Optical assembly

Abstract

An optical assembly (28) has at least one optical component (13) for guiding used light (4). A holder (29) for the optical component (13) is connected to the optical component (13) by way of an adhesive bond (31). At least one protective layer (33a, 33b) is arranged in such a way that it covers the adhesive bond (31) towards at least one protected side and prevents the adhesive bond (31) from being exposed to the used light (4) from the protected side. The result is an optical assembly with high stability.

Description

[0001] Optical assembly

[0002] The contents of German patent application DE 10 2024 210 358.6 is incorporated by reference.

[0003] The invention relates to an optical assembly with an optical component for guiding used light and with a holder for the optical component. The invention also relates to a retrofit kit for retrofitting such an optical assembly, to an illumination optical unit with such an optical assembly, to a projection optical unit with such an optical assembly, to an optical system with such an illumination optical unit and / or with such a projection optical unit, to a projection exposure apparatus with such an optical system, to a method for producing a micro structured or nano structured component part with such a projection exposure apparatus and also to a structured component part produced with such a method.

[0004] An optical assembly of the type mentioned at the beginning is known as a mounted optical component from WO 2005 / 015 310 A2, DE 10 2004 059 493 Al, WO 2009 / 095 052 Al, DE 196 53 983 Al, US 5,982,558, US 7,551,361 B2 and from WO 2016 / 188 739 Al. An optical mount is known from EP 0 895 113 Bl. Further optical assemblies and components for them are known from DE 10 2021 214 140 Al and DE 10 2011 080 639 Al.

[0005] It is an object of the present invention to develop an optical assembly of the type mentioned at the beginning in such a way as to result in high stability.

[0006] This object is achieved according to the invention by an optical assembly with the features specified in Claim 1. The protective layer prevents the adhesive bond from being unwantedly exposed to used light and / or stray light. Stray light may in this case be used light away from a desired used-light beam path or else light or radiation of a wavelength other than that of the used light. An unwanted degradation of the adhesive bond due to the effect of the used light or the stray light, and thus an unwanted impairment of the service life of the optical assembly, is thus prevented. The protective layer may be designed as absorbent and / or reflective and / or scattering. The used light may have a wavelength in the EUV range. The used light may have a wavelength of 193 nm. The used light may have a wavelength of 248 nm.

[0007] The protective layer may extend between the optical component and the holder. The protective layer may cover the whole adhesive bond or a section thereof. The protective layer may cover a boundary between the optical component and the adhesive bond. Alternatively or in addition, the protective layer may cover a boundary between the adhesive bond and the holder.

[0008] A design according to Claim 2 ensures particularly effective protection of the adhesive bond.

[0009] Protective layer thicknesses according to Claim 3 have proven themselves in practice and allow a compact design of the optical assembly. It is also possible to retrofit an already existing optical assembly with such a protective layer without changing the optical design. A thickness range of the protective layer may lie between 25 pm and 200 pm, between 30 pm and 100 pm and in particular in the range of 50 pm. A design of the protective layer according to Claim 4 has particularly proven itself. It is particularly advantageous if the protective film can be made precisely to meet requirements during the production of the optical assembly and, for example, is made of a film material which can be subsequently trimmed and / or tailored.

[0010] A design according to Claim 5 can avoid an additional supporting component for the protective layer.

[0011] A glued version of the protective layer according to Claim 6 can be realized with comparatively little production effort. The protective layer may be designed as self-adhesive. The adhesive layer may for example be made as thick as the protective film, but may alternatively be made thinner or, if necessary, thicker than the protective film. Alternatively or in addition to an adhesive bond, the protective layer may also be mechanically connected to the optical component and / or the holder.

[0012] Materials for the protective layer according to Claim 7 represent a good combination of used light shielding and mechanical and / or thermal stability. If a metal is used for the protective layer, it may in particular be coated with an absorbent coating. Alternatively or additionally, a surface of the protective layer may be designed as structured to optimize its shielding properties.

