Converged ion beam processing device

Abstract

A converged ion beam processing device (100) is provided for improving the cross-sectional shape and enhancing the working efficiency when cross-sectional processing is performed using a converged ion beam. The converged ion beam processing device (100) comprises an ion source (21), a sample stage (50) for holding a sample (200), a convergent lens (22), an aperture (24) having a slit (24s) with one side (24t) being linear, and a projection lens (28) disposed on a beam path between the aperture and the sample stage. When a cross-sectional shape is processed in the sample, when the converged ion beam (20A) is focused on the principal plane of the projection lens by Koehler illumination, the applied voltage of the convergent lens is set to be less than the prescribed voltage and not less than 80% of the prescribed voltage, and the position of the aperture is set so that the aperture blocks the converged ion beam in a state where the distance between the one side of the aperture and the center of the converged ion beam is greater than 0 μm and not more than 500 μm, thereby forming a transfer mode in which the shape of the slit is transferred to the sample.

Description

Technical Field

[0001] The present invention relates to a converged ion beam processing device for processing a cross section of a sample. Background Art

[0002] Conventionally, a sample is cross-sectioned using a focused ion beam processing device, and the cross section is observed.

[0003] like Figure 12 First, the sample 200 is irradiated with a converged ion beam 20A perpendicularly to the surface 200a of the sample 200. Then, the irradiation position of the converged ion beam 20A is scanned to excavate a cross section 200c perpendicular to the surface 200a of the sample 200 (parallel to the irradiation direction of the converged ion beam 20A).

[0004] However, the electron beam 10A and the converged ion beam 20A of the SEM column used to observe cross-section 200c after cross-section processing are at an angle. Therefore, the area separated from cross-section 200c does not need to be excavated as deeply as the area near the cross-section. Therefore, to shorten etching time and improve work efficiency, the cross-section 200c is processed into an inclined (inclined) surface that rises from the bottom surface of the cross-section 200c toward the surface 200a at a predetermined angle θ (e.g., 54 degrees). In conventional technology, considering processing time, the cross-section size is limited to tens of micrometers, with a maximum of less than 100 micrometers.

[0005] Furthermore, in recent years, there has been a desire to process samples such as semiconductor devices and minerals with cross sections of 100 μm or more. To shorten etching time, it is necessary to irradiate a converged ion beam with as high a current as possible.

[0006] Therefore, instead of a Ga metal ion beam, Xe ions are extracted from the plasma as a converged ion beam, thereby irradiating the sample with a beam with a current larger than that of the Ga ion beam.

[0007] The sample is then irradiated with this high-current converged ion beam in convergence mode for processing. Specifically, in convergence mode, a roughly parallel trajectory is formed between the converging lens and the objective lens, preventing the beams from crossing. A circular aperture located between the converging lens and the objective lens is used to adjust the angular spread of the beams, creating an optimal beam shape. The beam deflector then scans the resulting beam, allowing the production of a cross-section at the desired location.

[0008] However, in the aforementioned converging mode, high current increases the beam diameter, leading to problems such as rounded corners near the top surface of the sample cross-section and residual processing streaks and steps in samples containing materials with varying sputtering efficiencies, such as devices. Furthermore, if finishing is performed with a low-current beam to reduce these rounded corners and processing streaks, the total processing time required increases, reducing operational efficiency. In particular, when the cross-section depth (length) required for a high-current beam is large, finishing with a low-current beam requires even longer time.

[0009] On the other hand, there is a transfer mode in which an aperture having a slit in a shape other than a circular hole, such as a rectangular hole, is placed in the beam path between the converging lens and the objective lens of the FIB column. This slit blocks a portion of the converging ion beam, thereby irradiating a beam shaped into the slit shape. In the case of the transfer mode, the objective lens is referred to as the projection lens.

[0010] In the transfer mode, a converged ion beam blocked by an aperture is used. Therefore, compared with the convergence mode, it has a feature that a processed cross section can be sharpened.

[0011] As a technology using the transfer mode, a technology has been developed in which a cross-section of a sample is processed using a beam formed into a slit shape by an aperture (Patent Document 1).

