A method for FIB-based routine TEM sample site-specific re-thinning processing
By using a FIB-SEM dual-beam system to perform targeted thinning of transmission electron microscopy samples, the problems of insufficient sample thickness for high-resolution analysis and instability were solved, achieving efficient and accurate sample preparation and high-quality imaging.
Patent Information
- Application Number
- CN202610408867.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-31
- Publication Date
- 2026-08-25
AI Technical Summary
Existing technologies make it difficult to achieve precise thickness control of transmission electron microscopy samples, especially for point-to-point thinning of initially thicker regions. This results in sample thickness not meeting the requirements for high-resolution analysis, and the sample is prone to drift or vibration under electron beam observation, affecting imaging quality.
By employing a FIB-SEM dual-beam system, the target area is precisely located, and FIB is used for cutting, welding, and further thinning. Combined with SEM/STEM imaging and EBSD and EDS, precise positioning and visualization processing are achieved, ensuring that the sample thickness is within the range of 50 nm to 100 nm, thus solving the problems of sample instability and thickness not meeting the requirements.
It achieves a high success rate in preparing transmission electron microscopy samples, and the samples exhibit good stability under high-resolution observation. It is widely applicable to samples of various materials and shapes, significantly improving sample preparation efficiency and imaging quality.
Smart Images
Figure CN122631398A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of microstructure characterization technology, and in particular to a method for localized re-thinning of conventional TEM samples based on FIB. Background Technology
[0002] Transmission electron microscopy (TEM), as a high-resolution microscopic analysis instrument, is widely used in the microstructural analysis of various materials and substances. The imaging quality of TEM is highly dependent on the ultrathin characteristics of the TEM sample. Sample preparation for TEM often faces problems such as complex operation, long processing time, and low success rate. Conventional TEM sample preparation methods, such as ion thinning and electrolytic double-jet printing, struggle to achieve precise control of sample thickness. The resulting sample thickness often gradually increases outwards from the central aperture region. Often, the ideal (region of interest) location (grain) is too thick for high-resolution TEM analysis, especially for samples with extremely important orientation relationships (such as special precipitates or twin structures).
[0003] Current technologies focus on initial sample preparation and lack the ability to precisely locate and reprocess pre-formed TEM sections. No secondary thinning techniques for TEM thin section samples have been reported, resulting in important micro-regions becoming invalid samples due to thickness issues.
[0004] Therefore, it is of great significance to develop a conventional TEM sample localized re-thinning processing method based on FIB. Summary of the Invention
[0005] The purpose of this invention is to provide a method for fixed-point re-thinning of conventional transmission electron microscopy samples based on FIB, so as to solve the problems existing in the prior art.
[0006] The technical solution adopted to achieve the purpose of this invention is as follows: a conventional TEM sample localization and re-thinning processing method based on FIB, comprising the following steps:
[0007] 1) Identify the target region in the original conventional TEM sample using TEM.
[0008] 2) Transfer the original conventional TEM sample to the FIB-SEM dual-beam system and use SEM to lock the target area predetermined in step 1).
[0009] 3) Use FIB to cut out the target area and transfer it for welding onto a dedicated platform.
[0010] 4) Use FIB to further thin and clean the welded sample to obtain a TEM sample that meets the preset thickness requirements.
[0011] 5) Perform SEM examination on the TEM sample after secondary thinning. After confirming successful sample preparation, complete the TEM observation and microstructure analysis of the sample.
[0012] Furthermore, in step 2), the target area is located using STEM or BSE imaging mode.
[0013] Furthermore, step 3) specifically includes the following sub-steps:
[0014] 3.1) Precise demarcation and pre-isolation of the target region. A micron-level isolation zone is defined with the target region as the geometric center. U-shaped grooves are fabricated on both sides of the isolation zone to retain the critical connection between the target region and the substrate, forming a cantilever beam structure that includes the target region.
[0015] 3.2) Target region dissociation. Ion beam cleavage is performed in a safe zone ≥20μm from the target region to break the final connection between the target region and the substrate, forming a free sheet.
[0016] 3.3) Stage Transfer. Transfer the free section onto the transmission electron microscope stage.
[0017] Furthermore, step 4) specifically includes the following sub-steps:
[0018] 4.1) Deposit a protective layer on the surface of the target area using vapor deposition.