[0013] In the case of a design of the protective layer according to Claim 8, the protective layer may additionally have the function of a stop for the used light. The advantages of a retrofit kit according to Claim 9 correspond firstly to those which have already been explained above with reference to the optical assembly and with reference to the protective layer. The retrofit kit may have multiple protective films. The multiple protective films may have multiple sizes of aperture openings and / or multiple outer contour designs. The retrofit kit may also include processing tools for the making the respective protective film meet requirements, adhesive material as well as application and positioning aids for the correct application and positioning of the respective protective film on the optical component.

[0014] The advantages of an illumination optical unit according to Claim 10 and of a projection optical unit according to Claim 11 correspond to those which have already been explained above with reference to the optical assembly. These optical units may be part of a lithographic projection exposure apparatus.

[0015] The advantages of an optical system according to Claim 12, a projection exposure apparatus according to Claim 13, a production method according to Claim 14 and a structured component according to Claim 15 correspond to those which have already been explained above with reference to the optical assembly, the retrofit kit, the illumination optical unit and the projection optical unit. The light source of the illumination system may be a mercury- vapour lamp, an excimer laser or an LED light source.

[0016] A structured component, in particular a microchip, for example a memory chip, may be produced.

[0017] Exemplary embodiments of the invention are explained in more detail below with reference to the drawing, in which: Fig. 1 shows main optical groups of a microlithographic projection exposure apparatus in a meridional section, comprising an illumination optical unit for illuminating an object field with illuminating and imaging light and a projection optical unit for projecting an image of the object field into an image field, comprising a plurality of optical components for guiding the illuminating and imaging light;

[0018] Fig. 2 shows a broken axial section through an optical assembly of the projection exposure apparatus, comprising one of the optical components, a holder for this optical component and protective layers arranged on both sides of the optical assembly; and

[0019] Fig. 3 show a further embodiment of such an optical assembly in a sectional representation similar to Fig. 2, in this case not broken, comprising two spaced apart optical components, a holder for these optical components and a protective layer in this case arranged on one side of the optical assembly.

[0020] A projection exposure apparatus 1 is illustrated in meridional section in Fig. 1 in its main optical groups.

[0021] In order to facilitate the illustration of positional relationships, an xyz- coordinate system will be used below. In Fig. 1, the x axis extends into the plane of the drawing perpendicularly in relation thereto. The y axis extends towards the left in Fig. 1. The z axis extends upwards in Fig. 1. An optical axis 2 extending through an entire optical system of the projection exposure apparatus 1, proceeding from a light source 3, is indicated in a dashed maimer in Fig. 1. In the embodiment of the projection exposure apparatus 1 shown in Fig. 1, this optical axis 2 is folded a number of times by 90° in each case. Such foldings can also be designed differently or, if necessary, even be dispensed with entirely.

[0022] The light or radiation source 3 of the projection exposure apparatus 1 generates used light in the form of an illuminating or imaging beam 4, which is illustrated in Fig. 1 by marginal rays. The used light 4 is also referred to as illuminating light or as imaging light. The used light 4 has a wavelength in the deep ultraviolet (DUV) range, for example in the range between 100 nm and 200 nm, or in the ultraviolet (UV) range between 200 nm and 400 nm. Alternatively, the used light 4 may also have a wavelength in the extreme ultraviolet (EUV) range, in particular between 5 nm and 30 nm. Example wavelengths of the radiation source 3 are 365 nm, 248 nm, 193 nm. Depending on the radiation source 3 used, a used- wavelength spectrum used is narrowband, but it may also have a greater broadband capacity, for example if an Hg discharge lamp is used.

[0023] An illumination optical unit 5 of the projection exposure apparatus 1 guides the used light 4 along an illuminating-light beam path from the radiation source 3 towards an object plane 6 of the projection exposure apparatus 1. Together with the light source 3, the illumination optical unit 5 forms an illumination system of the projection exposure apparatus. An object, which is in the form of a reticle 7 and is to be imaged by the projection exposure apparatus 1, is arranged in the object plane 6. The reticle 7 is shown in a dashed manner in Fig. 1. The reticle 7 is carried by a holding device, not shown, with which a controlled scanning displacement or step-by-step displacement is possible. It is possible to use a transmissive reticle, as illustrated in Fig. 1, but also a reflective reticle, depending on the embodiment of the projection exposure apparatus 1. The reticle 7 is arranged in an object field 6a in the object plane 6.

