Imaging optical system and projection exposure installation for microlithography with an imaging optical system of this type

An imaging optical system has a plurality of mirrors which image an object field in an object plane in an image field in an image plane. The imaging optical system has a pupil obscuration. The last mirror in the beam path of the imaging light between the object field and the image field has a through-opening for the passage of the imaging light. A penultimate mirror of the imaging optical system in the beam path of the imaging light between the object field and the image field has no through-opening for the passage of the imaging light. The result is an imaging optical system that provides a combination of small imaging errors, manageable production and a good throughput for the imaging light.

FIELD

The disclosure relates to an imaging optical system with a plurality of mirrors, which image an object field in an object plane into an image field in an image plane. Furthermore, the disclosure relates to a projection exposure installation with an imaging optical system of this type, a method for producing a microstructured or nanostructured component with a projection exposure system of this type, and a microstructured or nanostructured component produced by this method.

BACKGROUND

Imaging optical systems are known from US 2006/0232867 A1 and US 2008/0170310 A1.

SUMMARY

The disclosure provides an imaging optical system having a combination of small imaging errors, manageable production and good throughput for the imaging light are achieved.

According to the disclosure, it is recognised that without relatively large losses in the imaging quality, it is possible, in a pupil-obscured system, in other words in an imaging optical system with a pupil obscuration, to configure the penultimate mirror with a continuous reflective face, in other words without a through-opening within the optically used region of the penultimate mirror. This facilitates the production of this penultimate mirror with an adequate mirror thickness and also allows an adequately large spacing between the side of the penultimate mirror facing the image plane and the image plane while at the same time minimising the size of the pupil obscuration. This facilitation of production is particularly important if this penultimate mirror is arranged on a mirror body and/or a mirror carrier which is thin in comparison to the other mirrors.

The numerical value for the pupil obscuration is produced by the ratio of the area within the exit pupil masked because of the pupil obscuration relative to a total area of an exit pupil of the imaging optical system. A pupil obscuration, which is less than 5%, makes possible a pupil obscured imaging optical system with a particularly high light throughput. Furthermore, the small obscuration according to the disclosure may lead to a small or negligible influence on an imaging quality of the imaging optical system, in particular on the imaging contrast. The pupil obscuration may be less than 10%. The pupil obscuration may, for example, be 4.4% or 4.0%. The pupil obscuration may be less than 4%, may be less than 3%, may be less than 2% and may even be less than 1%. The pupil obscuration of the imaging optical system may be predetermined by one of the mirrors, for example by a through-opening thereof or by an outer edging thereof, or by an obscuration stop or diaphragm, which is arranged in the beam path of the imaging light between the object field and the image field.

At least one of the mirrors of the imaging optical system according to one of the two aspects described above may have a reflection face, which is designed as a free-form face which cannot be described by a rotationally symmetrical function.

A working spacing of the penultimate mirror additionally facilitates its production. The working spacing may be at least 22 mm, at least 40 mm, at least 60 mm, at least 80 mm and may even be 85 mm. Even larger values for the working spacing are possible. The working spacing is defined as the spacing between the image plane and the portion closest thereto of a used reflection face of the closest mirror, in other words the penultimate mirror of the projection optical system. The image plane is the field plane, which is adjacent to the penultimate mirror, of the imaging optical system.

A maximum angle of incidence facilitates the configuration of a highly reflective coating on this mirror. This is advantageous, in particular, if imaging light with a small wavelength is used, for example with DUV (Deep Ultraviolet), VUV (Vacuum Ultraviolet), or EUV (Extreme Ultraviolet) wavelengths. A multi-layer coating with a small acceptance band width of the angle of incidence and a correspondingly high reflection may then be used, in particular. The maximum angle of incidence of the imaging light on the penultimate mirror in the beam path may be 34.5°, 30°, 25°, 20°, 16.9° or 15.9° in the meridional section of the imaging optical system.

An arrangement of the penultimate mirror leads to the possibility that a holder, which holds this penultimate mirror and mirrors of the imaging beam path in front of the imaging beam path section, between the third to last mirror and the penultimate mirror, may be relatively compact in design.

As an alternative to this, an arrangement of the penultimate mirror is possible.

An arrangement of the third to last and the sixth to last mirror back to back leads to a compact structure of the imaging optical system with good utilisation of the installation space.

Basically, instead of a back to back mirror arrangement, an arrangement is also possible in which reflection faces are provided on both sides of a monolithic base body, which correspond to the mirror faces of the mirror arrangement then replaced.

