Planar slice processing method for TEM (Transmission Electron Microscope) and planar slice

Abstract

The invention relates to a plane slice processing method for a TEM and a plane slice, and the method comprises the steps: selecting a target region and a point location to be detected of a sample to be detected, and depositing a first protection layer in the target region; cutting and separating the sample to be detected; the sample rough blank is placed on a table top, and the first protection layer is perpendicular to the table top; depositing a second protective layer on part of the top surface of the sample rough blank; digging and cutting the back of the sample rough blank to the edge of the second protective layer along the first direction; cutting off the position, corresponding to the target area, of the first protection layer; the back of the sample rough blank is cut until the target thickness requirement is met; and cutting the to-be-cut area along the height direction to form a sample slice. According to the technical scheme, after the sample rough blank is horizontally placed, the FIB equipment is used for cutting and thinning the sample rough blank to form the plane slices, the observation conditions of multiple to-be-detected point positions can be met at the same time, the separation operation of the slices is convenient and fast, the preparation technological process of the whole slices is simplified, and the preparation efficiency and the slice yield are improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of transmission electron microscope sample preparation, and in particular to a method for processing a plane slice for TEM and the plane slice. Background Art

[0002] Transmission Electron Microscope (TEM) is a microscope used for high-resolution imaging of the fine structure of tiny substances. It impacts the sample with an electron beam and can focus the electrons that penetrate the sample into a structural image of the sample for measurement and analysis. Usually, the sample needs to be an ultra-thin slice with a thickness of less than 100nm to allow the electron beam to pass through. Currently, a focused ion beam (FIB) instrument is often used to prepare TEM sample slices. FIB can quickly and accurately cut the target thickness directly from the micron or nanometer level in the sample to be tested. The general process is: place the sample to be tested on the sample stage, coat a metal protective layer on the area of ​​interest of the sample to be tested, use FIB to roughly cut the sample slice in the sample to be tested, transfer the sample slice to other fixed substrates (such as special copper mesh, etc.) through a probe or nanomanipulator, and then use FIB to thin the sample slice to the target thickness to complete the preparation.

[0003] In the related art, when roughly cutting a sample slice, one side of the slice must be connected to the sample base in a cantilevered manner, and then the slice must be transferred and welded to a fixed base using the corresponding tool. The operation is relatively complicated, and the slice is prone to flying away due to careless operation during the transfer and welding process. At the same time, when a sample slice has multiple points to be measured at similar locations, the vertical fixed cutting of the slice cannot meet the observation conditions of multiple points at the same time, and several points must be selectively abandoned, which increases the sample preparation cost and reduces the observation efficiency in disguise. Summary of the invention

[0004] The purpose of the present disclosure is to provide a method for processing a planar slice for TEM and the planar slice, so as to at least partially solve the problems in the above-mentioned related art.

[0005] In order to achieve the above-mentioned object, the first aspect of the present disclosure provides a method for processing a plane slice for TEM, characterized by comprising:

[0006] Step S101, placing a sample to be tested on a table of a sample table of a FIB device, selecting a target area and a point to be tested, and depositing a first protective layer on the target area, wherein the first protective layer is attached to an end surface of the sample to be tested in a first direction;

[0007] Step S102, cutting and separating the sample to be tested to form a block sample blank including at least the target area;

[0008] Step S103: Place the sample rough blank on the tabletop such that the first protective layer is perpendicular to the tabletop.

[0009] Step S104: Deposit a second protective layer on a part of the top surface of the sample rough blank.

[0010] Step S105: Cut the back of the sample rough blank along a first direction to the edge of the second protective layer.

[0011] Step S106: Cut off the position of the first protective layer corresponding to the target area.

[0012] Step S107: Cut the back of the sample rough blank until the thickness of the area to be cut along the first direction is less than or equal to the target thickness, and the target area is within the area to be cut; and

[0013] Step S108: Cut the area to be cut along the height direction to form a sample slice.

[0014] Optionally, the FIB device cuts the sample to be measured through an ion beam, and step S101 includes:

[0015] Step S201: Place the sample to be measured on the tabletop.

[0016] Step S202: Tilt the sample stage until the tabletop is perpendicular to the emission direction of the ion beam.

