Method for processing transmission sample by using focused ion beam

Abstract

The invention discloses a method for processing a transmission sample by using a focused ion beam, and the method comprises the following steps: carrying out the overall thinning of the transmission sample by using the focused ion beam to form an overall thinning region, the thickness of the overall thinning region being a first preset thickness, and forming a supporting cross beam at the periphery of the overall thinning region, the thickness of the supporting beam is larger than first preset thickness. And the focused ion beam is used for conducting zoned thinning on the overall thinning area of the transmission sample, so that at least two unit thin areas are formed in the overall thinning area, the thickness of each unit thin area is smaller than a second preset thickness, the transverse width of each unit thin area is a first preset distance, and the interval between every two adjacent unit thin areas is a second preset distance.

Description

Technical Field

[0001] The present application relates to the technical field of sample preparation, and in particular to a method for processing a transmission sample using a focused ion beam. Background Art

[0002] The semiconductor industry has been driven by a relentless pursuit of miniaturization, a trend that follows Moore's Law, which posits that the number of transistors on a microchip doubles approximately every two years, leading to ever-increasing performance and decreasing costs per transistor. This trend has led the semiconductor industry to focus on device scaling, which is the reduction of the size of semiconductor devices on a chip. The shift from deep ultraviolet to extreme ultraviolet lithography (the process of etching circuit patterns onto silicon wafers) has made it possible to define features much smaller than before, allowing semiconductor devices to continue to shrink in size. In 2017, semiconductor manufacturing processes entered the 10nm node, in 2018 the 7nm node, and in 2020 the 5nm process node.

[0003] Transmission electron microscope (TEM) plays a key role in the advancement and quality control of chip manufacturing processes, especially as the semiconductor industry moves towards a scale below 10nm. At these ultra-fine dimensions, the structural integrity, material composition, and electrical properties of semiconductor devices are increasingly sensitive to atomic-level defects. TEM has excellent spatial resolution and analytical capabilities, making it indispensable for ensuring the performance and reliability of nanoscale devices. Therefore, for electronic devices below 10nm process, it is necessary to achieve TEM sample preparation with a thickness of less than 10nnm.

[0004] On the other hand, processing the lens samples required for TEM to a thickness of less than 10nm is crucial for high-resolution atomic structure imaging. It not only improves image quality and contrast, but also reduces multiple scattering events and potential sample damage, ultimately achieving more precise and accurate atomic structure characterization. Especially for atomic-resolution scanning transmission electron microscopy (STEM) and differential phase contrast (DPC) characterization requirements, processing the sample thickness to less than 10nm can significantly improve the clarity and accuracy of the atomic structure diagram. This is particularly important in the fields of materials science and semiconductor devices, where understanding atomic-scale structures is the key to developing and regulating material properties.

[0005] The existing lens sample preparation scheme is to use a focused ion beam microscope (FIB) with low-energy ion milling or operation technology to thin the sample to the required thickness. It includes scheme (1) and scheme (2). Scheme (1) is to use the conventional FIB sample preparation method to process the lens sample to a thickness of 30nm, and then use the Ar ion beam milling method to process the sample thickness to less than 10nm.

[0006] Solution (2) is to use the lift-out technique to cut a small sample slice from the original sample, and then use a mechanical arm to rotate the sample slice, rotate the original surface 180 degrees, and then weld it to the TEM stage. The inverted thinning method can obtain a lens sample with a thickness of less than 10nm.

[0007] The inventors found in the process of implementing the present invention that the above-mentioned solution (1) increases the complexity of the sample preparation process because it requires the use of two devices, FIB and ion milling, to prepare lens samples. The lens samples prepared by conventional FIB can process thin areas with a width of 5-10um, but when the sample thickness is reduced to 10nm, the thin areas above the 5um scale will bend. Therefore, it is necessary to reduce the width of the thin area to a range of 2-3um, which leads to a reduction in the observable area. The positioning function of the current ion milling equipment is at a scale of 10-20um, so a large range of milling is required, and it is not easy to achieve the positioning thinning of the 2um thin area and the precise control of the thickness. If it is necessary to achieve ion milling with a thickness below 10nm, multiple parameter tests and thickness tests are required. Therefore, it is necessary to invest additional time and technical experience to achieve sample preparation of the target thickness.

