FIB-SEM double-beam precise section cutting method

Abstract

The invention discloses an FIB-SEM double-beam precise section cutting method, which is realized based on an FIB-SEM double-beam system, the FIB-SEM double-beam system comprises an SEM lens cone, an FIB lens cone, a six-axis high-precision sample table, a gas injection system and a signal acquisition system, and the method comprises the following steps: step 1, sample pretreatment: fixing a to-be-cut sample on the six-axis high-precision sample table, adding a gas injection system and a signal acquisition system, transferring into a sample chamber and starting a vacuum system to enable the vacuum degree of the sample chamber to reach 1 * 10 <-6 > mbar to 5 * 10 <-6 > mbar; the method has the beneficial effects that the SEM high-resolution positioning is combined with the photoelectric correlation technology, so that accurate positioning of a target area is realized, and the problem of inaccurate positioning of a traditional method is solved; meanwhile, the inclined axis design of the six-axis high-precision sample table is utilized to ensure that a target area does not deviate from a visual field during sample posture adjustment, and the positioning reliability is further improved; and a protective layer is deposited in a target area before cutting, so that direct impact of an FIB ion beam on the surface and the internal structure of the sample is effectively blocked, and melting, non-crystallization or crack damage of the sample is avoided.

Description

Technical Field

[0001] This invention belongs to the field of cross-section cutting technology, specifically relating to a FIB-SEM dual-beam precision cross-section cutting method. Background Technology

[0002] In fields such as semiconductor manufacturing, advanced materials research and development, and microstructure analysis, cross-sectional cutting technology is one of the core means to obtain information about the internal structure of samples. With the continuous development of technology, the feature size of semiconductor devices continues to shrink, and the microstructure of advanced functional materials becomes increasingly complex. The precision requirements for cross-sectional cutting have been raised to the nanometer level. Precise cross-sectional cutting not only needs to ensure the accurate positioning of the target area, but also needs to avoid damage, contamination or structural distortion of the sample during the cutting process to ensure the accuracy of subsequent analysis results.

[0003] Traditional cross-section cutting methods mainly include mechanical cutting, chemical etching, and single ion beam cutting, but all of these methods have significant technical drawbacks. Mechanical cutting removes material using hard tools such as diamond cutters, but this method generates significant mechanical stress, which can easily lead to cracks, deformation, and even damage to the internal microstructure of the sample. Moreover, the cutting accuracy is limited by the precision of the tool and the operator's technique, making it unsuitable for nanoscale processing. Chemical etching uses chemical reagents to selectively etch the sample to form a cross-section, but the etching process is difficult to control precisely, easily leading to over-etching or uneven etching, resulting in poor cross-section flatness. At the same time, chemical reagents may react with the sample, causing sample contamination or structural damage. While single ion beam cutting can achieve microscale cutting, it lacks effective target area positioning methods, making it prone to positioning errors. Furthermore, the high energy of the ion beam can easily cause the sample surface to melt and become amorphous, posing a very high risk of damage, especially to brittle materials or precision semiconductor devices.

[0004] While the advent of the FIB-SEM dual-beam system has enabled a preliminary combination of cutting and observation, existing technologies still have many shortcomings. In traditional dual-beam cutting methods, SEM is only used for post-cut observation and verification, failing to fully utilize its high-resolution positioning advantages, resulting in insufficient target area positioning accuracy. Furthermore, the lack of targeted protective measures during cutting means that the high-energy ion beam of FIB can easily damage the sample surface and internal structure. Simultaneously, cutting processes often employ a single beam intensity, making it difficult to balance processing efficiency and cross-sectional flatness. High beams in the roughing stage are prone to surface defects, while low beams in the finishing stage, if directly applied to large-area material removal, lead to low processing efficiency. Moreover, traditional methods lack a complete processing and verification closed loop, making it impossible to promptly detect and adjust deviations during the cutting process, further impacting the reliability of cross-sectional cutting. Summary of the Invention

