Charge particle blasting device and aberration correction method

Abstract

Charge particle beam device comprising: an optical charge particle system that irradiates a sample (220) with a charge particle beam (103, 104, 106, 108) from a charge particle source (201); a detector (215) that detects electrons emitted by an interaction between the charge particle beam (103, 104, 106, 108) and the sample (220); and a controller (238), wherein the optical charge particle system includes an aberration corrector (209) that corrects the aberration of the charge particle beam (103, 104, 106, 108) and has multipoles (101, 701-704) of several stages, each multipole (101, 701-704) containing several poles (102) and generating a predetermined multipole field by applying a predetermined correction voltage or a predetermined correction current to the several poles (102), wherein the aberration corrector (209) is able to generate several multipole fields in a superimposed manner in the multipoles (101,to generate the multiple stages (101, 701-704) in order to correct the aberration of the charge particle beam (103, 104, 106, 108), characterized in that the controller (238) corrects a value of the predetermined correction voltage or correction current for each first multipole field of the multiple multipole fields to be generated in a multipole (101, 701-704) of any stage from the multiple stages, which is to be applied to the multiple poles (102) of the multipole (101, 701-704) to generate the first multipole field, in order to correct a shift of an observation image obtained based on the electrons detected by the detector (215) by irradiating the sample (220) with the charge particle beam (103, 104, 106, 108) before and after the first multipole field is generated. eliminate, and if a diameter of a circle formed by connecting distal ends of the multiple poles (102) of the multipole (101, 701-704),μ is and a distance between the multipoles (101, 701-704) d is, a relationship of 5μ > d > 0.5μ is satisfied.

Description

Technical field

[0001] The present invention relates to a charge particle beam device and an aberration correction method for a charge particle beam device which includes an aberration correction device. background

[0002] In a semiconductor manufacturing process for a semiconductor device where miniaturization has progressed, dimensional measurement of the sample's structure and defect inspection are performed using a charge particle beam device. A scanning electron microscope (SEM), used for dimensional measurement and defect inspection, can scan a sample surface with a narrow electron beam in a vacuum, detect secondary electrons emitted by the sample, and display a magnified image of the sample surface on a monitor. Since the signal intensity of the secondary electrons emitted by the sample changes according to the sample's structure at an electron beam incidence position, the SEM can detect fine irregularities on the sample surface as the strength of the signal intensity.

[0003] The electron beam is affected by chromatic aberration, caused by fluctuations in electron energy, geometric aberration, represented by spherical aberration, diffraction aberration, caused by electron ripple, and similar aberrations, and is therefore not focused to a single point. As the beam diameter of the electron beam increases with the influence of aberration, the resolution of the SEM image decreases. The influence of aberration is particularly pronounced in electron beams with low accelerating voltages, which are used for dimensional measurement and defect inspection. To reduce the influence of these aberrations, some scanning electron microscopes for inspection or measurement applications capable of acquiring high-resolution SEM images are equipped with an aberration corrector that corrects both chromatic and geometric aberrations.

[0004] The aberration corrector contains multi-stage multipoles and generates several types of multipole fields in a superimposed manner to correct aberrations. However, the multipole field generated by the aberration corrector is sensitive to manufacturing variations such as processing, assembly, and power output of the aberration corrector, and the distribution of the multipole field generated by the aberration corrector deviates from a theoretically defined field distribution (hereafter referred to as multipole distortion). If multipole distortion is present, aberration correction cannot be performed according to theory.

[0005] PTL 1 discloses a configuration comprising “a device with an aberration corrector with multipoles mounted thereon, a device for correcting a parasitic dipole field and a device for correcting a parasitic 4-pole field, which are provided to correct a parasitic dipole field and a parasitic 4-pole field which are generated by mechanical and electrical deviation of the multipole when a sample surface is observed using charged particles, storage means for storing a correction value when a multipole field of a certain stage of the aberration corrector is shifted in advance by a predetermined amount in the X and Y directions, and correction means for correcting the parasitic dipole field and the parasitic 4-pole field using a correction magnitude stored in the storage means.”

[0006] PTL 2 describes how “an aberration correction magnitude is calculated by measuring an aberration coefficient of an optical system forming a charge particle beam device. At the same time, an actual value of a power supply control value to be applied to an aberration corrector is measured. Based on the aberration correction magnitude and the actual value of the power supply control value, an adjustment magnitude for parasitic aberration is calculated to suppress any parasitic aberration magnitude generated in the aberration corrector.” Citation list for patent literature PTL 1: JP 2006-114305 A PTL 2: JP 2013-149492 A Overview of the invention Technical problem

[0007] In the related prior art, the distortion of the multipole contained in the aberration corrector is considered a parasitic field, and the parasitic field is extended to several parasitic multipole fields. The techniques described in PTL 1 and PTL 2 also reduce the influence of the distortion of the multipole according to this concept.

[0008] In PTL 1, the parasitic field is extended to the parasitic dipole field and the parasitic 4-pole field to correct the parasitic field. Therefore, a correction magnitude for the parasitic dipole field and a correction magnitude for the parasitic 4-pole field per unit of the intensity of the multipole field are pre-stored for each multipole, and thus the multipole field is generated after the parasitic dipole field and the parasitic 4-pole field have been generated.

