Lamella transfer device and lamella transfer method

Abstract

The present invention reduces positional deviation of a lamella LM by preventing collision of tweezers 16 or the lamella LM with a sample SAM when obtaining the lamella LM from the sample SAM. The lamella LM is grasped with the tweezers 16, and then the tweezers 16 are moved in a direction from an end LMa of the lamella LM toward an end LMb of the lamella LM. Thereafter, the tweezers 16 are moved so that the lamella LM is separated from a connection part SAMa of the sample SAM, thereby obtaining the lamella LM from the sample SAM.

Description

Lamella Transfer Device and Method for Transferring Lamella

[0001] The present invention relates to a lamella transfer device and a method for transferring a lamella.

[0002] In recent years, with the miniaturization and high integration of semiconductor devices, their internal structures have become more complex. Therefore, when analyzing defects in semiconductor devices, in order to perform analysis with higher spatial resolution, for example, a transmission electron microscope (TEM: Transmission Electron Microscope) is used.

[0003] In order to produce a plate-like thin sample piece (lamella) to be observed, for example, a FIB-SEM composite device having both the functions of a focused ion beam (FIB: Focused Ion Beam) device and a scanning electron microscope (SEM: Scanning Electron Microscope) is used. In addition, the operation of transferring the lamella produced by the FIB-SEM composite device to a holder for observation with a TEM device is performed by a lamella transfer device.

[0004] For example, Patent Document 1 discloses a lamella transfer device including a light source lens barrel and an observation lens barrel. In this lamella transfer device, the process of acquiring a lamella from a sample and mounting the lamella on a holder is automatically repeated using tweezers.

[0005] International Publication No. 2022 / 163042

[0006] Figures 14 and 15 show a study example examined by the inventors of the present application. As shown in Figure 14, the produced lamella LM is connected to a connection part SAMa which is a part of the sample SAM. When acquiring the lamella LM from the sample SAM, the lamella LM is gripped by the tweezers 16, and the lamella LM is separated from the connection part SAMa by moving the tweezers 16.

[0007] Here, a certain amount of gripping force is required to grasp the lamella. However, as shown in Figure 15, if the gripping force is too large, a phenomenon occurs in which the tweezers 16 moves toward the connection part SAMa. Therefore, a problem arises in which the position of the lamella LM shifts while it is being grasped by the tweezers 16. For example, the lamella LM rotates with the connection part SAMa as the pivot point.

[0008] Furthermore, when the tweezers 16 are moved after the separation of the lamellar LM, the tweezers 16 or the lamellar LM may collide with the sample SAM, causing the lamellar LM to shift further or fall. In such cases, the lamellar LM relocation work cannot be continued.

[0009] Therefore, a technique is desired that can suppress collisions between the tweezers 16 or the lamellar LM with the sample SAM due to the movement of the tweezers 16 when the lamellar LM is grasped by the tweezers 16, and a technique that can suppress displacement of the lamellar LM. Other issues and novel features will become clear from the description and accompanying drawings herein.

[0010] A brief overview of some of the representative embodiments disclosed in this application is as follows:

[0011] In one embodiment, the lamellar transfer apparatus includes tweezers for grasping lamellae fabricated on a sample. The lamellae has a first end and a second end opposite to the first end, and the sample has a connecting portion connected to the first end. After grasping the lamellae with the tweezers, the tweezers are moved in a direction from the first end to the second end, and the lamellae is acquired from the sample by moving the tweezers so that the lamellae separates from the connecting portion.

[0012] A method for relocating a lamella in one embodiment includes the steps of: (a) preparing a sample on which a lamella has been made; (b) grasping the lamella with tweezers after step (a); (c) moving the tweezers after step (b) while the lamella is being grasped by the tweezers; and (d) obtaining the lamella from the sample by moving the tweezers after step (c) so that the lamella is separated from the connecting portion. The lamella has a first end and a second end opposite to the first end, and in step (a), the first end is connected to a connecting portion which is part of the sample, and in step (c), the tweezers are moved in the direction from the first end to the second end.

