High-sensitivity magneto-dependent sensor, preparation method thereof and electronic equipment

Abstract

The invention relates to a magneto-dependent sensor, a preparation method thereof and electronic equipment. According to an embodiment, a magneto-dependent sensor may include: a free magnetic layer on a substrate; an intermediate layer on the free magnetic layer; and a reference magnetic layer on the intermediate layer, in which the free magnetic layer has a circular or elliptical planar shape and has vortex magnetization, the reference magnetic layer has in-plane magnetization in a predetermined direction, and a planar maximum dimension of the reference magnetic layer is smaller than a circular diameter or an elliptical long axis of the free magnetic layer.

Description

Technical Field

[0001] This invention relates generally to the field of magnetism, and more particularly to a magnetic sensor that utilizes a magnetic vortex state and integrates magnetic flux, which has further improved sensitivity, and also to a method for fabricating such a magnetic sensor, and an electronic device including such a magnetic sensor. Background Technology

[0002] Magnetoresistive sensors have broad and significant application prospects in data storage, positioning and navigation, and signal detection. Early magnetoresistive sensors mainly included those based on the Hall effect and those based on the anisotropic magnetoresistance (AMR) effect; however, both types of magnetoresistive sensors had relatively low sensitivity. With the development of spintronics, magnetoresistive sensors based on the giant magnetoresistance (GMR) and tunneling magnetoresistance (TMR) effects have been widely researched and applied. This is mainly because these two types of magnetoresistive sensors have high magnetic field sensitivity, and their manufacturing processes are compatible with conventional semiconductor processes, making them suitable for large-scale industrial manufacturing.

[0003] The main performance indicators of magnetic sensors include sensitivity, noise, and linearity. Enhancing the sensor's detection capability, while ensuring the linearity of its response to external magnetic fields, is primarily achieved through two methods: increasing sensor sensitivity and reducing sensor noise. With technological advancements, the application scenarios for magnetic sensors have expanded, placing higher demands on their sensitivity. For example, in fields such as current detection, geomagnetic field navigation, and biomagnetic fields like magnetoencephalography (MEG), it is desirable for magnetic sensors to achieve a sensitivity of at least 1 picotesla (pT).

[0004] Therefore, there is still a need to provide magnetic sensors with higher sensitivity to meet the needs of fine magnetic field detection scenarios. Summary of the Invention

[0005] One aspect of the present invention provides a magnetic sensor comprising: a free magnetic layer on a substrate; an intermediate layer on the free magnetic layer; and a reference magnetic layer on the intermediate layer, wherein the free magnetic layer has a circular or elliptical planar shape and is vortex magnetized, the reference magnetic layer is in-plane magnetized along a predetermined direction, and the maximum planar dimension of the reference magnetic layer is smaller than the circular diameter or elliptical major axis of the free magnetic layer.

[0006] In one embodiment, the maximum planar dimension of the reference magnetic layer is less than or equal to two-thirds of the circular diameter or elliptical major axis of the free magnetic layer.

[0007] In one embodiment, the maximum planar dimension of the reference magnetic layer is less than or equal to half the circular diameter or elliptical major axis of the free magnetic layer.

[0008] In one embodiment, the thickness of the free magnetic layer is in the range of 10 nm to 500 nm, and the circular diameter or elliptical major axis of the free magnetic layer is in the range of 50 nm to 20 μm.

[0009] In one embodiment, the thickness of the free magnetic layer is in the range of 10 nm to 200 nm, and the circular diameter or elliptical major axis of the free magnetic layer is in the range of 50 nm to 2 μm.

[0010] In one embodiment, the center of the free magnetic layer is aligned with the center of the reference magnetic layer, and in each direction in the plane, the edge of the reference magnetic layer is recessed toward the center relative to the edge of the free magnetic layer.

[0011] In one embodiment, when the free magnetic layer has an elliptical shape, the detection direction of the magnetic sensor is parallel to the minor axis of the elliptical shape, and the predetermined direction of in-plane magnetization of the reference magnetic layer is parallel to the minor axis of the elliptical shape.

[0012] In one embodiment, the magnetic sensor further includes: an insulating layer formed on the substrate and covering the sidewalls of the reference magnetic layer, the intermediate layer, and the free magnetic layer, as well as the upper surface of the free magnetic layer not covered by the reference magnetic layer; and a magnetic flux focusing layer formed on the substrate and separated from the free magnetic layer by the insulating layer, wherein, in the detection direction of the magnetic sensor, the magnetic flux focusing layer is located on both sides of the free magnetic layer.

[0013] In one embodiment, the edge of the flux-accumulating layer adjacent to the free magnetic layer has a shape adapted to the shape of the free magnetic layer, thereby maintaining a constant distance between the flux-accumulating layer and the free magnetic layer.

[0014] Another aspect of the present invention provides a method for fabricating a magnetic sensor, comprising: sequentially forming a free magnetic layer, an intermediate layer and a reference magnetic layer on a substrate to obtain a magnetic multilayer film structure; etching the reference magnetic layer, the intermediate layer and the free magnetic layer using a first mask pattern to obtain a circular or elliptical columnar structure; and etching the reference magnetic layer using a second mask pattern such that the maximum planar dimension of the reference magnetic layer is smaller than the circular diameter or elliptical major axis of the free magnetic layer.

[0015] In one embodiment, the method further includes: forming an insulating layer to cover the magnetic multilayer film structure; etching the insulating layer using a third mask pattern to expose the upper surface of the reference magnetic layer; forming a fourth mask pattern having an opening that exposes the upper surface of the reference magnetic layer; depositing a top electrode metal layer in the fourth mask pattern and its opening; removing the fourth mask pattern and the top electrode metal layer thereon, leaving a top electrode located in the opening and in contact with the upper surface of the reference magnetic layer; etching portions of the insulating layer on both sides of the magnetic multilayer film structure using a fifth mask pattern, at least to the depth of the free magnetic layer, wherein the insulating layer is retained on the sidewalls of the magnetic multilayer film structure; depositing a flux accumulation layer; and removing the fifth mask pattern and the flux accumulation layer thereon, the remaining flux accumulation layer being separated from the magnetic multilayer film structure by the insulating layer.

