Optical system for lithography projection exposure apparatus

Abstract

The illumination optical unit is useful for use in a lithographic projection exposure apparatus. The illumination optical unit serves to direct illumination light (3) from a light source towards an object field, in which a structured object is arranged. The illumination optical unit is embodied in such a way that the object field illuminated by the illumination optical unit has a field range along a first field coordinate (x) and a field range along a second field coordinate (y) that is orthogonal to the first field coordinate (x) and is shorter compared to said field range. The illumination optical unit is embodied in such a way that the illumination light (3) incident on the object field is polarized with a polarization direction (24) that extends parallel to the shorter field range along the second field coordinate (y). This results in an illumination optical unit that firstly provides high structure resolution and secondly imposes manageable requirements on the optical design.

Description

[Technical Field]

[0001] This patent application claims priority to German Patent Application No. 10 2021 202 847.0, the contents of which are incorporated herein by reference.

[0002] The present invention relates to an optical system for a lithography projection exposure apparatus. Furthermore, the present invention relates to a projection exposure apparatus comprising such an optical system, a method for producing structured components, and microstructures or nanostructured components produced by this method. [Background technology]

[0003] Optical systems featuring the type of illumination optical unit described at the beginning are known from International Patent Application No. 2019 / 215 110, U.S. Patent Publication No. 2017 / 0 336 715, International Patent Application No. 2013 / 156 278, German Patent Application No. 10 2019 200 193, U.S. Patent No. 9,304,405, International Patent Application No. 2014 / 131 654, U.S. Patent No. 7,982,854, and German Patent Application No. 10 2012 208 521. [Overview of the project]

[0004] The objective of the present invention is to develop the type of optical system described above, which first provides high structural resolution and then imposes manageable requirements on the optical design.

[0005] According to the present invention, this objective is achieved by an optical system having the features described in claim 1.

[0006] The first finding of this invention is that an illumination optical unit that generates polarized illumination light parallel to a shorter field of view of the object field is particularly suitable for use in projection exposure apparatuses used for illuminating and imaging one-dimensional object structures. In particular, it has been found that this is advantageous if the illumination optical unit defines polarization parallel to a shorter field of view of the object field. Subsequently, illumination by an illumination pupil extending along the lateral dimensions in the direction of the one-dimensional object structure's spread becomes possible, resulting in projection exposure with high throughput and / or high structural resolution. In particular, the illumination light can be linearly polarized.

[0007] The principle used here is that the achievable contrast of the image representation depends on the polarization state of the emission. The effect of the polarization state is particularly significant for fine structures to be imaged, i.e., structures with short periods. For a given numerical aperture, the imageable structural dimensions of a one-dimensional structural arrangement are significantly smaller than those of a two-dimensional structural arrangement. Therefore, controlling the polarization state is especially important for optical systems designed to image one-dimensional object structures.

[0008] When an optical system is designed to image a one-dimensional object structure, the design requirements for the optical system are relaxed. And because precise resolution is usually not required along one direction of the structural extent of these object structures, the image quality in the direction of the structure's spread is relaxed accordingly, as are the design requirements for the optical system. In this case, it is particularly recognized that imaging a one-dimensional object structure only requires illuminating the image at significantly different angles along one direction of the pupillary extent. Therefore, the exit pupill of a projection optical unit can be designed with a pupil aspect ratio that is significantly different from 1, i.e., greater than 3, and may also be greater than 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9 or 9.5, or even greater than 10. In the lateral spread of a pupil, the optical components of the projection optical unit of the optical system close to the pupil require only a small spread compared to the vertical spread of the pupil, thus reducing the cost of manufacturing the optical components and the requirements for installation space. Furthermore, in the case of a projection optical unit with a direction-independent imaging scale, it may be sufficient to illuminate the object structure at significantly different illumination angles along only one direction of the pupil's spread. Subsequently, the illuminating pupil can be designed with a pupil aspect ratio significantly different from 1. In the lateral spread of a pupil, the optical components of the illumination optical unit close to the pupil require only a small spread compared to the vertical spread of the pupil, further reducing the cost of manufacturing the optical components and further reducing the requirements for installation space.

[0009] A one-dimensional object structure can be represented as a line profile. Objects with other forms of profiles can also be imaged accordingly.

[0010] The polarization deflection mirror described in claim 2 ensures the desired polarization of illumination light having a polarization direction parallel to the direction of the structure's spread. The deflection angle may be in the range of 75° to 95°, and in particular, in the range of 80° to 90°.

