Method for designing an imaging optical system for a projection exposure system, imaging optical system and projection exposure system

Abstract

A method for designing an imaging optical system for a projection exposure system (1) is presented and described, comprising at least the following step: a) Determining a final optical system for a projection exposure system (1), wherein the final optical system comprises at least one optical element, wherein, when determining the final optical system, at least one expected proportion of at least one imaging error contribution, particularly during the operation of a projection exposure system (1), is taken into account, in particular compensated, and wherein the expected proportion of the imaging error contribution is caused by at least one thermal manipulator of a projection exposure system (1) and / or by at least one thermal compensation means of a projection exposure system (1).To account for the influence of thermal manipulators and / or thermal compensation means on the imaging errors of a projection exposure system (1), the previously described method is proposed. An imaging optical system for a projection exposure system (1) and a projection exposure system (1) are also shown and described.

Description

[0001] The present invention relates to a method for designing an imaging optical system. The present invention further relates to an imaging optical system. The present invention also relates to a projection exposure system.

[0002] Microlithography is used to manufacture microstructured components, such as integrated circuits. The microlithography process is carried out, in particular, using a projection exposure system, which includes, among other things, illumination optics and / or projection optics. The structure of a mask (reticle) illuminated by the illumination optics is projected by the projection optics onto a substrate coated with a light-sensitive layer (photoresist) and arranged in the image plane of the projection optics, for example, a wafer, especially a silicon wafer, in order to transfer the mask structure to the light-sensitive coating of the substrate.

[0003] One of the goals in the development of projection exposure systems is to lithographically create structures with increasingly smaller dimensions on the substrate, for example, to achieve higher integration densities in semiconductor components. One approach is to work with shorter wavelengths of electromagnetic radiation. For example, optical systems have been developed that use electromagnetic radiation from the so-called "deep ultraviolet" range (DUV), preferably with operating wavelengths in the range between 150 nm and 400 nm, in particular 365 nm, 248 nm, or 193 nm, or from the extreme ultraviolet range (EUV), preferably with operating wavelengths in the range between 5 nm and 30 nm, in particular 13.5 nm.

[0004] In order to produce the structures on the substrate with the highest possible accuracy and thus maximize the yield in the microlithography process, imaging errors during operation of the projection exposure system must be kept to a minimum and corrected if necessary. Such imaging errors can be caused, for example, by the useful radiation of the projection exposure system, since the useful radiation continuously heats one or more of the optical elements of the projection exposure system during operation. The heating of the optical elements can lead to, for example, non-uniform deformation of the optical elements and thus to imaging errors. To counteract such problems, a number of methods and devices are known from the prior art, for example DE 100 00 191 A1, DE 10 2015 224 281 A1 or DE 10 2014 212 691 A1.Such methods and devices can, for example, preheat the optical elements to prevent uneven heating of an optical element or preheat an optical element before performing an exposure using the projection exposure system in order to minimize or even prevent a change in the temperature of the optical element during operation of the projection exposure system. Means acting in this way are also referred to as thermal manipulators. It is also possible to adapt an optical element, for example, the geometry of an optical element, in order to reduce or prevent aberrations due to the heating of the optical element. Means acting in this way fall, for example, under the term thermal compensation means.

[0005] However, it has been shown that the methods and devices intended to prevent aberrations due to the heating of the optical elements can themselves lead to aberrations. Such aberrations are also referred to as residual or parasitic aberrations. The parasitic aberrations can affect certain aberration contributions, in particular certain Zernike polynomials. This can result in a projection exposure system equipped with devices and methods intended to prevent aberrations due to the heating of the optical elements delivering unsatisfactory results, at least for certain aberration contributions.

[0006] Against this background, the present invention is based on the object of providing a method for designing an imaging optical system for a projection exposure apparatus, an imaging optical system and a projection exposure apparatus, which takes into account the influence of thermal manipulators and / or thermal compensation means on the imaging errors of a projection exposure apparatus.

[0007] The aforementioned object is achieved according to the invention by a method for designing an imaging optical system for a projection exposure apparatus, comprising at least the following step: a) determining a final optical system for a projection exposure apparatus, wherein the final optical system comprises at least one optical element. The optical element can be a lens and / or a mirror. The final optical system can also comprise a plurality of optical elements. Alternatively or additionally, the final optical system can be configured as an optical assembly.