[0016] Another aspect of the present invention provides a method for fabricating a magnetic sensor, comprising: sequentially forming a seed layer, a free magnetic layer, an intermediate layer, and a reference magnetic layer on a substrate to obtain a magnetic multilayer film structure; etching the reference magnetic layer and the intermediate layer using a first mask pattern to obtain a circular or elliptical columnar structure; etching the free magnetic layer and the seed layer using the first mask pattern and a sixth mask pattern located on both sides of the first mask pattern to obtain a circular or elliptical columnar structure corresponding to the first mask pattern and a magnetic flux accumulation layer corresponding to the sixth mask pattern, wherein the magnetic flux accumulation layer is located in the same layer as the free magnetic layer and the seed layer; and forming an insulating layer to cover the magnetic multilayer film. The structure includes: etching the insulating layer and the reference magnetic layer using a seventh mask pattern, such that the maximum planar dimension of the reference magnetic layer is smaller than the circular diameter or elliptical major axis of the free magnetic layer; forming an insulating layer to cover the magnetic multilayer film structure; removing the seventh mask pattern and the insulating layer thereon; etching the insulating layer using a third mask pattern to expose the upper surface of the reference magnetic layer; forming a fourth mask pattern having an opening that exposes the upper surface of the reference magnetic layer; depositing a top electrode metal layer on the fourth mask pattern and in its opening; and removing the fourth mask pattern and the top electrode metal layer thereon, leaving a top electrode located in the opening that contacts the upper surface of the reference magnetic layer.

[0017] Another aspect of the present invention provides an electronic device comprising the above-described magnetic sensor.

[0018] The above and other features and advantages of the present invention will become apparent from the following description of exemplary embodiments taken in conjunction with the accompanying drawings. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a magnetic sensor according to an exemplary embodiment of the present invention.

[0020] Figure 2 yes Figure 1 The image shows a top view of the magnetic sensor.

[0021] Figure 3 yes Figure 1 The diagram shown illustrates the working principle of the magnetic sensor.

[0022] Figure 4A , 4B Figures 4 and 4C are schematic diagrams of the structure of a magnetic sensor according to other exemplary embodiments of the present invention.

[0023] Figure 5A-5I This is a schematic diagram of a method for fabricating a magnetic sensor according to an exemplary embodiment of the present invention.

[0024] Figure 6A-6O This is a schematic diagram of a method for fabricating a magnetic sensor according to another exemplary embodiment of the present invention. Detailed Implementation

[0025] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. Note that the drawings may not be drawn to scale.

[0026] Figure 1 A schematic diagram of the structure of a magnetic sensor according to an exemplary embodiment of the present invention is shown. Figure 1 As shown, the magnetic sensor includes a seed layer 112, a free magnetic layer 114, an intermediate layer 116, a reference magnetic layer 118, a capping layer 120, and a top electrode layer 122, which are sequentially formed on a substrate 110.

[0027] Substrate 110 can be any suitable substrate, examples of which include, but are not limited to, Si substrates, SiC substrates, silicon-on-insulator (SOI) substrates, glass substrates, quartz substrates, sapphire substrates, polymer substrates, etc. Substrate 110 can have an appropriate thickness, for example, but not limited to, 0.2-2 mm.

[0028] The seed layer 112, also known as a buffer layer, provides a good growth interface for the free magnetic layer 114 above, thereby improving the film quality of the formed free magnetic layer 114. Therefore, a suitable material can be selected to form the seed layer 112 based on the material of the free magnetic layer 114. Generally, non-magnetic metals (including alloys) can be used to form the seed layer 112, examples of which include, but are not limited to, Ta, Ru, Cr, Au, Ag, Pt, Pd, Cu, CuN, etc. The seed layer 112 can be formed as a single layer or as multiple layers, for example, as a composite multilayer structure of non-magnetic and magnetic metal materials. The thickness of the seed layer 112 is generally in the range of, for example, 2-200 nm.

[0029] Although not shown, a bottom electrode layer may be formed between the substrate 110 and the seed layer 112, or the seed layer 112 itself may be used as a bottom electrode. When the seed layer 112 is used as a bottom electrode, it may have a large thickness, for example, a thickness on the micrometer scale.

[0030] Both the free magnetic layer 114 and the reference magnetic layer 118 can be formed of ferromagnetic materials. Note that the free magnetic layer 114 has vortex magnetization, while the reference magnetic layer 118 has in-plane magnetization along a predetermined direction, which will be described in further detail below. The magnetization direction of the reference magnetic layer 118 is fixed, while the magnetization of the free magnetic layer 114 can change in response to an external magnetic field, thereby changing the sensor resistance. Therefore, the magnitude of the external magnetic field in a specific direction can be measured by detecting the resistance of the sensor. The magnetic moment of the reference magnetic layer 118 can be fixed in various ways, such as by using a direct pinning structure or an indirect pinning structure. Direct pinning refers to the pinning layer formed of antiferromagnetic material (AFM) being in direct contact with the pinned ferromagnetic layer (FM), abbreviated as AFM / FM. Indirect pinning refers to inserting a thin non-magnetic metal layer (NM) between the antiferromagnetic material layer AFM and the ferromagnetic layer FM, abbreviated as AFM / NM / FM, or inserting a composite layer NM / FM between the two, abbreviated as AFM / FM1 / NM / FM2. By inserting an NM layer or an NM / FM composite layer between the AFM layer and the FM layer, and by adjusting the thickness of the insert layer, the pinning effect of the AFM pinning layer on the FM layer can be effectively controlled. Furthermore, the reference magnetic layer 118 can also employ a self-pinning structure to fix its magnetic moment direction. For example, a ferromagnetic material with high coercivity can be used to form the reference magnetic layer 118, or the reference magnetic layer 118 can be formed as an artificial antiferromagnetic (SAF) structure. The SAF structure includes FM1 / NM / FM2, where the two ferromagnetic layers FM1 and FM2 are antiferromagnetically (i.e., antiparallel) coupled to each other through a non-magnetically coupled layer NM. This reduces the influence of the external magnetic field on the magnetic moment of the SAF structure, achieving the effect of fixing its magnetic moment direction. The SAF also has a small net magnetic moment, reducing its influence on the nearby free magnetic layer 114 and improving sensor sensitivity, making it a preferred choice.

