Holding device for an optical component having an optical surface with a polygonal boundary and a columnar base

Abstract

The holding device (61) serves to hold an optical component (62) having an optical surface with a polygonal boundary and a cylindrical base (38) having a cylindrical side wall (39) with a polygonal cross section corresponding to the boundary of the optical surface. The holding device (61) has a holding frame (64). At least two bearings (66-68) of the holding device (61) serve to abut the side wall (39) of the base (38) via bearing portions (69-71) of the side wall (39). At least one pressure body (63) of the holding device (61) applies a bearing pressure (F) that presses the base (38) against the bearings (66-68). D As a result, a holding device is obtained that can securely hold an optical component having an optical surface with a polygonal boundary and a columnar base, and that can be mounted with high positional accuracy.

Description

[Technical Field]

[0001] This patent application claims priority from German Patent Application No. 10 2022 209 869.2, the contents of which are incorporated herein by reference.

[0002] The present invention relates to a holding device for an optical component having an optical surface with a polygonal boundary and a columnar body. The invention also relates to an optical assembly comprising such a holding device, a method for determining the position of an optical component in said holding device, an illumination optical unit comprising such an optical assembly, an optical system comprising such an illumination optical unit, an illumination system comprising such an optical system, and a projection exposure apparatus comprising such an illumination system. [Background technology]

[0003] A holding device for an optical component in the form of a rod for an illumination device is known from US Pat. No. 5,649,999.

[0004] Patent Document 2 discloses a device for attaching a reflector rod. Patent Document 3 discloses a polarization-optimized illumination system. Patent Document 4 discloses a holding structure for an optical integrator. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] DE 10 2007 050 456 A1 [Patent Document 2] DE 102 55 735 A1 [Patent Document 3] DE 103 11 809 A1 [Patent Document 4] Chinese Utility Model Patent No. 209 132 491 Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to provide a holding device that can securely hold an optical component having an optical surface with a polygonal boundary and a columnar base, and that can be mounted with high positional accuracy. [Means for solving the problem]

[0007] According to the invention, this object is achieved by a holding device having the features of claim 1.

[0008] According to the present invention, it has been recognized that the mount can be divided into functional groups, specifically, support bodies defining support points against the side walls of the base and at least one pressure body pressing the base of the optical component against the support. This allows for a clear, particularly positionally accurate, mounting of the optical component. At least two support bodies and / or at least one pressure body can contact the column side walls of the base via their respective contact points. The optical component can be an optical rod that can be used for light mixing, particularly in projection exposure apparatuses for microlithography. The polygon defining the optical surface with a polygonal boundary of the optical component is an n-gon with n vertices, where n is greater than 4, such as a pentagon, hexagon, or octagon. n is typically less than 100. The position of the holding frame of the holding device can be determined by the position of the holding mount of the holding device.

[0009] The holding device allows for a defined open-loop or closed-loop control of the position of the optical component, for which purpose the holding device may comprise at least one displacement actuator for at least one of the bearings and optionally a position sensor.

[0010] The holding device has at least two pressure bodies. Such an embodiment of the holding device has proven effective in practice.At least two pressure bodies can press the side wall of the base body in the same cross section via assigned support portions of the side wall of the base body. As a result, the base body is clearly held in an axial position between its two optical surfaces. The holding device can have exactly three pressure bodies, which define a holding plane via their assigned support portions and press the side wall of the base body by means of these support portions. This holding plane can be perpendicular to the cylindrical axis of the base body, i.e., parallel to the cross section of the cylindrical side wall.

[0011] An embodiment of the holding device according to claim 5 allows for a defined open-loop or possibly closed-loop control of the position of the optical component. In operation, the bearing can be adjusted towards or away from the bearing part. Such an adjustment can be performed by a motor. The bearing can then have an adjustment actuator.

[0012] The embodiment with three bearings as claimed in claim 6 allows for a predetermined positioning geometry.

[0013] This is particularly true for the contact geometry according to claim 7.