[0008] According to the method, it is further provided that when determining the final optical system, at least one portion of at least one aberration contribution to be expected, in particular during operation of a projection exposure system, is taken into account, in particular compensated. This ensures that certain expected portions of aberration contributions, in particular of parasitic aberrations, have no or only a minor influence on the imaging quality of the final optical system. The method can comprise determining at least one expected portion of at least one aberration contribution in step a). The expected portion of the aberration contribution can be determined, for example, by means of simulation. The aberration contribution is preferably described as a Zernike polynomial, in particular a Zernike decomposition of a wavefront. The expected portion of the aberration contribution does not have to be known exactly.It is sufficient if the amplitude and / or the amplitude dispersion of the corresponding aberration contribution curve, preferably a wavefront in the scanning direction of a projection exposure system, is known. The corresponding aberration contribution does not need to be completely corrected in step a); it is sufficient if the expected portion of the aberration contribution is compensated.The aberration contribution, in particular the amplitude and / or the scatter of the amplitude of the aberration contribution, should, preferably for the final optical system without thermal stress, be at least below a threshold value and / or at least smaller than the corresponding aberration contribution of an initial optical system that is not influenced by thermal manipulators, thermal compensation means, and / or by thermal influences from the useful radiation of a projection exposure system. The initial optical system just described is, in particular, the initial optical system, which will be explained in more detail below.

[0009] According to the method, it is further provided that the expected portion of the aberration contribution is determined by at least one thermal manipulator of a projection exposure system and / or by at least one thermal compensation means of a projection exposure system. The expected portion of the aberration contribution should therefore not be just any portion or any aberration contribution, but rather those portions and / or aberration contributions that are determined by devices and / or methods intended to counteract aberrations due to the heating of optical elements.A thermal compensation means is preferably a device and / or a method designed to compensate for effects induced by at least one component of a projection exposure system, in particular at least one optical element, by heating, for example, due to the effective radiation of a projection exposure system or due to a thermal manipulator. The effective radiation is the radiation generated by the radiation source of a projection exposure system and / or directed by means of an optical system for exposing a substrate to be arranged in a projection exposure system.The term “manipulator” preferably refers to a device that is particularly intended to actively influence individual optical elements, groups of optical elements, optical modules and / or groups of optical modules, in particular on the basis of at least one control signal, in order to change the optical effect of these elements, groups of elements, modules and / or groups of modules in the projection beam path of a projection exposure system. A thermal manipulator is therefore preferably a manipulator that uses thermal energy to change the optical effect accordingly. Manipulators are generally adjusted so that imaging errors detected by measurement can be specifically corrected. The projection exposure system described in the method, in particular in step a) and / or b), can be the same projection exposure system in each case.

[0010] In one embodiment of the method, it is provided that the expected portion of the aberration contribution is caused by at least one thermal influence from the useful radiation of a projection exposure system. The expected portion of the aberration contribution should therefore also include those portions and / or aberration contributions that are caused by the heating of optical elements. The thermal influence can be the thermal influence of at least one component of a projection exposure system, in particular at least one optical element.

[0011] In one embodiment of the method, it is provided that the method comprises the following step: b) defining an initial optical system for a projection exposure apparatus, wherein the initial optical system comprises at least one optical element, wherein in step a) the final optical system is determined based on the initial optical system. This simplifies the determination of the final optical system, since the final optical system is determined on the basis of an already existing optical system. In this case, step a) is in particular an optimization and not a completely new design of an optical system. The optical element of the initial optical system can be a lens and / or a mirror, for example, in accordance with the final optical system.

[0012] The term "final" and the term "initial" in the present disclosure serve only to distinguish between different features, for example the final optical system and the initial optical system, and are generally not to be interpreted in a restrictive manner, in particular with regard to the number and / or order of the features described thereby, unless otherwise described in the present disclosure.

