Magnetic shielding structure

Abstract

The invention discloses a magnetic shielding structure, and belongs to the technical field of sensors. The magnetic shielding structure comprises a film stack unit, and the film stack unit sequentially comprises a bottom antiferromagnetic pinning layer, an antimagnet layer, a barrier layer, a free layer, a soft magnetic layer and a pinning layer from bottom to top; the tunneling magnetic resistance unit is arranged below the membrane stack unit; the tunneling magnetic resistance unit and the film stack unit are both arranged on the substrate; the material of the free layer is CoFeB, and the thickness of the free layer is 2nm; the soft magnetic layer is made of NiFe, and the thickness of the soft magnetic layer is 30 nm; according to the magnetic shielding structure, the magnetic shielding effect is achieved by controlling the thickness of the permalloy, the high magnetic shielding multiple is achieved under the condition that the size is not greatly increased, and meanwhile the wide-range measurement range is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of sensors, in particular to a magnetic shielding structure. Background Art

[0002] Traditional magnetic field sensors such as Hall elements and magnetoresistive elements have low sensitivity, relatively small measurement range, and certain limitations in anti-interference ability. At the same time, magnetic field sensing elements are limited by the saturation of magnetic materials themselves. To achieve wide-range measurement of sensors, it is necessary to prepare very thick magnetic conductive structures or large magnetic conductive structures. Therefore, the present invention proposes a magnetic shielding structure based on tunnel magnetoresistive technology, which achieves a high magnetic shielding multiple without increasing a lot of volume, and at the same time achieves a wide-range measurement range of magnetic field sensing elements. Summary of the invention

[0003] In view of the above problems existing in the prior art, the present invention is proposed.

[0004] Therefore, the technical problem to be solved by the present invention is that in order to realize wide-range measurement of the sensor, it is necessary to prepare a very thick magnetic conductive structure or a magnetic conductive structure with a large volume.

[0005] To achieve the above object, the present invention provides the following technical solution: a magnetic shielding structure, comprising:

[0006] A film stack unit, wherein the film stack unit includes, from bottom to top, a bottom antiferromagnetic pinned layer, an antiferromagnetic magnet layer, a barrier layer, a free layer, a soft magnetic layer and a pinned layer;

[0007] A tunneling magnetoresistive unit, arranged below the film stack unit;

[0008] A substrate, on which the tunneling magnetoresistive unit and the film stack unit are both arranged.

[0009] As a further solution of the present invention: the material of the free layer is CoFeB, and its thickness is 2 nm.

[0010] As a further solution of the present invention: the material of the soft magnetic layer is NiFe, and its thickness is 30 nm.

[0011] As a further solution of the present invention: the film stack unit is arranged above the tunneling magnetoresistive unit by electroplating.

[0012] As a further solution of the present invention: the material of the bottom antiferromagnetic pinning layer is PtMn.

[0013] As a further solution of the present invention: the anti-ferromagnetic layer adopts an artificial anti-ferromagnetic structure, which includes a lower ferromagnetic layer, a magnetic spacing layer and a free layer from bottom to top;

[0014] The materials of the lower ferromagnetic layer, the magnetic spacing layer and the free layer are CoFe, Ru and CoFeB respectively.

[0015] As a further solution of the present invention: the tunneling magnetoresistance unit includes a push-type bridge arm tunneling magnetoresistance unit and a pull-type bridge arm tunneling magnetoresistance unit; the push-type bridge arm tunneling magnetoresistance unit and the pull-type bridge arm tunneling magnetoresistance unit are both composed of a free layer / tunneling layer / reference layer / pinning layer

[0016] As a further solution of the present invention: the material of the barrier layer is MgO.

[0017] As a further solution of the present invention: the material of the pinning layer is IrMn.

[0018] As a further solution of the present invention: a seed layer is provided between the tunneling magnetoresistive unit and the substrate;

[0019] The seed layer is made of Cu and Ti alloy.

