Method for preparing a fibrous sheet

Abstract

The present disclosure provides a method for preparing a FIB slice, comprising: rotating a raw sample to a coaxial angle, and the incident direction of a focused ion beam is perpendicular to the surface of the raw sample; cutting the raw sample by using the focused ion beam to obtain an initial sample, which has a first cutting surface and a second cutting surface, and a top surface; fixing the initial sample on the supporting wall of a carrier net; adjusting the angle of the carrier net or adjusting the tilt angle of the FIB machine, so that the initial sample is rotated to the coaxial angle; cutting the second cutting surface by using the focused ion beam to obtain an initial slice with a first side surface; adjusting the angle of the carrier net, so that the top surface is perpendicular to the incident angle of the electron beam; imaging by using SEM to measure the first height of the first side surface, the top width and the bottom width; calculating a compensation angle by using a trigonometric function, and adding / subtracting the compensation angle to the coaxial angle to obtain a corrected angle. By using the above scheme, the thickness uniformity of the slice can be improved.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor manufacturing and failure analysis technology, and in particular to a method for preparing thin films using FIB (fiber-insulated wafers). Background Technology

[0002] In semiconductor manufacturing, transmission electron microscopy (TEM) is typically used to detect and measure structures with high precision in order to confirm the presence of process defects or whether the process structure meets the standards.

[0003] However, traditional TEM sample preparation is affected by the energy decay from top to bottom during focused ion beam milling, which cannot guarantee the uniformity of the thickness of the entire thin region of the TEM sample. The non-uniformity of the thickness of the thin region of the TEM sample will reduce the quality of the TEM image.

[0004] Therefore, how to provide technical solutions to improve the thickness uniformity of thin films has become an urgent technical problem to be solved. Summary of the Invention

[0005] In view of this, the present disclosure provides a method for preparing thin films using FIB, which can improve the thickness uniformity of the thin films.

[0006] This disclosure provides a method for preparing thin films using FIB (Film Preparation by Focused Ion Beam), comprising: rotating an original sample along a first direction to a coaxial angle, the coaxial angle being used to make the incident direction of the focused ion beam perpendicular to the surface of the original sample, the first direction being selected from counterclockwise rotation or clockwise rotation; cutting the original sample using the focused ion beam to obtain an initial sample having a target structure, the initial sample having adjacent first and second cutting surfaces, and a top surface adjacent to the first and second cutting surfaces; fixing the initial sample to a support wall of a grid, with the first cutting surface in contact with the support wall; adjusting the angle of the grid, or adjusting the tilt angle of the FIB stage, so that the initial sample along... The first direction of rotation is the coaxial angle; wherein the top surface of the initial sample is perpendicular to the incident direction of the focused ion beam; the second cutting surface is cut using the focused ion beam until the cross-section of the target structure is exposed, resulting in an initial sheet; wherein the initial sheet has a first side surface fixed to the support wall of the carrier mesh, a top plane adjacent to the first side surface, and a bottom plane, and the first side surface is trapezoidal; the first height, top width, and bottom width of the first side surface are measured using SEM imaging; based on the first height, top width, and bottom width, a compensation angle is calculated using trigonometric functions, and the compensation angle is added / subtracted from the coaxial angle to obtain a correction angle.

[0007] Optionally, the method satisfies one or more of the following combinations: the first height is the distance from the top plane to the bottom plane of the initial sheet; the first height is the distance from the top plane to the bottom plane adjacent to the first and second cutting surfaces.

[0008] Optionally, the method includes: The formula used to calculate the compensation angle is:

[0009] in, Here, is the compensation angle; a is the length of the opposite side corresponding to the compensation angle |(W1-W2)| / 2, which is half the absolute value of the difference between the top width W1 and the bottom width W2; b is the first height; The formula used to calculate the correction angle is:

[0010] Where T is the correction angle. The coaxial angle is... The compensation angle is [value].

[0011] Optionally, the step of calculating the compensation angle based on the first height, top width, and bottom width using trigonometric functions, and then adding / subtracting the compensation angle from the coaxial angle to obtain the correction angle, further includes: adjusting the mesh angle, or adjusting the tilt angle of the FIB machine, so that the initial sheet rotates along the first direction to a first correction angle equal to the sum of the coaxial angle and the compensation angle; cutting the second side of the initial sheet using a focused ion beam; adjusting the mesh angle, or adjusting the tilt angle of the FIB machine, so that the initial sheet rotates along the first direction to a second correction angle equal to the difference between the coaxial angle and the compensation angle; and cutting the side opposite to the second side using a focused ion beam to obtain a sheet of uniform thickness; wherein the second side is adjacent to the first side.

[0012] Optionally, the step of calculating the compensation angle based on the first height, top width, and bottom width using trigonometric functions, and then adding / subtracting the compensation angle to obtain the correction angle based on the coaxial angle, further includes: rotating the second original sample along the first direction to a coaxial angle, wherein the coaxial angle makes the incident direction of the focused ion beam perpendicular to the surface of the second original sample; cutting the second original sample with the focused ion beam to obtain a second initial sample with the target structure; wherein the second initial sample has adjacent first and second cutting surfaces; adjusting the mesh angle, or adjusting the tilt angle of the FIB stage, so that the second initial sample rotates along the first direction to a third correction angle equal to the sum of the coaxial angle and the compensation angle; cutting the second cutting surface of the second initial sample with the focused ion beam; adjusting the mesh angle, or adjusting the tilt angle of the FIB stage, so that the initial sample rotates along the first direction to a fourth correction angle equal to the difference between the coaxial angle and the compensation angle; and cutting the opposite side of the second cutting surface of the second initial sample with the focused ion beam to obtain a thin sheet of uniform thickness.

[0013] Optionally, after obtaining the uniformly thick sheet, the method further includes: using SEM imaging to measure the top width and bottom width of the sheet; calculating the difference between the top width and bottom width of the sheet; wherein, if the difference is greater than a preset threshold, a new compensation angle is calculated using trigonometric functions based on the first height, the top width and bottom width of the sheet, and the new compensation angle is added / subtracted from the coaxial angle to obtain a new correction angle, and the ion beam cutting step is repeated until the difference is less than or equal to the preset threshold; the preset threshold ranges from 1 nm to 5 nm.

[0014] Optionally, the compensation angle can be added or subtracted based on the coaxial angle, including: when the top width is less than the bottom width, determining that the first side of the initial sheet is a trapezoid with a narrow top and a wide bottom, and adding the compensation angle to the coaxial angle; when the top width is greater than the bottom width, determining that the first side of the initial sheet is a trapezoid with a wide top and a narrow bottom, and subtracting the compensation angle from the coaxial angle.

[0015] Optionally, prior to the step of cutting the original sample using a focused ion beam, the method further includes: depositing a protective layer on the top plane of the original sample using a FIB; the protective layer is made of any one of platinum, carbon, or tungsten, and has a deposition thickness of 0.5 μm to 2 μm.

[0016] Optionally, the step of cutting the second cutting surface with a focused ion beam until the cross-section of the target structure is exposed includes: the beam current intensity of the focused ion beam is 50 pA to 500 pA, and the accelerating voltage is 5 kV to 30 kV; the cutting adopts a layer-by-layer scanning mode, and the single scan step depth is 10 nm to 50 nm.

