ABERRATION CORRECTOR, DEVICE COMPRISING A BEAM OF CHARGED PARTICLES AND CONTROL METHOD FOR CONTROLLING THE SAME

Abstract

An aberration corrector in which a relay lens is arranged between a first multipole and a second multipole to control fourth-order coma aberration, the aberration corrector characterized by comprising: a first deflector in which the first multipole and the second multipole form a multipole field including a six-pole field component, the first deflector controlling at least one of the distance between a charged particle beam incident on the first multipole and the axis of the optical system and the azimuth angle of the charged particle beam incident on the first multipole; a second deflector controlling at least one of the angle between the charged particle beam incident on an objective lens and the axis of the optical system and the azimuth angle of the charged particle beam incident on the objective lens;and a control unit that controls the first deflector and the second deflector, wherein the control unit performs a first control and a second control such that at least a part of the second-order coma aberration (B2) caused by the first control on the first deflector is canceled by the second-order coma aberration (B2) caused by the second control on the second deflector;

Description

Technical area

[0001] The present invention relates to a charged particle beam device, particularly to the correction of fourth-order coma aberration and sixth-order coma aberration. Technical background

[0002] A charged particle beam instrument, such as a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM), is an instrument that generates an observation image of a sample by irradiating it with a charged particle beam. To improve the resolution of the observation image generated by the charged particle beam instrument, it is necessary to correct the aberration generated in the electron optics system.

[0003] PTL 1 discloses a STEM that calculates an autocorrelation function for each of a plurality of images obtained by changing a focus, and corrects 2x astigmatism based on an aberration coefficient obtained by fitting an aberration function to an isointensity line of the autocorrelation function. It is also disclosed that coma aberration can be measured by changing the incident angle of an electron beam to obtain multiple images instead of changing the focus. Citation listPatent literature

[0004] PTL1: JP5188846A Summary of the inventionTechnical problem

[0005] However, in PTL 1, third-order or less aberration needs to be corrected, and the control of fourth-order coma aberration is not considered. In an energy-dispersive X-ray spectrometry (STEM-EDX) method for detecting fluorescent X-rays generated by electron beam irradiation at the time of STEM observation, which is one of the methods for generating an element distribution image of an observation sample, the generation of the element distribution image takes a long time because the generation efficiency of the fluorescent X-rays is low.In order to shorten the time required to generate the element distribution image without reducing the resolution, it is necessary to control the fourth-order coma aberration and the sixth-order coma aberration to maintain the diameter of the electron beam while broadening the angle at which the electrons are trapped and increasing the total amount of the electron beam.

[0006] Therefore, it is an object of the invention to provide an aberration corrector capable of controlling a fourth-order coma aberration or a sixth-order coma aberration, a charged particle beam apparatus including the same, and a control method for controlling the same. Solution

[0007] To achieve the above object, the invention is an aberration corrector in which a relay lens is arranged between a first multipole and a second multipole, the first multipole and the second multipole each forming a multipole field containing a component of a six-pole field, the aberration corrector comprising: a first deflector configured to control at least a distance between a charged particle beam incident on the first multipole and an axis of an optical system and an azimuth angle of the charged particle beam incident on the first multipole; a second deflector configured to control at least an inclination between a charged particle beam incident on an objective lens and the axis of the optical system and / or an azimuth angle of the charged particle beam incident on the objective lens;and a control unit that controls the first deflector and the second deflector, wherein the control unit executes a first control performed on the first deflector and a second control performed on the second deflector such that at least a part of a second-order coma aberration caused by the first control is canceled by a second-order coma aberration caused by the second control.;

[0008] The invention is a charged particle beam apparatus for forming an observation image of a sample by irradiating the sample with a charged particle beam, the charged particle beam apparatus comprising: the above-mentioned aberration corrector.

[0009] The invention is a control method for controlling an aberration corrector in which a relay lens is arranged between a first multipole and a second multipole, the control method comprising: performing a first control performed on a first deflector configured to control at least a distance between a charged particle beam incident on the first multipole and an axis of an optical system and an azimuth angle of the charged particle beam incident on the first multipole, and a second control performed on a second deflector configured to control at least an inclination between a charged particle beam incident on an objective lens and the axis of the optical system and an azimuth angle of the charged particle beam incident on the objective lens,such that at least a portion of a second-order coma aberration caused by the first control is canceled by a second-order coma aberration caused by the second control. Advantageous effects of the invention

