Aberration correction device and aberration correction method

Abstract

This aberration correction device for correcting aberration of an optical system has a first multipole lens that generates a first hexapole field, a second multipole lens that generates a second hexapole field, a first deflector that generates a first deflection field, and a second deflector that generates a second deflection field. The first deflector is disposed in a position of a beam cross between the first multipole lens and the second multipole lens, and the second deflector is disposed between the first deflector and the first multipole lens or the second multipolar lens. The aberration correction device deflects back, by means of the second deflector, a beam deflected by means of the first deflector, and passes the beam through the center of at least one of the first multipole lens or the second multipole lens, thereby correcting at least one of two-fold symmetric first-order astigmatism (A1) and five-fold symmetric fourth-order astigmatism (A4).

Description

Technical Field

[0001] The present invention relates to an aberration corrector and an aberration correction method, and for example, to a scanning transmission electron microscope equipped with the aberration corrector.

Background Art

[0002] In a scanning electron microscope (SEM) or a scanning transmission electron microscope (STEM), the higher the resolution, the thinner the diameter of the electron beam (probe) that scans the sample. The probe diameter is mainly limited by the third-order spherical aberration (C3) of the objective lens. In recent years, however, devices equipped with an aberration corrector for correcting this aberration have been put into practical use.

[0003] As an aberration corrector, there is known one in which two multipole lenses that generate a sextupole field and two axially symmetric lenses are arranged therebetween. For example, Patent Document 1 describes that "two circular lenses having the same focal length are arranged between a first sextupole and a second sextupole at an interval twice the focal length of each other, and further from a plane passing through the center of the sextupole adjacent to each circular lens, at an interval corresponding to the focal length of the circular lens."

[0004] In this way, the C3 aberration can be corrected by the aberration corrector. However, in practical use, aberrations called parasitic aberrations occur due to the incompleteness of the aberration corrector, that is, the displacement of the individual poles constituting the multipole lens, the variation in the magnetic characteristics of the pole material, and the axial displacement of each lens.

[0005] The generated parasitic aberrations of the third order or lower are a two-fold symmetric primary astigmatism (A1) aberration, a one-fold symmetric secondary coma (B2) aberration, a three-fold symmetric secondary astigmatism (A2) aberration, a two-fold symmetric tertiary star (S3) aberration, and a four-fold symmetric tertiary astigmatism (A3) aberration.

[0006] As parasitic aberrations, there are higher-order aberrations of the fourth order and above. When correcting the higher-order aberrations, the aberration-free angular range (flat area) is expanded. As a result, it becomes possible to achieve both a high probe current and a high spatial resolution. Examples of fourth-order parasitic aberrations include a fifth-order symmetric fourth-order astigmatism (A4) aberration, a first-order symmetric fourth-order coma (B4) aberration, and a third-order symmetric fourth-order three-lobe (D4) aberration.

[0007] Regarding a method for correcting the S3 aberration and the A3 aberration, which are the main third-order parasitic aberrations, Patent Document 2 discloses a method for independently correcting a second-order symmetric third-order star aberration (S3) and a fourth-order symmetric third-order astigmatism (A3) that are secondarily generated by providing a spherical aberration corrector. Patent Document 2 states that, "In a charged particle beam device including a spherical aberration correction device in which a transfer lens is disposed between a first multipole lens and a second multipole lens, a first deflecting means for deflecting a charged particle beam so as to incline the charged particle beam incident on the first multipole lens with respect to the optical axis, a second deflecting means for deflecting a charged particle beam so as to shift the charged particle beam incident on the second multipole lens with respect to the optical axis, a third deflecting means for deflecting a charged particle beam emitted from the second multipole lens so as to return it onto the optical axis, and a control means for controlling the first deflecting means, the second deflecting means, and the third deflecting means, the control means corrects the second-order symmetric third-order star aberration without affecting the fourth-order symmetric third-order astigmatism, or corrects the fourth-order symmetric third-order astigmatism without affecting the second-order symmetric third-order star aberration, and supplies a control signal to the first deflecting means and the second deflecting means so that the shift amount of the charged particle beam incident on the second multipole lens with respect to the optical axis changes in conjunction with the inclination angle of the charged particle beam incident on the first multipole lens with respect to the optical axis."

