Preparation method of heterostructure transmission sample

Abstract

The invention discloses a preparation method of a heterostructure transmission sample, and the method comprises the steps: fixing a heterostructure on a supporting column, the heterostructure comprises a substrate, a conductive column and a plurality of device layers, the substrate comprises a first surface and a second surface which are opposite to each other, and the conductive column extends into the substrate from the first surface; the plurality of device layers are sequentially stacked on the first surface; the extension direction of the conductive column is perpendicular to the length direction of the supporting column. And a focused ion beam is adopted to etch the heterostructure so as to reduce the thickness of the heterostructure, and the included angle between the incident direction of the focused ion beam and the extension direction of the conductive column is an obtuse angle. According to the technical scheme, the curtain effect generated by thinning of the heterostructure is weakened.

Description

Technical Field

[0001] This application belongs to the field of semiconductor technology, and particularly relates to a method for preparing a heterogeneous structure transmission sample. Background Art

[0002] A Transmission Electron Microscope (TEM) is a key tool for characterizing heterogeneous structures and can provide important insights valuable both academically and industrially. TEM provides high-resolution imaging and analysis capabilities, enabling researchers and engineers to observe and understand the atomic and electronic structures of materials. This understanding is crucial for developing devices that utilize the unique properties of heterogeneous structures. There are significant challenges in preparing TEM samples for heterogeneous structure devices. Since the sputtering rates of different materials during ion beam processing are different, harder materials are sputtered more slowly than softer regions, resulting in a "curtain effect" often occurring at the junction of the two materials. It appears as a series of parallel wavy stripes or curtains on the milled surface of the sample, similar to hanging curtains. This effect can obscure or distort the microscopic structural features of the sample, making analysis difficult or inaccurate. Summary of the Invention

[0003] This application provides a method for preparing a heterogeneous structure transmission sample, aiming to weaken the curtain effect generated by thinning of the heterogeneous structure.

[0004] To achieve the above object, an embodiment of this application provides a method for preparing a heterogeneous structure transmission sample, including:

[0005] Fix the heterogeneous structure on a support column. The heterogeneous structure includes a substrate, a conductive column, and a plurality of device layers. The substrate includes opposite first and second surfaces, and the conductive column extends from the first surface into the substrate; the plurality of device layers are sequentially stacked on the first surface; the extending direction of the conductive column is perpendicular to the length direction of the support column;

[0006] Use a focused ion beam to etch the heterogeneous structure to thin the thickness of the heterogeneous structure. The incident direction of the focused ion beam forms an obtuse angle with the extending direction of the conductive column.

[0007] In some embodiments, before fixing the heterogeneous structure on the support column, the preparation method further includes:

[0008] Provide the heterogeneous structure and the support column, and the extending direction of the conductive column is parallel to the length direction of the support column;

[0009] Rotate the heterogeneous structure by 90°, so that the extending direction of the conductive column is perpendicular to the length direction of the support column.

[0010] In some embodiments, after fixing the heterostructure on the support pillar and before etching the heterostructure, the preparation method further includes:

[0011] Rotating the support pillar by 15° to 30° to drive the rotation of the heterostructure, so that the included angle between the incident direction of the focused ion beam and the extending direction of the conductive pillar is an obtuse angle.

[0012] In some embodiments, after rotating the support pillar by 15° to 30° and before etching the heterostructure, the preparation method further includes:

[0013] Removing a part of the heterostructure close to the focused ion beam, so that the surface of the heterostructure close to the focused ion beam is perpendicular to the incident direction of the focused ion beam;

[0014] Forming a protective layer, and the protective layer covers the surface of the heterostructure close to the focused ion beam.

[0015] In some embodiments, before etching the heterostructure, the preparation method further includes:

[0016] Rotating the support pillar by 1.2° to 2.5° to drive the rotation of the heterostructure;

[0017] The rotation axis of the support pillar is perpendicular to the incident direction of the focused ion beam and perpendicular to the thickness direction of the heterostructure.

[0018] In some embodiments, along the thickness direction of the heterostructure, the heterostructure includes opposite first and second ends, and a target observation part located between the first end and the second end;

[0019] Etching the heterostructure includes:

[0020] Using a focused ion beam to etch the first end and the second end, and retaining the target observation part.