[0005] The purpose of this invention is to provide a FIB-SEM dual-beam precision cross-section cutting method. By optimizing the cutting process and process parameters, it solves the problems of easy sample damage, inaccurate positioning, and poor cross-section flatness in traditional methods, thereby improving the accuracy and reliability of cross-section cutting.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a FIB-SEM dual-beam precision cross-section cutting method, implemented based on a FIB-SEM dual-beam system, wherein the FIB-SEM dual-beam system includes a SEM lens barrel, a FIB lens barrel, a six-axis high-precision sample stage, a gas injection system, and a signal acquisition system, comprising the following steps: Step 1: Sample Pre-treatment: Fix the sample to be cut on a six-axis high-precision sample stage, move it into the sample chamber, and start the vacuum system to achieve a vacuum level of 1×10⁻⁶ in the sample chamber. -6 mbar~5×10 -6 mbar; Step 2: High-resolution SEM localization of the target area: Start the SEM tube in low-voltage imaging mode, acquire signals through the In-Lens ring SE detector, adjust the sample orientation to center the target area in the imaging field of view, and mark the cutting boundary. Step 3: Deposit protective layer: Deposit gas is introduced through a gas injection system to deposit a protective layer with a thickness of 50nm~200nm within the cutting boundary; Step 4: FIB roughing to remove excess material: Adjust the FIB tube parameters, emit an ion beam along the cutting path to remove excess material layer by layer, leaving a 1μm~5μm pre-reserved layer, and monitor in real time with SEM; Step 5: FIB finishing process to obtain a flat cross section: reduce the FIB beam current, perform cross-thinning finishing on the reserved layer, and simultaneously collect SE2 and BSE signals to observe the flatness of the cross section; Step 6: SEM Imaging Verification and Parameter Optimization: Perform high-resolution imaging on the cut cross-section to analyze whether it meets the accuracy requirements. If not, return to Step 5 for further refinement.

[0007] As a preferred technical solution of the present invention, in step two, SEM positioning uses photoelectric correlation technology combined with optical microscope fluorescence positioning.

[0008] As a preferred technical solution of the present invention, in step three, the edge of the protective layer extends beyond the cutting boundary by 0.5μm~1μm, and the deposition gas is a platinum precursor gas or a tungsten precursor gas.

[0009] As a preferred technical solution of the present invention, in step three, the flow rate of the deposition gas is 1 sccm to 5 sccm, and the deposition rate is 1 nm / s to 5 nm / s.

[0010] As a preferred technical solution of the present invention, in step four, the roughing process adopts a partitioned removal strategy, with the outer area being rapidly removed using a large beam current and the near-target area being gradually removed using a medium beam current.

[0011] As a preferred technical solution of the present invention, in step five, the non-leakage magnetic design of the FIB-SEM dual-beam system is used during the fine finishing process, the sample tilt angle is 45°~54°, and the thickness of each cut is 1nm~5nm.

[0012] As a preferred technical solution of the present invention, in step six, three-dimensional reconstruction technology is used during imaging verification to construct a three-dimensional model of the cross section and quantitatively analyze the flatness and dimensional accuracy.

