Ion milling device

Abstract

An ion milling device capable of increasing the reproducibility of ion distribution is provided. The apparatus has an ion source (101), a sample stage (102) on which a sample processed by irradiating a non-focused ion beam from the ion source (101) is placed, and a measuring member holding member (106) that holds an ion beam current measuring member (105). A covering material (120) is installed to cover at least the surface of the measuring member holding member (106) and the sample stage (102) facing the ion source (101). The material of the covering material (120) is composed mainly of an element having an atomic number smaller than that of the material of the structure on which the covering material is installed. In a state where an ion beam is output from the ion source (101) under a first irradiation condition, the ion beam current measuring member (105) is moved in the irradiation range of the ion beam, and the ion beam current flowing as the ion beam is irradiated onto the ion beam current measuring member (105) is measured.

Description

Technology Field

[0001] The present invention relates to an ion milling device. Background Technology

[0002] Patent Document 1 discloses an ion milling apparatus that generates plasma in an ion source to extract ions and irradiates the extracted ions to perform processing on a substrate, etc. This ion milling apparatus performs processing on, for example, a 4-inch (Φ100) substrate, and discloses controlling the distribution of the extracted ion beam by electrically controlling the plasma distribution within the ion source in order to obtain a large-diameter ion beam of uniform or desired distribution. As an example of a control method, it discloses measuring the distribution state of the ion beam using a Faraday cup and adjusting the voltage applied to the plasma control electrode based on the measurement result. Prior art literature

[0003] Japanese Publication No. 2002-216653 The problem to be solved

[0004] An ion milling device is a device for polishing the surface or cross-section of a sample (e.g., metal, semiconductor, glass, ceramic, etc.) by irradiating it with an unfocused ion beam and stresslessly ejecting atoms from the sample surface through the sputtering phenomenon. Some ion milling devices are used as pretreatment devices for observing the surface or cross-section of a sample using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Ion sources for such pretreatment devices often employ a penning method that is effective for miniaturizing the structure.

[0005] Since the ion beam from a Penning-type ion source is irradiated onto the sample without convergence, the ion distribution near the ion beam irradiation point of the sample exhibits the characteristic that the ion density is highest at the center and decreases from the center outward. Meanwhile, particularly in surface observation using an electron microscope, it is necessary to polish the sample surface smoothly in order to accurately observe the structure and composition. For this reason, the ion beam is irradiated at a low incidence angle while rotating the sample. This makes it possible to obtain a smooth processed surface over a wide area, including the surrounding region of the area being observed. Since ion density is directly related to the processing speed (milling rate) of the sample, the characteristics of the ion distribution significantly affect the shape of the processed surface of the sample.

[0006] It is known that ion sources employing the Penning method cause wear on internal components due to the ions generated and ejected from their structure. Furthermore, as a result of processing a sample, suspended microparticles generated from the processed surface adhere to the ion source, particularly the ion beam emission port, becoming a source of contamination. Due to these factors, continued use of the ion milling device alters the characteristics of the ion beam and, consequently, reduces the reproducibility of the processed shape of the sample's surface. When observation using an electron microscope is performed for mass production process control purposes, it is required to perform the same processing on a large number of samples; therefore, a decrease in the reproducibility of the processed shape of the ion milling device risks leading to a reduction in defect detection precision.

[0007] In light of these problems, the present invention provides an ion milling apparatus capable of adjusting the irradiation conditions of an ion beam suitable for an ion milling apparatus that performs pretreatment processing for observation of the surface or cross-section of a sample. means of solving the problem

[0008] An ion milling device of one embodiment of the present invention comprises an ion source, a sample stage on which a sample to be processed by irradiating an unfocused ion beam from the ion source is placed, a measuring member holding member that holds a linear ion beam current measuring member extending in a first direction, and a control unit, wherein a covering material is installed to cover at least the surface of the measuring member holding member and the sample stage facing the ion source, and the material of the covering material has a main component of an element having an atomic number smaller than that of the material of the structure on which the covering material is installed, and the control unit is located between the ion source and the sample stage and moves the ion beam current measuring member in the irradiation range of the ion beam while the ion beam is output from the ion source under a first irradiation condition along an orbit extending in a second direction orthogonal to the first direction, and measures the ion beam current flowing in the ion beam current measuring member by irradiating the ion beam to the ion beam current measuring member. Effects of the invention

[0009] The reproducibility of the ion distribution in the ion milling device can be improved.