[0013] According to one embodiment, when acquiring lamellae from a sample, collisions between the tweezers or lamellae and the sample can be suppressed, and displacement of the lamellae can be suppressed. Therefore, the lamellae relocation work can be continued.

[0014] This is a schematic diagram showing the lamellar observation system in Embodiment 1. This is a plan view showing the holder in Embodiment 1. This is a schematic diagram showing the lamellar relocation device in Embodiment 1. This is a flowchart showing the lamellar relocation method in Embodiment 1. This is a perspective view showing the sample and lamella in Embodiment 1. This is a perspective view showing the step of grasping the lamella with tweezers in Embodiment 1. This is a plan view showing the step of grasping the lamella with tweezers in Embodiment 1. This is a plan view showing the step following Figure 7. This is a plan view showing the step following Figure 8. This is a plan view showing the step following Figure 9. This is a perspective view showing the step following Figure 10. This is a side view showing the step of mounting the lamella on the holder in Embodiment 1. This is a side view showing the step following Figure 12. This is a side view showing the step of grasping the lamella with tweezers in the example. This is a side view showing the step following Figure 14.

[0015] The embodiments will be described in detail below with reference to the drawings. In all the drawings used to describe the embodiments, the same reference numerals are used for members having the same function, and repeated descriptions of them will be omitted. In addition, in the following embodiments, descriptions of the same or similar parts will not be repeated unless it is particularly necessary.

[0016] Furthermore, the X, Y, and Z directions described in this application intersect and are orthogonal to each other. In this application, the Z direction may also be described as the vertical direction, and the X or Y direction as the horizontal direction.

[0017] (Embodiment 1) <Lamellar Observation System> The lamellar observation system 100 in Embodiment 1 will be described below with reference to Figure 1. As shown in Figure 1, the lamellar observation system 100 comprises a FIB-SEM combined device 1, a lamellar relocation device 2, and a TEM device 3.

[0018] In the FIB-SEM combined device 1, a portion of the sample SAM is processed to produce a lamellar LM. The sample SAM containing the lamellar LM is transported from the FIB-SEM combined device 1 to the lamellar transfer device 2. In the lamellar transfer device 2, the lamellar LM is obtained from the sample SAM and mounted on the holder 21. The holder 21 containing the lamellar LM is transported from the lamellar transfer device 2 to the TEM device 3. In the TEM device 3, the lamellar LM is observed.

[0019] In Embodiment 1, the sample SAM is exemplified by a wafer on which various semiconductor devices are formed. For example, the sample SAM consists of a semiconductor substrate on which p-type or n-type impurity regions are formed, semiconductor elements such as transistors formed on the semiconductor substrate, and wiring layers formed on the semiconductor elements. Since the lamellar LM is a plate-like thin piece obtained from a part of the sample SAM, the lamellar LM includes all or part of the semiconductor substrate, semiconductor elements, and wiring layers. Furthermore, the sample SAM may be a structure used in technologies other than semiconductor technology.

[0020] As shown in Figure 2, the holder 21 has a grid frame 22 and a film 23. The grid frame 22 is a disc-shaped substrate with a plurality of holes formed in it. The film 23 is formed on the surface of the grid frame 22 so as to cover the plurality of holes. The film 23 is, for example, a carbon film or a polymer resin film and has the property of transmitting electrons.

[0021] The lamellars LM are placed on the membrane 23 such that, in a plan view perpendicular to the direction in which the lamellars LM are pressed against the membrane 23 (Z direction), each lamellar LM is located within a single pore. In other words, multiple lamellars LM are placed on the membrane 23 such that, in a plan view perpendicular to the Z direction, each of the multiple lamellars LM is located within a separate pore.

[0022] <Lamellar relocation device> As shown in Figure 3, the lamellar relocation device 2 comprises an optical system 4, a microscope tube drive mechanism 14, a sample transport device 15, tweezers 16, a tweezers drive mechanism 17, a control device 18, an input device 19, a display device 20, and a holder 21 for lamellae.

