Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/08—Mirrors
  • G02B5/0891—Ultraviolet [UV] mirrors
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
  • C03C17/22—Surface treatment of glass, not in the form of fibres or filaments, by coating with other inorganic material
  • C03C17/23—Oxides
  • C03C17/245—Oxides by deposition from the vapour phase
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C27/00—Joining pieces of glass to pieces of other inorganic material; Joining glass to glass other than by fusing
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B37/00—Joining burned ceramic articles with other burned ceramic articles or other articles by heating
  • C04B37/04—Joining burned ceramic articles with other burned ceramic articles or other articles by heating with articles made from glass
  • C04B37/045—Joining burned ceramic articles with other burned ceramic articles or other articles by heating with articles made from glass characterised by the interlayer used
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
  • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
  • G02B26/0816—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements
  • G02B26/0833—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD
  • G02B26/0858—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD the reflecting means being moved or deformed by piezoelectric means
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
  • G02B7/003—Alignment of optical elements
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
  • G02B7/008—Mountings, adjusting means, or light-tight connections, for optical elements with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
  • G02B7/18—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors
  • G02B7/181—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/70—Microphotolithographic exposure; Apparatus therefor
  • G03F7/70216—Mask projection systems
  • G03F7/70258—Projection system adjustments, e.g. adjustments during exposure or alignment during assembly of projection system
  • G03F7/70266—Adaptive optics, e.g. deformable optical elements for wavefront control, e.g. for aberration adjustment or correction
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/70—Microphotolithographic exposure; Apparatus therefor
  • G03F7/708—Construction of apparatus, e.g. environment aspects, hygiene aspects or materials
  • G03F7/7095—Materials, e.g. materials for housing, stage or other support having particular properties, e.g. weight, strength, conductivity, thermal expansion coefficient
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C2201/00—Glass compositions
  • C03C2201/06—Doped silica-based glasses
  • C03C2201/30—Doped silica-based glasses containing metals
  • C03C2201/40—Doped silica-based glasses containing metals containing transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn
  • C03C2201/42—Doped silica-based glasses containing metals containing transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn containing titanium
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C2218/00—Methods for coating glass
  • C03C2218/10—Deposition methods
  • C03C2218/15—Deposition methods from the vapour phase
  • C03C2218/152—Deposition methods from the vapour phase by cvd
  • C03C2218/153—Deposition methods from the vapour phase by cvd by plasma-enhanced cvd
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C2218/00—Methods for coating glass
  • C03C2218/10—Deposition methods
  • C03C2218/15—Deposition methods from the vapour phase
  • C03C2218/154—Deposition methods from the vapour phase by sputtering
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/06—Glass compositions containing silica with more than 90% silica by weight, e.g. quartz
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2237/00—Aspects relating to ceramic laminates or to joining of ceramic articles with other articles by heating
  • C04B2237/02—Aspects relating to interlayers, e.g. used to join ceramic articles with other articles by heating
  • C04B2237/04—Ceramic interlayers
  • C04B2237/06—Oxidic interlayers
  • C04B2237/062—Oxidic interlayers based on silica or silicates
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2237/00—Aspects relating to ceramic laminates or to joining of ceramic articles with other articles by heating
  • C04B2237/30—Composition of layers of ceramic laminates or of ceramic or metallic articles to be joined by heating, e.g. Si substrates
  • C04B2237/32—Ceramic
  • C04B2237/34—Oxidic
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/08—Mirrors
  • G02B5/10—Mirrors with curved faces