[0031] Examples of ferromagnetic materials used to form the free magnetic layer 114 and the reference magnetic layer 118 include, but are not limited to: ferromagnetic metallic materials with high spin polarization, such as Co, Fe, Ni, or alloys thereof, such as CoFe, CoFeB, NiFeCr, NiFe, CoFeBSi, CoFeBTa, etc.; dilute magnetic semiconductor materials, such as GaMnAs, GaMnN, etc.; and half-metallic materials, such as CoMnSi, CoFeAl, CoFeSi, CoMnAl, CoFeAlSi, CoMnGe, CoMnGa, CoMnGeGa, La, etc. 1-x Srx MnO3, La 1-x Ca x MnO3, where 0 < X ​​< 1. It should be understood that the ferromagnetic materials that can be used to form the free magnetic layer 114 and the reference magnetic layer 118 are not limited to the examples described above, but may include any ferromagnetic material used in the prior art or developed in the future that can be used to form ferromagnetic layers in giant magnetoresistive (GMR) spin valve structures or magnetic tunnel junctions (MTJs).

[0032] The intermediate layer 116 can be a non-magnetic metal layer or a non-magnetic insulating barrier layer. When the intermediate layer 116 is a non-magnetic metal layer, the resulting magnetic multilayer film structure is a multilayer film structure used in GMR devices, also known as a spin valve structure. The non-magnetic metal layer may include Cu, Cr, V, Nb, Mo, Ru, Pd, Ta, W, Pt, Ag, Au or their alloys, and the thickness may be 1-5 nm. When the intermediate layer 116 is a non-magnetic insulating barrier layer, the resulting magnetic multilayer film structure is a multilayer film structure used in TMR devices. The non-magnetic insulating barrier layer may include Al2O3, MgO, MgAl2O4, ZnAl2O4, SiAl2O4, SiZn2O4, MgZnO, AlN, Alq3, Ta2O5, ZnO, HfO2, TiO2, LB organic composite film, GaAs, AlGaAs, InAs, etc., preferably MgO, Al2O3, MgAl2O4, MgZnO, AlN, Alq3, LB organic composite film, and the thickness may be 0.5-5 nm.

[0033] The capping layer 120 is a metal layer with good conductivity and resistance to oxidation, to protect the underlying magnetic multilayer film structure from oxidation and corrosion. The capping layer 120 may include a single layer or a multilayer composite metal thin film, and examples of materials include, but are not limited to, Ta, Cu, Al, Ru, Au, Ag, Pt, etc., with a thickness of 2-50 nm.

[0034] The top electrode layer 122 is a metal layer with good conductivity, such as Cu, Al, Ag, etc. It is understood that the top electrode layer 122 can also protect the underlying magnetic multilayer film structure from oxidation and corrosion, so in some embodiments the capping layer 120 can be omitted.

[0035] Continue to refer to Figure 1The magnetic sensor may further include an insulating layer 124 and a flux-accumulating layer 126. The insulating layer 124 may be formed on both sides of the magnetic multilayer film structure of the magnetic sensor and covers the sidewalls of the magnetic multilayer film structure, exposing at least a portion of the upper surface of the magnetic multilayer film structure for connection to the top electrode 122. The insulating layer 124 may be formed of a non-magnetic insulating material such as SiO2. The flux-accumulating layer 126 may be formed on the substrate 110, located on both sides of the free magnetic layer, and separated from the magnetic multilayer film structure by the insulating layer 124. The flux-accumulating layer 126 may be formed of a ferromagnetic material, such as those used to form the free magnetic layer 114, preferably a soft ferromagnetic material with low coercivity, and may have a thickness of 2-200 nm, or may have a greater thickness. In the direction of external magnetic field detection, that is, in a direction parallel or antiparallel to the magnetization direction of the reference magnetic layer 118 (see, for example, [reference]). Figure 3 As shown), the flux-gathering layer 126 is located on both sides of the free magnetic layer 114 to gather and guide the external magnetic field to be detected to the free magnetic layer 114, thereby improving the sensitivity of the magnetic sensor. Although Figure 1 The flux-gathering layer 126 is located directly on the substrate 110. However, in some embodiments, an insulating layer may be formed between the flux-gathering layer 126 and the substrate 110. Furthermore, the flux-gathering layer 126 may extend to the portion of the free magnetic layer 114 not covered by the reference magnetic layer 118. The upper surface of the flux-gathering layer 126 and the free magnetic layer 114 (or intermediate layer 116), as well as the sidewalls of the reference magnetic layer 118, can be separated by an insulating layer 124. It should be understood that the reference magnetic layer 118 has a fixed magnetization direction, and the distance between the flux-gathering layer 126 and the reference magnetic layer 118 is much greater than the distance between the flux-gathering layer 126 and the free magnetic layer 114. Therefore, the magnetic flux gathered by the flux-gathering layer 116 acts almost entirely on the free magnetic layer 114, with little effect on the reference magnetic layer 118. The flux-gathering layer 126 can effectively concentrate the external magnetic field, thereby improving the sensitivity of the magnetic sensor. Therefore, the flux gathering layer 126 is preferred, but in some embodiments, the flux gathering layer 126 may be omitted.

