JP6683706B2 - Mirror for lithographic apparatus and lithographic apparatus - Google Patents

Description

  The invention relates to a mirror for a lithographic apparatus and a lithographic apparatus.

  The disclosure in the basic application claiming priority in this application, German patent application No. 102014224822 is hereby incorporated by reference in its entirety.

  A lithographic apparatus is used, for example, to image a mask pattern formed on a mask onto a substrate such as a silicon wafer when manufacturing an integrated circuit. In this case, the mask pattern is imaged on the substrate by using the projection optical unit. Such a projection optical unit is composed of a plurality of mirrors. In the configuration of the plurality of mirrors, the optimum configuration requirements from the optical viewpoint and the optimum configuration requirements from the dynamic viewpoint are not necessarily compatible with each other. The position where each mirror is to be positioned is defined by the projection optics unit. If there is only a small space at a specific place in the projection optical unit, the mirror can only be made thin. However, from a dynamic point of view, it may be advantageous to construct the mirror with a large thickness to improve its rigidity. This is because, for example, if the mirror is too thin and mechanically unstable, optical aberration may occur.

International Publication No. 2010/028748 Publication

  In view of the background circumstance mentioned above, the object of the invention is to provide a mirror for a lithographic apparatus capable of reducing optical aberrations, and in particular a lithographic apparatus comprising such a mirror.

  This problem is solved by a mirror for a lithographic apparatus comprising a mirror body having a surface. The surface of the mirror comprises an optically active region and an optically inactive region, at least a portion of the optically inactive region being located inside the optically active region. In addition to this, the mirror is arranged in the optically inactive region and further comprises means for reducing optical aberrations. In this case, the means for reducing optical aberration comprises mechanical stabilizing means.

  Advantageously, means are provided for reducing the optical aberrations of the mirror. Therefore, optical aberrations are avoided or reduced despite the fact that the mirror is constructed with a small thickness due to its position in the beam path. Instabilities due to the slight thickness in the mirror can be compensated by means of reducing optical aberrations. The means for reducing the optical aberrations in the mirror do not interfere with the beam path in the projection optics unit because they are arranged in the optically inactive region. Further, the mirror can be made compact.

  The means for reducing optical aberration includes mechanical stabilizing means. Depending on the arrangement of the mirror in the lithographic apparatus or in the projection optics unit, the mirror may be constructed with only a small thickness. This is because there is no space in the lithographic apparatus or in the relevant area in the projection optics unit for constructing the mirror with a greater thickness. Mirrors with a small thickness have less mechanical stability than mirrors with a large thickness. The use of mechanical stabilizing means makes it possible to increase the mechanical stability of the mirror, and even a mirror having a small thickness can be provided with mechanical stability.

  The optically active area on the surface of the mirror body refers to the area that causes reflection of the emitted wave during operation of the lithographic apparatus. An optically inactive area on the surface of the mirror body refers to an area which is not exposed to a radiation wave during operation of the lithographic apparatus due to the configuration of the apparatus or the projection optical unit.

  At least a portion of the optically inactive region is located inside the optically active region. In particular, all of the optically inactive region may be located inside the optically active region.

  Furthermore, the mirror may be thermally stabilized, for example by means of optical aberration reduction. This avoids or reduces deformation or vibration of the mirror. Therefore, the optical aberration in the mirror does not occur or becomes smaller, if any. Optical aberrations can be calculated, for example, by measuring the deviation of the actual wavefront from the ideal wavefront.

  The mirror body and / or the means for reducing optical aberrations may be composed of a ceramic material or a glass-ceramic material, for example Zerodur® (developed by Schott), preferably having a low coefficient of expansion. Other materials include silicon carbide, reactively sintered silicon carbide (SiSiC), carbon fiber reinforced silicon carbide (CSiC), silicon nitride (SiN) and titanium oxide-silicon oxide glass, such as ULE®. Good. Further, usable materials are also described on pages 16 and 17 of Patent Document 1 (International Publication No. WO 2010/028748), the entire disclosure content of which is incorporated herein by reference.

