Apparatus and method for coating a substrate of an optical element

Abstract

The invention relates to an apparatus and to a method for coating an optical element. The invention can be used in particular for coating an optical element for a microlithographic projection exposure system designed for operation in the DUV or EUV range. An apparatus according to the invention has a substrate holder (160) and a source unit (110, 120, 210, 220, 230, 310, 410, 510) for applying and / or modifying a coating on a substrate (100, 200, 300, 400, 500) located on the substrate holder (160) during operation of the apparatus, wherein, during operation of the apparatus, a relative position between the source unit and the substrate located on the substrate holder can be variably adjusted, wherein the coating effect achieved on the substrate by the source unit can be manipulated depending on the adjusted relative position, wherein the source unit (110, 120, 210, 220, 230) has a first source (111, 121, 211, 221, 231) and at least one second source (112, 122, 212, 222, 232), and wherein the first source (111, 121, 211, 221, 231) and the at least one second source (112, 122, 212, 222, 232) differ from one another in terms of the operating principle underlying how in each case the coating is applied to and / or modified on the substrate (100, 200).

Description

[0001] Apparatus and method for coating a substrate of an optical element

[0002] This application claims priority from German patent application DE 10 2024 201 328.5, filed on February 14, 2024. The content of this DE application is incorporated by reference into the present application text.

[0003] BACKGROUND OF THE INVENTION

[0004] Field of the invention

[0005] The invention relates to a device and a method for coating an optical element. The invention is particularly applicable to coating an optical element for a microlithographic projection exposure system designed for operation in DUV or EUV.

[0006] State of the art

[0007] Microlithography is used to manufacture microstructured electronic components. The microlithography process is carried out in a so-called projection exposure system, which has an illumination device and a projection lens. The image of a mask (= reticle) illuminated by the illumination device is projected by the projection lens onto a substrate (e.g., a silicon wafer) coated with a light-sensitive layer (photoresist) and arranged in the image plane of the projection lens in order to transfer the mask structure onto the light-sensitive coating of the substrate. In the case of optical elements, such as those in the form of lenses or mirrors in the DUV range (i.e., at wavelengths of, for example, approximately 365 nm, approximately 248 nm, or approximately 193 nm) or in the form of mirrors in the EUV range (i.e.,at wavelengths of less than 30 nm, in particular less than 15 nm), the optimization of the respective coating, e.g. an anti-reflective (AR) or highly reflective (HR) coating, e.g. as a multi-layer system, particularly in the case of more strongly curved optical surfaces, represents a demanding challenge in view of the increasingly strict requirements in lithography systems, e.g. concerning the minimization of wavefront aberrations.

[0008] In practice, there is therefore a need to be able to influence the properties of the coating applied to the respective substrate of the optical element in a targeted manner and in a flexibly adapted manner to the respective conditions (in particular any existing substrate curvature) when coating an optical element.

[0009] As an example, reference is made to DE 10 2012 215 359 A1 for the state of the art.

[0010] SUMMARY OF THE INVENTION

[0011] It is an object of the present invention to provide a device and a method for coating an optical element, which enable a coating that is specifically adapted to the respective conditions, in particular in the case of comparatively strongly curved surfaces.

[0012] This problem is solved according to the features of the independent patent claims.

[0013] According to one aspect, the invention relates to a device for coating a substrate of an optical element, comprising a substrate holder; and - a source unit for applying and / or modifying a coating on a substrate located on the substrate holder during operation of the device;

[0014] - wherein during operation of the device a relative position between the source unit and the substrate located on the substrate holder can be variably adjusted;

[0015] - wherein the coating effect achieved by the source unit on the substrate can be manipulated depending on the set relative position;

[0016] - wherein the source unit comprises a first source and at least one second source; and

[0017] - wherein the first source and the at least one second source differ from one another with regard to their operating principle underlying the respective application and / or modification of the coating on the substrate.

[0018] The invention is based in particular on the concept of designing a coating process in which a relative movement is carried out between a source unit and a substrate holder or a substrate located on this substrate holder, in such a way that the coating effect can be specifically manipulated or varied depending on the current substrate position (relative to the source unit). The coating effect can be influenced in different ways, as described below with reference to various embodiments, and can include, for example, the implementation of additional relative movements, in particular for the flexibly variable alignment or tilting of the source unit or substrate, or other measures (e.g., a time-varying activation of the source unit or a variation of a bias voltage that may be applied to the substrate).

