WO2024034231A1

WO2024034231A1 - Charge relaxation system, device having same, and charge relaxation method

Info

Publication number: WO2024034231A1
Application number: PCT/JP2023/019827
Authority: WO
Inventors: 奈浦寺尾; 俊之横須賀; 裕森田; 秀幸小辻
Original assignee: 株式会社日立製作所
Priority date: 2022-08-08
Filing date: 2023-05-29
Publication date: 2024-02-15
Also published as: JP2024022892A

Abstract

Provided are a charge relaxation system, a device having the same, and a charge relaxation method capable of easily and quickly eliminating electric charges.　In order to achieve the aforementioned purpose, this charge relaxation system for controlling the amount of electric charges on a target insulator is configured to include: a pulse power supply capable of applying a pulse voltage to the insulator or an electrode on the periphery thereof; a pulse power supply control unit for controlling the pulse power supply with a parameter indicating a combination of the applied voltage width and the applied time width of a pulse voltage; an ammeter for measuring the amount of electric charge flowing in the insulator due to the pulse voltage applied by the pulse power supply; and a storage unit for storing the relationship between the combination of the applied voltage width and the applied time width of the pulse voltage applied to the insulator or the electrode on the periphery thereof and the amount of electric charge measured by the ammeter.

Description

Charge mitigation systems, devices including them, and charge mitigation methods

The present invention relates to charge mitigation of insulators, and particularly relates to a charge mitigation system using electric field control.

In the manufacture of electronic devices, a processing apparatus is equipped with a mounting table for placing an object, and the mounting table generally includes an electrostatic chuck. A voltage is applied to the electrostatic chuck, and the object is attracted to the electrostatic chuck by the Coulomb force generated by this voltage. When the object is an insulator, the surfaces of the object and the electrostatic chuck are charged, and this charge may not be eliminated even after the voltage application is stopped. If you remove the object from the electrostatic chuck while the surfaces of the object and the electrostatic chuck are charged, a load will be applied to the object, which may cause the object to bend or crack. It is necessary to remove the static charge.

Furthermore, in charged particle beam devices that handle charged particles, such as electron microscopes, focused ion beam processing devices, and mass spectrometers, charging of the device and the observation target is an issue as it affects the control of charged particles. In particular, in the manufacturing process of semiconductor devices, in-line inspection and measurement using a scanning electron microscope (SEM) has become an important inspection item for the purpose of improving yield. In SEM, when the surface of the object to be inspected is an insulator, there is a problem in that the surface of the object is charged. Specifically, the electric field is distorted due to the charging of the object, and the trajectory of the charged particles changes, resulting in cases where the expected performance cannot be obtained. Therefore, it is necessary to remove or reduce the charge accumulated in the insulator.

Also, in general electrical appliances, charging accelerates insulation deterioration and increases the incidence of insulation defects. Therefore, it is also necessary to remove or reduce the charge accumulated on the insulator.

When considering the relaxation (removal) of the charge accumulated on an insulator, there are two possible methods. One is a method of extracting electric charge from an insulator through a medium different from the insulator, and a method of eliminating the electric charge through light, gas, charged particles (electrons, ions, plasma), etc. Since charging is alleviated through another medium, a device configuration that generates the medium and guides it to the insulator, and a configuration that appropriately eliminates the discharged charge are required. For example, when charging is relaxed using charged particles, it is important that the charged particles introduced for charging relaxation do not charge other parts, and the device configuration can be imagined to become complicated.

Another method is to move charges through the insulator itself. Charge is alleviated by moving the charge inside or on the surface of the insulator. The charges accumulated in the insulator are diffused over time according to the electric field formed by the charges themselves, and the charge is relaxed. At this time, the speed of charge movement differs depending on the insulator material. Generally, it is said that the speed of charge transfer between the interior of an insulator and the surface of an insulator is two orders of magnitude faster at the surface, and charge relaxation through the surface of the insulator is considered. By applying an electric field in the direction in which the charges move, it is possible to control the speed at which the charges move, so by changing the electric field applied to the object, we believe that the charges accumulated in the insulator can be moved and removed.