  The mirrors described above are in principle suitable for electromagnetic radiation waves of any wavelength. The mirror according to the invention is particularly suitable for the EUV (extreme ultraviolet) and DUV (far ultraviolet) wavelength ranges. In this case, the EUV wavelength range is 0.1 to 30 nm, and the DUV wavelength range is 30 to 200 nm.

  According to embodiments of the mirror, the optically active region comprises a polishing surface and / or a mirror coating. This advantageously makes it possible to reflect radiation of a desired wavelength using the mirror according to the invention.

  According to another embodiment of the mirror, the optically inactive region is located entirely inside and / or in the center of the optically active region. In this case, the optical aberration reducing means arranged in the optically inactive region are also preferably arranged completely inside and / or in the center of the optically active region.

  According to another embodiment of the mirror, the mirror comprises a volume above the optically active region and the optically inactive region, the means for reducing optical aberrations being within a partial volume of the total volume which is not used optically. Has rushed into. Since the means for reducing optical aberrations plunge into the optically unused partial volume, the means for reducing optical aberrations may have a corresponding spatial extent. Such spatial expansion is required because the means for reducing optical aberrations comprises mechanical or thermal stabilizing means.

  According to another embodiment of the mirror, the optically unused partial volume tapers towards a point and / or has a truncated cone shape and / or has an elliptical base surface. The partially unused volume may have essentially any shape. In this case, the optically unused partial volume occurs due to the diaphragm in the beam path.

  According to another embodiment of the mirror, the mechanical stabilizing means comprises a vibration damper. The vibration damper actively or passively damps vibrations that may occur in the mirror.

  According to another embodiment of the mirror, the mechanical stabilizing means comprises a tuned mass damper. The tuned mass damper comprises a weight and a spring. The weight and spring together form a pendulum. The natural frequency of the pendulum is adjusted to the vibration frequency to be removed, ie the vibration that can occur in the mirror. A tuned mass damper tuned to this frequency eliminates the vibrational energy that causes the natural oscillatory motion in the mirror. Therefore, preferably, the use of one or more tuned mass dampers damps the vibration of the mirror at a specific frequency or frequencies.

  According to another embodiment of the mirror, the mirror comprises a brace, the brace being connected at one end to the mechanical stabilizing means and at the other end to the mirror body. Advantageously, mechanical stabilization means and braces may increase the rigidity of the mirror. This reduces deformation and / or vibration of the mirror. Further, if the rigidity can be increased, a mirror having a small thickness can be used. Each brace is fixed to the mechanical stabilizing means and the mirror body and can be subjected to tensile and / or compressive loads depending on its construction. The brace may be constructed as a non-bendable element with great rigidity. In this case, compressive and / or tensile loads may be applied to the brace. However, the brace may also be constructed as a kind of rope, wire or cable. In this case, the braces can only be subjected to a tensile load.

  According to another embodiment of the mirror, a portion of each brace extends through the optically used partial volume. Each brace may protrude from an optically unused partial volume. In this case, each brace is arranged to interfere as little as possible with the beam path in the lithographic apparatus or the optical imaging of the projection optics unit. For this reason, each brace may be made thin.

  According to another embodiment of the mirror, each brace has a first end and a second end. In this case, the first end is connected to the mechanical stabilization means at a location remote from the mirror body and the second end is connected to the edge of the mirror. This allows the brace to be advantageously connectable, allowing the mirror to be stiffened and thus stabilized. The brace is fixed at a first end, preferably to the tip or top of the mechanical stabilizing means, and at a second end, preferably to the edge of the mirror outside the optically active region. Fixed. This may create tension between the edge of the mirror and the tip of the mechanical stabilizing means. This tension contributes to the reinforcement of the mirror and thus to the stabilization of the mirror.

  According to another embodiment of the mirror, the brace can be actively actuated to compensate for optical aberrations. In particular, the braces may be subjected to tensile loads. The mirror may be deformed by applying tensile and / or compressive loads to the individual braces. By deforming the mirror in this way, optical aberrations are compensated.

  According to another embodiment of the mirror, the brace is connected to the edge of the mirror via an actuator at the second end to allow active actuation. Advantageously, the brace may be actuated by an actuator. This creates tensile and / or compressive forces on the brace.