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, in the prior art, a method for accurately correcting fourth-order parasitic aberrations such as A4 aberration independently has not been established. When the A4 aberration becomes apparent, it is necessary to reassemble the aberration corrector, which is one of the reasons for the reduction in production yield.

[0010] As a method for correcting higher-order parasitic aberrations of fourth order or higher, there is a method of deflecting the trajectory of the electron beam passing through the multipole lens constituting the aberration corrector. However, when correcting higher-order aberrations in this way, there are secondary large parasitic aberration fluctuations of third order or lower (especially A1 aberration).

[0011] As the currently practical A1 aberration correction method, there are a method of translating the optical axis parallel to the multipole lens and a method of superimposing a quadrupole field on the multipole lens. The problem in the case of performing higher-order aberration correction by deflecting the trajectory of the electron beam passing through the multipole lens is that it cannot be compatible with the A1 correction method of translating the optical axis parallel to the multipole lens. This is because when the A1 aberration is corrected by translating the optical axis parallel to the multipole lens, the correction for higher-order aberrations is canceled.

[0012] Therefore, when performing higher-order parasitic aberration by deflecting the trajectory of the electron beam passing through the multipole lens, it is essential to superimpose a quadrupole field on the multipole lens as an A1 aberration correction method. In general, a multipole lens of 12 poles or more is required to superimpose a quadrupole field in an arbitrary direction on the multipole lens. This is because it is necessary to superimpose a sextupole field for correcting C3 aberration, a deflection field for canceling the deflection field generated secondarily during sextupole field generation, and a quadrupole field. Furthermore, in order to superimpose multipole fields of arbitrary intensities and directions, it is necessary to control each pole independently. Therefore, a power supply equivalent to the number of poles is required, and an increase in the number of power supplies increases the beam deflection sensitivity due to noise, which becomes a factor deteriorating the image resolution.

[0013] The present invention has been made to solve such problems, and an object thereof is to provide an aberration correction device and an aberration correction method capable of achieving both correction of A1 aberration or A4 aberration and improvement of image quality by reducing the beam deflection sensitivity of a multipole lens.

Means for Solving the Problems

[0014] An example of the aberration correction device according to the present invention is an aberration correction device for correcting the aberration of an optical system, a first multipole lens that generates a first hexapole field, a second multipole lens that generates a second hexapole field, a first deflector that generates a first deflection field, a second deflector that generates a second deflection field, and having the first deflector is disposed at the position of the beam cross between the first multipole lens and the second multipole lens, the second deflector is disposed between the first deflector and the first multipole lens or the second multipole lens, the aberration correction device returns the beam deflected by the first deflector by the second deflector, passes the beam through the center of at least one of the first multipole lens or the second multipole lens, thereby correcting at least one of the two-fold symmetric primary aberration (A1) or the five-fold symmetric fourth-order aberration (A4), characterized by

[0015] An example of the aberration correction method according to the present invention is an aberration correction method in a charged particle beam device including an aberration correction device for correcting the aberration of an optical system, the aberration correction device a first multipole lens that generates a first hexapole field, a second multipole lens that generates a second hexapole field, a first deflector that generates a first deflection field, A second deflector that generates a second deflection field, and has, The first deflector is disposed at the position of the beam cross between the first multipole lens and the second multipole lens, The second deflector is disposed between the first deflector and the first multipole lens or the second multipole lens, The aberration correction method is, Returning the beam deflected by the first deflector by the second deflector, Passing the beam through at least one of the centers of the first multipole lens or the second multipole lens, Thereby, correcting at least one of the two-fold symmetric primary aberration (A1) or the five-fold symmetric fourth-order aberration (A4), and includes.