[0020] Compared with the prior art, the beneficial effect of the present invention is that the magnetic shielding structure realizes the magnetic shielding effect by controlling the thickness of the Permalloy, achieves a high magnetic shielding multiple without increasing a lot of volume, and realizes a wide range of measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0022] Figure 1 It is a magnetic shielding structure based on tunnel magnetoresistance technology in an embodiment of the present invention.

[0023] Figure 2 It is a thin film structure based on tunnel magnetoresistance technology in an embodiment of the present invention.

[0024] Figure 3 This is a test result diagram of a non-shielding layer of an embodiment of the present invention.

[0025] Figure 4 It is a simulation of the shielding effect of the block Permalloy according to an embodiment of the present invention.

[0026] Figure 5 It is a simulation of the full-coverage Permalloy shielding effect of an embodiment of the present invention.

[0027] Figure 6 It is a simulation of the distance effect of the full-coverage Permalloy shielding layer of an embodiment of the present invention.

[0028] Figure 7 It is a schematic diagram of the effect of the magnetic stripe shielding solution of an embodiment of the present invention.

[0029] Figure 8 This is the simulation result of the suppression ratio of the magnetic field by the thickness of the magnetic shielding layer according to the embodiment of the present invention.

[0030] Fig. 9 This is the test result of the embodiment of the present invention under a 1 um shielding layer.

[0031] Fig.10 This is the test result of the embodiment of the present invention under a 5 um shielding layer.

[0032] Fig.11 This is the test result of the embodiment of the present invention under a 10 um shielding layer.

[0033] Fig.12 This is the test result of the embodiment of the present invention under a 20 um shielding layer.

[0034] Fig.13 This is the test result of the embodiment of the present invention under a 30 um shielding layer. DETAILED DESCRIPTION

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0036] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0037] Secondly, the present invention is described in detail with reference to the schematic diagram. When describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0038] Furthermore, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments.

[0039] Example 1

[0040] like Figures 1 to 5As shown, the present invention provides a technical solution: a magnetic shielding structure, comprising, a magnetic shielding structure, comprising, a film stack unit 100, the film stack unit comprises a bottom antiferromagnetic pinned layer 101, an antiferromagnetic magnetic layer 102, a barrier layer 103, a free layer 104, a soft magnetic layer 105 and a pinned layer 106 from bottom to top, constituting a Permalloy shielding layer; wherein the bottom antiferromagnetic pinned layer 101 is made of PtMn (20), and CoFeB (1.5) and NiFe (20) are a combination of a free layer and a soft magnetic layer to increase the range; the pinned layer 106 is made of IrMn, and the IrMn (16) pinned layer is used for orthogonal pinning to improve the stability and linearity of the film; the barrier layer 103 is made of MgO.

[0041] The tunneling magnetoresistive unit 200 is disposed below the film stack unit 100 ; and the substrate 300 , on which both the tunneling magnetoresistive unit 200 and the film stack unit 100 are disposed.

[0042] Further, the film stack unit 100 is disposed above the tunneling magnetoresistive unit 200 by electroplating;

[0043] Preferably, the thickness of the CoFeB free layer 104 is 2 nm, and the thickness of the NiFe soft magnetic layer 105 is 30 nm. The aspect ratio of the device is determined to be 3:1 and the annealing temperature is 200°C. Among them, the larger the thickness of the free layer (CoFeB) and the soft magnetic layer (NiFe), the larger the range but the worse the sensitivity. The range is increased directly through magnetic shielding. For the thin film structure, a film stack unit 100 is introduced and electroplated above the magnetic tunnel junction MTJ junction.

[0044] Furthermore, the anti-ferromagnetic layer 102 adopts an artificial anti-ferromagnetic structure, which includes a lower ferromagnetic layer, a magnetic spacer layer and a free layer from bottom to top; wherein the materials of the lower ferromagnetic layer, the magnetic spacer layer and the free layer are CoFe, Ru and CoFeB respectively, to achieve more stable pinning.