[0019] 4.2) At 30keV, the beam intensity is gradually reduced to perform preliminary thinning of the sample, reducing the sample thickness to below 200nm. During this process, the shape change of the target object must be monitored at all times to avoid damage to the target object due to excessive thinning of the front / back sides.
[0020] 4.3) Then, the thinned sample is cleaned with a low voltage and low beam current to remove the surface amorphous layer and further thin the sample to ≤100nm.
[0021] Further, in step 4.1), a 0.3 μm thick carbon protective layer and a 2 μm thick W or Pt protective layer are vapor-deposited on the surface of the target area.
[0022] Furthermore, in step 4.2), the beam current is gradually reduced from 0.23 nA to 40 pA at a voltage of 30 kV.
[0023] Furthermore, in step 4.3), the sample surface is deeply cleaned using two operating conditions: 5kV, 16pA and 2kV, 23pA.
[0024] Furthermore, after step 4), the thickness of the TEM sample is 50 nm to 100 nm.
[0025] Furthermore, in step 5), the sample is thinned using SEM or TEM and then subjected to quality testing and evaluation.
[0026] Furthermore, in step 5), precise positioning is achieved by combining SEM / STEM imaging, EBSD, and EDS.
[0027] The technical effects of this invention are beyond doubt:
[0028] A. Solving the problem of secondary thinning of thick TEM samples: TEM characterization requires extremely high sample thickness, typically less than 100 nm, or even less than 50 nm. However, targeted thinning of the target (initially thick) region of TEM thin sections is indeed extremely difficult. This is because the thinned TEM sample is very fragile, and the reprocessing operation can easily damage the sample; at the same time, conventional thinning techniques cannot achieve targeted thinning of micro-areas. Under these circumstances, developing a FIB-based secondary targeted processing and thinning technique for TEM samples is of great significance for solving problems such as secondary thinning of TEM samples.
[0029] B. Solving the problem of sample instability (suspended): Good sample stability (no drift or vibration) is crucial for obtaining high-resolution images in transmission electron microscopy (TEM). However, for TEM samples prepared by methods such as ion thinning, the numerous pores in the sample lead to unstable connections in some areas, causing the sample to "jitter" under electron beam observation, resulting in difficulties in high-resolution imaging (often manifested as high-frequency vibration). This stability problem can be effectively solved by transferring the region of interest to a dedicated stage and firmly welding it in place.
[0030] C. High repeatability and reliability, and high sample preparation success rate: The FIB-SEM system has the function of simultaneous observation and fixed-point micro-nano processing, which can accurately locate and visualize the processing of the region of interest, ensuring the reliability of sample processing and greatly improving the success rate of sample preparation.
[0031] D. Wide Applicability: FIB processing has broad applicability, effectively preparing transmission electron microscopy (TEM) samples from both metallic and non-metallic materials. Similarly, this FIB-based thinning technique can handle samples of various materials, shapes, and preparation methods for further thinning, thus demonstrating its wide applicability. Leveraging the high efficiency, precision, and speed of FIB micro / nano fabrication, this method can significantly optimize TEM sample quality, shorten sample preparation time, and improve experimental efficiency, saving researchers valuable time and providing new insights into challenging TEM samples. Attached Figure Description
[0032] Figure 1Flowchart of the fixed-point re-thinning process;
[0033] Figure 2 This is a schematic diagram of the fixed-point re-thinning process. Figure 2 a is a schematic diagram of the region of interest in the sample as determined by transmission electron microscopy; Figure 2 b is a schematic diagram of the isolation zone; Figure 2 c is a schematic diagram of the platform transfer; Figure 2 d represents the TEM sample after secondary thinning;
[0034] Figure 3 For EBSD diffraction patterns;
[0035] Figure 4 This is a diagram showing the orientation relationship between the precipitated phase and the matrix. Detailed Implementation
[0036] The present invention will be further described below with reference to embodiments, but it should not be construed that the scope of the present invention is limited to the following embodiments. Various substitutions and modifications made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention should be included within the scope of protection of the present invention.
[0037] Example 1:
[0038] See Figure 1 This embodiment provides a method for targeted re-thinning of conventional TEM (Transmission Electron Microscope) samples based on FIB (Focused Ion Beam), including the following steps:
[0039] 1) Identify the region of interest (ROI) in the original conventional TEM sample using TEM.
[0040] 2) Transfer the original conventional TEM sample to the FIB-SEM dual-beam system (Focused Ion Beam-Scanning Electron Microscope) and use SEM to lock the target area predetermined in step 1).