[0011] As an alternative to, or in addition to, polarization of illumination light by simple beam deflection, it is also possible to use the polarization concepts described in the prior art, such as International Patent Application No. 2013 / 156 278, German Patent Application No. 10 2019 200 193, U.S. Patent No. 9,304,405, International Patent Application No. 23014 / 131 654, U.S. Patent No. 7,982,854, and German Patent Application No. 10 2012 208 521.

[0012] Thanks to the embodied beam deflection geometry, the fixed, and therefore known orientation of the structure's extent can be advantageously utilized.

[0013] The collision of at least one additional mirror of the illumination optical unit according to claim 4 facilitates highly efficient reflection of illumination light. Furthermore, collisions having such small angles of incidence may offer placement advantages in the case of this additional mirror, for example, when the additional mirror is a pupil mirror. The angle of incidence of illumination light to this additional mirror may be less than 20°, less than 15°, or less than 10°.

[0014] The embodiments of the polarization-deflecting mirrors described in claims 5 to 7 have proven to be particularly advantageous. In the embodiment described in claim 7, a synergistic effect of the polarization effects of the two polarization-deflecting mirrors occurs.

[0015] The advantages of the optical system described in claim 8 correspond to those already described above.

[0016] The advantages described above apply particularly to the optical system having the orientation of the object structure described in claim 9. In particular, the optical system can be designed so that the object does not displace during imaging within the range of projection.

[0017] The orientation relationship described in claim 10 results in object illumination optimized for image formation of object structures facing the corresponding orientation.

[0018] The advantages of the projection exposure apparatus described in claim 11, the production method described in claim 13, and the microstructure or nanostructure components produced as described in claim 14 correspond to those already described above with reference to the optical system. Due to the short wavelength of the illumination light, the EUV light source facilitates particularly high structural resolution. Microstructure or nanostructure components, in particular semiconductor components, such as memory chips, can be produced using the projection exposure apparatus.

[0019] The optical system can be embodied particularly as a scanner. The object holder of the optical system does not need to be driven in sync with the substrate holder, but can securely hold the structure to be imaged. This can increase the throughput of the projection exposure apparatus when generating structured components, particularly by reducing the scanner's dead time.

[0020] The displacement direction of the substrate may proceed along a shorter field of view of the image field.

[0021] Hereinafter, exemplary embodiments of the present invention will be described in more detail with reference to the drawings. [Brief explanation of the drawing]

[0022] [Figure 1] This is a schematic diagram of a microlithography projection exposure system. [Figure 2]Particularly, in order to clarify the parallelism of the polarization direction first and then the spreading direction of the structure, a schematic plan view of the image field of the projection optical unit of a projection exposure apparatus having an imaged one-dimensional object structure of an illumination light beam including the polarization direction of the illumination light, and a schematic plan view of a cross section obtained on the pupil plane. [Figure 3] FIG. 3 is a schematic plan view of a schematic beam guide of illumination light in a modified example of an illumination optical unit of a projection exposure apparatus depicted from a line-of-sight direction corresponding to the line-of-sight direction of FIG. 1. [Figure 4] FIG. 6 is a view showing main components of the illumination optical unit as seen from the line-of-sight direction IV in FIG. 3. [Figure 5] FIG. 9 is a view showing a further embodiment of the arrangement of main components of an embodiment of an illumination optical unit for a projection exposure apparatus according to FIG. 1 in a representation similar to that of FIG. 3. [Figure 6] FIG. 12 is a view showing the embodiment according to FIG. 5 as seen from the line-of-sight direction VI in FIG. 5 in a representation similar to that of FIG. 4. [Figure 7] FIG. 15 is a view showing a further embodiment of the arrangement of main components of an embodiment of an illumination optical unit for a projection exposure apparatus according to FIG. 1 in a representation similar to that of FIG. 3. [Figure 8] FIG. 18 is a view showing the embodiment according to FIG. 7 as seen from the line-of-sight direction VIII in FIG. 7 in a representation similar to that of FIG. 4.