[0008] In the above scheme (2), after extracting the thin area of ​​the sample, the operation of rotating the slice 180 degrees has high requirements on the functional configuration and rotation alignment of the robot arm. In addition, the precise positioning of the inverted thinning also requires long-term FIB operation experience and a high level of technology. Therefore, the use of this scheme for 10nm thick TEM sample preparation has high requirements on the FIB equipment and FIB operators. Summary of the invention

[0009] The present application provides a method for processing transmission samples using a focused ion beam. Under the framework of conventional sample preparation technology, by designing a thinning structure, it is possible to achieve sample preparation with a thickness of less than 10 nm and simplify the operation process of existing solutions, making the preparation process of transmission samples with a thickness of less than 10 nm simple and efficient, and reducing the technical difficulty of sample preparation.

[0010] The present invention provides a method for processing a transmission sample using a focused ion beam, comprising the following steps:

[0011] The transmission sample is thinned as a whole by using a focused ion beam to form an overall thinned region, wherein the thickness of the overall thinned region is a first preset thickness, and a supporting crossbeam is formed around the overall thinned region, and the thickness of the supporting crossbeam is greater than the first preset thickness;

[0012] The overall thinned area of ​​the above-mentioned transmission sample is partitioned and thinned using a focused ion beam to form at least two unit thin areas in the above-mentioned overall thinned area, wherein the thickness of each unit thin area is less than the second preset thickness, the lateral width of each unit thin area is the first preset distance, and the interval between two adjacent unit thin areas is the second preset distance.

[0013] In some embodiments, the overall thinning of the transmission sample using a focused ion beam to form an overall thinned region includes:

[0014] Using a step-cutting mode, the transmission sample is first processed with a first ion beam voltage and current, a first cutting angle and a first cutting depth to form a first overall thinned region, wherein the first overall thinned region has a third preset thickness;

[0015] Using a step-cutting mode, continuing to process the transmission sample for a second time with a second ion beam voltage and current, a first cutting angle and a second cutting depth to form the overall thinned area, wherein the overall thinned area has a third preset thickness;

[0016] The transmission sample is processed for a third time with a third ion beam voltage and current, a first cutting angle and a third cutting depth, so that the thickness of the overall thinned area reaches a first preset thickness.

[0017] In some embodiments, the third cutting depth is equal to the first cutting depth and the second cutting depth, and is smaller than the longitudinal width of the transmission sample.

[0018] In some embodiments, the first switching cutting angle is 1.2 degrees, the third preset thickness is 500nm, the first preset thickness is 300nm, the first cutting depth, the second cutting depth and the third cutting depth are 4.5um, 1.5um and 6um respectively.

[0019] In some embodiments, the first ion beam voltage and current are 30 KV and 0.23 nA, the second ion beam voltage and current are 30 KV and 80 pA, and the third ion beam voltage and current are 30 KV and 40 pA.

[0020] In some embodiments, the above-mentioned using a focused ion beam to perform zone thinning on the overall thinned area of ​​the above-mentioned transmission sample to form at least two unit thin areas in the above-mentioned overall thinned area includes:

[0021] Performing a first processing on at least two unit thin regions in the overall thinning region at a fourth ion beam voltage and current, a first cutting angle and a fourth cutting depth to obtain at least two unit thin regions having a fourth preset thickness;

[0022] Performing a second processing on at least two unit thin regions in the overall thinning region at a fifth ion beam voltage and current, a first cutting angle and a fourth cutting depth to obtain at least two unit thin regions having a fifth preset thickness;

[0023] Performing a third processing on at least two unit thin regions in the overall thinning region at a sixth ion beam voltage and current, a second cutting angle and a fourth cutting depth to obtain at least two unit thin regions having a sixth preset thickness;

[0024] The at least two unit thin regions in the overall thinning region are processed for the fourth time with the seventh ion beam voltage and current, the second cutting angle and the fourth cutting depth to obtain at least two unit thin regions having a thickness less than the second preset thickness.

[0025] In some embodiments, the fourth cutting depth is less than or equal to the third cutting depth.

