Charged particle beam device
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Filing Date
- 2023-12-05
- Publication Date
- 2025-06-12
Abstract
Description
charged particle beam equipment
[0001] The present invention relates to a charged particle beam device.
[0002] As semiconductor patterns become finer and more highly integrated, even slight differences in the pattern shape affect the device's operating characteristics. Therefore, there is an increasing need for shape control of device patterns. As a result, scanning electron microscopes (SEMs), which are charged particle beam instruments used for semiconductor inspection and / or measurement, are required to provide higher sensitivity and precision than ever before.
[0003] A scanning electron microscope uses magnetic and / or electrostatic lenses to control electrons and scan them over a sample. Secondary electrons are emitted from the sample as the electron beam scans. The secondary electrons emitted from the sample are detected by a detector, and a signal waveform is generated, enabling, for example, measurement of the dimensions between peaks (pattern edges).
[0004] In wafer inspection during the semiconductor manufacturing process, early detection of foreign particles and defects leads to improved yield, so there is a growing need for full-surface wafer inspection for defect detection.However, full-surface inspection has the problem of reducing throughput.
[0005] To increase throughput, one approach is to use low-magnification imaging with a large current to simultaneously capture a wide field of view. However, the impact of sample charging caused by low magnification is becoming significant. Increased sample charging affects the trajectory of the electron beam (primary electrons) during electron beam scanning. Charging also affects the secondary electrons emerging from the sample, and changes in trajectory can result in image distortion, uneven brightness, ghosting, and other problems. Because sample charging can reduce the measurement accuracy of SEMs, effective removal of the charge is essential.
[0006] In addition, recent semiconductor devices are not only becoming smaller, but also becoming more multi-layered, resulting in the appearance of pattern shapes with high aspect ratios (hole depth / hole diameter). In such high aspect ratio samples, there is a demand for technology that can measure the hole bottoms with high precision and detect defects.
[0007] In a method for observing the bottom of a hole using an SEM, the sample surface is charged by irradiating it with primary electrons, creating an electric field that pulls up electrons from the bottom of the hole, thereby increasing the number of electrons detected from the bottom of the hole, making it possible to observe the bottom of the hole even in high aspect ratio samples.
[0008] As described above, the charged state of the sample significantly affects the behavior of primary and secondary electrons during SEM imaging, so it is important not only to remove the charge but also to control the state of the charge. By appropriately controlling the charge on the sample surface, it is possible to reduce the influence of the trajectories of primary and secondary electrons and to control the secondary electrons detected by the detector.
[0009] Patent Document 1 describes a technology for eliminating charging unevenness on the surface of a semiconductor device by irradiating the device with a charged particle beam using a pre-charge unit. The pre-charge unit uses a plasma irradiation method or the like, and irradiates the device by setting the bias voltage to 0 V, making it possible to bring the surface potential close to 0 and eliminate charging unevenness, and the effect is evaluated from an image.
[0010] Patent Document 2 describes a method of irradiating a sample with light to change the signal amount of secondary charged particles between when light is irradiated and when it is not irradiated, and determining the material or shape of the sample based on the changed signal amount, as well as a method of eliminating static electricity by light irradiation and light irradiation conditions suitable for eliminating static electricity.
[0011] Patent Document 3 describes a method for observing the bottom of a contact hole using an SEM, in which a signal from the bottom of the contact hole is obtained by surface charging caused by electron beam irradiation, followed by inspection and measurement. This method involves intentionally positively charging the sample surface through pre-irradiation (pre-dose) by scanning with a primary electron beam, and then obtaining an SEM image by pulling up signal electrons generated from the bottom of the hole through secondary scanning. In this case, to achieve both improved inspection throughput and the prevention of large charges from adhering to the sample, a method for setting beam irradiation conditions and a method for quickly finding appropriate charging conditions are proposed.
[0012] JP 2018-041737 A JP 2021-39844 A JP 2014-22163 A
[0013] In Patent Document 1, the sample before inspection is irradiated with plasma to remove charge and eliminate uneven charge, but there is no description of a charge control method. Furthermore, the effect of charge removal is evaluated based on the symmetry of the image, but there is no description of the plasma irradiation time required for charge removal.
[0014] Patent Document 2 describes the use of the charge removal effect of light irradiation to remove static electricity from an insulating film and calculate the film thickness, but does not mention a method for charging a sample.