[0013] In one embodiment of the method, it is provided that in step a) the geometry of the optical element of the initial optical system is changed, the position and / or orientation of the optical element of the initial optical system is changed and / or the number of optical elements of the initial optical system is changed. By making appropriate changes to the initial optical system, the expected proportion of the aberration contribution can be taken into account, in particular compensated for, in a structurally simple manner. The geometry of the optical element can be changed by changing the surface of the optical element. For example, at least one corrective asphere can be provided on the optical element. A corrective asphere is an at least section-wise adaptation of the surface of an optical element, so that the surface of the optical element is at least section-wise aspherical.Advantageously, in step a), the geometry of a plurality of optical elements of the initial optical system can be changed and / or the position and / or orientation of a plurality of optical elements of the initial optical system can be changed.

[0014] In one embodiment of the method, it is provided that in step a), the final optical system is determined using an optimization method characterized by a merit function, and that, preferably, the merit function includes, as an evaluation variable, the optical path length and / or the deviation of the optical path length of the initial optical system without thermal stress, the optical path length and / or the deviation of the optical path length of the initial optical system with thermal stress, and / or the optical path length and / or the deviation of the optical path length of an optical reference system. This simplifies the determination of the best possible final optical system.

[0015] The merit function can include the following term, which should be minimized: min(Wcold+Wthermal residuals−Wreference) W coldis the optical path length and / or the deviation of the optical path length of the final optical system without thermal stress.

[0016] W thermal residuals is the optical path length and / or the deviation of the optical path length of the initial optical system with thermal stress.

[0017] W reference is the optical path length and / or the deviation of the optical path length of an optical reference system.

[0018] The merit function can, for example, provide for a Zernike decomposition of the respective path lengths and for certain Zernike polynomials, groups of Zernike polynomials, and / or linear combinations of Zernike polynomials to be weighted differently. The deviation of the optical path length is, in particular, the deviation from the optical path length of an ideal optical system, whereby the ideal optical system is free of aberrations and, preferably, the structure of the ideal optical system is arbitrary. By using the optical path length and / or the deviation of the optical path length of the initial optical system without thermal stress, in particular those aberrations are taken into account that are not caused by thermal manipulators, thermal compensation devices, and / or thermal influences from the useful radiation of a projection exposure system.

[0019] In other words, those aberrations are taken into account that are caused by the “cold”, in particular non-operational, initial optical system. Such aberrations can be due, for example, to deviations in the geometry or arrangement of the optical elements from the nominal geometry or arrangement. By using the optical path length and / or the deviation of the optical path length of the initial optical system with thermal stress, in particular those aberrations are taken into account that are caused by thermal manipulators, thermal compensation means and / or thermal influences from the useful radiation of a projection exposure system. In other words, those aberrations are taken into account that are caused by the “warm”, in particular operational, initial optical system.By using the optical path length and / or the deviation from the optical path length of an optical reference system, aberrations are taken into account, which the final optical system to be determined should preferably exhibit. On the one hand, the optical reference system may not exhibit any aberrations, so the merit function is optimized to the global minimum so that the final optical system exhibits as few aberrations as possible. In this case, W would be in the above term. reference= 0. However, it can also be provided that the optical reference system should exhibit certain aberrations, in particular certain aberration contribution curves, i.e., certain curves of aberration contributions. For the operation of projection exposure systems, it is often advantageous if a new projection exposure system has essentially the same aberration contribution curve as an older projection exposure system. Thus, the same masks and / or the same settings can be used in the new projection exposure system as in the older projection exposure system. It may therefore be appropriate for the optical reference system to be the initial optical system.Thus, the final optical system is optimized in such a way that thermal manipulators, thermal compensation means and / or thermal influence by the useful radiation of a projection exposure system are taken into account, and at the same time the aberration contribution curve of the final optical system corresponds at least partially to the aberration contribution curve of the initial optical system.

[0020] In one embodiment of the method, it is provided that in step a), the expected proportion of the aberration contribution in the geometry of the optical element of the initial optical system, in the position and / or orientation of the optical element of the initial optical system and / or in the number of optical elements of the initial optical system is taken into account. In particular, the geometry of the optical element of the final optical system, the position and / or orientation of the optical element of the final optical system and / or the number of optical elements of the final optical system are designed such that the expected proportion of the aberration contribution is compensated. This provides an optical system for projection exposure systems whose aberration contribution curves are not or only insignificantly negatively influenced by thermal compensation means or thermal manipulators.The expected proportion of the aberration contribution can be taken into account, for example, by providing at least one correction asphere on the optical element.