[0019] With the device and method according to the invention, the coating effect of the source unit (or of a source belonging to it as described below) can be specifically masked out, in particular depending on the currently coated substrate position, in order to, for example, specifically influence the properties of the coating (e.g., roughness). According to the invention, in order to achieve the desired location-dependent coating effect, the use of extended apertures, which is conventionally used for this purpose, can be dispensed with. According to the invention, the source unit has a first source and at least one second source. Furthermore, the first source and the at least one second source differ from one another with regard to the operating principle underlying the respective application and / or modification of the coating on the substrate.For example, the first source may be configured to apply coating material to the substrate and the second source may be configured to implant another material into a coating material.

[0020] In embodiments of the invention, the sources can also be mounted on different flanges. The term "source unit" or the "source(s)" present in such a source unit is to be understood within the context of the present application to include source units or sources used to apply coating material to the substrate, source units or sources used to remove coating material (e.g., ion sources), sources used to implant another (solid or gaseous) material into a coating material, and also source units or sources used to modify or influence coating material (e.g., heaters or lasers).

[0021] The targeted influencing or variation of the coating effect can be achieved, depending on the current substrate position, by coating different substrate areas with different coating materials or different mixing ratios of coating materials, for example Al, B, BN, B4C, Si nitride, Si carbide, Si boride, Mo nitride, Mo carbide, Mo boride, Ru nitride, Ru carbide, C, Ce, Cr, La, In, Mo, Mg, Ni, NiCr, Nb, Pd, Pt, Si, Sc, Ru, Rh, Ir, Ta, Ti, TiQ2, V, W, Y, Hf and / or Zr. In particular, mixed layers made of several different materials can be produced in a flexible and spatially resolved manner, whereby, for example, gradients of the mixing ratio can also be set in the growth direction of the produced coating.

[0022] According to one embodiment, a spatial extension of both the first source and the at least one second source along at least one geometric axis, in particular along two mutually perpendicular axes, is smaller than the respective spatial extension of the substrate.

[0023] According to one embodiment, the first source and the at least one second source are operable independently of each other.

[0024] According to one embodiment, the first source and the at least one second source differ from one another with respect to a coating material deposited on the substrate. In this way, different mixing ratios of the respective coating materials can be set for different substrate positions during the coating process, for example.

[0025] According to one embodiment, the manipulability of the coating effect depends on the set relative position via a variable adjustability

[0026] - the alignment, in particular tilting, of at least one source of the source unit relative to the substrate; and / or

[0027] - a twist angle of the substrate is implemented.

[0028] According to one embodiment, the manipulability of the coating effect depends on the set relative position via a variable adjustability

[0029] - the deposition or removal rate of at least one source of the source unit; and / or

[0030] - the radiation characteristic of at least one source of the source unit is implemented.

[0031] The variation of the radiation characteristic can, in particular, comprise a (discrete or continuous) switching from a comparatively narrow radiation characteristic or a small radiation angle of the source unit to a comparatively wide radiation characteristic or a larger radiation angle of the source unit, or vice versa. According to a further embodiment, the manipulation of the coating effect is implemented depending on the set relative position via a variable adjustment of an electrical bias voltage applied to the substrate.

[0032] According to one embodiment, the variable adjustability of the relative position between the source unit and the substrate located on the substrate holder is implemented via a translational relative movement between the substrate holder and the source unit.

[0033] According to one embodiment, at least one source of the source unit comprises a heater.

[0034] According to one embodiment, at least one source of the source unit comprises a laser.

[0035] According to one embodiment, at least one source of the source unit comprises a measuring device.

[0036] The disclosure further relates to an apparatus for coating a substrate of an optical element, comprising

[0037] - a substrate holder; and

[0038] - a source unit for applying and / or modifying a coating on a substrate located on the substrate holder during operation of the device;

[0039] - wherein during operation of the device a relative position between the source unit and the substrate located on the substrate holder can be variably adjusted;

[0040] - wherein the coating effect achieved by the source unit on the substrate can be manipulated depending on the set relative position. The invention further relates to a method for coating a substrate of an optical element, wherein a substrate located on a substrate holder is coated via a source unit;

[0041] - wherein a relative position between the source unit and the substrate is variably adjusted;

[0042] - wherein the coating effect of the source unit on the substrate is manipulated depending on the set relative position;

[0043] - wherein the source unit comprises a first source and at least one second source, these sources being activated differently depending on the set relative position; and

[0044] - wherein during the coating, at least temporarily both the first source and the at least one second source are covered by the substrate.