Embodiments for Carrying Out the Invention

[0023] The microlithographic projection exposure apparatus 1 includes a light source 2 for illumination light or imaging light 3. The light source 2 is an EUV light source and generates light in a wavelength range, for example, between 5 nm and 30 nm, particularly between 5 nm and 15 nm. The light source 2 may be a plasma-based light source (laser-generated plasma (LPP), gas discharge-generated plasma (GDP)) or a synchrotron-based light source, such as a free-electron laser (FEL), and the synchrotron-based light source can be operated in a circularly polarized manner in particular. Specifically, the light source 2 can be a light source with a wavelength of 13.5 nm or a light source with a wavelength of 6.7 nm. Other EUV wavelengths are also possible. Generally, the illumination light 3 guided to the projection exposure apparatus 1 can have any desired wavelength, such as a visible wavelength, or even other wavelengths usable in microlithography (e.g., DUV, deep ultraviolet), and for that purpose, suitable laser and / or LED light sources (e.g., 365 nm, 248 nm, 193 nm, 157 nm, 129 nm, 109 nm) are available. The beam path of the illumination light 3 is shown very schematically in Figure 1.

[0024] The illumination optical unit 6 is used to guide illumination light 3 from the light source 2 to the object field of view 4 within the object plane 5. Using a projection optical unit or imaging optical unit 7, the object field of view 4 is imaged onto the image field of view 8 on the image plane 9 at a predetermined reduction scale. This reduction scale is also called the imaging scale and can be optionally direction-dependent, in which case the projection optical unit 7 is called anamorphic.

[0025] To facilitate the explanation of the projection exposure apparatus 1 and the various embodiments of the projection optical unit 7, the drawings show a Cartesian xyz coordinate system, from which the positional relationships of the illustrated components are clear. In Figure 1, the x-direction is perpendicular to the plane of the drawing. The y-direction extends to the right in Figure 1, and the z-direction extends upward.

[0026] In the projection optics unit 7, the object field of view 4 and the image field of view 8 may have curved, i.e., curved embodiments, particularly embodiments with a partial ring-like shape. The radius of curvature of this field of view curvature can be 81 mm on the image side. The basic shape of the peripheral contour of the object field of view 4 or the image field of view 8 has the corresponding curve. Thus, the ring field of view radius of the image field of view 8 is 81 mm. Details regarding this “ring field of view radius” parameter are described in International Patent Application No. 2005 / 098 506. The definition of the ring field of view radius is described in International Patent Application No. 2009 / 053 023. Alternatively, the object field of view 4 and the image field of view 8 can be embodied in a rectangular shape. Figure 2 shows such an embodiment of a rectangular image field of view 8. The image field of view 8 may be demarcated by a stop section, and the corresponding demarcated region of the object field of view 4 paired with the image field of view 8 is also called a scanning slot. The object field of view 4 and the image field of view 8 have an x / y aspect ratio greater than 1. Therefore, the object field of view 4 has a longer field of view dimension in the x-direction (field extent W) and a shorter field of view dimension in the y-direction (field extent H). These dimensions of the object field of view extend along the field coordinates x and y.

[0027] Therefore, object field of view 4 spans the first Cartesian object field of view coordinate x and the second Cartesian object field of view coordinate y. The third Cartesian coordinate z, which is orthogonal to these two object field of view coordinates x and y, will also be called the normal coordinate below.

[0028] In the case of the projection optical unit 7, the image plane 9 may be positioned parallel to the object plane 5. What is imaged in this case is a part of the lithography mask 10 that coincides with the object field of view 4, which is embodied as a reflective mask and also called a reticle. The reticle 10 is supported by a reticle holder 11. The reticle holder 11 is displaceable by a reticle displacement drive 12. The displacement direction of the reticle displacement drive 12 is the y-direction, also called the scanning direction. The reticle holder 11 is also called a mask holder. The reticle displacement drive 12 is also called a mask displacement drive. The reticle displacement drive 12 may be omitted in one embodiment of the projection exposure apparatus 1, and the reticle 10 does not displace during the projection operation of the projection exposure apparatus 1.

[0029] The reticle or lithography mask 10 supports a one-dimensional object structure that extends along the direction of its extension. This extension direction is in the y-direction. These one-dimensional object structures on the reticle 10 are imaged onto one-dimensional image structures 13 (see Figure 2) that also extend in the y-direction.

[0030] An example of a one-dimensional object structure is a dense line extending in the y-direction. An example relating to this is described in International Patent Application No. 2019 / 215 110.

[0031] Image formation of an object structure on the reticle 10 by the projection optical unit 7 is performed on the surface of a substrate 14 in the form of a wafer, which is supported by a substrate holder 15. The substrate holder 15 is displaced by a wafer displacement drive or a substrate displacement drive 16 (object displacement direction 16a, see Figure 2).