[0014] The advantages of the optical assembly as set forth in claim 8 correspond to those already mentioned above with regard to the holding device.

[0015] In an embodiment of the pressure body as claimed in claim 9, the support body can be used to positionally define the optical component relative to the holding device.

[0016] It is yet another object of the present invention to identify a method for determining the position of an optical component during use of a holding device.

[0017] This object is achieved according to the invention by a method for determining a position comprising the steps as set out in claim 10 .

[0018] By determining the angle and the relative positions of at least two of the bearing contact points, it is possible to determine the relative positions of the cross sections of the column sidewalls of the optical component in the holding device.

[0019] The advantages of the illumination optical unit according to claim 11, the optical system according to claim 12, the illumination system according to claim 13 and the projection exposure apparatus according to claim 14 correspond to the advantages already mentioned above with regard to the holding device, the optical assembly and the positioning method.

[0020] The illumination system may comprise a DUV (deep ultraviolet) light source.

[0021] In particular, microstructured or nanostructured components, in particular semiconductor chips, for example memory chips, can be produced using projection exposure apparatus.

[0022] Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. [Brief explanation of the drawings]

[0023] [Figure 1] 1 shows a schematic view of a meridian section of a projection exposure apparatus for microlithography with an optical rod for mixing illumination light; [Figure 2] 2 shows a cross section of one embodiment of an optical rod in a holding device not shown in FIG. 1. [Figure 3] 3 shows yet another embodiment of an optical rod in yet another embodiment of a holding device in a view similar to FIG. 2; [Figure 4] 4 shows a schematic diagram of the parameters involved in determining the position of the rod in the holding device of FIG. 3; DETAILED DESCRIPTION OF THE INVENTION

[0024] To illustrate the geometrical relationships, a Cartesian xyz coordinate system is shown in the drawings. In Figure 1, the x-axis extends perpendicular to and across the plane of the drawing. The y-axis extends upward in Figure 1. The z-axis extends to the left in Figure 1.

[0025] The projection exposure apparatus 1 for microlithography has an illumination system with an illumination optical unit 2 which illuminates a predetermined illumination and object field 3 at the location of an object and a reticle 4, which represents a template to be projected for the production of microstructures or microelectronic semiconductors. The reticle 4 is held by a reticle holder, not shown here.

[0026] A deep ultraviolet (DUV) laser is used as the source 5 of illumination light for the illumination system. This may be an ArF excimer laser. Other DUV sources are also possible.

[0027] By means of a beam expander 6 , for example a mirror arrangement known from DE 41 24 311 A1, the coherence is reduced and an expanded parallel rectangular cross section of the beam of illumination light 7 is produced.

[0028] A first diffractive optical raster element (DOE) 8 is arranged in the object plane of a condenser 9. This DOE 8 will hereinafter also be referred to as the intensity-directing element. The condenser 9 comprises an axicon pair 10 and a lens element 11 with a positive focal length. The spacing between the axicon elements of the axicon pair 10 and the position of the lens element 11 is adjustable along the optical axis 12 of the illumination optical unit 2, as indicated by double arrows 13, 14 in Figure 1. The condenser 9 therefore represents a zoom optical unit.

[0029] A further diffractive and / or refractive optical raster element (ROE) 16 is arranged in the exit pupil plane 15 of the condenser 9. If the raster element 16 is of the diffractive type, it may for example be in the form of a computer generated hologram (CGH). As an alternative or in addition to an embodiment as a diffractive optical element, the ROE 16 may also be of the refractive type, for example in the form of a refractive optical raster element, in particular a microlens array. Although diffractive embodiments are possible, the raster element 16 will be referred to below as an ROE.

[0030] By means of the first DOE 8, a predetermined intensity distribution in the pupil plane 15 is set at the location of the ROE 16. This results in a specified so-called illumination setting, i.e. a predetermined distribution of illumination angles across the object field 3. The first DOE 8 therefore represents an illumination angle specifying element that specifies the illumination angle distribution across the illumination field 3.

