DE102024203527A1 - OPTICAL SYSTEM, PROJECTION EXPOSURE DEVICE AND METHOD - Google Patents

Abstract

Optical system (100) for a lithography system (1), comprising an optical element (102) with an optically effective surface (106), a connection element (116, 128, 134) which is fastened to the optical element (102), and a holding element (118), wherein the connection element (116, 128, 134) is held on the optical element (102) with the aid of the holding element (118), and wherein the holding element (118) exerts a holding force (F1, F2, F3, F4) on the connection element (116, 128, 134).

Description

The present invention relates to an optical system, a projection exposure apparatus with such an optical system and a method for producing such an optical system.

Microlithography is used to produce microstructured components, such as integrated circuits. The microlithography process is carried out using a lithography system that has an illumination system and a projection system. The image of a mask (reticle) illuminated by the illumination system is projected by the projection system onto a substrate, such as a silicon wafer, that is coated with a light-sensitive layer (photoresist) and arranged in the image plane of the projection system in order to transfer the mask structure onto the light-sensitive coating of the substrate.

Driven by the pursuit of ever smaller structures in the manufacture of integrated circuits, EUV lithography systems are currently being developed that use light with a wavelength in the range of 0.1 nm to 30 nm, in particular 13.5 nm. Since most materials absorb light of this wavelength, such EUV lithography systems must use reflective optics, i.e. mirrors, instead of - as previously - refractive optics, i.e. lenses.

It is known within the company to equip optical elements of a lithography system, such as mirrors, with cooling, in particular water cooling. For example, the optical element for this purpose comprises cavities through which water flows. For this purpose, for example, water pipes are connected to the cavities. This can be done, for example, with the help of connection sockets. Attaching such a connection socket to the optical element is a challenge, since attaching the connection socket and possible aging processes can change a stress state in the optical element and thus deform an optically effective surface of the optical element. Such a deformation can have adverse effects on optical properties of the optically effective surface.

Against this background, an object of the present invention is to provide an improved optical system.

Accordingly, an optical system for a lithography system is proposed. The optical system comprises an optical element with an optically effective surface, a connection element which is fastened to the optical element, and a holding element, wherein the connection element is held on the optical element with the aid of the holding element, and wherein the holding element exerts a holding force on the connection element.

Because the connection element is attached and held to the optical element with the aid of a holding force, a permanent holding force can be ensured. A stable stress state in the optical element can therefore be ensured over the entire service life and, for example, additional joining components such as adhesives can be dispensed with. This means that the stress state is not changed by aging of the optical system due to a particularly permanent holding force. Preferably, less stress is introduced into the optical element with the aid of the holding element. This means that the optically effective surface retains its shape, so that precise light guidance can be ensured over a long service life. In particular, only the holding element exerts the holding force on the connection element. Preferably, the optical element is connected to a support structure with the aid of a fixed or actuated bearing. This actuated bearing comprises, for example, a piezo element.

For example, the connection element is designed to form a fluid-tight interface between a piping for a temperature control medium, in particular a coolant, and the optical element. “Holding force” here means, for example, a force that ensures that the connection element is fixed in at least one degree of freedom or at least two, at least three, at least four, at least five or at least six degrees of freedom. The holding force can include or be a contact force, tensile force, compressive force and/or load-bearing force. The connection element has a fixed connection to the holding element. The connection element can be manufactured integrally with the holding element or subsequently connected to it.

According to one embodiment, the holding force is a tensile force, wherein the holding element comprises a tensile element, preferably a tension rod.

This has the advantage that the holding force can be set precisely and in a targeted manner. The tensile force is set, for example, by means of an elastic stretching of the tension element. In particular, the optical system comprises at least three, four, five, six or more tension rods, which are connected to one another in a star shape, for example. The tensile force is preferably set by means of a thread of, preferably a threaded clamp.

According to a further embodiment, the optical element comprises a cavity.

The cavity is preferably channel-shaped and/or round and/or rotationally symmetrical, at least in sections. In particular, the cavity is designed to be tight.

According to a further embodiment, the cavity is designed as a temperature control channel for the optical element.

This advantageously makes it possible to provide a cooled optical element whose operating temperature can be regulated and/or kept constant. The temperature control channel is designed to receive and channel a temperature control medium, in particular a cooling liquid, such as water or oil. The temperature control medium preferably flows through the cavity.

According to a further embodiment, the tension element projects into the cavity and/or is located completely therein.

For example, the connection element is pressed against an outer surface of the optical element. Advantageously, this can preferably realize a contact force against the surface of the optical element, wherein the contact force is provided from within the optical element.

According to a further embodiment, the optical system comprises at least a first connection element and a second connection element.

In particular, the optical system comprises at least three, four, five or more, for example at least ten, connection elements. Advantageously, this allows a sufficiently large amount of tempering medium to be supplied to and removed from the optical element.

According to a further embodiment, the first connection element and the second connection element are attached to different sides of the optical element and clamped against each other.

For example, the clamping is carried out using a single tension element. The clamping can be carried out in particular using a thread, preferably a thread clamp.

According to a further embodiment, the connection element is fastened to the optical element by means of a frictional connection.

The holding force forms the normal force for the frictional connection, which acts as a contact force against the outer surface of the optical element.

According to a further embodiment, the optical system comprises a bearing, by means of which the optical element can be connected to a support structure, wherein the connection element can be separately connected to the support structure by means of the holding element, and wherein the holding force can be supported by means of the holding element and the support structure.

“Support structure” means, for example, a solid floor that can support forces and/or a wall that can support forces. Preferably, the connection element is connected to the support structure by means of a decoupling element that is designed to enable a relative movement between the support structure and the connection element in exactly one, two or three degrees of freedom. Alternatively, the connection element is connected to the support structure by means of a fixed bearing. Further alternatively, the connection element is connected to the support structure by means of an actuated bearing. Preferably, the optical element is connected to the support structure by means of a fixed or actuated bearing.

