Ion milling device, sample holding member, and ion milling method

Abstract

The present invention provides a feature that, when a sample is processed using plane milling, any rise in the temperature of a sample is suppressed by cooling. An ion milling device comprises: a sample chamber; a sample holding member that holds a sample assuming the form of a thin film, and that can be conveyed in and out of the sample chamber in a cooled state; a movable stage on which the sample holding member is mounted; and an ion source that directs an ion beam on the surface of the sample. The sample holding member contacts the back surface of the sample and holds the sample so that the irradiation region of the sample irradiated with the ion beam protrudes further than other regions of the sample.

Description

Ion milling apparatus, sample holding member, and ion milling method

[0001] The present invention relates to an ion milling apparatus, a sample holder, and an ion milling method.

[0002] An ion milling device is a device that irradiates a sample (e.g., metal, semiconductor, glass, ceramic, etc.) to be observed with an electron microscope with an unfocused ion beam in a vacuum, sputtering atoms off the sample surface, polishing the sample surface without stress and exposing the internal structure of the sample. The polished or exposed surface of the sample can be observed with a scanning electron microscope, transmission electron microscope, etc.

[0003] There are two main methods for processing samples using ion milling equipment. One is called plane milling or surface milling, in which the sample is placed on a flat surface on top of a sample holder and the sample is rotated while the ion beam is irradiated at an angle onto the sample surface. The other is called cross-section milling, in which a shielding plate is placed in front of the sample (the ion source side), the sample is swung, and the ion beam is irradiated onto the part of the sample protruding beyond the shielding plate.

[0004] Compared to cross-section milling, the flat milling method has the advantage of being able to obtain a wider range of processed surfaces and can be applied to any sample shape, making it suitable for a wide range of applications such as polishing sample surfaces and delayering semiconductors.

[0005] When processing polymeric materials that are easily melted or deformed using an ion milling device, the sample may be thermally damaged by ion beam irradiation, so the sample may be cooled via a sample holder during processing (see Patent Document 1).

[0006] Patent Document 1 discloses a configuration in which a cooling mechanism, which is liquid nitrogen placed in a dewar placed outside the device, is connected to a shielding plate fixed to a sample holding member (sample holder) via a copper braided wire and a cooling plate.

[0007] International Publication No. 2021 / 059401

[0008] As described in Patent Document 1, when processing a sample by cross-section milling, the sample can be cooled via a sample holder. On the other hand, when processing a sample by plane milling, the sample holder needs to be rotated during processing, making it difficult to connect a cooling mechanism to the sample holder. Therefore, when processing a sample by plane milling, it is difficult to suppress the temperature rise of the sample by cooling.

[0009] One object of the present disclosure is to provide a technique that makes it easier to suppress a rise in the temperature of a sample by cooling when processing the sample by plane milling.

[0010] The ion milling apparatus of the present disclosure, which solves the above-mentioned problems, comprises a sample chamber, a sample holding member that holds a thin-film sample and can be moved in and out of the sample chamber while cooled, a movable stage on which the sample holding member is mounted, and an ion source that irradiates an ion beam toward the surface of the sample, wherein the sample holding member is configured to abut against the back surface of the sample and to hold the sample so that the irradiation area of ​​the sample irradiated with the ion beam protrudes beyond other areas of the sample.

[0011] According to the present disclosure, it is possible to provide a technique that makes it easier to suppress a rise in the temperature of a sample by cooling when processing the sample by plane milling.

[0012] FIG. 1 is a diagram showing a schematic configuration of an ion milling apparatus according to an embodiment; FIG. 2 is a diagram showing a schematic configuration of an ion milling apparatus according to an embodiment; FIG. 3 is a perspective view showing an example of a sample holder according to an embodiment; FIG. 4 is an enlarged view showing an example of a sample holder according to an embodiment; FIG. 5 is a schematic view showing the state of a sample holder and an ion beam during sample processing; FIG. 6 is a schematic view explaining the relationship between the heat quantity of an ion milling apparatus during sample processing; FIG. 7 is a schematic view explaining the temperature gradient of a sample during sample processing; FIG. 8 is a diagram showing a cap member and a sample holder; FIG. 9 is a flowchart showing a sample processing procedure according to an embodiment; FIG. 10 is a flowchart showing a sample processing procedure according to an embodiment;

[0013] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0014] <Overall Configuration of Ion Milling Apparatus> First, the overall configuration of the ion milling apparatus will be described with reference to Figures 1 and 2. Figures 1 and 2 are diagrams schematically showing the main parts of an ion milling apparatus according to one embodiment, with Figure 1 showing the state before ion milling of a sample begins and Figure 2 showing the state during ion milling of the sample.