[0010] Other problems and novel features will become apparent from the description in this specification and the accompanying drawings. Brief explanation of the drawing

[0011] FIG. 1 is an example of the configuration of an ion milling device (schematic diagram). FIG. 2 is a diagram showing the configuration of an ion source and a power circuit. FIG. 3 is an example of the configuration of a driving unit. FIG. 4 is a diagram showing the measurement of the ion beam current in a comparative example. FIG. 5 is a diagram showing an ion beam profile measured by a comparative example. FIG. 6a is a diagram showing the measurement of the ion beam current in an embodiment. FIG. 6b is a diagram showing the positional relationship between the trajectory of the ion beam current measuring member and the electron trap in an embodiment. FIG. 7a is a diagram showing the measurement of the ion beam current in a modified example. FIG. 7b is a diagram showing the positional relationship between the trajectory of the ion beam current measuring member and the electron trap in a modified example. Figure 8 is a flowchart for adjusting ion beam irradiation conditions. Specific details for implementing the invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0013] FIG. 1 is a schematic diagram showing the main parts of an ion milling device (100) of an embodiment of the present invention from the top (with the vertical direction being the Y direction). In a sample chamber (108) capable of maintaining a vacuum state, an ion source (101) attached via an ion source position adjustment mechanism (104), a sample stage (102) for installing a sample to be processed, and a sample stage rotation drive source (103) for rotating the sample stage (102) with the rotation center R0 as the axis are installed. Since the ion beam from the ion source (101) is irradiated onto the sample without being focused, the ion beam distribution near the ion beam irradiation point of the sample has the characteristic that the ion density is highest at the center and decreases from the center toward the outside. Since ion density is directly related to the processing speed of the sample, the ion beam distribution near the ion beam irradiation point greatly affects the processing shape of the sample. For this reason, in order to measure the ion beam distribution of a non-focused ion beam from an ion source (101), the ion milling device (100) is equipped with an ion beam current measuring member (105) positioned in close proximity to the sample placement surface of a sample stage (102), a measuring member holding member (106) holding the ion beam current measuring member (105), a driving unit (107) that reciprocates the measuring member holding member (106) in the X direction, and an electron trap (112). Each mechanism constituting the ion milling device (100) is supplied with power from a power unit (110) and is controlled by a control unit (109). In addition, the control parameters or operating status of the device are displayed on a display unit (111).

[0014] Since the ion beam from the ion source (101) is emitted in a radially expanded state centered on the ion beam center B0, it is necessary to adjust the rotation center R0 of the sample stage (102) so that the ion beam center B0 coincides with it. To facilitate this adjustment, the ion source (101) is attached to the sample chamber (108) via an ion source position adjustment mechanism (104) that adjusts its position in the X direction, Y direction, and Z direction. By this, the position of the ion beam center B0 of the ion source (101), specifically the position on the XY plane (a plane including the X direction and Y direction) and the working distance (WD: Working Distance, position in the Z direction) can be adjusted.

