Precision vacuum window viewport and pellicle for fast metrology recovery

Abstract

Systems, apparatuses, and methods for optical metrology in an extreme ultraviolet (EUV) radiation system are provided. An example system can include a metrology system and a window. An example metrology system can be configured to be disposed in a first environment and perform one or more measurements of an area in a second environment along an optical axis of the metrology system. An example window can be configured to be disposed to intersect the optical axis and isolate the metrology system from the second environment. An example window can also be configured to limit a lateral displacement relative to the optical axis at a primary focus of a radiation collector to be less than about ±50 microns from a nominal lateral displacement relative to the optical axis.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Application No. 63 / 046,984, filed July 1, 2020, entitled “PRECISE VACUUM WINDOW VIEWPORTS AND PELLICLES FOR RAPID METROLOGY RECOVERY”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to measurement systems and windows for extreme ultraviolet (EUV) radiation systems. Background Technology

[0004] A lithography apparatus is a machine that applies a desired pattern onto a substrate (typically onto a target portion of the substrate). Lithography apparatuses can be used, for example, in the fabrication of integrated circuits (ICs). In this case, a patterning apparatus (or mask or photomask) can be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can then be transferred onto a target portion (e.g., a portion comprising one or more dies) on a substrate (e.g., a silicon wafer). The transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (e.g., resist) disposed on the substrate. Typically, a single substrate will contain a network of adjacent target portions patterned sequentially. Conventional lithography apparatuses include: a so-called stepper, in which each target portion is irradiated by exposing the entire pattern onto the target portion at once; and a so-called scanner, in which each target portion is irradiated by scanning the pattern with a radiation beam in a given direction (scanning direction) while simultaneously scanning the target portion parallel or antiparallel (i.e., opposite to) that scanning direction. A pattern can also be transferred from a patterning apparatus to a substrate by imprinting the pattern onto the substrate.

[0005] Extreme ultraviolet (EUV) light (e.g., electromagnetic radiation with wavelengths of about 50 nanometers (nm) or smaller (sometimes also referred to as soft X-rays, and including light with wavelengths of about 13 nm) can be used in or in conjunction with photolithography equipment to create extremely small features in or on a substrate (e.g., a silicon wafer). Methods for generating EUV light include, but are not limited to, converting materials comprising elements having emission lines in the EUV range (e.g., xenon (Xe), lithium (Li), or tin (Sn)) into a plasma state. For example, in one such method known as laser-generated plasma (LPP), plasma can be generated by passing an amplified beam, which may be referred to as a driving laser, through a radiating target material, which in the context of an LPP source is interchangeably referred to as fuel (e.g., in the form of droplets, plates, strips, streams, or clusters of material). For this process, the plasma is typically generated in a sealed container (e.g., a vacuum chamber) and monitored using various types of metrology equipment. Summary of the Invention

[0006] This disclosure describes various aspects of systems, apparatus, and methods for optical measurements, as well as various other aspects of extreme ultraviolet (EUV) radiation systems.

[0007] In some aspects, this disclosure describes a system for optical measurement in a radiation system (such as an EUV radiation system). The system may include a measurement system configured to be positioned in a first environment. The measurement system may also be configured to perform one or more measurements on a region in a second environment along the optical axis of the measurement system. The second environment may be different from the first environment. A window may be configured to intersect the optical axis. The window may also be configured to isolate the measurement system from the second environment. The window may also be configured to limit lateral displacement relative to the optical axis at the principal focus of the radiation collector to less than about ±50 micrometers from the nominal lateral displacement relative to the optical axis. In some aspects, the principal focus may be located at a distance of about 1 meter from the window surface.

[0008] In some aspects, the window can be configured to limit lateral displacement to less than about ±33 micrometers. In some aspects, the window can be configured to limit angular deviation along the optical axis to less than about ±0.5 arcminutes from the nominal angular deviation along the optical axis. In some aspects, the window can be configured to limit angular deviation to less than about ±0.1 arcminutes. In some aspects, the window can be configured to limit longitudinal displacement along the optical axis to less than about ±330 micrometers from the nominal longitudinal displacement relative to the principal focus. In some aspects, the window can be configured to limit longitudinal displacement to less than about ±200 micrometers.

[0009] In some aspects, the window may include a first component (e.g., a viewport) configured to intersect the optical axis. In some aspects, the window may also include a second component (e.g., a diaphragm) configured to intersect the optical axis and be opposite the first component. In some aspects, the window may include a wedge angle less than about ±0.1 arcminutes from the nominal wedge angle. In some aspects, the nominal wedge angle may be about zero degrees. In other aspects, the nominal wedge angle may be greater than about zero degrees.

[0010] In some respects, the measurement system can be modular. In some respects, the window can be configured to limit displacement to less than approximately ±50 micrometers when the measurement system is installed in the system. In some respects, the window can be configured to limit displacement to less than approximately ±50 micrometers without calibration.

[0011] In some aspects, this disclosure describes an apparatus for optical measurement in a radiation system, such as an EUV radiation system. The apparatus may include a first component (e.g., a viewport) configured to intersect an optical axis. The apparatus may also include a second component (e.g., a diaphragm) configured to intersect the optical axis and be opposite the first component. The apparatus may be configured to transmit radiation along an optical axis passing through both the first and second components. The apparatus may also be configured to limit lateral displacement relative to the optical axis at the principal focus of a radiation collector to less than about ±50 micrometers from the nominal lateral displacement relative to the optical axis.

[0012] In some aspects, the main focal point may be located at a distance of approximately 1 meter from the device surface. In some aspects, the first component may include a viewport. In some aspects, the second component may include a diaphragm. In some aspects, the device may include a wedge angle that differs from the nominal wedge angle by less than approximately ±0.1 arcminutes. In some aspects, the device may be or include a window as described herein.

[0013] In some aspects, this disclosure describes a method for optical measurement in a radiation system, such as an EUV radiation system. The method may include: setting up a measurement system in a first environment. The measurement system performs one or more measurements on a region in a second environment, different from the first environment, along the optical axis of the measurement system. The method may further include: isolating the measurement system from the second environment using a window configured to intersect the optical axis. The method may further include: based on the window configuration, limiting the lateral displacement relative to the optical axis at the principal focus of the radiation collector to a difference of less than about ±50 micrometers from the nominal lateral displacement relative to the optical axis.

[0014] Other features and advantages, as well as the structure and operation of various aspects, are described in detail below with reference to the accompanying drawings. It should be noted that this disclosure is not limited to the specific aspects described herein. These aspects are presented herein for illustrative purposes only. Additional aspects will become apparent to those skilled in the art based on the teachings contained herein. Attached Figure Description

[0015] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present disclosure and, together with the description, further serve to explain the principles of aspects of the present disclosure and to enable those skilled in the art to make and use aspects of the present disclosure.

[0016] Figure 1A This is a schematic diagram of an example reflective lithography apparatus based on some aspects of this disclosure.

[0017] Figure 1B This is a schematic diagram of an example transmission lithography apparatus based on some aspects of this disclosure.

[0018] Figure 2 Based on some aspects of this disclosure Figure 1A A more detailed schematic diagram of the reflective lithography apparatus shown.

[0019] Figure 3 This is a schematic diagram of an example photolithography unit based on some aspects of this disclosure.

[0020] Figure 4 This is a schematic diagram of an example radiation source for an exemplary reflective lithography apparatus according to some aspects of this disclosure.

[0021] Figure 5 This is a schematic diagram of a portion of an example EUV radiation system according to some aspects of this disclosure.

[0022] Figure 6A , Figure 6B , Figure 6C and Figure 6D This is a schematic diagram of a portion of an example EUV radiation system according to some aspects of this disclosure.

[0023] Figure 7A , Figure 7B and Figure 7C This is a schematic diagram of a quick-change window assembly based on some aspects of this disclosure.

[0024] Figure 8 These are example methods based on some aspects and several parts of this disclosure.

[0025] The features and advantages of this disclosure will become more apparent from the following detailed description set forth in conjunction with the accompanying drawings, in which similar reference numerals consistently identify corresponding elements. In the drawings, unless otherwise stated, similar reference numerals generally denote identical, functionally similar, and / or structurally similar elements. Additionally, generally, the leftmost(s) of the reference numerals identifies the drawing in which the reference numeral first appears. Unless otherwise stated, the drawings provided throughout this disclosure should not be construed as being drawn to scale. Detailed Implementation

[0026] This specification discloses one or more embodiments incorporating the features of this disclosure. The disclosed embodiments(s) are merely illustrative of this disclosure. The scope of this disclosure is not limited to the disclosed embodiments(s). The breadth and scope of this disclosure are defined by the appended claims and their equivalents.

[0027] The described embodiments and references to "an embodiment," "embodiment," "exemplary embodiment," etc., in the specification indicate that the described embodiments may include a particular feature, structure, or characteristic, but each embodiment may not necessarily include that particular feature, structure, or characteristic. Furthermore, these phrases do not necessarily refer to the same embodiment. Additionally, when a particular feature, structure, or characteristic is described in connection with embodiments, it should be understood that, whether explicitly described or not, incorporating other embodiments to affect that feature, structure, or characteristic is within the knowledge of those skilled in the art.

[0028] For ease of description, spatially relative terms such as “below,” “under,” “down,” “above,” “over,” and “up” may be used herein to describe the relationship between one element or feature shown in the figures and another element(s) or feature(s). In addition to the orientations depicted in the figures, spatially relative terms are intended to cover different orientations of the device in use or operation. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein may be interpreted accordingly.