There is Patent Document 1 as a prior art document in this technical field. Patent Document 1 describes a method for promoting the relaxation of accumulated charges on a sample, which is an observation target of an electron microscope, by reversing the polarity of a voltage applied to a surrounding structure, ie, an electrode. ing.

International Publication No. 2018/134870

Patent Document 1 is based on the premise of reversing the polarity of the applied voltage, and polarity reversal poses challenges such as increasing the size of the power supply system and speeding up processing until the voltage settles down. In particular, in an inspection device, inspection throughput is an important product value, but the time required for charge relaxation each time is directly linked to a reduction in throughput.

In view of the above-mentioned problems, the present invention provides a charge mitigation system and a charge mitigation method that are equipped with such systems and can eliminate charge easily and quickly.

To give one example, the present invention is a charge mitigation system for controlling the amount of charge on a target insulator, which includes a pulse power source capable of applying a pulse voltage to the insulator or an electrode surrounding the insulator, and a pulse A pulse power supply control unit that controls the pulse power supply using a combination of the applied voltage width and the application time width as parameters; an ammeter that measures the amount of charge flowing through the insulator due to the pulse voltage applied by the pulse power supply; The configuration includes a storage unit that stores the relationship between the combination of the applied voltage width and the applied time width of the pulse voltage applied to the surrounding electrodes and the amount of charge measured by the ammeter.

According to the present invention, it is possible to provide a charge mitigation system and a charge mitigation method that are equipped with a charge mitigation system that can easily and quickly eliminate charge.

1 is a schematic configuration diagram of a charge mitigation system in Example 1. FIG. It is a conventional block diagram which applies a voltage to an electrostatic chuck. FIG. 2 is a configuration diagram of applying voltage to the electrostatic chuck in Example 1. FIG. FIG. 3 is another schematic configuration diagram of the charge mitigation system in Example 1. FIG. FIG. 3 is a diagram showing changes in charge relaxation amount with respect to voltage application time in Example 1. FIG. 3 is a diagram showing changes in charge relaxation amount with respect to applied electric field strength in Example 1. 3 is an operation instruction screen for the charge mitigation system in Example 1. FIG. 3 is a flowchart of charging relaxation processing in Example 1. FIG. It is a block diagram of SEM in Example 2. 3 is a configuration diagram of another SEM in Example 2. FIG. FIG. 7 is a configuration diagram of applying a voltage to an object in a film winding process in Example 3.

Embodiments of the present invention will be described below with reference to the drawings. Note that in each drawing, the same components are denoted by the same reference numerals, and detailed explanations of overlapping parts will be omitted.

FIG. 1 is a schematic configuration diagram of the charge mitigation system in this embodiment. FIG. 1 shows the minimum configuration for realizing the effects of this embodiment, and when it is actually used, it is incorporated as a part of various products. As shown in FIG. 1, a pulse power source 130 is connected to an electrode 120 that contacts an object 110, which is an insulator, and a pulse voltage is applied. That is, FIG. 1 shows a configuration in which a pulse voltage is applied to an electrode in contact with an object to directly apply an electric field to the object. Pulse conditions such as applied voltage, application time, and pulse waveform are controlled by a pulse power supply controller 140. Further, an ammeter 150 is connected to the object 110 to measure the static elimination current. Then, the data of the measured static elimination current is integrated with the pulse conditions and stored in the storage unit 160. When object 110 is an electrostatic chuck, electrode 120 corresponds to the electrostatic chuck.

The ammeter 150 measures the amount of charge flowing through the insulator using the applied voltage and application time as parameters, and records it in the storage unit 160 as the amount of charge relaxation. Since the effect of charge mitigation varies depending on the material and shape of the insulator, this evaluation is performed for each material. Conditions for charge relaxation are determined from a map of the obtained charge relaxation amount, which will be described later. Although it varies depending on the target, the user can set conditions such as increasing the voltage application time if the throughput of charging relaxation is important.