[0045] Furthermore, the tunneling magnetoresistance unit 200 includes a push-type bridge arm tunneling magnetoresistance unit 201 and a pull-type bridge arm tunneling magnetoresistance unit 202; the push-type bridge arm tunneling magnetoresistance unit 201 and the pull-type bridge arm tunneling magnetoresistance unit 202 are both composed of a free layer / tunneling layer / reference layer / pinned layer; specifically, the tunneling magnetoresistance unit 200 adopts a magnetoresistance effect sensor (TMR), which utilizes the tunnel magnetoresistance effect of magnetic multilayer film materials to sense the magnetic field, and has a greater resistance change rate than the AMR elements and GMR elements discovered and applied previously; the magnetoresistance effect sensor (TMR) thin film components used are often more than ten layers or even dozens of layers. In order to increase the thickness of the bottom electrode and reduce the influence of the bottom electrode resistance on the magnetoresistance, this report grows Cu and Ti alloys as a buffer layer (seed layer).

[0046] Furthermore, a seed layer is disposed between the tunneling magnetoresistive unit 200 and the substrate 300 ; the seed layer is made of Cu and Ti alloy.

[0047] The seed layer plays a key role in the electroplating process. First, the seed layer provides a uniform and conductive surface, providing a good foundation for the deposition of the electroplating layer. During the electroplating process, metal ions are deposited from the electrolyte to the surface of the substrate through the conductive path on the seed layer to form a metal electroplating layer. The presence of the seed layer ensures the uniformity of the electroplating layer and avoids holes, cracks or unevenness in the electroplating layer. Secondly, the seed layer provides good adhesion. The adhesion of the electroplating layer is crucial to the reliability of the equipment or product. The close bonding between the seed layer and the substrate enables the electroplating layer to be firmly attached to the surface of the substrate, improving the bonding strength and durability of the electroplating layer. In addition, the quality and characteristics of the seed layer directly affect the performance of the electroplating layer. A high-quality seed layer can provide good conductivity and uniformity, ensuring that the electroplating layer has high conductivity and uniform thickness distribution.

[0048] The thickness of the seed layer has an important influence on the thickness of the electroplating layer. When the seed layer is thicker, the electroplating layer will also be relatively thicker. By controlling the thickness of the seed layer, the thickness of the electroplating layer can be regulated.

[0049] In this embodiment, the magnetic shielding effect is achieved by controlling the thickness of the Permalloy, so that a high magnetic shielding multiple is achieved without increasing the volume, and a wide measurement range is achieved.

[0050] Example 2

[0051] In order to ensure that the measurement range after the shielding layer is added meets the requirements, Comsol Multiphysics is used to simulate the efficiency of magnetic field shielding. The method is to create an air domain, compare the magnetic field size between the air domain and the TMR sensor site, calculate the efficiency, and achieve the magnetic shielding effect by comparing different layout structures.

[0052] 1. No shielding layer

[0053] 2. Block-type Permalloy shielding layer

[0054] 3. Full coverage Permalloy shielding layer

[0055] like Figure 3 As shown, when there is no shielding layer, when the linear range is <50Gs, the linearity is 1.57%.

[0056] like Figure 4As shown, considering the thickness of the seed layer, the surface of the free layer and the Permalloy layer is 2.1um; using a block-type Permalloy shielding layer, the magnetic shielding effect of different Permalloy thicknesses is calculated. It can be seen that below 2.5um, the shielding efficiency is higher than 50% (due to the surface seed layer and the insulating layer being too thick, in fact, using the magnetron sputtering solution, since a seed layer is not required, the efficiency of 400nm can also reach about 50%).

[0057] When the thickness of the electroplating layer is 10um, the shielding efficiency reaches 20%;

[0058] When it continues to increase to 35um, the shielding efficiency reaches 10%;

[0059] That is, the original range of the sensor is 30Gs and can be increased to 3000Gs;

[0060] In addition, it can be seen that there is an uneven spatial distribution of the magnetic field at the edge of the shielding layer, so it is necessary to ensure that the TMR is located in the middle functional area.