[0015] Although details will be described later, the ion beam current measuring member (105) is a conductive member, and the amount of ions colliding with the ion beam current measuring member (105) from the ion source (101) is measured by an ammeter (113) as the ion beam current between the ion source (101) and the ion beam current measuring member (105). The control unit (109) obtains the ion beam current at each position along the X direction by measuring the ion beam current by the ammeter (113) while moving the ion beam current measuring member (105) in the X direction, and displays it on the display unit (111) as an ion beam profile. Additionally, during the measurement of the ion beam profile, the electron trap (112) is positioned on the sample stage (102) side rather than the ion beam current measuring member (105), and also at a position where the ion beam current measuring member (105) and the electron trap (112) overlap when viewed from the ion source (101) at the intersection of the ion beam center B0 and the ion beam current measuring member (105). A predetermined positive potential is applied to the electron trap (112) from the power unit (110).

[0016] Additionally, a coating material (120) is installed on the structure placed within the sample chamber (108), specifically the measuring member holding part (106), the driving unit (107), the sample stage (102), the sample stage rotation driving source (103), and the inner wall of the sample chamber (108). As an example of the coating material (120), a light element such as carbon can be used. Carbon paste may be applied to the irradiation area of ​​the ion beam, or a carbon plate may be attached. In addition, a resin with high heat resistance may be applied. This is because organic materials contain carbon (C). Since the coating material (120) is heated when irradiated with an ion beam, heat resistance is required for the coating material. For example, polytetrafluoroethylene (PTFE) or aromatic polyetherketone (e.g., polyetheretherketone, PEK) may be applied. In addition, carbon particles may be mixed with the resin and applied. The function of the coating material will be described later.

[0017] FIG. 2 is a schematic diagram showing the internal structure of an ion source (101) and the power circuit of a power unit (110) that applies voltage to the ion source (101). Also, the power circuit shows only the circuit related to the ion source (101). FIG. 2 shows an ion source (Penning-type ion source) that employs the Penning method as the ion source (101). Inside the Penning-type ion source, an anode (203) to which a discharge voltage is applied from the power unit (110) is disposed between a first cathode (201) and a second cathode (202) that are at the same potential, and electrons are generated by the potential difference between the anode and the cathode. The generated electrons remain inside the ion source by a permanent magnet (204). Meanwhile, argon gas is introduced into the ion source from the outside through a pipe (206), and argon ions are generated by the collision of electrons and argon gas. Argon ions are attracted to an acceleration electrode (205) to which an acceleration voltage is applied, and are irradiated as an ion beam through an ion beam irradiation port (207).

[0018] During repeated beam irradiation of the ion source (101), the internal parts of the ion source (101) may wear out, or microparticles generated from the workpiece being irradiated may scatter and adhere to the ion beam irradiation port (207), causing the ion beam distribution irradiated by the ion source (101) to fluctuate. By performing maintenance such as replacing or cleaning the internal parts of the ion source (101), the wear of the internal parts and the adhesion of microparticles to the ion beam irradiation port (207) can be resolved, but it is not guaranteed that the ion beam distribution will return to the state before the fluctuation. Therefore, for example, after performing maintenance, the ion beam distribution is checked, and the operating distance, discharge voltage, and gas flow rate of the ion source (101) are adjusted so that the desired ion beam distribution is obtained. By doing this, the reproducibility of the processing by the ion milling device can be increased.

[0019] FIG. 3 shows an example of the configuration of a driving unit (107) that drives an ion beam current measuring member (105). In the drawing, a top view of the driving unit (107) and a cross-sectional view of the ion beam current measuring member (105) and the measuring member holding part (106) along line AA of the top view are shown. Also, the coating material is omitted from the drawing.

[0020] The measuring member holding member (106) is made of an insulating material, and a conductive ion beam current extraction member (310) is installed therein. The ion beam current measuring member (105) is attached to the ion beam current extraction member (310) and is connected to the ion beam current extraction wiring (311) through the ion beam current extraction member (310). The ion beam current extraction wiring (311) is connected to an ammeter (113).

