A method for preparing and transferring micro- and nano-scale samples using a focused ion beam system

Abstract

The present application relates to the technical field of micro-nano material preparation, and particularly relates to a method for preparing and transferring a micro-nano scale sample by using a focused ion beam system, comprising the following steps: cutting a surface to be cut of a large sample by using a focused ion beam to obtain a cut sample; fixing a nano mechanical needle to the cut sample and rotating the cut sample to thin and process the cut sample to obtain a deep-processed sample; and transferring the deep-processed sample to an observation area of a target carrier and cleaning, so as to complete the preparation and transfer of the micro-nano sample. The method of the present application overcomes many shortcomings in the traditional sample preparation method, simplifies the experimental process, improves the experimental efficiency, maximally avoids the pollution of the sample in the environmental and gas deposition process, as much as possible avoids the structural damage caused by excessive gallium ion injection into the sample, and improves the stability of the sample on the target carrier.

Description

Technical Field

[0001] This invention relates to the field of micro-nano sample preparation technology, and in particular to a method for preparing and transferring micro-nano-scale samples using a focused ion beam system. Background Technology

[0002] Focused ion beam (FIB) uses an electromagnetic field to focus an ion beam and scan the sample surface. During the scanning process, heavy ions bombard the atoms on the material surface, causing them to sputter. Most of these sputtered atoms are removed by a vacuum system, while a small portion deposits on nearby surfaces. FIB systems often include a gas-introducing device, allowing for localized chemical deposition during sample scanning. A typical FIB system also includes an electron beam, a secondary electron imaging system, and a nanomechanical tip. The FIB system used in this invention also has the capability to clean the sample using a low-pressure argon ion beam. Over the past two decades, FIB systems have been widely applied in materials science, biology, and semiconductor integrated circuits. These fields often require FIB systems for micro / nano fabrication, and the preparation and transfer of micro / nano samples is a crucial component.

[0003] In in-situ transmission electron microscopy (TEM) studies in materials science, researchers often need to prepare micro / nano samples on in-situ chips using a focused ion beam (FIB) system. Typically, bulk samples prepared on in-situ TEM chips are prepared using a FIB cutting and transfer method. The specific steps are as follows: (1) Using a focused ion beam, a cross-sectional thin slice is vertically extracted from the sample using a conventional "vertical cutting" method; (2) The sample is transferred to a dedicated FIB grid using a nanomechanical tip; (3) The sample is processed and thinned on the FIB grid; (4) The processed sample is then placed on the in-situ chip using a nanomechanical tip.

[0004] Currently, the above methods still have the following drawbacks: (1) The vertical cutting method is relatively limited, and it cannot be used for thin film samples and crystal samples with specific orientations; (2) After the sample is transferred to the FI B special carrier for processing and then transferred to the in-situ heated chip, the sample needs to be transferred twice. The repeated connection and disconnection of the sample will cause large-scale contamination. In addition, the sample may fall off multiple times during this process; (3) When the thin film sample is placed on the in-situ chip, the method of using gas deposition to connect the thin film sample and the in-situ chip will make the sample unstable during the movement and transportation. From a mechanical structure point of view, the sample may also be shifted or fall off when transferring the chip; (4) Since the in-situ chip generally contains many circuits, there is a risk of damaging the chip if the sample is further processed on the in-situ chip. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing and transferring micro / nano-scale samples using a focused ion beam system. This method overcomes many shortcomings of traditional sample preparation methods, simplifies the experimental procedure, improves experimental efficiency, minimizes environmental and gas deposition-related contamination of the sample, avoids excessive gallium ion injection causing structural damage, and enhances sample stability on the target support.

[0006] The purpose of this invention is to provide a method for preparing and transferring micro- and nano-scale samples using a focused ion beam system.

[0007] A method for preparing and transferring micro / nano-scale samples using a focused ion beam system according to a specific embodiment of the present invention includes the following steps:

[0008] S1: The surface of a large sample to be cut is cut using a focused ion beam to obtain the cut sample;

[0009] S2: Fix the nanomechanical needle to the cut sample and rotate the cut sample to thin and process the cut sample to obtain a deep-processed sample;

[0010] S3: Transfer the deep-processed sample to the observation area of ​​the target carrier, clean it, and the preparation and transfer of the micro-nano sample is completed.