[0032] Figure 1 schematically shows the beam 17 of illumination light 3 incident on the projection optical unit 7 between the reticle 10 and the projection optical unit 7, and the beam 18 of illumination light 3 emerging from the projection optical unit 7 between the projection optical unit 7 and the substrate 14. The numerical aperture (NA) of the projection optical unit 7 on the object field side is shown. O, yz) and numerical aperture (NA) on the image field side. I The coordinates (yz) are not accurately reproduced in Figure 1.

[0033] The projection optical unit 7 has an entrance pupil surface 21 and an exit pupil surface 21'. The entrance pupil 20 forms a region of the entrance pupil surface 21, demarcated by a peripheral contour. Similarly, the exit pupil 20' forms a region of the exit pupil surface 21', demarcated by a peripheral contour.

[0034] The shape of the boundary of the entrance pupil 20 is determined by the numerical aperture (NA) on the object field of view side. O , yz) and (NA O It can be described by the ratio of x and z. The shape of the boundary of the exit pupil 20' is the numerical aperture (NA) on the image field side. I , yz) and (NA I It can be described by the ratio of x(z).

[0035] The entrance pupil 20 and the exit pupil 20' are optically paired with each other. If the projection optical unit 7 is anamorphic, i.e., the imaging scale is direction-dependent, then the shape of the entrance pupil 20 is different from the shape of the exit pupil 20'. Such an anamorphic projection optical unit 7 is known, for example, from International Patent Application No. 2019 / 215 110.

[0036] The illumination optical unit 6, object holder or reticle holder 11, projection optical unit 7, and substrate holder 15 are components of the optical system 19 of the projection exposure apparatus 1. The optical system 19 is embodied to image a one-dimensional object structure. Criteria for such embodiments include, in particular, that the exit pupil 20' is not circular, but its diameter along a certain direction is much larger than its diameter along the direction perpendicular to it.

[0037] The upper part of Figure 2 shows a plan view of the image structure 13 that occurs in the image field of view 8. The substrate 14 on which the image structure 13 occurs is scanned in the y-direction, i.e., the object displacement direction 16a, using a substrate displacement drive 16. Since the image structure 13 is uniformly structured in this y-direction, the reticle 10 supporting the associated object structure does not need to be displaced in the y-direction either, and can remain stationary in the reticle holder 11, thereby improving the throughput of the projection exposure apparatus 1. Therefore, the orientation of the image structure 13 in the object displacement direction 16a is particularly advantageous and is utilized below.

[0038] The upper part of Figure 2 also shows the field of view range W in the x-direction and the field of view range H in the y-direction of the image field of view 8. The object field of view 4 has corresponding field of view ranges W and H, which are enlarged or reduced by the respective imaging scales of the projection optical unit 7.

[0039] Depending on the x / y aspect ratio greater than 1 of the object field of view 4 and the image field of view 8, the following holds true: W > H. The field of view W is typically 5 times, and even 10 times, larger than the field of view H. In the image field of view 8, the field of view W could be, for example, 26 mm, and the field of view H could be, for example, in the range between 1 mm and 2 mm.

[0040] The lower center of Figure 2 shows the peripheral contour of the entrance pupil 20, which can be filled entirely with illumination light 3. The xy cross-section of this approximately stadium-shaped peripheral contour of the entrance pupil 20 at the entrance pupil surface 21 of the projection optical unit 7 is shown (see Figure 1). Furthermore, the lower right of Figure 2 shows the associated exit pupil 20' of the projection optical unit, and the lower left shows the associated illumination pupil 22 of the illumination optical unit 6. Figure 2 is a schematic diagram that considers both the image plane 9 and the entrance pupil surface 21, and even if the entrance pupil surface, exit pupil surface, and image plane are spaced apart from each other, as shown in Figure 1, for example, the illumination pupil surface 23 and exit pupil surface 21' appear in the plane of the drawing.

[0041] The relative positions of the entrance pupil surface 21 and the illumination pupil surface 23 are either coincident or only slightly different. The illumination optical unit 6 may have an additional internal pupil surface paired with the illumination pupil surface 23. The entrance pupil 20 and the illumination pupil 22 often coincide, i.e., they have the same shape and relative position. However, the illumination pupil 22 may be larger or smaller than the entrance pupil 20, and in the first case, it is also called dark-field illumination.