At least one intermediate image leads to the possibility of guiding an imaging beam path section of the beam path of the imaging light between the object field and the image field closely past further components of the imaging optical system. The intermediate image may, in particular, be arranged in the region of the through-opening of the last mirror, which makes a small pupil obscuration possible. The imaging optical system may also have more than one intermediate image and may, in particular, have two intermediate images in the beam path of the imaging light between the object field and the image field.

A plurality of intermediate images may also be used to for correcting imaging errors or simplifying the design of the mirror forms involved.

At least one crossing or intersection region allows compact beam guidance. The imaging optical system may also have more than one intersection region of this type, in particular two, three or four intersection regions, between imaging beam path sections. One or all of the intersection regions may spatially overlap one another at least in portions. An intersection region is taken to mean the region in which the imaging beam path sections intersect in total. In the reflection on a mirror, the imaging beam path sections therefore, according to definition, do not intersect in an intersection region of this type.

A numerical aperture allows high resolution of the imaging optical system. The numerical aperture may be at least 0.4 and may also be at least 0.5.

A rectangular field facilitates the conducting of the lithography process when using the imaging optical system. A rectangular field of this type may be achieved, in particular, by the use of non-rotationally symmetrical free-form faces as reflection faces of the mirrors of the imaging optical system. At least one of the mirrors may be configured as a free-form face of this type. The image field may have dimensions of 2 mm×26 mm or of 2.5 mm×26 mm.

When using the imaging optical system as a projection optical system its advantages stand out, in particular.

The imaging optical system according to the disclosure may have precisely six mirrors.

The advantages of a projection exposure installation according to the disclosure correspond to those which were stated above with respect to the imaging optical system according to the disclosure. The light source of the projection exposure installation may be wide band in design and for example have a band width, which may be greater than 1 nm, which is greater than 10 nm or which is greater than 100 nm. In addition, the projection exposure installation may be designed such that it can be operated with light sources of different wavelengths. Light sources for other wavelengths used, in particular, for microlithography, can be used in conjunction with the imaging optical system according to the disclosure, for example light sources with the wavelengths 365 nm, 248 nm, 193 nm, 157 nm, 126 nm, 109 nm and, in particular, also with wavelengths, which are less than 100 nm, for example between 5 nm and 30 nm.

The light source of the projection exposure installation may be configured to produce illumination light with a wavelength of between 5 nm and 30 nm. A light source of this type uses reflection coatings on the mirrors which, in order to fulfil a minimum reflectivity, have only a small angle of incidence acceptance band width. Together with the imaging optical system according to the disclosure, this desire a small angle of incidence acceptance band width can be fulfilled.

Corresponding advantages apply to a production method according to the disclosure and the microstructured or nanostructured component produced thereby.

DETAILED DESCRIPTION

A projection exposure installation1for microlithography has a light source2for illumination light or imaging light3. The light source2is an EUV light source which produces light in a wavelength range of, for example, between 5 nm and 30 nm, in particular between 5 nm and 15 nm. The light source2may, in particular, be a light source with a wavelength of 13.5 nm or a light source with a wavelength of 6.9 nm. Other EUV wavelengths are also possible. In general, any wavelengths, for example visible wavelengths or else other wavelengths, which can be used in microlithography and are available for the suitable laser light sources and/or LED light sources (for example 365 nm, 248 nm, 193 nm, 157 nm, 129 nm, 109 nm), are even possible for the illumination light3guided in the projection exposure installation1. A beam path of the illumination light3is shown extremely schematically inFIG. 1.

An illumination optical system6is used to guide the illumination light3from the light source2to an object field4in an object plane5. The object field4is imaged in an image field8in an image plane9with the predetermined reduction scale using a projection optical system or an imaging optical system7. The image field8, in the x-direction, has an extent of 26 mm and, in the y-direction, an extent of 2 mm. The object field4and the image field8are rectangular. One of the embodiments shown inFIG. 2ff. can be used for the projection optical system7. The projection optical system7according toFIG. 2reduces by a factor of4. Other reduction scales are also possible, for example 5×, 8× or else reduction scales which are greater than 8×. The image plane9, in the projection optical system7in the embodiments according toFIG. 2ff. is arranged parallel to the object plane5. Imaged here is a portion, which coincides with the object field4, of a reflection mask10, which is also called a reticle.

The imaging by the projection optical system7takes place on the surface of a substrate11in the form of a wafer, which is carried by a substrate holder12.FIG. 1schematically shows, between the reticle10and the projection optical system7, a beam concentration13of the illumination light3running therein, and, between the projection optical system7and the substrate11, a beam concentration14of the illumination light3leaving the projection optical system7. A numerical aperture (NA) on the image field side of the projection optical system7in the embodiment according toFIG. 2is 0.50. This is not represented to scale inFIG. 1.

