Charged particle beam device

Abstract

The present disclosure provides a charged particle beam device capable of removal or control of an electric charge by plasma without affecting control of the charged particle beam. The charged particle beam device according to the present disclosure is provided with a charged particle beam optical system for emitting a charged particle beam onto a sample, a sample chamber provided with a stage on which the sample is placed, a plasma generating device for generating plasma to be emitted onto the stage so as to remove an electrification charge from the sample, and a coupling member coupling the plasma generating device to the sample chamber, the coupling member including an insulating spacer insulating the sample chamber and the plasma generating device.

Description

Technical Field

[0001] The present invention relates to a charged particle beam device.

Background Art

[0002] With the miniaturization and high integration of semiconductor patterns, a slight shape difference in the pattern has come to affect the operating characteristics of the device. For this reason, the need for shape management of patterns and the like of devices is increasing. As a result, a scanning electron microscope (SEM: Scanning Electron Microscope) as a charged particle beam device used for semiconductor inspection and measurement is required to have higher sensitivity and accuracy than ever before. A scanning electron microscope is configured to detect electrons emitted from a sample by a detector, generate a signal waveform thereof, and measure, for example, dimensions between peaks (pattern edges).

[0003] In wafer inspection in the manufacturing process, early detection of foreign matters, defects, etc. leads to an improvement in yield. Therefore, the need for full-surface inspection of wafers for defect detection is increasing, but there is a problem that full-surface inspection leads to a decrease in throughput. To increase throughput, an inspection that images a wide field of view at once by low-magnification imaging with a large current can be considered. However, in the case of a sample that is easily charged, the influence of charging of the sample due to low magnification becomes apparent, and there is a risk of image distortion, luminance unevenness, etc. Since charging of the sample also causes a decrease in the measurement accuracy of the SEM, it is required to effectively remove the charging.

[0004] As methods for reducing the influence of charging, a method of coating the sample with a conductor to suppress charging and a method of controlling the yield of secondary electrons by adjusting the voltage of primary electrons to be irradiated are known. However, these methods cannot be applied to in-line inspection, and it is difficult and unrealistic to adjust for a sample containing a plurality of materials or a sample in which patterns of various shapes are mixed. Therefore, charging removal / charging control that does not depend on the sample is required.

[0005] Patent Document 1 discloses a method of controlling the charging of a sample by controlling the energy of incident electrons. Patent Document 2 discloses a method of removing charging using ions generated when ultraviolet rays or X-rays are irradiated onto a gas.

[0006] As disclosed in Patent Document 1, it is possible to control the emission rate of secondary electrons by changing the energy of primary electrons irradiated onto a sample, and suppress the charging of the sample. However, it is necessary to change the imaging conditions depending on the material characteristics and patterns of the sample, and each time this is done, readjustment such as optical conditions and device settings is required, resulting in a problem of reduced throughput.

[0007] In Patent Document 2, high-frequency power is supplied to ions generated using ultraviolet rays or X-rays by a coil to generate plasma, and this plasma is used to remove charging and sample contamination. However, the removal of such charging is limited to the processing before and after imaging of the sample, and the influence of the plasma on the electric field space by the condenser lens for electron beam control and the method of irradiating the plasma onto the sample to which a voltage is applied for the control of the irradiated electron beam are not considered.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention has been made in view of the above problems, and provides a charged particle beam device capable of removing or controlling charging by plasma without affecting the control of the charged particle beam.

Means for Solving the Problems

[0010] The charged particle beam device according to the present invention is a charged particle beam device that irradiates a sample with a charged particle beam, and includes a charged particle beam optical system that irradiates the sample with the charged particle beam, a sample chamber having a stage on which the sample is placed, a plasma generation device that generates plasma to irradiate the stage, an insulating spacer that insulates the sample chamber and the plasma generation device, and a connecting member that connects the plasma generation device to the sample chamber.

Advantages of the Invention

[0011] According to the present invention, it is possible to provide a charged particle beam device capable of removing or controlling charge by plasma without affecting the control of the charged particle beam.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 4C

Figure 4D

Figure 4E

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0013] Hereinafter, this embodiment will be described with reference to the accompanying drawings. In the accompanying drawings, functionally identical elements may sometimes be denoted by the same reference numerals. Note that the accompanying drawings show embodiments and implementation examples in accordance with the principles of the present disclosure, but these are for the purpose of understanding the present disclosure and are not used to limit the interpretation of the present disclosure in any way. The description in this specification is merely a typical example and does not limit the scope of the claims or application examples of the present disclosure in any sense.