In FIG. 1, when a specific voltage, that is, a constant potential is applied to the object, a pulse voltage is applied to relieve the charge in a superimposed manner. Therefore, in this embodiment, the magnitude of the applied voltage is not important, but the width of change in the electric field is considered as a parameter.

FIG. 2 shows a conventional configuration in which the electrode 120 in FIG. 1 is an electrostatic chuck 121. As shown in FIG. 2, a voltage 510 has already been applied to the electrostatic chuck 121 to charge the electrostatic chuck.

FIG. 3 shows a configuration when a constant potential is applied to the object in this embodiment. As shown in FIG. 3, in order to eliminate static electricity from the object 110 and the electrostatic chuck 121, a pulse power source 130 for static elimination is connected in series with a voltage 510.

FIG. 4 is another schematic configuration diagram of the charge mitigation system in this embodiment. 4 differs from FIG. 1 in that the electrode 120 is not in contact with the object 110. That is, FIG. 4 shows a configuration in which a pulse voltage is applied to an electrode that is not in contact with the object, and an electric field is indirectly applied to the object. The electrode 120 may be a newly provided electrode for static elimination, or may be an existing electrode. For example, in the case of a SEM, the existing electrode refers to a booster electrode installed in an objective lens to pull up secondary electrons.

FIG. 5 is a diagram showing the relationship between the amount of charge relaxation and the voltage application time, that is, the time width of the pulse, when a voltage is applied in pulses to the insulator in this example. In FIG. 5, the applied electric field strength, that is, the voltage width of the pulse, is shown as a parameter, and the amount of charge relaxation increases in proportion to the voltage application time, and increases as the applied electric field strength increases. For example, when an applied electric field strength of 20 kV/mm is applied for 1 second to SiO ₂ of 1 cm x 1 cm x 1 μm, the charge relaxation amount is about 10 nC.

FIG. 6 is a diagram showing the relationship between the applied electric field strength and the amount of charge relaxation in this example. In FIG. 6, the voltage application time is shown as a parameter, and the charge relaxation amount increases in proportion to the applied electric field strength, and increases as the voltage application time increases. Therefore, if you want to increase the throughput, you can set the voltage application time short and then adjust the applied electric field strength to achieve the desired amount of charge relaxation, or if there is a limit to the electric field that can be applied, The electric field strength may be fixed and adjusted by the voltage application time.

When the electrode on the object is an electrostatic chuck, a charge relaxation amount Q ₀ that eliminates the desorption abnormality exists for each object, and the voltage application conditions that satisfy Q ₀ can be shown in a two-dimensional map of electric field and time. The user can determine the voltage application conditions from there. Note that since the charges accumulated on the electrostatic chuck are expected to be positive charges, the electric field is applied in the direction from the electrostatic chuck toward the object. If the electrostatic chuck is charged under unusual conditions and negative charges are accumulated, a reverse electric field may be applied.

FIG. 7 is an operation instruction screen (GUI) of the charge mitigation system in this embodiment. The charge mitigation system shown in FIGS. 1 and 4 operates under the control of a user by a control device (not shown). Further, the charge mitigation system includes a display device such as a touch panel for displaying an operation screen (not shown) for the user to input control details. FIG. 7 is an example of an operation instruction screen (GUI) of the charge mitigation system in this display device.

In FIG. 7, the user inputs the name of the object into the static elimination target input section 410, the material and shape of the object into the static elimination target object condition input section 420, and inputs the static elimination charge amount _Q0 required for static elimination. When inputted to the section 430, the control device of the charge relaxation system displays a two-dimensional map of the amount of charge relaxation on the voltage application condition display section 440, with electric field [kV/mm] and time [sec] as axes. On this map, the user selects the voltage application conditions (voltage application time and applied electric field strength) according to the desired charge relaxation amount, enters the applied electric field strength and voltage application time in the voltage application condition input section 450, and presses the apply button 460. By pressing , the voltage application conditions selected by the user are applied.