[0010] According to the invention, an aberration corrector capable of controlling fourth-order coma aberration and sixth-order coma aberration, a charged particle beam apparatus including the same, and a control method for controlling the same can be provided. Brief description of the drawings [ Fig. 1] Fig. 1 is a diagram showing an example of an overall configuration of a charged particle beam apparatus according to Embodiment 1. [ Fig. 2A] Fig. 2A is a diagram illustrating an example of a configuration of an aberration corrector according to Embodiment 1. [ Fig. 2B] Fig. Figure 2B is a diagram illustrating an example of a first multipole. [ Fig. 2C] Fig. Figure 2C is a diagram illustrating an example of a second multipole. [ Fig. 3A] Fig. Figure 3A is a diagram illustrating the control of a distance between a charged particle beam incident on the first multipole and an axis of an optical system. [ Fig. 3B] Fig. Figure 3B is a diagram illustrating the control of an angle between a charged particle beam incident on an objective lens and the axis of the optical system. [ Fig. 3C] Fig. Figure 3C is a diagram illustrating an example of controlling a fourth-order coma aberration (B4). [ Fig. 3D] Fig. 3D is a diagram showing the positions P0 to P4 of electron beams incident on the first multipole. [ Fig. 3E] Fig. Figure 3E is a diagram showing a pattern formed by the electron beam incident on P0. [ Fig. 3F] Fig. Figure 3F is a diagram showing a pattern formed by the electron beam incident on P1. [ Fig. 3G] Fig. Figure 3G is a diagram showing a pattern formed by the electron beam incident on P2. [ Fig. 3H] Fig. 3H is a diagram showing a pattern formed by the electron beam incident on P3. [ Fig. 3I] Fig. Figure 3I is a diagram showing a pattern formed by the electron beam incident on P4. [ Fig. 4] Fig. 4 is a diagram illustrating an example of a processing flow according to Embodiment 1. [ Fig. 5] Fig. Figure 5 is a diagram illustrating an example of an aberration adjustment screen. [ Fig. 6A] Fig. Figure 6A is a diagram illustrating another example of the aberration corrector. [ Fig. 6B] Fig. 6B is a diagram showing another embodiment of the aberration corrector. [ Fig. 7A] Fig. Figure 7A is a diagram illustrating an example of controlling a sixth-order coma aberration (B6). [ Fig. 7B] Fig. Figure 7B is a diagram illustrating another example of sixth-order coma aberration (B6) control. [ Fig. 7C] Fig. Figure 7C is a diagram illustrating another example of sixth-order coma aberration (B6) control. Description of the embodiments

[0011] Embodiments of a charged particle beam device according to the invention will be described below with reference to the accompanying drawings. In the following description and the accompanying drawings, components having the same functional configuration are denoted by the same reference numerals, and redundant descriptions thereof are omitted. Embodiment 1

[0012] An example of an overall configuration of a scanning transmission electron microscope, which is one of the charged particle beam devices, is described with reference to Fig. 1. The scanning transmission electron microscope is an instrument that generates a transmission electron image by irradiating a sample with an electron beam and detecting the transmission electrons that pass through the sample. It includes a lens body 100 and a control unit 110.

[0013] The control unit 110 is a device that controls the units included in the lens body 100 and generates an observation image based on a detection signal transmitted from the lens body 100, and is implemented, for example, by a computer.

[0014] The lens body 100 includes an electron source 101, a converging lens 102, a converging lens 103, an aperture 104, an aberration corrector 120, an objective lens 105, an intermediate lens 107, a projection lens 108, and a detector 109. An axis of each of the converging lens 102, the converging lens 103, the aperture 104, the aberration corrector 120, the objective lens 105, the intermediate lens 107, the projection lens 108, and the detector 109 is aligned with an axis 111 of an optical system.

[0015] The electron source 101 emits an electron beam to irradiate a sample 106. The emitted electron beam is accelerated by a predetermined acceleration voltage, focused by the converging lens 102 and the converging lens 103, and passes through the aperture 104. The electron beam passing through the aperture 104 is aberration-corrected by the aberration corrector 120 and then focused onto a surface of the sample 106 by the objective lens 105. The electron beam passing through the sample 106 is focused by the intermediate lens 107 and then projected onto the detector 109 through the projection lens 108. The detector 109 detects the projected electron beam and transmits the detection signal to the control unit 110. The control unit 110 generates the observation image based on the detection signal.

[0016] The scanning transmission electron microscope may further include an X-ray detector that detects fluorescent X-rays emitted by the sample 106 upon irradiation with the electron beam. The control unit 110 generates an element distribution image of the sample 106 based on a detection signal from the X-ray detector.

[0017] An example of a configuration of the aberration corrector 120 will be described with reference to Fig. 2A. The aberration corrector 120 includes a focusing lens 201, a first deflector 202, a first multipole 203, a relay lens 204, a relay lens 205, a second multipole 206, a second deflector 207, and a focusing lens 208. The relay lens 204 and the relay lens 205 are arranged between the first multipole 203 and the second multipole 206. The first multipole 203 and the second multipole 206 are in a conjugate relationship due to the relay lens 204 and the relay lens 205.