[0012] In the technology of Patent Document 1, Figure 13 A cross-sectional sample having a slope of 200s is prepared as shown. That is, an aperture 500 having a narrow strip-shaped slit 500s is used to irradiate the position farthest from the side of the cross-section 200c with the converged ion beam 20A having passed through the slit 500s, and a shallow hole of depth D1 is etched. Next, the irradiation area of ​​the ion beam is sequentially moved toward the side of the cross-section 200c and the etching time is extended to perform etching with a deeper depth. In this way, the hole processing is performed in a gradually deepening manner, and finally the etching processing of the deepest depth D2 for forming the cross-section 200c is performed to obtain Figure 13 The cross section of the final form.

[0013] Furthermore, in the transfer mode, the beam reaching the sample surface is minimally deformed on the optical axis, and image resolution deteriorates as the distance from the optical axis increases.

[0014] Therefore, a technique has been developed in which one side of a baffle forming a sample is aligned with the optical axis of the ion beam (Patent Document 2).

[0015] This allows the cross section of the sample to be processed sharply.

[0016] In addition, a technology has been developed in which, unlike the transfer mode, no projection lens is used, but a beam spot obtained by shaping the aperture of a mask is used for cross-sectional processing of a sample (Patent Document 3).

[0017] Patent Document 1: Japanese Patent No. 5247761 ( Figure 1 、 Figure 9 , paragraph 0025)

[0018] Patent Document 2: Japanese Patent No. 3531323

[0019] Patent Document 3: Japanese Patent No. 5048919

[0020] However, when the transfer mode is used, a portion of the ion beam is blocked by the aperture 500 and is not used for etching, so there is generally a problem that the working efficiency is low.

[0021] Furthermore, in the case of the technology of Patent Document 1, as Figure 13 As shown, using the stripe-shaped ion beam blocked by the aperture 500 requires performing multiple etching operations with successively varying etching times, which also reduces the operating efficiency.

[0022] Furthermore, in the case of the technology of Patent Document 2, the current distribution of the shaped beam obtained by shielding in the transfer mode is uniform ( Figure 6 The shadow R1) will be etched in a rectangular shape with a uniform depth on the surface of the sample. Figure 12 As shown, the required cross section is in the shape of a slope 200s connected to the cross section 200c. Unnecessarily digging deeper than the slope 200s will result in reduced work efficiency.

[0023] Furthermore, sputtered products from unnecessary etched portions adhere to the cross section, increasing the amount of finishing required to obtain a sharp cross section, thereby also reducing work efficiency.

[0024] Furthermore, in the case of the technology of Patent Document 3, no projection lens is used between the baffle and the sample to project the shape of the baffle opening toward the sample. Therefore, the beam shape is at most a few μm, which is small, and it is impossible to generate a shaped beam of a size that can be uniformly processed for cross-sections. Summary of the Invention

[0025] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a focused ion beam processing apparatus that improves the cross-sectional shape and enhances the working efficiency when performing cross-sectional processing using a focused ion beam.

[0026] In order to achieve the above-mentioned purpose, the converged ion beam processing device of the present invention comprises: an ion source; a sample carrier, which holds the sample; a converging lens, which converges ions emitted from the ion source into a converged ion beam; an aperture, which blocks a part of the converged ion beam converged by the converging lens, and has a slit with at least one side being a straight line for processing the sample into a desired shape; and a projection lens, which is arranged in the beam path between the aperture and the sample carrier, so that the converged ion beam passing through the aperture is focused on a specified position of the sample with the aperture as a light source, and a cross section parallel to the irradiation direction of the converged ion beam is processed in the sample, characterized in that the converged ion beam is focused on the main plane of the projection lens by the Koehler illumination method. When the applied voltage of the converging lens is a specified voltage, the applied voltage of the converging lens is set to be less than the specified voltage and more than 80% of the specified voltage, and the position of the aperture is set so that the aperture blocks the converging ion beam in the following state, that is, the distance between one side of the aperture and the center of the converging ion beam is greater than 0 μm and less than 500 μm, and the applied voltage of the projection lens is set to an applied voltage that focuses the image of the slit based on the aperture on the surface of the sample, forming the following transfer mode: the converging ion beam is not scanned, and the converging ion beam formed into the shape of the slit is irradiated onto the sample surface at one time, and the shape of the slit is transferred to the sample.