[0021] In some embodiments, etching the first end and the second end includes:

[0022] Performing a first etching on the first end and the second end, and the depth of the first etching is less than the dimension of the heterostructure along the incident direction of the focused ion beam.

[0023] In some embodiments, etching the first end and the second end further includes:

[0024] The first end portion and the second end portion are etched for a second time. The depth of the second etching is greater than the depth of the first etching and less than the dimension of the heterostructure along the incident direction of the focused ion beam.

[0025] In some embodiments, etching the first end portion and the second end portion further includes:

[0026] The first end portion and the second end portion are etched for a third time. The depth of the third etching is the same as the depth of the second etching;

[0027] After the third etching, both the first end portion and the second end portion include a first part close to the second surface and a second part far from the second surface;

[0028] After the third etching, the preparation method further includes:

[0029] The second parts of the first end portion and the second end portion are etched at least once.

[0030] In some embodiments, the second parts of the first end portion and the second end portion are etched multiple times so that the thickness of the thinnest part of the target observation portion is less than or equal to 10 nm.

[0031] An embodiment of the present application provides a method for preparing a transmission sample of a heterostructure, including: fixing the heterostructure on a support column. The heterostructure includes a substrate, a conductive column, and multiple device layers. The substrate includes opposite first and second surfaces. The conductive column extends from the first surface into the substrate; the multiple device layers are sequentially stacked on the first surface; the extending direction of the conductive column is perpendicular to the length direction of the support column; a focused ion beam is used to etch the heterostructure to reduce the thickness of the heterostructure. The included angle between the incident direction of the focused ion beam and the extending direction of the conductive column is an obtuse angle. The present invention combines the process of extracting the sample at a 90-degree turn and inclined thinning. During the thinning process of the heterostructure, the influence of the curtain effect is weakened, and the processing of the observation area with a relatively thin thickness at the interface is realized.

[0032] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be understood through the practice of the present application. Description of the Drawings

[0033] The above and / or additional aspects and advantages of the present application will become apparent and easy to understand from the description of the embodiments in conjunction with the following drawings, where:

[0034] Figure 1 is a schematic diagram of a corner structure of a transmission sample of a heterostructure provided by an embodiment of the present application;

[0035] Figure 2 Schematic diagram of a heterogeneous structure transmission sample structure provided by an embodiment of the present application;

[0036] Figure 3 Flow schematic diagram of a method for processing a transmission sample using a focused ion beam provided by an embodiment of the present application;

[0037] Figure 4 Specific process schematic diagram of thinning a transmission sample using a focused ion beam provided by an embodiment of the present application;

[0038] Figure 5 Schematic diagram of another heterogeneous structure transmission sample structure provided by an embodiment of the present application;

[0039] Figure 6 Schematic diagram and FIB operation diagram of extracting a heterogeneous structure transmission sample with a 90° rotation angle provided by an embodiment of the present application: (a-c) Weld the sample on the support post after rotating it by 90°; (d-f) After vertical extraction, rotate it by 90° and then weld it;

[0040] Figure 7 Top view of a heterogeneous structure transmission sample structure provided by an embodiment of the present application;

[0041] Figure 8 Effect diagrams of thinning operation (a), front thinning (b), and back thinning (c) of a support post rotating 15 degrees in a heterogeneous structure transmission sample provided by an embodiment of the present application;

[0042] Figure 9 TEM observation results of a heterogeneous structure transmission sample provided by an embodiment of the present application: (a) Bright field image of a thin area with a thickness of less than 10 nm observed by a STEM probe and (b) Image collected by a DF2 probe; (c) The iDPC diagram shows the position of oxygen atoms in the HfOx thin film, and (d) The DPC diagram shows the distribution of the electric field strength corresponding to the oxygen atoms. Detailed implementation manners

[0043] Next, in conjunction with the accompanying drawings, the technical solutions in some embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments provided by the present application, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present application.

[0044] Unless otherwise required by the context, throughout the specification and claims, the term "comprising" is interpreted as open and inclusive, that is, "including, but not limited to".

[0045] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the embodiments of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0046] When describing some embodiments, the expression "connected" and its derivatives may be used. The term "connected" should be understood in a broad sense. For example, "connected" may be a fixed connection, a detachable connection, or integrated; it may be directly connected or indirectly connected through an intermediate medium. For example, when describing some embodiments, the term "connected" may be used to indicate that two or more components have direct physical contact or electrical contact with each other.