[0011] The method for preparing and transferring micro-nano-scale samples using a focused ion beam system according to a specific embodiment of the present invention, wherein the bulk sample is any one of metal, ceramic, organic matter or biological sample.

[0012] According to a specific embodiment of the present invention, the method for preparing and transferring micro-nano-scale samples using a focused ion beam system, in step S1, is wherein the accelerating voltage of the focused ion beam is 0-30kV and the beam current density is 20-100000pA.

[0013] According to a specific embodiment of the present invention, the method for preparing and transferring micro / nano-scale samples using a focused ion beam system includes the following steps in step S1:

[0014] S11: Mount the bulk sample onto the FIB sample stage, tilt the FIB sample stage to 54°, so that the surface of the bulk sample to be cut is facing the focused ion beam.

[0015] S12: Select a flat cutting area on the surface to be cut, and control the focused ion beam to cut three of the four sides of the cutting area, while cutting the remaining side to preserve the physical connection between the cutting area and the bulk sample.

[0016] S13: Reset the FIB sample to 0° and control the focused ion beam to cut the bottom surface of the cutting area;

[0017] S14: After the nanomechanical needle is fixed to the sample in step S2, the physical connection is cut using a focused ion beam.

[0018] According to a specific embodiment of the present invention, in the method for preparing and transferring micro-nano-scale samples using a focused ion beam system, step S2 involves fixing the nanomechanical needle to the cut sample using gas tungsten deposition.

[0019] According to a specific embodiment of the present invention, in the method for preparing and transferring micro-nano-scale samples using a focused ion beam system, the rotation angle in step S2 is 180°.

[0020] According to a specific embodiment of the present invention, in the method for preparing and transferring micro-nano-scale samples using a focused ion beam system, in step S2, the deep-processed sample includes a thin sheet and two support portions, the two support portions being formed on one side of the thin sheet and disposed opposite to each other.

[0021] According to a specific embodiment of the present invention, in the method for preparing and transferring micro-nano-scale samples using a focused ion beam system, in step S3, the target carrier is any one of a single-crystal silicon wafer, an integrated chip, a micro-nano device, and a nanorobot.

[0022] According to a specific embodiment of the present invention, in the method for preparing and transferring micro-nano-scale samples using a focused ion beam system, step S3 involves cleaning using a low-voltage argon ion beam.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] 1. The method of the present invention is based on the "flat cutting" method, which has a wide range of applications and is less restricted by the sample itself during the sample preparation process.

[0025] 2. The method of this invention utilizes the property that a nanomechanical needle tip can rotate around its own axis to place the sample on the nanomechanical needle tip for processing and thinning, among other operations. Compared with other methods, this reduces many intermediate steps, eliminates the need for other intermediate connections in the sample, and reduces contamination caused by connections and shearing. It also reduces sample preparation time and improves experimental efficiency.

[0026] 3. This invention utilizes the argon ion beam cleaning function built into the focused ion beam system to clean the sample at the end of sample preparation. Afterward, the sample can be directly placed into a transmission electron microscope for in-situ heating experiments. This avoids contamination caused by re-placing the sample in a plasma cleaning instrument.

[0027] 4. Unlike traditional sample preparation methods that primarily target metallic samples, the method of this invention can also be used for ceramic, organic, and biological samples. The "flat cutting" method, unlike the traditional "vertical cutting" method, is not limited by sample thickness. Using a nanomechanical needle tip rotated 180° around its own axis before suspending and processing the sample side avoids multiple fixation connections, reducing contamination and improving processing efficiency. Processing the sample into a "thin sheet" shape with two triangular prisms provides the most stable shape, facilitating easy fixation to the target carrier. Furthermore, since both the sheet and the prisms are made from the same sample, there is no need to add other materials to the sheet during fixation. The target carrier in this invention can be various carriers such as single-crystal silicon wafers, integrated chips, micro / nano devices, and nanorobots. Finally, cleaning the sample with a low-voltage argon ion beam further reduces irradiation damage and contamination. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the method for preparing and transferring micro / nano-scale samples using a focused ion beam system provided by the present invention;

[0029] Figure 2(a) is a scanning electron microscope image of a sample extracted using a nanomechanical tip via a "flat cutting" method provided in an embodiment of the present invention;

[0030] Figure 2(b) is a scanning electron microscope image of a sample cross section extracted using the "vertical cutting" method provided in an embodiment of the present invention;

[0031] Figure 3 A scanning electron microscope image of a sample extracted and rotated 180° about the nanomechanical needle tip itself, provided for an embodiment of the present invention.