[0015] In Patent Document 3, the sample is charged by preliminary irradiation, and the method for optimally setting the irradiation conditions is described. However, because the electron beam used for imaging is used for preliminary irradiation, the area where charging is imparted is limited to the imaging FOV.
[0016] The present invention has been made in consideration of the above-mentioned problems, and provides a charged particle beam device that is equipped with a charge control component that is capable of wide-range charge control without using the electron beam used for imaging for charge control, and that is capable of removing or controlling the charge on a sample by using a database in which the control conditions are calculated from images.
[0017] An example of a charged particle beam apparatus according to the present invention comprises: a charged particle beam optical system that irradiates an electron beam onto a sample; a sample chamber having a stage on which the sample is placed; a detector that detects charged particles obtained by irradiating the sample with the electron beam; one or more computer systems that generate an image of the sample based on the output of the detector; a charge control component that controls the charge of the sample by generating at least one of electrons, ions, or light in accordance with charge control conditions; and an input device that accepts input of an index value related to the image, wherein the one or more computer systems control the charge control component based on the relationship between the index value and the charge control conditions and the index value.
[0018] According to the present invention, the control conditions of the charge control component for obtaining the desired image can be determined depending on the sample, and by feeding back the control conditions from the captured image, the search time for the imaging conditions can be shortened, thereby providing a charged particle beam device that suppresses a decrease in throughput.
[0019] 1 is a schematic diagram illustrating the configuration of a charged particle beam device according to a first embodiment; FIG. 2 is a schematic diagram illustrating the operation of a charged particle beam device according to a first embodiment; FIG. 3 is a schematic diagram illustrating the relationship between a charged state of a sample and an image according to a first embodiment; FIG. 4 is a schematic diagram illustrating the relationship between a charged state of a sample and an image according to a first embodiment; FIG. 5 is a schematic diagram illustrating the relationship between a charged state of a sample and an image according to a first embodiment; FIG. 6 is a diagram illustrating the relationship between a charged state of a sample and an image according to a first embodiment; FIG. 7 is a diagram illustrating the relationship between a charged state of a sample and an image according to a second embodiment; FIG. 8 is a diagram illustrating the relationship between a sample potential over time under different bias voltage conditions and an SEM image according to a first embodiment; FIG. 9 is a diagram illustrating the relationship between a luminance change of a sample and a bias voltage according to a first embodiment; FIG. 10 is a diagram illustrating a database creation procedure when the control conditions and imaging conditions in the charge control component and the sample are changed according to a first embodiment; FIG. 11 is an example of a model and a database according to SEM imaging conditions; FIG. 12 is a diagram illustrating an example of a GUI screen for setting SEM observation conditions, charge control component, and counter electrode control conditions; FIG. 13 is a flowchart of SEM imaging determined by a database based on sample information and SEM optical conditions; FIG. 14 is a diagram illustrating the change in sample potential over time under different bias voltage conditions according to a second embodiment; 10A and 10B are explanatory diagrams showing the distribution of equipotential lines (EPL) and the behavior of charged particles between a guide and a stage according to the third embodiment.
[0020] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the accompanying drawings, functionally identical elements may be designated by the same numerals. Note that the accompanying drawings show embodiments and implementation examples according to the principles of the present disclosure, but these are for understanding the present disclosure and are not to be used to interpret the present disclosure in any way as being limiting. The descriptions in this specification are merely typical examples and are not intended to limit the scope or application of the present disclosure in any way.
[0021] Although each embodiment is described in sufficient detail to enable a person skilled in the art to practice the present disclosure, it should be understood that other implementations and forms are possible, and that changes in configuration and structure and substitutions of various elements are possible without departing from the scope and spirit of the technical ideas of the present disclosure. Therefore, the following description should not be interpreted as being limited thereto.
[0022] [First Embodiment] A charged particle beam device according to a first embodiment will be described with reference to Fig. 1. The charged particle beam device can operate as a semiconductor measurement system and can also operate as a semiconductor inspection system.
[0023] In this embodiment, the charged particle beam device is an SEM, and includes, as an example, an electron beam optical system PS including an electron gun 1, a condenser lens 3, a deflector 4 (scanning deflector), and an objective lens 5. The electron beam optical system PS is an optical system that irradiates an electron beam 2 onto a sample 6, and is an example of a charged particle beam optical system. Below the electron beam optical system PS, a sample chamber 13 is installed, which includes a stage 7 on which the sample 6 is placed.