[0047] In addition, the use of "based on" means open and inclusive, because a process, step, calculation, or other action "based on" one or more of the stated conditions or values may, in practice, be based on additional conditions or values beyond those stated.

[0048] It should be understood that when a layer or element is referred to as being on another layer or substrate, it may be directly on the other layer or substrate, or there may be an intermediate layer between the layer or element and the other layer or substrate.

[0049] Exemplary embodiments are described herein with reference to cross-sectional views that are idealized exemplary drawings. In the drawings, the thickness of layers and the area of regions are exaggerated for clarity. Thus, variations in the shape relative to the drawings due to, for example, manufacturing techniques and / or tolerances are contemplated. Therefore, the exemplary embodiments should not be construed as limited to the shapes of the regions shown herein, but rather include shape deviations caused, for example, by manufacturing. Thus, the regions shown in the drawings are schematic in nature, and their shapes are not intended to show the actual shape of the regions of the device and are not intended to limit the scope of the exemplary embodiments.

[0050] Examples of the embodiments are shown in the drawings, where like or similar reference numerals designate like or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary only for explaining the present application and should not be construed as limiting the present application.

[0051] A heterostructure is a system composed of two or more material layers with different electronic and optical properties. These structures are crucial because they possess unique properties and functions that arise from the interfaces between different materials. The concept of heterostructures is of great importance in both academic and industrial fields. In academia, the interest in heterostructures mainly revolves around their fundamental electronics, optics, and magnetism. Researchers have studied how the interactions at the interfaces between different semiconductor materials lead to new physical phenomena. In the semiconductor industry, heterostructure device design plays a crucial role as they obtain enhanced properties by combining different semiconductor materials. These devices utilize the unique electronics, optics, and magnetism that occur at the interfaces between different materials. The continuous innovation of heterostructure technology has been driving the progress of various high-tech industries, making it a key area in academic research and industrial development.

[0052] Transmission electron microscopy (TEM) is a key tool for characterizing heterostructures and can provide important insights that are valuable both academically and industrially. TEM offers high-resolution imaging and analysis capabilities, enabling researchers and engineers to observe and understand the atomic and electronic structures of materials. This understanding is crucial for developing devices that utilize the unique properties of heterostructures.

[0053] However, there are significant difficulties in preparing TEM samples of heterostructure devices. Due to the different sputtering rates of ion beam machining for different materials, harder materials are sputtered more slowly than softer regions, resulting in a "curtain effect" often occurring at the junction of the two materials. It appears as a series of parallel wavy stripes or curtains on the milled surface of the sample, similar to hanging curtains. This effect can obscure or distort the microscopic structural features of the sample, making analysis difficult or inaccurate.

[0054] To solve the above problems, the embodiments of this application use two means, namely operation techniques and rotation angles, to change the angle between the ion beam and the heterostructure interface, as Figure 1 shown. In conjunction with the optimization of thinning parameters, it has achieved weakening the curtain effect generated by heterostructure thinning, including two cases of heterointerfaces, horizontal interfaces and vertical interfaces. And by adjusting the thinning parameters, a thin region with a thickness below 10 nm in the target area has been obtained.

[0055] Figure 3 FIG. is a schematic flow chart of a method for processing a transmission sample using a focused ion beam provided by an embodiment of this application. Figure 4 FIG. is a schematic specific flow chart of thinning a transmission sample using a focused ion beam provided by an embodiment of this application.

[0056] As Figure 3 shown, processing a transmission sample using a focused ion beam includes the following steps:

[0057] Step S301: Fix the heterostructure on the support column. The heterostructure includes a substrate, a conductive column, and a plurality of device layers. The substrate includes opposite first and second surfaces. The conductive column extends from the first surface into the substrate. The plurality of device layers are sequentially stacked on the first surface. The extending direction of the conductive column is perpendicular to the length direction of the support column.

