Charged particle beam device

Abstract

To provide a charged particle beam device capable of correcting aberrations that occur when observing the outer periphery of a sample.SOLUTION: A charge particle beam device includes a sample stage that holds a sample, a charged particle beam source that emits a charged particle beam to be irradiated onto the sample, a lens that focuses the charged particle beam on the sample, an aberration corrector that corrects aberrations in the charged particle beam, a deflector that scans the charged particle beam, a detector that detects charged particles emitted from the sample as a result of being scanned with the charged particle beam, and a control unit that generates an observation image of the sample on the basis of a detection signal output from the detector and that controls the operation of each of the units, and the control unit controls the aberration corrector by comparing the position of the sample stage when observing the outer periphery of the sample with a correction table showing the relationship between the position of the sample stage and the control amount of the aberration corrector.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a charged particle beam device, and particularly to the measurement and inspection of the outer peripheral portion of a sample.

Background Art

[0002] Charged particle beam devices such as electron microscopes and ion microscopes are used for observing various samples having fine structures. Particularly in the manufacturing process of semiconductor devices, they are used for dimension measurement and defect inspection of patterns formed on semiconductor wafers. In order to improve the yield of semiconductor devices, it is necessary to measure and inspect not only the central portion but also the outer peripheral portion of the semiconductor wafer. However, in the outer peripheral portion, the electric field is disturbed, and there are cases where the electron beam cannot be irradiated to a desired position.

[0003] Patent Document 1 discloses a semiconductor inspection device that corrects the disturbance of the electric field at the outer peripheral portion of a sample. Specifically, by applying a voltage to a correction electrode provided outside the lower portion of the sample to generate a correction electric field, the disturbance of the electric field at the outer peripheral portion of the sample is corrected. The voltage applied to the correction electrode is controlled according to the distance between the position where the electron beam is irradiated and the outer peripheral portion of the sample, the tapered shape of the outer peripheral portion of the sample, and the thickness of the sample. The distance between the electron beam irradiation position and the outer peripheral portion of the sample is obtained from the distance between the electron beam irradiation position and the diameter of the sample and the center position.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, Patent Document 1 does not consider the aberration generated when observing the outer peripheral portion of the sample. In the outer peripheral portion of the sample, the observed image is distorted due to aberration generated by the asymmetry of the structure, which hinders the observation of the sample.

[0006] Therefore, an object of the present invention is to provide a charged particle beam apparatus capable of correcting aberrations generated when observing the outer peripheral portion of a sample.

Means for Solving the Problems

[0007] To achieve the above object, the present invention provides a charged particle beam apparatus including a sample stage for holding a sample, a charged particle beam source for emitting a charged particle beam irradiated onto the sample, a lens for focusing the charged particle beam onto the sample, an aberration corrector for correcting aberrations of the charged particle beam, a deflector for scanning the charged particle beam, a detector for detecting charged particles emitted from the sample by being scanned with the charged particle beam, and a control unit for generating an observation image of the sample based on a detection signal output from the detector and controlling operations of each unit. The control unit controls the aberration corrector by collating the position of the sample stage when observing the outer peripheral portion of the sample with a correction table showing the relationship between the position of the sample stage and the control amount of the aberration corrector.

Effects of the Invention

[0008] According to the present invention, it is possible to provide a charged particle beam apparatus capable of correcting aberrations generated when observing the outer peripheral portion of a sample.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2A

Figure 2B

Figure 3

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Figure 5A

Figure 5B

Figure 6A

Figure 6B

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13A

Figure 13B

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Mode for Carrying Out the Invention

[0010] Hereinafter, an embodiment of a charged particle beam apparatus according to the present invention will be described with reference to the accompanying drawings. A charged particle beam apparatus is an apparatus that observes or processes a sample by irradiating the sample with a charged particle beam, such as a scanning electron microscope, a scanning ion microscope, or a scanning transmission electron microscope. Hereinafter, as an example of a charged particle beam apparatus, a scanning electron microscope that observes a sample using an electron beam, which is one of the charged particle beams, will be described.