[0024] An electron beam 2 (primary electron beam) generated and accelerated by an electron gun 1 is focused by a condenser lens 3 and further focused by an objective lens 5 onto a sample 6 on a stage 7. A deflector 4 causes the electron beam 2 to scan an electron beam scanning area of the sample 6.
[0025] By irradiating the sample 6 with the electron beam 2 while scanning it, electrons excited within 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. In this way, the secondary electron detector 8 functions as a detector for detecting charged particles obtained by irradiating the sample 6 with the electron beam 2.
[0026] A computer system 14 connected to the secondary electron detector 8 converts the detection signal into an image based on the output of the secondary electron detector 8 , thereby generating an image of the sample 6 .
[0027] The computer system 14 has a hardware configuration as a known computer, and includes, for example, a computing means and a storage means. The computing means includes, for example, a processor, and the storage means includes, for example, a storage medium such as a semiconductor memory device or a magnetic disk device. Some or all of the storage medium may be non-transitory storage media.
[0028] The computer system 14 may also include input / output means, which include input devices such as a keyboard and a mouse, output devices such as a display and a printer, and communication devices such as a network interface.
[0029] The storage means may store a program, which the processor executes to cause the computer system 14 to perform the functions described in this embodiment.
[0030] The charged particle beam device may include a plurality of computer systems 14 .
[0031] An energy filter 9 that enables separation of signal electrons by energy is provided in front of (on the incident surface side of) the secondary electron detector 8. The charged state of the sample 6 can be estimated from the change in the detection signal when the voltage applied to the energy filter 9 is changed.
[0032] The energy of the electron beam 2 (primary electron beam) scanning the sample 6 is determined by the acceleration voltage of the electron gun 1 and the voltage (retarding voltage) applied to the stage 7 from a voltage source 15 (first voltage source). The amount of emitted secondary electrons 10 is related to the energy of the incident primary electrons, and the charged state of the surface of the sample 6 changes depending on the magnitude relationship between the electron current of the electron beam 2 and the electron current of the secondary electrons 10. The amount of charge on the sample 6 also changes depending on the material properties and shape of the sample 6. Furthermore, the amount of charge on the sample 6 is not uniform across the entire surface of the sample 6, but has a distribution that varies depending on the position on the surface of the sample 6 due to the material properties, shape, etc.
[0033] The charged particle beam device of this embodiment has a charge control component 11 and a counter electrode 12 that controls the charge control conditions of the charge control component 11. The charge control component 11 controls the charge of the sample 6 by generating at least one of electrons, ions, and light in accordance with the charge control conditions. For this purpose, the charge control component 11 includes a laser irradiation device and / or a flood gun that irradiates an electron shower. With this configuration, the charging operation can be performed appropriately.
[0034] 2 shows the charged state of the sample surface when irradiated with electrons, ions, and / or light generated from the charge control component 11. The positive or negative charge generated by electron beam irradiation can be removed or controlled by the charge control component 11.
[0035] Negative charging caused by electron beam irradiation can remove positive charge from the surface or give a negative charge to an uncharged state, while positive charging caused by ion irradiation can do the opposite. Light irradiation can control the charge on the sample 6 by emitting electrons from the sample 6. In either method, charge can be removed or given by controlling the energy of charged particles or light from the sample or charge control component 11.
[0036] Furthermore, by applying a positive voltage to the counter electrode 12 for charge control, an electric field is created that pulls electrons away from the sample, making it possible to remove charge more quickly if the sample is negatively charged. Conversely, when a negative voltage is applied to the counter electrode 12, an electric field is created that pulls electrons back toward the sample, so low-energy electrons are pulled back toward the sample, slowing down the rate at which charge is removed.
[0037] When setting the charge control conditions using the charge control component 11, the control conditions required to generate a desired image change depending on the pattern shape and depth of the sample to be charge-controlled, and depend not only on the positive or negative voltage applied to the counter electrode 12, but also on its magnitude. Also, since the charge state after electron beam irradiation differs depending on the sample, it is not possible to derive a uniform set of conditions for achieving a desired charge state. For this reason, in the past, it was necessary to determine the control conditions for the charge control component 11 and the counter electrode 12 through trial and error.