[0021] In one embodiment of the method, it is provided that in step a) the final optical system is determined such that the aberration contribution profile, in particular without thermal stress, of the final optical system for at least one aberration contribution deviates by a maximum of 25%, preferably a maximum of 15%, more preferably a maximum of 10%, in particular a maximum of 5%, from the aberration contribution profile of the corresponding aberration contribution, in particular without thermal stress, of an optical reference system. For corresponding aberration contributions, in particular Zernike polynomials, the aim is thus to achieve the greatest possible agreement between the final optical system and the optical reference system. This makes it easier for the final optical system to be used with the same masks and / or the same settings as another, in particular older, optical system.It can be provided that in step a), the final optical system is determined such that the respective aberration contribution profile, in particular without thermal loading, of the final optical system for at least some of the aberration contributions deviates by at most 25%, preferably at most 15%, more preferably at most 10%, in particular at most 5%, from the respective aberration contribution profile of the corresponding part of aberration contributions, in particular without thermal loading, of an optical reference system. The thermal loading can be caused by thermal manipulators, thermal compensation means, and / or by thermal influences from the useful radiation of a projection exposure system.The at least one aberration contribution and / or the at least part of the aberration contributions of the final optical system, for which the aberration contribution curve deviates by at most the corresponding value, is in particular the aberration contribution(s) for which in the merit function W. thermal residuals = 0 and / or not the aberration contribution(s) for which the expected portion of an aberration contribution is taken into account, in particular compensated. The corresponding deviation of the aberration contribution(s) thus particularly affects those aberration contributions that are not affected by parasitic aberrations. The optical reference system can, in particular, be the initial optical system. The optical reference system can, in particular, be the initial optical system.

[0022] In the present disclosure, an aberration contribution curve is the curve of an aberration contribution, wherein the respective aberration contribution is preferably described as a Zernike polynomial, in particular a Zernike decomposition of a wavefront.

[0023] In one embodiment of the method, it is provided that in step a) the final optical system is determined such that the aberration contribution profile, in particular without thermal stress, of the final optical system for at least one aberration contribution deviates by at least 10%, preferably at least 25%, more preferably at least 40%, in particular at least 50%, from the aberration contribution profile of the corresponding aberration contribution, in particular without thermal stress, of an optical reference system. For corresponding aberration contributions, in particular Zernike polynomials, a certain deviation should therefore exist between the final optical system and the optical reference system. This provides sufficient leeway for the final optical system to have no aberration contribution profile or only a slightly worse aberration contribution profile for at least some of the aberration contributions under thermal stress.This makes it easier for the final optical system to be used with the same masks and / or the same settings as another, particularly older, optical system. It can be provided that in step a) the final optical system is determined such that the respective aberration contribution profile, particularly without thermal loading, of the final optical system for at least some of the aberration contributions deviates by at least 10%, preferably at least 25%, more preferably at least 40%, in particular at least 50%, from the respective aberration contribution profile of the corresponding part of aberration contributions, particularly without thermal loading, of an optical reference system. The thermal loading can be caused by thermal manipulators, thermal compensation means and / or by thermal influences from the useful radiation of a projection exposure system.The optical reference system can, in particular, be the initial optical system. The at least one aberration contribution and / or the at least part of the aberration contributions of the final optical system, for which the aberration contribution profile deviates by at least the corresponding value, are, in particular, the aberration contribution(s) for which W in the merit function. thermal residuals ≠ 0 and / or by the aberration contribution(s) for which the expected portion of the aberration contribution is taken into account, in particular compensated. The corresponding deviation of the aberration contribution(s) thus particularly affects those aberration contributions affected by parasitic aberrations. The optical reference system can, in particular, be the initial optical system.