[0009] If in PTL 2 a relationship between the correction magnitude for parasitic aberration with respect to the intensity of the multipole field changes depending on the intensity of the multipole field, although the relationship changes over time, the correction magnitude for parasitic aberration is determined taking the influence into account.

[0010] In any case, the correction magnitude is determined according to the intensity of the multipole field to be generated by the multipole. However, according to the inventors' study, an aberration measurement error is included in the measurement data of the aberration magnitude, proportional to the aberration magnitude itself. If the correction magnitude is determined according to the intensity of the generated multipole field, the correction magnitude for correcting the parasitic field deviates from the originally required correction magnitude due to the aberration measurement error, and thus the accuracy of the aberration correction is reduced.

[0011] The present invention was made with regard to the above problems and achieves a highly accurate aberration correction by directly suppressing a parasitic field due to the distortion of a multipole in a charge particle beam device that includes an aberration corrector, without having to determine a correction magnitude according to the intensity of a multipole field. Solution to the problem

[0012] A charge particle beam device, which is an aspect of the present invention, is provided with an optical charge particle system that irradiates a sample with a charge particle beam from a charge particle source, a detector that detects electrons emitted by an interaction between the charge particle beam and the sample, and a controller. The optical charge particle system includes an aberration corrector that corrects the aberration of the charge particle beam and has multi-stage multipoles, wherein the multipole contains several poles and generates a predetermined multipole field by applying a predetermined correction voltage or correction current to the multiple poles, wherein the aberration corrector is capable of generating multiple multipole fields in a superimposed manner in the multipoles of the multiple stages to correct the aberration of the charge particle beam.and the controller for a first multipole field, which is to be generated in a multipole of any stage of the several stages, corrects a value of the specified correction voltage or the specified correction current, which is to be applied to the several poles to generate the first multipole field, in order to eliminate a movement of an observation image, which is obtained based on the electrons detected by the detector by irradiating the sample with the charge particle beam before and after the generation of the first multipole field.

[0013] An aberration correction method for a charge particle beam device, which constitutes a further aspect of the present invention, is provided. The charge particle beam device comprises an aberration corrector that corrects an aberration of a charge particle beam, a detector that detects electrons emitted by an interaction between the charge particle beam and a sample, and a controller that controls the aberration corrector. The aberration corrector comprises multiple stages, the multipole having several poles and generating a predetermined multipole field by applying a predetermined correction voltage or correction current to the multiple poles. An aberration correction table is provided for calculating a theoretical value of the correction current or correction voltage to be applied to the multiple poles of the aberration corrector's multipole.to correct the aberration of the charge particle beam, and a distortion correction table for calculating a correction value of the correction current or correction voltage to be applied to the multiple poles of the aberration corrector multipole to correct the distortion of the aberration corrector multipole is stored, and the controller measures the aberration of the charge particle beam, obtains the theoretical value of the correction current or correction voltage to be applied to the multiple poles of the aberration corrector multipole to correct the aberration of the charge particle beam using the measured aberration of the charge particle beam and the aberration correction table, obtains a shift of an observation image for each of the multiple multipole fields to be generated in the multipoles of the multiple stages,which is obtained based on the electrons detected by the detector by irradiating the sample with the charge particle beam before and after the multipole field is generated, and obtains the correction value of the correction current or correction voltage to be applied to the multiple poles of the multipole to generate the multipole field using the shift of the observation image and the distortion correction table, and obtains the correction current or correction voltage to be applied to the multiple poles of the multipoles of the multiple stages by correcting the theoretical value by the correction value. Advantageous effects of the invention

[0014] Even if there is a distortion of the multipole, aberration correction can be performed with high accuracy by directly suppressing the parasitic field.

[0015] Further items and new features will become apparent from the description of this specification and the accompanying drawings. List of characters [ Fig. 1] Fig. Figure 1 is a representation describing a correction procedure for a distortion of a multipole. [ Fig. 2] Fig. Figure 2 is a schematic representation of a scanning electron microscope with an aberration corrector mounted on it. [ Fig. 3A] Fig. 3A is a flowchart of aberration correction by the aberration corrector. [ Fig. 3B] Fig. 3B is a detailed flowchart of step S109. [ Fig. 4] Fig. Figure 4 is a representation illustrating the types of multipole fields that will be generated by the aberration corrector for each multipole. [ Fig. 5] Fig. 5 is an example of a controller hardware configuration. [ Fig. 6] Fig. Figure 6 is a representation showing an example of an orthogonal coordinate system for performing distortion correction. [ Fig. 7] Fig. Figure 7 is a representation to describe a problem caused by an interaction between the stages. [ Fig. 8] Fig. 8 is an example of an operating screen in a simple mode. [ Fig. 9] Fig. Figure 9 is an example of an operating screen in precision mode. Description of the embodiments

[0016] A method for correcting a parasitic field due to distortion of multipoles in the present embodiment is described with reference to Fig. 1 described. An aberration corrector contains multipoles stacked in several stages. Fig. Figure 1 shows a beam shape of primary electrons (electron beam) passing through the multipole 101 of an arbitrary stage forming the aberration corrector. However, it is difficult to represent the beam shape of the electron beam precisely, which is why the beam shape is shown schematically.

