Method of fabricating magnetic tunnel junction and MRAM

Abstract

This application provides a method for fabricating a magnetic tunnel junction and a magnetic RAM. The method includes: providing a workpiece to be etched, the workpiece including a substrate, a magnetic tunnel junction film stack located on the substrate, and a mask layer located on the side of the magnetic tunnel junction film stack away from the substrate; controlling the workpiece to be etched to rotate, and using the mask layer as an etching mask, etching the sidewalls of the magnetic tunnel junction film stack in the rotating workpiece to be etched a predetermined number of times, wherein the etched magnetic tunnel junction film stack forms a magnetic tunnel junction, wherein the predetermined number of times is greater than or equal to 3, and in any two adjacent etching processes, the etching angle of the previous etching process is smaller than the etching angle of the subsequent etching process, and the etching angle is the angle between the incident angle of the etching ion beam and the thickness direction of the workpiece to be etched.

Description

Technical Field

[0001] This application relates to the field of magnetic random access memory, and more specifically, to a method for fabricating a magnetic tunnel junction and MRAM. Background Technology

[0002] Magnetic tunnel junctions (MTJs), as the core unit of spintronic devices, are widely used in magnetic random access memory (MRAM), highly sensitive magnetic sensors, and novel logic circuits. Their fabrication typically involves multilayer thin-film deposition, photolithography, and ion beam etching. The etching process directly determines the boundary morphology and magnetoelectric properties of the MMT. In traditional etching processes, due to the limited thickness of the mask material or uneven etching rates, a masking effect often occurs in the peripheral region of the MMT (i.e., boundary blurring, dimensional deviations, and sidewall roughness caused by mask thickness and ion orientation).

[0003] This masking effect causes irregularities in the edge contours of the tunneling layer and the electrode layer, making the actual morphology of the device more blurred and distorted than the ideal design. For multilayer nano-stacked systems such as magnetic tunnel junctions, boundary roughness, sidewall residues, and dimensional deviations significantly affect the tunneling magnetoresistance ratio, switching characteristics, and device stability, thus limiting their application in high-density storage and high-sensitivity detection. Summary of the Invention

[0004] The main objective of this application is to provide a method for fabricating a magnetic tunnel junction and MRAM, so as to at least solve the problem that the magnetic tunnel junction is prone to masking effect during the etching process in the prior art, which affects the performance of the magnetic tunnel junction.

[0005] To achieve the above objectives, according to one aspect of this application, a method for fabricating a magnetic tunnel junction is provided, comprising: providing a workpiece to be etched, the workpiece including a substrate, a magnetic tunnel junction film stack located on the substrate, and a mask layer located on the side of the magnetic tunnel junction film stack away from the substrate; controlling the workpiece to be etched to rotate, and using the mask layer as an etching mask, etching the sidewalls of the magnetic tunnel junction film stack in the rotating workpiece to be etched a predetermined number of times, wherein the etched magnetic tunnel junction film stack forms a magnetic tunnel junction, wherein the predetermined number of times is greater than or equal to 3, and in any two adjacent etching processes, the etching angle of the previous etching process is smaller than the etching angle of the subsequent etching process, the etching angle being the angle between the incident angle of the etching ion beam and the thickness direction of the workpiece to be etched.

[0006] Optionally, the workpiece to be etched is controlled to rotate, and the mask layer is used as an etching mask to etch the sidewalls of the magnetic tunneling film stack in the rotating workpiece a predetermined number of times, including: controlling the workpiece to be etched to rotate, and using an ion beam with an etching angle of 10° to 20° to perform a first etching on the sidewalls of the magnetic tunneling film stack; controlling the workpiece to be etched to rotate after the first etching, and using an ion beam with an etching angle of 30° to 60° to perform a second etching on the sidewalls of the magnetic tunneling film stack after the first etching; controlling the workpiece to be etched to rotate after the second etching, and using an ion beam with an etching angle of 80° to 90° to perform a third etching on the sidewalls of the magnetic tunneling film stack after the second etching.

[0007] Optionally, the sidewalls of the magnetic tunneling conjugate stack are etched for the first time using an ion beam with an etching angle of 10° to 20°, including: etching the sidewalls of the rotating magnetic tunneling conjugate stack using the ion beam with an etching angle of 10° to 20°, and controlling the magnetic tunneling conjugate stack to rotate at least 360° during the etching process to perform the first circumferential etching of the magnetic tunneling conjugate stack, wherein the beam spot diameter of the ion beam is greater than or equal to the height of the sidewalls of the magnetic tunneling conjugate stack along the thickness direction; obtaining the etching... The electrical information of the magnetic tunneling film stack during the etching process and the mass spectrum of the region to be etched in the magnetic tunneling film stack during the etching process are obtained. The orthographic projection of the region to be etched on the substrate does not overlap with the orthographic projection of the mask layer on the substrate. The electrical information is information characterizing the current-voltage characteristics of the magnetic tunneling film stack. Based on the electrical information and the mass spectrum, the etching stop time for the first etching is determined, and the first etching of the magnetic tunneling film stack is stopped when the first etching reaches the etching stop time.

[0008] Optionally, the electrical information includes resistance, the magnetic tunneling film stack includes a tunneling layer, and the etching stop time for the first etching is determined based on the electrical information and the mass spectrum, including: determining whether the resistance is less than or equal to a first predetermined threshold; determining whether the content of a predetermined element in the mass spectrum is less than or equal to a second predetermined threshold, wherein the predetermined element is an element contained in the tunneling layer; and determining the time when the resistance is less than or equal to the first predetermined threshold and the content of the predetermined element is less than or equal to the second predetermined threshold as the etching stop time.

[0009] Optionally, an ion beam with an etching angle of 30° to 60° is used to perform a second etching on the sidewall of the magnetic tunneling conjugate stack after the first etching. This includes: using the ion beam with a power of 115W to 135W and an etching angle of 30° to 60° to perform a second etching on the sidewall of the rotating magnetic tunneling conjugate stack after the first etching, and controlling the magnetic tunneling conjugate stack after the first etching to rotate at least 360° during the etching process to perform a second circumferential etching on the magnetic tunneling conjugate stack after the first etching. The beam spot diameter of the ion beam is greater than or equal to the height of the sidewall of the magnetic tunneling conjugate stack after the first etching along the thickness direction. If the etching time of the second etching reaches 5s to 15s, the second etching of the magnetic tunneling conjugate stack after the first etching is stopped.