[0013] As a preferred technical solution of the present invention, three-dimensional reconstruction technology is used during imaging verification, and the method for constructing a three-dimensional cross-sectional model is as follows: First, the parameters of the SEM tube and signal acquisition system were calibrated to ensure imaging consistency. The SEM accelerating voltage was set to 1kV~3kV, the magnification to 50KX~150KX, and the detector was a combination of an In-Lens detector and a backscattered electron (BSE) detector. At the same time, the initial attitude of the six-axis high-precision sample stage was adjusted so that the cutting section was perpendicular to the SEM electron beam incident direction at 90°. The X, Y, and Z axis coordinates and tilt angle of the sample stage at this time were recorded as the reference parameters for subsequent multi-angle imaging. Starting from the initial reference attitude, the sample is rotated stepwise along a rotation axis perpendicular to the cross-section using a six-axis high-precision sample stage. One cross-sectional image is acquired every 1° to 3° of rotation, covering a rotation range of -30° to +30°. After each rotation, the SEM imaging parameters remain unchanged. Once the sample stage attitude stabilizes, the signal acquisition system is activated to acquire the cross-sectional image. During the acquisition process, the sample stage rotation angle, coordinate position, and imaging time corresponding to each image are recorded simultaneously, forming an "image-attitude parameter" associated dataset to ensure that the spatial position information of each image can be traced during subsequent registration. The acquired multi-angle images are preprocessed to remove imaging noise and interference signals: First, the brightness and contrast of all images are unified by a grayscale correction algorithm; then, an edge enhancement algorithm is used to highlight the contour features of the cross section; finally, noise reduction filtering is used to remove noise caused by electronic noise and retain the true morphological information of the cross section. After preprocessing, image registration is performed based on the "image-pose parameter" association dataset: the image under the initial reference pose is used as the reference image, and the images at other angles are used as the images to be registered; the same cross-sectional feature points in all images are identified by the feature point matching algorithm, and the spatial transformation relationship between the image to be registered and the reference image is calculated by combining the sample stage rotation angle and coordinate space parameters; the pixel position of the image to be registered is adjusted according to the spatial transformation relationship so that the cross-sectional feature points in all images are accurately aligned, forming an image sequence with consistent spatial position; Based on the registered image sequence, a three-dimensional model of the cross section is constructed using a combination of "voxel stacking + surface reconstruction": First, each registered image is regarded as a "slice" of the cross section from the corresponding viewpoint. The coordinate position of each slice in three-dimensional space is calculated according to the rotation angle of the sample stage. All slices are stacked in the form of voxels according to their spatial positions to form a preliminary three-dimensional voxel model. Then, the surface contour of the cross section in the voxel model is extracted by the surface reconstruction algorithm, redundant background voxels are removed, and the three-dimensional surface structure of the cross section is preserved. Finally, the reconstructed surface contour is smoothed to eliminate surface jaggedness caused by image registration deviation, forming a three-dimensional model consistent with the actual cross section morphology.

[0014] Compared with the prior art, the beneficial effects of the present invention are: By combining SEM high-resolution positioning with photoelectric correlation technology, the target area is accurately located, solving the problem of inaccurate positioning by traditional methods. At the same time, the tilt axis design of the six-axis high-precision sample stage ensures that the target area does not deviate from the field of view when the sample attitude is adjusted, further improving the positioning reliability. Before cutting, a protective layer is deposited in the target area to effectively block the direct impact of the FIB ion beam on the sample surface and internal structure, avoiding melting, amorphization or crack damage to the sample. It is especially suitable for cutting brittle materials and precision semiconductor devices. The segmented cutting strategy of "roughing-finishing" is adopted. In the roughing stage, a large beam quickly removes excess material and improves processing efficiency. In the finishing stage, a small beam cross-thins is used to ensure that the cross-sectional flatness reaches the nanometer level, combined with real-time SEM monitoring, thus balancing processing efficiency and cross-sectional quality.

[0015] By utilizing the non-leakage magnetic field design and multi-channel imaging capabilities of the FIB-SEM dual-beam system, real-time observation and precise control of the cutting process can be achieved. At the same time, through subsequent SEM imaging verification and three-dimensional reconstruction analysis, a complete processing-verification closed loop is formed, which significantly improves the accuracy and reliability of cross-section cutting. Attached Figure Description