[0021] The drive unit (107) has a motor (301), a bevel gear (302), a gear (303), and a rail member (304). The bevel gear (302) and the gear (303), installed on the drive shaft of the motor (301), rotate to transmit drive to the rail member (304), thereby reciprocating the measurement member holding part (106) in the X direction. The track that reciprocates the measurement member holding part (106) is located between the ion source (101) and the sample stage (102). It is preferable to position it as close as possible to the sample stage (102). Additionally, the motor (301) does not need to be installed exclusively for the drive unit (107), and it is also possible to use it in combination with the sample stage rotation drive source (103) that rotates the sample stage (102).

[0022] The ion beam current measuring member (105) is in a state of being processed by irradiating an ion beam from an ion source (101) during the measurement of the ion beam current. Since the member is consumed with each measurement, a member with a low sputter yield that is difficult to process by ions is suitable. Additionally, by using a linear material as the ion beam current measuring member (105), the ion beam profile is measured by moving the ion beam current measuring member (105) over the non-focused ion beam irradiation range. This means that the diameter of the ion beam current measuring member (105) determines the spatial resolution of the measurable ion distribution. For this reason, it is preferable that the diameter of the ion beam current measuring member (105) be smaller than the half-width of the ion beam during processing. For example, a linear material of graphite carbon having a diameter of 0.2 mm or more and 0.5 mm or less can be used. In addition, to suppress the irregular behavior of ions caused by ions colliding with the ion beam current measuring member (105), it is preferable that the cross-sectional shape of the ion beam current measuring member (105) be circular. In addition to the graphite carbon wire material, the tungsten wire material can also be used. The ion beam current measuring member (105) is detachable from the measuring member holding member (106), and if the ion beam current measuring member (105) is consumed by the ion beam, it is replaced with a new ion beam current measuring member.

[0023] FIG. 4 is a schematic diagram showing the measurement of an ion beam current without installing an electron trap (112) and a coating material (120) as a comparative example. In this measurement method, the current flowing as a result of positively charged argon ions irradiated from an ion source (101) colliding with an ion beam current measuring member (105) is measured by an ammeter (113). However, in the configuration of this comparative example, it was confirmed that a current value is measured by the ammeter (113) even though the ion beam current measuring member (105) was moved to a position where the ion beam is not irradiated (first task). This is because secondary electrons or backscattered electrons are generated as argon ions collide with structures near the ion beam current measuring member (105), specifically the measuring member holding part (106), and the generated secondary electrons or backscattered electrons collide with the acceleration electrode (205) of the ion source (101), thereby increasing the current value measured by the ammeter (113).

[0024] FIG. 5 shows an ion beam profile measured by the comparative example of FIG. 4. The horizontal axis represents the beam measurement position, and the vertical axis represents the ion beam current I measured by the ammeter (113). In addition, the beam measurement position is indicated as the origin point at the intersection of the trajectory of the ion beam current measuring member (105) on the XZ plane and the ion beam center B0. As described above, the measured ion beam profile (500) is the sum of the actual ion beam profile (501) flowing as argon ions collide with the ion beam current measuring member (105) and the background noise profile (502) caused by electrons generated by the irradiation of the ion beam. In addition, FIG. 5 shows the background noise profile (502) simplified as a constant value, but in reality, it takes a value that varies depending on the measurement position due to the non-uniformity of generation of secondary electrons or backscattered electrons and the difference in the amount of electron collisions with the ion beam current measuring member (105) depending on the beam measurement position.

[0025] The actual ion beam profile (501) is thought to follow a Gaussian distribution. Therefore, the measured ion beam current I(x) can be expressed by (Equation 1).

[0026] [Equation 1]

[0027]

[0028] Here, A is the maximum value of the actual ion beam profile, and σ is the variance of the actual ion beam profile. That is, in order to obtain information of the actual ion beam profile (501), it is necessary to remove the influence of the background noise profile (502) from the measured ion beam profile (500).