[0010] Optionally, an ion beam with an etching angle of 80° to 90° is used to perform a third etching on the sidewalls of the magnetic tunneling junction film stack after the second etching. This includes: using the ion beam with a power of 115W to 135W and an etching angle of 80° to 90° to perform a third etching on the sidewalls of the rotating magnetic tunneling junction film stack after the second etching, and controlling the magnetic tunneling junction film stack after the second etching to rotate at least 360° during the etching process to perform a third circumferential etching on the magnetic tunneling junction film stack after the second etching. The beam spot diameter of the ion beam is greater than or equal to the height of the sidewalls of the magnetic tunneling junction film stack after the second etching along the thickness direction. When the etching time of the third etching reaches 20s to 40s, the third etching of the magnetic tunneling junction film stack after the second etching is stopped, and the remaining magnetic tunneling junction film stack is the magnetic tunnel junction.

[0011] Optionally, in any two adjacent etching processes, the ion beam power of the previous etching process is greater than the ion beam power of the subsequent etching process.

[0012] Optionally, the junction size of the magnetic tunnel junction is inversely proportional to the predetermined number of times.

[0013] Optionally, controlling the rotation of the workpiece to be etched includes: when the workpiece to be etched is a cylindrical structure, controlling the workpiece to be etched to rotate at a speed of 5 rpm to 30 rpm; when the workpiece to be etched is a cuboid structure, controlling the workpiece to be etched to rotate at a speed of 5 rpm to 15 rpm; and during each etching process, controlling the rotation speed of the workpiece to remain constant, and the rotation speed corresponding to any two etching processes is the same.

[0014] According to another aspect of this application, an MRAM is provided, comprising: a magnetic tunnel junction, said magnetic tunnel junction being prepared using any of the methods described.

[0015] The technical solution of this application first provides a workpiece to be etched, comprising a substrate, a magnetic tunneling junction (MTJ) film stack, and a mask layer. Then, the workpiece is rotated, and using the mask layer as an etching mask, the sidewalls of the MMT film stack in the rotating workpiece are etched multiple times (at least three times), with the etching angle increasing with each etch, ultimately resulting in a magnetic tunneling junction. Therefore, this application proposes a multi-angle step-by-step etching process. By gradually increasing the etching angle during the etching process, it ensures that the ion beam can more comprehensively cover the sidewalls of the film stack, effectively avoiding etching dead zones and improving the uniformity of sidewall etching. Simultaneously, the process incorporates full-process rotation control to ensure that the ion beam can act uniformly on the MMT film stack from multiple directions, reducing directional differences and effectively eliminating the masking effect. This results in a magnetic tunneling junction device structure with clear boundaries, accurate dimensions, and higher consistency, which is beneficial for improving the performance and reliability of the magnetic tunneling junction and plays a significant role in promoting technological advancements in magnetic storage, magnetic sensors, and other application fields. Attached Figure Description

[0016] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0017] Figure 1 A schematic flowchart of a method for preparing a magnetic tunnel junction according to an embodiment of this application is shown;

[0018] Figure 2 A schematic diagram of the first etching of the sidewall of a magnetic tunneling film stack according to an embodiment of this application is shown.

[0019] Figure 3 A schematic diagram of a second etching of the sidewalls of a magnetic tunneling film stack according to an embodiment of this application is shown;

[0020] Figure 4 A schematic diagram of a third etching of the sidewall of a magnetic tunneling film stack according to an embodiment of this application is shown;

[0021] Figure 5 A schematic diagram of the sidewall structure of a magnetic tunneling film stack after three etchings is shown according to an embodiment of this application;

[0022] Figure 6 The diagram shows a schematic image of the sidewall of a magnetic tunnel junction prepared by a method according to an embodiment of this application under a microscope.

[0023] Figure 7 A schematic diagram of the sidewall of a magnetic tunnel junction prepared by a method for preparing a magnetic tunnel junction according to the comparative example provided in this application is shown under a microscope.

[0024] The accompanying drawings include the following reference numerals:

[0025] 10. Substrate; 11. Fixing layer; 12. Tunneling layer; 13. Free layer; 14. Protective layer. Detailed Implementation

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0028] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be used interchangeably where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0029] As described in the background section, in the prior art, magnetic tunnel junctions are prone to masking effects during the etching process, which affects the performance of the magnetic tunnel junction. To solve this technical problem, the embodiments of this application provide a method for preparing a magnetic tunnel junction and an MRAM.

[0030] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0031] This application provides a method for preparing a magnetic tunnel junction. Figure 1 This is a flowchart of a method for preparing a magnetic tunnel junction according to an embodiment of this application. Figure 1 As shown, the method includes the following steps:

[0032] Step S201: Provide a part to be etched, the part to be etched includes a substrate, a magnetic tunneling membrane stack located on the substrate, and a mask layer located on the side of the magnetic tunneling membrane stack away from the substrate;

[0033] Specifically, the magnetic tunneling junction stack is a multilayer film structure used to construct magnetic tunneling junction devices. The mask layer is used to protect a portion of the magnetic tunneling junction stack during subsequent etching processes, ensuring that only the unmasked areas (also called the areas to be etched) are etched away. Due to the presence of the mask layer, the etching process is selective and directional, enabling precise control over the etched area and depth.

[0034] Step S202: Control the rotation of the workpiece to be etched, and use the mask layer as an etching mask to etch the sidewall of the magnetic tunneling junction film stack in the rotating workpiece to be etched a predetermined number of times. The etched magnetic tunneling junction film stack forms a magnetic tunneling junction. The predetermined number of times is greater than or equal to 3. In any two adjacent etching processes, the etching angle of the previous etching process is smaller than the etching angle of the next etching process. The etching angle is the angle between the incident angle of the etching ion beam and the thickness direction of the workpiece to be etched.

[0035] Specifically, the thickness direction of the part to be etched is perpendicular to the arrangement direction of the substrate and the magnetic tunneling junction film stack. The rotation of the part to be etched refers to rotation along the circumferential direction of the magnetic tunneling junction film stack. This rotation can be achieved through a combination of a wafer chuck and a rotation device. By performing three or more step-by-step etching processes, the sidewalls of the magnetic tunneling junction film stack can be finely processed layer by layer. The gradual increase in the etching angle during the step-by-step etching process means that the etching ion beam gradually shifts from the side of the magnetic tunneling junction film stack, becoming more perpendicular to its sidewalls.

