Contamination handling in metrology systems

Abstract

The present disclosure relates to a metrology system configured for handling contamination within a vacuum chamber. The metrology system includes a scanning electron microscope (SEM) module for imaging a sample, a sample handling module for handling the sample and generating contaminants, and a contamination handling module configured for preventing the contaminants from reaching the SEM module. The contamination handling module includes various components, such as a dynamic shutter, a static contaminant barrier, a contaminant cooling trap, an electrostatic collection field, and a protective gas environment, among others. These components work in concert and effectively manage the contaminants and maintain a clean environment for the SEM module to ensure high quality imaging results and reduce maintenance requirements.

Description

Technical Field

[0001] Various embodiments are generally related to contamination treatment in metrology systems. Specifically, various embodiments relate to contamination treatment in enclosed sample chambers or vacuum chambers of optical, electronic, and / or X-ray-based metrology systems, and more specifically to contamination treatment in metrology systems employing particle beam imaging processing (particularly scanning electron microscopy (SEM) processing) and / or beam-induced material removal or deposition or etching processing, such as using a material abrasive processing module like a focused ion beam (FIB) module. Background Technology

[0002] Enclosed sample chambers, especially vacuum chambers, are commonly used in metrology systems. However, contaminants generated during physical handling or sample alteration within the vacuum chamber can contaminate imaging processing modules, such as SEM processing modules. The accumulation of contaminants on the sample and SEM column can significantly degrade image quality and contrast over time. Therefore, effective contamination removal within the vacuum chamber is crucial for continuous, high-quality imaging processing.

[0003] Vacuum cavity cooling traps and plasma cleaning devices are known from US 2016 / 0343537 A1, US 2022 / 0208531 A1, US 2023 / 0350301 A1 and the paper “Decontamination in the Electron Probe Microanalysis with a Peltier-Cooled Cold Finger” by Buse et al., Microscopy and Microanalysis, 2016, pp. 981-986. Summary of the Invention

[0004] Therefore, advanced imaging techniques are needed to treat contamination in the vacuum chamber of the metrology system in order to mitigate or reduce at least some of the aforementioned drawbacks.

[0005] This requirement can be met by the features of the independent claims, while the features of the dependent claims define the specific embodiments.

[0006] The solution according to the invention will now be described with respect to a metrology system and corresponding methods and steps for operating the metrology system, wherein features, advantages, or alternative embodiments may be assigned to other categories, and vice versa. Therefore, it should be understood that the metrology system can be improved using the features described in the context of the method, and the method can be improved using the features described in the context of the metrology system.

[0007] This invention provides a metrology system comprising any or any combination of processing modules, such as SEM and / or FIB and / or gas injection system (GIS), configured to perform contamination treatment according to the technology of the invention. The metrology system can be configured to sequentially or simultaneously use one or more processing modules to perform one or more of the following operations on a sample on a sample stage in a vacuum chamber: inspection, imaging, processing, microprocessing, etching, deposition, or other operations. Therefore, the metrology system includes one or more contamination treatment modules and / or elements of one or more contamination treatment modules to provide contamination treatment within the vacuum chamber.

[0008] In various embodiments, the metrology system includes a vacuum chamber. The vacuum chamber in the metrology system can refer to an enclosed space in which a sample is located and / or processed and / or analyzed, with pressure significantly reduced compared to the atmospheric pressure surrounding the metrology system. This low-pressure environment allows the SEM module and other components to operate normally because it allows electrons to propagate with minimal interference from gas molecules.

[0009] In various embodiments, the metrology system includes a sample stage within a vacuum chamber configured to hold the sample to be processed. This sample stage within the vacuum chamber, which may be referred to as a platform or support, is designed to position the sample being analyzed or processed by various processing modules, such as imaging or sample processing modules. It may have the ability to move the sample in various directions (e.g., X, Y, and Z axes) and to rotate or tilt the sample to facilitate imaging and processing of different regions of the sample.

[0010] In various embodiments, the metrology system includes a scanning electron microscope (SEM) module within a vacuum chamber, configured to image the sample. The SEM module is an imaging processing module that uses a focused electron beam to scan the sample surface and create a high-resolution image. The SEM module operates within a vacuum chamber to maintain the integrity of the electron beam and prevent contamination of the sample and SEM components.

[0011] It should be understood that "prevention" can refer to preventing all contaminants or preventing a portion of contaminants from reaching the SEM module. Here, "prevention" is used to indicate that the contamination treatment module significantly reduces the amount of contaminants reaching the SEM module, thereby mitigating their impact on imaging processing. This may refer to one or more facts about the contamination treatment module preventing contaminants from reaching the SEM module. This could mean a substantial reduction in the amount of contaminants reaching the SEM module. The contamination treatment module can reduce the amount of contaminants reaching the SEM module, for example, by less than 30%, or less than 20%, or less than 10%, or less than 1%, compared to the amount of contaminants reaching the SEM module without the contamination treatment module.

[0012] In various embodiments, the metrology system includes a sample processing module within a vacuum chamber, configured to physically process or modify the sample or its structure, such as by removing material from the sample, thereby generating contaminants in the low-pressure atmosphere of the vacuum chamber. This sample processing module within the vacuum chamber can be deployed to alter or modify the physical structure of the sample or manipulate its physical structure. This processing may include techniques such as focused ion beam (FIB) milling, etching, or deposition, and may be performed by one or more corresponding sample processing modules at least partially disposed within the vacuum chamber. Such processing generates contaminants, such as particles or gases—in other words, debris—which, without appropriate mitigation measures, can interfere with SEM imaging.

[0013] In various embodiments, the metering system includes a contamination handling module, or in other words, a contamination management module, at least partially located within the vacuum chamber. This contamination handling module is configured to block or prevent contaminants, or at least some, more than 50% or 70% of the contaminants, or most or substantially all of the contaminants, from interfering with imaging processing, particularly preventing them from reaching the SEM module, especially the critical SEM module surface.

[0014] In various embodiments, a contamination treatment module may represent an element or component at least partially contained within a vacuum chamber and is designed to mitigate the effects of contaminants generated during physical sample handling. Its primary function is to prevent or hinder contaminants from reaching areas of the SEM module that would otherwise degrade imaging quality or damage sensitive components, particularly SEM electron emission and detection. This contamination treatment module may employ various techniques or combinations thereof for contamination treatment or management, such as dynamic or static physical barriers, protective airflows, or electrostatic fields, to effectively control and remove contaminants, as described below.

[0015] It should be understood that the disclosed contamination treatment techniques can be applied to various imaging and analytical instruments operating within vacuum chambers, or more generally within sample processing and analysis chambers. Although scanning electron microscope (SEM) modules are specifically mentioned in the claims, these techniques are not limited to SEM and can also be used in other systems where contaminants generated during sample processing may interfere with imaging or analytical processing.

[0016] Some non-limiting examples of other imaging and analytical techniques that may also benefit from the revealed contamination treatment methods include optical imaging modules and devices, transmission electron microscopy (TEM), which operates under vacuum conditions and involves the transmission of electrons through thin samples to create high-resolution images. Sample preparation techniques for TEM, such as ion milling or focused ion beam (FIB) thinning, can introduce contaminants that can affect image quality. Auger electron spectroscopy (AES) is a surface-sensitive analytical technique that uses an electron beam to probe the sample surface and measure the energy of emitted Auger electrons. Interaction between the electron beam and the sample can lead to the release of contaminants that can interfere with AES measurements. X-ray photoelectron spectroscopy (XPS) is a further surface analysis technique that uses X-rays to excite electrons from the sample surface, providing information about elemental composition and chemical state. Contaminants introduced during sample processing or transfer can affect XPS results. Secondary ion mass spectrometry (SIMS) is a surface analysis method that utilizes an ion beam to sputter the sample surface and analyze the emitted secondary ions. Sputtering processes can generate contaminants that can interfere with SIMS measurements or cause undesirable artifacts. In this or similar situations, the revealed contamination control techniques, such as cooling traps, dynamic shutters, static barriers, electrostatic shielding, protective gas environments, and directional airflow, can be adjusted and implemented to minimize the impact of contaminants on the corresponding imaging or analytical processing modules. Effective management of contaminants within vacuum chambers or sample handling and analysis chambers can significantly improve the quality and reliability of the results obtained by these instruments.

[0017] The disclosed pollution treatment module may include any one or any combination of the following examples, as shown in Table 1, and is described in further detail in this disclosure.

[0018]

[0019] Table 1

[0020] The contamination handling module may include a dynamic shutter. This dynamic shutter can be synchronized with the operation of the SEM module and the sample processing module. The dynamic shutter can be configured to block the direct path between the SEM module and the sample during sample processing module operation. The dynamic shutter can also be configured to image the sample during SEM module operation.

[0021] In various embodiments, the dynamic shutter may include a movable component within the contamination handling module that helps prevent contaminants from reaching the SEM module. It can be synchronized with the operation of both the SEM module and the sample handling module, ensuring that a direct path between the SEM and the sample is blocked during the handling phase, while allowing imaging during the SEM operation phase.

[0022] Dynamic shutters may include rotating blades or oscillating blades.

[0023] In various examples, the dynamic shutter can be implemented as a rotatable blade or an oscillating blade. The blade may have an opening aligned with the direct path between the SEM and the sample at the imaging position, allowing the electron beam to pass through and achieve imaging. In the processing position, the opening is offset from the direct path, effectively preventing contaminants from reaching the SEM module.

[0024] It should be understood that other mechanical shapes and forms of moving shutters can be used to achieve dynamic blocking and protection of the SEM from contaminants generated during sample processing. Some alternative designs for dynamic shutters may include, but are not limited to, sliding shutters, which may consist of one or more plates that slide in a linear planar motion to block or release the direct path between the SEM and the sample. The sliding motion can be synchronized with the operation of the SEM and sample processing module. Iris apertures can be modified for dynamic shutters. The aperture consists of a series of overlapping blades that can be opened or closed to varying degrees. When closed, the aperture blocks the direct path between the SEM and the sample, while when open, it allows the electron beam to pass through for imaging. Dynamic shutters can be designed as curved or faceted surfaces to optimize contaminant blocking. Curved or angled surfaces are more effective at deflecting contaminants away from the SEM module compared to planar blade designs. A dual-blade shutter system can be used here, where two blades move in opposite directions to block or release the path between the SEM and the sample. This design provides a more complete path seal when the blades are closed, further reducing the risk of contaminants reaching the SEM module. This design ensures contaminant blocking while minimizing interference with the operation of the SEM and sample handling modules. Furthermore, the material used for the dynamic shutter can be cooled to provide a cooling trap, where considerations similar to those revealed for the cooling trap can be applied.

[0025] The dynamic shutter can move between a first position and a second position. The dynamic shutter can rotate between the first position and the second position. This rotation can be synchronized with the operation phases of the SEM module and the sample processing module. The dynamic shutter can oscillate between the first position and the second position. This oscillation can be synchronized with the operation of the SEM module and the sample processing module.

[0026] During the imaging operation of the SEM module, this first position may correspond to the imaging position. During the operation of the sample processing module, this second position may correspond to the processing position. The movement of the dynamic shutter between the first (imaging) position and the (processing) position can be achieved by rotation or oscillation. The rotation or oscillation can be synchronized with the operation phases of the SEM module and the sample processing module to ensure that the shutter is in the correct position during its respective time period.

[0027] The dynamic shutter may include an opening. In the imaging position, this opening may be aligned with the direct path between the SEM module and the sample. In the processing position, the opening may be offset from the direct path between the SEM module and the sample, thereby blocking the direct path and preventing contaminants from reaching the SEM module.

[0028] By using a dynamic shutter, this metrology system effectively protects the SEM module from contaminants generated during sample processing, while still allowing imaging when needed. The synchronized shutter movement minimizes interference with the operation of the SEM and sample processing modules, ensuring the metrology system's high efficiency and reliability.

[0029] The contamination treatment module may include a static contaminant barrier. This static contaminant barrier may be configured to limit the volume of the vacuum chamber affected by contaminants while maintaining a direct path between the SEM module and the treatment location on the sample.

[0030] In various embodiments, a static contaminant barrier may be a fixed component or element within the contamination treatment module, configured to restrict the diffusion of contaminants within the vacuum chamber. Unlike a dynamic shutter, the static barrier does not move dynamically but provides a physical barrier by forming or defining a sub-volume or section within the vacuum chamber, thereby limiting or constraining the movement of contaminants into specific sub-volumes or sections of the vacuum chamber. The barrier may be designed to maintain a direct path between the SEM module and the treatment location on the sample, where imaging can still be performed.

[0031] In various embodiments, the static contaminant barrier may include a fixed wall or partition with openings to allow the electron beam from the SEM to reach the sample surface. The position and size of the openings can be adjusted to optimize contaminant control while minimizing interference with SEM imaging processing.

[0032] In various embodiments, the static contaminant barrier may be located between the SEM module and the sample processing module. The static contaminant barrier may be configured to divide the vacuum chamber into a first compartment housing the SEM module and a second compartment housing the sample processing module.

[0033] Positioning this static contaminant barrier, at least partially, between the SEM module and the sample processing module can help isolate the two modules and minimize contaminant diffusion into the SEM module. By dividing the vacuum chamber into two compartments, the barrier creates a separate environment for the SEM module and / or the sample processing module and / or the sample stage. This environment can be at least partially open to allow a direct path to the sample, but this restricts the movement of contaminants within the vacuum chamber.

[0034] In various embodiments, the static contaminant barrier may be a vertical wall or housing placed between the SEM column and the focused ion beam (FIB) or other sample processing modules. This wall may have a hole or opening that allows the electron and ion beams to reach the sample surface while still maintaining separation between the compartments.

[0035] The static contaminant barrier may include an aperture aligned with the direct path between the SEM module and the treatment site on the sample. This aperture may be configured to allow an electron beam to pass from the SEM module to the sample, and to allow secondary electrons or backscattered electrons to pass from the sample to the SEM module.

[0036] The aperture in this static contaminant barrier allows SEM imaging processing to occur while maintaining the barrier's ability to contaminate contaminants. The aperture is aligned with a direct path between the SEM module and the processing location on the sample, allowing the electron beam to pass through and interact with the sample. The aperture also allows secondary electrons or backscattered electrons generated by the interaction of the electron beam with the sample to return to the SEM module for detection and imaging.

[0037] In various embodiments, the aperture in this static contaminant barrier can be a small hole or a slit, the position and size of which are adjusted to accommodate the electron beam. The aperture can be optimized to minimize the amount of contaminants that can pass through, while still allowing sufficient signal from the sample to reach the SEM detector.

[0038] The static contaminant barrier may include a cooling surface configured to bind contaminants to the barrier. In various embodiments, incorporating a cooling surface into the static contaminant barrier enhances its effectiveness in capturing and containing contaminants. By keeping the surface at a low temperature, contaminants in contact with the barrier are more likely to condense or adhere to the surface, thereby preventing them from diffusing further along the barrier into the vacuum chamber in the SEM direction.

[0039] In various embodiments, the static contaminant barrier may include a cooling system, such as a Peltier cooler or a cryogenic cooling loop, which maintains the temperature of the barrier surface below the expected condensation point of the contaminant, as described with respect to the Peltier cooling trap disclosed according to the invention. This cooled surface may be located in the flow path of the contaminant from the sample toward the SEM on the barrier to maximize contaminant capture.

[0040] The static contaminant barrier may include multiple fins configured to deflect contaminant gas flow away from the SEM module, thereby preventing contaminants from reaching the SEM module.

[0041] In various embodiments, adding fins to a static contaminant barrier helps deflect the flow of contaminant gases away from the SEM module. The fins act as a physical barrier, altering the airflow direction and guiding contaminants toward the barrier edge or a designated exhaust location. By deflecting the contaminant gas flow, the fins reduce the likelihood of contaminants reaching and accumulating on sensitive components of the SEM module.

[0042] In various embodiments, the static contaminant barrier may have a series of vertical or angled fins located on the surface of the barrier facing the sample processing module. The fins may be arranged in a pattern to optimize the deflection of contaminant gases away from the SEM while avoiding obstruction of the electron beam path. The shape, size, and spacing of the fins can be customized based on the specific characteristics of the expected contaminant and the geometry of the vacuum chamber. In one embodiment, the fins may include a surface at an angle of less than 45°, 30°, or 20° to the axis defined between the SEM head and the sample.

[0043] The contamination treatment module may include a contaminant cooling trap configured to capture contaminants. Such a contaminant cooling trap and metering system (particularly a sample stage and / or vacuum pump and / or plasma cleaning system) may operate synchronously, as described in further detail herein.