[0023] Optical system 4 is, for example, a white light interference microscope. Optical system 4 includes a light-emitting light source 5, a filter 6, a first beam splitter 7, a second beam splitter 8, a first objective lens 9, a second objective lens 10, a fixed mirror 11, a third objective lens 12, and a photodetector 13. Optical system 4 separates the light emitted from the light source 5 to irradiate the object to be observed and the reference surface with light, and forms an interference image as interference light L3, which is a combination of reflected light L1R reflected from the object to be observed and reference light L2 reflected from the reference surface.

[0024] In other words, the light L0 emitted from the light source 5 passes through the filter 6 and is reflected by the first beam splitter 7. The reflected light L0 is separated by the second beam splitter 8 into light L1 directed toward the sample SAM, which is the object of observation, and reference light L2 directed toward the fixed mirror 11, which is the reference plane. Light L1 passes through the first objective lens 9, strikes the sample SAM, and is reflected as reflected light L1R. Reference light L2 passes through the second objective lens 10, strikes the fixed mirror 11, and is reflected. The reflected light L1R and the reference light L2 reflected by the fixed mirror 11 are combined by the second beam splitter 8 as interference light L3. The interference light L3 is detected by the photodetector 13. The photodetector 13 forms an interference image of the interference light L3 and outputs the image signal of the interference image to the control device 18.

[0025] The intensity of the interference light L3 changes depending on the phase difference between the reflected light L1R and the reference light L2 when they are combined in the second beam splitter 8. When the phase difference is in phase, the intensity of the interference light L3 is at its maximum. Conversely, as the phase difference approaches opposite phase, the intensity of the interference light L3 decreases.

[0026] Under the condition that the distance between the second beam splitter 8 and the fixed mirror 11 is constant, the optical system 4 is moved in the Z direction by the mirror tube drive mechanism 14, and by changing the distance of the optical path of light L1, the phase difference between the reflected light L1R and the reference light L2 changes, and the intensity of the interference light L3 changes. From the change in the intensity of the interference light L3, information about the position of the object in the Z direction and the shape of the object can be obtained.

[0027] The control device 18 is, for example, a processor, and is an arithmetic processing unit that includes multiple semiconductor circuits such as a CPU. The control device 18 is electrically connected to the light source 5, photodetector 13, microscope tube drive mechanism 14, sample transport device 15, tweezers drive mechanism 17, input device 19, and display device 20, and controls them. In other words, each control and operation performed by the lamellar relocation device 2 is performed by the control device 18. The control device 18 also has a memory that stores various information performed by the lamellar relocation device 2.

[0028] The microscope tube drive mechanism 14 moves the optical system 4 vertically (Z direction) to change the distance between the optical system 4 and the sample transport device 15. The control device 18 controls the drive of the microscope tube drive mechanism 14.

[0029] The sample transport device 15 can accommodate the sample SAM and holder 21. The sample SAM, including the lamellar LM fabricated in the FIB-SEM combined device 1, is transported onto the sample transport device 15. The sample transport device 15 can also be moved laterally (X direction, Y direction) under the control of the control device 18. By moving the sample transport device 15, the observation target of the optical system 4 can be changed.

[0030] The tweezers 16 consist of a pair of arms and are used to grasp the lamellar LM between the pair of arms. The tweezers 16 are made of, for example, silicon and a silicon oxide film covering the silicon. The distance between the pair of arms of the open tweezers 16 is, for example, 7 μm.

[0031] The tweezers drive mechanism 17 is electrically connected to the tweezers 16 and can move and control the orientation of the tweezers 16. For example, the tweezers 16, tilted at an arbitrary angle, can be translated in the X, Y, and Z directions while maintaining that position, and can rotate around the arm as an axis. The control device 18 controls the drive of the tweezers drive mechanism 17. Note that the means for transporting the lamellar LM is not limited to the tweezers 16; for example, a glass probe or a suction probe may also be used.