[0015] 1 and 2 , an ion milling apparatus 100 according to one embodiment is an apparatus capable of ion milling (plane milling) on ​​a sample S, and includes, as its main components, a sample chamber 110, an ion source 120, a sample holder 130, a movable stage 140, a vacuum pumping device 150, a high-voltage power supply 160, an ion beam current detection unit 170, and a cap attachment / detachment unit 180. Note that, of the above-described components of the ion milling apparatus 100, the components other than the sample holder 130 are existing components, and therefore will be briefly described below.

[0016] The ion milling apparatus 100 also includes a control unit (control device) 200 that comprehensively controls various devices including the ion source 120, the movable stage 140, the vacuum pumping device 150, the high-voltage power supply 160, the ion beam current detection unit 170, and the cap attachment / detachment unit 180. The control unit 200 is composed of, for example, a calculation unit such as a CPU (Central Processing Unit), a RAM (Random Access Memory) unit such as a semiconductor memory, a storage unit such as an SSD (Solid State Drive) or an HDD (Hard Disk Drive), a communication unit, and the like.

[0017] <Sample Chamber> The sample chamber 110 forms a space in which ion milling is performed on the sample 1000. A movable stage 140 is provided within the sample chamber 110, and processing of the sample S is performed by the plane milling method in a state in which a sample holding member 130 that holds the sample S is mounted on the movable stage 140.

[0018] A vacuum exhaust device 150 is connected to the sample chamber 110 and is configured to be able to maintain a vacuum state. The vacuum exhaust device 150 includes, for example, a rotary pump and a turbo molecular pump, and exhausts the sample chamber 110 to create a vacuum. In this example, the sample chamber 110 during ion milling is always maintained at a high vacuum (for example, 10 ―３ The temperature is kept at a constant value (below 100 Pa).

[0019] <Ion Source> An ion beam is irradiated from the ion source 120 toward the surface of the sample S placed in the sample chamber 110. The ion source 120 is provided on one side wall of the sample chamber 110, and the ion beam is irradiated from this ion source 120 toward the surface of the sample S in the Z-axis direction in the figure. The ion source 120 is of a so-called Penning type, and an unfocused ion beam is irradiated from the ion source 120 toward the sample S. A high-voltage power supply 160 is connected to the ion source 120, and a high voltage is applied to electrode components in the ion source 120 by the high-voltage power supply 160, thereby ionizing Ar gas introduced from outside and irradiating the ion beam toward the sample S.

[0020] <Movable Stage> The movable stage 140 is installed in the sample chamber 110, and is mounted with the sample holding member 130 that holds the sample S. The configuration of the sample holding member 130 will be described in detail later. The movable stage 140 includes a tilting stage including a drive source such as an electric motor (not shown), and is configured to be tiltable within a predetermined range. The movable stage 140 according to this embodiment is configured to be tiltable at a tilt angle θ with respect to the irradiation direction (Z-axis direction) of the ion beam from the ion source 120 within a range of 0 to 90 degrees. In other words, the movable stage 140 is configured to be oscillated within a range of 0 to 90 degrees around the X-axis (see FIG. 2) from an initial state (see FIG. 1) in which the surface of the movable stage 140 faces the Y-axis direction.

[0021] Furthermore, the movable stage 140 includes a rotation stage including a drive source such as an electric motor (not shown), and is configured to be rotatable about an R-axis extending in a direction perpendicular to the surface of the movable stage 140 (see FIG. 2 ). Processing of the sample S held by the sample holding member 130 is performed by rotating the movable stage 140 on which the sample holding member 130 is mounted, while tilting the stage 140, about the R-axis. That is, in processing the sample S using the plane milling method, an ion beam is irradiated obliquely onto the surface of the sample S while rotating the sample S about the R-axis. In the example of FIG. 2 , the ion beam is irradiated onto the surface of the sample S while the angle between the ion beam and a line perpendicular to the surface of the sample S (the R-axis) is a predetermined angle (the tilt angle θ).

[0022] By irradiating the sample S with an ion beam while rotating the sample S in this manner, the occurrence of unevenness due to differences in milling rate due to crystal orientation and composition can be suppressed compared to when irradiating the sample S with an ion beam without rotating the sample S, and a smoother processed surface of the sample S can be obtained.

[0023] The movable stage 140 has an eccentric mechanism that can change the position of the R axis, which is the center of rotation, within a range of approximately 0 to 5 mm from the center position of the movable stage 140 (the center position of the sample S). By adjusting this eccentric mechanism, it becomes possible to perform ion milling on a wider area of ​​the sample S.

[0024] The movable stage 140 also has a so-called eucentric function. Therefore, when the sample holding member 130 holding the sample S is assembled into the movable stage 140, the position of the sample S is adjusted by the movable stage 140 so that the irradiation position of the ion beam from the ion source 120 is the upper surface (front surface) of the sample S. The tilt angle of the movable stage 140 may be adjusted by the control unit 200, or may be manually adjusted.

