Method for electron beam processing of a surface, optical component, semiconductor technology system, and manufacturing system

Abstract

The invention relates to a method for electron beam processing of a surface (25a) of an optical component, in particular a mirror (25) or a mirror substrate, the method comprising: irradiating the surface (25a) of the optical component with at least one electron beam (26) which, during the electron beam processing, is deflected within an irradiation region (28a) relative to a beam direction (Z) of the non-deflected electron beam (26). During the electron beam processing of the surface (25a), the optical component (25) is moved relative to the irradiation region (28a). The invention also relates to an optical component (25), a semiconductor technology system, and a manufacturing system which is designed to carry out the method for electron beam processing.

Description

[0001] Method for electron beam processing of a surface, optical component, semiconductor technology system and manufacturing plant

[0002] Reference to related registration

[0003] This application claims priority over German patent application DE102024205315.5 of June 10, 2024, the entire disclosure of which is incorporated by reference into this application.

[0004] Background of the invention

[0005] The invention relates to a method for electron beam processing of a surface of an optical component, in particular a mirror or a mirror substrate, comprising: irradiating the surface of the optical component with at least one electron beam which, during electron beam processing, is deflected relative to a beam direction of the undeflected electron beam within an irradiation area. The invention also relates to an optical component and a semiconductor technology system comprising at least one such optical component. The invention also relates to a manufacturing system for electron beam processing of a surface of an optical component with at least one electron beam.

[0006] Electron beam processing can be performed on optical components, such as mirror substrates or pre-coated mirrors with a mirror substrate, in which the substrate material is locally compacted. This local compaction leads to a change in the surface shape of the substrate at the point where the electron beam strikes. If the local compaction, or the irradiation dose introduced locally into the material, is appropriately controlled, the surface shape of the irradiated surface can be corrected and a desired surface shape can be achieved (see, for example, WO2017 / 148577A1). The locally introduced irradiation dose depends on the exposure time and the electron current.

[0007] Electron irradiation to correct the surface shape is possible both before and after the application of a reflective coating to a substrate.

[0008] German patent DE102011084117A1 describes a method for producing a reflective optical element in which a substrate is irradiated with electrons and, after irradiation, coated with at least one layer subsystem suitable for the EUV wavelength range. The patent also describes a method for correcting the surface shape of a finished coated reflective optical element by electron irradiation.

[0009] In electron beam processing, the electron beam is deflected within an irradiation field and typically scanned across the surface. For optical components with a large surface area, the problem arises that the maximum deflection angle of the electron beam, and thus the irradiation area on the surface, is limited. To increase the irradiation area on the surface while maintaining the same maximum deflection angle, it is necessary to scale the distance between the surface and the electron beam source—more precisely, a deflection device of the electron beam source—as the surface area of ​​the optical component being processed increases. If the irradiation area is increased by enlarging the electron beam's irradiation field by increasing the maximum deflection angle, the problem arises that the tool, i.e.,The shape of the electron beam at any given position on the surface varies depending on the deflection angle of the electron beam, with the variation of the tool and thus the beam shape increasing with increasing deflection angle. Using a large maximum deflection angle leads to significant effects when electron beam processing optical components with large optical surfaces.

[0010] Object of the invention

[0011] The object of the invention is to provide a method for the efficient electron beam processing of optical components with a large surface area to be processed. The object of the invention is also to provide an optical component, a semiconductor lithography system, and a manufacturing system.

[0012] Subject matter of the invention

[0013] This task is solved, according to one aspect, by a method of the type mentioned above, in which the optical component is moved relative to the stationary irradiation area during electron beam processing of the surface. The irradiation area describes the region on the surface of the optical component that can be irradiated by the electron beam when the beam is deflected. The irradiation area is limited by the maximum deflection angle of the electron beam and, if necessary, by an aperture that limits the beam path or the irradiation field of the electron beam at its edges. In the prior art, the optical component is stationary during electron beam processing and is not moved relative to the also stationary electron source when the electron beam is deflected and scanned across the entire surface of the optical component.

