Sample holder assembly, charged particle beam device, and sample setting method

Abstract

Disclosed is a sample holder assembly for setting a sample in a sample chamber of a charged particle beam device, the sample holder assembly comprising: a sample holder (108) on which a sample is placed; and a cap (109) which is attachable to and detachable from the sample holder. The sample holder has a cylindrical part (108a) that is provided with a male screw part (201) on the side surface, and a flange part (108b) that is connected to the cylindrical part. The cap has a bottom surface, and an opening part (109b) that is connected to the opening of the bottom surface and is provided with a female screw part (202) on the side surface. The opening part is provided with a first vacuum seal structure (203) on the side surface, and is provided with a second vacuum seal structure (204) on the bottom surface. The female screw part of the cap is positioned between the bottom surface and the first vacuum seal structure, and when the female screw part of the cap is engaged with the male screw part of the sample holder so that the bottom surface of the cap is in contact with the flange part, the first vacuum seal structure is in contact with the cylindrical part.

Description

Specimen holder assembly, charged particle beam device, and specimen setting method

[0001] The present invention relates to a sample holder assembly, a charged particle beam device, and a sample setting method.

[0002] Charged particle beam devices such as ion milling machines and electron microscopes are used by placing samples on dedicated sample holders in a sample chamber maintained at a high vacuum. Charged particle beam devices irradiate samples with a charged particle beam to perform micro-level processing and nano-level observation. The charged particle beam devices mentioned above are used in research and development and manufacturing processes in a wide range of fields, including battery materials, semiconductors, electrical components, metals, and polymer materials. Currently, there is a growing demand for atmospherically sealed processing and observation, where samples placed on sample holders are placed in a sample chamber without coming into contact with the atmosphere.

[0003] Patent Document 1 discloses a sample holder equipped with a structure (vacuum seal structure) for mounting a cap to isolate the sample holder from the outside air. A sealant is incorporated into the cap, and the sealant seals the inside of the sample holder from the outside air. By removing the cap from the sample holder in an evacuated sample chamber or sample exchange chamber, it is possible to process or observe the sample without exposing it to the outside air.

[0004] JP 2013-201028 A

[0005] Among samples requiring air-tight processing and observation, highly active battery materials and the like undergo oxidation reactions even with trace amounts of oxygen. Therefore, when attempting to shut out the atmosphere using the cap disclosed in Patent Document 1, the space created by the cap and the sample holder must be highly airtight. A glove box is typically used to place such samples on the sample holder. During use, the glove box is filled with an inert gas to remove oxygen, water, and other substances, and its interior is maintained at a pressure higher than atmospheric pressure. Therefore, when the capped sample holder is transferred from the glove box to a charged particle beam device, the inside of the cap is under positive pressure, allowing the vacuum seal structure to effectively shut out the outside air.

[0006] However, when a sample preprocessed using an ion milling device is observed using a scanning electron microscope, or when the same sample is observed using an electron microscope equipped with a different detector, a process is required in which the sample is removed from the sample chamber of the first charged particle beam device and transferred to the sample chamber of the second charged particle beam device. In this case, the sample is removed from the first charged particle beam device into an atmospheric environment after the cap is reattached to the sample holder. Unlike when the sample is removed from a glove box, the inside of the cap is under negative pressure, making it easier for outside air to enter the inside of the cap. In other words, a higher level of airtightness is required for the vacuum seal structure in this process than for the process of transferring the sample from a glove box to the sample chamber of the first charged particle beam device. The vacuum seal structure disclosed in Patent Document 1 has a single sealant on the underside of the cap, which does not provide sufficient airtightness for samples that are particularly susceptible to chemical reactions.

[0007] A sample holder assembly that is one embodiment of the present invention is a sample holder assembly for setting a sample in a sample chamber of a charged particle beam device, and comprises: a sample holder on which the sample is placed; and a cap that is detachable from the sample holder; the sample holder has a cylindrical portion with a male thread portion on its side and a flange portion connected to the cylindrical portion; the cap has a bottom surface and an opening that connects to the opening in the bottom surface and has a female thread portion on its side; a first vacuum seal structure is provided on the side of the opening and a second vacuum seal structure is provided on the bottom surface; the female thread portion of the cap is located between the bottom surface and the first vacuum seal structure; when the female thread portion of the cap is engaged with the male thread portion of the sample holder and the bottom surface of the cap contacts the flange portion, the first vacuum seal structure contacts the cylindrical portion.