[0017] Step S203: Use the ion beam to mark on the surface of the sample to be measured to select the target area and the points to be measured; and

[0018] Step S204: Deposit Pt metal in the target area to form the first protective layer.

[0019] Optionally, step S102 includes: Cutting the sample rough blank from the sample to be measured along the target surface of the sample rough blank using an ion beam current of three thousand picoamperes.

[0020] Optionally, in step S103, placing the sample rough blank on the tabletop includes: Depositing Pt metal at two bottom corners of the sample rough blank along the first direction and away from the first protective layer to fix the sample rough blank to the sample stage.

[0021] Optionally, in step S104, the second protective layer is in contact with the first protective layer.

[0022] Optionally, in step S105, the back of the sample blank is inclined and cut along the first direction to the edge of the second protective layer so that the sample blank forms a trapezoidal shape.

[0023] Optionally, step S107 includes:

[0024] Step S301, roughly cutting and thinning the area to be cut of the sample blank along the first direction to a thickness of 120 nanometers;

[0025] Step S302, precisely cutting and thinning the area to be cut of the sample blank along the first direction to a thickness of 60 - 80 nanometers.

[0026] Optionally, step S108 includes:

[0027] Step S401, cutting one side of the sample slice along the height direction;

[0028] Step S402, cutting the other side of the sample slice along the height direction to separate the sample slice.

[0029] Optionally, step S402 includes:

[0030] Step S4021, partially cutting the other side of the sample slice along the height direction to form a suspension bridge;

[0031] Step S4022, cutting the suspension bridge along the height direction.

[0032] Optionally, step S402 includes:

[0033] Step S4021, partially cutting the other side of the sample slice along the height direction to form a suspension bridge;

[0034] Step S4023, depositing metal on the suspension bridge and fixing it to the probe;

[0035] Step S4024, moving the probe and separating the sample slice.

[0036] The second aspect of the embodiments of the present disclosure provides a planar slice for TEM, and the planar slice for TEM is prepared by using the processing method of the planar slice for TEM provided in the first aspect of the present disclosure.

[0037] Through the above technical solutions, after the sample blank is placed flat, the FIB device can be used to cut and thin it to form a planar slice, which can simultaneously meet the observation conditions of multiple points to be measured, and the separation operation of the slice is convenient, simplifying the overall slice preparation process flow and improving the preparation efficiency and the yield rate of the slice.

[0038] Other features and advantages of the present disclosure will be described in detail in the following detailed description section. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The accompanying drawings are used to provide a further understanding of the present disclosure, and constitute a part of the specification. They are used to explain the present disclosure together with the following detailed description, but do not constitute a limitation to the present disclosure. In the drawings:

[0040] Figure 1 FIG. is a schematic workflow diagram of a method for processing a planar slice for a TEM according to an exemplary embodiment.

[0041] Figure 2 FIG. is a schematic workflow diagram of marking a target area and depositing a first protective layer in a method for processing a planar slice for a TEM according to an exemplary embodiment.

[0042] Figure 3 FIG. is a schematic workflow diagram of thinning a region to be cut in a method for processing a planar slice for a TEM according to an exemplary embodiment.

[0043] Figure 4 FIG. is a schematic workflow diagram of separating a sample slice in a method for processing a planar slice for a TEM according to an exemplary embodiment.

[0044] Figure 5 FIG. is a schematic workflow diagram of separating a sample slice in a method for processing a planar slice for a TEM according to an exemplary embodiment.

[0045] Figure 6 FIG. is a schematic workflow diagram of separating a sample slice in a method for processing a planar slice for a TEM according to an exemplary embodiment.

[0046] Figure 7 FIG. is a schematic structural diagram of a sample to be measured after marking a target area according to an exemplary embodiment.

[0047] Figure 8 FIG. is a schematic structural diagram of a sample blank after cutting according to an exemplary embodiment.

[0048] Figure 9 FIG. is a schematic structural diagram of a sample blank after being fixed according to an exemplary embodiment.

[0049] Figure 10 FIG. is a schematic structural diagram of a sample blank after rough cutting according to an exemplary embodiment.