According to a further embodiment, the holding force can be supported from outside the optical element.

A force flow therefore flows from the connecting element, preferably directly, into the supporting structure.

According to a further embodiment, the connection element comprises a socket or is designed as such.

The bushing is, for example, round and preferably has rotationally symmetrical sections. A tempering medium supply line can preferably be connected or is connected to the bushing.

According to a further embodiment, a temperature control medium for cooling the optical element can be introduced into the optical element by means of the connection element.

In particular, the tempering medium is provided to the connection element by means of the tempering medium supply line and/or piping and is guided into the cavity of the optical element with the aid of the connection element.

According to a further embodiment, the optical element is designed as a mirror.

The mirror is, for example, a deflecting mirror or a facet mirror.

Furthermore, a projection exposure system with such an optical system is proposed.

The optical system is preferably a projection optics of the projection exposure system. However, the optical system can also be an illumination system. The projection exposure system can be an EUV lithography system. EUV stands for "Extreme Ultraviolet" and refers to a wavelength of the working light between 0.1 nm and 30 nm. The projection exposure system can also be a DUV lithography system. DUV stands for "Deep Ultraviolet" and refers to a wavelength of the working light between 30 nm and 250 nm.

In addition, a method for producing an optical system for a lithography system is proposed. The method comprises the steps: a) providing an optical element with an optically effective surface, a connection element and a holding element, and b) fastening the connection element to the optical element with the aid of the holding element in such a way that the connection element is held on the optical element with the aid of the holding element and the holding element exerts a holding force on the connection element.

For example, all connection elements are first attached to the optical element. In a next step, the optically effective surface is reworked, preferably treated with abrasion, in order to further improve and/or perfect the dimensional accuracy, as this is adversely affected by the attachment of the connection elements and the stresses introduced thereby.

The embodiments and features described for the optical system apply to the proposed projection exposure system and the proposed method accordingly and vice versa.

In this case, "one" is not necessarily to be understood as being limited to just one element. Rather, several elements, such as two, three or more, can also be provided. Any other counting word used here is also not to be understood as meaning that there is a limitation to the exact number of elements mentioned. Rather, numerical deviations upwards and downwards are possible, unless otherwise stated.

Further possible implementations of the invention also include combinations of features or embodiments described above or below with respect to the exemplary embodiments that are not explicitly mentioned. The person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

• 1 zeigt einen schematischen Meridionalschnitt einer Projektionsbelichtungsanlage für die EUV-Projektionslithographie;
• 2 zeigt eine schematische Ansicht einer Ausführungsform eines optischen Systems für die Projektionsbelichtungsanlage gemäß 1;
• 3 zeigt eine schematische Ansicht einer weiteren Ausführungsform eines optischen Systems für die Projektionsbelichtungsanlage gemäß 1;
• 4 zeigt eine schematische Ansicht einer weiteren Ausführungsform eines optischen Systems für die Projektionsbelichtungsanlage gemäß 1;
• 5 zeigt eine schematische Ansicht einer Ausführungsform eines Halteelements und eines Anschlusselements für das optische System gemäß 3 oder 4;
• 6 zeigt eine schematische Ansicht einer weiteren Ausführungsform eines Halteelements und eines Anschlusselements für das optische System gemäß 3 oder 4;
• 7 zeigt eine schematische Ansicht einer weiteren Ausführungsform eines Halteelements und eines Anschlusselements für das optische System gemäß 3 oder 4;
• 8 zeigt eine schematische Ansicht einer weiteren Ausführungsform eines Halteelements und eines Anschlusselements für das optische System gemäß 3 oder 4;
• 9 zeigt eine schematische Ansicht einer weiteren Ausführungsform eines optischen Systems für die Projektionsbelichtungsanlage gemäß 1;
• 10 zeigt eine schematische Ansicht einer weiteren Ausführungsform eines optischen Systems für die Projektionsbelichtungsanlage gemäß 1;
• 11 zeigt eine schematische Ansicht einer weiteren Ausführungsform eines optischen Systems für die Projektionsbelichtungsanlage gemäß 1;
• 12 zeigt eine schematische Ansicht eines Verbindungsschritts des optischen Elements und des Anschlusselements;
• 13 zeigt eine weitere schematische Ansicht eines Verbindungsschritts des optischen Elements und des Anschlusselements;
• 14 zeigt eine weitere schematische Ansicht eines Verbindungsschritts des optischen Elements und des Anschlusselements;
• 15 zeigt eine schematische Ansicht einer Ausführungsform eines Halteelements;
• 16 zeigt eine schematische Ansicht einer weiteren Ausführungsform eines Halteelements;
• 17 zeigt eine schematische Ansicht einer weiteren Ausführungsform eines optischen Systems für die Projektionsbelichtungsanlage gemäß 1;
• 18 zeigt eine schematische Ansicht einer weiteren Ausführungsform eines optischen Systems für die Projektionsbelichtungsanlage gemäß 1;
• 19 zeigt eine schematische Ansicht einer weiteren Ausführungsform eines optischen Systems für die Projektionsbelichtungsanlage gemäß 1;
• 20 zeigt eine schematische Ansicht einer weiteren Ausführungsform eines optischen Systems für die Projektionsbelichtungsanlage gemäß 1;
• 21 zeigt eine schematische Ansicht einer weiteren Ausführungsform eines optischen Systems für die Projektionsbelichtungsanlage gemäß 1;
• 22 zeigt eine schematische Ansicht einer weiteren Ausführungsform eines optischen Systems für die Projektionsbelichtungsanlage gemäß 1; und
• 23 zeigt ein schematisches Blockdiagramm eines Verfahrens zum Herstellen des optischen Systems.

Further advantageous embodiments and aspects of the invention are the subject of the subclaims and the embodiments of the invention described below. The invention is explained in more detail below using preferred embodiments with reference to the attached figures.