[0008] The present invention provides a sample holder assembly suitable for atmospherically shielded processing or atmospherically shielded observation using a charged particle beam device. Other objects and novel features will become apparent from the description of this specification and the accompanying drawings.

[0009] 1 is a schematic diagram showing the main parts of an ion milling apparatus. FIG. 1 is a schematic diagram showing the main parts of an ion milling apparatus. FIG. 2 is a schematic diagram showing the main parts of an ion milling apparatus. FIG. 3 is an enlarged view of a sample holder and a cap. FIG. 4 is an enlarged view of a sample holder and a cap. FIG. 5 is a diagram for explaining the effect of providing a double vacuum seal structure. FIG. 6 is a diagram for explaining the effect of providing a double vacuum seal structure. FIG. 7 is a diagram for explaining the positional relationship between the vacuum seal structure and the screw structure in the cap and the sample holder. FIG. 8 is a diagram for explaining the positional relationship between the vacuum seal structure and the screw structure in the cap and the sample holder. FIG. 9 is a diagram for quantitatively explaining the effect of providing a double vacuum seal structure. FIG. 10 is a diagram for quantitatively explaining the effect of providing a double vacuum seal structure.

[0010] 1A to 1C are schematic diagrams showing the main components of an ion milling device, which is an example of a charged particle beam device. Because ion milling devices can perform sample polishing and cutting with high throughput, they are used as pretreatment devices for observing sample surfaces or cross sections using a scanning electron microscope, which is also a charged particle beam device. FIG. 1A is a schematic diagram of a sample holder 108 with a sample 120 mounted thereon and a cap 109 attached, set on a tilting stage 106. FIG. 1B is a schematic diagram of FIG. 1A viewed from a different angle. FIG. 1C is a schematic diagram of the sample 120 being processed after the cap 109 has been removed from the sample holder 108 by a cap removal unit 110.

[0011] The ion milling apparatus 100 mainly comprises a sample chamber 101, an ion source 102, a high-voltage power supply 103, a vacuum pumping unit 104, a control unit 105, a tilt stage 106, a one-axis rotation stage 107, a sample holder 108, a cap 109, and a cap attaching / detaching unit 110. The combination of the sample holder 108 and the cap 109 is called a sample holder assembly.

[0012] During ion milling, the sample chamber 101 is always kept at a high vacuum (10 －３The pressure is maintained at a constant pressure (or less than 100 Pa). A high voltage is applied from a high-voltage power supply 103 to the ion source 102, generating a discharge. Ar gas introduced from the outside is ionized to generate monovalent Ar ions, which are then irradiated onto the sample as an ion beam, thereby processing the sample. The high-voltage power supply 103 and the vacuum pumping unit 104 are both controlled by a control unit 105. A one-axis rotation stage 107 is incorporated into the tilt stage 106, and the sample holder 108 is set on the one-axis rotation stage 107 and rotated around a rotation axis R. The tilt stage 106 can tilt the sample holder 108 around the tilt axis T within a range of θ = 0 to 90°. Here, θ is the angle between a vertical line V and a normal to the sample mounting surface of the sample holder 108 (a line parallel to the rotation axis R shown in Figure 1C). The tilt amount of the tilt stage 106 can be controlled manually or automatically. In the case of automatic control, it is controlled by the control unit 105. The rotation of the one-axis rotation stage 107 is automatically controlled by the control unit 105 .

[0013] When performing atmospheric blocking processing, the sample 120 is placed on the sample holder 108 in a glove box filled with inert gas, and after the cap 109 is attached to the sample holder 108, it is removed from the glove box and the sample holder 108 with the cap 109 attached is set on the tilt stage 106 in the sample chamber 101. The structure of the cap 109 will be described later; the cap 109 has a female thread portion, and is fixed to the sample holder 108 by screwing the cap 109 into a male thread portion provided on the sample holder 108. After the sample holder 108 is set on the tilt stage 106, the sample chamber 101 is evacuated by the vacuum exhaust unit 104.