[0014] In the method according to the first aspect of the invention, the optical component is moved relative to the electron beam irradiation area on the surface during electron beam processing. This movement of the optical component relative to the irradiation area allows for a comparatively small distance between the electron source or deflection device and the surface of the optical component when processing large optical components, thus reducing the height and dimensions of the electron beam processing apparatus. In this way, the spatial variation of the electron beam shape on the surface of the optical component can also be reduced, since the maximum deflection angle of the electron beam does not need to be increased during electron beam processing.

[0015] Preferably, the optical component is moved in a plane perpendicular to the direction of the undeflected electron beam, in particular by continuous or stepwise displacement or scanning. The movement of the optical component typically takes the form of a displacement in a plane perpendicular to the direction of the undeflected electron beam, which is also referred to as the center beam. The center beam is located in the middle or at a central position of the irradiation field and is oriented perpendicular to the exit aperture of the electron beam source. Generally, the electron beam can be deflected from the center position in two mutually perpendicular directions up to a maximum deflection angle, which can be the same or different for both directions. With a constant maximum deflection angle, the size of the irradiation area on the surface increases with increasing pointer length.with increasing distance to the electron source or to the deflection device.

[0016] The optical component is mounted on a support, such as a table or similar structure, or placed on the support. The support is moved by means of a suitably designed motion system. As described above, the support can be configured to displace the optical component in a plane perpendicular to the central beam. If the irradiation area is rectangular or square, the optical component is typically displaced along one or two directions parallel to the edges of the irradiation area.

[0017] In one variant, during electron beam processing, at least two sub-areas of the surface are processed successively with the electron beam, and the optical component is moved step by step, in particular shifted step by step, to position a respective sub-area in the irradiation area of ​​the electron beam.

[0018] In this variant, the surface is divided into several sub-areas or segments. Each sub-area is typically processed with the electron beam within the irradiation zone, with the optical component positioned at a fixed location. The residence time map for electron beam processing is adjusted according to the position of the optical component. Using this stepwise processing method, also known as "stitching," optical components with arbitrarily large surface areas can be processed with a limited pointer length. During electron beam processing of a specific sub-area, the electron beam is generally scanned multiple times across the sub-area to achieve the desired compaction of the optical component's material. When limiting the irradiation zone to treat relatively small sub-areas of the surface, it may be necessary to...The need for fixed apertures, which were previously attached to the optical component to limit the irradiation area and which had to be individually adapted for each type of optical component, can be eliminated.

[0019] The fact that the optical component is moved relative to the irradiation area during electron beam processing should not be interpreted as meaning that the surface must necessarily be irradiated with the electron beam during this movement. Rather, the electron beam can be switched off while the optical component is being moved to position the respective section within the irradiation area. In this case, electron beam processing comprises several processing steps, in which a specific section of the surface is treated with the electron beam. Between these processing steps, the optical component is moved without being irradiated with the electron beam. It is understood, however, that electron beam irradiation can also occur while the optical component is being moved.

[0020] In a further development of this variant, the optical component is moved when irradiating a boundary region between two adjacent sub-areas. As described above, in stepwise electron beam processing, each sub-area of ​​the surface is irradiated without moving the optical component. In a transition or boundary region between two adjacent sub-areas that are processed sequentially with the electron beam, undesirable edges can form during the "stitching" process. To avoid this, irradiation or scanning with the electron beam and movement of the optical component can be performed simultaneously in the transition or boundary region between two adjacent sub-areas, with a sliding adjustment of the image, the dwell time map, or the dwell time of the electron beam.In this way, a smooth transition between adjacent sub-areas can be achieved.

[0021] The movement, particularly the displacement of the optical component when irradiating the boundary region, can be faster than with a stepwise displacement of the optical component. This rapid displacement can be performed, in particular, parallel to the scanning direction of the electron beam to create an overlap region with the adjacent subregion at the lateral edge of a scan line. By moving the electron beam in the opposite direction in an adjacent scan line, the displacement can be reversed to irradiate the edge of the first subregion facing away from the boundary region with the electron beam. It may be necessary to adjust the residence time of the electron beam appropriately when irradiating the boundary region. For example, in the transition region or boundary region between the two adjacent subregions,Before the component is moved stepwise, only a portion, for example half, of the required dose is applied compared to the irradiation of a given sub-area. The remaining portion of the required dose, for example the second half, is applied in the boundary region after the component has been moved stepwise to position the second sub-area within the electron beam's irradiation area. This avoids sharp edges, as the two sub-areas overlap due to the rapid movement during the transfer, without requiring any reduction in size of either sub-area. It is also possible for the boundary region to be irradiated throughout the entire transfer of the optical component, i.e., until the transition between two adjacent sub-areas is complete.