[0025] <Ion beam current detection unit> The ion beam current detection unit 170 has an ion beam current detection part 171, a one-axis movable mechanism 172, and an ammeter 173, and is disposed between the ion source 120 in the Z-axis direction and the sample holding member 130 mounted on the movable stage 140. The ion beam current detection part 171 is a part onto which an ion beam is irradiated from the ion source 120, and is supported by the one-axis movable mechanism 172 so as to be movable in one axis direction. In this example, the one-axis movable mechanism 172 can move the ion beam current detection part 171 up or down in the Y-axis direction.

[0026] For example, when the sample holding member 130 holding the sample S is mounted on the movable stage 140, the ion beam current detection unit 171 is placed at a position where the ion beam is irradiated. At this time, if the ion beam current detection unit 171 is at a position where the ion beam is not irradiated, the ion beam current detection unit 171 is moved (lowered) by the one-axis movable mechanism 172 to a position where the ion beam is irradiated.

[0027] In this state, the ion beam current detection unit 170 measures the ion beam current IB with an ammeter 173 for an arbitrarily set time (several seconds to a maximum of 300 seconds) before the ion beam is irradiated onto the sample S. The ion beam current detection unit 171 also serves as a shutter that prevents the ion beam from being irradiated onto the sample S until the current of the ion beam output from the ion source 120 becomes stable.

[0028] After the set time has elapsed, the ion beam current detection unit 171 is moved (raised) by the one-axis movable mechanism 172 and retracted to a position where it is not irradiated with the ion beam. This starts ion beam irradiation of the sample S. That is, ion milling of the sample S is started.

[0029] <Sample Holding Member> Next, a description will be given of the sample holding member 130 that holds the sample S to be processed. Fig. 3 is a perspective view showing a schematic configuration of the sample holding member, and Fig. 4 is a cross-sectional view showing a schematic configuration of the sample holding member.

[0030] The sample holding member 130 holds a thin-film sample S, and as shown in Figures 3 and 4, its main components include a holding member (also called a sample stage) 131 that holds the periphery of the irradiation area A1 of the sample S where the ion beam is irradiated, and a support member (also called a sample holder) 132 that supports the holding member 131.

[0031] The ion milling apparatus 100 of this example performs ion milling on a thin-film sample S (also referred to as a thin-film sample) having a thickness of, for example, 1 mm or less. As an example, the sample S has a substantially circular outer shape, and the irradiation area A1 is set at the center of the sample S. That is, the ion beam from the ion source 120 is irradiated onto the center of the sample S (see FIG. 2).

[0032] The sample holding member 130 holds the sample S so that the irradiation area A1 of the sample S protrudes from other areas of the sample S. In this embodiment, the outer periphery of the sample S is held by a holding member 131, and this holding member 131 is supported by a support member 132 so that the irradiation area A1 of the sample S protrudes from other areas of the sample S.

[0033] The gripping member 131 includes a first member 1312 having a sample stage 1311 on which the sample S is placed, and a second member (also referred to as a pressing member) 1313 that presses the sample S placed on the sample stage 1311 toward the first member 1312. The sample S is gripped by the first member 1312 and the second member 1313.

[0034] The fixing structure between the first member 1312 and the second member 1313 is not particularly limited, but in this embodiment, they are connected by threaded portions provided on both members. More specifically, the sample stage portion 1311 of the first member 1312 has a diameter larger than the diameter of the sample S, and a threaded portion 1314 is formed on the outer circumferential surface of the sample stage portion 1311. Meanwhile, a recess 1315 large enough to accommodate the first member 1312 is provided on the surface of the second member 1313 facing the first member 1312, and a threaded portion 1316 is formed on the inner circumferential surface of this recess 1315. The first member 1312 and the second member 1313 are connected by these threaded portions 1314 and 1316. When the first member 1312 and the second member 1313 are fixed, the first member 1312 is accommodated in the recess 1315 of the second member 1313.

[0035] As described above, the gripping member 131 grips the outer periphery of the sample S, that is, the periphery of the irradiation area A1. Therefore, when the sample S is gripped by the gripping member 131, the portion of the sample S that will become the irradiation area A1 is exposed. In this example, the second member 1313 of the gripping member 131 has an opening 1317 at a position corresponding to the irradiation area A1 of the sample S, and the surface of the sample S is exposed within this opening 1317.

[0036] On the other hand, the first member 1312 has a through-hole 1318 formed in a position corresponding to the irradiation area A1 of the sample S, and the back surface of the sample S is exposed within the through-hole 1318. When the sample S is held by the holding member 131 in this manner, both the front and back surfaces of the sample S are exposed in the portion corresponding to the irradiation area A1.