[0031] An input coupling optical unit 17 downstream of the ROE 16 transmits the illumination light to an end face input surface 18 of a transparent optical rod in the form of a glass rod. Variations of the optical rod 19 and of the holding device for the optical rod 19 are also described below.

[0032] The optical rod 19 has a cross section that is different from a square or rectangular cross section. The rod cross section is generally polygonal, and may be, for example, hexagonal. Other cross section examples are also described below with reference to Figures 2 and 3.

[0033] The rod 19 mixes and homogenizes the illumination light by multiple internal reflections on the side walls of the rod 19. A reticle mask system (REMA) 21, i.e., an intermediate field plane where an adjustable field stop is located, is located directly at the end exit surface 20 of the rod 19 opposite the entrance surface 18.

[0034] With the ROE 16 , in particular the cross-sectional shape of the illumination beam 7 is adapted to the rectangular shape of the entrance face 18 of the rod 19 .

[0035] ROE 16, also referred to hereinafter as an optical rod illumination specifying element, functions to specify the illumination of entrance face 18 of rod 19 by illumination light 7. The illumination of entrance face 18 is specified to specify the distribution of illumination intensity as well as the illumination angle distribution across entrance face 18. The specified illumination intensity distribution across entrance face 18 deviates from a uniform distribution, as will be explained in more detail below.

[0036] DOE 8, the intensity specification element, is used to specify the illumination intensity distribution at ROE 16, the optical rod illumination specification element.

[0037] A condenser 22 is located downstream of the REMA 21. An aperture change holder 24 with several apertures or filters can be arranged in the exit pupil plane 23 of the condenser 22, of which two apertures 25, 26 are shown in FIG. 1. The aperture change holder 24 carries various apertures like an aperture carousel. For aperture exchange purposes, the carousel is driven around a drive shaft 27 of a drive motor 28, which is signal-connected to a central open-loop control device 28a of the projection exposure apparatus 1. The aperture of the aperture change holder 24 is divided into an even number of separate aperture sections. The aperture sections can be apertures that completely block the illumination light, neutral density filters that attenuate the illumination light by a certain percentage, or polarizing filters that linearly polarize the illumination light.

[0038] Another condenser with lens element groups 29, 30 is downstream of pupil plane 23, which is downstream of rod 19. A 90° deflection mirror 31 for the illumination light is arranged between the two lens element groups 29 and 30. Condenser 22 and the other condenser with two lens element groups 29, 30 form a lens 31a that images the intermediate field plane of REMA 21 onto reticle 4. Pupil plane 23 represents the internal pupil plane of this lens 31a.

[0039] A projection lens 32 images the object field 3 in an object plane 33 onto an image field 34 in an image plane 35. The image field 34 is a portion of the surface of a wafer 36 to be exposed, which is provided with a coating that is sensitive to the illumination light. The wafer 36 is held by a wafer holder, not shown here. During projection exposure, the reticle 4 and the wafer 36 are scanned synchronously with respect to one another. Intermittent displacements of the holder of the reticle 4 and the wafer 36, so-called stepper movements, are also possible.

[0040] With the exception of the deflection mirror 31, the various beam-guiding or beam-shaping components of the projection exposure apparatus 1 are shown as refractive components, however they can also be catadioptric or reflective components.

[0041] 2 shows a cross-section of a variant of an optical rod 37 which can be used in the projection exposure apparatus 1 instead of the optical rod 19. The optical rod 19 is an optical component having optical surfaces with polygonal boundaries, i.e. an entrance surface 18 and an exit surface 20 with polygonal boundaries (see also FIG. 1). The optical rod 37 has a cylindrical substrate or body 38 with a cylindrical side wall 39 having a polygonal cross-section corresponding to the boundaries of the optical surfaces 18, 20.

[0042] Overall, the optical surfaces 18, 20 of the rod 37 have an octagonal polygon boundary, and the corresponding vertices 40 of this cross-sectional polygon are numbered consecutively clockwise from the upper left vertex in FIG. 2 and are subscripted 401 through 408. i Seven of the eight vertices are convex vertices of base 38. Only one of the eight vertices, vertex 404, is a concave vertex of base 38. Therefore, the polygonal interior angle of base 38 is greater than 180° in the area of ​​vertex 404. All other polygonal interior angles are less than 180°.

