Preparation method of transmission electron microscope sample

Abstract

The invention provides a preparation method of a transmission electron microscope sample, which comprises the following steps: welding a prepared cross section TEM sample on a carrying net, horizontally placing the carrying net, and forming a first protection layer on the cross section; forming a limiting mark; forming a second protective layer on the first protective layer; after the part, close to the connecting end of the same carrying net, of the cross-section TEM sample is welded together with a nano manipulator, the sample and the carrying net are cut and separated at the connecting position; the nano manipulator is moved to the hovering position, and then the nano manipulator is taken back; overturning the sample table to enable the carrying net to be vertically placed; after adjustment preparation, the other end, opposite to the end connected with the nano manipulator, of the sample is welded to the carrying net; after the sample and the nano manipulator are cut and separated, the nano manipulator is taken back; and inclining the sample table to 52 degrees, and cutting and thinning the sample according to the limiting marks to obtain the required planar TEM sample. The purpose of comprehensively knowing the plane and section structure information of the sample can be achieved.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and particularly to a method for preparing a transmission electron microscope sample. Background Art

[0002] In the field of failure analysis of integrated circuits, using a Focused Ion Beam (FIB) to prepare a Transmission Electron Microscopy (TEM) sample is one of the important means to analyze the size, morphology, and elemental composition of chip samples.

[0003] For some samples with defects in the process, conventional sample preparation methods can only observe the information of the sample cross-section or plane, which has limitations for inferring the process sites with problems. Therefore, sometimes it is necessary to analyze the sample from multiple dimensions. The currently known sample preparation methods include preparing a planar TEM sample with a thickness of about 300 nm on a chip sample, observing the planar information of the sample, and then converting the prepared planar sample into a TEM sample with a thickness of less than 100 nm for observing the cross-sectional information of the sample. However, the planar information of the sample observed by this method is usually the structural information of multiple layers superimposed, and it is difficult to intuitively reflect the planar structural information of the current layer of the process site. Summary of the Invention

[0004] In view of the above-mentioned disadvantages of the prior art, the purpose of this application is to provide a method for preparing a transmission electron microscope sample, which is used to solve the problem that the planar information of the sample observed in the prior art is difficult to intuitively reflect the planar structural information of the current layer of the process site.

[0005] To achieve the above purpose and other related purposes, this application provides a method for preparing a transmission electron microscope sample, including:

[0006] Step 1, weld the prepared cross-sectional TEM sample on a carrier grid and then place the carrier grid horizontally, and form a first protective layer on this cross-section;

[0007] Step 2, form a limit mark;

[0008] Step 3, form a second protective layer on the first protective layer;

[0009] Step 4, weld the part of the cross-sectional TEM sample adjacent to the connection end with the carrier grid to the nanomanipulator, and then cut and separate the sample and the carrier grid at the connection;

[0010] Step 5, move the nanomanipulator to the hovering position, and then retract the nanomanipulator;

[0011] Step 6, flip the sample stage to place the carrier grid vertically;

[0012] Step 7: After making adjustment preparations, weld the other end opposite to the connection end with the nano manipulator of the sample onto the grid.

[0013] Step 8: After cutting and separating the sample from the nano manipulator, retract the nano manipulator.

[0014] Step 9: Tilt the sample stage to 52°, and perform cutting and thinning on the sample according to the limit marks to obtain the required planar TEM sample.

[0015] Preferably, an electron beam is used to form a first protective layer on this cross-section.

[0016] Preferably, the first protective layer is a platinum layer with a thickness of 0.05 μm.

[0017] Preferably, the steps of forming the limit marks include: First, use a line pattern to form two parallel marking lines on the first protective layer under the electron beam, and these marking lines are close to the connection end of the cross-section TEM sample and the grid; Then, rotate the sample stage so that the open end of the grid faces the equipment operator; Then, tilt the sample stage to 52°, and form the limit marks according to the marking lines.