[0022] In another variant, during electron beam processing of the surface, the optical component is continuously shifted in a displacement direction that is preferably oriented perpendicular to a scan direction of the electron beam. Electron beam processing can also involve a superimposed movement of the electron beam and the optical component. In the simplest case, the electron beam can be deflected in only one direction or along one axis, which forms the scan direction, and the optical component can be shifted in a second direction perpendicular to the first. However, it is also possible for the electron beam to be deflected in two directions while the optical component is simultaneously shifted. For example, an oscillating movement perpendicular to the scan direction can be superimposed on the movement of the electron beam along the scan direction.

[0023] The variant described here can be combined with the variant described above, in which different sections of the surface are processed step by step with the electron beam. This is useful, for example, if the width of the irradiation field in the scan direction is smaller than the width of the surface to be irradiated. In this case, adjacent sections of the surface in the scan direction can be processed sequentially. If the longitudinal direction of the optical component corresponds to the translation direction, surfaces of any length can, in principle, be processed with the electron beam.

[0024] In another variant, the electron beam irradiation field during electron beam processing is limited by a stationary aperture. Conventional electron beam processing methods typically use a separate aperture for each type of optical component being processed to limit the irradiation area on the surface, with the aperture being attached to the optical component. In the variant described here, a fixed aperture relative to the electron source used to generate the electron beam is employed, which does not move with the optical component during electron beam processing. The aperture, or more precisely, the aperture opening, limits the irradiation field at its edges, thus correspondingly limiting the irradiation area on the surface.

[0025] The aperture can be used, particularly when processing multiple sub-areas as described above, to prevent the irradiation from one sub-area from encroaching on an adjacent sub-area, for example, during processing phases where the electron beam moves from one grid line to an adjacent grid line during scanning. The aperture can also be used to sharply define a "scanner slit" during continuous movement of the optical component or to suppress the "image regression." The fixed aperture can be permanently fixed in a predetermined position within the electron beam processing device, or its location or position within the device can be adjusted to allow for the selection of a specific irradiation area. Even in this case, the aperture remains fixed in position during electron beam processing.The stationary aperture can have a fixed aperture with a predetermined geometry or area and allow the electron beam to pass only within a predetermined beam angle. Alternatively, the geometry or area of ​​the aperture itself can be adjustable to define the size of a given irradiation area. A second aspect of the invention, which can be combined with the first aspect described above, relates to a method of the type mentioned at the outset, further comprising: Simultaneously irradiating the surface of the optical component with at least one further electron beam, which is deflected to different positions within a further irradiation area during electron beam processing.

[0026] In this aspect of the invention, at least part of the electron beam processing is performed simultaneously or in parallel with at least two electron beams. The parallel use of two electron beams reduces the processing time compared to using a single electron beam. The parallel use of two or more electron beams is particularly advantageous for optical components with very large surface areas.

[0027] The simultaneous use of multiple electron beams is known from multi-beam microscopes, in which a multitude of electron beams are focused through a common objective lens onto the surface of a sample under investigation; see the

[0028] DE102021105201 A1 and DE102021205394B4 describe simultaneous electron beam processing with two or more electron beams for electron beam welding of two elongated material strips. However, electron beam processing of optical component surfaces to correct their surface shape is currently only performed with a single electron beam. It is understood that more than two electron beams can be used in electron beam processing to reduce the processing time. In one variant, during electron beam processing of the surface, the optical component is moved relative to the irradiation area of ​​the electron beam and / or relative to the further irradiation area of ​​the second electron beam.It is possible that the two or more electron beams on the surface of the optical component form two or more irradiation regions that partially overlap, are adjacent to one another, or are spaced apart. In all three cases, it is advantageous if the optical component can be moved relative to the irradiation region of a respective electron beam. The movement of the optical component can be carried out as described above in connection with the first aspect of the invention.