Definitions

• the invention relates to a method for connecting (at least) one attachment to a main body of an optical element, in particular to a main body of a reflecting optical element.
• the invention also relates to an optical element, in particular a reflecting optical element, comprising: a main body and at least one attachment.
• the optical element can be used in a lithography system, in particular in a projection exposure apparatus, for DUV or EUV lithography.
• the optical element is a reflecting optical element
• a reflecting surface is formed on the main body.
• the main body is occasionally also referred to as substrate below.
• the positions and/or orientations of the optical elements must be determined and actuated precisely, partially in all six rigid body degrees of freedom.
• substantially more degrees of freedom are actively adjusted in order to avoid aberrations and, accompanying these, impairments of the imaging result, or at least in order to reduce these to a tolerable level.
• an accuracy of the length measurement in the picometer range may be required.
• the connection of measurement targets of the measurement or sensor system to the (optical) substrate must be positionally stable.
• Adhesives are frequently used to attach actuators and sensor components, e.g., measurement targets, to optical elements.
• this joining method reaches its limits. In particular, this is due to the fact that the requirements in respect of stability are becoming ever more stringent.
• projection exposure apparatuses are becoming more sensitive to deformations and drifts of the optical surfaces.
• the limits for the use of adhesives are caused, in particular, on account of their changes in volume in different environments: Adhesives release water in dry environments, such as a vacuum. Conversely, they take up water when they are subject to cleanroom conditions (approximately 40% to 60% humidity). This is the case if the machine or the lithography system needs to be opened in order to exchange an (optical) component.
• This object is achieved by a method of the type mentioned at the outset, comprising: producing a bonding connection between a surface region, in particular a curved surface region, of the attachment and a surface region, in particular a curved surface region, of the main body.
• the invention it is proposed to produce at least one attachment and the main body by bonding, i.e. , by a joining agent-free, in particular adhesive-free joining method.
• a joining agent in particular an adhesive
• the bonding connection is produced by silicate bonding, by direct bonding, by fusion bonding or by direct laser bonding.
• various (wafer) bonding methods that require no joining agent, such as silicate bonding, direct bonding, fusion bonding (hot fusion bonding) or direct laser bonding.
• silicate bonding the surface regions involved are initially connected by an alkaline liquid. A subsequent heat treatment drives out the moisture. This creates an integral, strong connection.
• direct bonding the (glass) surface regions are cleaned and activated by means of a plasma process.
• the surface regions are contacted and connected by a heat treatment under pressure in vacuo.
• a heat treatment under pressure in vacuo.
• the surface regions or the materials present there are heated by heat treatment, as a rule to just below the melting point or until the transition temperature of the glass phase has been reached or exceeded, and - possibly under pressure in vacuo - are connected or fused to one another.
• direct laser bonding which is occasionally also referred to as laser welding
• laser pulses of an ultrashort pulse laser are radiated at high repetition rates into, or into the vicinity of, an interface between the two surface regions and are focussed there; cf., for example, the article “Strong connection: Welding of different kinds of glass using femtosecond laser pulses”, S. Russ et al. , Lasers in Manufacturing Conference 2017.
• glass materials e.g., ULE® (see below) can be connected to glass materials or to other materials.
• direct laser bonding the requirements in respect of the trueness of shape and in respect of the roughness of the surface regions to be connected to one another are typically less stringent than in the case of other bonding methods.
• form deviations of the surface regions in the micrometer range can be tolerated within the scope of direct laser bonding, and so complicated processing of the surface regions prior to the bonding can be avoided.
• direct laser bonding is also suitable, in particular, for connecting curved surface regions to one another. It is understood that other types of bonding connections that require no joining agent or no adhesive can also be used to produce a connection between the main body and the attachment.
• the surface regions or the surfaces of the attachment and of the main body, between which the bonding connection is produced can be planar surface regions; however, it is also possible that the surface regions between which the bonding connection is produced are curved, i.e. , have a curvature that deviates from a planar surface.
• the bonding connection forms an areal connection or a partial connection between the surface region of the attachment and the surface region of the main body.
• the bonding connection can be an areal connection between the two surface regions; however, it is also possible that the bonding connection is a partial connection between the two surface regions, i.e., that the surface regions are not connected to one another areally (or over the whole area).