[0018] Preferably, the marking lines are platinum lines.

[0019] Preferably, an ion beam is used to etch the first protective layer and the cross-section TEM sample at the positions where the marking lines are located in sequence to form two parallel slits to constitute the limit marks.

[0020] Preferably, when performing this etching, set the voltage and current of the ion beam to 30 kV and 26 pA respectively, and determine the etching depth according to actual needs.

[0021] Preferably, an ion beam is used to form a second protective layer.

[0022] Preferably, the second protective layer is a carbon layer.

[0023] Preferably, before performing the welding in Step 4, rotate the sample stage so that the open end of the grid faces away from the equipment operator.

[0024] Preferably, the hovering position is directly above or in the upper left of the grid.

[0025] Preferably, the adjustment preparations in Step 7 include implementing correlation and adjusting the confocal height to ensure that there is a real-time safe distance between the cross-section TEM sample and the observation lens.

[0026] Preferably, before welding in Step 7, insert the nanomanipulator with the cross-sectional TEM sample welded thereon and the gas injection system into the grid. After the other end of the cross-sectional TEM sample opposite to the connection end with the nanomanipulator contacts the grid, inject a deposit through the gas injection system to weld the cross-sectional TEM sample to the grid.

[0027] As described above, the method for preparing a transmission electron microscope sample provided by this application has the following beneficial effects: reprocessing the prepared cross-sectional TEM sample to obtain a TEM sample capable of observing the planar structure of the sample, thereby achieving the purpose of comprehensively understanding the planar and cross-sectional structure information of the sample. Description of the Drawings

[0028] To more clearly illustrate the specific embodiments of this application or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 Shown is a flowchart of the method for preparing a transmission electron microscope sample provided by an embodiment of this application;

[0030] Figure 2 Shown is a physical diagram of the state where the grid is placed horizontally;

[0031] Figure 3 Shown is an electron beam image of the sample cross-section after forming a marking line on the cross-sectional TEM sample;

[0032] Figure 4 Shown is a state diagram of the grid in the electron beam image after forming a marking line and rotating the sample stage;

[0033] Figure 5 Shown is an electron beam image of the sample cross-section after forming a limit marking;

[0034] Figure 6 Shown is an electron beam image of the sample cross-section after forming a second protective layer;

[0035] Figure 7 Shown is a state diagram of the grid in the electron beam image after forming a second protective layer and rotating the sample stage;

[0036] Figure 8 Shown is an electron beam image after the part of the sample adjacent to the connection end with the grid is welded to the nanomanipulator;

[0037] Figure 9 Shown is a physical diagram of the state where the grid is placed vertically;

[0038] Figure 10 It shows an electron beam image of the cross-section of the sample after welding the other end of the sample opposite to the connection end with the nano manipulator to the grid;

[0039] Figure 11 It shows an ion beam image of cutting and separating at the connection position between the sample and the nano manipulator;

[0040] Figure 12 It shows an electron beam image of the cross-section of the sample after implementing the method for preparing a transmission electron microscope sample provided in the embodiment of the present application. Detailed implementation manners

[0041] The following uses specific specific examples to illustrate the implementation manners of the present application. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. The present application can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0042] Next, the technical solutions in the present application will be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0043] In the description of the present application, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0044] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can also be the communication inside two elements. It can be a wireless connection or a wired connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0045] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0046] Please refer to Figure 1 , which shows a flowchart of a method for preparing a transmission electron microscope sample provided by an embodiment of the present application.