[0029] As used herein, the term “about” indicates the value of a given quantity that can vary based on a particular technique. Based on a particular technique, the term “about” can mean the value of a given quantity that varies within, for example, 10-30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

[0030] Overview

[0031] In one example, the window used in an EUV radiation system comprises a vacuum window (also known as a viewport) assembled with a second window (also known as a liner). Both the vacuum window and the liner are made of non-optical quality glass (e.g., soda glass). The vacuum window provides a vacuum seal for the EUV source container and allows measurements inside the container to be seen. The liner is located inside the vacuum container and provides a barrier to prevent tin debris from entering the vacuum window. The liner becomes contaminated with tin over time and must be replaced periodically. When replacing the liner, the entire viewport-liner assembly is replaced.

[0032] However, because the viewport and diaphragm are optical windows, they can introduce optical axis misalignment (offset and angular pointing error) and transmit aberrations to the wavefront. As a result, the viewport and diaphragm can lead to misalignment of the measurement optical axis. This misalignment may require realignment of the measurement when the viewport and diaphragm are replaced. Depending on the measurement module and the risk of B-time (e.g., recovery time) during realignment, this realignment process can add an additional recovery time (MTTR) on the order of approximately 1 to 10 hours. Furthermore, existing viewports and diaphragms may not have sufficiently well-controlled manufacturing tolerances to avoid interfering with the measurement optical axis. Additionally, since current vacuum window viewports may not be of optical quality, many specifications critical to measurement performance may be unknown (e.g., refractive index relative to wavelength, transmission wavefront error, wedge angle, etc.).

[0033] Conversely, some embodiments of this disclosure may provide windows with improved structure and tolerance to substantially reduce the impact of the window on the alignment of the measurement system coupled to the window.

[0034] In some aspects, this disclosure provides windows that utilize improved material structures (e.g., optical glass) for the viewport and coating to replace sodium glass in order to reduce transmission wavefront aberrations caused by (a) inhomogeneities in refractive index and (b) the presence of uncontrolled bubbles and streaks. For example, the material for the viewport and coating can be optical glass, such as borosilicate crown glass, with a transmission range of about 350 nm to about 2.5 μm and a refractive index of about 1.51680 at 587.5618 nm (e.g., yellow helium line). In some aspects, the viewport can be coated with an anti-reflective (AR) coating.

[0035] In some aspects, this disclosure also provides a window that improves the tolerances for: (i) the wedge angle of the viewport and diaphragm to reduce pointing errors; (ii) the thickness of the viewport and diaphragm to reduce centrifugal and focusing errors; (iii) the refractive index of the viewport and diaphragm to reduce focusing errors; (iv) the transmitted wavefront power of the viewport and diaphragm to reduce focusing errors; and (v) if necessary, using inter-element compensation (e.g., balancing negative and positive errors) to further reduce the total alignment error. In some aspects, this disclosure improves the alignment tolerances of the example windows disclosed herein compared to the conventional windows shown in Table 1 below.

[0036] Table 1: Alignment tolerance of the example window disclosed in this article compared to a traditional window.

[0037]

[0038] 1 Fine Droplet Steering Camera (FDSC).

[0039] In some respects, the improvements presented herein can reduce measurement alignment errors from approximately 600 micrometers of lateral and 2 millimeters of axial focusing error to less than approximately 30 micrometers of lateral and less than approximately 200 micrometers of axial focusing error. Due to this reduction in measurement alignment error, the measurement system will not require realignment after window replacement (e.g., viewport and diaphragm replacement).

[0040] In some respects, this disclosure improves the availability of EUV radiation systems by reducing the “green-to-green” time (also known as A-time) for viewport changes. Additionally, by eliminating measurement recovery actions, this disclosure eliminates the risk of something malfunctioning and taking longer than planned to recover (also known as B-time), which also improves availability.

[0041] In some aspects, this disclosure provides a technique for selecting the viewport to eliminate surface film errors, and vice versa. This technique provides more lenient manufacturing tolerances in exchange for more complex mating and building processes.

[0042] The window disclosed herein offers numerous advantages. For example, this disclosure provides manufacturing tolerances for precise control of the viewport and the liner, including: smaller wedge tolerances; tighter angular mounting tolerances; lower transmitted wavefront power tolerances; less stress on the vacuum window due to the use of an optically high-quality vacuum interface; optically high-quality glass instead of borosilicate glass used in existing viewports; and reduced recovery time for vacuum window replacement. In another example, the optical and mechanical tolerances of the window, viewport, and liner disclosed herein are significantly improved, which in some respects eliminates the need for a measurement recovery step after viewport and liner replacement.

[0043] In some respects, the optical and mechanical tolerances of the windows, viewports, and coatings disclosed herein also simplify the EUV source manufacturing process by eliminating setup and alignment steps. For example, a radiation source may have nine measurement systems, all of which need to be pointed to specific locations within the container. In some respects, the radiation source requires technicians to set up complex targets inside the container and align the measurement systems to these targets once mounted on the container. This is a time-consuming process that may not be completed correctly due to technician errors. In contrast, in other respects, the alignment tolerances of all relevant hardware (e.g., measurement systems, windows, container frame) can be small enough that these setup steps are no longer necessary. Therefore, once all relevant hardware has been assembled, it should be sufficiently well aligned so that no alignment action is required. The high-precision windows disclosed herein are crucial for achieving this.

[0044] As mentioned above, pointing error can have a critical impact on the overall alignment error budget of the measurement system, and consequently on the performance of the EUV radiation source. In an illustrative example, the optical distance from the viewport to the measurement position (the principal focus PF of the radiation collector) is approximately 1 meter. A wedge in the viewport introduces a pointing error proportional to the refractive index, as shown in the equation D = L * A * (n-1), where D = the distance offset at the principal focus PF, L = the distance from the principal focus PF, A = the wedge angle, and n = the refractive index. Existing wedge tolerances are ±3 arcminutes, or approximately ±870 microradians (urad). With a refractive index n of approximately 1.5 and a distance D from the principal focus PF of approximately 1 meter, the tolerance at the principal PF can be approximately 435 micrometers (e.g., 0.5 * 870) from the viewport alone. When the coating is also considered, the tolerance can be between approximately 600 and 870 micrometers.

[0045] Continuing the example above, the Droplet Detection Module (DDM) has a field of view (FOV) of approximately 540 micrometers. If the Droplet Illumination Module (DIM) viewport and liner are replaced, and an alignment error between approximately 600 and 870 micrometers is achieved, the DIM and DDM will need to be realigned, which could take up to 20 hours. For the window disclosed herein, the wedge tolerance for both the viewport and liner is approximately ±5 arcseconds, resulting in a deviation of less than approximately 30 micrometers at the principal focus (PF), entirely within the DDM's field of view.

[0046] In some respects, as a result of the techniques described herein, the viewport and coating disclosed herein can reduce uncertainties in the optical modeling of the measurement system. Furthermore, because the viewport and coating disclosed herein are of optical quality, many specifications critical to measurement performance can be known, such as refractive index relative to wavelength, transmission wavefront error, wedge angle, and other suitable characteristics. Additionally, the use of the tolerance viewport assembly allows for: (i) pre-alignment of the measurement module on the optical bench test stage; and (ii) direct replacement of the measurement module (e.g., in case of failure) without the need for realignment on the container, saving time (e.g., up to 10 hours per replacement).

[0047] However, it is beneficial to present example environments in which aspects of this disclosure can be implemented before describing these aspects in more detail.

[0048] Example lithography system

[0049] Figure 1A and Figure 1B These are schematic diagrams of lithography equipment 100 and lithography equipment 100', respectively, which can realize various aspects of this disclosure. For example... Figure 1A and Figure 1B As shown, lithography apparatuses 100 and 100' are shown from a perspective (e.g., a side view) orthogonal to the XZ plane (e.g., the X-axis points to the right and the Z-axis points upward), while patterning apparatus MA and substrate W are presented from an additional perspective (e.g., a top view) orthogonal to the XY plane (e.g., the X-axis points to the right and the Y-axis points upward).

[0050] Lithography apparatus 100 and 100' each include: an irradiation system (irradiator) IL configured to modulate a radiation beam B (e.g., a deep ultraviolet (DUV) radiation beam or an extreme ultraviolet (EUV) radiation beam); a support structure (e.g., a mask stage) MT configured to support a patterning apparatus (e.g., a mask, a stencil, or a dynamic patterning apparatus) MA and connected to a first positioner PM configured to precisely position the patterning apparatus MA; and a substrate holder (e.g., a wafer stage) WT, such as a substrate stage, configured to hold a substrate W (e.g., a wafer coated with resist) and connected to a second positioner PW configured to precisely position the substrate W. Lithography apparatuses 100 and 100' also have a projection system PS configured to project a pattern imparted by the radiation beam B by the patterning apparatus MA onto a target portion C (e.g., a portion including one or more dies) of the substrate W. In the lithography apparatus 100, the pattern forming apparatus MA and the projection system PS are reflective. In the lithography apparatus 100', the pattern forming apparatus MA and the projection system PS are transmissive.

[0051] The irradiation system IL may include various types of optical components, such as refractive, reflective, anti-refractive, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for guiding, shaping or controlling the radiation beam B.

[0052] The support structure MT holds the patterning apparatus MA in a manner that depends on the orientation of the patterning apparatus MA relative to the reference frame, the design of at least one of the lithography apparatuses 100 and 100', and other conditions such as whether the patterning apparatus MA is held in a vacuum environment. The support structure MT can use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning apparatus MA. The support structure MT can be, for example, a frame or a stage, which can be fixed or movable as needed. By using sensors, the support structure MT can ensure that the patterning apparatus MA is in a desired position, for example, relative to the projection system PS.

[0053] The term "patterning apparatus" MA should be interpreted broadly as any apparatus that can be used to pattern the cross-section of a radiation beam B in order to create a pattern in a target portion C of a substrate W. The pattern applied to the radiation beam B can correspond to a specific functional layer in a device that is created in the target portion C to form an integrated circuit.