[0041] 3) Use FIB (Film Injection Block) to cut out the target area and transfer it for welding onto a dedicated platform. Step 3) specifically includes the following sub-steps:
[0042] 3.1) Precise demarcation and pre-isolation of the target region. A micron-level isolation zone is defined with the target region as the geometric center. U-shaped grooves are fabricated on both sides of the isolation zone to retain the critical connection between the target region and the substrate, forming a cantilever beam structure that includes the target region.
[0043] 3.2) Target Region Dissociation. Ion beam cleavage is performed within a safe zone ≥20 μm from the target region to sever the final connection between the target region and the substrate, forming a free sheet. It is worth noting that, to minimize damage to the region of interest (ROI) during sample locating and cleaving in FIB-SEM (including ion irradiation, C deposition, etc.), sample transfer and welding operations should be performed relatively far from the RIO. The cleavage area should ideally be at least 20 μm away from the RIO.
[0044] 3.3) Stage Transfer. Transfer the free section onto the transmission electron microscope stage.
[0045] 4) Use FIB (Film Injection Brush) to further thin and clean the welded sample to obtain a transmission electron microscope (TEM) sample that meets the preset thickness requirements. Step 4) specifically includes the following sub-steps:
[0046] 4.1) Deposit a protective layer on the surface of the target area using vapor deposition.
[0047] 4.2) At 30keV, the beam intensity is gradually reduced to perform preliminary thinning of the sample, reducing the sample thickness to below 200nm. During this process, the shape change of the target object must be monitored at all times to avoid damage to the target object due to excessive thinning of the front / back sides.
[0048] 4.3) Then, the thinned sample is cleaned with a low voltage and low beam current to remove the surface amorphous layer and further thin the sample to ≤100nm.
[0049] 5) After the TEM sample has been thinned twice, it is first checked by SEM to ensure that the sample preparation is successful. Then, it is placed in a transmission electron microscope to complete the TEM observation and microstructure analysis of the sample.
[0050] This embodiment utilizes the pinpoint, visualization, and ultra-precision micro / nano fabrication capabilities of FIB to develop a technique for further thinning of transmission electron microscopy (TEM) samples. Through trial and error, a specific thinning technique and operational steps were developed and optimized, ultimately achieving secondary thinning of a magnesium alloy precipitate sample and obtaining high-quality TEM samples and microscopic analysis results. The establishment of this method solves the problem of thinning critical areas of thicker TEM samples, providing a reliable solution for the high-precision, high-quality preparation of specific samples and promoting the development and practical application of advanced electron microscopy.
[0051] Example 2:
[0052] See Figure 1 This embodiment provides a conventional TEM sample localization re-thinning method based on FIB, including the following steps:
[0053] 1) Identify the region of interest / target region in the original conventional TEM sample using TEM.
[0054] 2) Transfer the original conventional TEM sample to the FIB-SEM dual-beam system and use SEM to lock the target area predetermined in step 1).
[0055] 3) The target area is cut out using FIB and transferred and welded onto a dedicated stage. Cutting and transferring the target area is accomplished by using FIB ion beam, gas deposition, and robotic arms to cut, transfer, and weld the sample target area. Step 3) specifically includes the following sub-steps:
[0056] 3.1) Place the target area of the sample in the center, and use it as the center to determine and cut a sample block to be extracted with a length and width of (10um-20um) × (5um-10um);
[0057] 3.2) The sample is then placed into the robotic arm (W needle) and bonded to the sample block to be extracted using a gas deposition system. The connection between the sample block and the substrate is then severed, thereby transferring the sample block to the robotic arm.
[0058] 3.3) Transfer the sample block to a dedicated stage and weld it securely. To reduce damage or contamination to the target area during cutting and welding, the cutting and welding areas should be at least 20 μm away from the target area.
[0059] 4) Use FIB (Film Injection Brush) to further thin and clean the welded sample to obtain a transmission electron microscope (TEM) sample that meets the preset thickness requirements. Step 4) specifically includes the following sub-steps:
[0060] 4.1) Transfer the sample to a good sample and further remove the excess part to ensure that the target area is preferably located at the center of the sample. The final sample area to be thinned is preferably a rectangle of about 10um × 5um.
[0061] 4.2) A carbon protective layer of about 0.3 μm and a W or Pt protective layer of 2 μm thickness are deposited on the top of the sample to be thinned to protect the center of the sample during the thinning process (the type and thickness of the protective layer can be adjusted according to the material of the sample, the thinning situation, etc.).