[0043] A vertex 40 extends perpendicular to the plane of the drawing of FIG. 2 and parallel to each other between the entrance face 18 and the exit face 20 of the rod 37. i In between is a flat portion of the side wall 39 .

[0044] The optical rod 37 is held by a holding device 41, and its spatial positioning is defined. The holding device 41 has a holding frame 42 including two mount bodies 43, 44. The mount bodies 43, 44 are pressure bodies that bring the holding frame 41 into pressure contact with the side wall 39 of the base 38 at pressure-applied portions 45, 46 of the side wall 39. The pressure-applied portion 45 is located between vertices 401 and 402. The pressure-applied portion 46 is located between vertices 405 and 406. The pressure-applied portions 45, 46 are wall portions of the side wall 49 that extend parallel to each other.

[0045] The pressure bearing members 43 and 44 are provided on the pressure receiving portions 45 and 46 with a bearing pressure F. D1 , F D2 These bearing pressures F D1 , F D2 This is indicated by an arrow in Figure 2.

[0046] Support pressure F D1 , F D2 acts in the opposite direction. D1 , F D2 acts perpendicularly on the pressure-applied portions 45, 46.

[0047] The holding device 41 has a further pressure body 47 in the form of a pressing piece. The pressure body 47 is located between the vertices 407 and 408 (contact point A 47 2 ) against the pressure-applied portion 48 of the side wall 39. This contact is effected via the crown-shaped pressure body end portion 49. The contact of the pressure body end portion 49 against the pressure-applied portion 48 of the side wall 39 can approximate a point contact, or, depending on the embodiment of the pressure body end portion 49, can be perpendicular to the drawing plane of FIG. 2 , i.e., at the apex 40 i The pressure body end portion 49 may be designed like a convex crown-shaped columnar body portion.

[0048] The bearing pressure exerted by the pressure body 47 on the pressure-receiving part 48 along its longitudinal axis is indicated by arrow F in FIG. D3 Shown in.

[0049] Support pressure F D1 , F D2 , and F D3 All of these act in the plane of the drawing in Figure 2, i.e. parallel to the xy plane. D3 extends at an acute angle to the xz plane. D1 acts in the negative x direction. D2 acts in the positive y direction.

[0050] The three pressure bodies 43, 44, 47 of the holding device 41 serve to apply a bearing pressure, by which the base body 38 of the rod 37 is pressed against the bearing part of the holding device 41, which is formed by the two bearing bodies 50, 51 of the holding device 41.

[0051] The bearings 50, 51 are in the form of manipulators or positioning devices. The bearing end portions 52, 53 of the bearings 50, 51 apply abutment pressure to the side wall 39 of the base 38 via bearing portions 54, 55 of the side wall 39. The bearing end portions 52, 54 can be designed like the pressure body end portion 49 of the pressure body 47.

[0052] Bearing portion 54 is between apexes 402 and 403 of side wall 39. Bearing portion 55 is between apexes 403 and 404 of side wall 39.

[0053] The bearings 50, 51 are in the form of manipulators. The bearings 50, 51 may be in the form of adjustment screws. The bearings 50, 51 can be adjusted to predetermined positions towards and away from the bearing parts 54, 55, as indicated by double arrows 56, 57 in Figure 2. The adjustment direction is along the longitudinal axis L of each of the bearings 50, 51. 50 , L 51 This adjustment is achieved by adjustment actuators 58, 59 shown diagrammatically in FIG.

[0054] The adjustment direction 56 of the bearing 50 extends at an angle of approximately 45° to the xy and yz planes. The adjustment direction 57 extends at an angle of approximately 60° to the xz plane and 30° to the yz plane. Other angles of the adjustment directions 56, 57 to these planes xz, yz are also possible, ranging from 10° to 80°.