[0029] When using two or more electron beams for surface treatment, mutual interference between the electron beams can occur if they are directed at the surface at close intervals. It can therefore be advantageous to space the irradiation fields or areas between the electron beams. In this case, the optical component can be moved to irradiate surface areas located between the irradiation areas. Similarly, if the irradiation areas on the surface are adjacent, the optical component can be moved when irradiating a boundary between the irradiation areas or between adjacent irradiated surface areas to prevent the formation of edges at the boundary.

[0030] In a further development, during electron beam processing, a portion of the surface is processed with one electron beam and simultaneously another portion of the surface with a second electron beam. In this variant, as in the first aspect of the invention described above, "stitching" can be performed, i.e., the gradual processing of sub-areas with the two electron beams. However, it is also possible to choose a large number of electron beams, and thus a large number of sub-areas, so that the entire surface can be processed with the electron beams simultaneously without having to move the optical component.

[0031] In advanced scanning, the electron beam in one sub-area and the other electron beam in another sub-area are deflected synchronously (i.e., in the same direction) or asynchronously in the same scanning direction. Synchronous scanning prevents the two electron beams from approaching each other at the edges of adjacent sub-areas of the surface and thereby influencing or repelling each other due to their negative charges. The scanning direction is the direction along which the respective electron beams are scanned line by line across the surface. In synchronous scanning, the distance between the two electron beams on the surface in the scanning direction is essentially constant. Asynchronous deflection is also possible.

[0032] In a further development, the electron beam in one sub-area and the other electron beam in another sub-area are deflected synchronously or asynchronously, particularly in opposite directions, in a direction perpendicular to the scan direction. As described above, scanning along raster lines is performed line by line in the scan direction. At a respective lateral edge of the sub-area or irradiation area, the electron beam is deflected perpendicular to the scan direction in order to scan a raster line offset by the amount of the deflection. If the two electron beams are deflected in opposite directions perpendicular to the scan direction, the raster lines of the two sub-areas are scanned in opposite directions with the respective electron beams, and the distance between the two electron beams perpendicular to the scan direction is, on average, increased compared to a synchronous movement of the electron beams.In principle, a synchronous movement of the two electron beams in the direction perpendicular to the scan direction is also possible.

[0033] Another aspect of the invention relates to an optical component, in particular a mirror or a mirror substrate, which has a surface that has been processed by the electron beam processing method described above.

[0034] As described in the introduction, the process can be performed on either an uncoated optical component, such as a mirror substrate, or a coated optical component, such as a mirror. The optical component is made of a material that can be locally compacted by electron beam processing. This material can be, for example, glass, such as quartz glass, particularly titanium-doped quartz glass, or a glass-ceramic. Electron beam processing modifies the surface shape of the optical component, allowing it to approximate a desired surface shape.

[0035] In one embodiment, the surface has a maximum extent of more than 40 cm, preferably more than 70 cm, and particularly more than 90 cm. The maximum extent is understood to be the greatest possible distance between two points at the edge of the surface. In the case of a round surface, the maximum extent of the surface corresponds to the diameter of the surface. Another aspect of the invention relates to a semiconductor technology system, in particular an EUV lithography system, comprising: at least one optical component as described above. For the purposes of this application, a semiconductor technology system is understood to be an optical system for lithography, i.e., an optical system that can be used in the field of lithography.In addition to a lithography system used for the production of semiconductor components, the system may, 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.

[0036] Semiconductor technology systems can be operated using useful radiation in the form of EUV radiation. EUV radiation is defined as radiation in a wavelength range between approximately 5 nm and 30 nm, for example, at 13.5 nm. Since EUV radiation is strongly absorbed by most known materials, it is typically guided through the semiconductor technology system using optical elements in the form of EUV mirrors. These mirrors have a reflective coating applied to the surface of a substrate. This reflective coating can be a multilayer coating consisting of alternating layers of two materials with different refractive indices. When using EUV radiation at a useful wavelength of 13.5 nm in the semiconductor technology system, the materials are typically molybdenum and silicon.Another aspect of the invention relates to a manufacturing system of the type mentioned above, which is configured to carry out the electron beam processing method described above. The manufacturing system comprises at least one electron beam source for irradiating the surface of the optical component with at least one electron beam. The manufacturing system, more precisely the electron beam source, is typically configured to deflect the electron beam within an irradiation area relative to a beam direction of the undefended electron beam during electron beam processing.