[0036] This embodiment first provides a workpiece to be etched, comprising a substrate, a magnetic tunneling junction (MTJ) film stack, and a mask layer. The workpiece is then rotated, and using the mask layer as an etching mask, the sidewalls of the MMT film stack within the rotating workpiece are etched multiple times (at least three times), with the etching angle increasing with each etch, ultimately resulting in a magnetic tunneling junction. Therefore, this application proposes a multi-angle step-by-step etching process. By gradually increasing the etching angle during the etching process, the ion beam can more comprehensively cover the sidewalls of the film stack, effectively avoiding etching dead zones and improving the uniformity of sidewall etching. Simultaneously, the etching process incorporates full-process rotation control, ensuring that the ion beam can act uniformly on the MMT film stack from multiple directions to reduce directional differences. This effectively eliminates the masking effect, resulting in a magnetic tunneling junction device structure with clear boundaries, accurate dimensions, and higher consistency. This is beneficial for improving the performance and reliability of the magnetic tunneling junction and plays a significant role in promoting technological advancements in applications such as magnetic storage and magnetic sensors.

[0037] In specific applications, such as Figures 2 to 4 As shown, the magnetic tunneling membrane stack includes a fixed layer 11, a tunneling layer 12, and a free layer 13 stacked together.

[0038] In the actual fabrication of the magnetic tunneling junction (MTJ), a layer of magnetic material is first deposited using physical vapor deposition (PVD), chemical vapor deposition (CVD), or molecular beam epitaxy (MBE) to obtain a fixed layer. The magnetization direction of the fixed layer remains unchanged throughout the device's operation. Then, an extremely thin insulating material is deposited on top of the fixed layer as a tunneling layer. This step is crucial, as the thickness and quality of the tunneling layer directly affect the magnetoresistive effect and read / write performance of the MTJ. Finally, another layer of magnetic material is deposited using physical vapor deposition (PVD), chemical vapor deposition (CVD), or molecular beam epitaxy (MBE) to form a free layer, whose magnetization direction is altered by an external magnetic field or current.

[0039] In addition to these membrane layers, the magnetic tunneling membrane stack may optionally include an anti-exchange coupling layer located on the surface of the free layer away from the tunneling layer. This anti-exchange coupling layer is used to fix the magnetization direction of the free layer and prevent it from exchange coupling with the underlying fixed layer.

[0040] In other embodiments, the part to be etched may further include a bottom electrode located between the magnetic tunneling junction stack and the substrate. In still other embodiments, the part to be etched may further include a top electrode located on the surface of the magnetic tunneling junction stack away from the substrate. In addition to these layers, those skilled in the art can add other layers based on the existing layers according to actual design needs.

[0041] In some optional embodiments, the workpiece to be etched is controlled to rotate, and the sidewalls of the magnetic tunneling film stack in the rotating workpiece are etched a predetermined number of times using the mask layer as an etching mask, including: Figure 2 As shown, the workpiece to be etched is rotated, and an ion beam with an etching angle of 10° to 20° is used to perform the first etching on the sidewalls of the magnetic tunneling film stack; as shown... Figure 3 As shown, the workpiece to be etched is rotated after the first etching, and an ion beam with an etching angle of 30° to 60° is used to perform a second etching on the sidewalls of the magnetic tunneling film stack after the first etching; as shown Figure 4 As shown, the workpiece to be etched is rotated after the second etching, and an ion beam with an etching angle of 80° to 90° is used to perform a third etching on the sidewall of the magnetic tunneling film stack after the second etching.

[0042] In the aforementioned embodiment, the workpiece is rotated. First, a low-angle etching process is performed at 10° to 20°. This low angle gently removes some of the upper layer material of the magnetic tunneling junction and reduces the shading effect in areas with thicker masking, achieving initial shaping. Subsequently, the workpiece undergoes a second etching process while rotating. The ion beam angle is adjusted to 30° to 60°. This mid-angle etching combined with rotational control not only compensates for residual sidewall shadows from the low-angle etching but also enhances the etching capability at the edges of the magnetic tunneling junction, reducing masking and geometric defects, further refining the sidewall contour, optimizing the structure, and making the etching profile closer to the target design. This further improves sidewall uniformity and critical dimension consistency. Finally, a third etching process is performed at a near-vertical 80° to 90° angle. High-angle incidence combined with rotational finishing effectively removes redeposited material formed during etching, further reducing edge roughness. The entire process, through precise control of the etching angle and the rotation of the part to be etched, allows for adjustment of the sidewalls of the magnetic tunnel junction stack without affecting its main function. This further ensures the acquisition of a smooth and clear magnetic tunnel junction structure, improving the electrical performance and stability of the device.

[0043] In one exemplary embodiment, the etching angle remains unchanged during the first etching process; the etching angle remains unchanged during the second etching process; and the etching angle remains unchanged during the third etching process.

[0044] In another exemplary embodiment, during the first etching process, the etching angle may vary, but not exceeding the range of 10° to 20°; during the second etching process, the etching angle may vary, but not exceeding the range of 30° to 60°; during the third etching process, the etching angle may vary, but not exceeding the range of 80° to 90°.

[0045] It is understood that the etching angle mentioned in this application may refer to the incident angle setting value in the ion beam generator; or it may refer to the actual angle value between the incident angle of the ion beam and the thickness direction.

[0046] The multi-step, multi-angle etching method described in this application utilizes the differences in etching effects of the ion beam at different angles, making the etching process more controllable and effectively avoiding the excessive damage and structural inhomogeneity problems that may be caused by traditional single-angle etching. Through three etching steps, not only can the shape and size of the magnetic tunnel junction stack sidewalls be precisely controlled, but the roughness of the sidewalls can also be reduced to a certain extent, thereby improving the overall performance of the device.

[0047] Optionally, the first etching refers to etching the magnetic tunneling conjunctival film stack along its circumferential direction to achieve isotropic etching of the sidewalls of the magnetic tunneling conjunctival film stack, thereby removing the outer circumferential wall of the magnetic tunneling conjunctival film stack. Similarly, the second etching refers to etching the magnetic tunneling conjunctival film stack after the first etching along its circumferential direction to achieve isotropic etching of the sidewalls of the magnetic tunneling conjunctival film stack after the first etching, thereby removing the outer circumferential wall of the magnetic tunneling conjunctival film stack after the first etching. The third etching refers to etching the magnetic tunneling conjunctival film stack after the second etching along its circumferential direction to achieve isotropic etching of the sidewalls of the magnetic tunneling conjunctival film stack after the second etching, thereby removing the outer circumferential wall of the magnetic tunneling conjunctival film stack after the second etching.