Embodiment

[0011] The overall configuration of the scanning electron microscope according to Embodiment 1 will be described with reference to FIG. 1. In the housing 110 of the scanning electron microscope, an electron gun 101, a condenser lens 102, a detector 105, an aberration corrector 131, a deflector 106, an objective lens 107, and a sample stage 109 are provided, and their operations are controlled by a control unit 121. Further, an input / output unit 122 used for inputting and outputting various data related to the observation image and a storage unit 123 for storing various data are connected to the control unit 121. Furthermore, the inside of the housing 110 is evacuated by a vacuum pump or the like, and a sample 108 is held on the sample stage 109. The sample 108 includes a calibration sample and an observation sample. Hereinafter, each part will be described. In FIG. 1, the vertical direction is the Z direction, and the horizontal directions are the X direction and the Y direction.

[0012] The electron gun 101 emits an electron beam that irradiates the sample 108. The condenser lens 102 focuses the electron beam emitted from the electron gun 101. The deflector 106 deflects the electron beam so as to scan the observation region of the sample 108. The objective lens 107 focuses the deflected electron beam on the observation region of the sample 108. The sample stage 109 is, for example, an electrostatic chuck that holds the sample 108 and moves in the XY plane to set the observation region of the sample 108 at a desired position. The position of the sample stage 109 is transmitted to the control unit 121. The detector 105 detects charged particles such as secondary electrons and reflected electrons emitted from the sample 108 by the irradiation of the electron beam, and transmits a detection signal to the control unit 121.

[0013] The control unit 121 is, for example, an arithmetic unit, and generates an observation image of the sample 108 based on the detection signal transmitted from the detector 105. The generated observation image is displayed on the display unit included in the input / output unit 122 or stored in the storage unit 123, and is used for dimensional measurement, defect inspection, etc. of the sample 108.

[0014] The aberration corrector 131 is disposed between the condenser lens 102 and the deflector 106, and corrects the aberration of the electron beam so that it becomes less than a predetermined value. The aberration corrected by the aberration corrector 131 includes, for example, chromatic aberration, coma aberration, spherical aberration, etc. An example of the aberration corrector 131 will be described with reference to FIGS. 2A and 2B.

[0015] FIG. 2A illustrates a Wien filter that corrects chromatic aberration. The Wien filter is configured such that the electric field E formed by the pair of electrodes 201A and 201B and the magnetic field B formed by the pair of magnetic poles 202A and 202B are orthogonal. The intensity of the electric field E is controlled by adjusting the voltage applied to the electrodes 201A and 201B. The magnetic poles 202A and 202B are constituted by a coil or a combination of a coil and a magnetic body, and the intensity of the magnetic field B is controlled by adjusting the excitation current supplied to the coil. Since the orthogonal electric field E and magnetic field B as shown in FIG. 2A exert a force in the opposite direction on the electron beam traveling from the electron gun 101 to the sample 108, the chromatic aberration can be corrected to less than a predetermined value by controlling the intensities of the electric field E and the magnetic field B according to the energy of the electron beam. Note that the correction of chromatic aberration by the Wien filter illustrated in FIG. 2A is limited to the X direction, and thus it may be combined with a Wien filter that corrects chromatic aberration in the Y direction in order to correct chromatic aberration in an arbitrary direction.

[0016] Also, when the Wien filter illustrated in FIG. 2A is disposed on the side of the sample stage 109 rather than the detector 105, it is possible to facilitate the arrival of secondary electrons and reflected electrons emitted from the sample 108 at the detector 105. The Wien filter does not exert a deflecting action on the electron beam traveling from the electron gun 101 to the sample 108, while having a deflecting action on secondary electrons and reflected electrons moving from the sample 108 in the direction of the detector 105. Therefore, in addition to controlling the Wien filter for correcting chromatic aberration, the Wien filter can be controlled so that secondary electrons and reflected electrons are easily drawn into the detector 105. On the other hand, in order to correct chromatic aberration while avoiding the influence on secondary electrons and reflected electrons as described above, the Wien filter illustrated in FIG. 2A may be disposed at a position farther from the sample stage 109 than the detector 105.

[0017] FIG. 2B illustrates a hexapole for correcting coma aberration. The hexapole is composed of magnetic poles 211A and 211B, magnetic poles 212A and 212B, and magnetic poles 213A and 213B disposed at equal distances from the central position. Each magnetic pole is disposed with an angular deviation of 60° when viewed from the central position, and is composed of a coil or a combination of a coil and a magnetic body. The polarities of adjacent magnetic poles are different, and magnetic fields are formed from the magnetic pole 211A toward the magnetic poles 212B and 213B, from the magnetic pole 212A toward the magnetic poles 213B and 211B, and from the magnetic pole 213A toward the magnetic poles 211B and 212B. The formed magnetic field is controlled by adjusting the exciting current supplied to the coil. The coma aberration is corrected to be less than a predetermined value by controlling the magnetic field.