[0047] As shown in Figure 1 , the method for preparing a transmission electron microscope sample includes the following steps:

[0048] Step 1: After welding the prepared cross-sectional TEM sample on a grid, place the grid horizontally, and form a first protective layer on this cross-section;

[0049] Step 2: Form a limit mark;

[0050] Step 3: Form a second protective layer on the first protective layer;

[0051] Step 4: After welding the part of the cross-sectional TEM sample adjacent to the connection end with the grid to the nanomanipulator, cut and separate the sample and the grid at the connection;

[0052] Step 5: Move the nanomanipulator to the hovering position, and then retract the nanomanipulator;

[0053] Step 6: Flip the sample stage to place the grid vertically;

[0054] Step 7: After making adjustment preparations, weld the other end opposite to the connection end of the sample with the nanomanipulator to the grid;

[0055] Step 8: After cutting and separating the sample and the nanomanipulator, retract the nanomanipulator;

[0056] Step 9: Tilt the sample stage to 52°, and perform cutting and thinning treatment on the sample according to the limit mark to obtain the required planar TEM sample.

[0057] In Step 1, a cross-sectional TEM sample of a chip sample is prepared using a focused ion beam, and its preparation process is well-known to those skilled in the art and will not be elaborated here. As shown in Figure 2 , the prepared cross-sectional TEM sample is welded on a grid (Grid).

[0058] Before forming the first protective layer on this cross-section, the grid is placed horizontally (as shown in Figure 2 ), that is, the grid and the sample stage (Stage) are in a parallel relationship. As an example, an electron beam is used to form the first protective layer on this cross-section. Exemplarily, the first protective layer is a platinum layer of 0.05 μm.

[0059] In Step 2, the steps of forming the limit mark (FIB Mark) include: First, use a line pattern to form two parallel mark lines on the first protective layer under the electron beam (as shown in Figure 3 ), the mark lines are close to the connection end of the cross-sectional TEM sample and the carrier grid. Exemplarily, the mark lines are platinum lines; Then, rotate the sample stage so that the open end of the carrier grid faces the equipment operator (as shown in Figure 4 ), the carrier grid can only be tilted to 52° in this direction; Then, tilt the sample stage to 52°, and form a limit mark according to the mark lines (as shown in Figure 5 ), the limit mark locates the stop position of the subsequent sample cutting. Exemplarily, use an ion beam to etch the first protective layer and the cross-sectional TEM sample at the position of the mark lines in sequence to form two parallel slits. When etching, set the voltage and current of the ion beam to 30 kV and 26 pA respectively, and determine the etching depth according to actual needs, for example, about 0.5 microns.

[0060] In Step 3, as an example, use an ion beam to form a second protective layer on the first protective layer (as shown in Figure 6 ), Exemplarily, the second protective layer is a carbon layer.

[0061] Before performing the welding in Step 4, rotate the sample stage by 180° so that the open end of the carrier grid faces away from the equipment operator (as shown in Figure 7 ). After performing the welding, the nano manipulator (Easy lift needle) is welded to the part of the cross-sectional TEM sample adjacent to the connection end with the carrier grid (as shown in Figure 8 ).

[0062] When retracting the nano manipulator in Step 5, in order to prevent needle collision, first move the nano manipulator to the hover position (Park position), and then retract the nano manipulator completely. The hover position is located directly above or above the left of the carrier grid.

[0063] In Step 6, flip the sample stage by 90° to place the carrier grid vertically (as shown in Figure 9 ).

[0064] In Step 7, the adjustment preparation includes performing Link and adjusting the Eucentric Height to ensure that there is a real-time safe distance between the sample and the observation lens, preventing damage to the machine due to hitting the lens.

[0065] Before performing the welding, insert the nano manipulator with the welded sample and the gas injection system (GIS needle) into the carrier grid. When the other end of the sample opposite to the connection end with the nano manipulator contacts the carrier grid, inject a deposit through the GIS needle to weld the other end of the sample opposite to the connection end with the nano manipulator to the carrier grid (as shown inFigure 10 as shown

[0066] In step eight, after cutting and separating at the connection position between the sample and the nano-manipulator, the ion beam image obtained is as Figure 11 shown. While retracting the nano-manipulator, the GIS needle is also retracted.