[0024] A collector 8 in the form of an ellipsoidal mirror transfers the illuminating light 4 emanating from a source region of the light source 3 into an intermediate focus 9. A shutter is arranged there for the controlled release of the illuminating light 4 towards the components of the optical system that follow along the optical axis 2. There is also a safety shutter 10 arranged upstream of this intermediate focus shutter in the beam path of the illuminating light 4.

[0025] A pupil shaping optical unit 11 of the illumination optical unit 5 is arranged downstream of the intermediate focus 9 in the beam path of the illuminating light 4. The pupil shaping optical unit 11 serves to generate a defined intensity distribution of the illuminating light 4 in a downstream pupil plane of the illumination system. The pupil shaping optical unit 11 additionally serves as a setting device for predefining various illumination settings or various illumination settings with different maximum object field illumination angles. With the pupil shaping optical unit 11, an image of the light source at the intermediate focus 9 is projected into a pupil plane 12 of the illumination optical unit 5. The pupil shaping optical unit 11 includes an interference filter 13 and, arranged downstream thereof, an axicon module 14 with two axicon elements 15, 16. The axicon module 14 makes it possible to predefine a maximum object field illumination angle for illuminating the object field 6a in a settable maimer within an illumination angle range. As a measure of the maximum object field illumination angle set in each case by way of the pupil shaping optical unit 11, use is made of a pupil radius 090, which indicates for a specific pupil illumination of the pupil plane 12 or a downstream pupil plane of the illumination optical unit 5 the radius which encompasses 90% of an illuminating light energy radiated into this pupil plane. 090 is indicated in relative pupil coordinates. In this case, the value “090 = 1” indicates that an edge of a maximally illuminable pupil of the illumination system has been reached.

[0026] The pupil plane 12 is followed by an illuminating-light mixing unit 17. The illuminating-light mixing unit 17 includes an optical primary rod 17a in the illuminating-light beam path after the pupil plane 12 and an optical secondary rod 17b downstream in the illuminating-light beam path. The optical rods 17a, 17b may be rods with a hexagonal and / or rectangular cross section. Also, multiple successive rod sections, if necessary with a different cross section, may form the illuminating-light mixing unit 17. An entry plane of the optical rod of the illuminating-light mixing unit 17 may coincide with the pupil plane 12. The optical rods 17a, 17b are made of glass, for example boron crown glass or quartz glass. The rods 17a, 17b may also be produced as calcium fluoride (CaF2).

[0027] In the region of the illuminating-light mixing unit 17, an illuminating-light beam path is deflected by 90° by means of a deflection prism 18, such that the optical axis 2 from then on no longer extends along the positive z direction, but rather along the positive y direction of the xyz coordinate system of Fig. 1. The deflection prism 18 is made of glass, for example boron crown glass or quartz glass or CaF2. The two optical rods 17a, 17b and the intermediate deflection prism 18 form the illuminating-light mixing unit 17, which represents an optical assembly of the illumination optical unit 5. Variants of the design of this optical assembly are explained in still more detail below with reference to Figs. 2 and 3.

[0028] An intermediate field plane 19 of the illumination optical unit 5 is present where the illuminating light 4 exits from the illuminating-light mixing unit 17. A stop 20 for predefining a marginal boundary of the object field 6a lies in this intermediate field plane 19. The stop 20 is also referred to as a REMA stop (reticle masking system for stopping down the reticle 7).

[0029] An image of the intermediate field plane 19 is projected into the object plane 6 by an imaging optical unit 21, which is also referred to as a REMA lens. The imaging optical unit 21 includes a 90° folding mirror 21a, such that the optical axis 2, which up to that point has extended along the positive y direction, then extends in the negative z direction. A further pupil plane 22 lies between the field planes 19 and 6.

[0030] An image of the object field 6a is projected into an image field 24 in an image plane 25 by means of a projection optical unit 23. In the image plane 25, a wafer 26 is arranged in the region of the image field 24. This wafer is carried by a holding device, not shown, which with which a controlled scanning displacement of the wafer 26 or else a step-by-step displacement of the wafer 26 is possible.