  According to another embodiment of the mirror, the mirror comprises a support column, the column being connected at one end to a mechanical stabilizing means and at the other end in the optically active or optically inactive region. Connected to.

  The support column is an additional element provided to enhance the mechanical stabilization means and the stability of the mirror. The support column is fixed at one end to the mechanical stabilizing means and at the other end to the mirror body. Fixing to the mirror body may take place in the optically active region or in the optically inactive region.

  The support column may project from the partially unused volume. In this case, the support column is arranged so as not to interfere with the beam path in the lithographic apparatus or the optical imaging of the projection optics unit.

  According to another embodiment of the mirror, the region of the mirror body below the optically inactive region comprises a different material than the adjacent region of the mirror body. This advantageously makes it possible to increase the stability of the mirror.

  According to another embodiment of the mirror, the mirror comprises means for controlling the temperature of the mirror body. Providing the temperature control means of the mirror body makes it possible to avoid or reduce heat-induced deformation and / or destabilization of the mirror. The temperature of the mirror can be kept constant or nearly constant by means of the temperature control means of the mirror body. The mirror may be cooled or heated by the temperature control means of the mirror body.

  According to another embodiment of the mirror, the means for reducing optical aberrations comprises temperature control means for the mirror body. This advantageously uses the optically inactive region effectively.

  According to another embodiment of the mirror, the temperature control means of the mirror body is provided in the mirror body, especially below the means for reducing optical aberrations. In this case, advantageously, the temperature control means of the mirror body are pre-provided in the element, i.e. in the mirror body whose temperature should be kept as constant as possible.

  According to another embodiment of the mirror, the temperature control means of the mirror body comprises a plurality of heating elements. The use of a plurality of heating elements ensures a temperature distribution which is as uniform and constant as possible.

  According to another embodiment of the mirror, the heating elements are distributed on the mirror body and / or on the means for reducing optical aberrations. Advantageously, the heating elements may be arranged in a distributed manner. The heating element in the means for reducing optical aberrations may be a radiant heater that illuminates the optically active area of the mirror body.

  According to another embodiment of the mirror, the optical aberration reducing means has a conical shape. This advantageously allows the means for reducing optical aberrations to fit within the partially unused volume.

  According to another embodiment of the mirror, the mirror body is convex or concave in the optically active area.

  According to another embodiment of the mirror, the means for reducing optical aberrations are integrally constructed.

  Further provided is a projection system for a lithographic apparatus comprising a mirror as described above.

  According to an embodiment of the projection system, the projection system is arranged in its beam path and has an optically inactive region on the surface of the mirror body and an optically active region and an optical inactive region above the optically inactive region. And a diaphragm that produces an unused partial volume. Advantageously, the stop produces an optically inactive region and an optically unused partial volume, so that it is possible to easily arrange the means for reducing optical aberrations in the optically inactive region and the partial volume described above. it can.

  Further provided is a lithographic apparatus comprising a mirror or projection system as described above.

  Further embodiments achievable by the present invention also include combinations of features or embodiments not mentioned explicitly but mentioned above or below with respect to exemplary embodiments. In this case, those skilled in the art may add individual aspects to the basic aspects of the present invention as improvements or additions.

  Other advantageous configurations and aspects of the invention are as described in the dependent claims and in the exemplary embodiments of the invention described below. Hereinafter, the present invention will be described in more detail based on preferred embodiments with reference to the accompanying drawings.

1 is a schematic diagram of an EUV lithographic apparatus. 3 is a schematic diagram of a penultimate mirror according to an exemplary embodiment, shown as part of a projection optical unit. It is explanatory drawing of the pupil part in a projection optical unit. FIG. 3 is a plan view of the penultimate mirror in FIG. 2. FIG. 6 is an illustration showing a further exemplary embodiment of the penultimate mirror. FIG. 6 is an illustration showing a further exemplary embodiment of the penultimate mirror. FIG. 6 is an illustration showing a further exemplary embodiment of the penultimate mirror. FIG. 6 is an illustration showing a further exemplary embodiment of the penultimate mirror.

  Unless otherwise specified, the same reference numeral in the drawings indicates the same element in the structure or the function. It is also noted that each element in the figure does not necessarily reflect the actual size.