[0048] According to some embodiments of this application, based on the chemical reaction kinetics of the etching ion beam, the energy and momentum transfer mechanism between the etching ion beam and the material surface, and the influence of the physical geometric parameters of the etching equipment (including electrode structure, electric field distribution, and gas flow distribution) on the etching morphology, an etching kinetic model is established to describe the mapping relationship between etching angle and etching process parameters and etching morphology parameters. The etching process parameters include power, gas flow rate, temperature, cavity pressure, and bias voltage, while the etching morphology parameters include at least etching depth, sidewall angle, and surface roughness. In specific implementation, the etching process parameters corresponding to different etching angles are input into the etching kinetic model. The etching process is numerically simulated using simulation software to obtain the corresponding etching morphology prediction results. Based on this, the initial theoretical correspondence between etching angle, etching process parameters, and etching morphology parameters is extracted. Further, multiple sets of etching experiments are designed to verify the theoretical correspondence. The correspondence is verified and parameters are calibrated to revise and optimize the etching kinetics model, thereby obtaining the final correspondence between etching angle, etching process parameters, and etching morphology parameters. This final correspondence can be stored using a function model, lookup table, or data-driven model. During the actual etching process, online monitoring technology is used to acquire real-time status information of the etching process. Combined with the etching kinetics model or soft measurement algorithm, the current etching morphology parameters of the workpiece to be etched are estimated in real time. The deviation between the current etching morphology parameters and the target morphology parameters determines whether to terminate the current etching process. When the etching angle needs adjustment, the etching process parameters that meet the target morphology requirements are predicted based on the adjusted etching angle, the current etching morphology parameters, and the final correspondence. These predicted etching process parameters are then used as control commands to adjust the etching equipment, thereby achieving adaptive automated control of the etching process.

[0049] In other exemplary embodiments, the sidewalls of the magnetic tunneling membrane stack are first etched using an ion beam with an etching angle of 10° to 20°, including: etching the sidewalls of the rotating magnetic tunneling membrane stack using the ion beam with an etching angle of 10° to 20°, and controlling the magnetic tunneling membrane stack to rotate at least 360° during the etching process to perform the first circumferential etching of the magnetic tunneling membrane stack, wherein the beam spot diameter of the ion beam is greater than or equal to the height of the sidewalls of the magnetic tunneling membrane stack along the thickness direction; The electrical information of the magnetic tunneling film stack during the etching process and the mass spectrum of the region to be etched in the magnetic tunneling film stack during the etching process are obtained. The orthographic projection of the region to be etched on the substrate does not overlap with the orthographic projection of the mask layer on the substrate. The electrical information is information characterizing the current-voltage characteristics of the magnetic tunneling film stack. Based on the electrical information and the mass spectrum, the etching stop time for the first etching is determined, and the first etching of the magnetic tunneling film stack is stopped when the first etching reaches the etching stop time.

[0050] In this embodiment, a low-angle ion beam etching of 10° to 20° is used to gently and precisely remove the upper electrode material of the magnetic tunnel junction stack structure, gradually exposing the tunneling layer and reducing the shading effect in areas with large mask thickness, thus providing a uniform film structure for subsequent processes. Furthermore, during the etching process, the workpiece is rotated, ensuring that ion beams incident from different angles can uniformly bombard the sidewalls, reducing orientation dependence and avoiding asymmetric etching, thereby making the sidewall shape of the magnetic tunnel junction structure more regular and uniform. During the etching process, the etching stop time for the first etching is determined based on the electrical information of the magnetic tunnel junction stack and the mass spectrum of the area to be etched. Specifically, the first etching of the magnetic tunnel junction stack is stopped when a specific etching endpoint is detected, achieving precise control over the etching stop time. This effectively avoids problems caused by over-etching or incomplete etching, improves the controllability of the etching process and the manufacturing precision of the magnetic tunnel junction, and ultimately optimizes the electrical performance of the device.

[0051] Furthermore, the electrical information can be at least one of the resistance of the magnetic tunneling conduit, the current flowing through the magnetic tunneling conduit, and the voltage across the magnetic tunneling conduit. The mass spectrum can include any element contained in the etchable region of the magnetic tunneling conduit, such as the film elements contained in the fixed layer of the magnetic tunneling conduit, the film elements contained in the tunneling layer of the magnetic tunneling conduit, or the film elements contained in the free layer of the magnetic tunneling conduit, etc.

[0052] In some embodiments, the etching angle is 10° to 20°, specifically it can be an etching angle of 10°, 12°, 15°, 18°, 20°, or any value of etching angle within the range of 10° to 20°.

[0053] In other embodiments, the ion beam power for the first etching can be 15W to 35W. Specifically, the ion beam power for the first etching can be 25W.

[0054] In one exemplary scheme, the electrical information includes resistance, and the magnetic tunneling film stack includes a tunneling layer. Based on the electrical information and the mass spectrum, the etching stop time for the first etching step is determined, including: determining whether the resistance is less than or equal to a first predetermined threshold; determining whether the content of a predetermined element in the mass spectrum is less than or equal to a second predetermined threshold, where the predetermined element is an element contained in the tunneling layer; and determining the time when the resistance is less than or equal to the first predetermined threshold and the content of the predetermined element is less than or equal to the second predetermined threshold as the etching stop time. This scheme uses both resistance value and the content of the predetermined element in the tunneling layer as dual standards to accurately determine the etching stop time. A resistance less than or equal to the first predetermined threshold indicates a short circuit problem in the etched magnetic tunneling film stack, requiring a next etching step with a larger etching angle to eliminate the short circuit problem. A content of the predetermined element in the mass spectrum less than or equal to the second predetermined threshold means that the area to be etched has been completely etched. Using resistance and mass spectrum as indicators for etching control can effectively reduce uncertainties in the process window and improve the controllability and repeatability of the entire manufacturing process. Furthermore, this real-time monitoring and feedback mechanism avoids the problems of over-etching or under-etching that may occur due to post-analysis, and has a significant effect on improving the manufacturing yield and performance of MTJ devices.

[0055] In one specific embodiment, both the first predetermined threshold and the second predetermined threshold can be determined based on empirical values, or they can both be obtained through a limited number of experimental verifications. Optionally, the first predetermined threshold can be 0. The second predetermined threshold can be 0.

[0056] In another specific embodiment, the material of the tunneling layer includes MgO, and the predetermined element can be Mg.

[0057] In addition to the aforementioned materials, the tunneling layer may include MgO, AlO X MgAlO X TiO X TaO X GaO X With FeO X At least one of them.

[0058] Furthermore, the materials of the fixed layer and the free layer are independently selected from at least one of Co, Fe, Ni, CoB, FeB, NiB, CoFe, NiFe, CoNi, CoFeNi, CoFeB, NiFeB, CoNiB, CoFeNiB, FePt, FePd, CoPt, CoPd, CoFePt, CoFePd, FePtPd, CoPtPd, and CoFePtPd, and the material of the free layer includes at least one of Co, Fe, Ni, CoB, FeB, NiB, CoFe, NiFe, CoNi, CoFeNi, CoFeB, NiFeB, CoNiB, CoFeNiB, FePt, FePd, CoPt, CoPd, CoFePt, CoFePd, FePtPd, CoPtPd, and CoFePtPd.