To facilitate the description of the projection exposure installation1and the various embodiments of the projection optical system7, a Cartesian xyz-coordinate system is given in the drawing, from which the respective position reference of the components shown in the figures emerges. InFIG. 1, the x-direction runs perpendicular to the plane of the drawing and into it. The y-direction extends to the right and the z-direction downward.

The projection exposure installation1is of the scanner type. Both the reticle10and the substrate11are scanned during operation of the projection exposure installation1in the y-direction. A stepper type of the projection exposure installation1, in which a stepwise displacement of the reticle10and the substrate11in the y-direction takes place in between individual exposures of the substrate11, is possible.

FIG. 2shows the optical design of a first embodiment of the projection optical system7.FIG. 2shows the beam path of three respective individual beams15, which issue from five object field points spaced apart from one another in the y-direction inFIG. 2. The three individual beams15, which belong to one of these five object field points, are in each case associated with three different illumination directions for the two object field points. Main beams16, which run through the centre of a pupil in a pupil plane17of the projection optical system7, are drawn inFIG. 2only for graphical reasons as these are not real, but virtual imaging beam paths of the projection optical system7because of a central pupil obscuration of the projection optical system7. These main beams16firstly run divergently, proceeding from the object plane5. This is also called a negative back focal distance of an entry pupil of the projection optical system7below. The entry pupil of the projection optical system7according toFIG. 2is not located within the projection optical system7, but in the beam path in front of the object plane5. This makes it possible, for example, to arrange a pupil component of the illumination optical system6in the entry pupil of the projection optical system7in the beam path in front of the projection optical system7, without further imaging optical components having to be present between this pupil component and the object plane5.

The projection optical system7according toFIG. 2has a total of six mirrors, which are numbered consecutively by M1to M6in the order of their arrangement in the beam path of the individual beams15, proceeding from the object field4.FIG. 2shows the calculated reflection faces of the mirrors M1to M6or M5, M6. Only a small region of these calculated reflection faces is used, as can be seen in the view ofFIG. 2. Only this actually used region of the reflection faces is actually present in the real mirrors M1to M6. These useful reflection faces are carried in a known manner by mirror bodies.

All six mirrors M1to M6of the projection optical system7are designed as free-form faces which cannot be described by a rotationally symmetrical function. Other embodiments of the projection optical system7are also possible, in which at least one of the mirrors M1to M6has a free-form reflection face of this type.

A free-form face of this type may also be produced from a rotationally symmetrical reference face. Free-form faces of this type for reflection faces of the mirrors of projection optical systems of projection exposure installation for microlithography are known from US 2007-0058269 A1.

The free-form face can be described mathematically by the following equation:

j=(m+n)2+m+3⁢⁢n2+1(2)
Z is the rising height (sagitta) of the free-form face at the point x, y
(x2+y2=r2).
c is a constant, which corresponds to the vertex curvature of a corresponding asphere. k corresponds to a conical constant of a corresponding asphere. Cjare the coefficients of the monomials XmYn. Typically, the values of c, k and Cjare determined on the basis of the desired optical properties of the mirror within the projection optical system7. The order of the monomial, m+n, may be varied as desired. A monomial of a higher order may lead to a design of the projection optical system with improved image error correction, but is more complex to calculate. m+n may adopt values of between 3 and more than 20.

Free-form faces can also be described mathematically by Zernike polynomials, which are described, for example, in the manual of the optical design programme CODE V®. Alternatively, free-form faces may be described with the aid of two-dimensional spline surfaces. Examples of this are Bezier curves or non-uniform rational basis splines (NURBS). Two-dimensional spline surfaces may, for example, be described by a network of points in an xy-plane and associated z-values or by these points and gradients associated with them. Depending on the respective type of spline surface, the complete surface is obtained by interpolation between the network points using, for example, polynomials or functions, which have specific properties with regard to their continuity and differentiability. Examples of this are analytical functions.

The mirrors M1to M6have multiple reflection layers to optimise their reflection for the impinging EUV illumination light3. The reflection can be optimised all the better, the closer the impingement angle of the individual beams15on the mirror surface lies to the perpendicular incidence. The projection optical system7has small reflection angles overall for all the individual beams15.