[0027] In this converged ion beam machining apparatus, the absolute value of the voltage applied to the converging lens is reduced, so the probe current is concentrated near the center of the sample. Consequently, the sample is etched using a probe current with a current density distribution that peaks at the center of the converged ion beam and gradually decreases as it moves away from the center. Consequently, the deepest shape is excavated in the center where the current density is high.

[0028] On the other hand, the sample cross section required is a roughly V-shaped cross section with a slope connected to the cross section and cut out vertically from the sample surface. Therefore, as long as the probe current utilizing the above-mentioned current density distribution is etched to the sample, the sample will be etched with a roughly V-shaped profile similar to that formed by the cross section and the slope connected to the cross section. Therefore, in cross-section processing, ion beams can be utilized without waste in etching. Furthermore, as long as the peak value of the probe current is aligned with the part of the cross section that needs to be etched most deeply, even if additional etching is not performed, the cross section can be etched more deeply. Thus, operating efficiency is improved.

[0029] Furthermore, although sputtered products generated by etching adhere to the cross section to be observed, since etching of unnecessary areas can be reduced, adhesion of sputtered products to the cross section can be reduced, and work efficiency can be further improved.

[0030] Furthermore, an aperture having a slit with at least one linear side is used, and the slit is arranged so that the side is slightly offset from the center of the converged ion beam.

[0031] Thus, approximately half of the probe current distribution with the center as the boundary is blocked, and only approximately half on the opposite side with the center as the boundary acts as the probe current.

[0032] As a result, as described above, the probe current distribution approximates the outline of the substantially V-shaped cross section, and therefore, the ion beam can be used without waste during etching.

[0033] In addition, since the probe current passing through the aperture etches the contour of the roughly V-shaped cross section, the cross-sectional shape of the sample can be produced at one time using the aperture without scanning the converged ion beam, further improving the working efficiency.

[0034] Furthermore, since the cross section is etched by shielding the ion beam with one linear side of the aperture slit, rounded corners (steps) are less likely to be generated in the cross section, and the cross-sectional shape can be improved.

[0035] In the converged ion beam processing apparatus of the present invention, the beam size of the converged ion beam may be adjusted by adjusting a voltage applied to the projection lens.

[0036] In transfer mode, the shape of the converged ion beam reflects the shape of the slit, and the projection magnification of the transferred slit shape is uniquely determined by the aperture, projection lens, and sample geometry. Therefore, when changing the length of the cross-section during sample cross-section processing, the aperture shape must be changed. However, if, for example, a cross-section larger than the current slit is desired (e.g., 10% larger), installing a second aperture with a larger slit size, or adding additional slits within a single aperture, poses challenges in terms of both operational efficiency and equipment space.

[0037] Therefore, since the projection magnification can be changed by changing the applied voltage of the projection lens, the length of the cross section can be easily changed.

[0038] Furthermore, when the applied voltage of the projection lens is changed, the beam is deformed, making it difficult to accurately transfer the slit shape. However, there is no problem if the edge of the beam is straight when forming a cross section.

[0039] In addition, the "length of the cross section" is the length of the intersection line (ridge line) between the surface of the sample and the cross section.

[0040] In the converged ion beam processing apparatus of the present invention, the slit of the aperture may be rectangular.

[0041] According to this focused ion beam processing apparatus, rectangular etching is performed on a sample to obtain an appropriate cross section.

[0042] In the converged ion beam processing apparatus of the present invention, the ion source may also be a plasma ion source.

[0043] According to this converged ion beam processing apparatus, a large current ion beam can be obtained compared to an ion source such as Ga, thereby improving working efficiency.

[0044] Effects of the Invention

[0045] According to the present invention, a converged ion beam processing apparatus can be obtained that improves the cross-sectional shape and enhances the working efficiency when performing cross-sectional processing using a converged ion beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a diagram showing the overall structure of a converged ion beam processing apparatus according to an embodiment of the present invention.