• a partial connection, for example a punctiform or line-shaped connection, between the surface regions can be produced by the above-described direct laser bonding, for example.
• the laser pulses are radiated or focussed on a plurality of specified positions or along specified trajectories, e.g., in the form of rings, on the interface between the two surface regions.
• the bonding connection only forms in the regions of the interface irradiated by the pulsed laser beam. This, too, allows the production of a permanent connection with a sufficient breaking resistance between the attachment and the main body.
• the aforementioned bonding methods are particularly suitable for the connection of surface regions formed on glass surfaces. In the case where the surface regions of the attachment and of the main body are formed from different materials from glass materials or glass ceramics, the production of a bonding connection may not be readily possible under certain circumstances.
• the method comprises the following step: applying at least one bondable layer to the surface region of the attachment and/or to the surface region of the main body before producing the bonding connection.
• the surface regions of the components to be joined or only the surface region of one of the components to be joined are/is coated with a bondable layer or coating.
• the bondable layer renders materials bondable which, otherwise, could not be connected to one another by way of a bonding connection.
• the corresponding component (main body or attachment) is coated with the bondable layer, at least in the surface region that forms the joining region.
• the material of the bondable layer typically does not correspond to the (main) material or the main substance from which the respective component (main body or attachment) is formed.
• this also allows main bodies and components which are formed from different substances that cannot be directly connected to one another by a bonding connection to be connected to one another by a bonding connection.
• the main body or the substrate is formed from a glass material
• a bondable layer is applied to a (glass) material that is bondable with most materials, in particular if this is the only way to allow a bonding connection to be produced with the respective other material of the bonding connection.
• the bondable layer includes at least one material or consists of at least one material that is selected from the group comprising: metals, in particular Cr, and dielectric materials, preferably metal oxides or metal fluorides.
• the bondable layer can include least one material selected from the group comprising: S1O2 and AI2O3.
• the main body is formed from a silicate glass material, the application of a layer or a coating made of S1O2 to the material of the attachment was found to be advantageous.
• the at least one bondable layer is applied to the surface region of the main body or of the attachment by PVD (physical vapour deposition), in particular by evaporation or sputtering, by CVD (chemical vapour deposition), in particular by PECVD (plasma enhanced chemical vapour deposition) or LPCVD (low pressure chemical vapour deposition), or by ALD (atomic layer deposition).
• PVD physical vapour deposition
• CVD chemical vapour deposition
• PECVD plasma enhanced chemical vapour deposition
• LPCVD low pressure chemical vapour deposition
• ALD atomic layer deposition
• the main body is formed from a material selected from the group comprising: glass, preferably fused silica, in particular titanium-doped fused silica, or glass ceramic.
• glass materials are well suited to the above-described bonding methods, i.e. , these are bondable materials to which, as a rule, no additional coating/layer made of a bondable material needs to be applied.
• Titanium-doped fused silica e.g., ULE®
• ULE® Titanium-doped fused silica
• Certain glass ceramics, e.g., Zerodur® also have a low coefficient of thermal expansion or a very low dependence of the coefficient of thermal expansion on the temperature and can likewise be used as materials for the main body.
• the attachment is selected from the group comprising: actuators, in particular piezo-actuators, bushings, in particular for actuators, and sensor components, in particular measurement targets for a position sensor system.
• the attachment can be any desired component.
• the component can be coated with the above- described bondable layer in the surface region to be joined (see above).
• Fastening an attachment by means of a bonding connection is sensible, in particular, if the position of the attachment relative to the main body must not change.
• the attachment is an actuator, a bushing for an actuator, for example for an axle or a shaft of an actuator, or a sensor component.
• a change in the position or the orientation of the measurement target relative to the main body is particularly critical if the sensor component is a measurement target which serves to determine the position of the optical element and which is embodied to reflect measurement radiation that is emitted by a measuring device and that should be reflected back to the latter.
• the attachment is formed from a piezoelectric material or a (permanent) magnetic material, at least in the surface region.
• the piezoelectric material is a material with a high piezoelectric coefficient, for example a piezoelectric ceramic, e.g., PMN (lead magnesium niobate), or a piezoelectric crystal.
• the magnetic material is a material with a high magnetic permeability, e.g., Invar, a ceramic that is suitable for magnetic shielding, etc.
• the attachment forms a reinforcing component for reinforcing the main body.