The optical design data of the reflection faces of the mirrors M1to M6of the projection optical system7can be inferred from the following tables. The first of these tables gives, for the optical surfaces of the optical components and for the aperture diaphragm, the respective reciprocal value of the vertex curvature (radius) and a spacing value (thickness), which corresponds to the z-spacing of adjacent elements in the beam path, proceeding from the object plane. The second table gives the coefficients C, of the monomials XmYnin the free-form face equation given above for the mirrors M1to M6. Nradius is in this case a standardisation factor. According to the second table, the amount is still given in mm, along which the respective mirror, proceeding from a mirror reference design, has been decentred (Y-decentre) and rotated (X-rotation). This corresponds to a parallel displacement and a tilting in the free-form face design method. The displacement takes place here in the y-direction and the tilting is about the x-axis. The rotation angle is given in degrees here.

The mirrors M1, M2, M4and M6are configured as concave mirrors. The radius of curvature of the mirror M2is so large that it almost looks like a planar mirror inFIG. 2. The mirrors M3and M5are configured as convex mirrors.

The mirrors M1and M6and M3and M6are arranged back to back with regard to the orientation of their reflection faces.

The optically used regions of the mirrors M1to M5have no through-opening within the optically used region for the passage of imaging light, in other words are not obscured. The mirror M5, in other words the penultimate mirror in the beam path of the illumination light3between the object field4and the image field8, also has no through-opening for the passage of the imaging light or illumination light3. The mirror M5, in other words, has an uninterrupted used reflection face.

In the imaging beam path between the mirrors M4and M5, the individual beams15pass through a through-opening18in the mirror M6. The mirror M6is used around the through-opening18. The mirror M6is thus an obscured mirror.

The pupil plane17, in the imaging beam path in the projection optical system7, lies between the mirrors M2and M3. The pupil plane17also lies in the imaging beam path between the object field4and the through-opening18of the mirror M6. An obscuration stop or diaphragm for central shading of a pupil of the projection optical system7may be arranged in the pupil plane17. The obscuration diaphragm thus shades the central region of the imaging light3in the pupil plane17which does not contribute to the imaging of the object field4because of the through-opening18.

An intermediate image plane19of the projection optical system7is located in the imaging beam path between the mirrors M4and M5. The associated intermediate image is located adjacent to the through-opening18in the mirror M6. As a result it is possible to make this through-opening18small in comparison to the used reflection face of the mirror M8. A central pupil obscuration, in other words the ratio of an area blanked by the through-opening18or the obscuration diaphragm in the pupil plane17within an exit pupil of the projection optical system7relative to an overall face of this exit pupil, is 4.4% in the projection optical system7.

A working spacing dwbetween the image plane9and the portion closest to the image plane of a used reflection face of the mirror M5is 22 mm. A ratio of this working spacing dwto the overall length of the projection optical system7, in other words to the spacing between the object field4and the image field8, is 1.3%.

A further pupil plane20of the projection optical system7is located in the imaging beam path in the region of the mirror M5. A diaphragm may also be arranged here.

The angle of incidence of the individual beams15on the mirror M3in the meridional plane, which is shown inFIG. 2, is a maximum of 34.5°.

An imaging beam path section21runs between the third to last mirror M4in the imaging beam path and the penultimate mirror M5in the imaging beam path. This imaging beam path section21begins at the reflection on the mirror M4and ends at the reflection on the mirror M5. The imaging beam path in the projection optical system7in front of the imaging beam path section21, in other words the imaging beam path between the object field4and the mirror M4, on the one hand, and an imaging light bundle22in the region of the image field8, on the other hand, are guided on the same side of the imaging beam path section21. Accordingly, the object field4and the penultimate mirror M5are arranged on different sides of a main plane23which extends centrally through the image field8and is perpendicular to the meridional plane, in other words the plane of the drawing ofFIGS. 2 to 4.

FIG. 3shows a further embodiment of the projection optical system7. Components, which correspond to those of the projection optical system7according toFIG. 2, have the same reference numerals and are not discussed again in detail.

The optical design data of the projection optical system7according toFIG. 3can be inferred from the following tables, which correspond to the tables on the projection optical system7according toFIG. 2with respect to their structure.

In the projection optical system7according toFIG. 3, the mirror M5, in comparison to the projection optical system7according toFIG. 2, is present mirrored about the main plane23. The penultimate mirror M5and the object field4are arranged on the same side of the main plane23. The imaging beam path between the object field4and the mirror M2, on the one hand, and the imaging light bundle22in the region of the image field8of the projection optical system7according toFIG. 3, on the other hand, are guided on different sides of the imaging beam path section21. The imaging beam path section21and a further imaging beam path section24between the mirrors M2and M3intersect in the imaging beam path of the projection optical system7according toFIG. 3.