[0047] Figure 2 A diagram showing the structure of an FIB column.

[0048] Figure 3 A diagram showing the structure of a condenser lens, an aperture, and a projection lens in an FIB column.

[0049] Figure 4 1 is a diagram showing the relationship between the voltage applied to the focusing lens 22 and the trajectory of the focused ion beam.

[0050] Figure 5 It shows Figure 4 A diagram showing the distribution of the probe current in each track in the plane direction of the specimen.

[0051] Figure 6 It shows Figure 4 A graph showing the etching depth of the sample etched at various probe currents.

[0052] Figure 7 This is a diagram showing an aperture having a slit with one side being a straight line.

[0053] Figure 8 This is a diagram showing the probe current when one side of the aperture is aligned with the center of the converged ion beam and the etching depth of the sample caused by the probe current.

[0054] Figure 9 Graph showing the trajectory of a converged ion beam according to a change in the position of one side of the aperture.

[0055] Figure 10 It shows Figure 9 A diagram showing the distribution of the probe current in each track in the plane direction of the specimen.

[0056] Figure 11 It shows Figure 9 Figure 4. Planar profile of the final morphology of each track in the cross section of the specimen after etching.

[0057] Figure 12 A diagram showing the shape of a sample obtained by cross-section processing using a converged ion beam.

[0058] Figure 13 The aperture is used to Figure 12 Figure 2 shows an existing method for cross-section processing of a specimen.

[0059] Label Description

[0060] 20: Converging ion beam column;

[0061] 20A: Converging ion beam;

[0062] 21: ion source;

[0063] 22: Converging lens;

[0064] 24: aperture;

[0065] 24s: slit;

[0066] 24t: the straight side of the slit;

[0067] 28: projection lens;

[0068] 50: sample stage;

[0069] 100: Converged ion beam processing device;

[0070] 200: sample;

[0071] 200c: cross section of the specimen;

[0072] S: The distance from one side of the aperture to the center of the converged ion beam when the center of the converged ion beam is partially blocked by the aperture from one side. DETAILED DESCRIPTION

[0073] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0074] Figure 1 1 is a block diagram showing the overall structure of a converged ion beam processing apparatus 100 according to an embodiment of the present invention. Figure 1In the figure, the converged ion beam processing device 100 has an electron beam column (SEM column) 10, a converged ion beam column (FIB column) 20, secondary electron detectors 4, 5, a control unit 6, a display unit 7, an input unit 8 and a sample carrier 50. It can process the sample 200 arranged on the sample carrier 50 by using a converged ion beam and observe it by using an SEM.

[0075] In addition, although Figure 1 In FIG, the FIB column 20 is arranged vertically, and the SEM column 10 is arranged to be inclined at a predetermined angle relative to the vertical, but the present invention is not limited thereto.

[0076] Part or all of the components of the focused ion beam processing apparatus 100 are disposed in a vacuum chamber 40 , and the interior of the vacuum chamber 40 is decompressed to a predetermined vacuum level.

[0077] As described above, the sample 200 is placed on the sample stage 50. The sample stage 50 also includes a moving mechanism capable of shifting the sample 200 in five axes.

[0078] The control unit 6 can be comprised of a computer having a CPU (central processing unit), a memory unit (RAM and ROM) for storing data and programs, and input and output ports for communicating with external devices. The CPU of the control unit 6 executes various computations based on the programs stored in the memory unit, and the control unit 6 controls the various components of the converged ion beam processing apparatus 100. Furthermore, the control unit 6 is electrically connected to control wiring, etc., for the electron beam column 10, the converged ion beam column 20, the secondary electron detectors 4 and 5, and the sample stage 50.

[0079] Furthermore, the control unit 6 can drive the sample stage 50 according to software instructions or operator input, adjust the position and posture of the sample 200 , and adjust the irradiation position and irradiation angle of the electron beam 10A and the ion beam 20A on the surface of the sample 200 .