[0014] In this embodiment, although the description is made in sufficient detail for those skilled in the art to implement the present disclosure, other implementations and forms are possible, and it is necessary to understand that changes in configuration and structure and replacement of various elements can be made without departing from the scope and spirit of the technical idea of the present disclosure. Therefore, the following description should not be construed as being limited thereto.

[0015] [First Embodiment] Referring to FIG. 1, a charged particle beam apparatus according to the first embodiment will be described. As an example, this charged particle beam apparatus includes an electron beam optical system PS (charged particle beam optical system) including an electron gun 1, a condenser lens 3, a deflector 4, and an objective lens 5. Below the electron beam optical system PS, a sample chamber 12 having a stage 7 for placing a sample 6 therein is installed.

[0016] The electron beam 2 (primary electron beam) generated and accelerated by the electron gun 1 is converged by the condenser lens 3 and further converged onto the sample 6 on the stage 7 by the objective lens 5. The deflector 4 (scanning deflector) scans the electron beam 2 above the electron beam scanning region of the sample 6. By irradiating while scanning the electron beam 2 on the sample 6, electrons excited in the sample 6 are emitted from the sample 6 as secondary electrons 10. The emitted secondary electrons 10 are detected by the secondary electron detector 8, and an arithmetic unit (not shown) connected to the secondary electron detector 8 images the detection signal.

[0017] An energy filter 9 capable of separating signal electrons by energy is provided in front of the secondary electron detector 8 (on the incident surface side). It is possible to estimate the charging state of the sample 6 from the change in the detection signal when the voltage applied to the energy filter 9 is changed. Also, the energy of the electron beam 2 (primary electron beam) that scans the sample 6 is determined by the acceleration voltage of the electron gun 1 and the voltage applied to the stage 7. The emitted secondary electrons 10 are related to the energy of the incident primary electrons, and the charging state of the surface of the sample 6 changes depending on the magnitude relationship between the electron current of the primary electrons and the electron current of the secondary electrons 10. The charge amount of the sample 6 also changes depending on the material characteristics and shape of the sample 6, etc. Also, the charge amount of the sample 6 is not uniform over the entire surface of the sample 6 and has a distribution that changes depending on the position on the surface of the sample 6 due to material characteristics, shape, etc.

[0018] The charged particle beam apparatus of the present embodiment includes a plasma generation device 11 that generates plasma and radiates the plasma toward the stage 7 on which the sample 6 is placed in order to remove the charge of the sample 6. The plasma generation device 11 is connected to the wall surface of the sample chamber 12 by a connecting member 13 having an insulating spacer.

[0019] Referring to FIG. 2, the charge removal operation of the sample 6 using this plasma generation device 11 will be described. The plasma PZ generated by the plasma generation device 11 contains electrons and positive ions and is normally electrically neutral. However, when the plasma is irradiated onto the positively charged sample 6, the positive charges of the sample 6 are neutralized by the electrons in the plasma. As a result, the electrons in the plasma PZ decrease, the charge balance in the plasma PZ is disrupted, and a current flows through the plasma PZ to the inner wall of the grounded sample chamber 12 or the like, thereby removing the charge from the sample 6.

[0020] The plasma generation device 11 is connected to the inner wall of the sample chamber 12 by a connecting member 13 having an insulating spacer. The insulating spacer is made of an insulating material such as ceramics, for example, and has a role of electrically insulating the plasma generation device 11 from the sample chamber 12. Since the plasma generation device 11 is insulated from the sample chamber 12, the potential of the sample chamber 12 can be stably maintained regardless of the operating state of the plasma generation device 11.

[0021] [Second Embodiment] Next, the charged particle beam device according to the second embodiment will be described with reference to FIG. 3. FIG. 3 illustrates the configuration of the charged particle beam device according to the second embodiment. In FIG. 3, the same components as those of the charged particle beam device of the first embodiment are denoted by the same reference numerals as in FIG. 1, and thus redundant descriptions will be omitted below.

[0022] The plasma generation device 11 of this second embodiment is different from the first embodiment in that it includes a main body portion 11A that generates plasma and a guide 11B that extends from the main body portion 11A to the vicinity of the sample. The guide 11B is made of metal, and a hollow portion for guiding the plasma PZ generated in the main body portion 11A is provided inside thereof. The plasma PZ is discharged from the tip of the guide 11B through the hollow portion.