[0038] The charged particle beam device in this embodiment has an input device for inputting index values such as brightness values from an image generated by a computer system 14 that visualizes the detection signals, and the computer system 14 can determine the charge control conditions by modeling and / or creating a database of changes in image index values such as brightness values when the voltage of the opposing electrode 12 is changed.
[0039] The behavior of secondary electrons emerging from the sample when the charge of the sample 6 is changed by the charge control component 11 and the change in the SEM image at that time will be described with reference to FIGS.
[0040] Figure 3A shows the behavior of secondary electron beams when imaging a hole pattern. Secondary electrons 10 emitted when electron beam 2 is irradiated onto the bottom of the hole have various angular components and energies, but they are reduced by collisions with the hole walls during emission, resulting in fewer detected secondary electrons compared to the secondary electrons emitted from the sample surface. As a result, the hole pattern area appears dark, as shown in Figure 3B.
[0041] Figure 4A shows the behavior of secondary electrons when a positive charge is applied to the sample surface by plasma irradiation. Electrons emerging from the bottom of the hole are pulled upward by the electric field caused by the charge on the sample surface, increasing the number of detected electrons emerging from the bottom of the hole. As shown in Figure 4B, the hole pattern becomes brighter, allowing for control of the contrast of the SEM image.
[0042] In this way, by controlling the charge of the sample 6 using the charge control component 11 and the voltage applied to the opposing electrode 12, it becomes possible to control the detected electrons coming out of the sample, but depending on the sample pattern, the SEM image obtained will differ even if the same charge is applied.
[0043] The behavior of secondary electrons when the hole depth is increased will be explained using Figure 5. As shown in Figure 5A, if the amount of charge imparted to the sample surface is the same as in Figure 4A, the electric field acting on the secondary electrons emerging from the bottom of the hole will be relatively weaker than in Figure 4. As a result, the number of secondary electrons emerging from the bottom of the hole will decrease, and an SEM image like that shown in Figure 4B will not be obtained, and the hole pattern will be dark as shown in Figure 5B.
[0044] Conversely, the behavior of secondary electrons when the hole depth is shallower will be explained. In the example of Figure 6A, the hole depth is shallower than that of the sample shown in Figure 4A, so even if the same amount of charge is applied, the electric field acting on the secondary electrons emerging from the bottom of the hole becomes relatively stronger. As a result, the number of secondary electrons emerging from the bottom of the hole increases, and as shown in Figure 6B, the hole pattern area becomes even brighter in the SEM image.
[0045] The contrast of the SEM image can be controlled by controlling the voltage applied to the charge control component 11 and the opposing electrode 12, but the image obtained will differ depending on the pattern depth and shape of the sample even with the same charge amount. If the charge amount is too small, sufficient electrons cannot be extracted from the bottom of the hole, and if the charge amount is excessive, halation occurs and an appropriate image cannot be obtained. Therefore, it is preferable to determine the plasma irradiation conditions according to the sample pattern and control the charge amount.
[0046] 7 illustrates the change in potential over time when the magnitude of the bias voltage of the control voltage of the opposing electrode is changed from V1 to V2, ..., Vn. As described above, the potential of the sample 6 depends on the magnitude of the control voltage, and after a sufficient amount of time has passed, the potential of the sample 6 becomes saturated. Furthermore, the change in potential over time at this time becomes faster the larger the potential difference generated between the sample 6 and the sample, and depends on the potential difference from the initial charge V0 of the sample. Therefore, the larger the potential difference, the faster the change in potential over time, and as the charging of the sample 6 progresses and the potential difference becomes smaller, the change in potential over time becomes smaller.
[0047] 8 and 9, a database creation method using SEM images and the relationship between brightness and bias voltage when the voltage required to determine the conditions for charge control (for example, plasma irradiation) is changed will be described. Fig. 9 shows the procedure for creating the database.
[0048] As described above, the saturation potential differs depending on the voltages applied to the charge control component 11 and the counter electrode 12, and therefore, in step 101 of FIG. 9, the computer system 14 controls the charged particle beam device, and the charge control component 11 irradiates electrons, ions, or light for a sufficient time to saturate the charge on the sample 6.
[0049] Thereafter, in step 102, the computer system 14 controls the charged particle beam device to capture an SEM image in a state where the charge on the sample 6 is saturated.
