WO2025120733A1 - Charged particle beam device - Google Patents
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- WO2025120733A1 WO2025120733A1PCT/JP2023/043475JP2023043475WWO2025120733A1WO 2025120733 A1WO2025120733 A1WO 2025120733A1JP 2023043475 WJP2023043475 WJP 2023043475WWO 2025120733 A1WO2025120733 A1WO 2025120733A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/02—Details
- H01J37/20—Means for supporting or positioning the object or the material; Means for adjusting diaphragms or lenses associated with the support
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/02—Details
- H01J37/22—Optical, image processing or photographic arrangements associated with the tube
Definitions
- the present inventionrelates to a charged particle beam device.
- a scanning electron microscopeuses a magnetic field and/or an electric field lens to control electrons and scan them over a sample. Secondary electrons are emitted from the sample as a result of the electron beam scanning. The secondary electrons emitted from the sample are detected by a detector, and a signal waveform is generated, making it possible to measure, for example, the dimensions between peaks (pattern edges).
- one optionis to use low-magnification imaging with a large current to capture an image of a wide field of view at once, but the effects of sample charging caused by low magnification can no longer be ignored.
- Increased sample chargingaffects the trajectory of the electron beam (primary electrons) during electron beam scanning. Charging also affects the secondary electrons that emerge from the sample, and changes in trajectory can cause image distortion, uneven brightness, ghosting, and other problems. Sample charging can thus cause a decrease in the measurement accuracy of SEMs, so there is a need to effectively remove the charge.
- the sample surfaceis charged by irradiating it with primary electrons, creating an electric field that pulls up electrons from the bottom of the hole, making it possible to increase the number of electrons detected from the bottom of the hole, and thus making it possible to observe the bottom of the hole even in samples with a high aspect ratio.
- the charged state of the samplesignificantly 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 its state.
- By appropriately controlling the charge on the sample surfaceit is possible to reduce the effect of the trajectories on the primary and secondary electrons, and also to control the secondary electrons detected by the detector.
- Patent Document 1describes a technology that uses a pre-charge unit to irradiate the surface of a semiconductor device with a charged particle beam to eliminate charging unevenness.
- the pre-charge unituses a plasma irradiation method or the like, and irradiates the device by setting the bias voltage to 0V, making it possible to bring the surface potential close to 0 and eliminate charging unevenness, and the effectiveness of this is evaluated from images.
- Patent document 2describes how a sample is irradiated with light, changing the signal level of secondary charged particles between when light is irradiated and when it is not irradiated, and how the material or shape of the sample can be determined based on the changed signal level. It also describes a method of eliminating static electricity by irradiating the sample with light, and the light irradiation conditions suitable for eliminating static electricity.
- Patent Document 3describes 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 using surface charging caused by electron beam irradiation, followed by inspection and measurement.
- This methodinvolves intentionally positively charging the sample surface by pre-irradiation (pre-dose) using a primary electron beam scan, and then obtaining an SEM image by pulling up signal electrons generated from the bottom of the hole by a secondary scan.
- pre-irradiationpre-dose
- SEM imageby pulling up signal electrons generated from the bottom of the hole by a secondary scan.
- Patent Document 1the sample before inspection is irradiated with plasma to remove static charge and eliminate charging unevenness, but there is no mention of a charging control method.
- the effect of charging removalis evaluated based on the symmetry of the image, but there is no mention of the plasma exposure time required for charging removal, etc.
- Patent document 2describes the use of the charge removal effect of light irradiation to remove static electricity from insulating films and calculate film thickness, but does not mention a method for charging the sample.
- Patent document 3describes a method for optimally setting the irradiation conditions for charging the sample by preliminary irradiation, but because the electron beam used for imaging is used for preliminary irradiation, the area where the charge is applied is limited to the imaging FOV.
- the present inventionwas made in consideration of the above problems, and provides a charged particle beam device that is equipped with a charge control component that allows for a wide range of charge control without using the electron beam used for imaging for charge control, and that can remove or control the charge on a sample by using a database in which the control conditions are calculated from an image.
- An example of a charged particle beam deviceis a charged particle beam optical system for irradiating an electron beam onto a sample; a sample chamber including a stage on which the sample is placed; a detector for detecting charged particles obtained by irradiating the sample with the electron beam; one or more computer systems that generate images of the sample based on the output of the detector; a charge control component that controls the charge of the specimen by generating at least one of electrons, ions, or light according to charge control conditions; an input device that accepts an input of an index value related to the image; Equipped with The one or more computer systems control the charge control component based on a relationship between the index value and the charge control condition and the index value.
- the present inventionit is possible to determine the control conditions of the charge control component to obtain the desired image depending on the sample, and by feeding back the control conditions from the captured image, the search time for the imaging conditions is shortened, thereby providing a charged particle beam device that suppresses a decrease in throughput.
- FIG. 1is a schematic diagram illustrating a configuration of a charged particle beam device according to a first embodiment.
- 2is a schematic diagram for explaining the operation of the charged particle beam device according to the first embodiment.
- FIG. 5is a schematic diagram showing the relationship between the charged state of a sample and an image in Example 1.
- FIG. 5is a schematic diagram showing the relationship between the charged state of a sample and an image in Example 1.
- FIG. 5is a schematic diagram showing the relationship between the charged state of a sample and an image in Example 1.
- FIG. 5is a schematic diagram showing the relationship between the charged state of a sample and an image in Example 1.
- FIG. 1A and 1Bare diagrams showing the time change in sample potential and SEM images under different bias voltage conditions in Example 1.
- FIG. 1A and 1Bare diagrams showing the time change in sample potential and SEM images under different bias voltage conditions in Example 1.
- FIG. 13is a diagram showing the relationship between the luminance change and the bias voltage of a sample according to the first embodiment.
- 11A and 11Bare diagrams illustrating a procedure for creating a database when the control conditions, the imaging conditions, and the sample in the charge control component according to the first embodiment are changed.
- 13is an example of a model and a database according to SEM imaging conditions.
- 13is a diagram showing an example of a GUI screen for setting SEM observation conditions, a charge control component, and control conditions for a counter electrode.
- FIG. 13is a flowchart of SEM imaging determined by a database based on sample information and SEM optical conditions.
- FIG. 11is a diagram showing the change in sample potential over time under different bias voltage conditions in Example 2.
- FIG. 11is a schematic diagram illustrating a configuration of a charged particle beam device according to a third embodiment.
- 13is an explanatory diagram showing an equipotential line (EPL) distribution and charged particle behavior between a guide and a stage according to a third embodiment.
- EPLequipotential line
- Example 1A charged particle beam device according to a first embodiment will be described with reference to Fig. 1.
- the charged particle beam devicecan operate as a semiconductor measurement system and can also operate as a semiconductor inspection system.
- the charged particle beam deviceis 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 PSis an optical system that irradiates an electron beam 2 onto a sample 6, and is an example of a charged particle beam optical system.
- a sample chamber 13is installed below the electron beam optical system PS, which includes a stage 7 on which the sample 6 is placed.
- An electron beam 2(primary electron beam) generated and accelerated by an electron gun 1 is focused by a condenser lens 3 and then further focused by an objective lens 5 onto a sample 6 on a stage 7.
- a deflector 4scans the electron beam 2 over the electron beam scanning area of the sample 6.
- the secondary electron detector 8functions as a detector that detects charged particles obtained by irradiating the sample 6 with the electron beam 2.
- a computer system 14 connected to the secondary electron detector 8converts the detection signal into an image based on the output of the secondary electron detector 8, thereby generating an image of the sample 6.
- Computer system 14has a hardware configuration as a known computer, and is equipped with, for example, a computing means and a storage means.
- the computing meansincludes, for example, a processor
- the storage meansincludes, for example, a storage medium such as a semiconductor memory device and a magnetic disk device. Some or all of the storage medium may be non-transitory storage media.
- the computer system 14may also include input/output means.
- the input/output meansmay include, for example, 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.
- the storage meansmay store a program.