Advantages of the Invention

[0016] According to the aberration correction device and the aberration correction method according to the present invention, it is possible to achieve both correction of A1 aberration or A4 aberration and improvement of image quality by reducing the beam deflection sensitivity of the multipole lens.

Brief Description of the Drawings

[0017]

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Figure 11

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not construed as being limited to the description of the embodiments shown below. It will be easily understood by those skilled in the art that the specific configuration can be changed without departing from the spirit or gist of the present invention.

[0019] Expressions such as "first", "second", "third", etc. in this specification and the like are attached for identifying components, and do not necessarily limit the number or order.

[0020] In the drawings and the like, the positions, sizes, measurements, and ranges of each configuration shown may not represent the actual positions, sizes, measurements, and ranges in order to facilitate understanding of the invention. Therefore, in the present invention, it is not limited to the positions, sizes, shapes, and ranges disclosed in the drawings and the like.

[0021] (Example 1) <Configuration of Charged Particle Beam Device> FIG. 1 is a diagram showing an example of the configuration of a charged particle beam device according to Example 1 of the present invention. In Example 1, the charged particle beam device is a scanning transmission electron microscope (STEM: Scanning Transmission Electron Microscopy) device, but it may be other charged particle beam devices.

[0022] The STEM device 100 includes a lens barrel 101 and a control unit 102. The lens barrel 101 has an electron source 103 for generating an electron beam, a focusing lens group 104, an aberration corrector 105, an objective lens 106, a sample stage 107, a sample holder 108, an imaging lens group 109, an annular detector 110 for detecting electrons scattered by the sample, a transmission electron detector 111 for detecting electrons transmitted through the sample, and an imaging camera 112 for imaging a Ronchigram.

[0023] Although not shown in the figure, the control unit 102 includes an electron gun control circuit, an irradiation lens control circuit, a condenser aperture control circuit, an aberration corrector control circuit, a deflector control circuit, an objective lens control circuit, a camera control circuit, and the like.

[0024] The control unit 102 can acquire the values of the target devices via the control circuit, and can create arbitrary electron optical conditions by controlling the target devices via the control circuit. The control unit 102 is an example of a control mechanism for realizing the control of the lens barrel 101.

[0025] <Configuration of the Aberration Corrector> FIG. 2 is a diagram showing an example of the configuration of the aberration corrector 105 of Example 1. The aberration corrector 105 is a device for correcting the aberration of the optical system. The aberration corrector 105 has a first deflection coil 201, a first adjustment lens 202, a first multipole lens 203, a first transfer lens 204, a third multipole lens 205, a second transfer lens 206, a third transfer lens 207, a second deflection coil 208, a fourth transfer lens 209, a second multipole lens 210, a third deflection coil 211, and a second adjustment lens 212.

[0026] The first multipole lens 203 generates a first sextupole field, and the second multipole lens 210 generates a second sextupole field. The first multipole lens 203 and the second multipole lens 210 are in a conjugate relationship using the first transfer lens 204, the second transfer lens 206, the third transfer lens 207, and the fourth transfer lens 209. That is, in this configuration, since the principal plane of the first multipole lens 203 is projected 1:1 onto the second multipole lens 210, by applying a sextupole field to the first multipole lens 203 and applying a sextupole field of the same intensity but opposite phase to the second multipole lens 210 as that of the first multipole lens 203, the secondary astigmatism (A2) aberration can be canceled and a negative spherical aberration (C3) can be generated.

[0027] After correcting the C3 aberration of the objective lens with the negative C3 aberration generated in this way, a fifth-order astigmatism (A5) remains except for parasitic aberrations. By applying a sextupole field to the third multipole lens 205 disposed at an intermediate position between the first transfer lens 204 and the second transfer lens 206, an A5 aberration can be generated to cancel the remaining A5 aberration.

[0028] In this way, aberrations up to the fifth order can be corrected, but aberrations called parasitic aberrations occur due to misalignment of the individual poles constituting the multipole lens, variations in the magnetic properties of the pole materials, and misalignment of the axes of each lens.