At this time, the name, material/shape, and static charge amount of the target object are linked in advance and stored as a database in the storage unit 160, and by simply entering the name of the material in the static neutralization target input unit 410, the material and the charge amount are automatically The shape and the amount of charge to be removed may be output.

Next, an electric field is applied to the object by the pulse power supply control unit 140 and the pulse power supply 130, the static elimination current is measured by the ammeter 150, and the amount of charge Q that is actually eliminated is displayed on the static elimination charge amount output unit 470. . If the amount of charge Q matches the amount of charge removed _Q0 within the error range determined by the user, the user can press the end button 480 to complete the charge removal. Furthermore, if the amount of charge Q is significantly different from the amount of discharged charge _Q0 , the voltage application conditions can be selected again by pressing the correction button 490.

FIG. 8 is a flowchart of the charging relaxation process in this embodiment. In FIG. 8, first, a pulse voltage is applied to the insulator that is the object or the electrodes around it, and the amount of current flowing through the insulator is measured (S610). Next, the magnitude and time width of the applied pulse voltage, which are pulse voltage conditions, are changed (S620), and S610 and S620 are repeated until measurement under all pulse voltage conditions determined by the user is completed (S630). When measurements under all pulse voltage conditions are completed, pulse voltage conditions (magnitude and time width) to be applied to the insulator are determined according to the amount of charge to be relaxed (S640). Next, a pulse voltage determined by the pulse power source is applied (S650), and if the amount of charge relaxation calculated from the amount of current flowing through the insulator is equal to or greater than the allowable value (S660), static elimination is completed. If it is below the allowable value, the process returns to S640 and the conditions for applying the pulse voltage are determined again.

Note that the results of the magnitude and time width of the pulse voltage obtained in S610 and S620 of the flowchart in FIG. 8 can be stored as a database for each sample, so that when actually eliminating static electricity, it is possible to start from S640 of the flowchart. is also possible.

As described above, according to this embodiment, by controlling the magnitude and time width of the pulse voltage applied depending on the insulator, it is possible to promote charge relaxation of the insulator, and charge can be easily and quickly. It is possible to provide a charge mitigation system and a charge mitigation method that can eliminate the problem.

In this embodiment, as one application example of the charge mitigation system shown in Embodiment 1, an example will be described in which it is applied to an SEM, which is one of the charged particle beam devices.

FIG. 9 is a configuration diagram of the SEM in this example. In FIG. 9, in the SEM 1000, primary electrons 702 emitted from an electron source 701 are directed to a sample 706 on a stage 713 by a condenser lens 703, signal

electron deflectors

711 and 707, a primary electron deflector 704, and an objective lens 705. imaged. Primary electrons on the sample are scanned two-dimensionally by

signal electron deflectors

711 and 707. When the sample 706 is irradiated with the primary electrons 702, electrons such as secondary electrons and backscattered electrons are emitted from the irradiated area. The emitted electrons are accelerated toward the electron source by an acceleration effect based on the negative voltage applied to the sample, collide with the signal electron aperture 710, and generate secondary electrons. The secondary electrons emitted from the signal electron aperture 710 are captured by the detector 709, and the output of the detector 709 changes depending on the amount of captured secondary electrons. The brightness of a display device (not shown) changes in accordance with this output. For example, when forming a secondary electron image, the image of the scanning area is formed by synchronizing the deflection signals to the

signal electron deflectors

711 and 707 with the output of the detector 709.

In this way, in the SEM, a sample is irradiated with an electron beam, and secondary electrons emitted from the sample are detected and imaged. Therefore, if the balance between the irradiated electron beam and the emitted secondary electrons is disrupted, the sample becomes electrically charged. When a sample is charged, the electric field on the sample is distorted, causing changes in the electron beam and failure to capture secondary electrons emitted from the sample. These appear as image distortion and brightness unevenness in the detected image, reducing measurement accuracy.