[0017] Optionally, the initial thin film is cut using a focused ion beam in a layer-by-layer scanning mode, with a single scan step depth of 1 nm to 5 nm.

[0018] Compared with the prior art, the technical solution of the present disclosure has the following advantages: The method for preparing a thin film using FIB (Focus Ion Beam) according to embodiments of this disclosure includes: rotating the original sample to a coaxial angle so that the incident direction of the focused ion beam is perpendicular to the surface of the original sample; cutting the original sample using the focused ion beam to obtain an initial sample having adjacent first and second cut surfaces and a top surface; imaging with a scanning electron microscope (SEM) to measure the first height of the initial sample; fixing the initial sample to the support wall of a grid; adjusting the grid angle, or adjusting the tilt angle of the focused ion beam (FIB) stage, so that the initial sample is rotated to a coaxial angle; cutting the second cut surface using the focused ion beam to obtain an initial thin film with a first side surface; adjusting the grid angle so that the top plane is perpendicular to the incident angle of the electron beam; imaging with SEM to measure the top width and bottom width of the first side surface; calculating a compensation angle using trigonometric functions, and adding / subtracting the compensation angle from the coaxial angle to obtain a correction angle. By cutting the sample at a coaxial angle, the first side surface naturally forms a trapezoid that visually reflects the difference in thinning between the upper and lower parts. The width of the upper and lower bases and the height of the sample were precisely measured using SEM, and the compensation angle was calculated using trigonometric functions. Based on the coaxial angle, the compensation angle was used for correction, allowing the ion beam to selectively process the bottom of the initial sample first, thus offsetting the thinning difference caused by the energy decaying from top to bottom. This resulted in a more uniform thickness across the entire slice, effectively avoiding imaging blurring or measurement deviations caused by uneven thickness during large-area observation. Therefore, this method significantly improves the thickness uniformity of FIB-prepared slices, providing more reliable samples for subsequent high-precision TEM observation. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments disclosed in this specification, the drawings used in the description of the embodiments disclosed in this specification or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart illustrating a method for preparing thin films using FIB (fiber permeation). Figure 2 This is a schematic cross-sectional view of an original sample in an embodiment of this disclosure. Figure 3 This is a schematic cross-sectional view of an initial sample according to an embodiment of this disclosure; Figure 4 This is a three-dimensional structural schematic diagram of an initial sample according to an embodiment of this disclosure; Figure 5 This is a schematic cross-sectional view of another initial sample in an embodiment of this disclosure; Figure 6 This is a schematic diagram of an initial sample fixed to a carrier net in an embodiment of this disclosure; Figure 7 This is a schematic diagram of an initial sheet fixed to a carrier net in an embodiment of this disclosure; Figure 8 This is a schematic cross-sectional view of an initial sheet in an embodiment of this disclosure; Figure 9 This is a schematic diagram of an initial sheet fixed to a carrier net in an embodiment of this disclosure; Figure 10 This is a schematic diagram of a structure in which a thin sheet is fixed to a carrier net according to an embodiment of the present disclosure; Figure 11 This is a schematic diagram of a second initial sample fixed to a carrier net in an embodiment of this disclosure. Detailed Implementation

[0021] The technical solutions described herein will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of this disclosure and are used to illustrate the concept of this disclosure. These descriptions are illustrative and exemplary and should not be construed as limiting the implementation methods or the scope of protection of this disclosure. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0022] It should be noted that the accompanying drawings in this embodiment are schematic diagrams used to illustrate the concept of this disclosure, and to schematically show the shape and interrelationship of each part. It should be understood that, in order to clearly show the structure of each component of this disclosure, the drawings are not drawn to the same scale, and the same reference numerals are used to indicate the same parts in the drawings.

[0023] In semiconductor manufacturing, transmission electron microscopy (TEM) is typically used to detect and measure structures with high precision in order to confirm the presence of process defects or whether the process structure meets the standards.

[0024] However, traditional TEM sample preparation is affected by the energy decay from top to bottom during focused ion beam milling, which cannot guarantee the uniformity of the thickness of the entire thin region of the TEM sample. The non-uniformity of the thickness of the thin region of the TEM sample will reduce the quality of the TEM image.

[0025] Therefore, how to provide technical solutions to improve the thickness uniformity of thin films has become an urgent technical problem to be solved.

[0026] The method for preparing a thin film using FIB (Focus Ion Beam) according to embodiments of this disclosure includes: rotating the original sample to a coaxial angle so that the incident direction of the focused ion beam is perpendicular to the surface of the original sample; cutting the original sample using the focused ion beam to obtain an initial sample having adjacent first and second cut surfaces and a top surface; imaging with a scanning electron microscope (SEM) to measure the first height of the initial sample; fixing the initial sample to the support wall of a grid; adjusting the grid angle, or adjusting the tilt angle of the focused ion beam (FIB) stage, so that the initial sample is rotated to a coaxial angle; cutting the second cut surface using the focused ion beam to obtain an initial thin film with a first side surface; adjusting the grid angle so that the top plane is perpendicular to the incident angle of the electron beam; imaging with SEM to measure the top width and bottom width of the first side surface; calculating a compensation angle using trigonometric functions, and adding / subtracting the compensation angle from the coaxial angle to obtain a correction angle. By cutting the sample at a coaxial angle, the first side surface naturally forms a trapezoid that visually reflects the difference in thinning between the upper and lower parts. The width of the upper and lower bases and the height of the sample were precisely measured using SEM, and the compensation angle was calculated using trigonometric functions. Based on the coaxial angle, the compensation angle was used for correction, allowing the ion beam to selectively process the bottom of the initial sample first, thus offsetting the thinning difference caused by the energy decaying from top to bottom. This resulted in a more uniform thickness across the entire slice, effectively avoiding imaging blurring or measurement deviations caused by uneven thickness during large-area observation. Therefore, this method significantly improves the thickness uniformity of FIB-prepared slices, providing more reliable samples for subsequent high-precision TEM observation.

[0027] To make the above-described objects, features and advantages of this disclosure more apparent and understandable, the disclosure is illustrated below with reference to the accompanying drawings.

[0028] See Figure 1 , Figure 1 This is a schematic flowchart of a method for preparing thin films using FIB (fiber permeation). The method can be performed by executing the following steps S101 to S107.

[0029] In step S101, the original sample is rotated along a first direction to a coaxial angle, the coaxial angle being used to make the incident direction of the focused ion beam perpendicular to the surface of the original sample, the first direction being selected from counterclockwise rotation or clockwise rotation.

[0030] In step S102, the original sample is cut using a focused ion beam to obtain an initial sample with the target structure. The initial sample has an adjacent first cut surface and a second cut surface, as well as a top surface adjacent to the first cut surface and the second cut surface.

[0031] In step S103, the initial sample is fixed to the support wall of the carrier mesh, and the first cut surface is in contact with the support wall.

[0032] In step S104, the angle of the carrier grid is adjusted, or the tilt angle of the FIB stage is adjusted, so that the initial sample is rotated along the first direction to the coaxial angle; wherein, the top surface of the initial sample is perpendicular to the incident direction of the focused ion beam.