[0029] Parasitic aberrations include a two-fold symmetric primary astigmatism (A1) aberration, a one-fold symmetric secondary coma (B2) aberration, a three-fold symmetric secondary astigmatism (A2) aberration, a two-fold symmetric tertiary star (S3) aberration, a four-fold symmetric tertiary astigmatism (A3) aberration, a five-fold symmetric fourth-order astigmatism (A4) aberration, a one-fold symmetric fourth-order coma (B4) aberration, a three-fold symmetric fourth-order three-lobe (D4) aberration, etc. Correcting parasitic aberrations is important for the practical use of the aberration correction device.

[0030] Note that the configuration of the aberration correction device 105 shown in FIG. 2 is an example and is not limited thereto. It may include at least one transfer optical system (for example, a transfer lens) and at least two multipoles.

[0031] For the off-axis beam trajectory 213, the beam is inclined by the first transfer lens 204 to create a beam crossing with the third multipole lens 205 and is incident on the second transfer lens 206. That is, the third multipole lens 205 is arranged at the position of the beam crossing between the first multipole lens 203 and the second multipole lens 210. The number of positions of the beam crossing between the first multipole lens 203 and the second multipole lens 210 is two in the example of FIG. 2, but is not limited thereto. Note that it is preferable that the number of positions of the beam crossing between the first multipole lens 203 and the second multipole lens 210 is an even number.

[0032] The second deflection coil 208 is arranged between the third multipole lens 205 and the second multipole lens 210. As a modification, it is also possible to arrange the second deflection coil 208 between the third multipole lens 205 and the first multipole lens 203.

[0033] In this embodiment, the third multipole lens 205 acts as the first deflector to generate a first deflection field (Note: In this embodiment, the third multipole lens 205 instead of the first deflection coil 201 is referred to as the "first deflector"). Further, the second deflection coil 208 acts as the second deflector to generate a second deflection field.

[0034] <Configuration of the multipole lens> As the multipole lens used in the aberration correction device 105, for example, a 12-pole lens is used. FIG. 3 is an example of the structure of a 12-pole lens. By setting the number of poles to 12, the 6-pole fields in two directions can be added together, so that a 6-pole field with an arbitrary phase can be generated.

[0035] The 12-pole lens 300 has a configuration in which 12 magnetic poles 304, to which a main coil 302 and a sub-coil 303 are attached, are arranged with respect to a ring-shaped magnetic circuit 301. The main coil 302 is a coil for exciting a 6-pole field for generating negative third-order spherical aberration, and the sub-coil 303 is a coil for generating each multi-pole field for canceling a deflection field or a 4-pole field that is secondarily generated during the generation of the 6-pole field. In this embodiment, the 12-pole lens 300 shown in FIG. 3 is used as the first multi-pole lens 203, the second multi-pole lens 210, and the third multi-pole lens 205.

[0036] <Generation of 6-pole field> FIG. 4 shows an excitation method of the main coil for generating a 6-pole field. As shown in FIG. 4, the main coils 302 are connected in series with every other one. The directly connected main coils 302 are made to have opposite polarities to each other. By exciting these main coils 302 using a power source 401, it is possible to generate 6-pole fields in two directions (X direction and Y direction).

[0037] The current amount for exciting the main coil 302 is determined as follows, for example. Here, I A and I B are the current amounts flowing through their respective systems, and Xhex corresponds to the strength of the 6-pole field in the X direction to be generated, and Yhex corresponds to the strength of the 6-pole field in the Y direction to be generated. I A = Xhex … (Equation 1) I B = Yhex … (Equation 2) Thus, in order to generate 6-pole fields in an arbitrary direction using a 12-pole lens, it is sufficient to have at least two independent power sources. It is also possible to independently excite each pole using 12 independent power sources.

[0038] <Generation of deflection field> When generating deflection fields in two directions (X direction and Y direction) using 12 sub-coils 303, for example, the current amounts for exciting each sub-coil are determined as follows. Here, I nis the current flowing through the sub - coil in the n - o'clock direction (1 ≤ n ≤ 12), Xdef corresponds to the strength of the deflection field in the X - direction to be generated, and Ydef corresponds to the strength of the deflection field in the Y - direction to be generated.