[0054] The pattern forming apparatus MA can be transmissive (e.g., in...) Figure 1B In a lithography device 100') or a reflective type (such as in Figure 1A (In the lithography apparatus 100). Examples of pattern forming apparatus MA include photomasks, masks, programmable mirror arrays, or programmable LCD panels. Masks include mask types such as binary, alternating phase-shift, or attenuation phase-shift masks, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted to reflect incoming radiation beams in different directions. The tilted mirrors impart a pattern in the radiation beam B, which is reflected by the matrix of small mirrors.

[0055] The term "projection system" PS can encompass any type of projection system, including refractive, reflective, antirefractive, magnetic, electromagnetic, and electrostatic optical systems, or any combination thereof, suitable for the exposure radiation used, or suitable for other factors such as the use of an immersion liquid on the substrate W or the use of a vacuum. A vacuum environment can be used for EUV or electron beam radiation because other gases may absorb excessive radiation or electrons. Therefore, a vacuum environment can be provided throughout the beam path by means of vacuum walls and vacuum pumps.

[0056] The lithography apparatus 100 and / or lithography apparatus 100' can be of the type having two (dual-stage) or more substrate stages WT (and / or two or more mask stages). In such a "multi-stage" machine, additional substrate stages WT can be used in parallel, or preparation steps can be performed on one or more stages while one or more other substrate stages WT are used for exposure. In some cases, the additional stages may not be substrate stages WT.

[0057] Photolithography apparatuses can also be of the type in which at least a portion of the substrate can be covered by a liquid (e.g., water) with a relatively high refractive index to fill the space between the projection system and the substrate. Immersion liquids can also be applied to other spaces within the photolithography apparatus, such as the space between the mask and the projection system. Immersion techniques provide a means of increasing the numerical aperture of the projection system. As used herein, the term "immersion" does not imply that structures such as the substrate must be submerged in the liquid, but simply that the liquid is located between the projection system and the substrate during exposure.

[0058] refer to Figure 1A and Figure 1B The irradiation system IL receives the radiation beam from the radiation source SO. For example, when the radiation source SO is an excimer laser, the radiation source SO and the lithography apparatus 100 or 100' can be separate physical entities. In this case, the radiation source SO is not considered a component forming the lithography apparatus 100 or 100', and the radiation beam B is delivered by means of a beam delivery system BD including, for example, suitable directional mirrors and / or beam expanders (e.g., in...). Figure 1B (As shown in the diagram) the radiation is transferred from the radiation source SO to the irradiation system IL. In other cases, for example, when the radiation source SO is a mercury lamp, the radiation source SO may be a component of the lithography apparatus 100 or 100'. If desired, the radiation source SO and the irradiator IL, together with the beam delivery system BD, may be referred to as the radiation system.

[0059] The irradiation system IL may include an adjuster AD for adjusting the angular intensity distribution of the radiation beam (e.g., in...). Figure 1B (As shown in the diagram). Typically, at least the outer and / or inner radial ranges of the intensity distribution in the pupil plane of the irradiator can be adjusted (typically referred to as "σ-outer" and "σ-inner," respectively). Additionally, the irradiation system IL may include various other components (e.g., in...). Figure 1B (In the middle), such as integrator IN and radiation collector CO (e.g., a beam gatherer or collector optics). The illumination system IL can be used to adjust the radiation beam B to have a desired uniformity and intensity distribution in the cross-section of the radiation beam B.

[0060] refer to Figure 1AA radiation beam B is incident on a patterning apparatus (e.g., a mask) MA held on a support structure (e.g., a mask stage) MT and patterned by the patterning apparatus MA. In the lithography apparatus 100, the radiation beam B is reflected from the patterning apparatus MA. After being reflected from the patterning apparatus MA, the radiation beam B passes through a projection system PS, which focuses the radiation beam B onto a target portion C of the substrate W. The substrate stage WT can be precisely moved (e.g., to position different target portions C in the path of the radiation beam B) by means of a second positioner PW and a position sensor IF2 (e.g., an interferometric device, a linear encoder, or a capacitive sensor). Similarly, a first positioner PM and another position sensor IF1 (e.g., an interferometric device, a linear encoder, or a capacitive sensor) can be used to precisely position the patterning apparatus MA relative to the path of the radiation beam B. The patterning apparatus MA and the substrate W can be aligned using mask alignment marks M1 and M2 and substrate alignment marks P1 and P2.

[0061] refer to Figure 1B A radiation beam B is incident on a pattern forming apparatus MA held on a support structure MT and patterned by the pattern forming apparatus MA. After passing through the pattern forming apparatus MA, the radiation beam B passes through a projection system PS, which focuses the beam onto the target portion C of the substrate W. The projection system has a pupil PPU conjugate to the illumination system pupil IPU. The radiated portion is emitted from the intensity distribution at the illumination system pupil IPU and passes through the mask pattern unaffected by diffraction at the mask pattern, thus generating an image of the intensity distribution at the illumination system pupil IPU.

[0062] The projection system PS projects an image MP' of a mask pattern MP onto a resist layer coated on a substrate W, wherein the image MP' is formed by a diffracted beam generated from radiation from the marked pattern MP by an intensity distribution. For example, the mask pattern MP may comprise an array of lines and spacings. The diffraction of radiation at the array differs from zero-order diffraction, generating a diffracted beam with a directional change in a direction perpendicular to the lines. The undiffracted beam (i.e., the so-called zero-order diffracted beam) passes through the pattern without any change in its propagation direction. The zero-order diffracted beam passes through an upper lens or upper lens group upstream of the pupil conjugate PPU in the projection system PS to reach the pupil conjugate PPU. The portion of the intensity distribution in the plane of the pupil conjugate PPU and associated with the zero-order diffracted beam is an image of the intensity distribution in the illumination system pupil IPU of the illumination system IL. An aperture device PD is, for example, disposed or substantially disposed in the plane comprising the pupil conjugate PPU of the projection system PS.

[0063] The projection system PS is arranged to capture not only the zeroth-order diffraction beam but also first-order or higher-order diffraction beams (not shown) through a lens or lens group L. In some aspects, dipole illumination for imaging a line pattern extending in a direction perpendicular to the line can be used to utilize the resolution enhancement effect of dipole illumination. For example, a first-order diffraction beam interferes with the corresponding zeroth-order diffraction beam at the level of the substrate W to create an image of the mask pattern MP at the highest possible resolution and process window (i.e., the available depth of focus combined with tolerable exposure dose deviations). In some aspects, astigmatism can be reduced by providing a radiating pole (not shown) in the phase confinement of the illumination system pupil IPU. Furthermore, in some aspects, astigmatism can be reduced by blocking the zeroth-order beam in the projection system pupil conjugate PPU associated with the radiating pole in the phase confinement. This is described in more detail in U.S. Patent No. 7,511,799, entitled “Lithographic projection apparatus and a device manufacturing method,” published on March 31, 2009, the entire contents of which are incorporated herein by reference.

[0064] With the aid of a second positioner PW and a position sensor IF (e.g., an interferometer, a linear encoder, or a capacitive sensor), the substrate stage WT can be moved precisely (e.g., to position different target portions C within the path of the radiation beam B). Similarly, the first positioner PM and another position sensor ( Figure 1B (Not shown) can be used to precisely position the pattern forming apparatus MA relative to the path of the radiation beam B (e.g., after mechanical retrieval from the mask library or during scanning).

[0065] Typically, the movement of the support structure MT can be achieved using long-stroke positioners (coarse positioning) and short-stroke positioners (fine positioning), which form components of the first positioner PM. Similarly, the movement of the substrate stage WT can be achieved using long-stroke and short-stroke positioners, which form components of the second positioner PW. In the case of a stepper (opposite to the scanner), the support structure MT can be connected only to the short-stroke actuator or can be fixed. Mask alignment marks M1, M2 and substrate alignment marks P1, P2 can be used to align the patterning apparatus MA and the substrate W. Although the substrate alignment marks (as shown) occupy dedicated target portions, they can be located in the space between the target portions (e.g., scribe alignment marks). Similarly, when more than one die is provided on the patterning apparatus MA, the mask alignment marks can be located between the dies.

[0066] The support structure MT and patterning apparatus MA can be located within a vacuum chamber V, where an in-vacuum robot IVR can be used to move the patterning apparatus (such as a mask) into and out of the vacuum chamber. Alternatively, when the support structure MT and patterning apparatus MA are located outside the vacuum chamber, an external vacuum robot can be used for various transport operations, similar to the in-vacuum robot IVR. Both the in-vacuum and external vacuum robots need to be calibrated to smoothly transfer any payload (e.g., a mask) to a fixed motion support at a transport station.

[0067] Photolithography equipment 100 and 100' can be used in at least one of the following modes:

[0068] 1. In step mode, the support structure MT and substrate stage WT are kept essentially stationary while the entire pattern, supplied with radiation beam B, is projected onto the target portion C in one pass (i.e., single static exposure). The substrate stage WT is then shifted in the X and / or Y directions so that different target portions C can be exposed.

[0069] 2. In the scanning mode, the support structure MT and the substrate stage WT are scanned synchronously, while a pattern imparted by the radiation beam B is projected onto the target portion C (i.e., single dynamic exposure). The velocity and direction of the substrate stage WT relative to the support structure MT (e.g., mask stage) can be determined by the (de)magnification and image inversion characteristics of the projection system PS.

[0070] 3. In another mode, the support structure MT is kept substantially stationary to hold the programmable patterning apparatus MA, while the substrate stage WT, to which a radiation beam B is applied, is moved or scanned simultaneously onto the target portion C. A pulsed radiation source SO can be used, and the programmable patterning apparatus can be updated as needed after each movement of the substrate stage WT or between consecutive radiation pulses during scanning. This mode of operation can be readily applied to maskless lithography utilizing the programmable patterning apparatus MA (such as a programmable mirror array).

[0071] It is also possible to use a combination and / or variation of the described usage pattern or completely different usage patterns.