[0050] In step 103, the computer system 14 evaluates the captured SEM image. For example, the SEM image is analyzed to extract brightness information. From the brightness information, the relationship between brightness and the bias voltage applied to the counter electrode 12 can be obtained, as shown in FIG. 8 .
[0051] The relationship between the brightness and bias voltage obtained in step 103 depends on conditions such as the sample (pattern shape, material), SEM imaging conditions (e.g., optical conditions), charge control operation (irradiation conditions for electrons, ions, light, plasma, etc.), etc., so steps 101 to 103 are repeated while changing various conditions, and a model and database are created according to the pattern shape, material, and SEM imaging conditions, as shown in FIG. 10.
[0052] In step 104, the computer system 14 creates and stores a database for each material and / or pattern.
[0053] In the example of FIG. 10, a model for each material and a model for each pattern are shown, but a model may be constructed for each combination of material and pattern, or a model may be constructed taking other conditions into consideration.
[0054] In this procedure, by increasing the bias voltage, the charged potential on the sample surface can be increased accordingly, but once the charge exceeds a certain level, dielectric breakdown occurs, causing current to flow from the sample surface to SEM components such as the stage 7 or the counter electrode 12. Therefore, there is a limit to the bias voltage that can be applied to each sample, depending on the sample material, film thickness, etc.
[0055] Furthermore, increasing the bias voltage also increases the energy of the charged particles in the plasma irradiating the sample, which can cause damage such as etching of the sample surface. By storing this information in a database, it is possible to limit the irradiation conditions during plasma irradiation and prevent sample damage. For example, when controlling charge by plasma irradiation, it is possible to set an upper limit on the plasma irradiation (e.g., irradiation intensity, dose, irradiation time, etc.) regardless of the required brightness.
[0056] In this manner, the relationship between the brightness value of the SEM image and the charge control condition (e.g., bias voltage) can be represented by at least one of a model and a database, and the charged particle beam device (e.g., particularly the computer system 14) may include a memory for storing the model and / or the database.
[0057] The procedure for plasma irradiation and SEM imaging using a model and database will be explained with reference to FIGS.
[0058] In step 201, the optical conditions of the SEM are set in the computer system 14, and the created database (e.g., representing the relationship between potential and brightness) and sample information (e.g., material and / or pattern) are input via an input device. As shown in FIG. 11, the computer system 14 then displays a predicted image on the GUI screen.
[0059] Charge control conditions calculated from various conditions are displayed on the GUI, and in step 202 the computer system 14 automatically determines the conditions for charge control operations (for example, irradiation of electrons, ions, light, plasma, etc.).
[0060] Thereafter, in step 203, the computer system 14 controls the charged particle beam device based on the database, and the charge control component executes the charge control operation.
[0061] Thereafter, in step 204, the computer system 14 controls the charged particle beam device to capture and acquire an SEM image.
[0062] In step 205, the computer system 14 evaluates the charging potential of the sample based on the acquired image and the database.
[0063] If the user determines in step 206 that the acquired SEM image is the desired image, the process ends in step 207 .
[0064] If the user determines in step 206 that the SEM image is not the desired image, the computer system 14 repeats step 203 and subsequent steps. For example, if the user determines that a portion of the SEM image is too dark, the computer system 14 selects charge control conditions corresponding to a higher brightness. Also, for example, if the user determines that a portion of the SEM image is too bright, the computer system 14 selects charge control conditions corresponding to a lower brightness.
[0065] If there is a deviation from the desired image, the computer system 14 may be configured to refer to a database to more quickly determine the conditions for charge control. Also, the deviation from the desired image may be incorporated into the database, which will improve the accuracy of the database.
[0066] In this embodiment, a predicted image is obtained from the database and sample information under preset optical conditions, but it is also possible to set the optical conditions of the SEM by setting desired image conditions, such as specifying the potential or brightness of a specified area.
[0067] 11, the "Predicted Image" area has a field for inputting a desired brightness. The computer system 14 is provided with an input device (mouse, keyboard, touch panel, etc.) that accepts input into this field, and when a user inputs a desired brightness into this field as an index value related to the SEM image, the input device of the computer system 14 accepts this index value as input.
[0068] Then, the computer system 14 controls the charge control components based on the relationship between this index value and the charge control conditions and the index value itself, and executes an appropriate charge control operation (for example, determines a bias voltage).
