Semiconductor technology installation and method for inspecting an optical surface

Abstract

The invention relates to a semiconductor technology installation, in particular an EUV lithography installation, comprising: a housing (25), in which a plurality of preferably reflective optical elements (M1, M2,...) are provided in a beam path (33) of the semiconductor technology installation; and an inspection device, in particular a camera (30), which comprises an imaging optical unit (31) for imaging at least one sub-region (T1, T2,...) of an optical surface (M1', M2',...) of at least one optical element (M1, M2,...) to be inspected in the housing (25) onto a spatially resolving detector (32). The inspection device is designed to image at least the sub-region (T2, T3,...) of the optical surface (M2', M3',...) of the optical element (M2, M3,...) to be inspected via at least one optical surface (M1', M2',...) of at least one optical element (M1, M2,…), which is situated in the beam path (33) between the optical element (M2, M3,...) to be inspected and the inspection device in the housing (25). The invention further relates to an associated method.

Description

[0001] Stuttgart, December 1st, 2025 SZ00396PCT Rp / pt

[0002] Semiconductor technology system and methods for inspecting an optical surface

[0003] Reference to related registration

[0004] This application claims priority over German patent application DE 102024139070.0 dated 19.12.2024, the entire disclosure content of which is incorporated by reference into this application.

[0005] Background of the invention

[0006] The invention relates to a semiconductor technology system, in particular an EUV lithography system, comprising: a housing in which a plurality of preferably reflective optical elements are arranged in a beam path of the semiconductor technology system, and an inspection device, in particular a camera, which has an imaging optic for imaging at least a partial area of ​​an optical surface, in particular the entire optical surface, of at least one of the optical elements onto a spatially resolving detector.The invention also relates to a method for inspecting an optical surface of at least one optical element, preferably a reflective optical element, which is arranged in a housing of a semiconductor technology system, the method comprising: imaging at least a partial area of ​​the optical surface of the optical element by means of an imaging optic of an inspection device onto a spatially resolving detector of the inspection device.

[0007] For the purposes of this application, a semiconductor technology system is defined as an optical system or optical arrangement for lithography.

[0008] 2024P00464WO 01.12.25 SZ00396PCT understood, i.e., an optical system that can be used in the field of lithography. Besides a lithography system used for the production of semiconductor components, the system can, for example, be an inspection system for inspecting a photomask (hereinafter also called a reticle) used in a lithography system, for inspecting a semiconductor substrate to be structured (hereinafter also called a wafer), or a metrology system used for measuring a lithography system or parts thereof, for example, for measuring a projection system.

[0009] The optical surfaces of optical elements, especially the reflective optical surfaces of mirrors used in semiconductor technology equipment, can degrade during operation. This means that contaminants, such as particles, can accumulate on the optical surfaces, and / or defects, such as scratches or holes, can occur. Therefore, it is advisable to inspect and monitor particularly cleanliness-critical areas of optical elements for impurities, such as contaminating material or particles, even when the optical elements are housed within a semiconductor technology equipment enclosure and the equipment is in operation at the end customer's site. Such an optical inspection for visualizing the optical surfaces is essential.Defects in optical surfaces can, for example, be used to plan the replacement of an optical element at an early stage or to assess the result of cleaning the optical surface after cleaning.

[0010] However, the accessibility of optical elements in their installed state is hampered by the housing in which they are located. The optical surfaces of such elements are therefore not readily visible from outside the housing, and optical inspection for detection is difficult.

[0011] 2024P00464WO 01.12.25 SZ00396PCT Detect impurities, defects or the like on their optical surfaces is therefore not readily possible.

[0012] It is generally possible to remove an optical element or mirror module (in which the respective mirror is installed) from the semiconductor technology system and then inspect it optically, for example using a camera, or to perform a visual inspection by an operator. However, removing a mirror or mirror module from its housing is a time-consuming and labor-intensive process, and may not be easily accomplished.

[0013] To inspect a mirror installed in a housing without removing it from the housing, an optical inspection in the form of a visual check by an operator can also be carried out, provided that the mirror or its optical surface can be seen from outside the housing through an opening formed in the housing.

[0014] Another way to perform the inspection is to use an endoscope camera, which is typically inserted manually into the housing through an opening. However, due to the mechanical, manual guidance of the endoscope camera, the images captured are not readily comparable. Furthermore, image acquisition in this case usually involves local, spot-like illumination of individual areas of the optical surface, resulting in localized image capture that is not spatially clearly defined. The detection of defects or residues on the optical surfaces depends on the angle of incidence of the illumination radiation, as well as the wavelength and intensity of the radiation. Therefore, the detection of defects, flaws, or particles on the optical surface varies during manual use and cannot be complete.Accordingly, reproducibility of the inspection is important, especially if it is carried out by...

[0015] Since inspections are carried out by different operators (2024P00464WO 01.12.25 SZ00396PCT), this is not readily possible. Furthermore, information and media breaks typically occur during the inspection process, meaning that standardization and traceability of the generated information are not guaranteed. Additionally, there is a risk of collisions and damage to the optical elements or their optical surfaces caused by the endoscope.

