Optical imaging system with predefinable wavelength bandwidth of the imaging light

Abstract

An optical system is used to guide illuminating and imaging light (7) from a light source (5; 42) to an image field (34) in which a substrate (36) can be disposed. An optical assembly (31a, 32) is used to guide the illuminating and imaging light (7) along a beam path between the light source (5) and the image field (34) via at least one field plane (38, 33, 35) and via at least one pupil plane (23, 39). The light source (42) and / or a chromatic filter (37) disposed downstream of the light source (5) in the beam path is designed such that, for the imaging light (7) generated by means of the light source (5; 42), a wavelength bandwidth between a total wavelength bandwidth and a reduction wavelength bandwidth which is at least 10% smaller than the total wavelength bandwidth can be defined. The result is an optical system which improves the imaging performance for imaging in particular objects that have structures having different imaging requirements.

Description

[0001] Optical system for guiding illumination and imaging light from a light source to an image field

[0002] This patent application claims priority from German patent application DE 10 2023 210 775.5, the contents of which are incorporated herein by reference.

[0003] The invention relates to an optical system for guiding illumination and imaging light from a light source to an image field. Furthermore, the invention relates to a projection exposure system having such an optical system, a method for producing a micro- or nanostructured component using such a projection exposure system, and a micro- or nanostructured component produced using such a method.

[0004] Such an optical system is known from EP 1 959 302 B1 and WO 2019 / 145 126 A1. The use of filters in lithographic exposure systems is known from WO 2012 / 160 928 A1, US Pat. No. 8,760,628 B, and KR 20140051706 A. US Pat. No. 4,853,756 discloses a projection exposure system. US Pat. No. 2001 / 0028669 A1 discloses a laser that can be used as a light source in a projection exposure system. DE 10 2011 080 919 A1 discloses a microlithographic projection exposure system and a method for operating such a system.

[0005] It is an object of the present invention to further develop an optical system of the type mentioned above in such a way that its imaging performance is improved, particularly for imaging objects that have structures with different imaging requirements. This object is achieved according to the invention by an optical system having the features specified in claim 1, claim 12, and claim 13.

[0006] According to the invention, it was recognized that by varying the wavelength bandwidth of the illumination and imaging light used to image a structure on the object into the image field, a defocus tolerance on the one hand and a minimum contrast requirement on the other hand can be adapted to the respective object structure types. Imaging the object with the total wavelength bandwidth results in a high defocus tolerance, so that even object structures with a greater extent perpendicular to the field can be imaged. Imaging with the reduced reduction wavelength bandwidth results in a higher minimum image contrast, so that even object structures with higher contrast requirements, in particular finer object structures, can be imaged. The total wavelength bandwidth can be 2.5 nm with an average useful wavelength of 365 nm.With an average wavelength of 13.5 nm, the total wavelength bandwidth can be as high as 0.6 nm. In particular, contact holes with a larger extension perpendicular to the field can be imaged well using the total wavelength bandwidth, while simultaneously, using the reduction wavelength bandwidth, finer structures can be imaged on the same reticle.

[0007] A light source can be part of the optical system, but this is not mandatory as long as the optical system includes the chromatic filter, so the optical system can also be provided separately as a module that can be adapted to an external light source. The chromatic filter or light source is arranged in the area of ​​a field plane of the optical system. This enables field sections to be influenced section by section by appropriately designing the chromatic filter or light source with corresponding (field) section-wise spectral characteristics. Certain field regions can thus be specifically influenced spectrally differently than other field regions, so that an adapted spectral characteristic of the illumination and / or imaging light can be specified via the chromatic filter or light source, adapted to structural sections on the object to be imaged.For example, specific sections of the object to be imaged can then be specifically illuminated with a wavelength bandwidth adapted to the existing object structure sections to be imaged.

[0008] In one of the variants specified in claim 2, the light source is designed as a tunable light source and is then part of the optical system. The light source can comprise at least one laser diode with a temperature-dependent emission wavelength.

[0009] An arrangement of the chromatic filter according to claim 3 enables a good adaptation of the chromatic filter to the imaging conditions of the imaging optics. Alternatively, the chromatic filter can also be arranged in an illumination optics of the optical system for illuminating the object field.

[0010] An embodiment of the light source according to claim 4 enables a wavelength bandwidth to be spatially resolved to the imaging requirements of the optical system. The light source can comprise a plurality of corresponding individual light sources between a minimum number of, for example, three individual light sources and a maximum number of, for example, 1,000 individual light sources, in particular a number of individual light sources in the range between 10 and 100.