[0045] The disclosure further relates to a method for coating a substrate of an optical element, wherein a substrate located on a substrate holder is coated via a source unit;

[0046] - wherein a relative position between the source unit and the substrate is variably adjusted; and

[0047] - whereby the coating effect of the source unit on the substrate is manipulated depending on the set relative position.

[0048] The invention is not limited to the application to the coating of the substrate of an optical element of a projection exposure system designed for operation in the EUV. In particular, the invention can also be advantageously applied to optical elements in a projection exposure system designed for operation in the DUV (or at wavelengths less than 400 nm, in particular less than 250 nm, further in particular less than 200 nm) or in another optical system.

[0049] Further embodiments of the invention can be found in the description and the dependent claims. The invention is explained in more detail below with reference to exemplary embodiments illustrated in the accompanying drawings.

[0050] BRIEF DESCRIPTION OF THE DRAWINGS

[0051] They show:

[0052] Figures 1 a-1 c are schematic representations for explaining an apparatus and a method for forming a coating on a substrate of an optical element according to several embodiments of the invention;

[0053] Figures 2a-2c are schematic representations for explaining an apparatus and a method for forming a coating on a substrate of an optical element according to further embodiments of the invention;

[0054] Figure 3 is a schematic diagram illustrating an apparatus and a method for forming a coating on a substrate of an optical element according to a further embodiment of the invention;

[0055] Figures 4a-4c are a schematic illustration to explain an apparatus and a method for forming a coating on a substrate of an optical element according to a further embodiment of the invention; and

[0056] Figures 5a-5c are a schematic representation to explain a device and a method for forming a coating on a substrate of an optical element according to a further embodiment of the invention; Figure 6 is a schematic representation of the possible structure of a

[0057] Operation in a DUV-designed microlithographic projection exposure system; and

[0058] Figure 7 shows a schematic representation of the possible structure of a

[0059] Operation in the EUV designed microlithographic projection exposure system.

[0060] DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0061] Different embodiments of the realization of a coating on a substrate of an optical element are described below with reference to the schematic representations of Fig. 1a to Fig. 5c. The optical element can be intended in particular for use in a microlithographic projection exposure system designed for operation in DUV or EUV.

[0062] The embodiments described below have in common that, during operation of the device for coating a substrate, a relative position between a source unit and a substrate located on a substrate holder can be variably adjusted, wherein the coating effect achieved by the source unit on the substrate can be manipulated depending on the adjusted relative position.

[0063] Fig. 1 a-1 c show schematic representations to explain an apparatus according to the invention and a method according to the invention for forming a coating on a substrate designated "100", wherein a source unit 1 10 with a first source 1 1 1 and a second source 1 12 is used.

[0064] Fig. 1 a shows a plan view of an apparatus according to the invention with a substrate 100 located on a substrate holder 160 with a source unit 110 which has a first source 111 and a second source 112. Both the first source 111 and the second source 112 are arranged along a geometric axis (merely by way of example along the y-axis in the drawn-in coordinate system) and their spatial extent is each smaller than the respective spatial extent of the substrate 100. The substrate 100 located on the substrate holder 160 is moved translationally over the sources 111 and 112, as indicated by an arrow 140.

[0065] To explain a further embodiment of a device according to the invention, Fig. 1 b and Fig. 1 c show a top view (Fig. 1 a) and a side view (Fig. 1 c) respectively, with a substrate 100 located on a substrate holder 160 with a source unit 120 which has a first source 121 and a second source 122. Both the first source 121 and the second source 122 are, in their spatial extent along a geometric axis (x-axis in the drawn coordinate system), smaller than the respective spatial extent of the substrate 100. Furthermore, the first source 121 and the second source 122 are arranged comparatively close to one another along the respective geometric axis (x-axis). The substrate 100 located on the substrate holder 160 is moved over the sources 121 and 122 in a translational movement indicated by the arrow 140.

[0066] Fig. 2a-2c show schematic representations to explain further embodiments of a device according to the invention and of a method according to the invention for forming a coating on a substrate, wherein, in comparison to Fig. 1a-1c, analogous or essentially functionally identical components are designated by reference numerals increased by "100".