[0016] Figure 1 This is a flowchart of the cutting method of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1 Please see Figure 1 This is the first embodiment of the present invention, which provides a FIB-SEM dual-beam precision cross-section cutting method, based on a FIB-SEM dual-beam system. The FIB-SEM dual-beam system includes a SEM tube, a FIB tube, a six-axis high-precision sample stage, a gas injection system, and a signal acquisition system, and includes the following steps: Step 1: Sample Pre-treatment: Fix the sample to be cut on a six-axis high-precision sample stage, move it into the sample chamber, and start the vacuum system to achieve a vacuum level of 1×10⁻⁶ in the sample chamber. -6 mbar ensures that no impurities are adsorbed on the sample surface; Step 2: High-resolution SEM positioning of the target area: Start the SEM microscope tube, adopt low-voltage imaging mode, set the accelerating voltage to 0.5kV and the magnification to 10KX, and acquire the sample surface signal through the In-Lens ring SE detector; adjust the sample posture using a six-axis high-precision sample stage to center the target area of ​​the sample in the SEM imaging field of view, acquire a high-resolution image of the target area through the signal acquisition system, determine the cutting boundary based on the feature structure in the image, and mark the cutting start and end points to complete the target area positioning; photoelectric correlation technology combined with optical microscope fluorescence positioning is used for SEM positioning. Step 3: Deposit protective layer: Deposit gas is introduced through a gas injection system to deposit a protective layer with a thickness of 50 nm within the cutting boundary; the edge of the protective layer extends 0.5 μm beyond the cutting boundary; the deposit gas is a platinum precursor gas or a tungsten precursor gas; the flow rate of the deposit gas is 1 sccm, and the deposition rate is 1 nm / s. Step 4: FIB roughing to remove excess material: Adjust the FIB tube parameters, increasing the accelerating voltage to 20kV and the beam current to 100pA. Based on the cutting boundary marked in Step 2, control the FIB tube to emit an ion beam along the cutting path to remove excess material around the target area layer by layer. During roughing, retain a 1μm pre-reserved layer above the target area to avoid directly cutting to the target cross-section. During roughing, the SEM tube continuously maintains imaging status, monitors the material removal progress in real time, and compensates for sample attitude shift through a six-axis high-precision sample stage to ensure accurate cutting path. The roughing adopts a zoned removal strategy, using a high beam current for rapid removal in the outer area and a medium beam current for gradual removal in the near-target area. Step 5: FIB Refinement Processing to Obtain a Flat Cross Section: After rough machining, reduce the beam current of the FIB tube to 5pA while maintaining the accelerating voltage at 20kV. Refine the reserved layer using a cross-thinning method, adjusting the sample tilt angle to 45° via a six-axis high-precision sample stage, and perform multiple thin-layer cuts along the target cross section direction, each cut being 1nm thick. During the refinement process, utilize the multi-channel imaging function of the SEM tube to simultaneously acquire SE2 and backscattered electron (BSE) signals, observing the cross section flatness in real time until a scratch-free and distortion-free flat cross section is obtained. Step Six: SEM Imaging Verification and Parameter Optimization: After the fine-tuning is completed, adjust the imaging parameters of the SEM tube. Use an accelerating voltage of 1kV and a magnification of 50KX to perform high-resolution imaging of the cut cross-section. Analyze the flatness, target area integrity, and undamaged state of the cross-section image through the signal acquisition system. If the cross-section meets the preset accuracy requirements, the cutting is completed; otherwise, return to Step Five, adjust the FIB fine-tuning parameters, and reprocess until the requirements are met. For imaging verification, use 3D reconstruction technology to construct a 3D model of the cross-section and quantitatively analyze flatness and dimensional accuracy. The method for constructing the 3D model of the cross-section using 3D reconstruction technology during imaging verification is as follows: First, the parameters of the SEM tube and signal acquisition system were calibrated to ensure imaging consistency. The SEM acceleration voltage was set to 1kV and the magnification to 50KX. The detector was a combination of an In-Lens detector and a backscattered electron (BSE) detector. At the same time, the initial attitude of the six-axis high-precision sample stage was adjusted so that the cutting section was perpendicular to the SEM electron beam incident direction at 90°. The X, Y, and Z axis coordinates and tilt angle of the sample stage at this time were recorded as the reference parameters for subsequent multi-angle imaging. Starting from the initial reference attitude, the sample is rotated stepwise along a rotation axis perpendicular to the cross-section using a six-axis high-precision sample stage. One cross-sectional image is acquired for every 1° of rotation, covering a rotation range of -30° to +30°. After each rotation, the SEM imaging parameters remain unchanged. Once the sample stage attitude stabilizes, the signal acquisition system is activated to acquire the cross-sectional image. During the acquisition process, the sample stage rotation angle, coordinate position, and imaging time corresponding to each image are recorded simultaneously, forming an "image-attitude parameter" associated dataset to ensure that the spatial position information of each image can be traced during subsequent registration. The acquired multi-angle images are preprocessed to remove imaging noise and interference signals: First, the brightness and contrast of all images are unified by a grayscale correction algorithm; then, an edge enhancement algorithm is used to highlight the contour features of the cross section; finally, noise reduction filtering is used to remove noise caused by electronic noise and retain the true morphological information of the cross section. After preprocessing, image registration is performed based on the "image-pose parameter" association dataset: the image under the initial reference pose is used as the reference image, and the images at other angles are used as the images to be registered; the same cross-sectional feature points in all images are identified by the feature point matching algorithm, and the spatial transformation relationship between the image to be registered and the reference image is calculated by combining the sample stage rotation angle and coordinate space parameters; the pixel position of the image to be registered is adjusted according to the spatial transformation relationship so that the cross-sectional feature points in all images are accurately aligned, forming an image sequence with consistent spatial position; Based on the registered image sequence, a three-dimensional model of the cross section is constructed using a combination of "voxel stacking + surface reconstruction": First, each registered image is regarded as a "slice" of the cross section from the corresponding viewpoint. The coordinate position of each slice in three-dimensional space is calculated according to the rotation angle of the sample stage. All slices are stacked in the form of voxels according to their spatial positions to form a preliminary three-dimensional voxel model. Then, the surface contour of the cross section in the voxel model is extracted by the surface reconstruction algorithm, redundant background voxels are removed, and the three-dimensional surface structure of the cross section is preserved. Finally, the reconstructed surface contour is smoothed to eliminate surface jaggedness caused by image registration deviation, forming a three-dimensional model consistent with the actual cross section morphology.