[0055] Together with the optical rod 37 the holding device 41 forms the optical assembly of the projection exposure apparatus 1 .

[0056] To determine the position of the optical component 37, ie the rod, in the coordinates of the holding frame 42, the following procedure is performed.

[0057] The angle α between two polygonal faces of the pillar side wall 39, for example the angle between bearing portions 54 and 55, is determined.

[0058] Contact point A where the support bodies 50, 51 contact the side wall 39 50 and A 51The relative positions of the two frame points A and B of the holding frame 42 are determined.

[0059] Next, the relative position of the polygonal cross section of the column side wall 39 with respect to the holding device 41 is calculated using these data α, A 50 , A 51 , A, and B. Furthermore, the position of another point on the side wall 39 of the column, for example, the contact point A between the pressing body 47 and the pressurized portion 48 of the side wall 39, 47 or the position of further points, for example in the region of the bearing portions 54 or 55 of the pillar side wall 39, can also be used to determine the relative position of the polygonal cross-section of the pillar side wall 39 with respect to the holding device 41. The contact points where the pressure bodies 43, 44 of the holding device 47 abut against the pressure-received portions 45, 46 of the pillar side wall can also be additional relative positions, the knowledge of which makes it possible to determine the relative position of the polygonal cross-section of the pillar side wall 39 with respect to the holding device 41.

[0060] 3, another embodiment of a holding device 61 will be described below for mounting in place another embodiment of an optical component having an optical surface with a polygonal boundary and in the form of an optical rod 62. Components and features corresponding to those already described above with reference to FIGS. 1 and 2 have the same reference numerals and will not be described in detail again.

[0061] The holding device 61 has a pressure body 63 which is a mount body for mounting a holding frame 64 of the holding device 61 .

[0062] The optical rod 62 is designed with a substrate 38 having a polygonal cross section, which in the case of the optical rod 62 has a convex polyhedron (vertices 401-405) configuration.

[0063] The pressure body 63 applies a pressure F to the pressure-applied portion 65 of the side wall 39 of the rod 62. D2 , the rod 62 is pressed into the bearing portion formed by the three bearings 66, 67, 68, which define a concave contact shape. The convex cross-sectional areas of the optical rod 62, formed by the bearing portions 69, 70, 71 between the vertices 403 and 404, between the vertices 404 and 405, and between the vertices 405 and 401, are pressed into this concave contact shape of the bearings 66-68. The bearings 66-68 may be formed by bearing end portions, such as the bearing end portions 52, 54 of the embodiment shown in FIG. 2 , which may ensure point or line contact with the bearing portions 69-71 of the side wall 39.

[0064] Based on FIG. 4, a method for determining the position of the optical rod 62 during use of the holding device 61 will now be described.

[0065] First, the angle α between the two polygonal faces of the column side wall 39, in this case the angle α between the bearing portions 69 and 71, is similarly determined. Next, the contact points A where the bearings 66 to 68 abut against the bearing portions 69 to 71 of the side wall 39 are determined. 66 , A 67 , A 68 The relative position of the pressure body 63 of the holding frame 61 with respect to the two frame points A and B is then determined. The relative position of the cross section of the column side wall 39 with respect to the holding device 61, and therefore the relative position of the rod 62, is then calculated using these parameters α, A 66 ~A 68 , A, and B.

[0066] Alternatively or additionally, at least one position sensor, in particular a distance sensor, can be used to determine the position of the optical components 37, 62 in the respective holding devices 41, 61. Such a position sensor can in particular determine the position of one of the bearings 50, 51 (FIG. 2) or 66-68 (FIG. 3), respectively. The pressure body 47 of the embodiment shown in FIG. 2 can also have such a position sensor.

[0067] Corresponding position sensors can be used for closed-loop control of the positioning of the supports 50, 51. For this purpose, the actuators 58, 59 and the at least one position sensor are signal-connected to an open-loop control device 28a, which in this case is also in the form of a closed-loop control device of the projection exposure apparatus 1.

[0068] The mount of the retainer 41 or 61 may have a columnar overall form, but this is not shown.