• 1 shows a schematic meridional section of a projection exposure system for EUV projection lithography;
• 2 shows a schematic view of an embodiment of an optical system for the projection exposure apparatus according to 1 ;
• 3 shows a schematic view of another embodiment of an optical system for the projection exposure apparatus according to 1 ;
• 4 shows a schematic view of another embodiment of an optical system for the projection exposure apparatus according to 1 ;
• 5 shows a schematic view of an embodiment of a holding element and a connection element for the optical system according to 3 or 4 ;
• 6 shows a schematic view of another embodiment of a holding element and a connecting element for the optical system according to 3 or 4 ;
• 7 shows a schematic view of another embodiment of a holding element and a connecting element for the optical system according to 3 or 4 ;
• 8 shows a schematic view of another embodiment of a holding element and a connecting element for the optical system according to 3 or 4 ;
• 9 shows a schematic view of another embodiment of an optical system for the projection exposure apparatus according to 1 ;
• 10 shows a schematic view of another embodiment of an optical system for the projection exposure apparatus according to 1 ;
• 11 shows a schematic view of another embodiment of an optical system for the projection exposure apparatus according to 1 ;
• 12 shows a schematic view of a connecting step of the optical element and the connection element;
• 13 shows another schematic view of a connecting step of the optical element and the connection element;
• 14 shows another schematic view of a connecting step of the optical element and the connection element;
• 15 shows a schematic view of an embodiment of a holding element;
• 16 shows a schematic view of another embodiment of a holding element;
• 17 shows a schematic view of another embodiment of an optical system for the projection exposure apparatus according to 1 ;
• 18 shows a schematic view of another embodiment of an optical system for the projection exposure apparatus according to 1 ;
• 19 shows a schematic view of another embodiment of an optical system for the projection exposure apparatus according to 1 ;
• 20 shows a schematic view of another embodiment of an optical system for the projection exposure apparatus according to 1 ;
• 21 shows a schematic view of another embodiment of an optical system for the projection exposure apparatus according to 1 ;
• 22 shows a schematic view of another embodiment of an optical system for the projection exposure apparatus according to 1 ; and
• 23 shows a schematic block diagram of a method for manufacturing the optical system.

In the figures, identical or functionally equivalent elements have been given the same reference symbols unless otherwise stated. It should also be noted that the representations in the figures are not necessarily to scale.

1 shows an embodiment of a projection exposure system 1 (lithography system), in particular an EUV lithography system. An embodiment of an illumination system 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 separate module from the rest of the illumination system 2. In this case, the illumination system 2 does not comprise the light source 3.

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 via a reticle displacement drive 9, in particular in a scanning direction.

In the 1 For explanation purposes, a Cartesian coordinate system with an x-direction x, a y-direction y and a z-direction z is shown. The x-direction x runs perpendicularly into the plane of the drawing. The y-direction y runs horizontally and the z-direction z runs vertically. The scanning direction runs in the 1 along the y-direction y. The z-direction z runs perpendicular to the object plane 6.

The projection exposure system 1 comprises a projection optics 10. The projection optics 10 serves to image the object field 5 into an image field 11 in an image plane 12. The image plane 12 runs parallel to the object plane 6. Alternatively, an angle other than 0° between the object plane 6 and the image plane 12 is also possible.

A structure on the reticle 7 is imaged onto a light-sensitive layer of a wafer 13 arranged in the area 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 via a wafer displacement drive 15, in particular along the y-direction y. 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 one another.

The light source 3 is an EUV radiation source. The light source 3 emits in particular EUV radiation 16, which is also referred to below as useful radiation, illumination radiation or illumination light. The useful radiation 16 has in particular a wavelength in the range between 5 nm and 30 nm. The light source 3 can be a plasma source, for example an LPP source (Laser Produced Plasma, plasma produced with the aid of a laser) or a DPP source (Gas Discharged Produced Plasma (LPP). It can also be a synchrotron-based radiation source. Light source 3 can be a free-electron laser (FEL).

The illumination radiation 16 that emanates from the light source 3 is bundled by a collector 17. The collector 17 can be a collector with one or more ellipsoidal and/or hyperboloidal reflection surfaces. The at least one reflection surface of the collector 17 can be exposed to the illumination radiation 16 in grazing incidence (GI), i.e. with angles of incidence greater than 45°, or in normal incidence (NI), i.e. with angles of incidence less than 45°. The collector 17 can be structured and/or coated on the one hand to optimize its reflectivity for the useful radiation and on the other hand to suppress stray light.

After the collector 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 can represent a separation between a radiation source module, comprising the light source 3 and the collector 17, and the illumination optics 4.

The illumination optics 4 comprise a deflection mirror 19 and a first facet mirror 20 arranged downstream of this in the beam path. The deflection mirror 19 can be a flat deflection mirror or alternatively a mirror with a beam-influencing effect beyond the pure deflection effect. Alternatively or additionally, the deflection mirror 19 can be designed as a spectral filter which separates a useful light wavelength of the illumination radiation 16 from false light of a different wavelength. If the first facet mirror 20 is arranged in a plane of the illumination optics 4 which is optically conjugated to the object plane 6 as a field plane, it is also referred to as a field facet mirror. The first facet mirror 20 comprises a plurality of individual first facets 21, which can also be referred to as field facets. Of these first facets 21, only one is shown in the 1 only a few examples are shown.

The first facets 21 can be designed as macroscopic facets, in particular as rectangular facets or as facets with an arcuate or partially circular edge contour. The first facets 21 can be designed as flat facets or alternatively as convex or concave curved facets.

As for example from the DE 10 2008 009 600 A1 As is known, the first facets 21 themselves can also be composed of a plurality of individual mirrors, in particular a plurality of micromirrors. The first facet mirror 20 can in particular be designed as a microelectromechanical system (MEMS system). For details, see the DE 10 2008 009 600 A1 referred to.

Between the collector 17 and the deflection mirror 19, the illumination radiation 16 runs horizontally, i.e. along the y-direction y.