[0033] In step S105, the second cutting surface is cut using a focused ion beam until the cross-section of the target structure is exposed, resulting in an initial sheet; wherein the initial sheet has a first side surface fixed to the support wall of the carrier mesh, a top plane and a bottom plane adjacent to the first side surface, and the first side surface is trapezoidal.

[0034] In step S106, SEM imaging is used to measure the first height, top width, and bottom width of the first side.

[0035] In step S107, the compensation angle is calculated using trigonometric functions based on the first height, top width, and bottom width. The compensation angle is then added to or subtracted from the coaxial angle to obtain the correction angle.

[0036] Understandably, the method for preparing thin films using FIB may include more or fewer steps, and the order of the steps may be the same or different.

[0037] The following combination Figures 2 to 11 The above methods will be explained.

[0038] See Figure 2 , Figure 2 This is a schematic cross-sectional view of an original sample in an embodiment of this disclosure.

[0039] The original sample 200 refers to the initial block sample to be processed by focused ion beam (FIB). It can be directly derived from the wafer, chip or material slice to be analyzed, and can be selectively pretreated by mechanical grinding, polishing or depositing conductive film to ensure that the surface is flat and the conductivity meets the requirements of FIB processing.

[0040] The dimensions of the original sample 200 should be compatible with the sample stage specifications of the FIB-SEM dual-beam system, generally controlled to have a length and width not exceeding 1 cm and a height not exceeding 5 mm, to ensure that it can be stably fixed on the sample stage; the original sample 200, as the starting object of the entire sample preparation process, is rotated to a coaxial angle to establish a unified ion beam processing reference, and its interior contains the target structure to be observed.

[0041] The original sample 200 is rotated along the first direction at a coaxial angle.

[0042] The coaxial angle is used to ensure that the incident direction of the focused ion beam is perpendicular to the surface of the original sample 200.

[0043] The first direction is selected from counterclockwise rotation or clockwise rotation.

[0044] Specifically, the coaxial angle refers to the angle at which the incident direction of the focused ion beam coincides with the surface normal direction of the original sample 200, i.e., the angle at which the incident direction of the focused ion beam is perpendicular to the surface of the original sample 200. In a FIB-SEM dual-beam system, the coaxial angle typically corresponds to a specific tilt angle of the sample stage (e.g., 52° or 54° relative to the horizontal plane, depending on the equipment model). At this angle, the focused ion beam can bombard the sample surface perpendicularly with normal incidence, thereby ensuring that the cut surface has optimal straightness and positional accuracy.

[0045] The first direction refers to the direction in which the sample stage rotates about its rotation axis, and the first direction is selected from the counterclockwise rotation direction or the clockwise rotation direction.

[0046] In this embodiment of the disclosure, the adjustment of the coaxial angle and all subsequent operations involving restoring to the coaxial angle are performed along the same first direction to avoid mechanical backlash and angular errors introduced by bidirectional rotation, and to ensure the consistency of the sample posture each time it is adjusted to the coaxial angle.

[0047] After adjusting the original sample 200 to a coaxial angle, it can be ensured that the ion beam is incident on the sample surface at a vertical angle during subsequent focused ion beam cutting, thereby ensuring the straightness of the cut surface and providing reliable reference conditions for obtaining initial samples with regular geometric shapes and accurately measuring sample dimensions.

[0048] It should be understood that, Figure 2 The cross-sectional structure of the original sample 200 shown is only for illustrative purposes. Its specific shape, size and internal layered distribution characteristics are determined according to the type of the actual sample to be tested and the process requirements. This disclosure does not limit these characteristics.

[0049] See also Figure 2 and Figure 3 , Figure 3 This is a schematic cross-sectional view of an initial sample in an embodiment of this disclosure. Figure 3 It can be Figure 2 The structure within the dashed box is a schematic cross-sectional view of the initial sample with the target structure obtained by cutting the original sample 200 with a focused ion beam. The two figures are not drawn to the same scale.

[0050] The initial sample 210 has the target structure.

[0051] In chip failure analysis, the target structure is the structure that needs to be observed and analyzed, which covers all the key physical layers in the chip manufacturing and packaging process. Depending on the failure mode and analysis purpose, the target structures mainly fall into five categories: active regions and channel structures (source / drain regions, shallow trench isolation (STI), channel regions), used to analyze leakage current, breakdown, hot carrier injection (HCI), negative bias temperature instability (NBTI), and electrostatic discharge (ESD) damage; gate structures (polysilicon / metal gate, high-k dielectric layer, sidewalls), used to analyze time-dependent dielectric breakdown (TDDB), etching residue, and metal contamination; interconnect and metallization structures (contact holes, vias, metal interconnects, inter-metal dielectric (IMD)), used to locate electromigration, stress migration, short circuits / bridging, and open circuits / fractures; and packaging and interface structures (bonding wires, solder balls, under bump). Metallization (UBM), through silicon vias (TSV), and underfill are used to detect poor bonding, solder fatigue, thermal stress cracking, delamination, and electrochemical migration; as well as specific defect-capturing structures (Test Element Group (TEG) monitoring structures and breakpoint location structures) are used to simulate and capture defects introduced by specific process steps (such as chemical mechanical polishing (CMP) scratches and etching residues) during the process development phase.

[0052] See also Figure 3 and Figure 4 , Figure 4 This is a three-dimensional structural diagram of an initial sample according to an embodiment of this disclosure.

[0053] The step of cutting the original sample with a focused ion beam to obtain an initial sample with the target structure specifically includes sub-steps S1021 to S1025.

[0054] In step S1021, a focused ion beam is used to mill around the target structure to form an initial sample 210, while retaining the local connection between the initial sample 210 and the main body of the original sample 200.

[0055] Specifically, after precisely locating the target structure, a focused ion beam is used to perform a U-cut around the target structure. This U-cut cuts off the left, bottom, and right sides of the initial sample 210, but leaves the top or one corner of the initial sample 210 connected to the main body of the original sample 200, forming a local connection. This local connection allows the initial sample 210 to be suspended above the original sample 200 like a cantilever beam, ensuring the stability of the initial sample 210 in subsequent operations and providing operating space for the extraction by the nanomanipulator.

[0056] In some embodiments, the U-shaped milling employs a larger ion beam current (e.g., 20 nA) for rough cutting to improve processing efficiency. In some embodiments, the thickness of the initial sample 210 is 1 μm to 6 μm.

[0057] In some embodiments, prior to performing U-shaped milling, a protective layer (such as a platinum or carbon layer) is deposited over the target structure via ion beam-induced deposition to protect the target structure from ion damage during subsequent high-current milling. The thickness of the protective layer is 0.5 μm to 1.5 μm.

[0058] In step S1022, the nanomanipulator is moved so that it comes into contact with the initial sample 210.

[0059] Specifically, the tip of the nanomanipulator is controlled to move to the vicinity of the initial sample 210 using the operating software of the FIB-SEM dual-beam system. The nanomanipulator is driven by a piezoelectric motor, enabling precise positioning at the nanometer level. The nanomanipulator is controlled to descend slowly, so that its tip gently touches the suspended end of the initial sample 210 (e.g., the top corner).

[0060] In step S1023, the tip of the nanomanipulator is welded and fixed to the initial sample 210 by ion beam induced deposition.