[0037] The manufacturing system, or more precisely, a motion system of the manufacturing system, can be configured to move the optical component relative to the irradiation area during electron beam processing of the surface. Alternatively or additionally, the manufacturing system can be configured to simultaneously irradiate the surface of the optical component with at least one further electron beam, which is deflected within a separate irradiation area during electron beam processing. For this purpose, the manufacturing system can include at least one additional electron beam source. The manufacturing system can also include a stationary aperture that limits the irradiation field of the electron beam.

[0038] 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.

[0039] The schematic drawing illustrates exemplary implementations and explains them in the following description. It shows

[0040] Fig. 1 schematically shows a meridional section.

[0041] Projection exposure system for EUV projection lithography,

[0042] Fig. 2a-c schematic representations of electron beam processing of a mirror surface, in which three sub-areas of the surface are processed successively with an electron beam,

[0043] Fig. 3 shows a schematic top view of the surface of a mirror that is moved perpendicular to a scan direction of the electron beam during electron beam processing.

[0044] Fig. 4a, b schematic representations analogous to Fig. 2a-c, in which the mirror is irradiated simultaneously with two electron beams in two different sub-areas, as well as

[0045] Fig. 5 is a schematic representation analogous to Fig. 3 with a stationary aperture to limit the irradiation field of one of the electron beams of Fig. 4a.

[0046] In the following description of the drawings, identical reference symbols are used for identical or functionally equivalent components.

[0047] The following section 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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 plane 12 within the area of ​​the image field 11. The wafer 13 is held by a wafer holder 14. The wafer holder 14 can be displaced, particularly along the y-direction, via a wafer transfer drive 15. The displacement of the reticulum 7 via the reticulum transfer drive 9 and of the wafer 13 via the wafer transfer drive 15 can be synchronized with each other.

[0052] 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).

[0053] 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. After the collector mirror 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18.The 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.

[0054] 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.

[0055] 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.

[0056] 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 unit 1. 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 optical system. The projection optics 10 have 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.

[0057] The mirrors Mi, just like the mirrors of the lighting optics 4, can have a highly reflective coating for the lighting radiation 16.

[0058] Figures 2a-c show an optical component in the form of a mirror 25. The mirror 25 could, for example, be one of the mirrors Mi of the projection optics 10. The mirror 25 has a mirror substrate and a reflective coating for the illumination radiation 16, which comprises, for example, alternating layers of silicon and molybdenum. At the top of the uppermost layer of the reflective coating, the mirror 25 has a surface 25a that forms an interface with the environment.

[0059] The surface 25a of the mirror 25 is irradiated with an electron beam 26 to locally compact the substrate material of the mirror 25 and thus create a desired surface shape of the mirror 25. The electron beam 26 is generated by an electron beam source 27, which is configured to deflect the electron beam 26 within an irradiation field 28 in order to direct it to different positions in an irradiation area 28a on the surface 25a of the mirror 25. For this purpose, the electron beam 26 is deflected by means of a deflection device of the electron beam source 27 (not shown), which may, for example, include electrical or magnetic components.For details of the construction of the electron beam source 27 and for details of the relationship between the local compaction by the electron beam 26 and the local surface shape of the mirror 25, reference is made to WO2017 / 148577A1, which is incorporated in its entirety by reference into this application.

[0060] As indicated in Fig. 2a-c, the irradiation field 28 of the electron beam source 27 is limited in the X-direction of an XYZ coordinate system by a maximum deflection angle of the electron beam 26, which is determined by the deflection device. In the example shown, the stationary irradiation field 28 of the electron beam source 27 has a square base shape, such that an irradiation area 28a of the irradiation field 28 at the surface 25a, in which a first sub-area T1 of the surface 25a is positioned, also has a square base shape.