[0018] The first multipole 203 and the second multipole 206 form a multipole field, which is a rotationally symmetric electric or magnetic field, in a region through which the electron beam passes. Fig. The first multipole 203 shown in Figure 2B comprises six magnetic poles 211A to 213B and forms a six-pole field, which is a triply symmetric field, through a magnetic flux between the magnetic poles. The second multipole 206, shown in Fig. 2C, includes magnetic poles 221A to 223B and forms a six-pole field similar to the first multipole 203. These two six-pole fields generate second-order astigmatism (A2) and third-order spherical aberration (C3) components, each of which is triply symmetric. The third-order spherical aberration (C3) can be controlled by adjusting an optical relationship between the first multipole 203 and the second multipole 206 and a magnitude of each multipole field to cancel the second-order astigmatism (A2) between the first multipole 203 and the second multipole 206.

[0019] The first multipole 203 and the second multipole 206 are not limited to six-pole lenses with six magnetic poles, but can also be twelve-pole lenses with twelve magnetic poles. This means that the number of magnetic poles can be changed to control the orientation of the formed six-pole field or to form a different type of field.

[0020] Although the first multipole 203 and the second multipole 206 are in a conjugate relationship with each other due to the relay lens 204 and the relay lens 205 and can correct third-order or less aberrations, such as a third-order spherical aberration of the objective lens 105, it is difficult to independently control the fourth-order coma aberration (B4). Therefore, in Embodiment 1, a first controller for generating both the second-order coma aberration (B2) and the fourth-order coma aberration (B4) and a second controller for generating B2 and B4 are operated at a generation ratio different from that of the first controller, in an appropriate ratio to control B4 together with B2.That is, by operating the first controller and the second controller such that at least a portion of the B2 generated in the first controller is canceled out by the B2 generated in the second controller, the B4 can be controlled essentially alone. For example, the first controller is performed for the first deflector 202, and the second controller is performed for the second deflector 207.

[0021] The operation of the first deflector 202 is based on Fig. 3A. The first deflector 202 is arranged on one side of the electron source 101 relative to the first multipole 203 and changes a distance R1 between the electron beam incident on the first multipole 203 and the axis 111 of the optical system. When the distance R1 between the electron beam incident on the first multipole 203 and the axis 111 of the optical system changes, a distance R2 between the electron beam incident on the second multipole 206 and the axis 111 of the optical system also changes. The electron beams incident on the first multipole 203 and the second multipole 206 are typically parallel to the axis 111 of the optical system, but may also be non-parallel to the axis 111 of the optical system. When the electron beam is not parallel to the axis 111 of the optical system, the distance R1 and the distance R2 are defined using a reference, for example, a mid-thickness plane of each multipole.

[0022] As the electron beam incident on the first multipole 203 moves away from the axis 111 of the optical system, a first-order astigmatism (A1), a second-order coma aberration (B2), and a fourth-order coma aberration (B4) are generated in the first multipole 203. Similarly, a first-order astigmatism (A1), a second-order coma aberration (B2), and a fourth-order coma aberration (B4) are generated in the second multipole 206. When R1 = R2, the A1 generated in the first multipole 203 is canceled by the A1 generated in the second multipole 206.

[0023] The B2 generated in the first multipole 203 and the B2 generated in the second multipole 206 change according to an amount of the distance R1, the two B2 do not cancel each other out, and a sum of the two B2 remains as a B2 component.

[0024] The B4 generated in the first multipole 203 and the B4 generated in the second multipole 206 change according to an amount of distance R1. The two B4s do not cancel each other out, and a sum of the two B2s remains as a B4 component. That is, the B2 and the B4 are generated by an operation of the first deflector 202, and the amounts of the B2 and the B4 are adjusted by the amount of distance R1, which is controlled by the first deflector 202.

[0025] The function of the second deflector 207 is determined by Fig. 3B. The second deflector 207 is arranged between the second multipole 206 and the focusing lens 208 and controls an inclination θ1 between the electron beam incident on the objective lens 105 and the axis 111 of the optical system. When the electron beam incident on the objective lens 105 is inclined relative to the axis 111 of the optical system, a second-order coma aberration (B2) and a fourth-order coma aberration (B4) are generated in the objective lens 105. The amounts of B2 and B4 generated in the objective lens 105 are adjusted by an amount of inclination θ1 controlled by the second deflector 207.

[0026] The control of the fourth-order coma aberration (B4) is described with reference to Fig. 3C. A sum B2_tot of the B2 generated in the charged particle beam device when the first deflector 202 and the second deflector 207 are operating is approximately represented by the following equation. B2_tot=K1⋅R1+K2⋅R2+K3⋅θ1+B2_init

[0027] Here, K1 · R1 is a B2 component generated by a change in distance R1, K2 · R2 is a B2 component generated by a change in distance R2, K3 · θ1 is a B2 component generated by a change in inclination θ1, and B2_init is a B2 component originally present in the charged particle beam device. K1, K2, and K3 are coefficients determined by a magnitude or spatial shape of fields formed by the first multipole 203, the second multipole, and the objective lens 105.