[0023] The function of the guide 11B will be described. Since the plasma PZ generated by the plasma generation device 11 has no directivity, without the guide 11B, the plasma PZ diffuses from the main body 11A into the sample chamber 12 due to the electric field generated by the plasma PZ itself and natural diffusion. Without the action of an electric field or the like, the plasma PZ diffuses into the sample chamber 12. The plasma PZ can be attracted by the electric field generated by the charging of the sample 6, thereby removing (discharging) the charge of the sample 6. However, in the electron beam optical system PS connected to the sample chamber 12, a capacitor lens 3 for controlling the electron beam 2 and the like are arranged, and there is an electric field distribution inside the sample chamber 12. Such an electric field distribution affects the behavior of the plasma PZ. When the influence of the electric field given by the capacitor lens 3 or the like is large, it may affect the charge removal operation by the plasma generation device 11. Also, if there is a structure having a potential higher than the electric field distribution given by the charged charge of the sample 6, the charged particles in the plasma PZ are attracted to the structure, so the plasma PZ cannot sufficiently discharge the charge of the sample 6.

[0024] In contrast, in this second embodiment, the charged charge of the sample 6 is guided to the vicinity of the sample 6 through the guide 11B by the plasma PZ. Thereby, electrons or positive ions in the plasma PZ neutralize the charged charge of the sample 6, and the charged charge of the sample 6 is removed. Since the plasma PZ is guided to the vicinity of the sample 6 by the guide 11B, the sample 6 can be discharged without being affected by the surrounding electric field.

[0025] Also, since the guide 11B is made of metal, the inside of the guide 11B has the same potential in the length direction, and the plasma PZ can be irradiated onto the sample 6 without being affected by an external electric field. The electrons in the plasma PZ irradiated from the tip of the guide 11B are attracted to the positive potential on the surface of the sample 6, neutralizing the charged charge of the sample 6. The charged charge of the sample 6 is discharged by flowing as a discharge current Ir to the guide 11B through the plasma PZ.

[0026] The magnitude of the discharge current Ir depends on the density of the irradiated plasma PZ. If the density of the plasma PZ is high, the amount of charged particles for neutralizing charges and the charged particles mediating the discharge current Ir also increase. The magnitude of the discharge current Ir is also affected by the distance between the sample 6 to be discharged and the surrounding structures. At the same plasma density, the shorter the distance, the lower the plasma resistance, and more discharge current Ir can flow. In this embodiment, the discharge is performed mainly by flowing the discharge current Ir flowing through the plasma PZ mainly through the guide 11B. By flowing a current through the guide 11B arranged at a position close to the sample 6 which is the object to be discharged, rather than a structure arranged far away such as the inner wall of the sample chamber 12, more efficient discharge can be performed.

[0027] The stage 7 is configured to be able to apply a retarding voltage. The retarding voltage is a voltage for decelerating the electrons of the electron beam 2. The electron beam 2 irradiated from the electron gun 1 is converged by the condenser lens 3, the objective lens 5, etc. and irradiated onto the sample 6. The acceleration voltage of the electron beam 2 irradiated from the electron gun 1 is increasing to a high voltage for the purpose of improving the resolution. However, when the energy of the electron beam 2 irradiated onto the sample 6 is large, the generation efficiency of the secondary electrons 10 generated from the surface of the sample 6 deteriorates, and the charging of the sample 6 progresses. Also, depending on the sample 6, it may be damaged when irradiated with high-energy electrons. Therefore, a voltage (retarding voltage) for decelerating the electrons before they are irradiated onto the sample 6 is applied to the stage 7. Thereby, while aiming for high resolution of the image, damage and charging to the sample 6 can be prevented. The retarding voltage is applied by a voltage source 18 connected to the stage 7.

[0028] Using FIGS. 4A to 4E, the behavior of the plasma PZ when a voltage is applied to the stage 7 will be described. As shown in FIG. 4A, the plasma PZ generated in the main body 11A of the plasma generation device 11 moves through the guide 11B and approaches the sample 6 on the stage 7. Since the main body 11A of the plasma generation device 11 is electrically connected to the tip of the guide 11B and has the same potential, the plasma PZ is not affected by the electric field of the stage 7. However, when no voltage is applied by the voltage source 18, an equipotential line EPL as shown in FIG. 4B is formed in the gap between the tip of the guide 11B and the stage 7, and a potential difference (potential) represented by the equipotential line EPL occurs (see FIG. 4C). Electrons that cannot exceed this potential difference cannot reach the stage 7 and cannot contribute to the removal of the charge of the sample 6.