[0044] In various embodiments, a contaminant cooling trap may be a component within the contaminant treatment module, which utilizes low temperatures to condense and trap contaminants from the vacuum chamber atmosphere. By providing a cold surface, the trap allows contaminants to adhere to it, thereby removing the contaminants from the atmosphere and preventing them from reaching the SEM module.

[0045] In various embodiments, the contaminant cooling trap may be a cold plate or a series of cooling baffles located near the sample processing module. The trap maintains a temperature well below the expected contaminant condensation point, ensuring effective capture and removal.

[0046] The contaminant trap may include a Peltier cooling element configured to maintain the surface temperature of the contaminant trap below the contaminant condensation temperature.

[0047] In various embodiments, the Peltier cooling element can be a thermoelectric device that can be used to actively cool the surface of a contaminant trap. By supplying current to the Peltier element, heat is transferred from one side of the device to the other, forming a cold surface that can condense and trap contaminants. Using a Peltier cooling element allows for precise temperature control and can be adjusted to optimize the trapping efficiency of specific contaminants.

[0048] In various embodiments, the contaminant trap may include a Peltier cooling element. A cold plate connected to the Peltier cooling element acts as a trapping surface. The temperature of the cold plate can be adjusted by controlling the current supplied to the Peltier element.

[0049] The Peltier cooling element can also be operatively connected to a heat sink located outside the vacuum chamber. This heat sink can be configured to dissipate the heat generated by the Peltier cooling element.

[0050] In various embodiments, to maintain the efficiency of the Peltier cooling element and prevent heat buildup within the vacuum chamber, it is necessary to dissipate excess heat generated by the element. Connecting the Peltier element to a heat sink located outside the vacuum chamber provides effective heat dissipation because the heat sink can be designed with a larger surface area and can be cooled externally, such as by air or liquid cooling.

[0051] In various embodiments, the Peltier cooling element can be thermally coupled to a heat sink via a feedthrough in the vacuum chamber wall. The heat sink, which can be a finned heat sink or a water-cooled body, can efficiently transfer heat away from the Peltier element. By placing the heat sink outside the vacuum chamber, the cooling performance of the contaminant trap can be maintained without affecting the vacuum environment.

[0052] The contaminant trap can be located between the sample processing module and the SEM module, and is configured to capture contaminants generated by the sample processing module before they reach the SEM module.

[0053] In various embodiments, arranging a contaminant trap between the sample processing module and the SEM module helps to intercept and capture contaminants before they reach and accumulate in the SEM module (in other words, the SEM). By capturing contaminants at their source, the trap more effectively prevents the spread of contaminants within the vacuum chamber. By targeting contaminants near the SEM and / or along the straight airflow path from the sample to the SEM, the cooling trap more effectively protects the SEM from contamination.

[0054] In various embodiments, the contaminant trap can be mounted on a support structure that positions it directly above the sample processing area, for example, directly adjacent to a focused ion beam (FIB) or other material removal / deposition module. As contaminants are generated during processing, they rise and come into contact with the cold surface of the trap, where they condense and adhere, preventing them from reaching the SEM module. It can also be positioned directly near the SEM head or SEM end cap, for example, extending at least partially along or around the SEM end cap.

[0055] The metering system may also include a cleaning module configured to remove accumulated contaminants from the surface of the cooled contaminant trap during a cleaning phase, wherein such a cleaning module may correspond to or include at least some elements of the directional plasma cleaning system as described herein.

[0056] In various embodiments, over time, the contaminant trap may accumulate a significant amount of captured contaminants on its surface, reducing its capture efficiency and potentially becoming a source of contamination. To address this issue, a cleaning module can be incorporated into the metering system to periodically remove accumulated contaminants from the trap surface. This cleaning module can be activated during a dedicated cleaning phase, which can be scheduled between imaging or processing tasks or as part of a regular maintenance procedure.

[0057] In various embodiments, such a cleaning module may include a heating element or a reverse Peltier cooling element that raises the temperature of the contaminant trap surface above the evaporation point of the captured contaminants, thereby releasing them from the surface. Alternatively, the cleaning module may employ a mechanical scraper or gas nozzle to physically remove contaminants from the trap surface. The released contaminants can then be discharged from a vacuum chamber via a dedicated pumping system.

[0058] The cleaning module may include a plasma generator configured to direct a plasma stream to the surface of the cooled contaminant trap. The plasma stream may be configured to dissolve contaminants accumulated on the surface. A vacuum pump may be configured to evacuate the contaminant-containing cleaning plasma from the vacuum chamber.

[0059] In various embodiments, this plasma cleaning is an effective method for removing surface-accumulated contaminants. By generating a plasma flow and directing it to the surface of the contaminant trap, the high-energy particles in the plasma can interact with the contaminants, breaking their chemical bonds and promoting their removal. This plasma cleaning process can be performed in situ within a vacuum chamber without disassembling the trap or removing it from the system.

[0060] In various embodiments, the cleaning module may include a plasma source, such as a radio frequency (RF) or microwave generator, coupled to the gas delivery system. During the cleaning phase, a cleaning gas (e.g., oxygen or a gas mixture) is introduced into a vacuum chamber and ionized by the plasma source. The resulting plasma stream is directed to the surface of the contaminant trap, where it reacts with the accumulated contaminants, converting them into volatile compounds. A vacuum pump connected to the chamber then evacuates the cleaning plasma along with the contaminants, leaving the trap surface clean and usable for further use.

[0061] The pollution treatment module may include a first electrostatic collection field configured to deflect charged pollutant particles away from the SEM module.

[0062] In various embodiments, an electrostatic collection field can be used to manipulate the trajectory of charged contaminant particles and prevent them from reaching the SEM module. An electric field is generated by applying a voltage to a set of electrodes or plates within a vacuum chamber, which exerts a force on the charged particles. The direction and intensity of the electric field can be adjusted to deflect contaminants away from the sensitive components and guide them toward a designated collection area.

[0063] In various embodiments, the first electrostatic collection field may be established by a pair of parallel plates located near the SEM module. One plate may be positively charged, while the other is negatively charged, generating an electric field perpendicular to the plates. When charged contaminant particles enter this electric field, they are subjected to a force that deflects them toward the plate with the opposite charge, thereby effectively removing them from the SEM module.

[0064] The pollution treatment module may include a second electrostatic collection field with polarity opposite to that of the first electrostatic collection field.

[0065] Combining a second electrostatic collection field with the opposite polarity to the first field improves the efficiency of contaminant removal. This second electric field can be located near or around the SEM head, just like the first electric field. The fields with opposite charges work together to guide contaminants with different charges out of the SEM head, where they are then evacuated from the vacuum chamber.

[0066] In various embodiments, the second electrostatic collection field may be generated by a second set of parallel plates located near the first set. The polarity of the second set of plates may be opposite to that of the first set of plates, thereby generating an opposite electric field. Charged contaminant particles that are not deflected by the first field are then deflected by the second field. This dual-field configuration improves contamination treatment.

[0067] The first electrostatic collection field and / or the second electrostatic collection field can be a gradient field with the highest field strength, arranged near the SEM module.

[0068] In various embodiments, the contamination treatment module may include a plurality of electrodes arranged to generate an electrostatic collection field. The electrodes may be configured such that different potentials are applied to different electrodes to generate the electrostatic collection field. The electrostatic collection field may include a first field region and a second field region, wherein the first field region is configured to primarily attract particles of one polarity, and the second field region is configured to primarily attract particles of the opposite polarity.

[0069] Combining first and second field regions that attract particles with opposite charges improves the efficiency of contaminant removal. The electrodes generating the first and second field regions can be located near or around the SEM head. The combined effect of the field regions with opposite particle attraction deflects contaminants with different charges away from the SEM head, thereby evacuating them from the vacuum chamber.

[0070] In various embodiments, the first field region can be generated by a first set of electrodes, and the second field region can also be generated using a second set of electrodes. The potential applied to the second set of electrodes can be configured to generate the second field region, attracting particles with a potential of opposite polarity to that applied to the first set of electrodes. Charged contaminant particles not attracted by the first field region may be attracted by the second field region, and vice versa. This dual-field configuration improves contamination treatment.

[0071] In various embodiments, the electrostatic collection field is configured as a gradient field with the highest field strength near the SEM module, which improves contaminant deflection. In a gradient field, the electric field strength varies with distance, generating a force that pushes charged particles away from the region of highest field strength. By positioning the highest field strength closer to the SEM module, contaminants are more strongly repelled away from sensitive components, thereby reducing the likelihood of contamination.

[0072] In various embodiments, the electrostatic collection field can be designed as a series of electrodes arranged in a concentric circular pattern around the SEM module. Electrodes closer to the SEM module may be smaller than those further away, creating an electric field gradient. As charged contaminant particles approach the SEM module, they experience increasingly stronger repulsive forces, pushing them towards the outer region of the collection field where they can be removed.

[0073] The metrology system may also include an ion generator disposed at the end cap of the SEM module, which is configured to charge neutral contaminant particles. These neutral contaminant particles (in other words, contaminants) may be present in areas near the sample stage, the SEM module, or an electric field, where they may be ionized or charged.

[0074] In various embodiments, while the electrostatic collection field effectively manages charged contaminant particles, neutral particles are unaffected by the field. To overcome this limitation, an ion generator can be added to the system to charge neutral contaminant particles near the SEM, making them susceptible to the electrostatic collection field. This ion generator is typically located near the SEM module, allowing it to interact with contaminant particles before they reach the sensitive element.

[0075] For example, the ion generator can be a discharge device or an electron emission source located at the end cap of the SEM module. When neutral contaminant particles pass through the ion generator, they interact with charged particles (ions or electrons), transferring charge to the contaminants. Once charged, the contaminant particles are effectively manipulated by the electrostatic collection field and moved away from the SEM module.

[0076] The ion generator may include a laser source configured to emit continuous or pulsed high-energy laser radiation toward neutral contaminant particles, thereby ionizing the neutral contaminant particles by photoionization.

[0077] In various embodiments, photoionization using laser radiation is a precise and efficient method for charging neutral contaminant particles. By selecting a laser wavelength that matches the ionization energy of the contaminant particles, the laser can selectively ionize the particles without affecting other components within the vacuum chamber. Photoionization offers the advantage of being a non-contact method, minimizing the risk of introducing additional contaminants into the system.

[0078] In various embodiments, the ion generator may comprise a pulsed ultraviolet (UV) laser source that emits high-energy photons. The laser beam is directed at an area of ​​active SEM and / or electrostatic collection field (where neutral contaminant particles are expected to be present), or near the sample processing area. When a neutral particle absorbs a photon with sufficient energy, an electron is ejected from the particle, forming a positively charged ion. The newly charged ions are then affected by the electrostatic collection field and removed from the vicinity of the SEM module.

[0079] An ion generator may include an electron source configured to emit electrons toward neutral contaminant particles.

[0080] In various embodiments, the electron source ion generator operates by colliding neutral contaminant particles with an electron beam. When electrons collide with a neutral particle, one or more electrons are ejected from the particle, thereby generating positively charged ions. This process, known as electron-impact ionization, is a reliable and well-established method for charging particles in a vacuum system.

[0081] In various embodiments, the ion generator may use a thermionic emitter (e.g., a heated filament or field emission tip) to generate a focused electron beam. The electron beam is directed, either continuously or in pulses, along the path of the neutral contaminant particles. As the electrons interact with the particles, they ionize them, allowing the electrostatic collection field to effectively remove charged contaminants from the system.

[0082] The ion generator may include a plasma generator configured to generate plasma to charge neutral contaminant particles through collision.

[0083] In various embodiments, plasma-based ionization is a versatile method for charging neutral contaminant particles. Plasma is a partially ionized gas composed of electrons, ions, and neutral particles. When a neutral contaminant particle collides with electrons or ions in the plasma, it gains or loses electrons and becomes charged in the process. For example, plasma ionization can be very effective in the presence of high concentrations of contaminant particles.

[0084] In various embodiments, the ion generator may include a plasma source. The plasma source may be placed within a vacuum chamber, near an area where neutral contaminant particles are present, such as near an electrostatic collection field. Plasma can be generated by applying a high-frequency electric field to a low-pressure gas (e.g., argon or helium). When contaminant particles pass through the plasma, they collide with charged matter, causing ionization. The charged particles can then be effectively managed by the electrostatic collection field.

[0085] The contamination treatment module may include a protective gas environment within a vacuum chamber. This protective gas environment may include a protective gas inlet configured to supply a protective gas flow to purge contaminants, and a gas outlet configured to discharge contaminants carrying the protective gas.

[0086] In various embodiments, the protective gas environment may refer to a closed subenvironment within a vacuum chamber, where the atmosphere is primarily composed of protective gases to mitigate the impact of contaminants on the SEM module. By introducing a controlled flow of protective gas (e.g., nitrogen or argon), contaminant particles can be directed away from sensitive components and guided towards the gas outlet for discharge. The protective gas flow includes locally higher pressures within the protective gas environment and / or a flow of protective gas that obstructs the path of contaminants toward the SEM, thereby preventing contaminants from reaching the SEM module.

[0087] In various embodiments, a protective gas environment can be established by positioning a gas inlet near the sample processing area where contaminants are generated. This gas inlet is connected to a protective gas supply, such as nitrogen or argon, via a pressure regulator and flow controller. During operation, the protective gas is released into the vacuum chamber at a controlled rate, creating a laminar flow that carries the contaminants to a gas outlet. This gas outlet is connected to a vacuum pump that continuously removes the protective gas and entrained contaminants from the chamber.

[0088] In various embodiments, the protective gas environment may further include a protective gas housing within a vacuum chamber, the housing surrounding at least a portion of the SEM module and / or at least a portion of the sample stage. The housing may have openings for the SEM module, sample processing module, protective gas inlet, and gas outlet. In some embodiments, the protective gas environment is the interior of the housing surrounding the SEM head and / or SEM end cap. In some embodiments, the protective gas housing at least surrounds the emission and detection portion of the SEM head and includes openings for electron beam and secondary electron detection. The protective gas inlet may be located inside the housing, thereby enabling a positive pressure inside the housing relative to the atmosphere within the vacuum chamber through the protective gas, and / or an airflow of protective gas from inside the protective gas housing into the vacuum chamber.

[0089] Therefore, in various embodiments, an outer shell can be added within the vacuum chamber to enhance the effectiveness of the protective gas environment. This outer shell serves to restrict the flow of the protective gas and create a more localized clean environment around the SEM module and sample stage. Positive pressure isolates critical components from the rest of the chamber, and a stable flow of protective gas exits the outer shell, minimizing interference from the protective gas flow to other processes and reducing the amount of gas required to maintain a stable environment.

[0090] For example, the housing can be cylindrical or rectangular, made of a non-magnetic material such as aluminum or plastic. The housing is designed to mount around the SEM module and sample stage, with sufficient clearance to allow for sample movement and operation of the sample handling module. The housing has openings for the SEM module, sample handling module, protective gas inlet, and gas outlet. These openings are carefully positioned and sized to optimize gas flow patterns and minimize contaminant ingress into the main vacuum chamber.

[0091] The protective gas inlet can be located near the SEM module, and the gas outlet can be located near the sample processing module. This may create a protective gas flow from the SEM module to the sample processing module to remove contaminants.

[0092] In various embodiments, the relative positioning of the protective gas inlet and outlet affects the direction and effectiveness of the protective gas flow. A unidirectional flow can be established by placing the gas inlet closer to the SEM module and the outlet closer to the sample processing module. This arrangement ensures that clean protective gas passes first through the sensitive SEM components, then sweeps contaminants generated by the sample processing module towards the outlet.

[0093] In various embodiments, the protective gas inlet can be located directly above or to the side of the SEM module, guiding the protective gas downwards and across the surface of the SEM component. As the gas moves toward the sample processing area, it encounters contaminant particles and carries them along its path. The gas outlet can be located near the sample processing module, where the contaminant concentration is highest. The continuous flow of protective gas from the inlet to the outlet forms an airflow that effectively sweeps contaminants from the SEM module to the exhaust port.

[0094] This system can be configured so that the gas flow direction is substantially parallel to the top surface of the sample stage.

[0095] In various embodiments, this protective gas environment minimizes airflow interference with sample stage operation, ensuring sample stability and immunity from gas movement. The parallel flow mode helps maintain laminar flow. This configuration effectively removes contaminants from the sample surface and platform, preventing their deposition on the SEM module.