[0028] A sum B4_tot of the B4 generated in the charged particle beam device when the first deflector 202 and the second deflector 207 are in operation is approximately represented by the following equation. B4_tot=K4⋅R1+K5⋅R2+K6⋅θ1+B4_init

[0029] Here, K4 · R1 is a B4 component generated by a change in distance R1, K5 · R2 is a B4 component generated by a change in distance R2, K6 · θ1 is a B4 component generated by a change in inclination θ1, and B4_init is a B4 component originally present in the charged particle beam device. K4, K5, and K6 are coefficients determined by a magnitude or spatial shape of fields formed by the first multipole 203, the second multipole 206, and the objective lens 105.

[0030] When a ratio of B2 and B4 generated by the operation of the first deflector 202 differs from a ratio of B2 and B4 generated by the operation of the second deflector 207 and R1 = R2, Formula 1 and Formula 2 can be solved as simultaneous equations of R1 and θ1. That is, by adjusting R1 and θ1, B2_tot and B4_tot can be set to desired values, for example, zero.

[0031] In the above example, a case is described where an initial state before performing aberration control is a state where the electron beam passes through the centers of the lenses and the multipoles, that is, a state where the axis of the optical system and a trajectory of the electron beam coincide with each other. However, in an actual device, it is assumed that for an aberration other than coma aberration, control other than the one described above is used in combination. In such a case, in the initial state before performing the above control, the distances (R1, R2) between the electron beams incident on the multipole and the axis 111 of the optical system and the inclination (θ1) may have a value other than 0.Even in such a case, the same effect can be achieved by defining the distance R1, the distance R2, and the inclination θ1 in the above control by the relative distance from the electron beam orbit and a shift amount of the inclination in the initial state before performing the above control, instead of the distance and angle with respect to the axis 111 of the optical system. This is due to the fact that a change amount of coma aberration is approximately linear to a change in the position of the electron beam orbit and a change in inclination, and to the fact that addition and subtraction of aberration components can be performed between independent aberration components, as shown in (Formula 1).

[0032] A relationship between a position of the electron beam incident on the first multipole 203 and the second-order coma aberration (B2) generated in the first multipole 203 is described with reference to the Fig. 3D to 3I. A relationship between a position of an electron beam incident on a multipole other than the first multipole 203 and the second-order coma aberration (B2) is the same as in the case of the first multipole 203.

[0033] In Fig. 3D are represented by white circles in an XY plane orthogonal to the axis 111 of the optical system, P0, P1, P2, P3, and P4, which are the center positions of the electron beams incident on the first multipole 203. The center position of the electron beam is represented by (X, Y) coordinates or coordinates (R1, φ1) of the distance R1 from the axis 111 of the optical system and an azimuth angle φ1 around the axis 111 of the optical system. The azimuth angle φ1 in Fig. 3D is a tilt with respect to an x-axis.

[0034] Fig. Figure 3E shows a P0 pattern 300, which is a pattern formed on the sample by the electron beam incident on the point P0, which is the position of the axis 111 of the optical system. The electron beam incident on the first multipole 203 contains electrons emitted from the electron source with different inclinations and orientations. The P0 pattern 300 is obtained by connecting the positions where the electrons emitted at the same inclination reach the sample with lines. The P0 pattern 300 has an isotropic shape, indicating that no coma aberrations are generated.

[0035] Fig. Figure 3F shows a P1 pattern 301, which is a pattern formed on the sample by the electron beam incident on the P1, which is a position shifted from the P0 in an orientation of the azimuth angle φ1 = 0°. The P1 pattern 301 has a shape extending in the orientation of the azimuth angle φ1 = 0°, indicating that coma aberration arises in the orientation of the azimuth angle φ1 = 0°.

[0036] Fig. 3G shows a P2 pattern 302, which is a pattern formed on the sample by the electron beam incident on the P2, which is a position shifted from the P0 in an orientation of the azimuth angle φ1 = 45°. The P2 pattern 302 has a shape extending in the orientation of the azimuth angle φ1 = 45°, indicating that coma aberration is generated in the orientation of the azimuth angle φ1 = 45°.

[0037] Fig. Figure 3H shows a P3 pattern 303, which is a pattern formed on the sample by the electron beam incident on the P3, which is a position shifted from the P0 in an orientation of the azimuth angle θ1 = 90°. The P3 pattern 303 has a shape extending in the orientation of the azimuth angle φ1 = 90° and indicates that coma aberration is generated in the orientation of the azimuth angle φ1 = 90°.