In the beam path of the illumination optics 4, a second facet mirror 22 is arranged downstream of the first facet mirror 20. If the second facet mirror 22 is arranged in a pupil plane of the illumination optics 4, it is also referred to as a pupil facet mirror. The second facet mirror 22 can also be arranged at a distance from a pupil plane of the illumination optics 4. In this case, the combination of the first facet mirror 20 and the second facet mirror 22 is also referred to as a specular reflector. Specular reflectors are known from the US 2006/0132747 A1 , the EP 1 614 008 B1 and the US 6,573,978 .

The second facet mirror 22 comprises a plurality of second facets 23. In the case of a pupil facet mirror, the second facets 23 are also referred to as pupil facets.

The second facets 23 can also be macroscopic facets, which can be round, rectangular or hexagonal, for example, or alternatively facets composed of micromirrors. In this regard, reference is also made to the DE 10 2008 009 600 A1 referred to.

The second facets 23 can have planar or alternatively convex or concave curved reflection surfaces.

The illumination optics 4 thus forms a double-faceted system. This basic principle is also known as a fly's eye integrator.

It may be advantageous not to arrange the second facet mirror 22 exactly in a plane that is optically conjugated to a pupil plane of the projection optics 10. In particular, the second facet mirror 22 can be arranged tilted relative to a pupil plane of the projection optics 10, as is the case, for example, in the DE 10 2017 220 586 A1 described.

With the help of the second facet mirror 22, the individual first facets 21 are imaged in the object field 5. The second facet mirror 22 is the last bundle-forming or actually the last mirror for the illumination radiation 16 in the beam path in front of the object field 5.

In a further embodiment of the illumination optics 4 (not shown), a transmission optics can be arranged in the beam path between the second facet mirror 22 and the object field 5, which contributes in particular to the imaging of the first facets 21 in the object field 5. The transmission optics can have exactly one mirror, but alternatively also two or more mirrors, which are arranged one behind the other in the beam path of the illumination optics 4. The transmission optics can in particular comprise one or two mirrors for vertical incidence (NI mirrors, normal incidence mirrors) and/or one or two mirrors for grazing incidence (GI mirrors, grazing incidence mirrors).

The lighting optics 4 have in the version shown in the 1 As shown, after the collector 17 there are exactly three mirrors, namely the deflection mirror 19, the first facet mirror 20 and the second facet mirror 22.

In a further embodiment of the illumination optics 4, the deflection mirror 19 can also be omitted, so that the illumination optics 4 can then have exactly two mirrors after the collector 17, namely the first facet mirror 20 and the second facet mirror 22.

The imaging of the first facets 21 by means of the second facets 23 or with the second facets 23 and a transmission optics into the object plane 6 is usually only an approximate imaging.

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

In the 1 In the example shown, the projection optics 10 comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve or another number of mirrors Mi are also possible. The projection optics 10 is a double obscured optics. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation 16. The projection optics 10 has a numerical aperture on the image side that is greater than 0.33 and can also be greater than 0.6 and can be, for example, 0.7 or 0.75.

Reflection surfaces of the mirrors Mi can be designed as free-form surfaces without a rotational symmetry axis. Alternatively, the reflection surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one rotational symmetry axis of the reflection surface shape. The mirrors Mi, just like the mirrors of the illumination optics 4, can have highly reflective coatings for the illumination radiation 16. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

The projection optics 10 have a large object-image offset in the y-direction y between a y-coordinate of a center of the object field 5 and a y-coordinate of the center of the image field 11. This object-image offset in the y-direction y can be approximately as large as a z-distance between the object plane 6 and the image plane 12.

The projection optics 10 can in particular be anamorphic. In particular, it has different image scales Bx, By in the x and y directions x, y. The two image scales βx, βy of the projection optics 10 are preferably (βx, βy) = (+/- 0.25, +/- 0.125). A positive image scale β means an image without image inversion. A negative sign for the image scale β means an image with image inversion.

The projection optics 10 thus leads to a reduction in the ratio 4:1 in the x-direction x, i.e. in the direction perpendicular to the scanning direction.

The projection optics 10 leads to a reduction of 8:1 in the y-direction y, i.e. in the scanning direction.

Other image scales are also possible. Image scales with the same sign and absolutely the same in the x and y directions x, y, for example with absolute values of 0.125 or 0.25, are also possible.

The number of intermediate image planes in the x and y directions x, y in the beam path between the object field 5 and the image field 11 can be the same or can be different depending on the design of the projection optics 10. Examples of projection optics with different numbers of such intermediate images in the x and y directions x, y are known from US 2018/0074303 A1 .

Each of the second facets 23 is assigned to exactly one of the first facets 21 to form a respective illumination channel for illuminating the object field 5. This can in particular result in illumination according to the Köhler's principle. The far field is broken down into a plurality of object fields 5 using the first facets 21. The first facets 21 generate a plurality of images of the intermediate focus on the second facets 23 assigned to them.

The first facets 21 are each imaged onto the reticle 7 by an associated second facet 23, superimposing one another, to illuminate the object field 5. The illumination of the object field 5 is in particular as homogeneous as possible. It preferably has a uniformity error of less than 2%. The field uniformity can be achieved by superimposing different illumination channels.

By arranging the second facets 23, the illumination of the entrance pupil of the projection optics 10 can be defined geometrically. By selecting the illumination channels, in particular the subset of the second facets 23 that guide light, the intensity distribution in the entrance pupil of the projection optics 10 can be set. This intensity distribution is also referred to as the illumination setting or illumination pupil filling.

A likewise preferred pupil uniformity in the area of defined illuminated sections of an illumination pupil of the illumination optics 4 can be achieved by a redistribution of the illumination channels.

In the following, further aspects and details of the illumination of the object field 5 and in particular of the entrance pupil of the projection optics 10 are described.