[0016] DE 10 2021 201 690 A1 discloses in an embodiment that optical elements in an optical system, in particular in an optical system for EUV lithography, which are housed in a casing, can be inspected for impurities using a camera or a detector, which may be endoscopically designed. This takes advantage of the fact that openings can be provided permanently or temporarily, e.g., during maintenance breaks, in the optical system through which an endoscopic lens can be inserted to capture an image of the optical surface or element of interest. A light source, e.g., an LED, can be directed onto this optical surface through the same opening as the camera or through an additional opening.At the same time, it is possible to illuminate a light source directly from the object plane (reticule) or from the image plane (substrate) of a projection system of the EUV lithography system.

[0017] The optical system described in DE 10 2021 201 690 A1 can, in another embodiment, comprise the following: a light source for illuminating an illumination surface with light radiation, a detector with a detection surface for spatially resolved detection of the light radiation, a projection system configured to map the illumination surface onto the detection surface, and an evaluation device configured to use a

[0018] 2024P00464WO 01.12.25 SZ00396PCT The intensity of the illumination radiation at the detection surface is used to infer imperfections in optical elements in a beam path between the illumination surface and the detection surface. In this case, the optical system is configured to adjust different angular distributions of the illumination radiation traveling from the illumination surface to the detection surface, and the evaluation device is configured to infer imperfections in the optical elements, in particular the location of the imperfections, from the intensity of the illumination radiation at the detection surface at the different angular distributions.

[0019] Object of the invention

[0020] The object of the invention is to provide a semiconductor technology system and a method for inspecting an optical surface of an optical element in the installed state in a housing, which enable a reproducible inspection of the optical surface.

[0021] Subject matter of the invention

[0022] This problem is solved by a semiconductor technology system of the type mentioned above, in which the inspection device is designed to image at least the partial area of ​​the optical surface of the optical element to be inspected via at least one optical surface of at least one optical element arranged in the housing in the beam path between the optical element to be inspected and the inspection device.

[0023] The inventors recognized that it is advantageous to use the optical properties of the system for the inspection of optical surfaces of optical elements in a housing that are not accessible from the outside.

[0024] 2024P00464WO 01.12.25 SZ00396PCT to utilize semiconductor technology in which the optical elements to be inspected are installed. More precisely, the existing beam path of the optical elements in the semiconductor technology system is used for this purpose by performing the inspection over at least one optical surface or over at least one optical element that is arranged in the beam path between the optical element currently being inspected and the inspection device.

[0025] This is particularly possible if the optical element(s) are reflective and the optical surfaces are reflective surfaces where the beam path is folded or where the radiation propagating in the beam path is reflected or deflected. In this way, the optical element or surface to be inspected can be "reached" from the outside. The usually precisely known mounting positions of the respective optical elements in the housing, as well as the known optical properties of the optical elements, can be used to image the optical surfaces. The test specimen, i.e.,The entirety of the optical elements within the housing simultaneously serves as the imaging optics and generally enables the inspection of all optical elements arranged within the housing, particularly those that are inaccessible from outside the housing because there is no direct line of sight between the respective optical element to be inspected and the housing's surroundings. It is understood that the optical element(s) used for imaging do not necessarily have to be reflective; they can also be, for example, transmitting or semi-transmitting optical elements.

[0026] Typically, in the inspection of optical surfaces, a direct image is created between the optical surface to be inspected and the image.

[0027] 2024P00464WO 01.12.25 SZ00396PCT of the optical surface is evaluated on the spatially resolved detector, e.g., to identify scratches or the like on the imaged optical surface. With the type of imaging described here, it is advantageous or possibly necessary to link the primary information (i.e., the image) with knowledge of the optical properties of the semiconductor technology system, in particular the imaging optical properties of the semiconductor technology system, which are usually known in advance or can be determined by adjustment. For example, the image of a scratch on a surface, which is imaged by an intermediate mirror, can be altered by this mirror (e.g., by an imaging error in the form of distortion).At the same time, there may be properties of the optical surface of the intermediate optical element, for example, a mirror, that should be distinguished from the properties of the optical surface of the optical element to be inspected, e.g., scratches on the optical surface of the intermediate optical element. Such scratches can be detected by a prior inspection of the optical surfaces of optical elements located between the optical element to be inspected and the inspection device, and corrected accordingly during the inspection of the optical element to be inspected.

[0028] In one embodiment, the inspection device is positioned in the area of ​​an opening in the housing for the passage of the beam path. The housing typically has two openings, one for the entry and one for the exit of the radiation propagating along the beam path. The inspection device is typically arranged in the area of ​​one of the two openings to enable imaging of the optical element to be inspected. The inspection device, in the form of a camera, may optionally project wholly or partially into the interior of the housing.

[0029] 2024P00464WO 01.12.25 SZ00396PCT As a rule, at least part of the camera or camera housing is located outside the housing in which the optical elements to be inspected are located. This "external" inspection using the inspection device through the opening in the housing makes it possible to inspect the optical elements inside the housing without having to remove them.

[0030] In a further embodiment, the semiconductor technology system comprises at least one motion device for moving, in particular for displacement and / or rotation, at least the imaging optics and the spatially resolving detector of the inspection device relative to the housing. In particular, the entire inspection device, in the form of the camera, can be moved by means of the motion device(s), the movement preferably occurring in five or more degrees of freedom, typically three translational degrees of freedom and two rotational degrees of freedom. The movement of the inspection device or the camera makes it possible to inspect a desired partial area of ​​the optical surface of a respective optical element by adjusting a translational and rotational position of the camera or camera, which is usually determined beforehand by means of an adjustment.The imaging optics and detector are set to the optimal position for inspecting the respective mirror. It is understood that, if necessary, multiple translational and / or rotational positions of the camera can be set to inspect one and the same optical surface in order to inspect different sections of the optical surface. The focal length or focus position of the imaging optics can also be changed to inspect a specific section of the optical surface or the surfaces of different optical elements.