[0037] The support member 132 constituting the sample holding member 130 has a main body portion 1321 attached to the movable stage 140 and a protrusion portion 1322 protruding from the surface of the main body portion 1321 opposite the movable stage 140.

[0038] The gripping member 131 is fixed to a protrusion 1322 of this support member 132. A through hole 1318 of the gripping member 131 is formed with a size that allows the protrusion 1322 to be inserted therein. The gripping member 131 and the support member 132 are fixed together by inserting the protrusion 1322 of the support member 132 into the through hole 1318 of the gripping member 131. In this example, a threaded portion 1323 is formed on the outer peripheral surface of the protrusion 1322, and a threaded portion 1319 is also formed on the inner surface of the through hole 1318. The gripping member 131 and the support member 132 are screw-coupled together by these threaded portions 1319, 1323.

[0039] As described above, the back surface of the sample S is exposed in the through-hole 1318. Therefore, when the protrusion 1322 is inserted into the through-hole 1318, the tip surface of the protrusion 1322 abuts against the back surface of the sample S. Furthermore, the sample S is pressed from the back surface side by the protrusion 1322, and the irradiation area A1 irradiated with the ion beam protrudes more than other areas of the sample S. In this example, the irradiation area A1 protrudes more than the outer periphery of the sample S held by the holding member 131. In other words, the sample holding member 130 holds the sample S so that the irradiation area A1 protrudes more than the outer periphery of the sample S.

[0040] The protrusion amount (maximum protrusion amount d) of the irradiation area A1 of the sample S is not particularly limited, but is preferably set to a value large enough to prevent damage to the sample S. The maximum protrusion amount d of the irradiation area A1 of the sample S can be adjusted by the degree of fastening between the gripping member 131 and the support member 132 (the degree of fastening of the screw portions 1319, 1323).

[0041] Here, the tip surface of the protrusion 1322 that contacts the sample S is preferably formed in a spherical shape (or semi-spherical shape). In other words, the protrusion 1322 is preferably highest at the center (the amount of protrusion from the main body 1321 is greatest), gradually decreases in height as it approaches the outer periphery, and has a shape that does not have a boundary (sharp portion) between the tip surface and the outer periphery. In other words, the tip surface of the protrusion 1322 does not have to be a perfect sphere, and may be formed as a curved surface with the shape described above. This makes it possible to suppress damage to the thin-film sample S due to pressure from the protrusion 1322, compared to when the tip of the protrusion 1322 is not spherical.

[0042] Furthermore, in order to ensure that the ion beam is irradiated onto the surface of the sample S without being blocked by the gripping member 131, it is desirable that the diameter r of the opening 1317 of the first member 1312 be sufficiently larger than the size of the irradiation range A1.

[0043] As shown in FIG. 5 , when processing a sample S by plane milling, an ion beam is typically irradiated obliquely onto the surface of the sample S to prevent the formation of irregularities on the surface of the sample S. As an example, the tilt angle θ of the movable stage 140 (tilt angle of the sample S) relative to the ion beam irradiation direction (Z direction) is often set to approximately 70°, which increases the sputtering yield. Therefore, the diameter of the area where the ion beam is actually irradiated onto the sample S is calculated as R / cos θ, and is larger than the ion beam diameter R (the diameter of the ion beam in the Y-axis direction) immediately before irradiating the sample S. Therefore, it is preferable that the diameter r of the opening 1317 at least satisfies the condition of the following formula (1):

[0044] r>R / cos θ (1) This makes it easier to appropriately irradiate the ion beam onto the surface of the sample S without being blocked by the gripping member 131.

[0045] Furthermore, since the second member 1313 of the gripping member 131 covers a portion of the sample S and is exposed to the ion beam, it is desirable that the second member 1313 be made of a material with a low sputtering yield in order to protect the sample S. Specific examples of materials for the second member 1313 include graphite carbon and titanium. However, the material for the first member 1312 is not limited to these.

[0046] Furthermore, it is preferable that the through-hole 1318 of the first member 1312 is equal to or larger in size than the irradiation area A1 of the sample S that is irradiated with the ion beam. In this embodiment, the through-hole 1318 is formed with an inner diameter larger than the diameter of the irradiation area A1. Needless to say, the protrusion 1322 of the support member 132 is formed with an outer diameter that matches the inner diameter of this through-hole 1318.

[0047] Thus, the main functions of the support member 132 constituting the sample holding member 130 include holding the gripping member 131 and adjusting the height. However, the function of the support member 132 is not limited to these; for example, cooling the sample S is also one of the main functions. In order to cool the sample S, the sample holding member 130 including the support member 132 is cooled to around −20° C. in a freezer or the like before processing the sample S by the plane milling method. In other words, processing of the sample S by the plane milling method is performed with the support member 132 cooled.