[0011] A pupil plane arrangement according to claim 5 enables a chromatic adjustment of a wavelength bandwidth of the illumination and imaging light depending on the object illumination angle.

[0012] This is particularly possible with a configuration of the chromatic filter according to claim 6. An outer ring section of the chromatic filter can then transmit the illumination and imaging light with the reduction wavelength bandwidth, so that denser lines whose diffraction orders pass through this outer ring section are imaged with high contrast. Coarser structures, on the other hand, are imaged with an increased depth of field, since the depth of field is proportional to 1 / NA. 2 and the blocked light has a reduced NA, where NA denotes the image-side numerical aperture of the projection optics. Alternatively, such a section-wise influencing of a wavelength bandwidth can also be achieved by arranging the array light source in the pupil plane and correspondingly controlling the individual light sources.

[0013] An embodiment of the chromatic filter according to claim 7 can be adapted to a distribution of object structures on the object to be imaged. Field sections of the chromatic filter can then be specified with a corresponding wavelength-bandwidth filter effect. Alternatively, a corresponding field-dependent effect of the wavelength bandwidth can also be adjustable here via an array light source in a field plane.

[0014] An embodiment of the chromatic filter with a compensation filter section according to claim 8 makes it possible to ensure total transmission of the chromatic filter across the entire cross-section of the beam path, even if the chromatic filter only has a chromatic effect in a cross-sectional section of the beam path. The compensation filter section can be part of a filter unit that also includes the chromatic filter. Alternatively, the chromatic filter and the compensation filter section can be two separate components.

[0015] The compensation filter can be designed as a neutral density filter. Alternatively or additionally, the compensation filter can also be designed as a filter with a different chromatic effect. The compensation filter can have a spectral filter characteristic that differs from that of the chromatic filter.

[0016] A design of the chromatic filter as an interference filter has proven itself in practice.

[0017] Designing the chromatic filter as a high-pass filter ensures that, within the reduction wavelength bandwidth, advantageously smaller wavelengths of the total wavelength bandwidth are available for imaging, thus enabling a correspondingly high resolution. Alternatively, the chromatic filter can also be designed as a low-pass filter or a band-pass filter. A filter changer according to claim 11 enables the chromatic filter to be switched on as needed. Such a filter changer can also be used to switch between several different chromatic filters. This allows sequential exposure of one and the same object using different chromatic filters, or the chromatic filter can be adapted to different object structure distributions.

[0018] The advantages of an optical system according to claim 12 correspond in principle to those already explained above in connection with claims 1 and 3. In the optical system according to claim 12, the chromatic filter or the light source does not necessarily have to be arranged in the region of a field plane of the optical system.

[0019] Corresponding poison for the optical system according to claim 13, the advantages of which have already been explained in principle above in connection with claim 5. In the optical system according to claim 13, the chromatic filter or the light source does not necessarily have to be arranged in the region of a field plane of the optical system.

[0020] Optical systems according to claims 12 and / or 13 can be combined with the other features discussed above in connection with the optical system according to claim 1. The advantages of a projection exposure apparatus according to claim 14, a manufacturing method according to claim 15, and a micro- or nanostructured component according to claim 16 correspond to those already explained above with reference to the optical system.

[0021] The lighting system can have a DUV (deep ultraviolet) light source (wavelengths, for example, in the range between 150 nm and 380 nm) or an EUV light source (extreme ultraviolet, wavelengths between 5 nm and 100 nm).

[0022] The projection exposure system can be used to produce a micro- or nano-structured component, particularly a semiconductor chip, for example a memory chip.

[0023] Embodiments of the invention are explained in more detail below with reference to the drawings, in which:

[0024] Fig. 1 is a schematic overview of a microlithography projection exposure system in a meridional section, comprising an illumination optics for illuminating an object field and a projection lens for imaging the object field into an image field;

[0025] Fig. 2 shows, in a meridional section, an embodiment of a projection lens of the projection exposure system according to Figure 1;

[0026] Fig. 3 shows a diagram showing a dependence of an image contrast on a defocus value during imaging through the projection lens of the projection exposure system, shown for two wavelength bandwidths of illumination and imaging light, predetermined via a light source and / or via a chromatic filter of the projection exposure system arranged downstream of the light source in the beam path of the illumination or imaging light;

[0027] Fig. 4 a process window representation of a dose error depending on a defocus value and whether the chromatic filter is used in the beam path of the illumination or imaging light or not;

[0028] Fig. 5 is a plan view of the chromatic filter for placement in a pupil plane of the optical system;

[0029] Fig. 6 is a diagram showing a dependence of a transmission of an outer filter section of the filter according to Fig. 5 on a wavelength;

[0030] Fig. 7 is a plan view of an object in the form of a reticle that can be arranged in the object field of the projection exposure apparatus and is to be imaged during projection lithography;

[0031] Fig. 8 in a diagram similar to Figure 6 another

[0032] Execution of a transmission path of a variant and / or another section of the chromatic filter; Fig. 9 an embodiment of an objective of the illumination optics for imaging an intermediate field plane into the object field; and

[0033] Fig. 10 shows a plan view of an embodiment of a light source of the projection exposure system, designed as a hexagonal array of wavelength-tunable individual light sources.