[0032] The input device 19 is, for example, a keyboard or a mouse. By using the input device 19 to work on the display device 20, the user can send instructions to the control device 18 for each operation performed by, for example, the light source 5, the microscope tube drive mechanism 14, the sample transport device 15, and the tweezers drive mechanism 17.

[0033] The display device 20 displays various screens as a graphical user interface (GUI). For example, the GUI may include a screen that displays the emission conditions of light L0, a screen that displays the coordinates of the optical system 4 and the sample transport device 15, or a screen that displays the interference image. The GUI may also include screens for performing operations such as zooming in, zooming out, moving, and rotating the interference image.

[0034] <Method for relocating the lamellae> Steps S1 to S9 included in the method for relocating the lamellae LM in Embodiment 1 will be explained below with reference to Figure 4. Figures 5 to 13 will be used as needed when explaining each step S1 to S9. Steps S3 to S9 are performed automatically by the lamellae relocation device 2.

[0035] In step S1, the amount of movement of the tweezers 16 when grasping the lamellar LM is measured in advance. The amount of movement measured here corresponds to the amount of movement of the tweezers 16 in step S5, which will be described later.

[0036] First, the control device 18 moves the tweezers 16 using the tweezers drive mechanism 17 so that the pair of arms of the tweezers 16 are detected in the interference image output from the photodetector 13. Next, the tweezers 16 are gradually closed, and the movement of the pair of arms is stopped when the pair of arms make contact. At this time, the position of the tweezers 16 at the time of contact is measured by referring to the interference image (first measurement).

[0037] Next, the tweezers 16 are closed until the gripping force used to grasp the lamellar LM is generated. As the tweezers 16 move during this process, their position is measured by referring to the interference pattern (second measurement). Then, the amount of movement of the tweezers 16 is confirmed by comparing the results of the first and second measurements.

[0038] In step S2, a sample SAM with lamellar LMs is prepared. First, as shown in Figure 5, lamellar LMs are fabricated in the FIB-SEM combined device 1 by processing a portion of the sample SAM. Next, the sample SAM with the fabricated lamellar LMs is transported from the FIB-SEM combined device 1 to the lamellar transfer device 2, and the sample SAM is placed on the sample transport device 15.

[0039] The lamellar LM has an end LMa and an end LMb opposite to end LMa. The sample SAM has a connecting portion SAMa which is part of the sample SAM. At this point, the end LMa of the lamellar LM is connected to the connecting portion SAMa, and the lamellar LM and the sample SAM are integrated. The lamellar LM also has a thickness T1 in the Y direction, a thickness T2 in the X direction, and a thickness T3 in the Z direction. Thickness T1 is thinner than thicknesses T2 and T3. Thickness T3 is thinner than thickness T2. End LMa and end LMb are the ends of the lamellar LM in the X direction, respectively.

[0040] In step S3, as shown in Figure 6, the tweezers 16 are moved above the lamellar LM. First, the control device 18 controls the sample transport device 15 and the tweezers drive mechanism 17 while referring to the interference image output from the photodetector 13. That is, the control device 18 moves the sample SAM and the tweezers 16 so that the lamellar LM fabricated on the sample SAM and the tip of the tweezers 16 are simultaneously detected in the interference image.

[0041] In step S4, as shown in Figure 7, the tweezers 16 are lowered to the position of the lamellar LM. First, the control device 18 moves the optical system 4 in the Z direction using the lens barrel drive mechanism 14, and measures the positions of the sample SAM and the tweezers 16 in the Z direction based on the interference image output from the photodetector 13. Next, based on the measured position information of the sample SAM and the tweezers 16, the control device 18 moves the tweezers 16 to a position where they can grasp the lamellar LM.