[0048] This makes it easier to suppress a temperature rise in the sample S during processing. In this embodiment, as described above, the protrusions 1322 of the support member 132 abut against the back surface of the sample S, so that the irradiation area A1 of the sample S is in a protruding state. In other words, during processing by the plane milling method, the protrusions 1322 of the support member 132 are in close contact with the sample S. Therefore, the support member 132 can more reliably suppress a temperature rise in the sample S.

[0049] In order to easily maintain the temperature of the cooled support member 132, it is desirable that the support member 132 be made of a material with a large specific heat. Specific examples of materials for the support member 132 include metals such as copper and alloys such as stainless steel. However, the material for the support member 132 is not limited to these.

[0050] Furthermore, in order to easily maintain the cooling temperature of the support member 132, it is preferable that the support member 132 constituting the sample holding member 130 is mounted on the movable stage 140 via a heat insulating material 145. This makes it possible to suppress heat transfer between the support member 132 and the movable stage 140, making it easier to maintain the cooling temperature of the support member 132. There are no particular restrictions on the material of the heat insulating material 145, but it is desirable that it be a material with as low thermal conductivity as possible. Specific examples of materials for the heat insulating material 145 include polycarbonate and ceramics.

[0051] Here, a description will be given of heat transfer during processing of the sample S. Fig. 6 is a schematic diagram showing heat transfer during sample processing.

[0052] The heat quantity Q1 (J) due to the ion beam irradiated to the sample S can be calculated as the product of the potential difference Vacc (V) between the voltage applied to the ion source 120 and the sample S irradiated with the ion beam, the ion beam current IB (A), and the ion beam irradiation time t (s), as shown in the following equation (2):

[0053] Q1 = Vacc × IB × t (2) During the ion beam irradiation time t (s), the thermal energy transferred from the movable stage 140 to the support member 132 of the sample holding member 130 is Q2 (J), and the heat capacity of the support member 132 is C(J·K －１ ), where the temperature difference between the cooling temperature of the support member 132 and the heat resistance temperature (melting point or glass transition point) of the sample S is ΔT (K), in order to perform ion milling processing without the temperature of the sample S exceeding the heat resistance temperature, it is necessary to satisfy the condition shown in the following formula (3), for example, by providing a heat insulating material 145.

[0054] C×ΔT>Q1+Q2 (3) By performing plane milling that satisfies this condition, deformation and melting of the sample S during processing can be suppressed. Note that the sample chamber 110 is kept in high vacuum (1×10 －３ Since the pressure is kept at a constant level (approximately 100 Pa), heat transfer through the gas medium can be ignored.

[0055] 7, the temperature gradient of the sample S can be expressed as "TH-TL / L", where TH is the temperature on the ion beam irradiation side of the sample S (surface temperature), TL is the temperature on the support member 132 side of the sample S (backside temperature), and L is the thickness of the sample S. Note that the surface temperature TH of the sample S during plane milling is approximately 200°C to 250°C or higher, and the backside temperature TL is approximately -20°C. The thickness L of the thin film is 1 mm or less.

[0056] According to Fourier's law, the heat flux increases in proportion to the temperature gradient. Therefore, when the support member 132 is cooled and the temperature gradient (TH-TL / L) increases, heat can be sufficiently transferred to the support member 132, even for a sample made of a polymeric material with a low thermal conductivity. Furthermore, the sample S is pressed by the protrusions 1322 and fixed in a state of sufficient contact with the support member 132. Therefore, compared to fixing methods such as carbon paste and hot wax, the contact thermal resistance between the sample S and the support member 132 is smaller, and the amount of heat transfer is greater.

[0057] One method of reducing the contact thermal resistance between the sample S and the support member 132 is to apply grease or other material with excellent thermal conductivity. However, this is not desirable because the oil in the grease evaporates in a vacuum, which could lead to a decrease in vacuum pressure or a decrease in image quality due to the adhesion of contamination when observing with a scanning electron microscope.

[0058] <Cap Attachment / Detachment Unit> The ion milling apparatus 100 includes a cap member (hereinafter simply referred to as a cap) 190 that is detachable from the sample holding member 130 (see FIG. 1, etc.). As shown in FIG. 8, the cap 190 covers the sample S held by the holding member 131 and is attached to the support member 132.

[0059] For example, by attaching the cap 190 to the sample holding member 130 in a glove box filled with an inert gas such as dry nitrogen or argon gas, condensation on the sample S can be suppressed.

[0060] The cap 190 is also used, for example, to prevent condensation on the sample S when the cooled sample S is removed from the sample chamber 110. Furthermore, even if the sample S is particularly reactive (for example, a separator for a lithium ion battery), by attaching the cap 190 to the sample holding member 130 inside the sample chamber 110 after processing is completed and then opening the sample chamber 110 to the atmosphere, the sample S can be cut off from contact with the atmosphere and reaction between the sample S and the atmosphere can be prevented.