[0061] Specifically, at the point where the tip of the nanomanipulator contacts the initial sample 210, a precursor gas such as platinum (Pt), gold, or carbon is introduced, and a focused ion beam is used to scan the contact area. The energy of the ion beam decomposes the gas molecules, and platinum atoms are deposited on the contact interface between the tip and the initial sample 210, forming a solid weld point that firmly bonds the nanomanipulator to the initial sample 210, enabling the nanomanipulator to extract the initial sample 210 from the original sample 200 without detachment.

[0062] Understandably, welding is just one method of fixing the tip of the nanomanipulator to the initial sample 210, and any other suitable technique (including utilizing electrostatic attraction or adhesion) may also be applied.

[0063] In step S1024, the initial sample 210 is completely separated from the main body of the original sample 200 using a focused ion beam to form the initial sample 210.

[0064] Specifically, after the nanomanipulator is firmly welded to the initial sample 210, the aforementioned partial connection (i.e., the part retained after the U-shaped cut) is severed using a focused ion beam. After the connection is severed, the initial sample 210 is completely separated from the main body of the original sample 200, at which point the initial sample 210 is suspended and fixed only by the nanomanipulator.

[0065] In step S1025, the initial sample 210 is extracted from the original sample 200 by the nanomanipulator.

[0066] Specifically, the nanomanipulator is controlled to slowly rise and move away from the surface of the original sample 200, extracting the completely separated initial sample 210 from the original sample 200. During the extraction process, the initial sample 210 is fixed by the nanomanipulator, ready for the next step of transfer and fixation.

[0067] The initial sample 210 has an adjacent first cut surface 214 and a second cut surface 215, and a top surface 216 adjacent to the first cut surface 214 and the second cut surface 215.

[0068] In some embodiments, the initial sample 210 may be in the shape of a cuboid or a trapezoidal prism.

[0069] See Figure 5 , Figure 5 This is a schematic cross-sectional view of another initial sample in an embodiment of this disclosure.

[0070] In some embodiments, the initial sample 210 includes: a substrate 211 and a structural layer 212.

[0071] In some embodiments, the initial sample 210 includes a structural layer 212.

[0072] In some embodiments, the initial sample 210 includes: a substrate 211, a structural layer 212, and a gold-plated metal layer 213.

[0073] The substrate 211 is the underlying material that supports the entire device structure, and is usually a semiconductor material (such as single crystal silicon).

[0074] The substrate 211 provides mechanical support for the device structure and serves as an electrical reference ground for device operation, providing a grounding discharge path for injected charges.

[0075] The structural layer 212 is located above the substrate 211 and is the substantial structural layer for realizing the device's function. The target structure to be observed and analyzed is formed in the structural layer 212.

[0076] The gold-plated metal layer 213 is a continuous conductive film formed on the outermost surface of the original sample through a gold-plating process.

[0077] Specifically, a gold-plated metal layer 213 is formed on the surface of the original sample using a gold-plating process. The gold-plated metal layer 213 covers the upper surface of the original sample and provides a conductive path for the sample surface during SEM observation and FIB processing to improve the charging effect.

[0078] The material of the gold-plated metal layer 213 may include one or more combinations of gold (Au), platinum (Pt), or carbon (C).

[0079] In some embodiments, SEM imaging is used to measure the first height of the initial sample.

[0080] The initial sample was imaged using a scanning electron microscope (SEM), and the first height of the initial sample was measured based on the acquired SEM images.

[0081] Specifically, the first height refers to the vertical distance from the top surface of the initial sample, which is adjacent to both the first and second cut surfaces, to the bottom of the initial sample. In other words, the first height is the vertical distance from the top surface to the bottom surface adjacent to both the first and second cut surfaces, and this dimension reflects the thickness of the initial sample 210 in the ion beam incident direction.

[0082] The sample stage carrying the initial sample 210 is adjusted to a position where the SEM electron beam incident direction is perpendicular to the top surface to obtain a clear, distortion-free measurement image. In the SEM image, the value of the first height is read using image measurement software or a manual ruler. To ensure measurement accuracy, multiple measurements can be taken at different locations along the top surface, and the average value is calculated to reduce measurement errors introduced by local topographic undulations or image noise.

[0083] The SEM imaging can be performed in situ within the FIB-SEM dual-beam system, meaning the measurement can be completed without removing the initial sample from the device. This not only improves operational efficiency but also avoids potential positional shifts or contamination introduced during sample transfer. The measured initial height will serve as one of the key parameters for calculating the compensation angle in subsequent steps, providing dimensional data in the thickness direction for the trigonometric function relationships.

[0084] It should be understood that if the shape or fixing method of the initial sample changes, the measurement reference of the first height can also be adjusted accordingly, as long as the first height can characterize the characteristic dimensions of the initial sample between its top and bottom. This disclosure does not impose strict limitations on this.

[0085] See also Figure 4 and Figure 6 , Figure 6 This is a schematic diagram of an initial sample fixed to a carrier grid according to an embodiment of this disclosure. Direction F1 is the incident direction of the focused ion beam, perpendicular to the top surface 216 of the initial sample 210. Direction F2 is the incident direction of the electron beam from the scanning electron microscope, perpendicular to direction F1 and parallel to the first cut surface 214 of the initial sample 210.

[0086] In step S103, the initial sample 210 is fixed on the support wall of the carrier net 220, and the first cutting surface 214 is in contact with the support wall.

[0087] It should be noted that the side opposite to the first cutting surface 214 (not shown in the figure) is also the first cutting surface 214, and the side opposite to the second cutting surface 215 (not shown in the figure) is also the second cutting surface 215.

[0088] Specifically, the carrier net 220 has a support wall for supporting the initial sample 210. When the initial sample 210 is fixed to the support wall, the first cut surface 214 of the initial sample 210 is in contact with the surface of the support wall.

[0089] In some embodiments, the first cutting surface 214 and the second cutting surface 215 are perpendicular to each other, and when the initial sample 210 is attached to the support wall through its first cutting surface 214, the second cutting surface 215 is perpendicular to the support wall.

[0090] In some embodiments, the carrier mesh 220 is a copper mesh specifically designed for transmission electron microscopy, and the support wall is an "M-pillar" or "finger" structure on the copper mesh. The support wall of the carrier mesh 220 provides mechanical support and an electrical grounding path.

[0091] In some embodiments, the initial sample 210 is welded and fixed to the support wall of the carrier mesh 220 using metal, and the material of the metal is different from the material of the carrier mesh 220.

[0092] Specifically, platinum (Pt) is deposited at the contact angle between the initial sample 210 and the support wall using ion beam-induced deposition, forming a platinum solder joint to firmly fix the initial sample 210 to the support wall. The metal material differs from the mesh material 220, effectively preventing overlap between the characteristic X-ray signal of the solder metal and the background signal of the mesh, thus ensuring the accuracy of elemental analysis results; ensuring the mechanical connection strength and electrical connection reliability between the sheet and the mesh; providing a stable and reliable grounding path to eliminate charging effects; and ensuring that the solder joint is not corroded or oxidized in subsequent processes, thereby improving the process compatibility and success rate of the entire sample preparation process. For example, the solder metal material is one or more of platinum (Pt), gold (Au), and carbon (C), and the mesh material is copper (Cu).