[0042] At the exit pupil surface 21', the exit pupil 20' has a pupil aspect ratio greater than 3 between the longer pupil extent in the longitudinal direction of the spread parallel to the x-axis and the shorter pupil extent in the transverse direction of the spread parallel to the y-axis. Projection optical units having an exit surface 20' with a large aspect ratio are known, for example, from Figures 8 to 10 in International Patent Application No. 2019 / 215 110.

[0043] This aspect ratio is illustrated with reference to Figure 2, where the spread of a long pupil is plotted in L or L', and the spread of a short pupil is plotted in K or K'. In the illustrated embodiment, an exit pupil aspect ratio L' / K' of approximately 6:1 is obtained. Thus, the image structure 13 is incident in the xz plane with a fairly large incident angle bandwidth, and the incident angle bandwidth also includes illumination angles that are more inclined with respect to the field of view 9 than larger illumination angle bandwidths at impact planes parallel to the yz plane.

[0044] The entrance pupil surface 21 and the exit pupil surface 21' are paired with each other. If the projection optics unit 7 does not have an anamorphic embodiment, the imaging scales of the projection optics unit are directionally independent, so the entrance pupil aspect ratio L / K is equal to the exit pupil aspect ratio L' / K'. In this case, the object structure, and therefore the image structure 13, is incident on the xz plane at a fairly large incident bandwidth angle, in which case the incident bandwidth angle also includes illumination angles that are more inclined with respect to the field of view 5 than larger illumination angle bandwidths, i.e., smaller illumination angle bandwidths in the collision plane parallel to the yz plane.

[0045] If the projection optics unit 7 has an anamorphic embodiment, the imaging scale is direction-dependent, so the entrance pupil aspect ratio L / K is not equal to the exit pupil aspect ratio L' / K'. In this case, the condition L' / K' > 1 still applies to the exit pupil aspect ratio, but a general description cannot be made regarding the entrance pupil aspect ratio L / K. In Figure 2, the case of the anamorphic projection optics unit 7 is shown by the shape of the entrance pupil 20, which differs from the shape of the exit pupil 20'.

[0046] The extension direction of the structure, object structure, and image structure 13 extends parallel to the substrate displacement direction 16a (y direction).

[0047] On the one hand, the longitudinal x of the extent of the exit pupil 20' and the normal z to the object field of view 4 or image field of view 8 define the xz plane, and the direction of the structure's extent y is orthogonal to the xz plane. In the case of the non-anamorphic projection optical unit 7, the xyz coordinate system can also be defined by the longitudinal x extent of the pupils 20, 22.

[0048] Figure 2 shows the polarization directions 24 and 24', respectively, in which the illumination light 3 is polarized as it first strikes the object field of view 4 via the illumination pupil 22 and then strikes the projection optical unit 7 via the entrance pupil 20. In this case, the illumination light 3 is linearly polarized. The polarization directions 24 and 24' each extend in the y direction, i.e., parallel to the y-direction of the structure's spread. The preferred orientation of the structure's spread, further described above, results in this preferred orientation of the polarization direction 24. This allows for a fixed selection of the polarization direction 24, i.e., it does not necessarily need to be adjustable during the operation of the projection exposure apparatus 1.

[0049] Figures 3 through 8 below are used to illustrate various embodiments of the illumination optical unit used within the projection exposure apparatus 1 for the illumination optical unit 6 according to Figure 1, which helps to generate a polarization direction 24 parallel to the y-direction. Components and functions corresponding to those already described with reference to the aforementioned figures are given the same reference numerals and will not be discussed in detail again.

[0050] Common to all exemplary embodiments is that there is at least one reflection with beam deflection at an angle between 75° and 100°, during which the illumination light 3 spreads approximately in the xz plane. Thus, the y-axis extends approximately parallel to the surface of the mirror used for this reflection. As an example, the y-axis may be twisted by less than 15° with respect to the surface of the mirror.

[0051] The normal to the mirror used for beam deflection is always in the plane through which the incident and reflected illumination light 3 extends. Therefore, in exemplary embodiments, the normal to the mirror used for beam deflection is approximately in the xz plane and is twisted by, for example, less than 15° with respect to the xz plane.

[0052] Beam deflection angles between 75° and 100° are favorable for illumination light 3 having wavelengths in the EUV range. Generally, reflections that deflect the beam should occur at angles approximately twice the Brewster angle. Twice the Brewster angle can deviate significantly from 90°, especially for wavelengths in the DUV range. In particular, beam deflection can be performed at angles that deviate by 20% or less from twice the Brewster angle.