[0080] Furthermore, the control unit 6 is connected to an input unit 8 such as a keyboard for receiving input instructions from an operator and a display unit 7 for displaying an image of a sample and the like.

[0081] Although not shown, the SEM column 10 includes an electron source that emits electrons, and an electron optical system that forms and scans the electrons emitted from the electron source into a beam. When the sample 200 is irradiated with an electron beam 10A emitted from the electron beam column 10, secondary electrons are generated from the sample 200. These generated secondary electrons can be detected by a secondary electron detector 5 within the column or a secondary electron detector 4 outside the column to obtain an image of the sample 200. Furthermore, a reflected electron detector within the column can detect reflected electrons to obtain an image of the sample 200.

[0082] The electron optical system is configured to include, for example, a condenser lens for converging the electron beam 10A, an aperture for narrowing the electron beam 10A, an adjuster for adjusting the optical axis of the electron beam 10A, an objective lens for converging the electron beam 10A on the sample 200, and a deflector for scanning the electron beam 10A on the sample 200.

[0083] As will be described later, the FIB column 20 includes an ion source for generating ions and an ion optical system for shaping the ions emitted from the ion source into a converged ion beam and scanning the ions. By irradiating the sample 200 with the converged ion beam 20A as a charged particle beam from the FIB column 20 and performing etching, a cross section 200c of the sample 200 is machined (see Figure 12 ).

[0084] like Figure 2 As shown, the FIB column 20 includes, in order from the ion source 21 side toward the objective lens 28, an ion source 21 for generating ions, a converging lens 22 for converging ions emitted from the ion source into a converged ion beam 20A, a blanker 23 for turning the ion beam on and off, an aperture (movable aperture) 24, an aligner 25, an astigmatism corrector 26, a scanning electrode 27, and an objective lens 28 for focusing the converged ion beam 20A on a predetermined position of the sample 200. Furthermore, a secondary electron detector 29a and an air gun 29b are arranged around the objective lens 28.

[0085] The collimator 25 adjusts the trajectory of the beam so that the ion beam passes through the central axis of the objective lens 28. The astigmatism corrector 26 and the scanning electrode 27 have the functions of correcting astigmatism and scanning the beam on the sample, respectively.

[0086] The blanker 23 and the scanning electrode 27 constitute a deflector.

[0087] like Figure 7 As shown, aperture 24 blocks a portion of the converged ion beam 20A converged by converging lens 22 and has a slit 24s with at least one side 24t being linear for processing sample 200 into a desired shape. The present invention employs the following transfer mode, irradiating a beam formed into a slit shape by blocking a portion of the ion beam through slit 24s.

[0088] In addition, if Figure 7 As shown, the aperture 24 also includes a circular aperture 24h for convergence mode, enabling observation and processing of samples even when scanning the ion beam in convergence mode. The circular aperture 24h adjusts the angular spread of the ion beam. A drive unit (not shown) moves the aperture 24 within the aperture plane to select the desired slit 24s or circular aperture 24h, enabling switching between transfer mode and convergence mode.

[0089] Figure 3 Converging lens 22, aperture 24, and projection lens (objective) 28 are shown in FIB column 20.

[0090] The converging lens 22 is composed of two lenses 22a and 22b, which allow the probe current passing through the slit 24s of the aperture 24 to be adjusted. Increasing the probe current increases the angle of the beam passing through the aperture 24, increasing aberrations and sometimes preventing a sharp beam shape. Therefore, the optimal size of the slit 24s must be set based on the desired beam shape.

[0091] In addition, Figure 3 In FIG, the converging lens is composed of two layers 22a and 22b, but the present invention is not limited thereto and may be composed of a single layer.

[0092] The condensing lens 22 and the projection lens 28 are composed of electrostatic lenses.

[0093] In addition, when the transfer mode is adopted, the projection magnification of the aperture 24 is determined by the relationship between the aperture 24 , the projection lens 28 , and the distances among the sample 200 .