[0014] After the sample chamber 101 is placed in a high vacuum, the cap 109 is removed using the capping / removal unit 110. The capping / removal unit 110 includes a shaft 110b with a hook 110c at its tip and a shaft holder 110a that holds the shaft 110b. The shaft holder 110a can adjust the insertion position of the shaft 110b within the XZ plane and can also adjust the insertion depth into the sample chamber 101 in the Y-axis direction. A vacuum seal is provided between the shaft holder 110a and the shaft 110b to prevent outside air from entering through the shaft insertion hole in the sample chamber 101. A recess 109a is provided on the top of the cap 109, and the tip of the shaft 110b is inserted into the recess 109a. The cap 109 is rotated and removed from the sample holder 108 by rotating the shaft 110b with the hook 110c engaged with the inner wall of the recess 109a. 1C, the removed cap 109 is pulled up by the shaft 110b to a position where it is not hit by the ion beam, and is held by the shaft holder 110a. Note that the configuration of the cap attaching / detaching unit 110 is not limited to that illustrated above, as long as the shaft 110b and the cap 109 can be coupled together to attach / detach the cap 109 from the sample holder 108. For example, the shaft 110b may grip and rotate the cap 109.

[0015] The tilt stage 106 is adjusted so that the top surface of the sample 120 coincides with the eucentric position of the tilt stage 106, i.e., so that the tilt axis T of the tilt stage 106 passes through the top surface of the sample 120. Thereafter, as shown in Fig. 1C, the tilt stage 106 tilts the sample 120 at an arbitrary angle θ, and the ion source 102 irradiates the sample 120 with an ion beam. During processing, the sample 120 is rotated around the rotation axis R by the one-axis rotation stage 107.

[0016] After the processing using the ion beam is completed, the tilt stage 106 is returned to the horizontal position, and the cap 109 is attached to the sample holder 108 using the cap attaching / detaching unit 110. The cap 109 can be attached by following the removal procedure in reverse. That is, the shaft 110b is pulled down, and the sample holder 108 is inserted into the opening of the cap 109. The female thread of the cap 109 engages with the male thread of the sample holder 108, and the shaft 110b is rotated to screw the cap 109 onto the sample holder 108. When the bottom end of the cap 109 and the flange of the sample holder 108 come into tight contact and the shaft 110b can no longer be rotated, the hook 110c of the shaft 110b is released from the recess 109a of the cap 109, and the shaft 110b is removed from the cap 109 and pulled up.

[0017] The sample holder 108 with the cap 109 attached is removed from the sample chamber 101 and transported for observation using, for example, a scanning electron microscope. A similar cap attaching / detaching unit is provided in the sample exchange chamber of the scanning electron microscope, and the cap 109 is removed in the sample exchange chamber before being introduced into the sample chamber.

[0018] 2A and 2B show enlarged views of the sample holder 108 and the cap 109. The sample holder 108 has a cylindrical portion 108a and a flange portion 108b. It is desirable that the cylindrical portion 108a and the flange portion 108b are integrally formed. A male thread portion 201 is provided on the side of the cylindrical portion 108a. Meanwhile, the cap 109 has an opening 109b that is connected to the opening on the bottom surface and through which the cylindrical portion 108a of the sample holder 108 with the sample 120 placed thereon can be inserted. A female thread portion 202 and a first vacuum seal structure 203 are provided on the side of the opening 109b of the cap 109, and a second vacuum seal structure 204 is provided on the bottom surface of the cap 109. The female thread portion 202 is located between the bottom surface and the first vacuum seal structure 203. The first vacuum seal structure 203 is, for example, one in which an O-ring (sealing material) is placed in a groove provided on the side of the opening 109b, and the second vacuum seal structure 204 is, for example, one in which an O-ring (sealing material) is placed in a groove provided on the bottom surface of the cap 109.