In the projection optical system7according toFIG. 3, the mirror M2is configured as a convex mirror. Because of the very large radius of curvature of the mirror M2, the latter appears virtually to be a planar mirror inFIG. 3.

The intermediate image plane19, in the projection optical system7according toFIG. 3, lies practically precisely at the level of the through-opening18in the mirror M6.

The central pupil obscuration in the projection optical system7according toFIG. 3is 4.0%. The working spacing dwbetween the image plane9and the portion of the used reflection face of the mirror M5closest to the image plane is 85 mm. A radio of this working spacing dwto the overall length of the projection optical system7according toFIG. 3is 3.7%. The angle of incidence of the individual beams15on the mirror M5in the meridional plane, which is shown inFIG. 3, is a maximum of 16.9°.

FIG. 4shows a further embodiment of the projection optical system7. Components which correspond to those which have already been described above with reference to the projection optical system7fromFIGS. 2 and 3have the same reference numerals and are not discussed again in detail.

The optical design data of the projection optical system7according toFIG. 4can be inferred from the following tables, which correspond to the tables on the projection optical system7according toFIGS. 2 and 3with regard to their structure.

The imaging beam path between the intermediate image plane19and the image field8, in the projection optical system7according toFIG. 4, corresponds to that of the projection optical system7according toFIG. 3.

The object field4and the mirror M5are arranged on different sides of the main plane23.

The mirrors M1and M4on the one hand, and the mirrors M3and M6, on the other hand, in the projection optical system7according toFIG. 4, are arranged back to back.

The mirrors M1, M3and M6are concave. The mirror M5is convex. The mirrors M2and M4have a radius of curvature which is so great that they appear virtually to be a planar mirror inFIG. 4.

In the projection optical system7according toFIG. 4, an aperture diaphragm may be arranged in the region of the pupil plane17between the mirrors M2and M3.

The central pupil obscuration, in the projection optical system7according toFIG. 4, is 4.0%. The working spacing dwbetween the image plane9and the portion of the used reflection face of the mirror M5closest to the image plane is 85 mm in the projection optical system according toFIG. 4. A ratio of this working spacing dwto the overall length of the projection optical system7according toFIG. 4is 4.25%. The angle of incidence of the individual beams15on the mirror M5in the meridional plane, which is shown inFIG. 4, is a maximum of 15.9°.

In the following table, characteristics of the projection optical system

The main beam is the main beam16of a central point of the object field4. This central point is defined as the point which is located in the centre between the two edge object field points in the meridional section.

FIG. 5shows a further embodiment of the projection optical system7. Components, which correspond to those which have already been described above with reference to the projection optical system7fromFIGS. 2 to 4have the same reference numerals and are not discussed again in detail.

The imaging beam path between the object field4and the image field8in the projection optical system7according toFIG. 5is reminiscent of the imaging beam path of the embodiment according toFIG. 4. In comparison to the imaging beam path of the configuration according toFIG. 4, that according toFIG. 5with regard to the guidance of the imaging beams between the object field4and the mirror M4, appears mirrored about a plane lying virtually parallel to the xz-plane. In the imaging beam path of the projection optical system7according toFIG. 5, a part of the imaging beam path adjacent to the mirror M3lies on the same side of the imaging beam path section21as the imaging light bundle22in the region of the image field8. In the embodiment according toFIG. 5, a pupil plane17lies in the imaging beam path between the mirrors M2and M3and an intermediate image plane19lies between the mirrors M4and M5.

The projection optical system7according toFIG. 5has a numerical aperture NA on the image side of 0.33. The image field8has an extent of 26 mm in the x-direction and of 2.5 mm in the y-direction. The image field8is rectangular. A wave front error of the projection optical system7according toFIG. 5is in the region between 0.2 and 0.5λ (rms, Root Mean Square). This wave front error is given for a wavelength λ, of 13.5 nm.

FIG. 6shows a further embodiment of the projection optical system7. Components which correspond to those which have already been described above with reference to the projection optical system7fromFIGS. 2 to 5have the same reference numerals and will not be discussed again in detail.

The imaging beam path between the object field4and the image field8in the projection optical system7according toFIG. 6is comparable to the imaging beams path in the embodiment according toFIG. 5. The numerical aperture on the image side and the image field size and the image field form correspond to that which was described above in conjunction with the embodiment according toFIG. 5.

The projection optical system7according toFIG. 6has a numerical aperture NA on the image side of 0.33. The image field8has an extent of 26 mm in the x-direction and 2.5 mm in the y-direction. The image field8is rectangular.

The projection optical system7according toFIG. 6has an overall length of 1180 mm between the object plane5and the image plane9.