[0096] In various embodiments, the protective gas inlet and outlet may be located at opposite ends of the sample stage, with the inlet slightly higher than the outlet. The airflow is parallel to the top surface of the platform, forming a laminar flow pattern toward the sample. In this sense, the protective gas acts as a cleaning gas for the sample. As the gas moves through the platform, it collects contaminant particles that may have deposited on surfaces or generated by the sample processing module. This flow minimizes the vertical path of contaminants, ensuring their efficient delivery to the outlet and discharge from the system.

[0097] In various embodiments, the airflow may be parallel to the top surface of the platform, resulting in a flow pattern that depends on the ratio of the mean free path of gas molecules to the characteristic spatial size of the system. In various embodiments, the flow may be continuous, where molecular-to-molecular scattering is dominant. In this case, the airflow may be laminar. In various embodiments, the flow may be in a free molecular state, where molecular-to-wall scattering is dominant. In this case, gas molecules rarely collide with each other, and their motion is controlled by their interactions with the system walls. In various embodiments, the flow may be considered transitional, where both molecular-to-molecular and molecular-to-wall scattering occur significantly.

[0098] In each flow state, the protective gas acts as a cleaning gas for the sample. As the gas moves across the platform, it collects contaminant particles that may have deposited on the surface or been generated by the sample processing module. The flow direction parallel to the platform surface minimizes the vertical path of contaminants, ensuring their efficient delivery to the outlet and discharge from the system.

[0099] In various embodiments, the metering system may be configured such that the protective gas environment includes an SEM module head having an opening for the SEM bundle. The protective gas flow may be configured to maintain a positive pressure of the protective gas within the protective gas environment relative to the vacuum chamber, thereby preventing contaminants from entering the protective gas environment.

[0100] In various embodiments, creating a protective gas environment only at the head of the SEM module provides additional contamination protection. By maintaining a positive pressure of the protective gas within this environment relative to the surrounding vacuum chamber, contaminants are actively prevented from entering the area surrounding the SEM module. This positive pressure generates an outward protective gas flow through the openings of the SEM beam, effectively preventing contaminants from entering.

[0101] In typical SEM applications, the operating pressure within the main operating chamber may range from 10⁻⁵ to 10⁻⁶ mbar. Other variable pressure SEMs (VPSEMs), for example, can operate at pressures up to 100 mbar or higher. In some embodiments, the head of the SEM module may be enclosed in a compartment sealed to the SEM housing and connected to a protective gas inlet. This compartment may be designed to maintain a pressure higher than the main vacuum chamber pressure, for example, 1 × 10⁻⁶ mbar, or 1 × 10⁻⁵ mbar, or 1 × 10⁻², or even 1 mbar, or less than 10 mbar. This pressure difference is achieved by balancing the gas inflow rate with the pumping speed of the vacuum system. The opening for the SEM beam is the only channel for pressurized gas outflow, creating a localized outward flow to prevent contaminants from entering the compartment. Any contaminants that may be present within the compartment are continuously flushed away by the protective gas flow, thus maintaining a clean protective gas environment around the SEM module. A contamination treatment module may include a directional protective gas system configured to direct the protective gas flow from the SEM module head to the sample stage.

[0102] In various embodiments, the directional protective gas system is designed to establish a controlled airflow originating from the SEM module head and directed toward the sample stage. This configuration creates a clean environment around the SEM module and actively removes contaminants from sensitive components. By guiding the airflow from the SEM module head, the system ensures that the protective gas passes first through the critical components of the SEM before encountering contaminants generated by the sample processing module.

[0103] In various embodiments, the directional protective gas system may include a gas inlet manifold integrated into the head of the SEM module. This manifold is designed to uniformly distribute the protective gas around the perimeter of the SEM module, creating a uniform downward flow toward the sample stage. As the protective gas passes through the SEM components, it forms a protective barrier, preventing contaminants from reaching sensitive surfaces. The airflow continues toward the sample stage, where contaminants generated by the sample processing module are collected and carried away from the SEM module.

[0104] A directional protective gas system may include a protective gas inlet integrated into the SEM module, which is configured to direct the protective gas flow toward the sample stage.

[0105] In various embodiments, integrating the protective gas inlet directly into the SEM module allows for more targeted delivery of the protective gas flow. By positioning the inlet close to the SEM components, the system ensures that the protective gas flow effectively reaches critical areas. This direct integration also minimizes the distance the gas travels, reducing the possibility of contamination during transport.

[0106] In various embodiments, the protective gas inlet may be incorporated into the SEM module head as a series of nozzles or a circular groove surrounding the electron beam aperture. The inlet may be connected to a protective gas supply line that delivers the protective gas at controlled pressure and flow rate. As the gas exits the inlet, it is guided downwards to the sample stage, creating a directional airflow that sweeps contaminants away from the SEM module. The close proximity of the inlet to the SEM components ensures higher concentration and / or velocity and integrity of the protective gas.

[0107] A directional protective gas system may include a gas outlet located below the sample stage, which is configured to remove protective gas from the vacuum chamber.

[0108] In various embodiments, the gas outlet is located below the sample stage to remove gases and entrained contaminants from the vacuum chamber. The outlet's location below the platform ensures that the gas flow is kept away from the SEM module. This configuration helps prevent contaminant recirculation and maintains a clean protective gas environment around the SEM module.

[0109] In various embodiments, the gas outlet can be integrated into the bottom of the vacuum chamber, directly below the sample stage. This outlet can be connected to a vacuum pumping system that continuously removes protective gas and contaminants from the chamber. When the gas flow from the SEM module head reaches the sample stage, it is drawn downwards by the vacuum pump, carrying contaminants towards the outlet. The outlet's location below the platform creates an efficient unidirectional flow pattern, minimizing the possibility of contaminants recirculating back into the SEM module.

[0110] The SEM module may include an end cap facing the sample stage. This end cap may have multiple internal gas channels configured to direct protective gas flow to a protective gas inlet integrated within the end cap.

[0111] In various embodiments, the SEM module may include an end cap with internal gas channels. These channels are designed to guide protective gas from the supply line to inlet nozzles or grooves in the end cap. By evenly distributing the airflow across multiple channels, the system can establish a consistent laminar flow pattern, thereby providing optimal contamination protection.

[0112] In various embodiments, the end cap of the SEM module may include an internal network of gas channels. These channels may connect to a protective gas supply line and terminate at an inlet opening, such as a protective gas inlet nozzle or a groove around the end cap. When protective gas enters the channels, it is distributed and directed to the inlet opening. The geometry of the channels provides a constant gas velocity and minimizes turbulence.

[0113] The end cap may also include a central aperture configured to allow the electron beam to pass from the SEM module to the sample. A protective gas channel may be arranged around the central aperture. This configuration ensures that the gas flow does not interfere with the electron beam path and maintains a clean environment near the aperture.

[0114] In various embodiments, the end cap of the SEM module may include a central aperture aligned with the electron beam column. The aperture is sized to allow the focused electron beam to pass through while minimizing the escape of protective gas. Internal gas channels may be symmetrically arranged and / or form a circular pattern around the central aperture. As the protective gas exits the channels and flows through the inlet nozzle or groove, an annular flow is created. This configuration provides a protective airflow, preventing contaminants from entering the aperture and interfering with imaging processing.

[0115] The protective gas can be an inert gas selected from the group consisting of rare gases and nitrogen. Inert gases, such as rare gases (e.g., argon, helium, neon) and nitrogen, are preferred due to their chemical stability and non-reactive nature. These gases will not interact with the sample, SEM components, or contaminants.

[0116] The sample processing module can be set to grind or etch the sample, or deposit material onto the sample.

[0117] In various embodiments, the sample processing module is responsible for performing various physical or material operations on the sample, such as milling, etching, or material deposition. These processes are crucial for preparing images of samples, analyzing their composition, or fabricating nanoscale structures. However, these processes can also generate contaminants that may interfere with SEM imaging. This contamination treatment system is designed to mitigate the effects of these contaminants and ensure a clean environment for SEM.

[0118] Generally, a sample processing module may include various functions. In various examples, a sample processing module may include a focused ion beam (FIB) system, for instance, for grinding samples. An FIB system uses a focused ion beam to remove material from the sample surface. This process generates contaminants such as sputtered material, redeposited debris, or residual precursor gases, which the contamination handling system must effectively manage to maintain the integrity of the SEM imaging. In various examples, a sample processing module may include one or more of a focused ion beam (FIB) module, a gas injection system (GIS), or a laser processing module.

[0119] Gas injection systems (GIS) are used for site-specific material deposition on sample surfaces. GIS introduces a precursor gas into a vacuum chamber, which is then decomposed by an electron or ion beam to deposit the desired material. Common applications include depositing protective coatings, conductive layers, or insulating materials. GIS can generate contaminants in the form of residual precursor gas or unwanted deposits on SEM components.

[0120] Laser processing modules use focused laser beams to alter sample surfaces through ablation, melting, or selective heating. Laser processing is commonly used for micromachining, surface texturing, or material removal. The interaction between the laser and the material can generate debris, vapor, or plasma plumes, which, if not properly managed, can contaminate the SEM module.

[0121] Such sample processing modules pose a risk of generating contaminants that may interfere with SEM imaging processing. Contamination control modules are designed to ensure a clean and stable environment for SEM imaging processing.

[0122] The revealed technology can be further described through the following examples: The following will describe some general examples in more detail, as well as some examples of Peltier cooling traps used for contaminants in vacuum chambers.

[0123] In several embodiments, the metrology system includes a vacuum chamber. In various embodiments, the system includes a sample stage disposed within the vacuum chamber. The sample stage may be configured to hold a sample on a sample stage surface. The sample stage may be configured to position the sample at an operational position within the vacuum chamber during operation of the metrology system.

[0124] In various embodiments, the system includes a Peltier element at least partially disposed within a vacuum chamber. This Peltier element can serve as a cooler or cryogenic trap for contaminants present within the vacuum chamber. The Peltier element can be fully disposed within the vacuum chamber, wherein one surface of the Peltier element is cooled or heated by the Peltier effect and thermally connected to the vacuum chamber shell, allowing efficient heat transfer from or to the Peltier element, while another complementary cooled or heated surface of the Peltier element faces the interior of the vacuum chamber for capturing contaminants. In other words, the collection surface of the Peltier element for cryogenically capturing contaminants represents part of the entire Peltier thermoelectric module. This collection surface is actively cooled or heated depending on the polarity of the voltage applied to the Peltier element.

[0125] During operation, the complementary components of the Peltier element are heated or cooled respectively via the Peltier effect. These complementary components can be placed inside or outside the vacuum chamber to facilitate heat transfer and dissipation.

[0126] In various embodiments, the complementary Peltier components are thermally bonded and mounted onto the vacuum chamber housing, while the collection surface is located within the internal vacuum environment facing the sample stage and sample. Thus, the housing wall connects the complementary Peltier components to the external environment surrounding the vacuum chamber.

[0127] In other words, to bind contaminants within the vacuum chamber, the Peltier element includes a collection surface inside the vacuum chamber that can be cooled relative to the interior of the vacuum chamber. The collection surface may face the sample stage. The collection surface may at least partially surround the sample stage. The collection surface is configured to be cooled to below 0°C to bind contaminants within the vacuum chamber to the collection surface. The collection surface may be less than 5 cm or 10 cm from the sample stage surface where the sample is held. The collection surface may extend at least 20% or 50% along the sample stage surface. The collection surface may at least partially extend around one or more processing modules for inspecting and processing samples on the sample stage surface (e.g., a concave surface). The collection surface may be at least partially formed of a thermally conductive material (e.g., copper or aluminum), particularly in the core layer, to facilitate efficient heat transfer within the plate. The surface of the plate may include a layer of a different material, such as titanium.

[0128] In various embodiments, the Peltier collection surface is actively cooled to a cryogenic temperature when a sample is being detected or processed. This cooling causes contaminant molecules within the vacuum chamber to lose kinetic energy and bind to the collection surface at low temperature. Therefore, the Peltier collection surface effectively acts as a cooling trap, confining contaminants to the surface and preventing their accumulation and interference with the metrology system's optical components, the sample, or the chamber walls.

[0129] In various embodiments, the metering system may optionally include a plasma cleaning system. This plasma cleaning system may include a cleaning plasma source, a cleaning plasma inlet for injecting cleaning plasma into a vacuum chamber, and a cleaning plasma outlet for extracting contaminant-laden cleaning plasma from the vacuum chamber. The plasma cleaning system may be configured to clean the collection surface of the Peltier element.

[0130] In various embodiments, the system includes a plasma inlet to a vacuum chamber connected to a plasma source for providing a stream of clean plasma into the vacuum chamber. The system also includes a vacuum chamber plasma outlet opposite the plasma inlet for evacuating the stream of clean plasma containing released contaminants by a vacuum pump.

[0131] In various embodiments, the clean plasma flow can be directed toward or onto the collection surface of the Peltier cooling trap. In various embodiments, the clean plasma flow can essentially extend from the clean plasma inlet toward the collection surface along the clean plasma direction or axis. This plasma axis can be parallel to the collection surface, i.e., along the collection surface, or at a small angle of preferably <20° relative to the collection surface. In some embodiments, <15° or <10° are also possible.

[0132] The plasma injected into the vacuum chamber environment consists of a mixture of ionized gases, which can be designed to release or propel contaminants, or to chemically react with and decompose contaminants. Common gases such as oxygen, hydrogen, or nitrogen can be ionized into a clean plasma stream. These reactive plasma streams impact the accumulated contaminants with energy, gradually pushing molecular contaminants from the collection surface toward the clean plasma outlet and expelling them.

[0133] In addition to the chemical decomposition of contaminants, the physical momentum transfer of the directional plasma flow can also be used for sputter etching of the collection surface itself. This helps to keep the refreshed, activated surface cool again after the cleaning process is complete and the next metering phase of operation begins, optimized for cryogenic capture of additional contaminants. Optionally, as will be described in detail below, a replaceable sacrificial plate can be used as the collection surface, mounted on the cooling surface of the Peltier element.

[0134] Selectively, the Peltier element can be switched to a heated mode and operated before or during plasma injection, wherein the collection surface is heated to initially release previously bound contaminants, or at least to facilitate cleaning by the clean plasma. This allows the plasma flow to interact more effectively with the released contaminants, thereby promoting removal. However, the heating step is not necessary; even if some contaminants are bound to the cooled collection surface, they can still be released and expelled.

[0135] By integrating contamination treatment with Peltier cooling traps and plasma cleaning, contamination control can be improved, keeping optical and semiconductor components virtually uncontaminated, and enabling precise metrology and processing within a vacuum chamber.

[0136] In various embodiments, the metrology system may optionally include a sample stage moving mechanism connected to the sample stage, the mechanism being configured to remove the sample stage from the plasma cleaning stream.

[0137] In other words, the metrology system may include a movable sample stage that can be moved by a precision actuator, positioned and moved to an operating location for measurement or inspection. To protect the sample stage from exposure to the cleaning plasma used to remove contaminants from the Peltier cooling trap, in addition to conventional precision sample stage movement, the system may provide an additional sample stage movement mechanism to further translate the sample stage away from the plasma flow path during the cleaning process. In various embodiments, the sample stage movement mechanism may be configured to move the sample stage preferably by a distance greater than 15 cm in one or more directions (e.g., horizontally). However, it should be understood that the invention is not limited to this aspect, and any linear or even nonlinear movement in any direction outside the direct impact area of ​​the cleaning plasma flow can be achieved. In some embodiments, horizontal movement exceeding 5 cm, or exceeding 10 cm, or exceeding 20 cm, or exceeding 30 cm in the horizontal direction can be achieved. In some embodiments, this may be combined with additional linear or even rotational movement in the vertical direction.

[0138] In various embodiments, during the operation phase, the sample stage surface overlaps with the collection surface of the Peltier element in the horizontal direction, and during the cleaning phase, the sample stage is positioned such that the horizontal distance between the sample stage surface and the collection surface of the Peltier element is greater than 5 cm, or 10 cm, or 15 cm, or 20 cm, or 25 cm.

[0139] In various embodiments, the sample stage supporting semiconductor wafers, substrates, or other inspection items can be moved bidirectionally from the operating position to a safe cleaning position. This movement can be achieved via a motorized track system or other transfer mechanisms integrated within the vacuum chamber environment.