[0031] A pupil plane 27 of the projection optical unit 23 lies between the object plane 6 and the image plane 25. An aperture stop for marginally predefining a pupil of the projection optical unit 23 may be arranged in this pupil plane 27.

[0032] Within the illumination optical unit 5 with the pupil shaping optical unit 11 and the imaging optical unit 21 and also in the projection optical unit 23 of the projection exposure apparatus 1 there are a plurality of optical assemblies of which the optical components serve to guide the used light 4. These optical components are in each case held on a frame of the projection exposure apparatus 1 by a holder. Such an optical assembly 28 will be explained in more detail below with reference to Fig. 2 using the example of the interference filter 13 as an optical component of this optical assembly 28. Also, the other optical components for guiding the used light 4 between the light source 3 and the wafer 26 may be parts of corresponding optical assemblies.

[0033] In addition to the interference filter 13, the optical assembly 28 has a holder 29, which is designed as a filter mount and fixes the interference filter 13 on a supporting frame 30, which is shown in part in Fig. 2. The holder 29 is adhesively connected to the optical component 13 by way of a peripheral adhesive bond 31.

[0034] The optical component 13 has an aperture opening 32 for the used light 4 to pass through, which is illustrated in Fig. 2 as a plurality of parallel single rays. This aperture opening 32 is also shown broken off to the left according to the broken representation of the optical component 13 in Fig. 2.

[0035] Outside this aperture opening 32, protective layers 33a and 33b are arranged on both sides of the optical component 13, i.e. on an entry surface 13a and on an exit surface 13b. This arrangement of protective layers 33a and 33b on the optical component 13 is such that the adhesive bond 31 is covered on both sides, i.e. in the axial direction towards the entry surface 13a (opposite a radiating direction of the used light 4 in the used-light beam path) and also towards the exit surface 13b (in the radiating direction of the used light 4 in the used-light beam path), thus towards two protected sides.

[0036] The protective layers 33a and 33b each cover an edge region of the optical component 13, an edge region of the holder 29 facing the optical component 13 and the entire intermediate adhesive bond 31.

[0037] This arrangement of the protective layers 33a and 33b prevents the adhesive bond 31 from being exposed to the used light 4 and in particular stray light 4s scattered away from the desired illuminating and imaging beam path of the used light 4 from the respective protected side. This is illustrated by way of example in Fig. 2 by means of single stray-light rays 4s, which run from both sides of the optical assembly 28 in the direction of the adhesive bond 31 and do not penetrate into the adhesive bond 31 due to the protective layer 33a or 33b. The stray light 4s may have the wavelength of the used light 4. Alternatively, the stray light 4s may also have a wavelength different from the used light 4.

[0038] The protective layers 33a and 33b are designed to absorb the used light 4 and in particular the stray light 4s. Alternatively or in addition, a reflective or, if necessary, also scattering and / or diffractive design of the respective protective layer 33a, 33b is also possible. This safely prevents an unwanted degradation of adhesive material of the adhesive bond 31 under the influence of stray light 4s. The respective protective layer 33a, 33b has a layer thickness in the range between 10 pm and 1000 pm. This thickness may in particular lie in the range between 25 pm and 100 pm and for example in the range of 50 pm.

[0039] The respective protective layer 33a, 33b is designed as a protective film.

[0040] The respective protective layer 33a, 33b is connected both to the optical component 13 and to the holder 29, specifically is glued to it.

[0041] The protective layer 33a, 33b is designed as adhesive. The respective protective layer 33a, 33b is thus connected to the optical component 13 and to the holder 29 by way of an adhesive layer. The protective layer 33a, 33b is in this case designed as self-adhesive.

[0042] The adhesive layer may be made as thick as the layer thickness of the protective film. Alternatively, the adhesive layer may also be made to be of a lower or greater thickness than the protective film.

[0043] The respective protective layer 33a, 33b is made of polyamide. Alternatively, the protective layer may also be made of polyimide or metal. The respective protective layer 33a, 33b may have an absorbent and / or diffractive and / or scattering coating.