[0036] As mentioned above, the free magnetic layer 114 has vortex magnetization, and the reference magnetic layer 118 has in-plane magnetization along a predetermined direction. The desired magnetization can be achieved by controlling the shape and size of the free magnetic layer 114 and the reference magnetic layer 118. Figure 2 yes Figure 1 The image shows a top view of the magnetic sensor. Figure 2The free magnetic layer 114 can have a circular structure, which facilitates the formation of vortex magnetization within it. Furthermore, to ensure the ground state of the free magnetic layer 114 is a vortex state, the thickness and diameter of the free magnetic layer 114 need to be adjusted according to the specific ferromagnetic material used. Typically, the circular diameter of the free magnetic layer 114 can be in the range of 50 nm to 20 μm, or preferably in the range of 50 nm to 2 μm, and the thickness can be in the range of 10 nm to 500 nm, or preferably in the range of 10 nm to 200 nm. Generally, when the thickness of the free magnetic layer 114 is small, for example, below 5 nm, it is easy to form a single-domain structure; when the in-plane dimension of the free magnetic layer 114 is small, for example, below 20 nm, it is also easy to form a single-domain structure, neither of which is conducive to the formation of vortex magnetization. Furthermore, other shapes such as squares and rectangles are also not conducive to the formation of vortex magnetization. Therefore, by forming the free magnetic layer 114 as a circle and controlling its size, the magnetization can be arranged around the center in a vortex structure, such as... Figure 3 As shown in the diagram.

[0037] In other embodiments, the free magnetic layer 114 can also be formed in an elliptical shape, which can also achieve magnetization arranged in a vortex around the center. When the free magnetic layer 114 has an elliptical shape, the ratio of its major axis to minor axis is preferably greater than 1 and less than 4, preferably less than 3, and more preferably less than 2. A large major-to-minor axis ratio introduces shape anisotropy, causing magnetization to be aligned in a specific direction, which is undesirable for a vortex state. The magnetic field detection direction of the magnetic sensor is preferably the direction of the minor axis of the elliptical shape, and the magnetization direction of the reference magnetic layer 118 can be parallel to the minor axis direction, that is, parallel to the magnetic field detection direction of the magnetic sensor, which will be referred to below. Figure 3 The working principle of the magnetic sensor will be described in a more detailed manner.

[0038] Although Figure 2The reference magnetic layer 118 is also shown to have a circular shape, but it can have other shapes commonly used in the prior art, such as rectangular, elliptical, or square, to introduce shape anisotropy, aligning the magnetic moments of the reference magnetic layer 118 in a specific direction. The reference magnetic layer 118 can also have a thickness commonly used in the prior art. As mentioned earlier, the magnetization direction of the reference magnetic layer 118 can be self-pinned, pinned using an antiferromagnetic pinning layer, or pinned using an artificial antiferromagnetic structure, etc. These variations in the prior art can all be used for the reference magnetic layer 118 of the present invention. When the free magnetic layer 114 has an elliptical shape, the in-plane magnetization direction of the reference magnetic layer 118 is preferably parallel to the minor axis of the ellipse, i.e., parallel to the external magnetic field detection direction of the magnetic sensor. The center of the reference magnetic layer 118 can be aligned with the center of the free magnetic layer 114. The maximum in-plane dimension of the reference magnetic layer 118 can be smaller than the circular diameter or the major axis of the ellipse of the free magnetic layer 114. This helps to improve the sensitivity of the magnetic sensor, the principle of which will be explained below. Figure 3 Please describe in detail. For example... Figure 2 As shown, in various directions within the plane, the outer edge of the reference magnetic layer 118 can be recessed inward relative to the outer edge of the free magnetic layer 114, i.e., it has a smaller size. In some embodiments, the maximum planar size of the reference magnetic layer 118 can be less than or equal to two-thirds, or preferably one-half, of the circular diameter or elliptical major axis of the free magnetic layer 114. On the other hand, the maximum planar size of the reference magnetic layer 118 can be greater than or equal to, for example, one-tenth of the circular diameter or elliptical major axis of the free magnetic layer 114.

[0039] Continue to refer to Figure 2 In the direction of the external magnetic field detection of the magnetic sensor, the flux-gathering layer 126 can be located on both sides of the free magnetic layer 114, and the edges of the flux-gathering layer 126 adjacent to the free magnetic layer 114 also have a circular or arc shape, so that there can be a constant distance between them. Similarly, when the free magnetic layer 114 is elliptical, the edges of the flux-gathering layer 126 adjacent to the free magnetic layer 114 also have a corresponding / adaptive shape, so that the distance between the flux-gathering layer 126 and the free magnetic layer 114 remains constant. This is beneficial for uniformly guiding the external magnetic field to the free magnetic layer 114, so that the vortex magnetization of the free magnetic layer 114 can change in the desired form in response to the external magnetic field, thereby ensuring the sensitivity of the magnetic sensor, which will be referred to below. Figure 3 To explain in detail. For example... Figure 2 As shown, in the direction away from the free magnetic layer 114, the width of the magnetic flux gathering layer 126 can gradually increase, that is, the shape is funnel-shaped. This is beneficial to gather more magnetic flux to the free magnetic layer 114, thereby improving the sensitivity of the magnetic sensor.

[0040] It should be understood that the shape of the flux accumulation layer 126 is not limited to... Figure 2 The shape shown is not the only one that can be modified; it can have various variations, which will not be listed here.