[0026] In some embodiments, the second cutting angle is 3 degrees, and the second preset depth, the fourth preset depth, the fifth preset depth and the sixth preset depth are 10 nm, 150 nm, 100 nm and 30 nm respectively.

[0027] In some embodiments, the fourth ion beam voltage and current are 16KV and 23pA, the fifth ion beam voltage and current are 8KV and 21pA, the sixth ion beam voltage and current are 5KV and 7pA, and the seventh ion beam voltage and current are 2KV and 9pA.

[0028] In some embodiments, before the overall thinning of the transmission sample using a focused ion beam, the process further includes: forming a protective layer on the original surface of the lens sample, wherein the thickness of the protective layer is greater than 2.5 um.

[0029] The embodiment of the present application uses a focused ion beam to thin the transmission sample as a whole to form an overall thinned area, the thickness of the overall thinned area is a first preset thickness, and a supporting beam is formed around the overall thinned area, the thickness of the supporting beam is greater than the first preset thickness; the overall thinned area of ​​the transmission sample is partitioned thinned by using a focused ion beam to form at least two unit thin areas in the overall thinned area, the thickness of each unit thin area is less than the second preset thickness, the lateral width of each unit thin area is a first preset distance, and the interval between two adjacent unit thin areas is a second preset distance. The present invention adopts a preparation process of thinning the transmission sample as a whole first and then partitioning, which simplifies the operation process of preparing a 10nm thick transmission electron microscope sample, reduces the technical requirements for thinning, and avoids bending deformation of the film in the frame after the thickness is thinned by the setting of the supporting beam, thereby ensuring the stability and accuracy of the sample.

[0030] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0032] Figure 1 A schematic plan view of a transmission sample thinning structure provided in an embodiment of the present application;

[0033] Figure 2 A schematic cross-sectional view of a transmission sample thinning structure provided in an embodiment of the present application;

[0034] Figure 3 A flow chart of a method for processing a transmission sample using a focused ion beam provided in an embodiment of the present application;

[0035] Figure 4 A schematic diagram of a specific process for overall thinning of a transmission sample using a focused ion beam provided in an embodiment of the present application;

[0036] Figure 5 A schematic diagram of a specific process for thinning a transmission sample by partition using a focused ion beam provided in an embodiment of the present application;

[0037] Figure 6 A scanning electron microscope diagram of a transmission sample processed by a focused ion beam microscope provided in an embodiment of the present application;

[0038] Figure 7 This is a diagram showing the effect of the STEM probe provided in the embodiment of the present application observing a thin area of ​​a transmission sample with a thickness of less than 10 nm;

[0039] Figure 8 An atomic resolution transmission image of a transmission sample having a device stack structure of W / HfZrOx / W provided in an embodiment of the present application. DETAILED DESCRIPTION

[0040] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0041] The embodiment of the present application combines the conventional sample preparation extraction process with the undercut thinning process, performs zone thinning and undercut thinning in the plane, and achieves undercut thinning thickness of each zone to be less than 10nm. Figure 1 As shown, on a sample slice with a width greater than 10 μm, at least two partitions, namely unit thin regions, can be processed. The width of each partition and the spacing between the partitions can be designed according to actual needs, for example, Figure 1 As shown, three partitions can be set, the width of each partition can be 2um, and the interval can be 1um. Then each partition unit is thinned, and the parameters of inverted thinning are used to obtain the following Figure 2 The transmission electron microscopy observation area shown is less than 10nm thick.

[0042] Figure 3 A schematic diagram of a process for processing a transmission sample using a focused ion beam provided in an embodiment of the present application. Figure 4 A schematic diagram of a specific process for overall thinning of a transmission sample using a focused ion beam provided in an embodiment of the present application, Figure 5 A schematic diagram of a specific process for thinning a transmission sample by partition using a focused ion beam is provided in an embodiment of the present application.