The projection optics 10 can in particular have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

The entrance pupil of the projection optics 10 cannot usually be illuminated precisely with the second facet mirror 22. When the projection optics 10 images the center of the second facet mirror 22 telecentrically onto the wafer 13, the aperture rays often do not intersect at a single point. However, a surface can be found in which the pairwise determined distance of the aperture rays is minimal. This surface represents the entrance pupil or a surface conjugated to it in spatial space. In particular, this surface shows a finite curvature.

It is possible that the projection optics 10 have different positions of the entrance pupil for the tangential and the sagittal beam path. In this case, an imaging element, in particular an optical component of the transmission optics, should be provided between the second facet mirror 22 and the reticle 7. With the help of this optical element, the different positions of the tangential entrance pupil and the sagittal entrance pupil can be taken into account.

In the 1 In the arrangement of the components of the illumination optics 4 shown, the second facet mirror 22 is arranged in a surface conjugated to the entrance pupil of the projection optics 10. The first facet mirror 20 is arranged tilted to the object plane 6. The first facet mirror 20 is arranged tilted to an arrangement plane that is defined by the deflection mirror 19. The first facet mirror 20 is arranged tilted to an arrangement plane that is defined by the second facet mirror 22.

2 shows a schematic view of an embodiment of an optical system 100 for the projection exposure apparatus 1.

The optical system 100 can be a projection optics 10 as previously explained or part of such a projection optics 10. Therefore, the optical system 100 can also be referred to as a projection optics. However, the optical system 100 can also be an illumination system 2 as previously explained or part of such an illumination system 2. Therefore, the optical system 100 can alternatively also be referred to as an illumination system. However, it is assumed below that the optical system 100 is a projection optics 10 or part of such a projection optics 10. The optical system 100 is suitable for EUV lithography. However, the optical system 100 can also be suitable for DUV lithography.

The optical system 100 may comprise a plurality of optical elements 102, of which 2 however, only one is shown. Therefore, only one optical element 102 is discussed below. The optical element 102 can be one of the mirrors M1 to M6. The optical element 102 comprises a substrate 104 and an optically effective surface 106, for example a mirror surface. The substrate 104 can also be referred to as a mirror substrate. The substrate 104 can comprise glass, ceramic, glass ceramic or other suitable materials. The optically effective surface 106 is suitable for reflecting illumination radiation 16, in particular EUV radiation. The optical element 102 can have any geometry. In the 2 the optical element 102 and the optically effective surface 106 are shown only very simplified.

A plurality of temperature control channels 108 lead through the substrate 104, of which 2 However, only one is shown. Therefore, reference is made below to only one tempering channel 108. The tempering channel 108 can also be referred to as a cooling channel. The tempering channel 108 can be introduced into the substrate 104 using an abrasive manufacturing process, for example using deep hole drilling. In the simplest case, the tempering channel 108 can - as in the 2 shown - lead straight through the substrate 104. The temperature control channel 108 can, however, also be curved, for example curved in a meandering shape. However, not only the optical element 102 can have such a temperature control channel 108, but also any other components of the optical system 100, such as support structures of the optical element 102, can have such a temperature control channel 108.

The optical element 102 is assigned a temperature control device 110, which is part of the optical system 100. The temperature control device 110 can also be referred to as a cooling device. The temperature control channel 108 can be part of the temperature control device 110. With the help of the temperature control device 110, the temperature control channel 108 can be flushed with a temperature control medium K, for example in the form of demineralized water, in order to dissipate heat Q, which is introduced into the optical element 102, for example with the help of the illumination radiation 16, from the optical element 102. Conversely, heat Q can also be supplied to the optical element 102 with the temperature control medium K. However, it is assumed below that heat Q is dissipated with the help of the temperature control medium K. Therefore, the temperature control medium K can also be referred to as a cooling medium. The temperature control medium K is a liquid.

In addition to the temperature control channel 108, the temperature control device 110 has a pump 112, in particular a water pump, and a piping 114 which fluidically connects an inlet and an outlet of the pump 112 to the temperature control channel 108. Preferably, the piping 114 is - unlike in the 2 shown - not from the side of the optical element 102, but from the back. For this purpose, suitable connecting pieces can be provided on the optical element 102, to which the piping 114 can be flanged. The piping 114 can be flexibly deformable at least in sections.

3 shows a schematic view of another embodiment of an optical system 100 for the projection exposure apparatus 1.

The optically effective surface 106, the temperature control device 110, the pump 112, the temperature control medium K and the piping 114 are no longer shown below, but can be part of any other embodiment of the optical system 100 (see 2 ).

The optical system 100 comprises a connection element 116, which is attached to the optical element 102, and a holding element 118, wherein the connection element 116 is held on the optical element 102 by means of the holding element 118, and wherein the holding element 118 exerts a holding force F1 on the connection element 116. The connection element 116 is, for example, a socket or is designed as such. The temperature control medium K (see 2 ) for tempering the optical element 102 can be introduced into the optical element 102.

The temperature control channel 108 comprises a cavity 120. The holding force F1 is, for example, a tensile force. The holding element 118 is therefore a tensile element, preferably a pull rod. The holding element 118 protrudes into the cavity 120 and is located completely therein. The connection element 116 further comprises a channel 122 through which the temperature control medium K (see 2 ) for tempering the optical element 102 can be introduced into the optical element 102.

The optical system 100 further comprises a sealing element 124 that seals between the connection element 116 and the optical element 102. The sealing element 124 can be designed as an O-ring, for example, or can include it. The sealing element 124 is pressed onto the optical element 102 by means of the holding force F1. This creates a frictional connection, so that the connection element 116 is attached to the optical element 102 by means of the frictional connection. The sealing element 124 is pressed by means of the frictional connection, so that a reliable seal is created. The sealing and/or attachment of the connection element 116 can therefore preferably take place without a material-bonded joining process, for example without additional adhesive.