[0044] As an alternative to an adhesive bonding of the protective layer 33 a, 33b to the optical component 13 or the holder 29, the respective protective layer 33a, 33b may also be mechanically connected to the optical component 13 and / or to the holder 29, for example clamped to the holder 29. The protective layer 33a / 33b peripherally borders the aperture opening 32, i.e. the used aperture of the optical component 13, which is not shown in Fig. 2. The protective layer 33 (a / b), which can also be made in one piece, can simultaneously have the function of an aperture stop for the optical component 13, i.e. for the interference filter.

[0045] The protective layer 33a, 33b may be designed as a component part of a retrofit kit for applying the protective layer 33a, 33b to the respective optical component, for example the interference filter 13, to complete an assembly initially without such a protective layer to form an optical assembly with such a protective layer. Such a retrofit kit may comprise multiple protective layers, which in particular may be designed as, if necessary, self-adhesive protective films. These multiple protective layers of the retrofit kit may for example be designed as peripheral protective- layer stops with multiple aperture opening sizes and / or with multiple aperture outer contour designs and / or multiple protective layer thicknesses and / or multiple protective layer connection variants. These different types of connection may involve different adhesive bonding techniques (self- adhesive, additional adhesive, for example two-component adhesive) and / or variants of a mechanical connection.

[0046] Explained below with reference to Fig. 3 is a further design of an optical assembly 34 which, like the optical assembly 28 according to Fig. 2, can be used as a component part of an optical system of the projection exposure apparatus 1 for guiding the used light 4. The optical assembly 34 may in particular be designed as a correction component for correcting guiding or imaging errors of the illumination optical unit 5 and / or the projection optical unit 23. Components and functions corresponding to those which have already been explained above with reference to Figs. 1 and 2, and particularly with reference to Fig. 2, bear the same designations and reference signs and will not be discussed in detail again.

[0047] The optical assembly 34 has three optical components 35, 36, 37, which are illustrated in Fig. 3 as plane-parallel plates, but may also have a non-planar surface design of an entry or an exit surface.

[0048] A distance between the optical components 35, 36, 37 may be preset in the optical assembly 34 by means of spacers that are not shown. This distance is along an illuminating or imaging beam path of the used light 4.

[0049] By way of a holder 39, which once again is designed as a mount and may be of a multi-part form, the optical components 35 and 36 are connected to the in this case multi-part supporting frame 30 by way of adhesive layers 38. Appropriate adhesive layers 38 are used to bond the holder 39 on the one hand to the optical components 35 to 37 and on the other hand to the supporting frame 30.

[0050] The optical assembly 34 once again includes a protective layer 33, which is arranged on an exit side of the optical component 36 arranged downstream in the beam path of the used light 4 and is connected to the exit surface 13b of the optical component 36. This connection is in accordance with what has been explained above in relation to the protective layers 33 a, 33b according to Fig. 2.

[0051] The protective layer 33 of the optical assembly 34 covers beyond the aperture opening 32 an edge region of the optical component 36, an intermediate space between the optical component 36 and the supporting frame 30 and also an edge region of the supporting frame 30 facing the optical component 36.

[0052] As illustrated in Fig. 3 once again by single stray-light rays 4s, this arrangement of the protective layer 33 prevents adhesive bonds of the optical assembly 34 from being exposed to stray light 4s incident on the optical assembly 34 from the exit side of the optical component 36. This exit side is thus at the same time the protected side of the optical assembly 34.

[0053] The stray light 4s is effectively shielded by the protective layer 33 towards the protected side and cannot be incident on any of the adhesive layers 38 explained above between bonded-together elements of the optical assembly 34.

[0054] A degradation of the adhesive material of the adhesive layers 38 is effectively prevented by way of the protective layer 33 of the optical assembly 34.

[0055] On the entry side, an intermediate space between the entry surface 13a of the optical component 35 guiding in the beam path and in the supporting frame 30 is covered by a peripheral sealing body 40. This sealing body 40 is once again bonded by way of adhesive layers 38 on the one hand to the entry surface 13a of the optical component 35 and on the other hand to the supporting frame 30.