[0053] Figures 3 and 4 show the illumination optical unit 6 as a first embodiment that can be used in the projection exposure apparatus 1. In this case, Figure 3 shows a diagram corresponding to the orientation in Figure 1 with respect to the collision of the object field of view 4, and Figure 4 shows a diagram rotated 90° with respect to the z axis so that the object displacement direction y is toward the observer.

[0054] The illumination light 3, emerging from light source 2 and represented very schematically as a single beam, first passes through collector 25 and is then focused at the intermediate focal point IF (see Figure 4).

[0055] The illumination light 3, after passing through the intermediate focal point IF, is reflected by the field facet mirror 26 of the illumination optical unit, and in the process is deflected to a deflection angle U in the range of 75° to 100°. This deflection angle U is approximately 90° in the exemplary embodiments shown in Figures 3 and 4. As shown in Figure 4, the illumination light 3, which initially propagates in the x direction, is deflected to propagate approximately in the z direction. Thus, the illumination light 3 spreads approximately in the xz plane before and after reflection at the field facet mirror 26 of the illumination optical unit 6. As shown in Figure 3, the illumination light 3 after reflection at the field facet mirror 26 does not extend precisely in the z direction, but in the yz plane at an angle α with the z axis. z It forms. In Figure 3, angle α z This is approximately 20°. Therefore, the field-view facet mirror 26 is tilted with respect to the z-axis by half of this angle, i.e., approximately 10° in this case.

[0056] The illumination light 3 is reflected by the field facet mirror 26 and then reflected by the Pupil facet mirror 27 of the illumination optical unit 6.

[0057] Due to the 90° deflection during reflection at the field facet mirror 26, the illumination light 3 becomes s-polarized with respect to the incident plane at the field facet mirror 26, i.e., it has a polarization direction 24 approximately in the y direction. As a result, subsequent reflection of the illumination light 3 has virtually no change in the polarization direction 24.

[0058] The illumination light 3, after being reflected by the Pupil facet mirror 27, is directed toward the object field of view 4, as already described with respect to Figures 1 and 2, where it is reflected by the reticle 10.

[0059] Examples of the configurations of the faceted mirrors 26 and 27 of the illumination optical unit are described, for example, in U.S. Patent No. 9,304,405. One of the faceted mirrors may be embodied as a specular reflector, similar to that described in U.S. Patent No. 9,304,405, in conjunction with the embodiments shown in Figures 12 and 13, for example.

[0060] The field-view facet mirror 26 may have multiple or numerous field-view facets, in particular, field-view facets that can be switched between multiple tilt positions, which are not shown in further detail in the drawings. These field-view facets are imaged or virtually imaged within the object field-view 4 via downstream components of the illumination optical unit 6. Each of these field-view facets may be constructed from multiple individual mirrors, and dynamic assignment of individual mirror groups to the corresponding field-view facets is possible.

[0061] Each field of view facet mirror 26 may be assigned a pupil facet of pupil facet mirror 27 (which, likewise, is not shown in detail in the drawing).

[0062] The field facet mirror 26 is arranged in the region of the field surface of the illumination optical unit 6 that is paired with the object surface 5. The pupil facet mirror 27 is arranged in the region of the pupil surface of the optical system 19, particularly on the illumination pupil surface 23 or the surface paired with it. The illuminated pupil facets of the pupil facet mirror 27 help to define the illumination angle distribution when the object field 4 is illuminated by the illumination light 3. By making the field facets tiltable, it is possible to select which pupil facets of the pupil facet mirror 27 the illumination light 3 is actually incident on. As a result, it is possible to define the illumination angle distribution, that is, the illumination setting.

[0063] In the alternative illumination optical unit 30 according to FIGS. 5 and 6, the polarization direction 24 is generated during the reflection of the illumination light 3 in the pupil facet mirror 27, and in this embodiment of the illumination optical unit 30, it causes a deflection of about 90°. The deflection angle during the reflection of the illumination light 3 in the pupil facet mirror 27 is about 80°.

[0064] The beam guide of the illumination optical unit 30 (see FIG. 6) between the light source 2 and the field facet mirror 26 is initially the same as the beam guide of the illumination optical unit 6 according to FIGS. 3 and 4. As shown in FIG. 6, the illumination light 3 extends approximately along the x-axis before reflection by the pupil facet mirror 27, while it extends approximately along the z-axis after reflection by the pupil facet mirror. Therefore, the illumination light 3 spreads in the xz plane before and after reflection by the pupil facet mirror 27 of the illumination optical unit 6.