- the processormay execute this program, causing the computer system 14 to perform the functions described in this embodiment.
- the charged particle beam devicemay also include multiple computer systems 14.
- An energy filter 9is provided in front of the secondary electron detector 8 (on the incident surface side), which allows the separation of signal electrons by energy.
- the charged state of the sample 6can be estimated from the change in the detection signal when the voltage applied to the energy filter 9 is changed.
- the energy of the electron beam 2 (primary electron beam) that scans the sample 6is determined by the acceleration voltage of the electron gun 1 and the voltage (retarding voltage) applied to the stage 7 from the voltage source 15 (first voltage source).
- the amount of secondary electrons 10 emittedis 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 6also 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 changes depending on the position on the surface of the sample 6 due to the material properties and shape.
- the charged particle beam device of this embodimenthas a charge control component 11 and an opposing electrode 12 that controls the charge control conditions by the charge control component 11.
- the charge control component 11controls the charging of the sample 6 by generating at least one of electrons, ions, and light in accordance with the charge control conditions.
- the charge control component 11is equipped with a laser irradiation device and/or a flood gun that irradiates an electron shower. With this configuration, the charging operation can be performed appropriately.
- Figure 2shows 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 irradiationcan be removed or controlled by the charge control component 11.
- the negative charging action caused by electron beam irradiationcan remove positive charge from the surface or give a negative charge from an uncharged state, while the positive charging action caused by ion irradiation can do the opposite.
- the charge of the samplecan be controlled by the emission of electrons from the sample 6. With either method, charge can be removed or given by controlling the energy of the charged particles or light from the sample or charge control component 11.
- an electric fieldis created that pulls electrons away from the sample, making it possible to remove the charge more quickly if the sample is negatively charged.
- a negative voltageis applied to the opposing electrode 12
- an electric fieldis created that pulls electrons back toward the sample, so low-energy electrons are pulled back to the sample, slowing down the rate at which the charge is removed.
- the control conditions required to generate a desired imagechange 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.
- the charge state after electron beam irradiationdiffers depending on the sample, the derivation of conditions for achieving the desired charge state is not uniform. 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 by trial and error.
- the charged particle beam device in this embodimenthas an input device for inputting index values such as brightness values from an image generated by a computer system 14 that visualizes the detection signal, 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.
- Figure 3Ashows the behavior of the secondary electron beam when a hole pattern is imaged.
- the secondary electrons 10 that emerge when the electron beam 2 is irradiated onto the bottom of the holehave various angular components and energies, but as they are emitted, they are reduced by collisions with the hole walls, and the number of detected secondary electrons is low compared to the number of secondary electrons emerging from the sample surface. This causes the hole pattern area to become dark, as shown in Figure 3B.
- Figure 4Ashows the behavior of secondary electrons when a positive charge is applied to the sample surface by plasma irradiation.
- the electrons coming out from the bottom of the holeare pulled up by the upward electric field caused by the charge on the sample surface, increasing the number of detected electrons coming out from the bottom of the hole, making the hole pattern area brighter as shown in Figure 4B, and allowing the contrast of the SEM image to be controlled.
- the contrast of the SEM imagecan be controlled by controlling the voltage applied to the charge control component 11 and the opposing electrode 12, but the image obtained with the same charge amount will differ depending on the pattern depth and shape of the sample. If the charge amount is too small, not enough electrons can 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.
- Figure 7shows 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, V2, ... Vn.
- the potential of the sample 6depends 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 with the sample 6, and depends on the potential difference with 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.
- Figure 9shows the procedure for creating the database.
- the saturation potentialdiffers depending on the voltage applied to the charge control component 11 and the counter electrode 12, so in step 101 of FIG. 9, the computer system 14 controls the charged particle beam device and irradiates electrons, ions, or light from the charge control component 11 for a sufficient period of time to saturate the charge on the sample 6.
- step 102the computer system 14 controls the charged particle beam device to capture an SEM image when the charge on the sample 6 is saturated.
- step 103the 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 is obtained, as shown in FIG. 8.
- step 103The relationship between the brightness and bias voltage obtained in step 103 depends on the sample (pattern shape, material), SEM imaging conditions (e.g. optical conditions), charge control operation (irradiation conditions for electrons, ions, light, plasma, etc.), and other conditions, so steps 101 to 103 are repeated while changing various conditions to create a model and database according to the pattern shape, material, and SEM imaging conditions, as shown in Figure 10.
- SEM imaging conditionse.g. optical conditions
- charge control operationirradiation conditions for electrons, ions, light, plasma, etc.
- step 104the computer system 14 creates and stores a database for each material and/or pattern.
- the biased voltageby increasing the bias voltage, the charged potential on the sample surface can be increased accordingly; however, 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. For this reason, there is a limit to the bias voltage that can be applied to each sample, depending on the sample material, film thickness, etc.
- the bias voltagewhen the bias voltage is increased, the energy of the charged particles in the plasma irradiated to the sample also increases, which may cause damage such as etching of the sample surface.
- an upper limitcan be set for the plasma irradiation (e.g., irradiation intensity, irradiation amount, irradiation time, etc.) regardless of the required brightness.
- the charged particle beam devicee.g., particularly the computer system 14
- step 201the SEM optical conditions are set for 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 from an input device, and the computer system 14 displays a predicted image on the GUI screen, as shown in Figure 11.
- the created databasee.g., representing the relationship between potential and brightness
- sample informatione.g., material and/or pattern
- the charge control conditions calculated from various conditionsare displayed on the GUI, and in step 202 the computer system 14 automatically determines the conditions for the charge control operation (e.g., irradiation of electrons, ions, light, plasma, etc.).
- the conditions for the charge control operatione.g., irradiation of electrons, ions, light, plasma, etc.
- step 203the computer system 14 controls the charged particle beam device based on the database, and the charge control operation is performed by the charge control component.
- step 204the computer system 14 controls the charged particle beam device to capture and acquire an SEM image.
- step 205the computer system 14 evaluates the charged potential of the sample based on the acquired image and the database.
- step 206If the user determines in step 206 that the acquired SEM image is the desired image, the process ends in step 207.
- step 206the computer system 14 repeats steps 203 and onwards. 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.
- the computer system 14may be configured to refer to a database to determine the charge control conditions more quickly. Also, the deviation from the desired image may be incorporated into the database, which can improve the accuracy of the database.
- a predicted imageis 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 the desired image conditions, such as specifying the potential and brightness of a specified area.
- the "Predicted Image" areahas a field for inputting the desired brightness.
- the computer system 14is equipped with an input device (mouse, keyboard, touch panel, etc.) that accepts input into this field, and when the user inputs the 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.
- an input devicemouse, keyboard, touch panel, etc.
- the computer system 14controls the charge control components based on the relationship between this index value and the charge control conditions and the index value itself, and performs an appropriate charge control operation (e.g., determines a bias voltage).
- the charged particle beam devicecan determine the control conditions of the charge control component for obtaining a desired image according to the sample, and therefore the control conditions can be fed back from the captured image, thereby shortening the search time for the imaging conditions.
- Example 2A charged particle beam device according to a second embodiment will be described with reference to Fig. 13.
- the configuration of the charged particle beam device according to the second embodimentmay be the same as that of the charged particle beam device according to the first embodiment shown in Fig. 1, and therefore, in the following description, overlapping descriptions may be omitted.
- the charged potential of the sampledepends on the magnitude of the voltage applied to the opposing electrode 12.
- Using a databaseit is possible to obtain a desired SEM image of the sample, but by applying a larger bias voltage, the time required to obtain the desired image can be shortened, improving the throughput of SEM imaging.
- the relationship between brightness and charge control conditions as shown in FIG. 13is stored in advance in the database.
- the charge control conditionsinclude the time for which the bias voltage application continues.
- the bias voltage of the opposing electrode 12is V3
- the voltageshould be continued to be applied until time t2.
- V4bias voltage
- the charge change of the samplecan 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.