[0094] Furthermore, in the transfer mode used in the present invention, the voltage of the converging lens 22 is set so that the beam is converged (focused) on the principal plane of the projection lens 28 by the converging lens 22. The aperture 24 is provided between the converging lens 22 and the projection lens 28, and the voltage of the projection lens 28 is determined so that the opening shape of the slit 24s of the aperture 24 is transferred to the sample 200.

[0095] Therefore, if Figure 3 As shown in the trajectory from the aperture 24 toward the sample 200 (shown by the thick solid line), the beam formed into an aperture shape is irradiated onto the sample, and the aperture shape is transferred to the sample.

[0096] Here, in the transfer mode, in order to project the opening shape of the aperture 24 onto the sample 200, it is necessary to use the slit 24s of the aperture 24 as a light source and form an image of the light source on the sample 200 using the projection lens 28. Therefore, the voltage applied to the projection lens 28 is uniquely determined geometrically.

[0097] Next, refer to Figures 4 to 11 The characteristic features of the present invention will be described.

[0098] Here, as the degree to which the absolute value of the voltage applied to the converging lens 22 is reduced, if the voltage applied to the converging lens 22 when the converged ion beam 20A is focused on the principal plane of the projection lens 28 by the Koehler illumination method is a predetermined voltage, the voltage applied to the converging lens 22 is set to be less than the predetermined voltage and equal to or greater than 80% of the predetermined voltage. The aperture 24 corresponds to the "field aperture" in the Koehler illumination method.

[0099] Moreover, in Figure 4 In the above conditions based on the Koehler illumination method, the trajectory LA of the ion beam when the applied voltage of the converging lens 22 is a specified voltage, the trajectories LB and LC of the ion beam when the applied voltage is 89% and 85% of the specified voltage respectively are more concentrated at the center of the sample 200 than LA.

[0100] In addition, Figure 5 In the track LA, the probe current is uniform (rectangular) as it moves from the center O of the surface of the sample 200 toward the radial direction (outward in the surface direction).

[0101] On the other hand, in the tracks LB and LC, the probe current is strongest at the center O of the surface of the sample 200 and decreases toward the radial direction (outward in the surface direction).

[0102] As described above, the voltage applied to the condensing lens 22 is set to be lower than the predetermined voltage and equal to or higher than 80% of the predetermined voltage.

[0103] As described above, reducing the absolute value of the voltage applied to the focusing lens 22 allows the probe current to be concentrated near the center of the sample 200 , thereby improving the work efficiency when preparing the cross-sectional sample.

[0104] That is, Figure 6 As shown, since the probe current is uniform (rectangular) in the track LA where the applied voltage of the converging lens 22 is a predetermined voltage, when the sample 200 is etched using the probe current of the track LA, a uniform depth of the shape that is the inversion of the above-mentioned rectangle can be excavated.

[0105] In contrast, Figure 12 As shown, the desired cross-sectional specimen has a shape having a cross section 200c cut vertically from the specimen surface and a slope 200s connected to the cross section 200c. When etching is performed at a uniform depth, as shown in FIG. Figure 6 As shown by the shadow R1, the excavation depth will be deeper than the slope 200s, and the etching of the portion R1 is unnecessary, resulting in reduced work efficiency. On the other hand, when etching at a uniform depth, insufficient etching may occur in the portion of the cross section 200c, resulting in the need for additional etching time, which also reduces work efficiency.

[0106] Therefore, when the sample 200 is etched using a probe current having a peak at the center O of the track LB and a current density distribution that gradually decreases away from the center, etching is performed in a deepest shape at the center O where the current density is high.

[0107] As a result, the sample 200 is etched in a profile similar to the V-shape formed by the cross section 200c and the slope 200S connected to the cross section 200c. Therefore, the ion beam can be used without waste during etching. Furthermore, by aligning the peak of the probe current with the portion of the cross section 200c that needs to be etched the deepest, the cross section 200c can be etched deeply even without performing additional etching.

[0108] As a result, work efficiency is improved.

[0109] Furthermore, although sputtered products generated by etching adhere to the cross section to be observed, since etching of unnecessary areas can be reduced, adhesion of sputtered products to the cross section is also reduced, and work efficiency can be further improved.