[0019] The methods for quantitatively analyzing flatness and dimensional accuracy are as follows: Flatness quantification analysis Select the effective evaluation area of ​​the cross section in the 3D model, and calculate the flatness using the following method: Fitting the reference plane: The least squares method is used to fit the plane to all surface points in the evaluation area to obtain the ideal reference plane of the cross section (this plane represents the theoretical flatness of the cross section). Calculate the height deviation: Traverse each surface point within the evaluation area, calculate its vertical distance to the ideal reference plane (i.e., the height deviation), and record the height deviation values ​​for all points; Statistical flatness index: Calculate the absolute average of all height deviation values ​​(reflecting the overall flatness of the cross section), the maximum positive deviation (the highest protrusion height on the cross section surface) and the maximum negative deviation (the deepest depression depth on the cross section surface), and use "absolute average value ≤ 5nm and maximum deviation ≤ 10nm" as the flatness qualification standard (the standard threshold can be adjusted according to actual application needs).

[0020] Key dimensional parameters of the cross-section were extracted based on the 3D model, and the accuracy was verified. Extract theoretical dimensional parameters: Based on the cutting boundaries marked before cutting, determine the theoretical dimensions of the cross-section (such as cross-section length, width, thickness, or spacing and diameter of specific structures within the cross-section). Measure actual size parameters: In the 3D model, use a distance measurement tool to measure the actual value of the corresponding dimension along the preset measurement direction (such as parallel to the cross-sectional length direction or perpendicular to the thickness direction). Repeat the measurement 3 times for each dimension and take the average value as the final actual dimension.