[0041] Figure 3 The working principle of the magnetic sensor of the present invention is illustrated. For example... Figure 3 As shown, assuming the magnetic field direction of the magnetic sensor is horizontal, the reference magnetic layer 118 is represented by a solid circle with its fixed magnetization direction horizontal to the right, and the vortex magnetization of the free magnetic layer 114 is represented by a dashed hollow arrow. When the external magnetic field is 0, i.e., there is no external magnetic field, the reference magnetic layer 118 is basically located at the center of the vortex magnetization of the free magnetic layer 114, and the total magnetic moment of the vortex magnetization corresponding to the reference magnetic layer 118 is basically equal to 0. When the external magnetic field is less than 0, i.e., there is an external magnetic field in the horizontal left direction, under the action of this external magnetic field, the center of the vortex magnetization of the free magnetic layer 114 moves downward. At this time, the total magnetic moment of the vortex magnetization portion corresponding to the reference magnetic layer 118 is roughly in the horizontal left direction, which is antiparallel to the magnetic moment direction of the reference magnetic layer 118, thereby increasing the resistance of the magnetic sensor. When the external magnetic field is greater than 0, i.e., when an external magnetic field exists in the horizontal rightward direction, under the influence of this external magnetic field, the center of vortex magnetization in the free magnetic layer 114 moves upward. At this time, the total magnetic moment of the vortex magnetization portion corresponding to the reference magnetic layer 118 is approximately in the horizontal rightward direction, parallel to the direction of the magnetic moment of the reference magnetic layer 118, thereby reducing the resistance of the magnetic sensor. Therefore, by detecting the resistance of the magnetic sensor, the magnitude of the external magnetic field in the detection direction can be determined.

[0042] It should be understood that, Figure 3 The vortex magnetization shown in the diagram responding to the movement of an external magnetic field is merely illustrative. In reality, because the free magnetosphere has a fixed and finite size, the arrangement of vortex magnetization will change somewhat as the magnetization centers move from the center to the edge of the free magnetosphere in response to the external magnetic field, but overall it will remain similar to... Figure 3 The situation is similar to that shown, which will cause a change in the total magnetic moment of the vortex magnetization portion corresponding to the reference magnetic layer 118, thereby causing a change in the resistance of the magnetic sensor. The magnitude of the external magnetic field can be determined by detecting the resistance of the magnetic sensor.

[0043] In existing technologies, free magnetic layers with vortex magnetization have been proposed. However, these free magnetic layers and reference magnetic layers have the same planar dimensions, or even the reference magnetic layer has a larger planar dimension. In these cases, the reference magnetic layer detects only the overall change in the vortex magnetization of the free magnetic layer in response to the external magnetic field, resulting in low sensitivity. In this invention, by making the reference magnetic layer smaller than the free magnetic layer, the reference magnetic layer can detect the local change in the vortex magnetization of the free magnetic layer in response to the external magnetic field, which significantly improves the sensor's sensitivity. Furthermore, by using a flux-focusing structure, even higher detection sensitivity can be achieved, meeting the needs of fine magnetic field measurements.

[0044] It should be understood that the multilayer film structure of the magnetic sensor of the present invention is not limited to... Figure 1 The structure shown is not limited to the one described above; other structures can be flexibly employed. Some examples of magnetic multilayer film structures that can be used in magnetic sensors are shown below. Figure 4A , 4B And in 4C. First refer to Figure 4A , and Figure 1 The difference lies in the inclusion of a pinning layer 128 for pinning the magnetic moment of the reference magnetic layer 118, located between the reference magnetic layer 118 and the capping layer 120. The pinning layer 128 can be formed of an antiferromagnetic metal (including alloys), such as PtMn, IrMn, FeMn, and NiMn, with a thickness of 2-40 nm. The pinning layer 128 can fix the magnetic moment of the reference magnetic layer 118, so that the magnetic moment of the reference magnetic layer 118 does not change when an external magnetic field is present, thus facilitating the acquisition of linear output characteristics.

[0045] Figure 4B The structure shown is similar to Figure 4A The basic structure is the same, except that a coupling layer 130 is inserted between the pinning layer 128 and the reference magnetic layer 118. The coupling layer 130 can be formed of a non-magnetic metal (including alloys) material, such as Cu, Cr, V, Nb, Mo, Ru, Pd, Ta, W, Pt, Ag, Au, or alloys thereof, and its thickness can be 0.1-5 nm. By adjusting the thickness of the coupling layer 130, the coupling strength between the pinning layer 128 and the reference magnetic layer 118 can be adjusted, and the pinning direction can be adjusted, i.e., varying between ferromagnetic coupling and antiferromagnetic coupling.

[0046] Figure 4C The structure shown is similar to Figure 4AThe main difference lies in the use of an artificial antiferromagnetic (SAF) structure for the reference magnetic layer 118. Specifically, the reference magnetic layer 118, coupling layer 130, and ferromagnetic layer 132 form an artificial antiferromagnetic structure. By adjusting the thickness of coupling layer 130, the reference magnetic layer 118 and ferromagnetic layer 132 achieve antiferromagnetic (i.e., antiparallel) coupling. Pinning layer 128 indirectly pins the reference magnetic layer 118 by pinning the magnetic moment of ferromagnetic layer 132. The artificial antiferromagnetic structure reduces the net magnetic moment of reference magnetic layer 118, thereby reducing the influence of stray magnetic fields on free magnetic layer 114 and further improving the sensitivity of the magnetic sensor.

[0047] It should be understood that Figure 4A , 4B The examples shown in 4C are just a few examples. The embodiments of the present invention can also have other variations, such as adopting a double spin valve or a double tunnel junction structure, which will not be listed here.