[0031] In one embodiment, the movement device is located at a predetermined installation position in relation to the housing, in particular in

[0032] 2024P00464WO 01.12.25 SZ00396PCT The movement device for moving the inspection device, typically in the form of a camera, is positioned in relation to an optical element located in the beam path adjacent to the opening in the housing. This is typically a fixed, repeatable installation position relative to the housing or the optical elements to be inspected. For this purpose, the movement device can be attached to the housing or to a receptacle provided on the housing for mounting the movement device and, if necessary, fixed in place. It is also possible to position the movement device at an installation position in the form of a defined point relative to the housing or the optical elements to be inspected, e.g., in a receptacle provided for this purpose, possibly without fixing it there. The installation position is determined in advance, i.e.,Before the inspection, the positions of the optical elements or their surfaces within the housing are typically calculated based on their known positions. Due to the high installation accuracy of the optical elements within the housing, the positions of their surfaces are usually precisely known.

[0033] To achieve the movement, the camera can be positioned or mounted in a predefined reference position on the motion device, from which the movement originates. The motion device has a stationary base whose position relative to the housing or the optical elements to be inspected remains fixed. The camera is moved relative to this stationary base. The motion device can be any Cartesian kinematic system, such as an XYZ kinematic system or a polar kinematic system, for example, a ball joint with a pushrod. A hexapod or similar device can also be used as the motion device.

[0034] 2024P00464WO 01.12.25 SZ00396PCT In a further embodiment, the semiconductor technology system includes a light source for illuminating the optical elements within the housing, preferably positioned in the area of ​​a further opening in the housing for the passage of the beam path. As described above, the housing typically has two openings, one for the entry of radiation into the housing and the other for the exit of radiation from the housing. It is advantageous if the inspection device is arranged at one of the two openings and a light source at the other opening to enable sufficient illumination of the optical surfaces of the optical elements within the housing. Such a light source enables full-surface and reproducible illumination of the optical surfaces of the optical elements.

[0035] When using a light source for illumination, the principle is exploited that the light radiation propagates from the light source along the beam path in the region of the opening, and therefore typically reaches the optical surfaces of all optical elements arranged in the housing. The light source can also illuminate one or more of the optical elements through other openings in the housing. The light source can be positioned outside the housing, but it is also possible for the light source to be positioned inside the housing for the inspection to take place.

[0036] The illumination radiation generated by the light source can be in the visible wavelength range, possibly also containing components in the UV wavelength range. The light source can therefore be, for example, a white light source. In this case, a conventional standard industrial camera can be used, enabling two-dimensional image acquisition using visible light. The acquisition and interpretation of the properties of the inspected optical surfaces is thus practically...

[0037] 2024P00464WO 01.12.25 SZ00396PCT exclusively in the spectral range of visible light, possibly including UV light, similar to an inspection with the eye or a visual inspection.

[0038] In another embodiment, the optical elements arranged in the housing form a projection optic for the semiconductor technology system, used to image an object plane onto an image plane. In this case, the semiconductor technology system is typically a lithography system, more precisely an EUV lithography system, for imaging a structure on a mask (reticle) located in the object plane onto a photosensitive substrate (wafer) located in the image plane. The illumination source can be located at the radiation-entry opening of the housing, near which the object plane is situated. In this case, the inspection device is typically positioned near the other, radiation-exit opening of the housing, close to the image plane. However, the positions of the illumination source and the inspection device can also be reversed.In principle, the light source can be positioned anywhere within the beam path of the semiconductor technology system or outside the beam path. The light source can be located outside the housing, but it is also possible to integrate it wholly or partially into the housing, for example, to illuminate individual optical elements for inspection.

[0039] In a further embodiment, the imaging optics of the inspection device have an adjustable focal length in order to image the optical surfaces, preferably of all optical elements arranged in the housing, at least in a respective partial area onto the spatially resolving detector. For imaging a respective optical surface or partial areas of the optical surfaces onto the spatially resolving detector, it is typically necessary to adjust the focal length to the distance between the respective optical surface and that of the inspection device.

[0040] 2024P00464WO 01.12.25 SZ00396PCT to be adjusted. The focal length typically corresponds essentially to the distance between the inspection device and the respective optical element to be inspected, with the distance between the inspection device and the optical element to be inspected being measured along the beam path. The imaging optics may, for example, include a zoom lens or a varifocal lens for adjusting the focal length, in which at least one optical element, usually a lens, is moved along the beam path. It is understood that during an inspection, not all optical elements present in the beam path need to be inspected; rather, the inspection may be limited to one or more optical elements. As described above, only a single sub-area of ​​the optical surface of a given optical element can be inspected if, for example,It is known that this sub-area is particularly susceptible to contamination or damage; however, multiple sub-areas can also be inspected or images of multiple sub-areas can be captured. If necessary, it is also possible to image not just a specific sub-area, but the entire optical surface onto the detector.

[0041] Typically, a one-time adjustment is performed before inspecting the optical elements of a given semiconductor technology system. During this adjustment, the focal length of the imaging optics, as well as the translational and rotational positions of the inspection device or camera, are determined to ensure optimal inspection of a specific section of the optical surface. Alternatively, instead of manual adjustment, the optimal translational and rotational positions and focal length of the camera can be calculated in advance.