[0017] A first stage (the top stage) of Fig. Figure 1 shows a state without the application of a multipole field. An electron beam 103 passes through a central axis of the multipole 101, and the beam shape of the electron beam 103 is circular at this time.

[0018] The multipole 101 in this example 12 has poles 102, and the multipole fields can be superimposed by controlling the strength of an electric field (if the poles are electrodes) or a magnetic field (if the poles are magnetic poles) generated by each of the 12 poles 102. The beam shape of the electron beam is distorted by the effect of the multipole field generated by the multipole. Assuming that the beam shape without aberration is a perfect circle, the electron beam that actually enters has a beam shape distorted from the perfect circle due to the influence of the aberration on the aberration corrector.The aberration corrector, which contains the multipole, corrects chromatic aberration or geometric aberration by imparting a reverse aberration to the electron beam through the action of the multipole fields to correct the deformation of the beam shape and causes the beam shape of the electron beam to approximate the perfect circle (the ideal shape).

[0019] A second stage of Fig. Figure 1 shows a beam shape when the multipole 101 applies an undistorted 6-pole field, and the beam shape of an electron beam 104 is distorted into a triangle by the effect of the 6-pole field. When the multipole 101 generates the undistorted 6-pole field, no shift in the observed image occurs because there is no deviation of the center of mass of the electron beam. This is illustrated in the drawing by positioning a center of mass 105 of the electron beam 104 in the middle of the multipole 101.

[0020] A third stage of Fig. Figure 1 schematically illustrates a beam shape when the multipole 101 applies a distorted 6-pole field. The beam shape of an electron beam 106 at this time is deformed into a polygonal shape, which differs from a triangular shape (the ideal shape), due to the influence of the distortion. The center of mass 107 of the electron beam 106 is positioned at a location different from the center of the multipole 101. This indicates that the deviation of the center of mass of the electron beam occurs due to the influence of the distortion, resulting in a shift in the observed image. Since this distortion is caused by manufacturing variations such as processing, assembly, and power output of the aberration corrector, it is unavoidable.

[0021] A fourth level (lowest level) of Fig. Figure 1 illustrates a distortion correction method according to the present embodiment. In the distortion correction method of the present embodiment, attention is paid to a displacement of the observed image caused by distortion. A non-uniform field is superimposed by adjusting the strength of an electric or magnetic field generated by some poles (here pole 102c) of the 12 poles 102, thus positioning a center of gravity 109 of the beam shape of an electron beam 108 in the center of the multipole 101. As a result, the distortion resulting from manufacturing variations is canceled out by the non-uniform fields, and the beam shape of the electron beam 108 also becomes the triangular shape, which is the ideal shape.Note that although the example described is one where the number of poles to be set is one, the number of poles to be set can be single or multiple depending on the non-uniform field to be generated.

[0022] Note that although the example of a 6-pole field has been described, the same applies to a 4-pole field and an 8-pole field. There are two types of aberration correctors, a magnetic field type and an electrostatic type, classified by the type of pole, but an effect can be achieved for both types.

[0023] The multipole field generated by the multipole for aberration correction does not cause any movement of the observed image if there is no distortion of the multipole. In the present embodiment, a correction for generating the non-uniform field is performed in such a way that the movement of the observed image is eliminated for every multipole field for every multipole by utilizing this property, for the multipole field actually generated at the time of observation. Therefore, it is possible to precisely eliminate the influence of the multipole distortion.

[0024] Fig. Figure 2 is a schematic representation of a scanning electron microscope with an aberration corrector mounted on it. A cathode 201, a first anode 202, and a second anode 203 form a charge particle source (electron gun) and are controlled by an electron gun controller 223. The electron gun controller 223 applies an extraction voltage between the cathode 201 and the first anode 202, and therefore primary electrons are emitted from the cathode 201 at a predetermined current density. The primary electrons are accelerated by an accelerating voltage applied between the cathode 201 and the second anode 203 and emitted into the subsequent stage.

[0025] The emitted primary electrons are focused by a first condenser lens 204, the excitation current of which is controlled by a first condenser lens controller 224. The primary electrons focused by the first condenser lens 204 are limited to a predetermined current at the opening of a movable objective stop 205. The primary electrons that have passed through the movable objective stop 205 are aligned to a beam trajectory parallel to an optical axis by a second condenser lens 206, the excitation current of which is controlled by a second condenser lens controller 225.

[0026] The primary electrons, having passed through the second condenser lens 206, strike an aberration corrector 209 and are directed onto an electron trajectory to correct chromatic aberration, geometric aberration, or both. The excitation current and the applied voltage of the aberration corrector 209 are controlled by an aberration corrector controller 227. The primary electrons, having passed through the aberration corrector 209, are focused at a suitable position on an optical axis 214 by a third condenser lens 211, the excitation current of which is controlled by a third condenser lens controller 229. The primary electrons focused by the third condenser lens 211 are focused by an objective lens 218, whose excitation current is controlled by an objective lens controller 234, onto a wafer 220 arranged on a table 219.The excitation current of the objective lens 218 is set based on a working distance measured by a sample height measuring device 222 controlled by a table controller 235.