[0056] The adhesive material of the adhesive layers 31, 38 described above may be an acrylate adhesive material. In so far as the protective layer 33 (a / b) is designed to absorb the stray light 4s, the protective layer may be made of a material which is temperature resistant up to a temperature of 200°C, of 250°C, of 300°C, of 350°C or else of 400°C. The respective protective layer 33 (a / b) may be made of a material with a low outgassing rate, for example with outgassing values below 0.1 ng / (cm2h) for non-volatile substances (condensables).

[0057] With the aid of the projection exposure apparatus 1, which either comprises assemblies 28, 34 designed in accordance with the optical assemblies 28, 34 described above from the outset or in which such optical assemblies have been retrofitted by using a retrofit kit referred to above, an image of at least part of the reticle 7 is projected onto a region of a light-sensitive layer on the wafer 26 for the lithographic production of a micro structured or nanostructured component. Depending on the design of the projection exposure apparatus 1 as a scanner or as a stepper, the reticle 7 and the wafer 26 are moved in the y direction in a maimer synchronized in time, continuously in scanner operation or step by step in stepper operation.

Claims

Patent claims1. Optical assembly (28; 34) with at least one optical component (13; 35, 36, 37) for guiding used light (4), with a holder (29) for the optical component (13; 35, 36, 37), which is connected to the optical component (13; 35, 36, 37) by way of an adhesive bond (31; 38), with at least one protective layer (33a, 33b; 33), which is arranged in such a way that it covers the adhesive bond (31; 38) towards at least one protected side and prevents the adhesive bond (31; 38) from being exposed to the used light (4) from the protected side.

2. Optical assembly according to Claim 1, characterized by at least two protective layers (33a, 33b), which cover the adhesive bond (31) with respect to an arrangement plane of the optical component (13) towards both sides and prevent the adhesive bond (31) from being exposed to the used light (4) from these two sides.

3. Optical assembly according to Claim 1 or 2, characterized in that the protective layer (33a, 33b; 33) has a thickness in the range between10 pm and 1000 pm.

4. Optical assembly according to one of Claims 1 to 3, characterized in that the protective layer (33a, 33b; 33) is designed as a protective film.

5. Optical assembly according to one of Claims 1 to 4, characterized in that the protective layer (33a, 33b; 33) is connected to the optical component (13; 35, 36, 37) and / or to the holder (29).

6. Optical assembly according to Claim 5, characterized in that the protective layer (33a, 33b; 33) is connected to the optical component (13; 35, 36, 37) and / or to the holder (29) by way of an adhesive layer.

7. Optical assembly according to one of Claims 1 to 6, characterized in that the protective layer (33a, 33b; 33) is made of at least one of the following materials: polyamide polyimide metal.

8. Optical assembly according to one of Claims 1 to 7, characterized in that the protective layer (33a, 33b; 33) peripherally borders a used aperture (32) of the optical component (13; 35, 36, 37).

9. Retrofit kit with at least one protective film (33a, 33b; 33) according to one of Claims 1 to 8 for applying to an optical component (13; 35, 36, 37) to complete an optical assembly (28; 34) according to one of Claims 1 to 8.

10. Illumination optical unit (5) with an optical assembly (28; 34) according to one of Claims 1 to 8.

11. Projection optical unit (23) with an optical assembly (28; 34) according to one of Claims 1 to 8.

12. Optical system with an illumination optical unit according to Claim 10 for illuminating an object field (6a), in which an object (7) to beilluminated and imaged can be arranged, and / or with a projection optical unit (23) according to Claim 11 for projecting an image of the object field (6a) into an image field (24), in which a section of a substrate (26) can be arranged.

13. Projection exposure apparatus with an optical system according to Claim 12.

14. Method for producing structured components, with the following steps: - providing a wafer (26), on at least part of which a layer of a lightsensitive material has been applied,- providing a reticle (7) comprising structures to be imaged,- providing a projection exposure apparatus (1) according to Claim 13, - projecting at least part of the reticle (7) onto a region of the layer of the wafer (26) with the aid of the projection exposure apparatus -15. Structured component produced by a method according to Claim 14.

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