[0072] On the other hand, the lithography apparatus 100 includes an EUV source configured to generate an EUV radiation beam for EUV lithography. Typically, the EUV source is configured in a radiation system, and a corresponding irradiation system is configured to modulate the EUV radiation beam from the EUV source.

[0073] Figure 2 The lithography apparatus 100 is shown in more detail, including a radiation source SO (source collector device), an irradiation system IL, and a projection system PS. (As shown...) Figure 2As shown, the lithography apparatus 100 is illustrated from a view orthogonal to the XZ plane (e.g., a side view) (e.g., the X-axis points to the right and the Z-axis points upward).

[0074] The radiation source SO is constructed and arranged such that a vacuum environment can be maintained within the enclosed structure 220. The radiation source SO includes a source chamber 211 and a collector chamber 212, and is configured to generate and transmit EUV radiation. EUV radiation can be generated from a gas or vapor (e.g., xenon (Xe) gas, lithium (Li) vapor, or tin (Sn) vapor, wherein an EUV radiation-emitting plasma 210 is generated to emit radiation in the EUV range of the electromagnetic spectrum). For example, the EUV radiation-emitting plasma 210 (at least partially ionized) can be generated by, for example, a discharge or a laser beam. To efficiently generate radiation, a partial pressure of, for example, about 10 Pa of Xe gas, Li vapor, Sn vapor, or any other suitable gas or vapor can be used. In some aspects, an excited tin plasma is provided to generate EUV radiation.

[0075] Radiation emitted by EUV radiation-emitting plasma 210 is transmitted from source chamber 211 into collector chamber 212 via an optional gas barrier or contaminant trap 230 (also referred to in some cases as a contaminant barrier or foil trap), which is located in or behind an opening in source chamber 211. Contaminant trap 230 may include a channel structure. Contaminant trap 230 may also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap 230 further described herein includes at least a channel structure.

[0076] Collector chamber 212 may include a radiation collector CO (e.g., a clusterer or collector), which may be a so-called grazing incidence collector. The radiation collector CO has an upstream radiation collector side 251 and a downstream radiation collector side 252. Radiation passing through the collector CO may be reflected away from the grating spectral filter 240 to be focused on a virtual source point IF. The virtual source point IF is often referred to as the intermediate focus, and the source collector device is arranged such that the virtual source point IF is located at or near the opening 219 in the enclosed structure 220. The virtual source point IF is an image of the EUV radiation-emitting plasma 210. The grating spectral filter 240 is specifically used to suppress infrared (IR) radiation.

[0077] Subsequently, radiation passes through an illumination system IL, which may include a faceted field mirror assembly 222 and a faceted pupil mirror assembly 224. The faceted field mirror assembly 222 and the faceted pupil mirror assembly 224 are arranged to provide a desired angular distribution of the radiation beam 221 at the patterning apparatus MA, and to provide a desired uniformity of radiation intensity at the patterning apparatus MA. When the radiation beam 221 is reflected at the patterning apparatus MA, which is held by a support structure MT, a patterned beam 226 is formed, and the patterned beam 226 is imaged by a projection system PS via reflective elements 228 and 229 onto a substrate W held by a wafer stage or a support structure WT.

[0078] More components than are typically shown in the irradiation system IL and projection system PS. Optionally, depending on the type of lithography apparatus, a grating spectral filter 240 may be present. Furthermore, more than... Figure 2 The mirror shown has more mirrors, such as those with Figure 2 In contrast, the projection system PS can contain 1 to 6 additional reflective elements.

[0079] like Figure 2 As shown, the radiation collector CO is depicted as a nested collector with grazing incidence reflectors 253, 254, and 255, merely as an example of a collector (or collector mirror). The grazing incidence reflectors 253, 254, and 255 are arranged axially symmetrically about the optical axis O, and this type of radiation collector CO is preferably used in conjunction with a discharge-generated plasma (DPP) source.

[0080] Example lithography unit

[0081] Figure 3 The image shows a lithography unit 300, sometimes also called a lithocell or cluster. For example... Figure 3 As shown, the lithography unit 300 is illustrated from a view (e.g., a top view) orthogonal to the XY plane (e.g., the X-axis points to the right and the Y-axis points upward).

[0082] The lithography apparatus 100 or 100' may form components of the lithography unit 300. The lithography unit 300 may also include one or more devices for performing pre-exposure and post-exposure processes on the substrate. For example, these devices include a spin coater SC for depositing a resist layer, a developer DE for developing the exposed resist, a cooling plate CH, and a baking plate BK. A substrate processor RO (e.g., a robot) picks up substrates from input / output ports I / O1, I / O2, moves them between different processing devices, and delivers them to the loading chamber LB of the lithography apparatus 100 or 100'. These devices, generally referred to collectively as tracks, are under the control of a track control unit TCU, which is itself controlled by a supervisory control system SCS, which also controls the lithography apparatus via a lithography control unit LACU. Therefore, different devices can be operated to maximize throughput and processing efficiency.

[0083] Example radiation source

[0084] For example, reflective lithography exposure equipment (e.g., Figure 1A An example of the radiation source SO in the lithography equipment 100) Figure 4 As shown in the figure. Figure 4 As shown, the radiation source SO is illustrated from a view (e.g., a top view) orthogonal to the XY plane as described below.

[0085] Figure 4 The radiation source SO shown is of the type that can be referred to as a laser-generated plasma (LPP) source. A laser system 401, which may include, for example, a carbon dioxide (CO2) laser, is arranged to deposit energy into a fuel target 403' via one or more laser beams 402, such as one or more discrete tin (Sn) droplets supplied from a fuel target generator 403 (e.g., a fuel emitter, droplet generator). According to some aspects, the laser system 401 can be a pulsed, continuous-wave, or quasi-continuous-wave laser, or can operate in a pulsed, continuous-wave, or quasi-continuous-wave manner. The trajectory of the fuel target 403' (e.g., droplets) emitted from the fuel target generator 403 can be parallel to the X-axis. According to some aspects, one or more laser beams 402 propagate in a direction parallel to the Y-axis, which is perpendicular to the X-axis. The Z-axis is perpendicular to both the X-axis and Y-axis and generally extends into (or out of) the plane of the page, but in other aspects, other configurations are used. In some embodiments, the laser beam 402 may propagate in a direction other than parallel to the Y-axis (i.e., in a direction other than orthogonal to the X-axis direction of the trajectory of the fuel target 403').

[0086] Although tin is mentioned in the following description, any suitable target material can be used. The target material may be, for example, in liquid form and may be, for example, a metal or alloy. The fuel target generator 403 may include a nozzle configured to guide tin in the form of, for example, a fuel target 403' (e.g., discrete droplets) along a trajectory toward the plasma formation region 404. Throughout the rest of the specification, references to “fuel,” “fuel target,” or “fuel droplet” should be understood to refer to the target material (e.g., droplets) emitted by the fuel target generator 403. The fuel target generator 403 may include a fuel emitter. One or more laser beams 402 are incident on the target material (e.g., tin) at the plasma formation region 404. The deposition of laser energy into the target material generates plasma 407 at the plasma formation region 404. Radiation, including EUV radiation, is emitted from plasma 407 during the deexcitation and recombination of ions and electrons in the plasma.

[0087] EUV radiation is collected and focused by collector 405 (e.g., radiation collector CO). In some aspects, collector 405 may include a near-vertical incident radiation collector (sometimes more generally referred to as a vertical incident radiation collector). Radiation collector 405 may be a multilayer structure arranged to reflect EUV light (e.g., EUV radiation having a desired wavelength such as about 13.5 nm). According to some aspects, radiation collector 405 may have an elliptical configuration with two focal points. As discussed herein, the first focal point may be located at plasma formation region 404, and the second focal point may be located at intermediate focal point IF.

[0088] In some respects, the laser system 401 may be located at a relatively long distance from the radiation source SO. In this case, one or more laser beams 402 can be delivered from the laser system 401 to the radiation source SO by means of a beam delivery system (not shown) including, for example, suitable directional mirrors and / or beam expanders and / or other optics. The laser system 401 and the radiation source SO can be considered together as a radiation system.

[0089] Radiation reflected by collector 405 forms radiation beam B. Radiation beam B is focused at a point (i.e., intermediate focus IF) to form an image of plasma formation region 404, which serves as a virtual radiation source for irradiation system IL. The point where radiation beam B is focused may be referred to as intermediate focus IF (intermediate focus 406). Radiation source SO is arranged such that intermediate focus IF is located at or near opening 408 in the enclosed structure 409 of radiation source SO.

[0090] A radiation beam B is transmitted from a radiation source SO to an illumination system IL, which is configured to modulate the radiation beam B. The radiation beam B is transmitted from the illumination system IL and incident on a pattern forming apparatus MA held by a support structure MT. The pattern forming apparatus MA reflects the radiation beam B and patterns it. After reflection from the pattern forming apparatus MA, the patterned radiation beam B enters a projection system PS. The projection system includes multiple mirrors configured to project the radiation beam B onto a substrate W held by a substrate stage WT. The projection system PS can apply a reduction factor to the radiation beam to form an image in which features are smaller than corresponding features on the pattern forming apparatus MA. For example, a reduction factor of 4 can be applied. Although the projection system PS... Figure 2 The projection system is shown as having two mirrors, but the projection system may include any number of mirrors (e.g., six mirrors).

[0091] The radiation source SO may include Figure 4 Components not shown in the diagram. For example, a spectral filter can be provided in the radiation source SO. The spectral filter can be substantially transmissive to EUV radiation, but substantially block radiation of other wavelengths such as infrared radiation.

[0092] The radiation source SO (or radiation system) also includes a fuel target imaging system to obtain images of the fuel target (e.g., microdroplets) in the plasma formation region 404, or more specifically, to obtain a shadowed image of the fuel target. The fuel target imaging system can detect light diffracted from the edges of the fuel target. References to fuel target images below should also be understood as referring to shadowed images of the fuel target or diffraction patterns caused by the fuel target.