[0027] A braking power supply 221, controlled by a braking voltage controller 236, is connected to table 219. The primary electrons are slowed down by generating a voltage between the objective lens 218 and the wafer 220 using the braking power supply 221.

[0028] The primary electrons are scanned two-dimensionally onto the wafer 220 by a first scanning deflector 217, which is controlled by a first deflector controller 233. Secondary electrons are generated through an interaction between the primary electrons and the wafer 220. The generated secondary electrons pass through the objective lens 218 and form a scattering spot on a secondary electron conversion plate 212. The secondary electrons are scanned on the secondary electron conversion plate 212 by the first scanning deflector 217, and tertiary electrons are generated through an interaction with the secondary electron conversion plate 212. The tertiary electrons are deflected by an E × B deflector 213, whose applied voltage and excitation current are controlled by an E × B controller 232, in a direction of a detector 215 controlled by a detector controller 231 and are detected by a detector 215.The detected tertiary electrons are converted into an electrical signal, processed by the controller 238, and displayed as an SEM image on a display device 237. If a field of view of the SEM image is moved, the stage 219 is moved by the controller 235, or an irradiation position of the primary electrons on the wafer 220 is moved by an image-shift deflector 216 controlled by the first deflector controller 233.

[0029] If a central axis of the aberration corrector 209 deviates from the optical axis 214, the primary electrons incident on the aberration corrector 209 are aligned to an optical axis 150 by a two-stage deflector 208 controlled by a second deflector controller 226, and the primary electrons emitted by the aberration corrector 209 are aligned to the optical axis 150 by a two-stage deflector 210 controlled by a third deflector controller 228.

[0030] An astigmatism corrector 207 controlled by an astigmatism corrector controller 230 corrects a parasitic astigmatism of an electron optical system.

[0031] The Aberration Corrector 209 is an aberration corrector that is created by stacking the in Fig. The multipoles shown in Figure 1 are constructed in several stages and can correct chromatic and geometric aberrations. For example, in the case of a 4-pole and 8-pole aberration corrector, predefined electromagnetic 4-pole and 8-pole fields are formed by the multipoles of the stages of aberration corrector 209. If 12 poles (electrodes and magnetic poles) are used as multipoles, electromagnetic dipole, 6-pole, and 12-pole fields can also be generated in a superimposed manner, in addition to the 4-pole and 8-pole fields.

[0032] Note that the charge particle beam device equipped with the aberration corrector of the present embodiment is not based on the one described in Fig. 2 is limited to the scanning electron microscope shown and can also be applied to a scanning transmission electron microscope, a transmission electron microscope, a scanning ion microscope, a focused ion beam device and the like.

[0033] Fig. Figure 3A shows a flowchart of aberration correction performed by the controller 238 through the aberration corrector 209. The timing at which the aberration correction is performed according to this sequence is not particularly restricted. The timing is not limited to timing prior to the start of dimensional measurement or defect inspection, and examples include timing at which an optical condition such as an accelerating voltage is changed, timing at which atmospheric pressure or temperature is drastically changed, and the like.

[0034] Aberration correction is started (step S100), and first the stage controller 235 moves the stage 219 into an observation position (step S101). If a calibration sample for measuring the aberration, which will be described later, is mounted on the stage 219 as a standard sample, the stage 219 is moved so that the calibration sample enters the field of view of the SEM.

[0035] In step S102, an optical condition for acquiring the SEM image is set. The optical condition includes the accelerating voltage controlled by the electron gun controller 223, the braking voltage controlled by the braking voltage controller 236, the excitation currents of the condenser lens controlled by the condenser lens controllers 224, 225 and 229, the excitation current of the objective lens controlled by the objective lens controller 234 and the excitation currents of various deflectors.

[0036] In step S103, the correction current or correction voltage of the aberration corrector 209 is set according to the set optical state.

[0037] In step S104, the central axis of the aberration corrector 209 and the optical axis 214 are adjusted so that they are aligned with each other by the two-stage deflector 208, which is provided on the electron beam incidence side of the aberration corrector 209, and the two-stage deflector 210, which is provided on the electron beam emission side.

[0038] In step S105, the astigmatism is corrected by the aberration corrector 209 to increase the sharpness of the REM image.

[0039] In step S106, for example, the aberration of the SEM image of the calibration sample is measured. A known measurement procedure can be used to measure the aberration. It is determined whether the measured aberration is equal to or less than a target aberration magnitude (step S107), and if the measured aberration is equal to or less than the target aberration magnitude, the aberration correction process is terminated (step S110). If, on the other hand, the deviation is greater than the target aberration magnitude, a value for the correction current or voltage applied to each pole of the multipole forming the aberration corrector is calculated according to the magnitude of the aberration. The current or voltage value in this stage is the value of the correction current or voltage at which the multipole exhibits no distortion, that is, generates a theoretically defined multipole field (step S108).