[0038] P1, P2, and P3 are positions where the azimuth angle φ1 is different, but the distance R1 from P0 is the same. The patterns corresponding to P1, P2, and P3 differ from each other in orientation but have the same shape, indicating that the coma aberrations are generated with the same magnitude at different orientations.

[0039] Fig. 3I shows a P4 pattern 304, which is a pattern formed on the sample by the electron beam incident on the P4, which is a position shifted from P0 in a direction of the azimuth angle φ1 = 225°. The azimuth angle φ1 = 225° is obtained by rotating the azimuth angle φ1 = 45°, which indicates a direction of shift from P0 to P2, by 180°, and a distance between P0 and P4 is shorter than a distance between P0 and P2. The P4 pattern 304 has a shape extending in the orientation of the azimuth angle φ1 = 225°, indicating that coma aberration is generated in an orientation where the azimuth angle φ1 = 45° is rotated by 180°. However, the P4 pattern 304 remains close to the origin of the XY plane compared to the P2 pattern 302, which shows that the amount of coma aberration is small.

[0040] As in the Fig. As shown in Figures 3E to 3I, coma aberration has two components: magnitude and orientation. The magnitude changes according to the distance from the axis 111 of the optical system to the position where the electron beam is incident, and the orientation changes according to the azimuth angle of the position where the electron beam is incident. That is, to change the magnitude of coma aberration while maintaining the orientation in which the coma aberration occurs, it is sufficient to change the distance from the axis 111 of the optical system while maintaining the azimuth angle of the position where the electron beam is incident.To change the orientation in which the coma aberration is generated while maintaining the amount of coma aberration, it is sufficient to change the azimuth angle of the position at which the electron beam is incident while maintaining the distance between the position at which the electron beam is incident and the axis 111 of the optical system.

[0041] Because a magnetic field lens used in the optical system rotates the electron beam around the optical system's axis 111, a tilt offset occurs between the orientation of the azimuth angle of the position where the electron beam impinges and the orientation where coma aberration is generated. The tilt offset changes according to the optical system's conditions and the excitation amount of the magnetic field lens.

[0042] In the Fig. 3D to 3I, a case was described in which the incident positions of the electron beam were shifted from the position of the axis 111 of the optical system, but the relationship between the change in the incident position and the generated coma aberration is the same even if the electron beam is shifted from an arbitrary position.

[0043] Coma aberration, with its two components of magnitude and orientation, can be treated in a complex plane where a real axis and an imaginary axis are orthogonal to each other. When coma aberration is treated in the complex plane, the distance between the incident position of the electron beam and the axis 111 of the optical system and the azimuth angle of the incident position of the electron beam are also treated in the complex plane, and a real component and an imaginary component of the coma aberration change correspond to a real component and an imaginary component of the incident position of the electron beam.

[0044] If the inclination θ1 of the electron beam incident on the objective lens 105 is as in Fig. 3B, the amount of coma aberration generated in the objective lens 105 changes according to the amount of inclination θ1, and the orientation in which the coma aberration is generated changes according to the azimuth angle of the electron beam incident on the objective lens 105. When the coma aberration generated by controlling the inclination θ1 is treated in the complex plane, the amount of inclination θ1 and the azimuth angle of the incident electron beam are also treated in the complex plane, and the real component and the imaginary component of the coma aberration change correspond to the amount of inclination θ1 and the real component and the imaginary component of the azimuth angle of the incident electron beam.

[0045] As described above, similar to controlling the amount of coma aberration by adjusting the distance R1 and the inclination θ1, the orientation in which coma aberration is generated can be controlled by adjusting the azimuth angle of the electron beam incident on the first multipole 203 or the objective lens 105.

[0046] An example of a processing flow according to Embodiment 1 is described for each step with reference to Fig. 4 described. (S401)

[0047] The control unit 110 measures the second-order coma aberration (B2) and the fourth-order coma aberration (B4) based on the observed image or the pattern. The pattern used to measure B2 and B4 is, for example, a projection pattern such as a Ronchigram. The measured B2 and B4 correspond to B2_init in (Formula 1) and B4_init in (Formula 2). (S402)

[0048] The control unit 110 acquires change values ​​of B2 and B4 through the first control executed on the first deflector 202. Specifically, B2_0 and B4_0, which are B2 and B4 when the distance R1 is R1_0, and B2_0 + ΔB2 and B4_0 + ΔB4, which are B2 and B4 when the distance R1 is R1_0 + ΔR1, are measured, and ΔB2 / ΔR1 and ΔB4 / ΔR1 are calculated based on the measured values. ΔB2 / ΔR1 is approximately equal to K1 + K2 in (Formula 1), and ΔB4 / ΔR1 is equal to the coefficients K4 + K5 in (Formula 2). (S403)