[0050] Figure 11 FIG. is a schematic structural diagram of a sample after removing a first protective layer according to an exemplary embodiment.

[0051] Figure 12 It is a schematic structural diagram after thinning of a sample blank according to an exemplary embodiment.

[0052] Figure 13 It is a schematic structural diagram after separation of a sample slice according to an exemplary embodiment.

[0053] Description of reference numerals

[0054] 1 - sample to be measured, 2 - target area, 21 - point to be measured, 3 - first protective layer, 4 - sample blank, 5 - second protective layer, 6 - fixed point, 7 - sample slice, 8 - suspension bridge. Detailed implementation manners

[0055] The following will describe in detail the specific implementation manners of the present disclosure with reference to the accompanying drawings. It should be understood that the specific implementation manners described herein are only for explaining and interpreting the present disclosure, and are not used to limit the present disclosure.

[0056] In the present disclosure, unless otherwise stated, the orientation terms such as "top", "bottom", and "back" refer to the actual top, bottom, and back of the relevant workpiece to be cut relative to the tabletop of the sample stage during processing. Specifically, reference can be made to Figures 9 to 13 the drawing direction in, where the top and bottom of the drawing refer to the top and bottom of the sample blank in the current placement state, and the bottom of the drawing should be in contact with the tabletop of the sample stage, and the back of the drawing refers to the back direction away from the first protective layer along the first direction in the current placement state of the sample blank.

[0057] At the same time, the "first direction" represents the extending direction of the sample blank perpendicular to the plane where the target area is located, and the "height direction" refers to the height direction between the top and bottom of the relevant workpiece to be cut in the actual placement state. Specifically, reference can be made to Figures 7 to 13 the directions respectively indicated by the double arrows in, where when in Figure 8 , the first direction of the sample blank is the height direction. The terms "first", "second", etc. used in the present disclosure are used to distinguish one element from another, and do not have sequentiality and importance.

[0058] In the first aspect of the embodiments of the present disclosure, a processing method for planar slicing for TEM is provided. As shown in Figure 1 and Figures 7 to 12 , it includes:

[0059] Step S101: Place the sample 1 to be measured on the tabletop of the sample stage of the FIB device, select the target area 2 and the point 21 to be measured, and deposit the first protective layer 3 on the target area 2, where the first protective layer 3 adheres to the end face of the sample 1 to be measured in the first direction.

[0060] Step S102: Cut and separate the sample to be measured 1 to form a bulk sample blank 4 that at least includes the target area 2.

[0061] Step S103: Place the sample blank 4 on the tabletop such that the first protective layer 3 is perpendicular to the tabletop.

[0062] Among them, during the process of placing the sample blank 4 on the sample table with the first protective layer 3 perpendicular to the tabletop, the larger - area side of the sample blank 4 should be used as the bottom surface to contact the tabletop as much as possible, so as to reduce the center of gravity of the sample blank 4 in the height direction, improve its overall stability after placement, and facilitate subsequent cutting operations.

[0063] Step S104: Deposit a second protective layer 5 on a part of the top surface of the sample blank 4.

[0064] Step S105: Cut and dig the back of the sample blank 4 (i.e., the side away from the first protective layer 3) along the first direction to the edge of the second protective layer 5, so as to remove more unnecessary parts outside the target area 2 to be observed, reduce the corresponding workload for the cutting - thinning operation when preparing plane sections later, and improve the overall section - preparation efficiency.

[0065] Step S106: Cut off the position of the first protective layer 3 corresponding to the target area 2 to expose the point to be measured 21 on the surface, facilitating the observation after the section is made.

[0066] Step S107: Cut the back of the sample blank 4 until the thickness of the area to be cut off along the first direction is less than or equal to the target thickness. Among them, the area to be cut off is the required sample section 7 or should at least include the required plane - section part. According to the differences in processing techniques or different paths during the cutting process, it is allowed to retain some extra sample blank 4 as cutting allowance, but this plane - section part needs to satisfy including the part with the target area 2 and not causing damage to the target area 2 during the cutting process, so as to ensure the normal progress of the observation and the accuracy of the observation results. The target thickness refers to the observable thickness sufficient for application to TEM, for example, it can be 80nm, 100nm, etc.