[0093] A fuel target imaging system may include photodetectors, such as CCD arrays or CMOS sensors; however, it should be understood that any imaging device suitable for acquiring images of the fuel target may be used. It should be understood that, in addition to photodetectors, the fuel target imaging system may also include optical components, such as one or more lenses. For example, a fuel target imaging system may include a camera 410, such as a combination of a photosensor (or: photodetector) and one or more lenses. Optical components may be selected such that the photosensor or camera 410 acquires near-field and / or far-field images. The camera 410 may be positioned at any suitable location within the radiation source SO, having a line of sight from that location to the plasma formation region 404 and one or more markings provided on the collector 405. Figure 4(Not shown in the image). In some aspects, however, it may be necessary to position the camera 410 away from the propagation path of one or more laser beams 402 and away from the trajectory of the fuel target emitted from the fuel target generator 403 to avoid damage to the camera 410. According to some aspects, the camera 410 is configured to provide an image of the fuel target to the controller 411 via connection 412. Connection 412 is shown as a wired connection, although it should be understood that connection 412 (and other connections mentioned herein) may be implemented as a wired connection or a wireless connection or a combination thereof.

[0094] like Figure 4 As shown, the radiation source SO may include a fuel target generator 403 configured to generate and emit fuel targets 403' (e.g., discrete tin droplets) toward the plasma formation region 404. The radiation source SO may also include a laser system 401 configured to impinge one or more fuel targets 403' with one or more laser beams 402 to generate plasma 407 at the plasma formation region 404. The radiation source SO may also include a radiation collector 405 (i.e., a radiation collector CO) configured to collect radiation emitted by the plasma 407.

[0095] Figure 5 Figure 7 shows an example of a measurement system and window set up in a radiation source 50 for an example reflective lithography apparatus.

[0096] Example measurement system and window

[0097] Figure 5 The illustration shows an isometric side view 500 of an example enclosure 502 (e.g., enclosure 220, enclosure 409), which is configured to maintain a vacuum environment as a component of an example radiation source SO in an example reflective lithography apparatus. The example enclosure 502 can be configured to interact with a radiation collector 506 (e.g., Figure 2 The radiation collector CO shown Figure 4 The radiation collector 405 shown is adjacent to it. For reference, the principal focus 504 of the radiation collector 506 is illustrated with a Cartesian coordinate system including the X, Y, and Z axes, although any suitable relative or universal coordinate system may be used. In some aspects, the example closure 502 includes an opening 508 associated with a fuel target generator (e.g., fuel target generator 403, droplet generator DG) and an opening 509 associated with a fuel target receiver (e.g., tin trap TC).

[0098] like Figure 5As shown, according to some aspects of this disclosure, one or more example components may be mechanically connected (e.g., anchored or otherwise attached by one or more fasteners, clamps, adhesives, or combinations thereof) to example enclosure 502. Example components that may be mechanically connected to example enclosure 502 of radiation source SO may include, but are not limited to: measurement system 510 and window 511; measurement system 512 and window 513; measurement system 514 and window 515; measurement system 516 and window 517; measurement system 518 and window 519; measurement system 520 and window 521; measurement system 522 and window 523; measurement system 524 and window 525; measurement system 526 and window 527; any other suitable components, or any combination thereof. In some aspects, the main focus 504 may be located at a distance of approximately 1 meter from the surface of one or more of the windows 511, 513, 515, 517, 519, 521, 523, 525, and 527.

[0099] In some aspects, measurement system 510 may include a coarse droplet manipulation camera (CDSC), and measurement system 522 may include a fine droplet manipulation camera (FDSC). In some aspects, measurement system 512 may include a first droplet forming camera (DFC), and measurement system 520 may include a second DFC. In some aspects, measurement system 514 may include a droplet detection module (DDM). In some aspects, measurement system 516 may include a line laser module (LLM). In some aspects, measurement system 518 may include a droplet illumination module (DIM). In some aspects, measurement system 524 may include a first illumination module, such as a first backlight laser module (BLM), and measurement system 526 may include a second illumination module, such as a second BLM. In some aspects, measurement systems 524 and 526 (e.g., the first BLM and the second BLM) may be connected to measurement systems 512 and 520 (e.g., a pair of DFCs).

[0100] In some respects, one or more of windows 511, 513, 515, 517, 519, 521, 523, 525, and 527 can be constructed and arranged as described below: Figure 6A and Figure 6B The window 640 shown in Figure 7, the window 740 shown in Figure 7, the example quick-change window assembly 700 shown in Figure 7, any other suitable window or window assembly, any structure or feature included therein, or any combination thereof.

[0101] In some aspects, one or more of the measurement systems 510, 512, 514, 516, 518, 520, 522, 524, and 526 can be configured to be positioned in a first environment, such as the atmospheric environment outside a sealed container (such as example enclosure 502). In some aspects, one or more of the measurement systems 510, 512, 514, 516, 518, 520, 522, 524, and 526 can be configured to perform one or more measurements on a region in a second environment along the optical axis of the measurement system. In some aspects, this region can partially or completely encompass any suitable geometric region, such as the region inside the example enclosure including the main focus 504 of the radiation collector 506; Figure 4 The plasma formation region 404 is shown. Figure 6A and Figure 6C The region 601 shown; any other suitable region; or any combination thereof. In some respects, the optical axis of the measurement system can be, for example, Figure 6A and Figure 6C The optical axis 602 shown is the optical axis of the measurement system. In some aspects, the second environment may be a vacuum environment or a partial vacuum environment located inside a sealed container (such as example closed structure 502). In some aspects, one or more windows of 511, 513, 515, 517, 519, 521, 523, 525, and 527 may be configured to intersect the optical axis of the respective measurement system. In some aspects, one or more windows of 511, 513, 515, 517, 519, 521, 523, 525, and 527 may be configured to isolate the respective measurement system from the second environment.

[0102] In some aspects, one or more of windows 511, 513, 515, 517, 519, 521, 523, 525, and 527 can be configured to limit lateral displacement (e.g., lateral focusing error) at the principal focus 504 of radiation collector 506 to a lateral displacement tolerance less than about ±50 micrometers relative to the nominal lateral displacement relative to the optical axis (e.g., the corresponding measurement system of the particular window). In some aspects, one or more of windows 511, 513, 515, 517, 519, 521, 523, 525, and 527 can be configured to limit lateral displacement at the principal focus 504 of radiation collector 506 to a lateral displacement tolerance less than about ±33 micrometers relative to the nominal lateral displacement relative to the optical axis.

[0103] In some aspects, one or more of windows 511, 513, 515, 517, 519, 521, 523, 525, and 527 can be configured to limit angular deviation along the optical axis (e.g., the optical axis of the corresponding measurement system for a particular window) to an angular deviation tolerance less than about ±0.5 arcminutes from the nominal angular deviation along the optical axis. In some aspects, one or more of windows 511, 513, 515, 517, 519, 521, 523, 525, and 527 can be configured to limit angular deviation along the optical axis to an angular deviation tolerance less than about ±0.1 arcminutes from the nominal angular deviation.

[0104] In some aspects, one or more of windows 511, 513, 515, 517, 519, 521, 523, 525, and 527 can be configured to limit longitudinal displacement (e.g., axial focusing error) along the optical axis (e.g., the optical axis of the corresponding measurement system for a particular window) to a longitudinal displacement tolerance less than about ±330 micrometers relative to the nominal longitudinal displacement relative to the principal focus 504. In some aspects, one or more of windows 511, 513, 515, 517, 519, 521, 523, 525, and 527 can be configured to limit longitudinal displacement along the optical axis to a longitudinal displacement tolerance less than about ±200 micrometers relative to the nominal longitudinal displacement relative to the principal focus 504.

[0105] In some aspects, one or more of the measurement systems 510, 512, 514, 516, 518, 520, 522, 524, and 526 may be modular measurement systems. In some aspects, one or more windows 511, 513, 515, 517, 519, 521, 523, 525, and 527 may be configured to limit lateral displacement to less than about ±50 micrometers when the corresponding measurement system is installed in the radiation source SO. In some aspects, one or more windows 511, 513, 515, 517, 519, 521, 523, 525, and 527 may be configured to limit lateral displacement to less than about ±50 micrometers without calibration action (e.g., without the need for a separate calibration action).

[0106] Figure 6A , Figure 6B , Figure 6C and Figure 6D This is a schematic diagram of a portion of an example EUV radiation system according to some aspects of this disclosure. Figure 6A A schematic diagram of an example system 600 according to some aspects of this disclosure is illustrated. For example... Figure 6A As shown, example system 600 includes measurement system 630 and window 640. In some aspects, measurement system 630 may be or include Figure 5One or more of the measurement systems 510, 512, 514, 516, 518, 520, 522, 524, and 526 shown are included. In some aspects, window 640 may be or include... Figure 5 One or more of the windows shown in windows 511, 513, 515, 517, 519, 521, 523, 525 and 527.

[0107] In some respects, the measurement system 630 can be positioned in a sealed container (e.g., Figure 2 The closed structure 220 shown, Figure 4 The closed structure 409 shown is... Figure 5 The enclosed structure 502 shown is located in a first environment 680 (e.g., atmospheric environment) outside the enclosure and is removably attached (e.g., mechanically connected, anchored, or otherwise attached by one or more fasteners, clamps, adhesives, or combinations thereof) to the window 640. In some aspects, the window 640 may be removably attached to a sealed container (e.g., Figure 2 The closed structure 220 shown is... Figure 4 The closed structure 409 shown is... Figure 5 The sealed structure 502 shown is configured as a component of the example radiation source SO of the example reflective lithography apparatus to maintain a second environment 682 (e.g., a vacuum environment, a partial vacuum environment).