[0043] like Figure 3 As shown, processing a transmission sample using a focused ion beam includes the following steps:

[0044] Step S101: using a focused ion beam to perform overall thinning on the transmission sample to form an overall thinned region 102, wherein the thickness of the overall thinned region 102 is a first preset thickness, and a supporting beam 101 is formed around the overall thinned region 102, and the thickness of the supporting beam 101 is greater than the first preset thickness;

[0045] Prepare the transmission sample to be thinned and ensure that its surface is clean and free of contamination. Fix the sample on the sample carrier to ensure that the sample is stable and its position can be precisely controlled. Use the ion beam source in the focused ion beam microscope to irradiate the focused ion beam on a specific area on the sample surface. Adjust the current and voltage of the ion beam to control the intensity and direction of the ion beam to ensure that it accurately cuts and thins the sample. According to the preset first preset thickness, gradually adjust the parameters of the ion beam to thin the sample as a whole. During the thinning process, it is necessary to continuously monitor the morphology and thickness changes of the sample to ensure the controllability and accuracy of the thinning process. Around the overall thinning area 102, by adjusting the irradiation range and intensity of the ion beam, a support beam 101 with a thickness greater than the first preset thickness is formed. The presence of the support beam 101 can maintain the stability of the overall thinning area 102 and prevent it from being deformed or damaged during subsequent processing or use.

[0046] Step S102: Use a focused ion beam to perform partitioned thinning on the overall thinned area 102 of the transmission sample to form at least two unit thin areas 103 in the overall thinned area 102, wherein the thickness of each unit thin area 103 is less than the second preset thickness, the lateral width of each unit thin area 103 is the first preset distance, and the interval between two adjacent unit thin areas 103 is the second preset distance.

[0047] Exemplarily, the acceleration voltage, beam current, scanning speed and other parameters of the ion beam are set in the focused ion beam microscope to ensure accurate material removal, and the focused ion beam is used to form at least two unit thin areas 103 in the overall thinning area 102, the thickness of each unit thin area 103 is less than the second preset thickness, the lateral width of each unit thin area 103 is the first preset distance, and the interval between two adjacent unit thin areas 103 is the second preset distance, such as Figure 1 During the processing, it is necessary to pay close attention to the surface morphology and thickness changes of the sample and adjust the processing parameters in time to maintain the required accuracy and uniformity.

[0048] The embodiment of the present application uses a focused ion beam to thin the transmission sample as a whole to form an overall thinned area, the thickness of the overall thinned area is a first preset thickness, and a supporting beam is formed around the overall thinned area, the thickness of the supporting beam is greater than the first preset thickness; the overall thinned area of ​​the transmission sample is partitioned thinned by using a focused ion beam to form at least two unit thin areas in the overall thinned area, the thickness of each unit thin area is less than the second preset thickness, the lateral width of each unit thin area is a first preset distance, and the interval between two adjacent unit thin areas is a second preset distance. The present invention adopts a preparation process of thinning the transmission sample as a whole first and then partitioning, which simplifies the operation process of preparing a 10nm thick transmission electron microscope sample, reduces the technical requirements for thinning, and avoids bending deformation of the film in the frame after the thickness is thinned by the setting of the supporting beam, thereby ensuring the stability and accuracy of the sample.

[0049] The specific steps are as follows:

[0050] like Figure 4 As shown, in step S101 of the above embodiment, the transmission sample is thinned as a whole by using a focused ion beam to form an overall thinned region 102, which may include the following steps:

[0051] Step S201: adopting a step-by-step cutting mode to perform a first processing on the transmission sample with a first ion beam voltage and current, a first cutting angle and a first cutting depth to form a first overall thinned area 1021, wherein the first overall thinned area 1021 has a third preset thickness;

[0052] For example, Figure 1 As shown, the step-by-step cutting mode in the focused ion beam is adopted, the first ion beam voltage and current are set to 30KV, 0.23nA, the first cutting angle, i.e., the tilt angle of the transmission sample relative to the incident direction of the ion beam is 1.2 degrees, and the first cutting depth is 4.5um. With such a depth setting, a 1-2um wide bottom support beam can be retained to avoid bending deformation of the film in the frame after the thickness is thinned. Under the ion beam with a first ion beam current of 0.23nA, the thickness of the transmission sample is thinned to a third preset thickness of 500nm, and a first overall thinning area 1021 is formed.