- the charged state of the samplecan be changed more quickly, and the time required to obtain the desired image can be shortened. This makes it possible to speed up the SEM imaging sequence, improving throughput.
- the computer system 14determines the charging operation time of the charge control component 11 based on the index value related to the SEM image.
- the memory of the charged particle beam devicee.g., particularly the computer system 14
- the computer system 14determines the charging operation time of the charge control component 11 based on the index value related to the SEM image.
- plasma irradiationBy using the control method for charging operations (e.g., plasma irradiation) in this embodiment and the relationship information in the database of the bias voltage that leads to dielectric breakdown for each sample, plasma irradiation can be stopped before dielectric breakdown occurs, even when a large bias voltage that would lead to dielectric breakdown if applied for a long period of time is applied, and throughput can be improved without causing dielectric breakdown.
- control method for charging operationse.g., plasma irradiation
- a charged particle beam deviceaccording to a third embodiment will be described with reference to Fig. 14.
- Fig. 14the same components as those in the charged particle beam device of the first embodiment are given the same reference numerals as those in Fig. 1, and duplicated descriptions may be omitted below.
- the charged particle beam device of this third embodimentdiffers 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 in the plasma generating device 18.
- a connecting member 19that connects the sample chamber 13 and the plasma generating device 18 while insulating them from each other
- a guide 16that 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 in the plasma generating device 18.
- the counter electrode 12faces the guide 16 or the sample 6, and a bias voltage is applied to the counter electrode 12.
- the charge control component 11 in Examples 1 and 2includes a laser irradiation device and/or a flood gun, but the charge control component 11 in Example 3 includes a plasma generation device 18 instead of or in addition to these. This configuration allows the charging operation to be performed appropriately.
- the charged particle beam device according to Example 3controls the charging of the sample 6 by applying a DC voltage to the plasma generating device 18 and the guide 16.
- the charged particle beam deviceis equipped with a voltage source 15 that applies a potential to the stage 7, and a voltage source 17 that applies a potential to the plasma generating device 18.
- a voltage source 15that applies a potential to the stage 7
- a voltage source 17that applies a potential to the plasma generating device 18.
- the electric field between the stage 7 and the guide 16can be controlled by the voltage applied to the guide 16.
- a distribution of electric potentialshown by equipotential lines EPL
- EPLelectric potential
- the relationship between the voltage applied to the opposing electrode 12 and the charge potential of the sample 6is not uniquely determined, and it may be necessary to evaluate the charge potential using an energy filter or the like.
- plasmaAs 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.
- the saturation potentialis newly obtained as an index value for the image when creating the database.
- Example 3the 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.
- the plasma from the plasma generating device 18may lose its balance between electrons and ions during the diffusion process.
- differences in the mobility of the charged particles in the plasmamay cause a sheath to form, resulting in the formation of an area with different particle distribution, which may impair electrical neutrality.
- a loss of charge balancemay cause a change in the number of charged particles required for static elimination or charge control, but this phenomenon can be compensated for appropriately, and essentially, static elimination or charge control will not be an issue as long as electrons or ions can be irradiated.
- the present inventionis not limited to the above-mentioned embodiment, and various modified examples are included.
- the above-mentioned embodimenthas been described in detail to explain the present invention in an easy-to-understand manner, and is not necessarily limited to those having all the configurations described.
- it is possible to replace a part of the configuration of a certain embodiment with the configuration of another embodimentand it is also possible to add the configuration of another embodiment to the configuration of a certain embodiment.
- each of the above-mentioned configurations, functions, processing units, processing means, etc.may be realized by hardware, for example, by designing them as integrated circuits.
- each of the above-mentioned configurations, functions, etc.may be realized by software by interpreting and executing a program that realizes each function by a processor.
- Informationsuch as a program, table, file, etc. that realizes each function can be placed in a 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.
- Electron gun 2Electron 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 generating device 19: Connection member EPL: Equipotential line PS: Electron beam optical system PZ: Plasma
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Abstract
Description
Translated fromJapanese本発明は、荷電粒子線装置に関する。The present invention relates to a charged particle beam device.
半導体パターンの微細化および高集積化に伴って、パターンの僅かな形状差がデバイスの動作特性に影響を及ぼす。そのため、デバイスのパターンの形状管理のニーズが高まっている。これに起因して、半導体の検査および／または計測のために用いられる荷電粒子線装置としての走査電子顕微鏡（ＳＥＭ：Scanning Electron Microscope）は、高感度・高精度計測が従来に増して求められている。As semiconductor patterns become finer and more highly integrated, even slight differences in the shape of the pattern affect the operating characteristics of the device. This has led to an increased need for shape control of device patterns. As a result, there is a greater demand than ever for high sensitivity and high-precision measurements from scanning electron microscopes (SEMs), a charged particle beam device used for semiconductor inspection and/or measurement.
走査電子顕微鏡は、電子を磁場および／または電界レンズを用いて制御し、試料上を電子でスキャンする。電子線スキャンにより試料からは二次電子が放出される。試料から放出された二次電子を検出器において検出し、その信号波形を生成し、例えばピーク（パターンエッジ）間の寸法を測定することが可能となるように構成される。 A scanning electron microscope uses a magnetic field and/or an electric field lens to control electrons and scan them over a sample. Secondary electrons are emitted from the sample as a result of the electron beam scanning. The secondary electrons emitted from the sample are detected by a detector, and a signal waveform is generated, making it possible to measure, for example, the dimensions between peaks (pattern edges).
半導体製造プロセスにおけるウェハ検査において、異物や欠陥などの早期発見は歩留まり向上に繋がるため、欠陥検出を目的としたウェハの全面検査のニーズが高まっている。その一方で、全面検査はスループットの低下に繋がるという問題がある。In wafer inspection during the semiconductor manufacturing process, early detection of foreign objects and defects leads to improved yields, so there is a growing need for full-surface inspection of wafers to detect defects. However, full-surface inspection has the problem of reducing throughput.
スループットを上げるため、大電流による低倍率撮像で、広範囲の視野を一度に撮像する検査が考えられるが、低倍率化による試料の帯電の影響が無視できなくなっている。試料帯電の増加は、電子線スキャン時の電子線（一次電子）の軌道に影響する。帯電は試料から出てくる二次電子にも影響し、軌道変化により画像の歪や輝度ムラ、ゴーストなどが生じるおそれがある。このように試料の帯電は、ＳＥＭの計測精度の低下の原因ともなるので、帯電を効果的に除去することが求められる。In order to increase throughput, one option is to use low-magnification imaging with a large current to capture an image of a wide field of view at once, but the effects of sample charging caused by low magnification can no longer be ignored. Increased sample charging affects the trajectory of the electron beam (primary electrons) during electron beam scanning. Charging also affects the secondary electrons that emerge from the sample, and changes in trajectory can cause image distortion, uneven brightness, ghosting, and other problems. Sample charging can thus cause a decrease in the measurement accuracy of SEMs, so there is a need to effectively remove the charge.
また最近の半導体デバイスは微細化だけでなく、多層化も進んでおり、高アスペクト比（ホールの深さ／ホール径）なパターン形状も見られる。このような高アスペクト比サンプルにおいて、穴底を高精度で計測し、欠陥を見つける技術も求められている。In addition, recent semiconductor devices are not only becoming smaller, but are also becoming more multi-layered, and pattern shapes with high aspect ratios (hole depth/hole diameter) are also becoming more common. In such high aspect ratio samples, there is a demand for technology that can measure the bottom of holes with high precision and find defects.
ＳＥＭを用いてホールの穴底を観察する手法において、試料表面に一次電子照射により帯電を付与することで、穴底からの電子を引き上げる電界を形成し、穴底から検出される電子を増加させることが可能となり、高アスペクト比サンプルにおいても穴底の観察が可能となる。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, making it possible to increase the number of electrons detected from the bottom of the hole, and thus making it possible to observe the bottom of the hole even in samples with a high aspect ratio.