[0034] To clarify spatial relationships, a Cartesian xyz coordinate system is shown in the drawing. In Fig. 1, the x-axis runs perpendicular to the drawing plane and extends out of it. The y-axis runs upward in Fig. 1. The z-axis runs to the left in Fig. 1.

[0035] A microlithography projection exposure system 1 has an illumination system with illumination optics 2 for illuminating a defined illumination or object field 3 at the location of an object or reticle 4, which represents a template to be projected for the production of microstructured or microelectronic semiconductor components. The reticle 4 is held by a reticle holder (not shown).

[0036] A deep ultraviolet (DUV) laser serves as the light source 5 for the illumination system. This can be an ArF excimer laser. Other DUV sources are also possible. A variant of the light source 5 is explained below using Figure 10.

[0037] A beam expander 6, for example a mirror arrangement known from DE-A 41 24 311, serves to reduce coherence and to generate an expanded, collimated, rectangular cross-section of a beam of the illuminating light 7.

[0038] A first diffractive optical raster element (DOE) 8 is arranged in an object plane of a condenser 9. This DOE 8 is also referred to below as an intensity pre-fork element. The condenser 9 has an axicon pair 10 and a lens 11 with a positive focal length. The distance between the axicon elements of the axicon pair 10 and the position of the lens 11 are adjustable along an optical axis 12 of the illumination optics 2, as indicated in Fig. 1 by double arrows 13, 14. The condenser 9 therefore represents a zoom optics.

[0039] A further diffractive and / or refractive optical raster element (ROE) 16 is arranged in an exit pupil plane 15 of the condenser 9. If the raster element 16 is designed to be diffractive, it can be implemented, for example, as a computer-generated hologram (CGH). Alternatively or in addition to being designed as a diffractive optical element, the ROE 16 can be designed to be refractive, for example, as a refractive optical raster element, in particular as a microlens array. Although a diffractive design is also possible, the raster element 16 will be referred to below as an ROE.

[0040] The first DOE 8 sets a defined intensity distribution in the pupil plane 15 at the location of the ROE 16. This creates a predetermined illumination setting, i.e., a defined distribution of illumination angles across the object field 3. The first DOE 8 therefore represents an illumination angle specification element for specifying an illumination angle distribution across the object field 3. A coupling optics 17 arranged downstream of the ROE 16 transmits the illumination to an end-face entrance surface 18 of a transparent optical rod in the form of a glass rod 19.

[0041] The optical rod 19 has a rectangular cross-section. This rod cross-section is generally polygonal and can also be square or hexagonal, for example.

[0042] The rod 19 mixes and homogenizes the illumination light by multiple internal reflections at the jacket walls of the rod 19. Immediately adjacent to an end-side exit surface 20 of the rod 19 opposite the entrance surface 18 there is an intermediate field plane in which a reticle masking system (REMA) 21, an adjustable field diaphragm, is arranged.

[0043] With the ROE 16, among other things, the cross-sectional shape of the illumination beam 7 is adapted to the rectangular shape of the entrance surface 18 of the rod 19.

[0044] The ROE 16 is also referred to below as the optical rod illumination specification element. The ROE 16 serves to specify the illumination of the entrance surface 18 of the rod 19 with the illumination light 7. This specification of the illumination of the entrance surface 18 is such that it specifies a distribution of the illumination intensity and, at the same time, the illumination angle distribution across the entrance surface 18. The specified illumination intensity distribution across the entrance surface 18 deviates from a homogeneous distribution, which will be explained in more detail below. The DOE 8, i.e., the intensity specification element, serves to specify an illumination intensity distribution on the ROE 16, i.e., on the optical rod illumination specification element.