[0029] In addition, FIG. 5 shows a magnified waveform (504) of a portion (503) of the measured ion beam profile (500). In reality, the measured ion beam profile (500) contains high-frequency noise waveforms. Although it is possible to obtain a smooth profile waveform (waveform (505)) by averaging the data of the measured ion beam current values, if the noise component is large, the amount of data required to smooth the ion beam profile increases. Because of this, the movement speed of the ion beam current measuring member (105) cannot be increased, and thus the measurement time of the ion beam profile (500) cannot be shortened (second problem). This is because, since the ion beam is irradiated from the ion source (101) in a non-focused manner, the argon ions scatter over a wide area of ​​the sample chamber (108). Although the ion beam intensity is low, argon ions collide over a wide range of the inner wall of the sample chamber (108) or the structure within the sample chamber (108), generating secondary electrons or backscattered electrons, which then collide with the acceleration electrode (205) of the ion source (101) (see FIG. 4). These secondary electrons or backscattered electrons are measured as noise in the ion beam profile waveform.

[0030] FIG. 6a shows the installation of a plate-shaped electron trap (112) and a coating material (120) to measure the ion beam current. FIG. 6b also shows the positional relationship between the orbit of the ion beam current measuring member (105) (coordinates X0 to X5 indicate positions on the orbit) and the electron trap (112). Additionally, the intensity of the ion beam near the orbit of the ion beam current measuring member (105) is schematically shown by the shading. The ion beam intensity has the maximum intensity at the center of the ion beam B0 and decreases according to a Gaussian distribution as it moves toward the surrounding area. The region with high ion beam intensity is indicated as a high-concentration region, and the region with low beam intensity is indicated as a low-concentration region.

[0031] Since secondary electrons or backscattered electrons generated by collisions with argon ions have a negative charge, an electron trap (112) to which a positive voltage is applied is installed near the orbit of the ion beam current measuring member (105) to capture the generated secondary electrons or backscattered electrons. The voltage applied to the electron trap (112) is supplied from the power unit (110), and the voltage value is set by a control unit (109) not shown. The positive voltage applied to the electron trap (112) is set to a positive voltage that does not affect the measurement of the ion beam profile.

[0032] The electron trap (112) is positioned on the sample stage (102) side rather than the orbit of the ion beam current measuring member (105), so that when the ion beam center B0 and the ion beam current measuring member (105) intersect, the ion beam current measuring member (105) and the electron trap (112) overlap when viewed from the ion source (101). As shown in FIG. 6b, the ion beam intensity of the ion source (101) is highest near the ion beam center B0, and the amount and energy of secondary electrons or backscattered electrons generated are also high. Therefore, by positioning the electron trap (112) near the ion beam center B0, secondary electrons or backscattered electrons generated can be efficiently captured.

[0033] However, when the electron trap (112) is placed as in FIG. 6a, there is a concern that the electron trap (112) itself may become a source of secondary electrons or backscattered electrons due to collisions with argon ions. In particular, since backscattered electrons have high energy and high linearity, a large amount of electrons reach the acceleration electrode (205). Here, since it is known that the amount of backscattered electrons increases with increasing atomic number of the constituent element of the irradiation target, it is desirable to use a light element and a low sputter yield material for the electron trap (112). Specifically, it is desirable to use graphite carbon.

[0034] In this way, by removing the influence of secondary electrons or backscattered electrons generated from structures such as the measuring member holding part (106) by the electron trap (112), information of the actual ion beam profile (501) as indicated by the dashed line in FIG. 5 can be obtained. The electron trap (112) needs to have a certain area to efficiently capture secondary electrons or backscattered electrons, but its size is not limited. For example, it can be a plate electrode with a circular shape centered on the ion beam center B0, with the diameter being half the width of the ion beam, or a square shape centered on one side. Also, since it only needs to be able to trap electrons, it is not limited to a plate electrode, and a mesh electrode or other electrodes are allowed.

[0035] In addition, the amount of electrons generated by irradiating a relatively weak intensity ion beam through the covering material (120) is reduced, thereby reducing noise in the ion beam profile waveform. This is due to the following reason. As described above, the amount of backscattered electrons generated increases with increasing atomic number of the constituent elements of the irradiated target. By using a material as the covering material (120) in which the main component is an element with an atomic number smaller than that of the material of the covering structure or inner wall, the generation of backscattered electrons can be effectively suppressed.