[0042] During the inspection, the motion device is positioned with the camera at the installation position and a respective optical surface or a

[0043] 2024P00464WO 01.12.25 SZ00396PCT A specific section of an optical element to be inspected is inspected by setting the corresponding, pre-defined translational and rotational position of the camera relative to the base of the motion device or to the installation position of the motion device, as well as the camera's focal length. The images captured by the camera can be generated automatically, resulting in time savings. Due to the pre-settings described above and the arrangement of the motion device with the camera at the specified installation position, the images captured during inspection are reproducible, which increases their comparability and facilitates automated image analysis.

[0044] The captured images can be analyzed, for example, in an evaluation unit that is part of the semiconductor technology system. However, external analysis is also possible; that is, the evaluation unit does not necessarily have to be part of the semiconductor technology system. During inspection, a set or multiple images are typically captured. The properties or information in the images can then be spatially assigned to individual optical surfaces of the optical elements based on the known optical properties of the camera and the optical elements in the housing, as well as the translational and rotational position of the camera. Alternatively, the positions can be inferred from properties of the overall system.

[0045] Based on the images captured during inspection and the information contained therein, residues, contamination, and damage to the optical surfaces following accidents or similar events can be detected. The condition of the optical surfaces and the locations of anomalies, for example, for the identification and localization of particles on a specific optical surface and within the overall system, can be recorded during the inspection. Furthermore, a reproducible

[0046] 2024P00464WO 01.12.25 SZ00396PCT Comparison with the initial state of the optical surfaces of the optical elements is performed before operation of the semiconductor technology system or before a cleaning process. If necessary, suitable correction options or correction processes can be defined, carried out locally or across the entire surface, documented, evaluated, and assigned to the respective optical element to be inspected.

[0047] The inspection described here does not primarily focus on evaluating the optical properties of the overall system, such as the imaging characteristics of a projection optic system (i.e., wavefront, resolution, magnification, etc.). Instead, it prioritizes the optimal evaluation, detection, and, if necessary, correction of individual optical elements, such as mirror modules, as well as of corresponding systems. The inspection typically serves only as a qualitative optical assessment of surfaces within optical systems based on the degree of degradation, contamination, or damage.

[0048] The invention also relates to a method for inspecting an optical surface of an optical element as described above, in which the imaging of at least one partial area is carried out via at least one optical surface of at least another optical element arranged in a beam path between the optical element to be inspected and the inspection device in the housing. As described above in connection with the semiconductor technology system, optical elements arranged in the housing that are not accessible for inspection from outside the housing can also be inspected in this way, without having to insert an endoscope camera or the like into the housing for this purpose, which could potentially damage the optical elements or the optical surfaces.

[0049] 2024P00464WO 01.12.25 SZ00396PCT In one variant, imaging of at least a portion of the optical surface of the optical element is performed during or after a cleaning process for cleaning that portion of the optical surface. The inspection described above can be integrated into a process sequence for cleaning the optical surfaces of the optical elements. The inspection can serve, in particular, to reproducibly and repeatably detect, correct, and quantify cleanliness-critical conditions of the optical surfaces or portions thereof. The detection of the condition of the optical surface of a given optical element, as well as the cleaning effect, is reproducible and not dependent on a specific operator, as is the case with manual inspection.

[0050] Restoring optical properties during correction processes (e.g., cleaning, removing membrane residue, etc.) is possible when an endoscope camera is manually guided and appropriate local illumination and, if necessary, correction is performed. As described above, the concept described here also reduces collision damage because the illumination source, the inspection device, and, if applicable, the cleaning equipment or cleaning unit can be positioned far away from the optical surface. In particular, the cleaning unit is typically not spatially confined by the inspection device or by any illumination source used.

[0051] During the cleaning process, the cleanliness of the optical surface or a specific sub-area can be quantified after inspection. Based on this quantification, suitable measures can be defined, such as cleaning or replacing a particular optical element or mirror module. If cleaning is necessary, a suitable solution can be determined based on the inspection results.

[0052] 2024P00464WO 01.12.25 SZ00396PCT A cleaning strategy is defined and implemented. A subsequent inspection can follow the cleaning process or a specific cleaning step. Based on the inspection results, the cleanliness of the optical surface can be quantified again and compared to the target cleanliness level. If the target cleanliness level has not yet been reached, a new cleaning strategy can be defined, and the corresponding steps can be repeated—possibly several times—until the evaluation shows that the target cleanliness level of the optical element has been achieved.

[0053] In another variant, the inspection device is positioned in the area of ​​an opening in the housing for the passage of the beam path, wherein preferably at least a portion of an optical surface of an optical element arranged in the beam path adjacent to the opening in the housing is directly imaged onto the spatially resolving detector. As described above, the inspection device, particularly in the form of a camera, is generally positioned in the area of ​​an opening in the housing for the passage of the beam path. During inspection, the optical surface, or a respective portion thereof, of the optical surface of the optical element adjacent to the opening is typically imaged directly onto the detector by means of the imaging optics.

[0054] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments of the invention, with reference to the figures in the drawing, which show details essential to the invention, and from the claims. The individual features can be implemented individually or in any combination in a variant of the invention.

[0055] 2024P00464WO 01.12.25 SZ00396PCT Drawing

[0056] Examples of implementation are shown in the schematic drawing and are explained in the following description. It shows

[0057] Fig. 1 schematically shows a projection exposure system for EUV projection lithography in meridional section.