The pupil plane17in the imaging beam path between the mirrors M2and M3is accessible from all sides in the embodiment according toFIG. 6.

A maximum angle of incidence on the mirror M4may be 21° in the embodiment according toFIG. 6. The angle of incidence is a maximum angle of incidence here on the mirror M4in the plane of the drawing ofFIG. 6.

FIG. 7shows a further embodiment of the projection optical system7. Components which correspond to those which have already been described above with reference to the projection optical system7fromFIGS. 2 to 6have the same reference numerals and will not be discussed again in detail.

In the projection optical system7according toFIG. 7, the imaging beam path between the object field4and the mirror M4in total runs on the side of the imaging beam path section21opposing the imaging light bundle22between the mirrors M4and M5.

In the imaging beam path of the embodiment according toFIG. 7, no overall intersecting imaging beam path sections are present between the object field4and the mirror M4. The fact that individual beams of the imaging beam path sections intersect in the reflection path during the reflection on the mirrors M1to M4does not represent intersecting imaging beam path sections overall of the imaging beam path.

An imaging beam path section25extending between the mirrors M3and M4is guided past the mirror M6in the embodiment according toFIG. 7. A further intermediate image plane26in the imaging beam path section25lies in the region of this guiding past. The projection optical system7according toFIG. 7thus has, in addition to the intermediate image plane19, which lies close to the through-opening18in the imaging beam path, the further intermediate image plane26. Thus, two intermediate images are present in the imaging beam path between the object field4and the image field8in the projection optical system7according toFIG. 7.

FIG. 8shows a further embodiment of the projection optical system7. Components which correspond to those which have already been described above with reference to the projection optical system7fromFIGS. 2 to 7have the same reference numerals and will not be discussed again in detail.

In the projection optical system7according toFIG. 8, a portion of the imaging beam path associated with the reflection on the mirror M3is guided on the side of the imaging beam path section21opposing the imaging light bundle22.

An intermediate image plane26lies in an imaging beam path section27between the mirrors M1and M2. The second intermediate image plane19is arranged, as in the above-described embodiments, in the region of the through-opening18.

In the imaging beam path of the embodiment according toFIG. 8, the imaging beam path section24between the mirrors M2and M3, intersects an imaging beam path section28between the object field4and the mirror M1in a first intersection region29. The imaging beam path section21between the mirror M4and M5in turn intersects the imaging beam path section24between the mirrors M2and M3in a further intersection region30.

The projection optical systems according toFIGS. 8 to 17may have a numerical aperture NA of 0.33. An image field size of these projection optical systems may be 2.5 mm in the x-direction and 26 mm in the y-direction.

FIG. 9shows a further embodiment of the projection optical system7. Components which correspond to those which were already described above with reference to the projection optical system7fromFIGS. 2 to 8have the same reference numerals and will not be discussed again in detail.

The imaging beam path in the embodiment of the projection optical system7according toFIG. 9substantially corresponds to the imaging beam path of the embodiment according toFIG. 8. A difference lies in the guidance of the imaging beam path section28: this imaging beam path section28between the object field4and the mirror M1, in the embodiment according toFIG. 9, does not only intersect the imaging beam path section24between the mirrors M2and M3, but also the imaging beam path section25between the mirrors M3and M4and the imaging beam path section21between the mirrors M4and M5. An intersection region31of the intersection last mentioned between the imaging beam path section28and the imaging beam path section21in portions overlaps with the intersection regions29and30. In the imaging beam path of the embodiment according toFIG. 9, the intersection regions29and30also overlap one another.

An intersection region32of the intersection between the imaging beam path sections28and25is separated from the intersection regions29and30and partially overlaps with the intersection or crossing region31.

FIG. 10shows a further embodiment of the projection optical system7. Components which correspond to those which have already been described above with reference to the projection optical system7fromFIGS. 2 to 9, have the same reference numerals and will not be described in detail again.

An imaging beam path of the embodiment of the projection optical system7according toFIG. 10, apart from an arrangement mirrored about an xz-plane, is similar to the imaging beam path of the embodiment according toFIG. 2. In contrast to the imaging beam path according toFIG. 2, in the embodiment according toFIG. 10, the mirror M3is located closer to the mirror M6than the mirror M1. In the embodiment of the projection optical system7according toFIG. 2, the situation is precisely vice versa: there, the mirror M1is closer to the mirror M6than the mirror M3. In addition, in the embodiment of the projection optical system7according toFIG. 10, the mirror M2is located significantly closer to the object plane5than the mirror M4.