[0061] In some cases, a convex portion 1324 to which the cap member 190 is fastened is provided continuously around the protrusion 1322 on the upper surface of the support member 132 according to this embodiment. A threaded portion 1325 is formed on the outer peripheral surface of the convex portion 1324, and the cap 190 is attached to the support member 132 by fitting a threaded portion 191 provided on the inner peripheral surface of the cap 190 into this threaded portion 1325. The sample S held by the gripping member 131 of the sample holding member 130 is accommodated inside the cap 190 attached to the support member 132.

[0062] Furthermore, in this configuration, a groove 1326 is provided on the upper surface of the support member 132, extending continuously around the periphery of the protrusion 1324 on the outer side of the protrusion 1324, and an O-ring 1327 is disposed in the groove 1326. As a result, when the cap 190 is attached to the support member 132, the cap 190 abuts against the O-ring 1327, thereby improving the airtightness inside the cap 190.

[0063] The cap attaching / detaching unit 180 provided in the ion milling apparatus 100 is a unit for attaching / detaching the cap 190 to / from the sample holding member 130 in the sample chamber 110 .

[0064] The cap attachment / detachment unit 180 has a shaft holder 181 and a cap attachment / detachment shaft 182, and is disposed on the upper surface of the sample chamber 110 and directly above the sample holding member 130 mounted on the movable stage 140 (see FIG. 1 , etc.). The shaft holder 181 has a two-axis (X-axis and Z-axis) movement mechanism for adjusting the position of the cap 190 when attaching or detaching it, and a holding mechanism for holding the cap attachment / detachment shaft 182. The cap attachment / detachment shaft 182 is held by an O-ring provided inside the shaft holder 181, and is configured to be movable in the X-axis and Z-axis directions and rotatable while maintaining the vacuum inside the sample chamber 110.

[0065] The tip of the cap attachment / detachment shaft 182 is configured to be able to engage with and detach from a hole 192 provided in the upper surface of the cap 190. In this example, by rotating the cap attachment / detachment shaft 182 in one direction, the cap 190 rotates in one direction together with the cap attachment / detachment shaft 182, and the cap attachment / detachment shaft 182 engages with the hole 192 of the cap 190. Furthermore, by rotating the cap attachment / detachment shaft 182 in the other direction, the cap 190 rotates in the other direction together with the cap attachment / detachment shaft 182, and the engagement of the cap attachment / detachment shaft 182 with the hole 192 is released.

[0066] 9 and 10, an example of a processing procedure (ion milling method) for the sample S using the above-described ion milling apparatus 100 will be described. Figures 9 and 10 are flowcharts showing an example of the processing procedure for the sample according to this embodiment.

[0067] When processing a sample S by plane milling using the ion milling apparatus 100, first, in step S101, the sample S is set on the gripping member 131 of the sample holding member 130. More specifically, with the sample S placed on the sample stage portion 1311 of the first member 1312, the first member 1312 and the second member 1313 are fixed together, and the outer periphery of the sample S is gripped by the gripping member 131.

[0068] Next, in step S102, the gripping member 131 and the support member 132 are fastened together by the screw portions 1319 and 1323 so that the sample S gripped by the gripping member 131 is in sufficient contact with the tip surface of the protrusion 1322 of the support member 132. At this time, the irradiation area A1 of the sample S is made to protrude more than other areas of the sample S to an extent that the sample S is not damaged.

[0069] Next, in step S103, it is determined whether the reactivity of the sample S set on the sample holding member 130 is high, and if it is determined that the reactivity of the sample S is low (step S103: Yes), the process proceeds to step S104.

[0070] In step S104, the sample holding member 130 on which the sample S is set is cooled in a freezer. This cooling is continued until the support member 132 of the sample holding member 130 reaches a preset temperature (for example, about −20° C.).

[0071] Furthermore, if it is determined in step S103 that the reactivity of the sample S is high (step S103: No), the process proceeds to step S104 via step S105. In step S105, a cap 190 is attached to the sample holding member 130 under inert gas. As an example, the sample holding member 130 with the sample S set therein is placed in the sample chamber 110, and the cap 190 is attached to the sample holding member 130 by the cap attaching / detaching unit 180. Thereafter, the sample holding member 130 with the cap 190 attached is removed from the sample chamber 110, and the sample holding member 130 is cooled (step S104).