[0110] In addition, if Figure 7 As shown, in the present invention, a device having at least one side 24t in a straight line ( Figure 6 The aperture 24 is a slit 24s (which is rectangular in shape as a whole). Figure 8 As shown, one side of the aperture 24 is aligned approximately with the center O of the converging ion beam 20A.

[0111] That is, in Figure 8 In the ion beam track LB, the probe current has a distribution in which the current density is larger at the center O and the current density gradually decreases as it moves away from the center. Therefore, when the sample 200 is etched using the probe current of the track LB, a shape in which the shape of the current density distribution is reversed and the deepest shape is at the center O will be excavated.

[0112] In contrast, Figure 12 As shown in FIG. 1 , the required sample cross section has a cross section 200c cut perpendicularly from the sample surface and a slope 200s connected to the cross section 200c. Therefore, when one side 24t of the aperture 24 is aligned with the center O of the convergent ion beam 20A, the half of the probe current distribution in the track LB with the center O as the boundary ( Figure 8 The left side of the probe is blocked, and only the half on the opposite side with the center O as the boundary acts as the probe current LM.

[0113] As a result, a substantially V-shaped sample 200 formed by the cross section 200c and the slope 200s connected to the cross section 200c is etched. This approximates the contours of the cross section 200c and the slope 200s, and thus the ion beam can be utilized without waste in etching.

[0114] In addition, in this way, the probe current passing through the aperture 24 performs etching that is similar to the contours of the cross section 200c and the slope 200s. Therefore, the cross-sectional processed shape of the sample 200 can be produced at one time using the aperture 24 without scanning the converged ion beam, further improving the working efficiency.

[0115] Furthermore, since the cross section 200 c is etched by shielding the ion beam with the linear side 24 t of the slit 24 s of the aperture 24 , rounded corners (steps) are less likely to be generated in the cross section, and the cross-sectional shape can be improved.

[0116] Figure 9 Trajectories LD to LF of the converged ion beam 20A based on changes in the position of one side 24 t of the aperture 24 are shown.

[0117] The trajectory obtained by aligning the center of the slit 24s of the aperture 24 with the center O of the converged ion beam 20A is denoted as LD, and the trajectory obtained by aligning one side 24t of the aperture 24 with the center O of the converged ion beam 20A is denoted as LE. Furthermore, the trajectory obtained by aligning one side 24t of the aperture 24 with a position further inward than the center O of the converged ion beam 20A (i.e., a position where the portion of the aperture 24 starting from the one side 24t blocks the center O of the converged ion beam 20A) is denoted as LF.

[0118] Here, in the trajectory LF, it is assumed that the width (distance) of the one side 24 t from the center O of the converged ion beam 20A when the center O is partially blocked by the aperture 24 from the one side 24 t is S.

[0119] like Figure 10 As shown, the probe current in the orbit LD where one side 24t of the aperture 24 deviates from the center O of the convergent ion beam 20A reaches the highest peak at the center O.

[0120] On the other hand, the probe currents in the tracks LE and LF, which align one side of the aperture 24 substantially with the center O of the convergent ion beam 20A, are shown in FIG. Figure 8 As shown, only the right half from the center O has the shape, and the right half of the center O expands further outward in the radial direction than the track LD.

[0121] From this, it can be seen that by aligning one side 24t of the aperture 24 roughly with the center O of the converged ion beam 20A, rounded corners (steps) are less likely to be generated in the cross section, the cross-sectional shape can be improved, and the probe current is approximated to the profile of the slope 200s, so that the ion beam can be used without waste during etching.

[0122] Figure 11 It is a planar profile of the final shape of the cross section of the sample 200 after etching in each track LD to LF (the planar shape of the etching recess of the sample 200 when viewed from the irradiation direction of the converged ion beam).

[0123] In an ideal optical system, in the trajectory LE where one side 24t of the aperture 24 is aligned with the center O of the convergent ion beam 20A, a straight beam shape can be obtained along the one side 24t at the irradiation portion of the cross section 200c. However, ideal conditions cannot usually be achieved, such as Figure 11 As shown, there is a tendency that the trajectory LF set in such a way that the center O of the converged ion beam 20A is partially blocked by the aperture 24 from one side 24t is irradiated at the cross section 200c along the one side 24t ( Figure 11 A straight beam shape will be obtained at the straight part of the dotted line LF along the X direction).