[0067] In step nine, when performing the thinning process, thinning sample preparation in another direction can be achieved. The electron beam image of the TEM sample obtained after implementing step nine is as Figure 12 shown.

[0068] It should be noted that the illustrations provided in this embodiment only schematically illustrate the basic concept of the present application. Therefore, only the components related to the present invention are shown in the drawings, rather than being drawn according to the number, shape, and size of the components during actual implementation. The type, quantity, and proportion of each component during actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0069] In summary, the method for preparing a transmission electron microscope sample provided by the present application reprocesses the TEM sample that has been prepared into a cross-section to obtain a TEM sample that can observe the planar structure of the sample, so as to achieve the purpose of comprehensively understanding the planar and cross-sectional structure information of the sample. Therefore, the present application effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0070] The above embodiments are only illustrative of the principles and effects of the present application, and are not used to limit the present application. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present application.

Claims

1. A method for preparing a transmission electron microscope sample, characterized in that: The method comprises: Step 1, welding the prepared cross-section TEM sample to a grid and placing the grid horizontally to form a first protective layer on the cross-section; Step 2, forming a limit mark; Step three, forming a second protective layer on the first protective layer; Step 4, after welding the portion of the cross-sectional TEM sample adjacent to the connection end with the carrier grid with the nanomanipulator, the sample and the carrier grid are cut and separated at the connection; Step 5, moving the nanomanipulator to a hovering position, and then retracting the nanomanipulator; Step 6, flipping the sample stage so that the grid is placed vertically; Step 7, after adjustment and preparation, welding the other end of the sample opposite to the connection end with the nanomanipulator to the carrier grid; Step eight, after cutting and separating the sample and the nanomanipulator, retracting the nanomanipulator; Step nine, tilt the sample stage to 52 degrees, cut and thin the sample according to the limit mark to obtain the required planar TEM sample.

2. The method according to claim 1, characterized in that The first protective layer is formed on the cross section using an electron beam.

3. The method according to claim 1 or 2, characterized in that: The first protective layer is a 0.05 μm platinum layer.

4. The method according to claim 1, characterized in that: The steps of forming the limit mark include: first, using a line pattern to form two parallel marking lines on the first protective layer under an electron beam, the marking lines are close to the connection end between the cross-sectional TEM sample and the carrier grid; then, rotating the sample stage so that the open end of the carrier grid faces the equipment operator; then, tilting the sample stage to 52°, forming a limit mark according to the marking lines.

5. The method according to claim 4, characterized in that The marking wire is a platinum wire.

6. The method according to claim 4, characterized in that The first protective layer and the cross-sectional TEM sample at the position where the marking line is located are etched in sequence using an ion beam to form two parallel slits to constitute the limit mark.

7. The method according to claim 6, characterized in that When performing the etching, the voltage and current of the ion beam are set to 30 kV and 26 pA respectively, and the etching depth is determined according to actual needs.

8. The method according to claim 1, characterized in that: The second protective layer is formed using an ion beam.

9. The method according to claim 1 or 8, characterized in that: The second protective layer is a carbon layer.

10. The method according to claim 1, characterized in that Before performing the welding in step 4, the sample stage is rotated so that the open end of the carrier grid faces away from the equipment operator.

11. The method according to claim 1, characterized in that: The hovering position is located directly above or to the upper left of the carrier grid.

12. The method according to claim 1, characterized in that The adjustment preparation in step seven includes implementing correlation and adjusting the confocal height to ensure that the cross-sectional TEM sample and the observation lens are at a safe distance in real time.

13. The method according to claim 1, characterized in that Before implementing the welding in step seven, the nanomanipulator and the gas injection system grid with the cross-sectional TEM sample are welded together. When the other end of the cross-sectional TEM sample opposite to the connection end of the nanomanipulator contacts the grid, the deposit is injected through the gas injection system to weld the cross-sectional TEM sample and the grid together.

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