[0062] 4.3) Subsequently, the total thickness of the sample was reduced to less than 200 nm by controlling the thinning parameters. During this process, it is necessary to follow the principle of gradually decreasing the beam current in the conventional thinning process (the beam current at 30 kV is gradually reduced from 0.23 nA to 40 pA), while also paying close attention to the actual situation of the thinned area to avoid over-thinning of the sample in the thickness direction, which could damage the target area (during the thinning process, the shape change of the target object is used to determine whether it has been thinned to the required level, and the thickness of the sample on both sides is adjusted in real time accordingly).
[0063] 4.4) After thinning, the sample surface is then deeply cleaned by low voltage and low current (5kV, 16pA and 2kV, 23pA) to remove the surface amorphous layer and further reduce the sample thickness to below 100nm.
[0064] 5) After the TEM sample has been thinned twice, it is first checked by SEM to ensure that the sample preparation is successful. Then, it is placed in a transmission electron microscope to complete the TEM observation and microstructure analysis of the sample.
[0065] Example 3:
[0066] The main content of this embodiment is the same as that of Embodiment 1 or 2. However, after thinning the sample using SEM or TEM, quality inspection and evaluation are performed to ensure that the thickness of the target region meets the requirements for transmission electron microscopy microstructure research. Precise localization is achieved by combining SEM / STEM imaging, EBSD, and EDS.
[0067] Example 4:
[0068] The main content of this embodiment is the same as any one of embodiments 1 to 3, wherein the transmission electron microscope stage is a copper stage. Other materials can also be used, such as molybdenum, titanium, tantalum, etc., depending on the elemental composition of the sample being studied and the testing requirements.
[0069] Example 5:
[0070] The main content of this embodiment is the same as any one of embodiments 1 to 4. In this embodiment, when checking the thickness and quality of the thinned sample, the TKD mode of EBSD (parameters 30kV, 11nA) is used to acquire diffraction patterns to characterize the crystal structure of the sample. The obtained EBSD images are used to determine whether the sample thickness meets the requirements for transmission electron microscopy (TEM) observation. When the diffraction pattern and orientation distribution are clear, the sample thickness is considered appropriate; otherwise, thinning needs to continue until the thickness is suitable. EBSD can also analyze the orientation of different grains in the sample and the relationship between the precipitated phase and the matrix orientation, greatly facilitating subsequent TEM research. Besides using EBSD for sample thickness detection, scanning electron microscopes (STEM) or ETD detectors can also be used to determine the sample thickness in real time by measuring the sample contrast to ensure that the final sample thickness meets the requirements for TEM testing.
[0071] Example 6:
[0072] The main content of this embodiment is the same as any one of embodiments 1 to 5, wherein, see [link / reference]. Figure 2This embodiment focuses on the secondary thinning process of a transmission electron microscopy (TEM) sample containing a specific precipitate in a magnesium alloy, in order to better conduct analyses of its microstructure and orientation relationships. The original sample is a Mg alloy prepared by ion thinning. The region of interest is a certain precipitate that has a specific orientation relationship with the Mg matrix, but this region requires a relatively thick thickness for TEM observation (approximately 1 μm in actual thickness). Before the secondary thinning process, microstructure analyses such as EDS composition and electron diffraction of crystal phases and orientations can be performed on this region, but the excessive thickness makes high-resolution (especially atomic-scale) structural analysis impossible.
[0073] In step 2), the region of interest in the sample determined by the transmission electron microscope is located using scanning transmission imaging mode at 30kV and 1.4nA, such as... Figure 2 As shown in a.
[0074] In step 3), using the region of interest as the center, remove the excess sample portion surrounding it, such as... Figure 2 As shown in b, the region of interest is cut out using the FIB (Feature Injection Block), and the cut sample block is transferred and soldered onto the FIB's dedicated copper stage using a robotic arm, as shown in Figure b. Figure 2 As shown in c. The transferred sample block was first subjected to surface protection deposition (a 0.3 μm thick C layer and a 2 μm thick W layer). Then, conventional transmission electron microscopy (TEM) thinning methods were used for further thinning, i.e., the sample was gradually thinned to below 200 nm using beam currents of 0.23 nA, 80 pA, and 40 pA at a resolution of 30 kV. Finally, low-voltage cleaning was performed using parameters of 5 kV, 16 pA and 2 kV, 9 pA to remove amorphous layers and ensure the sample thickness reached below 100 nm, thus completing the TEM sample preparation. Figure 2 As shown in d.