[0059] In one embodiment, before determining the etching stop time for the first etching based on the electrical information and the mass spectrum, the method further includes: determining the device performance target of the magnetic tunnel junction, the device performance target including at least one of the following: maximizing TMR (Tunnel Magneto-Resistance), maximizing read / write speed, and maximizing durability; constructing a theoretical prediction model for device performance based on the physical model and process flow of the MTJ, used to describe the influence relationship between resistance and predetermined element content on the device performance of the magnetic tunnel junction, wherein the model uses resistance and predetermined element content as input parameters and the device performance of the magnetic tunnel junction as output parameters; collecting multiple sets of experimental data on the fabrication of the magnetic tunnel junction, including resistance measurement data, predetermined element content detection data, and corresponding device performance, and training a theoretical model using machine learning algorithms (such as support vector machines, neural networks); analyzing the sensitivity of different resistance values ​​and predetermined element contents to the device performance of the magnetic tunnel junction through the trained theoretical model, thereby determining the optimal range of resistance and predetermined element contents for TMR value, read / write speed, and durability, and obtaining the first predetermined threshold and the second predetermined threshold.

[0060] According to some alternative embodiments of this application, an ion beam with an etching angle of 30° to 60° is used to perform a second etching on the sidewall of the magnetic tunneling conjugate stack after the first etching, including: using the ion beam with a power of 115W to 135W and an etching angle of 30° to 60° to perform a second etching on the sidewall of the rotating magnetic tunneling conjugate stack after the first etching, and controlling the magnetic tunneling conjugate stack after the first etching to rotate at least 360° during the etching process to perform a second circumferential etching on the magnetic tunneling conjugate stack after the first etching, wherein the beam spot diameter of the ion beam is greater than or equal to the height of the sidewall of the magnetic tunneling conjugate stack after the first etching along the thickness direction; and stopping the second etching of the magnetic tunneling conjugate stack after the first etching when the etching time of the second etching reaches 5s to 15s.

[0061] In the second etching process described in this embodiment, by controlling the etching angle, power, and etching duration, precise etching of the sidewalls of the magnetic tunneling junction film stack can be achieved, maintaining the integrity and uniformity of the sidewalls. Specifically, by combining a mid-angle etching angle of 30° to 60° with rotation control, not only can the sidewall shadows remaining during low-angle etching be compensated, but the etching capability of the edge areas can also be enhanced, reducing mask occlusion and deficiencies caused by geometric topography. This makes the etching profile closer to the target design, improves sidewall uniformity and critical size consistency, and the sample rotation ensures uniform etching in all directions, reduces orientation dependence, and avoids non-uniform etching phenomena. Simultaneously, the power is controlled between 115W and 135W, providing high etching efficiency without being excessively high, thus avoiding damage to non-etched areas.

[0062] In some embodiments, the etching angle is 30° to 60°, specifically 30°, 35°, 40°, 45°, 50°, 55°, 60°, or any value within the range of 30° to 60°.

[0063] In other embodiments, the ion beam power for the second etching can be 125W.

[0064] In some alternative embodiments, an ion beam with an etching angle of 80° to 90° is used to perform a third etching on the sidewalls of the magnetic tunneling junction film stack after the second etching. This includes: using the ion beam with a power of 115W to 135W and an etching angle of 80° to 90° to perform a third etching on the sidewalls of the rotating magnetic tunneling junction film stack after the second etching, and controlling the magnetic tunneling junction film stack after the second etching to rotate at least 360° during the etching process to perform a third circumferential etching on the magnetic tunneling junction film stack after the second etching. The beam spot diameter of the ion beam is greater than or equal to the height of the sidewalls of the magnetic tunneling junction film stack after the second etching along the thickness direction. When the etching time of the third etching reaches 20s to 40s, the third etching of the magnetic tunneling junction film stack after the second etching is stopped, and the remaining magnetic tunneling junction film stack is the magnetic tunnel junction.

[0065] During the third etching process in the embodiment, the sample is kept rotating to ensure that the ion bombardment is evenly distributed in different directions. By combining the high-angle etching angle with rotational trimming, the redeposited material formed during the etching process can be effectively removed, further reducing the line edge roughness. This step can obtain a magnetic tunnel junction structure with smooth and clear boundaries, which can further significantly improve the consistency and electrical performance of the device.

[0066] In some embodiments, the etching angle is 80° to 90°, specifically 80°, 82°, 85°, 87°, 90°, or any value within the range of 80° to 90°.

[0067] In other embodiments, the ion beam power for the third etching can be 125W.

[0068] Optionally, in any two adjacent etching processes, the ion beam power of the preceding etching process is greater than that of the following etching process. In this embodiment, controlling the ion beam power of the preceding etching process to be greater than that of the following etching process allows for faster material removal during etching, which is suitable for the formation of the initial shape. Subsequently, the etching process with reduced power allows for more precise adjustment of the smoothness and clarity of the magnetic tunnel junction film sidewalls, significantly improving boundary quality and further enhancing the electrical performance and structural stability of the device.

[0069] Optionally, the junction size of the magnetic tunnel junction is inversely proportional to the predetermined number of etching steps. The smaller the junction size of the magnetic tunnel junction, the more precise the manufacturing process requires, which typically means more etching steps to achieve the desired dimensional accuracy, reduce sidewall effects, maintain good process tolerances, and avoid over-etching. Conversely, MTJs with large junction sizes can be achieved with fewer etching steps because they have relatively lower requirements for manufacturing precision and resolution.

[0070] Specifically, the junction size of the magnetic tunnel junction refers to the effective overlap area (including effective length and effective width) between the fixed layer 11 and the free layer 13 separated by the tunneling layer 12 in the magnetic tunnel junction.

[0071] According to some other embodiments of this application, controlling the rotation of the part to be etched includes: when the part to be etched is a cylindrical structure, controlling the part to be etched to rotate at a speed of 5 rpm to 30 rpm; when the part to be etched is a cuboid structure, controlling the part to be etched to rotate at a speed of 5 rpm to 15 rpm; and during each etching process, controlling the rotation speed of the part to be etched to remain constant, and the rotation speed corresponding to any two etching processes is the same. This solution controls the rotation speed according to the shape of the part to be etched. Specifically, the part to be etched with a cylindrical structure rotates at a speed of 5 rpm to 30 rpm, and the part to be etched with a cuboid structure rotates at a speed of 5 rpm to 15 rpm. By precisely controlling the rotation speed of the part to be etched, uniformity and depth control of the etching process are achieved, sidewall damage is reduced, process tolerance is optimized, thereby improving the manufacturing accuracy and consistency of MTJ devices.