[0061] like Figure 5 As shown, another solution is a full-coverage Mo alloy shielding layer, which requires a larger area; the uniform area is the central area, and the thickness required to achieve an efficiency of 10% is about 30um. That is, the shielding efficiency limit that can be achieved by the above schemes is about 10%, and the original range requirement of the magnetic sensitive film is not high.

[0062] If the seed layer thickness is slightly reduced, that is, the distance between the Permalloy and the film is closer, the simulation results are as follows: Figure 6 As shown in the figure, at a spacing of 30um thickness, the shielding efficiency can reach 3%, and theoretically it is not impossible to exceed the 1T range.

[0063] In actual situations, the seed layer thickness needs to be considered comprehensively to ensure good adhesion of Permalloy. The shielding efficiency is expected to be up to about 5%. Due to the alignment accuracy problem and combined with the simulation results, photolithography uses covered Permalloy graphics. Specific implementation plan: First, in the preparation and processing of the magnetic shielding material Permalloy, a magnetic strip shielding solution is adopted, that is, the Permalloy strip (1mm) is integrated in the core product, about 0.5mm away from the surface. After testing, the shielding efficiency is about 50%. Figure 7 As shown. (Shielding efficiency is defined as the range of the magnetic sensor after shielding / the original sensitivity range).

[0064] A full Permalloy coverage structure is adopted, that is, all TMRs are covered by the upper Permalloy. Figure 8 For the simulation results of the suppression ratio of the magnetic field by the thickness of the magnetic shielding layer, structures with thicknesses of 1um, 5um, 10um, 20um and 30um were used respectively. We first refer to the simulation results.

[0065] like Fig. 9 As shown in the figure, according to the previous calculation, the 1um shielding layer can magnify the range by about 5 times, but the actual measurement shows that its magnification is limited, the sensitivity is roughly 2.4mV / V / Gs, and the range is about 45Gs. When the linear range is <100Gs, the linearity is 1.28%.

[0066] like Fig.10 As shown in the figure, the measurement results of the 5um shielding layer, due to the shielding layer also brings about the non-uniformity of the magnetic field, it can be seen that its curve is relatively smooth and relatively declining. Correspondingly, even under the magnetic field of 4000Gs, its magnetization state is still not destroyed, and its sensitivity is reduced to about 0.3mV / V / Gs, and the range is about 700Gs. When the shielding layer is 5um, the linear range is >150Gs, and the linearity is about 1%.

[0067] like Fig.11 He Ru Fig.12 As shown in the figure, when the shielding layer thickness is 10um and 20um, the chip range is increased to 2000 and 2500Gs, respectively, and the sensitivity is 0.11mV / V / Gs and 0.08mV / V / Gs, respectively. When the linear range is ≥150Gs, the linearity is 0.76%.

[0068] like Fig.13 As shown in the figure, when the shielding layer thickness is 30um, due to the uneven distribution of the magnetic field, its linearity is severely damaged and cannot be used as a linear sensing function. In summary, the sensitivity of the magnetic field sensor element is relatively high, but when the shielding layer thickness is too thick, the uneven magnetic field distribution affects the linearity of its output. When the shielding layer is 30u, due to the enhanced magnetic field unevenness, the overall curve shape is greatly distorted.

[0069] The effects of different magnetic shielding structures on the magnetic saturation field and linearity were analyzed, and the range and sensitivity were comprehensively considered to realize a high-precision and low-power current sensor probe. The results show that the linear range of the sensor without a shielding layer is less than 50Gs. A certain shielding layer can increase the saturation magnetic field of the magnetic tunnel junction film. When the shielding layer is thicker, the saturation field and linear range of the magnetic tunnel junction film can be greatly improved (>150Gs linear range).