[0040] Fig. Figure 4 illustrates the type of multipole field to be generated in each multipole by the aberration corrector 209 for aberration correction. Each line indicates the chromatic or geometric aberration corrected by the aberration corrector 209, correcting a primary aberration up to a tertiary aberration. Each line illustrates the stage of the multipole. In this example, to correct the primary to tertiary chromatic aberrations or the primary to tertiary geometric aberrations listed as aberration names, it is necessary to generate the pole field surrounded by a frame 401 in the first-stage multipole by superimposing it.Since a ratio of the strength of the multipole field to be corrected is theoretically determined for each chromatic or geometric aberration of a given order, the correction current or voltage applied to each pole can theoretically be calculated according to the strength of each aberration to be corrected. However, due to the influence of the distortion of each multipole of the aberration corrector 209, this theoretical value is insufficient to achieve adequate aberration correction.

[0041] In step S109, the correction current or voltage applied to each pole of the multipole forming the aberration corrector is corrected to eliminate the influence of the multipole's distortion (hereafter referred to as "distortion correction"). Details of this step are described later. The aberration is then measured by the aberration corrector 209 after distortion correction (step S106). The distortion correction of the aberration corrector 209 is repeated until the measured aberration is equal to or less than the target aberration magnitude. Note that if, finally, the aberration measured in step S106 is found to be equal to or less than the target aberration magnitude, it is desirable to record the state of the aberration corrector.

[0042] Fig. Figure 3B shows a detailed flowchart of step S109. First, the multipole for correcting the parasitic aberration is selected (step S300). For example, the first-stage multipole is selected. Next, the multipole field output by the multipole is selected (step S301). For example, one of the multipole fields contained in frame 401 is selected (see Figure 3B). Fig. 4), for example, a slanted 4-pole field to correct an aberration ImA1, is selected. Subsequently, the correction current or correction voltage, which was selected in step S108 (see Fig. 3A) was calculated, applied to each pole of the first-stage multipole, and the slanted 4-pole field for correcting aberration ImA1 is generated (step S302).

[0043] In step S303, the displacement of the observed image due to the generation of the oblique 4-pole field for correcting aberration ImA1 is detected. If there is no distortion of the first-stage multipole, the generated oblique 4-pole field only deforms the beamform and does not cause a displacement of the observed image. Therefore, in step S304, a distribution of the multipole field is corrected to eliminate the displacement of the observed image. In particular, a non-uniform field with a direction and magnitude that shifts the center of gravity of the observed image to the center of the multipole can be superimposed. Therefore, the controller 238 maintains, in tabular form (table), the positional deviation of the center of gravity before and after the application of the multipole field and the correction magnitude of the correction current or voltage to be applied to each pole to correct the positional deviation.Such a correction of the multipole field distribution is repeated for all multipole fields to be generated by the multipole (step S305). As a result, in the example of... Fig. 4. The correction current or voltage for which the distortion is corrected is obtained such that the shift of the observed image does not occur when the multipole field is applied for each of the eight types of multipole fields to be generated by the first-stage multipole. When the distortion correction is complete for all multipole fields to be generated by the first-stage multipole, the distribution correction is performed similarly for each of the multipole fields for the other stages (step S306).

[0044] In the example of the first-stage multipole, the sum of the correction currents or correction voltages obtained in step S305 for the eight types of multipole fields is applied to the poles, thereby generating the eight types of multipole fields in which the distribution of the multipole field is corrected in a superimposed manner.

[0045] Next, the correction current, or the correction current for which the distortion is corrected, is set in the aberration corrector 209, and the optical axis adjustment (step S307) and astigmatism correction (step S308) are performed. These steps are the same procedure as steps S104 and S105 in [reference missing]. Fig. 3A.

[0046] Note that in step S303, either a sample structure image (for example, a structure of the calibration sample) or an electron source image can be used as the observation image. Since the sample structure image can be obtained by two-dimensional scanning of the electron beam through the first scanning deflector 217, when the sample structure image is used, the displacement of the observation image is derived from the movement of the sample structure's center of gravity before and after the application of the multipole field. Because the displacement of the observation image is derived from the movement of the sample structure's center of gravity, a highly accurate measurement can be performed. On the other hand, when the electron source image is used, the electron beam is scanned at the movable objective stop 205 by a second scanning deflector 239 controlled by a second scanning deflector controller 240.At this time, the primary electrons that can reach the wafer 220 are confined to the shape of the movable objective stop 205. If no aberration is present, the electron source image exhibiting the shape of the movable objective stop 205 is observed; if an aberration is present, the electron source image distorted by the aberration is observed. The shift of the observed image is obtained from the movement of the center of mass of the electron source image before and after the application of the multipole field. As described above, the distribution of the multipole field can be measured from the SEM image by using either the observed image of the sample structure or the electron source image.