[0019] 2A shows the state when the cap 109 begins to be screwed onto the sample holder 108. When the male thread portion 201 of the sample holder 108 and the female thread portion 202 of the cap 109 begin to engage, the first vacuum seal structure 203 and the second vacuum seal structure 204 of the cap 109 are not in contact with the sample holder 108. If the cap 109 is further screwed in from this state, the first vacuum seal structure 203 comes into contact with the cylindrical portion 108a of the sample holder 108. If the cap 109 is further screwed in, the second vacuum seal structure 204 comes into contact with the flange portion 108b of the sample holder 108, thereby isolating the opening 109b of the cap 109 from the outside environment. This state is shown in FIG. 2B.

[0020] 3A and 3B, the effect of providing a double vacuum seal structure to the cap 109 will be described. ０ The pressure inside the cap P ＣＡＰ 3A shows an enlarged view of the sealing surfaces of the first and second vacuum seal structures when the pressure P is positive. ０ is atmospheric pressure. Figure 3B shows the pressure outside the cap P ０ The pressure inside the cap P ＣＡＰ 3B shows an enlarged view of the sealing surfaces of the first and second vacuum seal structures when the pressure P is negative. ０ is atmospheric pressure. As shown in FIG. 3B, the pressure inside the cap P ＣＡＰEven when the pressure inside the cap is negative, the sealing surfaces of the first and second vacuum seal structures are in close contact with the cap wall surface due to the pressure difference between the inside and outside. As a result, even if outside air penetrates through the second vacuum seal structure 204, the first vacuum seal structure 203 prevents further penetration into the cap. Note that in the enlarged view, the groove width is drawn larger than the diameter of the seal material for ease of understanding, but the diameter of the seal material is selected to match the width of the groove in which the seal material is placed in order to enhance the sealing effect.

[0021] In this embodiment, a vacuum seal structure and a screw structure are provided on the side of the opening 109b of the cap 109, and a screw structure is provided on the cylindrical portion 108a of the sample holder 108. The positional relationship between these will be explained using Figures 4A and 4B. Here, the length from the bottom surface of the cap 109 to the first vacuum seal structure 203 is defined as h Ｃ１ , the length from the bottom surface to the underside of the female thread portion 202 is h Ｃ２ In addition, the length from the top surface of the flange portion 108b to the top surface of the cylindrical portion 108a of the sample holder 108 is defined as h Ｓ１ The length from the upper surface of the male threaded portion 201 to the upper surface of the cylindrical portion 108a is h Ｓ２ In this case, the following relationship is satisfied.

[0022] 4A shows a state in which the bottom surface of the cap 109 is in contact with the upper surface of the flange portion of the sample holder 108. In this state, the first vacuum seal structure 203 must be in contact with the sample holder 108, so Equation 1 must be satisfied. Ｃ１ <h Ｓ１ ...(Equation 1) This ensures airtightness inside the cap 109 with a double vacuum seal structure. In addition, since the cap 109 is screwed onto the sample holder 108 by engaging the male threaded portion 201 and the female threaded portion 202, it is necessary to satisfy Equations 2 and 3. Ｓ２ <h Ｃ１ ...(Formula 2) h Ｃ２ <h Ｓ１ -h Ｓ２ ...(Equation 3) Furthermore, it is necessary to satisfy (Equation 4). h Ｃ１ >h ｃ２ +h ｓ２...(Equation 4) This is due to the following reason.

[0023] 4B shows a state in which the cylindrical portion 108a of the sample holder 108 is inserted into the opening 109b of the cap 109 without the female thread portion 202 of the cap 109 engaging with the male thread portion 201 of the sample holder 108. For example, when the cap 109 is removed from the sample holder 108 in the sample chamber 101, this state occurs immediately after the female thread portion 202 and the male thread portion 201 are disengaged. If (Equation 4) is not satisfied, the first vacuum seal structure 203 will be in contact with the cylindrical portion 108a in a state in which the female thread portion 202 of the cap 109 and the male thread portion 201 of the sample holder 108 are disengaged. When the sample holder 108 is transferred from the glove box and the cap 109 is removed in a sample chamber that has been set to a high vacuum, the pressure inside the cap P ｃａｐ is equal to or greater than atmospheric pressure (101325 Pa), whereas the pressure outside the cap P ０ is 10 －３ Since the pressure is below 100 Pa, an extremely large pressure difference is applied to the first vacuum seal structure 203, causing the seal material to adhere to the side surface of the cylindrical portion 108a. This makes it impossible to pull out the cap 109 from the sample holder 108. By satisfying (Equation 4), this situation can be avoided.