[0140] In the operating position and / or operating phase, the sample is aligned with the head of the processing module for metrological measurement at a distance of less than 10 cm for inspection or treatment. In various embodiments, the sample may be located at a position less than 5 cm, 2 cm, 1 cm, or 5 mm. Therefore, before initiating the plasma cleaning sequence, the system controller sends a control signal to move the sample stage to the cleaning position used during the cleaning phase of the metrology system. This removes the sample stage from the area exposed to the cleaning plasma, for example by lowering the sample stage horizontally and / or vertically, and / or rotating the sample stage to a more protected cleaning position. During the cleaning phase and / or in the cleaning position, the sample stage may not hold the sample.

[0141] During the cleaning phase, the sample stage may remain outside the direct plasma path through the vacuum chamber as the cleaning plasma stream enters. It is also possible that the sample stage is still in operation, thus moving the sample stage may be selective. After the cleaning phase, the controller returns to the transfer mechanism, moving the sample stage back to its previous operating position. During the plasma cleaning phase, the sample may be outside the vacuum chamber.

[0142] In various embodiments, the sample stage moving mechanism is configured to move the sample stage from an operating position during the operation phase to a cleaning position for or during the cleaning phase. This cleaning position is located outside the path of the cleaning plasma flow. The system includes a controller. During the operation phase, the controller is configured to operate the Peltier element in a cooling mode to cool the collection surface, thereby binding contaminants within the vacuum chamber to the collection surface, while the sample stage is in the operating position. After the operation phase, the controller is configured to control the stage moving mechanism to move the sample stage from the operating position to the cleaning position. During the cleaning phase, the controller is configured to operate the plasma source to direct the cleaning plasma flow to the collection surface to release contaminants and to discharge the cleaning plasma flow along with the released contaminants through a plasma outlet, while the sample stage is located in the cleaning position outside the path. To evacuate the plasma with released contaminants through the plasma outlet, one or more vacuum pumps, such as turbomolecular pumps and roughing pumps, can be used.

[0143] The present invention combines a Peltier cooling trap and a plasma cleaning flow, while selectively removing sensitive elements within the vacuum chamber from the cleaning plasma flow, offering at least the following advantages: The disclosed technology extends the operating time of the metering system between required maintenance cycles. The disclosed technology shortens the maintenance time of the metering system between operational phases. By collecting contaminants on the plasma-cleanable Peltier cooling trap, the metering system can operate continuously for longer periods before requiring thorough cleaning of the vacuum chamber. The disclosed technology avoids the need to evacuate the vacuum chamber to atmospheric pressure for cleaning the cooling trap. Ventilation of the chamber can allow moisture and other contaminants to flow into the chamber from the atmosphere. By using a cleaning plasma flow for cleaning in a vacuum, directed only at the removable contaminant trap itself inside the vacuum chamber, and continuously evacuating the plasma (selectively simultaneously with plasma injection) by a vacuum pump, the vacuum of the chamber can be substantially maintained. The plasma flow effectively cleans the cooling trap, achieving a cleaning effect comparable to extraction and cleaning outside the vacuum chamber. The cyclical process of collecting contaminants in the cooling trap, followed by heating and plasma cleaning, allows the metering system to operate more continuously without evacuating the vacuum chamber. This increases throughput and productivity. Concentrating contaminants on the collection surface of the Peltier cooler protects other instruments, detectors, and stages within the vacuum chamber from performance degradation. If the trap unit itself degrades after numerous plasma cleaning cycles, only the module unit needs to be replaced, not the internal chamber components. The contaminant capture and collection concept is applicable to many different vacuum chamber installations and applications beyond metrology, and these principles remain valid regardless of whether optical instruments, electron microscopes, or other analytical tools are used in the chamber system.

[0144] An optional advantage of plasma cleaning Peltier elements is that heating or cooling can be set by changing the polarity of the voltage applied to the Peltier element to assist in the plasma cleaning process. Therefore, after cooling the collection surface to bind contaminants during the operation phase, the system controller can switch the Peltier element to heating mode. The collection surface is selectively heated to a sufficiently high temperature that the previously bound contaminants are re-evaporated and released back into the vacuum chamber environment. The Peltier element can be switched to heating mode before or during plasma injection to first release the previously bound contaminants back into the vacuum environment. This allows the plasma flow to interact more effectively with the released contaminants, thereby promoting removal.

[0145] Another optional advantage of the Peltier element is that a sacrificial plate can be mounted on the cooling / heating surface facing the sample stage, which can be easily replaced when it is degraded by the cleaning plasma, and the sacrificial plate provides or contains a collection surface.

[0146] In other words, a Peltier element, or more generally a metering system, may include a removable sacrificial plate mounted on a Peltier cooling trap, on which a collection surface for contaminant binding is formed and exposed to clean plasma. This plate is mounted on the cooling surface of the Peltier element while being exposed to an internal vacuum environment.

[0147] The sacrificial plate may comprise a high surface area material, optimized for the adsorption of common contaminant types encountered in metering vacuum chambers. Exemplary materials for the plate include, but are not limited to, titanium, platinum, ceramics, and other alloys that have an affinity for organic contaminant molecules under cooled conditions.

[0148] The main advantage of a removable sacrificial plate as a collection surface is its ease of replacement after multiple cleaning stages that expose it to contaminants. Instead of replacing the entire Peltier element, only the sacrificial plate needs to be replaced, potentially with a new plate of the same material specifications or a different material composition. Therefore, the sacrificial plate enhances collection capacity and can also be customized with a rough surface texture to maximize surface area.

[0149] The described metering system and apparatus can be configured to perform any of the methods, method steps, or combinations of methods or method steps described in this invention.

[0150] This document provides methods for removing contaminants from the corresponding metering system.

[0151] The metrology system includes a closed, sealed cavity, or in other words, a vacuum cavity, in which a movable sample stage is arranged. On the sample stage, a sample stage surface is provided for holding the sample, and the sample to be inspected or processed can be placed there. Furthermore, a Peltier element is at least partially arranged within the vacuum cavity, such that portions or surfaces of the Peltier element that can be cooled or heated are arranged within the vacuum cavity.

[0152] The revealed technology implements a dual-loop iterative operation / cleaning sequence, including an operation phase and a cleaning phase.

[0153] During the operation phase of the metrology system, the Peltier element is operated in a cooling mode, wherein the collection surface of the Peltier element, disposed within the vacuum chamber and facing the sample stage, is cooled to bind molecular contaminants present within the vacuum chamber to the collection surface. During this operation phase, the sample stage is in the operating position, allowing for inspection or handling of the sample on the sample stage. In the operation phase, the collection surface of the Peltier element is positioned close to and facing the sample stage surface and / or the sample; in other words, adjacent to the sample stage surface and / or the sample, so that contaminants that would otherwise bind to the sample surface can be collected and bound to the cooled collection surface of the Peltier element, which acts as a contaminant cooling trap.

[0154] In various embodiments, the cooling trap utilizes a temperature difference to capture or bind contaminant molecules in a gas or vacuum to a cold surface. In this case, the collection surface of the Peltier element provides a cold trapping surface within the vacuum chamber. The Peltier element typically generates independent cooling and / or heating elements. When an electric current is applied, i.e., when the Peltier element is electrically powered, one side cools while the other heats up. In cooling mode, the pumping action of the Peltier element transfers heat from the collection surface to the warmer side of the Peltier. The heating element of the Peltier element may be located outside the vacuum chamber. This makes the collection surface cooler than the surrounding chamber walls and components inside the vacuum chamber, allowing the collection surface to collect contaminants from the internal atmosphere. Contaminant molecules present in the vacuum chamber (particularly hydrocarbons or other organic compounds released from the sample) will randomly collide due to kinetic energy, preferably moving towards the cooled collection surface and condensing or freezing thereon. Thus, contaminants are bound and trapped on the cooled Peltier surface, rather than deposited elsewhere in the chamber. Stopping cooling, or even reversing the power, may cause the surface to heat up again, thereby de-adsorbing or evaporating contaminants back into the cavity and discharging them.

[0155] In an optional step, at least partially after the operation phase and at least while preparing for a subsequent cleaning phase, in various embodiments, the sample stage is removed from the Peltier cooling element during the moving phase. In this optional step, the sample stage is moved from the operation position where it was in the operation phase to a designated cleaning position. In addition to moving the sample stage, the Peltier element may also be moved to the cleaning position. Such a moving phase can be considered optional, as it may be at least partially included in or parallel to the operation and / or cleaning phases.

[0156] In this step, during the cleaning phase, contaminants are removed from the Peltier cooling trap (specifically the collection surface of the Peltier element) and the vacuum chamber. During the cleaning phase, a cleaning plasma flow is directed from the cleaning plasma inlet into the vacuum chamber. The cleaning plasma flow follows a defined cleaning plasma path towards the collection surface of the Peltier element. Thus, during the operation phase, the cleaning plasma pushes away contaminants bound to the collection surface. The cleaning plasma flow, along with the contaminants, is discharged from the vacuum chamber through the cleaning plasma outlet, carrying away the released contaminants. During this step, the sample stage remains in the clean position, outside the cleaning plasma path.

[0157] Optionally, after the operational metrology phase, the sample stage holding the sample for analysis can be moved from its original operational position to a designated clean position. This movement intentionally positions the sample stage away from the path of the clean plasma flow guiding the Peltier cooling trap.

[0158] In various embodiments, when inspecting samples, the platform may be positioned vertically close to and facing the collection surface of the Peltier cooling trap to allow contaminants to easily migrate to the cold collection surface. In various embodiments, the sample stage surface and the collection surface may overlap in a horizontal direction, which may be parallel to the sample stage surface. The collection surface and the sample stage surface may be directly opposite each other. The collection surface and the sample stage surface may be substantially parallel to each other. In a direction parallel to the sample stage surface (e.g., in the horizontal direction), the vertical distance between the sample stage surface and the collection surface may be less than 10%, 20%, or 30% of the sample stage size and / or the collection surface size. In some examples, the horizontal overlap between the sample stage surface on which the sample can be held and the Peltier collection surface may be greater than 20%, or 40%, or 60%, or 80% of the sample stage size and / or the collection surface size. Prior to the plasma cleaning phase, a platform translation mechanism (e.g., one or more actuators, such as an electric track, or a combination of linear and nonlinear actuators) may move the platform vertically and / or horizontally away from its original operating position. This provides separation from the cleaning plasma flow during plasma cleaning.

[0159] In various embodiments, during the operation phase, the sample stage surface can be preferably positioned less than 10 cm from the Peltier element collection surface. In some examples, the collection surface may also be positioned less than 5 cm from the sample stage surface, or more generally less than 20 cm from the sample stage surface. This allows contaminants in the atmosphere surrounding the sample to diffuse to and adhere to the cooled Peltier surface, which acts as a cryogenic cold trap.

[0160] In preparation for the cleaning phase (in which the cleaning plasma flow is directed to the collection surface), the sample stage is then moved away from the collection surface and the cleaning plasma path, for example, away from the path of the plasma flow perpendicularly.

[0161] The clean plasma inlet can be located anywhere suitable within the vacuum chamber housing. In various examples, it can be attached horizontally. It may be located on a vertical wall of the vacuum chamber housing. In some examples, the incoming clean plasma flow can be guided substantially horizontally. In some examples, the clean plasma flow can be directed to the Peltier collection surface.

[0162] The clean plasma outlet can be located at any suitable location within the vacuum chamber housing. In various examples, it can be located on the bottom wall of the vacuum chamber housing, such that the clean plasma flow path is directed to the bottom surface of the vacuum chamber. However, it can also be arranged at different locations within the vacuum chamber, for example, at a horizontal position across the Peltier collection surface.

[0163] In various examples, the distance between the plasma inlet and the Peltier collecting surface can range from 10 cm to 30 cm. In various examples, the plasma outlet can be located vertically below the Peltier collecting surface.

[0164] In various examples, the sample stage can be moved laterally, i.e., horizontally more than 5 cm, 10 cm, 15 cm, or 30 cm from the center of the clean plasma flow path. Optionally, the stage can be moved vertically along the plasma flow direction to further protect the sample stage from the impact of highly clean plasma. Furthermore, combinations of vertical and / or horizontal translational and / or rotational movements can be performed to reduce the impact of the clean plasma on the sample stage.

[0165] In some examples, the Peltier cooling trap can even be shifted toward the clean plasma inlet, i.e., a higher plasma concentration, or the collection surface can be rotated toward a higher angle of impact to achieve better cleaning results with reduced plasma flow.

[0166] In various examples, during the operation phase, the vertical distance from the collection surface to the sample stage is preferably less than 10 cm, and then the actuator horizontally repositions the sample stage to a position more than 20 cm vertically, and selectively more than 20 cm horizontally. This protects the sample from plasma backscattering while the opening is fully exposed to thoroughly clean plasma diffusion to / from the inlet / outlet across the entire collection surface.

[0167] Furthermore, during plasma cleaning, the stage can be moved vertically and / or horizontally into a partially enclosed internal space within the vacuum chamber, which may be a protected cavity region of the vacuum chamber. Optionally, the stage can be moved behind at least one wall that isolates the stage from the cleaning plasma inlet relative to a straight line or line of sight. This provides shelter for the incoming cleaning plasma flow.

[0168] In various examples, during the cleaning phase, the method may also include operating the Peltier element in a heating mode to heat (i.e., raise) the temperature of the collection surface and release contaminants bound thereon, facilitating removal by the cleaning plasma stream. The heat is applied to provide thermal energy capable of breaking any remaining chemical and physical bonds between the contaminants and the collection surface that were bound during the operation phase. Facilitating the release and removal of contaminants in this manner minimizes surface residue prior to subsequent operation phases and maintains optimal operating conditions over extended operation-cleaning cycles.

[0169] The collection surface of the Peltier element may also include a replaceable sacrificial plate to accumulate contaminants during the operation phase, wherein the sacrificial plate can be removed and replaced after multiple cleaning cycles of exposure to a directional cleaning plasma flow. In other words, the sacrificial plate can be placed on the cooling or heating surface of the Peltier element within the vacuum chamber to form a replaceable contaminant collection surface.

[0170] Thus, the sacrificial plate provides a regenerable layer of contaminant accumulation to maintain optimal function of the Peltier element. When the plate's performance deteriorates due to excessive plasma exposure after repeated cleaning stages, only the modular sacrificial plate needs to be replaced, without replacing the integrated Peltier element.

[0171] The surface roughness (Ra) of the sacrificial plate collection surface can be between 1 and 5 micrometers, or more specifically 2 to 3 micrometers, to provide optimal contaminant adsorption. The rough surface enhances contaminant adsorption during the operation phase by increasing the surface area.

[0172] The sacrificial plate may include or have a collection surface made of materials such as aluminum or titanium. Aluminum provides good heat transfer due to its high thermal conductivity, while remaining cost-effective as a replaceable unit. Titanium has good plasma resistance and can withstand longer periods of cleaning exposure.

[0173] The collecting surface may include material layers or coatings to further enhance specific properties. Among various examples, an aluminum core and a titanium layer are used. The sacrificial plate can be improved by selecting a suitable combination of base metals, alloys, or surface coatings with a roughness between 1 and 5 micrometers.

[0174] The clean plasma outlet can be located on the opposite side of the vacuum chamber relative to the collection surface of the Peltier element and the clean plasma inlet. The clean plasma path can extend in a substantially straight path from the clean plasma inlet toward the collection surface and continue toward the clean plasma outlet.

[0175] Positioning the plasma outlet opposite the plasma inlet allows the introduced plasma flow to pass directly and horizontally across and interact with the entire surface of the collection surface. Contaminants released by the plasma can then be propelled or carried through the cavity toward the clean plasma outlet located at the bottom of the vacuum cavity.

[0176] The cleaning phase can be carried out without emptying the vacuum chamber, that is, the vacuum chamber is essentially kept under vacuum or internal pressure.

[0177] Therefore, a cleaner plasma flow enables faster cleaning processes and eliminates the risk of moisture, oxygen, and other contaminants entering the chamber before vacuum conditions are re-established. Performing the cleaning protocol under vacuum further accelerates contaminant removal because time-consuming evacuation and purging steps are not required between the operation and cleaning phases. This increases uptime and sample throughput.

[0178] Generally, during the operation phase, the working distance (i.e., the distance between the sample surface and the processing module (e.g., the SEM pole piece)) is typically 5 mm. The maximum vertical travel range of the sample stage can be 5 mm or 10 mm, and in some examples, 20 mm or 30 mm. During the operation phase, the sample stage can be positioned less than 15 cm from the Peltier element's collection surface, specifically less than 10 cm or 5 cm. This effectively collects contaminants near the sample. The collection surface of the Peltier element can extend at least partially along the sample stage surface where the sample is mounted, specifically along more than 50%, or more than 70%, or more than 80% of the sample stage surface area.