[0047] Fig. Figure 5 shows an example of a hardware configuration of the controller 238. The controller 238 contains a processor 501, a random access memory (RAM) 502, a storage device 503, an input / output interface 504, a display interface 505, a network interface 506, and an input / output port 507, which are interconnected via a bus 508. A graphical user interface (GUI) is implemented by connecting the input / output interface 504 to an input device 509, such as a keyboard and a pointing device, and by connecting the display interface 505 to the display device 237. Note that in addition to the input device 509, user instructions can also be entered by speech. The network interface 506 is an interface for connecting to a network.It may be possible to send and receive commands and image data acquired by the charge particle beam device from another terminal (not shown) connected via a network. Input and output port 507 is equipped with an optical charge particle system as shown in [reference missing]. Fig. 2 shown charge particle beam device, a controller of a device forming the detector and a sensor provided in the charge particle beam device (for example a barometer or the like) and sends and receives commands and measurement data ("sensing data").

[0048] The memory device 503 is typically formed by non-volatile memory such as a hard disk drive (HDD), a solid-state drive (SSD), read-only memory (ROM), or flash memory, and stores a program executed by the controller 238, a table required for executing the program, image data acquired by the charge particle beam device, and the like. The RAM 502 temporarily stores a program, data required for executing the program, and the like, according to an instruction from the processor 501. The processor 501 executes a program loaded into the RAM 502 from the memory device 503.

[0049] The storage device 503 stores a program for controlling the charge particle beam device, control data, and image data, but only programs and control data specifically relating to the present embodiment are shown here. An aberration correction program 510 is a program that... Fig. 3A and Fig. 3B executes the sequence shown and represents as routines an aberration measurement unit 511 (which performs the processing of step S106), a distortion detection unit 512 (which performs the processing of step S303) and a distortion correction unit 513 (which performs the processing of step S304).

[0050] An aberration correction table 521 is a table used in step S108 and is a table for the theoretical calculation of the correction current or correction voltage to be applied to the aberration corrector 209 to correct the aberration measured by the aberration measuring unit 511. A distortion correction table 522 is a table used in step S304 and is a table for calculating the correction magnitude of the correction current or correction voltage to correct the displacement of the observed image detected by the distortion detection unit 512.

[0051] Note that distortion correction requires generating a non-uniform field to move the center of gravity of the observed image to the center of the multipole. When the displacement of the observed image is captured in an orthogonal coordinate system, the correction magnitude can be easily converted from a displacement magnitude. Furthermore, since the distribution correction of the multipole field is performed by the fixed poles forming the orthogonal axes, the reproducibility of the distortion correction can be improved.

[0052] Fig. Figure 6 shows an example of the orthogonal coordinate system for performing distortion correction. As in the upper part (orthogonal coordinate system 1) of Fig. As shown in Figure 6, the orthogonal coordinate system contains an h-axis (black) and a v-axis (gray) that are orthogonal to each other, and both axes intersect at a center O of the multipole. To move the multipole field by a vector that has the centroid 600 of the beam shape, which indicates the distortion of the multipole, as its starting point and the center O of the multipole as its endpoint, it is only necessary to generate a non-uniform field in the direction of the h-axis and the v-axis, with the magnitude projected onto the h-axis and the v-axis. A pole that generates a non-uniform field in one direction of the h-axis is a pole pair consisting of a pole 102h1 and a pole 102h2, and a pole that generates a non-uniform field in one direction of the v-axis is a pole pair consisting of a pole 102v1 and a pole 102v2.

[0053] Orthogonal coordinate system 1 is an example where the axis directions coincide on a straight line connecting opposite poles, but the axis directions can also be arranged between adjacent poles. Such an example is represented as orthogonal coordinate systems 2-1 and 2-2. In orthogonal coordinate systems 2-1 and 2-2, the h-axis and v-axis are interchanged. In each case, the non-uniform field in the direction of the h-axis is generated by four poles 102h1a, 102h1b, 102h2a, and 102h2b, and the non-uniform field in the direction of the v-axis is generated by four poles 102v1a, 102v1b, 102v2a, and 102v2b.Note that in the orthogonal coordinate systems 2-1 and 2-2, as shown in the diagram, a line connecting the pole pairs 102h1a and 102h2a and a line connecting the pole pairs 102v1a and 102v2a are orthogonal to each other, as are a line connecting the pole pairs 102h1b and 102h2b and a line connecting the pole pairs 102v1b and 102v2b. Pole 102h1a and pole 102h1b are adjacent to each other, pole 102h2a and pole 102h2b are adjacent to each other, pole 102v1a and pole 102v1b are adjacent to each other, and pole 102v2a and pole 102v2b are adjacent to each other. However, as in a middle part and a lower part of . Fig. As shown in Figure 6, in the case of the orthogonal coordinate system 2-1, the polarities of adjacent poles are the same, but the polarities of neighboring poles are opposite. The orthogonal coordinate system 1 is preferably used to correct the 6-pole field, and the orthogonal coordinate system 2-1 or 2-2 is preferably used to correct the 8-pole field.