[0039] When generating a deflection field in an arbitrary direction by controlling the current flowing through the 12 sub - coils in this way, 12 independent power supplies are required. I n = Xdef×cos(2π×n / 12) +Ydef×sin(2π×n / 12) … (Equation 3) Also, as shown in FIG. 5, a deflection field in two directions (X - direction and Y - direction) can be generated using two sets of sub - coils 303 facing four power supplies 501. For example, the four sub - coils can be excited as follows. I 12 = Ydef … (Equation 4) I3 = Xdef … (Equation 5) I6 = -Ydef … (Equation 6) I9 = -Xdef … (Equation 7) When generating a deflection field in an arbitrary direction by controlling the current flowing through the four sub - coils in this way, control is possible with a minimum of two independent power supplies. When controlling with two power supplies, the sub - coils in the 12 - o'clock direction and the 6 - o'clock direction are connected in series with opposite polarities to each other, and the sub - coils in the 3 - o'clock direction and the 9 - o'clock direction are connected in series with opposite polarities to each other.

[0040] <Generation of Quadrupole Field> When generating a quadrupole field in two directions (X - direction and Y - direction) using 12 sub - coils 303, for example, the current flowing through each sub - coil 303 is determined as follows. Here, I n is the current flowing through the sub - coil 303 in the n - o'clock direction (n = 1~12), Xquad corresponds to the strength of the deflection field in the X - direction to be generated, and Yquad corresponds to the strength of the deflection field in the Y - direction to be generated. When generating a deflection field in an arbitrary direction by controlling the current flowing through the 12 sub - coils 303 in this way, 12 independent power supplies are required. I n= Xquad×cos(4π×n / 12) +Yquad×sin(4π×n / 12) … (Equation 8)

[0041] <Superposition of multipole fields> When generating a sextupole field necessary for aberration correction with a multipole lens, not only the sextupole field but also a deflection field and a quadrupole field are generated due to the displacement of the positions of the individual dipoles constituting the multipole lens and the variation in the magnetic characteristics of the dipole material. Therefore, it is common to generate a sextupole field with the main coil and cancel out the unnecessary deflection field and quadrupole field with the sub-coil.

[0042] As described above, if twelve independent power supplies are used for the sub-coil, deflection fields and quadrupole fields in any direction can be superimposed. However, when using twelve independent power supplies, the influence of power supply noise increases.

[0043] Let the beam deflection sensitivity on the sample surface by each dipole in the multipole lens be d [pm / μA], the maximum current be I m [A], the power supply stability be s [ppm], and the number of poles be N. Then the total noise d N [pm] is given by the following equation. d N = 2×I m ×d×s×√N … (Equation 9) Therefore, it is desirable to minimize the number of power supplies used for the sub-coil.

[0044] If there is an unnecessary deflection field, there is a high risk that parasitic aberrations from low order to high order will increase due to the inclination of the beam central axis. Therefore, it is desirable to cancel out the unnecessary deflection field within the multipole lens. For an unnecessary quadrupole field, the central axis of the beam does not change and only the A1 aberration increases. Therefore, if correction means outside the multipole lens can be used, the number of power supplies used for the sub-coil can be reduced to a minimum of two.

[0045] <Method for correcting A1 aberration and A4 aberration> FIG. 6 is a diagram showing an example of a ray diagram when the conventional A1 aberration correction method currently in practical use is implemented using the aberration correction device 105 according to this embodiment.

[0046] The beam has a central orbit 601. In the aberration correction device 105, the optical axis passes through the center of each lens up to the third transfer lens 207. The optical axis is tilted by the second deflection coil 208, and the optical axis is translated parallel to the second multipole lens 210. The third deflection coil 211 is adjusted so that the optical axis passes through the center of the second adjustment lens 212.