[0179] Then, during the cleaning phase, the sample stage is preferably moved to a distance of more than 15 cm from the collection surface of the Peltier element and / or the path of the cleaning plasma, particularly away from the cleaning plasma path between the cleaning plasma inlet and outlet. The sample stage is moved such that the collection surface of the Peltier element no longer extends along the sample stage surface, i.e., no longer overlaps horizontally. In some examples, the sample stage may be moved horizontally from the operating position by a distance greater than 10 cm, or 15 cm, or 20 cm, or 25 cm, or up to 30 cm. Furthermore, regarding the cleaning plasma flow path, if the cleaning plasma flow has a vertical profile that is substantially perpendicular to the cleaning plasma path through the vacuum cavity, the profile of the cleaning plasma flow can be defined as a region where the plasma particle concentration of the cleaning plasma exceeds 60%, 70%, or 80% compared to the particle concentration at the center of the plasma flow. The sample stage can be moved out of this high-concentration region. This defined displacement protects the sample stage from potential degradation due to repeated exposure to the cleaning plasma. This movement also fully exposes the entire Peltier cooling trap to the cleaning plasma flow.

[0180] The collection surface of the Peltier element can extend substantially parallel, or within a small angular range of >0°, >5°, and / or <10° or <20° relative to the horizontal direction and / or the sample stage surface, and face the sample stage surface holding the sample during the operation phase, so that molecular contaminants released from the sample on the sample stage, or molecular contaminants moving toward the sample during the operation phase, can be easily captured on the collection surface.

[0181] The sample may be a semiconductor wafer or a substrate. The metrology system may be configured for at least one of the following: semiconductor wafer inspection, measurement, analysis, or processing.

[0182] The metrology system may include a scanning electron microscope (SEM) module configured to image a sample (e.g., a semiconductor wafer) within a vacuum chamber during the operation phase. The metrology system may also include at least one of a focused ion beam (FIB) system and a gas injection system (GIS) for sample processing. In this respect, the operation phase can also be considered as the acquisition and / or processing phase of the metrology system.

[0183] The method also includes monitoring the collection surface temperature of the Peltier element during the cleaning phase and adjusting the heating to maintain the temperature above 100 degrees Celsius.

[0184] Maintaining high temperatures facilitates the desorption of contaminants during plasma exposure and prevents re-adhesion and accumulation of contaminants between cleaning cycles. Higher heat allows the plasma flow to better expel and remove trapped particles, thus enabling continuous optimal operation.

[0185] The method also includes monitoring the collection surface temperature of the Peltier element during the operation phase and adjusting the cooling to maintain the temperature below 0 degrees Celsius.

[0186] Maintaining the collection surface at sub-zero temperatures allows for more efficient capture of gaseous contaminants and enhances adsorption rate and capacity through the cryogenic effect. Fine-tuning and maintaining cooling facilitates the accumulation of molecular contaminants during metering operations, rather than allowing them to diffuse within the vacuum chamber.

[0187] Below are some examples of Peltier cooling traps: 1. A method for removing contaminants in a metrology system, the metrology system comprising a sample stage located within a vacuum chamber and a Peltier element at least partially disposed within the vacuum chamber, the method comprising the steps of: - The operational phase of this metering system: The Peltier element is operated in a cooling mode, in which the collection surface of the Peltier element, disposed within the vacuum chamber and facing the sample stage, is cooled to bind molecular contaminants present within the vacuum chamber to the collection surface. The sample stage is located in the operating position, allowing for inspection or handling of the sample on the sample stage; - After the operation phase of the metering system, and in preparation for the cleaning phase of the metering system: Move the sample stage from the operating position to the cleaning position; and - Cleaning phase of the metering system: The clean plasma stream is directed from the clean plasma inlet of the vacuum chamber along the clean plasma path to the collection surface of the Peltier element, and contaminants are released from the collection surface. The clean plasma containing the released contaminants is then discharged through the clean plasma outlet of the vacuum chamber. The sample stage is located outside the clean plasma path of the clean plasma flow.

[0188] 2. The method as described in Example 1, wherein during the cleaning phase, the method further includes: The Peltier element is operated in heating mode to heat the collection surface and release contaminants bound thereto, thereby facilitating the removal of the contaminants through the clean plasma flow.

[0189] 3. The method described in any of the foregoing examples further includes: A replaceable sacrificial plate is installed on the Peltier element, which provides a collection surface for collecting contaminants during this operational phase. Replace the sacrificial plate after a predetermined number of cleaning cycles.

[0190] 4. The method as described in Example 3, wherein the sacrificial plate provides a collection surface with a surface roughness (Ra) between 1 micrometer and 5 micrometers.

[0191] 5. The method as described in Example 3 or 4, wherein the sacrificial plate has an outer layer of a first adsorbent material on top of an inner layer of a highly thermally conductive material.

[0192] 6. The method as described in any of the preceding examples, wherein the cleaning phase is performed without ventilating the vacuum chamber.

[0193] 7. The method as described in any of the preceding examples, wherein during the operation phase, the sample stage surface overlaps with the collection surface of the Peltier element in the horizontal direction, and during the cleaning phase, the sample stage is located at a position where the horizontal distance between the sample stage surface and the collection surface of the Peltier element is greater than 15 cm.

[0194] 8. The method as described in any of the foregoing examples further includes, during the operation phase, monitoring the temperature of the collecting surface of the Peltier element and adjusting the cooling to maintain the temperature below 0 degrees Celsius.

[0195] 9. The method as described in any of the foregoing examples further includes, during the cleaning phase, monitoring the temperature of the collecting surface of the Peltier element and adjusting the heating to maintain the temperature above 100 degrees Celsius.

[0196] 10. A metering system, comprising: - Vacuum cavity; - A sample stage disposed within the vacuum chamber, the sample stage being configured to hold the sample and position the sample at the operating position within the vacuum chamber during the operation phase of the metrology system; - A Peltier element at least partially disposed within the vacuum chamber, the Peltier element including a collection surface located within the vacuum chamber and facing the sample stage, the Peltier element being configured to be cooled during the operation phase for binding contaminants within the vacuum chamber to the collection surface; - A plasma inlet is provided in the vacuum chamber, which is connected to a plasma source to provide a clean plasma flow into the vacuum chamber during the cleaning phase; - The plasma outlet of the vacuum chamber is used to discharge a clean plasma stream containing released contaminants; - A stage moving mechanism connected to the sample stage, the stage moving mechanism being configured to move the sample stage from an operating position during the operation phase to a cleaning position during the cleaning phase, the cleaning position being outside the path of the cleaning plasma flow; - Controller, which is configured as follows: During this operation phase, the Peltier element is operated in a cooling mode in which the collection surface of the Peltier element is cooled to bind contaminants in the vacuum chamber to the collection surface of the Peltier element, while the sample stage is in the operation position. After this operation phase, control the stage moving mechanism to move the sample stage from the operation position to the cleaning position; During the cleaning phase, the plasma source is operated to direct the clean plasma stream from the plasma inlet along the clean plasma path to the collection surface of the Peltier element to release contaminants, and the clean plasma stream, along with the released contaminants, is discharged through the plasma outlet, while the sample stage is located at the cleaning position outside the path of the clean plasma stream.

[0197] 11. The system as described in Example 10, wherein the plasma outlet is located on the opposite side of the vacuum cavity relative to the collection surface and the plasma inlet of the Peltier element, and wherein the clean plasma path extends substantially along a line from the plasma inlet toward the collection surface and further toward the plasma outlet.

[0198] 12. The system as described in Example 10 or 11, wherein the collection surface of the Peltier element is substantially parallel to and faces the sample stage surface that holds the sample during the operation phase, such that molecular contaminants in the space between the sample on the sample stage and the Peltier element are captured by the extended parallel collection surface during the operation phase.

[0199] 13. The system of any one of Examples 10-12, wherein the sample is a semiconductor wafer or substrate, wherein the metrology system is configured for inspecting, measuring, analyzing or processing the semiconductor wafer.

[0200] 14. The system of any one of Examples 10-13, wherein the metrology system includes a scanning electron microscope (SEM) configured to image a semiconductor wafer within the vacuum chamber during the operation phase.

[0201] 15. The system as described in any one of Examples 10-14, wherein the metering system further comprises at least one of the following: a focused ion beam (FIB) system and / or a gas injection system for processing the semiconductor wafer.

[0202] The technology may include using a power supply during the operation and cleaning phases to operate one or more Peltier elements as cryogenic traps for contaminants.

[0203] A vacuum chamber, also known as a sealed or enclosed sample chamber, has an internal pressure lower than the local environment. During the operation phase, the vacuum pump may or may not operate.

[0204] During the operation phase, the collection surface may be located inside the vacuum chamber; in other words, it may form part of the inner surface of the vacuum chamber. The corresponding heating surface may be located outside the vacuum chamber or thermally coupled to the vacuum chamber wall or another heat dissipation system. During the cleaning phase, the inner surface may be heated while the corresponding outer surface may be cooled, and vice versa.

[0205] The method may include guiding a clean plasma flow onto or along a collection surface, particularly at an angle of less than 10° or 20° relative to the collection surface, to release contaminants from the collection surface and push them toward and out of a vacuum pump outlet. The collection surface may be arranged at the center of the clean plasma flow in terms of the plasma flow direction, wherein the concentration of the clean plasma is within 80%, 60%, or 40% of the maximum concentration in the cross-section passing through the collection surface.

[0206] This method may include moving or positioning the sample stage outside the area affected by the clean plasma flow. Specifically, outside the area 15 or 20 centimeters away from the connecting line between the clean plasma inlet and outlet.

[0207] The method may include covering a Peltier collection surface with a replaceable collection surface or plate, which is cooled or heated by a Peltier element and used to collect contaminants. In other words, the collection plate may also include or be covered by a replaceable sacrificial collection plate positioned to cover the cooled surface of the Peltier element. The collection plate may have a rough surface or a concave surface around the sample stage to improve the adhesion of molecular contaminants.

[0208] The method may include reversing the polarity of the power supply to the Peltier element to release collected contaminants, wherein the reversal may be controlled by a controller according to a predetermined temperature profile.

[0209] The SEM processing module in this metrology system can be configured to image the sample at an accelerating voltage between 500 V and 30 kV. The SEM processing module may include a low-vacuum SEM, configured to image the sample at a pressure between 10 Pa and 1000 Pa. Additionally, a FIB processing module may be included to mill or deposit material on the sample surface during the operation phase. Furthermore, a GIS processing module may be included to supply gas to the sample surface during the operation phase.

[0210] The method may include measuring the pressure within the vacuum chamber and, in response to determining that the pressure has risen above a critical pressure, initiating a cleaning phase.

[0211] The method may include visually inspecting the collection surface and, in response to determining a predetermined degree of degradation caused by plasma exposure, initiating the replacement of the sacrificial plate.

[0212] In some specific embodiments, the operation phase may include an image acquisition phase and / or a sample processing phase, which are carried out in parallel with each other.

[0213] In general, it should be understood that the disclosure of corresponding methods for operating the metering system and / or contamination treatment module or any or any combination of the examples disclosed herein, wherein functional and / or structural elements (in particular one or more controllers) are disposed within or at least partially disposed within the metering system and / or vacuum chamber to control the system and / or module to perform the operating steps.

[0214] The pollution treatment method for the disclosed metering system can achieve advantages corresponding to those described in the metering system.

[0215] It should be understood that the features and examples mentioned above, as well as the features and examples to be explained below, can be used not only in the corresponding combinations shown, but also in other combinations or individually, without departing from the scope of the invention. Specifically, the features of the disclosed specific embodiments can be combined with each other in further specific embodiments.

[0216] Therefore, the above description of the invention is only intended to provide a brief overview of some features of specific embodiments and implementations, and should not be construed as limiting. Other specific embodiments may include features other than those described above. Attached Figure Description

[0217] Those skilled in the art will recognize and understand these and other objects of the invention from the detailed description of preferred embodiments and the following drawings, wherein like reference numerals refer to like elements.

[0218] Figure 1 The illustration shows a metrology system comprising a SEM module and a FIB module for manipulating samples in a vacuum chamber, wherein the techniques according to the invention can be applied.

[0219] Figures 2 to 6 The illustrations illustrate examples of contaminant treatment modules, including cooling traps for capturing contaminants in a vacuum chamber.

[0220] Figure 2 Illustrative examples of metering systems during the operational phase, based on various examples.

[0221] Figure 3 The illustrations illustrate metering systems during the cleaning phase, based on various examples.

[0222] Figure 4 This schematically illustrates another metering system during the operational phase, according to various examples, wherein the clean plasma outlet is arranged on the bottom side of the vacuum chamber.

[0223] Figure 5 illustrative examples of various scenarios under the cleaning phase Figure 4 The measurement system.

[0224] Figure 6 The illustrations illustrate the steps of removing contaminants from a metering system according to various examples.

[0225] Figure 7 The illustrations depict dynamic shutter blades included in the pollution treatment module of a metering system based on various examples.

[0226] Figure 8 The illustrations depict static blades of a contaminant barrier included in a contaminant treatment module of a metering system according to various examples.

[0227] Figure 9 The illustrations illustrate the electrostatic shielding of the SEM head included in the contamination treatment module of a metering system according to various examples.

[0228] Figure 10The illustrations illustrate the protective gas environment of the dye treatment module valve in the vacuum chamber of a metering system according to various examples.

[0229] Figure 11 The illustrations depict the directional protective gas flow of a contamination treatment module in a metering system based on various examples. Detailed Implementation

[0230] Specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the following description of the specific embodiments should not be considered limiting. The scope of the present invention is not limited to the specific embodiments or drawings described below, which should be considered as illustrative examples of a general inventive concept. Unless otherwise expressly stated, features of various specific embodiments can be combined with each other.

[0231] The accompanying drawings are to be considered schematic representations, and the elements illustrated in the drawings are not necessarily shown to scale. Rather, the various elements are shown such that their function and general purpose will become apparent to those skilled in the art. Any connection or coupling between functional blocks, devices, components, or other physical or functional units shown in the drawings or described herein may also be achieved through indirect connection or coupling. Coupling between components may also be established via wireless connection. Functional blocks may be implemented in hardware, firmware, software, or a combination thereof.

[0232] Some examples of the present invention typically provide multiple modules or other electrical devices for metering systems. All references to modules and other electrical devices, and the functions provided by each device, are not intended to be limited to what is illustrated and described herein. While specific labels may be assigned to the various modules or other electrical devices disclosed, such labels are not intended to limit the scope of operation of the modules and other electrical devices. Such modules and other electrical devices may be combined and / or separated from each other in any way based on the specific type of mechanical and / or electrical implementation desired. It should be understood that any processing module or other electronic device disclosed herein may include any number of microcontrollers, graphics processing units (GPUs), integrated circuits, memory devices (e.g., flash memory, random access memory (RAM), read-only memory (ROM), electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or other suitable variations thereof), and software that cooperates with each other to perform the operations disclosed herein. Additionally, any one or more electrical devices may be configured to execute program code embodied in a non-transitory computer-readable medium, programmed to perform any number of functions in the present invention.

[0233] The following describes techniques for contamination treatment or removal in metrology systems used for imaging and processing microscopic samples using charged particle scanning systems such as SEM and FIB. It should be understood that the described techniques are applicable to any metrology system employing enclosed and / or sealed sample cavities (particularly vacuum cavities), including imaging processes (e.g., particle beam imaging) and material grinding processes that generate contaminants in the vacuum cavity that interfere with the imaging process (e.g., beam-induced material removal techniques or beam-induced deposition or etching techniques).

[0234] In the semiconductor industry, a 300mm platform refers to wafer fabrication equipment designed to handle silicon wafers with a diameter of 300mm. These platforms are equipped with advanced processing modules, including metrology systems, for manufacturing cutting-edge integrated circuits. One such metrology system is a dual-beam system, which combines a focused ion beam (FIB) for milling and a scanning electron microscope (SEM) for imaging within the same vacuum chamber. This optimized setup enables precise material removal and high-resolution imaging, which is crucial for process control and fault analysis in semiconductor manufacturing.

[0235] However, integrating FIB and SEM into a single cavity leads to a problem: material debris generated during the FIB milling process, which can also be considered contaminants in the gas within the vacuum chamber, can then deposit on the SEM column. This contamination of the SEM column adversely affects image quality, thereby severely impacting the accuracy and reliability of the metrology system.