このように試料の帯電状態はＳＥＭ撮像における一次電子、二次電子の振る舞いに大きく影響するため、帯電の除去だけでなくその状態の制御が重要となる。試料表面の帯電を適切に制御することで、一次電子や二次電子に対する軌道の影響を低減できたり、検出器で検出される二次電子の制御も可能となる。As such, 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 its state. By appropriately controlling the charge on the sample surface, it is possible to reduce the effect of the trajectories on the primary and secondary electrons, and also to control the secondary electrons detected by the detector.
特許文献１には半導体デバイス表面の帯電に対して、プレチャージユニットにより、荷電粒子線を照射して帯電ムラを無くす技術が記載されている。プレチャージユニットにはプラズマ照射方式などが用いられており、バイアス電圧を０Ｖにすることによりデバイスに照射し、表面電位を０に近づけたり、帯電のムラを無くすことを可能とし、その効果を画像から評価している。
特許文献２には、試料に対して光を照射することにより、光の照射時と非照射時との間で二次荷電粒子の信号量を変化させ、変化した信号量にしたがって、試料の材料または形状を判定することや、光照射による除電手法や除電するのに適した光照射条件について記載されている。
特許文献３には、ＳＥＭを用いてコンタクトホールの穴底を観察する方法として、電子線照射による表面帯電を用いてコンタクトホールの穴底からの信号を取得し、検査、計測する手法について記載されている。一次電子線の走査による予備照射（プリドーズ）によって試料表面を意図的に正帯電させ、二次的な走査で発生した穴底からの信号電子を引上げてＳＥＭ像を得る方法である。その際の、検査スループット向上と大きな帯電の試料への付着の両立の実現させるため、ビーム照射条件設定方法と、適正な帯電条件を早期に見出す手法について提案されている。
特許文献１では検査前の試料にプラズマを照射することで帯電を除去し、帯電ムラを取り除いているが、帯電制御手法に関する記載はない。また帯電除去の効果に画像の対称性から帯電除去の効果を評価しているが、帯電除去に必要なプラズマ照射時間などについて記載されていない。In
特許文献２では光照射による除電効果を利用して、絶縁膜の除電や膜厚算出など記載されているが、試料の帯電を与える手法については言及されていない。
特許文献３では試料への予備照射によって帯電させており、その照射条件の最適な設定方法について記載されているが、予備照射に撮像に用いる電子ビームを活用しているため、帯電付与領域は撮像ＦＯＶに限定されてしまう。
本発明は、上記のような問題に鑑みてなされたものであり、撮像に用いる電子線を帯電制御に用いることなく、広範囲の帯電制御が可能な帯電制御コンポーネントを備え、その制御条件を画像から算出したデータベースを用いることで試料の帯電除去又は制御が可能な荷電粒子線装置を提供する。The present invention was made in consideration of the above problems, and provides a charged particle beam device that is equipped with a charge control component that allows for a wide range of charge control without using the electron beam used for imaging for charge control, and that can remove or control the charge on a sample by using a database in which the control conditions are calculated from an image.
本発明に係る荷電粒子線装置の一例は、
電子線を試料に対して照射する荷電粒子線光学系と、
前記試料を載置するステージを備えた試料室と、
前記試料に対する前記電子線の照射によって得られる荷電粒子を検出する検出器と、
前記検出器の出力に基づいて、前記試料の画像を生成する１以上のコンピュータシステムと、
帯電制御条件に従って、電子、イオン、または光のうち少なくとも１つを発生することによって、前記試料の帯電を制御する帯電制御コンポーネントと、
前記画像に関する指標値の入力を受け付ける入力デバイスと、
を備え、
前記１以上のコンピュータシステムは、前記指標値と前記帯電制御条件との関係と、前記指標値とに基づいて、前記帯電制御コンポーネントを制御する。An example of a charged particle beam device according to the present invention is
a charged particle beam optical system for irradiating an electron beam onto a sample;
a sample chamber including a stage on which the sample is placed;
a detector for detecting charged particles obtained by irradiating the sample with the electron beam;
one or more computer systems that generate images of the sample based on the output of the detector;
a charge control component that controls the charge of the specimen by generating at least one of electrons, ions, or light according to charge control conditions;
an input device that accepts an input of an index value related to the image;
Equipped with
The one or more computer systems control the charge control component based on a relationship between the index value and the charge control condition and the index value.
本発明によれば、試料に応じて、所望の画像を得るための帯電制御コンポーネントの制御条件を決定でき、撮像した画像から制御条件をフィードバックすることで撮像条件の探索時間が短縮されることで、スループット低下を抑えた荷電粒子線装置を提供することができる。According to the present invention, it is possible to determine the control conditions of the charge control component to obtain the desired image depending on the sample, and by feeding back the control conditions from the captured image, the search time for the imaging conditions is shortened, thereby providing a charged particle beam device that suppresses a decrease in throughput.
以下、添付図面を参照して本発明の実施例について説明する。添付図面では、機能的に同じ要素は同じ番号で表示される場合もある。なお、添付図面は本開示の原理に則った実施例と実装例を示しているが、これらは本開示の理解のためのものであり、決して本開示を限定的に解釈するために用いられるものではない。本明細書の記述は典型的な例示に過ぎず、本開示の特許請求の範囲又は適用例を如何なる意味においても限定するものではない。Below, an embodiment of the present invention will be described with reference to the attached drawings. In the attached drawings, functionally identical elements may be indicated by the same numbers. Note that the attached drawings show embodiments and implementation examples according to the principles of the present disclosure, but these are for the purpose of understanding the present disclosure and are in no way to be used to interpret the present disclosure in a restrictive manner. 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.
各実施例では、当業者が本開示を実施するのに十分詳細にその説明がなされているが、他の実装・形態も可能で、本開示の技術的思想の範囲と精神を逸脱することなく構成・構造の変更や多様な要素の置き換えが可能であることを理解する必要がある。従って、以降の記述をこれに限定して解釈してはならない。Each embodiment is described in sufficient detail to enable a person skilled in the art to implement the present disclosure, but it should be understood that other implementations and forms are possible, and that configurations and structures can be modified and various elements can be substituted 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 to this.
［実施例１］
図１を参照して、実施例１に係る荷電粒子線装置を説明する。荷電粒子線装置は、半導体の計測システムとして動作することができ、また、半導体の検査システムとして動作することもできる。[Example 1]
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.