[0047] In such orbit control, mainly A1 aberration occurs, but slightly higher-order aberrations of the third order or more occur. Therefore, the problem in the method of correcting higher-order aberrations by deflecting the orbit of the electron beam passing through the multipole lens described above is that it cannot be compatible with the A1 correction method shown in FIG. 6. This is because when the optical axis is translated parallel to the multipole lens to correct the A1 aberration as shown in FIG. 6, the correction amount of the corrected higher-order aberration is canceled. In that case, as a method of correcting the A1 aberration, it is essential to superimpose a quadrupole field on the multipole lens. As described above, an increase in the number of power supplies increases the beam deflection sensitivity due to noise, which causes a factor that degrades the image resolution.

[0048] FIG. 7 shows an example of a ray diagram in a method of correcting A1 aberration and A4 aberration as an example of the aberration correction method according to this embodiment. The beam has a central orbit 701. In the aberration correction device 105 according to this embodiment, the optical axis passes through the center of each lens up to the first transfer lens 204. The optical axis is tilted by the third multipole lens 205 with a superimposed deflection field. The second deflection coil 208 is adjusted so that the optical axis passes through the center of the second multipole lens 210.

[0049] By such orbit control, it is possible to mainly control A1 aberration and A4 aberration. If this method is used, it can be used as a method of correcting the A1 aberration within a range where the A4 aberration does not become a problem. That is, it is possible to correct the A1 aberration. Further, when the A1 aberration is corrected by another method, it is possible to correct the A4 aberration.

[0050] As a method for correcting the A1 aberration, it is possible to correct it by using the method shown in FIG. 6, in which the optical axis is tilted by the second deflection coil 208 and the optical axis is translated parallel to the second multipole lens 210. It is also possible to correct it by superimposing a quadrupole field on the multipole lens described above. However, since the number of power supplies increases, it is desirable to correct the A1 aberration by the method shown in FIG. 6.

[0051] FIG. 8 shows a detailed procedure for performing the orbit control shown in FIG. 7. In the Ronchigram image, the movement of the field position with respect to the sample corresponds to the shift movement of the beam, and the movement of the shadow 805 of the aperture of the irradiation system corresponds to the change in the tilt component of the beam.

[0052] After aligning the target 806 on the sample and the shadow of the aperture with the center of the camera's field of view, when a deflection field is applied to the third multipole lens 205, the shadow of the aperture and the target move. FIG. 801 shows a diagram in which the target 806 and the shadow 805 of the aperture are aligned with the center of the camera's field of view, and FIG. 802 shows a diagram in which the shadow 805 of the aperture and the target 806 have moved.

[0053] The moved target 806 and the shadow 805 of the aperture are returned to the center of the camera's field of view using the second deflection coil 208. The second deflection coil 208 is a deflector composed of two upper and lower stages, and by appropriately setting the upper and lower ratio, it is possible to independently control the shift component and the tilt component with respect to the target 806. That is, in the aberration correction device 105 according to the present embodiment, the second deflection coil 208 includes two deflection elements (for example, an upper coil and a lower coil), and thereby, the second deflection coil 208 can independently control the deflection and parallel movement of the beam.

[0054] Fig. 803 shows a diagram in which the shadow 805 of the aperture is moved to the center of the camera's field of view. Fig. 804 shows a diagram in which the target object 806 is further moved to the center of the camera's field of view from the state of Fig. 803. At this time, by controlling while keeping the ratio of the magnitude of the deflection field applied to the third multipole lens 205 (for example, the excitation amount of the coil) to the excitation amount when returning with the second deflection coil 208 constant, when an arbitrary magnitude of deflection field is applied to the third multipole lens 205, orbit control for returning to the axis center as shown in Fig. 7 is possible.

[0055] In this way, the aberration correction device 105 according to this embodiment returns the beam deflected by the third multipole lens 205 with the second deflection coil 208 and passes the beam through the center of the second multipole lens 210. As a modification, the beam may be passed through the center of the first multipole lens 203, or the beam may be passed through the centers of both the first multipole lens 203 and the second multipole lens 210.