[0061] As can be seen in Fig. 2a, the surface area 25a of the mirror 25 is larger than the first sub-area T1. To irradiate the entire surface area 25a of the mirror 25, the mirror 25 is first irradiated in the first sub-area T1 by deflecting the electron beam 26 and scanning it over the first sub-area T1 until the entire first sub-area T1 has been irradiated. After irradiating the first sub-area T1, the mirror 25 is moved relative to the irradiation area 28a of the electron beam 26, more precisely, it is shifted in the X-direction. The X-direction lies in an XY plane that is perpendicular to the beam direction Z of the undeflected electron beam 25. The beam direction Z is oriented perpendicular to the flat surface 25a shown in the example.For displacement in the XY plane, the mirror 25 is mounted on a support 29 in the form of a movable table, which can be moved in the X direction and also in the Y direction by means of a motion system not shown in the image.

[0062] Starting from the position shown in Fig. 2a, the mirror 25 is moved until a second, adjacent sub-region T2 of the surface 25a is positioned within the irradiation area 28a of the electron beam source 27. In an irradiation step shown in Fig. 2b, the second sub-region T2 of the surface 25a is irradiated with the electron beam 26 by scanning the surface 25a and deflecting it within the irradiation field 28.

[0063] In a subsequent step, the mirror 25 is moved further in the X-direction until a third sub-area T3 of the surface 25a is positioned within the irradiation area 28a of the electron beam source 27. In a third irradiation step, the third sub-area T3 of the surface 25a is irradiated with the electron beam 26 by scanning it across the surface 25a. During the irradiation of the respective sub-areas T1, T2, and T3, the mirror 25 remains stationary. The electron beam 26 can be switched off during the stepwise movement of the mirror 25, but this is not strictly necessary.

[0064] During the electron beam processing described in connection with Fig. 2a-c, the surface 25a was divided into a total of nine sub-areas, three of which, T1, T2, and T3, are shown in Fig. 2a-c. Three of the six remaining sub-areas are arranged offset by the same amount in the Y-direction relative to the three sub-areas T1, T2, and T3 and can be processed with the electron beam 26 as shown in connection with Fig. 2a-c when the mirror 25 is moved accordingly in the Y-direction. In this way, the entire surface 25a of the mirror 25 can be processed stepwise with the electron beam 26. As can also be seen in Fig. 2a-c, each pair of adjacent sub-areas T1, T2; T2, T3 of the surface 25a abuts each other in the X-direction at a respective boundary region G12, G23. To eliminate edges or artifacts during the stepwise electron beam processing of the sub-areas T1, T2; T2, T3, ...To avoid this, it is advantageous if, during electron beam processing of the respective boundary area G12, G23, the mirror 25 is moved, more precisely shifted in the X direction.

[0065] For example, it is possible that the electron beam 26 is guided from left to right across the first sub-area T1 during scanning, so that it reaches the boundary region G12 at the end of the irradiation of the first sub-area T1. If the mirror 25 is moved in the X-direction to position the second sub-area T2 in the irradiation region 28a of the electron beam 26, the electron beam 26 can continue scanning the boundary region G12 while the electron beam 26 is deflected from the right side of the irradiation region 28 to the left side of the irradiation region 28a in a movement synchronous with the movement of the mirror 25. Once the second sub-area T2 of the mirror 25 is positioned in the irradiation region 28a, the irradiation of the second sub-area T2 can continue with the mirror 25 in a fixed position.It is also possible that when irradiating the respective boundary area G12, G23, the mirror 25 is moved quickly in the X direction and at the same time the residence time control is appropriately adjusted.