[0067] Fig. 2a shows a plan view of an apparatus according to the invention with a substrate 200 located on a substrate holder (not shown here) with a source unit 210 which has a first source 211 and a second source 212. Both the first source 211 and the second source 212 are arranged along a geometric axis and their spatial extent along two mutually perpendicular axes (x and y axes in the drawn coordinate system) is each smaller than the spatial extent of the substrate 200. The substrate 200 is moved over the sources 211 and 212 in a translational movement indicated by the arrow 240 and in a rotational movement indicated by the arrow 250.

[0068] Fig. 2b shows a plan view of an apparatus according to the invention with a substrate 200 located on a substrate holder (not shown here) with a source unit 220 having a first source 221 and a second source 222. Both the first source 221 and the second source 222 are smaller in their spatial extent along a geometric axis (x-axis in the drawn coordinate system) than the spatial extent of the substrate 200. Furthermore, the first source 221 and the second source 222 are arranged comparatively close to one another along the respective geometric axis (x-axis). The substrate 200 is moved over the sources 211 and 212 in a translational movement indicated by arrow 240 and a rotational movement indicated by arrow 250.

[0069] Although the illustrated embodiment shows a combination of a translational movement and a rotational movement, the invention is not limited to this. Thus, in further embodiments, movements along any spatial direction (in particular, different translational movements) can also be combined.

[0070] Fig. 2c shows a plan view of a device according to the invention with a substrate 200 located on a substrate holder (not shown here) with a source unit 230, which has a first source 231 and a second source 232. Both the first source 231 and the second source 232 are arranged along a geometric axis and their spatial extension along two mutually perpendicular axes (x and y axes in the drawn coordinate system) is smaller than the spatial extension of the substrate 200. In contrast to Fig. 2a, the sources 231 and 232 are arranged such that the source 232 is closer to the edge region of the substrate 200. The substrate 200 is moved over the sources 211 and 212 in a translational movement indicated by the arrow 240 and a rotational movement indicated by the arrow 250. Fig.3 shows a schematic view to explain a further embodiment of the device according to the invention and the method according to the invention for forming a coating on a substrate, wherein, in comparison to Fig. 2a-2c, analogous or essentially functionally identical components are designated by reference numerals increased by "100".

[0071] Fig. 3 shows a substrate 300 above a source unit 310 having a source 311, wherein an electrical bias voltage 312 is applied to the substrate 300. In this way, the substrate 300 can be used as a further means of influencing (alternatively or in addition to the presence of a second source within the source unit 310) to achieve the inventive manipulation or variation of the coating effect depending on the respective current relative position between the source unit and the substrate. The substrate 300 is moved over the source unit 310 in a translational movement indicated by the arrow 340.

[0072] Fig. 4a-4c each show a schematic view to explain a further embodiment of the device according to the invention and the method according to the invention for forming a coating on a substrate, wherein, compared to Fig. 2a-2c, analogous or essentially functionally identical components are designated by reference numerals increased by "200".

[0073] Fig. 4a shows a source unit 410 with a source 411 and a substrate 400, wherein the source 411 is aligned / tilted relative to the substrate 400 and wherein the substrate 400 is moved over the source 411 in a translational movement indicated by the arrow 440.

[0074] Fig. 4b and Fig. 4c show, starting from Fig. 4a, the orientation of the source 41 1 in the respective advanced translational movement sequence of the substrate 400, wherein the source 41 1 is still aligned / tilted relative to the substrate 400.

[0075] Fig. 5a-5c each show a schematic view to explain a further embodiment of the device according to the invention and the method according to the invention for forming a coating on a substrate, wherein, in comparison to Fig. 4a-4c, analogous or essentially functionally identical components are designated by reference numerals increased by "100".

[0076] Fig. 5a shows a source unit 510 with a source 511 and a substrate 500, wherein the substrate 500 is moved in a rotational motion over the source 511. In contrast to Fig. 4a, the source 511 is not aligned relative to the substrate 500.

[0077] Starting from Fig. 5a, Fig. 5b and Fig. 5c show the orientation of the substrate 500 with respect to the source 51 1 in the respective advanced rotational movement sequence, wherein the position of the source 51 1 does not change.

[0078] Fig. 6 shows a fundamentally possible structure of a microlithographic projection exposure system 600 designed for operation in DUV as an application example of an optical element coated according to the invention.