[0021] Example 2 Please see Figure 1 This is the second embodiment of the present invention, which is based on the previous embodiment, but differs in that; Step 1: Sample Pre-treatment: Fix the sample to be cut on a six-axis high-precision sample stage, move it into the sample chamber, and start the vacuum system to achieve a vacuum level of 3×10⁻⁶ in the sample chamber. -6 mbar ensures that no impurities are adsorbed on the sample surface; Step 2: High-resolution SEM positioning of the target area: Start the SEM tube, adopt low-voltage imaging mode, set the accelerating voltage to 1.2kV and the magnification to 55KX, and acquire the sample surface signal through an In-Lens ring SE detector; adjust the sample posture using a six-axis high-precision sample stage to center the target area of ​​the sample in the SEM imaging field of view, acquire a high-resolution image of the target area through the signal acquisition system, determine the cutting boundary based on the feature structure in the image, and mark the cutting start and end points to complete the target area positioning; photoelectric correlation technology combined with optical microscope fluorescence positioning is used for SEM positioning. Step 3: Deposit protective layer: Deposit gas is introduced through a gas injection system to deposit a protective layer with a thickness of 125 nm within the cutting boundary; the edge of the protective layer extends 0.7 μm beyond the cutting boundary; the deposit gas is a platinum precursor gas or a tungsten precursor gas; the flow rate of the deposit gas is 3 sccm, and the deposition rate is 3 nm / s. Step 4: FIB roughing to remove excess material: Adjust the FIB tube parameters, increasing the accelerating voltage to 25kV and the beam current to 300pA. Based on the cutting boundary marked in Step 2, control the FIB tube to emit an ion beam along the cutting path to remove excess material around the target area layer by layer. During roughing, retain a 3μm pre-reserved layer above the target area to avoid directly cutting to the target cross-section. During roughing, the SEM tube continuously maintains imaging status, monitors the material removal progress in real time, and compensates for sample attitude shift through a six-axis high-precision sample stage to ensure accurate cutting path. The roughing adopts a zoned removal strategy, using a high beam current for rapid removal in the outer area and a medium beam current for gradual removal in the near-target area. Step 5: FIB Refinement Processing to Obtain a Flat Cross Section: After rough machining, reduce the beam current of the FIB tube to 18pA while maintaining the accelerating voltage at 25kV. Refine the reserved layer using a cross-thinning method, adjusting the sample tilt angle to 50° via a six-axis high-precision sample stage, and perform multiple thin-layer cuts along the target cross section direction, each cut being 3nm thick. During the refinement process, utilize the multi-channel imaging function of the SEM tube to simultaneously acquire SE2 and backscattered electron (BSE) signals, observing the cross section flatness in real time until a scratch-free and distortion-free flat cross section is obtained. Step Six: SEM Imaging Verification and Parameter Optimization: After the finishing process is completed, adjust the imaging parameters of the SEM tube. Use an accelerating voltage of 3kV and a magnification of 125KX to perform high-resolution imaging on the cut cross-section. Analyze the flatness of the cross-section image, the integrity of the target area, and the undamaged state through the signal acquisition system. If the cross-section meets the preset accuracy requirements, the cutting is completed.