[0236] One effect of this is the emergence of skipped images, where rapid charge accumulation on contaminants within the SEM column causes subsequent images to capture a different field of view (FoV) than previous images. This can cause sudden shifts in the imaging area, particularly at smaller milling depths, deviating from the expected FoV. Another issue is drifting images, where slow charge accumulation on contaminants within the SEM column causes a gradual drift in the imaging FoV, resulting in deviations from the expected FoV at larger milling depths. Therefore, the imaging FoV of the volume differs from the expected value, potentially leading to inaccurate measurements and analyses.

[0237] Furthermore, charged particles can deflect the primary beam, causing imaging artifacts by altering the focal point and beam support; this phenomenon is called astigmatism. Astigmatism occurs when the electron beam is not perfectly circular, leading to image distortion. This is particularly problematic in metrology systems, where high-resolution imaging is crucial for accurate measurement and inspection.

[0238] To mitigate these issues, SEM columns require frequent cleaning. However, this process presents several challenges in terms of vacuum chamber and contamination handling. Cleaning SEM columns is labor-intensive, costly, and unreliable, as the precise removal of minute particles cannot be guaranteed. Furthermore, a broad support supply chain is needed, including specialized tools and trained personnel. Additionally, exposing the vacuum chamber to the natural environment while addressing contamination can lead to subsequent problems, such as the introduction of new contaminants or difficulty in re-establishing the required vacuum level.

[0239] This invention is based on the finding that the best approach to solving the debris deposition problem in dual-beam systems is to prevent contaminants from reaching the SEM column in the first place, rather than attempting to remove them afterward. Therefore, this invention presents various solutions for collecting and demonstrating how to protect the SEM column from contamination caused by debris generated by the FIB, or from general contaminants that may be present in the vacuum chamber (in the gas).

[0240] Various examples involve protecting the SEM column from contaminants (in other words, debris) generated during milling in a dual-beam system. These examples also involve metrology systems that include at least one or both of a SEM processing module and a FIB processing module.

[0241] The SEM processing module refers to a component of the metrology system configured to image a sample (e.g., a semiconductor wafer) within a vacuum chamber during the operational phase. An SEM column may refer to the vertical portion of the SEM extending into the vacuum chamber and containing electron beam optics. An SEM head and / or SEM end cap may refer to the bottom portion of the SEM column, which is closest to the sample and most susceptible to particle contamination generated during sample processing. The SEM head or end cap may be surrounded by a housing or shield to protect it from contamination.

[0242] The FIB processing module (which may include an FIB column) refers to a material grinding module in a metrology system, configured to mill the sample surface (i.e., remove material from the sample surface) during the operation phase of the metrology system. The FIB column generates a focused ion beam that impacts the sample surface at an angle, enabling it to process the sample in conjunction with SEM imaging. Together, the SEM and FIB processing modules enable the metrology system to image and physically process samples (e.g., semiconductor wafers) within a vacuum chamber.

[0243] Other processing modules (such as the GIS processing module) can be configured to supply gas to the sample surface during the operation phase of the metrology system. This gas can be used for various purposes, such as etching processes or providing a source of material deposited on the sample surface. The GIS can work in conjunction with the FIB and SEM modules to enable localized processing of samples within a vacuum chamber.

[0244] Figure 1The schematic illustration shows a dual-beam metrology system 1000 comprising a SEM processing module 1040 and a FIB processing module 1050 for manipulating samples in a vacuum chamber, wherein the technology according to the invention can be applied.

[0245] like Figure 1 As seen herein, the metrology system 1000 includes a wafer inspection system configured with a slicing and imaging method having a dual-beam configuration. Sample processing in this metrology system is typically performed in a sealed environment, such as a processing chamber, specifically in a vacuum chamber 10, which is schematically shown around the metrology system 1000.

[0246] The metering system 1000 is specifically located in, or at least partially located in, a vacuum chamber 10, and may include one or more contamination treatment modules and any corresponding devices, systems, apparatuses, or elements for contamination treatment as described in this invention. The metering system 1000 may also be configured to perform any method or combination of methods according to the invention. In various examples, the metering system may include a controller configured to control various elements for performing one or more contamination treatment methods.

[0247] According to the technology of the present invention, a processing module including, for example, SEM column 1040, FIB column 1050 and particle detector 1017 can extend from the outside of the vacuum cavity through the vacuum cavity housing 10 into the interior of the vacuum cavity housing 10.

[0248] For wafer 1008, multiple measurement positions are defined in a position map or inspection list generated from inspection tools or design information, including measurement positions 1006.1 and 1006.2. Wafer 1008 is placed on sample stage 1015. Sample stage 1015 is mounted on platform movement mechanism 1155 having actuators and position controller 1021. Actuators and devices for the precision controller 1021 of platform movement mechanism 1155, such as laser interferometers, are known in the art. Control unit 1016 receives actual position information about platform movement mechanism 1155 and controls platform movement mechanism 1155 to adjust measurement position 1006.1 of wafer 1008 at intersection 1043 of dual-beam device 1001. Dual-beam device 1001 includes FIB column 1050 with FIB optical axis 1048 and charged particle beam (CPB) imaging system 1040 with optical axis 1042 (e.g., SEM or HIM; see below). Figure 3 (Charged particle scanning microscope 160). At the intersection 1043 of the two optical axes in the FIB and CPB imaging systems, the wafer surface 1055 is configured at an angle GF to the FIB axis 1048. The sample is observed jointly by FIB and CPB. There is an angle GFE between the FIB axis 1048 and the CPB imaging system axis 1042. Figure 1In the coordinate system, the normal to the wafer surface is given by the z-axis. A focused ion beam (FIB) 1051 is generated by FIB pillars 1050 and impacts the surface 1055 of the wafer 1008 at an angle GF. The tilted cross-section surface can be milled into the wafer at a predetermined y-position at an inspection position 1006.1 with an angle of approximately GF, controlled by a platform movement mechanism 1155 and a position controller 1021. In the illustrated example, the tilt angle GF is approximately 30°. Due to beam divergence of the focused ion beam (e.g., a gallium ion beam) or due to variations in material properties during milling along the cross-section, the actual tilt angle of the tilted cross-section surface can deviate from the tilt angle GF by 1° to 4°. An image of the milled surface can be obtained using a charged particle beam imaging system 1040. Figure 1 In one example, the charged particle beam imaging system 1040 is arranged such that its charged particle beam 1044 is perpendicular to the wafer surface 1055 and parallel to the z-axis. In other configurations, the optical axis 1042 of the charged particle beam imaging system 1040 is at an angle to the z-axis.

[0249] During imaging, a charged particle beam 1044 is scanned by the scanning unit of the charged particle beam imaging system 1040 along a scanning path on the cross-sectional surface of the wafer at measurement position 1006.1, generating secondary particles and backscattered particles. Particle detector 1017.1 and optical internal particle detector 1017.2 collect at least some of the secondary particles and / or backscattered particles and communicate particle counts to control unit 1019. Detectors for other interaction products (e.g., X-rays or photons) may also be present. Control unit 1019 controls the charged particle beam imaging column 1040 and FIB column 1050 and is connected to control unit 1016 to control the position of the wafer mounted on sample stage 15 via platform movement mechanism 1155. Operation control unit 1002 communicates with control unit 1019 and then moves the platform movement mechanism to trigger, for example, the placement and alignment of the wafer at measurement position 1006.1 at intersection 1043, and repeatedly triggers FIB milling, image acquisition, and platform movement operations. The control unit 1019 and the operation control unit 1002 include memory for storing instructions in the form of software program code, and at least one processor for executing instructions during operation. The memory is also provided for storing digital image data. The operation control unit 1002 may also include a user interface or an interface to other communication interfaces for receiving instructions, previous information, and transmitting inspection results.

[0250] In such Figure 1 The demonstration metering system 1000 described above can be equipped with pollution treatment based on the technology of the present invention.

[0251] Figures 2 to 6The illustrations illustrate examples of contaminant treatment modules, including cooling traps for capturing contaminants in a vacuum chamber.

[0252] The contamination treatment module of the metering system may include a cooling trap configured to capture contaminants within a vacuum chamber. Specifically, the cooling trap may be a Peltier cooling trap, utilizing the Peltier effect to achieve efficient cooling and contaminant capture.

[0253] The Peltier cooling trap may include a Peltier cooling element configured to maintain the temperature of the surface of the contaminant trap below the condensation temperature of the contaminants present in the vacuum chamber.

[0254] In terms of placement, the contaminant trap can be located between the sample processing module (e.g., the FIB module) and the SEM module, for example, as a static contamination barrier, or in other locations within a vacuum chamber. This arrangement allows the trap to capture contaminants generated by the sample processing module before they can reach and potentially damage or interfere with the SEM module.

[0255] To further enhance the functionality of the cooling trap, the metering system may include a cleaning module configured to remove accumulated contaminants from the surface of the cooling trap during a cleaning phase. This cleaning module may include a plasma generator that directs a plasma stream to the surface of the cooling contaminant trap. The plasma stream interacts with the accumulated contaminants, effectively removing them from the trap surface. A vacuum pump is then used to evacuate the cleaning plasma along with the contaminants removed from the vacuum chamber, thereby maintaining the cleanliness and performance of the cooling trap during long-term operation.

[0256] By combining the Peltier cooling trap with an associated cleaning module, the contamination treatment module of this metrology system provides an efficient and reliable way to capture and remove contaminants from the vacuum chamber, ensuring a clean and stable environment for the SEM imaging process.

[0257] The cleaning module is specifically implemented as a plasma cleaning system, operating sequentially with alternating steps between the imaging / processing and cleaning phases. This sequential approach ensures effective removal of contaminants generated during sample imaging and processing, while maintaining the cleanliness of the vacuum chamber and the performance of the SEM module.

[0258] During the imaging / processing phase, the metrology system operates in a mode where the SEM module images the sample, and the sample processing module (e.g., the FIB module) performs any necessary modifications or analyses. During this phase, the Peltier cooling trap remains active and continuously captures contaminants generated by the sample processing module.

[0259] Once the imaging / processing phase is complete, the system transitions to the cleaning phase. During this phase, the plasma generator of the cleaning module is activated, directing a plasma flow to the surface of the Peltier cooling trap. The plasma flow interacts with contaminants accumulated on the trap surface, breaking them down and releasing them from the surface.

[0260] To facilitate cleaning, the Peltier cooling element can be temporarily disabled, or even its polarity reversed, to raise the temperature of the trap surface. This temperature change promotes the plasma flow to desorb adsorbed contaminants from the surface, thereby improving the efficiency of contaminant removal.

[0261] As the plasma stream removes contaminants from the trap surface, a vacuum pump continuously extracts clean plasma and released contaminants from the vacuum chamber. This continuous evacuation process ensures effective removal of contaminants from the system, preventing their redeposition on the trap surface or interference with the SEM module.

[0262] Once the cleaning phase is complete, the plasma generator will cease operation, and the Peltier cooling element will return to normal operating conditions, cooling the trap surface to the optimal temperature for contaminant capture. The system is then ready to begin another imaging / processing phase, where the cleaned Peltier cooled trap can once again effectively capture contaminants.

[0263] By cycling between the imaging / processing phase and the cleaning phase, this metrology system maintains a clean, contamination-free environment within the vacuum chamber. This sequential approach, facilitated by the plasma cleaning module and Peltier cooling trap, ensures that the SEM module operates at optimal performance, delivering high-quality imaging results without being affected by contaminants generated during sample processing.

[0264] Figure 2 The illustrative example illustrates a metering system 1000 during the operational phase, based on various examples.

[0265] like Figure 2As seen inside, the metrology system 1000 includes a vacuum chamber 10, wherein the vacuum chamber housing includes a clean plasma inlet 11 for injecting a clean plasma stream from a plasma source of a plasma cleaner. Additionally, the vacuum chamber housing contains a cable feeder 4 for powering a Peltier element 1 disposed within the vacuum chamber 10. The Peltier element 1 has a collection surface 2 implemented by a thermally conductive and replaceable sacrificial material plate 2, facing a sample stage 3, which is vertically adjacent to the collection surface 2 at a distance of less than 15 cm and also facing the collection surface 2. The collection surface extends substantially parallel to the sample stage surface. A corresponding other surface of the Peltier element 1 (for heating and cooling, respectively) is thermally connected to the vacuum chamber housing via a thermally conductive paste suitable for vacuum. A clean plasma outlet 12 is provided on the opposite side of the vacuum chamber housing, positioned opposite the inlet 11, defining a clean plasma path between them for extracting plasma and releasing contaminants. Figure 2 In this system, the sample stage is located near the operating position 5 of the Peltier device 1 and between the clean plasma inlet and outlet. The sample stage is configured to hold the semiconductor wafer sample and position it within the operating position 5 of the vacuum chamber during the operation phase of the metrology system, which may include, for example, […]. Figure 1 The SEM and FIB systems are shown. The Peltier element operates in a cooled mode, maintaining the collection surface at a low temperature, for example below 0 degrees Celsius, where the collection surface of the Peltier element is cooled to bind contaminants within the vacuum chamber to the collection surface of the Peltier element. When the sample stage is in operating position 5, adjacent to and facing the Peltier collection surface, it extends at least partially along the sample stage and the sample surface.

[0266] Figure 3 illustrative examples of the cleaning phase based on various examples. Figure 2 The metering system 1000.

[0267] like Figure 3 As can be seen from the inside, the metering system 1000 includes and Figure 2The same features are present, but the sample stage 3 is moved by a platform moving mechanism (not shown) to a cleaning position 6, i.e., a platform parking position for cleaning, at a distance greater than, for example, 30 cm from the Peltier element 1 and the collection surface 2, and located outside the cleaning plasma path between the plasma inlet 11 and the outlet 12. The plasma flow 7 flows from the plasma inlet 11 along the defined cleaning plasma path to the collection surface 2. The Peltier device 1 operates in heating mode, heating the collection surface to a high temperature, for example, above 100 degrees Celsius, and releasing the bound contaminants. The released contaminants are propelled by the cleaning plasma in the plasma flow 7, flowing directly along the collection surface 2, while gaseous contaminants are discharged via the plasma outlet 12 on the opposite side of the vacuum chamber. This cleaning phase is performed without emptying the vacuum chamber, i.e., essentially maintaining a vacuum or internal pressure.

[0268] Figure 4 This schematically illustrates another metering system during the operation phase, according to various examples, wherein the clean plasma outlet is arranged on the bottom side of the vacuum chamber.

[0269] like Figure 4 As seen inside, the clean plasma outlet 12 is located on the bottom side of the vacuum chamber, and this outlet is connected to one or more vacuum pumps for evacuating the clean plasma and gaseous contaminants. In this example, the plasma outlet is arranged below the operating position of the sample stage and / or below the collection surface of the Peltier element.

[0270] Figure 5 illustrative examples of the cleaning phase based on various examples. Figure 4 The measurement system.

[0271] like Figure 5 As seen inside, the clean plasma path extends horizontally from the plasma inlet towards the collection surface 2 of the Peltier device 1, with the sample stage 3 located in the clean position, i.e., outside the clean plasma path. Gaseous contaminants in the clean plasma are discharged through the bottom plasma outlet.

[0272] Typically, released contaminants can be effectively discharged by guiding clean plasma through the collection surface 2 of the Peltier element 1 toward the plasma outlet 12. Figure 3 and Figure 5 As seen inside, during the cleaning phase, the sample stage 3 is moved to a resting position 6. This resting position 6 is located outside the main cleaning plasma path between the plasma inlet 11 and the plasma outlet 12. By positioning the sample stage 3 outside this primary cleaning plasma flow 7, the plasma concentration and velocity at the resting position 6 are maintained below certain critical values ​​that would otherwise have undesirable effects on the sample stage.

[0273] In various examples, parking position 6 can be a location where the concentration of the clean plasma is less than 50% or less than 10% of the concentration at the Peltier element collection surface. 12 ions / cm 3 This includes areas with plasma velocities less than 50% of the plasma velocity at the Peltier element collection surface or below 10 m / s. High-energy plasma exposure may damage components of the sample stage. Parking the sample stage at position 6 away from the main cleaning plasma path and direction avoids undesirable effects of the cleaning plasma on the sample stage while still effectively cleaning the Peltier cooling trap.

[0274] Various specific embodiments can utilize different orientations between the plasma inlet 11, the collection surface 2, the sample stage parking position 6, and the plasma outlet 12 to effectively clean the Peltier element 1 while protecting the sample stage 3. Position 6 is merely exemplary and can be selected with various plasma concentrations and velocities depending on the cleanliness and contamination limitations of a given metrology system.