[0029] On the other hand, when a voltage is applied to the stage 7 by the voltage source 18, it becomes possible to make the plasma generation device 11 and the stage 7 have substantially the same potential, and a potential distribution (equipotential line EPL') as shown in FIG. 4D is obtained near the tip of the guide 11B. As shown in FIG. 4E, the potential difference between the plasma generation device 11 and the stage 7 disappears, and the plasma PZ can be irradiated from the tip of the guide 11B to the sample 6, enabling effective charge removal.

[0030] [Third Embodiment] Next, the charged particle beam device according to the third embodiment will be described with reference to FIG. 5. Since the overall configuration of the charged particle beam device of the third embodiment is substantially the same as that of the previous embodiment, duplicate explanations will be omitted. The third embodiment is different from the previous embodiment in the part related to the control of the plasma generation device 11. Specifically, the plasma generation device 11 of this third embodiment is configured to generate plasma at the timing between a plurality of frames and execute the charge removal operation of the sample 6.

[0031] Generally, when imaging the signal captured by the secondary electron detector 8, in addition to generating an image of the sample 6 from a single image (frame) obtained in one scan, a charged particle beam apparatus is configured to be able to execute an imaging mode in which the same field of view of the sample 6 is scanned multiple times, and a composite image is generated by synthesizing (overlaying) the obtained multiple images to obtain an image with high resolution (SN ratio). On the other hand, when the number of irradiations of the electron beam 2 increases by repeating the imaging operation multiple times within the same field of view, the charge amount of the sample 6 due to the electron beam 2 increases. An increase in the charge amount of the sample 6 may affect not only the electron beam 2 but also the secondary electrons 10.

[0032] Therefore, as shown in FIG. 5, the charged particle beam apparatus according to the third embodiment is configured to execute a charge removal operation of the plasma generation device 11 between the imaging of multiple frames. As shown in FIG. 5, by varying the timing of the imaging of the SEM (each frame) and the charge removal operation of the plasma generation device 11, it is possible to execute charge removal of the sample 6 without affecting the imaging.

[0033] Also, by performing the charge removal operation with the plasma generation device 11 for each frame, it becomes possible to remove the charge generated for each frame by imaging, reduce the influence on the image due to the accumulation of charge for each frame, and stably acquire the image. In FIG. 5, a sequence of performing the charge removal operation with the plasma generation device 11 for each frame is adopted. However, as shown in FIG. 6, it is also possible to adopt a sequence of performing the charge removal operation once for a plurality of frames. As the number of charge removal operations inserted between imaging increases, the throughput of imaging decreases accordingly. By inserting the charge removal operation within a range where the influence of the charge generated by the primary electrons does not substantially occur, it is possible to perform the charge removal operation while preventing a decrease in throughput. Here, the imaging refers to the period until the secondary electrons 10 emitted when the primary electrons are incident on the sample 6 are detected by the secondary electron detector 8. Also, the ON state of the plasma generation device 11 in FIGS. 5, 6, etc. means the period from when an ON signal is input to the plasma generation device 11 until a plasma PZ is generated, charge removal is performed, and an OFF signal is input to the plasma generation device 11.

[0034] Note that in FIGS. 5 and 6, an example of performing the charge removal operation between two frames has been described. However, the charged particle beam device of the present disclosure is not limited to this. For example, it is also possible to adopt a procedure of performing the charge removal operation once every time the imaging of a plurality of frames is completed. Alternatively, as shown in FIGS. 7 and 8, it is also possible to configure the plasma generation device 11 to be turned ON during the line scanning to perform the charge removal operation.

[0035] FIG. 9 is a flowchart showing the procedure when performing the charge removal operation for each scan of a predetermined number of lines in the third embodiment. After performing the scan of one or more lines (step S102), the plasma generation device 11 is turned ON to perform the charge removal operation (step S103), and then the plasma generation device 11 is turned OFF (step S104). Thereafter, the same operation is repeated until the scan within the designated field of view is completed (step S105).