[0108] For reference only. Figure 6A The illustration shows a radiation collector (e.g., Figure 2 The radiation collector CO shown Figure 4 The radiation collector 405 shown is... Figure 5 The radiation collector 506 shown has a main focal point 604 and an optical axis 602 of the measurement system 630. In some aspects, the main focal point 604 may be located at a distance of approximately 1 meter from the surface of the window 640. For example, the main focal point 604 may be located at a distance of approximately 1 meter from the surface 648b of the viewport 648. Figure 6B (As shown) at a distance of about 1 meter.

[0109] In some aspects, the measurement system 630 can be configured to perform one or more measurements on region 601 in the second environment 682 along the optical axis 602 of the measurement system 630. In some aspects, region 601 can partially or wholly encompass any suitable geometric region, such as the region inside an example enclosed structure including the principal focus 604 of the radiation collector; Figure 4The plasma formation region 404 shown; any other suitable region; or any combination thereof. In some aspects, the second environment 682 may be a vacuum environment or a partial vacuum environment located inside a sealed container. In some aspects, the window 640 may be configured to intersect with the optical axis 602 of the measurement system 630.

[0110] In some aspects, window 640 may include base structure 642, viewport mount structure 644, viewport 648, surface mount structure 652, surface 650, radiation shielding structure 646 (e.g., optical shielding), any other suitable components or structures, or any combination thereof. In some aspects, references... Figure 6B Window 640 is described in further detail.

[0111] like Figure 6B As shown, the base structure 642 of window 640 may include an O-ring 664 configured to be removably attached to the outer surface of the sealed container. The base structure 642 may include an O-ring 660 configured to be removably attached to surface 648b (e.g., inner surface) of viewport 648. The viewport mounting structure 644 may include an O-ring 661 configured to be removably attached to surface 648a (e.g., outer surface) of viewport 648. In some aspects, the radiation shielding structure 646 and the viewport mounting structure 644 may be configured to be attached to the base structure 642 using fasteners (e.g., eight hex socket flathead machine screws).

[0112] In some aspects, viewport 648 may include an anti-reflective (AR) coated optical glass, such as borosilicate crown glass, having a transmission range of about 350 nanometers to about 2.5 micrometers and a refractive index of about 1.51680 at 587.5618 nanometers (e.g., yellow helium line). In some aspects, coating 650 may include the same or different optical glass as that included in viewport 648.

[0113] In some aspects, window 640 may be configured to isolate measurement system 630 from second environment 682. For example, O-rings 661, 660, and 664 may separate first environment 680 from second environment 682. In some aspects, window 640 may include flow channel 668 configured to extend second environment 682 into the volume disposed between surface 650a and surface 648b.

[0114] In some aspects, window 640 may include a wedge angle that differs from the nominal wedge angle by less than ±5.0 arcseconds, or about ±0.1 arcminutes. In some aspects, the nominal wedge angle may be about zero degrees. For example, viewport 648, surface 650, or both may have a wedge angle that differs from a nominal wedge angle of zero degrees by less than ±5.0 arcseconds. In one illustrative example, the nominal wedge angle between surfaces 648a and 648b may be about zero degrees, and the wedge angle between surfaces 648a and 648b may be less than about -5.0 arcseconds and about 5.0 arcseconds. In another illustrative example, the nominal wedge angle between surfaces 650a and 650b may be about zero degrees, and the wedge angle between surfaces 650a and 650b may be between about -5.0 arcseconds and about 5.0 arcseconds.

[0115] In other respects, the nominal wedge angle may be greater than approximately zero degrees. For example, viewport 648, surface 650, or both may have a wedge angle less than ±5.0 arcminutes different from a nominal wedge angle greater than approximately zero degrees (e.g., approximately 58 arcminutes, 1 degree 56 arcminutes, 3 degrees 52 arcminutes, or any other suitable wedge angle). In one illustrative example, the nominal wedge angle between surfaces 648a and 648b may be approximately 3,480 arcseconds, and the wedge angle between surfaces 648a and 648b may be between approximately 3,475 arcseconds and approximately 3,485 arcseconds. In another illustrative example, the nominal wedge angle between surfaces 650a and 650b may be 6,960 arcseconds, and the wedge angle between surfaces 650a and 650b may be between approximately 6,955 arcseconds and approximately 6,965 arcseconds.

[0116] Figure 6C Area 601 is illustrated in more detail. It should be understood that area 601 is not necessarily drawn to scale, and furthermore, Figure 6C The linear two-dimensional depiction shown can actually refer to nonlinear aspects, three-dimensional aspects, any other suitable aspects, or combinations thereof.

[0117] like Figure 6C As shown, region 601 may include the main focus 604 of the radiation collector. The main focus 604 may be positioned along the optical axis 602 of the measurement system 630. Figure 6C The diagram also illustrates an axis 603 that is transverse to the principal focal point 604 and orthogonal (e.g., perpendicular) to the optical axis 602.

[0118] like Figure 6CAs further shown, region 601 may include a nominal displacement focus 606 (e.g., a predicted, estimated, planned, or designed focus error) of window 640 (e.g., in the case where window 640 is not an ideal window). The nominal displacement focus 606 may be positioned along the nominal displacement optical axis 605 of window 640 (e.g., a predicted, estimated, planned, or designed optical axis). As used herein, the term "nominal" may refer to a predicted, estimated, planned, or designed value, measurement, location, geometry, or other suitable characteristic.

[0119] In some aspects, the nominal displacement focus 606 may have a nominal lateral displacement 610 (e.g., a predicted, estimated, planned, or designed lateral focusing error) relative to the optical axis 602 at the principal focus 604 of the radiation collector. In an illustrative example, the nominal lateral displacement 610 may be about 1 mm. In some aspects, the nominal displacement focus 606 may have a nominal longitudinal displacement 611 (e.g., a predicted, estimated, planned, or designed axial focusing error) along the optical axis 602 relative to the principal focus 604. In some aspects, the nominal displacement focus 606 may have a nominal angular deviation 618 (e.g., a predicted, estimated, planned, or designed nominal angular deviation) relative to the optical axis 602.

[0120] In some respects, the nominal displacement focus 606 can be corrected through the initial measurement module alignment process, and therefore, the nominal displacement focus 606 can coincide with the principal focus 604. As a result of the initial measurement module alignment process, the nominal lateral displacement 610 can be approximately 0 micrometers, the nominal longitudinal displacement 611 can be approximately 0 micrometers, and the nominal angular deviation 618 can be approximately 0 degrees.

[0121] like Figure 6C As further shown, region 601 may include a displacement focus 608 of window 640 (e.g., actual focus error). The displacement focus 608 may be set along the displacement optical axis 607 (e.g., actual optical axis) of window 640.

[0122] In some aspects, the displacement focus 608 may have a lateral displacement 612 relative to the optical axis 602 at the principal focus 604 of the radiation collector (e.g., actual lateral focusing error). In some aspects, the displacement focus 608 may have a longitudinal displacement 614 along the optical axis 602 relative to the principal focus 604 (e.g., actual axial focusing error). In some aspects, the displacement focus 608 may have an angular deviation 619 relative to the optical axis 602 (e.g., actual angular deviation).

[0123] In some aspects, the displacement focus 608 may have an actual to nominal lateral displacement 613 relative to the nominal displacement focus 606, which is set within a lateral displacement tolerance 616 relative to the nominal displacement focus 606. In some aspects, the lateral displacement tolerance 616 may be less than about ±50 micrometers, less than about ±33 micrometers, or less than any other suitable tolerance.

[0124] In some aspects, the displacement focus 608 may have an actual to nominal longitudinal displacement 615 relative to the nominal displacement focus 606, which is set within a longitudinal displacement tolerance 617 relative to the nominal displacement focus 606. In some aspects, the longitudinal displacement tolerance 617 may be less than about ±330 micrometers, less than about ±200 micrometers, or less than any other suitable tolerance.

[0125] In some aspects, the displacement focus 608 may have an actual to nominal angular deviation 620 relative to the nominal displacement focus 606, which is set within an angular deviation tolerance 621 relative to the nominal displacement focus 606. In some aspects, the angular deviation tolerance 621 may be less than about ±0.5 arcminutes, less than about ±0.1 arcminutes, less than about ±5 arcseconds, or less than any other suitable tolerance.

[0126] In some aspects, window 640 can be configured to limit the lateral displacement 612 at the main focus 604 of the radiation collector to a lateral displacement tolerance 616 less than about ±50 micrometers from the nominal lateral displacement 610 relative to the optical axis 602. In some aspects, window 640 can be configured to limit the lateral displacement 612 at the main focus 604 of the radiation collector to a lateral displacement tolerance 616 less than about ±33 micrometers from the nominal lateral displacement 610 relative to the optical axis 602. In other words, window 640 can be configured to limit the actual to nominal lateral displacement 613 to less than about ±50 micrometers, limit the actual to nominal lateral displacement 613 to less than about ±33 micrometers, or limit the actual to nominal lateral displacement 613 to less than any other suitable tolerance.

[0127] In some aspects, window 640 can be configured to limit the longitudinal displacement 614 along the optical axis 602 to a longitudinal displacement tolerance 617 of less than about ±330 micrometers from the nominal longitudinal displacement 611 relative to the principal focus 604. In other aspects, window 640 can be configured to limit the longitudinal displacement 614 along the optical axis 602 to a longitudinal displacement tolerance 617 of less than about ±200 micrometers from the nominal longitudinal displacement 611 relative to the principal focus 604. In other words, window 640 can be configured to limit the actual to nominal longitudinal displacement 615 to less than about ±330 micrometers, limit the actual to nominal longitudinal displacement 615 to less than about ±200 micrometers, or limit the actual to nominal longitudinal displacement 615 to less than any other suitable tolerance.