[0124] Therefore, the position of the aperture 24 can be set so that when the center O of the converged ion beam 20A is partially blocked by the aperture 24 from one side 24t, the distance from the one side 24t of the aperture 24 to the center O is less than 500 μm (i.e., Figure 9 The distance S<500μm).

[0125] Here, as Figure 12 As shown, the length of the intersection line (ridge line) 200d between the surface 200a and the cross section 200c of the sample 200 is preferably 10 μm or more and 1 mm or less. To generate the length of the ridge line 200d, the length of one side 24t of the aperture 24 varies depending on the projection magnification of the aperture 24, but is generally set to 1 μm or more and 1 mm.

[0126] The present invention is not limited to the above-described embodiments, and naturally involves various modifications and equivalents included within the spirit and scope of the present invention.

[0127] The converged ion beam processing apparatus of the present invention only needs to have a converged ion beam column, and an electron beam column is not an essential structure.

[0128] In the converged ion beam processing apparatus of the present invention, the beam size of the converged ion beam can also be adjusted by adjusting the applied voltage of the projection lens.

[0129] In transfer mode, the shape of the converged ion beam reflects the shape of the slit, and the projection magnification of the transferred slit shape is uniquely determined by the aperture, projection lens, and sample geometry. Therefore, when changing the length of the cross-section during sample cross-section processing, the aperture shape must be changed. However, if, for example, a cross-section larger than the current slit (e.g., 10% larger) is desired, installing an additional aperture with a larger slit size, or adding additional slits within a single aperture, poses challenges in terms of both operational efficiency and equipment space.

[0130] Therefore, since the projection magnification is changed by changing the applied voltage of the projection lens, the length of the cross section can be easily changed.

[0131] Furthermore, when the applied voltage of the projection lens is changed, the beam is deformed, making it difficult to accurately transfer the slit shape. However, there is no problem if the edge of the beam is straight when forming a cross section.

[0132] Furthermore, when the ion source is a plasma ion source, an ion beam having a larger current than that of a Ga plasma source can be obtained, thereby improving working efficiency.

Claims

1. A converged ion beam processing device comprising: ion source; a specimen stage, which holds the specimen; a converging lens that converges ions emitted from the ion source into a converging ion beam; an aperture that blocks a portion of the converged ion beam converged by the converging lens and has a slit at least one side of which is linear for processing the sample into a desired shape; and a projection lens disposed in a beam path between the aperture and the sample stage, and focusing the converged ion beam having passed through the aperture on a predetermined position of the sample using the aperture as a light source; A cross section parallel to the irradiation direction of the convergent ion beam is machined on the sample, It is characterized by: When the voltage applied to the converging lens is a predetermined voltage when the converged ion beam is focused on the principal plane of the projection lens by Koehler illumination, the voltage applied to the converging lens is set to be less than the predetermined voltage and equal to or greater than 80% of the predetermined voltage; The position of the aperture is set so that the aperture blocks the converged ion beam in a state where the distance between one side of the aperture and the center of the converged ion beam is greater than 0 μm and less than 500 μm. The voltage applied to the projection lens is set to an applied voltage that causes the image of the slit formed by the aperture to focus on the sample surface. The transfer mode is configured such that the converged ion beam is not scanned but the converged ion beam formed into the shape of the slit is irradiated onto the sample surface at once, thereby transferring the shape of the slit to the sample.

2. The converged ion beam processing apparatus according to claim 1, wherein: By adjusting the applied voltage of the projection lens, the beam size of the converged ion beam can be adjusted.

3. The converged ion beam processing apparatus according to claim 1 or 2, wherein: The slit of the aperture is rectangular in shape.

4. The converged ion beam processing apparatus according to claim 1 or 2, wherein: The ion source is a plasma ion source.

5. The converged ion beam processing apparatus according to claim 3, wherein: The ion source is a plasma ion source.

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