The sealing element 124 is designed to seal the cavity 120 and the channel 122 against an external environment U of the optical system 100. The external environment U is, for example, a room, preferably a clean room, of the projection exposure system 1. The channel 122 is, for example, a bore, in particular a central bore, which is designed to convey the tempering medium K (see 2 ). For example, the connection element 116 is pressed against an outer surface 126 of the optical element 102, with the sealing element 124 being located directly between the optical ical element 102 and the connecting element 116 and is pressed against the outer surface 126.

The optical system 100 further comprises a connection element 128 (also referred to as a second connection element). The connection element 128 is designed, for example, like the connection element 116. The connection element 116 and the connection element 128 are attached to different sides, for example opposite sides, of the optical element 102 and are clamped against each other. The connection element 128 is held on the optical element 102 with the aid of the holding element 118, wherein the holding element 118 exerts a holding force F2 on the connection element 128. In this case, the holding force F1 is designed as a counterforce to the holding force F2. Both connection elements 116, 128 are clamped against each other with the aid of the holding element 118. This can be done, for example, with the aid of a thread (not shown), in particular a thread clamping device. Furthermore, the holding forces F1, F2 can be adjusted with the aid of the thread and a screwing movement. The thread is, for example, self-locking. The connecting element 128 acts as a counterholder for the connecting element 116. The holding forces F1, F2 are adjusted, for example, by means of an elastic expansion of the holding element 118.

The holding element 118 can also be designed as a flexible tension element, such as a wire or rope. The sealing element 124 can be clamped axially or in other planes against the optical element 102. The connection element 128 also comprises a channel 130. Between the optical element 102 and the connection element 128, a sealing element 132 is provided in analogy to the sealing element 124. Each connection element 116, 128 is designed to form a fluid-tight interface between the piping 114 (see 2 ) and the optical element 102. For this purpose, the piping 114 (see 2 ) is connected to the connection element 116, in particular detachably.

Grooves or other surfaces (not shown) can be provided for positioning and/or centering the holding element 118 and/or the respective connection element 116, 128. The respective holding force F1, F2 is set in such a way that a sufficient sealing effect of the sealing elements 124, 132 is ensured under operating loads and positioning and/or centering takes place. The cavity 120 is provided, for example, as a through-opening, in particular a through-bore.

When integrating the respective connection element 116, 128 within the optical element 102, bracing with the aid of the holding element 118, in particular the support elements, with compressive stress or a combination of compressive and tensile stresses can also be provided (not shown).

4 shows a schematic view of another embodiment of an optical system 100 for the projection exposure apparatus 1.

A further connection element 134 with a channel 136 is provided, which is attached to the optical element 102 in a fluid-tight manner with the aid of a sealing element 138. The holding element 118 comprises three sections 140, 142, 144, in particular tension elements such as tension rods, which are connected to one another in a star shape, for example, and press the connection elements 116, 128, 134 force-fittingly onto the optical element 102. The connection element 134 is designed like the connection elements 116, 128.

In particular, the holding element 118 comprises at least four, five, six or more sections 140, 142, 144, which are connected to one another in a star shape, for example, and each presses a connection element 116, 128, 134 onto the optical element 102. The optical system 100 can comprise any number of connection elements 116, 128, 134.

5 shows a schematic view of an embodiment of a holding element 118 and the connection element 116 from 3 or 4 .

On the left side of the 5 A schematic longitudinal sectional view is shown. On the right side, a plan view, for example from inside the cavity 120 (see 3 ) looking at the connection element 116. The holding element 118 comprises, for example, two pull rods 146, 148 arranged next to one another, in particular parallel, which protrude from an inner side 150 of the connection element 116 and extend into the cavity 120 (see 3 ). The inner surface 150 is the outer surface 126 (see 3 ). The tie rods 146, 148 are provided outside the channel 122. More than two tie rods 146, 148 can also be provided, for example at least three, four or five. The tie rods 146, 148 can be formed as a single piece with the connection element 116 or can be joined to it, in particular by means of a screw connection. The tempering medium K is therefore guided next to the holding element 118.

6 shows a schematic view of another embodiment of a holding element 118 and the connecting element 116.

In contrast to the 5 shows the 6 a holding element 118, which comprises a pull rod 152, a node section 154 and two pull rod sections 156, 158. The pull rod 152 is angled at the node section 154 to the pull rod sections 156, 158 and connected outside the channel 122, wherein the pull rod sections 156, 158 are angled to the inner side 150, in particular integrally or by means of a thread, and protrude from it.

7 shows a schematic view of another embodiment of a holding element 118 and the connecting element 116.

In contrast to the 6 the holding element 118 comprises the pull rod 152 and the pull rod section 156, which are connected to one another in a T-shape in the channel 122. The pull rod section 156 is connected to the connection element 116 in the channel 122.

8 shows a schematic view of another embodiment of a holding element 118 and the connecting element 116.

In contrast to the 5 , 6 and 7 the holding element 118 comprises channels 160, 162 which fluidically connect the channel 122 to the cavity 120. The channels 160, 162 each have a smaller cross-section than the channel 122 and are angled to one another and are also provided with the channel 122. The temperature control medium K is thus guided through the holding element 118, which is hollow at least in sections.

9 shows a schematic view of another embodiment of an optical system 100 for the projection exposure apparatus 1.

In contrast to the 3 In this embodiment, the connection elements 116, 128, 134 can be fastened to the optical element 102 independently of one another. It is provided that the support of the holding element 118 takes place within the cavity 120. The temperature control channel 108 begins with an inlet section 164 and merges into the cavity 120, wherein the cavity 120 has a larger cross-section than the inlet section 164. Therefore, the substrate 104 comprises an inner surface 166 within the cavity 120, which faces away from the outer surface 126 and is arranged in an undercut with respect to the connection element 116. The inlet section 164 is designed as a cavity.