[0128] In some aspects, window 640 can be configured to limit the angular deviation 619 along the optical axis 602 to an angular deviation tolerance 621 that differs from the nominal angular deviation 618 along the optical axis 602 by less than approximately ±0.5 arcminutes. In some aspects, window 640 can be configured to limit the angular deviation 619 along the optical axis 602 to an angular deviation tolerance 621 that differs from the nominal angular deviation 618 by less than approximately ±0.1 arcminutes.

[0129] In other words, window 640 can be configured to: limit the actual to nominal angular deviation 620 to less than approximately ±0.5 arcminutes, limit the actual to nominal angular deviation 620 to less than approximately ±0.1 arcminutes, limit the actual to nominal angular deviation 620 to less than approximately ±5 arcseconds, or limit the actual to nominal angular deviation 620 to less than any other suitable tolerance.

[0130] In some aspects, the measurement system 630 may be a modular measurement system. In some aspects, the window 640 may be configured to limit the lateral displacement 612 at the principal focus 604 of the radiation collector to a difference of less than about ±50 micrometers from the nominal lateral displacement 610 relative to the optical axis 602 when the measurement system 630 is installed in the radiation source SO. In some aspects, the window 640 may be configured to limit the lateral displacement 612 at the principal focus 604 of the radiation collector to a difference of less than about ±50 micrometers from the nominal lateral displacement 610 relative to the optical axis 602 without calibration action (e.g., without needing to perform a separate calibration action beyond the initial measurement module alignment process to adjust the nominal displacement focus 606).

[0131] like Figure 6DAs shown, viewport 648 can be configured to intersect optical axis 602. In some aspects, diaphragm 650 can be configured to intersect optical axis 602 and be opposite viewport 648 (e.g., at an angle of approximately zero degrees, at an angle greater than approximately zero degrees, or at an angle less than approximately zero degrees). For example, viewport 648 may have viewport axis 690, diaphragm 650 may have diaphragm axis 692, and the angle 691 between viewport axis 690 and diaphragm axis 692 may be greater than zero degrees (e.g., approximately 4.5 degrees) to reduce or prevent back reflection.

[0132] Example of quick window assembly replacement

[0133] Figure 7A , Figure 7B and Figure 7C This is a schematic diagram illustrating the quick replacement of window assembly 700 based on some aspects of this disclosure. For example... Figure 7A As shown, the example quick-change window assembly 700 may include a quick-change window 740 and a quick-change window frame 770 (e.g., a fixing mechanism). In some aspects, such as Figure 7A As depicted, the example quick-change window assembly 700 may include multiple fasteners, such as fasteners, pins, clips, rotating arms, and other such structures; for simplicity, these are referred to as... Figure 7A It is not marked in the text.

[0134] In some aspects, the quick-change window 740 may include a base structure 742, a viewport mount structure 744, a viewport 748 (e.g., an "optical flat" quality substrate), a surface mount structure (not shown), a surface film (not shown; e.g., angled relative to the viewport 748 to prevent back reflection), a radiation shielding structure (not shown), any other suitable components or structures, or any combination thereof. In some aspects, the quick-change window 740 may include a reference... Figure 5 The windows shown are 511, 513, 515, 517, 519, 521, 523, 525, and 527. Figure 6A and Figure 6B The window 640 shown describes one or more structures. In some aspects, one or more quick-change mounting structures (such as ball bearings 743a and 743b) may be connected to the base structure 742 for mounting, aligning, and removing the example quick-change window assembly 700.

[0135] In some aspects, the quick-change window frame 770 may include a frame structure 772 that can be attached to the quick-change window 740 (e.g., attached to a base structure 742). In some aspects, one or more quick-change mounting structures (such as ball bearings 774a, 774b, 774c, and 774d) may be attached to the frame structure 772 for mounting, aligning, and removing the example quick-change window assembly 700. In some aspects, the quick-change window frame 770 may include a tool 790 configured to receive mounting and dismounting tools. Figure 7B The receiving structure 776 (shown) is described. In some aspects, the quick-change window frame 770 may be a built-in fixing mechanism that ensures the consistent orientation of the quick-change window 740 relative to a reference surface on the radiation source container. In some aspects, the quick-change window frame 770 may use an "over-center" cam to provide reliable engagement and vacuum tightness. In some aspects, the quick-change window frame 770 may be configured such that wiping of the vacuum seal O-ring does not occur when vacuum sealing is performed using the radiation source container.

[0136] like Figure 7B As shown, the example quick-change window assembly 700 can be installed and removed by movement 792 of the installation and removal tool 790. In some aspects, the fixing components of the example quick-change window assembly 700 (e.g., the base structure 742 of the quick-change window 740) may include bearings (e.g., ball bearings 743a and 743b) that act as travel stops when the quick-change window 740 is inserted into its socket on the radiation source container 702. In some aspects, the example quick-change window assembly 700 may be configured such that no additional translation occurs (e.g., the orientation of the sealing O-ring relative to the sealing surface). In some aspects, the actuation installation and removal mechanism provides only the movement of compressing the sealing ring.

[0137] like Figure 7C As shown, the example quick-change window assembly 700 can be installed and removed from its socket on the radiation source container 702 via movement 794. During installation and removal, the measurement system 796 (e.g., Figure 5 The measurement system 522 shown can be kept fixed to the radiation source container 702.

[0138] In some examples, retention methods can be: (i) a loose metal seal with multiple retaining screws; (ii) a loose resilient seal with multiple retaining screws; and (iii) a loose resilient seal with supplementary loosening clamps. Furthermore, the vacuum viewport can include a glass-metal bond that applies stress to the window and thus causes deformation. Additionally, the diaphragm has a limited lifespan. For example, tin fragments from EUV plasma (via both vapor and ballistic particles) accumulate on the diaphragm, obscuring the area of ​​interest viewed by the measurement system (e.g., Figure 6A and Figure 6C The capability of region 601 shown. A protective film exists to protect the viewport window from contamination and the resulting thermal stress, which has historically led to window breakage and vacuum loss (e.g., system downtime). The orientation of the protective film relative to the viewport is somewhat random.

[0139] In some respects, the example quick-change window assembly 700 integrates the diaphragm into a precision housing with optics secured via O-rings, allowing for control and minimization of optical distortion. In some respects, installation and removal can be completed in seconds via an "eccentric self-locking" cam mechanism. Only a single-arm access is required to actuate the installation and removal mechanism. Viewport removal may also require a single-arm forward movement.

[0140] In some respects, the example quick-change window assembly 700 provides a viewport 748 with excellent optical properties (e.g., wavefront error) and optimized installation and removal features, maximizing the availability of the EUV radiation source. In some respects, the example quick-change window assembly 700 provides a sacrificial window (referred to as a diaphragm) in the same optical path. Therefore, the example quick-change window assembly 700 provides an optimized viewport that encompasses both the vacuum window and the diaphragm, while offering rapid installation and removal capabilities.

[0141] Example quick-change window assembly 700 can meet extreme availability requirements for EUV radiation systems and enables rapid completion of all maintenance actions. In other words, the quick-change time supports the need for extreme availability requirements in terms of system uptime and availability. In another example, the use of elastomeric seals, compared to glass and metal solder, promotes lower optical glass deformation and lower residual stress in the glass. As a result, there may be a lower risk of breakage, lower vacuum loss in the radiation source, and longer downtime for recovery (e.g., B-time).

[0142] Example procedures for optical measurement

[0143] Figure 8 It is based on some aspects or more parts of this disclosure for use in radiation systems (e.g., EUV radiation systems, such as...) Figure 1A , Figure 2 and Figure 4 Example method 800 for optical measurement in the example radiation source 50 shown. The operation described with reference to example method 800 can be performed by or according to any of the systems, devices, components, techniques or combinations thereof described herein, such as those described above with reference to Figures 1 through 7.

[0144] At operation 802, the method may include in a first environment (e.g., such as...) Figure 6A and Figure 6B A measurement system (e.g., in the atmospheric environment of the first environment 680 shown) is installed. Figure 5 The measurement systems shown are 510, 512, 514, 516, 518, 520, 522, 524 or 526; Figure 6A The measurement system 630 shown. The measurement system is along the optical axis of the measurement system (e.g., Figure 6A and Figure 6C The optical axis 602 shown is relative to a second environment (e.g., a vacuum or partial vacuum environment, such as...). Figure 6A and Figure 6B The area in the second environment 682 shown (e.g., Figure 4 The plasma formation region 404 is shown. Figure 6A and Figure 6C In the area 601 shown, one or more measurements are performed, and the second environment differs from the first environment. In some respects, the measurement system can be set up using suitable mechanical or other methods, and includes setting up the measurement system according to any aspect or combination of aspects described above with reference to Figures 1 to 7.

[0145] At operation 804, the method may include using a window (e.g., Figure 5 The windows shown are 511, 513, 515, 517, 519, 521, 523, 525, or 527; Figure 6A and Figure 6B The window shown is 640; Figure 7A The quick-change window 740 shown isolates the measurement system from the second environment; this window is positioned to intersect the optical axis. In some aspects, the isolation of the measurement system from the second environment can be performed based on a vacuum seal or partial vacuum seal provided by the window. In some aspects, the isolation of the measurement system can be achieved using suitable mechanical or other methods, and includes isolating the measurement system according to any aspect or combination of aspects described above with reference to Figures 1 through 7.

[0146] At operation 806, the method may include: window-based settings in the radiation collector (e.g., Figure 2 The radiation collector CO shown Figure 4 The radiation collector 405 shown is... Figure 5 The main focus of the radiation collector 506 shown (e.g., Figure 5 The principal focus shown is 504; Figure 6A and Figure 6C At the principal focal point 604 shown, the lateral displacement relative to the optical axis (e.g., Figure 6C The lateral displacement 612 shown is limited to the nominal lateral displacement relative to the optical axis (e.g., Figure 6C The nominal lateral displacement (610) shown differs by less than about ±50 micrometers. In some respects, the limitation of lateral displacement can be achieved by suitable mechanical or other methods, and includes limiting lateral displacement according to any aspect or combination of aspects described above with reference to Figures 1 to 7.