[0036] Generally, in a charged particle beam apparatus, imaging is performed by scanning a specified field of view of a sample 6 by multiple line scans using an electron beam 2. In FIG. 7, the electron beam 2 is irradiated from left to right on the paper surface, and then the electron beam 2 is irradiated in order downward on the paper surface. The scanning of the electron beam 2 is controlled by a deflector 4. As the number of scanned lines increases, the charging of the sample 6 also increases, and the influence on the electron beam 2 and secondary electrons 10 also becomes greater. The amount of charge due to the irradiation of the electron beam 2 also varies depending on the imaging conditions of the SEM, the pattern shape and material of the sample 6. As shown in FIG. 9, after scanning a certain number of lines, by performing charge removal, charge removal according to the amount of charge and the influence on the image becomes possible, and charging can be removed while minimizing the reduction in throughput.

[0037] [Fourth Embodiment] Next, a charged particle beam apparatus according to the fourth embodiment will be described with reference to FIG. 10. In FIG. 10, the same components as those of the charged particle beam apparatus of the first embodiment are denoted by the same reference numerals as those in FIG. 1, and thus redundant descriptions will be omitted below.

[0038] The charged particle beam apparatus of this fourth embodiment is different from the foregoing embodiments in that it includes a current measurement device 19 that measures the magnitude of a discharge current Ir, and is configured such that a discharge operation is executed according to the measurement result. The current measurement device 19 can be connected, as an example, to a current path that connects the stage 7 and the plasma generation device 11. Further, a voltage source 20 for applying a predetermined potential can be connected to this current path.

[0039] In static elimination using plasma PZ, the plasma PZ is irradiated toward the sample 6, and thereby the charged charges of the sample 6 are neutralized by electrons or positive ions in the plasma PZ. Due to the neutralization, the charge balance of electrons and positive ions in the plasma PZ is disrupted, and static elimination is performed by the flow of a static elimination current Ir through the plasma PZ. Since the static elimination current Ir flows through the plasma generation device 11 via the plasma PZ, the static elimination current Ir is measured by connecting a current measuring device 19 to the current path connecting the plasma generation device 11 and the stage 7. The charge amount of the sample 6 can be evaluated based on the magnitude of the static elimination current Ir.

[0040] As another method for evaluating the charge amount, it is possible to estimate the charge amount of the sample 6 from the change in the detection signal when the voltage applied to the energy filter 9 is changed. However, in this case, it is necessary to sweep the applied voltage. Further, the energy filter 9 selects the secondary electrons 10 that can be detected by eliminating the secondary electrons 10 having energy below the applied voltage, thereby improving the resolution of the image. For this reason, in normal wafer inspection, the voltage of the energy filter 9 is not changed and the energy filter 9 is used. Therefore, it is difficult to measure the charge amount of the sample 6 during the inspection due to the action of the energy filter 9.

[0041] According to the fourth embodiment, by measuring the magnitude and polarity of the static elimination current Ir that flows when the static elimination operation is performed with the plasma PZ, the charged state of the sample 6 can be known even during the inspection of the sample 6. If the imaging conditions are the same, since the charge amount of the sample 6 depends on the material characteristics and the sample pattern, the charge amount can be monitored, and abnormalities of the sample 6 can be detected from the change amount. For example, in a pattern that is easily charged, if there is a defect in the shape, the charge amount of the sample 6 changes. Therefore, according to this embodiment, it is possible to detect the occurrence of abnormalities such as defects in the shape of the sample 6.

[0042] Referring to the flowchart of FIG. 11, the measurement operation (discharge elimination operation) of the sample 6 in the charged particle beam apparatus according to the fourth embodiment will be described. After performing scanning of one or a plurality of lines (step S112), the plasma generation device 11 is turned on to execute the discharge elimination operation (step S113), and then the plasma generation device 11 is turned off (step S114). Thereafter, it is determined whether or not the discharge elimination current detected by the current measurement device 19 during the discharge elimination operation is equal to or less than X amperes (threshold value) (step S115). If the determination is affirmative, since there is no problem in measuring the sample 6, the process proceeds to step S116, and the above operations are repeated until the scanning within the designated field of view is completed (step S105). On the other hand, if the determination in step S115 is negative, it is determined that an abnormality has occurred in the sample 6, the imaging operation of the sample 6 is aborted, and the procedure of FIG. 11 ends (step S117).