[0058] Exemplarily, as Figure 2 shown, prepare a transmission sample to be thinned, ensuring that its surface is clean and free of contamination. The transmission sample is a heterostructure 101, where the heterostructure 101 includes a substrate 1011, a conductive column 1012, and a plurality of device layers 1013. The substrate 1011 includes opposite first surface P1 and second surface P2. Among them, the conductive column 1012 extends from the first surface P1 into the substrate 1011. The plurality of device layers 1013 are sequentially stacked on the first surface P1, and the surface of the support column 102 needs to be treated to ensure good contact and adhesion between it and the heterostructure 101. Welding technology can be used to connect the heterostructure 101 and the support column 102 together, and the extending direction of the conductive column 1012, i.e., the X direction, is perpendicular to the length direction of the support column 102, i.e., the Y direction, while ensuring that the sample is stable and its position can be precisely controlled.

[0059] Step S302: Use a focused ion beam to etch the heterostructure to thin the thickness of the heterostructure. The incident direction of the focused ion beam forms an obtuse angle with the extending direction of the conductive column.

[0060] Exemplarily, as Figure 1 shown, on the TEM sample stage, the support column 102 is placed obliquely so that the incident direction of the focused ion beam (FIB), i.e., the Y direction, forms an obtuse angle with the extending direction of the conductive column 1012. Then, use FIB to etch the heterostructure 101 to thin the thickness of the heterostructure 101.

[0061] An embodiment of the present application provides a method for preparing a heterogeneous structure transmission sample, including: fixing the heterogeneous structure 101 on the support column 102. The heterogeneous structure 101 includes a substrate 1011, a conductive column 1012, and a plurality of device layers 1013. The substrate 1011 includes opposite first surface P1 and second surface P2. The conductive column 1012 extends from the first surface P1 into the substrate 1011; the plurality of device layers 1013 are sequentially stacked on the first surface P1; the extending direction of the conductive column 1012 is perpendicular to the length direction of the support column 102; using a focused ion beam to etch the heterogeneous structure 101 to thin the thickness of the heterogeneous structure 101, and the incident direction of the focused ion beam forms an obtuse angle with the extending direction of the conductive column 1012. The present invention combines the process of extracting the sample at a 90-degree rotation and inclined thinning. During the thinning process of the heterogeneous structure, the influence of the curtain effect is weakened, and the processing of the observation area with a relatively thin thickness at the interface is realized.

[0062] The specific operation steps are as follows:

[0063] As Figure 4 shown, using a focused ion beam to thin the transmission sample specifically includes the following steps:

[0064] Step S401: Provide the heterogeneous structure 101 and the support column 102, and the extending direction of the conductive column 1012 is parallel to the length direction of the support column 102; rotate the heterogeneous structure 101 by 90°, so that the extending direction of the conductive column 1012 is perpendicular to the length direction of the support column 102.

[0065] Exemplarily, as Figure 6 a shows, using conventional sample preparation techniques, such as cutting, grinding, polishing, etc. to process the required thin slice, i.e., the heterogeneous structure 101, and then using a precise welding technique to weld the processed heterogeneous structure 101 to the tip of the robotic arm, ensuring that its surface is clean and pollution-free. At this time, the heterogeneous structure 101 is horizontally placed. Then rotate the tip counterclockwise by 180 degrees. At this time, the horizontal surface of the original heterogeneous structure 101 is rotated into a 90° vertical cross-section, as Figure 6 b shows. After rotation, the conductive column 1012 in the heterogeneous structure 101 changes from the original vertical direction, i.e., the Y direction, to the horizontal direction, the X direction. Then weld the rotated heterogeneous structure 101 to the support column 102, as Figure 6 c shows. Such a welding structure design can reduce the curtain effect between the conductive column 1012 and the substrate 1011.

[0066] Step S402: After fixing the heterogeneous structure 101 on the support column 102, rotate the support column 102 by 15° to 30°, driving the heterogeneous structure 101 to rotate, so that the incident direction of the focused ion beam forms an obtuse angle with the extending direction of the conductive column 1012.

[0067] Exemplarily, as Figure 1 shown, after fixing the heterostructure 101 onto the support post 102, rotate the support post 102. The purpose of this step is to change the angle of the heterostructure 101 relative to the incident direction of the focused ion beam, so as to optimize the processing effect of the focused ion beam. The rotation angle range is 15° to 30°, so that an obtuse angle is formed between the incident direction of the focused ion beam and the extending direction of the conductive post 1012. Thinning by the rotation angle can reduce the occurrence of the curtain effect in the device layer 1013 region of the horizontal structure, resulting in uneven thickness or excessive local layer damage. However, the specific angle needs to be determined according to the characteristics of the heterostructure 101, the parameters of the focused ion beam, and the required processing effect. During the rotation process, ensure the smoothness and accuracy of the rotation to avoid unnecessary damage or deformation to the heterostructure 101.