[0018] The aberration corrector for correcting coma aberration may be a multipole of hexapole or higher, and may be constituted by a plurality of electrodes that form an electric field instead of a plurality of magnetic poles that form a magnetic field. When the aberration corrector for correcting coma aberration is constituted by a plurality of electrodes, the electric field controlled by adjusting the voltage applied to the electrodes corrects the coma aberration to less than a predetermined value. Further, the aberration corrector 131 is not limited to those illustrated in FIGS. 2A and 2B. For example, it may be a multipole lens constituted by a plurality of electrodes or magnetic poles that form a multipole field for correcting a plurality of aberrations. Furthermore, these aberration correctors may be configured in multiple stages.

[0019] Incidentally, when observing the outer peripheral portion of the sample 108, the observation image is distorted due to the aberration generated by the structural asymmetry, which hinders the observation of the sample 108. The amount of aberration generated varies depending on the distance from the outer edge of the sample 108 to the observation region, that is, the position of the sample stage 109 when observing the outer peripheral portion of the sample 108.

[0020] Therefore, in the first embodiment, based on the position of the sample stage 109 when observing the outer peripheral portion of the sample 108, the aberration corrector 131 is operated to correct the aberration generated when observing the outer peripheral portion of the sample 108, and an observation image with suppressed distortion is acquired. In order to operate the aberration corrector 131 based on the position of the sample stage 109 when observing the outer peripheral portion of the sample 108, a correction table showing the relationship between the position of the sample stage 109 and the control amount of the aberration corrector 131 is created in advance.

[0021] Using FIG. 3, an example of the flow of the process for creating the correction table will be described step by step.

[0022] (S301) A calibration sample is loaded into the scanning electron microscope. The calibration sample is a sample used for creating the correction table, and is a sample with a known shape and size, such as a silicon wafer having a circular shape, and is placed at the center of the sample stage 109.

[0023] (S302) The control unit 121 moves the sample stage 109 so that the observation region of the outer periphery of the calibration sample is disposed at the position irradiated with the electron beam. Specifically, the sample stage 109 is moved so that the electron beam is irradiated to any one of a plurality of measurement positions 401 illustrated in FIG. 4. The measurement positions 401 in FIG. 4 are 36 points provided in rotational symmetry on concentric circles sharing the center point 400 of the circular sample stage 109. Note that the measurement positions 401 are not limited to those in FIG. 4.

[0024] (S303) The control unit 121 operates each part in the housing 110 to acquire an observation image of the outer periphery of the calibration sample.

[0025] (S304) The control unit 121 calculates an aberration based on the observation image acquired in S303. The aberration is calculated based on, for example, the blur included in the observation image. When there are observation images before and after controlling the aberration corrector 131, or when there are observation images before and after changing the control values of each part in the scanning electron microscope so as to change the energy of the electron beam, the aberration may be calculated based on a value based on the difference between the two observation images, for example, a shift amount obtained from the two observation images. FIGS. 5A and 5B show an example of observation images before and after controlling the aberration corrector 131. A shift amount is obtained from such two observation images, and a chromatic aberration generated as an influence of the shift of the position where the electron beam is focused is calculated from the shift amount.

[0026] (S305) The control unit 121 determines whether or not the value of the aberration calculated in S304 is less than a predetermined threshold value. If the value of the aberration is less than the threshold value, the process proceeds to S307, and if it is greater than or equal to the threshold value, the process returns to S303 via S306. That is, the processes of S303 to S306 are repeated until the value of the aberration becomes less than the threshold value. Note that the threshold value is predetermined based on the correction accuracy of the aberration.

[0027] (S306) The control unit 121 controls the aberration corrector 131. When the processes of S303 to S306 are repeated a plurality of times, the control amount of the aberration corrector 131 may be set based on the change in the aberration value calculated in S304. For example, when the aberration value increases by increasing the control amount of the aberration corrector 131, the control amount is decreased.