[0079] The projection exposure system 600 according to Fig. 6 has an illumination device 610 and a projection lens 620. The illumination device 610 serves to illuminate a structure-bearing mask (reticle) 615 with light from a light source unit 605, which comprises a laser light source, for example in the form of an ArF excimer laser for an operating wavelength of 193 nm (or also in the form of a KrF excimer laser for an operating wavelength of 248 nm or a mercury vapor lamp for an operating wavelength of 365 nm), as well as beam-shaping optics generating a parallel light beam.

[0080] The illumination device 610 has an optical unit 611, which, in the example shown, includes a deflection mirror 612. The optical unit 611 can, for example, have a diffractive optical element (DOE) and a zoom axicon system to generate different illumination settings (ie, intensity distributions in a pupil plane of the illumination device 610). In the light propagation direction downstream of the optical unit 611, a light mixing device (not shown) is located in the beam path, which, for example,in a manner known per se, an arrangement of micro-optical elements suitable for achieving light mixing, as well as a lens group 613, behind which is a field plane with a reticle masking system (REMA), which is imaged by a REMA objective 614 following in the direction of light propagation onto the structure-bearing mask (reticle) 615 arranged in a further field plane, thereby delimiting the illuminated area on the reticle. The structure-bearing mask 615 is imaged by the projection objective 620 onto a lens substrate or a wafer 630 provided with a light-sensitive layer (photoresist). The projection objective 620 can be designed in particular for immersion operation, in which case an immersion medium is located in front of the wafer or its light-sensitive layer with respect to the direction of light propagation. Furthermore, it can, for example, have a numerical aperture NA greater than 0.85, in particular greater than 1.1 .

[0081] Fig. 7 shows a schematic representation of the possible structure of a microlithographic projection exposure system designed for operation in the EUV as a further application example of an optical element coated according to the invention.

[0082] According to Fig. 7, the projection exposure system 1 comprises an illumination device 2 and a projection lens 10. One embodiment of the illumination device 2 of the projection exposure system 1 has, in addition to a light or radiation source 3, an illumination optics 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 module separate from the other illumination device. In this case, the illumination device does not include the light source 3.

[0083] A reticle 7 arranged in the object field 5 is exposed. The reticle 7 is held by a reticle holder 8. The reticle holder 8 can be displaced, particularly in a scanning direction, via a reticle displacement drive 9. For illustrative purposes, a Cartesian xyz coordinate system is shown in Fig. 7. The x-direction runs perpendicular to the drawing plane. The y-direction runs horizontally, and the z-direction runs vertically. The scanning direction in Fig. 7 runs along the y-direction. The z-direction runs perpendicular to the object plane 6. The projection lens 10 serves to image the object field 5 into an image field 11 in an image plane 12. A structure on the reticle 7 is imaged onto a light-sensitive layer of a wafer 13 arranged in the region of the image field 11 in the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 can be displaced, in particular along the y-direction, via a wafer displacement drive 15.The displacement of the reticle 7 on the one hand via the reticle displacement drive 9 and the wafer 13 on the other hand via the wafer displacement drive 15 can be synchronized with each other.

[0084] Radiation source 3 is an EUV radiation source. Radiation source 3 emits, in particular, EUV radiation, which is also referred to below as useful radiation or illumination radiation. The useful radiation has, in particular, a wavelength in the range between 5 nm and 30 nm. Radiation source 3 can be, for example, a plasma source, a synchrotron-based radiation source, or a free-electron laser (FEL). The illumination radiation 16 emanating from the radiation source 3 is bundled by a collector 17 and propagates through an intermediate focus in an intermediate focal plane 18 into the illumination optics 4. The illumination optics 4 has a deflection mirror 19 and, downstream of this in the beam path, a first facet mirror 20 (with schematically indicated facets 21) and a second facet mirror 22 (with schematically indicated facets 23).These facet mirrors can be realized in particular in the manner according to the invention, ie can be cooled as a mirror array via a heat sink designed in the manner according to the invention.

[0085] The projection lens 10 has a plurality of mirrors Mi (i = 1, 2, ...), which are numbered according to their arrangement in the beam path of the projection exposure system 1. In the example shown in Fig. 7, the projection lens 10 has six mirrors M1 to M6. Alternatives with four, eight, ten, twelve or a different number of mirrors Mi are also possible. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation 16. The projection lens 10 is a doubly obscured optic. The projection lens 10 has a numerical aperture on the image side that is greater than 0.5 and can also be greater than 0.6 and can be, for example, 0.7 or 0.75.