[0032] Figure 4 This is a scanning electron microscope image of a sample processed and thinned on a nanomechanical needle tip, provided in an embodiment of the present invention.

[0033] Figure 5 This is a perspective view of the deep-processed sample structure provided in an embodiment of the present invention;

[0034] Figure 6 A scanning electron microscope image of a deep-processed sample in the observation area provided in an embodiment of the present invention;

[0035] Figure 7 This is a transmission electron microscope (STEM) image of a deeply processed sample transferred to a portion of a region in a transmission electron microscope, provided in an embodiment of the present invention.

[0036] Figure 8 Scanning electron microscope (SEM) image of a sample placed using the method in a magnesium alloy micro / nano device, provided as an embodiment of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0038] Example

[0039] Based on the appendix Figure 1-8 This invention provides a method for preparing and transferring micro / nano-scale samples using a focused ion beam system, comprising the following steps:

[0040] S1: The surface of a large sample to be cut is cut using a focused ion beam to obtain the cut sample;

[0041] S2: Fix the nanomechanical needle to the cut sample and rotate the cut sample to thin and process the cut sample to obtain a deep-processed sample;

[0042] S3: Transfer the deep-processed sample to the observation area of ​​the target carrier, clean it, and the preparation and transfer of the micro-nano sample is completed.

[0043] In this embodiment, the focused ion beam system is a Hitachi-NX5000.

[0044] In some instances, the bulk sample is any one of metal, ceramic, organic, or biological samples.

[0045] In some instances, in step S1, the accelerating voltage of the focused ion beam is 0-30 kV, and the beam current density is 20-100000 pA.

[0046] In some instances, step S1 includes the following steps:

[0047] S11: Mount the bulk sample onto the FIB sample stage, tilt the FIB sample stage to 54°, so that the surface of the bulk sample to be cut is facing the focused ion beam;

[0048] S12: Select a flat cutting area on the surface to be cut, and control the focused ion beam to cut three of the four sides of the cutting area, while cutting the remaining side to preserve the physical connection between the cutting area and the bulk sample.

[0049] S13: Reset the FI B sample to 0° and control the focused ion beam to cut the bottom surface of the cutting area;

[0050] S14: After the nanomechanical needle is fixed to the sample in step S2, the physical connection is cut using a focused ion beam.

[0051] In some instances, in step S2, the nanomechanical needle is fixed to the cut sample by gas tungsten deposition.

[0052] In some instances, the rotation angle in step S2 is 180°.

[0053] In some instances, in step S2, the deep-processed sample includes a sheet and two supports formed on one side of the sheet and arranged opposite to each other.

[0054] In some instances, in step S3, the target carrier is any one of a single-crystal silicon wafer, an integrated chip, a micro / nano device, and a nanorobot.

[0055] In some instances, the cleaning in step S3 employs a low-voltage argon ion beam.

[0056] To further illustrate the advantages of the method for preparing and transferring micro / nano samples in a focused ion beam system according to the present invention, the following experiments were conducted:

[0057] Step 1: Select a relatively flat 10μm*12μm cutting area on the surface of the metal bulk sample to be cut, rotate the FI B sample stage by 54° so that the surface to be cut is facing the focused ion beam and the focused ion beam is perpendicular to the surface to be cut.

[0058] Step 2: Use focused ion beam to create grooves on the front, right, and rear sides of the cutting area, and make appropriate cuts on the left side while preserving the physical connection; then rotate the FI B sample stage to 0° and use focused ion beam to cut the lower side of the block sample from the side.

[0059] Step 3, as shown in Figure 2(a), use a nanomechanical tip to approach the front corner of the sample on the right side, use a gas deposition system to connect the nanomechanical tip and the sample together, and finally use a focused ion beam to cut the connection point, so that the sample is completely separated from the bulk sample, the sample is extracted, and the FIB sample stage is lowered.