[0049] The control unit 110 acquires change values ​​of B2 and B4 through the second control executed on the second deflector 207. Specifically, B2 and B4 are measured for the tilt θ1, and B2 + ΔB2 and B4 + ΔB4 are measured for the tilt θ1 + Δθ1. ΔB2 / Δθ1 and ΔB4 / Δθ1 are calculated based on the measured values. ΔB2 / Δθ1 corresponds to K3 in (Formula 1) and ΔB4 / Δθ1 corresponds to K6 in (Formula 2). (S404)

[0050] Based on the values ​​measured in S401 and the values ​​acquired in S402 and S403, the control unit 110 executes the first control and the second control so that the second-order coma aberration (B2) and the fourth-order coma aberration (B4) assume the desired values. That is, the first control and the second control are performed by solving (Formula 1) and (Formula 2) for R1 and θ1. For example, the desired values ​​of B2 and B4 are input by an operator via an aberration setting screen displayed on the control unit 110.

[0051] An example of the aberration adjustment screen is shown with reference to Fig. 5. In the Fig. On the screen shown in Figure 5, a correction value of each aberration is set in the upper stage, and a measured value of each aberration is displayed in the lower stage. The correction value of each aberration is set using increase and decrease buttons, indicated by an up arrow and a down arrow, and a numeric value input field. A relative value or an absolute value of the aberration is entered in the numeric value input field. Since aberrations, in addition to the spherical aberrations C1, C3, C5, and C7, have two components in a real (X) orientation and an imaginary (Y) orientation, the aberrations each have four buttons, including increase and decrease buttons for the real part and increase and decrease buttons for the imaginary part.

[0052] By the in relation to Fig. Using the processing procedure described in Figure 4, the second-order coma aberration (B2) can be adjusted to a desired value, and the fourth-order coma aberration (B4) can be controlled to a desired value. Since controlling B4 can increase the total amount of charged particle beams incident on the sample, the generation efficiency of the fluorescent X-rays detected in a STEM-EDX analysis can be improved, and the element distribution image can be obtained in a short time. The configuration of the aberration corrector is not limited to Fig. 2A limited.

[0053] Further examples of the aberration corrector are shown in the Fig. 6A and Fig. 6B. In Fig. 6A, the two transmission lenses 204 and 205 are in Fig. 2A is replaced by four relay lenses 601, 603, 605 and 606 and deflectors 602 and 604, and an adjusting lens 607 is added. In Fig. 6B is opposite Fig. 6A a multipole 608 was added. The same applies to Fig. 6A and Fig. 6B, except that the orientation of a multipole field formed in the second multipole 206 differs from the orientation in Fig. 2. That is, in each of the configurations of the Fig. 6A and Fig. 6B, a second-order coma aberration (B2) can be set to a desired value and a fourth-order coma aberration (B4) can be controlled to a desired value. Embodiment 2

[0054] In Embodiment 1, the fourth-order coma aberration (B4) is controlled to a desired value. In Embodiment 2, to further reduce the diameter of a charged particle beam directed onto a sample, control of a sixth-order coma aberration (B6) is described together with a fourth-order coma aberration (B4). Since some of the configurations and functions described in Embodiment 1 can be applied to Embodiment 2, the same configurations and functions are denoted by the same reference numerals, and their descriptions are omitted.

[0055] An example of a configuration for controlling sixth-order coma aberration (B6) is described with reference to Fig. 7A. In Fig. 7A is a third deflector 701 to the configuration in Fig. 2A, and a thickness of the second multipole 206 differs from a thickness of the first multipole 203.

[0056] The third deflector 701 is arranged between the relay lens 204 and the relay lens 205 and controls the distance R2 between the electron beam impinging on the second multipole 206 and the axis 111 of the optical system independently of the distance R1 between the electron beam impinging on the first multipole 203 and the axis 111 of the optical system. The second multipole 206, together with the six-pole field, forms a four-pole field superimposed on a six-pole field.

[0057] The total values ​​B2_tot of B2 and B4_tot of B4 generated in the charged particle beam device when the third deflector 701 is operated in addition to the first deflector 202 and the second deflector 207 are given according to (Formula 1) and (Formula 2), and the total amount B6_tot of the sixth-order coma aberration (B6) is given as follows. B6_tot=K7⋅R1+K8⋅R2+K9⋅θ1+B6_init

[0058] Here, K7 · R1 is a B6 component generated by a change in distance R1, K8 · R2 is a B6 component generated by a change in distance R2, K9 · θ1 is a B6 component generated by a change in inclination θ1, and B6_init is a B6 component originally present in the charged particle beam device. K7, K8, and K9 are coefficients determined by a magnitude or spatial shape of fields formed by the first multipole 203, the second multipole 206, and the objective lens 105. A spatial shape of a field in which a multipole is formed is controlled by a thickness of the multipole.