[0066] In this case, for example, in the example shown in Fig. 2a, the electron beam 26 can be moved scanning from left to right in the X-direction, and when the electron beam 26 reaches the right edge of the irradiation area 28a at the boundary region G12, the mirror 25 can be quickly moved to the left in the X-direction to create an overlap region with the adjacent subregion T2 at the lateral right edge of each scan line. When the electron beam 26 moves from the right to the left edge of the irradiation area 28a in an adjacent scan line offset in the Y-direction, the movement of the mirror 25 is reversed to also irradiate the left edge of the first subregion T1 with the electron beam 26. Additionally, when irradiating the boundary region G12, the residence time of the electron beam 26 is appropriately adjusted. Thus, for example, in the transition region or boundary region G12,Half the required dose is delivered compared to the irradiation of the first sub-area T1. The second half of the required dose is delivered in the boundary region G12 after the mirror 25 has been moved to position the second sub-area T2 in the irradiation region 28a of the electron beam 26, i.e., when the mirror 25 assumes the position shown in Fig. 2b. To deliver the second half of the dose, the mirror 25 is rapidly moved from the position shown in Fig. 2b, as described above. This procedure avoids sharp edges in the boundary region G12 between the two sub-areas T1 and T2, since the two sub-areas T1 and T2 overlap due to the rapid movement during the transfer, without the need to reduce the size of either sub-area T1 or T2 for this purpose.

[0067] Fig. 3 shows an example in which, during electron beam processing, the mirror 25 is also displaced relative to the irradiation area 28a of the electron beam 26, which in this example is linear. The irradiation area 28a in this example has an extension in the X-direction that is essentially limited to the width of the electron beam 26; that is, the electron beam 26 is deflected from its central position only in the positive and negative Y-directions, which correspond to the scanning direction of the electron beam 26. The mirror 25, whose surface 25a is shown in Fig. 3, is continuously displaced in the X-direction, i.e., transversely to the scanning direction Y, during electron beam processing. The electron beam 26 is indicated in Fig. 3 by a double arrow, the length of which corresponds to the extension of the irradiation area 28a on the surface 25a to be processed.

[0068] As can be seen in Fig. 3, the electron beam 26 can be moved in the scan direction Y across the entire width B of the surface 25a. The continuous translation of the mirror 25 in the X direction allows the entire surface 25a to be processed with the electron beam 26 without interrupting the electron beam processing. The maximum extent or length L of the surface 25a of the mirror 25 is greater than 40 cm in the example shown, but can also be greater than 70 cm or greater than 90 cm. The width B of the surface 25a is greater than 20 cm in the example shown.

[0069] Figures 4a and 4b show the electron beam treatment of the surface 25a of the mirror 25, in which, in addition to the electron beam source 27, a further electron beam source 27' generates a further electron beam 26', which is deflected within a further irradiation field 28'. The electron beam 26 irradiates a first sub-area T1 of the surface 25a of the mirror 25 in a first irradiation area 28a, while the further electron beam 26' simultaneously irradiates a second sub-area T2 of the surface 25a of the mirror 25 in a second irradiation area 28a'. The two irradiation areas 28a and 28a' of the electron beam sources 27 and 27' adjoin each other on the surface 25a of the mirror 25 in a boundary region G12 between the two adjacent sub-areas T1 and T2.If the surface 25a of the mirror 25 has only two sub-regions T1 and T2, it is not strictly necessary to move the mirror 25 during electron beam processing. However, rapid movement of the mirror 25 in the X-direction can be advantageous to avoid any edges or artifacts that may occur in the boundary region G12 between the two sub-regions T1 and T2. This may also be the case if the two sub-regions T1 and T2, or the irradiation fields 28 and 28' on the surface 25a, do not directly adjoin each other but overlap slightly.

[0070] A movement of the mirror 25 in the X-direction is also necessary if the two sub-areas T1, T2 or the irradiation fields 28, 28' of the two electron beam sources 27, 27' are spaced apart from each other, as shown in Fig. 4b. In this case, as described in connection with Figs. 2a-c, the mirror 25 can be moved in the X-direction to position a third and fourth sub-area T3, T4 of the mirror 25 in the respective irradiation area 28a, 28a' of the electron beam 26 or of the further electron beam 26'.

[0071] Due to the fact that the irradiation area 28a, and thus the irradiated sub-areas T1 and T2 of the surface 25a, are comparatively small, the use of apertures to limit the entire irradiation area can be dispensed with. However, it can be advantageous to use an aperture 30 to limit the irradiation field 28, as illustrated by way of example in Figs. 4a, b and in Fig. 5. The aperture 30 is fixedly arranged between the electron source 27 and the surface 25a of the mirror 25 and can, for example, be used to prevent the irradiation from extending into the adjacent sub-area T2 when switching from one grid line to the next during the scanning of the first sub-area T1, as shown in Fig. 5 for an aperture 30 with a rectangular aperture 31. An aperture of f / 30 can also be used to eliminate the "image relapse".In the example shown in Fig. 3, an aperture can also be used to define the “scanner slot”, i.e. the length and width of the irradiation area 28a used when scanning the electron beam 26.