[0060] Step four: Rotate the nanomechanical needle tip 180° around its own axis, causing the sample to rotate 180°. At this point, the shape and positional relationship of the extracted sample are as follows: Figure 3 As shown;

[0061] Step 5: The central rectangular region of the cut sample is removed using a focused ion beam, and then the thin sheet-like sample in the center is further processed to a thickness of 100 nm to meet the requirements for observation in a transmission electron microscope. The final overall shape of the processed sample is as follows: Figure 4 As shown;

[0062] Step six: Rotate the nanomechanical needle tip back to the 0° position. At this point, the sample's state is as follows: Figure 5 As shown, after deep processing, triangular prism-shaped support parts are provided on the lower side of the thin sheet;

[0063] Step 7: Transfer the deep-processed sample to the holes of the in-situ heated chip, and use a gas deposition system to connect the edges of the triangular prism to the silicon nitride film of the in-situ heated chip, such as... Figure 6 As shown, the nanomechanical needle tip is then cut off.

[0064] Step 8: Tilt the FI B sample stage with the in-situ heated chip mounted at 15°, and use an argon ion beam with an accelerating voltage of 2kV to scan and clean the surface of the deep-processed sample at a small angle to remove implanted gallium ions; place the prepared chip in a transmission electron microscope (TEM) and observe the changes in defects such as dislocations in the copper sample with increasing temperature using STEM mode, such as... Figure 7 As shown.

[0065] Using the aforementioned method, the deep-processed sample was transferred onto a micro / nano device made of magnesium alloy, and the results are as follows: Figure 8 As shown.

[0066] In existing technologies, the scanning electron microscope results after cutting ceramic samples using the "vertical cutting" method are as follows: Figure 2b As shown.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing and transferring micro / nano-scale samples using a focused ion beam system, characterized in that, The method includes the following steps: S1: The surface of a large sample to be cut is cut using a focused ion beam to obtain the cut sample; The cutting process includes the following steps: S11: Mount the bulk sample onto the FIB sample stage, tilt the FIB sample stage to 54°, so that the surface of the bulk sample to be cut is facing the focused ion beam. S12: Select a flat cutting area on the surface to be cut, and control the focused ion beam to cut three of the four sides of the cutting area, while cutting the remaining side to preserve the physical connection between the cutting area and the bulk sample. S13: Reset the FIB sample to 0° and control the focused ion beam to cut the bottom surface of the cutting area; S14: After the nanomechanical needle is fixed to the sample in step S2, the physical connection is cut using a focused ion beam; S2: Fix the nanomechanical needle to the cut sample and rotate the cut sample to thin and process the cut sample to obtain a deep-processed sample; the rotation angle is 180°. S3: Transfer the deep-processed sample to the observation area of ​​the target carrier, clean it, and the preparation and transfer of the micro-nano sample is completed.

2. The method for preparing and transferring micro / nano-scale samples using a focused ion beam system according to claim 1, characterized in that, The bulk sample can be any one of metal, ceramic, organic or biological samples.

3. The method for preparing and transferring micro / nano-scale samples using a focused ion beam system according to claim 1, characterized in that, In step S1, the accelerating voltage of the focused ion beam is 0-30kV and the beam current density is 20-100000pA.

4. The method for preparing and transferring micro / nano-scale samples using a focused ion beam system according to claim 1, characterized in that, In step S2, the nanomechanical needle is fixed to the cut sample by gas tungsten deposition.

5. The method for preparing and transferring micro / nano-scale samples using a focused ion beam system according to claim 1, characterized in that, In step S2, the deep-processed sample includes a sheet and two support portions, which are formed on one side of the sheet and are arranged opposite to each other.

6. The method for preparing and transferring micro / nano-scale samples using a focused ion beam system according to claim 1, characterized in that, In step S3, the target carrier is any one of a single-crystal silicon wafer, an integrated chip, a micro / nano device, and a nanorobot.

7. The method for preparing and transferring micro / nano-scale samples using a focused ion beam system according to claim 1, characterized in that, In step S3, the cleaning process uses a low-voltage argon ion beam.

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