[0048] Figure 5A-5I A schematic diagram illustrating a method for fabricating a magnetic sensor according to an exemplary embodiment of the present invention is shown. First, refer to... Figure 5A A seed layer 112, a free magnetic layer 114, an intermediate layer 116, a reference magnetic layer 118, and a capping layer 120 are sequentially formed on a substrate 110. These layers can be formed, for example, by magnetron sputtering, physical vapor deposition, or pulsed laser deposition. Then, a first mask pattern 202 can be formed on the magnetic multilayer film, for example, by spin-coating photoresist, drying, exposure, and development. The first mask pattern 202 can define the shape of the detection magnetic layer (i.e., the free magnetic layer) of the magnetic sensor, for example, it can be circular or elliptical.

[0049] use Figure 5A The first mask pattern 202 shown etches the underlying magnetic multilayer film structure, for example, using dry processes such as reactive ion etching or plasma etching, until both the free magnetic layer 114 and the seed layer 112 are etched. When there is a bottom electrode layer below the seed layer 112, an additional step can be used to etch the bottom electrode layer; when the seed layer 112 itself also serves as the bottom electrode layer, the first mask pattern 202 can be used to etch only up to the free magnetic layer 114, while an additional step is used to etch the seed layer 112 to obtain the bottom electrode shape.

[0050] Then, the first mask pattern 202 is removed, and a second mask pattern 204 is formed on the etched structure, as shown. Figure 5B As shown. The second mask pattern 204 defines the shape of the reference magnetic layer 118 in the magnetic sensor. An etching step is performed using the second mask pattern 204 to etch the capping layer 120 and the reference magnetic layer 118, obtaining... Figure 5CThe magnetic multilayer film shape is shown. This etching step can use the intermediate layer 116 as a stop layer to protect the underlying free magnetic layer 114 from etching. In some embodiments, at least a portion of the intermediate layer 116 may also be etched.

[0051] The second mask pattern 204 is then removed, and an insulating layer 124 is deposited on the resulting structure to cover the substrate 110 and the magnetic multilayer film structure thereon. A blanket deposition process can be used to form the insulating layer 124, and a planarization step is performed to obtain a flat upper surface. A third mask pattern 206 can then be formed on the insulating layer 124 to obtain… Figure 5C The structure shown. The third mask pattern 206 has openings for aligning the nanopillars of the magnetic multilayer structure (or aligning the capping layer 120 and the reference magnetic layer 118).

[0052] The insulating layer 124 is etched using the third mask pattern 206 to form an opening that exposes the upper surface of the capping layer 120 (or, when the capping layer 120 is not used, exposes the reference magnetic layer 118). Then, the third mask pattern 206 is removed, and a fourth mask pattern 208 is formed on the insulating layer 124, resulting in... Figure 5D The structure shown. The fourth mask pattern 208 has an opening that exposes the insulating layer 124 and is larger than the opening therein.

[0053] exist Figure 5D The structure shown employs a directional deposition process to form the top electrode layer 122, as... Figure 5E As shown. Due to the use of directional deposition process and the large thickness of the fourth mask pattern 208, the top electrode layer 122 is discontinuous at the opening sidewall of the fourth mask pattern 208, exposing a portion of the opening sidewall.

[0054] Then, the fourth mask pattern 208 and the top electrode layer 122 thereon can be removed, also known as a liftoff process, leaving the top electrode layer 122 in the mask opening. A fifth mask pattern 210 is then formed on the resulting structure, completely covering the top surface and opposite sides of the top electrode layer 122, as shown below. Figure 5F As shown. Then, the insulating layer 124 is etched using the fifth mask pattern 210 to obtain... Figure 5G The structure shown is illustrated. This step can obtain an insulating layer pattern, so that the insulating layer formed on the sidewall of the magnetic multilayer film structure (or free magnetic layer 114) has a reduced thickness, thereby controlling the spacing between the subsequently formed flux-accumulating layer 126 and the free magnetic layer 114.

[0055] In other embodiments, the insulating layer 124 can be etched in multiple steps. For example, in Figure 5GBased on the insulating layer 124 shown, a mask pattern can also be formed to etch a portion of the insulating layer 124 located on the portion of the free magnetic layer 114 and the intermediate layer 116 that is not covered by the reference magnetic layer 118, so that the magnetic flux gathering layer 126 formed later can overlap with the edge of the free magnetic layer 114, and the two are separated by the remaining insulating layer 124.

[0056] Continue to refer to Figure 5H A magnetic flux accumulation layer 126 can be deposited on the obtained structure using a directional deposition process to obtain... Figure 5H The structure is shown. Then, the fifth mask pattern 210 and the flux-gathering layer 126 located thereon are removed, leaving the flux-gathering layer 126 located on the substrate 110, to obtain... Figure 5I The structure shown.

[0057] Although not shown, a sixth mask pattern can also be formed, and the flux-accumulating layer 126 can be etched using the sixth mask pattern to obtain the desired flux-accumulating layer shape. In other embodiments, it is possible to... Figure 5G After etching the insulating layer 124 using the fifth mask pattern 210, in Figure 5H Before depositing the flux-accumulating layer 126, the fifth mask pattern 210 is removed, and a sixth mask pattern is formed, which has an opening defining the shape of the flux-accumulating layer. The flux-accumulating layer is then deposited again, and the sixth mask pattern and the portion of the flux-accumulating layer thereon are removed, leaving the flux-accumulating layer pattern located in the opening.

[0058] Figure 6A-6O A schematic diagram illustrating another method for fabricating a magnetic sensor according to an exemplary embodiment of the present invention is shown. First, refer to... Figure 6A A seed layer 112, a free magnetic layer 114, an intermediate layer 116, a reference magnetic layer 118, and a capping layer 120 are sequentially formed on a substrate 110. These layers can be formed, for example, by magnetron sputtering, physical vapor deposition, or pulsed laser deposition. Then, a first mask pattern 202 can be formed on the magnetic multilayer film, for example, by spin-coating photoresist, drying, exposure, and development. The first mask pattern 202 can define the shape of the detection magnetic layer (i.e., the free magnetic layer) of the magnetic sensor, for example, it can be circular or elliptical.