[0024] The sample holder assembly of this embodiment is structured so that when the cap 109 is screwed onto the sample holder 108, the vacuum seal structures on the inner surface and bottom of the cap 109 come into contact with the sample holder 108. Therefore, the cap 109 can be attached to and detached from the sample holder 108 by simply tightening and loosening a screw. Furthermore, when the screw structures on both sides are released, the vacuum seal structure is also released, so that the cap can be easily attached and detached even in a vacuum environment.

[0025] The effects of a double vacuum seal structure will be quantitatively explained using Figures 5 and 6. Figure 5 shows an experimental system for evaluating the vacuum seal structure. A sample holder 108 and a cap 109 can be attached to the experimental sample chamber 301. The experimental sample chamber 301 has a sample holder attachment section 301a that imitates the cap 109 and a cap attachment section 301b that imitates the shape of the sample holder 108. The sample holder 108 is attached to the sample holder attachment section 301a, and the cap 109 is attached to the cap attachment section 301b. The sample holder attachment section 301a is provided with a first vacuum seal structure 313 and a second vacuum seal structure 314, which are positioned in the same manner as the cap 109. The interior of the experimental sample chamber 301 is evacuated by a vacuum evacuation unit 302, and the pressure in the experimental sample chamber 301 can be measured by a full-range vacuum gauge 303.

[0026] After the experimental sample chamber 301 had been fully evacuated, the evacuation was stopped and the pressure in the experimental sample chamber 301 was recorded over time. The results are shown in Figure 6. The vertical axis represents the pressure (logarithmic) in the experimental sample chamber, and the horizontal axis represents time. The solid line represents the case where a single vacuum seal structure was used (comparative example), and the dotted line represents the case where a double vacuum seal structure was used (example). In the comparative example, only the second vacuum seal structure 204 was provided on the cap 109, and only the second vacuum seal structure 314 was provided on the sample holder mounting portion 301a. The initial pressure was 1.0 x 10 －３ The pressure in the experimental sample chamber after 30 minutes is below P Pa, but increases over time. However, it can be seen that the pressure increase is slower in the example than in the comparative example. Ｏ１ , in the embodiment, P Ｏ２ Then, P Ｏ２ <P Ｏ１ It was confirmed that there was a difference of about 3 to 5 times.

[0027] The present invention has been specifically described above based on the embodiments, but the present invention is not limited to the described embodiments and can be modified in various ways without departing from the spirit of the invention. For example, although the present invention has been described using an ion milling device as an example of a charged particle beam device, it can also be applied to a sample holder for a scanning electron microscope.

[0028] 100: ion milling device, 101: sample chamber, 102: ion source, 103: high-voltage power supply, 104: vacuum exhaust unit, 105: control unit, 106: tilt stage, 107: one-axis rotation stage, 108: sample holder, 108a: cylindrical portion, 108b: flange portion, 109: cap, 109a: recess, 109b: opening, 110: cap attachment / detachment unit, 110a: shaft holding portion , 110b: shaft, 110c: hook portion, 120: sample, 201: male thread portion, 202: female thread portion, 203: first vacuum seal structure, 204: second vacuum seal structure, 301: experimental sample chamber, 301a: sample holder mounting portion, 301b: cap mounting portion, 302: vacuum exhaust unit, 303: full-range vacuum gauge, 313: first vacuum seal structure, 314: second vacuum seal structure.