  FIG. 1 shows an overview of an EUV lithographic apparatus 100 that comprises a beam shaping system 102, an illumination system 104 and a projection system 106. The beam shaping system 102, the illumination system 104 and the projection system 106 are each provided in a vacuum housing, and each vacuum housing is evacuated by an evacuation device (not shown in detail). Each vacuum housing is enclosed in a mechanical space (not shown in detail) provided with drive means for mechanically moving or adjusting the optical elements. An electric control device or the like may be further provided in the machine space.

  The beam shaping system 102 includes an EUV light source 108, a collimator 110, and a monochromator 112. As the EUV light source 108, for example, a plasma source or a synchrotron that emits a radiation wave in the EUV range (extreme ultraviolet range), that is, a wavelength range of 5 nm to 20 nm may be provided. The radiation wave emitted from the EUV light source 108 is first focused by the collimator 110 and then the desired operating wavelength is filtered by the monochromator 112. Thus, the beam shaping system 102 adapts the wavelength and spatial distribution of the light emitted by the EUV light source 108. The EUV radiation 114 generated by the EUV light source 108 has a relatively low transmission through the air so that the beam guide spaces in the beam shaping system 102, the illumination system 104 and the projection system 106 are evacuated. Means

  In the illustrated embodiment, the illumination system 104 comprises a first mirror 116 and a second mirror 118. These mirrors 116, 118 may be formed, for example, as facet mirrors for forming the pupil part and transmit the EUV radiation wave 114 to the photomask 120.

  The photomask 120 may also be formed as a reflective optical element and located external to the system 102, 104, 106. The photomask 120 has a structure that is imaged by the projection system 106 in a reduced image on the wafer 122 or the like. For this reason, the projection system 106 has, for example, a third mirror 124 and a fourth mirror 126 in the beam guide space. It should be mentioned that the number of mirrors in the EUV lithographic apparatus 100 is not limited to the number shown, but more or fewer mirrors may be provided. Furthermore, each mirror is curved over its front side to allow beam shaping.

  The projection optics unit in the projection system 106 is represented very schematically with two mirrors 124,126. The projection optics unit preferably comprises a plurality of mirrors. FIG. 2 shows a part 200 of a projection optics unit comprising a plurality of mirrors.

  More precisely, FIG. 2 shows the two mirrors 202, 204 at the rearmost part in the projection optics unit. In the figure, the last mirror 202 in the projection optical unit and the penultimate mirror 204 in the projection optical unit are clearly shown. The penultimate mirror 204 in the projection optics unit may be elliptical. The last mirror 202 in the projection optics unit comprises an aperture 206 which allows the radiation to reach the two mirrors 202, 204 at the rear. The beam path shown in FIG. 2 is drawn based on the path (see arrow 212 in FIG. 2) after the first ray 208 and the second ray 210 have passed through the aperture 206 in the last mirror 202. The first ray 208 is incident on the optically active region 220 at the left side 214 of the penultimate mirror 204 and is reflected from the optically active region 220 towards the last mirror 202. The first light ray 208 is then reflected at the last mirror 202 towards the wafer 122. The second ray 210 is incident on the optically active region 220 at the right side 216 of the penultimate mirror 204 and is reflected from the optically active region 220 towards the last mirror 202. The second light ray 210 is then reflected at the last mirror 202 towards the wafer 122. The mask pattern of the photomask 120 is imaged on the wafer 122.

  The penultimate mirror 204 may be arranged near the pupil portion 300 (see FIG. 3) in the projection optical unit. The projection optical unit includes a shield diaphragm 302 arranged in the center of the pupil plane. This causes the central ray in the projection beam path assigned to the aperture 206 of the last mirror 202 to be blocked or masked. The first ray 208 and the second ray 210 are rays assigned to the optically used surface 304 area.