[0070] The use of a magnetic shielding solution can effectively improve the sensitivity and range of the component, thereby meeting the purpose of this report for linear measurement of magnetic fields within the range of 150Gs.

[0071] Importantly, it should be noted that the construction and arrangement of the present application shown in a number of different exemplary embodiments are only exemplary. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible, for example, the size, scale, structure, shape and proportion of various elements, and parameter values ​​such as temperature, pressure, etc., mounting arrangements, use of materials, color, directional changes, etc., without substantially departing from the novel teachings and advantages of the subject matter described in the application. For example, the element shown as integrally formed can be composed of multiple parts or elements, the position of the element can be inverted or otherwise changed, and the nature or number or position of the discrete element can be changed or changed. Therefore, all such modifications are intended to be included in the scope of the present invention. The order or sequence of any process or method steps can be changed or reordered according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure of the execution function described herein, and is not only structurally equivalent but also equivalent structure. Without departing from the scope of the present invention, other substitutions, modifications, changes and omissions can be made in the design, operating conditions and arrangement of the exemplary embodiments. Therefore, the invention is not limited to a specific embodiment, but extends to several modifications still falling within the scope of the appended claims.

[0072] Furthermore, in order to provide a concise description of exemplary embodiments, all features of an actual embodiment may not be described, i.e., those features that are not relevant to the best mode presently contemplated for carrying out the invention or those features that are not relevant to implementing the invention.

[0073] It should be understood that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but for those of ordinary skill having the benefit of this disclosure, the development effort will be a routine task of design, fabrication, and production without undue experimentation.

[0074] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A magnetic shielding structure, characterized in that: include, A film stack unit (100), the film stack unit comprising, from bottom to top, a bottom antiferromagnetic pinned layer (101), an antiferromagnetic magnet layer (102), a barrier layer (103), a free layer (104), a soft magnetic layer (105) and a pinned layer (106); A tunneling magnetoresistive unit (200) is arranged below the film stack unit (100); A substrate (300), wherein the tunneling magnetoresistive unit (200) and the film stack unit (100) are both arranged on the substrate (300).

2. The magnetic shielding structure according to claim 1, characterized in that: The free layer (104) is made of CoFeB and has a thickness of 2 nm.

3. The magnetic shielding structure according to claim 1 or 2, characterized in that: The material of the soft magnetic layer (105) is NiFe, and its thickness is 30 nm.

4. The magnetic shielding structure according to claim 3, characterized in that: The film stack unit (100) is arranged above the tunneling magnetoresistive unit (200) by electroplating.

5. The magnetic shielding structure according to claim 4, characterized in that: The material of the bottom antiferromagnetic pinning layer (101) is PtMn.

6. The magnetic shielding structure according to claim 3, characterized in that: The anti-ferromagnetic layer (102) adopts an artificial anti-ferromagnetic structure, which includes a lower ferromagnetic layer, a magnetic spacing layer and a free layer from bottom to top; The materials of the lower ferromagnetic layer, the magnetic spacing layer and the free layer are CoFe, Ru and CoFeB respectively.

7. The magnetic shielding structure according to any one of claims 4 to 6, characterized in that: The tunneling magnetoresistance unit (200) comprises a push-type bridge arm tunneling magnetoresistance unit (201) and a pull-type bridge arm tunneling magnetoresistance unit (202); The push-type bridge arm tunneling magnetoresistance unit (201) and the pull-type bridge arm tunneling magnetoresistance unit (202) are both composed of a free layer / tunneling layer / reference layer / pinning layer.

8. The magnetic shielding structure according to claim 7, characterized in that: The barrier layer (103) is made of MgO.

9. The magnetic shielding structure according to claim 8, characterized in that: The material of the pinning layer is IrMn.

10. The magnetic shielding structure according to claim 9, characterized in that: A seed layer is provided between the tunneling magnetoresistive unit (200) and the substrate (300); Wherein, the seed layer is made of Cu and Ti alloy.

Images