[0056] In this way, the aberration correction device 105 according to this embodiment corrects the A4 aberration, and the A1 aberration generated thereby is - deflecting the beam with the second deflection coil 208, and - translating the optical axis parallel to the hexapole field generated by the second multipole lens 210 to correct. In this way, both the A1 aberration and the A4 aberration can be corrected.

[0057] Note that although correcting both the A1 aberration and the A4 aberration as in this embodiment can reduce the aberration more comprehensively, in cases where it is not necessary to correct both, only either the A1 aberration or the A4 aberration may be corrected.

[0058] <Actual machine confirmation result> Luneburg diagrams with the A1 aberration after introducing a deflection field in four directions (X+ direction, X− direction, Y+ direction, Y− direction) of 0.02 AT each to the third multipole lens 205 from a state where the flat area (aberration-free angle range) has sufficiently expanded are shown in R1 to R4 of Fig. 9, respectively.

[0059] The Ronchiogram after introducing a deflection field in the X+ direction is R1, the Ronchiogram after introducing a deflection field in the X- direction is R2, the Ronchiogram after introducing a deflection field in the Y+ direction is R3, and the Ronchiogram after introducing a deflection field in the Y- direction is R4.

[0060] Since the A1 aberration appears as a two-fold symmetric figure on the Ronchiogram, 180° corresponds to one cycle. Therefore, if the rotation control of 180° can be achieved on the Ronchiogram, all phases of the A1 aberration can be generated.

[0061] When comparing R1 and R3, R3 and R2, R2 and R4, and R4 and R1 respectively, it can be seen that they are each rotated by 45 degrees relative to each other. From the above, when the deflection field applied to the third multipole lens 205 is rotated by 90° each time, it was confirmed in the actual machine that the shape of the A1 aberration appearing on the Ronchiogram is rotated by 45° each time.

[0062] Also, from the state where the flat area (aberration-free angle range) is sufficiently wide, a deflection field in four directions (X+ direction, X- direction, Y+ direction, Y- direction) of 0.3 AT is introduced to the third multipole lens 205 respectively, and after further correcting the aberration up to the third order, the Ronchiograms of the A4 aberration remaining are shown in R5 to R8 of FIG. 9 respectively.

[0063] The Ronchiogram when a deflection field is introduced in the X+ direction is shown as R5, the Ronchiogram when a deflection field is introduced in the X- direction is shown as R6, the Ronchiogram when a deflection field is introduced in the Y+ direction is shown as R7, and the Ronchiogram when a deflection field is introduced in the Y- direction is shown as R8.

[0064] Since the A4 aberration appears as a five-fold symmetric figure on the Ronchiogram, 72° corresponds to one cycle. Therefore, if the rotation control of 72° can be achieved on the Ronchiogram, all phases of the A4 aberration can be generated.

[0065] When comparing R5 with R7, R7 with R6, R6 with R8, and R8 with R5 respectively, it can be seen that they are each rotated by 18 degrees relative to each other. From the above, it was confirmed in the actual machine that when the deflection field applied to the third multipole is rotated by 90 degrees each time, the shape of the A4 aberration appearing in the Ronchi grating rotates by 18 degrees each time.

[0066] Figure 10 is a table showing the average value of the A4 aberration coefficient and the average value of the rotation angle of the A4 aberration pattern when a deflection field in four directions (X+ direction, X- direction, Y+ direction, Y- direction) is introduced at 0.3 AT and 0.6 AT for the third multipole lens 205 in a certain experiment.

[0067] Figure 11 is a graph showing the relationship between the coil excitation amount of the third multipole lens 205 and the generated A4 aberration coefficient in another experiment.

[0068] From Figure 11, it can be seen that the A4 aberration is linearly introduced with respect to the deflection field applied to the third multipole lens 205. This tendency holds for any of the four directions (X+ direction, X- direction, Y+ direction, Y- direction).

[0069] As described above, according to the aberration correction device and aberration correction method according to this embodiment, it is possible to achieve both the correction of the A1 aberration or A4 aberration and the improvement of the image quality by reducing the beam deflection sensitivity of the multipole lens.