[0275] In some specific embodiments, the sample stage 3 can also be further protected at the parking position 6 by using a plasma shield or plasma baffle. The plasma shield can be located between the main cleaning plasma flow 7 and the sample stage parking position 6. The plasma shield forms a shaded area to prevent the sample stage 3 from being directly exposed to the cleaning plasma.

[0276] Plasma shielding can take many forms, ranging from a simple rigid plate barrier between position 6 and the plasma inlet to a localized plasma containment system. By using shielding or baffles, the cleaning plasma cannot reach the sample stage 3 via a direct path (i.e., a straight line). This minimizes or eliminates any potential adverse contamination, material release, or degradation of sensitive sample stage components when the main optical path is exposed to concentrated direct plasma during the cleaning phase.

[0277] In addition, plasma suppressors based on magnetic, electrostatic, or fluid flow control methods can be installed around position 6. Compared to the main cavity, the effective concentration and velocity of the clean plasma around the shielded area can be reduced by locally canceling or diverting the propagation of the clean plasma. The combination of physical barrier shielding and active plasma suppression systems can maximize the protection of the sample stage in position 6 during Peltier element cleaning exposure.

[0278] Figure 6 The illustrations illustrate the steps of methods for removing contaminants in a metering system according to various examples.

[0279] The method begins with step S10.

[0280] The metrology system includes a sample stage inside a vacuum chamber and Peltier elements arranged at least partially inside the vacuum chamber.

[0281] In step S20, during the operation phase, the Peltier element collection surface inside the cavity and facing the sample stage is cooled to cryogenically bind contaminants present in the vacuum cavity environment to the collection surface. While the Peltier cooling trap is operating, contaminants are adsorbed, and the sample stage is in the operation position to allow for sample inspection or handling.

[0282] In step S30, which is an optional step, after the operation metrology stage is completed, the sample stage transfer mechanism moves the sample stage from the operation position to a defined cleaning position, which is located outside the subsequent plasma cleaning exposure area and is protected.

[0283] In step S40, a clean plasma flow is guided from the plasma inlet into the vacuum chamber, flowing along the clean plasma path and along the Peltier element collection surface to release accumulated contaminants. The clean plasma and the released contaminants are discharged through the plasma outlet on the opposite side of the vacuum chamber. During this plasma cleaning exposure, the sample stage remains in a protected clean position outside the flow path.

[0284] The method ends at step S50.

[0285] After the cleaning phase is completed, the sample stage mechanism returns the sample stage to the operating position so that the cleaned Peltier cooling trap can be used for the next metrology operation phase.

[0286] In various examples, spatial separation can be used to protect SEM pillars, particularly the spatial separation between the milling point and the SEM head.

[0287] Since both FIB and SEM focus on the same location on the sample, they both provide an unobstructed view of the debris generation site. This allows debris generated during milling to potentially be projected into the SEM direction. For example, an unobstructed view during milling can be avoided by introducing a dynamic physical shutter, such as... Figure 7 and Figure 8 As shown.

[0288] Figures 7 to 11 The techniques shown can also be included in any metering system, for example Figure 1 The metering system 1000.

[0289] from Figures 1 to 11 As can be seen, the metrology system 1000 includes at least a vacuum chamber, a sample stage located in the vacuum chamber and configured to hold the sample 16 to be processed, a scanning electron microscope (SEM) module 13 located in the vacuum chamber and configured to image the sample 16, and a focused ion beam (FIB) module 14 located in the vacuum chamber and configured to physically process the sample 16, thereby generating contaminants in the vacuum chamber.

[0290] Figure 7 The illustration shows the dynamic shutter blade 15 included in the pollution treatment module of the metering system 1000 according to various examples.

[0291] The metrology system 1000 includes a vacuum chamber (not shown), a sample stage (not shown) located in the vacuum chamber and configured to hold the sample 16 to be processed, a scanning electron microscope (SEM) module 13 located in the vacuum chamber and configured to image the sample 16, and a focused ion beam (FIB) module 14 located in the vacuum chamber and configured to process the sample 16, thereby generating contaminants in the vacuum chamber.

[0292] The contamination treatment module includes a dynamic shutter 15, which operates in sync with the SEM module 13 and the FIB module 14. The dynamic shutter 15 is configured as a rotatable blade arranged in front of the SEM head, having openings that can be positioned at a first position and a second position by rotating the blade along a rotation axis oriented along the axis of the SEM module 13.

[0293] By rotating the blade, an opening can be created to block and open the direct path between the SEM module 13 and the sample 16. When the sample 16 is processed or altered by the FIB module 14, the opening is arranged to block the direct path from the sample 16 to the SEM module 13, thereby preventing contaminants generated by the FIB module 14 from reaching the SEM module 13.

[0294] from Figure 7 It can be seen that the shutter opening rotates synchronously with the FIB-SEM operation. During the FIB operation, the opening blocks the direct optical path between the SEM module 13 and the sample 16. During the SEM operation, the shutter rotates to achieve imaging of the sample 16. The first position corresponds to the imaging position during the operation of the SEM module 13, while the second position corresponds to the processing position during the operation of the FIB module 14.

[0295] The dynamic shutter 15 includes an opening, which, in the imaging position, is aligned with the direct path between the SEM module 13 and the sample 16. In the processing position, the opening is offset from the direct path between the SEM module 13 and the sample 16, thereby blocking the direct path and preventing contaminants from reaching the SEM module 13.

[0296] The dynamic shutter 15 can rotate between a first position and a second position, and its rotation is synchronized with the operation phases of the SEM module 13 and the FIB module 14. Alternatively, the dynamic shutter 15 can oscillate between the first position and the second position, and its oscillation is synchronized with the operation of the SEM module 13 and the FIB module 14.

[0297] Other variations of the dynamic blades, such as blades that move in one direction (back and forth), can be implemented to cut off the direct contamination path between the SEM module 13 and the milling position on the sample 16. An example setup involves a synchronized rotatable shutter that cuts off the path between the sample 16 and the SEM module 13 during the FIB milling phase and reintroduces the optical path during the SEM imaging operation phase.

[0298] Figure 8 The static blade 17 of the pollutant barrier included in the pollution treatment module of the metering system 1000 according to various examples is illustrated.

[0299] like Figure 7 As shown, the static blade 17 can be used Figure 1 In the metrology system 1000, the contamination treatment module includes a static contaminant barrier 17, which is configured as static blades arranged in front of the SEM head. The static blades have openings that are positioned in front of the SEM module 13 to allow a direct path to be formed between the SEM module 13 and the sample 16. The static contaminant barrier 17 is located between the SEM module 13 and the FIB module 14, dividing the vacuum chamber into a first compartment accommodating the SEM module 13 and a second compartment accommodating the FIB module 14.

[0300] When sample 16 is processed or altered by FIB module 14, static contaminant barrier 17 limits the volume of the vacuum cavity affected by generated contaminants, thereby preventing contaminants from reaching and contaminating the SEM head. Static contaminant barrier 17 includes an aperture aligned with the direct path between SEM module 13 and the processing location on sample 16. This aperture is configured to allow an electron beam to pass from SEM module 13 to sample 16, and to allow secondary or backscattered electrons to pass from sample 16 to SEM module 13.

[0301] from Figure 8 As can be seen, the static blades are designed to prevent debris from appearing on the SEM module 13, while not restricting the direct optical path between the SEM module 13 and the milling position on the sample 16. Although it is impossible to avoid debris directly reaching the SEM column from the milling position, diffused debris from all other directions is physically shielded by the static blades.

[0302] The blades can be modified to handle various types of debris. For example, the static contaminant barrier 17 may include a cooling surface configured to bind contaminants to the barrier, preventing debris adhesion. Furthermore, the static contaminant barrier 17 may include multiple fins (not shown) configured to deflect contaminant airflow away from the SEM module 13, thereby preventing contaminants from reaching the SEM module 13.

[0303] The direct path between FIB module 14 and SEM module 13 is unrestricted. However, the cavity volume affected by diffused debris is restricted by the static blades of contaminant barrier 17, thus preventing contaminants from reaching SEM module 13.

[0304] In addition to the static blade configuration, the static contaminant barrier 17 can also take other forms, such as a partial shell or encapsulation surrounding the SEM module or sample processing area. Furthermore, the shell can be connected to the vacuum chamber housing wall to create a more isolated environment for the SEM module.

[0305] For example, a static contaminant barrier can be designed as a shell surrounding the SEM module, with openings to allow the electron beam to pass through and reach the sample. Furthermore, the shell can be attached to the wall of the vacuum chamber, effectively creating a separate compartment within the vacuum chamber that minimizes the interaction between contaminants generated by the SEM module and the sample processing module.

[0306] Another change might involve encapsulating the sample handling area by attaching a static contaminant barrier to the vacuum chamber walls, regardless of whether a FIB module is present. This configuration confines contaminants generated during sample handling to a specific area of ​​the vacuum chamber, thereby reducing their ability to diffuse and reach the SEM module.

[0307] Alternative forms of these static contaminant barriers include partial housings or encapsulations attached to the walls of the vacuum chamber, providing additional protection for the SEM module by physically isolating it from the contaminant-generating processes. Further minimizing the interaction between contaminants and the SEM module by creating separate compartments or confined spaces within the vacuum chamber enhances the overall effectiveness of the contaminant treatment module in maintaining a clean imaging environment.

[0308] Figure 9 The illustration illustrates the electrostatic shielding of the SEM head included within the pollution treatment module of a metering system 1000 according to various examples.

[0309] like Figure 9 As seen in the figure, the electrostatic shielding configuration included in the pollution treatment module can be deployed in the metering system 1000, for example... Figure 1 The metering system described in [the document].

[0310] The contamination treatment module includes a first electrostatic collection electrode 18 and a second electrostatic collection electrode 19 of opposite polarities, arranged around the SEM module 13, specifically around the SEM head and SEM end cap of the SEM column. The field generated by the opposite polarities of the electrostatic electrodes causes charged contamination particles of both polarities to deviate from or be drawn away from the SEM end cap towards the corresponding outlet 20 along the SEM head / column housing, where they can be extracted from the vacuum chamber by a vacuum pump.

[0311] The first and second electrostatic collection electrodes (18, 19) can be configured to generate an electric field or an electrostatic field to deflect and guide charged contaminants of both polarities away from the sensitive components of the SEM module.

[0312] To apply force to neutral charged debris particles, the contamination treatment module may also include an ion generator (not shown) disposed near the end cap of the SEM module 13. The ion generator is configured to charge neutral contaminant particles, making them susceptible to the effects of an electrostatic collection field. For example, the ion generator may be integrated below the SEM module or attached to its end cap.

[0313] Ion generators can take various forms, such as a laser source configured to emit laser radiation toward neutral contaminant particles, thereby ionizing the particles through photoionization. Alternatively, an ion generator may include an electron source configured to emit electrons toward neutral contaminant particles, or a plasma generator configured to generate plasma to charge neutral contaminant particles through collisions.

[0314] During the FIB milling process, atoms and ions are generated as contaminants. Ions can be deflected or pulled away from the SEM module 13 by electrostatic fields (18, 19). An electrostatic collection field is positioned near the primary flight path of the ions, essentially forming a trap to guide them to a vent or outlet for removal from the vacuum chamber. The guiding electric field can be turned off during the milling process to avoid interfering with FIB operation. For example, the guiding electric field can also be turned off during the imaging process. In various examples, it is only turned on during the cleaning or purging phase of the metrology system, where additional protective or cleaning airflow is used to remove contaminants, allowing for higher power operation during non-imaging phases.

[0315] Therefore, as Figure 9 As shown, the electrostatic shielding of the SEM column utilizes positive and negative electrodes (18, 19) to guide ion fragments generated during the FIB milling process away from the sensitive area of ​​the SEM module 13. The positioning and configuration of the electrodes (18, 19) maximize the deflection and removal of charged contaminants. Neutral contaminants can be handled by an ion generator (not shown) integrated near the SEM end cap, which charges the particles and makes them respond to the electrostatic field. During the SEM imaging phase, the electric field can be turned off so that the image quality is not affected.

[0316] In other words, ions can be deflected away from the SEM by an electrostatic field. The collection field is close to the main flight path of the ions, essentially forming a trap, and eventually leads to a vent or exhaust path, such as to the SEM column. In some examples, a primary electron beam with appropriate energy and defocus to maximize ionization directly below the column can be used to ionize neutral particles during sample handling or cleaning phases.

[0317] Figure 10The protective gas environment of the contaminant treatment module within the vacuum chamber of a metering system 1000 according to various examples is illustrated.

[0318] As shown in the previous figures, the metrology system 1000 includes a vacuum chamber (not shown), a sample stage (not shown) located in the vacuum chamber and configured to hold the sample 16 to be processed, a scanning electron microscope (SEM) module 13 located in the vacuum chamber and configured to image the sample 16, and a focused ion beam (FIB) module 14 located in the vacuum chamber and configured to process the sample 16, thereby generating contaminants in the vacuum chamber.

[0319] The contamination treatment module may include a protective gas environment 21 within a vacuum chamber. The protective gas environment 21 includes at least a portion of the FIB module 14, at least a portion of the SEM module 13, and at least a portion of the sample 16. The protective gas environment 21 is supplied with a protective gas flow through a protective gas inlet 22 and is configured to sweep contaminants toward a gas outlet 23, whereby the contaminants may be discharged from the protective gas environment or from the vacuum chamber.

[0320] The protective gas environment 21 may also include a housing within the vacuum chamber that surrounds at least a portion of the SEM module 13 and the sample stage. The housing has openings for the SEM module 13, the FIB module 14, the protective gas inlet 22, and the gas outlet 23. Furthermore, the housing helps to restrict the flow of the protective gas and establish a more localized clean environment around the SEM module and the sample stage, wherein the concentration of the protective gas inside the protective gas environment is more uniform and higher than outside. The protective gas environment may include the entire vacuum chamber or only a portion thereof.

[0321] The protective gas inlet 22 is located near the SEM module 13, while the gas outlet 23 is located near the FIB module 14. This arrangement creates a protective gas flow direction from the SEM module 13 to the FIB module 14, effectively sweeping contaminants from the SEM module to the outlet. The gas flow direction can be substantially parallel to the top surface of the sample stage, aligned with or perpendicular to the (tilted) direction of the SEM electron beam.

[0322] The protective gas environment 21 is designed to maintain a positive pressure of the protective gas relative to the surrounding vacuum chamber. This positive pressure prevents contaminants from entering the protective gas environment because the gas flow continuously exits through the orifice, thus forming a barrier to prevent contaminant entry.

[0323] During or after the FIB milling stage, neutral gases such as nitrogen are pumped into the protective gas environment 21 through gas inlet 22. These gases remove atoms and ions generated during the milling process and carry them out of the protective gas environment through gas outlet 23. The housing of the protective gas environment is configured to allow the SEM beam and FIB beam to pass through while minimizing contaminant escape.

[0324] To maintain the required pressure within the protective gas environment 21, appropriate design considerations are necessary, such as minimizing all openings in the protective gas environment. This helps to minimize the gas flow rate required to maintain positive pressure and reduces the impact on the vacuum level within the main chamber.

[0325] Therefore, as Figure 10 As shown, the protective gas environment 21 creates a locally clean environment within the vacuum chamber of the metering system 1000. By supplying a protective gas flow from the SEM module 13 to the FIB module 14 and sweeping contaminants toward the gas outlet 23, the SEM module is effectively protected from contamination generated during the FIB milling process. The housing design, with its positioned gas inlet and outlet and maintaining a positive pressure relative to the vacuum chamber, further enhances the effectiveness of the contamination treatment module in preventing contaminants from reaching the SEM module.

[0326] Figure 11 The schematic illustration shows the directional protective gas flow of the pollution treatment module within the metering system 1000 according to various examples.

[0327] As shown in the previous figures, the metrology system 1000 includes a vacuum chamber (not shown), a sample stage (not shown) located in the vacuum chamber and configured to hold the sample 16 to be processed, a scanning electron microscope (SEM) module 13 located in the vacuum chamber and configured to image the sample 16, and a focused ion beam (FIB) module 14 located in the vacuum chamber and configured to process the sample 16, thereby generating contaminants in the vacuum chamber.

[0328] The contamination treatment module may include a directional protective gas system configured to direct a protective gas flow (in other words, a purge gas) from the SEM module 13 toward the sample 16. This directional protective gas system includes a protective gas inlet integrated into the SEM module 13, which is configured to direct the protective gas flow toward the sample stage 16.