• the main body, on which the reflecting coating is formed can be connected to at least one reinforcing component by way of a bonding connection.
• the reinforcing component allows the thickness of the main body or of the substrate, on which the reflecting surface or coating is formed, to be reduced.
• the main body can have a flat embodiment, for example.
• This variant is advantageous, in particular, for the case where the reinforcing component is formed from a material that differs from the material of the main body. Since the reflecting coating or surface is formed on the main body, the number of materials that can be used for producing the main body is limited. As a rule, no reflecting surface is formed on the reinforcing component, and so the material of this component can be selected from a greater number of materials.
• two or more reinforcing attachments can also be connected to the main body, in each case by way of a bonding connection. Additionally, two or more reinforcing components can be connected to one another by way of at least one bonding connection where necessary.
• the material of the reinforcing component can be a technical ceramic material, for example, which has a high inherent stiffness, e.g., silicon carbide (SiC). It is advantageous if the stiffness of the material of the reinforcing component is greater than the stiffness of the material of the main body; however, this is not mandatory.
• SiC silicon carbide
• At least one cavity is formed between the main body and the reinforcing component and/or formed in the reinforcing component.
• the at least one cavity it is possible to realize a lightweight structure, e.g., in the style of a hollow mirror, since the cavity reduces the (effective) density of the optical element. As a result of this, it is possible to achieve a high stiffness of the optical element in the case of a low mass.
• the cavity can be closed, i.e. , completely sealed off from the surroundings.
• the cavity can be, in particular, a cooling channel, through which a cooling fluid can be guided in order to directly cool the optical element, i.e., without an additional heat sink.
• a further aspect of the invention relates to an optical element of the type set forth at the outset, in which a surface region of the attachment and a surface region of the main body are connected to one another by a bonding connection.
• a connection which makes do without a joining agent, in particular without an adhesive, can increase the positional stability of the attachment relative to the main body of the optical element.
• At least one bondable layer is applied to the surface region of the attachment and/or to the surface region of the main body.
• the material of the bondable layer can be one of the materials described further above in the context of the method.
• the attachment can be formed from a piezoelectric material or a magnetic material, at least in the surface region.
• the attachment is an actuator, in particular a piezo actuator, a bushing, in particular for an actuator, or a sensor component, in particular a measurement target for a position sensor system.
• the position sensor system allows the position and/or the orientation of the optical element to be determined in space relative to a reference component, for example a support frame or the like.
• the attachment forms a reinforcing component.
• at least one cavity can be formed between the main body and the reinforcing component and/or formed in the reinforcing component. This allows a lightweight structure to be produced and the optical element can be cooled or temperature-controlled directly with the aid of the cavity or cavities.
• the main body can be formed from a material selected from the group comprising: glass, preferably fused silica, in particular titanium-doped fused silica, or glass ceramic.
• the main body comprises a reflecting coating, which is embodied to reflect radiation in the EUV wavelength range or in the DUV wavelength range.
• the optical element is a reflecting optical element, for example a mirror.
• the EUV wavelength range is understood to be a wavelength range between approximately 5 nm and approximately 30 nm.
• the DUV wavelength range is understood to be a wavelength range between approximately 30 nm and approximately 370 nm.
• the reflecting coating need not be embodied to reflect radiation over the entire wavelength range. Depending on the application, a high reflectivity of the reflecting coating at one wavelength in the respectively specified wavelength range may be sufficient.
• Fig. 1a,b show schematic illustrations of a mirror with a piezo-actuator connected to the back side of a main body by way of a bonding connection
• Fig. 2 shows a schematic illustration of a mirror with a main body, to which two actuator bushings are connected via a respective bonding connection
• Fig. 3a, b show schematic illustrations of a mirror with a main body, to which two measurement targets are bonded, and
• Fig. 4a, b show schematic illustrations of two mirrors with a main body, which is connected to a reinforcing component by way of a bonding connection.
• FIGS 1a,b schematically show a reflecting optical element 1 in the form of a mirror.
• the mirror 1 has a main body 2 (referred to below as a substrate), a reflecting coating 3 being applied to the front side thereof.
• the reflecting coating 3 is embodied to reflect EUV radiation 4, which impinges on a surface region on the front side of the mirror 1 , to which the reflecting coating 3 has been applied.