[0058] Fig. 2a is a schematic representation of a projection optic arranged in a housing of the projection exposure system of Fig. 1 with an endoscope camera for inspecting mirrors arranged in the housing.

[0059] Fig. 2b shows a schematic representation of a mirror module of the projection optics from Fig. 2a after removal from the projection exposure system.

[0060] Fig. 3 is a schematic representation of the projection optics of Fig. 2a with a camera arranged in the area of ​​an opening in the housing for inspecting the mirrors in the housing and with a light source in the area of ​​another opening in the housing.

[0061] Fig. 4 shows a schematic representation of the degrees of freedom of the camera from Fig. 3 when moved by means of the motion device, as well as

[0062] Fig. 5 shows a schematic representation of a flowchart of a combined inspection and cleaning process.

[0063] In the following description of the drawings, identical reference symbols are used for identical or functionally equivalent components.

[0064] 2024P00464WO 01.12.25 SZ00396PCT The following describes, with reference to Fig. 1, the essential components of an optical arrangement for EUV lithography in the form of a projection exposure system 1 for microlithography. The description of the basic structure of the projection exposure system 1 and its components is not intended to be restrictive.

[0065] One embodiment of a lighting system 2 of the projection exposure system 1 has, in addition to a light or radiation source 3, a lighting optic 4 for illuminating an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 can also be provided as a separate module from the rest of the lighting system. In this case, the lighting system does not include the light source 3.

[0066] A reticule 7 located in the object field 5 is illuminated. The reticule 7 is held by a reticule holder 8. The reticule holder 8 can be moved, particularly in one scanning direction, via a reticule displacement drive 9.

[0067] Figure 1 shows a Cartesian xyz coordinate system for illustrative purposes. The x-direction runs perpendicular to the plane of the drawing. The y-direction runs horizontally, and the z-direction runs vertically. In Figure 1, the scan direction runs along the y-direction. The z-direction runs perpendicular to the object plane 6.

[0068] The projection exposure system 1 comprises a projection system 10. The projection system 10 serves to image the object field 5 onto an image field 11 in an image plane 12. A structure on the reticulum 7 is imaged onto a light-sensitive layer of a wafer 13 located in the image field 11 in the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 is moved by a wafer transfer drive 15.

[0069] 2024P00464WO 01.12.25 SZ00396PCT can be displaced, in particular along the y-direction. The displacement of the reticle 7 via the reticle displacement drive 9 and of the wafer 13 via the wafer displacement drive 15 can be synchronized with each other.

[0070] Radiation source 3 is an EUV radiation source. Specifically, radiation source 3 emits EUV radiation 16, which is also referred to below as useful radiation, illumination radiation, or illumination light. The useful radiation has a wavelength in the range between 5 nm and 30 nm. Radiation source 3 can be a plasma source, for example, an LPP source (laser-produced plasma) or a DPP source (gas-discharged produced plasma). It can also be a synchrotron-based radiation source. Radiation source 3 can be a free-electron laser (FEL).

[0071] The illumination radiation 16 emanating from the radiation source 3 is focused by a collector mirror 17. The collector mirror 17 can be a collector mirror with one or more ellipsoidal and / or hyperboloid reflective surfaces. The at least one reflective surface of the collector mirror 17 can be illuminated by the illumination radiation 16 at grazing incidence (Gl), i.e., with angles of incidence greater than 45°, or at normal incidence (NI), i.e., with angles of incidence less than 45°. The collector mirror 17 can be structured and / or coated to optimize its reflectivity for the useful radiation and to suppress stray light.

[0072] After the collector mirror 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18.

[0073] 2024P00464WO 01.12.25 SZ00396PCT Intermediate focus plane 18 can represent a separation between a radiation source module comprising the radiation source 3 and the collector mirror 17, and the illumination optics 4.

[0074] The illumination optics 4 comprise a deflecting mirror 19 and, downstream of this in the beam path, a first faceted mirror 20. The deflecting mirror 19 can be a planar deflecting mirror or, alternatively, a mirror with an effect that influences the beam beyond the mere deflection effect. Alternatively or additionally, the deflecting mirror 19 can be designed as a spectral filter that separates a useful wavelength of the illumination radiation 16 from stray light of a different wavelength. The first faceted mirror 20 comprises a plurality of individual first facets 21, which are also referred to as field facets in the following. Only a few of these facets 21 are shown by way of example in Fig. 1. Downstream of the first faceted mirror 20 in the beam path of the illumination optics 4 is a second faceted mirror 22. The second faceted mirror 22 comprises a plurality of second facets 23.

[0075] The illumination optics 4 thus form a double-faceted system. This basic principle is also known as a honeycomb condenser (fly's eye integrator). With the aid of the second faceted mirror 22, the individual first facets 21 are imaged into the object field 5. The second faceted mirror 22 is the last beam-shaping, or indeed the last, mirror for the illumination radiation 16 in the beam path before the object field 5.

[0076] The projection system 10 comprises a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the projection exposure system 1.

[0077] 2024P00464WO 01.12.25 SZ00396PCT In the example shown in Fig. 1, the projection system 10 comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve, or any other number of mirrors Mi are also possible. The penultimate mirror M5 and the last mirror M6 each have an aperture for the illumination radiation 16. The projection system 10 is a double-obscured optic. The projection optic 10 has an image-side numerical aperture greater than 0.4 or 0.5, and which can also be greater than 0.6, for example, 0.7 or 0.75.