[0045] A condenser 22 is arranged downstream of the REMA 21. A diaphragm changing holder 24 with a plurality of diaphragms or filters can be arranged in an exit pupil plane 23 of the condenser 22, two of which, 25, 26, are shown in Fig. 1. The diaphragm changing holder 24 carries the various diaphragms in the manner of a diaphragm carousel. For diaphragm changing, the carousel is driven by a drive shaft 27 of a drive motor 28, which is in signal communication with a central control device 28a of the projection exposure system 1. The diaphragms of the diaphragm changing holder 24 are divided into an even number of separate diaphragm sections. The diaphragm sections can be diaphragms that completely block the illuminating light, gray filters that attenuate the illuminating light by a predetermined amount, or polarization filters that linearly polarize the illuminating light.

[0046] A further condenser with lens groups 29, 30 is arranged downstream of the pupil plane 23 of the rod 19. A 90° deflecting mirror 31 for the illumination light is arranged between the two lens groups 29, 30. The condenser 22 and the further condenser with the two lens groups 29, 30 form an objective 31a that images the intermediate field plane of the REMA 21 onto the reticle 4. The pupil plane 23 represents an internal pupil plane of this objective 31a. One embodiment of the objective 31a is shown in meridional section in Figure 9 and is generally known from US Pat. No. 6,295,122 BL. A projection objective 32 images the object field 3, which lies in an object plane 33, into an image field 34 in an image plane 35. The image field 34 is part of the surface of a wafer 36 to be exposed, which is provided with a coating sensitive to the illumination light. The wafer 36 is held by a wafer holder (not shown).During projection exposure, the reticle 4 and the wafer 36 are scanned synchronously. Intermittent movement of the holders of the reticle 4 and the wafer 36, a so-called stepper operation, is also possible.

[0047] The various beam-guiding and beam-forming components of the projection exposure system 1, with the exception of the deflecting mirror 31, are indicated as refractive components. They can also be catadioptric or reflective components. The illumination optics 2, including the REMA lens 31a, and the projection lens 32, form an optical system of the projection exposure system 1.

[0048] Figure 2 shows an embodiment of the projection lens 32, again in a meridional section. Such a projection lens is known from US Pat. No. 8,970,964 B2.

[0049] In one embodiment of the projection exposure system 1, a chromatic filter 37 is arranged in the beam path of the illumination and imaging light 7 downstream of the light source 5. Example arrangement planes for the chromatic filter are a field plane 38 of the field stop 21, the exit pupil plane 23 of the objective 31a, an arrangement plane adjacent to the object plane 33, an exit pupil plane 39 of the projection objective 32, or an arrangement plane adjacent to the image plane 35 and located upstream of it in the beam path.

[0050] By way of example, for an arrangement within the illumination optics, arrangement positions of the chromatic filter 37 at the location of the field stop 21 and at the location of the stop 25 are illustrated in Figure 1. Further arrangement variants for the chromatic filter 37 are illustrated in Figure 2 near the object plane 33, in the exit pupil plane 39 and near the image plane 35 using the example of an exit surface of component F3 of the projection optics 32. Depending on the application described below, the chromatic filter 37 can be arranged in the region of an accessible field plane and / or in the region of an accessible pupil plane of the optical system in the beam path of the illumination and imaging light 7 in front of the image field 34.

[0051] The chromatic filter 37 is designed such that a wavelength bandwidth can be specified for the imaging light 7 in the beam path in front of the image field 34, which lies between a total wavelength bandwidth of the light source 5 and a reduction wavelength bandwidth. The reduction wavelength bandwidth is at least 10% smaller than the total wavelength bandwidth.

[0052] In one embodiment of the projection exposure system 1, the light source 5 is designed as a mercury vapor lamp, with the i-line of the emission spectrum being used as the illumination and imaging light 7. A total wavelength bandwidth emitted by the light source 5 as useful light can be around 2.5 nm, with an average useful wavelength of 365 nm. The chromatic filter 37 acts as a high-pass filter and / or as a low-pass filter and / or as a band-pass filter such that it reduces this total wavelength bandwidth by at least 10% to the reduction wavelength bandwidth, at least over a portion of an entire beam cross-section of the illumination and imaging light 7 in the beam path of the optical system.

[0053] Figure 3 illustrates the effect of this bandwidth reduction by the chromatic filter 37 on an image contrast K when imaging structures of the reticle 4 onto the wafer 36.

[0054] The ordinate of Figure 3 represents the image contrast K of this image, plotted in percent. K denotes the energetic Michelson contrast in the image of a given local object structure to be imaged, given by the ratio where I max and I min a maximum and a minimum illumination dose in the image field section of the image of the local object structure during an illumination process. The illumination dose is a function of the field point and is proportional to the intensity averaged over the wavelength spectrum and the exposure time when illuminating the local object structure to be imaged with the illumination light 9.