[0043] As described above, according to this fourth embodiment, the same effects as those of the above-described embodiment can be obtained. In addition, by measuring the discharge elimination current with the current measurement device 19, it becomes possible to detect an abnormality related to the sample 6.

[0044] [Fifth Embodiment] Next, the charged particle beam apparatus according to the fifth embodiment will be described with reference to FIG. 12. In FIG. 12, the same components as those of the charged particle beam apparatus of the first embodiment are denoted by the same reference numerals as those in FIG. 1, and thus redundant descriptions will be omitted below. The charged particle beam apparatus according to this fifth embodiment is different from the foregoing embodiments in that the stage 7 and the plasma generation device 11 are connected to different voltage sources 21 and 22, respectively, and are given different potentials.

[0045] In the foregoing embodiments, the case where the potentials of the main body 11A and the guide 11B of the plasma generation device 11 are made equal to the potential of the stage 7 has been described. Thereby, the potential difference between the tip of the guide 11B and the stage 7 is eliminated, and thereby, the plasma PZ can be irradiated onto the sample 6 without being affected by the surrounding electric field. On the other hand, in this fourth embodiment, it is possible to set the potentials applied to the main body 11A and the guide 11B of the plasma generation device 11 to be different from the potential applied to the stage 7.

[0046] A voltage V is applied to the stage 7 by a voltage source 21 in order to adjust the energy of the electron beam 2 (primary electrons) incident on the sample 6. s On the other hand, a voltage different from this voltage V is applied to the plasma generation device 11. s A voltage V different from this voltage V is applied to the plasma generation device 11. 1 The voltage V applied to the stage 7 varies depending on the pattern shape, material, etc. of the sample 6 in addition to the imaging conditions, but if various conditions are constant, the polarity and potential of the charge are constant. By arbitrarily changing the voltage V of the voltage source 19, a potential difference can be generated between the stage 7 and the guide 11B, the balance of electrons or positive ions can be changed, and either one can be selectively irradiated more. For example, when the charged charge of the sample 6 is negative, by making the voltage V of the voltage source 22 lower than the voltage V of the voltage source 21, a negative potential difference can be generated between the guide 11B and the stage 7. Thereby, more positive ions can be drawn out from the plasma PZ, and more efficient charge removal becomes possible. Conversely, when the charged charge of the sample 6 is positive, by making the voltage V of the voltage source 22 higher than the voltage V of the voltage source 21, a positive potential difference can be generated between the guide 11B and the stage 7. Thereby, more negative ions can be drawn out from the plasma PZ, and more efficient charge removal becomes possible. s The voltage V applied to the stage 7 varies depending on the pattern shape, material, etc. of the sample 6 in addition to the imaging conditions, but if various conditions are constant, the polarity and potential of the charge are constant. By arbitrarily changing the voltage V of the voltage source 19, a potential difference can be generated between the stage 7 and the guide 11B, the balance of electrons or positive ions can be changed, and either one can be selectively irradiated more. For example, when the charged charge of the sample 6 is negative, by making the voltage V of the voltage source 22 lower than the voltage V of the voltage source 21, a negative potential difference can be generated between the guide 11B and the stage 7. Thereby, more positive ions can be drawn out from the plasma PZ, and more efficient charge removal becomes possible. Conversely, when the charged charge of the sample 6 is positive, by making the voltage V of the voltage source 22 higher than the voltage V of the voltage source 21, a positive potential difference can be generated between the guide 11B and the stage 7. Thereby, more negative ions can be drawn out from the plasma PZ, and more efficient charge removal becomes possible. 1 The voltage V applied to the stage 7 varies depending on the pattern shape, material, etc. of the sample 6 in addition to the imaging conditions, but if various conditions are constant, the polarity and potential of the charge are constant. By arbitrarily changing the voltage V of the voltage source 19, a potential difference can be generated between the stage 7 and the guide 11B, the balance of electrons or positive ions can be changed, and either one can be selectively irradiated more. For example, when the charged charge of the sample 6 is negative, by making the voltage V of the voltage source 22 lower than the voltage V of the voltage source 21, a negative potential difference can be generated between the guide 11B and the stage 7. Thereby, more positive ions can be drawn out from the plasma PZ, and more efficient charge removal becomes possible. Conversely, when the charged charge of the sample 6 is positive, by making the voltage V of the voltage source 22 higher than the voltage V of the voltage source 21, a positive potential difference can be generated between the guide 11B and the stage 7. Thereby, more negative ions can be drawn out from the plasma PZ, and more efficient charge removal becomes possible. 