[0054] Furthermore, in the case of a small aberration corrector, an interaction (hereinafter referred to as the interstage interaction) between the poles of multipoles of different stages cannot be ignored. The present problem is addressed with reference to Fig. 7 described. In the example of Fig. The aberration corrector 209 contains multipoles 701 to 704. It is assumed that the multipoles have an inner diameter φ (here referred to a diameter of a circle formed by connecting the distal ends of the poles of the multipoles) and that adjacent multipoles have a distance d.

[0055] If the distance d is of a sufficient size, since there is no or negligible interaction between the stages, a parasitic field 710 generated by the distortion of the multipole and a non-uniform field 711, which corrects the distortion, act at the same position on the optical axis and cancel each other out. However, due to the presence of interaction between the stages, one point of action of the parasitic field 710 and the non-uniform field 711 deviates in one direction along the optical axis (direction of the Z-axis). In this case, the parasitic field 710 and the non-uniform field 711 cannot cancel each other out.

[0056] With reference to Fig. In the distortion correction method described in 3B, the distortion adjustment is performed directly on the multipole field generated according to the magnitude of the aberration for each multipole and each multipole field, and thus no new aberration is generated by the distortion correction. This minimizes the influence of the interaction between the stages during distortion correction. With the aberration corrector, the influence of the interaction between the stages appears when 5φ > d, but with the distortion correction method of the present embodiment, the distortion correction can be performed without the influence of the interaction between the stages when d > 0.5φ.

[0057] Fig. 8 and Fig. Figure 9 shows an example of an operating screen for performing distortion correction according to the present embodiment. Fig. Figure 8 is an example of an 800 operating screen in a simple mode. The 800 operating screen contains an image display area 801 for displaying the observation image, an area 802 for setting the observation conditions, and an area 803 for easily adjusting aberration correction. An input field for entering, for example, the magnification of the observation image, the number of imaging frames, the movement of the stage, and the like, is provided in area 802 for setting the observation conditions. A button for advancing the execution sequence of Fig. 3A and Fig. 3B is provided in area 803 for easy adjustment of aberration correction. For example, STEP 1 is an adjustment button for setting the optical condition (Step S102), STEP 2 is an adjustment button for setting the optical axis (Step S104), STEP 3 is an adjustment button for correcting astigmatism (Step S105), and STEP 4 is an adjustment button for correcting aberrations (Steps S106 to S109). As a result, aberration correction that would otherwise require complex adjustments can be easily performed by following this procedure.

[0058] Fig. Figure 9 is an example of an operating screen 900 in precision mode. In addition to the operating screen of the operating screen 800 in simple mode, operating screen 900 includes an area 901 for the precision setting of aberration correction. The area 901 for the precision setting of aberration correction allows the user to control the process of Fig. 3B to execute while manually determining the appropriate correction magnitude. For example, specifying the number of stages of the multipole to perform the distribution correction of the multipole field, specifying the multipole field, specifying the correction magnitude for the distribution correction, and automatically calculating the correction magnitude for the distribution correction can be performed. Reference symbol list 101, 701 to 704 Multipole 102 poles 103, 104, 106, 108 electron beam 105, 107, 109 Focus 201 Cathode 202 first anode 203 second anode 204, 206, 211 Condenser lens 205 movable lens stop 207 Astigmatism Corrector 208, 210 Second-stage deflector 209 Aberration corrector 212 Secondary electron conversion plate 213 E × B-deflector 214 optical axis 215 Detector 216 Image shift deflector 217 first scanning deflector 218 lens 219 Table 220 wafers 221 Brake power supply 222 Sample height measuring device 223 electron gun controller 224, 225, 229 condenser lens controller 226 second deflector controller 227 Aberration correction controller 228 third deflector controller 230 Astigmatism Corrector Controller 231 Detector Controller 232 E × B controller 233 first deflector controller 234 lens controllers 235 table controllers 236 Brake voltage controller 237 Display unit 238 Controller 239 second scanning deflector 240 second scanning deflector controller 501 processor 502 RAM 503 Storage device 504 Input and output I / F 505 Display-I / F 506 Network I / F 507 Entrance and Exit Port 508 Bus 509 Input device 510 Aberration Correction Program 511 Aberration measuring unit 512 Distortion Detection Unit 513 Distortion Correction Unit 521 Aberration correction table 522 Distortion correction table 710 parasitic field 711 uneven field 800, 900 operating screen QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] JP 2006114305 A

[0006] JP 2013149492 A

[0006]