[0053] Step S202: using a step-cutting mode, continuing to process the transmission sample for a second time with a second ion beam voltage and current, a first cutting angle and a second cutting depth to form an overall thinned region 102, wherein the overall thinned region 102 has a third preset thickness;

[0054] Exemplarily, the step-by-step cutting mode in the focused ion beam technology is adopted, and the voltage of the second ion beam is set to 30KV and the current is 80pA. The first cutting angle, that is, the inclination angle of the transmission sample relative to the incident direction of the ion beam, is set to 1.2 degrees. At the same time, the second cutting depth is set to 1.5um. Such a cutting depth setting can ensure that the thinning plane of the transmission sample has a uniform thickness and avoids the formation of a wedge-shaped thickness gradient at the bottom. While maintaining the second ion beam current at 80pA, the cutting is continued until the thickness of the sample is thinned to a third preset thickness, i.e., 500nm.

[0055] Step S203: Processing the transmission sample for a third time with a third ion beam voltage and current, a first cutting angle and a third cutting depth, so that the thickness of the overall thinned region 102 reaches a first preset thickness.

[0056] Exemplarily, the step-by-step cutting mode in the focused ion beam is adopted, and the parameters of the focused ion beam are set: the voltage of the third ion beam is 30KV, and the current is 40pA. At the same time, the inclination angle of the thin slice relative to the incident direction of the ion beam, that is, the first cutting angle, is set to 1.2 degrees. The cutting depth is set to the third cutting depth of 6um, where the third cutting depth is equal to the sum of the first cutting depth and the second cutting depth, and is less than the longitudinal width of the transmission sample of 10um. The thickness of the thin area of ​​the sample is thinned to the first preset thickness, that is, 300nm.

[0057] Then, the overall thinned region 102 of the transmission sample is thinned in sections using a focused ion beam to form at least two unit thin regions 103 in the overall thinned region 102 .

[0058] like Figure 5 As shown, in the above step S102, using a focused ion beam to thin the transmission sample by partition may include the following steps:

[0059] Step S301: performing a first processing on at least two unit thin regions 103 in the overall thinning area 102 with a fourth ion beam voltage and current, a first cutting angle and a fourth cutting depth to obtain at least two unit thin regions 103 with a fourth preset thickness;

[0060] Exemplarily, the whole-surface chipping mode is adopted, and the sample thin area is partitioned by a focused ion beam. The lateral width of each unit thin area 103 is a first preset distance of 2um, and the interval between two adjacent unit thin areas 103 is a second preset distance of 1um. The parameters of the focused ion beam are set: the voltage of the fourth ion beam is 16KV, and the current is 23pA. At the same time, the inclination angle of the thin film relative to the incident direction of the ion beam, that is, the first cutting angle, is set to 1.2 degrees. The cutting depth is the fourth cutting depth, wherein the fourth cutting depth is less than or equal to the third cutting depth of 6um. The thickness of the unit thin area 103 of the sample is thinned to the fourth preset thickness, that is, 150nm.

[0061] Step S302: performing a second processing on at least two unit thin regions 103 in the overall thinning area 102 with a fifth ion beam voltage and current, a first cutting angle and a fourth cutting depth to obtain at least two unit thin regions 103 having a fifth preset thickness;

[0062] Exemplarily, the whole surface chipping mode is adopted to perform a second processing on at least two unit thin areas 103 in the overall thinning area 102, and the parameters of the focused ion beam are set: the voltage of the fifth ion beam is 8KV, and the current is 21pA. At the same time, the inclination angle of the thin slice relative to the incident direction of the ion beam, that is, the first cutting angle, is set to 1.2 degrees. The cutting depth is the fourth cutting depth, wherein the fourth cutting depth is less than or equal to the third cutting depth of 6um. The thickness of the unit thin area 103 of the sample is thinned to the fifth preset thickness, that is, 100nm.

[0063] Step S303: performing a third processing on at least two unit thin regions 103 in the overall thinning area 102 with a sixth ion beam voltage and current, a second cutting angle and a fourth cutting depth to obtain at least two unit thin regions 103 having a sixth preset thickness;

[0064] Exemplarily, the whole surface chipping mode is adopted to perform the third processing on at least two unit thin areas 103 in the overall thinning area 102, and the parameters of the focused ion beam are set: the voltage of the sixth ion beam is 5KV and the current is 7pA. At the same time, the inclination angle of the thin slice relative to the incident direction of the ion beam, that is, the second cutting angle, is set to 3 degrees. The cutting depth is set to the fourth cutting depth, wherein the fourth cutting depth is less than or equal to the third cutting depth of 6um. The cutting position is precisely set to a rectangular frame of 2um in length and 1um in width, so as to form an inverted cut structure, such as Figure 2 As shown. The thinning position is selected as the target observation area or the stacking area. The cutting time is set to 20s. The operation sequence is to thin the front side first, and then process the back side, until the unit thin area 103 of the sample is processed to the preset sixth thickness, that is, 30nm.