In the imaging beam path section24between the mirrors M2and M3, in the embodiment according toFIG. 10, a diaphragm or stop33may be arranged in the region of a pupil plane of the projection optical system7according toFIG. 10. The imaging beam path section24is freely accessible from all sides in the region of this arrangement of the diaphragm33.

FIG. 11shows a further embodiment of the projection optical system7. Components which correspond to those which have already been described above with reference to the projection optical system7fromFIGS. 2 to 10have the same reference numerals and are not discussed again in detail.

The imaging beam path in the embodiment of the projection optical system7according toFIG. 11corresponds to the imaging beam path of the embodiment according toFIG. 8. In the projection optical systems according toFIGS. 11 to 14, mirrors M1to M6may be used that have different radii of curvature in two directions that are orthogonal to one another, in other words, on the one hand, in the xz-plane and, on the other hand, in the yz-plane.

The projection optical system7according toFIG. 11is telecentric on the object side.

FIG. 12shows a further embodiment of the projection optical system7. Components which correspond to those which have already been described with reference to the projection optical system7fromFIGS. 2 to 11have the same reference numerals and will not be discussed again in detail.

The imaging beam path in the embodiment of the projection optical system7according toFIG. 12is similar to that of the embodiment according toFIG. 2, apart from a view which is mirror-inverted about an xz-plane. In contrast to the embodiment according toFIG. 2, in the embodiment of the projection optical system7according toFIG. 12, in the imaging beam path section27between the mirrors M1and M2, there is an intermediate image in an intermediate image plane26in addition to the further intermediate image in the intermediate image plane19, which is located adjacent to the through-opening18. In the embodiment of the projection optical system7according toFIG. 12, the mirror M3is located closer to the mirror M6than the mirror M1. This also distinguishes the imaging beam path of the projection optical system7according toFIG. 12from that of the embodiment according toFIG. 2, where the mirror M1is closer to the mirror M6than the mirror M3.

The projection optical system7according toFIG. 12is telecentric on the object side.

FIG. 13shows a further embodiment of the projection optical system7. Components which correspond to those which have already been described above with reference to the projection optical system7fromFIGS. 2 to 12have the same reference numerals and are not discussed again in detail.

The imaging beam path, in the embodiment of the projection optical system7according toFIG. 12, is similar to the imaging beam path of the embodiment according toFIG. 8. In contrast to the embodiment according toFIG. 8, in the imaging beam path of the projection optical system7according toFIG. 13, in the imaging beam path section25between the mirrors M3and M4, there is an intermediate image in an intermediate image plane26, in addition to the intermediate image plane19, which is located in the region of the through-opening18.

The projection optical system7according toFIG. 13is telecentric on the object side.

FIG. 14shows a further embodiment of the projection optical system7. Components which correspond to those which have already been described above with reference to the projection optical system7fromFIGS. 2 to 13have the same reference numerals and are not discussed again in detail.

The imaging beam path in the embodiment of the projection optical system7according toFIG. 14is similar to the imaging beam path of the embodiment according toFIG. 9. In contrast to the embodiment according toFIG. 9, an intermediate image is present in the imaging beam path of the projection optical system7according toFIG. 14, in the imaging beam path section25between the mirrors M3and M4and not between the mirrors M1and M2, in an intermediate image plane26in addition to the intermediate image plane19, which is located in the region of the through-opening18.

FIG. 15shows a further embodiment of the projection optical system7. Components which correspond to those which have already been described above with reference to the projection optical system7fromFIGS. 2 to 14have the same reference numerals and will not be discussed again in detail.

The imaging beam path of the projection optical system7according toFIG. 15, between the mirror M2and the image field8, is similar to the imaging beam path of the embodiment according toFIG. 5.

The imaging beam path section27between the mirrors M1and M2, in the embodiment of the projection optical system7according to15, is guided past both the mirror M6and the mirror M4. Arranged adjacent to the mirror M4in the imaging beam path section27is an intermediate image in an intermediate image plane26in addition to the intermediate image in the intermediate image plane19, which is located close to the through-opening18.

FIG. 16shows a further embodiment of the projection optical system7. Components which correspond to those which have already been described above with reference to the projection optical system7fromFIGS. 2 to 15have the same reference numerals and will not be discussed again in detail.

The imaging beam path of the projection optical system7according toFIG. 16is similar to the imaging beam path according toFIG. 13. In contrast to the imaging beam path of the embodiment according toFIG. 13, in the projection optical system7according toFIG. 16, the imaging beam path section24between the mirrors M2and M3is guided past the mirror M6. In the embodiment according toFIG. 13, the mirrors M3and M6are arranged back to back.