[0036] The covering material (120) does not necessarily have to cover the entire front surface of the structure or the entire wall surface of the sample room (108), but it is preferable to cover at least the surface facing the ion source (101). This is because the ion beam has strong straightness, so the amount of secondary electrons and backscattered electrons generated per unit area from the surface facing the ion source (101) is greater than from other surfaces.

[0037] Figures 7a and 7b show variations of the electron trap. In Figure 6a, the electron trap is positioned behind the ion beam current measuring member (105) when viewed from the ion source (101), whereas in Figure 7a, the electron trap is positioned closer to the ion source (101) than to the ion beam current measuring member (105). Figure 7a shows a side view, and Figure 7b shows a top view. The voltage applied to the electron trap (700) is also supplied from the power unit (110), and the voltage value is set by a control unit (109) not shown. The electron trap (700) is positioned in an area where the ion beam from the ion source (101) is not irradiated, and captures the generated secondary electrons or backscattered electrons before they reach the acceleration electrode (205). Unlike the electron trap (112) shown in Figures 6a and 6b, since the ion beam is not irradiated, a highly conductive material such as copper or phosphor bronze can be used as the electron trap (700). In this example, a coating material (120) is also installed on the surface of the electron trap (700) (in FIG. 7b, the coating material (120) is omitted). Both the electron trap (112) and the electron trap (700) may be provided.

[0038] In the ion milling apparatus shown in FIG. 1, the method for acquiring an ion beam profile and adjusting ion beam irradiation conditions performed by the control unit (109) is explained using the flowchart of FIG. 8.

[0039] S801: The control unit (109) controls the driving unit (107) to move the ion beam current measuring member (105) to the origin position. Here, the origin position is set to be the center of the ion beam irradiation range, but the setting of the origin position is not limited to this.

[0040] S802: The control unit (109) controls the power unit (110) to output an ion beam from the ion source (101) according to the ion beam irradiation conditions maintained as the current settings. The current settings refer to the ion beam irradiation conditions determined as the processing conditions for the sample. Generally, the acceleration voltage, discharge voltage, and gas flow rate of the ion source (101) are determined when processing the sample.

[0041] S803: The control unit (109) controls the power unit (110) to apply a predetermined voltage to the electron trap (112) (and / or electron trap (700)). The positive voltage applied to the electron trap is set to a voltage range that does not adversely affect the measurement of the ion beam profile.

[0042] S804: After the ion beam output begins, the control unit (109) controls the driving unit (107) to move the ion beam current measuring member (105) back and forth in the X direction, and measures the ion beam current using an ammeter (113). The control unit (109) obtains an ion beam profile by matching the position of the ion beam current measuring member (105) in the X direction with the current value at that position. The obtained ion beam profile is displayed on the display unit (111).

[0043] S805: Read and input the ion beam profile to be adjusted and display it on the display unit (111). Also, this step may be performed before acquiring the ion beam profile (S804).

[0044] S806: The ion beam irradiation conditions are adjusted so that the ion beam profile acquired in S804 approximates the target ion beam profile read and input in S805. Specifically, one or more parameters among the operating distance of the ion source (101), discharge voltage, and gas flow rate are adjusted.

[0045] At this time, the acceleration voltage is not subject to adjustment. This is because if the acceleration voltage is changed, the processing speed (milling rate) of the sample changes drastically even with the same ion beam current.

[0046] S807: Acquire the ion beam profile again according to the adjusted ion beam irradiation conditions. The processing in S807 is the same as the processing in S804.

[0047] S808: Compare the ion beam profile acquired in S807 with the target ion beam profile read and input in S805. If the desired ion beam profile is acquired, terminate; otherwise, repeat the step from the adjustment of ion beam irradiation conditions (S806).