[0042] In step S5, as shown in Figure 8, the tweezers 16 are closed to grasp the lamellar LM. At this time, the tweezers 16 move, as explained in the example in Figures 14 and 15. That is, as shown in Figure 9, when the lamellar LM is grasped by the tweezers 16, the tweezers 16 move in the direction toward the connection part SAMa, that is, from end LMb toward end LMa.

[0043] In step S6, as shown in FIG. 10, with the lamella LM being gripped by the tweezers 16, the control device 18 moves the tweezers 16 by the tweezer drive mechanism 17 in the direction from the end LM a to the end LM b. That is, in step S6, the tweezers 16 are moved in the direction opposite to the direction in which the tweezers 16 moved in step S5.

[0044] At this time, the tweezers 16 are moved so as to reach at least the amount of movement of the tweezers 16 that moved in step S5. That is, the tweezers 16 are moved so as to reach at least the amount of movement of the tweezers 16 measured in advance in step S1.

[0045] In step S7, first, with the lamella LM being gripped by the tweezers 16, the control device 18 moves the tweezers 16 by the tweezer drive mechanism 17 so that the lamella LM separates from the connection part SAM a. Here, the tweezers 16 are moved at least in the direction (Y direction) in which the tweezers 16 grip the lamella LM. Operations such as rotating the tweezers 16 around the X direction as the central axis may be added to separate the lamella LM from the connection part SAM a. Thus, the lamella LM is acquired from the sample SAM.

[0046] Next, in step S8, as shown in FIG. 11, the control device 18 retracts the tweezers 16 in the Z direction by the tweezer drive mechanism 17 to a height at which the tweezers 16 do not contact the sample SAM.

[0047] As shown in FIG. 15, in the study example, when the lamella LM was gripped by the tweezers 16, a problem occurred in that the lamella LM rotated with the connection part SAM a as a fulcrum. In the first embodiment, in step S6, the tweezers 16 are moved in the direction opposite to the direction in which the tweezers 16 moved in step S5. Thereby, the displacement of the lamella LM can be restored to some extent.

[0048] For example, after step S5, the rotation angle of the lamella LM was about 10 degrees, but after step S6, the rotation angle of the lamella LM recovered to about 1 degree. Thus, by moving the clamp 16 in step S6, displacement of the lamella LM can be suppressed.

[0049] Also, in Embodiment 1, by moving the clamp 16 in step S6, when the clamp 16 is moved in step S7, the problem that the clamp 16 or the lamella LM collides with the sample SAM is suppressed. Therefore, problems such as further displacement of the position of the lamella LM or dropping of the lamella LM can be suppressed. Thus, the relocation operation of the lamella LM can be continued.

[0050] In step S9, as shown in FIGS. 12 and 13, the lamella LM is mounted on the holder 21. In FIGS. 12 and 13, only one arm of the clamp 16 is shown for easy viewing of the lamella LM.

[0051] First, as shown in FIG. 12, the control device 18 moves the holder 21 by the sample transfer device 15 and moves the clamp 16 by the clamp drive mechanism 17 while referring to the interference image output from the photodetector 13 so that the lamella LM exists above the lamella mounting planned position of the holder 21.

[0052] Next, as shown in FIG. 13, the control device 18 lowers the clamp 16 in the Z direction by the clamp drive mechanism 17 until the lamella LM contacts the holder 21. When the film 23 of the holder 21 is deformed due to contact with an object, the distance of the optical path of the light L1 changes, the intensity of the interference light L3 changes, and the interference image output from the photodetector 13 changes. Contact determination is performed by detecting this change in the intensity of the interference image. Also, after the lamella LM is brought into contact with the film 23, the clamp 16 is further lowered in the Z direction for a predetermined time, and the lamella LM is pressed against the film 23, whereby the lamella LM is adsorbed to the film 23.

[0053] Next, the control device 18 releases the tweezers 16 using the tweezers drive mechanism 17. At this point, the lamellar LM is placed on the film 23. Because the movement of the tweezers 16 in step S6 has improved the posture of the lamellar LM, the contact between the lamellar LM and the film 23 is improved, making it easier to place the lamellar LM on the film 23. Subsequently, the control device 18 raises the tweezers 16 in the Z direction using the tweezers drive mechanism 17, retracting the tweezers 16 from the holder 21.