[0059] When the thickness of the first multipole 203 and the thickness of the second multipole 206 are different from each other, K1 and K2 in (Formula 1) have different values, K4 and K5 in (Formula 2) have different values, and K7 and K8 in (Formula 3) have different values, even under the condition that the second-order astigmatism (A2) between the two multipoles is canceled. With K1 ≠ K2, K4 ≠ K5, and K7 ≠ K8, (Formula 1), (Formula 2), and (Formula 3) can be solved as simultaneous equations of R1, R2, and θ1. That is, by adjusting R1, R2, and θ1, B2_tot, B4_tot, and B6_tot can be set to desired values, for example, zero. Each of the coefficients K1 to K9 is calculated based on the change values ​​of B2, B4, and B6 caused by the control performed for each of the first deflector 202, the second deflector 207, and the third deflector 701. B6_init is measured together with B2_init and B4_init.

[0060] However, when the thickness of the first multipole 203 and the thickness of the second multipole 206 differ from each other, the first-order astigmatism (A1) generated in the first multipole 203 cannot be canceled by the A1 generated in the second multipole 206, provided that the second-order astigmatism (A2) between them is canceled. Therefore, in Embodiment 2, the four-pole field is superimposed on the six-pole field formed by the second multipole 206, and an amount of the superimposed four-pole field is controlled to cancel the remaining A1 component.

[0061] With reference to Fig. In the configuration described in Figure 7A, the sixth-order coma aberration (B6) can be controlled together with the fourth-order coma aberration (B4). Since the total amount of the charged particle beam irradiated onto the sample can be further increased by controlling B6, the element distribution image can be generated in a shorter time.

[0062] The configuration for controlling the sixth-order coma aberration (B6) is not limited to the Fig. 7A and may also include the Fig. 7B and Fig. 7C shown configurations. In Fig. 7B, the thickness of the first multipole 203 and the thickness of the second multipole 206 differ from each other, and the four-pole field superimposes the six-pole field formed by the first multipole 203. In Fig. 7C, the thickness of the first multipole 203 and the thickness of the second multipole 206 differ from each other, and the third multipole 702, which is arranged at a position that is visually different from that of the first multipole 203 and the second multipole 206, forms at least one of a four-pole field and a two-pole field. As shown in Fig. 7A, the third deflector 701 controls the distance R2 between the electron beam incident on the second multipole 206 and the axis 111 of the optical system independently of the distance R1 between the electron beam incident on the first multipole 203 and the axis 111 of the optical system.

[0063] Similar to the description of Embodiment 1, a case will be described where an initial state before the aberration control performed in the above control in the present embodiment is a state where the electron beams pass through the centers of the lenses and the multipole in the initial state, that is, a state where the axis of the optical system and the trajectory of the electron beam coincide with each other. When the initial state before the above control deviates from the initial state described above, the same effect can be achieved by defining the distance R1, the distance R2, and the inclination θ1 in the above control by the relative distance from the trajectory of the electron beam and a shift amount of the inclination in the initial state before the above control is performed, instead of the distance and angle with respect to the axis 111 of the optical system.

[0064] Also in the configurations of the Fig. 7B and Fig. 7C are solved by solving (Formula 1), (Formula 2), and (Formula 3) as simultaneous equations of R1, R2, and θ1. By adjusting R1, R2, and θ1, B2_tot, B4_tot, and B6_tot can be set to desired values, for example, zero. The first-order astigmatism (A1) caused by R2 ≠ R1 is canceled by controlling the magnitude of at least one of the four-pole field and the two-pole field formed by the third multipole 702.

[0065] The embodiments of the charged particle beam device according to the present invention have been described above. The charged particle beam device according to the present invention is not limited to the above-mentioned embodiments and can be implemented by modifying components without deviating from the spirit of the invention. A plurality of the components disclosed in the above embodiments can be combined as appropriate. Some of the components may be removed from all of the components disclosed in the above embodiments. Lists of reference symbols 100 lens bodies 101 Electron source 102 Converging lens 103 Converging lens 104 aperture 105 objective lens 106 Sample 107 Intermediate lens 108 Projection lens 109 Detector 110 Control unit 111 Axis of the optical system 120 Aberration Corrector 201 focusing lens 202 first distractor 203 first multipole 204 Transfer lens 205 transfer lens 206 second multipole 207 second deflector 208 focusing lens 300 P0 samples 301 P1 pattern 302 P2 pattern 303 P3 pattern 304 P4 pattern 601 transfer lens 602 deflectors 603 transfer lens 604 deflectors 605 transfer lens 606 transfer lens 607 focusing lens 608 Multipole 701 third deflector 702 third multipole QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 5188846A

[0004]