FIG. 17shows a further embodiment of the projection optical system7. Components which correspond to those which have already been described above with reference to the projection optical system7fromFIGS. 2 to 16have the same reference numerals and will not be discussed again in detail.

The imaging beam path of the projection optical system7according toFIG. 17, from the mirror M3, is similar to the imaging beam path of the embodiment according toFIG. 13. In contrast to this, the imaging beam path section28between the object field4and the mirror M1intersects the imaging beam path section24between the mirrors M2and M3. A further difference between the embodiments according toFIGS. 17 and 3is that in the embodiment according toFIG. 17in the imaging beam path section25between the mirrors M3and M4, an intermediate image is arranged in an intermediate image plane26. This intermediate image is present in turn in addition to the intermediate image in the intermediate image plane19close to the through-opening18.

FIG. 18shows a further embodiment of the projection optical system7. Components which correspond to those which have already been described above with reference to the projection optical system7fromFIGS. 2 to 17have the same reference numerals and will not be discussed again in detail.

The imaging beam path in the embodiment according toFIG. 18between the object field4and the mirror M4is guided in total on a side of the imaging beam path section21opposing the imaging light bundle22between the mirrors M4and M5. The imaging beam path of the embodiment according toFIG. 18differs in this regard from that of the embodiment ofFIG. 2. The course of the imaging beam path between the object field4and the mirror M4is otherwise reminiscent of the course of the imaging beam path in the projection optical system7according toFIG. 2. A further difference is that in the embodiment according toFIG. 18, a pupil plane17is arranged in the imaging beam path section27between the mirrors M1and M2. Between these two mirrors, the imaging beam path section27is accessible in broad regions from all sides.

The projection optical system7according toFIG. 18has a numerical aperture NA on the image side of 0.33. The image field has an extent of 26 mm in the x-direction and of 2.5 mm in the y-direction. The image field8is rectangular.

The projection optical system7according toFIG. 18has a wave front error in the range between 0.03 and 0.10λ (rms) over the image field8.

The mirrors M1to M6are designed as free-form faces of the tenth order.

The mirror M6has a diameter of 460 mm. The projection optical system7according toFIG. 18has an overall length of 1630 mm between the object plane5and the image plane9.

The maximum angle of incidence on one of the mirrors M1to M6may be 17°. The angle of incidence here is a maximum angle of incidence in the drawing plane ofFIG. 18.

The imaging beam path section27is guided past the mirror M6. The mirrors M3and M6are arranged back to back.

FIG. 19shows a further embodiment of the projection optical system7. Components which correspond to those which have already been described above with reference to the projection optical system7fromFIGS. 2 to 18have the same reference numeral and will not be discussed again in detail.

The imaging beam path in the embodiment of the projection optical system7according toFIG. 19is similar to that of the embodiment according toFIG. 18.

The projection optical system7according toFIG. 19has a numerical aperture NA on the image side of 0.50. The image field has an extent of 26 mm in the x-direction and of 2.5 mm in the y-direction. The image field8is rectangular.

The wave front error in the embodiment according toFIG. 19is a maximum of 0.25λ (rms) over the image field8.

The mirrors M1to M6are designed as free-form faces of the tenth order.

The mirror M6in the embodiment according toFIG. 19has a diameter of 700 mm. The overall length of the projection optical system7according toFIG. 19between the object plane5and the image plane9is 1800 mm.

FIG. 20shows a further embodiment of the projection optical system7. Components which correspond to those which have already been described above with reference to the projection optical system7fromFIGS. 2 to 19have the same reference numerals and will not be discussed again in detail.

The imaging beam path of the projection optical system7according toFIG. 20corresponds to that of the embodiment according toFIG. 18.

FIG. 21shows a further embodiment of the projection optical system7. Components which correspond to those which have already been described above with reference to the projection optical system7fromFIGS. 2 to 20have the same reference numerals and will not be discussed again in detail.

The imaging beam path of the projection optical system7according toFIG. 21corresponds to that of the embodiment according toFIG. 18.

No back to back arrangements are present in the embodiments according toFIGS. 18 to 21in the imaging beam path between the object field4and the mirror M4. In particular the mirrors M1and M4are not arranged back to back with respect to one another.

To produce a microstructured or nanostructured component, the projection exposure installation1is used as follows: firstly, the reflection mask10or the reticle and the substrate or the wafer11are provided. A structure on the reticle10is then projected onto a light-sensitive layer of the wafer11with the aid of the projection exposure installation. By developing the light-sensitive layer, a microstructure or nanostructure is then produced on the wafer11and therefore the microstructured component.