To solve this problem, in this embodiment, a pulse voltage is applied to the stage 713 on which the sample is placed. That is, in FIG. 9, a stage voltage from a stage power supply 715 for adjusting the incident energy of the electron beam is applied to a sample 706, and a pulsed voltage from a pulse power supply 130 is superimposed on this. Note that the pulse power supply control section 140, ammeter 150, and storage section 160 have the functions described in FIG. 1. At this time, there is no need to reverse the positive or negative polarity of the voltage applied to the sample, and it is sufficient to apply a voltage that changes the electric field with respect to the reference stage voltage. As the pulse application time width is on the order of several tens of milliseconds to several seconds, charging relaxation progresses, making it possible to perform measurements that minimize the impact on measurement throughput and eliminate the effects of charging. Although FIG. 9 describes the application of voltage to the stage on which the sample is mounted, as shown in FIG. The same effect can be obtained.

In the case of an electron microscope, there is a charge relaxation amount Q ₀ for each object that eliminates sample charging, and the voltage application conditions that satisfy Q ₀ can be shown in a two-dimensional map of electric field and time. The user can determine the voltage application conditions from there.

The operation instruction screen (GUI) of the SEM in this embodiment is basically the same as in the first embodiment, as shown in FIG. 7, but in addition to this, it may be possible to select the timing of static elimination. Specifically, if the static elimination time exceeds 1 second, static elimination is performed for each image taken, and conversely, if static elimination can be done in a short time, such as less than 1 microsecond, electron beam Static electricity removal may be performed every time one line of scanning is completed.

Also, in the case of the SEM in this example, the flowchart of the charge relaxation process is basically the same as that shown in FIG. 630), and from next time onwards, pulse conditions are specified from the database and used (S640 to 660). By creating a database of voltage application conditions and amount of charge removal for each object to be observed, smooth charge removal becomes possible.

As described above, according to this embodiment, by adding the pulse power supply 130, pulse power supply control section 140, ammeter 150, and storage section 160 to the SEM having the conventional configuration, and applying a pulse voltage to the stage 713, Similar to the first embodiment, it is possible to provide an SEM which is a charge mitigation system that can easily and quickly eliminate charges.

In this embodiment, as one application example of the charge mitigation system shown in Embodiment 1, an example in which the system is applied to a film winding device will be described.

FIG. 11 is a configuration diagram of the film winding device in this example. In FIG. 11, a film 901 is pulled out by a winding roller 903 from a roller 902 that has completed winding.

Most of the polymeric materials used in films are excellent insulators, so charges tend to accumulate on their surfaces. Electrification in the film or roller system causes problems such as electrostatic discharge, staining of the film, and inability to process, reducing the quality of the film. In particular, the film take-up roll is the final step in the film production and processing process, and there is a problem in that the electric charge caused by charging and discharging that occurs here is hardly processed and directly leads to a deterioration in the quality of the film product.

In order to solve this problem, in this embodiment, as shown in FIG. 11, a static elimination electrode 904 is provided at a position that contacts the drawn-out film 901, and by applying a pulse voltage, the static electricity of the film can be eliminated.

In the film winding process, there is a charge relaxation amount Q ₀ for each object in order to make the film's charge sufficiently small, and the voltage application conditions that satisfy Q ₀ can be shown in a two-dimensional map of electric field and time. . The user can determine the voltage application conditions from there. The operation instruction screen (GUI) and the flowchart of the charging mitigation process are the same as those shown in the first embodiment.

As described above, according to this embodiment, it is possible to provide a charge mitigation system that can easily and quickly eliminate charge even in a film winding device.

The embodiments according to the present invention have been described above, but the present invention makes it possible to easily and quickly eliminate the charging of an object, and solves the problem that the expected performance cannot be obtained due to charging.
Therefore, the present invention contributes to achieving a high level of economic productivity through technological improvement and innovation, particularly in item 8 of "decent work and economic growth" to realize SDGs (Sustainable Development Goals).

Further, the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the embodiments described above are described in detail to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to having all the configurations described. Furthermore, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Further, it is also possible to add, delete, or replace a part of the configuration of each embodiment with other configurations.