[0075] In step 5), EBSD is used to measure the thickness and analyze the orientation of the thinned sample. When a clear EBSD diffraction pattern and crystal orientation distribution map can be obtained in TKD mode at 30kV and 11nA, the sample thickness meets the requirements for transmission voltage observation, and the orientation relationship between the precipitated phase and the matrix can be analyzed through the orientation distribution map. Figure 3 and Figure 4 As shown, the TEM sample, after further thinning, is placed back into the transmission electron microscope for microstructure analysis. If a clear EBSD diffraction pattern cannot be detected in the sample, it indicates that the sample is too thick, and step 4) needs to be repeated until the thickness meets the requirements.
[0076] After secondary processing by FIB at specific points, the sample thickness can reach below 100 nm, which well meets the processing requirements of transmission electron microscopy.
Claims
1. A method for spot re-thinning of conventional TEM samples based on FIB, characterized in that, Includes the following steps: S1) Identify the target region in the original conventional TEM sample using TEM; S2) Transfer the original conventional TEM sample to the FIB-SEM dual-beam system and use SEM to lock the target area predetermined in step S1); S3) Use FIB to cut out the target area and transfer it for welding onto a dedicated platform; S4) Use FIB to further thin and clean the welded sample to obtain a TEM sample that meets the preset thickness requirements. S5) Perform SEM examination on the TEM sample after secondary thinning; after confirming successful sample preparation, complete the TEM observation and microstructure analysis of the sample.
2. The method for point-to-point re-thinning of conventional TEM samples based on FIB according to claim 1, characterized in that: In step S2), the target area is located using STEM or BSE imaging mode.
3. The method for point-to-point re-thinning of conventional TEM samples based on FIB according to claim 1, characterized in that, Step S3) specifically includes the following sub-steps: S3.1) Precise demarcation and pre-isolation of the target area; delineate a micron-level isolation zone with the target area as the geometric center; prepare U-shaped grooves on both sides of the isolation zone to retain the critical connection between the target area and the substrate, forming a cantilever beam structure containing the target area; S3.2) Target region dissociation: Ion beam cleavage is performed in a safe zone ≥20μm from the target region to break the final connection between the target region and the substrate, forming a free sheet; S3.3) Stage transfer; Transfer the free section onto the transmission electron microscope stage.
4. The method for point-to-point re-thinning of conventional TEM samples based on FIB according to claim 1, characterized in that, Step S4) specifically includes the following sub-steps: S4.1) Deposit a protective layer on the surface of the target area using vapor deposition; S4.2) At 30keV, the beam intensity is gradually reduced to perform preliminary thinning of the sample, reducing the sample thickness to below 200nm. During this process, the shape change of the target object must be monitored at all times to avoid excessive thinning of the front / back sides, which could damage the target object. S4.3) Then, the thinned sample is cleaned with a low voltage and low beam current to remove the surface amorphous layer and further thin the sample to ≤100nm.
5. The method for fixed-point re-thinning of conventional TEM samples based on FIB according to claim 4, characterized in that: In step S4.1), a 0.3 μm thick carbon protective layer and a 2 μm thick W or Pt protective layer are vapor-deposited on the surface of the target area.
6. The method for point-to-point re-thinning of conventional TEM samples based on FIB according to claim 4, characterized in that: In step S4.2), the beam current is gradually reduced from 0.23 nA to 40 pA at a voltage of 30 kV.
7. The method for point-to-point re-thinning of conventional TEM samples based on FIB according to claim 4, characterized in that: In step S4.3), the sample surface is deeply cleaned using two operating conditions: 5kV, 16pA and 2kV, 23pA.
8. The method for point-to-point re-thinning of conventional TEM samples based on FIB according to claim 1, characterized in that: After step S4), the thickness of the TEM sample is 50 nm to 100 nm.
9. The method for point-to-point re-thinning of conventional TEM samples based on FIB according to claim 1, characterized in that: In step S5), the sample is thinned using SEM or TEM and then subjected to quality testing and evaluation.
10. The method for point-to-point re-thinning of conventional TEM samples based on FIB according to claim 1, characterized in that: In step S5), precise positioning is achieved by combining SEM / STEM imaging, EBSD, and EDS.