Claims

1. A sample holder assembly for setting a sample in a sample chamber of a charged particle beam device, comprising: a sample holder on which a sample is placed; and a cap that is detachable from the sample holder, wherein the sample holder has a cylindrical portion with a male thread portion on its side and a flange portion connected to the cylindrical portion, the cap has a bottom surface and an opening that connects to the opening in the bottom surface and has a female thread portion on its side, and a first vacuum seal structure is provided on the side of the opening and a second vacuum seal structure is provided on the bottom surface, the female thread portion of the cap is located between the bottom surface and the first vacuum seal structure, and when the female thread portion of the cap is engaged with the male thread portion of the sample holder and the bottom surface of the cap comes into contact with the flange portion, the first vacuum seal structure comes into contact with the cylindrical portion.

2. A sample holder assembly as claimed in claim 1, wherein when the cylindrical portion of the sample holder is inserted into the opening of the cap without engaging the female threaded portion of the cap with the male threaded portion of the sample holder, the first vacuum seal structure does not come into contact with the cylindrical portion of the sample holder.

3. A sample holder assembly according to claim 1, wherein the first vacuum seal structure has a groove formed on the side of the opening of the cap, and a sealant is placed in the groove, and the second vacuum seal structure has a groove formed on the bottom surface of the cap, and a sealant is placed in the groove.

4. A charged particle beam device comprising a sample chamber or a sample exchange chamber into which the sample holder assembly according to claim 1 is introduced, wherein the sample chamber or the sample exchange chamber is evacuated and the sample holder with the cap attached is introduced into the interior thereof, and a cap attachment / detachment unit is installed outside the sample chamber or the sample exchange chamber into which the sample holder assembly is introduced.

5. A charged particle beam device according to claim 4, wherein the cap attachment / detachment unit comprises a shaft and a shaft holding portion that holds the shaft and is capable of adjusting the insertion position of the shaft into the sample chamber or the sample exchange chamber, and the cap attachment / detachment unit connects the shaft and the cap to attach and detach the cap from the sample holder.

6. A charged particle beam device according to claim 5, wherein the shaft has a hook at its tip, the cap has a recess into which the hook is inserted, and the cap is attached to and detached from the sample holder by rotating the shaft with the hook engaged with the inner wall of the recess in the cap.

7. A sample setting method for setting a sample in a charged particle beam device, wherein the charged particle beam device is provided with a sample chamber or a sample exchange chamber into which a sample holder on which a sample is placed is introduced, and a capping unit is installed outside the sample chamber or the sample exchange chamber into which the sample holder is introduced, the method comprising: a first step of introducing the sample holder on which a sample is placed and to which a cap is attached into the sample chamber or the sample exchange chamber, which has been evacuated; and a second step of removing the cap from the sample holder introduced into the sample chamber or the sample exchange chamber by the capping unit, wherein the sample holder has a cylindrical portion having a male thread portion on its side and a flange portion connected to the cylindrical portion, and the cap has a bottom surface and an opening connected to the opening in the bottom surface and having a female thread portion on its side, and a first vacuum seal structure is provided on the side of the opening and a second vacuum seal structure is provided on the bottom surface, and the female thread portion of the cap is located between the bottom surface and the first vacuum seal structure, A sample setting method in which, in the first step, the cap is attached to the sample holder by engaging the female thread portion of the cap with the male thread portion of the sample holder, the first vacuum seal structure of the cap contacts the cylindrical portion of the sample holder, and the second vacuum seal structure of the cap contacts the flange portion of the sample holder.

8. A sample setting method as claimed in claim 7, wherein in the second step, when the female threaded portion of the cap and the male threaded portion of the sample holder are disengaged, the first vacuum seal structure of the cap is not in contact with the cylindrical portion of the sample holder.

9. A sample setting method according to claim 7, wherein the first vacuum seal structure has a groove formed on the side of the opening of the cap, and a sealant is placed in the groove, and the second vacuum seal structure has a groove formed on the bottom surface of the cap, and a sealant is placed in the groove.

10. A sample setting method according to claim 7, further comprising a third step of removing the sample holder with the cap attached thereto from the sample chamber or the sample exchange chamber by the cap attaching / detaching unit.

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