[0022] Example 3 Please see Figure 1 This is the third embodiment of the present invention, which is based on the previous embodiment, but differs in that; Step 1: Sample Pre-treatment: Fix the sample to be cut on a six-axis high-precision sample stage, move it into the sample chamber, and start the vacuum system to achieve a vacuum level of 5×10⁻⁶ in the sample chamber. -6 mbar ensures that no impurities are adsorbed on the sample surface; Step 2: High-resolution SEM positioning of the target area: Start the SEM microscope tube, adopt low-voltage imaging mode, set the accelerating voltage to 2kV and the magnification to 100KX, and acquire the sample surface signal through the In-Lens ring SE detector; adjust the sample posture using a six-axis high-precision sample stage to center the target area of ​​the sample in the SEM imaging field of view, acquire a high-resolution image of the target area through the signal acquisition system, determine the cutting boundary based on the feature structure in the image, and mark the cutting start and end points to complete the target area positioning; photoelectric correlation technology combined with optical microscope fluorescence positioning is used for SEM positioning. Step 3: Deposit protective layer: Deposit gas is introduced through a gas injection system to deposit a protective layer with a thickness of 200 nm within the cutting boundary; the edge of the protective layer extends 1 μm beyond the cutting boundary; the deposit gas is a platinum precursor gas or a tungsten precursor gas; the flow rate of the deposit gas is 5 sccm, and the deposition rate is 5 nm / s. Step 4: FIB roughing to remove excess material: Adjust the FIB tube parameters, increasing the accelerating voltage to 30kV and the beam current to 500pA. Based on the cutting boundary marked in Step 2, control the FIB tube to emit an ion beam along the cutting path to remove excess material around the target area layer by layer. During roughing, retain a 5μm pre-reserved layer above the target area to avoid directly cutting to the target cross-section. During roughing, the SEM tube continuously maintains imaging status, monitoring the material removal progress in real time. A six-axis high-precision sample stage is used to compensate for sample attitude shift, ensuring accurate cutting path. The roughing adopts a zoned removal strategy, using a high beam current for rapid removal in the outer area and a medium beam current for gradual removal in the near-target area. Step 5: FIB Refinement Processing to Obtain a Smooth Cross Section: After rough machining, reduce the beam current of the FIB tube to 30pA while maintaining the accelerating voltage at 30kV. Refine the reserved layer using a cross-thinning method, adjusting the sample tilt angle to 54° via a six-axis high-precision sample stage, and perform multiple thin-layer cuts along the target cross section direction, each cut being 5nm thick. During the refinement process, utilize the multi-channel imaging function of the SEM tube to simultaneously acquire SE2 and backscattered electron (BSE) signals, observing the cross section smoothness in real time until a scratch-free and distortion-free smooth cross section is obtained. Step Six: SEM Imaging Verification and Parameter Optimization: After the finishing process is completed, adjust the imaging parameters of the SEM tube. Use an accelerating voltage of 5kV and a magnification of 200KX to perform high-resolution imaging on the cut cross-section. Analyze the flatness of the cross-section image, the integrity of the target area, and the undamaged state through the signal acquisition system. If the cross-section meets the preset accuracy requirements, the cutting is completed.

[0023] Although embodiments of the invention have been shown and described (see the detailed description above), it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A FIB-SEM dual-beam precision cross-sectioning method based on a FIB-SEM dual-beam system, the FIB-SEM dual-beam system comprising a SEM column, a FIB column, a six-axis high-precision sample stage, a gas injection system, and a signal acquisition system, characterized in that: The method comprises the following steps: Step Sample pre-treatment: The sample to be cut is fixed on a six-axis high-precision sample stage, moved into the sample chamber and the vacuum system is started, so that the sample chamber reaches a vacuum of 1 x 10 -6 mbar to 5 x 10 -6 mbar; Step two: SEM high-resolution positioning target area: start SEM lens low-voltage imaging mode, collect signals through In-Lens annular SE detector, adjust sample posture to make target area in the center of imaging field of view, mark cutting boundary; Step three: deposition of protective layer: pass deposition gas through gas injection system, deposit a protective layer with a thickness of 50nm-200nm within the cutting boundary; Step four: FIB rough machining to remove excess material: adjust FIB lens parameters, emit ion beam along the cutting path to remove excess material layer by layer, reserve 1-5um reserved layer, and monitor in real time by SEM; Step five: FIB finishing machining to obtain flat cross section: reduce FIB beam current, cross-thin the reserved layer for finishing, and synchronously collect SE2 signal and BSE signal to observe cross section flatness; Step six: SEM imaging verification and parameter optimization: high-resolution imaging is performed on the cut cross section to analyze whether the accuracy requirement is met, and if not, return to step five for re-finishing.

2. The FIB-SEM dual beam precise cross-sectioning method according to claim 1, characterized in that: In step two, photoelectric correlation technology is used in SEM positioning in combination with optical microscope fluorescence positioning.

3. The FIB-SEM dual beam precise cross-sectioning method according to claim 1, characterized in that: In step three, the edge of the protective layer exceeds the cutting boundary by 0.5-1um, and the deposition gas is platinum precursor gas or tungsten precursor gas.