[0054] This completes the transfer of the lamellar LM from the sample SAM to the holder 21. Although multiple lamellar LMs are fabricated in the sample SAM, if there are other lamellar LMs in the sample SAM that need to be transferred to the holder 21, steps S3 to S9 are performed for the other lamellar LMs as well.

[0055] Although the present invention has been described in detail based on embodiments for carrying it out, the present invention is not limited to the above embodiments and can be modified in various ways without departing from its essence.

[0056] 100 Lamellar Observation System 1 FIB-SEM Combined Device 2 Lamellar Transfer Device 3 TEM Device 4 Optical System 5 Light Source 6 Filter 7 First Beam Splitter 8 Second Beam Splitter 9 First Objective Lens 10 Second Objective Lens 11 Fixed Mirror 12 Third Objective Lens 13 Photodetector 14 Lens Tube Drive Mechanism 15 Sample Transport Device 16 Tweezers 17 Tweezers Drive Mechanism 18 Control Device 19 Input Device 20 Display Device 21 Holder 22 Grid Frame 23 Film L0 Light L1 Light L1R Reflected Light L2 Reference Light L3 Interfering Light LM Lamellar LMa, LMb End SAM Sample SAMa Connection

Claims

1. A lamellar transfer device comprising tweezers for grasping lamellae fabricated on a sample, wherein the lamellae has a first end and a second end opposite to the first end, and the sample has a connecting portion connected to the first end, wherein after grasping the lamellae with the tweezers, the tweezers are moved in a direction from the first end to the second end, and the lamellae is acquired from the sample by moving the tweezers so that the lamellae separates from the connecting portion.

2. A lamellar relocation device according to claim 1, wherein when the lamellar is grasped by the tweezers, the tweezers move in a direction from the second end toward the first end.

3. A lamellar relocation device according to claim 2, wherein the first amount of movement of the tweezers when the lamellar is grasped by the tweezers is measured in advance, and after the lamellar is grasped by the tweezers, the tweezers are moved in a direction toward the second end so as to reach at least the first amount of movement.

4. A lamellar relocation device according to claim 1, wherein the lamellars are acquired from the sample by moving the tweezers in at least the direction in which the tweezers are gripping the lamellars.

5. A lamellar transfer apparatus according to claim 1, further comprising a holder for mounting the lamellars, wherein after obtaining the lamellars from the sample, the lamellars are brought into contact with the membrane of the holder while being held by the tweezers, and the tweezers are released.

6. A method for relocating a lamellar, comprising: (a) preparing a sample on which lamellae have been fabricated; (b) grasping the lamellae with tweezers after step (a); (c) moving the tweezers while the lamellae is being grasped by the tweezers after step (b); and (d) obtaining the lamellae from the sample by moving the tweezers after step (c) so that the lamellae is separated from the connecting portion, wherein the lamellae has a first end and a second end opposite to the first end, in step (a), the connecting portion which is part of the sample is connected to the first end, and in step (c), the tweezers are moved in a direction from the first end to the second end.

7. A method for relocating a lamella according to claim 6, wherein in step (b), when the lamella is grasped by the tweezers, the tweezers move in a direction toward the first end.

8. A method for relocating a lamella according to claim 7, further comprising: (e) a step of measuring in advance the first amount of movement of the tweezers to be moved in step (b) before step (b); and in step (c), the tweezers are moved in a direction toward the second end so as to reach at least the first amount of movement.

9. A method for relocating a lamella according to claim 6, wherein in step (d), the tweezers are moved in at least the direction in which the tweezers are gripping the lamella.

10. A method for relocating a lamellar according to claim 6, further comprising: (f) after step (d), bringing the lamellar into contact with the film of the holder while the lamellar is being held by the tweezers; and (g) after step (f), releasing the tweezers.

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