[0072] When the support member 132 is cooled to a predetermined temperature, the sample holding member 130 is taken out of the freezer and set on the movable stage 140 of the sample chamber 110. Next, in step S106, the sample chamber 110 is evacuated to a vacuum. As an example, the inside of the sample chamber 110 is evacuated to a vacuum of 1×10 －３ The sample chamber 110 is evacuated by the vacuum pumping device 150 until the pressure reaches about Pa.

[0073] When the evacuation of the sample chamber 110 is completed, if the cap 190 is not attached to the sample holding member 130 (step S108: No), processing conditions are then set (step S109). On the other hand, if the cap 190 is attached to the sample holding member 130 (step S108: Yes), the process proceeds to step S110, where the cap attaching / detaching unit 180 detaches the cap 190 from the sample holding member 130.

[0074] Specifically, after the vacuum evacuation is completed, the biaxial movable mechanism of the cap attaching / detaching unit 180 is operated to adjust the position of the cap attaching / detaching shaft 182 so that the cap attaching / detaching shaft 182 is arranged coaxially with the cap 190. Thereafter, the cap attaching / detaching shaft 182 is inserted into a hole 192 provided in the upper part of the cap 190, and the cap attaching / detaching shaft 182 is rotated to remove the cap 190.

[0075] Then, the process proceeds to step S109, where processing conditions are set. In step S109, the high-voltage power supply 160 is adjusted via the control unit 200 to set the voltage to be applied to the ion source 120. The processing time and the flow rate of Ar gas to be introduced into the ion source 120 are also set in this process. In addition, the angle of the movable stage 140, in this example, the tilt angle θ with respect to the irradiation direction (Z-axis direction) of the ion beam from the ion source 120, is set to an arbitrary angle.

[0076] After the setting of the processing conditions is completed, processing of the sample S is started (step S111). In this example, the sample S is irradiated with an ion beam, and processing of the irradiation area A1 of the sample S is executed.

[0077] A sample holder 130 that holds the sample S is connected to earth while mounted on a movable stage 140. In the ion milling apparatus 100, due to the potential difference between the ion source 120 and the sample holder 130, Ar ions generated by the ion source 120 are extracted as an ion beam and irradiated onto the sample S. The Ar ions irradiated onto the sample S eject atoms that make up the surface of the sample S due to a sputtering phenomenon, smoothing the surface.

[0078] Furthermore, when processing the sample S by the plane milling method, the support member 132 of the sample holding member 130 is cooled, and the sample S is in close contact with the protrusions 1322 of the cooled support member 132. Therefore, the temperature rise of the sample S during processing can be suppressed, and the sample S can be processed appropriately.

[0079] For example, thin-film polymeric materials such as polyimide have a low specific heat capacity and, because they are thin films, a low heat capacity. Therefore, when applying the planar milling method to a low-melting-point sample made of a thin-film polymeric material, the heat generated during ion beam irradiation can cause the sample temperature to exceed its melting point or glass transition point, potentially resulting in thermal damage to the sample, resulting in deformation or melting. However, by cooling the support member 132 of the sample holder 130 as described above and placing the sample S in close contact with the protrusions 1322 of the cooled support member 132, deformation of the sample S due to ion beam irradiation can be suppressed.

[0080] Thereafter, when processing of the sample S is completed, the process proceeds to step S113, where the sample chamber 110 is opened to the atmosphere. However, before opening the sample chamber 110 to the atmosphere, the cap 190 is attached to the sample holding member 130 as necessary.

[0081] In this example, when processing of the sample S is completed, it is determined in step S112 whether or not the cap 190 was attached to the sample holding member 130 before processing. If the reactivity of the sample S is low and the cap 190 was not attached to the sample holding member 130 (step S112: No), the cap 190 is not attached, and the sample chamber 110 is opened to the atmosphere in step S113.

[0082] On the other hand, if the reactivity of the sample S is high and the cap 190 is attached to the sample holding member 130 (step S112: Yes), the process proceeds to step S114, where the sample chamber 110 is opened to the atmosphere with the cap 190 attached to the sample holding member 130. After the sample chamber 110 is opened to the atmosphere, the sample S is removed from the sample holding member 130. This completes the series of processing steps for the sample S.

[0083] The invention made by the inventor has been specifically described above based on an embodiment, but the present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the gist of the invention.

[0084] For example, in the above embodiment, an example was described in which the tip end surface of the protrusion 1322 of the support member 132 was formed in a spherical shape, but the protrusion 1322 may also be in a flat shape.

[0085] In the above embodiment, an example has been described in which the first member 1312 and the second member 1313 constituting the gripping member 131 are screw-coupled together using the threaded portions 1314 and 1316, but the fixing structure between the first member 1312 and the second member 1313 is not limited to this. For example, the first member 1312 and the second member 1313 can be fixed together by providing a screw hole on the side surface of the second member 1313 and fitting a set screw into the screw hole.