[0070] Note that the present invention is not limited to the above-described embodiments, and various modifications are included. Also, for example, the above-described embodiments are those in which the configuration is described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Also, for a part of the configuration of each embodiment, it is possible to add, delete, or replace other configurations.

Explanation of Reference Numerals

[0071] 100…STEM apparatus (charged particle beam apparatus) 101…Column 102…Control unit 103… Electron source 104… Condenser lens group 105… Aberration corrector 106… Objective lens 107… Sample stage 108… Sample holder 109… Image forming lens group 110… Annular detector 111… Transmission electron detector 112… Imaging camera 201… First deflection coil 202… First adjustment lens 203… First multipole lens 204… First transfer lens 205… Third multipole lens (first deflector) 206… Second transfer lens 207… Third transfer lens 208… Second deflection coil (second deflector) 209… Fourth transfer lens 210… Second multipole lens 211… Third deflection coil 212… Second adjustment lens 213… Beam orbit 300… Multipole lens 301… Magnetic circuit 302… Main coil 303… Sub coil 304… Magnetic pole 401… Power supply 501… Power supply 601… Central orbit 701… Central orbit 805… Shadow of aperture 806… Target object

Claims

1. An aberration correction device for correcting the aberration of an optical system, comprising: a first multipole lens that generates a first hexapole field; a second multipole lens that generates a second hexapole field; a first deflector that generates a first deflection field; a second deflector that generates a second deflection field; and having the first deflector is disposed at a position of a beam cross between the first multipole lens and the second multipole lens; the second deflector is disposed between the first deflector and the first multipole lens or the second multipole lens; the aberration correction device returns the beam deflected by the first deflector by the second deflector, passes the beam through the center of at least one of the first multipole lens or the second multipole lens, thereby correcting at least one of the two-fold symmetric primary aberration (A1) or the five-fold symmetric fourth-order aberration (A4); An aberration correction device characterized by the above.

2. The aberration correction device according to claim 1, wherein the aberration correction device corrects the two-fold symmetric primary aberration (A1) and the five-fold symmetric fourth-order aberration (A4).

3. The aberration correction device according to claim 1, wherein the number of positions of the beam cross between the first multipole lens and the second multipole lens is an even number.

4. The aberration correction device according to claim 1, wherein the first deflector is a multipole lens.

5. The aberration correction device according to claim 1, wherein the second deflector includes two deflection elements, whereby the second deflector can independently control the deflection and parallel movement of the beam.

6. An aberration correction method in a charged particle beam device including an aberration correction device for correcting the aberration of an optical system, wherein the aberration correction device a first multipole lens that generates a first hexapole field; a second multipole lens that generates a second hexapole field; a first deflector that generates a first deflection field; a second deflector that generates a second deflection field; and having the first deflector is disposed at a position of a beam cross between the first multipole lens and the second multipole lens; the second deflector is disposed between the first deflector and the first multipole lens or the second multipole lens; the aberration correction method returns the beam deflected by the first deflector by the second deflector; Passing the beam through the center of at least one of the first multipole lens or the second multipole lens; Thereby correcting at least one of the second-order symmetric primary aberration (A1) or the fifth-order symmetric fourth-order aberration (A4); A method characterized by including the above. **Claim 7** In the aberration correction method according to claim 6, the aberration correction device corrects the second-order symmetric primary aberration (A1) and the fifth-order symmetric fourth-order aberration (A4). An aberration correction method. **Claim 8** In the aberration correction method according to claim 6, the number of beam crossing positions between the first multipole lens and the second multipole lens is an even number. An aberration correction method. **Claim 9** In the aberration correction method according to claim 7, The aberration correction device The second-order symmetric primary aberration (A1) generated by correcting the fifth-order symmetric fourth-order aberration (A4) - Deflecting the beam by the second deflector, and - Translating the optical axis parallel to the second sextupole field An aberration correction method characterized by correcting by the above.

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