4. The FIB-SEM dual beam precise cross-sectioning method according to claim 1, characterized in that: In step three, the flow rate of the deposition gas is 1-5sccm, and the deposition rate is 1-5nm / s.

5. The FIB-SEM dual beam precise cross-sectioning method according to claim 1, characterized in that: In step four, the rough machining adopts a zoned removal strategy, the outer peripheral area is removed quickly with a large beam current, and the target area is removed gradually with a medium beam current.

6. The FIB-SEM dual beam precise cross-sectioning method according to claim 1, characterized in that: In step five, the finishing machining uses the no-leak magnetic design of the FIB-SEM double-beam system, the sample inclination angle is 45-54°, and the cutting thickness is 1-5nm each time.

7. The FIB-SEM dual beam precise cross-sectioning method according to claim 1, characterized in that: In step six, the three-dimensional reconstruction technology is used in imaging verification to construct a three-dimensional model of the cross section and quantitatively analyze the flatness and size accuracy.

8. The FIB-SEM dual beam precise cross-sectioning method according to claim 7, characterized in that: The three-dimensional reconstruction technology is used in imaging verification to construct a three-dimensional model of the cross section, and the implementation method is as follows: First, calibrate the parameters of the SEM lens and the signal collection system to ensure imaging consistency; set the SEM acceleration voltage to 1-3kV, the magnification to 50-150KX, and the detector to In-Lens detector and backscattered electron BSE detector combination, and adjust the initial posture of the six-axis high-precision sample stage to make the cutting cross section perpendicular to the SEM electron beam incidence direction at 90°, and record the X, Y, Z axis coordinates and inclination angle of the sample stage at this time as the reference parameters for subsequent multi-angle imaging; Start from the initial reference posture, rotate the sample along the rotation axis perpendicular to the cross section through the six-axis high-precision sample stage in steps, collect one cross section image every 1-3° of rotation, the rotation range covers-30° to +30°, after each rotation, keep the SEM imaging parameters unchanged, and after the sample stage posture is stable, start the signal collection system to obtain the cross section image; during the collection process, the sample stage rotation angle, coordinate position and imaging time corresponding to each image are recorded synchronously to form an "image-posture parameter" correlation data set, which ensures that the spatial position information of each image can be traced back during subsequent registration; The collected multi-angle images are pre-processed to remove imaging noise and interference signals: first, the brightness and contrast of all images are unified through a gray correction algorithm; then, an edge enhancement algorithm is used to highlight the profile features of the cross section; Finally, the noise reduction filter is used to remove the noise points caused by electronic noise and retain the true topographic information of the cross section; After pre-processing, the image registration is performed based on the "image-pose parameter" correlation dataset: the image under the initial reference pose is used as the reference image, and the images under other angles are used as the images to be registered; the feature point matching algorithm is used to identify the same cross section feature points in all images, and the spatial transformation relationship between the images to be registered and the reference image is calculated based on the sample stage rotation angle and coordinate space parameters; According to the spatial transformation relationship, the pixel position of the image to be registered is adjusted to accurately align the cross section feature points in all images, and a sequence of images with consistent spatial positions is formed; Based on the registered image sequence, a "voxel stacking + surface reconstruction" combined method is used to construct the cross section three-dimensional model: first, each registered image is regarded as a "slice" of the cross section under the corresponding viewing angle, the coordinate position of each slice in the three-dimensional space is calculated according to the sample stage rotation angle, and all slices are stacked in the form of voxels according to the spatial position to form a preliminary three-dimensional voxel model; then, the surface profile of the cross section in the voxel model is extracted through the surface reconstruction algorithm, the redundant background voxels are removed, and the three-dimensional surface structure of the cross section is retained; finally, the reconstructed surface profile is smoothed to eliminate the surface sawtooth caused by image registration deviation, and a three-dimensional model consistent with the actual cross section topography is formed.

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