[0048] Although the invention made by the inventors has been specifically described above based on embodiments, the present invention is not limited to the described embodiments and various modifications are possible within the scope of not departing from the gist thereof. For example, a structure located near the ion beam current measuring member (105) that does not operate during ion beam profile measurement, such as a sample stage, may be made to function as an electron trap by enabling the application of a positive potential. In addition, if the ion milling device is equipped with a sample stage position adjustment mechanism capable of moving the sample stage in the Z direction, the operating distance may be adjusted by the sample stage position adjustment mechanism. Furthermore, the material or method of the coating material may be different depending on the object to be coated. The range covered by the coating material is also not limited to the range described in the examples. For example, instead of covering all structures of the sample chamber (108), the measuring member holding part or the sample stage to which the ion beam is irradiated may be covered, and the coating material may not be installed on structures arranged in a way that makes it difficult for the ion beam to be irradiated by these structures. Additionally, although an example is shown in which a covering material is installed on the entire inner wall of the sample chamber (108) facing the ion source (101), the covering material may be installed only in the area where the ion beam intensity is relatively strong, centered on the intersection point between the ion beam center B0 and the inner wall.

[0049] In addition, regarding the adjustment of ion beam irradiation conditions, adjustment may be made based on the ion beam profile itself, or the characteristic quantity of the ion beam profile, such as the peak value and half-value width of the ion beam profile, may be calculated and the ion beam irradiation conditions may be adjusted so that the characteristic quantity matches. At this time, the display unit (111) may display the characteristic quantity used as the adjustment standard rather than the ion beam profile itself. Explanation of the symbols

[0050] 100 : Ion milling device 101 : Ion source 102: Sample stage 103: Sample stage rotation drive source 104: Ion source position adjustment mechanism 105: Ion beam current measuring element 106: Measuring member holding part 107: Driving unit 108 : Sample room 109 : Control unit 110: Power unit 111: Display unit 112: Electron trap 113: Ammeter 120 : Coating material 201 : First cathode 202: Second cathode 203: Anode 204: Permanent magnet 205: Acceleration electrode 206 : Piping 207 : Ion beam irradiation port 301: Motor 302: Bevel gear 303: Gear 304: Rail member 310: Ion beam current extraction unit 311: Ion beam current extraction wiring 700: Electron trap

Claims

Claim 1 The apparatus comprises an ion source, a sample stage on which a sample processed by irradiating a non-focused ion beam from the ion source is placed, a measuring member holding member that holds a linear ion beam current measuring member extending in a first direction, wherein the measuring member holding member is positioned between the ion source and the sample stage and is movable along a trajectory extending in a second direction orthogonal to the first direction, an electrode disposed near the trajectory, and a control unit, wherein a covering material is installed to cover at least the surface of the measuring member holding member and the sample stage facing the ion source, and the material of the covering material is composed mainly of an element having an atomic number smaller than that of the material of the structure on which the covering material is installed, and the control unit moves the ion beam current measuring member within the irradiation range of the ion beam when the ion beam is output from the ion source under a first irradiation condition, and measures the ion beam current flowing in the ion beam current measuring member as the ion beam is irradiated onto the ion beam current measuring member, and the electrode is the measuring member An ion milling device that removes secondary electrons generated from a retaining part. Claim 2 An ion milling device according to claim 1, wherein the control unit measures the ion beam current while applying a predetermined positive voltage to the electrode. Claim 3 An ion milling device according to claim 1, wherein the electrode is positioned on the sample stage side rather than the orbit, and also positioned at a location where the ion beam current measuring member and the electrode overlap when the ion beam center of the ion beam from the ion source intersects the ion beam current measuring member, as viewed from the ion source. Claim 4 An ion milling device according to claim 1, wherein the electrode is positioned on the ion source side rather than the orbit and is also positioned at a location where an ion beam from the ion source is not irradiated.

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