[0059] use Figure 6A The first mask pattern 202 shown etches the underlying magnetic multilayer film structure, for example, using dry processes such as reactive ion etching or plasma etching. Etching stops immediately upon reaching the free magnetic layer 114. Figure 6B .

[0060] Then, retaining the first mask pattern 202, a sixth mask pattern 212 is formed on the etched structure, as follows. Figure 6CAs shown. The sixth mask pattern 212 can define the shape of the free magnetic layer as the flux gathering layer 126. An etching step is performed using the first mask pattern 202 and the sixth mask pattern 212 to etch the free magnetic layer 114 and the seed layer 112, obtaining... Figure 6D The shape of the magnetic multilayer film is shown.

[0061] Then remove the first mask pattern 202 and the sixth mask pattern 212 to obtain Figure 6E The structure shown involves depositing an insulating layer 124 on the resulting structure to cover the substrate 110 and the magnetic multilayer film structure thereon. The insulating layer 124 can be formed using a blanket deposition process, and a planarization step can be performed to obtain a flat upper surface, such as... Figure 6F As shown. Then, a seventh mask pattern 214 can be formed on the insulating layer 124 to obtain... Figure 6G The structure is shown. The seventh mask pattern is used to etch down to the intermediate layer 116, as shown. Figure 6H As shown, the reference magnetic layer 118 and the layers thereon have the desired structure, and the reference magnetic layer 118 has a smaller planar dimension than the free magnetic layer 114.

[0062] Continue to refer to Figure 6I An insulating layer 124 is deposited to cover the sidewalls of the etched magnetic multilayer film structure. The same reference numeral 124 is used here to indicate the insulating layer deposited in two stages, as they can be formed from the same material and process, and ultimately form an integral insulating layer structure. Then, the seventh mask pattern 214 and the portion of the insulating layer thereon are removed to obtain... Figure 6J The structure shown; then, a third mask pattern 206 is formed, as shown. Figure 6K As shown, the third mask pattern 206 has an opening pattern corresponding to the reference magnetic layer 118.

[0063] The insulating layer 124 is etched using the third mask pattern 206 to form an opening that exposes the upper surface of the capping layer 120 (or, when the capping layer 120 is not used, exposes the reference magnetic layer 118), such as... Figure 6L As shown. Then, the third mask pattern 206 is removed, and the fourth mask pattern 208 is formed on the insulating layer 124, resulting in... Figure 6M The structure shown. The fourth mask pattern 208 has an opening that exposes the insulating layer 124 and is larger than the opening therein.

[0064] exist Figure 6M The structure shown employs a directional deposition process to form the top electrode layer 122, as... Figure 6N As shown. Due to the use of directional deposition process and the large thickness of the fourth mask pattern 208, the top electrode layer 122 is discontinuous at the opening sidewall of the fourth mask pattern 208, exposing a portion of the opening sidewall.

[0065] Then, the fourth mask pattern 208 and the top electrode layer 122 thereon can be removed, also known as a liftoff process, leaving the top electrode layer 122 in the mask opening, as shown. Figure 6O As shown.

[0066] The main steps in the fabrication process have been briefly described above. It is understandable that additional steps or details may be included, such as annealing the resulting structure to obtain a stable magnetic structure. This does not aim to provide an exhaustive description of all steps and details.

[0067] Exemplary embodiments of the present invention also provide electronic devices including the above-described magnetic sensors, such as smartphones, tablet computers, wearable electronic devices, in-vehicle electronic devices, biomagnetic detection devices, etc. In these devices, multiple magnetic sensors can be connected to each other, for example, in a Wheatstone bridge configuration, to improve detection sensitivity. Furthermore, multiple such magnetic sensors or circuits including them can be configured to detect three-dimensional magnetic fields in multiple directions, such as three dimensions.

[0068] Unless the context explicitly requires otherwise, throughout the specification and claims, the words “comprising,” “including,” “comprise,” “including,” etc., shall be interpreted in an inclusive sense, rather than an exclusive or exhaustive sense. That is, they mean “including but not limited to.” The term “connection” as commonly used herein refers to two or more elements that can be directly connected or connected via one or more intermediate elements. Furthermore, when used in this application, the terms “this,” “above,” “below,” and similar terms shall refer to the entire application and not any particular part thereof. Where the context permits, the term “or” refers to a list of two or more items, encompassing all of the following interpretations: any item in the list, all items in the list, and any combination of items in the list.

[0069] Furthermore, unless otherwise specifically stated or otherwise understood in the context in which they are used, the conditional language used herein, such as “can,” “may,” “possibly,” “can,” “for example,” “likely,” “such as,” etc., is generally intended to express that certain embodiments include certain features, elements, and / or states, while other embodiments do not. Therefore, such conditional language is not generally intended to imply that one or more embodiments require features, elements, and / or states in any way, or that one or more embodiments must include logic for making a decision, with or without author input or prompts, that determines whether such features, elements, and / or states are included in or will be performed in any particular embodiment.

[0070] While certain embodiments have been described, these embodiments are presented by way of example only and are not intended to limit the scope of this disclosure. In fact, the novel facilities, methods, and systems described herein can be embodied in a variety of other forms; furthermore, various omissions, substitutions, and changes can be made to the form of the methods and systems described herein without departing from the spirit of this disclosure. For example, although blocks are presented in a given arrangement, alternative embodiments may perform functions similar to different components and / or circuit topologies, and some blocks may be deleted, moved, added, subdivided, combined, and / or modified. Each of these blocks can be implemented in a variety of different ways. Any suitable combination of elements and actions of the various embodiments described above can be combined to provide further embodiments. The appended claims and their equivalents are intended to cover these forms or modifications that fall within the scope and spirit of this disclosure.