[0028] (S307) The control unit 121 determines whether the number of data is sufficient. If the number of data is sufficient, the process proceeds to S308, and if it is insufficient, the process returns to S302. That is, the processes of S302 to S307 are repeated until a control amount at which the aberration value is less than the threshold value is obtained at all of the measurement positions 401 illustrated in FIG. 4.

[0029] (S308) The control unit 121 creates a correction table using the control amount of the aberration corrector 131 at which the aberration is less than the threshold value at each of the measurement positions 401. The created correction table is stored in the storage unit 123.

[0030] An example of the correction table is shown in FIGS. 6A and 6B. The correction table in FIG. 6A includes the position of the sample stage 109, the control amount of the aberration corrector 131, and the aberration. Note that the aberration is not essential, and it is sufficient that the control amount of the aberration corrector 131 at which the aberration is less than the threshold value is stored in the correction table at each position of the sample stage 109. Also, even if the position of the sample stage 109 is the same, the aberration value changes if the electron beam irradiation conditions such as the acceleration voltage of the electron beam are different. Therefore, as illustrated in FIG. 6B, a correction table for each electron beam irradiation condition may be created.

[0031] (S309) The calibration sample is carried out of the scanning electron microscope.

[0032] A correction table showing the relationship between the position of the sample stage 109 and the control amount of the aberration corrector 131 is created by the processing flow described with reference to FIG. 3. The created correction table is used for aberration correction.

[0033] Using FIG. 7, an example of the process flow of aberration correction will be described for each processing step.

[0034] (S701) The observation sample is carried into the scanning electron microscope. The observation sample is a sample to be subjected to dimensional measurement, defect inspection, etc.

[0035] (S702) The control unit 121 moves the sample stage 109 so that the observation region of the outer peripheral portion of the observation sample is disposed at the position irradiated with the electron beam, and acquires the position of the moved sample stage 109.

[0036] (S703) The control unit 121 controls the aberration corrector 131 by collating the position of the sample stage 109 acquired in S702 with the correction table. That is, the control amount read by collating the position of the sample stage 109 when observing the outer peripheral portion of the observation sample with the correction table is set for the aberration corrector 131. The aberration is corrected by the aberration corrector 131 to which the control amount read from the correction table is set so as to be less than the threshold value.

[0037] When the position of the sample stage 109 acquired in S702 is not stored in the correction table, the control amount at that position may be calculated by interpolation processing. That is, the control amounts corresponding to four positions close to the position of the sample stage 109 acquired in S702 are read from the correction table, and the control amount at that position may be calculated by interpolation processing using the four read control amounts.

[0038] When a correction table for each electron beam irradiation condition as illustrated in FIG. 6B is created, the correction table is selected according to the electron beam irradiation condition set when observing the observation sample, and the aberration corrector 131 is controlled based on the selected correction table.

[0039] (S704) The control unit 121 operates each part inside the housing 110 to acquire an observation image of the observation sample. Since the aberration corrector 131 is controlled in S703 so that the aberration becomes less than the threshold value, in S704, an observation image with distortion caused by aberration suppressed can be acquired. The acquired observation image is displayed on a display screen exemplified in FIG. 8, for example. The screen in FIG. 8 has a "Correction ON / OFF" button, and when the button is pressed, the ON and OFF of aberration correction are switched. Note that instead of pressing the "Correction ON / OFF" button, the control unit 121 may control a parameter for switching the ON and OFF of aberration correction.

[0040] (S705) The observation sample is carried out from the scanning electron microscope.

[0041] According to the processing flow described with reference to FIG. 7, the aberration corrector 131 is operated based on the position of the sample stage 109 when observing the outer peripheral portion of the observation sample, and an observation image with distortion caused by aberration suppressed can be acquired. The observation image thus acquired can be used for dimensional measurement or defect inspection of the outer peripheral portion of the observation sample.

Example

[0042] In the first embodiment, the operation of the aberration corrector 131 based on the position of the sample stage 109 when observing the outer peripheral portion of the observation sample and aberration correction were described. The aberration generated when observing the outer peripheral portion of the sample of the observation sample varies depending on the cross-sectional shape of the outer edge of the observation sample and the positional deviation of the observation sample with respect to the sample stage 109. Therefore, in the second embodiment, the operation of the aberration corrector 131 based on the shape and positional deviation of the observation sample together with the position of the sample stage 109 will be described. Note that the same components and processes as those in the first embodiment are denoted by the same reference numerals, and the description is omitted or simplified.