[0065] The illumination light 3 coming from the intermediate focus IF is reflected from the xz plane by the field facet mirror 26 and enters the yz plane again. The illumination light 3 extends between the facet mirrors 26 and 27 at an angle with respect to all three Cartesian planes xy, yz, xz, not exactly along the x-axis. FIGS. 5 and 6 show these three angles α xy , α yz and α xzExamples of projections onto the yz-plane (see Figure 5) and the xz-plane (see Figure 6) are plotted.

[0066] The deflection angle U of the illumination light 3 in the Pupil facet mirror 27 is also specified in each case by its projection onto the yz-plane and xz-plane in Figures 5 and 6. This deflection angle U is approximately 80°.

[0067] Again, a polarization direction 24, almost in the y-direction, is generated by reflection in the Pupil facet mirror 27.

[0068] In the configuration shown in Figures 3 and 4, the field-view facet mirror 26 may be the only mirror in the illumination optical unit 6 that deflects the illumination light 3 at a deflection angle of approximately 90°. In comparison, the other mirrors may receive illumination light 3 at nearly perpendicular incidence angles, i.e., incidence angles that can be less than 25°, less than 20°, less than 15°, and even less than 10°.

[0069] Therefore, the Pupil facet mirror 27 of the illumination optical unit 30 shown in Figures 5 and 6 may be the only mirror that deflects the illumination light 3 at a deflection angle of about 90°, while all other mirrors of the illumination optical unit 30 receive the light almost perpendicularly.

[0070] Because the angle of incidence of illumination light 3 to the pupil facet mirror 27 in the embodiments shown in Figures 3 and 4 is small, there is an option to position the pupil facet mirror 27 in a good approximation to the pupil surface of the optical system 19. This makes it possible to illuminate the object field of view 4 from different illumination directions without unwanted field of view dependence. Subsequently, each field of view point of the object field of view 4 can be illuminated from various illumination directions with the same defined illumination light intensity.

[0071] Figures 7 and 8 show further embodiments of the illumination optical unit 32, which can be used in place of the illumination optical unit 6 or illumination optical unit 30 in the projection exposure apparatus 1.

[0072] In the illumination optical unit 32, the illumination light 3, emitted from the light source 2 and extending through the intermediate focal point IF after passing through the collector 25, initially extends in the z direction. Subsequently, the illumination light 3 is deflected by approximately 90° in the xz plane by the field facet mirror 26 and extends in the negative x direction. Then, it is deflected by another 90° in the xz plane, resulting in the illumination light 3 extending again in the z direction with a principal ray angle CRA of approximately 6° away (see Figure 7, where this principal ray angle CRA is plotted schematically). In the illumination optical unit 32, the polarization effect on the linear polarization of the illumination light 3 in the polarization direction 24 is amplified by two reflections, first at the field facet mirror and then at the Pupil facet mirror 27, in each case the deflection angle U is approximately 90°.

[0073] In the illumination optical unit 32, the light source 2 can be located one floor below the generation level in which the optical system 19, which includes the illumination optical unit 32 and the projection optical unit 7, is located.

[0074] The mirrors of various modifications of the illumination optical units 6, 30, and 32 can be provided with a coating that has high reflectivity to the illumination light 3. This coating can be implemented as a multilayer coating. In particular, the coating can be designed as a specific periodic sequence of layers made of two or more different materials. These materials may be molybdenum or silicon.

[0075] In the case of such coatings, and when the deflection angle is approximately 90°, i.e., the incident angle is approximately 45°, in each case, a large difference in reflectivity occurs between the s-polarized illumination light 3 and the p-polarized illumination light 3 with respect to the incident surface. In this case, the s-polarized illumination light 3 is reflected with much higher reflectivity than the p-polarized illumination light 3. Therefore, the correspondingly coated 90° deflection mirror acts as a polarizer for the illumination light 3. The best polarization effect occurs when the illumination light 3 is incident at an angle lower than the Brewster angle. For many materials, the Brewster angle for EUV wavelengths is not exactly 45°, but rather in the range between 40° and 45°, for example, 42°.