[0071] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the invention to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations therein.

Claims

1. A magnetic sensor, comprising: A free magnetic layer located on the substrate; The intermediate layer located on the free magnetic layer; as well as The reference magnetic layer located on the intermediate layer, The free magnetic layer has a circular or elliptical planar shape and exhibits vortex magnetization. The reference magnetic layer has in-plane magnetization along a predetermined direction, and the maximum plane dimension of the reference magnetic layer is smaller than the circular diameter or elliptical major axis of the free magnetic layer.

2. The magnetic sensor as described in claim 1, wherein, The maximum planar dimension of the reference magnetic layer is less than or equal to two-thirds of the circular diameter or the major axis of the ellipse of the free magnetic layer, or The maximum planar dimension of the reference magnetic layer is less than or equal to half the circular diameter or elliptical major axis of the free magnetic layer.

3. The magnetic sensor as described in claim 1, wherein, The thickness of the free magnetic layer is in the range of 10 nm to 500 nm, preferably in the range of 10 nm to 200 nm, and the circular diameter or elliptical major axis of the free magnetic layer is in the range of 50 nm to 20 μm, preferably in the range of 50 nm to 2 μm.

4. The magnetic sensor as described in claim 1, wherein, The center of the free magnetic layer is aligned with the center of the reference magnetic layer, and in each direction in the plane, the edge of the reference magnetic layer is recessed toward the center relative to the edge of the free magnetic layer.

5. The magnetic sensor as described in claim 1, wherein, When the free magnetic layer has an elliptical shape, the detection direction of the magnetic sensor is parallel to the minor axis of the ellipse, and the predetermined direction of the in-plane magnetization of the reference magnetic layer is parallel to the minor axis of the ellipse.

6. The magnetic sensor as described in claim 1, further comprising: An insulating layer is formed on the substrate and covers the sidewalls of the reference magnetic layer, the intermediate layer and the free magnetic layer, as well as the upper surface of the portion of the free magnetic layer not covered by the reference magnetic layer. as well as A magnetic flux focusing layer is formed on the substrate and separated from the free magnetic layer by the insulating layer. In the detection direction of the magnetic sensor, the magnetic flux gathering layer is located on both sides of the free magnetic layer.

7. The magnetic sensor as described in claim 6, wherein, The edge of the flux-accumulating layer adjacent to the free magnetic layer has a shape adapted to the shape of the free magnetic layer, thereby maintaining a constant distance between the flux-accumulating layer and the free magnetic layer.

8. A method for preparing a magnetic sensor according to any one of claims 1 to 7, comprising: A free magnetic layer, an intermediate layer, and a reference magnetic layer are sequentially formed on a substrate to obtain a magnetic multilayer film structure. The reference magnetic layer, the intermediate layer, and the free magnetic layer are etched using a first mask pattern to obtain a circular or elliptical columnar structure. as well as The reference magnetic layer is etched using a second mask pattern, such that the maximum planar dimension of the reference magnetic layer is smaller than the circular diameter or elliptical major axis of the free magnetic layer.

9. The method of claim 8, further comprising: An insulating layer is formed to cover the magnetic multilayer film structure; The insulating layer is etched using a third mask pattern to expose the upper surface of the reference magnetic layer; A fourth mask pattern is formed, which has an opening that exposes the upper surface of the reference magnetic layer; A top electrode metal layer is deposited on the fourth mask pattern and in its openings; Remove the fourth mask pattern and the top electrode metal layer thereon, leaving the top electrode located in the opening and in contact with the upper surface of the reference magnetic layer; The insulating layer is etched using a fifth mask pattern to the portions of the insulating layer located on both sides of the magnetic multilayer film structure, at least to the depth of the free magnetic layer, wherein the insulating layer is retained on the sidewalls of the magnetic multilayer film structure. Deposited magnetic flux accumulation layer; as well as The fifth mask pattern and the magnetic flux gathering layer thereon are removed, and the remaining magnetic flux gathering layer is separated from the magnetic multilayer film structure by the insulating layer.

10. A method for preparing a magnetic sensor according to any one of claims 1 to 7, comprising: A seed layer, a free magnetic layer, an intermediate layer, and a reference magnetic layer are sequentially formed on a substrate to obtain a magnetic multilayer film structure. The reference magnetic layer and the intermediate layer are etched using the first mask pattern to obtain a circular or elliptical columnar structure; The free magnetic layer and the seed layer are etched using the first mask pattern and the sixth mask pattern located on both sides of the first mask pattern to obtain a circular or elliptical columnar structure corresponding to the first mask pattern and a magnetic flux gathering layer corresponding to the sixth mask pattern, wherein the magnetic flux gathering layer is located in the same layer as the free magnetic layer and the seed layer. An insulating layer is formed to cover the magnetic multilayer film structure; The insulating layer and the reference magnetic layer are etched using a seventh mask pattern, such that the maximum planar dimension of the reference magnetic layer is smaller than the circular diameter or elliptical major axis of the free magnetic layer. An insulating layer is formed to cover the magnetic multilayer film structure; Remove the seventh mask pattern and the insulating layer thereon; The insulating layer is etched using a third mask pattern to expose the upper surface of the reference magnetic layer; A fourth mask pattern is formed, which has an opening that exposes the upper surface of the reference magnetic layer; A top electrode metal layer is deposited on the fourth mask pattern and in its openings; as well as Remove the fourth mask pattern and the top electrode metal layer thereon, leaving the top electrode located in the opening and in contact with the upper surface of the reference magnetic layer.

11. An electronic device comprising the magnetic sensor according to any one of claims 1-7.

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