[0043] The overall configuration of the scanning electron microscope according to Example 2 will be described with reference to FIG. 9. In the scanning electron microscope according to Example 2, a measuring instrument 901 is added to the configuration of Example 1. The measuring instrument 901 optically measures the shape and displacement of the sample 108, and is, for example, an optical sensor or an optical microscope, and performs measurement by bright-field observation, dark-field observation, or confocal observation. When the measuring instrument 901 measures the shape and displacement of the sample 108, the sample stage 109 moves directly below the measuring instrument 901.

[0044] With reference to FIG. 10, an example of the flow of the process for creating the correction table according to Example 2 will be described step by step. In Example 2, since S1001, S1002, and S1003 are added to the flow of the process illustrated in FIG. 3, the description of the process steps other than these will be simplified.

[0045] (S301) Similar to Example 1, a calibration sample is carried into the scanning electron microscope.

[0046] (S1001) The control unit 121 acquires the shape and position of the calibration sample carried in at S301. The shape and position of the calibration sample are acquired by being measured by the measuring instrument 901 or by reading a value measured in advance outside the scanning electron microscope.

[0047] The cross-sectional shape of the outer edge of the sample 108 will be described with reference to FIG. 11. The sample 108 has a bevel 1101 and an apex 1102 at its outer edge. The bevel 1101 is an inclined surface, and the apex 1102 is the vertex of the outer edge. Although the inclination angle of the bevel 1101 with respect to the horizontal plane and the distance from the center point of the sample 108 to the apex 1102 are defined by the specifications, there are variations for each sample 108. Therefore, in S1001, measurement values related to the bevel 1101 and the apex 1102 are acquired for each calibration sample.

[0048] The coordinates of the apex 1102 on the XY plane are measured at least at three positions, and the coordinates of the center point of the calibration sample are calculated based on the measured coordinates. Then, the positional deviation of the calibration sample with respect to the sample stage 109 is obtained from the coordinates of the center point of the calibration sample and the coordinates of the center point of the sample stage 109.

[0049] The measurement of the shape and position of the calibration sample is not limited to the use of the measuring instrument 901, and a height sensor exemplified in FIG. 12 may be used. The height sensor in FIG. 12 has a light emitting unit 1201 and a light receiving unit 1202, and measures the height of the sample 108 by detecting the light irradiated from the light emitting unit 1201 and reflected by the upper surface of the sample 108. Since the height sensor can measure in a shorter time than the measuring instrument 901, the throughput can be improved.

[0050] (S302) Similar to Example 1, the control unit 121 moves the sample stage 109 so that the observation region of the outer peripheral portion of the calibration sample is arranged at the position irradiated with the electron beam.

[0051] (S303) Similar to Example 1, the control unit 121 operates each part in the housing 110 to acquire an observation image of the outer peripheral portion of the calibration sample.

[0052] (S304) Similar to Example 1, the control unit 121 calculates the aberration based on the observation image acquired in S303.

[0053] (S305) Similar to Example 1, the control unit 121 determines whether or not the value of the aberration calculated in S304 is less than a predetermined threshold value. If the value of the aberration is less than the threshold value, the process proceeds to S307, and if it is equal to or greater than the threshold value, the process returns to S303 via S306.

[0054] (S306) Similar to Example 1, the control unit 121 controls the aberration corrector 131.

[0055] (S307) Similar to Example 1, the control unit 121 determines whether the number of data is sufficient. If the number of data is sufficient, the process proceeds to S1002; if it is insufficient, the process returns to S302.

[0056] (S1002) The control unit 121 determines whether it is necessary to replace the calibration sample. If there is no need to replace the calibration sample, the process proceeds to S308; if there is a need to replace it, the process returns to S1001 via S1003. Whether it is necessary to replace the calibration sample is determined based on whether the relationship between the shape and position of the prepared calibration sample and the control amount of the aberration corrector has been obtained for all of the prepared calibration samples. That is, if the relationship is obtained for all of the prepared calibration samples, it is determined that there is no need to replace the calibration sample.

