual-axis operation on the same chip according to claim 1, characterized in that, The Néel vector direction of the antiferromagnetic reference layer can be selectively set under the action of the write current and maintained after the write operation is completed, thereby providing a programmable reference direction in the device; the magnetic moment of the ferromagnetic layer changes under the action of an external magnetic field; The Néel vector of the antiferromagnetic free layer undergoes orientation modulation under the exchange coupling between the antiferromagnetic free layer and the ferromagnetic layer, thereby participating in the magnetic field sensitive output process.

3. The magnetic sensor that realizes full-bridge and dual-axis operation on the same chip according to claim 1, characterized in that, The heavy metal layer of the antiferromagnetic tunnel junction unit is electrically connected to the heavy metal write line so as to apply an in-plane write current to the heavy metal layer through the heavy metal write line.

4. The magnetic sensor that realizes full-bridge and dual-axis operation on the same chip according to claim 3, characterized in that, Two sets of heavy metal writing lines are respectively set for the two antiferromagnetic tunnel junction full bridge structures. One set of heavy metal writing lines is arranged along the X direction, and the other set of heavy metal writing lines is arranged along the Y direction. The X direction and the Y direction are perpendicular to each other.

5. The magnetic sensor that realizes full-bridge and dual-axis operation on the same chip according to claim 1, characterized in that, The formation process of each of the antiferromagnetic tunnel junction units includes: depositing a magnetic thin film on a substrate for forming the antiferromagnetic tunnel junction unit; forming a hard mask layer on the magnetic thin film and patterning the magnetic thin film by photolithography and etching processes to define the device pattern of the antiferromagnetic tunnel junction unit; and forming an electrode structure electrically connected to the antiferromagnetic tunnel junction unit by dielectric layer deposition, via etching, and deposition and patterning of a top electrode.

6. The magnetic sensor that realizes full-bridge and dual-axis operation on the same chip according to claim 2, characterized in that, The antiferromagnetic tunnel junction unit further includes a seed layer disposed on a substrate, and the heavy metal layer disposed on the seed layer.

7. The magnetic sensor that realizes full-bridge and dual-axis operation on the same chip according to claim 6, characterized in that, The antiferromagnetic tunnel unit also includes a protective layer disposed on the ferromagnetic layer.

8. The magnetic sensor that realizes full-bridge and dual-axis operation on the same chip according to claim 1 or 2, characterized in that, The antiferromagnetic reference layer is made of RuO2.

9. The magnetic sensor that realizes full-bridge and dual-axis operation on the same chip according to claim 1 or 2, characterized in that, The material used for the tunneling barrier layer is TiO2.

10. The magnetic sensor that realizes full-bridge and dual-axis operation on the same chip according to claim 1 or 2, characterized in that, The material of the antiferromagnetic free layer is RuO2.

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