• the substrate 2 is formed from titanium-doped fused silica (ULE®); however, it can also be formed from a different (glass) material or a glass ceramic with a low coefficient of thermal expansion.
• the mirror substrate 2 has a continuous opening 5, which connects the front side of the substrate 2 to the back side of the substrate 2 illustrated in Figure 1a.
• An attachment in the form of a piezo-actuator 6 is attached or fastened to the back side of the substrate 2.
• the front side and the back side of the substrate 2 are illustrated as plane surfaces in Figures 1a,b; however, it is understood that the back side and the front side of the substrate 2 can also be curved.
• the piezo-actuator 6 is illustrated in simplified fashion as made of a layer of a piezoelectric material, more precisely PMN; i.e., the illustration of a possibly present encapsulation, of electrical connections, etc., was dispensed with.
• PMN piezoelectric material
• the piezo-actuator 6 renders it possible to alter the surface shape of the mirror 1 on the back side, and consequently also in the region of the reflecting coating 3 on the front side of the substrate 2 as desired in order to correct aberrations of the mirror 1.
• a plurality of piezo-actuators 6 are fastened to the back side of the substrate 2 as a rule, which piezo-actuators can form an actuator group, in particular.
• Such an actuator group relates to a plurality of individually driveable piezo-actuators 6, which form a monolithic group which forms an attachment as a whole.
• the piezo-actuator 6 On its side facing the substrate 2, the piezo-actuator 6 has a surface region 6a which is connected by way of a bonding connection 7 to a surface region 2a on the back side of the substrate 2 facing the piezo-actuator 6. Since the piezoelectric material of the piezo-actuator 6 is not suitable for a bonding connection with a titanium-doped fused silica material of the substrate 2, a bondable layer 8, i.e., a layer made of a bondable material, is applied to the surface region 6a of the piezo-actuator 6. Here, the bondable layer 8 has been applied to the surface region 6a of the piezo-actuator 6 before the bonding connection 7 was produced. It is understood that, unlike what is illustrated in Figures 1a,b, the surface region 2a of the substrate 2 and the surface region 6a of the piezo-actuator 6, which are connected to one another by way of the bonding connection 7, can be curved surfaces.
• the bondable layer 8 was applied by PVD, more precisely by sputtering.
• the bondable layer 8 can also be applied to the surface region 6a to be joined by means of a different coating method, for example by means of CVD, in particular PECVD or LPCVD, or - for the purposes of producing a particularly thin or dense bondable layer - by ALD.
• the material of the bondable layer 8 is Si02.
• the bonding connection 7 is produced by silicate bonding: In this case, the surface of the bondable layer 8 and the surface region 2a of the substrate 2 were initially connected to one another by way of an alkaline liquid and the moisture was driven out by subsequent heat treatment in order to produce an integral, strong connection between the piezo-actuator 6 and the substrate 2. It is understood that the bonding connection 7 can be alternatively produced by direct bonding, by fusion bonding or by direct laser bonding, for example.
• the bonding connection 7 between the surface of the bondable layer 8 and the surface region 2a of the substrate 2 is not necessarily an areal connection. Rather, the bonding connection 7 can be punctiform or line-shaped if the pulsed laser beam is only radiated or focussed onto the interface between the surface region 2a of the substrate 2 and the bondable layer 8 at specified positions or along specified trajectories, e.g., along rings, in order to connect these regions to one another. Such a partial bonding connection can likewise have a high breaking resistance.
• Figure 2 shows a mirror 1 which is fastened to a support frame 10 via two magnetic actuators 6, said support frame serving to hold optical elements in an optical arrangement not illustrated pictorially, for example of a projection exposure apparatus.
• Two attachments in the form of bushings 9 for the two actuators 6 are fastened to the substrate 2.
• the bushings 9 are formed from Invar.
• the bushings 9 may be formed from any other material, for example magnetic material, which serves for magnetic shielding.
• the two actuators 6 allow the positioning of the mirror 1 to be altered relative to the support frame 10.
• the actuators 6 are attached to the back side of the substrate 2 and the reflecting surface or the reflecting coating 3 is formed on the front side of the substrate 2.
• the actuators 6 are only indirectly connected to the substrate 2 (via the bushings 9).
• the bushings 9 are each connected to the substrate 2 via a bonding connection 7 at a ring-shaped surface region 9a, which is formed on the side of the bushings 9 facing the substrate 2.
• a bondable layer is applied to the bushings 9 in the surface region 9a, said bondable layer not being shown in Figure 2 to simplify the illustration.
• the material of the bondable layer is AI2O3; however, it can also be any other dielectric or metallic material (e.g. , Cr, ... ) that is well-suited for the connection to the fused silica material of the substrate 2, for example a metal oxide or metal fluoride.
• FIGs 3a, b schematically show a reflecting optical element 1 for an EUV lithography apparatus, which comprises a substrate 2 and two measurement targets 11.
• the reflecting optical element 2 has a surface with a reflecting coating 3, which is embodied to reflect EUV radiation.