[0078] The mirrors Mi, just like the mirrors of the lighting optics 4, can have a highly reflective coating for the lighting radiation 16.

[0079] Fig. 2a shows a detail of a projection optic 10 of the projection exposure system 1 of Fig. 1 with a number i of mirrors Mi, which, as in Fig. 1, is i = 6, but can also be larger or smaller. The mirrors Mi are arranged in a housing 25, which has two openings 26a, 26b through which a beam path of the projection exposure system 1 (not shown in Fig. 2a) can pass. An endoscope camera 27 is inserted into the housing 25 through a first opening 26a and positioned near the third mirror M3 of the projection optic 10 for inspection. For this purpose, an operator can analyze the image captured by the endoscope camera 27 using a display 28 located outside the housing 25. During inspection, the operator typically guides the endoscope camera 27 manually through the housing 25 to a reflective optical surface M1', M2', M3', M4', ..., Mi' of a respective mirror M1 , M2, M3, M4, ... , Mi. However, due to the mechanical, manual guidance of the endoscope camera 27, the images recorded with the endoscope camera 27 are not readily comparable. There is also a risk of collision between the endoscope camera 27 and the respective surfaces to be inspected M1', M2', M3', M4', ... , Mi', which could result in damage. Alternatively or additionally

[0080] 2024P00464WO 01.12.25 SZ00396PCT a visual inspection can be carried out, as indicated by an eye in Fig. 2a. From outside the housing 25, typically only the mirror M1 adjacent to the first opening 26a can be inspected by visual inspection through the first opening 26a, and only the mirror Mi adjacent to the second opening 26b can be inspected through the second opening 26b.

[0081] Fig. 2b shows another possibility for inspecting the mirrors Mi, in which a mirror module 29, containing the fourth mirror M4, has been removed from the projection exposure unit 1. A visual inspection can be carried out on the removed mirror M4 (indicated by an eye in Fig. 2b) or the fourth mirror M4 can be inspected using a camera by taking an image of the reflecting optical surface M4' of the fourth mirror M4, as indicated by a camera in Fig. 2b.

[0082] To enable reproducible inspection of the optical elements M1, M2, ..., Mi in the housing 25, more precisely, reproducible inspection of their optical surfaces Mi', an inspection device in the form of a camera 30 is used in the embodiment shown in Fig. 3. The camera 30 is positioned in the area of ​​the first opening 26a in the housing 25. The camera 30 has imaging optics 31 for imaging at least a partial area T1, T2, ... of an optical surface MT, M2', ..., Mi' of each optical element M1, M2, ..., Mi to be inspected in the housing 25 onto a spatially resolving detector 32, which is also part of the camera 30. The camera 30 can be a conventional industrial camera sensitive to wavelengths in the visible and, if necessary, the UV wavelength range.

[0083] In the example shown in Fig. 3, the projection exposure system 1 also includes a movement device 34 for movement, in particular for

[0084] 2024P00464WO 01.12.25 SZ00396PCT Displacement and rotation, at least of the imaging optics 31 and the spatially resolving detector 32 of the camera 30 with respect to the housing 25 of the projection optics 10, or with respect to a fixed installation position EP of the movement device 34 with respect to the housing 25. In the example shown, the movement device 34 is configured to displace the entire camera 30 in three spatial directions x, y, z and to rotate it about two mutually perpendicular axes, as is greatly simplified in Fig. 4. Since the mirrors Mi are positioned at precisely predetermined positions within the housing 25, the installation position EP is also fixed with respect to the mirrors M1, M2, ... Mi arranged in the beam path 33.

[0085] The first mirror M1 is positioned at a distance L1 or d1 from the camera 30, more precisely from a predetermined position and orientation of the camera 30 with respect to the fixed installation position EP, along the beam path 33. The second mirror M2 is positioned at a distance d2 from the camera 30, which corresponds to the sum of the distance d1 and the distance L2 between the first mirror M1 and the second mirror M2 along the beam path 33, and so on. The distance dk of the mirror Mk (K = 1, ..., i), more precisely from its optical surface Mk' to the camera 30, is given by: d k = Ü k ■

[0086] The distance dk of the camera 30 to the optical surface MT, M2', ... , Mi' of the mirror M1 , M2, ... , Mi to be inspected is taken into account during the inspection by changing the focal length f of the imaging optics 31 of the camera 30 accordingly, so that the optical surface M1 ', M2', ... , Mi', more precisely a partial area T1 , T2, ... of the mirror M1 , M2, ... , Mi to be imaged, is located in the focal plane or imaging plane of the camera 30 and is imaged onto the spatially resolving detector 32.

[0087] 2024P00464WO 01.12.25 SZ00396PCT As can also be seen in Fig. 3, a partial area T1 of the optical surface MT of the first mirror M1 is imaged directly onto the spatially resolving detector 32 in this way. A partial area T2 of the optical surface M2' of the second mirror M2 is imaged onto the spatially resolving detector 32 via the first mirror M1 in the beam path 33, more precisely via its reflecting optical surface M2'. Similarly, a respective partial area T3, T4, ... of the third, fourth, ... mirror M3, M4, ... to be inspected is imaged onto the spatially resolving detector 32 of the camera 30 via the respective intermediate mirrors M2, M3, ... in the beam path 33, more precisely via their reflecting optical surfaces M2', M3', ... The size of the imaged partial area T1, T2, ...is usually limited by the size of the detector area of ​​detector 32, which typically cannot image the entire optical surface MT, M2', ... of a respective mirror M1 , M2, M3. ... .