[0065] Step S304: performing a fourth processing on at least two unit thin regions 103 in the overall thinning area 102 with a seventh ion beam voltage and current, a second cutting angle and a fourth cutting depth to obtain at least two unit thin regions 103 having a thickness less than a second preset thickness.

[0066] Exemplarily, the whole-surface chipping mode is adopted to perform the fourth processing on at least two unit thin areas 103 in the overall thinning area 102, and the parameters of the focused ion beam are set: the voltage of the seventh ion beam is 2KV, and the current is 9pA. At the same time, the inclination angle of the thin film relative to the incident direction of the ion beam, that is, the second cutting angle, is set to 3 degrees. The cutting depth is the fourth cutting depth, wherein the fourth cutting depth is less than or equal to the third cutting depth of 6um. The thickness of the unit thin area 103 of the sample is thinned to the second preset thickness, that is, 10nm. In the operation of the low-voltage thinning steps S303 and S304, holes may appear in the unit thin area 103, such as Figure 6 As shown in Figure 1, the thickness of the transmission electron microscope sample around such a hole is generally less than 10nm. During the low-voltage thinning process, it is necessary to control the thinning position and rate to ensure that the hole is close to the target thin area but does not damage the thin area.

[0067] In the embodiment of the present application, before the lens sample is thinned as a whole using a focused ion beam, a protective layer needs to be formed on the original surface of the transmission sample, and the thickness of the protective layer is greater than 2.5 um.

[0068] The scanning electron microscope effect of thinning using the above-mentioned focused ion beam sample preparation parameters is as follows Figure 6 As shown. On a focused ion beam microscope equipped with a scanning transmission electron microscope probe, a preliminary observation of the thin area can be made. The device stack structure used in this example is W / HfZrOx / W. After the partitioned inverted thinning, the W metal layer can be observed to have significant polycrystalline grain contrast in the DF2 observation mode of the scanning transmission electron microscope probe, indicating that the thickness of the sample has reached 10nm and can be used for subsequent transmission electron microscope characterization, such as Figure 7 shown.

[0069] The laminated structure samples with a thickness of less than 10 nm obtained by the above thinning method can provide very clear atomic resolution transmission images, such as Figure 8 As shown. By using DPC technology to observe such samples, the distribution of oxygen atoms and the distribution of atomic electric fields corresponding to oxygen atoms can be observed. This information provides very important data support for exploring the physical mechanism of materials.

[0070] The sample preparation method designed by the present invention has the following two advantages:

[0071] First, the sample preparation method designed by the present invention can achieve sample preparation with a thickness of less than 10nm by designing a thinning structure under the framework of conventional sample preparation technology. The present invention is an innovative sample preparation scheme formed by combining a conventional sample preparation scheme with a reverse cutting thinning scheme. By redesigning the structure used for thinning, the method can achieve higher precision and control, thereby being able to achieve a thickness of less than 10nm. The method of this invention improves the clarity and accuracy of collecting transmission electron microscopy data. It can be seen from the results of transmission electron microscopy characterization that the samples prepared by the present invention can effectively promote the quality of academic research and analysis.

[0072] Second, the method designed by the present invention simplifies the operation process of the existing scheme, making the preparation process of transmission samples with a thickness of less than 10nm simple and efficient, and reducing the technical difficulty of sample preparation. By comparing with the two existing schemes, it can be found that the scheme designed by the present invention does not require the Ar ion milling process after FIB processing, nor does it require the 180-degree rotation operation after sample extraction, which greatly simplifies the sample preparation process, saves sample preparation time, and improves sample preparation efficiency.