[0067] Step S108: Cut off the area to be cut off along the height direction to form the sample section 7.

[0068] Through the above - mentioned technical solution, after the sample blank 4 is placed flat, the FIB device can be used to cut and thin it along the first direction to form a plane section. The cutting process will not damage the point to be measured 21, can meet the observation conditions of multiple points to be measured 21 at the same time, and the separation operation of the section is convenient, simplifying the overall section - preparation process flow, and improving the preparation efficiency and the yield rate of the section.

[0069] It should be noted that the present disclosure does not limit the specific operation sequence between the above steps. Without contradiction, the order of different steps can be swapped. For example, in steps S106 and S105, their order can be swapped, and step S106 can also be executed after step S108. Specifically, it can be adaptively adjusted according to the actual operation situation.

[0070] According to some embodiments, the FIB device can cut the sample 1 to be measured by an ion beam. As Figure 2 、 Figure 7 and Figure 8 shown, step S101 may include:

[0071] Step S201, place the sample 1 to be measured on the tabletop.

[0072] Step S202, tilt the sample stage until the tabletop is perpendicular to the emission direction of the ion beam.

[0073] Among them, the ion beam cutting direction of the FIB device is fixedly set at a certain initial angle. Usually, this initial angle forms an angle of 38 degrees with the direction perpendicular to the tabletop of the sample stage. To make the ion beam satisfy the perpendicular cutting of the sample 1 to be measured, the tilt angle of the sample stage can be set to 52 degrees so that the tabletop is perpendicular to the emission direction of the ion beam. At the same time, when the initial angle of the ion beam cutting direction is other angles, the sample stage can also be adaptively adjusted to other tilt angles to satisfy that the tabletop is perpendicular to the emission direction of the ion beam. This embodiment does not make specific limitations on this.

[0074] Step S203, use the ion beam to mark the surface of the sample 1 to be measured to select the target area 2 and the measurement point 21.

[0075] Specifically, the target area 2 and the measurement point 21 can be marked by means of coating a special metal thin layer or surface etching dots and lines, etc., and can be freely marked according to the actual area of interest to construct the size and shape of the target area 2.

[0076] And step S204, deposit Pt metal in the target area 2 to form the first protective layer 3.

[0077] It should be noted that the first protective layer 3 is used to prevent damage to the surface of the target area 2 during the ion beam cutting process or deposition on the surface of the target area 2 after the edge material is sputtered. Usually, Pt (platinum) metal can be selected to deposit as the first protective layer 3, and other types of metals can also be selected to deposit as the first protective layer 3 according to the different properties of the material to be cut actually. This embodiment does not make specific limitations on this.

[0078] In some embodiments, step S102 may include: using an ion beam current of three thousand picoamperes to cut the sample blank 4 from the sample to be measured 1 along the target surface of the sample blank 4. The target surface is the surface of the sample blank 4 after cutting. Referring to the attached Figure 8 , the ion beam current may first horizontally cut the bottom surface of the sample blank 4 along the dashed line in the figure, and then cut the two side surfaces where the sample blank 4 is connected to the substrate of the sample to be measured 1 respectively, so as to separate the sample blank 4 from the sample to be measured 1.

[0079] Exemplarily, as Figure 9 shown, placing the sample blank 4 on the tabletop in step S103 may include: depositing Pt metal at the two bottom corners of the sample blank 4 along the first direction away from the first protective layer 3 to fix the sample blank 4 to the tabletop of the sample stage.

[0080] In the above embodiment, after the first protective layer 3 of the sample blank 4 is placed perpendicular to the tabletop, Pt metal can be deposited at the two bottom corners along the first direction away from the first protective layer 3 to form fixed points 6, and the sample blank 4 can be fixed on the tabletop of the sample stage to prevent it from moving during subsequent cutting operations, which is beneficial to the cutting of the sample blank 4.

[0081] According to some embodiments, as Figure 10 shown, in step S104, the second protective layer 5 can be in contact with the first protective layer 3 to cover the connection between the first protective layer 3 and the second protective layer 5 located on two adjacent surfaces of the sample blank 4 respectively, and protect the covered part to prevent the edge from being damaged after the sample blank 4 is prepared into a planar section, which affects the observation result.