[0069] In this way, according to the charged particle beam device of Example 1, the control conditions of the charge control component for obtaining a desired image can be determined depending on the sample, and therefore the control conditions can be fed back from the captured image, thereby shortening the search time for the imaging conditions.
[0070] [Example 2] A charged particle beam device according to Example 2 will be described with reference to Fig. 13. The configuration of this example can be the same as that of the charged particle beam device of Example 1 shown in Fig. 1, and duplicated descriptions may be omitted below.
[0071] As described in Example 1, the charged potential of the sample depends on the magnitude of the voltage applied to the counter electrode 12. Using a database can achieve a state in which a desired SEM image of the sample can be obtained, but applying a larger bias voltage can shorten the time required to obtain the desired image, thereby improving the throughput of SEM imaging.
[0072] The database stores in advance the relationship between brightness and charge control conditions as shown in Fig. 13. In this embodiment, the charge control conditions include the time for which the bias voltage application continues.
[0073] 13, in order to set the brightness value (index value) of the SEM image to I2, if the bias voltage V3 is set to the counter electrode 12, it is sufficient to continue applying the voltage until time t2. On the other hand, by applying a larger bias voltage V4 to the counter electrode 12, the charge change of the sample can be accelerated, and the desired image can be obtained by stopping the plasma irradiation at time t1, when it is estimated based on the database that the desired brightness will be achieved.
[0074] By further increasing the magnitude of the bias voltage applied to the counter electrode 12, the charged state of the sample can be changed more quickly, and the time required to obtain a desired image can be shortened. This enables the SEM imaging sequence to be performed at a higher speed, thereby improving throughput.
[0075] In this way, the computer system 14 determines the charging operation time by the charge control component 11 based on the index value related to the SEM image. For example, the memory of the charged particle beam device (e.g., particularly the computer system 14) stores information on the relationship between the surface potential of the sample 6 and the charging operation time of the charge control component 11 according to the charge control conditions. The computer system 14 determines the charging operation time of the charge control component 11 based on the index value related to the SEM image.
[0076] By using the control method for the charging operation (e.g., plasma irradiation) in this embodiment and the relationship information in the database regarding the bias voltage that leads to dielectric breakdown for each sample, even when a large bias voltage that would lead to dielectric breakdown if applied for a long period of time is applied, it is possible to stop the plasma irradiation before dielectric breakdown occurs, and to improve throughput within a range that does not cause dielectric breakdown.
[0077] Next, a charged particle beam device according to a third embodiment will be described with reference to Fig. 14. In Fig. 14, the same components as those in the charged particle beam device of the first embodiment are denoted by the same reference numerals as in Fig. 1, and redundant descriptions may be omitted below.
[0078] The charged particle beam device of this third embodiment differs from the previous embodiments in that it includes a connecting member 19 that connects the sample chamber 13 and the plasma generating device 18 while insulating them from each other, a guide 16 that extends from the plasma generating device 18 in the direction of the stage 7, and further includes a voltage source 17 (second voltage source) that can be controlled by voltage control.
[0079] The counter electrode 12 faces the guide 16 or the sample 6, and a bias voltage is applied to the counter electrode 12.
[0080] The charge control component 11 according to Examples 1 and 2 includes a laser irradiation device and / or a flood gun, but the charge control component 11 according to Example 3 includes a plasma generation device 18 instead of or in addition to these. With this configuration, the charging operation can be performed appropriately.
[0081] In addition, while the charged particle beam devices according to Examples 1 and 2 controlled the charging of the sample using the charge control component 11 and the counter electrode 12, the charged particle beam device according to Example 3 controls the charging of the sample 6 by applying a DC voltage to the plasma generation device 18 and the guide 16.
[0082] For this purpose, the charged particle beam device includes a voltage source 15 that applies a potential to the stage 7 and a voltage source 17 that applies a potential to the plasma generation device 18. This allows the potential control of the stage 7 and the potential control of the plasma to be performed independently or in an appropriate combination. Furthermore, applying a bias voltage to the counter electrode 12 enables even more flexible control.
[0083] 15, the electric field between the guide 16 and the stage 7 can be controlled by the voltage applied to the guide 16. By controlling the electric field, a potential distribution (shown by equipotential lines EPL) is formed, which makes it possible to selectively irradiate electrons or ions among the charged particles in the neutral plasma PZ within the guide 16. In addition, since both electrons and ions exist in the plasma PZ, it is possible to remove electricity and / or impart electricity to both positive and negative polarities.