[0024] Alternatively or additionally, it can be provided that in step a) the final optical system is determined such that the amplitude of the aberration contribution curve, in particular without thermal stress, of the final optical system for at least one aberration contribution deviates by at least 10%, preferably at least 25%, more preferably at least 40%, in particular at least 50%, from the amplitude of the aberration contribution curve of the corresponding aberration contribution, in particular without thermal stress, of an optical reference system. This also provides sufficient flexibility so that the final optical system has no aberration contribution curve or only a slightly worse aberration contribution curve for at least some of the aberration contributions under thermal stress.The at least one aberration contribution of the final optical system for which the amplitude of the aberration contribution curve deviates by at least the corresponding value is in particular the aberration contribution(s) for which in the merit function W. thermal residual ≠ 0 and / or by the aberration contribution(s) for which the expected portion of an aberration contribution is taken into account, in particular compensated. The corresponding deviation in the amplitude of the aberration contribution thus particularly affects those aberration contributions affected by parasitic aberrations. The optical reference system can, in particular, be the initial optical system.

[0025] The aforementioned object is further achieved according to the invention by an imaging optical system for a projection exposure apparatus, comprising at least one optical element, wherein the imaging optical system is defined according to one of claims 1 to 8. A correspondingly configured optical system has the advantages and properties explained in connection with the method. The optical system can be an optical assembly for a projection exposure apparatus. The optical element can be a lens and / or a mirror. The optical system can also comprise a plurality of optical elements.

[0026] The aforementioned object is further achieved according to the invention by a projection exposure system comprising an imaging optical system according to claim 9. A correspondingly configured projection exposure system has the advantages and properties explained in connection with the method. The projection exposure system can comprise projection optics, illumination optics, a radiation source, a mask holder, and / or a substrate holder, also called a wafer holder. The optical system can comprise the projection optics and / or the illumination optics.

[0027] Further features and advantages of the method, the imaging optical system and the projection exposure system will become apparent from the following description of embodiments, with reference to the attached drawing.

[0028] The drawing shows: Fig. 1 the basic structure of a projection exposure system, Fig. 2 aberration contribution curves of an aberration contribution, and Fig. 3 Aberration contribution curves of different aberration contributions.

[0029] Fig. 1 shows, by way of example, the basic structure of an EUV projection exposure system 1 for microlithography, wherein the disclosed method can be used for the optical system of the projection exposure system 1. An illumination system of the projection exposure system 1 comprises, in addition to a radiation source 3, illumination optics 4 for illuminating an object field 5 in an object plane 6. EUV radiation 14 generated by the radiation source 3 as useful radiation is aligned by means of a collector integrated in the radiation source 3 such that it passes through an intermediate focus in the region of an intermediate focal plane 15 before impinging on an optical element in the form of a field facet mirror 2. After the field facet mirror 2, the EUV radiation 14 is reflected by an optical element in the form of a pupil facet mirror 16.With the aid of the pupil facet mirror 16 and an optical assembly 17 with a plurality of optical elements, wherein the optical elements each comprise at least one mirror 18, 19, 20, field facets of the field facet mirror 2 are imaged into the object field 5. A mask 7 arranged in the object field 5 and held by a schematically illustrated mask holder 8 is illuminated. A projection optics 9, shown only schematically, serves to image the object field 5 into an image field 10 in an image plane 11. A structure on the mask 7 is imaged onto a light-sensitive layer of a wafer 12 arranged in the region of the image field 10 in the image plane 11, which is held by a wafer holder 13, also shown in detail. The radiation source 3 can emit useful radiation preferably in a wavelength range between 5 nm and 30 nm, particularly preferably 13.5 nm.

[0030] The disclosed method can also be used for a DUV system, which is not shown. A DUV system can, in principle, be constructed like the EUV projection exposure system 1 described above, wherein mirrors and / or lenses can be used as optical elements in a DUV projection exposure system, and the radiation source of a DUV projection exposure system emits useful radiation in a wavelength range from 150 nm to 400 nm.