[0055] A defocus value D in nm, centered around a defocus of 0, is plotted on the abscissa. The defocus value indicates how a focus of an imaging beam path of the projection lens 32, starting from an object point along the beam path, is distanced from the image plane 35. With a defocus of 0, the focus of this imaging beam path lies exactly in the image plane 35. The defocus values ​​are plotted on the abscissa in Figure 3 between values ​​of -200 nm and 200 nm.

[0056] Alternatively, when using an EUV projection exposure system, the total wavelength bandwidth can also be in the range between 13.2 nm and 13.8 nm, i.e., a bandwidth of 0.6 nm. In this case, the chromatic filter 37 reduces this total wavelength bandwidth from 0.6 nm by at least 10% to a maximum value of 0.54 nm.

[0057] Figure 7 shows, by way of example, a reticle 4 to be imaged using the projection exposure system 1. Several structural sections A, B are located on the reticle 4. Highlighted in Figure 7 is a structural section A on which coarser structures, for example, contact holes, are arranged. In comparison, the structural region B contains dense structures, for example, line structures with a small structural period.

[0058] Figure 3 illustrates contrast requirements on the one hand for the coarser structures A with a minimum contrast value KA of 50% and on the other hand for the finer structures B with a minimum contrast value KB of 70%.

[0059] The minimum contrast value KA for the coarser structures A is achieved when the coarser structures A are illuminated with the imaging light 7, having the total wavelength bandwidth. A contrast curve KG, which shows the contrast value K when illuminated with the total wavelength bandwidth as a function of the defocus value D, lies above the minimum contrast value KA over the entire defocus values ​​shown. The full useful light spectrum of the imaging light 7 is therefore used, which leads to a tolerable depth of field of the image by the P projection lens 32 over the entire defocus range between -200 nm and +200 nm. The coarse structures A, for example contact holes, can therefore be imaged with sufficient contrast even if they have an extension of up to 400 nm perpendicular to the image field 34.

[0060] The higher minimum contrast of 70% is not achieved at all when exposing object 4 with the full wavelength bandwidth (contrast curve KG). The maximum contrast value that can be achieved at defocus 0 with an exposure with the full wavelength bandwidth is approximately 60%.

[0061] When object 4 is exposed to imaging light 7 with the reduction wavelength bandwidth, a contrast curve KR results over the defocus, which has an imaging contrast maximum of 80% at a defocus of 0 and lies between defocus values ​​of -80 nm and 80 nm above the minimum contrast value KB for the finer structures B. When the finer structures of object 4 are exposed to imaging light 7 with the reduction wavelength bandwidth, a defocus between -80 nm and 80 nm can be tolerated, so that the dense structures are formed with sufficient contrast at an extension perpendicular to the image field of up to 160 nm.

[0062] Exposure with the total wavelength bandwidth thus enables imaging of the coarser structures A with high defocus tolerance and a sufficient minimum contrast value KA, whereas exposure of denser structures with the reduction wavelength bandwidth leads to imaging with an increased minimum contrast value KB at the expense of a lower defocus tolerance.

[0063] The defocus tolerance for the coarse structures A is shown in Figure 3 at AZA and the defocus tolerance for the fine structures B is shown at AZB.

[0064] Alternatively, for a given object structure to be imaged, an image can be described by the effect of the chromatic filter 37 in a projection exposure system 1 via its process window, defined as a set of tolerable (i.e., error tuples that do not impair the function of the projection system) error tuples consisting of relative CD error, dose error, and defocus. Figure 4 schematically shows an edge of such a process window for a dense line structure with a fixed maximum CD error, on the one hand with (solid line) and on the other hand without (dashed line) chromatic filter 37. A dose error DF is shown as a function of a defocus value D.

[0065] The chromatic filter 37 can, for example, act in the optical pupil area of ​​the pupil plane 23, 39 to illuminate the given object structure to be imaged, while the complement of this pupil area has other chromatic filters that serve to modify the process windows of other structures. Such filtering can also occur near a field plane.

[0066] In the example of Figure 4, an increased dose error tolerance results for smaller defocus values ​​D when using the chromatic filter 37. Figure 5 shows a plan view of an embodiment of the chromatic filter 37 for an arrangement in one of the pupil planes 23, 39 of the optical system of the projection exposure system 1. The chromatic filter 37 is divided into a core section 40 and an annular section 41 surrounding it.

[0067] In the core section 40, the chromatic filter 37 is designed to transmit the total wavelength bandwidth of the illumination and imaging light 7. In the outer ring section 41, the chromatic filter 37 is designed to transmit the reduction wavelength bandwidth.