[0072] For example, when the part to be etched is a cylindrical structure, the rotation speed can be 20 rpm. For example, when the part to be etched is a cuboid structure, the rotation speed can be 5 rpm.

[0073] In some alternative embodiments, controlling the rotation of the workpiece to be etched and using the mask layer as an etching mask to etch the sidewalls of the magnetic tunneling film stack in the rotating workpiece to be etched a predetermined number of times includes: controlling the rotation of the workpiece to be etched and sequentially using ion beams with etching angles of a first angle, a second angle, ..., an nth angle to etch the sidewalls of the magnetic tunneling film stack in the workpiece to be etched, wherein the first angle, the second angle, ..., the nth angle increase sequentially, and the etching power corresponding to the first angle, the second angle, ..., the nth angle decreases sequentially.

[0074] The multiple etching processes in this application can be achieved through ion beam etching, reactive ion etching (RIE), or other etching techniques.

[0075] In other embodiments, after forming the magnetic tunnel junction, the method may further include: as Figure 5 As shown, a protective layer 14 is formed on the sidewall of the magnetic tunnel junction. This protective layer 14 is used to prevent oxidation and contamination of the magnetic tunnel junction and to provide a smooth interface for subsequent multilayer deposition. In addition to forming the protective layer, the method may also include: high-temperature heat treatment or annealing to activate the magnetic moment orientation in the magnetic layer, improve the crystallinity of the tunneling layer, and optimize the magnetic tunnel resistance (TMR) value of the MTJ; depositing a top electrode layer and patterning the top electrode layer to obtain the top electrode, etc.

[0076] This application provides an etching method for removing the masking effect of magnetic tunnel junctions, applicable to the micro- and nano-fabrication of magnetic tunnel junction devices. This method combines segmented angle etching with rotational control to effectively eliminate the masking effect caused by mask thickness, sidewall obstruction, and redeposition, while ensuring critical dimension consistency. This results in a target structure with clear boundaries and precise dimensions. Figure 6 An exemplary schematic diagram of the sidewalls of a magnetic tunnel junction prepared by the method of this application is shown under a microscope, wherein, Figure 6 The black border marks the two corners of the magnetic tunnel junction's sidewall, such as... Figure 6 As shown, the subtunnel junction fabricated using the magnetic tunnel junction fabrication method of this application exhibits clear sidewall boundaries, free of irregular sidewall residues, and with a generally consistent etching depth at all sidewall locations (especially the corners). This is beneficial for improving the device's tunneling magnetoresistance ratio, switching characteristics, and device stability. Through the combined process of low-angle etching, medium-angle etching, high-angle trimming, and rotation control, this application can effectively suppress the masking effect during the magnetic tunnel junction etching process, avoiding the influence of sidewall shadows and redeposition on the structural contour, and ensuring the accuracy of critical dimensions and the clarity of boundaries. The resulting magnetic tunnel junction structure has smaller dimensional deviations, lower line-edge roughness, and higher tunneling magnetoresistance ratio, thereby significantly improving the device's performance stability and array uniformity.

[0077] Compared with existing etching methods for magnetic tunnel junctions, this application has the following highlights: 1) This application effectively weakens the superimposed effects of mask thickness and multi-directional scattering by using multi-angle segmented etching and full-process rotation control in the process scheme, making the etching profile closer to the target design, thereby ensuring high-fidelity pattern transfer and significantly reducing edge blurring and dimensional deviation. 2) The segmented angle etching proposed in this application, combined with rotation control, allows the ion beam to act uniformly on the array units from multiple directions, effectively weakening the proximity occlusion effect, thereby reducing line edge roughness, improving the consistency of critical dimensions within the array, and ensuring batch-to-batch stability. 3) This application directly introduces a "demasking" mechanism in the etching stage, achieving direct correction of the final morphology through a process sequence of low-angle exposure, medium-angle compensation, and high-angle trimming, supplemented by full-process rotation. This method reduces the reliance on complex front-end photolithography compensation, simplifies the entire process chain, expands the process window, and improves process robustness and manufacturability.

[0078] According to another aspect of this application, an MRAM is provided, comprising: a magnetic tunnel junction, said magnetic tunnel junction being prepared using any of the methods described.

[0079] The MRAM includes a magnetic tunnel junction fabricated using any of the methods described above. This method first provides a workpiece to be etched, comprising a substrate, a magnetic tunnel junction film stack, and a mask layer. Then, the workpiece is rotated, and using the mask layer as an etching mask, the sidewalls of the magnetic tunnel junction film stack in the rotating workpiece are etched multiple times (at least three times), with the etching angle increasing with each etch, ultimately resulting in a magnetic tunnel junction. Therefore, this application proposes a multi-angle step-by-step etching process. During the etching process, the etching angle is gradually increased, ensuring that the ion beam can more comprehensively cover the sidewalls of the film stack, effectively avoiding etching dead zones and improving the uniformity of sidewall etching. Simultaneously, the etching process incorporates full-process rotation control, ensuring that the ion beam can act uniformly on the magnetic tunnel junction film stack from multiple directions to reduce directional differences. This effectively removes the masking effect, resulting in a magnetic tunnel junction device structure with clear boundaries, accurate dimensions, and higher consistency, which is beneficial for improving the device performance and reliability of MRAM.

[0080] The magnetic tunneling structure and interlayer coupling effect described in this application will be specifically explained below with reference to specific embodiments and comparative examples.

[0081] Example 1

[0082] This embodiment provides a method for preparing a magnetic tunnel junction, including:

[0083] Provide a part to be etched, the part to be etched includes a substrate, a magnetic tunneling membrane stack on the substrate, and a mask layer on the side of the magnetic tunneling membrane stack away from the substrate;

[0084] The part to be etched is rotated 360° and the mask layer is used as the etching mask. An ion beam with an etching angle of 15° and a power of 25W is used to perform the first etching on the sidewall of the magnetic tunnel junction film stack. The etching time is controlled to be 40s and the etching rate is 20rpm (circular magnetic tunnel junction area) or 5rpm (elliptical magnetic tunnel junction area) to ensure the integrity of the longitudinal contour of the film stack, the controllable thickness of the interface layer, and to avoid introducing sidewall distortion.

[0085] The workpiece to be etched after the first etching is rotated 360°, and an ion beam with an etching angle of 45° and a power of 125W is used to perform a second etching on the sidewall of the magnetic tunnel junction film after the first etching. The etching time is controlled to be 9s, and the etching rate is 20rpm (circular magnetic tunnel junction area) or 5rpm (elliptical magnetic tunnel junction area). The sidewall geometry is adjusted to reduce roughness and edge defects.