[0057] (S1003) The calibration sample is carried out of the scanning electron microscope. After the calibration sample is carried out in S1003, another calibration sample is carried in in S301. (S308) Similar to Example 1, the control unit 121 creates a correction table using the control amount of the aberration corrector 131 for which the aberration is less than the threshold value at each of the measurement positions 401. The created correction table is stored in the storage unit 123.

[0058] Examples of the correction tables created in Example 2 are shown in FIGS. 13A and 13B. The correction table in FIG. 13A shows the relationship between the position of the sample stage 109 and the control amount of the aberration corrector 131 for each shape of the outer peripheral portion of the sample 108. The correction table in FIG. 13B shows the relationship between the position of the sample stage 109 and the control amount of the aberration corrector 131 for each positional deviation of the sample 108 with respect to the sample stage 109.

[0059] (S309) Similar to Example 1, the calibration sample is carried out of the scanning electron microscope.

[0060] Based on the processing flow described with reference to FIG. 10, a correction table showing the relationship between the position of the sample stage 109 and the control amount of the aberration corrector 131 is created for each shape and position of the sample 108. The created correction table is used for aberration correction in the same manner as in the first embodiment.

[0061] With reference to FIG. 14, an example of the processing flow of aberration correction in the second embodiment will be described step by step.

[0062] (S701) Similar to the first embodiment, an observation sample is carried into the scanning electron microscope.

[0063] (S1401) The control unit 121 moves the sample stage 109 that holds the observation sample carried in at S701 directly below the measuring instrument 901, and causes the measuring instrument 901 to measure the shape and position of the observation sample. The measuring instrument 901 measures the cross-sectional shape of the outer edge of the observation sample and the positional deviation of the observation sample with respect to the sample stage 109, and transmits the measurement value to the control unit 121.

[0064] Note that a height sensor exemplified in FIG. 12 may be used to measure the shape and position of the observation sample. Alternatively, the shape and position of the observation sample may be measured in advance outside the scanning electron microscope, and the pre-measured values may be read by the control unit 121. By using a height sensor or reading pre-measured values, the throughput can be improved.

[0065] (S702) Similar to the first embodiment, the control unit 121 moves the sample stage 109 so that the observation region of the outer peripheral portion of the observation sample is arranged at the position irradiated with the electron beam, and acquires the position of the sample stage 109 after the movement.

[0066] (S703) The control unit 121 obtains the control amount of the aberration corrector 131 by collating the cross-sectional shape and positional deviation of the observation sample measured in S1401 with the position of the sample stage 109 acquired in S702 against a correction table. The control amount obtained from the correction table is set in the aberration corrector 131, and the aberration is corrected so as to be less than the threshold value. If the cross-sectional shape and positional deviation of the observation sample measured in S1401 and the position of the sample stage 109 acquired in S702 are not stored in the correction table, the control amount at that position may be calculated by interpolation processing.

[0067] (S704) The control unit 121 operates each part in the housing 110 to acquire an observation image of the observation sample. Since the aberration corrector 131 is controlled in S703 so that the aberration becomes less than the threshold value, in S704, an observation image with distortion due to aberration suppressed can be acquired.

[0068] (S705) The observation sample is carried out from the scanning electron microscope.

[0069] According to the processing flow described with reference to FIG. 14, based on the position of the sample stage 109 when observing the outer peripheral portion of the observation sample and the cross-sectional shape and positional deviation of the observation sample, the aberration corrector 131 is operated, and an observation image with distortion due to aberration suppressed can be acquired. The observation image thus acquired can be used for dimensional measurement and defect inspection of the outer peripheral portion of the observation sample.

Example

[0070] In Example 1, the correction of the aberration generated when observing the outer peripheral portion of the observation sample was described. In Example 3, in addition to the correction of the aberration, the correction of the electric field disturbance at the outer peripheral portion of the observation sample will be described. The same components and processes as those in Example 1 are given the same reference numerals, and the description is omitted or simplified.

[0071] The overall configuration of the scanning electron microscope according to Example 3 will be described with reference to FIG. 15. In the scanning electron microscope according to Example 3, an electric field correction electrode 1501 is added to the configuration of Example 1. The electric field correction electrode 1501 generates a correction electric field for correcting the disturbance of the electric field generated at the outer peripheral portion of the sample 108, and has an annular shape surrounding the outer peripheral portion of the sample 108. When the control unit 121 applies a predetermined voltage to the electric field correction electrode 1501, a correction electric field is generated. The electric field correction electrode 1501 moves together with the sample stage 109.