[0093] In some embodiments, platinum solder joints need to be deposited at at least two corners where the initial sample 210 contacts the support wall to ensure the stability of the fixation.

[0094] In some embodiments, after the initial sample 210 is fixed to the support wall of the carrier mesh 220, the gold-plated metal layer 213 of the initial sample 210 is in contact with the support wall, and the substrate 211 is in contact with the support wall. The first cut surface 214 of the initial sample 210 simultaneously exposes the gold-plated metal layer 213 and the substrate 211. When the first side surface 211 is in contact with the support wall, both the gold-plated metal layer 213 and the substrate 211 are electrically connected to the carrier mesh 220 through the support wall. Through this dual grounding path, the charge accumulated inside the initial sample 210 can be effectively conducted away in subsequent steps, thereby eliminating the charging effect.

[0095] In some embodiments, the material of the gold-plated metal layer 213 is different from the material of the carrier mesh 220. For example, the material of the gold-plated metal layer 213 is gold (Au), platinum (Pt), or carbon (C), while the material of the carrier mesh 220 is copper (Cu). By selecting a gold-plated metal layer material that differs from the carrier mesh material, signal interference caused by identical materials can be avoided when energy dispersive spectroscopy analysis is required.

[0096] It should be noted that contacting the first cut surface 214 of the initial sample 210 with the support wall not only provides mechanical fixation for the initial sample 210, but also provides a grounding path for the initial sample 210 to conduct away charge, thereby reducing the charging effect and improving the quality of SEM imaging.

[0097] After the initial sample 210 is welded and fixed to the support wall of the carrier 220 by ion beam induced deposition, the initial sheet (i.e. the initial sample 210) is completely separated from the tip of the nanomanipulator using a focused ion beam.

[0098] Specifically, a focused ion beam is aimed at the solder joint between the tip of the nanomanipulator and the initial sample 210, and the solder joint is completely removed by ion beam milling, so that the initial sample 210 is physically separated from the nanomanipulator. After the separation operation is completed, the nanomanipulator is removed, moving it away from the initial sample 210 and the carrier net 220.

[0099] In step S104, the angle of the carrier grid is adjusted, or the tilt angle of the FIB stage is adjusted, so that the initial sample is rotated along the first direction to the coaxial angle; wherein, the top surface of the initial sample is perpendicular to the incident direction of the focused ion beam.

[0100] Specifically, after fixing the initial sample 210 onto the support wall of the carrier 220, the spatial orientation of the initial sample 210 relative to the focused ion beam is changed by adjusting the angle of the carrier 220 or the tilt angle of the FIB stage, so that the top surface 216 of the initial sample 210 is perpendicular to the incident direction F1 of the focused ion beam. Since the focused ion beam will graze the surface of the second cutting surface 215 at a near-zero incident angle, fine cutting of the second cutting surface 215 is achieved.

[0101] It should be noted that, in Figure 6 In the diagram, the dashed line A1 serves as the baseline and the starting line for angle calculation. The dashed line A1 can be a horizontal line, the ion beam optical axis direction line under the coaxial angle, or the zero-position tilt line of the sample stage in its initial state. Those skilled in the art can flexibly choose the reference object for the baseline according to actual needs and the coordinate system definition of the FIB-SEM dual-beam system, as long as the baseline can serve as a unified starting reference for subsequent calculations of the compensation angle. In some embodiments of this disclosure, a horizontal line is used as the baseline to facilitate direct reading of angle values ​​from geometric relationships; in other embodiments, the ion beam optical axis direction line under the coaxial angle is used as the baseline to simplify the superposition calculation process of the compensation angle and reduce errors caused by coordinate system conversion. This disclosure does not limit the specific selection method of the baseline.

[0102] The dashed line A2 is an inclined line that causes the initial sample to rotate along the first direction to the coaxial angle T0, that is, the angle between the dashed lines A1 and A2 is the coaxial angle T0. The dashed line A2 is perpendicular to the incident direction F1 of the focused ion beam.

[0103] In some embodiments, the carrier mesh 220 is mounted on a sample stage that can be tilted and rotated. By controlling the tilt and rotation of the sample stage, the carrier mesh 220 can be adjusted to a desired angle. In some embodiments, the tilt angle is 52 to 55 degrees.

[0104] See also Figures 6 to 8 , Figure 7 This is a schematic diagram of an initial sheet fixed to a carrier net in an embodiment of this disclosure; Figure 8 This is a schematic cross-sectional view of an initial sheet in an embodiment of this disclosure.

[0105] In step S105, the second cutting surface is cut using a focused ion beam until the cross-section of the target structure is exposed, resulting in an initial sheet; wherein the initial sheet has a first side surface fixed to the support wall of the carrier mesh, a top plane and a bottom plane adjacent to the first side surface, and the first side surface is trapezoidal.

[0106] Specifically, after rotating the initial sample 210 along the first direction to the coaxial angle T0, the focused ion beam is activated to cut the second cutting surface 215 layer by layer. As the cutting proceeds, the material of the second cutting surface 215 is gradually removed, and when the cutting depth reaches the location of the target structure, the cross-section of the target structure is exposed.

[0107] In some embodiments, prior to the step of cutting the original sample using a focused ion beam, a protective layer is deposited on the top plane 216 of the original sample 210 using a FIB; the protective layer is made of any one of platinum, carbon or tungsten, and the deposition thickness is 0.5 μm to 2 μm.

[0108] In some embodiments, the cutting is performed using a progressively decreasing ion beam current. Specifically, a larger ion beam current (e.g., several hundred picoamperes) is initially used for rough cutting to quickly remove most of the material; as the target structure approaches, the beam current is switched to a smaller ion beam current (e.g., tens of picoamperes) for fine cutting to avoid damaging the target structure. This method allows for obtaining a cross-section with good surface quality while ensuring cutting efficiency.

[0109] Specifically, in the step of cutting the second cutting surface with a focused ion beam until the cross-section of the target structure is exposed, the beam current intensity of the focused ion beam is 50 pA to 500 pA, and the accelerating voltage is 5 kV to 30 kV; the cutting adopts a layer-by-layer scanning mode, and the single scan step depth is 10 nm to 50 nm.

[0110] In some embodiments, during the cutting process, SEM is used to periodically observe (in real-time) or observe the cutting status of the second cutting surface 215 to determine whether the cross-section of the target structure has been exposed, thus obtaining the initial thin slice 230. Cutting is stopped when the cross-sectional morphology of the target structure can be clearly observed in the SEM image. Figure 7 This is the graphic after cutting.

[0111] The initial sheet 230 has a first side surface 231 fixed to the support wall of the carrier mesh 220, a top plane adjacent to the first side surface 231, and a bottom plane. After ion beam milling of the second cutting surface, the first side surface 231 is formed as a first cutting surface 214. Because the energy of the ion beam gradually decreases during the top-down milling process, the thinning rate of the top region is greater than that of the bottom region; therefore, the first side surface 231 has a trapezoidal shape in its longitudinal section.

[0112] In step S106, SEM imaging is used to measure the first height, top width, and bottom width of the first side.