[0068] Step S403: Remove the part of the heterostructure 101 close to the focused ion beam, so that the surface of the heterostructure 101 close to the focused ion beam is perpendicular to the incident direction of the focused ion beam; form a protective layer 103, and the protective layer 103 covers the surface of the heterostructure 101 close to the focused ion beam.

[0069] Exemplarily, as Figure 5 shown, remove the part of the heterostructure 101 close to the focused ion beam, so that the surface of the heterostructure 101 close to the focused ion beam is perpendicular to the incident direction of the focused ion beam, and then form a protective layer 103 by focused ion beam induced chemical vapor deposition (FIB-CVD) or direct ion beam deposition technology, where the protective layer 103 covers the surface of the heterostructure close to the focused ion beam.

[0070] Step S404: Rotate the support post 102 by 1.2° to 2.5° to drive the rotation of the heterostructure 101; the rotation axis of the support post 102 is perpendicular to the incident direction of the focused ion beam and perpendicular to the thickness direction of the heterostructure 101.

[0071] Exemplarily, rotate the support post 102 by 1.2° to 2.5° along the Z direction to drive the rotation of the heterostructure 101; the rotation axis of the support post 102 is perpendicular to the incident direction Y of the focused ion beam and perpendicular to the thickness direction of the heterostructure 101. The purpose is to make the FIB act on the target area and reduce the curtain effect.

[0072] Step S405: Along the thickness direction of the heterostructure 101, the heterostructure 101 includes opposite first and second ends, and a target observation part located between the first end and the second end; etch the heterostructure 101, including: using a focused ion beam to etch the first end and the second end, and retain the target observation part.

[0073] Exemplarily, the target observation area is located at the center of the conductive column 1012, and it is necessary to position and thin down to the conductive column 1012. Therefore, it is necessary to perform thinning that can be observed from both sides, that is, it is necessary to thin the first end 104 and the second end 105 of the heterostructure 101 along the thickness direction of the heterostructure 101, as Figure 7 and Figure 8 shown in Figures 8b and 8c. A sample stage in a 90-degree vertical manner can perform this operation. Such a sample stage allows the sample to be rotated 90 degrees, so that observation and processing can be performed on different planes.

[0074] Step S406: Etch the first end and the second end, including: performing a first etch on the first end and the second end, and the depth of the first etch is less than the size of the heterostructure 101 along the incident direction of the focused ion beam.

[0075] Exemplarily, for the first etch of the first end 104 and the second end 105, a step-by-step cutting mode is adopted. The ion beam voltage and current are set to 30 KV and 0.23 nA. The transmission sample, that is, the heterostructure 101, is tilted 1.5 degrees along the Z direction. For the first etch of the first end 104 and the second end 105, the etch depth is the micron number of the overall longitudinal width of the sample minus 3 um. For example, if the overall width of the sample is 5 um and after adding the thickness of the deposition layer 103 it is 7.5 um, then the depth during rough cutting with 0.23 nA should be set to 4.5 um. By using such a depth setting, a bottom support cross beam with a width of 1 - 2 um can be retained to avoid bending deformation after the thickness of the film inside the frame becomes thinner. Under the ion beam of 0.23 nA, the thickness of the sample thin slice is thinned to 500 nm along the Z direction.

[0076] Step S407: Perform a second etch on the first end and the second end. The depth of the second etch is greater than the depth of the first etch and less than the size of the heterostructure 101 along the incident direction of the focused ion beam.

[0077] Exemplarily, for the second etch of the first end 104 and the second end 105, a step-by-step cutting mode is adopted. The ion beam voltage and current are set to 30 KV and 80 pA. The thin slice is tilted 1.5 degrees along the Z direction. The cutting depth is the rough cutting depth plus 1.5 um and less than the size of the heterostructure 101 along the incident direction of the focused ion beam. By using such a depth setting, it can be ensured that the thickness of the thinning plane of the heterostructure 101 is uniform and a wedge-shaped thickness gradient will not be formed at the bottom. Under the ion beam of 80 pA, the thickness of the sample thin slice is thinned to 500 nm.