Claims

[1] Charge particle beam device comprising: an optical charge particle system that irradiates a sample with a charge particle beam from a charge particle source; a detector that detects electrons emitted by an interaction between the charge particle beam and the sample; and a controller wherein the optical charge particle system includes an aberration corrector that corrects the aberration of the charge particle beam and has multi-stage multipoles, The multipole contains several poles and generates a predetermined multipole field by applying a predetermined correction voltage or correction current to the several poles. wherein the aberration corrector is able to generate several multipole fields in a superimposed manner in the multipoles of the multiple stages in order to correct the aberration of the charge particle beam, and wherein the controller for a first multipole field, which is to be generated in a multipole of any stage from the multiple stages, corrects a value of the specified correction voltage or the specified correction current, which is to be applied to the multiple poles to generate the first multipole field, in order to eliminate a movement of an observation image obtained based on the electrons detected by the detector by irradiating the sample with the charge particle beam, before and after the first multipole field is generated. [2] Charge particle beam device according to claim 1, wherein the controller performs a distortion correction for each of the multiple multipole fields to be generated in the multipoles of the multiple stages in order to correct the value of the predetermined correction voltage or correction current to be applied to the multiple poles for generating the multipole field in such a way that the observation image obtained on the basis of the electrons detected by the detector by irradiating the sample with the charge particle beam is not moved before and after the multipole field is generated, and generates the multiple multipole fields in a superimposed manner by applying a correction voltage or correction current to the multiple poles of the multipoles of the multiple stages, to which the value of the predetermined correction voltage or predetermined correction current for which the distortion correction is performed is added. [3] Charge particle beam device according to claim 1, wherein the controller obtains a displacement of the observation image from the observation image before the first multipole field is generated and the observation image after the first multipole field is generated and generates a non-uniform field to eliminate the displacement of the observation image in a superimposed manner in the first multipole field. [4] Charge particle beam device according to claim 3, wherein The multipole contains several poles, first pairs of poles facing each other, and second pairs of poles facing each other, and a straight line connecting the first pairs of poles and a straight line connecting the second pairs of poles are orthogonal to each other. The controller generates the non-uniform field to eliminate the shift of the observed image by combining a first non-uniform field, to be generated by the first pairs of poles, and a second non-uniform field, to be generated by the second pairs of poles. [5] Charge particle beam device according to claim 3, wherein The multiple poles of the multipole contain the first to fourth pole pairs, which face each other; a straight line connecting the first pole pairs and a straight line connecting the second pole pairs are orthogonal to each other; a straight line connecting the third pole pairs and a straight line connecting the fourth pole pairs are orthogonal to each other; each of the first pole pairs is adjacent to each of the third pole pairs; and each of the second pole pairs is adjacent to each of the fourth pole pairs. The controller generates the non-uniform field to eliminate the shift of the observed image by combining a first non-uniform field, which is to be generated by the first and third pole pair, and a second non-uniform field, which is to be generated by the second and fourth pole pair. [6] Charge particle beam device according to claim 5, wherein the polarities of the pole of the first pole pair and the pole of the third pole pair that are adjacent to each other are the same, and the polarities of the pole of the second pole pair and the pole of the fourth pole pair that are adjacent to each other are the same. [7] Charge particle beam device according to claim 5, wherein the polarities of the pole of the first pole pair and the pole of the third pole pair that are adjacent to each other are different, and the polarities of the pole of the second pole pair and the pole of the fourth pole pair that are adjacent to each other are different. [8] Charge particle beam device according to claim 1, wherein, if a diameter of a circle formed by connecting distal ends of the multiple poles of the multipole is φ and a distance between the multipoles is d, a relationship of 5φ > d > 0.5φ is satisfied. [9] Charge particle beam device according to claim 1, further comprising a display device that shows an operating screen, wherein the controller corrects the value of the specified correction voltage or correction current to be applied to the multiple poles generating the first multipole field for the first multipole field of the multipole of any stage determined by the operating screen. [10] Aberration correction method of a charge particle beam device, wherein The charge particle beam device includes an aberration corrector that corrects the aberration of a charge particle beam, a detector that detects electrons emitted by an interaction between the charge particle beam and a sample, and a controller that controls the aberration corrector. the aberration corrector contains multiples of several stages, The multipole contains several poles and generates a predetermined multipole field by applying a predetermined correction voltage or correction current to the several poles. An aberration correction table for calculating a theoretical value of the correction current or correction voltage to be applied to the multiple poles of the aberration corrector multipole to correct the aberration of the charge particle beam, and a distortion correction table for calculating a correction value of the correction current or correction voltage to be applied to the multiple poles of the aberration corrector multipole to correct the distortion of the aberration corrector multipole, are stored, and the controller measures the aberration of the charge particle beam, Using the measured aberration of the charge particle beam and the aberration correction table, the theoretical value of the correction current or correction voltage to be applied to the multiple poles of the aberration corrector multipole in order to correct the aberration of the charge particle beam is obtained. for each of the multiple multipole fields to be generated in the multipoles of the multiple stages, a shift of an observational image is obtained, which is based on the electrons detected by the detector by irradiating the sample with the charge particle beam before and after the multipole field is generated, and the correction value of the correction current or correction voltage is obtained, which is to be applied to the multiple poles of the multipole in order to generate the multipole field using the shift of the observational image and the distortion correction table, and the correction current or correction voltage, which is to be applied to the multiple poles of the multipoles of the multiple stages, is obtained by correcting the theoretical value by the correction value. [11] Aberration correction method according to claim 10, wherein the distortion correction table stores as a correction value a correction current or a correction voltage to generate a non-uniform field to eliminate the shift of the observed image for each of the multipoles of the multiple stages. [12] Aberration correction method according to claim 10, wherein the controller applies the correction current or correction voltage, which is to be applied to the multiple poles of the multipoles of the multiple stages, to the aberration corrector and establishes an optical axis of the charge particle beam.

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