[0068] Figure 6 shows a variant of a wavelength-dependent transmission T of the chromatic filter 37 in the ring section 41. At wavelengths X that are greater than an edge wavelength Ao, the transmission T of the chromatic filter 37 in the ring section 41 decreases rapidly to values ​​in the range of 0%. At wavelengths below the edge wavelength Ao, the transmission of the chromatic filter 37 in the ring section 41 increases rapidly to values ​​in the range of 100%. An edge steepness of this transmission curve according to Figure 6 can be described via a wavelength increment 5, within which a decrease in transmission occurs from, for example, 99% (Xo - 5) to 1% (Xo + 5). 5 can be in the range between 0.01 nm and 1 nm, for example in the range between 0.05 nm and 0.5 nm.

[0069] The edge wavelength Ao is selected such that the total wavelength bandwidth of the illumination and imaging light 7 originally incident on the chromatic filter 37 is reduced to the reduction wavelength bandwidth. A total wavelength bandwidth of, for example, 2.5 nm can then be reduced, for example, to a value of 2.25 nm, 2 nm, 1.8 nm, or 1.5 nm. Figure 6 describes the chromatic filter 37 in the outer ring section 41 as a low-pass filter, in which a low-energy portion of the illumination and imaging light 7 with shorter wavelengths is passed through and a high-energy portion of the illumination and imaging light 7 with longer wavelengths is blocked. Alternatively or additionally, the chromatic filter 37 can be designed, at least in sections, as a high-pass filter or as a band-pass filter.

[0070] To ensure homogeneity of illumination intensity during imaging by means of the projection exposure system 1, a neutral section of the chromatic filter 37, for example, the core section 40 in the embodiment according to Figure 5, can be designed with a neutral filter effect, in particular as a gray filter. This neutral filter effect can be such that, normalized to the area, the same attenuation of the illumination and imaging light 7 passing through the chromatic filter 37 occurs in the neutral section as when passing through the wavelength-selective filter section, for example, through the ring section 41 in the embodiment according to Figure 5.Such a neutral filter effect can also provide an additional compensatory effect through the chromatic filter 37, for example, to compensate for illumination inhomogeneity effects that occur elsewhere within the illumination system or the optical system of the projection exposure system 1. The neutral section or core section 40 of the chromatic filter 37 is also referred to as the compensation filter section.

[0071] The chromatic filter 37 shown in Figure 5 can be used for projection exposure of a reticle 4 shown in Figure 7 as follows: For projection exposure of the coarse structures A, an illumination setting is selected in which the illumination and imaging light 7 passes exclusively through the core section 40 of the chromatic filter 37, i.e., an illumination setting with smaller illumination angles. The coarse structures A can then be imaged with the high defocus tolerance AZA.

[0072] For the projection exposure of the fine structures B of the reticle 4 according to Figure 7, an illumination setting is selected in which the ring section 41 of the chromatic filter 37 is exposed to the illumination and imaging light 7, i.e., an illumination setting with large illumination angles. In this case, the fine structures B are imaged within the defocus tolerance AZB with high minimum contrast.

[0073] The lighting setting variants explained above are set sequentially, but can in principle also be set in parallel.

[0074] Figure 8 shows a further embodiment of a wavelength-dependent transmission curve of at least one surface section of an embodiment of the chromatic filter 37. In the transmission curve according to Figure 8, the corresponding chromatic filter 37 or its filter section is designed as a high-pass filter. An edge wavelength lies in the range of a maximum of a usable total wavelength bandwidth of the i-line at 365 nm.

[0075] The chromatic filter 37 can be designed as an interference filter. In one variant of the projection exposure system 1, a reduction of the possible total wavelength bandwidth of the light source is achieved by appropriately controlling the light source itself.

[0076] Figure 10 shows a top view of such a light source 42. This is designed as an array of individual light sources 43 whose wavelengths can be independently tuned. This array is shown in Figure 10 as a hexagonal array. A different dense packing of the individual light sources 43, for example, in the form of a line grid array, is also possible.

[0077] Each of the individual light sources 43 is designed as a thermally tunable laser diode. Such laser diodes can, for example, have a central wavelength close to the i-line, for example, between 375 and 410 nm, as described in more detail at https: / / www.ushio.eu / de / produkt / uv-laserdioden-375nm- 410nm / .

[0078] A thermal tunability of the respective individual light sources 43 can be, for example, 0.25 to 0.3 nm / K.

[0079] The individual light sources 43 can be laser diodes arranged directly there or can be exit surfaces of optical fibers which guide the illumination and imaging light 7 from the laser diodes arranged at a distance to these exit surfaces.