本実施例では荷電粒子線装置はＳＥＭであり、一例として、電子銃１と、コンデンサレンズ３と、偏向器４（走査偏向器）と、対物レンズ５とを含む電子線光学系ＰＳを備える。電子線光学系ＰＳは、電子線２を試料６に対して照射する光学系であり、荷電粒子線光学系の例である。電子線光学系ＰＳの下方には、試料６を載置するステージ７を内部に備える試料室１３が設置される。In this embodiment, the charged particle beam device is an SEM, and includes, as an example, an electron beam optical system PS including an
電子銃１によって発生し加速された電子線２（一次電子線）は、コンデンサレンズ３によって集束され、更に対物レンズ５によってステージ７上の試料６上に集束される。偏向器４は、試料６の電子線走査領域上で電子線２を走査させる。An electron beam 2 (primary electron beam) generated and accelerated by an
電子線２を試料６上で走査させながら照射することによって、試料６内で励起された電子が二次電子１０として試料６から放出される。放出された二次電子１０は、二次電子検出器８により検出される。このように、二次電子検出器８は、試料６に対する電子線２の照射によって得られる荷電粒子を検出する検出器として機能する。By irradiating the
二次電子検出器８に接続されたコンピュータシステム１４が、二次電子検出器８の出力に基づいて、検出信号を画像化し、これによって試料６の画像を生成する。A
コンピュータシステム１４は公知のコンピュータとしてのハードウェア構成を有し、たとえば演算手段および記憶手段を備える。演算手段はたとえばプロセッサを含み、記憶手段はたとえば半導体メモリ装置および磁気ディスク装置等の記憶媒体を含む。記憶媒体の一部または全部が、過渡的でない(non-transitory)記憶媒体であってもよい。
また、コンピュータシステム１４は入出力手段を備えてもよい。入出力手段は、たとえばキーボードおよびマウス等の入力装置と、ディスプレイおよびプリンタ等の出力装置と、ネットワークインタフェース等の通信装置とを含む。The
記憶手段はプログラムを記憶してもよい。プロセッサがこのプログラムを実行することにより、コンピュータシステム１４は本実施例において説明される機能を実行してもよい。The storage means may store a program. The processor may execute this program, causing the
なお、荷電粒子線装置は、複数のコンピュータシステム１４を備えてもよい。The charged particle beam device may also include
二次電子検出器８の前段（入射面側）には、エネルギーによる信号電子の分別を可能とするエネルギーフィルタ９が備えられている。エネルギーフィルタ９に印加する電圧を変化させた際の検出信号の変化から、試料６の帯電状態を推定することが可能である。An
試料６を走査する電子線２（一次電子線）のエネルギーは、電子銃１の加速電圧と電圧源１５（第１電圧源）からステージ７に印加される電圧（リターディング電圧）で決定される。放出される二次電子１０の量は、入射される一次電子のエネルギーと関係しており、電子線２の電子流と二次電子１０の電子流の大小関係により、試料６表面の帯電状態が変化する。試料６の帯電量は、試料６の材料特性や形状などによっても変化する。また、試料６の帯電量は、試料６の表面全体において一様ではなく、材料特性や形状などにより、試料６の表面の位置によって変化する分布を有する。The energy of the electron beam 2 (primary electron beam) that scans the
本実施例の荷電粒子線装置は、帯電制御コンポーネント１１と、帯電制御コンポーネント１１による帯電制御条件を制御する対向電極１２を有する。帯電制御コンポーネント１１は、帯電制御条件に従って、電子、イオン、または光のうち少なくとも１つを発生することにより、試料６の帯電を制御する。このために、帯電制御コンポーネント１１は、レーザー照射装置、および／または、電子シャワーを照射するフラッドガンを備える。このような構成により、帯電動作を適切に実行することができる。The charged particle beam device of this embodiment has a
図２に、帯電制御コンポーネント１１から発生した電子、イオン、および／または光が照射された際の試料表面の帯電状態を示す。電子線照射で生じた正または負帯電は帯電制御コンポーネント１１により除去あるいは制御することができる。Figure 2 shows the charged state of the sample surface when irradiated with electrons, ions, and/or light generated from the
電子線照射に起因する負帯電動作により、表面の正帯電を除去したり、帯電していない状態から負帯電を与えることができ、イオン照射による正帯電動作ではその逆の作用が可能である。光照射では試料６からの電子放出により試料の帯電を制御することができる。いずれの手法でも試料もしくは帯電制御コンポーネント１１からの荷電粒子や光のエネルギーを制御することで帯電の除去や付与することができる。The negative charging action caused by electron beam irradiation can remove positive charge from the surface or give a negative charge from an uncharged state, while the positive charging action caused by ion irradiation can do the opposite. With light irradiation, the charge of the sample can be controlled by the emission of electrons from the
さらに帯電制御するための対向電極１２に正の電圧を印加することで、電子に対しては試料から引き上げられる電界となるため、試料が負帯電の場合はより速い帯電の除去が可能となる。反対に対向電極１２に負の電圧を印加した場合は、電子に対しては試料に戻るような電界となるため、エネルギーの低い電子は試料に引き戻されるため、帯電除去の速度は遅くなる。Furthermore, by applying a positive voltage to the opposing
帯電制御コンポーネント１１による帯電制御条件の設定においては、帯電制御する試料のパターン形状や深さによって所望の画像を生成するために必要な制御条件が変化し、対向電極１２に印加する電圧の正負だけではなく、その大きさにも依存する。また試料によっても電子線照射後の帯電状態が異なるため、所望の帯電状態にするための条件の導出は一律には定まらない。このため従来では、試行錯誤により帯電制御コンポーネント１１や対向電極１２の制御条件を決める必要があった。When setting the charge control conditions using the
本実施例における荷電粒子線装置は、検出信号を画像化するコンピュータシステム１４で生成された画像から輝度値などの指標値を入力する入力デバイスを有しており、コンピュータシステム１４は、対向電極１２の電圧を変化させた際の輝度値などの画像の指標値の変化をモデル化および／またはデータベース化することで帯電制御条件を決めることができる。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
帯電制御コンポーネント１１により試料６の帯電を変化させた時の試料から出てくる二次電子挙動とその時のＳＥＭ画像の変化について、図３および４を用いて説明する。The behavior of secondary electrons coming out of the sample when the charge of the
図３Ａはホールパターンを撮像した際の二次電子線挙動を示している。穴底に電子線２を照射した際に出てくる二次電子１０は、様々な角度成分、エネルギーを持っているが、放射される過程でホール壁面への衝突などにより減少し、試料表面から出てくる二次電子に対して検出数は少なくなる。その為、図３Ｂに示すようにホールパターン部分が暗くなる。Figure 3A shows the behavior of the secondary electron beam when a hole pattern is imaged. The
図４Ａはプラズマ照射により試料表面に正帯電を付与したときの二次電子挙動を示す。穴底から出てくる電子は、試料表面の帯電による上向きの電界で引き上げられ、穴底から出てくる検出電子が増加し、図４Ｂに示すようにホールパターン部分が明るくなり、ＳＥＭ画像のコントラストを制御することができる。Figure 4A shows the behavior of secondary electrons when a positive charge is applied to the sample surface by plasma irradiation. The electrons coming out from the bottom of the hole are pulled up by the upward electric field caused by the charge on the sample surface, increasing the number of detected electrons coming out from the bottom of the hole, making the hole pattern area brighter as shown in Figure 4B, and allowing the contrast of the SEM image to be controlled.
このように、帯電制御コンポーネント１１と、対向電極１２に与える電圧とにより試料６の帯電を制御することで、試料から出てくる検出電子の制御が可能になるが、試料パターンによっては、同じ帯電を付与した場合でも得られるＳＥＭ画像は異なる。In this way, by controlling the charge of the
図５を用いて、ホール深さが深くなった場合の二次電子挙動を説明する。図５Ａに示すように、試料表面に付与する帯電量が図４Ａと同じであれば、穴底から出てくる二次電子に対して働く電界は図４に対して相対的に小さくなる。そのため、穴底から出てくる二次電子の数は減少し、図４Ｂで示すようなＳＥＭ画像は得られず、図５Ｂに示すようにホールパターン部分は暗くなる。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 applied 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 smaller relative to that in Figure 4. As a result, the number of secondary electrons emerging from the bottom of the hole will decrease, an SEM image like that shown in Figure 4B will not be obtained, and the hole pattern area will be dark as shown in Figure 5B.
反対にホール深さが浅くなった場合の二次電子挙動を説明する。図６Ａの例では図４Ａで示した試料よりホール深さが浅くなっているため、同じ帯電量を付与した場合でも穴底出てくる二次電子に対して働く電界は相対的に大きくなる。そのため、穴底から出てくる二次電子の数は増加し、図６Ｂで示すように、ＳＥＭ画像において、ホールパターン部分はさらに明るくなる。The opposite behavior of secondary electrons when the hole depth is shallower will now be explained. In the example of Figure 6A, the hole depth is shallower than 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 is 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 part becomes even brighter in the SEM image.