1 The voltage V applied to the stage 7 varies depending on the pattern shape, material, etc. of the sample 6 in addition to the imaging conditions, but if various conditions are constant, the polarity and potential of the charge are constant. By arbitrarily changing the voltage V of the voltage source 19, a potential difference can be generated between the stage 7 and the guide 11B, the balance of electrons or positive ions can be changed, and either one can be selectively irradiated more. For example, when the charged charge of the sample 6 is negative, by making the voltage V of the voltage source 22 lower than the voltage V of the voltage source 21, a negative potential difference can be generated between the guide 11B and the stage 7. Thereby, more positive ions can be drawn out from the plasma PZ, and more efficient charge removal becomes possible. Conversely, when the charged charge of the sample 6 is positive, by making the voltage V of the voltage source 22 higher than the voltage V of the voltage source 21, a positive potential difference can be generated between the guide 11B and the stage 7. Thereby, more negative ions can be drawn out from the plasma PZ, and more efficient charge removal becomes possible. s The voltage V applied to the stage 7 varies depending on the pattern shape, material, etc. of the sample 6 in addition to the imaging conditions, but if various conditions are constant, the polarity and potential of the charge are constant. By arbitrarily changing the voltage V of the voltage source 19, a potential difference can be generated between the stage 7 and the guide 11B, the balance of electrons or positive ions can be changed, and either one can be selectively irradiated more. For example, when the charged charge of the sample 6 is negative, by making the voltage V of the voltage source 22 lower than the voltage V of the voltage source 21, a negative potential difference can be generated between the guide 11B and the stage 7. Thereby, more positive ions can be drawn out from the plasma PZ, and more efficient charge removal becomes possible. Conversely, when the charged charge of the sample 6 is positive, by making the voltage V of the voltage source 22 higher than the voltage V of the voltage source 21, a positive potential difference can be generated between the guide 11B and the stage 7. Thereby, more negative ions can be drawn out from the plasma PZ, and more efficient charge removal becomes possible. 1 The voltage V applied to the stage 7 varies depending on the pattern shape, material, etc. of the sample 6 in addition to the imaging conditions, but if various conditions are constant, the polarity and potential of the charge are constant. By arbitrarily changing the voltage V of the voltage source 19, a potential difference can be generated between the stage 7 and the guide 11B, the balance of electrons or positive ions can be changed, and either one can be selectively irradiated more. For example, when the charged charge of the sample 6 is negative, by making the voltage V of the voltage source 22 lower than the voltage V of the voltage source 21, a negative potential difference can be generated between the guide 11B and the stage 7. Thereby, more positive ions can be drawn out from the plasma PZ, and more efficient charge removal becomes possible. Conversely, when the charged charge of the sample 6 is positive, by making the voltage V of the voltage source 22 higher than the voltage V of the voltage source 21, a positive potential difference can be generated between the guide 11B and the stage 7. Thereby, more negative ions can be drawn out from the plasma PZ, and more efficient charge removal becomes possible. s The voltage V applied to the stage 7 varies depending on the pattern shape, material, etc. of the sample 6 in addition to the imaging conditions, but if various conditions are constant, the polarity and potential of the charge are constant. By arbitrarily changing the voltage V of the voltage source 19, a potential difference can be generated between the stage 7 and the guide 11B, the balance of electrons or positive ions can be changed, and either one can be selectively irradiated more. For example, when the charged charge of the sample 6 is negative, by making the voltage V of the voltage source 22 lower than the voltage V of the voltage source 21, a negative potential difference can be generated between the guide 11B and the stage 7. Thereby, more positive ions can be drawn out from the plasma PZ, and more efficient charge removal becomes possible. Conversely, when the charged charge of the sample 6 is positive, by making the voltage V of the voltage source 22 higher than the voltage V of the voltage source 21, a positive potential difference can be generated between the guide 11B and the stage 7. Thereby, more negative ions can be drawn out from the plasma PZ, and more efficient charge removal becomes possible.