[0080] With an alternative arrangement of the chromatic filter 37 in one of the field planes 38, 33, 35 of the optical system, a section-wise filter effect can also be precisely adapted to the position of the coarse structures A and the fine structures B of the respective reticle 4. In a plan view, such a chromatic filter 37 is then divided into sections with different filter effects, which are arranged like the reticle sections in the plan view of the reticle 4 according to Figure 7.

[0081] At the locations of the coarse structures A there is then in particular a neutral or compensation filter effect corresponding to the filter effect of the core section 40 of the embodiment of the chromatic filter 37 according to Figure 5.

[0082] At the locations of the fine structures B, there is a bandwidth-reducing filter effect of the chromatic filter 37, as explained above in connection with the ring section 41 of the embodiment according to Figure 5.

[0083] With this field plane arrangement of the chromatic filter 37, the coarse structures A are then imaged with the total wavelength bandwidth and the fine structures B with the reduction wavelength bandwidth, which leads to a high defocus tolerance for the coarse structures A and a high minimum contrast for the fine structures B.

[0084] By means of the array light source 42, depending on the arrangement of this light source 42 in a pupil plane or in a field plane of the optical system, a corresponding effect can be achieved that increases the imaging performance of the projection exposure system 1, as explained above in connection with the arrangement of the chromatic filter 37 in a pupil plane or a field plane of the optical system. With an arrangement of the array light source 42 in a pupil plane of the optical system, for example, an outer ring of the individual light sources 43 can be controlled such that the reduction wavelength bandwidth results there. Those individual light sources 43 that are arranged in an inner section of the array of the array light source 42 can, in turn, be controlled such that the total wavelength bandwidth is emitted.

[0085] When the array light source 42 is arranged in a field plane of the optical system, the individual light sources 43 can be controlled at the location of the fine structures B, for example, so that the reduction wavelength bandwidth results there. At the location of the coarse structures A, the individual light sources 43 arranged there can in turn be controlled so that the total wavelength bandwidth is emitted.

[0086] Exemplary arrangement options for the light source 42 in the optical system of the projection exposure system 1 are illustrated in Figure 1 at the location of the light source 5, corresponding to a pupil plane of the optical system, or at the location of the REMA field stop 21, corresponding to a field plane of the optical system. As long as the light source 42 is arranged at the location of the REMA field stop 21, upstream components in the beam path of the optical system according to Figure 1 can, of course, be omitted.

[0087] Depending on the design or operating requirements of the projection exposure system 1, a plurality of different chromatic filters similar to the chromatic filters 37 explained above can also be provided in order to adapt to the respective reticle 4 to be imaged. When arranged in a pupil plane of the optical system, these chromatic filters 37 can differ, for example, in the number and position of the ring sections around the core section. When the chromatic filter 37 is arranged in a field plane of the optical system, these different chromatic filters 37 can differ in the arrangement of the filter sections for generating the reduction wavelength bandwidth.

[0088] Such different filters can in turn be introduced into the beam path of the illumination and imaging light 7 by means of a filter interchangeable holder, which in terms of its structure can correspond to the diaphragm interchangeable holder 24, which was explained above in connection with Figure 5.

[0089] During the microlithographic production of a micro- or nanostructured component, the chromatic filter 37 and / or the light source 42 are first selected or adjusted depending on the reticle 4 to be imaged. The wafer 36 is coated, at least in sections, with a light-sensitive layer. A structure on the reticle 4 is then projected onto the wafer 36 using the projection exposure system 1. The exposed wafer 36 is then processed to form the microstructured component. A correspondingly micro- or nanostructured semiconductor component, for example, a microchip, in particular a memory chip, can be produced.

Claims

Patent claims 1. An optical system for guiding illumination and imaging light (7) from a light source (5; 42) to an image field (34) in which a substrate (36) can be arranged, the optical system being used to illuminate an object field (3) in which an object (4) to be imaged can be arranged, and / or to image the object field (3) into the image field (34), having an optical assembly (31a, 32) for guiding the illumination and imaging light (7) along a beam path between the light source (5; 42) and the image field (34) over at least one field plane (38, 33, 35) and over at least one pupil plane (23, 39), the light source (42) and / or a chromatic filter (37) arranged downstream of the light source (5) in the beam path being designed in such a way that for the object (4) to be imaged by means of the light source (5;42) generated imaging light (7) has a wavelength bandwidth between a total wavelength bandwidth and a reduction wavelength bandwidth which is at least 10% smaller than the total wavelength bandwidth, wherein the chromatic filter (37) or the light source (42) is arranged in the region of a field plane (38, 33, 35) of the optical system; 2. Optical system according to claim 1, characterized in that the chromatic filter (37) determines the total wavelength bandwidth of the Illumination and imaging light (7) is reduced towards the reduction wavelength bandwidth, and / or that the light source (42) is designed as a tunable light source.