Claims

1. An optical system (19) for a lithography projection exposure apparatus (1), - An illumination optical unit (6; 30; 32) is provided which illumination light (3) is guided from an EUV light source (2) to an object field of view (4), and a structured object (10) can be placed in the object field of view (4), -- The illumination optical unit (6;30;32) is implemented such that the object field of view (4) illuminated by the illumination optical unit (6;30;32) has a field of view range (W) along a first field of view coordinate (x) and a field of view range (H) along a second field of view coordinate (y) that is orthogonal to the first field of view coordinate (x), and is shorter than the field of view range (W). -- The illumination optical unit (6;30;32) is implemented such that the illumination light (3) incident on the object field of view (4) is polarized in a polarization direction (24) that extends parallel to the shorter field of view range (H) along the second field of view coordinate (y), - A projection optical unit (7) for guiding the illumination light and imaging light (3) from the object field of view (4) to the image field of view (8), wherein a substrate (14) can be placed inside the projection optical unit (7) and is intended to form an image of an object structure on it, - The optical system (19) is implemented to generate a one-dimensional image structure (13) by forming an image of the one-dimensional object structure of the object (10), - The exit pupil (20') on the pupil surface (21') of the projection optical unit (7) has a pupil aspect ratio (L' / K') greater than 3 between the longer pupil spread (L') in the vertical (x) direction and the shorter pupil spread (K') in the horizontal (y) direction. Optical system (19).

2. The optical system according to claim 1, wherein the illumination optical unit (6; 30; 32) comprises at least one polarization deflection mirror (26; 27; 26, 27) through which the illumination light (3) passes at a deflection angle in the range of 75° and 100°, and the polarization direction (24) is perpendicular to the plane of incidence of the illumination light (3) to the polarization deflection mirror (26; 27; 26, 27).

3. The optical system according to claim 2, characterized in that the illumination light (3) in at least one polarization deflection mirror (26; 27; 26, 27) travels in an incident plane deflected by 15° or less from a plane (xz) specified by the first field of view coordinate (x) and the normal (z) to the object field of view (4).

4. The optical system according to claim 2 or 3, characterized in that, in addition to the polarization deflection mirrors (26; 27), at least one further mirror (27; 26) composed of the illumination optical unit (6; 30) is incident on the illumination light (3) at an incident angle of less than 25°.

5. The optical system according to any one of claims 2 to 4, characterized in that the polarization deflection mirror (26) is in the form of a field-view facet mirror.

6. The optical system according to any one of claims 2 to 4, characterized in that the polarization deflection mirror (27) is in the form of a Pupil facet mirror.

7. The optical system according to any one of claims 2 to 6, wherein the illumination optical unit (32) comprises two polarization deflection mirrors (26, 27), the illumination light (3) is deflected by the polarization deflection mirrors (26, 27) to a deflection angle in the range of 80° and 100°, the incident planes (xz) of the illumination light (3) on the polarization deflection mirrors (26, 27) are parallel to or coincide with each other, and the polarization direction (24) is perpendicular to the incident planes (xz) of the illumination light (3) on the polarization deflection mirrors (26, 27).

8. The optical system according to any one of claims 1 to 7, characterized in that the illumination pupil of the illumination optical unit has a pupil aspect ratio other than 1.

9. The optical system according to any one of claims 1 to 8, wherein the image field (8) has a field range (W) along a first field coordinate (x) and a field range (H) that is shorter than the field range (W) along a second field coordinate (y) orthogonal to the first field coordinate (x), and the optical system (19) is embodied to form an image of a one-dimensional object structure extending in the direction of expansion (y) of the structure that extends parallel to the shorter field range (H) of the object field (4).

10. The optical system according to claim 9, characterized in that the vertical (x) spread of the exit pupil (20') and the normal (z) to the object field of view (4) define a plane (xz), and the direction of spread (y) of the shorter field of view range (H) of the object field of view (4) is orthogonal to the plane (xz).

11. A projection exposure apparatus comprising an optical system (19) according to any one of claims 1 to 10, the apparatus further comprising an object holder (11) for holding the object (10) and a substrate holder (15) for holding the substrate (14), wherein the substrate holder (15) is driveable and displaceable in the substrate displacement direction (y).

12. The projection exposure apparatus according to claim 11, comprising an EUV light source (2).

13. A method for generating structured components, comprising the following method steps: - Steps to prepare the reticle (10) and wafer (14), - A step of projecting the structure on the reticle (10) onto the photosensitive layer of the wafer (14) using the projection exposure apparatus according to claim 11 or 12, - A step of generating microstructures and / or nanostructures on the wafer (14), method.

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