The holding element 118 comprises an elongated pulling section 168 that extends through the entry section 164 and a counter-holding section 170, the entry section 164 being connected at its end to the counter-holding section 170. The counter-holding section 170 is arranged in the cavity 120 and is pressed against the surface 166 directly or by means of an optional pressure element 172. The pressure element 172 is, for example, a fixing element and/or a seal. The counter-holding section 170 extends radially beyond the entry section 164 and forms a positive connection with the substrate 104 in the direction of the connection element 116. The pulling section 168 is, for example, rotatable and formed with the aid of a thread relative to the connection element 116 and/or the counter-holding section 170. The pressure element 172 can be designed to be elastic in order to enable support on the optical element 102 after pressing.

The holding element 118 further comprises a head section 174, which rests on the connection element 116 and forms a positive connection with the connection element 116, in particular in the direction of the cavity 120. The pulling section 168 extends through the connection element 116 and is connected at its other end to the head section 174, wherein the head section 174 forms a radial expansion relative to the pulling section 168. By fixing the counter-holding section 170 and rotating the head section 174, a relative rotational movement can take place with the aid of the threaded connection (not shown) between the pulling section 168 and the counter-holding section 170, so that the head section 174 and the counter-holding section 170 are moved towards one another and the connection element 116 is clamped between the surface 126 and the head section 174.

10 shows a schematic view of another embodiment of an optical system 100 for the projection exposure apparatus 1.

The counter-holding section 170 comprises eccentric channels 176, 178 which create a fluid connection between the cavity 120 and the inlet section 164.

11 shows a schematic view of another embodiment of an optical system 100 for the projection exposure apparatus 1.

In contrast to the 10 the counter-holding section 170, the pulling section 168 and the connecting element 116 each have a central through-opening which forms a central through-channel 180.

12 , 13 and 14 show schematic views of connection steps of the optical element 102 and the connection element 116.

For example, the counter-holding section 170 can be designed to be foldable relative to the pulling section 168. In the folded state, the pulling section 168 can be introduced into the cavity 120 through the narrower entry section 164 ( 12 ). The counter holding section 170 can then be folded out as shown in the 14 shown, and then tightened, as in the 9 shown.

Alternatively, the counter-holding section 170 can be designed as in the 13 shown can be designed to be foldable and/or collapsible like an umbrella. The entry section 164 has, for example, a circular, oval or rectangular cross-section. Alternatively, a connection between the optical element 102 and the connection element 116 can be designed analogously to a bayonet lock.

15 shows a schematic view of an embodiment of a holding element 118.

The holding element 118 comprises a rectangular frame section 182, which is mounted in a rotational manner relative to the pulling section 168 by means of a bearing 184, in particular pivot pins, in order to 12 shown folded into the cavity 120. Furthermore, the pressure elements 172 are provided flat on the frame section 182 in order to be pressed against the inner surface 166 of the cavity 120 (see 9 ) to be pressed.

16 shows a schematic view of another embodiment of the holding element 118.

In contrast to the 15 the frame portion 182 is oval or elliptical.

17 shows a schematic view of another embodiment of an optical system 100 for the projection exposure apparatus 1.

In contrast to the 9 the counter-holding section 170 is fixed in the inlet section 164 and not in the cavity 120. The fixing is not done by a positive connection, but by a frictional connection. The frictional connection is formed by the fact that the counter-holding section 170 is designed to be radially expandable. The radial expansion of the counter-holding section 170 compresses the pressure element 172 and presses it into the inlet section 164. Radial expansion can be achieved, for example, by pushing wedges apart or pushing them into one another so that they move in the radial direction (not shown). Other expansion elements are also conceivable.

18 shows a schematic view of another embodiment of an optical system 100 for the projection exposure apparatus 1.

In contrast to the 9 the inner surface 166 of the substrate 104 in the cavity 120 is formed at an angle and not parallel to the surface 126. The surface 166 is formed, for example, in the shape of a truncated cone or a truncated pyramid. Alternatively, only two inclined surfaces 166 are formed. The pressure element 172 is pressed against the inclined surface 166 and compressed. This can provide, for example, centering.

19 shows a schematic view of another embodiment of an optical system 100 for the projection exposure apparatus 1.

The optical system 100 comprises a bearing 184, 186, with the aid of which the optical element 102 can be connected to a support structure 188, wherein the connection element 116 can be separately connected to the support structure 188 with the aid of the holding element 118. A holding force F3, F4 can be supported with the aid of the holding element 118 and the support structure 188. This directs a force flow from the connection element 116 into the support structure 188. The holding force F3, F4 is thus applied from outside the optical element 102 and not as in the 3 shown can be supported from within the optical element 102. Preferably, fixed direct connecting elements between the optical element 102 and the connection element 116 are omitted.

The holding element 118 thus functions as a bearing or is included in this. The connection element 116 includes, for example, an insertion section 190, which is preferably sealed radially in the cavity 120 with the aid of the sealing element 124. The bearings 184, 186, 118 are preferably not actuated. The bearings 184, 186, 118 are designed, for example, as fixed bearings.

For passive (i.e. non-moving) optical elements 102, the connection can be rigid to the support structure 188. The support structure 188 can be a floor on which the optical element 102 stands or an adjacent wall. Any support structure located in the machine can be used.

20 shows a schematic view of another embodiment of an optical system 100 for the projection exposure apparatus 1.

In contrast to the 19 the bearings 184, 186 are attached to the optical element 102 with the aid of actuators 192, 194. Furthermore, the holding element 118 is attached to the connection element 116 with the aid of an actuator 196. The optical element 102 and the connection element 116 are thus designed to be mounted in an actuated manner. The actuators 192, 194, 196 each comprise, for example, a piezo element.

21 shows a schematic view of another embodiment of an optical system 100 for the projection exposure apparatus 1.

In contrast to the 20 Instead of the actuator 196, a bearing 198 is provided which supports the connection element 116 at least in one axial direction, preferably in the direction of the cavity 120.

22 shows a schematic view of another embodiment of an optical system 100 for the projection exposure apparatus 1.