  By arranging the penultimate mirror 204 in the vicinity of the pupil part 300 in the projection optical unit, the shielding effect of the pupil part 300 in the projection optical unit also occurs in the penultimate mirror 204 in the projection optical unit via the shielding diaphragm 302. . The penultimate mirror 204 includes a mirror body 224 and a surface 226. On the surface 226 of the penultimate mirror 204 there is an optically inactive region 222 due to the shielding. Above the optically active region 220 and the optically inactive region 222 is an air space or volume 228. Due to the shielding, there is a partial volume 230 that is not optically used. The partially unused volume 230 is preferably located above the optically inactive region 222. However, a part of the partially unused volume 230 may be arranged above the optically active region 220.

  The optically inactive region 222 and the optically unused partial volume 230 may be used to stabilize the penultimate mirror 204. That is, the optical aberration reducing means 218 (see FIG. 2) may be arranged in the optically inactive region 222. In this case, the means 218 for reducing optical aberrations projects into the partially unused volume 230.

  The partially unused volume 230 can taper towards the last mirror 202. Further, the optically unused partial volume 230 and the optical aberration reducing means 218 may have a conical shape. Both the optically unused partial volume 230 and the base surface at the optically inactive region 222 may be elliptical in shape.

  The penultimate mirror 204 may have a small thickness due to its position in the projection optics unit. This causes the penultimate mirror 204 to be mechanically unstable and susceptible to vibration. Therefore, the optical aberration reducing means 218 comprises mechanical stabilizing means 232. That is, optical aberrations can be avoided even if the penultimate mirror 204 has a small thickness due to its position in the beam path. The optical aberration reducing means 218 and the mechanical stabilizing means 232 do not interfere with the beam path in the projection optical unit because they are arranged in the optically inactive region.

  The mechanical stabilizing means 232 may comprise a tuned mass damper. Such a tuned mass damper comprises a weight and a spring. The weight and spring together form a pendulum. The natural frequency of the pendulum is adjusted to the vibration frequency to be removed at the penultimate mirror 204. This causes the tuned mass damper to dissipate the vibrational energy that could cause the natural oscillatory motion in the penultimate mirror 204. One or more tuned mass dampers can be used. The tuned mass damper is preferably used at a particular vibration frequency. If there are multiple vibration frequencies to be removed, it is preferable to use multiple tuned mass dampers.

  Alternatively, the mechanical stabilizing means 232 may comprise any other vibration damper as an alternative or addition to the tuned mass damper. Such vibration dampers can actively or passively dampen vibrations that may occur in the mirror.

  FIG. 4 shows a plan view of the penultimate mirror 204 of the projection optical unit in FIG. In FIG. 4, optically active regions 220 and optically inactive regions 222 are represented. In this case, the optically inactive region 222 is located inside the optically active region 220. The optical aberration reducing means 218 includes a mechanical stabilizing means 232 and is arranged in the optically inactive region 222. Outside the optically active area 220, the edge 400 in the mirror body 224 of the penultimate mirror 204 is arranged. Further, the wafer 122 is arranged so as to be adjacent to the penultimate mirror 204.

  The optically active region 220 of the penultimate mirror 204 may have a polished surface. The optically active region 220 may alternatively or additionally have a mirror coating. In any case, the optically active region 220 is suitable for reflecting the emitted wave depending on its wavelength.

  As shown in FIG. 4, the optically inactive region 222 may be provided in the center of the optically active region 220. However, the optically inactive region 222 may be eccentrically provided in the optically active region 220. At least a portion of the optically inactive region 222 is located inside the optically active region 220.

  The mirror body 224 of the penultimate mirror 204 shown in FIG. 2 is convexly formed in the optically active region 220. Alternatively, the penultimate mirror 204 may be concavely formed in the optically active area 220 in the alternative projection optics unit.

  FIG. 5 illustrates another exemplary embodiment of the penultimate mirror 204 in the projection optics unit. In the illustrated embodiment, optical aberration reducing means 218, including mechanical stabilizing means 232, are located in the optically inactive region 222 of the surface 226 of the mirror body 224. The mechanical stabilizing means 232 plunge into the partially unused volume 230.

  Further, FIG. 5 shows a brace 500. The first end 502 of each brace 500 is connected to the tip 506 of the mechanical stabilizing means 232. In this case, the tip portion 506 refers to a position farthest from the mirror body 224 in the mechanical stabilizing means 232. The second end 504 of each brace 500 is connected to the edge 400 of the mirror body 224.