[0082] Exemplarily, in step S105, an ion beam can be used to obliquely cut the back of the sample blank 4 along the first direction to the edge of the second protective layer 5 so that the sample blank 4 forms a trapezoidal shape. In this embodiment, referring to the attached Figure 10 , on the back of the sample blank 4 in the first direction and away from the first protective layer 3, an ion beam can be used to cut and retain more of the redundant part outside the target area. Specifically, it can be obliquely cut along the first direction so that the sample blank 4 is trapezoidal and has an inclined surface after cutting off the redundant part. The inclined surface can uniformly extend from the bottom surface of the sample blank 4 to near the edge of the second protective layer 5, so that in subsequent operations, the height change and the horizontal distance from the first protective layer can be measured to accurately cut the back of the sample blank 4, improving the accuracy and intuitiveness of cutting and thinning.

[0083] In some embodiments, as Figure 3 、 Figure 11 and Figure 12 shown, step S107 may include:

[0084] Step S301: Control the ion beam to roughly cut and thin the area to be cut of the sample blank 4 along the first direction to a thickness of 120 nanometers.

[0085] Step S302: Control the ion beam to precisely cut and thin the area to be cut of the sample blank 4 along the first direction to a thickness in the range of 60 - 80 nanometers.

[0086] In this embodiment, when performing the thinning operation on the area to be cut of the sample blank 4, it is necessary to first thin the area to be cut to a thickness of 120 nanometers along the inclined surface from the back of the sample blank 4. This process is the rough cutting process, and the ion beam current and cutting speed can be appropriately increased. When the area to be cut is thinned to a thickness of 120 nanometers, the ion beam current and cutting speed can be appropriately reduced, and the area to be cut is precisely cut to control the thickness of the area to be cut within the range of 60 - 80 nanometers. At the same time, during this precise cutting process, the cutting area of the cross-section of the area to be cut can be appropriately reduced to reduce the cutting working hours and improve the efficiency of the thinning operation. However, the cutting area should be greater than the area of the target area 2 to ensure that the area to be cut can include the target area 2 after being prepared into the sample slice 7.

[0087] Exemplarily, as Figure 4 and Figure 12 shown, step S108 may include:

[0088] Step S401: Cut one side of the sample slice 7 along the height direction.

[0089] Step S402: Cut the other side of the sample slice 7 along the height direction to separate the sample slice 7.

[0090] Among them, the sample slice 7 is only connected to the substrate of the sample blank 4 on both sides. By cutting one side of the sample slice 7 and then cutting the other side of the sample slice 7, the sample slice 7 can be separated from the substrate of the sample blank 4. The separation process is simple, convenient, and easy to operate.

[0091] In some embodiments, step S402 may include:

[0092] Step S4021: Partially cut the other side of the sample slice 7 along the height direction to form a suspension bridge 8.

[0093] Step S4022: Cut the suspension bridge 8 along the height direction.

[0094] In this embodiment, as Figure 5 and Figure 13As shown, in a state where one side of the sample slice 7 has been cut off, the other side of the sample slice 7 can be partially cut first along the height direction and with a certain inclination angle, so as to retain a small part of the connection with the base of the sample blank 4 to form a suspension bridge 8, and then the suspension bridge 8 is cut along the height direction and deflected by a certain angle, so as to ensure that the slice can be safely and completely cut and separated. When the cutting allowance of the target area 2 is relatively tight, it is applicable to cut and protect the target area 2 to avoid damage to the target area 2 and affecting the observation result.

[0095] Exemplarily, as Figure 6 and Figure 13 shown, step S402 may further include:

[0096] Step S4021, partially cut the other side of the sample slice 7 along the height direction to form a suspension bridge 8.

[0097] Step S4023, deposit metal on the suspension bridge 8 and fix it to the probe.

[0098] Step S4024, move the probe and separate the sample slice 7,

[0099] Among them, a small part of the cutting allowance will be retained at the cut-off position of the suspension bridge 8 of the sample slice 7. This part of the allowance can be fixed by metal deposition with the probe without damaging the target area 2, which is convenient for transferring the sample slice 7 using the probe. This process can also use other auxiliary tools such as a nano manipulator to clamp this part of the cutting allowance to separate and transfer the sample slice 7 from the base of the sample blank 4. The operation is simple and convenient for moving and processing the sample slice 7.