[0078] Step S408: Perform a third etching on the first end portion and the second end portion. The depth of the third etching is the same as that of the second etching. After the third etching, both the first end portion and the second end portion include a first part close to the second surface and a second part away from the second surface. After the third etching, perform at least one etching on the second parts of the first end portion and the second end portion.

[0079] Exemplarily, perform a third etching on the first end portion 104 and the second end portion 105. The depth of the third etching is the same as that of the second etching. Adopt a step-by-step cutting mode. The ion beam voltage and current are set to 30 KV and 40 pA, which is consistent with the setting in step S207. The thin slice is tilted 1.5 degrees along the Z direction. The cutting depth is the rough cutting depth plus 1.5 um, i.e., 6 um, and the thickness of the sample thin slice along the Z direction is thinned to 300 nm. After the third etching, both the first end portion 104 and the second end portion 105 include a first part B1 close to the second surface P2 and a second part B2 away from the second surface P2, as Figure 7 shown; after the third etching, it is necessary to perform at least one etching on the second parts B2 of the first end portion 104 and the second end portion 105.

[0080] Step S409: Perform multiple etchings on the second parts of the first end portion and the second end portion to make the thickness of the thinnest part of the target observation portion less than or equal to 10 nm.

[0081] Exemplarily, for the thinning of the target area, that is, perform multiple etchings on the second parts B2 of the first end portion 104 and the second end portion 105. Adopt an overall cutting mode to make the thickness of the thinnest part of the target observation portion less than or equal to 10 nm. The specific thinning steps are as follows:

[0082] (1) Tilt the thin slice 1.2 degrees along the Z direction. Adopt an overall cutting mode. The ion beam voltage and current are set to 16 KV and 23 pA, and the depth is set to 0.3 um. Thin the target observation portion and process the thickness to 150 nm. When observing with a 3 KV electron beam, the target observation portion should present a semi-translucent state. If the above state is not reached, continue to thin with this parameter until the target thickness is achieved.

[0083] (2) Consistent with the setting in step (1), adopt the parameters of 8 KV and 21 pA to thin the thickness of the sample thin slice to 80 nm. When observing with a 3 KV electron beam, the target observation portion should present a semi-translucent state.

[0084] (3) The thin slice is tilted 2 degrees along the Z direction. In the overall cutting mode, the ion beam voltage and current are set to 5 KV and 7 pA respectively, and the thinning time is set to 20 s. The target observation part is thinned until the thickness is processed to 30 nm. When observing with a 2 KV electron beam, the target observation part should present a semi-translucent state.

[0085] (4) The thin slice is tilted 2.5 degrees along the Z direction. In the overall cutting mode, the ion beam voltage and current are set to 2 KV and 9 pA respectively, and the thinning time is set to 20 s. The target observation part is thinned until the thickness is processed to 10 nm. When observing with a 2 KV electron beam, the target observation part should present a fully-translucent state.

[0086] The effect of the Scanning Transmission Electron Microscopy (STEM) thinned using the above FIB sample preparation parameters is as Figure 9 shown in FIGS. 9a and 9b. On the FIB equipment equipped with a STEM probe, preliminary observation of the thin area can be carried out. The device stack structure used in this example is TiN / TaOx / HfOx(8 nm) / TiN / W. After the sample is subjected to corner bevel cutting, in the DF2 observation mode of the STEM probe, significant polycrystalline grain contrast can be observed in the W metal layer, which indicates that the thickness of the sample has reached 10 nm and can be used for subsequent TEM characterization. The sample prepared by the present invention can provide a very clear transmission image with atomic resolution, as Figure 9 shown in FIGS. 9c and 9d. By using the Differential Phase Contrast (DPC) technique to observe such a sample, the distribution of oxygen atoms in HfOx and the atomic electric field distribution corresponding to the oxygen atoms can be observed. These information provide very important data support for exploring the physical mechanism of the material.

[0087] The sample preparation method designed by the present invention has the following two advantages:

[0088] First, the sample preparation method designed by the present invention combines the operation techniques of 90-degree corner welded thin slices and inclined thinning. By optimizing the thinning parameters, the preparation of heterogeneous structure samples with a thickness below 10 nm is realized. Using the operation scheme designed by the present invention, the target observation area is transferred to the middle of the thin slice. By controlling the angle between the front thinning and the back thinning, the thin area of the sample can be located in the area with a smaller ion beam thinning angle, which helps to obtain a thinning thickness below 10 nm. It can be seen from the results of TEM characterization that the sample prepared by the present invention improves the clarity and accuracy of collecting transmission electron microscope data.