[0086] Although the invention has been described with reference to specific embodiments, numerous variations and alternative embodiments will become apparent to those skilled in the art, e.g., by combining and / or interchanging features of individual embodiments. Accordingly, it will be understood by those skilled in the art that such variations and alternative embodiments are encompassed by the present invention, and the scope of the invention is limited only by the appended claims and their equivalents.

Claims

Patent claims 1 . Device for coating a substrate of an optical element, with • a substrate holder (160); and • a source unit (110, 120, 210, 220, 230, 310, 410, 510) for applying and / or modifying a coating on a substrate (100, 200, 300, 400, 500) located on the substrate holder (160) during operation of the device; • wherein, during operation of the device, a relative position between the source unit (110, 120, 210, 220, 230, 310, 410, 510) and the substrate (100, 200, 300, 400, 500) located on the substrate holder (160) is variably adjustable; and • wherein the coating effect achieved by the source unit (1 10, 120, 210, 220, 230, 310, 410, 510) on the substrate (100, 200, 300, 400, 500) can be manipulated depending on the set relative position; • wherein the source unit (1 10, 120, 210, 220, 230) comprises a first source (1 1 1, 121, 21 1, 221, 231) and at least one second source (1 12, 122, 212, 222, 232); and • wherein the first source (1 1 1 , 121 , 21 1 , 221 , 231 ) and the at least one second source (1 12, 122, 212, 222, 232) differ from one another with regard to their operating principle underlying the respective application and / or modification of the coating on the substrate (100, 200).

2. Device according to claim 1, characterized in that a spatial extension of both the first source (1 11, 121, 21 1, 221, 231) and the at least one second source (112, 122, 212, 222, 232) along at least one geometric axis, in particular along two mutually perpendicular axes, is smaller than the respective spatial extension of the substrate.

3. Device according to claim 1 or 2, characterized in that the first source (1 1 1 , 121 , 21 1 , 221 , 231 ) and the at least one second source (1 12, 122, 212, 222, 232) can be operated independently of one another.

4. Device according to one of claims 1 to 3, characterized in that the first source (11 1 , 121 , 21 1 , 221 , 231 ) and the at least one second source (112, 122, 212, 222, 232) differ from one another with regard to a coating material deposited on the substrate (100, 200).

5. Device according to one of the preceding claims, characterized in that the manipulability of the coating effect depends on the set relative position via a variable adjustability - the alignment, in particular tilting, of at least one source of the source unit relative to the substrate; and / or - a twist angle of the substrate is implemented.

6. Device according to one of the preceding claims, characterized in that the manipulability of the coating effect depends on the set relative position via a variable adjustability - the deposition or removal rate of at least one source of the source unit; and / or - the radiation characteristic of at least one source of the source unit is implemented.

7. Device according to one of the preceding claims, characterized in that the manipulability of the coating effect is implemented depending on the set relative position via a variable adjustability of an electrical bias voltage applied to the substrate.

8. Device according to one of the preceding claims, characterized in that the variable adjustability of the relative position between the source unit (110, 120, 210, 220, 230, 310, 410) and the substrate (100, 200, 300, 400) located on the substrate holder is implemented via a translational relative movement between the substrate holder (160) and the source unit (110, 120, 210, 220, 230, 310, 410).

9. Device according to one of the preceding claims, characterized in that at least one source of the source unit has a heater.

10. Device according to one of the preceding claims, characterized in that at least one source of the source unit comprises a laser.

11. Device according to one of the preceding claims, characterized in that at least one source of the source unit has a measuring device.

12. A method for coating a substrate (100, 200, 300, 400, 500) of an optical element, wherein a substrate (100, 200, 300, 400, 500) located on a substrate holder (160) is coated via a source unit (110, 120, 210, 220, 230, 310, 410, 510); - wherein a relative position between the source unit (110, 120, 210, 220, 230, 310, 410, 510) and the substrate (100, 200, 300, 400, 500) is variably adjusted; - wherein the coating effect of the source unit (110, 120, 210, 220, 230, 310, 410, 510) on the substrate (100, 200, 300, 400, 500) is manipulated depending on the set relative position; - wherein the source unit (110, 120, 210, 220, 230) comprises a first source (111, 121, 211, 221, 231) and at least one second source (112, 122, 212, 222, 232), said sources being activated differently depending on the set relative position; and - wherein during the coating, at least temporarily both the first source (111, 121, 211, 221, 231) and the at least one second source (112, 122, 212, 222, 232) are covered by the substrate (100, 200).

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