帯電制御コンポーネント１１と対向電極１２の印加電圧を制御することで、ＳＥＭ画像のコントラストを制御できるが、試料のパターン深さや形状によって同じ帯電量でも得られる画像は異なる。帯電量が小さすぎると穴底から十分な電子を引き出すことができず、帯電量が過剰だとハレーションしてしまい、適切な画像を取得できない。そのため、試料パターンに応じてプラズマ照射条件を決定し、帯電量を制御することが好適である。The contrast of the SEM image can be controlled by controlling the voltage applied to the
図７に対向電極の制御電圧のバイアス電圧の大きさをＶ１、Ｖ２、…Ｖｎと変化させた場合の電位の時間変化について説明する。上述したように試料６の電位は制御電圧の大きさに依存し、十分な時間が経過すると、試料６の電位は飽和する。またこの時の電位変化の時間変化は、試料６との間に生じる電位差が大きいほど速くなり、試料の初期帯電Ｖ０との電位差に依存する。その為、電位差が大きいほど電位の時間変化は速く、試料６の帯電が進行して電位差が小さくなると電位の時間変化が小さくなる。Figure 7 shows 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, V2, ... Vn. As mentioned above, the potential of the
図８と図９を用いて、帯電制御（たとえばプラズマ照射）の条件決定に必要な電圧を変化させた際のＳＥＭ画像および輝度とバイアス電圧の関係を用いたデータベース作成手法について説明する。図９はデータベース作成の手順を示している。Using Figures 8 and 9, we will explain the 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. Figure 9 shows the procedure for creating the database.
前述したように、帯電制御コンポーネント１１と対向電極１２の印加電圧に応じて飽和電位が異なるため、図９の手順１０１では、コンピュータシステム１４が荷電粒子線装置を制御し、十分な時間、帯電制御コンポーネント１１により電子、イオン、あるいは光を照射し、試料６の帯電を飽和させる。As mentioned above, the saturation potential differs depending on the voltage applied to the
その後、手順１０２では、コンピュータシステム１４が荷電粒子線装置を制御し、試料６の帯電が飽和した状態でＳＥＭ画像を撮像させる。Then, in
手順１０３では、コンピュータシステム１４が、撮像したＳＥＭ画像を評価する。たとえば、ＳＥＭ画像を分析して輝度情報を抽出する。輝度情報から図８に示すような輝度と対向電極１２に印加するバイアス電圧の関係が得られる。In
手順１０３で得られた輝度とバイアス電圧の関係は、試料（パターン形状、材料）、ＳＥＭの撮像条件（たとえば光学条件）、帯電制御動作（電子、イオン、光、プラズマ、等の照射条件）、等の条件に依存するため、各種条件を変更して手順１０１～１０３を繰り返し、図１０で示すようにパターン形状や材料、ＳＥＭの撮像条件に応じたモデルやデータベースを作成する。The relationship between the brightness and bias voltage obtained in
手順１０４では、コンピュータシステム１４が、材料および／またはパターン毎にデータベースを作成して記憶する。In
なお図１０の例では材料ごとのモデルおよびパターンごとのモデルが示されているが、材料およびパターンの組み合わせごとのモデルを構築してもよく、さらに他の条件を考慮してモデルを構築してもよい。Note that in the example of Figure 10, a model for each material and each pattern is shown, but a model may be constructed for each combination of material and pattern, and a model may also be constructed taking other conditions into consideration.
本手順においてバイアス電圧を大きくすることで、その電圧に応じて試料表面の帯電電位を大きくすることができるが、ある一定以上の帯電になると、試料表面からステージ７もしくは対向電極１２などのＳＥＭの構成部品に電流が流れる絶縁破壊が生じる。そのため、試料の材料や膜厚などに応じ、試料毎に印加できるバイアス電圧に限界がある。In this procedure, by increasing the bias voltage, the charged potential on the sample surface can be increased accordingly; however, once the charge exceeds a certain level, dielectric breakdown occurs, causing current to flow from the sample surface to SEM components such as the
またバイアス電圧を大きくした場合、試料に照射されるプラズマ中の荷電粒子が持つエネルギーも大きくなるため、試料表面がエッチングされるなどダメージが生じる恐れがある。このような情報もデータベース内に蓄積することで、プラズマ照射時における照射条件に制限を掛けることができ、試料の破損を防ぐことができる。たとえば、プラズマの照射により帯電制御を行う場合には、要求される輝度に関わらず、プラズマの照射（たとえば照射強度、照射量、照射時間、等）に上限を設けてもよい。Furthermore, when the bias voltage is increased, the energy of the charged particles in the plasma irradiated to the sample also increases, which may cause damage such as etching of the sample surface. By storing such information in the database, it is possible to limit the irradiation conditions during plasma irradiation and prevent damage to the sample. For example, when controlling charging by plasma irradiation, an upper limit can be set for the plasma irradiation (e.g., irradiation intensity, irradiation amount, irradiation time, etc.) regardless of the required brightness.
このように、ＳＥＭ画像の輝度値と帯電制御条件（たとえばバイアス電圧）との関係は、モデルまたはデータベースのうち少なくとも１つによって表すことができる。荷電粒子線装置（たとえば、とくにコンピュータシステム１４）は、このモデルおよび／またはデータベースを記憶するメモリを備えてもよい。In this way, the relationship between the brightness values of the SEM image and the charge control conditions (e.g., bias voltage) can be represented by at least one of a model and a database. The charged particle beam device (e.g., particularly the computer system 14) may include a memory that stores the model and/or the database.
図１１、１２を用いてモデルやデータベースを用いたプラズマ照射とＳＥＭ撮像の手順を説明する。The procedure for plasma irradiation and SEM imaging using a model and database will be explained using Figures 11 and 12.
手順２０１では、コンピュータシステム１４に対してＳＥＭの光学条件を設定し、作成したデータベース（たとえば電位と輝度の関係を表すもの）と試料情報（たとえば材料および／またはパターン）を入力デバイスから入力すると、図１１に示すように、コンピュータシステム１４がＧＵＩ画面に予測画像を表示する。In
ＧＵＩ上には各種条件から算出された帯電制御条件が表示され、手順２０２にてコンピュータシステム１４が帯電制御動作（たとえば電子、イオン、光、プラズマ、等の照射）の条件を自動的に決定する。The charge control conditions calculated from various conditions are displayed on the GUI, and in
その後、手順２０３で、コンピュータシステム１４がデータベースに基づいて荷電粒子線装置を制御し、帯電制御コンポーネントによる帯電制御動作が実行される。Then, in
その後、手順２０４で、コンピュータシステム１４が荷電粒子線装置を制御し、ＳＥＭ画像を撮像して取得する。Then, in
手順２０５で、コンピュータシステム１４が、取得した画像とデータベースとに基づいて試料の帯電電位を評価する。In
取得したＳＥＭ画像が所望の画像であると手順２０６でユーザが判断した場合には、手順２０７で処理を終了する。If the user determines in
手順２０６で、ＳＥＭ画像が所望の画像でないとユーザが判断した場合には、コンピュータシステム１４は、もう一度手順２０３以降を繰り返す。たとえば、ＳＥＭ画像の一部が暗すぎるとユーザが判断した場合には、コンピュータシステム１４は、より高い輝度に対応する帯電制御条件を選択する。また、たとえば、ＳＥＭ画像の一部が明るすぎるとユーザが判断した場合には、コンピュータシステム１４は、より低い輝度に対応する帯電制御条件を選択する。If in
所望の画像からのずれがある場合には、コンピュータシステム１４は、データベースを参照してより速く帯電制御の条件を決定することができるように構成されていてもよい。また所望の画像とのずれをデータベースに取り込んでもよく、そのようにするとデータベースの高精度化が図れる。If there is a deviation from the desired image, the
本実施例ではあらかじめ設定した光学条件において、データベースと試料情報から予測画像が得られるが、指定した領域の電位や輝度を指定するなど所望の画像条件を設定することで、ＳＥＭの光学条件を設定することも可能となる。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 the desired image conditions, such as specifying the potential and brightness of a specified area.