  The rigidity of the penultimate mirror 204 can be increased by mechanical stabilizing means 232 and braces 500. This can reduce deformation and / or vibration of the penultimate mirror 204. The brace 500 can be loaded for tension and compression. When a compressive load is applied to the brace 500, a non-bendable element with great rigidity is required. A compressive load may be applied only if such elements are used. However, the brace 500 may be configured as a kind of rope, wire or cable. In this case, the brace 500 can only be loaded in tension.

  As shown in FIG. 5, the brace 500 projects from an optically unused partial volume 230. In this case, the brace 500 is constructed and / or arranged so as not to interfere with the beam path in the lithographic apparatus 100 or the optical imaging in the projection optics unit.

  In the embodiment of FIG. 5, the mechanical stabilizing means 232 may only be configured as an object in the central part, ie the element to which the brace 500 is fixed. Alternatively, the mechanical stabilizing means 232 may additionally comprise a vibration damper and / or a tuned mass damper.

  FIG. 6 illustrates another exemplary embodiment of the penultimate mirror 204 in the projection optics unit. In the following, only the differences from the penultimate mirror 204 shown in FIG. 5 will be mentioned. In the illustrated embodiment, the brace 500 may be activated to actively compensate for optical aberrations. That is, the mirrors may be deformed by tensile and / or compressive loads on individual braces to compensate for optical aberrations.

  As shown in FIG. 6, each brace 500 is connected at a second end 504 to an edge 400 of the penultimate mirror 204 via an actuator 600. Each brace 500 may be actuated by an actuator 600. Depending on the construction of the brace 500, tensile and / or compressive forces can act.

  As shown in FIG. 6, in this case too, the brace 500 projects from the partially unused volume 230. The illustrated brace 500 is also constructed and / or arranged so as not to interfere with the beam path within the lithographic apparatus 100 or the optical imaging within the projection optics unit.

  In an alternative configuration of the penultimate mirror 204, as shown in FIG. 6, the mirror body 224 is an area below the optically inactive area 222 that has a different material than the rest of the mirror body 224. 602 may be provided. If the material is chosen properly, it is possible to increase the stability of the penultimate mirror 204.

  In another alternative configuration of the penultimate mirror 204, the mirror 204 comprises a support column (not shown). The support column is an additional element provided separately to increase the stability of the mechanical stabilizing means 232 and the penultimate mirror 204. In this case, one end of the support column may be fixed to the mechanical stabilizing means 232 and the other end may be fixed to the mirror body 224. The fixing of the support column to the mirror body 224 is performed in the optically active region 220 or the optically inactive region 222.

  The support column may also protrude from the partially unused volume 230. In this case, the support column is constructed and / or arranged so as not to interfere with the beam path in the lithographic apparatus 100 or the optical imaging in the projection optics unit.

  FIG. 7 illustrates another exemplary embodiment of the penultimate mirror 204. The penultimate mirror 204 in the illustrated embodiment differs from the penultimate mirror 204 in the embodiment of FIG. 5 only in that it further comprises temperature control means 700 of the mirror body 224. The temperature control means 700 of the mirror body 224 may be configured as a radiant heater to generate radiation on the surface 226 of the mirror body 224.

  Alternatively, the temperature control means 700 of the mirror body 224 may be located within the mirror body 224. The temperature control means 700 of the mirror body 224 may be arranged in the mirror body 224 so as to be located below the optical aberration reducing means 218, in particular. Further, the temperature control means 700 of the mirror body 224 may include a plurality of heating elements. In this case, the heating elements may be distributed on the mirror body 224 and / or on the means 218 for reducing optical aberrations.

  The temperature control means 700 of the mirror body 224 makes it possible to avoid or reduce heat-induced deformation or destabilization. In this case, the temperature control means 700 of the mirror body 224 can maintain the temperature of the penultimate mirror 204 constant or almost constant.

  FIG. 8 illustrates another exemplary embodiment of the penultimate mirror 204. The penultimate mirror 204 in this embodiment differs from the penultimate mirror 204 in the embodiment of FIG. 5 only in that it does not have the brace 500. The mechanical stabilizing means 232 may in particular comprise a vibration damper and / or a tuned mass damper.