[0086] The workpiece to be etched after the second etching is rotated 360°, and an ion beam with an etching angle of 85° and a power of 125W is used to perform a third etching on the sidewall of the magnetic tunnel junction film after the second etching. The etching time is controlled to be 30s, and the etching rate is 20rpm (circular magnetic tunnel junction area) or 5rpm (elliptical magnetic tunnel junction area). The sidewall is directionally cleaned to remove residual magnetic particles, and the etched magnetic tunnel junction film forms a magnetic tunnel junction.

[0087] Example 2

[0088] This embodiment provides a method for preparing a magnetic tunnel junction. The only difference between this method and Embodiment 1 is that the etching angle in the first etching process is 10°.

[0089] Example 3

[0090] This embodiment provides a method for preparing a magnetic tunnel junction. The only difference between this method and Embodiment 1 is that the etching angle during the first etching process is 20°.

[0091] Example 4

[0092] This embodiment provides a method for preparing a magnetic tunnel junction. The only difference between this method and Embodiment 1 is that the etching angle in the second etching process is 30°.

[0093] Example 5

[0094] This embodiment provides a method for preparing a magnetic tunnel junction. The only difference between this method and Embodiment 1 is that the etching angle in the second etching process is 60°.

[0095] Example 6

[0096] This embodiment provides a method for preparing a magnetic tunnel junction. The only difference between this method and Embodiment 1 is that the etching angle in the third etching process is 80°.

[0097] Example 7

[0098] This embodiment provides a method for preparing a magnetic tunnel junction. The only difference between this method and Embodiment 1 is that the etching angle in the third etching process is 90°.

[0099] Example 8

[0100] This embodiment provides a method for preparing a magnetic tunnel junction. The only difference between this method and Embodiment 1 is that the etching angle in the first etching process in this embodiment is 5°.

[0101] Example 9

[0102] This embodiment provides a method for preparing a magnetic tunnel junction. The only difference between this method and Embodiment 1 is that the etching angle in the first etching process in this embodiment is 30°.

[0103] Example 10

[0104] This embodiment provides a method for preparing a magnetic tunnel junction. The only difference between this method and Embodiment 1 is that the etching angle in the second etching process in this embodiment is 20°.

[0105] Example 11

[0106] This embodiment provides a method for preparing a magnetic tunnel junction. The only difference between this method and Embodiment 1 is that the etching angle in the second etching process in this embodiment is 75°.

[0107] Example 12

[0108] This embodiment provides a method for preparing a magnetic tunnel junction. The only difference between this method and Embodiment 1 is that the etching angle in the third etching process in this embodiment is 70°.

[0109] Example 13

[0110] This embodiment provides a method for preparing a magnetic tunnel junction. The only difference between this method and Embodiment 1 is that the etching angle in the third etching process in this embodiment is 100°.

[0111] Comparative Example 1

[0112] This comparative example provides a method for preparing a magnetic tunnel junction, including:

[0113] Provide a part to be etched, the part to be etched includes a substrate, a magnetic tunneling membrane stack on the substrate, and a mask layer on the side of the magnetic tunneling membrane stack away from the substrate;

[0114] The part to be etched is rotated 360° and the mask layer is used as the etching mask. An ion beam with an etching angle of 30° and a power of 125W is used to perform the first etching on the sidewall of the magnetic tunnel junction. The etching time is controlled to be 9s and the etching rate is 20rpm (circular magnetic tunnel junction area) or 5rpm (elliptical magnetic tunnel junction area).

[0115] The workpiece to be etched after the first etching is rotated 360°, and an ion beam with an etching angle of 70° and a power of 125W is used to perform a second etching on the sidewalls of the magnetic tunneling junction film after the first etching. The etching time is controlled at 30s, and the etching rate is 20rpm (for circular magnetic tunneling junction regions) or 5rpm (for elliptical magnetic tunneling junction regions). The etched magnetic tunneling junction film forms a magnetic tunneling junction. The morphology of the sidewalls of this magnetic tunneling junction under a microscope is shown in the schematic diagram below. Figure 7 As shown.

[0116] The performance of the magnetic tunnel junctions prepared using the methods in Examples 1-13 and Comparative Example 1 was tested, and the test results are shown in Table 1. The sidewall morphology of the magnetic tunnel junctions prepared using the methods in Examples 1 and Comparative Example 1 was observed under a microscope, and a schematic diagram of the morphology of the magnetic tunnel junction of Example 1 is shown below. Figure 6 As shown, a schematic diagram of the morphology of the magnetic tunnel junction in Comparative Example 1 is as follows. Figure 7 As shown, Figure 7 The black frame in the image marks a corner of the sidewall of the magnetic tunnel junction.

[0117] Table 1

[0118]

[0119]

[0120] Depend on Figure 6 as well as Figure 7It can be seen that the edges of the magnetic tunnel junction after two etchings are relatively rough and the boundaries are not clear, resulting in a relatively obvious masking effect. In contrast to Comparative Example 1, the sidewalls of the magnetic tunnel junction obtained by three etchings in Example 1 are smoother and the verticality is higher, effectively eliminating the masking effect. As can be seen from the experimental data in Table 1, the magnetic tunnel junctions corresponding to Examples 1-13 have higher sidewall steepness and smaller interlayer coupling field, showing a significant advantage over Comparative Example 1. Compared to Comparative Example 1, the methods in Examples 1-13 are more effective at removing the masking effect. Furthermore, compared to Examples 8 and 9, the magnetic tunnel junctions obtained in Examples 2 and 3 have higher sidewall steepness and smaller interlayer coupling field, indicating that an etching angle of 10° to 20° is optimal during the first etching process. Compared to Examples 10 and 11, the magnetic tunnel junctions obtained in Examples 4 and 5 have higher sidewall steepness and smaller interlayer coupling field, indicating that an etching angle of 30° to 60° is optimal during the second etching process. Compared to Examples 12 and 13, the magnetic tunnel junctions obtained in Examples 6 and 7 have higher sidewall steepness and smaller interlayer coupling field, indicating that an etching angle of 80° to 90° is optimal during the third etching process.

[0121] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0122] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0123] As can be seen from the above description, the embodiments described in this application achieve the following technical effects:

[0124] (1) A segmented multi-angle etching process is proposed: This application adopts a segmented angle process route in the etching process of magnetic tunnel junctions, specifically including three stages: low angle, medium angle, and high angle. The ion incident angles are controlled within the ranges of 10°~20°, 30°~60°, and 80°~90°, respectively. Through this segmented etching method, the masking effect caused by mask thickness and geometry can be addressed in a targeted manner at different stages: low-angle etching is used to expose the tunneling layer and reduce under-etching at the bottom, medium-angle etching is used to eliminate the sidewall shadow area, and high-angle etching is used to trim the sidewall and remove redeposited material, thereby achieving consistency between the etching morphology and the target design.