[0147] While specific references may be made herein to the use of lithography equipment in IC manufacturing, it should be understood that the lithography equipment described herein may have other applications, such as manufacturing integrated optical systems, guiding and detecting patterns for magnetic domain memory, flat panel displays, LCDs, thin-film magnetic heads, etc. Those skilled in the art will understand that, in the context of such alternative applications, any use of the terms "wafer" or "bare die" herein may be considered synonymous with the more general terms "substrate" or "target portion," respectively. The substrate mentioned herein may be processed before or after exposure in, for example, a tracking unit (typically a tool for applying a resist layer to the substrate and developing the exposed resist), a measurement unit, and / or an inspection unit. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Furthermore, for example, to create multilayer ICs, the substrate may be processed more than once, such that the term "substrate" as used herein may also refer to a substrate that already contains multiple processed layers.

[0148] It should be understood that the wording or terminology used herein is for descriptive rather than limiting purposes, and that the terminology or terminology used herein should be interpreted by those skilled in the art based on the teachings herein.

[0149] As used in this article, the term "substrate" describes the material on which a layer of material is added. In some respects, the substrate itself may be patterned, and the material added on top of it may also be patterned, or it may remain unpatterned.

[0150] The embodiments disclosed herein are illustrative and not limiting. Other suitable modifications and adaptations to various conditions and parameters commonly encountered in the art (which will be apparent to those skilled in the art) are within the spirit and scope of this disclosure.

[0151] While specific aspects of this disclosure have been described above, it should be understood that these aspects may be practiced in ways other than those described. This description is not intended to limit the embodiments of this disclosure.

[0152] It should be understood that the Detailed Description section, rather than the Background, Summary, and Abstract sections, is intended to interpret the claims. The Summary and Abstract sections may set forth one or more, but not all, exemplary embodiments contemplated by the inventors(s), and are therefore not intended to limit the embodiments and the appended claims in any way.

[0153] The functional building blocks described above illustrate some aspects of this disclosure by way of illustrating the implementation of specific functions and their relationships. For ease of description, the boundaries of these functional building blocks are arbitrarily defined herein. Alternative boundaries can be defined as long as the specified functions and their relationships are performed appropriately.

[0154] The foregoing description of specific aspects of this disclosure will fully reveal the general nature of these aspects, and by applying knowledge in the art, others can readily modify and / or adapt these specific aspects for various applications without requiring excessive experimentation or departing from the general concepts of this disclosure. Therefore, based on the teachings and guidance given herein, such adaptations and modifications are intended to be within the equivalent meaning and scope of the disclosed aspects.

[0155] Other aspects of the invention are set forth in the following numbered clauses.

[0156] 1. A system comprising:

[0157] A measurement system is configured to be positioned in a first environment and to perform one or more measurements on a region in a second environment along the optical axis of the measurement system, wherein the second environment differs from the first environment; and

[0158] The window is configured to intersect the optical axis and is configured as follows:

[0159] Isolate the measurement system from the second environment; and

[0160] At the main focus of the radiation collector, the lateral displacement relative to the optical axis is limited to less than approximately ±50 micrometers from the nominal lateral displacement relative to the optical axis.

[0161] 2. In the system of Clause 1, the main focus is located at a distance of approximately 1 meter from the window.

[0162] 3. The system according to Clause 1, wherein the window is configured to limit lateral displacement to less than approximately ±33 micrometers.

[0163] 4. The system according to Clause 1, wherein the window is configured to limit the angular deviation along the optical axis to be less than about ±0.5 arcminutes from the nominal angular deviation along the optical axis.

[0164] 5. The system according to Clause 4, wherein the window is configured to limit the angular deviation to less than about ±0.1 arcminutes.

[0165] 6. The system according to Clause 1, wherein the window is configured to limit longitudinal displacement along the optical axis to a difference of less than about ±330 micrometers from the nominal longitudinal displacement relative to the principal focus.

[0166] 7. A system according to Clause 6, wherein the window is configured to limit longitudinal displacement to less than about ±200 micrometers.

[0167] 8. The system according to Clause 1, wherein the window includes:

[0168] The first component is configured to be intersected with the optical axis; and

[0169] The second component is configured to intersect the optical axis and be opposite to the first component.

[0170] 9. The system according to Clause 8, wherein:

[0171] The first component includes a viewport; and

[0172] The second component includes a protective film.

[0173] 10. The system according to Clause 1, wherein the window includes a wedge angle that differs from the nominal wedge angle by less than about ±0.1 arcminutes.

[0174] 11. In accordance with Clause 10, the nominal wedge angle is approximately zero degrees.

[0175] 12. A system pursuant to Clause 10, wherein the nominal wedge angle is greater than approximately zero degrees.

[0176] 13. The system according to Clause 1, wherein the measurement system is a modular measurement system.

[0177] 14. The system according to Clause 1, wherein the window is configured to limit displacement to less than about ±50 micrometers when the measurement system is installed in the system.

[0178] 15. The system according to Clause 1, wherein the window is configured to limit displacement to less than about ±50 micrometers in the absence of calibration action.

[0179] 16. A window, comprising:

[0180] The first component is configured to be intersected with the optical axis; and

[0181] The second component is configured to intersect the optical axis and be opposite to the first component.

[0182] The window is configured as follows:

[0183] Radiation is transmitted along the optical axis passing through the first and second components; and

[0184] At the main focus of the radiation collector, the lateral displacement relative to the optical axis is limited to less than approximately ±50 micrometers from the nominal lateral displacement relative to the optical axis.

[0185] 17. A window according to Clause 16, wherein the main focus is located at a distance of approximately 1 meter from the window.

[0186] 18. The window according to Clause 16, wherein the first component includes a viewport, and wherein the second component includes a film.

[0187] 19. The window according to Clause 16, wherein the window includes a wedge angle that differs from the nominal wedge angle by less than about ±0.1 arcminutes.

[0188] 20. A method comprising:

[0189] A measurement system is set up in a first environment, wherein the measurement system performs one or more measurements on a region in a second environment along the optical axis of the measurement system, the second environment being different from the first environment;

[0190] The measurement system is isolated from the second environment using a window configured to intersect the optical axis; and

[0191] Based on the window settings, the lateral displacement relative to the optical axis at the main focus of the radiation collector is limited to a difference of less than approximately ±50 micrometers from the nominal lateral displacement relative to the optical axis.

[0192] The breadth and scope of this disclosure should not be limited by any of the exemplary aspects or embodiments described above, but should be defined solely by the appended claims and their equivalents.

Claims

1. A system for optical measurement, comprising: A measurement system is configured to be set up in a first environment and to perform one or more measurements on a region in a second environment along the optical axis of the measurement system, wherein the second environment is different from the first environment; as well as The window is configured to intersect the optical axis and is configured as follows: The measurement system is isolated from the second environment; as well as At the main focal point of the radiation collector, the lateral displacement relative to the optical axis is limited to be less than 50 micrometers different from the nominal lateral displacement relative to the optical axis.

2. The system according to claim 1, wherein the main focus is located at a distance of 1 meter from the window.

3. The system of claim 1, wherein the window is configured to limit the lateral displacement to less than 33 micrometers.

4. The system of claim 1, wherein the window is configured to limit the angular deviation along the optical axis to be less than 0.5 arcminutes different from the nominal angular deviation along the optical axis.

5. The system of claim 4, wherein the window is configured to limit the angular deviation to less than 0.1 arcminutes.

6. The system of claim 1, wherein the window is configured to limit longitudinal displacement along the optical axis to a difference of less than 330 micrometers from the nominal longitudinal displacement relative to the principal focus.

7. The system of claim 6, wherein the window is configured to limit the longitudinal displacement to less than 200 micrometers.

8. The system of claim 1, wherein the window comprises: The first component is configured to intersect the optical axis; as well as The second component is configured to intersect the optical axis and be opposite to the first component.

9. The system according to claim 8, wherein: The first component includes a viewport; and The second component includes a film.

10. The system of claim 1, wherein the window includes a wedge angle that differs from the nominal wedge angle by less than 0.1 arcminutes.

11. The system of claim 10, wherein the nominal wedge angle is zero degrees.

12. The system of claim 10, wherein the nominal wedge angle is greater than zero degrees.

13. The system according to claim 1, wherein the measurement system is a modular measurement system.

14. The system of claim 1, wherein the window is configured to limit the displacement to less than 50 micrometers when the measurement system is installed in the system.

15. The system of claim 1, wherein the window is configured to limit the displacement to less than 50 micrometers in the absence of calibration action.

16. A window, comprising: The first component is configured to intersect the optical axis; as well as The second component is configured to intersect the optical axis and be opposite to the first component. The window is configured as follows: Radiation is transmitted along the optical axis passing through the first component and the second component; as well as At the main focal point of the radiation collector, the lateral displacement relative to the optical axis is limited to be less than 50 micrometers different from the nominal lateral displacement relative to the optical axis.

17. The window of claim 16, wherein the main focal point is located at a distance of 1 meter from the window.

18. The window of claim 16, wherein the first component includes a viewport, and wherein the second component includes a film.

19. The window of claim 16, wherein the window includes a wedge angle that differs from the nominal wedge angle by less than 0.1 arcminutes.

20. A method for optical measurement, comprising: A measurement system is set up in a first environment, wherein the measurement system performs one or more measurements on a region in a second environment along the optical axis of the measurement system, the second environment being different from the first environment; The measurement system is isolated from the second environment by using a window that is set to intersect the optical axis; as well as Based on the window settings, at the main focal point of the radiation collector, the lateral displacement relative to the optical axis is limited to be less than 50 micrometers different from the nominal lateral displacement relative to the optical axis.

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