Claims

[1] An aberration corrector in which a relay lens is arranged between a first multipole and a second multipole, the first multipole and the second multipole each forming a multipole field containing a component of a six-pole field, the aberration corrector comprising: a first deflector configured to control at least a distance between a charged particle beam incident on the first multipole and an axis of an optical system and an azimuth angle of the charged particle beam incident on the first multipole; a second deflector configured to control at least an inclination between a charged particle beam incident on an objective lens and the axis of the optical system and an azimuth angle of the charged particle beam incident on the objective lens; and a control unit configured to control the first deflector and the second deflector, wherein the control unit performs a first control performed on the first deflector and a second control performed on the second deflector such that at least a part of a second-order coma aberration caused by the first control is canceled by a second-order coma aberration caused by the second control. [2] The aberration corrector according to claim 1, wherein the control unit performs the first control and the second control based on a measurement value of a second-order coma aberration, a change in the second-order coma aberration caused by the first control, and a change in the second-order coma aberration caused by the second control. [3] The aberration corrector according to claim 2, wherein the control unit measures a second-order coma aberration using an observation image or a projection pattern. [4] A charged particle beam apparatus for producing an observation image of a sample by irradiating the sample with a charged particle beam, the charged particle beam apparatus comprising: the aberration corrector according to claim 1. [5] A charged particle beam apparatus according to claim 4, further comprising: a display unit configured to display at least one of an amount and an orientation of a measured aberration. [6] An aberration corrector in which a relay lens is arranged between a first multipole and a second multipole, the first multipole and the second multipole each forming a multipole field containing a component of a six-pole field, the aberration corrector comprising: a first deflector configured to control at least a distance between a charged particle beam incident on the first multipole and an axis of an optical system and an azimuth angle of the charged particle beam incident on the first multipole; a second deflector configured to control at least one of the following: an inclination between a charged particle beam incident on an objective lens and the axis of the optical system and an azimuth angle of the charged particle beam incident on the objective lens; a third deflector configured to control at least a distance between a charged particle beam incident on the second multipole and the axis of the optical system and an azimuth angle of the charged particle beam incident on the second multipole; and a control unit configured to control the first deflector, the second deflector and the third deflector, wherein the control unit executes a first control performed on the first deflector, a second control performed on the second deflector, and a third control performed on the third deflector such that at least a part of the coma aberrations caused by at least two of the first control, the second control, and the third control is canceled. [7] Aberration corrector according to claim 6, wherein an amount of the multipole field formed by the first multipole differs from an amount of the multipole field formed by the second multipole, or a thickness of the first multipole differs from a thickness of the second multipole. [8] The aberration corrector according to claim 6, wherein the control unit superimposes a four-pole field on at least one of the first multipole and the second multipole, and cancels, by the four-pole field, at least a part of a first-order astigmatism generated by at least one of the first controller, the second controller, and the third controller. [9] An aberration corrector according to claim 6, further comprising: a third multipole configured to form at least one four-pole field and one two-pole field, wherein the control unit cancels at least a part of a first-order astigmatism generated by at least one of the first control, the second control and the third control by at least one of the four-pole field and the two-pole field. [10] The aberration corrector according to claim 6, wherein the control unit executes at least two of the first control, the second control, and the third control based on a change in coma aberrations caused by at least two of the first control, the second control, and the third control. [11] The aberration corrector according to claim 6, wherein the control unit measures a coma aberration using an observation image or a projection pattern. [12] A charged particle beam apparatus for producing an observation image of a sample by irradiating the sample with a charged particle beam, the charged particle beam apparatus comprising: the aberration corrector according to claim 6. [13] A charged particle beam apparatus according to claim 12, further comprising: a display unit configured to display at least an amount and / or an orientation of a measured aberration. [14] A control method for controlling an aberration corrector in which a relay lens is arranged between a first multipole and a second multipole, the control method comprising: Performing a first control performed on a first deflector configured to control at least one of a distance between a charged particle beam incident on the first multipole and an axis of an optical system and an azimuth angle of the charged particle beam incident on the first multipole, and performing a second control performed on a second deflector configured to control at least one of an inclination between a charged particle beam incident on an objective lens and the axis of the optical system and an azimuth angle of the charged particle beam incident on the objective lens, such that at least a part of a second-order coma aberration caused by the first control is canceled by a second-order coma aberration caused by the second control. [15] A control method for controlling an aberration corrector in which a relay lens is arranged between a first multipole and a second multipole, the control method comprising: Performing a first control performed on a first deflector configured to control at least a distance between a charged particle beam incident on the first multipole and an axis of an optical system and an azimuth angle of the charged particle beam incident on the first multipole, a second control performed by a second deflector configured to control at least one of the following: an inclination between a charged particle beam incident on an objective lens and the axis of the optical system and an azimuth angle of the charged particle beam incident on the objective lens, and a third control performed by a third deflector configured to control at least a distance between a charged particle beam incident on the second multipole and the axis of the optical system or an azimuth angle of the charged particle beam incident on the second multipole so as to cancel at least a portion of the coma aberrations generated by at least two of the first control, the second control, and the third control.

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