たとえば、図１１の例では、「予測画像」エリアに所望の輝度を入力する欄がある。コンピュータシステム１４は、この欄への入力を受け付ける入力デバイス（マウス、キーボイード、タッチパネル、等）を備えており、ユーザがこの欄に、ＳＥＭ画像に関する指標値として所望の輝度を入力すると、コンピュータシステム１４の入力デバイスがこの指標値を入力として受け付ける。For example, in the example of FIG. 11, the "Predicted Image" area has a field for inputting the desired brightness. The
そして、コンピュータシステム１４は、この指標値と帯電制御条件との関係と、指標値そのものとに基づいて、帯電制御コンポーネントを制御し、適切な帯電制御動作を実行する（たとえばバイアス電圧を決定する）。Then, the
このように、実施例１に係る荷電粒子線装置によれば、試料に応じて、所望の画像を得るための帯電制御コンポーネントの制御条件を決定できるので、撮像した画像から制御条件をフィードバックすることができ、撮像条件の探索時間が短縮される。In this way, the charged particle beam device according to the first embodiment can determine the control conditions of the charge control component for obtaining a desired image according to the sample, and therefore the control conditions can be fed back from the captured image, thereby shortening the search time for the imaging conditions.
［実施例２］
実施例２に係る荷電粒子線装置を、図１３を用いて説明する。本実施例における構成は図１に示す実施例１の荷電粒子線装置と同一とすることができ、以下では重複する説明は省略する場合がある。[Example 2]
A charged particle beam device according to a second embodiment will be described with reference to Fig. 13. The configuration of the charged particle beam device according to the second embodiment may be the same as that of the charged particle beam device according to the first embodiment shown in Fig. 1, and therefore, in the following description, overlapping descriptions may be omitted.
実施例１で述べたように試料の帯電電位は対向電極１２に印加する電圧の大きさに依存する。試料のＳＥＭ画像として所望の画像を得られる状態にすることは、データベースを用いることで実現できるが、より大きなバイアス電圧を印加することで所望の画像にするための時間を短縮することができ、ＳＥＭ撮像のスループットを向上できる。As described in Example 1, the charged potential of the sample depends on the magnitude of the voltage applied to the opposing
データベースに、図１３に示すような輝度と帯電制御条件との関係が予め記憶される。本実施例では、帯電制御条件は、バイアス電圧の印加を継続する時間を含む。The relationship between brightness and charge control conditions as shown in FIG. 13 is stored in advance in the database. In this embodiment, the charge control conditions include the time for which the bias voltage application continues.
図１３に示すように、ＳＥＭ画像の輝度値（指標値）をＩ２にするには、対向電極１２のバイアス電圧Ｖ３とした場合、時刻ｔ２まで電圧を印加し続ければよい。一方で、対向電極１２により大きなバイアス電圧Ｖ４を印加することで、試料の帯電変化を速くすることができ、データベースに基づき所望の輝度になると推測される時刻ｔ１においてプラズマの照射を止めることで、所望の画像を得ることができる。As shown in FIG. 13, in order to set the brightness value (index value) of the SEM image to I2, if the bias voltage of the opposing
対向電極１２に印加するバイアス電圧の大きさをさらに大きくすると、試料の帯電状態をより速く変化させることができ、所望の画像を得るまでに必要とする時間もより短くできる。ＳＥＭ撮像シーケンスの高速化が可能となり、スループットを向上させることができる。By further increasing the magnitude of the bias voltage applied to the opposing
このように、コンピュータシステム１４は、ＳＥＭ画像に関する指標値に基づいて、帯電制御コンポーネント１１による帯電動作時間を決定する。たとえば、荷電粒子線装置の（たとえば、とくにコンピュータシステム１４の）メモリには、帯電制御条件に応じた、試料６の表面電位と帯電制御コンポーネント１１の帯電動作時間との関係情報が記憶されている。コンピュータシステム１４は、ＳＥＭ画像に関する指標値に基づいて、帯電制御コンポーネント１１の帯電動作時間を決定する。In this way, the
本実施例における帯電動作（たとえばプラズマ照射）の制御手法と、データベース内にある試料毎の絶縁破壊に至るバイアス電圧の関係情報を用いることで、長時間の印加により絶縁破壊に至るような大きいバイアス電圧を印加した場合でも、絶縁破壊する前にプラズマ照射を止めることができ、絶縁破壊を生じさせない範囲内でスループットを向上させることができる。By using the control method for charging operations (e.g., plasma irradiation) in this embodiment and the relationship information in the database of the bias voltage that leads to dielectric breakdown for each sample, plasma irradiation can be stopped before dielectric breakdown occurs, even when a large bias voltage that would lead to dielectric breakdown if applied for a long period of time is applied, and throughput can be improved without causing dielectric breakdown.
［実施例３］
次に、実施例３に係る荷電粒子線装置を、図１４を参照して説明する。図１４において、実施例１の荷電粒子線装置と同一の構成要素については、図１と同一の参照符号を付しており、以下では重複する説明は省略する場合がある。[Example 3]
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 given the same reference numerals as those in Fig. 1, and duplicated descriptions may be omitted below.
この実施例３の荷電粒子線装置は、試料室１３とプラズマ生成装置１８とを絶縁しつつ連結する連結部材１９と、プラズマ生成装置１８からステージ７の方向に延びるガイド１６とを備え、さらにプラズマ生成装置１８に電圧制御可能な電圧源１７（第２電圧源）を設けた点で、前述の各実施例と異なっている。The charged particle beam device of this third embodiment differs from the previous embodiments in that it includes a connecting
対向電極１２は、ガイド１６もしくは試料６に対向し、対向電極１２にはバイアス電圧が印加される。The
実施例１および２に係る帯電制御コンポーネント１１はレーザー照射装置および／またはフラッドガンを備えていたが、実施例３に係る帯電制御コンポーネント１１は、これらに代えて、またはこれらに加えて、プラズマ生成装置１８を備える。このような構成により、帯電動作を適切に実行することができる。The
また、実施例１および２に係る荷電粒子線装置は、帯電制御コンポーネント１１と対向電極１２で試料の帯電を制御していたが、実施例３に係る荷電粒子線装置は、プラズマ生成装置１８およびガイド１６に直流電圧を印加することで、試料６の帯電を制御する。In addition, while the charged particle beam devices according to Examples 1 and 2 controlled the charging of the sample using the
このために、荷電粒子線装置は、ステージ７に電位を与える電圧源１５と、プラズマ生成装置１８に電位を与える電圧源１７とを備える。これによって、ステージ７の電位制御と、プラズマの電位制御とを独立して、または適切に組み合わせて行うことができる。さらに、対向電極１２にバイアス電圧を印加することにより、さらに柔軟な制御が可能となる。To this end, the charged particle beam device is equipped with a
図１５に示すように、ガイド１６に印加した電圧によりステージ７との間の電界を制御できる。電界の制御によって、電位の分布（等電位線ＥＰＬによって示す）が形成され、これによって、ガイド１６内の中性のプラズマＰＺ中の荷電粒子のうち、電子あるいはイオンを選択的に照射することができる。またプラズマＰＺ中には電子とイオン両方が存在しているため、正負両極性について、除電および／または帯電を付与することができる。As shown in FIG. 15, the electric field between the
さらに、実施例１および２で記載した電子、イオン、光などの帯電制御コンポーネントを用いた帯電制御手法では、具体的構成によっては、対向電極１２に印加した電圧と、試料６の帯電電位の関係は一意には定まらず、エネルギーフィルタなどを用いて帯電電位を評価する必要がある場合がある。実施例３のようにプラズマを用いる場合、ガイド１６を通して試料から電流が流れるため、飽和電位と実際の試料６の帯電電位はガイド１６に印加した電位と等しくなる。データベースを作成する際の画像の指標値として、輝度情報だけでなく、新たに飽和電位が得られる。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 opposing
実施例３では、プラズマ生成装置１８で生成したプラズマを用いることで、試料６に生じた帯電の除去ができ、また、バイアス電圧を電圧源１７で制御することで試料６の電位制御に活用している。In Example 3, the plasma generated by the
ここで、プラズマ生成装置１８からのプラズマは、拡散の過程で電子とイオンとのバランスが崩れる場合がある。たとえば、構造物壁面では、プラズマの荷電粒子の移動度の差で、シースが形成されるなど、粒子分布が異なる領域が形成され、電気的中性が損なわれる場合がある。電荷バランスか崩れることで、除電や帯電制御に必要な荷電粒子の数が変化することがあるが、このような現象は適宜補償が可能であり、本質的には、電子もしくはイオンを照射できれば除電や帯電制御には問題ない。In this case, the plasma from the
［その他の実施例］
なお、本発明は上記した実施例に限定されるものではなく、様々な変形例が含まれる。例えば、上記した実施例は本発明を分かりやすく説明するために詳細に説明したものであり、必ずしも説明した全ての構成を備えるものに限定されるものではない。また、ある実施例の構成の一部を他の実施例の構成に置き換えることが可能であり、また、ある実施例の構成に他の実施例の構成を加えることも可能である。また、各実施例の構成の一部について、他の構成の追加・削除・置換をすることが可能である。また、上記の各構成、機能、処理部、処理手段等は、それらの一部又は全部を、例えば集積回路で設計する等によりハードウェアで実現してもよい。また、上記の各構成、機能等は、プロセッサがそれぞれの機能を実現するプログラムを解釈し、実行することによりソフトウェアで実現してもよい。各機能を実現するプログラム、テーブル、ファイル等の情報は、メモリや、ハードディスク、ＳＳＤ（Solid State Drive）等の記録装置、又は、ＩＣカード、ＳＤカード、ＤＶＤ等の記録媒体に置くことができる。[Other Examples]
The present invention is not limited to the above-mentioned embodiment, and various modified examples are included. For example, the above-mentioned embodiment has been described in detail to explain the present invention in an easy-to-understand manner, and is not necessarily limited to those having all the configurations described. In addition, it is possible to replace a part of the configuration of a certain embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of a certain embodiment. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration. In addition, each of the above-mentioned configurations, functions, processing units, processing means, etc. may be realized by hardware, for example, by designing them as integrated circuits. In addition, each of the above-mentioned configurations, functions, etc. may be realized by software by interpreting and executing a program that realizes each function by a processor. Information such as a program, table, file, etc. that realizes each function can be placed in a 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.