[0084] Furthermore, in the charge control methods using charge control components such as electrons, ions, and light described in Examples 1 and 2, depending on the specific configuration, the relationship between the voltage applied to the counter electrode 12 and the charge potential of the sample 6 is not uniquely determined, and it may be necessary to evaluate the charge potential using an energy filter or the like. When plasma is used as in Example 3, current flows from the sample through the guide 16, so the saturation potential and the actual charge potential of the sample 6 become equal to the potential applied to the guide 16. In addition to brightness information, the saturation potential is also newly obtained as an index value of the image when creating a database.
[0085] In Example 3, the plasma generated by the plasma generating device 18 is used to remove the charge generated on the sample 6, and the bias voltage is controlled by the voltage source 17, which is used to control the potential of the sample 6.
[0086] Here, the plasma from the plasma generating device 18 may lose its balance between electrons and ions during the diffusion process. For example, on the wall surface of a structure, differences in the mobility of charged particles in the plasma may form a sheath, creating an area with a different particle distribution, which may impair electrical neutrality. While the loss of charge balance may change the number of charged particles required for static elimination or charge control, this phenomenon can be compensated for appropriately, and essentially, static elimination or charge control is not a problem as long as electrons or ions can be irradiated.
[0087] [Other Embodiments] 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 to clearly explain the present invention, and are not necessarily limited to those including all of the described configurations. Furthermore, part of the configuration of one embodiment can be replaced with the configuration of another embodiment, or the configuration of another embodiment can be added to the configuration of one embodiment. Furthermore, part of the configuration of each embodiment can be added, deleted, or replaced with other configurations. Furthermore, the above-described configurations, functions, processing units, processing means, etc. may be implemented in hardware, in part or in whole, by, for example, designing them as integrated circuits. Furthermore, the above-described configurations, functions, etc. may be implemented in software, with a processor interpreting and executing a program that realizes each function. Information such as programs, tables, and files that realize each function can be stored in memory, a recording device such as a hard disk or SSD (Solid State Drive), or a recording medium such as an IC card, SD card, or DVD.
[0088] REFERENCE SIGNS LIST 1... Electron gun 2... Electron beam 3... Condenser lens 4... Deflector 5... Objective lens 6... Sample 7... Stage 8... Secondary electron detector (detector) 9... Energy filter 10... Secondary electrons 11... Charge control component 12... Counter electrode 13... Sample chamber 14... Computer system 15... Voltage source (first voltage source) 16... Guide 17... Voltage source (second voltage source) 18... Plasma generation device 19... Connecting member EPL... Equipotential line PS... Electron beam optical system PZ... Plasma
Claims
1. A charged particle beam device, comprising: a charged particle beam optical system that irradiates an electron beam onto a sample; a sample chamber having a stage on which the sample is placed; a detector that detects charged particles obtained by irradiating the electron beam onto the sample; one or more computer systems that generate an image of the sample based on an output of the detector; a charge control component that controls charging of the sample by generating at least one of electrons, ions, or light according to charge control conditions; and an input device that receives an input of an index value related to the image. The one or more computer systems control the charge control component based on a relationship between the index value and the charge control conditions and the index value.
2. The charged particle beam device according to claim 1, wherein the charge control component includes at least one of a plasma generation device, a laser irradiation device, or a flood gun that irradiates an electron shower.
3. The charged particle beam device according to claim 1, wherein the one or more computer systems determine a charging operation time by the charge control component based on the index value.
4. The charged particle beam device according to claim 1, wherein the charge control component includes a plasma generation device, a connecting member that connects the sample chamber and the plasma generation device, and a guide that extends from the plasma generation device in the direction of the stage. The charged particle beam device further includes a counter electrode that faces the guide or the sample, and a bias voltage is applied to the counter electrode.
5. The charged particle beam device according to claim 1, wherein the relationship between the index value and the charge control conditions is represented by at least one of a model or a database. The charged particle beam device includes a memory that stores the at least one of the model or the database. The memory stores relationship information between a surface potential of the sample and a charging operation time of the charge control component according to the charge control conditions. The one or more computer systems determine a charging operation time of the charge control component based on the index value.
6. In the charged particle beam device according to claim 1, the charge control component includes a plasma generation device, and the charged particle beam device further includes 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.