[0125] (2) Windowed control of etching parameters: In each etching stage at various angles, this application clearly sets the range of process parameters, including maintaining the power at approximately 125W, keeping the current at a stable level, controlling the etching time to 5–15 seconds in the mid-angle stage, and controlling the etching time to 20–40 seconds in the high-angle trimming stage. For low-angle etching, the characteristic signal of the tunneling layer is monitored in real time, and etching is terminated when the signal just appears but has not yet reached its peak. This windowed control of power, time, and endpoint not only improves the repeatability and reliability of the process, but also ensures the etching consistency between different sample batches.

[0126] (3) Full-process coupling of rotation control and etching: The sample remains rotated throughout the low-angle, medium-angle, and high-angle etching processes to further improve the uniformity of ion bombardment. For cylindrical magnetic tunnel junction structures, the rotation speed is set to approximately 20 rpm; for elongated structures, the rotation speed is set to approximately 5 rpm. The full-process introduction of rotation control allows the ion beam to act uniformly on the sample from multiple directions, effectively avoiding local shading or asymmetric etching problems caused by direction dependence, thereby significantly improving the overall uniformity of etching and the consistency within the array.

[0127] (4) High-angle trimming to improve sidewall quality: After completing low-angle and medium-angle etching, this application trims the sidewalls of the magnetic tunnel junction using high-angle (80°–90°) ion beam incidence. This process not only removes redeposited material and fencing effects generated during etching, but also effectively reduces edge roughness, making the sidewalls smoother and clearer. Through high-angle trimming, the boundary quality is significantly improved, thereby improving the electrical performance and structural stability of the device.

[0128] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a magnetic tunnel junction, characterized in that, include: A part to be etched is provided, the part to be etched includes a substrate, a magnetic tunneling membrane stack located on the substrate, and a mask layer located on the side of the magnetic tunneling membrane stack away from the substrate; The workpiece to be etched is controlled to rotate, and the mask layer is used as an etching mask to etch the sidewall of the magnetic tunneling junction film stack in the rotating workpiece at least three times at different etching angles. The three etching angles are: 10° to 20°, 30° to 60°, and 80° to 90° respectively. The etched magnetic tunneling junction film stack forms a magnetic tunneling junction. In any two adjacent etching processes, the etching angle of the previous etching process is smaller than the etching angle of the subsequent etching process. The etching angle is the angle between the incident angle of the etching ion beam and the thickness direction of the workpiece to be etched.

2. The method according to claim 1, characterized in that, The sidewalls of the magnetic tunneling film stack are first etched using an ion beam with an etching angle of 10° to 20°, including: The sidewalls of the rotating magnetic tunneling membrane stack are etched using the ion beam with an etching angle of 10° to 20°, and the magnetic tunneling membrane stack is controlled to rotate at least 360° during the etching process to perform the first circumferential etching on the magnetic tunneling membrane stack. The beam spot diameter of the ion beam is greater than or equal to the height of the sidewalls of the magnetic tunneling membrane stack along the thickness direction. The electrical information of the magnetic tunneling film stack during the etching process and the mass spectrum of the region to be etched in the magnetic tunneling film stack during the etching process are obtained. The orthographic projection of the region to be etched on the substrate and the orthographic projection of the mask layer on the substrate do not overlap. The electrical information is information characterizing the current-voltage characteristics of the magnetic tunneling film stack. Based on the electrical information and the mass spectrum, the etching stop time for the first etching is determined, and the first etching of the magnetic tunneling film stack is stopped when the first etching reaches the etching stop time.

3. The method according to claim 2, characterized in that, The electrical information includes resistance, the magnetic tunneling film stack includes a tunneling layer, and the etching stop time for the first etching is determined based on the electrical information and the mass spectrum, including: Determine whether the resistance is less than or equal to a first predetermined threshold; Determine whether the content of a predetermined element in the mass spectrum is less than or equal to a second predetermined threshold, wherein the predetermined element is an element contained in the tunneling layer; The etching stop time is determined when the resistance is less than or equal to the first predetermined threshold and the content of the predetermined element is less than or equal to the second predetermined threshold.

4. The method according to claim 1, characterized in that, Using an ion beam with an etching angle of 30° to 60°, a second etching is performed on the sidewalls of the magnetic tunneling film stack after the first etching, including: An ion beam with a power of 115W to 135W and an etching angle of 30° to 60° is used to perform a second etching on the sidewall of the rotating magnetic tunneling film stack after the first etching. The magnetic tunneling film stack after the first etching is controlled to rotate at least 360° during the etching process to perform a second circumferential etching on the magnetic tunneling film stack after the first etching. The beam spot diameter of the ion beam is greater than or equal to the height of the sidewall of the magnetic tunneling film stack after the first etching along the thickness direction. If the etching time of the second etching reaches 5 to 15 seconds, the second etching of the magnetic tunneling film stack after the first etching is stopped.

5. The method according to claim 1, characterized in that, Using an ion beam with an etching angle of 80° to 90°, a third etching is performed on the sidewalls of the magnetic tunneling film stack after the second etching, including: An ion beam with a power of 115W to 135W and an etching angle of 80° to 90° is used to perform a third etching on the sidewalls of the rotating magnetic tunneling film stack after the second etching. The magnetic tunneling film stack after the second etching is controlled to rotate at least 360° during the etching process to perform a third circumferential etching on the magnetic tunneling film stack after the second etching. The beam spot diameter of the ion beam is greater than or equal to the height of the sidewalls of the magnetic tunneling film stack after the second etching along the thickness direction. If the etching time of the third etching reaches 20s to 40s, the third etching of the magnetic tunneling film stack after the second etching is stopped, and the remaining magnetic tunneling film stack is the magnetic tunneling junction.

6. The method according to claim 1, characterized in that, In any two consecutive etching processes, the ion beam power of the previous etching process is greater than the ion beam power of the subsequent etching process.

7. The method according to claim 1, characterized in that, The size of the magnetic tunnel junction is inversely proportional to the number of etching operations.

8. The method according to claim 1, characterized in that, Controlling the rotation of the workpiece to be etched includes: When the part to be etched is a cylindrical structure, the part to be etched is controlled to rotate at a speed of 5 rpm to 30 rpm. When the workpiece to be etched has a cuboid structure, the workpiece is controlled to rotate at a speed of 5 rpm to 15 rpm. During each etching process, the rotational speed of the workpiece to be etched is kept constant, and the rotational speed is the same for any two etching processes.

9. An MRAM, characterized in that, include: A magnetic tunnel junction, wherein the magnetic tunnel junction is prepared by any one of claims 1 to 8.

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