[0088] The movement device 34, which can be designed, for example, as a hexapod or as Cartesian kinematics, e.g., as XYZ kinematics, or as polar kinematics, e.g., as a ball joint with a push rod, is used to set a translational and rotational position of the camera 30 that is optimal for inspecting the respective mirror M1, M2, ... or the respective sub-area T1, T2, ... to be imaged. It is understood that, if necessary, several translational and / or rotational positions of the camera 30 can be set for inspecting one and the same optical surface MT, M2', ... in order to inspect more than one sub-area T1, T2, ... of the respective optical surface M1, M2, ... . As a rule, the distances Lk along the beam path 33 change when imaging different sub-areas of one and the same mirror M1, M2, ... , Mi, which is relevant during imaging or...The distance dk is taken into account when setting the focal length f.

[0089] The position of the camera 30 to the respective optical surface MT, M2', ... , Mi' or to the respective sub-area T1 , T2, ... to be imaged also depends on the rotational and translational position of the camera 30 determined in advance by the adjustment, which is also taken into account during imaging or when setting the focal length f.

[0090] A control device of the projection exposure system 1, which may be designed in the form of suitable hardware and / or software, can be used to adjust the focal length f of the imaging optics 31 as well as the respective translational and / or rotational positions of the camera 30.

[0091] A light source 35 is also provided in the housing 25 for illuminating the optical elements M1, M2, ... In the example shown in Fig. 3, it is positioned in the region of a second opening 26b of the housing 25 for the passage of the beam path 33. The first opening 26a is arranged near the image plane 12 of the projection optics 10 of the projection exposure system 1 of Fig. 1, and the second opening 26b is arranged at or near the object plane 6 of the projection optics 10 of Fig. 1. The light source 35 is designed as a white light source in Fig. 3 and generates illumination radiation essentially in the visible wavelength range as well as in the UV wavelength range. The illumination radiation enters the housing 25 at the second opening 26b and is reflected by the optical surfaces MT, M2', ...within the beam path 33, the light is reflected, thus enabling illumination of all optical elements M1, M2, ..., Mi arranged in the housing 25. It is also possible to arrange the light source 35 or, if necessary, another light source within the housing 25, e.g., to selectively illuminate one of the optical elements M1, M2, ..., Mi.

[0092] 2024P00464WO 01.12.25 SZ00396PCT The illumination source 35 ideally illuminates the entire optical surfaces MT, M2', ... of the optical elements M1, M2, ... in the beam path 33. The size of the imaged sub-areas T1, T2, ... is determined in this case by the size of the detector area of ​​the detector 32 (so). In the event that the illumination source 35 only partially illuminates the optical surfaces MT, M2', ... it may be necessary, similar to the camera 30, to provide a movement device with translational and / or rotational degrees of freedom for the illumination source 35 in order to illuminate a respective sub-area T1, T2, ... of a respective optical surface MT, M2', ... imaged onto the detector 32. It is also possible that the lighting source 35 is designed to adjust different lighting settings in order to enable optimal illumination of the respective optical surfaces MT, M2', ... .For this purpose, the light source 35 can, for example, have adjustable apertures or the like. Changing the wavelength of the illumination radiation is also possible. For this purpose, the light source 35 can, for example, have adjustable wavelength filters.

[0093] The inspection of mirrors M1, M2, ..., Mi in housing 25, as described above, can be carried out at different times, for example, immediately after commissioning the projection optics 10 or after commissioning the projection exposure unit 1. It is also possible to use a different type of trigger to detect the cleanliness status of mirrors M1, ..., Mi through inspection. This might be the case, for example, if cleaning of mirrors M1, M2, ..., Mi is required, typically because the transmission of the projection optics 10 falls below a threshold during operation and / or because image aberrations become more pronounced.

[0094] Fig. 5 shows in a flowchart how the process described above works.

[0095] Inspection can be used during a cleaning process. In a

[0096] 2024P00464WO 01.12.25 SZ00396PCT In the first step, the inspection device, in the form of the camera 30, is inserted into the projection exposure unit 1, specifically in the area of ​​the first opening 26a in the housing 25. In a subsequent step, the cleanliness of the mirrors M1, M2, ..., Mi is evaluated and quantified based on the images taken during the inspection of the respective sub-areas T1, T2, ..., Ti of the optical surface MT, M2', ..., Mi' of the respective mirrors M1, M2, ..., Mi. The evaluation can be automated or, if necessary, performed by an operator. Measures to be carried out on the mirrors M1, M2, ..., Mi can be derived from the evaluation, whereby the measures can be defined individually for each of the mirrors M1, M2, ..., Mi.

[0097] In this evaluation step, it can be decided, for example, that cleaning a particular inspected mirror M1, M2, ..., Mi is not possible and that the respective mirror M1, M2, ..., Mi needs to be replaced. In this case, the respective mirror M1, M2, ..., Mi is replaced by removing the corresponding mirror module from the housing 25, e.g., as shown in Fig. 2b for the fourth mirror M4. It can also be determined that the respective mirror M1, M2, ..., Mi should only be replaced at a later date.