[0047] In static elimination using plasma, for the positive charging of the sample 6, electrons in the plasma neutralize the positive charge, and for the negative charging of the sample 6, positive ions neutralize the negative charge to perform static elimination. Therefore, when the charging polarity is unknown or there is a distribution, it is more efficient to perform static elimination with the same ion balance of electrons and positive ions. However, as shown above, if the conditions are constant, the energy filter 9 can grasp the charged state in advance, and the charged state and polarity can be known. By adjusting the voltage sources 21 and 22 according to the grasped charged state and polarity, a more efficient static elimination operation can be executed.

[0048] Note that the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention and are not necessarily limited to those having all the configurations described. Also, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, for a part of the configuration of each embodiment, addition, deletion, or replacement with other configurations is possible. Also, each of the above configurations, functions, processing units, processing means, etc. may be realized in hardware, for example, by designing a part or all of them with an integrated circuit. Also, each of the above configurations, functions, etc. may be realized in software by a processor interpreting and executing a program for realizing each function. Information such as a program, table, file, etc. for realizing each function can be placed in a memory, a recording device such as a hard disk or an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.

Explanation of Reference Numerals

[0049] 1… Electron gun, 2… Electron beam, 3… Condenser lens, 4… Deflector, 5… Objective lens, 6… Specimen, 7… Stage, 8… Secondary electron detector, 9… Energy filter, 10… Secondary electron, 11… Plasma generation device, 11A… Main body, 11B… Guide, 12… Specimen chamber, PZ… Plasma, 13… Connecting member, 16… Equipotential line, 18, 21, 22… Voltage source, 19… Current measurement device.

Claims

1. A charged particle beam apparatus for irradiating a sample with a charged particle beam, comprising: a charged particle beam optical system for irradiating the sample with the charged particle beam; a sample chamber having a stage on which the sample is placed; a plasma generation device for generating plasma to irradiate the stage; an insulating spacer for insulating the sample chamber and the plasma generation device, and a connecting member for connecting the plasma generation device to the sample chamber ; The plasma generation device includes a main body that generates plasma, and a guide that extends from the main body in the direction of the stage and is electrically connected to the main body. The charged particle beam apparatus is characterized by this.

2. The charged particle beam apparatus according to claim 1, further comprising a voltage source for applying a potential substantially the same as the potential of the plasma generation device to the stage.

3. The charged particle beam apparatus according to claim 1, wherein the plasma generation device is configured to generate plasma during an interval between frames for imaging the sample and perform a charge removal operation on the sample.

4. The charged particle beam apparatus according to claim 1, wherein the plasma generation device is configured to generate plasma during a plurality of line scans for imaging the sample and perform a charge removal operation on the sample.

5. The charged particle beam apparatus according to claim 1, further comprising a current measurement device for measuring a charge removal current flowing through the plasma generation device.

6. The charged particle beam apparatus according to claim 5, wherein when the charge removal current measured by the current measurement device exceeds a predetermined threshold value, the imaging operation of the sample is aborted.

7. A first voltage source for applying a potential to the stage; a second voltage source for applying a potential to the plasma generation device The charged particle beam apparatus according to claim 1, further comprising.

8. A charged particle beam apparatus for irradiating a sample with a charged particle beam, comprising: a charged particle beam optical system for irradiating the sample with the charged particle beam; a sample chamber having a stage on which the sample is placed; a plasma generation device for generating plasma to irradiate the stage ; The plasma generation device includes a main body that generates plasma, and a guide that extends from the main body in the direction of the stage and is electrically connected to the main body ; The charged particle beam apparatus is characterized by this.

9. The charged particle beam apparatus according to claim 8, further comprising a voltage source for applying a potential substantially the same as the potential of the plasma generation device to the stage.

10. The charged particle beam apparatus according to claim 8, wherein the plasma generation device is configured to generate plasma during a frame for imaging the sample and perform a charge removal operation on the sample.

11. The charged particle beam apparatus according to claim 8, wherein the plasma generation device is configured to generate plasma during a plurality of line scans for imaging the sample and perform a charge removal operation on the sample.

12. The charged particle beam apparatus according to claim 8, further comprising a current measurement device that measures a charge removal current flowing through the plasma generation device.

13. The charged particle beam apparatus according to claim 12, wherein an imaging operation of the sample is aborted when the charge removal current measured by the current measurement device exceeds a predetermined threshold value.

14. A first voltage source that applies a potential to the stage, and a second voltage source that applies a potential to the plasma generation device The charged particle beam apparatus according to claim 8, further comprising.

Images