[0072] Alternatively or in addition to electron beam irradiation of a coated mirror 25, a mirror substrate or another type of optical component, e.g., a lens, a plane-parallel plate, or the like, can also be subjected to electron beam processing in the manner described above. This is particularly advantageous if the optical component has a large surface area 25a.

[0073] The process described above can be carried out in a manufacturing plant designed for electron beam processing of the surface 25a of the optical component 25 with at least one electron beam 26, 26a. As described above, the manufacturing plant has for this purpose an electron beam source 27 and, optionally, at least one further electron beam source 27'.

Claims

Patent claims 1. Method for electron beam processing of a surface (25a) of an optical component (25), in particular a mirror or a mirror substrate, comprising: Irradiation of the surface (25a) of the optical component (25) with at least one electron beam (26), which is deflected relative to a beam direction (Z) of the undeflected electron beam (26) during electron beam processing within an irradiation area (28a), characterized in that the optical component (25) is moved relative to the irradiation area (28a) during electron beam processing of the surface (25a), wherein at least two sub-areas (T1, T2, T3, ...) of the surface (25a) are processed successively with the electron beam (26), wherein the optical Component (25) for positioning a respective sub-area (T1 , T2, T3, ...) in the irradiation area (28a) of the electron beam (26) is moved stepwise, in particular shifted stepwise, and wherein when irradiating a boundary area (G12, G23) between two adjacent sub-areas (T1 , T2; T2, T3) the optical component (25) is moved and a residence time of the electron beam (26) is adjusted to achieve a smooth transition between the two adjacent sub-areas (T1 , T2; T2, T3).

2. Method according to claim 1, wherein the optical component (25) is moved in a plane (X, Y) perpendicular to the beam direction (Z), in particular continuously or stepwise moved or scanned.

3. Method according to claim 1 or 2, wherein an irradiation field (28) of the electron beam (26) is limited by a fixed aperture (30).

4. Method according to the preamble of claim 1, in particular according to one of the preceding claims, further comprising: Simultaneous irradiation of the surface (25a) of the optical component (25) with at least one further electron beam (26') which is deflected within a further irradiation area (28a') during electron beam processing.

5. The method of claim 4, wherein during electron beam processing the surface (25a) the optical component (25) is moved relative to the irradiation field (28) of the electron beam (26) and relative to the further irradiation field (28') of the further electron beam (26').

6. Method according to claim 4 or 5, wherein at Electron beam processing involves irradiating a sub-area (T1) of the surface (25a) with the electron beam (26) and simultaneously another sub-area (T2) of the surface (25a) with the further electron beam (26'). / .Method according to claim 6, wherein the electron beam (26) in the sub-region (T1 ) and the further electron beam (26') in the further sub-region (T2) are deflected synchronously or asynchronously in the same scan direction (X).

8. Method according to claim 6 or 7, wherein the electron beam (26) is located in the partial region (T1) and the further electron beam (26') is located in the further The sub-area (T2) is deflected synchronously or asynchronously, in particular in the opposite direction, in a direction (Y) perpendicular to the scan direction (X).

9. Optical component, in particular mirror (25) or mirror substrate, which has a surface (25a) that is processed by an electron beam processing method according to any one of claims 1 to 8.

10. Optical component according to claim 9, wherein the surface (25a) has a maximum extent (L) of more than 40 cm, preferably more than 70 cm, in particular more than 90 cm.

11. Semiconductor technology system, in particular EUV lithography system (1), comprising: at least one optical component according to claim 9 or 10.

12. Manufacturing plant for electron beam processing of a surface (25a) of an optical component (25), in particular a mirror or a mirror substrate, with at least one electron beam (26, 26a), characterized in that the manufacturing plant is designed to carry out the method according to one of claims 1 to 8.

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