• a respective measurement target 11 is connected to the substrate 2 via a bonding connection 7.
• the bonding connection 7 runs in ring-shaped fashion between a substantially conical surface region 11a of the measurement target 3 and a substantially conical surface region 2a of the substrate 2.
• Each of the two measurement targets 11 comprises a reflecting coating 12, which is embodied to reflect measurement radiation that is emitted by a measuring device 13 shown in Figure 3b and that is reflected back to the latter.
• the measuring device 13 renders it possible to determine an actual position of the measurement target 11 , more precisely of the reflecting coating 12 of the measurement target 11 , with a high accuracy.
• this also allows the position of the substrate 2, more precisely of the reflecting coating 3, to be determined with high accuracy.
• the measurement target 11 is formed from a glass material which can be connected to the material of the substrate 2 by a bonding connection without the measurement target 11 having to be coated with a bondable material to this end. Therefore, the two surface regions 2a, 11a are directly connected to one another by way of the bonding connection 7.
• a layer or a coating made of a bondable material can be applied to the surface region 11a of the measurement target 11 to be joined, depending on the material of the measurement target 11.
• a layer or a coating made of a bondable material can also be applied, where necessary, to the surface region 2a of the substrate 2 to be joined.
• Figures 4a, b each show a reflecting optical element 1 , which comprises a substantially flat substrate 2, on the front side of which a reflecting coating 3 is applied.
• the flat substrate 2 is formed from fused silica.
• a surface region 2a on the back side of the substrate 2 is connected to a surface region 14a of an attachment in the form of reinforcing (substrate) component 14 (or a substrate part) by way of a bonding connection 7.
• a sealed cavity 15 is formed between the substrate 2 and the reinforcing component 14, said cavity being delimited to the side in the region of the bonding connection 7 by the surface region 2a of the substrate 2, extending circumferentially in ring-shaped fashion, and the surface region 14a of the reinforcing (substrate) component 14, extending circumferentially in ring-shaped fashion.
• An optical element 1 with a lightweight construction can be realized by the sealed cavity 15. It is understood that, instead of the sealed cavity 15, one or more cavities that are open to the surroundings can be formed between the substrate 2 and the reinforcing component 14.
• the surface region 2a In the case of the reflecting optical element 1 in the form of a mirror shown in Figure 4b, the surface region 2a, to which the substrate 2 with the reinforcing component 14 is connected, extends over the entire back side of the substrate 2. Accordingly, the surface region 14a, at which the reinforcing component 14 is connected to the substrate 2, also extends over the entire side surface of the reinforcing component 14, which is plane in the example shown. Cavities 15 are introduced into the reinforcing component 14 in the example shown in Figure 4b, it being possible to guide a cooling fluid through said cavities so that the mirror 1 can be cooled directly.
• the reflecting coating 3 is embodied to reflect DUV radiation.
• the substrate 2, to which the reflecting coating 3 has been applied is formed from fused silica in the example shown.
• the component 14 stiffening the main body or the substrate 2 is formed from a technical ceramic substance, more precisely SiC, in the example shown.
• the reinforcing component 14 can also be produced from other materials, which preferably have a high (inherent) stiffness.
• the material of the reinforcing component 14 itself is bondable, i.e. , suitable for producing a bonding connection 7 to the substrate. Should this not be the case, a bondable layer 8 can be applied to the surface region 14a of the reinforcing component 14, which is joined to the surface region 2a of the substrate 2, as indicated in Figure 4b.
• optical elements 1 described further above are mirrors; however, it is understood that other - reflecting or transmitting - optical elements 1 can be connected to attachments in the manner described above, i.e., by way of a bonding connection 7, in order to avoid the disadvantages of an adhesive connection.
• a reflecting coating 3 it may under certain circumstances not be necessary for a reflecting coating 3 to be formed on the substrate 2; instead, a surface region of the substrate 2 can serve as an optical surface for reflecting the incident radiation 4 after an appropriate surface treatment (polishing, etc.).

Landscapes

• Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• General Chemical & Material Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Life Sciences & Earth Sciences (AREA)
• Health & Medical Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• Epidemiology (AREA)
• Public Health (AREA)
• Structural Engineering (AREA)
• Optical Elements Other Than Lenses (AREA)

Applications Claiming Priority (4)

Publications (1)

Family

ID=75268493

Family Applications (1)

Country Status (3)

Cited By (1)

Families Citing this family (2)

Citations (4)

Family Cites Families (3)

• 2019
  • 2019-11-11 DE DE102019217389.6A patent/DE102019217389A1/de not_active Withdrawn
• 2020
  • 2020-10-12 WO PCT/EP2020/078557 patent/WO2021074054A1/en active Application Filing
  • 2020-10-16 TW TW109135838A patent/TW202129310A/zh unknown

Patent Citations (4)

Also Published As

Similar Documents

Legal Events