[0031] Fig. Figure 2 shows aberration contribution curves of an aberration contribution. The ordinate Y of diagram I indicates the amplitude of the aberration contribution curves, and the abscissa X indicates the extent of the image field 10 perpendicular to the scanning direction. The aberration contribution for which the two aberration contribution curves are shown is, in particular, a Zernike polynomial of a Zernike decomposition of a wavefront. The solid line shows the aberration contribution curve of an optical reference system. The optical reference system comprises at least one optical element and is provided in a projection exposure system 1, wherein this projection exposure system 1 does not comprise any thermal manipulators or thermal compensation means.

[0032] Consequently, the aberration contribution curve of the optical reference system is not influenced by corresponding thermal manipulators and / or thermal compensation means. The dashed line, in turn, shows the aberration contribution curve of an adapted optical system. This adapted optical system can essentially correspond to the optical reference system, but the adapted optical system is provided in a projection exposure system 1 which comprises thermal manipulators and / or thermal compensation means. It can be seen that the amplitude of the aberration contribution curve of the adapted optical system is greater, at least for the illustrated aberration contribution, and thus the aberration quality is poorer, at least for the illustrated aberration contribution of the adapted optical system, than that of the optical reference system.This is due to the thermal manipulators and / or thermal compensation means acting on the adapted optical system. It has been shown that thermal manipulators and thermal compensation means, which are intended to prevent aberrations due to the heating of the optical elements of a projection exposure system 1, can themselves lead to aberrations. Fig. 2 shows the aberration contribution curves under thermal stress of the respective optical system.

[0033] Fig. Figure 3 shows aberration contribution curves for different aberration contributions. The respective ordinate Y of the diagrams I*, II*, III* shows, as already in diagram I, the Fig. 2 the amplitude of the aberration contribution curves and the respective abscissa X the extent of the image field 10 perpendicular to the scanning direction. The left diagram I* shows the aberration contribution curves for the same aberration contribution as in the diagram I of the Fig. 2. The solid line in diagram I* shows how in Fig. 2 the aberration contribution curve of the optical reference system. The dashed line in the diagram I* shows the Fig. 3, however, now shows the aberration contribution curve for a final optical system. In Fig. 3, the aberration contribution curves are shown without thermal loading of the respective optical system. The final optical system is based on the optical reference system, which in the illustrated embodiment is also referred to as the initial optical system. The final optical system comprises at least one optical element and is provided in a projection exposure system 1. The final optical system is comparable to the adapted optical system from Fig. 2 - in a projection exposure system 1, which comprises thermal manipulators and / or thermal compensation means. When determining, in particular designing, the final optical system, the proportion of an imaging error contribution to be expected during operation of a projection exposure system, which is attributable to thermal manipulators and / or thermal compensation means, was taken into account. This was achieved by using an optimization method characterized by a merit function when determining the final optical system. The merit function includes, as evaluation variables, the deviation of the optical path length of the initial optical system without thermal stress, the deviation of the optical path length of the initial optical system with thermal stress, and the deviation of the optical path length of the reference optical system, i.e., in the present case, the initial optical system.Based on the optimization process, the geometry of the optical element of the initial optical system was modified, for example, by arranging at least one corrective asphere on the optical element of the initial optical system. Other modifications to the initial optical system, such as the arrangement of the optical elements or the number of optical elements, are also conceivable. The aberration contribution curve of the final optical system, shown as a dashed line, has a lower amplitude than the aberration contribution curve of the initial optical system, shown as a solid line, due to the consideration of the expected proportion of the aberration contribution.This provides sufficient latitude in the final optical system so that, under thermal stress, the final optical system exhibits no aberration contribution curve, or only a slightly worse aberration contribution curve, than the initial optical system, for at least the aberration contribution shown in diagram I*. When operating a projection exposure system 1 with the final optical system, the amplitude of the aberration contribution curve increases more sharply due to the thermal manipulators and / or thermal compensation means than the amplitude of the aberration contribution curve when operating a projection exposure system 1 with the initial optical system. However, due to this latitude, the amplitude of the final optical system is then approximately at the level of the initial optical system.Due to the optimization procedure, in this case the sum of the amplitude of the dashed lines of diagram I and diagram I* is even smaller than the sum of the amplitude of the solid lines of diagram I and diagram I*.