[0113] Specifically, after obtaining the initial sheet 230 through ion beam cutting in step S105, the first side 231 of the initial sheet 230 presents a trapezoidal shape in longitudinal section. In order to quantitatively describe the geometric characteristics of this trapezoid and provide accurate parameter basis for subsequent angle compensation calculation, it is necessary to use SEM to perform high-precision imaging and dimensional measurement of the first side 231.

[0114] Before performing SEM imaging, the angle of the sample stage carrying the mesh 220 is first adjusted so that the top and bottom planes of the initial sheet 230 are perpendicular to the incident direction of the SEM electron beam (first angle). Since the top and bottom planes are parallel planes, when both are perpendicular to the incident direction of the electron beam, the obtained SEM image is an orthographic projection view of the first side 231, which can accurately reflect the contour shape and actual size of the side, effectively avoiding projection distortion or measurement errors caused by sample tilt. Then, the angle of the sample stage carrying the mesh 220 is adjusted to a second angle, which is perpendicular to the first angle, to measure the vertical distance between the top and bottom planes of the initial sheet 230.

[0115] After obtaining a clear SEM image, measure the following three dimensional parameters using SEM image measurement software or by manual ruler reading: First, the vertical distance between the top and bottom planes of the initial sheet 230 is measured and denoted as the first height H. This first height H corresponds to the total height of the initial sheet 230 in the ion beam incident direction, which is the actual value of the first height of the initial sample measured in the aforementioned steps after cutting, reflecting the characteristic dimensions of the sheet in the vertical direction.

[0116] Second, measure the width of the edge of the first side 231 on the side near the top plane, and denot it as the top width W1.

[0117] Third, measure the width of the edge of the first side 231 on the side near the bottom plane, and record it as the bottom width W2.

[0118] Specifically, the top width of the first side 231 is W1, and the bottom width of the first side 231 is W2. The top width W1 refers to the width of the edge of the first side 231 closest to the top plane, and the bottom width W2 refers to the width of the edge of the first side 231 closest to the bottom plane. It should be noted that the first side 231 can be an isosceles trapezoid or a right trapezoid, etc. This embodiment uses an isosceles trapezoid as an example, but this disclosure is not limited to this.

[0119] The first height H is the vertical distance from the top plane to the bottom plane of the initial sheet 230, which is also the thickness of the initial sheet 230 in the ion beam incident direction. This first height H corresponds to the first height of the initial sample measured in the previous steps. During the ion beam cutting process, since the positions of the top plane and the bottom plane may change slightly, the first height H in this step is based on the actual measured value after the cutting is completed.

[0120] like Figure 7 As shown, to further quantitatively describe the relationship between the trapezoidal features of the first side surface 231 and subsequent angle compensation, taking an isosceles trapezoid as an example, a right triangle is cut out from the trapezoidal section of the first side surface 231 along the vertex of the trapezoid using an auxiliary dashed line. The three sides of this right triangle are a, b, and c, where: The length of side a is equal to half the absolute value of the difference between the top width W1 and the bottom width W2, i.e., a = |W1-W2| / 2; The length of side b is equal to the first height H, and this side length corresponds to the height of the trapezoid in the vertical direction; Side c is the hypotenuse of the right triangle, and its direction is consistent with the inclination direction of the side of the second side 232.

[0121] The angle between side b and side c is the compensation angle T1. Based on trigonometric relationships, the formula used to calculate this compensation angle is:

[0122] in, denoted as the compensation angle; a is the length of the opposite side corresponding to the compensation angle |(W1-W2)| / 2, which is half the absolute value of the difference between the top width W1 and the bottom width W2; b is the first height.

[0123] It should be understood that the compensation angle T1 physically represents the equivalent tilt angle of the difference in thinning rate on one side caused by the energy decay of the ion beam from top to bottom. In subsequent steps, by superimposing this compensation angle T1 on the coaxial angle T0, the incident direction of the ion beam can be corrected so that it can preferentially process the bottom region, thereby compensating for the uneven thinning at the top and bottom caused by energy decay in terms of rate, and finally obtaining a thin sheet with uniform thickness.

[0124] It should be noted that, Figure 8 The dashed lines are merely illustrative of auxiliary geometric relationships and do not represent any cutting lines or interfaces in the actual structure. The right-angled triangles are geometric models constructed based on measurement parameters, used to quantitatively solve for the compensation angle using trigonometric functions, rather than involving any substantial removal of the initial sheet 230. Those skilled in the art should understand that regardless of whether the first side 231 is an isosceles trapezoid or a right-angled trapezoid, as long as the top width W1, bottom width W2, and first height H are measured, the corresponding compensation angle T1 can be calculated according to the geometric relationships. For non-isosceles trapezoids, the trapezoid can be decomposed into a combination of a rectangle and one or two right-angled triangles, and the same trigonometric function relationships can be used for calculation, which can also obtain the compensation angle T1, and therefore also falls within the protection scope of this disclosure.

[0125] In step S107, the compensation angle is calculated using trigonometric functions based on the first height, top width, and bottom width. The compensation angle is then added to or subtracted from the coaxial angle to obtain the correction angle.

[0126] The formula used to calculate the correction angle is: T=T0±T1 Where T is the correction angle, T0 is the coaxial angle, and T1 is the compensation angle.

[0127] It should be noted that the direction of the "addition / subtraction" compensation angle, i.e., whether to perform addition or subtraction on the coaxial angle T0, is determined by the trapezoidal shape of the first side surface 231 of the initial thin sheet 230. The specific determination rules are as follows: When the top width W1 is less than the bottom width W2, the first side 231 of the initial sheet 230 is determined to be a trapezoidal shape, narrower at the top and wider at the bottom. This shape indicates that during the top-to-bottom milling process of the ion beam, the thinning rate of the top region is greater than that of the bottom region, resulting in excessive thinning of the top and insufficient thinning of the bottom. To compensate for this rate difference, a compensation angle T1 needs to be added to the coaxial angle T0, that is, the tilt angle of the sample needs to be further increased based on the coaxial angle T0. In this way, the ion beam will be shifted towards the bottom region relative to the incident direction of the sample, so that the ion beam can preferentially bombard the thicker area at the bottom, thereby compensating for the thinning rate at the bottom and ultimately making the thinning amount of the top and bottom parts more consistent.

[0128] When the top width W1 is greater than the bottom width W2, the first side 231 of the initial sheet 230 is determined to be a trapezoid, wider at the top and narrower at the bottom. This shape indicates that during ion beam milling, the thinning rate of the bottom region is relatively fast, leading to excessive thinning at the bottom. In this case, it is necessary to subtract the compensation angle T1 from the coaxial angle T0, that is, to reduce the tilt angle of the sample based on the coaxial angle T0, in order to avoid excessive bombardment of the bottom region by the ion beam and to balance the thinning rates of the upper and lower parts.

[0129] It should be understood that the aforementioned operation of "adding" or "subtracting" the compensation angle T1 corresponds to adjusting the tilt angle of the sample stage or the incident angle of the FIB tube in actual machine control, so that the sample continues to rotate in the same direction (adding an angle) or in the opposite direction (subtracting an angle) based on the coaxial angle. Through the above determination and calculation, a correction angle T applicable to the actual state of the current sample can be obtained. This correction angle T reflects the actual ion beam incident attitude required to obtain a uniformly thick sheet after considering the ion beam energy attenuation factor, providing precise angle control parameters for the precision cutting of the ion beam in subsequent steps.