１…電子銃
２…電子線
３…コンデンサレンズ
４…偏向器
５…対物レンズ
６…試料
７…ステージ
８…二次電子検出器（検出器）
９…エネルギーフィルタ
１０…二次電子
１１…帯電制御コンポーネント
１２…対向電極
１３…試料室
１４…コンピュータシステム
１５…電圧源（第１電圧源）
１６…ガイド
１７…電圧源（第２電圧源）
１８…プラズマ生成装置
１９…連結部材
ＥＰＬ…等電位線
ＰＳ…電子線光学系
ＰＺ…プラズマ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 generating device 19: Connection member EPL: Equipotential line PS: Electron beam optical system PZ: Plasma
Claims (6)
Translated fromJapanese電子線を試料に対して照射する荷電粒子線光学系と、
前記試料を載置するステージを備えた試料室と、
前記試料に対する前記電子線の照射によって得られる荷電粒子を検出する検出器と、
前記検出器の出力に基づいて、前記試料の画像を生成する１以上のコンピュータシステムと、
帯電制御条件に従って、電子、イオン、または光のうち少なくとも１つを発生することによって、前記試料の帯電を制御する帯電制御コンポーネントと、
前記画像に関する指標値の入力を受け付ける入力デバイスと、
を備え、
前記１以上のコンピュータシステムは、前記指標値と前記帯電制御条件との関係と、前記指標値とに基づいて、前記帯電制御コンポーネントを制御する、荷電粒子線装置。A charged particle beam device, comprising:
a charged particle beam optical system for irradiating an electron beam onto a sample;
a sample chamber including a stage on which the sample is placed;
a detector for detecting charged particles obtained by irradiating the sample with the electron beam;
one or more computer systems that generate images of the sample based on the output of the detector;
a charge control component that controls the charge of the specimen by generating at least one of electrons, ions, or light according to charge control conditions;
an input device that accepts an input of an index value related to the image;
Equipped with
The one or more computer systems control the charge control component based on a relationship between the index value and the charge control condition and the index value.
プラズマ生成装置、
レーザー照射装置、或いは、
電子シャワーを照射するフラッドガン、
のうち少なくとも１つを備える、荷電粒子線装置。2. The charged particle beam device according to claim 1, wherein the charge control component comprises:
Plasma generating device,
Laser irradiation device, or
Flood guns that emit electron showers,
A charged particle beam device comprising at least one of the following:
プラズマ生成装置と、
前記試料室と前記プラズマ生成装置とを連結する連結部材と、
前記プラズマ生成装置から前記ステージの方向に延びるガイドと、
を備え、
前記荷電粒子線装置はさらに対向電極を備え、
前記対向電極は、前記ガイドもしくは前記試料に対向し、
前記対向電極にはバイアス電圧が印加される、
荷電粒子線装置。2. The charged particle beam device according to claim 1, wherein the charge control component comprises:
A plasma generating device;
A connecting member that connects the sample chamber and the plasma generation device;
a guide extending from the plasma generation device toward the stage;
Equipped with
The charged particle beam device further includes a counter electrode,
the counter electrode faces the guide or the sample,
A bias voltage is applied to the counter electrode.
Charged particle beam device.
前記指標値と前記帯電制御条件との前記関係は、モデルまたはデータベースのうち少なくとも１つによって表され、
前記荷電粒子線装置は、前記モデルまたは前記データベースのうち前記少なくとも１つを記憶するメモリを備え、
前記メモリには、前記帯電制御条件に応じた、前記試料の表面電位と前記帯電制御コンポーネントの帯電動作時間との関係情報が記憶され、
前記１以上のコンピュータシステムは、前記指標値に基づいて、前記帯電制御コンポーネントの帯電動作時間を決定する、
荷電粒子線装置。2. The charged particle beam device according to claim 1,
the relationship between the index value and the charge control condition is represented by at least one of a model or a database;
the charged particle beam device includes a memory that stores at least one of the model or the database;
the memory stores information on a relationship 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 determining a charging operation time of the charge control component based on the index value.
Charged particle beam device.
前記帯電制御コンポーネントはプラズマ生成装置を備え、
前記荷電粒子線装置は、
前記ステージに電位を与える第１電圧源と、
前記プラズマ生成装置に電位を与える第２電圧源と、
を更に備える、荷電粒子線装置。2. The charged particle beam device according to claim 1,
the charge control component comprises a plasma generating device;
The charged particle beam device comprises:
a first voltage source that provides a potential to the stage;
A second voltage source that applies a potential to the plasma generating device;
The charged particle beam device further comprises:
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| PCT/JP2023/043475WO2025120733A1 (en) | 2023-12-05 | 2023-12-05 | Charged particle beam device |
| TW113134279ATW202524536A (en) | 2023-12-05 | 2024-09-10 | Charged particle beam device |
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| WO2019123604A1 (en)* | 2017-12-21 | 2019-06-27 | 株式会社日立ハイテクノロジーズ | Charged-particle beam device |
| WO2023276127A1 (en)* | 2021-07-01 | 2023-01-05 | 株式会社日立ハイテク | Charged particle beam device |
- 2023
- 2023-12-05WOPCT/JP2023/043475patent/WO2025120733A1/enactivePending
- 2024
- 2024-09-10TWTW113134279Apatent/TW202524536A/enunknown
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| JP2013243368A (en)* | 1999-01-08 | 2013-12-05 | Applied Materials Inc | Detection of microstructure defect |
| JP2002313862A (en)* | 2001-04-13 | 2002-10-25 | Mitsubishi Electric Corp | Semiconductor device inspection method and inspection device |
| JP2014116316A (en)* | 2010-04-12 | 2014-06-26 | Ebara Corp | Specimen observation method |
| JP2012156076A (en)* | 2011-01-28 | 2012-08-16 | Hitachi High-Technologies Corp | Scanning electron microscope |
| WO2019123604A1 (en)* | 2017-12-21 | 2019-06-27 | 株式会社日立ハイテクノロジーズ | Charged-particle beam device |
| WO2023276127A1 (en)* | 2021-07-01 | 2023-01-05 | 株式会社日立ハイテク | Charged particle beam device |
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