[0098] If replacement of the respective mirror M1, M2, ..., Mi is not required, a cleaning strategy can be individually defined for each mirror M1, M2, ..., Mi, which will be implemented during subsequent cleaning. This cleaning could involve, for example, cleaning with a cleaning gas, such as carbon dioxide or CO2 snow, or another type of cleaning method.

[0099] In a subsequent inspection step following the cleaning step, the cleanliness of the optical surfaces MT, M2', ... , Mi' can be quantified again.

[0100] 2024P00464WO 01.12.25 SZ00396PCT and are evaluated against a target state. The fact that the images B (see Fig. 3) recorded by the spatially resolved detector 32 during inspection are reproducible is advantageous here, meaning that a comparison between the actual state and a predetermined target state regarding the cleanliness of the respective sub-area T1, T2, ..., Ti of the corresponding surface MT, M2', ..., Mi' is easier than if the images B were recorded by an operator by inserting an endoscope camera or the like into the housing 25 is advantageous.

[0101] Depending on the result of the comparison between the actual state and the target state of the optical surface MT, M2', ... , Mi', the cleaning process is either terminated (OK in Fig. 5) or a new cleaning strategy is defined (NOK in Fig. 5) and further cleaning is carried out, followed by inspection and evaluation of the cleanliness. It is understood that the cleaning steps may need to be repeated several times until the target state or a sufficiently small deviation from the target cleanliness state of the respective mirrors M1 , M2, ... , Mi is achieved.

[0102] 2024P00464WO 01.12.25 SZ00396PCT

Claims

Patent claims 1. Semiconductor technology system, in particular EUV lithography system (1), comprising: a housing (25) in which a plurality of preferably reflective optical elements (M1, M2, ... ) are arranged in a beam path (33) of the semiconductor technology system, an inspection device, in particular a camera (30) which has an imaging optic (31 ) for imaging at least a partial area (T1, T2, ... ) of an optical surface (MT, M2', ... ) of at least one optical element (M1, M2, ... ) to be inspected in the housing (25) onto a spatially resolving detector (32), characterized in that the inspection device is configured to image at least the partial area (T2, T3, ... ) of the optical surface (M2', M3', ... ) of the optical element (M2, M3, ... ) to be inspected via at least one optical surface (MT, M2', ... ) of at least one in the beam path (44) between the optical element to be inspected (M2, M3, ...) and the optical element (M1 , M2, ... ) arranged in the housing (25) of the inspection device.

2. Semiconductor technology system according to claim 1, wherein the inspection device is positioned in the area of ​​an opening (26a) in the housing (25) for the passage of the beam path (33).

3. Semiconductor technology system according to claim 1 or 2, further comprising: at least one motion device (34) for moving, in particular for displacing and / or rotating, at least the imaging optics (31) and the spatially resolving detector (32) of the inspection device in relation to the housing (25). 2024P00464WO 01.12.25 SZ00396PCT 4. Semiconductor technology system according to claim 3, wherein the motion device (34) is positioned at a predetermined installation position (EP) with respect to the housing (25), in particular with respect to an optical element (M1) arranged in the beam path (33) adjacent to the opening (26a) in the housing (25).

5. Semiconductor technology system according to one of the preceding claims, further comprising: an illumination source (35) for illuminating the optical elements (M1 , M2, ... ) in the housing (25), which is preferably positioned in the area of ​​a further opening (26b) of the housing (25) for the passage of the beam path (33).

6. Semiconductor technology system according to one of the preceding claims, wherein the optical elements (M1 , M2, ... ) arranged in the housing (25) form a projection optic (10) of the semiconductor technology system for imaging an object plane (6) onto an image plane (12).

7. Semiconductor technology system according to one of the preceding claims, wherein the imaging optics (31) of the inspection device has an adjustable focal length (f) to image the optical surfaces (MT, M2', ...) preferably of all optical elements (M1, M2, ...) arranged in the housing (25) at least in a respective partial area (T1, T2, ...) onto the spatially resolving detector (32).

8. Method for inspecting an optical surface (M2', M3', ... ) of at least one optical element, preferably a reflective optical element (M2, M3, ... ), which is arranged in a housing (25) of a semiconductor technology system, in particular a semiconductor technology system according to one of the preceding claims, comprising: 2024P00464WO 01.12.25 SZ00396PCT Imaging at least one partial area (T1 , T2, ... ) of the optical surface (M2', M3', ... ) of the optical element (M2, M3, ... ) by means of an imaging optic (31 ) of an inspection device, in particular a camera (30), onto a spatially resolving detector (32) of the inspection device, characterized in that the imaging of the at least one partial area (T2, T3, ... ) is carried out via at least one optical surface (MT, M2', ... ) of at least one further optical element (M1 , M2, ... ) arranged in a beam path (44) between the optical element (M2, M3, ... ) to be inspected and the inspection device in the housing (25).

9. Method according to claim 8, wherein the imaging of at least one partial area (T2, ... ) of the optical surface (M2', ... ) of the optical element (M2, ... ) is carried out during or after a cleaning process for cleaning the partial area (T2, ... ) of the optical surface (M2', ... ).

10. Method according to claim 8 or 9, wherein the inspection device is positioned in the area of ​​an opening (26a) in the housing (25) for the passage of the beam path (33), wherein preferably at least a partial area (T1 ) of an optical surface (MT) of an optical element (M1 ) arranged in the beam path (33) adjacent to the opening (26a) in the housing (25) is directly imaged onto the spatially resolving detector (32). 2024P00464WO 01.12.25 SZ00396PCT

Images