[0100] The second aspect of the embodiments of the present disclosure provides a planar slice for TEM, which is prepared by using the method for processing a planar slice for TEM provided in the first aspect of the embodiments of the present disclosure, and has all the beneficial effects of the above processing method, which will not be elaborated here too much.

[0101] The preferred embodiments of the present disclosure have been described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

[0102] In addition, it should be noted that, in the various specific technical features described in the above specific embodiments, they can be combined in any appropriate manner without contradiction. To avoid unnecessary repetition, the present disclosure will not separately describe various possible combination methods.

[0103] In addition, any combination can be made among various different embodiments of the present disclosure, as long as it does not violate the idea of the present disclosure, and it should also be regarded as the content disclosed by the present disclosure.

Claims

1. A processing method for planar slices used in TEM, characterized in that, it includes: Step S101: Place the sample to be measured on the surface of the sample stage of the FIB device, select the target area and the points to be measured, and deposit a first protective layer in the target area, wherein the first protective layer adheres to the end face of the sample to be measured in the first direction; Step S102: Cut and separate the sample to be measured to form a blocky sample rough blank at least including the target area; Step S103: Place the sample rough blank on the stage so that the first protective layer is perpendicular to the stage; Step S104: Deposit a second protective layer on a part of the top surface of the sample rough blank; Step S105: Cut the back of the sample rough blank along the first direction to the edge of the second protective layer; Step S106: Cut off the position of the first protective layer corresponding to the target area; Step S107: Cut the back of the sample rough blank until the thickness of the area to be cut off along the first direction is less than or equal to the target thickness, and the target area is in the area to be cut off; and Step S108: Cut off the area to be cut off along the height direction to form a sample slice.

2. The method according to claim 1, characterized in that, the FIB device cuts the sample to be measured through an ion beam, and step S101 includes: Step S201: Place the sample to be measured on the stage; Step S202: Tilt the sample stage until the stage is perpendicular to the emission direction of the ion beam; Step S203: Use the ion beam to mark on the surface of the sample to be measured to select the target area and the points to be measured; and Step S204: Deposit Pt metal in the target area to form the first protective layer.

3. The method according to claim 1, characterized in that, step S102 includes: Cutting off the sample rough blank from the sample to be measured along the target surface of the sample rough blank using an ion beam current of three picoamperes.

4. The method according to claim 1, characterized in that, in step S103, placing the sample rough blank on the stage includes: Depositing Pt metal at two bottom corners of the sample rough blank along the first direction away from the first protective layer to fix the sample rough blank to the sample stage.

5. The method according to claim 1, characterized in that, in step S104, the second protective layer is in contact with the first protective layer.

6. The method according to claim 1, characterized in that, in step S105, cut the back of the sample rough blank along the first direction obliquely to the edge of the second protective layer so that the sample rough blank forms a trapezoidal shape.

7. The method according to claim 1, characterized in that, step S107 includes: Step S301: Coarsely cut and thin the area to be cut off of the sample rough blank along the first direction to a thickness of 120 nanometers; Step S302: Finely cut and thin the area to be cut off of the sample rough blank along the first direction to a thickness of 60 - 80 nanometers.

8. The method according to claim 1, characterized in that, The said step S108 includes: Step S401, cutting one side of the sample slice along the said height direction; Step S402, cutting the other side of the sample slice along the said height direction to separate the sample slice.

9. The method according to claim 8, wherein, the said step S402 includes: Step S4021, partially cutting the other side of the sample slice along the height direction to form a suspension bridge; Step S4022, cutting the suspension bridge along the height direction.

10. The method for preparing a planar slice of TEM according to claim 8, wherein, the said step S402 includes: Step S4021, partially cutting the other side of the sample slice along the height direction to form a suspension bridge; Step S4023, depositing metal on the suspension bridge and fixing it on a probe; Step S4024, moving the probe and separating the sample slice.

11. A planar slice for TEM, wherein, the planar slice of TEM is prepared by using the processing method for the planar slice of TEM according to any one of claims 1 - 10.

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