  The exemplary embodiments described above describe the penultimate mirror 204 in the projection optics unit. However, the arrangement described above may in principle also be applied to any other mirror in the projection optics unit and in the lithographic apparatus 100, if that mirror has an optically inactive region.

  Furthermore, the exemplary embodiments described above describe the penultimate mirror 204 in the EUV lithographic apparatus 100. However, the invention is not limited to the EUV lithographic apparatus 100 and may be applied to other lithographic apparatus.

  Although the present invention has been described based on various exemplary embodiments, the present invention is not limited to those embodiments and various modifications may be made.

100 EUV lithography system
102 beam shaping system
104 lighting system
106 Projection system
108 EUV light source
110 collimator
112 Monochromator
114 EUV radiation
116 First mirror
118 Second mirror
120 photo mask
122 wafers
124 Third mirror
126 Fourth mirror
200 Part of projection optical unit
202 The last mirror of the projection optics unit
204 penultimate mirror of projection optics unit
206 Aperture in the last mirror
208 First ray
210 Second ray
212 arrows
214 Left of the penultimate mirror
216 Right side of penultimate mirror
218 Optical aberration reduction means
220 Optically active area
222 Optically inactive region
224 Mirror body
226 surface
228 volume
230 Optically unused partial volume
232 Mechanical stabilization means
Pupil in 300 projection optical unit
302 Shield diaphragm
304 Optical surface
400 mirror edge
500 brace
502 1st end of brace
504 Second end of brace
506 Tip of mechanical stabilization means
600 actuator
602 The area of the mirror body below the optically inactive area
700 Mirror body temperature control means

Claims (15)

A mirror (204) for a lithographic apparatus (100), comprising:
A surface (226) comprising an optically active region (220) and an optically inactive region (222), at least a portion of said optically inactive region (222) being located inside said optically active region (220). ) Having a mirror body (224),
Means (218) for reducing the optical aberration of the mirror (204), which is arranged in the optically inactive region (222) and comprises a mechanical stabilizing means (232);
With a mirror.   The mirror according to claim 1, wherein the optically active region (220) comprises a polishing surface and / or a mirror coating.   The mirror according to claim 1 or 2, wherein the optically inactive region (222) is entirely disposed inside and / or in the center of the optically active region (220).   4. The mirror according to any one of claims 1 to 3, wherein the mirror (204) has a volume (228) above the optically active region (220) and the optically inactive region (222). A mirror having the optical aberration reducing means (218) projecting into a partial volume (230) of the volume (228) that is not used optically.   5. The mirror according to claim 4, wherein the optically unused partial volume (230) tapers toward a point and / or has a truncated cone shape and / or an elliptical shape. A mirror having a base surface.   The mirror according to any one of claims 1 to 5, wherein the mechanical stabilizing means (232) comprises a vibration damper.   A mirror according to any one of claims 1 to 6, wherein the mechanical stabilizing means (232) comprises a tuned mass damper.   The mirror according to any one of claims 1 to 7, wherein the mirror (204) comprises a brace (500), the brace (500) being at one end on the mechanical stabilizing means (232). A mirror that is connected and is connected at the other end to the mirror body (224).   The mirror of claim 8, wherein the brace (500) is actively actuatable to compensate for optical aberrations.   The mirror according to any one of claims 1 to 9, wherein a region (602) of the mirror body (224) below the optically inactive region (222) is the mirror body (224). A mirror made of a different material from the adjacent area.   The mirror according to any one of claims 1 to 10, further comprising a temperature control means (700) of the mirror body (224).   The mirror according to claim 11, wherein the optical aberration reducing means (218) includes the temperature control means (700) of the mirror body (224).   The mirror according to claim 11, wherein the temperature control means (700) of the mirror body (224) is provided in the mirror body (224) below the optical aberration reducing means (218). A mirror.   The mirror according to any one of claims 1 to 13, wherein the optical aberration reducing means (218) has a conical shape.   A lithographic apparatus (100) comprising a mirror (204) according to any one of claims 1-14.

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