In contrast to the 21 no bearing 198 is provided. The holding element 118 is thus designed as a fixed bearing. A relative movement between the optical element 102 and the connection element 116 is thus possible. For example, sliding over the sealing element 124 can take place.

The optical system 100 can also be used, for example, in a DUV lithography system.

23 shows a schematic block diagram of a method for producing an optical system 100 for a lithography system 1.

In a step S1, an optical element 102 with an optically effective surface 106, a connection element 116, 128, 134 and a holding element 118 are provided. In a step S2, the connection element 116 is fastened to the optical element 102 with the aid of the holding element 118 in such a way that the connection element 116, 128, 134 is held on the optical element 102 with the aid of the holding element 118 and the holding element 118 exerts a holding force F1, F2, F3, F4 on the connection element 116, 128, 134.

For example, all connection elements 116, 128, 134 are first attached to the optical element 102. In a step S3, the optically effective surface 106 is machined again, preferably treated with abrasives, in order to further improve the dimensional accuracy in particular, since this is adversely affected by the step S2 of attaching the connection elements 116, 128, 134 and the stresses introduced thereby.

Although the present invention has been described using exemplary embodiments, it can be modified in many ways.

REFERENCE SYMBOL LIST

1

projection exposure system

2

lighting system

3

light source

4

lighting optics

5

object field

6

object level

7

reticle

8

reticle holder

9

reticle displacement drive

10

projection optics

11

image field

12

image plane

13

wafer

14

wafer holder

15

wafer relocation drive

16

illumination radiation

17

collector

18

intermediate focal plane

19

deflecting mirror

20

first faceted mirror

21

first facet

22

second facet mirror

23

second facet

100

optical system

102

optical element

104

substrate

106

optically effective surface

108

tempering channel

110

tempering device

112

pump

114

piping

116

connecting element

118

holding element

120

cavity

122

channel

124

sealing element

126

outer surface

128

connecting element

130

channel

132

sealing element

134

connecting element

136

channel

138

sealing element

140

Section

142

Section

144

Section

146

drawbar

148

drawbar

150

inside

152

drawbar

154

node section

156

tie rod section

158

tie rod section

160

channel

162

channel

164

entry section

166

Area

168

train section

170

counterholding section

172

pressure element

174

head section

176

channel

178

channel

180

through channel

182

frame section

184

storage

186

storage

188

supporting structure

190

introductory section

192

actuator

194

actuator

196

actuator

198

camp

F1

holding power

F2

holding power

F3

holding power

F4

holding power

K

tempering medium

M1

Mirror

M2

Mirror

M3

Mirror

M4

Mirror

M5

Mirror

M6

Mirror

Q

warmth

S1

Step

S2

Step

S3

Step

U

Vicinity

x

x-direction

y

y-direction

z

z-direction

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 10 2008 009 600 A1 [0052, 0056]
• US 2006/0132747 A1 [0054]
• EP 1 614 008 B1 [0054]
• US 6,573,978 [0054]
• DE 10 2017 220 586 A1 [0059]
• US 2018/0074303 A1 [0073]

Claims (15)

Optical system (100) for a lithography system (1), comprising an optical element (102) with an optically effective surface (106), a connection element (116, 128, 134) which is fastened to the optical element (102), and a holding element (118), wherein the connection element (116, 128, 134) is held on the optical element (102) with the aid of the holding element (118), and wherein the holding element (118) exerts a holding force (F1, F2, F3, F4) on the connection element (116, 128, 134). Optical system according to claim 1 , wherein the holding force (F1, F2) is a tensile force, and wherein the holding element (118) comprises a tensile element (146, 148, 152, 156, 158, 168), preferably a tension rod. Optical system according to claim 1 or 2 , wherein the optical element (102) comprises a cavity (120, 164). Optical system according to claim 3 , wherein the cavity (120, 164) is designed as a tempering channel (108) for the optical element (102). Optical system according to claim 3 or 4 , wherein the tension element (146, 148, 152, 156, 158, 168) projects into the cavity (120, 164) and/or is located entirely therein. Optical system according to one of the Claims 1 - 5 , further comprising at least a first connection element (116) and a second connection element (128). Optical system according to claim 6 , wherein the first connection element (116) and the second connection element (128) are attached to different sides of the optical element (102) and clamped against each other. Optical system according to one of the Claims 1 - 7 , wherein the connection element (116, 128, 134) is fastened to the optical element (102) by means of a frictional connection. Optical system according to one of the Claims 1 - 8 , further comprising a bearing (184, 186) by means of which the optical element (102) can be connected to a support structure (188), wherein by means of the holding element (118) the connection element (116, 128, 134) can be separately connected to the support structure (188), and wherein the holding force (F3, F4) can be supported by means of the holding element (118) and the support structure (188). Optical system according to one of the Claims 1 - 9 , wherein the holding force (F3, F4) can be supported from outside the optical element (102). Optical system according to one of the Claims 1 - 10 , wherein the connection element (116, 128, 134) comprises a socket or is designed as such. Optical system according to one of the Claims 1 - 11 , wherein a tempering medium (K) for cooling the optical element (102) can be introduced into the optical element (102) by means of the connection element (116, 128, 134). Optical system according to one of the Claims 1 - 12 , wherein the optical element (102) is designed as a mirror (M1, M2, M3, M4, M5, M6). Projection exposure system (1) with an optical system (100) according to one of the Claims 1 - 13 . Method for producing an optical system (100) for a lithography system (1), comprising the steps: a) providing (S1) an optical element (102) with an optically effective surface (106), a connection element (116, 128, 134) and a holding element (118), and b) fastening (S2) the connection element (116, 128, 134) to the optical element (102) with the aid of the holding element (118) such that the connection element (116, 128, 134) is held on the optical element (102) with the aid of the holding element (118) and the holding element (118) exerts a holding force (F1, F2, F3, F4) on the connection element (116, 128, 134).

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