[0130] Figure 8 A geometrical diagram illustrating the principle of adding / subtracting compensation angles in this step is shown, where the calculation method of compensation angle T1 and its superposition relationship with coaxial angle T0 are visually demonstrated using the side-angle relationship of a right triangle. Based on the teachings of this disclosure, those skilled in the art can calculate the specific correction angle by substituting the actually measured values ​​of W1, W2, and H into the above formula, and input this angle parameter into the system through the sample stage control interface of the FIB-SEM dual-beam system to achieve automated or semi-automated angle compensation operation.

[0131] See also Figure 7 , Figure 9 and Figure 10 , Figure 9 This is a schematic diagram of an initial sheet fixed to a carrier net in an embodiment of this disclosure. Figure 10This is a schematic diagram of a structure in which a thin sheet is fixed to a carrier net in an embodiment of this disclosure.

[0132] Based on the calculated correction angle, the initial sheet 230 is subjected to double-sided cutting correction to obtain a sheet with uniform thickness.

[0133] Specifically, the angle of the sample stage carrying the carrier mesh 220, or the tilt angle of the FIB machine, is adjusted so that the initial sheet 230 fixed to the support wall of the carrier mesh 220 rotates along the first direction to a first correction angle T0 + T1 (T), where T0 is the coaxial angle and T1 is the compensation angle. At this first correction angle, the ion beam incident direction is shifted towards the bottom region relative to the coaxial angle, allowing the ion beam to preferentially bombard the thicker bottom region of the initial sheet 230.

[0134] Then, the second side surface 232 of the initial sheet 230 is milled using a focused ion beam. The second side surface 232 is adjacent to the first side surface 231, that is, the second side surface 232 is an exposed surface on the initial sheet 230 that shares a side with the first side surface 231. By performing ion beam milling on the second side surface 232 at a first correction angle, excess material in the bottom region can be selectively removed, thereby compensating for insufficient bottom thinning caused by energy decay.

[0135] Next, the sample stage angle or FIB machine tilt angle is adjusted again so that the initial sheet 230 rotates along the first direction by a second correction angle T0-T1, which is the coaxial angle minus the compensation angle. At this second correction angle, the ion beam incident direction is shifted towards the top region relative to the coaxial angle, allowing the ion beam to preferentially bombard the thicker bottom region of the opposite side of the initial sheet 230. The double-sided correction of the initial sheet 230 is completed by using a focused ion beam to cut the side opposite to the second side 232 (i.e., the other side opposite to the second side 232).

[0136] By first cutting the second side 232 at an angle of T0+T1 and then cutting the opposite side at an angle of T0-T1, the thinning rate on both sides of the sheet can be symmetrically compensated, and a sheet 233 with uniform thickness along the top to bottom direction can be obtained.

[0137] It should be noted that in the subsequent refinement stage, the initial thin film is cut using a focused ion beam in a layer-by-layer scanning mode, with a single scan step depth of 1 nm to 5 nm. This refinement step forms a clear phased process connection with the cutting process in the aforementioned roughing step, which uses a cutting depth of 10 nm to 50 nm. The aforementioned roughing stage rapidly thins the sample with a higher beam current (e.g., 50 pA to 500 pA) and a larger step depth (10 nm to 50 nm) to bring the thin film close to the target thickness (e.g., about 100 nm). In contrast, this refinement stage switches to a lower beam current (e.g., 10 pA to 50 pA) and a significantly reduced step depth (1 nm to 5 nm) to finely polish the surface of the thin film. This aims to remove the surface damage layer and amorphous layer introduced by the previous roughing process layer by layer, making the surface of the thin film smooth and the thickness precisely controllable. At the same time, angle compensation is performed in conjunction with the aforementioned correction angle. From the two dimensions of thickness control and surface quality, the final thin film meets the stringent requirements of TEM high-resolution observation.

[0138] See also Figure 10 and Figure 11 , Figure 11 This is a schematic diagram of a second initial sample fixed to a carrier net in an embodiment of this disclosure.

[0139] In some embodiments, the removed second original sample can also be directly subjected to angle-compensated cutting.

[0140] Specifically, the second original sample is rotated along a first direction to a coaxial angle T0, where the incident direction of the focused ion beam is perpendicular to the surface of the second original sample. The second original sample is then cut using the focused ion beam to obtain a second initial sample 240 with the target structure, having adjacent first and second cut surfaces. Subsequently, the mesh angle or FIB stage tilt angle is adjusted to rotate the second initial sample 240 along the first direction to a third correction angle (T0 + T1) equal to the sum of the coaxial angle T0 and the compensation angle T1. The second cut surface of the second initial sample 240 is then cut using the focused ion beam. The mesh angle or FIB stage tilt angle is then adjusted again to rotate the second initial sample 240 along the first direction to a fourth correction angle (T0 - T1) equal to the difference between the coaxial angle T0 and the compensation angle T1. The opposite sides of the second cut surface of the second initial sample are then cut using the focused ion beam, resulting in a thin sheet of uniform thickness in a bulk state.

[0141] In some embodiments, after obtaining the uniformly thick sheet 233, the method further includes a closed-loop verification and iterative correction step to ensure that the sheet thickness uniformity meets a preset requirement. Specifically, the top width W1' and bottom width W2' of the sheet are measured using SEM imaging, and the difference W = |W1' - W2'| between the top width W1' and the bottom width W2' is calculated. If the difference ΔW is greater than a preset threshold (the preset threshold ranges from 1nm to 5nm, for example, 1nm, 2nm, 3nm, 4nm, or 5nm), it indicates that the current sheet thickness uniformity has not yet met the requirements and further correction is needed.

[0142] Based on the first height H, and the top width W1' and bottom width W2' of the sheet obtained in this measurement, a new compensation angle T1' is calculated again using trigonometric functions. This new compensation angle T1' is then added to or subtracted from the coaxial angle T0 to obtain a new corrected angle T'. The ion beam cutting step is then repeated. Each iteration calculates the compensation angle based on the latest measured top width W1' and bottom width W2', and adjusts the cutting posture accordingly. Iteration stops when the difference W between the measured top width W1' and bottom width W2' is less than or equal to the preset threshold, at which point the sheet thickness is determined to meet the uniformity requirements.

[0143] Through the aforementioned closed-loop iterative correction steps, precise control of the sheet thickness uniformity can be achieved. Since SEM measurements are performed after each cutting and the compensation angle is recalculated and corrected based on the measured results, this iterative process can effectively eliminate residual thickness inhomogeneities caused by factors such as material redeposition, ion beam fluctuations, and sample material differences, ultimately obtaining TEM sheets with extremely high thickness uniformity.

[0144] The foregoing describes several embodiments of the method for preparing thin films using FIB. The various optional methods described in each embodiment can be combined and cross-referenced without conflict, thereby extending to a variety of possible embodiments. These can all be considered as embodiments disclosed in this disclosure.