[0069] For the microlithographic production of microstructured or nanostructured components, the wafer 36 is first coated, at least in certain locations, with a photosensitive layer. Subsequently, the structure on the reticle 4 is projected onto the wafer 36 using the projection exposure apparatus 1. The exposed wafer is then processed to form the microstructured components.

Claims

1. A holding device (41; 61) for an optical component (19; 37; 62) having an optical surface (18, 20) with a polygonal boundary and a cylindrical base (38) with cylindrical side walls (39) with a polygonal cross section corresponding to the polygonal boundary of the optical surface (18, 20), comprising: a holding frame (42; 64), The base body (38) has at least two bearings (50, 51; 66-68) that abut against the column side wall (39) via bearing portions (54, 55; 69, 71) of the column side wall (39), The support pressure (F) that presses the base body (38) against the support body (50, 51; 66-68) Ｄ ) and at least one pressure body (43, 44, 47; 63) arranged to directly press against the column side wall (39) of the base body (38).

2. 2. A holding device according to claim 1, characterized in that it comprises at least two pressure bodies (43, 44, 47).

3. In the holding device according to claim 2, the two pressure bodies (43, 44) are Ｄ１ , F Ｄ２ ) is designed to act on the base (38) of the optical component (37) from different directions.

4. 4. The holding device according to claim 3, wherein the bearing pressure (F Ｄ１ , F Ｄ２ ) is a holding device characterized by acting in the opposite direction.

5. A holding device according to any one of claims 1 to 4, characterized in that at least one of the bearings (50, 51) is in the form of a manipulator.

6. A holding device according to any one of claims 1 to 5, characterized in that it comprises three bearings (66-68).

7. 7. The holding device according to claim 6, characterized in that the three bearing bodies (66-68) define a concave contact shape into which a convex cross-sectional area (69-71) of the optical component (62) can be pressed by the at least one pressure body (63).

8. An optical assembly comprising a holding device (41; 61) according to any one of claims 1 to 7 and an optical component (37; 62) held thereby.

9. 9. The optical assembly according to claim 8, comprising the holding device according to claim 4, Ｄ１ , F Ｄ２ 1. An optical assembly, characterized in that two pressure bodies (43, 44) acting in opposite directions on the side wall (39) are designed to press against mutually parallel surfaces (45, 46) of the side wall (39).

10. 10. A method for determining the position of an optical component (19; 37; 62) having an optical surface (18, 20) with a polygonal boundary and a cylindrical body (38) with cylindrical side walls (39) with a polygonal cross section corresponding to the polygonal boundary of the optical surface (18, 20), wherein the optical component (19; 37; 62) is held in a holding device (41; 61) according to any one of claims 1 to 7, determining the angle (α) between two polygonal faces (54, 55; 69, 71) of the cylinder side wall (39); At least two mutually spaced contact points (A) are in contact with the column side wall (39), one of the support bodies (50; 68) is in contact with one of the two polygonal faces (54; 69) and another of the support bodies (51; 66) is in contact with the other of the two polygonal faces (55; 71). ５０ , A ５１ ;A ６６ , A ６７ , A ６８ ) relative to at least two frame points (A, B) of said holding device (41; 61); determining the position of the cross section of the pillar side wall (39) relative to the holding device (41; 61) from the determined angle (α) and the determined relative position; A method comprising:

11. An illumination optical unit (2) comprising an optical assembly according to claim 8 or 9, for illuminating an object field (3) in which an object to be illuminated (4) can be arranged.

12. 12. An optical system comprising an illumination optical unit (2) according to claim 11 and a projection optical unit (32) for imaging an object field (3) into an image field (34).

13. An illumination system comprising an illumination system according to claim 12 and a light source (5).

14. 14. A projection exposure apparatus comprising: an illumination system according to claim 13; a reticle holder for holding a reticle (4) in an object plane (33); a projection lens (32) for imaging an object field (3) in an image plane (35) into an image field (34); and a wafer holder for holding a wafer (36) in the image plane.

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