[0086] Furthermore, although the gripping member 131 and the protrusion 1322 of the support member 132 are fixed together by fitting the threaded portions 1319 and 1323 together, the fixing structure between the gripping member 131 and the protrusion 1322 of the support member 132 is not limited to this. Similar to the fixing structure between the first member 1312 and the second member 1313, a screw hole can be provided on the side surface of the first member 1312 constituting the gripping member 131, and the gripping member 131 and the protrusion 1322 can be fixed together by a set screw that is fitted into this screw hole.

[0087] Even when such a fixing structure of the gripping member 131 and the protrusion 1322 is adopted, the sample S can be held by the sample holding member 130 so that the irradiation area A1 of the sample S protrudes more than other areas of the sample S. In addition, the protrusion amount d of the sample S can also be adjusted.

[0088] Furthermore, in the above-described embodiment, an example has been described in which the support member 132 constituting the sample holding member 130 has the protrusion 1322, and this protrusion 1322 abuts against the back surface of the sample S, causing the irradiation area A1 of the sample S to protrude from other areas of the sample S. However, the configuration of the sample holding member 130 is not limited to this, and any configuration may be used as long as it abuts against the back surface of the sample S and causes the irradiation area A1 of the sample S to protrude from other areas of the sample S.

[0089] REFERENCE SIGNS LIST 100... ion milling apparatus, 110... sample chamber, 120... ion source, 130... sample holding member, 131... gripping member, 1311... sample stage portion, 1312... first member, 1313... second member, 1314... threaded portion, 1315... recessed portion, 1316... threaded portion, 1317... opening portion, 1318... through hole, 1319... threaded portion, 132... support member, 1321... main body portion, 1322... protrusion portion, 1323... threaded portion, 1324... convex portion, 1325... threaded portion, 1326... groove portion, 1327... O-ring, 140... movable stage, 150... vacuum exhaust device, 160... high voltage power supply, 170... ion beam current detection unit, 180... cap attachment / detachment unit, 190...cap, 200...control unit (control device)

Claims

1. An ion milling apparatus comprising: a sample chamber; a sample holding member that holds a thin-film sample and can be moved in and out of the sample chamber while cooled; a movable stage on which the sample holding member is mounted; and an ion source that irradiates an ion beam toward the surface of the sample, wherein the sample holding member abuts against the back surface of the sample and holds the sample so that an irradiation area of ​​the sample that is irradiated with the ion beam protrudes beyond other areas of the sample.

2. An ion milling apparatus according to claim 1, wherein the sample holding member comprises: a gripping member that grips the periphery of the irradiation area of ​​the sample; and a support member that abuts against the back surface of the sample and supports the gripping member so that the irradiation area of ​​the sample protrudes beyond the periphery of the irradiation area.

3. An ion milling apparatus according to claim 2, wherein the support member has a main body portion fixed to the movable stage, and a protrusion portion protruding from the main body portion and having a tip surface that abuts against the back surface of the sample.

4. An ion milling apparatus according to claim 3, wherein the gripping member is supported by the support member in such a manner that the amount of protrusion of the irradiation region can be adjusted.

5. An ion milling apparatus according to claim 4, wherein the gripping member is screwed to the outer periphery of the protrusion.

6. An ion milling apparatus according to claim 3, wherein the tip surface of the protrusion is formed in a spherical shape.

7. An ion milling apparatus according to claim 1, wherein the sample holder is mounted on the movable stage via a heat insulating member.

8. An ion milling apparatus according to claim 7, wherein the heat insulating member has a lower thermal conductivity than the sample holding member.

9. A sample holding member used in an ion milling device that processes a thin-film sample by irradiating the surface of the sample with an ion beam in a sample chamber, which holds the sample and can be taken in and out of the sample chamber in a cooled state, and which holds the sample so that the irradiated area of ​​the sample that is irradiated with the ion beam abuts against the back surface of the sample protrudes more than other areas of the sample.

10. An ion milling method for processing a thin-film sample by holding the sample with a cooled sample holding member and irradiating the surface of the sample with an ion beam from an ion source, the method comprising the steps of abutting the sample holding member against the back surface of the sample and irradiating the sample with the ion beam while the irradiation area of ​​the sample irradiated with the ion beam protrudes beyond other areas of the sample.

11. An ion milling method according to claim 10, comprising, before the step of irradiating the sample with the ion beam, the steps of holding the sample using the sample holding member and cooling the sample holding member in a freezer while the sample holding member is equipped with a cap that prevents the sample from coming into contact with the atmosphere, and placing the cooled sample holding member in a sample chamber and removing the cap from the sample holding member while the sample chamber is evacuated.

12. An ion milling method according to claim 11, wherein the cap is attached to the sample holding member while the sample holding member is placed in the sample chamber and the sample chamber is evacuated to a vacuum.

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