110: Target object, 120: Electrode, 121: Electrostatic chuck, 130: Pulse power supply, 140: Pulse power supply control section, 150: Ammeter, 160: Storage section, 410: Static electricity removal object input section, 420: Static electricity removal object Condition input section, 430: Static elimination charge amount input section, 440: Voltage application condition display section, 450: Voltage application condition input section, 460: Apply button, 470: Static elimination charge amount output section, 480: End button, 490: Modify button , 510: Voltage, 701: Electron source, 702: Primary electron, 703, 708: Condenser lens, 704: Primary electron deflector, 705: Objective lens, 706: Sample, 707, 711: Signal electron deflector, 709 : Detector, 710: Signal electronic aperture, 715: Stage power supply, 801: Secondary electron pulling electrode, 904: Static elimination electrode

Claims

A charge mitigation system that controls the amount of charge on a target insulator,
a pulse power source capable of applying a pulse voltage to the insulator or the electrodes surrounding it;
a pulse power supply control unit that controls the pulse power supply using a combination of an applied voltage width and an application time width of the pulse voltage as parameters;
an ammeter that measures the amount of charge flowing through the insulator due to the pulse voltage applied by the pulse power source;
Charge relaxation characterized by comprising a memory unit that stores the relationship between the combination of the applied voltage width and the applied time width of the pulse voltage applied to the insulator or the electrodes surrounding the insulator and the amount of charge measured by the ammeter. system.
The charging mitigation system according to claim 1,
The pulse power supply control unit calculates a voltage according to the amount of charge flowing through the insulator based on the applied voltage width and application time width of the pulse voltage applied to the insulator or the electrodes surrounding the insulator, and the amount of charge to be relaxed. A charge mitigation system characterized in that: an applied voltage width and an applied time width are determined as application conditions of the pulse voltage to be applied, and the pulse voltage is controlled to apply the pulse voltage under the application conditions.
The charging mitigation system according to claim 2,
a display unit that displays the magnitude of the charge amount with respect to the applied voltage width and application time width of the pulse voltage as a two-axis map based on the measured amount of charge;
storing the map in the storage unit;
A charge mitigation system comprising an input section through which a user sets conditions for applying a pulse voltage based on information on the display section.
The charging mitigation system according to claim 1,
The pulse power source is configured to be capable of applying a pulse voltage superimposed on the specific voltage when a specific voltage is applied to the insulator or the electrodes surrounding it in advance, and the pulse power source control The charging mitigation system is characterized in that the part controls the pulsed power supply, applies the pulsed voltage superimposed on the specific voltage, and controls the electric field applied to the insulator or an electrode around the insulator.
The charging mitigation system according to claim 1,
The charging mitigation system is characterized in that the pulse power control unit changes an applied voltage width and an application time width, which are application conditions of the applied pulse voltage, depending on the insulator.
The charging mitigation system according to claim 1,
The storage unit stores, for each insulator, an applied voltage width and an applied time width that are application conditions of the applied pulse voltage,
The charging mitigation system is characterized in that the pulse power supply control section reads and sets application conditions of the pulse voltage stored in the storage section according to information on the insulator, and controls the pulse power supply.
A charged particle beam device comprising the charged relaxation system according to any one of claims 1 to 6,
The target insulator is a target sample of the charged particle beam device,
The electrode is a stage on which the sample is placed or an electrode of the charged particle beam device,
A charged particle beam device characterized in that a pulse voltage is applied by the pulse power source to a stage on which the sample is placed or to an electrode of the charged particle beam device.
A film winding device comprising the charge mitigation system according to any one of claims 1 to 6,
The target insulator is a film,
The electrode is a static elimination electrode provided at a position in contact with the film,
A film winding device characterized in that a pulse voltage is applied to the static elimination electrode by the pulse power source.
A charge mitigation method for controlling the amount of charge on a target insulator,
It has a pulse power source capable of applying a pulse voltage to the insulator or the electrodes surrounding it,
A charge mitigation method comprising controlling the pulse power source using a combination of the amount of charge flowing through the insulator due to the pulse voltage applied by the pulse power source, and the applied voltage width and application time width of the pulse voltage as parameters.