[0073] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0074] In addition, the terms "first" and "second" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "N" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. Any process or method description in the flowchart or otherwise described herein may be understood to represent a module, fragment or portion of a code including one or more N executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes additional implementations, in which the functions may not be performed in the order shown or discussed, including in a substantially simultaneous manner or in reverse order according to the functions involved, which should be understood by a technician in the technical field to which the embodiments of the present application belong.

Claims

1. A method for processing a transmission sample using a focused ion beam, characterized in that: The following steps are involved: Using a focused ion beam to thin the transmission sample as a whole to form an overall thinned area, wherein the thickness of the overall thinned area is a first preset thickness, and a supporting beam is formed around the overall thinned area, and the thickness of the supporting beam is greater than the first preset thickness; The overall thinned area of ​​the transmission sample is partitioned and thinned using a focused ion beam to form at least two unit thin areas within the overall thinned area, wherein the thickness of each unit thin area is less than a second preset thickness, the lateral width of each unit thin area is a first preset distance, and the interval between two adjacent unit thin areas is a second preset distance.

2. The method according to claim 1, characterized in that The overall thinning of the transmission sample by using a focused ion beam to form an overall thinned region includes: Using a step-cutting mode, the transmission sample is first processed with a first ion beam voltage and current, a first cutting angle and a first cutting depth to form a first overall thinned region, wherein the first overall thinned region has a third preset thickness; Using a step-cutting mode, continuing to process the transmission sample for a second time with a second ion beam voltage and current, a first cutting angle and a second cutting depth to form the overall thinned region, wherein the overall thinned region has a third preset thickness; The transmission sample is processed for a third time with a third ion beam voltage and current, a first cutting angle and a third cutting depth, so that the thickness of the overall thinned area reaches a first preset thickness.

3. The method according to claim 2, characterized in that The third cutting depth is equal to the sum of the first cutting depth and the second cutting depth, and is smaller than the longitudinal width of the transmission sample.

4. The method according to claim 3, characterized in that The first cutting angle is 1.2 degrees, the third preset thickness is 500nm, the first preset thickness is 300nm, and the first cutting depth, the second cutting depth and the third cutting depth are 4.5um, 1.5um and 6um respectively.

5. The method according to claim 4, characterized in that The voltage and current of the first ion beam are 30 KV and 0.23 nA, the voltage and current of the second ion beam are 30 KV and 80 pA, and the voltage and current of the third ion beam are 30 KV and 40 pA.

6. The method according to any one of claims 2 to 5, characterized in that: The method of thinning the overall thinned area of ​​the transmission sample by using a focused ion beam to form at least two unit thin areas in the overall thinned area includes: Performing a first processing on at least two unit thin regions in the overall thinning region with a fourth ion beam voltage and current, a first cutting angle and a fourth cutting depth to obtain at least two unit thin regions with a fourth preset thickness; Performing a second processing on at least two unit thin regions in the overall thinning region at a fifth ion beam voltage and current, a first cutting angle and a fourth cutting depth to obtain at least two unit thin regions having a fifth preset thickness; Performing a third processing on at least two unit thin regions in the overall thinning region at a sixth ion beam voltage and current, a second cutting angle, and a fourth cutting depth to obtain at least two unit thin regions having a sixth preset thickness; The at least two unit thin regions in the overall thinning area are processed for the fourth time with a seventh ion beam voltage and current, a second cutting angle and a fourth cutting depth to obtain at least two unit thin regions having a thickness less than a second preset thickness.

7. The method according to claim 6, characterized in that The fourth cutting depth is less than or equal to the third cutting depth.

8. The method according to claim 7, characterized in that The second cutting angle is 3 degrees, and the second preset thickness, the fourth preset thickness, the fifth preset thickness and the sixth preset thickness are 10 nm, 150 nm, 100 nm and 30 nm respectively.

9. The method according to claim 8, characterized in that The voltage and current of the fourth ion beam are 16 KV and 23 pA, the voltage and current of the fifth ion beam are 8 KV and 21 pA, the voltage and current of the sixth ion beam are 5 KV and 7 pA, and the voltage and current of the seventh ion beam are 2 KV and 9 pA.

10. The method according to claim 1, characterized in that Before the overall thinning of the transmission sample by using a focused ion beam, the method further comprises: A protective layer is formed on the original surface of the transmission sample, and the thickness of the protective layer is greater than 2.5 um.

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