[0034] The middle diagram II* and the right diagram III* of the Fig.3 each show the aberration contribution curve for aberration contributions other than the left-hand diagram I*. Here, too, the solid line shows the aberration contribution curve of the initial optical system, and the dashed line the aberration contribution curve of the final optical system. The aberration contribution curves shown in diagrams II* and III* are not significantly influenced by the thermal manipulators and thermal compensation means, so that the thermal manipulators and thermal compensation means do not need to be taken into account in these aberration contribution curves. When determining the final optical system, it is therefore particularly important that the aberration contribution curves of the final optical system for such aberration contributions deviate as little as possible from the corresponding aberration contribution curves of the initial system.Since the respective aberration contribution curves hardly differ from each other, it is made easier for the final optical system to be used with the same masks and the same settings as the initial optical system. List of reference symbols 1 projection exposure system 2 field facet mirrors 3 Radiation source 4 Lighting optics 5 Object field 6 Object level 7 Mask 8 mask holders 9 Projection optics 10 image field 11 Image plane 12 wafers 13 wafer holders 14 Radiation 15 Intermediate focal plane 16 Pupillary facet mirrors 17 Assembly 18 mirrors 19 mirrors 20 mirrors I, I*, II*, III* diagram X abscissa Y ordinate QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 100 00 191 A1

[0004] DE 10 2015 224 281 A1

[0004] DE 10 2014 212 691 A1

[0004]

Claims

[1] Method for designing an imaging optical system for a projection exposure apparatus (1) comprising at least the following step: a) determining a final optical system for a projection exposure system (1), - wherein the final optical system comprises at least one optical element, - wherein, when determining the final optical system, at least one portion of at least one aberration contribution to be expected, in particular during operation of a projection exposure system (1), is taken into account, in particular compensated, and - wherein the expected proportion of the aberration contribution is determined by at least one thermal manipulator of a projection exposure system (1) and / or by at least one thermal compensation means of a projection exposure system (1). [2] Method according to claim 1, characterized bythat the expected proportion of the aberration contribution is caused by at least one thermal influence by the useful radiation of a projection exposure system (1). [3] Method according to claim 1 or claim 2, characterized by that the procedure includes the following step: b) Defining an initial optical system for a projection exposure system (1), - wherein the initial optical system comprises at least one optical element, - wherein in step a) the final optical system is determined based on the initial optical system. [4] Method according to claim 3, characterized by that in step a) the geometry of the optical element of the initial optical system is changed, the position and / or orientation of the optical element of the initial optical system is changed and / or the number of optical elements of the initial optical system is changed. [5] Method according to one of claims 1 to 4, characterized by that in step a) the final optical system is determined using an optimization method characterized by a merit function and that, preferably, the merit function comprises as evaluation variable the optical path length and / or the deviation of the optical path length of the initial optical system without thermal stress, the optical path length and / or the deviation of the optical path length of the initial optical system with thermal stress and / or the optical path length and / or the deviation of the optical path length of an optical reference system. [6] Method according to one of claims 1 to 5, characterized bythat in step a) the expected proportion of the aberration contribution in the geometry of the optical element of the initial optical system, in the position and / or orientation of the optical element of the initial optical system and / or in the number of optical elements of the initial optical system is taken into account. [7] Method according to one of claims 1 to 6, characterized by that in step a) the final optical system is determined such that the aberration contribution profile, in particular without thermal stress, of the final optical system for at least one aberration contribution deviates by at most 25%, preferably at most 15%, more preferably at most 10%, in particular at most 5%, from the aberration contribution profile of the corresponding aberration contribution, in particular without thermal stress, of an optical reference system. [8] Method according to one of claims 1 to 7, characterized bythat in step a) the final optical system is determined such that the aberration contribution profile, in particular without thermal stress, of the final optical system for at least one aberration contribution deviates by at least 10%, preferably at least 25%, more preferably at least 40%, in particular at least 50%, from the aberration contribution profile of the corresponding aberration contribution, in particular without thermal stress, of an optical reference system. [9] Imaging optical system for a projection exposure apparatus (1), comprising at least one optical element, wherein the imaging optical system is determined according to one of claims 1 to 8. [10] Projection exposure apparatus (1) comprising an imaging optical system according to claim 9.

Images