[0329] The protective gas inlet is directly connected to the SEM's direct path, and its design does not affect the SEM lens or electronic source settings. The purge gas is pumped to the sample 16 at a pressure higher than the sample environment, creating a localized high-pressure zone that prevents debris from entering the SEM module 13. It can also be shut off during the imaging phase of the metrology system.

[0330] SEM module 13 includes an end cap facing the sample stage, which may have one or more internal or external gas channels 24 for directing protective gas flow to a protective gas inlet integrated in the end cap. The end cap may include a central aperture configured to allow an electron beam to pass through the SEM module 13 and reach the sample 16, wherein the protective gas channels 24 are arranged around the central aperture.

[0331] The directional protective gas system may also include, for example, a gas outlet (not shown) located below the sample stage, configured to remove protective gas from the vacuum chamber. The protective gas flow flows from the SEM module 13 to the sample 16 to remove contaminants generated during the FIB milling process, preventing them from reaching and accumulating on the SEM module components.

[0332] The protective gas used in the directional protective gas system or protective gas environment is a neutral gas selected from the group consisting of nitrogen, argon, xenon, and other inert gases. The choice of specific gas depends on the expected mass of the fragment particles, aiming to maximize momentum transfer and optimize the removal of contaminants from the vicinity of SEM module 13.

[0333] The protective gas is injected at a pressure higher than that of the surrounding sample environment, forming an airflow and a protective barrier that carries contaminants away from the sensitive components of the SEM module 13.

[0334] Therefore, as Figure 11 As shown, the directional protective gas system provides a directional and targeted airflow within the metrology system 1000. By guiding the protective gas from the SEM module 13 toward the sample 16 and expelling it through the gas outlet, the system creates a localized high-pressure zone, protecting the SEM module from contaminants generated during sample processing. The protective gas inlet is integrated into the SEM module end cap, and the arrangement of the gas channels and central aperture ensures effective airflow guidance without interfering with the electron beam. The selection of a neutral gas based on the expected contaminant particle mass further enhances the effectiveness of the protective gas system in removing debris and maintaining a clean environment for SEM imaging processing.

[0335] From the above, we can draw some general conclusions: A contamination handling module, also known as a component of the metrology system, is designed to restrict or impede the free movement of contaminants within a vacuum chamber, particularly their movement and interference with imaging modules such as the SEM module. This can be achieved by implementing active modules or mechanisms, passive modules or mechanisms, or a combination of both, within the contamination handling module. The contamination handling module can prevent (in other words, hinder) contaminants in the vacuum chamber from reaching the SEM module by using active mechanisms (actively controlling or moving contaminants) and / or passive mechanisms (relying on physical barriers or geometric design to block contaminants). This ensures a clean and stable environment for the SEM imaging process.

[0336] For example, an active module may refer to a component or system that actively controls, redirects, or removes contaminants from the path of a SEM module. These modules typically include an external power source, control system, or triggering mechanism for effective operation. Examples of active modules may include one or more of the following: Electrostatic field, in other words, an electric field, where an electrostatic field can be used to actively deflect or pull charged particles (such as ions or electrons) away from the SEM module in the low-pressure gas environment of a vacuum chamber. An electric field is generated by applying a voltage to a set of electrodes or plates, which alters the trajectory of charged contaminants, causing them to move away from sensitive components. Plasma cleaning, where a plasma source can be used to actively remove contaminants from a vacuum chamber. The active material generated by the plasma interacts with the contaminants, breaking them down into volatile compounds that can then be easily extracted from the system. Protective gas flow, where an active gas flow system can be used to establish a positive pressure environment around the SEM module, preventing contaminants from reaching sensitive components. The gas flow is typically controlled by valves, mass flow controllers, or pressure regulators to maintain a stable and effective protective environment. Cooling trap, where cold surfaces can be used to condense and trap contaminants, effectively removing them from the vacuum environment. By placing a cold trap (e.g., a liquid nitrogen-cooled surface) in the path of the contaminant, the contaminant can be encouraged to adhere to the trap instead of reaching the SEM module.

[0337] On the other hand, passive mechanisms rely on physical barriers, geometries, or material properties to prevent contaminants from reaching the SEM module. These mechanisms do not require external power sources or active control systems, making them simpler and more reliable in some cases. Examples of passive mechanisms may include one or more of the following: Physical barriers may include fixed shields, baffles, or holes that can be used to block contaminants from directly entering the SEM module. These barriers can be designed to allow the electron beam to pass through while preventing most contaminants from reaching sensitive components. The geometry of the vacuum chamber can minimize the direct path of contaminants into the SEM module. By carefully positioning the sample handling module, SEM module, and other components, the system can be designed to naturally guide contaminants away from sensitive areas.

[0338] The contamination treatment module can include various solutions, including active modules and passive mechanisms, which can be combined together to work synergistically and enhance the overall effectiveness of the system in preventing contaminants from reaching the SEM module.

[0339] For example, the interaction between electrostatic fields and physical barriers can produce synergistic effects. Electrostatic fields can effectively deflect charged contaminants, such as ions or charged particles, but their effect on neutral contaminants may be limited. On the other hand, physical barriers can block both charged and neutral contaminants, but may not provide complete coverage or may interfere with the electron beam path. By combining electrostatic fields with placed physical barriers, the system can better control the contaminant path. Electrostatic fields can deflect charged contaminants away from the barrier, reducing contaminant accumulation on the barrier surface and extending the barrier's effectiveness. For example, such electrostatic or electrocollecting fields can be implemented using one or more barrier elements as electrodes to prevent residual contaminants from flowing to the SEM. The combination of protective and cleaning gas flows with passive physical barriers can also produce synergistic effects. Plasma cleaning is effective at removing surface contaminants, but its effectiveness is limited. Physical barriers and geometric design can help confine contaminants to specific areas of the vacuum cavity and define protective and / or cleaning plasma flow paths.

[0340] The following maintenance aspects can be combined with any of the described systems or methods.

[0341] Regular maintenance plans can be used to periodically replace components directly affected by debris buildup during system operation, such as cooling sinks, electric fields, and blades. Regular maintenance ensures that these critical components are replaced before they fail or are damaged by debris accumulation. The system includes appropriate mechanisms to report the status of these components and trigger maintenance operations when necessary.

[0342] This system performs predictive maintenance techniques to estimate the time required for the next cleaning or component replacement. This is achieved by monitoring and tracking various measurements related to system operation, such as the volume of the processed grinding sample, the amount of debris collected, and the total exposure time of the pump and electric field. By analyzing this data, the system can predict when maintenance will be needed and schedule it accordingly. The system also includes a reporting mechanism to alert operators to anticipated maintenance needs and request appropriate remedial action.

[0343] The metering system can be configured to monitor and / or track sensor measurements related to the system's operational status and / or the processes performed, including measurements of the volume of the ground sample being processed, the amount of debris collected, and the total exposure time of the pump and electric field. Furthermore, the metering system can be configured to process the monitoring data to estimate which components will require cleaning or replacement next, and / or to implement reporting mechanisms to alert operators to anticipated maintenance needs and required maintenance work.

[0344] In summary, the present invention provides a metrology system and method for treating contamination within a vacuum chamber. The metrology system includes a scanning electron microscope (SEM) module and a sample processing module, such as a focused ion beam (FIB) module, operating within a vacuum chamber. To prevent contaminants generated by the sample processing module from reaching and interfering with the SEM module, the system includes a contamination treatment module.

[0345] The contamination treatment module may include any one or any combination of components, including a dynamic shutter synchronized with the operation of the SEM and the sample processing module, a static contaminant barrier with apertures for the SEM bundle, a contaminant cooling trap with Peltier cooling elements, an electrostatic collection field for deflecting charged contaminants, and a protective gas environment with directional airflow.

[0346] These components work together to effectively manage contaminants, maintain a clean environment for the SEM module, and ensure high-quality imaging results. The dynamic shutter blocks the direct path between the SEM and the sample during processing, while the static barrier limits the volume affected by contaminants. The cooling trap traps contaminants, and the electrostatic field deflects charged particles away from sensitive components. A protective airflow sweeps contaminants out of the SEM module and directs them to the exhaust port.

[0347] By implementing these systems and methods, the metrology system effectively mitigates the effects of contaminants, extends the lifespan of the SEM module, and reduces the need for frequent maintenance. This improves the efficiency, reliability, and productivity of semiconductor manufacturing and other applications involving vacuum chamber metrology systems.

[0348] Although the invention has been shown and described with reference to certain preferred specific examples, equivalents and modifications will occur to those skilled in the art upon reading and understanding this specification. The invention includes all such equivalents and modifications and is limited only by the scope of the dependent claims.

Claims

1. A metering system, comprising: Vacuum cavity; The sample stage inside the vacuum chamber is configured to hold the sample to be processed. The scanning electron microscope (SEM) module inside the vacuum chamber is configured to image the sample. The sample processing module inside the vacuum chamber is configured to process the sample, thereby generating contaminants inside the vacuum chamber. as well as The contamination treatment module within the vacuum chamber is configured to prevent contaminants from reaching the SEM module.

2. The measurement system of claim 1, wherein the contamination treatment module includes a dynamic shutter configured to synchronize with the operation of the SEM module and the sample processing module, the dynamic shutter being configured to block the direct path between the SEM module and the sample during the operation of the sample processing module, and to achieve imaging of the sample during the operation of the SEM module.

3. The metering system of claim 2, wherein the dynamic shutter comprises a rotatable blade or an oscillating blade.

4. The metrology system of claim 2 or 3, wherein the dynamic shutter is movable between a first position and a second position, the first position corresponding to the imaging position during operation of the SEM module, and the second position corresponding to the processing position during operation of the sample processing module.

5. The metrology system of claim 4, wherein the dynamic shutter includes an opening, and wherein the opening is aligned with a direct path between the SEM module and the sample at the imaging location.

6. The metrology system of claim 5, wherein the opening is offset from the direct path between the SEM module and the sample at the processing location, thereby blocking the direct path and preventing contaminants from reaching the SEM module.

7. The metrology system of any one of claims 2 to 6, wherein the dynamic shutter is rotatable between the first position and the second position, wherein the rotation is synchronized with the operation phase of the SEM module and the sample processing module.

8. The metrology system of any one of claims 2 to 6, wherein the dynamic shutter is configured to oscillate between the first position and the second position, wherein the oscillation is synchronized with the operation of the SEM module and the sample processing module.

9. The metrology system as claimed in any of the preceding claims, wherein the contamination treatment module includes a static contaminant barrier configured to limit the volume of the vacuum chamber affected by the contaminant while maintaining a direct path between the SEM module and the treatment location on the sample.

10. The metrology system of claim 9, wherein the static contaminant barrier is located between the SEM module and the sample processing module, and the static contaminant barrier is configured to divide the vacuum chamber into a first compartment containing the SEM module and a second compartment containing the sample processing module.

11. The metrology system of claim 9 or 10, wherein the static contaminant barrier includes an aperture aligned with a direct path between the SEM module and the processing location on the sample, the aperture being configured to allow an electron beam to pass from the SEM module to the sample and to allow secondary electrons or backscattered electrons to pass from the sample to the SEM module.

12. The metering system of any one of claims 9 to 11, wherein the static contaminant barrier includes a cooling surface configured to bind contaminants to the barrier.

13. The metering system of any one of claims 9 to 12, wherein the static contaminant barrier comprises a plurality of fins configured to deflect contaminant gas flow away from the SEM module, thereby preventing contaminants from reaching the SEM module.

14. The metering system as claimed in any of the preceding claims, wherein the contamination treatment module includes a contaminant cooling trap configured to capture the contaminant.

15. The metering system of claim 14, wherein the contaminant trap includes a Peltier cooling element configured to maintain the surface temperature of the contaminant trap below the condensation temperature of the contaminant.

16. The metering system of claim 15, wherein the Peltier cooling element is operatively connected to a heat sink located outside the vacuum chamber, the heat sink being configured to dissipate the heat generated by the Peltier cooling element.

17. The metrology system of any one of claims 14 to 16, wherein the contaminant trap is located between the sample processing module and the SEM module, configured to capture contaminants generated by the sample processing module before they reach the SEM module.

18. The metering system of any one of claims 14 to 17, further comprising a cleaning module configured to remove accumulated contaminants from the surface of the cooled contaminant trap during a cleaning phase.

19. The metering system of claim 18, wherein the cleaning module includes a plasma generator and a vacuum pump, the plasma generator being configured to direct a plasma stream to the surface of the cooling contaminant trap, the plasma stream being configured to dissolve accumulated contaminants, and the vacuum pump being configured to evacuate the plasma stream containing the contaminants from the vacuum chamber.

20. The metering system as claimed in any of the preceding claims, wherein the contamination treatment module includes a first electrostatic collection field configured to deflect charged contaminant particles away from the SEM module.

21. The metering system of claim 20, wherein the contamination treatment module includes a second electrostatic collection field with a polarity opposite to that of the first electrostatic collection field.

22. The metering system of claim 20 or 21, wherein the first electrostatic collection field and / or the second electrostatic collection field are gradient fields with the highest field strength arranged near the SEM module.

23. The metering system of any one of claims 20 to 22 further includes an ion generator disposed at the end cap of the SEM module, the ion generator being configured to charge neutral contaminant particles.

24. The metering system of claim 23, wherein the ion generator includes a laser source configured to emit laser radiation toward the neutral contaminant particle, thereby ionizing the neutral contaminant particle by photoionization.

25. The metering system of claim 23, wherein the ion generator includes an electron source configured to emit electrons toward the neutral contaminant particle.

26. The metering system of claim 23, wherein the ion generator includes a plasma generator configured to generate plasma to charge the neutral contaminant particles by collision.

27. The metering system as claimed in any of the preceding claims, wherein the contamination treatment module includes a protective gas environment within the vacuum chamber, the protective gas environment including a protective gas inlet configured to supply a protective gas flow to purge the contaminant, and a gas outlet configured to discharge the contaminant carrying the protective gas.

28. The metrology system of claim 27, wherein the protective gas environment further includes a housing within the vacuum chamber, the housing at least surrounding a portion of the SEM module and the sample stage, the housing having openings for the SEM module, the sample processing module, the protective gas inlet, and the gas outlet.

29. The metering system of claim 27 or 28, wherein the protective gas inlet is positioned close to the SEM module and the gas outlet is positioned close to the sample processing module, thereby forming a protective gas flow direction from the SEM module toward the sample processing module to remove the contaminant.

30. The metrology system of any one of claims 27 to 29, wherein the gas flow direction is substantially parallel to the top surface of the sample stage.

31. The metering system of claim 27, wherein the protective gas environment includes a head of the SEM module having an opening for an electron beam, and a protective gas flow configured to maintain a positive pressure of the protective gas within the protective gas environment relative to the vacuum chamber, thereby preventing the contaminant from entering the protective gas environment.

32. The metrology system as claimed in any of the preceding claims, wherein the contamination treatment module includes a directional protective gas system configured to guide protective gas from the head of the SEM module toward the sample stage.

33. The metrology system of claim 32, wherein the directional protective gas system includes a protective gas inlet integrated into the SEM module, the protective gas inlet being configured to direct the protective gas flow toward the sample stage.

34. The metrology system of claim 32 or 33, wherein the directional protective gas system further includes a gas outlet located below the sample stage and configured to remove the protective gas from the vacuum chamber.

35. The metrology system of any one of claims 32 to 34, wherein the SEM module includes an end cap facing the sample stage, the end cap having a plurality of internal gas channels configured to direct a protective gas flow toward a protective gas inlet integrated in the end cap.

36. The metrology system of claim 35, wherein the end cap further includes a central hole configured to allow an electron beam to pass through the SEM module to the sample, wherein the protective gas channel is arranged around the central hole.

37. The metering system according to any one of claims 27 to 36, wherein the protective gas is an inert gas selected from the group consisting of rare gases and nitrogen.

38. The metrology system of any of the preceding claims, wherein the sample processing module is configured to grind the sample, etch the sample, or deposit material onto the sample.

39. The metrology system as claimed in any of the preceding claims, wherein the sample processing module is one of a focused ion beam (FIB) module, a gas injection system (GIS), or a laser processing module.

40. The metering system of claim 19, further comprising: The platform moving mechanism is configured to move the sample stage from the operating position during the operation phase to the cleaning position during the cleaning phase. In this clean position, the sample stage is located outside the path of the plasma flow toward the surface of the cooled contaminant trap.

Images