[0072] With reference to FIG. 16, an example of the flow of the process for creating the correction table according to Example 3 will be described step by step. In Example 3, since S1601 is added to the flow of the process illustrated in FIG. 3, the description of the process steps other than S1601 will be simplified.

[0073] (S301) Similar to Example 1, a calibration sample is carried into the scanning electron microscope.

[0074] (S302) Similar to Example 1, the control unit 121 moves the sample stage 109 so that the observation region of the outer peripheral portion of the calibration sample is arranged at the position where the electron beam is irradiated.

[0075] (S1601) At the position of the sample stage 109 moved in S302, the control unit 121 adjusts the voltage applied to the electric field correction electrode 1501. That is, the voltage is adjusted so that the electron beam is irradiated at a desired position.

[0076] (S303) Similar to Example 1, the control unit 121 operates each part in the housing 110 to obtain an observation image of the outer peripheral portion of the calibration sample.

[0077] (S304) Similar to Example 1, the control unit 121 calculates the aberration based on the observation image obtained in S303.

[0078] (S305) Similar to Example 1, the control unit 121 determines whether the value of the aberration calculated in S304 is less than a predetermined threshold value. If the value of the aberration is less than the threshold value, the process proceeds to S307. If it is greater than or equal to the threshold value, the process returns to S303 via S306.

[0079] (S306) Similar to Example 1, the control unit 121 controls the aberration corrector 131.

[0080] (S307) Similar to Example 1, the control unit 121 determines whether the number of data is sufficient. If the number of data is sufficient, the process proceeds to S1202. If it is insufficient, the process returns to S302.

[0081] (S308) Similar to Example 1, the control unit 121 creates a correction table using the control amount of the aberration corrector 131 at each measurement position 401 where the aberration is less than the threshold value. The correction table also stores the voltage applied to the electric field correction electrode 1501.

[0082] FIG. 17 shows an example of the correction table created in Example 3. In the correction table of FIG. 17, the applied voltage to the electric field correction electrode 1501 and the control amount of the aberration corrector 131 are associated with each position of the sample stage 109. The created correction table is stored in the storage unit 123.

[0083] (S309) Similar to Example 1, the calibration sample is removed from the scanning electron microscope.

[0084] According to the processing flow described with reference to FIG. 16, a correction table showing the relationship between the position of the sample stage 109, the applied voltage to the electric field correction electrode 1501, and the control amount of the aberration corrector 131 is created. The created correction table is used for aberration correction in the same manner as in Example 1.

[0085] Using FIG. 18, an example of the processing flow of aberration correction in Example 3 will be described for each processing step.

[0086] (S701) Similar to Example 1, the observation sample is carried into the scanning electron microscope.

[0087] (S702) Similar to Example 1, the control unit 121 moves the sample stage 109 so that the observation region of the outer peripheral portion of the observation sample is disposed at the position irradiated with the electron beam, and acquires the position of the sample stage 109 after the movement.

[0088] (S1801) The control unit 121 obtains the applied voltage to the electric field correction electrode 1501 by collating the position of the sample stage 109 acquired in S702 with the correction table. The applied voltage acquired from the correction table is set to the electric field correction electrode 1501, and the disturbance of the electric field generated at the outer peripheral portion of the sample 108 is corrected. When the position of the sample stage 109 acquired in S702 is not stored in the correction table, the applied voltage at the position may be calculated by interpolation processing.

[0089] (S703) The control unit 121 obtains the control amount of the aberration corrector 131 by collating the position of the sample stage 109 acquired in S702 with the correction table. The control amount acquired from the correction table is set to the aberration corrector 131, and the aberration is corrected so as to be less than the threshold value. When the position of the sample stage 109 acquired in S702 is not stored in the correction table, the control amount at the position may be calculated by interpolation processing.

[0090] (S704) The control unit 121 operates each part in the housing 110 to acquire an observation image of the observation sample. Since the aberration corrector 131 is controlled in S703 so that the aberration is less than the threshold value, in S704, an observation image with distortion due to aberration suppressed can be acquired.

[0091] (S705) The observation sample is carried out of the scanning electron microscope.