[0089] Second, the sample preparation method designed by the present invention effectively reduces the curtain effect at the heterostructure interface. After the operations of 90-degree corner welding and inclined placement, the angle between the W / SiO2 interface and the ion beam incident direction changes from parallel to obtuse, and such a relative position maximally reduces the curtain effect on this soft-hard interface. At the same time, the W hard material is sufficiently thinned to avoid excessive W thickness, which may affect the thinning and observation of the HfOx layer, thus improving the effectiveness of TEM sample preparation and characterization.

[0090] As described above, the above are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application, thinking of changes or substitutions, should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing a heterostructure transmission sample, characterized in that: include: The heterostructure is fixed on the support column, wherein the heterostructure includes a substrate, a conductive column and a plurality of device layers, wherein the substrate includes a first surface and a second surface opposite to each other, the conductive column extends from the first surface into the substrate; the plurality of device layers are sequentially stacked on the first surface; and the extension direction of the conductive column is perpendicular to the length direction of the support column; The heterostructure is etched by using a focused ion beam to reduce the thickness of the heterostructure, and the angle between the incident direction of the focused ion beam and the extension direction of the conductive column is an obtuse angle.

2. The preparation method according to claim 1, characterized in that: Before fixing the heterogeneous structure on the support column, the preparation method further comprises: Providing the heterostructure and the support column, wherein the extension direction of the conductive column is parallel to the length direction of the support column; The heterostructure is rotated 90° so that the extension direction of the conductive column is perpendicular to the length direction of the support column.

3. The preparation method according to claim 1, characterized in that: After fixing the heterostructure on the support column and before etching the heterostructure, the preparation method further comprises: The support column is rotated 15° to 30° to drive the heterostructure to rotate, so that the angle between the incident direction of the focused ion beam and the extension direction of the conductive column is an obtuse angle.

4. The preparation method according to claim 3, characterized in that: After rotating the support column by 15° to 30° and before etching the heterostructure, the preparation method further comprises: Removing a portion of the heterostructure close to the focused ion beam so that a surface of the heterostructure close to the focused ion beam is perpendicular to an incident direction of the focused ion beam; A protection layer is formed, wherein the protection layer covers a surface of the heterostructure close to the focused ion beam.

5. The preparation method according to claim 1, characterized in that: Before etching the heterostructure, the preparation method further comprises: Rotating the support column by 1.2° to 2.5° to drive the heterostructure to rotate; The rotation axis of the support column is perpendicular to the incident direction of the focused ion beam and perpendicular to the thickness direction of the heterostructure.

6. The preparation method according to claim 1, characterized in that: Along the thickness direction of the heterostructure, the heterostructure includes a first end and a second end opposite to each other, and a target observation portion located between the first end and the second end; Etching the heterostructure, comprising: The first end and the second end are etched by using a focused ion beam to retain the target observation portion.

7. The preparation method according to claim 6, characterized in that: Etching the first end portion and the second end portion comprises: The first end portion and the second end portion are first etched, and a depth of the first etching is smaller than a dimension of the heterostructure along an incident direction of the focused ion beam.

8. The preparation method according to claim 7, characterized in that: Etching the first end and the second end, further comprising: The first end portion and the second end portion are etched for a second time, wherein a depth of the second etching is greater than a depth of the first etching and is smaller than a dimension of the heterostructure along an incident direction of the focused ion beam.

9. The preparation method according to claim 8, characterized in that: Etching the first end and the second end, further comprising: Performing a third etching on the first end portion and the second end portion, wherein the depth of the third etching is the same as the depth of the second etching; After the third etching, the first end and the second end both include a first portion close to the second surface and a second portion away from the second surface; After the third etching, the preparation method further comprises: The second portion of the first end portion and the second end portion are etched at least once.

10. The preparation method according to claim 9, characterized in that: The second portion of the first end portion and the second end portion is etched multiple times so that the thickness of the thinnest portion of the target observation portion is less than or equal to 10 nm.

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