[0145] It should be noted that, in this specification and accompanying drawings, for the purpose of clearly describing the technical solutions and structural features of this disclosure, descriptions of geometric, positional, and directional relationships such as "parallel," "perpendicular," and "relatively arranged" are all based on theoretical design conditions and ideal assembly conditions. Those skilled in the art should understand that, in actual product manufacturing and sample preparation processes, due to factors such as machining accuracy, assembly tolerances, structural deformation, thermal expansion effects, and measurement errors, there may be acceptable deviations between the actual shape, relative position, and orientation of the prepared components and the theoretical design. For example, "parallel" should be understood as "basically parallel," "perpendicular" as "approximately perpendicular," and "relatively arranged" as "basically relative." As long as these deviations do not substantially affect the implementation of the technical solutions disclosed in this disclosure and the resulting technical effects, they should be considered within the scope of protection of this disclosure. Manufacturing and assembly tolerances known in the art, as well as dimensional, positional, and angular variations allowed by industry standards, are all within the scope of this specification.

[0146] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article indicates that the preceding and following related objects have an "or" relationship.

[0147] In the embodiments of this application, "multiple" refers to two or more.

[0148] The descriptions of "first," "second," etc., appearing in the embodiments of this application are for illustrative purposes and to distinguish the objects being described. They have no order and do not indicate any special limitation on the number of objects in the embodiments of this application. They cannot constitute any limitation on the embodiments of this application.

[0149] While the embodiments disclosed herein are as described above, this disclosure is not limited thereto. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this disclosure; therefore, the scope of protection of this disclosure should be determined by the scope defined in the claims.

Claims

1. A method for preparing thin films using FIB (fiber peroxide) technology, characterized in that, include: The original sample is rotated along a first direction to a coaxial angle, the coaxial angle being used to make the incident direction of the focused ion beam perpendicular to the surface of the original sample, the first direction being selected from counterclockwise rotation or clockwise rotation; The original sample is cut using a focused ion beam to obtain an initial sample with a target structure. The initial sample has an adjacent first cut surface and a second cut surface, as well as a top surface adjacent to the first cut surface and the second cut surface. The initial sample is fixed to the support wall of the carrier mesh, and the first cut surface is in contact with the support wall; Adjust the grid angle, or adjust the tilt angle of the FIB stage, so that the initial sample rotates along the first direction to the coaxial angle; wherein the top surface of the initial sample is perpendicular to the incident direction of the focused ion beam; The second cutting surface is cut using a focused ion beam until the cross-section of the target structure is exposed, resulting in an initial sheet; wherein the initial sheet has a first side surface fixed to the support wall of the carrier mesh, a top plane and a bottom plane adjacent to the first side surface, and the first side surface is trapezoidal; Using SEM imaging, the first height, top width, and bottom width of the first side were measured respectively. Based on the first height, top width, and bottom width, the compensation angle is calculated using trigonometric functions. The correction angle is obtained by adding / subtracting the compensation angle from the coaxial angle.

2. The method according to claim 1, characterized in that, A combination of one or more of the following is satisfied: The first height is the distance from the top plane to the bottom plane of the initial sheet; The first height is the distance from the top plane to the bottom plane adjacent to the first and second cutting surfaces.

3. The method according to claim 1, characterized in that, include: The formula used to calculate the compensation angle is: in, Here, is the compensation angle; a is the length of the opposite side corresponding to the compensation angle |(W1-W2)| / 2, which is half the absolute value of the difference between the top width W1 and the bottom width W2; b is the first height; The formula used to calculate the correction angle is: Where T is the correction angle. The coaxial angle is... The compensation angle is mentioned above.

4. The method according to claim 3, characterized in that, The step of calculating the compensation angle using trigonometric relationships based on the first height, top width, and bottom width, and then adding / subtracting the compensation angle from the coaxial angle to obtain the correction angle, further includes: Adjust the carrying net angle, or adjust the tilt angle of the FIB machine, so that the initial sheet rotates along the first direction to a first correction angle that is the sum of the coaxial angle and the compensation angle; The second side of the initial thin film was cut using a focused ion beam. Adjust the carrying angle, or adjust the tilt angle of the FIB machine, so that the initial sheet rotates along the first direction to a second correction angle that is the difference between the coaxial angle and the compensation angle; A thin sheet of uniform thickness is obtained by cutting the side opposite to the second side using a focused ion beam. The second side is adjacent to the first side.

5. The method according to claim 3, characterized in that, The step of calculating the compensation angle using trigonometric relationships based on the first height, top width, and bottom width, and then adding / subtracting the compensation angle from the coaxial angle to obtain the correction angle, further includes: The second original sample is rotated along the first direction to a coaxial angle, the coaxial angle causing the incident direction of the focused ion beam to be perpendicular to the surface of the second original sample; The second original sample is cut using a focused ion beam to obtain a second initial sample with the target structure; wherein the second initial sample has adjacent first and second cutting surfaces; Adjust the angle of the carrier net, or adjust the tilt angle of the FIB machine, so that the second initial sample rotates along the first direction to a third correction angle that is the sum of the coaxial angle and the compensation angle; The second cutting surface of the second initial sample is cut using a focused ion beam. Adjust the angle of the carrier net, or adjust the tilt angle of the FIB machine, so that the initial sample rotates along the first direction to a fourth correction angle that is the difference between the coaxial angle and the compensation angle; The second initial sample is cut with a focused ion beam to obtain a thin sheet of uniform thickness by cutting the side opposite the second cut surface.

6. The method according to claim 4 or 5, characterized in that, After obtaining the thin sheet with uniform thickness, the method further includes: The top and bottom widths of the slice were measured using SEM imaging. Calculate the difference between the top width and the bottom width of the sheet; If the difference is greater than a preset threshold, a new compensation angle is calculated using trigonometric functions based on the first height, the top width and the bottom width of the sheet. The new compensation angle is added to or subtracted from the coaxial angle to obtain a new correction angle. The ion beam cutting step is repeated until the difference is less than or equal to the preset threshold. The preset threshold value ranges from 1nm to 5nm.

7. The method according to claim 1, characterized in that, Based on the coaxial angle, the compensation angle is added / subtracted, including: When the top width is less than the bottom width, it is determined that the first side of the initial sheet is a trapezoid that is narrower at the top and wider at the bottom, and the compensation angle is added to the coaxial angle. When the top width is greater than the bottom width, it is determined that the first side of the initial sheet is a trapezoid that is wider at the top and narrower at the bottom, and the compensation angle is subtracted from the coaxial angle.

8. The method according to claim 1, characterized in that, Prior to the step of cutting the original sample using a focused ion beam, the procedure also includes: A protective layer is deposited on the top plane of the original sample using FIB; The protective layer is made of any one of platinum, carbon, or tungsten, and has a deposition thickness of 0.5 μm to 2 μm.

9. The method according to claim 1, characterized in that, The step of cutting the second cutting surface using a focused ion beam until the cross-section of the target structure is exposed includes: The focused ion beam has a beam current intensity of 50 pA to 500 pA and an accelerating voltage of 5 kV to 30 kV. The cutting process employs a layer-by-layer scanning mode, with a single scan step depth ranging from 10 nm to 50 nm.

10. The method according to claim 4, characterized in that, The initial thin film is cut using a focused ion beam in a layer-by-layer scanning mode, with a single scan step depth of 1 nm to 5 nm.

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