[0092] Based on the position of the sample stage 109 when observing the outer peripheral portion of the observation sample, the voltage applied to the electric field correction electrode 1501 and the control amount of the aberration corrector 131 are controlled according to the processing flow described with reference to FIG. 18. As a result, the displacement of the electron beam irradiated onto the observation sample is suppressed, and an observation image with corrected aberration can be obtained. The observation image thus obtained can be used for dimensional measurement or defect inspection of the outer peripheral portion of the observation sample.

[0093] As described above, a plurality of embodiments of the charged particle beam apparatus of the present invention have been described. The present invention is not limited to the above embodiments, and components can be modified and embodied without departing from the gist of the invention. Also, a plurality of components disclosed in the above embodiments may be appropriately combined. For example, a correction table obtained by appropriately combining the correction tables illustrated in FIGS. 6B, 13A, 13B, and 17 may be used for aberration correction. Furthermore, some components may be deleted from all the components shown in the above embodiments.

Explanation of Reference Numerals

[0094] 101... electron gun, 102... condenser lens, 105... detector, 106... deflector, 107... objective lens, 108... sample, 109... sample stage, 110... housing, 121... control unit, 122... input / output unit, 123... storage unit, 131... aberration corrector, 201A... electrode, 201B... electrode, 202A... magnetic pole, 202B... magnetic pole, 211A... magnetic pole, 211B... magnetic pole, 212A... magnetic pole, 212B... magnetic pole, 213A... magnetic pole, 213B... magnetic pole, 400... center point, 401... measurement position, 901... measuring instrument, 1101... bevel, 1102... apex, 1201... light emitting unit, 1202... light receiving unit, 1501... electric field correction electrode.

Claims

1. A charged particle beam apparatus comprising: a sample stage for holding a sample; a charged particle beam source for emitting a charged particle beam irradiated onto the sample; a lens for focusing the charged particle beam onto the sample; an aberration corrector for correcting the aberration of the charged particle beam; a deflector for scanning the charged particle beam; a detector for detecting charged particles emitted from the sample when scanned by the charged particle beam; and a control unit for generating an observation image of the sample based on a detection signal output from the detector and controlling the operation of each part, wherein the control unit controls the aberration corrector by collating the position of the sample stage when observing the outer peripheral portion of the sample with a correction table showing the relationship between the position of the sample stage and the control amount of the aberration corrector.

2. The charged particle beam apparatus according to claim 1, wherein the correction table is created for each irradiation condition of the charged particle beam, and the control unit controls according to the irradiation condition of the charged particle beam together with the position of the sample stage when observing the outer peripheral portion of the sample.

3. The charged particle beam apparatus according to claim 1, further comprising a measurement unit for measuring the cross-sectional shape of the outer peripheral portion of the sample, wherein the correction table is created for each cross-sectional shape of the sample, and the control unit controls according to the cross-sectional shape of the sample together with the position of the sample stage when observing the outer peripheral portion of the sample.

4. The charged particle beam apparatus according to claim 1, further comprising a measurement unit for measuring the displacement of the sample with respect to the sample stage, wherein the correction table is created for each displacement of the sample with respect to the sample stage, and the control unit controls according to the displacement of the sample with respect to the sample stage together with the position of the sample stage when observing the outer peripheral portion of the sample.

5. The charged particle beam apparatus according to claim 1, further comprising an electric field correction electrode for generating a correction electric field for correcting the disturbance of the electric field generated at the outer peripheral portion of the sample, wherein the correction table further shows the relationship between the position of the sample stage and the voltage applied to the electric field correction electrode, and the control unit further controls the voltage applied to the electric field correction electrode according to the position of the sample stage when observing the outer peripheral portion of the sample.

6. The charged particle beam apparatus according to claim 1, further comprising a display screen on which the observation image is displayed, The display screen has a button for switching between ON and OFF of the control of the aberration corrector, and a charged particle beam apparatus characterized by this.

7. A charged particle beam apparatus according to claim 1, wherein the aberration corrector includes a chromatic aberration corrector for correcting chromatic aberration, and a charged particle beam apparatus characterized by this.

8. A charged particle beam apparatus according to claim 1, wherein the aberration corrector includes a coma aberration corrector for correcting coma aberration, and a charged particle beam apparatus characterized by this.

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