3. Optical system according to claim 1 or 2, characterized in that the chromatic filter (37) is arranged in an imaging optics (32) of the optical system for imaging the object field (3) into the image field (34).

4. Optical system according to claim 1 or 2, characterized in that the light source (42) is designed as an array of individual light sources (43) whose wavelength can be tuned.

5. Optical system according to one of claims 1 to 4, characterized in that the chromatic filter (37) and / or the light source (5; 42) is arranged entirely in the region of a pupil plane of the optical system.

6. Optical system according to claim 5, characterized in that the chromatic filter (37) has a chromatic filtering effect only in a portion (41) of a pupil.

7. Optical system according to one of claims 1 to 6, characterized in that the chromatic filter (37) has a chromatic filtering effect only in a section (B) of the field (34).

8. Optical system according to one of claims 1 to 7, characterized in that, if the chromatic filter (37) is only in a section (41, B) of an entire cross-section of the beam path of the illuminating and imaging light (7) has a chromatic filter effect, a remaining section of the beam path is covered by a compensation filter section (40, A).

9. Optical system according to one of claims 1 to 8, characterized in that the chromatic filter (37) is designed as an interference filter.

10. Optical system according to one of claims 1 to 9, characterized in that the chromatic filter (37) is designed as a high-pass filter.

11. Optical system according to one of claims 1 to 10, characterized by a filter changing holder (24) in which the chromatic filter (37) is held so that it can be displaced between a use position in which the chromatic filter (37) is arranged in the beam path and a neutral position in which the chromatic filter (37) is arranged outside the beam path.

12. Optical system for guiding illumination and imaging light (7) from a light source (5; 42) to an image field (34) in which a substrate (36) can be arranged, wherein the optical system is used to illuminate an object field (3) in which an object (4) to be imaged can be arranged, and / or to image the object field (3) in the image field (34) with an optical assembly (3 1a, 32) for guiding the illumination and imaging light (7) along a beam path between- view of the light source (5; 42) and the image field (34) via at least one field plane (38, 33, 35) and via at least one pupil plane (23, 39), wherein the light source (42) and / or a chromatic filter (37) arranged in the beam path after the light source (5) is designed such that a wavelength bandwidth between a total wavelength bandwidth and a reduction wavelength bandwidth can be specified for the imaging light (7) generated by means of the light source (5; 42), which is at least 10% smaller than the total wavelength bandwidth, wherein the chromatic filter (37) is arranged in an imaging optics (32) of the optical system for imaging the object field (3) in the image field (34).

13. Optical system for guiding illumination and imaging light (7) from a light source (5; 42) to an image field (34) in which a substrate (36) can be arranged, wherein the optical system serves to illuminate an object field (3) in which an object (4) to be imaged can be arranged, and / or to image the object field (3) into the image field (34), having an optical assembly (31a, 32) for guiding the illumination and imaging light (7) along a beam path between the light source (5; 42) and the image field (34) over at least one field plane (38, 33, 35) and over at least one pupil plane (23, 39), wherein the light source (42) and / or a chromatic filter (37) arranged in the beam path downstream of the light source (5) is designed such that for the imaging light generated by means of the light source (5; 42) (7) a wavelength bandwidth between a A total wavelength bandwidth and a reduction wavelength bandwidth can be specified which is at least 10% smaller than the total wavelength bandwidth, wherein the chromatic filter (37) and / or the light source (5; 42) is arranged as a whole in the region of a pupil plane of the optical system.

14. Projection exposure system with an optical system according to one of claims 1 to 13, a reticle holder for holding a reticle (4) in an object plane (33), a projection lens (32) for imaging the object field (3) in an image field (34) in an image plane (35) and with a wafer holder for holding a wafer (36) in the image plane.

15. Process for producing a micro- or nano-structured component, comprising the following process steps: Providing a projection exposure system according to claim 14 with a light source (42) adapted to the object (4) to be formed and / or a chromatic filter (37) adapted to the object (4) to be imaged, providing the object (4) and a wafer (36), imaging a structure on the object (4) with the projection exposure system (1) on the wafer (36), Processing the exposed wafer (36) to form the microstructured component.

16. Component manufactured by a method according to claim 14.

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